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Leo Simpson and Greg Swain present ... SERVICING - HIFI - Features: Electronics in the Jaguar XJ40 Easy tips on epairing phones fian ,::, i 'i heMlglnal End-of-file indicator for modems 200 watt stereo power amplifier Create a sonic masterpiece in your own home. The names VIFA SCAN-SPEAK and DYNAUDI0 are recognised internat ionally as the finest speaker drivers available today. If you were to open the cabinets of many world-acclaimed loudspeakers you would find that they contain these drivers as their reproduction source. Now you have the opportunity to construct loudspeakers offering virtually identical performance using complete kits supplied by Scan Audio - for a fraction of the price. By doing your own assembly you will save literally hundreds, even thousands, of dollars in expensive freight, duty, handling and of course, labour charges. If you would rather invest money in your own pleasure than in other people's pockets, you must investigate the potential of assembling your own kit speakers from the wide range we offer. Currently there are ten kits available ranging from under $500 to $4000 per pair including cabinets. For free brochures, performance data, reviews, price lists and more information about drivers and kit speakers please, contact the Australian distributors Scan Audio. ~59!10"" ~ ~ 52 Crown Street, Richmond, Vic 3121 Phone: Melbourne (03) 429 2199 Sydney (02) 871 2854 Brisbane (07) 357 7433 Perth (09) 322 4409 • ..... • "' • • ~T,~,Jij,jf.j G: Vtl•i#iil)§;i ., 11=•1 - --= - f" 5&1 4624 ....- .. =:.,._. __,.. : VOLUME 1 ::= __=I ~ ~ _. _. .__. ..._. ---------. --------------- _y _. _. ----__.. _. _. _. __. _. __. ----- ~ -J/1 ~ -I __. .. :::ii _. _. __. ~ --I -J ,._. ~ - - _,I - _. -I _,~__._ _, __. _._, _, -I -I -I ~ _. _. ,.. .. _. -I _. _. _. --&. _... __, ---... _.... _. __. _. _. _. _. __, __. _. _. _. _. _. _. _. _. :::: ._.. - - ..... - .... _. _. _. ..» __, ...,.. 5 -I ...J ----- _. ...... .... ___,I __ __ _. ----I ---::: ---= - ~ ----- - ...J ....I ....J -I ---' ____, ~ _. --- - - - :::: _. __, __. -I _. _. FEBRUARY 1 988 FEATURES 6 Electronics and the Big Cat by Leo Simpson SONY'S NEW CONTROL amplifier and power amplifier give exotic performance but don't have an exotic price. We take a look at this potent combination starting page 30. Multiple microprocessors work their magic 14 Easy Tips on Headphone Repair by Leo Simpson Jacks and plugs give the most trouble 30 Sony Enters the Big Power Stakes by Leo Simpson Superb new preamp/amp combination 50 South Pacific: The Electronic Version by J.L. Elkhorne A tropical servicing adventure 80 The Evolution of Electric Railways by Bryan Maher Pt.4 - Australia's first 100 years 85 Digital Fundamentals, Pt.4 by Louis Frenzel Understanding & using flipflops PROJECTS TO BUILD 18 Protector Car Burglar Alarm by John Clarke Refined circuit has every wanted feature 36 Studio 200 Stereo Power Amplifier by Leo Simpson High power and easy to build 46 End-of-File Indicator for Modems by Greg Swain It buzzes when a file is finished 53 Build the Door Minder by John Clarke Uses an ingenious pressure sensor 56 Low Ohms Adaptor for Multimeters by John Clarke Accurately measures down to 0.01 ohms THIS RUGGED STEREO power amplifier puts out a genuine 100 watts per channel into 8-ohm loads and 160 watts into 4-ohm loads. Full circuit and construction details begin on page 36. SPECIAL COLUMNS 60 Serviceman's Log by the original TV serviceman His Master's Voice 70 The Way I See It by Neville Williams Worth preserving: a colourful slice of electronic history 74 Amateur Radio by Garry Cratt Line isolation unit for phone patch operation DEPARTMENTS 2 Publisher's Letter 4 News & Views 17 Bookshelf 34 Circuit Notebook 92 Product Showcase 94 Ask Silicon Chip 96 Market Centre SILICON CHIP'S NEW car burglar alarm has internal and external siren alarms, backup battery, ignition killer and dashboard flasher. Turn to page 18. SILICON CHIP PUBLISHER'S LE'l-l'ER Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E . SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd , Waterloo, NSW 2017 . Printing: Macquarie Publications Pty Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates are currently $42 per year (12 issues). Outside Australia the cost is $62 per' year surface mail or $120 per year air mail. Liability: 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. Address all mail to: Silico.n Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935 . ISSN 1030-2662 * Recommended and maximum Australian price only. 2 SILICON CHIP The fascination of electronics While the vast majority of the population may be keen to have the latest electronic whizbang, only a relatively small proportion of people really know what makes the products of this technological age tick. Take such a ubiquitous product as the quartz controlled watch with an analog movement or liquid crystal display. These are a miracle of electronics. They usually run from a 32kHz crystal (actually 32,768Hz) and have a 15-stage divider to derive one second pulses which drive a very efficient stepper motor and gear train in the case of analog movements. In the case where a liquid crystal display is used, the one-second pulses drive a counter which then drives the display. Either way, the watch will be powered from a tiny 1.5V silver oxide cell which may last 12 to 18 months or even more in some cases. And the accuracy of these mass-produced timepieces is such that it would amaze watch manufacturers from twenty years ago. Yet if you ask a typical person why the battery in his watch lasts so long, he is likely to reply that batteries have improved enormously in the last few years. Well, batteries have improved but not to that extent. The real reason that watch batteries last is that the single IC used to drive a watch needs only a few microamps to work. It really does run on the "sniff of an oily rag" in the electronic sense. And what about those liquid crystal displays? Isn't the concept of a "liquid crystal" fascinating? You can make a liquid transparent or opaque just by applying a small AC voltage to it. Amazing. That such a phenomenon can be used to create complex moving displays and even replace the television tube is mind-boggling indeed. To us, these are just two of a vast number of facets of electronics which are truly fascinating. In a way, electronics is a modern for~ of black magic. The practitioners of this art use black boxes and are able to achieve feats which were impossible a generation ago. Electronic magic allows us to store and process vast quantities of mforma tion, enables millions of people to communicate over vast distances simultaneously, and allows us to stretch and use our natural resources much more efficiently. It is our business to report on this magic, to translate its language and explain its diverse manifestations, and to show how you can use it for your benefit. Electronics really is fascinating. Leo Simpson THE ELECTRONICS MAGAZINE FOR THE ENTHUSIAST WE INvITE You To BECOME A SUPPORTER Because we strongly believe that many more people should come to know about and enjoy electronics, we decided to form a new magazine devoted to electronics enthusiasts. We have called it SILICON CHIP, a name which encapsulates the driving force behind all of today's electronics technology. SILICON CHIP is starting off as an independent magazine, founded by Leo Simpson and Greg Swain. We have a very small team of devoted staff including our full-time electronics engineer, John Clarke and our very experienced draughtsman, Bob Flynn. We have started as a completely independent magazine, free from the influence of any existing publishing company, because we wanted to establish the highest possible standards for accuracy and attention to detail. We also wanted complete editorial freedom. Every article you see in this magazine has been carefully selected and prepared by us to establish this high standard right from the outset. Similarly, our circuit and wiring diagrams have been very carefully laid out by our draughtsman Bob Flynn to make them as logical and as easy to understand as possible. Regular Features * The Constructional Projects For Enthusiast * HiFi Review * Digital Electronics Course * The Serviceman's Log * Amateur Radio, by Garry Cratt, VK2YBX * The Way I See It, by Neville Williams Junk mail Most magazines sell their subscriber lists to mail order companies, to earn extra income. We will not do this. We will lose some money by adopting this policy but we believe that your privacy is paramount. You can help us establish a high standard for our publication by becoming a supporter. The more subscribers we get, the more resources we can devote to improving the quality of our magazine and to the promotion of the understanding of electronics. ----------------------- *--FREEPOST SUBSCRIPTION COUPON To: Freepost 25, Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097, Australia. NO POSTAGE STAMP REQUIRED IN AUSTRALIA NAME ...................... .... ................ ..... .... ........................................ .............. 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Note: Photocopy this coupon if you don't wish to cut the magazine. NEWS&VIEWS Solar Car on display at Jaycar store The Australian Geographic solar car Team Marsupial will be on display at Jaycar's Gore Hill store in Sydney, during the month of February. The car came fourth overall in last year's Darwin to Adelaide Solar Challenge. While it was overshadowed by the performance of the General Motors' winning entry Sunraycer which managed to get ahead of some foul weather, Robots to pick fruit in the future The University of Florida has announced that it has made encouraging progress in the development of a fruit-picking robot. Several approaches to mechanical harvesting have been tried in the past, including air blast systems and tree shakers but they have not had the ability to distinguish between ripe and unripe fruit. The new robot consists of a single Team Marsupial still gave a credible performance, achieving speeds in excess of 85km/h at times during the race. The 5. 5 metre long car weighs only 255kg when empty and is valued at $150,000. It is well worth a close look. Jaycar Electronics was one of the sponsors of Team Marsupial. picking arm fitted with a colour television camera to give the ability to distinguish colours. A sonar sensing unit gives the robot's computer information on how far the arm is from each piece of fruit. Proposed commercial fruitpicking robots would have between six and twelve picking arms and would be able to pick six pieces of fruit every second. We think it will be a long time before human fruit pickers have to worry. Such machines will not be cheap. USSR and Australia to create giant radio telescope Now that scientific cooperation between the USSR and Australia is to be renewed, the CSIRO has announced project Radioastron. This will link a network of radio telescopes in Australia and the USSR with an orbiting Soviet satellite. Taken together, all the telescopes will effectively form an enormous antenna much bigger than the diameter of the Earth. The main aim of the project is to explore the heart of Centaurus A, the nearest active galaxy and to study how energy is transferred near to its centre. Radioastron in Australia will receive $400,000 from the CSIRO and $900,000 from the Department of Industry, Technology and Commerce, to be allocated in future budgets. Almost $1 million is for the development and manufacture of low noise amplifiers, necessary for deep space radioastronomy. Future cars may use liquid crystal windows In most large car companies there is a continuing conflict between the stylists and the engineers. The stylists want more and more glass, less headroom, less ventilation and all those impractical aspects of modern cars. The engineers know darn well that more glass leads to heat build up inside the ea bin and therefore more loading on the air-conditioning. Now there is news that 4 SILICON CHIP General Motors in the USA is experimenting with liquid crystal technology for car windows. Just a twist of a potentiometer knob would black out the glass and thus cut down on glare. The drawback to this idea is that heat buildup is still a problem. General Motors already have an answer to this, even though it may be expensive. Their Sunraycer research solar car used very thin gold plating on the glass over the ea bin to block out infrared radiation and thus control heat build up. We can see an even better application of liquid crystals to window glass. What about windows in homes? Wouldn't it be good to be able to progressively darken your window glass just by turning a knob? There would no further need of curtains. The idea has often been suggested in science fiction literature. More weather reports for Sydney mariners As from Jaunary 1st this year, OTC's Sydney Radio has introduced two early morning weather reports for mariners and fishermen heading out to sea. This is in addition to its existing twelve daily weather schedules which will now be broadcast at 48 minutes past the even hour in summer (eg, 0648) and 48 past the odd hour in winter (eg, 0548). Mariner$ wanting further information on Sydney Radio weather info should call OTC Maritime on (02) 287 4146. Backwards clock runs forward Readers who peruse the catalogs of the major kitsellers will probably be aware that Dick Smith Electronics sell a novelty item in the form of a clock that runs anticlockwise. Recently their service department had to deal with one of these clocks which was faulty. The hands persisted in running clockwise! That would be a conundrum. You could always fix it by changing the dial to one with figures that run clockwise. Philips to make cellular phones With the increasing penetration of cellular phones in Australia, we have been concerned that this is yet another import to worsen our national balance of payments problems. So it is good news to learn that one company has geared up to make them in large numbers, in Australia. Philips recently spent several million dollars in its mobile radio plant at Clayton, Victoria with the installation of surface mount assembly equipment. This is to enable Philips to manufacture a range of ultra-compact gear such as the model FM9010 cellular phone. Philips has already received export orders for this product which is designed for operation in New Zealand, Canada and the USA. Enquiries should be directed to Philips Communications Systems. Phone (03) 542 4500. NEWS BRIEFS Compact disc supply outstrips demand Safety at the keyboard Ever since compact disc players were introduced some five years ago, demand for the shiny discs has been well ahead of supply and so the prices have been very high. Now, with all the CD plants coming on-stream around the world, supply is about to exceed demand. In fact the situation has turned around so rapidly in the last six months that any future plants could be doubtful investments they could lose money. The good news is that compact disc prices will come down, as has already been presaged by Virgin CDs. The drop in prices can't come quickly enough, as far as we are concerned. The Commonwealth Schools Commission has just issued a booklet on computer ergonomics and safety issues to teachers. The idea is to make teachers more aware of computer technology and to increase their knowledge of possible health and safety hazards. The booklet details all sorts of computer hazards such as overcrowding, incorrect screen positioning, dangling electrical cords, ionising and non-ionising radiation, and, never let it be forgotten, RSI (repetitive strain injury; hardly likely to be a problem in schools). From what we have seen of children using computers in schools, the greatest danger is not from computers at all. It's slovenly posture which eventually leads to back problems. Central Coast Amateur Radio Club Field Day Don't forget the 1988 Field Day for the Central Coast Amateur Radio Club. It will be held Sunday, 21st February at the Gosford Showground. It's open to everybody whether you're an amateur or not. Potential trade exhibitors should contact the club at PO 238, Gosford NSW 2250. FEBRUARY1988 5 ELECTROMCS '111f. BIG CAT By LEO SIMPSON Prestige cars used to a be relatively cheap in Australia but they are now again truly prestige. Cars such as the Jaguar cost more than the average price of a threebedroom home in many Australian cities. With that sort of price you expect something more than just good paintwork, plush upholstery and a powerful engine. With the Jaguar, you get a car with an astonishing amount of electronics as well as all the normal attributes of a high-performance luxury saloon. Jaguar owners are not technofreaks. So Jaguar had to incorporate all the new technology into the XJ40 without making it too obvious to the driver or the passengers. In fact, if you went for a short ride in the XJ40 you could easily miss out on the subtle evidence that a lot of electronics is at work. Take the braking system for example. To the casual driver, the Jaguar's brakes are perfectly con- ventional and not at all unusual. But under the skin, they incorporate anti-skid which means a lot of control circuitry. In addition, the XJ40 is the only domestic car in the world (that we know of) to use a high pressure hydraulic servo system rather than the conventional vacuum-assisted brakes found on all other cars. And the braking system has all sorts of monitoring to tell whether the system is working up to par: low brake fluid, low brake pressure, handbrake on, pad wear and so on. The new Jaguar X/40 hos been selling in Australia for about a year now, but very few people know just how much electronics it employs. 6 SILICON CHIP Fuel bleed return Air temperature sensor Ignition coil Ignition power stage 1.....11--- ---------------------------....J Fuel used and diagnostics input to VCM Fig.1: the engine management system. Timing information comes from a toothed-wheel pickup on the crankshaft. Or take the suspension. On the Sovereign and Daimler models, the rear suspension has automatic selflevelling, controlled by electronics. Or the air-conditioning. It is totally electronically controlled. There are no mechanical linkages, flap valves or whatever. The system controls the temperature and humidity, with differential settings for both the driver and passengers, front and rear. And it senses the effect of sunshine in determining whether more cold air is needed. Even if you lift the bonnet, there is no great evidence of electronics at work. Sure, there is a thumping big six cylinder double overhead cam 24-valve [four valves per cylinder) engine with fuel injection and electronic ignition but superficially, the electronics are fairly low key. So where is all the electronics? All told, there are no less than seven different microprocessor controlled systems in the Jaguar. They are used for the following functions, some of which we have already noted: (a) engine management; [b) instrument panel and trip computer; [c) air conditioning; [d) anti-lock braking; [e) cruise control; [f) suspension levelling [where fitted); and [g) central processor. In addition there are other electronic modules to control such functions as central door locking, courtesy light switching, and bulb failure warning. Just touching on the courtesy light switching for a moment: if one of the doors is left open for more than two minutes the interior cabin lights and door ("puddle") lights are turned off to conserve the battery. [Jaguar calls them "puddle" lights because they let you see puddles when getting out of the car in: the dark). Engine management The engine management system was developed and made by Lucas to Jaguar requirements. It uses one microprocessor to control both the spark timing and the duration of fuel injection for each cylinder firing. As well, it maintains a constant engine idle speed regardless of whether various accessory pumps are being driven or not. Fig.1 shows the engine management system in schematic form. The distributor is simply a rotating switch which delivers the high voltage output of the ignition coil to the respective spark plugs. There is no .vacuum advance diaphragm, centrifugal advance weights, points or variable reluctance pickup to control the current through the ignition coil. Instead, timing information comes from a toothed-wheel pickup on the crankshaft, adjacent to the fan pulley. It has 60 equally spaced slots with three teeth missing, at intervals 120° apart. The microprocessor recognises the short term changes in frequency associated with the missing teeth and uses this · to provide the necessary timing information for fuel injection and ignition. There are six solenoid controlled fuel injectors, one for each cylinder inlet port. These are not controlled individually but are operated together by the microprocessor. Both the ignition timing and that of fuel injection are varied in response to a number of parameters, including the temperature of the engine, the air-flow into the manifold, throttle position and the lamda sensor, which monitors exhaust emissions [actually monitoring oxygen Gontent). The engine temperature is FEBRUARY1988 7 + ++ + + + ++ + + + ++ + + ++ + + + 5 ++ ++ + ♦ ♦ + E .., 4 ++ ++ + + ++ .; > ·;; 0- 3 ++ ++ + + ++ -£ + + + + + + + + + + + + + + .., u 8 ++ ♦♦ ♦ 7 +♦ ++ ♦ • 6 ++ ~ Detonation critical zones Typical full throttle advance requirement >, u ~ 0 ... ,: ·.; B 00 C :~ _. . fu advance cha~acteristic Mechamcal centn ga1 C .g ·a ~ Areas of compromise with conventional mechanical systems ~ !! 2 ++ ++ ·;;; 3"' Static setting limited by starting and/or idle quality requirement + + ♦♦ + + + + + ++ + ++ ++ + + +♦ + + + + + ++ + 5 6 -0 I 0 monitored by an NTC [negative temperature coefficient) thermistor situated in the water jacket of the engine. Air flow into the manifold is monitored by a heated sensor wire in the venturi between the air cleaner and the throttle body. Actually, the hot wire sensor is mounted in a bypass port off the main venturi so that, in the event of an engine backfire through the manifold, the sensor is not blown apart. Throttle position is measured by a potentiometer coupled to the accelerator linkage. Separate microswitches are also mounted on the throttle body to detect the idle and full load settings. Road speed is also monitored, as noted later. Conventional engines with distributors having vacuum and centrifugal advance on the ignition have a lot of compromises on the ignition timing. And rarely is the timing consistent from engine to engine. With the digital system used on the Jaguar, the ignition timing can be precisely optimised to take care of a very wide range of engine operating conditions. For example, when the engine is under heavy load and above 3000 RPM, the ignition is retarded by 3 ° for every"10°C rise above 30° of the inlet air temperature. This was found necessary due to the tendency of the engine to "ping" when the air temperature was around 45 to 50°C [that's 113-122° on the Fahrenheit scale). Those temperatures are common in summer in central Australia. 8 SILICON CHIP 3 4 Engine speed r/min x 1000 Engine speed Fig.2: ignition timing versus speed map. The digital system gives precise control of timing. 2 Fig.3: the load versus speed map is used to derive ignition timing and fuelling control. The air mass flow signal from the hot wire sensor is converted by the processor into a measurement of mass flow per engine cycle. This information is then used to derive the ignition timing and fuelling control. Fig.2 and Fig.3 show the igntion timing versus speed map and the load versus speed map, respectively. Fuel cut-off As with a number of other current cars with electronic fuel injection, the Jaguar XJ40 cuts off fuel when the engine is on a trailing throttle (overrun) above a certain RPM. This gives a worthwhile increase in fuel economy and also helps to reduce unwanted exhaust emissions. In the Jaguar, fuel injection ceases when the throttle is closed, for engine speeds above 1100 RPM, provided that deceleration started from a hove 1500 RPM. This hysteresis is built in to avoid cycling in and out of fuel cut-off when decelerating down to rest. This means that the engine speed has to rise a hove 1500 RPM before fuel cut-off will again occur on a trailing throttle. A refinement of the system has been added to the XJ40, to stop drive line oscillations which can occur when fuel injection restarts in response to opening the throttle. This would normally cause a sudden increase in engine power. To soften this transition, the ignition timing is momentarily retarded and the fuel mixture is weakened slight ly, to reduce the power output. Idle speed control Many modern cars have quite a high idle speed because they have to cope with the load of automatic transmission in Drive, airconditioning, the alternator and other accessories. On the Jaguar for example, there are additional engine-powered pumps for the braking system, air-injection and power steering. If the idle speed was set high enough to cope with all these loads simultaneously, as does happen, the engine would race when the loads were removed. To avoid this, the engine management system uses a stepper motor to control a valve in a throttle bypass port. This system operates to control the idle speed only when the throttle is closed, the fuel system is not cut off and the road speed is under Bkm/h. The idle speed varies depending on whether the engine is cold or hot. At other times the stepper motor continually adjusts the idle setting depending on whether the transmission is in Drive or Neutral and the air-conditioning compressor is clutched in or not. This provides a nominal idle setting at all times so that when the engine does actually come back to idle speed, the control system has a minimum of correction to do. The closed loop idle speed in Drive when the engine has warmed up is below 600 RPM which is a low figure for cars these days. The engine management- processor also provides fuel informn- tion to the trip computer via an interface. The fuel signals are dependent on the injector pulse duration and frequency. The output is equivalent to 50,000 pulses per Imperial gallon. Self-diagnostics and limp home All cars with electronic engine management have a "limp-home" feature in the event of a fault developing in the system. The Jaguar is no exception to this and has comprehensive programming to deal with the failure of each sensor in the system. Anti-lock braking Antiskid braking systems (ABS) are becoming more common on upmarket cars these days but few people are aware that these entail a microprocessor control system. The ABS fitted to the Jaguar XJ40 is made by Bosch. It consists of four speed sensors, one for each wheel, the microprocessor module which is placed in the boot, and a pump with three electrically controlled valves, which is in the engine compartment. The valves control the pressure applied to the disc calipers. There is one control valve for each of the front wheels while the third valve controls the pressure to the rear disc calipers. The speed sensors consist of a 48-tooth ring on each wheel which is adjacent to a variable reluctance pickup (a permanent magnet with a coil of wire wound around it). The pickup generates a frequency corresponding to the speed of the wheel. The ABS processor works by evaluating the speed signals from each wheel and then calculating the deceleration rates. The processor can then tell whether a particular wheel is slipping more than it should for maximum braking (in other words it detects the onset of a skid). With the onset of skid, the processor opens a valve to reduce the pressure applied to the affected wheel so that it can speed up to the same rate as the other wheels. The ABS then reapplies the pressure by pulsing the brake line to the point where the wheel then achieves This is one of the many microprocessors used in the Jaguar XJ40. They provide such functions as engine management, anti-skid braking, and suspension levelling. ( BULB FRIWIIE ) CIRCUIT FR/LURE PRRK BRRKE ON Fig.4: warning symbols are displayed on the car's dashboard by the vehicle condition monitor (VCM). Each display consists of a graphic symbol combined with a two-line text message. maximum retardation. This cycle is repeated several times a second so that the car is brought to rest quickly and with much greater steering control than would be possible in a conventional system. The important safety aspects of ABS are that not only does it allow heavy braking in slippery conditions, it also allows much better control of the steering while under braking. Fail-safe operation With all that control possible over the brakes they need to be absolutely failsaf e. To do this, the control system goes through a series of checks when the vehicle is first started and as it moves off and passes . through the speed of 5.75km/h. The first set of tests includes a check to see that the battery voltage is above 10 volts (it would have to be above this value for the engine to have started). Then, as the vehicle moves off, the control valves are turned on for 20 milliseconds and the current through them is checked. FEBRUARY1988 9 variable reluctance sensor working from a toothed wheel on the back axle which generates 4887 pulses per kilometre (7870 pulses per mile). This signal is variously processed and fed to the engine management processor, cruise control, the analog speedometer, the large seven-segment digital speedometer and the odometer (which has non-volatile memory). The tachometer is a conventional electronic instrument, driven by pulses derived from the primary of the ignition coil. The meters for fuel level, coolant temperature, oil pressure and battery condition are all vacuum fluorescent bargraph displays, with variable colour coding to distingguish normal and dangerous conditions. Vehicle condition monitor A computer-controlled diagnostics system is used to track down any faults that may develop. It plugs into a number of connectors around the vehicle. The control pump is also checked in the same way. This checks for short and open circuits. The processor also checks that the signal frequencies from the wheel sensors do not suddenly change (eg, from loss of signal or amplitude). In all cases of a fault being detected, an alarm is displayed on the instrument panel and the system deenergises the control valves so that the car is left with normal braking. Cruise control The Jaguar's cruise control is designed and partly made by Rella of Germany who also supply the majority of relays on the car. The system uses a vacuum actuator on the throttle linkage and an electric vacuum pump with electronically 10 SILICON CHIP controlled regulator and dump valves to control the engine speed. The system operates completely separately to the engine management system and is effectively in parallel with it. Instrument panel At first sight the instruments are conventional circular analog for the speedometer and tachometer but the remainder aredefinitely all electronic. Even the first two instruments are not completely conventional although they are based on moving coil meters with about 240° rotation. Both meters are back lit (variable) and their pointers are illuminated by optical fibres. The speedometer is driven from a A particular feature of the Jaguar's instrument panel is the VCM or vehicle condition monitor. This is a dot matrix vacuum fluorescent display (32 x 32 dot) combined with a 14 segment 2 x 10 character alphanumeric display positioned next to the tachometer. It displays any vehicle faults with graphic symbols and text. The VCM effectively eliminates the multitude of warning lights found in most modern cars and adds a great deal of monitoring which would otherwise just not be possible. Fig.4 illustrates some of the variety of faults which can be displayed on the VCM. Note that each display consists of a graphic symbol combined with a two-line text message. A secondary function of the VCM is to act as a display for the trip computer. This is a facility found in many modern cars and cm the Jaguar it provides the readouts of functions such as: average speed of journey, average fuel consumption, range on current fuel, and fuel used so far. The trip computer's function switches are arranged on a small panel just to the right of the steering wheel housing and integrated with those for the cruise control. Central processor Since the Jaguar has so many microprocessor-controlled systems, the company was very concerned 12 V Power to load microprocessor Fig.5 (above): the XJ40 employs a common + 12V line to all electrical accessories which are switched on by transistors in rewsponse to a microprocessor signal. The vehicle condition monitor (VCM) at left displays vehicle faults with graphic symbols and text. about overall reliability. The possibility of bad connections, susceptibility to voltage spikes and EMI (electromagnetic interference) is a nightmare for designers of automotive electrical systems. After a lot of research, Jaguar adopted a signal wire earth switching system for the electrical system. This employs a common + 12V line to all electrical accessories which are then turned on by transistors in response to a microprocessor signal. The normal convention of using the car body for all negative return currents has been abandoned. The respective microprocessors respond to switches, operated by the driver, which cause only very small currents to flow in the common earth return line. Since all the control switches now only handle very small currents, the normal automotive style switches with their wiping contacts are no longer suitable. Such switches rapidly become unreliable when switching small currents. Instead, all switches in the Jaguar are effectively sealed membrane switches (as used in most computer keyboards) with noble metal contacts. The switches have a toggle mechanism to give a positive toggle action. The relays , connectors and harness all had to be completely redesigned to give a much higher order of reliability than has previously been obtained. The whole car electrical system is designed to operate over the ex- treme temperature range of - 40 to + 85°C. In addition, the vehicle was developed to be proof against electromagnetic interference at levels of: 25 volts/metre for noncritical items; 50 volts/metre for moderately critical items; and 200 volts/metre on critical items These very high levels of interference apply for signal frequencies all the way up to one Gigahertz (one thousand Megahertz). Reverse polarity and voltage surge protection is provided for all microprocessors and logic units with automatic resetting in the unlikely event of a microprocessor crash. By the way, the central processor not only provides the timing for all system functions but also controls such things as the flash rate of the traffic indicators, the timing of the heated seats (these can be heated to 30°C in a short time in even the coldest climates), the rear window heating, the windscreen and headlamp washers and so on. A central locking switch locks all doors, the boot and the sunroof, and raises all the windows in a rapid sequence. Repairing the system Clearly, no automotive electrician, no matter how well trained, could hope to diagnose and repair such a complex electrical system. It has over 100 multiway plugs and sockets and countless relays and switches. To aid the finding and repair of faults, Jaguar has developed a computer controlled diagnostics system in conjunction with GenRad of the USA. This can be plugged into a number of connectors around the vehicle and will lead the automotive electrician through a series of tests to discover the fault. How else would you do it? Interestingly, Jaguar staff in Australia have played a large part in the rigorous program of testing of pre-production models before the car was released. To the north of Sydney and around Cobar (NSW), about two million miles of testing have been run up on Jaguars to ensure they could withstand the extremes of dust heat and rough roads. For extremes of cold, testing was done in Canada during the winter months where temperatures down to - 45°C were regularly experienced. Driving the big Cat Well, as part of this report, we couldn't let an opportunity to drive these advanced cars go by. On a visit to the Jaguar facility at Liverpool in Sydney we had a chance for a short drive and we can report that the Jaguar drives exactly as you would expect a large high performance saloon to do. It is fast, quiet and handles extremely well although it does not have the neck-snapping acceleration of high performance cars qf a decade ago. And certainly the electronic aspects are never obtrusive. They work. They probably represent a glimpse of the future for the cars we'll be driving in years to come. FEBRUARY1988 11 BUILD-IT-YOURS SAVE$$$$! Flip-top steel case 200W Power Supply At last! The perfect opportunity to get yourself the perfect computer ... perfect because it has in it what YOU want! All the features of the'AT': Range of pre-asse~ blinding speed, expandability, compatability, and so on. cards available - graphics, But you pay much, much less because you put it together yourself! disk controllers, ports, etc No, there's no soldering or other difficult work required. All that's already done for you. Every pcb is pre-assembled and pre-tested 'Baby AT' mother b ~ (there's even a 12 month guarantee on every component!). All you do with 8 expansion is select what you want in your computer and connect it together, using & provision for 1 Mb RAM the cables and connectors supplied -from the detailed instruction manuals included with each component! Yes, it's that simple! And it's guaranteed to be that simple: everything you buy is designed to fit together .. . holes line up, slots are in the right place, etc etc. No more hassles with bits and pieces from various suppliers which sometimes fit, sometimes don't! :t::i: "" WHY BUILD YOUR OWN COMPUTER? Apart from the reasons above (ie, you get what you want and you pay less - two of the best reasons ever invented!!!) there are a few other big reasons to 'do it yourself': (1) You'll learn as you go! Nothing teaches you more about how something functions than constructing it yourself. It's the best way for anyone to gain an understanding of the fundamentals of computer operation - even if you've never looked inside one before! Suddenly all those 'buzz words' you've often wondered about will start taking on meaning ... (2) Imagine being able to say 'I built it myself!' Yes, just imagine. It must be one of the ultimate projects! School & Tech students - think of how this will shape up as your major project: and think of how much value it will be to you in the future! Business People: now the computer you've always wanted at work can be the one you have. And with the money you'll save, there'll be enough left over for another one at home! Hobbyists: how long is it since you've really been able to get your teeth into a 'real' project? (3) We've made it so affordable! You don't have to outlay a large amount in one hit: this computer has been deliberately kept in 'modular' form so you can buy the individual bits and pieces when you want them - and when the pocket will allow them! 4 clock speeds from 6 to 12MHz inbuilt Keyboard lock for security BRIEF Mother Board: 80286 CPU 6, 8, 10 & 12MHz speed (selectable) Provision for 256K, 512K, 640K or 1024K RAM on board CHIPSet technology & IC's 7 Channel OMA 16 Level Interrupt Award BIO$ (fully licensed) Real time clock on board (battery b/u) 8 Input/Output Slots (6 with 62 and 36 pin connector, 2 with 62 only) CMOS Memory to Maintain System Configuration IBM PC/AT compatible All LSI & RAM IC's fully socketed 80287 Co-processor socket provided 1 ELF'AT Buy what you want, as you want it ... 'Baby AT' Motherboard: Complete with 8 expansion slots, back-up battery, speaker, manual and all lC's except RAM. catx-1000 $799 Hinged Steel Case F~otprint lust 430m~ square, case covered In quality bone crinkle finish. Pre-drilled, slotted, etc as required, complete with front panel. cat x.1005 '175 200W Power Supply With enough capacity for full expansion, complete with whisper quiet fan, on/off switch and input/ output connectors. Cat x-1010 '275 DISK CONTROLLERS: Floppy Controller:- Up to 2 360K or 1.2Mb drives. CatX-2014 Hard/Floppy Controller: Handles 2 of each hard/floppy. CatX-2008 s129 •399 DISK DRIVES: '269 •795 1.2Mb Floppy Disk Drive Complete with cables cat x-2200 20Mb Hard Disk Complete with cables cat x-2203 PLUG-IN CARDS: •129 •1 49 •399 '139 CGA & Parallel Printer: Cat x-2010 MGA & Parallel Printer: catX-8141 EGA card with Hercules Compatability: cat x-2013 Serial/Parallel/Game Port Card: cat x-2012 KEYBOARDS 1.2Mb Floppy and/or 20Mb Hard Disk 84 Key 'IBM' Format Cat X-3820 101 Key Expanded Style: (direction keys and extra function keys) cat X-3821 MEMORY Fast (120ns) top quality 41256 RAM chips. 