July 1999 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Collie's new coal-burning power station
Feature: Tiny, Tiny Spy Planes by Bob Young
Book Store
Feature: Sydney's Superstorm by Michael Bath
Project: Build The Dog Silencer by Branco Justic
Project: A 10µH to 19.99mH Inductance Meter by Rick Walters
Project: An Audio-Video Transmitter by John Clarke
Product Showcase
Project: Programmable Ignition Timing Module For Cars; Pt.2 by Anthony Nixon
Subscriptions
Vintage Radio: A mainland Chinese radio receiver from the 1960s by Rodney Champness
Project: An X-Y Table With Stepper Motor Control; Pt.3 by Rick Walters
Feature: CLIO: PC-Driven Loudspeaker Testing by Ross Tester
Project: The Hexapod Robot by Ross Tester
Notes & Errata: Sustain Unit for Electric Guitars, March 1998
Market Centre
Advertising Index
Outer Back Cover

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SPECIAL OFFER: ONLY NORMALLY 269 $ 249 $ Excluding Tax Excluding Tax ( 293 Tax Inc) $ Once oscilloscopes were heavy and clumsy to handle but over the years they have got smaller and smaller. The latest development in this field has just arrived: a digital storage oscilloscope in a handy slim housing, scarcely longer than a pencil and about as thick as your thumb! Despite its small size, its performance can match that of a service oscilloscope. With a sampling rate of up to 20MS/s even signals in microprocessor circuits can be recorded. Using its voltmeter function, numeric AC and DC voltages can be easily measured. The osziFOX has many uses. It can be used for taking measurements in amplifiers, digital circuits, telephone installations, hobby electronics, production-line tests, servicing and on-the-spot measuring. With the supplied software for DOS and Windows (3.1x & Win95) recorded signals can be shown simultaneously on a PC screen using the supplied interface cable. For documentation purposes, the recorded signals can be saved to disk or printed. Technical Specifications Sample rates: 50ns, 100ns, 0.5µs, 1µs, 5µs, 10µs, 50µs, 0.1ms, 0.5ms, 1ms Input ranges: 1V, 10V, 100V No of channels: 1, 1MΩ AC/DC coupled Trigger: Internal, external Resolution: 6 bit Buffer size: Voltmeter Display Supply voltage: PC connection: Accessories: 128 byte AC, DC 16 x 32 backlit LCD 9-13V DC <at> 13mA (cable supplied) D9 to serial port via supplied cable Cables, documentation and software EMONA INSTRUMENTS NSW VIC QLD WA Phone (02) 9519 3933 (03) 9889 0427 (07) 3367 1744 (08) 9361 4200 Fax (02) 9550 1378 (03) 9889 0715 (07) 3367 1497 (08) 9361 4300 ORDER ON LINE: http://www.emona.com.au Contents Vol.12, No.7; July 1999 FEATURES 4 Tiny, Tiny Spy Planes Is it a fly or is it really a miniature aircraft? – by Bob Young 10 Sydney’s Superstorm Australia’s most costly natural disaster – by Michael Bath 67 SPECIAL OFFER: Subscribe At 1998 Prices Beat the magazine price rise – and GST – by subscribing now 80 CLIO: PC-Driven Loudspeaker Testing Low-cost system turns your PC into a professional test centre – by Ross Tester Tiny, Tiny Spy Planes – Page 4. PROJECTS TO BUILD 18 Build The Dog Silencer Fed up with the barking dog next door? This could be the answer to your prayers – by Branco Justic 26 A 10µH to 19.99mH Inductance Meter It uses readily available parts and has a 4-digit LCD – by Rick Walters Build A Dog Silencer – Page 18. 36 An Audio-Video Transmitter Use it to monitor a surveillance camera or to transmit your VCR’s signal to another TV set – by John Clarke 60 Programmable Ignition Timing Module For Cars; Pt.2 All the installation and programming details – by Anthony Nixon 72 An X-Y Table With Stepper Motor Control; Pt.3 Building the Z axis – by Rick Walters & Ken Ferguson 84 The Hexapod Robot Microcontroller fun: build a weird six-leg walker – by Ross Tester SPECIAL COLUMNS 42 Serviceman’s Log TV servicing can be frustrating – by the TV Serviceman 68 Vintage Radio A mainland Chinese radio receiver from the 1960s – by Rodney Champness DEPARTMENTS 2 25 53 56 58 Publisher’s Letter Mailbag Product Showcase Electronics Showcase Circuit Notebook 67 91 93 94 96 10µH to 19.99mH Inductance Meter – Page 26. Video Transmitter – Page 36. Subscriptions Form Ask Silicon Chip Notes & Errata Market Centre Advertising Index JULY 1999 1 PUBLISHER'S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Regular Contributors Brendan Akhurst Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW Bob Young 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: $59 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2 Silicon Chip Collie’s new coalburning power station On Friday, 4th June 1999, Australia’s newest coal burning power station was formally opened at Collie in Western Australia. When all of the current issues are considered, it should be the last of its kind. There is no excuse for building any more of these dinosaurs. It matters not that Collie will be the cheapest to operate of any coal-fired power station in Western Australia, its capital cost means that it should probably not have been built at all. Its capacity is 300 megawatts, it cost $830 million, and it adds just 10% to WA’s grid. On those figures, it appears that the Collie power station cost more than twice the price of equivalent power stations in other states and a good deal more than the cost of a wind-power generating facility. As a basis of comparison, the average capital cost of recent coal-burning power stations in other Australian states is around $1200 per kilowatt. The cost of the wind-power facility at Crookwell (featured in our January 1999 issue) was around $2000 per kilowatt). However, a wind-power station burns no coal or any other fuel. In any case, you would think that a better option for a new thermal power station in Western Australia would have been a gas-fired system. These days, gas-fired combined-cycle power stations are capable of thermal efficiencies as high as 60%, they have benign combustion products, particularly when compared to coal-fired stations and they leave no huge scar on the landscape, in the form of an open cut mine, ash dumps or cooling towers. And this is without a mention of greenhouse gas emissions. I am also of the opinion that the cost of coal extracted from open-cut mines does not take into account the cost of reinstatement of the environment once mining has stopped. In fact, when you think about it, it’s difficult to see how environmentalists would let any new open-cut coal mine start operation. Mind you, with the low export prices being obtained for Australia’s coal these days, the trend to close rather than start mines will continue. But the most obvious power station option for Western Australia is not a gas-fired one but one based on solar panels. Maybe 10 years ago such an option was not viable but with the advances in solar technology which are forecast for the next five years or so, any future large power station project must seriously consider the solar option. Australia can certainly make the vast number of panels which would be required and I have no doubt we could also make all the inverter and control gear required. In fact, if governments seriously took up the solar option we could become a world leader in this technology. Let’s do it. Leo Simpson ¡¢ *Full details at www.tol.com.au ¤ ¥ ¥ ¥ § ¡ ¢ ¢ ¢ £ ¢ ¢ £¦ ¦ £ ¡ ¡ ¡ E & OE All prices include sales tax MICROGRAM 0799 Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 FreeFax 1 800 625 777 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 JULY 1999 3 Are you absolutely certain that the fly sniffing around your lunch really is a fly? Or is it really Big Brother in disguise? Outrageous? Impossible? Well, no. It could happen – sooner than you think! By BOB YOUNG Micro Aerial Vehicles I N THE RECENT Bruce Willis’ scifi movie “The Fifth Element”, there is a scene in which the baddies send a remote sensor disguised as a cockroach to check on matters at the nerve centre. This poor little creature is abruptly sent to robotic cockroach heaven as a result of being suddenly swatted – scratch one multi-million dollar hitech toy. It was a funny scene and the audience chuckled at such crazy stuff. But is it so crazy? In 1992 the American Defence Advanced Research Projects Agency (DARPA) held a workshop on future technologies for military operations at Rand Corporation, the initiators of the micro air vehicle (MAV) concept. T h e n - s e n i o r- s c i e n t i s t B r u n o Aug-enstien led a panel on micro 4 Silicon Chip vehicles, including aircraft systems ranging in size from a hummingbird down to less than 1cm in diameter. Yes, 1cm; much smaller than a 5c piece! Rand published a widely-circulated report on the work in 1994. The Lincoln Laboratory was initially sceptical but its own research also concluded that MAVs were becoming feasible. What then is an MAV? DARPA’s own definition alludes to a class of significantly smaller vehicles than the traditional UAV (Unmanned Aerial Vehicle). An arbitrary size limit of 150mm has been imposed and to meet the definition an aircraft must not exceed this limit in length, breadth or height. To fully appreciate the quantum reduction in size, compare the proposed 150mm vehicle to the smallest UAV in current service. This is the US Naval Research Laboratory’s “Sender”, a conventional monoplane with a wing-span of 1.2 metres, weighing 4.5kg and featuring a range of 160 kilometres. From that, an MAV represents a startling step! DARPA held an MAV feasibility workshop in November 1995, a briefing to industry in March 1996 and a user and development workshop in October 1996. These were mainly paper exercises with little to show in the way of hardware. The main thrust of all of this from a military point of view is to provide the individual soldier with battlefield surveillance equipment, far in advance of that which currently exists. These aircraft must fit easily into a soldier’s battlefield pack with little trade-off in food and ammunition and require only one man for launch, control and recovery. Thus the aircraft must be autonomous in operation and hence it will not fly like a model aeroplane. These devices must perform reliably in the hands of unskilled operators under very trying conditions. The last thing a soldier in combat needs is to be totally engrossed in controlling a twitchy little brute of an aircraft. Auto stabilisation is therefore a major consideration in the design. I n 1 9 9 7 , D A R PA s t a r t e d a US$35-million, four-year effort to develop and demonstrate affordable MAVs. The agency wants aircraft with a maximum dimension of 152.4mm (6 inches), range of up to 10km and speeds of up to 80km/h for missions that span from 20 minutes to 2 hours. The development programs are aimed at producing vehicles for operations in three main environments: relatively open terrain, urban areas and jungle. These MAVs are to be deployed by hand, by munitions launch or from larger aircraft. Missions would include reconnaissance, targeting, placing sensors, communications relay and sensing dangerous substances. They are viewed as one-use, one-way missions. Stealth is to be a major factor in the design and thus electric propulsion is favoured in this regard. The hope is that such tiny surveillance vehicles will not attract any attention or better still, be mistaken for birds or insects. In 1997, DARPA’s Tactical Technology Office awarded nine Phase 1, US$100,000 small business innovative research contracts to either pursue system development or a specific technology and in so doing signalled that the chase is on. Are there any readers out there that hold any doubts that once the money starts to flow, answers will soon follow? The awarded contracts cover a variety of projects which include a hovering flying saucer called “Hyperav”, a 1.4f/lb thrust turbine, about 76mm long and 43mm in diameter, possibly for use in “Hyperav”, and a solid oxide fuel cell for MAVs which will provide sufficient energy to power a Photo 1: that’s not a giant butterfly, it’s a regular-sized Monarch with a wingspan of about 70mm or so. In front are the aircraft receiver and processor with the video camera at the bottom. The devices on the right are tiny (3mm diameter) actuator motors. On the left is the propulsion motor. 50 gram MAV for several hours as well as providing power for the payload. Ornithopters (flapping wing aircraft) are included in the list, as the problems of Reynolds numbers in extremely small aircraft steer development in that direction. The Reynolds number is an expression of the wing chord (width) to airspeed over the wing. Reynolds numbers reduce as the size goes down. Readers who have followed previous radio control articles will understand only too well just how large a part Reynolds numbers play in successful operation of aerodynamic devices. Flapping wings allow an increase in Reynolds numbers without increasing the size of the vehicle. The faster the wings flap, the higher the Reynolds numbers. The 150mm disc shown in Photo 2 has a Reynolds number of approximately 100,000. Urban and jungle areas tend to require hovering aircraft and orni-thopters are one way of achieving this result. Flapping wings also add to the stealth of the aircraft, as they become more difficult to distinguish from birds. Investigations are also under way into the use of piezoelectric transducers that would resonate thin metallic structures that will actuate the wings in ornithopters. Miniature engines (both internal combustion and turbine) and waste heat recovery devices are also included in the list of Phase 1 grants. There is absolutely no room for waste or inefficiency in these machines. An interesting project grant is for the development of a shirt-button size turbine that will be made of ceramic and produce 13 grams of thrust. The turbine in the engine will spin at 1,000,000 rpm! This will power a 50-gram MAV. One of the most serious problems facing the ultra-miniature aircraft is that of video power. High resolution and frame rate make it easier for an unskilled operator to fly the aircraft but that requires more power for the greater bandwidth. As the size of the aircraft shrinks, propulsive power and hence battery capacities go down but the video power required remains the same. Ultimately, continuing the shrinkJULY 1999 5 age means that all that is left is the video power source, a ridiculous situation. Yet even here, experimental work is already being undertaken into beaming microwave power into the vehicle. However, all of the foregoing is in the future. Let us now look at some of the more practical considerations affecting MAVs. Practical MAVs AeroVironment Inc has made the most hardware progress to date, with one 6-inch disc achieving 22-minute flights. Their Phase 1 study concluded that a disc was the best configuration for the open terrain option since it gave the most wing area and a relatively good lift to drag ratio. At first AeroVironment were achieving only a few seconds for each flight, then 10 seconds, a minute and finally, using NiCd cells, 2.5 minutes. The 22-minute flights were achieved using experimental high-energy lithium batteries costing US$200 each. Photo 2 shows one of the AeroVironment discs whilst Photo 3 shows a mock-up of a projected disc several years from realisation. A novel approach to control actuation is with the use of electrostrictive polymer artificial muscles. These would actuate the controls directly and change their length in direct proportion to the applied voltage. The disc shown in photo 2 uses a simple UHF receiver to give a small antenna size and the combined weight of the receiver with command processor and four actuators is under 3 grams. However, in a disc only three channels are required (throttle, pitch and roll) and this installation comes in at 2 grams. The actuators use “smoovy” motors made by RMB Miniature Bearings in Switzerland and are amongst the world’s smallest. They weigh a mere 0.35 grams each and a 25:1 reduction gearbox is available which boosts the weight by 0.5 gram! Sufficient power is available from the geared motor to drive the control surfaces directly via pushrods. The actuators measure 10.16mm x 3.05mm and are brushless. They move the controls in about 60 discrete steps via the command processor. The discs shown in Photos 2 and 3 use direct drive motors in which the 6 Silicon Chip motor shaft is connected directly to the propeller but this is a very inefficient method. By adding a reduction gearbox to the motor, larger diameter propellers with better Reynolds numbers may be fitted and the motor runs faster and uses less current. This also means that the efficiency of the whole system is better as the endurance of any given size of battery is improved as the current is reduced. However MAV designers are not as concerned with endurance as they are with control, stabilisation and navigation. AeroVironment has built a complete navigation package that weighs 4.5 grams and consumes negligible power. It consists of two gyros (1.8g), a compass (2g) and an anemometer (0.5g). The black & white camera is less than 25mm long and weighs 2.2g. Such is the state of the art at present. What of the future? Future developments By March 2000, the disc is to carry a colour camera, operate at 3km, have a 20-minute endurance and perform automatic flight to way points with dead reckoning navigation using airspeed and magnetic compass. This requires about 10 times more effective TV transmitter power to triple the video range. Various tricks will be used to compensate for this increase in power by using lower frame rates and resolution when possible, steering the ground antenna for higher gain and commanding less power if there is excess signal strength at the TV receiver. Assuming the MAV quest is successful and there is every reason to believe that it will be, we could shortly see the following scenario played out: “The small speck in the sky approaches in virtual silence, unnoticed by the large gathering of soldiers below. In flight, its tiny size and considerable agility evade all but happen-stance recognition. After hovering for a few short seconds, it perches on a fifth floor window sill, observing the flow of men and machines on the streets below. “Several kilometres away, the platoon leader watches the action on his wrist monitor. He sees his target and sends the signal. The tiny craft swoops down on the vehicle, alighting momentarily on the roof. It senses the trace of a suspected chemical agent and deploys a small tagging Photo 2: this disc plane is about 150mm in diamater and can carry a television camera aloft with a link back to earth. Power is required not only to launch and keep the craft flying but also to keep the video system working. Table 1: AeroVironment Proposed 150mm Disc Micro Air Vehicle • • • Line-of-sight operation within 1km radius 10 minute duration Black & white video payload Aircraft Subsystem Weight Peak Power (grams) (mW) Lithium battery 25 0 Propulsion motor 7 4000 Gearbox 1 0 Propeller 2 0 Airframe 4 0 Control actuators 1 200 Receiver & CPU 1 50 Downlink transmitter 3 1200 B&W video camera 2 150 Interface electronics 1 50 Roll rate gyro 1 60 Magnetic compass 1 180 TOTAL 50 5890 device, attaching it to the vehicle. Just seconds later it is back in the sky, vanishing down a narrow alley. Mission accomplished....” (From the introduction to the DARPA web site, www.darpa.mil/tto/mav/ mav_auvsi.html) This is not science fiction but a serious military aim being pursued with relentless determination by groups scattered all over the world. Before scoffing too loudly, spare a thought for the dreamers who have given us notebook computers more powerful than mainframes of 10 years ago or the dreamers who put a model size aeroplane on a solo flight across the Atlantic, as featured in SILICON CHIP last month. We dream and so it will be! The predicted range of 21st century conflict has influenced and motivated the new development. The shift toward a more diverse array of military operations, often involving small teams of soldiers operating in non-traditional environments (eg, urban centres) is already more than evident in post cold war experience. MAVs are envisioned as an asset at the platoon level or below. They will give the individual soldier on-demand information about his surroundings, resulting in greater effectiveness and fewer casualties. Probably the most commonly identified scenario for this type of vehicle is the classic over-the-hill reconnais- Average Power (mW) 0 4000 0 0 0 200 50 300 50 50 60 180 2890 sance mission in which the MAV ranges out some 10km, loiters for an hour or so and sends back real-time images of the terrain below and all of the surprises it may or may not hold in store. Allied to this type of mission is the use by road transport in which an MAV is sent along the road ahead to locate an ambush, downed bridges or road-blocks. However the most dangerous of all conflicts are the house-to-house fighting undertaken in urban situations. Here the MAV will come into its own. While the previous missions could (and actually are) undertaken by more conventional sized UAVs, only a hovering MAV could scout ahead in urban canyons or more demanding still, enter buildings to give the individual soldier a look at what is inside. The savings in casualties could be enormous. Thus there are great benefits to be derived from the quest for SC the successful MAV. Acknowledgments: AeroVironment Inc. (web site www.aerovironment.com) Aviation Week and Space Technology. June 8th 1998. DARPA web site. www.darpa.mil NICAD BOOST BATTERY GPS RECEIVER AND "X" ANTENNA ELEVON ACTUATOR RECEIVE/TRANSMIT CIRCUITRY AND ANTENNAS AIRSPEED AIRSPEED SENSOR SENSOR X,Y,Z, X,Y,Z, AXIS AXIS MAGNETOMETERS MAGNETOMETERS LITHIUM LITHIUM BATTERIES BATTERIES PITCH, PITCH, ROLL ROLL PIEZO PIEZO GYROS GYROS Photo 3: a mock-up of an autonomous MAV fitted with a video camera and downlink. The theory is fine but this MAV is several years from reality. JULY 1999 7 TECHNICAL LOOK: TEN NEW NEW! TCP/IP EXPLAINED By Philip Miller. Published 1997. $ 90 This concise and practical book offers readers an in-depth understanding of the Internet Protocol suite. It assumes no prior knowledge of TCP/IP, only a basic understanding of LAN access protocols, explaining all the elements and alternatives. It leads the reader through the Internet protocols, combining study questions with reference material. Examples of network designs and implementations are given. 518 pages, in paperback, at $90.00. LOCAL AREA NETWORKS: An Introduction to the Technology NEW! SETTING UP A WEB SERVER A complete reference for anyone setting up a web server. Covers all major platforms, software, links and web techniques. It details each step required to choose, install and configure the hardware and software elements, create an effective site and promote it successfully. The book covers the main web server software applications, how they differ, and which work best in each environment. 273 pages, in paperback, at $65.00. NEW! 65 By Tim Williams. First published 1991 (reprinted 1997). By PK McBride & Nat McBride. Published 1999. $ O R D E R H E R E 29 95                 If you want to create web pages for your business or your own home site, but don't know where to start . . . or if you have some experience of Web page design and now need to master all aspects of HTML form then “HTML4.0 Made Simple” is for you. it uses a combination of tutorial approach, carefully focussed examples and quick reference guides. 198 pages, in paperback, at $29.95. TCP/IP EXPLAINED.............................................$90.00 LOCAL AREA NETWORKS..................................$65.00 HTML 4.0 MADE SIMPLE...................................$29.95 SETTING UP A WEB SERVER.............................$65.00 THE CIRCUIT DESIGNER’S COMPANION...........$59.95 ELECTRIC MOTORS AND DRIVES......................$59.95 UNDERSTANDING TELEPHONE ELECTRONICS....$55.00 AUDIO ELECTRONICS........................................$79.00 GUIDE TO TV & VIDEO TECHNOLOGY...............$55.00 EMC FOR PRODUCT DESIGNERS.......................$95.00 THE ART OF LINEAR ELECTRONICS..................$80.00 INTERNET HOME PAGES MADE SIMPLE...........$24.95 DIGITAL ELECTRONICS .....................................$59.95 ESSENTIAL LINUX..............................................$85.00 ORDER TOTAL: $............. 8 Silicon Chip Includes grounding, printed circuit design and layout, the characteristics of practical active and passive components, cables, linear ICs, logic circuits and their interfaces, power supplies, electromagnetic compatibility, safety and thermal management. Aimed at the practising designer who needs straightforward, easy-to-follow advice. 302 pages, in paperback, at $59.95. $ HTML 4.0 MADE SIMPLE $ 65 $ THE CIRCUIT DESIGNER’S COMPANION NEW! By John E. McNamara. 2nd edition 1996. Intended for those who want to become more familiar with local area networks (LANs) without facing the challenge of a 400-page text. The goals of the book are to give prospective LAN users or purchasers familiarity with the concepts involved and to provide a head start for reading more detailed texts. 191 pages, in paperback, at $65.00. NEW! By Simon Collin. Published 1997. 59 95 ELECTRIC MOTORS AND DRIVES NEW! By Austin Hughes. Second edition published 1993 (reprinted 1997). This book is for non-specialist users of electric motors and drives. The author explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction motors (mains and inverter-fed), stepping motors, synchronous motors (mains and converter-fed) and reluctance motors. 339 pages, in paperback, at $59.95. 59 95 $ Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ___________________________________ Postcode_______________ Daytime Phone No. (______) __________________________________ STD  Cheque/Money Order enclosed OR  Charge my credit card –  Bankcard  Visa Card  MasterCard Signature_________________________ Card expiry date______/______ PLUS P&P (if applic): $.............. TOTAL$ AU.................... ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. BOOKSHOP WANT TO SAVE 10%? SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL PURCHASES! TITLES AVAILABLE! UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. $ 55 (To subscribe, see page 53) A very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $55.00. AUDIO ELECTRONICS GUIDE TO TV & VIDEO TECHNOLOGY $ By John Linsley Hood. First published 1993. NEW SECOND EDITION 1998. 80 All you need to get started. Create and design your own Internet home pages that include both text and graphics, using this practical, easy to follow, jargon free guide. This edition has been enhanced and updated and now covers HTML 4.0. 182 pages, in paperback, at $24.95. 79 $ Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback, at $55.00. 55 EMC FOR PRODUCT DESIGNERS NEW! P&P Add $A5.00 per book – Orders over $100 P&P free in Australia. NZ: Add $A10 per book, $A15 elsewhere 24 95 $ DIGITAL ELECTRONICS – A PRACTICAL APPROACH By Richard Monk. Published 1998. $ 59 95 With this book you can learn the principles and practice of digital electronics without leaving your desk, through the popular simulation applications, EASY-PC Pro XM and Pulsar. Alternatively, if you want to discover the applications through a thoroughly practical exploration of digital electronics, this is the book for you. A free floppy disk is included, featuring limited function versions of EASY-PC Professional XM and Pulsar. 249 pages, in paperback, at $59.95. ESSENTIAL LINUX By Steve Heath. Published 1997. By Tim Williams. First published 1992. Second edition 1996. Widely regarded as the standard text on EMC, this book provides all the information necessary to meet the requirements of the EMC Directive. It includes chapters on standards, measurement techniques and design principles, including layout and grounding, digital and analog circuit design, filtering and shielding and interference sources. The four appendices give a design checklist and include useful tables, data and formulae. 299 pages, in soft cover at $95.00. NEW! By Lilian Hobbs. First published 1996. Second edition 1999. By Eugene Trundle. First published 1988. Second edition 1996. $ This practical handbook from one of the world’s most prolific audio designers has been updated and amended to make it the leading practical source of information for those interested in linear electronics and its applications, particularly in the world of audio design. 348 pages, in paperback, at $80.00. DESIGNING INTERNET HOME PAGES MADE SIMPLE By John Linsley Hood. First published 1995. Second edition 1999. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover at $79.00. THE ART OF LINEAR ELECTRONICS NEW! 95 $ Provides all the information and software that is necessary for a PC user to install and use the freeware Linux operating system. It details, setp-by-step, how to obtain and configure the operating system and utilities. It also explains all of the key commands. The text is generously illustrated with screen shots and examples that show how the commands work. Includes a CD-ROM containing Linux version 1.3 and including all the interim updates, basic utilities and compilers with their associated documentation. 257 pages, in paperback, at $85.00. 85 $ NEW! POST 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 December JULY 1999 9 Wednesday, April 14: Sydney’s Superstorm By Michael Bath* At SILICON CHIP, we have something of a fascination about lightning. Perhaps it’s the immense amount of energy involved. Perhaps it’s because of the damage we’ve seen it cause. Perhaps it’s because it IS fascinating! It’s It's when the lightning is a little close to home, though, that fascination can turn to fear! This is the story of the “big one” which didn’t get away – officially Australia’s most costly natural disaster. O ur fascination pales into insignificance when compared to some “storm chasers”: amateurs (mostly) who study storms – and all their components – with amazing dedication. Often they’re more up-todate than the official Weather Bureau! Michael Bath is one such storm chaser. We’ve seen his work before in SILICON CHIP. Michael not only chases storms, he photographs them. He writes about them. He follows their progress as closely as he can. He has even set up a website dedicated to them (see separate panel). Which brings us to early in the day of April 14, 1999. Michael takes up the story: In the hours before the storm which hit Sydney, the email, internet connections and phones of the storm chasers were buzzing. The weather bureau issued no warnings – it was as if they missed the event completely despite being contacted with very reliable information (as you will read later). The day started out with a casual 10 Silicon Chip comment that “maybe a storm is possible today”. Some altocumulus cloud about, a moisture haze and a forecast of a thundery day for Canberra were the reason for this outlook. By late morning small cumulus clouds had developed in a line from the far southwest towards the coast south of Sydney. But by early afternoon some were starting to spread out as altocumulus – not usually a good sign for thunderstorm development. One or two of the larger clouds actually glaciated (meaning they took on a classic, towering anvil shape) but with very low tops, probably no more than 4-5,000 metres but these were persisting somewhat (something I had observed a few times in the past, but I did not make the connection at the time). Altocumulus began to dominate and it became mostly cloudy during the middle of the afternoon. The only sign that something may occur later was more crisp cumulus congestus (large cumulus cloud masses which grow higher than they are wide – a classic sign of a cloud mass developing into a storm) way to the south, just visible under the altocumulus in Sydney. Around 4pm it became apparent that the congestus to the far south was certainly looking promising and worth keeping an eye on. I suspected that some storms might get going very close to the coast south of Sydney and then remain out to sea, but perhaps a lightning show would result. By 5pm I could see that a thunderstorm was gathering strength about 80km SSE. Having a good feel for locations/distance of storms, I made a mental note that it appeared to be over land in the southern Wollongong area. It would most likely just move offshore and that would be it. However, the tower had a very strong vertical appearance (on the NW flank that I could see), indicating a very strong updraft and the potential for severe weather. I wanted to check the radar to give me an indication of any other develop- matically on its NW flank as the storm edged over the coast, indicating that it could clip the coast again to the north – over Sydney’s southern suburbs. “The bureau was warned. . .” The classic anvil-shaped thunderhead towering sometimes thousands of metres above the surrounding cloud. This is caused by the updraft of moisture-laden air currents in the cell. When the moisture condenses in the cold higher levels, the air current cannot support it and it falls as rain. If it freezes, it can fall as hail, although most of it melts before it reaches the ground. ment and to determine the direction of movement of the storm but didn’t get to see it until after 6.30pm. Lightning could now be seen about 50km SE at this stage. From a website I subscribe to, I downloaded the latest Sydney radar images covering the period 5.30pm to 6.30pm local time. Then I received my email. A message on the aussie-weather mailing list reported that a severe storm had just been through the Shellharbour area (about 100km south of Sydney) and that golf ball sized hail was reported to the local radio station. The storm looked very severe with lowerings, or parts of the clouds jutting out significantly lower than the rest or the base of clouds, almost to the ground. The system was back-building dra- The email author said that he had in fact phoned the Bureau of Meteorology at 6pm to report the storm, only to be greeted with scepticism. If we could see what was happening, why couldn’t the Bureau? Obviously he was dismissed as an unreliable spotter as no severe thunderstorm advice or warning was issued (although one was belatedly issued at 10.20pm, long after the storm had passed). By 7pm it was obvious on both radar and visually (my home is about 40km from the coast) that the storm was moving directly NNE and heading straight into the southern Sydney suburbs. In fact by 7pm there was already maximum reflectivity on the radar and the storm was over the Royal National Park on Sydney’s southern outskirts, heading towards Botany Bay and Sydney Airport. Lightning was frequent to the south-east but it seemed that a dead cell or other cloud was to the west of the storm, blocking the view of any lightning bolts. I could however see the glowing outline of the storm tops and reflections around the rest of the sky. Visually it continued like this until Left: thermal image of the storm taken by the NOAA12 satellite at 7.13UCT (9.13pm Sydney time); courtesy of CSIRO. Above is the radar image taken at around the same time with the storm sited directly over Sydney’s eastern suburbs, which copped the brunt of the damage; courtesy Bureau of Meterology. JULY 1999 11 Everyone has a story... by James Crouch, Rushcutters Bay. It was about 7:35pm. I had about two minutes warning – I could hear a distant roar but didn’t know what it was at first. It just got louder and louder. Things started breaking as soon as the first isolated hail stones began falling: neighbour’s windows, roof tiles, that sort of thing. The roar was quite loud but still distant. For a moment it sounded like “things” were falling out of the sky and I actually feared for a few seconds that it was debris, not ice!! The tiles on my roof were taking a pounding, ceiling plaster was flaking off all over (I guess a combination of hail and tile impacts). There was nothing I could do and I didn’t have a view, so I went down to the street and sat under shelter with a few neighbours and watched as 70mm hailstones slammed into the footpath. I couldn’t see much in the way of cloud but there was lightning every 2-3 seconds. Bayswater Rd, empty of traffic, was covered in a 50mm layer of ice (ice was still piled up in corners 3 hours later). The heaviest hail lasted about 10-15 minutes and then it rained (showered, whatever) until 2am-ish. That was the killer. I drilled a few holes in my ceiling where it was sagging the worst (and until I ran out of pots and pans) and then checked my neighbours. I wasn’t the worst; the girl across the landing had a 2-3 litre per minute flow from the light in her kitchen for a while, and sundry other leaks of various flow rates. I climbed up into the ceiling: there were at least 300 tiles shattered or cracked; you could see the sky all over the place. Once they’d isolated her power and we’d drilled holes in other peoples ceilings, I went and checked my car. It was a Daihatsu Feroza. The bonnet was trashed – 20-odd 4-5cm dents and one of the rear side windows was smashed – with a bit of resultant water damage. Not so bad. . . I haven’t got onto the insurance company yet so I have no idea when it’ll have a chance to get fixed up. Meantime I guess that I’m up for driving on storm chases! I had a pleasant night’s sleep on cushions in the hallway – that was the only place that didn’t have leaks!! just as in Sydney. It can also make the storm rotate and is the phenomenen which also breeds tornados. In most thunderstorms, the updrafts of air reach a point where the water and ice they contain cannot be supported and they collapse, dumping their rain and sometimes ice (as hail) in the process. A second storm Towards 9pm, fresh southeast winds spread in with a layer of strato-cumulus, blocking the storm as it edged out over the northern beaches. At about the same time the first reports of giant hail began to filter in and the discussions on the ’net got quite excited. Also at this time, another storm with hail passed through the eastern suburbs on a similar track to the supercell. Later (between 10pm and 11pm) a storm with some intense cloud-toground strokes spread through the western suburbs dumping some heavy rain but no hail. Brief blackouts occurred including at my place at 11pm. It wasn’t until the next day that the analysis of the day’s observations and the radar clearly showed the significance of the event. The radar patterns were classic supercell from about 6.30pm onwards with a clearly defined V-notch most of the time. The V-notch is a particular shape of the radar image on the screen, well known to meteorologists as an indication of a very severe storm. Almost a tornado 8pm though was now much closer and bigger. Radar showed the most intense part of the storm was right over the eastern suburbs and city and would have been smashing these areas with hail officially measured to 9cm diameter, with larger stones probable. Just after 8pm the storm became much more spectacular from my vantage point to its west – continuous cloud to cloud lightning, cloud to air, and cloud to ground, though I could only see the top half of these. It coincided with a rapid propagation and development to the NW of the main thunderstorm, making the whole structure visible with each lightning flash. Is it a supercell? With a boiling rear flank, a rock 12 Silicon Chip solid backshearing anvil punching well through the tropopause and the continuous lightning, I soon came to realise this was no ordinary storm. In fact, it looked to me like the western flank of a supercell thunderstorm. In fact, after spending some time taking lightning photographs I made the remark that I thought it was a supercell and wondered what damage had occured or was currently occurring in the most densely populated parts of Sydney. A supercell thunderstorm is fairly rare – perhaps one a year or so in the Greater Sydney area – and occurs when the updrafts and downdrafts of air currents within the storm occur at the same time due to windshear. This makes the storm self-sustaining. A supercell is much more likely to do a lot of damage over a wide area – It was disturbing to see a most prominent hook echo on the radar screen when the storm was right over the eastern suburbs, though no damaging winds were experienced there. A hook echo on the screen can indicate precipitation actually wrapping around a meso-cyclone. Imagine if a large tornado had touched down as well! The storm tracked to the NNE and was well defined for almost four hours. Contrary to some early reports, there was no cell splitting or another storm suddenly developing closer to Sydney – the one storm cell just propagated on its NW flank continuously. The early afternoon observation of persisting low topped glaciated cells has preceded supercell development on other occasions. As at 11th May, the total insured damages bill is in excess of $A1.4 billion, now making it the most costly natural disaster in Australian history, surpassing the Newcastle earthquake (1989) and Tropical Cyclone Tracy in Darwin (1974). Although the time of year and the area affected by the storm is unusual for a supercell, many hailstorms with similar-sized hail (but officially recorded hail sizes slightly smaller than this event) have occurred in Sydney, even in recent years. Most notable were the supercell hailstorm of Sunday 18th March 1990 affecting the western suburbs and the supercell of Monday 21st January 1991 affecting the northern suburbs. However, insured loses for these two events are far lower than for the April 1999 event. Just after 8pm the storm became much more spectacular from my vantage point to its west – continuous cloud to cloud, cloud to air, and cloud to ground lightning, though I could only see the top half of the latter. * Michael Bath is the editor of the severe weather newsletter, “Storm News” and has a huge library of storm and lightning photo-graphy. He also conducts a website dedicated to the subject of severe weather at www. australiansevereweather.simplenet.com On this site there are links to many other sites on similar subjects. Radar Image courtesy Bureau of Meterology. Satellite image courtesy CSIRO. Tracking the Storm by Tracking the Lightning Regular S ILICON C HIP readers would be aware of the LPATS Lightning Positioning and Tracking System (see the article in the November 1996 issue). As you might expect, Kattron's Ken Ticehurst had been monitoring the storm earlier in the day, just as had Michael Bath. “We could see the storm's path bearing down on Sydney and were amazed that the weather bureau didn’t issue any warnings,” said Ken. “In the overall scheme of things, though, this thunderstorm didn’t look all that big because most of the lightning was CC strokes”. LPATS works by detecting the electromagnetic radiation of a cloudto-ground (CG) lightning stroke between 2 and 450kHz. Some cloud-to-cloud (CC) strokes are also detected but as their radiation is mainly in the VHF range, the detection range is much less. In most thunderstorms, CCs are usually 90% of the lightning activity. In this storm, with all the hail, it may well have been higher. Certainly from the SILICON CHIP offices (close to the coast in northern Sydney) the impression was overwhelmingly CC, even with the numerous CG strokes witnessed (actually CW or cloud-towater because most of the activity was by this time off shore). The lightning display, by the way, was rated by SILICON CHIP staff as easily the most spectacular they had ever seen). But in terms of CG activity this storm was not all that ferocious – with around 600 strokes per hour at its peak (11.30pm). At 8.30pm, about the peak of damage in the Eastern Suburbs, it was recording 120 strokes per hour. We have seen thousands of CG strokes per hour (over a greater area) in other storms. (The November 1996 article shows a graph of lightning strokes in Central NSW during November 1995 peaking at more than 3800 mainly C-G strokes per hour!) The map above shows one of the lightning stroke “maps” plotted by Kattron during the storm. The colour bars on the images represent % of strokes in 10 minute intervals from the time shown (top left of each image), starting with gray. Each screen in the full series represents 1 hour. SC JULY 1999 13 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au Design by BRANCO JUSTIC* Build the Dog Silencer . . . and quieten that noisy mutt Fed up with the barking dog next door? This Dog Silencer circuit could be the answer to your prayers. It gives the dog a retaliatory blast of high-frequency noise that’s beyond the limits of human hearing. Barking dogs are one of the worst sources of noise pollu tion in Australia. They cause more arguments between neighbours than any other problem and are by far responsible for the majority of noise complaints to local councils. 18 Silicon Chip One thing that’s particularly galling to near neighbours is the selective deafness of inconsiderate dog owners. They couldn’t care less how much distress their dog causes and simply ignore complaints. In other cases, the owners are unaware of the problem because their dog barks only while they are away. This device will let you get back at your neighbour’s barking dog without anyone else knowing about it. When the dog barks, you press a button on the front panel and it gives the dog a blast of high-intensity frequency-modulated ultrasonic sound. This lasts for as long as you hold the button down. Because this sound will be somewhere in the 20-31kHz range, humans cannot hear it but most dogs can. That’s because dogs are able to hear much higher frequencies than humans – unless, of course, the dog is old or deaf, in which case the Dog Silencer will have no effect. The barking loop So why does the dog stop barking? We’re not too sure but one theory is that the sudden sound burst interrupts the “barking loop” (good term, that) that some dogs get themselves into. You’ll probably be familiar with this problem – the dog starts barking and doesn’t know how to stop. Basically, the Dog Silencer is an attention-getting device; it distracts the dog and he forgets to continue barking. Another theory is that the sound burst serves as a sharp reprimand. And of course, if the sound is unpleasant, the dog will quickly learn to modify its behaviour. Think of this as being a high-tech equivalent to the time-honoured “shaddup-barkin-yermangey-so-and-so” bellow out the bedroom window at 4 o’clock in the morning. The real beauty of this device is that your inconsiderate neighbour doesn’t know that you’re reprimanding his equally inconsiderate mutt. Mind you, such subtlety is not for one person that we know. Fed up with the barking dog next door, he phoned his soundly-sleeping neighbour at three in the morning. And his response to his neighbour’s complaint at being phoned at that hour was an equally subtle “well if your dog’s keeping me awake, I don’t see why Warning! The output from this unit is extremely loud and could seriously damage your hearing if you get close to the tweeters while it is operating. This warning applies even though the unit operates beyond the range of human hearing. For this reason, be sure to install the tweeters in a location where they cannot cause hearing damage and observe the precautions detailed in the text when testing the unit. you shouldn’t also be awake”. Of course, we don’t claim that this unit will be effective on all dogs. If the dog is deaf or just plain stupid, nothing works unless the owner is prepared to do something. Then again, it might just depend on the breed of dog or its temperament. What we do say is that the Dog Silencer will deter many dogs from barking, provided they are not too far away. It’s a bit hard to set a precise value for the effective range but it’s probably somewhere around 30 metres. It certainly wouldn’t stop a dog that’s barking at the other end of the street, for example. Roo scarer One report we’ve had suggests that it’s also very effective on kangaroos. No, it doesn’t stop them from barking; that’s not what we mean at all. What we do mean is that it scares them away. And according to our inform ant, the roos don’t just casually hop away. The word he used was “stampede” but we’re not too sure whether that term is really appropriate for kangaroos! Another term he used was “press the button and whacko! – they’re gone”. In short, he found that it was very effective at scaring away kangaroos from the paddock adjacent to his home in rural Queensland. This means that there’s another possible role for the unit – it could be fitted to a vehicle and used as a “roo scarer”. This could be useful when driving on outback roads at night, for example. We must stress though that we haven’t tested the unit in this role and in any case, it might only “stampede” Queensland kangaroos (only joking). Circuit details Refer now to Fig.1 for the full circuit details of the Dog Silencer. It’s built around IC1 which is a TL494 pulse width modulation (PWM) controller. The TL494 is normally used in switchmode power supplies but is suitable for virtually any PWM application. In this circuit though, we don’t pulse width modulate the output. Instead, the outputs either operate at full duty-cycle or are off. Fig.1: the circuit is based on a TL494 PWM controller IC. This IC provides complementary square signals at its pin 9 & 10 outputs and these drive transistors Q2 and Q3, the centre-tapped transformer T1 and the tweeters. JULY 1999 19 Fig.2: this block diagram shows the internal circuitry of the TL494 PWM controller. It includes a sawtooth oscillator, a PWM comparator, a dead-time control comparator, two error amplifiers and a 5V reference. Emitter followers Q1 & Q2 provide the complementary square-wave output signals at pins 9 & 10. Fig.2 shows a block diagram of the TL494. It contains the following circuitry: • An internal oscillator which has its frequency set by capacitor CT at pin 5 and resistor RT at pin 6. • A stable +5V reference at pin 14. • A “dead-time” comparator with one input driven from the oscillator. • Two error amplifiers with their outputs ORed together via diodes (pin 3). • A PWM comparator with one input derived from the oscillator and the other from the ORed output of the two error amplifiers. • A flipflop which is driven (via a NOR gate) by the dead-time and PWM comparators. • Two 200mA output transistors with uncommitted emitters (pins 9 & 10) and collectors (pins 8 & 11). The bases of these two transistors are driven in anti-phase by the outputs of the flipflop. As used in the Dog Silencer, the internal oscillator of the TL494 Fig.3: the top waveform in this scope shot shows the 2V p-p sawtooth waveform at the anode of PUT1. This waveform is used to frequency modulate the output. 