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Especially For Model Railway Enthusiasts Order Direct From SILICON CHIP Order today by phoning (02) 9979 5644 & quoting your credit card number; or fill in the form below & fax it to (02) 9979 6503; or mail the form to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. This book has 14 model railway projects for you to build, including pulse power throttle controllers, a level crossing detector with matching lights & sound effects, & diesel sound & steam sound simulators. If you are a model railway enthusiast, then this collection of projects from SILICON CHIP is a must. Price: $7.95 plus $3 p&p Yes! Please send me _______ copies of 14 Model Railway Projects Enclosed is my cheque/money order for $­_________ or please debit my  Bankcard    Visa Card    Master Card Card No. Signature­­­­­­­­­­­­_________________________ Card expiry date_____/_____ Name _________________________Phone No (____)_____________ PLEASE PRINT Street ___________________________________________________ Suburb/town __________________________ Postcode____________ Vol.7, No.12; December 1994 FEATURES FEATURES THE 9-BIT WIDE SIMMs in your computer may not be true 9-bit devices at all because of a new cost-cutting trend in the Asian market. We take a look at the possible consequences & what you can do to guard against it – see page 10.   4 Cruise Control: How It Works by Julian Edgar Electronics plays a vital role 10 The Great RAM Scam Of 1994 by Darren Yates Cut price memory has no parity bit 54 The Stamp Microcontroller Board by Bob Nicol It’s not much bigger than a large postage stamp 92 Index To Volume 7, Jan - Dec. 1994 All the year’s features & circuits PROJECTS PROJECTS TO TO BUILD BUILD 18 Dolby Pro-Logic Surround Sound Decoder; Pt.1 by John Clarke Reproduce the big sound of the movies in your living room NOW YOU CAN HAVE the big sound of the movies in your living room with this Dolby Pro Logic Surround Sound Decoder. This is the genuine article, approved & licensed by Dolby Labora­tories in California. Pt.1 starts on page 18. 29 Clifford – A Pesky Little Electronic Cricket by Darren Yates He chirps & flashes his eyes – but only when it’s dark 32 An Easy-To-Build Car Burglar Alarm by Bernie Gilchrist Features battery backup & optional central locking 60 A 3-Spot Low Distortion Sinewave Oscillator by Darren Yates Generates signals at 100Hz, 1kHz & 10kHz SPECIAL SPECIAL COLUMNS COLUMNS 42 Computer Bits by Darren Yates MEET CLIFFORD – our new little pesky insect friend. He only chirps & flashes his eyes if it gets dark &, if he’s well hidden, he can be very annoying. Build him just for fun – see page 29. The Electronics Workbench revisited 58 Amateur Radio by Garry Cratt AR8000 handheld scanner reviewed 72 Serviceman’s Log by the TV Serviceman Purity is not always only in the mind 78 Vintage Radio by John Hill Valves & miniaturisation: some remarkable receivers 84 Building A Radio Control System For Models; Pt.1 by Bob Young Tailor it to suit your application DEPARTMENTS DEPARTMENTS   2 16 16 53 Publisher’s Letter Circuit Notebook Notes & Errata Order Form 87 90 94 96 Product Showcase Ask Silicon Chip Market Centre Advertising Index DON’T FORK OUT BIG dollars for a car burglar alarm. This unit can be built for far less than the cost of a commercial unit & features battery backup, a flashing deterrent LED & an optional central door locking interface. It can also be mated to an optional remote control. Turn to page 32 for the details. December 1994  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson Phone (02) 979 5644 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman, VK2ZLZ John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Philip Watson, MIREE, VK2ZPW Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $49 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. PUBLISHER’S LETTER A few milestones & a nasty discovery This month there are a number of topics I want to comment on and the first of these concerns our Dolby® Pro Logic Surround Sound decoder article which starts on page 18 of this issue. This project has been a long time coming for us but is one that we are very pleased to present. As far as we know it is the first time that an electronics magazine has presented a Dolby Laboratories approved and licensed decoder design. Yes, it’s a world first and we are very proud of it. The second project article of note is Bob Young’s remote control receiver series which starts on page 84. Again, this is a milestone and is the first time for almost 30 years that such a series has been presented in an Australian electronics magazine. And although this point has not been highlighted in the article, it is only the second which makes extensive use of surface mount components. The first was Bob Young’s speed control which was presented in a series beginning in November 1992. Now if you shudder at the thought of working with surface mount components, you are not alone. I have been concerned for some time about the ever-reducing size of componentry and it was the subject of the Publisher’s Letter in last month’s issue. So surface mount components are another inevitable step in the process. But apart from my suggestion last month that a good pair of close-up specs is now very worthwhile for many people engaged in electronics, it is about time we faced up to surface mount anyway. In the remote control receiver case, there are very good reasons to use SMDs – short lead lengths, ability to withstand high vibration and G-forces and so on. And if you follow the procedure which Bob Young will be presenting in a future issue, it is possible to work with SMDs without any special equipment. It’s time to get with it, so we’re giving you adequate warning. Finally, I must comment on the use of bogus RAM SIMMs with parity generator chips. The story about these bogus SIMMs is presented on page 10. Apparently they are becoming very widespread and could conceivably cause users a lot of trouble in the future. Now as far as I am concerned, and I am sure most readers will agree, if ever there was an outrageous rip-off, this is it. What can you do about it? Not much, if you’ve already been caught. But at least new computer buyers will know to ask about RAM SIMMs with genuine parity. But it’s a pretty crook situation, isn’t it? 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 Cruise Control: How It Works One option that has become popular on cars in recent years is the cruise control. Here’s a quick rundown on how they work. By JULIAN EDGAR Cruise control systems are now widely used in cars. A cruise control allows the driver to select a speed, with the system then maintaining that speed irrespective of gradient or aerodynamic loadings. Cruise controls have benefits in reducing fuel consumption, decreasing driver fatigue, and – sometimes – avoiding speeding tickets! All cruise control systems compare the actual vehicle speed with the speed set in the system’s memory. A signal is then transmitted according to the difference between the two. This signal is used to control an actuator linked to the throttle butterfly, with the throttle being opened or closed as appro­priate. Fig.1 shows the layout of a typical Aftermarket cruise control systems generally use a magnetic pickup sensor to determine vehicle speed. The magnets are typi­cally attached to the tailshaft or to the transaxle, 4  Silicon Chip cruise control sys­tem, in this case from a Subaru. The major input signal is derived from the speed sensor. Depending on the car, this sensor can be located on the tail­shaft, within the transmission or within the speedometer. The location of the sensor will depend on its design and whether the system is an aftermarket unit or one designed and fitted by the vehicle’s manufacturer. Aftermarket cruise controls generally use an inductive pulse sensor, whereby bar magnets are attached to the tailshaft and a pick-up coil is positioned close to the rotating shaft. Fig.2 shows an example of this type of sensor. It generates a waveform whose frequency is proportional to the car’s speed. By contrast, original equipment Hall Effect sensors (Fig.3) are usually mounted on the transmission and generate a square-wave output. Yet another scheme uses optical sensors mounted within the speedometer assembly, or a reed switch excited by the speedometer drum can be used to make and break the cir­cuit. Other input signals to the ECU are also used. An engine rpm signal is derived from the engine management system in some cars, while brake and clutch position indicators (usually simple switches) and automatic transmission status inputs are also utilised. The latter are used to disable the cruise control function if the brake or clutch pedals are depressed, or if the transmission is shifted into neutral. Electronic control unit Fig.4 shows the layout of a typical Bosch cruise control ECU. During op- Fig.1: the cruise control system used in the Subaru Liberty is typical of current designs. The electronic control unit receives inputs from a number of sensor and activates sole­noid-operated pressure control valves to permit the engine vacuum to control the actuator. The actuator in turn controls the throt­tle valve via a cable. Note that the cruise control throttle cable operates in parallel with the cable from the accelerator pedal. eration, the speed sensor (1) provides an AC vol­tage signal to the evaluation circuit (7), which is a frequency to voltage converter. The actual speed signal is then compared with the set speed stored in the memory (12). Once the Activate/Set button (2) is switched, the speed at which the vehicle is travelling when the button is pressed is stored digitally in the set-speed memory (12). Older systems used capacitor storage of the set-speed December 1994  5 Fig.2 (above): aftermarket cruise controls often use an inductive speed input sensor. This comprises magnets attached to the driveshaft which then spin past a pick-up coil. In systems employing a Hall Effect speed input sensor (Fig.3, right), the device is usually installed on the gearbox. but the more-modern digital approach has advantages in terms of ease and precision, particu­larly when it comes to long-term storage. A control circuit (8 & 9) acts on the comparison between the actual and set speeds. The acceleration controller (8) acti­vates when the car is travelling more slowly than the set speed. The speed controller (9), operates within the control range. If the speed is within the control range, the position controller (10) receives a signal which is proportional to the deviation between the set and actual speeds. This deviation is the refer­ence input signal for the electromagnetic actuator used in this system. The potentiometer (18) registers the position of this actuator, giving closed-loop feedback. The actuator (17) is driven by the output stages (11). Should the brake (5), clutch (6) or Off switch (4) be acti­vated, then the cruise control is disabled. It is also disabled if the car’s speed drops below the Vmin (minimum velocity) threshold (14), or if the rate of speed change (ie, acceleration) exceeds a preset value. In the Subaru Liberty, this preset accel­eration value is 25 km/h per second. Fail-safe functions Most cruise controls use a vacuum operated servo to open and close the throttle butterfly. These photos show two examples. 6  Silicon Chip The Bosch unit discussed above does not have extensive fail-safe functions. However, current units are designed so that a breakdown (eg, of a component) will not cause a dangerous situation to develop; eg, if an erroneous circuit or switch operation is sensed, then the cruise control will be switched off or the memory speed cancelled. One of the conditions which would cause this to occur is if the actuator’s output signal was on for at least a second – something which would not normally happen. (1) SPEED SENSOR (7) (8) EVALUATION CIRCUIT V1st/Vact FINAL CONTROLLING ELEMENTS ACCELERATION CONTROLLER (10) (17) (11) POSITION CONTROLLER M OUTPUT STAGES (9) SPEED CONTROLLER (18) CLOCK SIGNAL (13) STEERING COLUMN SWITCH (2) ACTIVATE SET Vmin THRESHOLD (15) DISCONNECT LOGIC AND RELAY (14) DIGITAL SET-SPEED MEMORY Vset v THRESHOLD (19) (3) COUPLING RE-ACTIVATE (4) OFF (20) (5) DRAG SWITCH BRAKE (6) (21) SAFETY CIRCUIT CLUTCH Fig.4: this diagram shows the basic circuit elements of the electronic control unit in the Bosch cruise control. The cruise control is deactivated immediately if the brake or clutch are operated. RELAY Self-diagnostics are incorporated into some ECUs. In one system, a handheld “Select Monitor” (a proprietary service tool) is used. Diagnostics can be conducted in either real time or by using the service tool’s memory. During real-time fault diagnos­es, the Select Monitor is used to enter dummy data to simulate operating conditions. Output actuators The electronic control module accepts inputs from the speed sensor & the various control switches & outputs a signal that controls the throttle opening via an actuator. While an electromagnetic actuator is used to change the throttle butterfly opening in the Bosch control system, most systems use an actuator that’s operated by the engine vacuum. The vacuum servo output device uses the low pressure ex­ perienced in the manifold of a throttled engine (and hence at­mospheric air pressure) to do the hard work. Engine vacuum and atmospheric pressure are admitted to one side of a diaphragm. Depending on the opening and closing of the solenoid pressure control valves, the diaphragm will be deflected by December 1994  7 Different control stalks & panels are available for use with cruise control systems, with two stalks & a control switch plate shown here. varying amounts. This diaphragm is attached to a throttle cable which operates in parallel with the usual cable connected to the accel­ erator and so the throttle valve is opened and closed appro­priately. The amount of manifold vacuum available at large throttle openings is small (and a positive pressure will, of course, exist in the manifold at large throttle openings in a turbocharged car). In some cars, a vacuum accumulator (Fig.5) is used in conjunction with a one-way valve, to provide a reservoir of low pressure. Stepper motors and electric DC motors used in conjunction with an epicyclic gear train have also been employed by some manufacturers as the actuator. However, by far the most common servo is the vacuum-assisted SC design. Fig.5: a vacuum reservoir is used in some systems so that actua­tor operation can still occur at the low vacuum levels experi­enced at large throttle openings. 8  Silicon Chip December 1994  9 The Great RAM Scam Of 1994 The 9-bit wide SIMMs in your computer may not be 9-bit devices at all. Your PC could be headed for a fall because of a new cost-cutting trend in the Asian market. We take a look at the possible consequences & what you can do to guard against it. By DARREN YATES Picture this: you’re sitting at your PC and working away feverishly. All of a sudden, for no explained reason, your PC crashes and you’ve lost the last half hour’s work. Believe it or not, this is becoming a more common event than most people re­ alise but more often than not it is blamed on the old dreaded “power glitch”. While the adoption of the IBM standard has ensured that software designed to run on the PC will run on most “compatible” machines, it seems the same cannot be said for the hardware side of things. As the number of manufacturers climbing onto the PC bandwagon appears to be forever increasing, so too are the chanc­es of hardware clashes and conflicts. And we’re not only talking about add-on boards here. In the last few weeks, we’ve found an alarming trend in the one area you would have thought was considered safe against the ever-vigilant eye of the penny-pinchers – the RAM modules. We recently received information from a couple of readers, David Eather and Pat Andersen from the Queensland University of Technology, about a new RAM scam: some 1Mb and 4Mb 9-bit 3-chip single in-line memory modules (SIMMs) are being supplied with only 8-bit wide RAM with the socalled parity bit RAM being replaced with a cheaper parity generator chip instead. To understand the consequences of this fully, let’s look at the basics of a RAM module. In the IBM PC, memory is organised into rows of eight bits, called bytes, into which information is stored. To their credit, the designers of the IBM PC incorporated parity error detection. Parity error detection goes back a long way and was first used in computers during the 1950s. There are two different parity error detection systems: odd and even. SIMM modules with the bogus parity chip are readily identified at present because they have two surface mount resistors on the chip-side of the board. These are not present on the “real” modules but it is ex­pected that they will disappear eventually. To make matters worse, the parity chips are labelled in such a way that they can easily be mistaken for 1Mb chips. 10  Silicon Chip Both add a single bit to an 8-bit data word and its value is determined by the number of ‘1’ digits in the data word. That extra bit is referred to as the parity bit. In an odd parity system, as used in the IBM PC, the parity bit is assigned a value of one or zero so that the total number of ‘1’ digits in the transmitted word is odd. For example, if an eight bit data word 01011010 is to be transmitted, the parity bit becomes 1, to give five 1s in the 9-bit transmitted word 101011010. Now if a 1-bit error in any digit position occurs in the storage (writing) or retrieval (reading) process, the actual parity of the received data word will not agree with the parity bit. Hence the error can be detected. However, there is no way of knowing which bit is wrong. Furthermore, if there are an even number of 1-bit errors in a single data word, the parity of the received data word will not change and the errors will not be detected. So parity only provides a limited degree of error detec­tion. Be that as it may, it is better than no error detection at all. And when you have a SIMM with a parity bit generator instead of genuine parity bits, you do indeed have no error detection at all. Bogus SIMMs have no parity bit What is happening now in a few Asian manufacturing houses is that this parity bit RAM is being replaced by what they call a parity generator. This chip looks at the 8-bit data words stored in memory and generates the parity bit itself. So instead of the computer receiving what it thinks is 8-bit data words together with the parity bits stored in RAM, the parity generator IC feeds it a parity based on what it sees in the RAM. So even if the stored data in the RAM is wrong, the corresponding parity bit received by the computer is correct and no bit errors are detected. It simply boils down to the fact that with these SIMM modules, no parity checking is being done at all and the data, warts and all, is being processed as normal. This is basically a scam - people think they are getting 9-bit wide RAM with error checking when in fact they are being sold 8-bit wide RAM with no error checking. Time delay errors However, there is something potentially more dangerous in this bogus system of generating the parity bit and that concerns the time delay. When parity is retrieved from memory, it is available at the same time as the byte of information required so there is no time delay. With parity generation, as is the case with these new SIMMs, there is an inevitable time delay between the byte of information appearing and the parity bit being produced as the parity generator chip does its calculation. Our information is that this delay could be anywhere bet­ween 7ns and 30ns. Now while that might not sound like much of a delay, most memory today runs at 60ns. A 30ns delay constitutes half a clock cycle on these SIMM modules and this could cause severe timing problems within the computer. There are many functions being performed on memory in just one clock cycle. Things such as refreshing memory and multiplex­ing of address lines so that the correct byte can be found are all performed within a clock period. To now have a parity bit arriving up to 30ns late could easily prove disastrous, particu­larly if the time “window” for obtaining the value of the parity bit has come and gone. Can it really be true When we first heard of this, we thought it too fantastic to be true, even though our correspondents David Eather and Pat Andersen had provided us with a sample bogus SIMM. To get confir­mation, we called RAM suppliers Pelham Pty Ltd (who, by the way, do not supply these bogus SIMMs) to check the story and they con­firmed it to be true. Apparently it is widespread. So why do the manufacturers do it? Well, surprise, sur­prise, there are big savings to be had. Based on the information from Pelham, it seems that there is a $5 saving in production costs by replacing the parity bit RAM with a parity generator chip. Now that may not seem like much but it gets better (or worse, depending on how you look at it). For a 4Mb SIMM, the saving increases to $19. For an 8Mb (72-pin) SIMM, it’s $27 and this increases to a whopping $137 for a 32Mb 72-pin SIMM! Yet only a tiny portion of these savings is passed on to the consumer who remains “in the dark”. When you consider the huge quantities of SIMMs produced, it adds up to millions of dollars. SATELLITE SUPPLIES Aussat systems from under $850 SATELLITE RECEIVERS FROM .$280 LNB’s Ku FROM ..............................$229 LNB’s C FROM .................................$330 FEEDHORNS Ku BAND FROM ......$45 FEEDHORNS C.BAND FROM .........$95 DISHES 60m to 3.7m FROM ...........$130 What can you do? If you’ve bought a new PC or upgraded your current PC in the last couple of years, then chances are you’ve bought some SIMMs along the way. So how can you check to see if your have the ridgy-didge item? At present, those SIMM modules with the bogus parity chip have two surface mount resistors on the chipside of the board. These are not present on the “real” modules, however, it is ex­pected that they will disappear eventually. What makes it even worse is that the parity chips are labelled in such a way that they can easily be mistaken for 1Mb chips. The sample that we have, as you can see from the photo­ graph, has the parity chip labelled as BP41C1000A-6. Now the “1000” code is commonly used to designate a 1Mb x 1-bit wide RAM chip. So the use of this code for the parity chip is clearly meant to deceive the purchaser. The less scrupulous resellers are supplying these SIMMs in place of the proper item. However, we have been assured by Pelham that they only stock the genuine 9-bit wide SIMMs. The basic lesson here is be careful if you come across cheap SIMMs. Chances are, they could be dodgy. And when you are buying a new system, it would be wise to specify SIMMs with SC genuine parity bits! LOTS OF OTHER ITEMS FROM COAXIAL CABLE, DECODERS, ANGLE METERS, IN-LINE COAX AMPS, PAY-TV DECODER FOR JAPANESE, NTSC TO PAL TRANSCODERS, E-PAL DECODERS, PLUS MANY MORE For a free catalogue, fill in & mail or fax this coupon. ✍     Please send me a free catalog on your satellite systems. Name:____________________________ Street:____________________________ Suburb:_________________________ P/code________Phone_____________ L&M Satellite Supplies 33-35 Wickham Rd, Moorabin 3189 Ph (03) 553 1763; Fax (03) 532 2957 December 1994  11 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au 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. Power supply for subsidiary amplifier .01 240VAC This circuit was produced for a reader who wanted to use an LM1875 25W amplifier module (published December 1993) together with the LM3876 50W module described in the March 1994 issue of SILICON CHIP. The two amplifier modules were to be part of an active speaker system and both amplifiers were required to run from the same power supply. The 50W module has supply rails of ±35V while the smaller module needs ±25V. Since the maximum current drawn by the 25W module can be expected to be about 850mA, it is only feasible to derive the ±25V rails from the ±35V supplies using adjustable 3-terminal regulators. Accordingly, the circuit uses an LM317T for the +25V rail and an LM337T for the -25V rail. Both will need to be mounted on substantial A F1 2A BR1 PW04 +35V 25V IN 240VAC 25V LM317T ADJ 2200 63VW N OUT +25V 120  100 25VW 10 16VW 2.2k 10 16VW 2.2k E 0V CASE 2200 63VW 100 35VW 120  ADJ IN LM337T -25V OUT -35V heatsinks as they will each need to dissipate around 8W or more at maximum power output. Both regulators must be isolated from the heatsinks using the standard mounting kits, with mica washer, insulating bush and heatsink compound. Silicon Chip staff +V IC1a 4093 1 A 10k 14 D1 1N914 3 10k 1 13 IC1b 14 11 12 2 3 +V BOURNES ROTARY ROTARY ENCODER FARNELL FARNELL 109-113 109-113 B 5 10k 6 IC1c 7 Rotary encoder decoder A rather neat alternative to using two pushbuttons for up/down or option selection in a design is to use a rotary encoder. A rotary encoder looks like a normal potentiometer but delivers two square waves spaced 90° apart, allowing speed and direction of rotation to be determined. 16  Silicon Chip D2 1N914 4 10k 5 D CK S IC2a 4013 4 1 8 IC1d 7 Q Q R 6 1 2 1 2 IC3a 3 COUNT UP 4 COUNT DOWN 4081 5 6 10 14 IC3b 7 9 One such device is made by Bourns and sold by Farnell Electronic Components as a “109-113”. This encoder gives 24 “clicks” per rotation, much like the detented pots found on some upmarket audio gear. The accompanying circuit uses three standard CMOS ICs to decode the waveforms and provide pulses to indicate either clockwise or anticlockwise rotation. The 4093 (IC1) buffers and de- bounces the waveforms from the encoder before passing them to a 4013 flipflop (IC2a). The Q and Q-bar outputs of the flipflop go high to indicate direction of rota­ tion which when, NANDed with either of the incoming signals, gives one positive-going pulse per “click” of the encoder in the appro­priate direction. G. Sheridan, Ashfield, NSW. ($25) Simple 1-chip logic probe +5V 19 LED1 10 This simple logic probe can detect low, high and floating logic levels, single short pulses and pulse trains. When the probe is connected to logic 0, the transistor (Q1) is off and there­fore LED 2 does not light. However, if the logic 0 is floating, a small current from IC1 will keep the transistor on slightly, causing LED 2 to glow dimly. LED 1 is only on when the monostable is triggered, which occurs with a logic 1 to 0 transition at the input. For a single pulse, there is only one transition and, thus, one flash from LED 1. A pulse train will continually retrigger the monostable and so the LED will keep flashing. Note that high frequency pulse trains cause LED 1 to glow brighter than low frequencies. 6V to 12V converter 14 POWER S1 F1 5A C1 11 INPUT IC1 74121  220   0V 220  1 4 7 LED2 Q1 BC548 68k The 68kΩ resistor may need slightly adjusting so that a floating logic 0 will cause LED 2 to glow dimly. C1 must also be large enough to produce a flash from LED 1 with each pulse. A. Chin, Heidelberg, Vic. ($20) 0.1  5W 180  6V ZD1 This circuit was origL1 15V BATTERY D1 6 7 8 inally produced for a 1W BY229 reader who wanted to 1 +13.8V run a 12V radio-cassette Q1 IC1 OUTPUT 1000 player in her 6V Volks­ BD679 MC34063A 16VW 0V 2 wagen. It is a modifica22k tion of the Portable 12V 4.7k 3 4 5 SLA Battery Charger .001 featured in the July 1992 The circuit is particularly issue of SILICON CHIP. suitable for use in VWs That circuit produced & other old cars with 6V 2.2k L1: 2 LAYERS OF 0.5MM ENCU ON a slight step-up of the electrical systems. NEOSID 17-742-22 TOROID voltage from a car’s cigarette lighter socket, sufficient to charge 12V batteries for back resistors set the output voltage up rather than laid flat. It could be camcor­ ders. The slightly modified to +13.8V. secured to the board with Nylon straps circuit presented here steps up 6V to The modification involves reducing or with epoxy adhesive. It may also be 13.8V with a maximum output current the current sensing resistor between necessary to fit a flag heatsink to Q1 of 1A, which should be adequate for pins 6 & 7 to 0.1Ω 5W and using a larger and perhaps also to diode D1. most run-of-the-mill radiocassette toroid for inductor L1. This should be Kits for this project are still available players. a Neosid sintered iron toroid wound from Jaycar Electronics (Cat KC-5119) The circuit is based on the Motorowith two layers of 0.5mm enamelled and they can also provide the larger la MC34063 DC-DC con­troller IC and copper wire. Neosid toroid specified on the circuit. switches Darlington transistor Q1 The modified circuit can be as- You can also purchase the PC board on and off at a frequency between sembled onto the PC board specified from RCS Radio Pty Ltd. Phone (02) 24kHz and 42kHz, as set by the originally (ie, code 14107291) but the 587 3491. .001µF capacitor connected to pin 3. larger induc­tor will need to be stood Silicon Chip staff The resulting current pulses through inductor L1 cause a step-up in voltage each time Q1 turns off and the Errata For LED Brake Light Array 1000µF capacitor is charged above Super Bright LED Brake Light Array, November 1994: we suggested a the supply voltage via fast recovery modification to this circuit whereby the flashing LED (LED 14) could be rediode D1, a BY229. placed by a standard LED to provide a non-flashing display. The designer, The voltage ultimately reached by E. Kochnieff, has pointed output that this will cause the circuit to destroy the the 1000µF capacitor is determined middle column of LEDs when power is applied. To avoid this problem, LED by the 22kΩ and 2.2kΩ feedback re14 should be replaced with a 470Ω 1W resistor, if you want a non-flashing sistors connected to pin 5 of IC1. In display. conjunction with a reference voltage source (1.25V) inside IC1, the feed- December 1994  17 SPE FEA CIAL PRO TURE JEC T DOLBY PRO-LOGIC SURROUND SOUND DECODER; PT.1 By JOHN CLARKE Now you can have the big sound of the movies in your living room with this Dolby* Pro Logic Surround Sound Decoder. This is the genuine article, approved & licensed by Dolby Labora­tories in California. In the October 1994 issue, we featured a preview article on Dolby Surround Sound and now, as promised, we present the Dolby Surround Sound Decoder. We believe that this is the world’s first do-it-yourself Dolby Surround Sound Decoder to be described in an electronics magazine. This has been made possible by a great deal of cooperation between SILICON CHIP 18  Silicon Chip and Jaycar Electronics. SILICON CHIP has produced the design while Jaycar have been responsible for the licensing of the design (necessary if kits are to be made available with Dolby decoder chips) and for a considerable amount of liaison with Dolby Laboratories. Our particular thanks to Bruce Routley of Jaycar Electronics for helping make it all happen. To keep costs as low as possible, this Surround Sound Decoder has no built-in amplifiers. It has four audio outputs, two to drive the front speakers in a conventional stereo setup, one to drive the centre-front channel and one to drive the rear speakers. Most readers will already have an existing stereo system so they will need another three power amplifiers and three loudspeakers. Alternatively, if you elect to use the “phantom mode” for the centre front channel (ie, centre channel simulated with the stereo speakers), you can get away with just an addi­tional stereo amplifier to drive the rear speakers. The Surround Sound Decoder is housed in a compact plastic case INPUTS LEFT + AUTOMATIC BALANCE IC1 SELECTOR IC1 RIGHT + DOLBY PROLOGIC ADAPTIVE MATRIX IC1 LEFT +10dB VOLUME CONTROL IC3 RIGHT CENTRE +10dB SURROUND NOISE SEQUENCER IC1 ANTIALIAS FILTER IC2 20ms DELAY IC2 7kHz LOW PASS FILTER IC1 MODIFIED DOLBY BTYPE NOISE REDUCTION UNIT IC1 Fig.1: this is the block diagram of the Surround Sound Decoder. Virtually all the circuit functions are provided by IC1 (a Dolby Pro Logic decoder chip) & by IC2 (a digital delay chip). measuring 255 x 80 x 180mm. On the front panel are the on/off switch, noise sequencer switch, channel selector, the centre and surround trim controls and the volume control. As well, there are 3-position switches for mode and centre channel selection. At the rear are the RCA sockets for the left and right inputs, and the left, right, centre and surround outputs. The noise sequencer is an aid in setting up the balance between the channels. When switched on, a noise signal is sent to the selected channel. By selecting each channel in turn, the centre and surround channel outputs can be adjusted to