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R AUSTRALIA’S BEST AUTO TECH MAGAZINE It’s a great mag... but could you be disappointed? If you’re looking for a magazine just filled with lots of beautiful cars, you could be disappointed. Sure, ZOOM has plenty of outstanding pictorials of superb cars, but it’s much more than that. If you’re looking for a magazine just filled with “how to” features, you could be disappointed. Sure, ZOOM has probably more “how to” features than any other car magazine, but it’s much more than that. If you’re looking for a magazine just filled with technical descriptions in layman’s language, you could be disappointed. Sure, ZOOM tells it in language you can understand . . . but it’s much more than that. If you’re looking for a magazine just filled with no-punches-pulled product comparisons, you could be disappointed . Sure, ZOOM has Australia’s best car-related comparisons . . . but it’s much more than that If you’re looking for a magazine just filled with car sound that you can afford, you could be disappointed. Sure, ZOOM has car hifi that will make your hair stand on end for low $$$$ . . . but it’s much more than that. If you’re looking for a magazine just filled with great products, ideas and sources for bits and pieces you’d only dreamed about, you could be disappointed. Sure, ZOOM has all these . . . but it’s much more than that. But if you’re looking for one magazine that has all this and much, much more crammed between the covers every issue, there is no way you’re going to be disappointed with ZOOM. Look for the June/July 1998 issue in your newsagent From the publishers of “SILICON CHIP” Contents Vol.9, No.12; December 1996 FEATURES    8 CD Recorders: The Next Add-On For Your PC Creating your own CD-ROMs is fast and easy with the latest generation CD recorders. We take a look at what’s involved – by Greg Swain 20 Mitsubishi’s Intelligent Automatic Transmission This smart new automatic transmission adjusts its shift points to suit the driving conditions & even provides engine braking – by Julian Edgar 100 Annual Index For Volume 9 CD RECORDERS: THE NEXT ADDON FOR YOUR PC – PAGE 8 All the articles, projects & columns for 1996 PROJECTS TO BUILD 24 Active Filter Cleans Up Weak CW Reception Build this low-cost filter & dig those weak CW signals out of the noise. It connects between the receiver & an external speaker – by Leon Williams 38 A Fast Clock For Railway Modellers Run your trains to a realistic schedule. This circuit interfaces to a low-cost clock module & runs 4.5-8.5 times faster than normal – by Leo Simpson 58 Build A Laser Pistol & Electronic Target Hit the bullseye & you’re rewarded with a siren sound. Miss and you get the sound of a machine gun as the target “shoots” back – by Rick Walters 66 Build A Sound Level Meter ACTIVE FILTER FOR IMPROVED CW RECEPTION – PAGE 24 Measures sound pressure levels from below 20 to 120dB with high accuracy & displays the result on a digital multimeter – by John Clarke 80 An 8-Channel Stereo Mixer; Pt.2 Second article has all the constructional and details – by John Clarke SPECIAL COLUMNS 44 Serviceman’s Log There’s a long, long trail a’winding – by the TV Serviceman 57 Satellite Watch The latest news on satellite TV – by Garry Cratt FAST CLOCK FOR RAILWAY MODELLERS – PAGE 38 76 Vintage Radio A new life for a battered Astor – by John Hill DEPARTMENTS   2   4 19 30 36 94 Publisher’s Letter   98 News & Views  99 Mailbag 102 Bookshelf 103 Circuit Notebook 104 Product Showcase Ask Silicon Chip Notes & Errata Order Form Market Centre Advertising Index BUILD A LASER PISTOL & ELECTRONIC TARGET – PAGE 58 December 1996  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Christopher Wilson Phone (02) 9979 5644 Mobile 0419 23 9375 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill 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. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $54 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Going for the big clean-out Are you reluctant to throw out old electronic components? If you are anything like me, you are. I hate to see electronic equipment or components being junked. However, while this may be a good and worthwhile attitude and may often save you money in the long run, there is the other side of the coin to consider. After a while, you get too much junk. About a year ago I moved house and there was a lot of stuff that I didn’t have time to sort out at the time so it all went into boxes “to be looked at later”. Now I am slowly wading through it. I have to face up to the fact that I have “electronic stuff” that I haven’t touched for 20 years or more. Much of it, and I am talking about all sorts of small components here, is probably still as good as the day it was made. But I’ll never use it; not ever. I’ve had to bite the bullet. Some stuff I’m saving and some I’m giving away but a good deal of it has to go in the bin – there’s just no way that anybody would use it. Some of the com­ponents I’ve had so long that the leads have corroded; that’s a hazard of where I live, close to the sea. Inevitably too, there is stuff that I didn’t know I had and some that I thought I’d lost or given away years ago. I am sure that there are many readers who are in a far worse situation. Instead of half a dozen boxes of junk, they have a shed, a garage or even rooms full of it. Like me, they will probably never use it. And sooner or later they will have to face up to doing something about it, especially if they ever have to move to a smaller house. If you are one of these people, why not attack the problem this evening? You will feel a lot happier when it is sorted out. You will probably find that you have so much more room to move as well and you will be able to accommodate all that new stuff you want. You have to be ruthless about it. If you find something that you have had no use for in the last five years, it probably should be given away or pitched out. Any components which look corroded or discoloured in any way should be tossed as well. If you can find an electronics club that wants your electronic bits, so much the better. In fact, if electronics clubs thought about taking small classified ads they would probably end up with a lot of good material. While you’re in clean-up mood, why not sort out all those floppy discs around your place? Reformat them and put them back into general use. You can do the same with all your VCR tapes. You’ll probably be amazed at how many you have lying around. So have a look around you and see if you’ve been hit by the “hoarding virus”. It is curable and most people live happily thereafter. Leo Simpson ISSN 1030-2662 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. 2  Silicon Chip 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. Macservice Pty Ltd News & Views Home Computers More Popular Recently the Australian Bureau of Statistics released the results of a comprehensive survey on the use of computers in Australian households. It found a considerable increase in com­puter usage but we still lag behind the US and Britain. Interestingly, most computers are still used for playing games. According to the survey, almost two million Australian households (30%) used a com­puter as at February 1996, compared to 1.5 million (23 percent) of households in February 1994. Over the same period, the total number of computers in use in households had risen to 2.5 million from 1.9 million. In February 1996, 23% of households using computer technol­ogy had a modem or external link compared with 17% two years ago. Desktop or personal PCs increased from 75% to 81% of the total number of household computers and use of facsimile machines increased from 4% to 10% of all households. The use of peripheral equipment also increased with CD-ROMs increasing most, from 13% to 41% of households with comput­ers. Computer use and modems Approximately 80% of computers were owned by a household member. Married couples with children continued to show the highest percentage use of computers or 45% of an estimated 2.4 million. Of the 4.7 million households without a computer, 41% said they had no use for a computer and 31% said that costs were too high. Of the 1.5 million households which have a computer but do not have a modem, 45% indicated that they were not in- When the off switch no longer really means off Some of the new hifi equipment now on sale features on/off switches which don’t stay off when you turn them off. We recently saw a Denon DCM-27 carousel CD player which is apparently typical of this trend. If you turn the set off by the front panel switch or remote control it turns off, as you would expect. But if you then have a blackout and the power comes back on, so does the player. If the power comes back on and 4  Silicon Chip you have disc in the ma­chine, it will go straight into play mode – not very convenient if you happen to be asleep at 2 o’clock in the morning! Apparently the only way you can be sure of turning these units off is to switch it off at the power point. This seems like a backward step. Maybe the designers had better go back to the drawing board on this one and have a think about the consequenc­es. terested or would not use a modem and 27% indicated that costs for a modem were too high. Computer activities The most popular use for home computers was playing comput­er games. 50% of games players were aged 17 years or less. Of the 2.3 million persons 5 years or older who play computer games on their home computer, 68% spent one to five hours per week and 12% spent from six to 10 hours per week playing computer games. Educational activities were also highly popular with just over one The most popular use for home computers was playing comput­er games. million home users indicating the use of mainly educa­tional products. 833,000 thousand persons used their household computer for doing work relevant to their employment, excluding their own businesses. 422,000 thousand persons used it for doing work for their home-based businesses, 379,000 used it for doing work for their own (non-home based) business and 23,000 used it for other paid work from home via computer. There were 1.6 million household computer users doing work relevant to studies, with 46% of these aged from 5-17 years. Expenditure Households which used a computer spent approximately $3 billion in the 12 months to February 1996 on computer related goods and services. This represents $1500 per household where a computer is used in Australia. An estimated $870 million was spent on desktop or personal com- Next Year’s Flat-Screen TV Philips has given its first public demonstration of large-screen FlatTV at the CeBIT Home exhibition in Hanover. The Flat-TV has a plasma display panel with a screen diameter of 107cm (42 inches) and with a depth of less than 10cm, can be hung on a wall like a painting or suspended from a ceiling. Although the model shown at CeBIT Home is a first genera­tion prototype, Philips says it plans to introduce the Flat-TV onto the market in the first half of next year, at an expected price of around 22,000 guilders (US$13,000). Initial demand is expected to come from businesses wanting to use the Flat-TV for multimedia displays and from home cinema fans. Philips expects the total market to grow to around one million units a year by 2000. The company will also sell the system to other suppliers on an OEM basis. Philips sees increased numbers of people moving towards large and wide screen TVs with home cinema capabilities. At the same time that they want bigger screen sizes, people also want less bulk in their sets. puters, $550 million on software and $680 million on computer peripherals. Of the 6.6 million households in Australia, 19% intended to purchase computer equipment in the 12 months from February 1996 and a further 11% intended to spend an amount of money in the 12 months from February 1997. Internet There were 262,000 people (178,000 males and 84,000 fe­males) who indicated that they were using the Internet from home. People in the 26-40 years age group were the highest users of the Internet (38%), followed by those aged 41-55 years (28%) and 18-25 years (18%). There were about 141,000 household computer users who used electronic mail and about 116,000 households who accessed other on-line services/databases. However, when all households were asked about their With the largest cathode ray tube tele­ vision sets already weighing over 100kg, bigger conventional screens are impractical. The Flat-TV is capable of receiving PAL, PALplus, Secam and NTSC signals and offers full VGA resolution, for use with a PC. The plasma display technology used in Flat-TV gives it a 160° viewing willingness to use other technologies, 78% said “no” to home shopping, 70% said “no” to home banking and 95% said “no” to home gambling. angle, far greater than LCD screens, which are extremely difficult to make in such large sizes. The power supply, electronics and connections are housed separately in a TV receiver. All connections with external equip­ment go through this box, with only one pair of cables going directly to the flat display. BassBox ® Other technologies 24% of all households owned or were paying for a mobile phone and 25% of households had an answering machine. However, 52% of all households do not own or pay for any communication technologies apart from a telephone connection. Finally, 3% (200,000) reported having Pay TV with the majority of these households being in capital cities (85%). Further details and other aspects of the use of various technologies by Australian households are contained in “Household Use of Information Technology”, February 1996 (Cat No 8128.0), available from ABS bookshops in capital cities. Design low frequency loudspeaker enclos­ures fast and accurately with BassBox® software. Uses both Thiele-Small and Electro-Mechanical parameters with equal ease. Includes X. Over 2.03 passive cross­over design program. $299.00 Plus $6.00 postage. Pay by cheque, Bankcard, Mastercard, Visacard. EARTHQUAKE AUDIO PH: (02) 9948 3771 FAX: (02) 9948 8040 PO BOX 226 BALGOWLAH NSW 2093 December 1996  5 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 COMPUTERS CD Record The major components of the COMPRO CD-R kit include: (1) a CD-R drive, (2) a SCSI interface card, and (3) Gear pre-mastering software on a CD-ROM. The kit also includes two blank CD-ROMs and a SCSI driver installation disc for Windows 3.1. Creating your own CD ROMs is fast and easy with the latest generation CD recorders. And the cost is coming down all the time. Although CD ROM drives have been the norm in PCs for some years now, CD recorders have been much more esoteric devices with price tags to match. Until now that is – in the last 12 months, CD recorder prices have plummeted dramatically, placing them in reach of just about anybody. For little more than a grand, you can now choose from a range of CD recorder kits that you can install 8  Silicon ilicon C Chip hip yourself or have installed for you. Alternatively, you can now specify a CD recorder as one of the options if you’re buying a new PC. If you need a reliable method of archiving and storing (or transferring) large amounts of data, a CD ROM is well worth consid­eration. A CD-ROM can store up to 650Mb of information and this can either be added in one session or, provided the system is ca- pable of it, in multiple sessions. But while data archiving is the biggest application for a CD recorder (CD-R), there are other applications. CD-R lets you create your own audio and video CD titles, for example. Some systems even have the capability of copying tracks from an exist­ing audio CD onto your PC’s hard disc so that they can then be recorded onto a CDROM. Not all CD-R drives support By GREG SWAIN ders: The next add-on for your PC copying audio tracks however, so check carefully when buying a CD recorder kit if this particular feature is important to you. CD-R drives A CD-R drive looks exactly the same as a conven­tional (read only) CD-ROM drive and can simply be substituted for the existing unit. CD-R drives are invariably SCSI devices (Small Computer Systems Interface) and so a SCSI interface card is required. A CD-ROM is not like a floppy or hard disc drive, so it’s not just simply a matter of copying files to it. Instead, you have to use special pre-mastering software and this is normally supplied with the kit. The pre-mastering software is necessary because CD-ROMs use a different file format to DOS-formatted discs – typically the ISO 9660 standard. In practice, the pre-mastering software is used to create a “virtual image” file of the CD. A virtual image file lists all the file names and directories to be copied and contains other information necessary for writing to Because it is a SCSI device, the CD-R drive requires a SCSI interface card. This card is plugged into a spare ISA slot on the motherboard. a CD-ROM. It does not include the actual data files, however. It’s also possible to create what is known as a “physical image” file on the hard disc. This is an exact copy of all the information as it is to be The CD-R drive is slit into a vacant drive bay from the front of the computer. We disabled our existing CD-ROM drive to obtain a spare power connector. recorded onto the CD-ROM and is creat­ed after the virtual image has been created. A physical image file is usually only necessary if you have a slow hard disc. That’s because CD recording is a The free end of the ribbon cable from the SCSI interface card is plugged into the back of the CD-R drive, along with the power connector. No audio cable is supplied with the kit. D December ecember 1996  9 Creating A CD-ROM: The Basic Steps Using 1 Fig.2: type in the image filename in the space provided, then click the Create button. The image file is created and the program returns you to the workbench. Note that only capital letters, the numbers 0-9 and the underscore character (_) are valid characters for ISO filenames. 2 3 continuous process and there must be no serious interruptions while record­ ing is taking place. If there is an interruption (eg, because the hard disc can’t keep up and the data buffer empties), the recording process will be aborted and the CDROM will be ruined. You can then either toss it in the garbage or use it as a drinks coaster. Because a physical image takes less 10  Silicon Chip Fig.1: select the CD type to be created at the Gear workbench, the click the Create Image button. time to read than a virtual image, it reduces the likelihood of the buffer running out of data during the recording process. The downside is that you need lots of space on your hard disc, since all the files to be written to the CD are duplicated. The good news it that a virtual image file is all that’s required in most cases, particularly if you have a computer with a fast hard disc. It pays to de- Fig.3: click the Edit Image button to bring up the Data Editor. fragment the disc on a regular basis though, to eliminate any possible problems. CD-Recorder Kit Typical of the equipment now available in this field is the Compro CD-Recorder Kit. It comes with an internal SCSI CD-R drive, a fast SCSI-2 interface card, Gear pre-mastering software (supplied on CD-ROM), a SCSI g The Gear Pre-Mastering Software 4 Fig.4 (above): edit the virtual image using the Data editor. Just select the source drive and drag the files you want to the My ISO Track window. 5 Fig.5: click the test button on the workbench to begin a test write. Alternatively, you can bypass the test procedure and write straight to the disc. 6 driver installation disc (for Wind­ows 3.11 users) and a SCSI interface cable. Thrown in for good measure are a couple of blank CD ROMs, plus a user manual and an installation guide for the SCSI card. Our first impressions of this kit were very favourable, as only good quality components have been included. The CD-R drive is a Matsushita CW-7501 Plug and Play unit, while the SCSI card Fig.6: click Yes to automatically write the image to the disc if the test is successful or No for a test write only. is an Adaptec AHA-1520B. The SCSI card features automatic termination which means that you don’t have to worry about removing terminat­ ing resistors if a device is plugged into the external connector. The CD-R is capable of reading a CDROM at quad-speed (4x) and writing at double speed (2x). The pre-mastering software also lets you write at single speed if you have a computer with a slow hard disc drive. Unlike some CD recording kits, this particular setup sup­ports a wide range of recording formats. It’s lets you create multi-session and mixed-mode discs and it supports CD-ROM Modes 1 & 2 (ISO), CD-ROM XA (extended architecture), CD-I, CD Enhanced (also known as CD Plus), and CD digital audio (Red Book audio). A multi-session disc is one on which December 1996  11 Fig.7: a physical image can be created if you have a slow hard disc or for maximum reliability. It requires a lot more hard disc space than a virtual image however, since it makes a complete copy of the files to be written to the CD-R. Fig.8: the “show log” option lists the steps that have been taken in creating a CDROM. This can be handy if you get interrupted during the process. data has been added during several different sessions. This is useful for archiving data or updating a catalog on a regular basis, for example. When the disc is read back, the CD-ROM reader automatically presents all link­ed sessions as one. You are not aware of the number of sessions on the disc. With a multi-session disc, you can keep on adding data until the disc is full. Note, however, that each session intro­duces a data overhead of about 15Mb. This data overhead consists of track lead in and lead out information. You can also effectively delete and update files on a multi-session disc. This is done by adding (appending) a new session. During this process, the software reads back the last session and creates a virtual image of it. You then edit (update, delete or add) the file contents of this virtual image before writing the new image to disc. Of course, data is not really deleted from a CD-ROM – it’s just that there’s no longer any reference to it in the new table of contents that’s created 12  Silicon Chip when the new session is added. So as far as the user is concerned, the file is no longer there – just as if it had been deleted. One variation of the multi-session format is the CD-En­ hanced (or CD Plus) disc. This is handy when creating a mixed mode disc containing both computer data and CD audio. It lets you “hide” the audio from the data and vice versa. Under this format, the audio tracks are written during the first session while the data tracks are written during subsequent sessions. An audio player will then only detect the first session and so will only play the audio. Conversely, a CD-ROM drive will show only the data that’s recorded on the disc. Installing the hardware We chose a Pentium machine with PnP BIOS and Windows 95 as our test bed for the Compro CD Recorder Kit. Both the CD-R and the SCSI card are Plug and Play (PnP) items, so they are easy to install and get going. Unfortunately, when we opened the case, we didn’t have a spare power connector for the new CD-R. We solved that problem by disabling our existing quad-speed CD-ROM drive. Before pulling the power connector however, we booted Windows 95 and removed the CD-ROM device driver (just go to Control Panel, double-click the System icon, select the CD-ROM and click Remove). Of course, there’s nothing to stop you from keeping your existing CDROM drive if you have enough power connectors. Indeed, this would be desirable if your existing drive is an 8x speed (or higher) unit, for example. The SCSI card plugs into a spare ISA slot on the mother­ board, after which the SCSI cable is attached to the internal SCSI connector. This connector is keyed, so the cable can only be attached one way which is just as well because the COMPRO In­stallation Guide shows the colour stripe on the wrong side of the cable (the Adaptec Installation Guide is correct). The CD-R slides into a spare drive bay and is secured using the four screws supplied. It’s then just a matter of plugging in the free end of the SCSI cable and attaching the power connector. A minor niggle here is that no audio cable is included for attaching the CD-R to a sound card. This won’t be missed by most people; an audio cable is only necessary if you want to play CD audio discs. You can still copy audio CD tracks however, since this data is sent via the SCSI bus. COMPRO’s excuse is that they don’t know what kind of sound card you have but we think that a cable suitable for a Sound Blaster card should have been included. The installation guide also incorrectly shows the pin connections for the audio socket, so be warned if you intend buying a cable from your local comput­er store. Fortunately, the correct pin connections are clearly labelled on the back of the drive itself. When we rebooted the system, Windows 95 automatically detected the SCSI card and the new CD-R drive and installed the appropriate device drivers. If you don’t have a PnP system, it may be necessary to change some of the settings for the SCSI card to avoid a hardware conflict (eg, with a sound card). You do that by using the embed­ded SCSISelect utility. This Fig.9: the “Multi Session” option must be enabled if you want to add data to a CD-ROM over several sessions. The verify and physical image options are also set here. is accessed by pressing Ctrl-A during the boot-up procedure, after which you can change a range of settings, including the IRQ channel and the SCSI ID number. You can also choose from one of three termination options (Enabled, Disabled or Automatic) and disable the host adapter BIOS. In fact, Adaptec recommend that you disable the BIOS if the peripherals on the SCSI bus are all controlled by device drivers and do not need the BIOS. By default, the SCSI card uses I/O port address 340 and IRQ 11 and these are also typically the default settings for a Sound­Blaster card. If this applies to your setup, it will be necessary to change the settings on one card to avoid problems. Using the software The Gear pre-mastering software comes on a CD-ROM which in­cludes both Windows 95 and Windows 3.1 versions (versions are also available for OS/2 and the Mac OS). In addition, the CD-ROM includes a comprehensive manual on the Gear pre-mastering soft­ ware in portable document format (pdf) plus a full working copy of Adobe Acrobat Reader 2.1 (to let you view pdf files). The first thing to do after installing the software is to turn off any screen savers and anything else that could interrupt the recording process (eg, a fax modem). For the same reason, the manual also instructs you to turn off the “Auto Insert Notifica­tion” option for the CD-R drive and gives the step- Fig.10: we initially had problems with buffer under-run. Ditching the cyclical buffering option and selecting doublebuffering instead solved these problems. by-step procedure for doing this. The basic procedure for “burning” a CD-ROM is clearly set out in the manual. First, you have to choose the CD type to be created (eg, CD-ROM) and create a new image file (Figs.1 & 2) You then open the Gear Data Editor, select the source drive and drag the files you want to the My ISO Track window. If you make a mistake here, you just delete the track that you don’t want from the image. Closing the Data Editor now returns you to the workbench, at which point it is a good idea to run a test write. This useful feature does everything except actually write to the CD and is used to confirm that the data throughput from the hard disc to the CD is high enough. You can also elect to automatically write to the disc immediately after a successful test and there’s a verify after write option. Alternatively, you can bypass the test procedure and write straight to the CD. A bargraph shows the progress of the record­ing and the disc is automatically ejected when the procedure is completed (as it is at the end of a successful test run). The Gear software is easy to use although the Data Editor is a little clumsy. First, it’s default window sizes are too small and although they can be easily resized, they don’t stay that way when the Data Editor is closed. Another problem is that the folders on the hard disc are not presented in alphabetical order. That said, both these criticisms are fairly minor. Sorting out the wrinkles Our initial tests with small files were successful but we quickly ran into problems when we tried to write large amounts of data to disc. These problems centred around the type of buffering used. By default, the Gear software installs with cyclic buffer­ ing selected, as Using Gear For Data Backups A CD-ROM is useful as a secure medium for backing up data and Gear includes various archive setting op­tions to make the job easy. By enabling the archives reset feature, the software will automatically reset the archive bit for each file that is loaded into the image. Any files that are then subsequently modified or created will have their archive bit set again by DOS. Provided that the archives only feature is enabled, you can now simply drag all files across to the image when writing the next session. However, only those files that have been modified or created will be loaded and added to the CD-ROM. Those files that haven’t been modified remain in the previous session(s), thus giving a complete backup. Other options let you choose whether or not to load hidden and system files. December 1996  13 Fig.11 (right): clicking the DiscInfor button on the Gear workbench toolbar brings up this dialog box. This lets you select and copy individual tracks (eg, from an audio CD) to the hard disc. Fig.12 (below): once the tracks are on the hard disc, the virtual image for an audio CD is created in the same way as for a data CD-ROM. opposed to the alternative double-buffering option. During the recording process, the buffer stores data from the hard disc and streams it in a continuous fashion to the CD-R. If the buffer runs out of data, any interruption to the data stream from the hard disc aborts the recording process. With cyclic buffering selected, we found that the buffer initially filled (as indicated by a bargraph) but then slowly emptied during the first few minutes of the recording process. After this, the hard disc really rattled along as it attempted to keep up with the demands of the CD-R. When large amounts of data were involved, the process inevitably fell over. Once, we were about two thirds of the way into writing 600Mb of data when it crashed, despite a successful test run. On another occasion, we didn’t even get to the halfway point. We tried everything to solve this problem, including chang­ i ng the buffer size, writing at single speed and