Fullscreen HTML5Med Res (??MB)HTML4

SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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 Vol.9, No.2; February 1996 Contents THREE REMOTE CONTROLS TO BUILD – PAGE 76 FEATURES 4 Fluke 98 Automotive ScopeMeter This versatile, comprehensive vehicle engine test centre fits in the palm of your hand. Along with "on board" measurements, it has the option of later analysis of measured data with a personal computer – by Julian Edgar 26 Racing On Air: Germany's New MagLev Train Imagine a train without wheels, safely and almost noiselessly gliding along at 500km/h, thanks to magnetic levitation. It's not just a designer's dream – the prototype TransRapid has already clocked up 200,000km on its test track. PROJECTS TO BUILD 8 Fit A Kill Switch To Your Smoke Detector A simple and cheap modification to your smoke detector will stop it shrieking every time someone burns the toast! – by Rick Walters 12 Build A Basic Logic Trainer Learn all about the basic operation of digital ICs. It makes a great teaching and demonstration aid – by Rex Callaghan 22 Low Cost Multi-Tone Dashboard Alarm Take one $4 toy phone, add a few components and you'll have a 9-tone alarm module to alert you to a range of vehicle problems – by Julian Edgar 36 Woofer Stopper Mk 2 - Now It's Even Better! FIT A 10-MINUTE KILL SWITCH TO YOUR SMOKE ALARM - PAGE 8 Troubled by barking dogs in your neighbourhood? The Woofer Stopper barks back with an ultrasonic blast that can help train Fido to be socially responsible! – by John Clarke 60 Surround Sound Mixer & Decoder - Part 2 We continue our description of a state-of-the-art mixer and decoder for surround sound: this month, final construction details and test procedure – by John Clarke 76 Three Remote Controls To Build Your choice of a single channel UHF, a dual channel UHF or an eight channel infrared remote control. Full constructional details included – by Branco Justic SPECIAL COLUMNS A $4 TOY PHONE MAKES A GREAT DASHBOARD ALERT – PAGE 22 54 Serviceman’s Log The dingiest corner of a dingy room – by the TV Serviceman 85 Computer Bits Use your personal computer as a reaction timer – by Rick Walters 88 Vintage Radio The basics of reflex receivers – by John Hill & Rodney Champness CONTROL BARKING DOGS WITH THE WOOFER STOPPER Mk.2 – PAGE 36 DEPARTMENTS 2 Publisher’s Letter 7 Mailbag 25 Order Form 32 Circuit Notebook 72 Product Showcase 92 Ask Silicon Chip 94 Notes & Errata 95 Market Centre 96 Advertising Index February 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 Enquiries Leo Simpson Phone (02) 9979 5644 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 Photography Stuart Bryce 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: $49 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 Welcome to the 100th issue of SILICON CHIP Can it really be? Yes, this issue is our 100th. SILICON CHIP started operations back in August 1987 and the November 1987 issue, Volume 1, Number 1, was launched in the preceding month, October. At the time, there were many people who thought we were extremely foolhardy in starting this magazine, given that there were already three Australian contenders well established and lots of imported electronics magazines as well. Indeed, we felt rather audacious ourselves. There were tough times in those first few years but I am glad to write that virtually all of the people who were involved in the production of that first issue are still associated with us today. And many of our readers who purchased our first issues are still buying it and looking forward to its arrival each month. To those people in particular, we extend our thanks because without a large and loyal readership no magazine can exist for long. Our thanks too, to our regular advertisers, whose loyalty also contributes to the content and viability of SILICON CHIP. I should also single out Gary Johnston of Jaycar Electronics for special thanks. Without his promise of advertising support and his encouragement in our tentative beginnings, SILICON CHIP would not have started. Today, the electronics magazine field has changed markedly from the position when we started. Now there are only two Austra­lian electronics magazines and many of the foreign magazines have dropped by the wayside as well or at least they are no longer available in newsagents. As we look forward to producing our 200th issue, we are sure that the electronics scene will continue to be as dynamic as it has been. Computers will continue to inexorably make their presence felt in every line of human endeavour and integrated circuits will continue to get smaller and yet more powerful. Most importantly, people who know and keep informed about electronics will continue to have an edge. They will always be more likely to be employed and they will enjoy rather than shun new technology. We feel that as technology and society grow ever more com­plex, those who have at least some understanding of electronics will always be better prepared to adapt and prosper. It is our continuing challenge to keep you, the readers, always informed about and entertained by electronics. Thanks for your continuing support. 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 Engine Analysis On The Run . . . Fluke 98 Automotive ScopeMeter Every auto shop these days has an extensive array of electronic engine analysis equipment. Now there's one that fits in the palm of your hand for "real life" measurements and even personal computer analysis. By RICK WALTERS T HE FLUKE 98 AUTOMOTIVE Scope­Meter provides a compact measuring system with a large liquid crystal display which will allow auto mechanics to carry out a wide range of diagnostic measurements, both on the bench and on the road. When it was released, the Fluke ScopeMeter was a clever concept which was immediately accepted by the electronics industry. Now Fluke has produced a new version aimed at the car service industry, the Automotive ScopeMeter. The measurements available include voltage, resistance, dwell angle, oxygen sensor, general sensors, RPM, primary and secondary ignition, relative compression and EFI duty cycle. In addition, by using the optional diesel probe set, diesel injector pressure pulse 4  Silicon Chip and diesel advance measurements can be made. Engines catered for include three, four, five, six and eight cylinders, two and four cycles, diesel or petrol and 6V, 12V & 24V batteries. It also can measure conventional Kettering ignition systems with a distributor, vehicles such as the Holden V6 with distributorless ignition and vehicles with a coil for each spark plug. Probably one of the most useful features of the ScopeMeter, especially for new users, is the help system. The trouble with most modern electronic equipment, from the humble video to even the mobile phone, is that the number of functions packed into the unit is so great that the manual is needed each time you need to carry out more than the basic operations. The Fluke has a big yellow MENU button which, when pressed, brings up the menu screen. The selected function is shown in reverse video and the up and down arrow buttons are used to scroll through the menus. Above the F5 button the SELECT legend is shown (1-7). Once the choice is made, full instructions appear, showing which leads to use and which Scope­Meter input to connect (1-8). This “connection help” function can be turned off once the user is completely familiar with the unit. As well as the menu help, there is a key labelled “i” which, when pressed, displays information about the highlighted menu choice, while you are in the menu program (1-12) or information about the function keys, when a test is running (1-14). Fig.1: this graph shows the relative compression of each of the eight cylinders in a Holden V8, recorded at a cranking speed of 133RPM. The "best" cylinder (in this case cylinder 6) is rated at 100%, with all others relative. The variations between cylinders in this 85,000km-old motor are clearly evident. The ScopeMeter is normally powered from its internal nicad battery, with a mains plugpack supplied to recharge or trickle charge it. In emergencies, four standard “C” cells can be used but these cannot be recharged. The use of batteries allows “on-road” testing to be readily carried out. One very useful accessory supplied as standard is the automotive demonstration board. This small PC board simulates five functions, allowing you to become familiar with the operation and functions of the ScopeMeter at your leisure instead of under the bonnet of a car. The board outputs are labelled injection, secondary ignition, sweep, general sensors and oxygen sensor. Chapter two of the comprehensive manual includes a tutorial using the demonstration board to carry out eight simulated tests. It starts by taking you through the process of measuring the voltage of the 9V battery supplied to power the PC board. The next tests are resistance measurement and two plots of the voltage across the SWEEP potentiometer on the PC board for clockwise and anticlockwise rotation. This is followed by a measurement of the oxygen sensor signal, using the RPM potentiometer to vary the viewed waveform. Next are general sensor Fig.2: data from the Fluke 98 (screen shot at left) has been transferred to the personal computer database for this particular vehicle. A profile of vehicle performance over time is a very handy aid in vehicle diagnostics. and RPM measurements, again using the RPM potentiometer to vary the displays. The last tests measure a simulated secondary ignition coil voltage and an injector waveform. By the time you have worked through these examples you will be quite conversant with the selection of the menu screens and the interpretation of the readouts. The tutorial continues with a description of the methods used to plot one parameter over a period, how to plot a trend which will compute the maximum, minimum and average values over the period and how to use the “flight record”. This flight record is a very useful function, allowing you to store up to 1280 divisions in a cyclic memory, the length in time being equal to 1280 times the timebase setting in seconds. This means, for example, that if the time­base speed is 10ms per division, you could store 12.8 seconds of information. So what use is it? Let’s say that you have a vehicle with an engine misfire under load and you don’t have a dynamometer. To diagnose the problem, you turn on the Fluke, select ignition, secondary, OK, record and flight record, connecting the leads as instructed. You then take the car for a run and when the fault occurs, you press the clear mem­ory button. This starts saving the measurements into memory. Once you have felt the misfire, you press any button to store the information. When you get back to the workshop you can analyse the stored information and decide on the steps necessary. Among the options is SW98W, FlukeView 98 for Windows Software. This allows the transfer of any stored waveforms to an IBM or compatible PC with, at minimum, an 80386 processor and Windows 3.1. Once in the computer, you are able to read, document, save and print any results from the Fluke. The software allows you to keep a record of the relevant parameters for particular cars or perhaps even particular clients. By comparing current data with previously stored information, the present state of tune can be readily established. These records are kept in a database which can be set up in a way which best suits your application. For example, you can group the information as Manufacturer, Model, Engine Capacity, Test Category, Test 1, Test 2, or Manufacturer, Engine Capacity, Test Category, Test 1, etc. A neat feature of the database is that when you are selecting a previously saved screen, as you change the model or capacity, the thumbnail sketch of February 1996  5 Fig.3: this graph shows the firing voltages for each of the cylinders of the Holden V8 engine. Note again the variations from cylinder to cylinder. the graph changes immediately, to reflect your choice. This helps greatly in locating a particular record, especially if you know what the waveform you are searching for looks like. Once you have become familiar with the operation of the ScopeMeter, the 94 pages of chapter five of the manual, headed automotive applications, describe the procedures for testing all vehicle sensors, along with expected readings and waveforms. Fig.4: an "ideal" injection pulse for a specific engine as shown by the Fluke 98 software database. This allows mechanics to instantly compare results achieved during tests with manufacturer's specifications. Sections follow on air/fuel, ignition, electrical system and finally diesel RPM and advance measurements. This review has only covered some of the wide range of measurements of which the unit is capable. Features such as single shot function, dual trace operation, etc are all fully covered in the comprehensive user manual. The current cost of the Fluke 98 Automotive ScopeMeter is $3990. An automotive temperature probe is Protect your valuable issues Silicon Chip Binders $330. The FlukeView 98 for Windows software is $435 which includes the optical connecting cable. The diesel probe set is $440. All the above prices exclude sales tax which must be added to the figures quoted. The review sample came from Philips Test & Measurement. For further information, contact the distributors, Obiat Pty Ltd, 129 Queen St, Beaconsfield, NSW 2014. Phone (02) 698 4111. Fax (02) 699 9170. sub Buy a get scriptio a di n& the scount o bind n er These binders will protect your copies of SILICON CHIP. They feature heavy-board covers, are made from a distinctive 2-tone green vinyl and hold up to 14 issues. ★ High quality with heavy board covers ★ Each binder holds up to 14 issues ★ 80mm internal width ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Just fill in & mail the order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. 6  Silicon Chip MAILBAG There's many a myth in sound reproduction In his criticism of your July review of Jamo speakers, R. W. Field in the September issue seems to be putting Martin Colloms on something of a pedestal. Mr Colloms undoubtedly has a great knowledge of loudspeakers, having made a very successful career in this field. I have the 3rd edition of his “High Performance Loudspeakers” and a skim through the 4th edition did not reveal any significant additional information. He does not mention bi-wiring in the 3rd edition so has physics changed from one edition to the next or is it simply fashion? Sound reproduction is wide open for the dissemination of myths and folk-law because the golden-eared fraternity can always hear things which are denied to us lesser mortals. There is no compelling reason to conduct rigorous AB testing to clear away the fantasies and the GEF would not believe the results anyway. Mr Colloms is sufficiently commercially aware not to rock the boat too much and indeed there are many controversial aspects of speaker design. For example Mr Colloms says at one point “... asymmetrical placement of the drive units is beneficial as it results in unequal path lengths from the drivers to the edge of the enclosure”. At another he says “the need for a uniform, symmetrical directivity in the horizontal plane dictates that the main drivers be mounted in a vertical-in-line formation”. At another point he quotes work by KEF and B&W on complaint driver mounting which was thought to be beneficial at one stage. However, it was subsequently found that there was then a loss in upper range detail and designers returned to rigid driver fixing with which conclusion I totally agree. As you say, there is simply no justification for bi-wiring. In my cynical view, the meretricious bi-wiring fashion was dreamed up by those same characters who decided we all needed monster OFC cables, simply to double their market! The choice of drivers, cabinet design, crossover frequencies, filter de- sign, speaker placement and listening room acoustics will all far outweigh any real or imagined consequence of such esoteric matters as bi-wiring or monster cables, whether oxygen free or not. A. March, North Turramurra, NSW. Making a case for a larger case With regard to the Digital Effects Unit for Musicians – a great idea and all of the most useful effects for a melodic musician! My comments are: a unit of this type could easily be in a box twice the size (and reasonably) – with a printed circuit not so jam-packed together. The fun of assembling a kit such as this is largely negated by absurdly having to use a magnifying glass to find out if some parts of the print are shorts or not, and in some places requiring unreasonable demands on dexterity in soldering . All OK for those with microscope eyes and “pin” soldering irons! These kits should be laid out to a size to suit assemblers of reasonable dexterity; eg, such as the ETI 1424 preamplifier which has reasonably spaced PC tracks. I’ve had to separate two places that were, or were almost, shorts on print 01301951, leaving one or two others that are too close for comfort. The main circuit’s mate, board 01301952, is more reasonable and easy to track. I suggest in future the main printout should be larger to accommodate similar spacing! T. Ford, Malanda, Qld. Comment: your remarks highlight the dilemma that we have concerning many of our designs. Some readers regard our boards as much too large and state that we could shrink them to less than half the size and indeed we could. Then there are readers such as you who say that the end product is too small. We should also comment that the cost of metal work is a major item in kits and if we can base a design on a standard plastic case, then that can be a big factor in a kit’s success but it does also set the size of the board. Serviceman cartoonist is a genius After some years of thinking about it I am at last com­pelled to write and congratulate you on your perspicacity and business acumen in seizing upon the very considerable talents of the illustrator supreme who applies his genius to the “Service­man” in your worthy monthly. This genius (and I use the word in its fullest meaning) is apparently an electronics tradesman of considerable experience, as shown by the many convolutions of electronic parts in his draw­ings, all of which demonstrate a thorough practical knowledge. He also shows a grasp of the psychology of his human (and animal) subjects. These convey at a glance the impression of flawlessly catching the theme of each situation in the very human terms portrayed. The animation of each portrait (I can no longer use the lesser term ‘drawing’) cap­tures the very essence of the infinite variety of everyday life in the day of a serviceman, from the humorous to the scary. Although I have never been employed in the public sector of servicing, half my own career has been spent repairing so-called professional equipment. A common thread runs through this work in this age of increasing costs and decreasing incomes. This forces me to buy SILICON CHIP and I cheerfully admit to buying an issue or two for the artistry of this man alone. He is a real asset to your magazine and is cer­tainly streets in front of any illustrator I have ever seen in any technical magazine. If, as I expect, the illustrator and the Serviceman are one and the same, then this man’s future is assured should he ever put away his soldering iron in favour of the pen. Thank you again SILICON CHIP for the many moments of light relief afforded me, from involuntary chuckles to deep belly laughs, all of which have done me a power of good over the years. John Byers, Midland, WA. Comment: our cartoonist and Serviceman writer are actually two separate people. Together, we think they produce a brilliant result. February 1996  7 No more morning din! Fit a kill switch to your smoke detector These days, with more and more homes being fitted with smoke detectors, a problem has arisen. The alarm goes off when you burn the toast! This little circuit copes with that problem. By RICK WALTERS You are in your normal early morning daze preparing breakfast, when the smoke alarm starts screaming. The toast has jammed in the pop-up toaster and smoke is wisping (billowing?) up into the alarm. Sure, you can turn the toaster off but how long does it then take to clear the smoke? In the meantime the alarm is sounding off, giving you and the rest of the household a high stress factor. The only solution is to climb up on a chair and disconnect the battery. Peace and quiet at last! Of course, you don’t have time to reconnect the battery now, as you have to get away, but you will do it tonight or as soon as you get round to it. Well, that is your plan anyway. How long will it be before you actually do it? Smoke detectors with the battery disconnected are useless. Problem solved! The problem is solved with this simple kill circuit which will cost about $2 and take five minutes to build. It won’t stop you from burning the toast but it will disable the alarm for 10 minutes to allow the smoke to clear. Only a few components are required, including a miniature pushbutton switch which is mounted on 8  Silicon Chip Fig.1: FET Q1 is normally turned on fully because the 330µF capacitor at its gate is charged to +9V. When kill switch S1 is pressed, the capacitor is discharged, Q1 turns off and the smoke alarm is disabled for about 10 minutes while the 330µF capacitor charges up again via the 4.7MΩ resistor. Fig. 2: this is how easy it is to build. Most of the components (three out of four) are mounted on the back of the 9V battery connector, while the 100Ω resistor is wired directly to the kill switch (S1). 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.avico.com.au the lid of the smoke detector – this is the “kill” switch. Now, when you burn the toast and the alarm goes off, climb on a chair or grab a broom handle and push the “kill” switch. The alarm will stop and will be disabled for 10 minutes. After that time, the smoke detector will be powered up again. If smoke is still present, it will immediately sound off again but if the smoke has cleared, the alarm will merely “chirp” to indicate that it is back in business. The smoke alarm we modified for this article was a Kambrook unit but most battery operated smoke detectors should work equally as well with this kill circuit. How it works Fig.1 shows the circuit. A low cost Be sure to disconnect the battery before soldering the parts to the connector. February 1996  9 Most smoke detectors will easily accommodate the extra parts on the battery snap connector. The switch mounts on the lid of the case. Left: be sure to sleeve the switch contacts and the 100Ω resistor with plastic sleeving, to prevent shorts when the case is assembled. N-channel Mosfet (Metal Oxide Silicon Field Effect Transistor) is used as a switch. It is connected between the battery and the smoke detector circuit. As you can see from the circuit (Fig.1), the gate is con­nected to the battery positive via a 4.7MΩ resistor. Normally, this will keep the 330µF capacitor charged to +9V and so the FET will be turned fully on and the smoke detector will work. If it detects smoke 10  Silicon Chip it will sound the alarm in the normal way and will keep sound­ing until the smoke has dispersed. However, if you’ve burnt the toast and pressed the kill switch, the capacitor will be dis­charg­ed, thereby turning the FET, and the alarm, off. The 4.7MΩ resistor will now take about 10 minutes to charge the 330µF capacitor to around +5V. At this point, the FET will start to turn on but will not be fully turned on until the gate reaches more than +6V. It is while the FET is turning on that the smoke detector will give an audible chirp or two, tell­ing you that it is back in business. The audible chirp is not a part of the kill circuit but is a feature of most battery-operated smoke alarms: when PARTS LIST 1 BS170 or BS170P Mosfet (Q1) 1 330µF 10VW PC electrolytic capacitor 1 4.7MΩ 0.25W, 5% resistor 1 100Ω 0.25W, 5% resistor 1 pushbutton momentary contact switch, DSE Cat P-7560 or equivalent (S1) the battery gets low, they chirp once every thirty seconds or so. Building it Because there are so few components, a PC board is not necessary. Instead, the parts are mounted on the top of the battery connector – see Fig.2. You will need to drill a 6mm hole in the lid of the smoke detector to accommodate the kill switch and run a couple of insulated wires to it. When you have installed the kill switch circuit, check the smoke detector for normal operation. Do this by pushing the test button and also by exposing it to smoke. If it responds by sound­ing the alarm, then all is well. It should then be mounted on the ceiling. Now try not to burn the toast. It SC makes such an awful smell! SATELLITE WATCH 1996 looks set to be a bumper year for satellite enthusiasts with a number of new satellites due to be launched. • INTELSAT 704-66 E longitude, C band: No new reports from this satellite. Worldnet programming, as well as CFI from Paris continue to be visible. CFI operate a rather low sound subcarrier of 5.84MHz. • APSTAR 2R—77 E longitude, C band: Although not yet launched, the APT satellite company have advised that this will be the new location for APSTAR 2R (APSTAR 2 failed at launch December 1994). As there are also 2 THAICOM satellites co-located at 78 E, and a current ITU reservation exists for ASIASAT III at 77.5 E, there is bound to be plenty of controversy over this move. China is not a member of the ITU, and is there­fore not bound by ITU convention. • GORIZONT 24—80 E longitude, C band: Russian signals can be seen on IF 1475MHz on a 24 hour basis. Watchable signals can be achieved using a 3m dish and low threshold receiver from the east coast of Australia, as long as the dish is located for a very low “look” angle (7 degrees). • GORIZONT 28—90 E longitude, C band: Network 1 programming can be seen at IF 1475MHz. East coast dishes must have a look angle of 15 degrees or so. • GORIZONT 19—96.5 E longitude, C band: The Russians seem to have changed their Network 1 logo, and now identify with “OPT” in the top right hand corner of the screen. CCTV 4 continues at 1325MHz, but Az Tv has disappeared from 1425MHz. • ASIASAT II—100.5 E longitude, C band: November 28 1995 saw the successful launch of Asiasat 2, with test pattern first observed December 18. Covering 53 countries, the signals from this satellite promises to provide an enormous range of free to air programming. *Garry Cratt is Managing Director of Av-Comm Pty Ltd, suppliers of satellite TV reception systems. Compiled by GARRY CRATT* A Russian satellite has been park­ ed at this location since early December, broadcasting Net­work 1 programming. Precisely why this location has been chosen is unknown, and would seem to contravene ITU designated orbital allocations. • GORIZONT 25-103 E longitude, C band: Signals from this satellite have increased in strength. This satellite regularly carries the Australian soapie “Neighbours”, and various music videos, in PAL from 0800 AEST. No further active tran- Fig.1: the test pattern from the new Asiasat II sponders have been observed. satellite, launched last November • ASIASAT 1-105.5 E longitude, C band: Regular proAustralia, ATVI has begun a double hop gramming continues without change. link via Subic Bay (Phillipines) linking For those able to receive this satellite, their Palapa B2P signal to Rimsat G1 (IF a fax polling service, operated by Hong 1325MHz). The signal is being carried Kong Telecoms, is available. Dial 852 172 by at least one cable operator in India. 