match the sound levels from the left and right channels. Balance between the left and right channels is set using the balance control on the stereo amplifier. The mode switch selects stereo, 3-stereo or surround sound. Stereo selection simply passes the stereo input signals through to the output without processing. The 3-stereo position adds in the centre channel, while the surround position processes the input signals to provide the centre and surround channels. The centre switch allows selection of Normal, Phantom and Wideband signal for the centre channel. The Normal setting is for loudspeakers which do not have bass response below 100Hz; it has a low frequency rolloff below about 100Hz. The bass signals from the centre channel are not lost though, since they are added equally to the left and right channels at a -3dB level so that the overall bass response is correct. As you might expect, Phantom gives a pseudo centre chan­ nel, with the centre signal being produced by the left and right loudspeakers. Finally, the Wideband setting is used if you have a full-range loudspeaker for the centre channel. Block diagram Fig.1 shows the block diagram for the Surround Sound Decoder. Virtually all the circuit functions are provided by IC1 and IC2. The left and right channel encoded signals are initially processed by the automatic balance circuit. This detects any difference between the left and right channel signal levels and adjusts the gain until the difference is nulled out. Precise balance between the left and right channels is important for obtaining the best separation between each of the four chan­nels. The selector block provides switching between the signal output from the automatic balance circuit and the noise sequenc­er. When the noise sequencer is selected, a white noise signal is passed through to the Left, Centre, Right or Surround outputs. The Dolby Pro Logic Adaptive Matrix is the heart of the decoder. This • • • • • • • • OUTPUTS LEFT Features Genuine Dolby Pro Logic surround sound decoding Meets all Dolby specifications Stereo, 3-stereo or surround selection Normal, wideband (full range) or phantom centre channel Noise sequencer to set up balance between channels Trim controls for centre and surround channels Master volume control for all channels Line outputs for each channel RIGHT CENTRE TRIM 0dB-+20dB CENTRE SURROUND TRIM 0dB-+20dB SURROUND was shown in detail on page 8 of the October 1994 issue. The surround signal output from the adaptive matrix is sent to an anti-aliasing filter (IC2) before being fed through the 20ms delay circuit. Following the delay, the surround signal is passed through a 7kHz low pass filter and then a modi­ fied Dolby B-type noise reduction circuit to suppress high fre­quency noise. The resulting surround sound signal now passes to the main volume control which handles all four channels simultaneously. The left and right outputs are then amplified by a factor of three (+10dB), while the centre and surround outputs are ampli­fied by a factor of zero to 10 times, depending on the setting of the trim controls. As can be seen from Fig.1, most of the functions of the decoder are provided in IC1, a Mitsubishi M69032P Dolby Pro Logic Surround Decoder. Its internal block diagram is shown in Fig.2. Apart from all its signal processing features, it provides a +4V DC reference at its pins 43 & 44 and this is used for biasing some of its other pins, as detailed later in this arti­cle. Fig.3 shows the internal diagram of the M65830P digital delay chip. It uses adaptive delta modulation (ADM) in its anal­og-to-digital converter and stores the signal in its 16K bit memory. After the preset delay, the digital signal is read out from the memory and converted back to an analog signal. The length of delay can be controlled via the REQ, SCK and DATA inputs at pins 4, 5 & 6 respectively. Depending on the signals on these pins, the delay can be set anywhere between 0.5ms and 32ms. However, to keep the circuit as simple as possi­ ble, we used the standard fixed delay of 20ms. Circuit description Now let’s have a look at the complete circuit which is shown in Fig.4. This December 1994  19 L R C S RECT RECT RECT RECT OUT OUT OUT OUT 3 2 1 56 LRECT 8 TC RRECT11 TC CRECT 5 TC SRECT 4 TC LBPF 6 OUT LBPF 7 IN RBPF 10 IN RBPF 9 OUT LPF 48 +IN LPF 47 -IN VCS VLR VCS VLR VCS VLR TC1 TC1 TC2 TC2 TC3 TC3 53 54 52 55 51 50 MODIFIED DOLBY-BTYPE NR DECODER CENTRE MODE CENTRE MODE CNT CNT 36 31 30 4x COMBINING NETWORKS 2x POLARITY SPLITTERS L+R L-R 1 S' OUT 39 29 2x DUAL TIME CONSTANT AND THRESHOLD SWITCHES 2x LOG DIFFERENCE AMPLIFIERS 4x FULL-WAVE RECTIFIERS NR NR NR NR IN TC WT VCF 42 49 45 41 OPERATION AND CENTRE MODE CONTROL 34 L+R OUT 33 38 8x VCA 37 43 1 40 46 LPF OUT AUTOBALANCE SERVO AUTOBALANCE VCA AUTOBALANCE VCA NOISE SEQUENCER NOISE SEQUENCER 13 14 AB AB GATE HOLD TC 15 16 L AB L AB IN OUT 22 21 R AB R AB IN OUT 26 27 28 NOISE NOISE NOISE REF HPF LPF 24 25 23 NOISE NOISE NOISE CNTA CNTB CNTE Fig.2: this block diagram shows the internal circuitry of the M69032P Pro Logic surround sound decoder IC. This complex chip processes the incoming audio inputs & determines which signals require subsequent directional enhancement. comprises five ICs, two regulators, five diodes, four reed relays and numerous capacitors and resistors. As noted above, IC1 and IC2 do most of the work. The left and right channel inputs are applied to pins 15 & 22 (AB in) of IC1 via 10µF capacitors and 10Ω resis­tors. A 22kΩ resistor at each pin biases the inputs to +4V, while the 10Ω resistors prevent high frequency instability. The auto-balance (AB) circuit adjusts the gain of its left and right channel voltage controlled amplifiers as discussed above. The auto-balance time constant is at pin 14 and consists LPF1 IN 23 LPF1 OUT 22 OP1 OUT 21 of a 10µF low leakage capacitor with a 10MΩ discharge resistor across it. This long time constant prevents the auto-balance circuit from modulating the audio signal. The outputs from the left and right buffers (pins 18 & 19) connect internally to the VCA circuitry and to bandpass filters (at pins 6 & 7 and pins 9 & 10 respectively) which roll off frequencies above 5kHz and below 200Hz. The signals are then applied to the full wave rectifier circuitry and the L+R and L-R networks. Output filter capacitors for the full wave rectifiers on each Left, Right, OP1 IN 20 CC1 18 OP2 IN 16 CC2 17 4.7k LPF1 1 4.7k LPF2 MODULATOR 13 LPF2 OUT DEMODULATOR OP1 OP2 REF19 24 VCC D1 DO0 DO1 MO MAIN CONTROL 0.5VCC RESET CLOCK MI DELC 1 VDD 16K BIT SRAM 11 12 AUTO RESET OSCILLATOR 2 XIN 20  Silicon Chip 3 XOUT DELAY TIME CONTROL 4 REQ 5 SCK 6 DATA 7 IDSW 8 IDFLAG 9 TEST1 10 TEST2 C OUT VCC VREF VREF IREF 19 R BUFF OUT 12 GND 18 20 L R IN BUFF OUT Centre and Surround channel connect to pins 3, 2, 1 and 56 respectively. The Rectifier Time Constant (RTC) capacitors within the log difference amplifiers for these chan­nels are at pins, 8, 11, 5 and 4. Finally, time constant capaci­tors which control the rate at which the sounds can move from one channel to another are at pins 50-55. The rate control time constants are important since they prevent the system from plac­ing sounds in the incorrect channel if subject to sudden tran­sients or loss of signal due to dropouts. The external noise sequencer components are at pins 26, 27 and 28. The noise is filtered with a bandpass filter so that the output signal is centred around 500Hz. S2a selects the noise when pin 23 is tied to ground. LED 2 OP2 LPF2 OUT IN 15 14 COMP 17 L IN 1 R OUT 32 L OUT 44 7kHz LPF S OUT 35 L-R OUT DGND AGND Fig.3: internal diagram of the M65830P digital delay chip. It uses adaptive delta modulation (ADM) in its anal­og-to-digital converter & stores the signal in a 16K bit memory. After the preset delay, the digital signal is read out from the memory and converted back to an analog signal. SPECIFICATIONS Dolby Requirement Performance of Prototype Freqeuncy Response -3dB <at> 50Hz & 15kHz L & R channels; -3dB <at> 50Hz & 6-8kHz S channel; -3dB <at> 50Hz & 15kHz wideband C channel; -3dB <at> 90-140Hz & 15kHz wideband C channel -3dB <at> 14Hz & 40kHz; -3dB <at> 17Hz & 7.2kHz; -3dB <at> 16Hz & 40kHz with C trim centred; -3dB <at> 110Hz & 40kHz with C trim centred Signal to Noise Ratio (wrt reference & 100mV at C output) 65dB CCIR/ARM, C & R channels; 65dB CCIR/ARM S channel 700dB unweighted Distortion <1% <at> 300mV in & 1kHz .05% R, L & C outputs; 0.15% S output Headroom 15dB above reference R, C, L & S channels 17dB S output; 17.5dB R, C & L outputs Input Sensitivity <350mV RMS 300mV RMS Crosstalk 25dB minimum between channels L-R 44dB; C-L or C-R 30dB; S-L, R or C 37dB Volume Tracking within 3dB over top 40dB range between R, C, L & S outputs <0.2dB to -70dB; <1dB to -80dB S Channel Delay 20ms fixed or 15-30ms adjustable 20ms fixed Auto Balance Between L & R Inputs 27dB L-R rejection ±4dB error for 27dB L-R rejection Noise Sequencer 10-15dB below reference -12dB Output Clipping 2V RMS 2V RMS Gain Trim ±10dB for C & S outputs ±10dB for C & S outputs Note: reference level is 300mV & 1kHz <at> C out (pin 30 of IC1) Most of the parts for the Surround Sound Decoder are installed on a single PC board, so the construction is relatively straightforward. Full constructional details will be provided in next month’s issue. December 1994  21 22  Silicon Chip +4V 15k 0.1 0.1 .0047 47k R BPF IN R BPF OUT 1 C RECT O/P FILTER 2 R RECT O/P FILTER 3 L RECT O/P FILTER 26 27 NOISE REF NOISE HPF 37 IC1 M69032P R BUFFER OUT R BUFFER IN R AB OUT R AB IN 14 AB HOLD TC 10 9 19 20 21 L BPF IN L BPF OUT L BUFFER OUT L BUFFER IN L AB OUT L AB IN 0.1 56 S RECT O/P FILTER 0.1 0.1 0.1 10 10M 10 LL 680pF 47k 7.5k +4V 7 10  22 680pF 22k 10 +4V 15k 0.1 6 18 17 16 10  15 7.5k +4V 22k 10 0.1 100k RIGHT INPUT LEFT INPUT 44 43 S' OUT 39 8.2k NR 49 TC 330k .047 NR 45 WT 15k 15k 10 10 10 10 0.68 .0022 NR 41 .0056 VCF LPF 46 OUT 42 NR IN LPF 47 -IN 470pF LPF 48 +IN +4V +4V 29 22k 33 22k 38 22k CENTRE 30 CONTROL 220 VREF VREF S OUT R OUT C OUT 22k L OUT 32 100 1 15k 15k 15k .0056 7.5k 14 LPF IN2 LPF OUT2 470pF 5.6k 18k 100pF X1 2MHz X OUT 22 7 LPF OUT1 23 LPF IN1 3 9 0.1 OP OUT1 10 11 12 LK1 19 47 18 0.1 17 0.1 100 6 LK3 5 LK2 4 1 24 +5V 10 8.2k 8.2k 8.2k .068 21 30  OP 20 IN1 REF CC1 CC2 DATA SCK REQ VDD VCC 1k GND IC2 M65830P 22K 16 17 VCA OUT 39k VC1 VC2 VREF 9 10 8 3 2 15 VCA VCA OUT IN 39k .068 16 OP IN2 15 OP OUT2 2 X IN 1M 470pF 18k 13 VOLUME VR1 5K LIN 2.7k 13 12 4 VCA VCA OUT IN IC3 TDA1074A VP 11 39k 10 6 7 14 VCA VCA OUT IN 100pF .0033 .0056 1 39k DECOUPLE 18 1 100 +12V 5 VCA IN +12V 10 10 8.2k 10 IC4c 180pF 15k IC4b 4 14 1 5 6 IC4d 11 180pF 7 SURROUND TRIM VR3 4.7k 50k LOG 12 13 3 2 180pF 4.7k 8 CENTRE TRIM VR2 50k LOG IC4a 10 TLO74 9 180pF 15k 47k 10 47k 10 47k 10 0.1 47k 10 RLY4 RLY3 RLY2 +12V 100k 100 100k 100  100k 100  100k RLY1 100  SURROUND OUT RIGHT OUTPUT CENTRE OUTPUT LEFT OUTPUT Q1 BC338 RLY4 B K A 3 I GO 10k 7 IC5a 5 LM358 4 K  NOISE LED2 A NOISE TEST S2a ON OFF +4V 40 12 100k IREF NOISE TEST E VLRTC 4.7 54 VCSTC 4.7 53 VLRTC 0.22 55 GND 23 31 MODE VCSTC 0.22 52 VCSTC 51 0.22 470  +5V 1 2 3 1 MODE S5 2 0.18 CENTRE 36 MODE VLRTC 50 0.22 S2b +4V ON OFF 1.8k CASE E CENTRE S4 3 10 S RTC 4 .022 C RTC 5 DOLBY PRO LOGIC SURROUND SOUND DECODER S3: 1: LEFT 2: CENTRE 3: RIGHT 4: SURROUND S4: 1: NORMAL 2: PHANTOM 3: WIDEBAND S5: 1: STEREO 2: 3-STEREO 3: SURROUND 47 25VW D4 1N4148 D3 1N4004 100 +15V 100k 1M 10k S’ output 10k 6 8 GND 22 25VW 1000 25VW 0.47 N 1 25 NOISE TEST B .022 .047 11 R RTC NOISE TEST A 8 L RTC .047 E C VIEWED FROM BELOW 22 IC5b 2 0.1 10 OUT 7812 IN REG1 D2 12V 1N4004 0V 240VAC 2 3 S3b 4 1 2 +4V A 1 10k D5 1N4004 82  100  +12V 0.1 10 GND 22 25VW 12V S1 F1 250mA E B POWER LED1 470  A K  C RLY3 RLY1 RLY2 +5V OUT 7805 REG2 IN 47  1W 47  1W D1 1N4004 T1 POWER .001 250VAC 3 4 CHANNEL SELECT 24 S3a 28 NOISE LPF 22 indicates when the noise sequenc­er is on and it is fed via S2b and a 470Ω resistor from the +5V supply rail. Channel selection for the noise source is made with switches S3a & S3b via the A and B noise test inputs at pins 24 and 25. Switch S5 is the mode selector. Note that S5 is a centre-off switch and that its position 3 connects the pin 31 mode input to +4V. Switch S4, the centre channel selector switch, is also a centre-off switch and at its positions 1 & 3, the bass response is varied by the 10µF and 0.18µF capacitors which are bypassed to earth via the 220µF filter capacitor for the +4V reference at pins 43 & 44. The output at pin 39 is labelled S’ to differentiate it from the S surround signal after the delay. The S’ output is fed to an 8.5kHz low pass anti-alias filter formed by the op amp at pins 22 & 23 of IC2 (the digital delay) and the associated resistors and capacitors. IC2 is clocked by a 2MHz crystal and this precisely sets the delay period. The two 0.1µF capacitors at pins 17 & 18 are for the delta modulation circuit in the analog-to-digital and the digital-to-analog conversion. The 30Ω resistor and the .068µF capacitor between pins 20 & 21 determine the response rate of the op amp used for delta modulation. The demodulated delayed signal is at the output of the op amp at pin 15. The .068µF capacitor between pins 15 & 16 sets the low frequency rolloff for this op amp in the demodulation pro­cess. Finally, the op amp between pins 13 and 14 is connected using the associated resistors and capacitors to form a second order 7kHz low-pass filter. Its output at pin 13 is connected to a similar 7kHz filter involving the op amp at pins 46 & 47 of IC1. So we Fig.4 (left): despite the complicated processing that takes places, the final circuit uses just five ICs. IC1 & IC2 form the heart of the circuit, while IC3 is a quad voltage controlled amplifier (VCA) which controls the signal level fed to op amp output stages IC4aIC4d. IC5a & IC5b control relays RLY1-RLY4 which mute the outputs at switch on & switch off. December 1994  23 PARTS LIST 1 PC board, code 02311941, 204 x 151mm 1 Dynamark front panel, 230 x 62mm 1 Dynamark rear panel, 106 x 50mm 1 HB-5930 Jaybox, 250 x 170 x 75mm 1 12-0-12V 15VA toroidal mains transformer (T1) 1 illuminated mains rocker switch (S1) 2 SPDT centre off switches (S4,S5) 1 DPDT toggle switch (S2) 1 2 pole 6-position rotary switch (S3) 1 2MHz crystal (X1) 1 5kΩ linear pot (VR1) 2 50kΩ log pots (VR2,VR3) 1 6-way RCA socket panel 1 3-core mains lead with moulded 3-pin plug 1 500mm length of single shielded audio cable 1 500mm length of twin shielded audio cable 1 250mm length of dual shielded audio cable 1 500mm length of 7.5A brown mains rated wire 1 250mm length of 7.5A green/ yellow mains wire 1 500mm length of red hookup wire 1 500mm length of green hookup wire 1 250mm length of yellow hookup wire 1 500mm length of 3-way rainbow cable 1 200mm length of 0.8mm tinned copper wire 1 2-way mains terminal block 1 TO-220 heatsink, 30 x 25 x 13mm 3 16mm black anodised knobs 1 22mm black anodised knob 4 5V reed relays, Jaycar Cat. SY4036 (RLY1-RLY4) 1 M205 panel mount fuse holder (F1) 1 250mA M205 fuse 6 3mm screws, nuts & star washers 1 3mm countersunk screw, nut & star washer 3 solder lugs 6 self-tapping screws for securing PC board to case 2 3mm LED bezels 10 100mm long cable ties 1 mains cord grip grommet now have a 4-pole 7kHz filter which removes any signal above 7kHz in the surround channel signal that passes to the Dolby B-type noise reduction unit within IC1. From there, the signal is internally connected to the operation and combining network circuit block. The four output channels from this combining network appear at pins 32, 38, 33 & 29, representing the left, centre, right and surround signals. Each output is AC-coupled using 10µF capacitors to pins 5, 14, 4 & 15 of IC3, a TDA1074A quad voltage controlled amplifier. It can provide a 110dB control range with 80dB separation and excellent tracking between channels. VR1, the main volume control, adjusts the voltage on pins 9 & 10 to set the gain. Pins 7, 12, 2 & 17 of IC3 are the outputs for the left, centre, right and surround channels respectively and these are AC-coupled via 10µF capacitors to quad op amp IC4. IC4a and IC4c provide a nominal 10dB of gain for the left and right chan­nels, as set 24  Silicon Chip Semiconductors 1 M69032P Mitsubishi Dolby Pro Logic decoder (IC1) 1 M65830P Mitsubishi digital delay (IC2) 1 TDA 1074A quad voltage controlled amplifier (IC3) 1 TL074 quad op amp (IC4) 1 LM358 dual op amp (IC5) 1 7812 12V 3-terminal regulator (REG1) 1 7805 5V 3-terminal regulator (REG2) 1 BC338 NPN transistor (Q1) 4 1N4004 1A 400V rectifier diodes, (D1,D2,D3,D5) 1 1N4148, 1N914 diode (D4) 2 3mm green LEDs (LED1,LED2) Capacitors 1 1000µF 25VW PC electrolytic 1 220µF 16VW PC electrolytic 4 100µF 16VW PC electrolytic 1 47µF 25VW PC electrolytic 1 47µF 16VW PC electrolytic 2 22µF 25VW PC electrolytic 2 22µF 16VW PC electrolytic 19 10µF 16VW PC electrolytic 1 10µF 16VW RBLL electrolytic 2 4.7µF 16VW PC electrolytic 2 1µF 16VW PC electrolytic 1 0.68µF MKT polyester 1 0.47µF MKT polyester 4 0.22µF MKT polyester 1 0.18µF MKT polyester 14 0.1µF MKT polyester 2 .068µF MKT polyester 3 .047µF MKT polyester 2 .022µF MKT polyester 3 .0056µF MKT polyester 1 .0047µF MKT polyester 1 .0033µF MKT polyester 1 .0022µF MKT polyester 1 .001µF 250VAC metallised paper (Wima MP3-Y or equivalent) 2 680pF ceramic 3 470pF ceramic 4 180pF ceramic 2 100pF ceramic Resistors (0.25W 1%) 1 10MΩ 1 5.6kΩ 2 1MΩ 2 4.7kΩ 1 330kΩ 1 2.7kΩ 7 100kΩ 1 1.8kΩ 6 47kΩ 1 1kΩ 4 39kΩ 2 470Ω 7 22kΩ 5 100Ω 2 18kΩ 1 82Ω 9 15kΩ 2 47Ω 1W 4 10kΩ 1 30Ω 5 8.2kΩ 2 10Ω 3 7.5kΩ Miscellaneous Heatshrink tubing, solder by the 8.2kΩ input resistors and the 15kΩ feedback resistors. The 180pF capacitor across each feedback resistor provides a high frequency rolloff at about 40kHz. The amplifiers for the centre and surround signals (IC4b & IC4d) have a variable gain of between 0dB and 20dB, as set by VR2 and VR3. Reed relays RLY1-RLY4 feed the signals to the output sockets. The reed relays are included to prevent large switch-on and switch-off thumps. At switch-on, comparator IC5a and its associated components delay the relay actuation closure until all the capacitors in the circuit have charged to their resting DC voltage. At power off, the relays open immediately to disconnect the outputs and prevent any DC shifts from being coupled into the following power ampli­fiers. IC5a is connected as an inverting Schmitt trigger and it monitors the voltage across the 100µF capacitor at pin 6. At switch-on, the 100µF capacitor begins to charge via the 100kΩ resistor from the +15V rail. Initially, the output of IC5a is high and pin 5, the non-inverting input, is held at about +9V. After about 10 seconds, pin 6 reaches the 9V threshold, causing pin 7 to switch low. The pin 5 input is now pulled to about +3V via the 10kΩ feedback resistor. This 6V of hysteresis gives a sharp Schmitt trigger action and prevents the output from dithering when the 100µF capacitor gets close to the +9V threshold. IC5b acts as an inverter for IC5a so that when IC5a’s output at pin 7 goes low, IC5b’s output goes high and turns on Q1. The reed relays now switch on. Note that each relay coil is rated at 5V *Trademarks & Program Requirements Note 1: “Dolby”, “Pro Logic” and the Double-D symbol are trade­marks of Dolby Laboratories Licensing Corporation, San Francisco, CA 941034813 USA. Note 2: this Surround Sound Decoder requires a stereo program source such as a stereo television or hifi stereo VCR. For sur­round sound, the program must be Dolby Surround encoded as indi­cated in the movie credits by the Dolby Double-D symbol. For unencoded stereo signals, the Dolby 3-stereo selection will provide the centre front channel. The decoder will not operate from a mono signal. and draws 10mA, so we have connect­­ ed two pairs of coils in series across a 10V supply. This is derived from a +15V rail via 100Ω and 82Ω dropping resistors. The 15V rail is provided by D3 and a 47µF capacitor. When power is switched off, the 47µF capacitor supplying the relays quickly discharges. This also discharges the 100µF capacitor at pin 6 of IC5a via diode D4 and the 1.8kΩ resistor. This causes IC5b to switch low and turn off Q1. As a consequence, the reed switches are de-energised and any switch-off transients are avoided. Power for the circuit is derived from a 12-0-12V toroidal transformer (T1) which is connected in a full wave centre tapped configuration to charge a 1000µF capacitor to about 15V via diodes D1 and D2. The resulting DC voltage is regulated to +12V by 3-terminal regulator REG1. This supplies power to IC1, IC3 and IC4. IC2’s supply comes from REG2, a 5V regulator fed via two 47Ω resistors from the main 15V supply. That completes the circuit description of the Surround Sound Decoder. In Pt.2 next month, we will describe the construction and testing proceSC dure. AC/DC digital clamp meter with 4000 count display and bargraph! ● High speed auto-or manual ranging ● High speed sampling for 40 segment bargraph display ● Average, Temperature test, Max hold, Peak hold functions ● Sleep mode to reduce battery con- sumption ● Continuity beeper, Data hold, Diode test and analog signal output ● Battery or AC adaptor operation Brief Specifications Functions : AC/DC current, AC/DC voltage, Ohms, Continuity, Diode test, Frequency, Temp, Data/ Peak/Max hold, Average., Analog signal output Display : LCD 3.5 digits, 4000 (Hz: 9999) count Bar Graph Display : 40 segments Ranges : Auto or manual ranging Aac, Adc : 400, 1000A Vac, Vdc : 40, 400, 650V Frequency : 10.0-999.9Hz Temperature : -50.0 to +150°C Jaw Opening : 55 mm ø or 65 x 18mm busbar Withstand Voltage: 2.5kVac, 1 minute Lloyd’s Register Quality Assurance to ISO-9001 2343 – one of the NEW Generation of Multimeters from Centrecourt D3, 25-27 Paul Street North, North Ryde Call Robyn for more information on (02) 805 0699 or fax : (02) 888 1844 December 1994  25 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 Clifford – a pesky little electronic cricket Meet Clifford – our new little pesky insect friend. A cousin of Horace the Cricket, he has a lot to say – provided it’s dark. He’s easy to look after & doesn’t eat very much – one 9V battery does him for around a month! By DARREN YATES Once upon a time in an old project box, there lived a cricket. Many of you will have seen this cricket before. It was Horace! He was famous a few years ago (SILICON CHIP, August 1990) when he first appeared but now he was looking rather tired and dirty. He hadn’t had a feed of his favourite 9V batteries for a very long time. One day, a young inquisitive and sentimental designer tried to see if he could bring ol’ Horace “back to life”. Having spent five minutes rummaging around for a 9V battery, the designer slipped it into place. Nothing happened. The designer looked and looked but there was no sign of life and so tossed him back in the box – so much for sentiment! But as Horace landed on his head, he let out a bleat. The designer had forgotten that like all well brought-up crickets, he only speaks when spoken to – literally! So after a confusing conversation over the next few minutes, with both of them talking at the same time, Horace told the designer of his little cousin, Clifford. Now Clifford was a different type of cricket, much smaller but just as potentially annoying. Having lived in this dark corner of the store room for some time, he wasn’t short of a word. He basically said that Horace had it all wrong! Crickets aren’t supposed to talk when you make a noise – they’re only supposed to talk when it’s dark. And so Horace was given the boot and the designer took Clifford upstairs and gave him pride of place on the workbench. He sat him on the bench with a nice fresh 9V battery and turned out the lights. One second ... two seconds ... nothing. But a couple of seconds later, the office echoed with the cacophony of cricket chorales. This little bloke really makes a racket. The designer turned the lights on and almost instantly Clifford was as quiet as a church cricket. The designer tried this for the next two days by which time the rest of the office staff were looking for a suitable piece of rope and a rickety chair. The designer knew he was onto a winner and was so happy with his new charge that he took him home and they lived happily ever after. The circuit diagram Clifford is based around a single CMOS 4069 hex inverter IC, a handful December 1994  29 47k 470k 100 16VW A 4069 IC1a IC1b 2 3 4 11 K A D1 D1 1N914 1N914 13 IC1c 12 10k 2.2 25VW 10k 11 IC1d 10 7 100k  LED2 Q1 BC548 10k B 1k IC1e 14 .047 6 5  LED1 LED1 LDR1  100 16VW D2 1N914 1k K 8 4.7k Q2 BC558 B E C 100K 100k PIEZO BUZZER 3.3k C E 9 IC1f B1 9V B A K E C E B C VIEWED FROM BELOW CLIFFORD - HORACE'S COUSIN Fig.1: Clifford starts chirping when the light level falls & the resistance of LDR1 rises. When that happens, pin 4 of IC1b snaps high & this enables the two main oscillators based on IC1c & IC1d and on IC1e & IC1f. Transistor Q1 flashes Clifford’s eyes (LED1 & LED2), while Q2 drives the piezo buzzer to produce the chirping sound. of resistors, a few other components and that’s about it. So that he can fit into the smallest of spaces for maximum annoyance, he is built onto a tiny circuit board measur­ing only 40 x 35mm. Looking at his internals in Fig.1, his light sensor is a light-dependent resistor or LDR. When light falls on an LDR, its resistance falls and when it’s dark, its resistance increases. This LDR is connected to the input of IC1a which along with IC1b forms a Schmitt trigger. The 470kΩ feedback resistor between pins 1 & 4 provides the necessary positive feedback for this to work. The Schmitt trigger has two functions. First, it ensures that when Clifford speaks, he starts and stops instantly rather than slowly building up. However, we don’t want Clifford to start talking as soon as the lights go out and we don’t want him to stop instantly either (Oh, yes we do! Editor). So, we’ve added a 100µF capacitor to the input of IC1a. This slows the rise and fall of the input as the LDR changes its resistance to give this delay. Secondly, the Schmitt trigger controls the two main oscil­lators which produce the chirping sound. IC1c/d and IC1e/f form two square-wave oscillators and these are enabled or disabled by diodes D1 and D2, respectively. With the output of IC1b 30  Silicon Chip PARTS LIST 1 PC board, code 08112941, 41 x 36mm 1 9V battery snap connector 1 9V battery 1 piezo buzzer Semiconductors 1 4069 CMOS hex inverter (IC1) 1 BC548 NPN transistor (Q1) 1 BC558 PNP transistor (Q2) 2 5mm green LEDs (LED1,2) 2 1N914 signal diodes (D1, D2) 1 light dependent resistor (LDR1) Capacitors 2 100µF 16VW electrolytic 1 2.2µF 25VW electrolytic 1 .047µF MKT polyester Resistors (0.25W, 1%) 1 470kΩ 1 4.7kΩ 2 100kΩ 1 3.3kΩ 1 47kΩ 2 1kΩ 3 10kΩ Miscellaneous 1 x 100mm length of light-duty figure-8 cable (to connect buzzer), solder, PC stakes to terminate external wiring connections to batt­ery & buzzer (optional). normally low (that is in the presence of light), diodes D1 and D2 are forward biased and so hold the inputs to IC1d and IC1f at 0.6V. This prevents either oscillator from starting up. Because pin 9 of IC1f is held low, the output at pin 8 is high, which ensures that the following PNP transistor Q2 (which we’ll get to shortly) is turned off. Similarly, because pin 11 is held low by D1, pins 10 & 13 are high and pin 12 is low. This ensures that Clifford’s “eyes” or LEDs 1 and 2, which are con­trolled by NPN transistor Q1, remain off. When the light level drops, the LDR’s resistance increases to the point where the upper threshold of the Schmitt trigger is surpassed and the output of IC1b snaps high. Diodes D1 and D2 are now reversed biased and the two oscillators are allowed to run free. IC1e and IC1f oscillate at a frequency of about 160Hz with the output driving output transistor Q2. This BC558 transistor drives a low-current piezo buzzer. Now since this buzzer produces a 2kHz tone of its own, the job of this circuit is to simply modulate it to make it sound more like a cricket. The oscillator based on IC1c and IC1d has two jobs. First­ly, it drives Clifford’s green eyes, flashing them on and off at a frequency of around 25Hz. Secondly, the output is mixed togeth­ er with the output of IC1f. The result is that the output of IC1f is frequen- cy-modulated by the signal from Q1 to produce the “shrill” in Clifford’s chirp. Feeding requirements Clifford lives off a 9V battery but he certainly doesn’t waste his food. While sitting quietly, he consumes around 1mA which rises to 8mA when he’s talking. However, the good thing is that Clifford will operate from a battery voltage of just 4.5V, so you can wring every last bit of power out of the battery. If you have an old 9V battery from your multimeter, it should work for quite a while to keep Clifford happy. The 100µF capacitor provides the circuit with a reservoir which lowers the supply’s impedance when the battery is going flat. Construction Clifford is created on a small PC board, measuring 40 x 35mm and coded 08112941. To help keep his size down, all of the resistors and diodes are mounted end-on and close together so you’ll need to have a fine-tipped soldering iron to do the job. Before you begin any soldering, check the board thoroughly for any shorts or breaks in the copper tracks. These should be repaired with a small artwork knife or a touch of the soldering iron where appropriate. Once you’re happy that everything appears to be OK, you can begin construction by installing the IC – see Fig.2. This is the lowest-profile component and is more easily installed first. After that, continue by installing the resistors, diodes, transistors, LEDs and capacitors. The resistors are installed vertically with the leads bent over at right angles, as shown in the photo. When installing the diodes, make sure that you follow the over- Fig.2: install the parts on the board as shown here, taking care to ensure that all polarised parts are correctly oriented. Check each resistor on your multimeter before installing it on the board & note that the resistors are all mounted end-on to save space. Fig.3 at right shows the full-size PC pattern. lay wiring diagram and insert them correctly. The LEDs are also installed with their legs bent at right angles and then gently twisted away from each other to give that cute insect look. When you have completed this, check each com­ponent against the wiring diagram (Fig.2) to ensure that it is correctly positioned. In particular, check that all polarised parts are correctly oriented and be careful not to confuse the two transistors. Q1 is a BC548 NPN type while Q2 is a BC558 PNP type, so don’t get them mixed up. The LDR is a non-polarised device and may be installed either way around. Once you are satisfied that everything is correct, connect the piezo buzzer via a 100mm length of figure-8 cable and install the 9V battery snap connector. PC stakes can be used at the external wiring points on the PC board if you wish but these are entirely optional. His first meal Now install the 9V battery in series with your multimeter and set the DMM to a low milliampere range. The current consump­tion should be slightly over 1mA. Now cover the LDR with your finger to block out all light. The current should start to rise slowly and, after a few seconds, Clifford should burst into life. The current consumption should initially be around 9mA and should drop down to around 8mA. If the LEDs don’t light up, check the connection to the base of Q1 and check that the LEDs are correctly installed. If the piezo buzzer doesn’t sound, check that you have its polarity correct. The negative pin should go to ground. Uses Clifford is best used for maximum effect in a well lit area but somewhere inconspicuous. The area of my workbench was pretty good – there’s lots of junk on it which made it hard for anybody to find anything. While the light level is high enough, he won’t make a noise. When the light goes out, there should be enough of a delay to convince someone that there is a real cricket some­where in the room. When the light goes back on, he should also turn off fast enough to make it difficult for the person to locate the offending source. If you’re looking to really drive people batty, remove the two 5mm LEDs so that they can’t see him in the SC dark at all! RESISTOR COLOUR CODES ❏ No. Value 4-Band Code (1%) 5-Band Code (1%) ❏ 1 470kΩ yellow violet yellow brown yellow violet black orange brown ❏ 2 100kΩ brown black yellow brown brown black black orange brown ❏ 1 47kΩ yellow violet orange brown yellow violet black red brown ❏ 3 10kΩ brown black orange brown brown black black red brown ❏ 1 4.7kΩ yellow violet red brown yellow violet black brown brown ❏ 1 