even creating a physical image of the 14  Silicon Chip files to be written. But no matter what we did, the buffer still emptied after just a few minutes and the hard disc rattled its head off. Unfortunately, initial test writes with double buffering selected didn’t hold much promise. Although the hard disc now worked at a fairly leisurely rate, the bargraph always show­ed an empty buffer which didn’t even fill before recording started. With two dead discs sitting on the table, it was time to call the local COMPRO distributor. Their advice: (1) ditch the cyclic buffering and use double buffering; (2) create a physical image of the data; and (3) record at double speed. And the empty bargraph indicator when double buffering is selected? Apparently, that’s normal; it only works for cyclic buffering (it’s just a pity that the manual doesn’t say that). And that solved all our problems. With double-buffering selected, we successfully recorded large amounts of data onto six CD-ROMs without a hitch. In fact, with our setup, it wasn’t even necessary to create a physical image file. A virtual image was sufficient, even when writing at double speed. Adding a new session Adding a new session is quite straightforward. You just insert the CDROM, click the Append button on the Gear toolbar, edit the CD-ROM image and write the data as before. The only proviso here is that the Multi Session option must have been selected before any previous sessions were written to the CD-ROM. It’s important to realise here that only the changes that you make to the image are written to the disc. If you want to keep a file, it must not be deleted from the existing image. If you do, it will appear as though the file has been deleted. Of course, you might want to “delete” files from a previous session on purpose. Each new session is added to the disc using one of several “append” Writing The Data To Tape Instead of writing to a CD, you can use the Gear software to write the data to tape. This tape can then be sent to a CD-ROM mastering plant so that multiple CDs can be produced. An unwanted by-product of this feature is that the Gear software always looks for a SCSI tape drive when it is booting up and if it doesn’t find one, comes up with the error message “No SCSI tape units found”. This doesn’t create any problems but can become annoying if you do a lot of archiving. Fortunately, it’s easy to disable this feature by editing the gear. ini file. You can do this is any ASCII text editor such as Notepad – just look for the line TapeInterface = 1 under the [tape] section and change it to TapeInterface = 0 options. Normally, for adding or deleting data, the Automatic Append option is used but there are also Manual, New and Multi-Volume Append modes. The Manual Append mode lets you select the track you want to add data to and is useful for recovering data deleted in a later session. By contrast, the New Append mode writes an empty track so that all previous sessions become inaccessible. Accord­ ing to the manual, this feature can be used to recycle a disc that has suffered a write failure (presumably after a previously successful session). Finally, the Multi-Volume Append mode is used for creating multi-volume discs. Making an audio CD The procedure for recording an audio CD is slightly differ­ent to making a CD-ROM, since you first have to copy the tracks to your hard disc. First, you insert an audio CD in the drive and click the DiscInfor button on the toolbar. This brings up the dialog box shown in Fig.6, after which you can select and copy individual files to your hard disc. A separate dialog box prompts you to name each file just before it is copied. From there, the process is almost identical to creating a CD-ROM, the main difference being that you choose CD-Audio as the CD type before creating and editing the image file. Another difference is that the recording bargraph indicates the progress of each individual track instead of the entire session. In our case, we successfully created a test CD with 17 tracks. It played back on an audio CD player just like any other CD, although we did notice a faint click between a couple of the tracks. As a point of interest, it is possible to create an audio CD over several sessions despite the fact that an audio CD is basically a single-session disc. You might want to do this if you have limited hard disc space and cannot load all the wanted tracks in one session, for example. By now, you will have gathered that the Gear pre-mastering software is extremely versatile, with a host of features – so many in fact that we didn’t have time to explore them all. Despite this, it is an easy package to use. In summary, our impressions of this CD-R kit are very fa­vourable. The complete package retails for $1295.00 and is avail­able from Rod Irving Electronics, 56 Renver SC Rd, Clayton 3168; phone (03) 9543 7877. MICROWAVE PARTS & REPAIRS WARNING!: All microwave repairs must be done by a qualified microwave technician. All text within is to be used as a guideline only. We recommend reading “MICROWAVE OVEN OPERATION AND SERVICING MANUAL” (code: MAN-MICRO, cost $19.95) for full safety instructions. Shailer Park Electronics will NOT take liability in any form for safety, health or work done. MICROWAVE OVEN LAMPS Hard to Find Range of Microwave Resistant Lamps Code Volts Watts Baseφϕ $ CL818 240V 25W 13mm $8.50 CL819 125V 25W 13mm $9.50 CL821 240V 20W 15mm $8.50 CL822 125V 20W 15mm $9.50 Base φ MICROWAVE SHORT PROTECTOR Blowing mains fuse? This short protector may be blown. It’s located across the high voltage cap which holds approximately 2300V. This short protector can be tested by first unplugging mains lead and then discharging the high voltage cap with a 1kΩ resistor. The short protector can then be safely measured out of circuit. REPLACE SHORT PROTECTOR IF FOUND DEAD SHORT. Code: 2X062H $14.95 MICROWAVE HIGH VOLTAGE CAPACITORS MICROWAVE HIGH VOLTAGE CAPACITORS Code Value Voltage Cost Is your microwave oven blowing the main fuse? The high voltage capacitor may be faulty. These high voltage, low tolerance capacitors are used in microwave ovens to complete a resonance circuit with the magne­tron which is inductive. A faulty capacitor may upset the lead-lag factor of the resonance circuit and cause the transformer to labour (hum) or blow short protector and/or main fuse. The high voltage capacitor, which holds approximately 2300V, can be tested by unplugging the mains lead and then discharging the capacitor with a 1kΩ resistor, after which it can be safely measured out of circuit. REPLACE CAPACITOR IF FOUND FAULTY OR DEAD SHORT MWC65 MWC70 MWC83 MWC85 MWC86 MWC90 MWC95 MWC100 MWC105 MWC110 MWC113 MWC114-6 MWC120 0.65µF 0.70µF 0.83µF 0.85µF 0.86µF 0.90µF 0.95µF 1.00µF 1.05µF 1.10µF 1.13µF 1.14µF 1.20µF 2300V 2300V 2300V 2100V 2100V 2100V 2100V 2100V 2100V 2100V 2100V 2100V 2100V $35.50 $36.50 $39.50 $36.50 $39.50 $39.50 $39.50 $50.50 $42.50 $44.95 $45.50 $44.95 $44.95 MICROWAVE OVEN ROOF LINING Does your microwave throw sparks inside cavity? The roof lining may need replacing. This lining is made of a special material to diffuse the microwave beam for even distribution. You will find the lining if you open the door and look up inside the cavity; it is a flat sheet held in by screws or clips. With age, the microwave beam will burn through this lining causing sparks inside. We supply 13cm x 17cm sheet, simply cut and shape to size. MICROWAVE OVEN ROOF LINING Code Type Size 13cm Price MRL20 Microwave 13cm x 17cm $15.50 MRL50 Microwave 13cm x 17cm $17.95 17cm MICROWAVE FUSES Our range of original microwave fuses are time delayed, ceramic tube, with brass nickel plated contact cups and have a high breaking capacity of 500A/500V. Never use conventional fuses as they may explode and shatter throwing pieces of glass inside the food cavity, which may be a health risk. MICROWAVE FUSES Code Rating Length Price AF010P 6.3A 5mm x 20mm $2.50 AF011P 8A 5mm x 20mm $2.50 AF012P 10A 5mm x 20mm $2.50 AF019L 6.3A 6.35mm x 32mm $2.50 AF020L 8A 6.35mm x 32mm $2.50 AF021L 10A 6.35mm x 32mm $2.50 MICROWAVE TURNTABLE BELTS Code Dimensions (A x B x C) Length Cost MWB95 95 x 7.0 x 0.6 300 $11.65 MWB100 100 x 7.5 x 0.6 320 $11.75 MWB105 105 x 4.0 x 1.0 330 $11.80 MWB110 110 x 7.0 x 0.6 340 $11.70 MWB165 116 x 4.0 x 1.0 520 $15.65 MWB210 210 x 2.5 square 650 $14.95 MWB260 260 x 3.0 square 800 $14.90 MWB280 280 x 3.0 square 880 $13.30 MWB175 175 x 2.5 round 550 $19.95 MICROWAVE TURNTABLE MOTORS Postage & Packing $3.50 SHAFT A 2.5 rpm Code: MWM91 Cost $34.95 SHAFT B 5 rpm Code: MWM16 Cost $36.95 ORDER HOTLINE: (07) 3209 8648. FREE CALL: 1800 63 8722. FAX: (07) 3806 0119 SHAFT C 2.5 rpm Code: MWM159 Cost $39.95 SHAILER PARK ELECTRONICS KP Centre, Cnr Roselea & Lyndale St, Shailer Park, Qld 4128. December 1996  15 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.altronics.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.altronics.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.altronics.com.au MAILBAG Dead wrong on the Internet I saw your editorial on the Internet in the October issue. Please take it from me you are in a goldfish bowl and are dead wrong. I see my fax bill has gone down from $US250/month to $US40. The cost of a web page is not “very” substantial; I know, since I have set one up. It runs on my server for free. The only cost is my time. I can now get any data sheet within one minute – no more data books. Wonderful. Here are two examples to suggest you are wrong: (1) Most of the electronics magazines in the world now have web pages so no support for your position there. Popular Electronics, Electronics Now, Everyday Practical Electronics, Elektor, Nuts, all have good pages I look at regularly. Maplin has just started (all URLs on my web site); (2) Circuit Specialists (www.cir.com) have reduced their hardcopy catalog from 300,000 per year to 50,000. They now have the catalog on the web; instant changes and additions possi­ble. The USA electronics magazines generally do not have an editorial/ publisher’s Letter. This may be an idea for you to adopt for your magazine. P. Crowcroft, Hong Kong. Video transmitter needs blocking capacitor I had trouble with the twisted-pair video transmitter/re­ ceiver project in the October issue. I don’t like RF stuff (and TV sets in particular – even though I have managed to repair a couple in the last 20 years) and the problem with this project had me bluffed for about three days. I am using a small mono­chrome camera from Oatley Electronics as the signal source and direct into the TV video line this gave an excellent picture. However, via the twisted pair Tx/ Rx I got a blank screen. Examining the output of the Tx unit revealed no signal, so the Tx must be faulty! Except that I could find no fault, even with a new IC and the Maxim data sheet. I just could not get the system to work but, out of spite, I eventually connected a VCR output to the Tx/ Rx and into another TV and presto, it works. But why? After carefully studying the waveform from the camera and that from the VCR on the scope, I realised that the VCR waveform was AC and the camera most definitely DC. Obviously the Tx unit expected an AC input (but the TV would tolerate either). The answer is to insert a 100µF tantalum capacitor in the video signal line from the camera to the Tx unit. The article high­lighted the situation of using a small monochrome camera with this project to provide a remote video system but does not mention that such cameras may have a DC output waveform. There could well be a lot of other people out there who need “spoon feeding” when dealing with RF stuff (as I do) and this may solve their problems getting this project going. A. Mott, Blackburn, Vic. The UV People ETCH TANKS ● Bubble Etch ● Circulating LIGHT BOXES ● Portuvee 4 ● Portuvee 6 ● Dual Level TRIMMER ● Ideal PCB DRILL ● Toyo HiSpeed MATERIALS ● PC Board: Riston, Dynachem ● 3M Label/Panel Stock ● Dynamark: Metal, Plastic ✴ AUSTRALIA’S NO.1 STOCKIST ✴ 40 Wallis Ave, East Ivanhoe 3079. Phone (03) 9497 3422, Fax (03) 9499 2381 Waste not, want not I have read your July 1996 editorial on the subject of appliance servicing. I agree that it is wasteful to throw away appliances when economic repair is possible. One area which could improve the situation is dedicating a section of your magazine to swapping of major spares for TVs and videos, as quite a number of readers would be involved in servicing of these appliances either professionally or as a hobby. A lot of servicemen have a large collection of spares from writeoff equipment gathering dust. If these parts could be sold they could be used to repair equipment that could not otherwise be repaired. I own two VCRs which need head-drum assembles. One is an Akai VS-35, the other a Sharp VC682. If anyone has these parts from writeoffs, I would be grateful as it would mean an economic repair. I don’t expect these items for free but $200+ is more than they’re worth. I have a writeoff National NV-370 and an Akai CS-112 for parts, if they’re of assistance to anyone. J. Ellis, 15 View St, Norah Head, NSW. TRANSFORMERS • TOROIDAL • CONVENTIONAL • POWER • OUTPUT • CURRENT • INVERTER • PLUGPACKS • CHOKES STOCK RANGE TOROIDALS BEST PRICES APPROVED TO AS 3108-1994 SPECIALS DESIGNED & MADE 15VA to 7.5kVA Tortech Pty Ltd 24/31 Wentworth St, Greenacre 2190 Phone (02) 9642 6003 Fax (02) 9642 6127 December 1996  19 Engine braking from an automatic! Mitsubishi’s int automatic tran Mitsubishi’s smart new automatic transmission adjusts its shift points to suit the driver’s style. What's more, it shifts gear in a much more intelligent manner than previous automatic transmissions. Here's how it works. By JULIAN EDGAR 20  Silicon Chip Many automatic transmissions are now at least partially electronically controlled. Some use a hybrid system of electronic and hydraulic control, while others are fully electronic. The latest innovation is the adaptive “self-learning” au­ tomatic transmission, as fitted to the new TE Magna from Mitsu­ bishi. In this system, a transmission control unit is used to constantly monitor the driver’s style. Depending on what it “learns”, it then adjusts its control behaviour accordingly. With this type of system, the economy/power switch fitted to some transmissions is made redundant. Drive the car hard and the gear changes will occur at higher engine speeds; gently toddle along and the changes will slur through early. However, there’s more to adaptive shift control technology than changing gear shift points, as we shall see. Common problems In most modern automatic transmissions, gear selection is based mainly on throttle position and vehicle speed. However, there are many situations where the gear selected is not appro­ priate for the driving conditions – the control system literally selects the “wrong” gear. A good example of this occurs when driving an automatic car uphill along a winding road. In this situation, a slight easing of the throttle prior to each corner can result in an up-shift, the transmission then down-shifting again after the corner has been negotiated. Obviously, if driving a manual car, the driver would not change into a higher gear prior to entering a corner. Because the automatic transmission does, it losses engine braking and so some degree of control is lost. Fig.1: Mitsubishi’s earlier “Fuzzy Shift Scheduling” system allowed the transmission control unit to use engine brak­ing and hill-climbing modes. Self-learning was not incorporated into the system, however. Downhill driving in a conventional automatic also results in a lack of engine braking, unless the driver manually selects a lower gear. (Incidentally, it is good driving practice to manual­ly lock a conventional auto into a single appropriate gear in both of the above scenarios – lazy drivers take note!) Getting back to the TE Magna, Mitsubishi’s research indi­ cated that a conventional automatic transmission could be in the “wrong” gear for a given situation up to 60% of the time telligent nsmission – an extraordinarily high figure and perhaps only possible if the car were being driven on a racetrack! However, there are certainly times when the control system needs more brains. For Mitsubishi, the first step in overcoming these problems involved the development of “Fuzzy Shift Scheduling” – see Fig.1. In this system, additional inputs are used to allow the system to select from three shift modes: engine braking, standard and uphill. The current Mitsubishi system is an extension of this design. Fig.2 shows the basis of the new system. The engine Elec­tronic Control Unit (ECU) and the Transmission Control Unit (TCU) are linked, and exchange data on engine speed and airflow rate (ie, engine load). In addition, the TCU receives additional inputs on the throttle position, brake operation, steering angle and the transmission shaft speeds. The throttle opening is de­rived from a throttle position sensor, the frequency and/or duration of brake operation by monitoring the brake Fig.2: the new Mitsubishi adaptive system accepts additional inputs, including steering angle and the frequency and/ or dura­tion of brake application. This allows the system to better calculate appropriate shift behaviour during downhill coasting and to match the style of the driver. December 1996  21 Fig.3 (above): if the TCU selects a gear which is too low and thus provides excessive engine braking, the action of the driver applying throttle will cause a correction to the downshift. Conversely, applying the brakes excessively when coasting down a hill – as in Fig.4 (right) – will cause the TCU to shift to a lower gear, thus increasing engine braking. light switch, and the steering angle by a dedicated sensor. The speed of both the input and output shafts of the auto transmission is also measured. This allows the TCU to monitor road speed and to calculate the amount slippage occurring through the transmission. It can then use these inputs as a feedback mechanism to reduce “shift shock”. In some versions of the sys­tem, longitudinal and lateral accelerometers are also employed. Engine braking Engine braking is achieved by calculating an index called “engine brake applicability”. This is carried out by a so-called “neural network” which links together the road gradient, vehicle speed, braking frequency and steering angle with varying degrees of importance. The influence of these various factors depends on empirical data originally gathered by monitoring the gear-shift­ing behaviour of experienced drivers. The aim here is to approximate the decision-making process adopted by a driver in a manual car. However, while downshift timing is primarily controlled by the “neural network” from empirically-collected data, the calculat­ ed timing is not appropriate for all drivers because of their individual preferences and driving styles. A feedback mechanism dubbed “Learning Control” has therefore been added. This judges the driver’s dis­satisfaction with the amount of engine braking being provided by the TCU and corrects the downshift condition until the driver’s preference is reached. This judgement is carried out by monitoring the frequency and/or duration of brake use and by monitoring throttle varia­tions when the vehicle is coasting downhill. If throttle needs to be applied (Fig.3) then the transmission is in too low a gear. Conversely, if the brake is applied (Fig.4) the gear selected is too high. Fig.5 shows how the learning system changes the ease with which up-shifts and down-shifts occur in response to brake and accelerator movement during downhill coasting. Variable shift patterns Fig.5: the self-learning behaviour of the system can be seen here, where the ease of selection of either a downshift or upshift varies with the driver’s preference – as sensed by the TCU through brake or accelerator application while driving down­hill. 22  Silicon Chip A conventionally-controlled transmission has a shift pat­tern similar to that shown in Fig.6. An upshift from second to third, for example, occurs at a certain combination of throttle position and vehicle speed. Similarly, at another precise mix of speed and throttle, the downshift from third to second will occur. It’s this fixed approach which causes the problem of upshifts before corners when climbing a hill. To avoid this, it is necessary to move the upshift lines to a higher speed range. Just how much the upshift points are moved depends on the road gradient, as derived from the TCU sensors. Variations in individual driving styles also require changes to the shift points. For example, a “sporty” (or aggres­sive) style means that the lower gears need to be held to higher engine speeds and also selected more readily. The driving style is evaluated by a variable that Mitsubishi’s engineers call the “Sporty Driving Index”. The “Sporty Driving Index” is calculated by selecting the larger of two input factors – either the engine load index or the tyre load index. On some Mitsubishis (but not on the Australian Mag­na), the tyre load index is calculated by comparing the actual lateral and longitudinal accelerations with the maxima of which the tyre is capable. Similarly, the engine load index is calculated by measuring the actual acceleration and comparing this with the maximum possible acceleration. How hard the car is being cornered or accelerated varies the “Sporty Driving Index”, with the shift point maps then moved as a result. Fig.7 shows a schematic summary of the complete TCU system. Does it work? According to Mitsubishi, the new system selects the correct gear for 80% of the time. This represents a considerable improve­ment on the 40% of a conventional auto transmission and 55% for their second-generation fuzzy system. In Australian Government AS2877 fuel economy tests, the V6 automatic transmission Magna has equal econ­ omy to its manual equivalent on the highway cycle and is only 5% worse Fig.6: in a conventional shift control system the up and down changes always occur at a precise combination of speed and throt­tle position. in the city cycle. By comparison, the current model automatic Commodore is 6% worse than the manual version on the highway and 9.5% worse on the city cycle. It would certainly appear that the more sophisti­ cated transmission control system of the Magna yields economy benefits! So what’s it like to drive? We took an automatic TE Magna sedan for a run to find out. On the road we found that the electronic control system had some noticeable advantages over more traditional transmission control systems. Most obvious was the transmission down-changing to provide engine braking when slowing for a red traffic light, for example. And on country roads, the downhill engine braking was also noticeable. However, many of the traditional disadvantages of an au­tomatic transmission appeared to remain. Any demand for instant power (eg, when overtaking on a country road) still results in a relatively slow response, there being approximately a 1-second time lag for the transmission to “think” and then change down a gear. A quicker response was possible by manually changing down. Jerky changes also occurred in some situations – for example, when accelerating hard away from a standstill and then suddenly lifting the throttle. That said, Mitsubishi’s new adaptive control system repre­sents a real improvement in automatic transmission technology. It matches the shift points to suit the driver and it provides superior shift patterns in certain driving situations. And it does this unobtrusively. Certainly it never occurred to me that the transmission was pre-empting my decisions or matching its change SC patterns to my driving style! Fig.7: block diagram of the TCU. The shift pattern is calculated from a range of input data. December 1996  23 By LEON WILLIAMS VK2DOB ACTIVE FILTER cleans up weak CW reception Dig out those weak CW signals from the noise and inter­ference with this simple filter unit. It easily connects between any receiver and an external speaker. Unlike other designs that use a fixed narrow filter this unit has a variable filter control for obtaining optimum reception. Most radio receivers are only intended to receive voice signals and are required to have an audio bandwidth of several kilohertz. A typical amateur band receiver fitted with a SSB filter has an audio frequency response from 300Hz to 2700Hz, giving a bandwidth of 2400Hz. By contrast, the frequency compon­ ents of a CW signal only occupy a bandwidth of 100Hz or so, depending on the sending speed. It is quite obvious that there is plenty of room in the receiver bandwidth 24  Silicon Chip to fit a little CW signal. This situation is quite OK until another CW signal or some interfering signal is received perhaps only a few hundred Hertz away. We are now in the situation of trying to decipher a CW signal amongst a whole lot of other sounds. It’s a bit like trying to listen to a small voice in a noisy crowd of people. The solution is to narrow the audio frequency response so that the interfering signal is filtered out, leaving the wanted signal on its own. There are two main ways of doing this. First, a narrow crystal filter can be switched in to the intermediate frequency (IF) circuits of a superheterodyne receiver. A typical bandwidth might be 500Hz. When normal voice signals are to be received, the narrow filter can be switched out and a wider (2400Hz) filter switched in. Filters such as this are quite expensive and you would have to be a keen CW operator to consider this. The second alternative is to switch in and out a narrow audio bandpass filter somewhere in the audio stages of the receiver. This technique can be used in both superheterodyne and direct conversion receivers. Direct conversion receivers do not have IF stages. Once again, the filter needs to be switched out when voice signals are received, because the narrow filter would eliminate too many frequency components of the voice and probably make it unintelligible. A recent innovation is the use of out­ board DSP processors which digitise the voice signals and through digital manipulation result in various filter responses. These units are expensive, costing hundreds of dollars. This Adjustable CW Filter has a number of advantages over the methods mentioned above. Firstly, it is self-contained, is powered from a DC plugpack and no modifications need to be done to the receiver. Also it is inexpensive to build, uses standard parts and it simply connects between the speaker socket or audio output of the receiver and an external speaker. The front panel has two controls, Volume and Filter. The filter control can be adjusted to give any bandwidth between wide open (no filtering) and a very narrow band pass response centred on 800Hz. The filter control can also be used to good effect with voice signals by acting to reduce the level of high frequency noise and interference. If 800Hz is not your favourite frequency this can be changed, as explained later on. Fig.2 shows the range of filter responses provided by the unit. A special feature is a LED on the front panel that is turned on when 800Hz is detected. This gives an indication that you are tuned correctly to the CW signal and also it is an oppor­tunity to learn to “read” CW by decoding the flashes with the volume turned down. Circuit description The complete circuit is shown in Fig.1. Audio signals from the receiver are fed to the 10kΩ trimpot VR1. The minimum input level that the tone decoder will function correctly is about 70mV RMS or 200mV peak-peak. Following VR1 is op amp IC1a which has a gain of two. A 560pF capacitor connected across the 100kΩ feedback resistor from pin 2 to pin 1 provides some low pass filtering. As we are not using separate positive and negative power supply rails, the non-inverting input (pin 3) is biased Fig.1 (right): the circuit is a variable bandpass filter centred on 800Hz and includes a tone decoder (IC2) to indicate when the receiver is correctly tuned for CW transmissions. December 1996  25 PARTS LIST 1 metal case, 102 x 62mm x 148mm (W x H x D) 1 PC board, code 06112961, 97 x 68mm 1 9-12V DC plugpack 1 DC panel socket 1 6.5mm mono jack socket 1 RCA panel socket 2 20mm knobs 1 LED bezel clip 1 10kΩ log potentiometer (VR4) 1 10kΩ dual linear potentiometer (VR2a,VR2b) 2 10kΩ horizontal trimpots (VR1,VR3) 17 PC pins Semiconductors 1 TL074, LF347 quad op amp (IC1) 1 LM567 PLL tone decoder (IC2) 1 LM386 audio amplifier (IC3) 1 1N4004 diode (D1) 1 5.6V 1W zener diode (ZD1) 1 5mm green LED (LED1) Capacitors 1 1000µF 25VW electrolytic 1 470µF 25VW electrolytic 3 100µF 25V electrolytic 6 2.2µF 63V electrolytic 5 0.1µF MKT polyester 1 .047µF MKT polyester 4 .022µF MKT polyester 2 560pF ceramic Resistors (0.25W, 1%) 6 100kΩ 2 820Ω 4 47kΩ 1 180Ω 2 10kΩ 1 100Ω 1 5.6kΩ 2 10Ω 1 1kΩ Miscellaneous Screws, nuts, spacers, hook-up wire to half the supply voltage by two 10kΩ resistors. A 100µF capacitor helps filter out noise. This half supply voltage point is also connected to the non-inverting inputs of the other three op amps in IC1. The output of IC1a is split into two paths. First, it is applied to the input of an audio bandpass filter using IC1b. This stage has been designed for a centre frequency of 800Hz, unity gain in the passband and a -3dB bandwidth of 150Hz. 26  Silicon Chip AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz) 5.0000 01 NOV 96 13:53:59 0.0 -5.000 -10.00 -15.00 -20.00 -25.00 -30.00 -35.00 -40.00 -45.00 20 100 1k 10k 20k Fig.2: this diagram shows some of the bandpass respons­es available from a filter, ranging from a deep notch to quite wide. When calculations are done for any audio filter circuit, it’s almost certain that non-standard value components will be called for. The components specified in the parts list are close enough to the calculated values without greatly affecting the performance. The output of this stage is connected to an identi­cal stage using IC1c. The combination of these two bandpass stages provides a narrow response with high attenuation of fre­quencies either side of the passband. Fig.3 shows the general filter configuration and the formulas used in the design calcula­tions. The output of IC1c is coupled to one half of a dual-gang potentiometer (VR2b) by a 2.2µF capacitor while the output of IC1a is coupled via another 2.2µF capacitor to the second gang (VR2a). The mixer stage uses IC1d and has unity gain. The wipers of VR2a and VR2b are each connected to the mixer stage by a 100kΩ resistor and a 0.1µF capacitor in series. The point to note is that when VR2 is fully anticlockwise, no signal is passed from the bandpass filter output to the mixer, while the full output of the unfiltered signal from IC1a is fed through. When VR2 is rotated fully clockwise, the reverse occurs and only the output of the bandpass filter is fed to the mixer. By varying the position of VR2 we can obtain any degree of filtering between narrow in the clockwise position and wide in the anticlockwise position. The output of IC1d is coupled to the Volume control (VR4) via a 2.2µF capacitor. VR4 varies the signal level applied to the audio power amplifier IC3, an LM386. This drives an external speaker. The 2.2µF capacitor from pin 7 to 0V is included to reduce the level of hum to an acceptable level when a plugpack power supply is used. The 10Ω resistor and .047µF capacitor help keep the amplifier stable at high frequencies. 