77700/01/02/16 or 20 for STAR TV ser• GORIZONT 25-140 E longitude, C vices on this satellite (normal IDD rates) band: Two transponders have been • PALAPA B2P-113 E longitude, C noted operating on this satellite. Russian band: This satellite was finally placed network 1 programming is broadcast into an inclined orbit on December 8, using RHCP on 3760MHz IF, whilst Mosto conserve station keeping fuel. The lem Television (MTA) is broadcast on replacement satellite Palapa C1 promis­es IF 1430MHz every evening from 10pm, good signal levels across Australia. It is using LHCP. anticipated a 2.3m dish will be required • RIMSAT G2-142.5 E longitude, C along the east coast of Australia for good band. ATN continue to operate two reception. adjacent half transponders, at great­ ly • JCSAT 3-128 E longitude, C band: No reduced power. A 3.7m dish will be renew reports from this satellite. We do quired for reasonable reception of these know that the space­craft testing is comtwo channels. New Zealand viewers plete, and that a full 50 channel digital report a 5m dish is required for half TV service is planned for Japan mid 1996. transponder reception. EM TV from New • RIMSAT G1-130 E longitude, C band: Guinea remains at the same power level. Testing of two adjacent half transponders • OPTUS B3-156 E longitude, K band: (IF 1460 and 1480MHz) carrying RAJ The OTEN educational TAFE channel, TV programming has been seen since shared by NSW and Vic­torian Education late November. Noise free signals have Departments and carried on transponder been observed using a 1.8m dish along 5, has now been encrypted using “Crypto­ the east coast of Australia. New Zealand vision” addressable decoders. E-PAL viewers report noise free signals using vision has been seen on transponders 4L 3M dishes across that country. Although and 5L some weekends. SC this signal is barely visible from northern February 1996  11 Build This Basic Logic Trainer And learn all about digital ICs This Basic Logic Trainer from Dick Smith Electronics is just the shot for teaching digital electronics and demonstrating digital logic concepts. It’s easy to build, easy to operate and runs from a 9V DC plug­pack supply. Design by REX CALLAGHAN As shown in the photograph, the Basic Logic Trainer is built around a central prototyping board. The trainer provides the necessary power supply rails (5V DC), clock signals and logic inputs to this board, while a number of LEDs are used to indicate logic outputs. The connections to and from the prototyping board are made using single strand telephone cable, as are the connections bet­ween IC pins on the board itself. You can make the test 12  Silicon Chip circuit as simple or as complicated as you like – anything from just one digital logic IC to 10 or more ICs. Two large banana plug sockets are used for the power supply terminals and these are located directly above the prototyping board. This regulated 5V supply is current limited and is there­ fore protected against short circuits. Because it has no heatsink or securing bolt, the regulator will thermally shut down some­where near its rated current if there is an overload. The choice of a single 5V DC supply makes this unit suit­able for use with 74 series TTL integrated circuits (74xx, 74LSxx, 74HCxx, 74Cxx, etc) and with 4000 series CMOS logic ICs. The latter will operate over a supply range from 3-15V DC and therefore will work from a 5V supply without problems. All logic inputs to the test circuit are buffered and these are set by four switches immediately to the left of the prototyp­ing board. When a switch is in the up position, the corresponding logic input is high. Conversely, when a switch is in the down position, the corresponding logic input is low. These buffered inputs are labelled B0-B3 and are brought out via a 5-way vpin header socket. The fifth terminal on the header socket provides the clock pulses from an additional circuit hidden behind the front panel. The pulse Fig.1: IC1 (a TLC555 timer) is used to provide the clock pulses, while IC3a and IC3b form a window comparator to provide the logic probe function. IC2b-f and IC4a-d buffer the logic signals to and from the test circuit. is high or low, or is alternating between these two logic states. How it works output provides either a single pulse if its associated switch (at top, left) is pushed down momentarily, or a stream of clock pulses if the switch is in the clock position. At the other end, the logic output(s) from the test circuit are fed to a 4-way pin header socket. Each output is then fed to a buffering circuit and these in turn drive four LEDs (labelled Q0-Q3) to show the logic states at up to four different points on the test circuit. By the way, the fact that the outputs from the test circuit are “buffered” means that they do not need to be driven with the full LED current. That’s taken care of by the buffering circui­try. Each buffer stage has a high input impedance, to avoid loading the outputs of the test circuit. Logic probe Another very worthwhile feature is the provision of a simple logic probe. This uses a standard multimeter test lead which plugs into a 3.5mm socket on the front panel. The probe can be used to establish the logic states at various points on the test circuit. Connecting the probe to a logic 0 level will cause a green LED to light. Conversely, connecting to a logic 1 level will illuminate a red LED. The two indicator LEDs are immediately to the right of the probe socket. They simply indicate whether a point Refer now to Fig.1 for the circuit details of the Basic Logic Trainer. As stated above, power for the circuit comes from a 9V DC plugpack supply. Diode D1 provides protection against reverse supply polarity. Its output feeds 3-terminal regulator REG1 which produces a regulated +5V DC rail at its OUT terminal. LED 1 provides power on/off indication, while R101 limits the current through the LED. The output from the regulator is also connected directly to the +5V output terminal and it supplies the ICs. The negative output terminal connects to the negative supply line. IC1, a TLC555 timer, is used to provide clock pulses. It is wired as February 1996  13 Take care with the orientation of polarised components (ICs, diodes, LEDs and electrolytic capacitors) when assembling the PC board. The LEDs and pin header sockets are soldered after the board is secured to the front panel. an astable oscillator, the frequency of which is deter­mined by the total resistance present between pin 3 and the 0.47µF capacitor (C2) on pin 2. Normally, when SW1 is in the centre-off position, pin 3 of buffer stage IC2a is held low by R1 and so pin 4 (reset) of the timer is also held low. This effectively holds IC1 in the reset state, with its output at pin 3 remaining low. When SW1 is in the CLOCK position, pin 4 of IC1 is pulled high via SW1a and IC2a and the reset is released. At the same time, SW1b shorts out R3 and so the timing for the circuit is set by R2, R4 and C2. This causes IC1 to oscillate at a 2Hz rate. Conversely, when SW1a is in the PULSE (spring loaded, momentary contact) position, R3 is switched in series with the timing circuit. As a result, IC1 runs much more slowly than before, to produce one pulse about every 1.6 seconds. Thus, by momentarily flicking SW1 to the PULSE position, IC1 outputs a single clock pulse. Diode D2 ensures that C2 rapidly discharges when SW1 returns to its centre-off position. The output from IC1 is fed to pin 14 of non-inverting buffer stage IC2b. This in turn drives the PULSE terminal, to provide either a continuous clock signal or a one-shot pulse signal. Switch logic The PC board is mounted on the rear of the lid using 12mm tapped spacers and secured using short machine screws. Note how the 1000µF electrolytic capacitor is mounted. The remaining gates in IC2 (IC2cIC2f) are used to buffer the logic setting switches (SW2-SW5). When a switch selects the +5V rail, the output of its corresponding buffer is high. Con­versely, when ground is selected, the output of the buffer is low. The RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 1 1 2 1 1 8 1 1 1 1 4 6 14  Silicon Chip Value 1MΩ 470kΩ 390kΩ 150kΩ 130kΩ 100kΩ 62kΩ 47kΩ 36kΩ 10kΩ 2.7kΩ 220Ω 4-Band Code (1%) brown black green brown yellow violet yellow brown orange white yellow brown brown green yellow brown brown orange yellow brown brown black yellow brown blue red orange brown yellow violet orange brown orange blue orange brown brown black orange brown red violet red brown red red brown brown 5-Band Code (1%) brown black black yellow brown yellow violet black orange brown orange white black orange brown brown green black orange brown brown orange black orange brown brown black black orange brown blue red black red brown yellow violet black red brown orange blue black red brown brown black black red brown red violet black brown brown red red black black brown buffered logic outputs appear at pins 10, 6, 12 & 4 of IC2 and are fed to the B0-B3 terminals respectively. LEDs 2-5 are used to indicate the logic states. These LEDs are driven using inverting buffer stages IC4a-IC4d via 220Ω current limiting resistors. Normally, R13-R16 hold the inputs to these buffer stages low. This means that their outputs are all normally high and so the LEDs are all off. However, if any of the Q0-Q3 inputs is pulled high, the corresponding buffer input is also pulled high and so its output switches low and lights the relevant LED. Resistors R9-R12 protect the inputs of the 4049. Logic probe IC3a and IC3b form the logic probe circuit. These two op amps are wired in a standard window comparator configuration and drive two logic indicator LEDs (LED6 & LED7). Resistors R22-R26 set the bias voltages on the op amp in­puts. As indicated on the circuit, pin 5 is biased to +2V, pins 6 & 3 to +1.4V and pin 2 to +0.9V. As a result, the non-inverting input of each op amp is normally above the inverting inputs and so the op amp outputs are normally high and the LEDs are off. If, however, the probe input is connected to a logic high (ie, 2- 5V), pin 6 of IC3a will also be pulled high. As a result, pin 7 of IC3a switches low and this lights LED7 (red) to indicate that the high logic state has been detected. IC3b will not change state and so LED6 will remain off. Conversely, if the probe input is connected to a logic low (ie, less than 0.9V), pin 3 is also pulled low and the output of IC3b switches low instead. This lights LED6 to indicate that a logic low has been detected. Diode D3 is there to clip any large negative-going pulses that might be picked up via the probe input, to prevent damage to the op amps. Construction Construction of the Basic Logic Trainer is easy, since virtually all the parts mount onto a single large PC board. The exceptions are the banana sockets which mount directly onto the front panel and the 3.5mm panel socket for the plugpack supply. Refer to Fig.2 when installing the parts on the PC board. Begin by installing the resistors, followed by the Fig.2: install the parts on the PC board as shown here. Note particularly that the 1000µF electrolytic capacitor is mounted on the copper side of the board. February 1996  15 PARTS LIST 1 console case 1 front panel 1 prototyping board 1 PC board (© DSE) 1 test lead (for logic probe) 1 9V 200mA plugpack supply 4 SPDT miniature toggle switches 1 DPDT centre off, momentary on toggle switch 1 red banana socket (large) 1 black banana socket (large) 1 yellow banana socket 4 12mm tapped spacers 1 3.5mm DC panel socket 1 14-pin wire-wrap socket 4 self-tapping screws (to secure front panel) Semiconductors 1 TLC555 timer IC (IC1) 1 4050 hex non-inverting buffer (IC2) 1 LM393 dual op amp (IC3) 1 4049 hex inverting buffer (IC4) 1 78M05 3-terminal regulator (REG1) 1 1N4004 silicon diode (D1) 2 1N4148 silicon diodes (D2,D3) 6 5mm red LEDs (LED1-5, LED7) 1 5mm green LED (LED6) Capacitors 1 1000µF 16VW electrolytic 1 0.47µF monolithic 5 0.1µF ceramic 1 .01µF ceramic Resistors (0.25W, 1%) 1 1MΩ 1 62kΩ 1 470kΩ 1 47kΩ 2 390kΩ 1 36kΩ 1 150kΩ 1 10kΩ 1 130kΩ 4 2.7kΩ 8 100kΩ 6 220Ω Wire & cable 1 200mm-length 0.71mm tinned copper wire (for links) 1 500mm-length single strand telephone cable 2 400mm-lengths of hook-up wire, red & black WHERE TO BUY A KIT A kit of parts for the Basic Logic Trainer is available from Dick Smith Electronics stores & by mail order from PO Box 321, North Ryde, NSW 2113. Phone (02) 888 2105. The cost is $129 + $8 p&p. Please quote catalog number K3010 when ordering. Note: PC artwork copyright © Dick Smith Electronics. 16  Silicon Chip ceramic ca­pacitors, the diodes and the ICs. Note that D1 is a 1N4004 type, while D2 and D3 are 1N4148s. The five wire links can be installed now, using the off-cuts from resistor leads. This done, install the 7805 3-terminal regulator, noting that its leads are bent through 90° so that its metal tab sits flat against the PC board. The 1000µF electrolytic capacitor is installed on the underside of the PC board. Its leads are also bent through 90°, so that it can be laid flat against the board surface. Be sure to install this part the right way around. The five toggle switches are mount­ ed directly on the PC board. Push them right down onto the board before soldering their leads and note that S1 must be oriented with its momentary (ie, spring-loaded) position towards the bottom. The switch nuts can be either omitted or screwed all the way down. By this stage, the board will be complete except for the LEDs and the pin headers. The LEDs can be installed now (the green one is LED 6) but do not solder their leads yet, as they must first be adjusted for height when the front panel is in­ stalled. Take care with the orientation of the LEDs – the cathode (K) lead will be the shorter of the two. In addition, the cathode lead is adjacent to a flat edge at the bottom of the LED body. The 4-way and 5-way pin headers are obtained by cutting down a single 14-pin wire-wrap socket. To do this, first cut the wire-wrap socket in half using a pair of sharp sidecutters, to obtain two 7-pin sockets. The unwanted pins can then be removed and the socket bodies carefully trimmed and filed to size to that they fit the slits in the front panel. Do not mount the pin headers yet; that step comes later when the front panel is fitted. Hardware assembly Begin the hardware assembly by attaching the prototyping board to the front panel using double-sided tape. This done, fit the three banana sockets to the front panel. Use the red socket for the positive terminal, black for the negative terminal and yellow for the logic probe terminal. Do these sockets up tight and connect appropriately coloured leads (eg, red for positive, black for negative) to their solder lugs. These leads should all be about 60mm in length, so that they can be run to their respective points on the PC board. The 3.5mm DC socket is mounted on the bottom lefthand hand side of the rear panel (as viewed from the rear). This socket is wired via two 150mm long leads (red for positive, black for nega­tive) to the plus (+) and minus (-) inputs on the PC board. Twist these leads together to keep things neat and tidy. Note that the positive lead must go to the tip terminal of the DC socket, while the black lead must go to the collar (or sleeve) terminal. Now for the final assembly. First, fit the four 12mm-long spacers to the PC board and secure them with the short screws supplied. This done, fit the 4-way and 5-way pin headers to the PC board, then fit the front panel and secure it in position. The various LEDs and the pin headers can now be pushed through their respective holes on the front panel and carefully aligned. When everything looks OK, solder the leads to secure them in position. Finally, fit the lid to the case and secure it using the four self-tapping screws supplied. Testing When power is applied, the red LED next to the +5V socket should illuminate. If it doesn’t, then the LED is either in backwards, there is a fault in the regulator circuit, the supply polarity is incorrect, or the regulator output is short-circuited to ground. In particular, check that D1 and REG1 are correctly oriented. The 5V DC output terminals are a convenient place to check the 5V supply at any time. The power on/ off LED will provide a handy quick visual indication of the state of the 5V supply; eg, you may see this LED dim if a heavy load is placed across the supply, or extinguish if the power supply is inadvertently short-circuited on the protoboard. Assuming that the power supply is OK, the next step is to check out the logic probe circuitry. To do this, simply plug the probe in and touch the positive and negative supply terminals in turn. Check that the red LED (High) lights when the positive terminal is touched and that the green LED (Low) lights when the negative terminal is touched. If the logic probe doesn’t work, first check that the vol­tages on pins 2, 3, 6 & 5 of IC3 match those marked on the cir­ cuit. If they don’t, then it’s likely that one of the bias resis­tors (R22-R26) is incorrect or D3 is back to front. Check also that D3, IC3 and the two LEDs are correctly oriented. Once the logic probe is working correctly, it can be used to check the rest of the circuit. For example, by touching the probe on the PULSE terminal, you can check the clock circuitry (IC1). The green LED should light when S1 is in the centre-off position, while the red LED should flash at a 2Hz rate when S1 is in the CLOCK position; ie, the logic probe should show the indi­ vidual positive going clock pulses as they occur. You should get a much slower rate if S1 is held in the PULSE position (ie, one pulse about every 1.6 seconds). If you don’t get any clock pulses, check the circuitry around IC1. Similarly, use the logic probe to confirm that SW2-SW5 can be used to set their corresponding outputs (B0-B3) high or low. The output indicator circuitry can be tested by setting B0 high and connecting a lead from this terminal to Q0, Q1, Q2 & Q3 in turn. In each case, the corresponding output LED should light. If it doesn’t, check the resistor values at the inputs to IC4a-IC4d. Using the trainer By this stage, you have checked that the individual compon­ents of the Basic Logic Trainer are functioning correctly. Having done this, you will have a basic knowledge of how to use these components; ie: (1) the logic switches (SW2-SW5) are used to set the logic states on B0-B3 (high or low); (2) the Q0-Q3 terminals are continually monitored and their status indicated by individual LEDs; (3) the clock/pulse generator switch can provide either a train of clock pulses or individual pulses as required; and (4) the logic probe can be used at any time to check the logic state at different positions on the test circuit. We recommend using the insulated single-strand wire to make the various wiring connections. One length of 500mm can be cut into many smaller lengths, each of which should have about 5mm of insulation stripped back SC at either end. Basic Logic Trainer Demonstration As an example, we’ll wire up a common CMOS flipflop and exercise it. The device is the 14-pin CMOS 4013 which is a dual D-type flipflop. Its pin connections are shown in Table 1. Table 1: 4013 Pin Connections Function Pin No. Function Pin No. Q1 1 Vdd (+) 14 Q1 2 Q2 13 Clock 1 3 Q2 12 Reset 1 4 Clock 2 11 Data 1 5 Reset 2 10 Set 1 6 Data 2 9 Vss (-) 7 Set 2 8 The step-by-step procedure is as follows: (1) Insert the IC into the proto­ board, such that pin 1 is at the top left and pin 14 at the top right. The IC should be inserted so that the two vertical columns of pins are either side of a channel in the prototyping board, so that they are not shorted together. (2) Using suitable leads, connect the +ve and -ve supply termi­nals to the +ve and -ve supply buses on the prototyping board. A short lead can then be connected from the +ve bus to pin 14, while a second lead can be connect from the -ve bus to pin 7. You can check that these two connections are correct by using the logic probe. This should show a low state at pin 7 and a high state at pin 14. (3) Configure flipflop 1 by connecting: (i) a wire from pin 6 to B0; (ii) a wire from pin 4 to B1; (iii) a wire from pin 5 to B2; (iv) a wire from pin 1 to Q3; (v) a wire from pin 2 to Q2; and (vi) a wire from pin 3 to PULSE/ CLOCK The above procedure connects the four inputs and the two outputs of flipflop 1 on the 4013. Table 2 shows these various test connections. Now let’s explore the basic operation of the flipflop: (1) set B0-B2 to logic 0; (2) push the Pulse switch once. LED Q3 should be off (logic low or 0) and LED Q2 should be on (logic high or 1); (4) set switch B2 to a logic 1; and (5) Push the Pulse switch once. This should clock the new data (ie, a logic 1 from B2) through to the outputs and so the logic states on Q3 and Q2 should reverse (ie, Q3 now on, Q2 now off). Further pulses should not alter this, until the DATA 1 input (B2) is altered again. This shows the basic operation of a D-type flipflop; ie, the logic level on the Data input is transferred through to the Q output (pin 1) on receipt of a clock pulse. What this means is that you can get the flipflop to au­tomatically toggle on the receipt of each clock pulse by connect­ing its Q-bar output to its Data input. To do this: (1) remove the wire between B2 and pin 5 of the 4013; and (2) connect a wire between pin 2 and pin 5 of the 4013. Now when you work the pulse switch or switch to the CLOCK position, the two output LEDs should flash on and off alternately. Further experiments (1) Connect an additional wire between pin 3 of the 4013 and LED output Q1. This will allow you to observe the relationship bet­ween the clock input to the 4013 (on LED Q1) and the 4013 Q and Q-bar output levels (on LED Q2 and LED Q3). Because the Q-bar (inverted) output of flipflop 1 is fed into the Data input, each clock pulse will change the exist­ing state of the Q output. This is the classic divide-by-two configuration of the basic flipflop and is used in many circuit applications. Table 2: Test Connections Protoboard Connections IC Pin Function Pin No. Clock/pulse Switch Clock 1 3 Switch B1 Reset 1 4 Switch B2 Data 1 5 Switch B0 Set 1 6 LED Q3 Q1 1 LED Q2 Q1 2 February 1996  17 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au The starting point for the multi-tone warning module is this toy cellular phone. It cost just $4. A low-cost multi-tone dashboard alarm An audible alarm in a car is a useful indicator. It could accompany an oil pressure warning light, it could remind you to turn off the fullhouse car alarm or provide an engine overtemperature alarm. Here, we show you how to organ­ise a 9-tone alarm module for about $4! By JULIAN EDGAR The basis of the alarm is a toy cellular telephone – yes, you read that right! Toy phones have an integrated circuit, sound transducer (often a small speaker) and a battery holder all combined into an incredibly cheap package. Pressing the phone’s button makes noises and these can be useful for more than just entertaining 2-year olds. However, before throwing down this magazine and charging off to the local discount store, read on. During the extensive research for this feature, I investi­gated three different toy phones – and beware, only one was suit­able. Suitability of the phone for this 22  Silicon Chip application requires the following: (1) continuous sound when a button is held down. Some phones emit the tone only for a short time, irrespective of how long the button’s pressed. (2) a number of different tones. Some phones have very few different tones, even though there’s lotsa buttons! (3) tones which are appropriate in a car warning situa­ tion. But then again, maybe you’d like your dash to yell in monkey-talk “Sorry the line is busy now”. (4) as loud a sound output as possible. These toy phones vary in price from $2 to $4, too – so shop around. The phone which I used was unbranded but don’t let that worry you. Any toy phone which satisfies the above criteria will be adequate. Pull it apart OK. You’ve got the phone home and extracted it from the grasp of your little brother/kid who lives across the road/ intel­ligent dog/your own baby. You’ve put up with the sweet smile of your partner who has decided that your movement back towards childhood has become extreme and you’re waiting breathlessly for the next piece of invaluable advice. It’s pretty simple: pull the phone apart. Mine took a couple of turns of a Phillips head screwdriver; others inspected pulled apart with brute force. Once opened, you should be able to see the sound transducer, the keypad and the integrated circuit (no, it’s not a neat little package with legs but instead a blob on the board). Talking about the keypad, if it seems to have fallen apart don’t worry. On the printed circuit board there should be a pattern of tracks, with the tracks coming close together in a meshed The toy phone pulls apart to reveal a speaker, sound generator integrated circuit (the blob on the board) and a keypad. pattern under each key. When the keys are pressed, a conductive material on their ends squashes down onto the printed mesh, bridging the circuit and making the thing work. It’s just a cheap switch – and a wetted finger will often work in the same way. Now this bit’s for Serious Modifiers only. You can change both the loudness of the tones and their pitch by making some electronic modifications. The simplest way of increasing the sound volume is to connect the module to a 200 watt amplifier ... er, just kidding. The cheapest way of increasing the sound output level is to use a more efficient speaker than the one provided. I happened to have an old 8-ohm cone tweeter lying around and that worked fine. If you don’t, then investing $2.50 in a 57mm speaker will almost certainly lift the sound output level. If it doesn’t, then give the newly-bought speaker to the little brother/kid who lives across the street/intelligent dog/ your baby to eat. Changing the tone and speed of the recital on my phone was as easy as changing the value of about the only component which was accessible – a resistor. It started off as 268kΩ but experi­ mentation showed that add- ing a 1MΩ resistor in parallel both increased the speed with which the sounds were played (the guy inside the blob went into overtime) and also increased the pitch at which it happened. Next up is the decision about which tones you want to use. The keypad pushbuttons will still work while pulled apart if they’re pressed against the PC board or alternatively, you can simply bridge the conductors by using a screwdriver to replay all of the sounds. Pick the keypads which give the right sounds and then carefully solder two wires to the PC pads, with each wire soldered to the different conductors on the intermeshed grid. Check that when these wires are joined the wanted tone sounds continuously. The power supply can be either de- The keypad uses these conducting buttons which, when pressed, squash down on a PC grid pattern, joining the two conductors. February 1996  23 The resistor seen here can be changed in value to modify the sound output. Adding a 1MΩ resistor in parallel made the man inside the blob go into overtime! Pairs of wires are soldered to the selected switch pads, to trigger the different sounds. The pads are picked on the basis of the sound generated – you pick which warning tones you want to use. The finished warning module. The wire pairs on the left are used to trigger the different sounds, while an old cone tweeter has been substituted for the original speaker to increase the output volume. 