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New Series: Electronic Engine Management $4.50 OCTOBER 1993 NZ $5.50 INCL GST SERVICING – VINTAGE RADIO – COMPUTERS – AMATEUR RADIO – PROJECTS TO BUILD MINI DISC IS HERE! REGISTERED BY AUSTRALIA POST – PUBLICATION NO. NBP9047 Revolutionary new audio system records & plays back from a disc only 64mm in diameter SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.6, No.10; October 1993 FEATURES FEATURES   4 Darwin To Adelaide On Solar Power by Brian Woodward The 1993 World Solar Challenge   8 Electronic Engine Management, Pt.1 by Julian Edgar The advantages of electronic control 16 Mini Disc Is Here! by Leo Simpson All set to displace the analog compact cassette THE UNDER-BONNET view of a typical car has undergone dramatic changes in the last 10 years due to the introduction of electronic engine management. This month, in the first of a new series, we look at the advantages of electronic control of engine functions – see page 8. 28 Review: Magnet LS-621 2-Way Loudspeakers by Leo Simpson Compact 2-way bass reflex system 80 Programming the Motorola 68HC705C8 by Barry Rozema Lesson 2: addressing modes PROJECTS PROJECTS TO TO BUILD BUILD 30 Courtesy Light Switch-Off Timer For Cars by John Clarke Build it & avoid the dead battery blues 40 Stereo Preamplifier With IR Remote Control, Pt.2 by John Clarke Full circuit details plus a parts list 57 A Solid State Message Recorder by Greg Swain Low-cost unit comes as a pre-assembled module 66 FM Wireless Microphone For Musicians by Branco Justic Well-proven circuit has excellent frequency stability 70 Build A Binary Clock by Michael Vos A clock with no hands or digits SPECIAL SPECIAL COLUMNS COLUMNS 34 Computer Bits by Darren Yates Using DOS 6.0’s DoubleSpace HAVE YOU EVER not properly closed a car door & returned later to find that the courtesy lights had flattened the battery? This simple project will avoid the dead battery blues – see page 30. This new FM wireless microphone uses a well-proven circuit & has excellent frequency stability. We show you how to build it starting page 66. 58 Serviceman’s Log by the TV Serviceman Dead sets aren’t always easy 68 Amateur Radio by Garry Cratt, VK2YBX Judging receiver performance 86 Remote Control by Bob Young Servicing your R/C transmitter, Pt.2 94 Vintage Radio by John Hill Those never-ending repair problems DEPARTMENTS DEPARTMENTS   2   3 24 26 39 Publisher’s Letter Mailbag Circuit Notebook News Update Order Form 90 98 100 103 104 Product Showcase Back Issues Ask Silicon Chip Market Centre Advertising Index MINI DISC has been a long time coming but will be well worth the wait. It records on & plays back from a disc only 64mm in diameter & is likely to eventually displace the analog compact cassette – full details page 16. October 1993  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates, B.Sc. Reader Services Ann Jenkinson Sharon Macdonald Marketing Manager Sharon Lightner Phone (02) 979 5644 Mobile phone (018) 28 5532 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman, VK2ZLZ John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Philip Watson, MIREE, VK2ZPW Jim Yalden, VK2YGY 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: $42 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 1a/77-79 Bassett Street, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. PUBLISHER'S LETTER The technical aspects of modern blockbuster movies All right, hands up! How many of you have already seen the new blockbuster movie, “Jurassic Park”? A fair proportion of you, I’ll bet. By the time this issue goes on sale, “Jurassic Park” will have been shown in Australia for about three weeks and already will be ranking as one of the all-time best in box-office takings. I saw it just after it opened in Sydney and can state that I thoroughly enjoyed it. The realism of the recreated dinosaurs is quite incredible and the surround sound really does help the movie along. It’s well worth seeing. But forgetting all the hype for a moment, and ignoring some of the “issues” that some people are concerned about, such as the manipulation of genes and DNA, factors on which the movie is based, there is another aspect which should not escape observant readers of this magazine. For while Steven Spielberg has done a marvellous job of portraying prehistoric monsters, there are many technical aspects of his movie which just don’t stand up and I’m thinking particularly about electricity and electronics. For example, in a great many scenes of the movie, there are massive electric fences which are supposed to keep the prehistor­ic beasties safely corralled. Now I’m not giving away any of the plot to state that the way the fences are depicted is just plain silly – they couldn’t work in the way they are shown. And why do the battery operated cars which take visitors around Jurassic Park have to be guided around by two heavy rails? Haven’t the producers heard of buried wire guidance systems? In fact, there are many of these technical aspects in the film which are just plain ludicrous. You have to wonder whether anyone in Hollywood or anywhere else in moviedom knows how elec­tricity behaves when circuits are made or broken. The classic and oft-repeated examples of this are when a “super computer” in a film is somehow damaged and then sparks, smoke, flames and all the rest are emitted. In my experience, whenever a computer dies it expires quietly and then just sits there in an inert condition, perhaps accompanied by an unpleasant burning smell – not spectac­ular enough for the moviemakers. So by all means enjoy these blockbusters for their specta­cle – I’ll certainly go and see Jurassic Park again – but look for those other technical aspects which the general public never sees. Why not make an effort to spot as many of these kerfuffles as you can? It can add to the enjoyment of what is really just another monster movie. 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 MAILBAG Appliance servicing wanted I recently noticed a letter in the “Ask Silicon Chip pages entitled “More wanted on appliance servicing”. Hopefully your excellent publication will move deeper into this area in the immediate future. My concern in this area is for a simple accurate procedure for the recalibration of thermostat’s found in my wife’s cooking appliances such as Sunbeam frypans, sandwich makers, grillers, etc. Perhaps in the near future your team could find time to have a look at this situation. V. McMunn, Mermaid Waters, Qld. Comment: provided there is an adjustment screw, recalibration of your thermostats should be simply a matter of using an accurate thermocouple probe. Antenna tuners article I refer to the article by Garry Cratt on antenna tuners in the July 1993 issue of SILICON CHIP. The caption associated with Fig.3 states in part: “Both capacitors C1 & C2 are variable and are usually ganged together”. However in the actual circuit diagram shown, C1 is the tuning capacitor and C2 is the loading or matching capacitor. Under these circumstances C1 would normal­ly have a much lower value than C2 and as their functions are entirely different, it would be very unusual for them to be “ganged together”. Perhaps the Author was getting confused with the fact that often to get the larger value of capacitance required by the loading capacitor, manufacturers may gang two capacitors togeth­er. Doug Rickard, Upper Coomera, Qld. Comment: the caption is wrong, as you say, but it was our mistake, not the author’s. Checking transistors under working conditions I heartily enjoy SILICON CHIP, especially The Serviceman and Vintage Radio columns. However, I must take The Serviceman to task regarding the testing of semiconductors. In the story re­garding the Samsung model CB-518F, a fundamental error has been made. While the horizontal output transistor was tested and checked out good on the bench it was not tested under operating and voltage conditions. With modern day multimeters, it would be checked at approximately 9V at best which is a far cry from actual working conditions. I do agree it is difficult to check semiconductors with protective devices across the necessary junctions. I hope this clears up the doubt regarding the apparent soundness of the semiconductor in question. M. Gunning, Orange, NSW. Comment: the Serviceman is well aware that simple meter checks do not always tell the story. After all, he himself makes the comment that “it wouldn’t be the first time that such a transistor had cheated the testing procedure”. Old reference & data books I read your Publisher’s Letter in the July issue of SILICON CHIP and I heartily agree with you, particularly with regard to data books. Of particular importance are the old Fairchild books. Fairchild was bought (I think) by National Semiconductor and while NS are manufacturing some of the Fairchild parts, they are certainly not supplying data on all Fairchild parts. This is no help if you have to fix something that has a Fairchild part that no-one else covers. Old data books are the only way to find out what these bits are. Also, some manufacturers do not release data on all their current devices every time they publish new books. The new data books are basically updates, giving data only on new devices. The current Burr Brown “Integrated Circuits Data Book, Volume 33” was published in 1989. The “In­ tegrated Circuits Data Book Supplement Volume 33c” (1992) is just about the same size, with little duplication. It seems that cost is the most probable motive behind this, which is fine. P. Denniss, Sydney, NSW. October 1993  3 Not only does the Cd have to be low, but the driver has to be fit to cope with high temperatures (typically over 50°C in the cockpit). Toyota’s head driver is a champion tri-athlete. Darwin to Adelaide on solar power By the time you read this, competitors in the 1993 Daido Hoxan World Solar Challenge will be making their final prepara­tions for a gruelling race. 55 vehicles are expected to start in Darwin on Sunday, 7th November. The winning vehicle is expected to take approximately five days to reach Adelaide, travelling at more than 70km/h over the distance of 3004 km. By BRIAN WOODWARD 4  Silicon Chip Some of the world’s largest companies, including car makers and famous educational institutions, are involved in the race. The World Solar Challenge is held every three years. The inaugural event in 1987 was won by the GM Sunraycer. General Motors in the United States went on to develop the Impact, a prototype electric commuter vehicle designed for everyday public use, using technology and knowledge gained in the World Solar Challenge. General Motors-Holden’s remains the only Australian manu­ facturing company to sponsor the World Solar Challenge. As well as being the event’s official vehicle supplier, Holden’s sponsor­ ship extends to aiding two Australian universities and two schools with funding and support vehicles. The sponsor for the 1993 World Solar Challenge is Daido Hoxan Inc, the leading supplier of industrial gases in Japan. Daido Hoxan is also involved in frozen foods, medical equipment and solar power. The company competed in the first two World Solar Challenges. Official suppliers and supporters of the event are the Australian De­ partment of the Environment, Sport and Territories, the Northern Territory Government, General Motors-Holden’s, United States Department of Energy, Australian Department of Primary Industries and Energy, GS Batteries, Sumitomo Corporation, Sumitomo Marine, JTB Travel, Omega, and the Government of South Australia. Of the 55 entries, Japan has the most with 24, including Honda, Nis­ san, Hokkaido, Toyota and Kyo­cera. There are 12 en­tries from the USA, mostly universities, while Australian entries include Dripstone High School, Monash University/Melbourne Uni­ versity, NT Institute of TAFE, NT University, Mitcham Girls High School, Aurora Vehicles Association, Mor­ phett Vale High School and Meadow­ bank TAFE. From England, there are three entries: Battery Vehicle Society, Solar Flair/Phil Farrand and TR50/J G Riches. Caught at the side of the road during shakedown trials on the Stuart Highway in the Northern Territory in February this year, the Toyota team checks vehicle functions. This model Toyota (now believed to have been scrapped in favour of a more advanced car) has single rear left wheel drive using a DC chopped motor and a toothed rubber belt. The Silver Zinc batteries from Eagle Picher in the USA typically cost $40,000 for a maximum of 5kW. They can be cycled on 10 to 20 times after which they are only good for making cutlery! Actually, two important automotive sporting events start on the same day, (7th November). One is the Adelaide Formula One Grand Prix and the other is the World Solar Challenge. Cars in the Grand Prix will run out of fuel in two hours, after covering just 306 kilometres. Competitors in the World Solar Challenge will race on for another four days and cover almost 10 times the distance and sunlight will be their only fuel. The World Solar Challenge has spawned many similar events in other countries, especially in Europe, Japan and the USA. But no other solar electric car event has yet equalled the rigid rules, the distance, nor the gruelling conditions of the world’s toughest solar race. Last time it was won by the team from the Engineering School of Biel in Switzerland. The 1987 winner, GM’s Sun­ raycer, averaged 66.92 km/h. Its record still stands. Car companies have taken the event very seriously this year, in the knowledge that winning the race will given them an enormous advantage marketing cars in the USA, particularly in California when the new zero emissions regulations are about to take ef­fect. Cars will be scrutineered for safety and compliance with the regulations before the event begins. All cars must have a minimum speed Solar race cars are permitted a solar array no larger than eight square metres. This car capability of 38km/h and has used the area on a body shape known as “modified cockroach” after the first winner the winning car is ex­pected in 1987 – the GM SunRaycer which used a full cockroach shape. At 15-20% efficiency, the average more than 70km/h. cells can then gather 1.2-1.5kW to propel the vehicle. October 1993  5 Electronic Engine Management Pt.1: Introduction – by Julian Edgar In some respects, the internal combustion engine which powers cars has barely changed in design over the last 80 years. As far back as the 1920s, some Alfa Romeo engines boasted twin overhead camshafts, six cylinders and supercharging. An engine designer from that early period (if brought back to life!) could look at the internals of a 1993 engine and instantly recognise almost all of the components. So if little fundamental mechanical change has occurred, why has the under-bonnet view of a typical car undergone such a dramatic change over the last 10 or 15 years? Engine management The answer to that question includes A BMW Motronic electronic control module. All modern cars make extensive use of electronic circui­try to control engine functions, to ensure maximum performance & economy. 8  Silicon Chip aspects like pollution control plumbing and the use of front-wheel drive. However, a major part of the change has been in the use of electronic engine management techniques. Electronic engine management is responsi­ble for governing fuel induction and ignition timing in all current cars, as well as controlling more exotic aspects in some machines like camshaft timing, turbocharger boost, inlet manifold tuning and automatic transmission control. The accuracy and resolution of these electronic control mechanisms has greatly improved the efficiency of the internal combustion engine, while the use of ram-tuned intake manifolds (which engine management allows) has revolutionised engine ap­pearance. In many ways, a current automotive engine is a strange mix of old mechanical technology and the very latest in electron­ic control techniques. The effectiveness of this approach can be seen by comparing an electronically-controlled engine with an engine produced 25 years ago. The examples contrasted here are the 1.8-litre overhead cam (OHC) engine used in the old Datsun 180B and the 1.8-litre OHC engine used in the 1988 GM Holden Astra. The old Datsun 180B engine used a single carburettor to control fuel/air mixing, with points, weights, springs and a vacuum canister controlling THROTTLE BODY FUEL PRESSURE REGULATOR CONTROL SOLENOID VALVE OXYGEN SENSOR THROTTLE VALVE SWITCH AUXILIARY AIR CONTROL VALVE FAST IDLE CONTROL DEVICE FUEL PRESSURE REGULATOR AIR FLOW METER AIR REGULATOR ROTOR PLATE COOLANT TEMPERATURE SENSOR CRANK ANGLE SENSOR INJECTOR IGNITION COIL Fig.1: this diagram shows the locations of the main components in the Holden VL Commodore engine management system. ignition timing. As Table 1 shows, power, torque, performance and fuel economy are all greatly improved in the engine-managed car, despite the fact that the mechanical design of the engines is very similar. Note that the power and torque figures for the Datsun are based on the then-current SAE system of measurement – widely regarded as being 10-15% optimistic compared to current DIN measurement standards. What is not shown by the table is that the modern car runs on unleaded fuel of a lower octane rating than the super petrol used in the older design. Exhaust gas pollutants are also much lower in the engine-managed car. Advantages Electronic engine management gives advantages over the use of carbies and conventional ignition TABLE 1 1972 Datsun 180B 1988 Holden Astra Type 4-door sedan 4-door sedan Mass 1000kg 1020kg 4-cylinder, in-line 4-cylinder, in-line Body Engine Type Volume 1770cc 1796cc 2-barrel carb. multi-point EFI Power* 78kW 79kW Torque* 146Nm 151Nm Induction POWER TRANSISTOR timing control in the fol­ lowing areas: power, torque, fuel econ­omy, engine responsiveness and exhaust gas emissions. Much to the surprise of early sceptics, electronic engine management has also proved to be very reliable in the field. This is partly because most engine management systems feature “limp-home” modes, which come into effect if a breakdown occurs in the system. In one BMW model, “limp-home” is a relative term – a top speed of 200km/h is allowed while lame! Electronic fuel injection Performance 0-100km/h 12.4 secs 11.0 secs Standing 400m 18.4 secs 17.6 secs Top Speed 165km/h 185km/h 11 litres/100km 8 litres/100km Fuel Economy * Datsun 180B figures use SAE measurement; Astra use DIN. Engine management systems used to be referred to as “elec­tronic fuel injection” (EFI) systems. Early fuel injection sys­tems were mechanical in nature but were quickly replaced with electronically-controlled injection. Initially, the fuel system remained entirely separate from the October 1993  9 then realised. As a result, all modern cars now run combined electronic fuel injection and ignition systems, thus giving rise to the overall term of “engine manage­ment”. Inputs & outputs Electronic engine management gives major power, economy & drive­ability advantages compared to carburettors, even sophisti­cated units like this Weber. ignition system. In fact, some early fuel injected cars ran an electronically-controlled injection system alongside an old points-and-weights Kettering ignition system. The 1974 BMW 3.0si, for example, ran an injection-only system – which still gave a 15kW power gain over the twin-carby version of the same engine. Manufacturers – with Bosch being the prime mover in the automotive electronics area – soon realised that the sensors being used to monitor the engine for the EFI system could also be used to determine ignition timing. The extra complexity and expense was relatively minor compared with the potential advan­tages which could be CRANK ANGLE SENSOR AIR FLOW METER FUEL INJECTION INJECTORS IGNITION TIMING CONTROL POWER TRANSISTOR IDLE SPEED CONTROL AUXILIARY AIR CONTROL VALVE FUEL PUMP CONTROL FUEL PUMP FUEL PRESSURE FUEL PRESSURE REGULATOR CONTROL SOLENOID VALVE SELF-DIAGNOSIS INSPECTION LAMPS COOLANT TEMPERATURE SENSOR IGNITION SWITCH THROTTLE VALVE SWITCH BATTERY VOLTAGE ECCS CONTROL UNIT AIR CONDITIONER SWITCH VEHICLE SPEED SENSOR OXYGEN SENSOR PARK/NEUTRAL SENSOR Fig.2: inputs & outputs of the VL Commodore engine management system. The inputs are monitored by the control module which then controls the various engine parameters. 10  Silicon Chip All engine management systems can be analysed in terms of their inputs and outputs to and from the computer, or Engine Control Module (ECM) as it is referred to in automotive circles. Fig.2 shows a typical system, as used in the Holden VL Commodore 6-cylinder (Nissan) engine. Each input on the lefthand side of the diagram is used to sense a different engine operating parame­ter. For example, the Crank Angle Sensor indicates to the ECM where the crankshaft is in its rotation. This sensor is often mounted within the distributor. Another sensor known as the Airflow Meter indicates, by means of a varying voltage signal, the mass of air passing into the engine. And, as its name im­plies, the Coolant Temperature Sensor tells the ECM whether the engine is cold or hot. One of the more obscure inputs is the exhaust gas Oxygen Sensor, which compares the concentration of oxygen in the air with that in the exhaust gases, and indicates to the ECM the fuel/air mixture strength. The Battery Voltage is also used in some systems as one of the idle-speed control inputs – if the battery voltage is too low, then the ECM increases the idle speed to help recharge the battery! The outputs from the ECM in this relatively simple approach control mainly fuel injector pulse width and ignition timing. The fuel pressure in this system can also be electrically controlled – generally, it’s controlled mechanically by a pressure regula­tor. In this particular car, fuel pressure is increased during cranking if the engine coolant temperature is above 95°C. This prevents vapour-lock problems during hot starting. The Self Diagnosis function is very important. Because of the complexity in finding loom and sensor faults, almost all systems run a self-diagnosis output. When activated, this indi­cates codes which show that the system is fine, or that problems exist with certain sensors or wiring. In the Nissan system shown here, two LEDs mounted in the ECM box flash the codes. Other manufacturers This turbocharged, intercooled, four-valves-per-cylinder, 2-litre Subaru flat four engine has a maximum power output of 147kW. Without modern engine management techniques, such an engine would be impossible. use a “Check Engine” light mounted on the dashboard as the communications interface. Early EFI systems often didn’t have a self-diagnosis capability, which makes fault-finding much more difficult. Performance & economy An example of an engine management input sensor. This crankshaft position sensor is mounted at the end of one of the camshafts & uses an optical sensor to monitor the slots & holes cut into the spinning endplate. As an example of the upper extreme in current engine man­agement techniques, the Subaru Liberty RS Turbo uses a system with 14 input sensors and 12 output signals. A self-learning air/fuel mixture mode is used, where individual driving styles and engine wear are internally catered for. Separate coils di­rectly mounted on each spark-plug are used and a 3-dimensional ignition advance map is employed. The power output from the engine is 147kW and the 4-door car will acceler­ate to 100km/h in 6.7 seconds – faster than any of the tradition­al Australian “muscle car” V8s. This level of performance – matched with economy – from a 2-litre 4-cylinder engine would be simply impossible without full electronic engine manSC agement. October 1993  11 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 MINI DISC IS HERE! At long last, Mini Disc has been released onto the Australian market. Developed by Sony, Mini Disc comes in two forms –playback only & recordable. Both types have high quality sound, random access & up to 74 minutes playing time, all from a disc only 64mm in diameter. By LEO SIMPSON Sanyo’s MDG-P1 player is particularly compact & weighs a mere 250 grams. With shockproof memory & rapid track access, it will be the ideal player for people on the move. The Mini Disc has been a long time coming but will prove well worth waiting for. When the compact disc was released, a little over 10 years ago, it caused a sensation and now it has completely displaced the vinyl record from the marketplace. Mini Disc is claimed to have the same quality sound as the compact disc and is likely to eventually displace the analog compact cassette. Mini Disc is small, absurdly so. It looks like a tiny version of a 3.5-inch floppy disc except that the disc itself is a mere 64mm in diameter. The disc housing is 72 x 68mm and just 5mm thick. Like a 3.5-inch floppy, it has a metal shutter and this slides across to expose the disc to the laser pick-up when it is being played but covers it at other times. The play-only version of the Mini Disc uses the same opti­cal technology for data storage as the compact disc but the recordable version is a combination of optical and magnetic storage technology. Advantages of the new format Sony has really worked hard to address all the disadvantag­es of current tape recording formats while keeping the advantages of compact disc: long playing time, quick random access and excellent sound quality. The Mini 16  Silicon Chip Disc is aimed squarely at the analog compact cassette, a 30-year old medium which has been developed and refined so that it is now far removed from the original dictation machine cassette. The main market for the compact cassette is as a music medium for cars and Walkman-style players and its disadvantages are well known and are responsible for its steady decline. The sound quality of cassettes is perceived by most people to be poor (and it is poor when used in most run of the mill players), it has no random access facility and it cannot cope with shock or vibration. Nor can it accommodate the contents of the longest CDs which exceed 70 minutes in playing time. Mini Disc, the new medium, has been developed to hit the compact cassette where it hurts. It has excellent sound and can accommodate up to 74 minutes playing time, enough to record the contents of any CD. It has the same quick random access to any selection as a CD player and it goes one better – it has excel­lent resistance to shock and vibration. It is possible that the Walkman style Mini Disc player could be dropped and still the listener would hear no disruption to the music! And since the Mini Disc is just as convenient to handle as a floppy disc, it is less susceptible to damage than a CD. Anoth­er advantage compared to analog tapes is that it is not possible to record over a playback-only (pre-recorded) Mini Disc (because of the different formats). Finally, since the Mini Disc uses a non-contact method for recording and playback, Sony claim that, in principle, it can be played and re-recorded at least a million times. Since that could take more than eleven years, it is a claim that is not likely to be put to the test. New technology So how does this radically smaller recording medium achieve all these advantages? Sony has borrowed freely from current computer technology to produce the Mini Disc but as we shall see, Mini Disc will have important ramifications for personal comput­ers in the near future, since it stores far more than current floppy discs – up to 100 times more, in a much smaller format. Let’s talk about the playback-only Sony’s MZ-1 Walkman portable Mini Disc machine is tiny but is a high performance stereo recorder which also provides all the playback functions you would expect to find on a CD player. Mini Disc first, since it is the most closely related to CDs. Like the CD, the recording information (digital data) is stored in the form of pits which are read off the rotating disc by the laser pick-up. The data is read into a one megabit dynamic RAM chip at 1.4 megabits/second but since the following decoder circuitry only requires the information at a rate of 0.3 megabits/ second, the RAM chip acts like a large data buffer. This means that even if the Mini Disc player is jarred sufficiently hard for the laser pick-up to lose its place on the disc, it has plenty of time in which to find its correct position and resume playback. In the meantime, there is no disruption to the music. In effect, the laser pick-up could take up to three seconds of being disrupted and then resuming operation and still there would be no interruption to the music. Selective compression While the method of data storage on the Mini Disc is essen­ tially the same as the compact disc (ie, 44.1kHz sampling fre­quency, 16-bit A-D and D-A conversion), its smaller diameter means that it could only store about 10 minutes of stereo music if it used the same linear recording technique. Rather than increasing the pit density, which could lead to problems of reliability, Sony has adopted a system of data compression. Called ATRAC (Adaptive TRansform Acoustic Coding), it is similar in some aspects to the PASC data compression method used in the digital compact cassette (DCC). While CD uses 16 bits of data for every 0.02ms sample, re­ gardless of the signal amplitude (or even if there is no signal), ATRAC analyses the digital data for waveform content and encodes only those frequency components which are audible. Two psycho­a­coustic principles, “threshold of audibility” and “masking”, are taken into account in identifying those signals which are audi­ble. As most readers are aware, the sensitivity of the ear varies widely October 1993  17 120 SOUND PRESSURE LEVEL (dB) AUDIBLE 60 NOT AUDIBLE 0 200 20 1k FREQUENCY (HERTZ) 5k 20k Fig.1: this diagram illustrates two psychoacoustic principles on which the ATRAC data compression system relies – masking & the threshold of hearing. Sounds below the threshold of hearing are not recorded & frequencies which are close together can mask each other. 120 SOUND PRESSURE LEVEL (dB) AUDIBLE 60 NOT AUDIBLE 0 200 20 1k FREQUENCY (HERTZ) 5k 20k Fig.2: this diagram shows how the sound spectrum in Fig.1 would be recorded by ATRAC & thus a lot of data storage is avoided. with frequency, being most sensitive to frequencies around 3kHz to 4kHz, as shown by Fletcher-Munson curves. At higher and lower frequencies, the sensitivity of the ear is progressively reduced. Therefore, sounds below the threshold of audibility can be removed without affecting the reproduction at all. “Masking” is a less well-known principle whereby a loud sound can mask a soft sound at an adjoining frequency, provided it is within a range called the “critical bandwidth”. The closer the two frequencies, the greater the masking effect. Thus, only those signal components which are deemed to be audible are ENCODER MUSIC SIGNAL INPUT NON-UNIFORM FREQUENCY-TIME SPLITTING encoded. As a result, the signal can be represented with adequate resolution with only 20% of the data which would be required under the 16-bit linear recording method used by compact discs. This data economy allows 74 minutes of music to be stored on a 64mm disc and as we have seen, because it is read off the disc much faster than is needed by the 16-bit D-A converter, it confers a high degree of resistance to shock. Figs.1 & 2 help illustrate the ATRAC encoder principle, while Fig.3 illustrates the recording and playback process of Mini Disc. Another important facet of the ATRAC data compression system is non-uniform frequency and time MiniDisc BIT ALLOCATION DECODER NON-UNIFORM FREQUENCY-TIME ALLOCATION MUSIC SIGNAL OUTPUT Fig.3 shows the recording & playback chain of a Mini Disc. The music signal is encoded & compressed & the data must be reconsti­tuted after being read off the disc by the laser. 