9 required per 256K bank. catZ-9313 SPECIFICATIONS Hard/Floppy Disk Controller: Controls 1 or 2 hard disks Ind. standard ST-506/ST-412 Interface Up to 2048 cylinders Up to 16 read/write heads Data Transfer rate 5Mb/s Controls 1 or 2 floppy disk drives Interface similar to FD-55F mlnlfloppy Double density 320/360Kb or 1601180kb High density 1.2Mb Rated to work up to 12MHz Graphics Cards: MGA, CGA & EGA available Ports: Keyboard port on motherboard Parallel, serial & game ports on interface Monitor port on appropriate graphics card *1 29 *149 Special price for 18 or more: (each): (each): *10" •9• EXCLUSIVE TO IJICKiJSMITH EL iCS PTY LTD DSEB465/RT1087 p FJ> 'DJ . '"(,i (.' ,_,/_' t /'0\-, '.: .,..:.,.;;::~-..,--~ lt -often takes very little effort ·:.i/xpense to put new life into · defective stereo headphones. · . . By HOMER L. DAVIDSON Don't cry if your headphones become defective. Because there are only a few parts that can be defective, most headphone problems are very simple to troubleshoot. By making the repairs yourself you can save money too. Most service organisations would charge too much to make it worth your while to have headphones repaired and it would be cheaper to throw them away and buy a new pair. Unlike other audio devices which need expensive test equipment for effective servicing, headphone repairs require only a small soldering iron, a screwdriver or two, a pocket knife, and a multimeter when you need to make a continuity test. In fact, you don't even need a multimeter. To test continuity all you need is a battery and torch globe. headphones for use with stereo amplifiers have an impedance of about 8 ohms. Some headphones, such as those made by Sennheiser, have a typical impedance of about 400 ohms. Noisy Plugs Sometimes you'll hear noise that sounds similar to radio static whenever you touch or move the headphones' cable. This noise is often caused by tarnish on Many Different Kinds Stereo headphones are available in many different models and price ranges. You can purchase a budget pair of stereo headphones for just under ten dollars. On the other hand, better quality high-fidelity headphones can range up to several hundred dollars or more. Most stereo headphones have an impedance in the range of 8 to 50 ohms. Many of the headphones used with Walkman-type AM-FM radios and cassette players are around 32 ohms , while more conventional 14 SILICON CHIP The impedance of headphones used with personal portables and hifi systems is usually between II and 50 ohms. The most common prohlem is a wire breakage at the plug. the headphones' plug contacts - the tarnish actually functions as an insulator. If you can move the plug around in its jack and make the noise cut in and out, it's possible that the problem is tarnish. This can be removed from the plug's contacts with a paper towel moistened with contact-cleaning fluid (ie, Servisol). Defective Cord and Plug of the braid. (The common ground is usually found in budget-priced headphones). Obtain a replacement stereo phone plug from your favourite electronics store. Whether the plug is a fullsize 6.5mm type, or a miniature 3.5mm type, a stereo plug will have three individual metal rings. By contrast, a mono plug has only two metal rings for contacts. Suspect a broken cord, plug, or jack when one side or both earphones sound erratic or intermittent. If both are erratic, suspect a broken cord or poor connections at the plug at the end of the headphones' cable. Wiggle the cable close to the plug and near each earphone while listening to the music. You've discovered a break in the wire when the sound cuts in and out. More often than not, the wire(s) in the cable break right at the plug, or where it enters the earphone's case; rarely is there a break in the middle - between the plug and the earphone itself. Notice that there are three metal rings on the stereo plug. The ground (common) wire(s) connects to the largest (or outside) terminal. Slip the new plastic plug cover over the headphone cable. Solder the shield or common wire to the largest (or outside) terminal. (The common or ground connection goes to the longest metal ring area on a plug - the part called the sleeve). Connect and solder the remaining two wires to the plug's small terminals - these connections go to the tip and ring. Broken Junction Often, one of the leads in the cord breaks close to the plug. If the plug is a moulded-type, it may be cut off and replaced with a universal type. Always solder the connections; don't twist them. If there appears to be a break in the wire at the plug, cut off the broken cable at least two centimetres from the plug and strip back about 15mm of the outer insulation to reveal the wire leads from the earphones. Now separate the outside shield from each lead- this outside shield or braided wire is common to both earphones. In some cases, there might be three separate leads, with one lead serving as the common connection {ground) between the left and right earphones instead Sometimes, you may find a break in the cable where the wires connect at the cable junction - where the wires from the left and right earphones come together. To repair a break at the junction, remove the outside insulating material to get at each wire. Some flexible cables use tinsel wire wrapped around cloth threads and are difficult to solder because the wire often burns before the solder takes. To make sure you get the connection right the first time, apply a coating of rosin core soldering paste (not acid paste) to the tinsel wire(s) before you try to make a solder connection. Once you have tried and failed, it's usually too late to use soldering paste. Wrap a layer of plastic tape over each wire, and then one complete layer of tape over the spliced area. Defective Earphones You can check the headphone's wires for a break between the plug and the individual earphones by using two sewing needles and a multimeter or DMM (Fig.1). The needles are used to provide a connection to the wires without having to cut away the insulation. Simply push a needle through the insulation and into a wire. If you push a needle into the wire just where it enters the earphone, the wire can be checked for continuity from the plug to the needle by connecting your multimeter (switched to a low "ohms" range) between the needle and its matching contact on the plug. FEBRUARY1988 15 LEFT RIGHT set of headphones, you are no further behind. For low-cost headphones, pry off the plastic lid with a pocket knife to get at the earphone's speaker coil and connecting wires. The foam ear pad and plastic lid may be glued together after repairs are made. Fig.1: the earphone coils and their wires can be checked with the low range of a multimeter or DMM. Needles jabbed through the insulation provide direct connections to the wires for the test leads. Suspect a defective earphone if the continuity of each wire is normal to each needle. If only one earphone is defective, its resistance may be compared to that of the normal earphone. Sometimes, the earphone may be damaged - actually burned open - by excessive volume. This is possible because an earphone is essentially a miniature dynamic speaker, consisting of a magnet, a diaphragm, and a voice coil attached to the diaphragm. Excessive volume overheats and burns out the voice coil. Taking headphones apart to get at the driver inside generally involves a little butchery because they are usually glued together. However, any splits or cracks in the housings which may result when they are pulled apart can generally be made good by a little glue. And remember, if you don't manage to repair a defective GJ DMM An adaptor plug/jack will convert a miniature or subminiature plug for use with standard 6.5mm phone jacks. Check the continuity of an earphone's speaker-coil by using your multimeter's low ohms range. On most headphones, you should get a resistance reading somewhere between 8 and 50 ohms. Try to locate the wires from the cable that are soldered to the earphone's coil. Inspect the soldered connections. Sometimes, the coil's ultra-fine wire breaks off right at the connection. A mushy sound out of one earphone may indicate a defective integrated circuit or power amplifier, or a defective cone in the earphone's speaker. A defective earphone may be located by reversing the earphone leads at the plug. If the same earphone is distorted, suspect a defective cone. Check the amplifier circuit if the suspected earphone is normal when the wires are reversed. Trouble At The Socket While a headphones' stereo plug is often a cause for erratic or intermittent operation, the jack socket can also be troublesome. If you get erratic, intermittent or noisy operation and the plug checks out OK, wiggle the plug at the radio or cassette player's headphone socket and note if the problem persists. Sometimes you will hear sound if you push sideways on the plug, indicating a worn socket. If the problem appears to be in the socket, check it carefully no matter how good it looks. Often, the terminals of a headphone socket become fatigued with the repeated insertion of the plug and the only repair is simply to replace it. ic Fig.2: both the continuity of the cable and the individual earphones may be checked with the ohmmeter. The DMM resistance measurement is approximately equal to the earphone impedance. A very high or infinity reading means that the channel is open circuit. 16 SILICON CHIP Adapted from an original article which appeared in Hands-On Electronics. Copyright (c) Gernsback Publications, USA. BOOKSHELF Computer-aided logic design Computer-Aided Logic Design, by Robert M. McDermott. Published 1985 by Howard W. Sams & Co, Inc Indianapolis, Indiana USA. Hard covers, 248 x 189mm, 432 pages. ISBN 0-672-22436-4. Price $44.95 (from Jaycar stores). A number of books we have seen on the topic of computer aided design assume the availability of a mainframe computer, which makes them less useful than they otherwise might be. By contrast, this book covers the design of logic circuitry using an IBM Personal Computer or equivalent. There are eleven chapters covering basic digital circuitry beginning with Boolean Logic and progressing through logic gates, combinational logic, minimisation, memory, counters, sequential logic, finite state machines, self timed systems and Tri-State logic. Each chapter is illustrated using circuits, truth tables, diagrams and data for the PROTOSIM Logic Simulation Program. The PROTOSIM logic simulator allows for the simulation of digital logic such as AND, OR, NANO, NOR, XNOR, D, J-K and T flipflops, multiplexers, latches and Tri-State gates. The program was written for a TRS-80 computer and should be compatible with other computers using Microsoft BASIC. These include Apple, Commodore 64 and IBM-PC. A logic minimisation program is also supplied which computes the minimum product of sums to implement the function. Appendices list the two above programs plus the codings required for common 7400 series logic gates. This information can be adapted for other types of logic such as 4000 series CMOS. This is an excellent book for those wanting to learn about digital systems and how to test circuitry using computer analysis. Our copy came from Jaycar Electronics. Elements of antennas with a glossary of antenna terminology which will be quite useful to the beginner. In summary, we regard this little book as a reasonable but by no means exhaustive introduction to the subject of antennas. As such, it should be ideal for the beginner. Our copy came from Tandy Electronics. Electronic fundamentals Understanding Antennas, by Robert Comrie. Published 1986 by Prentice-Hall of Australia. Soft covers, 151 x 220mm, 143 pages. ISBN O 7248 1237 7. Price $14.95 (from Tandy stores). If you are not too clued up on antennas, this book is for you. It is an elementary text beginning with simple explanations of radio wave generation, propagation and basic antenna theory. There are four chapters devoted to television, covering the various types of TV antenna, antenna installation, multiple set installations and rotators. These are followed with a chapter on antennas for FM reception. We noted that a list of FM stations in Australia is included but it is far from comprehensive. Many stations have been omitted. Four chapters are devoted to Citizens Band (CB) antennas, with specific chapters on standing wave ratio (SWR), base station and mobile installation. A chapter on antennas for scanner receivers is also included. The book concludes Electric Circuits, by J. Richard Johnson. Published 1984 by Hayden Book Company, Inc, Hasbrouck Heights, New Jersey. Hard covers, 185 x 260mm, 888 pages. ISBN O 8104 0655 1. This text is evidently written for tertiary students of electronics but would be a valuable reference to any technician or keen enthusiast. It is a well planned book with many diagrams and worked examples. The book assumes only an elementary understanding of calculus and that use will be made of a scientific calculator. The first 13 chapters cover principles of direct current. They begin with electricity and the structure of matter, then discuss the basics of atoms and electron flow before moving on to units and the basic electrical laws. Chapters on resistance, conductance, energy and power follow, then chapters on series and parallel circuits, capacitors, inductors, magnetism, sources of EMF and DC measurement. The AC chapters cover sine waves, vectors, AC circuits, bridges, power, resonance, linear circuits, polyphase circuits, transformers and AC measurements. Three appendices cover exponential functions, units and mathematics. In summary, this is a very well produced book. Our copy came from the publishers. FEBRUARY1988 17 BUILD 'I'Hf: PROTECTOR -CAR BURGLAR ALARM This refined car burglar alarm has just about every feature you could want but is easy to build. It incorporates internal and external siren alarms, back-up battery, ignition killer and dashboard flasher. Design by JOHN CLARKE Over the years there have been many refinements in the design of car burglar alarms, so much so that the best commercial alarms are now highly effective deterrents to car thieves. That fact is recognised by some of the larger insurance companies who give small discounts in premiums to those who have approved alarms fitted. The problem is that most approved alarms cost many hundreds of dollars to purchase and have fitted; money that the average motorist can ill afford. With that in mind, we at SILICON CHIP have examined the features of the best car alarms· and have come up with a design which incorporates the most desirable and effective features while still keeping the overall cost to a manageable figure. We've also included a number of features which, to our knowledge, are not included in commercial alarms but which are very effective theft deterrents. Alarm features Let's list the major features of the Protector: • Delayed input to monitor all doors. This let's you safely enter and leave your vehicle without setting the alarm off and disturbing the whole neighbourhood. Entry and exit delay times can each be adjusted to ten seconds. 18 SILICON CHIP The PC board is designed to fit into a standard plastic case and can be assembled by an experienced constructor in an hour or so. The two relays are used to drive an external siren and to disable the car's ignition, so that the thief can not drive away with the alarm sounding. All external connections are via multiway insulated terminal blocks. • Non-delayed (instant response) input to monitor your car's boot and bonnet. As soon as the boot or bonnet are opened, the alarm will sound. • Automatic alarm cut-out and reset: after the alarm is triggered the sirens will sound for 90 seconds and then stop. The alarm resets automatically. The alarm time is adjustable. • Ignition killer: as soon as the alarm is triggered the ignition circuit is disabled so that the thief cannot drive away with the alarm sounding. • Separate siren alarm: since car thieves often cut the wires to the horn, by gaining access underneath the vehicle, the Protector has provision to switch on a separate siren alarm which can be mounted in a more inaccessible position in the engine compartment. • Separate internal alarm: as well as having a conventional siren alarm under the bonnet, the Protector has an extremely loud piezoelectric siren mounted inside the vehicle. When it goes off inside the confines of your vehicle, it is so loud and painful that any thief will instantly break into a sweat and panic. No-one could possibly stay in the vehicle while the alarm is soun- This is what the completed alarm looks like. It should be mounted in an inaccessible location under the car's dashboard or under the rear parcel shelf. ding. It is the feature that we're particularly proud of. • Back-up battery and battery sense: since car thieves also often cut the wires to the vehicle's battery, the Protector has a back-up battery and monitors the input from the main car battery at all times. If the battery wires are cut, the alarm will sound. • Ignition sense: any attempt to start the vehicle (supposing that the thief has entered by opening a door, letting the alarm time out, and then coming back to have another go) will trip the alarm and immobilise the vehicle. • Dashboard flasher: this is a most effective deterrent in a car alarm. While ever the Protector is enabled, its dashboard lamp will flash. FEBRUARY1988 19 and Q4 to turn on while it is pressed. Q3 discharges the 0.047 µ,F capacitor at the base of Q2 and 2 1 N5404 3A diodes thereby causes Q2 and Ql to turn 2 1N4002 1A diodes off. Q4 discharges all circuit 10 1N4148, 1N914 signal capacitances via its associated diodes 2700 resistor and thereby makes 1 1 6V 1 W zener diode sure that the circuit is completely Capacitors dead. 1 4 70µF 16VW PC electrolytic While S1 can be combined with 1 4 7µF 16VW PC electrolytic the dashboard flasher, the OFF 2 1 Oµ,F 16VW PC electrolytic switch S2 should be concealed in a 2 2 .2µ,F 16VW PC electrolytic spot not easily found by the poten2 0.22µ,F metallised polyester tial thief. (greencap) An alternative arrangement 1 0.1 µ,F metallised polyester which could be used to switch the 1 .04 7 µ,F metallised polyester Protector is a radio transmitter and 2 .022µ,F metallised polyester receiver. This has the advantage Resistors (0 .25W, 5%) that the alarm can be controlled 2 4 70k0, 2 x 220k0, 3 x 1 OOkO, remotely so that the exit and delay 2 x 47k0, 1 x 22k0, 5 X 10k0, 3 times can be eliminated or minimisx 3.3k0, 2 x 2.2k0, 1 x 2700, 1 ed. It would improve the security of X 330, 1 X 220 5W, 2 X 0 .470 the alarm, since the burglar will not 5W, 2 x 220k0 vertical miniature be able to find the OFF switch. trimpots, 1 x 22k0 vertical We will be publishing a suitable miniature trimpot UHF radio switch in a future issue. Miscellaneous With Ql turned on, most of the Machine screws and nuts, circuitry is fed via a 330 resistor hookup wire, alarm stickers, l while zener diode D3 protects the spring-loaded switch (for I circuitry from any voltages above bonnet). 16 volts. The associated 0.1µ,F capacitor is used for decoupling the supply. The alarm is enabled by pressing Having discussed the power inthe ON switch S1. This provides a put circuitry, let's flick up to the top kick start to Ql and Q2 to get the left-hand portion of the circuit to circuit going. Before S1 is pressed, the delayed input. This uses D4 and Ql and Q2 are off and neither can exclusive-OR (XOR) gate ICla. As conduct because Q2 controls Ql with all XOR gates, IC1a's output is and Ql provides base current to low unless its two inputs are difQ2 . When S1 is pressed, this Mex- ferent; ie, one high, one low. ican standoff is ended as the 10µ,F The delayed input monitors the capacitor feeds a pulse of current door switches and will work with into the base of Q2 , enabling it to door switches which short to turn on. This allows Ql to conduct chassis (OV) or those that switch and from then on Q2 obtains its + 12V to the cabin lights. In the base current from the collector of former case, the delayed input will Ql via a lOkO resistor. always by high when all doors are The reason for the lOµF closed. This means that pins 1 and 2 capacitor is so that a push-on/push- of ICla will both be high and its outoff switch can be used for S1 rather put will be low. than a momentary contact switch. When a door is opened, D4 will These are available with integral pull pin 2 low and pin 3, the output, lamp indicators which would will go high until the 2.2µF enable the ON switch to do double capacitor at pin 1 discharges via duty as the dashboard flasher . Note the associated 470k0 resistor. that if a push-on/push-off switch is With door switches that switch used for S1, it must be pushed off + 12V, the delayed input is wired to before it can be pushed on again to the lamp side of the switches. This power up the circuit. means that when all doors are closThe alarm is disabled by pressing ed, the delayed input is low and the OFF switch S2. This causes Q3 both pins 1 and 2 of ICla will be PARTS LIST ~ 1 PCB, code SC3-1-0188, 178 x 89mm 1 plastic· box, 195 x 113 x 60mm 1 Scotchcal front panel, 1 O7 x 191mm 1 12V relay, 1 OA OPOT contacts 1 12V relay, 5A SPOT contacts 1 1 2V push on/push off switch with integral 1 2V lamp 1 momentary contact pushbutton switch 1 piezo siren horn 1 self-driven weatherproof horn 1 in-line fuse holder 1 3A fuse 1 12V, 1.2AH gel battery 1 1 0-way PCB terminal block 1 8-way PCB terminal block 4 4mm PCB standoffs Semiconductors 1 4093 quad NANO Schmitt trigger 1 4030 quad XOR gate 1 4027 dual JK flipflop 4 BC33 7 NPN transistors 5 BC54 7 NPN tr~nsistors 1 BC557 PNP transistor We have not used a keyswitch to turn the alarm on and off. Keys are a hassle in this regard and no-one wants to fumble with keys if they have inadvertently set the alarm off or they know the alarm will go off any second. With that potent piezo siren in mind, a hidden switch to disable the alarm is what is required. Circuit features Considering the number of features in the Protector, its circuit is quite simple. It uses just three low cost CMOS integrated circuits, ten transistors, two relays plus several resistors, capacitors and diodes. Let's begin the circuit description by looking at the power input from the car battery. This is connected via diode D1. If the car battery is disconnected, power is obtained from the back-up battery via diode D2 . The back-up battery is maintained on a constant floating charge from the main battery via a 220 5W resistor. 20 SILICON CHIP V2+ ENTRY DELAY VR3 220k 011 1N4148 16 470k 04 1N4148 220k 10 J 10 DELAYED INPUT 4027 IC2b 13 CK 220k ALARM TIME VR2 220k - 14 a .,. ':'" 0.22t 013 1N4148 010 1N4148 Vl+ + Cl 470 16VW? V2+ DASHBOARD FLASHER INSTANT INPUTS V2+ V2+ 01 6 J C2 47 16VW ALARM OUTPUT + - 3 V-0 c-.-0 07 BC337 4 E .,. .,. .,. V1+ PIEZD SIREN V1+ .,. .,. ---------v1+ OFF 09 .E. 01 1N5404 1,2 33!l 7B +12V0--4-*-J-!.::: • t----+---..-~,r""><'---+~W.-.---.--'°------+--V2+ FROM VEHICLE BATTERY 22 1l 5W .,. 0.47!l 5W 6 -...IIWI..-OGROUND 1N~iD4 6 .,. GRDUNDi .,. BC337 D.47!l E 5W 8 EOc 31 12V 1.2AH ; BATTERY 1 BACK-UP .J.. 1. 10k VIEWED FROM BELOW .,. CAR BURGLAR ALARM SC31-0188 Fig.1: the circuit diagram. Dual JK flipflop IC2 takes care of the entry and exit delays and the alarm duration. low. When a door is opened, D4 pulls pin 2 high and pin 3 then goes high and the 2.2µ,F capacitor at pin 2 charges towards + 12V. The instant (non delay) input using ICl b and D5 operates in exactly the same manner as ICla and provides a high pulse whenever the input goes high or low. Battery sense This input monitors the car bat- tery and while ever it is connected Q5 is conducting. If the battery is disconnected, Q5 turns off and provides a momentary positive pulse via the 0.022µ,F capacitor to pin 9 of IClc. This causes the output of IClc FEBRUARY1988 21 0 IGNITION COIL NEGATIVE GROUND ALARM OUTPUT IGNITI INSTANT IN~ DASHBOARD FLASHER DELAYED 1riful PIEZD SIREN 1~ 0 Fig.2: assemble the PC board exactly as shown here. Make sure that you use the correct transistor at each location and note that the ICs all face in the same direction. to go high for the duration of the pulse from the 0.022µ.F capacitor. The ignition input is used to sense any unauthorised attempt to start the engine. Therefore Q6 is normally off and only conducts once the ignition sustem is energised. Pins 13 and 12 of ICld are normally high and when Q6 turns on it pulls pin 12 low for a brief period, determined by the associated 0.022µ.F capacitor. This causes the output of IC1d to go high for a brief period. The outputs from IC1 b, c and d are coupled via diodes D7, DB and D9 to the clock input of IC2a, which is half of a dual J-K flipflop. When one of the instant outputs goes high the clock input is triggered and the Q output of IC2a latches high. This also triggers the clock input to IC2b, via D10. The output of IC1a, the delayed input, also connects to the clock input of IC2b via D6. So ICla or IC2a can trigger flipflop IC2b. IC2b provides both the exit delay and the alarm duration, via the circuitry associated with Cl. IC2a and IC2b provide the entry delay. Initial power up Now consider what happens when the circuit is powered up, by pressing the ON switch Sl. Initially, capacitor Cl is discharged and the output of IC3b, a Schmitt NAND gate, is high. This high output resets both IC2a and IC2b so that their Q outputs are low and their Q-bar out22 SILICON CHIP puts (the complements) are high. Cl begins to charge through two paths, via D11 and trimpot VRl and via the 220k0 resistor and trimpot VR2. The VRl path is dominant, however, because of its lower resistance and charges Cl after about 10 seconds. This causes the output of IC3b to go low. This is the exit delay and after this time the circuit is fully alarmed since the reset inputs of IC2a and 2b are no longer held high. When IC2b is triggered, either by ICla or IC2a, its Q-bar output (pin 14) goes low and Cl begins to discharge via VR2 and the 220k0 resistor. Note that the VRl path plays no part here because D11 is reverse biased. With the Q-bar output of IC2b low, the output of NAND gate IC3d (towards the bottom right-hand corner of circuit) goes high and switches on transistor Q9 and its relay, RLA2. This disables the ignition while the alarm sounds. The relay 3as two sets of 10A contacts which are connected in parallel and are used to short across the ignition points (or transistor switching element for electronic ignition systems) via the two series 0.470 resistors. This prevents the ignition coil from firing. Note also that the second input of IC3d is connected to the collector of Q6 at the ignition input. Thus, if the alarm has already been tripped, say by a door being opened, the alarm will sound again, immediately any attempt is made to start the car or hot-wire the ignition. This is a "belts and braces" aspect of the circuit which means that if the ignition is hot wired, or otherwise interfered with, the ignition cut-out relay will be permanently energised, regardless of whether the alarm is sounding or not. This stops the thieves from attempting to drive the vehicle away, in spite of its alarm sounding at intervals. After all, we must acknowledge that in some circumstances people will ignore an alarm and so the Protector has been designed to make things impossible for the potential thief. Alarm outputs Two alarm outputs are available, the high intensity piezo siren and a relay, RLA1 , for an external powered siren. Transistor Q7 drives RLA1, while transistor QB drives the piezo siren. These transistors are driven by the output of IC3a. IC3a goes high to drive the alarm outputs either immediately, if one of the instant inputs triggers the alarm, or after a period set by the entry delay trimpot VR3 and capacitor C2 , if the delayed input triggers the alarm. At the time the Q-bar output of IC2b goes low, C2 (associated with pins 1 and 2 of IC3a) begins to discharge via VR3 and its series zzokn resistor. When the voltage reaches the lower threshold of IC3a, the output, pin 3, goes high and the alarm outputs are activated (this assumes that the delayed input caused the alarm). When the instant input triggers the alarm, diode D12 at the Q-bar output of ICZa discharges CZ and the alarm output operates immediately. The alarm continues to sound until Cl discharges and allows IC3b to reset the flipflops, ICZa and ICZb. The Q-bar of ICZb thus goes high and charges Cl again. This means that the alarm can now be triggered again, if another attempt to made to steal the car. The dashboard flasher involves gated Schmitt trigger oscillator IC3c and transistor QlO which drives the lamp. Pin 8 of IC3c connects to Cl. When Cl is charged up to + 12V, IC3c is enabled and the dashboard lamp begins flashing. r- I= u -] we >z -::::, en a: i1:i + ~o I- w a: c., a: (.) ~ ci5 <( w c., I<( 0 z z Li [&j ...J 0 (.) z 0 I- z c., 0 (.) ~ a: <( ...J <( <( Ll) C 0:: a: <( 0 m J: en <( C w en Construction Building the Protector is a straightforward process and will probably take no more than an hour or so. All the circuitry is accommodated on one printed board measuring 178 x 89mm (code SC3-1-0188). All the connections to and from the board are made via multiway insulated terminal blocks (Utilux or equivalent). The printed circuit board is mounted in a plastic box measuring 195 x 113 x 60mm which is fitted with a label having a legend for all the board connections. You can begin assembly by installing the two wire links, the diodes, resistors and capacitors. Note that the diodes and electrolytic capacitors must be installed the right way around to observe correct polarity. The trimpots and transistors can be mounted next. Make sure that each transistor installed is the correct type and that it is oriented correctly, according to the parts layout diagram. Each transistor should be pushed down so that its lead length a hove the board is about 5mm or so. The large resistors and the three integra ted circuits can then be mount ed, followed by the two rela ys and the two insulated termina l blocks. The ICs are CMOS r-- CD u, -=:t M N ::::, LL <( C") >en a: Iw =:; I- > Ic.. <( m ::::, w ~ >...J (.) C a: <( (.) zW m ::::, IJ: 0 Iw >> a: a: ~ w c,wzt0 II- 1a:...JOZ> <( w (.) i= <( <( > m 3=--1N ..... 0 zli:om Zen ijj + 1-ooc..>S:2~c r~ □ L:.. 1~"'"' .. "'"' . . =m~I _:J Fig.3: actual size reproduction of the front panel artwork. devices so their supply pins should be soldered first to enable their static protection diodes . For ICl and IC3 , solder pins 7 and 14 first. For ICZ, solder pins 8 and 16. When the board is complete it can be mounted in the plastic case. You will need a hole drilled in each end of the case to allow for cable entry and four holes for screws or standoffs for the board. Note that the corners of the board must be removed to prevent interference with the corner posts of the case. The Scotchcal panel can now be affixed to the lid of the case. FEBRUARY1988 23 input panel} needs to be tied high and then disconnected. The ignition input (terminal 8} needs to be pulled high while the other instant input (terminal 9} can be pulled high or low to test it. • Check that relay RLA1 is closed for 90 seconds after the alarm is triggered. This time can be adjusted with VR2 . . • Check that relay RLA2 is closed for the same length of time as RLA1. • Check that relay RLA1 closes ten seconds after the delayed input is triggered. This is done by pulling the input low and then disconnecting it, or pulling it high and then pulling it low. The ten second delay can be obtained by adjusting VR3. • Having triggered the alarm once with the battery input, check that when the ignition input is pulled high, RLA2 closes and stays closed after RLA 1 opens, as long is the ignition input is pulled high. • Connect the piezo siren to terminals 1 and 8 on the output panel. Muffle it thoroughly under a cushion before letting it sound otherwise your ears will be subjected to considerable discomfort and possible damage. We ' re serious about this. The piezo alarm is excruciatingly loud. Check that the piezo alarm sounds each time relay RLA1 closes. Installation Fig.4: here is the etching pattern for the PC board. Testing When the Protector is fully assembled, a number of tests should be made to ensure that all functions are working. The tests are as follows: • Connect + 12V to the circuit and check that no voltage appears across zener D3 until switch S1 is 24 SILICON CHIP pressed. After S 1 is pressed, the dashboard flasher lamp should stay illuminated for ten seconds and then begin flashing. This time can be adjusted using VR1. • Check that the three instant inputs instantly cause relay RLA1 to close when triggered. To do this, the battery input (terminal 7 on the Make sure you install the Protector alarm in a professional manner. Mount the case securely and use a 10 x 0.2mm (or thicker} hookup wire for external connections. It is a good idea to purchase a crimp connector kit for this job so that all your connections are secure. Probably the best and easiest place to mount the alarm will be under the parcel shelf inside the boot. The same goes for the back-up battery which should be securely clamped in a place where· it won't be damaged by miscellaneous boot debris. The self-powered siren should be mounted in the engine compartment but make sure that its wiring is inaccessible from underneath the vehicle. Finally, put warning stickers on your car. These are another effec• tive deterrent. ~ + VEll1CLE BAffiRY ALARM UNIT + 12V 8,7 --,,""'-- • IGNITION COIL NEGATIVE 6 ~ • , 680UND5 ~ . ..v ...1· -....!.l___,.!....~--- ALARM OUTPUT 4,3 • DASHBOARO FLASHER 2 PIEZO SIREN 1 • e-+-1-.. . . . ._--........ ~ I e ·•- - - -- - --------------' I'-----------~ 11 DASHBOARD FLASHER PIEZO SIREN BONNET • Fig.5: here's how to wire the Protector alarm into your vehicle. Use a crimp connector kit to terminate external leads as appropriate and note that S2 (off) should be hidden. S1 and the dashboard flasher can be a single switch/lamp combination. The complete alarm system (from top left): 12V 1.2Ah battery, 12V siren, pushbutton switches with integral 12V lamp, bonnet switch, alarm module, piezo siren and (centre) warning sticker. (Accessories kindly supplied by Jaycar Electronics). FEBRUARY1988 25 JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYC; JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYC, JAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCAR JAYCARJAYC, JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAA JAYCAA JAYCAR JAYCAA JAYCAA JAYCAR JAYCAA JAYCAR JAYCAA JAYCAA JAYCAR JAYCAR JAYCAA Due to the unbelievable response in January we are extending our pre-catalogue sale for one more month. Sale definitely ends JAYCAA JAYCAA · last day in February - no exceptions. JAYCAR JAYCAR That's right! No Exceptions. Every single item in your local Jaycar Store is Discounted for a strictly limited time. We have to JAYCAA remove hundreds of old lines for our brand new March '88 Catalogue so that we can fit many great new products in. Rather JAYCAR JAYCAR than just discount the old lines the Boss told us - Discount everything! JAYCAA But you must hurry. Any regular line that is in stock at the time of purchase qualifies for the 15% discount. Wewill not back JAYCAA JAYCAR order goods that are out of stock during the sale at the discount price. If any out of stock item comes back into stockduring JAYCAA JAYCAA the sale, you will get it at the discount price! JAYCAA (Please do not ask for the discount price after the sale). JAYCAA JAYCAA So now is the time to make a significant saving on that big kit, and other major purchases. JAYCAA JAYCAR JAYCAR JAYCAA JAYCAA LOW DISTORTION AUDIO OSCILLATOR JAYCAA Ref: EA Dec 1986 JAYCAA last It's available, the metered version of our auudlo oscillator. Compares with the vety best laborato,y JAYCAA LOW COST UTILITY TIMER At standard sine wave equipment available. JAYCAA Ref: EA Feb 1988 JAYCAR Cat. KA-1677 Whether you wish JAYCAR your egg soft. but JAYCAA JAYCAA not too soft. or SUPER SIMPLE MODEM JAYCAR whether you want JAYCAA to add the time Kef: AEM Sept 1986 JAYCAR Due to customer demand, we have decided to introduce this Into our range. It's vety cheap and It factor. to a game JAYCAR works well. Kit Is supplied with RS232 female connector and all other parts except power pack, ofTt1Vlal Pursuit. JAYCAR which Is extra $13.95 (Cat. MP-3020) JAYCAA this utility timer Is JAYCAA Cat. KM-3046 ideal. JAYCAA Complete kit JAYCAR Cat. KA· 1697 JAYCAA JAYCAR LOW OHMS ADAPTOR FOR DMM's JAYCAA Ref: Stllcon Chip Feb 1988 JAYCAA Another handy kit from SC which utilises your dtgttal multimeter. JAYCAA Cat. KC-5023 JAYCAR JAYCAR JAY<::AA TRANSISTOR, FET AND JAYCAR MODEM END OF FILE INDICATOR JAYCAR JAYCAR Ref: Silicon Chip Feb 1988 ZENER TESTER JAYCAR PC board and all parts supplied including switch. . Ref: EA Feb 1988 JAYCAA Cat. KC-5024 JAYCAR Revamped version of an oldie. Checks transistors, fets and JAYCAA zeners as well as checking transistor breakdown voltages. JAYCAA Great for the workbench, and also for showing how LESS 15% JAYCAA DOOR MINDER semiconductor deVlces operate. Complete kit includes box, JAYCAA Ref: Silicon Chip Feb '88 meter, transformer and all parts. OFF ALL JAYCAR New generation door opener alarm. 9V power supply Cat. MP-3010 $18.50 Cat. KA-1698 JAYCAR Cat. KC-5020 PRICES JAYCAR JAYCAR JAYCAR JAYCAR TELEPHONE INTERCOM JAYCAR ULTIMATE CAR BURGLAR ALARM Ref: ETI Feb 1988 IAYCAA Ref: Silcon Chip Feb '88 Use 2 old telephones IAYCAA Includes flashing light switch, back-up batte,y and tgnttlon killer. IAYCAR to make ·an intercom. IAYCAA Cat. KC-5021 -:;; ( Kit Includes power IAYCAR ' ~ · ♦ -,.G supply, filter IAYCAA • -<> capacitors, box and IAYCAA all parts. IAYCAA Extras · Siren Hom 1 .,M-tv~. •..... . ..,-":;:." , Cat. KE-4731 IAYCAR Cat. U\-5700 IAYCAR $26.50 IAYCAA TElf:Pt-iONE lNtfACOM IAYCAA., ETl-291: Screamer Piezo IAYCAR ':',: Cat. U\·5255 IAYCAA,(. . t} AYCAA':':. $17.95 AYCAA":::' AYCAA ':'.' AYCAA \. NEW KITS FOR FEBRUARY $165 $85.00 $21.95 $29.95 $9.95 $37.50 $55.00 $79.50 ". '\f· $59.95 f ,:"'«c'-N :~g:~ · .___________::::::===============:._~====== AYCAR AYCAAJAYCARJAYCARJAYCAAJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAAJAYCARJAYCARJA AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCA AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCAAJAYCAR JAYCARJAYCARJAYCARJ vr: Q I Vf"':.6.Q I Vt"':.6.Q I vr.Aa 1.6.Vr: .6. R .1.6.Vf"':.6.A .1.6.Vr..6.R _I vr..6.R -1.6.Vr.4.R J~ A Y C A A 16YC6A 1.6.VCAP IAYCAO IAYCAO lA V C AD l ♦ YC tD 1010 4D JATvA t1 J A T1.,A t1 J1\T\.,1\t1 J1\Tl.,1\t1 J1\T<.;A t1 JA Y<.;At1 JAY <.;AH JAY<.;AH JAY'-'AH JA YvAH JAY v A H JAYvAH JA YvAH JAYvA H JAYl:A H JAYl:AK JAYl:A K J A Yl:A K J AY l:AK J AYl:AK J AYl:A K JAY JAYCARJAYCARJAYCARJ AYCARJ AYCARJAYCARJ AYCARJ AYCARJ AYCARJAYCARJAYCARJ AYC ARJAYCARJ AYCARJAYCARJ AYCARJAYCA~JAYCARJ AYCARJAYCAR JAYCA RJAY JAYCARJ AYCARJAYCARJAYCARJ AYCARJAYCARJ AYCARJAYCARJ AYCARJAYCARJAYCAR JAYCARJAYCARJ AYCARJ AYCARJAYCARJAYCARJAYCARJ AYCARJAYCAR JAYCAR JAY JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR WAS SALE Cat EA60/60 KIT JAYCAR PRICE JAYCAR 60W rms 8'' 2 way with boxes Elect ronics Australia Kita JAYCAR KA-1010 Mustcolor 4 $125.00 $106.25 JAYCAR JAYCAR KA-ll09 Electric Fence $23.50 $19.97 JAYCAR KA-lll5 300Wampmodule $ll9.95 $101.96 JAYCAR KA-1116 300W power supply $99.50 $84.58 JAYCAR AEM6102 KIT KA-1117 300W speaker protector $23.50 $19.97 JAYCAR lOOW rms 8" 2 way with boxes KA-1119 Transistor tester $21.50 $18.28 JAYCAR KA-1220 Signal tracer $27.95 $23.76 JAYCAR JAYCAR KA-1390 Frequency Counter 50MHz $169.50 $144.08 JAYCAR KA-1428 Function Generator $129.50 $110.08 JAYCAR KA-1430 Vocal Canceller $24.95 $21.21 JAYCAR KA-1505 TAI Hall Effect $44.95 $38.20 JAYCAR AEM6103 KIT KA-1506 Transistor Assisted Ignition $42.50 $36.13 JAYCAR 150W rms 10' 3 way with boxes KA-1508 Touch Light Dimmer $29.95 $25.46 JAYCAR JAYCAR KA-1522 Guitar Effects BBD $115.00 $97.75 1 JAYCAR KA-1535 Ignition Killer $23.50 $19.98 JAYCAR KA-1550 Deluxe Car Alarm $89.50 $76.08 JAYCAR KA-1555 CQAM Stereo Decoder $26.50 $22.53 JAYCAR KA-1556 Ultra Sonic Movement DeL $34.95 $29.70 JAYCAR KA-1560 Rallmaster Controller $109.95 $93.46 JAYCAR JAYCAR KA-1574 30V IA Power Supply $89.50 $76.08 JAYCAR KA-1582 HouseAlarm $169.00 $143.65 We ·have purchased a surplus Job lot of HIGH JAYCAR KA-1595 Dlgltal Capacitance Meter $85.00 $72.25 QUALrlY 5" 8 ohm speakers with a huge magneL JAYCAR KA-1598 40W Inverter 12/230V $99.95 $84.96 These are made in New Zealand and at the sale JAYCAR KA-1610 300W Inverter 12/230V $249.00 $211.65 price represent a bargain. JAYCAR KA-1635 AM/FM Stereo Tuner $599.00 $509.15 Power handling is 10 watts. JAYCAR JAYCAR KA- 1636 AM/FM Remote Control $99.50 $84.58 Don't miss this bargain. JAYCAR KA-1650 Playmaster 60/60 $299.00 $254.15 10 up $3.50 each a o JAYCAR NORMALLY $8.95 each KA-1652 Blueprint 60/60 $349.00 $296.65 Cat. AS-3010 JAYCAR KA-1660 Electric Fence $59.50 $50.58 JAYCAR KA-1674 Dlgltal Photo Timer $89.95 $76.46 JAYCAR KA-1675 Screacher Car Alarm $34.95 $29.70 JAYCAR JAYCAR KA-1677 Audio Oscillator (metered) $165.00 $140.25 JAYCAR KA-1679 Turbo Timer $29.95 $25.46 JAYCAR KA-1681 3 Band Short Wave Radio $79.50 $67.58 JAYCAR Finally available, our updated guitar speakn with KA-1682 Dual Tracking Power Supply$129.95 $ll0.46 JAYCAR extended frequency response. Especially suited for KA-1683 BatteryMonttor $14.95 $12.71 JAYCAR not only Bass guitar buy Rythm & Lead as well. KA-1684 8 Channel 1/R Transmitter $45.00 $38.25 JAYCAR Spec!f!cations JAYCAR KA-1685 IR Receiver (St,!) $127.95 $108.76 Resonant Frequency 60Hz (was 80Hz) JAYCAR KA-1686 IR Receiver (add-on) $55.00 $46.75 Impedance 8 ohms JAYCAR KA-1687 Electronic Rain Guage $49.95 $42.46 JAYCAR Freq. Response 60 5000Hz (was 80 4000) KA-1690 DI Box $39.95 $33.96 JAYCAR Power Handling 100 watts KA-1691 TV Colour Bar/Pettem Gen $159.00 $135.15 JAYCAR Magnet Weight 40 oz JAYCAR Net Weight 3610 grams (was 3520g) JAYCAR AUSTRALIAN ELECTRONICS MONTHLY KITS Sensitivity 102dB JAYCAR KM-301060WMosfetamp $59.50 $50.58 But the best news ts the price NO INCREASE JAYCAR KM-3012 120W Mosfet amp $79.50 $67.58 JAYCAR Cat. CG-2380 KM-3015 Listening Post $39.95 $33.96 JAYCAR KM-3016 RTIY Encoder $29.95 $25.46 JAYCAR KM-3020 6000 Power Amp $998.00 $848.30 KM-3030 Ultrafldeltty Preamp $359.00 $305.15 JAYCAR KM-3040 Dual Speed Modem $169.00 $143.65 JAYCAR KM-3042 Speech Synthestscr $43.50 $36.98 JAYCAR 5 or more $79.50 KM-3050 Workhorse Amp $35.00 $29. 