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Contents Vol.16, No.3; March 2003 www.siliconchip.com.au FEATURES 8 GM’s Hy-Wire Fuel-Cell Car World-first concept car from GM combines a hydrogen fuel-cell power plant with drive “by-wire” technology. And just look at the styling! 13 A Look At Emergency Beacons An emergency beacon could save your life. Here’s a rundown on the various types that are available and how they work – by Peter Holtham GM’s “Hy-Wire” Fuel-Cell Car – Page 8. 76 Review: Canon’s Image Stabilised Binoculars Whether you’re into bird watching or astronomy (or anything else), these image-stabilised binoculars will get rid of the shakes – by Leo Simpson PROJECTS TO BUILD LED Lighting For Cars – Page 22. 22 LED Lighting For Your Car Replace your car’s filament lamps with LEDs for improved safety. There are several designs to build, all using high-brightness LEDs – by Peter Smith 36 Peltier-Effect Tinnie Cooler It’s based on a Peltier-effect module fitted with a fan-cooled heatsink. You just install it in a 6-pack Esky and to keep your tinnies cool – by Ross Tester 56 The PortaPAL Public Address System; Pt.2 Here’s the good oil on putting it together and getting it to work. We even describe an easy way to build the box – by John Clarke & Leo Simpson 66 12V SLA Battery Float Charger It’s intended for the PortaPAL but it also makes a great general-purpose 12V SLA battery charger – by John Clarke & Leo Simpson 68 The Little Dynamite Subwoofer Build this compact subwoofer for very little money. It’s ideal for use in a car or home unit – by Julian Edgar 79 More Fun With The PICAXE: A Shop Door Minder Peltier-Effect Tinnie Cooler – Page 36 Part 2 of this series shows you how to build a “Shop Door Minder . . . With Attitude” – by Stan Swan 82 SuperCharger Addendum Did you build the SuperCharger described in Nov-Dec 2002. If so, you need this simple 2-transistor add-on board – by Peter Smith SPECIAL COLUMNS 32 Circuit Notebook (1) Automatic Headlight Switch; (2) Simple Universal PIC Programmer; (3) Bat Detector Picks Up Ultrasound; (4) Junkbox-Parts Oven Timer 12V SLA Battery Float Charger – Page 66. 40 Serviceman’s Log Bring your hammer-drill and muscles – by the TV Serviceman 84 Vintage Radio Antennas & earthing systems for crystal sets – by Rodney Champness DEPARTMENTS 2 4 53 55 Publisher’s Letter Mailbag Product Showcase Silicon Chip Weblink www.siliconchip.com.au 90 92 93 95 Ask Silicon Chip Notes & Errata Market Centre Advertising Index The Little Dynamite Subwoofer – Page 68. March 2003  1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Peter Smith Ross Tester Jim Rowe, B.A., B.Sc, VK2ZLO Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson Phone (02) 9979 5644 Fax (02) 9979 6503 Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $69.50 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip LED lighting for cars – it’s about time This month we feature a major article on using high bright­ness LEDs in cars. We have wanted to do this for some time but it is only recently that really bright LEDs have become available at reasonably cheap prices. In this article, we have majored on the Centre High Mount Stop Lamp (CHMSL) and stop lights, plus the so-called festoon lamps used for vehicle interiors. We would have liked to have taken the concept much further but you have to stop somewhere if you are ever going to publish. Fairly obviously, the bayonet lamp assembly could be modified to make a bayonet stop/tail light assembly and the smaller festoon LED assembly could be fitted with high-brightness amber LEDs to be fitted into traffic indica­tor repeater lights on the sides of cars. However, the broad thrust of the article is rear end colli­sion avoidance. The extra stopping time given by LED stop lights could mean the difference between a severe collision with major damage and injuries and maybe no accident at all - just some fevered breathing afterwards. If you do nothing else, you prob­ably should convert your own car’s centre high mount stop lamp to LED operation – it could save a life. Victoria to stop DIY mains wiring? This issue just won’t go away. A recent issue of the Mel­bourne Herald-Sun notes that “Electrical goods such as cabling, power points and safety switches will be banned from public sale under proposals to be presented to the State Government this week.” “Electricians, tired of having their lives endangered by “dodgy” cabling installed illegally by home handymen, have called for a new code of practice that would restrict the sale of ca­bling and switches to licensed operators”. In fact, the proposed code of practice is already part of a new Enterprise Agreement between the Victorian branch of the ETU and the National Electrical Contractors association. Isn’t that nice and cosy? This has nothing to do with safety. Electricians aren’t in danger from DIY wiring. Check the website of the Office of Chief Inspector: www.ocei.vic.gov.au and click on “incidents”. Not only does it show that fatalities over the last 10 years have been very low, it also shows that members of the public have very low fatalities. We doubt whether any electrician has ever been killed by DIY wiring. If an electrician is in danger, he shouldn’t be practising – he is not competent. In fact, I have seen plenty of dodgy wiring done by li­censed contractors installing kitchens, dishwashers, air-condi­tioners and hot-water systems. DIY wiring is not a safety issue. In fact, if sales of cables, switches, etc are banned, safety will be prejudiced. Whereas before, if a power point or wall switch failed, the competent handyman would just replace it, now it is likely to be left in an unsafe state. And if an appliance cord frays, it will be left unsafe; if you can’t buy the cord, you can’t do the repair. And will all lighting stores close their doors? After all, most light fittings are fitted by home handymen, aren’t they? So if you have been quietly and happily doing your own 240VAC wiring up till now, you can forget it. We did mount a campaign to make it legal but apathy got in the way. Once again, if you’re not happy about this revolting development, contact your local MP and make a lot of noise. Finally, in an encouraging development, a group is being formed in Queensland to have the Electrical Safety Act changed or repealed. If you are a technician repairing anything from air-conditioners to sewing machines, computers or anything else powered by 240VAC, contact the AETA (All Electronic Technicians Association) by fax on 07 4093 9700 or email: cairnscomms<at>ipri­mus.com.au Leo Simpson www.siliconchip.com.au FireWire Interfaces A new desktop computer that requires less desk! PCMCIA to Firewire Cat 2821-7 $129 FireWire USB 1.1 Combo PCI Card Cat 2823-7 $129 FireWire USB 2.0 Combo PCI Card Cat 2877-7 $179 Low Profile FireWire card for Cat 2621 “designer” cases Cat 2992-7 $99 FireWire Card with Video Studio PCI Cat 2621-7 $199 FireWire 3 Port PLUS USB 2.0 4 Port Cat 2873-7 $189 A really nice, VERY small footprint computer utilizing the Eden 533 Mhz CPU and an ITX form factor motherboard. Requires hard drive, Memory and CD/DVD. 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Cat 1008059 0.8mm thick $4.50 Watch Dog = software reset Cat 1008058-7 Proximity Card Watch Dog 2 = power reset. 1.8mm thick $3.25 Cat 17050-7 Watch Dog 2 ISA $399 Cat 1008059-7 Proximity Key Tag $6.50 Cat 17044-7 Watch Dog ISA $165 Cat 1008057-7 Proximity Reader Cat 17070-7 Watch Dog PCI $332 (200mm range) $269 Cat 17076-7 Watch Dog 2 PCI $649 Cat 17070 Cat 1008080-7 Proximity Cat 2857 Easy Transfer Bay Reader (80mm range) $209 Cat 2857-7 Use your spare Cat 1008079-7 Door floppy drive bay to provide Controller – Stand alone front access for FireWire, USB (1.1) and Serial, $269 plus an Audio in and Audio out (RCA) $89 Cat 1008079 More than one computer? Control them with one keyboard/monitor/mouse. Save space and big dollars in both redundant hardware cost, and wasted power. Cat 11654 Cat 11654-7 Manages 2 computers ideal for small office/home $139 Cat 11655 Cat 11655-7 Manages four computers $269 Cat 11656-7 Manages eight computers $949 Cat 11657 Cat 11657-7 Manages 16 computers $1299 Cat 11658-7 USB KVM switch manages 2 computers - needs only USB Cat 11658 and a VGA cable $219 Cat 11659-7 USB KVM switch - 4 comps $449 BlueTooth Cat 11902-7 BlueTooth Compact Flash Card for Pocket PC’s with CF slot $199 Cat 11902 Cat 11907-7 BlueTooth Head Set, no more wires or “radiation” issues, try this incredibly small mobile solution Cat 11907 with a 10-metre range $199 Cat 11901-7 BlueTooth Cat USB Adapter (Class 2) $139 11901 Cat 11906-7 BlueTooth Internet Access Point Cat 11906 100 metre range $349 Cat 11904-7 BlueTooth USB Dual-Dongle 100 metre range $259 Cat 11903-7 Bluetooth USB Single-Dongle 100 metre range $149 Cat 11905-7 Bluetooth USB adapter (plastic case) $119 All “range” capabilities are for “free-air” situations. We have a range of Thin Client terminals to suit most emulations - Serial, Windows based & Linux MicroGram Computers Ph: (02) 4389 8444 FreeFax: 1800 625 777 sales<at>mgram.com.au info<at>mgram.com.au Vamtest Pty Ltd trading as MicroGram Computers ABN 60 003 062 100, 1/14 Bon Mace Close, Berkeley Vale NSW 2261 All prices subject to change without notice. For current pricing visit our website. Pictures may be indicative only. SHOREAD/MGRM0303 MAILBAG Motherboard for a silent PC I have a brief response to the query by Peter Humphreys, in Mailbag, October 2002 issue, for a silent personal computer. VIA make a fanless motherboard – the web address is: http://www.via.com.tw/en/Digital%20Library/pr_luckystar.jsp To ensure complete quietness, a linear power supply would be required as well. Geoff Perrin, via email. Nokia Datasuite is great After “bagging” Nokia in these columns some time ago for being unable to produce a decent comms suite at a reasonable price to go with their phones, I thought I must set the record straight now. I have just purchased their latest CDMA offering, the “6385” and I must say I am impressed with the connectivity of­fered now. Everything works as expected, including infrared link-up with current versions of Windows. What’s more, the soft­ware is available free to download from their website. And to top it all, all the gadgetry, including car kits from the 5100 and 6100 series can be used as well. Good one, Mr Nokia. Horst Leykam, via email. Multi-sport scoreboard wanted After spending a winter struggling with rusty steel number plates hanging on bent nails (Footy scoreboard), I started dream­ing about an electronic scoreboard. Suddenly, it was cricket season – back to the drawing board! So how about a multi-sport scoreboard project ? Many features are common to all sports but a modular ap­proach would allow it to be configured to suit. Features needed would include large character displays, optional multiple dis­plays, programmable control unit, timer/clock function, IR remote control and team ID display. There must be thousands of sporting clubs: cricket, soccer, footy, bowls, etc all with this need but which cannot afford a commercial unit. You could 4  Silicon Chip start with a single-character display with a simple rotary switch. Martyn Davison, Paynesville, Vic. Comment: how about it readers? Get your thinking caps on. Shamrock monitors not popular I read Serviceman’s Log in the December 2002 issue with some bad memories of the same situation I was in with a Shamrock monitor. A lot of the older computer monitors use Shamrock cir­ cuits. We had a few waiting for the scrap heap. I emailed the company that made these boards and asked if we could acquire a circuit diagram in Australia. They responded with “No, we do not give out circuit diagrams”! I could not believe this response. I work at a TV station and we can usually source a diagram for just about anything, either from the manufacturer or good ol’ High Country Service. Needless to say these monitors did go to the scrap heap and we have not bought anything with their logo on it again! Jamie Marschke, Coffs Harbour, NSW. Out-of-date website Could you tell me why your website is so out of date? I went there recently for information on the December 2002 issue and the “current issue” displayed on the opening page was July 2002. Hardly current! Can’t you guys spend a bit of time and fix it? You refer readers to the site for software and PC boards and so on but that’s not much use if we have to wait months for them. J. S., via email. Comment: the www.siliconchip. com.au website is updated at least once a month, usually just after the issue goes to the press. Where necessary, (eg, to repair faulty links, etc), updates are done even more regularly. Because our website is operated “in house” we can make changes almost immediately. We get this “out of date” comment quite regularly and in­variably when we contact the writer, he or she doesn’t realise their computer is caching websites – not just ours but every one they visit. Or even worse, the person has installed web “go-fast” software which often does the same thing (but worse). The answer is simply to hit your browser’s refresh button on a regular basis. Having said that, we do appreciate feedback if you do find an error, broken link, etc. Queensland licences in the police state We l c o m e t o p o l i c e s t a t e , Queensland. I waded through the many pages of officialspeak on www. eso.qld.gov.au as referred to in the Publisher’s Letters on January and February 2003. I did confirm that mere mortals, ie, non electrical workers, are still allowed to insert or remove 3-pin plugs and replace faulty light globes. Other than that, I am at a loss to understand if they have really changed. I have a restricted licence that allows me to work on medical and electronic equipment. Last week, I assisted a licenced electrical contractor with the repair of a portable compressor with a capacitor-start/ca­pacitor-run single phase motor. He had absolutely no idea what function the capacitors filled, apart from “they help the motor start”. He was unable to test the capacitors for low capacitance or leakage and had no idea what sort of capacitor to get to replace the one that proved faulty. This is not only sad but downright scary. I have worked in radio (including high-powered transmit­ ters), the www.siliconchip.com.au power generation industry and in medical electronics; most of this experience was overseas. According to the Queensland electrical authority though, I am not competent to fit a 3-pin plug onto a portable appliance. What does a qualified person like myself do in Queensland? Drive a taxi? This makes me seriously consider returning overseas where technical expertise can actually gain you employment. All this Labor Party sloganeering about “clever country” and “Queensland Smart State” is totally the reverse of the legislation we get saddled with. It is no wonder that countries with more intelli­gent governments regularly outperform Australia. Keith Johnson, Brisbane, Qld. Schools caught in the legislation as well I run my own consultancy business (The Computer Bloke) as well as being the sole IT/Network administrator/ PC support at a northern Gold Coast private college. As a result of the Publisher’s Letter in the January 2003 issue, I down­ loaded the legislation, amendments and other forms from the ESO website and started reading. I very quickly dis­missed my first impression of the editorial as a silly New Year joke and now suspect this is actually a case of farcical stupidi­ty on behalf of the Queensland Government. As a computer consultant/repair person running my own busi­ ness, I am breaking some law every time I open a PC case (Section 18(1)) to work on any components. Yet, as the IT/network adminis­trator of a private school, using the same tools, doing the same tasks, on the same equipment, the work I do is quite legal. Or am I missing some arcane point? That is, the school needs to be licenced as an electrical contractor. The implications of such a proposal are too monstrous to consider when the entire education system, both public and pri­vate, repair their own PCs. But then again, that can’t happen, as I am my own supervisor, and according to Section 41(1) (c) (amended) need to be personally licenced. This draconian legislation will not www.siliconchip.com.au further the notion of “the smart state” as frequently proposed by the Premier. Smart businesses will move south, others will close their doors, all to the detriment of the state and ordinary Queenslanders. This legislation will not save any extra lives. Education and training will. Although it would be presumptuous to think any revenue raised as a result of the licence fees would be used for such a purpose, there can be no other justification for this legisla­tion. Personally, I can’t see that happening. I’m now seriously considering moving back to Australia. Kris Zalkalns, MCSE, via email. Repairers going out of business I am writing in response to Paul Betterige’s letter in the February 2003 issue. Paul seems to have confused the issue of being qualified to work in the electrical industry as a tradesman or technician, and being allowed to by virtue of buying, at some expense, membership of the Contractors’ Club. The point being, in Queensland at least, that if you are not a member of the club then you cannot carry out the business of electrical work. The membership of the Contractors Club has recently been dressed up in quasi-safety and consumer protection terms however the basic issue was that Contractors felt that there were too many people ‘back-yarding’ and competing ‘unfairly’ because they did not have the overheads of larger businesses. This was spelled out to me by an employee of the Electrical Safety Office early in the ‘consultation’ process. Just by the way, I don’t see TETIA or TESA complaining about the issue . . . I have operated as an electronics repairer employing at one stage three technicians in a Queensland country town. I had $10M public liability insurance, $30K of insurance on customers goods (2 - 3 times the average level of items under my control), Work­ers Compensation Insurance, Fire Insurance, Flood Insurance, Motor Vehicle Insurance, Electrical Workers Licences and all sorts of other guff to carry on business. On top of that, were I still in busi- The Tiger comes to Australia The BASIC, Tiny and Economy Tigers are sold in Australia by JED, with W98/NT software and local single board systems. Tigers are modules running true compiled multitasking BASIC in a 16/32 bit core, with typically 512K bytes of FLASH (program and data) memory and 32/128/512 K bytes of RAM. The Tiny Tiger has four, 10 bit analog ins, lots of digital I/O, two UARTs, SPI, I2C, 1-wire, RTC and has low cost W98/NT compile, debug and download software. JED makes four Australian boards with up to 64 screw-terminal I/O, more UARTs & LCD/keyboard support. See JED's www site for data. Intelligent RS232 to RS485 Converter The JED 995X is an opto-isolated standards converter for 2/4 wire RS422/485 networks. It has a built-in microprocessor controlling TX-ON, fixing Windows timing problems of PCs using RTS line control. Several models available, inc. a new DIN rail mounting unit. JED995X: $160+gst. Www.jedmicro.com.au/RS485.htm $330 PC-PROM Programmer This programmer plugs into a PC printer port and reads, writes and edits any 28 or 32-pin PROM. Comes with plug-pack, cable and software. Also available is a multi-PROM UV eraser with timer, and a 32/32 PLCC converter. JED Microprocessors Pty Ltd 173 Boronia Rd, Boronia, Victoria, 3155 Ph. 03 9762 3588, Fax 03 9762 5499 www.jedmicro.com.au March 2003  5 Mailbag: continued ness, I would now have to greatly increase my in­ surance levels (the ESO seems to feel that one size, large, fits all). I gave up the unequal struggle against costs some five years ago and sold the business. My successor ran on until the end of last year. Faced with increasing his insurances to levels way out of proportion with the size of his turnover and paying for a Contractors’ Licence he too has given up and shut down. By the way, I don’t do repairs for anybody any more. David Pennycuick, via email. An electrician’s view After reading the January editorial, I felt I would be letting myself and other electricians down if I didn’t make an effort to state my case over both the implications that electri­cians are somehow working in collaboration with bureaucracy to force electronic repair businesses to shut up shop, and that technicians are smarter cookies than electricians. I have been disappointed with the way your editorials have covered this licensing issue over the last couple of years, and fellow sparkies have agreed with me. You make a few unquantified statements regarding the impact of these requirements but it remains to be seen how things really pan out. Believe me, we are all in the same boat when it comes to having more and more rules, regulations, fees, charges and the rest imposed on us. I sometimes think that Governments are trying to force small businesses out of existence with new and additional costs and requirements. But what the Government is requiring of elec­tronic and appliance repair shops is what has been required of us in the electrical trade for years and the burden is increasing. Peter Cairns, via email. Quiescent current trimpot should be fail-safe I am writing concerning the new SC480 power amplifier fea­ tured in the January & February 2003 issues. In regards to the trimpot (VR1) which 6  Silicon Chip sets the quiescent current of this and many other amplifier designs, there is no “safety valve” if this goes open-circuit. Fitting a fixed resistor of suitable value in parallel with the trimpot stops the output stage from having no control of quiescent current whatsoever, usually taking out a pair of output transistors, at least. Commenting on the ETI480 in general, I’ve used it in many general purpose applications and never had it oscillate. Atten­tion to proper earthing procedures and layout produces a very stable unit. The ETI480 module can be run from ±63V to give much more grunt than originally designed (into 4Ω too!) with some tweaking and appropriately substituted devices. How’s does the SC480 go on higher supplies? Yeah, I know, “you don’t recommend it” but if you start from scratch with new devices, not reusing the old 2N3055s, why not? Brad Sheargold, via email. Comment: VR1 is fail-safe. If the wiper goes open circuit or the pot itself goes open-circuit, Q7 is biased into full conduction. This drops the bias on the output transistors and reduces the output stage quiescent current to near zero. In fact, the same comment applies to the ETI480 circuit. Stability is a relative thing – we’ll bet that many of the ETI480 amps you thought were stable were in fact prone to para­sitic oscillation at 10MHz or above – you just never observed it. As you predict, there is no way we would recommend an in­ crease in supply to the SC480. You will probably get away with it when driving resistive loads but as soon as you start driving complex loudspeaker loads, the output transistors will be taken far in excess of the SOAR ratings and you will pop ‘em. Don’t use WD-40 on noisy volume controls I refer to the “tip” on curing noisy volume controls in the “Ask SILICON CHIP” pages of the October 2002 issue, in which the writer is a proponent of the WD-40 school of electrical fix-alls. Spraying a highly flammable residual liquid in an area where there is a high likelihood of arcing switch contacts (ie, the back of an old pot) is a recipe for disaster. I have seen many efforts by WD-40 jockeys, spraying entire amplifier chassis, TV PC boards and my favourite, the mechanism of a VCR. WD-40 is for loosening rusty nuts in the engine bay of Dad’s Holden, not for electronic switch, wiper or pot cleaning. There are plenty of far superior products that spring to mind, the most useful being CRC2-26 which, by the way, is not flamma­ble, non-damaging to plastic or rubber, doesn’t attract dust and smells a lot nicer. Please don’t publish such “tips” as they only encourage people to squirt the wretched stuff into the innards of anything electronic that isn’t working. John, via email. Move to stop DIY wiring I thought I’d let you know that my “rights” are under threat once again. I read in the Sunday edition of the “Herald-Sun” (dated 26/1/03 on page 30) under the title of “Union Bid To Switch Off DIY” that the electrical union wants to outlaw the sale of power points, cabling and safety switches from public sale. Is this all they want to ban? Below is a copy of the text as printed: “Electrical goods such as cabling, power points and safety switches will be banned from public sale under proposals to be presented to the State Government this week. Electricians, tired of having their lives endangered by “dodgy” cabling installed illegally by home handymen, have called for a new code of practice that would restrict the sale of ca­bling and switches to licensed operators. Electrical Trades chief Dean Mighell said the proposed code of practice was already part of a new Enterprise Agreement bet­ween the Victorian branch of the ETU and the National Electrical Contractors association. The Union has met with Victoria’s chief electrical inspec­tor and this week will seek support for the code from the State government. Mr Mighell said electrical wholesalers and hardware stores which sold specialist electrical parts to the public www.siliconchip.com.au were ignor­ing their duty of care.” Is this another Labor government/ union ploy to seal the closed shop approach on a protected industry? Are they so desper­ate for a dollar that they want to seal up the market place so we treat them as gods? That’s what they will be when you phone them up and ask to have a faulty power point replaced. We will all be put into a queue depending on how much work we give them or are prepared to pay. As a repairer of electrical/electronic equipment, I occa­ sionally require items from these businesses to complete repairs. I use an assortment of parts which can only come from electrical wholesalers. Are they going to stop me from earning an honest dollar? I don’t advocate the illegal wiring of buildings but common sense must prevail when we look at the big picture. Name supplied but withheld at writer’s request. Contractor licences in Queensland Thank you for bringing to the Industry’s attention the issue of ‘Contractor Licensing’ for appliance repairers, in the January 2003 Publisher’s Letter. Our Association understands your concerns. There are many facets to this debate and I am sure it will divide opinion in Queensland as well as the rest of the Australian States! Unfortunately, the Electronics Industry in Australia, both Manufacturing/Supply and the Service/Repair side has no single, united voice. The closest we ever came to a single voice was the Australian Council of Electronics Associations (ACEA) which, although still an entity, is in a state of limbo due to lack of unanimous support in the Service sector (and we had not even started on the manufacturing sector)! Due to this lack of unanimity and the diversified nature of the industry, it is very difficult to access the opinion and input of the many people involved (and let us just talk about the Service Industry here). Thousands of Australians beaver away at repairs having absolutely no idea of what others are doing and what commonalities they share. The CETA Information List www.siliconchip.com.au (CINL­ IST) has made some inroads into bringing these people into con­ tact although it does suffer from the anonymity of a List Server. In the issue of the introduction of Contractor Licensing for Repairers in Queensland, the case for this was put through the Queensland Electrical Safety Office as you are aware and, as you have commented in SILICON CHIP, was open for discussion for many months before the legislation was enacted. As a Trade Asso­ciation, we at CETA (Certified Electronic Technicians Associa­tion) received very little comment on this issue even though we brought it to the attention of our members over the same long period. I’m afraid that we can only blame ourselves for this ap­palling situation in the Electronics Industry and until we can learn to get on together and take a united approach to the obsta­ cles and decisions that affect us, I’m afraid that things will only get worse, not better. Martin Shepherd, Executive Officer, CETA. BBC still broadcasts shortwave I was amazed to learn from the December 2002 article on receiving satellite TV that “the BBC no longer transmits on shortwave” as I listen to them almost every night. While it’s true that they’ve cut back on shortwave in recent years, choosing to reach audiences via broadcast FM, AM or streaming Internet audio, they do broadcast comprehensively via shortwave. There’s a listing at: http://www.bbc.co.uk/worldservice/ schedules/frequencies/index.shtml I’m sure that shortwave enthusiasts are looking forward to the launch of DRM which promises high quality digital audio over shortwave. See http://www.drm.org/ for more information and downloadable software for decoding. Peter Marks, via email. Degradation of CDs I note with interest the comments of your correspondent, John Tingle, about the degradation of CDs from storage problems and other damage, in the January 2003 issue. Some years ago, it came to my attention that it was the top or non-reading side of discs which was more prone to damage. In an effort to overcome deterioration from ‘dulling’, scratching and chipping of the reflective layer, I developed a self-adhesive label which covers the entire top side of the disc. Much work went into the design to come up with the right adhesive/ stock combination to ensure that it was entirely inert and did no damage to the disc or degraded the sound or data quality in any way. As the labels are virtually non-removable, they also provide a bonus benefit of permanent security marking of any disc they are applied to. They have since been patented. We sell hundreds of thousands per year into the video games and DVD hire industry but (not surprisingly) we cannot interest the record producers in them. What we do find astonishing is that music retailers are almost completely uninterested in stocking them, although they stock read-side protectors and scratch repair kits. Our protective covers have been fitted to discs for the last 10 years and not one is showing any signs of degradation. The material also stops the disc from sticking to the leaves in CD storage folders, a problem we have found in that type of storage. If any of your readers are interested in obtaining some covers, they are available from our web site at: www. disc-over.com.au A. Bryan Fricker, Managing Director, via email. ABC radio delay explained I noted the letter from a reader in the “Ask SILICON CHIP” pages of the January 2003 issue concerning the 1 to 2-second delay between ABC TV sound and ABC Radio on Parliament broad­ casts. Your response attributed the delay to propagation delays through the possibly long path that the signal has to travel. The delay is probably to do with the 2-second delay that talkback radio stations add to the transmitted signal. This is done so that the announcers have time to stop calls if they get abusive, without the abusive words being transmitted. SC Shuni Francis, via email. March 2003  7 GM’s HyGeneral Motors has unveiled the Hy-wire concept car, the world’s first drivable vehicle that combines a hydrogen fuel cell with by-wire technology. The heart of the Hy-wire is an innovative “skateboard” chassis, which contains all of the sedan’s propulsion, transmission, steering and braking components within its 279mm high frame and provides a single electrical connection to the body. In essence, fuel cells enable a skateboard chassis and this flat plane provides unprecedented freedom for designing the vehicle body. 8  Silicon Chip Complementing this, the by-wire systems allow a single docking connection between the skateboard chassis and the body, and this creates great opportunities for reinvesnting the interior layout. Hy-wire was literally designed from the inside out, with form following function. The flexibility of the chassis accommodates multiple interchangeable “snap on” body styles that can be customised to meet customers’ various lifestyles. Fuel Cell Propulsion System Inside, between the aluminium beams of the skateboard chassis, GM engineers have integrated an impressive technology package. A 3-phase electric motor, mounted transversely, drives the front wheels via a single-stage planetary gear with a transwww.siliconchip.com.au mission ratio of 8.67:. It generates a maximum power of 60kW and delivers a maximum torque of 215Nm. Maximum speed is 12,000 rpm. The fuel cell stack consists of 200 single fuel cells connected in series and is roughly the size of a PC tower. It is located in the rear of the skateboard chassis and is cooled using a conventional radiator. The stack, which operates under a pressure of 1.52.7 Bar, has a power density of 1.60kW/l and produces 94kW continuously, with a peak power of 129kW. This delivers between 125V and 200V DC, depending on the load. This is boosted to 250-380V and then converted to 3-phase AC to drive the electric motor. Unlike other fuel cell vehicles, there is no battery in Hy-wire to provide extra power for peak loads. It uses only the fuel cell to provide power, thus simplifying the development and integration. The fuel cells obtain the hydrogen fuel from tanks mounted securely in the centre of the skateboard. The three cylindrical compressed hydrogen storage tanks are made of carbon composite material, have a total weight of only 75kg and store a total of 2kg of gaseous hydrogen at 350 Bar. Yes, you read that correctly – 350 Bar, about 5,000 pounds per square inch! Incidentally, the next stage of development will increase the tank pressure from the current 350 Bar to 700 Bar. GM and QUANTUM Fuel Systems Technologies Worldwide received certification from the top German safety -wire www.siliconchip.com.au institute for a 700 Bar (10,000 psi) hydrogen storage system that could ultimately allow fuel cell vehicles to drive 300 miles depending on the storage volume. Drive-By-Wire, BrakeBy-Wire, Steer-By-Wire, Docking Connection Developed by Swedish-based SKF, the “by-wire” technology enables all of Hy-wire’s major driver-control functions, including steering, accelerator and brakes, to be consolidated into a flexible, hand-controlled unit called the X-drive. It is similar to today’s advanced aircraft controls, where commands are transmitted digitally from the cockpit through electrical cables, or “by wire”, to the various parts of the plane. Hy-wire uses the same technology, allowing the driver to easily control the vehicle with either the right or left hand from the X-drive unit. Drivers also have the option of driving from the left or right driving position because the X-drive is located in a centre console that shuttles from left to right. Because it uses fully electronic connections and controls, the by-wire system simply plugs into the docking connections on the Hy-wire chassis. At the heart of the by-wire system March 2003  9 are smart electro-mechanical actuating units, which convert the driver’s commands from electronic signals to motion. The by-wire system also provides dynamic feedback to the driver via electronic signals. The advantages of by-wire technology in automobile applications include the elimination of steering columns and foot pedals and allows greater design freedom, simplified production of left and right-hand drive models and improved passive safety for the driver. The elimination of mechanical and hydraulic linkages saves   weight and simplifies maintenance because there are fewer moving parts that can wear out. By-wire is more environmentally friendly because hydraulic fluids required for steering and braking are eliminated. Software allows the driver to personalise the handling characteristics of the vehicle by adjusting the feel of steering, braking and acceleration. Adjusting them is as simple as loading a new program. 