3.3kΩ orange orange red brown orange orange black brown brown ❏ 2 1kΩ brown black red brown brown black black brown brown December 1994  31 An easy-to-build car burglar alarm Don’t fork out big dollars for a car burglar alarm. This unit can be built for far less than the cost of a commercial alarm & can be mated to an optional remote control unit. Design by BERNIE GILCHRIST Most car alarms are complicated to build or only offer a limited range of features but not this unit. It’s based on the Philips OM1681C car alarm IC and has a range of features that rival many commercial units. Those features are all listed in the accompanying panel and include presettable entry and exit delay periods, delayed and immediate trigger inputs, voltage drop sensing, a flashing status LED, automatic resetting after 60 seconds, battery backup and the ability to 32  Silicon Chip automatically operate a central door locking system. The alarm itself consists of two main parts: (1) a control unit that mounts somewhere out of sight (normally under the dashboard); and (2) a horn siren module with internal (nicad) battery backup that mounts under the bonnet. These two items are connected together via a 3-pin plug and socket, while the control unit is connected to the battery, the various sensors, the status LED and to other items (eg, the central locking circuitry) via an additional 12-pin plug and socket assembly. In operation, the alarm can be armed/disarmed either manu­ally via a hidden toggle switch and/or via an optional UHF remote control unit (to be described in a forthcoming issue). If the remote control unit is used, then the toggle switch can be delet­ed and the exit and entry delay periods set to zero. Alternatively, you can retain the toggle switch as a backup to disarm the unit if the remote control fails. Note, however, that this toggle switch will normally need to be kept in the ARM position. The UHF remote control will be unable to arm the alarm if the toggle switch is in the DISARM position. The alarm is armed by either setting the toggle switch to ARM or by pressing the button on the optional remote control transmitter until a “chirp” is heard from the horn siren. When this occurs, the status LED lights and remains on continuously for the period of the exit delay, after which it flashes on and off once every second to indicate that the alarm is armed. During the exit delay period (ie, while the LED is continu­ously lit), the alarm cannot be triggered. This gives you time to manually arm the system and leave the car without setting off the alarm. Alternatively, if the exit delay set to zero (ie, the optional UHF remote control is being used), then the status LED will begin flashing immediately. The unit is disabled by either setting the toggle switch to DISARM or by pressing the button on the UHF remote control trans­mitter until the status LED switches off. Note that the siren does not “chirp” when the alarm is disarmed, the status LED being the only indicator in this case. Once it has been disarmed, the alarm sounds only if the battery leads are cut or the leads to the siren module are cut (provided the backup battery is switched on). Triggering After it has been armed, the alarm can be triggered in three different ways: • First, it can be triggered if the battery voltage drops suddenly; eg, if the brake lights are activated or a dome light comes on (when a door is opened). When this happens, the status LED switches off for a period equal to the entry delay and then the alarm sounds. The purpose of the entry delay is to allow you time to gain access to the hidden toggle switch to disable the alarm before the siren goes off. Of course, if the UHF remote control is used instead, the entry delay can be set to zero. If the siren does go off, the alarm will automatically reset after 60 seconds, after which it is ready to be triggered again. The status LED will now flash at a rate of four flashes per second to indicate that an alarm has occurred; • Secondly, the alarm will trigger if a sensor connected to the immediate (or instant) sense input causes that input to change state (ie, switch from high to low or low to high). For example, if a • • • • • • • • • • • • Main Features Uses Philips new OM1681C car alarm processor IC Supplied with pre-built horn siren containing backup battery Flashing deterrent LED which indicates armed, disarmed and memory states Compatible with an optional UHF dual channel remote control kit (DSE Cat. K-3260) Siren is triggered if car battery or horn siren wires are cut Alarm automatically resets to armed state after 60 seconds Output available to operate central door locks or to flash the hazard lights to indicate arming & disarming (for use with UHF remote control option only) Adjustable entry and exit delays Reverse polarity protection Immediate and delayed sensor inputs (one each) for use with external switches (eg, door switches & auxiliary pin switches) Voltage drop sensing to detect unwanted operation of lights, etc. Relay output to beep horn or flash hazard lamps when alarm triggers (optional) sensor switch is open when the alarm is armed and then subsequently closes, the alarm will trigger. Conversely, the alarm will also trigger if the switch is closed when the alarm is armed and subsequently opens. The sensors connected to the immediate input can be either normally open (NO) or normally closed (NC) but they must all be of the one type. You cannot have a mixture of both. These sensors would normally be spring-loaded (pin) switches that are used to protect the bonnet and boot. Note that the entry and exit delays do not apply to any sensors connected to the immediate input. Instead, the siren sounds immediately when the alarm is triggered. As before, the alarm automatically resets after 60 seconds and the status LED flashes at four times per second to indicate that the alarm has been triggered; • Finally, the alarm will trigger if one of the sensors connected to the delayed sense input closes and pulls that input low. These sensors must all be normally open and must pull the input low to trigger it. Typically, the door switches would be used here, provided that they are in the earth circuit of the vehicle. The normal entry and exit delays apply to this input and again the circuit automatically resets after 60 seconds with the LED flashing at four times per second to indicate that the unit has triggered. Backup battery The horn siren module contains a rechargeable 7.2V nicad backup battery which ensures that the siren continues to sound even if the main battery leads or the leads to the siren are cut. In this situation, the siren will continue to sound until the backup battery goes flat, since it can no longer be reset by the control unit. Because power is applied to the siren circuit at all times, the backup battery is normally kept fully recharged via an inter­nal regulator circuit. It should provide about two hours of useful output if either the siren leads or the main battery leads are cut. The backup battery can be switched on or off during in­stallation by means of the keyswitch at the rear of the siren module. If the backup battery is switched off, the siren will still function normally if the alarm is triggered, provided that the car’s battery is not disconnected or the leads to the siren are not cut. Flashing lights/beeping horns By installing a single link on the PC board, the alarm can also be made to flash to the car’s headlights or beep the car’s horn when triggered – this in December 1994  33 34  Silicon Chip C10 0.1 D6 1N4148 R22 4.7M R21 1.5M R20 10k 100k C4 10 R5 33k C2 1 R9 R8 100k C1 1 C3 0.1 VR1 2k R4 33k D1 1N4148 R2 470k R3 1M IC1c +12V R24 4.7M R23 1M D7 1N4148 C11 0.47 2 1 R27 2.2k R26 680  ENTRY DELAY VR2 50k D8 1N4004 R10 10k R18 10k MIC IN 3 C6 0.1 1 2 E RL2 C Q4 BC328 E B D9 1N4148 C12 0.1 7 6 R31 D10 1M 1N4148 CAR BURGLAR ALARM R29 1.5M R28 4.7M R30 4.7M R32 100k D12 1N4004 1 B R15 2.2k R33 680  R34 2.2k E R14 10k C13 10 RL3 Q5 BC328 C E D11 RL1 R17 15  C7 10 1N4004 RL1 D5 1N4004 Q3 BC549 C B 12 C14 0.47 IC3b D2 1N4004 Q1 BC557 R16 470  C E Q2 BC549 C B  3 4 D3 1N4148 STEADY 18 GND R13 16 270k FLASH 1 IC2 OM1681C HAZARD LIGHTS ARE REQUIRED WHEN ALARM TRIGGERS C8 0.1 R19 10k EXIT 5 IMMED 6 DELAY 15 14 ENTRY R11 10k B 330  R12 ONLY INSERT LINK 3-4 IF A BEEPING CAR HORN OR FLASHING C9 0.1 EXIT DELAY VR3 50k 13 DISARM STATUS 17 9 ARM 7 DOOR LOCK/INTERFACE CIRCUIT R25 100k 14 12 IC1b ZD1 6.8V 1N4736 3 3 IC1a LM339 14 4 5 6 7 IC3a 9 LM339 8 VOLTAGE DROP SENSOR 8 9 R1 10k R7 1M R6 1M C5 10 +7.3V +12V RL3 RL2 1N4004 D4 0V RESET +12V 3 11 7 8 12 4 9 1 2 6 10 E C E C B A C B A B VIEWED FROM BELOW B DOORS UNLOCK DOORS COMM DOORS LOCK 0V IMMEDIATE DELAYED ARM/DISARM LED RELAY NC RELAY COMM RELAY NO 12-PIN NYLON PLUG 5 +12V TO SIREN MODULE 3-PIN NYLON PLUG 15 14 +12V 13 C addition to sounding the siren. This function is provided by a floating relay output; ie, the relay contacts are not connected to anything inside the alarm. When the alarm is triggered, the relay contacts open and close at a rate of about once every second. This internal relay is not capable of switching more than 2A and so should be used to switch external heavy duty relays if currents higher than this are involved; eg, it could be used to switch the hazard lights relay to flash the hazard lights or the horn relay to “beep” the horn. If this feature is not re­quired, then the internal relay can be disabled by leaving out the link between pads 3 and 4 on the main alarm PC board. Note that there is no backup battery for this feature. If the supply leads to the alarm are cut (or the battery is discon­nected), then the hazard lights (or the horn) will cease operat­ ing. Only the siren module will continue operating, as this is the only item that does have battery backup. operating central door locking systems can vary from car to car. Some have solenoid-operated locks which only require a short pulse to operate them (as described above), while some have motor-operated locks which may require a much longer pulse (eg, up to 10 seconds) to fully operate. It’s quite easy to increase the output pulse period if required, simply by changing a few component values (see in­stallation procedure). In addition, some door locking systems must be connected to a +12V control signal to operate them, while others must be con­nected to ground (0V). It’s simply a matter of connecting the common output from the locking circuit to +12V or to ground, as required. The door locking circuitry is all contained on a separate (optional) interface PC board that sits inside the same case as the main alarm board. If you don’t want (or need) the central door locking option, just leave the interface board out. Central locking How it works In addition to its alarm functions, the control unit also provides a 3-wire output for automatically operating central door locking systems. These three connections are designated common, lock and unlock. The central locking facility is intended for use only if you have central locking on your car and only if you also use the optional UHF remote control. It works as follows: When the alarm is armed, a relay in the control unit con­nects the lock output to common for about two seconds to operate the door locking solenoids. Similarly, when the alarm is dis­armed, a second relay connects the unlock output to common for about two seconds to operate the unlocking solenoids. Note, however, that the method of Refer now to Fig.1 – this shows the full circuit details of the alarm control unit, including the optional door locking interface circuitry. As already indicated, the circuit is designed around the versatile Philips OM1681C alarm control and timing circuit (IC2). The power supply for this IC and for most of the rest of the circuit on the main board is derived from the car’s battery via reverse polarity protection diode D4. In addition, IC2 has an internal shunt regulator which, in conjunction with current limiting resistor R12, sets the supply voltage to this IC and to IC1 to 7.3V. Capacitor C7 provides filtering for the +12V rail from D4, while C5 provides filtering for the +7.3V rail. IC2 (OM1681C) can be armed/disarmed using one of two meth­ods. The one which is not used here is to apply a short pulse to the TOGGLE input (pin 8). This input responds to the falling edge of the applied pulse, each pulse causing the chip to alternately arm and disarm. The second method is to control the chip via its separate ARM (pin 9) and DISARM (pin 7) inputs. Unlike the TOGGLE input, these inputs are level triggered, with ARM responding to a low level and DISARM to high level. Because they respond to Fig.1 (left): the circuit is based on the Philips OM1681C alarm control IC. It is armed when pin 9 is pulled low via IC1a, while VR2 & VR3 set the entry & exit delays. Comparator stage IC1c & its associated parts form the voltage drop sensor, while IC3a, IC3b, Q4 & Q5 & their associated relays make up the door lock interface circuit. PARTS LIST Main alarm 1 horn siren module with backup battery 1 PC board, code DSE ZA-1286 1 miniature 12V DPDT relay (RLY1) 1 12-pin nylon plug & socket 1 3-pin nylon plug & socket 5 3-metre lengths of mediumduty hookup wire (red, white, black, blue & yellow) 1 2kΩ trimpot (VR1) 2 50kΩ trimpots (VR2,VR3) 1 plastic zippy case, 41 x 68 x 130mm 1 plastic cable tie 2 car alarm stickers 2 bonnet/boot switches Semiconductors 1 LM339 quad comparator (IC1) 1 OM1681C alarm control & timing IC (IC2) 1 BC557 PNP transistor (Q1) 2 BC549 NPN transistors (Q2,Q3) 2 1N4148 signal diodes (D1,D3) 3 1N4004 silicon diodes (D2,D4,D5) 1 1N4736 6.8V 1W zener diode (ZD1) Capacitors 2 1µF 50VW electrolytic (C1,C2) 4 0.1µF (100nF) MKT polyester (C3,C6,C8,C9) 3 10µF 16VW electrolytic (C4,C5,C7) Resistors (0.25W, 1%) 6 10kΩ – R1,R10,R11,R14, R18,R19 1 470kΩ – R2 3 1MΩ – R3,R6,R7 2 33kΩ – R4,R5 2 100kΩ – R8,R9 1 330Ω – R12 1 270kΩ – R13 1 2.2kΩ – R15 1 470Ω – R16 1 15Ω – R17 comple­mentary levels, they can be tied together, as in this circuit, to provide a single arm/disarm input. To arm the circuit, the ARM/DISARM input (pin 9 of the 12-pin plug) must be pulled low, either via a toggle switch or the optional remote control. December 1994  35 D12 LOCK 7 RL2 D8 R8 R9 R5 C2 C5 C1 R23 D6 R21 R22 R24 D7 IC3 LM339 10 NO 2 NC 14 DC OUTPUT 12 IMMEDIATE 4 DELAYED 9 ARMDISARM 8 0V IN C8 3 1 Q3 Q2 1 C6 R14 R17 D4 C9 ZD1 RELAY OUT D2 Q1 D3 R13 R15 VR2 VR3 R11 D5 R16 R4 4 2 R12 VR1 C10 RL1 C7 IC2 OM1681C IC1 LM339 C12 R19 1 R1 R2 R10 R18 C4 +12V IN 13 +12V OUT A  +12V OU T B  DOORS DOORS B R3 R6 C11 6 COMM Q5 RL3 C3 D1 R7 R25 1 1 STATUS LED (a) D11 +12V A 15 0V 0UT C 0V OUT C13 Q4 UNLOCK 3 0V C R34 R33 R26 R27 R20 R32 C14 R30 D10 R31 D9 R29 R28 COMM 11  PLACE A 10k RESISTOR BETWEEN "A" AND "B" IF THE DOOR L OCK I NTERF ACE I S NOT USED Fig.2: install the parts on the two PC boards exactly as shown here & don’t forget to bridge pads 3 & 4 (immediately above IC2) if you want to use RLY1 to flash the hazard lights or beep the horn when the alarm triggers. When this happens, the resulting 0V signal is fed via filter components R2 & C3 to pin 7 of compara­tor IC1a and to pin 4 of comparator IC1b. Diode D1 provides transient and reverse voltage protection for these two comparator inputs. As a result, pin 1 of IC1a goes low and pulls the ARM input (pin 9) of IC2 low, thereby forcing IC2 into its armed state. At the same time, the output of IC1b goes high and this does two things. First, it briefly pulls pin 8 of IC3a in the door locking interface circuit high via C10 to generate the door locking pulse (more on this later). Second, it briefly turns transistor Q2 on via C6 & R13. This, in turn, briefly turns Q3 off which releases the RESET line to the siren module. The siren now briefly “chirps” to indicate that the circuit is armed. Note that Q3 is normally biased on and clamps the RESET line low to keep the siren off. The status LED is driven by transistor Q1 via R16 and diode D5. Q1 and the LED are turned on when the STATUS output (pin 17) of IC2 goes low when the circuit is armed. Initially, the STATUS output remains low until the end of the exit delay 36  Silicon Chip period. It then briefly switches low once every second to flash the status LED on and off. Note that the STATUS output of IC2 is capable of sinking up to 100mA but Q1 was used so that the return path for the LED could be 0V rather than +12V. Trimpots VR1 and VR2 set the entry and exit delays for the delayed sense input by applying preset voltages to pins 14 & 15 of IC2 respectively. These inputs, in turn, feed internal analog-to-digital converters which process the input voltage level to give one of eight delay values ranging from 0 to 28 seconds. The delay and immediate sensors connect to pins 4 & 12 respectively of the 12-pin plug. These sensors trigger the DELAY & IMMED inputs (pins 5 & 6) of IC2 via transient filter networks R18 & C8 and R19 & C9. The state of each of these inputs is stored by IC2 at the moment of arming, so that the alarm can be triggered by either a low to high or high to low transition. Comparator stage IC1c and its associated parts form the voltage drop detector. Its function is to detect the small nega­tive-going transitions that occur on the +12V supply when any lamps (eg, interior or brake lamps) switch on. Let’s take a closer look at how this works. As shown on Fig.1, both inputs of IC1c are biased from the +7.3V regulated supply rail and VR1 is adjusted so that the vol­tage on pin 9 is normally 100mV higher than the voltage on pin 8. As a result, pin 14 of IC1c will be high and this high is fed to pin 6 (the DELAY input) of IC2. When a negative-going transient occurs on the +12V supply (eg, if a lamp turns on), it is filtered by R1, C1 and C2, to remove very slow transients, and coupled to pin 9 of IC1c (via C2). As a result, any transient that is greater than 100mV causes pin 9 to go more negative than pin 8 and so pin 14 of IC1c brief­ly switches low and triggers the delayed sense input (pin 6) of IC2. Note that because the output from the voltage drop sensor (IC1c) is normally high, the other sensors used on the delay input at pin 4 of the plug must not normally pull this input low. If they do, the voltage drop sensor will be disabled. Alarm outputs The two outputs from the OM1681C that are used here are FLASH (pin 1) and STEADY (pin 18). These are both open collector outputs (active low) As an alternative to operating the central locking circuit, the optional door lock interface board could be used to briefly flash the hazard lights each time the alarm is armed or disarmed. If you elect to use the latter option, reduce C11 to 0.22µF so that the arming flash is shorter than the disarming flash. The main alarm board can be used on its own with the siren module to form a complete working alarm with battery backup. The two trimpots at bottom right set the entry & exit delay periods. capable of sinking 100mA. The FLASH output causes relay RLY1 to switch on and off at a 1-second rate when the alarm is triggered and this can then be used to trigger other relays to beep the car’s horn or to flash the hazard lights. The STEADY output, on the other hand, provides a constant low signal when the alarm is triggered. This low turns off tran­sistor Q3 which thus releases the RESET line and so the siren sounds. An internal timing circuit inside IC2 now takes over and, after 60 seconds, IC2 resets and its FLASH & STEADY outputs effectively go open circuit. RLY1 thus remains off, while Q3 turns on again and resets the siren module. IC2 is now ready for the next trigger input. Note that both outputs from IC2 are connected via links to allow them to be disconnected or rearranged if required. The normal configuration is to have pads 1 & 2 connected to use the external siren module. Pads 3 & 4 are only connected if other external devices are to be pulse driven (eg, the hazard lights or the horn). The alarm circuit is disarmed by opening the switch (or relay contacts if the remote control is used) on pin 9 of the plug. When this happens, pin 7 of IC1a is pulled high by R3 and so pin 1 switches high and IC2 switches to the disarmed state. At the same time, pin 2 of IC1b switches low and applies a brief low-going signal to pin 7 of IC3b via C12 to generate the door unlocking pulse. Door lock interface circuit The central door locking interface circuit consists of two monostables, one positive edge triggered and the other negative edge triggered. The positive edge triggered section is based Twist all related leads together in groups of three to keep them tidy before making the final connections to the boards & to the plug. A piece of cardboard is used to separate the two boards inside the case. December 1994  37 MAIN ALARM PCB 1 14 12 4 9 8 5 TO 12-PIN PLUG RED RED RED BLA WHI BLU YEL BLU WHI 10 2 6 1 12 4 9 8 WHI BLU WIRES 30cm LONG YEL 13 A B C 15 BLA 6 YEL 2 BLA 10 WIRES 10cm LONG 5 7 11 3 WIRES 34cm LONG TO 3-PIN PLUG 14 13 15 WIRES 2m LONG DOOR LOCK INTERFACE PCB B C A 3 11 7 Fig.3: run the wiring to the PC boards & to the two plugs as shown on this diagram. If you don’t need the optional door lock interface PC board, just leave it out & connect a 10kΩ resistor between A & B on the main alarm board. on comparator IC3a and provides the locking pulse, while the nega­tive edge triggered section uses IC3b to provide the unlocking pulse. The way in which these two circuit sections work is quite straightforward. Let’s look at the locking circuit first. Normally, the voltage on pin 9 of IC3a is greater than the voltage on pin 8 and so the output at pin 14 is high. This means that transistor Q4 and RLY2 will be off. However, when the cir­cuit is armed, a brief positive-going pulse is applied to pin 8 of comparator IC3a via C10 as described previously. This momen­tarily pulls pin 8 above pin 9 and so pin 14 switches low and Q4 turns on. This in turn drives RLY2 which closes to generate the locking signal. At the same time, pin 9 of IC3a is 38  Silicon Chip also pulled low via feedback timing components R25 & C11. C11 now charges via R23 until the voltage on pin 9 exceeds the voltage on pin 8. When this happens, pin 14 switches high again and Q4 and RLY2 turn off to end the lock signal. D7 is included to ensure that pin 9 can not be pulled below -0.6V when pin 14 of IC3a goes low. Comparator stage IC3b, on the other hand, ignores the high-going signal from IC1b when the circuit is armed. That’s because a brief positive-going pulse is coupled to its pin 7 input via C12 and this input is already higher than pin 6. However, when the circuit is disarmed, the low-going pulse applied to pin 7 causes pin 1 to switch low and this turns on Q5 and RLY3 to generate the unlocking pulse. YEL BLA RED BLU WHI YEL Note that in this case, the RC timing network (R32 & C14) is connected to the collector of Q5 instead of to the output of the op amp. This is done to ensure that pin 6 is initially pulled high when pin 1 of IC3b switches low. The duration of the lock pulse is thus determined by R25 & C11, while R32 & C14 set the duration of the unlock pulse. These pulse widths can be altered if required (eg, for motor operated locking mechanisms) by increasing the capacitor values. Construction The assembly is straightforward since all the parts mount on two small PC boards. Fig.2 shows the parts layout on the two PC boards (main board at bottom, optional door lock interface board at top). Begin the assembly by installing all the wire links on the alarm PC board (code ZA-1286), then install Arming/Disarming Options As it stands, the circuit is designed to briefly “chirp” the siren when it is armed and this is particularly handy if you are using a remote control. There is no “chirp” from the siren when the circuit is disarmed, however. Instead, you have to confirm that the status LED has stopped flashing and this can only be done by inspection. A better way to confirm arming or disarming is to briefly flash the hazard lamps, as is done by many commercial circuits. This can easily be done by using the relays on the door lock interface PC board. As it stands, this circuit activates RLY2 for two seconds when it is armed and RLY3 for two seconds when it is disarmed. Thus, by connecting the NO contacts of these two relays in parallel across the hazard lights switch, the hazard lamps will briefly flash whenever the circuit is armed or disarmed. Note, however, that the relay contacts can no longer be connected to operate the door locking solenoids if you do this (otherwise the door locking solenoids will operate repeatedly if you have occasion to activate the hazard lights). If you do intend using the board to flash the hazard lights, reduce C11 from 0.47µF to 0.22µF. The circuit will now flash the hazard lights for one second when it is armed and flash them for two seconds when it is disarmed, thus making it easier to differen­tiate between the two states. 13 14 15 3-PIN PLUG ALLOCATIONS 3-PIN NYLON PLUG VIEWED FROM BACK 13 +12V TO SIREN MODULE 14 SIREN TRIGGER (0V = OFF) 15 0V TO SIREN MODULE PARTS LIST Door Lock Interface 1 PC board, code DSE ZA-1287 2 miniature 12V DPDT relays (RLY2,RLY3) Semiconductors 1 LM339 quad comparator (IC3) 2 BC328 PNP transistors (Q4,Q5) 4 1N4148 signal diodes (D6,D7,D9,D10) 3 1N4004 silicon diodes (D8,D11,D12) Capacitors 1 10µF 16VW electrolytic (C13) 2 .01µF (10nF) MKT polyester (C10,C12) 2 0.47µF (470nF) monolithic (C11,C14) Resistors (0.25W, 1%) 1 10kΩ - R20 2 1MΩ - R23,R31 2 100kΩ - R25,R32 2 2.2kΩ - R27,R34 2 1.5MΩ (5%) - R21,R29 4 4.7MΩ (5%) - R22,R24,R28, R30 2 680Ω - R26,R33 12-PIN PLUG ALLOCATIONS 1 2 3 4 5 6 7 8 9 10 11 12 12-PIN NYLON PLUG VIEWED FROM BACK 1 TO ANODE OF STATUS LED 2 ALARM RELAY OUTPUT (NC) 3 CENTRAL DOOR LOCK (UNLOCK) 4 DELAYED ALARM SENSING (0V SENSING) 5 +12V INPUT 6 ALARM RELAY OUTPUT (COMMON) 7 CENTRAL DOOR LOCK (LOCK) 8 0V INPUT 9 ARM (0V)/DISARM (OPEN) 10 ALARM RELAY OUTPUT (NO) 11 CENTRAL DOOR LOCK (COMMON) 12 IMMEDIATE ALARM SENSING (0V OR 12V SENSING) Fig.4: this diagram shows the pin allocations for the 3-pin & 12 pin plugs (as viewed from the back, or wiring side, of each plug). the resistors and capacitors. It’s a good idea to check each resistor value on your multimeter before installing it on the board, as some of the colours can be difficult to decipher. Take care to ensure that the electrolytic capacitors are correctly oriented. Normally, pads 1 & 2 on the PC board should be linked to­gether so that the external siren can be used. Pads 3 & 4 should only be linked if you wish to use RLY1 to drive other external devices (eg, the horn or hazard light relays) when the alarm triggers. The transistors, diodes and IC can be mounted next, again taking care to ensure that these parts are correctly oriented. In particular, take care with the ICs; they must be oriented so that their notched ends exactly match the wiring diagram (the label on each IC does not indicate orientation). Be careful when pushing the transistors into the board as the hole spacing is greater than the lead spacing and the tran­sistors may be damaged if pushed down too far – just push them down onto the board as far as they will comfortably go before soldering their leads. Finally, the board can be completed by installing the three trimpots (VR1, VR2 & VR3) and the relay. Note that VR1 is a 2kΩ vertical mounting pot while VR2 & VR3 are 50kΩ horizontal types, so there should be no confusion here. If exit and entry delays are not required (ie, if the optional UHF remote control is used), VR2 and VR3 should be set fully clockwise (0V) to get no delay. VR1 is used to set the sensitivity of the voltage drop sensor and can be set to its mid-point for the time being. The door lock interface PC board can now be assembled in similar fashion. As before, make sure that all polarised parts are correctly oriented and note that Q4 and Q5 face in opposite directions. Important: if this board is not being used, a 10kΩ pullup resistor must be connected between external wiring points A and B on the main board. Wiring Fig.3 shows how the two boards are wired together, while Fig.4 shows the connections to the 12-pin and 3-pin plugs. Cut the various coloured leads to the lengths indicated and twist them December 1994  39 SIREN MODULE FUSE BLOCK KEY 12V BATTERY DOME LIGHT DOME LIGHT FUSE TRIGGER 14 13 15 +12V 5 0V 8 STATUS LED 1 ARMDISARM 9 DELAY SENSE ALARM CONTROL UNIT ANODE STATUS LED 4 IMMEDIATE SENSE 12 RELAY NO 10 RELAY NC 2 RELAY COMM. 6 DOORS LOCK 7 DOORS UNLOCK DOORS COMM. DOOR PIN SWITCHES 3 13 12-PIN NYLON PLUG AND SOCKET DUAL CHANNEL UHF REMOTE CONTROL K-3260 ARMDISARM SWITCH AUX PIN SWITCHES ARM DISARM 9-PIN NYLON PLUG AND SOCKET SHORT WIRE ANTENNA +12V 4 0V 6 CH1 RELAY NO 2 CH1 RELAY NC 1 CH1 RELAY COMM. 3 CH2 RELAY NO 8 CH2 RELAY NC 7 CH2 RELAY COMM. 9 UHF REMOTE ARMDISARM OPTION COMMON TO HORN OR HAZARD LIGHTS SWITCH 40  Silicon Chip TO CENTRAL DOOR LOCK IF THE CAR HORN OR HAZARD LIGHTS OPTION IS USED THEN LINK PADS 3 AND 4 ON THE MAIN ALARM PCB 5 Fig.5: use this wiring diagram as a general guide when installing the alarm but note that the details may have to be varied to suit your particular car (see text). The ARM/DISARM switch can be deleted if the UHF remote control is used. together in groups of three, keep­ing related leads together, before making the final connections to the boards and the plugs. Note that Fig.4 shows the two plugs as viewed from the back. Each lead is terminated by first soldering it to a special pin which is then pushed into its appropriate location from the back. Each pin is spring-loaded and snaps into position when pushed home inside the plug body. Make sure that you install each pin in its correct location, as they are impossible to get out again if you make a mistake. The two PC boards are designed to fit into a small plastic zippy case and are separated by a 125 x 33mm piece of stiff card­board which slides LOCK UNLOCK between the middle end slots – see photo. A notch will have to be filed in one end of the case to provide an exit point for the wiring loom, while a plastic cable tie can be used as a restraining clamp. Installation Building the alarm is the easy part; by far the most time-consuming part of the job will be installing it (neatly) in a car. Fig.5 shows the recommended wiring details, including the wiring to the optional UHF remote control & the beeping horn (or hazard flasher) option. Note, however, that this diagram is a guide only and some of the details may have to be varied to suit your car’s wiring. For example, in most cars the door switches connect to earth but a few have their switches in the positive supply line. Unfor­tunately, the latter cannot be used on the DELAY input so check carefully first and be prepared to install additional door switches if necessary. A wiring diagram of your car’s electrical system will be an absolute must when it comes to installing this alarm. This will be necessary for tracking down the wiring to the horn and hazard light switches, checking whether the door switches go to the +12V supply or to earth, and locating the control wiring for the central locking. Make sure that you install the alarm in a professional manner so that it doesn’t interfere with any of the car’s existing functions. The general procedure is as follows: (1). Choose a secure location under the bonnet for the siren module where it is not likely to get damaged by flying stones or covered in mud. The keyswitch on the back of the unit should be accessible so that the unit can be disabled if the battery needs to be removed for servicing. (2). Mount the control unit in a secure location (eg, under the dashboard) and mount the status LED on the dashboard so that it can be readily seen from outside the car. The ARM/ DISARM switch (if used) should be mounted in a suitable hidden location (no; not inside the glovebox) but should still be readily accessible. (3). Connect suitable lengths of medium-duty hookup wire to the 12pin female socket, then run each lead to its correct destina­tion. The 0V (ie, the negative supply) lead should be connected as close as possible to the negative terminal of the battery, while the +12V lead should be connected to either the fuse block, the dome light +12V lead, or to some other point that is fed from the fuse block and still has +12V on it when the ignition is switched off. If you elect to use the beeping horn option, it should be simply a matter of connecting the NO relay contacts (pins 10 & 6) across the horn switch. Alternatively, connect these contacts across the hazard light switch if you want the hazard lights to flash when the alarm triggers. Note that you can either have the beeping horn or flashing hazard light