75 JAYCAR KM-305864 PktRadto $59.95 $50.96 LESS 15% $67.58 JAYCAR KM-3060 Balanced Line Driver $99.50 $84.58 JAYCAR JAYCAR KM-3061 Microphone Preamp $36.95 $31.41 JAYCAR KM-3062 RSTrue 232 Interface $24.95 $21.21 JAYCAR KM-3063 Uo Satellite Decoder $55.00 $46.75 JAYCAR JAYCAR ET1 KITS JAYCAR Save your car for less than $20 KE-4013 Microwave Leak Detector $17.95 $15.26 JAYCAR JAYCAR It's a black box with 12 digits on the KE-4014 Mixer Preamp $39.50 $33.58 JAYCAR top (like a calculator) and a KE-4023 Signal Spk Manfacturer $22.50 $19.13 JAYCAR flashing LED. KE-4029 NtCad Battery Charger $16.95 $14 .41 JAYCAR It looKB vety similar to the controller on KE-4033 Temperature Probe $32.95 $28.00 JAYCAR a very expensive car alarm KE-4050 ETI480 50W amp module $27.50 $23.38 JAYCAR (the one that guarantees your car won't KE-4052 ETI480 lOOW amp module $34.50 $29.33 JAYCAR JAYCAR be stolen). $29.50 $25.08 KE-4048. ETI480 power supply JAYCAR So with this sitting on your dash, would KE-4200 5000 Power Amp $499.00 $381.65 JAYCAR be thieves will think you KE-4202 5000 Preamp $399.00 $339.15 JAYCAR have a high quality alarm, and move on. KE-4204 5000 1/3 Octave Eq. $219.00 $186.15 JAYCAR Can be used on Hs own, or to complement KE-4220 ETI499 150W Mosfet amp $109.50 $93.08 JAYCAR any existing alarm system. KE-4666 RS232 Centrontcs Interface $32.50 $27.63 JAYCAR JAYCAR Use on cars, around the home, on boats, etc. I KE-4678 ETI340 Car Alarm $79.50 $67.58 JAYCAR KE-4690 ETI342 CDI Kit $79.50 $67.58 Easy to install, size 70 x 50mm, sticky tape '-1/)rg:..;..:q,i;;~ JAYCAR already supplied on back. KE-4698 4 Sector House Alarm $29.95 $25.48 JAYCAR $42.50 $36. 13 Includes alartn stickers. Requires 2 x MA KE-4708 DI Box JAYCAR batteries (not supplied), ,.,, $9.95 $8.46 KE-4711 Mint FM Transmitter JAYCAR Cat. SB-2375 $1.95 for 2. JAYCAR KE-4 720 Dtgttal Sampler $119.00 $101.15 JAYCAR Cat. IA-5090 KE-4722 RS232 Commodore $16.95 $14.41 JAYCAR KE-4724 Parametric Equaliser $23.50 $19.98 JAYCAR KE-4725 Solder Iron Temp Control $39.50 $33.58 JAYCAR JAYCAR BELOW 1/2 PRICE SIUCO N CHIP KITS JAYCAR KC-5010 Capacitance Meter/DMM $27.95 $23.76 JAYCAR JAYCAR KC-5011 Off Hook Indicator $12.95 $11.00 JAYCAR KC-5012 Car Radio Power Supply $28.95 $24.60 JAYCAR ETl684 Intell1gent modem at a silly price. It appeared in ETI December 85, Feb/March/June/July & August JAYCAR 1986. JAYCARKITS JAYCAR $42.50 $36.13 KJ -6502 Syntom Drum Synth JAYCAR NORMAL PRICE $379.00 $595.00 $505.75 JAYCAR KJ-6504 8 Channel Mixer JAYCAR $119.00 $101.15 KJ-6505 Console P/supply above 49.95 JAYCAR $239.00 $203.15 KJ-6531 2801 1/3 Octave Eq. JAYCAR TOTAL $428.95 $169.00 $143.65 KJ-6535 2010 10 Band Stereo Eq. JAYCAR $19.95 $16.96 KJ -7000 Red Light Flasher tncludtng power supply below costJII JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYC AR JAYCAR JAYCAR JA> l t, R JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYl JAYCARJAYCARJAYCARJAYCARJAYCAHJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAYCARJ AYCARJAYCAR JAYCAR JAY < JAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAVCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYC ARJAYCARJAYCAR JAYCAR JAY< VIFA SPEAKER KITS - LESS 15% $449 LESS 15% $381.65 $799 LESS 15% $679.15 $1199 LESS 15% $1,019.15 SPEAKER BARGAIN FEB 1/2 PRICE $4.48 ~~~15% 12" GUITAR SPEAKER NEW MODEL ., ., ~ STILL ONLY $89.50 LESS 15% $76.07 j~~g:~ CAR THEFT DETERRENT =-- $19.95 LESS 15% 16.96 SAVE AN AMAZING $229.20 INTELLIGENT MODEM KIT - (BELOW COST) Power Supply ~ $ SALE PRICE $235 LESS 15% $199 •75 \!"C' AO IA Y C AA IA Y C A A I AY CAO I AYr______A_A t.A V,.C_A.R..J . .6.YCAR.... 1~ 1 1 . Y C A . . Q _J.AY:.C.A.A JA.V_C _AR ..J .AYJ::~.A.J;2_ 1..6..._YC.AQ ..J ...A..VCAO I AYC A P -1.A._VC'AP I AYCAP I AYCAC I AVf' A.Q.. l A._V.1_ ji.\ 1cAFi jAv'i':AFi jAvcAFi jAvcAR jAvcARJAYCAR JAYCARJAYCARJAvcAFi JAYCARJAvcAFi JAYcAFi JAYcAFi JAYcAFi JAYcARJAYcARJAvcARJAvcARJAvcAfi-1AvcAR:iAvcAR:;;;:.;,c; JAYCARJ AYCARJAYCAR JAYCARJ AYCAR JAYCAR JAYCAR JAYCARJ AYCARJAYCARJAYCARJ AYCA RJAYCARJ AYCAR JAYCARJ AYCARJ AYCARJAYCAR JA'r'.<at>AR JAYCAR JAYCAR JAYC1 JAYCAR JAYCARJAYCARJ AYCARJ AYCARJAYCAR JAYCAR JAYCAR JAYCARJAYCARJAYCARJ AYCARJAYCARJ AYCARJAYCARJ AYCARJAYCARJAYCAR j AYCARJAYCAR JAYCAR JAYC, JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR The model gf-2310 ls a sldeband M11l!volt meter for measuting AC voltages from 0 .3mV to lOOV In 12 ranges JAYCAR wlt.h bandwidth of 5Hz to 1MHz. Each range shares 10 dB. The effective sensitivity at 0 .3mV range ls 30uV. JAYCAR Equipped with 3 colour scales, volt, dB and dBm. JAYCAR JAYCAR Specifications: JAYCAR Voltage Range: 0.3 1 3 10 30 100 100V JAYCAR 0.3 1 3 10 30 100, In 12 ranges JAYCAR -70 -60 -50 -40 -30 -20 -10 0 +10 dB Range: . JAYCAR +20 +30 +40dB. dB (OdB=lV rms. OdBm=0.775V) JAYCAR • Capacitance tester Accuracy: ±3% of fuU scale to lkHz or 400Hz JAYCAR • Transistor tester JAYCAR Input Impedance: l0Mohm for each range. 40pF or less • 20 amp current JAYCAR Bandwidth: ±3% 20Hz - 200kHz JAYCAR • Htgh Impact case ±5% l0Hz - 500kHz JAYCAR Cat. QM-1555 ±10% 5Hz - lOOOkHz JAYCAR Amplifier Output 1 Vrms at fuU scale 600 ohm Impedance ' JAYCAR 240V operated IAYCAR -· IAYCAR Cat. gf-2320 IAYCAR fcc,1,11,ii IAYCAR 10.A IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR IAYCAR TURN YOUR SURPLUS STOCK INTO CASH!! Sine Wave Output IAYCAR Jaycar will purchase your surplus stocks of components and Range: l0Hz - 1MHz IAYCAR Features: equipment. We are continually on the lookout for sources ofprtme Output Voltage: 8Vrms max. IAYCAR • High frequency stability: within ±2Hz quaIt ty merchandise. IAYCAR Output Distortion: Less than 0.05% • Output voltage tloatlng: within ± ldB CALL GARY JOHNSfON OR BRUCE ROUfLEY IAYCAR 400Hz - 20kHz • Sine wave signal output: more than 8Vrms IAYCAR NOW ON (02) 747 2022 Less than 0.3% 20Hz - 200kHz • Equ ipped with synchronised Input terminal of IAYCAR Less than 0.05% 500Hz - 50kHz - signals, thus enables the high power output signals IAYCAR Less than 0.5% 50Hz - 500kHz IAYCAR lo be accurately contro1led by small signals. AUOICGENl!:AA TOR Output Flatness: ±ldB (lkHz) IAYCAR Specifications: IAYCAR Square Wave Output Frequency Range: l0Hz - 1MHz 5 decade bands IAYCAR Range: 20Hz - 20kHz Accuracy: ±3% +2.Hz IAYCAR OutputVoltage: 15Vp-pmax NEW ' IAYCAR Output lmpedance:600 ohms unbalanced Rise Time: 0.5uS 7( IAYCAR Output Control: Htgh, Low (-40dB) and fine adjuster IAYCAR IAYCAR Cat. QT-2310 IAYCAR IAYCAR IAYCAR IAYCAR 1AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR Don't keep wasting money buying SHRINKS WITH A MATCH AYCAR ·throw-awaybattertes. Step up to N!Cad • 2 colours - red and black AYCAR , - L_E_S_S-15I 0 rechargeables. • Are you happy with your • remains flexible after shtinktng AYCAR AYCAR SUPERB ROCKET BRAND • all supplled In 1 metre lengths present electronics supplier? AYCAR Size Red Black Price AA PENLIGHT 450mA AYCAR • Do you get instant credit? WH-5540 WH5530 $1.75 Cat. SB-2452 AYCAR WH-5541 WH-5531 $1.75 AYCAR • If not, try Jaycar - we offer AYCAR WH-5542 WH-5532 $1.85 AYCAR - SPEEDY SERVICE WH-5543 5mm WH-5533 $1.95 AYCAR - INSTANf ACCOUNTS AYCAR 7mm WH-5544 WH-5534 $2.10 AYCAR WH-5545 10mm WH-5535 $2.25 - REASONABLE PRICES AYCAR AYCAR 16mm WH-5547 WH-5537 $3.25 - GREAT RANGE OF AYCAR Shtinks to 1/2 the size listed. ~ ! AYCAR COMPONENTS ~ <at>lm AYCAR AYCAR AYCAR AYCAR • BURGLAR ALARMS AYCAR The great new LED bezels are made of black plastic, and are supplied In two parts. AYCAR • PASSIVE INFRA RED Simply push part A Into the panel (you will need a 10mm hole), then put the LED AYCAR Into part Band Insert part B (with LED) Into part A for a tight flt. You end up with a AYCAR DETECTORS very professional LED bezel at about 1/4 the price of chrome ones. AYCAR • SPEAKERS Also. lfyou have the need for a hole In a panel up until now Its been extremely hard to AYCAR AYCAR disguise It. Simply mount one of these without the LED. Ideal for Internal mounted buzzers • RESISTORS AYCAR - lamps etc. • TRANSISTORS AYCAR W CAR Cat. HP-1105 Pkt of 10 • CAPACITORS AYCAR • WIRE • BOOKS WCAR Cat. HP-1106 Pkt of 100 W CAR • PLUGS AND SOCKETS WCAR WCAR • ROBOTS WCAR • MULTIMETERS WCAR WCAR • SOLDERING IRONS TWO BRAND NEW MODELS, BOTH FULLY APPROVED BY \YCAR • TOOLS \YCAR THE ELECTRICITY AUTHORITY \YCAR 2 OUTLET • MODEMS • F:ANS IYCAR 4 OUTLET The two outlet will handle up to \YCAR • TV ANTENNAS 7.5amps. IYCAR The MS-4020 will supply up to 4 appliances. Each 240V socket Is independently • HEADPHONES The two sockets are not \YCAR filtered. The filter will suppress Interference from RF sources, spikes, transients \ YCAR independently and lighting. and supply up to 4 outlets with a total load of 10 amps. • SOLDER \ YCAR filtered although. Cat MS-4020 IYCAR • BISHOP GRAPHICS Cat. MS-4025 IYCAR •LEDS IYCAR \YCAR • SWITCHES \YCAR IYCAR • BOXES \YCAR \YCAR • CROSSOVERS 1YCAR •RACK BOXES \YCAR 1YCAR • TRANSFORMERS \YCAR 1YCAR • KITS BEWARE! There are many mains filters on the market. One sample we evaluated had only one capacitor in 1U 1YCAR 1YCAR 1YCAR 1YCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYC!\R JAYC AR JAYC AR JAYC AR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR J!\YCAR JAYCA R JAYC. 1YC AR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYC AR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JAYC ,YCARJAYCARJAYCARJAYC ARJ AYCARJAYCARJAYCARJAYCARJ AYCARJ AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCA R JAYCAR JAYC ARJ AYC DIGITAL MULTIMETER WITH FREQUENCY COUNTER $159 LESS 15% $135.15 AC MILLIVOLT METER [/9.99 .J ~:Im ~ ~ ,1,1-• .., .... i $225 LESS 15% $191.25 AUDIO GENERA TOR - - -------23 9 LESS. 1501.:0 8 $203.15 , PENLIGHT ;, --------, NiCads I l I I 1$4.25 each :LESS 15% ~3.6~each M Jl!ID% I l -vo..... Schools, Technical Colleges, Universities J .&11lla 1rrnu~~JJ; lJl~<at>IID11lJ©1r~ LED BEZELS ~ - - -' $2.99 $26.95 [D SQUEAKY CLEAN MAINS FILTERS $269.00 LESS 15% $228.65 $99.00 LESS ~·~15% $84.15 ... . . , .., . . . , .. . . , ..., • • , . . . . . . , ......... . . ... . . . , ........ , , .. .... . ........ , , .,,.... , ...,,...,, ..,,... , ....,,.,,, .. ,.... t ...,,., , , ... ,.. , ...., , , , , un 1 VMll UM ! VM l l Ul"\ I VMfl ..in I VM n UMI V l"\I, .JM I vM n JM T VM n JMT VMn JMIVMn JM T VMn .J MTVl"\ n J M. T Vl-\n Jl\1 ' J AYCA R J AYCAR J AYCAR J AYCAR J AYCAR JAYCAR J AYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCA R JAY, JAYCAR J AYCAR JAYCAR JAYCARJAYCARJAYCARJ AYCAR JAYCARJAYCARJAYCARJAYCAR J AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR J AYCARJAY < JAYCARJ AYCAR JAYCAR JAYCARJAYCARJAYCAR J AYCAR JAYCARJAYCARJAYCARJAYCAR J AYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCARJAYCAR JAYCARJAY< JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR Ref: Stllcon Chip Jan '88 JAYCAR 1.25 to 18.5V DC. Vo huge metering. JAYCAR JAYCAR LED dropout Indicator, short JAYCAR circuit protected. Full kit. JAYCAR Ref: EA Jan '88 JAYCA R Cal ({C::~~ Cal KA- 1696 JAYCAR JAYCAR Ref: AEM Dec '87 JAYCAR Thfs one octave EQ JAYCAR module is suited for JAYCAR PA and professional JAYCAR use. Kit supplied with JAYCAR JAYCAR all components, pots, JAYCA R PCB. No box or JAYCA R hardware. JAYCA R Cal KM-3064 JAYCA R JAYCAR JAYCAR JAYCAR Ref: Silicon Chip Jan '87 JAYCAR If you 11red of the sound of your · JAYCAR Ref: EA Nov 1987 . ./ /. ·:_ . JAYCAR phone, by thfs kit. Mounts Inside Thi• handy voltage and ~ ·,/ . . '] phone - tncludes buzzer. Ref: Stltcon Chip Nov 1987 JAYCAR JAYCAR C~~~illl _ • continuity tester tests AC · l . •.. .•· · .• Cat. KC-5015 JAYCAR and DC voltages and also ·. _,,#- ~ JAYCAR continuity tn wires and cables. •. . · ··-~ JAYCAR Cat. KA-1694 7 JAYCAR JAYCAR JAYCAR Ref: ETl Dec '87 JAYCAR Cal KE-4730 JAYCA R JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR Ref: Stltcon Chtp Dec '87 JAYCAR JAYCAR Kits Include PCB all parts and heat stnk bracket JAYCA R (Thermistors not supplted). JAYCAR .· Ref: Sfltcon Chip Jan '88 50 WATT Cal KC -5018 JAYCAR Liste n l o hidden transmissions on FM broadcasts. PC board and JAYCAR ThermfstorRDEll5 Ref: Stltcon Chip Nov 1987 components. Cat. KC-5014 J AYCAR Cat. RN-3415 A great project from a new JAYCAR $8.95 monthly electronics JAYCAR magaztne - Stltcon Chtp. JAYCAR 100 WATT Thermistor RDE245A Add a two range JAYCAR Cal KC-5019 Cat. RN-3418 Ref: ETI Nov 1987 JAY CAR capacitance tester for 95 JAYCAR Features the ETI 1424 Include a top boost and normal Input. only $27.95. $l0. JAYCAR two pre-eq ltne tnputs, bass & treble controls, effects send and Ranges are O - 2200pF JAYCAR return, sweep eq, 4 post eq & ltne Inputs and master volume. and O - 2 .2µF. JAYCAR Pots supplted when available. 6.5mm sockets, transformer and Complete kit. JAYCAR knobs are not supplted. Cat KC -5010 JAYCAR Cat. KE-4729 JAYCAR JAYCAR JAYCAR Ref: EA October 1987 JAYCAR 1 Thta generator will produce: colour bars, red scteen, JAYCAR white screen, black screen, crosshatch, vertical ltnes Ref: Stltcon Chip Nov '87 JAYCAR and hortzon ta! ltnea and dot patterns - 8 patterns JAYCAR Ref: Stltcon Chip Dec '87 Thts superb 1GHz dtgttal frequency meter will tn all! JAYCAR Well suited to run 12 volt appliances from 24 volt. outperform any other tnstrument tn tts prlce range. JAYCAR Separate outputs for RF (channel O or 1), composite Can deltver up to 5 amps. it uses the highest performance !Cs, provides both JAYCAR video, horizontal and vertical sync pulses. The sync frequency and period measurements, and features an Comple te ktt JAYCAR pulses are available tn both positive and negative 8 dtgtt LED readout Cat. KC-5017 JAYCAR going logic. Cal KC-5013 JAYCAR The Jaycar kit tncludes all specified (or equivalent) JAYCAR components tncludtng Scotchcal front and rear JAYCAR JAYCAR panels, plastic tnstrumen t case etc. JAYCAR Cal KA-1691 JAYCAR Power supply extra JAYCAR Cal MP-3020 $1 3 .95 JAYCAR JAYCAR JAYCAR UNIVERSAL SPEED JAYCAR Ref: EA Nov 1987 JAYCAR JAYCAR Pr1nted ctrcutt board and JAYCAR electronics supplted. No box. LAMP DIMMER JAYCAR Cal KA-1693 JAYCAR Ref: SIiicon Chip Dec '87 JAYCAR Cal KC-5016 JAYCAR JA v·cAR No,1 FOR THE LATEST KITS ECONOMY TEMPERATURE PROBE FOR MULTIMETER DUAL TRACKING POWER SUPPLY OCTAVE EQUALISER MODULE $99.95 .$19.95 VOLTAGE & CONTINUITY TESTER ) .rfi€.1 ~ Y i. J -,tj "~ ..... are $19.95 $29.95 $49.95 TELEPHONE RINGER SOLAR GENERATOR OFF HOOK INDICATOR FOR $12 95 PHONE HIGH IMPEDANCE AC/DC MILLIVOLTMETER ~~- ~-~~ $46.50 $12.95 50 & 100 WATT AMPLIFIER MODULES CAPACIT METERFO D.M.M. "'·"·SUB CARRIER ADAPTORS FOR FM TUNERS $22.95 $32.95 HIGH QUALITY GUITAR PREAMP $38. 95 TV COLOUR BAR & PATTERN GENERATOR $45.00 $27.95 24 TO 12V CONVERTER $59.00 GHz Digital Frequency Meter! ONLY $299.00 $ 1 59 •00 CONTROL $18.95 & $ 19.95 w✓//////////////////////////////////////////~//////////////////////////'.d. 7.h'»✓. ~r ~~ ~ ~~ ~~, • 117YorkSt. (02)2671614- ~ ~ Mon-Fn 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 Cnr Carlingford & Pennant Hills Rd (02) 872 4444 Mon-Fn9-5.30Thurs8.30pm - Sat9-2pm ~ ~,~~ CAR LING FORD ••t...••-···' • •· lr; '7/////////////////////////////////~///////////////////~:~g:~ ~SYDNEY• CITY ~CONCORD ~ , _/4HURSTVILLE HEAD OFFICE ~ 115 Parramatta Road ~ Concord 2137 ~ (02)7472022 Telex 72293 FACSIMILE (02)7440767 MAIL ORDERS PO Box 185 · · Conco rd2137 lN~8~8 ~ AYCAR ~:~g:~ ~:~g:~ ~ AYCAR ~ AYCAR 11sParramartaRd (02)7453077Mon-Fn8.30-5.30-Sat8.30 - 12 ~ ~ AYCAR ~ \ l.' 121ForestRd(02)5707000~ ~ AYCAR Mon-Fn9-5.30Thurs8.30pm-Sat9-12 -,Z~ ',,-- y ---. ·i POST&PACKING %GORE HILL 188Pacij1cHwycnrBellevueAve(02)4394799 ~ ~ AYCAR ~ f . '. \ $5 $9.99 $ 2.00 :% Mon-Fn 9 - 5.30 Sat 9 - 4pm ~ AYCAR 0 1 1 4 9 3 75 ~ ( Mast■reard. s o S2 . 9 s . ~BURANDAQLD 144LoganRd(07)3930777~ 0 AYCAR Mon-Fr, 9 - 5.30 Thurs 8.30- Sat 9 - 12 OVER$100 $10.00 % MELBOURNE-CITY Shop2,45A'BeckettSt C1ty(03) 6632030 FOR ORDERS ONLY 0 AYCAR ~ VISA AMERICAN ROAD FREIGHT % Mon-Fn9-5.30Fn8.30-Sat9-12 ~ TOLLFREE ~ AYCAR •••• EXPAESS IN 50 SPRINGVALE VIC 887-889 Springvale Road Mulgra~e (03) 5471022 (008) 022 888 Nr Cnr. Dandenong Road Mon-Fn 9 - 5.30 Fn 8.30 • Sat 9- 12 ~ /4AYCAR ~ , & / / / / / / / / / / / / / / / / / , MAIL ORDER VIA YOUR PHONE 1/////////////ff0W/////////////////////#'JAYCAR JAYCAR ~ \.__ )(.__,/_ ~ ■iiiill■■I ~ 0 ••• W$////////4. f~g :~:~~ f ::~ ~ Allr1'1r~:13· '-~~ ~ ~ ~ ~ (o~f ~:~g~ ~:~g:~ ~:~g:~ JAYCARJ AYCARJAYCAR JAYCARJ AYCARJAYCARJ AYCAR J AY CAR J AYCARJAYCARJAYCARJ~YCARJAYCARJAYCARJAYCAR J AYCARJAYCARJAYCARJAYCA R JAYCAR J AvJt~~:~ JAYCAR J AYCARJAYCARJ AYCAR J AYC ARJAYCARJ AYCARJAYCA RJ AYCAR JAYCAR JAYCARJAYCARJAYCARJAYCAR JAYCARJ AYCARJAYCAR JAYCAR J AYCA RJAYCAR J AYCAR JAY ~~~9~ ~ ~~X2~ ~ ~~X2~~ ~~X2~ ~ ~~X2 ~ ~YC AR J AYCAR JAYCAR J AYCAR JAY CAR JAYCAR J AY CAR JAY CAR J AYCAR JAYCAR JAYCAR JAYCAR JAYCAR J AYCA_R JAYCAR_,J AYCA R JAY HIFIREVIEW The TA-N77ES stereo power amplifier: beautifully finished, superlative performance. Sony enters the big po"7er stakes Sony don't make a separate stereo preamplifier and high power amplifier do they? They never have. Well now they do. Just released, the new Sony ES-series preamplifier and power amplifier set new standards for audio quality. Reviewed by LEO SIMPSON Sony has long been at the forefront of audio but it is a long time since they have brought out something really new in the category of amplifiers. Sony were one of the first manufacturers to pioneer the use of high power Mosfets in their amplifiers and it was quite long time ago too; around 15 years or so. Now Sony have released this interesting duo, the TA-E77ES stereo control amplifier and the TA-N77ES 30 SILICON CHIP stereo power amplifier. Sony's designation of the former unit is a little odd; it has no power amplifiers as such although it does have an inbuilt stereo headphone amplifier. Conventionally, the TA-E77ES would be described as a stereo control preamplifier but no doubt Sony feel justified in calling it a control amplifier because of particular features of its construction. We are inclined to agree with their thinking, as you will see later. For the moment though, the Sony control amplifier looks like a very well specified control preamplifier. It can handle the full range of audio program sources plus three video program sources. The latter may be two video recorders, hifi or otherwise, and perhaps a videodisc player, or it could be one of the soon-to-be-released CD video players. The unit has circuitry to switch both the video and audio signals. Moving magnet or moving coil cartridges may be selected for the phono player and the moving coil cartridge may be selected as either a low or medium impedance unit. Apart from phono, five high level sources may be selected: CD (compact disc), tape 1, tape 2, tuner and auxiliary (such as DAT). All told then, a total of nine program sources may be selected, when the video sources are included. Each program source is selected by means of a microswitch button which controls a relay. And each button has very discrete red illumination to show it has been selected. Very suave. The signals from these sources may be routed through the tone controls, stereo/mono switch and balance control in the usual way, or via an Adaptor which would usually be a graphic equaliser. Alternatively, the user can select Direct. The Direct mode connects the selected source direct to the output, bypassing all other controls. This feature is becoming more common on upmarket amplifiers although it usually only applies to CD. It is intended to give the minimum possible deterioration of the compact disc signal. In making the Direct mode available for all sources, Sony has taken note of the marketplace and is acknowledging that in every category - CD, hifi VCR, DAT or FM tuner - there are program sources which challenge the best amplifiers and control units currently available. It therefore makes sense to give lovers of high fidelity sound two options: the absolute minimum signal processing or tone controls and filters when they are needed. Since it features the Direct mode, the Sony control amplifier does not feature tone control cancel buttons. Instead there are two buttons to change the turnover frequencies : 200Hz or 400Hz for the Bass con- Specifications TA-N77ES Stereo Power Amplifier Continuous power output per channel (both channels driven) Dynamic power Rated harmonic distortion Damping factor Slew rate Frequency response Input sensitivity Signal-to-noise ratio 270W into 40; 200W into 80 520W into 40; 300W into 80 .006% into 40; .004% into80 100 (at 1 kHz) into 80 150V/µ,sec 1Hz to 300kHz (-3d8) 1V, 30k0 -1 20dB (A-weighted) TA-E77ES Stereo Control Amplifier Rated harmonic distortion Frequency response Phono equalisation Signal-to-noise ratio phono MC phono MM CD, Tuner, etc trol and 3kHz and 6kHz for the Treble control. These are handy if you wish to carefully tailor the amount of Bass or Treble boost applied to your speakers. Remote control An interesting feature of the Sony control amplifier is the companion RM-177 infrared remote control. This includes the following functions: power on/off, volume adjust, program switching, and Direct and Adaptor switching. The remote volume control facility is very nice. Push the button and the volume control on the amplifier .001% 3Hz to 300kHz (-3dB) RIAA curve ±0.2dB -83dB (A-weighted) -95dB (A-weighted) - 1 05d8 (A-weighted) rotates smoothly and quietly for as long as you hold the button down. An illuminated red cursor on the knob shows the volume setting in unambiguous fashion. A small motor .on the rear of the control provides the drive. Another interesting feature is that when you first turn the amplifier on it is muted for several seconds. So that you don't rashly turn up the volume setting in your impatience to hear the sounds of your choice, the LED on the volume knob flashes a clear warning that it " ain't ready yet" . The headphone socket with its The TA-E77ES stereo control amplifier can handle the full range of audio signals plus three video program sources. Both moving magnet (MM) and moving coil (MC) cartridges are catered for. FEBR UA RY1988 31 Inside the stereo control amplifier. Special attention has been paid to circuit shielding. The chassis is a heavy glass reinforced epoxy casting. own inbuilt amplifier is a good idea. It lets you leave the power amplifier off if you are only going to listen to headphones. Inside the case, the Sony control amplifier is unlike any preamplifier/control unit we have seen to date. It has two power transformers, one small and the other a large toroidal unit which is larger than the transformer in many medium power stereo amplifiers. The main filter capacitors are large too, especially for a preamplifier unit. They comprise two 4700µF 63VW electrolytics. The small power transformer is powered up permanently and it keeps the remote control section of the circuitry awake. This means that you can turn on the whole system with the remote control. Neat. The most unusual feature is the chassis. This is Sony's "Gibraltar" chassis, a very heavy and rigid glass reinforced epoxy casting. Sony claims that it is much less resonant than any metal chassis and so less likely to rattle, buzz or otherwise make a contibution to the program signal. We agree; it is as dead as a door nail. Sony have gone to similar trouble with the top lid of the case. It is a 32 SILICON CHIP substantial piece of sheet steel, 2mm thick. It alone weighs 1.9kg. The whole unit weighs 12.1kg. Overall dimensions are 470 x 128 x 365mm, including knobs and rear projections. Other features inside the chassis are the three flat Bowden cables for the various rotary selectors on the front panel, the many miniature relays for switching and the special care taken with shielding. At various places on top of the printed circuit boards are long strips of copper to act as shields for vital parts of the circuit. switch selects either one or both pairs of loudspeakers, via relays. On the righthand side of the front panel are three knobs. One is a two position rotary switch to select either the variable or fixed inputs while the other two are independent level controls for the variable inputs. Sony have provided this facility so that the power amplifier can be used directly with a high quality program source such as a compact disc player. This truly would be an ultimate quality hifi set up since the amplifier has a weighted signal-tonoise ratio of 120dB with respect to full power. Thus, unlike most integrated stereo amplifiers presently available, the Sony power amplifier is a lot quieter than any compact disc player. It would have made more sense though, to make the level control a dual ganged potentiometer; two controls are a bit clumsy. On the rear panel are two pairs of RCA sockets for the inputs just referred to and eight massive shrouded binding posts for the two pairs of loudspeaker outputs. Removing the heavy perforated The power amplifier But if the Sony control amplifier is impressive, the stereo power amplifier is truly something to behold. It is built like a battleship. Immediately obvious are the two large power meters on the front of the amplifier, calibrated to read up to 600 watts into 80 loads. The meters can be switched on or off and when in use are illuminated in red which is easy on the eye but eye-catching as well. On the lefthand side of the front panel are two rotary switches and a large pushbutton which is the power switch. One rotary switch turns the meters on and off, as already mentioned. The other The companion IR remote control provides volume adjust and signal switching facilities. steel lid reveals the more or less standard features of today's high power amplifiers. There is a big power transformer with a copper strap around the laminations to eliminate flux leakage, a bank of electrolytic filter capacitors, a large chimney-style heatsink for the power transistors and so on. What really had us stumped was the large rectangular unit which took up the full depth and height of the chassis. Sony labelled this an "audio capacitor". What's an audio capacitor? It wasn't until we carefully examined the circuit digram that we realised that this "audio capacitor" was in fact a dual 22,000µ,F B0VW electrolytic capacitor which feeds the output stages of both power amplifiers. What we had thought was the main capacitor bank was in fact the electrolytics (4 x 4700µ,F B0VW) which supply the driver stages of both power amplifiers. So Sony have really done some work on the power supply of this brute. Sony haven't told us the concept of this "audio capacitor" but we can say that it is very large, even considering that it does contain 44,000µ,F of capacitance rated at 80 volts. We can only assume that it has a very high current rating. This is important if an amplifier is to deliver a very high current output. The rectangular case raises some interesting questions too. Presumably it is made of some plastic or epoxy material. How is it sealed and does it have safety venting? The seal of the can on a conventional electrolytic is quite critical. It must be absolutely moisture and air-tight otherwise the capacitor will deteriorate over time. But it must also have a safety vent which can blow and safely exhaust the copious volume of gas produced if an electrolytic fails and then seriously overheats. Again, this amplifier employs the Gibraltar-style cast chassis and the whole unit is laid out with the same detailed attention to shielding as in the control amplifier. Testing Testing the performance claims of such amplifiers challenges the test equipment of any organisation. Inside the stereo power amplifier. The "audio capacitor" is actually a dual 22,000µF 80VW electrolytic capacitor that feeds the output stages of the power amplifiers. Note the large chimney-style heatsink. Consider that the Sony power amplifier is continuously rated at 200 watts per channel into 80 loads and 270 watts per channel into 40 loads. We made up some large water cooled loads for our tests but we had to stop periodically because the water kept boiling. Measuring harmonic distortion was a problem. The control preamplifier has a rated harmonic distortion of .001 % while the power amplifier has a rated distortion of less than .004 % from 2 50 milliwatts up to 200 watts per channel into 80 loads. We can measure distortion down to less than .0007 % but there were times when our distortion measurements merely reflected the residual distortion of our equipment. Signal-to-noise ratio was another problem measurement. The control amplifier is rated at better than 105dB A-weighted for the high level inputs and better than 95dB Aweighted for the moving magnet phono input. These are the best figures we have seen to date for any stereo preamplifier. Even better is the power amplifier. As already mentioned, it has a signal-to-noise ratio of better than 120dB A-weighted with respect to full power. To measure such figures reliably you need an audio millivoltmeter set-up which will reliably measure down to less than 30 microvolts . Well, we were able to confirm the figure but not without difficulty. Indeed, as far as we could determine, all of Sony's performance specifications are met by both the control amplifier and the power amplifier. What more can we say? This Sony gear is too good for us to presently sonically test. They must be among the highest performing audio amplifiers available, regardless of price. Price of the control amplifier together with its remote control is $1799 while the power amplifier is priced at $2399. For further information, contact your Sony dealer or Sony (Australia) Pty Ltd, 33-39 Talavera Road, North Ryde, NSW 2113. Phone (02) 887 6666. it FEBRUARY1988 33 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. Thermatic Fan Timer for Cars This circuit is for use with a thermatic fan in a car. It can be fitted to vehicles used to tow caravans or boats and is useful for cooling down the engine at the start of steep hills etc. The circuit is based on an LM3905 precision timer (ICl) from National Semiconductor. Normally, Q2 is off and no power is applied to the IC. Sl is a centre-off switch which is spring loaded on one side (DSE Cat. S1287). When Sl is set to Auto, the fan operates in the normal fashion. When Sl is set to On, Q3 is biased on by current flowing through its lOk!J base resistor. This turns the relay on so that the fan now operates continuously. If Sl is momentarily switched to the Timer position, a pulse is applied to the trigger input (pin 1) of ICl via C2, and to the V + input (pin Dynamic Noise Reduction for Cassette Players This circuit was designed to remove hiss from tapes which were not recorded using Dolby. The circuit operates by rolling off frequencies above about 1.5kHz when the signal level is low but allowing the full frequency range to pass when the signal level increases above a set level. With a high signal level, the background noise tends to be masked by the program material. The unit is connected between the output of the tape recorder and the input of the amplifier. For portable cassette players, the connection should be made betwen the output of the preamplifier and input to the main amplifier, which is usually at the volume control. The circuit operates by using a 34 SILICON CHIP +12V 02 BC558 S1 01 1N914 AUTO R3 10k C2 .01 R1 1M R2 47DO 112V RELAY IC1 LM3905 v 3 8 • • TO EXISTING FAN SWITCH 4 4.7k 4.7k ....__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ DV 5) via Dl. Because of the way in which an internal transistor in ICl is connected, current now flows into pin 6 and Q2 latches on and supplies power to the IC. At the same time, Ql is turned on and quickly discharges the 220µF timing capacitor (Cl). Pin 7 thus switches high and turns on Q3 via D2 and the l0k!J base resistor. Cl now charges via the lM!J timing resistor towards the 3.15V reference voltage on pin 2. As soon as the voltage on pin 3 reaches 2V, pin 7 switches low again and Q3 turns off. The fan thus runs for the duration of the timing constant set by Rl and Cl; ie, about four minutes. Note that the relay outputs are simply wired in parallel with the existing fan relay switch. $15 to David Duffy, Thornlands, Qld. 4.7k 1NPUTO-_....;.__ _ _ _ _ _-¥,llf------------1r-oourPur -l\:,-ov POWER VR1 47k. 0--+9V S1 0.22 10k FET as a variable resistance to provide the change in rolloff frequency. When FET Q2 is off, the rolloff is determined by the 4. 7k!J resistor between the input and output terminals, the 0.022µF capacitor and the 470k!J resistor to ground. The rolloff in this case is insignificant and the full signal passes from input to output. When Q2 is biased on, the rolloff is determined by the 4. 7k!J resistor and the 0.022µF capacitor now brought to ground by the FET. The rolloff now begins at about 1.5kHz. Biasing for Q2 is provided by the remaining components. Ql is an amplifier with the level of input signal set by VR 1. This determines the level at which the FET switches from the on to the off state. Following the Ql gain stage is a rectifier and filter to supply DC to the gate of Q2. 47!l +12V 100 + 16VW! 470 .,. CHASSIS DOOR SWITCH .,. 100 + + 16VW! + 22 16VW! POSITIVE . DOOR SWITCH El Cheapo Car Burglar Alarm An ear piercing piezo siren which is triggered from the door switches is the main feature of this alarm. It is low in cost, includes entry and exit delays, and uses just a single IC. The input can work with door switches which connect to chassis or + 12V. The circuit shows both switch connections, but only one type or the other can be used on the circuit. Note that door switches are normally open when the car doors are closed. Our circuit shows the car door switches closed. The chassis door switch input operates by pulling pin 2 of ICla Sl { DISABLE,- low, causing its output to go high. The O.ZZµF capacitor then charges via the 220k0 resistor at pin 2 of ICla and after about 50 milliseconds ICla's output again goes low. By contrast, the positive door switch input operates by pulling one side of its associated 0.22µF capacitor high. This momentarily pulls the pin 5 input of I Cl b high which then goes low again as the 0.22µF capacitor charges. Depending on whether chassis or positive door switch inputs are required, link 1 or link 2 is connected to the pin 5 input of IClb. The output of ICl b goes low for 50ms every time a door switch is closed provided that the pin 6 input is high. This Handy hints and tips Hint #1: Have you ever found yourself short of a low voltage diode to complete a circuit when your parts shop has closed? You can substitute a zener diode instead. Make sure you get the polarity right though. The line around one end of the diode body indicates the cathode, whether it is a zener or ordinary diode. If the diode in question is always forward biased (ie, no reverse voltage is applied), you can use the base emitter connections of a transistor instead. For an NPN transistor, the base becomes the anode and the emitter becomes the cathode. Hint #2: Need a high current diode with a low voltage rating? The base-emitter junction of typical power transistors can handle several amps with ease provided they are not reversebiased at any time by more than a few volts. For a higher current rating, short the base to the collector. This gives a diode which can handle currents up to the collector rating of the power transistor although a heatsink may be required. For NPN transistors, the collector is equivalent to the anode of a diode while the emitter becomes the cathode. For PNP transistors the connections are reversed. PIEZO 1SIREN . turns on transistor Qt which discharges the 220µF capacitor via D2 and pulls pin 8 of IClc low. Diode DZ is included to prevent reverse breakdown of the base emitter junction of Ql. When pin 8 of IClc is pulled low, its output goes high and begins to charge the 22µF capacitor at pin 12 of ICld. After about 10 seconds, (the entry delay), the ZZµF capacitor charges sufficiently to cause the output of ICld to go low. This switches on transistor QZ to turn on the piezo siren. When the ZZOµF capacitor recharges to the upper threshold of the pin 8 input of IClc, the pin 10 output goes low and the alarm switches off after the 22µF capacitor at pin 12 of ICld discharges. The sum of these two capacitor time constants gives the total alarm time. Pin 6 of IClb and pin 13 of IGld are connected to the disable switch and the RC delay consisting of a 22µF capacitor and 470k0 charging resistor. When the disable switch is closed, both IClb and ICld are disabled and the alarm will not sound. When the disable switch is opened, the 22µF capacitor charges via the 470k0 resistor and after about 10 seconds the ICl b and ICld gates are enabled. This is the exit delay. The disable switch should be hidden beneath the car's dashboard. It can be a double pole type to also disable the ignition for added security. The piezo siren should be installed in a relatively inaccessible position in the cabin of the vehicle but not so that its output is muffled. FEBRUARY1988 35 By LEO SIMPSON & BOB FLYNN 200 Power Amplifier This rugged stereo amplifier puts out a genuine 100 watts per channel into 8-ohm loads and more than 160 watts per channel into 40. Every now and again we have a brainwave at SILICON CHIP. Truly! We were considering the design of a stereo power amplifier which had to have a genuine power output of at least 100 watts per channel into 8-ohm loads. It had to be rugged, easy to build and reasonably priced. While we discussed the pros and cons of various design approaches, we realised we already had the basis of a suitable design, the 50 and 100-watt modules described in our December issue. As it stands the circuit of the module described in our December issue cannot be pushed any harder to deliver more power. The supply rails cannot be increased because the 2N3055/MJ2955 output transistors would not stand it. Nor could the transistors for the first and se- cond differential amplifier stages. Then one of us had a flash of insight and after a minute or two of checking the concept on a plastic brain (calculator), we knew we had a simple solution: increase the power supply rails from ± 40 volts DC to ± 50V and swap the 2N3055/MJ2955 output transistors for the more highly rated MJl 5003/4 transistors. Naturally, we had to follow up with a lot more calculations, plotting load lines for drivers and output transistors and so on, but the concept was confirmed. We modified a power module to put the concept into practice, building a big power supply with a well regulated output of ± 50 volts DC and changing all the transistors which needed higher voltage ratings. Now, after considerable cooperation from Altronics of Perth in supplying key components, we present the "Studio 200" stereo power amplifier. The Studio 200 is a rugged stereo power amplifier housed in a large rack mounting case. It is eminently suitable for work in discos, bands and in the home. It is rugged but that does not mean it is not hifi. It has very good performance figures and excellent power output. Music power output, as measured by the IHF method (Institute of High Fidelity), is 120 watts per channel for 80 loads and 190 watts per channel for 40 loads. This gives a dynamic headroom figure of 0.8dB for both 40 and 80 loads. Typical harmonic distortion for powers of less than 90 watts into 80 loads is less than .01 % . Frequency response is 20Hz to lOOkHz ± ldB. Signal to noise ratio is better than 105dB unweighted with respect to 100 watts into 80. The Studio 200 stereo power amplifier features protection The Studio 200 stereo power amplifier is built into a large rack mounting case from Altronics. It has excellent specs and can be used for home hifi, or put to work in discos and bands. FEBRUARY1988 37 How the Circuit Works Thirteen transistors and three diodes make up each power amplifier. The input signal is coupled via a 1 JLF capacitor and 2.2k0 resistor to the base of 02 which together with 03 makes up a differential pair. 01 is a "constant current tail" which sets the current through 02 and 03 and renders the amplifier insensitive to variations in its supply rails (this is known as supply rejection). Signals from the collectors of 02 and 03 drive another differential pair, 04 and 05, which have a "current mirror" as their load. The current mirror, 06 and D3, does not give this second stage a particularly high gain but it does make it very linear (ie, relatively distortion free). The output of 05 is then used to drive the class-AS output stage consisting of drivers 08 and 09 and power transistors O 1 o, O 11 , 012 and 013 . 