800Hz indicator IC2 is an LM567 tone decoder, which turns on the LED (LED1) when 800Hz is applied to its input. The LM567 is actually a phase locked loop circuit which compares an internal oscillator to an external signal at pin 3. When they are within a few hundred Hertz of each other, the open collector output at pin 8 switches to 0V and lights LED1. The frequency of the internal oscillator is determined by the resistance between pins 5 & 6 and the capacitor from pin 6 to ground. With the values shown on the circuit the frequency can be varied between about 600Hz and 1500Hz by VR3. The capacitors from pins 1 & 2 to ground provide filtering for the internal circuits and also affect Fig.3: the general filter configuration & the formulas used in the design calculations. the detection bandwidth. The values shown on the circuit were arrived at through experimentation by monitoring LED1 for correct operation under various signal condi­tions. A 180Ω resistor, a 5.6V zener diode ZD1 and a 100µF capaci­tor provide a regulated 5.6V power supply for IC2. The full circuit is powered by a 9-15V 500mA DC plugpack. Typically this will be a 12V 500mA plugpack. Diode D1 provides protection against the power supply being connected with reverse polarity. A 10Ω resistor and a 1000µF capacitor decouple the power supply line and reduce the level of hum. Construction The prototype Adjustable CW Filter was housed in a standard metal case measuring 102mm wide, 62mm high and 148mm deep. The parts are mounted on a PC board measuring 97 x 68mm and coded 06112961. The PC component overlay and wiring diagram is shown in Fig.4. Start construction by assembling the Fig.4: the PC component overlay and wiring diagram for the CW filter. Check your work carefully before applying power. PC board. Inspect the board for shorts between tracks and correct hole sizes. The holes for the trimpots, PC pins and diodes may need enlarging. Use the component overlay as a guide and solder in the resistors, trim­pots and diodes first. In some cases, a low impedance termination will be required by the amplifier in the receiver; eg, 8Ω or 10Ω. If this is the case, an 8Ω or 10Ω 0.5W resistor can be connected across VR1; provision has been made for this on the PC board, Install the PC pins next, followed by the capacitors. Double check the polarity of the electrolytic capacitors to make sure they are installed correctly. Finally, solder in the three integrated circuits, again checking that they are in the correct positions. The parts list details the components associated with the bandpass filters for a centre frequency of 800Hz. If you want to change this, use the equations in Fig.3 to calculate the new values. When it is complete, put the PC board aside and mark out and drill December 1996  27 The completed CW filter is easy to set up and adjust, provided you have access to a multimeter and an audio signal generator. Use cable ties to keep the wiring neat and tidy. the holes in the metal case. There are three holes required on the front and back panels and four mounting holes in the base. Install the sockets on the rear panel and the pots and LED on the front panel. The LED is held in place with a plastic bezel clip. Mount the PC board in the case with 3mm screws and nuts and 6mm spacers. This done, connect the sockets, pots and LED to the PC board with hook-up wire. The prototype used separated cores from rainbow ribbon cable which makes the job of tracing wires easy. If you have trouble identi­ fying the tags of the DC socket, plug the plugpack into the socket, turn on the power and check the voltage and polarity with a multimeter. Finally, fit the two knobs and adjust them so that when the pointer is vertical the pots are at mid-position. Fig.5: actual size artwork for the PC board. Testing To test and adjust the filter you should have a multimeter and an audio generator. If you don’t have an audio generator, try to borrow one as it makes the setting up process easy. Turn the filter and volume pots fully anticlockwise and the input trimpot VR1 and the decoder trimpot VR3 fully clockwise. Plug a speaker into the speaker socket, connect the DC plug­ pack and connect the audio generator to the receiver socket. Power up the CW filter and measure the voltage between pin 6 of IC3 and 0V. If you are using a 12V plugpack 28  Silicon Chip Fig.6: actual size artwork for the front panel. this reading will probably be around +14V. Most plugpacks are unregulated and only really get to their rated voltage at full load, so don’t get too alarmed if the reading seems high. If the reading is 0V or close to 0V, check to see if the plugpack polar­ity is reversed or that diode D1 is around the wrong way. If these check out OK there may be a short circuit in the PC board. Turn off the power straight away and check the PC board for problems. There could be a component in the wrong way, shorts between tracks or a wiring error. If everything appears OK, set the audio generator to 800Hz (or the alternate frequency chosen for the bandpass filters) with an output of around 100mV RMS. Adjust the volume pot so that you can hear the tone in the speaker. Now, using a small screwdriver, turn the decoder trimpot VR4 until the CW LED turns on and note VR4’s position. Keep rotating VR4 until the CW LED turns off, again noting the position. This done, return VR4 to the midpoint between these two positions, disconnect the audio generator and check that the CW LED turns off. That’s all there is to setting up the CW filter. The lid can now be fitted to the base using four self-tapping screws. Using the filter The CW filter is designed to sit alongside your receiver and be permanently connected. The method of connection to the receiver will depend on the specific receiver. Probably it will have an external speaker socket. When using this option you will need to check that the internal speaker is disconnected otherwise you will hear both the unfiltered and filtered signal at the same time. Some receivers have an output that is not directly from the speaker but from a low level audio signal point before the speak­er. If you use this option you will need to once again make sure the speaker in the receiver is turned off. As mentioned previous­ly, if the output of your receiver overdrives the CW filter, adjust the input trimpot VR1 until the sound from the speaker is undistorted. If you don’t have an external speaker for your receiver, now is the time to get one. There are commercially available speaker boxes specifically suited for this purpose or you could buy yourself a cheap speaker and build a box to mount it in. The cheapest solution could be to use a small speak­er box from a discarded mini stereo system. In any event, the sound from an external speaker will almost always be better than that obtained from the little speak­ers found in most receivers. To operate the CW filter, turn the filter control to the wide position and adjust the volume control to suit. Tune in a CW signal on the receiver and watch the CW LED until it flashes in time with the bursts of tone. Turn the filter control clockwise until the CW signal is clear of any interference and easy to listen to. If the interfering signal is wideband it won’t be possible to completely filter it out as some of it will lie in the filter passband but a significant improvement will be heard anyway. You will be amazed how effective the CW filter can be when listening to a noisy crowded band. A small CW signal can sometimes hardly be heard but when the filter control is turned to narrow, the CW signal seems to jump out from the noise. Of course, if the band conditions are good the filter con­ SC trol can be left in the wide position. 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.winradio.com/ December 1996  29 BOOKSHELF Understanding & Servicing Compact Disc Players Understanding and Servicing CD Players by Ken Clements. Published September 1994 by Newnes. ISBN 0 7506 0934 6, 255 x 195mm, hard covers, 202 pages. R.R.P. $69.95. To most of us, the compact disc player is still a black box into which we place our discs, press a button and music issues forth. It is only when the music doesn’t play that we wish we knew more about them. This book, written by the former technical training manager of Pioneer in the UK, will certainly fill the gap in knowledge. The Author begins with an introduction to the principles of CD playback, goes on to discuss optical assemblies and servo systems, then analyses the various types of circuits used to control and decode the disc information. Further chapters cover test modes and adjustments, system control and fault diagnosis. There is also one chapter covering the similarities and differences between domestic and car play­ers. For anyone to successfully service any electronic equip­ment, it is necessary to have a reasonable understanding of the theory behind that product. To this end the Author begins in chapter 1 by giving some technical details on the playback of compact discs. Unlike vinyl records which rotate 30  Silicon Chip at a constant 331/3 RPM from outside to inside (constant angular velocity), the CD starts playing from near the centre at a speed of around 500 RPM and finishes at around 200 RPM at the edge. This is done to retain a constant linear velocity which allows a lot more music to be recorded on the disc. Clements explains how the original audio is processed, with error correction bits and synchronising words added, before the digital data is encoded on the disc. This description is helpful for, if you are unaware of the encoding process, when the decod­ing processes are described, they will not make much sense. Chapter two gets down to the actual details of the CD player itself. The optical assembly, which recovers the data from the disc, is obviously one of the most important assemblies in the unit. Being a mechanical system which has to track the data across the disc, it can be expected to be one of the more trou­blesome areas as well. Once the information is recovered from the disc it is fed to an RF amplifier to increase the signal level. This high level signal is then fed to a focus servo, a tracking servo and a decoder to recover the audio. The optical system needs to be focused precisely on the compact disc pits to ensure that the recovered information is as accurate as possible. As well as focusing, the optics need to move from centre to edge, to track the “groove” as the disc rotates. These functions are carried out by servo amplifiers and servo motors. Chapter 3 covers the various types of optical assemblies. These can be a single beam device with radial tracking, or single or 3-beam devices with linear/straight line tracking. Philips CD players are typical of those using the first system. The second type is found in Technics models, although Pioneer used this system in its early car players. The 3-beam system is used by Akai, JVC and Kenwood among others. The chapter explains how 4-diode and 6-diode tracking and focus sensors are affected by misalignment between the laser and the disc. It also describes the various methods used to drive the tracking amplifier. Chapter 4 delves into the servo systems used to keep the beam in focus on the disc and to drive the optical system across the disc. The tracking servo drives a tracking coil (similar to a tiny loudspeaker), which has a range of around 2mm, as well as the tracking servo motor. This lets small adjustments to the tracking be carried out by the coil and the larger movements by the motor. The spindle motor, which spins the disc at a continuously varying speed, is controlled by another servo which compares the motor speed with the reference sync frequency of 7.35kHz from the disc. The spindle speed does not have to be stable; in fact it can be varied up and down to ensure that the data read from the disc does not overflow the digital storage area. The virtually immeasurable wow and flutter of CD players is obtained by clocking the data out of the storage area under crystal oscillator control, the stability of a crystal oscillator being typically a few parts per million. Early players used a large range of discrete components, which made them expensive to build. The latest units use just a few large scale integrated (LSI) circuits specifically designed for the task. The fifth chapter describes the operation of some of these integrated circuits and lists the part numbers of those used for the RF processing, servo operation and decoding. Most players use a selection of either Philips or Sony chips. The 36 pages of this chapter discuss, using block diagrams, the following circuits; focus error, focus OK, EFM comparator, disc defect, radial error processor, spindle, VCO and data decod­ers. We now come to the chapter which tells us how to locate and (hopefully) repair faults. The main instruments needed, apart from a few basic tools, are a multimeter and an oscilloscope. Some players such as the Philips and Pioneer have a built-in service mode whereby you can test functions like the focus and tracking. This mode is enabled by holding down a combination of front panel buttons before turning on the mains power. Naturally, someone unfamiliar with CD players should not attempt any repairs without the service manual, as “twiddling” adjustments without fully understanding the outcome can only cause further problems. For optical alignment a suitable test disc is really neces­sary. These are made by various companies including Philips, Sony and Technics. As many of the circuits in a CD player are DC (direct coupled), it is necessary to ensure that all oscilloscope measurements are made with the input coupling set to DC and preferably using a 10:1 probe. Many service people are used to leaving the input coupling on AC. With AC coupling any DC offset adjustments to the player may appear to work, as the trace will move up or down, but even­tually it will return to the original position, probably causing a search for a non-existent fault. The Author recommends that electrical adjustments be car­ried out in the following order: focus offset, tracking offset, RF offset, laser power, tracking balance, focus balance, focus bias, photodiode balance, RF level, focus gain, tracking gain and VCO frequency. If mechanical adjustments are need­ ed, the recommended se­quence is as follows: turntable height, tangential adjustment, lateral adjustment and diffraction grating adjustment. This chapter covers both the electrical and mechanical procedures for a varie­ty of different brands of players. The next chapter briefly covers system control, which is the interface between the buttons on the front panel or remote control and the electronics, usually via a microprocessor. Chapter 8 is a summary of car CD players with emphasis on the multi-disc variety and their start-up procedures, as well as the differing power supply requirements of car systems, which must operate from a 12V battery. The final chapter, titled fault diagnosis, contains a number of block diagrams which give a step-by-step guide to checking the various functions in a logical sequence, with advice on the adjustment to be made if the test fails. Obviously, the initial checks should be for cleanliness of the lens system and correct operating voltages. The 28 pages of this chapter cover tests on a number of proprietary players as well as general tests. It also shows a number of typical oscilloscope waveforms to be expected at vari­ous points in the circuits. I believe this is an ideal book for any person who is not already into CD service and is thinking of doing so, or for the inquiring mind that likes to keep up with the theory and operation of modern electronic equipment. However, it was pub­lished in 1994 and while the principles remain the same, most current CD players will probably not use the ICs re­ferred to in the text. Our copy was supplied by Butter­ worth-Heinemann, West Chats­wood, SC NSW. (R.J.W.) Are you frustrated using DOS or non-compliant Windows software? If so then you may be interested in the following schematic design software trade-in offer from OrCAD. Here are 7 good reasons to trade-in your old schematic software tool to OrCAD Capture for Windows… ❶ De-facto standard schematic capture software. OrCAD is the best-selling package with over 180,000 licensed users worldwide. ❷ Easy to use and learn. Capture has an online tutorial and hypertext ‘Help’. ❸ Works on Windows 3.x, Windows 95 and Windows NT. Support for all platforms provided in one box. ❹ True 32-bit application. Faster processing on 32-bit platforms. ❺ Cut, copy and paste between Capture and other Windows compliant software. Developed to comply with Microsoft Foundation Class. ❻ Supports hierarchical designs. Create complex designs in modular form. ❼ Only $799 (Trade-in offer to all registered owners of Protel schematics and selected other schematic capture software tools. Normally $2195). ✄ Please send me more information on OrCAD Capture for Windows. My details are: Name: Company: Address: Phone: Fax: I am using the following brands of software: Schematic Entry: Simulation: PCB Design: (Fax this form to EDA Solutions on 02-9413 4622 or ring and ask for Richard on 02-9413 4611) SC11/96 Level 3, South Tower 1-5 Railway Street CHATSWOOD NSW 2067 Australia Ph: +61-2-9413 4611 fax: +61-2-9413 4622 email: info<at>eda.com.au Offer for a limited time only. December 1996  31 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 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. Overload protected power supply Many regulated power supplies make use of LM78xx or LM317 series devices which are cheap and perform well. These ICs are protected from overloading but under short circuit conditions they allow a small yet significant current to flow. This can be enough to damage the device connected to the power supply. By contrast, this circuit employs a series transistor to shut off current when an overload condition occurs. Power is not restored until a reset button is pressed. The circuit consists of three func36  Silicon Chip tional blocks: current sensing circuits based on Q1 & Q2, a bi­stable protection circuit (Q3 & Q4), and positive and negative 3-terminal regulators (REG1 & REG2). Q1 turns on when a current of more than 1A flows through current sensing resistor R1. The RC network at the base of Q1 provides filtering to prevent transients from triggering the protection circuit. When an overload does occur, the bistable protection circuit is triggered and Q4 turns on. A 2N3904 was chosen here due to its low VCES of about 0.2V. When Q4’s collector goes low, Q5 & Q6 are turned off, as are Q7, Q8 & Q9; ie, both supply rails shut down. Similarly, R2 and Q2 provide current sensing for the negative supply rail and they turn Q3 off in the bistable protection circuit when an overload occurs. This then turns Q4 on and so Q5, Q6, Q7, Q8 & Q9 off to shut down the supply rails, as before. Switch S2 is used to reset the bistable protection circuit after the cause of the overload has been removed. The regulator section uses LM317 and LM337 adjustable regu­lators, with a 2-pole, 6-position switch providing output voltages of 3, 5, 6, 9, 12 and 15V. Note that both regulators should be mounted on a heatsink. B. Low, Gwynneville, NSW. ($35) Adding 1/4 stops to the Phototimer The Phototimer published in the April 1995 issue provides a range of exposure times with the individual range steps increas­ing by a factor of 1.414; ie, the square root of 2. Thus, each switched increase in exposure is equivalent to opening the en­larger aperture by a half-stop. However, one of our readers has pointed out that this ratio between switch steps is still a little too coarse for photograph­ic work and that an ability to provide for quarter stops would be better. Ac- cordingly, this circuit modification involving an extra switch (S3) provides that facility. In the upper setting, S3 provides an exposure increase equivalent to a quarter stop while the lower setting provides a quarter stop decrease in exposure time. S3 and the associated two resistors act to shift the threshold voltage at pin 5 by approximately +1.2:1 and -0.85:1; ie, roughly quarter stop ratios. The precise factors are 1.189 and 0.84. S3 is a centre-off switch. SILICON CHIP VCO has constant mark/space ratio The standard 555 astable circuit can be made into a VCO by varying the capacitor charging voltage. However, the discharge period is fixed by the resistor between the discharge and threshold pins (2 & 6), limiting the range of frequencies available. In addition, the charge time must always be greater than the discharge time, limiting further the range available. In this circuit, the capacitor discharge time of IC1 is controlled by op amp IC2. The DC voltage at pin 3 of IC1 is compared to a reference and the op amp adjusts its output to maintain a constant mark-space ratio. This gives a much greater range of control and, as a bonus, a greater control range of the mark space ratio if desired. The circuit operates as follows. When charging the capaci­ t or the output is high and Q1 is off, so that the charge period is determined by R1/C1. When the capacitor reaches 2/3Vcc, the output switches low, Q1 turns on and the capacitor is discharged by the op amp until 1/3Vcc is reached and pin 3 of IC1 switches high. R3 and C3 average the output to provide the mark-space ratio feedback for the op amp (IC2). The time constant of this network should be at least 100 times the period of one output cycle at the lowest frequency of operation. This time constant determines the settling time for the output after a control input change. A voltage reference for the op amp is provided by voltage divider R5 & R6; equal values provide an output mark-space ratio of about 50%. By running the 555 from a split supply the circuit can be used to drive a transformer directly to ground. In this case, if the op amp reference is connected to ground, no DC will flow through the transformer primary. D. Timmins, St Peters, NSW. ($35) Especially For Model Railway Enthusiasts THE PROJECTS: LED Flasher; Railpower Walkaround Throttle; SteamSound Simulator; Diesel Sound Generator; Fluorescent Light Simulator; IR Remote Controlled Throttle; Track Tester; Single Chip Sound Recorder; Three Simple Projects (Train Controller, Traffic Lights Simulator & Points Controller); Level Crossing Detector; Sound & Lights For Level Crossings; Diesel Sound Simulator. PRICE: $7.95 (plus $3 for postage). Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. December 1996  37 Fast clocks running at six to eight times actual speed are desirable for model railways which run a 24-hour schedule in a compressed time of three to four hours. A fast clock for railway modellers Are you a keen railway modeller? Do you run your trains to a schedule? If so, you will want to build this fast clock which can be set to run at between 4.5 and 8.5 times faster than normal. By LEO SIMPSON Why would anyone ever want a fast clock? Surely time passes rapidly enough as it is, except, of course, in the afternoons at school or work. But there is a sound reason and it has to do with running trains to a schedule on a model railway layout. Because model railway layouts are always much smaller with respect to scale than the real thing, the times taken to run a train from one point to another are ridiculously small, in real time. 38  Silicon Chip For example, while the distances on real railways can be hundreds of kilometres and the trains can take many hours or even days to get to their destination, a typical large model railway would be unlikely to have more than 50 metres of track. For HO scale (1:87), this equates to 4.3 scale kilometres; for N scale (1:160) it equates to 8 scale kilometres. Even on these large layouts, the time for a train to make several circuits will be measured in minutes rather than hours. So to inject a little more realism into a model railway train schedule, it makes sense to use a “fast clock”. But there is another more practical reason which has nothing to do with scale factors and this has more to do with the number of spare hours in an evening. Typically, a model railway club will have a running session which lasts around three hours in an evening but a “realistic” operating session should last at least one day, or 24 hours. So the club needs to squeeze 24 hours of operation into a real time of three hours or so. The reason for the fast clock now becomes clear – it needs to run about 6 to 8 times faster than normal. The question is, how do you make a clock run this fast? Our approach was to take a typical crystal controlled clock movement which is more or less Fig.1: this is a typical circuit for a 1.5V crystal controlled clock movement. It uses a 32kHz crystal and drives the clock stepper motor coil with pulses at 1-second intervals. typical in zillions of battery operated clocks. Fig.1 shows a typical circuit using a Samsung chip. It uses a single CMOS IC operating from a 1.5V AA cell and con­trolled by a 32kHz crystal. The IC has an internal divider chain which produces complementary pulses to drive a stepping motor. Fig.2 shows the oscilloscope waveforms from the clock movement used in this article. As can be seen, there are two pulse trains, each with pulses about 30ms long and exactly two seconds apart. The pulse trains are staggered by one second. What actually happens is that the IC applies a pulse to the clock coil (the stepper motor) in one direction and then one second later, applies the same pulse in the opposite direction. This operates the escapement which makes the ticking sound and drives the clock hands. Our first approach was to see if we could make the chip operate six to eight times faster than normal. The simplest way to do this would be to Fig.2: this digital oscilloscope printout shows the waveforms from the circuit of Fig.1. In effect, there are two pulse trains with pulses two seconds apart. A pulse is applied to the coil in direction (upper trace) and then a pulse in the opposite direc­tion is applied to the coil (lower trace). The oscilloscope timebase for these waveforms is 500ms/div; the printout is five seconds long! replace the 32kHz crystal with one of 192kHz but such crystals are not readily available. Hence, we decided to remove the 32kHz crystal and to drive one of the oscillator pins of the chip with an external oscillator based on a 7555 CMOS timer. The first hurdle with this approach is that a 7555 will not operate at 1.5V. It will operate with a 3V supply so we cobbled together a suitable circuit with a voltage divider at the output, to make the signal compatible with the 1.5V clock chip. Fig.3 shows this approach. Did it work? Well, yes and no. It would work up to about 100kHz or so but higher than that and the clock mechanism itself refused to work. The reason appears to be the length of the Fig.3: our first attempt at a speed-up circuit involved using a 7555 CMOS chip driving one of the crystal input pins on the clock chip. The circuit conked out if we attempted a speed-up of more than four times. pulses applied to the clock stepper motor. In the standard clock, the pulses are typically 30ms or 46ms long and their length is a fixed relationship to the 32kHz crystal. At an oscillator frequency of, say, 128kHz, the clock pulses would only be one quarter as long (ie, 7.5 or 11.5ms) and this appears to be insufficient to operate the motor reliably. We tried a number of circuit variations, such as operating the clock chip from 3V which is in excess of the ratings but it still did not work. Final circuit The next approach was to scrap the crystal controlled cir­cuit and develop a new circuit to drive the clock stepper motor directly. This is shown in Fig.4. Again it is based on a 7555 CMOS timer, IC1. This operates at a frequency of between 4.5Hz and 8.5Hz, as set by the components at pins 2, 6 & 7. The fre­ quency is adjustable by trimpot VR1. The output of IC1 can be varied between 4.5Hz and 8.5Hz and thus the speed-up factor can be varied between 4.5 and 8.5 times by trimpot VR1. The output from pin 3 is inverted and buffered by NAND gate IC2a and then applied to IC3, a 74HC76 flipflop. This divides the output by two and produces complementary outputs at pins 14 and 15. These are gated toDecember 1996  39 PARTS LIST 1 1.5V crystal controlled clock movement 1 PC board, code 09112961, 67 x 38mm 2 1.5V AA cells 1 double-AA cell holder and battery snap connector 1 1MΩ trimpot (VR1) Fig.4: our final circuit for the Fast Clock Driver uses three ICs: a 7555 CMOS timer, a 74HC76 flipflop and a 74HC00 NAND gate chip. The circuit drives the clock coil directly, dispensing with the internal clock circuitry. gether with the pulses from pin 11 of IC2a to provide complementary pulses from pins 3 & 6 and of IC2. Fig.5 & Fig.6 shows the output waveforms at two different clock speeds, six times and eight times. Fig.5 shows the waveforms when the clock is operating at six times normal speed while Fig.6 shows it operating at eight times normal speed. Considering Fig.5, the upper trace (Ch1) is the waveform at pin 3 of IC2b while the lower trace (Ch2) is the waveform at pin 6 of IC2c. In effect, while the period of both waveforms in Fig.5 is 333ms, the clock coil receives stepping pulses 166.5ms apart which is six times faster than the normal stepping rate of one per second. A similar situation applies in Fig.6 except that the period of both waveforms is 250ms and the speed-up is eight times. Notice that the pulse width applied to the motor is between 15 and 16ms which is half that applied to the clock in normal operation and as shown in Fig.2. There are two reasons for this. First, the clock motor itself is designed to run from a circuit powered with a 1.5V cell whereas our circuit uses 3V. We have used 3V because the CMOS chips specified will not run reliably below 2V. This means that the pulses delivered from the modified circuit were twice the voltage they should be. Paradoxically, because the clock coil was being driven so hard, its operation became unreliable at the higher speeds. We could correct that problem by inserting a 330Ω resistor in series with the clock coil but then the effective battery life would be reduced; as the battery voltage dropped, the pulse drive was unduly reduced by the series resistor. Our final version, presented in Fig.4, Fig.5: waveforms from the circuit of Fig.4, taken at pins 3 & 6 of IC2. The speed-up factor is six times. The oscillo­ scope time­base is 50ms/div. 40  Silicon Chip Semiconductors 1 7555, LMC555 CMOS timer (IC1) 1 74HC00 quad 2-input NAND gate (IC2) 1 74HC76 dual JK flipflop (IC3) Capacitors 1 100µF 16VW electrolytic capacitor 3 0.1µF MKT polyester 1 .01µF MKT polyester Resistors (0.25W, 1%) 1 820kΩ 0.25W resistor 1 150kΩ 0.25W resistor compensates for the higher pulse amplitude by halving the pulse width and eliminating the series 330Ω resistor. This has the benefit of allowing the circuit to work reliably down to below 2V which means that the batteries last longer. PC board We designed a small PC board to take the circuit of Fig.4. It measures 67 x 38mm and is coded 09112961. Its component layout is shown in Fig.7. Fig.6: waveforms from the circuit of Fig.4, taken at pins 3 & 6 of IC2. The speed-up factor is eight times. The oscillo­ scope timebase is 50ms/div. Left: when you pull the back off the clock movement, it will look like this. Be careful not to scatter the parts. If you lift off the two top gears, you will be able to remove the PC board and coil assembly. The photo above shows how we made two cuts to the PC tracks and then connected two fine gauge enamelled copper wires direct to the clock coil terminals. Fig.7: follow this parts layout to build the Fast Clock Driver circuit of Fig.4. When assembling it, make sure that all three ICs are correctly oriented and that the 100µF electrolytic ca­pacitor is correctly polarised. You will need four PC stakes, two for the battery connec­tions and two for the clock coil connections. Assembling the PC board and get- Fig.8: this is the actual size artwork for the PC board. Check your board carefully before installing any of the parts. ting it going is the easy part. Pulling the clock apart and making the connections to the clock coil are a little trickier but it just takes a little care. Essentially what must be done is to remove the hands and time-setting knob, undo one screw and unclip the clock case. Then, while the clock is This photo shows the assembled Fast Clock Driver. Two wires connect it to the clock movement. face down, lift out two gears and then the internal PC board. In practice, you will find that the PC board actually sup­ports the coil so it cannot be removed and discarded. Instead, you must cut the PC tracks where they connect to the coil. Then you need two fine wire connections to the coil which can be brought out through the side of the clock case. You can then reassemble the clock and connect it to the new driver board. When power is applied the clock should immediately start running and the speed-up factor should be variable between about four and nine times, depending on the setting of trimpot VR1. We suggest that you leave the second-hand off the clock; it will go around so fast that the effect will be SC ludicrous. December 1996  41 Silicon Chip Back Issues September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Operating an R/C transmitter; Index to Volume 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages; A Look At Very Fast Trains. 