20 Silicon Chip operates at somewhere between 40kHz and 60kHz and this produces complementary pulse trains (at half this frequency) at the emitters of the internal output transistors (E1 & E2). Notice that, in this circuit, the collectors of these two transistors are tied to the positive supply rail, so that they function as emitter followers. The E1 and E2 outputs from the TL494 drive NPN transistors Q2 and Q3 (TIP41C) in push-pull fashion and these in turn drive centre-tapped trans- Fig.4: the bottom waveform in this shot (collector of Q2) shows the drive to transformer T1, while the top waveform shows the signal drive to one of the tweeters. Parts List 1 PC board (available from Oatley Electronics) 1 plastic case with label 1 prewound centre-tapped transformer (T1) 2 10µH inductors (L3,L4) – see text 1 pushbutton switch (S1) 2 piezoelectric tweeters 1 5kΩ horizontal-mount linear trimpot (VR1) The inductors and the centre-tapped transformer (T1) are supplied prewound, to make the assembly as easy as possible. Make sure that all polarised parts are oriented correctly. former T1. The secondary winding of the trans former then drives two piezoelectric tweeters which, together with inductors L1-L4, form two series resonant circuits connected in parallel. OK, so that’s how the circuit works in a nutshell. In practice, it’s a little more complicated than that, as we shall see. Rather than provide a fixed frequency output, this circuit uses an external oscillator to provide frequency modulation. This circuit is based on programmable unijunction transistor PUT1, which is set up as a relaxation oscillator. R1 & R2 bias the gate of the PUT to about 3V, while R3 & C1 set the frequency of oscillation. In operation, the PUT conducts each time its anode voltage rises 0.6V above the gate voltage and stops conducting when C1 discharges (ie, when the holding current drops below the threshold value). The result is a 2.7Hz 2V peak-to-peak sawtooth waveform at the anode. This signal is buffered by emitter-follower stage Q1 and applied to pin 6 of IC1. The scope shot of Fig.3 shows this 2.7Hz sawtooth waveform. It varies the voltage applied to pin 6 of IC1 and the result is a frequency modulated waveform which constantly sweeps over a range of about 3kHz. To explain this point further, depending on the setting of trimpot VR1, the output frequency can vary from 21 to 24kHz and back again, 2.7 times a second. While this is beyond the limit of our hearing, it would sound like a shrieking siren to a dog. The frequency modulated waveform is shown as the lower trace in Fig.3 but the scope shows it as a jumbled waveform because the frequency is far above the sampling rate at its sweep setting of 100ms/div. Trimpot VR1 sets the basic oscillator frequency. At one extreme, it varies the frequency modulated output from about 18-21kHz, while at the other extreme the output varies from 28-31kHz. Power for the sawtooth oscillator circuit is derived from the VREF output (pin 14) of IC1. This output provides a regulated +5V rail. Trigger circuit Switch S1 and its associated parts provide the trigger circuit. This connects via R8 to the dead-time (DT) input of IC1 at pin 6. Normally, the DT control input is pulled high via R8 & R9, which means that the dead-time is at maximum. This also means that the two internal transistors are held off, so there is no drive to Q2 & Q3. When S1 is pressed, pin 4 is pulled low via R8 and so the dead time decreases to its minimum value. As a result, IC1’s E1 and E2 outputs provide maximum drive to Q2 and Q3. D1 & D2 protect Q2 & Q3 from damage due to inductive switching spikes. Note that the non-inverting inputs (IN+) of the two error amplifiers are Semiconductors 1 TL494 PWM controller (IC1) 1 BC548 NPN transistor (Q1) 2 TIP41C NPN transistors (Q2,Q3) 1 programmable unijunction transistor (PUT1) 2 BA159 diodes (D1,D2) Capacitors 1 470µF 25VW (C6) 1 100µF 16VW electrolytic (C5) 1 1µF 16VW electrolytic (C2) 2 0.47µF MKT polyester (C1,C4) 1 .0022µF greencap (C3) Resistors (0.25W, 1%) 2 470kΩ (R3,R8) 1 100kΩ (R2) 1 68kΩ (R1) 1 47kΩ (R6) 1 22kΩ (R9) 1 12kΩ (R7) 1 10kΩ (R5) 1 1kΩ (R4) 2 120Ω (R10,R12) 2 47Ω (R11,R13) Miscellaneous Machine screws & nuts, insulated hookup wire. connected to the VREF, while the two inverting inputs are connected together. This effectively disables the error amplifiers and ensures the maximum duty-cycle at the outputs. The lower waveform in Fig.4 was taken from the collector of Q2 and shows the drive to the transformer (T1). Note that this is a square-wave signal. Q3 drives T1 in exactly the same manner, except that its output is 180° out of phase with Q2’s. However, because each tweeter is connected in a series resonant circuit across T1’s secondary, the resultant tweeter signal voltage is not only JULY 1999 21 Fig.5: install the parts on the PC board as shown in this wiring diagram. Note that Link 1 and Link2 should be replaced with 200µH inductors if square tweeters are supplied. sinusoidal but is also much greater in amplitude. This is shown as the top waveform in Fig.4, which has an amplitude of 59.2V peak-to-peak or about 21V RMS. As a result, the total output power from both tweeters is equivalent to about 100W (assuming 8Ω tweeters). Power for the circuit can be derived from any 10-16V DC source capable of supplying at least 1A. A 12V battery or 1A 12V DC plugpack supply would be ideal for this job. Building it All the parts for this design are available from Oatley Electronics, so you don’t have to scrounge about for individual bits and pieces. The accom panying panel shows all the details. The job of assembly mainly consists of installing the parts on the PC board. This board comes with a screened parts overlay and the transformer and inductors are all supplied prewound, to make the assembly as easy as possible. Fig.5 shows the parts layout on the PC board. Begin by installing the resistors, diodes and the wire links, then install the capacitors. Take care to ensure that the three electrolytic capacitors are all correctly oriented. Note that Link 1 and Link 2 are installed only if you are using rectangular tweeters. If you are supplied with square tweeters, these links should be replaced with inductors L1 and L2 (both 200µH); ie, the square tweeters each require two series inductors while the rectangular tweeters only require one. The extra inductors will automatically be supplied in the kit if you are supplied with square tweeters. The transistors can go in next, along with the IC and the trimpot. Make sure that the semiconductors are all correctly oriented. Q2 & Q3 are both mounted with their metal tabs towards transformer T1, while IC1 has its pin 1 adjacent to the 470µF capacitor. The transformer can now be soldered into position, after which you can install the external wiring for the power supply, Trigger switch (S1) and the tweeters. Use medium-duty hook up wire for the tweeter and switch leads and heavy-duty hookup wire for the supply leads. Work can now begin on the plastic case. The PC board is mounted on the lid of the case using machine screws and nuts, as shown in the photo. You can use the PC board as a template for drilling the four mounting holes in the lid. The decorative label is affixed to the bottom of the case and this becomes the front panel. There’s only one hole to drill and that’s for the Trigger switch. You will also have to file three notches in the top rim of the case, to provide clearance for the external leads. Two of these notches provide clearance for the tweeter leads, while the third provides clearance for the power supply leads. If you are using a plugpack supply, Resistor Colour Codes  No.  2  1  1  1  1  1  1  1  2  2 22 Silicon Chip Value 470kΩ 100kΩ 68kΩ 47kΩ 22kΩ 12kΩ 10kΩ 1kΩ 120Ω 47Ω 4-Band Code (1%) yellow violet yellow brown brown black yellow brown blue grey orange brown yellow violet orange brown red red orange brown brown red orange brown brown black orange brown brown black red brown brown red brown brown yellow violet black brown 5-Band Code (1%) yellow violet black orange brown brown black black orange brown blue grey black red brown yellow violet black red brown red red black red brown brown red black red brown brown black black red brown brown black black brown brown brown red black black brown yellow violet black gold brown SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Use these REFLEX® chargers for all your Nicads and NIMH batteries: Power tools  Torches  Radio equip.  Mobile phones  Video cameras  Field test instruments  RC models incl. indoor flight  Laptops  Photographic equip.  Toys  Others  Rugged, compact and very portable. 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Testing Before testing the unit, check your work carefully for wiring errors. This done, solder a .0033µF capacitor in parallel with C3 (it can be tacked to the copper side of the board). This will reduce the output frequency to around 10kHz, so that it will be audible and you can tell whether or not the unit is working. Be warned, however, that the output will be extremely loud, although you might not think so because it’s operating at a high frequency. This means that it could damage your hearing if you are not careful. For this reason, always position the tweeters face down on the bench and cover them with a blanket for testing. By the way, this warning is equally valid when the unit is operating beyond the limits of human hearing. Even though you cannot hear the noise, it could still seriously damage your hearing if you are careless enough to get close to the tweeters. Do not, under any circumstances, get in front of the teeters while they are operating. Another way to reduce the output for testing is to solder a 1kΩ resistor in series with each tweeter. Once you have everything set up, apply power and press the Trigger switch. If the unit is working properly, you will hear a modulated high-frequency sound. If the unit fails to work, switch off immediately and check for wiring errors. If all appears to be OK, reapply power and check for +12V on pins 8, 11 & 12 of IC1 and at the collectors of Q1 & Q2. Q1’s collector should be at +5V, while the gate of PUT1 should be at about 3V. ELECTRONIC COMPONENTS & ACCESSORIES • RESELLER FOR MAJOR KIT RETAILERS • • PROTOTYPING EQUIPMENT • FULL ON-SITE SERVICE AND REPAIR FACILITIES • LARGE RANGE OF ELECTRONIC DISPOSALS (COME IN AND BROWSE) CB RADIO SALES AND ACCESSORIES Ph (03) 9723 3860 Fax (03) 9725 9443 Come In & See Our New Store M W OR A EL D IL C ER O M E The prototype was built into a low-cost plastic case, with the PC board mounted on the lid. Note the notches filed into the case for the tweeter and supply leads. Truscott’s ELECTRONIC WORLD Pty Ltd ACN 069 935 397 27 The Mall, South Croydon, Vic 3136 email: truscott<at>acepia.net.au www.electronicworld.aus.as JULY 1999 23 The PC board is attached to the lid of the case using machine screws and nuts. Use medium-duty hookup wire for the tweeter and switch leads and heavy-duty hookup wire for the supply leads. Fig.6: transistors Q2 and Q3 must be heatsinked if you intend building a “roo scarer”. Be sure to isolate their metal tabs from the heatsink metal using a TO-220 mounting kit, as shown here. Assuming that everything works properly, remove the 1kΩ series resistors (if fitted) from the tweeters and the .0033µF capacitor from the back of the board. Now, with the tweeters face down on the benchtop, briefly press the button again. This time, you shouldn’t be able to hear anything because the unit will be operating in the ultrasonic range. If you do hear a faint high-pitched noise, adjust VR1 until all is quiet. Don’t keep the Trigger switch press ed for too long when testing the unit at this stage, otherwise Q2 & Q3 could overheat. The unit is designed for intermittent use only and provided it is used in the manner, there’s no need to fit heatsinks to the two driver transistors. Installation The best location to mount the tweeters is under the eaves of the house, so that they are protected from the weather. Try to position them so Where To Buy The Parts All parts for the Dog Silencer are available from Oatley Electronics. The pricing details are as follows: Complete kit (includes box, label, wiring kit and two tweeters but does not include plugpack supply) ............................................ $43.00 PC board plus all on-board parts and one tweeter ......................... $30.00 Extra tweeter ..................................................................................... $5.00 Box, label, switch and wiring kit ......................................................... $8.00 13.8V 1A plugpack power supply ......................................................... $10 Please add $6.00 for postage and packing. To order, contact Oatley Electronics at PO Box 89, Oatley, NSW 2223. Phone (02) 9584 3563; fax (02) 9584 3561; email oatley<at>world.net 24 Silicon Chip that are as close to the offending dog as possible, while keeping them hidden from view. Mounting them up out of the way also means that humans cannot get too close. You should also cover the tweeters with a thin plastic membrane or house them in a suitable cover, to prevent them from getting wet. After that, it’s simply matter of pressing the button for a few seconds each time the mutt next door barks. Over time, you may find that the dog realises that it’s going to cop this every time it barks and so eventually ceases to be a problem. Building a “roo scarer” Finally, if you intend fitting this circuit to a vehicle as a “roo scarer”, use a rocker or toggle switch for S1 so that the unit can be operated continuously. A toggle switch with an illuminated rocker is preferable here, so that you know when the unit is on. Heatsinking will also be required for the two TIP41C output transistors. One tweeter should be quite sufficient in the roo scarer role, so a couple of flag heatsinks should do the job. These will have to be securely anchored, to prevent the transistor leads from lifting the pads on the PC board due to vibration. Note that the heatsinks must not short against anything else or touch each other, since they will be at collector potential. A better idea would be to build the circuit into a rugged metal diecast case. Q2 & Q3 could then be bolted to the case for heatsinking and connected to the PC board using flying leads. Both transistors will have be electrically isolated from the case using standard TO-220 mounting kits (mica washer plus mounting bush), as shown in Fig.6. After mounting the transistors, it’s a good idea to check that their metal tabs are indeed isolated from the case using the low-ohms range of a multimeter. Power should be taken from the fused side of the ignition switch, so that the unit can only be operated when the ignition is on. Note that all external wiring connections should be run using automotive cable. The tweeter can be mounted behind the grille and must be waterproofed by covering it with a thin plastic memSC brane. MAILBAG Image resolution in satellite pictures Thanks for a really enthusiastic and fun article on the Microsoft Terra Server web site. I’ve been working in the field of remote sensing for nearly 15 years and it’s good to see this information starting to become available to the public at reasonable prices and in the form of a technology that is easy to use. I have just a couple of corrections that I think are important enough to cause me to write to you. First, in the article you state that the US images are taken by a USGS satellite. This is not correct. All the US images provided by the USGS in the project are digitised versions of conventional aerial photography from the National Aerial Photography Program (NAPP). Second, there are some comments about the reported resolu t ion of so-called “spy satellites”, with the author adding that “number plates with their 100mm high letters are said to be a doddle” and further on that “today’s spy satellites are good enough to pick up the dateline on the front of a newspaper”. It would be wonderful if it were true but the evidence from a variety of military and civilian sources would tend to indicate that it is not. Now, I shall be the first to admit that trying to find the actual resolution of current spy satellites is going to be difficult. The claim of “being able to read a newspaper from space” is a very old myth that originated from the cold war, when fiction became the official truth and the truth was far less interesting than the story. However, there are a couple of ways in which the true resolution of the current optical surveillance satellites has been estimated and more-or-less verified. First, a slip-up in security has resulted in images from the satellites appearing in the US Congressional Record from time to time. Second, the general size of the satellites, including most importantly the estimates of the dimensions of their optics, has enabled watchers of these satellites to estimate the likely ground resolution. These and other sources of information all lead to the general conclusion that the best available resolution would be no better than about 8-10cm, and probably worse. Of course, this is not the whole story. The US has radar satellites which have a ground resolution probably at the metre level, which greatly extends its surveillance capability. And most importantly, it has a powerful communications, processing and interpretation intelligence community that can access, analyse and deliver imagery to its personnel in the field very quickly. In the civilian community, aside from the few short-term film-return missions operated by SPIN-2, the best ground resolution currently available is five metres in black-and-white, from the Indian Remote Sensing satellite IRS-1C. For colour images, the best available are the 20-metre resolution images from the French SPOT satellite. Images from both these satellites are available of Australasia, although IRS-1C imagery can be very difficult to acquire. In Australia, there is a huge amount of imagery from the Landsat-4 and -5 satellites, all available from the Australian Centre for Remote Sensing (ACRES) and used extensively for the agricultural, mapping, mineral exploration and other industries. Technologies like Microsoft’s Terra Server are going to increase in prominence over the next decade. There are certainly problems with the current offerings in terms of coverage, quality and timeliness but it is a beginning. This is an exciting area to watch! Stephen McNeill, Christchurch, New Zealand. Dimensional confusion in TerraServer article With reference to your TerraServer article: a terametre is perhaps a bit larger than the average distance to Jupiter, so a square terametre would be a very large territory indeed and 500 square terametres would greatly exceed the area of the Solar System. The area of the Earth, on the other hand, is about 500 million square kilometres, or, if you like, 500 square megametres, or maybe even 500 tera square-metres. That’s a trifle smaller than 500 square terametres. Indeed, all of this can be tera-bly confusing! Paul Schick (via email) Comment: Hmm. Yes, we were a bit confused, weren’t we. Request for historical radio material For some time now I have been researching the history of radio communications in the outback of Australia. I am writing a book that will be titled “Radios of the Outback – from Flynn to Satellites “ or some similar title. I expect it to be ready to put on bookstalls in mid 2001, maybe before. This is a very intriguing subject. Many people will have read books on Rev John Flynn, Alf Traeger and the Royal Flying Doctor Service. These books cover various aspects of the development of radio but mostly the social history. I am looking more at the technical side of this history and in fact there will be some circuit diagrams of early HF transceivers in the book that may never have been seen before by the general public. It has been assumed by most people that Traeger designed and built all of the HF transceivers (pedal radios). Well, that isn’t quite true, as a very talented chap by the name of Harry Kauper was very much involved with the early work of developing sets. He was Traeger’s mentor. AWA also had a pedal radio available at the time the first AM/CW sets were being introduced into the outback. The voltage output from the pedal generators has been quoted in various articles as 180, 200-240 or 300-400V. The nominal output voltage was 180V and not any of the other voltages as will be explained in the book. It is proving to be a fascinating exercise doing this research. I haven’t got all of the story together as yet and would appreciate any information and photographs that readers could supply to me to assist in making the book as accurate and interesting as possible. If copyright exists please let me know. Rodney Champness, VK3UG, 6 Mundoona Court, Mooroopna, Vic 3629. JULY 1999 25 This easy-to-build test instrument can measure inductances over the range from 10µH to 19.99mH with an accuracy of about 5%. It uses readily available parts and has a 4-digit LCD readout. By RICK WALTERS Build this: 10uH to 19.99mH Inductance Meter 26 Silicon Chip A N INDUCTANCE METER can be a handy test instrument in many situations. It can be used for servicing (eg, in TV sets), selecting coils for RF circuits, checking coils for switchmode power supplies and for measuring coils in many other applications. The instrument to be described here measures from 10µH to 19.99mH over two ranges and has the twin virtues of being easy to build and easy to use. As shown in the photos, there are just three front panel controls: a range switch (µH or mH), a pushbutton switch and a potentiometer. An AC plugpack is used to supply power, so there is no on/off switch to worry about. To make a measurement, you first connect the inductor to the test terminals and switch to the µH range. You then press the “Null” button and rotate the knob until the LCD panel meter reads zero, or as close to zero as you can get (ie, a null). This done, you release the button and read the inductance directly off the display. If the meter over-ranges (ie, it only displays a 1 at the lefthand digit), you simply switch to the mH range before reading the inductance value from the meter. The value indicated on the scale by the potentiometer is the DC resistance of the inductor (although, in practice, this reading may not be all that accurate). Block diagram Fig.1 shows the block diagram of the Digital Inductance Meter. It uses a 3.2768MHz crystal oscillator (IC1a) to generate a precise clock frequency and this is divided by 20 and filtered by IC5 to give a 163.84kHz sinewave signal. In addition, the signal from the divide-by-20 stage is divided by 100 and filtered by IC6 to give a second frequency of 1638.4Hz. Main Features • Two ranges: 10-1999µH & 1-19.99mH • Indicates inductor DC resistance • Operates from a 9V AC plugpack supply • Accuracy typically 5% from 10µH to 19.99mH Range switch S2a selects between these two frequencies and feeds the selected signal to a nulling circuit. This circuit is used to null out the DC resistance of the inductor being measured. The output from the nulling circuit is then fed to positive and negative peak detectors and these in turn drive a digital panel meter (DPM). Circuit details Let’s now take a look at the circuit diagram of the Inductance Meter – see Fig.2. NAND gate IC1a and its associated components function as a square wave oscillator. It oscillates at a frequency of 3.2768MHz, as set by crystal X1. The 33pF, 270pF and 100pF capacitors provide the correct loading for the crystal and ensure that it starts reliably when power is applied. Pushbutton switch S1 is used to disable the oscillator. Normally, the output of IC1a (pin 3) clocks the pin 15 (CA-bar) input of IC2b. However, when S1 is pressed, pin 1 is pulled low and IC1a’s pin 3 output remains high. We’ll explain why this is done later on. IC2b, part of a 74HC390 dual 4-bit decade counter, divides the clock signal from IC1a by 10. The divided 327.68kHz output appears at pin 9 and in turn clocks pin 1 of IC3a. IC3a is one half of a 74HC112 dual J-K flipflop. In operation, it toggles its Q and Q-bar outputs on each falling edge of the clock pulse and thus divides the frequency on its pin 1 input by 2. The resulting 163.84kHz square wave signal on the Q output (pin 5) is then applied to op amp IC5 which is configured as a Multiple Feedback Bandpass Filter (MFBF). Because a square wave is made up of a fundamental sinewave frequency plus multiple harmonics, we can configure IC5 to recover virtually any harmonic. In this case, we are using IC5 to recover the 163.84kHz fundamental frequency, as determined by the three resistors and two capacitors between the output of IC3a and its inverting input. The recovered 163.84kHz sinewave output appears on pin 6 of IC5 and due to the bandwidth limitations of the IC, it is a little “notchy”. For this reason, it is further filtered using a 1.5kΩ resistor and a 470pF capacitor to remove these high frequency artefacts. This filter circuit also reduces the amplitude of the sinewave to around 5V peak-to-peak. The filtered sinewave is then fed to VR1 which is the calibration control for the µH (microhenry) range. Similarly, for the mH range, IC3a’s Q-bar output is fed to pin 4 of IC2a which in conjunction with IC1c and IC1d is wired as a divide-by-5 counter. Its output appears at pin 3 and clocks decade counter IC4. IC4 divides the frequency on its pin 15 input by 10 and in turn clocks JK flipflop IC3b which divides by two. The signal is then fed to MFBF filter stage IC6, in this case centred on 1638.4Hz. The output from pin 6 of IC6 is a 1638.4Hz sinewave (also at 5V p-p) and this is fed to calibration control VR2. Range switch S2a selects between the two output frequencies Fig.1: the block diagram for the Digital Inductance Meter. Two precise sinewave frequencies are derived and these are fed to a null circuit which contains the inductor under test. The following circuitry then measures the impedance of the inductor and displays its inductance in µH or mH. JULY 1999 27 Parts List 1 PC board, code 04107991, 124mm x 101mm 1 plastic case, Jaycar HB6094 1 front panel label 1 Digital Panel Meter, Jaycar QP5550 (or equivalent) 1 9V AC plugpack 1 chassis mount power socket, to suit plugpack 1 DPDT toggle switch (S1) 1 pushbutton switch, (PB1), Jaycar SP0710 (or equivalent) 1 speaker connector panel, Jaycar PT3000 (or equivalent) 1 knob to suit front panel 1 ferrite core set, Altronics L5300 (or equivalent) 1 bobbin, Altronics L5305 (or equivalent) 20m 0.25mm enamelled copper wire 2 5kΩ multi-turn trimpots (VR1-2) 1 10Ω wirewound potentiometer (VR3) (see text for alternative) 3 20kΩ vertical mounting trimpots (VR4-VR6) 1 3mm x 20mm bolt 1 3mm nut 1 3mm flat washer 1 3mm fibre washer 13 PC stakes Semiconductors 1 74HC00 quad 2 input NAND gate (IC1) 1 74HC390 decade counter (IC2) 1 74HC112 dual JK flipflop (IC3) 1 4029 binary decade counter (IC4) and applies the selected signal to the bases of transistors Q1 and Q2 via a 10µF capacitor. Nulling circuit OK, we now have two precise frequencies, either of which can be selected and fed to the bases of PNP transistors Q1 and Q2. These are wired in a nulling circuit. Let’s take a closer look at their operation. The thing to remember here is that the emitter of a PNP transistor is always 0.6V more positive than its base (0.6V more negative for an NPN transistor). Thus, if the base of Q1 is at 5.7V, its emitter sits at 6.3V. Because the supply voltage is 9V, this means that 2.7V must appear across 28 Silicon Chip 4 LM318 op amps (IC5, IC7-IC9) 1 TL071 op amp (IC6) 1 TL072 dual op amp (IC10) 1 7809 TO-220 9V regulator (REG1) 1 78L05 TO-92 5V regulator (REG2) 1 79L05 TO-92 -5V regulator (REG3) 2 BC559 PNP transistors (Q1,Q2) 4 1N914 silicon diodes (D1-D4) 2 1N4004 1A power diodes (D5,D6) 1 3.2768MHz crystal (X1), Jaycar RQ5271 (or equivalent) Capacitors 4 470µF 16VW PC electrolytic 7 100µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 7 0.1µF monolithic ceramic 5 0.1µF MKT polyester 3 .01µF MKT polyester 1 .0047µF MKT polyester 1 470pF ceramic or MKT polyester 2 270pF NPO 5% ceramic 1 220pF NPO 5% ceramic 3 100pF NPO 5% ceramic 1 33pF NPO 5% ceramic 2 22pF NPO 5% ceramic Resistors (0.25W, 1%) 1 8.2MΩ (select on test) 1 1MΩ 2 5.6kΩ 2 820kΩ 3 4.7kΩ 2 200kΩ 1 1.5kΩ 5 100kΩ 2 1kΩ 1 68kΩ 2 470Ω 1 47kΩ 2 270Ω 1 33kΩ 1 180Ω (calibration) 2 20kΩ 4 100Ω 14 10kΩ 1 3.3Ω (calibration) 1 7.5kΩ the associated 270Ω emitter resistor and this translates into a current of 10mA through the resistor. This (constant) current will also flow in the collector circuit of Q1, regardless of the load resistance (provided this resistance is not too large). If the base of Q1 is now modulated by a sinewave, its collector current will vary sinusoidally, the average still being 10mA. Q2 has the same value of emitter resistor as Q1 so its collector current will be the same as Q1’s; ie, 10mA. This collector current flows through potentiometer VR3 to ground. Note that high beta (gain) transistors are used for Q1 and Q2 to reduce the base current, which is a small fraction of the emitter current. Because the current through Q2 is 10mA, VR3 (10Ω) will have the same voltage across it as an inductor with a 10Ω resistance connected between Q1’s collector and ground. This position is labelled on the circuit as “DUT”, which means “Device Under Test”. The scale for VR3, on the front panel, is calibrated from 0-10. We will come back to it shortly. Q1’s collector is connected to the positive (red) input terminal of the inductance meter, while the other input terminal is connected to ground. When an inductor is connected across these terminals, a voltage appears across it. This voltage consists of two components: (1) a voltage due to the DC resistance of the inductor (as just described); and (2) a voltage due to the inductive reactance. In operation, Q1 drives pin 3 of differential amplifier stage IC7 via a resistive divider (10kΩ & 20kΩ), while Q2 drives the pin 2 input via VR3. IC7 and the following parts, including the LCD readout, function as a digital voltmeter. Before taking a measurement, the resistive voltage component must be cancelled out. This is done by pressing switch S1 which shuts down oscillator stage IC1a and effectively “kills” the sinewave signals selected by S2a. Potentiometer VR3 is then adjusted so that the signal on pin 2 of differential amplifier stage IC7 is the same as the signal on pin 3, as indicated by a 0.00 reading on the LCD readout. Note that when the meter reads zero, the control knob on VR3 indicates the inductor’s DC resistance on the calibrated scale. Making the measurement If S1 is now released, the selected sinewave modulates the 10mA collector current of Q1. This in turn generates a sinusoidal voltage across the inductor (DUT), the amplitude of which is proportional to the inductance. The resulting sinewave signal from IC7 is subsequently rectified by peak detectors IC8 & IC9, summed Fig.2: the complete circuit diagram of the Digital Inductance Meter. IC1 is the oscillator, while ICs2-5 divide the oscillator signal to produce the two precise sinewave frequencies. Constant current sources Q1 & Q2 form the null circuit. JULY 1999 29 Fig.3: install the parts on the PC board as shown here, taking care to ensure that all polarised parts are correctly oriented. Note that two 8.2MΩ resistors are shown connected to pin 2 of IC7 but only one is used in practice and is selected on test (see text). Note also that the metal case of the pot is connected to earth via one of its terminals. 