but not both. Do not connect these switches in parallel, otherwise the hazard lights will flash each time you blow the horn in normal use and vice versa. Note that the status LED must be connected with the correct polarity for it to work. Its cathode can be connected via a short lead to some convenient earth point. (4). Connect the leads from the DELAY (pin 4) and IMMEDIATE (pin 12) inputs to the various sensors. Remember that the sensors connected to the DELAY input must all be normally open and must pull the input low to trigger it. Either normally open (NO) or normally closed (NC) switches can be connected to the IMMEDIATE input but, as previously men­ tioned, you can only use one type; ie, they must either be all NO or all NC. If normally closed switches are used, they must The horn siren module comes with an internal nicad backup battery & this may be turned on or off using a key-operated switch. In normal use, the backup battery is kept fully charged by the car battery via an internal regular circuit. be wired in series (NO switches are wired in parallel). (5). Connect the siren module (via the 3-pin plug) & connect the lock, unlock and common outputs (pins 7, 3 & 11) to the central locking system. As described, the circuit should be suitable for solenoid-operated systems (2-second pulse width). If the pulse width needs to be increased, for example, to 10 seconds for motor driven door locks, replace C11 and C14 (0.47µF) with 2.2µF bipolar capacitors. If you want a shorter pulse, use values that are less than 0.47µF. Test & adjustment Once the installation is complete, the unit can be tested for correct operation and the entry and exit delays set. VR2 sets the entry delay, while VR3 sets the exit delay. For both trim­ pots, the fully clockwise position is zero delay and fully anti­clockwise is a 28-second delay. Only the following delay periods can be obtained: 0, 4, 8, 12, 16, 20, 24 & 28 seconds. Finally, VR1 can be adjusted to set the sensitivity of the voltage drop sensor. The best way to do this is to initially set the trimpot fully anticlockwise (least sensitive), arm the alarm, and then try to trigger it by switching on the dome light or brake lights. Note that this sensor connects to the DELAY input of IC2, so the alarm will not sound until the end of the delay period. Note also that all other sensors connected to the DELAY input must be opened for the voltage drop sensor to work, so do not open a car door during this procedure. If the alarm fails to trigger, rotate VR1 slightly clock­wise and try again. Repeat this procedure until the alarm trig­gers reliably but don’t make the setting too sensitive otherwise you SC may get false triggering. Where to buy a kit of parts This alarm circuit was designed by Dick Smith Electronics and kits are available from all DSE stores or by mail order from PO Box 321, North Ryde, NSW 2113. Phone (02) 888 2105. Prices are as follows: Main Alarm Circuit (complete kit with case, PC board, siren module with backup battery, two boot/bonnet switches and alarm stickers, but not including door lock inter­face components); Cat. K4312 .................................. $89.95 Door Lock Interface Circuit (optional), Cat. K4314 .......................... $16.95 Please add $7.00 for packaging & postage if kit K4312 ordered, or $8.00 if both K4312 and K4314 are ordered. Note: copyright of the two PC board artworks associated with this project is retained by Dick Smith Electronics. December 1994  41 COMPUTER BITS BY DARREN YATES The Electronics Workbench revisited: new version has optional modules A couple of years ago, we reviewed the first version of this PC-based circuit simulation software. Now with the release of Version 3, we take another look & see what improvements have been made. You only need to have had a quick look at a first year tech course to know that even the most basic electronic circuits need a whole range of mathematical equations to characterise their operation. The idea of circuit analysis or “modelling” is not a new one and was probably thought of as soon as computers came on the scene. But as circuits increase in complexity, so do the number and size of the equations. As the PC (and the Macintosh) increases in computing power, the availability of maths/simulation packages has increased enormously. However, because of the complexity of the pro­gramming required, the cost of these packages has kept them firmly in university and design laboratories. The Electronics Workbench attempts to bridge this gap with a reasonably priced package which enables users to create, simu­late and analyse analog and digital circuits. The package As you would expect, there are no wires, signal generators or breadboards to be found in the Electronics Workbench package – just a 300-odd page manual and the floppy discs. Most common analog circuits can be handled by the Electronics Workbench. This LC oscillator circuit has the oscilloscope tool attached to it to show a reasonably accurate waveform. 42  Silicon Chip Installation is fairly straightforward but make sure that you read all of the loose sheets that come with the package before you install it. The reason for this is that Interactive Image Technologies Ltd, the makers of the Electronics Workbench, has used some frustrat­ing techniques to ensure that you don’t copy the discs. In fact, you can’t even make backup copies of them. Bad sectors have been introduced into the floppy discs to ensure that any copies made will not work. They’ve also made it quite clear that you can only use these discs to have one copy of the soft­ware in a machine at a time. Now while we in no way support software pirating, this system is not only cumbersome and frus­trating, it also can leave legitimate users in real difficulties. If for some reason you need to remove the Electronics Workbench from your PC, you must insert the first This 3-stage amplifier is fed using the function generator which can produce signals from a Hz to MHz. The CRO looks at both the input & output signals & these are colour-coded to make them easy to distinguish on-screen. EWB also has the ability to create “repeatable errors” by allowing any one or a number of components to be either open or short-circuit. Students can then try to diagnose the fault using standard fault-finding techniques. floppy disc and run the “Uninstall” program. If you simply erase or move the program without running this Uninstall program from the floppy, these discs are programmed to not allow installation again and are effectively useless. Interactive Image Technologies is not the only company to persist with this form of copy protection. A number of other well-known software packages, including the accounting package “Attache5”, also include this style of once-only no-backup in­ stallation. It’s worth noting that most of the larg­er software manufacturers, such as Micro­ soft, abandoned this some time ago. During the installation, you are asked whether you wish to use ANSI or DIN component symbols. In the circuit diagrams for SILICON CHIP, we use the ANSI standard which are clearly much easier to understand if a little harder to draw. The European DIN standard replaces zigzag resistor symbols with blocks, the familiar logic symbols with blocks, and the triangular op amp symbols with blocks; in fact, anything which isn’t a circle becomes a block in the DIN standard ... well, almost. Descriptions can be added to each circuit, which is helpful when producing “faulty” circuits. Normally, the faulty component is hidden by a password to prevent easy discovery by the student. • • • a Microsoft-compatible mouse; EGA or VGA display; and DOS 3.0 or later. After using the package, we further recommend that you have a 386 with a co-processor to help speed up calculations, particu­larly during analog circuit simulation. A VGA display is also recommended for visual clarity. If your hard drive is running DoubleSpace or Stacker, then you’ll need to have around 7Mb of space available. What can it do? The Electronics Workbench is designed to simulate and analyse both analog and digital circuits. Creating Requirements As with most software these days, your computer needs to have at least the following: • a 286 processor; • a hard disc drive with at least 4Mb free; • 1Mb RAM; The Electronics Workbench comes with a comprehensive 300-page manual. A range of optional modules is also available. the circuits is quite easy. You have a “parts bin” from which you can pull an unlimited number of components and you connect between them by clicking and dragging lines with the mouse. The selection of components has been expanded and now includes JFETs and MOSFETs. One of the drawbacks of version 1 was its inability to combine both analog and digital components together in the one circuit, which is very common these days. This makes it diffi­cult, if not impossible, to analyse most of the circuits pub­lished in SILICON CHIP and many “real world” circuits. Unfor­ tunately, this latest version still has the same problem. We would really like to see it able to handle digital and analog components together. Still, at a price of only $495 for the DOS, Windows and Apple Mac versions, it certainly wasn’t meant to be equivalent to circuit analysis packages which cost thousands of dollars. What it does do is allow students of electronics to get a feel for how components fit together to form recognisable circuits, as well as being able to perform some reasonably simple analysis of the results. There have been some media claims that it can be used to replace the workbench and allow students to work straight from the PC or Mac instead. This is simply nonsense as it could never be used to replace “hands-on” practical circuit design. Problems such as earth-loops or thermal runaway in audio amplifiers cannot be simulated December 1994  43 The digital section of EWB allows you to mix any of the normal logic functions into a circuit. These functions are available from the toolbox on the right hand column & are selected by dragging them across to the work area. using a computer. However, as a means of introducing students to electronic circuits, particularly the simpler cir­ cuits such as RC networks, rectifiers and filters, single stage amplifiers and the like, it is very effective and probably a good deal more efficient than using breadboards and actual components. When combined with practical laboratory work, the Electronics Workbench would become a powerful teaching tool. This is especially so in the digital side of things where it includes a “word generator” to produce streams of 16 8-bit words which can be fed to circuits one bit at a time, in bursts or cycled through continuously. It also includes an 8-channel logic analyser and again, the efficiency of teaching logic prin­ciples on a simulator would be difficult to overestimate. Manual On the other hand, it could be made somewhat easier to use. If anything, at 300 pages, the manual could have been a little more comprehensive. Some things, such as how to hook up the in­struments correctly, are not clearly explained and you have to look at the examples to see how it’s done. There are quite a few examples supplied with the software which will give you food for thought and you can modify them as you wish and save them for later use. As one of the options, you can obtain a set of models which contain the parameters for over 300 active components. These include BC548 44  Silicon Chip The Word generator allows you to feed specific digital signals to a circuit to observe the results, which can be seen on the Logic Analyser. This circuit is a simple 7-segment decoder. and BC558 transistors, op amps such as the 741 and LM324, and audio amplifiers such as the LM1875 which we featured in our 25W amplifier module in the December 1993 issue of SILICON CHIP. This package is an extra $89. Fault Finding Probably the best feature as far as students are concerned is EWB’s ability to give them experience in fault-finding. Once a circuit has been loaded, the teacher can select any number of components to be faulty –either short or open circuit. This fault is noted by the software and can be held under password protection. The students can then try to find out what the fault is and where it has occurred by observing the circuit’s behaviour on the instruments provided. Fault finding is one of those areas that you can’t teach all that well unless you have a specific, “re­peat­able” fault which all students can try to find. Fault finding is really only taught by experience but the Electronics Workbench goes quite a way to giving students a head start. This feature alone makes it a worthwhile addition to the electronics teaching laboratory. Another optional package is called the Troubleshooting Circuit Set and contains a number of circuits with predefined faults for analysis. This package retails for $49.95. Other extras Other optional extras include a package called “Practical Teaching Ideas” which was written by a Canadian lecturer and designed for teachers as an aid to implementing EWB as part of a basic electronics course. Included with the disc/manual set are example assignments and exam papers which could be used as the basis for a course. For those who don’t want to spend time laying out circuits, a 150-circuit package is also available. This contains 150 common circuits laid out with the appropriate instruments for immediate use with the software. This is well thought out and well worth the price of $49.95. Since it is most suited for teaching applications, network versions of EWB catering for small (10 users) and large (25 users) labs are also available. Conclusion Overall, the Electronics Workbench is suitable as a teacher or lecturer’s aid, enabling students to have a good introduction to the practical use of components and how they join together as circuits. While it shouldn’t be suggested as a replacement for the breadboard, it will give students a controlled introduction into the sometimes difficult world of circuit design. At $495, it is quite reasonable value for money and, if purchased, we can recommend the optional add-on packages listed above. For further information on Electronics Workbench and its optional packages, contact Emona Instruments, PO Box 15, Camperdown, NSW 2050. SC Phone (02) 519 3933. 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. 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Please have your credit card details ready ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail coupon to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia December 1994  53 Many of us have had a dream of building up a small general purpose board with a CPU, a bit of memory & some I/O lines. Then we could write programs to handle small applications. One easy way to do it would be to use the Stamp, a complete selfcontained microcontroller board the size of a large postage stamp. A look at the Stamp microcontroller board By BOB NICOL If you take the conventional approach to designing a micro­controller board, you have quite a few steps to go through. But once you had the basic design produced, it would make applica­tions a lot easier. Ideas could be tried out swiftly and easily, without the need to get parts together, before a start could be made. Such a device could be used on many projects and should a project fail, the board would not be wasted but used again with­out major changes. Once one starts building such a board, one will be up for paraphernalia to do the job efficiently – an assembler, an in-circuit emulator, and the need to put your own PC board together. And in the middle of all this, one is probably struggling to learn a new programming language. Now you will be exposed to the write, burn, try, debug, erase, edit, reburn, etc merrygo-round. And that time consuming procedure will occur for each new appli­cation of your board. With all the above to cope with, it is little wonder that few people turn the dream into reality – there is too much work involved. So here is a much less expensive and more comfortable alternative. It uses an EEPROM and 54  Silicon Chip reprograms in around a second! Called the Stamp, it is a small board, measuring only 60 x 35mm (not much bigger than a typical stamp). The board uses a PIC16C56 microcontroller and a memory chip, a ceramic resonator, a 5V regulator, two resistors, three capacitors, a transistor and a 14-pin connector. Also on the board are the battery connectors, a 3-pin header for programming by a PC-compatible computer, and a 10 x 14 plated-through hole work area. The complete circuit is shown in Fig.1. Made by Parallax, USA, the Stamp has 33 instructions to do some usual and unusual things with eight I/O lines. The Stamp is small and simple and comes close to being a programmable in­tegrated circuit. Take a look at the list of application notes in Table 1 and you will see that although the instruction set is small, sophisticated tasks can be achieved by the Stamp. At the time of writing, 19 application notes are sent with each Stamp programming package. Simplicity has been achieved by using the PIC16C56 which includes a BASIC-like interpreter. It has some familiar BASIC commands such as FOR, NEXT and LET, plus some unusual commands like MAX, MIN, PULSIN, PULSOUT, BUTTON and POT. An EEPROM is used to store a program. This same EEPROM may be used to store data from the PC when initially loading a pro­gram and via the WRITE command which allows the Stamp to write data into its own EEPROM. The exact amount of memo­ry available for data storage is determined by what is left spare in the 256 byte EEPROM after storing your program. One has to be careful not to overwrite the program with data. REM statements may be used in your program; these are not sent to the Stamp but kept in FILENAME.BAS which is stored by the Stamp editor/ programmer. To program the Stamp one needs an IBM compatible PC, a Stamp programming cable, software and the instruction book. To save the cost of a power supply, the Stamp may be powered by a 9V battery. Writing software To any one who has used a text editor, the editor/program­ming software supplied with the Stamp will have a familiar feel about it. It is a full screen editor with all the usual file handling PC PROGRAMMING CONNECTOR DATA 8 VCC VCC 4.7k 3 BUSY 2 16 15 VDD 4.7k RA0 17 18 RA1 RTCC RA3 RA2 1 11 IC1 PIC16C56XT OSC1 OSC2 4MHz MCLR 4 Q1 2N3906 RB0 6 VSS 5 OUT VCC (+5V) 2.2M 10 2.2M VSS 5 USER PROGRAMMABLE I/O PORT RB2 8 RB1 7 470k CS ORG 6 13 RB7 RB6 12 RB5 11 RB4 10 RB3 9 VCC Table 1: Applications 4 D0 3 D1 IC2 2 CLK 93LC56 IN COM 9V Fig.1: the circuit of the Stamp uses a PIC16C56 microcon­troller and a 93LC56 EEPROM. The 2N3906 is used for resetting the micro and is a surface mount device on the copper side of the board. functions, while movement through text on the screen is via the normal cursor keys, with HOME and END as well as PAGE-UP and PAGE-DOWN being appropriate commands. The editor does not use a mouse, however CUT, COPY, PASTE and SEARCH/REPLACE are easily accomplished using keyboard strokes. There are nine pages in the 63page instruction book ex­ p laining how to use the editor, four pages of introduction, 12 pages for explaining hardware, and 37 pages devoted to commands. Using some of the commands requires a little extra circuitry, as detailed below. BUTTON is the command used for connecting push buttons, keys, or switches to the Stamp. The Stamp’s in+5V 10k terpreter debounces the switch action; all the user needs to do is specify pin number, whether the transition will be high to low or vice versa, and auto repeat requirements. The two button circuits are shown in Fig.2. POT is a command which could be used to read the angular setting of a potentiometer. The command also works well with thermis­tors, light dependent resistors, etc. When using POT the program­mer needs to specify which pin the variable resistor is connected to and set a scale factor. There is a convenient setup facility in the program writing editor: just press <ALT>P and you will be guided through a setting up routine. Measurement of the resistor value is achieved by measuring the time taken +5V TO I/O PIN 10k TO I/O PIN Fig.2: these are two circuits for use with the BUTTON command. The button can switch the input high or low. 5-50k TO I/O PIN 0.1 0.1 Fig.3: the POT command uses this circuit to charge a 0.1µF ca­pacitor and the charging time is measured by the micro. (1) LCD user interface terminal (2) Interfacing an A/D converter (3) Hardware solution for keypads (4) Controlling and testing servos (5) Practical pulse measurements (6) A serial stepper controller (7) Sensing temperature with a thermistor (8) Sending messages in Morse code (9) Constructing a dice game. (10) Sensing humidity and temp­ erature (11) Wireless infrared communication (12) Cheap sonar rangefinding with the Stamp (13) Using (extra) serial EEPROMs (14) Networking multiple Stamps (15) Using PWM for analog output (16) Keeping Stamp private (17) The solar powered Stamp (18) One pin, many switches (19) Using BUTTON effectively to charge the capacitor in the circuit shown in Fig.3. PWM is virtually the reverse of the POT command. PWM with appropriate circuitry will give an analog representation of a value contained in a variable. This variable could have been accessed by the Stamp from a serial data input, a variable resis­tor input from POT, or could be derived from calculations done on variables, constants and look-up tables. The circuit used is an RC integrator as shown in Fig.4 but it will need to be followed by an op amp buffer. SERIN is the Stamp’s command for reception of serial data from another Stamp, a PC, logging device, a modem or whatever. The programmer needs to specify pin number and speeds from 300-2400 baud are available. One may invert the mark/space of the bits; this makes it easy to use other interface ICs where a more sophisticated system may be in use. The SERIN command may be set to wait for a specific character or string before doing anything. The circuit (Fig.5) is simply a resistor between the ±10V serial input and the designated I/O pin. SEROUT is exactly the reverse of SERIN and may be used to send mesDecember 1994  55 Table 2: Stamp Command Set Branching IF THEN BRANCH GOTO GOSUB Looping FOR.NEXT Numerics (LET) Compare and conditionally branch Branch to address specified by offset Branch to address Branch to Subroutine, up to 16 allowed. Establish a FOR-NEXT loop Perform variable manipulation, such as A=5, B=A+2, etc. Possible operations are add, subtract, multiply, divide, maxlim­it, minlimit, and logical operations, AND, OR, XOR, ANDNOT, ORNOT and XORNOT. Note variables handle integers only. LOOKUP Lookup data specified by offset, and store in variable. This instruction provides the means to make a look up table. LOOKDOWN Find target’s match number (0-N) and store in a vari­able. RANDOM Generate a pseudo random number. Digital I/O OUTPUT Make a pin an output LOW Make pin output low HIGH Make a pin output high TOGGLE Make a pin an output, and toggle its state PULSOUT Output a timed pulse, by inverting a pin, for a time. INPUT Make a pin an input PULSIN Measure an input pulse REVERSE If pin is an output, make it an input, or if output, make it an input. BUTTON Debounce button, perform an auto repeat, and branch to address if button in target state. Serial I/O SERIN Serial input with optional qualifiers and variables for storage of received data. If qualifiers are given, then the instruction will wait until they are received before filling variables or continuing to the next instruction. Baud rates of 300, 600, 1200, and 2400 are possible. Data received must be with no parity, 8 data bits and 1 stop bit. SEROUT Send data serially. Data format the same as SERIN command. Analog I/O PWM Output PWM, then return to input. This can be used to output analog voltages (0-5V) using a capacitor and resistor. POT Read a 5-50kΩ potentiometer and scale the result. Sound SOUND Play notes. Note 0 is silence, notes 1-127 are ascending tones, and notes 128-255 are white noises. EEPROM Access EEPROM Store data in EEPROM before downloading BASIC program. READ Read EEPROM byte into variable. Time PAUSE Pause execution for 0-65536 milliseconds. Power Control NAP Nap for a short period. Power consumption is reduced. SLEEP Sleep for 1-65536 seconds. Current consumption is reduced to about 20uA. END Sleep until the power cycles, or the PC connects. Current consumption is reduced to 20uA. Program Debugging DEBUG Send variables to PC for viewing. 56  Silicon Chip sages to a network of Stamps, pulling each Stamp into use as needed. Again the circuit is dead simple, as shown in Fig.6. SOUND puts out a tone on the specified pin. Pitch may be specified in the command line or may be taken from a variable. A conventional speaker may be driven by putting a capacitor in series as shown in Fig.7, while a piezo speaker can be directly connected without the capacitor. As with any program writing exercise, the jobs that may be done with the Stamp are limited only by the user’s imagination, skill with the commands, and the facilities of the hardware supplied. To help the user get started, 19 application notes are supplied with the Stamp programming kit. These are listed in Table 1. One of these application notes is reproduced here. This application note presents a program in Parallax BASIC that ena­bles the BASIC Stamp to operate as a simple user interface termi­nal. Many systems use a central host computer to control remote functions. At various locations, users communicate with the main system via small terminals that display the system status and will accept inputs. The BASIC Stamp’s ease of programming and built-in support for serial communications make it a good can­didate for such user interface applications. The liquid crystal display (LCD) used in this project is based on the popular Hitachi 44780 controller IC. These chips are the heart of LCDs ranging in size from two lines of four charac­ters (2 x 4) to 2 x 40. When power is first applied, the BASIC program initialises the LCD. It sets the display to print from left to right and enables an underline cursor. To eliminate any stray characters, the program clears the screen. After initialisation, the program enters a loop, waiting for the arrival of a character via the 2400 baud RS-232 interface. When a character arrives, it is checked against a short list of special characters (Backspace, control C and RETURN). If it is not one of these, the program prints it on the display and re-enters the waiting for data loop. If a backspace is received, the program moves the LCD cursor back one space, prints a blank (space) character to blot out the character that was there, and then moves back again. The second move back is necessary because the LCD automatically advances the cursor. If a control C is received, the program issues a clear instruction to the LCD, which responds by filling the screen with blanks and returning the cursor to the left most position. If a RETURN character is received, the program interprets the message as a query, requiring a response from the user. It enters a loop, waiting for the user to press one of the four push buttons. When he does, the program sends the character (0 through 3), representing the button number back to the host system. It then re-enters its waiting loop. Because of all this processing, the user interface cannot receive characters sent rapidly at the full baud rate. The host program must put a little breathing space between characters; perhaps a 3ms delay. If you reduce the baud rate to 300 baud and set the host terminal to 1.5 or 2 stop bits, you may avoid the need to program a delay. From an electronic standpoint, the circuit employs a couple of tricks. The first involves the RS-232 communication. The Stamp’s processor, the PIC16C56, is equipped with static protection diodes on its input/output pins. When the Stamp re­ceives RS-232 data which typically swings between -12V and +12V, these diodes serve to limit the voltage actually seen by the PIC’s internal circuitry to 0V and +5V. The 22kΩ resistor limits the current through the diodes to prevent damage. Sending serial output without an external driver circuit exploits another loophole in the RS-232 standard. While most RS-232 devices expect the signal to swing between at least -3V and +3V, most will accept the 0 and +5V output of the PIC without problems. This setup is less noise immune than circuits that follow the RS-232 rules. If you add a line driver/receiver such as a MAX232, remember that these devices also invert the signals. You’ll need to change the baud mode parameter in the instructions SERIN and SEROUT to T2400 where T stands for true signal polari­ty. If greater noise immunity is required, or the interface will be at the end of a long cable, use an RS-422 driver receiver. This will require the same changes to SERIN and SEROUT. Another trick allows the sharing of input and output pins be- 10k FROM I/O PIN ANALOG OUTPUT 1 Fig.4: this integrator is used for the PWM command but will probably need to be followed by an op amp buffer for many appli­cations. FROM I/O PIN 10k TO OTHER STAMPS Fig.6: a loading resistor is all that is required to implement the SEROUT (serial data out) command. TO ±10V 22k SERIAL I/O INPUT PIN Fig.5: just one resistor is needed to implement the SERIN (serial data in) command. FROM I/O PIN 10 40  Fig.7: by using the SOUND command, any of the I/O pins may be used to drive a 40Ω speaker via a capacitor. Note that if an 8Ω speaker is used, a series resistor of 33Ω will be required and this will inevitably reduce the available sound level. Fig.8: the BASIC Stamp Programming package includes a number of application notes, including one that enables the Stamp to operate a simple LCD user interface terminal – see text. tween the LCD and the push­butttons. What happens if the user presses the buttons while the LCD is receiving data? Nothing. The Stamp can sink enough current to prevent the 1kΩ pullup resistors from affecting the state of its active output lines. And when the Stamp is receiving input from the switches, the LCD is disabled, so its data lines are in a high impedance state. These points allow the LCD and the switches to share the data lines without interference. Finally, note that the resistors are shown on the data side of the switches, not on the +5V side. This is an inex- pensive precaution against damage or interference due to electrostatic discharge from the user’s fingertips. Currently the Stamp is available in Australia at three levels: Starter level is a programming kit containing software, instruction book, a programming cable and one Stamp. This is priced at $270 including sales tax. For a second stage, extra Stamp modules are available at $79.85 each including sales tax. Postage and packing on all orders is $8.00. Send all orders to MicroZed Computers, PO Box 634, Armidale, NSW 2350. Phone (067) 72 2777 or SC fax (067) 72 8987. December 1994  57 AMATEUR RADIO BY GARRY CRATT, VK2YBX Review: the AR 8000 handheld scanning receiver When we reviewed the AR 2800 mobile & AR 1500 handheld units from AOR in March 1992, we really thought that the limits of scanner technology had been reached. But now AOR has pushed the limits even further & produced what must be close to the ultimate, the AR 8000, a handheld unit capable of receiving frequiencies up to 1900MHz. It is obvious from the construction and mode of operation that the AR 8000 is a brand new design, not a variation of a previous model. The receiver offers multimode operation up to 1900MHz and features 1000 memory channels comprising 50 memory banks, each with a 20-channel capacity. Apart from being more manageable than the more conventional configuration of 10 banks, each of 100 channels, the AR8000 allows the user to label each bank with a 7- letter alpha identifier, allowing names such as AIR, AMATEUR, MARINE, CB, etc to be programmed into the unit. This helps easily identify the user of any frequency in memory. The programmed data is displayed on a 4-line LCD dot matrix panel above the keyboard. One really helpful item is the comprehensive handbook, containing 115 pages of user information. Considering the scant details given in previous AOR instruction manuals, this is a pleasant surprise. Lest the experienced scanner user be put off by the enormity of the manual, it is sensibly divided into two skill sections, “NEWUSER” and “EXPERT”. The “NEWUSER” option places the scanner into a mode 58  Silicon Chip where all parameters are programmed for common default values, simplifying initial operation. The “EX­PERT” option allows an