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Electric Cars: Is The Future Here Now? SILICON CHIP $5.50* JULY 1997 NZ $6.50 INCL GST C I M A N Y D 'S A I AUSTRAL NE I Z A G A M S C I N O ELECTR SERVICING - VINTAGE RADIO - COMPUTERS - SATELLITE TV - PROJECTS TO BUILD Remote Volume Control for Your Hi-Fi Interfacing Your Computer to the Real World GETTING THE BIG PICTURE: The Inside Story on Philips’ Huge New Rear-Projection TV PLUS: l Points controller for model trains ISSN 1030-2662 07 9 771030 266001 l Low-cost waveform generator l Building the TV pattern generator PRINT POST APPROVED - PP255003/01272 July 1997  1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au Contents Vol.10, No.7; July 1997 FEATURES   4  Electric Vehicles: Where Are They Now? Electric vehicles are making it to market in the USA. We take a look at the latest offerings from GM, Ford and Toyota – by Sammy Isreb   7  Review: Philips 48-Inch Rear Projection TV No, it’s not like the projection TVs you’ve seen in clubs. This unit has a big, bright, beautiful picture & it won’t break the bank – by Leo Simpson 66  How Holden’s Electronic Control Unit Works; Pt.1 Electric Vehicles: Where Are They Now? – Page 4 We unravel some of the mysteries hidden in this very clever engine management system – by Julian Edgar PROJECTS TO BUILD 14  Infrared Remote Volume Control Simple unit controls a dual-ganged pot & two relays. Build it for your stereo system or model railway – by Leo Simpson 23  A Flexible Interface Card For PCs Addressable I/O card plugs into the parallel port & has eight opto-isolated inputs & eight relay outputs – by Rick Walters 29  Points Controller For Model Railways Infrared Remote Volume Control – Page 14 Build this $10 circuit & prevent solenoid coil burnouts in your points switching machines – by Rick Walters 42  Simple Waveform Generator Compact unit generates square & triangle waves from 100Hz to 20kHz. Use it to test amplifiers, filters, tone decoders & digital circuits – by John Clarke 54  Colour TV Pattern Generator; Pt.2 The operation may be complicated but it’s easy to build – by John Clarke SPECIAL COLUMNS Flexible Interface Card For PCs – Page 23 38  Serviceman’s Log The neighbour who made things worse – by the TV Serviceman 63  Computer Bits Removing programs from Windows 95 – by Jason Cole 78  Radio Control An in-line mixer for radio control receivers – by Bob Young 82  Vintage Radio Revamping an old Radiola – by John Hill DEPARTMENTS  2  Publisher’s Letter 22  Order Form 32  Circuit Notebook 71 Bookshelf 75  Product Showcase 91  Ask Silicon Chip 93  Notes & Errata 94  Market Centre 96 Advertising Index Simple Square/Triangle Waveform Generator – Page 42 July 1997  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Brendon Sheridan Phone (03) 9720 9198 Mobile 0416 009 217 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Mike Sheriff, B.Sc, VK2YFK Ross Tester Philip Watson, MIREE, VK2ZPW Bob Young Photography Glenn A. Keep SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $54 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Backing up is not hard to do These days most of us have a computer or have access to a computer and so most people are familiar with the concept of backing up their work. The reasons for doing so are plain common­sense. If you do have a computer failure and you have religiously backed up your files, then you won’t have lost a lot of work. I’m not just thinking about people in business in raising this topic. Many people with computers in their homes use them for quite crucial aspects of their lives. Students use them for writing essay assignments, for keeping track of research work and for writing theses. For an undergraduate to lose most or all of a thesis would be traumatic indeed. Similarly, people might use their computer for club records, for their medical records, financial records, share dealings, hobbies and so on. In every case, the loss of all this information can happen so quickly, in the blink of an eye so to speak, that the event can be emotionally shattering. And finan­cially shattering as well. And since hard discs are becoming larger all the time, the size of the potential data loss is also growing, at an exponential rate. Just recently, one of the machines in the SILICON CHIP office had such an event. One moment the machine was working perfectly normally, as it always had since the day it was pur­chased. The next moment, there was a screen message to say that one of the 1.6GB discs was unreadable. Just like that! As it happened, we were just about to replace that particu­lar disc drive with one of 3.2 gigabytes so the physical loss of the drive was of no particular concern. It turned out not be damaged anyway. But what about the files? Well, running CHKDSK produced many hundreds of files which all had to be renamed and then imported to be checked. Many were OK but some were not. The upshot was that we lost several days of work on this machine. All of this was in spite of the fact that we have backup procedures in place, whereby all working files are copied to the server every day and all those files are then backed up onto a DAT drive. Its capacity is 8GB. In theory, all we should ever lose, even if the server and all our computers were stolen or destroyed in a fire, would be one day’s work. But in practice, who knows? In fact, this one machine and the server’s drives were so full that the backup procedure had become a little loose. We could have lost a lot more work. We often hear of much worse cases, where people have not backed up anything for weeks, months or maybe never. Sooner or later, those people will suffer the consequences. Leo Simpson ISSN 1030-2662 WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 2  Silicon Chip FIBRE OPTIC NIGHT VISION TUBES Used US-made night vision tubes with blemishes. Have 25/40mm diameter, fibre-optically coupled input and output windows. The 25mm tube has an overall diameter of 57mm and is 60mm long; the 40mm tube has an overall diameter of 80mm and is 92mm long. Produces a good image in approximately 1/2 moon illumination, when used with a suitable lens, but can also be IR assisted to see in total darkness: 880nm illuminator is suitable. Excellent resolution, suitable for low-light video preamplifiers, etc. Each of the tubes is supplied with an EHT power supply kit that operates from 9V DC: $60 for a slightly blemished 25mm intensifier tube-supply kit, $80 for a slightly blemished 40mm intensifier tube-supply kit. We also have some tubes with more blemishes and are suitable for very sensitive IR testers: $35 for a slightly blemished 25mm intensifier tube-supply kit, $55 for a slightly blemished 40mm intensifier tube-supply kit. 110V TRANSFORMERS Used 240-110V transformers, about 100VA: $15. HELIUM-NEON LASER BARGAIN Large 2-3mW HeNe laser head plus a compact potted USmade laser power supply. The head plugs into the supply, and two wires are connected to 240V mains. Needs 3-6V 5mA DC to enable. Bargain: $100. 20A DC MOTOR SPEED CONTROLLER A slightly modified design to the one published in the June 97 issue of SC. PCB plus all on-board components (with two power MOSFETs!), plus the flyback diode and the capacitor needed across the motor: $18. 27MHz TRANSMITTERS New tested PCB assembly. Xtal locked on 26.995MHz, designed for transmitting digital information. Circuit features 5 transistors and 8 inductors – circuit provided. Power varies from 100mW to a few watts; 3-12V DC operation. Sold for parts/experimentation, should not be connected to an antenna as licensing may be required: $7 each or 4 for $20. MINI TV STATION Make your own mini TV station with this metal-cased, commercial transmitter with telescopic antenna. Dimensions 123 x 70 x 20mm, 12V operation. Includes power switch, indicator LED, RCA audio and video connectors, twin RCA-RCA lead. Our 32mm AUDIO PREAMPLIFIER kit ($8) comes (with an electret microphone) and a CCD camera will complete the station. Transmitter $30 or $20 when purchased with a CCD camera. REGULATED 10.4V-500mA PLUGPACK to power the whole system: $10. AUDIO - VIDEO MONITOR Compact high resolution 5-inch screen B/W audio and video monitor. Has two-way audio, built-in microphone, audio amplifier, speaker and pushbutton “talk” switch. Needs a preamplifier and microphone for remote audio monitoring (our 32mm audio preamplifier is ideal). Has two camera inputs to allow manual or auto switching (adjustable speed) between each camera. Needs 12V DC 1A (our switched mode supply is ideal), size 160 x 190 x 150mm, has audio and video outputs for connecting to a VCR etc. Monitor and 6-way mini input connector only: $125. Kit includes a large used 1.8° (200 step/rev) motor and used SAA1042A IC. Can be driven by an external or on-board clock; has a variable frequency clock generator. External switches (not provided) or logic levels from a computer etc determine CW or CCW rotation, half or full-step operation, operation enable/disable, clock speed. PCB and all on-board components: $18 for kit with 1 motor, $28 for kit with 2 motors. DIAMOND TESTER KIT Test if they’re real! PCB, on-board components and meter movement: Available late this month: $15. DC MOTOR New, Australian-made (Preslite) 12V DC motor used to power golf buggies. Low speed, very high torque. 75mm dia, 150mm long, 7mm dia 30mm long shaft, weight 2kg. Has three 5mm tapped holes for mounting. No load current 4A, loaded current 10A. Great for experimenting with battery-powered vehicles, wind generators etc. Limited supply at a small fraction of their real value: $36. A suitable speed controller is the 20A DC MOTOR SPEED CONTROLLER mentioned elsewhere in this advertisement. WOOFER STOPPER MkII Works on dogs and most animals, ref SC Feb 96. PCB and all on-board components, transformer, electret mic & horn piezo tweeter: (K77) $43. Extra tweeters (drives 4): $7 each. Approved 12V plugpack (PP6) $14. UHF REMOTE TRIGGER single channel Rx and Tx: (K77T) $40. MASTHEAD AMPLIFIER KIT Our famous MAR-6 based masthead amplifier. Two-section PCB (so power supply section can be indoors) and components kit (KO3) $15. Suitable plugpack (PP2): $6. Weatherproof box: (HB4) $2.50. Box for power supply: (HB1) $2.50. Rabbit-ears antenna (RF2) $7. (MAR-6 available separately). USED ICs Guaranteed, previously socketed ICs, never soldered to. Data not supplied. ♦146818P: real time clock: $4 ♦R65C21P2: 6821 PIA: $2 ♦P8031: 8-bit CPU: $2 ♦6803: 8-bit CPU: $4 ♦HD680G: 8-bit CPU: $4 ♦R6545: CRT controller: $2 ♦HD6845: CRT controller: $2 ♦HD6821: interface adaptor: $1 ♦AY3-1015: 8-bit UART: $4 ♦27C64: EPROMS: $2 ♦27C256: EPROMS: $3 USED PIR MOVEMENT DETECTOR Commercial quality 10-15m range, used but tested and guaranteed, have open collector transistor (BD139) output and a tamper switch, 12V operation, circuit provided: $10. 650nm VISIBLE LASER POINTER KIT YES, NEW 650nm kit!!! Very bright! Complete laser pointer that works from 3-4V DC. Includes 650nm/5mW laser diode, new handheld case 125 x 39 x 25mm, adjustable collimator lens, PCB battery holder: $35. SWITCHMODE POWER SUPPLY Compact (50 x 360 x 380mm), in a perforated metal case, 240V AC in, 12V DC/2A and 5VDC/5A out: $17. DISCO LASER LIGHT SHOW PACK The above 5mW/650nm kit plus our AUTOMATIC LASER LIGHT SHOW: $99. CCD CAMERA Tiny (32 x 32 x 27mm) CCD camera, 0.1 lux, IR responsive (works in total dark with IR illumination), connects to any standard video input (eg VCR) or via a modulator to aerial input: $120. 650nm LASER POINTER SPECIAL Light weight (2 x AAA) pen-sized pointer with 650nm laser diode!! Very bright!: $55. KITS FOR CCD CAMERA SECURITY New INTERFACE KIT FOR TIME LAPSE RECORDING: now has relay contact outputs! Can be directly connected to a VCR or via a learning remote control: $25 for PCB and all on-board components, used PIR to suit: $12. 32mm 10-LED IR ILLUMINATOR: new IR (880nm) LEDs have an output about equal to our old 42 LED IR illuminator: $18. 32mm AUDIO PREAMPLIFIER: an $8 kit that produces a “line level” signal from an electret microphone, connect the output to our UHF VIDEO TRANSMITTER: ($30) or $20 when bought with the camera for a complete audio-video link. 32mm AUDIO AMPLIFIER: an LM380-based $9 audio power amplifier which can directly drive a speaker – needs the 32mm preamplifier. WHAT IS 32mm? All boards are 32mm, so you can house these kits in a plastic 32mm joiner: cheap plumbing part. 12V VCR IR remote controlled 12V operated VCR with record and playback function (no tuner): $299. STEPPER MOTOR DRIVER KITS 650nm LASER MODULE Our new module is fitted with a 650nm laser diode!! Very small: $50. 12V - 2.5W SOLAR PANEL KIT US amorphous glass solar panels with backing glass: (S12) $22 each, 4 for $70. WIRELESS IR EXTENDER Converts the output of any IR remote control to UHF. Self-contained transmitter attaches to IR remote. Kit includes two PCBs, all components, 2 plastic boxes, Velcro strap: (K89) $39. (9V battery not included). Plugpack for Rx (PP10): $11. SUPER BRIGHT BLUE LEDS BY FAR THE BRIGHTEST BLUE EVER OFFERED, super bright at 400mCd: $1.50 each or 10 for $10. 5mm LEDS AT SUPER PRICES 1Cd red: 10 for $4. 300mCd green: $1.10 each or 10 for $7 (make white light by mixing the outputs of red, green and blue). 3Cd red: $1.10 each or 10 for $7. 3Cd yellow (small torch!) also available in 3mm: 10 for $9. Super bright flashing LEDs: $1.50 each or 10 for $10. BATTERY BONUS Twin AAA battery holder and two AAA batteries for 60c with any LED purchase: flash a high intensity LED for a month! Limit of 3 per customer. COMPUTER CONTROLLED STEPPER MOTOR DRIVER KIT PCB and components kit plus information and PC software: (K21) $35. Kit plus 2 stepper motors (small M17 or large M35) (K21M): $48. CAR ALARM KIT WITH THE LOT This kit can armed/disarmed by a hidden switch, or by a UHF REMOTE CONTROL which also has provision for operating a CENTRAL LOCKING KIT. The CAR ALARM kit includes a PCB, all on-board components and ultrasonic transducers. It features ultrasonic movement detection, provision for bonnet-boot protection (pin switches not supplied), vibration detector and a flashing high intensity LED. Four LEDs make for easy diagnostics and setting up: $35. CENTRAL LOCKING This four-door central locking kit is a commercial product that includes 2 master and 2 slave actuators, wiring loom, control unit, necessary hardware and instructions: $60. The UHF REMOTE CONTROL KIT has a switched relay output for operating an alarm etc, an indicator output for driving a buzzer etc, and logic level outputs for operating the CENTRAL LOCKING KIT. Comes with a ready-made transmitter with two pushbuttons (lock, relay on - unlock, relay off), and a receiver PCB and all on-board components. 5 LEDs make for easy tuning and diagnostics: $35. SIREN KIT includes speaker $12. NICAD CHARGER & DISCHARGER Professional, fully assembled and tested fast NICAD battery charger and discharger PCB assembly. Switchmode circuit, surfaced mounted on a double-sided PCB with gold-plated through holes and pads. Has 6 ICs, 3 indicator LEDs, 3 power MOSFETs, a toroidal inductor and many other components: over 100 in total. Nominal unregulated input 13.7V DC, 900mA charge current. Appears to use voltage slope detection for charge terminating, also has a timer (4060) to terminate the charge. We supply a thermistor for temperature sensing. Probably for fast-charging 7.2V AA nicads. Three trimpots allow some adjustment. Basic information provided, plugpack not included. Incredible pricing: $9 each or 3 for $21. MOVING MESSAGE DISPLAY PCB Used, complete PCB assembly with bright dot matrix red LED displays and driver. Circuitry includes twenty 74HC164 ICs. Has 20 displays each with 35 LEDs (700 LEDs!). Displays are in a single line to form a continuous display. Display size is 280 x 18mm, PCB 330 x 75mm. Needs external 5V supply. Includes a simple program on disk and instructions to make the display scroll number “1” through all displays, via a computer parallel port. Limited quantity: $40. MOTOR AND PUMP New, compact plastic pump with a 240V AC 50Hz 0.8A 91W 2650 RPM induction motor attached. Probably a washing machine part. Very quiet operation, made in Japan, overall dimensions 160 x 90 x 90mm, weight 1.2kg, inlet 25mm diameter, outlet 20mm diameter. Other end of motor has 20mm long 4mm diameter shaft. Motor can be rewound for lower AC voltage and/or reduced power operation without disassembling the unit. We calculated 5.5 turns per volt: $19. SOLAR REGULATOR Ref: EA Nov/Dec 94 (intelligent battery charger). Designed to efficiently charge 12-24V batteries from solar panels, but can also be used with simple car battery chargers (like Arlec 4A chargers) to prevent overcharging. Regulates by sensing battery voltage. Has voltage reference IC. Suitable for currents up to 16A, and can be easily modified for higher currents (by paralleling MOSFETs and Shottky diodes). Extremely high efficiency due to the very efficient MOSFET switch and Shottky isolation diode. Has negligible standby current consumption. The PCB is now smaller and we offer a 7.5A or 15A kit. The 7.5A kit has one Shottky diode and the 15A kit has two: $26/$29 (K09). OATLEY ELECTRONICS PO Box 89, Oatley NSW 2223 Phone (02) 9584 3563 Fax (02) 9584 3561 orders by e-mail: oatley<at>world.net WEB SITE: http://www.ozemail.com.au/~oatley major cards with phone and fax orders, P&P typically $6. July 1997  3 The GM EV1 electric vehicle – on sale this year in the United States. Electric Vehi Where are they now? During the early 1990s there was great media publicity concerning electric cars. They were to be the solution to the world’s pollution problems, with some of the more optimistic industry experts predicting that we would be driving them before the turn of the century. So where are they now? By SAMMY ISREB 4  Silicon Chip icles Several of the world’s leading car manufacturers have been developing electric vehicle technology during the past few dec­ades, with Ford and General Motors leading the way. Ford’s latest electric vehicle, the 1998 Ford Ranger EV, is due for release in the near future, GM has the EV1 passenger car and Toyota has an electric version of the RAV4. The Ford Ranger EV was designed using data obtained from the Ford Ecostar test program, which began in 1993 and involved 103 Ecostar two-passenger EV delivery vans, operating throughout the US, Canada and some of Europe. Powered by a sodium-sulphur battery, the Ecostar fleet has covered over 1,000,000 kilometres, the greatest of any EV fleet so far. Much of the new technology to be incorporated in future electric vehicles has been tested in the Ecostar. This includes: (1). Traction Battery: An advanced sodium sulphur battery oper­ates at a temperature of over 200°C and features an energy density three times greater than conventional lead acid batteries. (2). PEC (Power Electronics Centre): The Ford Ecostar contains an advanced power control system, incorporating an inverter to produce AC power for the motor. (3). DDLM (Diagnostic Data Logger Module): Records every aspect of the vehicle’s performance, allowing for later engineering analysis. (4). Solar Energy: Using solar panels mounted above the wind­ shield, accessories such as fans can be powered from the sun, saving on air-conditioning and thus the battery. (5). Multiplexing: Because of the complexity of the different electronics modules in the Ecostar, conventional wiring would require 200 separate circuits. Multiplexing allows the eight different modules to communicate over a single pair of wires. To be released in the United States next year, the 1998 Ford EV Ranger shares the body of the petrol-driven Ranger but that is where the similarities end. This pickup truck features 4-wheel ABS brakes, dual airbags, climate control, power steering and regenerative braking. The Ranger uses a 90 horsepower 3-phase AC induction motor with no gearbox and it is rear-wheel driven. An inverter works with the 312V, 23kW sealed lead-acid battery system to convert the high voltage DC to 3-phase AC. Low rolling resistance tyres and lightweight aluminium wheels, together with the regenerative braking, give the Ford Ranger a range of about 90 kilometres, with an electronically-governed top speed of 120km/h. Both the Ecostar and the Ranger use a conductive charging system. This system automatically checks for a proper electrical connection to the vehicle, checks that the charging station is ready to charge the battery, confirms the battery type and charge station capacity, and ensures that all safety systems are working before proceeding to charge the vehicle. A full charge is achieved in 4-6 hours, depending on the state of battery dis­ charge. GM’s EV1 electric vehicle Set to challenge Ford in the EV market place is General Motors, with their new electric vehicle, inventively named the EV1. It has recently gone on sale in America and sells for about $US35,000. The EV1 is a front wheel driven aluminium-bodied 2-door passenger coupe. The designers of the EV1 have tried to boost the range of the vehicle, not by using special batteries but by taking other measures, such as lowering body weight and drag. In fact, the EV1 has a drag coefficient of 0.19, compared to between 0.30 and 0.40 for a standard production car. This was achieved by taking extraordinary steps such as closing off the underside of the car, covering the rear wheels with skirts, using low rolling resistance tyres, and even building the radio antenna into the roof rather than having a standard extendable antenna. A 137-horsepower 3-phase AC-motor drives the EV1. This motor is water cooled and revs from 0 - 13,500 rpm. This wide rpm range, coupled with a broad torque curve, eliminates the need for a transmission. Acceleration is quite good, with the motor propelling the EV1 from 0 to 100km/h in around nine seconds. Powering the EV1 is a 312V battery pack, made up of 26 maintenance-free, valve-regulated, lead-acid modules. Environmen­talists will be able to drive the EV1 knowing that the batteries are 98% recyclable. Because safety is a crucial factor in any electric vehicle, the batteries are of sealed construction in which all the liquid acid is encapsulated in a diaper-like mate­rial between the individual lead plates. This results in a bat­tery so safe that a hole could be made in the case and no liquid would flow out. Clever electronics At the heart of the vehicle’s electronics system is the inverter. This uses six Insulated Gate Bipolar Transistors (IGBTs) which perform the high power switching needed to convert the 312V DC from the battery system to AC for the motor. These IGBTs can July 1997  5 passes it through the car in order to heat it. Cooling is achieved through a CFC-free energy efficient air-conditioning system. Inductive charging A 137 horsepower 3-phase AC motor drives the EV1. It is powered by 312V battery pack, made up of 26 maintenance-free lead-acid modules. The motor is water-cooled and revs from 0 - 13,500 rpm which eliminates the need for a transmission. handle up to 600V at 750A, making them very rugged indeed. An inventive electronic circuit controls the drive and braking system. Known as the Galileo Braking System, it uses software to constantly monitor the driving conditions and selects ABS braking or traction control when appropriate. This electronic system also monitors tyre pressure and inflates the tyres when necessary. In addition, a regenerative braking system is used to charge the battery during braking and this significantly boosts the range of the vehicle. Another major design feature of the EV1 is the inclusion of a heat pump. This works as a heat exchanger to move hot or cool air inside and outside the car. The pump takes coolant from the motor and inverter electronics and Toyota plans to release an electric version of its RAV4 to fleet buyers in the United States in early 1998. The EV RAV4 is basically a reworked petrol RAV4 featuring a nickel metal hydride battery. 6  Silicon Chip The EV1 features an inductive charging system that is far superior to the chargers used by many other electric vehicles. Instead of using a conventional electrical connector, it uses a fairly bulky paddle, encapsulated in an insulating material, that is plugged into the car. The great plus of this system is that there are no exposed conductive parts, as the electrical energy is transferred inductively; a great safety feature. The paddle can be immersed in water, run over by a car and so on, without any risk. If the cable to the charging paddle is severed, this will be detected and the power shut off within a few microseconds. Whilst the complexity of this charging system will boost its price, inductive charging seems the way of the future. Toyota’s RAV4 Set to rival both Ford and GM, Toyota plans to release an electric version of its RAV4 to fleet buyers in the United States in early 1998. The EV RAV4 will basically be a reworked petrol RAV4 featuring a nickel metal hydride battery. With a top speed of 125km/h and a range of 190km, the RAV4 is competitive. However, the RAV4 will not become eco­nomically viable for the mass market in the near future, due to the high price of the nickel metal hydride batteries and the fact that (unlike the EV1) large scale production is not envisaged for the moment. Over the next few years, only 320 EV RAV4s will be produced for fleet trials. Although this article has described the market-leading electric vehicles that have emerged in the past few years, there are quite a few others from smaller car manufacturers that have not been mentioned. And although the EV1, Ecostar and Ranger are set for large-scale production, their sales are likely to be limited to the US and parts of Europe. As yet, no electric vehicle is widely available in Austra­ lia and none is likely to be for some time. It will probably be the better part of a decade before we see serious EV trials SC in Australia. Get that home theatre experience. . . Philips 48-inch rear projection TV Up till now, large projection TV sets have been far beyond the reach of all but the most wellheeled buyers and even then, the picture quality has been pretty ordinary at best. But now the scene has changed with the introduction of the Philips 48P977 rear projection TV set. We recently had a chance to review one of these sets in the home. By LEO SIMPSON July 1997  7 This rear view of the set has been taken after the sloping mirror has been removed. The aspheric Fresnel lens at the back of the screen can be clearly seen. T HESE DAYS, there is enormous interest in home cinema. People are spending big dollars on Dolby Surround sound systems so that they can experience the “big sound” of the cinema in their own home. Trouble is, they usually don’t experience the “big picture” as well so the total effect is somewhat lacking. Now Philips have released their 48inch rear projection TV and this is set to change the way people think about TV in the home. While most people think that a 68cm TV is a large set, this rear projection TV has a screen diagonal measurement of 122cm, giving it a viewable screen area more than three times the size of the 68cm set. The difference in image size, with the projec­tion TV set in a typical room, 8  Silicon Chip is little short of staggering. This is TV with real “big picture” impact. Not only is the screen large but the overall set is really dominating – it is visually as big as the largest 2-door refrig­erator. Measurements will give some idea of its size but they don’t prepare you for its impact. It stands 1407mm high, 1041mm wide and 573mm deep. And it weighs all of 86kg, so it is fortu­nate that it rolls easily on its castors. Actually, it is not all that deep at 573mm. That is not as deep as some conventional 68cm or 63cm sets so it really does not take up a lot of floor space. But even in a large room, it is hard to ignore its presence, even if no picture is showing. Where the Philips rear projection TV differs radically from conventional TV sets is that its screen image is projected on to the rear of a flexible plastic screen by three 7-inch cathode ray tubes. Each CRT produces one colour – red, blue and green – and the three beams are projected onto the screen to produce the colour image. Before going into the details of the Philips rear projec­tion TV, we must emphasise the critical viewing angle of the set. Horizontally, it is 160° which means that it is at least as good as a conventional direct-view set (ie, with a single large picture tube) when viewing from the side. But the vertical viewing angle is only 16° which means that optimum viewing is obtained when you are sitting in front of the set. If you are tall and your eyes are above the top of the cabinet and you are, say, less than three metres away from the set, the picture is very dim. In brief, if you sit down the picture is brilliant; if you stand up and you are tall, it’s a non-event. It will be interesting to see how these sets are demonstrated in large department stores. If the sales-people don’t make the potential buyers sit down to watch, they won’t sell many sets! Another point which must be emphasised is that this new Philips projection set is a lot better than the average rear projection TV set you can see in many clubs and hotels. These generally give a poor picture and their only virtue is a large, albeit anaemic-looking, screen image. Now let’s have look at the technology of the Philips 48P977 set. It is made in the USA where it is sold under the Magnavox brand name. The small signal processing circuitry copes with NTSC, SECAM and PAL standard signals so it is fully compatible with Australia. Features As with most modern large sets these days, the list of control features seems to go on forever so we’ll just cover the main points. All the features are accessible via the large remote control and pressing every button seems to bring