07 is a Vbe multiplier, so called because it multiplies the voltage between its base and emitter by the ratio of the resistors between its base and collector and base and emitter, respectively. It effectively maintains a fixed voltage between its collector and emitter, regardless of the drive current delivered to the output stage by 05. The voltage is adjusted by trimpot VR1. The function of 07 is to set the DC voltage applied between the bases of 08 and 09 . By doing this it sets the "quiescent current" through the output stage (ie, the current when no signal is present) . This minimises crossover distortion The complementary output transistors are connected in parallel to give high current output capability. Each output transistor has its own 0 .4 70 emitter resistor. These are included to ensure that the output current is shared more or less equally between the output transistors and to help stabilise the quiescent current. Negative feedback is applied from the output stage back to the base of 03 via a 22k0, resistor. The level of feedback, and therefore the voltage gain , is set by the ratio of the 22k0 resistor to 1 kO . The low frequency rolloff is· set by the ratio of the impedance of the 1 kO resistor to the impedance of the 4 7 µF capacitor. This sets the - 3dB point at about 3Hz . The 1 J,tF input capacitor and the 22k0 base bias resistor feeding 02 have a more important effect and set a - 3dB point at about ?Hz . The two time-constants together give an overall - 3dB point at 1 OHz. The 330pF capacitor and the 2 .2k0 resistor feeding 02 forms a low pass filter which rolls off frequencies above 200kHz . The 68pF capacitor between base and collector of 05 rolls off the open-loop gain to ensure its in- against short circuits and against damaging loudspeakers if it is seriously overdriven (which often blows tweeters) or develops an internal fault. This protection is provided by the same PTC (positive temperature coefficient) thermistors used in our lOOW modules featured in the December issue of high power amplifiers used for disco and rock bands is an internal fault which not only blows the amplifier 's output transistors but burns out the speakers as well. Repairing the amplifier is relatively cheap but repairs to loudspeakers can be very expensive. By incorporating the Polyswitch PTC thermistors into each channel of the amplifier, you can effectively insure against amplifier and loudspeaker damage. SILICON CHIP. Apart from its generous power output capability and high fidelity performance, we regard the simple and effective protection incorporated in the Studio 200 as its most important feature. An expensive and common occurrence in 38 SILICON CHIP The circuit The circuit is shown in Fig.1. This shows the power supply and one herent stability with feedback applied . Another contributor to the amplifier's excellent stability is the output network consisting of a 6 .8JLH air-cored choke, a 6 .80 resistor and 0.15J,tF capacitor. Instead of using relays for loudspeaker protection each power amplifier uses a Polyswitch (made by Raychem Corporation, USA) . This device is a positive temperature coefficient thermistor with a very low resistance value, under normal operating conditions. When the current through a Polyswitch goes above a set value, it immediately switches to a high resistance state and stays in that state until the fault condition is removed . It's like a fuse which can repair itself. The resistance of the Polyswitch is so low (typically much less than 0.10) that it has a negligible effect on amplifier performance. The distortion figures we quote are applicable whether or not the Polyswitch is used . The Polyswitches give comprehensive protection . They allow the amplifier to deliver full power on program signals but the moment a short circuit is applied or the amplifier is seriously overdriven, the Polyswitch goes high in resistance to give protection . If a transistor fails, and causes the amplifier to deliver a large DC voltage to the speaker, again the Polyswitch goes high to give protection . channel, to save space. It is identical in configuration to the circuit of the lOOW module referred to previously but most of the semiconductors have been changed and so have some of the resistors. For those who have not read the abovementioned article, a brief description of the power amplifier circuit is given in one of the accompanying panels. Most of the changes we 've made relate to the higher supply voltages necessary to extract higher power from the amplifier. We'll discuss the main changes briefly. As already noted, the main 01 1N4002 • I 680 +49.5V 5A 0.1+ 48.1V 8 ! 8 0.1 J .012 INPUT 22k cr22k 1k 2x8F469 04 2.2k ~ 1.9V 2.2k _J B C 8 ' 48.3V :--, 1.9V :....J l 1.3V t - - 4 - - - ' - - + - - - - - - - - - -.....- - - 4 9 .5V 0.ll * ROE245A (80 LOAD) POWER RDE390A (4!1 LOAD) 240VAC - - - - - - - - - - - - - - - - - + 4 9.5V 8000 63VW N + 8000 _ 63VW + - 10k 1W ,--c B 0 ELJc 0.22 100V 0 8 VIEWED FROM BELOW .,. PLASTIC-0 CASE 8000 63VW - 8000 63VW - 10k 1W moE 0.22 100V LED1 111 ECB STUDIO 200 STEREO POWER AMPLIFIER SC1·1 -288 Fig.1: this diagram shows one powe.r amplifier and the power supply for the Studio 200. The circuit is essentially the same as the 100W module published in our December issue. Note that two of the 8000µF 63VW filter capacitors can be regarded as optional although they do give a worthwhile reduction in hum and a small increase in continuous power output. change is to the power output transistors which are now MJ15003 (NPN type) and MJ15004 (PNP type). These rugged bipolar transistors have a maximum power dissipation rating of 250 watts (at a case temperature of 25°C), a collector current rating of 20 amps and a collector voltage rating of 140 volts. So they are considerably more rugged than the MJ2955/2N3055s that they replace. They also have better high frequency gain which means that it is possible to obtain better high fre- Performance of Prototype Output Power (RMS) Music Power Frequency Response Input Sensitivity Harmonic Distortion Signal to Noise Ratio Protection Damping Factor Stability 1 00W into 8 ohms; 160W into 4 ohms 120W into 8 ohms; 190W into 4 ohms 20Hz-1 00kHz ± 1dB 1.25V < 0 .01 % (20Hz-20kHz) >105dB 5A fuses plus optional Polyswitch > 100 Unconditional FE BRUARY1988 39 600..----.---~-----.-------.---,----r------.----.-----, i < 300 i:l The input transistor pair is now 2 x BC556 instead of BC557s but apart from a higher collector voltage rating, these transistors (Vceo 65V instead of 45V for BC557) are otherwise identical. The second transistor pair and current mirror are now 2 x BF469 and BF470 instead of BC639s and BC640. The substituted transistors are normally used in high-voltage video output stages in TV sets and consequently have a very high collector voltage rating of 250 volts and excellent beta linearity which again improves performance. Power supply 10 20 30 60 40 70 80 90 VOLTAGE (VOLTS) Fig.2: this is the load line diagram for the MJE340/350 driver transistors. The straight line shows the resistive load reflected by the output transistors while the arched line shows a severe reactive load. The concave line to the right is the maximum power dissipation (20W) hyperbola of the transistors with SOAR derating included. 14--------.---.. . . . .-..-----,,---,-----,------r----.-----, f :E ~ i 61----4------+-------4----+-------il-_,-....,__ _ _ _ _ _ _ _--t = .., :::, The Studio 200 stereo amplifier has a very good power supply and this is the main reason it is able to deliver so much power. It uses a large toroidal power transformer with a centre tapped secondary winding of 35 volts a side, with a nominal rating of 300VA. This transformer has excellent regulation and very low hum radiation. It is also a lot more compact and weighs less than a conventional transformer of equivalent rating. Teamed with the transformer is a chassis mounting bridge rectifier and four B000µF 63VW electrolytic capacitors. These deliver balanced supply rails of ± 50V DC. Really, we are gilding the lily by putting in four B000µF electrolytics as it only makes a relatively small difference to the maximum continuous and music power capability. You can save about $40 by just using two B000µF 63V capacitors. Chassis 10 30 40 60 70 90 VOLTAGE (VOLTS) Fig.3: load line diagram for the MJ15003/4 output transistors. The straight line is for a 40 resistive load while the arched line is for a reactive load of 2.75 ± j2.750. The concave curves to the right are for the transistors' maximum power hyperbola (2 x 250W) with SOAR derating included. quency distortion performance from them. The driver transistors are unchanged but we have plotted load lines for both the drivers and output 40 SILICON CHIP transistors to check that they can safely deliver the much higher power output of this amplifier. The load line graphs are shown in Fig.2 and Fig.3. The chassis is a nicely finished 'three unit high' rack mounting case from Altronics (Cat No H-0418). This has heatsink extrusions at the sides on which we mounted the amplifier modules, one each side. To save chassis space we mounted the toroidal transformer directly to the front panel. This is more or less standard practice with rack amplifiers as the front panel is usually much thicker and stronger than the top or base panels. Order of assembly If you are buying a complete kit for this amplifier, no drilling of metalwork will be necessary but if mF and Music Power The music power rating of the Studio 200 was measured according to the method outlined in the Institute of High Fidelity's specification IHF-A-202. This uses a pulsed 1kHz waveform with a duration of 20 milliseconds . To conveniently measure power according to this method and those which use longer pulse durations, we have designed a self-contained test instrument. It will be described in a coming issue of SILICON CHIP. '· . f! » . . l's::d.f.i:t.s:Ll2:JEY.2:2:L:1t:i:J!S<at>E2:JER~D![Jl" M'f\$'. ,:,··. ''f&WtW<at>/;"»~f?&~: -v INPUT - - - T03 DEVICE . :__ ~ .i:?- +V Fig.4: here's how to assemble the power amplifier modules. Be sure to use the correct transistor at each location and take care with component polarity. For 80 loads, use the RDE245A thermistor; for 40 loads, use the RDE390A. 0 !r -INSULATING SLEEVES -~O-~ ~ II HEATSINK PCB I SHAKE-PROOF ·--~-WASHERS ~-- 9-NUTS Fig.5: mounting details for the TO-3 transistors. Trim the mica washers so that they do not overlap. The power amplifier modules are screwed to the heavy heatsink extrusions that make up the sides of the case. Use PC stakes to terminate all external wiring to the module. Note: the PTC thermistor has been replaced here by a wire link but should be included in all kit versions. you are working from scratch, any drilling of the case, heatsink brackets or whatever should be done before any assembly work gets under way. Kits for the Studio 200 stereo amplifier will be available shortly after this issue goes on sale from Altronics of Perth at $399. The first step in putting the amplifier together is to assemble the power supply into the chassis. You can fit all the other hardware at the same time. To prevent marking your workbench or table, we suggest that the case be fitted with four large rubber feet (32mm in diameter). The ones we used are sold in hardware stores as rubber door stops. Mount all the hardware bits on the rear panel and then mount the transformer and hardware on the FEBRUARY1988 41 All the power supply and amplifier output wiring should be run using heavy duty hookup wire. Take care when putting the lid on the case so as not to damage the outer insulation of the transformer. Note: some of the internal wiring in this photo differs slightly from the wiring diagram. The PTC protection thermistors are also not shown. front panel. We used a bolt with a blackened head to mount the transformer so that the bolt head would not be so obvious on the front panel. You can obtain one from a hardware store. The mains cord should be J-se•~ WASHER -10126 ~~~::;~. 0 -HEATSINK PCB ..l_ - - SHAKE-PROOF WASHER (8-NUT Fig.6: mounting details for the T0-126 transistors. Note that heatsink compound should be lightly smeared on the mounting surfaces. 42 SILICON CHIP secured in the rear panel of the chassis with a cord grip grommet. It is also anchored along the righthand side of the chassis (looking from the front) by two cord clamps. Wire up the transformer exactly as shown in the wiring diagram. Both the active and neutral wires from the power cord are terminated at the insulated terminal strip, as is the blue primary wire from the transformer (joined to the incoming neutral wire). Cut a short length off the brown wire from the transformer and strip both ends. One end goes to the incoming active wire while the other end goes to the power switch. The brown primary wire from the transformer also goes to the power switch. Before soldering these wires to the switch, slip a length of shrinkable sleeving over the pair. After soldering, push the tubing up over the switch and then apply heat from a hairdryer to shink it on. Wire up the bridge rectifier and filter capacitors using heavy duty hookup wire. Do not omit the lOkO 1W resistors wired across each supply rail. These are there to safely discharge the capacitors in the event the fuses to the amplifiers blow. Check all your wiring carefully at this stage and then apply power. The supply rails should be close to ± 50V DC. Switch off and allow all the capacitors to discharge. Now you can assemble both the amplifier modules. We suggest you assemble one module and test it before doing the other. That way, if you make a mistake on the first, you won't do it on the second. The procedure for each board is as follows. First mount all the small components leaving the power transistors and heatsink till last. The component overlay for the modules is shown in Fig.4. Note that the 68pF compensation capacitor associated with Q5 should have a voltage rating of at least 100 volts and so should the 0.15µF capacitor in the output filter network. The 6.BµH choke is wound with 24.5 turns of 0.8mm enamelled cop- HEATSINK HEATSINK BRACKET LEFT AMPUAER -V r-l-.1 . I I Q 22 0.22 '' ' POWER TRANSFORMER (MOUNTED ON FRONT PANEL) 1 I/I -V +v RIGHT AMPLIFIER v. /1 .... LED1~ 2 . <at>t - .- -.- - ,. - ~ \ HEATSINK BRACKET ' POWER CORD HEATSINK Fig.4: this diagram shows the wiring details of the amplifier and power supply. Note that for minimum hum output from both channels of the amplifier, the transformer must be rotated so that its leads exit as close as possible to the base of the case. Note the single point earth wiring which is essential for low hum output. per wire on a 13mm diameter plastic former . Alternatively, Jaycar Electronics supply the choke ready wound (Cat No EE-4030). Mount the four 0.470 5W wirewound resistors so that they are off ihe board by about 1mm or so. This aids power dissipation. Now mount the heatsink bracket. It is secured to the board by the mounting screws for the four output transistors and the driver transistors. Mount the power transistors first. These must all be isolated from the heatsink by using mica washers and insulating bushes, as depicted in Fig.5. Smear all mounting surfaces with heatsink compound before assembly. Solder the mounting nuts to the PCB pattern after FEBRUA RY1988 43 PARTS LIST 1 rack-mounting case with side heatsink extrusions (Altronics H-0418) 1 70V centre-tapped 300VA toroidal transformer (Altronics M-3092) 1 push on/push off mains switch with black button (Altronics S-1 090) 1 red LED and bezel 1 3-core mains cord and moulded 3 -pin plug 1 cord-grip grommet 2 plastic cord clamps 1 3 -way mains insulated terminal block 4 binding post terminals, 2 red, 2 black 1 2-way RCA panel socket 3 plastic cable ties 2 solder lugs 4 large rubber feet (as sold by hardware stores as door stops) 1 50mm of twin shielded cable 500mm red heavy duty hookup wire 500mm black heavy duty hookup wire 2 8000µF 63VW chassis mount capacitors (optional) 1 BR104 400V 10A bridge rectifier or equivalent 2 0 .33µF metallised polyester capacitors 2 1OkO 1W resistors 1 5 .6k0 1W resistor 4 2 2 2 4 Amplifier modules Capacitors 2 4 7 µF 16VW PC electrolytic 2 1µF metallised polyester (greencap or miniature) 2 0 .15µF metallised polyester 10 0.1 µF metallised polyester 2 0.012µF metallised polyester 2 330pF ceramic or miniature metallised polyester 2 68pF 1OOVW ceramic Power supply Semiconductors 2 B000µF 63VW chassis mount capacitors 6 BC556 PNP transistors 2 BF4 70 PNP transistors assembly to ensure reliable contact. Alternatively, if the nuts are nickel plated or stainless steel, use lockwashers. Depending on whether you intend to use the amplifier with 40 or 80 loudspeakers, you have a choice of PTC thermistors for protection. ,For 80 loads, use RDE245As. For 40 loads, use the higher current RDE390As. The two driver transistors and the Vbe multiplier (Q7) are bent over and also attached to the heatsink bracket using T0-126 mounting kits (see Fig.6). When the whole assembly is completed, the heatsink bracket should be attached to one of the heatsink extrusions in the chassis. Heatsink compound should be used between the bracket and the heatsink to improve heat transfer. Powering up Before applying power remove 44 SILICON CHIP 2 printed circuit boards, code SC11-1287, 121 x 133mm 2 heatsink brackets 8 3AG fuse clips 4 5A 3 AG fuses 12 PC pins 2 plastic formers, 13mm dia x 10mm, plus 1-metre 0 .8mm enamelled copper wire (ECW) ; or 2 x 6.8µH aircored chokes 2 Raychem RDE245A polyswitch PTC thermistors for 80 loads or RDE390A for 40 loads 8 T0-3 transistor mounting kits 6 T0-126 transistor mounting kits the two fuses from the board clips and set VRl fully anticlockwise. This gives the setting for minimum quiescent current through the output transistors. Solder a 5600 5W wirewound resistor across each fuseholder . Set your multimeter to the ZOOVDC range (or no lower than 50V DC if an analog meter). Now apply power and measure BF469 NPN transistors 8D139 NPN transistors MJE340 NPN transistors MJE350 PNP transistors MJ 15003 NPN power transistors 4 MJ 1 5004 PNP power transistors 6 1 N4002 diodes Resistors (0.25W, 5%) 2 x 56k0, 4 x 22k0, 2 x 18k0, 2 x 8.2k0 1W, 6 x 2.2k0, 2 X 1 kO, 2 x 4700, 2 x 2700, 6 x 1 ooo, 4 X 680, 2 X 6 .80 1 W, 8 X 0.470 5W wirewound, 2 x 5000 trimpots (Bourns cermet horizontal mount, 0 .2 x 0 .4-inch) Miscellaneous Screws, nuts, washers, solder, heatshrink tubing for mains switch insulation . the positive and negative supply rails. Again, they should be within a few volts of ± 50V. Now measure the other volta ges on the circuit. They should all be within ± 10% of the nominal values. The voltage at the output should be within ± 30mV of OV. No load should be connected at this stage, by the way. continued on page 95 The rear panel carries a 2-way RCA panel socket for the inputs and two sets of binding post terminals for loudspeaker connections. VOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR C 23 Pin "D" Connectors No it's not a misprint - there are now 23 pin D-<:onnectors on a couple of the newer PC's. So if you're finding it hard to get plugs and sockets to match , Geoff of course has 'em . Connectors - Male $3.50 Female $3.50 Backshell $3.50 Seven Segment Display Specials HD1107R Common Cathode 10mm (0 .4 ") character height with righ t hand decimal point. Typical 350uCd intensity at 1OmA. Measures 13. 1mm x 10mm x 7.2mm . Standard PC grid. Only$1.50 each or $1.25 for 10+. Thermalloy Heatsink 6129 National Miniature Relay Special Geoff is stocking the 6129 because of its low (under half an inch) profile. Easy to install Fins are on one side only. Suits all power Genuine Matsushita OS-Series double pole changeover relay with a contact rating of GOW, 125VA. Will handle 240Vac and upto 2A switching. 12V coil Measures only 20mm x 10mm x 9.3mm. 1500V surge rating . Fits standard IC soc ket. Only pLI11Ct1·:11r1=v ~~ ~= ~ I ~8 o.-, ~g $3.50 devices. Excellent the mi al resistance . 3" long with mounting holes on 2.5" centres . $2.50 (1-9) or $2.00 ( 1O+) Audio Alarm Special Geoff has secured a limited quantity of electronic warbling alarms. Contains a 5 transistor circuit and small loudspeaker in a weather resistant horn type case measuring 90mm dia x 60mm deep. Also has adjustable mounting bracket. Works off a nominal 12V de supply. Only $12.50. 1- - - -- -.;:·~ So many people have been asking for a simple, inexpens ive IDC connector to fit the usual 0.1" grid. Now Geoff has tracked 'em down. 10 way, easy to install and only 10-Way IDC Mai Connectors $2.50. LT4940AHR High Efficiency High efficiency type means a luminous intensity between 1400 and 2400uCd at 10mA. 10mm (0.4") character height with right hand decimal point. Measures 1S.75mm x 9.Smm x 5.1mm. Only $1.50 each or $1.25 for 10+. Get a few tubes of these Gates ... 74LS27 $2 .50 for a tube of 25 - that's only 10c each 1 SN74SOON $7.50 for a tube of 25.Genuine TI - that's only 30 cents each I Or you can have them in 1OO's for $22.50. Cheap Transistors MJE13007 NPN , 400V SA, hfe 5-30, Ft 4MHz , T0-220 $1.00 each (10-99 80c or 100+ 50c) 8D646 PNP , Silicon Darlington , 60V SA , hfe 750m in, Ft 1OOkHz typ . T0-220 50c each ( 10 99 45c or 100+ 30c) Built-In Flint lighter ~ .,., 0 Cl AVAILABLE AT LAST ... PORTASOL PROFESSIONAL COMPLETE KIT It's a gas soldering iron .. .h's a blow torch ... it's a hot knife ... it's a hot blow. And it comes in a neat carry kit complete wnh a bit wiper. No cords or batteries yet it gives the equivalent of a 1Oto 60W iron . You can get up to 90 minutes average continuous use from a single fill. And you refill it in seconds using a standard butane gas lighter refill. Tip temperatures as high as 400°C can be set. The kn includes one soldering tip, a hot kntte , blow torch and hot blow. The cap contains a flint lighter. The complete kit comes in a handy case (with stand for the iron) which just about fits in your pocket. Porta-Sol Professional is $81.00. PORTASOL STANDARD SOLDERING IRON Geoff has sold hundreds of 'em to servicemen and technicians. Ccmplete and ready to use like the Professional but you only get th e iron and bit $39.95. PORTASOL TTPS Expand the capability of your Portasol Iron with spare tips -available for standard iron in 1mm, 2.4mm , 3.2mm, 4.8mm and hot knife tip. Professional tips come in same sizes plus hot blow and blow torch. Tips are .o..QJ. interchangeable between irons, so specify Standard or Professional when ordering. Tips are all $12.95 each. 0 JJ C""l :i: ~ ~ .,., 0 Cl 0 JJ 2 ~ ~ 0 Cl .,., 0 JJ C""l :i: ~ ~ 8.30 to 5 Monday to Friday. 8.30 to 12 Sat. Mail Orders add $5 UO to co ver postal c harges. (t All prices INCLUDE sales tax. GEOFF WOOD ELECTRONICS P/L (02) 427 1676 Ta x exemption r: r:rt1l1cates ac cepted ,t line value exceeds $1 0.011 229 BURNS BAY RD. (CORNER BEATRICE ST) LANE COVE WEST N.SW ~ ....0 Cl 0 i BANK CARO. M AS TFH CARD, VISA. CHEQUES TWX 71996 PO. BOX 671 LANE COVE N.SW 2066 OR CASH CHEERFULLY ACCEPTED specialising in electronic components for the professional and hobbyist. ~ .,., 0 Cl 0 JJ C""l :i: ~ Audible end of file Don't tie up your phone line for longer than you have to. This simple project can be easily fitted to most modems and sounds a buzzer at the end of a file transmission. By GREG SWAIN They say that necessity is the mother of invention. This simple project was born out of necessity at the SILICON CHIP office. It's fitted to one of our own modems and has proven to be a real timesaver. At SILICON CHIP, we use a modem to send text files from our computers directly to a typesetting terminal some 30km away. This highly efficient practice virtually eliminates keystrokes at the typesetting end and gives us fast and accurate turnaround on our text and drawing labels. This system works extremely well, saving us both time and money. But we did strike one pro- blem. Because we are transmitting data down the line at just 300 baud, some of the longer files can take 1O minutes or more to send. So unless someone is actually watching the computer monitor or the transmit LED on the modem, it's all too easy to miss the fact that transmission has ended. As a result, both the telephone and the computer can be tied up for much longer than is actually necessary. We were particularly keen to solve this problem because, initially, we didn't want the phone line tied up for longer than necessary. At the same time, the person who was sending the data didn't wish to be tied to the computer, waiting for the monitor to indicate that transmission had finished. No doubt a whiz at programming could come up with a simple routine to sound a tone from the computer when transmission had ceased but we wanted a more general solution. What was needed was a simple circuit that would sound a buzzer when the transmission was completed. It also had to be cheap and easy to install. The answer is the circuit presented here. It is suitable for use in all modems that use the AM7910 world modem chip, which means virtually all modems which work at 300 baud duplex. Circuit details Fig.1 shows the circuit. It is essentially a missing pulse detector that monitors the TD (transmit data) pin of the AM7910. The circuit uses just two active components: a 555 timer (IC1) and a PNP transistor (Ql). Normally, the base of Ql is held high by the 47kQ resistor. This means that Ql is off, the 2.2µF capacitor on pins 2 and 6 of IC1 is charged, and pin 3 is low. Thus, if Sl were closed, the buzzer would sound continuously. In practice, Sl is normally left open so that the buzzer is off. The switch is closed only after data transmission commences. R tJll\:\ ·;:>< ~' lII_TI S1 The unit is built on a small PC board that mounts on the rear panel, inside the modem. Flying leads connect the indicator to the modem circuitry. 46 SILICON CHIP Fig.2: parts layout and wiring diagram for the PCB version. The buzzer should be a 6V type from Tandy. indicator for modems +5v---------------------. PARTS LIST + 2.2 16VWJ 8 4 470k 47k 5V BUZZER ICl 555 ... B ELJc VIEWED FROM BELOW MODEM "END OF FILE" INDICATOR SC7-1-288 Fig.1: the circuit uses a 555 timer IC wired as a missing pulse detector. During transmission, Qt pulses on and off and discharges the 2.2µF capacitor. Now consider what happens during data transmission. Qt is rapidly switched on and off by data pulses from pin 10 of the AM7910 modem chip. This discharges the 2.2µF capacitor which means that pin 3 is now high and the buzzer is off. The circuit remains in this state for as long as data is transmitted down the line. As soon as transmission ceases, Qt remains off and the 2.2µF capacitor charges via the 470k!l resistor. After about one second, the voltage on pins 2 and 6 reaches 2/3 Vee and pin 3 switches low. The buzzer now sounds to indicate the end of the file. ., :e . :,.· BU~ER ,: . t TO PIN 10 OF AM7910 ✓ ('" , ., , .) f , V Power for the circuit is derived from a + 5V regulated rail in the modem. Because the AM7910 requires a + 5V rail, this voltage is already there. Construction We built our End of File Indicator onto a small PCB coded SC7-1-288 (44 x 39mm). Fig.2 shows the wiring details. As an alternative, the circuit can be built on a small piece of Veroboard measuring 50 x 39mm - see Fig.3. You can mount the parts on the board in any order you like, but take care with the orientation of the IC, transistor, electrolytic cap- r.SC7-1-288 1 PCB, code SC?-1-288, 44 x 39mm (or Veroboard, 50 x 39mm) 1 6V DC buzzer (Tandy Cat. 273-054) 1 SPOT toggle switch 1 555 timer 1 BC55 7 PNP transistor 2 2 .2µF 16VW electrolytic capacitor 1 4 70k!l 0.25W resistor 1 47k!l 0.25W resistor Miscellaneous Hookup wire, solder, screws, nuts etc . acitor and buzzer. Be sure to use a 6V buzzer for this project, as sold by Tandy Electronics (Cat. 273-054). Don't use a 12V buzzer most will not operate reliably at 5V. We built our End of File Indicator into a commercial modem which has a relatively large case but the PCB is small enough to fit inside virtually any modem, including the Avtek Multi-Modem and the Beemodem. In our case, we mounted the PCB inside the rear panel and secured it using the buzzer mounting screws. Flying leads were then run from the PCB to the switch, power supply and to pin 10 of the AM7910. ~ ' GNU Fig.3: parts layout and wiring for the Veroboard version of the indicator. Fig.4: here is actual size reproduction of the printed circuit artwork. Close up view of tht! PCB version. Note the orientation of the IC and the two electrolytic capacitors. FEBRUARY1988 47 The indicator is small enough to fit inside virtually any modem, including the Avtek Multi-Modem and the Beemodem. The flying leads connect to the power supply, front panel switch, and pin 10 of the AM7910. With some modems, it may be easier to make these connections to the underside of the board rather than to the component side. If your modem has a transmit (TXD) LED, you can connect the base of Ql to the LED cathode instead of to pin 10 of the modem chip. The on/off toggle switch (S1} is mounted on the front panel of the modem. The + 5V supply can be picked up at pin 2 of the AM7910 or at the output of the + 5V regulator in your modem. Similarly, the ground connection can be obtained from the ground terminal of the regulator. Finally, the End of File Indicator has no effect on the way in which you use the ·modem. You simply send data in the usual manner. All you have to do is switch S1 on as soon as data transmission begins so that the circuit is activated. 't: 48 SILICON CHIP A small toggle switch fitted to the front panel (top right) is the only external change necessary. The circuit could also be built into a separate case. WE GUARANTEE YOU A STYLUS! That's right: we guarantee to supply you with a stylus to suit your hi fi turntable ... no matter what type, brand or model. As long as it is a modern (ie microgroove) type we either have it in stock - or we'll get it for you WITHIN 3 DAYS! We have almost 100 different stylii IN STOCK in all our stores. These stylii will suit at least 95% of turntable types in use today. Each DSE store has a cross reference manual to ensure you get the exact type to suit your turntable. If it is a real "oddball", the store will order the stylus required from our suppliers, who carry literally thousands of stylii types in stock. And they'll get it back for you within three working days. That's service: the DSE Stylus Service. Look for the special stylus display in every Dick Smith Electronics store. f3~~ · ~~~ ~~e) ~ IS YOUR TURNTABLE HERE? ~ r1 • • Stylii to suit the following turntable brands 0 . ~. ~.'0 , ~ ADC ♦ AIWA ♦ AKG ♦ AKAi ♦ AUDIO EMPIRE ♦ AWA ♦ ♦ AU DIO TECHNICA ♦ AUDIO REFLEX ♦ AZDEN ♦ BSR ♦ CDC ♦ CEC ♦ ♦ COLUMBIA ♦ DENON ♦ COLLARO ♦ DUAL ♦ ELAC ♦ EXPO ♦ ♦ EXCEL SOUND ♦ GENERAL ELECTRIC ♦ GARRARD ♦ GOLD RING ♦ ♦ HANIMEX ♦ HITACHI ♦ HMV ♦ JVC ♦ JELCO ♦ JORGAN ♦ JICO ♦ ♦ KRIESLER ♦ KENWOOD ♦ LENCO ♦ LINEAR DESIGN ♦ MARANTZ ♦ ♦ MICRO ♦ MITSUBISHI ♦ NAGAOKA ♦ NATIONAL ♦ NEAT ♦ NIVICO ♦ ♦ ONKYO ♦ ORTOFON ♦ OSAKA ♦ PHILIPS ♦ PICKERING ♦ PIEZO ♦ PYE PIONEER RAMBLER RANK ARENA REALISTIC ♦ RONETTE ♦ ROTEL ♦ SANSUI ♦ SANYO ♦ SEEBURG ♦ SHARP ♦ ♦ SHERWOOD ♦ SHURE ♦ SILVER ♦ SONOTONE ♦ SONY ♦ STANTON ♦ ♦ TANDY ♦ TEAC ♦ TECHNICS ♦ TECTRON ♦ TETRAD ♦ THORN ♦ ~_0 ; ♦ ♦ ♦ TO~ ♦ ♦ ♦ DICK0 SMITH ELECTRONICS PTY LTD Also available through DSXpress Toll Free (008) 22 6610 , ~ ♦ v;;~~~t;~•;~~l~~~N f•~~s;s~~;;A ;~~95! 49(tf~ ~ ~ t7 ~~~6 How often should you change your stylus? The stylus can make or break your record collection. A worn or damaged stylus will tear the sides from the record track and can completely ruin a record with just one play. A diamond stylus can be expected to give around 200 to 300 hours of playing time. This, of course, assumes the pick-up is correctly balanced, anti-skating is set correctly, and so on. 200 hours for the normal user equates to approximately six months, so if you replace your stylus every six months or so, your record collection will say "thanks!" Needless to say, if the pick-up is dropped the stylus can be damaged, so you should also change your stylus at the first sign of sound distortion, etc. SOUTH ELECTR )))). 0-----------------• money. But those of you who've brought back a bomb from overseas know how hard it is to get service, much less warranty repairs. John wanted to give everyone a fair go; even passing tourists he'd probably never see again. Although we on government contracts were I • • assumed to be 24-hour-a-day b employees, the rule was more ~ 0 _: honoured in the breach. So I spent ,!, I\,./ l five or six hours a week when off• 'O tl duty, checking amps and cassette decks and the like . •• • t>• .. • I"""- ,. What do the natives do when their electronic organ fails? Call a serviceman of course. But the serviceman can get more than he bargained for. By J.L. ELKHORNE "How are you on organs?" I looked bemusedly at the telephone handset; I'd always wondered what an obscene phone call sounded like. After a moment's pause, the voice continued: ''Hello, hello, are you there?" There was silence for a second. Then: "Joe, is that you?" Now I recognised the voice. Not a phone phreak after all, but a New Zealand bloke who ran a big duty-free shop on the South Pacific island where we had lived for two years. In addition to providing genuine bargains for the tourists, he worked 50 SILICON CHIP up a thriving trade with the indigenous population and the hundreds of contract workers that were temporary strangers in paradise. Unlike some of his counterparts in the "civilised" world, John insisted that every piece of electronic gear be subject to a real quality control test before it was sold. One Japanese manufacturer averaged 40% failure rate right out of the export cartons; their quality assurance tags didn't mean much! Once the bugs were found (and they were generally minor) the equipment proved itself value for The job The telephone call I'd just received, on my day off, seemed to be an intrusion into my plans for scubadiving. It was not an emergency call, however; immediate action was not necessary, but there was a big problem. John had sold a large organ to the villagers on an adjoining island. These industrious and thrifty people had saved for seven years to purchase an instrument suitable for their church. It had worked splendidly for the first few weeks. Now, it seemed, there was not a peep out of it. A bit of service information had come from the manufacturer, and I had a fairly complete service kit and test equipment. But, in itself, getting to Manua (part of American Samoa) was the hard part. A supply boat made the trip once a week. It had left yesterday. There were a couple of flights by a Fokker Islander; if the seats weren't filled with passengers, excess cargo was thrown in. More than once, a small pig was admitted on board, even if he didn't pay full fare. John arranged that I should go to the airport on Tuesday of the next week. I was given the name of a villager who would escort me, since after the flight. there was still the PACIFIC: 'IHE OMC VERSION little matter of an hour's drive to the village itself - somewhere. With eager anticipation, I arrived at the airport as arranged. And waited. Long after the Fokker had climbed into the azure sky, I stood there. I even tried to call my part-time employer but the phones were out. That wasn't unusual - if the phones weren't dead, other public services would likely be impaired on our tropical paradise. The local power operators frequently put a generator on-line unphased - or tried to. Grumbling more than a little, I drove to the duty-free shop. John seemed surprised to see me. When I told him that the villager had been a no-show, he sent one of his lads out to find the bloke. When they located him, it took three days for him to dry out. Getting over to the 'big island' was quite a treat for him; it happened so seldom he wanted to make the most of it. Out from under the eyes of the village elders and the minister, our hero found the native version wine, women and song. The flight Several days after the first attempt, we managed to get underway. I'd never flown from our island in a small airplane before. It was different. The gusty crosswinds didn't seem to bother our pilot. I glanced at the Rolls Royce nameplate on the port engine for reassurance. I recalled that the last flying accident here had been ari aircraft stalling at the end of the runway and dropping onto the reef. But Snoopy powered us into the sky and, in a few minutes, we levelled off a hove the ocean. The afternoon sun bored in through the perspex windows; the drone of the two engines lulled one into a lethargic state. Surprise! One minute a person saw, despite drooping eyelids, the cobalt of the Pacific. Then, all at once, a sheer cliff of rocks and foliage soared up to the belly of the Fokker. There wasn't even time for one's life to flash before his eyes! My reaction must have given quite some amusement to the other passengers. They knew the airstrip had been bulldozed off the side of the mountain. The pilot simply took off and reached his flight altitude. He didn't even have to make a descent to land; he just took careful aim, throttled down and hit the binders. The Fokker came to a shuddering halt one metre from a wall of jungle. We got out with some haste, and a couple of husky fellows helped the pilot turn the plane around. My guide said, "There's our people". The Land Rover I turned to see three natives leaning on a vintage Land Rover. We picked up our parcels and went to meet them. After lengthy introductions, our drive began. And went on and on. It wouldn't have been unpleasant - what with the lush scenery - except for the fact that the supports on the hardtop had rusted and the passengers had to hold the damned thing together. It took some 45 minutes to make the side trip to my escort's £ale (village house). I couldn't exactly understand the driver's parting words to him, but I got the impression the poor fellow wouldn't be getting off Manua for quite some time thereafter. Eventually, we arrived at the village. The driver led me to the village elders and ritual introductions were exchanged. One had to move at their pace, of course; it was no use being impatient to get started with the job I had come for. But these people were impatient, too, to hear the majestic tones of their expensive instrument. ----------- SOR"R.'11 'BIGt-P\~S f>A'1 FULL f'A"R.~ ••• - - - - - ~ r··.- . . FEBRUARY1988 51 My surprise was indeed great when I was led to a large open fale. This is the classic structure of the islands, of course. Why I should have expected a conventional church, I can't imagine. Inside, on the woven grass mats - well away from the open side walls - sat a large bulky tarpaulin-wrapped object. To be sure, a fale has woven curtains that can be controlled at the sides, to keep out most of the rain ... when someone remembers. The tarp was used for added protection. It also ensured the containment of the wonderful 90% relative humidity salt air. I dreaded what I would see when this mummy was unwrapped. Fortunately, it was not too bad. Someone found an extension cord. Of course they had electricity - US surplus military generators have to go somewhere! I plugged the instrument in and turned it on gingerly. The power light came on. I tried both manuals, the pedals, several stops. Nothing. At least I had been spared an intermittent fault. Or an instrument that was three-quarters right but with irregular voicing faults, or some such. [Bear in mind that I had never worked on a large organ before but electrons is electrons). In a trice, I whipped the back off. Previous study of the available service information had paid off. I had a fair idea of the circuit flow - all I needed initially was to find the damned modules. Luckily, the power supply was screwed to the bottom of the console where it was easy to get at and the plug-in preregulator lived next to it. Begin at the beginning I told myself. Yes, of course there is AC in and DC out. No inordinate amount of hum. On to the the pre-regulator connector. Unregulated voltage in and naught out. Eureka! On to the circuit board. Hey, this is going well. The circuit used discrete components - with the spares I carried, there would be no problem, I reckoned. I thought I must have shaken something up when my trusty analog meter told me that there was good regulated voltage right through the PCB to the edge connector. Walking around the organ, I reached out and tapped a couple of keys. Then my foot nudged a pedal. Nothing at all. Curiouser and curiouser. Back at the back I picked a board at random and looked for the supply rail. No rail. I then used my meter on the amps scale to bridge the edge connector of the preregulator. Nothing blew up Tt\\S l S "<OU~ ES~-C-: and I got ~ reasonable > current readmg. VJ \-\0 W \ \.