experienced user to reconfigure virtually all parameters for specialist reception. The unit is equipped with two VFOs, allowing the user to swap between the two with a single keystroke. The two VFOs can be operated in different modes and each has 10 mem­ ory positions, each identified with an alpha identifier,“A”-“J” for one VFO and “a”-“j” for the second VFO. Those memories identified with a lower case letter can be protected by a user password. This protects confidential frequency entries and their identifying names. The twin VFOs are also useful for toggling between input and output frequencies of a repeater. One outstanding feature is the ability to quickly store active frequencies found during searching into memory. This can be done with a single keystroke. The unit has preprogrammed search increments of 1, 2, 5, 6.25, 9, 10, 12,5, 20, 25, 30, 50, 100, 200, 250, and 300kHz. If none of these are suitable, the user can preprogram any multiple of 50Hz up to 999.995kHz. Another unique feature is the The AR 8000 features multimode operation up to 1900MHz & 1000 memory channels. Broadcast band reception One surprising feature of this receiver is reception of broadcast band AM signals. The receiver incorporates a ferrite rod antenna and a sensitive front end. The ability to select the correct channel spacing of 9kHz for the Australian AM band re­sults in the user being able to sequentially step through the entire band without missing a station. In fact when we tried this, even during daylight hours, there were very few channels where we could not hear an AM station. For those interested in broadcast band DX reception, this is a real bonus. Technically, the AR 8000 specifications are similar to most other modern scanning receivers. What sets this model apart from others is the frequency coverage to 1900MHz, the multitude of user features, preprogrammed defaults, the respectable HF and broadcast band performance, and the comprehensive user manual, catering for inexperienced users. The AR 8000 is available from Access Communications, exclu­ sive importers of many AOR products, who also hold spares and technical data on this unit. The AR 8000 is expected to sell for $1295, exceptional value compared to other brands, and is avail­able from Phonetronics stores and Access Communications in most states. For further information, contact Access Communications, 33 Alleyne Street, Chatswood NSW 2067. Phone SC (02) 417 5311. SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 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). ✂ “band­scope” function, not found on other models. This function is available from the VFO mode and allows the user to visually monitor the five adjacent channels either side of the nominated centre frequency using the LCD display – in effect, a narrow band spectrum display! One function available in earlier AOR models, such as the AR 3000, and AR 2500, is the serial control of the receiver by a computer. The AR 8000 also has this facility, the first handheld receiver we have ever seen so equipped. The optional CU-8232 cable/interface is required, as is communications software. Like an increasing number of new technology radios, the AR 8000 also has the ability to “clone” programmed data from memory into an identical receiver, using the same cable used for comput­er control. December 1994  59 3-Spot Low Distortion Sinewave Oscillator This sinewave oscillator is ideal for testing audio equipment & loudspeakers. It provides three switch-selectable spot frequencies at 100Hz, 1kHz & 10kHz, with levels up to 2V RMS & less than 0.004% distortion. By DARREN YATES Sinewave oscillators are among the toughest circuits to get working well. There are many circuits around which use a couple of transistors and produce a sinewave with about 1% distortion which may be OK for some applications. However, when it comes to producing very clean (minimal distortion) sinewaves, the circuits really start to thin out. 60  Silicon Chip There are several reasons for this. Oscillators are basi­ cally amplifiers with positive feedback. For a square­ wave oscil­ lator, the basic rule is “more positive feedback, please!” but for sinewave oscillators, a more controlled method is required. Sinewave oscillators come in many shapes and forms but the one characteristic they have in common is that they require a precise amount of positive feedback to obtain the cleanest wave­ f orm possible. The most common sinewave oscillator circuit is probably the Wien Bridge configuration. An example of this type of circuit using an op amp is shown in Fig.1. As you can see, it uses two RC time constants to pro­vide positive feedback, one in series between the output and the non-inverting input (R1 & C1) and the other in parallel between the non-inverting input and ground (R2 & C2). These positive feedback components set the frequency of oscillation. In order for this circuit to oscillate, the theory states that it must have an overall gain of three, as set by the nega­ tive feedback components between the C1 R1 AMPLIFIER R2 C2 R3 LG1 Fig.1: typical Wien bridge oscillator circuit. The light globe (LG1) in the feedback network stabilises the output amplitude. output and the inverting input (R3 and L1). This would give a pure sinewave with no dis­tortion at all. But like most things in electronics, the perfect isn’t possible so in order for the circuit to keep oscillating, the gain must be slightly greater than three. And this causes other problems. The first of these is that because the circuit uses posi­ tive feedback, any gain above that just required for oscillation will cause an increase in output amplitude. This increase causes even further increases in amplitude and before you know it, you’ve got a lovely squarewave staring at you from the CRO! This in turn leads to a second problem – increased distortion. The most common solution is to use some non-linear element, such as a light globe, to regulate the amount of gain. As shown in Fig.1, the globe is connected in the negative feedback path of the circuit. When the circuit begins to oscillate, the output voltage increases which causes an increased current flow through the globe. The good thing about globes is that they have a positive thermal coefficient (PTC) which means the more current you try to pump through them, the more their resistance increases. This increased resistance counteracts any tendency for the output amplitude to rise by reducing the gain of the circuit. In other words, if the output amplitude goes up, the re­sistance of the globe also goes up, which reduces the gain of the circuit and thus brings the amplitude back under control. This technique is used in countless low-distortion sinewave oscillator circuits. Its main drawback is that a globe does not have an instantaneous response, so if you change frequency, the output amplitude will “bounce around” for a short period until a new equilibrium is established. Another problem is that while we now have a very stable waveform in terms of output voltage, the non-linearities of the lamp filament introduce distortion into the waveform. One way to reduce this distortion is to simply filter the output signal to remove the unwanted harmonics. Since we are only interested in one particular frequency, a “brick wall” filter (ie, a low-pass filter with a very steep cutoff) can be used to remove the un­ wanted harmonics and hence reduce the distortion. The project presented here uses both these techniques and can be switched to produce one of three output frequencies – either 100Hz, 1kHz or 10kHz. It provides up to 2V RMS output into a 600Ω load with a distortion figure of less than .004%. Circuit details Fig.2 shows the complete circuit details for the Low Dis­tortion 3-Spot Oscillator. It is based on three identical circuit topologies, each with an oscillator and filter, the only dif­ference between each section being the necessary changes in com­ponent values to obtain the desired frequencies. The reason for using three separate oscillators to generate the three frequencies is to reduce the required switching to a minimum. For example, we could have used just one oscillator to produce all three frequencies but then switching would be re­ quired for the frequency determining components. This extra switch­ing would inevitably lead to large transients when the frequency was switch­ed and the overall envelope stability would not be as good. For ease of understanding, we shall explain only one sec­tion but note that all three work in exactly the same manner. Looking at the 100Hz (top) section, IC1a and IC1b form a modified Wien bridge oscillator. Its frequency of operation is set by the 0.1µF capacitors and the 15kΩ resistors in the posi­tive feedback loop and follows the standard Wien bridge formula: F = 1/(2πRC). IC1b is connected as an inverter to drive the negative feedback network of IC1a; ie, it drives lamps LG1 and PARTS LIST 1 PC board, code 01110941, 158 x 100mm 1 front panel artwork 1 zippy box, 195 x 113 x 60mm 1 3-pole 3-position rotary switch (S1) 1 SPDT toggle switch (S2) 1 3.5mm socket 1 RCA panel-mount socket 2 knobs to suit 1 10kΩ log potentiometer (VR5) 1 12-way length of Molex pins 1 16VAC plugpack 6 12V DC switch replacement globes (Jaycar Cat. SL-2636) 4 rubber feet Semiconductors 7 LM833 dual low-noise op amps (IC1-4, IC6-8) 1 TL072 dual op amp (IC5) 1 7812 3-terminal regulator 1 7912 3-terminal regulator 2 1N4004 diodes (D1,D2) 2 OA91 germanium diodes (D3,D4) 1 5mm red LED (LED1) 3 100Ω 5mm horiz. trimpots (VR1-VR3) 1 10kΩ 5mm horiz. trimpot (VR4) Capacitors 2 470µF 25VW electrolytics 2 100µF 16VW electrolytics 9 0.1µF 63VW MKT polyester 3 .015µF 63VW MKT polyester 5 .01µF 63VW MKT polyester 3 .0015µF 63VW MKT polyester 5 .001µF 63VW MKT polyester 3 150pF ceramic Resistors (0.25W, 1%) 9 47kΩ 2 10kΩ 9 36kΩ 1 2.2kΩ 1 27kΩ 1 1kΩ 9 24kΩ 1 560Ω 9 15kΩ 3 68Ω Miscellaneous Light duty hook-up wire, light-duty speaker cable, machine screws & nuts, washers. LG2. In effect, IC1a and IC1b drive the feedback network, including the lamps, in bridge mode. This effectively halves the voltage swing at the output of both op amps and the result is an oscillator with a quick settling time. December 1994  61 0.1 15k 7 36k 24k 68  0.1 0.1 5 0.1 6 IC1a LM833 VR1 100  15k .015 47k IC2a 5 LM833 7 +12V .015 .015 36k 24k 6 47k 0.1 0.1 8 2 2 3 -12V E .01 15k 5 .01 6 7 36k 24k 68  .01 .01 IC3a LM833 VR2 100 15k .0015 47k IC4a 5 LM833 .0015 47k 36k 24k 6 7 .01 .01 +12V 8 2 6 IC7b 5 LM833 .01 7 -12V B 1kHz OSCILLATOR LG4 F 1 IC3b 4 G .001 15k 5 .001 6 7 36k 24k 68  .001 .001 IC5a TLO72 VR3 100  15k 150pF 47k 6 7 IC6a 5 LM833 150pF 47k 36k 24k .001 .001 +12V 8 2 LG6 15k D F 1kHz S1b E 1 IC5b G 4 S2 B S1a 1k LEVEL VR5 10k 10kHz 5 6 -12V IC8b 7 VR4 10k D1 1N4004 16VAC D2 PLUG1N4004 PACK 470 25VW 7812 7812 GND OUT 100 16VW +12V 0.1 100 GND 16VW IN 62  Silicon Chip 7912 7912 OUT 7812 7912 I GO GIO A 0.1 0.1 LED1  K -12V 27k +12V 2.2k 0.1 0V 470 25VW OUTPUT 560W 560W S1c 10kHz IN 1 1kHz 100Hz 1kHz 8 IC7a 3 LM833 4 -12V 100Hz A +12V 2 -12V 10kHz OSCILLATOR 100Hz +12V 150pF 47k 36k 24k .001 .001 4 10kHz 8 1 IC6b 3 LG5 3 .0015 47k 36k 24k 4 8 2 1 IC4b 3 LG3 3 A -12V 1 4 2 1 D 8 15k 8 IC8a 3 LM833 4 100Hz OSCILLATOR LG2 IC1b 2 0.1 0.1 4 LG1 15k 1 IC2b 3 +12V .015 .015 47k 36k 24k A D3 OA91 D4 OA91 K LOW-DISTORTION 3-SPOT OSCILLATOR 10k 100uA 10k Use light duty hook-up wire for the front panel connections & bind the leads with cable ties to keep the layout tidy. The PC board is secured to the base of the case using machine screws & nuts, with additional nuts used as spacers. ▲ Note that the final circuit uses two lamps in series in­ stead of just one lamp. This has been done to further reduce the initial distortion of the oscillator sections. VR1 sets the gain of IC1a and is adjusted to provide a 2V output with the level control at maximum during the setting-up procedure. The remaining section of the circuit consists of three op amps connected as a 6th-order Butterworth low-pass filter. It’s made up of three cascaded second-order filters which gives an ultimate slope of 36dB/octave above the cut-off frequency. This topology is known as a multiple feedback (MFB) filter. The cutoff frequency of the circuit Fig.2 (left): the circuit uses three similar Wien bridge oscillator & filter sections to generate three spot frequencies at 100Hz, 1kHz & 10kHz. IC8b amplifies & buffers the selected frequency, while D3, D4 & their associated parts provide drive to an optional 100µA level meter. is below the oscillator frequency; ie, around 75Hz for the 100Hz oscillator. Thus, the second and higher harmonics will be heavily attenuated with respect to the fundamental. As a result, we end up with a circuit which has fast settling time and very low distortion. The output from the filter stage appears at pin 1 of IC8a and is fed to S1a which is one pole of a 3-pole 3-position rotary switch. From there, the selected signal is fed via level control VR5 to op amp IC8b. This functions as a unity gain buffer stage and drives the output socket via a 560Ω current limiting resis­tor. This resistor ensures that IC8b is not damaged if the output is shorted out. IC8b also drives an optional output signal metering circuit via VR4 and a 27kΩ resistor. The metering circuitry consists of a pair of germanium diodes (D3 & D4) connected in a bridge arrange­ment with two 10kΩ resistors. Trimpot VR4 allows the meter to be adjusted to produce a full-scale read- ing when the level control is set to maximum. As indicated previously, the 1kHz and 10kHz oscillator/filter stages function in exactly the same manner as the 100Hz stage. There is one anomaly, however – the 10kHz oscil­lator is based on a TL072 dual op amp, whereas the other two oscilla­tors use LM833 devices. The reason we’ve used a TL072 op amp for the 10kHz oscilla­tor is that we found that the LM833 produced some very high frequency bursts in parts of the 10kHz waveform. By replacing it with an op amp with a lower transition frequency (Ft), this problem is eliminated. The LM833 devices are a little cheaper than the TL072 and perform flawlessly at the lower frequencies. Power supply Power for the circuit is derived from a 16VAC plugpack connected via on/ off switch S2. This eliminates the need for a mains transformer inside the case and the attendant hum and distortion problems that this would create. The AC voltage from the plugpack is halfwave rectified by D1 and D2, filtered December 1994  63 OUTPUT SOCKET 36k 24k 0.1 0.1 15k IC1 LM833 IC2 LM833 0.1 TOMETER .015 36k 47k 1 47k LG2 1 .015 36k 24k 0.1 15k 4 D4 IC8 LM833 1 1 LG1 27k VR4 D3 VR5 VR1 1k 560  15k 68 47k .015 0.1 24k 1 15k 10k 47k 36k 0.1 0.1 24k 10k .0015 .01 LG4 .01 6 2.2k 24k .0015 7 100uF 47k LG3 1 24k 15k 3 IC4 LM833 .01 1 .01 .01 IC3 LM833 VR2 36k S1 2 15k 68  5 0.1 100uF 0.1 4 150pF LG6 36k 47k 1 .001 470uF 470uF 1 150pF 150pF 3 36k LG5 IC7 LM833 .0015 47k 1 LED1 7912 2 IC6 LM833 47k VR3 15k S2 IC5 TLO72 36k 5 7812 .0015 2x.001 24k 7 24k 15k 6 15k 68  47k 36k .001 D1 D2 24k Fig.3: install the parts on the board as shown here, taking care to ensure that all polarised parts are correctly oriented. Note particularly that IC5 is a TL072 device; the remaining ICs are all LM833 types. Be sure to mount the 7912 3-terminal regulator adjacent to the edge of the board. and regulated by two 78-series regulators to produce ±12V rails to power the op amps. 64  Silicon Chip LED 1 and its associated 2.2kΩ current limiting resistor provide power on/off indication. PLUG-PACK SOCKET To further ensure that the output signal is as clean as possible, the two unwanted oscillator sections are shut The light globes are installed by plugging them into 2-way pin headers derived from a Molex pin strip. They should be left until last. down to eliminate crosstalk. This is achieved by switching the supply rails to the oscillator stages using switches S1b and S1c. When a particular frequency is selected, these two switch poles select the ±15V supply rails for that oscillator and switch out the other two. As a result, only one oscillator section is powered up at any one time and this completely eliminates cross-coupling bet­ween oscillator stages. Construction Most of the parts for the 3-Spot Sinewave Oscillator are installed on a PC board coded 01110941 and measuring 158 x 100mm. Before you begin construction, check the board carefully against the published pattern for possible etching defects. In the vast majority of cases the board will be perfectly OK but it’s always a good idea to make sure. Fig.3 shows where the parts go on the PC board. Begin by installing PC stakes at the external wiring points, then install the wire links and resistors. It’s a good idea to check each resistor value on your DMM as it is installed, as some of the colours can be diffi­cult to decipher. Once the resistors are in, install the capacitors and the trimpots. Take care with the electrolytic capacitors – they must be inserted with the correct polarity. The light globes (LG1-LG6) are all mounted using 2-way pin headers (derived from a Molex pin strip) and these may be in­stalled now. Do not plug the globes in yet though, as they are easily damaged. The board assembly can now be Fig.4: this is the full-size etching pattern for the PC board. completed by installing the ICs, regulators and diodes. Note that the ICs are all oriented in the same direction and be sure to use a TL072 for IC5. The two regulators are mounted with their leads bent at 90° so that their metal tabs sit flat against the board surface. Make sure that the LM7912 regulator is adjacent to the edge of the board. Although the level meter is optional, its asso­ciated driver circuitry should be installed regardless as to whether you intend using a level meter or not. That’s because this circuit is used later during the adjustment procedure, either with the optional meter or with a multimeter in its place. Final assembly A plastic zippy case measuring 195 x 113 x 60mm is used to house the circuitry. The first step involves mounting the PC board – it’s secured to the base using 6mm standoffs and machine screws and nuts. You can use the board as a template for marking out its mounting holes. This done, attach the front panel label to the lid and use this as a template for drilling the holes for the front-panel controls and the LED. Additional holes December 1994  65 will also have to be drilled at either end of the case to accommodate the plugpack socket and the RCA output socket. Note that it’s best to drill all holes to 3mm and then enlarge them as necessary using a tapered reamer. As supplied, switch S1 will be a 3-pole 4-position type. It must be converted to a 3-position type by lifting the locking ring at the front of the switch bush and rotating it anticlock­wise one 66  Silicon Chip Test & adjustment Fig.5: this full-size artwork can be used as a drilling template for the front panel. POWER FREQUENCY (kHz) 10 0.1 1 LOW-DISTORTION 3-SPOT SINEWAVE OSCILLATOR LEVEL the switch connec­tions and light-duty speaker cable for the connections to the pot (VR5), output socket and LED. Take care to ensure that the LED is wired with the correct polarity. The assembly can now be completed by plugging the six light globes into their 2-way pin headers and fitting four rubber feet to the base of the case. position. Check that the switch now has three positions before mounting it in place, along with the other items of hard­ware. Note that the rotary switch must be oriented so that the point­er on the knob aligns with the 0.1kHz position when the switch is set fully anticlockwise. The wiring between the PC board and the external hardware items is run using light-duty hook-up wire for To test the unit, you will need to monitor the output using either an oscilloscope, a frequency counter or an audio amplifi­ er. Initially, set all trimpots in the oscillator stages to midrange, then apply power and check that the ±12V rails from the 3-terminal regulators are correct. Switch off immediately if you encounter an incorrect reading here and correct the fault before proceeding further. If you have an oscilloscope, check that a sinewave trace appears when each range is selected and that its frequency is in the ballpark. Alternatively, you can measure the frequency di­rectly if you have a frequency counter or simply listen for a tone if you are feeding the output into an audio amplifier. Assuming that the circuit is working correctly, VR1-VR3 can now be adjusted to provide the correct levels. The procedure is as follows: (1). Select the 100Hz range, set the Level control (VR5) to maximum and connect a multimeter set to a low AC voltage range across the output (ie, across the RCA output socket). (2). Adjust VR1 for a 2VAC reading on the multimeter. (3). If you have installed the optional 100µA level meter, adjust VR4 so that this meter reads full-scale when the output level is at 2VAC. This done, select the 1kHz range and adjust VR2 for a full-scale reading. Finally, select the 10kHz range and adjust VR3 for a full-scale reading. (4). If you are not using a level meter, ignore step 3, set VR4 to midrange and connect the multimeter across the meter termi­nals. Select a low DC voltage range, check that the level control is still at maximum and note the reading on the multimeter. Finally, select the 1kHz and 10kHz ranges in turn and adjust VR2 and VR3 respectively to give the same reading. That completes the adjustment procedure. Your Low-Distor­tion 3-Spot SC Oscillator is now ready for use. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SERVICEMAN’S LOG Purity is not always only in the mind The last few years have seen many changes in TV receiver design, mainly in the form of “improvements” supposedly intended to make the viewer’s life easier. But one of these, the remote control facility, has turned out to have a nasty sting in its tail. This story concerns a Panasonic colour set, model TC-29V26A. This is what is known as a “large screen” set, ranging around the 70cm mark, and while the problems encountered are in no way peculiar to this type of set, there is a feeling that they might be just that little more critical than their smaller brethren. Be that as it may, it provides a good opportunity to look at an old problem – purity error – which appears to have been given a new lease of life by modern developments. It all started when I received a phone call from a local large appliance retailer. The staff member calling, having con­firmed that he had the right person, then asked if I was an accredited service centre for Panasonic. I confirmed that I was and it was then that a problem arose. “Well,” said the caller, “will you go out to Mr So-and-So’s place, at such-and-such an address, and fix his TV set”. And, in spite of the nature of the wording, it was not a request; it was a command – almost a royal command. It was not an approach calculated to put me in a good mood. I don’t take kindly to being ordered to do things, even if it involves a normal service. And in this case it didn’t. Like most of my colleagues, I am doing my best to avoid house calls these days. One cannot ignore the travelling costs and, with modern sets, more often than not the job cannot be done in the home anyway. Granted, there are exceptions but, one way or another, the extra costs have to be met. And, in the case of 72  Silicon Chip warranty service, there is no way that these can be met. Most warranty payments are pretty tight anyway. So it’s not surprising to find that almost all appliance warranties require the purchaser to return a faulty appliance to the manufacturer or his accredited service centre. So, in a nutshell, I don’t do house calls on warranty jobs in any circumstances. And I advised the caller accordingly. He became a mite shirty at this and tried to pull rank and insist that I do what he wanted. I let him carry on until he ran out of puff and then suggested that he advise his customer to contact me, so that I could liaise with him and come to some mutually convenient arrangement. So, after some mumbling and grumbling, he reluctant­ly agreed to do this. In due course, the customer contacted me and I explained the above policy to him. Rather ironically, this didn’t worry him in the least. He had suitable transport and was quite happy to bring the set into the shop. So much for the other fellow’s huffing and puffing. Having clarified that point I asked the customer what the problem was. He said that, in general, he was very happy with the set but that it had a patch of bluish colour in one corner of the screen. In short, we had a purity error. Check list I went through a standard check list with him. Were there any loudspeakers near the TV set? No, that was ruled out. Any magnetic devices of any kind on top of the set, in particular, children’s toy cars with electric motors in them? Some of these motors have powerful magnets and I have known them to create just such problems. No; so we ruled that out too. Had the set been moved recently? Many larger sets are on mobile stands these days and can be readily moved, typically to suit a changed room layout. But that was not so in this case. With all those points covered, there was one more thing to try. I suggested that, over the next day or so, he resort to switching the set on and off at the power point, rather than via the remote control system. Which brings me to a point which has been largely over­looked in modern set design. Sets using electronic on-off switch­ i ng, as with remote control systems, no longer activate the degaussing system every time the set is turned on. In fact, if the power point is left turned on – which is the normal situation to permit full use of a remote control – the degaussing circuit may not activate from one year’s end to another. As a result, any purity problems which would normally be cured at the next switch-on remain unresolved. And the fact that I had to advise the customer of this situation is another oversight; there is no mention of this problem, or how to cure it, in this set’s user manual. Nor have I been able to find it in any other manuals. Anyway, I left the customer with that suggestion, and ad­vised him to call me in a couple of days if the problem persist­ed. Well, it did persist and he called me and reported this. And so I suggested that he bring the set in. That was no problem; he had a 4-wheel drive wagon and plenty of assistance to load it. And since I imagined that it would be a simple case of overall degaussing with the degauss wand, I said I could probably do the job while he waited. He duly turned up as arranged and we manhandled the set onto the bench. And the problem was just as he had described it; a bluish patch in the top right hand corner. While not all that strong, it would be a quite an intolerable distraction in prac­tice. So I fired up the degauss wand and went right over the set; front, sides, top and back of the cabinet. And that cured it. There was no doubt in my mind, or that of the customer’s, that the bluish patch had been completely eliminated. I made out the necessary warranty claim for Panasonic and we loaded the set back into the wagon. And, before the customer left, I was most careful to emphasise that he should contact me immediately if there were any further problems. Many weeks went by and I heard nothing further, which lead to the natural assumption that all was well. It came as something of a shock, therefore, when I received a call from the service manager at Panasonic, concerning a complaint from a customer about a set. Initially, I didn’t connect this with the aforementioned customer, due to some confusion over the name, but the address provided the clue. Anyway, it appeared that he was still not satisfied with the set and had written to Panasonic to have something further done about it. By all accounts, it wasn’t an unpleasant letter but it was unfortunate that he felt impelled to do this. I thought I had made the position quite clear. I can only imagine that he thought he had to go through Pana­sonic in order to initiate another warranty call. Anyway, I eventually contacted him again and we made anoth­er appointment. But I explained to him that this time I would need to keep the set for several days. My idea was to go through a complete purity and static convergence routine. He was quite happy about this arrangement. So the set finished up back on the bench. But these large sets are no snack to handle. Just getting it up on the bench is a two-man operation and then there is the job of getting the back off. This is not the simple job that it was in the old days. The set has to be turned on its face, many screws removed, and the back very carefully lifted off, taking care not to knock the neck off the picture tube! (Yes, I understand that it has happened). And when the back is removed, there is not much cabinet left to support the works in an upright position. But everything was sorted out eventually. Checking the set’s performance con­ firmed that the original purity problem had returned. Exactly why was not clear, although subsequent discoveries may provide a partial explanation. Purity adjustments The first thing I did was plug in the degauss wand and give the whole of the inside of the set a thorough going over. Again, this seemed to clear the problem but, having been caught once, I wasn’t taking any chances. And so it was on to the purity adjustment. Old hands may recall that for the early colour tubes, using the delta (triangu­lar) gun configuration, the purity adjustment was done using the red December 1994  73 SERVICEMAN’S LOG – CTD gun. The procedure was to unclamp the deflection coils and move them back as far as possible, then adjust the purity magnets for a pure red area in the centre of the screen. This was then expanded to cover the whole screen when the coils were moved forward. These days, with the in-line gun configuration, the green or centre gun is used but otherwise the procedure is much the same. The red and blue guns are turned off and the scan coil assembly unclamped and moved back. But the result will not be quite the same. What we are aiming for now is a vertical green block, about 300mm wide, in the middle of the screen. 