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. April 1990: Dual Tracking +/-50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car; Fitting A Fax Card To A Computer. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band; the Bose Lifestyle Music System. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2; The Snowy Mountains Hydro Scheme. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Step-By-Step Vintage Radio Repairs. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; ORDER FORM Please send me a back issue for: ❏ July 1989 ❏ September 1989 ❏ January 1990 ❏ February 1990 ❏ July 1990 ❏ August 1990 ❏ December 1990 ❏ January 1991 ❏ May 1991 ❏ June 1991 ❏ October 1991 ❏ November 1991 ❏ April 1992 ❏ May 1992 ❏ September 1992 ❏ October 1992 ❏ April 1993 ❏ May 1993 ❏ September 1993 ❏ October 1993 ❏ February 1994 ❏ March 1994 ❏ July 1994 ❏ August 1994 ❏ December 1994 ❏ January 1995 ❏ May 1995 ❏ June 1995 ❏ October 1995 ❏ November 1995 ❏ March 1996 ❏ April 1996 ❏ August 1996 ❏ September 1996 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ September 1988 October 1989 March 1990 September 1990 February 1991 July 1991 December 1991 June 1992 January 1993 June 1993 November 1993 April 1994 September 1994 February 1995 July 1995 December 1995 May 1996 October 1996 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ April 1989 November 1989 April 1990 October 1990 March 1991 August 1991 January 1992 July 1992 February 1993 July 1993 December 1993 May 1994 October 1994 March 1995 August 1995 January 1996 June 1996 November 1996 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ May 1989 December 1989 June 1990 November 1990 April 1991 September 1991 March 1992 August 1992 March 1993 August 1993 January 1994 June 1994 November 1994 April 1995 September 1995 February 1996 July 1996 Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ____________________________ Card expiry date_____ /______ Name _______________________________ Phone No (___) ____________ PLEASE PRINT Street ________________________________________________________ Suburb/town ________________________________ Postcode ___________ 42  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. ✂ v SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. December 1993: Remote Controller For Garage Doors; LED Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Door Minder; Adding RAM To A Computer. November 1991: Build A Colour TV Pattern Generator, Pt.1; Junkbox 2-valve receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; A Talking Voltmeter For Your PC, Pt.2. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. February 1994: 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags - How They Work. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. September 1995: Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Directories; Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Multi-Station Headset Intercom, Pt.2. August 1992: An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; MIDI Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Windows-based Logic Analyser. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Build a Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: Dolby Surround Sound - How It Works; Dual Rail Variable Power Supply; Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Temperature Controlled Soldering Station; Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford - A Pesky Electronic Cricket; Cruise Control - How It Works; Remote Control System for Models, Pt.1; Index to Vol.7. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Preamplifier;The Latest Trends In Car Sound; Pt.1. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. March 1995: 50W/Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. April 1995: Build An FM Radio Trainer, Pt.1; A Photographic Timer For Darkrooms; Balanced Microphone Preamplifier & Line Filter; 50-Watt Per Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. May 1995: What To Do When the Battery On Your PC’s Mother­ board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. November 1993: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Transverter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. March 1996: Programmable Electronic Ignition System; Zener Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. May 1996: Upgrading The CPU In Your PC; High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluores­cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; September 1996: Making Prototype Parts By Laser; VGA Oscilloscope, Pt.3; Infrared Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­grammable Ignition (see March 1996). October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; Infrared Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: Adding An Extra Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, May 1990, February 1992, September 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc at $10 including packing & postage. December 1996  43 SERVICEMAN'S LOG There’s a long, long trail a’winding Well, in the words of the popular song, that’s what it seemed like; a long, long trail through circuits and PC boards in search of the most elusive combination of intermittent faults that has been my misfortune to encounter for many years. It is a story about an Akai video cassette recorder, model VS-35 and the problem was an intermittent sound fault. Not just any intermittent sound fault, mind you. This was an intermittent sound fault the like of which I have never seen before – and I hope I never see again. The machine came to me from a colleague, who felt that he could no longer cope with the problem. And so it landed on my bench along with a “best of British luck” attitude. While there was some history of the problem, I suspected that there had been more than one finger in the pie before it reached me. Anyway, I was saddled with it. The gist of the problem was faulty sound on playback although, as far as I could determine, the sound always recorded normally. To test this theory, my first step was as to make a test recording on the machine immediately after observing the sound problem. This tape subsequently played perfectly on another machine, which seemed to clarify this point. But putting such doubts aside, the extent and nature of the faulty sound was the real problem. Sometimes, at switch on, the sound would be perfect for a few minutes, then become intermit­tent. And when it went intermittent, the whole machine became mechanically sensitive; the lightest tap anywhere could turn the sound on or off, as the case may be. Initially, I couldn’t believe what I was observing. It seemed impossible that there would not be some variation in sensitivity which, in turn, would give a clue as to the general location of the fault. But no; touching anything – boards, leads, the deck itself – produced an equal response. Making a start The setup consists of a large mother­ board, a small chroma board, a power supply board and a preamp­ lifier/ audio board. Initially, to the extent that there was any particular sensitivity anywhere, I sensed that the area around the preamplifier/audio board might be marginally more sensitive. I even reached the stage where I could achieve a response by flexing or tapping the board, without it being sup­ported in any way but simply connected by the various leads. I was convinced that this was where the trouble lay. And I wasn’t particularly impressed by the soldering on the underside. There had been some work done on it but there was still a large number of original joints which were, at least, suspect. I set to and checked every suspicious joint and remade anything which looked even remotely suspect. I spent a lot of time on it and by the time I had finished was prepared to bet my reputation on it. Initially, it appeared that the fault 44  Silicon Chip had been cured. But not for long. After a few minutes it was back just as it was before. Well, not quite; the equipment as a whole seemed just as sensitive as before but it now appeared that the area of sen­sitivity had moved to the motherboard. To the extent, that is, that I could be sure of anything. But if it was on the motherboard the implication was that I was chasing two faults; one which I might have found on the preamplifier board and one still to be found. So was it a case of two faults producing essentially identical symptoms? It seemed like an impossible long shot but I was ready to believe anything. Assuming that there had been a fault in the preamplifier board, and that it had been fixed, the next logical step was to investigate the motherboard. Parts of the underside of this had also obviously been worked on, while other untouched areas needed closer scrutiny. The upshot of this was a major overhaul of this board. Any suspect connection, whether it had already been reworked or not, was tackled. It was a long process but when I finished I felt reasonably confident that I had done a thorough job. And so it seemed. When I replaced the board and set every­thing working the machine came good. There was no sign of the sound fault and the machine was seemingly immune from its previ­ous mechanical sensitivity. I let it run for about half an hour or so, giving it an occasional prod or bash, and all seemed well. Or at least it was until I put everything back into place and prepared to fit the cover. Then it was back into fault condi­tion, exactly as it was before. I won’t bore the reader with all the emotions and rude words which resulted from that discov­ery. Suffice it to say that it was back to taws. The methodical approach By now it appeared that the mass soldering approach had served its purpose. If it had done any good at all, it wasn’t good enough. What was now needed was a methodical approach. A major problem here is how best to convey all the circuit ramifications to the reader. We are talking about several A3 sheets, covering both circuit and PC board patterns. Obviously, reproducing these is out of the question and the best I can do is present a Fig.1: part of the audio preamplifier board in the Akai VS-35. Audio from the A/C head (top, right) goes to pins 3, 4 & 5 of IC700, comes out on pin 16, and then goes to the motherboard via pin 12 of connector WF10. word picture which I hope will help the reader follow the story. First, it is it necessary to visualise the audio signal paths where a fault is likely to be. And there are, initially, two sources of audio signal. One comes from the audio track on the tape, feeding the Audio/Control (A/C) head on the deck. These signals are fed to the preamplifier board, on pins 3, 4 & 5 of IC700, come out on pin 16, and go to the motherboard via pin 12 of connectors WF10 (“A.OUT”). The other source comes from the tuner and the IF system on the motherboard, which demodulates the sound IF and delivers an audio signal. These signals involve a longer path but eventually find their way back to the preamplifier board, where the two audio signals are combined into a single audio path which then reappears on the motherboard. This path eventually goes to the modulator but, on the way, connects to an RCA socket, designated as A.OUT, December 1996  45 Serviceman’s Log – continued on the rear of the chassis. This provides a convenient audio check point and the first thing I did was to organise an external amplifier to moni­tor the audio at this point, which is close to the end of the combined audio line. At the same time I arranged things so that the output from the VCR was fed into a TV set. This simple test confirmed that the fault was present at both the RCA A.OUT socket and the TV set. At this point I had to choose between the two audio paths. I was convinced that, whatever I did, it would be wrong (Murphy would see to that) but I had to start somewhere. So, for better or for worse, I elected to check the line coming from the IF system. The signal from the tuner is pro- cessed to IF level, desig­nated on the circuit as VIF, and applied to pins 4 & 5 of IC1 (M51496P) – see Fig.2. The audio signal then comes out on pin 11 of IC1, which was where I started tracing the signal. For this pur­pose, I used a simple audio probe which I have mentioned in previous notes. This confirmed that the signal was intact out of the IF system at pin 11 of IC1, even though the fault was evident at both the TV monitor and the A.OUT socket. Well, that was a good start. From here, via a long path on the circuit, I traced the audio signal to pin 5 of IC201 and then out again on pin 4. It then went to the base of transistor TR213, the signal from the emitter then going to line “SELECT.A” and thence to pin 11 of a 12-pin connector WF10. And the audio signal was still fault free at this point. Now, from pin 11 of connector WF10 on the motherboard, the circuit goes to a similar WF10 connector on the preamplifier board, then into pin 13 of IC700 and out on pin 16. And, as men­tioned earlier, the audio signal from the A/C head on the deck also appears at pin 16. In short, the two signals are combined at this point and the combined signal goes to pin 12 of WF10 and then back to pin 12 of WF10 on the motherboard. And I still had a clean signal at this last point. I was getting close now because there was not much circui­try left between this point and the A.OUT RCA socket where the fault was obvious. But where was it? From pin 12 the signal goes direct- THE “HIGH” THAT LASTS IS MADE IN THE U.S.A. Model KSN 1141 The new Powerline series of Motorola’s 2kHz Horn speakers incorporate protection circuitry which allows them to be used safely with amplifiers rated as high as 400 watts. This results in a product that is practically blowout proof. Based upon extensive testing, Motorola is offering a 36 month money back guarantee on this product should it burn out. MOTOROLA PIEZO TWEETERS AVAILABLE FROM: DICK SMITH, JAYCAR, ALTRONICS AND OTHER GOOD AUDIO OUTLETS. IMPORTING DISTRIBUTOR: Freedman Electronics Pty Ltd, PO Box 3, Rydalmere NSW 2116. Phone: (02) 9638 6666. 46  Silicon Chip Frequency Response: 1.8kHz - 30kHz Av. Sens: 92dB <at> 1m/2.83v (1 watt <at> 8Ω) Max. Power Handling Capacity: 400W Max. Temperature: 80°C Typ. Imp: appears as a 0.3µF capacitor Typical Frequency Response YOU CAN AFFORD AN INTERNATIONAL SATELLITE TV SYSTEM SATELLITE ENTHUSIASTS STARTER KIT Fig.2: IF signals are applied to pins 4 & 5 of IC1 on the mother board (Akai VS-35) and appear as demodulated audio on pin 11. From there, the signal eventually goes to pin 11 of connector WF10 and then to the preamplifier board where it is combined with the audio from the A/C head. ly to a 680Ω resistor, R276, which is mounted alongside the WF10 connector. There was a clean signal on both sides of R276 so I traced the copper track to the next convenient point, a jumper link about 12cm away, near the edge of the board. And bingo! – there was a faulty signal at this point. The fault was somewhere along that 12cm of track. I pulled the motherboard out and examined that length of track in the minutest detail, using my most powerful glass. I couldn’t pick it so I resorted to cleaning away small areas of lacquer on the track, allowing the probe to make contact, until I narrowed the fault to a small length near resistor R270 and transistor TR214. It was then that I noticed a hole in the board through which a mounting screw was fitted. Suppose someone had been a mite too heavy handed in fitting that screw; could it have cracked the track? Now that the search area had been narrowed to within a couple of centimetres I took a long hard with the glass. And, yes, there was no doubt about it; the finest and faintest of cracks could be discerned but only because I knew where to look. As usual, once a fault is found, the whole thing becomes something of an anticlimax; a spot of solder was all that was needed to bridge the gap. Then, just to be on the safe side, I fitted a wire link anyway. That fixed it. No amount of bashing, prodding, or soak testing produced any sign of the fault. I progressively put everything back in place and there was no sign of trouble. Final­ly, I phoned the customer and told him to collect it. He indicat­ed that he would come around immediately. The unbelievable Now you’re not going to believe this. No sooner had I hung up than the machine went into its act again. It is not enough to say that words failed YOUR OWN INTERNATIONAL SYSTEM FROM ONLY: FREE RECEPTION FROM Asiasat II, Gorizont, Palapa, Panamsat, Intelsat HERE'S WHAT YOU GET: ● ● ● ● ● ● 400 channel dual input receiver preprogrammed for all viewable satellites 1.8m solid ground mount dish 20°K LNBF 25m coaxial cable easy set up instructions regular customer newsletters BEWARE OF IMITATORS Direct Importer: AV-COMM PTY. LTD. PO BOX 225, Balgowlah NSW 2093 Tel: (02) 9949 7417 / 9948 2667 Fax: (02) 9949 7095 VISIT OUR INTERNET SITE http://www.avcomm.com.au YES GARRY, please send me more information on international band satellite systems. Name: __________________________________ Address: ________________________________ ____________________P'code: Fig.3: this is connector WF10 on the mother board. The audio signal was clean until after R276, on the way to the modulator. __________ Phone: (_______) ________________________ ACN 002 174 478 December 1996  47 me; no, that wouldn’t be anywhere near strong enough. Unfortunately, no amount of wailing and gnashing of teeth was going to solve the problem. I just had to get stuck into the monster and start all over again. Nor was it any help to know that the customer was on his way and that I would be under pres­sure to either come up with a quick fix or some kind of an excuse, although I couldn’t imagine what it would be. As it transpired, I had a reprieve. The customer had been delayed and rang back after a short time to say that he couldn’t make until the next day. But a reprieve was all it was; I still had to start all over again. By the time I had delved back to where I started I was shocked to find that the fault now appeared to have shifted back to the preamplifier board. Indeed, I quickly found that by flexing it at one corner I could create the fault. After seeking desperately for some kind of inspiration, I finally decided to look more closely at a number of surface mounted components on this board. I was clutching at straws but it was all I could think of. To tell the truth, surface mount components do not usually cause problems – at least not in my experience. Of course, there are a lot of factors that must be considered at the manufacturing level but, provided due care is taken, a surface mount assembly is extremely reliable. So had I overlooked something? As I said, I was clutching at straws but, after going over this part of the board and re-soldering everything yet again, it did appear that the problem was fixed. Mind you, I could be pardoned for being sceptical. Anyway, all seemed well for a while until I started to put everything back together again. Then the fault reappeared only this time it was pretty clear that it was on the motherboard. What was more, after more prodding and flexing, it appeared that the sensitive area was now back near where I had found the origi­nal crack. I fished out the audio probe and began tracing the audio path as before. But this time there was a difference. Originally, the audio signal had appeared as a clean signal on pin 11 of socket WF10 on the mother board, having originated from IC201. And, after its journey to the preamplifier board, it was still clean when it reappeared on pin 12 of WF10. But not this time – the fault was now obvious on pin 11 of WF10. Now the important point about this is that the copper track running from pin 11 runs parallel to the track from pin 12 –the very track containing the fault which I had originally repaired. Another crack It didn’t take Sherlock Holmes to suspect that there might be another crack in the adjacent track. And so it was; this crack was even more difficult to see and the audio probe gave the only positive indication. Any­way, I bridged it as before and tried again. And this time the job held in spite of all I could do it. I even finished the job before the customer turned up. Con­sidering everything, I would have preferred to give the machine a much longer test but the customer wanted it back as soon as he could get it. Yes, I thought the worst every time the phone rang for the next few days but there was no sign of a bounce. A phone call to the customer several weeks later confirmed that the machine hadn’t missed a beat. Still, I’m SC keeping my fingers crossed! 48  Silicon Chip 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 SATELLITE WATCH Compiled by GARRY CRATT* Gorizont 42-142.5°E longitude: Papua New Guinea broadcaster EM TV has commenced limited encryption using a UK-designed Video­crypt scrambling system, for several “premium” USA programs, to protect the original copyright holder. Initially, the decoders will be operate without a subscriber “smart card” but that initial familiarisation period will expire within a month or so. EM TV regularly run an advisory screen explaining these changes. Subscriptions are available only to residents of PNG. Elsewhere on this satellite, Asia Music continues to oper­ate at 1470MHz and RAJ TV, seen until mid-October on the neigh­bouring Gorizont 41 satellite at 130°E, has moved temporarily to this satellite at IF 1420MHz. RAJ TV will eventually move to an Intelsat satellite over the Indian Ocean. Meanwhile, India’s first adult channel “PLUS 21” has yet to commence regular opera­tions, despite a publicised start-up date of October 1st. Gorizont 41 (130°E) now has only one occupant, “Laos TV”, operating at IF 1375MHz. The satellite has been sold by the Russian Space Agency “Inter­sputnik, to the Philippine Agila Satellite Corpora­ tion. To be called “Agila 1”, the satellite will be moved to either 148°E or 153°E and placed in an inclined orbit. The reason for the purchase is the requirement for coverage of the Asia Pacific Economic Cooperation Forum, held in the Philippines during November. Earlier, Agila had expressed inter­est in acquiring Intelsat 505, in return for Intelsat dropping their objection to Agila’s application for the orbital location of 161°E. Intelsat 505 is currently located at 69.7°E. Another Philippines broadcaster, RPN, operating on Gorizont 42 has changed to MPEG format. The broadcaster has adopt­ed the Scientific Atlanta PowerVu platform, limiting the type of receiv­er that can be used to the S/A D9223. Palapa C2M-113°E longitude: there has been only one recent change to this satellite: Star TV’s “Channel V” has changed to MPEG digital format. Now appearing at 1300MHz IF, the transmission uses a Symbol rate of 26.85 and an FEC of 7/8. Presently, sub­scriptions are not available to Australian residents, although this could change after deregulation in July 1997. All other transponders remain unchanged in frequency and a spectral analysis of transponders shows equal power distribution, after several months of adjustment by the satellite operator, Satelindo. This means that CFI, ABN, ATVI, SCTV, Anteve, TVI, TPI, GMA and RCTI can now all be received quite well along the east coast. However, reports from Perth indicate signal levels are well down in the west. One additional signal now carried on Palapa C2 is TVSN, the TV shopping network, also carried on Panam­sat PAS-2 and Asiasat 2. In late October, the signal appeared on the transponder utilised by ATVI, the international Australian ABC channel. TVSN now appears there for several hours each morn­ing, prior to comm­ence­­ment of regular ATVI broadcasts. The TVSN signal on Asiasat 2 has dropped dramatically in power and now requires a 3m dish for good results. Intelsat 703 177°E longitude: in addition to the AFRTS (US Armed Forces TV) B-MAC signal at IF 968MHz (radio service 7.4MHz), a Korean broadcaster has been regularly using this satellite on IF 984MHz. AFRTS utilises LHCP, while the Korean signal uses RHCP (righthand circular polarisation). This is the new logo of French broadcaster RFO, indi­cating that a new channel may commence soon. A Korean channel using righthand circular polarisation is now available on Intelsat 703 at 177°E longitude. Intelsat 511 180°E longitude: primary channels of interest on this satellite continue to be Worldnet (1175MHz IF) and French channel RFO. For many months a rumour has persisted that the French broadcaster will soon commence operation of a second channel. That rumour seems confirmed now that RFO have changed their logo to “RFO 1”. Elsewhere, vidiplexed feeds for Network 7 are still carried on this satellite (984MHz IF) and there are several itinerant feeds each day. SC *Garry Cratt is Managing Director of Av-Comm Pty Ltd, suppliers of satellite TV reception systems. December 1996  57 A game to improve your hand/eye coordination Build a laser pistol & electronic target Most people can’t legally own guns any more so if you have a yen for target shooting, this project will fit the bill. It uses a visible LED laser in the pistol & a bullseye target which responds visibly & audibly when you score a direct hit. By RICK WALTERS Most people are attracted to the idea of target shooting even if they have no wish to own a gun. With this project, you can indulge that whim in a completely harmless way and have a lot of fun in the process. The game consists of a laser pistol and an electronic tar­get. The pistol is a readily available plastic toy which has been modified to hold a battery, a switch for the trigger and a 5mW red laser. Each time it is fired, the laser 58  Silicon Chip emits a brief pulse. Holding down the trigger does nothing; you must pull the trigger fully each time to fire it. The target is quite different from anything you might have experienced in the past. It is active rather than passive and it gives you immediate feedback, if you hit the bullseye or if you miss. While it uses the “Official 100-yard small bore rifle target”, as produced by the National Rifle Association of the USA, we have mod- ified it with quite a bit of electronic circui­try. Around the outer ring of the target are 24 evenly spaced LEDs which chase around the circle for a random period while a siren sounds. Then all LEDs go out and you must fire the pistol within one second and hit the bullseye. If you miss, you get the sound of a machine gun which means you have been SHOT. If you hit the target, you get one of three different sound effects which can be a police siren, ambulance or fire-engine. These are selected randomly by the circuit as your reward for hitting the bullseye. At the bullseye is a PIN diode which is matched to the gun’s laser. If the laser beam hits this diode at the appropriate time, the police siren or one of the other reward sounds will indicate that you hit your target. PARTS LIST (TARGET BOARD) Fig.1: the circuit of the laser pistol. Each time switch S1 is closed, the laser circuit dis­ charg­es the 100µF capacitor to give a brief pulse. The target’s electronics is powered by a 9V DC plugpack. How it works Let’s start with the pistol circuit shown in Fig.1. The 100µF capacitor is always charged by the battery to 3V via the 1.5kΩ resistor. When the trigger is pulled, the switch closes, rapidly discharging the capacitor through the laser diode and associated circuit. The current drawn is such that the laser only emits one pulse of light before the voltage drop across the 1.5kΩ resistor causes it to turn off. Therefore you can’t cheat by holding the trigger down and pointing the barrel at the bullseye. The laser diode assembly consists of a near infrared emit­ter optically cou- pled to a detector diode. This is used to moni­tor the light output from the IR emitter and keep it constant, even while the battery voltage is falling. Q2 monitors the voltage across the 330kΩ resistor, this voltage being proportional to the light output from the diode. The voltage across LED1 is used as a reference for Q2’s emitter. The difference between its base and emitter voltages cause just enough collector current to flow through the 10kΩ resistor to turn Q1 on to give the required light output. The 4.7µF and 0.47µF capacitors slow the rate of rise of the current to ensure that there is no overshoot, which could damage the IR diode. WARNING: the pulse of light from the pistol, while of short duration, is dangerous. It should never be point- PARTS LIST (PISTOL) 1 toy pistol, Toys-R-Us Power Ranger Dart 099236 or equiv­. 