10  Silicon Chip The Hy-wire’s X-Drive replaces the usual round steering wheel and pedals, giving drivers the option to brake and accelerate with either the right or left hand. The driver accelerates by gently twisting either the right or left handgrip and brakes by squeezing the handgrips. The handgrips glide up and down for steering, somewhat different than today’s vehicles where the steering wheel revolves around a steering column. The X-Drive also incorporates an electronic monitor for rear- view and vital car functions and shuttles easily from side-to-side on a horizontal bar that stretches across the full width of the vehicle. The steering system highlights the basic functions of the by-wire controls. A conventional vehicle uses a direct mechanical or hydraulic connection between the driver’s control www.siliconchip.com.au Specifications: GM Hy-Wire Vehicle: Seating capacity: Fuel storage system: device and the relevant component. For example, the commonly used rack-and-pinion steering system uses a small toothed wheel (the pinion) to engage the rack and to shift it left or right. Tie rods then carry the motion to the steering arms at the wheel. By-wire technology, in contrast, translates the driver’s commands into electrical impulses. If the driver turns the handgrips of the X-Drive, sensors capture this motion digitally and send a signal to an electrical motor that moves the steering rack as instructed. Acceleration is similar to the throttle on a motorcycle, except that a throttle cable does not mechanically activate the throttle valve of the power plant. The by-wire system transmits an electronic signal to the electric motor that drives the Hy-wire’s front wheels. Braking is achieved by squeezing either the left or right hand grip. Grip www.siliconchip.com.au Length/diameter: Total capacity: Total weight: Fuel cell stack: Voltage: Length/width/height: Pressure: Continuous rating: Power density: Electrical traction system: Operating voltage: Maximum rating: Maximum torque: Maximum rpm: Transmission ratio: Total weight: Skateboard chassis: Body: Length: Vehicle weight: Wheel base: Fuel cell and by-wire technology, front-wheel drive, luxury sedan Five Three cylindrical high-pressure tanks of carbon composite material, mounted in the middle of the skateboard chassis 1,161/241mm 2kg 75kg 200 single fuel cells; connected in a series 125-200 Volt 472/251/496 mm 1.5-2.7 Bar 94kW, peak of 129kW 1.60 kW/l, 0.94 kW/kg 3-phase asynchronous electric motor with integrated power electronics and planetary gear 250-380 Volt 60kW 215Nm 12,000 8.67:1 92kg Length/width/height: 4,357/1,670/ 279mm Aluminium frame Steel and fibreglass 5 metres 1,900kg 3,114mm March 2003  11 sensors determine how much hand pressure the driver is exerting and these transmit a signal which applies the brakes. The system, developed together with the Italian specialist, Brembo, works with conventional brake calipers but responds faster. Maximum reliability and safety are essential features of the data-transmission system in by-wire control. All safety systems have built-in redundancy and a back-up power supply similar to those used in fly-by-wire systems. Body and Interior Since Hy-wire’s skateboard-like chassis contains all of the propulsion and control systems – a fuel cell and by-wire technology – designers were free to consider a number of body styles and interiors with what amounts to a fresh canvas to explore an endless range of possibilities for the body style and interior package. GM wanted an obvious transition from where vehicle design is now to where the technology could take it and intentionally designed a vehicle that will highlight the openness in the interior and leave it to the occupant’s imagination to consider the possibilities. The break with conventional automobile architecture is obvious on the very first encounter with the car, which is 5-metres long, 1.87-metres wide and 1.57-metres high. Glass is used extensively, giving 12  Silicon Chip passers-by a full view inside and the passengers a perfect view of the world outside. The absence of a conventional engine means there is no need for a grille up front. So the question became what to do with the open front face where you’d typically put a grille. The designers chose to enclose it with glass, allowing the driver to have a view of the road ahead that has never been possible before. You can see immediately that there is no engine at the front, the pedals and instrument panel are superfluous and the floor is flat from front to back. Hy-wire features large side windows and no B-pillars (the traditional post between the front and rear windows). The rear doors are hinged at the back, allowing the four doors to open very wide, providing very easy access. Anyone who accepts the invitation aboard can look forward to a comfortable and exciting journey. Apart from the unmatched panoramic view for the driver and passengers and spacious interior, Hy-wire offers several other key features. The fuel cell and by-wire systems eliminate the need for a traditional engine bonnet and centre tunnel, resulting in improved legroom. The lack of foot pedals means the driver is not restricted to a specific leg position. Flexibility The X-Drive can slide across for left or right side driving, emphasizing Hy-wire’s outstanding flexibility. Pressing a button on the X-Drive starts the Hy-wire vehicle. Buttons also engage the vehicle’s forward, reverse, and neutral drive conditions. The X-Drive attaches to a very light and transparent-looking centre console. Integrated in this console is a second 15cm colour monitor which allows the driver to view radio controls, heating, ventilation, air conditioning and navigation systems. The design team’s work was characterised by a feeling of freedom – freedom, for example, to position the seats and control module where they wanted to, without any restrictions. They paid particular attention to the seats when developing the Hy-wire’s interior. The five-passenger vehicle has front and rear bucket seats; the centre rear seat folds up to create a table. Lightweight materials accentuate the vehicle’s openness, and the overall environmental-friendly concept is expressed by the choice of natural colours. The sporty yet elegant four-door vehicle has short overhangs, eight-spoke light-alloy wheels with 20-inch tyres in front, and 22-inch tyres in the rear. Cameras have replaced the rearview mirrors and the headlamps and tail-lamps feature LED technology. This technology allows the lamps to be packSC aged in a very small space. www.siliconchip.com.au Emergency beacons Australia is a huge continent, surrounded by the vast Indian, Pacific and Southern oceans. If you get lost in the outback or have to abandon ship far out to sea, you could be in very serious trouble. T wenty years ago you almost certainly would have been in trouble. Rescuers might have searched for days to find you – once they even knew you were overdue. Today the Cospas-Sarsat satellite system, set up by Russia, Canada, France and the USA in 1982, takes much of the search out of search and rescue. A constellation of satellites quickly detects signals from emergency radio beacons and alerts search and rescue authorities around the world. Since the system became fully operational in 1985, 29 other countries, including Australia, have become involved and more than 11,000 people have been rescued. Carrying an emergency beacon means you can be certain help will be on its way when you need it. If you activate a beacon, it starts transmitting a low-power radio signal. Satellites in geostationary and low earth orbits pick up the signal and relay it to ground receiving stations, called Local User Terminals (LUTs). The LUTs locate the beacon position and pass it to Mission Control Centres (MCCs) which coordinate the search and rescue effort (Fig.1). Beacons Beacons come in many shapes and sizes. There are Emergency Locator Transmitters (ELTs) fitted in aircraft, Emergency Position Indicating Radio Beacons (EPIRBs) in ships, and hand-held www.siliconchip.com.au By PETER HOLTHAM Personal Locator Beacons (PLBs). The oldest type of emergency beacon operates on 121.5MHz (Table 1). They were originally designed in the mid 1970s as ELTs for crashed aircraft. Nowadays there are about 600,000 low-cost EPIRBs and PLBs also using this technology worldwide. Designed for detection by search aircraft not satellites, their simple analog signal doesn’t tell the rescue authorities who or what is in trouble, or exactly where the emergency is. What is worse, only about three in 100 alerts worldwide are genuine. Accidental or malicious activation, faults in the beacons, non-beacon transmissions on 121.5MHz, even ‘hard’ landings by aircraft with G-switch activated ELTs cause the rest. But each alarm must be tracked to its source, wasting the time and resources of search and rescue teams. Because the false alarm rate is so high, Cospas-Sarsat will stop processing signals from these beacons after February 1st 2009, and they will be obsolete. Newer beacons, specifically designed for detection and location by satellites, operate on 406MHz (Table 2). Frequencies in the March 2003  13 Fig 1: Basic Concept of the Cospas-Sarsat System 406-406.1MHz band are reserved solely for these beacons, which helps minimise the number of false alarms. The beacons transmit a 5W burst of radio frequency (RF) every 50 seconds. The high power increases the chance of detection, while the low duty cycle saves power and allows more than 90 beacons to be operating at once in view of one satellite. Each burst of RF carries a digitally encoded message, which identifies the owner of the beacon and its country of origin. Search and Rescue authorities worldwide keep a register of owners and can quickly make a phone call to check if an emergency is genuine or not. Most 406MHz beacons also include a 121.5MHz transmitter and a flashing strobe light for search vessels to home in on during the last stages of a rescue. Second-generation beacons, available since 1997, add position data in the digital message, from an internal or external GPS receiver. Because the performance of the Cospas-Sarsat system depends on the quality of the 406MHz beacons, manufacturers must get type-approval. Australian and New Zealand Standard AS4280 describes the rigorous durability tests a beacon must pass before it is approved for use. Only two Australian companies have gained type-approval for their beacons, and they manufacture them only for the Defence Forces. Table 2: 406MHz beacon data Transmitted power 5W ± 2dB Transmission life at least 24 hours at minimum temperature 50-100 mW peak effective radiated power relative to a quarter wave monopole Frequency 406.025 ±0.005MHz Modulation phase modulation, bi-phase L data encoding Transmision life 48 hours Transmission time Frequency 121.5MHz ±6kHz 440ms (short message) 520ms (long message) Modulation type AM (amplitude modulation), greater than 85% Message length 112 bits (short) 144 bits (long) Modulation Swept audible tone, 300-1600Hz (at least 700 Hz) at a rate of 2-4Hz Message repetition time 50s Operating temperature -40 to +55°C Table 1: 121.5MHz beacon data Transmitted power 14  Silicon Chip www.siliconchip.com.au Fig 3: Approximate 121.5MHz Beacon Coverage from Australian and New Zealand LUTs. Fig 2: Satellite in Polar Orbit Showing a Single Orbital Plane. Inmarsat, the organisation responsible for worldwide ship-to-shore communication, also operates an EPIRB tracking system using satellites as part of its commitment to the safety of life at sea. Inmarsat EPIRBs operate at 1.6GHz (Table 3). Like 406MHz beacons, they also transmit identification and GPS-derived position information. Some also have a ‘will to live’ feature – as soon as an Inmarsat land earth station (LES) receives an emergency signal, it bounces it back to the beacon. The beacon recognises its own code and shows a telltale visual indication. Survivors in the water can see that their distress signal has been received and that help is on the way. Satellites The Cospas-Sarsat system uses low-earth orbiting (LEOSAR) and geostationary (GEOSAR) satellites. The LEOSARs are in polar orbits 800-1000km above the Earth. They complete an orbit every 100 minutes or so, listening for both 121.5MHz and 406MHz beacons. The system uses a minimum of four LEOSARs to speed Table 3: Inmarsat-E Beacon Data Transmitted power 1W Transmission life 48 hours minimum Frequency 667 channels at 1.645GHz Modulation Frequency shift keying. www.siliconchip.com.au up detection of activated beacons (Table 4). With a single satellite, it takes at most one half rotation of the Earth (twelve hours) for any location to pass under the orbital plane (Fig.2). A second satellite with its orbital plane at right angles to the first reduces the time to six hours. Using four satellites ensures the time taken to detect a beacon is less than one hour at mid-latitudes and slightly longer nearer the equator where the LEOSARs are more spread out. With 121.5MHz beacon signals, LEOSARs simply act as repeaters, relaying the signal to a LUT for processing. For an emergency beacon to be noticed, a LEOSAR has to be in view of the beacon and a LUT simultaneously for at least four minutes. If it is not, the emergency will be missed until a more suitable pass occurs, which can take several hours. This constraint limits the use of these beacons to within a 3000km radius of the LUT (Fig.3). Table 4: LEOSAR Satellites Satellite Spacecraft Status Cospas-6 Nadezda-3 Operational Cospas-8 Nadezda-5 Operational Cospas-9 Nadezda-6 Operational Sarsat-4 NOAA-11 Operational Sarsat-6 NOAA-14 Operational Sarsat-7 NOAA-15 Operational Sarsat-8 NOAA-16 Operational March 2003  15 Looking for all the world like the lighthouses of yesterday, Australia's two Local User Terminals (LUTs) are located at Albany, WA (left) and Bundaberg, Qld (right). The inset in the middle is an on-ground shot inside a LUT antenna dome. Because LEOSARs were specifically designed to detect 406MHz beacons, they do more than just relay the signal. An on-board Search and Rescue Processor (SARP) decodes and time-stamps the beacon’s digital signal and measures the Doppler shift (the change in frequency caused by the relative movement between the satellite and the beacon), locating the beacon to within 5km. In 95% of cases, the location is determined on the first orbit after detection. Second generation 406MHz beacons transmitting GPS-derived position data can be located to within 120m. In local mode, the satellites immediately transfer the information to the 1545MHz downlink, for transmission to any LUT that may be in view. In global mode, the satellites also store the data in memory and continuously re-broadcast it on the downlink frequency. This means all LUTs tracking the satellite are able to locate the beacon, giving the system global coverage. There is no waiting until the satellite can see both the beacon and a LUT simultaneously, reducing the time taken to launch a rescue. Data storage gives the LEOSARs global but not continuous coverage; there may still be a delay before a satellite comes into view. So the Cospas-Sarsat system also uses three geostationary satellites (GEOSARs) orbiting Table 5: GEOSAR Satellites Satellite Status GOES-8 Operational 75° W GOES-10 Operational 135° W GOES-11 In orbit spare INSAT-2B Operational 93.5° E 16  Silicon Chip 36,000km above the equator (Table 5). These communications and weather satellites carry 406MHz beacon receivers as secondary payloads. GEOSARs provide a continuous watch and can send an alert as soon as a beacon is activated but there are some disadvantages. As GEOSARs are stationary relative to the Earth, there is no Doppler effect on the received signal to provide position information. Unless it is encoded in the digital message, LEOSARs must still be used for beacon location. Hilly ground or other obstructions can also hide the GEOSARs from view, especially at high latitudes; neither can they cover the polar regions, latitudes greater than 75° (Fig.4). But even with this limitation, GEOSARS can see about 97% of the Earth’s surface. Four geostationary communication satellites spaced around the equator detect Inmarsat EPIRBs. Like GEOSARs, Inmarsat satellites cannot see the polar regions but this is not a major problem as very little commercial shipping enters these regions. Local User Terminals (LUTs) Local User Terminals are unmanned ground stations that receive the downlink signal from the orbiting LEOSARS as a 2400kbps data stream. They consist of an antenna, a 1545MHz receiver, a computer to process the data, and an MCC interface. The antenna and receiver automatically acquire, track and receive the downlink signal from all non-conflicting LEOSAR passes. There are 45 LEOSAR LUTs worldwide (Fig.5). Two are in Australia, one on the east coast at Bundaberg and one on the west coast at Albany. New Zealand has one LUT, near Wellington, while to our north there are LUTs in Indonesia, Singapore and Guam. All LEOLUTs are expected to be available 24 hours a day, every day, with less than 5% downtime a year. www.siliconchip.com.au Fig 4: Geosar Footprints Fig 5: Worldwide location of Leoluts and Geoluts Once a 121.5MHz beacon signal is received, the LUT roughly fixes its position from the Doppler shift. Initially two mirror-image positions are calculated, one on either side of the satellite ground track. It takes until the next orbit, 90 minutes later, to resolve the ambiguity and fix the position to within 20km. The data from 406MHz beacons is simpler to deal with, since the Doppler shift is measured and time-tagged by the SARP onboard the LEOSAR. Within minutes of the satellite disappearing over the horizon, all stored data has been processed and passed to the nearest Mission Control Centre. Another seven GEOLUTS worldwide receive and process alerts relayed by GEOSAR satellites (Fig.5). In the southern hemisphere, there are GEOLUTS in New Zealand and Chile. Separate Land Earth Stations (LES) operated by Inmarsat (including one in Perth) monitor the signals from the Inmarsat-E beacons. Inmarsat Land Earth Stations. Because a 406MHz emergency is usually processed by more than one LUT, the MCCs are networked together so that alerts can be rapidly sorted and passed to the nearest search and rescue team for action. The MCC for the Australasian region is in Canberra and is operated by Australian Search and Rescue (AusSAR), part of the Australian Maritime Safety Authority. About 60 search and rescue specialists and support staff work in the Centre, which operates 24 hours a day, 365 days of the year. As well as managing the Australasian segment of the Cospas-Sarsat system, AusSAR coordinates Australia’s Search and Rescue Region. Covering 53 million square kilometres or one tenth of the Earth’s surface, it includes the nation as well as vast areas of the Indian, Pacific and Southern Oceans. The search and rescue teams coordinated by the Centre come from the private sector, the police, volunteer groups and the Defence Forces. How long will it be before you’re rescued once you’ve switched on your beacon? AusSAR has one of the best search and rescue response times in the world. During 2000-2001, it took an average of just 57 minutes to get a rescue underway after receiving an alert. But how long it takes to get to you will depend on where you are and whether there are ships or aircraft nearby. But unlike 20 years ago, at least you can be certain SC that you will be found. Mission Control Centres (MCCs) 24 Mission Control Centres around the world receive alert and location data from LUTs, other MCCs and   The GlobalFix 406 is the next generation of EPIRB featuring an internal GPS engine to add latitude/longitude coordinates to the emergency signal. It is available in either Category I (automatically deployable) or Category II (manually deployable) models. The beacon’s self-test features include a thorough analysis of the GPS’s circuitry (each time you self-test the EPIRB, the GPS is tested as well). When used in an emergency, the GlobalFix 406 will automatically change its operating “red” flash to “green”, to confirm the exact time the GPS coordinates are received and re-broadcast in the EPIRB’s transmission. (EPIRB pictures supplied by Tony Smith & John Bell, ACR Electronics Inc.) www.siliconchip.com.au Acknowledgement: Thanks for the assistance of Ben Mitchell of AusSAR in preparing this feature. Cospas Sarsat ELT EPIRB LES LUT MCC PLB Abbreviations COsmicheskaya Sistyema Poiska Avariynich Sudov (Space system for the search of vessels in distress) Search and Rescue Satellite Aided Tracking Emergency Locator Transmitter Emergency Position Indicating Radio Beacon Land Earth Station (Inmarsat) Local User Terminal Mission Control Centre Personal Locator Beacon March 2003  17 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Replace your car’s filament lamps with LEDs for improved safety By PETER SMITH LED Lighting For Your Car I NCREDIBLY BRIGHT Light Emitting Diodes (LEDs) have recently become available in standard 5mm packages – bright enough, we believe, to rival incandescent bulbs in some applications. This month, we present five simple and easy-to-build modules based on these new, ultra-bright LEDs. These modules can be used to replace or supplement a variety of existing automotive lights to improve safety. Safer, huh? Do you know why the centre highmount stop lights of some vehicles use LEDs rather than conventional filament lamps? For the “high-tech” look, perhaps? Maybe, but there’s a much more important reason; LEDs reduce the 22  Silicon Chip incidence and severity of rear-end collisions! So how is this possible? The answer is based on the fact that filament lamps typically take between 120ms and 250ms to ‘light up’ when you hit the brakes. If that doesn’t sound like much, Convert These to LEDs • • • • • • • • High-mount stop lights Trailer lights Breakdown lights Clearance lights Interior (festoon) lights Bayonet lamps Wedge lamps Almost anything! then consider the distance travelled in 200ms at 100km/h: 100km/h x 1/3600 x 200ms = 5.5m Those 5.5 metres could make all the difference in an emergency braking situation – a serious accident or none at all! The good news is that you can get that distance back with LED-based stop lamps, because LEDs ‘light up’ almost instantaneously. Not only that but the fast turn-on of LEDs makes them more conspicuous; they have greater attention-getting power. LEDs have a number of other advantages over filament lamps, too. They load vehicle electrical systems by at least one third less, generate little heat, require less space and have a very long service life. siliconchip.com.au With all these positives, it seems ludicrous that most new vehicles aren’t fitted with the latest high-brightness LED technology. Sure, you’ll see them in high-end vehicles like the Jaguar and Maserati. Less-expensive vehicles, such as Holden’s Monaro, use them in the centre high-mount stop light (CHMSL) but generally speaking, their use in tail, stop and turn indicators is not widespread. We’re ignoring spoiler-mounted CHMSLs here, by the way, because they’re available only on a limited number of models and are usually optional. As far as we can determine, the only reason for this apparent short sightedness is cost. And that, of course, is poised to change in the very near future, as LED prices come down (and intensities go up). But why wait? You can now convert your old-technology CHMSL to the latest and greatest with the aid of our LED CHMSL module and a few simple tools. This particular module consists of a single, 150mm-long PC board strip carrying 16 high-intensity red LEDs, four resistors and two diodes. It should fit inside most CHMSL housings without too much difficulty, replacing the standard 21W filament lamp. But before we describe how that’s done, let’s take a look at how it works. How the modules work. All modules are of the simplest design possible. They consist of one or more strings of LEDs, current limiting resistor(s) and in most cases a diode or two as well. Referring to the circuit diagram for the CHMSL module (Fig.1), you can see than the LEDs are arranged in four strings. Each string consists of four LEDs in series with a current limiting resistor. The resistor sets the current through the string, as follows: I = V/R = VBATT – VDIODE – (4 x VLED) / R = 12.8V – 0.7V – (4 x 2.0V) / 150Ω = 27.3mA VLED is the forward voltage of the LEDs at the intended current, in our case about 27mA. This value will vary between LED types, so you may need to adjust your resistor values for optimum results. Although the high-brightness red LEDs we’ve specified can be driven at much higher current levels (up to siliconchip.com.au Fig.1: circuit diagrams for all of the red LED modules. Note that we’ve reduced LED current on the Multidisc and Wedge lamp modules by increasing the resistor values from 150Ω to 180Ω. This is to allow for the higher temperatures present in tightly grouped LED arrays. 50mA), we recommend derating to a maximum of 30mA to allow for the high temperatures found in automo- tive interiors. If you’re using different LEDs, then derate even further to 25mA. March 2003  23 Fig.2: follow this diagram when assembling your centre high-mount stop lamp board. This view shows the fully-assembled CHMSL board, ready for installation inside the housing. Note that this particular unit is fitted with a “wedge” plug, made by sandwiching two blank PC boards together as described in the text. VDIODE is the forward voltage of the 1N4004 diode. The purpose of this diode is to protect the LEDs from the large negative voltage transients (up to 400V) often present in automotive electrical systems. Typical LED reverse breakdown voltage is somewhere in the region of 5-6V, so with four LEDs in series the best we could hope to “stand off” without the additional diode would be about 24V. In cases where there are less than three LEDs in a string, the 1N4004 also provides reverse polarity protection. Without protection, accidental lead reversal could cause your mega­buck LED bank to glow brighter than the Sun for a few milliseconds! An example OK, let’s look at an example. Suppose you’re using different LEDs to those shown in the parts list and you’ve determined that they drop about 1.8V at 25mA (the forward voltage can be determined from the LED data sheets or by trial and error). What value resistors would you use on the CHMSL module? 