24  Silicon Chip rived from the original button cell or from AA batteries (both last a very long time in this application), or a trimpot can be used to provide the supply voltage from the car battery. You don’t need to supply an exact (regulated) 3V to power the thing; anything around that value will work fine. Making the connections So how do you connect the Sound Module (you don’t call it a toy phone any more) to the engine? If you’re mon­itoring tempera­ture sensors which trigger warning lights by switching to ground, then wiring the switch output directly to a module input (with the other module input wire earthed) will trigger the sound at the same time as the light comes on. If the trigger is an output voltage, for example, when monitoring an ECU “Check Engine” light, then a low-current relay (less than $3) can be wired into the warning circuit to work the module. The module can be mounted in a Jiffy box or simply wrapped in electrical tape and mounted under the dash. The speaker does­n’t need to be close to the module, meaning that it can be locat­ed where the sound will be heard the loudest. When you consider the horrible possibilities of a missed warning light, $4 and a few hours’ work doesn’t seem SC too bad, does it? 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 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 February 1996  25 26  Silicon Chip February 1996  27 M AGLEV TRAINS USE roughly 30% less energy than conventional trains travelling at the same speed and they compare even more favourably with cars and air­planes. In terms of energy demand per passenger, cars consume 3.5 times as much energy, while airplanes consume four times as much as a maglev travelling at 400km/h. Dispensing with wheels also means that Transrapid generates no audible rolling noise, even during acceleration and braking. Its aerodynamically related noise becomes perceptible only at speeds over 200km/h, making it ideal for densely populated areas. And because it wraps around its guideway, rather than perching on a track, it cannot derail. Furthermore, since the guideways are usually elevated, nothing can cross a maglev’s path. All of this should add up to an unprecedented level of safety. In fact, 28  Silicon Chip studies indicate that maglev trains should be 250 times safer than conventional rail transportation, 20 times safer than air travel and 700 times safer than road transportation. Nor does maglev technology pose problems for passengers with pacemakers, as the magnetic field inside the cabin is the same order of magnitude as the Earth’s natural field. Made of non-flammable materials developed for aviation, Trans­­ rapid also offers the very best in fire prevention. Magnetic levitation represents the most environmentally responsible form of mass transportation available. In addition to minimal energy demand and low noise, maglev technology allows for grades as steep as 10% and a track radius of 2.2km for a speed of 300km/h. This means that the maglev guide­ way can be flexibly adapted to the landscape. Whether elevated or at ground level, it requires less area and has less environmental impact than other ground transportation systems. Magnetic attraction Transrapid uses the forces of magnetic attraction and repulsion for suspension and guidance, while propulsion and braking are managed by a synchronous long-stator motor. The levitation system is based on the attractive and repulsive forces of the electromagnets that are in the vehicle and on the ferromagnetic reaction rails in the guideway. Suspension magnets draw the vehicle along the guideway and guidance magnets keep it laterally on “track”. The maglev propulsion system is based on a synchronous long-stator linear “motor”. The motor consists of stator cores with a three-phase winding installed under the guideway together with vehicle-mounted electromagnets. An electric travelling-wave field generated by current in the windings of the stator cores pulls the vehicle along by attracting its suspension magnets which also act as the exciter section of the linear motor. In other words, unlike the drive principle behind traditional propulsion systems, the maglev’s primary propulsion system is not on the vehicle itself but in the guideway. Compared to conventional locomotives which must have enough on-board propulsion capacity to overcome the steepest grades, maglev trains rely on individual track sections to supply them with the appropriate amount of power. Thus, in sections requiring greater thrust, the output of the guideway motor is boosted as the vehicle passes. Furthermore, by activating only those sections of track being used at Right, a section of the highly automated Transrapid modular control system, developed by Siemens. February 1996  29 Energy supply Switch (closed) Guidance rail Guidance magnet Switch (open) Switch (closed) Motor winding Stator pack Energy supply Support magnet Fig. 1: Transrapid’s levitation system is based on the attraction of electromagnets in the vehicle and the ferromagnetic (steel) guidance rails. any given moment, energy losses are minimised. Financing the project Officially authorised by Germany’s lower house of parliament, the Bunde­ stag, on March 2nd, 1994, the DM 8.9 billion ($A8.4b) Transrapid project will be financed by a combination of public and private interests. A government holding company will be responsible for managing DM 5.6 billion in right-of-way and site preparation investments, while a consortium that includes banks, insurance companies, German Rail (DB) and Lufthansa will provide the remaining financing. Based on technology developed in cooperation with the German Federal Ministry for Research and Technology, the trains are being built by Thyssen, AEG and Siemens. Siemens has developed a highly automated operations control system for the management of maglev trains. Fig. 2: the linear motor, essentially a stretched out stator in the guideway, is divided into sections. A given section is energised only when the train is crossing it. When a maglev train leaves a station, a control centre takes responsibility for all the associated operational tasks and peripheral systems. A fundamental subsystem is the “wayside-installed decentralised vehicle control”. Responsible for set­ point optimisation, as well as route and vehicle protection, this system is in constant contact with the propulsion unit, vehicle and guideway, as well as systems within the operations centre. As the train travels along the guide­ way, decentralised control and operation units exchange information with the main control centre in what is essentially a local area network. Siemens’ decentralised operations control equipment has been extensively tested and meets the demanding requirements of multiple train operation. In addition, under the leadership of Maglev Systems Testing and Planning Ltd, Transrapid has been tested since the mid-80s under near Transrapid 105 TGV-A 100 IC 95 Suburban train 90 85 TRANSRAPID 07 80 Freight train 75 70 A competitor for air travel Transrapid is far more than a stylish new train. Because of its remarkable speed, it offers an unbeatable alternative to the automobile and the airplane. Operating at ten minute intervals, as plans for the Berlin-Hamburg route call for, Transrapid can be expected to significantly reduce traffic density and associated air pollution between major cities. In fact, planners expect the train to attract some 14.5 million passengers each year. Because of its minimal space requirements it can, in many cases, be added to existing railway right-ofways while freeing up conventional SC track for freight traffic. Track-mounted drive Maximum Noise Level at 25 m Distance Ref.: Noise Measurements T†V Rheinland and Others (1989) 110 routine service conditions at a facility in Emsland in northern Germany. In November, 1991, German Rail pronounced the maglev system ready for revenue service and by June 1995 Transrapid had clocked more than 200,000km on its test track. 0 50 100 150 200 250 300 350 400 450 500 km/h Fig. 3: travelling below 200km/h, magnetic levitation trains generate no audible rolling noise, even during acceleration and braking. 30  Silicon Chip Power supply Railroad Gradient (10%) Vehicle-mounted drive Gradient (max. 4%) Fig. 4: the guideway motor system provides increased power in those sections with steeper gradients. Because the guideway linear motor rather than on-board engines does the work, maglev trains can be lighter and negotiate much steeper grades than conventional trains. Acknowledgement: this article has been reproduced by ar­rangement from Siemens Review, Volume 62, May 1995. 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. Australian Defence Force – Navy 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. Reluctor circuit for high energy ignition This modified reluctor circuit has been produced to provide more sensitivity from the circuit which was originally published in the May 1990 issue of SILICON CHIP. The modifications are only minor and provide a small bias voltage to the reluctor and a negative-going pulse via diode D1 to the dwell reference buffer at pin 4 of IC1. This ensures reliable operation at starting. In other respects, the circuit operation is unchanged. C. Daly, South Hobart, Tas. ($35) Intercom uses surplus telephones This circuit provides a 2-way intercom based on standard tele­phone handsets. It operates as follows. At first, both phones are “on hook” and both relays are at rest. Assuming that phone 1 is picked up, relay RLY1 operates, its NC contacts open and the NO contacts close. The NO contacts feed +Vcc to pin 8 of IC1, a 555 timer operating as a pulse generator. IC1 then sends pulses via R3 to Q1. Negative supply is then fed via the NC contacts of relay RLY2 to buzzer BZ/B. When phone 2 is picked up, relay RLY2 operates and its NC contacts open. Buzzer BZ/B stops buzzing. Both parties can then talk across the “Stone Transmission Bridge” consisting of RLY1/TXA/C1/C2/RLY2/TXB. Older 800 series dial phones and the new T-2000 phones will work equally well with this circuit. The DC supply (Vcc) can range from 15 to 18VDC at 500mA. The two relays can be any 6 or 12V DPDT type. A. Hellier, Alice Springs, NT. ($40) 32  Silicon Chip The circuit for the intercom is based on two surplus telephones. 4-channel mixer modifications These modifications to the 4-Channel Guitar Mixer board featured in the January 1992 issue will convert two of the line inputs to microphone inputs and provide an inverted output to drive bridged amplifiers. In the modified circuit, the feedback resistors have been altered for inputs three and four to give a gain of 565 instead of 19, which should be adequate for all types of microphones. If the gain is too high for your application, just reduce the value of the 220kΩ feedback resistor. Using a 100kΩ resistor will reduce the gain to 257 (gain = 100k/390 + 1). Provision is shown to terminate a 600Ω microphone should you require it. You would need to mount a switch on the front panel for each channel. Keep the mic gain controls at minimum when no microphone is connected. The reason for this is that these stages have much higher gain than the line input stages and so hum and noise could otherwise become a problem. The inverted output only requires four additional compon­ents and employs an unused op amp, IC6b. These components could all be mounted on the copper side of the PC board although, if you were really keen, you could drill 0.9mm holes and mount them on the component side, bending the leads to reach the required IC pin. Pin 5 of IC4b is already connected to ground on the PC board. SILICON CHIP. WANTED: YOUR CIRCUIT & DESIGN IDEAS Do you have a good circuit idea? Is so, why not sketch it out, write a brief description and send it to us. Provided your idea is original, we’ll pay up to $60 for a really good circuit. Send your idea to: Silicon Chip Publications, PO Box 139, Collaroy Beach, 2097; or fax (02) 9979 6503 February 1996  33 NICS O R T 2223 LEC 7910 y, NSW EY E OATLBox 89, Oa8t5leFax (02) 5s7a0 C a rd MANY OF THE PRICES LISTED APPLY DURING APRIL AND MAY ONLY Vi PO 49 fax ) 579 e r C a rd , 2 0 ( ne & rs: choice for a special price. Choose motors from e o t n s h o a p h P M17 / M18 / M35. $44. , M ith rde d o w r a d d c e You can also purchase this kit with the B a n k x accepte most mix 0. Orders stepper motor pack described above: $65. e r 1 o m $ f A ) l i P Kit without motors is also available: $32. & & ma r i P a ( . s order 4-$10; NZ world.net FLUORESCENT TAPE $ <at> High quality Mitsubishi brand all weather Aust. IL: oatley 50mm wide red reflective tape with self A by EM adhesive backing: 3 metres for $5. MISCELLANEOUS ITEMS LED BRAKE LIGHT INDICATOR: make a 600mm long high intensity line display, includes 60 high intensity LEDs plus two PCBs plus 10 resistors: $20 (K14). AC MOTOR: 1RPM geared 24V-5W synchronous motor plus a 0.1 to 1RPM driver kit to vary speed; works from 12V DC: $12 (K38 + M30). TOMINON SYMMETRICAL LENS: 230mm focal length - f1:4.5, approximately 100mm diameter an 100mm long: $25 (O14). SPRING REVERB: 30cm long with three springs: $30 (A10). MICROSONIC MICRO RECORD PLAYER: includes amplifier: $4 (A11). MOTOR DRIVEN POTENTIOMETER: dual 20k with PCB: $9. ANGLED TELEPHONE STANDS: Angled, smoky perspex: 4 for $10 (G47). LARGE METER MOVEMENTS: moving iron, 150 x 150mm square face, with mounting hardware: $10. New ARLEC brand 24VDC-500mA approved plugpacks: $9. One FARAD 5.5V capacitors: $3. SPECIALS – POLLING FAX LINE Poll our 579 3955 fax number for new items and some very limited quantity specials. ALCOHOL TESTER KIT Based on a high quality Japanese thick film alcohol sensor. The kit includes a PCB, all on board components and a meter movement: $30. The circuitry includes a latching alarm output that can be used to drive a buzzer, siren etc. We should also have other gas sensors available for this kit. WIND POWER GENERATOR KIT In late April we will have available a low cost kit that employs a low cost electric motor, as used in car radiator cooling systems, to serve as a wind powered electricity generator. Construction drawings for an 800mm 2 blade propeller are supplied. The combination puts out up to 30W of power in high winds. Electronic kit price should be approximately $30. Price of a used suitable motor (available from car wreckers) should be under $40. We will have a limited quantity available for $35. LED FLASHER KIT 3V operated 3 pin IC that can flash 1 or two 2 high intensity LEDs. Very bright and efficient. IC plus 2 high intensity LEDs plus small PCB: $1.30. SIMPLE MUSIC KIT 3V operated 3-pin ICs that play a single tune. Two ICs that play different tunes plus a speaker plus a small PCB: $2.50. CD MECHANISMS AND CD HEADS Used CD mechanisms that have a small motor with geared worm drive assy. Popular with model railway enthusiasts: $5. Also new CD heads that include a laser diode, lenses etc: $3. STEPPER MOTOR PACK Buy a pack of 7 of our stepper motors and save 50%!! Includes 2XM17, 2XM18, 2XM35 and 1 used motor. Six new motors and one used motor for a total of: $36. COMPUTER CONTROLLED STEPPER MOTOR DRIVER KIT This kit will drive two 4, 5, 6 or 8-wire stepper motors from an IBM computer parallel port. The motors require a separate power supply (not included). A detailed manual on the computer control of motors plus circuit diagrams and descriptions are provided. Software is also supplied, on a 3.5" disk. NEW SOFTWARE WILL DRIVE UP TO 4 MOTORS (2 kits required), with LINEAR INTERPOLATION ACROSS FOUR AXES. PCB: 153 x 45mm. Great low cost educational kit. We provide the PCB and all on-board components kit, manual, disk with software, plus two stepper motors of your 34  Silicon Chip UHF REMOTE VOLUME CONTROL SPECIAL As published in EA Dec 95-Jan 96. We supply two UHF transmitters, plus a complete receiver kit, including the case and the motorised volume control potentiometer: $60. PC CONTROLLED PROGRAMMABLE POWER SWITCH MODULE This module is a four channel programmable on/off timer switch for high power relays. The timer software application is included with the module. Using this software the operator can program the on/off status of four independent devices in a period of a week within a resolution of 10 minutes. The module can be controlled through the Centronics or RS232 port. The computer is opto isolated from the unit. Although the high power relays included are designed for 240V operation, they have not been approved by the electrical authorities for attachment to the mains. Main module: 146 x 53 x 40mm. Display panel: 146 x 15mm. We supply: two fully assembled and tested PCBs (main plus control panel), four relays (each with 3 x 10A / 240V AC relay contacts), and software on 3.5" disk. We do not supply a casing or front panels: $92. (Cat G20) STOP THAT DOG BARK Troubles with barking dogs?? Muffle the mongrels and restore your sanity with the WOOFER STOPPER MK2, as published in the Feb 96 edition of Silicon Chip. A high power ultrasonic sweep generator which can be triggered by a barking dog. We supply a kit which includes a PCB and all the on-board components: all the resistors, capacitors, semiconductors, trimpotentiometers, heatsinks, and the transformer. We will also include the electret microphone. Note that our kit is supplied with a solder masked and silk screened PCB, and a pre-wound transformer!: $39. Single Motorola piezo horn speakers to suit (one is good, but up to four can be used): $14. Approved 12VDC-1A plugpack to suit: $14. UHF REMOTE CONTROL FOR THE DE-BARKER OF ANNOYING DOGS Operate your Woofer Stopper remotely from anywhere in your house, even your bedside. Allows you to remotely trigger your Woofer Stopper at any time. Nothing beats a randomly timed “human touch”. We supply one single channel UHF transmitter, one suitable UHF receiver and very simple interfacing instructions: $28. Based on the single channel transmitter and a slightly modified version of the 2 channel receiver, as published in the Feb 96 edition of Silicon Chip. Note that the article features 3 low cost remote controls: 1 ch UHF with central locking, 1-2 ch UHF, and an 8 ch IR remote. MOTOR DRIVEN VOLUME CONTROL/POT New high quality motor driven potentiometer, intended for use in commercial stereo sound systems. Includes clutch, so can also be manually adjusted. Standard 1/4" shaft, stereo (dual 20k pots) with 5V/20mA motor: $12 (Cat A13). MINI HIGH VOLTAGE POWER SUPPLY Miniature potted EHT power supply (17 x 27 x 56mm) that was originally designed to power small He-Ne Laser tubes. Produces a potent 10mm spark when powered from 8-12V / 500mA DC source. Great for experimentation, small portable Jacobs Ladder displays, and cattle prods. Use on humans is dangerous and illegal. A unit constructed for this purpose would be would be considered an offensive weapon. Inverter only: $25. CCD CAMERA SPECIAL Very small PCB CCD camera including auto iris lens: 0.1 Lux, 320K pixels, IR responsive; overall dimensions: 38 x 38 x 25mm. We will include a free VHF modulator kit with every camera purchase. Enables the viewing of the picture on any standard TV on a VHF Channel. Each camera is supplied with instructions and a 6 IR LED illuminator kit. $170. CCD CAMERA - TIME LAPSE VCR RECORDING SYSTEM This kit plus ready made PIR detector module and “learning remote control” combination can trigger any domestic IR remote controlled VCR to RECORD human activity within a 6M range and with an 180 deg angle of view! Starts VCR recording at first movement and ceases recording a few minutes after the last movement has stopped: just like commercial CCD/TIME LAPSE RECORDING systems costing thousands of dollars!! CCD camera not supplied. No connection is required to your existing domestic VCR as the system employs an “IR learning remote control”: $90 for an PIR detector module, plus control kit, plus a suitable “lR learning remote” control and instructions: $65 when purchased in conjunction with our CCD camera. Previous CCD camera purchasers may claim the reduced price with proof of purchase. SOUND FOR CCD CAMERAS/UNIVERSAL AMPLIFIER (To be published, EA). Uses an LM386 audio amplifier IC and a BC548 pre-amp. Signals picked up from an electret microphone are amplified and drives a speaker. Intended for use for listening to sound in the location of a CCD camera installation, but this kit could be used as a simple utility amplifier. Very high audio gain (adjustable) makes this unit suitable for use with directional parabolic reflectors etc. PCB: 63 x 37mm: $10. (K64) LOW COST IR ILLUMINATOR Illuminates night viewers or CCD cameras using 42 of our 880nm/30mW/12 degrees IR LEDs. Power output (and power consumption) is variable, using a trimpotentiometer. Operates from 10 to 15V and consumes from 5mA up to 0.6A (at maximum power). The LEDs are arranged into 6 strings of 7 series LEDs with each string controlled by an adjustable constant current source. PCB: 83 x 52mm: $40 (K36). MASTHEAD AMPLIFIER SPECIAL High performance low noise masthead amplifier covers VHF - FM UHF and is based on a MAR-6 IC. Includes two PCBs, all on-board components. For a limited time we will also include a suitable plugpack to power the amplifier from mains for a total price of: $25. VISIBLE LASER DIODE KIT A 5mW/660nM visible laser diode plus a collimating lens, plus a housing, plus an APC driver kit (Sept 94 EA). UNBELIEVABLE PRICE: $40. Suitable case and battery holder to make pointer as in EA Nov 95 $5 extra. SOLID STATE “PELTIER EFFECT” DEVICES We have reduced the price of our peltiers! These can be used to make a solid state thermoelectric cooler/heater. Basic information supplied. 12V-4.4A PELTIER: $25. We can also provide two thermal cut-out switches and a 12V DC fan to suit the above, for an additional price of $10. PLASMA EFFECTS SPECIAL Ref: EA Jan. 1994. This kit will produce a fascinating colourful changing high voltage discharge in a standard domestic light bulb. Light up any old fluorescent tube or any other gas filled bulb. Fascinating! The EHT circuit is powered from a 12V to 15V supply and draws a low 0.7A. Output is about 10kV AC peak. PCB: 130 x 32mm. PCB and all the on-board components (flyback transformer included) and the instructions: $28 (K16). Note: we do not supply any bulbs or casing. Hint: connect the AC output to one of the pins on a fluorescent tube or a non-functional but gassed laser tube for fascinating results! The SPECIAL???: We will supply a non-functional laser tube for an additional $5 but only when purchased with the above plasma kit: TOTAL PRICE: $33. 