1 PC board, code 08112961, 43mm x 16mm 1 momentary contact toggle switch C&K 7109 or equivalent (S1) 2 AAA 1.5V batteries 1 AAA or AA battery holder 1 BC338 NPN transistor (Q1) 1 BC328 PNP transistor (Q2) 1 3mm red LED (LED1) Semiconductors 1 660nm 5mW laser diode and lens assembly, Oatley Electron­ ics 660-5I or equivalent Resistors (0.25W, 1%) 1 330kΩ 1 470Ω 1 10kΩ 1 1.5Ω 1 1.5kΩ Capacitors 1 100µF 16WV electrolytic 1 4.7µF 16WV electrolytic 1 0.47µF MKT 63VW or monolithic ceramic 1 PC board, code 08112962, 140mm x 80mm 1 38mm 8-ohm loudspeaker 1 National Target Co target, TQ-4(T) or equivalent 1 sheet of white perspex to suit target, 355 x 355mm 1 9V DC plugpack 2 10mm x 3mm tapped spacers 2 3mm x 5mm countersunk screws 2 3mm x 5mm screws 24 5mm LED bezels 11 PC stakes Semiconductors 1 40106 hex Schmitt trigger (IC1) 1 555 timer (IC2) 2 4017 counter (IC3, IC5) 1 4093 quad 2-input NAND Schmitt trigger (IC4) 1 4016 or 4066 quad bilateral switch (IC6) 1 UM3561A sound effects generator DSE Z-6203 (IC7) 1 LM311 comparator (IC8) 1 BC338 NPN transistor (Q1) 8 BC328 PNP transistor (Q2-Q9) 1 PIN diode (PD1) Oatley Electronics 04PC2 or equivalent 1 3.3V 500mW zener diode (ZD1) 8 1N914 signal diodes (D1-D8) 1 1N4004 rectifier diode (D9) 24 5mm red LEDs (LED1-LED24) Capacitors 1 100µF 16WV electrolytic 2 10µF 16WV electrolytic 4 4.7µF 16WV electrolytic 3 1µF 16WV electrolytic 3 0.1µF MKT polyester 1 .022µF MKT 1 .01µF MKT Resistors (0.25W 1%) 1 4.7MΩ 1 220kΩ 1 3.9MΩ 1 150kΩ 1 2.7MΩ 4 100kΩ 1 1.8MΩ 5 10kΩ 1 1.5MΩ 1 1.8kΩ 1 1.2MΩ 1 1.5kΩ 3 1MΩ 6 820Ω 1 470kΩ December 1996  59 60  Silicon Chip Fig.2: the target circuit has a LED chaser driven by IC3, a sound effects circuit based on IC5 & IC7, and a random timer based on IC1a, IC1b & IC1c. ed at anyone’s eyes as damage could result. Target circuit Now let’s have a look at the target circuit in Fig.2. We’ll start with the chaser circuit which is based on IC3, a 4017 decade counter. We are using just six of its outputs. As it counts, each of the six outputs will go high (+V) while the rest are low (0V). IC3 is clocked by a Schmitt trigger oscillator based on IC1e together with the 1.5MΩ resistor and the 0.1µF capacitor. Since five of the outputs of IC3 will always be low, five of the six groups of four LEDs will always be turned on by the emitter followers Q4-Q9. Each time the oscillator clocks the counter, the “off” group will step, giving the appearance of rotation. The oscilla­tor resistor and capacitor values are selected to make the target LEDs appear to rotate at a suitable speed. Pin 5 of IC3 (the seventh output) is connected to the reset terminal, so each time the 4017 steps to this output it will reset itself and start over again. Switching another resistor in parallel with the 1.5MΩ resistor using IC6a increases the speed of rotation, as we will see later on. Random timer Schmitt triggers IC1a, IC1b and IC1c, together with their resistors and capacitors, are three oscillators running at slightly different frequencies. Fig.3: dimensions of the bracket for mounting the trigger switch. Their outputs are fed to an AND gate formed by diodes D1-D3. When all three oscillator outputs are low, the voltage across the associated 100kΩ resistor will also go low. The diode AND gate is connected to the input of IC1f via a .01µF capacitor and so when the AND gate output goes low, IC1f’s input will be pulled momentarily low. This causes pin 12 of IC1f to go high and this will rapidly charge the 10µF capacitor at pins 2 & 6 of IC2, via diode D6. IC2 is a 555 timer but the way in which it is connected is not conventional. In effect, it is a monostable and when pins 2 & 6 are taken high via diode D6, the output at pin 3 goes low for a period set by the 100kΩ resistor and 10µF capacitor on pins 2 & 6; ie, around one second. IC2’s output is normally high and when it goes low it af­fects four functions. First, the oscillator formed by IC1a will stop as D5 will hold its input pin near 0V. Second, the monostable formed by IC4a and IC4b will be triggered, taking pin 4 of IC4 high. This will hold the voltage across the 100kΩ resistor high through D4, preventing any further pulses being applied to IC1f for around four seconds. The third consequence will be for all the chaser LEDs to extinguish, as the output pin of IC2 is the supply voltage for them. The LEDs going out is the signal to shoot at the target. The fourth effect is that pin 3 of IC4 will go low and will take pin 1 of IC8 low, thereby grounding the emitter of an inter­ nal transistor which allows its output (pin 7) to go low. If the PIN diode (PD1) is now illuminated by the laser pistol, its current will increase, pulling pin 2 of comparator IC8 below its pin 3. This causes pin 7 of IC8 to go RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 1 1 1 1 1 1 3 1 1 1 1 4 6 1 2 6 1 1 Value 4.7MΩ 3.9MΩ 2.7MΩ 1.8MΩ 1.5MΩ 1.2MΩ 1MΩ 470kΩ 330kΩ 220kΩ 150kΩ 100kΩ 10kΩ 1.8kΩ 1.5kΩ 820Ω 470Ω 1.5Ω 4-Band Code (1%) yellow violet green brown orange white green brown red violet green brown brown grey green brown brown green green brown brown red green brown brown black green brown yellow violet yellow brown orange orange yellow brown red red yellow brown brown green yellow brown brown black yellow brown brown black orange brown brown grey red brown brown green red brown grey red brown brown yellow violet brown brown brown green gold brown 5-Band Code (1%) yellow violet black yellow brown orange white black yellow brown red violet black yellow brown brown grey black yellow brown brown green black yellow brown brown red black yellow brown brown black black yellow brown yellow violet black orange brown orange orange black orange brown red red black orange brown brown green black orange brown brown black black orange brown brown black black red brown brown grey black brown brown brown green black brown brown grey red black black brown yellow violet black black brown brown green black silver brown December 1996  61 This is what the pistol looks like after being disassembled and having the electronics installed. The spring-loaded switch is operated by the existing pistol trigger. low, discharging the 1µF capacitor on pin 13 of IC4 via D7. Phew! But we’re not finished yet, as this convoluted circuit has more tricks up its sleeve. We will now talk about the functions of gates IC1d, IC4c & IC4d, counter chip IC5, quad analog switch IC6 and IC7, the sound effects chip. If PD1 is illuminated while pin 1 of IC8 is high, the output will not change. This prevents anyone cheating by continu­ously shooting at the target, hoping to hit the bull just before the LEDs go out. When pin 3 of IC2 goes high after its 1s period, it pulls pins 8, 9 & 12 of IC4 high via the 1µF capacitor. Pin 10 will always go low, turning on Q2, thus applying power to the sound effects chip IC7 and to pin 13 of IC6a via a 10kΩ resistor. This causes the LED flasher to speed up. There will be two different outcomes from the sound effects chip, depending on whether the bullseye was hit or not. IC7 is a low-cost sound effects chip. If pin 1 is taken to the chip’s supply voltage (+3.3V), a machine gun sound is generated, regardless of the voltage on pin 6. If pin 1 is left floating (ie, open circuit), three additional sounds can be generated. If pin 6 is high, a fire engine sound is generated; if low, an ambulance sound; and if left floating, a police siren sound will be heard from the speaker. If the bullseye is missed, both inputs of IC4d go high and its output goes low to turn on Q3. Q3’s collector going high will take pin 12 of switch IC6d high, to connect pin 11 to pin 10. This generates the machine gun sound and YOU ARE DEAD! At the same time, pin 13 of IC6a will be pulled low via D8, switching out the additional 1MΩ feedback resistor for IC1a, thus returning the chaser speed to normal. Conversely, if the photodiode is illuminated while the LEDs are off (IC2, pin 3 low), then D7 will discharge the 1µF capacitor. When pin 3 of IC2 goes high again after one second, Q2 will apply power to the sound chip as previously. As both inputs of IC4d are not high, its output will stay high and Q3 will stay off. This leaves pin 1 of IC7 floating; (ie, IC6d open-circuit). IC1d with its associated resistor and capacitor form an oscillator which clocks IC5, another 4017 decade counter. This time we only use three outputs, resetting it on the fourth. When pin 3 of IC5 is high, the SEL1 input of IC7 is connected to ground and the output sound will be an ambulance. If pin 4 of IC5 is high, the SEL1 input will be high and the sound will be a fire engine. When pin 2 of IC5 (the Q1 output) is high, both IC6b and IC6c are open circuit and therefore the SEL1 input will be float­ing and the sound will be a police siren. Note that pin 2 of IC5 is not connected in the circuit and therefore is not shown. When Q2 turns on it takes the Clock Enable (pin 13) of IC5 high, effectively freezing the selected output. This prevents the selected siren sound from changing halfway through. Thus, IC1d and IC5 together randomly select the siren “reward” sound heard each time the bullseye has been hit. In both the above cases (ie, bullseye or no bullseye), after the 2.7MΩ resistor on IC4 pin 12 has discharged the 1µF capaci­tor, the outputs of IC4c and IC4d will go high again, turning off the siren and returning the chaser to normal speed. The 4-second inhibit monostable (IC4a & IC4b) operating via diode D4 Fig.4: this diagram shows the wiring details of the laser pistol. Make sure the IR1 (the laser diode) is wired correctly and take care to ensure that Q1 (BC338) and Q2 (BC328) are the correct type numbers. 62  Silicon Chip Fig.5: the parts layout for the target PC board. Note that IC3 & IC5 face in the opposite direction to the other ICs. prevents the random timer (IC1a, 1b & 1c) from almost immediately starting the “fire” sequence again, which could be the case from time to time. Pistol assembly Our prototype pistol was purchased from Toys R Us. The red plastic pieces on the handle were prised apart with a knife blade, giving access to three small Phillips head screws which hold the main body together. Once the pistol is apart the black pillar on each half near the trigger must be cut off to make room for the spring-loaded switch. The type of switch we specified springs back to the off position and is actuated by the existing plastic trigger of the pistol. We made a small metal bracket (see Fig.3) to mount the switch and positioned it so that it operated smoothly with the plastic trigger. When the trigger is released the switch pushes it back to the rest position. The elastic bands which previously restored the trigger can be discarded. Most of the laser circuit of Fig.1 was supplied assembled and tested by Oatley Electronics, as a laser pointer. While it could have been used like this, we still required the 1.5kΩ resistor and the 100µF electrolytic to be mounted somewhere. As the parts can be supplied in kit form, we elected to make another small PC board which would accept all the components and be a better fit inside the pistol barrel. Its component layout is shown in Fig.4. Having so few parts it should only take a few minutes to build. Just ensure that the electrolytic capacitors are inserted with the correct polarity and make doubly sure that the wires to the laser diode are con­nected to the correct pins. The pistol wiring is straightforward and should cause no problems. An AAA battery holder is not readily available so we used an AA holder. If the batteries are loose, stretch the springs a little until they are held firmly. The pistol barrel comes with a white plastic tubular insert which was used to hold the dart. The dart is discarded and the tube trimmed 10mm from the end. This piece is used to hold the laser diode in the end of the barrel. Test your work before re-assembling the pistol by pointing the laser at a wall and pulling the trigger. A brief pulse of red light should be seen. The lens will also need to be focused before final assembly. Stand at about the distance you intend to be from the target and, with the 1.5kΩ resistor shorted out, hold the trigger down and rotate the end of the lens until the spot of light is as small as you can get it. Remove the short and assemble the pis­ tol. The red barrel needs to be superglued to the black butt on both pieces before assembly. Target PC board The component layout for the target This close-up view shows the assembled target PC board. Note how the infrared diode sits directly behind a small hole which is drilled through the bullseye. December 1996  63 Fig.6: this diagram shows how the LEDs are wired around the target. PC board is shown in Fig.5. After checking the PC board for open or shorted tracks and undrilled holes, the first step is to fit and solder the 13 links and 11 PC stakes. Fit the resistors, diodes, ICs and other low-profile components first, then move on to the taller components. Be sure to double-check the diode and electrolytic capaci­tor polarities. You should also carefully check the orientation of the various ICs and that the single BC338 transistor (Q1) is in 64  Silicon Chip the cor­rect place. Testing This board can be tested now, before you wire up the target LEDs. Solder the cathodes of each of six LEDs onto the six PC stakes near the 820Ω resistors, with all six anodes connected in parallel to the LED common pin. Connect the speaker to its terminals and connect the DC plugpack or a power supply to the +9V and 0V pins. Apply power and five of the six LEDs should light. After a short time each of the six LEDs should have turned off, but not in sequence, then they should all go out and a second later a burst of machine gun fire should be heard from the speak­er. If all is OK so far, ground pin 7 of IC8. Over a period you should hear the three different sirens. If the board is working, continue with the target wiring, as shown in Fig.6. Fault finding If the LEDs don’t light, check that their polarity is cor­rect by reversing one of them. Pin 3 of IC2 should measure around 11V or thereabouts, depending on the actual output voltage of the 9V DC plugpack. If pin 3 of IC2 is at 0V, look for shorts or a faulty chip. If the LEDs don’t step, check around IC3 or IC1e for faulty or incorrect components or perhaps a blob of solder shorting two pins. If the three siren sounds are not produced (after a number of tries) suspect IC5 or IC1d and its components or a solder bridge. To force a burst of machine gun fire, use a jumper lead from pins 8 & 9 of IC4 to Vcc. If pin 13 is then grounded the other sirens should be heard. Target wiring The cardboard target specified is available from most gun shops. We mounted ours on a piece of white perspex. Before drilling the 24 LED holes, we drilled a hole at the bullseye and two holes to mount the pillars which support the target PC board. These were positioned so that the PIN diode sat behind the bull­seye. The LEDs are wired in series in groups of four, one in each quadrant as shown in Fig.6. If you use a different coloured wire for each group it will help you to keep track of them. All the anodes in the first quadrant are commoned and con­nected to the LED common PC stake. The last LED We used a sheet of white perspex to hold the target. The loudspeaker and PC board mount on the back, with the PIN diode behind the bullseye hole. in the first group should be connected to Q4’s 820Ω resistor, the last LED in the second group to Q5’s 820Ω resistor and so on, until the sixth group LED is connected to Q9’s resistor. You will have to follow the PC overlay of Fig.5 carefully, as the transistors are not in sequence. Now power up the target and check that all functions are working. You will need to carefully “sight” the pistol so that it shoots straight and then you will find that you need a fair amount of practice to hit the target consistently. Have fun. SC Fig.7: here are the fullsize etching patterns for the laser pistol (above) and the target board (right). December 1996  65 Build This Sound Level This Sound Level Meter adaptor will measure sound pres­sure levels from below 20dB up to 120dB with high accuracy. It connects to any standard digital multimeter and has inbuilt filters for A and C-weighting. Noise can have a huge affect on the quality of our lives. A reliable measuring instrument is a must for those interested in finding out just how much noise is in their environment. Just how much noise is present at any time is very subjec­tive. If you are confined to a soundproof room for a period of time, even the sound of a pin dropping will seem quite loud. But if you are in a normal home or office environment, the dropping of a pin is likely to be completely inaudible. And even the sounds of people on the telephone or using computers may be completely drowned out if a semi-trailer passes down your street or a jet flies overhead. The above examples show just how exceptional our ears are in responding to the possible range of sounds in our environment. In fact, we could expect to experience a sound pressure range of about three million to one. Because of this huge range of values sound pressure levels are usually expressed in decibels, a loga­rithmic ratio where 20dB (decibels) is equivalent to 10:1; 40dB is 100:1 and 60dB is 1000:1, all compared to a reference level. The overall 3,000,000 to 1 range can then be expressed as 130dB (20 log 3,000,000). Since the dB is a ratio it must be referenced to • • • • 66  Silicon Chip 66  Silicon Chip Main Features Connects to any digital multimeter Calibration method uses loudspeaker & pink noise source A and C weighting plus flat (unweighted) filters Slow, Fast and Peak response By JOHN CLARKE Meter a particu­lar pressure level of 20.4µPa (micro Pascals). Usually sound pressure levels are quoted as so many dBSPL, indicating that the 0dB reference is 20.4µPa. On the dBSPL scale, 0dB is virtually inaudible, 30dB might be the sound level in a quiet rural area with no wind while a noisy home kitchen might be 80dB or more. Heavy traffic can easily be 80-90dB while a suburban train in a tunnel can produce 100dB. Electric power tools or pneumatic drills can easily run at 110dB and some can go into the pain level at 120dB. Measuring SPL The S ILICON C HIP Sound Level Meter is designed to produce accurate readings of sound pressure which are displayed on a digital multimeter. It Fig.1: this graph shows the differences between A and C-weighting and flat (unweighted) responses in the Sound Level Meter. comprises a handheld case with a short tube supporting the microphone at one end of the unit. Flying leads with banana plugs connect to the multi­meter. A slide switch provides A-weighting and C-weighting filt­ers to tailor the measurement readings. A-weighting is called for in many measurements to Australian standards although it is not really appropriate for louder sounds where C-weighting or a flat response (unweighted) can give more meaningful results. Fig.1 shows the differences between A and C-weighting and flat (unweighted) responses in the Sound Level Meter. Slow and fast response times are provided as well, so that sudden noise can be filtered out, if need be. A “peak detect” facility has also been included which will give an indication Fig.2: the block diagram of the Sound Level Meter. IC4b controls the gain of IC2 so that the output from the full-wave rectifier is constant. IC4b’s output is atten­uated by IC3b and fed to an external multimeter. December 1996  67 Fig.3: apart from the use of a VCA (IC2), an unusual feature of the circuit is the use of IC5 to evenly split the 18V supply. This has been done because the negative rail is subjected to a higher current drain than the negative rail, which would shorten the life of battery B2. of the noise waveform shape. If there is no or little difference between the peak and the fast reading then the noise waveform can be assumed to be relatively sinusoidal. If, however, the peak level is greater than the fast reading, then the noise waveform has a lot of transient bursts. These may result in a low average value as shown on the slow 68  Silicon Chip or fast re­sponse settings but are easily captured by the peak detect cir­cuitry. The cost of the Sound Level Meter has been kept low by using a multi­ meter as the display. Logarithmic conversion As already noted, the Sound Level Meter will read from below 20dBSPL to 120dBSPL, a range of 100dB. That’s a pretty stiff requirement. The circuit has to provide a direct logarith­ mic conversion over 100dB, producing an output of 10mV per dB. In practice, the signal fed to the multimeter ranges from 200mV at 20dB to 1.2V at 120dB. This means that all readings can be made on the 2V range of the multimeter; there is no need to switch ranges. Fig.2 shows the block diagram of our sound level meter. Signal from the microphone is amplified by op amp IC1a and then fed to either the A or C-weighting filters which involve switch S2 and op amp IC1b. IC2 is a voltage-controlled amplifier (VCA) which can either amplify or attenuate the signal from IC1b, depending on the voltage at its control input. This input operates in a loga­rithmic fashion so that small control voltage changes can produce large variations in the output signal. IC2’s output is full wave rectified by IC3a & IC4a and the rectified signal fed to the Slow, Fast or Peak filters involving switch S3. The resulting DC voltage is compared in error amplifier IC4b against a 20mV reference. IC4b’s output then controls the VCA so that it produces a constant output regardless of changes in the microphone signal. As well as driving the control input of the VCA, IC4b drives op amp IC3b which modifies the signal so that it provides the required 10mV per dB, to drive the external multimeter. Circuit description Fig.3 shows the complete circuit for the Sound Level Meter. It uses five ICs, three of which are dual op amps (IC1, IC3 & IC4). IC2 is the VCA, which can be considered as an op amp with a DC gain control. IC5, a TL071 single op amp, is used to accurate­ly split the 18V battery supply; more of that later. The microphone is an electret type which is biased via a 10kΩ resistor from the +9V supply. Its signal is coupled to op amp IC1a which has a gain of 7.9 (+18dB), as set by the 68kΩ and 10kΩ feedback resistors. This gain has been selected for the specified microphone and will need to be altered if other types are used. IC1a drives both the C and A-weighting filters. These are selected at positions 1 and 2 of switch S2a respectively. Posi­tion 3 selects IC1a’s output directly for the flat or unweighted signal mode. IC1b is simply a unity gain amplifier to buffer the filters and prevent loading of the filter signal. IC1b’s output is fed to IC2 via switch S2b and a 10µF coupling capacitor. Note that in positions 1 and 3 of S2b, the 4.7kΩ and 12kΩ resistors are connected in series while for position 2, the 4.7kΩ resistor is bypassed. This allows a 3dB higher gain for IC2 when A-weighting is selected. The gain adjustment is necessary to maintain the Fig.4: waveforms from the precision full-wave rectifier. The top trace (Ch1) shows the input sinewave while the lower trace (Ch 2) is the rectified version. Note that the RMS values are slight­ly different due to small offsets in the op amps. same 1kHz signal level applied to IC2 for all posi­tions of switch S2. IC2 is an Analog Devices voltage-controlled amplifier (VCA). It has a dynamic range of 117dB, .006% distortion at 1kHz and unity gain, and a gain control range of 140dB. The DC control input operates at -30mV per dB gain change. IC2’s gain is set by the voltage at pin 11 and the ratio of resistance between pins 3 and 14 and the input at pins 4 & 6. The 100kΩ resistor between pin 12 and the +9V rail sets the bias level for the output at pin 14. This bias can be selected for class A or B operation. Class A gives lower distortion but slightly higher noise. We opted for class B bias for best noise performance. A .001µF capacitor between pins 5 & 8 compensates the gain control circuitry. Precision rectifier IC2 is AC-coupled to the precision full wave rectifier formed by op amps IC3a & IC4a. For positive signals the output of IC3a goes low to reverse bias diode D1. Positive-going signals are then summed in inverter IC4a via the 20kΩ resistor R1 to produce a negative output at pin 7. The gain is -1. Diode D2 and the 20kΩ series resistor limit the op amp’s negative excursion. For negative signals D1 conducts and IC3a acts as an in­verting amplifier with a gain of -1 to sum into IC4a via R5. Negative-going signals are also summed in IC4a via R1. Since the voltages across R1 and R5 are equal but opposite and the value of R5 is exactly half R1, the net result of the sum into IC4a is a negative output with an overall gain of 1. So for positive signals applied to the full wave rectifier the gain is -1 and for negative signals the gain is 1. Thus IC3a and IC4a form a precision full wave rectifier. The 10kΩ and 5.6kΩ resistors at IC3a’s and IC4a’s non-inverting inputs minimise any offset voltages in the op amps. Fig.4 shows the oscilloscope waveform of the precision full wave rectifier. The top trace shows the input sinewave while the lower trace is the rectified version. Note that the RMS values are slightly different due to small offsets in the op amps. The switched feedback across IC4a provides filtering of the rectified signal as well as gain control. In the ‘slow’ setting of S3a, the 20kΩ resistor sets the gain and the 470µF capacitor controls the response. Similarly, for the ‘fast’ setting of S3a, the 100µF capacitor sets the response. In the ‘peak’ position of S3, diode D3 charges the 10µF capacitor to the peak value of the waveform while the 12kΩ resistor sets December 1996  69 Fig.5: follow this diagram when installing the parts on the PC board and take care to ensure that all polarised parts are correctly oriented. Note that REF1 and a number of capacitors must be laid flat on the PC board (see text). the gain. This is lower than the 20kΩ value used in the other S3 positions so that the output at the wiper of S3b is the same as for the slow and fast settings when a sinewave is applied. VR1 allows precise adjustment of this calibration, providing a divide by 4.6 to 1.8 range. VR2 is the offset adjustment. Error amplifier If, after reading the circuit description so far, you are unclear about its operation, do not despair. Let’s summarise what really happens. Op amp IC4b, the error amplifier, is really the The filter signal at the wiper of S3b is monitored with error amplifier IC4b. This has a gain of -100 (ie, it is an inverting amplifier) and compares the rectified signal from switch S3b against the -20mV reference at the non-inverting input, pin 3. IC4b’s output drives pin 11 of IC2. The -20mV reference is derived from the 2.49V reference REF1 via 560kΩ and 4.7kΩ resistors. REF1 is an LM336-2.5 preci­ sion reference diode which has facility for a small amount of adjustment although it is not used here. REF1 is also used to provide a calibration offset for op amp IC3b. IC3b attenuates the logarithmic DC control voltage for IC2 to convert its nominal 30mV/dB calibration to 10mV/dB. 70  Silicon Chip The big picture CAPACITOR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ Value 0.56µF 0.22µF 0.18µF 0.15µF .047µF .0027µF .001µF 100pF 33pF 12pF IEC EIA 560n 564 220n 224 180n 184 150n 154 47n 473 2n7 272 1n 102 100p 101 33p   33 12p   12 heart of the circuit. It continually adjusts the control voltage fed to IC2 so that the negative DC voltage fed from the wiper of S3b to its pin 2 is always very close to the -20mV at its pin 3. In fact, VCA IC2 does not really operate as an amplifier for most of the time. For example, when a signal of 120dBSPL is fed to the microphone, the output of IC1a and IC1b is close to clipping; ie, around 14V peak-to-peak or 5V RMS. This is heavily attenuated by IC2 so that around 30mV RMS (see Fig.4) is applied to the input of the precision rectifier, IC3a. Actually, it is only for signals of around 20mV or less from IC1b that the circuit involving IC2 has any gain; the rest of the time it is attenuating and the actual degree of attenua­tion depends on the size of the signal coming from IC1a. Typical­ly, the control voltage delivered by IC4b ranges from about +3V, corresponding to maximum attenuation in this circuit, to about -1V, corresponding to maximum gain. Hence, IC4b makes sure that its two inputs are very simi­lar, and in doing so, it produces a control voltage which happens to be 30mV/dB. This is then further attenuated by IC3b to produce an output of 10mV/dB which can be read out as a measure of the sound pressure level. Looked at this way, the output voltage read by the external multimeter is almost just a byproduct of the overall circuit operation. The assembled PC board is secured to the base of the case using four small self-tapping screws. Battery supply Two 9V batteries in series provide an 18V supply. The 18V is divided using two series connected 10kΩ resistors, to produce a 0V reference and this is buffered by op amp IC5. IC5’s output feeds a 100Ω resistor and two 100µF capacitors. These decouple the op amp’s output and ensure that it has a very low output impedance at all frequencies of interest. The result is a dual-tracking supply which is nominally ±9V. Now why go to all that trouble when we could have used the midpoint of the two 9V batteries to do the same thing? The reason is that there is more current drain from the negative rail in this circuit and so the negative 9V battery would normally be discharged faster than the positive 9V battery. This would be a problem because the circuit require more negative output swing. By using the op amp split supply RESISTOR COLOUR CODES ❏ No. ❏  1 ❏  1 ❏  1 ❏  3 ❏  1 ❏  1 ❏  1 ❏  1 ❏  6 ❏  1 ❏  2 ❏  9 ❏  1 ❏  1 ❏  1 ❏  2 ❏  2 ❏  2 ❏  1 Value 2.2MΩ 560kΩ 180kΩ 100kΩ 68kΩ 33kΩ 22kΩ 24kΩ 20kΩ 18kΩ 12kΩ 10kΩ 8.2kΩ 6.8kΩ 5.6kΩ 4.7kΩ 3.9kΩ 150Ω 100Ω 4-Band Code (1%) red red green brown green blue yellow brown brown grey yellow brown brown black yellow brown blue grey orange brown orange orange orange brown red red orange brown red yellow orange brown red black orange brown brown grey orange brown brown red orange brown brown black orange brown grey red red brown blue grey red brown green blue red brown yellow violet red brown orange white red brown brown green brown brown brown black brown brown 5-Band Code (1%) red red black yellow brown green blue black orange brown brown grey black orange brown brown black black orange brown blue grey black red brown orange orange black red brown red red black red brown red yellow black red brown red black black red brown brown grey black red brown brown red black red brown brown black black red brown grey red black brown brown blue grey black brown brown green blue black brown brown yellow violet black brown brown orange white black brown brown brown green black black brown brown black black black brown December 1996  71 shown in Fig.5, to allow room for the battery to lie on top of the PC board. For the same reason, the .001µF capacitor near IC2, the 0.18µF capacitor near VR2 and the 100pF capacitor near VR1 should be inserted so that they lie flat on the board. The electrolytic capacitors must be oriented as shown. Insert and solder LED1 at the end of its leads to allow it to protrude through the front panel when assembled. Insert trimpots VR1 and VR2 and cut the ‘A’ PC stakes slightly higher than the trimpot height. This will prevent the batteries pressing on the trimpots and altering the set values. Now fit the assembled PC This battery holder was made by soldering several pieces of double-sided PC board board into the base of the case material together. The three smaller pieces fit into the integral slots moulded into the and secure it with four small lid of the plastic case. self-tapping screws. Wire up the 9V battery clips and multimeter method, the current drain from the assembly of components. Begin by leads as shown. Prepare the two wires two 9V batteries must always be the inserting the two links and all the for switch S1. same and the battery life will be exresis­ tors. The accompanying table Fit the Dynamark adhesive label to tended. For the same reason, LED1 is can be used as a guide for the resistor the lid of the case and drill and file connected across the full 18V supply colour codes. Alternatively, use your out the holes for the switches and via a 10kΩ resistor. multimeter to check each resistor as LED. Attach S1 with the screws and it is installed. connect its wiring. Construction Next, insert and solder in the PC The rear end panel can be drilled stakes. These are located at all external The SILICON CHIP Sound Level Meto accept a small grom­met. Pass the wiring points, the ‘A’ positions and for ter is housed in a plastic case measmultimeter leads through the gromuring 150 x 80 x 30mm and uses a PC the eight switch terminal locations for metted hole and attach the banana S2 and S3. board coded 04312961 and measuring plugs to it. 67 x 120mm. The microphone is held Next, the ICs can be inserted and Microphone mounting inside a copper tube which protrudes soldered in. Take care with the orifrom the front of the case. This is done entation of each and make sure that An 80mm length of 12.7mm copper to prevent sound reflections from the IC5 is the TL071 (or LF351). Diodes tube is soldered to a 12 x 30mm piece case from upsetting the read­ing. D1-D4 can now be inserted, taking care of 1mm thick copper sheet (or PC to ensure that they are also correctly board). The copper sheet becomes a Fig.5 shows the component layout oriented. Switches S2 and S3 can be flange for easy attachment to the front for the PC board. You can start construction by checking the PC board mounted by soldering their pins to the end piece of the box. Drill holes in top of the PC stakes. for any shorts or breaks in the copthe flange and front end plate to allow per tracks. Repair any faults before REF1 is mounted on its side as it to be secured with two screws and Fig.6: this is the set up used for calibrating the Sound Level Meter. It relies on using a speaker of known sensitivity. Most manufacturers quote sensitivity figures for their loudspeakers. 