30 Silicon Chip in IC10b and applied to the digital panel meter. IC8 is used to detect and rectify the positive sinewave peaks. It works like this: when the output of IC7 swings positive, pin 6 of IC8 swings negative and charges a 100µF capacitor via D4 and a series 100Ω resistor to the peak level of the waveform. As a result, the voltage across the 100µF capacitor is equal to but opposite in polarity to the peak positive input voltage. D4 prevents the 100µF capacitor from discharging as the input level falls and the voltage on pin 6 starts to rise. In addition, D3 is reverse biased during this time and so has no effect. Conversely, when IC7’s output swings negative, IC8’s output swings positive and is clamped by D3 so that it is 0.6V above the virtual earth input at pin 2. As a result, the voltage across the 100µF capacitor is “topped up” only during positive signal excursions at the output of IC7. IC9, the negative peak detector, works in exactly the same way but with opposite polarity. It charges its 100µF capacitor to the positive peak of the applied waveform. Thus, the positive peak voltage is represented by a negative DC voltage, while the negative peak voltage is represented by a positive DC voltage across the lower 100µF capacitor. Due to the bandwidth limitations of the ICs, this rectification is not perfect at the higher frequency. This limits the accuracy below 10µH and readings below this value should only be used for comparison measurements. The output signals from the positive and negative peak detectors are summed in amplifier stage IC10b. This stage operates with a gain of .056, as set by the 5.6kΩ and 100kΩ feedback resistors, to match the signal to the sensitivity of the DPM (200mV FSD). IC10b drives op amp IC10a which operates with a gain of two and this then drives the IN+ input of the panel meter. Note that the IN- input of the panel meter takes its reference from the 9V supply rail and normally sits at about 6.3V. As a result, IC10a must also operate as a level shifter. This is achieved by biasing pin 3 of IC10 to half the IN- reference voltage (using two 10kΩ resistors). Thus, under no signal conditions, pin 1 also sits at 6.3V and the meter reading is zero. Trimpot VR6 is used to compensate Table 1: Capacitor Codes           Value IEC Code EIA Code 0.1µF 100n 104 .01µF 10n 103 .0047µF 4n7 472 470pF 470p 471 270pF 270p 271 220pF 220p 221 100pF 100p 101 33pF 33p 33 22pF 22p 22 for any offset voltage at the output of IC10a and allows us to set a zero reading on the DPM when the output of IC7 is at ground. Similarly, VR4 and VR5 compensate for any offset voltages at the outputs of the peak detectors. Range switch S2b switches the decimal point on the panel meter, so that it displays the correct value when we switch from µH to mH. In effect, this switch divides by 10 while S2a divides by 100, so that we get an overall range division of 1000 when switching from the µH to the mH range. Power supply Power for the Digital Inductance Meter is derived from a 12VAC AC plugpack supply. Its output is halfwave rectified by diodes D5 and D6 to derive +12V and -12V rails and these are filtered and fed to 3-terminal regulators REG1 & REG3 respectively. Quite a few changes were made to the PC board of the Digital Inductance Meter after this photograph was taken. Table 2: Resistor Colour Codes  No.  1  1  2  2  5  1  1  1  2  14  1  2  3  1  2  2  2  1  4  1 Value 8.2MΩ 1MΩ 820kΩ 200kΩ 100kΩ 68kΩ 47kΩ 33kΩ 20kΩ 10kΩ 7.5kΩ 5.6kΩ 4.7kΩ 1.5kΩ 1kΩ 470Ω 270Ω 180Ω 100Ω 3.3Ω 4-Band Code (1%) grey red green brown brown black green brown grey red yellow brown red black yellow brown brown black yellow brown blue grey orange brown yellow violet orange brown orange orange orange brown red black orange brown brown black orange brown violet green red brown green blue red brown yellow violet red brown brown green red brown brown black red brown yellow violet brown brown red violet brown brown brown grey brown brown brown black brown brown orange orange gold brown 5-Band Code (1%) grey red black yellow brown brown black black yellow brown grey red black orange brown red black black orange brown brown black black orange brown blue grey black red brown yellow violet black red brown orange orange black red brown red black black red brown brown black black red brown violet green black brown brown green blue black brown brown yellow violet black brown brown brown green black brown brown brown black black brown brown yellow violet black black brown red violet black black brown brown grey black black brown brown black black black brown orange orange black silver brown JULY 1999 31 This photograph shows the completed Digital Inductance Meter with the calibration inductor connected to its test terminals – see text. REG1 provides a +9V rail, while REG3 provides a -5V rail. In addition, REG1 feeds REG2 which provides a regulated +5V rail. The ±5V rails supply most of the op amp stages, while the +9V rail supplies the digital panel meter and the constant current sources in the null circuit. The +12V rail is used for the positive supply to IC10, as its output needs to swing up to near the 9V supply of the DPM. Putting it together Building the circuit is a lot easier than understanding how it works. 32 Silicon Chip Most of the parts are mounted on a single PC board and this is coded 04107991. This, together with the digital panel meter, fits inside a standard plastic case with a sloping front panel. As usual, check the PC board for etching defects by comparing it with the published pattern (Fig.4). Any defects should be repaired before proceeding. In addition, part of the PC board will have to be filed away along the bottom lefthand and bottom righthand edges, so that the board will fit between the mounting pillars of the case. Check also that the body of switch S1 fits through its matching clearance hole in the board. Enlarge this hole with a tapered reamer if necessary, so that it clears the switch. The same goes for the threaded bush of pot VR3. Fig.3 shows the assembly details. Begin by fitting 13 PC stakes for the external wiring points, then fit the 11 wire links on the top of the board (including the one under VR3). This done, fit the resistors, diodes and transistors. Table 2 shows the resistor colour codes but check them with a DMM as well, just to make sure. Take care to ensure that all the transistors and diodes are installed the correct way around and make sure the correct part is used at each location. Once these parts are in, install the capacitors (watch the polarity of the electros), the regulators and the ICs. We used IC sockets in the prototype but suggest that you solder your ICs directly to the PC board. Again, be sure to use the correct device in each location and note that the ICs don’t all face in the same direction. The trimpots can now all be installed, followed by poten tiometer (VR3). As shown in the photo, VR3 is installed from the component side of the PC board and is secured using a nut on the copper side. Its terminals are connected to their pads on the PC board using short lengths of tinned copper wire. Once the pot is in, you have to run two insulated wire links between its terminals and points CT & CW on the PC board – see Fig.4. These points are located near Q2, towards the bottom righthand corner. Note also that the metal case of the pot is connected to earth via one of its terminals. That completes the board assembly. Before placing it to one side though, go over your work carefully and check for errors. In particular, check for missed solder joints and incorrectly placed parts. Final assembly Next, attach the artwork to the front panel and use it as a drilling template for the switches, the potentiometer, the test terminals and the panel meter. The square cutout for the meter is made by first drilling a series of small holes around the inside of the marked area, then knocking out the centre piece and filing the edges to shape. This done, use a sharp chisel to remove the short mounting pillar inside the case, to prevent it from fouling the panel meter. You will also have to drill a hole in the top rear panel for the 3.5mm power socket – see photo. Be sure to position this hole so that the socket clears the panel meter when it is mounted. The various components can now all be installed in the case, starting with the switches and the input connector block which carries the test terminals. Bend the lugs on the input connector block so that they are parallel to the front panel, to prevent them shorting to the PC board. The board can then be fitted inside the case and secured using two self-tapping screws into the short mounting pillars. Before fitting the digital panel meter, it should have a link fitted from N to OFF (to disable the polarity indication). In addition, you have to fit three 100kΩ resistors from P1, P2 and P3 to OFF. These modifications are all shown on Fig.3 (do not forget the link). The panel meter we used has an external dress bezel with two captive mounting screws. This bezel is mounted from the front and the panel meter then fitted over the screws and secured using nuts and fibre washers. The assembly can now be completed by running the point-to-point wiring. Note the connections between S2 and the panel meter. In particular, the middle lefthand terminal of S2 goes to the ON pad on the meter board (not to resistor P3). By contrast, the top and bottom lefthand terminals are connected to the resistors on P2 and P1 respectively. Fig.4: two insulated flying leads must be run on the copper side of the PC board, between the pot terminals and points CT & CW, as shown in this diagram. Test & calibration Before you begin testing, you need to wind an inductor which is used later during the calibration procedure. To do this, wind around 300 turns of 30 B&S wire on the L5305 bobbin, then fit the cores and clamp them together using a 20mm bolt, flat washer, fibre washer and nut. Once the coil has been wound, clean and tin the ends, then connect a 180Ω 1% resistor in parallel with it. Now put the coil to one side – you’ll need it shortly, for Step 7 of the following procedure. To test the unit, apply power and check that D5’s cathode is at about 12V. This voltage will depend on the particular plugpack you use and is not too critical. Next check the +9V, Fig.5: check your PC board by comparing it with this full-size etching pattern before installing any of the parts. JULY 1999 33 H SILICON CHIP INDUCTANCE METER 4 5 6 7 3 2 8 9 1 PRESS AND ADJUST FOR METER NULL +5V and -5V rails – these should all be within 5%. The panel meter should show a reading of around 16.00 or 160.0, depending on the range. Now check the supply rails at the IC pins. If these are OK, you are ready to calibrate the instrument using the following step-by-step procedure: Step1: connect a multimeter across the test terminals and set it to a range suitable for measuring 10mA DC. Step 2: press S1 and check the current on the multimeter. It should be close to 10mA. Step 3: release S1, rotate VR3 fully anticlockwise (0Ω), remove the multimeter and connect a 3.3Ω resistor across the test terminals. Step 4: switch your multimeter 34 Silicon Chip 0 10 Fig.6: this full-size artwork can be used as a drilling template for the front panel. mH to a low voltage range and connect it between pin 6 of IC7 and ground. Short switch S1’s terminals using an alligator clip, then adjust VR3 (on the front panel) for a 0V (or as close as you can get) reading on the multimeter. Step 5: connect the multimeter across the 100µF capacitor at the output of IC8 and (with S1 still shorted) adjust VR4 for a reading of 0V. Now adjust VR5 for 0V across the 100µF capacitor at the output of IC9. Step 6: adjust VR6 for a zero reading on the panel meter and remove the shorting clip from S1. Step 7: remove the 3.3Ω resistor from the test terminals and fit the inductor that you wound earlier (with its parallel 180Ω 1% resistor). Step 8: rotate VR3 to the zero ohms position and measure the voltage on pin 6 of IC7. It must be adjusted to zero by fitting a resistor between pin 2 and either the +5V or -5V rail. Two sets of pads have been placed on the PC board for the resistor, from pin 2 to each supply. Our unit needed an 8.2MΩ resistor to the negative rail. Step 9: set S2 to µH and adjust VR1 until the panel meter reads 174.9. Step 10: switch to the mH range and adjust VR2 for a reading of 17.49. That completes the calibration procedure. You can now close the case and begin using your new inductance meter. By the way, if you find that you cannot zero (or null) the panel meter when measuring an inductor, even with VR3 rotated fully clockwise, it means that the resistance of the inductor is greater than 10Ω. Despite this, the inductance reading displayed when S1 is released should be close to the correct value. What if it won’t work? If you have problems, the first step is to check your sol dering. In particular, look for missed solder joints and shorts between adjacent tracks and IC pins. A few voltage checks can also help pinpoint problems. First, check for + 2.5V on pins 5, 6 and 9 of IC3. Pin 6 of IC5 and pin 6 of IC6 should be around 0V DC and 4-5V AC. Most meters will give quite a low reading on the AC output of IC5. As long as you get an indication, the signal is probably OK. The bases of Q1 and Q2 should be at 5.7V and their emitters at 6.3V. The collector of Q2 should read 100mV. Note that when the unit is working properly and there is no inductor across the terminals, the meter will read around 16.00 or 160.0, depending on the range. This is due to the positive peak detector swinging to full output and is normal. Variations VR3 can be changed if you wish to measure inductors with DC resistances greater than 10Ω. For example, a 25Ω pot will allow inductors with resistances up to 25Ω to be measured. Naturally you will have to recalibrate the potentiometer scale or you can simply multiply the front panel readSC ing by 2.5. NEW SUPER LOW PRICE + LASER AUTOMATIC LASER LIGHT SHOW KIT: MKIII. 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Australia June 99). we have plans/notes COMPLETE INTELLIGENT BATTERY / CHARGER PCB (to suit above 6 cell for $9 (on floppy) & info to find POWER MANAGEMENT SYSTEM packs) 7.2V trickle charger add $5 lots of info on the net . For the home or car New Battery Monitor 16 X 2 LINE LCD CHARACTER Kit:12v / 24v monitor with DISPLAY + 1M IDC ext. cable, LED, low voltage cutout, audible buzzer & switch on a PCB. $12 or 3 for $30 alarm before cutout. $199 PAIR $25 $45 LOOK! $10 www.oatleyelectronics.com PC CONTROLLED DIGITAL LIGHTING SYSTEM PC PARALLEL PORT $8Ea. $18 $6 www.oatleyelectronics.com major cards with ph. & fax orders, Post & Pack typically $6 Prices subject to change without notice $20 POSSIBLE WATER LOSS 24V 29.2 14.2 28.4 13.8 27.6 13.4 26.8 COOL BATTERY 12.6 25.2 12.2 24.4 13.0 OFF LOW BATTERY 12V 14.6 FULLY CHARGED WARM BATTERY ON SOUND WARNING LOW VOLT CUT OUT 26 11.8 23.6 11.4 22.8 11.0 22.0 10.6 21.8 10.2 20.4 BATTERY MANAGEMENT SYSTEM NORMAL CHARGING OVER CHARGED BATTERY CONDITION OATLEY ELECTRONICS ***NEW******NEW*****NEW******NEW*** SAW RESONATOR LOCKED. NO TUNING 433 MHz UHF DATA TX & RX MODULES +ENCODER PCBs TO SUIT. Many security codes, 4 zones, multi channel. 100 See our WEB SITE for more TX module $11 TX + encoder $18 RX module $18 RX + encoder $25 AT LAST! A COLOUR CMOS CAMERA WITH GOOD RESOLUTION + BUILT IN AUDIO + FREE PLUG PACK + F R E E V H F M O D U L AT O R . Available with swivel mount or dome mount housing. $160 $160 BNC connector (video), DC connector (power), RCA connector (audio). 330000 pixel. 330 TV line res. 7-12Vdc 55mA max. INTRO PRICE $160 NEW 12VDC-240VAC/300VAINVERTER This new design is very efficient, is rated at 300VA constant not peak (when our transformer is used). It has auto switch on and uses High power MOS-FETS that require very minimal heat-sinking. The kit inc. PCBs, all onboard components, 4 high power MOSFETs and all for $35 To save money you Designed to use minimal can use your power & has a battery own transformer saving 12 led bar-graph or we can supply indicator. Kit inc PCB, all the Kit + a high quality compact toroidal onboard parts, label, 10A transformer plus wiring kit plus a used cutout MOSFET + suitable surplus case for $32....For 50A MOSFET large electrolytic capacitor for $89 (IRFZ44) add $3. ** CCD CAMERA SPECIAL ** WITH A FREE UHF MODULATOR To complete your solar system we have The best "value for money" CCD camera 12-24V SOLAR REGULATOR KIT: on the market! 0.1 lux, High IR response & 15A Kit inc all onboard parts & PCB. $25 hi-res. Better than most MINI AUDIO MODULE - (Pre-built) cheaper models. 32 X 32mm This amp/pre-amp is Ideal $99... With 1of these for use with our lenses pinhole cameras. 12Vdc, (60deg.), 92 deg.; Hi sensitivity, 0.6W output 120 deg. or forJULY 1999 35 (150 deg) add $10 operation includes electret mic. $10 SC-JLY-99 $10 CHECK OUR WEB SITE FOR MORE (NEW) 12V / 2.3Ah AUDIOVOX LEAD ACID BATTERY (Model BTR-1900). Priced at a fraction of their real value (as used in video cameras & older mobile phones - same as panasonic batteries we sold before). 180 (L) x 60 (H) x 22 (W) mm, 0.67Kg, made in Japan. The contacts PO Box 89 Oatley NSW 2223 (which are easily solderable) are at one Ph ( 02 ) 9584 3563 Fax 9584 3561 end of the battery. 2 batteries + suitable orders by e-mail: oatley<at>world.net float charger. 4 CHANNEL VIDEO SWITCHER KIT This kit can switch manually or sequentially up to 4 audio/video sources. Features inc. VCR relay output for STOP / REC, can be switched with PIR or alarm inputs Add a security channel to your TV with a VHF modulator, watch TV & flick channels & see who’s at the door can be auto switched using PIR units Kit + PCB + all on-bourd parts $50. Optional VHF modulator / mixer $18 PELTIER EFFECT DEVICES Make a solid state food cooler / warmer for the car etc. with 2 heatsinks, a fan and one of the following. Could be used for cooling overclocked PC CPUs. All 40 X 40mm. 4A T 65deg. Qmax 42W $25 6A T 65deg. Qmax 60W $27.50 8A T 65deg. Qmax 75W $30 Device comes with instructions to build cooler / heater plus data. Some used surplus heatsinks avail. ***NEW*****NEW*****NEW*****NEW*** QUALITY AUSTRALIAN MADE FEATURE PACKED MINI ALARM SYSTEM. Features inc. boot release, central locking output, imobiliser output, indicator flash relay. Has with 2 key-fob transmitter keys. Drawn in proportion Audio-Video Transmitter Whether you are want to monitor a surveillance camera or transmit your VCR’s signal to another TV set, this Video Transmitter will come in handy. It avoids the need for difficult cabling and can send signals over a 20-metre range. By JOHN CLARKE I T IS BECOMING MORE and more common to install video surveillance cameras, to improve safety and to deter thieves. You can use them to monitor the swimming pool, the front or rear door and the baby sleeping. But while they provide you with a clear coverage of the area under surveillance, they can be very difficult to install. This is because you need to run wiring between the camera and monitor which can involve drilling through brick walls and accessing tight spots in the ceiling or under the floors. Using a Video Transmitter removes the need to run the wiring. It also means that you can use a television set to receive the signal. This is because the video signal from the camera is modulated and transmitted through the air just like a miniature TV station. Note that a video monitor cannot directly be used to receive the signal. If you want to use a video monitor, you will need to use a VCR to receive the signal 36 Silicon Chip first. The video output from the VCR can then be connected to the monitor. The Video Transmitter can also be used to transmit signals from a VCR to a second or remote TV set in the home without interconnecting wires. The Video Transmitter is housed in a small plastic case. It has a telescopic antenna to transmit the signal and is powered from a 12VAC plugpack. It has a 12VDC output for powering a video camera and audio board. The transmitter’s modulator will accept both video and sound inputs. The schematic arrangement for the Video Transmitter circuit is shown in Fig.1. It comprises a power supply, a video modulator and two wideband amplifiers. The video modulator produces a modulated television transmission on VHF channel 0 or channel 1. This radio frequency signal is then boosted by the two amplifiers to a sufficient level for transmission via the telescopic whip antenna. The transmission range depends on the transmitting and receiving antennas. From our experiments you can expect good reception using a short antenna over a 15m range in Fig.1: block diagram of the video transmitter. The video modulator operates at VHF channel 0 or 1. a typical single level home, while reception over a 20m range requires both antennas to be adjusted in length to match the transmission frequency. If you have a 2-storey home, you will probably be able to obtain satisfactory results from one level to another but if your home has reinforced concrete floors (ie, with steel mesh), the system will not work from floor to floor. Circuit description The circuit for the Video Transmitter is shown in Fig.2. The video signal Main Features • • • • • • Transmits over a 20m range. Provides both video and mono sound. Channel 0 or channel 1 selection. 12VAC plugpack operation. 12V DC output for a video camera. 