400 x 128 LCD DISPLAY MODULE - HITACHI These are silver grey Hitachi LM215 dot matrix displays. They are installed in an attractive housing. Housing dimensions: 340 x 125 x 30mm. Weight: 1.3kg. Effective display size is 65 x 235mm. Basic data for the display is provided. Driver ICs are fitted but require an external controller. New, unused units. $25 ea. (Cat D02) 3 for $60. VISIBLE LASER DIODE MODULE SPECIAL Industrial quality 5mW/670nM laser diode modules. Consists of a visible laser diode, diode housing, driver circuit, and collimation lens all factory assembled in one small module. APC control circuit assures. Features an automatic power control circuit (APC) driver, so brightness varies little with changes in supply voltage or temperature. Requires 3 to 5V to operate. Overall dimensions: 12mm diameter by 43mm long. Assembled into an anodised aluminium casing. This module has a superior collimating optic. Divergence angle is less than 1 milliradian. Spot size is typically 20mm in diameter at 30 metres: $65 (Cat L10). This unit may also be available with a 635nm laser diode fitted. dimensions: 25 x 43mm. Construction is easy and no coil winding is necessary as the coil is pre-assembled in a shielded metal can. The solder masked and screened PCB also makes for easy construction. The kit includes a PCB and all the on-board components, an electret microphone, and a 9V battery clip: $12 ea. or 3 for $33 (K11). CYCLE/VEHICLE COMPUTERS BRAND NEW SOLAR POWERED MODEL! Intended for bicycles, but with some ingenuity these could be adapted to any moving vehicle that has a rotating wheel. Could also be used with an old bicycle wheel to make a distance measuring wheel. Top of the range model. Weather and shock resistant. Functions: speedometer, average speed, maximum speed, tripmeter, odometer, auto trip timer, scan, freeze frame memory, clock. Programmable to allow operation with almost any wheel diameter. Uses a small spoke-mounted magnet, with a Hall effect switch fixed to the forks which detects each time the magnet passes. The Hall effect switch is linked to the small main unit mounted on the handlebars via a cable. Readout at main unit is via an LCD display. Main unit can be unclipped from the handlebar mounting to prevent it being stolen, and weighs only 30g. Maximum speed reading: 160km/h. Maximum odometer reading: 9999km. Maximum tripmeter reading: 999.9km. Dimensions of main unit: 64 x 50 x 19mm: $32 (Cat G16). FM TX MK 3 This kit has the most range of our kits (to around 200m). Uses a pre-wound RF coil. The design limits the deviation, so the volume control on the receiver will have to be set higher than normal. 6V operation only, at approx 20mA. PCB: 46 x 33mm: $18 (K33). PASSIVE TUBE - SUPPLY SPECIAL Russian passive tube plus supply combination at an unbelievable SPECIAL REDUCED PRICE: $70 for the pair! Ring or fax for more information. 27MHZ RECEIVERS Brand new military grade 27MHz single channel telemetry receivers. Enclosed in waterproof die cast metal boxes, telescopic antenna supplied. 270 x 145 x 65mm 2.8KG. Two separate PCBs: receiver PCB has audio output; signal filter/squelch PCB is used to detect various tones. Circuit provided: $20. BATTERY CHARGER WITH MECHANICAL TIMER A simple kit which is based on a commercial twelve-hour mechanical timer switch which sets the battery charging period from 0 to 12 hours. Employs a power transistor and five additional components. It can easily be “hard wired”. Information that shows how to select the charging current is included. We supply the information, a circuit and the wiring diagram, a hobby box with an aluminium cover that doubles up as a heatsink, a timer switch with knob, a power transistor and a few other small components to give you a wide selection of charge current. You will also need a DC supply with an output voltage which is greater by about 2V than the highest battery voltage you intend to charge. As an example, a cheap standard car battery charger could be used as the power source to charge any chargeable battery with a voltage range of 0 to 15V. Or you could use it in your car. No current is drawn at the end of the charging period: $15. SIREN USING SPEAKER Uses the same siren driver circuit as in the “Protect anything alarm kit”. 4" cone / 8 ohm speaker is included. Generates a very loud and irritating sound that is useful to far greater distances than expensive piezo screamers. Has penetrating high and low frequency components and the sound is similar to a Police siren. Output has frequency components between 500Hz and 4KHz. Current consumption is about 0.5A at 12V. PCB: 46 x 40mm. As a bonus, we include all the extra PCBs as used in the “Protect anything alarm kit”: $12. FM TRANSMITTER KIT - MKII Ref: SC Oct 93. This low cost FM transmitter features preemphasis, high audio sensitivity (easily picks up normal conversation in a large room), a range of around 100 metres, and excellent frequency stability. Specifications: tuning range: 88-108MHz; supply voltage 6-12V; current consumption <at> 9V: 3.5mA; pre-emphasis: 75uS; frequency response: 40Hz to greater than 15KHz; S/N ratio: greater than 60dB; sensitivity for full deviation: 20mV; frequency stability with extreme antenna movements: 0.03%; PCB MOTOR SPEED CONTROLLER PCB Simple circuit controls small DC powered motors which take up to around 2 amps. Uses variable duty cycle oscillator controlled by trimpot. Duty cycle is adjustable from almost 0 - 100%. Oscillator switches P222 MOSFET. PCB: 46 x 28mm. $11 (K67). For larger power motors use a BUZ11A MOSFET: $3. 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 (K47). DC MOTORS We have good stocks of the following high quality DC motors. These should suit many industrial, hobby, robotics and other applications. Types: Type M9: 12V. I no load = 0.52A <at> 15800 RPM at 12V. Weight: 150g. Main body is 36mm diameter. 67mm long: $7 (Cat M9). Type M14: made for slot cars. 4 to 8V. I no load = 0.84A at 6V. At max. efficiency I = 5.7A <at> 7500 RPM. Weight: 220g. Main body diameter is 30mm. 57mm long: $7 (Cat M14). MAGNETS: HIGH POWER RARE EARTH MAGNETS Very strong. You will not be able to separate two of these by pulling them apart directly away from each other. Zinc coated. CYLINDRICAL 7 x 3 mm: $2 (Cat G37) CYLINDRICAL 10 x 3 mm: $4 (Cat G38) TOROIDAL 50mm outer, 35mm inner, 5mm thick: $9.50 (Cat G39) CRYSTAL OSCILLATOR MODULES Small hermetically sealed, crystal oscillator modules. Used in computers. Operate from 5V and draw about 30mA. TTL logic level clock output. Available in 4MHz, 4.032MHz, 5.0688MHz, 20MHz, 20.2752MHz, 24.74MHz, 40MHz, and 50MHz.: $7 ea. (Cat G45) 5 for $25. XENON FLASH BOARDS Flash units with small (2cm long) xenon tube, as used in disposable cameras. Power from one AA 1.5V battery. Approx 7 joules energy: $3 (Cat G48). INDUCTIVE PICKUP KIT Ref: EA Oct 95. Kit includes coil pre-wound. Use receiver in conjunction with a transmit loop of wire which is plugged in in place of where a speaker is normally used. This wire loop is run around the perimeter of the room / house you wish to use the induction loop in. We do not supply the transmit loop wire. Also excellent for tracing AC magnetic fields. PCB: 61 x 32mm. Kit contains PCB and all on board components: $10 (K55). SLAVE FLASH TRIGGER Very simple, but very effective design using only a few components. Based on an ETI design. This kit activates a second flash unit when the master, or camera mounted, flash unit is activated. This is useful to fill in shadows and improve the evenness of the lighting. It works by picking up the bright flash with a phototransistor and triggering an SCR. The SCR is used as a switch across the flash contacts. This circuit does not false trigger even in strongly lit rooms, but is sensitive enough to operate almost anywhere within even a quite large room. Of course, by making more of these and fitting them to more slave flash units even better lighting and more shadow reduction is obtained. PCB: 21 x 21mm: $7 (K60). SOUND ACTIVATED FLASH TRIGGER Based on ETI project 514. Triggers a flash gun using an SCR, when sound level received by an electret microphone exceeds a certain level. This sound level is adjustable. The delay between the sound being received and operation of the flash is adjustable between 5 and 200 milliseconds. A red LED lights up every time the sound is loud enough to trigger the flash. This is handy when setting the unit up to suit the scene, without waiting for the flash unit to recharge or flatten its batteries in the process. This kit allows you take interesting pictures such as a light bulb breaking. PCB: 62 x 40mm: $14 (K61). OPTO PHOTO INTERRUPTER (SLOTTED): an IR LED and an phototransistor in a slotted PCB mounting assembly. The phototransistor responds to visible and IR light. The discrete components are easy to separate from the clip together assembly. Great for IR experiments: $2 ea. or 10 for $15. IR PHOTODIODE: similar to BPW50. Used in IR remote control receivers. Peak response is at 940nm. Use with 940nm LEDs: $1.50 ea. or 10 for $10. VISIBLE PHOTODIODE: this is the same diode element as used in our IR photodiode but with clear encapsulation, so it responds better to visible and IR spectrum: $1.50 ea. or 10 for $10. LDRs: large, 12mm diameter, <20ohm very bright conditions, >20Mohm very dark conditions: $1. LEDs BRIGHTNESS RATING: Normal, Bright, Superbright, Ultrabright. BLUE: 5mm, 20mA max, 3.0V typical forward voltage drop. $2.50 RED SUPERBRIGHT: 5mm, 0.6 to 1.0 Cd, 30mA max, forward voltage 1.7V, 12 degrees view angle, clear encapsulation: 10 for $4 or 100 for $30. BRIGHT: 5mm. Colours available: red, green, orange, yellow. Encapsulation colour is the same as the emitted colour. 30mA max.: 10 for $2 or 100 for $14. BRIGHT NARROW ANGLE: 5mm, clear encapsulation, 30mA. Colours available: yellow, green: 10 for $2.50 or 100 for $20. TWO COLOUR: 5mm, milky encapsulation, 3 pins, red plus green, yellow by switching both on: $0.60. ULTRABRIGHT YELLOW: Make a LED torch!: $2.50. PACK OF 2mm LEDs: 10 each of the following colours: red, green, amber. We include 30 1.0K ohm resistors for use as current limiting. Great for model train layouts using HO gauge rails: $10. IR LEDs: 800nm. Motorola type SFOE1025. Output 1mW <at> 48mA. Forward voltage 1.7V. Suitable for use with a focussing lens. At verge of IR and visible, so has some visible output. Illuminates Russian and second generation viewers: $2. HIGH POWER IR LEDs: 880nm/30mW output <at> 100mA. Forward voltage: 1.5V. The best 880nm LEDs available. Excellent for IR illumination of most night viewers and CCD cameras. We use these LEDs in our IR illuminator kit K36. Emits only a negligible visible output. Both wide angle (60 degrees) and narrow angle (12 degrees) versions of these LEDs are available. Specify type required: 10 for $9 or 100 for $80. IR LEDs: 940nm. Commonly used in IR remote control transmitters. Good for IR viewers with a deeper IR response. No visible output. 16mW output. 100mA max. Forward voltage is 1.5V: 10 for $5. 18V AC <at> 0.83A PLUGPACKS Also include a diecast box (100 x 50 x 25mm): Ferguson brand. Australian made and approved plugpacks. Output lead goes to diecast box with a few components inside. Holes drilled in box where LED and 2 RF connectors are secured: $8 (Cat P05). CASED TRANSFORMERS 230Vac to 11.7Vac <at> 300mA. New Italian transformers in small plastic case with separate input and output leads, each is over 2m long. European mains plug fitted; just cut it off and fit the local plug. This would be called a plugpack if it sat on the powerpoint: $6 (Cat P06). FREE CATALOGUE WITH YOUR ORDER Ask us to send you a copy of our FREE catalogue with your next order. Different items and kits with illustrations and ordering information. And don’t forget our website at: http://www.hk.super.net/~diykit February 1996  35 Control barking dogs with the Woofer Stopper Mk.2 This completely new version of the Woofer Stopper has much higher power, with pulsed and variable output frequency between 20kHz and 25kHz. It automatically senses the barking of a dog using an inbuilt electret microphone. By JOHN CLARKE 36  Silicon Chip Now it’s your turn to get back at your neighbour’s barking dog without anyone knowing about it. The Woofer Stopper will give a blast of high intensity sound every time the dog barks. When subjected to this treatment, most dogs quickly learn that barking means punishment and they stop. Don’t get us wrong. The Woofer Stopper Mk.2 will not stop all dogs from barking. Some dogs are deaf or are completely stupid and would continue to bark under any circumstances. Provided they are not too far away from the Woofer Stopper though, say 30 metres or less, most dogs will be deterred from barking. Our first Woofer Stopper, published in the May 1993 issue, created a huge amount of interest. Obviously, barking dogs are a source of much annoyance to many people. While the Woofer Stopper was successful in many cases, we have had readers calling for more power and for automatic sensing of the dog barking. The result is the Woofer Stopper Mk.2. This version has a far greater voltage output and can drive a maximum of four pie­zo­ Fig.1: this is the block diagram of the Woofer Stopper Mk.2. An electret microphone electric tweeters. These can be in is used to pick up the sound of a dog barking, to provide an automatic trigger for the form of four single devices or the circuit. The output stage can drive up to four piezo tweeters. two duals. To obtain the maximum possible sound output, we have re­sorted to two types of tweeter. The first is the 1177A TD Twin Tweeter. It produces Motorola KSN 1005A Super Horn. 99dB SPL at 1-metre and 2.82V RMS a number of measures. First, instead It can produce a 94dB SPL (sound drive and is rated at 28V maximum. of driving the tweeter with a constant Note that the second type is a dual high frequency of around 20kHz, pressure level) at 1-metre with 2.82V we frequency modulate the signal RMS drive. They are rated at 15V RMS tweeter and this accounts for the 5dB continuous and 24V RMS maximum. increase in SPL. Other types can be between 20kHz and 25kHz. This has The second type is the Motorola KSN used, although we do not know how been done to overcome the inevitable peaks and dips in the response of piezo tweeters. By modulating the output frequency over a 5kHz range, we obtain a high effective output. Second, instead of driving the tweeters at a constant vol­ tage, we pulse them at a voltage much higher than their continu­ous rating – again to produce a higher output level. And third, instead of driving them with a square wave signal, we drive them with a sinewave. While developing the Woofer Stopper Mk.2, we found that driving piezo tweeters with high-voltage square These are the two piezo tweeters waves caused them to fail. This is recommended for use with because they are essentially a capacthe Woofer Stopper Mk.2. The Motorola KSN 1177A TD Twin itor, with a capacitance ranging from Tweeter is at left while the KSN .01µF to 0.3µF, depending on the mod1005A Super Horn is shown el. Driving such a capacitance with above. high-voltage square waves at around 20kHz or more causes very high peak currents and this caused the internal SPECIFICATIONS connecting wires to fuse. Since we wanted a lot more power than proSupply Voltage: 12VDC duced by the previous design, we Output Voltage (two transducers driven; deduct 20% for four devices): could not use square waves; sinewave    (a) 21.4VRMS peak and 14.2VRMS continuous with 13.8V supply drive was the way to go.    (b) 18.5VRMS peak and 12.4VRMS continuous with 12V supply Recommended tweeters Peak burst duration: 100ms every 1 second Since the Mk.2 version produces a lot more output than the original version, it makes sense to team it with highly efficient piezo tweeters which can handle the high power levels involved. Using cheap tweeters will be a waste of money. We recommend Total output duration: 5,10,20,40 & 160 seconds Standby current: 30mA Current while driving transducers: 1A average Output frequency: shifted continuously between 20kHz and 25kHz every 220ms February 1996  37 Fig.2: the full circuit diagram of the Woofer Stopper Mk.2. Note the audio amplifier involving IC6 and tran­sistors Q1 & Q2. These provide increased power and can drive up to four piezo tweeters via step up transformer T1. they will respond to the high voltage drive. Bark sensing & timer The Woofer Stopper Mk.2 has an inbuilt electret microphone to sense 38  Silicon Chip the sound of a dog barking and start the unit operating. While this is adjustable in sensitivity, it is quite likely that it will be triggered by other loud sounds and this could ul­timately be counterproductive. We see the pur- pose of the Woofer Stopper Mk.2 as a teaching aid – to stop a dog from barking. If it is triggered by other noises, it may not be as effective. However, we have included this feature because it has been re­quested frequently by readers. The unit can also be triggered into operation by pushing a button and in either case, the tweeter will sound for a preset period which can be programmed, from five seconds to 160 seconds. The idea of having the timer is to avoid the possibility of the unit being turned on for long periods which would waste power and possibly reduce its effectiveness in teaching the dog not to bark. The Woofer Stopper can be run from a 12V battery or a DC power supply capable of delivering one amp or more. Block diagram Fig.1 shows the block diagram of the Woofer Stopper Mk.2. It shows an electret microphone fed to IC1a & ICb, comparator IC2 and flipflop IC3 which controls the counter IC4. IC5 and IC2c comprise the 20kHz oscillator which is fre­quency modulated by IC2b. Finally, there is the power amplifier comprising IC6, Q1 and Q2, which drives a step-up transformer T1. The gain of the power amplifier is periodically increased by the burst oscillator IC2d and Q3. Counter IC4 resets the flipflop after a preset time and the 20kHz oscillator is reset. Thus, sound from the transducer is stopped until retriggered by the microphone. Note that because the microphone will also respond to the transducer sound, the reset time for the flipflop is made long enough to prevent re­triggering at the end of the time period. Circuit details The complete circuit for the Woofer Stopper Mk.2 is shown in Fig.2. The electret microphone is biased by a 4.7kΩ resistor and its signal is coupled to op amp IC1 via a .022µF capacitor. IC1a is a non-inverting amplifier with its low frequency response curtailed below 1600Hz, by virtue of the 10kΩ resistor and .01µF capacitor at pin 6. Its gain is set by trimpot VR1. IC1a’s output is coupled to a virtually identical stage, apart from the sen­sitivity control, comprising op amp IC1b. Its gain is 19 and is also rolled off above 5kHz by the 150pF capacitor shunting the 180kΩ feedback resistor. IC2a squares up the output signal of IC1b. IC2a is connect­ed as a Schmitt trigger with positive feedback between the non-inverting input at pin 3 and its output at pin 1. When flipflop IC3 is triggered by a high-going pulse from IC2a, its Q output goes high which allows IC5, a 7555 timer, to begin os- PARTS LIST 1 plastic case, 198 x 113 x 63mm 1 PC board, code 03102961, 153 x 103mm 1 self-adhesive label, 107 x 193mm 1, 2, 3 or 4 KSN 1005 Motorola superhorn loudspeakers (DSE Cat C-2205) or 1 or 2 KSN 1177 Motorola twin tweeters (DSE Cat C-2204) 1 red binding post 1 black binding post 1 2.5mm DC panel socket 1 2.5mm DC panel plug 1 SPDT toggle switch (S1) 1 momentary pushbutton switch (S2) 1 electret microphone insert 1 ETD29 3C85 or 3F3 transformer cores, bobbin and clips (Philips 2 x 4312 020 37502 , 1 x 4322 021 34381 , 2 x 4322 021 34371) (T1) 2 mini heatsinks, 25 x 30 x 13mm 1 4.5m length of 0.5mm diameter enamelled copper wire 1 140mm length of black hook-up wire 1 200mm length of red hook-up wire 1 200mm length of 0.8mm tinned copper wire 8 PC stakes 2 3mm screws and nuts 2 5mm LED bezels 1 200kΩ horizontal trimpot (VR1) 1 20kΩ horizontal trimpot (VR2) Semiconductors 1 LF353, TL072 dual op amp (IC1) 1 LM324 quad op amp (IC2) cillating. At the same time, the Q-bar output of IC3 goes low to release the reset on counter IC4 which begins to count the clock pulses from oscillator IC2b. IC4 counts for a period selected by installing the appro­priate link (LK1LK5). When the selected Q output goes high, the 33µF capacitor at pin 4 of IC3 is charged via D2 to reset the flipflop. The Q output of IC3 now goes low to stop IC5 from oscillating and the Q-bar output goes high to reset counter IC4. Now the selected Q 1 4013 dual D flipflop (IC3) 1 4020 binary counter (IC4) 1 7555, LMC555CN, GLC555 CMOS timer (IC5) 1 NE5534N op amp (IC6) 1 MJE3055 TO220 NPN transistor (Q1) 1 MJE2955 TO220 PNP transistor (Q2) 1 BC338 NPN transistor (Q3) 1 1N4004 1A rectifier diode (D1) 2 1N914, 1N4148 switching diodes (D2,D3) 1 5mm red LED (LED1) 1 5mm green LED (LED2) Capacitors 2 470µF 16VW PC electrolytic 1 47µF 16VW PC electrolytic 1 33µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 1 2.2µF 16VW PC electrolytic 1 0.1µF MKT polyester 2 .022µF MKT polyester 3 .01µF MKT polyester 1 .0022µF MKT polyester 1 150pF ceramic 1 120pF ceramic 1 82pF ceramic 1 39pF ceramic Resistors (0.25W, 1%) 1 1MΩ 15 10kΩ 1 560kΩ 2 6.8kΩ 1 180kΩ 2 4.7kΩ 5 100kΩ 2 2.2kΩ 1 68kΩ 1 560Ω 1 47kΩ 1 100Ω 1 15kΩ Miscellaneous Solder, insulating tape. output on IC4 goes low and the 33µF capacitor at pin 4 of IC3 discharges (or actually charges) via the 100kΩ resistor to ground. This means that IC3 is again ready to respond to the signal from IC2a and recommence the sequence. 20kHz oscillator The main oscillator is based on IC5, a CMOS 7555 timer which is connect­ ed in an unconventional way. It successively charges and discharges the .0022µF capacitor at pin 2 & 6 via the February 1996  39 Fig.3: install the parts on the PC board and complete the wiring as shown here. In particular, take care to ensure that all polarised parts are correctly oriented and note that the metal tabs of audio output transistors Q1 and Q2 are bolted to small U-shaped heatsinks and to the PC board. 15kΩ resistor from pin 3. Instead of using the square wave output signal at pin 3, we take the triangle waveform at pin 6. This triangle waveform is buffered by unity gain op amp IC2c and then fed to a low-pass filter comprising a 100kΩ resistor and 120pF capacitor. This network effectively 40  Silicon Chip removes the higher harmonics and the result is a clean sinewave at around 20kHz. However, the timer/oscillator IC5 is also frequency modu­lated by the triangle signal applied to pin 5 from pin 6 of IC2b, a low frequency oscillator. Op amp IC2b is connected as a Schmitt trigger oscillator. It charges and discharges the 2.2µF capacitor at pin 6 via the 100kΩ resistor from pin 7. The result is a square wave at about 2.5Hz at pin 7 and a triangle waveform of the same frequency at pin 6 (ie, across the 2.2µF capacitor). As noted above, the square wave pulses from CAPACITOR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ Value 0.1µF .022µF .01µF .0022µF 180pF 120pF 82pF 39pF IEC 100n 22n 10n 2n2 180p 120p 82p 39p EIA 104 223 103 222 181 121 82 39 IC2b are used to clock counter IC4 while the triangle pulses frequency modulate IC5. IC6 amplifies the frequency-modulated sinewave from IC2c. Its current drive capability is boosted by common emitter output transistors Q1 & Q2. The 560Ω resistor between the base and emitter connections provides a current path for the output of the amplifier whenever Q1 or Q2 is biassed off and helps prevent instability. The 39pF compensation capacitor between pins 5 & 8 and the 82pF feedback capacitor roll off the amplifier gain above about 40kHz. Gain boosting The gain of IC6 is pulsed up and down by the waveform from oscillator IC2d which switches transistor Q3 on and off. With Q3 off, the gain is about 1.5, set mainly by the 68kΩ resistor across Q3. When Q3 is on, the gain can be set between 11 and 2.9 The electret microphone insert is a flush fit in one end of the case, as shown here. Connect the microphone so that its positive terminal goes to the 4.7kΩ resistor. The terminal that’s connected to the case goes to ground. by adjusting trimpot VR2. Thus, the gain varies between about 1.5 and a figure set by VR2 at a rate controlled by IC2d. IC2d operates in a similar manner to oscillator IC2b. The 10µF capacitor at pin 13 is charged via the 10kΩ resistor and diode D3 when pin 14 is high and discharges via the 100kΩ resis­tor when pin 14 is low. Thus, the output is high for only a short time. The duty cycle of the pulse waveform is about 1:10. Transformer T1 steps up the voltage from the output amplifi­er by a factor of 10. Thus, the output across the piezo tweeters can be as much as 75V peakpeak. In practice, the actual setting will depend on the tweeters used. Above a certain voltage level, the tweeter will overload and will protest audibly. It would not be wise to run tweeters under this overload condition for long as you risk burning them out. Power supply Power for the circuit is derived from a 12V battery or DC power supply capable of supplying at least 1A. Diode D1 provides polarity reversal RESISTOR COLOUR CODES ❏ No. ❏   1 ❏   1 ❏   1 ❏   5 ❏   1 ❏   1 ❏   1 ❏ 15 ❏   2 ❏   2 ❏   2 ❏   1 ❏   1 Value 1MΩ 560kΩ 180kΩ 100kΩ 68kΩ 47kΩ 15kΩ 10kΩ 6.8kΩ 4.7kΩ 2.2kΩ 560Ω 100Ω 4-Band Code (1%) brown black green brown green blue yellow brown brown grey yellow brown brown black yellow brown blue grey orange brown yellow violet orange brown brown green orange brown brown black orange brown blue grey red brown yellow violet red brown red red red brown green blue brown brown brown black brown brown 5-Band Code (1%) brown black black yellow brown green blue black orange brown brown grey black orange brown brown black black orange brown blue grey black red brown yellow violet 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 green blue black black brown brown black black black brown February 1996  41 These two oscilloscope photos show the output waveform of the Woofer Stopper. The photo at left shows the frequency modulation while the shot at right shows the pulsed wave­form. protection while the associated 470µF capacitor decouples the supply for the high current pulses drawn by the amplifier. Construction Fig.4: the full-size etching pattern for the PC board. Check the board carefully for defects before installing any of the parts. 