72  Silicon Chip nuts. Also drill a hole central to the flange and end plate for the shielded cable to pass through the tube. The tube and flange can be painted if desired. Connect the microphone using shield­ed cable and attach some heat­ shrink tubing around its body. Shrink the tubing down with a hot air gun and insert the wire and microphone into the tube. Leave the microphone flush with the end of the tube. The flange can be attached to the end plate of the case with the screws and nuts. The shielded cable is clamped with a solder lug attached to one of the screws. The batteries are held in place on the lid of the case using three pieces of double-sided PC board (73 x 5mm) which are inserted in the integral slots. Two pieces of double sided PC board, measuring 30 x 15mm, are soldered in place between the transverse pieces so that they provide a snug fit for the battery and clip assemblies. Check that the lid will fit onto the base of the case. Voltage checks Switch on and connect the red multimeter lead from the Sound Level Meter to the common input of the multimeter and then measure voltages on the circuit with the other lead of the multimeter. Check that there is +9V at pin 8 of IC1, IC3 and IC4; at pin 7 of IC5; and at pin 2 of IC2. There should be -9V at pin 4 of IC1, IC3, IC4 & IC5 and at pins 10 & 16 of IC2. REF1 should have -2.49V at its anode and pin 3 of IC4b should be -20mV. LED1 should also be lit. Connect both output leads from the sound level meter to the multimeter. Performance ‘A’ response .......................................... -18dB at 100Hz, -10dB at 20kHz (see Fig.1) ‘C’ response ......................................... -5dB at 20Hz, -13dB at 20kHz (see Fig.1) Overall flat response (input versus multimeter reading) .................. -3dB at 28Hz and 50kHz Log conversion accuracy at multimeter output ................................ <0.5dB over a 100dB range from 0.550V RMS to 5.5µV input level Temperature stability ............................ <10mV (1dB) change per 30°C Slow response time constant ............... 9.4 seconds Fast response time constant ................ 2 seconds Peak response ...................................... 1.5ms attack; 120ms decay Power ................................................... 12-18V at 32mA Microphone Performance (ECM-60P A version) Sensitivity �������������������������������������������� -56dB ±3dB with respect to 0dB+1V/µbar <at> 1kHz Microphone response .......................... within ±3dB from 50Hz to 3kHz and ±6dB from 3kHz to 8kHz. Above 8kHz and below 50Hz unspecified. Maximum SPL ..................................... 120dB Note: filter responses measured at VCA output with control input (pin 11) grounded. it is greater than 400mV, rotate VR1 slightly clockwise. Conversely, if the multimeter reading is less than 400mV, rotate VR1 slightly anticlockwise. Now measure the difference again with the 0dB/ -60dB switch. You will note that the reading will now not be 1V for the 0dB setting. However, what we are look- ing for is a 600mV change between the 0dB and -60dB pink noise level settings (ie, 10mV per dB). After some repeat adjust­ments of VR1 it should be possible to obtain close to 600mV variation between the 0dB and -60dB settings. Calibration now only requires the offset adjustment trimpot VR2 to be Calibration Calibration is done in two steps and a pink noise source is required for both steps. We will describe a suitable pink noise source in next month’s issue of SILICON CHIP and we assume that you will also build that or have access to an equivalent source. First, connect the pink noise source to the electret microphone input of the sound level meter. Select 0dB on the pink noise source (equivalent to 60mV RMS) and adjust trimpot VR2 for a read­ing on the multimeter of 1V DC. Now switch to -60dB on the pink noise source and check that the multimeter reading is 400mV. If Fig.7: check your etched PC board against this full-size artwork before installing any of the parts. December 1996  73 PARTS LIST 1 plastic case, 150 x 80 x 30mm 1 PC board, code 04312961, 67 x 120mm 1 front panel label, 75 x 144mm 1 ECM-60P type A electret microphone (sens. -56dB with respect to 1V/1µbar at 1kHz) 3 pieces of double sided PC board, 73 x 5mm 2 pieces of double sided PC board, 30 x 15mm 1 DPDT slider switch and mounting screws (S1) 2 DP3P slider switches (S2,S3) 1 50kΩ horizontal trimpot (VR1) 1 100kΩ horizontal trimpot (VR2) 2 9V battery snaps 2 9V batteries 1 black banana plug 1 red banana plug 1 250mm length of shielded cable 1 500mm length of black hookup wire 1 500mm length of red hookup wire 1 50mm length of 0.8mm tinned copper wire 30 PC stakes 2 3mm x 10 screws and nuts 4 small self-tapping screws (to secure PC board) 1 solder lug 1 small rubber grommet 1 small cable tie 1 SSM2018P voltage controlled amplifier (IC2) 1 TL071, LF351 op amp (IC5) 4 1N914 signal diodes (D1-D4) 1 LM336-2.5 2.5V reference (REF1) 1 3mm red LED (LED1) Semiconductors 3 LM833 dual op amps (IC1,IC3,IC4) Miscellaneous 12mm diameter heatshrink tubing, solder. Capacitors 1 470µF 16VW PC electrolytic 5 100µF 25VW PC electrolytic 1 47µF 16VW PC electrolytic 3 10µF 16VW PC electrolytic 1 0.56µF MKT polyester 1 0.22µF MKT polyester 1 0.18µF MKT polyester 2 0.15µF MKT polyester 1 .047µF MKT polyester 2 .0027µF MKT polyester 1 .001µF MKT polyester 1 100pF ceramic 1 33pF ceramic 1 12pF ceramic Resistors (0.25W 1%) 1 2.2MΩ 2 12kΩ 1 560kΩ 9 10kΩ 1 180kΩ 1 8.2kΩ 3 100kΩ 1 6.8kΩ 1 68kΩ 1 5.6kΩ 1 33kΩ 2 4.7kΩ 1 24kΩ 2 3.9kΩ 1 22kΩ 2 150Ω 6 20kΩ 1 100Ω 1 18kΩ set. This is done using the setup shown in Fig.6. You will need an amplifier, the pink noise source and a woofer or tweeter with known sensitivity. All manufacturers of loudspeakers provide a sensitivity rating for their units and these are specified as a dBSPL when driven at 1W and at 1m on axis. Note that if you use a tweeter, the manufacturer’s speci­fied filter should be used when making the measurement. For example, a loudspeaker may be rated at 88dB when mount­ed on a baffle and driven from a 2.828V AC source at a distance of 1m. The loudspeaker impedance is 8Ω. Note that 2.828V into 8Ω is equivalent to 1W. Use your multimeter to measure the voltage applied to the loudspeaker and set the amplifier’s volume control to deliver 2.828V AC for an 8Ω system and 2V AC for a 4Ω speaker. Be sure to set your amplifier’s tone controls to the flat settings (ie, centred or switched off) and make sure that the loudness switch is off. Now connect the multimeter to the sound level meter (with the unweight­ ed and slow settings selected) and with the micro­phone at 1-metre and on axis to the speaker. Adjust trimpot VR2 to obtain the loudspeaker sensitivity. For our 88dB example, the multimeter should read 0.88V or 880mV DC. Alternatively, if you have a calibrat­ ed sound level meter, adjust VR2 for the same readings. Make sure that both sound level meters are set with the same filtering and responses. SC 74  Silicon Chip (10mV/dB) CONNECT TO MULTIMETER FILTER C-WEIGHTING A-WEIGHTING UNWEIGHTED + SOUND LEVEL METER RESPONSE SLOW FAST PEAK + OFF + ON + Fig.8: this is the actual size artwork for the front panel. VISIT OUR WEB SITE OUR COMPLETE CATALOGUE IS ON OUR SITE. A “STOP PRESS” SECTION LISTS NEW AND LIMITED PRODUCTS AND SPECIALS. VISIT: https://www.oatleyelectronics.com/ SWITCHED MODE POWER SUPPLY:Compact (50X360X380mm), enclosed in a perforated metal case, 240V AC in, 12V DC/2A and 5VDC/5A out: $17 ...HP POWER SUPPLIES: Compact (120X70X30mm) HP switched mode, power in plastic case, 100-240V AC input, 10.6V/1.32A DC output, slightly soiled: $14 ...LASER MODULE: Very bright (650nM/5mW) focusable module, suit many industrial applications, bright enough for a disco laser light show, good results with the Automatic Laser Light Show: $75 ...AUTOMATIC LASER LIGHT SHOW KIT: 3 motors, mirrors plus PCB and comp. kit, has laser diode reg. cct, could be powered by the above 12V switched mode power supply, produces many different patterns, can be used with the laser module: $70 ...LASER POINTER: Our new metal laser pointer (With keychain) is very bright, with 650nM/5mW diode: $65 ... LEDS SUPER PRICES, INCLUDING A SUPER BRIGHT BLUE!: All the following LEDS are in a 5mm housing ...By far THE BRIGHTEST BLUE EVER OFFERED, superbright at 400mCd: $1.50Ea. or 10 for $10 ... 1C red: 10 for $4 ...300mC green: $1.10Ea. or 10 for $7 .. MAKE WHITE LIGHT BY MIXING THE OUTPUT OF THE PREVIOUS 3 LEDS? ..3Cd Red: $1.10Ea. or 10 for $7 ... 3Cd yellow (Small torch!) also available in 3mm: 10 for $9 ... Superbright flashing LEDS: $1.50 Ea. or 10 for $10 ... PHOTOTRANSISTORS: Enclosed in clear 5mm housing similar to the 5mm LEDS, 30V/3uS/<100nA dark current: $1.30 or 10 for $9 ...CONSTANT VOLTAGE DIODES: 1.52-1.66V <at> 10uA: 10 for $7 ...MASTHEAD AMPLIFIER PLUS PLUGPACK SPECIAL: Our famous MAR-6 based masthead amplifier plus a suitable plupack to power it: $20, Waterproof box: $2.50, bottom box:$2.50 ...17mm MAGNIFIERS: Made in JAPAN by Micro Design these eyepiece style metal enclosed magnifiers will see the grain of most papers, used, limited qty.: $4 Ea. ...HF BALLASTS: Single tube 36W Dimmable high frequency ballasts: $18 Ea. ...12V SLA BATTERY CHARGERS: INTELLIGENT “PLUGPACK” 240V-12V GEL BATTERY CHARGERS, 13.8V / 650mA, proper “switching” design with LED status indicator: $8.80 ...LASER POINTER KIT: A special purchase of some 660nM/5mW laser diode means that we can reduce the price of our Laser Pointer kit, includes everything except the batteries: $29 ...SPECIAL BATTERY AND CHARGER OFFER: When our 7AHr/12V SLA battery ($30) is bought with the SLA battery charger the total price for both is: $33 ...USED BRUSHLESS DC FANS: 4"/12V/0.25A: $8, 24V/6"/17W: $12 ...100,000uF ELECTROLYTIC CAPACITORS: 30V/40Vsurge, used but in exc. cond.:$10 ...12Hr. MECHANICAL TIMERS: 55X48X40mm, 5mm shaft (Knob not supplied), two hours timing per 45deg. rotation, two 25V/16A SPST switches which close at the end of the timing period: $5 ...USED IEC LEADS: Used Australian IEC leads: $2.50 ...STANDARD PIEZO TWEETERS: Square, 85X85mm, 4-40KHz, 35V RMS: $8, Wide dispersion, 67X143mm, 3-30KHz, 35V RMS: $9 ...COMPUTER POWER SUPPLY: Standard large supply as used in large computer towers, +5V/22A, +12V/8.5A, -5V/0.5A, -12V/0.5A, used but in excellent condition, guaranteed: $30 ...MAGNIFIERS: Small eyepiece: $3, 30mm Loupe: $8, 75mm Loupe: $12, 110mm Loupe: $15, a set of one of each of these magnifiers (4): $30 ... NEW NICAD BATTERY BARGAIN: 6 PACK (7.2V) OF 1.2V / 800 mAHr. AA NICAD BATT’s plus 1 X thermal switch, easy to seperate: $4 per pack or 5 packs for $16, FLAT RECTANGULAR 1.2V, 400mAh NI-CAD BATTERIES with thermal switch, easy to seperate, (Each batt: 48x17x6 mm): $4 per pack or 5 packs for $16 ...UV MONEY DETECTOR: Small complete unit with cold cathode UV tube, works from 2 X AA batteries ( Not supplied), Inverter used can dimly light a 4W white fluoro tube: $5Ea. or 5 for $19 ...MISCELLANEOUS USED LENS ASSEMBLIES: Unusual lens assemblies out of industrial equipment: 3 for $22 ...USED PIR MOVEMENT DETECTORS: Commercial quality 10-15M range, used but tested and guaranteed, have O/C transistor (BD139) output and a tamper switch, 12V operation, circuit provided: $10 Ea. or 4 for $32 ...CCD CAMERA WITH BONUS: Tiny (32X32X27mm) CCD camera, 0.1lux, IR responsive (Works in total dark with IR illumination), connects to any standard video input (Eg VCR) or via a modulator to aerial input: $125, BONUS: With each camera you can buy the following at reduced prices: COMMERCIAL UHF TRANSMITTER for $15 (Normally $25), IR ILLUMINATOR KIT with 42 X 880nM LED’s for $25 (Normally $35), REGULATED 10.4V PLUGPACK for $10 (Normally $25) ...PIR CASE FOR CCD CAMERA: Used PIR cases of normal appearance, use to hide the CCD camera, plenty of room inside: $2.50 Ea. or 4 for $8 ...CAMERA-TIME LAPSE VCR RECORDING SYSTEM: Includes PIR movement detector and interface control kit, plus a learning remote control, combination can trigger any VCR to start recording with movement and stop recording a few minutes after the last movement has stops: $90 ...GEIGER COUNTER KIT: Based on a Russian tube, has traditional “click” to indicate each count. Kit includes PCB, all on-board components, a speaker and Yes, the geiger counter tube is included: $30 ...RARE EARTH MAGNETS: Very strong! 7X3mm $2, 10X3mm $4, Torroidal 50mm outer, 35mm inner, 5mm thick: $10 ...IR TESTER: Kit includes a blemished IR converter tube as used in night vision and an EHT power supply kit, excellent for seeing IR sources, price depends on blemishes: $30 / $40 ...ARGON-ION HEADS: Used Argon-Ion heads with 30-100mW output in the blue-green spectrum, power supply circuit provided, size: 350X160X160mm, weight 6Kg, needs 1KW transformer available elsewhere for about $170, head only for: $350 ...DIGITAL RECORDING MODULES: Small digital voice recording modules as used in greeting cards, microphone and a speaker included, 6 sec. recording time: $9 ...WIRED IR REPEATER KIT: Extend the range of existing IR remote controls by up to 15M and/or control equipment in other rooms: $18 ...12V-2.5W SOLAR PANEL KIT: US amorphous glass solar panels, 305X228mm, Vo-c 18-20V, Is/c 200mA: $22 Ea. or 4 for $70 ...MIDI KEYBOARDS: Quality midi keyboard with 49 keys, 2 digit LED display, MIDI out jack, Size: 655115X35mm, computer software included, see review in Feb. 97 EA: $80, 9V DC plugpack: $10, also available is a larger model which has mor features and has touch sensitive response keys: $200 ...STEREO FM TRANSMITTER KIT: 88-108MHz, 6-12V DC supply, 8mA <at> 9V, 25X65mm PCB size, PCB plus all on-board comp’s, plus battery connector and 2 electret mic’s: $25, plastic case to suit: $4 ...WOOFER STOPPER KIT: Stop that dog bark, also works on most animals, refer SC Feb. 96, Kit includes PCB and all on board comp’s, wound transformer, electret mic., and a horn piezo tweeter: $39, extra horn piezo tweeters (drives up to 4) $6 Ea. ...ALCOHOL BREATH TESTER KIT: Based on a thick film alcohol sensor. The kit includes a PCB, all on board comp’s and a meter : $30 ...CENTRAL LOCKING KIT (NEW): A complete central locking kit for a vehicle. The kit is of good quality and actuators are well made, the kit includes 4 actuators, electronic control box, wiring harness, screws, nuts, and other mechanical parts: $60, The actuators only: $9 Ea. ...CODE HOPPING UHF CENTRAL LOCKING KIT PLUS A ONE CHANNEL UHF REMOTE CONTROL: Similar to above but this one is wireless, includes code hoping Tx’s with two buttons (Lock-unlock), an extra relay in the receiver can be used to immobilise the engine, etc., kit includes 4 actuators, control box, two Tx’s, wiring harness, screws, nuts, and other mechanical parts: $109 ...ELECTROCARDIOGRAM PCB + DISK: The software disk and a silk screened and solder masked PCB (PCB size: 105 x 53mm) for the ECG kit published in EA July 95. No further components supplied: $10 ...SECURE IR SWITCH: IR remote controlled switch, both Rx and Tx have Dip switches for coding, kit includes commercial 1 Tx, Rx PCB and parts to operate a relay (not supplied): $22 8A/4KV relay $3 ...FLUORESCENT TAPE: High quality Mitsubishi brand all weather 50mm wide Red reflective tape with self adhesive backing: 3 meters for $5 ...LOW COST IR ILLUMINATOR: Illuminates night viewers or CCD cameras using 42 of our 880nm / 30mW / 12 degrees IR LEDs. Power output is varied using a trimpot., operates from 10 to 15V, current is 5-600mA ...IR LASER DIODE KIT: Barely visible 780nM/5mW (Sharp LT026) laser diode plus constant current driver kit plus collimator lens plus housing plus a suitable detector Pin diode, for medical use, perimeter protection, data transmission, experimentation: $32 ...WIRELESS IR EXTENDER: Converts the output from any IR remote control into a UHF transmission, Tx is self contained and attaches with Velcro strap under the IR transmitter, receiver has 2 IR Led’s and is place near the appliance being controlled, kit includes two PCB’s all components, two plastic boxes, Velcro strap, 9V transmitter battery is not supplied: $35, suitable plugpack for the receiver: $10 ...NEW - LOW COST 2 CHANNEL UHF REMOTE CONTROL: Two channel encoded UHF remote control has a small keyring style assembled transmitter, kit receiver has 5A relay contact output, can be arranged for toggle or momentary operation: $35 for one Tx and one Rx, additional Tx’s $12 Ea. OATLEY ELECTRONICS PO Box 89 Oatley NSW 2223 Phone (02) 9584 3563 Fax (02) 9584 3561 orders by e-mail: branko<at>oatleyelectronics.com major cards with phone and fax orders, P&P typically $6. December 1996  75 VINTAGE RADIO By JOHN HILL A new life for a battered Astor Not all vintage radios are highly sought after items. A mid-1950s 4-valve Astor can often be picked up for just a few dollars and is usually quite easy to repair and get going again. Vintage radio receivers vary from those rare relics from the 1920s to the mass-produced plastic mantel models of the 1950s and 1960s, with a multitude of makes and models in between. Although some collectors specialise in a particular era or brand name, many collect whatever comes their way, regardless of age or whether it is housed in a timber, bakelite or plastic cabinet. From a writing point of view, I like to produce a similar variety in my monthly column and endeavour to give my readers a mixed bag of stories about the many and varied aspects of vintage radio. It appears that a restoration story on a relatively late-model valve receiver is just as interesting, in its way, as a similar story on an older and rarer set that few of us are ever likely to own. In fact, far more readers can relate to a late-model receiver because that is what most people are likely to collect. It so happened that a particular repair came my way recent­ly and it seemed to be a good one to write about for the simple reason the receiver is so ordinary and unspectacular. It was a mid-1950s 4-valve Astor mantel with odd control knobs and a smashed speaker grille – the sort of wreck that can be picked up at a garage sale for $10 or less. Apart from the broken cabinet, the receiver was in poor condition and although it supposedly “worked” when purchased, it made no sound other than a badly distorted whimper. The first step with the grille repair was to make up a plastic louvre to replace the missing one. The handle of a plas­tic knife was used for this purpose. 76  Silicon Chip In fact, it was the type of set that one would normally buy for spare parts. In this instance, however, the receiver was brought to me to be repaired. As the woman who owns it is a friend of the family, I really couldn’t say no. Of course, she realised when she bought the set that it needed a lot doing to it but thought that it would be no trouble for me to fix it because my magic wand can mend just about anything. Oh – such faith! Grille repairs I decided to attempt the broken grille repair first and it was fortunate that the damage was not as bad as it could have been. One broken piece had already been glued back in place while the other piece was missing. This meant that a new section had to be made and glued into position. Finding something suitable from which to make a new grille part was the problem. Eventually, the handle of a takeaway plastic knife supplied the necessary material. It was shaped with a file until it wedged firmly into position, then it was glued in place. A couple of smaller fragments were then used elsewhere to fill in a few missing chips. Although the broken grille louvres had been successfully replaced, the stark white plastic replacements stood out like a neon sign compared to the rest of the speaker grille. The repair area needed a touch up with a matching paint but obtaining the correct colour match was a near impossible task. So instead of a match, a contrast was used, and the whole grille area was painted an off-white. The result was pleasing enough and at the same time disguised the repair area reasonably well. With the grille reconstruction completed, the circuitry was next on the agenda. Speaker repairs In order to work on the speaker grille, the speaker had to be removed from the cabinet. This should have been a simple operation requiring the removal of four spring steel clips from the plastic studs they fit onto. Alas, two of the studs snapped off! Removing the speaker revealed that whatever smashed the grille also damaged the speaker cone – it was torn from rim to centre. Repairing the split with silicone rubber (Silastic®) cured the problem and while such cone patch-ups aren’t always the neatest looking repairs, they are effective and long lasting. The speaker, by the way, is unusual in that it is a very small oval type measuring 125 x 75mm (5 x 3 inches), so replace­ment was not an option. As an aside, most 4-valve receivers from the 1950s used 125mm (5-inch) speakers so it appeared that the little Astor might be at a disadvantage as far as a good sound reproduction was concerned. However, after the restoration had been completed, the midget Rola performed really well and the set’s tonal quality was excellent. A close-up view of the finished grille repair. The whole louvre area was painted off-white to disguise the repaired section. Although not a totally invisible repair, there were no complaints from the owner. Original parts Checking out the chassis revealed everything to be original and the state of the 40-year old Ducon paper capacitors was not good. They appeared to have been overheated, having bulged ends and droplets of solidified wax hanging from their undersides. Naturally, they were replaced and that, in itself, would have au­ tomatically solved a number of problems. The valves were checked next and the valve tester’s neon quickly indicated an intermittent short in the 6BE6. These valves often flash the shorts/ leakage neon on my valve tester but, despite this, they usually function Spring-steel clips are used to hold the loudspeaker in place. As is often the case, the plastic stud breaks off when the clip is removed. This is the miniature (125 x 75mm) Rola loudspeaker that was used in the old Astor. Note the missing retaining clips and the repaired cone areas at 12 o’clock and 2 o’clock. The cone repair was completely satisfactory. quite normally. The rest of the valves checked OK. Numerous other items needed attention. The 200Ω back-bias resistor had split, a noisy volume control required cleaning, a new power cord was needed, the dial cord was about to let go, both dial lamps were burnt These two spring retaining clips are all that hold the cabinet together. This view shows how the clips are fitted to the underside of the cabinet. December 1996  77 The two odd knobs at left were replaced with a pair of Radiola knobs which matched the maroon colour of the Astor cabinet per­fectly. out, and the chassis was just floating around loose inside the cabinet. An ohmmeter check on other resistor values cleared them all as being well within tolerance. The intermediate frequency, power, and output transformers also passed inspection, as did the aerial and oscillator coils. Testing After replacing all the necessary parts it was time for a tryout. While the receiver worked, there was very little volume and an incredible amount of distortion. Distortion in a valve radio can often be caused by a leaky coupling capacitor from the plate of the driver stage to the grid of the output valve. This allows the plate voltage to be applied to the control grid of the output valve, thus biasing the grid positive instead of negative. As the little Astor had just had all of its old capacitors replaced, a faulty coupling capacitor seemed unlikely. However, a voltmeter check of the output valve’s control grid revealed a high positive potential. The coupling capacitor was replaced but the situa- The little Astor is of simple construction and is a very basic 4-valve receiver. It was straightforward to repair and get going. 