12V output for a microphone adaptor. Fig.2: two cascaded wideband monolithic wideband amplifiers boost the video modulator’s signal so that it has a range of about 15 metres in a typical single-storey household. JULY 1999 37 Fig.5: winding details for the input filter inductor L1. The signal at the wiper of VR1 is AC-coupled to the emitter of transistor Q1 which acts as a DC level shifter and clamp to provide DC restoration. In fact, Q1 is connected as an emitter follower which is biased by trimpot VR2. So how does Q1 work? What happens is that the voltage at the emitter is held constant at 0.6V (nominal) below the base. The video signal is AC-coupled to the emitter of Q2 via a 470µF capacitor and while it is able to drag the emitter up in voltage it cannot pull it down below the level set by VR2. This means that the bottom of the sync pulses are clamped to the emitter voltage while the video signal can ride up above this level. Hence, DC restoration has been applied to the video signal before it is fed to the modulator. So what does all that mean in practice? It allows the best contrast range in the transmitted picture; ie, the full range from black to white in a B&W picture or luminance in a colour picture. The audio signal for the modulator is coupled in via two 10µF capacitors connected back-to-back. The RF output from the modulator is applied to two monolithic amplifiers, IC1 & IC2, connected in cascade. The specified amplifier, uPC1688G, is a wideband surface mount device capable of providing amplification for frequencies up to 1GHz and the power gain at 500MHz is typically 21dB. A .001µF capacitor couples the signal from the video modulator to the Fig.3: wiring layout for the video transmitter. The two surface-mount wideband amplifiers are mounted on the copper side of the PC board – see photo. Fig.4: actual size artwork for the PC board. is AC-coupled via two back-to-back 470µF capacitors to remove any DC offset and then applied to trimpot VR1 which sets the video level applied to the modulator. If the video level is set too high, the modulator will produce a signal that is received as overly bright and washed out. Conversely, if the video signal is too low, the picture will appear unsaturated (dark) and may have a tendency to roll due to an inadequate sync signal. Table 1: Resistor Colour Codes  No.  1  2 38 Silicon Chip Value 10kΩ 82Ω 4-Band Code (1%) brown black orange brown grey red black brown 5-Band Code (1%) brown black black red brown grey red black gold brown Parts List Fig.6: this is the full-size artwork for the front-panel label. input of IC1 while and 82Ω resistor provides loading for the signal. The output of IC1 is then AC-coupled to IC2 via another .001µF capacitor and loading is provided by an 82Ω resis tor connected in series with a .001µF capacitor. With two of these amplifiers working in cascade you might think that there would be quite a strong signal being fed to the whip antenna but the reality is a little different. Let’s look at what happens. First, the nominal output level from the video modulator is 78dBµV and this means that the output is 78dB above 1µV. This corresponds to about 8mV of signal into 75Ω or 0.85µW. The two uPC1688G amplifiers each have a power gain of about 21dB (at or below 500MHz) and so we are amplifying by a total of 42dB. This corresponds to a power amplification of 15,848 and the total expected power at the antenna is 13.4mW. That’s in theory. In practice, the coupling losses caused by loading mis matches at each stage and to the whip antenna mean that the signal radiated by the whip antenna is really quite small but adequate to give a maximum range of about 20 metres inside a typical home. Power for the circuit comes from a 12VAC plugpack which is fed via a low-pass filter consisting of inductors Table 2: Capacitor Codes    Value IEC Code EIA Code .01µF 103 10n .001µF 102 1n L1a & L1b, wound on a balun core, together with two .01µF capacitors. These prevent video signals from being radiated from the mains leads and also prevents hum modulation in the video transmission. The filtered AC voltage is full wave rectified using diodes D1-D4 and smoothed with a 470µF capacitor. It is then fed to two 3-terminal regulators. REG1 provides the +5V supply for the modulator and amplifiers while REG2 provides +12V for a video camera. Construction The Video Transmitter is constructed on a PC board coded 0240-5991 and measuring 105 x 60mm. It is housed in a plastic case measuring 130 x 68 x 41mm. You can begin construction by checking the PC board against the published pattern. Check that the hole sizes are correct and that there are no shorts or breaks between tracks. Check also that the PC board clips neatly into the integral clips within the plastic case. Fig.3 shows the PC board component overlay and wiring layout. Install the resistors first, using Table 1 as a guide to the colour codes for each value. Then insert the PC stakes at the input terminals, the antenna output, the RF output from the modulator and the three anchor points for the vertical shield between the RF output and the 3-terminal regulators. Install the video modulator and be sure to solder its three earth pins to the PC board groundplane. The RF output from the modulator requires an RCA plug to be inserted with a short length 1 PC board, code 02405991, 105 x 60mm 1 single sided blank PC board, 15 x 50mm 1 front panel label, 125 x 65mm 1 VHF video modulator (Jaycar LM 3850) 1 plastic case, 130 x 68 x 41mm 1 12VAC 300mA plugpack 1 balun former 1050/2/F29, L1 2 RCA panel-mount sockets 2 DC panel sockets 1 TV telescopic antenna 1 RCA line plug 1 150mm length of 0.63mm enamelled copper wire 1 150mm length of medium duty hookup wire 2 spade or eyelet connectors 1 6mm spacer 1 M3 x 15mm screw and two nuts 1 M3 x 10mm screw, star washer and two nuts 14 PC stakes Semiconductors 2 uPC1688G wideband amplifiers (IC1,IC2d) (DSE Z-6011) 1 7805 5V regulator (REG1) 1 7812 12V regulator (REG2) 1 BC337 NPN transistor (Q1) 4 1N4004 1A diodes (D1-D4) Capacitors 1 470µF 25VW PC electrolytic 3 470µF 16VW PC electrolytic 5 10µF 16VW PC electrolytic 4 .01µF ceramic 4 .001µF ceramic Resistors (1%, 0.25W) 1 10kΩ 2 82Ω 1 1kΩ horizontal trimpot, VR2 1 100Ω horizontal trimpot, VR1 of hookup wire soldered to the centre terminal. This centre terminal wire connects to the PC stake as shown. Solder a short length of wire at the side of the RCA plug and connect it to the earth PC stake. The remaining components can now be mounted. The electroly tic capacitors must be inserted with the correct polarity while the small ceramic types can be inserted either JULY 1999 39 The vertical shield piece consists of a piece of blank 15 x 50mm PC board and is installed by soldering it to three PC stakes, as shown here. A piece of tinplate could also be used for the shield if you don’t have any blank PC board. way round. The codes marked on the side indicate their value and Table 2 shows the possible markings for the two values used in this circuit. The ceramic capacitors should be mounted as close as possible to the PC board. The 100Ω trimpot (VR1) may be marked with a 101 code while the 1kΩ trimpot (VR2) may be marked 102. Install these in the positions shown. Diodes D1-D4 must be oriented as shown and when installing the regulators be sure you position the 5V one (REG1) nearest to diode D2. The regulators are mounted with a 6mm spacer between them, with a 15mm M3 screw and nut clamping them together. This acts as a form of heatsinking for REG1 and as an earth point for the supply filter. The vertical shield is made from a piece of blank PC board (or tinplate) measuring 15 x 50mm. It is mounted as shown by soldering the copper to all three of the PC stakes. Amplifiers IC1 & IC2 are tiny surface-mount devices which are mounted on the copper side of the PC board. The surface-mount package is rectangular with a tab connection at each corner. You will need a soldering iron with a very small tip and ideally, you should use a desk mount magnifier lamp when doing the job. You will certainly need it to identify pin 1 on each uPC1688G package. It is slightly wider than the remaining three pins and must be positioned as shown on the PC board. Inductor L1 is wound as shown in Fig.4. Use 0.6mm enamelled copper wire and wind on two coils of five turns each, in the directions shown, for L1a and L1b. Use the panel label as a guide to drilling the holes for the RCA sockets and the DC sockets in the side of the box. A 3mm hole is also required for the antenna mounting screw which is positioned adjacent the antenna output PC pin. Drill out these holes and position the PC board in the box. Wire up the antenna to an eyelet terminal and secure it with the 3mm screw, star washers and two nuts. If you do not want to use a tele scopic antenna, you can use a length of wire instead. Fit the RCA sockets and wire these up with hookup wire. The 12V DC socket can also be connected with hookup wire. The 12VAC socket is wired via inductor L1 and the terminals are bypassed with the .01µF ceramic capacitors. These are earthed to a solder lug eyelet which is secured to the screw located on the regulator tabs. Testing With all the wiring complete, check your work carefully against the dia- PIN 1 PIN 1 You will need to use a fine-tipped soldering iron, a pair of tweezers and a magnifying lamp when soldering the two uPC1688G wideband amplifiers (circled) to the copper side of PC board. Be sure to correctly identify pin 1 (the wider pin) of each IC before soldering it into place. 40 Silicon Chip This close-up view shows how the telescopic antenna is mounted on the side of the case using an M3 x 10mm machine screw, two nuts and a star washer. If you don’t want to use a telescopic antenna, you can use a length of wire instead. The two 3-terminal regulators are bolted together with a 6mm spacer between them, using a 15mm M3 screw and nut. This acts as a form of heatsinking for REG1 (5V). Be sure to orient these two device correctly; their metal tabs both face towards the shield piece. grams of Fig.2 & Fig.3. Then apply 12V from an AC (or DC) plugpack to the input socket and measure the voltage at the outputs of REG1 and REG2. You should obtain +5V and +12V respectively. The supply pins to IC1 and IC2 can be measured on the .01µF capacitor leads and should be +5V. Similarly, the input and output DC voltages on IC1 & IC2 can be measured on the .001µF coupling capacitors. They should be +0.91V on the input and about +3.3V at the output. You can test the transmitter by applying a video signal to the input. This signal can be obtained from the output of a VCR, a video camera or a TV pattern generator. Connect an antenna to the TV set using a set of telescopic “rabbit ears”, a “spiral” dipole or a ribbon cable dipole. Alternatively, you may be able to receive the signal via your roof mounted TV antenna. Adjust trimpot VR1 slightly anticlockwise from its fully clockwise setting and set VR2 fully clockwise. Check that the TV can receive the signal transmitted by tuning the TV set to the transmitted channel. The channel switch on the video modulator is channel 0 when positioned towards the outside of the case and on channel 1 when positioned towards the RF socket. Now adjust VR1 for the best picture contrast. In some cases, you may need to adjust VR2 slightly anticlockwise to improve the contrast from a video camera. You should not need to use this adjustment when the video signal is from a good program source such as from a VCR recording or off-air signal. Antenna adjustments If you want the maximum range from the Video Transmitter you will need to carefully adjust the element length of both receiving and transmitting antennas and make sure that both antennas are oriented identically. For example, they can be mounted both upright or both horizontal. For channel 0, the antenna can be 1/4-wavelength (whip) at 810mm long or half wavelength (dipole) at 1.62m. The channel 1 antenna length should be 660mm (whip) or 1.3m (dipole). Note that these lengths may need to be made about 5-10% shorter to compensate for the effect of the antenna thickness on the radiation impedance. You can make small adjustments to the antenna lengths to obtain the best transmission. In most cases, a nominal 1/4-wavelength whip antenna on the transmitter will give good results but 1/2-wavelength antennas will provide better distance reception. Note that we have not provided an on/off switch for the Video Transmitter. This is because it is envisaged that the transmitter will mainly be used for surveillance cameras where the power will be on all the time. Alternatively, if the transmitter is used to send signals to a second TV set for occasional usage, you can turn the transmitter off by switching off the plugpack at the power point, by unplugging the plugpack from the Video Transmitter socket or by installing a switch in the Video SC Transmitter box. JULY 1999 41 SERVICEMAN'S LOG TV servicing can be frustrating A most frustrating experience is to expend lot of time, money and effort on a set, only to find that it has to be written off anyway. One of my stories this month emphasises this downside of servicing. Mr Walter’s TV set is a Samsung CB230Z 30cm AC/DC model, employing a TK-100 chassis. This model is unusual in that the power supply is designed and manufactured for Sam sung by another manufacturer. Furthermore, there are at least three variants on the power supply circuit that I know of, with each version becoming more complex. Consequent- ly, when they fail, the latest version is harder to fix than the earlier ones. By the time I received this set, it had already been “fixed” several times by a person or persons unknown, leaving it for me to guess what parts had been replaced and whether they were the correct replacements. The first thing I did was to obtain the service manual with most of the modifications added, which established that it was approximately similar to a “version three”, with a few additional parts. The power supply had destroyed itself fairly violently, with a shattered mains fuse and a short-circuited IC901 (STR58041). I also found that resistors R908 (0.22Ω) and R913 (10Ω) were burnt. As these were closely associated with transis t or Q901 (2SC2335), I measured it and it too was faulty. Measuring and checking all the other components didn’t show much else wrong. I replaced resistors R903 and R916 (180kΩ) to be on the safe side but everything else looked OK. I didn’t replace the electrolytic capacitors as they looked fairly new. I then switched the power supply on carefully, using a 200W globe in series to limit the current. The set came on without distress and even with the globe removed, it was quite content, delivering 24V to the set, which gave a good picture and sound. I let it run for the rest of the day and it was still going well five hours later. The heatsinks were warm without being hot and I was quite happy to pronounce it fit and well. Pyrotechnics The owner couldn’t pick it up straight away so I left it on test. Of course, you can guess what happened when he finally showed. I was demonstrating the set to him, flicking channels with the remote control, and everything was fine until I switched it to standby and 42 Silicon Chip then on again. The noise was spectacular, as were the pyrotechnics which almost matched my red face. As you can imagine, Mr Walters was not impressed. When he had gone and the smell and smoke had subsided, it was back on to the bench. I replaced all the parts I had already changed and I also fitted new EXR electrolytic capacitors for C915 (10µF, 100V) and C913 (47µF, 100V) for good measure. EXR capacitors are a new range of 105°C types, designed for switchmode power supplies. This turned out to be the right move because what I thought were new capacitors were actually very clean original Samsung units. And this, I believe, was what had caused the trouble because, even a week later with constant switching on and off with the remote control, the set was still working. Mr Waters kept asking me about the length of the warranty and wasn’t happy until I wrote down an extra three months on top of the three months I normally give. I don’t normally do this but in the circumstances, he probably had a point. A frustrating failure My next customer was a Mr Milano, who has a large extended family so, naturally, when his Philips 21CT8873/75Z (KR5187R) TV set stopped, he took it to his cousin Angelo who fixes hifi systems. Angelo kept the set for about three months before finally admitting that he couldn’t fix it. Actually, I think his excuse was “I can’t get the parts . . .” Mr Milano finally decided to give it to me for a second opinion. At first I thought the repair was going to be straightforward as the mains fuse kept blowing. I hoped it would just be a faulty bridge rectifier or dual posistor. Unfortunately it wasn’t. It was the chopper transistor, BUW12A (7687), which was short circuit. This sent alarm bells ringing. This set (2BS chassis) uses a SOPS (Self Oscillating Power Supply) and if the chopper transistor goes, it is usually due to loss of oscillation. That’s be cause the chopper is turned full-on continuously, destroying itself and all its drivers. This means that the feedback circuit has to be checked for faults before switching it back on – very carefully – with a Variac. If there is no feedback and no oscillation, the chopper will again self-destruct immediately, so the Variac has to be used very judiciously above 90V, while monitoring the 140V rail. Also, to protect the secondary circuits, it is a good idea to short the base and emitter of the horizontal output transistor (25D1577PV) to turn it off and connect a 100W globe load to the 140V rail instead. And although the SOPS is short-circuit proof, it is wise to check there are no shorts on each of the five voltage rails, otherwise one could get misleading results. The SCR (6727) should also be checked. Unsoldered parts It was while I was preparing to do all this that I noticed various components were unsoldered, which made me even more concerned. So, just to be cautious, I spent some considera- ble time checking these components with the ohmmeter. The haul I collected included the horizontal output transistor, the two SOPS drivers, the optocoupler and fuse 1601 (125mA). After replacing these I set to work, using the Variac to wind up the input voltage. I took it right up to 240V without any drama and the 140V rail was stable. Unfortunately, when I removed the shorts, globe and Variac, the set fired up but nothing happened. The 140V rail had dropped dramatically and the horizontal output transistor was very hot. I diagnosed that the horizontal output transformer (5620) was almost certainly faulty. This is very common on the 2BS chassis – and also presents the difficulty of unsoldering the legs through the rivets. OK, so this repair was going to be expensive but this was commensurate with the set’s features. It is, after all, a 51cm stereo remote TV set and looks the part. It cost about $1500 in 1988 and this one was well looked after. But wait; there’s more. After the new horizontal output transformer was fitted, I expected JULY 1999 43 Silicon Chip Binders Serviceman’s Log – continued These binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a dis tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. to see a picture but no. We still had almost exactly the same symptoms. The 140V rail could still be restored by shorting out the base and emitter of the horizontal output transistor (7618), so I concluded that either the new transformer was faulty or there was a short across its secondary from some other part of the circuit. DC checks revealed that the four voltage rails derived from the transformer were OK, as indeed were all the other circuits connected to it. After removing the jumper across the base/ emitter leads of the horizontal output transistor, I unplugged the leads (D17) to the horizontal deflection yoke. Everything now came on properly, with the 140V rail at its correct level. Removing the deflection yoke finally revealed a sorry mess that had been responsible for all the trouble.  Hold up to 14 issues Stopgap yoke  80mm internal width The next problem was to replace the yoke (5990), as it was beyond repair. The yoke is not listed as a spare part and is only sold with the self-converging picture tube A51 EBS60X. Initially, I found and fitted an old deflection coil from a KT3 chassis, to confirm that my diagnosis was correct. That restored the picture, even though REAL VALUE AT $12.95 PLUS P&P  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p. Available only in Australia. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my  Bankcard  Visa  Mastercard Card No: ________________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ 44 Silicon Chip the geometry and convergence were wrong. The closest deflection yoke available as a spare part was a type 4822 150 10282. However, this is not designed for use with a self-converging picture tube like this. Although others have had some limited success fitting this yoke on this tube, I have found the dynamic convergence to be unacceptable. This particularly applies to the top and bottom of the screen where it is over 2mm out, even when an additional magnet ring assembly is fitted and adjusted carefully. The impedance of the coils matches close enough, the horizontal being 2Ω and the vertical 13Ω, but the coil construction layout is completely different. The final straw The sad thing was that this was the straw that finally broke the camel’s back. The additional cost of even a substitute yoke, giving a not-so-good picture, could not be justified for an 11-year old set and so it had to be scrapped. To ease my pain for the amount of time spent on it, Mr Milano gave me the set for spares and it now sits in the corner supporting other junked sets. And he went out and SC bought a new one. Ce la vie. Acknowledgements To Reader’s Letters I would like to acknowledge two letters from readers offering advice, prompted by stories in recent columns. These letters were published in the May 1999 “Mailbag” pages. First, I am indebted to Mr T. Cairn ey for his five minute replacement technique tip for the Akai loading arm block (prompted by the Akai VP170 story, January 1999). This technique is fine if the spring doesn’t come off with its broken axle (which it invariably does) and lodges between the white slide plate and jams the mechanism. Then, unfortunately, the only answer is to remove the deck. It is interesting to see some of the decks fitted in this series of Akai VCRs; many differ considerably from the exploded diagrams in the service manuals. Second, I was very interested in Paul Schick’s comments (prompted by the Masuda T1092 story, April 1999) on why diodes get hot. I find it very difficult to get specifications and equivalent books or software on diodes or, indeed, any information at all on the huge variety available. This sometimes makes it extremely difficult to find substitutes that work. I would find it very useful to have the differences between the various diode types explained. These include high-speed switch i ng, switching, modulator, controlled avalanche, valley point current and general purpose types. It would also be useful to have a reference that deals with the number codes for zener diodes, which differ between manufacturers. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au PRODUCT SHOWCASE 7500A Universal Clamp When Tech Rentals say they have a high current universal clamp meter available, they mean high current: this Technic P75.3C clamp meter measures up to 7500A, AC or DC. It is intended to be used in conjunction with a voltmeter, chart recorder or oscilloscope, having no readout device of its own but giving a DC voltage output in proportion to the measured current. Output “full scale” is 1.5V for a 7500A current. Using a Hall-effect sensor, the clamp covers a range of DC to 1000Hz and can clamp a cable up to 83mm in diameter, and busbars of 122 x 54mm or 100 x 64mm. For more information, contact Tech Rentals, 12 Maroondah Hwy, Ringwood, Vic 3134. Phone 1800 632 652; fax (03) 9879 4310 Speakerphone + Caller ID from DSE A new phone from Dick Smith Electronics features both hands-free (speakerphone) operation and an inbuilt caller ID display. The LCD screen displays the caller's number and, if that number is programmed into memory, the name of the caller. Up to 13 numbers can be stored (including 3 one-touch redial) and the phone remembers the previous 99 calls for later review, if required. The DSE Speakerphone with Caller ID (model F 4518) also has mute, redial, recall, flash and pause buttons plus adjustable ringer tone and volume. With a recommended retail price of $98 it is available from Dick Smith Electronics Stores, resellers and the Direct Link mail order service. Two very different power supplies The programmable Californian Instruments 2001RP precision AC power supply can provide up to 2000VA at frequencies from 16Hz to 5000Hz. A Windows graphical interface permits control of the supply from a PC. Intended for such tasks as development and ATE, it can provide high peak currents and power factors of 0.0 to 1.0 without derating. An optional power meter module provides measurements including RMS current, voltage, true power, crest factor and peak current, thus allowing the 2001RP to be used as a “single box” power test system. An optional IEEE488 or RS232 interface is also available. For more information, contact Westek Industrial Products, Unit 2, 6-10 Maria St, Laverton Nth, Vic 3026. Phone (03) 9369 8802; fax (03) 9369 8006; email westek<at>projectx. com.au By contrast, this is a more “traditional” supply from Nilsen Technologies. The Thurlby-Thandar EX725M multi-mode power supply has two independent, fully isolated adjustable outputs of 0 - 75V DC at 2A each, or can operate in a single mode delivering an output of 150V DC <at> 2A, or 75V DC <at> 4A. It is provided with special safety binding posts which can accept spade terminals, 4mm plugs or bare-end wires without exposing any metal parts. For more information, contact Nilsen Technologies, 150 Oxford Street, Collingwood, Vic 34066. Phone 1800 623 350; fax 1800 067 263. JULY 1999 53 PCB Mounting Toroidal Transformers Learning Remote Mounting any transformer on a PC board can be difficult if they are not intended for the task but toroidal transformers are often more difficult. That’s why these new series of 10VA and 30VA toroidals from Altronics are likely to be welcomed by manufacturers and enthusiasts alike. The transformers are “potted” before being encased in a finned plastic case. A thermal fuse is also fitted. All connections are via the PC board mounting pins which are close to the four corners of the case, with provision also made for a centre self-tapping bolt for extra stability or security. The smaller 10VA model, cat no M4506, measures 53mm square x 28mm high. The larger 30VA model measures Snap-in IEC mains filter with the works! for up to 10 devices 63mm square x 33mm high. Both have two 120V primaries, obviously to be connected in series for 240V AC. There are four transformers in each range. Each has two identical secondaries which can be series or parallel connected. The 10VA model has 6+6V <at> 0.83A, 9+9V <at> 0.5A, 12+12V <at> 0.4A and 15+15V <at> 0.3A. The 30VA model has 6+6V <at> 2.5A, 9+9V <at> 1.6A, 12+12V <at> 1.2A and 15+15V <at> 1.0A. For more information, contact Altronic Distributors in Perth (08 9328 2199), Altronics resellers around Australia or refer to page 63 of the 1999/2000 Altronics Catalog. This 10-in-1 learning remote control can control up to 10 devices, with 47 storage keys for each device. It features multi-codes, multi-languages, label editing, programmable macros, a liquid crystal display with back-lighting, date/time alarm function and more. The macro feature allows the user to transmit up to 20 codes at once, with just 2 buttons. It suits most brands of equipment controlled by infrared remotes such as TV sets, CD and DVD players, video cassette recorders, amplifiers and so on. It has a recommended retail price of $129.95 (Cat AR-1708) For more information, contact any Jaycar Electronics store or their head office on (02) 9743 5222; fax(02) 97432066. (www.jaycar.com.au) New gas soldering irons from Altronics Westek Industrial Products have released this Schaffner “snap into place” IEC mains input connector which also incorporates a filter, mains switch, fuse holders and voltage selector. The FN300 is IEC 950 compliant and snaps into an appropriate mounting hole without screws or nuts. Two sets of metal fingers provide excellent contact with panels and the filter earth terminals, ensuring good high frequency performance. The unit has a double-pole mains switch, 115/230V selector and filters which operate over the mains frequency range of 50-400Hz. For more information, contact Westek Industrial Products, Unit 2, 6-10 Maria St, Laverton Nth, Vic 3026. Phone (03) 9369 8802, fax (03) 9369 8006, email westek<at>projectx.com.au 54 Silicon Chip Whether you’re looking for a small soldering iron for delicate jobs or a larger model with plenty of heat, Altronics Distributors say they have you covered with these two gas-powered models from Iroda. Both models use liquid butane as used in many cigarette lighters. The Solderpro 50 is a 50W model with a tip temperature of between 210°C and 400°C, depending on setting. At mid-setting it gives around 30 minutes of soldering capacity with a full tank. With cap, the iron measures 153mm long and weighs 60g. The cap also contains a lighter. The recommended retail price of this iron (cat no. T2595) is $29.95. The larger Solderpro 100 is a 120W model with a tip temperature up to 500°C. With a larger 20ml tank, it can give around 120 minutes at mid setting. This model is significantly larger at 233mm (including cap) and weighs 142g. It also includes an auto-igniter: when the iron is turned on, a piezo igniter lights the gas. This iron sells for $69.00 (Cat no. T2598) Neither iron is supplied with butane: this is available from Altronics or from many tobacco shops, hardware stores and some supermarkets. Both irons are supplied with a standard soldering tip; a range of spare tips, including an air blower and blow torch, is available for the 120W model. For more information, contact Altronic Distributors in Perth (08 9328 2199), Altronics resellers around Australia or refer to page 98 of the 1999/2000 Altronics Catalog. 