24  Silicon Chip R = V/I = 12.8V – 0.7V – (4 x 1.8V) / 25mA = 196Ω The closest readily available value to 196Ω is 200Ω, so that would be your final choice. A 0.25W power rating is sufficient in most cases. So far, we’ve only talked about the CHMSL module but there is little dif- WARNING If you have a late-model car, it may have a lamp failure detector in the brake lamp circuit. If you convert just the CHMSL to LED operation, it is unlikely to be affected. However, if you also convert the stop lamps to LED operation, the lamp failure detector will almost certainly operate each time you press the brake pedal. The fault may even be recorded in the computer’s diagnostic memory. In some prestige cars, such as the Lexus LS400 and LS430 models, the CHMSL also has a lamp failure detector and it will “detect” a lamp failure if the LED conversion is present. At present, we have no solution for this problem. Fig.3: you may need to trim away the standoffs on the LED leads so that they can be positioned right down on the PC board surface. ference in operation between the five modules. Some have less LEDs per string, some have just one (the 10mm LED on the wedge lamp, for example) and one requires the diode to be fitted externally. Note, however, that we’ve listed LED colours with each module. This is because white and blue LEDs have a significantly higher forward voltage than red (and other colours) and therefore will not work on modules that have four LEDs in series. Likewise, reds (and other colours) cannot easily be used on the modules specified for white and blue without considering the increased resistor power dissipation requirements. CHMSL module assembly Referring to the overlay diagram in Fig.2, begin by installing the two diodes and four resistors. Take care with diode orientation, noting that D1 and D2 go in different ways around. Next, install all 16 LEDs, aligning the side with the ‘flat’ (the cathode) as indicated. This should also be the side with the shorter lead. We mention this because the 10mm LEDs we received siliconchip.com.au Converting A High-Mount Stop Light To LEDs Fitting the CHMSL module (shown at left) to an existing housing can be achieved with a little ingenuity. Here’s how we did the job on a late-model Honda Accord. (1). The Accord’s CHMSL sits on the parcel shelf and is retained with two clips accessible from within the boot space. The entire assembly came away in less than 10 seconds! (3). In our case, the replacement LED module was just the right length for the job. We made a couple of small right-angle brackets to hold the board and screwed these to the top of the reflector. Many other mounting methods are possible, depending on shape and available space; eg, nylon stand-offs, cable ties, M2.5 screws, neutral cure silicone sealant, etc. Make sure that the rear of the PC board cannot contact anything metallic, though. (2). Once we had the assembly on the bench, it was a simple matter to separate the red lens from the reflector to get to the insides. Be careful with the clips that hold these parts together, as the plastic is very brittle. recently were incorrectly polarised; the flat side was next to the anode (longer lead). If you’re not sure, use your multimeter on “diode test” to verify polarity. The LEDs should be seated right down on the PC board surface. Some LEDs have large standoffs formed into their leads, making this impossible. If you have this problem, then measure between the underside of the LED and the start of the standoffs (see Fig.3). If you measure 2.5mm or more, then you can cut the leads off right at the edge of the standoffs, as there will be sufficient length remaining for soldering. Try just one LED first, though! siliconchip.com.au If the standoffs are closer than 2.5mm to the body, then shorten the leads to about 4mm and using a fineedged pair of electronics sidecutters, carefully snip away the shoulders of the standoffs (see Fig.3). To finish, install the +12V link and two 150mm flying leads for the +12V and 0V connections. Any light duty multi-strand hook-up wire will do. CHMSL module installation We chose a late model Honda Accord for our prototype installation – see photos. We didn’t hack off any “unnecessary” bits along the way, thus allowing return to the standard (4). We didn’t want to modify the vehicle’s wiring, so we powered the LED module directly from the old filament lamp socket. A suitable plug can be fashioned from two pieces of PC board, some glue and a length of tinned copper wire (see wedge lamp details). Be sure to tin all bare copper areas to prevent corrosion. filament lamp configuration if need be. Adapt our methods to suit your particular vehicle. If the module is too long for your housing but there is plenty of vertical space, then you can cut it in half and mount one section directly above the other. This is possible because we’ve designed the two sides of the board in “mirror image”. These smaller sections could be useful for other applications as well. Multidisc module assembly As the name suggests, the Multidisc module has multiple uses, some of which will require the PC board to be March 2003  25 Fig.4: the overlay diagram for the Multidisc module. Form the leads of each resistor so that its body sits directly between adjacent LEDs. circular in shape. Manufacturers will probably supply this PC board as a square, so if you need it to be round, now is a good time to cut and/or file it to shape. That done, install the LEDs, aligning all cathodes (flat sides) towards the centre of the board. The LEDs must be mounted right down on the PC board surface. If your LEDs have large standoffs that prevent this, then refer to the assembly instructions for the CHMSL module for the solution. Install the three resistors next. Now turn the board over to the copper side and install an insulated wire link as shown on the overlay diagram (Fig.4). Finally, solder two lengths of light duty hook-up wire to the +12V (+) and 0V (-) points and pass the ends through the cable hole. Unlike the other modules, this one doesn’t have a diode in series with the supply. We recommend installing a 1N4004 diode in series with either the positive or negative lead and insulating it with heatshrink tubing. tube with a fine scouring pad or ink rubber and clean with alcohol. Insert the tube 2-3mm into the base rim and solder in place. (4). Centre the Platform PC board over the end of the tube and solder in place. Apply your iron to the copper tube rather than the PC board so as not to overheat the latter. (5). Trial fit an assembled Multidisc module on the Platform board to de­ termine the required lead length. Trim the +12V wire to length and strip and tin the end. Pass it through the centre hole in the Platform board and solder it to the base tip, building up the solder as needed to get a nicely curved “bump”. (6). Pass the 0V (GND) wire through the outer board hole and trim to 1015mm in length. Stip and tin the end. (7). Trim both leads of a 1N4004 diode to about 6mm in length and solder the anode end to the 0V (GND) wire. Slip a length of heatshrink tubing over Bayonet lamp assembly Below are the instructions for the bayonet lamp assembly, presented in a step-by-step format to help make the job easier – see Figs.5 & 6. (1). Remove the glass bulb and filament from a standard 21W automotive bayonet lamp. Clean the glue from around rim of base and several millimetres into the interior. Polish the area with a fine scouring pad or ink rubber and clean with alcohol. (2). Remove solder from the tip. (3). Cut a standard 14.5mm O.D. copper water pipe joiner in half and chamfer one end with a file. Polish the 26  Silicon Chip Fig.5: the Platform PC board is unetched (blank copper). To make one, cut the 26.5mm disc from blank circuit board material and drill six 2.5mm holes as show here. The Multidisc PC board can be used as a template. the diode to insulate the connection. Solder the other (cathode) end of the diode to the underside of the Platform PC board. (8). Attach the Multidisc assembly to the Platform board using small cable ties, or for a more permanent job, use several ‘blobs’ of neutral cure silicone sealant. Wedge lamp “skeleton” assembly (Fig.7) (1). Prepare the blank (non-copper) sides of two wedge PC boards so that all edges are free of burrs and the surfaces are completely smooth and clean. (2). Bond the blank sides together (copper sides facing out) using a very thin smear of cyanoacrylate-based adhesive. Pay particular attention to alignment; the boards must be exactly aligned, such that they appear to be one single unit after bonding. (3). Touch up the sides with a fine jewellers file to bring the edges into perfect alignment. Also, file the shoulders if necessary to ensure that they are horizontal and in line. (4). Trial fit the assembly to a wedge lamp socket. A small chamfer on the leading edges of the wedge assembly may make insertion easier. (5). As supplied, the Disc PC board may have a series of three holes rather than a slot in the middle. You’ll need to file a slot that is just large enough to accept the head of the wedge assembly. Make the fit as firm as possible. You may also need to cut and/or file the board outline into a circular shape, as some manufacturers will undoubtedly supply it as a square. (6). Assemble the boards, making siliconchip.com.au Bayonet Lamp Assembly Details Fig.6: follow this diagram and the step-by-step instructions in the text to make the Bayonet lamp assembly. The Multidisc assembly can be fixed in place with neutral cure silicone sealant. sure that the shoulders of the wedge assembly firmly contact the underside of the Disc board. Solder the three pads on the wedge assembly to the pads on the underside of the Disc board. Repeat for the second side. If the Disc board is double-sided (has copper on both sides), then repeat on the top side. (7). Mount all components as per the overlay diagrams in Fig.8 and the text that follows. The LED bayonet lamp is made by scrounging the base from a conventional bayonet lamp and fitting it with a Multidisc module. Note that the latter sits on top of a Platform PC board (the two are secured using silicone sealant). Wedge lamp assembly With the wedge lamp “skeleton” complete, it’s time to mount all the components. Begin with the eight 5mm LEDs on the Disc board, aligning the cathode (flat) sides towards the centre of the board. Fit the 10mm (centre) LED last. The flat (cathode) side must be aligned towards the “dot” side of the board. The “dot” side is marked with a small copper dot (pad without a hole) on the underside. Form the leads as shown in Fig.7 and push the LED down until it makes contact with the head of the Response Times: LEDs Versus Conventional Filament Lamps After upgrading the Honda’s CHMSL to LEDs, we decided to “get technical” and actually measure the difference in response between the old and the new. We made up a couple of phototransistor-based sensors and positioned one behind the CHMSL and the other behind one of the stop lights. Our Tektronix scope captured the waveforms at right when we tapped the brake pedal. As you’d expect, the blue trace represents the LED CHMSL light output whereas the yellow represents the conventional stop light. A rough estimate shows the filament lamp to be about 150ms behind the LEDs, with full brilliance at least 200ms later. The rounding on the leading edge of the LED waveform is caused by voltage drop in the wiring loom, a result of the stop lamps’ cold filament current, which momentarily exceeds about 40A. siliconchip.com.au March 2003  27 Wedge Lamp Skeleton Fig.7: here’s how to put together the Wedge lamp “skeleton”. After soldering the Wedge and Disc boards together, inspect your work for potential solder bridges between pads. This is only important on the “dot” side, as all pads on the opposite side will be connected with a wire link anyway (see Fig.8). wedge board assembly. The three resistors and 1N4004 diode can go in next (see Fig.8). Note that it is vital that these components go on the right sides of the wedge assembly. As shown in Fig.7, the resistors mount on the “dot” side and the diode on the other. Component mounting is unconventional in that the leads should not pass through both PC boards and protrude from the opposite side. The PC board holes have been deliberately offset to prevent this from happening. You’ll need to bend the leads of each component and trial fit it in place, trimming back lead lengths just enough so that they enter their respective holes before soldering in place. Finally, solder lengths of tinned copper along the tracks exactly as shown in Fig.8. The vertical lengths at the bottom take the place of the filament Fig.8: the Wedge lamp assembly details. Be sure to assemble the “skeleton” before mounting any of these components. Orientation of the Disc board can be determined by a dot on the copper side. This, strangely enough, is the “dot” side! The wedge lamp is made up using the Disc board and two identical Wedge boards. It all goes together as shown in Figs.7 & 8. 28  Silicon Chip The LED-powered wedge lamp can be used to replace a conventional filament lamp in some situations and will generate much less heat. siliconchip.com.au 31mm & 41mm Festoon Lamp Assemblies Fig.9: the circuit details for the 41mm & 31mm festoon lamps. Fig.10: the assembly details for the 31mm (left) & 41mm (right) festoon lamp modules. The end caps are soldered to the PC boards after the parts have been installed. The completed festoon lamp assemblies can be plugged straight into a conventional festoon lamp holder but must be oriented with the LEDs facing outwards. lead-outs on the base of a wedge lamp and need to be positioned so that they mate with the contacts in the wedge socket. The horizontal lengths replace the “bump” on the wedge bulb base that is captured by a spring clip in the socket in order to retain the bulb. The three current-limiting resistors are mounted vertically on the wedge assembly and can be insulated with heatshrink tubing if desired. The diode goes on the other side of the wedge assembly. The three long pads on both wedge boards are soldered to matching pads on the disc board. siliconchip.com.au Festoon lamp assembly This LED equivalent of the festoon (interior) lamp can be built in either a 31mm (2 LED) or 41mm (3 LED) version. As mentioned previously, you have the choice of using either white or blue LEDs. Referring to Fig.10, begin by installing the LEDs, aligning the flat (cathode) sides as shown. Be sure that you have the PC board oriented as shown on the overlay; the positive side must be on the left. The “+” and “-” symbols on the copper side allow you to determine correct polarity. Now flip the board over and install the resistor and diode on the copper side. Both of these components should be insulated with heatshrink tubing to prevent short circuits. However, only the leads of the resistor should be insulated (not the body), otherwise heat dissipation will be impaired. Next, solder 10mm lengths of 0.71mm tinned copper wire to each end of the board, forming axial “pigtails”. These wires will make the March 2003  29 Parts List High-Mount Stop Lamp (HMSL) Module 1 PC board, code 05103033, 11.45mm x 149.2mm 16 5mm 20,000mcd red LEDs (LEDs1-16) (Vishay TLCR5800) 2 1N4004 diodes (D1, D2) 4 150Ω 0.25W 1% resistors 200mm length of red light-duty hookup wire 150mm length of black light-duty hookup wire Multidisc Module 1 PC board, code 05103036, 26.5mm diameter 12 5mm 20,000mcd red LEDs (LED1 - LED12) (Vishay TLCR5800) 1 1N4004 diode (D1) 3 180Ω 0.25W 1% resistors 10mm length of 0.71mm tinned copper wire 20mm length of 5mm-diameter heatshrink tubing 150mm length of red light-duty hookup wire 150mm length of black light-duty hookup wire Wedge Lamp 1 PC board, code 05103031, 22mm diameter (Disc) 2 PC boards, code 05103032, 31.5mm x 16mm (Wedge) 8 5mm 20,000mcd red LEDs (LEDs1-8) (Vishay TLCR5800) 1 10mm 6,000mcd (min.) red LED (LED9) 1 1N4004 diode (D1) 1 470Ω 0.5W 1% resistor 2 180Ω 0.25W 1% resistors 60mm length of 0.71mm tinned copper wire Cyanoacrylate-based adhesive (super glue) Bayonet Lamp 1 assembled Multidisc module 1 PC board, code 05103037, 26.5mm diameter (Platform) 1 14.5mm O.D. copper water pipe joiner 1 12V 21W single filament automotive bayonet lamp 31mm Festoon Lamp 1 PC board, code 05103034, 8mm x 24mm 2 5mm 15,000mcd white LEDs (LED1, LED2) 1 1N4004 diode (D1) 1 220Ω 0.5W 1% resistor 1 31mm automotive festoon lamp 20mm length of 0.71mm tinned copper wire 35mm length of 5mm diameter heatshrink tubing 5-minute epoxy 41mm Festoon Lamp 1 PC board, code 05103035, 8mm x 33mm 3 5mm 15,000mcd white LEDs (LED1 - LED3) 1 1N4004 diode (D1) 1 82Ω 0.25W 1% resistor 1 41mm automotive festoon lamp 20mm length of 0.71mm tinned copper wire 35mm length of 5mm-diameter heatshrink tubing 5-minute epoxy 30  Silicon Chip connections to the end caps. With the board assembly complete, the next step is to fit the end caps. Begin by removing the glass cylinder and filament from a standard festoon lamp. Take care to remove all glass fragments from inside the caps. Desolder the holes in the cap peaks and then slip them over the pigtails. Push the PC board as far as it will go into each cap. The assembled size should be close to the 31mm (or 41mm) mark. Snip the wires off so that they only just protrude through the cap peaks. Now solder in place and smooth off with fine glass paper or similar. Check that your completed lamp works in-situ and, assuming all is well, fill the end caps with 5-minute epoxy to make the job permanent. Automotive lamps vs. LEDs The extremely narrow emission angle of these ultra-bright LEDs (4°) makes them well suited for use in high-mount stop lights. However, in the case of conventional tail, stop and turn indicators, there are some potential visibility issues. When viewed on-axis, a tight grouping of these LEDs certainly appears to equal (or even surpass) the intensity of a 21W filament bulb. The bulb, however, emits light over a much larger area, resulting in good visibility over more than 180°. Naturally, the reflector and diffuser in light housings is designed to take this into account, so if we were to simply switch the standard bulb for a bunch of LEDs, the resultant light pattern would be entirely different. Simply put, direct replacement of filament lamps with LED lamps in existing automotive tail, stop and turn assemblies will not always be possible. This applies particularly to “wraparound” styles, which must provide light to both the rear and side of the vehicle. This problem is easily solved by designing the assemblies Where To Get The LEDs Jaycar Electronics stock suitable 5mm red LEDs (20,000mcd), Cat. ZD-1790. Oatley Electronics have the 5mm white LEDs (15,000mcd) and a good selection of other colours as well. Our 10mm red LEDs came from Dick Smith Electronics, Cat. Z-4067. siliconchip.com.au Fig.11: here are the full-size etching patters for all the PC boards. Check your boards carefully for defects before installing any parts. specifically for LEDs, a task best left to the experts. Having said that, we believe that our modules have a multitude of highly practical uses. Here are just a few examples: Where to use LED lamps Why not add a centre-mount stop light to your trailer or van? The small size and shape of the Multidisc module will allow it to fit neatly within commonly available trailer stop light assemblies. Do you own a motorcycle? What about a truck? Install LED lamps and get noticed! A couple of these hooked up to a simple flasher circuit and mounted under the boot lid or on a moveable panel would make the ultimate emergency beacon for late-night breakdowns. They will flash for days without running your battery flat! In addition, the Multidisc module could be fitted with IR LEDs for use with CCD cameras and night viewers. The LED festoon lamps don’t put out as much light as the originals but they don’t get hot and they won’t run your battery flat in a hurry. Fit a couple under the hood, in the boot, along siliconchip.com.au Although not readily apparent from the photo, the modified high-mount stop lamp with the LEDs is brighter than the conventional lefthand & righthand stop lamps. Its response time is quite a bit shorter as well (ie, it turns on much faster when the brakes are applied). the floor line or in the door panels. For that high-tech look, try blue (or even true green) LEDs instead of white. If you don’t want to modify existing light housings, then the LED wedge or bayonet lamps are a good option. They’re plug-in replacements for two popular auto lamp styles. If your vehicle uses different lamp styles, then you may be able to modify our designs to come up with something suitable. SC Have fun! March 2003  31 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Automatic headlight switch This circuit will switch on your car’s headlights at a presettable ambient light level. It has a delayed switch-on time of about 15 seconds so that the headlights don’t switch on unne­ cessarily when driving under trees, overpasses, etc. The circuit is based on a 555 mono­ stable timer circuit which is triggered by a decrease in light level. Power is applied permanently to the circuit from the 12V battery but the circuit is disabled by the relay contacts which pull pin 2 high. When the 12V relay is energised (when the ignition is turned on), the relay contacts open and the voltage at pin 2 is now set by the voltage divider comprising the light dependent resistor (LDR1), resistor R1 and trimpot VR2. Sudden changes in this voltage are impossible due to the 470µF capacitor C1, connected across LDR1. It eliminates sen­sitivity to sudden changes in light level. However, once the light level drops, the resistance of LDR1 increases and so the voltage at pin 2 drops and triggers the timing circuit. At the same time, the base of Q1 is pulled low and this discharges the timing capacitor, C3. The pin 3 output of IC1 now goes high to turn on Q2 which drives the headlamp and parking lights relays. Q2 remains on while capacitor C3 charges towards +12V via resistor R2 and the delay trimpot VR1. VR1 sets the on-time for a period of up to two minutes. However, if the light level stays low, Q1 holds C3 in the discharged state and the lights stay on. The 2-minute delay time avoids any erratic switching of the headlights due to street lights and also allows the head­lights to stay for a short time after you turn off the engine. Rick Goodwin, Moonah, Tas. ($35) Simple universal PIC programmer This simple programmer will accept any device that’s supported by software (eg, IC-Prog 1.05 by Bonny Gijzen at www.ic-prog.com). The circuit is based in part on the ISP header described in the SILICON CHIP “PIC Testbed” project but also features an external programming voltage supply for laptops and for other situations where the voltage present on the RS232 port is insufficient. This is done using 3-terminal regulators REG1 & REG2. The PIC to be programmed can be mounted on a protoboard. This makes complex socket wiring to support multiple devices unnecessary. 16F84A, 12C­509, 16C765 and 32  Silicon Chip other devices have all been used successfully with this device. Luke Weston, Wycheproof, Vic. ($30) Note: this simple circuit will not work with older laptop computers that use low voltage (5V) RS-232 signals. www.siliconchip.com.au Bat detector picks up ultrasound It is well known that bats use ultrasound for navigation and the location of prey. Typically, bats emit rapid bursts of ultrasound in the region of 15-200kHz (ie, beyond the range of human hearing), with wide variations in frequency, depending on the species. This bat detector is a highly sensitive circuit that “hears” bats in the range of about 20-80kHz. Although this does­ n’t cover the full range of sounds that many bats emit, it is more than sufficient to detect the average bat at a range of tens of metres. In operation, the circuit uses an array of LEDs to give a visual indication of a bat’s presence, instead of reproducing the audio at a lower frequency. This has two advantages: (1) the absence of headphones en­ ables you to hear sounds that would otherwise be obscured – eg, the flutter of a bat’s wings or the lowest frequencies which a bat emits (sometimes audible as high-frequency, “scratchy” sounds); and (2) it effectively eliminates low frequency sounds (such as hands holding the detector), which can be the bane of budget bat detectors. The ultrasound is picked up with www.siliconchip.com.au a standard 40kHz ultraso­nic transducer. This transducer is effective up to about 80kHz, although its sensitivity drops off either side of 40kHz. A quali­ty piezo transducer could also be used here but note that this will only be effective up to about 50kHz (if that). Op amps IC1b-IC1d are wired as a very high gain preamplifi­er, amplifying the signal millions of times. This produces suffi­ cient signal amplitude at pin 14 of IC1d to directly clock decade counter IC2 (4017). IC2 is reset at regular intervals by op amp IC1a which is wired as an oscillator. This resets IC2 at about one tenth the rate of the highest detected frequency. Therefore if, for an example, a 30kHz signal is received, IC2 might only sequence two or three LEDs before being reset. By contrast, if an 80kHz signal is received, IC2 will sequence all the LEDs. This technique thus provides a visual indication of the re­ceived frequency. Note that ultrabright LEDs are recommended for LEDs 1-6, since the LEDs have only a 10% duty cycle. In use, trimpots VR1 (frequency adjust) and VR2 (gain) are initially both set to mid-position. These may then be further adjusted later on, as required. Once the circuit has been built, switch on and rub your hands together near the ulThomas Scarbo rtrasonic transducer. ough is th is m onth’s winThis should light at ner of the Wav etek least one (and perMeterman 85XT haps all) of the LEDs. true RMS digita l If the circuit is funcmultimeter. tioning correct­ ly, it should respond to your hands being rubbed together at a 1-metre distance. If VR1 is set so that IC1a operates at 10kHz, LEDs 1-6 will represent 20-80kHz in 10kHz increments. At least, that’s the theory – in practice, IC1a is adjusted using VR1 so that the LEDs match the range of the transducer that’s been used. Besides being used as a Bat Detector, the circuit could also be used as a simple tool to indicate frequency, to find tyre punctures (which emit ultrasound), and to detect other creatures which emit ultrasound (such as certain insects). And at its lowest frequency setting, it could even be used as a simple frequency-to-light convertor, with the LEDs dancing to nearby music. Thomas Scarborough, Cape Town, South Africa. March 2003  33 Circuit Notebook – continued 34  Silicon Chip www.siliconchip.com.au Junkbox-parts oven timer The motivation for this project came when the timer on our oven failed for the second time. It uses parts that were mostly scrounged from my junkbox. The resulting timer is very user friendly. You simply dial in the required timing interval in minutes using rotary switches S2 (units) and S3 (tens) and then hit the start switch (S1). Any time up to 99 minutes can be selected. When S1 is turned on, the display LEDs light, initially indicating “00” and then advancing “01”, “02”, . . . , “09”, “10”, “11”, etc until the selected timing interval has been reach­ed. The timer then stops counting and sounds a buzzer until the start switch is turned off. The indicator LEDs can be arranged in semicircular fashion around the switches (ie, one LED at each switch position), thus giving a very effective display. This was much simpler than using a digital readout. The circuit itself is based on four low-cost CMOS ICs. IC1, is a 4060 14-stage binary counter/divider/ oscillator. It’s set up to produce a positive-going pulse at its pin 3 output (O13) every minute, as set by the timing components on pins 9, 10 & 11. This means that O13 must have a period of two minutes – ie, it will be low for the first minute and then go high for the next minute. This high-going pulse is then applied back to IC1’s reset pin (pin 12) via AND gate IC4b and diode D3. The counter thus restarts and begins counting the next minute interval and so on. The period of oscillation is approximately 2.2RC where R is the resistance connected to pin 10 of IC1 (27kΩ, VR1 & VR2) and C is the capacitance on pin 9. VR1 and VR2 provide coarse and fine adjustment of the oscillator frequency, respectively. IC2 & IC3 are two 4017 decade counters, each having 10 out­puts (O0, O1, O2 and so on up to O9). Only one output of each counter will be high at any one time. The counters are reset by taking their pin 15 (MR) inputs momentarily high and this takes the O0 outputs of each counter high. These outputs in turn drive www.siliconchip.com.au LEDs 1 & 11 and this indicates zero or “00” (the initial state of the counting process). Each positive-going pulse on pin 14 (CP0) of IC1 advances the count by one, with LEDs 2-10 turning on in sequence to in­dicate the number of elapsed minutes. When nine pulses have been counted, LED10 will be on. The tenth pulse then resets IC2 (ie O0 goes high and turns on LED1). In addition, IC1’s carry out pin (pin 12) goes from low to high and this clocks IC3. As a result, IC3 counts in tens on minutes while IC2 counts the units. By using the 1-minute pulses from IC1 to clock IC2, the two counters are capable of recording the elapsed time up to 99 minutes, after which both counters are reset to zero and the count restarted. Both counters can be halted at any time by taking their enable pins (pin 13) high. If this is done, the counter outputs will remain locked at the prevailing count at the time of receiv­ing the disable signal. As well as driving LEDs 1-9, IC2’s outputs are also con­nected to S2, a single-pole 10-position rotary switch. Similarly, IC3’s outputs are connected to rotary switch S3. The wipers of S2 and S3 connect to AND gate IC4a and when both inputs to this gate are high, its pin 3 output goes high and disables the counters. At the same time, the output of IC4d (pin 11) goes high and turns on transistor Q1 to sound the buzzer. The counters then remain locked in this count position and the alarm continues to sound until the start switch, S1, is turned off. Because the 4017 ICs can only source a small amount of current, special low-current LEDs must be used. The types used in the prototype were from RS Components, stock number 590-547. These operate with just 2mA of current, with a maximum forward current of 7mA. Power for the circuit comes from a 9V DC plugpack. Note that the start switch is placed after the 1000mF reservoir ca­pacitor. This prevents the buzzer from making an awful “dying noise” as the capacitor discharges when the timer is switched off. Jack Holliday, Nathan, Qld. ($50) Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. VGS2 Graphics Splitter NEW! HC-5 hi-res Vid eo Distribution Amplifier DVS5 Video & Audio Distribution Amplifier For broadcast, audiovisual and film industries. Wide bandwidth, high output and unconditional stability with hum-cancelling circuitry, front-panel video gain and cable eq adjustments. 240V AC, 120V AC or 24V DC. High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email: questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC’s, Converters, etc. QUESTRONIX All mail: PO Box 348, Woy Woy NSW 2256 Ph (02) 4343 1970 Fax (02) 4341 2795 Visitors by appointment only March 2003  35 Last century, we described a Peltier-powered tinnie cooler which could be built into a reasonably large Esky and so keep your food and drinks cool. Here’s another one – quite a bit smaller and just right to build into a 6-pack Esky to really cool down the tinnies. As a bonus, it will also keep food warm! By Ross Tester E very true-blue Aussie knows there is nothing worse than a warm beer (or soft drink, for that matter). But how do you get your drinks cold – and keep them cold? There’s the old ice-in-the-Esky routine. But ice melts – especially if you keep putting warm cans in. Wouldn’t it be nice to have the cooler itself cool your cans? This one does! Just plug it into your car cigarette lighter (or any other 12V DC supply) and it will silently cool cans down to the “aaaaaaahhhhhh” level. Like the cooler we presented back in September 1999 (see, it was last century!) this one is based on a Peltier Effect device. We explained this semiconductor device and its operation in some detail in that issue (and in the August 1999 issue) so we won’t go into too much detail again. Suffice to say that it consists of a number of P-N junctions sandwiched between two metal plates. Pass current through the junctions one way and they absorb heat – one of the plates gets very much colder than the other. Pass current through the other way and the reverse happens, the plate which was cold heats up. If you thermally bond the Peltier (that’s shorthand for Peltier Effect device!) to another object, that object will either cool down or heat up, depending on the polarity of supply to the Peltier. That’s why a Peltier can be used for both cooling and heating. If you’d like more info on the op- eration of Peltier Effect devices, we suggest you refer to the issues mentioned above. Peltier “module” There are two major differences between this project and the earlier one. First, it’s much smaller – this one is designed to fit into a 6-pack cooler (the earlier one fitted a larger cooler). It really is intended as a drink cooler, not a mobile fridge! Second, and most importantly, this Just in case you haven’t seen one before, this is what the Peltier device looks like. This is a lower rated device than the one in this module. 36  Silicon Chip www.siliconchip.com.au in mind the comments above before switching over! Thermal bonding (Above): the Peltier module attached to the top of the cooler lid while below is the view from inside the cooler. The reason we placed the module in the lid of the cooler was that it was convenient to do so. It’s also true that cold air falls, so theoretically the air inside the cooler would eventually cool down via convection currents. However, as every good cook will tell you, the secret in heating or cooling food or drinks is the thermal bond between the cold/heat source and the item being cooled/heated. Now we have to say that the thermal bond between the aluminium plate and the cans in the cooler is not that great. The reason for this is that air is not particularly efficient at transferring cold/heat. It’s a bit like trying to boil a kettle by holding it above a hotplate rather project is based on an almost-complete Peltier module. The earlier project required you to source the bits individually; this one has a pre-assembled Peltier module which includes a fan, heatsink, thermal switch, aluminium block and gasket. All you have to supply is an aluminium plate (size to suit your cooler) and a small piece of, say, 15mm-wide polystyrene foam (such as used for packaging). The aluminium sheet needs to be as large as possible to ensure good heat transfer. We used a sheet 3mm thick because it was available – even thicker would be better still. Incidentally, the module comes from Oatley Electronics and costs the princely sum of just $33.00 (plus p&p). Not real shabby, that: we’ve seen similarly rated Peltier Effect devices alone advertised for the best part of $150.00 Oh, nearly forgot: you also have to supply the cooler! Thermal shock Before we go too much further, a warning: one thing you cannot do with a Peltier is switch it between heating and cooling (or vice versa) without waiting for it to cool (or heat) back to room temperature. This would place enormous stresses on the device and would quite likely damage or even destroy it. We have shown a “reversing” switch in our circuit of the device but bear www.siliconchip.com.au March 2003  37 than placing it on it. Sure, the kettle will eventually get hot – but nowhere near as fast or efficiently as it would placed directly on the hotplate. Similarly, it would be much better if the cans could be placed in intimate contact with the aluminium plate attached to the Peltier. One way to achieve this would be to place the Peltier module not on the lid but on the side of the cooler, with an “L” shaped aluminium plate running down the side of the cooler and across the bottom, so that the cans actually sat on the cooling plate. Even better would be to sit the cans in a small amount of water because this would achieve a much better thermal bond with the cans than the air in the cooler. Indeed, using a cooler is not the only possibility. We’ve had thoughts about using a small length of suitably-sized aluminium tube, maybe a yacht mast extrusion, which often has a flat on one side suitable for mounting the block (or maybe even the Peltier This very simple circuit could be made even simpler if you don’t want the “heat” option: leave out the switch and thermal switch. direct). We haven’t tried this yet – but will do so when we find a suitable extrusion. We’ll leave you with those thoughts in case you want to experiment. Placing the module in the lid of a cooler, as we have done, is certainly not the only possible approach. Assembly Because the Peltier module is pre-assembled, building this project is pretty simple: you cut an appropriate hole in the cooler (slightly larger than the aluminium block), pass the cooler module through it, fit the styrene foam seal and screw on your aluminium plate. Connect power and it’s done. The power lead would ideally be a suitable length (but shorter rather than longer) of polarised (red/black?) 10A figure-8 cable, fitted with a car Here's how the whole thing fits together. As mentioned in the text, the majority of this project is pre-assembled as a single module – everything between the finger guard and the aluminium block, in fact. All you have to do is fit it to the cooler and attach the aluminium heat transfer plate. 