42  Silicon Chip The Woofer Stopper is housed in a plastic case measuring 198 x 113 x 63mm and the components are mount­ ed on a PC board coded 03102961 and measuring 153 x 103mm. The component layout for the PC board is shown in Fig.3. Start construction by checking the PC board against the published pattern. Repair any shorts or breaks in the tracks before assembly of the components. There should be 3mm holes drilled for mounting Q1 and Q2 on their heatsinks. First, install the eight PC stakes and the bare wire links. Insert LK2 at this stage. This gives a 10-second period of operation and you can change this later to the desired setting. Next, the resistors can be inserted and soldered, using the accom­panying resistor code table as a guide when selecting each value. If in doubt, use your multimeter to check the resistance values. Next, insert the ICs, making sure that each one is in its correct place and oriented correctly, then do the capacitors. Note that the electrolytic capacitors must be oriented as shown in Fig.3 for correct polarity. Mount trimpots VR1 & VR2 and transistor Q3. Transistors Q1 and Q2 are mount­ed horizontally on small heat­sinks. Bend their leads so that they will fit neatly into the PC board and secure the transistor tab to the heatsink with a 3mm screw and 0N + + START + + TRIGGERED WOOFER STOPPER MKII SPEAKER TERMINALS nut before soldering the leads to the PC board. Winding the transformer is straightforward. The winding details are shown in Fig.6. Terminate one end of the 0.5mm enam­elled copper wire to pin 9 of the bobbin. To do this, you will need to strip the end of the wire of insulation and then tin it with solder. Wind on eight turns and terminate the end of the winding to pin 11 of the bobbin. Apply a layer of insulating tape over this winding. The secondary winding is done in a similar manner by starting at pin 2 and winding on 80 turns in several layers. Insulate each layer with tape and finally terminate onto pin 5. The transformer is then assembled by sliding the cores into each end of the bobbin and securing them with the clips. Mount the transformer onto the board and solder the pins in place. Work can now begin on the case. Attach the adhesive label to the case lid and drill the switch, LED bezel and corner mount­ing holes. Drill holes in one end of the box for the DC socket and electret microphone and at the opposite end for the tweeter terminals. Make sure that the electret microphone is a tight fit in its mounting hole. If necessary, secure it with a drop of 5-minute epoxy adhesive. Clip the PC board into the base of the case. The tweeter terminal eyelet connections can be soldered directly to the PC stakes or you can use short lengths of tinned copper wire. Testing When wiring is complete, you should check your work care­fully for errors. Once you are satisfied that all is correct, you are ready to connect up power. The Woofer Stopper will operate from a 12V gel cell battery rated at 1.2Ah or higher. It can also be run from a DC power supply capable of at least 1A at 12V. Apply power and check voltages on the circuit. There should be +12V at pin 8 of IC1, pin 4 of IC2, pin 14 of IC3, pin 16 of IC4, pins 8 of IC5 and pin 7 of IC6. Check that the power LED lights. Connect your multimeter across the output terminals and set it to read 20VAC. Wind trimpot VR1 fully clockwise for maximum microphone sensitivity and check that there is an output signal on the meter when triggered by tapping the microphone. POWER IN (12VDC + ) Fig.5: this full size artwork can be photocopied and used as a drilling template for the front panel. You will find that the microphone sensitivity is very high at this set­ting. Reduce VR1 to a setting which will only retrigger the circuit with a reasonable amount of noise. Trying barking yourself if the mood takes you. Test the manual trigger switch as well. Note that LED2 should light whenever the circuit is triggered. Note that the reading on the meter will not necessarily be the true output level. This is because some multi­ meters do not respond well at 20kHz. Connect up your piezo tweeters and again apply power. The level of VR2 should be adjusted so that you do not hear the sound output during the bursts. Unless you can actually February 1996  43 Fig.5: follow this winding diagram when making the step-up transformer (T1). The primary is wound on first and is covered with a layer of insulating tape. The secondary is then wound over the top of the primary. hear 20kHz, any audible sounds from the tweeters is distortion and is quite small relative to the fundamental output at 20kHz. If you want to check that the circuit is working you can lower the frequen- Transistors Q1 and Q2 are mounted horizontally on small heat­ sinks. Bend their leads so that they fit neatly into the PC board and secure their tabs to the heatsinks and the PC board using machine screws and nuts. cy of oscillation by adding a second .0022µF capacitor between pins 2 and 1 of IC5. This will halve the output frequency to 10kHz. Be warned that the output is extremely loud and will damage your ears if you do not use ear plugs. You can also use a 1kΩ resistor or high value resistor in series with the tweeter to reduce the output level. Return the circuit to 20kHz operation by removing the ca­pacitor and you are ready to test it on an unsuspecting dog. As mentioned, you can use up to four piezo tweeters in parallel (two KSN 1177A or four KSN 1005A tweeters). These can be mounted on a board and oriented either horizontally or vertical­ly, depending on the sound pattern you require. Do not use con­ventional tweeters (ie, those with voice coils). The circuit cannot handle them. Note that you can omit the electret microphone if you wish and just use manual triggering. Alternatively, you could add in a switch to turn off the microphone when you want to use manual triggering only. You could also incorporate UHF remote triggering, as was used for the original version of the Woofer Stopper. The details were published in the June SC 1993 issue of SILICON CHIP. Warning! This internal view of the Woofer Stopper shows how the board fits neatly in the case. The step up transformer and opera­tion with sinewave drive are the main factors in the increased output. 44  Silicon Chip The output from this Woofer Stopper is at a very high level. Even though you cannot hear the noise, take care to keep away from the front of the tweeters when they are being driven. They may cause ear damage. 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 SILICON CHIP BOOK SHOP Newnes Guide to Satellite TV 336 pages, in paperback at $49.95. 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. Servicing Personal Computers By Michael Tooley. First pub­ lished 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. 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. Optoelectronics: An Introduction By J. C. A. Chaimowicz. First published 1989, reprinted 1992. This particular field is about to explode and it is most important for engineers and technicians to bring themselves up to date. The subject is comprehensively covered, starting with optics and then moving into all aspects of fibre optic communications. 361 pages, in paperback at $55.95. Digital Audio & Compact Disc Technology 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 format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. Power Electronics Handbook 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. Surface Mount Technology By Rudolph Strauss. First pub­ lish-ed 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. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First pub­ lished 1989. 6th edition 1994. This just has to be the best reference book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order ❏ 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. semicustom electronics & data communications. 63 chapters, in paperback at $140.00. Radio Frequency Transistors Principles & Practical Appli­ cations. By Norm Dye & Helge Granberg. Published 1993. This timely 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 techniques, impedance matching & CAD. 235 pages, in hard cover at $85.00. Newnes Guide to TV & Video Technology By Eugene Trundle. First pub­ lish-ed 1988, reprinted 1990, 1992. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 432 pages, in paperback, at $39.95.  Title Price  Newnes Guide to Satellite TV  Servicing Personal Computers  The Art Of Linear Electronics  Optoelectronics: An Introduction  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Surface Mount Technology  Electronic Engineer's Reference Book  Radio Frequency Transistors  Newnes Guide to TV & Video Technology $55.95 $59.95 $49.95 $55.95 $55.95 $59.95 $99.00 $140.00 $85.00 $39.95 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 February 1996  53 SERVICEMAN'S LOG The dingiest corner of a dingy room I have a story about another long-in-thetooth set this month – one with a nasty sting in its tail. And the situation wasn’t helped by having to work in an anything-but comfortable environment. The set in question was a Pye model 48SL1, a 48cm set, fitted with what Pye called a T38 chassis. It was, in fact, a Philips KT3A-1 chassis, one of several Philips KT3A chassis, some of which were live. The KT3A-1 had an earthed chassis, however, and this particular model would be about 13 years old. It was owned by a lady and the complaint, as nearly as I could determine from her description, was a virtually 54  Silicon Chip complete failure which possibly involved a hiccuping condition. Well, that was fair enough and I didn’t anticipate that it would be a particularly difficult job. But there was one snag – the lady insisted that the job be done in her home; she didn’t want the set to leave the house. Don’t ask me why but she is not the first person I have struck who had a thing about not letting a set out of their sight. And, as I was to discover, the lady was rather eccentric in other ways as well. I try to avoid house calls if possible. It is impossible to take everything one is likely to need for the job and it invariably tran­spires that the one thing you do need is back at the shop. But the lady was insistent and, since she was willing to pay any additional costs, I agreed. The lady’s house turned out to be what was once undoubtedly a Victorian-style luxury home but which had seen better days. But what really struck me, even before I pulled the bell knob, was the modern security fittings. The door was fitted with heavy security bars, was obviously fitted with more than one lock, and every window was fitted with heavy security shutters. All of which should not have worried me except that, when I moved inside, I realised that the security Fig.1: the vertical output stage of the Pye 48SL1. The blanking pulse is derived from the junction of resistors R531 and R532 and is fed to line A51. Note the waveform at this point. to tackle a fault like that anywhere away from the shop, let alone in this Victor­ian chamber of horrors. Naturally, the lady protested at this suggestion but I explained, as politely as I could, that there was no alternative; I needed equipment and facilities which I simply could not provide in her lounge room. So, finally, she agreed, albeit reluctantly. Back at the ranch shutters not only kept out the burglars but kept out the light as well. It would not have been so bad if the rooms were reasonably well lit. However, I doubt that any of the light fittings boasted a globe larger than 40 watts. Again, I cannot explain why. I can only assume that it was an attempt to recreate what she imagined would have been the dingy atmosphere of the house in its heyday. It was a weird setup; the only thing that seemed to be missing was a black cat named Salem! But speculation aside, the result was that I found myself down behind the set, in the dingiest corner of a dingy room, hoping that I could manage to see what I was doing. In fact, when my eyes became dark adjusted, and with the aid of a hand lamp, I was able to find my way around without too much difficulty. These chassis are well laid out and this, cou­ pled with the fact that I am reasonably familiar with them, also helped. The hiccups And so to the problem itself. My original assumption was correct; the set was hiccuping madly, which invariably means an overload on the power supply due to a breakdown of some kind. But the question was, where? My first checkpoint was the main electrolytic capacitor, C298, off the bridge rectifier. This can produce symptoms like this if it dries out and, with a set of this age, it was a prime suspect. But no; it checked OK and there was about 350V across it, which was normal. I also made a routine check for dry joints but, as far as I could see, there was nothing obvious. The next step was to isolate the horizontal output stage and the quickest way to do that was to pull the deflection yoke plug, which carries a protective link. That cured the hiccups and allowed the main HT rail to come up to a steady 131V. So, the fault was somewhere in the output stage. I narrowed this a little, after replacing the yoke plug, by short­ ing the base and emitter of the output stage transistor, Q562. This also cured the hiccups. I spent some time checking various possibilities. I discon­nected the tripler and, in turn, the various auxiliary voltage rails off the output transformer secondary. And I went over the transistor stage itself, checking all the components around it. I even checked the output transformer for shorted turns but to no avail. And, remember, all this was done in the confined space and poor lighting I have previously described. I sat for a few moments and had a bit of a think. Somehow, my thoughts came back to the transistor itself (Q562). Perhaps it had a weird fault in it. I decided to pull it out and check it or, if necessary, replace it. I didn’t get that far. As I removed the transistor there was the fault staring me in the face; a black spot on the insu­lating washer, where the voltage had punched through. Fancy being caught with that old chestnut. I fitted a new washer, the hiccups vanished, and I had a picture on the screen. But it was a hollow victory; the top half of the picture was riddled with horizontal retrace lines. I baulked at that. No way was I going When I got back to the ranch, I hoisted the monster onto my workbench and set to work. Since it was obviously a vertical blanking problem, I went over the circuit to familiarise myself with the blanking circuitry. It is fairly straightforward really. A deflection pulse is taken off the vertical deflection output stage (Q530 & Q532) and goes to a pulse processing stage (Q535). This stage is biased so that it conducts only during the vertical flyback period and delivers a series of square pulses of about 1V amplitude to the blanking section (pin 9) of the chomi­ nance/luminance IC (IC192). At least, that is the theory of the circuit. And as far as I could determine, this was what appeared to be happening. There was an appropriate waveform at the vertical output stage and a replica of it, somewhat attenuated, at the base of the processing stage (Q535). And there were pulses out of Q535 being applied to pin 9. So why wasn’t the system blanking? The only clue I had – if it could be called that – was the discovery that the problem varied with the height control setting; reducing the height would eliminate the lines, as would increasing it beyond a normal setting. And that, if it suggested anything, point­ed to the vertical stage. As a result, I made a whole swag of checks around this stage, including changing transistors, likely electro­ lytics and any resistors which were marginally high. It was all to no avail. Next, I went back to the shaping stage and, in spite of what the CRO had told me, I changed transistor Q535. It wouldn’t have been the first time that such a trick had paid off, contrary to all the tests. But not this time. Nor did a detailed check of all the associated components. In a fit of desperation, I hooked up the CRO again and made another check of the waveforms around this February 1996  55 not contain much detail. It simply indicated a square pulse with an amplitude of 0.9V and this amplitude appeared to be correct. But the manual gave no indication of the pulse width and this was what I was now querying. It wasn’t an easy point to check. Apart from the lack of detail in the manual, the CRO wasn’t too happy trying to resolve the pattern. Pin 9 takes in both vertical and horizontal pulses and, while in theory one can resolve either one, Fig.2: the vertical blanking pulse from the according to the selectvertical output stage in the Pye 48SL1 comes ed timebase, this is not in on line A51 (bottom, centre) and is fed to always so in practice the base of Q535 via R540. The base bias on this transistor is set by R529 and R534. The and there was some processed blanking pulse at the collec­tor is difficulty locking the fed via D467 to pin 9 of the chrominance + image. luminance IC (IC192). Nevertheless, now that my suspicion was aroused, the CRO patstage. There didn’t seem to be any tern seemed to confirm it. And from doubt about the waveform into Q535 this observation came the thought that but closer examination of the pulses Q535 was not being turned fully on coming out made me suspicious. I during this portion of the waveform. could­n’t be sure they were exactly as That, in turn, directed my attention to they should be. The waveform given resistors R529 and R534, both 6.8kΩ. in the manual – waveform 32 – did These set the bias for this stage; 15V at the base – from the 30V rail – against 13V at the emitter. Suppose I reduced that 15V bias on the base? Suiting the action to the thought, I unsoldered one end of R534 and substi­tuted the nearest appropriate value to hand, which happened to be 10kΩ. And, presto! – the lines vanished. Problem solved? Well, fault cured, which is not exactly the same thing. Naturally, there was a temptation to leave the circuit like that, since it obviously worked. But I’m never happy with such situations. Was I simply curing the fault by brute force without actually finding it? While trying to decide how to resolve this question, the answer was almost literally served up to me on a plate – well, on the shop counter to be correct. It was another Philips set, this time with a KT3A-2 chassis, which is virtually identical. Its fault was simple enough and I soon had it up and running, which provided an excellent opportunity to make comparative voltage and waveform measurements. In fact, I didn’t need to go that far. As soon as I moved to this part of the set the answer was plain to see; R534 in this set was 8.2kΩ. And it was obviously the original component, which I subsequently confirmed by reference to the KT3A-2 circuit. I fitted an 8.2kΩ in place of my 10kΩ and it worked just 20 Electronic Projects For Cars Yes! Please send me ___ copies of 20 Electronic Projects For Cars Enclosed is my cheque/money order for $­________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Price: $8.95 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 the coupon to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 56  Silicon Chip Signature­­­­­­­­­­­­________________________ Card expiry date_____/______ Name _______________________Phone No (_____)____________ Street PLEASE PRINT _________________________________________________ Suburb/town _____________________________ Postcode_________ Fig.3: the power supply circuitry for the NEC N-3540. Note the “HOT” and “COLD” designations and the COLD secondary of T601. IC651 is at top left and portion of IC1001 at right. as well. Problem solved. Obviously, the fault I’d been chasing was not the first in this type of set. There must have been previous cases which had prompted this modification. Nor does it answer all the questions. Why did this set suddenly develop the fault when it had obviously performed satisfactorily for all those years? I can only assume that the original design was a bit mar­ginal, so that minor changes in components as the set aged were enough to tip the balance. Anyway, that was the end of the story. All that remained was to return the set to the dingy recesses of the customer’s abode. I hope I don’t have to go back, although it was a valuable lesson learned. Hot & cold NEC My next story is from the much more convenient and familiar atmosphere of my own workshop. It concerns an NEC colour set, model N-3450, the 34 indicating 34cm. It was fitted with a typi­cal infrared remote control system. According to the owner, the set was completely dead but he didn’t think there was much wrong with it, because the stand-by LED was on. He also indicated that he didn’t want to spend a great deal on a repair. Apart from the fault itself, the interest in the set con­cerns a rather unusual circuit arrangement. It is a live chassis arrangement but with considerably more of it being live than in most cases. And the circuit is clearly marked “HOT” and “COLD”, as appropriate – see Fig.3. Well, at least one is warned. As is usual, the mains connects straight to a bridge recti­ f ier and thence to a switchmode power supply, involving a trans­ former T601 plus a switching transistor and error amplifier in one package (IC601). The primary winding of T601 and one of two secondary windings is on the HOT side, but the other secondary is COLD. This provides a 20V rail via diode D650. Back on the HOT side, the output from IC601 is the main HT rail at 115V. This supplies the horizontal output section, con­sisting of horizontal driver transistor Q501, horizontal output stage Q502, and the primary of the output transformer, all still on the HOT side. The input to Q501 is from the main IC (IC701) via transformer T503, which has a COLD primary and a HOT second­ary. All the output transformer secondaries are COLD. Having digested all that, I turned my attention to the problem itself. The fact that the stand-by LED was on suggested that at least some part of the power supply was working. And, in fact, checks confirmed that the previously mentioned 20V and 115V rails were functioning. On the other hand, there was no horizontal waveform on any part of the horizontal system. This made me suspect that the fault could be in the remote control system; either the remote control receiver (PWC 3607C) or the microprocessor (IC1001) which it controls. In other words, the set was simply not being switched on. With the aid of the CRO, I established that the remote control receiver was working and delivering a signal to pin 14 of IC1001 (not the easiest path to trace on the circuit). However, there was no signal coming out on pin 33 of February 1996  57 YOU CAN AFFORD AN INTERNATIONAL SATELLITE TV SYSTEM SERVICEMAN’S LOG – CTD SATELLITE ENTHUSIASTS STARTER KIT 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: __________ Phone: (_______) ________________________ ACN 002 174 478 58  Silicon Chip IC1001 to switch the set on. The signal from pin 33 is applied to transistor Q1072, then to Q1071 to turn it on – see Fig.3. Q1071 functions as a voltage regula­tor, generating a 12V rail from the 20V rail. This 12V rail powers IC701 which contains the horizontal oscillator and this feeds horizontal driver transistor Q501. And that is how the set is turned on and off – by switching this 12V rail. With no 12V rail, there is no signal to drive the output stage or, in fact, any other function depending on IC701. Voltage checks OK, so why no signal on pin 33? It could be a fault in IC1001 of course but I wanted to check everything else before I pulled that out. And the first and obvious check was the voltage supplying this IC. It is a 5V supply, derived from a 3-terminal voltage regulator (IC651) operating from the 20V rail. Well, it was delivering voltage all right – too much vol­tage; it was closer to 8V than 5V. At the same time, I was prompted to look more closely at the 20V rail. In fact, that 20V figure is a nominal one. According to the circuit, it can vary from 22.4V on stand-by to 18.7V when the set is running. This is why I was deceived when I first confirmed that this part of the set was working. With the set switched off, that rail should have been at 22.4V, whereas it was slightly less than 20V, a value which had appeared to be close enough at first glance. But it was the 8V at the regulator output which was the real clue. I pulled IC651 out and replaced it. And that was it – there were now normal input and output voltages and the set was up and running. IC651 had broken down and was acting more like a resistor than a regulator, thereby placing a heavier load on the 20V rail and applying excessive voltage to the microprocessor. And it would appear that it was that excessive voltage which upset the microprocessor. The 5V rail feeds several pins on this IC and it is not surprising that the excessive voltage upset some of the internal logic functions. After all, it was not without good reason that the rail was regulated in SC the first place. 