18  Silicon Chip splitting. In some ways, this is similar to the frequency band splitting used by the PASC compression system for digital cassettes (DCC). Both are an attempt to overcome the limited data storage of the media without unduly compromising sound quality. For most of the time in such a band splitting system, the signals will be recorded and subse­quently reconstituted with virtually no degradation. However, there will be times when the signal is especially com­plex and this will lead to some form of bandwidth reduction or perhaps a reduction in signal-tonoise ratio or perhaps both. Is it as good as CD? This will be a key question among hifi enthusiasts and the answer seems to be, at this stage, that in the environment it is intended to be used, in cars and Walkmans, Mini Disc will be virtually indistinguishable from CDs. Sony also state that CD will continue to be preferred as the quality sound source in homes. We take that to mean that CD still has the edge but we have had no chance to listen for ourselves at this stage. Nor have we had any chance to make measurements to test the efficacy of the ATRAC data compression system. As far as frequency response and dynamic range specifica­tions are concerned, CD and Mini Disc appear to be identical, depending on the player; ie, frequency response from 20Hz to 20kHz ±0.5dB and a dynamic range of 96dB. At this stage though, we have seen no figures for harmonic distortion and linearity. So far then, we have only discussed the playback version of Mini Disc, which is the format used for pre-recorded discs. Com­pared with CD, Mini Disc represents yet another big step in miniaturisation, a process which has continued unabated ever since integrated circuits were introduced. Even if Mini Disc was available only in play­back form, it would still be a big enough step forward in technology but when we look at the recordable version, we are looking at a whole new ball-game. It will have far-reaching implications for sound technology and computer data storage. Recordable Mini Discs Recordable Mini Discs use a combination of magnetic and optical storage technology. Whereas the playback Playback of recordable discs While the laser and magnetic head RECORDING HEAD WRITING SIGNAL 0 1 0 1 0 OLD NEW DISC ROTATION RECORDABLE MiniDisc CROSS SECTIONAL VIEW OBJECTIVE LENS LASER Fig.4: recordable Mini Discs use a combination of optical & mag­netic technology & hence need a laser & magnetic recording head used together during the recording process. act in concert to record the disc magnetically, the magnetic head is not used in playback; the laser is. How’s that again? Magnetic fields are not read; light polarisation is. It works like this: Upon striking the magnetic layer of the disc, the light from the laser pick-up will be reflected back in one of two direc­tions, depending on the plane polarisation, and this varies in accordance with the magnetic orientation. The fact that light is reflected not from pits but according to magnetic orientation is central to the record/ playback capability of a Mini Disc. This is demonstrated in Fig.6. Notice how the polarisation axis changes according to the magnetic orientation (north or south). Just how this is achieved is a mys- tery at this stage as Sony in Australia were not able to furnish any additional information. Dual function laser pick-up Since playback-only and recordable Mini Discs are read in different ways, they cannot be played back with the same laser pick-up. For this reason, Mini Disc players make use of a dual function pick-up. It is based on the conventional CD player pick-up but incorporating a polarised beam splitter to detect magneto-optical playback signals as well. It has two photo­detec­ tors, one for each type of disc. Fig.7 shows the set up for playback-only discs while Fig.8 shows the arrangement for playback of recordable discs. Natural­ly, the user is unaware of all this electronic jiggery-pokery and PR E-G RO OV E Mini Disc has a shutter on only one side of the disc, allowing access for the laser pick-up, the recordable Mini Disc shutter exposes both sides of the disc. One side of the disc is read by a laser pick-up in the conventional way but in the record mode a laser head and magnetic head are used on both sides of the disc. This is Sony’s Magnetic Field Modulation Overwrite System - see Fig.4. The MO system employs the magnetic head and the laser head together to erase and record the digital information and this is where it gets very clever indeed. On a normal floppy disc or cassette, the orientation of magnetic fields on the recording medium is simply changed by the recording head. But even if the Mini Disc is exposed to quite intense magnetic fields alone, its data will not be affected. It must be heated beyond its Curie point of 180°C and then the orientation of the stored magnetic field can be changed from north to south or vice versa. A couple of diagrams will help to explain the principles of the recordable disc. Fig.5 shows the various layers of the disc. As with CDs and play-only Mini Discs, the recordable version is based on transparent poly­ carbonate but whereas CD has three layers – polycarbonate with pressed in pits, a metallisation layer and a protective layer plus the label – the recordable version has six layers. Above the polycarbonate substrate, there is a magnetic layer sandwiched between two dielectric layers. For recording, a magnetic head works in conjunction with a laser, with the magnetic head above the disc and the laser below. As the disc rotates, the laser heats up a particular spot. At the same time, the magnetic head creates a magnetic field corres­ pond­ing to the data signal, at the spot at which the laser is fo­ cused. The laser heats the spot to the Curie point (180°C) which dissipates its existing magnetic orientation and allows it to take the orientation being applied by the magnetic head. As this spot on the disc moves away from the laser and cools below the Curie point, it retains its new magnetic polarity and the next spot is processed. PROTECTIVE LAYER REFLECTIVE LAYER DIELECTRIC LAYER MAGNETIC LAYER DIELECTRIC LAYER POLYCARBONATE SUBSTRATE 1.1  0. 5m Fig.5: whereas a playback Mini Disc has only three layers, the recordable version has six with the transparent polarising mag­netic layer being the key to the whole process. October 1993  19 Fig.6: this diagram shows the function of the magnetic layer. Its magnetic orientation affects the way in which it polarises laser light at 780nm. POLARISATION AXIS MAGNETIC DIRECTION S MAGNETIC DIRECTION N the two types of discs appear to behave identically during play­back. At this early stage, the technical information is pretty sketchy and the details of the recording and playback of Mini Discs were not available at the time of writing. We hope to publish more on this subject as the information comes to hand. However, we can briefly allude to some intriguing aspects which will be fully explained in the future. The pre-groove signal LASER 1 0 0 0 1 0 1 0 1 PREMASTERED MiniDisc CROSS SECTIONAL VIEW DISC ROTATION OBJECTIVE LENS ANALYSER PD1 OUTPUT PD2 LASER Fig.7: playback of a pre-recorded Mini Disc is essentially the same as with a CD, with a laser reading the pits. 1 0 0 0 0 1 1 What’s available 1 0 RECORDABLE MiniDisc CROSS SECTIONAL VIEW DISC ROTATION OBJECTIVE LENS ANALYSER PD1 OUTPUT PD2 LASER Fig.8 this diagram demonstrates the dual function laser pickup which reads differ­ences in light polarisation rather than differences in light intensity. 20  Silicon Chip One aspect of the recordable disc which we found particu­larly intriguing is the way in which the laser pick-up is continu­ally informed of its position on the disc, so that even if it is jolted away from its correct position, it can quickly find its way back. This is achieved by what Sony refer to as the “pre-groove” signal. This is depicted in Fig.9. It apparently updates the position information for the laser pick-up every 13.3 milli­seconds. There is another interesting difference between the play­ back and recordable versions of Mini Disc. The diagram of Fig.10 shows that the surface of the Mini Disc is devoted to data. There is a lead-in area followed by the program area and then the lead out area. As with CD, the Mini Disc is played from the inside out and it spins at anywhere between 400 and 900 RPM (faster than CD) to give a relatively constant linear velocity of 1.2 to 1.4 metres/second. However, with the recordable Mini Disc, an area called the UTOC – User Table of Contents – is interposed between the lead-in area and the program area. This UTOC appears to function in a similar way to the File Allocation Table (FAT) of a computer hard disc. Sony has announced the release of three products for Mini Disc. The first of these is the MZ-1 Walkman portable Mini Disc recorder. As its name suggests, it can play and record Mini Discs. Measuring 114 x 139 x 43mm and weighing approximately 690 grams with its rechargeable battery fitted, it offers the same playback and random access facilities as a CD player. As a recorder, the MZ-1 offers automatic or manual gain control and has facilities for disc and track titles which are shown on the liquid The MDS-101 incorporates all the features found in the MZ-1 Walkman recorder & features a comprehensive infrared remote control & styling to match Sony’s FH mini hifi range. crystal display. Each recording can be time and date stamped, which could be handy for those using the MZ-1 in professional or semi-professional applications. Recording on a Mini Disc is no more complicated than stor­ing a file on a floppy disc. You just press the record button and the MZ-1 automatically records on a blank portion of the disc. Alternatively, you can erase a selected track and all tracks will re-number. And there are other interesting possibilities such as dividing, swapping and combining tracks, all of which were un­heard of with analog cassette recorders. The MZ-1 incorporates SCMS (Serial Copy Management System) which allows single generation copies from digital systems incor­porating a digital output, which means there is minimal signal degradation. The frequency response is quoted as being from 20Hz to 20kHz. The recommended retail price of the Sony MZ-1 is $1499. Also released by Sony is the MDS101, another Mini Disc recorder intended for use in the home and matching the styling of Sony’s FH range of mini hifi equipment. The MDS-101 has all the facilities of the 22  Silicon Chip Mini Disc is built like a 3.5-inch floppy disc. It has a rigid outer case & a shutter which slides back to expose the disc for playback or recording. Playback-only discs have a shutter opening on one side only; recordable discs have a doublesided shutter. MZ-1 Walkman plus a comprehensive infrared remote control and a bigger liquid crystal display. It measures 225 x 75 x 285mm (W x H x D) and has a recommended retail price of $1799. Finally, there is the MDXU1 Mini Disc car player which incorporates an AM/FM tuner. To provide even more shock resist­ ance, this player has a 4-megabit DRAM which stores about 10 seconds of music. Some pundits have joked that the only way you will ever hear this player mistrack is if you have an impact great enough to trigger the car’s airbag in your face! The recommended retail price of the MDXU1 is $1999. PRE-GROOVE LASER SPOT Sanyo’s Mini Disc player While many electronics companies have indicated that they ultimately will have Mini Disc products, Sanyo is one of the very first to have a player available. It is the model MDG-P1 which weighs just 250 grams. It has high speed track access, the shock­ proof memory feature and a liquid crystal display to show track and time information. The Sanyo MDG-P1 will be on sale during October at a recom­ mended retail price of $1399.00. Sanyo will also release Mini Disc recorders and players for cars. Mini Disc players will also be available from Sharp and Aiwa, while TDK has already announced the availability of recordable Mini Discs in 60-minute and 74-minute ver­sions for $19.95 and $23.95. Sony’s recordable discs will have the same prices. DISC SUBSTRATE Fig.9: Mini Discs have a “pre-groove” layer underneath the entire program area of the disc & this informs the player of the laser pick-up’s position every 13.3ms. LEAD-IN AREA PROGRAM AREA LEAD-OUT AREA Music titles available According to Sony, some 200 music titles are already avail­able and this should increase to around 500 by Christmas. The titles are mostly popular but some classics are included. They will retail at $29.95, the same as premium priced CDs. Initially, all Mini Discs sold in Australia will be pro­duced by Sony MUSIC DATA Fig.10: music data on the Mini Disc is spread over a tiny area. The diameter of the lead-in track is only 29mm & the track pitch is 1.6 microns. plants in Austria, Japan and the USA. However, plans are under way to add Mini Disc production to the new Sony CD plant at the Huntingwood Estate, west of Sydney, to provide for the SC Australian and export markets. Mini Disc For Computers Not only has Sony borrowed from computer technology in developing the Mini Disc but the resultant product is likely to be very important for computers in the future. Sony has announced the development of standards for Mini Disc (MD) DATA which will be available in three formats, all of which will be useable in a single drive mechanism. The first of these will be pre-mastered (MD-ROM), intended for electronic publishing and software distri­ bution. Second, there will be a recordable MD intended for data storage appli- cations and thirdly, there will be the Hybrid MD which will be a disc which is partially pre-recorded, while the remainder will be recordable by the user. This is seen as being suitable for interactive applications. The overwhelming advantage of the MD DATA format, as it is presently known, is that it offers a capacity of 140 megabytes and data transfer rate of 150KB/sec. This rivals hard disc stan­dards. The disc could store up to 2000 still images and the transfer rate is sufficient to allow full motion video to CD standard. On a more mundane level, it will probably find wide application in personal and laptop computers. A new file system which determines how data is encoded has been developed for the MD as part of the overall standard. It is claimed that this will facilitate compatibility between computers with different operating systems. The manufacturing technology for MD DATA is identical to that for audio Mini Discs, which will keep costs low. But to avoid confusion, the MD DATA discs will be encoded in such a way as to make them unplayable or recordable on audio players. October 1993  23 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. OUT 10 16VW 82  REG2 IN 7805 GND D1 1N914 1k TP1 2 IC1 TANDY CAT 276-137 1 IC2a 7404 1 14 VC1 2-7pF 4.7pF 6.8k 2 7 3 L1 ETCHED ON PCB TP2 4 150   .001 D2 1N4002 TP2 7 100  1,3,6, 8,10,11,12 TP3 7404 1 5 3 14 2 7 IC1b 10k D1 1N914 Q1 BC548 4 IRLED1 VR1 10k 4 3 IC3 555  560  LED2 REG2 IN 7812 GND +15V OV  D2 1N4002 TP5 5 6 2 5 IC1c 8 7 27k 100 25VW 390  TP4 1k 1k RECEIVER MODULE 150  0V  OUT REG2 IN 7805 GND 10 16VW 9 .001 LED3 Fig.1: IR pulses from the handpiece are picked up by IC1 & fed to the UHF transmitter circuit based on Q1. ANTENNA TP1  +15V OATLEY UHF REMOTE TRANSMITTER BOARD LED1 2 560  LED2 Q1 2SC3355 100 25VW REG1 IN 7812 GND 1k IC2b 3 304MHz SAW FILTER 6.8pF OUT 1 .01 560pF 6 150  LED1  RF-linked IR remote control extender This circuit uses a UHF radio link to extend the range of an infrared (IR) remote control to about 100 metres (line of sight). It’s based on the Oatley Electronics UHF transmitter and that company’s pre-assembled 304MHz receiver module. In many remote handpieces, the transmitted code pulses a 40kHz carrier frequency. These 40kHz IR pulses are detected by IC1 (see Fig.1) which filters out the 40kHz carrier and the resulting pulses inverted by IC2a. IC2a in turn switches transistor Q1 which is wired as a Hartley oscillator. It operates at 304MHz as set by the 24  Silicon Chip Fig.2: the UHF transmission is picked up by a pre-built receiver module & the detected pulses used to control oscillator stage IC3. IC3 in turn drives IRLED1 to duplicate the original pulses from the handpiece. parallel tuned circuit in its collector. The components inside the dotted lines come complete with the transmitter from Oatley Electronics. IC2 is not inserted until VC1 is adjusted (using an insulated screw driver). Initial­ly, VC1 is adjusted until LED 2 comes on (this is when the tank circuit is at its lowest impedance). VC1 is then backed off until LED 2 just turns off. IC2 can now be installed and LED 1 will let you see the sequence of pulses from the handpiece. The coded RF pulses, now with a 304MHz carrier frequency, are picked up by the pre-assembled (and prealigned) receiver module via a 250mm antenna – see Fig.2. This module processes the received signal to give the original coded pulse sequence. IC1a inverts the pulses from the front-end module and drives transistor Q1, causing it to pulse on and off. IC3 is a 555 timer and is wired as an oscillator. When Q1 is on, the oscillator is off and vice versa. IC3 drives IRLED1 (the repeater LED) which thus flashes to duplicate the original pulses from the handpiece. VR1 sets the 555 output frequency to 40kHz, LED 1 lets you see that coded pulses are being received and LED 2 provides power-on indication. Finally, note that this circuit will only work with hand­pieces that transmit on 40kHz. C. Angus, Mackay, Qld. ($35) +8-12V RESET S1 4.7k VR1 220  4001 13 14 IC1b 47k  5 IC1d 2 IC1a 8 3 IC1c 12 9 LED1 1 11 47k 4.7 25VW 4 2.2k A mouse in the house is not nice but a conventional trap can be rather messy. If you don’t like the mess or the thought of killing the little critter, try this electronic mousetrap. It closes the door to a chamber when the mouse enters and breaks a light beam, thus trapping the mouse inside. The light barrier consists of LED 1 and light dependent resistor LDR1, while IC1 (a 4001 quad 2-input NOR gate) provides the logic. When the light beam is intact, the LDR has low resist­ance. Pin 8 of IC1a is thus held low, pin 10 is held high and pin 11 of IC1b is held low. 10 D1 1N4004 7 When the light beam is broken by the mouse, the resistance of the LDR rises and takes pin 8 of IC1a high. Pin 10 now switches low and so pin 11 of IC1b switches high. This high triggers a mono­ stable multivibrator consisting of gates IC1c and IC1d. Initially, pins 5 and 6 of IC1d are pulled high by a 47kΩ resistor and thus pin 4 is low. When a high pulse is subsequently applied to pin 1 of IC1c, pin 3 switches low and pulls pins 5 and 6 low via a 4.7µF capacitor. Pin 4 of IC1d thus switches high and turns on Darlington transistor pair Q1 and Q2. Q1 and Q2 drive a small 9V DC motor and this in turn is rigged to close the trapdoor via a lever. Electronic starter for fluorescent lights If you dislike the “blink-blink” effect of fluorescent lights when they are starting up, then this electronic starter circuit is the answer. It can be built into a con­ventional starter case and provides virtually instantaneous starting. When power is applied, D1 halfwave rectifies the positive-going cycle of the mains waveform and Q1 turns on by virtue of the current applied to its base via the 1µF capacitor. This applies gate current to SCR1 which also turns on. Q1 subsequently turns off as the mains nears the transition to the negative-going half cycle, while SCR1 turns off when the current through it falls to zero some time later. This causes the ballast to generate the striking voltage for the tube. 0V Q2 BD139 6 LDR1 Electronic mousetrap catches ‘em alive 1000 25VW Q1 BC548 D1 1N4004 A 56k Q1 BC547 SCR1 C122E 1 50VW 2.2k 33k N The prototype was assembled on a small piece of stripboard, cut into a circular shape to fit inside the starter case. The gaps between the tracks are narrow and should be carefully check­ ed after assembly to ensure that there are no shorts. An old starter case can be salvaged by carefully extracting the connecting foot from the plastic case. The existing mercury vapour switch and capacitor M The drive to the motor ceases after about one second, due to charging of the 4.7µF capacitor via the 47kΩ resistor on pins 5 and 6. IC1a and IC1b ensure that no further triggering can occur once the circuit has been triggered. The circuit can only be reset by pressing normally open pushbutton switch S1, thus pull­ing pin 13 of IC1b high. The trap itself consists of a plastic instrument case which is divided into two chambers. One chamber houses the LED and the LDR and is fitted with the trapdoor. The other chamber houses the motor and most of the electronic circuitry. P. Gallus, Emerald, Qld. ($25) must be removed, so that the elec­tronic starter can be substituted. Metal film resistors should be used, as these will fuse rather than burn in case of a short. The starter should work in either direction but one side – ie, SCR cathode to Neutral – will provide faster starting. When the switch is first turned on the fitting emits a 50Hz hum. This is due to vibrations from the ballast while the start­er is on and should last for no more than 0.5s. Note that the slim-line (25mm-dia) fluorescent tubes cannot be successfully started because the voltages generated are insufficient to in­crease the current to striking level. Note also that the circuit operates at mains potential so make sure it is installed in its case before plugging it in. K. Benic, Forestville, NSW. ($20) October 1993  25 News Update Interactive Pay TV Following our crystal ball gazing on the subject of interactive pay TV and optical fibres in the Publisher's Letter for the August 1993 issue, the news has begun to flow thick and fast. First, Philips has released details of a new chipset and Telecom has decided to give the public a glimpse of the future but first, the Philips story. Eindhoven - Philips Consumer Electronics has announced a compact prototype digital set-top decoder for Video on Demand (VOD) applications over telephone wires. Designated the Home Interactive Multimedia Terminal, the decoder converts 1.5 megabits/second digital TV signals into NTSC or Pal analog signals for display via standard television receivers. First applications are expected to be on Video Dial Tone (VDT) in the USA where telephone companies are experimenting with delivering digital TV signals into the home via existing twisted-pair telephone lines. Typical- Adilam gets SGS Thomson As of 1st August, Adilam Electronics has been appointed a distributor for the range of seminconductors from SGS Thomson. Adilam will servicing all trade requirements for SGS semis and can handle small orders from readers via their cash sales counter. For further information, ring Adilam at (03) 761 4466 in Melbourne or (02) 584 2755 in Sydney. Telecom & the Powerhouse Museum Telecom has announced the opening of an exhibition called "Telecom Laserlink: At home in the future" at Sydney's Powerhouse Museum. This will stress the importance of optical fibre communications in the future in the provision of services such as video 26  Silicon Chip ly, hundreds of movies will be stored on a telephone network server. The user at home will view an on-screen catalog of the available movies and select a program to watch. It will then start to `play' just like a VCR. The highly integrated Home Interactive Multimedia Terminal, incorporating key ICs from Philips Full Motion Video system for CD-I, combines three systems in one compact unit: a standard T1 communications interface system, an MPEG-1 decoder and a control system. While viewing television, it will be possible to use the line for regular telephone calls. Billing for telephony can also be separated from billing for the TV services. The MPEG-1 decoding system uses a Constraint System Parameter Set built around a Philips/ Motorola chipset. SIF resolution is 1.536 megabits/second. The design of the audio/video/data demultiplexer is flexible, enabling easy adaptation to various MPEG-1 system layer definitions. The control system receives signals from an infrared remote control and relays them back into the communications network. This enables interactive control of remote source material with VCR-like functions such as play, stop, pause, etc. It also allows data from the video server - such as the movie catalog - to be displayed on the screen. This is the first of a series of Terminals which will include versions suitable for use in ADSL and broadband fibre networks as well as for applications using satellite, cable, broadcast and other media. It will also play a useful role in business networks. The announcement of the prototype Terminal follows the formation of a joint working relationship between Philips Consumer Electronics Company, Knoxvbille, TN, BroadBand Technologies, Inc, based in Research Triangle Park, NC, and Compressions Labs, Inc, San Jose, California, to develop technology critical to the provision of interactive "Video Dial Tone" services by telephone companies in the United States. The Terminal is now available in prototype quantities to broadcasters, Telcos and other program providers. Consumer versions will be available once providers have finalised their specifications. library access, 24 hour news services, home education services, shopping, high definition television and the soon to be announced videophones. The major supporter of the exhibition is Telecom Australia, with additional support from Philips Australia and Apple Computer. technology to schools and provide a resource for teachers of science, technology and physics. The Federal Government grant is under the Projects of National Significance Program which develops quality education for Australian school students, promotes innovation in education and improves experience, knowledge and skills of primary and secondary students. Fibre optics in teaching The Federal Government has not been slow in recognising the significance of current developments in optical fibres. The Minister for Schools, Vocational Education and Training, the Hon. Ross Free MP has announced funding of $109,000 to develop a computer fibre optics training program for secondary students. The University of Sydney's Optical Fibre Technology Centre will develop the program to introduce optical fibre Kenwood's Amateur Newsletter Kenwood have published the first edition of their "Amateur News Action" newsletter. It includes the latest news on the company's communication equipment, club news and promotions. The newletter is available at selected Kenwood amateur radio dealers. If you or your club would like to receiver the newsletter regularly, ring Kenwood on (02) 746 1888. SC Review: Magnet LS-621 2-way loudspeakers The magnet LS-621 loudspeakers are a compact bass reflex system which will fit well into most lounge rooms. Magnet will be a loudspeaker brand name new to most Austra­lians. It is a company based in Thailand which makes loudspeakers designed by engineers from Holland. The European link is claimed to give the speakers a natural sound which otherwise might not be there if they had been designed in the East. The LS-621 system we reviewed is a compact 2-way system based on a 165mm polypropylene woofer and a 25mm tweeter. The bass reflex enclosure is wedge-shaped, tapering from the bottom to the top to angle the front baffle in such a way as to give some time-correction to the tweeter. That and the small frontal dimensions of the speaker combine to make it quite unobtrusive in appearance. Its dimensions are as follows: 435mm high, 206mm wide, 312mm deep at the base and 275mm deep at the top, with the grille cloth frame. Actually, the cabinet is also slightly tapered at the front which makes it look slightly smaller than its measure­ments suggest. Internal volume is 15 litres. The enclosure is ported with a tube of 55mm internal dia­meter and surprisingly long at 220mm. That is probably part of the reason why the enclosure is tapered, to allow a long port without making the box too deep overall. The cabinets are fin­ished in simulated walnut veneer with a black grille cloth. We removed the woofer to have a look at the internal de­tails of the enclosure and found that, surprise, surprise, the woofer is not of Asian origin at all but made by Peerless of Denmark, although we don’t know the model number. It is a well-made unit with a large magnet and a neoprene rubber roll surround for the poly­prop­ y­lene cone. And having revealed that the woofer is of European origin, the ferrofluid-cooled 25mm soft dome tweeter is too, made by Philips of Belgium. The two drivers are coupled together via quite a complex crossover network and this has an air-cored inductor wound with heavy gauge enamelled copper wire and uses wirewound resistors and a mixture of plastic and non-polarised electrolytic capacitors. The system is bi-wired so you can drive the tweeter and woofer with separate amplifiers, if you wish. The enclosure The enclosure is lined with bonded acetate fibre or a similar material and interestingly, there is an internal sloped shelf which undoubtedly adds to cabinet rigidity but we don’t know if it serves any other purpose. The four terminal posts are deeply recessed in a panel at the rear of the enclosure. This makes it quite difficult to make wire connections to the termi­nals unless you have the wires fitted with jacks. The terminal panels are so deeply recessed that the terminal posts do not protrude at all and this means you could set the cabinets right up flush to a wall, if desired. Frequency response of the enclosure is quoted as being from 40Hz to 22kHz within 1dB and -6dB. We do not have access to an anechoic chamber so we continued on page 93 28  Silicon Chip Don’t get caught with a flat battery! A courtesy light switch-off timer for cars Have you ever left a car door slightly ajar & returned later to find a flat battery? Or maybe your kids have been play­ing in the car & left the interior light on. This simple circuit will automatically switch the light(s) off after two minutes to save the battery. er saves your battery by switching off the power to the interior lamps after about two minutes. If necessary, the lamps can then be relit for another two minutes simply by closing and reopening the door to restart the timer. The timer connects in series with the positive supply to the interior light circuit, so that it can control the power supplied to the lamps. Apart from that, the timer circuit does not interfere with the operation of the courtesy lights. The lights continue to come on immediately a door is opened and will go out as soon as the door is closed in the normal manner. By JOHN CLARKE Unfortunately, it’s all too easy to leave the interior lights in your car on. In most cars, the lights remain on if a door is not properly closed (ie, is on the first catch) and that can easily occur if you’re in a hurry or struggling with shopping bags. If the lights are left on for long enough, the result is a flat battery and loads of frustration. This problem is particularly prevalent in later model cars which have a number of interior lights; eg, one on each door sill, one in the roof and one for the ignition lock. If all these lamps are alight, it doesn’t take long for the battery to discharge. This Courtesy Light Switch-Off Tim- +12V (VIA INTERIOR LAMP FUSE) INSERT INTERIOR CAR LAMP TIMER HERE LAMP LAMP DOOR SWITCH DOOR SWITCH E 10k D1 1N4148 470k 4 8 Q1 BD650 C IC1 7555 6 1 3 5 D2 1N4148 LAMP 470  1W 1k DOOR SWITCH .01 4.7k Q2 BC337 B C 0.1 BCE E .01 COURTESY LIGHT SWITCH-OFF TIMER 30  Silicon Chip TO LAMPS 100k 2 7 220 16VW DOOR SWITCH B 10 100 16VW Fig.1 shows the standard circuit for the interior lamps. In some cars, all the lamps and switches are in parallel. This means that as soon as one switch closes, all the lamps turn on. In other cases, each door switch only activates some of the lamps (eg, the lamp associated with that door plus the main interior lamp). In order to make sure that the power to all the interior lamps can be inter- Fig.1: the timer is installed between the courtesy light circuit & the fuse. Note that the door switches are usually on the negative side of the lamps but this is not always the case. +12V (VIA INTERIOR LAMP FUSE) ZD1 16V 1W Interior light circuit SEPARATE COURTESY LAMP B E VIEWED FROM BELOW C Fig.2: the circuit is based on a CMOS 7555 timer (IC1), wired as a monostable. When the door switch closes, IC1 is triggered via the .01µF capacitor on pin 2 & switches its pin 3 output high. This turns on Q2 & Q1 to light the lamp. IC1 then times out two minutes later & switches Q2, Q1 and the lamp off. The circuit can be retriggered for a further two minutes simply by closing and re-opening the door. PARTS LIST 1 plastic case, 54 x 82 x 30mm 1 PC board, code 05209931, 46 x 61mm 1 U-shaped heatsink, 18 x 19 x 10mm 1 3mm screw and nut 1 10mm rubber grommet 1 20mm length of 0.8mm tinned copper wire 3 PC stakes The circuit is assembled on a small PC board which is then clipped into a plastic utility case so that the parts cannot short against other wiring in the car. Note the small heatsink fitted to Darlington transistor Q1. rupted, regardless of the door switch arrange­ment, the timer circuit must be installed into the positive supply line as shown. If the timer were to be installed between the lamps and switches, we would not be able to switch off a separately switched courtesy lamp. As shown in the photograph, the circuit is built on a small PC board and this is clipped into a plastic utility case. This will provide a good insulating barrier to prevent the board from shorting onto any part the car body. Circuit description Fig.2 shows the circuit for the interior car lamp timer. It’s based on a CMOS 7555 timer (IC1) and this drives transistors Q2 & Q1 to switch the power to the lamps. IC1 is connected as a standard monostable timer, the duration of which is set by the 470kΩ resistor and 220µF capaci­tor on pins 6 and 7. When IC1 is triggered, either by a low signal to its pin 2 trigger input or when power is first applied, pin 3 goes high. This turns on Q2 which then turns on Darlington transistor Q1 via a 470Ω resistor to supply power to the lamp circuit. At the same time, the 220µF capacitor charges toward the +12V (Vcc) supply via the 470kΩ resistor. The capacitor voltage is monitored by pin 6 and when it reaches 2/3Vcc at the end of the timing period, pin 3 goes low and the 220µF capacitor dis­charges via pin 7. Q2 now turns off and so Q1 also turns off and the lamps go out. For a monostable circuit such as this, the period (T) for which pin 3 is high is given by the equation T = 1.1RC. In this case, R = 470kΩ and C = 220µF and so the period works out to 114 seconds (ie, slightly less than two minutes). In practice, the time delay is slightly longer than 114 seconds due to leakage and the fact that most electrolytic capacitors have a capacitance which is greater than the marked value. To obtain correct operation, IC1 must