38  Silicon Chip www.siliconchip.com.au cigar lighter plug at one end. Note that there are some “cheap” cigar lighter plugs around that are real junk – their springs aren’t and deform badly after a few uses. It’s better to pay a little bit more and get a good’n. For safety’s sake we have incorporated a 10A fuse in the + line between the changeover switch and the cigar lighter plug. 10A is more than is needed by the Peltier and fan but should protect in case of catastrophic short circuit. Speaking of catastrophic, we have shown an “exploded” drawing of the assembly but that’s just in case you need to know how it all goes together. However, you should not need to disassemble the Peltier module. One thing you will note on the drawing is the use of heatsink compound, especially between the aluminium block and the aluminium plate. This will ensure maximum heat transfer. The thickness of the styrene block depends on the thickness of the lid (or wall) of your cooler. The idea is that it compresses slightly when the aluminium plate is screwed to the block, making a nice airtight seal against the cooler lid/wall but still allowing the block to make intimate contact with the aluminium plate. The high density foam gasket (supplied with the module) forms the airtight seal on the outside of the cooler. The two seals probably won’t be watertight but with a bit of work with silicone sealant could possibly be made so. Just make sure you don’t get any sealant between the heatsink and Peltier, the Peltier and block or the block and plate – it is a good way to stop heat transfer! The thermal switch The project has a 65° thermal switch mounted on the side of the aluminium block. This only comes into play when used as a heating device and is designed to prevent the thing getting so hot it starts melting (or at least Upside-down view of the module as supplied by Oatley. Note the liberal use of heatsink compound on the aluminium block – you cannot see it in this photo but there is also a good dollop of the stuff on both sides of the Peltier device. deforming) the plastic lid or body of the cooler. If you are not intending to use the device as a food heater, it (and of course the reversing switch) can be left out. Power supply The 50W Peltier device draws around 3.5A at 12V (DC). Therefore it is going to place a fairly significant load on your car battery if the engine is not running – certainly enough to prevent you starting the car after a day out. Still, if you are caught out in the sticks with a battery that’s too flat to start your car, your drinks will be beautifully cold. . . Of course, you could also run it from a suitable 12V (or 13.8V) DC power supply – a typical “CB” power supply is rated at about 4-5A so would be perfect. Parts List – Tinnie Cooler 1 Peltier Effect module (Oatley Electronics) 1 6-pack plastic cooler 1 3mm thick aluminium plate, size to suit cooler Suitable fig-8 connecting cable with car cigar lighter plug In-line fuseholder and 10A fuse (can be integrated with cigar lighter plug) Heatsink compound 1 DPDT switch, 5A DC contacts (optional, see text) www.siliconchip.com.au Where from, how much? The Peltier Device Module, complete with heatsink, fan, aluminium block, thermal switch and gasket, is available from Oatley Electronics for $33.00. The various components may be purchased separately elsewhere but be prepared to pay at least $100! You need to supply the cooler (and the drinks to go in it!), aluminium plate, polystyrene foam, power lead, inline fuseholder and fuse, cigar lighter plug, heatsink compound and (if required) the DPDT changeover switch. As a special bonus, Oatley Electronics will also include a quality car cigar lighter plug, with integral fuseholder already connected to a 1.8m length of heavy duty figure-8 cable, if you tell them you are building the SILICON CHIP Cooler project. Contact Oatley Electronics via phone (02) 9584 3563; fax (02) 9584 3561; email – sales<at> oatleyelectronics.com or via www.oatleyelectronics.com March 2003  39 SERVICEMAN'S LOG Bring your hammer-drill & muscles A serviceman does not just fix faults, advise customers on new equipment, or fit a new antenna. Many new, large sets often require a lot of muscle and constructional skills outside electronics. And I had another job this month which should have been avoided. I can’t help myself. Yes, I did it again; lumbered myself with a repair that I should have stayed well clear of. But I did have some mitigating circumstances. It’s my wheels. Because I’m so badly paid, I have to use secondhand vehicles and my old Ford Laser was just about to dump its gearbox. Ouch! Anyway, I was sulking over this latest problem one morning when in 40  Silicon Chip waltzes an old colleague. And in the ensuing conversa­ tion, he mentions that he is trying to fix a Philips FL1.1 with an east-west pincushion fault. I told him to wash his mouth out for mentioning such words in my presence. But grateful that it was someone else who was suffering from such misfortune, I of­ fered as much free advice as I could – as long as he was doing the work. That is, until it turned out that his client was a Ford transmission expert and repairs them all day long. Suddenly I realised that a dangerous contra deal was in the air but I quick­ly lost all sense of reasoning. I mean, how bad can a TV fault be? And after all, I could end up saving many hundreds of dol­lars. In due course, my car went east and his TV set came west; straight into my workshop. And being a 33-inch (80cm) set, I almost had to rebuild the workshop around it to get it to fit. The set turned out to be a model 33FL1880/75R, the same as one I wrote about in last month’s issue. This set had the same problems as the one in that article and my friend patiently worked through it until, finally, he too discovered that capaci­tor C2523 (8.2nF, 2kV) capacitor was the cause. He then replaced all the blown up bits and that fixed everything except the east/west fault which had him stumped. I had hoped for a minute that it was just transistor Q7610 (2SA1359) that was faulty, as in the earlier set, but he had already changed that. Anyway, I own two working FL1 TV sets and another which also has an east-west pincushion fault, though none of them are 33-inch models. I checked all my friend’s work first and apart from replacing the horizontal output transistor ON4673 with a BU508A (a BU508AF is an even better choice), nothing apart from a few faulty joints was obvious. However, the voltage on the emitter of Q7610 was only 1.8V instead of 14V and neither the width adjustment (VR-3601) nor the pincushion control (VR3602) had any effect. I had heard that shorted turns in coil L5526 could cause this fault, so I swapped this coil with the one in the good set. Unfortunately, it made no difference to either model and both coils had an inductance of 11mH. I then decided to try similarly swapwww.siliconchip.com.au ping transformers 5521. This turned out to be a monstrous mistake, as it instantly took out both horizontal output transistors. After replacing these, I still couldn’t get the set to start and there was no 141V rail. Eventually, after a lot of messing about, I discovered that Q7610 was short circuit but the set was still dead when this was re­placed. Next, I unsoldered pin 8 (141V input) to the horizontal output transformer and horizontal output stages and fitted a 100W globe across the rail instead. This time when I switched it on, there was an enormous bang, like a shotgun going off. Believe me, it was loud enough to have awoken the New Zealanders. Well, at least I had produced a measurable reaction – a small earthquake! The only trouble was I didn’t have a Richter meter to measure it! In fact, it was C2512 in the horizontal centring circuit which had exploded. It took quite a while to realise that Q7512, Q7513, R3514, R3537, R3515 and D6515 had also been destroyed. When I finally put it all back to where I started, I made an emphatic mental note: not all FL1.1S chassis are the same and not everything is interchangeable. However, the east-west circuits are similar and therefore the voltages and waveforms between the sets should also be simi­lar. As a result, I spent an hour or so measuring the good 29inch set’s east-west correction circuit voltages and drawing the oscillograms. As I have mentioned on previous occasions, access to this chassis is rather difficult. The so-called service position is with the main chassis (small and large signal panel) pulled right back and up. You then have to balance it on its edge, taking care not to short out the CRT socket with the heatsinks. The control panel and mains filter panel remain behind. The chassis is bulky and heavy, with modules and heatsinks everywhere – mostly soldered in. The voltages in some parts are very high, with sensitive surface mounted components nearby. Replacing a part requires access to both sides of the board, which means moving them up and down. Finally, just to make life interesting, the 315V main HT line remains charged even after the set is switched off – not to mention the 200V rail for the RGB output amplifiers. And www.siliconchip.com.au because the whole chassis is precariously balanced in the “service” position, it’s impossible to safely attach a probe onto a submin­iature component and take a reading. It’s also impossible to make any service adjustments while in this service position, as the controls are all on the inacces­ sible side of the board. In fact, even in the so-called “accessi­ble” position, they aren’t easy to get at! For example, to meas­ ure and adjust the 141V rail, it’s necessary to attach the probe onto test point TP57 (cathodes of D6237 and D6238). What they don’t tell you is that these sit right between a heatsink and the SOPS module and there is very little clearance between these two parts. In practice, it is necessary to go to standby, connect an insulated crocodile clip onto the diode, then switch on using the remote control and adjust R3371. And you really have to watch yourself: one third of the large signal panel is at full mains potential and the other two thirds is at chassis – and the divid­ing line is not easy to see. No wonder noone likes fixing these beasts. Basically, the east-west circuitry converts vertical pulses derived from the vertical deflection output into upside-down parabolas. These are then fed to the east-west output transistors which in turn drive one end of the deflection yoke via a variety of tuning components. The other end of Items Covered This Month • Philips Matchline • • • • 33FL1880/75R TV set. Panasonic “Progressive Wide Plasma Displays” (Model TH42PWS) – installation. Akai TX-140 stereo unit. JVC AV-21 TEAU TV set (MZ2 chassis). Faulty remote controls the deflection yoke is fed with 1000V horizontal pulses. EHT information is also applied to prevent picture blooming on bright screens. The preamplifier stages consist of four surface-mounted transistors which are controlled by the width and pin controls. Unfortunately, the circuit diagram is full of errors, with few voltages and waveforms. I replaced all the surface-mount transistors and all the electrolytics but the fault persisted. Despite that, the two sets compared quite well, although factors such as the control posi­tions, the size of the sets and the beam current due to picture content made it difficult to work out what was important and what wasn’t. The main factor was the voltage on the emitter of the east-­ west output transistor (Q7610) which was constantly far too low. The breakthrough came when I noticed that one of the March 2003  41 Serviceman’s Log – continued east-west modulator diodes, D6526 across the horizontal output transistor, went to C2504 and not to the emitter. I also noticed a thick black jumper lead across the two emitters of Q7504 and Q7506. However, this lead was unnecessary because they already had a link on the other side. Granted, it’s not uncommon in TV sets to have what may be considered redundant links. Sometimes it’s because there is high current and sometimes it is to limit inductance. However, the link was not fitted in the 29-inch model, so what was it’s purpose? There seemed to be no reason – unless the link was in the wrong place. Could it be that, in the course of changing the horizontal output transistors, my friend removed the link and put it back in the wrong position? Well, of course, it was in the wrong position. Both C2504 and D6526 weren’t connected properly into the circuit – and rerouting this link quickly fixed that. But I wasn’t quite 42  Silicon Chip out of the woods yet. The east-west controls now had an effect but not enough. The voltage on the emitter of transistor Q7610, which was previously too low, was now too high – at times nearly 60V! More careful examination revealed that R3611 (2.7kΩ) and R3614 (1.5kΩ) were both high. Replacing them brought both con­trols within a tolerable range. Finally, I replaced the back and left the set on soak test. I hope that its owner has done as good a job on my trans­mission! Plasma sets My next story is not, strictly speaking, about a conven­tional service job; rather, it was an installation job. More exactly it involved installing two Panasonic “Progressive Wide Plasma Displays” (Model TH-42PWS). These are very large units, measuring 1020 x 610 x 89mm (plus the speakers), and are designed for wall mounting using special brackets. It needs at least two people to safely manhandle these mon­sters, since the total weight (display and speakers) is 32.7kg. The special wall-hanging brackets (TY-WK42PV1) that are used to support the display are made of heavy-gauge steel and weigh a further 6kg each! Panasonic recommends that the brackets be mounted using at least six bolts but I fitted 12 just to make sure. After all, plasma displays don’t take too kindly to a fall, this being the most common reason for failures. The first thing to do was work out the optimum height for the display (in most cases, eye height) and then drill one hole at top centre to hang the bracket. The bracket is then initially attached using a single M6 bolt, then adjusted with the aid of a spirit level and used as a template to drill the holes for the remaining bolts. It was also necessary to mark a cable access hole on the bottom lefthand side. This hole (30 x 100mm) needs to be drilled right through to the brick cavi- ty in order to accommodate the cables. Another hole then has to be drilled where the cables are to emerge and connect to the associated AV equipment – VCR, DVD player, digital set-to box, amplifier, etc. I was annoyed that most of the accessories were not immediately avail­able from Panasonic and I hope they will fix this soon. For example, I wasn’t able to get the TV-PT600E (and TY42TM5H, TY-SCP15C03, TY-42TM5T) tuner/receiver. Instead, I had to use an existing NV-FJ630A hifi VCR as the main tuner. One of the display units had to be fitted across a corner, which I thought was a waste. However, that’s what the customer wanted and he was paying. To do this, we made up a solid metal panel which was bent over at 45° at each end and mounted vertically in the corner. We used 2mm-thick aluminium for this and I was initially worried about its rigidity but when the set was mounted, it was very solid. I also fitted brackets to hold and conceal the VCR, which I modified so that the infrared remote control receiver was exter­nal and just peeping over the top of the display. Interestingly, I found it to be more sensitive facing the wall than looking back out towards the viewer. When it was all finally connected, the digital reception was exceptionally good. Overall, the effect was fantastic. I just wish I could afford one! Akai TX-140 stereo unit A young woman brought in her Akai TX-140 stereo unit with the complaint that it wouldn’t play CDs. As sometimes happens with these types of systems, I was expecting that either the laser and/or the disc motor had failed. In the former case, the disc starts to spin and the laser comes on and tries to focus. If it fails to read, the CD stops. I removed the top cover to watch what happened and found that the three CDs on the carousel would not stop rotating around the platter. What’s more, they would not line up with the CD reader. I prised off the platter and saw how the deck worked. Each disc had a series of plastic tongues on the underside of the platter, one for disc one, two for disc two, etc. These gave a digital pulse as they passed between www.siliconchip.com.au an optocoupler. What was fairly obvious was that the optocoupler wasn’t working. The optocoupler is mounted on a small board with a 5-strand flexi-lead between it and the platter motor. The flexi-cable seemed to be the obvious culprit and I checked the continu­ity with an ohmmeter. As I suspected, two of the conductors were open circuit. I tried repairing it by running a parallel wire with flexi-cable but it wasn’t possible to solder it on, so I ordered a longer generic flexi-cable. When this arrived, I cut it to size and stripped back the insulation about 2mm to solder onto the sub-board. Because of its size and the heat of the iron, it was quite difficult not to make a complete mess of it but with a bit of perseverance, I finally managed to solder it on. The reassembly was a breeze and the job was done. JVC TV set When a rather ordinary-looking 51cm JVC AV-21 TEAU (MZ2 chassis) was brought in, I wasn’t really expecting anything other than a mundane repair. The set was dead and it didn’t take a mental giant to figure out that the horizontal output transistor (Q522, 2SD1878-YD) was short circuit. The only replacement I had was a 2SD1878, which wasn’t fully isolated like the original but this was easily fixed with a mica washer. However, when I switched the set on there was a split second during which the normal static field around the picture tube was very much higher than normal. As I say, it was only very brief, then it was back to square one. But while it lasted, the effect was so great that I re­ceived a shock and there was also a flash-over inside the picture tube. Initially, this made me think that perhaps the picture tube was down to air. It took another transistor failure to prove it wasn’t the tube, as I had totally disconnected it by then. The most common problems that can cause horizontal output transistors to cark it are: (1) a faulty horizontal output trans­former; (2) a faulty deflection yoke; (3) excessive HT; and (4) crook tuning capacitors – although not necessarily in that order. I unsoldered and measured tuning capacitor C524 as well as C525, but both were spot on. I then removed the deflection yoke and examined it www.siliconchip.com.au carefully but it too appeared to be OK. I also reworked the solder on the motherboard but no joy. Unfortunately, my copy of the service manual didn’t have the circuit diagram or service adjustments for this set, which was extremely frustrating. I did have the circuits for an AV-G21AU, which is a CA2, and an AV-G25AU, which also uses an MZ2 chassis, but neither was quite close enough. I assumed that the HT (B1) rail, at test point TP-91, should be at 114V. To confirm this, I had to replace the horizon­ tal output transistor, short out its base and emitter and connect a 100W globe. It was spot on at 114V. So all that seemed to be left was the horizontal output transformer. My shorted turns tester could not detect any shorts across pins 9 and 10 but that doesn’t mean very much; high vol­tage failure in the secondary can’t be detected at low voltage. Finally, I ordered a new horizontal output transformer, confident that that was it. However, after fitting it, the set behaved exactly as before and then died. I can’t lie that I was the great brain that discovered the cause of this one – instead, it was Technical Support at Hagemey­er. Though I thought I had been completely thorough in resol­ dering everything on the motherboard, I had in fact neglected to check and resolder the connection to the horizontal oscillator ceramic resonator/crystal (CF-561) on pins 14 and 17 of the jungle IC (IC201). And that was what wrong with the set in the first place, causing it go wildly off frequency and the EHT to rise spectacularly. After realigning the yoke and CRT p/c magnetic rings, everything was fine except for one slightly bizarre problem. I didn’t have the remote control but I noticed that by pushing the channel (CH) up and down buttons on the set itself, I could select “AV” input. The problem was that the video from March 2003  43 Serviceman’s Log – continued my signal generator wasn’t going in via the AV sockets at the rear. Conversely, I could tune it in when I plugged the generator into the antenna socket while still in the AV mode. Initially, I thought that the AV switching ICs had failed, along with a transistor controlled by the microprocessor. Later, when I read the instruction book on this model, I learnt that it is necessary to select either “TV” or “Video” with the remote control to change the source. The “AV” mode in this set really just denotes the change in sync time constant that is required to prevent “flag waving”. Now, on a lighter note, here is a contribution from K. A. of Kingston, Tasmania. This is how he tells it. Unreliable remotes? A friend had been grizzling on and off over several months that all 44  Silicon Chip the remote controls for her new and expensive TV, DVD, and VCR were unreliable. The problem wasn’t so much presented as “It’s busted, will you fix it?” but during dinners as part of idle chit-chat about growing old and coping increasingly less well with new fangled gadgets. It took ages for the various bits of information to com­pletely emerge. Apparently, the batteries in the remotes had been replaced umpteen times, the gadgets had been taken back to the shop umpteen times (they were still under warranty) and experts had visited umpteen times. Furthermore, red herrings like too much sunlight, too much light in general, interference from modern high efficiency lights, etc had all been eliminated. There was some hazy information that the various remotes weren’t all equally unreliable. However, the details were con­fused and this infor- mation was no help at all. One day, a really weird piece of information emerged; the remotes all worked well for my friend but not for her teenage son. Now if this had been the other way round, it wouldn’t have been significant; teenagers often successfully use gadgets that have adults baffled. Lacking any solid clues, I continued to offer sympathy rather than useful advice and left the problem as one of life’s little puzzles. And then one day, I was visiting their home while the teenage son was watching TV and wrestling with one of those (expletive deleted) remote controls. Aha! Problem solved! Have you seen the way teenagers sit in chairs to watch TV? His feet were on a footstool, his backside was dangling over the edge of the cushion, his back was where his backside should have been and his head was propped up against the back rest. Bone surgeons will make a fortune 30 years from now recon­ structing his neck! But that’s not all. The remote control was on his tummy and his great big size-15 feet were between it and the IR sensors on the TV, VCR and DVD! IR light doesn’t shine through feet! – no wonder it wouldn’t work. The equipment itself was installed in a typical cabinet with the VCR on the bottom, then the DVD and the TV on top. The TV could occasionally get a glimpse of the remote control over the teenage son’s toes and so it worked sometimes. By contrast, the VCR was in a deep, dark, gloomy shadow and SC almost never worked! www.siliconchip.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au PRODUCT SHOWCASE The ultimate hard disk music storage system? Looking for somewhere to store (and retrieve) all your music? Linn Products have a solution – if you’re prepared to pay for it! The Kivor Index music library is a storage/retrieval and playback harddisk-based system that can be used as a stand-alone unit or together with other Knekt Kivor products. It provides up to 500 hours of full bandwidth, pitch accurate hard disk music storage and allows up to eight users to have concurrent access to high quality, full bandwidth music in a multi-room system or a hard disk component source in any audio system. Whether you have a huge library of LPs or CD discs, or like to download MP3 music, the Kivor Index hard disk records and creates playlists of your favourite tracks by genre, artist, mood or date. Available in two configurations, the Kivor Index provides either 250 or 500 hours of storage that can be increased up to tenfold when using compressed audio. Music is simply loaded into the Kivor Index via its integrated CDROM and a built-in modem downloads Internet material for ‘manipulation’ on Linntek, Linn’s PC set up and control utility software. Available in either black or silver, the Linn Kivor Index music library is rack mountable for installation with any multi-room amplification system. Covered by a two-year parts and labour warranty, the Kivor Index (250 hours storage) has an RRP of $14,999 and the Kivor Index (500 hours storage) has an RRP of $19,999. Contact: Linn Products Ph: 1800 642 922 email: info<at>audioproducts.com.au 330-1500µF, ultra-low ESR tantalums A new series of solid tantalum chip capacitors from Vishay Intertech-nology, Inc. features ultra-low equivalent series resistance (ESR) and high capacitance values in new “E” and “R” case sizes. The Vishay Sprague conformal-coated 597D multi-anode capacitors provide increased reliability and improved reception in DC-DC conversion, line cards, mother boards and power supply applications in end products including test equipment, PCs and base stations. The devices’ ultra-low maximum ESR values range from 13mΩ to 35mΩ at +25°C and 100kHz. Capacitance values range from 330µF to 1500µF with standard tolerances of ±10% and ±20%, and working voltage ranges from 4-10VDC. Maximum current leakage ranges from 27µA to 68µA, and the maximum dissipation factor is 6% at +25°C and 120Hz. www.siliconchip.com.au Foxie lowpower SBC The LP3500 Fox low-power single-board computer is intended for applications where power is limited, such as in portable, hand-held, battery-powered, and remote monitoring systems. It features built-in analog and digital I/O and consumes less than 20mA when fully operational and less than 100µA in power-save mode It has 25 industrialised I/Os plus a relay and has eight analog/digital converter inputs with programmable gain. Six serial ports are provided (1x RS-485, 3x RS-232 and 2x TTL) and there are optional peripherals including keypad/display, serial flash, etc. Contact: Dominion Electronics Ph: (02) 9906 6988 Website: dominion.net.au TOROIDAL POWER TRANSFORMERS Manufactured in Australia Comprehensive data available Contact: Vishay Intertechnology Inc PO Box 231, Sanford, ME 04073 USA Seaford Vic 3198 Ph: (0011 1) 207 490 7240 Website: vishay.com Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 March 2003  53 Cellular call diverter: 50-80% telephone bill savings claim A Gold Coast-based telecommunications company, Powertec, has announced the development of a new Cellular Diverter that they claim will save users between 50% and 80% off their regular landline and mobile telephone accounts. The Managing Director of Powertec, Mr Ray Smith, says the new diverter revolutionises the manner in which small and/or home business operators are charged for landline calls diverted to mobiles. “At present whenever a home or office telephone call is diverted to a mobile phone the owner pays charges for the diversion, in conjunction with the caller paying costs as well,” said Mr Smith. “The new Powertec CellularDiverter turns that landline component into a mobile call, so users can then benefit from special mobile-to-mobile rates,” he said. “This means that a 10 minute diverted call which would normally cost up to $2.50 will now only cost 20 cents,” he added. “Any business making calls to mobiles or receiving calls from their own mobiles can take advantage of the new cost saving system even when they do not use the diverter,” he said. Mr Smith says the new Powertec Cellular Diverter is the result of more than two years of research and development, at a cost of thousands of dollars. He says the device is Australian compliant and has patents pending. They are used in conjunction with the Ericsson Fixed Cellular Terminal which was released on the Australian market, late last year. Powertec is offering to loan the system to approved customers at no cost to prove that the technology is beneficial in saving on phone bills for small business and home users. Contact: Powertec Telecommunications 19 Short St, Southport Qld 4215 Ph: 1800 MOBILE Website: powertec.com.au 54  Silicon Chip Increased airflow inside racks and enclosures American Power Conversion (APC) has available a new compact air distribution unit that increases airflow inside racks and enclosures. APC’s NetworkAIR Rack Mounted (RM) Air Distribution unit works in tandem with an existing precision air conditioning system in enclosed environments to pull air from beneath the raised floor directly into the rack enclosure, before it can mix with room air. It eliminates dangerous hot spots in data centres by boosting the conditioned air volume within the rack itself and improving air delivery in poor static pressure areas. In environments without raised floors, the NetworkAIR RM Air Distribution unit uses air from under and around the bottom of the rack or enclosure where the air is coldest. This boosts the amount of air supplied to ensure the necessary amounts of airflow to equipment. Contact: American Power Conversion (APC) Ph: 9955 9366 Website: apcc.com Need more “oomph” from your wireless LAN? When your wireless LAN needs more output, these cards will do the job. They represent the next generation of wireless equipment offering both robust construction and a choice of a both high power (200mW) and standard (100mW) models. They are ideal for wireless ISPs. The detachable external antenna further enhances their overall perfor- mance. If you use them with a high gain antenna, make sure you don’t exceed the 4W EIRP legal limit. They support both peer-to-peer and infrastructure communications and are usable with WiFi (WECA) certified products. Operating systems supported include Win 95, 98, 2000, NT, ME and XP. Memory size is 128K x 16 SRAM and 128K x 8 flash ROM. Contact: Microgram Computers Unit 1/14 Bon Mace Cl, Berkeley Vale NSW 2261 Ph: (02) 4389 8444 Fax: (02)4389 8388 Website: microgram.com.au TDK’s one-chip smart card terminal controller TDK Semiconductor Corp. now offers the 73S1121F smart card terminal controller – said to be the first true system on a chip for smart card terminals. The new low-cost device integrates all the functionality for implementing a complete range of smart card terminals for network access security, e-purse terminals, payphones, vending machines and inexpensive POS terminal applications. It includes an 8052 processor, a USB interface, two built-in smartcard interfaces with a dedicated hardware ISO7816 UART, multiple card terminals. development software layers, extensive I/Os, 64KB of Flash, 4KB of user-RAM and a PIN pad interface all on a single chip. This solution will significantly reduce cost and component count for implementing smart Contact: Adilam Electronics Pty Ltd Ph: (03) 9737 4900 Fax: (03) 9737 4999 Website: adilam.com.au www.siliconchip.com.au SILICON CHIP WebLINK How many times have you wanted to access a company’s website but cannot remember their site name? Here's an exciting new concept from SILICON CHIP: you can access any of these organisations instantly by going to the SILICON CHIP website (www.siliconchip.com.au), clicking on WebLINK and then on the website graphic of the company you’re looking for. It’s that simple. No longer do you have to wade through search engines or look through pages of indexes – just point’n’click and the site you want will open! Your company or business can be a part of SILICON CHIP’s WebLINK . For one low rate you receive a printed entry each month on the SILICON CHIP WebLINK page with your home page graphic, company name, phone, fax and site details plus up to 50 words of description– and this is repeated on the WebLINK page on the SILICON CHIP website with the link of your choice active. Get those extra hits on your site from the right people in the electronics industry – the people who make decisions to buy your products. Call SILICON CHIP today on (02) 9979 5644 SPECIALISTS in AUDIO, VIDEO, CD, DATA Media and Multimedia manufacturing & wholesale. We also specialise in DVD Production & editing. We can produce Short Run or Bulk CD Audio, CD Rom & DVD projects. Distributor of Emtec (by Basf) TDK, HHB and Quantegy Professional Products. PRO-COPY JED designs and manufactures a range of single board computers (based on Wilke Tiger and Atmel AVR), as well as LCD displays and analog and digital I/O for PCs and controllers. JED also makes a PC PROM programmer and RS232/RS485 converters. Jed Microprocessors Pty Ltd Tel: (08) 9375 3902 Fax: (08) 9375 3903 Tel: (03) 9762 3588 Fax: (03) 9762 5499 WebLINK: procopy.com.au WebLINK: jedmicro.com.au We specialise in providing a range of Low Power Radio solutions for OEM’s to incorporate in their wireless technology based products. The innovative range includes products from Radiometrix, the World’s leading manufacturer. TeleLink Communications Tel:(07) 4934 0413 Fax: (07) 4934 0311 WebLINK: telelink.com.au A 100% Australian owned company supplying frequency control products to the highest international standards: filters, DIL’s, voltage, temperature compensated and oven controlled oscillators, monolithic and discrete filters and ceramic filters and resonators. Hy-Q International Pty Ltd PIC chip specialists – microEngineering Labs and others. Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. See our website for new range of ATOM products! MicroZed Computers Tel:(03) 9562-8222 Fax: (03) 9562 9009 Tel: (02) 6772 2777 Fax: (02) 6772 8987 We’re one of Australia’s most innovative electronic equipment suppliers. For over 10 years we’ve served Australian industry with an extensive range of electronic components and equipment from the world’s leading suppliers. We ensure our customers have the best selection and service. RCS Radio has available EVERY PC Board ever published in SILICON CHIP, EA, ETI and AEM (copyrighted boards excepted). Many late boards are available ex stock, others can be made to order within a few days.Custom & production boards too! · Hifi upgrades & modification products - jitter Tel: (02) 9482 1944 Fax: (02) 9482 1309 WebLINK: clarke.com.au Tel: (02) 9738 0330 Fax: (02) 9738 0334 Clarke & Severn Electronics WebLINK: www.hy-q.com.au RCS Radio WebLINK: cia.com.au/rcsradio WebLINK: microzed.com.au reduction and output stage improvement. · Danish high-end hifi kits - including preamps, phono, power amps & accessories. · Speaker drivers including Danish Flex Units plus a range of accessories. · GPS, GSM, AM/FM indiv. & comb. aerials. Soundlabs Group Syd: (02) 9660-1228 Melb: (03) 9859-0388 WebLINK: soundlabsgroup.com.au Controller upgrade brings new life to old machine JAR Engineering faced the prospect of scrapping their Kasuga Machining Centre while the core of the CNC machine was still fully functional. The problem: the Kasuga controller was: “Old and slow – a case of a still young body under the direction of an old, slow brain!” said Roy Milan of JAR. But scrapping the machine and buying a new system would have involved a large capital investment. Instead, JAR Engineering contacted H & H Machine Tools and investigated the possibility of a controller www.siliconchip.com.au transplant. The result: the Kasuga is now working at double the previous feed rate. Mr Milan says: “The system used to operate in a jerky, stop, start motion. The new Fidia controller provides a continuous smooth movement and reads at a very high rate of knots. We are frequently recording savings of $500 a day or higher —savings that will rapidly pay out the upgrade cost.” He adds that his company has found the Fidia controlled machine “very user friendly, with the need for operator training minimised.” Contact: H&H Machine Tools Ph: (03)9719 7729, Fax: (03) 9719 7298 email: gmann<at>h-h.com.au March 2003  55 Building The Our state-of-the-art portable public address amplifier Last month, we introduced this compact and powerful portable PA amplifier based on the Philips TDA1562Q 70W class-H power IC. This month, we conclude with the description of the power supply, cabinet and PC board construction and the parts list. A S NOTED last month, the power supply is effectively a battery charger with the 7 amp-hour SLA battery permanently connected. Since the charger has other uses and could be used in any situation where a float charger is required, we are describing its circuit operation and construction separately, on pages 64 and 65. We’re also detailing the box construction separately – you’ll find this on pages 66 and 67. While we give detailed dimensions, this is not the only approach possible. We’re sure some readers will come up with completely different ideas for the enclosures. Construction The PortaPAL PA Amplifier is housed in a timber cabinet measuring 480 x 280 x 240mm which is covered in speaker carpet. Corner protectors, a speaker grille, a speaker stand socket and a handle are included. The electronics is accommodated on four PC boards: the microphone PC board coded 01103032 (64 x 73mm), the auxiliary PC board coded 01103033 (109 x 35mm) and the main PC board coded 01103031 (199 x 90mm). These are mounted on an L-shaped metal bracket, the reverse of which becomes the front panel. The charger PC board coded 01103034 (132 x 66mm) mounts on the side of the box with its indicating LEDs protruding through the front panel. You can begin construction by checking the PC boards for shorted tracks or any breaks in the copper patterns. Also check that the holes are drilled to the correct sizes to suit the components. In particular, check the 56  Silicon Chip siliconchip.com.au PortaPAL FEAT P RO J U R E ECT PART 2: BY JOHN CLARKE & LEO SIMPSON corner mounting hole sizes and the holes for the pots, RCA, 6.35mm jack and XLR sockets. Microphone board Assembling the microphone PC board is simple, as shown in Fig.1. Begin by installing the LM833 op amp (IC1), together with all the resistors and capacitors. Use the resistor colour code and capacitor code tables to guide you in selecting the correct values, and/or check the resistor values with a digital multimeter. Also, the electrolytic capacitors need to be oriented with the polarity shown. Note that the 10kΩ resistors and 10µF capacitor marked with an asterisk (*) are optional for powering electret microphones. These components are not needed for dynamic microphones but will not do any harm to a dynamic mic if you regularly swap microphones. There are a couple of PC stakes required to be installed for test points TP1 and TP2. Next, insert the 90° 6-way pin header into the PC board as shown. Before mounting the two XLR sockets, screw the M3 x 10mm screws into the mounting pillars from the back of the socket and then secure the M3 tapped 6mm long spacers from the front side of the sockets. Then mount the XLR sockets directly into the PC board holes provided. Main PC board The main PC board accommodates all the potentiometers and the TDA1562Q power amplifier module. Its component layout is shown in Fig.2. siliconchip.com.au Apart from the charger/supply board, everything mounts on an L-shaped bracket, the opposite side of which also acts as the front panel. Here everything is assembled, ready for placing inside the enclosure. Aaah . . . the enclosure. Did we forget to mention you have to build that too? You can start its assembly by installing all the links, the resistors and then the ICs but not the TDA1562Q. The 2.2Ω 1W resistors need to have an over-wind of 16 turns of 0.5mm diameter enamelled copper wire. These windings are shown on the circuit published last month, as L1 & L2. Start with a short length of 0.5mm copper wire, strip and tin one end and solder it to one end of the 2.2Ω resistor. Then wind on 16 turns. Strip and tin the other end and solder it to the other end of the resistor. Repeat the process for the second 2.2Ω resistor. Then solder each resistor into the PC board. Insert all the PC stakes used for the test points and also the PC-mount spade connectors. Mount the capacitors as shown with the electrolytics marked as polarised with the correct orientation. Electrolytics marked BP (ie, non-polarised) can be inserted either way. March 2003  57 The main PC board shown here without the heatsink attached. Note the inductors wound over the resistors (near IC9). Note also that the 10µF capacitor near IC2 must be bent over the top of IC2. This is to allow clearance when the microphone PC board is plugged into the header socket. Insert the 6-way and 8-way headers, as shown. Transistor Q1, diodes D1 and D2 and the power amplifier (IC9) can be inserted. IC9 is positioned with the centre-line of its mounting holes exactly 12mm above the top face of the PC board. Be sure to solder all the pins of the amplifier and take care not to have any of the pins shorted. Diode D3 is mounted onto a 6mm spacer and secured with a nylon screw and another 6mm tapped spacer on the underside of the PC board. The nylon screw is required to prevent the tab of the diode shorting to the metal panel when it is finally assembled. The two LEDs are mounted using LED mounts. The LEDs are inserted into the mounts from the front and the leads bent over at 90° within the mount before being inserted into the PC board. Be sure that the 58  Silicon Chip orientation is correct before bending the leads. Finally, the potentiometers can be installed – take care to place each one in its correct position. The potentiometer bodies are all tied together with a length of 0.8mm tinned copper wire soldered to the top of each body. It is difficult to solder to the passivated metal, so you will need to scrape away the passivation coating (with a knife or screwdriver) before soldering the wire. The wire is then connected to the PC stake adjacent to the 330nF earthing capacitor. Place a dab of red paint or nail polish next to the positive spade lug near the 22Ω resistor and the TP GND PC stake. Fig.1: PC board overlay and same-size photo of the microphone input board. siliconchip.com.au shown. Finally, install the PC stake for the test point, TP3. Support bracket The bracket which supports the amplifier also doubles as the front panel. It is made from 195 x 240 x 1.5mm aluminium, bent at 90° to form an L-shape. The dimensions of the panel, hole positioning and sizes are shown in Fig.4. The panel can be drilled and the larger holes cut before the panel is bent and the label attached. We expect that if you purchase a kit, the panel will already be drilled and bent and will come screen printed. Those building from scratch will need to prepare the panel as shown. The dress panel artwork (like the PC board artwork) can be downloaded from the SILICON CHIP website, siliconchip.com.au and printed, then glued to the aluminium panel. Place nuts on all the pot bushes for the main board and then mount the board on M3 tapped 6mm standoffs, with M3 x 6mm screws and star washers. The standoff beneath D1 is secured in place with an M3 nut and star washer. Secure the pots with nuts on the outside of the panel. Drilling the heatsink Fig.2: install the parts on the PC board as shown on this wiring diagram. Note how the potentiometer bodies are linked together and earthed at a single point. This is for easy identification when connecting the supply wires. Auxiliary board The auxiliary PC board carries the four RCA sockets and the jack sockets. Its component layout is shown in Fig.3. siliconchip.com.au First, install all the resistors and the TL071 (IC3) op amp. Then insert the capacitors, again taking care with the polarity of the electrolytic capacitors. The 6.35mm jack sockets and the stereo RCA sockets are directly mounted onto the PC board. An 8-way pin header is mounted with the orientation The holes in the main heatsink can be drilled as shown in Fig.6. Apply a smear of heatsink compound on the face of the power amplifier and attach the heatsink to the baseplate with M6 screws into the heatsink mounting screw points. Then attach the amplifier to the heatsink with two M3 x 15mm screws, two flat washers and two nuts. Attach the auxiliary board to the front panel by first fitting fibre washers onto the 6.35mm jack socket bushes and then mating them up the relevant panel holes; secure with the nuts. The RCA stereo sockets are secured with M3 x 6mm screws tapped into the plastic mounting pillars. Plug the microphone board pin header into the control PC board socket and push the sockets into the front panel holes. Secure with M3 x 6mm screws into the 6mm standoffs already attached to the XLR sockets. Make up a lead that connects the 8-way pin header sockets using 8-way rainbow cable. This connects the auxiliary board to the main board. Make sure the orientation is correct, with no twist in the wiring. March 2003  59 Power switch S1, the fuseholder and the 3-pin DIN socket can now be attached. The DIN socket is secured with M3 x 6mm screws, star washers and nuts. Connecting the boards Fig.3: the auxiliary PC board has the line in/out and guitar input sockets – it connects to the main board via the 8-way header. Fig.5 shows the wiring to the boards, battery and speaker. The battery and speaker connections are run in 7.5A figure-8 wire and crimp plugs. Use the lengths detailed on the diagrams for the charger and Fig.5. Be sure to use blue crimp connectors for the negative lead connections and red connectors for the positive leads. That way, there is less chance of wrong polarity connections. Also note that the amplifier power leads should be connected to piggyback connectors for the battery terminals, so that the charger leads can also be connected to the battery. Making the cabinet The box is made using 16mm Medium Density Fibre board (MDF) or craftwood and 16 x 16mm Meranti for the cleats. Because many home constructors may not have precision Fig. 4: this drilling template should help you with the front panel/amplifier bracket. 60  Silicon Chip siliconchip.com.au Parts List – PortaPAL PA (Main Section) 1 mic input PC board, code 01103032, 64 x 73mm 1 auxiliary input PC board, code 01103033, 109 x 35mm 1 control PC board, code 01103031, 199 x 90mm 2 450 x 900 x 16mm sheets of MDF board or craftwood 1 4m length of 12 x 12mm Meranti 1 195 x 240mm sheet of 1.5mm aluminium for panel 1 aluminium vent strip, 240mm long 15 x 12mm channel with holes or slots (eg, slotted shelf support strip) 1 200mm (8-inch) 4Ω coaxial loudspeaker (Altronics C 2006) 8 speaker box corners, 55 x 35 x 35mm 1 speaker box “top hat” stand socket (Altronics C 3602) 1 200mm speaker grille (Altronics C 3708) 1 strap handle (Altronics C 3660) 1 1m x 1.8m length of speaker box carpet (Altronics C 3530) 1 heavy duty heatsink 110 x 33 x 72mm (Altronics H 0560) 1 M205 fuse holder (Altronics S 5992) 1 7.5A M205 fuse (F1) 4 blue knobs 2 grey knobs 3 16mm PC-mount 10kΩ log pots (VR1-VR3) 1 16mm PC-mount 5kΩ log pot (VR4) 2 16mm PC-mount 100kΩ linear pots (VR5,VR6) 1 SPST 6A rocker switch (S1) 2 6.35mm PC-mount jack sockets (Altronics P 0073) 2 stereo PC-mount RCA sockets (Altronics P-0210) 2 PC-mount XLR/6.35mm jack socket without locking tab (Altronics P-0960) 1 6-way header connector with 90° bend pins (2.54mm spacing) 2 8-way header connectors with straight pins (2.54mm spacing) 2 8-way header sockets (2.54mm spacing) 1 6-way PC-mount header socket (2.54mm spacing) 2 piggy-back 6.3mm crimp connectors 7 red female 6.3mm spade lug crimp connectors 5 blue female 6.3mm spade lug crimp connectors 4 6.3mm spade PC board connectors with 5mm pitch PC lugs (Altronics H 2094) 10 6mm tapped standoffs 10 M3 shakeproof washers 2 M3 flat washers 3 M3 nuts 10 M3 x 6mm screws 2 M3 x 15mm screws (for amplifier to heatsink connection) 4 M3 x 10mm screws (for 6mm standoffs on XLR sockets) 1 M3 x 20mm nylon screw (for diode D3 mounting and PC board mounting point) 2 M6 x 15mm screws (to secure heatsink to baseplate) 6 4G x 16mm countersunk wood screws for securing control panel and charger PC board 4 6G x 10mm cheese-head wood screws for mounting loudspeaker 4 6G x 20mm to mount speaker stand socket 3 6G x 30mm countersunk wood screws to secure MDF battery cover 2 8G x 25mm cheese-head wood screws to mount handle siliconchip.com.au 32 4G x 16mm countersunk wood screws to mount corner protectors 2 5G x 20mm countersunk wood screws to mount aluminium vent strip 1 500mm length of 0.5mm enamel copper wire 1 2m length of 7.5A rated figure-8 wire 1 600mm length of 0.8mm tinned copper wire 1 120mm length of 8-way rainbow cable Semiconductors 3 LM833 op amps (IC1,IC2&IC4) 1 TL072 op amp (IC5) 2 TL071 op amps (IC3,IC8) 1 LM358 op amp (IC6) 1 7555 CMOS timer (IC7) 1 TDA1562Q power amplifier (IC9) 1 BC337 transistor (Q1) 2 1N914, 1N4148 diodes (D1,D2) 1 15A diode (MUR1550 or similar TO-220 package) (D3) 2 5mm high brightness red LEDs (LED1,LED2) 2 PC board LED mounts (Altronics H 1543) Capacitors 2 4700µF 16V PC electrolytic 1 2200µF 25V PC electrolytic 2 100µF 16V PC electrolytic 8 47µF 16V PC electrolytic 14 10µF 16V PC electrolytic 2 2.2µF BP* electrolytic 1 2.2µF 16V PC electrolytic 4 1µF 16V PC electrolytic 5 1µF BP* electrolytic 1 330nF MKT polyester 4 220nF MKT polyester 1 100nF MKT polyester 2 15nF MKT polyester 2 1.5nF MKT polyester 1 680pF ceramic 1 560pF ceramic 2 390pF ceramic 3 330pF ceramic 2 220pF ceramic 4 150pF ceramic 1 39pF ceramic 1 22pF ceramic 1 10pF ceramic Resistors (0.25W, 1%) 1 10MΩ 1 1MΩ 1 47kΩ 1 39kΩ 4 15kΩ 21 10kΩ 8 1kΩ 5 150Ω * BP (bipolar) capacitors are also known as NP (non-polarised) 3 470kΩ 2 22kΩ 4 4.7kΩ 2 2.2Ω 1W 5 100kΩ 2 18kΩ 5 2.2kΩ Miscellaneous PVA (timber) adhesive, contact adhesive, black paint, Bag of TEK particle board screws (for box assembly) Optional: 3-pin mains socket, panel mounting – not connected but mounts inside bottom of box to act as a storage holder for plugpack when not in use. March 2003  61 Fig.5: when you have all the boards assembled, connecting them together is as simple as following this diagram. Parts List – PortaPAL SLA Float Charger 1 SLA battery charger PC board coded 01103034, 132 x 66mm 1 16VAC 1.5A plugpack 3-wire earthed type (Altronics M 9332) 1 PC board fin heatsink 84 x 24 x 28mm (Altronics H 0668) 1 12V relay with 6A contacts (RELAY1) (Altronics S 4160A) 1 3-pin 180° DIN plug 1 3-pin 180° DIN chassis socket 2 5mm high brightness red LEDs (LED3, 4) 2 PC board LED mounts (Altronics H 1543) 4 6.3mm spade PC board connectors with 5mm pitch PC lugs (Altronics H 2094) 2 M3 x 6mm screws (for DIN socket) 2 M3 x 10mm screws (for heatsink) 4 M3 nuts 4 3mm star washers 1 50mm length of 0.8mm tinned copper wire 62  Silicon Chip 4 4G x 16mm countersunk wood screws for securing charger PC board Semiconductors 1 LM317T regulator (REG1) 2 BC337 transistors (Q2,Q3) 9 1N4004 1A diodes (D4-D12) Capacitors 1 4700µF 25V PC electrolytic 1 4700µF 16V PC electrolytic 1 470µF 25V PC electrolytic 2 10µF 16V PC electrolytic Resistors (0.25W, 1%) 2 2.2kΩ 3 1kΩ 3 470Ω 1 220Ω 0.5W, 5% 1 1Ω 5W wirewound 1 500Ω horizontal trimpot (VR7) 1 120Ω siliconchip.com.au Resistor Colour Codes      No. p 1 p 1 p 3 p 5 p 1 p 1 p 2 p 2 p 4 p 21 p 4 p 7 p 11 p 3 p 1 p 5 p 1 p 2 Value       4-Band Code (1%)        5-Band Code (1%) 10MΩ brown black blue brown brown black black green brown 1MΩ brown black green brown brown black black yellow brown 470kΩ yellow violet yellow brown yellow violet black orange brown 100kΩ brown black yellow brown brown black black orange brown 47kΩ yellow violet orange brown yellow violet black red brown 39kΩ orange white orange brown orange white black red brown 22kΩ red red orange brown red red black red brown 18kΩ brown grey orange brown brown grey black red brown 15kΩ brown green orange brown brown green black red brown 10kΩ brown black orange brown brown black black red brown 4.7kΩ yellow violet red brown yellow violet black brown brown 2.2kΩ red red red brown red red black brown brown 1kΩ brown black red brown brown black black brown brown 470Ω yellow violet brown brown yellow violet black black brown 220Ω red red brown brown red red black black brown 150Ω brown green brown brown brown green black black brown 120Ω brown red brown brown brown red black black brown 2.2Ω red red gold brown red red black silver brown woodworking equipment (nor skills!) we have described the box construction in detail overleaf. Once the box is completed you can install the speaker in its rebated hole in the front panel. We used some self-adhesive foam tape underneath the speaker to make it an airtight seal. Fit the speaker grille over the front of the speaker and screw in the four mounting screws. The grille may seem like overkill because the speaker cone is so far back from the front panel – but if you don’t fit one it won’t be long before you wished you did! Testing Before installing the assembly into the box, you can test the circuit by applying power using the battery. At switch-on, the power LED should flash at a one-second rate. Check that there is power to the op amps by testing for 12V between pins 4 and 8 of the LM833, TL072 and LM358 op amps (IC1, IC2, IC4, IC5, IC6) and at pins 4 and 7 for the TL071 op amps (IC3, IC8). IC7 should have 12V between pins 1 and 8. The output of IC4b (pin 7) should be at half supply, at around +6V. Similarly, the outputs of IC1a (pin 1), IC1b (pin 7), IC2a (pin 1), IC2b (pin 7), IC3 (pin 6), IC4a (pin 1), IC5a (pin 1), IC5b (pin 7) and IC8 (pin 6) should be also at about +6V. Check that the circuit works by consiliconchip.com.au Capacitor Codes Value 330nF 220nF 100nF 15nF 1.5nF 680pF 560pF 390pF 330pF 220pF 150pF 39pF 22pF 10pF IEC Code 330n 220n 100n 15n 1n5 680p 560p 390p 330p 220p 150p 39p 22p 10p EIA Code 334 224 104 153 152 681 561 391 331 221 151 39 22 10 the cleat frame with 4G x 16mm long screws. The battery leads for the amplifier and charger pass through from the rear of the battery compartment . The battery cover is secured with three 6G x 30mm countersunk screws. With the dimensions shown, the battery should be a snug fit but if necessary, pack some pieces of foam into the compartment to stop it moving around in transit. Finally, a chassis-mounting 3-pin mains socket, screwed to the inside bottom of the case but not connected to anything, makes an ideal plugpack holder when the plugpack is not being used to charge or power the SC PortaPAL. necting the loudspeaker and applying an audio signal to one of the inputs. Turn up the volume and the speaker should begin to produce sound. The power LED should light continuously when not muted. Check operation of the charger by connecting the output leads to the piggyback battery terminals (make sure the polarity is correct) and connecting the DIN socket to the AC input on the charger. Switch on power to the plugpack and the charger LED should light and possibly the charging LED will light depending on battery charge. Mount the charger board on the inside of the cabinet, making sure that the two LEDs align and protrude through their respective holes in the control panel. Use 4G x 16mm screws to attach it in place. We used a small rubber grommet cut in half to lift the two front mountings of the PC board off the cleats by about 1mm. The L-shaped amplifier bracket/panel is installed into the box by sliding it into the 2mm Fig.6: this template can be used to ensure your drill gap and securing it to holes on the heatsink are in exactly the right place! March 2003  63 MAKING THE BOX One of the areas where home constructors come unstuck is in the cutting-out of speaker box panels. It is essential that the edges are not only straight and square but opposite panels also need to be exactly the same size – otherwise the box may be crooked or there may be air gaps. For a typical part-time woodworker using typical home workshop tools (as distinct from a pro who does it all the time!), achieving perfectly straight, smooth and square cuts with a hand saw or any type of hand-held power saw is difficult. Yes, it can be done – but it is difficult. However, there is a delightfully easy way to ensure that at least three sides of each panel have perfectly straight and parallel sides/right angles – and that is to use sheets of pre-cut board. (If the manufacturers can’t get it straight and square then we are all in trouble!) For this reason, we have elected to use two sheets of 16mm, 450 x 900mm craftwood (MDF would also be suitable). We have made the three vertical panels (ie front and both sides) 450mm high. Originally we had planned to use a single sheet of 900 x 900mm board but fortunately couldn’t find any in our local hardware store. So we purchased two 450mm wide sheets and suddenly realised what an advantage that was! Cut the two sides (240mm wide) from the top of each sheet and the front (247mm wide) from the bottom of one of the sheets (as shown on the cutting diagram) and you’ll have three edges on each panel perfectly square. The fourth edge depends on how accurately you cut. The identical top and bottom pieces (240 x 280mm) and the various bits and pieces which form the battery holder, etc, can be cut from what is left over. The vertical panels sit between (ie, inside) the top and bottom pieces, making the overall height of the box 482mm (450+16+16). One reason for placing the vertical panels inside the top and bottom, rather than vice-versa, is for strength. As made, the box will easily handle someone using it as a seat (as will inevitably happen). The front panel and the various rear pieces are recessed – the front back far enough to accommodate the speaker grille, while the rear is even further recessed. Recessing both front and back will allow the box to fall over and not break or damage the speaker itself, pot knobs or other controls. It might appear that 247mm is wrong for the front panel: if the base is 280mm wide and the two sides are 16mm wide, surely it should be 248mm (28016-16)? That extra 1mm off allows the front panel to be a snug, but not too tight fit. We cut suitable lengths of 16 x16mm meranti (which we happened to have on hand – just about any softwood will be OK) for the cleats – all around the front inside of the box for the box front (speaker baffle) to attach to and in strategic locations on the rear inside as shown by our drawings. Before assembling the box proper, we 64  Silicon Chip glued’n’screwed the cleats in position. The “L”-shaped aluminium plate holding most of the amplifier electronics screws to these cleats. After the cleats were done, the top, bottom and two side box panels were glued and clamped together, and allowed to dry overnight. The (unglued) front panel was placed in position as formwork to keep the whole thing square, When dry, we pushed out the front panel and on it marked and cut (with a jigsaw) a 185mm circle right in the centre. Naturally enough, this is where the speaker mounts – but first, the hole needs a 7mm deep, 10mm rebate all around from the front (using a router) to allow the speaker to sit flush. A 200mm metal speaker grille goes over the speaker later on to protect it. The final bit of woodwork is the mounting of the various bits of craftwood (or MDF) which hold the battery and other components in place. These mount as shown in our detailed drawing opposite. The finished box, measuring 280(w) x 240(d) x 482mm(h), can be painted, veneered, or as we have done, covered in speaker “carpet”. A lot of pro audio gear is covered in this stuff because it helps it absorb knocks and scrapes on the job or in transit. It also hides any “sins” you might have created along the way. The carpet is glued on with contact adhesive, making sure it is stretched nice and tight over and around the box. Edges are trimmed with a sharp knife and also glued. We also completely covered the inside of the box (and even the back of the speaker magnet) with the carpet to act as a sound deadening and resonance-reducing agent. siliconchip.com.au It looks schmick, too! All these pieces need to be cut to the appropriate size before gluing in place. Eight plastic speaker box corners were fitted on all corners (top and bottom) to protect them from damage. For ease of transportation we added a flexible carry handle. As we mentioned before, a metal speaker grille is fitted over the front of the speaker cone to protect it. In perhaps a bit of overkill, we added a “top hat” stand mount to the bottom of the box. This allows the box to be mounted “up high” on a standard 35mm speaker stand (or even a length of 35mm OD water pipe driven into the ground). Raising the box above the heads of an audience dramatically improves the sound “throw”, allowing greater coverage without the use of a second box or extension. Finally, the “aluminium air vent” shown above is simply an offcut from a length of U-shaped slotted aluminium channel used for shelf support verticals (the kind that brackets clip into to hold shelves). This should be available at any hardware store. It even comes with the slots pre-cut for you! These three shots, along with the diagram above, give a pretty good idea of how we constructed our box. Of course, other approaches may be just as valid – and because it is for PA (not hifi) use, dimensions are not particularly critical with the exception of the speaker cutout, battery compartment and, of course, the amplifier mounting arrangement. siliconchip.com.au March 2003  65 12V SLA BATTERY FLOAT CHARGER Some readers will be aware that we produced a 12V DC float charger in October 1998. Why not simply employ that circuit in the PortaPAL PA amplifier? The answer is that we did try it in our first prototype but it was found to be unsuitable for this application, for the following reasons: First, the October 1998 charger feeds pulses of rectified AC to the battery and while this is perfectly valid for battery charging, the resulting ripple across the battery and hum radiation from the battery leads was enough to be picked up by the sensitive microphone circuitry to become quite audible. Plainly, this was a major drawback, especially as most users would want to use mains power where it was convenient and available. Second, once power is removed from the input to the charger, it pulls a significant current from the battery. This would totally discharge the battery if the PA system was 66  Silicon Chip not used for a few weeks. Such an occurrence would destroy the battery. Not good. Hence, our new float battery charger feeds pure DC to the battery and is disconnected from the battery when the AC input is removed. With no input power and the PA amplifier also switched off, there is no current drain from the battery and it should have a shelf life of many months, if not years. The charger circuit is shown below. As mentioned before, this also makes a perfect general-purpose 12V SLA battery float charger. Power for the charger circuit comes from a 16V 1.5A AC plugpack which feeds diodes D4-D9 to produce two DC supplies. The main supply comes from diodes D4-D6 and the siliconchip.com.au You’ll find the complete parts list for the 12V SLA Battery Float Charger on page 62. 4700µF capacitor. The capacitor is necessary to ensure that the battery is charged with DC that is free from ripple. Any ripple would be heard in the amplifier’s output. 