74  Silicon Chip And when the coils are moved forward again, the result should be an even green display over the whole screen. In fact, this didn’t happen. When I moved the coils back, the green pattern was substantially to the right of centre, facing the screen. Correction is by means of the purity rings, the first two behind the scan coils. In this case, the pattern responded as it was supposed to and was moved to the centre of the screen. It also responded correctly when I moved the coils forward and we had a nice even screen pattern. If it is not quite right, the purity magnets can be adjusted slightly again for best re­sults. The scan coil clamps can be tightened at this stage but it is a good idea to feed in a cross hatch pattern first, to make sure that the picture has not been rotated in the process. The next step is to energise the red and blue guns in turn and check that they are even and pure. Again, this didn’t happen quite according to the book. The blue gun gave an accept­able pattern but the red gun produced a faint orange cast in the top right corner. It took some more minor juggling of the purity magnets to correct this. Finally, I fed in the cross hatch pattern again and checked the static convergence in the centre of the screen. There was a slight error, which was easily corrected with the static convergence magnets. That done, I considered the job finished and judged that the customer should have no more cause for complaint. But I did take the opportunity to make one more test, which was quite revealing. The set had been sitting on the bench on an east/west line and I turned it, while running, through 90 degrees into a north/south alignment. The result was a fairly substantial purity error; substan­tial enough to risk a customer reaction. I turned the set off, waited long enough for the degauss thermistor to cool and turned it on. Result; no purity error. I repeated the exercise in reverse, turning the set back to its original east/west alignment. Again, it gave substantial purity error which was cured by a switch-off/switch-on routine. The overall conclusion was that the set was quite sensitive to prevailing magnetic fields – mainly the Earth’s I imagine. There is nothing new about this; it has been with us ever since the advent of colour. Nor am I suggesting that this set is any worse than any other set. What I am saying is that we have tended to forget about this sensitivity because the degaussing systems have kept it under control. But now, with remote control switching bypassing the degauss systems, it is rearing its ugly head again. So that’s one to watch. More from the motel My next story is a continuation of the Contec saga I start­ed in the November notes. Readers will no doubt remember the puzzling symptoms -31V 5V 4 3 F F 12V 1 F 2 F 1 E 2 E 8 1 D510 C514 47 7 6 240V D511 3 4 2 5 R519 1k IC 510 IC502 330 C515 470 0.1 Q506 T501 Q505 T502 Q507 114.9V C 5 Fig.1: the power supply circuit for the Contec MSVR-5383. The -31V rail is derived from transformer T501 (pins 6 & 8), via D510, C514 and R519. A simple fault can cause the weirdest symptoms. caused by the failure of the 31V rail supplying pin 2 of IC802. So this is about another Contec MSVR-5383 from the same local motel. And the symptoms still involved the memory function which were involved previously but there the similarity ended; they were really weird this time. The customer’s story was somewhat similar to the previous one. If the set was left in standby mode there was no problem but if it was turned off at the mains and – most important – left off for about half an hour, there was an apparent loss of memory. And that “apparent” qualification is really the heart of the story because it is about the only word I can think of which even approaches describing the problem. The only real way to describe it is to give an example. Let’s assume that the set has been programmed for five channels, using positions 1-5. Position zero is blank. Let us further assume that the set, when switched off, was running on position 2. Now, in the normal course of events, the set could be switched off, even at the mains and, when switched on again any time later, would come up 6 D516 C C523 C 1 2 3 Q508 Q509 on position 2. Not so with this set. Assuming that it had been off at the mains for about half an hour or more, the most likely scenario would be that it would come up on position zero and thus give a blank screen and white noise. So let’s try the remote control and call for position 1. Result: no response. Ditto for position 2 and so on. But suddenly at, say, position 4, there is the channel programmed for channel 4. But the sound is at full blast, prompting a frantic stab at the volume down button. And this works, allowing the volume to be set to a normal level. So let’s try position 5. It may or may not respond. Moving back down the scale, a previously dead position, say 2, might now respond. So might position 1. But go back to position 4 and it may no longer be available. Now all that is purely hypothetical, because the response at any time is completely random and unpredictable; there was absolutely no pattern of any kind. And if that isn’t enough to give a bloke nightmares, I don’t know what is. But that was it and I was stuck with it. Remembering the previous experi- ence, I went straight to the supply to pin 2 of IC802, although it was more in desperation anything else. And that qualification was justified, because pin 2 was sitting at 31V, exactly as it should be. A crook IC802? That seemed to be the next most likely pos­sibility and I had a spare on hand. It took only a few minutes to fit it and I gave it a test run, feeling fairly confident that it would come good. No way mate, as they say in the classics; it was exactly the same as before. Where to now? So where to from here? I looked at the circuit and it looked right back at me. The only likely possibility seemed to be IC804, which is obviously a companion to IC802 and performs several similar functions. The only immediate problem was that I didn’t have a replacement. Nor was it available from my normal supplier. I would have to go back to the Contec service organisa­tion. Perhaps that was just as well; it made me think a bit harder. And some of the things it made me think about were other weirdos I’d experienced December 1994  75 SILICON CHIP BOOK SHOP Newnes Guide to Satellite TV 336 pages, in paperback at $49.95. Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Servicing Personal Computers By Michael Tooley. First pub­ lished 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. Optoelectronics: An Introduction By J. C. A. Chaimowicz. First published 1989, reprinted 1992. This particular field is about to explode and it is most important for engineers and technicians to bring themselves up to date. The subject is comprehensively covered, starting with optics and then moving into all aspects of fibre optic communications. 361 pages, in paperback at $55.95. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. Power Electronics Handbook Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Surface Mount Technology By Rudolph Strauss. First pub­ lish-ed 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First pub­ lished 1989. 6th edition 1994. This just has to be the best reference book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. 76  Silicon Chip semicustom electronics & data communications. 63 chapters, in paperback at $140.00. Radio Frequency Transistors Principles & Practical Appli­ cations. By Norm Dye & Helge Granberg. Published 1993. This timely book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering techniques, impedance matching & CAD. 235 pages, in hard cover at $85.00. Newnes Guide to TV & Video Technology By Eugene Trundle. First pub­ lish-ed 1988, reprinted 1990, 1992. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 432 pages, in paperback, at $39.95.  Title Price  Newnes Guide to Satellite TV  Servicing Personal Computers  The Art Of Linear Electronics  Optoelectronics: An Introduction  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Surface Mount Technology  Electronic Engineer’s Reference Book  Radio Frequency Transistors  Newnes Guide to TV & Video Technology 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 $55.95 $59.95 $49.95 $55.95 $55.95 $59.95 $99.00 $140.00 $85.00 $39.95 SERVICEMAN’S LOG – CTD let it stand, I then patched in the good capacitor and switched on. No problem; the set came up on the original channel and all other channels could be called up correctly. I repeated this exercise several times during the day, and it worked every time. In short, the ripple did not seem to pres­ent any difficulties about programming the set, only about the subsequent recalling function. A possible theory One theory that has been advanced is that erratic recall behaviour was a function of the exact moment when the remote control message was received, relative to the phase of the rip­ ple. If it occurred at the exact moment when the ripple was at its cross­over point – ie, neither adding or subtracting anything from the DC rail, then response would be normal. At all other times, there would be a risk of failure. Well, it is an interesting theory but I’m afraid that is all it will ever be. I can’t think of any way of proving it. In any case, it still leaves a lot of other questions unanswered. But at least I’d SC found and fixed the fault. TRANSFORMERS • TOROIDAL • CONVENTIONAL • POWER • OUTPUT • CURRENT • INVERTER • PLUGPACKS • CHOKES –not necessarily involving memory sys­ tems – where the most bizarre symptoms could result from rela­tively simple faults. And one of the simple faults which had tricked me in the past was ripple on a supply rail. I could hardly wait to get the CRO probe on pin 2 of IC802. And there it was – about 5V of ripple on what should have been a DC supply. An easy cure The reason was almost too obvious to justify mentioning; it just had to be C514, a 47µF 60V electrolytic capacitor in the 31V supply rail. I pulled it out and checked it and it was struggling to make 5µF. I patched in a new one, put the set though all its paces, and it came up trumps; nothing I could do would cause it to lose its memory. So, in practical terms, that was the end of the exercise. Why did it do what it did? Frankly, I have little or no idea. But I did try a few tricks before the set went home. Before permanently fitting the new electrolytic, I patched the old one back in, programmed the set, then switched it off and let it stand for the prescribed period. There was some doubt about this exact period. The customer had suggested half an hour and I worked to this for a while. Later I realised that this was more than necessary; about 10 minutes was sufficient but it had to be at least this. Anyway, having programmed it and STOCK RANGE TOROIDALS BEST PRICES APPROVED TO AS 3108-1990 SPECIALS DESIGNED & MADE 15VA to 7.5kVA Tortech Pty Ltd 24/31 Wentworth St, Greenacre 2190 Phone (02) 642 6003 Fax (02) 642 6127 December 1994  77 VINTAGE RADIO By JOHN HILL Valves & miniaturisation: a look at some remarkable receivers Prior to the introduction of transistors, many attempts were made to miniaturise equipment by making the valves smaller & by packing the components more efficiently into the available space. A number of remarkable receivers were produced, most capable of good performance. There’s no doubt about it – the transistor paved the way for miniaturisation in the field of electronics. Prior to the transistor, most electronic circuits used valves and while they did the job, they were large, fragile, limited in their applica­tion, and highly inefficient to say the least. The cathode in a thermionic valve must be red hot in order to maintain an electron stream. As a result, valves used a con­siderable amount of power compared to the amount of work they did. On the other hand, the transistor was what early radio technicians dreamed of – a valve without a heater. As much as I hate to admit it, valve equipment is, by modern standards, big, heavy and expensive to run. The latter is particularly true of any battery-operated apparatus. But develop­ ment over a long period eventually produced smaller and more efficient valves than the early types, resulting in some extreme­ly compact receivers being made towards to end of the valve era. Some valve types were so small that they no longer used a socket; leads out of their bases were wired directly into the circuit. These ultra-small valves found a use in remote control applications, such as radio control receivers for model aircraft and boats. They were also used in early hearing aids and no doubt many other devices where space was limited. When I first became interested in flying radio-controlled models in the mid 1960s, some model boat enthusiasts were still using valve equipment. It would appear that the survival rate was considerably better in boats than in aircraft. A comparison of the two is interesting in that the new transistorised transmitters were fully self-contained in a handheld unit, whereas a valve transmitter was housed in a sizable cabinet that stood on the ground, with a separate hand control for the operator. What’s more, where the transistorised equipment used six AA cells in the transmitter and a standard 9V battery in the receiver, the valve set required A and B batteries (for filament and plate) in both the transmitter and receiver. The battery complement alone was heavy, bulky and expensive. No wonder their owners couldn’t sell them! Early hearing aids Over the years, valves diminished in size to quite a remarkable degree. This view shows, from left, a 45, 6G8, 6V6, 6BE6 & a Z7OU. The latter is a truly miniature triode. 78  Silicon Chip I often remember Mr Kennedy, a nice old chap I knew in my youth. One interesting aspect about Mr Kennedy was his hearing aid which would have been built using early 1950s technology. Natu­rally, it was an old valve type and heavy on batteries. The hear­ing aid most likely ran on a 1.5V filament battery and a 67.5V B battery, The model 100 Philips “Philipsette” is a particularly good performer for a 4-valve radio. It is a full superhet design with a 5-inch loudspeaker. the latter being made especially for hearing aid appli­cations. Whether all this equipment was self-contained or dis­tributed throughout a number of pockets I never found out but it was probably a single unit. Because of the hearing aid’s heavy battery consumption, it was usually switched off until someone approach­ ed; then there were a few moments of fumbling in a vest pocket to find the switch to turn it on. Once on the air, however, he could carry on a normal conversation without much trouble. That hearing aid – or the manner in which Mr Kennedy used it – had its shortfalls, though. It seemed he could never judge the engine revs when driving his nice new Austin A70. He would back out of his driveway and over a steep gutter with the accel­ erator nearly to the floor. In fact, he managed to scrub out a clutch plate in only 12,000km – but you can’t blame the valves in his hearing aid for that. Those old valve hearing aids worked quite well but they were bulky and battery hungry. Miniaturisation, as such, wasn’t all that important in the valve era. Who really needed a radio any smaller than a 4-valve mantel or, later on, a TV set smaller than a monochrome valve set with a 17-inch screen? Even the car radio manufacturers of those days had learned how to pack comparatively large components into a relatively confined space. But power consumption was another matter. While not all that important for mains-powered equipment, it was a serious matter for battery-operated The STC Bantam is unique in that it is a very small radio that was been built using full sized components. Like the Philips set it is a full superhet design & is a good performer. equipment. As already implied, hear­ ing aids were very costly to run, so much so that they were only turned on when needed. A modern hearing aid, by contrast, will run continuously for, typically, 15 hours a day over about 16 days on a tiny 1.5V battery costing less than a dollar. The same limitations applied to portable receivers but the hardest hit were country people, who depended on battery operated sets for their only contact with the outside world for weeks at a time. And they cost a fortune to run. The military were among the first to explore the benefits of miniaturisation. And one of the first applications, towards the end of World War ll, was the development of an electronic proxim­ity fuse robust enough for use in anti-aircraft shells. Its main feature was the use of printed wiring and components, in place of hard wiring and discrete components. But the real boost to miniaturisation came during the space race days of putting a man on the Moon. Now transistorised equip­ ment shrank to integrated circuit sized equipment, thus allowing lightweight computers and other essential goodies to be packed into those cramped Moon vehicles. That was where miniaturisation really mattered – not in the domestic market! However, these developments eventually spun off to other areas and the integrated circuit has revolu­tionised the electronics industry. Everything has benefited while many new things have been made possible, including This is the view inside the back of the Philipsette. Everything is neat & tidy. December 1994  79 The main reason for compiling all this informa­tion has been for the benefit of younger readers, who may have little or no idea of the various fields in which the old valve has been used. In addition to their use in radio and TV, includ­ing colour TV, valves found use in early computers, sonar, metal detectors, photoelectric devices, radar, long distance telephone communications, electronic organs and radio astronomy – the list is long indeed. Much of today’s electronic wizardry saw its humble beginnings in cumbersome valve operated equipment. The transistor and the integrated circuit have only streamlined some of those old ideas. Humans have short memories and some seem to think that all these modern electronic miracles have happened only in the past 20 years or so This neat little set is unbranded but was obviously made in Australia. It is a TRF design & has severe overload problems when tuned to local stations. However, it is a worthwhile collector’s item due to its very small size. VCRs, CD players, personal computers and engine management systems for cars. Portable chronograph As a matter of interest, I have a fairly high-tech elec­tronic instrument called a portable chronograph. It is approx­imately 23 years old, is not much larger than a brick, has four­ teen ICs in it and operates on three D cells. But what the heck does it do, you may ask. The chronograph is a specially made instrument designed solely to help calculate the velocity of rifle bullets. It accu­rately times a bullet’s passage between two electrical screens spaced exactly five feet apart. If the time and distance are known, the velocity is easily calculated or, in this instance, found from a list of tables. More modern chronographs have photo­electric screens and digital readouts in either feet or metres per second. But what’s all this to do with valves or miniatur­ isa­tion? Well, in the days before my chronograph, there were valve chronographs that did exactly the same thing. With the valve unit, however, it was the size of a large suitcase and that did not include the battery pack which was housed in a smaller suit­case. As I said earlier, valves could do a lot of 80  Silicon Chip things in the field of electronics but they were nowhere near as power or space efficient as modern equipment. I might add that my chronograph has never been serviced and is still in working order. For those who may be interested, a crystal oscillator in the chronograph operates at 400kHz, which translates to 2.5µs per cycle. The count for a humble little .22 long rifle bullet to pass through the timing screens is around 1550, which gives some indication of how fast the count rate is. It will accurately time velocities to Mach lV, which is well beyond the capabilities of any rifle bullet. This photo shows the author’s vintage chronograph. This instrument has been specially designed to measure the time it takes a bullet to travel a given distance. Miniature valve receivers In my collection of valve radios, there are four receivers that deserve a mention in this story on miniaturisation because they are significantly smaller than the average set of their day. What is interesting is that some of these receivers used no specially made miniature parts but used standard size components instead. What’s more, some also maintained the traditional 5-inch (125mm) loudspeaker that was almost an industry standard for 4-valve receivers and although these sets were relatively small, they still had a reasonable sound. Sound quality is one of the characteristics that separate larger valve radios from their smaller transistorised brethren. Valve receivers typically have larger loudspeakers which gives them a decidedly better sound reproduction than transistor sets with much smaller loudspeakers. Play a small transistor radio through a large extension loudspeaker and it will sound a good deal better. The two most common contenders for the title of smallest mantel valve radio would be the STC “Bantam” and the Philips “Philipsette”, as I have heard it called. There is not much to choose from here and both receivers are well packed into their cabinets, with the STC being the most compact. The little Philips receiver (shown in some of the accompa­ nying photographs) was originally bought in 1947 and apart from still being in near perfect condition, came complete with its original sales docket and guarantee card. The Philips valve complement is: ECH35, EBF35, 6V6 and 6X5 rectifier. It is not hard to guess from that line-up that the little set is a superhet and, in this particular case, a very good one at that. I suspect that a reflex circuit gives it its performance. One odd aspect of this receiver is that the circuit does not incorporate AGC (automatic gain control) and special mention is made in the operating instructions about backing off the volume control to avoid “blaring” on the stronger local stations. It might appear as though the little Philips set was made to a price which did not include AGC. It is more likely, however, that the use of a reflex circuit made the provision of AGC too diffi­cult. The tiny unbranded mantel receiver (see photograph) is considerably smaller than the Philips or STC models. It is a 3-valve radio with a bakelite cabinet and a 4-inch (100mm) speaker. This Australian-made midget receiver sounds more like a small transistor radio than a valve radio because of the small speaker. It is a 3-valve TRF (tuned radio frequency) setup, using a 6CU8 (triode/pentode), a 6V6 output and a 6V4 rectifier. It has no AGC, no worthwhile performance, and is more a novelty than a practical radio receiver. Powerful stations produce distorted sound which is not corrected when the volume is reduced. The only way this little receiver will handle strong stations is to use a very short aerial, which is no good for receiving distant stations. It seems fairly obvious that the volume control should be in the RF sec­tion as it was with TRFs of old and not immediately ahead of the output valve, as in this case. The valve radio that really takes the miniaturisation honours is the little Japanese “Starlite”. It really is no larger than a small transistor receiver even though it is a 4-valve unit. It is interesting to note that it is made under license to RCA of America. Externally, it looks just like a little transis­tor radio because it has the same direct drive dial, earphone jack, and general proportions that we have become accustomed to in small pocket radios. A single C cell is used for an A supply and one of the previously mentioned 67.5V hearing aid batteries for The Japanese-made Starlight pocket portable was similar in ap­pearance to later-model transistor radios. It featured a combined volume on/off control, a direct drive dial, a carry handle & an earphone socket. The Starlight 4-valve superhet is neatly constructed so as to fit everything into a confined space. While a remarkable feat in its day, it is now quite obsolescent. the B sup­ply. The C cell would need replacing at fairly regular intervals and may only last a few hours. As the back view of the Starlite shows, the receiver uses four miniature valves (1R5, 1T4, 1U4 and 3S4) in a superhet circuit. The little valve receiver works every bit as well as a transistor radio of comparable size, except that the latter is much more economical on batteries. So, while many ultra-small valve radios have been made in the past, they were more of a novelty than anything else. Of the four receivers mentioned in this article, the only useful ones are the Philips Philipsette and the STC Bantam. These 4-valve super­hets with their 5-inch speakers give excellent performance for their size. Perhaps the STC is the more notewor­thy of the two, as it uses all large-scale components and it does have AGC. There is no waste space in this set. When one compares the STC and Philips with the little TRF receiver, it seems incredible that a TRF circuit was considered as an alternative to a superhet. Price must have been the only consideration. As for the Starlite, its compactness places it in a special category of its own. But how outdated it is today in the light of modern technology. SC December 1994  81 SPECIALS BY FAX If your fax has a polling function, dial (02) 579 3955 and press your POLLING button to get our latest specials, plus our item and kit listing. Updated at the start of each month. HF ELECTRONIC BALLASTS Brand new “slim line” cased electronic ballasts. They provide instant flicker free starting, extend tube life, reduce power consumption, eliminate flicker during operation (high frequency operation), and are “noise free” in operation. The design of these appears to be similar to the one published in the Oct. 94 SILICON CHIP magazine. One of the models even includes a DIMMING OPTION!! Needs external 100K potentiometer or a 0-10V DC source. We have a good but limited stock of these and are offering them at fraction of the cost of the parts used in them! Type A: Designed to power two 32W - 4' tubes, will power two 40W - 4' tubes with no noticeable change in light output, has provision for dimming: $26 Type B: Designed to power two 16W - 18" tubes, will power two 18W - 18" tubes with no noticeable change in light output: $18 MISCELLANEOUS FLAT NOSE PLIERS: $4 per pair. BATTERY CHARGER: S2 accessory set for Telecom Walkabout “Phones”. Includes cigarette lighter cable, fast rate charger, and desktop stand. Actually charges 6 series connected AA Nicad batteries: $27. BATTERY PACKS: Contain 6 AA Nicad batteries wired in series, can easily be pulled apart, used units, satisfaction guaranteed: $2 per pack. LITHIUM BATTERIES: Button shaped with pins, 20mm diameter, 3mm thick. A red led connected across one of these will produce light output for over 72 hours (3 days): 4 for $2. CIGARETTE LIGHTER LEADS: Cigarette lighter plug with 3 metres of heavy duty fig. 8 flex connected. Should suit load currents up to 20A: 5 for $5. SUPERCAPS: 0.047F/5.5V capacitors: 5 for $2. HOUR METER: Non resettable, mains powered (50HZ), WARBURTON FRANKI, 100,000 Hours maximum, 0.01Hr resolution: $15. PCB MOUNTED SWITCHES 90 deg. 3A-250V, SPDT: 4 for $2. AC POWER SUPPLY: Mains in, two separate 8.5V/3A outputs, in plastic case with mains power lead/plug and output leads/plugs: $15 Ea. MONITOR PCB’s: Complete PCB and yoke assembly for high resolution monochrome TV monitors (no tube). Operate from 12V DC, circuit and information provided: $15. MODEMS: Complete mains powered non standard 1200 baud Telecom approved modems. We should have brief information available. Limited stock at below the price of the high quality case that these are housed in: $30 for 2 modems. MEDICAL LASER One only water cooled medical laser with selectable outputs: Argon (7W multiline) or Dye laser (1W red). Large water cooled unit with a separate control box and accessories (350kg): $15,000 LEVEL RECORDER One only, Bruel & Kjaer level recorder type 2305, in good condition: $300 82  Silicon Chip DIE CAST BOXES These large (187 x 120 x 56mm) aluminium die cast boxes have several holes drilled in them and have a C&K toggle switch and a 6.25mm phono socket fitted. New units from an unfinished production project: $4 Ea. WELLER SOLDERING IRON TIPS New soldering iron for low voltage Weller soldering stations and mains operated Weller irons. Mixed popular sizes and temperatures. Specify mains or soldering station type: 5 for $10. NICAD BATTERY PACKS Brand new Toshiba 7.2V-2.2AHr Nicad Battery packs in a plastic assembly: $20 Ea. If you purchase three packs we will supply a matching fast charger (90min.) that can charge up to three of these batteries (one at a time). Modern unit that employs “delta V” voltage detection to terminate charge, needs an external 12V-2.2A unregulated supply: $60 for three battery packs and a three way charger. PLUGS/SOCKETS 3 pin chassis mounting socket and a matching covered three pin plug. Good quality components that will handle a few amperes at low voltage: $5 for 4 pairs. DYNAMIC MICROPHONES Low impedance dynamic microphones with separate switch wiring, 3.5mm mic. plug, 2.5mm switch plug, as used on most cassette recorders: $4 Ea. 40mW IR LASER DIODES New famous brand 40mW-830nM IR laser diodes, suit medical and other applications: $90 Ea. Constant current driver kit to suit: $10. HIGH POWER LED IR ILLUMINATOR This kit includes two PCBs, all on-board components plus casing: Switched mode power supply plus 60 high intensity 880nm IR (invisible) LEDs. Variable output power, 6-20VDC input, suitable for illuminating IR responsive CCD cameras, IR night viewers etc. Professional performance at a fraction of the price of the commercial product. COMPLETE KIT PRICE: $60 LOW COST 1-2 CHANNEL UHF REMOTE CONTROL Late in October we will have available a single channel 304MHz UHF remote control with over 1/2 million code combinations which also makes provision for a second channel expansion. The low cost design includes a complete compact keyring transmitter kit, which includes a case and battery, and a PCB and components kit for the receiver that has 2A relay contact output! Tx kit $10, Rx kit $20. Additional components to convert the receiver to 2 channel operation (extra decoder IC and relay) $6. INCREDIBLE PRICES: COMPLETE 1 CHANNEL TX-RX KIT: $30 COMPLETE 2 CHANNEL TX-RX KIT: $36 ADDITIONAL TRANSMITTERS: $10 FIBRE OPTIC TUBES These US made tubes are from used equipment but in excellent condition. Have 25/40 mm 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. The gain of these is such that they would produce a good image in approximately 1/2 moon illumination, when used with suitable “fast” lens, but they can also be IR assisted to see in total darkness. Our HIGH POWER LED IR ILLUMINATOR kit, and the IR filter are both suitable for use with these tubes. The superior resolution of these tubes would make them suitable for low light video preamplifiers, wild life observation, and astronomical use. Each of the tubes is supplied with an 9V-EHT power supply kit. INCREDIBLE PRICES: $120 for the 25mm intensifier tube and supply kit. $180 for the 40mm intensifier tube and supply kit. We also have a good supply of the same tubes that may have a small blemish which is not in the central viewing area!: $65 for a blemished 25mm intensifier tube and supply kit. $95 for the blemished 40mm intensifier tube and supply kit. SIEMENS VARISTORS 420VAC 20 joule varistors that are suitable for spike protection in Australian 3 phase systems: 10 for $5. TAA611C ICs TAA611C Audio power amplifier ICs, no more information: 5 for $5. INTENSIFIED NIGHT VIEWER KIT SC Sept. 94. See in the dark! Make your own night scope that will produce good vision in sub-starlight illumination! Has superior gain and resolution to all Russian viewers priced at under $1500. We supply a three stage fibre-optically coupled image intensifier tube, EHT power supply kit, and sufficient plastics to make a monocular scope. The three tubes are supplied already wired and bonded together. $290 for the 25mm version $390 for the 40mm version We can also supply the lens (100mm f2: $75) and the eyepiece ($18) which would be everything that is necessary to make an incredible viewer! MAINS POWERED GAS LASER Includes a professional potted mains power supply and a new 3mW red tube to suit. One catch, this supply requires a 4-6V (TTL) enable input which is optically isolated, to make the unit switch ON. Very low consumption from a 4.5V battery. $100 for a new 3mW tube plus a TTL mains power supply to suit. SUPER DIODE POINTERS - HEADS These pointers probably represent the best value when you compare them on a “brightness per dollar” basis. They are about 5 times brighter than 5mW/670nm pointers! They have an output of 2.5mW at 650nm, which is about equal in brightness to a 0.8mW HE-NE tube!! SPECIAL INTRODUCTORY PRICE: $150 We will also have available some of the 3V diode modules used in these pointers at approximately $125, and also some 2.5mW/635nm laser diode modules with special optics at approximately $280. VIDEO TRANSMITTERS Low power PAL standard UHF TV transmitters. Have audio and video inputs with adjustable levels, a power switch, and a power input socket: 10-14V DC/10mA operation. Enclosed in a small metal box with an attached telescopic antenna. Range is up to 10m with the telescopic antenna supplied, but can be increased to approximately 30m by the use of a small directional UHF antenna. INCREDIBLE PRICING: $25 TDA ICs/TRANSFORMERS We have a limited stock of some 20 Watt TDA1520 HI-FI quality monolithic power amplifier ICs, less than 0.01% THD and TIM distortion, at 10W RMS output! With the transformer we supply we guarantee an output of greater than 20W RMS per channel into an 8ohm load, with both channels driven. We supply a far overrated 240V-28V/80W transformer, two TDA1520 ICs, and two suitable PCBs which also include an optional preamplifier section (only one additional IC), and a circuit and layout diagram. The combination can be used as a high quality HI-FI Stereo/Guitar/P.A., amplifier. Only a handful of additional components are required to complete this excellent stereo/twin amplifier! Incredible pricing: $25 for one 240V-28V (80W!) transformer, two TDA1520 monolithic HI-FI amplifier ICs, two PCBs to suit, circuit diagram/layout. Some additional components and a heatsink are required. LIGHT MOTION DETECTORS Small PCB assembly based on a ULN2232 IC. This device has a built in light detector, filters, timer, narrow angle lens, and even a siren driver circuit that can drive an external speaker. Will detect humans crossing a narrow corridor at distances up to 3 metres. Much higher ranges are possible if the detector is illuminated by a remote visible or IR light source. Can be used at very low light levels, and even in total darkness: with IR LED. Full information provided. The IC only, is worth $16! OUR SPECIAL PRICE FOR THE ASSEMBLY IS: $5 Ea. or 5 for $20 GAS LASER SPECIAL We have a good supply of some He-Ne laser heads that were removed from new or near new equipment, and have a power output of 2.5-5mW: very bright! With each head we will supply a 12V universal laser power supply kit for a ridiculous TOTAL PRICE of: $89 AA NICADS Brand new AA size Saft brand (made in France) 500mA Hr. batteries, also have solder connections (can be removed): $2 Ea. or 10 for $ 16. TWO STEPPER MOTORS PLUS A DRIVER KIT This kit will drive two stepper motors: 4, 5, 6 or 8 eight wire stepper motors from an IBM computer parallel port. Motors require separate power supply. A detailed manual on the COMPUTER CONTROL OF MOTORS plus circuit diagrams/descriptions are provided. We also provide the necessary software on a 5.25" disc. Great “low cost” educational kit. We provide the kit, manual, disc, plus TWO 5V/6 WIRE/7.5 Deg. STEPPER MOTORS FOR A SPECIAL PRICE OF: $42 CAMERA FLASH UNITS Electronic flash units out of disposable cameras. Include PCB/components and Xenon tube/reflector assembly. Requires a 1.5V battery. $2.50 IR LASER DIODE KIT auto iris lens. It can work with illumination of as little as 0.1Lux and it is IR responsive. Can be used in total darkness with Infra Red illumination. Overall dimensions of camera are 24 x 46 x 70mm and it weighs less than 40 grams! Can be connected to any standard monitor, or the video input on a Video cassette recorder. NEW LOW PRICE: $199 IR “TANK SET” A set of components that can be used to make a very responsive Infra Red night viewer. The matching lens tube and eyepiece sets were removed from working military quality tank viewers. We also supply a very small EHT power supply kit that enables the tube to be operated from a small 9V battery. The tube employed is probably the most sensitive IR responsive tube we ever supplied. The resultant viewer requires low level IR illumination. Basic instructions provided. $140 BRAND NEW 780nm LASER DIODES (barely visible), mounted in a professional adjustable collimator-heatsink assembly. Each of these assemblies is supplied with a CONSTANT CURRENT DRIVER kit and a suitable PIN DIODE that can serve as a detector, plus some INSTRUCTIONS. Suitable for medical use, perimeter protection, data transmission, IR illumination, etc. For the tube, lens, eyepiece and the power supply kit. 5mW VISIBLE LASER DIODE KIT We include a basic diagram-circuit showing how to make a small refrigerator-heater. The major additional items required will be an insulated container such as an old “Esky”, two heatsinks, and a small block of aluminium. $40 Includes a Hitachi 6711G 5mW-670nm visible laser diode, an APC driver kit, a collimating lens - heatsink assembly, a case and battery holder. That’s a complete 3mW collimated laser diode kit for a TOTAL PRICE OF: $75 BIGGER LASER We have a good, but LIMITED QUANTITY of some “as new” red 6mW+ laser heads that were removed from new equipment. Head dimensions: 45mm diameter by 380mm long. With each of the heads we will include our 12V Universal Laser power supply. BARGAIN AT: $170 6mW+ head/supply. ITEM No. 0225B We can also supply a 240V-12V/4A-5V/4A switched mode power supply to suit for $30. 