up an on-screen message or menu. The on-screen messages can be in English, Chinese or Malay. Naturally, it has picture-in-picture (PIP) which involves two VHF/UHF tuners and two sets of video processing circuitry. Teletext is a standard feature This view shows the chassis in the bottom of the cabinet. As well as an antenna connection, the set can be connected to two VCRs or a variety of video sources such as a laser disc player or video game machine. too, as is multi-standard recep­tion (ie, PAL, NTSC & SECAM), as mentioned above. You can have as many as 100 preset channels, although no-one is ever likely to approach that limit in Australia. Stereo sound is incorporated but not Dolby Surround decod­ing. There is a feature called “Incredible Sound” but it is essen­tially an enhanced stereo mode with apparently wider channel dispersion. Interestingly, on sports programs it brought up the audience noises to the point where they were quite intrusive. Other features are Dynamic Noise Reduction (DNR), Child Lock, Timer, Message, Smart Picture and Incredible Picture. DNR is supposed to reduce noise (snow) in the picture but its effect was never readily apparent. Child Lock does nothing of the sort (sadly) but does prevent certain channels from being selected from the buttons on the front of the set. However, if the said child has access to the remote control (and they always do, don’t they?), then anything can be watched. Timer is a facility to switch the TV to another channel at a specific time. You can set it to switch to two separate pro­grams at different times. It could be handy if you are prone to forget to watch a particular program. Message is a facility to display a message on the screen. You use the remote control to create and store the message which can then be run continuously while the set is on. One message which comes to mind is “Do your homework”! Incredible Picture is anything but. Pressing the relevant button brings about a minor change to the contrast, to the point where it is probably closer to the optimum setting. I was under­ whelmed, just as I was with “Incredible Sound”. Smart Picture is accessed by one button on the remote con­ trol and repeated pressings brings up settings called Rich, Natural, Soft, Personal and Game. In practice, unless you carefully tweak your Personal settings (brightness, contrast, colour and white point), all will be wrong. “Rich” is too dark with too much colour, “Soft” is just that and “Natural” is fairly close to the mark but the contrast setting means that the dark greys are pushed into the black. “Game” turns up the contrast so that you get a very bright picture and the sound is modified too, with bass boost. Projection system Most readers would be aware of the general principle of projection TV whereby separate red, green and blue cathode ray tubes are used to project a colour image onto a screen. The CRTs are typically 7-inch diagonal units and they are driven quite hard to obtain sufficient brightness. For rear projection sets there is an additional problem in that because the CRT beams are projected at an oblique July 1997  9 Three 7-inch CRTs are liquid coupled to complex plastic lenses to provide the red, green and blue beams. The blue lens has a slightly shorter focal length (77cm instead of 78cm) than the red and green lenses and has a slightly larger aperture. angle, a lot of the light bounces off the rear of the screen and what does pass through is cut down by the opacity of the screen. That is why many rear projection sets have dim picture. In this Philips set, by contrast, the screen is actually a large lens system and it results in a picture which is claimed to be three times brighter than conventional rear projection sets. Fig.1 shows the general arrangement of the CRTs and screen in the Philips set. The beams are bounced off a mirror and then onto the rear of the screen. The light beams are bent through an angle of 72° which enables the cabinet to be quite shal­low. The CRTs each have a curved faceplate which leads to better corner illumination than is possible with a flat faceplate. The curved faceplate is coupled to a complex multi-element plastic lens system by a fluid consisting of an ethylene glycol mixture which has a refractive index very similar to that of the CRT glass and that of the lens system. The fluid serves two purposes. First, it acts as a coolant, allowing the CRTs to be driven much harder for a brighter picture. Second, by occupying the space between the tube faceplate and lens system, the fluid virtually eliminates any reflective surfaces which could reduce image contrast. It also eliminates the possibility of dust being deposited on the tube faceplate which would otherwise be certain to occur. The CRTs, by the way, are operated 10  Silicon Chip with an EHT of 30kV. Because, the CRTs produce different colours, they have different lens systems, to cope with the different refractive index of the lens material for each of the colours. Hence, while the lens system for red and green is same, the lens for the blue beam has a slightly shorter focal length and a slightly larger aperture. The three beams from the CRTs are aimed at an angled mirror which folds the light path and throws it onto the screen. This is where it becomes quite complex because the screen is not simply a sheet of semi-transparent material which is what it looks like at a casual glance. Instead, the rear surface of the screen is actually a large fresnel lens. This gathers the light emitted from the CRTs and focuses it on the front screen or “lenticular lens” as it is referred to in the Philips technical literature. The lenticular lens provides a light dispersion pattern of 160° on the hori­zontal axis and 16° on the vertical axis. To accomplish this, the Fresnel lens is optically ground in an aspherical pattern to project the light out in a horizontal beam, more or less. But first the light must pass through the lenticular lens at the front of the screen. This consists of fine vertical grooves with a pitch of 0.78mm. The surface between the grooves has a parabolic convex cross-section to spread the light out in the horizontal axis. The combination of the Fresnel lens at the back of the screen and the lenticular lens at the front is responsible for a very much brighter screen image than was possible in the past with rear projection sets. TV circuitry Apart from the fact that this is a multi-standard projec­ tion set, the electronics is not much different from a normal TV set. Of course, there are three CRTs and each has its own deflec­ tion yoke, video neck board and EHT connection. But there are no purity magnets. Convergence is much more complex than on conven­ tional sets but the adjustment process is more straightforward because of the inclusion of digital convergence circuitry. The set also generates its own white cross symbol on the screen which can be used (by the consumer or a technician) to adjust the conver­gence at any time. Fig.1: the CRTs in the Philips rear projection set are angled towards the back of the cabinet and the mirror deflects the light beams through an angle of 72°. Watching the set We talked about viewing angle towards the start of this article and how the large image has a lot of impact but that does not really tell the whole story. With this set, images of people This view shows the neck boards on the three CRTs. They operate with an EHT of 30kV and a focus voltage of 15kV. are often so much larger than life-size, just as they are in your local cinema (although not quite that large). You become very aware of blemishes on the faces of TV personalities where pre­ viously, watching a normal TV set, you were blissfully unaware of these defects. By the same token, signal quality becomes critical. Where you might have tolerated a noisy, “ghosty” signal on a small con­ventional set it becomes unwatchable on the projection set. Even quite good signals on normal sets are mercilessly revealed to have defects. Perhaps there might be low-level herringbone inter­ ference, the faint vertical lines due to sync pulse ghosts, rapid flutter due to aircraft passing overhead or the often very poor quality picture from a VCR running a rental videotape. On our review sample, we also had an interference band down the left­ hand side of the screen on the UHF SBS channel which was completely invisible on a 63cm set fed from the same outlet and we were unable to track where it was coming from. On the other hand, if you have a first class TV signal, a video signal from an S-video or digital camcorder or laser disc player, the picture is very pleasant. Picture brightness is still not quite as good as from the latest 68cm high contrast picture tubes but is still quite satis­factory, even in a brightly lit room. Most people who saw the review set were impressed with the overall picture brightness. Critical viewers will note that the picture is not as sharp as on a 68cm set and that must be expected. After all, the same program information is being blown up to produce an image more than three times larger than on a normal set. If you view from about four metres or further away, the picture sharpness is entirely satisfactory. You need a big room for a big set; it’s that simple. All programs have greater impact and visual interest and this applies particularly to sporting events. You find yourself looking at particular points of interest on the screen rather than the screen as a whole. And while movies shown in “letter box” format have always tended to be less satisfying on conventional TVs, because of the black bands at top and bottom of the screen, this does not apply to this Philips set. Because the screen size is so large to begin with, the “letter box” picture is satisfying. In conclusion, if you want a big picture in your home cinema setup, it would be hard to go past the Philips 48-inch rear projection set. How much is it? Well, what does it cost? In the overall scheme of things, not a lot. When you consider how much money many people are already spending on surround sound setups, the cost of this set is not huge. Its recommended retail price is $5999.00. It comes with a one-year parts and labour warranty. It is available from Myer/Grace Bros, David Jones, Brashs, Chandlers, Harvey Norman, Vox, selected Retra­vision and Betta stores and selected special­ ists Australia-wide. As part of the deal, Philips is offering free delivery and installation into consumers’ homes in most areas. A trained Philips technician will connect the projection TV to all existing equipment, provide a product demonstration and remove the packag­ ing material for recycling. For more information, contact Philips Customer Information centre SC by phoning 131 391. July 1997  11 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au IR Remote Control Build this general purpose unit for your stereo system or model railway Want an IR remote control setup for your stereo amplifier, lighting system, model railway or any other system? This cheap set-up offers a motor-driven dual-ganged 20kΩ potentiometer and two relays. By LEO SIMPSON Based on the 8-channel infrared remote control featured in our February 1996 issue, this setup could be expanded to control up to six relays, in addition to the dual-ganged 20kΩ potentiome­ter. This could be useful for mode and source selection in an audio system, for controlling a lighting system or possibly for selecting various functions in a model railway layout. As presented in the February 1996 issue, the 8-channel remote control was just a bare-bones transmitter and receiver board. Of the eight decoded outputs on the receiver board, six 14  Silicon Chip were momentary outputs and two were toggle or latching outputs. The momentary outputs were high only while the respective buttons on the remote control were pushed, while the latched or toggle outputs would latch high for one press of their respective buttons and then latch low for the next press; ie, they provided “toggle” operation. Now while this system was attractive for many users, quite a few readers wanted more functions, which is why we are present­ing this enhanced system. The enhanced system has a modified transmitter board and adds a PC board which controls the motor­ ised potentiometer and two relays. The board can be split so that the relay section is separate from the potentiometer section. The motorised potentiometer is similar to those used for the volume control of millions of remote controlled home sound systems. It consists of the dual ganged potentiometer itself, a 4.5V DC motor and a gear and clutch system. The clutch lets the motor keep running even when the potentiometer has reach the end of its travel and so no cutout switches are required. Note that you could run more than one motorised pot from the infrared receiver if you wanted to. We’ll briefly mention the details later. But first, as they say on TV news programs, let’s have a look at the transmitter and receiver sections. The transmitter handpiece measures 155 x 35 x 16mm and is branded Mag­ navox. The seven buttons are labelled Tuner, CD, Track, Standby, Stop, Play and Volume. The last button is elongated and can be pressed at either end to make the Volume setting go up or down. When the Tuner or CD button is pressed, it operates one of the latched outputs on the receiver board. To unlatch the respective output, you need to press the same button. We use both latched outputs to drive relays so to operate a relay, you press the Tuner or CD button and to de-energise the relay you press the same button again. The remaining buttons control momentary outputs on the receiver board; they each go high, for as long as the respective button is pressed. The transmitter circuit is shown in Fig.1 and consists simply of an SM­ 5021B encoder (IC1) together with two transistors which drive the infrared light emitting diode, IRLED1. IC1 uses a 455kHz ceramic resonator as the oscillator and this is divided internally to give a 38kHz carrier frequency which is gated on and off by the data, according to which button is pressed. The 38kHz data pulse train appears at pin 15 and is amplified by the Darlington-connected transistors Q1 & Q2 to drive IRLED1. When buttons are not being pressed, pin 15 is low so no current passes through the transistors and the chip itself has negligible current drain. There are two links marked on the circuit: LK1 & LK2. These are coding links and should normally be left open circuit. The only reason for installing these links would be if you were using Fig.1: the 8-channel infrared transmitter. We suggest that the coding links LK1 & LK2 be omitted unless you are going to use two remotes in the one area. more than one of these remotes in the same location. In that case, you might, for example, install LK1 in one transmitter and LK2, in another transmitter. If you do this, you must ensure that the respective receiver boards have the same links installed. Speaking of the infrared receiver board, the circuit is shown below in Fig.2. It is almost as simple as the transmitter. As can be seen, it consists of an infrared receiver diode and preamplifier (IC2) feeding an SM­5032B decoder, IC1. This has eight outputs, six of which are high while the relevant transmitter button Fig.2: the 8-channel receiver circuit. Outputs G & H are latching while the other six are high only while the relevant transmitter button is pressed. July 1997  15 Fig.3: the relay/potentiometer board circuit. The motor drive circuit is inherently fail-safe since even if both the UP and DOWN inputs are high, no damage can result. 16  Silicon Chip is pressed and two of which are latching, as already mentioned above. Actually, IC2 is a three-lead device and it is more than just a preamplifier. It contains the IR photodiode, an amplifier tuned to 38kHz, an AGC circuit and a detector. Its output is a digital pulse train identical to that generated at pin 15 of the transmitter IC but inverted in polarity. Transistor Q1 changes the signal polarity before feeding it to pin 2 of IC1. Transistor Q2 and zener diode ZD1 act as a simple regulator circuit to provide a 5.6V supply to IC1 & IC2. The eight outputs of IC1 can only provide a drive current of about a milliamp or so, so any circuit driven by these pins must be designed accord­ingly. This brings us to the add-on board which drives two relays and the stereo potentiometer. Relay & potentiometer board Fig.3 shows the circuit of this board and, as you can see, it is split into two parts. One part takes care of the relays and the other section controls the motor-driven potentiometer. Let’s discuss the latter part first. Transistors Q1 & Q2, together with 150Ω resistors R4 & R7, form a bridge circuit to drive the motor. Normally, only one transistor can be turned on at any time. If Q1 turns on, current flows via R4 which has almost the full 12V across it but current also flows via R7 and the motor, causing it to turn in one direc­tion. Similarly, if Q1 is off and Q2 is on, the full 12V is ap­ plied to R7 but current also flows via R4 and the motor, causing it to rotate in the opposite direction. Diodes D1D4 protect the transistors from damage which could be caused by voltage spikes from the motor. LEDs 1 & 2 light to indicate the motor direction. As la­ belled on the circuit, the input for Q1 is UP, corresponding to clockwise rotation of the motor. When Q1 is on, LED1 will be on. Similarly, the input for Q2 is labelled DOWN, corresponding to anticlockwise rotation of the motor. When Q2 is on, LED2 will be on. Note that this circuit has a built-in safety feature in that even if Q1 and Q2 were both turned on simultaneously, no damage would result. In that circumstance, both R4 and R7 would have the 12V applied but no voltage would appear across the motor. Relay circuit Now let’s have a look at the relay circuit, comprising Q3 & Q4. These transistors would normally be driven from the latched outputs of the receiver board (ie, G & H). There’s nothing magic about the circuit. When the input to Q3 goes high, it turns on and operates relay 1. Similarly, when the input to Q4 goes high, relay 2 operates. LEDs 3 and 4 come on when the associated relay is operated. Diodes D4 & D5 protect Q3 & Q4 against any voltage spikes generated by the relays when they are switched off. Building a remote control system In presenting this system, we are not proposing a cut and dried solution, so we are just featuring the three PC boards and not giving full details on how they should be hooked up to con­trol an audio system, lighting system or whatever. We’ll leave the details up to you and The IR transmitter board should only take a few minutes to assemble. Note that this photo shows an early version. The final version shown in Fig.4 differs slightly in a few respects. LED and a few of the other passive components. Do not lose the rubber keyboard mat because it mates with the new PC board. You now have to assemble the new transmitter board which uses the SM5021B encoder chip. Just assemble it as shown in Fig.4. The next step is to assemble the receiver board, with the details shown in Fig.5. Unless you intend operating more than one of these remote control systems, leave the coding links off the transmitter and receiver boards. Next, assemble the motor drive and relay board. This board will be supplied as one unit but it can be split into two boards, as shown in the lead photo. Mount all the small components first before installing the motor driven poten­tiometer. If you mount the potentiometer first, you will be unable to fit all the components which lie underneath it. Once the two relays have been mounted you will need to wire the two protection diodes, D5 and D6, underneath the board, across the relay coils. One of the photos shows these diodes in place. When all the boards are complete, you are ready to test each one in turn and this should be done before the receiver board and relay/potentiometer Fig.4: the component overlay for the transmitter PC board. just indicate how the boards should be connected to provide the control functions you want. Now let’s describe the transmitter assembly. As supplied, the transmitter is fully assembled and operational but it won’t work with the corresponding decoder chip. You have to pull the transmitter apart by unclipping the case halves. You can do this by inserting a screwdriver into the case join down the side and levering it apart. Don’t apply too much force when doing this otherwise you will damage the case. Now lever out the existing PC board with its surface mount encoder chip. You will need to salvage the battery clips, the ceramic resonator, infrared Fig.5: the component overlay for the receiver PC board. Fig.6: the parts layout for the relay/potentiometer board. Mount all the small components before the motor-driven potentiom­eter is installed. You will need to run two wires from the motor itself to the “motor” pins on the PC board. July 1997  17 PARTS LIST 8-channel IR transmitter 1 Magnavox handpiece (includes 455kHz resonator & IR LED) 1 PC board 2 AAA 1.5V cells Semiconductors 1 SM5021B encoder (IC1) 1 BC548 NPN transistor (Q1) 1 C8050 NPN transistor (Q2) Capacitors 1 10µF 16VW PC electrolytic 2 100pF ceramic Resistors (0.25W, 1%) 2 1kΩ 1 4.7Ω 8-channel IR receiver 1 PC board 10 PC stakes Semiconductors 1 SM5032B decoder (IC1) 1 PIC12043 IR receiver (IC2) 2 BC548 NPN transistors (Q1, Q2) 1 6.2V zener diode (ZD1) Capacitors 1 100µF 25VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.47µF monolithic ceramic 1 .001µF ceramic Resistors (0.25W, 1%) 1 39kΩ 1 10kΩ 1 4.7kΩ 1 1kΩ Relay/potentiometer board 1 PC board 20 PC stakes 1 motor-driven dual-ganged 20kΩ potentiometer 2 12V relays with SPDT contacts 4 C8050 NPN transistors (Q1,Q2,Q3,Q4) 4 GIG silicon diodes (D1,D2,D3,D4) 2 1N4004 silicon diodes (D5,D6) 4 red LEDs (LEDs1-4) 2 100µF 16VW PC electrolytic capacitors 4 .015µF ceramic capacitors Resistors (0.25W, 1%) 4 120kΩ 7 3.3kΩ 2 150Ω 18  Silicon Chip The relay/potentiometer PC board can be split into two parts, each of which can operate independently of the other. This is the potentiometer section. board are wired together. We suggest you test the relay/ potent­ iometer board first. You will need a 12V power supply and a short lead with alligator clips at each end. The relay and potentiometer sections of the board have their own supply pins so each section can be tested independently. Apply 12V DC to the potentiometer board and observe that nothing happens (ie, no LEDs light, pot shaft does not rotate). Now take your clip lead and connect the UP input pin to the +12V pin on the board. The potentiometer shaft should rotate fully clockwise and then the motor should keep running, with the gearbox clutch slipping. LED1 should also light. Now take the clip lead and connect the DOWN input pin to the +12V pin on the board. The potentiometer shaft should rotate fully anticlockwise and then the motor should keep running, Don’t forget to add the two diodes on the back of the relay PC board. as before. LED2 should also light. Now test the relay board. Apply 12V DC and note that noth­ing happens, then use your clip lead to connect pin 1 on the board to +12V. You should hear relay 1 click and LED3 should light. Similarly, use your clip lead to connect pin 2 on the board to +12V. KIT AVAILABILITY These remote control boards are available from Oatley Electronics, who own the design copyright. Their address is PO Box 89, Oatley, NSW 2223. Phone (02) 9584 3561; fax (02) 9584 3563. The prices are as follows: 8-channel IR transmitter...............................................................................$20 8-channel IR receiver....................................................................................$20 Relay/potentiometer board plus parts for motor drive section......................$16 Complete kit with suitable plugpack & RCA leads (includes all of above but does not include parts for relay section).................................................$55 Parts for relay section.....................................................................................$8 Please add $5 to all prices for postage and packing. You should hear relay 2 click and LED2 should light. Testing the transmitter SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. CD pin H Tuner pin G Track pin E Standby pin B Stop pin F Play pin A Volume - pin D Volume + pin C ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 Note that pins G & H are the latching pins and these drive the relays. ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 Connecting up If you’ve got this far, making the board-to-board connec­tions won’t be a problem. Pin C on the receiver board is connect­ed to the UP input on the potentiometer board while pin D is connected to the DOWN input. Pins H & G are connected to input pins 1 & 2 respectively on the relay board. If you wanted to connect a second potentiometer board, you could use any of pins A, B, E and F for the UP and DOWN func­tions. Alternatively, you could use any of the same pins to operate additional relay boards, although they would only be energised while the relevant transmitter button was pressed. Finally, if you have previously purchased the 8-channel IR transmitter and receiver boards, the transmitter buttons will not provide the correct functions. On the previous transmitter board (February 1996), the Volume button controlled latching outputs which is not appro­ priate for controlling the potentiometer board. SC ORDER FORM PRICE POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏  3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________  Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ Testing the transmitter on its own is not practical unless you have a cam­ corder or some sort of video camera. If you do, you can use the camera’s viewfinder to see if light is emitted when any of the transmitter buttons are pressed. However, while that tests the infrared side of things, it does not indicate that the buttons control the right receiver outputs. The way around this is to first con­nect 12V DC to the receiver board, then check that around +5.6V is present at the emitter of Q2, at pin 14 of IC1 and at pin 3 of IC2. Now aim the transmitter LED at the receiver’s detector window and use your multimeter to check that each output pin on the board goes high when the relevant button is pressed. The outputs should be as follows: July 1997  19 Silicon Chip Back Issues January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car; Fitting A Fax Card To A Computer. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Operating an R/C Transmitter; Index to Vol. 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages; A Look At Very Fast Trains. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band; the Bose Lifestyle Music System; The Care & Feeding Of Battery Packs; How To Make Dynamark Labels. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2; The Snowy Mountains Hydro Scheme. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Turn-stile Antenna For Weather Satellite Reception. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. ORDER FORM Please send me a back issue for:   July 1989   September 1989   January 1990   February 1990   July 1990   August 1990   December 1990   January 1991   May 1991   June 1991   November 1991   December 1991   May 1992   June 1992   October 1992   January 1993   May 1993   June 1993   October 1993   November 1993   March 1994   April 1994   August 1994   September 1994   January 1995   February 1995   June 1995   July 1995   November 1995   December 1995   April 1996   May 1996   September 1996   October 1996   February 1997   March 1997   September 1988   October 1989   March 1990   September 1990   February 1991   July 1991   January 1992   July 1992   February 1993   July 1993   December 1993   May 1994   October 1994   March 1995   August 1995   January 1996   June 1996   November 1996   April 1997   April 1989   November 1989   April 1990   October 1990   March 1991   September 1991   March 1992   August 1992   March 1993   August 1993   January 1994   June 1994   November 1994   April 1995   September 1995   February 1996   July 1996   December 1996   May 1997   May 1989   December 1989   June 1990   November 1990   April 1991   October 1991   April 1992   September 1992   April 1993   September 1993   February 1994   July 1994   December 1994   May 1995   October 1995   March 1996   August 1996   January 1997   June 1997 Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 20  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503.  Card No. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Multi-Station Headset Intercom, Pt.2. August 1992: An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; MIDI Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; A Windows-Based Logic Analyser. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. November 1993: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. December 1993: Remote Controller For Garage Doors; LED Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags - How They Work. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. March 1996: Programmable Electronic Ignition System; Zener Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: Dolby Surround Sound - How It Works; Dual Rail Variable Power Supply; Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Temperature Controlled Soldering Station; Engine Management, Pt.13. May 1996: Upgrading The CPU In Your PC; Build A High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford - A Pesky Electronic Cricket; Cruise Control - How It Works; Remote Control System for Models, Pt.1; Index to Vol.7. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluores­cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Preamplifier;The Latest Trends In Car Sound; Pt.1. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. April 1995: Build An FM Radio Trainer, Pt.1; A Photographic Timer For Darkrooms; Balanced Microphone Preamplifier & Line Filter; 50-Watt Per Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; An 8-Channel Decoder For Radio Remote Control. May 1995: What To Do When the Battery On Your PC’s Mother­board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Door Minder; Adding RAM To A Computer. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. September 1995: Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­ verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. September 1996: VGA Oscilloscope, Pt.3; Infrared Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­grammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; Infrared Stereo Headphone Link, Pt.2; Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: Adding An Extra Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. December 1996: CD Recorders ­– The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. January 1997: How To Network Your PC; Using An Autotransformer To Save Light Bulbs; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (for Sound Level Meter calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. February 1997: Computer Problems: Sorting Out What’s At Fault; Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Madel Railways; Build A Jumbo LED Clock; Audible Continuity Tester; Cathode Ray Oscilloscopes, Pt.7. April 1997: Avoiding Windows 95 Hassles With Motherboard Upgrades; A Low-Tech Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; Installing A PC-Compatible Floppy Drive In An Amiga 500; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. May 1997: Windows 95 – The Hardware Required; Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, May 1990, August 1991, February 1992, September 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc at $10 including packing & postage. July 1997  21 ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. TOTAL $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  GIFT SUBSCRIPTION DETAILS RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. 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Please have your credit card details ready 22  Silicon Chip OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia This addressable interface card provides eight opto-isolated inputs and eight relay outputs. A flexible interface card for PCs This addressable interface card provides eight opto-isolated inputs and eight relay outputs. It is addressed from the parallel port of your computer and you can have more than one card, each with a different address, hooked to the same port. By RICK WALTERS Got a control application for your computer that can’t be done with your existing hardware? Perhaps you want to design a security system around an older computer. Whatever the reason, there are a host of applications for this input/output card which can be connected to any PC with a standard parallel port. That means it can be used with old PC XTs, 286 or 386 machines which might otherwise be gathering dust. And of course, it can be used with 486 and Pentium machines as well. You could have up to eight of these cards daisy chained and connected to one parallel printer port on a PC. The cards can be set up with an address from 1 to 8, making them individually addressable, or if the need arises, two or more can be coded with the same address in a master-slave setup. Capabilities This interface card is capable of monitoring eight opto-isolated input lines. The inputs to the PC port are normally high and are taken low (via the opto-isolator) when the card input line is grounded. These eight input lines and ground are accessi­ble via a 9-pin “D” female connector. The card can also switch eight relays. Each relay has changeover July 1997  23 PARTS LIST 1 PC board, code 07107971, 177 x 125mm 8 PC-mount relays (RLY1-RLY8) (Altronics S-4160; Jaycar SY4066) 1 D25 PC-mount male connector 1 D25 PC-mount female connector 1 D25 male connector (solder cup or IDC) 1 D9 PC-mount female connector 1 D9 male connector (solder cup or IDC) 1 8 x 2-pin strip 1 shunt for above 1 3-pin terminal block (5.08mm pitch) Semiconductors 1 74HC137 decoder (IC1) 2 74HC573 8-bit latch (IC2,IC3) 1 74HC02 quad NOR gate (IC4) 1 ULN2803 octal buffer (IC5) 8 4N28 opto-isolators (O1-O8) 9 1N914 small signal diodes Capacitors 2 100µF 25VW PC electrolytic 3 0.1µF monolithic ceramic 1 .01µF MKT polyester 2 .001µF MKT polyester Resistors (0.25W, 1%) 2 47kΩ 1 10kΩ 8 4.7kΩ 1 47kΩ SIP (8 resistor 9 pin) Fig.1 (right): the circuit uses a BCD decoder (IC1) and an 8-bit latch (IC2) to control the eight relays. Eight optoisolators are coupled to 8-bit latch IC3 to drive PortB and PortC of the paral­lel connector CON1. confuse you by calling it card 0 we have labelled them cards 1 to 8. If the output which goes low is jumpered to pin 2 of IC4a, and remembering that pin 4 is high, we then have both inputs of IC4a low, which means that its output will be high. This will latch the data present on PortA (pins 2-9 of CON1) into IC2 and output it on pins 12-19. Pins 12 to 19 of IC2 connect directly to IC5, an octal (eight) buffer. This chip accepts 5V logic levels at its input and has open-collector outputs which can switch up to 50V 0.5A loads. Operating the relays (SPDT) contacts and depending on the type used, the contacts may be rated 6A at 240VAC and 12A at 28VDC (Altronics S-4160) or 3A at 12V (Jaycar SY-4066). All relays are accessed via a 25-pin “D” female connector. Note that the PC board tracks and the connector are not rated for 240VAC and they would not carry this current but if high currents were to be switched, connec­tions could be made straight to the relay pins. These features make the card suitable for a wide range of interface applications. capacitor. Thus if pin 4 of IC4b goes high, the latch pin will immediately go high then return to a low level as the 10kΩ resistor discharges the capacitor. This is how we select the card from the parallel port. The three input lines can only address outputs 0 - 7 so rather than Circuit description The full circuit is shown in Fig.1. IC1 is a 74HC137 latched one-of-eight active-low decoder. This means that any BCD (binary coded decimal) code which is present on the three input lines (A,B,C) will cause the output corresponding to this code to change from its normal level of +5V (high) to 0V (low). The eight outputs are pins 7 and 9 to 15. While the latch enable, pin 4, is high, the outputs will change in sympathy with the input code but once the latch pin is low, the input code is stored or latched. This allows us to select one of the outputs, latch it, then alter the code on the input lines while that output stays selected. To this end, the latch enable pin is AC-coupled through the .001µF 24  Silicon Chip The I/O Card is addressed from the parallel port of your computer and you can have more than one card, each with a different address, hooked to the same port. Note that this is the prototype card and some changes have been made, as can be seen from the component overlay diagram of Fig.4. The current artwork uses a 16pin chip for IC1. OK, so how do we operate the relays? The procedure is to apply the code for the particular relays (see Table 1) to PortA then apply the card select code to PortC, taking pin 1 (which is normally high) low, then back high again. Reading the eight inputs is not quite so straightforward. In the newer PCs, the PortA lines are bidirectional; ie, they can be used for inputs as well as outputs. With the older-style machines they can only be used as output lines. Fortunately, the PortB and PortC lines can be used as inputs but we have to use them both to get our eight lines. Now you will realise why it was necessary to latch the PortC data in IC1. The eight inputs (pins 2-9) of IC3 are pulled high with 47kΩ resistors and each resistor has an opto-isolator output connected between it and ground. If the LED in the opto is lit the transistor will pull the pin low. This will be the case if the corresponding diode is grounded. Unfortunately, computer boffins count from zero, unlike normal human beings who were taught to start from one. This means that diode D1 controls input port D0 and so on. We could label the IC pins D1-D8, but we prefer to draw ICs the way you will find them in the data book, otherwise there could be even more confusion. With the I/O card de-selected, pin 1 of IC4a will be low and therefore pin July 1997  25 Fig.2: the top trace shows the strobe pulse at pin 4 of IC4. The middle trace is the differentiated pulse which is present at pin 4 of IC1. This latches the card address when it is high. The bottom trace is the integrated pulse at pins 8 & 9 of IC4. You can see that the capacitor has not charged up to the 2.5V neces­sary to change the output. Fig.3: these scope waveforms show how the card opto-isolator inputs are read. The strobe goes high and stays high long enough for the input of IC4c to pass through the logic switching threshold. Note that the time constant here is 10 times longer than the latch enable time constant for IC2. The LED test jig is used to verify the opera­tion of the eight relays. Table 1: Port A Code To Energise Relays 1, 5 & 8 BCD Value 128 64 32 16 8 4 2 1 Data Line D7 D6 D5 D4 D3 D2 D1 D0 Relay 1 Relay 2 Relay 3 Relay 4 Relay 5 Relay 6 Relay 7 Relay 8 Total 1 0 0 0 1 0 0 1 128 +16 The value to apply to PORTA is 10010001 binary or 145 decimal. 26  Silicon Chip +1 = 145 10 of IC4c and pin 1 (the output enable) of IC3 will be high. This means that pins 12-19 of IC3 will be floating and therefore at the logic levels on the PortB & PortC pins. When pin 1 of IC3 is taken low the logic levels present on the D (data) inputs are transferred to the Q pins. To read the inputs the first step is to select the card as described previously. Under normal conditions, when we select the card and toggle the relays, the time constant of the integrator at the input of IC4c prevents any change in its output (see the scope waveforms of Fig.2). This time, after selecting the card, we set all the lines of PortB and PortC high, except PortC pin 1, which is held low as we now want to charge the capacitor on pins 8 & 9 of IC4c and take its output low (see the scope waveforms of Fig.3). The 47kΩ resistor and this capacitor form an integrator, at the input of IC4c, which will take 10 times longer to reach the logic switching level than the latch enable network on IC2. Once IC4c changes state, the logic levels at IC3’s inputs will be transferred to its outputs which are connected to PortB and PortC and this binary value can be read by the computer software. D9 ensures that the outputs of IC3 are quickly disabled when PortC pin 1 goes high. In practice, the computer software drives the card and you don’t really Fig.4: the component overlay for the PC board. The card selection jumper is to the right of IC1. For conven­ience, all the input-output connections to the card are made with D connectors. have to think about the circuit machinations in order to be able to use it. Building the card The component overlay of the PC board is shown on Fig.4. You can begin by checking the etch pattern on the PC board with the full size artwork of Fig.6. Fix any faults that might be present before you start installing the parts. Fit and solder the 23 links, followed by the resistors and diodes. Next, insert the ICs along with the resistor network (black dot adjacent to pin 1) noting that IC1, IC2, IC4 and IC5 face one edge of the board and the rest face the other edge. The last group is the capacitors, connectors and relays. Check all the soldering again once you have finished as it is quite easy to miss a row of IC pins or one resistor network pin. Testing it For the big test you will need a 25way D cable to connect your computer printer port to the card and a power supply which can deliver 5V and 12V. Connect the power supply to CON4, check­ing that the +5V on the supply goes to the correct connector terminal. Set the jumper to C1. Connect the male end of the cable to the computer printer socket, the female end to the card and turn on the power supply. Relay test It is possible that several relays will click in, depending on the logic levels on the output of IC2. If nothing is heard don’t despair. Load BASIC into your computer and type in lines 10100 of the program shown in Listing 1. You need not type the comments (lower case); they are only there to explain what each line does. When you run it, each relay should energise in turn, with a 1-second delay between steps. If your relays don’t step at all, first check that you have selected card one. Next, check the voltage at pin 2 of IC4. It should be 0V. If you remove Fig.5: use this circuit to make up a jig for checking relay operation on the board. OUT PORTC,10 from line 50 and run the program again, both pin 2 and pin 3 of IC4 should be low and consequently pin 1 should be high. Fig.5 shows the circuit of a LED array which can be con­nected to a July 1997  27 Fig.6: actual size artwork for the PC board. Check your PC board’s copper tracks for defects before you start assem­bly. LISTING 1 10 CLS: KEY OFF: DEFINT A, B, C ‘define A, B, C as integers 20 PORTA = &H378: REM &H378 is for LPT1. use &H278 for LPT2 30 PORTB = PORTA + 1: PORTC = PORTB + 1 ‘define port addresses 40 OUT PORTA,0: OUT PORTC,10 ‘turn all relays off, take C0 high 50 OUT PORTC,11: OUT PORTC,10 ‘select card one, C0 low then high 60 FOR A = 0 TO 7 ‘relays are coded 1, 2, 4, 8, 16, 32, 64, 128 70 OUT PORTA,2^A ‘select relay 1 to 8 in turn 80 OUT PORTC,11: OUT PORTC,10 ‘select card one, strobe high then low 90 B$ = RIGHT$(TIME$,2): WHILE RIGHT$(TIME$,2) = B$: WEND ‘wait one second 100 NEXT A 110 OUT PORTA,0: OUT PORTC,11 ‘turn all relays off 120 OUT PORTB,120: OUT PORTC,5 ‘take input lines high 130 FOR A = 1 to 200: NEXT ‘delay for IC4c increase value if necessary 140 LIN = 0: B = INP(PORTB): C = INP(PORTC) ‘read port input values 150 IF (B AND 128) THEN BIN = B - 135 ELSE BIN = B + 121 ‘comple­ment bit 8 160 CIN = C AND 14 ‘mask high bits and C0 170 IF (C AND 2) = 0 THEN CIN = CIN + 2 ELSE CIN = CIN - 2 ‘co­mplement bit 2 180 IF (C AND 8) = 0 THEN CIN = CIN + 8 ELSE CIN = CIN - 8 ‘co­mplement bit 8 190 CIN = INT (CIN/2): TIN = 255 - (BIN + CIN) 200 FOR A = 0 TO 7: IF TIN/2^A = 1 THEN LIN = A + 1 ‘find low line 210 NEXT 220 LOCATE 24,20: PRINT “Line”;LIN; ‘print it 230 GOTO 140 ‘loop 28  Silicon Chip 25-way D-connector to check relay operation. This is much more effective than trying to listen for relays clicking. Input test Now add the remaining lines (110230) of Listing 1 and run the program again. After the relays stop sequencing, the number 0 should appear at the bottom of the screen. Ground the cathodes of D1-D8 in turn and the corresponding line number should show on the screen. Pressing the Ctrl and C or Ctrl and Break keys together will get you out of the loop. The fun and games in lines 150-190 compensate for the logic inversion of B7, C1 and C3 on CON1. If you have problems with this section you will have to ground the diode and check that the corresponding data input on IC3 goes low. With pin 1 of IC3 low, the Q output should mimic the D input. If this is working, then check for open circuit tracks between IC3’s Q outputs and the corresponding SC pin on CON1. Points Controller FOR MODEL RAILWAYS This Points Controller board uses a capacitor discharge circuit to energise the coils on a twin-solenoid switch machine. One Points Controller board can be used to operate all the points on a model railway layout. Most model railway enthusiasts operate their points with a twin solenoid connected to a 15V supply. However, if you keep your finger on the button for just a moment too long, you can easily burn out the solenoid coil. This points controller avoids that problem. Design by RICK WALTERS As any keen model railway enthusiast can confirm, even the simplest of model layouts include a few sets of points and most feature quite a few, for sidings, shunting yards and spur lines. While you can operate points by hand (the “big hand in the sky”) or by Bowden cables, that rapidly becomes unwieldy and unrealis­tic for all but the smallest layouts. Hence most enthusiasts operate their sets of points by twin solenoid assemblies which are usually referred to as switch machines. The most commonly available type is made by Peco and can be used for O, HO and N scale layouts. They are available from model railway retailers for about $7. As can be seen from one of the photos accompanying this article, these twin solenoid assemblies consist of two coils which drive a common solenoid shaft and a rightangle pin which protrudes from both sides of the assembly. The switch machine is mounted under the baseboard of the model railway layout and the solenoid operated pin fits into a hole in the sleeper of the move­able rail section of the points. To operate the points in one direction, one of the sole­noids is briefly energised, after which the points lock into their new position. To move the points back again, the other solenoid is briefly energised. In normal practice, the solenoid coils are energised from a 16V AC or DC power supply, with each coil connected via a push­button switch. The idea is that you briefly push the switch to operate the points for the new train direction. The operative word here is “briefly”. If you lean on the switch for more than a few seconds, the energised coil will burn out. The reason for burn out is pretty easy to understand. Each solenoid coil is wound with lots of turns of very fine enamelled copper wire and the total coil resistance is typically around 4.5Ω. With 15V across the coil, the internal dissipation will be V2/R = (16)2/4.5 = 50W. No wonder they can expire in a brief puff of smoke! The solution to this problem is to energise the solenoid coils with July 1997  29 14 Model Railway Projects Shop soiled but HALF PRICE! This book will not be reprinted Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097.  Use this handy form Enclosed is my cheque/money order for $________ or please debit my    Bankcard   Visa   Mastercard Card No: ______________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ 30  Silicon Chip Fig.1: the 2200µF capacitors are charged via D1, Q1 and the 47Ω resistor. The capacitors’ charge can then be dumped into the solenoid coils via pushbutton switches S1 or S2. a capacitor discharge circuit. This charges up a capacitor to around 15V or so and then the capacitor’s charge is dumped via the respective pushbutton into the solenoid coil to be energised. This operates the points, discharges the capacitor and even if the push­ button remains depressed, no harm can be done to the solenoid coil since the capacitor cannot supply any more current. Fig.1 shows the circuit. The power supply can be any 12V to 15V DC or AC source, with a 12V plugpack being a safe and con­venient approach. This is fed via diode D1 and transistor Q1 to one or two 2200µF capacitors. From there, diode D2 couples the capacitors’ voltage to pushbutton switches S1 and S2. These switches then discharge the 2 x 2200µF capacitors via one or other of the twin solenoids in the switch machine. When power is first applied, the 470Ω resistor between collector and base of Q1 ensures that it is fully turned on and so it charges the 2200µF capacitors. The charge current is limit­ ed to a safe level (250mA maximum) for Q1 by the series 47Ω resistor at its emitter. The capacitors only take a few seconds to fully charge, by which time LED1 will be fully alight. The 1.2kΩ and 470Ω resistors form a voltage divider which prevents LED1 turning on until the voltage across the capacitor reaches 10V. This means that LED1 acts as a “ready” indicator. When either S1 or S2 is pressed, not only does it discharge the 2200µF capacitors, it also pulls the base of Q1 below its emitter, so it is completely turned off. Thus, once the capacitor is fully discharged, the only current which flows into the coil is from the 470Ω base pull-up resistor. As this current is around 20-30mA, depending on the supply voltage, there is no chance of damaging the solenoid coil. Q1 stays turned off, until the push­button is released, whereby the 2200µF capacitors begin to charge again. You might wonder about the functions of the three diodes in the circuit. Are they really necessary? Well, yes. Otherwise we would not have included them. Diode D1, provides reverse polar- PARTS LIST 1 PC board, code 09107971, 51 x 38mm 2 momentary contact pushbutton switches (S1, S2) 1 BC639 NPN transistor (Q1) 3 1N4001 or 1N4004 silicon diodes (D1-D3) 1 red LED (LED1) 1 or 2 2200µF 25VW PC electrolytic capacitors (see text) 1 1.2kΩ 0.25W, 1% resistor 2 470Ω 0.25W, 1% resistor 1 47Ω 0.25W, 1% resistor ity protection for the circuit if a DC supply is used and acts as a rectifier if AC is used. Diode D3 is include to prevent damage to the base of Q1 from voltage spikes which can be produced by the solenoids if there is contact bounce in the pushbutton switches (virtually all switches have some contact bounce). Finally D2 is included to allow Q1 to turn on and turn off correctly. Without D2, the base of Q1 would be connected directly to the 2200µF capacitors and so the transistor would be biased off. Assembling the board With such a small PC board, it will not take long to assem­ble all the components onto it. Make sure the diodes and transis­tor are installed correctly, otherwise the circuit won’t work. Our circuit and photos show the PC board fitted with two 2200µF capacitors but only one may be necessary. How do you know? Well, you could try the circuit with only one 2200µF capacitor fitted and see if it works satisfactorily. If so, then that’s all you need. However, if your input voltage to the circuit is 12V or less, you may need to fit two 2200µF capacitors to ensure that you have enough energy storage to fire the solenoids every time. We envisage that the points controller board will be in­stalled under the control panel for your layout. LED1 will be mounted on the control panel, adjacent to the pushbuttons S1 & S2. By the way, we suggest you try connecting the board to a switch motor and operating it before it is installed in your layout. Multiple points operation Note that while the circuit of Fig.1 and the PC overlay diagram of Fig.2 show provision for only two push­ This close-up view shows how the twin-solenoid switch machine fits under the points. A pin is fitted at rightangles to the solenoid shaft to drive the moveable rail section of the points. Points or Turnouts? If you are a model railway enthusiast you will find that American, Australian and European modelling magazines have dif­ ferent terminology for items such as points. Australian and English magazines refer to them as “points” while American maga­ zines refer to them as “turnouts” or “switches”. In fact, operations in railway marshalling yards are re­ferred to as “switching” in American parlance and “shunting” in Australian or English magazines. buttons, S1 & S2, you only need to build one of these point controller boards to drive all the points switch motors on your layout. All you need to run extra points is an extra pair of push­buttons for each set. So in theory, you could have 50 sets of points and 50 pairs of push­ buttons all run from the one points controller board. In practice though, it might be prudent to run no more than a dozen sets of points from each board. This would simplify the wiring and make troubleshooting easier if you ever have a short or an open circuit in your wiring. If you do decide to run multiple points controller boards, you can power them all from the same 12-15V SC source. Fig.2 (left): the component overlay for the PC board. Note that you can fit one or both of the 2200µF capacitors, depending on your input supply voltage (see text). Fig.3 at right shows the actual size artwork for the PC board. July 1997  31 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. JFET tester adaptor for DMMs Many designers avoid using junction FETs (JFETs) even though many circuits would benefit, such as those requiring very high input resistance, high upper frequency and (relatively) low noise. But it is much harder to design with JFETs because even devices from the same batch will have widely varying pinch-off voltage (Vp) and drain saturation current (Idss). These parame­ters are paramount in establishing proper DC biasing. The tester described here enables one to quickly measure these vital parameters of an N-channel JFET to approximate for­ ward conductance and to match transistors (eg, for use in a differential long-tailed amplifier stage). With switch S1 open, op amp IC1 functions as a current regulator to the JFET under test. The voltage drop across resis­tor RD, due to the JFET’s drain current, is compared with a portion of the reference voltage de- rived from diode D1. Both the voltages being compared will be close to the posi­tive supply rail and the TL071 op amp specified can cope with this condition. As a result of the voltage comparison at its inputs, the op amp adjusts the JFET’s source voltage accordingly. The gate of the JFET is tied to 0V. The resulting current through the JFET is about 2.8µA and the voltage between gate and source, as measured by the DVM, is the pinch voltage. With switch S1 closed, the gate and source of the JFET under test are at equal potential. Under these conditions, the DVM measures the voltage across the source resistor RS and when the measurement value is divided by 10, the result is the drain saturation current (Idss). Resistors R4 and RG must be included. These will limit the current flowing through the gate-channel junction if the JFET is inserted incorrectly. Note that interchanging drain and source is normally not dangerous to the device tested. In most instances Cheap heatsink temperature sensor While there are many accurate temperature sensing ICs available, they are not readily available in packages such as TO-220 which ensure reliable thermal contact for monitoring heat­sinks. This circuit was used as an over-temperature cutout for an intermittently operated inverter that had to be encapsulated. Q1 is a BD140 connected as a diode and its forward voltage is monitored by the LM393 comparator. The temperature coefficient of the forward voltage is roughly -2.1mV/°C. Q1’s forward voltage is compared with a voltage at pin 2, set by trimpot VR1. For reasonable stability of this voltage, the supply 32  Silicon Chip voltage should be regulated. C1 may be necessary if the BD140 has long wires or the environment is electrically noisy as in a switch­ mode power supply. R1 adjusts the comparator’s hysteresis and for most applications doesn’t have to be reduced. G. LaRooy, Christchurch, NZ. $35) the FET will function normally. Ceramic capacitor CF prevents op amp instability or oscillation. The tester was designed to operate from a 12V DC plugpack to ensure sufficient drain-source voltage but it could be operat­ed from a 9V battery. Comparison tests were carried out with sup­plies of 12V, 9V and 6V (the end-of-life voltage of a 9V battery) using a random-selected 2N5486 FET. With this range of supply voltage the indicated pinch-off voltage dropped from 3.19 to 3.16V (insignificant) and drain saturation current dropped from 9.7mA to 9.3mA. Battery operation has one serious disadvantage – from theory of JFET operation, Idss should be tested with the FET’s drain-source voltage being at least equal to its pinch-off vol­tage. For battery operation R3 should be reduced to 470Ω. Minimum supply voltage for the TL071 is specified as ±3.5V but the device used in the prototype did function with a 6V supply. M. Frankowski, Warszawa, Poland. ($40) KITS-R-US RF Products FMTX1 Kit $49 Single transistor 2.5 Watt Tx free running 12v-24V DC. FM band 88-108MHz. 500mV RMS audio sensitivity. FMTX2A Kit $49 A digital stereo coder using discrete components. XTAL locked subcarrier. Compatible with all our transmitters. FMTX2B Kit $49 3 stage XTAL locked 100MHz FM band 30mW output. Aust pre-emphasis. Quality specs. Optional 50mW upgrade $5. FMTX5 Kit $98 Both a FMTX2A & FMTX2B on 1 PCB. Pwt & audio routed. FME500 Kit $499 Broadcast specs. PLL 0.5 to 1 watt output narrowcast TX kit. Frequency set with Dip Switch. 220 Linear Amp Kit $499 2-15 watt output linear amp for FM band 50mW input. Simple design uses hybrid. SG1 Kit $399 Broadcast quality FM stereo coder. Uses op amps with selectable pre-emphasis. Other linear amps and kits available for broadcasters. Brings you advanced technology at affordable prices As featured in ‘Silicon Chip’ Jan. ’96 This REFLEX® charger charges single cells or battery packs from 1.2V to 13.2V and 110mAh to 7Ah. VERY FAST CHARGING. Standard batteries in maximum 1 hour, fast charge batteries in max. 15 minutes Single gate oscillator Normally, at least two gates are needed for an RC oscillator if a Schmitt trigger gate isn’t available. This circuit was employed to switch a DC buzzer on and off. In effect, the circuit runs as a conventional phase shift oscillator with the three time constants providing a 180° phase shift at the operating frequency. G. LaRooy, Christchurch, NZ. ($20) SMART ® FASTCHARGERS AVOID THE WELL KNOWN MEMORY EFFECT. NO NEED TO DISCHARGE. Just top up. This saves time and also extends the life of the batteries. SAVE MONEY. Restore most Nicads with memory effect to remaining capacity and rejuvenate many 0V worn-out Nicads EXTEND THE LIFE OF YOUR BATTERIES Recharge them up to 3000 times. DESIGNED AND MADE IN AUSTRALIA 12V-24V Converters, P. supplies and dedicated, fully automatic chargers for industrial applications are also available. This simple circuit operates as a conventional phase shift oscillator. PO Box 314 Blackwood SA 5051 Ph 0414 323099  Fax 088 270 3175 AWA FM721 FM-Tx board $19 Modify them as a 1 watt op Narrowcast Tx. Lots of good RF bits on PCB. AWA FM721 FM-Rx board $10 The complementary receiver for the above Tx. Full circuits provided for Rx or Tx. Xtals have been disabled. MAX Kit for PCs $169 Talk to the real world from a PC. 7 relays, ADC, DAC 8 TTL inputs & stepper driver with sample basic programs. For a FREE detailed technical description please Ph: (03) 6492 1368 or Fax: (03) 6492 1329 2567 Wilmot Rd, Devenport, TAS 7310 Protect Your Valuable Issues Silicon Chip Binders ETI 1623 kit for PCs $69 24 lines as inputs or outputs DS-PTH-PCB and all parts. Easy to build, low cost. ETI DIGI-200 Watt Amp Kit $39 200W/2 125W/4 70W/8 from ±33 volt supply. 