3-terminal regulator REG1 sets the maximum battery charge voltage to 13.8V. It operates as follows. The voltage between its output and adjust (ADJ) pin is fixed at 1.25V and this voltage is applied across the 120Ω resistor (neglecting the small current drawn by the ADJ pin). The resulting 10mA through the 120Ω resistor flows through the 1kΩ resistor and series 500Ω trimpot VR7 to provide a voltage across them, effectively jacking up the regulator voltage. Trimpot VR7 is adjusted for an output of 13.8V. The 10µF capacitor connected to ADJ terminal of REG1 should be omitted, if used with the PortaPal. When power to the charger is switched off, the battery could be drained back via the resistors across REG1. To stop that, we added the relay circuit, to disconnect the battery from the charger if no mains power is present. Diodes D8 & D9, in conjunction with diodes D4 & D6, produce a separate supply from the 16VAC plugpack. This is filtered with a 470µF capacitor and then fed through a 220Ω resistor so that the relay is driven with 12V. The 4700µF capacitor across the relay coil delays the relay switch-on until the 4700µF capacitor for REG1 is fully charged. Without this delay, the initial switch-on of the charger would cause a loud hum in the loudspeaker until the 4700µF capacitor for REG1 was fully charged. LED4 provides power ON indication. Current limiting The 12V SLA float charger is assembled on a PC board measuring 133 x 66mm, coded 01103034. It has a single-sided heatsink for the regulator (REG1) measuring 84 x 24 x 28mm (Altronics H-0668 or equivalent). The component overlay is shown above. Once you have checked the board for obvious defects such as open-circuit tracks, shorts and undrilled holes, install the small components such as diodes and resistors first. Watch the polarity of the diodes. That done, install the two transistors, 500Ω trimpot, the electrolytic capacitors and the relay. Again, watch the polarity of the electrolytics. When mounting the 1Ω 5W wirewound resistor, make sure there is about 1mm clearance between the resistor body and the PC board. This improves cooling for the resistor. The two high brightness LEDs are mounted in right-angle PC mounts (Altronics A 1Ω 5W wirewound resistor is used to monitor the charging current. The voltage developed across it is monitored by transistor Q2. When the voltage across the 1Ω resistor reaches 1V, corresponding to a charging current of 1A, the base voltage of Q2 reaches about 0.5V and it begins to conduct, pulling the ADJ pin of REG1 lower to reduce the output voltage of REG1. This limits the charging current to 1A. Transistor Q3 also monitors the voltage across the 1Ω resistor. Q3 turns on whenever the resistor voltage is above about 0.5V to drive LED3, the charging indicator. So provided the charging current is more than about 500mA, LED3 will be alight. Once the battery voltage reaches 13.8V, the charging current drops to zero and the battery is effectively “on float”. siliconchip.com.au Charger board assembly H-1543 or equivalent). These enable the LEDs to mate precisely with the control panel of the amplifier. The 3-terminal REG1 is mounted on the heatsink with its leads bent, inserted and soldered into the PC board holes. The heatsink and regulator tab are then secured to the PC board with two M3 x 10mm screws. Nuts and star washers are used on the underside of the PC board. Four spade lugs are inserted and soldered into the PC board for the input and output connections. The positive spade lug output near the relay should be marked with red paint or nail polish, to ensure correct connection to the battery. Testing Before you can test the charger board, you will need to wire up the 16VAC plugpack which comes with bare 3-wire cable, one lead of which is intended to be earthed. The cable is wired to a 3-pin DIN plug. The earth wire must go to the centre pin of the DIN plug while the other two wires go to the remaining pins. You will then need to temporarily wire up a DIN socket with the two AC wires going to pins 1 & 2 (not the centre pin) of the socket. These wires then should be fitted with spade connectors to fit the spade lug inputs on the charger board. Switch on the plugpack and the charger LED should light and possibly the charging LED will also light depending on battery charge. That done, disconnect the battery and then set the trimpot for an output of 13.8V, using a digital multimeter. SC The charger is now ready to go. March 2003  67 By JULIAN EDGAR Little Dynamite Subwoofer Build your own compact subwoofer – ideal for use in a car or home unit S UBWOOFERS ARE NOW almost universal in any car system that attempts to produce quality music. They’re also prevalent in home theatre systems and also make a great upgrade for a compact sound system that needs a bit more punch. The subwoofer described here is dead-easy to make and gives excellent perfor­mance, considering its compact size and low cost. And if you think that it’s really a 68  Silicon Chip bit too limited in power handling and low-down frequency response, stay tuned – we’ve got another more complex, higher-power design coming soon. But honestly, unless you want to make a social statement to sidewalk pedestrians or your neighbours, this subwoofer will be more than adequate for most music! The design We’d been considering doing a sub- woofer project for some time – and in fact went as far as designing a bandpass model using a 10-inch driver. However, by the time we’d priced the particle board and added in carpet, glue, terminals and a grille, the cost was around $130 for the enclosure alone. What’s more, it would have taken quite some effort to build. It was about this time that Jaycar Electronics released a range of sub-woofer enclosures, all pre-built www.siliconchip.com.au Main Features • • • • • Small enclosure 125 watts power handling Excellent in-car response Competent in-room response Easy to build & low cost and finished with carpet and loudspeaker terminals. Their boxes start at just $59.50, so we made a radical change to our plans. The bandpass design was scrapped and we set about designing a traditional ported design instead. A ported enclosure is one of the oldest box types around (see “Ports Enclosure Size & Other Design Considerations”). However, the design of this type of enclosure has been revolutionised in recent times with the devel­opment of loudspeaker design computer software. Rather than building a box and then laboriously testing it in many different configurations, computer software now allows the virtual con­struction of dozens of different enclosures. In addition, good subwoofer design software (like the Bass­ Box package that we used) makes various suggestions during the design process. However, if you want to aim for an optimal trade-off in terms of size, response, sensitivity and power handling, such a design process can still take many hours to complete. The first step in the design can be either the selection of the driver or the enclosure. In our case, we did a The driver used in the Little Dynamite subwoofer is 10 inches (25.4cm) in diameter, is rated at 125W RMS and uses a voice coil 50mm in diameter. It costs $99 and is available from Jaycar. bit of both. First, the enclosure – the new pre-built subwoofer boxes come in 25, 35 and 45-litre nominal interior volumes (we’ve written “nominal” for good reasons which we’ll come back to later) and the hole for the driver is already cut. This means that if you want to use a 10-inch driver, then the 25-litre box is the only one to go for (the 35-litre box is precut for a 12-inch driver, while the 45-litre box is cut for a 15-inch driver). Note that the boxes are available in both sealed and ported designs. We leaned towards a 10-inch driver as in general terms they’re cheaper than larger sizes and can usually be fitted into a smaller box, which again has a cost advantage. Choosing the subwoofer So with the 25-litre box the chosen BassBox: Loudspeaker Design Software The BassBox software package is available in two forms – BassBox Lite and the BassBox Pro professional version. The Lite version is quite sufficient for any speaker design work that most people will want to carry out and is the package that was used to design this subwoofer. In addition to being able to model the performance of bass-reflex (ported) speaker enclosure designs, this software can also model sealed and passive radiator boxes and a range of bandpass designs. The Lite version comprises just a single CD www.siliconchip.com.au and the Help and background explanations are all available on-screen. In fact, this information is very good indeed – with some study, there’s enough information for even a beginner to start designing sophisticated speaker enclosures. And if you have a background in audio, the flexibility and detail of the program will be even more useful. BassBox Lite is available in Australia for $165 from ME Technologies at www.me-au.com and also from Harris Technologies at http://www. ht-audio.com March 2003  69 The “step” in the inner surface of the port that would otherwise be formed between the flared ports and the plastic pipe is smoothed away using a half-round file and sandpaper. The port is formed from two flared speaker vents (available from Jaycar) joined by a length of 65mm-diameter plastic pipe. we’d like is sensitivity – with a sound pressure level (SPL) of 88.2dB at 1 Watt 1 metre, it needs to have both an enclosure design which is efficient and a power amplifier with at least 100 watts RMS behind it. Port size The completed port – the two flared ends reduce turbulence so that there are no problems with port noise. Make sure that you don’t glue the ends on at this stage, though – otherwise you’ll never get the assembly into the box! enclosure, which speak­er would be suitable for it? Keeping it in the Jaycar family, we opted for the CS-2274, a 10-inch “titanium” finish driver with 125W RMS power handling, an X-max (maximum cone movement) of 9mm, a voice coil diameter of 50mm and a 70  Silicon Chip resonant frequency of 33Hz. What these specs add up to is a competent driver that should be able to produce good bass in the right enclosure with­out breaking the bank (the driver retails for just $99). The only spec that isn’t quite as good as While free speaker design software is available on the web, we’ve not seen any program that comes close to BassBox – so it makes sense to pay the necessary dollars if you want this kind of package. One area that we were very conscious of when software modelling the design was the behaviour of the air within the port. Typically, ports are made too small in diameter – it’s easy that way because then they can be made shorter for the same box tuned frequency. However, small ports give rise to high air velocities, which in turn causes port noise or “chuffing”. Bass-Box can pre­dict maximum port velocities and recommend minimum port diameters to eliminate this problem. However, after looking at the modelled behaviour of a system using the prebuilt ported enclosures (the 25-litre box comes with one 50mm ID port), we decided to buy a sealed box and then cut a hole for a port of our own making. So what does the final design look like? First, the Jaycar “25-litre” box is actually 23 litres – an important difference when it comes to the design. Second, the volume taken up by both the driver and the port need to be subtracted from the available internal volume (BassBox does both of these things automatically if the right data is entered). In addition, the effect of www.siliconchip.com.au Ports, Enclosure Size & Other Design Considerations A speaker’s role in life is to create sound waves and it does this by moving its cone back and forth in response to elec­trical signals. When it pushes forward, higher air pressure is created in front of the cone; conversely, when it moves back, lower air pressure is the result. If a bare woofer is sat on the bench and driven by a bass signal, the pressure waves find their way around the edge of the frame and partially cancel each other out. A fundamental task of a loudspeaker enclosure is to prevent this wave cancellation and its adverse effect on bass response. A sealed enclosure, for example, dissipates the energy from the back of the cone into the box (and/or the box filling). However, because these pressure waves are being wasted, the efficiency of a sealed enclosure is not as high as for a ported enclosure. In a ported enclosure, radiation from the back of the cone is used to reinforce the pressure waves being generated by the front of the cone. This is achieved by using a tunedlength port or vent, which has the effect of altering the phase of the waves emanating from the rear of the speaker. Put your hand near the port used in this type of design and you’ll notice that as the woofer cone moves forward, so does the air in the port – the pressure waves from the back of the cone are now reinforcing those coming from the front. However, if the port isn’t just the right length and dia­ meter, the response of the speaker can be all “wrong”. For exam­ple, in this design, we used a port 63mm in diameter and 360mm long. But what if the port had been only 150mm long? the acrylic speaker fill also needs to be taken into account (confus­ ingly, the fill expands the volume that the driver sees). In the end, we had 19.5 litres available and chose to use a port 63mm in diameter and 360mm long. This gives a box tuned frequency of 33Hz. Note that the tuned frequency in a ported design is often close to the speaker’s resonant frequency (in this case, it is identical). www.siliconchip.com.au Fig.1: the red curve show the in-car response of the subwoofer using a 360mm-long port, while the yellow curve plots the predicted response if the port is reduced to just 150mm long. Fig.2: the green curve here shows the effect of dropping the enclosure volume to 12 litres and using a 75mm-diameter port that’s just 100mm long. Fig.1 shows the changed response – the red line is the in-car performance of the subwoofer as described in this article, while the yellow line shows the predicted response with the shorter port. As shown, with the shorter port, the bass falls away more quickly and is also “peakier”. (Actually, the selected driver is quite tolerant of design changes – with some speakers, the results of such a port mismatch would be much worse!) The speaker enclosure volume is Modelled in a car environment, the response is effectively strong down to 15Hz, while in a room the -3dB point is at 38Hz. The modelled maximum port velocity is only 23 metres/second at 125W input power and 22Hz which – not coincidentally – are also the exact conditions where the cone reaches its maximum excur­sion. To avoid any possibility of port noise in this long vent, both ends of the vent are flared. This is achieved by using also a vital part of the design. In the case of the response curve indicated by the green line in Fig.2, we’ve dropped the enclosure volume to 12 litres and used a short, fat port – 75mm in diameter and 100mm long. The re­sulting in-car response is very peaky at 100Hz. As a result, this type of enclosure design that would give “one-note” bass, a problem often found in ported loudspeakers enclosures that are not well de­signed. two Jaycar CX-2688 flared speaker vents, joined with 65mm-dia­ meter plastic pipe. The two vents slip tightly into the pipe, allowing the easy construction of a double-ended flared port. Building It If you have available an electric jigsaw, some hand tools and a tube of general purpose building adhesive (eg, water clean-up Liquid Nails), building the complete subwoofer will March 2003  71 Parts List 1 10-inch Response Subwoofer; Jaycar Cat. CS-2274 1 25-litre sealed subwoofer enclosure; Jaycar Cat. CS-2520 1 acrylic speaker damping material; Jaycar Cat. AX-3690 1 10-inch protective grille; Jaycar Cat.AX-3522 2 flared speaker ports; Jaycar Cat. CX-2688 1 500mm (approx.) length 65mm-dia. plastic pipe 1 short length heavy-duty speaker wire 1 tube building adhesive (eg, Liquid Nails) 8 speaker attachment screws The hole for the port is marked on one side of the enclosure, to­wards the back of the woofer. This 85mm-diameter food tin was an ideal size for marking out the hole which was the cut out using a jigsaw. take you nearly no time at all – in fact an hour, tops! The first step is to remove the sharp inside edge of the flared speaker vents; ie, at the end opposite the flare. This is done to eliminate any sharp steps between the flared vents and the plastic pipe when they are joined together. You can use a round or half-round file for this job, finishing off with some fine sandpaper. If you don’t have any sandpaper handy, a stainless steel kitchen scourer works quite well on the soft plastic. With these edges smoothed, cut the plastic pipe to the right length so that when both flared ends are pushed firmly into it, the total port length is 360mm. Don’t be tempted to glue both flared ports to the plastic pipe at this stage – you still need to fit the port into the enclosure! Once the port has been assembled, spray some black paint inside it to cov- Drill a hole just inside the marked area for the port cutout to allow the insertion of the electric jigsaw blade. 72  Silicon Chip er any scratches that you have made and to hide the white plastic. The next step is to cut the hole for it in the side of the speaker box. An 85mm hole is ideal – we drew the cutting line with the help of a can of food that conveniently had the right diameter. The port must be placed at the magnet end of the speak­er to give sufficient clearance, with the hole cut in an end wall. Before marking the hole, consider the placement of the terminal strip and how you intend positioning the box in its final home, as these might have a bearing on where you want the port to be. The hole should be cut so that the edge of the flare ends up about 20mm in from the edges of the box. This causes the other end of the port to sit with its flared outer edge against the inner walls of the box, allowing it to be further held in place with some dobs of adhesive. For environments where the subwoofer will be subjected to lots of shaking, use an additional internal fastening to hold the port tube in place – for example a bracket made from aluminium strip wrapped around the port and then at­tached to the inner panel of the box with short woodscrews. The flared port can now be assembled within the box. If you push the ends on after you’ve applied a smear of adhesive to the pipe, they will be held in place firmly. The flared end that sits flush on the surface of the box needs to be thoroughly sealed from behind using Liquid Nails or a www.siliconchip.com.au silicone sealant. Make sure that you give the sealant time to set! Next, the acrylic speaker damping material can be cut to size and stuck to the inner walls of the box. We suggest 350 grams/square metre material (Jaycar AX-3690) but any similar material is fine – eg, acrylic quilt wadding. Be careful that you don’t block the port – in fact it is wise to be quite sparing in your use of the material around the port entrance. Next solder some heavy duty speaker cable to the box termi­nals and attach the other ends to the screw terminals on the loudspeaker. Make sure that the positive terminal on the box is con­ nected to the positive terminal of the loudspeaker and similarly for the negative terminals! The woofer can then be slipped into its precut hole and the positions marked for its mounting screws. That done, remove the speaker and drill small diameter pilot holes for the screws. Clean away any shavings, then rein­stall the driver and fasten it into place using eight coarse-thread MDF screws. Here’s an important note: the carpet will compress as you tighten the screws, so go right around the speak­er at least three times, tightening them each time. You’ll note that we’ve left off the protective grille at this stage. Instead, it’s time to do some testing. A jigsaw will make quick work of the port hole. The rim of the flared port covers the edge of the hole so don’t worry if you don’t cut a perfect circle. Testing two reasons for this buzz. First, at high output levels, the interior of the car was getting excited – ie, bits of trim inside the car were resonating. And second, we were driving the 150 watts/ channel ampli­fier so hard that it was going into distortion. The latter is pretty important to avoid – while this is a rugged speaker with cone movement well controlled down to about 22Hz, start pumping up the SPL and you might find that The first step is easy – apply a 1.5V battery across the terminals and make sure that when the positive and negative battery terminals are applied to the positive and negative sub­woofer terminals respectively, the woofer cone moves forward. If it moves backwards, open up the enclosure and swap the wiring connections at the speaker! The next step is to connect the subwoofer to an amplifier. Begin by driving the unit quite gently. Moisten a finger and move it around the edge of the driver, to check for any air leaks past the frame. Now do the same around the edge of the port – there will be air movement within the port itself but there shouldn’t be any around the edge of the flare. Next, listen carefully for buzzes, rattles and whistles. During the prototype’s development, we had a buzz that we chased and chased and chased. It turned out that there were The flared speaker port inserted through the hole. The striped background is the rug on which the box is sitting while the work is being done – unlike an untrimmed box, this one needs to have its finish protected during the build process. www.siliconchip.com.au you’re working the amplifier harder than you thought. And remember: more speakers get destroyed by pushing the amplifier into distortion than ever get damaged by exceeding the speaker’s limits! If everything seems fine at low volume, wind up the wick a bit more. Naturally, during this test procedure, you should disconnect all the other speakers, so that you’re just listening to the subwoofer. It won’t sound won- March 2003  73 This is the inside view – the plastic pipe is slid over the external flared port after which the second flared port is added at the other end. derful (no subwoofer does on its own) but it will allow you to easily identify any problems. As stated earlier, because of its relatively low sensitivi­ty, this subwoofer isn’t going to deliver ear-splitting SPLs from modest amplifiers. However, if you have 100-125W available, it should be capable of delivering lots of low-end bass. If all is well, you can now reconnect the other speakers and then balance the system for the bass response that you want. Finishing Acrylic filling is glued to the walls of the enclosure, making sure that the port entrance remains clear. The port is held in place by sealant/glue applied at each end. If the subwoofer is going to be subjected to lots of movement, add an extra bracket to secure the port tube in place. 74  Silicon Chip The final step is to attach the protective speaker grille. To do this, you’ll have to take the driver out again so that you can place the “T” nuts on the back of the baffle. While the speaker is out, check that the port is still rigidly held in place by its glue and/or brackets and that none of the acrylic speaker filling has moved around. You should especially check that the port entrance has remained clear. It’s then just a matter of completing the assembly and enjoying the fruits SC of your labours! www.siliconchip.com.au 110mm NEAR HALF PRICE SOLAR PANELS $199 2W 315 X 162 X 19 ... $29 (SP2) 4W 315 X 315 X19... $59 (SP4) 14W 315 X 925 X19... 199 (SP14) N 28mm I A G R BA $33 77mm $29 All of our panels are amorphous, aluminium framed, backed and water-proof. COOL NEW ITEM HEATER / COOLER This new cooler / heater assembly includes a 90mm fan, heat-sink, 65deg. thermal cut-out switch (used when heating), spacer block and a 50W Peltier device. Just cut a hole in your ESKI or insulated cooler box & fit an aluminum plate or heat-sink (not supplied) to this assembly to turn your ESKI into a fridge for the car or boat. requires 12VDC SWITCHING SOLAR REGULATOR KIT: This easy to assemble kit is designed to efficiently charge batteries from solar cells. It has Special intro price of only $33 (pelt1). charge / discharge indicator LEDs. Kit contains PCB plus all on-board components. KIT NEW PRODUCT PRICE: (K008B) $15 BARGAIN 12VAC POND PUMP 10 LED LAMP KIT: Why spend a small fortune on This kit uses 10 Ultra-bright LEDs (equivalent to around 6W a new water feature when you incandescent) with far less current drain than normal incandescent ST 0 could build your own. Requires U J light bulbs but with a brighter, whiter light. It uses a constant current 12VAC (We have a suitable 4.5 plug-pack available for $1 circuit & draws 120mA. (This means is your get many more hours of just$6). Pumps a head of up light with a smaller & cheaper battery & solar cell. Kit contains a to 500mm at 300L p/h via a small PCB, 10 White Ultra-bright LEDS & all on-board components. 8mm outlet. (PP1) Easy to assemble. 10 LED Kit $20 (K199_10) (NEW) 433.92MHz MINI 12V / 7AH SEALED LEAD ACID BATTERY: TRANSMITTER Fresh stock batteries, now is the time to pick up a real bargain, 2.6kg, AND RECEIVER MODULE: 150 x 65 x 92mm.(PB6) $25 each NEAR ACTUAL HOW ABOUT A COMPLETE SOLAR LIGHTING SYSTEM FOR YOUR CAMP, SIZE CARAVAN OR WEEKENDER: There are 4 main components to this system, 2W Solar Pre-built superhetrodyne surface mount transmitter module which is saw resonator locked at 433.92MHz. Panel, Switching Solar Regulator kit, Battery and 2 X 10 LED Lamp Kits. This combination Operates from 3 ~ 12V DC and has 7 connections. When of solar panel, charger and battery will power 1 of the LED lamp kits for over 7hrs with only use in conjunction with RX434, the pair can give a range of up to 2km when the transmitter is powered by 12V DC. 5hrs of sunlight. Central Australia receives around 10 hrs per day. (SL2W): $99 Dimensions: 20mm (L) x 8mm (W). (Same diameter as a UPGRADE TO A BIGGER PANEL!!! For just $25 more. 5c coin). Click here for data: (TX434) $11 You can upgrade from a 2W to a 4W panel in your Solar Lighting System . (SL4W) total (NEW) 433.92MHz MINI RECEIVER MODULE: price.$124 (RX434) $21( "LOOK NEW KIT" LOTS OF AMAZING OPTICAL BARGAINS ***LOOK***LOOK***LOOK*** STEREO FM TRANSMITTER KIT HIGH POWERED LEDS, LASERS WARNING!!! This professionally designed stereo transmitter These magnets are so strong they are POINTERS & LASER DIODES uses a special IC that produces the MPX AMAZINGLY BRIGHT MINI KEY-CHAIN LED TORCHES, ALL ARE AROUND 8 TO 10 Cd. WHITE ...$7 RED ...$4 BLUE ...$6 GREEN ...$6 All of the following are up to 10cD, 20mA max and narrow angle. dangerous!!! signal only plus a stable transmitter new neodymium rare earth magnets from 20 that uses discrete components: $22.50 for a complete kit inc. case. (k094b) cents each Dew to popular request we have introduced some smaller magnets to our range similar to those used in magnetic therapy etc. 20 X 10mm$6.00... 10 X Bulk Red LED SPECIAL 5mm$1.20... 10 X 3 mm$0.70... 7 X 3mm $0.55... 7 X 20 or more red LEDs for $0.60ea 2.5mm $0.45... 3 X 2mm $0.25... 10cD White...$2.00 ea Red...80c Yellow ...70c 3 X 1.5mm$0.20. Green...$2.10 Blue...$2.20 UV LED's ..$1.60 Less 10% for 10 or more of any mix Money Detector Pens These use a very bright UV LED. Check Australian currency for counterfeits by looking at the hidden UV (USED) BWD 603B FUNCTION GENERATOR MINIprinting on them. ...$4.50 LAB: This single unit includes a 0.1Hz to 1MHz Function Extra AG13 batteries ...15c as used in the key-chains, Generator, a power differential amplifier with an ad3 req. Extra AG3 batteries...6c as used in pens, 4 req. justable gain of 1 to 100 <at> 1A out, a bi-polar power supply / power amp with a voltage range of -15 to +15V <at> Don't forget our bargain OPTO PACK...K147 1A, a +voltage power supply with a voltage range of 1 to Pack inc. total of 103 opto semiconductors. 91 various 15V <at> 1A, a negative voltage power supply with an colours & types of visible LED's, 1 x IR LED, 6 x Photo- voltage range of 1 to 15V <at> 1A, a 0 to 200V + power transistors, 2 x high speed PIN photodiodes, 1 x HC312 IR supply & a 12.6V center tapped 50Hz AC voltage source Receiver Module. KIT PRICE: (K147) $10 each pack (6.3V 0 6.3V). In excellent condition: (ZC0211) $250 PICAXE-08 CHIPS... See Silicon Chip FEB 03 The PICAXE processors use a R.I.S.C (Reduced Instruction Set Controller ) system, and are easy to program. It is said to be like a Basic Stamp clone in single chip. $5.50ea. Lots of info available on the Internet. We may have other PICAXE chips in the future. MINI FM TRANSMITTER KIT K189 This kit is easy to build with just a few simple steps to complete and test it. It measures only 32mm X 13mm X 24mm and draws only 5.8mA from it's 1.5V LR44 button cell (supplied). Kit comes complete with a metal case, battery, prebuilt PCB and double sided tape for quick and easy installation. (K189) $39 NEW 6mm MINI ELECTRET MICROPHONE Recover this mini electret microphone and other parts from this NOKIA 5110 / 6110 personal hands free kit (or use them as is). snaps apart in just seconds. Don't pay $3 or more for just one, Our price... 6 for $2 FERRITE CORES Ideal for switch mode power supplies and experimenters. 15mm X 29mm X 9mm. Sorry we don't have any bobbins to suit. 4 pairs for $2 (FC1) Our famous wiring looms are still available for just $1 ea Suppliers of kits and surplus electronics to hobbyists, experimenters, industry & professionals. Orders: Ph ( 02 ) 9584 3563, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89 Oatley NSW 2223 major credit cards accepted, Post & Pack typically $7 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081 www.oatleyelectronics.com SC_MAR_03 product review Canon’s image stabilised binoculars W hether you like to watch whales, birds or sport, a pair of binoculars is a great accessory. How ever, they do have disadvantages. Most binoculars are not light and the longer you use them, the more tired you become. And the more tired you become, the harder it is to hold them steady and this problem is worse if you are using magnification of x10 or more. The only practical solution to both of these related problems is to use a tripod. This relieves the strain on your arms and holds the binoculars absolutely steady but most people would find a tripod just another piece of gear that they don’t want to carry. Canon’s solution to the problem is to produce binoculars with inbuilt image stabilisation. They compensate for the inevitable “shakes” you get when using binoculars and they are much more pleasant to use. We reviewed two of the Canon range: the 15x50IS model which has 50mm objective lenses and x15 magnification and the 10x30IS which has 30mm lenses and x10 magnification. Cutting straight to the chase, the x15 model is the one of most interest, since that degree of magnification is almost impossible to use without having a tripod. In fact, unless you are experienced in using binoculars, it is difficult to imagine how difficult such a seemingly modest degree of magnification is. 76  Silicon Chip This cutaway diagram shows the disposition of the major components in the Canon image stabilised binoculars. Note the compact Porro prisms which erect the inverted image for normal viewing. www.siliconchip.com.au by Leo Simpson The Canon 10x30IS binoculars (above) are much more compact and half the weight of the higher power 15x50IS model (left) but use the same image stabilisation system. In effect, even if you are pretty steady on your feet, and you brace yourself against a wall, table or whatever, you will find the object you are looking at shakes around so much that you quickly get frustrated with the attempt – it is that hard. But switch on the Image Stabilisation and all of a sudden the images snap into a rock steady condition and you can view in much more comfort. You can pan around and even view from a boat or moving car. In short, Image Stabilisation makes viewing at x15 magnification entirely practical and satisfying. It is even more effective on the smaller x10 binoculars and their much lighter mass means that you can view for much longer before arm fatigue gets you. flat glass connected by flexible bellows which can expand and contract as required. The bellows are filled with a silicone-based oil which has a high refractive index (presumably the same as that of the glass plates). One glass is driven to compensate for pitch movement while the other is driven to compensate for yaw movement. The drive system is a yoke (coil) and magnet system for both X and Y axes with Hall Effect sensors for feedback while the movement sensing is done by accelerometers. While there is a separate vari-angle prism for the left and right eye optical paths, both prisms are linked together and driven by the X and Y axes yoke/magnet systems. We include a cut-away diagram showing the major internal features of the Canon binoculars. Notice that they do include Porro prisms to erect the image but the overall So how do they work? shape of the Canons might suggest that they are using the more compact roof prism construction. Another diagram Broadly speaking, there are two methods of image shows more detail of the image stabilising mechanism, stabilisation. The first is widely used in camcorders and including the yoke and magnet drive systems. involves using only part of the image produced by the CCD By way of explanation, all binoculars (except opera glasssensor. In effect, the internal computer looks for the steady es) require prisms to erect the inverted virtual image for part of the image from the sensor and continually “edits normal viewing. Most out” the shaking borders, conventional binoculeaving a much steadier cenSpecifications lars use Porro prisms tral image to be displayed as 15 x 50 10 x 30 which give a Z-path the video output. Magnification 15 10 to the light beams – The second method, used this accounts for the in these Canon binoculars Objective lens diameter 50mm 30mm big offset between and in some high-priced Real field of view 4.5° 6° the objective lenses telephoto lenses, is to staField of view at 1000m 79m 105m and the eye-pieces. In bilise the image itself by binoculars with roof Focus range 6m to infinity 4m-infinity passing it through a prism prisms, the light travwhich can be continually Exit pupil diameter 3.3mm 3mm els in a straight line moved to compensate for Eye relief 15mm 14.5mm and therefore they the shaking of the binoculars Dimensions 152 x 193 x 81mm 127 x 150 x 70mm are generally more themselves. compact. Canon uses what they call Weight (excl batteries) 1200g 630g The Canon Image a “vari-angle prism” which Battery life (alkaline) 2.5 hours 4 hours Stabilisation are obconsists of two pieces of www.siliconchip.com.au March 2003  77 The drive system for the vari-angle prisms uses yoke coils and magnets to compensate for pitch and yaw of the binocular body. Motion sensing is performed by solid-state accelerometers. viously using a different arrangement of Porro prisms because the two objective lenses are solidly fixed within the binocular body while the two eye-pieces can be rotated to change the inter-ocular distance. The result is that the Canons are quite a bit more compact than conventional roof prism binoculars. Another interesting feature is the inclusion of a doublet field flattener in the eye-piece lenses. This reduces the curvature of the field and avoids the usual distortion at the periphery of the image. It also gives long “eye relief” which means that people with glasses can comfortably use the binoculars. The Canon 15x50IS binoculars are powered by two AA cells which last for up to 2.5 hours continuous use for alkalines or Nicad cells (at 25°C). If you use lithium batteries, this can be extended out to 8 hours continuous use. Alkaline battery life for the smaller 10x30IS model is 4 hours. Using them Referring to the Canon 15x50IS model first, they are comfortable to hold and easy to focus. However, people with small hands will find them difficult to grasp, even though they do have a non-slip rubber skin. And at over 1kg, most users will find that they are tiring to use for more than a few minutes at a time. They do have a tripod socket, so a monopod would be very worthwhile if you need to use them for extended periods. 