486 motherboards with CPU – less than $20! Oatley Electronics has available a brand new PC motherboard, complete with 486/40 processor, for the princely sum of $18.00 (plus p&p). The motherboard is a “baby AT” size, measuring just 180 x 220mm but has standard mounting hole positions and standard locations for expansion slots and keyboard connector, so it should fit a standard PC case. The board is supplied with a “UMC” brand 40MHz 486SX chip but with a bus speed of 25, 33 or 40MHz, will also handle AMD, Cyrix and Intel chips up to DX4/75 and DX-4/100 in the standard socket 5 configuration. An unusual feature is the inclusion of both 30 and 72pin SIM sockets, giving a maximum RAM of 32MB. The motherboard can also support cache memory from 32K to 512K. There are five 16-bit and one 8-bit expansion sockets and Award ROM Bios is supplied. The question must be asked, of course, “why on earth would anyone these days want or need a 486 motherboard?” At $18 and brand new, these Y2K compliant mother-boards would make an excellent upgrade path for an old PC – a 386, 286 or perhaps even an old 8086 machine. They could also be used in a variety of control applications or, with the addition of a power supply, RAM, I/O cards and a monitor, as a “test bed” for hardware or software which you don’t want to risk running on your main PC. For more information, contact Oatley Electronics on (02) 9584 3563, email oatley<at>world.net or via their website, www.oatleyelectronics.com.au FULL RANGE ELECTROSTATIC $2990! INTRODUCTORY PRICE N ow you can afford the legendary clarity, transparency, depth, dimension and precision that only an electrostatic speaker can deliver. The new Vass ELS-5 is a full range electrostatic speaker that consists of dual electrostatic panels with separate bass and treble sections to cover the entire frequency range between 40Hz and 20kHz.  Diaphragm mass equivalent to a sheet of air 3mm thick  5 year warranty  Wide selection of finishes available  Each speaker individually hand built and tested  Four other models priced from $6,990 to $25,000 Also available, the Vass SW-P pyramidal subwoofer designed to complement electrostatic speakers in high ceiling rooms, RRP $1,500 TOROIDAL POWER TRANSFORMERS We exclusively use and recommend ME amplifiers. Please contact us for a demonstration of this brilliant combination • • UNIT 1, 42-44 GARDEN BVDE, DINGLEY, VICTORIA 3172 Manufactured in Australia Comprehensive data available HARBUCH ELECTRONICS PTY LTD 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 ELECTRONICS PH (03) 9558 0970 Fax (03) 9558 0082 email: vass<at>hotkey.net.au JULY 1999 55 ECTRONICSHOWCASELEC MicroZed Computers GENUINE STAMP PRODUCTS FROM Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (02) 6772 2777 – may time out to Mobile 0409 036 775 Fax (02) 6772 8987 http://www.microzed.com.au Most Credit Cards OK Need prototype PC boards? We have the solutions – we print electronics! • Four-day turnaround, less if urgent • Artwork from your own positive or file • Through hole plating • Prompt postal service • 29 years technical experience • Inexpensive • Superb quality NEW FROM QUESTRONIX DVS5 Video & Audio Distribution Amplifier DVS5 Video & Audio Distribution Amplifier VGS2 Graphics Splitter Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. VGS2 Graphics Splitter High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email - questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC's, Converters, etc. QUESTRONIX All mail: PO Box 548, Wahroonga NSW 2076 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only Do you want YOUR product or service showcased to Australasia's most important electronics marketplace? Printed Electronics 12A Aristoc Rd, Glen Waverley, Vic 3150. Phone: (03) 9545 3722 Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. SWITCHMODE POWER SUPPLIES 25W500W Extensive Range EMC Technologies' internationally recognised Electromagnetic Compatibility (EMC) test facilities are fully accredited for emissions, immunity and safety standards. EMC Technologies Melbourne: (03) 9335 3333 Sydney: (02) 9899 4599 CALL ME: RICK WINKLER on (02) 9979 5644 and let me explain how cost effective the SILICON CHIP ELECTRONICS SHOWCASE can be for YOU! 6 Sarich Court, Technology Park, Bentley WA 6102 Ph: 08 9470 1177 Fax 08 9470 2844 web: www.computronics.com Silicon Chip Binders 129 5 REAL VALUE AT $  Heavy board covers with 2-tone green vinyl covering PLUS P &P  Each binder holds up to 14 issues  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Price: $A12.95 plus $A5 p&p each (Australia only; not available elsewhere). Buy five and get them postage free. 56 Silicon Chip 56 Silicon Chip CTRONICSHOWCASELECTR BUSINESS FOR SALE: SPEAKER SALE For the very first time we are having a sale of selected loudspeaker drivers from the prestige MOREL line. On sale are two drivers: MW 265 222mm Shielded Woofer, Fs 30Hz ,Vas 88.6L Qts 0.44 Power 150W Hexatech voice coil Normally $190 DMS 30S • • • • • • • • NOW $130 27mm Shielded Dome Tweeter, 94mm dia. Fs 650Hz Power 200W Hexatech voice coil Double chambered Sens 90dB Normally $129 • Escape to the sun in beautiful Coffs Harbour! Stable electronic retail business Easily run by husband and wife team. Agent for GSM carrier Access to large electronics suppliers (niche market). Very strong customer base inc Government depts and schools etc. Five year rental option on current highway premises. Full figures available. Current owners (12 years) are moving to a new business. Price only $55,000 + SAV. Enquiries: Hunter & Associates (02) 6651 6818 NOW $75 All other MOREL products available – many ex-stock We are sole Australian Distributors for: • CLIO Electro-Acoustic Measurements • SOFIA Vacuum Tube Curve Tracer • JASPER Power Router Circle Jigs Australian Audio Consultants PO Box 11, Stockport SA 5410 Phone / Fax 08-85-282-201 E-mail aac<at>rbe.net.au IN YOUR NEXT ISSUE OF Items planned for the August issue*, due on sale at your newsagents July 28. Subscribers receive their copies a little earlier. POWERED COOLER Take one commercial cooler, add this Peltier-effect device and you have a cooler that really keeps the cans cold! Operates from your car's cigarette lighter. LIGHTS ON FOR SAFETY Clever circuit runs your car's headlights at about 80% brightness during the day so you can be seen – but full brilliance at night. * These features currently in production but are subject to alteration PLUS: • COMPUTER MONITOR MONITOR – Check out any EGA/VGA monitor • X-Y Table – Controlling the stepper motors • Plus a special feature on HOME THEATRE – all you need to know And all the popular features: • Serviceman's Log • Circuit Notebook • Radio Control • Product Showcase • Vintage Radio • Ask SILICON CHIP SUBSCRIBE TO SILICON CHIP AND $AVE! As a subscriber, you will not only receive your copy earlier – you will actually save money! Check it out: 12 issues from the news-stand = $71.40; 1 year subscription: $59 AND we pay the postage! See the handy order form on page 67 of this issue. JULY 1999 57 JUNE 1999 57 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. DTMF decoder and 1Hz timebase The MC145436 Motorola DTMF decoder chip, if fitted with a 3.579545Hz crystal, will decode the standard international DTMF codes as used by most telephone dialing systems around the world, and by other DTMF equipment such as mobile phones, answering machines, etc. If the MC145436 chip is fitted with a 3.2768MHz crystal, as shown in the diagram, and if the matching encoder chip, TCM5087, is fitted with the same frequency crystal, then the MC145436 chip will decode the “modified” DTMF tones successfully but not decode the standard international tones. This modified DTMF code structure could have applications where remote controlled equipment systems are custom-made. A second useful result of this circuit is to provide an accurate crystal-locked 1Hz timebase which is better than an RC time-constant method, suitable for digital clock circuits or precise one second timing circuits and applications. The MC145436 chip has a divide-by-8 output on pin 11, which divides the 3.2768MHz frequency down to 409,600Hz. This frequency is then divided down by the 4020 counter, by a factor of 16,384, to 25Hz. The two 4018 counters then divide the 25Hz output down to 1Hz. The 4081 AND gates are required to enable the 4018 to divide by the odd number of 5. P. Howarth, Gunnedah, NSW. ($35) Auto nicad charger with float This circuit was built to charge a 7.2V 1800mA.h battery pack for an underwater flash gun and it utilises the supplied DC plugpack for the power supply. When the battery pack is connect ed, the normally closed pushbutton switch S1 is momentarily pressed to turn the charger on and the red LED operates, indicating charging (about 200mA) via Q1 and R1. When the battery voltage exceeds about 9V (ie, when the battery is charged), the output of comparator IC1 goes high 58 Silicon Chip to trigger SCR1 which turns off Q1. The green LED also operates and a low (about 40mA) trickle charge is then supplied via R2 & R1. P. Boyle, Edithvale, Vic. ($30) Rev limiter modification for points distributors One of the drawbacks of the Rev Limiter (April 1999) is that it will produce quite rough engine operation on older cars which have points distributors. This is because its rev limiting action will confuse its own speed sensing circuit by also interrupting the engine timing pulses from the points. Mains-powered remote control tester This handy remote control tester will respond to the signal from any infrared handpiece and will light the LED and sound the buzzer (if fitted). The 5V DC supply for the IR receiver and transistor Q1 is derived directly from the 240VAC mains supply via the 1µF capacitor and 100Ω limiting resistor. The 5.6V zener diode and 1N4004 diode set the supply to 5V and it is filtered by the 470µF capacitor. The IR receiver can be obtained from an old VCR or can be purchased from Oatley Electronics or Dick Smith Electronics. The solution is to add a “sample and hold” circuit to hold the output of the LM2917 speed sensing circuit constant while the ignition blocking action is taking place. This is done by using Mosfet Q5 as an analog switch between pin 3, the output of the frequency to voltage converter in the LM2917, and pin 4, its non-inverting comparator input. The gate of the Mosfet is controlled by the signal from the collector of Q3 on the Ignition Switcher PC board. What happens is this: when the Ignition Switcher is inac tive (ie, no rev limiting taking place), the collector of Q3 is high and Mosfet Q5 is on, connecting pin 4 to pin 3 of the LM2917. When the Ignition Switcher is active, the collector of Q3 is low and Mosfet Q5 is off and so the voltage stored at pin 4 by the 2.2µF capacitor provides the “hold” action. The result is smoother rev limiting action. Note: this modification is applicable only to older cars with points distributors. Brett Hirshman, West Pymble, NSW ($35) WARNING! ALL PARTS in this circuit operate at 240VAC. Do not build it unless you know exactly what you are doing. Since the circuit is directly powered from the 240VAC supply, all parts operate at high voltage. This means that it must be fully isolated from the user by safely building it into a plastic case or an earthed metal enclosure. Lee Martin, Belconnen, ACT. ($25) JULY 1999 59 Last month, we presented part 1 of this 2-part article on the Programmable Ignition Timing module which is teamed up with our High Energy Ignition System, as described in the June 1998 issue. This month we give the details of installation and programming. By ANTHONY NIXON Pt.2: Installation & Programming A S WE NOTED LAST month, do not attempt to hook up the PIT module to the High Energy Ignition (HEI) system until you have had the HEI system running in your car for at least a few weeks. This is good practical advice, as a number of constructors have installed the two systems straight into their cars and then had a torrid time trying to get it all working. So now we assume that you have the HEI installed and working and that the PIT module has been assem60 Silicon Chip bled and the initial checks have been performed. The exact installation of the PIT module will depend on your particular vehicle but it should be somewhere not too obvious. Don’t mount the unit in the engine compartment though, as the parts are not rated for high temperatures. The keypad can be removed from the PC board after programming if you wish, as an added security measure. Be sure to run all the wiring in a professional manner, using automo- tive cable and connectors to ensure reliability. HEI connections You will need to make five wire connections from the PIT module to the HEI board, as shown in Fig.8. The +12V supply from the ignition switch is fed to the HEI board, which then supplies 12V and 0V for the PIT module. A +5V connection is taken from the 78L05 (REG1) on the PIT module to the HEI to power the MC3334P chip. Two other wires are used to connect the “Trigger In” from the HEI board and the output from the PIT module to pin 5 of the MC3334P on the HEI board. DO NOT connect a separate ground wire from the PIT module to the vehicle chassis. If the ground wire from the HEI board goes open-circuit, the high coil currents will try to flow through the small PC board tracks on the PIT module, possibly causing them to burn off and damage the ICs. Vacuum switch Fig.9 shows the mounting details for microswitch S1. It is mounted on a rightangle bracket which is attached to the vacuum actuator. The arm of the microswitch sits in a slot cut into the vacuum actuator and in the absence of vacuum, is normally held down. When vacuum is present, the actuator moves upward and the microswitch arm releases. Be sure to connect the leads to the microswitch exactly as shown; ie, the lead from pin 3 of the PIC goes to the contact marked “NO”). As mentioned previously, the advance plate in the distributor must be clamped with the weights in the outward position. If you do not wish to use the electronic vacuum advance, then you can leave the original setup as is and leave the vacuum advance input (RA4) disconnected. Another use for the vacuum advance input is to interface it to the Knock Sensor project, as published in the April 1996 issue of SILICON CHIP. The filtered output from the knock sensor is fed to an LM311 comparator. When this voltage goes higher than that preset on the inverting input pin 3, the output at pin 7 will go high. When the PIC detects this high it will retard the ignition by an amount set This view shows the assembled PC board without the keypad. The keypad plugs into the connector located near the bottom edge. by the user. Fig.10 shows the circuit. In effect, it works in the opposite manner to which it was intended. As the output of the LM311 is open-collector, it provides compatibility between the 8V circuitry of the Knock Sensor and the 5V supply of the PIT module. Note: this circuit arrangement has not been tested on a vehicle. Rotor contact modification Normal ignition advance in a conventional distributor is achieved with a mechanical setup using bob weights and springs and the amount of advance depends on the throttle opening and engine RPM. The changes in advance also change the position at which the rotor button passes by the spark lead contacts in the rotor cap when a spark is produced. To cater for this, the end of the rotor button contact is usually flared so that it is able to conduct the high voltage to the spark plug contacts over the full advance range. Fig.11 shows what is required. The PIT module has 45° of advance JULY 1999 61 Fig.8: use this diagram when connecting the PIT module to the HEI system. available. This means that your rotor button may need to be modified so that it will stay in contact with the spark lead connections over this advance range. Remember that we are talking about 45° of crank advance. This translates into 22.5° of distributor advance because the distributor cam turns at half the speed of the crankshaft. Therefore the flared end of the rotor button must be elongated to function over 22.5° and possibly more, if the 62 Silicon Chip original vacuum advance is left connected. If the extension is too narrow or too wide, then a spark might be missed or worse, the spark may “jump” to the wrong spark contact, causing misfiring. Fine tuning this part of the project may require a little trial and error to get it right. Initial timing setup When the engine is first started, the PIT module retards the ignition by 45 crank degrees (22.5 distributor degrees) and stays constant at this value until the engine RPM reaches the user programmed MIN RPM value. The timing will then begin to advance at the programmed rate. Before attempting to modify the distributor or change its position, make a note or mark the position it is currently in. In last month’s article, it was mentioned that the distributor is modified by wiring its advance weights in the fully out position and the vacuum advance plate is clamped Fig.9: the vacuum actuator is modified to operate a microswitch. At low vacuum, the microswitch arm is held down. Conversely, when manifold vacuum is high (ie, at light engine loads), the microswitch arm is released. so that it cannot move. This will give a certain amount of advance from your base setting. Use a protractor to find out how much “distributor” advance this is and subtract it from 22.5. If the answer is positive, advance the dis tributor from its original position by this amount. Then when the engine starts, the PIC will retard the timing back to the original base setting and begin advancing it again as the RPM rises. If the result was negative, the advance value that your engine gives is greater than the advance range that this system can cater for and may not work. When the ignition is timed (using a timing light), the vacuum advance must be disabled. This is accomplished by removing and blocking off the vacuum hose so that it has no effect on the vacuum switch. Static timing To time the engine with the engine stopped (ie, static timing), turn the crankshaft to the correct position, then rotate the distributor until the LED just turns on. This indicates that the points have just opened. The LED will be off when the PIC detects that the points are closed. This method will not work with a reluctor pickup. Note that because the LED drive signal frequency is proportional to the engine RPM, this signal can be used to drive a tachometer. Programming There are nine parameters that must be programmed into the PIC to make up each data set. Every parameter, as well as the correct number of digits for these parameters, must be entered. The PIC will monitor the digit entry and display each numerical keypress. After the last digit of the last parameter has been entered, only the centre segment of the display will be illuminated. If this segment fails to light, then you have not entered enough data. If the segment lights before you have finished, then you are trying to enter too much data. In Table 1: Data Set Contents Parameter Digits Example Mi n RPM 4 0800 Mi d RPM 4 3000 Mi d Advance 2 20 Max RPM 4 500 0 Max Advance 2 30 D w el l 2 20 Vacuum Advance 2 10 C yli nders 2 06 Security Code 2 99 either of these two cases, you must enter the complete set of data again. You will notice that the data for the MIN RPM and Cylinders both have leading zeros. The MIN RPM value is allocated four digits, so four digits must be entered. Similarly, the Cylinders value is allocated two digits, so two digits must be entered. You cannot enter an RPM value that is lower than a previous RPM value. For example, MID RPM cannot be lower than the MIN RPM value of 0800. The PIC has two internal advance ranges from 30 to 300 RPM and then from 300 RPM to the MIN RPM value that you specify and for this RPM range the timing is fully retarded. The MAX Advance value can be greater than, equal to, or lower than the MID Advance value. This allows the second stage advance to have a retarding effect, if needed, rather than continuing to advance the timing until MAX RPM is reached. The negative advance feature is common to both data sets, which means that if you want a negative advance setting for one set, you must also have a negative advance setting for the other. If one is positive and the other negative, then the positive data set will malfunction (see the note at the end of this article). The absolute minimum dwell width that the software will generate JULY 1999 63 Fig.10: this circuit could be used to enable the PIT module to operate in conjunction with the Knock Sensor featured in the April 1996 issue of SILICON CHIP. Fig.11: the trailing end of the rotor button contact needs to be extended and the leading edge trimmed to cope with the modified operation of the distributor. Note that fine tuning this part of the project may require some trial and error to get it right. 