be triggered each time a door is opened and one of the door switches closes. This has been achieved by AC-coupling a low-going trigger signal to pin 2 of IC1 via a .01µF capacitor. Let’s see how this works. Initially, when all the door switches are open, Q1’s collec­tor is pulled to the +12V supply via the 1kΩ and 10kΩ resistors. IC1’s pin 2 input is also held high (ie, to +12V) via its associated 100kΩ pull-up resistor. When a door switch closes, Q1’s collector is initially pulled to ground via the lamp filament. This low is coupled to pin 2 of IC1 via the 1kΩ resistor and the .01µF capacitor and so IC1 triggers and begins its timing cycle. When this happens, pin 3 goes high and Q2 and Q1 turn on to provide power to the lamps (ie, Q1’s collector quickly reverts to +12V). Note that during the timing period, one side of the .01µF capacitor is held low via diode D2 and transistor Semiconductors 1 BD650 PNP Darlington transistor (Q1) 1 BC337 NPN transistor (Q2) 1 ICM7555 or LMC555CN CMOS timer (IC1) 1 16V 1W zener diode (ZD1) 2 1N4148 diodes (D1,D2) Capacitors 1 220µF 16VW PC electrolytic 1 100µF 16VW PC electrolytic 1 0.1µF MKT polyester 2 .01µF MKT polyester Resistors (0.25W, 1%) 1 470kΩ 1 1kΩ 1 100kΩ 1 470Ω 1W 5% 1 10kΩ 1 10Ω 0.25W 1 4.7kΩ Miscellaneous Automotive cable, insulated bullet connectors, automotive eyelet connector, cable ties. Q2. The voltage at pin 2 of IC1 goes high shortly after triggering, when the .01µF capacitor is charged via the 100kΩ resistor. If the door switch is now opened (ie, the door is closed) before IC1 times out, the lamps immediately go out. If, however, the door switch is left closed, the lamps will go out at the end of the 2-minute timing period, as described previously. When this happens, Q1’s collector will be pulled low via the lamp filament and the closed door switch but IC2 cannot be retriggered because D2 and Q2 have kept one side of the .01µF capacitor low during the timing period. When the door switch is subsequently opened, Q1’s collector will be pulled to +12V via the 1kΩ and 10kΩ resistors. Diode D1 clamps the pin 2 input of IC1 to the supply rail to protect the IC from damage when October 1993  31 TO DOOR LAMPS TO +12V 10  470  1W TO CHASSIS (GROUND) Q1 ZD1 Q2 470k 1k 10k 100k IC1 7555 D2 .01 4.7k D1 .01 220uF 0.1 1 100uF Fig.2: install the parts in the PC board exactly as shown in this layout diagram & don’t forget the wire link. The external wiring should be run using automotive cable. this occurs. The circuit is now armed and will be retriggered the next time a door switch closes. The supply for IC1 is decoupled from the main +12V rail using a 10Ω series resistor, a 100µF capacitor and a 16V zener diode (ZD1). ZD1 protects IC1 from the voltage spikes that occur in automotive supplies. Note that IC1 is powered all the time. It only draws a nominal 400µA and so has negligible affect on the battery. Construction The PC board for this project is coded 05209931 and measures 46 x 61mm. Fig.3 shows the component locations on the board. Begin the board assembly by installing PC stakes at the three external wiring points. The remaining parts can be in­stalled in virtually any order but take care to ensure that IC1, transistor Q2 and the diodes are all correctly oriented. The 470Ω 1W resistor should be mounted slightly proud of the PC board to aid heat dissipation. The two electrolytic capacitors must also be correctly oriented. Note that the 220µF capacitor is mounted on its side so that it doesn’t later foul the case lid (see photo). Position it so that it lies on top of the 4.7kΩ resistor and diode D1, and bend its leads at right angles so that they pass through the appropriate holes in the PC board. Transistor Q1 is the last component to be installed. It is fitted with a small finned heatsink to keep it cool and is bolted to the board using a screw and nut. Bend the leads of the tran­sistor at right angles so that they fit the holes in the board before finally tightening the nut. Once the PC board has been completed, you can drill a hole in the end of the case for the rubber grommet. The PC board can then be clipped into position and the three external leads fitted (use automotive cable). Installation Before commencing the installation, check the car’s wiring diagram to determine the best place to connect the cir­cuit. In some cars, you may be able to make the connection at the fusebox, provided that the fuse only supplies the interior lamps. The circuit should be installed directly after the fuse as shown in Fig.1. Do not bypass the fuse otherwise you could get a fire if a fault develops in the car’s wiring. In most cars, however, other equipment will be powered via the same fuse (eg, the clock, radio, boot light and instrument lights). If this is the case, you will have to tap into the wiring further down the line, after the supply points for this equipment. Disconnect the battery before installing the wiring, to prevent any Fig.3: this is the full-size etching pattern for the PC board. inadvertent shorts. The procedure is to cut the positive supply lead to the interior lamps and fit bullet connec­ tors to the cut ends. The appropriate leads from the timer are then plugged into these connectors (be careful not to get the leads transposed), while the ground lead is fitted with an eyelet connector and bolted to a suitable chassis point. The timer itself can be mounted beneath the dashboard and secured using cable ties. Check that the interior lights operate normally when a door is opened and that the lights go out after about two minutes if the door is left open, or immediately if the door is closed again. Finally, check that the interior lights can be made to come on again at the end of the timing period by closing and re-opening the door. All other items in the car should function as normal, regardless of the status of the timer circuit. If the circuit fails to operate correctly, check that all parts are in their correct locations on the PC board and that they are correctly oriented. SC RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 1 1 1 1 1 1 1 32  Silicon Chip Value 470kΩ 100kΩ 10kΩ 4.7kΩ 1kΩ 470Ω 10Ω 4-Band Code (1%) yellow violet yellow brown brown black yellow brown brown black orange brown yellow violet red brown brown black red brown yellow violet brown brown brown black black brown 5-Band Code (1%) yellow violet black orange brown brown black black orange brown brown black black red brown yellow violet black brown brown brown black black brown brown yellow violet black black brown brown black black gold brown LED BRAKE LIGHT INDICATOR This “brilliant” brake light indicator employs 60 high intensity LEDs (550-1000mCd) to produce a display that is highly visible, even in bright sunlight. The intensity produced is equal to or better than the LED brake indicators which are now included in some late model “upmarket” vehicles. The LED displays used in most of these cars simply make all the LEDs turn on every time the brakes are applied. The circuit used in this unit can perform in this manner and, for non-automotive applications, it can be customised to produce a number of sweeps (110) starting at the centre of the display and with a variable sweep rate. It not only looks spectacular but also attracts more attention. All the necessary “electronics” is assempled on two identical PCBs and the resulting overall length of the twin bargraph dis­play is 460mm. It’s simple to install into a car since only two connections are required: Earth and the brake­ LASER SCANNER ASSEMBLIES These are complete laser scanners as used in laser printers. Include IR laser diode optics and a very useful polygon scanner ( motor-mirror). Produces a “fan” of light (approx. 30 deg) in one plane from any laser beam. We provide information on polygon scanner only. Clearance: $60 400 x 128 LCD DISPLAY MODULE – HITACHI These are silver grey Hitachi LM215XB dot matrix displays. They are installed in an attractive housing and a connector is provided. Data for the display is provided. BRAND NEW units at a low: $40 LASER OPTICS The collimating lens set is used to improve the beam (focus) divergence. The 1/4-wave plate and the beam splitter are used in holography and experimentation. All are priced at a fraction of their real value: 1/4 wave plate (633nM) ..............................$20 Collimating lens sets ..................................$45 Polarizing cube beam splitters ....................$65 GREEN LASER TUBES We have a limited supply of some 0.5mW GREEN ( 560nm) HeNe laser tubes. Because of the relative response of the human eye, these appear as bright as about a 2mW red tube: Very bright. We will supply this tube and a suitable 12V laser power supply kit for a low: $299 CCD ELEMENT BRAND NEW high sensitivity monolythic single line 2048 element image sensors as used in fax machines, optical charachter recognition and other high resolution imaging applications: Fairchild CCD122. Have usable response in the visible and IR spectrum. Supplied with 21 pages of data and a typical application circuit. $30 INFRARED TUBE AND SUPPLY These are the key components needed for making an INFRARED NIGHT VIEWER. The tubes will convert infrared light into visible light on the phosphor screen. These are prefocussed tubes similar to type 6929. They do not require a focus voltage. Very small: 34mm diameter, 68mm long. All that is needed to make the tube light connecting wire. The case for the prototype unit which would be suitable for mounting on the rear parcel shelf, was mainly made from two aluminium “L” brackets that were screwed together to make a “U” section. A metal rod and its matching holders (commonly available from hardware shops) are used for the supporting leg. $60 for both the PCBs, all the onboard components & instruc­tions: the 60 LEDs are included! We also have available a similar kit that does not have the sweeping feature. It produces similar results to the commercial units installed in cars: all the LEDs light up when power is applied. $40 for both the PCBs and all the onboard components. This kit is also supplied with the 60 LEDs and it uses different PCBs, that have identical dimensions to the ones supplied in the above­ mentioned kit. operational is a low current EHT power supply, which we provide ready made or in kit form: powered by a 9V battery and typically draws 20mA. INCREDIBLE PRICING: $90 For the image converter tube and an EHT power supply kit! All that is needed to make a complete IR night viewer is a lens an eyeiece and a case: See EA May and Sept. 1990. ALUMINIUM TORCHES – INFRARED LIGHTS These are high quality heavy-duty black anodised aluminium torches that are powered by four “D” cells. Their focussing is adjustable from a spot to a flood. They are water resistant and shock proof. Powered by a krypton bulb – spare bulb included in cap. $42 Note that we have available a very high quality INFRARED FILTER and a RUBBER lens cover that would convert this torch to a good source of IR: $15 extra for the pair. PASSIVE NIGHT VIEWER BARGAIN This kit is based on an BRAND NEW passive night vision scope, which is completely assembled and has an EHT coaxial cable connected. This assembly employs a high gain passive tube which is made in Russia. It has a very high luminous gain and the resultant viewer will produce useful pictures in sub-moonlight illumination. The viewer can also be assisted with infrared illumination in more difficult situations. It needs an EHT power supply to make it functional and we supply a suitable supply and its casing in kit form. This would probably represent the best value passive night viewer that we ever offered! BECAUSE OF A SPECIAL PURCHASE OF THE RUSSIAN-MADE SCOPES, WE HAVE REDUCED THE PRICE OF THIS PREVIOUSLY ADVERTISED ITEM FROM $550 TO A RIDICULOUS: $399 This combination will be soon published as a project in EA. NOTE THE REDUCED PRICE: LIMITED SUPPLY. Previous purchasers of the above kit please contact us. 24VDC TO MAINS VOLTAGE INVERTERS In the form of UNINTERRUPTABLE POWER SUPPLIES (UPS’s).These units contain a 300W, 24V DC to 240V 50Hz mains inverter. Can be used in solar power systems etc. or for their original intended purpose as UPS’s. THESE ARE VERY COMPACT, HIGH QUALITY UPS’s. They feature a 300W - 450W (50Hz) SINEWAVE INVERTER. The inverter is powered by two series 12V 6.5Ahr (24V). batteries that are built into the unit. There is only one catch: because these NEW units have been in storage for a while, we can not guarantee the two batteries for any period of time but we will guarantee that the batteries will perform in the UPS’s when these are supplied. We will provide a 3-month warranty on the UPS’s but not the batteries. A circuit will also be provided. PRICED AT A FRACTION OF THEIR REAL VALUE: BE QUICK! LIMITED STOCK! $239 ATTENTION ALL MOTOROLA MICROPROCESSOR PROGRAMMERS We have advanced information about two new STATE OF THE ART microprocessors to be released by Motorola: 68C705K1 and 68HC705J1. The chips are fully functional micros containing EPROM/OTPROM and RAM. Some of the features of these new LOW COST chips include: *16 pin DIL for the 68HC705K1 chip * 20 pin DIL for the 68HC705J1 chip * 10 fully programmable bi-directional I/O lines * EPROM and RAM on chip * Fully static operation with over 4MHz operating speed. These two chips should become very popular. We have put together a SPECIAL PACKAGE that includes a number of components that enable “playing” with the abovementioned new chips, and also some of the older chips. IN THIS PACKAGE YOU WILL GET: * One very large (330 x 220mm) PCB for the Computer/Trainer published in EA Sept. 93; one 16x2 LCD character display to suit; and one adaptor PCB to suit the 68HC705C8. * One small adaptor PCB that mates the programmer in EA Mar. 93 to the “J” chip, plus circuit. * One standalone programmer PCB for programming the “K” chip plus the circuit and a special transformer to suit. THE ABOVE PACKAGE IS ON SPECIAL AT A RIDICULOUS PRICE OF: $99 Note that the four PCBs supplied are all silk screened and solder masked, and have plated through holes. Their value alone would be in excess of $200! A demonstration disc for the COMPUTER/TRAINER is available for $10. No additional software is currently available. Previous purchasers of the COMPUTER/ TRAINER PCB can get a special credit towards the purchase of the rest of the above package. PLASMA BALL KIT This kit will produce a fascinating colourful changing high voltage discharge in a standard domestic light bulb. The EHT circuit is powered from a 12V supply and draws a low 0.7A. We provide a solder masked and screened PCB, all the onboard components (flyback transformer included), and the instructions at a SPECIAL introductory price of: $ 25 We do not supply the standard light bulb or any casing. The prototype supply was housed in a large coffee jar, with the lamp mounted on the lid – a very attractive low-cost housing! Diagrams included. LASER DIODE KIT – 5mW/670nm Our best visible laser diode kit ever! This one is supplied with a 5mW 670nm diode and the lens, already mounted in a small brass assembly, which has the three connecting wires attached. The lens used is the most efficient we have seen and its focus can be adjusted. We also provide a PCB and all on-board components for a driver kit that features Automatic Power Control (APC). Head has a diameter of 11mm and is 22mm long, APC driver PCB is 20 X 23mm, 4.5-12V operation at approx 80mA. $85 PRECISION STEPPER MOTORS This precision 4-wire Japanese stepper motor has 1.8 degree steps – that is 200 steps per revolution! 56mm diameter, 40mm high, drive shaft has a diameter of 6mm and is 20mm long, 7.2V 0.6A DC. We have a good but LIMITED supply of these brand new motors: $20 HIGH INTENSITY LEDs Narrow angle 5mm red LED’s in a clear housing. Have a luminous power output of 550-1000mCd <at> 20mA. That’s about 1000 times brighter than normal red LED’s. Similar in brightness SPECIAL REDUCED PRICE: 50c Ea or 10 for $4, or 100 for $30. IR VIEWER “TANK SET” ON SPECIAL is a set of components that can be used to make a complete first generation infrared night viewer. These matching lenses, tubes and eyepieces were removed from working tank viewers, and we also supply a suitable EHT power supply for the particular tube supplied. The power supply may be ready made or in kit form: basic instructions provided. The resultant viewer requires IR illumination. $180 We can also supply the complete monocular “Tank Viewer” for the same price, or a binocular viewer for $280: Ring. MINI EL-CHEAPO LASER A very small kit inverter that employs a switchmode power supply: Very efficient! Will power a 1mW tube from a 12V battery whilst consuming about 600 mA! Excellent for high-brightness laser sights, laser pointers, etc. Comes with a compact 1mW laser tube with a maximum dimension of 25mm diameter and an overall length of 150mm. The power supply will have overall dimensions of 40 x 40 x 140mm, making for a very compact combination. $59 For a used 1mW tube plus the kit inverter. OATLEY ELECTRONICS PO Box 89, Oatley, NSW 2223 Phone (02) 579 4985. Fax (02) 570 7910 MAJOR CARDS ACCEPTED WITH PHONE & FAX ORDERS P & P FOR MOST MIXED ORDERS AUSTRALIA: $6; NZ (Air Mail): $10 COMPUTER BITS BY DARREN YATES Using DOS 6.0’s DoubleSpace If you’re having problems with hard disc space, then you should take a long look at DoubleSpace in DOS 6.0. It will com­press existing drives as well as create compressed drives inside your current setup. No matter how big your hard disc is, you never seem to have enough space on it. One reason: computer programs are getting bigger. Take a look at the evolution of MS-DOS, for example. Version 3.3 occupied 500Kb or so, while version 6.0 takes 6-7Mb. But that’s not large compared to some programs. The current version of Corel­Draw requires upwards of 30Mb of disc space! To alleviate space problems, many computer users rely on file compression programs such as LHARC and PKZIP. These are great little programs which can compress most files down drive – you simply save your files to that disc and they are automatically compressed. It can even compress some of your files so that they are 16 times smaller than the original size. The obvious benefit is that it dramatically increases disc space. And although it will marginally slow things down, as files compress and decompress, it is still many times faster and re­ quires less work than LHARC or PKZIP. Running DoubleSpace To get DoubleSpace up and running, simply type DBLSPACE<return> at DoubleSpace can create a compressed drive which, for all the world, looks & acts just like an ordinary drive – you simply save your files to that disc & they are automatically compressed. to a fraction of their former selves. However, they do require some effort on your part in order to compress files and delete the originals. To recover the original files, you then have to run the compression program in reverse to decompress the files back to their original size. DOS 6.0’s DoubleSpace goes a step further by making this process automatic. DoubleSpace can create a compressed drive which, for all the world, looks and acts just like an ordinary 34  Silicon Chip your C:\DOS prompt. Once the program appears, you will be given the choice of running two methods of setup – express or custom. Express setup automatically selects all files on drive C: to be compressed and sets the compression ratio as well. The custom option allows you to set the size of the drive and specify a free space ratio from 2:1 to 16:1. In addition to hard disc compression, DoubleSpace also has the ability to compress other drives that MS-DOS can access, except CD-ROMs and the like. This means that you might want to compress a 1.44Mb floppy, for example, to transfer files from one machine to another without having to compress part of the C: drive as well. Fortunately, there is a way around Microsoft’s statement that “once a drive has been compressed it can’t be decompressed”. The method is as follows: (1) Use the Custom Setup and select the option for creating a new compressed drive. This new drive will come from the remaining space left on your existing C: drive. (2) Follow the options through but don’t change any of the de­faults to create the new compressed drive. This will be designat­ed as drive H:. (3) Once that’s completed, exit out of DoubleSpace. DoubleSpace is now installed on the hard drive and can be accessed as a normal program. To retrieve your original disc space and remove the compressed drive H:, the steps are as fol­lows: (4) Return to the root directory of your C: drive – you will find that you have around 2.5Mb of memory left. This is determined by the custom setup procedure in DoubleSpace. ( 5 ) Ty p e AT T R I B - S - H - R DBLSPACE.*[enter], then DIR[enter]. You will find two new files with the DBLSPACE prefix. One of these, DBLSPACE.001, will be approximately the same size as the space originally remaining on your hard disc minus the 2.5Mb now remaining. (6) The ATTRIB statement allows this file to be seen and, more importantly, to be deleted. If you now type DEL DBLSPACE.001[enter], you’ll find that you’re just about back to the same space you started with. Now go back into DoubleSpace and check that the drive is no longer there. This should be apparent on the opening screen. It will either show that there is no compressed drive or that it still thinks drive H: exists. If the latter is the case, just select the UNMOUNT option from the DRIVE menu. This will remove it from DoubleSpace’s setup files and you can now compress other drives without having your hard disc disturbed. User environment Once you start using DoubleSpace, you’ll find it an easy program to work with. As with all Microsoft software these days, it comes with a context-sensitive help reference that is quite thorough and contains information that doesn’t appear in the DOS 6 handbook. If at any point you get stuck, simply press F1 and Double­Space will give you information on your current position. There are four main options displayed across the top menu bar: DRIVE, COMPRESS, TOOLS and HELP. This second help option allows you to look up anything you want at any particular time, instead of being context sensitive. The DRIVE menu contains the main disc-based commands which include MOUNT and UNMOUNT. These are the commands for loading and unloading a compressed disc into your current system. You can’t just load a compressed floppy into your B: drive and expect it to work immediately; you have to use the MOUNT and UNMOUNT commands to tell DOS that the current floppy is either a compressed or normal disc. Other commands included are CHANGE RATIO and CHANGE SIZE. The change ratio command allows you to modify the estimated disc space displayed. When a drive is initially compressed, the amount of free space is only an estimate. Because not all files compress equally, it is difficult to forecast how much compressed space remains on a drive. Once you begin using the drive, the free space shown will be based on the average compression ratio of all files stored so far. You can check the average compression ratio for all files in a directory by typing DIR/C[enter]. This will also give the compression ratios on each file as well. Note that the CHANGE RATIO command changes the estimated disc space remaining but not the compression ratio of any stored data. When DOS shows how much space remains on a compressed disc, it is an estimate based on a theoretical compression ratio of 2:1. You can increase this up to 16:1, which is the limit of the compression range. In practice, it really depends on the files the disc will contain. If you’re only copying text files, which compress up much tighter than 2 to 1, changing the ratio make sense but if the disc contains .LZH, .EXE or .BIN files, which don’t compress anywhere near 16:1, then it would be pointless as the free space shown will be inaccurate. The CHANGE SIZE command allows you to change just how much of a drive is compressed and how much is normal storage space. This can be very handy indeed. Since Double­ Programming Tip This tiny batch file, A_.BAT, will automatically mount your compressed floppy disc and get you into the A: drive. For other drives, simply change the drive letter. Just type A_[enter] and it does the rest. The <at> symbol stops unnecessary messages appearing on the screen: <at>dblspace/mount a: <at>a: part of a drive that you already have in use. The Create New Drive option allows you to create a new drive from an existing hard disc which has its own designation letter; eg; you can create a new drive G: from space left over on your C: drive. This is handy if you wish to separate users or programs, or both. Tools menu In a way, DoubleSpace is a disc operating system within another and this is shown up in the way that DoubleSpace looks after its own compressed drive. An example of this is the Tools Menu. This contains two options: defragmentation and error remov­al. The defragmentation option rewrites all file fragments into consecutive sections of disc. This speeds up file loading as well as reducing disc wear and tear, since the drive only has to look at one place on the drive to find the complete file. Error removal is achieved using a modified version of the CHKDSK program. This unmounts the disc so that it appears as an ordinary disc and runs a CHKDSK test looking for errors such as bad sectors or lost files. Once found, they are then removed. There aren’t many commands in DoubleSpace and this makes running a compressed disc drive system easier than you might have thought. If you find this a bit cumbersome, then you’ll be pleased to know that DoubleSpace is also operable from the DOS command line. DOS commands Space always gives compressed drives a new letter designation, you could quite easily put program .EXE files on the normal section of the disc and then place work files such as text and database files on the compressed section. This will give you an optimum arrangement between maximum storage and speed. Compress menu Moving across to the Compress menu, this gives you the option of compressing an existing drive or creating a new com­pressed drive. Now you might think this sounds like the same thing but there is a difference. The Compress Existing Drive command allows you to compress all or By typing DBLSPACE /?[enter], Double­Space will give you the list of switches which can be used to achieve all of the above options directly from the DOS prompt rather than having to access the main user interface. This is ideal for batch file programming or for using DoubleSpace in your own programs. And by chaining in the DOS commands, you can access the features on DoubleSpace quickly and easily (see the programming tip in this column). So that’s it. You may have dismissed DoubleSpace as just a sales gimmick the boffins in the computer stores use but it is a definite winner and well worth using if a hard disc upgrade is beyond your budget. For the money, SC it’s a bargain. October 1993  35 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. 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Please have your credit card details ready ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail coupon to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia October 1993  39 Stereo preamplifier with IR remote control Last month, we gave the block diagram of the Studio Remote Control Preamplifier & also described the transmitter circuit. In Pt.2 this month, we give the full circuit details of the main preamplifier unit. PART 2: By JOHN CLARKE Because of its size, the circuit has been split into two separate diagrams. The first diagram is designated Fig.5 and this shows the input selection circuitry, the phono preamplifier stage and the associated control circuitry and LED displays. The second diagram, Fig.6, shows the digital volume control and its asso­ciated LED displays, the remote control receiver stages, the tone control stage, and the headphone amplifier stage. For the sake of clarity, only the left channel of the stereo circuitry 40  Silicon Chip is shown on each diagram. The ICs for the left channel are numbered as shown on Fig.5 and Fig.6, while the right channel ICs are numbered by adding 100 to the equivalent left channel number; eg, IC1 in the left channel is equivalent to IC101 in the right channel. Note that we have mainly used lownoise NE5534AN op amps to buffer or amplify the audio signal, the one exception being an OP27GP in each channel for the volume control. The 5534 op amp is amongst the best available for low distortion and noise, while the OP27 also has low noise and distortion plus extra low input offset voltage. This latter specification is necessary to allow the op amp to be connected to the D-A converter. Phono amplifier We’ll begin the circuit description by looking at Fig.5. IC1 is the phono preamplifier and RIAA/IEC equalisation stage. It takes the low level signal from a moving magnet cartridge and amplifies this by 56 at the mid-band frequency of 1kHz. The equalisation network ensures that we get less gain at frequencies above 1kHz and more gain below 1kHz. More specifically, a 100Hz signal is boosted by 13.11dB while a 10kHz signal is cut by 13.75dB. The phono signal is fed directly from the input socket via a small inductor (L1), a 150Ω resistor and 47µF bipolar capacitor to the non-inverting Left: the 68HC705C8P microprocessor (IC14) is mounted in a socket near the centre of the main PC board. This IC sets the volume by providing control signals to a dual D-A converter (IC15) & drives the digital readout & the balance display LEDs. more than one, a situation that could otherwise lead to non-symmetrical clipping and premature overload in the preamplifier. Source selection input (pin 3) of IC1. The inductor, series resistor and 100pF shunt capacitor form a filter to remove any RF signals which might be picked up by the phono leads. The 100pF capacitor is also necessary to provide correct loading for the magnetic cartridge. Most cartridges need to be loaded with a capacitance of 200-400pF for best results. When combined with the usual 200pF or so of cable capacitance (from the phono leads), this 100pF capacitor will ensure optimum load­ing. The RIAA/IEC equalisation is provided by the feedback components between pins 2 and 6 of IC1. These components provide the standard time constants of 3180µs (50Hz), 318µs (500Hz) and 75µs (2122Hz), as required for RIAA equalisation. The IEC recom­mendations also include a roll-off below 20Hz (7950µs). This is provided by the .068µF output coupling capacitor, the 1MΩ resis­tor and the 330kΩ resistors following IC2 and IC3, and other low frequency roll-offs in the circuit. One of these roll-offs (at about 4Hz) is provided by the 100µF capacitor and its series 390Ω resistor on pin 2 of IC1. The 390Ω resistor sets the gain for AC signals above 4Hz, while the 100µF capacitor ensures unity DC gain. This unity DC gain ensures that any input offset voltages are not amplified by IC2 is a CMOS analog switch which provides source selection for the PHONO, TUNER, CD, VCR and AUX inputs. Each input, except for the phono input on pin 14, is loaded with a 47kΩ resistor to protect the IC from damage due to electrostatic charges, as could occur if the inputs are left unconnected. The A, B and C control inputs at pins 9, 10 and 11 are used to select which source is switched through to the output at pin 3 (more on this later). The signal from pin 3 of IC2 is now fed via two paths. First, it is fed directly to the pin 12 (ax) input of IC3, anoth­er CMOS analog switch. Second, it is fed via a 100Ω resistor to the pin 3 input of unity gain buffer stage IC8. The output from IC8 appears at pin 6 and provides the TAPE OUT signal via another 100Ω resistor. This resistor provides short circuit protection for the op amp and also isolates the output of the op amp from the signal leads to prevent RF feedthrough. IC3 is used to select either the source signal from IC2 or the TAPE IN input for tape monitoring. This IC also provides for mono/stereo switching. Just how this is achieved is best under­stood by first noting that IC3 is essentially a 3-pole 2-position switch. The three poles are designated “a”, “b” and “c” and each pole can select either its corresponding “x” input or its corresponding “y” input, depending on the status of the A, B and C control inputs at pins 9, 10 and 11. In other words, pole “a” can select ax or ay, pole “b” can select bx or by, and pole “c” can select cx or cy. As shown on Fig.5, the left channel program and tape moni­ tor inputs are applied to the ax and ay inputs respectively (note: the right channel inputs are applied to bx and by, although this is not shown here). Thus, depending on the status of the A, B and C control lines, either the selected program signal on the ax input or the TAPE IN signal on the ay input will be switched through to the “a” output at pin 14. The “c” pole is used to provide stereo/mono switching. This pole is connected to the left channel signal path via a 4.7kΩ resis­tor, while the cy terminal is connected to the right channel via another 4.7kΩ resistor. In stereo mode, the “c” pole selects the cx terminal (which is not connected to a signal), while in mono mode, the “c” pole selects the cy terminal so that left and right channel signals are mixed together. Op amp IC4 is used to buffer the left channel signal. Its input (pin 3) is fitted with a 1kΩ “stopper” resistor to prevent the possibility of RF breakthrough from mobile phones and 2-way radios. The buffering provided by IC8 and IC4 at the outputs of CMOS switches IC2 and IC3 is vital in order to obtain very low levels of distortion. The distortion from these switches is typically .04% for a 1kHz 5V p-p signal when driving a 10kΩ load. However, if the load is greater than 220kΩ, as provided by the op amps, the distortion is less than .005%. To obtain maximum signal handling capability, the two CMOS switch ICs are powered from ±7.5V rails. These supply rails are derived from ±15V rails via 1kΩ limiting resistors and zener diodes ZD1 and ZD2. The ±15V rails are in turn derived from regulators in the main power supply circuit. Control circuitry IC9, IC10, IC12 and IC13 make up the program selection control circuitry. IC9, a 7-stage Darlington transistor driver, is used to convert the 0-5V signals from the IR remote control decoder chip (IC23) to 0-7.5V signals, as required by the CMOS switches. The A-E inputs at pins 1-7 of IC9 each connect to the base of a Darlington transistor via an internal 10kΩ resistor. These Darlington transistors have open collector outputs at pins 1016 and these are all tied to the +7.5V rail via 10kΩ pull-up resis­tors. The emitters all connect to pin 8 which goes to ground. October 1993  41 42  Silicon Chip DATA A B C D E FROM IC23 TAPE IN TAPE OUT AUX2 AUX1 VCR TUNER CD PHONO 4 16 1 8 15 14 2 3 6 IC13a 11 2 IC13b .01 14 14 5 3 1 12 15 13 14 5 7 4 10k 1M 100  13 13 5 .068 12 4011 10k D3 1N4148 100  6 11 10k .015 5% 100  .0047 5% 200k 8 4 -15V 16k IC1 5534 6 10k 100 BP 390  2 5 10k 100pF 5 4 10k 100k 3 10pF 10 10k 100k 150  7 +15V 7 IC9 ULN2003 5-7.5V CONVERTER 47k 47k 47k 47k 47k 47k L1 47 BP L D3 D2 D1 D4 5 4 3 2 0 1 A B C 11 10 9 8 IC10 4042 16 +7.5V Q3 Q2 Q1 POL 12 9 3 6 TO IC102 (OTHER CHANNEL) 8 IC2 4051 16 330k 100k 10 7 6 4 2 3 -7.5V 2 100  3 7 5 100  4 8 6 -15V 10pF IC8 5534 +15V 13 12 ay ax A 11 B 10 IC3 4053 16 C 100k 3 7 4 330k 8 14 6 9 10 10 11 11 16 +7.5V C B A 6 2 330W -7.5V 4.7k 7 IC11 4051 3 +5V 4 1k +7.5V POWER-ON MUTE TO IC104, PIN3 (OTHER CHANNEL) 9 cy c a INH 10 8 2 3 5 A 1 A 12 A 15 A 13 A      K K K K K LED1-LED6  K 14 A 100  4 8 -15V 10pF 5 IC4 5534 7 +15V 6 AUX2 AUX1 VCR TUNER CD PHONO TO IC15 PIN4 10 16VW ZD2 7.5V 400mW 1k 0.1 STUDIO REMOTE CONTROL PREAMPLIFIER (1) -7.5V +7.5V 2x 10 16VW ZD1 7.5V 400mW 1k K 330   3 CK2 S 11 CK1 D2 9 IC13d 9 IC13c 10 12 8 13 +7.5V 11 .01 D4 1N4148 10k 5 D1 8 S 6 7 Q2 Q1 12 2 330  LED7 TAPE MON. A K IC12 13 4013 Q2 Q1 1 100k 10 R 4 R  LED8 MONO A +5V -15V +15V POWER-ON RESET +7.5V 10 14 Fig.5 (left): this diagram shows the phono preamplifier stage (IC1), the input selection circuitry (IC2 & IC3), & the associated control circuitry (IC9-IC12) & LED displays. Fig.6 on the following pages shows the digital volume control circuit (IC14 & IC15), the remote control receiver & decoder stages (IC22 & IC23), the tone control stage (IC6), & the headphone amplifier stage (IC7, Q1 & Q2). As well as providing level translation, the Darlington transistors inside IC9 also function as inverter stages; ie, they invert the signals from IC23. Note that we have not used the Darlington transistor which connects to pins 4 and 13. IC10, IC12 and IC13 monitor the outputs of IC9. These outputs are all normally high except for the pin 16 output which is normally low. When a valid infrared transmission is decoded, pin 16 goes high while the other outputs variously go low or stay high depending upon the transmitted code. Note that pin 15 will always switch low if an input source is being selected. Similarly, pin 14 always switches low for Tape/Mode selection. IC10 is a 4042 quad latch and initially, at power up, its D1-D3 data inputs (pins 4, 7 & 13) are high, while its polarity input (POL) at pin 6 is pulled high by a 10µF capacitor. When pin 6 is high, the levels at the Data inputs are inverted and fed to the Q-bar outputs (pins 3, 9 & 12), provided the latch (L) input at pin 5 is also high. This latch input is initially high, since pin 1 of NAND gate IC13b is pulled low (by pin 16 of IC9) and thus the output at pin 3 is forced high. As a result, IC10’s Q-bar outputs are all initially set low, since they invert the Data inputs. This means that the A, B and C control inputs of IC2 and IC11 are also all low and so IC2 selects the CD input (ie, input 0 at pin 13). At the same time, IC11 switches its pin 13 terminal to pin 3 to light the CD LED (LED 2). The 330Ω resistor in series with pin 3 limits the cur­rent through the LED to about 10mA. Thus, each time the preamplifier is switched on, the CD input is selected by default. Following switch-on, the 10µF capacitor on pin 6 of IC10 charges via a 100kΩ resistor until pin 6 is at 0V (ground). This means that the signals on the data inputs are now inverted and transferred to the Q-bar outputs when the latch input at pin 5 is low. When a decoded signal is received by IC9, its pin 16 output goes high (this is the data acknowledge signal). If an input is being selected, then pin 15 goes low and this low is inverted by IC13a and applied to pin 2 of IC13b. Thus, pin 3 of IC13b switch­es low and momentarily pulls pin 5 of IC10 low to latch the new signal at the data inputs to the Q-bar outputs. As a result, a new code is applied to the A, B and C inputs of IC2 and IC11 and so a new source is selected and the appro­priate indicator LED is lit. Note that IC10 can only latch through the signal at its Data inputs when its Latch input (pin 5) goes low. This only occurs when pin 15 of IC9 goes low. In practice, this means that the pin 10-12 outputs of IC9 can be used to control other parts of the circuit without affecting IC10 (and thus the program selection), simply by keeping pin 15 of IC9 high. Tape/source selection The Tape/Source/Mode selection circuitry functions in simi­lar fashion to the program selection circuit. In this case, however, the data signals from pins 10 & 11 of IC9 are controlled by IC12, a 4013 dual-D flipflop. Its Q outputs in turn control CMOS switch IC3 (to select between source and tape) while its Q-bar outputs switch the Tape Monitor and Mono indicator LEDs (LEDs 7 & 8). When the appropriate button on the transmitter is pressed, pin 14 of IC9 goes low and pin 16 goes high. These outputs are decoded by IC13c and IC13d to provide a clock pulse to IC12. Each time a clock pulse is received, the data levels on pins 5 and 9 are clocked through to the Q outputs and applied to IC3. IC12 is reset at power-on to force the Q1 and Q2 outputs low. This corresponds to a stereo source selection. The power-on reset circuit consists of the 10µF capacitor and the 100kΩ resis­tor on pins 4 & 10. Volume control Let’s now take a look at the volume control stage – see Fig.6. The audio October 1993  43 .01 +5V 17 3 RFBA OUT A 4 VIN A FROM IC4 13 13 14 14 15 15 55 DAC A A GND 2 2 1 7 10 9 8 2 20 WR 7 A/B 16 RFBB 4 6 TO IC105 -15V .0047 4.7k 4.7k 7 1k +15V 19 120  0.5W 6 120  0.5W D10 1N4004 470 25VW RL1 47  6.8 47 2 22 5 4 330 5 7 4 6 IC22 SL486  D B IC23 MV601 1 C B 6 X2 500kHz 4.7k A 7 CLR 8 0.15 15 14 13 12 100pF 15 E 100pF OE 2 9 DATA 10k E V NEG. F1 500mA POWER A S1 T1 20VA D5-D8 4x1N4004 30V 27  5W +21V 15V 240VAC 0V N D9 1N4004 E CASE 44  Silicon Chip 10 25VW 4700 25VW 10 25VW 4700 25VW 10 25VW -21V 7805 GND 13 12 11 D11 10 1N914 8 D12 IN REG2 7815 GND GND IN 7915 REG3 10 25VW +15V 10 25VW 2x0.1 10 25VW 2x0.1 D15 D16 5x1N914 5x0.1 OUT OUT D13 +5V OUT 10 25VW A DATA K REG1 IN TO IC9 C B 14 D14 .0047 240VAC D  0.1 .015 10k 10k A LED9 ACK A 3 9 11 16 MOM .0047 16 16 IRD1 BPW50 +5V 0.22 3 .0047 TREBLE VR2a 25k LIN 1.5k V NEG 10 22k 22k 8 6 330pF IC116 OP27GP 100pF DB2 DB3 DB4 DB5 DB6 DB7 11 5 IC5 5534 4 2 DAC B 12 7 3 4 3 DGND 18 18 VIN B 1k 6 -15V IC15 AD7112CN CS BASS VR1a 100k LIN 22k 10pF IC16 OP27GP 3 OUT B FROM IC104 100pF DB1 DB0 +15V +15V DOWN S2 UP S3 MUTE S4 9x0.1 -15V STUDIO REMOTE CONTROL PREAMPLIFIER (2) +15V Q1 BC338 B 10k 10pF +15V 10pF 7 5 2 8 IC6 5534 3 TONE CONTROLS S5a 10pF IN 6 7 3 S6a OUT 10k HEADPHONES AMPLIFIER 4 RL1a -15V E B 6.8 BP OUTPUT 47k 22pF FROM OTHER CHANNEL C Q2 BC328 10k -15V 10k HEADPHONES 33  D2 1N4148 4 100 BP 100  33  8 6 IC7 5534 2 E D1 1N4148 5 C 10k LEFT 10k 40 21 21 22 23 24 25 26 27 28 37 1 PC5 29 30 11 8 6 12 13 14 10 IC17 ULN2003 PC4 9 RIGHT h +5V 11 12 C VIEWED FROM BELOW 13 8 IC18 ULN2003 PC3 PC2 7 PC1 PCO PA7 PB0 PB5 2 3 E PC6 PB3 36 0 9x 330  10 PB4 33 3  PC7 PB2 34 6 B 1 R PB1 32 9 BALANCE LED10-18 3 IC14 MC68HC705C8P 31 h PB6 PD2 PB7 PD3 PD4 PA0 PD5 PA1 PD7 PA2 PA3 IRQ PA4 PD0 PA5 PD1 PA6 4.7M X1 3.58MHz 5 39pF 3 7 6 5 78-- 7915 I GO G IO 4 12 13 14 15 16 17 K A 18 K A 19 11 10 9 8 7 6 5 5 20 16 6 LE D 2 C 4 +5V 7 1 B A a b c d 5 16 8 IC19 4511 3 6 LE D e f 4 g 15 14 +5V 7 1 B A b c d 8 5 4 2 3 2 LE f 13 12 11 10 9 g a 15 14 B A IC21 4511 3 e 7 1 C 4 8 7x 330  10 9 5 16 IC20 4511 a 7x 330  2 C 3 13 12 11 10 9 39pF 4 4 +5V 38 39 6 b c d D e f 6 8 g 13 12 11 10 9 15 14 10 9 2 7x 330  10 9 8 5 4 2 3 8 5 4 3 a f e +5V b g c d DISP1 HDSP7803 DISP2 HDSP7803 DP 1,6 1,6 7 330  DISP3 HDSP7803 1,6 ATTENUATION (dB) October 1993  45 PARTS LIST FOR REMOTE CONTROL STEREO PREAMPLIFIER Main preamplifier 1 1-unit high rack mounting case 1 screen printed front panel to suit case 1 rear panel self adhesive label 1 PC board, code 01308931, 350 x 230mm 1 PC board, code 01308932, 243 x 25mm 1 neutral Perspex® sheet, 130 x 20 x 3mm 1 plastic film mask for front panel LED displays 1 2 x 15VAC 20VA low profile transformer (Transcap) plus four screws & nuts to suit 1 240VAC panel-mount mains switch (S1) 1 mains cord & plug 1 cord grip grommet 1 3-way mains terminal strip 1 M205 panel-mount fuse holder (F1) 1 500mA 2AG fuse 2 micro U heatsinks, 18 x 19 x 10mm (Altronics H 0504 or equival­ent), plus screws & nuts 1 TO-220 heatsink, 30 x 25 x 12mm (Jaycar HH-8504 or equivalent) plus screw & nut 2 16mm brushed black aluminium knobs 1 6.35mm stereo DPDT switched insulated phones socket (Altronics P 0076 or equivalent) 1 micro PC-mount 12V DPDT relay (Altronics S 4150 or equivalent) 1 16mm 100kΩ linear dual- output from IC4 (Fig.5) is fed into pin 4 of IC15, an AD7112 dual logarithmic D/A converter (DAC). As stated in Pt.1, this device is used as a programmable resistance to control the gain of op amp stage IC16 and thus the level of the audio signal. The way in which this works was described in detail in Pt.1. An internal resistor inside IC15, designated RFBA (at pin 3), sets the maximum gain of IC16 to -1, while the 100pF feedback capacitor ensures high 46  Silicon Chip ganged pot (DSE R-7661 or equivalent) 1 16mm 25kΩ linear dualganged pot (DSE R-7657 or equivalent) 1 PC-mount DPDT push-on/ push-off switch plus a black knob (S5) 3 snap-action PC-mount switches (S2-S4) 1 black panel-mount banana socket 18 panel-mount insulated RCA sockets (Arista RCA31 or equivalent), or use an insulated sub-panel plus screws & nuts 2 2µH wideband chokes (Philips 4330 030 3896) 1 40-pin IC socket 45 PC stakes 5 rubber feet 6 6mm standoffs plus screws & nuts 10 cable ties 1 4-metre length of 0.8mm tinned copper wire 1 2.5-metre length of shielded audio cable 1 120mm length of twin shielded audio cable 1 400mm length of green hookup wire 1 400mm length of green/yellow mains rated wire 2 solder lugs 1 screw, nut & star washer 1 Murata CSB500E 500kHz ceramic resonator 1 3.579545MHz parallel resonant crystal Semiconductors 12 NE5534AN low noise op amps (IC1, IC4, IC5, IC6, IC7, IC8, IC101, IC104, IC105, IC106, IC107, IC108) 3 4051 8-channel analog multiplexers (IC2, IC102, IC11) 1 4053 triple 2-channel multiplexer (IC3) 3 ULN2003 7-way Darlington drivers (IC9, IC17, IC18) 1 4042 quad latch (IC10) 1 4013 dual D-flipflop (IC12) 1 4011 quad NAND gate (IC13) 1 MC68HC705C8P programmed microprocessor (IC14) – see footnote 1 AD7112CN dual log D/A converter (IC15) – NSD Aust. 2 OP27GP op amps (IC16, IC116) 3 4511 BCD to 7-segment LED display drivers (IC19-IC21) 1 SL486 IR receiver (IC22) 1 MV601 IR decoder (IC23) 1 7805 5V 3-terminal regulator (REG1) 1 7815 15V 3-terminal regulator (REG2) 1 7915 -15V 3-terminal regulator (REG3) 2 BC338 NPN transistors (Q1, Q101) 2 BC328 PNP transistors (Q2, Q102) 12 1N914, 1N4148 diodes (D1, D2, D101, D102, D12-D15) 6 1N4004 1A diodes (D5-D10) 2 7.5V 400mW zener diodes (ZD1, ZD2) 3 HDSP7803 0.3-inch green LED displays (Disp1-Disp3) frequency stability. Both DACs inside IC15 are individually controlled by the DB2-DB7 inputs and these in turn are controlled by microprocessor IC14. This allows the left and right channel gains to be adjusted separately (in 1.5dB steps) to provide the volume and balance functions. resistor to prevent RF breakthrough. This stage has a gain of 2.5, as set by the 1.5kΩ and 1kΩ feedback resistors, while the 330pF feedback ca­pacitor rolls off the high-frequency response to ensure low RF sensitivity and to provide stability. IC5 in turn drives the tone control stage which is based on IC6. This arrangement has the tone controls connected in the feedback network. When the bass and treble controls are centred, the gain of the stage is -1. Tone controls The audio output from IC16 is coupled to non-inverting amplifier stage IC5, again via a 1kΩ stopper 9 3mm green LEDs (LED1-9) 9 rectangular green LEDs (LED10-LED18) 1 BPW50 IR diode (IRD1) Capacitors 2 4700µF 25VW PC electrolytic 1 470µF 25VW PC electrolytic 4 100µF 50VW bipolar electrolytic 2 47µF 50VW bipolar electrolytic 1 47µF 16VW PC electrolytic 1 22µF 16VW PC electrolytic 14 10µF 25VW PC electrolytic 2 6.8µF 50VW bipolar electrolytic 1 6.8µF 16VW PC electrolytic 1 1µF 16VW PC electrolytic 1 0.22µF MKT polyester 1 0.15µF MKT polyester 20 0.1µF MKT polyester 2 .068µF MKT polyester 2 .015µF MKT polyester (5%) 1 .015µF MKT polyester 4 .01µF MKT polyester 2 .0047µF MKT polyester (5%) 5 .0047µF MKT polyester 1 .0047µF 240VAC polyester 2 330pF ceramic 4 100pF ceramic 2 39pF ceramic 2 22pF ceramic 13 10pF ceramic Resistors (0.25W, 1%) 1 4.7MΩ 2 1.5kΩ 2 1MΩ 8 1kΩ 4 330kΩ 35 330Ω 2 200kΩ 2 150Ω 7 100kΩ 2 120Ω 0.5W 14 47kΩ 10 100Ω 6 22kΩ 1 47Ω 2 16kΩ 4 33Ω 22 10kΩ 1 27Ω 5W 7 4.7kΩ Winding the bass or treble controls towards the input side of IC6 (ie, the output of IC5) increases the gain for frequencies above 2kHz for the treble control and below 300Hz for the bass control. The reverse happens when the tone controls are rotated in the opposite direction. This has the effect of increasing the negative feedback at bass and/or treble frequencies to provide bass or treble cut. The amount of treble boost or cut provided by IC6 is limit­ ed by the Remote transmitter 1 remote control case (DSE ZA4666) 15 chrome buttons to suit case 1 switch membrane to suit case 1 PC board, code 01308933, 59 x 62mm 1 PC board, code 01308934, 57 x 72mm 1 Dynamark front panel label, 73 x 63mm 1 9V battery & clip 1 Murata CSB500E 500kHz ceramic resonator 1 100mm length of 11-way rainbow cable 1 250mm length of 0.8mm tinned copper wire Semiconductors 1 MV500 remote control IC (IC1) 1 MTP3055E or MTP3055A N-channel Mosfet (Q1) 2 CQY89A IR LEDs (LED1, LED2) Capacitors 1 220µF 16VW PC electrolytic 2 100pF ceramic Resistors (0.25W, 1%) 1 10kΩ 1 2.2Ω 1 10Ω Footnote: the coded 68HC705C8P microprocessor is available from Silicon Chip Publications Pty Ltd & is priced at $45 plus $6 p&p any­ where in Australia (price includes sales tax). Payment may be made via cheque, postal order or credit card authorisation (Bankcard, Visa & Mastercard. 4.7kΩ resistors on either side of the treble pot. Similarly, the amount of bass boost and cut is limited by the 22kΩ resistors on either side of the bass control pot. Tone bypass Switch S5 bypasses the tone control circuitry when switched to the OUT position, or selects the output from the tone control circuitry in the IN position. From there, the signal passes via headphone-operated switch S6a, relay contacts RLY1a and a 6.8µF bipolar capacitor to the output terminal. The 6.8µF capacitor prevents any DC offset that may appear at the output of IC6 from being fed to the input of the stereo power amplifier. Relay RL1 is used to isolate the outputs from S6a and S6b at switch on and switch off. This is mainly to prevent a chirp from the preamplifier circuitry from being fed through to the exter­ nal power amplifier after switch off. If a set of headphones is plugged in, S6a diverts the audio signal from S5a to the headphone amplifier. This consists of IC7 and transistors Q1 and Q2. The two transistors boost the output current capability of the NE5534 op amp and are slightly forward biased (to keep crossover distortion to a mini­ mum) by diodes D1 and D2. IC7 functions with an overall gain of 5.7, as set by the 47kΩ and 10kΩ feedback resistors. The 22pF capacitor in the feedback path reduces the high frequency gain above 150kHz, while the two 33Ω emitter degeneration resistors provide local negative feedback to reduce distortion and improve the temperature stabil­ ity of the output stage. The output of the headphone amplifier is coupled to the headphone socket via a 100µF bipolar capacitor and series 100Ω resistor. This provides short-circuit protection for the op amp and protects the headphones from damage if one (or both) of the output transistors fails. Infrared receiver IC22 and IC23 form the heart of the infrared receiver cir­cuit. The incoming IR signals from the transmitter are picked up by photodiode IRD1 and the resulting current pulses applied to differential inputs at pins 1 & 16 of IC22, an SL486 infrared preamplifier IC. The received pulses are then amplified and filtered before appearing at the output (pin 9). The capacitors at pins 2, 3, 5, 6 & 15 of IC22 roll off the frequency response of the internal gain stages to filter out any 100Hz signals. This ensures that the circuit is immune to mains lighting interference. One important feature of the SL486 is an automatic gain control circuit and this is provided by an internal peak detector which measures the output signal on pin 9. The 0.15µF October 1993  47 Despite the complicated circuit, the IR Remote Control Preamplifier is easy to build. That’s because many of the control functions are taken care of by the microprocessor (IC14), while two CMOS switch ICs take care of the input selection. The microprocessor automatically switches to static idle mode when no IR signals are being received, to ensure excellent noise specifications. capacitor on pin 8 filters the output of the peak detector and the result­ing signal is used to control the internal amplifier stages. IC23, an MV601 remote control receiver, decodes the pulse signal from IC22. This device operates at 500kHz, as set by ceramic resonator X2, and provides five BCD outputs (A, B, C, D & E), the exact code depending on which transmitter button is pressed. In this application, momentary operation of the BCD outputs has been selected by tying pin 5 of IC23 high. In addition to the five BCD outputs, IC23 provides a Data-bar signal (pin 10) which goes low whenever a valid code is received. The five BCD outputs and the Data-bar output are ap­plied to microprocessor IC14 and also to IC9, the 5-7.5V convert­er (see Fig.5). The Data-bar output of IC23 also drives an AC­ Knowledge LED (LED 9), which indicates that an infrared signal is being received. Microprocessor control IC14 controls the digital portion of the circuit. It oper­ates from a clock based on a 3.579545MHz crystal connected bet­ween pins 38 and 39. This clock frequency is internally divided 48  Silicon Chip by two, so that the microprocessor actually runs at 1.78MHz. The microprocessor decodes the BCD signals from IC23 on its PD2-PD7 lines and uses its PA0-PA7, PB0-PB7 and PC0-PB7 lines to control the LED displays and the D/A converter (IC15) according­ly. In greater detail, the PA0-PA6 output lines control IC19-IC21 which are 4511 BCD to 7-segment display drivers. These drive the 7-segment LED displays via 330Ω current limiting resistors to in­dicate the attenuation level. The display drivers are only ac­ cessed by IC14 when the volume level is to be changed. Outputs PA7 and PB0-PB7 of IC14 control the balance display LEDs via Darlington transistor drivers IC17 and IC18, while outputs PC0-PC7 control the D/A converter (IC15) to set the volume level. The Down, UP and Mute switches on the front panel are monitored by the PD0, PD1 and IRQ (interrupt request) lines of IC14. Normally, these lines are tied high via 10kΩ resistors. When the Down switch is pressed, the PD0 input is pulled low and the IRQ input is also pulled low via D13. Similarly, the Up switch pulls PD1 low and pulls the IRQ line low via D14. The Mute switch pulls both PD0 and PD1 low via diodes D15 and D16 and pulls the IRQ line low via D12. In each case, a low IRQ level tells the microprocessor to “wake up” from its idle state, check its PD inputs and act accordingly. Power Power for the Remote Control Preamplifier is derived from a mains transformer with two separate 15VAC windings which are series connected to provide 30VAC. This is rectified by diodes D5-D8 and D9 and filtered by two 4700µF capacitors. The resulting ±21VDC rails are applied to 3-terminal regulators REG1, REG2 and REG3 to obtain +5V and ±15V rails. The ±15V rails power the op amps, while the +5V rail powers the microprocessor, LED dis­plays and associated ICs. The relay coil (RLY1) is supplied from the negative recti­ fied line via two series 120Ω 0.5W resistors. These resistors reduce the supply to a nominal -12V. Diode D9 isolates the relay supply from the 4700µF filter capacitor in the negative rail so that the relay switches off quickly when the power is switched off. That’s all we have space for this month. Next month, we shall present the assembly details for the IR Remote SC Control Preamplifier. 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 Low-cost unit comes as a pre-assembled module Solid-State Message Recorder This simple device uses a surface-mounted IC & allows you to record & playback sound for periods of up to 16 seconds. It comes as a preassembled module – you just supply the case & batteries. In the July 1993 issue of SILICON CHIP, we described a solid-state message recorder that could record up to 16 seconds of audio and featured a non-volatile memory; ie, the chip re­tained the recorded message even when the power was switched off. The design was based on the ISD­ 1016AP message recorder IC, a relatively new device that samples the incoming audio signal and stores the samples as analog voltages in an internal EEPROM. This technique is PLAY (OUT) AUX IN 11 C5 22 16VW S2a 28 ON/ START (IN) OFF (OUT) 16 27 REC (IN) OFF (OUT) more efficient than digital storage techniques and provides somewhat better sound quality. If you don’t want to go to the trouble of building the circuit yourself, then this pre-assembled module is the answer. It uses the same chip as the SILICON CHIP design and provides the same functions – ie, a 16-second recording time, non-volatile memory and automatic power down when not in use. Fig.1 shows the circuit details. Two pushbutton switches are used R3 2k S1 S2b K  ON/ START (IN) LED1 C1 0.1 23 R2 10k 24 A 25 C4 0.22 50VW 17 VCCA SPKR+ P/R A K SPKR- AUX IN VCCD IC1 ISD1012/1016A/1020A CE ANA OUT PD ANA IN EOM MIC A0 ELECTRET MIC to control the playback and record functions. To record a message, S1 is pressed in to select REC and then S2 is pressed in to start the 16-second recording period. A LED comes on when recording starts and turns off when the 16 seconds is up or if S2 is pressed again to end the recording session. To play the recording, S1 is set to the OUT position to select play and then S2 is pressed. As with recording, the LED comes on at the start and automatically switches off at the end. Power for the circuit is derived from a 6V battery consist­ing of four 1.5V AA cells. The solid-state recorder comes complete with a microphone and battery holder and sells for $34.95. It is available from your nearest Dick Smith SC Electronics store (Cat. K 9200). 1 A1 2 A2 A3 3 4 A4 5 A5 6 A6 9 AGC TEST A7 (CLK) VSSA VSSD 10 26 13 12 14 8O SPEAKER 15 21 20 C2 1 50VW C6 0.1 B1 6V Fig.1: circuit details of the pre-assembled voice recorder module from Dick Smith Electronics. It provides up to 16 seconds of recording time in a non-volatile memory. 19 R1 510k C3 4.7 50VW ANALOG RECORDER October 1993  57 SERVICEMAN'S LOG Dead sets aren’t always easy Most servicemen regard a completely dead set as a snack. The symptom is obvious & there is no hint of the dreaded inter­mittent. It should be a simple matter of seek-until-you-find but it isn’t always that easy. The set was a Panasonic TC-48P10, a 48cm colour set fitted with an M15D chassis. And the “D” in that chassis number is important; it indicates a “dead”, or mains isolated, chassis. An “L” suffix would indicate a live chassis (heaven forbid)! The customer was not very happy. The set was only 18 months old which meant that it was no longer covered by the normal 12 months warranty. To make matters worse, he had already had an unfortunate experience with his previous set; a different make which had given a lot of trouble due, at least in part, to poor service from another organisation. In regard to this set, he described it as being completely dead. This was a fair enough description from his point of view but not strictly accurate. 58  Silicon Chip It could best be described as “mostly dead”. And as readers would know, there is a world of difference between “completely dead” and “mostly dead”. When I first turned it on there were several signs of life which, while brief, provided important clues. First, there was the usual “boing” from the degaussing system, indicating power in that part of the circuit. There was also some weak distorted sound and, for a second or so, I could hear the EHT system start before then shutting down. The sound continued however, since the relevant circuitry is powered directly from the switch­ mode power supply. I switched the set off for a minute or so, then tried again. It gave a repeat performance. On the next occasion, I hooked an EHT probe onto the ultor connection and was rewarded with a brief EHT response. The needle had time to swing up to a few thousand volts before the system shut down. All of which was very valuable information. This set, along with most other Panasonics from the same era, is fitted with a very comprehensive protection circuit. Among other things, it monitors the 24V rail for excessive current, checks for excess beam current, checks for over-voltage on the CRT heater, and checks for shorted turns in the EHT transformer wind­ings. It was obvious that this protection circuit was being trig­gered in some way and would have to be disabled. That’s because there is no way that the set can be serviced while ever the protection circuit continues to operate. The set must be made to function, even with a potentially destructive fault condition, before one can come to grips with the problem. If the protection circuit is not disabled, one can fiddle around until doomsday with little hope of progress. It is also important to realise that, once triggered, the protection circuit will remain operative until the set is switched off. Regular readers may recall that I dealt with a similar situation back in August 1990, involving a TC-1480A receiver. But I am emphasising these points again, because the manuals contain little or no information on how to disable the protection cir­cuits. Circuit details The accompanying circuit (Fig.1) should help the reader to follow the story. I don’t have a suitable circuit for the M15D chassis and this circuit is taken from an M15L chassis manual (the two are virtually identical). The protection circuit is at top right and involves transistors Q503 and Q504. The horizontal output transformer (T501) is at lower centre, while a portion of the jungle chip, IC601, is at the top. One of the easiest sections of the protection circuit to disable is that from the CRT heater. The CRT heater voltage appears at pin 5 of the EHT transformer and is monitored via R540. This resistor is quite easy to lift and, in fact, this was what I did back in August 1990. And it worked on that occasion because the fault was in the CRT heater supply. I tried this again, with more hope than conviction. Well, blessed is he who expecteth nothing, as they say, because that is what happened. Oh well, it hadn’t needed any great effort. So what now? The circuit indicates that there are several other ways of disabling the protection circuit, including lifting R529 from pin 3 of the EHT transformer. Unfortunately, R529 is almost impossible to get at, (pin 41) and to the collector of the horizontal driver transistor (Q502). Switching on for a short burst revealed a square wave signal of about 5.6V p-p at pin 41. In terms of amplitude and shape, it was very close to the waveform in the manual but the frequency was way out. Naturally, the situation at the collector of Q502 was similar. Which really didn’t tell me much more than I already knew. What about the voltages on the relevant pins of IC601? Pin 42 is shown as +8.5V which was correct. The voltages for the other pins (37, 38, 39, 40 & 41) are given elsewhere in the manual and these were all close to specification. Next, I examined the components around pin 38, particularly C502 and C504, since they normally control the horizontal oscil­ lator frequency. But again, I drew a blank. In fact, I was run­ning out of ideas and rapidly painting myself into a corner, where IC601 seemed the only suspect. The same corner Fig.1: the horizontal deflection circuitry in the Na­tional TC-48P10. The protection circuitry, built around Q503 and Q504, is at centre right, while part of jungle chip IC601 is at the top. being packed in by other components, including a heatsink. What about disconnecting the lead at pin 3 of T501? No way; the transformer terminals are soldered into tubular rivets mount­ed on the board. Unless the whole transformer is lifted, it is almost impossible to break this connection. A better approach, though still not easy, is to remove Q503. This was also partly blocked by the heatsink and needed quite a spot of jiggling to get it out but the job was eventually done. I was now ready for a cautious test. I decided to keep my finger on the switch to enable a quick shut-down, and my eyes, ears and nose were on alert for the first sign of trouble. OK; switch-on. It was pretty much an anti-climax; no smoke, no flame, no explosions – not even a warning smell. The set was up and running. Well, sort of. There was a problem in that there were multiple pictures on the screen, rolling over one another in an unlocked medley. In short, the horizontal system was running wild, and several times too fast. It isn’t wise to run a set like this for lengthy periods. Subsequent tests would have to be made in short bursts. The first thing I checked, almost instinctively, was the horizontal hold control (R506) which forms part of a network on pin 39 of IC601. This had some effect but it was only slight; the system was still running wild. Next, I hooked up the CRO to the horizontal pre-drive output of IC601 I went over everything again, check­ ed and double checked, and found myself back in the same corner. I’m not all that keen on blaming an IC –particularly a 42-pin IC – simply because I can’t think of anything else. ICs are remarkably reliable these days and even when I do change one, when it seems like the last resort, I’m wrong more often than not. But I really was all out of ideas and, since I had a spare IC on hand, I took the plunge. And this time I was right; that was it. The set warmed up to reveal a single picture – slightly out of sync due to my previous fiddling – but which locked in immediately with a touch of the horizontal hold control. From there it was mainly a routine tidy-up. The most im­portant part was to restore the protection circuit. And I empha­sise that word “important”. Buoyed up by having solved a tricky problem and faced with a fiddly replacement job, there may be a temptation to skip this operation. After all, the set is working and the customer won’t know the difference. Don’t be tempted. For one thing, there is the risk to one’s reputation should the set subsequently suffer unnecessary damage due to the lack of this protection. There is also a legal angle. By implication, in this context, one is required to restore a piece of October 1993  59 SERVICEMAN'S LOG – CTD equipment to its original condition. In the event of a fault causing damage to other property, or injury or worse (eg, due to a fire), the serviceman may well be liable if it transpires that this was due to his failure to restore the protection circuitry. It doesn’t take much imagina­tion to appreciate the seriousness of such a situation. Anyway, this set was fully restored and returned to the customer. I trimm­ ed the account as much as possible and he was a good deal happier all round, knowing that the fault had been positively found and fixed. The picture that jumped And now, from my Tasmanian colleague, J. L., comes a way-out story about a 56cm Sanyo fitted with a 79P chassis. According to J. L., the 60  Silicon Chip complaint was that the picture was jumping up and down. By all accounts, that turned out to be a gross understate­ ment. For my money, the fault should really take the way-out prize for the year – any year. I have never heard of anything like it and I doubt whether anyone else has. In fact, it was so way-out, that one of the hardest parts