78  Silicon Chip Since I am interested in astronomy, I was keen to check how they would perform when viewing planets and stars. Unless you have a tripod/chair setup, the common way to use binoculars when viewing the sky is to lie down on the ground or on a reclining chair. But even this method can be very tiring and the star images tend to dance about all over the place after a few minutes. With the Canon 15x50IS, it is a much more satisfying experience. Stars and planets can be held steady and you can easily achieve optimum focus. There is some flare and signs of chromatic aberration on star images but generally this is at a low level; after all, they are not really intended for astronomical use. By contrast with the Canon 15x50IS, the 10x30IS are much more comfortable to grasp and hold, due to their much smaller size and weight (630g). However, with a magnification of x10 and good optics, they are very usable and compare very well with conventional 10x50 binoculars. We like them a lot. Pricing This is great technology but there is no getting away from the fact that these Canon Image Stabilisation binoculars are expensive. The recommended retail price for the 15x50IS model is $2499 including GST while the 10x30IS sells for $1249 including GST. For further information, contact Canon at 1800 816 001 SC or www.canon.com.au www.siliconchip.com.au MORE FUN WITH THE PICAXE – PART 2 A Shop Shop A Shop Door Minder . . . Door Minder . . . Door Minder . . . with attitude! with with attitude! attitude! by Stan Swan L ast month (Feb 2003) we introduced the innovative PICAXE08 IC and a simple application, a flashing LED, all built into a solderless “PICNIK box”. If you didn’t see last month’s issue, it will pay you to get a copy and read it because some of the concepts might be a little different to what you’re used to, such as BASIC Stamps, etc. By now, readers should have familiarised themselves with basic operations and the commands high, low, pause and goto. PICAXE instructions are much the same as used in classic BASIC programming. There are a lot of BASIC texts around (no pun intended!), such as Greg Perry’s “QBASIC by Example” (QUE 1993) or from the Parallax BASIC Stamp Programming Manuals. There’s also a huge amount of information available on the ’net. Given that you don’t need to be a programming guru to use PICAXE instructions, initial applications here will be educational rather than exotic. PICAXEs have only enough RAM for about 40 program lines, so there’s some incentive to code efficiently! Our simple application here uses about half the memory available, so room remains for your own tweaking. buzzer sound long enough to be noticed; sometimes the buzzer “locks on” when it is actuated to behave more like an alarm. This month’s circuit acts as a “shop door minder with attitude”, since it not only sounds a buzzer when the light beam is broken but also provides a simple “traffic” indication by flashing a LED at an increasingly faster rate with each event. Now that could be handy – if you don’t happen to own a shop and wish to count customers, this project could, at a glance, tell you the number of times your cat door is opened! Don’t own a cat? You’ll think of something to count! The flash rate increases are not linear but counts per minute can be noted and related to visitor numbers via a simple lookup table. A further LED could even be added (pin 0?) to indicate a count of 10 had been reached, at which point the main counter could drop back to a slow rate again. By this means, up to perhaps 30 events can be quite reliably “read off ”. If a PC remains attached, the exact count (to 255 events) can be just read off using debug. Mmm – 255 cats visited last night ? What IS in your pantry! The circuit Aside from the core parts mentioned last month, just a few extra resistors are Shop Door Minder A shop door minder usually consists of a light source which creates a beam, a light sensor which detects that beam and a buzzer circuit which sounds when the beam is broken. Sometimes there is a delay circuit to make the www.siliconchip.com.au If you don’t happen to own a shop, you can always find something else to count – just remember to take into account four legs and a tail . . . March 2003  79 A “debug” screen shot. This reveals just how useful such PC feedback is – you can note all the variables ticking away nicely! used, one of which is a light dependent resistor, or LDR. Your setup values may vary depending on your application but 100Ω in the voltage divider, plus similar as a LED dropping resistor, should do. For initial trials a small bright light (perhaps a white LED) is also needed. More practical setups could see the light path extended with lenses, shrouds or even a mirror. Only small currents pass along the wires so leads to the LDR and light can be conveniently placed. Things really depend on the stray background light seen by the LDR, although this can be allowed for to some extent by altering readadc threshold values. For a longer light path the lens from a pocket torch may help to concentrate the beam, while the LDR could even be recessed into the torch If this looks somewhat similar to last month’s project, it just might be! The basic differences are the LED and LDR which provide an “analog” input to the PICAXE. The PICAXE programming does the rest. base to give shading from stray light. The program’s readadc threshold value, initially 160, may need lowering to suit of course. To prevent false triggering from shadows, reflections or visitor legs (or tails!), a small delay, perhaps “pause 500”, may be needed in the readadc loop. Obviously this delay may cause the unit to become unresponsive if events occur too rapidly. Having a light on to hold the alarm off may be wasteful of battery power of course. Perhaps you could modify the program so that darkness holds the sensor off and room light alone is enough to trigger things – much as would occur when a medicine cupboard door was opened. The point of these PICAXE circuits is to stimulate your interest, to see what can be done very cheaply and to help you come up with your own variations. Of course, we will help you along the way with more applications to keep those creative juices flowing! Incidentally, if you come up with a scathingly brilliant PICAXE application that you would like to share with the world (and perhaps feature on these pages), please feel free to email me – s.t.swan<at>massey.ac.nz Where to get the PICAXE-08 Currently there is no Australian distributor. Order direct from the UK agents (Revolution Education) on line shop www.techsupplies.co.uk – they are very prompt. There are a few differences between the photo above and the Protoboard layout at right. Follow the layout and you shouldn’t go wrong! 80  Silicon Chip www.siliconchip.com.au PICAXE-08 COMMANDS USED THIS MONTH readadc PICAXEs have a valuable Analog to Digital Conversion (ADC) feature, which in theory converts “real world” analog voltages into 256 steps of digital equivalents. There’s an unavoidable deadspot on the upper range however and the resulting 160 divisions are treated in blocks of 10, so only 16 discrete values are available! Although obviously unsuitable for MP3 encoding or the like, this is quite enough for many simple applications. In fact our circuit here uses ADC at just a yes/no level in response to an LDR’s (light dependent resistor) resistance changes with illumination, so not even all these 16 divisions matter. Pin 1 ADC input needs a voltage rather than a resistance, so the old voltage divider trick is rustled up, involving two series resistors connected between +ve and ground with their midpoint delivering a variable voltage as the LDR value changes. The readadc command finally assigns this ADC value to a program variable at pin 1. Alter the readadc threshold value or resistor (here 160Ω and 100Ω) to fine tune with your LDR and light path. Incidentally, LDRs typically have a resistance of 1 MΩ + in the dark and around 1 kΩ in bright light, with a quite rapid response as illumination alters. sound With the suggested piezo speaker, sounds can be directly produced from output pins using the sound command. Most piezos are optimised for high frequencies (typically 4kHz) so fidelity may be poor for other tones. It’s worth experimenting with your setup, since a more distinctive “fruity” alert may be produced with two sounds together. debug If the serial programming cable remains connected during PICAXE runs, program data values can be usefully monitored on the PC screen. Up to 16 “byte” variables (b0 - b15) can have tabs kept on them. pulseout This provides timed duration output pulses (to microseconds) at specified pins, and effectively packages up HIGH, PAUSE and LOW in one efficient command . for - next (step) Creates a repeating loop that executes program lines between the FOR and NEXT statements as it increments. The optional STEP value defaults to 1 unless specified. maths operations Variables to a maximum value of 255 (at which point they roll over) can be added, subtracted, multiplied or divided, with left to right solving but with only integer solutions. Hex and binary are also handled but brackets are disallowed and fractional portions of results are discarded (although clever techniques can off set this). BASIC PROGRAM LISTING (This can also be downloaded from http://picaxe.orconhosting.net.nz/adcprog.bas) ‘ Demo program for March 2003 SilChip PICAXE-08 article Ver1.0 20th Jan 2003 ‘ Best assembled & tested with solderless “PICNIK” box as detailed SilChip Feb03 ‘ Refer http://picaxe.orcon.net.nz for background info & potential of PICAXE-08 ‘ Extra parts = LDR, White LED, Red LED, 2 x 100 Ohm, 1 x 330 Ohm, piezo speaker ‘ LDR & illuminating light can be moved apart- maybe use lenses & light guides? ‘ New commands here = sound, readadc, debug, pulsout, for-next & simple maths. ‘ Ref.PICAXE prog.editor .pdf help files,& BASIC Stamp manuals etc for insights ‘ via Stan SWAN (MU<at>W, New Zealand) => s.t.swan<at>massey.ac.nz <= ‘—————————————————————————————————— ‘ Byte variables b0 = LDR “resistance value” b1 = event counter ‘ b2 = pulse delay in msec b3 = sound loop ‘ Strictly only the LHS code below is needed. Remarks (‘) can be ignored ‘—————————————————————————————————— sound 4,(100,10,80,10) ‘initial dual sounds to inform that powered up ldrdemo: readadc 1,b0 debug b0 if b0 <160 then beeper b2 = 250/b1 if b2 =0 then ldrdemo pulsout 2,1000 pause b2:pause b2:pause b2 goto ldrdemo ‘ LDR resistance monitoring routine ‘ read LDR low resolution value via voltage divider ‘ show variable LDR value(s) to attached PC screen ‘ warbling alert tones when LDR shaded ‘ produce delay value.NB max variable value is 255 ‘ prevents LED flash when not yet triggered ‘ pulse LED pin 2 for 1000x10 microsec = 10millisec ‘ more events give decreasing delay between pulses ‘ continually loop unless LDR shaded beeper: for b3= 1 to 3 sound 4,(100,20,80,20) next b3 b1=b1+1 goto ldrdemo ‘ piezo speaker 2 tone sound routine ‘ loop to sound tones 3 times ‘ repeating dual tones each 20 msec ‘ sound loop increment ‘ event counter increment ‘ return to monitoring routine www.siliconchip.com.au Some more references . . . 1. “QBASIC by Example” Greg M Perry (Que Books 1993) 2. Parallax Inc, the BASIC Stamp originators, have free resource downloads (.PDF files) via their web site (www.parallax.com) BASIC Stamp Users Programming Manual Version 2. (351 pages, 3.2MB download) BASIC Stamp 1 Application Notes Ver 1.9 (126 pages, 1MB download). 3. “The Art of Electronics” Horowitz and Hill (Cambridge University Press 1989). Chapter 9 offers good ADC insights. NEXT MONTH: The Picaxe by now you should know, Gives sounds & makes LEDs glow, But it also does more, Next ’tis a PWM chore, And all for very small dough! SC March 2003  81 SuperCharger Addendum Did you build the SuperCharger described in the November & December 2002 issues of SILICON CHIP? If so, you need this add-on to ensure correct operation under all conditions. By PETER SMITH During finalisation of the firmware for this project, we were surprised to discover that under certain conditions, the 111kHz PWM section of the circuit became unstable. In fact, with high cell counts, high charge currents and low input voltages, such as could be the case in an automotive environment, the switching frequency halved to about 50kHz. When low cell counts (1-2 cells) and low charge currents are combined, a lower operating frequency is of no consequence. However, at high power levels, it will cause inductor L1 to overheat and damage the PC board and surrounding components. It may also eventually cause MOSFET Q2 to fail. Quite frankly, this problem initially had us stumped. The data sheets for the LTC1325 suggest that our design operates within specifications. In addition, the LTC1325 has no provision for external compensation, which is often employed in switchmode circuits to maintain loop stability. After much head scratching, we devised a simple little circuit that modifies the feedback signal applied to pin 11 of the LTC1325. The purpose of the circuit is to both provide ramp compensation as well as to alter the shape of the waveform applied to this pin, so ensuring that the internal integrator is “reset” every cycle. As this project includes a number of surface-mounted components, it would be very difficult for readers that have already built the project to transfer these to another, modified PC board. Therefore, rather than modifying the main PC board layout, we have designed a small “add-on” board that carries the necessary components. Construction & checking The add-on PC board simply attaches to one of the existing corner mounting points (see Fig.4) and connects to the main PC board via four wires. The overlay diagram for the add-on board is shown in Fig.2 and the wiring diagram in Fig.3. Fig.1: the add-on circuit uses just two transistors plus a few resistors and capacitors. Its job is to modify the sense signal to the LTC1325 IC. 82  Silicon Chip SuperCharger Add-on Parts List 1 PC board coded 14111024, 31.2mm x 16.1mm 2 2N3904 transistors (Q1, Q2) Capacitors 1 1µF 50V monolithic ceramic (C1) 1 100nF (0.1µF) 63V MKT polyester (C3) 1 1nF (.001µF) 63V MKT polyester (C2) Resistors (0.25W 1%) 1 15kΩ (R3) 1 10kΩ (R2) 1 470Ω (R4) 1 100Ω (R5) 1 10Ω (R1) Miscellaneous 1 M3 x 10mm tapped spacer 1 M3 x 16mm pan head screw 70mm 4-way ribbon cable Fig.2: the extra parts all fit on this small PC board. www.siliconchip.com.au Fig.3: four leads stripped from a length of ribbon cable are used to connect the add-on board to the main PC board of the SuperCharger. The four connection points should be present on all manufactured boards. If you have access to an oscilloscope, you can check that the addon board is doing its job. Ideally, you should run your tests with six 1800mAh NiMH (or 1200mAh or higher NiCd) cells on the rapid charge setting. If you’re providing power via the DC input, be sure that the supply voltage doesn’t dip below 13.8V, otherwise the charge will terminate with error code 11. Start the charge and measure the switching frequency on the drain of MOSFET Q2; it should be about 100kHz. Continue to monitor the frequency as the cell voltage rises and the charge nears completion; the frequency should always be around the 100kHz mark. Note that switching is not continuous for the first five minutes of operation, as the charger is in “Soft Start” mode. You’ll also note than switching occurs in one-second bursts with short (about 50ms) rest periods; this is completely normal. We should also point out that inductor L1 normally runs quite hot to the touch, even at 100kHz. It is rated for a 40°C temperature rise above ambient and at higher power levels will get close to this value. Ventilation Although we didn’t make mention www.siliconchip.com.au Subscribe & Get This FREE!* Fig.4: the add-on board is mounted at one end of the main PC board as shown in this diagram. of it in the original construction details, one of the reasons we chose the specified case is because it has generous ventilation slots. If you decide to use a case other than the one shown in the parts list, then you’ll almost certainly need to add some ventilation holes. In particular, drill several holes directly below the inductor (L1) and the diode bridge (DB1). Match these with more holes on or near the top of the case to make the most of the “chimney” effect. Rubber feet Regardless of which case you use, be sure to fit rubber feet on the underside to allow air to flow up through the SC assembly. *Australia only. Offer valid only while stocks last. THAT’S RIGHT! Buy a 1- or 2-year subscription to SILICON CHIP magazine and we’ll mail you a free copy of “Electronics TestBench”, just to say thanks. Contact: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097 Phone Orders: (02) 9979 5644 Fax Orders: (02) 9979 6503 Email Orders: office<at>silchip.com.au March 2003  83 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG Antennas & earthing systems for crystal sets Crystal sets and other low-sensitivity receivers require good aerial and earth systems to give their best performance. Here’s what you can do to improve broadcast band AM radio recep­tion on these simple receivers. Due to the improved sensitivity of receivers after the mid-1930s and the increasing power of AM broadcast transmitters, large antennas quickly become redundant as far as the general public was concerned. In fact, most people now don’t like having to extend the whip antenna on a portable FM receiver to get the best reception. Unfortunately, the use of metallic/ bituminous insulation paper in the walls of many modern homes now acts as an RF shield, reducing the level of the radio signal penetration. For this reason, good reception on older, less-sensitive receivers may require an outside antenna and this is particularly so for crystal sets. In the November 1998, December 1998 and January 1999 is­ sues, we looked at various methods for improving AM radio recep­tion and reducing interference. This article is not intended to supersede those articles but to give enthusiasts a few ideas on suitable antenna systems that will achieve good results in most situations. The early days Experimental broadcasting commenced not long after the end of World War I. Amateurs produced programs on a nightly or weekly basis and the general populace was keen to listen to these new transmissions. The output power of these early experimental stations varied considerably but most were well under 100 watts. The radiating systems connected to the transmitters were also quite varied, some consisting simply of an inverted “L” receiving type antenna fed against an earth that consisted of a metre or so of pipe driven into damp soil. Others were more ostentatious, being something like the smaller broadcasting masts that can be seen around the countryside today. Official broadcasting commenced in Australia in late 1923 (2SB/2BL) and the power of the stations varied from around 50W to 5kW (5000 watts). In most cases, the power ratings were for input power, not output power, so a 5kW transmitter may have had an output power of just 1.5kW. Fig.1: the earth stake or pipe should be driven a metre or so into the ground, with a small depression around the top. This depression is filled with water at regular intervals, to keep the soil around the earth stake moist. Fig.2 (right) shows how to install an effective earth through concrete. 84  Silicon Chip www.siliconchip.com.au “Egg” insulators will be required at the support points if you use bare wire for the antenna. Alternatively, you can use polyproylene pipe. and earth system for low sensitivity receivers such as crystal sets. Getting a good earth Fig.3: a “clothesline” type aerial frame can be used in back yards where space is a problem. It’s not as effective as a long, straight run of wire but is still quite good. Gradually the standards for broadcast transmitting stations became more uniform. The commercial class B stations that came into being were rated at an output of 2kW in the country and 5kW watts in the city, whilst Class A (ABC) stations used upwards of 10kW (today, the ABC stations run upwards of 50kW in many in­stances.) At the same time, strategically placed low-power sta­tions (50-500W) were used to provide signals in areas where the high power stations were relatively ineffective (such stations are still used today). Because of the low power of early transmitting stations and the general insensitivity of receivers up until the mid-1930s, large outside antennas were mandatory for reasonable reception during that period. Many different antenna types were used in an attempt to get the best performance possible. Some were a lot of work to install but may not have worked any better than much simpler structures. But they did look commanding! A receiver using a large earth (mat) system (much like transmitting installations use) will work a little better than a receiver using the common, relatively inefficient receiver earths. In practice, transmitting stations go www.siliconchip.com.au for the most effi­ cient antenna and earth system that is economically feasible. That’s because they need to provide the strongest signal possible for receivers that are using inefficient antenna systems, eg, a few metres of wire. The reasoning here is that it is better to have efficient transmitting installations so that receivers can get by with convenient low-cost antenna systems. Having said that, it is still necessary to use a relatively efficient antenna The earth lead can be attached to the pipe using a metal hose clamp. Wrap the wire around the clamp several times to ensure it makes good contact. In an ideal situation, a 1-metre length of pipe or metal stake driven into the ground in a damp location will provide an adequate earth for most receivers. This earth should be as close as practical to the receiver so that the minimum length of con­ necting wire is used back to the earth terminal of the receiver. This also helps to reduce the effect of mainsborne interference, particularly in more sensitive receivers. In my case, I have often used 19mm galvanised water pipes as the earth stake. However, because I am an amateur radio opera­tor, I need a better earth than a 1-metre length of pipe can provide. For this reason, I commonly use up to three 2-metre lengths of pipe driven into the ground, leaving about 300mm above ground level. The tops of the pipes/stakes are quite close and are bonded together but their bottom ends are quite some distance apart, as the pipes are driven into the ground at angles to each other. In order for the earth to be effective, the whole length of the pipe/stake and the earth around it needs to be kept moist (not just the top few centimetres of the soil). This is achieved by making a small depression around the top of the pipe(s) and a bucket of water then poured into this depression at regular intervals. A single pipe driven at least a metre into the ground is usually quite adequate as an earth for radio receivers (providing it is in moist ground). Fig.1 shows the details. The wire (preferably multi-strand) March 2003  85 This simple antenna tuner uses a multi-tapped coil wound on a cylindrical former. It’s tuned by sliding the ferrite rod inside the former and by changing the coil tapping. Fig.4: this diagram shows how to add a dial drive system to the antenna tuner shown in the photo at the top of this page. You can scrounge the parts from a junk radio or buy them from an electronics retailer. going from the earth to the receiver earth terminal should be 1-2.5mm2 in cross-sectional area (equivalent to the average earth wire on the mains). It doesn’t have to be insulated but insulated wire is easier to handle if it is likely to be close to any other metal, including the Sisalation type material used in the walls of modern homes. Don’t let a bare wire brush up against any metallic object as noise and “crackles” (interference) may be induced into the wire and thus into the receiver. Unfortunately, it’s not practical to solder the end of the wire directly to the earth stake or pipe. That’s because the metal mass is too great to allow it to get to the melting point of solder when using a soldering iron that’s suitable for elec­tronic work. Instead, an electrician’s earth clamp or a screw type hose clamp can be used to hold the earth wire firmly against the pipe. The wire should be wrapped through the clamp a few 86  Silicon Chip times to make sure it will not move once clamped. Before doing this though, clean the pipe using sandpaper to get rid of any oxidation at the contact point. Once the earth wire has been clamped to the pipe, the assembly should be painted to stop any corrosion. Alternative methods Not everyone has an ideal location to install earth stakes and so other methods of obtaining an earth must be used. For example, many premises today have large areas of concrete which this can make things quite difficult. Drilling a hole through the concrete to accept an earth pipe is one possibility but make sure that you check the loca­tions of water, drainage, gas, telephone and electrical lines before doing this. You will need a large masonry bit and a hammer drill for the job. Begin by drilling a series of holes around the circumfer­ence of a circle large enough to accept a 100mm-diameter plastic stormpipe. A cold chisel and heavy hammer will be required to break up the pieces but even so, it usually isn’t easy getting the pieces out. In fact, it’s probably a good idea to send the family out for the day so that they don’t learn any new words! The storm piping should protrude about 200mm above the ground and can be fixed into position using cement or silicone sealant. This stormpipe is then filled with water to keep the earth pipe moist - see Fig.2. If metal water pipes are used, it’s possible to clamp the earth wire onto these and obtain quite good earthing. However, earthing to a water pipe does raise the possibility of circulat­ing currents through the pipe system and anything connected to the mains earth. To overcome any chance of electrolysis (which can cause corrosion of the pipes), it’s a good idea to install a capacitor in series with the earth wire near the radio. This can range in value from .001µF up to 0.1µF - preferably one of each in paral­lel. Note that this is necessary only if the receiver is mains operated and has its chassis earthed through the mains. Gas pipes are not to be used under any circumstances. For people in units, an earth via the mains may be the only viable alternative. Any piece of electrical equipment that has a 3-core power lead and has its metal frame earthed can be used as the “earth”. All you have to do is attach a wire from the metal frame of the earthed appliance to the earth terminal of the set. This provides a reasonable earth but make sure the ap­pliance has a relatively short lead to the power point. Do not attempt to obtain a mains earth in any other way - the possibility of making a fatal mistake is much too great. A good antenna The old saying of “the higher and longer the better” when referring to antennas for crystal sets and other low-performance sets is still true today. If you live out on a farm, erecting an effective antenna is relatively easy. A good standby is the old standard www.siliconchip.com.au Looking for an old valve? or a new valve? BUYING - SELLING - TRADING Australasia’s biggest selection Also valve audio & guitar amp. books SSAE DL size for CATALOGUE ELECTRONIC VALVE & TUBE COMPANY PO Box 487 Drysdale, Victoria 3222. Tel: (03) 5257 2297; Fax: (03) 5257 1773 Mob: 0417 143 167; Email: evatco<at>mira.net Premises at: 76 Bluff Road, St Leonards, Vic 3223 www.evatco.com.au Provided it’s fitted with a good aerial and earth, this simple “two circuit” crystal set is quite a good performer. inverted “L” antenna some 30 metres long across the top and 13 metres high. “Higher and longer” will capture even more signal and possibly also lightning, so lightning arresters are desirable on antennas of this size. Most of us do not have the wide open spaces to install this type of broadcast receiving antenna so we have do the best we can with the available space. It’s also necessary to comply with local council bylaws. In most cases, any antenna that’s erected will be a compro­mise between performance and available space. The installation must also be safe and must not be an eyesore to neighbours or others living on the premises. It is possible to run an antenna (flat top section) around the yard, with one end attached to the chimney (if the house has one) or to a TV antenna mast – see Fig.3. Specialist TV antenna supply shops, such as Lacey’s Australwww.siliconchip.com.au ia in Frankston, Victoria, have a wide variety of TV antenna mounting masts, brackets and other items which can be used for this job. A number of the advertisers in SILICON CHIP, such as Jay­ car, Dick Smith Electronics and Altronics, also have a range of TV-antenna bits and pieces. Check out their catalogs and you should have little difficulty in choosing the necessary parts to make your antenna effective, safe and aesthetically pleasing. Commonly, in the past where there was little space for an antenna, it was made to look something like a clothes line, as shown in Fig.3. This is an effective way of getting a consider­able length of wire up into the air in a confined space. It may not be as effective as a long, straight run of wire but it is still quite good. Regrettably, some people are not allowed to have any outside antenna KALEX PCB Makers! • High Speed PCB Drills • 3M Scotchmark Laser Labels • PCB Material – Negative or Positive Acting • Light Boxes – Single or Double Sided; Large or Small • Etching Tanks – Bubble • Electronic Components and Equipment for TAFEs, Colleges and Schools • Prompt Delivery We now stock Hawera Carbide Tool Bits 718 High Street Rd, Glen Waverley 3150 Ph (03) 9802 0788 FAX (03) 9802 0700 ALL MAJOR CREDIT CARDS ACCEPTED March 2003  87 Above: this miniature 2-circuit crystal set uses all ferritecored coils and is quite a good performer. Its circuit is shown in Fig.5, for those who want to make their own. At left is an old ferrite-cored tuned circuit crystal set, complete with wooden case and a set of high-impedance headphones. system at all (perhaps for “aesthetic” reasons). However, all is not lost as outside antenna systems can be erected at night by suitable mechanisms and pulled down after use. Some people have even disguised an antenna mast as a flag pole. A little ingenuity is sometimes needed here. If that doesn’t suit, an antenna in the ceiling space can be much better than nothing at all. There are a few provisos, however – the house must have a gable roof and the roofing must not be metallic. Nor should there be any metallic foil underneath the tiles (metal acts as a shield for radio signals). To build a ceiling space antenna, install several folded lengths of insulated wire near the peak of the roof and bring one end down to where the receiver is located. Thirty metres of wire should give reasonable performance. It cer- tainly won’t be up to the standard of a high outside antenna but it’s much better than nothing. Antenna wire An outside antenna lead can be made from single or multi-strand copper or galvanised iron wire. It can be insulated or bare but it must not too thin, otherwise it will break in the wind or if a bird flies into it. I use common gardening tie wire (available at hardware stores) of around 16 gauge – it’s cheap and solders quite well. If you use bare wire, it is necessary to also use egg insu­lators (available from stores selling electric fence components and major electronic stores) at the points where it is supported,. Alternatively, the polyproylene pipe used for garden­ ing systems can be used in some situations. The down lead to the receiver from Fig.5: this simple “2-circuit” crystal set uses coils wound on ferrite rods. The constructional details are in the text. 88  Silicon Chip the antenna should be run using insulated multi-strand cable, such as one half of twin-flex cable used on small electrical appliances. Any joins in the antenna wire must be soldered. If they are not soldered, scratchy noises will be heard in the radio or variations in level will occur after only a few weeks. That’s because the wires oxidise and intermittent good and bad contact between the joined wires will occur. Finally, to alleviate any stress on the lead in, it should be attached to the antenna proper in a manner similar to that shown in one of the photos. Optimising performance A normal AM broadcast antenna is an aperiodic device, mean­ing that it is not tuned to any particular frequency. By con­trast, if it were tuned to a specific frequency, the amount of signal picked up by the antenna would rise noticeably. In other words, tuning the antenna system can greatly im­prove its performance and this can be done quite easily. Fig.4 shows the details. First, obtain 150mm of 20mm-diameter PVC electrical conduit and wind about 180 turns of 0.5mm (24B&S) enamelled copper wire onto it, with tappings made at every 20 turns. The tappings can be made by inserting a match under a turn, winding some more turns on and then sliding the match further along as you progress, keeping each tapping point proud of the coil. www.siliconchip.com.au One end of the finished coil is then wired in series with the antenna lead, while a “fly lead” fitted with a small alliga­tor clip is soldered to the other end. This fly lead allows sections of the coil to be shorted out if necessary. Alternatively, either the antenna or the receiver aerial lead can be terminated on one of the terminals along the coils, as shown in one of the photographs. Once the coil is in place, it is then time to trial the tuner by sliding a 180mm-long (not critical) x 9mm-diameter ferrite rod into the coil and observing the results. Try differ­ ent coil tappings until you get the nest performance. Once the correct tapping is found for the coil, altering the position of the ferrite rod in the coil will peak the perfor­ mance on any particular station. Note that this coil will also work with the average domestic receiver, although its performance at the low-frequency end of the dial can be unpredictable due to the way some aerial coils were designed. More turns may be re­quired on the peaking coil in some cases. Initially, the rough and ready method described above will give good results. However, it can all be made much tidier. Excess turns on the coil can be removed if desired and a more sophisticated method of adjusting the position of the ferrite rod inside the coil can be constructed – see Fig.4. Jaycar Electronics can supply suitable ferrite rods (Cat. LF-1012) for an antenna tuner but loopstick antenna rods scrounged from defunct sets are also quite suitable - just remove the windings from the rod. If the rod has been broken and you have all the pieces, it is often possible to effectively rejoin them provided the breaks are clean and the two sides of a break mate without gaps. You can use Aral­ dite or some other similar adhesive for this job. Crystals sets & antenna tuners On my own crystal sets, I can receive just one station without the antenna tuner. By contrast, if the antenna tuner is used, I can receive four stations, including a Melbourne station some 150km away! The tuning is also much sharper than normal and the aerial tapping is quite low on the coil. Initially, however, I found that the www.siliconchip.com.au Photo Gallery: Tecnico Aristocrat Model 651 Radio Built in 1946, the Tecnico Aristocrat featured a distinctive “mottled” bakelite cabinet. This cabinet was completely different to those used by other manufacturers, some of which were still using cabinets from their pre-war models. The set pictured here is a 5-valve dual-wave radio with a 20cm (8-inch) permanent magnet speaker (loudspeakers of this size were rarely seen in mantel or table radio). A colourful badge and dial glass complete the attractive presentation. The set was advertised as being available in various colours and Tecnico