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 KITS-R-US PO Box 314 Blackwood SA 5051 Ph 018 806794 TRANSMITTER KITS $49: a simple to build 2.5 watt free running CD level input, FM band runs from 12-24VDC. •• FMTX1 FMTX2B $49: the best transmitter on the market, FM-Band XTAL locked on 100MHz. CD level input 3 stage design, very stable up to 30mW RF output. $49: a universal digital stereo encoder for use on either of our transmitters. XTAL locked. •• FMTX2A FMTX5 $99: both FMTX2A & FMTX2B on one PCB. FMTX10 $599: a complete FMTX5 built and tested, enclosed in a quality case with plugpack, DIN input •connector for audio and a 1/2mtr internal antenna, also available in 1U rack mount with balanced cannon input sockets, dual VU meter and BNC RF $1299. Ideal for cable FM or broadcast transmission over distances of up to 300 mtrs, i.e. drive-in theatres, sports arenas, football grounds up to 50mW RF out. FMTX10B $2599: same as rack mount version but also includes dual SCA coder with 67 & 92KHz subcarriers. Protect your valuable issues Silicon Chip Binders • AUDIO Audio Power Amp: this has been the most popular kit of all time with some 24,000 PCBs being •soldDIGI-125 since 1987. Easy to build, small in size, high power, clever design, uses KISS principle. Manufacturing rights available with full technical support and PCB CAD artwork available to companies for a small royalty. 200 Watt Kit $29, PCB only $4.95. AEM 35 Watt Single Chip Audio Power Amp $19.95: this is an ideal amp for the beginner to construct; uses an LM1875 chip and a few parts on a 1 inch square PCB. Low Distortion Balanced Line Audio Oscillator Kit $69: designed to pump out line up tone around studio complexes at 400Hz or any other audio frequency you wish to us. Maximum output +21dBm. MONO Audio DA Amp Kit, 15 splits: $69. Universal BALUN Balanced Line Converter Kit $69: converts what you have to what you want, unbalanced to balanced or vice versa. Adjustable gain. Stereo. • • •• COMPUTERS I/O Card for PCs Kit $169: originally published in Silicon Chip, this is a real low cost way to interface •to Max the outside world from your PC, 7 relays, 8 TTL inputs, ADC & DAC, stepper motor drive/open collector 1 amp outputs. Sample software in basic supplied on disk. PC 8255 24 Line I/O Card Kit $69, PCB $39: described in ETI, this board is easy to construct with •onlyIBM3 chips and a double sided plated through hole PCB. Any of the 24 lines can be used as an input or output. Good value. 19" Rack Mount PC Case: $999. •• Professional All-In-One 486SLC-33 CPU Board $799: includes dual serial, games, printer floppy & IDE hard disk drive interface, up to 4mb RAM 1/2 size card. PC104 486SLC CPU Board with 2Mb RAM included: 2 serial, printer, floppy & IDE hard disk $999; VGA •PC104 card $399. KIT WARRANTY – CHECK THIS OUT!!! If your kit does not work, provided good workmanship has been applied in assembly and all original parts have been correctly assembled, we will repair your kit FREE if returned within 14 days of purchase. Your only cost is postage both ways. Now, that’s a WARRANTY! KITS-R-US sell the entire range of designs by Graham Dicker. The designer has not extended his agreement with the previous distributor, PC Computers, in Adelaide. All products can be purchased with Visa/Bankcard by phone and shipped overnight via Australia EXPRESS POST for $6.80 per order. You can speak to the designer Mon-Fri direct from 6-7pm or place orders 24 hours a day on: PH 018 80 6794; FAX 08 270 3175. These beautifully-made binders will protect your copies of SILICON CHIP. ★ Heavy board covers with 2-tone green vinyl covering ★ Each binder holds up to 14 issues ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Just fill in & mail the order form on page 101; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. February 1996  59 Surround Sound MIXER & DECODER PART 2 – By JOHN CLARKE Last month, we described the circuit details for the Surround Sound Mixer & Decoder and gave the parts layout for the main PC board. This month, we complete the construction and give the test procedure. We’ll begin this month with the display driver PC board assembly – see Fig.5(a). Among other things, this board carries the four display driver ICs (IC12-IC15) plus four 11-way pin header sockets which make the connections to the display board. Begin by installing PC stakes at the external wiring points. This done, 60  Silicon Chip install the wire links, resistors, capacitors and diodes D1-D4, taking care with the diode orienta­tion. The four ICs (IC12-IC15) can now be installed, followed by transistors Q1-Q4. Trimpot VR1 (shown dotted) must be mounted on the underside of the board – see also Fig.6. Do not insert the pin headers yet; that step comes later when the display board is mounted. Fig.5(a) also shows the LED display board. Begin by soldering in the four 150Ω resistors. This done, the 40 LEDs can all be mounted, taking care to ensure that they are correct­ly oriented (the anode lead is the longer of the two – see Fig.3). Do not solder the LED leads yet, since the LEDs must all be later adjusted for height when the board is fitted to the front panel. Preparing the case The Surround Sound Mixer and Decoder is built into a cabi­net with a sloping front panel. This cabinet measures 170 x 213 x 31 x 82mm and is fitted with two self-adhesive labels. Begin by affixing the appropriate label to the rear panel, then drill pilot holes for the DC power socket, the RCA sockets and the 6.35mm stereo jack sockets. These holes can then all be Fig.5(a): install the parts on the display driver board and the LED display board as shown here. Do not solder the LED leads until after the board has been fitted to the front panel. carefully reamed to size. This done, mount the DC socket and the three top 6.35mm sockets in position. Once the rear panel is completed, the front panel can be prepared in similar fashion. Note that the holes for the LEDs and the display board Fig.5(b): these are the full size etching patterns for the display driver and LED display PC boards. Check the boards carefully for etching defects before installing any of the parts, as this can eliminate a lot of hassles later on. mounting holes should all be drilled to 3mm. The four mounting holes for the lid can be cut out using a knife and lightly finished using a reamer. Final assembly The major hardware items can now be fitted to the recommended case. Attach the small plastic feet to the underside of the case first, then install the main PC board. This board is simply slid into the bottom of the case so that the input and output sockets protrude through their matching holes February 1996  61 62  Silicon Chip Fig.6: shielded audio cable is used for most of the wiring from the main PC board to the front panel controls and the input sockets. Check the wiring carefully as it is installed, as it is easy to make a mistake which would be difficult to trace afterwards. in the rear panel. Attach the nuts to the 6.35mm sockets, then secure the board to the integral standoffs in the base using the self-tapping screws that come with the case. Cut each pot shaft to length before mounting all the pots on the front panel. The pots should all be oriented so that the markers on the knobs line up correctly with the front-panel markings. The toggle switches all mount towards the rear of the front panel. Once all the hardware items are in position, the LED dis­play board can be completed. First, mount the board to the underside of the front panel using four untapped 6mm spacers and 12mm-long screws, with the four 9mm tapped spacers used as nuts to hold the board in position. This done, push each LED into its front panel hole, check that the top surfaces are all aligned and solder the leads. Next, solder the 11-way pin headers to the underside of the display board, adjacent to each row of LEDs. Now plug the display driver board into these pin headers and secure this board to the tapped spacers using 6mm-long screws. Complete the assembly by soldering the pin headers to the driver board – see photo. Fig.6 shows the internal wiring details for the unit. Use medium-duty hook-up wire for the wiring to the display driver board and for the power supply connections. It’s a good idea to use red wire for the +12V wiring, green for the GND wiring, blue for the 0V wiring, and yellow for the DC socket and power switch (S7) wiring. The remaining wiring must all be run using shielded audio cable. This includes the wiring between the main board and all the pots, the top row of 6.35mm sockets and the remaining toggle switches. Keep these leads as short as possible while still allowing sufficient length for the lid to be opened comfortably and use cable ties to bundle them into neat looms – see photo in Pt.1. Test & adjustment Before applying power, check thoroughly for possi­ble wiring errors. This done, apply power and check the voltages on the main PC board. If all is well, there should be 12V between the +12V and GND terminals, while the GND terminal should be at about 5.45V with respect to the 0V rail. If these are incorrect, switch off power February 1996  63 immediately and locate the fault before proceeding. Assuming that all is OK, check that pin 8 of each LM833 IC (IC1-IC10) is at +12V with respect to 0V. You can also check the supply to the ICs on the display driver board (IC12-IC15). In each case, pin 3 should be at +12V. All other voltages are measured with respect to GND. Check the pin 1 and pin 7 outputs of IC1-IC11. These should all be within 100mV of the GND voltage. If all these voltage checks are OK, set VR1 to midway, then rotate it clockwise so that all the LEDs in each display are just extinguished. The mixer can now be tested with a signal. However, before doing this, it may be necessary to make up some adaptor leads; eg, leads with an RCA to mono 6.35mm plug and/or leads with an XLR socket to stereo plug. This latter adaptor is depicted in Fig.9. The rear panel carries the six phono input sockets, four RCA output sockets (L, R, C & S) and a power socket. This view shows the completed display board assembly, prior to installation on the front panel. Make sure that the LEDs are all correctly oriented. The LED display board in mounted on the driver board using 12mm spacers and the connections made via four pin header sockets. Fig.7: this full-size artwork can be used as a template when drilling the rear panel. + 12VAC IN A INPUT L INPUT C INPUT + + + L OUT + + C OUT B INPUT R INPUT S INPUT R OUT + + S OUT + + + 64  Silicon Chip Fig.8: this is the full-size etching pattern for the main PC board. Check the board carefully for etching defects by comparing it against this pattern before installing any of the parts. To test the unit, first secure the lid and rotate all level controls fully anticlockwise. This done, connect a signal to the Left input and adjust the output and left level pots so that a reading appears on the left bargraph display. Check that there is a 20dB change in level when switching between the LINE and MIC inputs. If the Left channel checks out OK, Fig.9: this diagram shows how to wire an adaptor cable with an XLR socket on one end and a stereo phono plug on the other. Be sure to use 2-core shielded audio cable. February 1996  65 4-CHANNEL + L + C MIC LINE + A-CHANNEL MIC + LINE SURROUND SOUND MIXER & DECODER B-CHANNEL MIC + LINE + R POWER S + OUTPUT INPUTS + C C + + 3 0 L LEFT PAN R L PAN R -3 -6 -9 + -12 + + -15 -18 CENTRE C PAN S C PAN -21 S -24 SIGNAL LEVEL (dB) L + C R S RIGHT + + + + SURR LEVEL LEVEL OUTPUT LEVEL Fig.10: this full-size artwork can be used as a drilling template for the front panel. you can test the Centre, Right and Surround channels in exactly the same manner. Now feed the signal source into the A channel input and check the opera66  Silicon Chip tion of the Pan and Level pots. Note the interac­tion between each channel as the knobs are rotated. This done, test the B channel in the same way. Assuming that everything checks out, you are now ready for some surround sound recording. You will probably need some prac­tice to get everything just right but the results SC will be well worth the effort. 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 New CD changers from Yamaha Yamaha Music Australia has introduced three CD changers which incorporate a new drive mechanism which allows the disc drawer to open fully, allowing removal and replacement of all five discs simultaneously. The three models, designated CDC-755, CDC-655 and CDC-555, also feature the company’s patented Play­Xchange system, which permits up to four discs to be removed and replaced while the fifth is still playing. The top of the range model CDC-755 incor­ porates S-Bit Plus technology and PRO-Bit processing, previously only available on Yamaha’s flagship CDC-845. According to Yamaha engineers, the new models are also quieter than in the past thanks to the new drive system. Newly designed and improved gear drives and roller mechanisms provide nearly silent disc drawer operation. PRO-Bit produces a more accurate and musical representation in the digital domain prior to the S-Bit Plus D/A conversion. The major advantage claimed for the 20-bit format is lower quantisation noise during the analog-to-digital conversion, which results in better sound quality for low amplitude signals. The output of the translator goes to a 22-bit 8-times oversampling filter, which in turn delivers the signal to a 22-bit to 18-bit noise shaper, and from there to Yamaha’s S-Bit Plus DAC and then to high quality analog output circuitry. Another new feature, incorporated in all three new models, is an “intelligent” digital servo system. The new circuitry uses a Yamaha-developed microprocessor to monitor the signal and adjust the laser pickup’s tracking and focus and the motor speed to EPROM writer can also operate from a PC printer port The “Leaper 3”, a new EPROM writer introduced by L&M Satel­ lite Supplies, can not only operate in the normal stand-alone A to B EPROM “copy” mode but also write an EPROM using data stored in a personal computer. A software driver and connecting cable are included to enable the Leaper 3 to operate from any PC paral­lel (printer) port. The device, measuring 160 x 110 x 45mm, can operate from a mains supply via a 9V/500mA supply (included) or from an internal battery (9V) for on-site EPROM burning. Along 72  Silicon Chip with 2732-27080 EPROMs, it will also handle a range of EEPROMs, Flash EPROMs and SRAM devices. Various function keys can be used to set the programming flow chart, voltages, pulse width and other par­ ameters. A 2-line, 16-character liquid crystal display ensures the operator is kept fully informed. For further information on this, or other EPROM writers in the Leaper range, contact L&M Satellite Supplies, 33-35 Wickham Road, Moorabbin, Vic 3189. Phone (03) 9553 1763; fax (03) 9532 2957. better compensate for disc warpage and dust. The new CDC-755 has been restyled and features Yamaha’s new, more rounded, front panel. It has a recommended retail price of $599. The new CDC-655 incorporates many of the features found on the more expensive 755 at $499 and features 10-key front panel operation. The model 555, priced at $399, incorporates the intel­ ligent digital servo system and S-Bit D/A conversion. For further information, please contact Yamaha Music Aus­tralia. Phone (03) 9699 2388, 1800 805 413, or fax (03) 9699 2332. Hand-held satellite GPS unit from DSE Global Positioning Systems have now reached the point where it is completely practical for bushwalkers, for example, to keep a unit in the back-pack. The Magellan GPS2000 Satellite Navigator from Dick Smith Electronics is small enough to hold in the hand (it’s about the same size as a mobile phone and weighs in at 283 grams), yet accurate enough to give you your position – anywhere in the world –to within a hundred metres or so. GPS units such as the Mag­ ellan rely on the US Department of Defence’s 24-satellite network which continuously update position information, ensuring very high degrees of accuracy. Unlike terrestrial or stellar navigation or positioning methods, the GPS­2000 is unaffected by cloud, fog or other similar barriers. The device can also be used to direct you from your current location to a position with known map co-ordinates, or you can store up to 100 “way points” and the GPS2000 will display the distance travelled, the remaining distance to travel, the speed and course direction. As such, The Magellan GPS2000 is certain to find a ready market amongst the boating and fishing fraternity (that favourite “hot spot” can be always found again and again). The unit is priced at $595 and is available from Dick Smith Electron­ ics stores. Second generation 2.5-inch hard drives A new “second generation” family of disc drives has been introduced by Hitachi Australia, offering high performance and sizes up to 1.3Gb. With a density of 450 bits per inch, they are 50% denser than Hitachi’s previous 2.5-inch models. The new drives have an operating shock resistance of 150G and a non-operating shock resistance of 250G’s, suiting notebook computers. They offer a 300,000 hour MTBF (mean time between failure) rating (approximately five years) and have a power consumption (for seek and read/write operations) of 2.0 watts. The DK212A series (height 19mm) is available up to 1.08Gb, while the DK222A series (height 12.5mm) is available up to 1.3Gb. Both types have an average seek time of 12ms and an ATA-2 interface. The drives are marketed through Hitachi distributors DCS Austra­lia Pty Ltd, phone (03) 9878 0344. February 1996  73 Programmable video generator The Black Star PVG100 Programmable Video Generator is a high performance instrument which enables virtual­ly all CRT monitors to be evaluated, qualified, tested and aligned. The instrument has a 2048 x 2048 pixel capability, with 1600 x 1280 pixels displayed at 16 colours from a palette of 16 million colours. The test patterns include text, grating, dots, horizontal and vertical lines, circles, colour bars, grey­s­c ale, check­e r­b oard and a border pattern, plus multiburst, purity, high voltage regulation and windows. The clock speed is 100MHz (135MHz optional) with a resolution of 100kHz. The non-volatile system memory incorporates 100 standard systems and allows for up to another 100 user-defined sys- tems to be programmed. Automatic sequencing of selected programs is available. TTL outputs for programmable sync and video are provided, along with analog outputs for both SMPTE and NTSC levels and an RS­232 interface for connection to a PC or terminal to allow remote programming. The front panel of the PVG1000 is laid out in a clear, easy-to-use format, making the instrument suitable for both production and servicing environments. All timing, parameters, patterns etc, are programmed from the front panel, while all system information is displayed on a 2-line LCD and status LEDs. The pushbutton keyboard ensures error-free setting and programming. For more information contact Obiat Pty Ltd, 129 Queen Street, Beacons­ field, NSW 2014. Phone (02) 698 4111, fax (02) 699 9170. Free quarterly EMC newsletter Schaffner’s EMC WORLD 12-page newsletter is distributed every three months and covers many EMC issues that are relevant to the new mandatory standards being introduced by many countries around the globe. A worthwhile feature is the guide to Electro­magnetic Immunity Standards, “Standards-UPDATE”, which lists the types of EMC test, the relevant IEC test number and a brief description of the test parameters. Other issues commonly covered are EMC instrument calibration/ certification, new products, application notes and new publications and handbooks. For further information on EMC WORLD, contact John Thompson, West­inghouse Industrial Products, Locked Bag 66, South Melbourne, Vic. 3205. Phone (03) 9676 8888. 74  Silicon Chip Loudspeaker design course at Sydney Uni Neville Thiele and Glenn Leem­ bruggen will be running a 26 hour loudspeaker design course during Semester 1 this year as part of the Sydney University Audio Program or as a standalone course. Some enrol­ ments may still be available – contact the Audio Program Coordinator on (02) 351 2686; fax (02) 351 3031. A new series of Megger testers Nilsen Technologies has released a new range of the famous brand "Megger" insulation and continuity testers – the BM120 series. The BM121, with a test voltage of 500V, will measure insulation resistance to 0.5MΩ, while the BM122 measures insulation resist­ance to 1MΩ (test voltage 1kV). The full measuring range is from 0.01MΩ to 999MΩ on insulation resistance and automatic dis­charge of the circuit under test is provided. They are protected against accidental connection to phase to earth volt­ages of 300V and 440V AC phaseto-phase. In addition, a warning signal will flash if the unit is connected to a circuit with more than 25V present. Continuity tests, which can be done hands free, have a maximum current of 200mA and an open circuit voltage of 5V. Continuity range is from .01Ω to 99.9Ω. The instruments are provided with automatic shutdown of power after five minutes of non-use. For further information, contact Nilsen Technologies, 150 Oxford St, Collingwood, Vic 3066. Phone (03) 9419 9999; fax (03) 9416 1312. STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids Proposed CD-erasable specifications Philips Electronics has announced proposed specifications for an erasable compact disc format, indicating significant progress in enabling companies to bring CD-erasable products to market in 1996. With a data capacity of up to 680Mb per disc, CD-erasable provides additional benefits to applications currently served by CD-recordable products. CD-recordable discs provide more Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 476-5854 Fx (02) 476-3231 permanent data storage, while CD-erasable allows data to be updated and disc space to be reused. CD-E drives will be capable of reading all existing CD formats. For more information, please contact Philips Electronics Australia Ltd. Phone (02) 925 3281 or fax (02) 929 SC 4784. TWO MORE UNBEATABLE OFFERS FROM MACSERVICE TEKTRONIX 100kHz to 1800MHz Spectrum Analyser System WAVETEK Signal Generator/ Deviation Meter Consisting of: 7613 Storage Mainframe Model 3000-200 incorporates a complete 1 to 520MHz FM, AM and CW Signal Generator with an FM Deviation Meter in one convenient instrument. 7L12 1.8GHz Spectrum Analyser Plug-In 7A17 Amplifier TR501 1.8GHz Tracking Generator TM503 3 Slot Mainframe $4250 Please phone or fax today for a full specification sheet incorporating all the system’s features. Frequency Range: 1-520MHz selectable in 1kHz steps; 1kHz resolution; frequency programmable via rear-panel connector. RF Output Level: +13dBm to -137dBm (1V to .03µV RMS); output level continuously adjustable in 10dB steps and with an 11dB vernier; impedance = 50 ohms. RF Output Protection: resettable RF circuit breaker; RF trip voltage = 5V RMS nominal; maximum reverse power = 50W. Specrtal Purity: harmonic output > 30dB below fundamental from 10520MHz; residual AM > 55dB below carrier in a 50Hz to 15kHz post-detection bandwidth; residual FM <200Hz in a 50Hz to 15kHz post-detection bandwidth (100Hz typical). Amplitude Modulation: internal 400Hz and 1kHz ±10%; external DC to 20kHz; range 0-90%; distortion 3% to 70% AM at 1kHz. Frequency Modulation: internal 400Hz and 1kHz (±10%); 50Hz to 25kHz; accuracy ±500Hz on x1 range, ±5kHz on x10 range; distortion 4% at 1kHz. FM Deviation Meter: frequency range 30-500MHz; input level range 10mV to 5V RMS; impedance 50 ohms; deviation range 0 to ±5kHz, 0 to ±50kHz MACSERVICE PTY LTD Australia’s Largest Remarketer of Test & Measurement Equipment 20 Fulton Street, Oakleigh Sth, Vic, 3167. Tel: (03) 9562 9500; Fax: (03) 9562 9590 $1250 **Illustrations are representative only. Products listed are refurbished unless otherwise stated. February 1996  75 Do you have an application for a remote control? If you do, then take your pick from these three units. Two operate at UHF, while the third is an infrared unit which can handle up to eight channels. All are inexpensive and easy to build. 