12V-2.5 WATT SOLAR PANEL SPECIAL These US made amorphous glass solar panels only need terminating and weather proofing. We provide terminating clips and a slightly larger sheet of glass. The terminated panel is glued to the backing glass, around the edges only. To make the final weatherproof panel look very attractive some inexpensive plastic “L” angle could also be glued to the edges with some silicone. Very easy to make. Dimensions: 305 x 228mm, Vo-c: 18-20V, Is-c: 250mA. SPECIAL REDUCED PRICE until the end of 94!: $20 Ea. or 4 for $60 Each panel is provided with a sheet of backing glass, terminating clips, an isolating diode, and the instructions. A very efficient switching regulator kit is available: Suits 12-24V batteries, 0.1-16A panels, $27. Also available is a simple and efficient shunt regulator kit, $5. CCD CAMERA Monochrome CCD camera which is totally assembled on a small PCB and includes an SOLID STATE “PELTIER EFFECT” COOLER-HEATER These are the major parts needed to make a solid state thermoelectric cooler-heater. We can provide a large 12V-4.5A Peltier effect semiconductor, two thermal cutout switches, and a 12V DC fan for a total price of: $45. ITEM No. 0231 RUSSIAN NIGHT VIEWER We have a limited quantity of some passive monocular Russian made night viewers that employ a 1st generation image intensifier tube, and are prefocussed to infinity. CLEARANCE: $180 INFRA RED FILTER A very high quality IR filter and a RUBBER lens cover that would fit over most torches including MAGLITEs, and convert them to a good source of IR. The filter material withstands high temperatures and produces an output which would not be visible from a few metres away and in total darkness. Suitable for use with passive and active viewers. The filter and a rubber lens cover is priced at: $11 DOME TWEETERS Small (70mm diam., 15mm deep) dynamic 8ohm tweeters, as used in very compact high quality speaker systems: $5 Ea. We also have some 4" woofers: $5 Ea. VIDEO ZOOM LENSES Wire antenna - attached, Microphone: Electret condenser, Battery: One 1.5V silver oxide LR44/G13, Battery life: 60 hours, Weight: 15g, Dimensions: 1.3" x 0.9" x 0.4". $25 REEL TO REEL TAPES New studio quality 13cm-5" “Agfa” (German) 1/4" reel to reel tapes in original box, 180m-600ft: $8 Ea. MORE KITS-ITEMS Single Channel UHF Remote Control, SC Dec. 92 1 x Tx plus 1 x Rx $45, extra Tx $15. 4 Channel UHF Remote Control Kit: two transmitters and one receiver, $96. Garage/Door/Gate Remote Control Kit: Tx $18, Rx $79. 1.5-9V Converter Kit: $6 Ea. or 3 for $15. Laser Beam Communicator Kit: Tx, Rx, plus IR Laser, $60. Magnetic Card Reader: professional assembled and cased unit that will read information from plastic cards, needs low current 12VDC supply-plugpack, $70. Switched Mode Power Supplies: mains in (240V), new assembled units with 12V-4A and 5V-4ADC outputs, $32. Electric Fence Kit: PCB and components, includes prewound transformer, $28 High Power IR LEDs: 880nm/30mW/12deg. <at> 100mA, 10 for $9 Plasma Ball Kit: PCB and components kit, needs any bulb, $25. Masthead Amplifier Kit: two PCBs plus all on board components: low noise (uses MAR-6 IC), covers VHF-UHF, $18. Inductive Proximity Switches: detect ferrous and non-ferrous metals at close proximity, AC or DC powered types, three wire connection for connecting into circuitry: two for the supply, and one for switching the load. These also make excellent sensors for rotating shafts etc. $22 Ea. or 6 for $100. Brake Light Indicator Kit: 60 LEDs, two PCBs and ten Rs, makes for a very bright 600mm long high intensity Red display, $30. IEC Leads: heavy duty 3 core (10A) 3M LEADS with IEC plug on one end and an European plug at the other, $1.50 Ea. or 10 for $10. IEC Extension Leads: 2M long, IEC plug at one end, IEC socket at other end, $5. Motor Special: these motors can also double up as generators. Type M9: 12V, I No load = 0.52A-15,800 RPM at 12V, 36mm Diam.-67mm long, $5. Type M14: made for slot cars, 4-8V, I No load = 0.84A at 6V, at max efficiency I = 5.7A-7500 RPM, 30mm Diam-57mm long, $5. EPROMS: 27C512, 512K (64K x 8), 150ns access CMOS EPROMS. Removed from new equipment, need to be erased, guaranteed, $4. Green Laser Tubes: Back in stock! The luminous output of these 1-1.5mW GREEN laser diode heads compares with a 5mW red tube!: $490 for a 1-1.5mW green head and a 12V operated universal laser inverter kit. 40 x 2 LCD Display: brand new 40 character by 2 line LCD displays with built in driver circuitry that uses Hitachi ICs, easy to drive “standard” displays, brief information provided, $30 Ea. or 4 for $100. RS232 Interface PCB: brand new PCB assembly, amongst many parts contains two INTERSIL ICL232 ICs: RS232 Tx - Rx ICs, $8. Modular Telephone Cables: 4-way modular curled cable with plugs fitted at each end, also a 4m long 8-way modular flat cable with plugs fitted at each end, one of each for $2. 12V Fans: brand new 80mm 12V-1.6W DC fans. These are IC controlled and have four different approval stamps, $10 Ea. or 5 for $40. Lenses: a pair of lens assemblies that were removed from brand new laser printers. They contain a total of 4 lenses which by different combinations - placement in a laser beam can diverge, collimate, make a small line, make an ellipse etc., $ 8. Polygon Scanners: precision motor with 8 sided mirror, plus a matching PCB driver assembly. Will deflect a laser beam and generate a line. Needs a clock pulse and DC supply to operate, information supplied, $25. PCB With AD7581LN IC: PCB assembly that amongst many other components contains a MAXIM AD7581LN IC: 8 bit, 8 channel memory buffered data acquisition system designed to interface with microprocessors, $29. EHT Power Supply: out of new laser printers, deliver -600V, -7.5KV and +7kV when powered from a 24V-800mA DC supply, enclosed in a plastic case, $16. Mains Contactor Relay: has a 24V-250ohm relay coil, and four separate SPST switch outputs, 2 x 10A and 2 x 20A, new Omron brand, mounting bracket and spade connectors provided, $8. FM Transmitter Kit - Mk.II: high quality high stability, suit radio microphones and instruments, 9V operation, the kit includes a PCB and all the on-board components, an electret microphone, and a 9V battery clip, $11. FM Transmitter Kit - Mk.I: this complete transmitter kit (miniature microphone included) is the size of a “AA” battery, and it is powered by a single “AA” battery. We use a two “AA” battery holder (provided) for the case, and a battery clip (shorted) for the switch. Estimated battery life is over 500 hours!!: $11. High Power Argons: the real thing! Draw pictures on clouds, big buildings etc., with a multiline water-cooled Argon laser with a few watts of output. “Ring” for more details. Argon-Ion Heads: used Argon-Ion heads with 30-100mW output in the blue-green spectrum, will be back in stock soon, priced at around $400 for the “head” only, power supply circuit and information supplied. Two only 10:1 video zoom lenses, f=15150mm, 1:1.8, have provision for remote focus aperture and zoom control: three motors, one has a “C” mount adaptor, 150mm diam. by 180mm long: OATLEY ELECTRONICS MINIATURE FM TRANSMITTER Phone (02) 579 4985. Fax (02) 570 7910 $390 Ea. Not a kit, but a very small ready made self contained FM transmitter enclosed in a small black metal case. It is powered by a single small 1.5V silver oxide battery, and has an inbuilt electret microphone. SPECIFICATIONS: Tuning range: 88-108MHz, Antenna: PO Box 89, Oatley, NSW 2223 Bankcard, Master Card, Visa Card & Amex accepted with phone & fax orders. P & P for most mixed orders: Aust. $6; NZ (airmail) $10. December 1994  83 REMOTE CONTROL BY BOB YOUNG Building a complete remote control system for models This month, we begin what will be a series of articles on the design & construction of a complete R/C system for models. In its simplest form, it will be a 4-channel transmitter & re­ceiver, while the most complex version will cater for up to 24 channels. Over the past 20 years, R/C systems for models have come a long way and in that time there has been nothing published in Australia on the design and construction of these systems, with the exception of my own article in “Electronics Australia” in 1966 (or CONTROL PANEL 12 thereabouts). This unit was a state-ofthe-art single channel relay receiver featuring such advanced concepts as a super-regen valve front end driving transistorised (gasp) audio and relay driver stages. I received enquires for that kit for over 10 years so this CH24 MODEL 12 CONTROL PANEL 3 CH6 CH5 MODEL 3 CONTROL PANEL 2 CH4 MODULATOR TRANSMITTER CH3 MODEL 2 CONTROL PANEL 1 CH2 CH1 MODEL 1 CLOCK Fig.1: up to 24 channels could be controlled via this proposed transmitter system. It could be applied to model aircraft & possibly enable formation flying, with each operator having loose control for trim & one master operator controlling the formation. It could also be applied to a large model railway layout. 84  Silicon Chip one should take us all into the 21st cen­tury. From the outset, I must stress that the following system is intended for those who want a reliable, simple-tobuild system which will use over the counter components. If you are looking for a fully computerised system then look elsewhere, for you will not find it in this series. The design as presented will be a modular system featuring a 24-channel transmitter, made up of 3 x 8 channel encoder mod­ules and a plug-in transmitter module which will be available in both AM and FM versions. All channels may be switched, propor­tional or a mixture of both. The versatility of this system is so great that it will be impossible for me to present the full system in all its forms. Instead, suggestions will be made along the way, to lead the reader towards construction of the system that best suits his or her own requirements. The basic system presented and thus available in kit form will consist of a 2-stick, 4-channel Tx case, an 8-channel encod­er with mixing and servo reversing, and an RF module (either AM or FM). The choice and layout of the mechanical arrangement of the last four channels will be left to the reader to decide. These may be slide controls (proportional) or switched as for retracts, dropping bombs, waving pilots, turning on and off devices such as tape decks, internal lighting, etc. The circuits and PC boards presented will at all times show the way to the full 24-channel system so that readers may then construct their own mechanical layouts to suit their own parame­ters. A mechanical layout for These views show the top side & underside of the AM receiver module which will be described in detail next month. Most of the components, apart from the coils, ceramic resonator & crystal, are surface mount devices which have the virtue of being able to withstand very high levels of vibration & impact shock. a full 24-channel system will not be presented, although photographs of some 16 and 24-channel transmitters will be shown. The receiver is a three-PC board affair with PC board 1 for the receiver, PC board 2 for the first 8-channel decoder, and PC board 3 for the 16-channel add-on decoder to take the system to 24 channels. All of the above will be housed in a robust alumini­um case measuring approximately 43 x 33 x 35mm. The photos show one of the three prototype AM receiver boards currently being test flown. The construction article for this receiver will appear next month, followed by the 8-channel decoder and then the 16-channel add-on. FM or AM? The receiver also comes in an AM or FM version, so you can see that we have covered all possibilities from a cheap 2-channel AM system to an all-singing, all-dancing 24-channel FM system for those who love spending money. Now before we proceed any further I must stop to explain a few things to the hardheads who by now will have collapsed on the floor laughing. “24 channels! Who is he kidding? How do you control 24 channels with two thumbs? Perhaps he is planning to sell these things to Octopi, HO, HO, HO”. “And AM? He has set the movement back 20 years!” Over the years, I have built and installed literally hun­dreds of oddball R/C installations for all kinds of uses – from the R/C boat pond in Coney Island, Luna Park to real time acting robots in Hollywood, USA. All of these installations had one thing in common – they all used 24 channels or more. Now there are two factors which played an important part in making such installations viable: (1) the operator had more than two hands(!); and (2) some of these installations had a very elabo­rate tape deck control which allowed us to prefabricate a tape by programming four channels at a time. Thus on the first pass, channels 1-4 were programmed, then channels 5-8 and so on. In this way, a full 24-channel tape could be assembled very easily by one man. The film robots used this system. Computers have long ago rendered this system obsolete but, at the time I was in Holly­wood, we led the world in this type of system. I was voted an honorary puppet master by the camera crews, many of whom had worked with the Star Wars robots and had learned to hate them with a passion. That was before they stuck little men inside them. But that is another story. Getting back to the more than two hands business, some of the funniest scenes in my memory of my Hollywood days is when the director would announce a sudden change to the scene which of course rendered the pre-programmed tape completely useless. We would then need up to 10 people to get their hands onto the transmitter at once, so that we could ad-lib the controls. You should try it some time – very cosy, especially with those Holly­wood starlets. As people with more than two hands are hard to find in Australia, and keeping in mind the above experience, we must make it possible to get as many hands around the transmitter as possi­ ble if there is no tape control. Preferably this should be done in comfort and this can be done quite simply by breaking the control panel into smaller sections. By plugging six 4-channel control boxes into the master transmitter, we could have six people controlling a 24-channel robot in complete comfort if not very economically. A more practical application would be to plug 12 2-channel control boxes into the master transmitter. We can now, for example, control 12 model cars very economically, both financially and from a spectrum point of view, from the one transmitter. This was how the Luna Park installation was set up, only the control boxes were huge, fitted as they were with what looked like Mississippi paddle steamer steering wheels and engine con­trol pedestals. The boats were all fitted with 24-channel receiv­ers and to code a boat to any one control station, we simply plugged the two servos into the appropriate channels. Thus, boat number nine used channels 17 and 18. Let me tell you, keeping RF out of the encoder with half a mile of cabling running around the room was my biggest headache. Keeping water out of the boats was their biggest headache. Corrosion was the bane of their lives and eventually led to the demise of the system. Multiple applications Thus, you can see that this system is not designed solely for model aircraft but for the person who has a situation in which radio control will help solve their control problems. The uses are myriad and include the control of multiple model trains on a single layout, multi-channel robots, commercial R/C car tracks and a host of other applications not named. As stated previously, the versatility of the system is staggering and limited only by the operator’s imagination. As an extreme example, one very interesting concept which arises from having 24 channels is the possibility of accurately controlling up to six aircraft in formation from a single trans­mitter. Formation flying has long been a dream of R/C pilots but the difficulties are formidable. The main problem is depth per­ception but there are many more, not the least being the coordi­nation called for when six people attempt to get their timing into sync – not all that important on a slow moving robot but life and death stuff at 200km/h. Using this system, it will be possible to plug six 4-channel transmitters into December 1994  85 the master transmitter. From there, with what amounts to an elaborate dual control system, each pilot hands over control to the master pilot who then proceeds to fly all six aircraft at once. By now the hardheads, who hopefully sobered up and picked themselves up off the floor during the previous explanation, will be back there doubled up in hysterics. “All six models flown by one pilot! The man has left the planet and now resides in cloud cuckoo land!” Allow me to complete the explanation. I did say with what amounts to a very elaborate dual control system. However this system has one major difference. By injecting the control inputs through the mixer, some control would be retained by each pilot, sufficient to allow each pilot to trim his aircraft to keep it in formation, in spite of small differences in speed, wind gusts, turning radius of the model, etc. Thus, whilst the master pilot initiates all manoeuvres, each pilot is still in control, working to keep his model in perfect formation. At any time, control could be taken back by any one pilot, thus allowing complete safety at all times. It is an interesting concept and I will be curious to see if anyone takes up the challenge. Hot potato So now we come to the hot potato. Why present an AM system at all? Everybody knows that FM is better than AM so why do it? I have dealt with this subject at length before so I will just recap what I said previously. FM undoubtedly is much better than AM in audio transmission, especially when the full 50-70kHz shift is used. This results in an excellent signalto-noise ratio with the results we all expect. What everybody does not seem to realise is that model FM systems do not use FM. They use NBFSK (narrow band frequency shift keying), with the emphasis on narrow band. Most model systems shift the carrier by only 400500Hz, a paltry figure which results in signal-to-noise ratios no better than AM, or in most cases worse. From a home constructor’s point of view, NBFSK also presents serious difficulties with regard to setting up the transmitter and viewing the modulation. This calls for specialised instru­ ments which few home constructors have access to. The situation with AM, on the other hand, calls for very few instruments, the most elaborate being a CRO if one is available. The modulation on a 29MHz transmitter is clearly visible, even on a cheap 10MHz oscilloscope. However the most serious problem with FM in regard to the concepts presented in this series is the cost of crystals. Here we are talking about a single transmitter using up to 12 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 + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 979 5644 & quote your credit card number; or fax the details to (02) 979 6503. Please specify 3.5-inch or 5.25-inch disc. 86  Silicon Chip receiv­ers in some installations. The difference in the price of AM and FM crystals is great ($17 per pair for AM versus $49 per pair for FM – most model shops will not sell you one crystal). Multiply that price difference by 12 and you can spend hundreds of unne­cessary dollars on one installation. I say unnecessary because AM will perform equally as well as NBFSK in 99 out of 100 applications, even in model aircraft, despite what the pundits will try to tell you. What annoys me in this argument is that people come to me all the time asking does AM still work, so great is the anti-AM propaganda. We flew for more than 20 years on AM systems and very successfully I might add. I am still flying with AM and feel no need to go to NBFSK. Where NBFSK does outperform AM is in two areas. One is on very crowded model fields where the maximum utilisation of the frequencies available is required and 10kHz band spacing is the order of the day. Second, the AGC time constants must be very carefully set in AM model aircraft receivers to avoid glitches due to rapidly fluctuating AGC levels. On the first count, most applications of the system to be presented do not call for narrow band spacing. Quite the contrary in fact, because here I am proposing a single transmitter to control 12 models – no frequency clutter here. On the second count, model trains do not roar past the transmitter at 200km/h, so the AGC time constants do not present much of a worry. Also the AM receiver to be presented has an excellent AGC system and is free of this problem. So to reiterate, unless you love spending money unnecessar­ily or are forced to go to NBFSK for your application, use AM. There are also some interesting applications which arise from the system to be presented. The modular receivers lend themselves to all sorts of applications. The system can be tuned over the range from 27-50MHz with suitable coil and capacitor changes, allowing use in such applications as garage door openers, etc. Next month, I will present the circuit description of the receiver followed the month after by a detailed procedure on how to build it. See you SC then. PRODUCT SHOWCASE For further information, contact Philips Scientific & Industrial, 34 Waterloo Rd, North Ryde, NSW 2113. Phone (02) 888 8222. ProToolbox – an enhancement for Protel Function generator has 40V P-P output Fluke Corporation has released the model PM 5138A function generator which has an output voltage of up to 40 volts peak to peak. This is envisaged as being particularly useful in the automotive industry, where test voltages need to be higher than vehicle system levels in the 12-16V range. The output is short-circuit proof and the impedance is selectable between 50 and 6000. Seven standard waveforms are available, including sine, square, triangle, positive and negative pulses and ramp functions. In addition, up to 24 arbitrary waveforms can be stored in the instrument’s nonvolatile memory and extensive modulation capabilities are available, including AM, FM, PSK, burst, gating and linear or logarithmic sweep. Frequency bandwidth is 0.1mHz to 10MHz, with variable duty cycle and a sweep mode with variable sweep times from 10ms to 999 seconds. Digital IC tester for TTL & CMOS You’ve dreamed about be­ing able to test ICs before installing them and now you can do it with this little tester called the Leaper-1. A little larger than a typical digital multimeter, it features a 16-character alphanumeric liquid crystal display and a 24-pin zero insertion force socket so it can accept a wide selection of ICs. The Leaper-1 will test 4000 and 4500 series CMOS chips, 41/44 series DRAMs and 7400 series TTL devices. Average search time is 0.8 seconds and the unit will identify an unknown logic IC when AUTO is selected and will test the IC and display PASS or FAIL for its truth table. For further information, contact L&M Satellite Supplies, 33-35 Wickham Rd, Moorabbin, Vic 3189. Phone (03) 353 1763. Protel for DOS has become the standard when designing and laying out printed circuit boards. With its schematic-to-board design capabilities, single and multilayer boards can be designed quickly and easily. Now there’s a utilities collection from SWR Computer Solution called ProToolbox which will make Prate! even more popular with designers and enthusi­asts. ProToolbox is a collection of six useful utilities that expand Protel for DOS, giving it more options and greater versatility. The first of these utilities, Parts”, will generate a parts and wire list from any schematic or Autotrax net list. It can produce ei­ther full or summary parts lists with all components given sorted compo­nent identifiers (ie, Rl, R2, etc). It’s great for making sure that you haven’t left any components off the circuit! The output is in a form suitable for importing into spreadsheets or data­bases, both DOS and Windows ver­sions. “ReAnnotate” allows you to reannotate or renumber component identifiers on a PC board pattern and it automatically back annotates to the schematic drawing. This is great for making components easier to identify on the board, as well as eliminating skipped numbers, making servicing a much easier task. instead of having identifiers randomly spread around the board, they can be now allocated to different regions which you can specify by defining board “strips”. All components inside a particular strip will be annotated in numerical order, with each strip following on from the last. The strips can be made any size and work both vertically and horizontally. Other options include the ability to lock in particular components to prevent renumbering as well as a choice of numbering schemes. December 1994  87 Programmable power supplies from Tektronix Tektronix has introduced a range of four program­ mable power supplies with keypad entry for complex testing routines. Two models have GPIB interfaces which suport the SCPI (standard commands for pro­grammable instruments) format. The PS2510 and PS2510G (G indicates GPIB interface) deliver 0-36V and up to 3.5A, while the PS2511 and PS2511G deliver 0-20V and up to 7A. All models allow programs with up to 100 different combinations of voltage, current and timing to enable the automation of repetitive tests. For further information, contact Tektronix Australia Pty Ltd, 80 Waterloo Rd, North Ryde 2133. Phone (02) 888 7066. “Rotate” allows you to rotate either components or entire PC board patterns or sections by any angle in 0.01 degree increments. Rotation can be about the component reference point or any desired point on the board. No more of Autotrax’s 90-degree-only moves! If you’re looking to pack in the components into a tiny space then this program will help you manoeu­vre them into the optimum position. “NetComp” is a quality-control utility which allows the user to compare two net lists and report on any discrepancies between them. You can compare two PC board patterns, PC board to schematic, schematic to PC board or two schematic files. Smart error sensing within the program reduces the number of unnecessary or duplicate errors displayed. This is a handy little program which can find errors in any part of the de­sign process from schematic drawing to the final board artwork. It could save lots of hassles by getting rid of the bugs before production begins. The last two utilities are conver­sion programs, one for PC board files and the other for graphics informa­ tion. The former is called “PCBtoCSV”, which converts the information from a PC board file into a CSV (Comma Separated Variable) file, which is suitable for databases. The file contains component identifiers and values, as well as board coordinates which is not only great for robotic assembly plants and pick & place machines but for generating parts lists straight from the PC board file. The last utility is “SchToDXF” which, as its name might suggest, con­verts the schematic file to a DXF draw­ing file. This utility makes it so much easier to import schematic files into drawing programs such as AutoCAD and Generic CAD. All of the programs run under DOS and are very easy to use with file Electronics parts trays from Jaycar These trays are made from white styrene with little rectangular com­ partments, making them suitable for small components such as tran­ sistors resistors, capacitors and di­ o des. Each tray has 36 compart­ments, each measuring 70 x 24 x 15mm, in three rows of 12. The overall dimensions are 395 x 260 x 20mm deep. They can be supplied with a snugly fitting lid, which would help avoid accidental spill­age. Being white, the tray 88  Silicon Chip can be directly written on for the purposes of labelling using a permanent marker. The tray is available from all Jaycar Electronics stores at $6.95 each (Cat HB-6340), while the lids are priced at $2.75 (Cat HB-6341). menus and 3tep-by-step instructions, making it a fast and suitable addition for Protel. This collection really does add the finishing touches to what is already an industry-standard PC design package. For more information and a free demonstration disc, call Scott Robinson at SWR Computer So­lutions on (015) 213 400. Kenwood car amplifiers have built-in equaliser For some years now car audio prod­ ucts have been designed with equalis­ing circuits separate to the main power amplifier. By incorporating the equal­iser directly into the amplifier, Ken­wood has been able to dispense with the need for a dash mounted unit, creating a less cluttered appearance. Designed to fit under the seat or in a boot installation, the KAC-Q74 delivers 180W per channel maximum in stereo (bridge) mode or can deliver 80 watts into four channels for front and rear sound. Both models can also be configured for Kenwood’s unique trimode operation driving 3 channels, for example left and right channels, with the third channel driving a subwoofer. The 5-band equalizer (one for each channel on the KAC-Q74) provides ±10dB in 12 steps at 50Hz, 200Hz, 800Hz, 3.2kHz and 12.8kHz. The KAC­ Q74 is priced at $699 and the KAC­-Q62 at $499 and are provided with gold plated line jacks and speaker ter­minal screws. For further information on these and other Kenwood car products call Kenwood on (02) 746 1888. Audio engineering degree from Sydney The University of Sydney is currently planning a program for diploma and masters degrees in audio engi­neering. The program will be based in the University’s