achieved this by painting over the bakelite. This particular unit has been fully restored by its owner, Maxwell Johnson, Kingston, Tasmania. (Photo: Ross Johnson). crystal sets were not performing at all well, barely receiving the local station just 20km away. I tested the germanium diodes using the diode tester function on my digital multimeter and found that the forward voltage drop had increased from 0.2V to 0.8V, while the reverse voltage conduction point was down to 3V. The diodes were con­signed to the rubbish bin and new ones installed. The crystal sets in the photos belong to members of the local vintage radio club. Two are very nice looking sets and perform quite well. The small one in the jiffy box (130 x 65 x 40mm) is extremely interesting as it uses ferrite cores on all coils and a tapped antenna loading coil (possibly to resonate the antenna). I have not heard this latter set in operation but have heard others claim that it is a particularly good performer. As a result, its circuit is enclosed for readers who may care to experiment - see Fig.5. All the coils are wound using 0.5mm (approx.) enamelled copper wire. L1 and L2 are wound on the same piece of ferrite rod but at opposite ends of the rod which is around 50mm long. Coils L3 and L4 are wound on two ferrite rods, each around 30mm long. The amount of coupling between L2 and L3/L4 is open to experimentation – around 50mm apart should give good results. Summary A high and long antenna coupled with a good earth system is important if worthwhile results are to be obtained from crystal sets and other low-performance sets. In some cases, it may also be necessary to tune the antenna to the frequency of the desired radio station (ie, by using an antenna tuner). As for crystal sets, the best performing types are those using two tuned circuits – as in Fig.5. Also, it’s necessary to use a germanium diode for the detector and a pair of high-impedance SC (2-4kΩ) headphones. March 2003  89 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097; or send an email to silchip<at>siliconchip.com.au Upgrading the SC480 amplifier doubt whether there would be any improvement. With respect to your new SC480 amplifier modules, how can these be connected together or modified to produce 100W. Also, would there be any sound quality advantage in changing the 1µF bipolar input series capacitor to a metallised polypropylene type, as used in crossovers? (P. R., St Lucia, Qld). • We actually went through the same process way back in February 1988 when we upgraded our original December 1987 design. The process basically involves increasing the main supply rails to ±50V, changing the output transistors to MJ15003/MJ­15004 (TO-3 types), Q1Q3 to BC556, Q4 & Q5 to BF469 and Q6 to BF470 and increasing the power supply capacitor values and voltage ratings to 63V. Naturally a much bigger transformer is also required. We think a better and more cost-effective approach would be to build the Plastic Power amplifier from the April 1996 issue. We can supply the issue for $8.80 including postage. You could change the input capacitor to an MKT type but we very much Reproducing old wireless sound Tacho fix for positive chassis car I’ve recently built the Digital Tacho from the April 2000 issue and have successfully connected it to my 1988 Ford Laser in which it appears to work exactly as described. My problem is that I actually want to connect it to my 1956 Austin A30 which has a positive chassis. When I connect the coil to the tachometer, the numbers displayed are wrong. At idle it shows ‘000’ when it is clearly doing about 1000 RPM. The numbers do increase with engine revs but don’t appear to be 90  Silicon Chip I am a member of an amateur theatre company and we are planning to stage a comedy “Lend me a Tenor”, set in Chicago in 1934. There are three or four occasions where the performer is supposed to be listening to the radio, to works by Giuseppe Verdi. For effect, I’d like to try to approximate the type of reception people may have experienced at that time. I don’t want the audience to ‘hear’ excerpts from Verdi’s operas via a CD and a late 1990’s full-range, 500W public address system in the theatre – that would be too much of an anachronism. Clearly the radio systems were AM (ie, limited bandwidth and noisy). In addition to this, receivers were low-powered but with (relatively) efficient loudspeakers. The efficiency came at a cost, though – that of frequency response. What would the frequency response of the recovered audio have been like? What sort of signal-to-noise ratio might have been expected? I have some ideas stable (that is, they go up and down by several hundred while the engine is at a constant speed). Do I need to do something clever to make this tachometer work correctly with this car? The documentation makes no mention of cars with a positive earth but I can’t imagine that I’m the first person to try this kit with that type of car. (R. S., via email). • We do not think that the positive chassis is causing the erratic display reading. Try changing the 0.056µF capacitor at the ignition coil input to something smaller; 0.022µF (22nF) may be small enough for correct operation. about the answers to these questions but am seeking your expert opinion. I plan to record the relevant tracks, modify the ‘system’ frequency response to something similar to that you nominate and add appropriate amounts of both white and impulse noise. Hopeful­ly the end product will have a big degree of realism. (R. W., via email). • Your question is quite complex. In reality, the AM broadcast system was, and still is, capable of very good results. Today, with the very best receivers, you can get a result which is practically indistinguishable (for most listeners) from FM stereo. In years past, the main limitations were the radio re­ceivers but even the best of those could sound quite good. In reality, the frequency response from a good console radio (wire­less!) could be up to 5kHz while the signal-tonoise ratio would be around 40-50dB or thereabouts. A good portion of the back­ground noise would be hum. If you can get to a radio museum, have a listen for yourself. However, there were other limitations on the sound quality. If it was a live broadcast you need to imitate the effects of the microphones and their placement (they did not have multiple microphones and multi-channel mixers). Some of the old style microphones are still available and sort after by groups who want to produce that “sound”. If the performance was recorded it would generally have been on 16-inch 78RPM transcription discs and these also had a sound all their own because the magnetic pickups of the day had quite a lumpy frequency response and recording equalisa­tions were not standardised. The old turntables also suffered from wow and flutter and there was considerable surface noise, clicks and pops, etc. To do what you ask and keep things simple, we would be inclined just to limit the frequency response to no more than 5kHz and just see what it www.siliconchip.com.au sounds like. The illusion would be helped by having the listener actually switch on a radio. You could also take it further and have the sound broadcast via an AM transmitter and then mike the sound from the radio (oops, we mean wireless!) We described a low power AM transmitter in the January 1993 issue of SILICON CHIP. Compatibility between DVD players and TVs We have a Philips 26CE1991 tele­ vision which when connected directly to the DVD player pulsates its picture light and dark. The DVD player has been checked by two service centres and seems to be OK. Philips tell me that this TV is too old and we should simply buy a new one. Are there any mods that are known to overcome this problem or are we stuck with the Macro­vision pro­tection breaking through? (E. G., via email). • Our information is that this set was made in 1991 by Sampo for Philips and was designed before Macrovision. It is there­fore unable to cope with large chunks of signal being removed. The only real cure is to build the Doctor Video kit from the April 2001 issue of SILICON CHIP. This copes well with Macro­vision 1 & 2 but not Macrovision 3. Otherwise, the only solution is to buy a new set. Upgrading the 24V/20A speed control I recently assembled the 10A Motor Speed Control from the June 1997 issue of SILICON CHIP. I did it to teach myself more about DC motor control, as I have started working in the electric forklift servicing field. I increased the controller’s capacity to 20A by installing the second Mosfet, as suggested in the kit instructions. I would like to know how to modify the kit to handle the much higher currents found in DC electric machines, from a hundred and possibly up to 1000A and also to handle higher voltages such as 24V and 48V. Would it simply be a matter of continuing to add Mosfets in parallel or would the circuit driving the Mosfets need to be upgraded as well. Also the instructions said the controller could be used to run 12V motors www.siliconchip.com.au How to control radiator cooling fans I’m intending to use one of your temperature switch kits to control a pair of cooling fans which I want to fit to an old car of mine. My ig-norance of thermocouples prompts me to seek advice from you before I embark on this project. Jaycar’s advert and photograph shows an already constructed kit which is supplied with an NTC thermocouple which, by observation of the picture, is the small component on one corner of the board looking like a tag tantalum capacitor. Would it be possible to use a wire type “K” thermocouple as I reckon it would need to be able to sense the temperature of the engine cooling water direct. I think I could in 24V systems. Could it be used to run 24V com­ponents in 48V machines? (P. R., Jerrambombera, NSW). • While in theory, the specified Mosfets could run with supply voltages up to 48V, it would not be good practice. We would prefer to see much more rugged Mosfets used, with much higher voltage ratings. Running at much higher currents is also possible in theory but in practice, the very small PC board would mean that the extra Mosfets would have to be off-board and that can lead to problems; you need individual gate drive to each Mosfet and heavy conductors for the commoned Drain and Source connections. In addition to the above, the 12V regulator feeding the TL494 has an absolute maximum input voltage of 35V, so you would need to add a pre-regulator circuit to ensure that this rating was not exceeded, if you wanted to run the whole circuit at 48V. In summary, the practical limit of the circuit is 24V and not a lot more than 20A. 24V needed for Mustang A/C I am working on the air-conditioning for an old Ford Mus­tang and I need a 12V-24V step-up inverter to operate the clutch solenoid. Can you tell me if there is one available or if you have encase the business end of one of these in a metal device to protect it from getting wet and then the casing complete with protected thermocouple could be installed for immersion in the cooling water. Is all that practical and if so, would I need to make any alterations? (P. W., via email). • The kit you refer to has not been published in SILICON CHIP. The fact that it uses a thermistor means that it will not have the necessary high gain circuitry to work with a thermocou­ple. In fact, we would not recommend this kit for control of fans in a car. We would suggest you consider the thermostatic switch for car radiator fans published in March 1992. We can supply this issue for $8.80 including postage. described a suitable circuit? (K. W., Nevertire, NSW). • The only 12V-24V inverter that we know of is a small one from Jaycar (Cat AA-0264). This is said to double the input voltage (from 6V to 12V or 12V to 24V) and has a maximum output current of 2A; we assume this is at 12V out. This may not be enough to pull in the solenoid but should be enough to maintain it in the closed position once it has operated. You may need to connect a large electrolytic capacitor across the output to provide the pullin current. We suggest you try a value of at least 10,000µF at 25V or higher. Delay for Battery Guardian I have a quick comment/observation about the Battery Guard­ ian published in the May 2002 issue of SILICON CHIP. I like the solid state and low current draw but I am having problems with it dropping out on start-up, particularly if the load is more than 10A or so. Would it be possible to delay the voltage sensing for about five seconds so that it does not detect the initial load droop? (J. H., via email). • The solution is to increase the 10µF capacitor asso­ciated with ZD2 to 100µF. This will filter out the voltage droop when a 10A load is applied. March 2003  91 Hang problem with mixture meter I recently purchased and built the Digital Fuel Mixture Meter, as published in the September & October 2000 issues. It has a problem in which at power-up, it will sit for a few minutes, reading (L) for low and no matter what input level you put into it (0-1V), it will hang. This problem often goes after two minutes but may remain in a hang state for longer. It is not yet in a vehicle and is being fed constant 13.5V and a constant input at 0.5V. (F. N., via email). • This is indeed an unusual problem. It is possibly caused by pin 4 of Zero voltage switch for wall oven Some 15 years ago I redesigned our kitchen wall oven to something akin to ‘burst firing’ electronic control of the heat­ing elements. I used a combination of an Analog Devices AD595 Ther­ mocouple Amplifier with a ramp-driven 14-pin CA3059 zero voltage switch IC to control a suitably-sized Triac. It has proved to be accurate to ±1° and quite reliable. Recently though, the CA3059 failed and I have not been able to locate a replacement. Harris and then OnSemi manufactured them but discontinued about a year ago. I was wondering if you could help with the name of a supplier. (J. N., Tauranga, NZ). • We do not know of a substitute for a CA3059 but if you want a zero voltage switching power control circuit, have a look at the Heat Controller published in the July 1998 issue. This used the IC1 being open circuit, either within the IC socket or where soldered to the PC board. Alternatively, the crystal may be a slow starter, causing the software to latch up as it will not be reset properly. Try using smaller value capacitors from the crystal to ground at pins 15 and 16. Values ranging from 10pF to 15pF should be suitable. The other problem could be with the power supply you are using. If this supply rises slowly to 12V at switch-on, the circuit could exhibit the problem you experience. Try connecting the circuit to the power supply terminals after it is powered up. 1988 and October/November 1998. We can supply the 1998 back issues for $8.80 each, including postage and the 1988 articles as photo­stats, again for $8.80 each, including postage. Braking system for a wheelchair readily available MOC3041 zero voltage switching Triac optocoupler. We can supply the July 1998 issue for $10 including airmail postage. I am a Year 12 student starting my Major Design Project. My project is a wheeled walker for the disabled. My current need is for a braking system and an easier way of going about it. I want to create a one-off braking system using electronics and two motors with a simple on/off sequence and a button on each handle to easily apply the brakes. What do you suggest? (D. G., via email). • We suggest you build a speed control with inbuilt braking. Have a look at the 50A speed control published in the May 2000 issue. We can supply this issue for $8.80, including postage. Audio frequency power meter wanted Notes & Errata I am in need of an audio frequency power meter. I’m think­ing of something that reads in dB and mV and takes an electrical input (rather than including a microphone). It needs to be accu­rate across the audio spectrum. While the option of a microphone input would be nice, this is a considerably harder proposition, since the characteristics of the microphone would have to be compensated for and accurate calibration would probably require specialist equipment. (A. M., via email). • We have published two AC milli­ voltmeters which would suit your application, in August/September RIAA Preamplifier, March 2002: the 10µF across the ±15V rails should be 35V not 16V. Smart Card PIC Programmer Interface, February 2003: the clock connection from the card socket should go to pin 12 of the 18-pin socket, not pin 16. PortaPAL Portable PA Amplifier, February and March 2003: there is a circuit error concerning both the microphone MIC1 and MIC2 inputs. The circuit shows two 10kΩ resistors in parallel connecting from pin 2 to ground whereas one of these resistors should connect to pin 3 instead. The SC PC board is correct. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 92  Silicon Chip www.siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $20.00 (incl. GST) for up to 20 words plus 66 cents for each additional word. Display ads: $33.00 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ www.siliconchip.com.au FOR SALE WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Eco Watch phone: (03) 9761 7040; fax: (03) 9761 7050; Unit 5, 17 Southfork Drive, Kilsyth, Vic. 3137. ABN 63 006 399 480. UNIVERSAL DEVICE PROGRAMMER: Low cost, high performance, 48-pin, works in DOS or Windows incl. NT/2000. $1364. Universal EPROM programmer $467.50. Also adaptors, (E)EPROM, PIC, 8051 programmers, EPROM simulator and eraser. Dunfield C Compilers: Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $198 each. Demo disk available. ImageCraft C Compilers: 32-bit Windows IDE and compiler. For AVR, 68HC­ 08, 68HC11, 68HC12, 68HC16. $385.00 Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x, 89Sxx in both DIP and PLCC44 and some AVR’s, most 8-pin EEPROMS. Includes socket for serial ISP cable. $220, $11 p&p. SOIC adaptors: 20 pin $132.00, 14 pin $126.50, 8 pin $121.00. Full details on web site. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. (02) 9896 7150 or http://www.grantronics.com.au SPEAKER AND HOME THEATRE SUPPLIES. New and Secondhand Speaker Drivers. Speaker Repairs and Kits. Projectors and Screens. Delivery anywhere in Australia. Melb. (03) 5986 1128; www.penhometheatre.com.au KITS KITS AND MORE KITS! Check ’em out at www.ozitronics.com March 2003  93 Silicon Chip Binders New New New Mark22-SM Slimline Mini FM R/C Receiver REAL VALUE AT $12.95 PLUS P&P These binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf.  80mm internal width • • • • • 6 Channels 10kHz frequency separation Size: 55 x 23 x 20mm Weight: 25gm Modular Construction Price: $A129.50 with crystal Electronics PO Box 580, Riverwood, NSW 2210. Ph/Fax (02) 9533 3517 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard ❏ Visa   ❏ Mastercard Card No: _________________________________ Card Expiry Date ____/____ Signature ________________________ Name ____________________________ Address__________________________ __________________ P/code_______ 94  Silicon Chip Need prototype PC boards? We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. For price list, write Acetronics 5/32 Seton Rd, Moorebank 2170 or email acetronics<at>acetronics.com.au Phone (02) 9600 6832 www.acetronics.com.au  Buy five and get them postage free! Silicon Chip Publications PO Box 139 Collaroy Beach 2097 AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au email: youngbob<at>silvertone.com.au Website: www.silvertone.com.au  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5.50 p&p. Available only in Australia. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. Microzed.com.au PIC CHIP SPECIALIST PO Box 634 ARMIDALE 2350 (296 North Cooke’s Rd) Ph: (02) 6772 2777 – may time out to Mobile 0438 277 634. Fax: (02) 6772 8987 RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production. Tel (02) 9738 0330; Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio USB KITS: Stepper Motor Controller, DTMF Transceiver, Thermometer, DDS HF Generator, Compass, 4-Channel Voltmeter, I/O Relay Card. Also available: Digital Oscilloscope, Temperature Loggers, VHF Receivers and USB Active X (and USBDOS.exe file) to control our kits from your application. www.ar.com.au/~softmark LABJACK USB DATA ACQUISITION MODULE features 8 12-bit analog inputs, 20 digital I/O, 2 analog outputs and high speed counter. Free software and ActiveX component. DAS005 Parallel Port Data Acquisition Module features 8 12bit Analog inputs, 4 digital I/Ps & 4 digital O/Ps. Free windows software. FAB Programmable Logic Controllers. Low cost, high performance. Programming software and SCADA software free. Heaps of features. Full details and credit card ordering available at: www.oceancontrols.com.au Audio, Video, S-Video and VGA cables distribution amps, switchers, adaptors, price lists at: www.questronix.com.au FOR SALE: Moama TV and Video Service. Suit sole trader. Servicing TVs, videos, computer monitors, audio, microwaves, etc. Large client base. Established ten years. Owner can train. Located busy tourist town - Echuca/ Moama. High growth area, low outgoings. $24,000 WIWO. Phone owner 03 5482 6047. PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Elec­tronics (02) 9586 4771. sesame777<at>optusnet.com.au; http:// members.tripod.com/~sesame_elec www.siliconchip.com.au Subscribe & Get This FREE!* *Australia only. Offer valid only while stocks last. Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Silverwater in Sydney. A genuine interest in electronics is a necessity. Phone 02 9741 8555 for current vacancies. Relay version (SC, 7/2002) to its full potential controlling 10 relays. Uses PIC16F628. See it at: www.ozitronics.com ADD SPEECH, SONAR OR DIRECTION SENSING to your next project. Fully contained modules. Full specs on website www.robotparts.com.au Ph 0412 350671 KIT ASSEMBLY THAT’S RIGHT! Buy a 1- or 2-year subscription to SILICON CHIP magazine and we’ll mail you a free copy of “Electronics TestBench”, just to say thanks. Contact: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097 Phone Orders: (02) 9979 5644 Fax Orders: (02) 9979 6503 Email Orders: office<at>silchip.com.au Classifieds: continued from p.94 C.R.O. D/T as new $390, P/S.W.R. meter $90, Freq. Counter $80 plus lots more. (02) 6658 3181. HALF RETAIL PRICE! Used Solar Panels, Inverters, Batteries, Surplus Components and more. See our specials pages at www.kcsolar.com.au 10-RELAY ROLLING CODE UHF REMOTE CONTROL Expands the 4 NEVILLE WALKER KIT ASSEMBLY & REPAIR: • Australia wide service • Small production runs • Specialist “one-off” applications Phone Neville Walker (07) 3857 2752 Email: flashdog<at>optusnet.com.au Advertising Index Acetronics....................................94 Altronics........................ loose insert Av-Comm Pty Ltd.........................94 Clarke & Severn...........................55 Dick Smith Electronics........... 18-21 Eco Watch....................................93 Elan Audio....................................83 Evatco..........................................87 Grantronics..................................93 Harbuch Electronics.....................54 Instant PCBs................................94 Hy-Q International........................55 Jaycar .............................. 45-52,95 JED Microprocessors................5,55 Kalex............................................87 WANTED Microgram Computers...................3 AVO VALVE CHARACTERISTIC METER VCM163 and Marconi Bridge TF2700. Must be in working order, preferably with operating instructions. dongmack<at>chariot.net.au MicroZed Computers..............55,94 EARLY HI FI’S AMPLIFIERS, Speakers, Turntables, Valves, Books ; Quad, Leak, Pye, Lowther, Ortofon, SME, Western Electric, Altec, Marantz, McIntosh, Goodmans, Wharfedale, Tannoy, radio and wireless. Collector/Hobbyist will pay cash. 02 9440 1267. johnmurt<at>highprofile.com.au Oatley Electronics........................75 Printed Electronics...................... 94 Procopy........................................55 Quest Electronics.........................35 RCS Radio..............................55,94 RF Probes...............................55,87 Silicon Chip Binders............94,OBC Silicon Chip Bookshop..........96,IBC NOW AVAILABLE FROM Silicon Chip TestBench.........95,IFC Silvertone Electronics..................94 www.siliconchip.com.au Project Reprints Limited Back Issues Limited One-Shots If you’re looking for a project from ELECTRONICS AUSTRALIA, you’ll find it at SILICON CHIP! We can now offer reprints of all projects which have appeared in Electronics Australia, EAT, Electronics Today, ETI or Radio, TV & Hobbies. First search the EA website indexes for the project you want and then call, fax or email us with the details and your credit card details. Reprint cost is $8.80 per article (ie, 2-part projects cost $17.60). SILICON CHIP subscribers receive a 10% discount. We also have limited numbers of EA back issues and special publications. Call for details! visit www.siliconchip.com.au or www.electronicsaustralia.com.au www.siliconchip.com.au Soundlabs Group.........................55 Telelink Communications.............55 _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. March 2003  95 REFERENCE GREAT BOOKS FOR ALL PRICES INCLUDE GST AND ARE AUDIO POWER AMPLIFIER DESIGN HANDBOOK PIC Your Personal Introductory Course A handbook for professionals and students from one of the world’s most respected audio authorities. New edition is more comprehensive than ever with a new chapter on Class G amplifiers and further new material on output coils, thermal distortion, relay distortion, ground loops, triple EF output stages and convection cooling. 427 pages in paperback. Concise and practical guide to getting up and running with the PIC Microcontroller. Assumes no prior knowledge of microcontrollers, introduces the PIC’s capabilities through simple projects. Ideal introduction for students, teachers, technicians and electronics enthusiasts – perfect for use in schools and colleges. 270 pages in soft cover. by Douglas Self 3rd Edition 2002 89 $ by John Morton – 2nd edition 2001 NEW NEW NEW NEW 46 $$ VIDEO SCRAMBLING AND DESCRAMBLING AUDIO ELECTRONICS If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! Encoding/decoding systems (analog and digital systems), encryption, even schematics and details of several encoder and decoder circuits for experimentation. Intended for both the hobbyist and the professional. 290 pages in paperback. For anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover. By John Linsley Hood. First published 1995. Second edition 1999. FOR SATELLITE AND CABLE TV by Graf & Sheets 2nd Edition 1998 4th EDITION $ 70 87 $ EMC FOR PRODUCT DESIGNERS 3rd EDITION UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. 4th edition 2001 Based mainly on the American telephone system, this book covers conventional telephone fundamentals, including analog and digital communication techniques. Provides basic information on the functions of each telephone component, how dial tones are generated and how digital transmission techniques work. 402 pages, soft cover. 103 $$ By Eugene Trundle. 3rd Edition 2001 3rd EDITION Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback. Widely regarded as the standard text on EMC, provides all the key information needed to meet the requirements of the EMC Directive. Most importantly, it shows how to incorporate EMC principles into the product design process, avoiding cost and performance penalties, meeting the needs of specific standards and resulting in a better overall product. 360 pages in paperback. 63 $ By Ian Hickman. 2nd edition1999. Essential reading for electronics designers and students alike. It will answer nagging questions about core analog theory and design principles as well as offering practical design ideas. With concise design implementations, with many of the circuits taken from Ian Hickman’s magazine articles. 294 pages in soft cover. by Dogan Ibrahim. Published 2000. by Steve Roberts. 2nd edition 2001. Based mainly on British practice and first published in 1997, this book has much that is relevant to Australian systems as a guide to home and small business installations. A practical guide to installation of telephone wiring, ranging from single extension sockets to PABX, with the necessary tools, test equipment and materials needed by installers. 178 pages in soft cover. 89 $$ Microcontroller Projects in C for the 8051 TELEPHONE INSTALLATION HANDBOOK 69 By Tim Williams. First pub­­lished 1992. 3rd edition 2001. ANALOG ELECTRONICS GUIDE TO TV & VIDEO TECHNOLOGY $ 92 $ $ 73 Through graded projects the author introduces the fundamentals of microelectronics, the 8051 family, programming in C and the use of a C compiler. The AT89C2051 is an economical chip with re-writable memory. Provides an interesting, enjoyable and easily mastered alternative to more theoretical textbooks. 178 pages in paperback. BOOKSHOP ENQUIRING MINDS! LOWER THAN RECOMMENDED RETAIL PRICE WANT TO SAVE 10%? 10% OFF! SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! Power Supply Cookbook Analog Cct Techniques With Digital Interfacing by T H Wilmshurst. Published 2001. by Marty Brown. 2nd edition 2001. An easy-to-follow, step-by-step design framework for a wide variety of power supplies. Anyone with a basic knowledge of electronics can create a very complicated power supply design . Magnetics, feedback loop, EMI/RFI control and compensation design are all described in simple language. 265 pages in paperback. 99 VIDEO & CAMCORDER SERVICING AND TECHNOLOGY by Steve Beeching (Published 2001) $ 69 $ $ Provides fully up-to-date coverage of the whole range of current home video equipment, analog and digital. Information for repair and troubleshooting, with explanations of the technology of video equipment. 318 pages in soft cover. 69 Antenna Toolkit by Joe Carr. 2nd edition 2001. Together with the CD software included, the reader will have a complete solution for constructing or using an antenna - bar the actual hardware. The software is based on the author’s Antler program, which provides a simple Windows-based aid to carrying out the design calculations at the heart of successful antenna design. 253 pages in paperback. NEW NEW NEW NEW PIC IN PRACTICE O R D E R H E R E by Howard Hutchings. Revised by Mike James. 2nd edition 2001. 63 $$63 $ Anyone interested in ports, transducer interfacing, analog to digital conversion, convolution, filters or digital/analog conversion will benefit from reading this book. The principals precede the applications to provide genuine understanding and encourage further development. 302 pages in paperback. PRACTICAL RF HANDBOOK by Ian Hickman 3rd Edition 2002 by D W Smith Published 2002 Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcon-trollers for hobbyists, students and professionals. 255 pages in paperback. 87 $ Interfacing With C Electric Motors And Drives by Austin Hughes. 2nd edition 1993. Reprinted 2001. For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. Covers all the analog electronics needed in a wide range of higher education programs: first degrees in electronic engineering, experimental science course, MSc electronics and electronics units for HNDs. Text is supported by numerous worked examples and experimental exercises. 312 pages in paperback. 52 69 $$ $$ A guide to RF design for engineers, technicians, students and enthusiasts. Covers all of the key topics in RF: analog design principles, transmission lines, transformers, couplers, amplifiers, oscillators, modulation, transmitters and receivers, propagation and antennas. 279 pages in paperback. NEW NEW NEW NEW TAX INVOICE ANALOG CIRCUIT TECHNIQUES W/DIGITAL INT............$69.00 Your Name_________________________________________________ ANALOG ELECTRONICS..................................................$89.00 PLEASE PRINT ANTENNA TOOLKIT.........................................................$87.00 Address ___________________________________________________ AUDIO ELECTRONICS.....................................................$92.00 ___________________________________ Postcode_______________ AUDIO POWER AMPLIFIER DESIGN...............................$89.00 Daytime Phone No. (______) __________________________________ ELECTRIC MOTORS AND DRIVES..................................$63.00 STD EMC FOR PRODUCT DESIGNERS.................................$103.00 Email___________________<at>_________________________________ GUIDE TO TV & VIDEO TECHNOLOGY............................$63.00 INTERFACING WITH C.....................................................$63.00 ❏ Cheque/Money Order enclosed OR M'CONTROLLER PROJECTS IN C FOR 8051..................$73.00 ❏ Charge my credit card – ❏ Bankcard ❏ Visa Card ❏ MasterCard PIC IN PRACTICE............................................................$52.00 PIC - YOUR PERSONAL INTRODUCTORY COURSE........$46.00 No: POWER SUPPLY COOKBOOK..........................................$99.00 PRACTICAL RF HANDBOOK............................................$69.00 Signature______________________Card expiry date TELEPHONE INSTALLATION HANDBOOK.......................$69.00 UNDERSTANDING TELEPHONE ELECTRONICS.................$70.00 PLUS P&P (if applic): $........................... TOTAL$ AU.............................. VIDEO & CAMCORDER SERVICING/TECHNOLOGY........$69.00 VIDEO SCRAMBLING/DESCRAMBLING..........................$87.00                Orders over $100 P&P free in Australia. POST TO: SILICON CHIP Publications, PO Box 139, Collaroy NSW, Australia 2097. AUST: Add $A5.50 per book OR CALL (02) 9979 5644 & quote your credit card details; or FAX TO (02) 9979 6503 NZ: Add $A10 per book, $A15 elsewhere ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ P&P ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. ALL PRICES INCLUDE GST