27,000 built since 1987. Easy to build. ROLA Digital Audio Software Call for full information about our range of digital cart players & multitrack recorders. ALL POSTAGE $6.80 Per Order FREE Steam Boat For every order over $100 re­ceive FREE a PUTT-PUTT steam boat kit. Available separately for $19.95, this is one of the greatest educational toys ever sold. REAL VALUE AT $11.95 ★  Heavy board covers with 2-tone PLUS P green vinyl covering &P ★  Each binder holds up to 14 issues ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. July 1997  33 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SERVICEMAN'S LOG The neighbour who made things worse Why do some people allow friends or neighbours to “have a go” at their VCR or TV when it fails? If their motive is to save money, the ploy usually backfires. More often than not, an amateur serviceman only makes things worse and the job ends up costing more. My first customer of the morning was Mr Davis who brought in a Sharp VCA34X mid-drive video. He cheerfully admitted he knew nothing about it and informed me that he “was only deliver­ing it for his wife”. When I turned it on, I noticed that it was patterning severely in playback mode and when the test switch was on. In addition, I was unable to receive any channel in the E-E mode. The patterning was very similar to the symptoms displayed when an electrolytic capacitor has failed in the power supply and the effect actually seemed to change when I hit some of the small electros in this part of the circuit with the freezer. It seemed initially that one or possibly two electros were susceptible and as I felt sure that I was on the right track, I decided to change them without further ado. In fact, I changed all the electros because if one was faulty, it was possible that the others wouldn’t be far behind it. As it turned out, I was just guessing because changing them made no difference at all. The CRO and multimeter showed that all voltages were clean and correct and so my suspicions now turned to the RF modulator. To check this, I decided to feed the audio/video outputs from the VCR directly into a monitor. When I played a tape the picture was now clear but there was still no TV channel reception (just snow). It was then that I noticed that when the VCR was switched off, a TV channel appeared quite clearly. This meant that the TV was tuned into a TV station and that the VCR was transmitting right on top of it. As the output of this VCR is on UHF and can be adjusted easily, I retuned it to approximately Ch.37 and the pattern­ing disappeared completely. It is difficult to comprehend the misleading effects I had in the power supply. Perhaps they were due to the proximity of my hands and arms to the antenna but it’s hard to tell sometimes. The real complaint At this stage, I thought that it would be a good idea to talk to Mrs Davis (the VCR’s owner), to find out what was really meant to be wrong with the unit. As it turned out, her only complaint was that it was unable to record TV stations. I asked about the pattern­ing on playback but she said she really hadn’t noticed it as their reception was pretty poor any way. Well, at least I now knew what the complaint was. The only thing that couldn’t be explained was why the RF output was so far off the factory set Ch.37. Perhaps someone had had a fiddle? So I now had to address the real 38  Silicon Chip knowledge being a dan­gerous thing. By the way, out of curiosity, I check­ed the faulty transis­tor on my multi­meter – it still read perfectly, with no leakage indicated. I then held it up to the light and looked at the legs with a magnifying glass. At last a clue – I could just detect some signs of corrosion where the legs entered the transistor case. My conclusion was that this may have been enough to at least make it intermittent. Play it again Sam problem – no TV tuning. To reach the tuner, the top board has to be removed and the bottom board extracted from its well in the plastic case. After gingerly laying out the boards on the bench, I switched it on and measured the voltages to the tuner. All were correct except for the tuning voltage which was permanently stuck on 33V, even when I invoked the tuning mode and sent it searching from band I to band IV. The only changes that occurred were on the band switching rails. Because I didn’t have the correct service manual, I worked from a VCH83/85X manual. This model is a hifi mid-drive unit which is similar to the VCA34X and I found that I could follow the relevant part of the circuit quite easily, the main dif­ference here being circuit reference numbers. Tracing back the circuit from the tuner, I arrived at the top board and eventually came to Q1401 (2SC1740­ SQR) which also had an unchanging 33V on its collector. However, its base voltage was changing as the tuning was adjusted. It was at this stage that I noticed fresh soldering all around the area. Someone had definitely been there before me. I measured the transistor in circuit and it was fine. I then put the CRO on the base and could see the mark-space ratio of the pulses change in response to the tuning but there was still no change in the collector. The transistor must be lying – there just had to be something wrong with it! I decided to replace it with a BC547 as I didn’t have the original 2SC­1740SQR. It worked – all the stations could now be tuned properly and locked into memory. When Mrs Davis picked it up I asked her if someone had looked at it before. She wasn’t nearly as fierce as I had imagined her to be and she graciously admitted that the culprit was her next door neighbour who had also mistuned the RF output. I put it down to a case of a little I was grateful to the Jones family when they decided to bring their Samsung into the workshop because it is a large 68cm stereo TV. Their two sons carried it in from the station wagon and put it on the bench. I gave it immediate priority so that I could get it out of my cramped workshop, the only problem being that one of the two symptoms described was intermittent. The set was a CB7230WT using an S60MT chassis and apparently it didn’t always want to start unless they hit it! And now it had a white line across the screen. Serves them right for assaulting the poor monster! Removing the back revealed a flat horizontal chassis divid­ed into two boards. Access was poor due to the usual short con­necting leads to the front and because the large reflex cabinets for the speakers got in the way. The lefthand board had the power deflection functions, while the righthand board carried the small signal circuits. On switch on, it displayed the classic vertical deflection collapse symptom; ie, a white line across the screen, just as described. It didn’t take a mental giant to work out that the 9-pin flat-pack TDA3654 (IC301) attached to a heatsink was the vertical output IC (IC301), especially as it got very hot. Access to the underside of the board was difficult but manageable once it was unscrewed from its support frame. I fitted a new IC and this cured this fault. Unfortunately, having just fitted the last screw in the back, I found that it wouldn’t switch on – not even after I had assaulted it, as well! There was just the momentary sound of EHT static and then nothing, so out it all came again. With the power board delicate­ly balanced on its side and meter probes at the ready, July 1997  39 Serviceman’s Log – continued I could determine that all three motors could be made to rotate but only intermittently and not necessarily in the correct sequence. This erratic behaviour lead me to suspect that it was either a noisy mode select switch or a crook microprocessor. I took the line of least resistance and went for the form­er. I removed the front escutcheon, then the top board, and gingerly unscrewed the loading motor assembly, being careful not to let the loading arms spring out. I then unsoldered the old white mode select switch, installed the new blue type (part no. 79TD3895) and carefully aligned the pointer as before. When I got it all back together again, I switched it on with a cover over the ejector and pressed the off/eject button. Just like a trained dog, it immediately stopped sulking and proffered me my tape. I tested it thoroughly with all sorts of tapes before phoning Mr Bryant. My only fear was his statement about it “chewing tapes” –surely he meant swallowing them whole? My pal the Palsonic I switched it on again and it came on perfectly. Well, to cut a long story short, I jiggled and poked, bent and hit the boards until finally I established the fault was associated with relay RL801, which switches the 21V and 16V rails. So was it the relay that was at fault or the relay driver circuit? I traced the line from the relay back towards the driver circuit and eventually came to pin 2 of connector CNP801. It was then that I noticed that the orange 5V lead that goes to pin 1 was not quite properly in its plug receptacle. It didn’t take long to fix this and confirm that this was indeed the culprit for the intermittent start-up problem. I tested it frequently until the Jones’s gratefully picked their set up later that evening. The greedy VCR I had asked Mr Bryant to also bring his remote control and instruction 40  Silicon Chip booklet when he brought in his Daewoo-made NEC VN22 VCR and he was as good as his word. Although he complained that it was “just chewing tapes”, it simply swallowed my dummy test tape and alarmingly wouldn’t regurgitate it when the eject button was pressed. The only dis­play was a cyclical presentation of all modes. The instruction booklet describes this function indicator as the emergency mode and advises the user to push the reset button. However, pushing this and/or any other button was an exercise in futility. This sucker wasn’t going to give me back my tape whatever I did! I attacked it with my electric screwdriver and soon had the covers off and then tried to persuade it to give it back. It took me a little while to realise that, with no covers, the end sen­ sors were exposed to incandescent light and this was adding to my woes. Having overcome this problem, So far the day was going well. With any luck, I would be able to knock over two more jobs before the end of the day. The next in line was a Palsonic 3428 TV set which uses a Goldstar PC04X chassis. The guy who brought this in claimed that he was a technician and that the “electros from the picture tube had caused the fault to occur”. I remained unconvinced and I suspected that he had had a go himself and so I was very reluct­ant to proceed. However, the bank keeps telling me I need money and so I can’t turn everything away. When I switched it on, the set displayed a bright uncon­trollable raster which is quite a common symptom for this model. Unfortunately, it has many causes, the most usual being IC501, a Telefunken TDA35622A. For this reason, I have saved the chroma module and also the CRT board from a wrecked set so that I can quickly test these components. The chroma module comes in two different interchangeable sizes. It is also worth remembering that the heat­ sink around the power supply will often retain its high voltage for some time after the set has been turned off. A shock from this certainly won’t im­ prove your temper as you struggle to remove this chroma card. After substitution, the screen control on the tripler often needs realigning to obtain the correct operating point for the tube and it doesn’t behave like any other I know. The darkest picture is somewhere in the centre of its range with each end of the control giving a bright raster! What’s more, the effect on the picture can vary, with some colours disappearing completely at certain settings. In this case, the substitute chroma module made no dif­ference, so next I swapped the CRT board. This fixed the problem once the screen control had been adjusted for the darkest pic­ture. OK, so what was wrong with the CRT board from the custo­mer’s set. The circuit (see Fig.1) consists of seven transistors (two for each gun plus a common one), plus three diodes and various resistors and capacitors. Because the overall tint of the white raster was correct, the greyscale was also correct which surely meant that the three amplifiers were working OK, giving even quantities of red, green and blue. Anyway, I checked the voltages all over the board but could find nothing wrong. Next, I changed the five components that are common to all three driver stages (D901, Q907, C1, R922 and R923) but they made no difference. I disregarded the screen and heater components (C907, C908, R924 and R925) as being too fanciful and there were no cracks in the board or dry joints. So if it wasn’t something common, then perhaps there was some other component failure that was upsetting the whole cir­cuit. What I did discover was that hitting the components with freezer produced a positive result –the raster immediately began to darken and a picture began to emerge. And this could be fur­ ther improved by finding the correct point with the screen con­trol. Eventually, after repeated freezing and heating, especially on or around D902, D903 and D904, the picture was completely restored to normal. At this stage, I put all the old parts back in (except for C1) and carefully checked the diodes and their associated paral­lel capacitors (C904, C902 & C906) after first removing them from circuit. I couldn’t find anything wrong with these parts, so I replaced them and put the set aside to soak Fig.1: the CRT board circuit for the Palsonic 3428 TV set. It uses seven transistors (two for each gun plus a common one), plus three diodes and various resistors and capacitors test. As it subse­quently turned out, it was still behaving normally some two weeks later. So what caused the problem? My only theory (and I admit that it’s rather a lame one) is that one or more of the diodes was internally intermittent and this was affecting the beam current. And this in turn was being shifted well beyond the operating point of the tube so that normal operation was no longer possible. Or is the explanation much simpler? In all the swapping around of components, have I merely fixed a poor solder joint on the PC board. It is an unsatisfactory result and I invite readers to speculate. A dead Philips The last set of the day was a Philips KR66875 2B-S chassis stereo TV which was dead. There was voltage going to the chopper transistor but no B+. I couldn’t find any shorts on this rail or to the line output transistor and felt pretty sure that the line output transformer was faulty. To test this, I shorted the base of the line output transistor to its emitter and connected a voltmeter to the collector. On switch on, the collector voltage rose to the full B+ line. Fortunately, I had a flyback trans- former in stock but removing the old one is fairly hairy in that it is hard to remove the solder between the pins and the rivets in the chassis. A combination of solder sucker, solder wick and bad language does the trick and I finally managed to edge the old one out. The next challenge is to remove the EHT and focus leads which clip into receptacles. These were eased out using side cutters and pushed into their new homes. The new transformer was then installed and, as a precaution, I also replaced the 68µF electro feeding the vertical output IC and soldered a few suspicious looking joints on the main board. I also checked out the memory backup battery. By the way, access to this set is rather difficult and I find it easier to work with the entire cabinet upside down on a towel rather than trying to find a service position for the chassis. Fortunately, the new flyback transformer did the trick so that was another one knocked over. Why can’t they make TV sets easier to service? Still, I mustn’t grumble too much ­­– apart from the Palsonic, the day had gone fairly well. And even then, I managed to get the set fixed, or so it appears. SC Only time will tell. July 1997  41 Simple Waveform Generator This compact unit produces both square and triangle waves over the frequency range from 100Hz to 20kHz. Build it and use it to test audio amplifiers, filters, tone decoders and digi­tal circuits. By JOHN CLARKE A SIMPLE WAVEFORM generator is always useful to have on your workbench. It can be used as a signal source for all sorts of circuits, to test that they are operating correctly. A wave­form generator, even a simple unit such as that described here, is particularly useful for troubleshooting or when building circuits from scratch. This unit lets you select between triangle and square waves and you can vary the frequency output from about 100Hz to 20kHz using a single potentiometer. A second potentiome­ ter lets you vary the output level from 0-10.5V p-p for square waves, or from 0-4V p-p for triangle waves. All the parts, including the two pots, are mounted on a compact PC board, so that the assembly is really easy. But first, let’s find out how it works. Circuit details Fig.1 shows the circuit details. As can be seen, it’s based on the common 42  Silicon Chip 555 timer IC which is wired as an astable oscilla­tor. The timing components are connected to pins 6 & 2 of the IC, with the .01µF capacitor being alternately charged and discharged via VR1 (the frequency control) and its series 2.2kΩ resistor. The circuit works like this. Initially, when power is first applied, the .01µF timing capacitor is discharged and IC1’s pin 3 output is high. The .01µF capacitor now charges via the 2.2kΩ resistor and VR1 until it reaches twothirds the supply voltage (ie, 2/3Vcc). At this point, an internal comparator connected to pin 6 (the threshold input) of IC1 trips and this switches pin 3 low. The capacitor now discharges via VR1 and the series 2.2kΩ resistor until it reaches 1/3Vcc (the lower threshold). This point is detected by the trigger input (pin 2), which switches pin 3 high again. Thus, the cycle repeats indefinitely and pin 3 of IC1 alternately switches high and low while ever power is applied. Because it controls the charge/discharge times for the timing capacitor, VR1 effectively sets the frequency of oscillation. The nominal frequency (f) is given by the formula: f = 0.7/R1.C1 where R1 is timing resistance and C1 is the timing capacitance. In this case, R1 = VR1 + 2.2kΩ and C1 = .01µF. These values give a calculated frequency range of 200Hz to 45kHz. However, these figures don’t apply in practice because the output of IC1 does not go fully high. An 820Ω pullup resistor is used to pull pin 3 higher than it would otherwise go to give a more symmetrical waveform. However, the resulting frequency range of 100Hz to 20kHz is still less than calculated. The waveform at pin 3 is a nominal square wave, as shown in Figs.2 & 3. These show the square wave output at 19.7kHz and 122Hz, respectively. The duty cycle is not exactly 1:1 because of Fig.1: the circuit uses a 555 timer IC which is wired as an astable oscilla­tor. Transistor Q1 buffers the triangle output. pin 3 not going fully high but is near enough for our purposes. The waveform on pins 2 & 6 is triangle shaped since it represents the charging cycles of the timing capacitor. This output has a fairly high impedance, particularly at low frequen­ cies when VR1 is above 100kΩ. Transistor Q1 is used to buffer the triangle waveform. This transistor is wired as an emitter follower, which means that the signal on the emitter follows the signal applied to the base. Fig.4 shows the appearance of the triangle waveform when the frequency is about 5.4kHz. Switch S2 selects between the square wave at pin 3 of IC1 and the triangle waveform at the emitter of Q1. From there, the signal is fed to level control VR2 and then AC-coupled to the output termi­ nals via a 10µF capacitor. This capacitor ensures that the output signal has no DC component, while the associated 10kΩ resistor ensures that the output is always load­ed. Power for the circuit can be derived from virtually any supply capable of providing between 5V and 15V DC at about 20mA. The most convenient source for this would be a plugpack supply. Diode D1 provides reverse polarity connection protection, while LED1 is the power indicator. A 100µF capacitor decouples the supply to the circuit. Construction All the parts for the Waveform Generator are installed on a PC board coded 01307971. Fig.5 shows the wiring details. Begin the assembly by installing PC stakes at all external wiring points and at the connection points for the FEATURES Output waveform ................................................... Triangle or square wave Frequency range ..................................................100Hz to 20kHz nominal Square wave amplitude ....................................... 0-10.5V p-p (12V supply) Triangle wave output ................................................ 0-4V p-p (12V supply) Power supply ............................................................................... 5-15V DC Protection .......................................................... Reverse polarity protected Output impedance .............................................................................. <1kΩ Fig.2: this is the waveform that appears at pin 3 of IC1 when the output frequency is 19.69kHz. Fig.3: the waveform at pin 3 of IC1 when the output freq­uency is 122Hz. The duty cycle is not exactly 1:1. July 1997  43 Fig.4: this scope shot shows the triangle waveform at a frequency of about 5.4kHz. Note that this waveform was captured at the emitter of buffer transistor Q1. PARTS LIST 1 PC board, code 01307971, 60 x 105mm 1 500kΩ linear pot (VR1) 1 1kΩ linear pot (VR2) 2 knobs 2 DPDT slider switches (S1,S2) 10 PC stakes 1 20mm length of 0.8mm tinned copper wire Semiconductors 1 555 timer (IC1) 1 BC548 NPN transistor (Q1) 1 1N4004 1A diode (D1) 1 5mm red LED (LED1) Capacitors 1 100µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 .01µF MKT polyester Resistors (0.25W, 1%) 2 10kΩ 1 820Ω 2 2.2kΩ Fig.5: install the parts on the PC board as shown in this diagram. Make sure that all polarised parts are correctly orientated. rectly on the PC board, while the two pots are mounted by soldering them to their PC stakes. Cut the pot shafts to length before installing them and note that VR1 is a 500kΩ pot, while VR2 is a 1kΩ pot. Finally, complete the assembly by fitting rubber feet to the corners of the PC board. Testing Fig.6: this is the full-size etching pattern for the PC board. pots. Once this has been done, you can install D1, the resistors and the wire link. The IC and the transistor can go in next, followed by the capacitors and the LED. Take care to ensure that all polarised parts are correctly orientated. It’s 44  Silicon Chip quite easy to identify the LED leads, as the anode lead is the longer of the two. In addition, you will find a small flat area on the flange that runs around the bottom of the LED. This flange is always adjacent to the cathode lead. The two switches are mounted di- To test the unit, connect the output terminals to an audio amplifier, set the level control fully anticlockwise and apply power. If everything is working correctly, you should hear a tone in the amplifier’s loudspeaker when the level control is ad­vanced. Check that the frequency of this tone can be varied using the frequency control –this should range from 200Hz to beyond the limit of audibility. Alternatively, you can check that the unit is working properly by using an oscilloscope to monitor the output signal. If it doesn’t work correctly, check the board for solder bridges and missing solder joints. You should also check the supply rail to IC1 and to Q1’s collector. If the unit gives square waves but there is no output when triangle waves are selected, check the SC circuit around Q1. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au tronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semicustom electronics & data communications. 63 chapters, in hard cover at $120.00. Silicon Chip Bookshop Radio Frequency Transistors Newnes Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Guide to TV & Video Technology By Eugene Trundle. First pub­lish-­ ed 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $49.95. Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Digital Audio & Compact Disc Technology Electronics Engineer’s Reference Book Hard co Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM Power Electronics Handbook Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order  ve Edited by F. F. Mazda. version nowr available First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, elec- ❏ Bankcard  ❏ Visa Card  ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $85.00. Surface Mount Technology By Rudolph Strauss. First pub­ lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $52.95.  Title ☐ ☐ Newnes Guide to Satellite TV ☐ Guide to TV & Video Technology ☐ Servicing Personal Computers ☐ The Art Of Linear Electronics ☐ Digital Audio & Compact Disc Technology ☐ Power Electronics Handbook ☐ Electronic Engineer's Reference Book ☐ Radio Frequency Transistors ☐ Surface Mount Technology ☐ Audio Electronics Price $55.95 $39.95 $59.95 $49.95 $55.95 $59.95 $120.00 $85.00 $99.00 $52.95 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ & PNG add $10.00 per book, elsewhere add $15 per book. TOTAL $A July 1997  53 Colour TV pattern generator; Pt.2 While the Colour Television Pattern Generator is rather complex in its operation, the circuitry is straightforward. This is because all the patterns are stored in the ROM. This month, we present the circuit and give the construction and testing de­tails. By JOHN CLARKE 54  Silicon Chip connection. With LK1a in position (run mode), counter IC2 is clocked by a 3.2768MHz oscillator based on IC6a, with IC6b serving as a buffer stage. Note that pin 13 of IC6a is tied high while its pin 12 input is connected to its pin 11 output via a 4.7MΩ resistor. This biases the gate in the linear mode so that it operates as an inverting amp­ lifier. The 33pF capacitors to ground on either side of crystal X1 provide the correct loading. Fig.9 (right): the complete circuit diagram of the pattern generator. All the patterns are stored in the EPROM (IC1) and this is programmed via the parallel port of a PC.  