3 Remote Controls The first of these units, operating in the UHF band at 304MHz, has been designed specifically for retrofitting central locking to a car but any project that requires a simple on-off control could use it. The second, also operating at UHF (304MHz), is a 2-channel unit. The compact keyring transmitter (50 x 35 x 15mm) has two buttons, each of which controls a latching relay in the receiver. The third unit is the 8-channel infrared remote control and it operates in the same way as the remotes for your TV, VCR or audio gear. Now to the nitty-gritty. Designs by BRANCO JUSTIC 76  Silicon Chip Remote Control 1 – Single Channel UHF T HE KEYRING TRANSMITTER case for the single channel transmitter is 57 x 30 x 12mm and has an 18mm dimple for your thumb. Very cunningly, there is no external pushbutton; you actually squeeze the two halves of the case together and this actuates the internal switch. A 3mm LED comes on when the unit is transmitting. The circuit, shown in Fig.1, consists of one IC, one transistor and a few small components. ly into the main PC board. Its output, pin 5, connects to the input (pin 14) of decoder IC1. For the receiver to acknowledge the transmitter, both units must be set to the same code; ie, the corresponding pins on the encoder and decoder ICs must be con­nected in the same way (high, low or open circuit). Provided they are identical the decoder output, pin 17, will go high (+5V) and clock IC2 whenever a valid code is detected. When power is first applied, IC2 is reset by C9 and R4, which causes pin 1 to go low. Conversely, pin 2 will go high, locking the doors. When IC2 is clocked, pin 1 will go high, oper­ating RL1 and RL3 for about one second and turning RL4 on. RL1 will unlock the doors and RL3 will flash the indicators if the relay is fitted and wired to these lights. RL4, if fitted, could be used to turn a car alarm on and off. It would be wired to turn the alarm off now. The next time a valid code is re- The keyring transmitter (above) is shown only slightly smaller than full size. This mates with the receiver (right). While intended for motor vehicle use, this remote control has many other applications. When SW1 is closed, power is applied via LED1 to encoder IC1 and also to L1, the feed to the oscillator. The code at IC1 pin 17 depends on whether the coding inputs are tied to pin 18 (high), pin 14 (low) or left floating. This code gates oscillator Q1 on and off, which results in bursts of 304MHz. If you look at the PC board pattern you will see that L1 is a conventional inductor but L2 is actually a loop of copper on the board. As well as being the oscillator tank coil, this loop is used as the antenna. L1 isolates the tank circuit from the bat­tery supply. The receiver (Fig.2) consists of a tiny pre-built, pre-aligned UHF receiver module with 12 pins that solder direct- Fig.1: the transmitter is based on encoding chip IC1 (AX5326) and a single transistor transmitter. It outputs a coded pulse stream which is interpreted by the receiver. The circuit fits neatly into the keyring case above. February 1996  77 Fig.2 (left): the receiver circuit may look complex but is mostly controlled by just three ICs. The various relays, along with their appropriate driver components, may be included or omitted to suit the application. ceived, IC2 will be clocked again. Pin 2 now goes high, pulsing RL2 for one second and locking the doors. R12 is a 2.2MΩ resistor and this will give a one second flash from the indicator lamps. PARTS LIST Single Channel UHF Transmitter 1 plastic case 1 PC board 1 12V alkaline battery 1 PC board mounting switch 1 AX5326 encoder (IC1) 1 BF199 NPN RF transistor (Q1) 1 3mm red LED 1 10µH choke Capacitors 2 .001µF ceramic 2 4pF NPO ceramic 1 2-10pF variable Resistors (0.25W 1%) 1 1MΩ 1 100Ω 1 22kΩ Single Channel UHF Receiver 1 PC board 1 UHF receiver module 2 or 4 SPDT 12V PC-mount relays Semiconductors 1 AX5328 decoder (IC1) 1 4013 dual D flipflop (IC2) 1 4093 quad Schmitt trigger (IC3) 5 C8050 NPN transistors (Q1Q5) 8 G1G diodes (D1-D8) 1 5.6V 500mW zener diode (ZD1) Capacitors 2 100µF 16VW PC electrolytic 6 0.47µF monolithic ceramic 1 .015µF ceramic Resistors (0.25W 1%) 5 2.2MΩ 5 4.7kΩ 2 1MΩ 1 3.3kΩ 4 10kΩ 1 22Ω 78  Silicon Chip If you want a longer indication, change R12 to 10MΩ, which will cause RL3 to operate for around five seconds when the doors are locked. With no voltage on the base of Q5 (as pin 1 of IC1 is now low), RL4 will be de-energised. This relay would now turn the car alarm on. The circuit shows the wiring for conventional locking systems with bidirectional motors. Fig.3 shows the method used to connect the relays for two wire motors. Assembly is reasonably straightforward, with some care being required when soldering the components on the rather small transmitter board. The transmitter overlay is shown in Fig.4 while the receiver layout is shown in Fig.5. Fig.3: if you intend to use the single channel remote in a vehi­cle with central locking, this circuit shows how the various connections should be made. Relay 4 in the receiver is not shown: this can be used to arm/ disarm the vehicle’s alarm system. This photograph clearly shows the mounting position for the pre-built UHF receiver module. While IC sockets were used in the prototype, they are not essential and, indeed, better reliability can often be achieved without them. Fig.4: compare this transmitter PC board layout with the photograph above when placing components. Fig.5: the printed circuit overlay for the single channel receiv­er, reproduced actual size. The antenna can be a short (say 250-500mm) length of insulated hook-up wire. Keep all component leads as short as possible, both on this board and on the transmitter. February 1996  79 Remote Control 2 – Dual Channel UHF T HE SECOND TRANSMITTER is shown in Fig.6. As mentioned previously, it has two momentary contact pushbuttons, either of which apply power to the encoder IC and the rest of the circuit. Note that the encoder chip used here is the same as for the single channel transmitter. Switch SW1 takes pin 13 (D3) of IC1 high, while SW2 takes pin 12 (D2) high. When a button is pressed, the IC outputs one of two different codes, depending on the linking of pins 1-8. The oscillator is similar to the one described in the previous transmitter. One button on this transmitter could be coded to operate the central locking unit previously described, while the other could operate an automatic garage door, using one channel of the receiver described below. Receiver circuit The circuit of the dual channel receiver is shown in Fig.7. This has a discrete component UHF receiver instead of the pre-built surface-mount receiver used in the single channel circuit of Fig.2. L1 and L2 are copper tracks on the PC board, with L1 being damped by resistor R1 to broaden its response. L2 is tuned to the trans­mitter frequency by variable capacitor VC1 and the signal applied via C3 to the base of Q1, a self-detecting regenerative UHF amplifier. The detected output appears at the emitter of Q1 and is coupled via the 4.7µF capacitor to the inverting input of IC1a. The 2.2kΩ resistor and the 470pF capacitor prevent any RF signals being fed into op amp IC1a. This has a gain of 214 and rolls off the Fig.6: the circuit for the dual channel transmitter is very similar to the single channel version but uses separate pushbutton switches to transmit two different codes. 80  Silicon Chip Fig.7: the dual channel receiver is more complex than the single channel version. It has two decoding circuits and a discrete component receiver is used instead of the pre-built UHF module. February 1996  81 PARTS LIST Dual Channel UHF Transmitter 1 plastic case 1 PC board 1 12V alkaline battery 2 battery contacts 2 PC board mounting switches 1 10µH choke Semiconductors 1 AX5326 encode (IC1) 1 BF199 NPN RF transistor (Q1) 2 1N914, 1N4148 diodes (D1,D2) 1 3mm red LED Fig.8: two switches, and therefore a slightly larger case, are required for the dual channel transmitter. Compare the PC board overlay above, to the photograph at right. Capacitors 1 0.1µF monolithic ceramic 1 .001µF ceramic 1 3.9pF NPO ceramic 1 2.2pF NPO ceramic 1 2-10pF variable Resistors (0.25W 1%) 1 1MΩ 1 100Ω 1 22kΩ Dual Channel UHF Receiver 1 PC board 2 SPDT 12V PC relay Semiconductors 1 CA3401 quad op amp (IC1) 2 AX5328 decoder (IC2, IC3) 1 4013 dual D flipflop (IC4) 1 BF199 NPN transistor (Q1) 4 BC548 NPN transistor (Q2-Q5) 3 1N914, 1N4148 diodes (D1-D3) 3 1N4004 diodes (D4-D6) 1 15V 1W zener diode (ZD1) Capacitors 1 100µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 2 4.7µF 16VW PC electrolytic 4 0.47µF monolithic ceramic 2 .001µF ceramic 1 470pF ceramic 1 330pF ceramic 1 220pF ceramic 1 33pF NPO ceramic 1 15pF ceramic 1 1.5pF NPO ceramic 1 0.5-5pF trimmer Resistors (0.25W 1%) 1 4.7MΩ 1 33kΩ 3 2.2MΩ 1 22kΩ 4 1MΩ 7 10kΩ 1 470kΩ 1 6.8kΩ 4 220kΩ 1 2.2kΩ 1 100kΩ 1 100Ω 2 47kΩ 1 15Ω 1.0W 5% 1 39kΩ 82  Silicon Chip Fig.9: when constructing the receiver board, ensure that the component leads are kept as short as possible. Some resistors mount end-on to the board. response above 2.2kHz due to the 15pF capacitor across the 4.7MΩ feedback resistor. The following op amp, IC2b, has a gain of 23 and rolls off the response above 3.3kHz. The signal is then fed to Schmitt trigger IC1c, which cleans up any noise and interference on it. The final operational amplifier, IC1d, inverts the signal, making it the correct polarity for the decoders. Thus, the signal at pin 5 of IC1 is similar to that generat­ed by the transmitter. This is fed to two identical de­cod­ers – IC2 and IC3. One of these ICs has pin 13 connected to the +12V rail, while the other has pin 12 connected to this rail. Thus, SW1 on the transmitter will be decoded by IC3 and SW2 by IC2. Each output (pin 17) is fed to the clock input of one half of a dual type “D” flipflop, IC4. Each time the clock input goes high, the output (pin 1 or pin 13) will toggle (low to high or high to low), causing relays RLA or RLB to alternately latch or release. The outputs of IC2 and IC3 are “ORed” by D2 and D3 so that when either receives a valid code, the collector of Q3 will go low for about half a second. This could be used to actuate a buzzer or if the values of C12 and R24 are increased, a 12V globe could be switched on for a reasonable time. Building it The component overlay of the transmitter board is shown in Fig.8. Once again, the transmitter board is fairly compact and extra care should be taken with its assembly. By contrast, the receiver board depicted in Fig.9 should not present any difficulties. Some of the resistors stand vertically and they should be pushed right down against the PC board. The alignment procedure for each board is covered in the instructions supplied with the kit. Remote Control 3 – 8 Channel Infrared T HE THIRD OF THESE remote controls goes from the exotics of UHF at 304MHz to a more mundane infrared (IR) transmitting LED and an IR receiver module. But while the UHF remotes had only one or two outputs, the IR system has six momentary and two latching outputs available for controlling devices. The transmitter handpiece, branded Magnavox, measures 155 x 35 x 16mm. The eight buttons on it are labelled Tuner, CD, Track, Stand-by, Stop, Play and Volume up/down. When any one of the first six transmitter buttons is pressed, the corresponding receiver output (A-F) goes high momentarily. The Volume buttons toggle the G and H outputs; ie, latching them high on one press, low on the next. The transmitter circuit is shown in Fig.10 and as with the UHF circuits, there is not much to it; just an encoder IC and a couple of transistors to drive the IR light emitting diode, IRLED1. IC1, an SM5021B, uses a 455kHz ceramic resonator as the oscillator. This is divided internally by 12, giving near enough to a 38kHz carrier frequency which is gated on and off by the data. The pulse train appears at pin 15 and drives LED1 through Darlington transistor driver Q1, Q2. If several of these transmitters were to be used in the same vicinity, the coding links LK1 and/or LK2 could be fitted but otherwise they are not necessary. Receiver The receiver circuit is shown in Fig.11 and is almost as simple as the transmitter thanks to the use of IC2, a PIC12043. This device contains an IR receiver diode, an amplifier tuned to 38kHz, a bandpass filter, an AGC section and a detector circuit. Its output is a digital pulse train identical to that generated by the transmitter but inverted. Q1 changes the polarity to make it suitable for IC1, the decoder. Q2 and ZD1 regulate the input voltage to +5.7V, to prevent damage to IC2. The coding links LK1 and LK2, if fitted, must match those in the transmitter. The outputs of IC1 can only supply around one milliamp, so a buffer or Fig.10: the infrared transmitter circuit. Links LK1 and LK2 are coding links and are only required if another infrared remote is used in the same area. February 1996  83 Fig.11: only one relay driver is shown here for simplicity but each of the receiver outputs (A-H) requires a driver. Outputs A-F are momentary action, while G and H toggle. PARTS LIST Fig.12: very little assembly is required on the transmitter board. Watch the polarity of the infrared LED: its anode leg is longer than its cathode. Compare the overlay with the photograph at left. 8-Channel IR Transmitter 1 Magnavox handpiece (includes 455kHz resonator & IR LED) 1 PC board 2 AAA 1.5V batteries Semiconductors 1 SM5021B encoder (IC1) 1 BC548 NPN transistor (Q1) 1 C8050 NPN transistor (Q2) Capacitors 1 10µF 16VW PC electrolytic capacitor 2 100pF ceramic capacitor Resistors (0.25W, 1%) 2 1kΩ 1 4.7Ω 8-Channel IR Receiver 1 PC board 10 PC stakes Semiconductors 1 SM5032B decoder (IC1) 1 PIC12043 IR receiver (IC2) 2 BC548 NPN transistor (Q1,Q2) 1 6.2V 500mW zener diode (ZD1) Capacitors 1 100µF 25VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.47µF monolithic ceramic 1 .001µF ceramic Resistors (0.25W, 1%) 1 39kΩ 1 4.7kΩ 1 10kΩ 1 1kΩ 84  Silicon Chip Fig.13: the receiver board for the 8-channel infrared remote is very simple but take care to ensure that none of the outputs are shorted, as their holes are close together. relay driver (as shown on the receiver circuit) is necessary to interface each output to the real world. So if you want six momentary outputs, for example, you will need six relay drivers. The transmitter PC board is shown in Fig.12 while the receiver board is shown in Fig.13. These two PC boards are easy to build as there are very few parts. Additionally, there are no setting-up adjust­ments (apart from the SC coding links). Kit Availability These remote control kits are all available from Oatley Electronics, 51 Lansdowne Parade, Oatley West. Phone (02) 579 4985. The prices are as follows: Single channel UHF transmitter ..............$10.00 Single channel UHF receiver (2 relays) ...$36.00 (extra relays $3.00) Two channel UHF transmitter ..................$18.00 Two channel UHF receiver ......................$26.00 (only 1 channel: $20.00) Eight channel IR transmitter ....................$18.00 Eight channel IR receiver ........................$18.00 COMPUTER BITS BY RICK WALTERS Test your reaction time using a PC Are you are one of those people who doesn’t believe your reaction time is affected by “a drink or three”. This simple reaction timer will correct that perception once and for all. This reaction timer uses a PC-compatible computer and a simple Basic program to generate an audio cue and/ or a visual prompt via the screen. It then measures the time delay before a key on the computer’s keyboard is pressed. Alternatively, if you connect a switch to the games port and fabricate the equivalent of a brake pedal, you can compare your hand and foot response times. When the software is run, the screen shows all the options that are available – see Fig.2. First, you can elect to have the trigger stimulus as an audible beep, a visual red rectangle or both. Second, either the keyboard (for hand reaction time) or the external switch (for foot reaction time) can be selected. And finally, you can choose between a single reaction time display or have the display show the last five reaction times and their average. The test is started simply be pressing the spacebar. The program now generates the cue (or stimulus) at some random time up to 10 seconds later, after which you press the spacebar again (or the foot switch) as quickly as possible. Your reaction time in milliseconds (a time of 160ms is pretty good) is then dis­played along the bottom of the screen. If you press the spacebar before the stimulus appears, the screen displays the message “No cheating – wait for stimulus”. The program We have elected to write the software in GW-BASIC, as virtually all computers will have a copy supplied with DOS. If you have Qbasic, you may need to allocate the odd line number for subroutines. A fully compiled version of the program is also available. The full listing is almost two pages long and the chances of errors creeping in, if you have to type all the code, are quite high. To overcome this problem, we have listed the minimum code which will allow you to measure your reaction time. This “simple” version provides for keyboard reaction time only and doesn’t display any screen options. The full listing with all the options and the fancy screen is available from SILICON CHIP on a floppy disc, This optional footswitch can be made up from scrap material and plugs into the games port of the computer. February 1996  85 The optional external foot switch is connected to the games port via a 15-pin male D-connector. Note that the Port A and Port B inputs are wired in parallel. This close-up view shows the switch mounting details, Virtually any heavy-duty pushbutton switch with normally closed contacts can be used. Fig.1: connect the leads to the 15-pin D-connector, as shown here. The other end of the cable goes to the switch. along with the compiled version of the program. Minimum version If you want the simple version only, it’s just a matter of typing in the listing published here. If this is the first time you have attempted to enter a Basic program, go back to the DOS prompt (C:>), change to the DOS directory (CD DOS), type GWBASIC and press ENTER. The screen should read something like this: Fig.2: the opening screen when the program is loaded. The test is started by pressing the spacebar and waiting for the stimulus. GW-BASIC 3.23 (C) Copyright Microsoft 1983 1984 (etc) 60300 bytes free OK The message on your machine may vary slightly from that shown above, depending on the particular version, but if GW-BASIC is present you are ready to begin. Start by typing the first line at the cursor; ie, 10 REM REACT1.BAS #1.0 R.W. 20/09/95. At the end of each line 86  Silicon Chip Fig.3: the reaction time is listed immediately below the visual stimulus (if selected). Pressing the Esc key allows you to change the operating setup. press ENTER. Don’t worry if one or two long lines get to the righthand edge of the screen – just keep typing. The line will wrap automatically. When you have finished, or are tired of typing, finish the current line, press ENTER, then type “SAVE C:REACT1”,A then press ENTER, or if using a different drive, substitute that drive letter for C. Note that the “A” suffix saves the file as ASCII text, so that you can read it on a word processor. If this suffix is omitted, the file would be saved in GW-BASIC format which appears on the screen as “garbage”. To run the program while in Basic, type RUN and press enter. If you have made any typing errors, the program will stop and give you a message telling you the line number where the problem occurred. The usual troubles are commas for colons, one pair of quote marks omitted, or a missing bracket. You don’t have to retype the line, just move the cursor along with the right arrow, until you reach the problem, overtype with the correction and press ENTER. You don’t even have to go to the end of the line. To exit from Basic, just type SYSTEM. To run the program at a later time, type GWBASIC REACT1. To quit the program, you just press the END key. Full version As mentioned above, the full version of the software allows you to select the games port, instead of the keyboard, as the stimulus input. To run the compiled (executable) version of the program, type REACTION at the DOS prompt. Alternatively, you can run the program in Basic by typing GWBASIC REACTION. We made a foot pedal using a heavy- duty pushbutton switch with normally-closed (NC) contacts, a right angle bracket, some bolts and nuts, and a couple of pieces of timber which were hinged at one end – see photos. The connection to the games port is made via a 15-pin male “D” connector, with the leads from the NC contacts of the switch wired as shown in Fig.1. Reaction Timer Listing (Simple Version) 10 REM REACT1.BAS #1.0 R.W. 20/09/95 20 GOSUB 1000 ‘Initialise 30 GOSUB 2000 ‘Generate random delay, store time1 40 GOSUB 3000 ‘Wait for keypress, store time2 calc. reaction time 100 GOTO 30 ‘Do it again 999 END 1000 ‘*********** 1010 ‘INITIALISE. 1020 ‘*********** 1030 DEFINT A-Z: DEF FNCENTRE$(M$) = SPACE$((80-LEN(M$))/2) + M$ ‘Centre text 1040 KEY OFF: CLS: SCREEN 9: COLOR 8,3 1050 DEF FNR = CSRLIN: DEF FNC = POS(X): DEF FNCEOL$ = STRING$(79FNC,” “) 1060 DEFSTR E,K: ESC = CHR$(27): ENTER = CHR$(13) 1070 KEYSP = CHR$(32): KEYEND = CHR$(207) 1080 LOCATE 2,25: PRINT “SILICON CHIP REACTION TIMER”; 1099 RETURN 2000 ‘********************** 2010 ‘GENERATE RANDOM DELAY. 2020 ‘********************** 2030 M$ = “Press SPACE-BAR to test, END to finish” 2040 GOSUB 5030 2050 IF K = KEYEND THEN CLS: SYSTEM 2060 IF K < > KEYSP THEN 2040 2070 LOCATE 23,22: PRINT FNCEOL$; 2080 LOCATE 25,1: PRINT FNCEOL$; 2090 RANDOMIZE TIMER: RANDNO = INT((RND*10)/2) + 1 2100 DEF FNSEC = VAL(RIGHT$(TIME$,2)) 2110 NEWSEC = (FNSEC + RANDNO) MOD 60 2120 WHILE FNSEC < NEWSEC: WEND 2130 TIME1# = TIMER: BEEP: RETURN 2199 RETURN 3000 ‘********************** 3010 ‘COMPUTE REACTION TIME. 3020 ‘********************** 3040 K = INPUT$(1) 3050 TIME2# = TIMER 3060 DELAY = CINT((TIME2# - TIME1#) * 1000) ‘milliseconds 3070 LOCATE 23,2: PRINT FNCEOL$; 3080 IF DELAY = 0 THEN LOCATE 23,25: PRINT “No cheating - wait for stimulus!”;: GOTO 3099 3090 LOCATE 23,22: PRINT “Your reaction time was”;DELAY;”milli­seconds”; 3099 RETURN 5000 ‘******************* 5010 ‘CLS & WRITE CENTRE. 5020 ‘******************* 5030 LOCATE 25,1: PRINT FNCEOL$;: LOCATE 25,1 5040 PRINT FNCENTRE$(M$); 5050 K = INKEY$: WHILE K = “”: K = INKEY$: WEND 5060 IF LEN(K) = 2 THEN K = CHR$(ASC(RIGHT$(K,1)) OR &H80) 5099 RETURN Software availability The compiled and Basic listings of the full version of the program (Reaction.exe and Reaction.bas) are available on a floppy disc from Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy 2097. The price is $A7 plus $A3 p&p (Aust., NZ & PNG; $5 p&p elsewhere). Payment may be made by cheque or money order. Alternatively, phone (02) 9979 5644 with your credit card details, or fax the details to (02) 9979 6503. Please indicate the disc size required (either 3.5-inch or a 5.25inch). SC February 1996  87 VINTAGE RADIO By JOHN HILL & RODNEY CHAMPNESS The basics of reflex receivers The reflex circuit gave many early valve radio receivers a substantial performance lift without the expense of an extra valve. Here, we take a look at the reflex circuit & explain how it works. Anyone who reads this column regularly will know that I am only a hobbyist with a keen interest in vintage radio. I have had no formal training in electronics and there are no letters after my name. But such a situation has been to my advan­tage. Because I lack a lifetime of servicing experience and a deep theoretical knowledge of radio, most of my stories are, at best, only semi-technical in content. However, this seems to be about the right mix to hold the interest of novice vintage radio repairers, of which there are many. When a collector friend, Rodney Champness, suggested that I write something on reflexing, my eyes glazed over a little and I mumbled incoherently in reply. Although I know the basic function of reflexing (using the one valve to amplify both radio and audio frequency signals simultaneously), writing a detailed account on the subject is quite another matter. This month, I would like to introduce Rodney to Vintage Radio readers and allow him to explain the function This timber cabinet Radiola Model 27 was the first of the Radiolette series to use a reflex circuit. Reflex receivers were common throughout the 1920s, 1930s and 1940s and were par­ticularly popular in Australia. 