-l- GU l'DE" '{ 0 U Around to the front and SA.i='E.L"f TO '{0\)~ a stroke on the keyboard elicited a nice full note 'DE.STH,JP\T IOl'J, o, and an "Ahhh!" from the \ '\ onlookers. Every time I ~\~~ ~~ looked up, I saw more peo~ C ~~~~;> ple. By the time repairs <at> ,;::;;; •. . . ~-::;,_were completed, virtually · • lj ~ the whole village was -=watching. ~ Cutting the power o and pulling the preregulator, I saw the signs of corrosion on the contacts. A minute's work with a typing eraser and 52 SILICON CHIP aerosol spray solved the problem that had brought me on my adventure. Not that it had ended. I powered up and checked several things in the works. I tested stops and all keys and pedals. Everything seemed "go" so I buttoned it up. The music I went to the head man and told him it was finished. "No!" he responded. A short conference with the driver as translator indicated that while it made sounds, it hadn't made music. "You know about the organ, so play it," the head man was saying. "I know about the organ to fix it," I told him. The elder fixed me with a steely gaze and mumbled something to the driver who mumbled and said, "We must have some music before the chief is satisfied". Fortunately, many years before, I had studied piano [thanks Mum), even into university. Though a habit of playing jazz put paid to a glorious career in the concert halls, a knowledge of music certainly seemed worthwhile at the present moment. "Unfortunately, I don't think I know any hymns," I said, glancing at the band of people around me. The driver conveyed this to the chief, who shrugged and muttered a terse reply. "Is not Sunday," the driver translated. I'm not sure if any of those people ever had heard of Fats Waller but they sure seemed to enjoy "Ain't Misbehavin"' and other of his classics. Every time I stopped playing, someone said, "More!" Well, if I could get away with Waller, a bit of Jelly Roll Morton never harmed anyone. Next followed Cole Porter and it still wasn't enough. I switched tactics. A bit of my formal training came to the rescue and a free-form version of J.S. Bach's "Toccata and Fugue in D Minor" nearly took the thatched roof of the £ale. Phantom of the Opera, eat your heart out! When the last note died away, I raised my hands from the keyboard and dusted them symbolically. "Uma lava pisupo," I stated. Which continued on page 65 This project will sense a door opening in a large or small room and will sound a two-tone chime. By LEO SIMPSON & JOHN CLARKE While the most obvious application of this project would be as a door monitor for shop keepers, it could have applications in offices, workshops, doctors' and dentists' waiting rooms, child-minding centres and in the home. It could also be used as a sensor in a burglar alarm. In the past, the classic ways to detect the opening of a door have been either to use a microswitch mounted on the doorway or to use a light beam relay circuit. The latter method has the advantage that it does not have to be attached to the door and it can be made to work with any type of door, hinged or sliding. The disadvantage is that it must be near the doorway or an adjacent passageway and it must be carefully set up in the first place, to work correctly. The Door Minder presented here can be placed anywhere in the room; it does not have to be anywhere near the doorway. It can even be placed in an adjoining room. The prototype Door Minder was built into a small plastic case. It can be placed anywhere in the room. How does it work? When a door is closed it can be regarded as a very large piston in a close-fitting rectangular cylinder. When you push a door open you cause quite a large momentary increase in pressure in the adjoining room. The Door Minder senses this increase in pressure and sounds a two tone chime. The Minder can be used on either side of a door because it also senses a momentary drop in pressure. So it works equally well with inward- opening or outward opening doors. Nor does the room need to be tightly sealed. Windows can be open, provided they are not really large. Because it senses pressure, the Minder can be placed anywhere in the room. It work will work in very large rooms too, up to several hundred square metres (say 2000 sq ft or more). In our offices at SILICON CHIP we have three adjoining rooms. Open- I---- +8V PLUG-PACK + 47 470P. FROM 9V-12V, 300mA 25VWI 0.1 T 330k 2200 330 16VW IC2 SAB0602 ELECTRET MICROPHONE 4 + 0.33+ 8 0.1 '7r1 8(! ~SPEAKER 33k DOOR MINDER SC032-0188 Fig.1: the circuit uses a microphone, a bandpass filter stage (ICla), a comparator (IClb) and a two-tone chime (IC2). FEBRUA RY1988 53 ing the door to the first room will trigger the Door Minder in the third room, even with the windows open. It is highly effective and does not respond to wind or to loud noises. What is the pressure sensor? Possibly some of our readers are thinking that we have used a fancy expensive pressure sensor for this project but they are wrong. The pressure sensor is nothing more than a cheap electret microphone insert which can be bought for a couple of dollars. Isn't that ingenious? We think it is. The electret microphone is used with an amplifier circuit which only responds to extremely low frequencies. It does not respond to audible sounds at all. The amplifier is used to trigger a special integrated circuit which produces the chime sounds. And that is virtually all there is to it. Unlike light beam relays, the circuit uses very little power and could, if you wished, be run from batteries. The circuit The circuitry for the Door Minder comprises the electret microphone insert, a small loudspeaker, two integrated circuits, a 3-terminal regulator and a few resistors , capacitors and diodes. It is powered from a 12V DC plugpack. To describe how the circuit works, let us start right at the beginning, at the electret insert. This contains an internal field ·effect transistor {FET) which is connected as a source follower. Bias for the internal FET is provided by the 4.7kn trimpot which does double-duty as a sensitivity control. With the wiper adjusted up to the + 8V supply rail, no signal is fed to the following circuitry; with the wiper adjusted at the extreme opposite setting, maximum signal is fed to the following circuitry. ICl is a dual op amp. ICla is connected as a narrow bandpass filter stage with a gain of about 80. It responds to frequencies within the range of about 0.5Hz to 3Hz. What this means is that the amplifier will respond only to brief positive or 54 SrLICON CHIP ~ + 9V-12V, 300mA PLUG-PACK 811 SPEAKER Fig.2: install the parts on the PCB as shown here. Power for the circuit is supplied via an external plugpack transformer. negative decreases in pressure, as sensed by the electret. Note that the non-inverting input {indicated with a + sign) of ICla is set at + 3.3V by the 47kn and 33kn resistors. A lµF capacitor decouples this input from the supply. This sets the output of ICla to + 3.3V too, which is important as far as the following circuitry is concerned. ICl b is connected as a comparator. Its inverting input {indicated with a - sign) is held at + 3.6V due to the 330kn and 270kn resistors forming a voltage divider across the 8V supply. The noninverting input is held at 3.0V with the 300kn and 180kn resistors. The output of ICla is connected to the two inputs of ICl b by diodes Dl and D2. Under quiescent conditions neither of the diodes conduct since the voltage across each is only 0.3V. Note that the voltage at the inverting input is higher than the noninverting input by 0.6V and so the output of IClb is low. When the output of ICla swings high, diode D2 conducts and brings the non-inverting input of IClb higher than the inverting input and so the output of IC1 b goes high. Similarly, when ICla's output swings low, D1 conducts and pulls the inverting input lower than the noninverting input and the output of IC1 b again goes high. Each time the output of IC1 b goes high, it triggers the two-tone chime IC, the SAB0602. This produces a rich, heavily modulated chime sound which is attention-arousing without being too obtrusive. The output from IClb is divided using a 1okn and 2.7kn resistor divider before being applied to the input of IC2. This is necessary because when the output of IC1 b is PARTS LIST 1 9VDC or 1 2VDC plugpack 1 PCB, code SC03-2-188, 87 x 58mm 1 plastic utility case, 1 30 x 6 7 x 41mm 1 57mm an loudspeaker 1 electret microphone insert 1 1 OµF 16VW PC electrolytic 1 1µF 1 6VW RBLL or tantalum electrolytic 1 1µF 1 6VW PC electrolytic 1 0 .33µF metallised polyester 2 0. 1µF metallised polyester 1 .0068µF metallised polyester Semiconductors 1 TL082, TL072 dual op amp 1 SAB0602 two tone chime ringer 1 7805 3-terminal regulator 2 1 N4148, 1 N914 diodes Resistors (0.25W, 5%) 1 x 3 .9M!l, 1 x 330k~, 1 x 3ookn 1 %, 1 x 270kn , 1 x 180kn, 2 x 4 7kn, 2 x 33kn, 1 x 10kn, 1 x2 .7kn, 1 x470n, 1 x 2200, 1 x 4. 7k0 miniature vertical trimpot. Capacitors 1 330µF 16VW PC electrolytic 1 47µF 25VW PC electrolytic Miscellaneous Hookup wire, solder, etc Construction ' View inside the case. The PCB clips into slots in the side of the case while the loudspeaker is secured using small clamps. low, it sits at about + 1.5V or so, which is not low enough to prevent continual triggering of IC2. Hence, the voltage divider which fixes the problem. IC2 drives an 811 loudspeaker via a 330µ,F capacitor. The 0.1µ,F capacitor and 33k11 resistor set the operating frequency of the chime tone, while at the output, a 0.33µ,F capacitor provides a degree of high frequency filtering. As mentioned above, power for the circuit is provided by a 9V or 12V DC (nominal) plugpack. This is fed to 7805 3-terminal regulator which has its output set to about + 8V by the associated 47011 and 22011 resistors. This setting was used to satisfy the supply voltage requirement of between 7V and 11 V DC for the SAB0602 chime IC. L _J 0 --, 0 Fig.3: the PC artwork is reproduced here actual size. r All the components, with the exception of the loudspeaker, are mounted on a printed circuit board measuring 87 x 58mm and coded SC03-2-188. No special procedure needs to be followed when assembling the board apart from ensuring that tlll the polarised components such as the diodes, electrolytic capacitors and ICs are wired in the right way around. This is shown on the component layout diagram. Most electret microphone inserts do not have their leads labelled but most tend to be sold with specs showing how they are connected. Make sure you obtain this info when purchasing. The 3-terminal regulator is laid flat on the PCB and the tab held down with a wire lug soldered to the board. When installed flush on the bottom of the case, there is adequate clearance between the components and the speaker magnet. The loudspeaker can be mounted onto the front panel using an expoxy adhesive or small clamps and screws. We used the latter. Before doing that though, you need to drill holes in the lid to let the sound out. You also need to drill two holes in the case itself - one for the twinlead from the DC plugpack and the other to allow changes in pressure to be sensed by the electret. Setting up This is easy. Apply power and measure the voltage oh the output pin of the 7805 regulator. It should be close to + 8V. Check that the same voltage appears at pin 8 of ICl and pin 2 of IC2. Now check the voltage as pins 1, 3, 5 and 6 of ICl. They should be close to the values nominated on the circuit. Now set the trimpot to about half setting and open a door. The chime should sound. Place the Minder where convenient and that's all there is to it. Incidentally , the Siemens SAB0602 is very similar to the SAB0600 which is a three-tone chime IC. The latter is already available from a number of kitset suppliers and could be substituted if the SAB0602 is temporarily unavailable. ~ FEBRUARY1988 55 ·1--------------------------------Low ohms tester for digital multimeters 1 Want to accurately measure low value resistors down to 0.010? This simple adaptor circuit will do the job. It plugs directly into your digital multimeter. By JOHN CLARKE Most digital multimeters can accurately measure resistance values down to only about five ohms. Below that figure, you quickly run into resolution problems and you get nonsense readings. There are many situations where accurate low resistance measurements are necessary. These include checking meter shunts, designing loudspeaker crossover networks and amplifier output stages, servic56 SILICON CHIP ing power supplies and, indeed, servicing any circuitry where low value resistors are used. Normally, when measuring a o.rn resistance on a 3-1/2 digit multimeter by itself, you would have to switch to the 2000 range and the reading would be O. rn ± 1 digit. In other words, the resolution of the multimeter would limit the accuracy of the measurement to ± 100% which is ridiculous. Similarly, if you measure a 10 resistor on the 2000 range of a DMM, the best you can expect is a reading of 1.00 ± ldigit; ie, best accuracy is ± 10%. So the meter resolution drastically reduces the accuracy of the measurement even though most DMMs are accuracte to within ± 1 % when measuring values at the top of their respective ranges. This Low Ohms Tester overcomes the limitations of conventional analog and digital multimeters. It plugs straight into the terminals of your DMM (digital multimeter) and can accurately measure resistance values from lkO down to a.am. Below this figure, errors start to become significant due to contact resistance in the test terminals and connecting wires. At the other end of the scale, readings above lkO lose accuracy due to limitations in the constant current source used in the circuit. In any case, digital multimeters by themselves are more than adequate to accurately measure resistance values above 1000 or more. All the circuitry for the Low Ohms Tester is housed in a small plastic case. On the front panel are two binding post terminals to which the resistor to be measured is connected. There is also a rotary 4-position range switch (xl, xlO, xlOO, xlOOO) and a pushbutton test switch. Two banana plugs protrude from the rear of the case at the correct spacing to allow the Low Ohms Tester to plug into virtually any digital multimeter made. The plug spacing, by the way, is 19mm (or PARTS LIST TEST _a, 1 VR1 1k + 16VW+ -4_,-+-~ T 16VWI 9V: ..,. 220pF .J- i OFFSET ADJUST VRJ 100k S2b .,. 10k 1% .,. ~" S2 : 1 : xl 2 : ,10 3 : ,100 4 : ,1000 1001! 1% LOW OHMS TESTER SC4-1-288 Fig.1: the circuit consists of a 5V regulator (78L05), a constant current source (D1, D2 and Ql), and an op amp gain stage (ICl). 1 PCB, code SC4-1-388 , 61 x 95mm 1 front panel artwork, 125 x 63mm 1 plastic case, 130 x 68 x 43mm (Jaycar HB-6013 , Altronics H-0203) 2 banana plugs 2 binding post terminals 1 3-pole 4-position rotary switch 1 momentary pushbutton switch 1 9V battery, Eveready 21 5 or equivalent 1 9V battery clip 1 small knob Semiconductors 1 CA3130 op amp 1 78L05 low power 5V regulator 1 BC559 PNP transistor 2 1 N4148 , 1 N914 s ilicon diodes Capacitors 1 4 .7 µF 16VW PC electrolytic 1 1µF 16VW PC electrolytic 1 220pF polystyrene capacitor Resistors 1 1 1 1 1 1 1 OkO 0.25W 1 % 1 kO 0.25W 5% 1000 0.25W 1 % 1 OOkO multiturn trimpot 1 kO multiturn trimpot 1 000 multiturn trimpot Miscellaneous Hookup wire, solder, tinned copper wire (for wire links), doublesided tape , plastic foam . TO METER Fig.2: wiring details for the PCB. Trim the switch shaft to a length of 10mm before soldering it to the board and don't forget the two wire links. more precisely, 3/4-inch) between plug centres. The output from the Low Ohms Tester is a voltage which is directly proportional to the resistance being measured. In practice, the unit is calibrated so that H2 gives an output of lmV x Range. For example, on the x 1000 range, H2 is equivalent to 1mV x 1000 = 1V. On the xlO range, rn is equivalent to lOmV, and so on. How it works The circuit consists of a 5V regulator, a constant current source (Dl, D2 and Ql), and an op amp gain stage (I Cl). Power for the circuit is provided by a 9V battery which is regulated to + 5V by the 3-terminal regulator. This provides a stable supply for the constant current source and the op amp. Test switch S1 simply switches the supply to the circuit so that current is drawn from the battery only while a measurement is being made. Dl, D2, Ql and the lkO resistor make up the constant current source. Ql is really an emitter follower. It reproduces the voltage fed to its base at its emitter less its 0.6V base-emitter voltage drop. Series diodes Dl and D2 set the base of Ql to a constant 1.2V below the + 5V supply line. This means that the emitter of Ql is always 0.6V below the + 5V line. The lkO resistor sets the current through the diodes to 5mA. The resulting 0.6V across either VRl or VR2, as selected by S2a, sets the current through Ql and the test resistor Rx. When VRl is selected, the test current is lmA; when VR2 is selected, the test current is lOmA. FEBRU ARY1988 57 The PCB should only take you a few minutes to assemble, and clips directly into the plastic case. Note the location of the two jacks on the rear panel. On the lower two ranges (xl and xlO), the voltage across Rx is applied directly to the DMM terminals. On the upper two ranges, the op amp gain stage (ICl) is switched into circuit and the DMM measures the voltage between the op amp output (pin 6) and the test resistor Rx. ICl is connected as a noninverting op amp stage with a fixed gain of 1 + lOkn/1000 = 101. Because we want a gain of precisely 100, we measure the voltage between the output of the op amp and the voltage across Rx. Thus, when S2 is in position 3, the current set by the constant current source is lmA and so the multiplying factor for Rx is xlO0. + r· Rx L. , ,,,.,.J-fJWJ.' When S2 is in position 4, the current is lOmA and the multiplying factor is 100 x 10 = 1000. VR3 adjusts the offset of the op amp so that, with no voltage across Rx, (ie, with the measurement terminals short circuited) the output is zero. Construction Assembly of the unit is a snack. Most of the parts, including the rotary switch, are mounted a small PC board (code SC4-1-388, 61 x 95mm). The board clips into a plastic project box with a plastic lid (Jaycar HB-6013 or Altronics H-0203). Begin construction by installing all the parts on the PCB as shown in Fig.2. Make sure that you don't confuse the transistor and the low power 3-terminal regulator, as they come in identical packages. Check the orientation of the IC before soldering it into circuit. The notched end, adjacent to pin 1, goes towards the centre of the board. Similarly, watch the orientation of the diodes, electrolytic capacitors, transistor and 3-terminal regulator. Trim the switch shaft to a length of 10mm before soldering the switch directly to the PCB. Don't forget the two wire links. You can now affix the front panel label to the case and drill mounting holes for the test terminals and switches. Ream the holes to size, then mount the terminals and test + x10 x100 x1 \ / x1000 ' • / H2 = 1mV x RANGE • TEST LOW OHMS METER Fig.3: this artwork can be used as a drilling template for the front panel. -1- ta --,- ~~ ~ 2mA scale. Set switch S2 to the xl position and adjust VR1 for a reading of lmA. This done, set your DMM to the DC 20mA scale, set S2 to the x10 position and adjust VR2 for a reading of 10mA. Calibration can now be completed by adjusting the offset voltage. To do this, disconnect the meter and set it to the DC 200m V range. This done, set S2 to the xlOO position, short the Rx terminals with the shortest possible length of tinned copper wire and plug the banana plugs of the Tester into the COM and vm terminals of your DMM. Adjust VR3 for an initial reading just above OmV, then adjust back for a reading of exactly Orn V on the DMM. ~~ ~:...t- Fig.4: actual-size etching pattern for the PC board. Final assembly switch and wire them to the PCB. The next step is to trim the plastic shrouds of the two banana plugs to a length of 13mm. The plugs can now be mounted on the lid of the case, adjacent to one edge (see photo). The leads from the plugs are wired directly to the copper pads on the back of the board. Finally, solder the battery con- · nectar leads to the board and clip on the 9V battery. The unit is now ready for calibration. Calibration Apply power by pressing S1 and check that there is + 5V at the output of the regulator and about 3.8V across the lkO resistor in series with the Dl and D2. Now connect your DMM across the Rx terminals and set it to the DC You can now clip the PCB into the plastic case and secure the rotary switch to the front panel. After that, it's simply a matter of covering the copper tracks of the PCB with a layer of plastic foam , securing the battery to the inside of the lid with a piece of double-sided tape, and screwing down the lid. Your Low Ohms Tester is now completed and ready for work. ~ issues? Issue Highlights November 1 98 7: Car Stereo in Your Home; 1 GHz Frequency Meter; Capacitance Adaptor for DMMs; Off-hook Indicator for Phones . Please send me a back issue for D November 1987 D December 1987 D January 1988 Enclosed is my cheque or money order for $ ....... . or please debit my D Bankcard D Visa Name ... ...... ... ._ ................ .. ... ..... ....... ... .... ..... ...... ..... ........ .... ..... ..... . Address .... .... ... .... .. ......... ... .... ... ..... ........ ... .. .. .. ... .. ..... .. .......... ... ... . . Suburb/town ..... ...... .... ........ ...... .. .... .... ... ..... ..... Postcode .... ........... . Card No .. .. ....... ......... ...... ...... ..... ... .... .. .. ... .. ... ......... ....... .. ...... .... ... . Signature .. .... .. ...... .. ....... .. ..... .... ..... .. Card expiry date .. .... ./ .. .. .. ./.... ... L __________ _____________ December 1987: 100W PmNer Amplifier Module; Passive Infrared Sensor for Burglar Alarms; Universal Speed Control and Lamp Dimmer; 24V to 12V DC Converter. I I I ! ! I January 1 988: 4-bay Bowtie UHF Antenna; Dual Tracking Power Supply; Custom Phone Ringer; Subcarrier Adapator for FM tuners. Price: $5.00 each (incl. p&p). Fill out the coupon at left (or a photostat copy) and send it I to: S1ucoN CHIP. PO Box 139, Collaroy Beach, 2097. 1_ _ _ _ _ ___ ___ __ I ~ FEBRUARY 1988 59 His Master's Voice ae- IT HAS 1t> SOME11\lNG One of the side effects of TV servicing is the opportunity - albeit enforced - to study a wide variety of customer's personalities. While most customers are fairly easy-going and philosophical about an equipment failure, there is a small percentage who exhibit a variety of strange - and sometimes irritating - quirks. While these idiosyncrasies cover a wide range, there are a few that can be fairly well categorised. For example, there is the silent type; the customer who is completely unable or unwilling to provide any information whatsoever - particularly over the phone - concerning the symptoms, any relevant history, or even the model of device involved. One is lucky to get the maker's name. Their philosophy is: "It's stopped - you fix it". Then we have the exact opposite; the loquacious type who insists on providing every tiny - and usually irrelevant - detail surrounding the failure. They will have noted the exact time, the progam that was running, and the details of the drama being unfolded on the screen, including pistol shots, body blows, and car crashes. Why they believe such information is important I can't imagine, but at least they tend to be amenable to answering questions. Another one is what I call the pessimistic type. Whenever a fault blacks out the screen he automatically assumes - indeed insists - that the picture tube has failed. Not only that, but he often positively resents any attempt on the part of the serviceman to discount this possibility. It seems to be an obsession amounting almost to a death wish. This type has his opposite also, although I think that the motivation is easier to understand. He insists 60 SILICON CHIP that " .. .it has to be something simple". Various reasons can be offered for this assumption, ranging from the fact that the set has only recently been serviced, to observations that it ran for only a few seconds after switch-on or, conversely, it ran for several hours before it failed. Unfortunately, I have never been able to see the relevance of any of these two points. But I have no doubt that, basically, this is a type of wishful thinking; if it is a simple fault, it won't cost much. More than that I suspect that it is a way of putting pressure on the serviceman; they hope to bluff him into believing that they know it is only a simple fault and that therefore a large bill is inappropriate. Some carry the idea a stage further by nominating the faulty component and insisting that this, and only this, is what needs to be changed. Which brings me to Bill, because Bill is just such a character. Bill Special Notice These notes are being contributed by the author who, from 1950 until July last year, wrote "The Serviceman" in another magazine. We feel sure that regular readers of that series will welcome the opportunity to continue following his adventures in SILICON CHIP. 5\MPL-E: J> TlE O PT'tN\\ s 'T lives not far from my shop and I have known him at a casual level for many years. Now Bill is a nice enough bloke in most respects very kind to his mother and all that - but he can be a bit of a nuisance when a service job is involved. Basically, the problem seems to be that he attaches more significance to our acquaintanceship than is really justified; at least from where I stand. One of his nasty habits is to ring me up immediately, either at the shop or at my home, whenever his TV set fails. This can be at 5.30 in the morning or 10.30 at night. But the real irony of this situation is that, when he does ring, he always insists that the problem is not urgent, pointing out that he has another set! If you're wondering where all this is heading, the answer is simple; this month's story is about Bill's set and the merry dance it led me I I lI <at>f] - ·~ ~ I FIRS 1007 DC- \ 0101 REGULATOR BZXBXIVS RVIOl~t--±::-:11.. I I I.__,,A ~/"I1,.._~ ~~r I RIOS IKB IV P/SMB RI002 3R8 7W BAYaf~4tN4148 - I V Z ' - - - - - + - - - 4 -..... -~_._--------~r-.,,:;;';;;_..,--+..J RIOS n ~n 47 CI07 - ·- -· 0047 P/ SM3 FSIOI P/ SMS cm c122 Cl20 HO UOZ ll07 400U j RIIO IMO 17¥1 -1v, LI L--Si i ~~~: 4W t VIN.TAGES MARKED t Ill MEASURED WAT. ,w 101 All WAVEFORMS ON , .c.1.1 102 ./1 - 0 ' - - - - · - - - · - - - ·- - - · - - - ~ - _33V Amox1MATUY 20KHZ I I ~ · - - - · - - - - ~- ~ There's not much to the chopper power supply of the HMV C221 but there's quite enough to give plenty of trouble. over a period of some 12 months. This was not helped by Bill looking over my shoulder and telling me what he was convinced needed to be done. The set in question is an HMV model C221, the second-generation colour set made by HMV in Australia. The C221 is fairly old now but there are plenty of them about and, by and large, they have proved to be very reliable. In fact, Bill's set had given very little trouble until about 12 months ago, when Bill called me at home at some inconvenient time one evening tO report that the set had failed, adding the first of many similar remarks that I was to hear over the next 12 months: "It's got to be something simple". It's the switch Because Bill lives so close to the shop I elected to call on him at the first convenient time next day. He was· still insisting that it had to be something simple, but had now added his own diagnosis. "I reckon it's the switch. Change that and I reckon it'll fix it," he declared. I didn't enquire as to the basis of his diagnosis but I gained the im- pression that it was along the line that, since nothing happened when the switch was activated, the switch must be at fault. In fact the set was completely dead and it was not unreasonable to suspect the power supply, which is a fairly standard arrangement with a bridge rectifier fed directly from the mains and delivering · about 300V to a switchmode system. To placate Bill, I checked the output of the bridge rectifier, which is quite readily accessible. It was delivering its rated voltage, which immediately cleared not only the switch, but the rectifier, a couple of RF chokes, a couple of fuses, and sundry minor components. I even went so far as to point this out to Bill, but it didn't seem to register. With the system cleared thus far, it was time to remove the cover from the switchmode section and delve a bit deeper. When these power supplies fail, it is usually because the chopper transistor, TR103 (BU326A), has broken down. When it does, it usually takes out the 2-amp fuse (FS101) and usually the regulating thyristor, TR102 (BR203). So I looked first at the fuse, ex- pecting it to be a blackened mass. But it wasn't and the meter confirmed that voltage was being applied to the collector of the chopper transistor. So where to from here? There were a whole host of components in this section, any one of which could shut the system down if it failed, so it was largely a matter of trying to pick the most likely culprit. I decided to check the three solid state devices first, commencing with the chopper transistor, mainly because it's easy to remove. And would you believe it, I picked it in one? A check with the multimeter indicated that the base-emitter junction appeared to be intact but the collector-base junction was open-circuit. This was something I hadn't expected because, as I intimated earlier, the usual failure of this device is a breakdown. Anyway, I had a spare device in the van and it took only a few moments to fix it. And of course, that was it; the set came good immediately and Bill expressed his delight, even though I had effectively disproved his diagnosis. He was strangely quiet about that as we settled up. FEBR UA RY1988 61 SERVICEMAN'S LOG IT'S STOFf'EO \SN"f' \i... ~ Y' orta change the switch Naturally, I hoped that would be the end of Bill and his C221. But it was not to be. All went well for about three months, then Bill was on the phone again at some inconvenient hour, complaining that.the set had stopped again. Again he was adamant; "I reckon it's the switch. Y'orta change the switch". So once again it was into Bill's lounge room and into the works of the set. As before, the set was completely dead, with all the indications that the power supply was out of action. I went through the same routine as before; voltage across the bridge, fuse obviously intact, voltage at the chopper collector, but no switching action. All this time Bill was muttering away in the background about the switch and I was feeling heartily fed up with his domineering manner. I happened to glance at the manufacturer's logo and mentally translated the "HMV" into "His Master's Voice" and, as I did so, realised that this expression had a much more significant meaning here than its creator had ever intended. From now on, Bill would be nicknamed "His Master's Voice". For the second time I pulled out 62 SILICON CHIP if!l't'""• the chopper transistor and checked it. But it wasn't going to be that easy; this time it was OK. Then I remembered a nasty fault I had encountered many years ago in this set's predecessor, the C211. A lt.tF capacitor, C104, in the thyristor circuit, had a nasty habit of dropping its value and, when it did, the system simply would not work. In fact, the CZ 11 had a lot of capacitor faults, mainly involving low value Japanese electrolytics, which were very prone to premature drying out. When the C221 appeared it was significant that these had been replaced by European types. These proved so reliable that I cannot recall ever having to replace one. Nevertheless, there could always be a first time so I pulled C104 out and checked it. It came up spot on value and I discarded that theory. The other two active devices, TR101 and TR102, are fairly easily checked in situ, at least for any catastrophic failures, and these were both cleared. So what now? Again I was reminded of the C211, which had a nasty reputation, at least in early production runs, of dry joints in its version of this board. This was a problem which was overcome with the advent of the C221, but again there could be a first time. I pulled the board out and, armed with the jeweller's loupe, began a detailed examination of the copper side. It wasn't the best environment for such an examination. It was late in the afternoon and the lighting in Bill's lounge room, both natural and artificial, left much to be desired. Nevertheless, I did find a dry joint. It involved a 750, 10W resistor, Rl 14, one of several high wattage resistors on this board. These are IRC wirewound resistors enclosed is a square section ceramic case, about 4.5cm long, and which normally run at a fairly high temperature at their maximum rating. A further refinement is that, in this set, they are fitted with a three-legged metal frame which supports them vertically, with the bottom of the resistor case about 2cm above the board. The lower pigtail goes straight down through the board, while the upper one is bent through 180°, lies along the side of the resistor, and is spot welded to the metal frame. Lugs on the metal frame pass through holes in the board and make contact with the copper pattern. It is a very effective arrangement, supporting the resistor clear of the board and other heatsensitive components and also assisting the flow of air around it. And, significantly, I cannot recall any of these resistors ever having failed. Nor was there anything wrong with the resistor in this case, just the dry joint on the board which was quickly fixed. And away went the set again, effectively silencing the mutterings about the switch. Again I hoped that that would be the end of the matter. It's gotta be the switch No such luck. Another three or four months went by then the phone rang early one morning and, with a sinking heart, I recognised His Master's Voice. The set had stopped again and he was convinced it was the switch! I didn't argue; I simply told him I would be around later in the day. Not to labour the point, I found the situation exactly as before; voltage on the chopper transistor, all active components cleared, but no switching action. Of course, it could have been a failed component anywhere and I was conditioning myself to a component by component check. But I was also thinking again of dry joints. I had already found one and there could possibly be more that I had missed. So I pulled the board out and went over it again. I found a couple of joints which were suspect and resoldered them without any great conviction. Then I put the board back and switched on. The set came good, but with one qualification; I felt sure that there was a small delay after switch-on before the set leapt into action. Sure enough, it ran for about half a minute then stopped. And no amount of prodding or bashing would start it again. So I had an intermittent and, in view of what I had already found, I knew I had to rule out the possibility of more dry joints before I looked further. I also decided that Bill's lounge room with its limited lighting was no place for the job. It needed the good lighting I had on my workbench, plus some peace and quiet away from His Master's Voice. Since I didn't fancy carting the whole set back to the shop I simply pulled the board out and took it with me. And when I finally set it up under R good light I was shocked at the number of faulty or highly suspect joints I found. So much so that I stopped looking after a while, A faulty spot weld on the frame of this wirewound resistor gave no trouble for 10 years and then played merry hell. and simply reached for the iron and went right over the board, remaking every joint. Unfortunately, I had no way of checking what I had done, since I had no similar set in the workshop. So, at the first opportunity, it was back to the set where I plugged the board in and switched on. Need I spell it out? The set was just dead as it had ever been. Bill wasn't impressed. "I reckon it's the switch, y'know. Orta change that switch". "Yes Bill!" It was all I could trust myself to say. I decided the best thing to do was to bring the whole set back to the workshop where I could really get to grips with it, and where I could work in peace until I was convinced that the fault had been found and fixed. So, back at the shop, I pulled the board out and went over the copper side again in case I had C.'MON, UE: H€,.. GIVEM£ ;J""OST A L11TL£ CLU£ ... WHA"r HAPP&A>ED? ~ ~~ .. ··. ~ ~ missed anything. I found nothing, so I turned my attention to the component side. The truth is I wasn't quite sure what to try next and was simply looking at the board hoping for inspiration. And suddenly there was the culprit. It was another one of those vertically mounted IRC resistors, R112, an 8.20 5W unit. More specifically it was the lead from the top of the resistor and its connection to the metal frame. The frame is made with a small tongue punched out of the body, under which the pigtail is placed, the tongue pressed down and the junction spot welded. Only in this case the pigtail had simply been pushed under the tongue and left at that. The tongue had never been pressed down and there was certainly no sign that a spot welder had ever been anywhere near it. The wonder, of course, is not that it had failed but that it had worked for 10 years or more before it did so. I pulled out the whole unit, cleaned and tinned the pigtail, did the same to the tongue and surrounding metal frame, secured the pigtail properly under the tongue, then finished it off with a generous blob of solder. The set sprang into life immediately I switched it on, and I had no doubt that I had finally fixed it. I gained the impression that Bill wasn't so sure when I returned the set and tried to explain to him.what I had found. But that was many months ago and I have not heard from him since. I'm sure I will if all is not well, so I'm keeping my fingers crossed. A weird National My next story concerns a rather weird set of symptoms as displayed by a National colour TV set, model FEBRUARY 1988 63 TC2004. And, if there is anything to be learned from it, it is probably that one should never judge the complexity of a fault by the symptoms; an apparently straightforward fault can turn out to have the most complex and obscure cause, while a complex combination of apparently unrelated faults can sometimes have a quite simple cause - though not necessarily one which is easy to find. The story started with a phone call from the owner who complained that he had no picture. I tried to determine whether there was a raster on the screen, and whether there was any sound. I didn't learn much. Apparently there was some sound but it was "kinda funny", while the description of the screen was that there was a bright band in the middle and a wide black band top and bottom. Well, it didn't sound like a set of symptoms I would like to tackle in the lounge room, so I suggested it would be better, and a bit cheaper for him, if he could bring the set in. And so the set duly landed on my counter. I plugged it in and turned it on while the owner was still there, just in case there were any points to be clarified. In fact, the owner's description was not all that far out. There was a raster, about 15cm high, in the middle of the screen, which was blacked out above and below. There was absolutely no sign of a picture and the sound was somewhat distorted. In addition, the raster was overly bright possibly because of its reduced height - but more importantly would not respond to the brightness control and only very slightly to the contrast control. Well, with a list of symptoms like that, the real question was where to start. Basically, it was a toss-up between the loss of vertical scan and the loss of luminance, or video signal. Hopefully, the lack of response to the brightness and contrast controls might be related one to the other. Waveform checks I decided to tackle the vertical fault first and, as a preliminary check, tried adjusting the height control, but I wasn't really surpris64 SILICON CHIP TETIA CORNER Sony KV1800-AS Symptom: picture collapsed down to 5cm high. Vertical hold, height and linearity controls all seem to work OK, but only on the low raster. Cure: C512 (2200µF 16VW) open circuit. Without this emitter bypass, negative feedback in 0502 vertical amplifier reduces its gain and causes low height. A clue is that all DC voltages around the circuit seem close to normal. ed when it had only minimal effect. Connecting the CRO to appropriate points around the vertical output stage, TR407 and TR408, left no doubt that the amplitude was way down. On the other hand, all the voltages applied to these transistors were virtually spot on. I moved back to the oscillator section, TR402 and 403, and checked the waveforms here. Results here were less conclusive. The waveforms were close to those shown on the circuit, but far enough away to make me suspicious. Subsequent checks at the intermediate stages, TR404 and 405, showed that the waveforms had now deteriorated quite significantly. It all added up to a rather puzzling situation whereby the fault seemed to be present to some degree everywhere in the chain, yet nowhere in particular. To be frank, I wasn't quite sure what to try next and eventually decided to put that problem on hold and track down the loss of video. At least I would be doing something worthwhile. The video signal is handled by a 16-pin IC, IC301, type AN-425. In simple terms it takes the video signal in on pin 14 and delivers it on pin 6. Feeding a colour bar generator into the set produced a typical staircase pattern at pin 14, exactly according to the circuit, and similarly on pin 6. So far, so good. From pin 6 the signal goes to the base of video amplifier TR301, functioning as an emitter follower. The signal was normal at both the input and output of this stage, which is the last before the red, green and blue output stages on the neck board. The signal goes via pin 6 of a plug and socket combination, CO-lP and CO-lS, then to the Y7 terminal on the neck board, and then to the emitters of the three output stages, for mixing with the chrominance signals which are applied to the bases of these stages. I traced the signal through to the three aforementioned emitters and SERVICE.MAN'S LOG found that all was well up to these points. But that was as far as it went; there was virtually no signal on any of the collectors. And since it was unlikely that all three transistors had failed simultaneously, it just had to be a voltage problem. A clue at last The voltage on these collectors is supposed to be around 125V but the best I could find was a mere 12V; small wonder we had nothing on the screen. But at least I had a clue to one of the faults - all I had to do now was find where this voltage originated and why it wasn't being supplied. Unfortunately, it is not practical to reproduce the circuit since it would be far too large to encompass all the points involved. In brief, however, the collector voltages are derived via 10k0 load resistors from a common 160V supply line. This line leaves the neck board at "Yl ", goes to pin 3 of socket C0-2S, and then to plug C0-2P on the horizontal scan board. (This plug and socket pair are separated by nearly the width of the circuit). From here the line follows a rather circuitous route to the vicinity of the horizontal output transformer, and pin 6-2 of this transformer in particular. In greater detail, this rail is derived from pin 6-2 via a 3.30 resistor, a small choke, a diode D553, and a lOµF 250V electrolytic filter capacitor, C564. Naturally, these few components were prime suspects although I couldn't rule out that a fault somewhere else was loading the line. The choke and resistor were quickly cleared, then I lifted one end of diode D553 and checked it. But the diode checked OK, leaving only the electrolytic capacitor (C564). I pulled the electro out and measured it. And that was it; instead of the supposed lOµF the best it could manage was a mere .OlµF. Well, at least I had solved one problem; replace the capacitor and I should have a picture on the screen, even if it was squashed. Then I could concentrate on the scan fault. So the electro was replaced and I switched on hopefully. And sure enough, up came a picture in full colour. But that wasn't all; all the other faults had vanished as well. The picture was back to normal height, the brightness and contrast controls were functioning correctly, and the distortion had vanished from the sound. All with one capacitor. Naturally, I was both delighted and surprised; delighted because I didn't have to look for any more faults and surprised because I hadn't realised the full ramifica- Servicing in the South Pacific literally translates as "The pea soup is finished," but really conveys finality. Cross-cultural relationships create some interesting language. Having acquitted myself of that sticky situation, I now found I had to face the honour of a meal. Four serving girls brought a number of curious dishes - which I alone ate in the centre of a throng of people, all eyes on me. Perhaps to see if I would refuse their food? Not likely, mate. For one who has shared unnamed delicacies in Saudi Arabia, few culinary surprises are left. continued from p52 I'm not sure, but I think they then made me an honorary member of the village. Suddenly, the driver realised how late it was and shouted, "The plane, the plane!" Bidding the people a fond and hasty farewell, we raced to the Land Rover - which no longer had its insecure hardtop. If that driver ever comes to Australia, he could have the pole position at the Adelaide Grand Prix, no risk! With not a moment to spare, we screeched to a stop at the airstrip. Lo, the Fokker was already revving its engines. I raced to the port side and tions of the 160V rail. I reached for the circuit again and indulged in a spot more tracing. Not surprisingly, I found that this rail also supplies the vertical oscillator circuit or, rather, part of it. As I mentioned earlier, this stage consists of two transistors, TR402 and TR403, employing a fairly straightforward feedback arrangement. But TR402 is fed from a 24V rail, while TR403 is fed from the 160V rail via the height control. Apparently, the 12V I found on the 160V rail was sufficient to keep the stage oscillating, but at a reduced amplitude. This aspect puzzled me somewhat because the waveform checks I had made, while not perfect, had not been all that far out. Then I looked at the circuit again and realised that the waveforms shown, and which I had checked, were all associated with TR402, which was functioning more or less normally from the 24V rail. The only remaining puzzle concerns the sound fault. I can find no direct relationship between the 160V rail and the sound system. The sound IC, IC251, appears to derive its supply from the commutator section on the deflection board and I have not been able to relate this to the 160V rail. Unfortunately, there is a limit to the time one can spend trying to work out all the smart tricks the designers pull. For the present, I am happy to accept that the fault has been cured, even if I'm not quite sure why. ~ threw myself into a seat as the craft started down the strip. If landing was a shock, the takeoff was a real thrill. At maximum revs, it was as though the island fell away under us. As I stared down at the blue Pacific, I noticed that one of my meter leads was caught in the door. The slipstream knocked it about until it frayed apart and dropped far down to the ocean beneath us. As we drew closer to the big island, I reflected that the life of a field service engineer holds many surprises - and that technical knowledge is often the least of your worries. ~ FEBRUARY1988 65 1988 ELECTRONIC COMPONENTS CATALOGUE * * SIiicon Chip Readers ring Us Toll Free Right Now on 008 999 007 And We'll Post You One Absolutely Free * * REMEMBER Altronics Staff are all keen Electronics Enthusiasts - just like yourself - so when you need a little technical help, give us a call • Quality Products at direct import prices • Save up to 50% on our competitors prices • Overnight delivery Australia wide• Bankcard phone order service to 8pm Monday-Friday FOR THE VERY QUICK! JACK O'DONNELL Managing Director Here are some incredible bargains. We suggest you phone order now to reserve yours. Please check inside our Catalogue for full specifications on these items. Speclal prices are avallable on current stocks only, sorry no back orders, strlctly "lst come - 1st served". ' Polyprop Woofer 300MM (12") Massive 1.4Kg Magnet. 