78  Silicon Chip tion remained the same – the control grid was still positive! Studying the circuitry more closely revealed a 100pF sil­vered mica capacitor connected between the plate of the 6AQ5 output valve and its control grid, via a 47kΩ stopper resistor. This capacitor is designed to apply a small amount of negative feedback to the control grid of the output valve, to improve the audio frequency response of the receiver. It was reasonable to assume that this mica capacitor was faulty and it was! Removing the capacitor immediately cured the distortion problem and the set sounded normal – but not for long. After about a minute or two, the distortion returned and the volume faded to almost nothing. At this stage, I recalled the short indication when testing the 6BE6. The valve was replaced and that fixed that problem – no more distortion and stable volume. A new 100pF capacitor was also fitted in place of the faulty one and repairs were nearing com­pletion. There was still one remaining problem with the receiver – it was full of whistles. The 6AD8 IF (intermediate frequency) amplifier valve was replaced and that eliminated the birdies, so the valve obviously had some sort of an internal fault or a shielding problem. RESURRECTION RADIO VALVE EQUIPMENT SPECIALISTS AVAILABLE RADIO & AUDIO * Circuits * Valves * Parts * Books Fully restored radios for sale WANTED for CASH * Valves and radios The finished Astor mantel receiver looked quite presentable. It’s not the sort of receiver that collectors would fight over but its owner was very pleased to have it restored to working order. An alignment session peaked the IF transformers and aligned the aerial and oscillator circuits. That completed the restora­tion except for a few minor details. One of these details was the mounting of the loudspeaker. It has already been stated that two of the mounting lugs broke off when removing the speaker’s re­taining clips. This is not an uncommon happening with this method of mounting and can make remounting the speaker difficult. Perhaps the easiest way out of this situation is to glue the speaker back in place but this should be done with care. Some modern glues can be rather tenacious, so use them sparingly in case the speaker has to be removed some time in the future. Also, it is advisable to fit a grille cloth to minimise the accumula­tion of dust and fluff that builds up between the bottom of the speaker cone and the speaker baffle. Checking mica capacitors A megohmmeter test on the suspect mica capacitor revealed a serious leakage problem. Capacitors which work at high voltages should be tested at high voltages. Perhaps some comment should also be made regarding that leaky mica capacitor. The faulty capacitor was the only silvered mica capacitor in the receiver. As time progresses, more and more of these capacitors give trouble and need replacing but it is not always easy to detect faults in mica capacitors. When checking the suspect capacitor with a multimeter set to the ohms x 1000 scale, the meter needle showed not the slight­est deflection. To many vintage repairers this would indicate that the capacitor was not leaking or shorted and not the cause of the problem. Not necessarily so! When the same suspect capacitor Send SSAE for Catalogue Visit our Showroom at 242 Chapel Street (PO Box 2029), PRAHRAN, VIC 3181. Phone: (03) 9510 4486; Fax (03) 9529 5639 was checked at 500V using a megohm meter, the meter reading was about 0.5MΩ and that sort of leakage is quite unacceptable under the conditions in which the capacitor operates. Leakage and resistance might be regarded as two different effects. A good component will measure the same whether checked on a multimeter at 3V or a megohmmeter at 500V. But leakage in a faulty component can increase with voltage. Which is why capaci­tors that work under high voltage conditions should be checked for leakage at high voltages. In conclusion, this somewhat undesirable wreck of a radio was brought back from the dead and is once more an operative and useful receiver. With its repaired and painted speaker grille it has little appeal to serious collectors but its owner was absolutely thrilled with the transformation. The little Astor now has pride of place in her bedroom and is looked on as a treasured posses­sion. This only goes to prove that beauty is in the eye of the beholder. What may not appeal to some can be simply SC wonderful to others. December 1996  79 Build an 8-cha stereo mixer; Building the new 8-Channel Stereo Mixer is straightforward since nearly all the parts are mounted on one large PC board. A second, much smaller board takes care of the power supply components. By JOHN CLARKE 80  Silicon Chip The general arrangement of the new mixer can be quickly gleaned from the accompanying photos. As shown, the main board mounts on the back of the front panel, while the power supply board mounts on the base of the case. The main board is coded 01210961 and measures 400 x 290mm, while the power supply board is coded 01210962 and measures 105 x 67mm. Begin construction by checking the PC boards for shorted or broken tracks annel Pt.2 and by checking the hole sizes. All holes for the pots should be just large enough to accept the threaded section, while the holes for the 6.35mm stereo sockets should be 11mm in dia­meter (to accept the stub at the end of each socket). Rotary switch S9 is mounted directly on the main board and should be test fitted to ensure that its mounting holes are large enough to accept the switch pins. The eight toggle switches (S1-S8), the 6.35mm socket contact points and the three power supply inputs are all soldered to PC stakes. Check that the relevant holes are large enough to accept the PC stakes supplied. The holes for the XLR sockets and plugs should also be tested for correct size. In addition, there should be a 12mm hole directly below S9 and in line with the Effects pots. This hole allows the relevant leads to pass through the PC board on their way to the mains switch (S10) and to an adjacent earth solder lug bolted to the front panel. Finally, there are 11 mounting holes for attaching the PC board to the front panel (via 3mm screws and 25mm standoffs). Check that all these holes are drilled to 3mm. Fig.4 shows the assembly details for the main PC board. Begin by inserting the PC stakes, wire links and resistors. The PC stakes are installed at the S1-S8 switch positions (three for each switch), at the 6.35mm socket connection points (tip, ring and ground), and at the +15V, GND and -15V power supply points located near LED1. Table 2 shows the resistor colour codes but we also suggest that you check each value using a digital multimeter, just to make sure. That’s because some colours can be difficult to deci­pher and it’s easy to make a mistake when there are lots of resistors to be installed. The next step is to install the ICs. Be sure to install the correct op amp in each location and with the correct orientation. In particular, note that IC6 and IC8 are oriented differently to the remaining ICs. Once the ICs are in, install the two signal diodes (D1 and D2) and transistors Q1 and Q2. Don’t get these two transis­tors mixed up – Q1 is a BC338 NPN type, while Q2 is a BC328 PNP type. The capacitors are next. Note that the electrolytics with 10µF and 100µF markings are polarised and must be oriented as shown on Fig.4. The remaining electrolytics are NP (nonpolar­ised) and can be oriented either way around. Table 1 shows the codes used for the ceramic and polyester capacitors. It’s now time to install the switches. The toggle switches (S1-S8) are simply soldered to the tops of their corresponding PC stakes. Take care to ensure that each switch is centred over its PC stakes and that it is at right angles to the PC board before soldering all the connections. Rotary switch S9 is mounted directly on the PC board. Push this switch all the way down onto the board before soldering its pins. This done, remove and discard the locking ring that’s located under the mounting nut and star washer. The 6.35mm sockets are mounted with their rear stubs in­serted into the PC board holes. Note that it is necessary to bend the Tip (end terminal) outwards and the GND terminal (front) inwards so that they contact their corresponding PC stakes. The Ring (centre terminal) is left unchanged. The Tip and Ring terminals can now be soldered directly to the Tip and Ring PC stakes. The connection from the GND terminal to the GND PC stake requires a short length of tinned copper wire to bridge the gap. Note that only the Tip and GND terminals are used in some cases, and the Ring terminal is left unconnected. For the headphone socket, however, the Tip and Ring terminals are connected together, so that the sound is fed to both sides of the head­phones. Potentiometers There are 54 potentiometers to be mounted on the board, so installing them all will take some time. The main thing to watch out for here is that their values differ, so be sure to install the correct pot at each location. As shown, the pots are all mounted from the underside of the PC board. Before doing this however, it is necessary to fit a 10.5mm ID x 2mm thick plastic washer to the threaded bush of each pot. This is to prevent the pot bodies from shorting the copper tracks on the PC board. In addition, the locating tag on the side of each pot must be bent sideways (to clear the PC board), while the centre terminal must be bent at right angles, towards the shaft. This done, secure each pot to the PC board in turn and solder its centre terminal directly to its PC board pad. The outer pot terminals are wired using short lengths of tinned copper wire. Once all the pots are in, trim the plastic shaft of switch S9 to the same height as the pot shafts. The XLR sockets and plugs can now all be soldered in place, making December 1996  81 82  Silicon Chip December 1996  83 Fig.4: follow the order suggested in the text when installing the parts on the PC board and note that the pots are fitted with an insulating washer (see text) and installed from the copper side. Take care to ensure that all polarised parts are correctly oriented and that the IC type numbers are correct. Repeated from last month’s issue, this photo shows the fully-assembled PC board. Note that a few changes were made to the board after this photo was taken and so it will differ slightly from the layout shown in Fig.4. sure that they sit square with the PC board. This done, insert the two LED bar­ graphs. Note that, in each case, the anode (longer) lead goes towards switch S9. Similarly, install LED21 but do not solder this LED or the bargraphs just yet; first, we have to temporarily fit the front panel. The front panel is straightforward to fit. Begin by fitting the 25mm spacers to the PC board,. There are 11 spacers in all and these should be firmly secured using 3mm machine screws. Once the spacers are in place, fit the front panel over the top of the PC board, so that it sits on the standoffs. The toggle switches (S1-S8) and 6.35mm socket securing threads should protrude through the panel, although you may need to slightly adjust the toggle switches for correct alignment. Check also that the XLR sockets and plugs sit flush with the underside of the panel. When everything fits correctly, secure the 84  Silicon Chip panel from the top using 3mm screws into the spacers. The LED bargraph displays and LED21 can now be pushed into their respective holes in the front panel and their leads sol­dered. This done, remove the front panel and fit the mains toggle switch (S10). In addition, an earth solder lug should be securely bolted to the back of the front panel, immediately to the left of the mains switch. Be sure to scrape away the paint around the mounting point to ensure a good earth contact. Power supply It’s now time to build the power supply and this can begin with the PC board assembly – see Fig.5. The four diodes (D3-D6) can go in first, followed by PC stakes at the six external wiring points. The two 1000µF electrolytic capacitors are mounted side-on, which means that the leads must be bent at right angles to go through the PC board. Take care to ensure that they and the smaller 10µF capacitors are mounted with the correct polarity. It’s a good idea to glue the bodies of the 1000µF capacitors to the PC board, so that they cannot move and place stress on their leads. The two 3-terminal regulators are fitted with small heat­ sinks and the assemblies secured to the PC board using 3mm screws and nuts. There’s no need to isolate their tabs from the heat­sinks but note that REG1 is a 7815 while REG2 is a 7915, so don’t get them mixed up. Bend the regulator leads at right angles so that they go through the holes in the board and trim off any excess after soldering. The remaining power supply items are mounted on the chassis – see Fig.6. If you are making your own metalwork, you will need to drill holes for the fuseholder, cordgrip grommet, transformer mounting screw, earth screw and the mains terminal block. Four mounting holes are also required for the power supply board. The board can then be mounted on 6mm standoffs and the other major hardware items installed. Note that the earth solder lugs must be securely bolted to the case using a screw, nut and starwasher. A second nut can then be used to lock the first, so that there is no chance of it coming loose. As before, scrape away the paint from around the mounting hole before installing this assembly, to ensure a good earth contact. Follow the layout shown in Fig.6 exactly when installing the mains wiring. The mains cord enters the case through the cordgrip grommet and must be securely clamped (check this care­fully). The Neutral (blue) lead goes directly to the main termi­nal block, while the Active (brown) lead goes to the fuseholder. A mains-rated lead is then run from the other terminal on the fuseholder to the terminal block. Slip a short length of heatshrink tubing over the leads before soldering them to the fuseholder. This done, solder the leads, then push the heatshrink tubing over the fuseholder and shrink it down using a hot-air gun. Do not neglect this step – it is an important safety measure to prevent accidental contact with the mains. The Earth lead (green/yellow) from the mains cord must be securely soldered to the earth lug. Leave this lead longer than the others, so that it will be the last lead to break should the mains cord ever come adrift due to some brute force. After making the Fig.5: this is the parts layout for the power supply PC board. Use PC stakes at the external wiring connections and make sure that you don’t get the positive and negative 3-terminal regulators mixed up connection, use a multimeter to confirm that there is zero ohms resistance between the earth pin of the mains plug and the case. The remaining connections to the terminal block involve the transformer primary leads plus a 3-wire mains-rated cable that runs to switch S10 on the front panel and to the adjacent earth solder lug. Note the .001µF 2kV ca­pacitor that’s connected to the terminal block in parallel with these leads. The leads are fed through the 12mm hole in the PC board below S9, before being connected to the power switch. As with the fuseholder, be sure the shroud the switch body with heat­ shrink tubing – ie, slip heatshrink tubing over the leads before soldering them to the switch terminals, then Below: the view from the rear of the PC board, with all the pots in place. The two outer terminals of each pot are soldered directly to the copper pads, while the centre terminals are connected via a wire link. December 1996  85 Fig.6: install the power supply wiring as shown in this diagram. Note that the leads to power switch S10 must be mains rated, as must the Earth lead to the adjacent solder lug. push the tubing over the switch body and shrink it down. The transformer secondary leads can now be connected to the power supply board but don’t connect the supply leads to the main (mixer) PC board at this stage. That step comes later, after the power supply has been tested. Use cable ties to secure the mains wiring and transformer leads. Testing When the wiring is complete, go 86  Silicon Chip back over your work and check carefully for any wiring errors. In particular, check that the mains wiring is correct and that all exposed switch and fusehold­er terminals have been shrouded with heatshrink tubing. Now carry out the following test procedure: (1). Disconnect both power switch leads and the .001µF capacitor from the mains terminal block and connect an insulated link across the vacant terminals (this disconnects and bypasses the mains switch). (2). Install the fuse, apply power and check that the +15V and -15V supply rails are present on the power supply board. (3). Switch off and run the supply leads (+15V, GND, -15V) from the power supply board to the main board (immediately below the left bargraph). These leads can be run using medium-duty hookup wire. Twist the leads together to keep them neat and tidy and make sure you don’t get them mixed up; ie make sure that The power transformer and the power supply board are mounted on the base of the chassis. Make sure that the mains cord is securely anchored via its cordgrip grommet and be sure to cover all exposed terminals with heatshrink tubing. +15V goes to +15V, GND to GND, and -15V to -15V. (4). Reapply power and check that the power LED lights. If it doesn’t, check the LED orientation. Check each LM833 IC for +15V on pin 8 and -15V on pin 4. The SSM2017 and OP27GP ICs should have +15V on pin 7 and -15V on pin 4, while the LM3915s (IC6 & IC8) should have +15V on pins 3 and 9. (5). Connect a signal source to one of the inputs and check that the LED bargraph displays operate correctly. The headphone output can be checked by plugging in a set of headphones. (6). Check that the corresponding pan control shifts the signal from left to right, as indicated by the displays and the head­phone output. Do this for each of the eight main channels, then test the Auxiliary input and its pan control. (7). Check for signal at the left, right, monitor and effects outputs using an oscilloscope or a multimeter set to read AC volts. All that remains now is the final assembly. First, check that the mains plug has been pulled out of the wall TABLE 1: CAPACITOR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ Value .01µF .0047µF .001µF 270pF 180pF 27pF 10pF IEC 10n 4n7 1n0 270p 180p 27p 10p EIA 103 472 102 271 181 27 10 socket, then remove the insulated link from the terminal block and reconnect the switch leads and the .001µF 2kV capacitor. TABLE 2: RESISTOR COLOUR CODES ❏ No. ❏   5 ❏ 47 ❏ 36 ❏ 46 ❏ 19 ❏ 25 ❏ 44 ❏ 10 ❏   2 ❏   7 ❏   3 ❏   2 ❏ 23 Value 68kΩ 22kΩ 15kΩ 10kΩ 6.8kΩ 4.7kΩ 2.2kΩ 330Ω 270Ω 100Ω 68Ω 33Ω 10Ω 4-Band Code (1%) blue grey orange brown red red orange brown brown green orange brown brown black orange brown blue grey red brown yellow violet red brown red red red brown orange orange brown brown red violet brown brown brown black brown brown blue grey black brown orange orange black brown brown black black brown 5-Band Code (1%) blue grey black red brown red red black red brown brown green black red brown brown black black red brown blue grey black brown brown yellow violet black brown brown red red black brown brown orange orange black black brown red violet black black brown brown black black black brown blue grey black gold brown orange orange black gold brown brown black black gold brown December 1996  87 PARTS LIST 1 metal case, 430 x 300 x 132mm 1 front panel (484 x 309mm) with screen printed artwork plus securing screws 1 PC board, code 01210961, 400 x 290mm 1 PC board, code 01210962, 105 x 67mm 1 20VA 2 x 15VAC toroidal transformer (T1) (Jaycar MT-2086) 1 2AG panel mount fuse holder 1 2AG fuse (F1) 8 SPDT toggle switches (S1-S8) 1 single pole 12-way rotary switch (S9) 1 SPST mains rocker switch (S10) 12 6.35mm stereo sockets (Altronics P-0075 or equiv.) 8 straight pin PC mount XLR panel sockets (Altronics P- 0883) 2 straight pin PC mount XLR panel plugs (Altronics P-0881) 29 10kΩ log pots with 38mm long shaft (VR1, VR2, VR5, VR7-10, VR12-14, VR17, VR19, VR20, VR23, VR25, VR26, VR29, VR31, VR32, VR35, VR37, VR38, VR41, VR43, VR44, VR47, VR49, VR50, VR53) 9 10kΩ lin. pots with 38mm long shaft (VR6, VR11, VR18, VR24, VR30, VR36, VR42, VR48, VR54) 8 100kΩ lin. pots with 38mm long shaft (VR3, VR15, VR21, VR27, VR33, VR39, VR45, VR51) 8 20kΩ lin. pots with 38mm long shaft (VR4, VR16, VR22, VR28, VR34, VR40, VR46, VR52) 9 red knobs 10 blue knobs 16 grey knobs 10 green knobs The front panel can now be refitted. Check that the LED displays and power LED fit their respective holes before securing the panel to the standoffs using 3mm screws. The front panel is further secured by fitting the nuts to the 6.35mm sockets and to the toggle switches, and by fitting the self-tapping screws that come with the XLR plugs and sockets. This done, the entire assembly can be fitted to the case and secured using the 88  Silicon Chip 10 black knobs 1 mains cord and plug 1 cord grip grommet 3 solder lugs 1 3-way mains terminal block 2 heatsinks, 29 x 30 x 12mm 4 6mm standoffs 10 25mm tapped standoffs 59 PC stakes 4 rubber feet 30 3mm dia. x 6mm long screws 1 3mm dia. x 9mm screw, nut and star washer 2 3mm dia. x 12mm screws and nuts 2 3mm nuts 20 self-tapping screws for XLR sockets and plugs 54 10.5mm ID x 2mm high plastic spacers for pots (Farnell 3 x 582-591 or similar) 1 6m length of 0.8mm tinned copper wire 1 300mm length of sheathed twin mains wire 1 300mm length of red hookup wire 1 300mm length of green hookup wire 1 300mm length of black hookup wire Semiconductors 8 SSM2017P balanced microphone preamplifier ICs (IC1, IC13, IC16, IC19, IC22, IC25, IC28, IC31) 8 OP27GP op amps (IC3, IC15, IC18, IC21, IC24, IC27, IC30, IC33) 14 LM833 op amps (IC2, IC4, IC5, IC7, IC9, IC10, IC11, IC14, IC17, IC20, IC23, IC26, IC29, IC32) 1 TL071 op amp (IC12) self-tapping screws supplied. It’s now simply a matter of fitting the push-on knobs to the potentio­meter and switch shafts. We suggest that red knobs be used for the Monitor controls, black for Effects and Auxiliary, red for Pan, grey for Treble, green for Bass and blue for Main. The final testing is best done using all inputs with microphones and instruments. Note that the mixer is intended to operate with the signal GND 2 LM3915 log LED bargraph drivers (IC6, IC8) 1 BC337 NPN transistor (Q1) 1 BC327 PNP transistor (Q2) 2 1N914, 1N4148 diodes (D1,D2) 4 1N4004 diodes (D3-D6) 1 15V positive regulator (REG1) 1 15V negative regulator (REG2) 4 5-segment LED bargraph displays (LEDs 1-20) (Altronics Z 0179) 1 3mm LED (LED21) Capacitors 2 1000µF 25VW PC electrolytic 2 100µF 16VW PC electrolytic 6 47µF 50V non-polarised PC electrolytic 35 10µF 35VW PC electrolytic 8 6.8µF 50V non-polarised PC electrolytic 40 2.2µF 50V non-polarised PC electrolytic 4 1µF 50V non-polarised PC electrolytic 8 .01µF MKT polyester 16 .0047µF MKT polyester 2 .001µF MKT polyester 27 270pF ceramic 2 180pF ceramic 5 27pF ceramic 8 10pF ceramic 1 .001µF 2kV ceramic Resistors (0.25W, 1%) 5 68kΩ 10 330Ω 47 22kΩ 2 270Ω 1W 36 15kΩ 7 100Ω 46 10kΩ 3 68Ω 19 6.8kΩ 2 33Ω 25 4.7kΩ 23 10Ω 44 2.2kΩ Miscellaneous Solder, heatshrink tubing. earthed at one point. This is usually done at the power amplifier. If this is not the case, then earth the signal GND to chassis at the mixer. Finally, note that the maximum input levels before clipping were incorrectly listed in the specifications panel on page 23 of the November issue. The correct levels are 260mV RMS on the Low setting and 3V RMS on the High setting (not 2.9V and 9V, SC as shown). 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. Rod Irving Electronics Pty Ltd 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: Rod Irving Electronics Pty Ltd 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. Rod Irving Electronics Pty Ltd 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: Rod Irving Electronics Pty Ltd 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. Rod Irving Electronics Pty Ltd PRODUCT SHOWCASE 200MHz TekScope from Tektronix Tektronix has announced the THS730A, the top of the range oscilloscope/ DMM in its TekScope family of products. The THS730A model operates at 200MHz, with 1Gs/s sampling rate and features the Tektronix exclusive Isolated Channel Architecture for user and circuit safety as well as wide bandwidth. Developed for electronics design and test engineers, as well as for field troubleshooting, the THS730A offers high speed dual channel/dual digitiser measurement and triggering capabili­ ties for quick timing error detection. The THS730A utilises the TekScope graphical user interface (GUI). Other features of this oscilloscope include comprehensive and advance triggering, glitch capture, dB and dBm measurements. Other members of the THS700 oscilloscope family include the THS­ STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 94  Silicon Chip 710A, THS720A and THS720P. The THS720P, designed for electrical service and power electronics testing, can make measurements to 1kV RMS. For further information, contact Tektronix Australia Pty Ltd, 80 Waterloo Rd, North Ryde, NSW 2113. Phone (02) 9888 0100; fax (02) 9888 0125. Thingamebobs & Douvres MicroZed Computers has released two kits for making pro­totypes. Intended for use with BASIC Stamp control computers, these kits are designed to minimise soldering, speed proto­typing time and allow reuse of prototypes. Stamp boards, like most other small computers, come with a 0.1-inch matrix of plated through holes. Soldering and unsolder­ ing more than a few times deteriorates the prototype area of the board. MicroZed’s Thingamebob wiring kit is a low-cost, ready-made solution to match the Stamp’s header strip connections. The basic wiring kit has 20 x 150mm coloured wires, two each of the 10 colours used for resistor values. Each wire is terminated with a single pin plastic housed socket for slipping onto a header pin. A feature of the Thinga­mebob kit is that a selection of multiple pin housings are supplied, so that a multi-pin socket can be made. A 40-pin single row header strip is supplied, so that the idea may be interfaced to “breadboard” style proto­ typing kits, used to connect to other circuits, or to “daisy chain” Thinga­ me­bob wires, where multiple power, common or communication lines are needed. Five spare header connecting sockets are supplied, to use on your own wires. Recommended maximum current capacity for Thinga­ mebob wires is 1000mA. Warning: Thingamebobs are not suit­ able for use on 240V mains wiring. Douvres for Stamps is a small kit of simple circuits, already wired and ready for attachment to the header pins. Each Douvre kit contains seven circuits: a piezo sounder, a thermistor circuit, a potentiometer circuit, a pushbutton circuit and three LED circuits (red, green and orange). Purchasing a Douvres kit allows a novice user to learn and use Stamp commands within an hour of opening a kit. Professional users, on the other hand, will find that they eliminate the tedium of search­ ing for parts and making up mundane circuits. Packed in a small reusable plastic box, Thinga­me­bobs are priced at $24.00 and Douvres $34.00, including sales tax. Quant­ity and tax exempt prices are available. Contact MicroZed Computers (067) 722 777 (or see the adver­tisement in the Market Place of this issue). 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.emona.com.au/ Component counting scales Manual component counting for batching or stock-take is one of the big time-wasters in the electronics industry. Fortunately, most electronic components are very nearly identical in weight, allowing them to be easily counted by weight. The PS1015 is a high resolution, portable counting scale. A rechargeable battery is installed to allow a full day’s work, before overnight recharging with the power pack supplied. An internal resolution of 40mg ensures accurate counting of small components and pins used in many products. The maximum capacity of 1.5kg allows counting of some of the larger components, in­cluding electrolytic capacitors, or the large quantities found in some bulk packs. The three panel display shows total weight, unit weight and current count simultaneously. Back lighting provides for easy viewing, even in the dim back corners of some stores. When not in use, the display can be folded down for storage and transport. The measuring tray is 230 x 280mm, large enough to accom­modate a wide range of containers. The one-touch Tare button returns the display to zero for counting after a new container is placed on the platform. For further information, contact Com­p­u­tronics International Pty Ltd, 31 Kensington St, East Perth 6004. Phone (09) 221 2121; fax (09) 325 6686. December 1996  95 PIC development tool kit The universal and affordable ICEPIC tool kit, for the Microchip range of PIC microcontrollers, includes 20MHz in-circuit emulation, a simulator, a programmer and an assembler. The package presents emulation data by their symbolic names, allows assembling and automatic back notation of edited error-report files, and generates extensive assembly warnings to prevent those pitfalls. The tool kit runs on an IBM compatible PC. System require­ments are 386+, DOS, mouse, printer port and a small amount of extended memory under himem.sys or equivalent. The user-screen presents all information required for emulation and simulation and provides immediate access to the accompanying PICASM assembler and user-supplied editor. A multi-function oscillator is included. The user can select the clock source to be a user-supplied crystal or oscilla­tor, a special clock signal located on the target board, or the stable (5kHz- 20MHz) VFO on the ICE card. The VFO frequency is selected in four Programmable video generator Leader Instruments has released a new programmable video generator, the LT 1610. The unit can drive a wide range of displays from LCD to CRT and can be easily controlled from an external personal computer through an RS232C interface. The LT 1610 is provides full digital 8-bit 120MHz output of dot clock and analog RGB 150MHz output of dot clock. It enables easy programming of the following functions under the Windows environment: horizontal timing, vertical timing, output conditions and output patdecades and can be fine adjusted, with the ICEPIC screen acting as an accurate digital frequency meter. An on-board switching power supply generates all the re­ quired voltages from an external 12-24VDC or AC power source. The ICE card communicates bi-directionally with a printer port on the user’s PC. This link transfers operational code, target ICEPIC - In Circuit Emulation for Microchip PIC FREE - 30 Day Money Back Guarantee !! MADE BY ELECTRONIC EMULATION CORP. Non-intrusive realtime in-circuit emulations up to 20MHz. Downloads in under 2 seconds. Conditional assembling and include files. Page, bank or segmentation error checking. View any register, or state, in multiple windows. User-friendly 8051-type source code instruction option. Microchip & Parallax syntax compatible assembler. Single step, run to breakpoint, or run continuously. Edit errors in listing file & back notate to source. Realtime & transparent emulator with no register loss. Full source code debugging with register & bit symbolic names. Change a register, value, or port in decimal, hex, binary, ASCII. Easy switch between emulator, simulator or editor & assembler. Now Only $ 1,200:00 FREE delivery anywhere in Oz!, Order one NOW ! Neil Kirkness, 29 Pacific Sands, Poinciana Rd, Holloways Beach QLD 4878. Tel: (070) 55-0242, Fax: (070) 55-9077, E-mail: nwk<at>ozemail.com.au ( Shipped direct to you, import levies are not included ) Includes:- Simulator, Emulator, 16/17Cxx Assembler, 16C5x ICE pod. 1 year’s FREE software upgrades! Unconditional 30 day refund! 96  Silicon Chip terns. It is also possible to draw patterns using a graphics function. For further information, contact Stantron Australia Pty Ltd, Suite 1, Unit 27, 7 Anella Ave, Castle Hill, NSW 2154. Phone (02) 9894 2377; fax (02) 9894 2386. emulation code and emulation information back and forth. Downloading the ICE operational code from the PC to the ICE card ensures easy upgrading in the field as further enhancements become available. For further information, contact Neil Kirkness, 29 Pacific Sands, Poinciana Road, Holloways Beach, Qld 4878. Phone (070) 55 0242; fax (070) 55 9077. KITS-R-US RF Products FMTX1 Kit $49 Single transistor 2.5 Watt Tx free running 12v-24V DC. FM band 88-108MHz. 500mV RMS audio sensitivity. FMTX2A Kit $49 A digital stereo coder using discrete components. XTAL locked subcarrier. Compatible with all our transmitters. FMTX2B Kit $49 3 stage XTAL locked 100MHz FM band 30mW output. Aust pre-emphasis. Quality specs. Optional 50mW upgrade $5. FMTX5 Kit $98 Both a FMTX2A & FMTX2B on 1 PCB. Pwt & audio routed. FME500 Kit $499 Broadcast specs. PLL 0.5 to 1 watt output narrowcast TX kit. Frequency set with Dip Switch. 220 Linear Amp Kit $499 2-15 watt output linear amp for FM band 50mW input. Simple design uses hybrid. SG1 Kit $399 Broadcast quality FM stereo coder. Uses op amps with selectable pre-emphasis. Other linear amps and kits available for broadcasters. PO Box 314 Blackwood SA 5051 Ph 0414 323099 Fax 088 270 3175 AWA FM721 FM-Tx board $19 Modify them as a 1 watt op Narrowcast Tx. Lots of good RF bits on PCB. AWA FM721 FM-Rx board $10 The complementary receiver for the above Tx. Full circuits provided for Rx or Tx. Xtals have been disabled. MAX Kit for PCs $169 Talk to the real world from a PC. 7 relays, ADC, DAC 8 TTL inputs & stepper driver with sample basic programs. ETI 1623 kit for PCs $69 24 lines as inputs or outputs DS-PTH-PCB and all parts. Easy to build, low cost. ETI DIGI-200 Watt Amp Kit $39 200W/2 125W/4 70W/8 from ±33 volt supply. 