The circuit for the Colour Television Pattern Generator is shown in Fig.9 and comprises 11 ICs in total. Central to the circuit is IC1 which is the 64K EPROM or OTP memory (note: this device was incorrectly referred to in Pt.1 as an EEPROM). This IC has its address lines connected to counters IC2, IC3, IC4 & IC5. Counter IC2 is driven by a clock signal from either IC6b or IC6c, depending on the link (LK1a or LK1b) LK1b is substituted for the program mode, in which case IC2 is clocked via inverter stage IC6c from the D2 line on Port C of the computer. The 100kΩ pullup resistor connected to IC6c’s inputs prevents them from floating when Port C is disconnected, while the associated 680pF capacitor provides transient suppres­sion. This prevents false clocking which could otherwise occur whenever there are level changes in the data lines on Port A. IC2 is an up/down pressettable synchronous 4-bit counter with a carry out (CO) output at pin 12. This output is fed to the clock input of the following counter (IC3), which is connect­­ed in cascade with IC2. IC4 & July 1997  55 PARTS LIST 1 PC board, code 02305971, 173 x 142mm 1 plastic instrument case, 200 x 155 x 65mm, with aluminium front panel 1 front panel label, 195 x 63mm 1 rear panel label, 31 x 25mm 1 video modulator, Astec UM1285AUS 0/1 (DSE Cat K-6043 or equiv­alent) 1 12VAC 500mA plugpack 1 DC power socket 3 SPDT toggle switches (S1,S3,S4) 1 2-pole 6-way rotary switch (S2) 1 3.2768MHz parallel resonant crystal (X1) 1 4.433619MHz parallel resonant crystal (X2) 2 panel-mount RCA sockets 1 25-pin D socket, PC board mounting (not right angle) 1 mini TO-220 heatsink, 19 x 19 x 9mm 1 4-way pin header 1 20-way pin header 5 jumper shunts 1 28-pin DIL IC socket 1 8mm ID solder lug 17 PC stakes 1 15mm diameter knob with position indicator 3 3mm x 6mm long screws plus nuts 2 3mm x 12mm long screws plus nuts 2 6mm untapped standoffs 4 self-tapping screws to mount PC board 1 200mm length twin shielded wire 1 350mm length black hookup wire 1 200mm length blue hookup wire 1 50mm length yellow hookup wire 1 50mm length green hookup wire 1 60mm length of 4-way rainbow cable 1 650mm length of 0.71mm tinned copper wire IC5 are also cascaded to provide a total of 16 address lines for IC1. The clear (CLR) input of each counter is normally tied low via a 100kΩ resistor. When these inputs go high, the counter outputs are reset low. LK5b 56  Silicon Chip Semiconductors 1 programmed NM27C512N120 OTP or 27C512-10, 27C512-12 EPROM (IC1) – see text 4 74HC193 4-bit presettable up/down counters (IC2-IC5) 1 74HC00 quad dual input NAND gate (IC6) 1 555 timer (IC7) 1 4053 3-pole 2-way analog switch (IC8) 1 74HC04 hex inverter (IC9) 1 AD722 RGB to NTSC/PAL encoder (IC10) 1 74HC27 triple 3-input NOR gate (IC11) 4 1N4004 1A rectifier diodes (D1-D4) 1 1N914 signal diode (D5) 1 3mm green or red LED (LED1) Capacitors 1 1000µF 25VW PC electrolytic 2 470µF 16VW PC electrolytic 8 10µF 16VW PC electrolytic 8 0.1µF MKT polyester 2 0.01µF MKT polyseter 2 680pF MKT polyester or ceramic 1 100pF ceramic (see text) 2 33pF ceramic 1 4-40 3-pin trimmer capacitor (VC1) Resistors (0.25W, 1%) 1 4.7MΩ 1 1kΩ 1 330kΩ 1 680Ω 8 100kΩ 3 330Ω 3 10kΩ 1 180Ω 1 2.2kΩ 1 120Ω 3 2kΩ 1 75Ω Software 1 Software disc (optional) – available for $10 (incl. p&p) from Silicon Chip Publications Miscellaneous Medium-duty hookup wire, rainbow cable, 25-pin D-plug lead (optional for programming), solder. is installed for programming mode, which means that the CLR inputs of IC2-IC5 are all momen­ tarily pulled high via a 10µF capacitor when power is applied. This resets the counters so that all output lines are low. Conversely, in the run (pattern producing) mode, LK5a is installed and the counters are now reset via IC11c’s output. The D4, D5 & D7 data lines of IC1, corresponding to the blue, green and composite sync outputs, are NORed in IC11a. All these lines go low after the 312th line of data has been produced and IC11a’s output goes high. This is inverted by IC11b and so the .01µF capacitor on IC11c’s inputs quickly discharges via D1. IC11c’s output thus goes high and resets the counters. This reset signal stays high while the .01µF capacitor at IC11c’s input charges via the 2.2kΩ resistor. This ensures that all the counters reset correctly. The delay circuit is necessary because data lines D4, D5 & D7 are no longer all low once the memory has returned to the start of line 1. Programming pulse IC1’s E-bar input at pin 20 determines whether the device is in program or read mode. When link LK2a is in position, pin 20 is tied low and the data lines becomes outputs. This is for the run mode. Conversely, when LK2b is in position, a programming pulse circuit consisting of 555 timer IC7 and inverter IC6d is connect­ed to the E-bar input of IC1. This circuit is in turn controlled by the -D1 line of computer Port C. Initially, pin 2 of IC7 is held high via a 10kΩ resistor which connects to the +5V supply rail. However, when -D1 of Port C goes low, it pulls pin 2 of IC7 low via a .01µF series ca­pacitor. This triggers IC7 so that pin 3 goes high for the time set by the 330kΩ resistor and 0.1µF capacitor tied to pins 6 & 7. Pin 6 is the threshold input and this switches the pin 3 output low again once its voltage reaches 66% of the supply voltage. This is nominally after 33ms. IC6d inverts the signal to provide the correct programming pulse level to the E-bar input of IC1. Note that the E-bar input of IC1 is monitored via the D4 input of computer Port B. This allows the software to detect when the programming pulse has finished. The Vcc input to IC1 at pin 28 needs to be 5V when the unit is operated in run mode and 6V when operated in program mode. Links LK3a and LK3b provide this by selecting either the output from REG1 or the output from The 25-pin D socket is mounted on the PC board and is connected to the parallel port of the computer to program the EPROM. Once programming has been completed, the unit operates independently of the computer. REG2 respectively. Simi­larly, the G/ Vpp input at pin 22 requires 12.5V for programming but 0V when outputting the data. This is achieved using links LK4a and LK4b. LK4b selects the 12.5V output from regulator REG3, while LK4b connects the G/Vpp pin to ground. The circuit is powered from a 12VAC plugpack via switch S1. Diodes D1-D4 rectify this and the resulting DC is filtered using a 1000µF capacitor. REG1, REG2 and REG3 regulate the voltage down to 5V, 6V and 12.5V respectively. REG1 and REG2 are standard 3-terminal regula­ tors which provide 5V and 6V rails, respectively. The 10µF capacitors at their outputs are there to prevent instability and provide improved transient response. LED1 is connected across the 5V supply via a 680Ω resistor to give power-on indication. REG3 is an adjustable regulator which produces a nominal 1.25V between its adjust and output terminals. The 120Ω resistor across these terminals sets up a current of around 10mA which flows through the 1kΩ resistor and 200Ω variable resistor VR1. VR1 is adjusted to set the output voltage to 12.5V. Rotary switch S2a selects between the checkerboard, dot, crosshatch/circle and raster patterns available at the D0-D3 outputs of IC1. The selection is applied to the ax input (pin 12) of IC8, a 4053 CMOS analog switch. Input ax is the red signal for the selected pattern, while the bx and cx inputs (pins 2 & 5) are for the green and blue signals. The latter are normally connected to the ax input via switch S2b, except for position 2 when the red raster is select­ed. In that case, the green and blue inputs are tied high via a common 100kΩ resistor. IC8 basically behaves as a 3-pole 2-position switch. The a, b & c outputs at pins 14, 15 & 4 respectively are the three poles. The ax, bx and cx connections are switched through when the A, B and C control lines at pins 11, 10 & 9 are low and this occurs when switch S3 is in position 1. Depending on the position of S2, this provides the signals for either the white raster, the red raster, crosshatch/circle, dot or checkerboard pattern. Conversely, when S3 is open, the A, B and C inputs are pulled high via a 100kΩ resistor and the alternative ay, by & cy inputs (pins 13, 1 & 3) are switched through instead. This pro­ vides the colour bar pattern from the D6, D5 & D4 data lines of IC1. RGB-to-PAL encoding The a, b and c outputs of IC8 are July 1997  57 Table 1: Resistor Colour Codes  No.   1   1   8   3   1   3   1   1   3   1   1   1 Value 4.7MΩ 330kΩ 100kΩ 10kΩ 2.2kΩ 2kΩ 1kΩ 680Ω 330Ω 180Ω 120Ω 75Ω buffered using inverters IC9a-IC9f which are connected as three parallel pairs. This is necessary to allow the signals to be fed to the following atten­ uator stages, each of which only has a nominal 2.33kΩ impedance. These attenuators reduce the 5V signal outputs from IC9 to 700mV, as required to produce a full white signal from the following RGB-to-video encoder stage based on IC10. As shown in Fig.9, the signals from the attenuators are applied to the RGB inputs (pins 6, 7 & 8) of IC10. In addition, the composite sync signal from D7 of IC1 is applied to IC10’s pin 16 input. The 4.43MHz crystal on pin 3 provides the colour burst frequency, while the internal phase lock loop multiplies the crystal frequency by four to produce the timing signals for the PAL encoder. Trimmer capacitor VC1 allows the colour burst frequency to be set to 4.43619MHz. IC10 produces composite video, luminance and chrominance signals at pins 10, 11 and 9 respectively. Switch S4 selects the composite video signal for colour patterns and the luminance output for black and white or grey­ scale. The only difference between the composite video and the luminance signal is that the latter does not include the chrominance (or colour) information. The luminance and chrominance outputs can be used to pro­vide S-video signals if required. To add this facility, you would have to install a 75Ω resistor and 470µF capacitor in series with the luminance output and a 75Ω 58  Silicon Chip 4-Band Code (1%) yellow violet green brown orange orange yellow brown brown black yellow brown brown black orange brown red red red brown red black red brown brown black red brown blue grey brown brown orange orange brown brown brown grey brown brown brown red brown brown violet green black brown resistor and 0.1µF capacitor in series with the chrominance output. The video signal on S4’s wiper is fed to the video output socket via a 470µF capacitor and 75Ω resistor. It is also fed to a video modulator via VR2 and a 470µF capacitor. VR2 sets the signal level into the modulator, while the associated 10kΩ resis­tor biases the modulator input to its correct black level. The modulator also has an audio input and this is fed via a 10µF capacitor. The maximum level that can be applied here is 5V p-p. Power for the modulator is derived from the +12.5V supply from REG3 and is fed via a 180Ω resistor to limit the current through an internal zener diode. The RF output from the modulator is on either channel 0 or 1, as set by link LK6. Construction Despite the complicated way in which it works, this unit is really easy to build. Virtually all the parts are mounted on a single PC board coded 02305971 (173 x 142mm) and this is housed in a standard plastic instrument case with an aluminium front Table 2: Capacitor Codes  Value IEC Code EIA Code  0.1µF  100n   104  0.01µF   10n   103  680pF  680p   681  33pF   33p    33 5-Band Code (1%) yellow violet black yellow brown orange orange black orange brown brown black black orange brown brown black black red brown red red black brown brown red black black brown brown brown black black brown brown blue grey black black brown orange orange black black brown brown grey black black brown brown red black black brown violet green black gold brown panel. Adhesive dress labels were fitted to the front and rear panels of the prototype to provide a professional finish. Begin the construction by carefully checking the PC board for shorts between tracks and breaks in the copper pattern. Usually, there will be no problems here but it’s best to check before installing any of the parts. In some cases, it may be necessary to enlarge the mounting holes for the 25-pin D-socket and for the regulator tabs (these holes should all be 3mm). You should also check the hole sizes for the modulator earth mounting lugs, as well as the four corner mounting holes for the PC board. Fig.10 shows the wiring diagram. Begin the board assembly by installing the links and the resistors. Table 1 shows the resistor colour codes but you should also check each value on a digital multimeter, as the colour bands can sometimes be diffi­cult to read. The diodes can then be installed, taking care to ensure that they are correctly oriented. Note that two different diode types are used on the PC board, so be sure to use the correct type at each location. The 1A 1N4004s have a black body, while the smaller 1N914s are usual­ly orange in colour. Seventeen PC stakes are specified in the parts list and these are installed on the PC board at the external wiring points. The exceptions here are points 1-4 adjacent to IC1, where a 4-way pin header is installed to terminate four of the leads from switch S2. Note: The patterns produced by the TV Pattern Generator are slightly off-centre due to a slight displacement in the line sync signal. In most cases, the normal over-scanning of each line on the TV screen will mask out this small shift. It can be corrected by adding an RC network to delay the line sync by the requisite 1.5µs. This involves adding a 4.7kΩ resistor between the D7 output of IC1 at pin 11 and the sync input of IC10 at pin 16. The pin 16 input of IC10 is bypassed to ground with a 270pF capacitor. The resistor is best placed instead of the link on the PC board above the three 330Ω resistors near IC10. The capacitor can connect from pin 16 to pin 1 of IC10 on the underside of the PC board. Fig.10: take care to ensure that all parts are correctly orientated when assembling the PC board. Next, install the ICs in the locations indicated, taking care to ensure that the notched end of each device agrees with the wiring diagram. Use a socket for IC1 and leave this IC out until the testing stage described later on. IC10 is a surface mount device and is installed on the underside of the PC board as shown in one of the photos. To do this, first pre-tin the copper pad areas where the IC pins will be located, then solder the IC in place using a fine-tipped soldering iron. When you have finished, inspect your work care­fully to ensure that there are no July 1997  59 4 terminal. The 25-pin D-socket is mounted on 5mm spacers and secured using 3mm screws and nuts. It’s 25-pin connections are then soldered to the copper pads of the board. Link pairs LK1a/LK1b through to LK5a/LK5b are based on 2-pin headers. A jumper shunt is fitted to each pair and, in each case, is normally placed in the “a” position for run mode. Alter­natively, the links are all moved to the “b” positions for the programming mode. Either a single-in-line 20-way pin header or a dual-in-line 10-way pin header will be supplied for the link pins. In either case, you simply cut the header into 10 2-way pin headers using side cutters. Final assembly Once the EPROM has been programmed, move the LK1-5 jumpers to the rear (ie, to the “a” position) of their pin header pairs. Programming is unnecessary if you purchase a pre-programmed EPROM. solder bridges between adjacent pins of the device. The three regulators are mounted with their leads bent at right angles, so that their metal tabs sit flat against the PC board. The metal tabs are then secured to the board using 3mm screws and nuts. Note that REG1 (7805) is fitted with a small U-shaped heatsink but no heatsink is required for the other two regulators. Take great care when mounting the regulators. They are all different, so don’t get them mixed up. REG1 is a 7805 5V regula­ tor, REG2 is a 7806 6V regulator and REG3 is an LM317 adjustable regulator. The capacitors can be installed next, making sure that the electrolytic types are correctly orientated. Table 2 shows the codes used on the MKT polyester and ceramic types. This done, install the two trimpots, trimmer capaci­tor VC1, crystals X1 (3.2768MHz) and X2 (4.43MHz), and LED1. The latter should be mounted at full lead length, so that it can later be bent over and pushed into its mounting bezel on the front panel. It’s easy to identify the LED leads 60  Silicon Chip –the anode lead will be the longer of the two. The video modulator is mounted by soldering its earth tags to the PC board and inserting its four leads into the holes provid­ed. By default, link LK6 is open circuit and the modulator is set to channel 1. If you want channel 0 instead, bridge the two copper pads that sit adjacent to the modulator’s pin The AD722 RGB-to-PAL encoder (IC10) is a surface mount device and is installed on the underside of the PC board as shown here. Before installing the board in the case, it will be neces­sary to drill a number of holes in the front and rear panels. The first step is to fit the adhesive label to the aluminium front panel. This label can then be used as a template for drilling out the holes for the three toggle switches, the rotary switch and the bezel for the power indicator LED. You also have to drill holes in the rear panel for the RCA sockets, the DC power socket and the RF OUT socket. The various switches and sockets can then all be mounted in position. Note that switch S4 is fitted with a solder lug, to allow the front panel to be earthed. Before mounting the rotary switch, lift up the locking tab located under the mounting nut and move it to position 5 (rotate the switch fully anticlockwise first). This ensures that the switch only has the required five positions. Next, use an oversize drill to remove all the integral standoffs in the base of the case, except for those in the four corners. This done, fit the PC board and the rear panel to the base and secure the board to the corner standoffs using self-tapping screws. All that remains now is to complete the wiring. Use medium-duty hookup wire for the DC socket, switches S1 and S3, and for terminals 5 & 6 on S2. The connections to terminals 1-4 of S2 are run using rainbow cable, while the connection to the bottom terminal of S4 is run using hookup wire. The remaining connec­tions to S4 and to Fig.11: check your board for defects by comparing it with this full-size etching pattern, before installing any of the parts. the RCA sockets must be run using screened cable. Finally, complete the construction by pushing the power indicator LED into its bezel and attaching the knob to the rotary switch. Testing Before applying power, check to ensure that IC1 has not yet been installed and that the jumpers are in the LK1a, LK2a, LK3a, LK4a and LK5a positions (ie, run mode). This done, you can proceed with the following tests: (1) Connect the plugpack, apply power and check for 5V between pins 7 & 14 of IC6, IC9 & IC11. Similarly, there should be 5V between pins 8 & 16 of IC2-IC5 & IC8 and between pins 14 & 28 of the socket for IC1. (2) Monitor the output of REG3 and adjust VR1 for a reading of 12.5V. This done, check for 6V at the output of REG2 and for 0V at pins 20 & 22 of IC1. (3) If you have a preprogrammed ROM for IC1, switch off the power and plug it into its socket. You can now jump to the section headed “Trying it out”. (4) If your ROM is not preprogrammed, switch off and move the jumpers to LK1b, LK2b, LK3b, LK4b & LK5b. Now reapply power and check that pin 28 of IC1 is at 6V. Pin 20 should be at 5V and pin 22 should be at 12.5V. If you have access to an oscilloscope, you can check the pulse into pin 20 of IC1 when the -D1 Port C input is pulled low. You can do this by momentarily connecting a jumper lead between the -D1 line and ground. The resulting pulse at pin 20 of IC1 should be low for about 33ms. If all is correct, insert IC1 into its socket and proceed with the programming (not necessary if you have a pre-programmed ROM). Programming The ROM is programmed using either Quick Basic files or executable files. The procedure for programming the ROM using the executable files is as follows: (1) Check that the jumpers are in the LK1b, LK2b, LK3b, LK4b & LK5b positions. (2) Connect a 25-pin D-plug to 25-pin D-plug lead between the on-board socket and LPT1 of a PC. (3) Apply power to the pattern generator. (4) Insert the program floppy disc into drive A: (or B:), go to the A: prompt, type TVINSTAL and press Enter. This will automati­cally decompress and install the files contained within TVPATT.EXE into a directory called July 1997  61 COLOUR + (POWER 12VAC 500mA) (RF OUT CH1 OR 0) VIDEO OUT + POWER + ++ RED WHITE + GREY SCALE COLOUR TELEVISION PATTERN GENERATOR AUDIO IN Fig.12: these are the fullsize artworks for the front and rear panel labels. Basic on the C drive. To start the programming, simply type TVPGRM at the C:\Basic prompt. This automatically runs all the rele62  Silicon Chip vant .exe files to pro­gram the ROM. Note that the program first prompts you to apply power to the unit after ensuring that all the links are in the program position – see Fig.13. Once programming has started, the screen indicates the number of bytes programmed and which programs are to still to run – see Fig.14. The entire programming process will take about 45 minutes. Alternatively, if you want to program the ROM using the Basic files instead (eg, if you want to customise a pattern or you are not using parallel port LPT1 or the default address for this port), then follow this procedure: (1) Carry out steps 1 & 2 listed immediately above. (2) Copy the Basic software supplied on the floppy disc to a separate directory on your hard disc drive called “Basic”. There are seven files stored in this directory: TVPATT1.BAS – TVPATT7. BAS. All these files are necessary because a QBASIC program is limited in size to 64Kb. The first six programs are each about 56Kb, while the sev­enth is only about 16Kb. The first six programs are large mainly because of the 312- line DATA statements which each have 210 separate DATA items. Each program needs to run before the ROM is fully programmed but this happens automatically after TVPATT1.BAS is run. Note that the programs run in QUICK BASIC, so you will need to have this installed on your computer. The address of the port used is 378(HEX) to 37A(HEX). If you want to use a different port, then the address in each program will have to be altered to suit. The address used is the standard LPT1 port found in virtually all PCs. (3) Start by opening TVPATT1.BAS in QUICK BASIC and then running it by clicking on the RUN command. The screen shown in Fig.13 appears. (4) Wait a few seconds after switch on to give time for the power-on reset to take place, then press Enter on the keyboard to start the programming. When TV­PATT1.BAS has finished, the next program (TVPATT2.BAS) will automatically run and so on in sequence until programming is complete. As before, the entire process takes about 45 minutes. Note that each location in memory takes at least 33ms to program because of the programming pulse length and that repre­ sents a total of 36 minutes programming time Fig.13: this is the opening screen when you run the programming soft­-ware. It prompts you to check that links LK1-LK5 are each in the program (“b”) position. Fig.14: during programming, the software indicates the number of bytes that have been programmed and tells you which programs are to yet to run. alone (since there are 65,536 locations to program). Trying it out To test the unit, move the jumpers to LK1a, LK2a, LK3a, LK4a & LK5a. This done, connect the video output from the unit to the video input of a VCR and tune a TV set to the video channel. Alternatively, if the TV has a direct video input, you can connect the pattern generator to this instead. Apply power and check that all the patterns can be selected via the front panel switches. If the TV does not show colour for the colour bar selection, adjust VC1 until colour appears. Note that, with some EPROMs, the display may rapidly switch between colour and b&w. This can be cured by connecting a 100pF ceramic capacitor between pins 11 & 14 of IC1 (on the underside of the PC board). Finally, connect the RF output from the pattern generator to the antenna input of the TV set and tune the set to the appro­priate channel (0 or 1). Adjust VR2 for best colour bar reception. If the signal level from VR2 is too low, the colours will not be saturated. Conversely, if the signal level is too high, SC there will be no colour at all. COMPUTER BITS BY JASON COLE Removing programs from Win95 Windows 95 has changed the way that PC users install and uninstall software. No longer are you left to your own resources. Instead, a wizard takes over and guides you through the process. A “wizard” is a function that guides the Windows 95 user through various steps and options by means of a series of dialog boxes, often with a quick sentence or two about what it is doing. Sometimes, the use of a wizard is optional but when in­stalling hardware and software, they appear automatically. A wizard makes the process of installing and removing hardware and software a truly “user friendly” operation. Once upon a time, before Windows 95, you were presented with a list of options when installing a program in DOS or Windows 3.x. Typically, there could be messages concerning the sound card, the program loca­tion, the monitor resolution and so on. Those people with experience in computers knew that these were questions, not statements; that the computer was asking you what sound card you had, where the program was to be copied to and what screen resolution you wanted to run. By contrast, in Windows 95, the installation’s wizard will ask something like: “Please select the location your program should be installed to”. Of course, the wizard will usually show a default location. You can either use this default location or you can easily select another location. The wizard steps you through your selections, prompts you for information, and gathers other details which are already known to Windows 95; eg, your name and organisation. When it has all the necessary information, the wizard works with Windows 95 to correctly install the software and will report on the success of your task. Uninstalling programs Fig.1: the Add/Remove Programs icon is in the Windows 95 Control Panel (click Start, Settings, Control Panel). Windows 3.x did not come with an uninstall utility, so deleting programs could be tricky unless you used a third party uninstall utility or the program came with an uninstall option. That situation changed with Windows 95. Once again, a wizard is used to uninstall programs. There are a number of ways to remove programs from Windows 95. The most common method is to use the Add-Remove Programs Icon in the Control Panel. You access the Control Panel by clicking Start, Settings, Control Panel. A window similar to that shown Fig.1 will appear. You then double-click the Add-Remove Programs icon to start the wizard – see Fig.2. To uninstall a program, simply highlight its name and click the Add/Remove button. Another dialog box will appear asking for confirmation. If there are multiple versions installed or if companion products were installed, a further dialog box will appear to make your uninstall requests more specific. The wizard will delete all components of the program, with the exception of custom documents or images. A comprehensive uninstall removes all relevant files and folders belonging to the program, as well as any July 1997  63 Fig.2: double-clicking the Add/Remove Programs icon in the Win95 Control Panel starts the Install/Uninstall wizard. information that may have been added to the Win.ini and System.ini files when the program was originally installed. When the uninstall process is complete, the wizard returns you to the original Add-Remove Programs dialog box. Occasionally, the uninstall option for a program may also appear in the Start menu or it may only be found there. For example, you uninstall Adobe PageMaker 6.5, by clicking Start, Programs, Adobe, PageMaker 6.5, Uninstall PageMaker 6.5. The wizard will report any problems that it encounters during the unistall process and you can refer to Windows Help (F1) if you don’t understand the message. This should help you overcome any problems. For example, files that cannot be located by the wizard can be removed manually. If the uninstall wizard asks for the installation disks, then provide them. If you cannot do this, make a note of the message and select “Ignore” to continue. In some cases, you may need to reinstall a program to enable correct uninstallation. If the wizard does not give you the ignore option or stops working, end the task by pressing Ctrl + Alt + Delete at the same time and then choosing close. In this case, manual deletion may be the only option left. If another program stops working after an uninstall, a quick reinstallation of the affected program will fix the prob­lem. A common problem with uninstall occurs when multiple ver­sions of Microsoft Office have been installed. This may happen, for example, where Office 97 has been installed but the previous version has been kept to give the user time to adjust to the latest offering. If the user subsequently decides to delete the old version, he quickly discovers that the wizard can only delete the new Office 97 version. The previous version isn’t an option any more. Microsoft overcame this problem by including a program called OFFCLN97.EXE (Office Clean 97) on the new CD. This program goes through the hard disc drive and removes any remnants of Office 95 or Office Ver. 4.X, so keep this in mind if you are ever in this situation. Occasionally a program may require an uninstallation Problems with uninstall As is the way with computers, an uninstall procedure does­n’t always go smoothly and the wizard may encounter a few prob­lems. A few typical examples are as follows: (1). The uninstall wizard may not be able to find all the program files. This is because some files have already been removed or relocated. (2). When removing some programs, you may be asked if you want to remove a file that’s shared by another program. Unless you know for certain that the file is not used by another program, do not remove it. Removing shared files can stop other programs from working correctly. For example, a spelling dictionary may be shared by Micro­soft Word and Microsoft Access. Remove it for one and it is no longer available for the other. Of course, this is just one example; other file types, including DLLs (dynamic link libraries), may also be also shared. (3). Sometimes, the original installation CD or disc must be in the drive in order for the wizard to work. 64  Silicon Chip Fig.3: to locate a DOS program, right click its shortcut icon, then click Properties and select the Programs tab. The program’s location is indicated by the Cmd line entry. is locat­ed? Simple – just highlight the program’s icon, then click File, Properties (or press ALT-Enter). The program’s location is indicated by the Command Line entry. The working directory will often be in the same location but this is not always the case. Once the relevant directory has been located, it can be erased using File Manager. To remove the program’s icon, simply select it and press the Delete key. A program group is removed in the same way. DOS programs & Windows 95 Fig.4: unwanted shortcuts and/or folders are deleted from the Start menu using the Taskbar Properties options. procedure that the standard uninstall wizard does not handle. In that case, the Setup utility that came with the program will usually do the job. A typical example is Microsoft Plus! (the add-on enhance­ment pack for Windows 95). Its setup program gives you three options: (1) Add/Remove; (2) Reinstall; and (3) Remove All. These first option is quite powerful because it lets you selectively delete (or add) certain elements of Plus! Windows 3.x As mentioned above, Windows 3.x did not come with an uni­nstall wizard. And although some Windows 3.x programs came with an uninstall option, most did not. Apparently, the programmers thought that once you started using a program, you wouldn’t want to delete it! Those programs that did provide an uninstall option worked in a similar way to those that ran under Window 95. However, they were often harder to understand and occasionally failed, either not working at all or only deleting part of a program. Sometimes, the uninstall utility