of the whole affair, for both of us, was finding a way to de­scribe the symptoms. J. L.’s initial description left me somewhat confused which merely serves to emphasise just how bewildering the whole thing was. Eventually, having resorted to message sticks and jungle drums, a somewhat clearer picture emerged (no pun intended). I had suggested to J. L. that he try to draw a sketch of the image on the screen. His answer was that he was better brain surgeon than an artist. I must remember not to develop a headache if I ever travel to Tasmania! Anyway, his latest message stick starts off, “You’re con­ fused? What about me?” He then submits the following expanded explanation. Imagine a perfectly normal picture of (say) a newsreader. The various lines that make up the picture are lying one after the other – line one (in field one) followed by line two (in field two) and so on down the screen. In other words, the inter­lace is working normally. Now, something happens that causes field two to be delayed by 0.1ms. The interlace is no longer normal and field two would be displayed a millimetre or so below field one. This gives rise to an annoying vertical jitter, but the two images (field one and field two) would not appear to be separated. As the delay increases, field two is displayed further and further down the screen and a point is reached where the images are visually separated (ie, displaced one below the other). What had at first looked like vertical bounce has given way to severe flicker, as each field is displayed alternately. Now suppose that the field two delay increases to 10ms. The separation is now quite dramatic, with field two beginning half way down the screen (one field = 20ms). Well, that’s J. L.’s explanation so far and a very good one it is. However, in an effort to make the explanation as clear as possible, he has deliberately, in his own words, “...run the tape backwards.” In other words, he has reversed the sequence of events; the description in the previous paragraph was the situation when he first switched the set on. OK, J. L., you take it from there. Let’s look at that description again. As the set came on we saw two pictures. One was in the usual position, with the news­reader centred on the screen. In the other picture he was centred near the bottom of the screen. Most of his face was in the bottom half and his collar and tie in the top half. Over the next five minutes, as the set warmed up, field two drifted up the screen so that soon only the tie was at the top, with the face and most of the collar at the bottom. Then, as the two images came closer together, the flicker changed to bounce, then to jitter. Finally, the two images coalesced into an accept­ ably normal picture. The only other major symptom was a degree of non-linearity in both images. However, when I changed channels, the two separated images were back. This time it took only about 30 seconds to recover to an almost satisfactory picture but however long it took, it was a fault that the owner would not tolerate. And I don’t blame him. A thermal problem The fault had every appearance of being a thermal one. The initial five minutes settling time was about as long as most sets take to stabilise their temperature. And the shorter time needed to settle down after a channel change could be explained by the very short disturbance between channels. So I began to search for a heat sensitive part around the vertical circuits. The sync separator, vertical oscillator and vertical drive circuits are all inside IC401, an LA1460 located towards the back of the circuit board – see Fig.2. The various resistors and capacitors associated with the sync separator circuits are arranged around this chip and it was to this area that I first turned. The video input enters the chip at pin 21 and is fed to a sync amplifier. It then exits on pin 20 and is fed to a wave-shaping network built around R404, R406 and C403. The modified video subsequently goes into the sync separator at pin 19 and exits as separated sync on pin 17. From pin 17, the sync pulses go in two directions: (1) via R424 to the horizontal AFC; and (2) via the vertical integrator (R431, C431, R432 & C432) to the vertical oscillator input at pin 1. Inside the chip there is the vertical oscillator, then a P.W. (pulse width?) control and the vertical drive stage. The vertical drive exits on pin 5 on its way to the vertical output stage. With so much going on around the vertical parts of the chip, it was hard to nominate a likely place to start the inves­tigation. However, there was one part that stood out on the circuit AUSTRALIAN MADE TV TEST EQUIPMENT 12 Months Warranty on Parts & Labour HIGH VOLTAGE PROBE Built-in meter reads positive or negative 0-50kV. For checking EHT & focus as well as many other high tension voltages. $120.00 + $5.00 p&p DEGAUSSING WAND Great for comput er mon­­­i t­o rs. Strong magnetic field. Double insulated, momentary switch operation. Demagnetises colour picture tubes, colour computer monitors, poker machines video and audio tapes. 240V AC 2.2 amps, 7700AT. $85.00 + $10.00 p&p TV, VCR TUNER REPAIRS From $22. Repair or exchange plus p&p. Cheque, Money Order, Visa, Bankcard or Mastercard TUNERS Phone for free product list 216 Canterbury Rd, Revesby, NSW 2212, Australia. Phone (02) 774 1154 Fax (02) 774 1154 October 1993  61 Fig.2: the horizontal & vertical drive circuitry in the Sanyo 79P chassis. IC401 is at left, C436 above & to the right, C437 to the right again, diodes D454 & 456 at upper right, & R457 to the right again. All responded to freezer so it was difficult to track down the villain. diagram, although it was very hard to find on the PC board. C403, between the sync amp and the sync separator, is a 1µF 16V electro. These low value electrolytics are notorious for losing capacitance and/or going leaky. If I ever find one of these in the vicinity of a fault, I waste no time in reefing it out and replacing it with a new one. The new capacitors are probably no more reliable than the old ones but at least they eliminate one source of trouble! This capacitor is a tiny device about 2-3mm in diameter and about 5mm long. It was tucked away at the back of the board and it took me quite some time to find and replace it. But it was all to no avail; the picture was still bouncing when I switched the set back on. Although there were other electrolytics in the vicinity, they were larger value items and therefore less suspicious. So I was thrown back onto the idea of a thermal fault, either in the resistors or the IC itself. I used the last quarter of a can of freezer spray going over everything around the chip. None of the resistors responded to being cooled but the IC was another matter. A light spray on the centre of the chip produced no reac­tion but a good hard blow, enough to put a layer of frost over the top and around the pins, sent the picture into a frenzy of bouncing. And, as the frost dissipated, the picture slowly re­verted to normal; three minutes later all was at peace again. I repeated the experiment several times, emptying one spray can in the process and making a big impression on the cont­ents of another. But it was quite unequivocal – cold the picture jittered, warm and it didn’t. In keeping with my luck, I didn’t have an LA1460 in stock and had to wait several days before one became available. But it was all another waste of time. The new chip was exactly the same as the original. It must have been just coincidence that freezing the chip produced the same symptoms as the fault I was chasing. Another clue It was about this time that I noticed something about the jitter that sent me off on another course of investigation. The jitter was worse at the top of the screen than at the bottom. At its worst, the separation of the images was some 100mm at the top of the screen but only about 60mm at the bottom. When the picture stabilised, the image at the top of the screen was jittering about 1 or 2mm while the 62  Silicon Chip Little left By this time there was very little left to test. In fact, there were just two items – both of them in that narrow strip of vertical circuitry that I mentioned earlier. One was C437, a 0.33µF greencap in the height circuit. This was a good candidate for the villain of the piece but changing it did nothing. The next and last item was another capacitor, C436, a 10µF electrolytic forming part of the time constant network on the pulse width control in the chip. And this was finally nailed as the villain. I don’t know what kind of a fault the capacitor was suffer­ing from since it measured correctly and showed no leakage. But replacing it finally restored stability to the set and I was able to return it to the owner, confident that the fault had been found and cured. It’s strange, though. There were at least three other com­ponents that responded in the same way as the real culprit and they were separated by quite some distance from that item, which precludes overspray as an explanation for the results. It took nearly two cans of freezer to sort that one out. I hope there aren’t too many of those waiting for me out there! A similar effect Fair enough, J. L., and I hope so too, for your sake. But mulling over the initial description of the fault, as we finally worked it out, I was reminded of a somewhat similar effect that I saw some years ago. This wasn’t a fault; it was quite deliberate. I had the privilege of being shown over one of our TV stations by one of the engineers. And their pride and joy at the time was a recently installed satellite circuit, bringing in programs from overseas, mainly from the United States. Having shown me the dish, he took me inside to view the incoming picture. Talk about visual garbage. As the engineer quickly pointed out, to make the best possible use of time on the circuit, two programs were transmitted at once; one on each field of a normal transmission. So the image on the screen was an interlaced presentation of two completely different pictures. It was no big deal to separate the two fields, but that left each picture with only 262.5 lines. Again, no problem: each missing line was then replaced with one synthesised from the line before it and the line after it, making a full 525-line picture. That’s all something of a diversion I know, but J. L.’s story brought back the vision of the incomprehensible image I saw on that primary monitor. And, conversely, it helped me visualise SC what he was describing. Protect your valuable issues Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. ★ High quality ★ Hold 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). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. Use this handy form ➦ bottom of the image was perfectly still. All of which suggested that the problem might be somewhere around the linearity circuits or in the feed­back network from the output stage. It didn’t take all that long to find the linearity control and the circuits around it, because it was clearly labelled and close to the front of the board. What did surprise me was the way so much of the vertical circuitry was arranged in a narrow strip right across the board, from front to rear. A collection of resistors, capacitors and diodes was clus­tered near the front of the board, a long way from where I would have expected to find them. And it was this that had led me away from the true location of the cause of my troubles. Apart from the chip, I had been spraying in all the wrong locations! I resumed my search by dosing the vertical and linearity trimpots. This made no real difference to the set’s performance but, purely by chance, some overspray landed on one of the two diodes in the linearity circuit and the jittering started up again. The diodes, D454 and D456, and their associated resistors (R463 and R464) were all arranged close together, just behind the linearity pot. It was almost impossible to spray any one part in isolation. So I let my head go and replaced all four items. Unfortunately, when I switched the set back on, the fault was still there! I started spraying again and this time it was R457 in the side pincushion network that proved to be heat sensitive. The resistor is a 33Ω unit that feeds vertical parabola waveforms into the transductor. I couldn’t see any connection with vertical jitter but cooling it brought on the jitter and warming it re­duced the symptoms. I replaced the resistor and when I switched the set back on, the *!<at>% fault was still there! (Really J. L. – please!) Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard   ❏ Visa   ❏ Mastercard Card No: ______________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ October 1993  63 An FM wireless microphone for musicians This new FM wireless microphone looks good & works well. It uses a well-proven circuit which has excellent frequency stability & good range. It operates from a 9V battery with a current drain of 3.5 milliamps. Design by BRANCO JUSTIC FM wireless microphones can be temperamental devices to use, particularly as far as frequency drift is concerned and there are several causes for this. The first of these is due to a drop in the supply voltage as the battery ages. The second is due to capacitance effects between the user’s body and the dangling antenna. Third, and not usually recognised, is drift due to change in temperature. When you set up an FM wireless microphone to operate at a particular frequency, say 95MHz, you don’t expect it to drift much. If it only drifts by a small amount, the AFC (automatic frequency control) circuits of your FM tuner should cope with the change in frequency so that the signal is always received clear­ly. But there is a limit to the AFC range of any FM tuner, per­ haps ±100kHz, and beyond that, the signal will start to dis­tort badly and ultimately, will not be received at all. That is why drift caused by body capacitance can be so annoying as ANTENNA S1 22k Q2 BF199 10k 560  B 0.1 0.1 220k 0.1 B 8.2k 100pF MIC 100k .047 Q3 BF199 B C 1k 33pF External features 1pF 12k L1 B FM WIRELESS MICROPHONE C E 15pF E 100pF 6.8k C E 22pF 9V Q1 BC549 270 E 680  Q2, Q3 C Q1 B E C VIEWED FROM BELOW Fig.1: Q1 functions as a preamplifier, while Q2 & Q3 form a modulated oscillator with good isolation between the antenna & the tank circuit. 66  Silicon Chip it varies all over the place. We make these comments about drift essentially because this design does not have these problems. We tested it in a number of ways, including heating up the PC board with a hot air gun and even then, drift was not a problem. After five minutes under a heat gun, the operating frequency shifted from 95.422MHz to 95.452MHz and by that time the circuit components were pretty hot. That order of change is only +0.03%. In fact, drift due to supply voltage variations of ±1V for a 9V supply is also quoted as less than ±0.03%. Operating range is quoted as better than 100 metres with a good quality tuner. Other relevant specs are: signalto-noise ratio >60dB; pre-emphasis 50µs; frequency response 40Hz to 15kHz. 15pF The unit is housed in a rugged black anodised aluminium tube measuring 210mm long and 40mm in diameter. At one end of the tube is a miniature slide switch and exit hole for the wire antenna. At the other end, which is open, is the PC board and electret microphone insert with is covered by a foam plastic windshield, mak- 560  10k 100pF 22k 270  6.8k 0.1 220k 0.1  MIC 100k 1k .047 9V Q1 8.2k Q2 15pF 680  22pF 100pF Fig.2: install the parts on the PC board exactly as shown in this wiring diagram. ANTENNA Q3 L1 15pF 1pF 12k ing the unit quite professional in its appearance. The PC board measures only 26 x 44mm and is held inside the aluminium tube by foam plastic. Also inside the tube is a stan­ dard alkaline 9V battery and battery snap connector. Fig.1 shows the circuit which uses three NPN transistors. Transistor Q1 is an audio preamplifier which steps up the signal from the electret microphone insert. The output of Q1 is coupled via a 0.1µF capacitor and 8.2kΩ resistor to the base of Q3 which is the lower half of a cascode oscillator circuit. The cascode con­ figuration is the secret of this circuit’s excellent rejection of body capacitance effects on the operating frequency. The operating frequency is set by the parallel network comprising the 1pF capacitor and adjustable coil L1 at the base of Q3. By virtue of the cascode configuration, the components which set the operating frequency are well and truly isolated from the antenna which is connected to the collector of Q2. Building it Assembling the board is simply a matter of inserting and soldering the components into the board and this is a pretty straightforward process. The 33pF most important point to remember is to keep all the component leads to an absolute minimum length because at the operating frequency of the FM band, even short lead lengths have significant inductance and this can prejudice the circuit operation. The second point to consider is that the PC board is actu­ally double sided, with the top of the board being a ground plane. Hence some component leads will need to be soldered to the copper on both sides of the board. This means that all the com­ponent leads which connect to the 0V line in the circuit must be soldered on both side of the board. This includes the negative lead from the battery, the negative lead of the electret and the can of the adjustable coil L1. The negative lead of the electret supplied in the kit is the one connected to the case. All the resistors are soldered “endon” to save space on the tiny PC board. The length of the antenna wire is up to you. You can have it short and unobtrusive or long and thereby obtain better range. We suggest a length of about 80-90cm as the best length for overall range. Any longer and the range will be re­duced. Once all the components are soldered to the board, you are ready to test continued on page 93 PARTS LIST 1 PC board, coded FMTX, 44mm x 27mm 1 electret microphone insert 1 9V alkaline battery 1 9V battery snap 1 subminiature former with core, can and base (L1) 1 SPST miniature slide switch (S1) 1 BC549 NPN transistor (Q1) 2 BF199 NPN RF transistors (Q2,Q3) Capacitors 3 0.1µF monolithic 1 0.047µF monolithic 2 100pF ceramic 1 33pF ceramic 1 22pF ceramic 2 15pF ceramic 1 1pF ceramic (see text) Resistors (0.25W, 5%) 1 220kΩ 1 8.2kΩ 1 100kΩ 1 6.8kΩ 2 22kΩ 1 1kΩ 1 12kΩ 1 680Ω 1 10kΩ 1 270Ω Kit availability This FM wireless microphone has been produced by Oatley Electronics who own the design copyright. They can supply the kit in several parts. First, a kit including the PC board, omnidirec­ tional elec­tret microphone insert and all the board parts is $11.00. A unidirectional insert is available for $6, while the black anodised tube & windshield is $9. Postage & packing is $4. The company’s address is PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. Keep all leads as short as possible when mounting the parts on the PC board (above). The view at right shows how the completed assembly is wedged in position in the aluminium tube using pieces of foam rubber. October 1993  67 AMATEUR RADIO BY GARRY CRATT, VK2YBX Judging receiver performance Prospective purchasers of communications receivers often judge the performance by sensitivity alone. This article sets out to explain the various parameters considered by designers & why they are critical to overall receiver performance. High quality filters This basic “adjacent channel rejection” performance is largely determined by the quality of the IF filters used. As radio spectrum availability is reduced, commercial users are being forced to adopt narrow channel allocations. Commercial channel spacings of 12.5kHz are now common. This means that a receiver must be able to reject strong signals having 60dB or so more amplitude, 12.5kHz away from the operating channel. This kind of selectivity can only be achieved through the use of high quality filters having steep skirts. Such filters should be used at all intermediate frequencies (IF) used in the receiver. Hence, commercial receivers must have adequate sensitivity (typically 0.3µV for 12dB Sinad) whilst maintaining a high level of adjacent 68  Silicon Chip channel selectivity. The Department of Transport and Communications specification for 25kHz spaced equipment is 73dB, and for 12.5kHz the specification is 65dB. This is a good indica­tor of the importance of adjacent channel rejection. In addition to the narrow-band IF filters necessary for tight channel spacing, care must also be given to the specifica­tion of any “mix down” crystals used in IF conversion. Such crystals must have tight frequency tolerance and temperature drift specifications, as the narrower channel spacing makes it far easier for the receiver to drift off the nominal fre­quency. Front end selectivity is also an important parameter. Interfering signals f1 AMPLITUDE Whilst it is certainly true that the ability of a receiver to detect and produce intelligible audio from a weak signal is a very important performance parameter, there are other more important characteristics rarely appreciated by the end user. A receiver must not only have the ability to “hear” minute signals and discriminate against noise, but it must also have the ability to reject adjacent signals having a power level of up to one million times that of the “on channel” signal (+60dB). 3rd f2 3rd 5th 5th 7th 470 7th 480 490 500 510 520 FREQUENCY (kHz) 530 540 Fig.1: this diagram shows 3rd, 5th & 7th order products in a 144MHz receiver. A good receiver should exhibit 60dB of intermodulation immunity to two mathematically related interfering signals within several hundred kilohertz of the wanted input frequency. which can cause spurious responses are the intermediate frequency, the image frequency fc - IF (or fc + IF if the local oscillator is above the input frequency), fc - 2IF (or fc + 2IF), fc ± 455kHz, fc ± 2 x 455kHz. By using a bandpass filter comprising several tuned circuits, correctly matched to the RF amplifier and the mixer stage, up to 50dB of image suppression can be achieved, without compromising receiver sensitivity, or selectivity. Choice of IF Careful choice of IF is also important. By selecting a first IF high in frequency, say 70MHz or so, all images will fall well outside the passband of the receiver, increasing the atten­uation of any image frequency. Of course, selection of a suitable IF is governed to a large degree by commercial avail­ability of multi­pole crystal filters. Another cause of degraded receiver performance is non line­arity of the RF stages. The linearity of an RF amplifier is always best at low levels. This means that there are two con­flicting design goals; ie, to maximise amplifier gain for best sensitivity, and to minimise RF gain to ensure linearity. The solution is to distribute the gain of the receiver across several stages. It is better to reduce the frontend gain of the receiver by several dB, thereby improving the front-end overload immunity by 10dB or more, and make up for the reduction in gain after conversion. Another beneficial effect of reducing the RF gain of the receiver input stage is to minimise the affect of compression or “blocking”. Blocking occurs when a strong signal is present within the passband of the receiver front end, causing the first stage to become saturated and therefore unable to pass AMPLITUDE LOCAL OSCILLATOR OSCILLATOR NOISE FLOOR (a) FREQUENCY AMPLITUDE LOCAL OSCILLATOR NOISE SIDEBANDS (b) FREQUENCY Fig.2: this diagram shows the difference between a clean & a dirty local oscillator. The sideband noise can fall within the IF passband & therefore become audible. a weak signal. Blocking immunity is thus a measure of the ability of a receiver to detect the wanted signal without exceeding a pre­scribed level of degradation, caus­ed by the presence of an un­wanted signal. A typical blocking test for commercial receivers calls for 90dB of immunity to any interfering signal from 1-10MHz either side of the wanted signal. Intermodulation When two or more interfering signals combine in any non-linear semiconductor, the result is a set of intermodulation products. For example, if there are only two signals present, the primary result will be f1-f2 and f1 + f2. These are called second order products. The additional products of 2f1, 2f2, 3f1 and 3f2 are normally well outside the coverage of the receiver. However, odd order intermodulation products (ie; 3rd, 5th and 7th order harmonics) can be a problem. Using two input signals, f1 and f2, 3rd order products of 2f1 - f2 and 2f2 - f1 are generated, as are 5th order products 3f2 - 2f1 and 3f1 - 2f2, and 7th order products 4f2 - 3f1 and 4f1 - 3f2. Each pair of products is separated from its partner by a frequency equal to the difference frequency of the two originating signals. Fig.1 shows 3rd, 5th and 7th order products in a 144MHz receiver. A good receiver should be able to exhibit 60dB of intermodul­ ation immunity to two mathematically related simultaneous interfering signals within several hundred kilohertz of the wanted input frequency. When a combination of products is fed into a mixer stage having some degree of non linearity, a spurious response is generated. This is further complicated when one or both of the original signals is modulated. Careful allocation of gain is essential and the importance of linearity can also be seen. The commercial market demands receivers able to exhibit at least 70dB of spurious response immunity from 100kHz to 1000MHz, regardless of operating frequency. Equally important is the design of the local oscillator. An impure local oscillator can cause a significant problem in receiver perfor­mance, called “reciprocal mixing”. This problem is caused when the receiver local oscillator signal contains significant noise sidebands. Fig.2 shows the difference between a clean and a “dirty” local oscillator, caused by a poorly designed syn­thesis­er. The combina­tion of an off-channel input signal and the sideband noise of a dirty local oscillator produces a signal in the receiver IF passband, along with the on-channel signal, degrading the input signal due to noise masking. In general this problem is limited to synthesised designs (crystal oscillators are normally quite clean) and hence is a very important consideration. Most of the above characteristics relate to the internal effects of mixing products. However, it is just as important that no conducted spurious signals emanate from the receiver to the antenna system. Commercial specifications limit conducted spuri­ ous emis­­sions to an absolute level of -57dBm for mobile tran­sceivers and -47dBm for handheld transceivers. Careful considera­tion must therefore be given to effective antenna filtering which minimises spurious emissions, without adversely affecting receiver sensitivity. From these few points, it can be seen that there are a significant number of factors which affect the design of a receiver. Having an appreciation for these factors can result in a better selection for a given application. SC October 1993  69 WHICH CLOCK? A BINARY CLOCK! Which clock tells the time yet has no hands, face or digits? Which clock counts off the time in inexorable fashion & is almost hypnotic as you watch it? Which clock painlessly teaches binary numbers & tells the time too? A binary clock, of course! Design By MICHAEL VOS* This clock uses 17 large LEDs to display the time in binary fashion. Anyone who sees it remorselessly counting away cannot help being intrigued. And while we don’t think it will suddenly dis­place conventional clocks and watches, it presents a different and interesting way of telling the time. And it can be used to teach the system of binary numbers. In a binary clock, six digits are required to display sec­onds or minutes. In other words, we need a 6-bit system with each bit weighted according to its position in the sequence. So with six bits or six LEDs we can display any number between zero and 63. In 70  Silicon Chip practice, for a binary display of minutes or seconds, we only count from zero to 59. To display hours, we need only five bits (or LEDs) since we need only count up to 23. This clock will display 12 or 24-hour time. Circuit description Since this clock counts in binary rather than decimal, it is ideally suited to logic circuitry. However, rather than use standard logic ICs, the designer has opted to use GALs from Lattice Semiconductors, Inc of the USA. GAL stands for Generic Array Logic and is a variant of the programmable logic array devices produced by a number of semiconductor companies. In effect, GALs, PALs, PLAs or whatever they are called, can be programmed by fusing internal links so that arrays of gates can be made to perform a wide variety of functions. In effect, they give the advantage of custom ICs without the design and manufacturing expense. Three GALs have been used in this circuit and they have been individually programmed to provide the seconds, minutes and hours counters. Each of these counters can be pre-loaded with a value using a set of DIP switches and this provides a method of setting the time. With GALs providing the basic time counting circuitry, it only remains to provide a 1Hz pulse signal and this is provided by IC3 and IC4. One inverter inside IC3, a 74HC4060 ripple counter, is connected with a crystal to oscillate at 4.194304MHz. The crystal is temperature compensated with the ceramic capacitors connected to pins 10 and 11. This clock frequency is divided by 256 and 1.2k 1% VR1 500  OUT IC8 LM317T 120  ADJ 1% 100k VCC 6.8 25VW 1 ZD1 4.3V 2 3 4 IN 5 6 S5 S4 S3 S2 S1 S0 S1 SECONDS 12 11 10 9 8 7 I1 I2 I3 1 2 3 5x 0.1 IC5 OUT 7805 GND 6.8 GND 25VW 6 5 7 4 8 J1 DC3 BINARY CLOCK D1 1N4001 6.8 25VW 1 2 IN 3 12 11 10 9 M5 M4 M3 M2 M1 M0 S2 MINUTES I1 I2 1 2 IOR1 K A 6 IC8 IC5 I GO 8 IC7c 11 10 I3 10k 11 IC7a 2 7 3 IC7b 5 RUN SET S4 10k 10k VC1 30pF 33pF 56pF X1 4.1943MHz 10M PO 10 8 RST 12 PI 11 4 14 6 74HC00 VCC 8 14 Q8 IC3 74HC4060 33pF N750 12 12 RST 12 3 Q14 11 11 PI IC4 74HC4060 16 16 VCC 13 13 IC7d 3 20 AO I 5 4 3 2 1 16 IOR4 12/ H4 H3 H2 H1 H0 24 12 11 10 9 8 7 9 I1 I2 IOR1 1 2 19 10 S3 HOURS IOR8 K 15 IOR5 IC2 GAL16V8B  K 8 K 17 IOR3 A 4  16 LED1-5 18 IOR2  K 2 A  1 K 14 IOR6  A 1k 1k A 1k 1k A I4 I5 I6 I7 I8 I9 I10 4 5 6 7 8 9 11 12 9VDC 20 VCC 19 18 IOR2 K 17 IOR3 10 16 IOR4 IC1 GAL16V8B 14 IOR6 K 15 IOR5 K  K 4  K 16 I4 I5 I6 I7 I8 I9 I10 4 5 6 7 8 9 11 IOR8 1 K 13 IOR7  12 19 18 IOR2 20 VCC IOR1 K 17 IOR3 K 16  10 I4 I5 I6 I7 I8 I9 I10 4 5 6 7 8 9 11 12 IC6 GAL16V8B 14 IOR6 16 IOR4 K 4 K 15 IOR5 K  A 2  A 8  32 A  A 2  A 8  32 Construction Assembly of the clock is just a matter of installing all the components on the PC board. This should be cleaned and thor­oughly inspected before you begin inserting components. Install all the resistors, diodes and the zero-ohm link first, then insert the crystal. Tin the case end of the crystal with solder, install a discarded component pigtail lead through the PC board hole at the crystal end. Solder the wire to the crystal and PC board. This provides a ground shield, mechanical stability and thermal coupling to the capacitors. Next, install the trimmer capacitor. The flat end goes to the left. This orientation grounds the rotor so you can use a screwdriver without affecting frequency adjustment. Both 3-terminal regulators are mounted on the copper side of the PC board and their mounting tabs are bolted to the board for heatsinking. Install the three DIP switches (S1,S2,S3) so the individual switch numbers are on the bottom and read from left to right. The momentary pushbutton switch can also be installed at this stage. IOR8  K 13 IOR7 A  1 1k A 1k 1k A 1k 1k 1k LED12-17 A 1k A 1k 1k A 1k 1k 1k LED6-11 A the output at pin 14 is 16384Hz. This is divided by IC4, another 74HC4060 ripple counter, to provide an output signal of 1Hz at pin 3. The outputs of the GALs directly drive the 17 LEDs from a supply rail which is adjustable to provide variable display brightness. The variable supply is provided by IC8, an LM317T adjustable 3-terminal regulator. Its ADJ terminal can be adjusted from zero to 4.3V, as set by the zener diode ZD1, and thus its output can be varied from +1.2V to +4.9V. IC5, a 5V 3-terminal regulator, powers the rest of the cir­cuitry and diode D1 protects both regulators from reversed input supply connections. Power is provided by a 9V DC plug­pack. 1k ▲ Facing page: own a binary clock & be one up (two up) on your neigh­bours who have to make do with digital or analog clocks. 