150W Max. Input 8 Ohm. C 3070 Normally $139 THIS MONTH Fantastic Bargain 150MHz Frequency Counter Q 1520 Save $50 SPECIFICATIONS:Frequency Range Gate Time Accuracy Max. Input Senaltlvlty:• 10Hz - 30 MHz • 10MHz - 150MHz s85 Top Selling Blood Pre11ure Machine & Heart Rate Monitor X 3055 Was $110 Now$85 10Hz - 150MHz 1 sec , 6 sec. · +/ - 1 count 20V P-P Quality 20W . Loudhaller Fantastic Performer Normally $125 Now s75 Portable Multimeter 25mV- 100mV 100mV - 300mV 1 20K Ohm/Volt s149 •·········••f a 1018 Normally $39.95 s25 : : ~+-~,:,,,,,,,)ff£t ": : : 12V Lead Acid ..... Rechargeable: ~ ,,,,.. '; ~,~ Professlonal Infra Red Movement Detector , 1.2aH Capacity $17 ea 4 or More $ 15 Mini Mains Transformer Nifty Little Chassis Maker and Pan Brake Bender 240V/l2.6V CT<at> 150mA. M 2851 Nlcad Superbuy Quality , 500mAH S 5020 $3.00 ea. 20 or More s2.70 ea Save 33% s4 Famous Bel Mlcroeye Compuhetrodyne Microprocessor Radar Detector Clips onto sunvisor - virtually invisible from outside the vehicle. Detects X and K bands. 12V DC operated Incredibly sensitive. 2 function lens perm its wide angle (for rooms) or narrow angle(corridors) operation. Superb Eleco Wireless Microphone System uses Dual Diversity Receivers for Long Range, Noise Free Pure Fidelity Reproduction. · Now Available In Australia For Less Than $1,000 Altronics proudly release the Eleco System - Used Worldwide by Entertainers i.e. Rolling Stones, Dire Straites, Tina Turner and 1000's more! Superb Microphone Reproduction Compares with Shure,Beyer and AKG Unique Microphone design completely Eliminates "Dangling" Antenna Breathtaking performance without signal drop-out or noise interference . The Eleco Wirel ess Microphone Sy stem is virtually the ultimate in an Entertainers Microphone system (or for any roving mic rophon e application for that matter!) All the annoying wireless microphone characteristics such as " drop out" , static and noise are completely eliminated by use of auto switching dual diversity receivers. The output of each recei ver is continually monitored, with the strongest and clearest signal always selected . Dynamic Range exceeding 100 db is obtained by employment of a Patented special Parabola level compressor and Dynamic expander. The operating range Is a minimum of 50 metree (often this can he extended to 200 metres and more in normal circ umstances). Several Frequencies are available to aleviate cross interference when two or more system s are used in proximity. Brief Specifications Frequency 202.1, 202 .9, 203 .7 MHz (Please specify if you have a preference) Mlc Carrier Power 50mW (Ma x) Mlc Antenna built-in Dynamic Range over 100db S/N Ratio better than 90db Frequency Response 20Hz to 16KHz + or - 3db Mlc Battery 4 x AA cells Battery Life over 24 hours continuous operation . Receiver Sensitivity 12db/ micro volt for60db S/ N ratio Pre emphasis/De emphasis sous. Receiver output unbalanced 6.3mm phone jack and balanced 3 pin cannon type . Output Level (adjustable) Unbalanced 0-2 .SV Balanced Oto + or - .3V into 600 ohms. Receiver Power Supply 200 - 260VAC . Prices (A) Dual Diversity Receiver $729.00 (8) Entertainment Microphone (hand held type) (C) Lavalier Type Microphone $349.00 Frequencies Dual Diversity Receiver Dual Diversity Receiver Dual Diversity Receiver C 0121 Entertainm ent Microphone C 0123 Entertainment Microphone C 0125 Entertainment Microphone C 0131 Lavalier Microphone C 0133 Lavalier Mic rophone C 0135 Lavalier Microphone C 0111 C 0113 C 0115 $349.00 Bonus Offer SAVE $78 Choose Receiver and Either Microphone For Just $999 Please Note 3 different operating frequencies are available (you will need to specifica ll y nominate desired frequency only if the equipment is being used in proximity with other Eleco Systems on the 200MHz band . · 202.1MHz 202 .9MHz 203 .7MHz 202.1MHz 202.9MHz ~o~ 7MHz 202.1MHz 202.9MHz 203.7MHz $729 $729 $729 $349 $349 $349 $349 $349 $349 1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111 ' Wide Range Weatherproof Extension Speakers For Your Stereo System AT LAST Design Quality Weather Proof Speakers And Sound Columns By Redford Great For The Back Patio,Swimming Pool, Games Room, Den, Pool Room Etc. • Rugged extruded aluminium construction • Superb powdercoat industrial paint finish • Engineered in Australia • Excellent reproduction • Superior to imports - Yet just a fraction of the price! Dimensions 260mm wide x 170mm high x 150mm D. (Mounting brackets are Included) Altroni cs proudl y announce the release of the superb Redford Weatherproof Speaker and Sound Column Range. Imagine a wide range speaker system which is highly directional and with efficienc y approaching that of reflex horns! Redford is·the solution for high quality sound reproduction outdoors. The Five Models to choose from " Fill the Bill " from applicat ions on boats to high grade paging and music entertai nment installations. 15 Watt 4 and 16 Ohm Models Using a dual doped cone driver these fantast ic weatherproof speakers are of quite surprising performance. The 4 Ohm models are intended for use as main speakers i.e. for car sound systems/ graphic equalisers on your boat or Four Wheel drive etc. Th e 16 Ohm versions are intended for use wit h higher power systems. 16 ohms is employed to give a generally correct volume balance when used as extension speakers to the main speaker system - An added bonus is your amplifier load is kept to respectabl e limits! Great for back patio, den etc. C 0932 White 4 Ohm C 0938 White 16 Ohm C C·934 Black 4 Ohm C 0940 Black 16 Ohm All $99 each or $190 per Pair RUGGED EXTRUDED CONSTRUCTION These vi brati o n free encl osures are constructed fro m die extruded heavy gauge aluminium and fini shed with incredibly durable industrial powdercoat enamel. The speaker ends are sealed via gaskets and tough moulded " LURAN S" UV 20 Watt 8 Ohm {Max 30 Watt) Use 2 special duai doped cone drivers for those wanting a bit more umph! resistant end c ap s. The end result is " Good Looks " together with assured rugg ed durability for the Australian en vi ron men t . C 0943 C 0944 Black White $139ea $139ea $260 per pair $260 per pair EXCELLENT REPRODUCTION 1 he drivers have been chosen fo r w ide range .low disto rt ion, mid range " presence" (essential for high grade vocal wo rk ) and high effi c iency in general. Power Capacity for short term use, the drivers will safely handle 150% of rated powe r. Aco ustic wadd ing is used to dampen Bass resonan ce. Weather Proof Construction and use of "Doped Cones" Foam plastic and c loth is sand wiched between Baffle and Fro nt G rill to preven t water ingress. A first fo r Redford is the use of a patented co ne m o isture repellant proces s fo r all models. f 100 Volt Line Models For Use With Professional PA And Music Systems Using Q " Do ped " w ide range drivers and fitted with grain oriented steel line transformer Output ca ble allows connection to 10W/ 5W/ 2.5W with 10 watt models, 20W/ 10W/ 5W wi th 20 watt models and 40W/ 20W/ 1OW with th e 40 watt versions. 10W/100V line Black $1 t9ea $220 per pair 10W/100V line White $119ea $220 per pair 20W/100V line Black $169ea $299 per pair 20W/100V line White $169ea $299 p~r pair 40W/100V line Black $225ea $399 per pair 40W/100V line White $225ea $399 per pair Altronics Will Deliver Any Of These Quality Products To Your Door Faster Than Any Other Australian Supplier Or Your Monev Back (Within 24 Hours To Every Capital City and Suburbs - AlloGr Addltonal 24 - 48 Hours For Country Areas) II IIIIII II IIIIIHlll 1111111111111 IIIIIIII IIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIII IIIIIIII II llllllllllll lllllll II IIII II Ill Ill Ill 111111 II Ill II II II II lllll IIIIII II Ill Ill llll lllll II 11111111111111111 300 Watt Inverter With Auto Start The Power House Arrives Massivefrom 600 Watt Inverter 12 or 24 Volt 1y1lem1 Oper■ IH vi■ lnlem ■ I wiring connection, Big brother to our 300W Model this brilliant design can ba internally connected for either 12 or 24V operation. Full 600 watt output - and that will power a fantastic array of appliances e.g. Lighting, Electric Motors, Electric drills, Hi Fi, TV Sets, Computer. An ebaolute muat f~r H~u~ ~ .!!!'. or I~( tl!.! Jruc:k, J)!9!~'...!.tc. OperatH From 12V Car Battery Just think how handy It would be to have 240 Volt AC Mains Power when camping or for your boat or Caravan. Auto Start draws power from your battery only when appliance is plugged in and "turned on". i.e. battery can ba left permanently connected ii desired . Th■ rm■ I Over Load. Curret1I Retul■ lecl. Current Overload K 6752 Complete Kit Fully Built & Tested Two Great Kits To Build Complete Kit $399.oo Fully Built & Tested $499.oo The First Detector with GaAs Diodes RF Signal Generator An RF signal generator is an absolute must when it comes to radio servicing. With provision for both internal.and external modulation this .generator Is a winner. ...... . . • •• fD • SPECIFICATIONS:Frequency Range 100KHz • 150MHz In 6 Ranges RF Output Level 100mV RMS Accura~ +/- 3% Modulation:• Internal (30% Depth, 1KHz • External 50Hz - 20KHz • Crystal Locked Oscillator Q 1550 ....... .. $199.oo We believe the Vector to be one of the finest and most sensitive Radar Detectors available in the World today. Approximately 4db greater sensitivity than the A 1520 Until now, GaAs diodes have only baen used in sophisticated military radar equipment. The Microeye Vector is the first consumer electronics product equipped with this new technology. Why G ■ A• Diode• Make The Dllference: • Lower threshold allows for a better signal to noise ratio. • Lower signal conversion loss. • Higher barrier reduces noise. Quite Simply, GaAs diodes increase the sensitivity of the Microeye Veclor. Fe■lurea: • Separate audio alerts for X and K Band. • Three operational switches: Power: On and Off: RSD (Radar Signal Discriminator) to minimize extraneous signals with a LO (local) positon and a LA (Long Range) position; FIiter Mode designed for instant computerized analysis of incoming signals with LO and LA positions. Invisible from outside your car. The Vector simply clips onto your sun visor. Thus the Gendames and would be villains are non the wiser. Counter Kit : (See Silicon Chip Mag . Nov 1987 for Details) Our Congratulations to Leo and Greg at Silicon Chip for this Great Australian Design . $499 A 1;30 UV Eprom Eraser Erase your EPROMS quickly and safely. This unit is a cost effective solution to your problems. It will erase up The Technical excellence of this counter to 9 x 24 pin devices in complete safety in about 40 places it with Hew!'ett Packard and other minutes tor 9 chips (less for less chips). world famous test equipment makers. •Eraae up to 9 chip• al• time• Chip drawer has conductive foam pad • Mains Powered K 2515 Due Mid Dec' • High UV intensity at chip surface ensures thorough erase• Engineered to prevent UV exposure• Long Lile UV tube• Dimensions 217x80x68mm • Weight 670g. $299 Super Bargain 1/2 Price Fantastic Negative Ion Generator There have been volumes written about the benefits of negative ions combating air pollution , cigarette smoke etc. can be very beneficial to Asthma suffer~rs. Our grE:at little Rover generates billions of ions per second! Includes tester. Audio Frequency Generator Often in testin9 audio circuitry it is necessary to have an accurate and adjustable audio signal source available. This little generator even allows you to test 455KHz IF stages! .SPECIFICATIONS:• Frequency Range 10Hz • 1MHz +/- 3% + 2Hz Sine/Square Sine : ev RMS Square: 10V P-P Output Attenuator 0,-20 db,-40 db and fine adjust. Accurecy Output Waveform, Ou~t Lenl For In Circuit Testing "NO NEED ro UNSOLDER FEATURES: * Output 3 to 30V at 1A * Short circuit protected• Load switching* Current limiting . Dual scale meter• Housed in our Deluxe "ABS" instrument case . SPECIFICATIONS: * Output Voltage - 3 to 30V * Output Current - 0 to 1 amp (fully variable)• Load Regulation - Better than 0.2% from Oto ful l load * Output Ripple-Less than 2mV RMS . Cat. K 3210 TRANSISTOR ASSISTED IGNITION WITH DWELL EXTENSION Dead easy to build and (even better) there are only 3 electrical connections required to the car wiring system . Low-Cost Unit Checks Values from 1pf -100uf #/JtffgrroRs" Upgraded Digital Capacitance Meter The readout consists of a bright 4-digit LED display and the full scale readings for each range are 9999.9nF and 99.99uF. No adjustments are FEATURES: necessary when taking a reading. You simply connect the capacitor to the • Tests both NPN and PNP transistors in test terminals and select the appropriate range. The circuit can accurately circuit at the touch of a switch • Tests measure capacitance down to one picofarad (1 pF). This is made possible Diodes and SCRS as well • No need to by the internal nulling circuit which cancels any stray capacitance switch between NPN and PNP-its automatic. Two LED indicators are used to between the test terminals or test leads. So when you measure a 5pF show condition of device being tested. capacitor, the unit will display 5pF. Altronlcs Kit Feature - "ABS" jiffy box and test leads supplied. Cat. K 2530 K 2522 ................. . .. . ........... . . Screecher Car Burglar Alarm This alarm drives off wouldbe thieves with an ear splitting modulated tone. Once activated it is near impossible to stay within the confines of the car. Featureo: Entry Delay • Exit Delay • Alarm Timer • Lamp Flasher • Three second soft alarm reminder. Piezo siren produces modulated tone of 110dbat 1 metre. Simple to build and install. Two Sentor Input, $79.oo Ultrasonic Movement Detector This Ultrasonic Movement Detector provides added protection agai•n st illegal entry via. an open window etc. Connects directly to an alarm with a normally open input. Detects any movement up to 3 metres within an angle of 30 degrees. Will operate directly off 12V i.e. Car Battery etc. K 4400 $29.50 Video Enhancer $42.so Sharpen• up your picture when Copying Video to Video Here's a tlmple but effective video enhancer'that is super ea,y to build at a fraction of the cost of commercial mod~ls. Unit sharpens picture detail, and can. actually improve the quality of a copy by amplyfying the top end of the video signal K 5825 174 Roe St. Perth WA 6000 PHONE T OLL FREE 008 999 007 Perth Metro & After Hours (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Perth Mail Exchange W.A.6000 PACKIN G & DELI VERY. CHARGE $3.00 DELIVERY AUSTRALI A WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 7 days from day you post order to when you receive goods. Weight limited 1 Kgs. $6.00 OVERNIGH T JET SER VICE - We process your order the day rece ived and despatch v1_a. Overnight Jettervlce Courier for delivery next day Country areas please allow add1t1onal 24-48 hours. Weight limit 3Kgs. $6.00 HEAV Y SERVICE - For deliveries exceeding 3Kgs and less than 10Kgs - allow 7 days for delivery $10.00 HEAVY HEAV Y SERVI CE - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. INSU_RAN CE - As with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1) . When phone ordering please request " Insurance". TOLL FREE PHO NE ORDER - Bankcard Holders can phone order toll free up to 6pm Eastern Standard Time . Remember with our Overnlg_ht Jetservlce we deliver next day . ALTRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. Pleate Note: Resellers have to pay the cost of freight and msurance and therefore the prices charged by individual Dealers may vary slightly tr:om_ ~his Catalogu~ - in many cases, however, Dealer prices will still represent a s1gnif1cant cost saving from prices charged by Altronics Competitors. Don't forget our Exprett Mall and Phone Order Service • for the coat of a local call Bankcard, Visa or Ma1terc1rd holders can phone order for same day despatch. ' MORE AL TRON/CS DEALERS WANTED If you have a Retail Shop, you could increase your income significantly by becoming an Altronics Dealer, Phone Colin Fobister (09) 328 2199 for Details. WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K .B.Electronics & Marine 212176 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronics 854836 MANDURAH Lance Rock Retravision 351246 NEWMAN Watronics 751734 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521713 Farmer Electronics 522967 ACT CANBERRA Bennett Commercial Electronics 805359 Scientronics 548334 VICTORIA CITY Active Wholesa!e ■ 6023499 All Electronic Components 6623506 SUBURBAN ASPENDALE Giltronics 5809839 CHELTENHAM Talking Electronics 5502386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUl'\:TRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 SWAN HILL Cornish Radio Services 321427 QUEENSLAND CITY Delsound P/ L 8396155 SUBURBAN FORTITUDE VAi.LEY Economic Electronics 523762 Fred Hoe & Sons Electronics 2774311 PADDINGTON SLACKS CREEK David Hall Electronics 2088808 TOOWONG Techniparts 6710879 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Supertronics 724321 MACKAY Philtronics ■ 578855 NAMBOUR Nambour Electronics 411604 PALM BEACH The Electronic Centre 341248 ROCKHAMPTONAccess Electronics (East St.) 221058 Electron World 278988 Purely Electronics (Shopping Fair) 280100 Xanthos Electronics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 SA CITY Electronic Comp & Equip. 2125999 Force Electronic ■ 2122672 SUBURBAN BRIGHTON Brighton Electronics ■ 2963531 CHRISTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 PROSPECT Jensen Electronics ■ 2694744 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON Advanced Electronics 315688 George Harvey ■ 316533 Nichols Radio TV 316171 NSW CITY David Reid Electronics ■ 2671385 SUBURBAN BLACKTOWN Wavefront Electronics 8311908 C A RINGHAH Hicom Unitronics 5247878 LEWISHAM PrePak Electronics 5699770 SMITHFIELD Chantronics 6097218 COUNTRY ALBURY Webb's Electronics ■ 254066 COFFS HARBOUR Coifs Habour Electronics 525684 GOSFORD Tomorrows Electronics ■ 247246 NEWCASTLE Novocastrian Elect.Supplies ■ 621358 NOWRA Ewing Electronics ■ 218412 ORANGE RAYMOND TERRACE Alback Electronics 873419 TENTERFIELD Na.than Ross Electronics 362204 WINDSOR M & E Electronics ■ Communications 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 Blue Ribbon Dealers are highlighted with a ■ . These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. THE WAY I SEE IT By NEVILLE WILLIAMS Worth preserving: a colourful slice of electronic history! Talk to someone who worked in a radio factory during the '20s and '30s and you'll probably hear about makeshift working conditions, sudden standdowns, heavy-handed bosses and light-fingered staff. But much of it will be lost to future generations, unless some of us share those memories, before we 're too frail to push a pen or commit them to tape! We talked endlessly about situations and events when it was all happening, especially in the early '30s, comparing notes and swapping stories as we followed the jobs, at various levels, from one radio factory to the next - a real life game of musical stools! Some of the stories were apocryphal, I'm sure, based on fact but suitably embellished to improve the telling. Maybe the odd junior was the victim of not-so-innocent pranks by male and/or female process workers, but I doubt that they were quite as spectacular as sometimes claimed. Maybe, on their way out the back door, someone did once burst into the manager's office at Stromberg Carlson and call him everything under the sun but, in factory folklore, every red-blooded wirer who was ever sacked from the place was credited with having done the same thing! Continuity of work was a major problem, in those days, with the factories loaded to the limit in winter and reduced to a skeleton staff in summer. A lot of process workers in their late teens and ear70 SILICON CHIP ly twenties simply made the best of it but others, hoping for a career in radio, worked hard to becomf:l part of the "skeleton" that the management did their best to hang on to. Apart from lay-offs during- the summer months, sudden standdowns were very much part of the scene, especially in the larger factories. If production was threatened by a temporary shortage of key components, workers on the line were simply stood down for as many hours as it took to sort out the problem. Where the unions figured I'm not sure but they didn't seem to count for much in that situation. In case you think I'm exaggerating, let me quote from an article "Fifty Years of Broadcasting in Australia", from the IREE Golden Jubilee Publication (1932-82), written by that well known electronics engineer Neville Thiele. I quote: The receiver industry was lively and competitive, ruthless to its employees. Old hands used to tell of being laid off for hours at a time, waiting in a back lane behind the factory whenever components ran out, and being sacked just before Christmas, to be re-engaged after the new year. Production fluctuated with the seasons. If talk meant anything, the word "ruthless" accurately sums up the attitude of many employers, although the truth probably is that, in the cut-throat competition of the post-depression era, they were operating on margins about as fine as those of the people who worked for them. Tricks of the trade Loyalty, either way, was also pretty thin on the ground and ''pinching parts" was rife, plainly dishonest to some but accepted by others as anything from a challenge to a way of getting even with the boss. Keep in mind that, while they/we were spending all day building radios for other people, few could afford a radio of their own. Boarding alone in Sydney, all I could listen to at night was the wailing of cats under the house! Chatting about all this, recently, with retired engineer Winston Muscio, he recalled how wirers used to smuggle switches and other small parts through security at the STC factory in Alexandria, Sydney. Said he: "They'd knot them into a length of cord and walk out with them hung over the crutch in their pants!" I'd heard about the same technique at another factory except that it was used to pinch valves. Of course, that only worked because of the then current fad for loose-fitting trousers. "Oxford bags", I think they were called. But for sheer finesse, it's hard to beat the routine described to me by former colleague Phil Watson: At one time, as a goodwill gesture, management at the HMV factory at Homebush, NSW, where Phil once worked, agreed to an arr ang em en t whereby factory workers could borrow portable test instruments over the weekend for their own personal use. The scheme proved, however, to be a "Trojan Horse" in reverse, when somebody thought up the idea of taking the instruments out packed with loose components, and bringing them back empty! Power transformers were a problem because of their size and weight but the same resourceful workers managed to get them out by lobbing them from a window into the long grass on a nearby railway embankment. Fortunately, there was a positive side to all this. The factories did provide a way to meet expenses (just!) for those of us who had a genuine interest in radio and whose prime ambition was to get a foot on the ladder: assembler, wirer, inspector, tester, troubleshooter, laboratory assistant and perhaps, one day, engineer! Or, as they used to be (and still are) called: a "ginger beer". Men in white coats! Mind you, on the factory floor, engineers were often regarded as a rather odd breed. They kept pretty much to themselves, wore white dustcoats and worked in a locked room that no one else ever entered, except the top brass; they got more money than the rest of us, were never stood down and didn't have to punch the bundy. How one got to be an engineer wasn't clear. They didn't feature much in factory small talk, perhaps because they were seen as neuters neither workers nor bosses. But a chief engineer who doubled as a production manager was another matter; that put him squarely in the firing line! In retrospect, getting to be an engineer in the '20s and early '30s was not as mysterious a rite as many of us might then have believed. Mainly, it involved: An old AWA Radiola of about mid-1920s vintage. What was life like in a radio factory in the '20s and '30s? (Photo courtesy Orpheus Radio Museum, Ballarat). Having a good general knowledge of radio, however acquired; and (2). Being in the right place at the right time when the particular vacancy had to be filled. Thinking back over the technical pace setters up to and through the '20s, some had gained their knowledge as traditional radio amateurs, pursuing wireless/radio as a hobby and adding to their skills by contriving, building and using their own transmitters and receivers. Others had started out as ordinary hobbyists and, with or without back-up courses, had become sufficiently expert to build and service radio equipment privately, moving later into fullscale professional activities of one kind and another. And, of course, there were those who had trained as wireless operators, or as electrical technicians or engineers, who later broadened their technical skills to embrace the new field of radio. In Australia, at least, specially trained professional radio engineers only began to inherit the white coats from the mid to late '30s. (1). What about the details? It's not difficult to reminisce in a general way, because I lived through the period, but all that I've said could too easily be a one-eyed view. Yet I cannot remember ever having read another article recalling life in a radio factory in the '20s and '30s. For many, it may have been tough, tedious and highly forgettable but now, in this Bicentenary year, it's a human story worth the telling. Even so Stephen Rapley, currently producing the ABC Radio series "Talking History" is also finding it hard to dig out the details. I've mentioned StrombergCarlson, STC and HMV but there were others like AW A, Airzone and Breville that I didn't hear much about, plus component manufacturers like Radiokes, Henderson, Efco and ETC. There were factories in Melbourne, too - Eclipse, Rola, Astor, etc - and elsewhere interstate but, for all we knew of them in the Sydney workplace, they might as well have been a world away. I personally learned the ropes at Reliance Radio in Sydney, a small family company where, of necessity, management and staff worked side by side. But there must have been dozens of other small companies out there with stories and situations as varied as their names. Here's hoping that at least a few retired readers of SILICON CHIP will be able to resurrect information about some of those pioneer Australian radio and components factories - who they were, where they were, how large they were, FEBRUARY1988 71 Servicing - "I feel like closing the doors!" Dear Sir, I would like to add some comments to Neville Williams' "The way I see it", in your Nov.'87 issue. From first-hand observation, I can nominate a few reasons for repair delays: (1 ). Too many new models, with too many changes to internal components, for the sake of change. It is now just about impossible to stock all items for all models of all brands of even one product (eg. VCRs). In a lot of cases, this means ordering parts for each job - hence delays. (2). Products like CD players are not economical to repair when new ones can be bought for $1 99. Agreed, not all are as cheap as that but you try to justify a repair bill of $150 on any CD player, when the owner has seen a new one down the road for $49 dollars more! (3). Lack of properly qualified and experienced technicians prepared to work for comparatively low wages. (4). One major company no longer supplies even authorised agents direct. The parts have to be what they produced, and what they were like to work for. Clippings, photostats, anecdotes in letter form or on cassette could provide interesting reading and help fill in what is currently a pretty sparse outline. Electronic non-servicing To change the subject completely, a reader from of Cairns, Qld, a professional electronic serviceman, takes up my theme from the November issue: "They'll sell you anything - but don't ask them to fix it!" In drawing attention to the now almost routine 6-week turnaround time in getting electronic equipment repaired, I was conscious that my remarks might have been seen as unduly negative but, in essence, M.K. agrees: modern electronic servicing is very much a problem area. 72 SILICON CHIP ordered through a reseller who holds very little stock, resulting in a delay of at least six weeks. Crazy! Unaware of how high-tech modern products are, customers often hunt around for "bargain" repairs by backyard operators offering free service calls, weekend service, etc, but with little access to manuals or assistance from manufacturers, and very few spare parts. Too frequently, reputable repairers have to sort out somebody else's mess and cop the abuse for the added cost and delay. Service calls are a thing of the past. A mobile repairman cannot possibly remember every.model or even carry enough manuals - let alone parts. Customers want a service call but are reluctant to pay for it. We offer a pick-up and delivery service for larger sets for $20 (both ways) which nowhere near covers the cost, but customers argue that even this is too high. Quotes are another tricky area because, to give an "honest" quote, the item must be repaired. If the customer doesn't accept the quote, who pays for the time spent. I'll bet they don't work for His letter is reproduced in an accompanying panel. If you haven't read it already, read it now, and come back to the following brief comments: • There usually is a legitimate reason for changing components. Whether it's sufficient to justify creating yet another service problem is something else. • The notion that a repair must somehow be scaled to the cheapest possible replacement unit is emotive but none the less real. • Qualified technicians used to work for very low wages, but that was fifty years ago! • Price quotes and ''backyarders" have this much in common: they are both unpredictable! • If the purchase price is already too low to adequately cover a year's "free" service, I'd be even more in- free, but try explaining that. Warranty service (including calls) will continue to cause problems while ever new items are so inexpensive. How can anyone expect a free home call on a TV set costing $420 retail? At such a ridiculous price, they are lucky it has any warranty at all. Many of our customers, seeking warranty repairs, become abusive. They seem to forget that we didn't sell it to them in the first place and that we are here to help. As much as I hate to suggest it, I feel that electronic repairs will soon be a thing of the past, as new items become progressively cheaper and more hi-tech. Customers may have to accept that electronic goods will simply have to be replaced when they stop working, whether they be one week or ten years old. Personally, I often feel like closing the doors and letting customers fend for themselves so rarely do they seem to appreciate the job we do for them. It can't get much worse, so it might just get better! Mike Kalinowski , Cairns Electronics. trigued to know how several years' extra warranty can be obtained by paying a relatively small surcharge. • A modern-day nonsense: the ultimate in design is to produce something that doesn't need fixing but, if it does, you can't! From a "backyarder"? Another reader, this time from Western Australia, comments about servicing problems and says that he falls into the category described by my third option, which he defines as: Ask a mate who knows something about electronics and see if they can fix it. What I actually said in the November article (see page 14, second column) was: " ... or, failing that, an individual on-the-spot repairman that other consumers are prepared to recommend on the basis of experience''. Whether he The ultimate in design is to produce something that doesn't need fixing hut, if it does, you can't! fits what I said or what he merely thinks I said is anybody's guess. If he is just "a mate who knows something a bout electronics", it's perhaps as well that he lives as far as he does from our Cairns correspondent! Be that as it may, his first anecdote (abbreviated) runs like this: A friend asked me to look at his rather expensive cassette radio, which ceased to talk after he accidentally reversed the polarity, when plugging it into his car cigarette lighter. He took it into the company service centre for the particular make but, when they heard what had happened, they suggested that he would be better advised to buy a new one. So he passed it over to me. I found that the two audio ICs were blown, plus a couple of diodes, and while there may have been other problems, I estimated the cost at around $20. However, when the service centre discovered that I was not a service agent, they quoted me $25 each for replacement ICs. After picking myself off the floor, I called in to a local electronics store, where I bought the required ICs for just $4.00 each. I can only assume that the $25 figure was outright extortion, in an attempt to force abandonment of the project and the purchase of another unit. Without knowing the value and condition of the particular receiver, it is difficult to judge whether the fixed cost of a formal service job, plus the uncertain cost of repair and parts from their replacement stock, would have represented money well spent. A point to consider is whether the overheads on stocking obligatory replacement components for one-off docketed sales are higher than for casual sales, although the difference between $25 to $4 does take a bit of swallowing! I note, however, that the correspondent makes no mention of any charge other than the cost of parts, implanting in the reader's mind an all-up figure of $10-odd, against maybe $70-80 had the work been done in the service centre. But what would the correspondent have had to charge if, as a professional serviceman, dependent on the work for his living, he had included all the costs and overheads that must be taken into account. This must be done if a serviceman is not going to end up "broke". Anecdote number two concerned a CD player from a different manufacturer, purchased by the same friend. Nine months after purchase, it began to skip tracks erratically or refuse to load discs altogether. The local service centre for that brand insisted that the problem was in the discs - even though they behaved normally in another player. The argument dragged on until the warranty expired, at which time the service centre said that the owner would now have to pay for any further service calls. I quote: Learning of this, he phoned Consumer Affairs, who informed him that, because no parts were replaced during the warranty period, the period would only run the normal time. The owner had little option but to try to have the player repaired at his own expense. This time around, the service centre identified the problem as a defective laser sensor, the cost of replacement being such that he would be well advised simply to buy a new player! That's how it, too, ended up at his mate's place. Missing assembly screws and wiring ties provided evidence enough that it had been messed about with but the indications were that the diagnosis was correct. So to the question: why was it that the problem was only identified after the time had passed when the supplier was obligated to repair the unit gratis or replace it with a new one? The correspondent's conclusion: It appears to me that certain companies are deliberately relaxing their repair services to oblige customers to buy a new unit. When I expressed misgivings, in the November issue, about what seemed to be happening in the service industry, I was concerned that I might be painting the picture in too dark a shade of grey. Looking back over those two letters, from readers on different sides of the continent, and different sides of the servicing scene, they've re-worked the picture in black! As I see it, the advice which rounded off that first article, makes better sense than ever: When selecting a piece of new electronic equipment, don't just look at the price, appearance and specifications. Satisfy yourself that, if something does go wrong, proper provision exists to have it fixed. That's the way I see it! lb FEBRUARY1988 73 AMATEUR RADIO By GARRY CHATT, VK2YBX Build this line isolation unit for phone patch operation At long last, amateurs can legally hook up to the telephone lines. Here we describe a Telecomauthorised Line Isolation Unit for amateur phone patch operation. Since 1980, when Third Party Traffic privileges were announced by the Minister for Posts and Telegraphs, amateurs have been frustrated by red tape and government regulations in their efforts to operate phone patch legally. Despite many representations on behalf of Australian amateurs, phone patch remained illegal until the announcement of a recent agreement between Telecom and the WIA. This agreement allows the use of a Telecom-authorised Line Interface Unit (LIU) to link amateur radio equipment to the Public Switched Telephone Network (PSTN). Apart from the original third party objections which made the use of phone patch "expressly not authorised for personal use" or for use with the Citizens Band Radio Service or Amateur Radio Service, there existed a number of technical reasons why Telecom would not permit direct connection to the PSTN. In particular Telecom was (rightly) concerned that the safety of their telephone technicians could be compromised. Unless special precautions are taken, equipment connected directly to the telephone system can, under fault conditions, place dangerous voltages (eg, 240V) across the line. The possibility of equipment damage from precisely the same type of fault was also of The Line Isolation Unit is built into a plastic case with a plastic on-off switch. It must be built exactly as described in this article. 