64 Silicon Chip is 1ms. In this system, this is the time that the coil is OFF. If you enter a “00” value for the Dwell, then a constant 1ms will be set automatically. If any angle is calculated to be less than 1ms, then 1ms will be used. In addition, as the engine RPM increases, a point may be reached when the dwell width is calculated to be less than 1ms. When the PIC detects this, it sets the minimum to 1ms. The dwell angle from any input device has no effect on the system dwell times, however it is good practice to set the points normally, as specified by the manufacturer. The PIC will debounce the points signal, whether points or electronic sensors are used. If you do not wish to use the electronic vacuum advance then enter “00” for that parameter. After you enter a security number, you must remember it. If you forget, you will not be able to gain access to the system unless you tediously go through the 99 code combinations, one by one. If you do not want to use a security code then just enter “00”. You must press the “*” key after entering all the data as this tells the PIC to run the calculations and store the results into the EEPROM. If you do not do this before removing power, the new data set will be lost. Due to memory restrictions, the PIC does not do any error checking on entered data. The Cylinder value and the Security Code are common to both data sets. If you change the cylinder value in one data set, then you must re-enter the other data set with the new cylinder value as well and run the calculations again. For example, if you entered 6 cylinders for data set one, and afterwards you enter 8 cylinders for data set two, then the calculations will be wrong in data set 1 because they were based on 6 cylinders. You only have 45° of advance to “play” with, so any data you enter that goes outside this range may result in erratic operation. The software can handle an advance value plus a dwell value greater than 45° but as soon as the points open, the PIC will “chop” the last timing sequence off in favour of the new one when it becomes necessary for the coil to be switched off. This may only result in a shorter dwell time but it may also result in misfiring. The software is trying to cater for a wide range of operating conditions, but it may not be able to operate with values that are too far out of the ordinary. Operational modes There are two modes of operation for this system: Data Entry Mode and Engine Run Mode. If you look at the system flow chart featured in last month’s article, you should be able to follow how everything works. If there is no data set stored in EEPROM for the current level, then the system will power up in Data Entry Mode and the centre display segment will be lit. If there is data, then the system will power up in Engine Run Mode. Data Entry Mode The PIC will be waiting for a keypress to select a particular programming function. These are the ones that are available: Function Key Read RAM 3 Read EEPROM 4 Enter New Data 5 Clear Display 6 Change Data Set 7 Display Data Set 8 Calculate/Store data * Exit # • Read RAM - Key 3: After pressing this key, repeatedly pushing the “*” key will display the data stored in RAM. Each parameter is separated by a “-” character. If there is no data in RAM then an error condition will be displayed. Press key “#” to exit. • Read EEPROM - Key 4: This transfers the current data set from EEPROM to RAM. Any previous RAM contents will be lost but the EEPROM contents will remain unchanged. After pressing this key, repeatedly pushing the “*” key will display the data now stored in RAM. Each parameter is separated by a “-” character. If there is no data in the EEPROM then an error condition will be displayed. Press key “#” to exit. • Enter New Data - Key 5: After pressing this button, a “0” will be displayed and you can then enter a new data set. From the example in Table 1, you would enter the data as follows: 080030002050003020100699 After the last “9” key is pressed, the display will show “-” to indicate that all data has been entered. Because all timing is now controlled electronically, the advance plate inside the distributor must be securely clamped in the fully-advanced position and its advance weights wired in the fully out position. In effect, the Programmable Ignition Timing Module retards the timing from the preset maximum to give the correct value according to engine speed and load. If a mistake is made while entering the data set, you can press the “#” key to abort. Press key “5” again to restart the data entry process. • Clear Display - Key 6: “-” is displayed. • Change Data Set - Key 7: This key alternates between the two data sets available. When data set one is selected, “1” is displayed. Similarly, when data set two is selected, “2” is displayed. You can alternate between the two sets even though they do not have data stored, but you will not be able to start the engine if the selected set does not have valid data. This key can also be used while the engine is running but only if both sets have valid data. • Display Data Set - Key 8: This key displays the currently selected data set. • Calculate/Store Data - Key *: When this key is pressed, a set of engine operating parameters will be calculated according to the data that was entered. The results, along with the user data in RAM will be stored into EEPROM so that they are available each time the ignition is turned on. If there is no valid data in RAM an error message will be displayed. • Exit - Key #: Pressing this key terminates functions 3 and 4. If the system is in Data Entry Mode waiting for a function to be selected and there is data available in the current set, then the system will go into Engine Run Mode and wait for the engine to start. If the current data set is not valid then the system will stay in Data Entry Mode. The error condition that is displayed is similar to a “?” character. Quick programming review (1) Turn Power on. (2) Select data set – Key “7” (3) Begin data entry – Key “5” (4) Key in data – eg, 080030002050003020100699 (5) “-” will be displayed (6) Calculate/Store data – Key “*” (7) Either enter other data set, back to step 2, or press key “#” to allow engine start. Engine Run Mode If the “#” key was pressed while in Data Entry Mode with a valid data set available, then the current data set will be displayed, and the system will wait for the engine to start. If the system is powered up and JULY 1999 65 Reprogramming Existing Chips Any new software can be reprogrammed into your existing chips if they are sent to the author with a $5.00 fee for postage, etc. There is one small problem here. Originally the software was written for the PIC 16C84 which only has 36 bytes of RAM. These chips are now obsolete and were replaced by the newer 16F84s which have 68 bytes of RAM. The latest software needs 38 bytes of RAM to operate so the 16C84s cannot be reprogrammed. Programmed 16F84s are available and are still at the original $27 which includes postage & packing. Chips can be returned for reprogramming or ordered from: Anthony Nixon, 8 Westminster Court, Somerville Vic 3912. If you return the chip, please make sure it is properly packaged to prevent mechanical as well as static damage, as no responsibility can be taken by the author if a chip is damaged in transit. There is some basic information about the ignition module as well as an email link at http://www.picnpoke.com the current data set is valid, then two things can happen. If there is no Security Number then the software will wait for the engine to start and the display will show the data set that is being used. If there is a Security Number then the display will be blank and you must type in the exact two-digit code to unlock the controller. If the wrong code is entered, then the software will do nothing at all, so you must turn the power off and start again. If the correct code is entered, the software t bu d e l i o s p o h S E! C I R P F L HA will wait for the engine to start and the display will show the data set that is being used. While the PIC is waiting for the engine to start, you can go into Data Entry Mode by pressing key “9”. You cannot do this after the engine starts. When the engine is running, you can alternate between data sets by pressing key “7”. There must be valid data in both sets for this to happen. Problems with installation The PIC is a pretty robust little chip but it is sensitive to static electricity and also to electromagnetic interference (EMI), so when handling the chip try not to touch the pins. Do not be tempted to try the project out on the bench if it is connected to the HEI module and a coil and spark plug. The open spark will cause the PIC to run erratically due to the EMI produced and will fool you into thinking something is wrong. Keep all of the PIT module wiring away from the ignition coil as the electrical noise produced here may interfere with the PIC. Negative advance addendum Nearly all of the PICs that have been supplied in the past with the negative advance feature have a small white dot on the top surface of the chip. When using these chips, both data sets must be programmed for either positive or negative advance, not mixed, or the positive data set will treat the data as being negative and give improper operation. There was a great deal of time taken to scrounge up enough memory to change this so that this restriction no longer applies. Either set can now be positive or negative. The PICs programmed with this software will have a coloured dot instead of white placed SC on the top surface of the chip. 14 Model Railway Projects THE PROJECTS: LED Flasher; Railpower Walkaround Throttle; SteamSound Simulator; Diesel Sound Generator; Fluorescent Light Simulator; IR Remote Controlled Throttle; Track Tester; Single Chip Sound Recorder; Three Simple Projects (Train Controller, Traffic Lights Simulator & Points Controller); Level Crossing Detector; Sound & Lights For Level Crossings; Diesel Sound Simulator. Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop-soiled or have minor cover blemishes. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) This book will not be reprinted Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 66 Silicon Chip $ L PECIARIPTION UBSC AVER $ WANT TO SAVE $$$ ON ? You have probably noticed a cover price rise from this issue, due to signficant cost increases. That's the bad news – and we apologise. But there is good news: if you take out a SILICON CHIP subscription NOW, you won't pay the higher prices! That's right: you'll save for your whole subscription! And if you're already a subscriber, you can renew your subscription now and lock in the this low rate for your entire subscription – regardless of the actual renewal date! 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia JULY 1999 67 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG A mainland Chinese radio receiver from the 1960s It’s not often that one gets to work on a radio set that was manufactured in mainland China during the 1960s. The set described here had some interesting features, including valves that were pin-for-pin compatible with western types. Occasionally, one gets the opportunity to examine vintage radios from behind the Iron Curtain. Many of us are familiar with the Russian transistorised multi-band portable radios that appeared from time to time on the market. One example was the Selena, which evoked curiosity from 68 Silicon Chip the electronic fraternity in the 1970s. This interesting set used a turret tuner to do the band changing, something rarely used by western manufacturers. But what about sets that were made behind the other end of the Iron Curtain (or was it the Bamboo Curtain)? What did the communist Chinese make in the way of radio receivers? They didn’t export valve radio equipment to the Free World and they were, in fact, quite insular at the time. An opportunity to see what they did in the 1960s presented itself towards the end of 1997, when a friend obtained a set from a market in Shanghai. I was keen to see this set and to gain some idea of what the Chinese were doing in electronics around 1963, the year the set was manufactured. It is quite an interesting radio, with one or two unusual ideas. The receiver itself is a 4-valve BC superhet, designed for use on either 110VAC or 220VAC, with a transformer power supply. The various views of the set show the wiring style used and what the various components looked like. Some aspects of the set’s electronic and mechanical design are similar to our methods. However, we tended to use point-to-point wiring during that era, while this receiver used tag strips quite extensively. This meant that some wiring was unnecessarily long – it certainly wasn’t point-to-point. In addition, the capacitors were generally larger than the types used here for the same ratings. But some things never change – they suffer exactly the same problems of excessive leakage. The resistors Vintage Radio Repairs Sales Valves Books Spare Parts See the specialists * Stock constantly changing. * Top prices paid for good quality vintage wireless and audio amps. * Friendly, reliable expert service. Call in or send SSAE for our current catalogue The 455kHz IF transformers are unusual in that the adjustment slugs are at the back of the cans. Obviously, the coils are mounted side by side, a technique used in some early Australian IF transformers. were similar to the ones used by the Japanese of the same era but appeared to be of better quality. IF transformers The accompanying photographs show that the 455kHz IF transformers are rather different to those used by Australian manufacturers. The adjustment slugs are at the back of the cans and it is obvious that the coils are mounted side by side, as were some early Australian IF transformers. The aerial and oscillator coils are similar to the slug-tuned coils of the same era in Australia. Aligning the oscillator and aerial coils at the high frequency end of the tuning range is a bit of a problem. The trimmer capacitors are similar to the all-wire types used by Philips and some other manufacturers. They use a 16-gauge (or thereabouts) enamelled wire as one lead and fine tinned wire wound around the enamelled wire as the other lead. They can only be easily adjusted once. I removed the one on the aerial coil and replaced it with a conventional trimmer capacitor, which is easier to adjust. Chassis layout From the photographs, it can be seen that the chassis layout is quite conventional. However, there is one thing I really do like about this receiv- er when it comes to servicing – tip it upside down and it rests fairly evenly on the two IF transformers and the power transformer. This makes it very easy to work on the under-chassis components. The set will also sit quite nicely on the end that’s adjacent to the power transformer. It’s a pity more Australian radios weren’t made like this – servicing them would have been so much easier. Getting the set out of the cabinet is a breeze too. First, you remove the plywood back panel (no cheap cardboard here) by removing four screws. After that, you simply pull the two knobs off, unscrew two bolts on the back of the chassis and pull it out. One point of interest is that the front edge of the chassis is wedged into a slot made in the plastic, which stops it from moving around. Operatic sets used a similar method of attaching the chassis to the cabinet. The set had previously been serviced on a few occasions and the work was rather rough, so some of my criticisms regarding the layout are not entirely directed at the manufacturer. That said, the manufacturer must have had some training on wiring from Radio Corporation, as single-strand insulated wire was used and the wires were all wrapped around their respective terminals several times! This means that the parts RESURRECTION RADIO 242 Chapel Street (PO Box 2029) PRAHRAN, VIC 3181 Tel (03) 9510 4486 Fax (03) 9529 5639 can only be easily removed by cutting them out, as it isn’t easy to unwind the soldered leads without cooking everything in the near vicinity. Circuit details I find that having a circuit of a set makes servicing so much easier. Unfortunately, my trusty copies of the Australian Official Radio Service Manuals were of no help this time, so I had to trace the circuit out myself. I started by checking the valve types, as this can give a good idea of the style of circuit used. The line-up included a 6A2, a 6K4, a 6N1-J and a 6Z4, none of which I’d ever heard of before. They are all miniature types and all have seven pins except the 6N1-J which is a 9-pin valve. These valves are taller than a 6BA6 but shorter than a 6AQ5. In short, the valves were all “homegrown” types, the exception being the 6Z4 which appears to be a miniature version of the 84/6Z4. These unknown valves certainly added to the difficulties of tracing out the circuit. The set appeared to be a superhet of some sort, with two coils JULY 1999 69 CHINESE MAINLAND SET CIRCA 1963 Notes: 6A2 is pin compatible with the 6BE6 6K4 is pin compatible with the 6BA6 6N1-J is pin compatible with 6BQ7A (inc. shield) and is compatible with the 12AU7/12AT7 except for heater pins The 6Z4 is a near equivalent to the 6X4 (but is not pin compatible) Fig.1: this is the circuit diagram of the receiver, as traced out by the author. It is a 4-valve set with a twin-triode output stage. and a valve (6A2) close to the tuning gang – obviously a converter of some sort. As a starting point, I carefully traced each lead, checked continuity through the coils and traced out a circuit up to the pins of this valve. It looked like a circuit that a pentagrid converter would use, so I checked out a circuit based on a 6BE6 and the two looked remarkably similar. In fact, the 6A2 even used the same pins as the 6BE6 for each function. I then checked the next section (around the 6K4) and this appeared to be a conventional IF stage. I drew the circuit out with the valve pins numbered and then checked it against a circuit using a 6BA6. The pin-outs were almost identical! The detector turned out to be a germanium diode. From there, the demodulated signal is fed to the volume control, which was followed by some sort of 2-stage audio amplifier (6N1-J). I was having some trouble here as the speaker transformer had gone open circuit in the primary. This means that the screen of the audio output valve cops quite a wallop and can glow rather too brightly. Initially, I suspected that the valve was probably a triode pentode but that didn’t appear to be the case when I took a closer look. There was no 70 Silicon Chip screen – just two cathodes, two grids, two plates and one pin earthed. It all seemed a bit strange until I checked to see what the earthed pin did inside the valve. It was a shield between the two sections and this indicated that the valve was a twin triode, not a triode pentode as expected. It is certainly unusual to find a triode output stage. Interestingly, the pin outs are the same as for the 6BQ7A twin triode RF amplifier, as commonly once used in TV tuners. The audio section even has negative feedback! The power supply is based on the 6Z4 and was quite conventional. Unfortunately, one half of the transformer’s secondary HT winding was open circuit. This version of the 6Z4 has similar ratings to the familiar 6X4, although its pin out is not quite the same. The final circuit is shown as Fig.1. As you can see, it’s quite straightforward and it certainly makes the set easy to service. Repairs It was now time to actually service the receiver. First, the various capacitors were checked and those with excessive leakage were replaced. The resistors all appeared to be within tol- erance but the loudspeaker transformer was faulty and had to be replaced. The rest of the set appeared to be in good condition so I applied power and used a multimeter to check the voltages. These were OK and the set worked but its performance was initially quite poor. This improved quite markedly after a full alignment but there were still problems. At times, the set appeared to be unstable, particularly when I added an extra RF bypass near the front end of the receiver (more on this later). One of my pet hates is having to guess where the dial pointer should be when I align the oscillator, so that the dial calibrations are accurate. This is always a problem when the dial-scale remains in the case of the set when the chassis is withdrawn. This receiver falls into that category but because the pointer is so far behind the dial-scale, parallax error is quite significant anyway. As a result, the dial pointer position isn’t all that critical, which is just as well. Because of the similarity of the 6A2 and 6K4 valves to the 6BE6 and 6BA6 respectively, the latter were substituted and the results were quite satisfactory. I then tried a 6BQ7A in lieu of the 6N1-J and the performance decreased somewhat but was otherwise OK. I then substituted another 6BQ7A and it really went well except that it was unstable. The audio amplifier appeared to be taking off due to RF signal from the IF strip feeding back into it. This problem was cured by placing a 47kΩ resistor in series with the grid (pin 7) of the audio amplifier output stage. This was yet another example where insufficient IF filtering in the audio amplifier causes trouble. I didn’t try substituting a 6X4 rectifier in place of the 6Z4, as a wiring modification would have been necessary. However, I’m sure it would have worked well had this been necessary. Other problems By now the set wasn’t performing too badly but there were still a few things to be sorted out. First, the power transformer had one half of its HT secondary winding open circuit and I suspect that it had been in this condition for quite some time. To overcome this problem, the two plate leads (pins 1 and 7) of the 6Z4 were joined together and the faulty winding lead was cut off. This step increased the HT voltage by about 20V. In addition, a 240V AC supply is rather high for a set designed for run off 220V AC, so a 180Ω 5W resistor was wired in series with the mains. This gave a nominal 220V AC on the primary of the transformer. Running the set for a few hours in this condition showed no abnormal temperature rise in the transformer despite the open circuit winding. As pointed out, the valves used are similar to ones we know and they draw the same heater currents, the exception being the 6N1-J which draws 0.6A compared to the 6BQ7A’s 0.4A. For replacement purposes, the 6A2 = 6BE6, 6K4 = 6BA6, 6N1-J = 6BQ7A and the 6Z4 = 6X4 (with some wiring modifications). Did the Chinese copy our valve types and give them different type numbers or was it just coincidence? Summary The Chinese receiver used tag strips quite extensively, while Australian sets of the same era mainly used point-to-point wiring. In addition, the capacitors are generally larger than the types used here for the same ratings. In many ways, the set is not greatly different from the average Australian 4/5 valve superhet radio of the era. As already pointed out, the main difference concerns the use of a twin-triode audio output stage. I suspect that the pin-for-pin com- patibility of valves and the general similarity in many areas to sets in the West is just too much of a coincidence. However, other areas of the set’s design are quite original and different. It’s hard to judge what market it was intended to fill but at a guess it was probably intended for the upper class market in China of that period. A similar set here would have been considered an austerity model. SC JULY 1999 71 -Y TABLE Part.3: Building The Z Axis WITH STEPPER MOTOR CONTROL OK; you thought that the XY table was heading in the right direction but wouldn’t really do the job you wanted it to. Well, you’re right. You can’t really do much with it without the third axis control. Mechanical Design & Construction by Ken Ferguson Electronics by Rick Walters 72 Silicon Chip T HE Z AXIS IS constructed as an additional frame to which the XY table is bolted. It is capable of supporting a pen, a small electric drill or some other tool you may deem useful. We used a Dremel drill and stand, mainly because we already had it to hand and we made up a pen holder which will be described in a future article. A third stepper motor was used to drive the Z axis but instead of the threaded lead-screw system used for the X and Y axes, we used a crank system to move the tool. While there is nothing essentially wrong with using another threaded lead screw, it is not cheap and we didn’t really feel that it was necessary. The Z axis stepper motor is driven by the single stepper motor driver board which was featured in SILICON CHIP in August 1997. The board should have the modification detailed in the May 1999 issue. If you don’t already have these, we have now modified the stepper motor drive boards and these will be featured as part of this series of articles on the XY Table. For convenience, and also to keep them safe from harm, we mounted both the stepper motor boards in a small plastic case with a 12-way terminal strip on the back. The terminal strip provides a convenient termination point for the leads from the three motors. An additional 4-way connector terminates the wires from the power supply. We brought the LEDs, which were originally mounted on the PC board, to the front panel so we could monitor each board’s operation. If you don’t fit the modification featured in May 1999, you MUST turn the 5V supply on first then load and run the software, turning on the other supplies at the opening screen. As we explained last month, it is possible for the ICs to turn on in a manner which can cause some of the output transistors to fail if this procedure is not followed; not a nice sight or smell! With the modified PC boards, this procedure will not be necessary. We set the jumper to select board 2 for the dual stepper driver and board 3 for the single stepper. If you plan to use the relay interface board, which was described in the July 1997 issue of SILICON CHIP, with this setup (or even if you don’t) we suggest that you Fig.13: the Z axis frame is made from 20mm x 20mm steel tubing which is welded into a frame measuring 830mm x 240mm. (Drawing scale 1:5). Stepper motor driver JULY 1999 73 Fig.14: details of the top motor mounting bar. This is made by cutting two pieces of 10mm x 10mm bar 280mm long. One piece of 27mm x 10mm x 10mm is then welded at each end to make a slotted bar with a ¼” Whitworth slot running almost the full length. (Drawing scale 1:2). Fig.15: details of the motor mounting bracket. It is folded from a piece of 3mm plate and has an outrigger bracket 50mm x 25mm x 5mm welded to one side to mount a terminal strip. (Drawing scale 1:1). bypass IC4c as this makes that board compatible with the current software. Z axis frame The Z axis frame is made from 74 Silicon Chip 20mm x 20mm steel tubing which is welded into a frame measuring 830mm x 240mm. The details are shown in Fig.13. The bottom left and right ends protrude about 50mm at the front and back to form the supports for adjustable feet. A 20mm x 20mm plate 5mm thick is welded at each end, then drilled and tapped to support the 1¼” Whitworth bolt which is used to level Parts List 4 790mm 20 x 20mm tube 4 470mm 20 x 20mm tube 2 340mm 20 x 20mm tube 2 240mm 20 x 20mm tube 1 50 x 50 x 5mm plate 4 20 x 20 x 5mm plate 2 260mm 25 x 25mm angle 1 13mm 20mm rod 1 15mm 15mm rod 1 12mm 15mm rod 2 125mm 50 x 5 bar 2 270mm 25 x 5 bar 4 50mm 25 x 5 bar 2 130mm 12 x 5 bar 1 70mm 12 x 5 bar 2 280mm 10 x 10 bar 2 27mm 10 x 10 bar 14 1¼” x ¼” Whitworth bolts 16 1½” x ¼” Whitworth bolts 22 flat washers 22 ¼” Whitworth nuts 4 plastic inserts 2 4mm grub screw Fig.16: the motor crank is made from a circular piece of 5mm plate 50mm in diameter. A ¼” clearance hole was drilled at 20mm radius. A piece of 15mm diameter rod 15mm long was cut and slotted at one end to fit over the motor pin. It was then welded to the crank to form a boss. (Drawing scale 1:1). the frame. Fit a nut to the bolt before screwing it in and use the nut to lock the adjustment. Four plastic inserts are fitted into the open ends of the tubing to finish off the stand. Drill stand support The drill stand was mounted upside down and its baseplate was supported by two pairs of brackets made from 270mm lengths of 25mm x 5mm steel bar. Clearance holes were drilled 10mm and 50mm from each end and the brackets were mounted either side of the top rails and clamped together with 1½” bolts. Obviously you will have to drill mounting holes in the bars to suit your particular base. Fig.17: this diagram shows the details of the crank pushbar. This attaches to the motor crank and moves the drill up and down. (Drawing scale 1:2). Motor mounting The top motor mounting bar (Fig.14) is made by cutting two pieces of 10mm x 10mm bar 280mm long. One piece of 27mm x 10mm x 10mm is welded at each end to make a slotted bar with a ¼” Whitworth slot running almost the full length. Cut two pieces of 25mm x 5mm bar each 50mm long and drill clearance holes 10mm from each end of both bars. Four 1½” Whitworth bolts and nuts are used to clamp these to the top bar. The details of the motor mounting bracket are shown in Fig.15. It is