27,000 built since 1987. Easy to build. ROLA Digital Audio Software Call for full information about our range of digital cart players & multitrack recorders. ALL POSTAGE $6.80 Per Order FREE Steam Boat For every order over $100 re­ceive FREE a PUTT-PUTT steam boat kit. Available separately for $19.95, this is one of the greatest educational toys ever sold. 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.oatleyelectronics.com/ 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. Torch dimmer wanted Have you designed a dimmer for torches? I’ve searched through your floppy index files but can find no mention of a suitable circuit. I think a 555 could be made to do the job. (A. K., Belmont, Vic). • The closest we can come to nominating a suitable circuit is the Mini PCB Drill Speed Controller featured in the January 1994 issue of SILICON CHIP. It uses a 7555 and a BDY79 Darlington transistor but it was designed to run from voltages in the region of 12V or more whereas torches typically run from 3V or 4.5V. This does not present a problem for the 7555 which will run down to 2V but the BD679 is another matter. Since it is a Dar­lington transistor, there will always be a loss of 1V or more across it. This is immaterial in a 12V speed control circuit but it’s a big problem in a torch dimmer; 1V lost in a 3V circuit amounts to a large permanent reduction in brightness. You could overcome this problem Dolby ProLogic kit is motor-boating I have a problem with the Dolby ProLogic kit regarding beat effects. On effects mode with surround selected I am finding the unit is very unstable and will break into low frequency motor boating. This does not occur in the other two positions. In the ProLogic position, the sound output is very distorted and signif­icantly down in volume from the surround speakers. When noise mode is selected in either effects or ProLogic position, similar motorboating is experienced except in the stereo position of S4. All voltages are correct or very close to those specified. I have checked and rechecked the wiring 98  Silicon Chip by using an IRF540 FET instead, as used in our Torch Battery Saver circuit featured in the January 1995 issue. At 4.5V supply, it will typically have a voltage loss (Drain-Source voltage) of 0.2V which is acceptably low. Note that you would have to twist the leads of the IRF540 to match the PC board. Other modifications which would be desirable would be to omit the 9.1V zener and its 220Ω resistor. You could also omit the heatsink for the transistor and the protection diode D1. Queries on power supply I am writing in reference to the circuit for the 100Hz Tone Burst Generator published in the “Circuit Notebook” pages of the August edition of SILICON CHIP. After reading the article I was a little bewildered by the description for the power supply. The article states: “power is derived from a 15V transformer. D1-D4 rectify the AC, while a 7815 regulator provides to S3, S4 & S2 and believe these to be correct and all other functions of the unit work as per spec. If you can short circuit my agony and tell me I’m an idiot for having a wire out of place I will thank you very much. If you can point me in a direction of changing bits and what to check I also have access to a scope but the readings have been somewhat obscure without some form of reference. (N. R., Melbourne, Vic). • After checking power supply voltages, compare the PC board around IC1 against the published pattern. You possibly have a short between tracks or IC pads. This could be with a large solder bridge or slither of solder. Scrape between tracks and pads with a sharp knife. the circuit with a 15V supply”. This doesn’t seem to work, for the following reason: 15V is being supplied to the rectifier circuit D1-D4. Assuming a 600mV drop for each diode, that would leave 13.8V peak, less if you take the filtered voltage, available to the input of the regula­tor. The 7815 regulators have a dropout voltage of 2V and a minimum input voltage to maintain line regulation of 17.7V (National Semiconductor Voltage Regulator Handbook). What it boils down to is you can’t get something for nothing. 13.8V in (or less) and 15V out? Am I missing something or what? (C. B., Sale, Vic). • The circuit description of the power supply is correct. The 15V transformer delivers a sinewave which will have a peak-to-peak voltage of 42.4V or 21.2V peak. After allowing for the voltage drop in the diodes, this will produce a filtered DC voltage of about +20V. This is then regulated by the 7815 to produce 15V DC. Measuring insulation resistance I wish to congratulate you on the superb performance of the Insulation Tester published in the May 1996 issue. I have used it to measure the insulation resistance between tracks on Veroboard and was surprised that when heated, the insulation resistance dropped below 1GΩ. The same effect occurred with many complete white goods appliances. This brings me to a question. Is there an Australian Stan­dard (or other standards) regarding insulation resistance of components and of completed hardware? I have an outstanding washing machine which uses the latest technology and yet measures only 20MΩ. I presume that it must have a mains filter with capacitors and discharge resistors to prevent mains-borne interference. I have always assumed that we measure the insulation re­sistance at working voltages because the “tracking” carbon has a negative resistance coefficient and therefore, only becomes visible at higher voltages, and hence higher dissipation, when the tracking resistance drops substantially. (V. E., Highett, Vic). • Australian Insulation standards for household appliances are available from Standards Australia – phone (02) 9746 4700 or fax (02) 9746 8450. An insulation resistance of around 20MΩ for a washing machine is fairly typical. The low resistance is unlikely to be due to any mains filter but is due to the insulation of the heating element (if it has one) or the insulation of the various timer switching contacts, solenoids and the motors. In fact, washing machines with heating elements often cause nuisance tripping with core-balance safety switches and it is a good idea to have them protected separately from other household circuits. Smoking inductor in power supply We are having difficulties with the 40V/8A power supply meeting the specifications outlined in your January/February 1992 issues. The unit is smoking the inductor L1 which is the 17-745-22 powdered iron core wound with 10 turns of 1.2mm enamelled copper wire. This is heating up to the point of it being a fire hazard if left to draw more than about 4.5A for more than a few minutes. (P. S., Perth, WA). • It does seem strange that this problem is appearing after four and a half years. However, the Neosid 17-745-22 core is not ideal for the job. The 17745-23 is better. Also reducing the turns to four or five rather than six will reduce core satura­tion. Similarly, using a few 0.8mm wires in parallel rather than 1 x 1.2mm wire for winding should reduce resistive losses. Alter­ natively, use an ETD49 transformer core as per the Nicad Charger in October 1995. Use the 0.5mm gap and 10 turns of 4 x 0.8mm wire as shown on page 59 of this issue. The secondary winding is not required. Notes & Errata Woofer Stopper MkII; February 1996: depending on which type of piezo loudspeakers are used, they can pro- Fence controller needs more output I would like to make some comments about two of your pro­jects I constructed. The first is the Electric Fence Controller described in the July 1995 issue. It was constructed correctly and all components, including the ignition coil work OK. Unlike electric fences on different properties that I have been to, the output of this device has very little bite. I made changes to replace the timing resistors so as to give a 0.1 second pulse every second and increase the wattage of the 6.8Ω resistor. I also built the Engine Immobiliser described in Decem­ber 1995 – a great idea. However, the 75V zener diodes shorted after testing and driving my car. This may be an isolated incident but to make sure I placed a 560Ω 0.5W resistor in series with the new 75V zeners and placed a 0.22µF 630VW capacitor across the collector and emitter of Q1. There has been no trouble since. (D. C., Narangba, Qld). • We should point out that Notes duce audible clicking at the rate the signal bursts to a high and low level. This can be cured by adding a 47µF 16VW electrolytic capacitor between the base and emitter of transistor Q3. The positive side of the capacitor connects to the base. The capacitor effectively slows down the rate that the burst signal rises and falls to eliminate any audible noise in the speaker. We should also point out that if the tweeter drive level control (VR2) is set too high, it can cause the same symptom. Minivox Voice Operated Relay; September 1994: diode D1 is shown with the incorrect polarity on the overlay diagram on page 33. LPATS: Striking A Blow Against Lightning; November 1996: the text on page 8 and in Fig.1 on page 6 refers to parabolas as the paths of possible lightning strikes. The term used should have been “hyperbola”. Engine Immobiliser; December 1995: there have been reports of the zener diodes in this circuit failing. In line & Errata were published on the Electric Fence Controller in the December 1995 issue. These noted that Australian Standard AS/NZS 3129: 1993 now specifies a maximum output voltage of 10kV instead of 5kV. In order to increase the output voltage by the required amount, the 6.8Ω 1W resistor should be changed to 1.2Ω 0.5W. While the coil on-time for the electric fence may need some minor adjustment for different coils we are inclined to the view that if the coil does not give a good output it is probably defective. We have seen one kit version of our electric fence controller where the circuit was working correctly but the HT output was non-existent. It turned out that the coil was a dud. As far as adding a resistor in series with the zeners for the engine immobiliser, this cannot be recommended as it will prevent the zeners from protecting the MJ10012 transistor. Howev­ er, in line with our circuit practice for high energy ignition systems, the specified zener diodes should be rated at 5W instead of 1W. with our circuit practice for high energy ignition systems, the specified zener diodes should be rated at 5W instead of 1W. Video Transmitter/Receiver; October 1996: it has been pointed out that some video camera modules have a DC output instead of AC. If these are used with the Video Transmitter it will not work. The cure is to connect a 100µF non-polarised electrolytic capacitor in series with the input socket. This can be wired directly between the RCA input socket and the input on the PC board. Fuel Injector Monitor; August 1995: we have recently seen a fuel injector monitor in which only eight of the LEDs would light instead of the full 16. The problem is that differing switching thresholds on the 4053 (IC2) can cause faulty switching of the LM3914 dot/ bar modes. If this occurs, the cure is to replace zener diode ZD1 with a 1µF electrolytic capacitor, with its negative lead SC connected to pin 3 of IC5. December 1996  99 Index to Volume 9: January-December 1996 Features 01/96 4 Living With Engine-Managed Cars 01/96 10 Recharging Nicad Batteries For Long Life 01/96 53 Satellite Watch 02/96 4 Fluke 98 Automotive ScopeMeter 02/96 26 Germany's New MagLev Train 03/96 4 Traction Control: The Latest In Car Technology 03/96 12 Cathode Ray Oscilloscopes, Pt.1 03/96 77 Satellite Watch 04/96 4 Refill Your Dead Mobile Phone Battery With Standard AA Rechargeable Cells 04/96 14 Traction Control In Motor Racing, Pt.2 04/96 12 Cathode Ray Oscilloscopes, Pt.2 05/96 6 Cathode Ray Oscilloscopes, Pt.3 05/96 22 Upgrade Your PC In 10 Minutes 06/96 4 Review: BassBox 5.1 Design Software For Loudspeaker Enclosures 06/96 26 'MV Oriana' – Luxury And Technology Afloat 06/96 53 Satellite Watch 07/96 4 Installing A Dual-Boot System On Your PC 07/96 10 Fuel Injection In Economy Cars 07/96 82 Review: The Tektronix THS720 Tekscope 08/96 4 Electronics On The Internet 08/96 38 Satellite Watch 08/96 64 Cathode Ray Oscilloscopes, Pt.4 08/96 76 An Introduction To IGBTs 09/96 10 Making Prototypes By Laser 09/96 53 Neville Thiele Awarded IREE Medal Of Honour 09/96 68 Cathode Ray Oscilloscopes, Pt.5 10/96 4 An Introduction To Smart Cards 10/96 25 Snappy: Capturing High Quality Video Images On A Personal Computer 10/96 75 Satellite Watch 11/96 4 LPATS: Striking A Blow Against Lightning 11/96 82 Adding An Extra Parallel Port To Your Computer 12/96 8 CD Recorders: The Next AddOn For Your PC 100  Silicon Chip 12/96 20 Mitsubishi's Intelligent Automatic Transmission 12/96 57 Satellite Watch Serviceman’s Log 01/96 80 Sanyo 6627-79P; Telefunken ICC4 02/96 54 Pye 48SL1; NEC N-3450 03/96 48 NEC N-4830 C500; Philips 20CT6750/75Z CTO-S 04/96 38 Superstar 1401R Remote Colour TV; Toshiba 207E9A 05/96 40 National Panasonic TC-68A61/ M16M 06/96 54 National Panasonic TC-1407 M12H; Mitsubishi VS-405R 07/96 40 National Panasonic RX-DT610 Portable Stereo CD Player; Akai VS-8 VCR 08/96 40 Teac CT-M515S; Sanyo CTP6626 80P; Sanyo CCC3000 80P 09/96 40 General CG187; Sharp DC1600X 10/96 40 Grundig Receiver 3000 (GB); National NV-180 Portable Video Recorder 11/96 38 Tascam Ministudio Cassette Deck; Marantz 740A VCR; GC181 TV; Philips Trakka KA212 12/96 44 Akai VS-35 VCR Computer Bits 01/96 32 Upgrading Your PC: Is It Worthwhile? 02/96 85 Use Your Personal Computer As A Reaction Timer 03/96 74 Electronic Organisers And Your Personal Computer 05/96 22 Upgrade Your Personal Computer In 10 Minutes 05/96 74 Create Your Own Home Page On The World Wide Web 06/96 10 Overcoming The 528Mb Hard Disc Barrier In Older PCs 07/96 4 Installing A Dual-Boot Windows 95/Windows 3.1x System On Your PC 07/96 22 Dressing Up The Screen In Basic 08/96 82 Customising The Win95 Desktop & Start Menus Radio Control 03/96 54 A Multi-Channel Radio Control Transmitter For Models, Pt.2 04/96 65 A Multi-Channel Radio Control Transmitter For Models, Pt.3 05/96 53 A Multi-Channel Radio Control Transmitter For Models, Pt.4 06/96 60 A Multi-Channel Radio Control Transmitter For Models, Pt.5 07/96 77 A Multi-Channel Radio Control Transmitter For Models, Pt.6 08/96 72 A Multi-Channel Radio Control Transmitter For Models, Pt.7 10/96 82 A Multi-Channel Radio Control Transmitter For Models, Pt.8 11/96 54 AM Vs FM: The Real Facts In The Argument Vintage Radio 01/96 86 Converting From Anode Bend To Diode Detection 02/96 88 Reflex Receiver Basics 03/96 86 A Look At A 1948 Model 4-Valve Peter Pan 04/96 84 Early Transistor Radios 05/96 88 A Look At Early Radiograms 06/96 86 Testing Capacitors At High Voltages 07/96 86 Making A Few Odd Repairs 08/96 86 A Rummage Through My Junk 09/96 84 Vintage Radio And Collecting 10/96 88 A New Life For An Old Hotpoint 11/96 88 A Pair Of Astor Valve Radios 12/96 76 New Life For A Battered Astor Circuit Notebook 01/96 16 Automatic Level Control For Line Signals 01/96 16 Bilge Pump Timer Uses A Mercury Switch 01/96 17 PWM Speed Controller 01/96 17 Pot Plant Moisture Monitor 01/96 17 DC Amplifier For A CentreZero Meter 02/96 32 Reluctor Circuit For High Energy Ignition 02/96 32 Intercom Uses Surplus Telephones 02/96 33 4-Channel Mixer Modifications 03/96 40 Model Railway Level Crossing Control 03/96 40 Binary Counting Demonstrator 03/96 40 Charge Controller For A Transceiver 03/96 41 Precision Timer Uses Cheap Crystal 03/96 41 Brake Pedal Alarm Circuit 04/96 80 Body Filler Depth Detector 04/96 80 Micropower Low-Voltage Indicator 04/96 81 RS232 Modem Switcher Projects to Build 04/96 72 Knock Indicator For LeadedPetrol Engines 05/96 14 Duplex Intercom Using FibreOptic Cable 05/96 30 High Voltage Insulation Tester 05/96 53 A Multi-Channel Radio Control Transmitter For Models, Pt.4 05/96 57 Motorised Laser Lightshow 05/96 80 Knightrider Mk.2 LED Chaser 06/96 14 High Performance Stereo Simulator 06/96 22 Party Rope Light 06/96 31 Build A Laser Pointer From A Kit 06/96 40 A Low Ohms Tester For Your Digital Multimeter 06/96 60 A Multi-Channel Radio Control Transmitter For Models, Pt.5 06/96 70 Automatic 10-Amp Battery Charger 07/96 26 VGA Digital Oscilloscope, Pt.1 07/96 31 Remote Control Extender For VCRs 07/96 54 2A SLA Battery Charger 07/96 60 Minilog: An 8-Bit SingleChannel Data Logger 07/96 70 3-Band Parametric Equaliser 07/96 77 A Multi-Channel Radio Control Transmitter For Models, Pt.6 08/96 14 Electronic Starter For Fluorescent Lights 08/96 20 VGA Digital Oscilloscope, Pt.2 08/96 30 A 350-Watt Audio Amplifier Module 08/96 54 Portable Masthead Amplifier For TV & FM 08/96 72 Multi-Channel Radio Control Transmitter For Models, Pt.7 08/96 75 6-12V Alarm Screamer Module 09/96 16 VGA Digital Oscilloscope, Pt.3 09/96 28 3-Band HF Amateur Receiver 09/96 54 Infrared Stereo Headphone Link, Pt.1 09/96 60 High Quality PA Loudspeaker 09/96 80 Feedback On The Programmable Ignition System 10/96 12 Send Video Signals Over Twisted Pair Cable 10/96 22 Power Control With A Light Dimmer 10/96 32 600W DC-DC Converter For Car Hifi Systems, Pt.1 10/96 53 Infrared Stereo Headphone Link, Pt.2 10/96 66 Build A Multimedia Sound System, Pt. 1 10/96 82 A Multi-Channel Radio Control Transmitter For Models, Pt.8 11/96 20 8-Channel Stereo Mixer, Pt.1 11/96 30 Low-Cost Fluorescent Light Inverter 11/96 42 How To Repair Domestic Light Dimmers 11/96 59 Build A Multimedia Sound System, Pt. 2 11/96 79 Digital Speedometer & Fuel Gauge For Cars, Pt.2 11/96 66 600W DC-DC Converter For Car Hifi Systems, Pt.2 12/96 24 Active Filter For Improved CW Reception 12/96 38 Fast Clock For Railway Modellers 12/96 58 Laser Pistol & Electronic Target 12/96 66 Sound Level Meter 12/96 80 8-Channel Stereo Mixer, Pt.2 04/96 81 Single Rail Operation For The TDA1514 05/96 38 Reluctor Version Of Programmable Ignition 05/96 38 Larger Search Coils For The Metal Locator 05/96 39 0-18V Power Supply With Current Limiting 05/96 39 Electrolytic PC Board Etcher 06/96 32 Bridge Operation For LM3886 Stereo Module 06/96 33 Stereo Preamplifier With Selectable Gain 06/96 33 Novel Modulator For Signal Generators 07/96 16 Multi-Cell Charging With The TEA1100 07/96 16 Random Number Generator 07/96 17 0-16V 15A Power Supply With Current Limiting 08/96 8 Tone Burst Source For Loudspeaker Testing 08/96 9 Cordless Telephone Ring Tone Booster 09/96 8 Low Cost Monitor Amplifier For 32Ω Headphones 09/96 8 Pulse Stretcher For Printer Signals 09/96 9 A Digital Display For The Geiger Counter 10/96 8 Muting The LM3886 Module 10/96 8 Printer Port Zero Voltage Detector 10/96 9 6V Motor Speed/Direction Controller 11/96 16 Swimming Pool Lap Counter 11/96 16 Obtaining Balanced & Isolated 9V Supply Rails 11/96 17 Thermostatic Fan Controller 11/96 17 9V Nicad Battery Saver/Reg. 12/96 36 Overload Protected Power Supply 12/96 37 Quiet Line/Buzzer Alert For Communications Handset 12/96 37 VCO With Constant Mark/ Space Ratio 02/96 94 Subwoofer Controller, December 1995 04/96 93 Radio Control 8-Channel Encoder, March 1996 06/96 93 Insulation Tester, May 1996 07/96 94 Digital Voltmeter For Cars, June 1993 09/96 94 Stereo Simulator, June 1996 09/96 94 16V 15A Power Supply, Circuit Notebook, July 1996 10/96 94 2-Amp SLA Battery Charger, July 1996 10/96 94 Fluorescent Lamp Starter, August 1996 11/96 94 Photographic Timer, April 1995 11/96 94 175W Power Amplifier, April 1996 12/96 99 Minivox, September 1994 12/96 99 Fuel Injector Monitor, August 1995 12/96 99 Engine Immobiliser, December 1995 12/96 99 Woofer Stopper, MkII, February 1996 12/96 99 Video Transmitter/Receiver, October 1996 12/96 99 LPATS: Striking A Blow Against Lightning, November 1996 01/96 22 Surround Sound Mixer & Decoder 01/96 40 Magnetic Card Reader & Display 01/96 54 The Rain Brain Automatic Sprinkler Controller 01/96 56 IR Remote Control For The Railpower Mk.2 02/96 8 Fit A Kill Switch To Your Smoke Detector 02/96 12 Build A Basic Logic Trainer 02/96 22 Low-Cost Multi-Tone Dashboard Alarm 02/96 36 Woofer Stopper Mk.2 02/96 60 Surround Sound Mixer & Decoder, Pt.2 02/96 76 Three Remote Controls To Build 03/96 22 Programmable Electronic Ignition System For Cars 03/96 32 A Zener Diode Tester For Your DMM 03/96 42 Automatic Level Control For PA Systems 03/96 54 A Multi-Channel Radio Control Transmitter For Models, Pt.2 03/96 60 A 20ms Delay For Surround Sound Decoders 03/96 84 Simple Battery Tester For Around $3.00 04/96 22 A High-Power Hifi Amplifier Module 04/96 53 Replacement Module For The SL486 & MV601 Remote Control Receiver ICs 04/96 65 A Multi-Channel Radio Control Transmitter For Models, Pt.3 Notes & Errata 01/96 94 Dolby Pro Logic Surround Sound Decoder, Mk.2, November & December 1995 01/96 94 Five-Band Equaliser, December 1995 02/96 94 Dolby Pro Logic Surround Sound Decoder, Mk.2, November & December 1995 December 1996  101 ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. TOTAL $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. GST)**  $A159  $A83 New Zealand (airmail)  $A145  $A77 Overseas surface mail  $A160  $A85  $A250 Overseas airmail  $A125 **1 binder with 1-year subscription; 2 binders with 2-year subscription YOUR DETAILS Your Name_________________________________________________ GIFT SUBSCRIPTION DETAILS Month to start__________________ Message_____________________ _____________________________ _____________________________ Gift for: Name_________________________ (PLEASE PRINT) Address______________________ _____________________________ (PLEASE PRINT) Address___________________________________________________ State__________Postcode_______ ______________________________________Postcode_____________ Daytime Phone No.____________________Total Price $A __________ Signature  Cheque/Money Order  Bankcard  Visa Card  Master Card ______________________________ Card No. Card expiry date________/________ Phone (02) 9979 5644 9am-5pm Mon-Fri. Please have your credit card details ready 102  Silicon Chip OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE SATELLITE DISHES: international reception of Intelsat, Panamsat, Gori­ zont,Rimsat. Warehouse Sale – 4.6m dish & pole $1499; LNB $50; Feed $75. All accessories available. Videosat, 2/28 Salisbury Rd, Hornsby. Phone (02) 9482 3100 8.30-5.00 M-F. EASY PIC’n Beginners Book to using MicroChip PIC chips $50, Basic Compiler to clone Basic Stamps into cheap PIC16C84’s $135, CCS C Compiler $145, heaps of other PIC stuff, Programmers from $20, Real Time Clock, A-D. Ring or fax for FREE promo disk. WEB search on Dontronics, PO Box 595, Tullamarine 3043. Phone 03 9338 6286. Fax (03) 9338 2935. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 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 below & 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. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ MICROCRAFT PRESENTS: Dunfield (DDS) products are now available exstock at a new low price; please ask for our catalogue. Micro C, the affordable “C” compiler for embedded applications. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $139.95 each + $3 p&h • Now on special is the SDK, a package of ALL the DDS “C” compilers for $399 + $6 p&h • EMILY52 is a PC based 8051/52 high speed simulator $69.95 + $3 p&h • DDS demo disks $7 + $3 p&h • VHS VIDEO from the USA (PAL) “CNC X-Y-Z using car alter­nators” (uses car alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Device programming EPROMs/PALs etc from $1.50 • Fixed price electronic design and PCB layout • Credit cards accepted • All goods sent certified mail • Call Bob for more de­tails. MICRO­CRAFT, PO Box 514, Concord NSW 2137. Phone (02) 9744 5440 or fax (02) 9744 9280. LARGE 7 SEGMENT DISPLAYS: super bright red 660nm. 120mm x 90mm. Digit is 100mm high. Common anode. $14.50 each + p&p. Vacuum Tube Stereo Amplifiers 150W & 300W outputs. Preamps & surround sound processors. Call for pricing and specs. Koph Trading. Ph (02) 9831 8065. Fax (02) 9831 6103. 50W AUDIO AMP: short form kit, pcb & TDA7294. As per Nov 96 Elektor. $25. Tel (09) 447 7248. Fax (09) 447 4856. Email rossco<at>via­net.net.au ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 9587 3491 December 1996  103 New stamp instruction book version 1.7. 280 pages BS1, BS2 & app. notes. Special for December $30 plus $8 post. MicroZed Computers Scott Edwards Electronics Microchip OPTO 22 NEW Micro Micro Engineering Labs (PICBASIC) MICROMINT PicStic DOMINO BLACKJACK PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Advertising Index Allmedia Electronics..................104 Ph (067) 722 777 – may time out to Mobile 014 036 775 Fax (067) 728 987    (Credit Cards OK) Altronics................................. 16-18 http://www.microzed.com.au Av-Comm.....................................47 Specialising in easy-to-get-going hard/software kits. Send 2 x 45c stamps for information package Stamp kits now have a compiler for 16C58 Your next project will be easy, fast and satisfying with a development kit Dick Smith Electronics.... 6-7, 32-35 Earthquake Audio..........................5 EDA Solutions.............................31 Emona.........................................95 MEMORY * MEMORY * MEMORY SPECIAL! (Ex Tax) 1Mbx9 – 70ns $15 30-pin Simms For Quality Assembly On Time Every Time 356 Gilbert Rd. West Preston Victoria 3072 PCB Assembly PCB Design Prototyping Wiring Looms OEM Manufacture Mobile 018 378750 SATELLITE TV confidential newsletter “Coops Technology Digest” covers the latest activities by satellite operators, broadcasters and programmers, covering free to air and pay broadcasts. Issued 10 times per year. For those who need to know. One year subscription A$175. Send for your free sample issue. Av-Comm Pty Ltd, 198 Condamine St (PO Box 225), Balgowlah, NSW 2093. Tel (02) 9949 7417 or fax (02) 9949 7095. MicroZed WEB PAGE always changing. http://www.microzed.com.au 68HC705 Development System: Oztechnics, PO Box 38, Illawong NSW 2234. Phone (02) 9541 0310. Fax (02) 9541 0734. http://www.oz­technics.com.au/ BUSINESS FOR SALE: if you are interested in valve equipment and particularly vintage radio, this is the business for you. Technical skill is not essential. Established in 1987 and with a huge stock of rare parts, valves and test equipment, this is a suitable operation for a sole proprietor or partnership. A secure lease in Melbourne’s premier shopping strip and with an Australia-wide customer base, there is opportunity for expansion and growth. 104  Silicon Chip SIMMS (Parity/No Parity) 4Mb 30 PIN-70 $45 $38 4Mb 72 PIN-70 $43 $29 8Mb 72 PIN-70 $83 $56 16Mb 72 PIN-70 $190 $140 32Mb 72 PIN-70 $342 $288 EDO SIMMS 8Mb (1Mbx32) – 60ns $56 16Mb (2Mbx32) – 60ns $144 32Mb (4Mbx32) – 60ns $280 MAC MEMORY 8/16Mb DIMMS $69/125 32/64Mb DIMMS $288/594 16Mb P’BOOK 520/540 $257 LASER PRINTER MEMORY 4Mb HP 4&5 $52 COMPAQ 8Mb CONTURA AERO $147 All other models available $Call TOSHIBA 8Mb Portege/ Sat EDO $133 16Mb Portege/ Sat EDO $229 16Mb Tecra 500/610 Sat $229 All other models available $Call CACHE 256Kb PIPELINE BURST $25 256Kb 7200/8500 $93 VIDEO MEMORY 256K x 16 70ns (SOJ) $17 1Mb 7200/7500/9500 $83 SO DIMMS 8Mb/16Mb $92/180 Ex Tax Pricing – Delivery $8. Pricing as at 31/10/96. Phone for latest. Sales Tax 22%. Credit Cards Welcome. We Also Buy And Trade-In Memory. PELHAM Memory Pty Ltd Suite 6, 2 Hillcrest Rd, Ph: (02) 9980 6988 Pennant Hills, 2120. Fax: (02) 9980 6991 Email: pelham1<at>ozemail.com.au Genuine enquiries to Arthur Courtney, Resurrection Radio (03) 9510 4486. MicroZed have 16C84 at $8, 16C58A at $5. Discounts start at 10 pieces. Add $5 post on IC orders. RAIN BRAIN 8-STATION SPRINKLER KIT: Z8 smart temp sensor, LED display, RS232 to PC. Uses 1 to 8 DALLAS DS1820. Call Mantis Micro Products, 38 Garnet Street, Niddrie, 3042. P/F/A (03) 9337 1917. mantismp<at>c031.aone.net.au Freedman Electronics..................46 Harbuch Electronics....................94 Instant PCBs..............................104 Jaycar ................................... 49-56 Kalex............................................19 Kits-R-US.....................................96 Macservice....................................3 MicroZed Computers.................104 Neil Kirkness...............................96 Oatley Electronics...................75,97 Pelham......................................104 RCS Radio ................................103 Resurrection Radio......................79 Rod Irving Electronics .......... 89-93 Rosetta Laboratories...................29 Shailer Park Electronics..............15 Silicon Chip Bookshop...............IBC Silicon Chip Back Issues....... 42-43 Silicon Chip Car Projects.........OBC HOMEMADE GENERATORS: how to instructions. Eight pages free text and colour photos on the Internet at http:/ www.onekw.co.nz/ Zoom Magazine.........................IFC _________________________________ Microprocessor For Digital Effects Unit Printed circuit boards for SILICON CHIP projects are made by: This is the 68HC705-C8P pro­gramm­ ed micro­pro­cessor IC for the Digital Effects Unit (see Feb­. 1995). Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Pub­lica­ tions. Phone (02) 9979 5644; Fax (02) 9979 6503. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. Tortech.........................................19 PC Boards • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semicustom electronics & data communications. 63 chapters, in hard cover at $120.00. Silicon Chip Bookshop Radio Frequency Transistors Newnes Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Guide to TV & Video Technology By Eugene Trundle. First pub­lish-­ ed 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $49.95. Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Digital Audio & Compact Disc Technology Electronics Engineer’s Reference Book Hard cove Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM Power Electronics Handbook Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order r Edited by F. F. Mazda. version now available First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $85.00. Surface Mount Technology By Rudolph Strauss. First pub­ lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $52.95.   Title  Newnes Guide to Satellite TV  Guide to TV & Video Technology  Servicing Personal Computers  The Art Of Linear Electronics  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Electronic Engineer's Reference Book  Radio Frequency Transistors  Surface Mount Technology  Audio Electronics Price $55.95 $39.95 $59.95 $49.95 $55.95 $59.95 $120.00 $85.00 $99.00 $52.95 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ & PNG add $10.00 per book, elsewhere add $15 per book. TOTAL $A December 1996  105