74 SILICON CHIP considerable concern. Commercial radio users were permitted manual or semiautomatic access to the STN provided they used a commercially designed and Telecom-authorised line isolation unit. Such devices comply with strict technical standards and provide isolation from dangerous voltages, even under fault conditions. Amateur lobbying There were, however, those in the amateur fraternity who refused to give up, notably Sam Varon VKZBVS, Jim Linton VK3PC, and Jack O'Sh_anassy VK3SP. Because of their lobbying, and that of many other amateurs as well, aH "policy" objections to phone patch use by amateurs were eventually resolved. The technical objections were solved by Geoff Donnelly VKZEGD, a Telecom designer who, with the approval of his supervisors, designed the Line Isolation Unit described here. This unit was originally described in Amateur Radio, the of• ficial journal of the WIA, and reappears here with their permission. Intending constructors should note that the cost of gaining Telecom authorisation for this Line Isolation Unit was borne by the WIA. Because of this, all units must be built in strict accordance with the design published here, and must be submitted (free of charge) to the WIA for checking prior to use (details later). Circuit details Fig.1 is a block diagram showing PARTS LIST TELEPHONE PLUG AND DOUBLE ADAPTOR EXCHANGE TELEPHONE I 1 600-ohm line isolation transformer (Telecom approved), Arlec 45035, DSE M-1 21 0, Jaycar MA-1510 1 plastic zippy box with plastic lid, DSE Cat. H-2851 . 1 DPDT switch (plastic), DSE Cat. S-1393 2 banana sockets 4 adhesive rubber feet 1 Telecom cord, part number 4544/16/1800 (available from Telecom Business Offices) 1 Telecom 605 plug 1 telephone double adaptor 1 LED mounting bezel RADIO PHONE PATCH APPROVED LIU TRANSMITTER -----RECEIVER Fig.1: the Line Isolation Unit (LIU) is plugged into a telephone double adaptor socket, in parallel with the existing telephone. how the Line Isolation Unit is used. Note that suitable phone-patch equipment is required to link the transceiver to the LIU. In its simplest form, this could consist of a manual switching system. This would direct the telephone line to either the receiver output or the transmitter input as appropriate. Alternatively, the more traditional hybrid circuit or some sort of relay switching system could be used. Fig.2 shows the circuit details. As can be seen, the Amateur to Telecom Line Isolation Unit is operated in parallel with a standard Telecom telephone. When S1 is closed, DC continuity is achieved via R1, R2, diodes D1-D4, and transformer T1. This means that once a call has been received or originated, the standard Telecom phone can be hung up, as the LIU will hold the line in the "looped condition". Zener diode D5, LED 1 and current limiting resistor R5 form the visual "looped line" circuit. Diode bridge D1-D4 ensures that the LED will light regardless of line polarity. Capacitors C1-C3 prevent RF energy from reaching the diode bridge. If this was not done, detected RF would appear as noise on the telephone line. R1 and R2 also provide RF protection and some degree of current limiting should T1 's primary short circuit. On the amateur side of T1, R4 and R5 provide current limiting in the event of an RF source being placed across the line. C4 limits the current through D6 and D7 if 240V AC is accidentally connected to the LIU from the amateur side. The normal function of diodes D6 and D7 is to serve as an audio signal clipper. This limits the signal voltages to 0.6V peak. Longitudinal voltages are prevented from passing through the LIU by transformer T1, Note: for the purpose of this article, transverse voltages are those appearing between the two input lines. Longitudinal voltages are common mode voltages; ie, they may be AC or DC above or below earth. It is extremely important that no longitudinal voltage (eg, 240V AC) is fed into the telephone lines. The isolation transformer Semiconductors 6 1 N4004 diodes 1 3.3V 1W zener diode 1 5mm red LED Capacitors 1 2µF 440V capacitor, Jaycar EE5120 (Telecom approved) 1 2µF 100V polyester 2 0.1 µF 1 00V ceramic 1 0 .01 µF 1 00V ceramic Resistors 4 100, 0.5W 1 2200, 0.25W prevents this from happening. Safety The LIU must be able to withstand 3500V AC (RMS) at 50Hz applied between either side of the Telecom line and any external wiring to the amateur equipment. For * C4 R4 10!l o- ¥+\1f 0 2 440V I C1 2 2x1N4004 AMATEUR EQUIPMENT VIA BANANA SOCKETS 06 R5 10!l 07 100V soon S1a . . A - - - 0 2 WHITE 05 3.3V C2 0.1 100V CERAMIC TELEPHONE TYPE CORD 4S44116/1800 TO 605 PLUG 600!l C3 .01 100V CERAMIC R2 10!l 0 S1b - ~ - - - 0 6 BLUE *TELECOM APPROVED AMATEUR TO TELECOM LINE ISOLATION UNIT Fig.2: the complete circuit diagram for the Line Isolation Unit. Transformer Tl and capacitor C4 provide the necessary isolation and must he Telecom-approved components (see parts list). FEBRUARY1988 75 FROM AMATEUR EQUIPMENT Fig.3: PCB parts layout and wiring diagram. Take care with component orientation. this reason, the unit is double insulated (ie, installed in a plastic box with a plastic on-off switch). When a test voltage of 264V AC at 50Hz (with a source impedance of less than 100) is applied across the amateur side of the LIU, the voltage across a lMO resistor connected across the Telecom line side must be less than 30V peak. If you build the unit correctly according to this design, these requirements will be easily met. In particular, you must use the exact parts specified in the parts list if your unit is to satisfy Telecom standards. Construction Printed circuit boards for this project are available from RCS Radio (651 Forest Rd, Bexley. Phone 587 3491). Alternatively, you can use the PCB artwork reproduced with this article to etch your own board (Fig.4). Constructors making their own PCBs should use goodquality fibreglass circuit board, with a minimum thickness of 2mm. This grade of circuit board is called FR-4. The parts layout on the PCB is shown in Fig.3 and the accompanying photographs. Prior to assembly, check the PCB pattern carefully to ensure that there are no shorts between the tracks. Use a scalpel or Exacto knife to remove any pieces of unetched copper. No particular procedure need be followed when installing the parts on the PCB, although it's a good idea to mount the low-profile components first. Be sure to install the diodes the right way round. Similarly, be sure to orient the LED correctly - it is connected to the PCB via two 100mm-long flying leads. Sleeve the leads of the LED with plastic tubing to prevent possible contact with "live" components. The assembled PCB slides directly into the slots of a plastic zippy case (DSE Cat. H-2851). Fig.5 shows the drilling details for the case. Note that the inside wall adjacent to the cutout for the moulded Telecom cable grommet must be filed to a thickness of 2mm. It will also be necessary to file a slot in the lip of the lid to clear the grommet. You can now fit the switch, LED and banana sockets to the case and complete the wiring to these items as shown in Fig.2. Now comes the tricky part: that of connecting the Telecom cable to the PCB. The problem here is that the leads of this cable are terminated by small connectors which are crimped to plastic-covered tinsel (not wire). If these are heated excessively (by soldering), the connectors will separate from the tinsel and you'll have to discard the cable and buy a new one. The solution is to make up two small spade terminals which will accept the crimp connectors on the Telecom cable. You can do this by AIIATIUII TO TRLICO■ LINI IIOLATION UNIT Fig.4: etching pattern for the PC board. 76 SILICON CHIP be operated in parallel with the telephone. Note that only the blue and white wires are connected to the PCB. The red and black wires can be cut off at the grommet. The other end of the cable is terminated with a standard Telecom 605 plug. This is plugged into a telephone double adaptor in parallel with the telephone. Telephone double adapators and plugs are available through electronics stores. The Telecom cable can be purchased from Telecom Business Offices. Alternatively, you can buy an extension cable and adapt it to suit the LIU by removing the socket. Rules of operation The PCB slides directly into the grooves in the plastic case. Note that the Telecom cable is connected to spade terminals on the back of the PCB. FRONT VIEW 158 REAR VIEW - - ~ 1 0 DIA. •~-¥10DIA. lr, I: 30 I 120 DIMENSIONS IN MILLIMETRES Fig.5: drilling details for the plastic Zippy case. hammering flat two 12mm lengths of 16-gauge tinned copper wire until they are a tight fit into the crimp connectors. The two terminals are then re-tinned, bent through 90° at their mid-points, and soldered to the "line" pads on the copper side of the PCB. No connection is made to the "phone" pads on the PCB. These were made redundant when Telecom agreed that the LIU could The normal mode of phone-patch operation is restricted to a home station, and only at one end of a radio link. In a normal single-ended phone-patch connection, the relevant third party regulations apply. Phone-patch access for mobiles is permitted via a home station, but not directly via a repeater. Repeater contacts can be phonepatched, but only by a home station. Under WICEN operation (as distinct from "normal" operation), or other emergencies involving natural disasters or life' threatening situations, double-ended phonepatch operation will be permitted as a special condition. Under duly authorised WICEN exercises, training involving the use of double ended phone-patch will be permitted on a self regulatory basis by the WIA. The WIA will be responsible for authorising such exercises and will keep a record of such exercises and training arrangements. These records will include the details of radio amateurs involved, their callsigns, and the period of authorisation. This authorisation procedure will be available to any radio amateur wishing to establish local community emergency arrangements to the WIA's standard of service. This can include appropriate community service activities, and public displays of the hobby. Operating guidelines To operate phone-patch legally, the following guidelines must be observed: FEBRUARY1988 77 (1) Only Telecom authorised equipment may be connected to the telephone network. (2) Operators must use phonepatch in accordance with Department of Transport and Communications regulations, particularly in relation to handling Third Party traffic, and must provide station identification at least every 10 minutes. (3) Brief the phone party on what is acceptable and unacceptable conversation over an amateur radio link. Any matter which is profane, obscene, or otherwise objectionable is not permitted. Transmissions from Third Parties must be limited to remarks of a personal nature, for which, by reason of their unimportance, recourse to the public telecommunications network is not justified. No commercial communication of any sort is permitted and no charge can be made by amateurs for providing a phone patch. Do not hesitate to interrupt a conversation being patched through your station if you consider that it may breach regulations. (4) Explain that the patched conversation will be one way at a time, and that each party should indicate that it is the other person's turn to speak by saying "over". (5) Keep in mind that the quality of the phone-patch relies on the standard of "off air" signals, and that the transmission of poor quality signals from an amateur station is not permitted. A poor quality patch will not assist either party, and will give amateur radio a bad name. (6) Avoid putting to air unnecessary dial clicks and telephone tones. (7) If you, as a radio amateur, use the telephone end of a phone-patch, avoid the use of your callsign if the transmission is on a band for which you are not authorised. Approval procedure Prior to connection to any Telecom lines, the LIU must be submitted for approval to the Wireless Institute of Australia, VK2 Division, PO Box 1066, Parramatta, NSW 2150. You should also include your callsign, name, address, telephone 78 SILICON CHIP Close-up view showing how the Telecom cable is connected to the two spade terminals on the back of the PCB. The terminals can be made from tinned copper wire. The completed unit with a Telecom authorisation label attached. number and return postage. When the unit is received, it will be passed on to Telecom for inspection and testing. If all is well, the unit will be returned to the constructor, with an authorisation label attached. This label will contain an individual serial number and must remain on the LIU as proof of inspection. Returned units will be accompanied by two relevant connection forms. However, as this unit is authorised for self-connect, these forms will serve only as a notation on Telecom records that the equipment for your location is authorised for use. You will also be debited $24 per year "rental" which will automatically be billed to your telephone account. Recommended reading "Interconnection of Mobile, Amateur and Citizen Band Radiocommunication Services with the Public Switched Telephone Network", Policy and Conditions Issue 2, June 1985. Available from Telecom Regulatory Branch, Melbourne. Acknowledgements The author wishes to acknowledge the following for their assistance in the preparation of this article: The Wireless Institute of Australia (WIA), VK3PC, VK2EGD, VK2ZPW, Telecom Regulatory Branch (Melbourne), and RCS Radio Pty Ltd (Sydney).~ BUILD AC) BICENTENNIAL KIT Build a low cost (high spec) stereo amplifier! Economy it might be - but in name and price only! Outstanding specifications for a built-it-yourself stereo amp - just look! Single PC B construction, five inputs, around 9W/channel with less than 0.05% THD . . . it'll be perfect for your stereo system and it WON'T break the bank. Housed in an attractive slim-line steel case with screened front panel included! Cat K-4001 • Perfect for the flat, unit, home! • Great specifications! • Very low cost! • Looks great! Cat K-4001 All this for only s 12995 FunWay 1 Gift Box TV Pattern Generator Free Teletext! Makes an ideal birthday or Christmas present... and who knows, it could be the start of an absorbing hobby in electronics, or even an exciting career! A build-it-yourself bargain for the serviceman . With just seven IC's you get three patterns: dot, crosshatch and blank raster. Includes deluxe front pane) and VHF modulator. Operates from plugpack adaptor (9V DC). Cat K-3472 Yep, the Teletext transmissions are yours absolutely free of charge, courtesy of your local TV station (not in all areas - sorry!) . All you need is a Teletext decoder to pick up the latest news, sports results, financial info, stocks & shares, recipes, ~ c.:_ Cat K-2605 ,Jfl,,~;iiii,I~ . Build your own Teletext decoder - it works through your VCR so you save a fortune. Complete with hand controller. CatK-6315 s2&9 lnfrared Remote Switch FunWay 2 Gift Pack With the fantastic lnfrare Remote Control Switch you can switch on or off the TV, lamp, radi many mains appliances witho moving from the comfort from your chair . It will operate up to 12 metres from the switch Here's a gift bargain! Over $50 worth of value for less than $40! This gift pack has been specially selected for quality and for value. Cat K-2620 · • . .. Total Sound Control! sages VK Powermaster Electronic Siren Just what you need with the alarm! Also makes a great sound effects circuits · and FunWay 2 tells you what to do! Cat K-2636 sees Want an amplifier for the 'walkie' stereo or radio? Don't be tied to 'phones: use this project and listen in comfort! Or you can build this into a mini PA amplifier. Cat K-2667 . $ 1865 H·u ge 25A peak with suitable transformer! That's power ... and it's simple to build. For HF gear, linears, and so on, this one has the oomph you need . Short-form kit: you choose the transformer you want to suit the output required : M-2010 transformer gives 14A continuous M-2000 transformer gives 6A continuous Cat K-3448 How's this? An. infra red remote control for your sound system that also gives you full tone , balance, volume and switching control from your armchair! It's great to be able to settle back in your armchair and change the sound! Complete kit includes remote control handpiece, adapts to virtually ANY audio system. Cat K-4003 s129es Mini Stereo Amp ~ Cat K-3428 j J _...___ ~p~ Musicolor IV What's better than a colour organ and chaser? The Musicolor Mk IV: it combines both in one unit! Four chase patterns plus auto chase and reverse chase ~~~:,e,:; °""°"'' -: :~ ff s135 colo"mgaowi>o bW,.~i" mic DICK<at>SMITH ELECTRONICS PTY LTD •' ; h • Also available through DSXpress Toll Free (008) 22 6610 PT. ·4 - AUSTRALIA'S FIRST 100 YEARS i'OF RAIL 'I'HE EVOLUTION OF ELECTRIC RAILWAYS Australia entered the railway age around 1850. In the following years, railways changed the face of our country, sometimes at a startling rate. By BRYAN MAHER In Sydney, a start was made at Redfern and a ceremonial sod was turned in 1850, but progress was slow and arguments raged over what gauge to choose. The companies knew full well that the English Parliament Bill of 1840 required all railways to be built to the standard 4ft 8-1/2in, but were also 80 SILICON CHIP aware that the same Parliament had ratified Ireland's decision to adopt the 5ft 3in "Irish" gauge. Now the Sydney Railway Company had employed an Irishman, Mr. Shields, as chief designer who promptly decided that Sydney's railway should be built to 5ft 3in gauge. Simultaneously, another group, the Hunter River Railway Company, was formed to construct a standard gauge system from Newcastle to Maitland and north, while three different companies were making plans to link Melbourne with Port Melbourne and Geelong. Of the three Melbourne starters, only one, the Melbourne And Hobson's Bay Railway Company, actually built a railway. They also had an Irish engineer who, reinforced by the Sydney Railway Company's choice of a 5ft 3in gauge, chose that gauge for Victoria. Their first train ran from Flinders Street to Sandridge in September 1854, winning the honour as the first train in Australia. THE NSW "58" CLASS steam locomotive weighed 228 tonnes, developed 2475 horsepower (1.85MW), and produced 51,000lhs drawhar pull. (Photo courtesy ◄ SRA, NSW). By 1857 a service was opened from Geelong to Melbourne, partly by train and partly by ferry. Sad to say, by 1861 the Railway Company was no longer financially viable and a State Government takeover was necessary. Meanwhile, back in Sydney town, engineer Mr. Shields had been succeeded by Mr. Wallace, an Englishman and proud of it, a staunch believer in Rule Britannia and English laws and customs. Yes you guessed it, bemused reader, their new engineer would have no part of this 5ft 3in nonsense and pointing out the error of their ways told his masters, the Sydney Railway Company, that he would build to the English standard 4ft 8-1/2in gauge. And he did. The next year, 1855, some 379 days behind the Victorians, the first train in NSW ran from Redfern to Granville (then called Parramatta). Within five years the line had been extended to Blacktown, with Penrith reached by 1863. In Newcastle, the Hunter River Railway Company opened its line in 1857. This was after four years of planning, surveys, financial troubles and building, but the company had been forced to accept Government intervention. Both the Sydney and the Hunter r TRAINS IN THE STREETS: the "space-age" 520 class 4-8-4 express locomotive was once the pride of the South Australian Railways. It is shown here standing at Port Pirie station in 1947. (Bryan Maher photo). River Railway Companies remained solvent for less than one year from their start of operations. By the end of 1855 both had been taken over by the NSW Government, believed to be the first time ever a Government had owned and operated a railway. South Australia joined the club only 210 days after Sydney's big opening ceremony by building a 5ft 3in gauge line from Adelaide to Port Adelaide. This extended to Gawler the next year, 1857, and to Victor Harbour by 1864. Queensland, for economy, chose the narrow 3ft 6in gauge for their first line which was nowhere near Brisbane, but ran west from Ipswich to Grandchester in 1865 and to Gatton the next year. Construction of the next westward stage to Toowoomba involved the ascent of the Great Dividing Range but remarkably that task took only one more year, in 1867. Turning south, the builders constructed their line along the western side of and roughly parallel to the range to reach Warwick in 1871. Only then was Brisbane City to enter into the railway age, the extension from Ipswich to Brisbane being completed in 1875. PICTURED AT Port Pirie Junction in 1949, the Commonwealth Railways Class CN 75 was a 4-6-0 locomotive of American-style design. (Bryan Maher photo). FEBRUARY1988 81 THE FIRST FIVE NSW "38" class steam locomotives were streamlined, weighed 201 tonnes, produced 2250 horsepower and were built by Clyde Engineering. The one-piece cast steel mainframe included the front buffer beam, all cylinders and the main air reservoir, as well as mountings for the axle-boxes, boiler, air pumps and firebox. (Photo courtesy SRA). In company with Queensland, and again for economic reasons, Western Australia, Tasmania and Northern Territory all finished up with narrow gauge 3ft 6in systems, although for a short while Tasmania went through a silly period with two different companies building in different gauges, 5ft 3in and 3ft 6in. After a Western Australian logging line had run from Brusselton to Yogamw for seven or eight years, a passenger and freight railway was put into operation from Geraldton to Northampton in 1879. Thus it was not until 1881 that the citizens of Perth saw their first line from Perth to Fremantle. The Geraldton and Perth systems remained separate for another 13 years until finally joined in 1894. 82 SILICON CHIP New South Wales The NSW system quickly extended westwards over the Blue Mountains, reaching Bourke by 1885. Simultaneously, construction proceeded south from Sydney to reach Albury by 1881 with connection to Melbourne two years later. All this time, Newcastle had been the centre of the thriving Northern Railway System. By 1857, the track extended as far north as Maitland, then followed more tracklaying through the lush green Hunter River valley via Singleton, Muswellbrook and Murrurundi. So far so good. But ahead was the steep climb up the Great Dividing Range. Undaunted, the builders attacked the mountain and with many a twisting turn and some large creek bridges managed to reach the summit in the middle of the Ardglen tunnel. From there, the line proceeded down a steep slope to the plateau levels of Willow Tree and Quirindi. To this day that section remains exactly the same steep, single track, but track circuit signalling, heavy rail and centralised traffic control keep trains moving quickly. Loaded trains still require doubleheading over the peak of the grade with the powerful 81 class dieselelectric locomotives. Driving on northwards the track builders reached Tamworth by 1878, famous for having installed the first electric street lighting in an Australian country city. But the proposed line ahead looked awesome indeed. To reach prospective customers the line ascended ever upward to Armidale, Guyra and Glen Innes. And it reached higher still through the tiny town of Ben Lamond, at 4517 feet above sea level, the highest trainline on this continent, and higher than most standard gauge railways of Europe. Thankfully, from this point, the terrain falls all the way to the Queensland border and Newcastleto-Brisbane travel was a safe, comfortable affair by 1888. Farmers Australia-wide then twisted the political arms of every government and in short order branch lines snaked out all over the country, giving rail access to 90% of our sons-of-the-land and their produce by 1900. Built partly as "ballot box expediency", many branches were built too cheaply and quickly, with steep grades, sharp curves and very light rail. Our entire country is even yet suffering the resultant legacy of slow running speeds and high operating costs. Locomotives NSW locomotives began with little No.1, an 0-4-2 type, to be followed by a few small designs until mass production of the fast "12" class began in 1877. The heavier but slower "S" or "30" class, a 4-6-4 tank type of which hundreds were built, was the mainstay of Sydney's suburban steam trains from 1880 to 1930, and of Newcastle's right up to the late 1950's. Between 1890 and the turn of the century, two steam locomotive classes important to the development of the state were built. These were the 4-6-0 "P" or 32 and 33 class for passenger service, and the 2-8-0 "T" or 50 and 51 class built in Sydney by the Clyde Engineering Company. More than 100 of each class were built and all did stirling service for 70 or so years. The pride of the state for many years was the "36" class. Especially at night, their "snorting" sound and the glare of their headlamp gave such an impression of immense power wanting to be unleashed that the lure of being carried to places unknown changed many FI bystander into an avid woulrl-be traveller. Every night the EXPERIMENT AL ELECTRIC tram car No.3, as used in Sydney· during the 1890s. It used a direct current overhead trolley wire system. (Photo SRA/UTA Archives). prestige Melbourne Limited Express roared out of Sydney headed by two of these well-loved machines and who could but not watch in awe. Forty two of this class were built from 1924 on, but around 1942 even they were eclipsed by New South Wales' last steam design, the "C38" class. South Australia South Australia in 1886 made history by joining the Victorian system at Serviceton using the same 5ft 3in gauge. After further expansion, South Australia declared the broad gauge too expensive for some small lines and built tracks north of Port Pirie in the cheaper 3ft 6in gauge. Years later, in 1917, the Federal Government, to its everlasting credit, built the Trans-Australian Railway from Port Augusta to Kalgoorlie in the English standard gauge, extending to Port Pirie in 1937. Thus it is that Port Pirie (along with the city of Vaxjo in Sweden) qualifies as a member of a very exclusive club - those having railway yards where some tracks have four rails. Parts of the Port Pirie yard use one common rail on the left, a second rail 3ft 6in to the right, a third rail at 4ft 8-1/2in and a fourth rail at 5ft 3in. Wow! The sight of a set of points on such a track is a joy to behold! That changed again in December 1986 when Australian National changed the 5ft 3in Adelaide-Port Pirie track to standard gauge by moving one rail inwards 165mm over the whole 160km length of single track. It also constructed 12km of new track. Islington terminal now has mixed-gauge tracks, including dual-gauge points. South Australia's 5ft 3in Irish gauge system could boast some excellent examples of large steam locomotive design in the American style. This was exemplified in the 520 class streamlined 4-8-4 express locos and the 500 class 4-8-4 which were among the most powerful locomotives ever to run in this country. The 500 class was unique in that they had an extra set of steam pistons and cylinders driving the four trailing bogie wheels under the firebox. This increased the drawbar pull at low speeds, being disconnected for high speed running. The present scene in Queensland holds records for the longest regular trip in one state-operated train, while their coal trains are FEBRUARY1988 83 copper conductors, that span with a 61-metre sag in the middle has each phase supported by a pyramid structure made of three 18-metre wooden poles sunk 4.3 metres into the rocky hilltop. The whole 66kV line from Hamilton substation in Newcastle to St. Leonards substation in Sydney was designed to carry 200 amperes, and at full current 6000 volts was lost over the length of the line. For the first time in Australia, two large cities had their power systems synchronised and joined. Victorian electrics INTRODUCED IN 1923, the LP class was the first electric tram car in Newcastle. (Photo SRA/UTA Archives). believed to be the second largest in the world on narrow gauge, but more of that in a later episode. A side effect of the choice of narrow gauge is the ability to turn a train in a tighter curve, allowing branch and main lines to be laid in a city street and even turn a 90 degree corner. Rockhampton and other cities regret this to the present day. Even Brisbane people suffered freight trains in the streets of "The Gabba" up until 1973. Early electrification The absolute first Electric Traction of any type in Australia was an electric tramway using a direct current overhead trolley wire system in Sydney, from Waverley to Bondi Junction. This was in operation from 9th November, 1890. Direct current supply was generated by the New South Wales Railways at an installation a short distance away in the direction of Randwick. That little DC generator near Randwick marked the first entry into the electricity generating business by the NSW Railways, starting an enterprise which continued to grow for the following seventy years. The Railways Department during that time not only generated all power used by electric trams, trains, stations , yardlighting, workshops and signals in the Newcastle, Sydney and Blue Mountains districts, they also supplied, 84 SILICON CHIP owned and operated at Newcastle the largest electric and hydraulic coal loading wharf system on the Pacific Ocean. Furthermore, in that period the New South Wales Railways operated 50Hz and 25Hz coal burning power stations at Ultimo and White Bay in Sydney and at Zara Street in Newcastle, and for a long time owned some of the largest synchronous motors in Australia, 10 megawatts in Newcastle and 30 megawatts in Sydney. During that time the Zara Street plant supplied 90 percent of all power used in Newcastle and its suburbs by domestic and industrial users. Expanding gradually, the Railways Department built and operated a large system of high voltage feeders from their power stations to many country towns and cities. 33kV lines ran from Newcastle to the Hunter River Valley and up the north coast towards Grafton. 66kV lines ran from Sydney to the Blue Mountains and also Australia's first intercity power line interconnector, also a 66kV line, was built in 1942 to join Newcastle and Sydney. One 960-metre long span of that Newcastle-Sydney interconnector across the Hawkesbury River was believed to be the longest power line span on wooden poles in the world. Originally built using 19-strand 10-gauge cadmium- Melbourne became the first Australian city to boast electric suburban trains when in 1918 some wooden carriages , previously steam-hauled, were converted to electric traction by the fitting of pantographs, control gear and new bogies containing electric motors. Overhead wiring construction was proceeding on a number of suburban lines and the first electric train ran from Sandringham to Essendon in 1919. Construction of AC-DC substations and overhead conductors above the tracks continued and Melbourne's 1500 volt DC electric suburban railway system eventually grew very large. Australia's early use of electric locomotives was confined to the coalfields in the eastern corner of Victoria where the very considerable brown coal deposits are mined by open cut methods. Victoria's first electrically hauled coal train ran in 1923. Melbourne trams The Melbourne Electric Tramway system has, since quite early days, been working with the railways in shifting millions of people. Nowadays this system is the only extensive electric tramway system remaining in Australia. A shining example to the rest of Australia, Melbourne has extended its tram-tracks and purchased many new tramcars. The up-to-date "Z" class, of which 215 new cars have been put into service over a ten-year period, are being augmented by the latest order of 52 modern "A" class trams. In 1985, a $100 million contract continued on page 93 ' ' 1f1-'l There are two basic types of digital logic circuits, combinational and sequential. Combined circuits are made up of logic gates connected in a variety of configurations. Combinational circuits typically have multiple inputs and outputs. Their outputs are a function of the input states, the types of gates used, and how they are interconnected. Sequential logic circuits also contain gates, but their main element is a logic circuit we have not yet discussed; it's called the flipflop. A flipflop is a circuit used for storing one bit of data. Because flipflops are a kind of memory circuit, they permit a variety of storage and timing operations to be performed. Some of those operations include counting, shifting, sequencing and delay generation. In this lesson, you are going to learn about the various types of flipflops and how they are used. In a future lesson, we will cover more advanced sequential logic circuits, including counters and shift registers. Note: in the following discussion, we use the expression "high" to refer to a binary 1 logic level or some positive voltage in the + 3V to + 5V range. "Low" is used to designate a binary 0 logic level, which is ground or Oto + 0.2V. Data latches The simplest form of flipflop is the latch or RS flipflop. Like all other flipflops, this type is capable of storing one bit of data. It has two inputs and two outputs, and is usually represented by the simple logic block shown in Fig.1. For example: to store a binary 1, you apply a signal momentarily to the set input. To store a binary 0 in the latch, you momentarily apply a logic signal to the reset input. Once the latch is set or reset by the input pulse, it remains in that state. The flipflop remembers which state it was set to (0 or 1) until the state is changed, or until power to the circuit is removed. To determine which bit is stored in the latch, you look at the outputs. By examining the normal output with a voltmeter, logic probe or oscilloscope you can determine which state the flipflop is in. If the normal output is binary 1, then the flipflop is set and storing binary 1. If the normal output is binary 0, the flipflop is reset and binary 0 is being stored. The complementary output is an inverted version of the normal output and is useful when the latch is used to drive other logic circuits. Incidentally, you will note that in Fig.1 the outputs of a flipflop are normally labelled with letters of the alphabet. Q is commonly used with flipflops, but other letters of the alphabet or other multi-letter combinations can be used too. Also, when a line or a bar appears over a letter as in Q, that signal is the reverse of its counterpart, Q. That is to say, if Q is low, then Q (Qbar) will be high and vice versa. A latch or RS flipflop is easily constructed with NAND gates as shown in Fig.2. The gates are conINPUTS OUTPUTS SET~NORMAL RESET--l_r-coMPLEMENT Fig.1: the logic symbol for an RS (reset-set) flipflop. Note the complementary outputs (Q and Q-bar). 1-"EBRUARY 1988 85 nected with the output of each connected to the input of the other. The operation of a latch is easy to understand if you remember how a NAND gate works. The simple truth table in Fig.2 will refresh your memory. TRUTH TABLE OF NANO GATE INPUTS A D 1 1 1 D 1 0 0 Q Fig.2: an RS flipflop constructed of NAND gates. When power is first applied to a flipflop circuit, it comes up in one of its two stable states. Because of minor differences between the two gates, the circuit will flip to either the set or reset state immediately upon power-up. It is not possible to predict which state will occur. Let's assume that the flipflop initially comes up in its set state. That means that the Q output is binary 1. This binary 1 also appears at the input of gate 2 together with the reset input. The reset input is shown open here and this has the same effect as a binary 1 input. With those conditions on gate 2, its output will be a binary 0. The output of gate 2 is applied back to the input of gate 1. The set input is open and has the effect of a binary 1. However, it has no effect on the circuit, because the binary 0 input to gate 1 causes its output to remain high. Just to be sure you understand the idea, trace the circuit state by assuming the flipflop comes up in the reset condition. Start out with the Q-bar output being binary 1 and repeat the above analysis. Keep in mind that the set and reset inputs will not normally be open. Instead, they will be held at binary 1 level. To change the state of the flipflop, either the set or reset input must be pulled momentarily to the binary O level. Assume that the flipflop is initially set with the Q output being binary 1. If we want to reset the latch, we simply apply a brief pulse that switches from binary 1 to binary 0 and back again. The•binary 0 input on gate 2 immediately forces its output high. That high output to the input of gate 1 along with the high set input causes the Q output to go low. The flipflop thus changes state from set to reset. Incidentally, if another reset pulse is applied to the reset input, no additional change of state will occur. Similarly, if the flipflop is already set, additional set pulses will have no effect on the circuit. u--~___.r 1 C D 1 D 1 I I RESET:---,---~ OUT , B D D 1 1 1 SET 0 AMBIGUOUS STATE'_/ Fig.4: input and output waveforms for a latch. show all possible states of a latch. The truth table in Fig.3 shows the various combinations of inputs and outputs. We should explain that there are two special input conditions. When both inputs are binary 1, the state of the latch is not affected. Since we don't know which state the latch is in, we simply designate the output with the letter X - which, of course, can represent 1 or 0. Another special condition occurs when both inputs are binary 0. That will force both outputs to the binary 1 level. Looking at the Q output, you will see a binary 1 output and, therefore, would suppose that the the flipflop is set. However, that is not the case because the Q-bar output is also a binary 1, implying that reset is an ambiguous state that does not represent either the set or reset condition. It should be avoided by eliminating the possibility that both inputs could go to binary 0 simultaneously. The operation of the latch can also be illustrated with input and output waveforms as shown in Fig.4. Take a minute to look over those signals to be sure you understand the operation of a flipflop. The way to do it is simply to observe the Q output to determine the state of the flipflop. Note how the set and reset inputs change it. The Q-bar output, of course, is simply an inversion of the Q output except in the ambiguous state. You can also construct a latch using NOR rather than NAND gates. A NOR latch is shown in Fig.5. The flipflop has normal and complement outputs, but note that the positions of the set and reset inputs have been reversed. Because the operation of a NOR gate is different to that of a NAND gate, the signals used to change the state of the flipflop must be binary 1 rather than binary 0, as with NAND gates. To tell the truth Fig.5: RS flipflop constructed of N OR gates. As with logic gates, a truth table can be used to IT INPUTS OUTPUTS II S R 0 0 0 1 0 1 1 0 0 1 X 1 1 Fig.3: the truth table for an RS flipflop. 