88  Silicon Chip of reflexing. If he is well received (excuse the pun), we may call on him again for an in-depth study of another subject. Reflexing of domestic valve radio receiver circuitry was more common in Australia than in other countries and was usually done to keep manufacturing costs down – particularly the economy sets. One of the most expensive components in early receivers was the valve and if the price of a valve could be saved while still retaining good performance, then it was well worth the effort. The reflex concept A reflex circuit has both audio and RF signals amplified in the one valve at the same time. Reflexing will only work where the two bands of frequen- Another reflexed Radiolette receiver. Reflexing gave a receiver a substantial performance lift without the expense of adding another valve but the circuit had to be carefully designed. Left: this little Peter Pan 4-valve radio is reflexed and its performance is quite outstanding. It also has excellent tonal quality for such a small receiver. Below: the diminutive 4-valve Philips Philette is a typical reflex receiver. It may have been small but it gave big performance for its size. cies are significantly different from each other. In some early sets, it was possible to find an RF valve acting also as the first audio amplifier. In later superhet reflex receivers, the IF valve would amplify both the IF signal and do the job of the first audio amplifier. In addition to this, the same valve could also be supplying the AGC and detection functions using its two inbuilt diodes – quite a busy little valve! Reflexing not only saved the cost of a valve but in battery receivers it saved LT (low tension) and HT (high tension) current as well. However, a reflex circuit can be quite a fickle beast if the operating conditions are not carefully selected. Quite often, reflexed stages did not use AGC as it would have upset the audio gain, caused distortion or accentuated the minimum volume effect. In reflex sets, the volume usually could not be reduced to zero (minimum volume effect) due to the com­pro­mise operating conditions. Reflexed stage valves also usually had to be replaced more often than valves in other stages, due to the Fig.1: block diagram of a reflexed radio receiver. The reflexed valve has a signal com­bin­­er at its input which combines the IF and audio signals, the combined signal then being fed to the valve for amplification. operating condi­tions not being optimum in some designs. However, these things aside, the reflex circuit is fascinating, effective and not deserving of the bad PR that it seems to suffer. A well-designed reflexed set works well and is no more critical of a valve’s condition than a set not using reflex circuitry. I have a couple of reflex sets, have worked on many others and find them no more tricky than conventional sets. Don’t be afraid of them – they are just another variation in design that sets have had over the years. To make things easier for those who have had little experience with reflex sets and find them hard to comprehend, the following may help to make February 1996  89 combiner which in turn applies it to the IF/audio valve. Here, the audio signal is amplified and then fed to the selective filter, after which it is fed to the audio output valve. Basically, that is all that occurs. A practical circuit The Astor “Football” was a 3-valve reflexed TRF receiver. The 6B8-G valve in the little Astor provided RF and AF amplification plus detection, so it was quite a busy little valve. reflexing a little more under­ stand­ able. Refer now to Fig.1 which is a block diagram of a reflexed radio receiver. The reflexed valve has a signal com­ bin­­er at its input. This combines the IF and audio signals, the combined signal then being fed to the valve for amplification. From there, the amplified signal is fed to a circuit which se­lects and directs the audio to the audio output valve. Similarly, the IF signal is selected and fed to a detector. Following the detector, the RF is filtered out and virtual­ly pure audio is applied to the signal combiner and thus to the valve. The circuit that selects and directs signals of differing frequencies in different directions can be called a diplexer or a selective filter. However, it may be easier to understand if it is explained as follows. The IF signal is applied via the signal combiner to the IF valve, where it is amplified and applied via a selective filter to the detector. The IF (RF) signal is then removed and the virtually pure audio is applied to the signal Refer to the schematic diagram of Fig.2. The valve used in the reflex circuit was often a 6AR7-GT in the octal days, while the 6N8 and 6AD8 were used more in the miniature valve days. These particular examples are duo diode variable mu pentodes. In most cases, AGC is applied to the valve, although gener­ally at a lower level than if it were to be used as a straight IF amplifier. There are two reasons for this. First, the valve may be taken into an operating area where its distortion is in­creased. And second, with AGC applied to what is the first audio valve, the volume may decrease with an increase of signal level due to the AGC action. The IF signal is applied to the grid in the normal way, although it will be noticed that C1 is much smaller than normal. It acts as a bypass for the IF signal but has little effect on the audio signal. After amplification by the valve, the IF signal is fed to the IF transformer primary as usual and by mutual inductance into the secondary and thence to a conventional diode detect­ or. On the primary side, C8 is again smaller than usual but still bypasses the IF signal at the end of the transformer to earth. Following the detector, the audio Fig.2: a practical reflex circuit. The valve used was often a 6AR7-GT in the octal days, while the 6N8 and 6AD8 were used more in the miniature days 90  Silicon Chip Fig.3: in some reflex sets, the audio is taken from the screen of the audio valve instead of from the plate. This circuit shows the basic scheme. K ALEX The UV People ETCH TANKS ● Bubble Etch ● Circulating LIGHT BOXES ● Portuvee 4 ● Portuvee 6 ● Dual Level TRIMMER signal with some IF signal imposed on it is fed to the volume control via an IF rejection filter. This stage consists of a resistor-capacitor network and is also used in non-reflexed sets. Now the interesting things occur! The audio level is picked off by the moving arm of the volume control and applied via C6 and R10 to the grid of the IF valve as an audio signal. C1 has little effect on the audio signal and the secondary of the IF transformer has even less effect. The audio signal is now amplified through the IF-cum-audio valve and the amplified signal impressed across plate load resistor R7. This gives an alternating voltage which is applied to C9 and thence through the network to the grid of the audio output valve. The audio signal is unaffected by the primary of the IF transformer in the plate circuit and capacitor C8 also has little effect on this signal. Note that many sets just apply the signal from C9 direct to the grid of the audio output valve. This is not a good move although some manufacturers did this and got away with it. In this circuit, R8 and C10 act as an IF filter to remove about 90% of the IF signal left after the filtering by C8. It is important that the IF signal be reduced to a low level as the audio output valve will amplify IF signals as well and these could easily feed back into an earlier stage. In addition, the output valve is driven harder than most other valves. If it is amplifying unwanted IF as well as audio signals, distortion/overload may occur well before expected. You will notice that R7 is much smaller than normal for an audio amplifier such as this (the values used are commonly 15kΩ, 22kΩ, 47kΩ and 68kΩ). This is because the valve must be run with a reasonably high voltage on the plate for efficient IF amplifi­cation. The audio amplification is lower than normal at around 12-15 times but is sufficient for the output valve to be driven quite hard, even on weak stations. The screen resistor value is within the normal range for a valve used as an IF amplifier. Not all reflex sets take the audio from the plate circuit of the IF valve. Some take it from the screen of this valve instead. In this case, the RF bypass capacitor is reduced to about .001µF and the normal bypass capacitor is swung across to feed the grid circuit of the audio output valve. Fig.3 shows a skeleton circuit of this. The plate circuit is as used in a non-reflexed IF stage. The audio gain remains much the same as for a reflex­ ed amplifier using the plate circuit to supply audio. In Fig.2, there are two circuit points marked “A” and “B”. If the “A” end of capacitor C6 is lifted and attached to “B” and C9 removed from that point, the set will revert to non-reflexed operation. Of course, the audio gain will be down as there will now be one less audio stage in the receiver. ● Ideal PCB DRILL ● Toyo HiSpeed MATERIALS ● PC Board: Riston, Dynachem ● 3M Label/Panel Stock ● Dynamark: Metal, Plastic ✸ AUSTRALIA’S NO.1 STOCKIST ✸ K ALEX 40 Wallis Ave, East Ivanhoe 3079. Phone (03) 9497 3422, Fax (03) 9499 2381 TRANSFORMERS • TOROIDAL • CONVENTIONAL • POWER • OUTPUT • CURRENT • INVERTER • PLUGPACKS • CHOKES Parts count If you look carefully at the parts used in a reflexed set and a set with two normal audio stages, you will find that there is very little difference in the number of passive compon­ents. The valve is really the only extra part. As pointed out earlier in the article, valves were much more expensive than capacitors and resistors, so reflex sets had a small following right throughout the valve era. However, with the advent of the transistor, the need to use reflex circuitry became unnecessary. Semiconductors are cheap and using an extra transistor or so is SC no hardship. STOCK RANGE TOROIDALS BEST PRICES APPROVED TO AS 3108-1990 SPECIALS DESIGNED & MADE 15VA to 7.5kVA Tortech Pty Ltd 24/31 Wentworth St, Greenacre 2190 Phone (02) 642 6003 Fax (02) 642 6127 February 1996  91 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. Power problems in the boondocks Living as I do right at the end of SEQEB’s power grid, the continuity of mains supply can best be described as fortunate; ie, fortunate if it stays on without ‘blips’ every 10 minutes or so. I know exactly what’s going on at any given blip; who’s just started which irrigation pump, roughly how far away and how intense the pending storm is going to be and so on. Trouble is, my PSU & motherboard know all these things too ... which isn’t exactly conducive to smooth computer opera­tions. Now whilst I’ve taken all the normal steps to iron out most of the spikes and blips on my mains feed to the PSU & moni­tor, the inclusion of a mains filter/surge buster is no match for a ‘good’ blip, which might see the mains voltage drop below 220VAC for up to five seconds. Obviously, what I really need is an uninterruptible power supply (UPS but the cost of such units relegates them to the wish of dreams. Did you ever do a UPS project by chance? If not, would you consider doing so? Whilst most folk who live in or around a city might deem such things as luxurious accessories, out here in the country at the ends of the electrical tendrils, they’re almost a necessity if you run a computer. I imagine it’s a Reversing switch for Railpower Mk.1 I am using two Railpower Mk.1’s (as published in the April & May 1988 issues of SILICON CHIP) on my HO layout. I now require to add additional controllers, hence I would like to upgrade to the Railpower Mk.2. But . . . I have a reversing loop and when the loco is in the loop, I currently flick from forward to reverse without slowing down, so that the loco comes out of the loop reversed and 92  Silicon Chip similar story in most other country locations too. The other thing I wanted to say was about the model train projects, specifically, the sound simulator projects. I used to have a model train layout in my youth and wish I had all these new sound effects and other doo­ hickies back then. However, it occurred to me that whilst you’ve presented projects for whistles, horns, bells, diesel and steam engine sounds, there’s no such project to recreate the wonderful electric whining of modern day real-life electric locos, especially the sound of the traction engines as they back-EMF to a halt. It’s not important as such, but I figure if one never airs one’s ideas, they might never get heard. I think the sound of these big ’leccy motors is really something else. I always sit above a drive bogie when I travel by train. (D. M., Rathdowney, Qld). • We have not designed a UPS project. We don’t really think it practical as the kit would almost certainly be more expensive than equivalent commercial units, particularly when the cost of batteries is included. In fact, we are inclined to the view that if you have unreliable power then you would be better off with a laptop computer. That might seem like an expensive luxury but it really does solve the problem of unreliable mains voltage. at the same speed. It would seem that this is not possible with the Mk.2 without slowing down. Your comments, please. (M.A. Ferntree Gully, Vic). • Your assumption is correct. The Mk.2 must come to a stop before changing direction. There is no way this can be changed. One possibility is to wire an additional changeover switch to alter the track polarity while in the loop. However, if this is not possible with your layout, you will have to stay with the Mk.1. Sound effects really do add to model railway operation but trying to simulate the sound of electric motors under dynamic braking would be rather tricky. It could be done but it would probably require a microprocessor to do it. Using fax/modems in computers I use an external fax/modem (Net­ comm AutoModem E7F) with my 586-75 PC. I am frustrated by the fact that the PC must be left on in order to receive faxes that I only expect once or twice a month. Is it possible to make a device to automatically switch the PC on when an incoming fax signal is detected? If not practical (due to boot up time?), is there a way to drastically cut power consumption of the PC in a standby mode? I also own a television without remote control but I am able to operate it remotely via the VCR remote control, except for muting. Is there a simple single function IR transmitter and receiver kit that could be put in the audio line from VCR to TV to cut the audio signal during commercials? (S. G., Gooseberry Hill, WA). • Apart from using one of the latest PCs which has power management, we cannot think of any easy way to overcome the delay in boot up each time a fax call comes in. However, we suggest that you at least turn the monitor off, if you are not already doing so. Check this month’s feature article on remote controls. The single channel version will do the job of switching the audio line to your TV. Modified Dolby decoder has distortion Help! I constructed the original Dolby decoder published in December 1994 and it works fine. I now wish to upgrade it by adding the power amplifiers described in the November & December 1995 issues. I have constructed the power supply and three amplifiers Woofer Stopper with standard speakers Will the Woofer Stopper described in the May 1993 issue of SILICON CHIP work with normal tweeters, normal woofers or stereo/hifi speakers? I thought that if I could use one the hifi speakers, I wouldn’t need to have an extra speaker around my house. (J. M., Glen Huntly, Vic). • You can use a conventional speaker or tweeter with the original Woofer Stopper circuit but we would not recommend it. For a start, the current drain from the according to the circuit diagrams but when connected to the surround outlet terrible distortion results! I have tried several modifications to the input of the LM1875, including the addition of a 1MΩ resistor according to the manufacturers’ recommendations, as per page 212 of the Dick Smith catalog circuit. I have fiddled around for some hours now and am completely at a loss to know what to do next. (A. W., Sunbury, Vic). • The 1MΩ resistor is superfluous in this situation. We suspect that the earth connections are faulty. Note that the original Prologic circuit had only a single supply rail to op amp IC4. The pin 11 supply connection was made to ground. The Prologic Mk.2, however, has a split supply for these op amps (now IC4 and IC5). Note that the surround power amplifiers IC8 and IC9 do not have their signal earths connecting to the centre input earth on the PC board. They were earthed via the shielded cable. Ensure that all earths are connected. Jacob’s Ladder has only one spark I am having trouble with the Jacob’s Ladder project as published in the September 1995 issue. According to the article, the spark should climb the wires with one spark following the other but no matter what I try I can only get a single spark which climbs to the top, and then starts at the bottom again. I wonder if your technical staff could suggest what I might have done battery will be considerably higher and you will probably need to fit heatsinks to the Mosfets. Tweeters would be better than just ordinary speakers because of their improved high frequency response. Don’t use a low frequency driver (woofer) because its response at 20kHz is non-existent. In general though, we strongly recommend that you use only piezoelectric tweeters because of their efficiency and low current drain. Note that the Woofer Stopper Mk.2 described this month must not be used with conventional speakers or tweeters. wrong to cause this problem. (A. P., Wingham, NSW. • As outlined in the text, there is only one spark discharge at any one time although the sparks are produced at about 130 per second. As you have found, the spark discharge starts at the bottom and then climbs up and then restarts at the bottom again. Earth loop in VCR/ stereo connection I have a video and TV setup next to my hifi unit. I would like to connect a cable from the audio output of the video player to an input on the amplifier. It seemed straightforward enough until I tried it. I was rewarded by a good audio signal and a lot of hum. I haven’t measured it but I am sure it’s mains hum. The only way to stop this hum is to disconnect the TV antennas. What do I do? On another question, I have analog and digital multimeters but neither of them has a battery testing setting on them. I believe batteries should be tested under load. What is a good load and what voltages should be expected for a good cell? G. E., Armidale, NSW). • It seems likely that both your VCR and TV set are double-insulated but the antennas (or masthead amplifier) are earthed; hence the earth loop involving your earthed stereo system. The way around this is to break the earth connection in the antenna cable to your VCR and this can be effectively done with a 1:1 balun. You can wind this yourself using a balun and a few 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.ozitronics.com Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a dis­tinctive 2-tone green vinyl & will look great on your bookshelf. Price: $A11.95 plus $3 p&p each (NZ $8 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. February 1996  93 turns of light gauge enamelled copper wire for each winding. As far as battery testing is concerned, the ideal load for a particular battery really depends on your application. A battery intended for use in a torch will have a far greater operating load (and high current demand) than one intended for use in a remote control handpiece. In practice, a useful load for typical single cells and 9V batteries is one which draws about a watt or so. Hence, for a single AA cell, you would need a resistor of about 2.22.7Ω, with perhaps lower values for C and D size cells. In fact, a good D cell should comfortably deliver 1A or more for a short period. Under the above load condition, a 1.5V cell should deliver at least 1.2V; the more, the better. For a 9V transistor battery, the load should draw about 100mA and this means a resistor of around 82Ω. Under these conditions, we would expect a good battery to deliver at least 7.5V; again, the more, the better. By the way, these load tests should only be applied for a few seconds or so; anything more will needlessly SC discharge the battery. SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 Notes & Errata POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). 94  Silicon Chip ✂ Street ___________________________________________________________ Prologic Surround Sound Decoder Mk.2; November & December 1995: The +5V and GND connections for the microprocessor board (01409954) are shown transposed on the overlay diagram on page 72 of the December issue. The wiring diagram on page 74 of the same issue needs to be altered so that wire “26” goes to the left pin while the wire from the power supply board goes to the right pin. Wires shown connecting to switch S4 are correct. Also, the reference to IC4 in the 7th line, third column on page 78 should be to IC6. Subwoofer Controller, December 1995: the circuit diagram on page 40 should show R34 directly connected to +12V to agree with the PC board overlay diagram on page 41; R34 does not connect to R7, C5 and pin 8 of IC2a as shown on the circuit. While the board will work, it ideally should be altered to agree with the circuit. D1 & D2 on the same board diagram are shown transposed although this has no effect on circuit operation. SC MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. ETI PIC Basic Interpreter: BASIC57/ XT/P $45, BASIC84/04/P $45. 2K EEPROM $8, 8K EEPROM $16. PC serial port driven. 18 and 28-pin PCB to suit $20, MAX-232 $10, 4MHz Xtl $5. Windows Software free. P&P $3. Visa-MCBC. Fax (03) 9338 2935. Don McKenzie, 29 Ellesmere Cr., Tulla­ marine 3043. Phone (03) 9338 6286 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) 482 3100 8.30-5.00 M-F. START WITH A MicroZed KIT then when your "test the market" small run project hits the big league, MicroZed can help with alternative schemes and quantities ex stock at the right pricing. 68HC705 DEVELOPMENT SYSTEM: Oztechnics, PO Box 38, Illawong, NSW 2234. Phone (02) 541 0310, fax (02) 541 0734. Email: info<at>oztechnics.­com.au WWW: http://www.hutch.com.­au./~ozt­ ech/index.htm. EDUCATIONAL ELECTRONIC KITS: Easy to build. Guaranteed to work. Good quality. Latest technology. Cheap. Good selection. LESSON PLANS FOR TEACH­ERS. Send $2 stamp for catalogue and price list. Log onto our bulletin board for full details. DIY Elect­ ron­ ics, 22 McGregor St, Numurkah 3636. Ph/Fax (058) 62 1915. E-Mail: laurie.c<at>cnl.com.au BBS (058) 62 3303. NEW SPRINKLER CONTROLLER KITS: RAIN BRAIN version uses ‘C8 and switch mode supply. Features galore!! Contact Mantis Micro Pro­ducts, 38 Garnet St, Niddrie 3042. Phone/fax (03) 337 1917. 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 & 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) 979 6503. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ ✂ FOR SALE _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ 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) 587 3491 Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ February 1996  95 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) 744 5440 or fax (02) 744 9280. COMPLETE WORKSHOP PROGRAM: suit IBM compatible 386 or better computer. Handles: Stock Control, Sales, Service Records, Debits, Credits, Faults, Service Manuals and Phone Directory. PCB ASSEMBLY SPECIALISTS ·ALL FACETS OF THRU-HOLE & SMT ASSEMBLY · ALL BATCH SIZES CATERED FOR · HIGH QUALITY BRM ELECTRONICS Highest a quality at able PO Box 727, Narrabeen NSW 2101. on ry ve reas price Ph/Fax: 9948 8807 Mobile: 015 101 682 MicroZed Computers To order or enquire: PO Box 634, ARMIDALE 2350. (296 Cook’s Rd) Ph (067) 722 777  Fax (067) 728 987 Mobile (014) 036 775 Credit Cards OK MEMORY * DRIVES * MODEMS SPECIAL! (Incl Tax) 1Mbx9 – 70ns Simm $60 1Mbx9 – 80ns Simm $45 SIMMS (Parity/No Parity) 4MB 30 PIN-70 $179 $185 4MB 72 PIN-70 $177 $148 8MB 72 PIN-70 $353 $303 16MB 72 PIN-70 $695 $605 32MB 72 PIN-70 $1389 $1210 EDO SIMMS 4MB (1Mbx32)-70ns $198 8MB (2Mbx32)-70ns $370 MAC 8MB P’BOOK $437 VIDEO MEMORY 256KX16 70ns (SOJ) $24 256KX16 70ns (ZIP) $58 LASER PRINTER MEMORY HP 2MB UPGRADE $156 CO-PROCESSORS 80387SX/DX to 40MHz $90 COMPAQ 8MB CONTURA AERO $445 TOSHIBA PORTEGE/SATELLITE 8MB / 16MB $650 / $1218 DRIVES SEAGATE 850MB EIDE 11ms 3yr $325 1080MB EIDE 10.5ms 3yr $360 2150MB SCSI 9ms 5yr $1033 MODEMS (Includes Sales Tax) 14,400 BANKSIA 5yr W $283 14,400 SPIRIT 2yr W $203 28,800 BANKSIA V.FC $321 28,800 SPIRIT V.34/V.FC $410 Phone for other products not listed EX TAX PRICING AS AT JANUARY ‘96 Sales Tax 22%, O/Night Delivery $8. Ring For Latest Prices. Credit Cards Welcome. We Also Buy And Trade-In Memory. PELHAM Ph: (02) 9980 6988 Fax: (02) 9980 6991 Suite 6, 2 Hillcrest Rd, Pennant Hills, 2120. Full price $399.00. For demo disk, phone or fax your details to (045) 71 1640. Jack Albers Electronics & Software Development. MicroZed HAVE LARGE STOCKS of easy to use and easy to learn controller boards with on board interpreters. Ideal for one offs and small run production. Altronics ....................................IFC Av-Comm.....................................58 Avico Electronics...........................9 BRM Electronics..........................95 Car Projects Book....................OBC Defence Force Recruiting............31 Dick Smith Electronics........... 18-21 Emona.........................................73 Harbuch Electronics....................75 Jaycar ................................... 45-52 Kalex............................................91 Kits-R-US.....................................59 Macservice........................3, 59, 75 MicroZed Computers...................96 Oatley Electronics.................. 34-35 Ozitronics.....................................93 Pelham........................................96 Railway Projects Book...............IBC RCS Radio ..................................95 SERVICE & REPAIRS PATRA ELECTRONICS: assembly and repairs of all kits. Repairs of electronic equipment. Call Peter on 02 718 1202 or 015 215957. NEW Micro Rod Irving Electronics .......... 67-71 Scan Audio..................................74 Silicon Chip Bookshop.................53 Software Sales House.................94 Tortech.........................................91 _________________________________ PC Boards 68HC11 F1 boards and now 80535 (up spec 8051) both boards with BASIC, FORTH, ASM, Small C 80535 board has 8052AH INTEL BASIC installed Printed circuit boards for SILICON CHIP projects are made by: 24 I/O expansion board now in stock for both boards • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. Versa Tech BASIC Stamp I and II TICkit – a 21 I/O PIC based controller Scott Edwards Electronics Get your project on the way in hours, not months. Accessories for Stamp and second source for Stamp 1 Recently developed accessories now available Advertising Index Send two 45c stamps for information package • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. Microprocessors For Silicon Chip Circuits We have stocks of the 68HC705-C8P pre-programmed micro­pro­cessor ICs for the Digital Effects Unit (Feb­ruary 1995) and the Remote Controlled Stereo Preamplifier (Sept.-Oct. 1993). Also available is the pre-programmed Z86E08 microprocessor for the Railpower Mk.2 Model Railway Controller. Price: 68HC705-C8P – $45 ea; Z86E08 $18 ea. Price includes postage. Payment by cheque, money order or credit card to: Silicon Chip Pub­lica­tions, PO Box 139, Collaroy, NSW 2097. Phone (02) 9979 5644; Fax (02) 9979 6503. 96  Silicon Chip Especially For Model Railway Enthusiasts Order Direct From SILICON CHIP Order today by phoning (02) 9979 5644 & quoting your credit card number; or fill in the form below & fax it to (02) 9979 6503; or mail the form to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. This book has 14 model railway projects for you to build, including pulse power throttle controllers, a level crossing detector with matching lights & sound effects, & diesel sound & steam sound simulators. If you are a model railway enthusiast, then this collection of projects from SILICON CHIP is a must. Price: $7.95 plus $3 p&p Yes! Please send me _______ copies of 14 Model Railway Projects 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____________