17 large LEDs indicate the time & they are driven by GALs (Generic Array Logic ICs). Fig.1: the circuit is essentially in two parts: (1) an oscillator & divider chain to produce a 1Hz signal; & (2) three GALs in a synchronous counter. October 1993  71 Install the 17 LEDs carefully so that they are aligned with each other. The shorter lead of each LED goes towards the GAL ICs. Install ICs 3, 4 and 7 and then the GAL ICs. Note that these are individually programmed and are coded with paint dots on their undersides. IC1 has one paint dot, IC2 has two paint dots and IC6 has no paint dots. If desired, the PC board can be mounted on an aluminium stand using the screws which retain the two 3-terminal regulators. This is available as an option with the kit. Install a PCB mount DC socket if you want power entry from the component side of the board. Alternatively, if PARTS LIST 1 PC board, 303 x 101mm 1 9V 500mA DC plugpack 1 2.1mm DC socket 1 aluminium stand (optional) 3 6-way DIP switches (S1, S2, S3) 1 momentary contact SPDT switch (S4) 1 4.1943MHz crystal 1 500Ω trimpot (VR1) Semiconductors 3 GAL16V8B 15ns ICs (IC1, IC2, IC6) 2 74HC4060N ripple counters (IC3, IC4) 1 74HC00N quad NAND gate (IC7) 1 LM7805T 5V regulator 1 LM317 adjustable 3-terminal regulator 17 10mm red 200mcd LEDs (LED1-LED17) 1 1N4001 1A rectifier diode (D1) 1 79C4V3 4.3V 400mW zener diode Capacitors 3 6.8µF 25VW tantalum electrolytic 5 0.1µF 50V monolithic ceramic 1 56pF N1500 ceramic 1 33pF N150 ceramic 1 33pF N1500 ceramic 1 2-30pF N750 ceramic trimmer Resistors 1 10MΩ 1 100kΩ 3 10kΩ 1 2.2kΩ 1 1.2kΩ 17 1kΩ 1 120Ω 1 0Ω link 72  Silicon Chip This photograph shows how the 3-terminal regulators (in this case the 7805) are mounted & fitted with insulated standoffs for mounting the board on the optional aluminium stand. Also shown is the panel-mounting DC power socket. your are using the aluminium stand, you will need to use a panel-mount DC socket and wire it to the PC board. Testing Rotate trimpot VR1 fully anti-clockwise and apply 9V DC to the board from a plugpack or power supply. Check that the LM7805 regulator output is +5V ±5%. Check that the trimpot varies the LM317 regulator output from +1.25V to +4.9V ±10%. With the trimpot fully clockwise to give full LED bright­ness, you should see the seconds LEDs change every second. Set all the DIP switches to the position marked “ZERO”. Press the pushbutton and all the LEDs should Specifications Clock time reference 4.194304 MHz quartz crystal. Accuracy ±1 second per 48 days when calibrated to within ±1Hz at 25°C. Worst case unadjusted: ±1 second every 11 hours based on ±100Hz deviation. Adjustment range Approx. ±100Hz. Clockwise adjustment of trim­mer capacitor speeds up clock. Operating temperature 0 to +50°C. Storage temperature 0 to +85°C. Power source 9V DC plugpack <at> 340mA min. 2.1mm DC2 type connec­tor. Brightness control Variable from 0 to 30mcd per lamp. Where to buy the kit 1.2k LED16 2 1k LED15 4 1k LED14 8 1k LED13 16 S4 1 10k 10k 10k 33pF 1k IC6 GAL16V8B 1 LED12 32 0 S1 1 1 0.1 1 1k LED11 1 1k LED10 2 1k LED9 4 1k LED8 8 1k LED7 16 0 S2 1 1 0.1 1 1k LED6 32 S3 1 1 0.1 LED5 1 1k LED4 2 LINK IC4 74HC060 1k 0 1 33pF VC1 0.1 TP 56pF LED3 4 1k LED2 8 1k 2.2k 10M IC3 74HC060 1k X1 1 0.1 LED1 16 6.8uF 100k 6.8uF 7805 D1 GND DC3 J1 Fig.2: the three GAL ICs are individually programmed & are coded with paint dots on their undersides. IC1 has one paint dot, IC2 has two paint dots & IC6 has no paint dots. The two 3-terminal regulators are mounted on the copper side of the PC board. 1k ZD1 120  IC7 74HC00 1k LED17 1 Setting the clock Setting the clock is a process of first setting switch 1 of DIP switch S3 for 12 or 24-hour mode. This done, set the hours, minutes and seconds for the appropriate time and press and hold the pushbutton until that occurs. This can be done while you are listening to the Telecom time signal. Having set the time, continue to check the time signal to ensure that the clock is in synchronism. You can use the decimal equivalent number shown under each LED to work out the DIP switch settings for any value between 0 and 63. The seconds and minutes are each set using six switches, while five switches are used for the hours setting. Note: the clock counting logic does not check for valid time settings and/or valid modes on the switches. It is possible to set the minutes and seconds to a maximum of 63 decimal, while the hours can be set to a maximum of 31 decimal. If these times are indeed set up on the switches, the clock will count until it reaches maximum, then SC resets to zero. VR1 6.8uF IC1 GAL16V8B 1 DOT go out. Now set each DIP switch to the position marked “ONE” and press the pushbutton. All LEDs should light up. Set the mode DIP switch (on S3) to “12”, set the DIP switches for a time of 12:59:59, press the pushbutton and one second later the LEDs should read 1:0:0. Set the mode DIP switch to “24”, leave the same time on the other switches, press the pushbutton and one second later the LEDs should read 13:0:0. Set the time DIP switches for 23:59:59, leave the mode DIP switch at “24” , press the pushbutton and one second later the LEDs should read 0:0:0. If you have a frequency counter you can adjust the crystal exactly to frequency although the board should be allowed to run for at least an hour before the adjustment is made. Connect the frequency counter to TP1. Adjust the trimmer capacitor to set the frequency at 4.194304MHz. Note that the initial accuracy will only be as good as your frequency counter. If you do not have a frequency counter, setting the crystal for best accuracy will be a process of trial and error, by com­paring the clock with VNG or Telecom time signals. LM317 IC2 GAL16V8B 2 DOTS The complete kit for the Binary Clock, including PC board, large LEDs and programmed GAL ICs, is available for $75 plus $5 postage and handling from Prototype Electronics, 1/29 Stewart St, Parramatta, NSW 2150. Phone (02) 683 3510 or Fax (02) 630 3148. The optional folded aluminium stand is also available at $25. Note: The above price does not include a 9V DC plugpack. October 1993  73 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. 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. 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. Rod Irving Electronics Pty Ltd Lesson 2 Programming the Motorola 68HC705C8 microcontroller In Lesson 1, we discussed the following: (1) Programming Concepts; (2) Machine Code; (3) Mnemonics; (4) 6805 Programming Model; (5) Flowcharts. In this lesson, we will discuss Addressing Modes. To write a program for a micro­ controller, we need to go from a concept to machine code. The concept may be made easier to follow by using a flow chart, from which we can start writing mnemonics. The mnemonics and an addressing mode will enable us to arrive at the machine code which will ultimately run in our micro­ controller. Mnemonics The MC68HC705C8 has instructions that are one, two or three bytes long, depending on what they have to do. We refer to the differences in length of these instructions as addressing modes. The MC68HC705C8 has 62 basic instructions and 10 different ad­ dressing modes, giving a total of 210 different op-codes. Table 1 shows the 6805 CMOS mnemonics and addressing modes. It is usually referred to as the instruction set. If you count the mnemonics in the instruction set, you will get more than 62. This is because some of the mnemonics are repeated and some have the same op-code. When you write a program for a microprocessor, some mnemon­ i cs are straightforward and require need no further information; eg, Transfer Accumulator to indeX register (TAX), or CLear Carry bit (CLC). However, some instructions, like LoaD Accumulator (LDA) or STore Accumulator (STA), do need more information; eg, load with what or load/store from/to 80  Silicon Chip where? The added information, if any, and the length of the instruction (in bytes) is governed by the addressing mode. In this lesson, we will explain three of these addressing modes: (1) Inherent Addressing Mode Symbol for Inherent addressing: none. The CPU only requires one byte of data to process this in­struction. This byte is the opcode. All information required by the CPU is “inherently” known. In other words, the instruction needs no further information from the programmer. The first three addressing mode columns in Table 1 are inherent (INH), inherent accumulator (INHA) and inherent index register (INHX). The latter two are sometimes referred to as register addressing modes but in these lessons we will class them as inherent; eg, DECA, DECX, NOP, SWI, COMA, STOP, RORA and ROLX. (2) Immediate Addressing Mode Symbol for Immediate addressing: # The CPU requires two bytes of data to process this instruc­tion. The first byte is the op-code, while the second byte is the operand. The CPU requires the operand (byte) immediately follow­ing the op-code. This byte is known at the time the program is written and it becomes a permanent part of the program. The programmer uses the immediate byte for things like setting outputs, maths, logic and compare variables, etc; eg, ADD #, AND #, ORA #, EOR #, LDA #, LDX #, CMP # and CPX # (3) Extended Addressing Mode Symbol for Extended addressing: $$ or none. The CPU requires three bytes of data to process this in­struction. The first byte is the op-code, while the second and third bytes are the High and Low address (16-bit word) of the operand in memory. The CPU requires the operand (byte) which is extended any­where in mem­ ory. The memory location for this byte is known at the time the program is written. The extended address can be the address of an output or input port, a register in a timer/counter, or any address used by the microprocessor. In these lessons, we will use the “$$” symbol to indicate the extended addressing mode. Remember it as two hex 8-bit bytes which make a 16 bit word; eg, ADD $$, AND $$, ORA $$, EOR $$, LDA $$, STA $$ and LDX $$. The instruction set in Table 1 is presented in various forms. The MC68HC705C8 technical summary has the instruction set on page 30. It shows the mnemonics, addressing modes, op-code and number of bytes in a form similar to Table 1. It also shows the number of cycles each instruction takes to execute. Other Motoro­la publications show the instruction set in different forms again and the one you use is a matter of personal choice. As an exercise, try filling out Table 2 from the Motorola 6805 instruction set. If you want the number of cycles, you will need the MC68HC705C8 technical summary or some other 6805 in­struction set. This program, like most of the programs that are written for the MAL-4, starts at location $0030. This is the first RAM location – see page 18 of the manual for the memory map. This shows us all the memory locations in “map” form. We can determine which addresses are usable for RAM and where the input and output ports are, etc. Example program Let’s write a simple program to demonstrate the things we have covered so far. We will make the LEDs on the output port (port B) flash in an inward pattern at 0.5-second intervals. The first (and most important) task is to write a flow chart – see Fig.1. It shows us what to do in picture form. The steps for the program are as follows: (1). Turn off all the LEDS at the output port. (2). Wait for 0.5 seconds. (3). Turn on the four outside LEDs at the output port. (4). Wait for 0.5 seconds. (5). Turn on all the LEDs at the output port. (6). Wait for 0.5 seconds. (7). Go back and do it all again. Writing the code Program sheet Fig.1: the flow chart for our example program. The program first turns on the four outside LEDs at the output port, then waits 0.5 seconds before turning on the remaing four LEDs. The program has been written on the MAL-4 program sheet – see Table 3. A blank copy of this sheet comes with the MAL-4 manual and you should photocopy as many as you need for writing programs. An explanation of each column follows: Address: the address where the program is to be written. Code: the 1, 2 or 3 bytes of machine code. Label: A place for notes and program entry positions. Mnemonic: the instruction mnemonic. Operand: the operand byte or address. Comment: a place to write plain English comments. The first part of the program (comment box 1) is a load/store operation. The load part uses the mnemonic LDA. We want to clear the output port, so we load the accumulator with $00. Because this is known, we will use the Immediate addressing mode. If we look up the code for LDA # (immediate), it is $A6 and it is a 2-byte instruction. The first byte is $A6 and the second byte is $00 (because we want to load the accumulator with $00). The address location is then incremented by two to become $0032. In the Store part of the operation, the mnemonic used is STA. We want to store the contents of the accumulator at the output port (Port B). A look at the memory map shows port B at memory location $0001. Since this address is known, we use the Extended addressing mode. If you look up the code for STA $$ (Extended) it is $C7 and it is a 3-byte instruction. The second and third bytes are the address of the memory location, so it becomes C7 00 01. The address is now in­crement­ed by three and becomes $0035. Silicon Supply and Manufacturing 74HC11 $0.45 74HC27 .40 74HC30 .40 74HC76 .55 74HC86 .45 74HC138 .85 74HC139 .50 74HC154 3.15 74HC165 .85 74HC174 .65 74HC373 1.05 74F00 74F02 74F08 74F10 74F11 74F20 74F21 74F27 74F30 74F32 74F36 .40 .40 .40 .40 .40 .40 .40 .40 .40 .40 .85 74F38 74F151 74F163 74F169 74F175 74F241 74F244 74F257 74F258 74F353 74LS00 .65 .55 .70 1.92 .65 .95 .90 .60 1.80 1.45 .50 74LS01 74LS02 74LS03 74LS05 74LS11 74LS12 74LS13 74LS14 74LS20 74LS21 74LS27 MAIL ORDER SPECIALIST .50 .50 .45 .45 .50 .50 .85 .55 .55 .40 .40 74LS30 74LS33 74LS49 74LS73 74LS74 74LS83 74LS85 74LS90 74LS92 74LS109 74LS126 .40 .50 2.35 1.10 .45 .75 .60 .90 1.20 .90 .50 PO Box 92 Bexley North NSW Australia 2207 74LS138 74LS139 74LS147 74LS148 74LS151 74LS155 74LS158 74LS160 74LS164 74LS175 74LS191 Credit Cards welcome -Visa, Mastercard, Bankcard. Plus Sales Tax, packing and postage .60 .60 2.35 1.05 .50 .50 .70 .75 .75 .80 .80 74LS193 74LS196 74LS240 74LS241 74LS245 74LS257 74LS273 74LS366 74LS368 74LS373 74LS374 .80 1.35 .90 .95 .80 .60 .80 .55 .60 .80 .85 Ph.: (02) 554 3114 Fax: (02) 554 9374 After hours only bulletin board on (02) 554 3114 (Ringback). Let the modem ring twice, hang-up, redial the BBS number, modem answers on second call. October 1993  81 TABLE 1 Mnemonic Description Addressing Modes IMM DIR EXT IX0 IX1 IX2 ADC Add with carry INH A9 B9 C9 F9 E9 D9 ADD Add without carry AB BB CB DB EB DB AND Logical AND A4 B4 C4 F4 E4 D4 ASL Arithmetic shift left (same as LSL) 48 58 38 78 68 ASR Arithemtic shift right 47 57 37 77 67 BCC Branch if carry clear (same as BHS) BCLR 0 Clear bit 0 in memory 11 BCLR 1 Clear bit 1 in memory 13 BCLR 2 Clear bit 2 in memory 15 BCLR 3 Clear bit 3 in memory 17 BCLR 4 Clear bit 4 in memory 19 BCLR 5 Clear bit 5 in memory 1B BCLR 6 Clear bit 6 in memory 1D BCLR 7 Clear bit 7 in memory 1F BCS Branch if carry set (same as BLO) 25 BEQ Branch if equal 27 BHCC Branch if half carry clear 28 BHCS Branch if half carry set 29 BHI Branch if higher 22 BHS Branch if higher or same (see BCC) 24 BIH Branch if interrupt pin is high 2F BIL Branch if interrupt pin is low 2E BIT Bit test BLO Branch if lower (same as BCS) 25 BLS Branch if lower or same 23 BMC Branch if interrupt mask is clear 2C BMI Branch if minus 2B BMS Branch if interrupt mask is set 2D BNE Branch if not equal (to zero) 26 BPL Branch if plus 2A BRA Branch always 20 BRCLR 0 Branch if bit 0 is clear 01 BRCLR 1 Branch if bit 1 is clear 03 BRCLR 2 Branch if bit 2 is clear 05 BRCLR 3 Branch if bit 3 is clear 07 BRCLR 4 Branch if bit 4 is clear 09 BRCLR 5 Branch if bit 5 is clear 0B BRCLR 6 Branch if bit 6 is clear 0D BRCLR 7 Branch if bit 7 is clear BRN Branch never BRSET 0 Branch if bit 0 is set 00 BRSET 1 Branch if bit 1 is set 02 BRSET 2 Branch if bit 2 is set 04 BRSET 3 Branch if bit 3 is set 06 BRSET 4 Branch if bit 4 is set 08 BRSET 5 Branch if bit 5 is set 0A 82  Silicon Chip INH INH REL B5C BTB 24 A5 B5 C5 F5 E5 D5 0F 21 Mnemonic Description Addressing Modes INH INH INH IMM DIR EXT IX0 IX1 IX2 REL B5C BTB BRSET 6 Branch if bit 6 is set OC BRSET 7 Branch if bit 7 is set OE BSET 0 Set bit 0 in memory 10 BSET 1 Set bit 1 in memory 12 BSET 2 Set bit 2 in memory 14 BSET 3 Set bit 3 in memory 16 BSET 4 Set bit 4 in memory 18 BSET 5 Set bit 5 in memory 1A BSET 6 Set bit 6 in memory 1C BSET 7 Set bit 7 in memory BSR Branch to subroutine CLC Clear carry 98 CLI Clear interrupt mask bit 9A CLR Clear CMP Compare accumulator with memory COM Ones complement CPX Comapre index register with memory DEC Decrement EOR Exclusive OR ACC with memory INC Increment JMP Jump JSR Jump to subroutine LDA Load accumulator from memory A6 LDX Load index register from memory AE LSL Logical shift left (same as ASL) 48 58 LSR Logical shift right 44 54 MUL Multiply unsigned NEG Negate 40 50 NOP No operation ORA Inclusive OR ACC with memory ROL Rotate left 49 59 ROR Rotate right 46 56 RSP Reset stack pointer 9C RTI Return from interrupt 80 RTS Return from subroutine 81 SBC Subtract with carry SEC Set carry bit 99 SEI Set interrupt mask 9B STA Store accumulator STOP Enable IRQ, stop oscillator STX Store index register SUB Subtract SWI Software interrupt 83 TAX Transfer accumulator to index register 97 TST Test for negative or zero TXA Transfer index register to accumulator 9F WAIT Enable interrupt, stop processor 8F 1E AD 4F 43 4A 5F 3F A1 B1 A3 B3 53 33 5A C3 3A A8 4C C1 5C B8 C8 3C 7F 6F F1 E1 73 63 F3 E3 7A 6A F8 E8 D1 D3 D8 7C 6C BC CC FC EC DC BD CD FD ED DD B6 C6 F6 E6 D6 BE CE FE EE DE 38 78 68 34 74 64 30 70 60 FA EA 39 79 69 36 76 66 42 9D AA A2 BA CA DA B2 C2 F2 E2 D2 B7 C7 F7 E7 D7 B5 CF FF EF DF B0 C0 F0 E0 D0 7D 6D 8E A0 4D 5D 3D October 1993  83 Table 2 Opcode Mnemonic A. Mode No. Bytes No. Cycles A6 LDA IMM 2 2 LDA EXT SWI INH STA EXT JMP EXT 43 A3 11 Box 2 is the 0.5-second time delay. Microprocessors are de­signed to run very fast, so it is sometimes necessary to slow down their operation. We do this by making them count a large number down to zero and this requires a time delay loop. The MAL-4 has a number of time delays in its monitor pro­gram. They are in a form called subroutines. You use a subroutine by jumping to it and the program remembers the point to which it is to return. Subroutines and time delay loops will be covered in later lessons. Time delay subroutines The time delay subroutines in the MAL-4 use the accumulator to vary the length of the delay (delay x acc), so you must load the accumulator before jumping to the subroutine. The delay subroutines and their addresses are as follows: D10µs: Delay = 10µs x Accumulator – $1498 D100µs: Delay = 100µs x Accumulator – $14A1 D1ms: Delay = 1ms x Accumulator –$14BD D10ms: Delay = 10ms x Accumulator – $14D9 D100ms: Delay = 100ms x Accumulator – $14E6 D1sec: Delay = 1 sec x Accumulator – $14F3 D1min: Delay = 1 min x Accumulator – $1500 We want a 0.5 second delay so the D10ms delay subroutine will do. This box requires a load accumulator immediate (LDA #) and a Jump to SubRoutine extended (JSR $$). The op-code for LDA # is $A6. The second byte of code will need to be 50 in hex or $32, since 50 x the 100ms delay subroutine gives a delay time of 0.5ms. If you look up JSR extended, it is a 3-byte instruction and the op-code is $CD. The second and third bytes will be the high and low address bytes of the location of the D100ms subroutine, Table 3 ADDRESS CODE LABEL MNEMONIC OPERAND COMMENT 0030 A600 START LDA #$00 0032 C70001 STA $$0001 Clear accumulator & store at output 0035 A632 LDA #$32 0037 CD14D9 JSR $$14D9 003A A6C3 LDA #$C3 003C C70001 STA $$0001 003F A632 LDA #$32 0041 CD14D9 JSR $$14D9 0044 A6FF LDA #$FF 0046 C70001 STA $$0001 0049 A632 LDA #$32 004B CD14D9 JSR $$14D9 Set time delay 50 ($32) x ACC = 0.5 seconds 004E CC0030 JMP $$0030 Jump to start 84  Silicon Chip Set time delay 50 ($32) x ACC = 0.5 seconds Load accumulator & store at output Set time delay 50 ($32) x ACC = 0.5 seconds Load accumulator & store at output $14D9. Don’t forget that the address is incremented by one, two or three bytes as the instruction requires (in this case, it is incremented by three bytes – $37 + $3 = $3A). Box 3 is almost the same as box 1 but instead of clearing the output port, we now want to switch on the LEDs on bits 7, 6, 1 & 0. This pattern corresponds to 11000011 in binary or $C3 in hex. Box 4 is a 0.5-second time delay and is the same as box 2. Box 5 is almost the same as box 1 but instead of clearing the output port, we now want to switch on all the LEDs. This means that the immediate byte will be $FF (ie, 11111111 in binary). Box 6 is a 0.5 second time delay and is the same as box 2. Box 7 (which is not really a box) needs to be a jump in­struction. This tells the processor to jump to an address loca­tion, in this case to the start address ($0030). The mnemonic and addressing mode will be JMP $$ (Extended). If you look this up in the instruction set you will find it to be a 3-byte instruction with an op-code of $CC. The second and third bytes will be the high and low bytes of the destination address $0030. Load the program into the MAL-4 and run the program from location $0030. The output port LEDs should flash in the pattern described. If not, go back and check that the program has been entered correctly. Mode 2 (the disassemble) mode may help you find your mistake. Things to do (1). Rewrite the flow chart and the program to make the LEDs turn on in a smooth inward pattern. In other words, make the LEDs turn on one bit at a time instead of two. (2). Experiment with the time delay to give a better visual effect. (3). Rewrite the flow chart and the program to make a 8-bit “Kitt” scanner; ie, one LED on at a time switching from left to right and back again. This will take up lots of RAM and you may need to jump to the RAM located at $0150 (page 1) and back again. This done, try writing programs for other time delays and patterns. (4). Do further reading on instructions and addressing modes, especially if you can get detailed information on the 6805 instruction set from a SC Motorola text/reference book. REMOTE CONTROL BY BOB YOUNG Maintaining your R/C transmitter; Pt.2 Last month, we left off in the middle of a discussion on the modern approach to battery housings. This month, we continue with hints on maintaining transmitter reliability. One curious fact that I forgot to mention last month, in regard to the “black wire” problem, is that the black or negative wire is attached to the non vented end of the battery. If “black wire” is caused by chemicals leaking from the vent, they should attack the red or positive lead which is attached to the vented terminal. This is rarely the case and in spite of the Editor’s note seeking to explain the mystery, I remain unconvinced. My guess is that the process involves some sort of electrolysis. I also failed to stress that the PVC insulation covering the wires must be stretched back to reveal the con- can do to prevent the problems of old age in this area. Firstly, the batteries are mounted in many different ways in modern transmitters but the most satisfactory way, from a day-to-day operational point of view, is for the batteries to be in a welded pack and hard wired into the transmitter. This is the only 100% foolproof method of ensuring battery continuity. We have already discussed (last month) the very valid rea­sons for welded packs in self-contained hous­ings, which make contact with nickel plated slide-in contacts. This arrangement, as good as it is, does leave the battery pack vulnerable to mishandling. In I cannot recommend cycling chargers too highly, for all sorts of reasons. Preventative maintenance is an absolute must in model flying &, for that matter, in all modelling. ductors. The wires should be bright silver or copper. If “black wire” is present, the wire will appear dark grey to gloss black. The wire will also probably come away in your hand with the slightest tug. Do not attempt to re-solder it for it will not solder properly and will also contaminate your soldering iron tip. Before leaving the batteries, there are several things the handy modeller 86  Silicon Chip time, with continual use and the odd removal and re-insertion for examination, the slide-in contacts can be com­pressed and become intermittent. So keep these clean and correc­ tly tensioned. CRC-226 sprayed on the battery pack ends and con­tacts will help prevent corrosion forming in this very vulnerable area. A very common method of inserting batteries into R/C trans­mitters is to clip nicad AA cells into dry battery holders. Here we have a potential catastrophe just waiting to happen. Most AA-cell holders that I have encountered appear to be made of green cheese and in time, due to constant pressure from the terminal springs, the plastic at the ends bends away from the batteries and contact pressure is lost. Hard wire the batteries My advice here is to dump the battery box and hard wire the batteries into the transmitter. If this is too hard, then examine the battery box closely for signs of distortion at the ends. If this is occurring, dump that battery box and look for one made of rigid plastic and with adequate webbing to support the ends. Make sure the battery ends, springs and terminals are free from corrosion and that the springs are correctly tensioned. Finally, spray the battery pack ends and terminals with CRC-226. One word of caution in regard to battery boxes: the trans­ mitter is a portable unit and is subject to bumps and knocks. Some of these jolts are severe enough to flick a battery from the box and then power is lost completely. Make sure that the batter­ies are locked into place by wrapping some insulation tape or elastic bands around each set of four batteries. This applies to the battery box in the model as well but the 8-cell boxes are the worst as the cells tend to spring up into a “V” if knocked. In fact, I do not recommend battery boxes at all in the model, due to the effects of engine vibration. Soldering cells together And now I should comment on soldering to nicad cells. The manu- facturers do not recommend soldering to cells direct and they warn that cells can explode or at least be damaged by the heat. You would have to apply an awful lot of heat for one to explode but they are relatively easily damaged during soldering. For this reason, welded tabs are vir­ tually a must on cells intended to be soldered together. However if you do wish to solder cells with no tabs or replace a tab that has come adrift, then here is the procedure. File both ends of the battery until the area to be soldered is quite clean. This is an absolute must! – use a very hot soldering iron, with a good thermal mass. A large Scope iron is quite good for this job. Tin the cell ends first by simultaneously applying the solder (resin cored 60-40) and the iron to the terminal points. A quick dab is all that should be necessary. If the iron is hot enough, the solder will flow immediately with minimum heat transfer to the battery internals. However, if the iron is too cold or the thermal mass insuf­ficient, you will need to hold the iron in contact with the battery for an extended period. This will result in a build up of heat to the battery internals and almost certain permanent damage to the cell. Now tin the wire ends and, with a quick dab of the hot iron, solder the lead to the cell. Always remember that perfectly clean contacts, a good hot iron and quick dabs are all that are needed. Do not leave the iron in contact with the battery for any extended period. Now we come to the problems associated with ordinary (non-rechargeable) AA-cell batteries. By definition, these need to be replaced often and most of the above comments apply to this type of battery. Lock the cells into place with tape or elastic bands and keep the contacts clean and tight. They will also corrode the terminals, particularly if they are left to go flat, so keep up the CRC-226. The process of generating the electrical energy in a dry cell battery calls for the zinc case to be consumed. In time then, the case will begin to leak as the internal chemicals eat their way through the case. For this reason, it is important to remove the cells if they are flat or are to be left standing for any period of time. We are all too familiar with the mess that develops inside a battery-powered device in which the batteries have been left too long. Manufacturers these days put a second case of steel or cardboard around the zinc case to help contain this corrosion. This is only a help, not a cure, so take those old cells out. Again, a similar process of electrolysis takes place and the terminals will begin to corrode before the batteries show visible signs of leakage. Constant inspection and lubrication with CRC226 is the only answer to the problems of corroded terminals. If you must solder to dry cells, exactly the same procedure must be followed as above, with one extra precaution. The nega­tive end on some cells is not actually the end of the battery, but is a pressed metal disc, held in place by the rolled over ends of the outer casing (see Fig.1). This disc relies almost entirely upon the terminal CUT HERE ROLLED END ZINC BATTERY CASE METAL DISC ROLLED END Fig.1: the nega­tive end on some cells is a pressed metal disc, held in place by the rolled over ends of the outer casing. Soldering a wire to this disc can result in the negative terminal going open-circuit. spring pressure to force it against the bottom (negative) casing. Thus, if a wire is soldered to this disc, there is a very real risk of an open circuit on the nega­tive terminal. The cure is to remove this disc with a sharp knife and solder directly onto the zinc casing. Simply cut down through the outer casing about 2mm behind the end cap. This only applies to cells with a cardboard casing. A steel casing cannot be cut and such batteries should be used in a battery box. The positive terminal needs no attention other than filing. Many years back, I lost several good models before I dis­covered this trick. Modern transmitters run on 9.6V (eight cells). Using the voltmeter, check to see that the battery pack comes up to approx­imately 1.25V per cell when it comes off charge. Many of the new breed of transmitters have an inbuilt voltmeter with a liquid crystal display, so this is a routine matter. Always check this voltage with the transmitter switched on. Most transmitters will work with one or even two cells short circuited but range will be down. When one is flying and the model is 600 metres away, it’s not the ideal time to discover that your Tx pack is down one or two cells. If you are using a cycling battery charger, then a shorted cell will show up as an extraordinary reduction in time to discharge. I cannot recommend cycling chargers too highly, for all sorts of reasons. Preventative maintenance is an absolute must in model flying and, for that matter, in all modelling. Ponds are cold places to enter in winter, while car tracks are very busy and nicely built and painted cars soon look very second­hand after a few collisions. I have spent a considerable amount of time on the battery packs for good reason. It is the area where butchery abounds. I get transmitters in for repair with batteries soldered with blow torches, acid flux, and with brands of nicads mixed together, a very poor practice. I get “black wire”, batteries that look like a salt cellar in the rainy season, and in these I also get holes eaten clean through the aluminium transmitter case by the battery chemicals. I get battery boxes that look as if they have never made contact in their life and dry cell batteries that are flat out lifting the needle off the voltmeter stops. I get PC boards that are green and black and with the copper tracks eaten clean off the substrate. I also get components growing whiskers and with legs corroded completely through. All of these faults were easily preventable yet most had resulted in crashed models. Most transmitters will run for their entire lives with no electrical faults. However, if you keep the transmitter in service long enough, you will encounter battery problems. From here, it is a short step to damaged components and PC boards. For this reason, I strongly recommend routine replacement of the nicads once every five years. My own transmitter was built in October 1993  87 1974 and apart from the replacement of nicads, is still original. It is interesting that even though I built later models than this transmitter, it was my favourite model so I just hung on to it. I have never felt the need for FM, PCM or bells and whistles; just a simple to operate, reliable transmitter. The receiver nicads call for the same attention but here I also recommend that the receiver pack be replaced after any physical damage, even if it appears to be working satisfactorily. Meter circuits The meter circuit in some of the older sets is often a source of mystery to many modellers. There are several reasons for this. Basically, there are two sorts of metering circuits, “battery test” and “RF indication”. RF indication is the most useful but it can be confusing for it seems to give a different reading every day and is an endless source of complaint and enquiry. For this reason, most manufacturers these days fit the more simple and predictable “battery indication” meter. To use it correctly, extend the antenna fully and hold the transmitter in both hands with the antenna vertical and the meter at eye level. The meter will now indicate RF power and battery condition very predictably, provided the same routine is carried out each time. If the needle falls out of the normal range under these conditions, then do not fly until you have checked out why. I find battery indication meters a real pain. In testing, I am forever swapping the transmitter crystal from the transmitter to my signal generator. If I forget to put the crystal back in the transmitter, the battery meter indicates action but the receiver does not agree. On the other hand, RF indication tells me straight away to “put the crystal back in dodo”. An RF indication meter can even be used as a field strength meter if another transmitter is brought close to the antenna, with your transmitter