of one program removed files that were also used by other programs. Always check the manual for a program when removing it from Windows 3.x. Often, it will give step-by-step instructions for removing the program and will list the entries that were added to System.ini and Win.ini. DOS programs & Windows 3.x DOS programs that run inside Windows 3.x are usually easy to unistall. Typically, this involves deleting: (1) program files and folders; and (2) Windows icons and groups. The question is, how do we know where the program The manual removal of DOS programs in Windows 95 is similar to the above procedure. The location of the program can be found by right clicking its shortcut icon and then clicking Properties and selecting the Program tab to bring up the dialog box shown in Fig.3. You also have to remove the shortcut, either from the desktop or from the Start menu (or both). If the shortcut is on the desktop, simply highlight the icon and hit the Delete key. If the shortcut is in the Start menu, you delete it using the Taskbar Properties option. To do that, click Start, Settings, Taskbar, then select the Start Menu Programs tab to get the dialog box shown in Fig.4. You then click the Remove button to get a list of directories and files similar to those shown by Explorer (only smaller in size). Now find the shortcut you don’t want, highlight it and press Remove. The shortcut will be sent to the Recycle Bin. You can delete unwanted folders from the Start menu in exactly the same fashion. Windows 3.x programs & Windows 95 What about Windows 3.x programs that have been installed under Windows 95? Those that don’t have an uninstall option are removed in the same manner as for Windows 3.x, except that files and folders are deleted using Explorer rather than File Manager. Another approach is to purchase an uninstaller program. An uninstaller program tracks the installation and keeps a record of it, so that it can uninstall the application later on. A popular choice is Uninstaller 4 which is designed for Window 95 and Windows NT but there’s also a version for Windows 3.x. Registry & ini files Windows 3.x used “ini” files to store program settings, the two most important being System.ini and Win.ini which are stored in the Windows directory. Any programs installed in Window 3.x added entries to these and to other ini files. That’s be­cause, during the Windows boot sequence, these files tell Windows what’s installed and where to find it. With Windows 95, however, most of the information is stored in the registry. It still stores some information in Win.ini and System.ini but this is for compatibility with older programs. By the way, Windows 3.x also stored some information in a registry but it was not used extensively. Do not go into the registry unless you have a backup and know exactly what you are doing. The registry is an important part of Windows 95 and should not be treated lightly. Remove the wrong bit of information and you SC may have to reinstall Windows 95. July 1997  65 How Holden’s electronic control unit works; Pt.1 The latest engine management control systems are very clever in their operation. We unravel some of the mysteries hidden in the Holden system. By JULIAN EDGAR A LTHOUGH THERE have been many articles published on elec­ tronic engine management systems, a detailed analysis of how the program in an Electronic Control Unit (ECU) works has been lack­ing. This The Holden system uses a MemCal – a plug-in module con­taining both the EPROM and limp-home data memory. This approach allows the same ECU to be used in a wide variety of cars. is because the manufacturers do not publish such stud­ies and usually no other sources have sufficient depth. However, the way in which one ECU calculates its outputs can now be re­ vealed. Ken Young, an Australian computer programmer, has developed a sophisticated software package that allows the AC-Delco engine management system to be reprogrammed. This is the engine manage­ment system used on the Holden Commodore. In order to develop an effective, user-friendly software package (plain English is used on the screen), he needed to com­ pletely lay bare the programming of the ECU. This he has done and much of what follows is drawn with his permission from the manuals for his KAL Software Dyno­ Cal package. The story reveals the almost unbelievable sophistication of the modern engine management ECU. Indeed, the GM-Delco ECU is far more complex in its operation than most aftermarket programmable systems. Note that while all the variables can be altered using the DynoCal software, the values used as examples here are from a standard Holden VR V6 automatic program. Note also that what follows relates mainly to engines which use a MAP (manifold absolute pressure) sensor, as opposed to engines using an airflow meter (as in the EcoTec engine fitted to the VS Commodore). Basic ECU layout As with all engine management systems, the GM-Delco ECU accepts 66  Silicon Chip This Holden Commodore VR station wagon has an engine man­agement system that was once undreamt of. inputs from a variety of sensors, makes appropriate decisions, and then outputs various signals. The various sensors provide either analog voltage inputs (throttle position sensor, oxygen sensor); pulse inputs (distributor reference, speed); or simple on/off logic inputs (airconditioner compressor clutch, gear lever neutral/drive position). The various outputs consist of pulse width modulated pulses (for the trip computer), simple on/off outputs (engine check light & radiator fan), timed spark pulses and injector pulses (to control the fuel injectors). In the GM-Delco system, both the program and the data are stored on a single EPROM. In GM-talk, this EPROM is called the “MemCal” and by using different MemCals, GM has been able to use the same basic ECU on a variety of engines, including fours, sixes and eights. The program tells the controller what to do and consists of machine code, while the data is made up of an incred­ ible 300+ variables which tailor the program to the specific drivetrain application. Over the years, Holden has used three different ROM sizes in the GM-Delco systems. The first systems used a 16Kb EPROM but this was later doubled in size to 32Kb. Of this, about 30Kb was used for the program and the remaining 2Kb for the calibration data. Holden subsequently added automatic transmission control to the ECU. This new ECU is now called a PCM (Powertrain Control Module) and its EPROM has again doubled in size to 64Kb. Variables There are four different types of variables used by the program: (1). So-called zero dimension variables – these are used to specify the number of engine cylinders, whether there is an automatic or manual gearbox installed, etc. (2). One dimensional variables – these are used to represent counters, delays, air/fuel ratios, etc. (3). Two dimensional variables – these are look-up tables com­prising such factors as idle air motor steps versus rpm, air/fuel ratios versus time, etc. (4). Three dimensional variables – these are the 3D maps; eg, air/fuel ratio versus rpm versus MAP (manifold absolute pressure). The program logic can be divided into six main areas of operation: fuel, spark, idle air control, diagnostics, output logic and variables. In addition, the program determines a number of internal modes, such as whether the engine is cranking or running and whether or not the oxygen sensor is operational. These modes are saved and used in various calculations. Only two of the program areas are examined here: fuel and spark. Let’s see how the program actually calculates the various outputs? Calculating fuel injection The step-by-step process followed to calculate the required amount of fuel is: (1). Estimate of the mass of air entering the engine; (2). Look-up the desired air/fuel ratio for the engine speed and MAP; (3). Multiply the air mass by the fuel/air ratio to give the fuel mass required; (4). Use the fuel mass to calculate the injector pulse width. The air mass per cylinder is calculated from the manifold pressure, intake air temperature and engine speed. This figure is then multiplied by the volumetric efficiency of the engine. A 3-dimensional table is used to specify low rpm volumetric efficien­ cy, which is calculated as a function of engine speed and MAP. Another similar look-up table is used for high rpm volumetric efficiency. If the coolant temperature is below 44°C, a correction is applied to the air/ fuel ratio to enrich the mixture. Two July 1997  67 Volumetric Efficiency Fig.1: the volumetric efficiency (VE) of the engine is held as a 3-dimensional map. Here, the VE is shown as a function of engine speed and manifold pressure. Note that for some combinations of manifold vacuum and engine speed, the charging efficiency is markedly improved – probably as a result of the tuned-length intake system. Air/Fuel Ratio Fig.2: this map shows the desired air/fuel ratio for each combi­nation of engine speed and manifold vacuum. For general running, the engine management system is programmed so that it maintains these ratios as closely as possible. fur­ ther single-dimension variables control the decay rate of this enrichment and the minimum to which it 68  Silicon Chip can fall. The main air/fuel ratio lookup table uses three dimensions, with air/fuel ratio expressed as a function of MAP and engine speed – see Fig.2. Injector opening delays due to variations in battery vol­tage are compensated for by adding a bias to the injector pulse width. For example, at a battery voltage of 11.2V the bias is 1.16 milliseconds. A 2-dimensional table is used to apply further corrections for very brief injector openings, to achieve the non-linear biases required at this end of the scale. In operation, the mechanical fuel pressure regulator main­tains the fuel pressure at a fixed headroom above the manifold pressure. Despite this, battery voltage changes apparently cause sufficient variation in fuel pump pressure to require another correction factor. This works as a function of the battery vol­tage. Another correction factor can be introduced to delay the injector operation. This is used only when the ECU is used to control a single point injection system to give better air/fuel mixing. It is not used in the Commodore, since the V6 employs multi-point fuel injection. Lean cruise mode One of the factors giving the Commodore such good open-road fuel consumption is the lean cruise mode. Lean cruise is enacted when the coolant temperature is above 80°C and the road speed higher than 68km/h. After 150 seconds, the air/fuel ratio is increased in 0.1 steps at 0.2 second intervals. This increase is ultimately limited to a value derived from a 3-dimensional look-up table and depends on the engine speed and MAP. As you might expect, the way in which the fuel injectors are controlled during engine starting is rather complicated. There are preset variables for cranking pulse width and also for the decay rate of this base crank pulse width. The steps at which the pulse width decays are also specified. The clear flooding throttle position is set at 98% opening or more and the injector pulse width is reduced to 7.895 milliseconds during cranking with the throttle in this position. No less than 22 different variables are used to control the mixture during acceleration and deceleration! These variables include coolant temperature which is used to control the rate at which the mixture is leaned off during deceleration. A large number of variables are also used for closed loop running, whereby the oxygen sensor controls the mixture. The minimum coolant temperature at which closed loop running will start is 44°C at idle and 31.25°C for running conditions. The program takes six seconds before it switches from open loop to closed loop after acceleration and it will do this only with a manifold vacuum of more than 5kPa. Main Spark Advance Fuel trim The Short Term Fuel Trim is a fast-acting air/fuel ratio correction system which relies on the output of the oxygen sen­sor. In operation, the oxygen sensor outputs a voltage signal which is categorised as either rich or lean. The longer the ECU receives a rich (or lean) signal, the greater the correction that is applied. This results in an air/fuel ratio under closed loop condi­tions that oscillates around the stoichiometric point (this characteristic cycling of mixtures can be seen on the SILICON CHIP mixture meter – see November 1995). Further corrections are applied by the Long Term Fuel Trim (LTFT) which uses an array of 24 block memory cells. Each cell corresponds to an rpm and MAP range, with the array covering the engine’s operating range. When the engine is operating in closed loop mode, the fuel term is calculated and then multiplied by the cell which corre­ sponds to the rpm and MAP conditions present. If the engine has operated with that manifold vacuum and engine speed for a number of seconds, a learning process takes place. The data in one block can affect the data in neighbouring blocks, thereby allowing smooth interpolation to take place between them. Disconnecting the battery clears these mem­ory cells, which means that a car may operate below its optimum performance level for a short period of time when it is driven again. The LTFT RAM data can be accessed after the event, meaning that the ECU has continuous on-board data logging of the air/fuel ratio at 24 different load/rpm sites. For the LTFT to become active, the oxygen sensor must be working correctly and the engine speed must be constant. Over-revving is prevented by cutting off the fuel at 5800 rpm and restoring it again when the engine speed falls below 5700 rpm (ie, there is 100 rpm Fig.3: the main spark advance chart is just one of a number of maps used to calculate the spark advance. If the engine is at idle, the timing is taken from a 2-dimensional look-up table as a function of MAP. At other engine speeds, the initial spark value is derived from this 3-dimensional table which shows spark advance as a function of engine speed and MAP. Long Term Fuel Trim Fig.4: the Long Term Fuel Trim (LTFT) is an inbuilt form of data logging. It stores the corrections made to the injector pulse widths so that the air/fuel ratios depicted in Fig.3 are main­tained. A count of 128 indicates that no correction has been required, while a count that’s less than 128 means that the engine has been running lean. Conversely, a count greater than 128 indicates that the engine has been running rich. It can be seen that this particular engine has required only minor on-going corrections. July 1997  69 Table 1: Rewriting The Program Variable Spark High Advance Rate (degrees/1000 rpm) Spark Maximum Retard (degrees) Fuel Max Pulse Width (milliseconds) Fuel Cut Low RPM Fuel Cut High RPM Fuel Cut Time Delay (seconds) Idle Air Control Max Position (steps) Idle Air Control Closed Loop Threshold (kPa) Idle Air Control Warm Up Delay (seconds) Idle Air Control Deadband (rpm) Idle Air Control Sag (rpm) Spark Idle Air Control Advance (degrees) (kPa MAP) 20 30 40 50 60 70 Spark Attack Rate (degrees/count) (rpm) 1600 3200 4800 6400 Fuel Volumetric Efficiency (%) (kPa at 400 rpm) 20 40 60 80 100 (kPa at 1600 rpm) 20 40 60 80 100 (kPa at 3200 rpm) 20 40 60 80 100 (kPa at 6400 rpm) 20 40 60 80 100 of hysteresis to prevent osc­ ill-ation around the cutoff point). The same technique is also used to limit the road speed, with the VR V6 automatic 70  Silicon Chip Modified Holden V6 Standard Holden V6 1.96 9.84 24.002 6300 6400 0.04 220 39.86 10 18 206 2.03 8.09 10.986 5715 5817 0.10 196 34.33 5 50 400 20.39 24.26 30.59 31.99 30.94 26.37 26.02 26.02 26.02 26.02 26.02 26.02 0.038 0.065 0.069 0.080 0.030 0.030 0.030 0.030 13.3 16.4 20.3 26.6 33.6 53.5 62.5 53.5 58.2 71.1 31.2 37.1 40.2 50.0 62.1 44.9 67.2 73.4 78.9 81.2 44.9 53.5 64.5 70.3 76.2 60.5 82.4 85.5 87.1 84.4 66.0 70.3 76.2 89.1 99.6 50.6 62.5 74.2 78.1 78.1 model limit­ed to 210km/h. During manufacturing, the program is configured to recog­nise a stoichiometric air/fuel ratio whose value corresponds to the switching voltage of the oxygen sensor being used. An in­jec­t­or constant is also programmed, allowing larger or smaller injectors to be used in place of the standard units. Spark timing The initial timing information for the ECU is derived from a crankshaft position sensor at 60° or 70° before top dead centre (TDC). The ECU then calculates the required spark timing, counts forward and delivers the spark. If the engine is at idle, the timing is taken from a 2-dimensional look-up table as a function of MAP. At other engine speeds, the initial spark value is derived from a 3-dimensional table which shows spark advance as a function of engine speed and MAP. At low MAP pressures (ie, high vacuum), the table has increased resolution. In addition, for engine speeds above 4800 rpm, a high-rpm correction figure is added to the main ad­vance rate. The output of the 3-dimensional coolant correction chart is then used to modify the timing. This chart shows the correction as a function of coolant temperature and MAP. Negative coolant corrections are made by subtracting another variable (coolant offset) from the positive value coolant correction chart. If exhaust gas recirculation were to occur, the spark would be further advanced as a function of MAP and engine speed. Howev­er, this function is not currently employed. Another correction not currently used (but available) is for barometric pressure. Timing refinements While the timing procedure so far is fairly straightfor­ward, there are a num­ ber of refinements. For example, when the automatic transmission is shifted from Park or Neutral into Drive, the timing is retarded by 5.98° if the engine speed is above 3600 rpm. This is done to cushion shift-shock (the lurch that occurs when shifting into gear). The spark advance is also increased by an amount propor­tional to the rate of acceleration. However, the maximum rate of change in spark timing is limited to 0.01°/milliseconds on the VR V6 engine. Depending on the coolant temperature, the rate of change for the throttle position can also be used to retard the spark timing. However, the spark retard logic is bypassed if the vehi­cle speed is less than a preset variable or if the engine speed is higher or lower than other preset values. When deceleration fuel cutoff is employed, the spark timing is decayed until a minimum value is reached before the actual fuel cutoff starts. During starting, an initial timing value is selected and this is then modified according to the cranking speed by a 2-dimensional chart. However, if the cranking speed falls below 400 rpm, the crankshaft position sensor output becomes inaccurate. When this happens, the spark is generated by the ignition module using a backup mode. The ECU switches the spark timing back to its normal mode when the engine speed rises above 400 rpm. Once the engine is idling, a 2-dimensional table stores the timing values as a function of MAP. Interpolation is used if the MAP value falls between two points. At the end of the timing calculations, the calculated advance angle is checked against a 1-dimensional variable which set the maximum and minimum values. These are at 60.2° and -17.8°, respectively. Another spark timing variable set during manufacture estab­ lishes the engine position at which the distributor reference pulse occurs. There is also a crankshaft position sensor lag correction factor. This correction compensates for the electronic delays in the sensor and pick-up and is set to 200 microseconds for the V6. In fact, more than 70 variables (ranging from 1-dimensional to 3-dimensional) are used in the calculation of the final spark advance! As a comparison, some aftermarket programmable engine management systems rely on just five or six variables. Rewriting the program One way to examine the capabilities of the ECU is to exam­ine a rewritten program. Table 1 shows a small extract which compares new software for a modified V6 Holden against a standard program. The modified engine featured a new camshaft, higher com­pression ratio and bigger valves. The program revisions were carried out by Awesome Automo­tive in Adelaide using the DynoCal software package. Awesome Automotive can be contacted on (08) 8277 3927, while KAL Software (Brad Host) is on 0412 SC 266 758. BOOKSHELF Video scrambling & descrambling for satellite & cable TV Video Scrambling & De­scram­ b­­ling for Satellite & Cable TV, by Rudolf F. Graf and William Sheets. Published 1987 by Butter­worth-Heine­mann. Soft covers, 215 x 278mm, 246 pages. ISBN 0 7506 9945 0. Price $34.95. Even though Pay TV is now a (loss-making) reality in Austra­lia, there is still considerable interest in satellite TV recep­tion by virtue of the greater variety of programs and the fact that no monthly rental fees are payable. However, quite a few satellite broadcasts are scrambled and naturally there is dearth of information about the techniques involved. This book sets out to answer many of the questions although the authors stress that they in no way condone the misuse of the information. And while it was first published in 1987, the techniques of scrambling and encryption have not changed much since then. I should say at the outset, that while reading this book may give you a good understanding of the various techniques used in video scrambling, it probably won’t be of much help if you wish to do some unauthorised descrambling on an encrypted satellite signal. On the other hand, if you wish to be able to scramble and unscramble video for your own use, then this book could be very useful. It has 12 chapters devoted to scrambling methods. The first two chapters start with the basic methods such as video inver­sion, sine­ wave addition and sync alteration and proceeds to digital techniques which even involve pixel scrambling. Chapters 3 & 4 become more specific, with circuit examples. Chapter 5 covers the SSAVI system which stands for Sync Suppression and Active Video Inversion. Chapter 6 discusses the VideoCypher system. Chapter 7 is devoted to political, legal and consumer aspects of scrambling which will be of little interest to technical readers. Chapter 8 continues with digitising of audio and video signals. Chapter 9 is of particular interest with cable and satellite decoders, and working circuits are included. Chapter 10 covers the VCII and BMAC (used in Australia) systems. Chapter 11 is of general interest, talking about satellite TV signal strength and interference and finally, chapter 12 covers the DES (Data Encryption Standard) algorithm. Chapter 13 is devoted to semiconductor data sheets and chapter 14 covers three relevant US patents on the subject of scrambling. In short, a very interesting and useful text. It will be available to order from the SILICON CHIP office. Phone (02) 9979 5644. (L.D.S.) July 1997  71 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au PRODUCT SHOWCASE A handheld LCD oscilloscope There have been a number of handheld multimeter/oscillo­scope instruments produced in the last few years but most of them have been priced well above what the average technician or hobby­ ist could afford. This new unit made by Velleman is much more affordable. All told, this new instrument has a surprising number of features packed into its compact 600 gram (excluding batteries) package. The case dimensions of 230 x 130 x 43mm allow it to be comfortably held in the average hand. When fitted with six AA rechargeable batteries it will operate for up to five hours or it can be powered from an external 9V DC 300mA plugpack. Its full specifications are listed in Table 1. The unit boasts a full auto setup function which means that any signal can be connected and immediately a stable waveform is displayed. Not only this but the period and frequency of the input can be read from the righthand side of the LCD panel. As well, the meter function button can select one additional read­out, either of the waveform’s peak-to-peak voltage, RMS voltage, signal level in dB or DC voltage. While the waveform display area itself is rather tiny (50 x 40mm) it gives a good portrayal of most waveforms. All functions are controlled by membrane switches on the front panel and these are more or less self-explanatory for anyone who has used an oscilloscope previously. A red pushbutton labelled Markers switches four different backgrounds on the display. The first is a plain background, the second provides a dot grid with 5mm spacing which, on the dis­play, is 9 dots across by 8 dots high. The third provides cen­trally lo- cated X and Y axes and the last has two pairs of cursors which can be moved to make peakto-peak voltage and period meas­urements. The Y position buttons move one of the P/P cursors while the trigger level buttons move the other. By positioning them at the maximum and minimum of any waveform the peak- to-peak value can be read. Similarly, by using the Time/div and Trigger mode buttons, the period between any two points on the waveform can be measured. Getting back to the oscilloscope functions, the BNC input has an impedance of 1MΩ and 25pF which is similar to many oscil­loscopes. A small slide switch below the BNC connector lets you select AC or DC coupling for the input signal and the input sensitivity is controlled by the adjacent Volt/div pushbuttons. To increase the sensitivity of the input amplifier you push the button with the big sinewave on it, while pushing the button with the small sinewave reduces the sensitivity. Below the input buttons is the normal on/off pushbutton. If this is used to turn the unit on it will turn itself off about eight minutes after the last keypress. If this is not convenient, the unit can be turned on permanently by using the Markers key. If the scope is to be operated manually (as distinct from the auto setup mode) then the Time/div buttons operate like a normal scope, with the Trigger mode buttons allowing normal, auto or single sweep operation. Another button toggles the trigger from positive edge to negative edge, with the two buttons above it letting you move the trigger point amplitude up and down. The only controls we still have to mention are the Y posi­tion, Dot/Join and Hold buttons. The Y position controls only operate in manual mode because, as we explained previously, in Auto mode they move the cursor. The Dot/join button does just that. It allows the display to show the digitised values as dots, or in the join mode it connects all the points, displaying July 1997  75 Table 1. Technical Data Maximum sample rate ������������������������ 5MHz for repetitive signals; 0.5 MHz for single shot signals Input amplifier bandwidth ������������������� 750kHz (-3dB at 0.4V/div setting) Input impedance ��������������������������������� 1MW // 20pF Maximum input voltage ���������������������� 100V peak (AC+DC) 600V with 10x probe Input coupling ������������������������������������� DC, AC or ground Vertical resolution ������������������������������� 8 bit (6 bit on LCD) Linearity ���������������������������������������������� ±1 bit A/D converter accuracy ���������������������� ±2 bit LCD graphics ������������������������������������� 64 x 128 pixels, 64 x 96 for signals dB measurement (0dB = 0.775V) �������� from -73 to +40 ±0.5% True RMS range (AC only) ������������������ 0.1mV to 80V, 2.5% accuracy Peak-to-peak and DC range ����������������� 0.1mV to 180V, 2% accuracy Timebase range ����������������������������������� 20s, 10s, 5s, 2s, 1s – 10ms, 4ms, 2ms/div Input sensitivity ����������������������������������� 5mV, 10mV, 20mV, 50mV, 100mV – 2V, 4V, 8V, 20V Sinewave generator ����������������������������� 400Hz 1V RMS max (adjustable) Square-wave output ���������������������������� 400Hz 3.5V p-p Plugpack voltage ��������������������������������� 9V DC 300mA Rechargeable batteries (opt.) �������������� 6 AA, 750 or 900mAh Charge time ����������������������������������������� 14 hours Battery operation �������������������������������� 5 hours (900mAh) Operating temperature ������������������������ 0-50°C Dimensions ����������������������������������������� 230 x 130 x 43mm Weight ������������������������������������������������ 600 grams (excludes batteries) This series of screen shots show a number of operating features of the Velleman HHS5 handheld scope. The top screen shows a waveform bracketed by vertical and horizontal cursors for peak to peak & frequency measurements. The second screen shows a sinewave with a true RMS readout. The trigger level is indicated by a break in the lefthand vertical axis line. A dot grid is also displayed. The third screen shows a square wave with peak-to-peak readout and centrally located horizontal & vertical axes. The fourth screen shows a sinewave in “dot join” mode while the fifth screen shows the same waveform in “dot” mode. 76  Silicon Chip the conven­tional continuous trace we are more familiar with. The Hold control freezes the display, allowing you to exam­ine any particular aspect of the waveform. As well, it lets you send a digitised data stream of the displayed signal to the RS232 port on a computer. The information is sent as a table of 96 samples, each having a value between 0 and 255 as well as the Y sensitivity and the zero reference value. This information could be used by a spreadsheet or Basic program to process the details of the display in any required manner. One unusual but welcome feature of this instrument is the inclusion of a circuit diagram and PC board parts overlay in the back of the manual. Our only complaint was that the righthand edge of the LCD display was covered by the front panel mask and we could not read the last digit of the readout. We could also see the left­hand silver edge of the LCD surround but not the righthand one. When we opened the case we found that the perspex mask was held in by two pieces of sticky tape. Removing this mask, rotating it 180° and replacing it cured the problem completely. Perhaps the only real drawback of this scope is the limited bandwidth of 750kHz. Having said that, it is true that the major­ ity of measurements that need to be made in most situations are normally well below this frequency. On the positive side, the advantages of true RMS measure­ments and auto setup along with all the other features make this unit an attractive purchase for the technician or hobby­ist. The recommended retail price of the unit is $449 and it is available from all Jaycar Electronics stores. (R.J.W.) AUDIO MODULES Fast slewing operational amplifier Analog Devices has introduced the industry’s fastest slew­ing monolithic operational amplifier. The current feedback AD8009 features a 5500V/µs slew rate, more than twice that of its near­est equivalent, with 10% faster rise and fall times at 725ps for a 4V step. As a simple gain stage or buffer amplifier in high frequen­cy instrumentation or in high speed test gear (as a pulse ampli­fier where a combination of high slew rate and low distortion is needed to inject signals of high integrity), the AD­ 8009 outperforms all other devices. Small signal (-3dB) bandwidth is 1GHz at unity gain and 700MHz with a gain of +2. Dynamic performance is excellent: spurious free dynamic range is 74dBc at 5MHz, 53dBc at 70MHz, and 44dBc at 150MHz. For mul- broadcast quality ti-tone signals, such as RF/IF signals, the 3rd order intercept is specified at 26dBm at 70MHz and 18dBm at 150MHz. Settling time to within 0.1% of full scale signals is 10ns. For further information, contact Hartec, 205A Middleborough Rd, Box Hill, Vic 3128. Phone 1 800 335 623. 