Department of Archi­tectural and Design Science and will utilise courses from the Master of De­ sign Science program together with courses from the Departments of Music and Electrical Engineering and the School of Physics. Scheduled to begin in 1996, the program will initially be available on a part-time basis, two nights per week. Some courses will be available in 1995, with successful passes being credited towards enrolment in 1996. Portable DRAM tester The Chroma 3201A is a portable instrument capable of testing all types of dynamic memory devices such as 30-pin 8 or 9-bit SIMMs, with 64Kb, 256Kb, 1Mb, 4Mb or 16Mb capacity, IBM PS2 72-pin 32 or 36 bit SIMMs and all types of single DRAM chips. Adapters to suit non-standard memory modules are also avail­able. Key features of the unit include cycling and bouncing of the test­ ing voltage setup; quick, normal and loop test modes; automatic search mode; statistics mode for The diploma will require two years’ study while the masters degree will require three years. The program is open to people with undergraduate degrees or other terti­ary qualifications, members of the Audio accumulated error counts; and in­ built printer interface. For further information, contact Nucleus Computer Services Pty Ltd, 9b Morton Avenue, Carnegie, Vic 3163. Phone (03) 569 1388. Engineering Society and peo­ple with substantial experience in the audio industry. For further information, contact Associate Professor Fergus Fricke on (02) 351 2686. Affordable vice has tilting head Scope Laboratories has released a tilting head vice with a capacity of 90mm. The base of the Panavice Model 201 ‘junior’ has three mounting holes and is designed to be fastened to a bench. A ball joint connects the head of the vice to the base. A single locking action allows the head to be fixed in any position. The jaws are deep and have four V­grooves to grip any round object or a PC board. With a recommended price of $49.50, it is suitable for modellers and electronics enthusiasts alike. For more information, contact Scope Laboratories, 3 Walton St, Airport West, Melbourne, Vic 3042. Phone (03) 338 1566. December 1994  89 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. FM stereo tuner wanted I would be grateful if you could supply a design for an FM stereo tuner or tell me where I could buy a suitable kit. (R. C., Montagu Bay, Tas.) • We have not published an FM stereo tuner and since you can buy a complete tuner from retail outlets such as Brashs very cheaply there is not much chance that we will ever do so. We would need a strong indication from readers wanting a good FM stereo tuner before we would commit to do the design work. We did, however, publish a low-cost FM mono tuner, in the November 1992 issue of SILICON CHIP. We can supply a photostat copy of this article for $7 including postage. A kit for the project is avail­able from Dick Smith Electronics or Jaycar Electronics. Another fast nicad charger wanted I recently built your fast charger for 2 and 4-cell nicad battery packs. It operates as advertised and I am very Testing a microwave oven leakage detector If a microwave oven leakage detector does not register then you’d think that either the oven door seal is excellent or the detector is dead or the oven is not working, or both. You’re uncertain and no wiser. How do you check a microwave oven leakage detector to see if it’s working properly? I have found that when you place one (eg, Dick Smith Electronics Cat. Y-4100) inside an oven, its internal detec­tor diode goes short circuit, even under the lowest cooking power. Also, what are and how does the safety threshold on the meter scale compare with the relevant Standards Association of 90  Silicon Chip pleased with it. My interest is (apart from electronics) radio controlled model aircraft, which use 8 and 4-cell packs for transmitter and receiver respectively. I wrote to you and you gave me the value of the voltage sense resistor to enable charging 8-cell nicad packs. You also said that a 20VDC supply is needed. Have you published any project or circuit that increases a 12VDC output to 20VDC (or 24VDC) at currents of at least one amp? If so, could you please advise which issue? (M. B., Kew, Vic). • We have published two circuits which could serve as the basis for a suitable design: the DC-DC battery charger, September 1988, which uses an LM3524 and the Portable SLA Battery Charger, July 1992, which uses an MC34063. Both these designs were for SLA batteries and both used boost converters. Perhaps the September 1988 design is the most relevant. However, using this circuit to boost the voltage to feed the TEA1100 seems wasteful since it should be possible to make the TEA1100 drive its own boost circuit. While we cannot give details of how Australia figures? Before I buy a new one and wreck it, could you suggest a better way of testing it? (V. S., Launceston, Tas). • There would seem to be two ways to approach your question of how to test these devices. First, you could check the internal detector diode with your multimeter and if it is intact, you can probably assume that the whole device works. Second, you could try it in the vicinity of a cellular phone or UHF CB transceiver. These won’t be on the right frequency but they may put out enough signal to show a response. Any test involving a microwave oven itself must be regarded as dangerous either to the user or to the tester. to do this at the moment, we will add this to our list of project ideas to be published in the future. Obtaining stereo TV signals While reading through the June 1994 issue of SILICON CHIP, I came across the article entitled “Convert the Phono Inputs on Your Amplifier”. I have a stereo system by JVC, model DR-E1BK/DR-E1LBK, which has a double cassette, AM/FM tuner and phono inputs. I also have an old HMV TV set, model A480I (48cm). The circuit in your article has two inputs and two outputs. Can this circuit be used from the TV set which has a single speaker into the phono inputs of the JVC stereo? What changes are needed for mono input to get stereo output? (K. R., Boonah, Qld). • Obtaining stereo TV signals requires a decoder to process the two sound IF signals from the TV’s tuner, at 31.133MHz and 31.375MHz. The required circuit is quite complex and you would need a fair degree of know­ ledge in order to be able to extract the IF signals from your TV set. We have considered designing a stereo TV decoder based on a VCR but the necessary IF signals would still need to be extracted from inside the machine, a task that would be difficult in many VCRs. The only stereo TV decoder circuit that we know of was published about 10 years ago and was available as a kit from Dick Smith Electronics but this was discontinued quite some time ago. Dimmer buzz a problem I am interested in building your High Power Dimmer (August 1994) to dim a number of transformer-driven quartz halogen lamps. However, before embarking on this project, I have one concern: will the transformers deliver an audible buzz when the dimmer is operating? The reason I ask is that when I have tried dimming one of these with a commercial 400W dimmer (Arlec), there was a con­ siderable noise generated within the transformer. Your article states that the Triac in your dimmer is per­forming a similar function to that in any commercial light dimmer and I assume that its output is therefore similar also. (A. S., Denmark, WA). • Since the dimmer uses a phase controlled Triac, it is highly likely that the transformers will buzz audibly. This buzzing is almost impossible to avoid because even if the transformer lami­ nations themselves don’t buzz due to magnetostriction, the wind­ings will inevitably rattle. There are a few ways to eliminate this problem. First, you could try “potting” the transformer(s) in epoxy resin to silence them. Second, you could house them in a soundproof box but you would have to ensure that they did not overheat; such transform­ers may rely on adequate ventilation to remain reasonably cool. Third, you could take the more elegant approach and use a switch­mode DC dimmer on the 12V side of the transformer. You would have to rectify and filter the 12VAC and this would result in a DC supply of about +18V. This could then be controlled by a switchmode circuit which would ideally operate at 20kHz or above so that it would be completely inaudible. Unfor­ tunately, we have not published a circuit which directly meets these requirements but the low cost speed controller featured in the November & December 1992 issues could be used as a starting point. This circuit uses FETs and switches at a maximum speed of 2.5kHz. This might be good enough but could be modified fairly simply to run at 20kHz. If required, we can supply photostat copies of the relevant articles at $7 each, including postage. Servo possibilities I am writing to you in regards to the article “Simple Drivers For Radio Control Servos” in the May 1994 issue of SILI­CON CHIP. I took great interest in the first circuit as I am trying to build a computer controlled robot arm for my senior electronics project at school. Servos seem to be the easiest way to Problems with stepper motor controller I recently purchased the stepper motor controller kit, as described in the January 1994 issue. The transistors supplied were BD680 and BD681. I have constructed the unit to operate with bipolar stepper motors; ie, all components have been fitted to the PC board. Without the stepper motor (only one at this time) connected and with a supply of 12V DC, the unit draws between 90mA and 120mA and the 7805 5V regulator gets fairly hot. All other components remain cool or cold. Using the TEST part of the program set for Card 2 and the jumper positioned for the same card, I am not getting a reading on the various pins as advised. However, I am getting a 12V reading on pins 1 & 2 at the same time for Card 1. I would greatly appreciated any assistance you may be able to provide. (J. B., Tingalpa, Qld). control a robot arm as they will always return to the same position for a given input pulse width and so eliminate the need for a complex feedback system. I intend to use the 8-bit data from the printer port on my PC. The circuit seems fairly simple, with the pulse width being set by VR1, VR2, VR3 and a 100Ω resistor. I have decided to replace VR1 with the output of a digital-to-analog converter with a variable current output. The chip is an 8-bit DAC0800LCN (available in the Altronics catalog). I have obtained a copy of the pinouts of this chip but I don’t know what some are for and how they are used in a circuit. Could you give any suggestions as to how this IC could be used in this circuit. I have included a copy of the pinouts for your convenience. Just out of interest I decided to have a go at building the second circuit. On looking through my spares box, I didn’t have a CMOS 4001 quad 2-input NOR gate. However, I did have what ap­ peared to be a TTL compatible 74LS02 quad 2-input NOR gate. I figured it should work as the supply voltage was 5V and they were both 2-input NOR gates but the circuit simply • You have two problems; that of the 5V regulator getting hot and the other of not getting the correct voltages on the outputs when you run the test program. The 5V regulator could be drawing excess current for one of two reasons. The first could be that one of the outputs of the logic chips is shorted, either to the supply, ground or more likely another output. If so, it is a matter of checking the board carefully, especially around the pads of the ICs. The other reason could be that pin 11 of the 74HC374 is floating and not connected to the parallel port. This could lead to the pin oscillating and thus drawing higher than normal cur­rent from the regulator. Check the voltage on pin 11 – it should be high. When data is loaded into the latch, it should pulse low and return high. You should also check to see that the data that is being written to the latch is appearing on the outputs (pins 19, 2, 16, 5, 15, 6, 12 & 9). refused to func­ tion. I tried another 74LS02 but the results were the same, so I purchased a CMOS 4001 from my local electronics store and the circuit worked perfectly. Why wouldn’t the 74LS02 work? The only explanation I can give is that for a 5V supply, the 74LSxxx series uses over 2V for logical on and under 0.8V as logical off, whereas the CMOS 40xx series uses over 3.5V as a logical on and under 1.5V as logical off. Am I correct in assuming this to be the reason or is there some other explanation? (L. T., Sawtell, NSW). • Unfortunately, we have not published any information on the DAC­ 0800LCN D/A converter. The only source of this information would be the relevant National Semiconductor databook. As far as the circuit using the 4001 is concerned, the reason why it did not work with a 74LS02 is that it is a much lower impedance device. It should be possible to make the circuit work but you will have to reduce the feedback impedance by around 200 times; ie, reduce the 1.8MΩ resistor to say 10kΩ, increase the 0.1µF capacitor to 2.2µF SC and so on. December 1994  91 Index to Volume 7: January-December 1994 Features 01/94   4 The World Solar Challenge 01/94  7 Mazda's Collision Avoidance System 01/94 30 Luxman A-371 Amplifier & D-351 CD Player 01/94 37 Active Filter Design For Beginners 01/94 88 Review: Kenwood’s DCS-9120 Oscilloscope 02/94   4 Airbags: More Than Just Bags Of Wind 02/94 10 Data On The ISD259OP Voice Recorder IC 02/94 22 Instrumentation Programming The Graphical Way 03/94   6 High Energy Batteries For Electric Cars 03/94 14 Latest Nissan Uses Head Up Display 03/94 44 Switching Regulators Made Simple 03/94 80 Manufacturer’s Data On The LM3876 IC 04/94 36 Microcontrollers With Speed 04/94 56 PC Product Review: The Video Blaster 04/94 70 Spectrum Analysis With The Icom R7000 04/94 82 G-Code: The Easy Way To Program Your VCR 05/94   8 The Fingerscan ID System 05/94 14 Passive Rebroadcasting For TV Signals 06/94   4 News: Nissan’s Future Electric Vehicle 06/94 11 Moving Map Display For Helicopters 06/94 29 The Emperor’s New Clothes 06/94 69 Review: Visual Basic 3.0 - The New Standard? 07/94  6 More TV Satellites To Cover Australia 07/94  9 Silicon Chip/Tektronix Reader Survey Winners 07/94 77 Review: Yokogawa’s 7544 01 5-Digit Multimeter 07/94 80 TV Coder: The Sequel To Video Blaster 08/94  4 Review: Philips Widescreen Colour TV Set 08/94 80 Review: Philips P65 UHF CB Set 09/94   6 How To Use The TEA1100 Fast Nicad Charger IC 09/94 87 Review: Metex M3850 Digital Multimeter 10/94   4 Dolby Surround Sound: How It Works 11/94   6 Anti-Lock Braking Systems: How They Work 11/94 80 How To Plot Patterns Directly To PC Boards 12/94   4 Cruise Control: How It Works 92  Silicon Chip 12/94 10 The Great RAM Scam Of 1994 12/94 54 The Stamp Microcontroller Board Engine Management 01/94  8 Pt.4: Changing The System 02/94 42 Pt.5: The Oxygen Sensor - How It Works 03/94 32 Pt.6: System Operation - How It Works 04/94   4 Pt.7: Other Input Sensors 05/94   4 Pt.8: Books & Journals 06/94   6 Pt.9: Fault Diagnosis & Codes 07/94 22 Pt.10: A Look At Ignition Systems 08/94 14 Pt.11: Fuel & Air Systems 09/94 16 Pt.12: Fueltronics’ Turbo Control Centre 10/94 14 Pt.13: Electronic Transmission Control Vintage Radio 01/94 52 Realism Realized - The Precedent Console Receiver 02/94 82 Building a Simple 1-Valve Receiver 03/94 76 Refurbishing A Trio 9R-59D Communications Receiver 04/94 86 Bandspread Tune-Up For An Old Astor Multiband Receiver 05/94 80 Trash Or Treasure - Recognising The Good Stuff 06/94 80 Timber Cabinets, Antique Dealers & Vintage Radio Prices 07/94 84 Crackles and What Might Cause Them 08/94 84 Watch Out for Incorrect Valve Substitutions 09/94 80 Building A Classic Crystal Set 10/94 78 The Winners Of The Hellier Award 11/94 70 Resurrecting A Pair Of Old AWA C79 Chassis 12/94 78 Valves & Miniaturisation: Some Remarkable Receivers Serviceman’s Log 01/94 56 HMV 12642/JVC 7765AU; Sharp VC-505X VCR 02/94 50 NEC FS-6831S; National TC2178 M14 03/94 50 Samsung CB-515F; Akai CTK115 04/94 40 Rank-NEC C-1413; AWA-Thorn 3504 05/94 58 HMV B4803A; National TC-2658 M14 06/94 40 Hitachi-Fujian HFC-1421B F87PT; Hitachi VT-M818E VCR 07/94 66 Sharp CX1020 Portable Colour TV/Radio/Cassette Tape Recorder; Rank Arena C2205 08/94 56 National NV-370 VCR; Hitachi Fujian HFC-1425B TV 09/94 40 Panasonic VCRs: NV-J1A; NVFS90A; NV-FS65A; NV-L20 10/94 40 AWA 4303 “Q”; HMV 12641 11/94 32 Contec MSVR-5383; Samsung CB-349F; HMV 8010501 Portable 12/94 72 Panasonic TC-29V26A; Contec MSVR-5383 Remote Control 01/94 70 More On Servicing Your R/C Transmitter 03/94 72 How To Service Servos And Winches 05/94 88 How To Service Servos And Winches, Pt. 2 06/94 72 Servicing Batteries & Chargers 08/94 65 Modellers With Dedication 09/94 84 Modellers with Dedication, Pt. 2 11/94 83 Modellers with Dedication, Pt. 3 12/94 84 Building A Radio Control System For Models; Pt. 1 Computer Bits 01/94 65 Even More Experiments For Your Games Card 02/94 79 Experiments For Your Games Card, Pt. 4 03/94 66 A Binary Clock Of The Software Kind 04/94 54 Experiments For Your Games Card, Pt. 5 05/94 74 What’s Your Free Disc Space? 06/94 66 BIOS Interrupts: Your Computer’s Nuts & Bolts 07/94 72 BIOS Interrupts: Speeding Up The Keys 10/94 88 Placing Directories Into Programs 11/94 77 Review: Visual BASIC For DOS 12/94 42 The Electronics Workbench Revisited Circuit Notebook 01/94 24 Amended Pulser Probe (see July 1993) 01/94 24 Beta Measurements With An Analog Multimeter 01/94 25 Induction Motor Speed Controller 01/94 25 Single-Pot Wien Bridge Oscillator 02/94 20 Using Two Train Controllers To Operate One Section 02/94 20 Replacing Selenium Cells With Solar Cells 02/94 20 Digital Tachometer & Dwell Angle Meter 03/94 48 Resistance & Capacitance Meter 03/94 48 Adding Latched Outputs To The IR Train Controller Projects to Build 05/94 18 Fast Charger For Nicad Batteries 05/94 24 Two Simple Servo Driver Circuits 05/94 34 Induction Balance Metal Locator 05/94 54 Dual Electronic Dice 05/94 64 Multi-Channel Infrared Remote Control 06/94 14 200W/350W Mosfet Amplifier Module 06/94 20 Coolant Level Alarm For Cars 06/94 30 An 80-Metre AM/CW Transmitter For Amateurs 06/94 36 The Stoney Broke Loudspeaker System 06/94 54 Convert Your Phono Inputs To Line Inputs 06/94 62 PC-Based Nicad Battery Monitor 07/94 17 SmallTalk: A Tiny Voice Digitiser For The PC 07/94 32 4-Bay Bow-Tie UHF Antenna 07/94 43 The PreChamp 2-Transistor Preamplifier 07/94 54 Steam Train Whistle & Diesel Horn Simulator 07/94 62 Portable 6V SLA Battery Charger 08/94 24 High-Power Dimmer For Incandescent Lights 08/94 37 Microprocessor Controlled Morse Keyer 08/94 40 Dual Diversity Tuner For FM Microphones 03/94 49 Low Power Voltage Booster 03/94 49 Simple Quiz Game Adjudicator 04/94 10 Battery-Life Indicator For Radio Microphones 04/94 10 Block Signalling For Model Trains 04/94 11 Simple 4-Step Voltage Comparator 05/94 32 Battery Voltage Indicator For Cars 05/94 32 Light Meter Adaptor For A DMM 05/94 33 Delayed Reset For PCs & Compatibles 05/94 33 Six-Way Decision Maker Uses Two ICs 06/94 58 Variable Constant Current Load 06/94 58 RF Actuated CW Sidetone Unit 06/94 59 Photographic Lightmeter Adapter 06/94 59 Discrete Monostable Multivibrator 07/94 14 Positive To Negative DC Inverter 07/94 14 Floating Constant Current Limit 07/94 15 Tester For IR Remote Controls 07/94 15 Analog To Digital Interface Circuit 08/94 50 Theft Protection For Automatic Cars 08/94 50 Sensitive Lightmeter For The Darkroom 08/94 51 Low-Cost LED Level Display 08/94 51 Optoelectronic Pickup For Ignition Systems 09/94 24 Timer For Security Lights 09/94 25 Tester For Radio Control Servos 09/94 25 Automotive Voltage Regulator 10/94 24 Test GPO For Workshops 10/94 24 Flashing Battery Monitor 10/94 25 PC Alert - A Simple Watchdog Alarm 10/94 25 Auto-Shutoff For Battery Circuits 11/94 64 Super Bright LED Brake Light Array 11/94 64 12-24V Circuit Tester For Cars & Trucks 11/94 64 Display Dimmer For LED Clocks 11/94 65 Low Cost Photo Timer 12/94 16 Power Supply For Subsidiary Amplifier 12/94 16 Rotary Encoder Decoder 12/94 17 Simple 1-Chip Logic Probe 12/94 17 6V To 12V Converter 12/94 17 Errata For LED Brake Light Array 01/94 16 40V 3A Variable Power Supply 01/94 40 Switching Regulator For Solar Panels 01/94 44 Printer Status Indicator For PCs 01/94 50 Simple Low-Voltage Speed Controller 01/94 80 Control Stepper Motors With Your PC 02/94 16 90-Second Message Recorder 02/94 26 Compact & Efficient 12-240VAC 200W Inverter 02/94 46 Single Chip Audio Amplifier 02/94 56 6-Metre Handheld Transceiver 02/94 58 Novel LED Torch 02/94 66 40V 3A Variable Power Supply, Pt.2 03/94 16 Intelligent IR Remote Controller 03/94 22 50W Audio Amplifier Module 03/94 38 Level Crossing Detector For Model Railways 03/94 56 Voice Activated Switch For FM Microphones 03/94 62 Simple LED Chaser 04/94 16 Remote Control Extender For VCRs 04/94 22 Sound & Lights For Level Crossings 04/94 29 Discrete Dual Supply Voltage Regulator 04/94 32 Low-Noise Universal Stereo Preamplifier 04/94 60 Digital Water Tank Gauge Notes & Errata 01/94 94 Solar Powered Electric Fence, April 1993 01/94 94 UHF Remote Switch, December 1989 04/94 93 Stereo Preamplifier With IR Remote Control, September, October & November 1993 06/94 93 Champ Audio Amplifier, February 1994 06/94 93 Remote Control Extender For VCRs, April 1994 06/94 93 Induction Balance Metal Locator, May 1994 07/94 92 12-240VAC 200W Inverter, February 1994 07/94 92 Fast Charger for Nicad Batteries, May 1994 08/94 52 Simple Go/No-Go Crystal Checker 08/94 68 Nicad Zapper 09/94 18 Automatic Discharger For Nicad Battery Packs 09/94 31 MiniVox Voice Operated Relay 09/94 34 Image Intensified Night Viewer 09/94 54 AM Radio For Aircraft Weather Beacons 09/94 66 Dual Diversity Tuner For FM Microphones, Pt.2 09/94 80 Classic Crystal Set 10/94 26 Beginner’s Dual Rail Variable Power Supply 10/94 37 Talking Headlight Reminder 10/94 42 Electronic Ballast For Fluorescent Lights 10/94 65 Temperature Controlled Soldering Station 11/94 14 Dry-Cell Battery Rejuvenator 11/94 20 Novel Alphanumeric Clock 11/94 36 UHF Radio Alarm Pager 11/94 53 80-Metre DSB Amateur Transmitter 11/94 66 Twin-Cell Nicad Discharger 12/94 18 Dolby Pro-Logic Surround Sound Decoder; Pt. 1 12/94 29 Clifford - A Pesky Little Electronic Cricket 12/94 32 An Easy-To-Build Car Burglar Alarm 12/94 60 A 3-Spot Low Distortion Sinewave Oscillator 12/94 84 Building A Radio Control System For Models; Pt 1 Amateur Radio 02/94 56 Convert An Inexpensive WalkieTalkie To The 6-Metre Amateur Band 03/94 60 Lowe’s HF-150 General Coverage Shortwave Receiver 05/94 86 The Rhombic: A High Gain Wire Antenna For HF 06/94 84 Review: Kenwood’s TS50S HF Transceiver 09/94 63 Using Two-Line Keplerian Elements To Track Satellites 12/94 58 AR8000 Handheld Scanner Reviewed 09/94 93 Microprocessor-Controlled Nicad Battery Charger, September 1993 09/94 93 Discrete Dual Supply Voltage Regulator, April 94 09/94 93 Fast Charger For Nicad Batteries, May 1994 09/94 93 4-Bay Bow Tie UHF Antenna, July 1994 09/94 93 Dual Diversity FM Tuner, Pt.1, August 1994 10/94 93 40V/3A Adjustable Power Supply, January/February 1994 10/94 93 12-240VAC 200W Inverter, February 1994 12/94 17 High Brightness LED Brake Light Array, Circuit Notebook, November 1994 December 1994  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. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 979 6503. REAL TIME ICE!!! The only way to go. MOTOROLA 6805 EMULATOR and programmers. Prices and data from Graham Blowes, Mantis Micro Products, 38 Garnet Street, Niddrie 3042. Phone (03) 337 1917 (a/h), (03) 575 3349 (b/h). Fax (03) 575 3369. _____________ _____________ _____________ _____________ _____________ COLLINS 51J4 communications receiver. 500kHz - 30MHz. $300 ono. Phone (02) 450 1602. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ REVOX C274 4TRK REEL TO REEL, fully optioned, control track, autolocator, etc. Fully serviced, beautifully kept superfluous machine. New $11,000, sell $6500. Ring Andrew 03 817 4566. R/C MOTOR SPEED CONTROLLER IC: (PIC 16C71) for R/C models etc. Intelligent, PWM output, $25 (includes p&p). Mark Griffin, 2 Nish Pl, Fraser ACT 2615. Ph (06) 274 8417 (ah). DON’S SHORT FORM KITS: PIC­ 16C54-58/71/84 Universal PCB $23; Basic Stamps $65; Serial Driven 18 I/O $70; Parallel Driven 64 I/O $38; Relay8 PCB $10-$20; Z80 Dev. $38-$52; 8K-4Mb Print Buff. $38-$52. Promo Disk for all projects $2. Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. Phone (03) 338 6286. Parallax “BASIC STAMP”: 8 I/O pins, board space includes proto­typing area. Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Card No. ✂ ❏ Bankcard   ❏ Visa Card   ❏ Master Card Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 KIT SPEAKERS We can obtain any drivers worldwide. Dynaudio, Vifa, Scanspeak, Morel. Wide range of enclosures. Full consulting Service Available Home Theatre Specialists For further details contact: Australian Audio Consultants Box 1031, Aldinga Beach, SA 5173 Phone or fax on (085) 56 6370 YUGA ENTERPRISE BA, LA, LB, LC, UPA, UPB, UPC, TA, Buy TBA, TDA, TEA, & 2SA, 2SB, 2SC, Sell ese 2SJ, 2SK, SAA, Japan STA, STK, STR, ICs & tors HA, AC, KA, KIA, Transis IX, LM, MN, PA TEL: (65) 741 0300 FAX: (65) 749 1048 705 Sims Drive #03-09 Shun Li Industrial Complex Singapore 1438 TRANSFORMER REWINDS ALL TYPES OF TRANSFORMER REWINDS Program it on a PC (only 33 instructions) with development kit, which includes one “BASIC STAMP” ($270). Xpress post $8. Extra modules ($79.85) also Chipset and Resonator to make your own $30.25 each. Xpress Post $5 set. Send one, two or three 45c stamps for up to 19 application notes, average 6 per envelope. Parallax Distributor and technical support in Australia MicroZed Computers, PO Box 634, Armidale, NSW 2350. Facsimile (067) 728 987. MicaSOFT Electronics and Computing tutor program, written in UK, ideal for TAFE, schools or individual use. Now available in Australia. Send 4 x 45c stamps for demo disk (tell us what size). MicroZed Computers, PO Box 634, Armidale 2350. WEATHER FAX programs for IBM XT/ATs *** “RADFAX2” $35 is a high resolution, shortwave weather fax, Morse & Rtty receiving program. Suitable for CGA, EGA, VGA and TRANSFORMER REWINDS Reply Paid No.7, PO Box 1058, St Marys, NSW 2760. Ph: (02) 833 1146. Fax: (02) 623 5559. Hercules cards. Needs SSB HF radio & Radfax decoder. *** “SATFAX” $45 is a NOAA, Meteor & GMS weather satellite picture receiving program. Needs EGA or VGA plus “WEATHER FAX” PC card. *** “MAXISAT” $75 is similar to SATFAX but needs 2Mb expanded memory (EMS 3.6 or 4.0) and 1024 x 768 SVGA card. All programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, Qld 4005. Phone (07) 358 2785. MEMORY & DRIVES PRICES AT DECEMBER, 1994 SIMM (all 70ns) Parity/No Parity 1Mb 30-pin $57/55 4Mb 30-pin $192/185 2Mb 72-pin $130 4Mb 72-pin $230/210 8Mb 72-pin $480/440 16Mb 72-pin $740/670 32Mb 72-pin $1520/1340 MAC 8Mb P’BOOK CO-PROCESSORS 387S/DX to 40 $405 $90 LASER PRINTER HP with 2Mb $200 COMPAQ CONTURA 8Mb $550 DRAM DIP 1Mb x 1 256 x 4 70ns 70ns $7.20 $7.20 IBM PS.2 THINKPAD L40/N33 90/95 8Mb 8Mb 4Mb $655 $513 $230 TOSHIBA 3100SX 44/6400 4Mb 4Mb $285 $265 SUN SPARC 10/20 16Mb SPARC 10/20 64Mb $965 $4080 DRIVES – SEAGATE 261Mb 16ms 3yr wty $230 545Mb 14ms 3yr wty $335 1052Mb 9ms 5yr wty $695 Sales tax 21%. Overnight delivery. Credit cards welcome. RING FOR LATEST PRICES 1st Floor, 100 Yarrara Rd, PO Box 382, Pennant Hills, 2120. Tel: (02) 980 6988 Fax: (02) 980 6991 PELHAM INTELLIGENT INFRARED RECEIVER (ref SILICON CHIP, March 94). Now with 8 outputs. Use your TV or VCR infrared remote control trans­mitter to control your TV or hifi appliances with an intelligent infrared receiver kit. Also available infrared transmitters, preprogrammed and learning models. For details call BENETRON P/L (018) 20 0108. U N U S UA L B O O K S : E l e c t r o n i c Devices, Fireworks, Locksmithing, Radar Invisibility, Surveillance, SelfProtection, Unusual Chem­ istry and more. For a complete catalog, send 95 cents in stamps to Vector Press, Dept S, 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. AVAILABLE FROM MicroZed Computers PO Box 634, ARMIDALE 2350 V (067) 722 777 F (067) 728 987 See advert in these columns 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) 979 5644 & quote your credit card number; or fax the details to (02) 979 6503. Please specify 3.5-inch or 5.25-inch disc. December 1994  95 SmallTALK for PCs: voice digitiser for 286’s and up Play speech on your PC’s speaker with no sound card! 3 minute version $34.95 HDD version $39.95 Optional QLB/LIB libraries $14.00 All orders add $3.05 p+p. Send your cheque/order to: RAT Electronics AUSTRALIA PO Box 641, Penrith, NSW 2750 Ph: (047) 77 4745 Fax: (047) 77 4745 Microprocessor For Stereo Preamplifier Now back in stock: the 68HC705-C8P pre-programmed micro­pro­cessor for the Infrared Remote Controlled Stereo Preamplifier (Silicon Chip, Sept.-Oct. 1993). Also suits the Remote Volume Control (May & June, 1993). Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Phone (02) 9795644; Fax (02) 979 6503. PO Box 434, Brighton, SA 5048. BINARY CLOCK - OCTOBER 1993: complete documentation supplied, includes introduction to binary, how it works, PLD source list­ings, conversion tables. Kit with PC board and all components $75 plus $5 p&p. Optional Z frame stand (includes spacers and chassis DC connector) $25 plus $5 p&p. Available from Prototype Electronics, 1/29 Stewart St, Parra­ matta, NSW 2124. Phone (02) 890 2960; Fax (02) 630 3148. Pay by cheque, money order, credit card. PRINTED CIRCUIT BOARDS for the hobbyist. For service & enquiries contact: T. A. Mowles (08) 326 5590. 68705 DEVELOPMENT SYSTEM: In Circuit Simulator/Emulator and SECONTRONICS Advertising Index COMPONENTS, COMPUTERS, ELECTRON TUBES S/H TEST EQUIPMENT, COMPUT­ ER REPAIRS Access Communications ..............8 RECYCLED EPROMS: ALL ARE CLEANED, ERASED AND BLANK TESTED. 2716 2732 2764 27128 27256 $1.50 ea or 10 for $12 $1.50 ea or 10 for $12 $2.00 ea or 10 for $16 $3.00 ea or 10 for $26 $3.50 ea or 10 for $32 Aust Audio Consultants...............95 Av-Comm..................................9,89 David Reid Electronics................25 TRANSISTORS, ICs, DIODES 2N3440 $0.50 ea or 10 for $4 2N7000 $0.80 ea or 10 for $6 TIP122 $1.20 ea or 10 for $10 74HC04 $0.60 ea or 10 for $5 1N5060 diodes 100/$10 or 1000 for $70 7406 $0.25 ea or 25 for $5 LM380N $2.50 ea or 10 for $20 DAC O8EP $5.00 ea or 10 for $45 Dick Smith Electronics........... 12-15 QQV07/50 $15 6SG7 $6 1S2 $3 6AS7 $8 Oatley Electronics.................. 82-83 VALVES: 12AV7 $4 1B3GT $5 6J6WA $5 3D21 6U8A 6080WA 6X5GT $6 $6 $9 $5 Instant PCBs................................95 Jaycar ................................... 45-52 Macservice....................................3 MicroZed Computers...................95 Pelham........................................95 Phone, mail or fax your orders. Credit cards accepted for orders $20 & over. Mail orders to PO Box 2215, Brookside, Qld 4053. Or shop sales at 143 Grays Rd, Enoggera Qld. Hours: Thursday 4pm-9pm; Sat 9am-4pm. Phone (07) 353 4919, Fax (07) 855 1014. RAT Electronics ..........................96 programmer board. Suppor ts all 68HC705 range including C4, C8, J2, K1, P9, C9, D9 & 68705P3, U3, R3 microcontrollers. For more information contact Oztechnics, PO Box 38, Illawong NSW 2234, Phone (02) 541 0310, Fax (02) 541 0734 Email oztec<at>ozemail. com.au. Silicon Chip Binders..................IBC WANTED Tortech.........................................77 WANTED: made in USA or Western Europe audio valves, vintage audio equipment and books about valve technology. Contact Wai Kei Leung, Block B, 5th Floor, 7 Kweilin St, Shamshuipo, Kowloon, Hong Kong. Fax: (852) 387 5560. Transformer Rewinds...................95 SILICON CHIP BINDERS These beautifully-made binders will protect your copies of SILICON CHIP. To order just fill in & mail the order form in this issue, or phone or fax your order to: Silicon Chip Publications PO Box 139, Collaroy Beach 2097. Phone (02) 979 5644. Fax: (02) 979 6503. 96  Silicon Chip Altronics ................................ 26-28 RCS Radio ..................................94 Rod Irving Electronics .......... 67-71 Secontronics................................96 Silicon Chip Bookshop.................76 Silicon Chip Projects Book........IFC Silicon Chip Software..................59 Silicon Chip Wallchart..............OBC Yokogawa....................................25 Yuga Enterprise...........................95 _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. • H. T. Electronics, 35 Valley View Crescent, Hackham West, SA 5163. Phone (08) 326 5590.