switched off. I have often confirmed transmitter failures on the field with my own transmitter using this technique. An RF indication meter is very reliable & is much more indicative of transmitter health if used correc­tly. It can even be used as a field strength meter. The problem with RF indication is that it draws a small amount of RF energy from the base of the antenna, rectifies it and uses the derived DC voltage to drive a meter. The problem is that the voltage available at the base of the antenna varies if the antenna is collapsed or extended, the user’s hands are on the transmitter or off, or even if the transmitter is lying on its back on the ground. All of these will give a different meter reading which often throws the uninitiated into a complete spin. Visions of intermittent transmitter operation are imme­diately conjured up in the mind of the modeller and the poor manufacturer or distributor is bombarded with questions for a week thereafter. In fact, an RF indication meter is very reliable and is much more indicative of transmitter health if used correc­tly. 88  Silicon Chip Finally, check all wiring for frayed or otherwise suspect appearance. If a lead comes off one of the control pots, results will vary from the pulses disappearing from that pot to the pulse returning to neutral. Rarely, if ever, have I seen a wiring fault in well-built transmitters. Transmitter checks If you have access to an oscilloscope, then look for the output of the modulator and check that all of the pulses are jitter free and move smoothly with each pot. A noisy pot will show up as extra pulses appearing in the pulse train or a sudden jump in pulse width on one channel. A similar effect will show up on the old half-shot encoders if an earth fault is present. Included in earth faults is “black wire” syndrome and if extra pulses are present, check all earth wiring for this problem. If a noisy pot is encountered, sometimes a spray of CRC-226 on the pot shaft will eventually work its way down onto the pot element and clean it. If not, replace the pot. There should be one more pulse in the pulse train than the number of channels. Thus, a 4-channel set will show five pulses, a 7-channel set will show eight pulses, and so on. As stated last month, RF tuning is rarely necessary but if it is, a spectrum analyser is a must. Some of the output coils are wave traps for harmonics and should be treated as such. To check the modulation on an AM transmitter, clip the earth lead to the input probe, thus making a loop. Place this in close proximi­ty to the fully extended transmitter antenna and set the scope’s vertical gain to maximum. A solid green band, blocked off by the modulation, should appear on the screen, the amplitude of which will depend on scope’s bandwidth. Check that all of the pulses are present, with no extras, and that they vary smoothly when the control sticks are moved. Check that the green band is an even colour. If there is fading from the centre out, then there is distortion in the RF output, often an indication of parasitic oscillation. If you do not know how to fix this, then send it off for service as you may be causing problems for other modellers on the field. For FM sets, the problem of viewing the modulation is a little more difficult. A modulation meter is virtually a must. The receiver is the next best thing and the pulse checks men­tioned above can be carried out with the scope connected to the receiver’s demodulator. You can check the RF output with the loop to see if the RF output is free of parasitics. Check also that collapsing the antenna does not introduce parasitics. Often a badly-tuned transmitter will break into oscillation when the antenna is fully or partially collapsed. Again, this may cause trouble to others on the field. This one is particularly troublesome at times, as a lot of operating takes place in the pits with collapsed antennas. Whilst on this point, do not run transmitters for any extended time with the antenna collapsed as it may result in overheating of the output transis­tor. That’s it for this month. Next month, I will discuss the care and mainteSC nance of receivers. CEBus AUSTRALIA KITS CEBus Australia has opened the Circuit Cellar door to bring you a range of high quality, educational electronics kits. There are three types of kit available: an Experimenter’s Kit which includes the PCBs, manuals, any key components that are hard to find and the basic software required by the finished product. Then there is the Complete Kit which includes everything above plus the additional components required to complete the kit. Finally, there is the complete kit with Case & Power Supply. Regardless of which kit you purchase you get the same high quality solder masked and silk screened PCB and the same prime grade components. Our range of kits includes: HAL-4 4 Ch, EEG Monitor, Complete kit only ................... $356.00 Experimenter’s Kits: SmartSpooler, 256K print spooler ..................................... $214.00 IC Tester, Tests 74xx00 family ICs .................................... $233.00 Serial EPROM Programmer, For 27xxx devices ............... $214.00 Ultrasonic Ranger Board with Transducer.......................... $194.00 NB: The above prices DO NOT include sales tax. Don’t forget we also have the HCS II, Home Control System, available, Its features include: Expandible Network, Digital & Analog 1/O, X-10 Interface, Trainable IR Interface and Remote Displays. Call fax or write to us today for more information. Bankcard, Mastercard & Visa accepted. CEBus AUSTRALIA. Ph (03) 467 7194. Fax (03) 467 8422. PO Box 178, Greensborough, Vic 3087. October 1993  89 PRODUCT SHOWCASE Kenwood’s TS-950SDX HF transceiver Kenwood’s TS-950SDX is the company’s flagship wideband HF communications transceiver, designed for all modes of transmission and recep­tion including SSB, CW, AM, FSK and FM on the 10 12, 15, 17, 20, 30, 40, 80 and 160 metre bands. The TS-950SDX incorporates DSP (digital signal processing) circuitry that assists in the modulation and filtering stages. Traditional RC circuits and analog ICs are replaced with digital circuitry that assists the suppression of unwanted sidebands. Up to 15 low pass filters are selectable Power line monitor from Westinghouse The PQM-1000 power monitor is programmed to log the 15 most common types of mains line disturbances. This is done using volt­age and frequency thresholds that are applicable for malfunctions and data corruption in sensitive elec­tronic, industrial controls and com­puter systems. A 2-line liquid crystal display provides a readout of line voltage and frequency, high frequency noise (L-E & N-E) and disturbance event counts. The battery backed memory holds data during pro­ longed power failures. LED indicators are provided to show 90  Silicon Chip in SSB and CW modes with cut off frequencies ranging from 600Hz to 6kHz. In FSK mode, three bandpass filters are selectable with the centre frequency of 2200Hz. Band selection is made by use of 10 direct band/keys that select any one of the amateur bands. When this fea­ture is used in conjunction with the ENT key and Kenwood’s Quick Memory feature, up to five of the most used channels are stacked for quick reference. In addition, another 100 memories are reserved for most used channels. Kenwood claims that the TS950SDX has unprecedented frequency stability and resolution due to its temperature compensated crystal oscillator and microprocessor controlled PLL and DDS circuits. The TS-950SDX also offers a dual-frequency receive facility which allows two frequencies to be received simultaneously. An RX-SUB key allows instant swapping between the two frequencies. A TF-W key is particularly useful for monitoring the transmit frequency. With external speakers or headphones, main and sub receivers can be monitored simultaneously. The TS-950SDX wideband trans­ ceiver has a recommended retail price of $6990 and is available at selected Kenwood dealers. For further information on the TS-950SDX and other Kenwood products, contact Kenwood on (02) 746 1888. New factory for Harbuch Electronics Harbuch Electronics Pty Ltd, makers of power, toroidal and audio transformers, now have a new manufacturing facility at 9/40 Leighton Place, Hornsby. Harbuch has been involved in the design and manufacture of conventional audio and power transformers the occurrence of past or present disturbances. The 15 power disturbance event counters log power failures, voltage drop (sags), low line voltage (brownouts), voltage surges, high line voltages (over voltage), voltage spikes (impulses), high frequency noise and high/low line frequency. Two keys enable the user to scroll up or down through the different displays and event counts. Both keys are pressed at the same time to clear the event counters. For further information, contact John Thompson, Westinghouse Industrial Products, 59 Stephenson St, Spotswood, Vic 3015. Phone (03) 391 1300. for over fifteen years. Increased demand for toroidal transformers has led to the requirement for larger and more efficient premises. A comprehensive stock of most standard items means that overnight delivery is available within Australia. The ability to quickly produce custom designs is a special service, with quotations and full specifications available within 24 hours of request. Steven Whitaker, sales manager for Harbuch, is confi­ dent that the company is now better equipped to re­spond to individual customer requirements. The com­pany is currently undertaking an in depth review of quality assurance procedures in order to achieve Australian Standards Accreditations in the near future. For more information about the products and services offered by Harbuch Electronics phone (02) 476 5854. High density DC/DC converters Computer Products Inc has announced a new series of medium power, high density converters. Designated BASiX, the new converters use a patented Resonant Transition Zero Voltage Switching technique that cuts losses to yield higher efficiency, to offer a high perform­ ance unit with a power density of 36 watt/in3. BASiX provides internal input and output filtering, protection features, true current sharing, redundancy and a 40-amp output capability, all contained in the industry standard 4.6 x 2.4 x 0.5-inch package. There is a choice of input voltage of 40-60V or 36-75V DC. Output voltages are either 3, 5, 12, 15, 24 or 48V DC, and power outputs range from 130W to 200W. The new converters have a constant 700kHz switch­ing frequency for easier system filtering, advanced aver­age current-mode secondary side control, and an inter­nal EMI filter. For further information, contact Amtex Electronics, 13 Avon Road, North Ryde, NSW 2113. Phone (02) 805 2113. New Tektronix scope has colour display Tektronix has announced its newest and lowest priced colour digital oscilloscope, the TDS 524A. It includes the same graphical user interface (GUI), acquisition proc­ess, triggering section and analysis as the recently intro­duced colour TDS 544A. The TDS 524A includes the Tektronix proprietary October 1993  91 Surround sound speakers from Dali Dali has announced the availability of two surround-sound speakers for home theatre systems. The Dali CS-1 is a slim, compact centre channel speaker using high quality drivers. The speakers are magnetically shielded, allowing close placement to a television set without affecting picture quality. The twin 10cm bass/midrange drivers feature polypropylene cones while the 25mm tweeter from Vifa features ferro-fluid oil cooling and mu-metal magnetic shielding. The NuColor full-colour monitor, 500MHz analog bandwidth, 500 megasamples/ second maximum sample rate, up to 50,000 points-per-channel record length (15,000 points standard) and two channel plus two auxiliary channel input. The scope includes a 1.44MB floppy disc drive, an optional video trigger with HDTV triggering, FFT with averaging, and expanded template compact dimensions of 125 x 430 x 180mm (H x W x D) enable the speaker to fit easily above or below the television set. Retail price for the CS-1 is $299 per pair. The Dali-SAT is a compact satellite with two drivers. It has “ball and socket” mounting, allowing the speaker to be tilted and turned to suit individual rooms and systems. Available in both black and white finishes, Dali-SAT retails for $299 per pair. For further information, contact Scan Audio Pty Ltd, 52 Crown St, Richmond, Vic 3121. Phone (03) 429 2199. testing to include maths waveforms. For fur­ther information on the Tektronix col­our and new monochrome TDS oscil­loscopes, phone Tektronix on (02) 888 7066. 20-bit process control engine board Boston Technology Pty Ltd has announced the release of the LLAD 57 VIDEO & TV SERVICE PERSONNEL TV & VIDEO FAULT LIBRARIES AVAILABLE AS PRINTED MANUALS $90 EACH + $10 DELIVERY BOTH MANUALS VIDEO & TV $155 + $15 DELIVERY OR AS A PROGRAM FOR IBM COMPATIBLES $155 + $10 DELIVERY FOR MORE INFORMATION CONTACT TECHNICAL APPLICATIONS FAX / PHONE (07) 378 1064 PO BOX 137 KENMORE 4069 92  Silicon Chip 20-bit process control board for PCs and compatibles. The LLAD 57 is a multi-function board for process applications built around a high-precision temperature-stabilised bridge. It is optimised for weighing applications but is adapt able to a wide range of uses. The board’s circuitry has been specially designed to withstand corrosive industrial environments, and optical iso­lation prevents various functions from interacting even under fault condi­tions. Among the LLAD 57’s features are four isolated 24-240VAC/DC inputs, four 24-230VAC relay outputs, 16 TTL-level digital inputs, 16 digital outputs, one isolated 4-20mA current-loop analog input with programma­ b le speed, and linearity of 0.1% full scale. Comprehensive software is pro­vided for use with the board. For further information, contact Boston Technology Pty Ltd, PO Box 1750, North Sydney, NSW 2059. Digital Power Meter from Yokogawa Yokogawa has announced the release of their new 3-phase 2533E Digital Power Meter for R&D, industrial and production applications. The 2533E uses a 16-bit pulse width modulation technique to measure DC and AC voltage, current and power to an accuracy of up to 0.1% in single phase, 3-phase 3-wire and 3-phase 4-wire power circuits. Offering a frequency response of 30Hz to 30kHz as well as DC capability, the 2533E is also capable of accurately measuring the power of distorted and inverter waveforms. Three large bright displays simultaneously show any three values of measured or computed data. These can include, for example, voltage, cur­rent, power per phase, total power, apparent power and power factor. As well, the 2533E provides 12 analog output signals for connection to auxiliary instruments such as recorders and FFT analysers. Several other computation functions are provided, such as mean value of phase or line voltage and mean value of phase current. An integration option is available, allowing meas­urement of amp-hours or watt-hours to an accuracy of ±0.2% + 1 digit up to a period of 999 hours. A further op­tion allows frequency measurement over the range of 20Hz to 200kHz with an accuracy of ±0.1 % + 1 digit. GPIB and RS232C options are provided, allowing the 2533E to be re­motely controlled and output data to be transferred to a PC. For further information, contact Tony Richardson, Yokogawa Australia Pty Ltd, Centrecourt D3, 25-27 Paul St North, North Ryde, NSW 2113. Phone (02) 805 0699. Economy soldering irons from Scope Two new low cost 25W and 40W utility irons for electronic work have been released by Scope Laboratories. These mains voltage irons feature long-life iron-plated tips that operate at around 380°C, a stainless steel barrel, a non-rolling impact-resistant handle and four tip shapes. For further information, contact Scope Laboratories by phone on (03) 338 1566. LS621 Loudspeakers – continued from page 28 are unable to verify this claim although the response is quite smooth overall. At the bass end there is usable response down to below 45Hz although if pushed hard, the woofer does tend to frequency double. At the high end, the tweet­er is a little prominent in the region of 7- 8kHz and then tapers off a little above that although it is smooth right to the limits of audibility. Efficiency is quoted as 87.5dB at one watt and one metre and the unit is claimed to be suitable for amplifiers rated from 15 watts to 150 watts. Our impressions were that you would need an amplifier of at least 40 to 50 watts and that anything much over 100 watts on program would be too much. That is backed up by the stated maximum SPL (sound pressure level) of 106dB. On music, the Magnet LS-621s give a good account of them­selves although the tweeter seems a little muted for our tastes. We found that they sound rather better with the grille cloth frames off and we think most people would listen to them in this way. On voice, they sound very natural without any tendency to chestiness or emphasis of sibilants. Our overall impression was that they were very satisfying on classical music, especially chamber works, and they give a good account of themselves on jazz material. If you are a heavy rock fan, you will want bigger guns and it would not be fair to expect them to do the job. Recommended retail price of the Magnet LS-621s is $1150 a pair and they are available from A-One Electronics, 432-434 Kent St, Sydney, NSW 2000. They have recently fitted out a sound lounge and to introduce the Magnets they have them on sale at $950 a pair, so get in quickly. Phone A-One Electronics on (02) 267 4819. (L.D.S.) SC FM Wireless Microphone – continued from page 67 it and set the operating frequency. For this you need an FM radio. Connect the 9V battery and turn on your FM radio. Now tune across the band until the speaker squeals. The frequency on your dial is now the operating frequency of the circuit. Now if you want to adjust the frequency of operation, you reverse the process. Tune your radio to a vacant part of the band. Let’s say this frequency is 99MHz. All you should be get­ting is hiss from the loudspeaker of the radio. Now adjust the slug of coil L1 until you get a continuous squeal from the radio. That’s it, the job is complete. In more detail, the tuning range of the wireless microphone can be adjusted upwards by removing the 1pF capacitor. With this capacitor in circuit, the tuning range of L1 will be in the lower region of the FM band: from This close-up view shows how the on/ off switch is fitted to the end-plate at one end of the tube. below 88MHz to about 102MHz. With the 1pF capacitor in circuit, the tuning range will be from about 95MHz. You have to decide which portion of the band you want your cir­cuit to operate in and then pull the capacitor out or leave it in. You then adjust the slug of L1 as described above. After you have adjusted coil L1 to your satisfaction, move the microphone well away from the radio so that the acoustic feedback squeal and distortion is no longer apparent. You should now be able to speak into the microphone and your voice should come from the radio with clean reproduction. You can now complete the construction of your microphone by wiring up the on-off switch and then installing the board and battery inside the anodised aluminium tube. They are held in place by pieces of foam plastic. The PC board is positioned so that the electret protrudes slightly from the end of the tube, after which the foam plastic windshield is fitted. The slide switch is attached to an endplate with epoxy adhesive and then the end plate itself is glued into the tube with the same epoxy. SC October 1993  93 VINTAGE RADIO By JOHN HILL Those never-ending repair problems This month, I have a couple of special repairs to dis­cuss; you know the type – those nasty, hardto-find problems that nearly drive you crazy trying to locate them. The first one was for a collector friend who had a 1938 dual-wave console type receiver with no maker’s name on it. It was a well-made set with a big 12-inch electrodynamic loudspeaker and a magic-eye tuning indicator. It worked fairly well too –but only on shortwave. My job was to replace all of the original paper capacitors and get the broadcast band working again. At first glance, it seemed an easy job – probably a dirty wave-change switch. Usually, the problem is reversed; the broad­cast band works but the shortwave band doesn’t. As the wave-change switch may not have been used for the last 20-30 years, it is not surprising that the contacts become dirty and no longer make reliable connections. On the other hand, I was a little apprehensive about some aspects of the job because someone had recently worked on the set. The original electrolytics had been replaced with modern 450V units and the dial light wiring had been altered. There is nothing worse than trying to troubleshoot someone else’s mis­takes. The usual solution to dirty switch contacts is to give them a good squirt Access to the far side of the wave-change switch in the old console receiver was not easy. The troublesome switch con­tacts were bypassed by using an unused section of the switch. 94  Silicon Chip with contact cleaner while rotating the switch back and forth. This treatment usually brings the dead band back to life again and all is well. But in this instance, no amount of contact cleaner made any difference. Naturally, the next step was to check a few other compon­ents, namely the broadcast band aerial and oscillator coils. These checked out OK, so that turned my attention back to the wavechange switch again. Prodding and probing at each individual contact revealed that the broadcast band would work when pressure was brought to bear on certain switch contacts. As Murphy would have it, these contacts were on the most awkward side of the switch to work on. Unused contacts Fortunately there were two other unused sets of contacts on the switch. They were originally used to switch the dial lights so that different sections of the dial would light up depending on the position of the wave-change switch. This dial wiring had been disconnected at some time in the past and rewired to a common circuit that lit all the lamps, regardless of the position of the wave-change switch. Nothing is ever as simple as it first appears. After dis­connecting the leads from the faulty section of the switch, I soon discovered that they were too short to reach the alternative contacts. All three wires had to be extended by joining on extra lengths. Success at last! On completion of the change over, the receiver worked on the broadcast band – but not for long. After three or four switch operations, the broadcast band went dead once again. At this stage, I decided to check each set of contacts on the wave-change switch with a multimeter. This showed The troublesome padder capacitor (right) compared to a similar undamaged unit. A small nut & bolt proved to be an adequate replacement for the broken rivet. The author had not encountered this sort of problem before & it took quite some time to locate. that there were no faulty contacts and each set cut cleanly in and out of circuit. After double checking, the wave-change switch was given a clean bill of health. By now, I was in a quandary. What seemed a straightforward job at first had developed into quite a puzzling mystery. There had been a fault in the switch but after fixing it another prob­lem had arisen somewhere else. A puzzling intermittent Then came the big breakthrough. I dropped a pair of pliers on the workbench and the set burst into life. There was a loose contact somewhere and it did not take much of a jolt to trigger it on or off. The mysterious loose connection was so sensitive it was hard to locate. The slightest tap anywhere would send static-like reverberations through the speaker. Tapping the broadcast band oscillator coil can seemed to have the most effect so the can was removed to see if there was something shorting out inside. Noth­ing – all was in order and by this stage everything had gone quite dead. A pair of long-nose pliers was then used to wrench all the wiring joints (insulated handles of course). This seemed to indicate that the trouble spot was in or around the padder. The receiver had a typical 1930s padder – one of those white porcelain ones as fitted to so many old sets. But how often does one find a defective padder? Well, this was one such time! The tubular rivet that holds the moveable plate to the body of the padder had broken and had let the plate come adrift. This wasn’t very noticeable because the wire that was soldered to the loose part was short and thick and held everything in place fairly well. The rivet head was also still in place and everything looked normal. However, after removing the padder and replacing the broken rivet with a small nut and bolt, my problems were over. I have never encountered a faulty padder before, so there is always a first time for everything. A dangerous repair The next problem was one that made me feel ill when I saw it. It was the most dangerous and irresponsible repair I had ever seen and who ever did the job should be lined up in front of a firing squad and shot! The repair involved a power transformer change-over where a considerably different unit to the original was used as a substi­tute. While the transformer’s voltages were OK, the mounting method used was dreadful. All the transformer connections were above chassis, completely unprotected Oh what a feeling! – if you happened to touch those transformer connections. The near side row of connections are for the 240V primary winding. It’s a very makeshift repair that has been done without thought or consideration for the well being of others. October 1993  95 would do a job that has the potential to kill. IF transformers This intermediate frequency (IF) transformer has been repaired by bridging a corroded lead-out wire. Similar problems are also often found in the aerial & oscillator coils of old radios & are enough to stop a set dead. A satisfactory repair can usually be carried out on such coils, although it can be a fairly tedious job. On another tack, I have recently had a run on faulty IF transformers and, in every case, it was easier and possibly quicker to repair the transformer, rather than scrounge around looking for a suitable replacement. In the case of the unit in the accompanying photograph, corrosion in one of the leads rendered the bottom winding open circuit. It is often possible to bridge the break with a piece of copper wire and the unit will function once again. If repairing a transformer that uses Litz wire, a thick piece of joining wire would be better than a thin piece. If it is an earlier type of transformer using single strand copper wire, then it doesn’t matter much what gauge of wire is used. These fiddly repair jobs are often in the microsurgery class and a small soldering iron tip and a low-powered magnifying glass are handy tools to have. Good light comes into the equation too! A repair of this nature will frequently solve an IF trans­former problem. It is always advisable to disconnect the trans­former and remove it from the chassis before doing any further work. Attempting the repair while the transformer is on the chassis is usually quite difficult. It should also be mentioned that exactly the same problem is often found in aerial and oscillator coils and they usually respond to similar treatment. Loudspeaker repairs A 5-valve Radiola receiver from the early post-war era. A common problem with this model is a “rattly” loudspeaker, caused by the cone detaching itself from the frame. Fortunately, this problem is usually repairable & a replacement loudspeaker is not necessary. and within easy reach of an unsuspecting victim. As shown in the photograph, the nearest row of connections are for the 240V primary winding. What a lethal booby trap! Any repairer who had even the slightest regard for his customers would have mounted the transformer properly. The guy who did this job 96  Silicon Chip simply couldn’t be bothered to cut the necessary rectangular shaped hole in the chassis so as to accommodate the replacement transformer in the correct manner. As radio repairers – vintage or otherwise – it is our re­sponsibility not to make repairs in such a manner that they are a danger to others. Whether a qualified person or not, only a half-wit My final tip involves repairing those “rattly” loudspeakers that are so common in early post-war AWA Radiolas. The problem is caused by the speaker cone detaching itself from the frame, allowing it to buzz, rattle and produce distorted sounds. The speakers at fault include both electrodynamic and permag (permanent magnet) types covering from about 1946 through to the late 1950s. The first step in the repair process involves removing the speaker from the set. This amounts to a little more work than one might initially expect, because the whole front of the receiver has to be removed and that includes the dial and grille cloth. VINTAGE RADIO We are moving in February 1994 MORE SPACE! MORE STOCK! Radios, Valves, Books, Vintage Parts BOUGHT – SOLD – TRADED Send SSAE For Our Catalogue These intermediate frequency (IF) transformers are from mid-1930s radio receivers. It is often easier & quicker to repair these items than look for replacements. A visual check with a magnifying glass will soon locate a corroded section of lead-out wire. WANTED: Valves, Radios, etc. Purchased for CASH RESURRECTION RADIO Call in to our NEW showroom at: 242 Chapel Street (PO Box 2029), Prahran, Vic 3181. Phone: (03) 5104486; Fax (03) 529 5639 D & K WILSON ELECTRONICS An old loudspeaker can often be salvaged simply by gluing its cone back into position using a suitable adhesive & a handful of clothes pegs. Detached cones are a common problem in post-war Radiola mantle radios. Once the speaker is out, the problem is obvious and in bad cases the cone is free of the frame all the way around. The remedy is simple – glue the cone back where it belongs. Use a rubbery type of contact cement (eg, Selleys Kwikgrip®) and hold the cone in place with clothes pegs until the glue has set – see photo. Often a bit of manoeuvring is required to position the cone centrally and a spot must be found where the cone moves freely without the voice coil fouling on the magnet. While the speaker is on the workbench, it is a great oppor­ tunity to clean the dial glass (be careful not to remove the markings) and, if necessary, fit a new dial cord and grille cloth. If the grille cloth is fitted to the cabinet instead of to the cardboard speaker mounting baffle, it gives easy access to the speaker if it needs to be removed or replaced at some time in the future. That’s it for Vintage Radio this time. I hope you will join me again next SC month. Have you found those components yet? We know that it can be difficult, frustrating and a waste of your valuable time. So why haven’t you contacted us? We specialise in hunting down and locating components – old, obsolete, leading edge, normally available but now scarce due to allocation by overseas manufacturers. Integrated circuits, resistors, capacitors, transistors, diodes, valves, varistors, etc. Any brands Let us save your valuable time Contact us now on 833 1342 We are also distributors for Electrolube lubricants and chemi­cals Hakko - desoldering & soldering irons; SMD tools; replacement parts NTE - replacements semiconductors 2/87a Queen St, St Marys, NSW 2760. Phone (02) 833 1342 Fax (02) 673 4212 October 1993  97 Silicon Chip Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC. BACK ISSUES September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice; Motorola MC34018 Speakerphone IC Data; What Is Negative Feedback, Pt.4. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man’s Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone; How To Quieten The Fan In Your Computer. December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor For Shortwave Receivers; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; 120W PA Amplifier (With Balanced Inputs) Pt.1; How to Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. February 1989: Transistor Beta Tester, Cutec Z-2000 Stereo Power Amplifier, Using Comparators To Detect & Measure, Minstrel 2-30 Loudspeaker System, VHF FM Monitor Receiver, LED Flasher For Model Railways, Jump Start Your New Car March 1989: LED Message Board, Pt.1; 32-Band Graphic Equaliser, Pt.1; Stereo Compressor For CD Players; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Map Reader November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. For Trip Calculations; Electronics For Everyone – Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; All About Electrolytic Cap­acitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Rad­ios; Universal Temperature Controller; Understanding CRO Probes; LED Message Board, Pt.4. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector; Simple DTMF Encoder; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: Introducing Remote Control; FM December 1989: Digital Voice Board (Records Up To Four Separate Messages); UHF Remote Switch; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Installing A Clock Card In Your Computer; Index to Volume 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speed­ing Up Your PC; Phone Patch For Radio Amateurs; Active Antenna Kit; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/12V Charger For Sealed Lead-Acid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception; How To Find Vintage Radio Receivers From The 1920s. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To A Computer. July 1990: Digital Sine/Square Generator, Pt.1 Please send me a back issue for: ❏ January 1989 ❏ February 1989 ❏ June 1989 ❏ July 1989 ❏ December 1989 ❏ January 1990 ❏ June 1990 ❏ July 1990 ❏ November 1990 ❏ December 1990 ❏ April 1991 ❏ May 1991 ❏ September 1991 ❏ October 1991 ❏ February 1992 ❏ March 1992 ❏ July 1992 ❏ August 1992 ❏ December 1992 ❏ January 1993 ❏ May 1993 ❏ June 1993 ❏ October 1993 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ September 1988 March 1989 September 1989 February 1990 August 1990 January 1991 June 1991 November 1991 April 1992 September 1992 February 1993 July 1993 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ November 1988 April 1989 October 1989 March 1990 September 1990 February 1991 July 1991 December 1991 May 1992 October 1992 March 1993 August 1993 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ➦ Use this handy form to order your back issues December 1988 May 1989 November 1989 April 1990 October 1990 March 1991 August 1991 January 1992 June 1992 November 1992 April 1993 September 1993 Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ____________________________ Card expiry date_____ /______ Name _______________________________ Phone No (___) ____________ PLEASE PRINT Street ________________________________________________________ Suburb/town ________________________________ Postcode ___________ 98  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 979 5644 & quote your credit card details or fax the details to (02) 979 6503. ✂ Card No. (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station; Weather Fax Frequencies. Ultralights, Pt.1; Build A Fax/Modem For Your Computer; The Basics Of A/D & D/A Conversion; Windows 3 Swapfiles, Program Groups & Icons. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders & Ultralights, Pt.2; Getting To Know The Windows PIF Editor. September 1990: Music On Hold For Your Tele­ phone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. November 1991: Colour TV Pattern Generator, Pt.1; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Modifying The Windows INI Files. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; Using The NE602 In Home-Brew Converter Circuits. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Solid-State Laser Pointer; Colour TV Pattern Generator, Pt.2; Windows 3 & The Dreaded Un­ r ecov­ e rable Application Error; Index To Volume 4. November 1990: How To Connect Two TV Sets To One VCR; A Really Snazzy Egg Timer; Low-Cost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Simple 6-Metre Amateur Transmitter. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Automatic Controller For Car Headlights; Experiments For Your Games Card; Restoring An AWA Radiolette Receiver. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape – A Game Of Skill; Wiper Pulser For Rear Windows; Versatile 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. February 1992: Compact Digital Voice Recorder; 50-Watt/Channel Stereo Power Amplifier; 12VDC/240VAC 40-Watt Inverter; Adjustable 0-45V 8A Power Supply, Pt.2; Designing A Speed Controller For Electric Models. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty Stereo Amplifier, Pt.1; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Direct­ ories; Valve Substitution In Vintage Radios. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateurs & TV. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1; Setting Screen Colours On Your PC. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Reception; Electric Vehicle Transmission Options; Tuning In To Satellite TV, Pt.1. July 1991: Battery Discharge Pacer For Electric Vehicles; Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2; PEP Monitor For Amateur Transceivers. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Installing Windows On Your PC; Step-By-Step Vintage Radio Repairs. September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & April 1992: Infrared Remote Control For Model Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; LowCost Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; Infrared Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; What’s New In Oscilloscopes?; A Look At Hard Disc Drives. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Off-Hook Timer For Tele­phones; Multi-Station Headset Intercom, Pt.2. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; Dummy Load Box For Large Audio Amplifiers; Internal Combustion Engines For Model Aircraft; Troubleshooting Vintage Radio Receivers. September 1992: Multi-Sector Home Burglar Alarm; Heavy-Duty 5A Drill speed Controller (see errata Nov. 1992); General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads; Build A Relative Field Strength Meter. October 1992: 2kW 24VDC To 240VAC Sine­wave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Electronically Regulated Lead-Acid Battery Charger. November 1992: MAL-4 Microcontroller Board, Pt.1; Simple FM Radio Receiver; Infrared Night Viewer; Speed Controller For Electric Models, Pt.1; 2kW 24VDC to 240VAC Sinewave Inverter, Pt.2; Automatic Nicad Battery Discharger. December 1992: Diesel Sound Simulator For Model Railroads; Easy-To-Build UHF Remote Switch; MAL-4 Microcontroller Board, Pt.2; Speed Controller For Electric Models, Pt.2; 2kW 24VDC to 240VAC Sinewave Inverter, Pt.3; Index to Volume 5. January 1993: Peerless PSK60/2 2-Way Hifi Loudspeakers; Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Simple Projects For Model Railroads; A Low Fuel Indicator For Cars; Audio Level/VU Meter With LED Readout; Build An Electronic Cockroach; MAL-4 Microcontroller Board, Pt.3; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.5; Making File Backups With LHA & PKZIP. March 1993: Build A Solar Charger For 12V Batteries; An Alarm-Triggered Security Camera; Low-Cost Audio Mixer for Camcorders; Test Yourself On The Reaction Trainer; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Build An Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Step-Up Voltage Converter; Digital Clock With Battery Back-Up; A Look At The Digital Compact Cassette. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Remote Volume Control For Hifi Systems, Pt.1; Alphanumeric LCD Demonstration Board; Low-Cost Mini Gas Laser; The Micro­soft Windows Sound System. June 1993: Windows-Based Digital Logic Analyser, Pt.1; Build An AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; A Digital Voltmeter For Your Car; Remote Volume Control For Hifi Systems, Pt.2; Double Your Disc Space With DOS 6. July 1993: Build a Single Chip Message Recorder; Light Beam Relay Extender; Build An AM Radio Trainer, Pt.2; Windows Based Digital Logic Analyser; Pt.2; Low-Cost Quiz Game Adjudicator; Programming The Motorola 68HC705C8 Micro­ controller – Lesson 1; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60LED Brake Light Array; A Microprocessor-Based Sidereal Clock; The Southern Cross Z80-based Computer; A Look At Satellites & Their Orbits; Unmanned Aircraft – Israel Leads The Way; Ghost Busting For TV Sets. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Electronic Cockroach; Restoring An Old Valve Tester; Servicing An R/C Transmitter, Pt.1. October 1993: Courtesy Light Switch-Off Timer For Cars; FM Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1; Mini Disc Is Here; Programming The Motorola 68HC705C8 Micro­ controller – Lesson 2; Servicing An R/C Transmitter, Pt.2. PLEASE NOTE: all issues from November 1987 to August 1988, plus October 1988, January, February, March & August 1989, May 1990, and November and December 1992 are now sold out. All other issues are presently in stock, although stocks are low for some older issues. For readers wanting articles from sold-out issues, we can supply photostat copies (or tearsheets) at $7.00 per article (incl. p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. October 1993  99 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. Universal timer for main appliances I am interested in the Universal Timer For Mains Appliances described in the 1990 issue of SILICON CHIP. However, I need a timer with a 30-minute limit, rather than the nine minutes of your circuit. Can you please tell me how to increase the limit of this timer or, failing that, is there a similar timer on the market but with a 30 minute limit? (J. L., Wembley Downs, WA). • The time limit can be easily increased to 30 minutes by changing the .047uF capacitor at pin 2 of IC1 to 0.15uF. Electronic watchdog for house alarm Have you ever published a project for an electronic watch­dog? The type I refer to is the box that produces the sound of a large dog barking. I am currently installing an alarm system in my house with reed switches on each door and window and movement sensors in selected rooms and the hallway. I intend to use a 4-sector master control similar to the Dick Questions on light dimmers How do domestic 240VAC light dimmers work? Will dimming lights lower power consumption? – my own vague understanding is that a Triac is used to chop each half-cycle of the mains sinew­ave. Are the SEC power consumption meters able to detect this and save me money? I’ve puzzled over these questions for a long time and most local electricians don’t know the answers. (H. P., San Remo, Vic). • As you have surmised, light dimmers use a Triac which is triggered 100  Silicon Chip Smith L-5145 or your own design from June 1990 and would like to be able to connect the “watchdog” so that anyone trying to enter the house will think that there is a big dog in the next room. If you have published this type of circuit, could you please tell me how to go about obtaining a photocopy of the article or the appropriate back copy of the magazine. If you have not published one of these would you please consider designing one. (B. M., ACT). • We have not described such a project. However, you can purchase an alarm of this type from Jaycar. It is priced at $139.50 and the catalog number is LA-5280. Alternatively, you could consider using the Single Chip Message Recorder published in the July 1993 issue of SILICON CHIP and record the sound of a dog barking. This project is available in kit form from Dick Smith Electronics and Jaycar. Doubts on nicad discharger Recently I built the Nicad Battery Discharger described in the November 1992 issue of SILICON CHIP. While on either earlier or later in each mains half-cycle. For high power, the Triac is triggered early in each half-cycle and for low power, it is triggered late in each half-cycle. The watt-hour meter in your meter box is able to respond to this chopped waveform and it is quite accurate. However, you don’t really save much power (or money) by dimming lamps. The problem is that incandescent lamps are a non-linear resistive load, so that a reduction in light output of, say, 60% may only result in a power reduction of 20%. Hence, there is very little saving. everything tested OK as per your criteria, I do have a problem. My main application for this device is to discharge my Amstrad ALT386SX laptop computer battery pack. In office use, the computer is running off the mains (which charges the battery). The battery always runs the computer (good in the event of a power failure) and I use an external monitor, mouse and keyboard, printer, etc. However, when I travel I often use my computer away from a power point and have had a lot of trouble with “memory effect”. Amstrad told me I should get about three hours of continuous use from one charge but I am lucky to get 45 minutes. They then recommended leaving the computer turned on overnight, (sort of a deep discharge), then recharging in the morning – a 3-hour pro­cess (do this for three nights). This remedy worked once or twice at first but is most inconvenient at times and is not a good practice in my opinion anyway, as there is no way to monitor what is happening. The battery is a 12V 2400mA/h seal­ ed unit consisting of one negative and two positive terminals, each reading 12.4V when fully charged, according to my DMM. I guess it must have some type of double bank arrangement since each +12V terminal must be discharged separately. Even though the Discharger’s discharge cycle seems to work properly and has been set to cut off at 11V as per your recommendations, a measurement of the discharged state of the battery pack still shows 12.4V, again using a digital multi­ meter. I am unable access the terminals to load test the pack when it is in place, which could help, since plugging the “dis­charged” pack into the computer results in the “low battery” warning and about two minutes of use before the computer shuts down as an act of self preservation. Therefore, I still have my original problems, which are that I don’t know the actual discharged battery voltage; I don’t know if the discharger is doing its job properly and I don’t know if the computer is shutting down because the battery is still exhibiting “memory effect” or because the battery pack is indeed fully discharged to 11V. Can you advise me on some way to solve my problem? I thought that the Discharger would be the answer. Maybe it is and I am missing something. (P. S., Gold Coast, Qld). • From your description, the Discharger is working exactly as it should. This is confirmed by the fact that the discharged battery pack works for only two minutes before your computer shuts itself off. The problem is that when you are measuring the battery pack with your digital multimeter, there is no load current and therefore you are reading the open circuit battery voltage. To obtain a proper indication of the battery state, you need to measure it with a reasonable load. For example, since you can’t measure the battery voltage when they are operating your computer, we suggest you connect a 68Ω 5W resistor across the battery pack and then measure the voltage. The resistor will draw about the same current as the discharger. Hence, a discharged battery pack should read close to 11V. Queries on the AM stereo tuner I recently bought a kit of parts for your Stereo AM Tuner as described in the February and March 1991 issues of SILICON CHIP. The only difficult part was the soldering of the micropro­ cessor chip but it does all it’s supposed to do so I must have done it right. The front panel is a work of art spoiled only by those bits on the end which I think I’ll cut off. When was the last time the manufacturers of these cases looked at current design trends. I haven’t seen a preamplifier, cas­sette player, tuner, etc with rack mount lugs for years. Very large power amplifiers sometimes have handles fitted but rarely holes at the ends. The tuner is complete and working but signals down here are not strong; even for the local station, 2ST, I only get three LEDs lit but I feel it’s more the area than any fault in the set. Would it be possible to fit antenna and earth Electrically activated pendulum clock I was recently reading an old magazine which included a reprint of a 1944 article on making a pendulum clock. The pendulum swung so that it passed over an electromagnet. When the pendulum lost a certain amount of momentum, a small trailer pushed a set of contacts together which, in turn, energised the electromagnet. Thus, every 40 swings or so, the electromagnet would be energised and give the pendulum some additional acceleration. While this idea was good for its time, the mechanical switching used a fair bit of energy. I was going to design a similar pendulum clock but use an IR detector and transistor switching. Before doing this, however, I thought that I would connectors on the back as I would like to connect an aerial wire or possibly the loop antenna featured in the June 1989 issue of SILICON CHIP. I tried loosely wrapping a wire around the ferrite rod coil and running it some distance away and it did improve the signal. I found coil L5 was hard to adjust as others did. The amount of adjustment is very small and so it’s hard to determine a centre point. I got 2.3V on a new digital meter I bought for the job. Because our local station isn’t in stereo and the ones that are are so weak, I’m not sure if the stereo reception is reli­able. I have had brief periods of stereo but it didn’t lock for long due to signal strength. In fact, I was surprised I got any­thing – one station locked with no signal strength LEDs lit at all but dropped in and out. My Sherwood tuner gives me a clean “lofi” signal on 2ST and a slightly noisy but listenable signal (during the day) on 2UE with a short wire stretched over the curtain rod. I’m aware signals aren’t terrific in my area (16km from Nowra on the coast), as even my car radio fades and is noisy when I drive out from Nowra to home, on 2ST. I’d appreciate your comments. (P. G., Orient Point, NSW). first check with you to see whether this has already been done – I don’t particularly want to re-invent the wheel! Thus if you have any information on using batteries to power old pendulum clocks I would be grateful for your comments. (L. T., Shelley, WA). • It is true that the switching system used in a pendulum clock of this sort would use a small amount of power. However, if you were to use an IR detector and transistor switching, they would probably use more power. A better way may be to use an integrated circuit from a typical quartz crystal clock. These energise the movement once a second and are very economical when it comes to the batteries. You would need to use a frequency divider system if you wanted to energise the coil at a lower pulse rate. • We don’t like rack mounting cases either, so your comments are apt. Extra signal strength can be attained by winding a few turns of wire around the ferrite rod at the opposite end to the main coil assembly. Connect one end to earth and the other to a long antenna lead. A loop antenna cannot be connected without a major redesign of the front end of the tuner. L5 is tricky to adjust but note that your multimeter will be quite slow to respond, as is any digital multimeter, so the adjustment must be done slowly. Stereo reception is only possible when a good strong signal is received; any noise will force it into mono reception. Problem with the home weather station The Home Weather Station in the April 1993 issue is a great little exercise but is quite expensive, as stated in article. There is one little hiccup – I can’t get the humidity sensor circuit to function properly. The temperature and baromet­ric readouts are OK but all I get with the humidity display is “-1” and the decimal point. October 1993  101 Reducing hash in the digital voice board I have just assembled the Digital Voice Recorder board, as de­scribed in the December 1989 issue. You mention the trade- off between recording speed/time and voice quality but the problem I have is that the playback voice is just recognisable at the fastest speed and time of approximately five seconds. Trying to record anything slower is impossible and is fraught with D/A hash. Could you please advise what the problem could be? (C. P., New Plymouth, NZ). A friend checked the circuit board with a scope and found that the two 555 ICs weren’t oscillating. He “piggy backed” the 15pF capacitor with a greencap (I don’t know what valve) and says that they now oscillate properly. My friend said that everything on the board looks as it should. By the way he’s an ex-navy communications technician. I am a fitter and machinist (first class), with electronics only as a hobby. I’ve built several kits in past and all have worked. The best two would have to be the remote controller for roller doors and a stereo amplifier. Another anomaly with the weather station is the order of the functions provided by the selector switch; ie, Barometer, Humidity and Temperature instead of Humidity, Temperature and Barometer as shown in the article. My switch wiring is the same as the wiring diagram. (R. B., Clare­ mont, Tas). • With regard to the humidity sensor operation, we suspect you are not using CMOS 555 timers for IC3 and IC4. They should be marked TLC555, LMC555CN, ICM7555 or GLC555. If the labelling is simply LM555CN or TL555, they are the standard 555 timers and will not work in this circuit. The strange switch allocations for Barometer/Humidity and Temper­ ature are probably due to the switch stopper in S2 being in­ stalled incorrectly. Take the stopper out by unscrewing the switch nut and fully turn the switch anti-clockwise. The 102  Silicon Chip • This unit does have some background hash but it should not be as bad as your’s appears to be. We can make two suggestions which may help. First, ensure that the input supply voltage is sufficient so that the 5V regulators do not drop out of regula­tion. Second, make sure the electret microphone is connected with the case terminal to ground. Some electrets have two supply leads, both of which are isolated from the case, so you need to earth the case as well. Shielded cable is also recommended for the microphone lead. stopper should now be installed in position 3. The switch should now stop at the third position and give the correct Humidity, Temperature, Barometer settings. Woofer Stopper is audible I have received a number of complaints regarding this pro­ ject (see SILICON CHIP, May 1993). The output frequency to the horn is 20kHz but this can be heard by people with good hearing response. Are they hearing a harmonic of the square wave output? The sound is very annoying. Can anything be done about this? (Alphatran Electronics, Woy Woy, NSW). • People who cannot hear anywhere near 20kHz are still able to hear a high frequency noise from the tweeter when they are rea­sonably close to it. We are not certain of the mechanism but evidently it is a sub-harmonic that they can hear. In fact, we think that this is useful since it tells you that the device is actually working. There is nothing that you can do to stop it. Query on drill speed controller I recently bought a kit for the 5A Drill Speed Controller published in September 1992). As I have worked as an electronics technician for many years, I feel particularly confident that I have put the kit together correctly. However, I have found the low speed regula­tion to be very poor. My primary use for the controller is to drill holes in metal where you need to run the drill exceptionally slow to prevent overheating of the bit. Unfortunately, at about a tenth of the normal running speed of the drill, the controller continu­ally chops the power to the drill and also causes power surges. I have had a look at the waveform to the drill at low speed and it appears that the Triac is being switched on intermittently instead of at every positive half cycle. Also the chopping ap­pears to start after turn on reaches the 90° point. The result of this chopping action causes the drill to shudder quite dramatically, similar to the sort of thing that happens to a 4-cylinder car that is running on two cylinders. However, when loaded down the torque is good, which I guess proves that the back-EMF power correction is working well. Per­haps you are aware of this problem and don’t recommend that the con­troller be used at very low speeds, or I suppose there could be a problem with my project. Anyhow, my problem is that, apart from the fact that it is annoying having the drill shuddering, I am worried about damage to the drill motor or gearbox. Could you please advise me as to what you think is happen­ing with the controller. (R. R., Subiaco, WA). • The problem you have experienced when running your drill at very low speeds is quite normal with any SCR speed controller. The problem is caused, as you have found, by erratic triggering of the SCR and is caused by the interaction of the commutator with the mains frequency. Unfortunately, this cogging effect is inevitable and cannot be cured if you want to run the drill at very low speed. We would also caution you against running your drill at very low speed because its internal fan will not be running fast enough to provide any cooling for the armature which can get quite hot. This is essential­ly because the peak current through the armature can be higher than normal at these very low speeds. In short, you need a drill which can run at a lower chuck speed as part of its normal operation. It may be wise to consider using a battery driven drill or screwdriver which can be fitted with a chuck. This would certainly give you SC a low drill speed. MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. ANTIQUE RADIO ANTIQUE RADIO RESTORATIONS: specialist restoration service provided for vintage radios, test equipment & sales. Service includes chassis rewiring, recondensering, valve testing & mechanical refurbishment. Rejuvenation of wooden, bakelite & metal cabinets. Plenty of parts – require details for mail order. About 1200 radios within 16,000 square feet. Two-year warranty on full restoration. Open on Saturday 10am-4.30pm; Sunday 12.30-4.30pm. 109 Cann St, Bass Hill, NSW 2197 Phone (02) 645 3173 BH or (02) 726 1613 AH. FOR SALE WEATHER FAX programs for IBM XT/ ATs *** “RADFAX2” $35 is a high resolution, shortwave weather fax, Morse & RTTY receiving program. Suitable for CGA, EGA, VGA and Hercules cards (state which). Needs SSB HF radio & Radfax decoder. *** “SATFAX” $45 is a NOAA, Meteor & GMS weather satellite picture receiving program. Needs EGA or VGA plus “WEATHER FAX” PC card. *** “MAXISAT” $75 is similar to SATFAX but needs 2Mb expanded memory (EMS 3.6 or 4.0) and 1024 x 768 SVGA card. All programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, Qld 4005. Phone (07) 358 2785. THE HOMEBUILT DYNAMO: (plans) brushless, 1000 DC watt at 740 revs. $A85 postpaid airmail from Al Forbes, PO Box 3919 - SC, Auckland, NZ. Phone Auckland (09) 818 8967 any time. Rotor magnets (3700 gauss) kit now available. PEER TO PEER NETWORK SOFTWARE: for IBM PCs. The “$25 Network” links 2 or 3 PCs via serial ports at up to 115K bps. Uses only 15K RAM. Only $40. “Little Big LAN” offers multi-user record locking, linking via serial, parallel and/or Arcnet cards, up to 250 nodes 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): $20 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly on a separate sheet of paper, fill out the form below & send both with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. and print spooling. Only $95. Both support printer re-direction. Prices are for a whole network. Add $3 for postage in Australia. For more information, send SASE to GRANTRONICS, PO Box 275, Wentworthville 2145. Phone A/H (02) 631 1236. TEST EQUIPMENT: Trio CS2070 4-channel CRO with probes, Philips PM6456 FM MPX Signal Generator, Philips PM5326 AM/FM RF Signal Generator & Sweep Oscillator, Philips AM/SSB 201 CB Transceiver incl. mic, Leader LPM880 RF Power Meter, Leader LMV181A AC Millivoltmeter, Heath IG18 Sine/Square Audio Generator, Yaesu FT200 Transceiver incl. mic & speaker. All in good condition and in working order. Service manuals available for most items. The lot $3000 or will negotiate separately. Contact Norm Hughes (018) 38 2288. PC PRINTER PORT controlled I/O, 32 bits in, 32 bits out. Expandable. Heaps of demo programs, flow charts, circuits, drivers in 8088 & Basic. Short form kit, includes promo disk $35. Don McKensize, 29 Ellesmere Crescent, Tullamarine 3043. Phone (03) 338 6286. SUBSTITUTE FOR A HANDFUL OF ICs: Parallax “BASIC STAMP”. A gen­er­al purpose small circuit module, it is really a 25 x 50mm board with a computer chip (4MHz PIC 16C56), EEPROM, 8 I/O pins, board space includes prototyping area. Program it on a PC (only ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 October 1993  103 TRANSFORMER REWINDS ALL TYPES OF TRANSFORMER REWINDS TRANSFORMER REWINDS Reply Paid No.2, PO Box 438, Singleton, NSW 2330. Ph: (065) 76 1291. Fax: (065) 76 1003. ICL 286 Board Kits All in one board with two serial, printer, IBM keyboard, high density floppy & IDE mono video interface. Up to 4Mb RAM, 80286-16cpu, MS-DOS compatible, 130 page manual, small size 170mm x 255mm. Max I/O kit for PCs, 7 relays, ADC, DAC, stepper driver, TTL inputs, with software $169 PC I/O card with 8255 chip 24 I/O lines programmable as inputs or outputs $69 1.5 watt AM broadcast transmitter XTAL locked $49 2.5 watt FM broadcast transmitter 88-108MHz. $49 Digi-125 audio power amp (over 19,000 sold since 1987) 50 watt/8 $14 125 watt/4 $19 New 200 watt/2 version $29 Infrared relay kit $9 Remote control tester $4 $299 Ampo little PC All in one NEC V40 CPU board, MS-DOS compatible, high density floppy. SCSI hard disk, 2 serial, printer, solid state hard disk, IBM keyboard interface, (4W), CMOS single +5V rail, up to 768Kb RAM, 384Kb ROM, 145mm x 250mm, 98page manual. $299 P.C. Computers 36 Regent St, Kensington, SA. Phone (08) 332 6513. MEMORY & DRIVES PRICES AT OCTOBER 2ND, 1993 SIMM 1Mb x 3 70ns 1Mb x 9 70ns 4Mb (72-pin) 4Mb x 9 70ns 4Mb x 8 80ns $80 $95 $320 $270 $250 DRAM DIP 1 x 1Mb 70ns 256 x 4 70ns 1Mb x 4 Z DRIVES SEAG 42Mb SEAG 107Mb SEAG 130Mb SEAG 214Mb SEAG 261Mb 28ms 15ms 16ms 16ms 16ms $10 $8 $35 $190 $283 $290 $343 $390 IBM PS.2 50/55/70 70/35 90/95 2Mb 4Mb 4Mb $130 $320 $320 TOSHIBA T3200SX T44/6400 T5200 4Mb 4Mb 8Mb $340 $340 $680 MAC 2Mb SI & LC 4Mb P’Book $150 $330 CO-PROCESSORS 387SX to 25 $110 387DX to 33 $110 Laser PTR HP with 2Mb $203 Sales tax 21%. Overnight delivery. Credit cards welcome. SPRINKLER CONTROLLER KITS: standard and enhanced versions avail­ able. Very reliable and versatile designs control 8 stations and have 32 programmable START and RUN times. These kits use latest technology I2C chips (refer SILICON CHIP July 1992). All settings stored in EEPROM. Kits come complete with LCD and case. Standard version $135 incl. p&p. Enhanced version uses 68705U3 and has built-in calendar, al104  Silicon Chip Antique Radio Restorations.......103 A-One Electronics.................. 64-65 Applied Electro Systems..............85 Av-Comm.....................................69 Binary Engineering......................91 Cebus Australia...........................89 Darren Yates................................61 David Reid Electronics ..............89 Dick Smith Electronics........... 12-15 D & K Wilson Electronics.............97 Emtronics.....................................21 1st Floor, 100 Yarrara Rd, PO Box 382, Pennant Hills, 2120. Harbuch Electronics....................89 Tel: (02) 980 6988 Fax: (02) 980 6991 PELHAM LCD Alphanumeric Display Board Software Remote Preamplifier Microprocessor VALVE TESTERS, meters, valve hifi, broadcast microphones. SAE to P, Hadgraft, 17 Paxton St, Holland Park, Qld 4121. Altronics .........................IFC, 36-38 Ring for Latest Prices Software allows a PC to drive the Alphanumeric display board (SC May 93). Available in 5.25" or 3.5" MS-DOS format for only $9.95 + $2.05p+p. 33 instructions) with development kit which includes one “BASIC STAMP” ($245 incl. post), extra modules ($66 incl. post). Send 45c stamp for more information. Parallax distributor and techni­cal support in Australia: MicroZed Computers, PO Box 634, Armi­ dale, NSW 2350. Facsimile (067) 72 8987. MICASOFT Electronics and Computing tutor program, written in UK, ideal for TAFE, schools, or individual use. Now available in Australia. Send $1.80 in stamps for demo disk (tell us what size). MicroZed Computers, PO Box 634, Armidale 2350. Advertising Index Heart of Remote preamplifier project (SC Sept 93) and Remote Volume Control (SC June 93). 68HC705C8P preprogrammed microprocessor. Only $45 + $6p+p. SILICON CHIP magazine, (02) 979 5644. Payment by cheque/money order or credit card (BankCard, MasterCard, Visa) Instant PCBs..............................104 Jaycar ................................... 49-56 JV Tuners.....................................61 Kenwood Australia.......................29 Macservice................................ 6-7 Oatley Electronics........................33 PC Computers...........................104 Pelham......................................104 Peter C. Lacey Services..............58 Resurrection Radio......................97 RCS Radio ................................103 Rod Irving Electronics .......... 74-79 Silicon Chip Back Issues....... 98-99 Silicon Chip Binders....................63 Silicon Supply & Manufacturing...81 Technical Applications.................92 EEM Electronics Printed circuit board assembly, switchmode power supplies repaired. Design work from start to finish. Ring anytime 9am-9pm Mon-Sun. (03) 4011393 lowing day of fortnight watering, (ie SA, SU, MO, etc), externally triggerable cycles and rain switch software. $175 incl. p&p. Requires 24V AC. Relays extra at $3.75 each (require 9 for full kit). Kits and further info from Graham Blowes, Mantis Micro Products, 38 Garnet St, Niddrie 3042. Phone (03) 337 1917 (AH), (03) 575 3349 (BH). Fax (03) 575 3369. VISIBLE RED 5mW LASER diode brass module, 18.5mm long x 11.5mm diameter. Just add 2 x 1.5V batteries. Switch, holder included. $109. Hitachi 5mW laser diode HL6711G 670nm Tektronix......................................27 Transformer Rewinds.................104 Yokogawa..................................IBC _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. • H. T. Electronics, 35 Valley View Crescent, Hackham West, SA 5163. Phone (08) 326 5590. $52. Alpine Technologies, phone/fax (03) 751 1989. PRINTED CIRCUIT BOARDS for the hobbyist. For service & enquiries contact: T. A. Mowles (08) 326 5590.