86 SILICON CHIP u 1 INPUTS ij I SET RESET 1• . D D D 1 1 1 i X = EITHER D DR 1 • = AMBIGUOUS STATE Fig.6: truth table for a NOR latch. D 1 D 1 OUTPUTS 0 ij X D X 1 D 1 D o· X = EITHER D DR 1 • = AMBIGUOUS STATE , SET 0 , nJ1 I 0:J I ~1I I I I I I RESET 0 I ,I 0 I L I I I i n AMBIGUOUS S ! A T E ~ Fig.7: timing waveforms for a NOR latch. Normally, both the set and reset inputs will be binary 0. At that time, the flipflop will either be in its set or reset state. To change the state of the flipflop, a momentary binary 1 pulse is applied to either the set or reset input. Fig.6 shows the truth tble for a NOR latch. The operation of that circuit is further described by the timing waveforms shown in Fig.7. clearly defined logic levels are created by that simple circuit, the problem lies in the garbage generated by the switch in the brief time while it being is opened or closed. The waveforms of Fig.8 illustrate that effect. Fig.9 shows a latch debounce circuit. A singlepole, double-throw (SPDT) switch must be used in this application. While the contacts still bounce at the inputs to the latch, they have no affect on the output. Recall that if a signal is repeatedly applied to the set or reset input, the flipflop will not change. The result is an output signal that follows the switch conditions, but whose transitions from Oto 1 to Oare clean. A NOR latch can also be used for switch debouncing, as shown in Fig.10. However, note that the switch input is + 5V, or a binary 1, rather than ground (binary 0) as in the NAND latch. Apart from that, the operation of the circuit is similar. .,. +5V . Debounce A popular application for a latch is switch debouncing. Whenever two metal contacts are opened or closed, they will often vibrate or not cleanly make contact for a short duration. Any dirt or other foreign matter on the contacts will aggravate the problem. The result is multiple pulses or spikes during opening or closing. Such noise can falsely trigger logic circuits. A typical arrangement is shown in Fig.8. With the switch open, the output is a binary 1 level, as seen through the resistor. When the switch is closed, the output is brought to ground or binary 0. While clean, CONTACT BOUNCE NOISE SWITCHOPEN(+5V) ~ / ~ t Fig.10: a NOR latch used for switch de bouncing . Clocked RS flipflop The latch or RS flipflop is an asynchronous sequential circuit. That means that the output changes state immediately upon application of the input signals. On the other hand, some logic circuits act in response to a master timing signal called a clock. A clock is an oscillator circuit that generates a fixed-frequency periodic sequence of pulses that are used to control all timing and sequencing operations in a digital circuit. Logic circuits controlled by a clock are referred to as synchronous because all changes of state are initiated and occur in step with the clock signals. Clocked logic circuits are more predictable and are generally immune to "race" conditions that exist in some ,,T oi------ Fig.11: a clockdriven RS flipflop. SWITCH CLOSED (OV) Fig.8: waveform for undesired switch-contact bounce , SET 0 +5V RESET ~~, I OL~ I..---_ a o- - - - ---, I CLOCK +5V Fig.9: a NAND latch used for switch debouncing. 0 Fig.12: timing waveforms for a clocked latch. FEBRUARY1988 87 OATAINPUT=O=Q CLOCK CK Q Fig.13: logic symbol for a D-type flipflop D CK Q 0 0 0 1 0 1 X 0 X 1 1 1 1 D 0 III 1 CK Fig.15: truth table for a D-type flipflop. 0 I Fig.16: timing waveforms for a D-type flipflop. Fig.14: a D-type flipflop made from a quad 2input NAND integrated circuit chip. asynchronous circuits. A basic latch can be used synchronously, as shown in Fig.11. Here the set and reset inputs are buffered by NAND gates. The operation of those NAND gates is controlled by the clock. It is assumed that the latch is a NAND flipflop with set and reset inputs which must momentarily be switched to the binary O condition to cause a change of state. To set the latch, a binary 1 is applied to the set input and a binary O is applied to the reset input. With those inputs, the latch does not change state immediately. The reason for this is that the clock is normally in the low position. That inhibits the NAND gates, keeping their outputs high and the latch unaffected. When a binary 1 clock pulse occurs, the NAND gates are enabled and the set and reset input signals are applied to the S and R inputs of the latch. The S input goes low while the R input remains high. The result is that the latch is set and the Q output goes to binary 1. To reset the latch, the reset input is made binary 1 and the set input is made binary O. When a binary 1 clock pulse occurs, the latch changes states. This form of synchronous operation is better illustrated with timing diagrams as shown in Fig.12. Various input and output conditions are illustrated. Note that the actual change of state occurs on the positive-going or O to 1 transition of the first clock pulse following an input-state change. input is required to initiate the change of state. Note that when the clock is 0, the flipflop simply remains in the state to which it changed on a previous clock pulse. When the clock pulse is binary 1, the latch stores the input state. If the input is binary 1 while the clock is high, the latch will set and its output will be binary 1. If the input is binary O while the clock is high, the latch will reset and the normal output will be binary 0. Keep in mind that while the clock input is high, the normal output directly follows the signal applied to the D input. Ordinarily the clock only occurs for a very short interval. Because of the input gating circuits, ambiguous states cannot occur in D-type flipflops. The waveforms in Fig.16 summarise the operation of the D-type flipflop. All possible combinations of inputs and outputs shown in the truth table are repeated in the timing diagrams. Take a look through them to confirm your knowledge of the circuit's operation. Storage registers One of the main uses for D-type flipflops is to form storage registers. A storage register is a circuit capable of storing a binary word. One flipflop is need+5V0---+------+------<1---- D-type flipflop The D-type flipflop is a variation of the gated latch and it is a synchronous circuit in that it uses a clock signal to control the setting and resetting operations. The main difference between the D-type flipflop and the gated latch is that the D-type circuit has a single input, as shown in Fig.13. To set the flipflop, a binary 0 is applied to the data input. The flipflop transfers the input value to its output when a clock pulse occurs. Fig.14 shows a D-type flipflop with NAND gates. With that arrangement, a D-type flipflop can be quickly constructed out of a standard quad 2-input NAND gate. However, that is not usually necessary as ICs containing 2, 4 or 8 D-type flipflops are readily available. The truth table in Fig.15 illustrates D-type flipflop operation. Here we are assuming that a binary 1 clock 88 SILICON CHIP r· ------- ------- ------- --- - , O I SWITCH I REGISTER I O I I I I _ I I . I ----- ------ ----- +5V0-------------4>----___, Fig.17: a 4-bit storage register. ___ J ed for each bit in the word. For example, to store one byte of data, eight flipflops are needed. Fig.17 shows a storage register for a 4-bit word. The parallel inputs to the register are supplied by a set of switches referred to as a switch register. The switch register allows you to manually select a binary word to be stored in the register. The output of the register drives light-emitting diode (LED) driver circuits, to indicate the flipflop states. Note that flipflop A is designated as the most significant bit (MSB), while flipflop D is the least significant bit (LSB). Therefore, in Fig.17, the word stored is 1010. JK flipflops The most versatile form of storage circuit is the JK flipflop. It can perform the functions of both RS and Dtype flipflops but also has its own unique features. The JK flipflop is widely used to form storage registers but finds its greatest application in sequential logic circuits such as counters and registers. You will learn more about these circuits in a future lesson. The symbol used to represent a JK flipflop is shown in Fig.18. We won't discuss the internal logic circuits of a JK flipflop because they are somewhat complex. Besides, you don't really need to know what's inside to understand its operation or to use it. The JK flipflop has five inputs and two outputs. The S and C inputs, meaning "set" and "clear", are similar in operation to the set and reset inputs on a basic latch. The J and K inputs are synchronous inputs similar to the set and reset inputs on a gated latch. "J" means set while "K" means reset. The T input is for the clock. Finally, standard normal (Q) and complement (Q-bar) outputs are generally provided. The S and C inputs are asynchronous in nature. Those inputs are normally held high and in that state have no affect on the operation of the flipflop. However, to set or reset the flipflop as you would an ordinary latch, momentary low signals are applied as needed. For example, to reset the flipflop, a binary 0 pulse would be applied to the C input. The normal output would then go to the binary O state. The truth table in Fig.19 illustrates the effect that the S and C inputs have on the outputs. The results are identical to those obtained with the NAND latch discussed earlier. It is necessary to avoid the condiSET SET Fig.18: logic symbol for a JK flipflop. NORMAL CLOCK--T RESET COMPLEMENT CLEAR Fig.19: truth table for the S and C inputs of a JK flipflop. INPUTS OUTPUTS s C Q Q 0 0 1 1 0 1 D 1 1 0 X 1• 1 0 1 x X = EITHER 1 OR 0 • = AMBIGUOUS STATE AB (a) (b) Fig.20: clock pulses showing negative (a) and positive (h) edge triggering. tion where both Sand C inputs are low, so that the ambiguous state can be avoided. The asynchronous S and C inputs override the J, K and T synchronous inputs and their effect is immediate. The main application for the S and C inputs is presetting. To preset a flipflop means to put it into one state or another prior to another operation taking place. An example is the resetting of a storage register. Resetting or clearing a register means setting all the flipflops to the binary O state. That can be done by connecting all the C inputs of the flipflops together and applying a low pulse. The register is then said to be cleared. Presetting can also mean setting the flipflop. Occasionally it is necessary to load a specific binary number into a register prior to another operation beginning. By the use of external gates connected to the S and C inputs, any binary number can be preloaded into the register. Now let's consider the synchronous inputs. As in a gated latch, the J and K inputs are used to set and reset the flipflop but under the control of a clock pulse. If the J input is made binary 1 and the K input binary 0, the flipflop will be set when the clock pulse occurs. If the J input is a binary O and the K input is a binary 1, the flipflop is reset on the occurrence of the clock pulse. In most JK flipflops, that change of state occurs on the trailing or negative edge of the clock signal, as illustrated in Fig.20a. Some flipflops initiate a set or reset operation on the positive or leading edge of the clock signal as shown in Fig.20b. Negative edge triggering, however, is more common. When both the J and K inputs are held at binary 0, nothing happens. Even when a clock pulse occurs, no change of state occurs. The flipflop simply remains in the state in which it was previously set. When both the J and K inputs are binary 1, an unusual action occurs. When a clock pulse appears, the flipflop will be toggled or complemented. What that means is that on the trailing edge of the clock pulse, the flipflop will simply change state. That unique feature of the JK flipflop allows it to be used in a variety of counter and frequency divider circuits as you will see. Fig.21 illustrates the toggling or complementing mode of operation. Synchronous operation of the JK flipflop is summarised by the truth table in Fig.22 which shows the four possible combinations of the JK inputs. Note that the output is expressed in two ways. First, the Qn column is the normal output state of the FEBRUARY1988 89 f--:- CLOCK PERIOD M 1 CLOCK 0 1 0 CLOCK (T) 01---' I OUTPUT PERIOD • 0 I 1---...; Q Fig.21: the toggling or complementing of a JK flipflop by a clock when the JK inputs equal 1. I• INPUTS J K 0 0 0 1 1 1 D 1 0 Fig.23: synchronous timing waveforms of a JK flipflop. OUTPUTS On On+1 X X X 0 1 X X X 3.2MHz Fig.22: truth table showing synchronous operation of a JK flipflop. 6.4MHz CLOCK INPUT X=EITHEROOR1 flipflop. All entries in that column are designated X which means that the flipflop may be either set or reset. The other output column is designated Qn + 1 . That is also the normal output, but it designates the state of the flipflop after the occurrence of a clock pulse with the designated JK inputs. Fig.23 shows the timing waveforms of a JK flipflop. Work your way through those diagrams from left to right to be sure that you understand all conditions trailing edge triggering is assumed. Frequency dividers As indicated earlier, the JK flipflop finds its greatest use in various kinds of registers and counters. We won't discuss those here as a complete lesson is devoted to them later. However, we do want to illustrate several simple applications. A major JK flipflop application is in frequency A.C.E. R s NOTE: ALL JK INPUTS = 1 Fig.24: cascading JK flipflops to form a frequency divider. dividers. Refer to the input and output signals of a typical JK flipflop as shown previously in Fig.21. Note that each time a negative-going transition occurs, the flipflop will toggle. Because of that, the output of the flipflop is one half the frequency of the input. We say that the flipflop is a divide-by-2 circuit. If a 100Hz input signal is applied to the flipflop, the output will be a 50Hz signal. JK flipflops can be cascaded to perform frequency division by multiples of 2 (4, 8, 16, 32 etc). In Fig.24 we show four JK flipflops cascaded with the normal output of one connected to the T input of the next. Naturally, each flipflop divides by 2. With the 6.4MHz ESTABLISHED OVER THIRTY YEARS 1 0B/3 Kenneth Road, Manly Vale 2093. Telephone (02) 949 4871. cn microbee 0/1/)computer COMPUTERS & COMPONENTS Reconditioned "pre-loved" Microbee 32K personal computers. These units are in good condition, requiring only a suitable 12V DC power supply and interface cable to put it to work on your VDU. 1 1r·i·•:,~1-'.ttta A genuine bargain at only $210.00 . P&P NSW $4.30; interstate $6.50. The Compack Printer Stacker - dispenses your printer paper, eliminates cluttered table tops. Will support a 30kg printer. Tray capacity 500 cont. sheets (8.5 x 11 in). Price $30.60. P&P $3.50. SILICON CHIP 400kHz BOOkHz ELECTRONICS CENTRE The solution to paper & printer problems! 90 . 1.6MHz 12V DC 1 amp power supply - $15.95. P&P NSW $3 .50; interstate $5.00. New PC Boards MB8431 Anti Glitch Card ........ $3.50 MB8346 Viatel Card ............ ......... $3.50 Give your floppies a safe home DX-100B diskette file - stores 100 5.25in floppies; lockable (2 keys supplied). Special price to SILICON CHIP readers: only $26.50. P&P $2.00. We also have a 3.5in version that holds 90 disks. Price $18.95 plus $2.00 P&P. These p1 ices can 't last so get in quickly. +5V I II III II II I I II I I I II I I II I 112•74LS113 14 I I IIIIIII I III 11 I 1 1 - 1k 10k 1 _____, ~---'-------'---'---'I 1 -'--J.. 1 1 1 1 1 1 I I I I I 1 I r L Fig.25: output waveforms from a 4-stage frequency divider. Negative edge triggering is used. input shown , the flipfl op outputs are 3.2MHz. 1.6MHz, 800kHz and 400kHz. The wa veforms of Fig.25 show th e full operation of the circuit. The division fa ctor for a given number of flipflops is shown by the equation below. F represents the frequency division rati o whi ch is equal to 2 raised to the power n, whe re n is the number of flipflops in the c hain . With four flipfl ops. the frequ ency ra tio is : F = 2 11 = 2 4 Learn by building Fig.26 shows a simple circuit you can build to unde rstand the opera tion of a JK flipflop. Here a 555 time r IC is connected as a clock. It generates a clock signal that will r epea tedly toggle the JK flipflop whenever the pushbutton switch is depressed. When the switch is r eleased, the JK inputs a re held low a nd .,. > NORMALLY CLOSED PUSH BUTTON SWITCH Fig.26: a coin flipflop simulator illustrating the operation of a JK flipflop. the clock has no effect on the flipflop. The outputs of the JK flipflop are connected to LED driver circuits. You will find that the outputs will always be complementary, with one LED on while the other is off. The circuit simulates the flipping of a coin. For example, heads might represent set while tails indicates reset. To flip the coin, all you do is press the pushbutton switch. The JK inputs go high. The flipflop will then toggle repeatedly for a period of time. When you release the pushbutton, the JK inputs go low. The flipflop will then be set or reset depending upon where the flipflop was just prior to releasing the switch. Because of the high-speed nature of the clock, and the random depressing and releasing of the pushbutton, the circuit accurately simulates the random flipping of a coin. Reproduced from Hands-On Electronics by arrangement. Gernsback Publications, USA . it © SHORT QUIZ ON LESSON 4: UNDERSTANDING FLIPFLOPS 1 . When a flipflop is storing a binary 1 , it is said to be: b. set a. reset 2. Another name for a latch is_ _ _ _ _ _ __ 3. A common application of a latch is,_ _ _ __ 4 . To clear a flipflop means to: a. reset it to O b. preset it to 1 5. Flipflops such as the D and JK types which change state on the occurrence of a clock pulse are said to be _ _ _ _ _ _ _ _ _ _ _ _ __ 9. A 6-bit register is made up of 0-type flipflops. The flipflops are labelled A to F with A being the LSB and F being the MSB. The flipflop outputs are A =low , B = high, C = high, D = low, E = high , F = high , where high = 1 and low = 0 . The decimal equivalent of the binary number stored in the register is_ _ _ _ _ _ _ _ __ 1 0 . A frequency divider made up of seven cascaded JK flipflops generates an output frequency of_ __ ,kHz from an input of 51 2kHz ANSWERS TO QU IZ 6 . When the JK inputs are O and a clock pulse occurs, the flipflop will: a. set b. reset c. tog£)1e d. not change state 7. When the JK inputs are 1 and the clock pulse occurs, the flipflop will : b . reset a. set d. remain in the same c. complement state 8. The clock input to a D flipflop is high . The D input is low. The complement output will be_ __ (ZH)1J7 = LG + ZH)1"?, ~9) ZH)1J7 ·o ~ (v9 = o~~o~~ = 'v'B:Jm.::1l t9 ·5 ·peJJeAUI eq ll!M 1nd1no 1uewe1dwoo e41 ·1ndu1 a e41 se ewes e41 eq IIIM 1nd1no 1ewJou e41'46141ndu1 )100!0 941411M ·4614 ·g e16601 JO 1uewe1dwoo ·p ·z e1e1s e6ue40 1ou ·p ·g SllOUOJ40UAS . 9 o 01 11 1eseJ ·e ·v 5upunoqep 1oe1uoo JO 4011Ms ·s dOIJdllJ S8 ·c ies ·q · ~ FEBR UARY1988 91 2 piece computer service kit If you are doing service work there is nothing more frustrating than making do without the correct tools. This 12-piece toolkit from Dick Smith Electronics goes a long way towards solving that problem. It has four screwdrivers, two with Phillips head, two nutdrivers, a reversible torque screwdriver and a pair of needlenose pliers. Also included is an IC extractor and an IC inserter (both with pin straighteners), a pair of tweezers and a Arista stereo mixer for disco or PA 3-claw part holder. The whole kit is packed in a convenient zippered case measuring 23 x 15cm. The kits are on sale at all Dick Smith Electronics stores. Printer sharer Most offices have more than one computer but seldom need one printer per computer. More often, there are a couple of printers which need to be shared around. The best way of coping with these situations is to have a printer sharer, preferably with a large memory buffer. The buffer allows files to be dumped so that the computer concerned can go on with other tasks. Logo Computer Centre have produced three printer managers for these applications. There is the model BF64U universal model with Centronics and serial interfaces, the 64D which allows two printers to work with one computer and the BF64MD which comes in several configurations which all include a 256K buffer. For further information, contact Logo Computer Centre on (02) 819 6811. Many clubs and small organisations can use a small mixer for discos, fetes and meetings. This MM5 mixer can handle one microphone input, two stereo magnetic cartridge phono inputs and two stereo line inputs (tuner, tape etc). It has bass and treble controls, headphone monitoring and provision for talk-over which allows the microphone to over-ride the program signal. For futher information, contact your local Arista stockist or phone Arista Electronics Pty Ltd on (02) 648 3488. Thumbwheel switches from Geoff Wood 10 disc file for safe data storage Anyone who becomes seriously involved with computers quickly finds that conveniently storing the floppy discs becomes a problem. Ideally they should be stored upright and away from dust, dirt and splashes from coffee or beer. This deluxe file holds up to 100 5.25in floppies in safety. It is well made with a lockable smoked plastic cover. Ace Radio presently have these 100 disc files and a similar version for the smaller 3.5in flopoies at a special price (see their advertisement on page 90). 92 . SILICON CHIP The 5.25in disc files would also make a fancy storage case for compact discs. They would hold about 36 CDs. Contact Ace Radio, 10B/3 Kenneth Road, Manly Vale, NSW 2093. Phone (02) 949 4871. When it comes to mounting a lot of rotary switches close together, thumbwheel switches cannot be beaten. They can be mounted very close together, are easy to set and the setting can be seen at a glance. These C&K thumbwheel switches come in decade and BCD types and are available from GRoff Wood Electronics. Geoff's price is $6.85 for each thumbwheel switch and $1.90 for a pair of end plates. Phone (02) 427 1676. New cases from Geoff Wood Problems? As you will quickly find when you start to look for instrument cases, there is not a wide range available. We need more, whether they are wider, higher, smaller or better looking. Now Geoff Wood Electronics have put a range of instrument cases from Spain into stock. These are nicely finished and some have sloping fronts. Our photographs show two of the boxes available, both of which are priced at $41.95. For further information, contact Geoff Wood Electronics, 229 Burns Bay Road, Lane Cove West, NSW 2066. Phone (02) 427 1676. ... and you don't have our 112 page catalogue ... Evolution of Electric Railways: ctd from p.84 was let by Melbourne city's Metropolitan Transport Authority for the supply of 130 Articulated Light Rail Vehicles for use on long tram routes and later on two converted railway routes. These advanced vehicles consist of two cars sharing three bogies. Propulsion by two 600 volt DC 195kW AEG traction motors can speed the 32.5 tonne vehicle with its 182 passengers along at a brisk 72 km per hour. The modern control system uses AEG thyristor DC-to-DC chopper circuits. Melbourne showed the world that the age of construction of 1500 volt DC city underground railways was still alive and well by opening their City Loop Line in 1981. Circling around the city from Spencer Street Station via Flagstaff, Museum and Parliament Stations to Flinders Street or outer suburbs, this new line takes suburban passengers within walking distance of their city workplace, easing street traffic congestion. Adelaide's longest surviving Electric Tramway, the famous fast Glenelg Tram, has always been an example to Australia of the quickest way to move people. The people of Brisbane were for many years served well by an electric tramway installation which reached the peak of its importance about 1930. Sadly, Brisbane eventually followed the lead of many other cities and scrapped all electric trams in favour of diesel buses. Next month, we continue with a description of the Newcastle and Sydney tram systems. ~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB & front panel published in SILICON CHIP, ET! and EA. you've got real problems! ARISTA ... your one-stop problem solver. Audio leads ... Batteries ... Chargers ... Battery holders ... Cables .. . Car accessories ... CD accessories ... Converters ... "Cutec" ... Earphones ... Fuses ... Headphones ... Intercoms ... Knobs ... Microphones and accessories .. . Mixers ... Multimeters ... Plugs/Sockets, etc .. . Plug adaptors ... Power packs and leads ... PA .. . Disc and Tape care ... Security equipment ... Signal modifiers ... Solderless terminals ... Storage boxes .. . Switches ... Telephone and TV accessories ... Tools and Technical aids ... Video accessories ... Wiring accessories ... You name it and we're bound to have it ... Try us ... NOW! Get your catalogue ... it'II solve a whole lot of your problems! Just send $2 + 50c p&h and your return address to: 651 Forest Road, Bexley, NSW 2207 Phone (02) 587 3491 for instant prices ARISTI\. 4-HOUR TURNAROUND SERVICE PO BOX 191, LIDCOMBE, NSW 2141 ELECTRONICS PTY LTD FEBRUARY1988 93 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Infrared security beam I am desperate for a circuit which gives me an infrared security beam with a logic circuit that will only allow a buzzer to operate when people pass in one direction. I live on acreage and currently use an Arlec security beam at the gate to let me know when people come in the gate but it doesn't discriminate between in/out or ants! Also, I'd like a circuit to turn on the lights when I walk in the room and which will count the number of people coming and going and switches off when the last one leaves. It must, of course, only operate at night. (L.W., Caboolture, Qld). • Both circuit concepts you propose seem quite feasible although the second one could involve quite a lot of circuitry. To produce a circuit which detects people moving in only one direction, you need two infrared beams, each with their own transmitter and receiver circuitry. The beams would be arranged so that the person breaks one beam before moving through the other. Then you would need logic built into the circuit so that if the second beam was broken before the first, caused by a person going out the gate, nothing would be registered by the circuit. While the idea sounds fairly complicated, it could probably be achieved quite easily with one or two flipflops and some gating. But would such a scheme be good enough? Could you rely on people walking through the gate in single file so as to make it easy for the circuit to count them? And would the circuit cope with vehicles and people at the same time, as would happen with the gate being opened and shut to allow a vehicle to pass through? You would have to think fairly carefully about these problems before a suitable circuit could be designed. As far as the circuit to turn on the lights in a room is concerned, it would also need two infrared beams or equivalent sensors to count people. The counting could be performed by an up/down counter such as the CMOS 4029. Having rabbited on about the concept, we'll see what we can produce and perhaps publish the results in the Circuit Notebook pages of a future issue. Higher power car stereo conversion I purchased a kit for converting a car stereo to a mantel radio [page 54, November 1987). The kit was simple enough to put together but when I turn the volume up to anywhere around half way, or if the bass is turned up, as the bass beats come through [either from the radio or cassette) the LEDs on the unit fade slightly and the sound distorts. The radio-cassette player in question is a Sansui RX-7101 and it is rated at 15 watts per channel with a peak of 20. The fuse in the power lead is rated at 4 amps. If you could possibly shed some light on this problem I would be grateful. (H.P., Beverley Park, NSW). • Your car stereo requires more current than the modest power supply we have designed can supply. You need a bigger transformer to supply more current. We suggest that you substitute one sold by Jaycar, Cat. MM-2005. This modestly priced multitap transformer can supply 15 volts AC at 4 amps which 94 SILICON CHIP + MEMORY 4700 25VW + _ 4700 25VW + - 13.4V Fig. 1: the output of the car radio supply can be boosted by adding a PNP power transistor. Mount the transistor on a heatsinlc. is just what you want. The same tranny is available from Altronics, Cat. M-2165. You also need a higher current 3-terminal regulator. You can buy 12V 3-amp regulators in a TO-3 metal package but these can be hard to get and are a lot more expensive than the 7812 TO-220 style regulators we specified originally. You could also use the LM350 adjustable 3-amp regulator. We suggest you boost the output of the existing regulator with the circuit shown in Fig.1. It uses the 7812 to control an MJ2955 power transistor. It works as follows . If the 7812 is called upon to deliver one amp, 2.2 volts will be dropped across the associated 2.20 resistor. By emitter follower action, the MJ2955 will then develop 2.2 volts across its associated 10 resistor and therefore the transistor will deliver 2.2 amps from its collector. Hence the whole circuit will deliver about three times the maximum current capability of the 7812 regulator. The power transistor should be mounted on a heatsink. +15 >'-+-----OUTPUT TO MODULE 1 0.1 Bridging 100W amplifier modules I am interested in the 100W amplifier module described in the second issue of SILICON CHIP. Over the next six months I propose to build at least six of these modules, incorporated into three stereo slave amplifiers, for public address applications. There are a couple of issues I would like to raise. Assuming PA applications, is it possible to easily switch such a stereo amplifier into a bridged mono mode? Second, is it proposed to develop a project along similar lines to this 100W project but with an output of the order of 300 to 500 watts into 40, so that it too can be incorporated into a stereo slave amplifier, with a bridging operation as well? Lastly, how about a versatile, high quality 8 - (or 12-) 4-2-1 mixer and a simpler 6-2 mixer, to complement the power amplifiers described above? (R.W., Scoresby, Vic). • Yes, it is quite easy to use the 100W power modules in bridge mode but there are a number of points to consider before you rush off to buy the parts. First, if you wish to use the 100W modules in bridge mode, you will only be able to do so if you use the bridged amplifier to drive an 80 load. You could not use it with a 40 load. The reason is that each amplifier in a bridge configuration "sees" half the real load impedance. Therefore, if you were to use a 40 load, each amplifier module would "see" a 20 load and would be overloaded. If you were using the PTC thermistors we specified for protection, they would operate prematurely and the effective power output would be low. Bridged power output into an 80 load would be close to 200 watts, depending on the regulation of the power supply. This general rule about bridging applies to all amplifiers, by the way, so there is no way around it. If INPUT C>-:-11--e--"" 220k 10k 1'/o -15V 10k 1% ... > - - - - OUTPUT TO MODULE 2 Fig. 2: this simple circuit allows two power amplifier modules to be driven in bridge mode. Be sure to use 8-ohm loads. we had been designing the amp modules to drive 40 loads in bridge mode we would have had to make sure that each module could safely handle a 20 load. That would have made them much more expensive. If you want more power, and you want to drive a 40 load, you would be better off considering the Studio 200 stereo power amplifier presented in this issue. It is essentially the same design but upgraded with a bigger power supply and higher-rated output transistors. By using one of these upgraded modules you get a lot more bang for your buck. With one module driving 40 you could get close to 200 watts, if you had a very well regulated power supply. That would mean using a transformer rated at around 400V A or more. Again, you could use the upgraded modules in bridge mode and probably get somewhere around 350 watts into an 80 load, depending on how big and how well regulated your power supply was. Again, you would need a big transformer, rated at 600VA or more. A suitable circuit to enable the modules to be driven in bridge mode is shown in Fig.2. This uses a dual op amp, type TL072. There is one more point to consider. You mention using the amplifiers for public address applications but you have not specified if you will be using them to drive line output transformers. If that is what you intend, you are suggesting a whole new ball game and one for which these modules were not designed. We'd be wary about using them for driving line transformers without at least incorporating flyback diodes across each of the paralleled output transistors and without a means of adjusting the DC output offset voltage close to zero. The offset voltage needs to be very low othenvise substantial DC will flow in the transformer. This would cause problems in the transformer and could cause excessive dissipation in one half of the power amplifier. We have not done any work along these lines and so we hesitate to recommend them in this more stringent application - they may work OK but we couldn't guarantee it. We'll have a look at your suggestion for a mixer project but it is likely to take some time to develop. In the meantime, have a look at the Jaycar 8002 8-channel mixer. It would take a lot of careful design to better its excellent performance. ~ Stereo Amplifier continued from page 44 Now switch your multimeter back to the 200V DC range and connect it across one of the 5600 resistors. Adjust VRl for a reading of 28 volts. This gives a total quiescent current of 50 milliamps. After five minutes or so, check the quiescent current and readjust VR 1 if necessary to get the correct voltage across the 5600 resistor. Now switch off, remove the two 5600 resistors and insert the fuses. If all is well, you can now assemble the second module and go through the same procedure. ic FEBRUARY1988 95 CEN'I' Cash in your surplus gear. Advertise it here in Silicon Chip. We now offer a short form kit for the alkaline (lighter) battery, and the "Satellite Siren". What's in this kit? - 1 , complete receiver PCB kit for only x PCB and components kit, 1 x bat$39.95 including pack and post. Yes, NEARLY 1500 printer buffer kits now that's everything you need and yes, . tery holder, 1 x barrel keyswitch with sold . Prices start at $39 for a 256K two keys, a suitable plastic box. All it's dirt cheap! short form kit. All items advertised are in this for only $29.00 including pack Stereo VU Meter (June 87 EA). Comstock. Dealer enquiries welcome. Bulk and post. So what else will you need plete kit featuring a dual mechanical VU discounts. Schools, Govt. Depts. later to complete the unit? - 4 x AA meter. Easy to assemble; even the orders accepted. Oh yes!!, IBM comnicad batteries at $3.00 each and 1 x meter is soldered directly to the printed patible. Australian designed and 12V piezo siren at $16 each. Yes, all circuit board. Any audio signal can drive manufactured. Ideal project for user these prices are unbeatable! it since its sensitivity is adjustable from groups or students. For a free catalog Passive lnfrared Movement Detector volts right down to 3mV! Can double up send a 37c stamp to: Don McKenzie, (PIR) (Dec.87 SILICON CHIP). A PIR as a microphone preamplifier. Features 29 Ellesmere Cres., Tullamarine 3043. detects body heat and is the most optional backlighting; incandescent reliable type of detector currently lamps provided in kit. This unit is inexOATLEY ELECTRONICS - for exavailable. This unit employs a dual elepensive at its normal price of $1 7. 90, clusive and selected kits. Take note of ment pyroelectric detector and its perhowever during February you can buy it our low prices and some February formance is equalled only by the more for only $9.95 (p&p included). Yes it is specials: expensive commercial units. With the a bargain; at this price you can afford UHF Remote Controlled Key (Jan. 86 wide angle lens fitted, it has a viewing to build one into every piece of audio EA). A proven and reliable wireless angle of 90 ° and a useful range of equipment you own! remote switch; 1000s sold! Has more more than 25 metres! Satellite Siren (Sept. 87 EA). Add the than 13,000 possible code combinaprotection of this complete second This unit can easily double up as a selftions. Multiple outputs and an on-board alarm system into your existing alarm contained alarm since provision is made off-on indicator enable this unit to system . Automatically gain the benefit to extend its 'on" time. This facility also remotely switch car burglar alarms, car makes it useful for activating outside of back-up battery operation and a comcentral locking systems, home burglar plete and remotely placed second lights when people enter your alarms, etc. The small transmitter also alarm system! This unit is simple to inpremises; just add an external relay. has provision for a key ring . Our stall; it requires only two connections to During February, we will provide a special February package includes 1 your existing alarm system. Comes into complete kit for the PIR, including x transmitter PCB kit, 1 x transmitter · action when the main alarm is vandalisboth the narrow and wide angle plastic case with battery clips and ed, the main alarm power is interrupted, lenses for only $59.95, p&p included. pushbutton switch, 1 x miniature 12V or the vehicle battery is disconnected. Mail address: Oatley Electronics, PO Box 89, Oatley, NSW 2223. Shop address: 5 Lansdowne Pde, Advertising rates for this page: Classified ads - $7.00 for up to 15 words plus 40 cents Oatley West, Sydney, NSW 2223. for each additional word; Display ads (casual rate) - $20 per column centimetre (max. Phone (02) 579 4985. 10cm) Closing date: five weeks prior to month of sale. If you use a PO Box number, you must You can ask us to include our stock list include your permanent address and phone number for our files. We cannot accept ads with your next purchase or, for more insubmitted without this information. formation only, send us a selfTo run your own classified ad, put one word on each of the lines below and send this form addressed envelope (21 x 8cm). with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. FOR SALE PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) 16($7.40) 17 ($7.80) 19 ($8.60) 20 ($9.00) Name .. 18 ($8.20) ....... .. .. ... ··· ················ Address Suburb/Town Enclosed is my cheque or money order for $ ....... ....... . Bankcard □ Visa □ Card No Signature .............. .. .... . . 96 SILICON CHIP Postcode . .............. or please debit my Advertisers Index Our advertisers are vital to the success of SILICON CHIP . Please give them your support. Ace Radio ............ .. ... .......... 90 Altronics ... ........ .... .... ..... 66-69 Arista Electronics .... .. ........... 93 Dick Smith Electronics .... 1 2, 1 3, 49,79 Elmeasco ..... .. ...... ............. IFC Geoff Wood Electronics ........ 45 Jaycar Electronics .......... 26-29 Oatley Electronics ..... .... ...... 96 RCS Radio ............. ... .......... 93 Scan Audio .. .. ......... ...... .... . IBC VSI Electronics ................. OBC Fluke. First Family of DMMs. When accuracy, performance and value are important, professionals the world over look to Fluke - the first family of DMMs. Reliable Fluke-quality 3½- or 4½-digit DMMs fit every need - from design engineering to industrial troubleshooting. There's the low-cost 70 Series - the most DMM you can get for the money. The tough 20 Series - totally sealed and built to survive the dirtiest, grimiest, roughest jobs. The reliable 8020B Series - made to withstand the rigors of the field service environment. The precise 8060A Series the most powerful and complete test and measurement system available in Phandheld package. And, of course, the versatile Bench/Portables that carry on the Fluke tradition for precision and durability in lab-quality bench instruments. Fluke comes in first again with the world's largest selection of quality accessories to help extend the capabilities of your DMM even further. There's no need to look anywhere else. Uncompromising Fluke design and leading edge technology are the reasons why attempts at imitation will never fool the millions of professionals that accept nothing less than a Fluke. FROM THE WORLD LEADER IN DIGITAL MULTIMETERS. IFLUKEI ® ELMEASCO ln11trument11 Pt11. Ltd. Dealer enquiries welcome raik to your local Elmeasco distributor about Fluke • A.k..L._ John Pope Electrical (062) 80 6576 • J Blackwood & Sons (062) 80 5235 • George Brown (062) 80 4355 • ~ Ames Agency 699 4524 • J Blackwood & Sons • George Brown 519 5855 Newcastle 69 6399 • Auto-Catt Industries 526 2222 • D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Ebsen 707 2111 • Macelec (042) 29 1455 • Novacastrian Electronic Supply (049) 62 1358 • Obiat Ply Ltd 698 4776 • Petro✓ect 569 9655 • David Reid 267 1385 • Selectroparts 708 3244 • Geoff Wood 427 1676 • N.TERRITORY J Blackwood & Son (089) 84 4255, 52 1788 • Thew & McCann (089) 84 4999 • OJfEN~N£ Auslec (07) 8541661 • G.Brown Group (07) 252 3876 • Petro-Ject (075) 91 4199 • St Lucia Electronics 52 7466 • Cliff Ele rorncs 1 55 • Nortek (Townsville) (077)79 8600 • L.E.Boughen 369 1277 • Fred Hoe & Sons 277 4311 • The Electronics Shop (075) 32 3632 • Thompson IQstruments (Cairns) (070)51 2404 • SAUSTRALIA Protronics 212 3111 • Trio Electrix 212 6235 • Industrial Pyrometers 352 3688 • J Blackwood & Sons 46 0391 • Petro -Ject 363 1353 • TASMAWA George Harvey (003) 31 6533 (002) 34 2233 • VICTORIA Radio Parts 329 7888 • George Brown Electronics Group 878 8111 • G.B. Telespares 328 4301 • A.W.M. Electrical Wholesalers • Petro-Ject 419 9377 • J Blackwood & Sons 542 4321 • Factory Controls (052) 78 8222 • Mektronics Co 690 4593 • Truscott Electronics 723 3094 • W AUSTRALIA Atkins Carlyle 481 1233 • Debbie Instruments 276 8888 • Protronics 362 1044