25W external power supply Today’s electronic equipment can encounter a myriad of approvals and assessment before it can be put on the market. Usually the two main hurdles are safety and EMI. Amtex Electron­ ics have attempted to overcome the majority of these by introduc­ing the SCL25 series of external switching power supplies. The SCL25 series are fully approved, carrying local office of energy and Austel approvals, and soon to carry the new C-Tick mark. As well, they carry international approval, such as UL, CSA and VDE for safety, as well as FCC and CE for EMI noise. The SCL25 series come in a sturdy moulded plastic case. The input is 90264VAC via an IEC input socket and single output voltages ranging from 5VDC to 48VDC are available, as well as dual and triple output units of 5V and ±12V or ±15VDC. Output is via an 8-pin mini-DIN or 2.5mm jack plug. The units also feature an output LED indicator, regulation of ±4% and up to 60ms hold up time. For further information, contact Amtex Electronics, Power Supply Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 The two diodes may also be connected to operate in parallel due to their matched on-state voltage drops. The modules have an isolation voltage rating of 3000V (RMS) and are UL recognised. Major applications for these diode modules include rectify­ ing the AC output from high-frequency inverters. For further information, contact GEC Electronics Division, Unit 1, 38 South St, Rydalmere, NSW 2116. Phone (02) 9638 1888; fax (02) 9638 1798. Rugged 600V IGBT Division, 2A Angas St, Meadowbank, NSW 2114. Phone (02) 9809 5022; fax (02) 9809 5077. 1200V fast recovery diode modules IXYS Corporation has announced the availability of the MEK 75-12DA fast recovery diode module in the industrial standard TO-240 package. It consists of two matched, 1200V rated, 75A(avg), fast diodes with common cathode connection. The two epitaxial diodes have low reverse recovery current and short reverse recovery time (trr = 450ns maximum at TJ = 100°C) and they exhibit soft reverse voltage recovery to minimise EMI. BBS Electronics has released rugged versions of Harris Semiconductors’ ultrafast switching IGBTs rated at 600V and 20A at 110°C. These new devices allow motor-controller de­ signers to replace power transistors with IGBTs to maximise efficiency (due to IGBTs’ lower conduction losses), without rede­ signing their present short-circuit protection circuits. This series of devices has a short-circuit withstand time of 10µs, the maximum for any IGBT, at 440V and 150°C. Be­cause Harris rates SCWT at 150°C instead of 125°C, designers can use smaller heatsinks. For further information, contact BBS Electronics Australia Pty Ltd, Unit 24, 5-7 Anella Ave, Castle Hill, NSW 2154. Phone (02) 9894 5244; fax (02) SC 9894 5266. July 1997  77 RADIO CONTROL BY BOB YOUNG An in-line mixer for radio control receivers This month, we will look at a simple 2-channel in-line mixer for use with R/C systems that are not equipped with mixers in the transmitters. This can be used to control two servos together when complex models are involved. This mixer was to have been the ultimate “simple job” – take a through-hole design that has been in produc­tion for 20 years and convert it to surface mount components, greatly reducing the size in the process. No electronic redesign, no black magic RF or other issues to get underfoot, just relay the PC board. Pretty simple, right? . . . WRONG! The original unit was designed for Silvertone in the golden years before tariff reductions cut the heart out of the business. This mixer was developed by Bob Lawrence, a very clever engineer and the man who designed the last television set pro­ duced in Australia. Bob consulted on many jobs for me in those days, even though the concepts and challenges I presented him with used to drive him to his limits. The only thing that kept Bob Lawrence coming back for more was the fact that the jobs we gave him were so interesting. Now I look back and shudder and wonder what possessed me to undertake some of the jobs I became involved with. There were 32-channel robotic puppets, radio-controlled fullsize motor vehicles, R/C machines six stories high, 80-tonne R/C shot blast trolleys and RPVs, to name just a few. Years later, I lost touch with Bob and have not seen him to this day. By now you are all asking what on earth has all this to do with this column? The fact is that when the first prototype SMD mixer refused to work I found myself wishing that Bob La­ w­rence was still around. It is a very clever little circuit and quite tricky to service. That night I went home and who should be on the TV (Good Medicine) telling the story about the great new breath test for Heliobacta Bacillus (the bug often associated with ulcers)? . . . none other than Bob Lawrence (Bob, if you read this I would like to hear from you). Reversed inputs Fig.1(a): mixed elevators/flaps are used for aerobatics or as compensation for trim shift. Fig.1(b) shows elevator trim compensation for the pitch changes that takes place when the takeoff or landing flaps are selected. 78  Silicon Chip As it turned out, I did not need Bob’s help for I discov­ e red after hours of hair-tearing effort that the Protel schematic library component for the 3900 op amp has the input pins re­versed. This meant that the PC board was wrong and that I had no hope of making that mixer work. I also checked the new Protel for Windows (Advanced PCB) and found that the error was in that library as well. I have enormous confidence in the Protel Auto­trax system and never Fig.2: the circuit takes in separate input channels and converts them into two separate composite signals, Common out and Comple­mentary out. Mixing is set by trimpot RV2. once questioned the schematic or PC board. It was only after I had exhausted all other avenues that I had to look further. I might add that this is the first time that Protel has ever let me down. The second prototype worked perfectly once I had corrected the schematic library and located the solder bridge I had created across two of the pot pins (even the experts do it). So much for the so-called “simple job”. Mixing concepts For those not familiar with the concept of mixing as ap­plied to R/C transmitters, see the article entitled “The myster­ies Of Mixing” in the December 1995 issue and the October 1996 issue which featured the “Multi-Channel Radio Control Transmit­ter; Pt.8”. These articles give a full and detailed explanation of the intricacies of electronic mixing of flight controls. Whilst these articles deal mainly with mixing in transmitters, the principles still apply to add-on mixers for receivers. Briefly, mixing is the coupling of controls so that moving one control results in one or more servos operating simultaneous­ ly in ratios and directions preset by the operator. Common applications include elevons for tailless aircraft, collective and tail-rotor pitch for helicopters, and coupled aileron/rudder and flaps with elevator compensation on fixed wing aircraft. Less common are twin screw boats and tracked vehicles which incorporate speed and steering by the common/differential use of throttle. As you can see, mixing is a very important feature, making models simpler to operate and the modern R/C transmitter reflects this with all sorts of mixing features built in. Unfor­tunately, such features usually come with a built-in high price tag as well. However, owners of older transmitters without mixing may fit an in-line mixer in the model itself and this will work almost as well. I say almost because usually two functions are the maximum available in an in-line mixer. Transmitters with electronic mixing usually allow multiple point mixing but as most applications use 2-point mixing this is not a serious disadvan­tage. Setting up an in-line mixer can be a tricky business, espe­cially with transmitters without servo reversing so I should repeat some of the October 1996 article dealing with setting up for delta mix. Before proceeding any further, there is a very important point to bear in mind when setting up mixing functions. Each mixer input has an additive effect on servo throw and this must be taken into account when setting mix ratios. Failure to observe this may result in the servo being driven into its internal mechanical end stops with attendant gear damage. Therefore, be sure to check the final servo travel with the full extremes of mixing applied, as servo travel varies with the brand of servos used and the transmitters used. An illustration To illustrate the point being made in the above warning, let us examine the mixing process for a delta aircraft featuring elevons (delta mix). Such an aircraft uses two control surfaces, one on each wing and each control surface performs two functions, aileron and elevator control; hence the name elevon. The diagram of Fig.1 shows the control sequence in detail. To bank such an aircraft, one control surface goes up and the other goes down, thereby imparting a rollJuly 1997  79 Fig.3: these diagrams show the component layout on the top and bottom of the PC board. Install all the surface mount components first then mount the trimpots and other component on the top of the board. Fig.4: the full size etching patterns for the PC board. ing motion to the aircraft. For pitch control, both control surfaces go up to raise the nose and down to lower the nose. Complications arise when one wants to bank and climb simul­ taneously. If full throw on the aileron servo gives the desired rate of roll what happens when we then apply full up elevator to impart a climbing motion to the aircraft? If we are turning left then some UP mixed into the right elevon (which is DOWN in a left roll) is easily accommodated. However, there is no more travel available in the left servo which is already full UP. To apply an additional pulse width variation will only drive the servo hard into the end stops and possibly strip the gears. Therefore, the controls must be mech­anically arranged so that 50% differential servo travel (one UP, one DOWN) gives the maximum rate of roll and 50% common servo travel (Both UP or DOWN) gives the maximum pitch angle. Then we may apply full pitch and roll commands simultane­ously. Oddly enough, at this point only one servo actually moves and it goes to full travel. The two commands on the opposing servo cancel each other out and 80  Silicon Chip the servo remains in neutral. Elevon controls are very complex controls to set up correctly, especially when you start to consider the reflex and unequal differential angles which must be taken into account for the correct aerodynamic conditions required by tailless aircraft. Circuit description The full circuit is shown in Fig.2. Briefly, the circuit takes in two separate input channels and converts them into two separate composite signals. The primary input is defined as the common input and it must come first in the input channel trans­ mission order. For example, if we are mixing for elevons (ailer­on/elevator) and the transmitter channel order is Aileron, Chan­nel 1 and Elevator, Channel 2, then the common input is plugged into the Aileron Channel. It is for this reason that the common input lead must be clearly identified on the finished mixer. A short piece of heatshrink tubing shrunk onto the lead just behind the servo plug does the trick nicely. It is a good idea to similarly mark the common output as an aid to testing. The operation of the common input is fairly straightfor­ward. IC1c is the input buffer/inverter and it drives, IC2b, another buffer inverter which feeds the mix ratio trimpot RV2. Following RV2, the two resistors R5 & R6 form a splitter network and feed the two pulse converter op amps IC3a & IC3b. The two identical op amp pulse converters consist of IC3a, IC3c & IC1a for the Complementary section and IC3b, IC3d & IC1b for the Common section. IC1a & IC1b are used as buffer/inverters to provide the desired positive-going output pulse. Differential input channel The operation of the differential input channel input is a little more tricky. The buffer/inverter IC2a drives a monostable oscillator consisting of NAND gates IC2c & IC2d. The mon­ ostable pulse width at pin 4 of IC2c is set to twice the neutral pulse width used by the R/C system the mixer is fitted to. As most modern R/C systems use a 1.5ms neutral pulse, RV1 is therefore set for a monostable pulse of 3ms. This 3ms pulse is used to generate the complement of the differential channel in IC2d using the gating action of the 4011. Thus if the differential channel moves to 2ms then the complement is 1ms. Likewise, if the differential channel moves to 1ms then the complement is 2ms. At neutral both input pulses are set to 1.5ms, therefore the complement is 1.5ms. The common control pulse and the 3ms pulse are added in RV2 to produce a composite with a variable ratio but constant sum. Diode D3 gates out the control pulse part of the 3ms pulse so that the sum of the common pulse plus the complement of the differential pulse is applied to the pulse converters to produce the complementary output pairs. The final composite outputs are a true mix of both input channels. Thus the differential channel adds to the common output channel and subtracts from the complementary output channel in a ratio again set by the mix ratio pot RV2. As a corollary, the common input adds or subtracts from both outputs in equal amounts, again in a ratio set by RV2. The range of the mix is set by R8 & R12. As the operation of the mixer becomes non-linear beyond 80-20%, I suggest using 75-25%. This is more than adequate for the real world. Where To Buy A Kit Of Parts The inline mixer module is available as follows: SOUND EASY V2,BOXCAD V2 BY BODZIO SOFTWARE Comprehensive s/design software available distributed by WAR AUDIO Fully assembled module complete with servo leads ........................$69.50 Complete kit with PC board and servo leads....................................$49.50 PC board only ..................................................................................$11.50 When ordering, purchasers should nominate the R/C system they are using. Postage & packing for the above kits is $3.00. Payment may be made by Bankcard, cheque or money order to Silvertone Elec­tronics. Send orders to Silvertone Electronics, PO Box 580, Riverwood, NSW 2210. Phone/fax (02) 9533 3517. Inside the suggested range the mixer holds neutral to within 5% over a temperature range of 10°C to 50°C and a voltage range from +4V to +5.2V. RV3 is a balance control to set the neutral on the second servo. The neutral on the first servo may be set by the comple­mentary pot RV1. Diode D1 performs a dual function. Firstly, it protects against re­ verse polarity. Secondly and more importantly, it drops the rail voltage to +4.2V. This is an important point for compatibil­ity with imported sets, particularly with some of the newer sets that have output pulse voltages under 3V. CMOS chips need the input to exceed one half rail voltage for reliable switching. Resistor R4 and capacitor C6 provide a supply decoupling network for IC1 and IC2. IC1f in the 40106 hex inverter is unused. Board construction Construction is very straightforward, with surface mount components used for maximum reliability and minimum size. If you have not worked with surface mount before then once again I would suggest reading “Working With Surface Mount Components” in the January 1995 issue of SILICON CHIP. Install the surface mount components first and the through-hole components next. Fit the servo leads, remembering to slip the short piece of heatshrink tubing over the common input and output leads before soldering them into the PC board. Testing First, set up the transmitter trims to neutral and plug two servos into the channels to be mixed to ensure that both servos are on neutral. Set all mixer control pots to mid range and plug the input leads into the receiver and the servos into the mixer servo sockets. Adjust trimpot RV1 to neutralise the servo in the common output. Set the neutral on the servo in the complementary output using RV3. Now move the transmitter sticks first in one axis and then the other, checking to ensure that both servos travel in approx­ imately equal amounts on each axis. Moving the common axis stick will result in both servos moving in the same direction. Moving the differential axis stick will result in the servos moving in opposite directions. This of course assumes that both servos rotate in the same direction without the mixer. It may be neces­sary to reverse one servo to get the correct direction of rota­tion on both outputs. Now wind the mix ratio pot RV2 fully anticlockwise. One stick axis should barely move the servos, whilst the other should give almost full travel in both servos. If this checks out, wind RV2 fully clockwise and ascertain that the opposite is true. The full travel axis should now be reduced to almost zero travel whilst the reduced travel axis should now deliver almost full range. One small warning here. If the trims are not on exact neu­tral the servos will appear to move off neutral as the ratio of mix is increased. This is deceiving for what is actually happen­ing is that the servo movement is increasing and moving the servo away from its original position. This is most noticeable if the ratio of mix is changed when the throttle channel is one of the mixed channels and the throttle stick is at one end of its range. That’s it – you are now in business. SC Add the case and go and fly. Windows interface.SVGA. Box modelling , 7 type enclosures, 10 alignments for box optimizer, Box time response, Room placement, Import Clio, Lms, Imp, Mlissa etc, Crossover modelling , Optimizing , D’APPOLITO modelling and much more. BOX CAD includes complex impedence and electrical modelling and more. $350.00 upgrades from $60.00. Clio Professional electro-acoustic measurement system $1650.00 Frequency Response • Electrical & Acoustical Phase • FFT Analysis • THD • Anechoic Transfer Function • MLS Analysis • Impulse Response • ETC • Waterfall • Impedance THD+Noise 0.015% • T/S Parameters • 1/3 Octave RTA • Signal Generator / Level Meter • Oscilloscope • SPL • dBV • Volt Amplitude • LC Meter • 16-Bit D/A • Freq. Range 1Hz22kHz ±1dB • Freq. Accuracy > 0.01% • WAR AUDIO U203/396 Scarb Bch Rd Osborne Park W.A. 6017 Ph 09-2425538 F 09-4452579 ACUTTON, AXON, FOCAL, RAVEN LUMINOUS, NEW, CABASSE, Coming Next Month* 600 watt power amplifier So you haven’t been impressed by amplifier modules delivering 350 watts into 4Ω loads? Well, you’re not alone because we have had many requests for bigger amplifiers. Now, after a lot of R&D work, we have come up with the goods. This new design will deliv­er 600 watts into a 4Ω load. It’s a big brute, it won’t be cheap but it’s got the power. TENS unit for pain relief TENS stands for Transcutaneous Electrical Neural Stimulation and is widely used by physiotherapists for relief of chronic pain. This compact design offers variable pulse width, pulse rate (frequency) and variable voltage output. It is battery operated for safety. On sale 30th July Australia-wide *Note: the preparation of these articles is well advanced but circumstances may change the final content. July 1997  81 VINTAGE RADIO By JOHN HILL Revamping an old Radiola Take one Radiola cabinet, add an Airzone circuit, make a few other alterations and what have you got? A real “bitzer”, that’s what! This Radiola that has been completely re­worked but, despite that, it still looks the part. In the November 1992 issue, I described how an old 1935 battery-powered Radiola was converted to 240V operation. It was a big job as far as I was concerned, for the simple reason that I had never tackled such a project before. What’s more, I didn’t know how successful the conversion would be until the job was completed. The set was originally built from parts salvaged from two wrecked receivers, both of which were battery models. Some time later, a better cabinet was found and so the old Radiola ended up being rebuilt from three separate receivers. The conversion to AC required the almost complete stripping of the chassis – not even the valve sockets could be used in the rebuild! The only original components that were retained were the dial, the tuning capacitor and its associated coils, the two 175kHz IF transformers, and the permanent magnet loudspeaker. Retaining the permag speaker may seem an odd approach to an AC conversion since mains-powered receivers used electrodynamic types in those days. However, there were good reasons for keeping it. The cabinet could use only a particular type and size of speaker. Because the heads of the speaker mounting bolts are exposed at the front of the cabinet, moving the bolts to accom­modate another speaker All the original coils and IF transformers were dis­carded when the old Radiola was rebuilt. They were replaced with more modern components. 82  Silicon Chip was out of the question. As it turned out, the 60-year-old permag speaker worked amazingly well and kept up with anything the single type 42 output valve could throw at it. While there was some apprehension about using the speaker during the construction stage, it soon proved itself once the set was operational. As an added bonus, the speaker actually looks like an electrodynamic type and it re­quires a close examination to see the difference. Dial drive problems Restoring any vintage radio receiver to working order is often fraught with problems. One particular headache with the Radiola was the friction drive dial mechanism, a common fault with many old receivers. Having two to choose from didn’t help much as each one was as worn and useless as the other. The only practical solution was to completely modify the tuning mechanism and the friction drive was replaced with a more conventional cord drive setup. This amounted to adding a drum and a suitable control spindle, specially made to do the job. Converting a battery receiver to AC operation and altering a useless friction drive to a cord type seemed to be a logical approach to the problems at hand. But not everyone agreed with my line of thought. Apparently, some vintage radio collectors were horrified at such desecration and I received a few critical letters as a result. The debate about the set’s originality continued off and on for about two years before the matter was finally laid to rest. Apparently, vintage radios should be restored exactly as they were originally made, without alterations to circuits or de- vious modifications. Well, so I’m told! Unfortunately, that’s not always possible. Beside, I like to restore an old receiver in a manner that suits me and I base my decisions on such things as cost, the availability of parts and other practical aspects of getting a derelict old radio working again. It is interesting to note that during the war years thou­sands of 1930s vintage battery receivers were converted to AC operation. As new receivers were unavailable at the time, converting battery sets to AC operation became a booming business. It’s strange that such a conversion was OK then but not the done thing today. Major rework Since then, the Radiola AC conversion has undergone a major rework. No doubt it will please my critics to know that I haven’t chosen another set to convert, so hopefully I won’t draw any further flak from those opposed to such things. It’s just an extension of the previous modification. The incentive for the rework came about because the old Radiola developed an odd intermittent fault. Sometimes it would work normally, while at other times it would not. And when it played up, part of the broadcast band would move off the low-frequency end of the dial. While the fault was obviously caused by a considerable shift in oscillator frequency, the problem could not be corrected by tapping components or waggling connections. Wheth­er or not it worked properly was a decision that only the receiver made, depending on its mood. After several unsuccessful attempts at locating the elusive intermittent fault, a big decision was made. The whole chassis was stripped with the exception of the tuning capacitor, dial mechanism, and power transformer. It was then rebuilt using fresh components. The last time this was done, an Airzone 517 circuit was used to build the detector and audio stages. This time the whole circuit was used. The Airzone 517 is nothing special; just a fairly standard late 1930s broadcast band 5-valver with simple AGC and octal valves. My version, however, used pre-octal valves with similar characteristics. There were also a few alterations to the circuit. For starters, the local/ The “new” IF transformers are from a late 1940s Radiola and were mounted on the top of the chassis (the originals were mounted below). These transformers were chosen mainly because their large size seemed appropriate to the generous dimensions of the chas­sis. The original tuning capacitor now operates on only two of its three gangs, as the preselector bandpass stage has been removed. Note the large diameter cord drum that has been fitted to the tuner spindle so as to incorporate a cord drive. distance and tone switches were eliminated, with a potentiometer being substituted for the latter. A high-tension choke was also incorporated to substitute for the nonexistent field coil. Previously, a 20W resistor had been used in the HT line but this resulted in a low-level hum in the speaker. While this hum was not intrusive, it has been virtually eliminat­ed by the addition of the choke. A pair of large postwar IF transformers were selected to replace the old 175kHz originals. These were chosen mainly for their size as everything about the old Radiola is big, the chas­ sis being about 125mm high. The IF transformers were mounted on top of the chassis, as opposed to the under-chassis mounting arrangement of the originals. When these transformers were taken from their derelict receiver, the various connections were noted before disconnecting the wiring. They were also marked IF1 and IF2 because they bore different part numbers and so should not to be treated as inter­ changeable units. The air-cored aerial and oscillator July 1997  83 of this nature somewhat difficult. While the IF trans­formers tuned OK to 455kHz, I encountered difficulties in getting the dial to track when aligning the aerial and oscillator cir­cuits. Most of the broadcast band was there but the frequencies did not line up correctly with the dial. This problem was eventually solved by adding more ca­ pacitance to the padder capacitor and attaching a 7pF capacitor to the oscillator tuning gang. After some juggling with the padder adjustment and the oscillator trimmer, the dial tracked quite well, being less than 10kHz out at its worst point of error. In the circumstances, that was better than anticipated. The dial used on the old Radiola is typical of AWA units from the mid 1930s. It is marked with station call signs around the outside, wavelengths in metres on the left, and fre­quencies in kHz (KC) on the right. The original batteryoperated set had no dial lighting but this was added during the conversion to mains power. coils were taken from an old Astor chassis. Again, as the coil connections were un­marked, notes were made as to which tag went where. It would have been nice to have taken all these components from the one chassis but it turned out that they were all compat­ible when the rebuild was completed. Another major change to the circuit was the removal of the preselector bandpass filter. A bandpass filter, or an RF stage, was employed on early superhets using 175kHz IFs and was essen­tial to avoid double spotting, a natural characteristic of re­ceivers with low intermediate frequencies. Receivers with higher IFs around 455kHz do not require the bandpass filter. As a result, the new circuit uses only two of the three sections of the tuning capacitor. There were no great problems putting all the parts together and the work progressed without incident. Having all the neces­sary components laid out ready for use prevented any hold-ups. A few additional tag strips were used to advantage with the under chassis wiring, the end result being a better layout than my previous effort. Problems Using odd components from various makes and models can make a project This 60-year old AWA permanent magnet loudspeaker looks identi­cal to the electrodynamic version. It is not the one from the receiver but is kept as a spare. It is also handy for on-the-bench testing when the chassis is out of the cabinet. 84  Silicon Chip A good performer It was only after the alignment had been completed and the chassis fitted into its cabinet that I realised that this was a really good receiver. Its ability to pull in distant stations was excellent and a number of Tasmanian stations came in loud and clear. The rebuilt Radiola-cum-Airzone receiver performed very well indeed. It is probable that the original aerial, oscillator and preselector bandpass coils, plus the 175kHz IF transformers, left something to be desired with the initial conversion. Using early 1930s coils and IF transformers is not the best way to go about building a radio receiver. The components from that era are nowhere near as efficient as those from the late 1930s and 1940s. By replacing these parts, the general performance has been greatly improved, particularly at the high frequency end of the dial. This photo shows the tuning shaft modification that was used to convert the slipping friction drive mechanism to a less trouble­some cord drive. Why such a modification should be criticised by some collectors is beyond the author’s comprehension. Vintage Radio Repairs Sales Valves Books Spare Parts See the specialists * Stock constantly changing. * Top prices paid for good quality vintage wireless and audio amps. * Friendly, reliable expert service. Call in or send SSAE for our current catalogue RESURRECTION RADIO 242 Chapel Street (PO Box 2029) PRAHAN, VIC 3181 Tel (03) 9510 4486 Fax (03) 9529 5639 SUNSHINE DEVICE PROGRAMMERS While far from original inside, the old Radiola receiver still retains its vintage appearance. Its current performance is far in excess of that delivered by the original design, thanks to a complete circuit revamp. The three controls (from left to right) are: volume, tuning and tone. So once again the old Radiola has gone through a major transformation and the IF transformers on top of the chassis betray the extent of the modifications. But that’s not a problem as far as I’m concerned because the alterations have been for the better. Upgrading to more modern coils and IF transformers has made a really big difference to the set’s performance. Little cost In money terms, the initial outlay of $20 for the two bat­tered receivers was not great and they have provided me with many hours of constructional pleasure. The cost of converting junk to an operational radio has been almost zero because all the necessary components were on hand. Despite the various modifications and the replacement Airzone circuit, the reworked Radiola still looks an acceptable valve radio. Only vintage radio collectors familiar with that particular make and model would notice that the chassis is not what it SC really should be. Power 100 Universal Programmer 48-pin Textool Socket para I/F ............$1371 Hep 101 Value for Money 8MB E(E)PROM - 1 slave socket ...................$283 Hep 808 High Speed 8MB E(E)PROM programmer 1 master 8 slave sockets .. $790 Jet 08 Production Series E(E)PROM Programmer Stand alone or PC (para) .$1590 PEP01 Portable 8MB E(E)PROM series Programmer, Parallel Port ....................$295 EML2M EPROM Emulator ....................$480 Picker 20 Stand Alone IC Dram CMOS Portable Tester ......................................$199 RU20IT 16 Piece UV EPROM Eraser with timer .............................................$187 Plus converters, adapters & eproms. Contact us for other spe­cialised development tools or data acquisition, industrial elec­tronics, computer and electronic parts and service. Available from: D.G.E. Systems; Nucleus Computer; Stewart Electronics; TECS; X-ON. SUNSHINE ELECTRONICS 9b Morton Ave, Carnegie, Vic, 3163 TEL: (03) 9569 1388 FAX: (03) 9569 1540 Email: nucleus<at>ozemail.com.au July 1997  85 SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. NTSC-to-PAL converter enquiry I have an 8mm NTSC camcorder and I would like to use it to record on a PAL-standard VCR. Can I use the NTSC-to-PAL converter published in the May 1997 issue to do it? I note that there was a comment about this converter not being suitable for recording from the NTSC format to PAL but I am hoping you can tell me how it might be done. (A. K., Yass, NSW). Well, we hate to give negative answers but you can’t use the NTSCto-PAL converter for recording. The problem is that the converter does not change the field frequency of 60Hz to suit the PAL standard of 50Hz. While most video monitors and TV sets can quite happily cope with the difference, a PAL VCR cannot. It must have a TV signal with a field frequency of 50Hz. • No vibrato in Digital Effects Unit I have a Digital Effects Unit, as described in the February 1995 issue, in for repair. The fault is no vibrato. On basic checking I note that there is no output at pin 7 of IC1d when the More queries on shunting meters I see you answered an enquiry about shunting meters last month. I have a similar problem. I have a 1mA 200Ω meter movement that I want to measure currents up to 10mA. I can see the general method but I am uncertain about the result I get. Is a shunt resistor of 20Ω correct for my application? (B. B., St Andrews, NSW). You have followed the procedure outlined last month but you have neglected the 1mA current drawn by the meter itself. Perhaps we did not make that point quite • Effects switch is in and Echo off. Further tracing of audio via headphones revealed a 1kHz tone at pin 24 with Vibrato off and a switching noise with Vibrato on. Any comments? (A. B., Wollon­gong, NSW). The 1kHz tone and noise at pin 24 of IC1 is correct. The fault is probably in the signal path of the delay unit IC3. Check the switching to IC3 at S3a and S3b. Also there could be a short or open circuit connection to S3a from IC3. published in the June 1997 issue will drive your 12V air horn, assuming that it has a motor driven pump. And as far as your CD player and 12V alarm are concerned, the best way to power them would be to use the 24V-12V converter published in the December 1987 issue. While no longer available as a kit, all the parts and the PC board are obtainable. 24V to 12V conversion for truck accessories I would like to relate a recent experience I had concerning the 40W Inverter published in the February 1992 issue of SILICON CHIP. At switch on, it clattered into life, then promptly died! The 5A fuse was open, so I replaced it with an 8A type. As I had used the larger 60VA transformer, I simply put the fuse failure down to that. I say “failure” as the fuse had not blown violently. When I measured the no-load output I had 210VAC; nothing like 279VAC as stated in the article. With a 40W load, this dropped to a crazy 185VAC. The output was terrible, virtually useless. The lamp was flickering at a rapid rate, almost going completely off, then on again. This effect lasted about five minutes, after which the in­verter “died” again. Instead of using a flat metal plate as the heatsink, I used a proper finned type. It was incredibly hot, much more so that it should have been. I suspected a circuit fault, a not so uncommon failing these days. But it was not that at all, I’m pleased to relate. When I bought the necessary components, I purchased more than needed to make up a spare parts kit. The inverter is for a friend of mine in Goulburn and the parts could be very difficult to find in that town. I was aware that MTP3055A power FETs were unsuitable for this circuit, so I made sure that the ones I had were the right type (the “E” version). However, I suspect they were substandard. They were made in Mexico. The pair in the spare parts kit, ironically, had a • I have a 24V truck. It has a 12V air horn set, a 12V CD player and a 12V alarm system. The current drain ranges up to 3.5A. The horn doesn’t get used much at all. Neither does the CD player now but the alarm is armed for a considerable portion of the day, draining one battery. I swap the batteries around every month but what I require is a 24V-12V regulated supply to suit. Can you help? (C. S., Napier, NZ). Unfortunately, there is no one project which will satisfy all your requirements. The 24V/12V speed control • clear, although it was alluded to. In essence, you want 10mA to be read by the meter and so the total meter and shunt resistance should carry that current at full scale deflection. If you allow for the 1mA current drawn by the meter itself, that means that the shunt must carry 9mA. Now we know that the meter is 200Ω so that must mean that the voltage across it (the “burden” voltage) is 200mV for 1mA FSD. Therefore we want a shunt resistor which will carry 9mA with 200mV across it. Using Ohm’s Law, R = V/I = 200mV/9mA, we get an answer of 22Ω which is convenient because it is a preferred value. 40W inverter must use name-brand semis July 1997  91 Multimedia & dual diversity I have questions on two separate topics. Recently my son completed construction of the Multimedia Amplifier described in the October & November 1996 issue of SILICON CHIP. However, before inserting the power link, the voltage on pins 1, 3, 4, 6 & 9 of all three power ICs was 0V not 6V as stated in the article. We have thoroughly checked the board for solder bridges, incorrect insertion of polarised components, etc and cannot deter­ mine what the problem is if there is one at all. Currently we are stalled with speakers assembled and the board constructed await­ing connection of the “power links” but unsure if it is safe to do so. Any ideas as to the likely cause of the missing voltage or if it is safe (for the computer especially) to connect the power links as is. Second, in August & September 1994 you published articles describing a diversity tuner for FM microphones. It comprised a single tuner with an antenna switching circuit to select the better reception from one of two antennas rather than use different brand stamped on them. They were made in Malaysia and carried an ST brand name. (Silicon Technology?) The other discovery was the LM339 quad comparator IC. It was a DBL339! Now it could have been the same thing but I re­placed it with a proper LM339, fitted the new ST brand FETs and gingerly switched on. The inverter now works like a bought one! With a 40W load, there is 230VAC on the output and with a 60W load, 200VAC precisely. After several hours use, the heatsink barely gets warm. I am very pleased with the circuit. There is, however, a valuable lesson in this. I bought the components from a small Melbourne firm. They used to be cheap but not any more! In fact, I no longer deal with them. (N. B., Canterbury, NSW). Component substitutions are always a concern to us, as they can lead to disappointment for the constructor. In this respect you are almost always • 92  Silicon Chip two receivers. Is it possible to adapt the antenna switching circuit to an existing non-diversity VHF (200MHz) FM microphone receiver to reduce drop out etc? (G. C., Hazelwood Park, SA. We’re afraid that there is an error with the test procedure. You were the first to let us know. Without the link installed, pins 1 and 9 measure about 0.5V and pin 7 measures 12V. No vol­tage is present on the other pins. With the link in, pins 1 and 9 measure 2.2V, pins 3, 4 & 6 measure 5.6V and pin 7 measures 12V. While it is possible to adapt the Dual Diversity antenna switching circuitry to an existing 200MHz receiver, some circuit modifications may be required. The AGC voltage for the dual diversity receiver is applied to IC4a via a 3.3kΩ resistor and requires a voltage that rises with the strength of the signal. No signal is represented by 0V. In your receiver, the AGC voltage may be inverted and offset from 0V. If so, it would have to be level shifted and inverted by op amp level circuitry. Adjustment of the gain is done by changing the 220kΩ resistor between pins 5 and 7 of IC4a. • better off buying a kit if it is available, rather than obtaining parts from other outlets. Upgrading the 45V 8A power supply I am considering building the 0-45V 8A power supply fea­tured in the January 1992 issue but I have the following ques­tions: (1) Can the optical link (IC1/LED1) be replaced with an optocoupler, with a suitable buffer transistor to provide some gain on the output to drive Q2, if necessary? The optical link arrangement seems to be a slight overkill and is not readily available here whereas optocouplers are. If this is practical, what type of opto would you recommend and how would you configure it? I realise that this modification would need to be mounted on a sub-board off the main PC board. (2) The transformer I intend to use has a lower output at 25V AC but has a higher current capability at 450VA. What I would like to do is raise the overall specs by two amps; ie, full current at 10A with foldback occurring at 11A. The switchmode part of the circuit appears able to sustain this increase, so it would only seem necessary to alter the point at which foldback occurs. This could be done by altering the voltage divider network consisting of the 22kΩ, 27kΩ, 820Ω and 1.1kΩ resistors so that it now senses 0.55V across R1/R2, corresponding to 11A. Assuming this is prac­tical, which resistors would you change and to what values? To enable the current limiting to pass 10A before it lim­its, my calculations indicate that the 270kΩ resistor above VR1 needs to be changed to 243kΩ. This will allow the voltage at the non-inverting input of IC5b to reach approximately 0.52V, which for the same voltage developed across R1/ R2 would mean a current through the latter of just over 10A. Your comments and suggestions would be much appreciated. (S. W., Hamilton, NZ). The reason we have used the optical link was to obtain sufficient speed to drive the switching Mosfet. If you can obtain a really fast optocoupler (most are relatively slow), you could probably substitute it without too many problems. If we were to redesign the power supply today, we would probably use a high-side switching IC. We would be wary about increasing the output of the power supply, even only marginally. The main switching inductor has proved to be critical in this design and we would not like to prejudice its reliability. • Float switch for a jet ski I am interested in building an electronic float switch for a bilge pump in a jet ski. I cannot fit a normal float switch as I’m limited for room. Would you be able to supply me with a circuit diagram of one or advise me of where I could get one, please? (F. D., Innisfail, Qld). We have published three circuits for bilge pump controllers, in December 1989, February 1990 and March 1990. In each case they employed the National Semiconductor 1830 fluid sensor IC. The most appropriate circuit for your • application would be the March 1990 design which featured a 15-second sloshing delay. All the circuits referred to were published in the Circuit Notebook pages and so no PC board designs are available. Query on variable ignition timing My query is related to John Clarke’s Knock Indicator for leaded-petrol engines, as featured in the April 1996 issue. I own a 1980 Volvo 264 GLE with the Bosch K-Jetronic mechanical fuel injection system and the Bosch contactless electronic ignition. This is the V6 engine used in Volvo, Renault & Peugeot cars and in some of the later Volvos in an EFI version. As was usual in those days, the engine was designed to run on 97RON leaded petrol and had a reasonably high compression ratio. I had to do a recent valve regrind and decoke on the engine and having restored it to full compression again, it now “pings” at a specific rev range on a very light throttle, exactly as John Clarke has described. I define a “ping” as more a “breaking glass” type sound as opposed to a “knock” or heavy “pinking”. Fortunately, it does not knock or ping at any other point except at about 3000 revs with a high manifold vacuum, which equates to just over 80km/h. If the vacuum advance is disconnected, there is no ping at all, confirming that somewhere along the extra 10 degrees of advance provided by the vacuum unit, it is too advanced for the lower lead petrols available today. However, the vacuum unit is necessary for good performance through­out the rev range. This engine/ignition has a very aggressive advance curve with very high advance figures in the mid to higher rev range. I have just purchased the Knock Sensor kit from Jaycar electronics after seeing just such a kit in operation on another car and am impressed by its performance. Before I put this kit together, may I ask for the possibility of an extension to the design? The circuit provides 10 points of reference when pinging occurs, to trigger the LED displays. Could one or all of these points be utilised to trigger a time-delay circuit inserted between the distributor and the electronic ignition amplifier unit to effectively Multimedia power worries I am interested in making the Multimedia Amplifier featured in the October & November 1996 issues of SILICON CHIP. However, I am concerned because the circuit has been described to me as a most irresponsible design as it takes absolutely no account of the limitations imposed by most computer power supplies. Is this a reasonable comment? What would be the maximum additional load that the power supply would be expected to deliver during normal use of the amplifier? (L. S., Kenthurst, NSW). As far as power supply capacity is concerned, we would not have published the project if there was any risk of running computer power supplies into overload. The typical computer power supply these days is rated at 250 watts and this usually includes 5V 20A (100W) and 12V 12A (144W) supply rails. A typical 1.6GB drive consumes 0.4A at 5V and 0.27A at 12V DC. A typical CD-ROM • retard the spark timing by a specific factor when pinging occurs? Once the pinging ceases, the delay unit would pass the distributor impulse straight through the amplifier as normal. This would have the effect of dynamically modulating the impulse signal only if and when required and would alleviate the need to start tampering with the advance weight springs in the distributor. Please believe me when I tell you (through experi­ence) that tampering with the advance curve in this manner on an engine like this is a horrendous task, even with access to the appropriate distributor timing machine levels. Besides, I only have the problem at a specific rev range. I appreciate that I could fit the entire electronic kit described in a previous edition of SILICON CHIP and do away with the existing ignition control unit but arriving at the desired advance curve with this new unit is a very daunting task. Bosch Australia is a very helpful organisation but they just drive might pull 1.8A at 5V and 1.5A at 12V. Unless your computer is loaded up with lots of accessory cards and has perhaps two or three hard disc drives, CD-ROM, etc your computer’s power supply will have lots of current capacity to spare. By way of comparison, we would expect the total current drain of the multimedia amplifier card to be less than 250mA for virtually all of the time. Even if all amplifiers were driven into serious clipping simultaneously, which should never happen, the total current drain would be no more than about 2A at the maximum. If you did manage to drive the multimedia amplifiers into serious overload, their own protection circuitry would quickly shut them down. In any case, your computer’s power supply has over­load protection and in the event of a serious overload, which is very unlikely to be due to the multimedia amplifier card, the worst that might happen is that your hard disc might slow down momentarily. do not have all this data for the older cars (I have tried). (G. D., Berowra Heights, NSW). Your suggested concept of using the Knock Indicator to modulate the ignition advance curve is certainly feasible and is the same principle as used in cars with full engine management systems. However, designing such a system with hardware would be quite complex. Nor could we necessarily produce a circuit which would be compatible with the many ignition systems available. • Notes & Errata Multimedia Amplifier, October 1996: There is an error with the test procedure for the PC board. Without the power link in­stalled, pins 1 and 9 of IC3, IC4 and IC5 are at about +0.5V and pin 7 is at +12V. No voltage is present on the other pins. With the link in, pins 1 and 9 are at about +2.2V; pins 3, 4 & 6 are at +5.6V; and pin 7 SC measures +12V. July 1997  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES FOR SALE Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. C COMPILERS: Ever ything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086 or 8096: $140.00 each. Macro Cross Assemblers for these CPUs + 6800/01/03/05 and 6502: $140.00 for the set. Debug monitors: $70 for 6 CPUs. All compilers inc ‘HC12, XASMs and monitors: $480. 8051/52 or 80C320 Simulator (fast): $70. Disassemblers for 12 CPUs only $75. Try the new C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo disk: FREE. All prices + $5 p&p. GRAN­ T RONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph/Fax (02) 9631 1236 or Internet: http://www.mpx.com.au/~lgrant. To run your classified ad, print it clearly on a separate sheet of paper, fill out the form below & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________  Bankcard    Visa Card    Master Card Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my Signature­­­­­­­­­­­­__________________________  Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip MICROCRAFT IS NOW ON THE WEB: Dunfield (DDS) products are now available ex-stock at a new low price; please ask for our catalogue. Micro C, the affordable “C” compiler for embedded applications. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $139.95 each + $3 p&h • EMILY52 is a PC based 8051/52 high speed simulator $69.95 + $3 p&h • DDS demo disks $7 + $3 p&h • VHS VIDEO from the USA (PAL) “CNC X-Y-Z using car alter­nators” (uses car alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Fixed price electronic design and PCB layout • Credit cards accepted • All goods sent registered mail • Call Bob for more de­ t ails. MICRO­CRAFT, PO Box 514, Concord NSW 2137. Phone (02) 9744 5440 or fax (02) 9744 9280. http://www.micro.com.au email sales<at>micro.com.au MAGNETIC CARD READER/WRITER. Program your own (swipe) cards. Reads/writes to all three tracks alpha/ numeric to 1.5.0 standards 7811/2 P.O.A. (03) 9729 8448. Mobile 015 539191. VIDEO CAMERAS & EQUIPMENT Only: $79! PCB VIDEO CAMERAS with Board or Pinhole Lens - Only: $79! INFRARED ILLUMINATORS & KITS Com­plete Lamp 240 vac Auto on/off $149. 52mm Round Lamp Tubular/Hooded Style Enclosure 50 LED 12 Watt $50. Rectangular 88 LED 22 Watt $72, 180 LED 845nm 45 Watt $113, 210 LED 52 Watt 845nm $135. Options: 820, 845, 880, 940nm, 22, 24, 50, 60 Degree Radiation Angles. PCB Modules 420 Line 0.05 lux $144. PCB PINHOLE 460 Line 0.05 lux $177. 28x28mm PCB Modules - THE TINIEST! Robust Mini Cube Cameras $147. Dome Ceiling Cameras $197. C Mount Cam­eras - Only! $99. JAPANESE CS MOUNT LENSES! 8mm Adjustable Iris $66. 8mm Automatic Iris $79. Colour Modules & Cameras $449. Pre-Amp/Microphone Modules $35. Video Transmitter Modules $54. Baluns 100/75 Ohm - Use UTP or Telephone Cable for Video - Only! $19. Monitors 5.5, 7, 9, 12 Inch from $119. Quad Screen Processors from $410. Colour Quads 512 x 512 from $929. Wireless CCTV Video/Audio Sets TX Camera & Receiver from $373. Plus Ancillary & Specialised items: 11 Board, 5 Pinhole, 15 C/CS Lenses. InfraRed Cut, Pass & Polarising Filters. 74mW InfraRed LEDs from 48 cents! BEFORE YOU BUY! Ask for our Detailed, Illustrated Price List & Application Notes. Also available CCTV Technical, Design, Refer­ence Manuals & CD ROM. Prices include tax. Discounts available! Allthings Sales & Services 08 9349 9413 fax 08 9344 5905. PCBs MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics (02) 9554 9760. Fax: 9718 4762. Email: skybus<at>zip.com.au Microprocessor For Digital Effects Unit This is the 68HC705-C8P pro­ gramm­ed micro­pro­cessor IC for the Digital Effects Unit (see Feb­. 1995). Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Pub­ lica­ tions, PO Box 139 Collaroy 2097. Phone (02) 9979 5644; Fax (02) 9979 6503. MicroZed Computers BASIC STAMPS & PIC Tools With third party supporting products, all in stock. Easy to learn, easy to use sophisticated CPU based controllers. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (067) 72 2777 – may time out to Mobile 014 036775 Fax (067) 72 8987 http://www.microzed.com.au/~microzed Credit cards OK. Send two 45c stamps for info RAIN BRAIN AND DIGI-TEMP KITS: 8-station controller and 8-chan­ n el, RS232 digital thermometer uses the incredible DS1820 sensor. Call Mantis Micro Products, 38 Garnet St, Niddrie, 3042. P/F/A (03) 9337 1917. http://www.home.aone.net.au/mantismp MicroZed have S3 RAMPack, serial port access to 64K bit RAM, board will take NVRAM. HOMEMADE GENERATORS: how to instructions. Eight pages free text and colour photos on the Internet at: http://www.onekw.co.nz/ GOLD COAST/TWEED Electronic Kit Assembly and Troubleshoot­ing Service. Ph Geoff (07) 5570 7435. MicroZed have 12Cxx Microchip CPU 8 pins with 6/I-O from as little as $3.50 small qty (+ st). MEMORY * MEMORY * MEMORY SIMMS Parity/Standard 4Mb 30-pin 60ns $42 $38 4Mb 72-pin 60ns $47 $32 8Mb 72-pin 60ns $94 $66 16Mb 72-pin 60ns $144 $117 32Mb 72-pin 60ns $272 $232 EDO SIMMS 72pin 60ns 4Mb / 8Mb $36 / $60 16Mb / 32Mb $116 / $233 64Mb / 128Mb $984 / $1,920 DIMMS 168-pin 60ns 8Mb / 16Mb $70 / $126 32Mb / 64Mb $243 / $473 SDRAM 168-pin 12ns 8Mb / 16Mb $84 / $132 32Mb / 64Mb $278 / $660 TOSHIBA 16Mb Tecra 500/650 Sat. $201 16Mb Tecra 700 > 740 $272 GATEWAY 2000 16Mb Solo 2100/2200 $215 16Mb P5 166XL/G6-200 $169 IBM 16Mb Thinkpad 760, 365 $182 32Mb Aptiva S P200 $402 DELL 16Mb Latitude 4100 MX, MC, LC $205 32Mb Dimension M -SDRAM $422 16Mb Optiplex GS $224 HEWLETT PACKARD 8Mb Laserjet 4,5,6P/MP $83 8Mb Laserjet 5L, 6L $151 16Mb Omnibook 800 $224 CAMERA CARDS 8Mb Compact Flash $170 12Mb Compact Flash $315 8Mb ATA Flash $171 12Mb ATA Flash $234 We carry over 600 different modules for all makes, including ACER, AST, CANON, APPLE, NEC, ZENITH, SUN & SILICON GRAPHICS Pricing as at 04/06/97. PHONE FOR LATEST EX TAX PRICING OVERNIGHT DELIVERY $8 LIFETIME WARRANTY!! SALES TAX – 22% CREDIT CARDS WELCOME PELHAM Pty Suite 6, 2 Hillcrest Rd, Ph: (02) 9980 6988 Pennant Hills, 2120. Fax: (02) 9980 6991 Ltd Email: pelham1<at>ozemail.com.au A SIMPLE PIC84 PROGRAMMER: LED model 6 lights $70, LCD model 16 x 1 char. $80, pp $5. Others available. EST Electronics (02) 9789 3616. Fax (02) 9718 4762. MicroZed have 16C84/10P $6 ea + st in small qty. MicroZed have S3 pocket watch. MicroZed have S3 SV UPS, uses 2 x AA cells. SILICON CHIP FLOPPY INDEX WITH FILE VIEWER Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. Price $7.00 each + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 9979 5644 & quote your credit card number; or fax the details to (02) 9979 6503. Please specify 3.5-inch or 5.25-inch disc. July 1997  95 MicroZed say why buy a tube of ICs just to try an idea. We have small qtys available, tube qtys too! STEPPER MOTORS for automation, coil winding, experiments, models, robots, 4 assorted $49 inc freight. Also EPROMs 2708-27256 $4. Many other electronic/computer parts available. Peter, 9 Morton Ave, Carnegie 3163. Ph (03) 9569 1388. Fax 9569 1540. WANTED WANTED URGENT: Picture tube suit Philips CTV Model KR5987 type A59EAK 10 x 03. Ph/Fax (03) 6247 6683. Circuit Ideas Wanted Do you have a good circuit idea. If so, why not sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We’ll pay up to $60 for a really good circuit but don’t make them too big please. Send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 14 Model Railway Projects Shop soiled but HALF PRICE! Advertising Index Altronics................................. 72-74 Dick Smith Elect........... 12,13,34-37 Harbuch Electronics....................77 Instant PCBs................................95 Jaycar ............................IFC, 45-52 Kits-R-US.....................................33 MicroZed Computers...................95 Model Railways Book..................96 Oatley Electronics..........................3 Pelham.........................................95 Resurrection Radio......................85 Rod Irving Electronics .......... 82-86 Silicon Chip Back Issues....... 20-21 Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) This book will not be reprinted Yes! 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Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Card No. Street Silicon Chip Binders................OBC Silicon Chip Software..................19 Silicon Chip Wallchart..............OBC Smart Fastchargers.....................33 Sunshine Electronics...................85 WAR Audio..................................81 Zoom Magazine.........................IBC _____________________________ Signature­­­­­­­­­­­­___________________________  Card expiry date______/______ Name Silicon Chip Bookshop.................53 ______________________________________________________ PLEASE PRINT ______________________________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: Suburb/town_________________________________ Postcode_________ •  RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). •  Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. 96  Silicon Chip