fold- Fig.18: the stand actuator lever is made from a piece of 25mm x 5mm bar 60mm long and has a 20mm-diameter x 15mm long boss welded to one end. (Drawing scale 1:1). JULY 1999 75 Fig.19: the fixed XY table clamp is made by cutting a piece of 25mm x 25mm angle 260mm long. This is welded in position and needs two slots centred 107.5mm either side of the centreline in the vertical face. (Drawing scale 1:2). Fig.20: the adjustable XY table clamp is slotted in both directions so that it can be pushed close to the XY table before the bolts are tightened. (Drawing scale 1:2). ed from a piece of 3mm plate. Two clearance holes were drilled on the centreline 20mm and 40mm in from one end. The other end had four holes drilled to mount the stepper motor. An outrigger bracket 50mm x 25mm x 5mm was welded on one side to mount a terminal strip. Motor crank Fig.16 shows how the motor crank was made from a circular piece of 5mm plate 50mm in diameter. A ¼” clearance hole was drilled at 20mm radius. A piece of 15mm diameter rod 15mm long was cut and slotted at one end to fit over the motor pin. It was then welded to the crank to form a boss. The centre of the crank (and boss) was then drilled to neatly 76 Silicon Chip fit over the motor shaft. The boss was tapped for a 4mm grub screw to allow it to be locked onto the motor shaft. Crank pushbar The details of the crank pushbar are shown in Fig.17. A piece of 15mm rod 12mm long was welded to a bar 12mm x 5mm, 70mm long. The rod was then drilled for ¼” Whitworth clearance. Two pieces of 12mm x 5mm bar 130mm long were cut, then eight holes were drilled in each bar, the first 10mm from one end then every 10mm. These were then welded to each side of the 70mm bar as shown in Fig.17. Stand actuator lever The stand actuator lever is shown in Fig.18. It was made from a piece of 25mm x 5mm bar 60mm long. A boss 20mm in diameter 15mm long was cut and welded to one end of the bar. The centre was drilled out to fit the shaft of the drill stand and the boss was tapped for a 4mm grubscrew. The other end was drilled ¼” clearance 10mm from the end. XY table base clamps These were made by cutting two pieces of 25mm x 25mm angle 260mm long. The fixed one is welded in position and needs two slots centred 107.5mm either side of the centreline in the vertical face. These should be made around 8-9mm wide to allow a little clearance, as shown in Fig.19. Fig.20 shows the adjustable clamp. It is slotted in both directions to al- Table 1: Example Files LCOSW.TOL PROTEL TRAXPLOT Version 1.61 NCDrill Tool Loading Specification PCB File : C:\PROTEL\PCB\LCOSW.PCB Date : 10/03/1999 Time : 15:41:41 T01 31 T02 51 T03 39 This shows that all the holes under the T01 header should be drilled with a #31 Imperial drill. The Windows versions of Protel give a Metric drill size as well. Those under T02 should be drilled with a #51 drill and the T03 (nothing to do with a T03 transistor) group of pads should have a #39 hole. This close-up view shows how the drill stand is clamped to the top of the Z-frame. It also shows how the push bar is attached to the drill and to the circular crank attached to the stepper motor. low the XY table to be bolted to the fixed clamp, then this one is pushed close and tightened both to the base and to the table. The bolt heads for this bracket which pass through the base bar should have their heads tack-welded. Software The software we have supplied for this stage allows you to drill a PC board which has been laid out with Protel Autotrax V1.61 or Easytrax V2.06. As Easytrax (and Easyplot) was a free layout package you should, with a little effort, be able to get your hands on a copy (try www.cia.com.au/rcsradio). Using Traxplot or Easyplot, load the board you plan to drill then select NC drill from the menu. Three files will be generated: FILENAME.TOL, FILENAME.DRL and FILENAME.TXT. With Traxplot, the drill sizes for the different pads are listed in the FILENAME.TOL; with Easyplot the TOL file is empty. This is not a problem as you will normally drill all holes with an 0.8mm or 0.9mm drill, then redrill those that need to be larger. FILENAME.TXT contains a list of the X and Y co-ordinates for each hole. Thus by locating the XY table at 0,0 it can then be moved to each pad centre. If the Z axis drill is then moved down, a hole will be drilled. The software will read the next pad centre from the list then move the table to that location. Once LCOSW.TXT M48 T01F00S00 T02F00S00 TO3F00S00 % T01 X00825Y008 X00575 X00825Y0065 | | | Y00375 Y00275 T02 X004Y0085 Y003 X02525Y008 Y004 X03175Y00775 T03 X01275Y008 etc to last entry M30 There were actually 38 holes to be drilled T01 (#31) size, only five T02 (#51) size and 18 for the T03 drill size. If you don’t select the redrill option the software only reads through the file once, drilling each hole in turn. As we have already said, use an 0.8 or 0.9mm drill for all holes, then manually redrill those holes that need enlarging. If the redrill option is selected, the software will finish drilling that size hole, home the table, advise the next drill to be fitted then drill those holes, repeating the sequence until all the holes are the correct size. JULY 1999 77 The XY table sits on the base of the Z frame and is secured using a fixed clamp and an adjustable clamp. The completed unit can be used to automatically drill PC boards, or can be used for other tasks. The drill stand is clamped to the top of the Z frame using two pairs of flat metal brackets made from 270mm lengths of 25mm x 5mm steel bar. Clearance holes were drilled 10mm and 50mm from each end and the brackets were mounted either side of the top rails and clamped together with 1½” x ¼” Whitworth bolts. 78 Silicon Chip the PC board is drilled, the table will return to 0,0. Just in case you experience problems while drilling, you only have to press any key and the program will abort, homing the table (to 0,0). The software consists of the following seven files: PCBDRILL.BAS, PCBDRILL.EXE, DRLSETUP.BAS, DRLSETUP.EXE, DRLSETUP.FIL, DRLTEST.BAS and DRLTEST.EXE. These are available free from our web site, or on a floppy disk (price is $7.00 including packaging and postage from SILICON CHIP). The first two files are self explanatory; they drill a PC board. The BAS file has been provided to allow you to modify the software if you wish. The setup files let you key in the maximum X and Y values for the table position and the table stepping speed. They also allow you to allocate the addresses of the XY and Z stepper driver boards, select an Imperial or metric display and select which Above & bottom right: these two views clearly show the drill stand set-up in relation to the XY table. parallel printer port you plan to use to drive the stepper boards. The software which drives the Z axis moves the drill down close to the PC board surface (assuming we plan to drill a PC board) as soon as the program begins, then moves it the shorter distance through the board each time a hole is drilled. This reduces the time taken to drill the board. Both these adjust ments can be set or changed in the setup programs. The last setup option either allows the program to go through the drill cycle once, as would be the case with Easyplot, or home the tool. It will then ask for the next drill size and redrill these holes, until the board is completed, with each hole the size that you specified when you were laying out the board. The DRLTEST programs allow you to move the drill up and down to fine tune the initial drill down position and then the fully down position. Obviously, you should move the PC board out of the way of the drill until your adjustments are correct. You can use the XYTABLE program, which we talked about in a previous article, to do this. The Protel TOL (TOOL) file and an extract from the same PC board TXT file is shown in Table 1 SC on page 77. JULY 1999 79 Just how DO you test a loudspeaker? CLIO: PC-driven loudspeaker evaluation Testing speakers, particularly hifi speakers, has always been something of a problem. Either you had a fully set up anechoic chamber with a raft of professional (read expensive!) test equipment . . . or you relied on your ears. Review by Ross Tester F or the most part, the latter has been the “norm”. Not that this has been a necessarily bad thing – after all, it’s your ears that are going to be the final arbiters anyway. But as test equipment, they suffer from a few major drawbacks. First, ears are subjective. Did I really hear that or am I just imagining it? Second, it’s very difficult to find two sets of ears calibrated exactly the same. In fact, calibration often varies between otherwise matched pairs, especially as they age! Third, and perhaps most important, ears cannot be calibrated anyway – so what’s the standard? If only there was a low-cost way to objectively measure and test speakers . . . You’ve probably already guessed that all this is leading to just that: a (relatively) low cost but accurate speaker test and measurement system. It’s called CLIO and is manufactured in Italy by Audiomatica SRL. The CLIO system has two basic components: a dedicated 8-bit PC Card which slots into a vacant ISA socket in an IBM-compatible PC (386 or higher) and the software to run it. Audiomatica recommend a minimum 386-DX33 with 2MB RAM, VGA video card and a hard disk drive. A math co-processor is not essential but is highly recommended. Of course, running CLIO on a 486 or better automatically gets a maths co-processor. Also supplied with the CLIO system under review were a 2.75m long RCA to RCA “noiseless signal cable” (oxygen-free copper), two 1m long RCA to alligator clip leads, an Audiomatica MIC-01 calibrated condenser electret microphone. The 25cm long microphone is accurate to within ±1dB from 20Hz to 10kHz and within ±2dB from 10-20kHz. It comes with a mounting bracket intended to be attached to a small microphone stand. An optional Audiomatica amplifier, calibrated to the electret microphone, is also available. This 10W, 0.004% THD amplifier makes the system self-contained. With internal switching, the impedance and frequency response 80 Silicon Chip of a loudspeaker can be checked without changing wiring. For this review, we used our own audio amplifier so the supplied amplifier was not required. Its main function is for automatic or manual quality control setups. What does CLIO do? CLIO works as a precision A/D and D/A converter frontend for your PC. Using the power of the PC, it generates a range of audio signals to drive an amplifier connected to the speaker under test. Using a microphone calibrated to the system, it listens to the speaker output and compares this with the test signals. CLIO uses several measurement methods, possibly the most important being the well established maximum length sequence (MLS) analysis technique. car speaker installations – it also automates IASCA scoring), Fast Fourier Transforms (FFT) with the ability to switch back and forth between time and frequency domains. An inbuilt control panel also gives you the ability to set and display a wide range of input and output settings and even display the output on a screen based “oscilloscope”. It even has an inbuilt L/C meter. As you can see, CLIO is an extremely versatile system. And we have only talked about some of its testing capabilities. It does a lot more than this! Getting it going We must admit that we had some difficulty in getting the system to work. This is the “heart” of the CLIO system, an 8-bit card which plugs into a vacant We’ll explain why so readers won’t expansion slot in any PC from a 386 up. It should be fitted as far away from experience similar problems. the video card as possible to minimise interference. At right is the card end-on, Fitting the card is simple: you simply showing the input and output RCA connectors. The top connector is channel A find a vacant slot (as far as possible input, next down channel B input, next channel A output and the bottom from your video graphics card) and channel B output. During setup the channel A input and output are shorted. plug CLIO in as you would any other This has become an international standard for accurate expansion card. The software, likewise, loads easily to anechoic analysis and for room acoustics. In MLS the your hard disk from the INSTALL command on the flopimpulse response is measured very quickly and with high py disk supplied. Theoretically, that’s all there is to basic accuracy, with the computer analysing the data. installation but in our case . . . not quite. From the impulse response it is possible to obtain a The first computer we tried to use was a 300MHz Pentium variety of measurements, such as frequency response, II machine but it turned out to be too fast. (The software phase response, minimum phase, phase with group delay has since been changed to allow even the fastest PCs to removed, the energy time curve, cumulative spectral decay operate). When we had no joy there, we went to a 50MHz (or “waterfall”) and reverberation time. 486 machine but it still wouldn’t behave. Different probCLIO analysis allows a wide range of control over these lem, though: a “run time” error which we simply couldn’t various tests to suit either the equipment under test, the eliminate. environment, or both. Perhaps there was a conflict in I/O addresses? The CLIO Another analysis method is the tradition sinusoidal board has a jumper to adjust the address from 300H (factory measurement, which can test frequency and phase re- default) to 310H. So we changed the jumper – alas, still sponse, distortion, impedance and automatic evaluation no joy. A lot of head scratching and to-and-froing between of Thiele-Small parameters. ourselves and the Australian distributors of CLIO (Audio It will undertake third octave analysis (very popular in Consultants, of Stockport, SA) eventually solved the prob- Two plots representing the same thing: the impedance (in ohms) vs frequency of a quality speaker system. On the left is the plot produced by SILICON CHIP's Audio Precision Test Setup, while the plot on the right is that produced by CLIO. As you can see, with only a minor difference between 10 and 20Hz, the plots are virtually carbon copies of each other. JULY 1999 81 lem: some type of conflict between the CLIO card and a network card fitted to the PC. This should have been evident from the very first – a conflict should show in the Windows control panel. But for some reason it did not. Anyway, to cut a long (actually very long!) story short, when we removed the network card from the machine CLIO burst into life. We also possibly made a mistake in trying to operate the system under DOS. Our reading of the instructions suggested it had to run that way. CLIO requires 575K of free memory and we were having some trouble achieving this with what was loaded in the machine. In the end, a chance remark from Audio Consultants about operating under Windows 95 led us in that direction – and success. So what is the wash-up of all this? When installing CLIO, put it into a “bare bones” computer (ie, no extra cards) running only Windows 95/98 and you shouldn’t have any problems. You were wondering what to do with that pensioned-off 486, weren’t you? Running the calibration procedure takes a few minutes but is fully detailed in the manual, so we won’t repeat it here. Suffice to say it basically runs itself. Testing a speaker Once everything is working satisfactorily, setting up CLIO is quite simple. You need to verify system performance and operation, then calibrate the system to your PC. The instruction manual covers this more than adequately. During the calibration process, a loopback cable is required – that is, the input and output of the “A” channel need to be shorted with a suitable RCA-RCA lead (one was supplied in the package). One point to note, though, the four RCA sockets on the card backplane are not labelled – in a normal PC the “A” input will be the top socket, the “A” output will be the third socket down. They are clearly labelled in the instruction manual. After all our (mis)adventures installing CLIO, this part was a bit of an anticlimax. It ran like clockwork! We put CLIO through a range of tests measuring a high quality 2-way speaker system. The first test we ran was (at least to us) one of the most interesting: we wanted to compare the results obtained by CLIO against the results of our laboratory Audio Precision test equipment. The speaker impedance was first measured and plotted by the Audio Precision (incidentally, about $20,000 worth!) and then repeated using CLIO (at less than a tenth the price!). The results speak for themselves – above about 20Hz, the plots are virtually identical. We then ran a variety of tests using CLIO, some of which are reproduced on these pages. (We actually ran many tests over several days but space precludes us from showing the results. The ones shown are typical tests but of course CLIO is capable of much more than those shown here). We were mainly interested in looking at the basic parameters of the speaker: its frequency response, for example, is one of the fundamental tests and most-quoted figures when a salesman is extolling a speaker's virtues! (Like most quoted figures, though, frequency response can be fudged, especially if no amplitude reference is given.) We also looked at the interaction between the listening environment and the speaker. Unfortunately we were limited in the size of room in which we could conduct our tests and this became very evident as we progressed. We expected severe room interaction – and CLIO proved that we got it! One of the beauties of CLIO, though, is that these The CLIO instruction manual is basically well-written, although there is some evidence of Italian/English translation going just a little awry. Compared to some Asian manual translations, though, it's good. Accessories supplied with the CLIO system: two RCA to alligator clip leads and a long (2.7m) high-quality RCA to RCA lead. The lower pic shows the 25cm-long high quality calibrated microphone mounted on its stand adaptor. Setting it up 82 Silicon Chip The MLS (maximum length sequence) test is a de-facto standard for analysing room acoustics. The microphone picks up a combination of sound from the speaker and sound reflected in the room. As the system knows what the speaker should have been reproducing itself, it can analyse the effects of the listening environment. effects can be cancelled out if required. We checked the phase output, showing just how good (or bad) the speaker components (particularly the cross-over) were. Speaker manufacturers go to extreme lengths to get the cross-overs “just right”. Sometimes they win, sometimes they lose. CLIO in quality control Having computer power to make all the calculations gives CLIO a huge advantage over other forms of testing. Tests that used to take hours of measuring and calculating are performed In this test, the speaker is “swept” with a 2.82V sine wave from 200Hz to 20kHz and the microphone is placed 500mm from the speaker. The sound pressure level is then plotted. Below 200Hz, room reflections (especially in a small, non anechoic room) tend to make the readings meaningless. in seconds (actually in milliseconds!). This makes CLIO an ideal candidate for use in quality control applications. Indeed, there is an option for CLIO which is intended for just that. (The QC option wasn’t supplied for evaluation but its operation is covered in the manual. We have no doubt it would acquit itself with the same performance as the rest of the CLIO package). How much? CLIO is not cheap – but it’s a bargain. The accompanying panel shows the price and availability. We’re im- Cumulative spectral decay, otherwise known as a “waterfall” plot, looks at the way the speaker behaves immediately after it is hit with a pulse. In a perfect world, the decay would be linear with time but speakers are not perfect devices. The results would have been much better in a larger room. pressed with its seemingly endless features, its ease of use and the way it works. And, with only a minor reservation after our difficulties getting it going, we give it the thumbs up! SC Recommended retail price of the CLIO system, not including amplifier, is $1840.00 ($1551 if tax exempt). The amplifier sells for $605.00 ($457 tax exempt). Enquiries to the Australian distributors, Australian Audio Consultants, PO Box 11, Stockport SA 5410. Phone/Fax (08) 8528 2201 A perfect loudspeaker would be phase-linear; that is, the sound output would be a perfect reproduction of the input signal. However crossovers and even the speakers themselves introduce phase distortion. This test shows the difference between the input signal and the output. JULY 1999 83 Microcontroller Fun: The Hexapod Robot Hexapod? It’s a weird name for a weird looking animal. It “walks” on six legs. How on earth can something walk on six legs? Build it and find out! By Ross Tester 84 Silicon Chip The kit unpacked: the large yellow sheet contains the mechanical components to be assembled onto the Hexapod body. The three servos and their actuator arms are at the top – the circular actuators already fitted are discarded. The manual on the left is for the BASIC Stamp controller, the manual on the right is for the robot itself. T he Hexapod Walker is a fasci nating little kit which will pro vide a lot of enjoyment – not only in building it but seeing what it does. And it will give you a good insight into basic robotics (and you will see shortly that basic plays a significant part!) plus computer control. When completed, the Hexapod Walker also looks like a large insect. In operation it looks somewhat like a large insect, whirring along as it somewhat clumsily moves along one step at a time. But it’s no accident that the Hexapod looks like an insect: that was obviously the designer’s idea. In fact, options are given in the instructions to make it look even more insect-like. What you get The Hexapod Walker kit is supplied as a number of bags of “bits” and the walker components themselves stamp-ed from a large-ish sheet (about 300 x 200mm) of bright yellow plastic, about 3mm thick. The Hexapod “body” is of the same material but about 7mm thick. Incidentally, if you want to change the colour (bug black, maybe?) it can be spray-painted with acrylic lacquer such as auto touch-up spray paint. The bags of bits contain almost all the components you need to put the robot together. For example, there are three servos (the type used in most radio controlled cars/planes/boats, etc), along with various control arms to suit. You’ll only need one type of arm so the rest can go into your junk box – just in case. There’s another bag containing a small PC board (about 37 x 57mm) and all the components you’ll need to build the BASIC Stamp robot controller. Did we forget to mention that’s how the robot is driven? Sorry! Yet another bag contains “hardware” – Nylon screws and nuts, a couple of battery holders, some rubber feet, tinned copper wire and so on, with all the above housed in a large bag which also contains an assembly manual and microcontroller manual, along with a program floppy disk. What you don’t get There are a couple of things you’re going to have to buy, scrounge or otherwise procure before you can build the robot. We’ll warn you about them now because when we started to put the kit together it was after the local shops had closed and we had to wait! The most important thing is some double-sided foam adhesive. This is sold by hardware stores for sticking photos, mirrors and anything else to walls. It’s also available from large supermarkets. We used a packet containing 32 mounts pre-cut into 10 x 20mm rectangles. It’s a handy way to buy them (ours were “Permastik” brand and cost about three dollars for the packet). You’ll also need some super glue – not just ordinary super glue, but the gel variety. Super Glue Gel gives a slightly longer working time and is less likely to stick your fingers together. But like ordinary super glue, it does go off fairly quickly and it can stick your fingers together if you let it. We used Selleys Fix’n’Go Supa Glue Gel – a 3g tube also cost about three dollars. A sheet of sandpaper is also required to smooth the edges of the robot components where they break away from the carrier sheet. JULY 1999 85 The kit requires two power pins (the gap between the pins sources – a 9V battery for the is very small). processor and 4 x 1.5V “AA” Don’t place the ICs in their cells (6V) for the servos. None sockets yet. of these are supplied in the The pin spacing for the kit. Alkaline batteries would three sets of header pins is of course be preferable. also very close, so be extra As far as tools are concareful when soldering these cerned, you will need a sol(especially the middle row dering iron (with a nice fine of the three-way set!). The tip) and solder (electronic short-er pins go through the type, of course!), a PhilipsPC board to be soldered. head screwdriver and a pair Place and solder in the RJ11 of pliers with cutting blade (to connector (it can only go one cut and bend the wire). way) followed by the two One option which is almost The assembled First Step BASIC Stamp controller. It 3-pin semiconductors (these essential (unless you want to is programmed from a PC via the large socket on the could, with difficulty, be inright which looks like a telephone connector. make your own) is the proserted incorrectly!). gramming cable: a short cable Finally, insert the 18-pin fitted with a standard computer parallisted in the manual are actually sup- and 8-pin ICs into their respective lel port plug one end and an RJ-11 plug plied. The way the bags are sealed sockets. This is one area where a lot (what looks like a modular tele-phone of problems occur; you have to ensure it would be very surprising to find plug) the other. Be warned: it’s NOT to anything missing (but stranger things all the IC pins are inserted into their be plugged into the telephone socket; have happened. . .) mating sockets. It’s easy for pins to this is the plug which enables you to Start by placing and soldering in the be bent in this process, so take care. program the Hexapod from your PC. You have now finished the controlresistors except R4 & R5 (10kΩ). These Oh yes, you need a PC of some sort, are not required in this version of the ler board. After thoroughly checking too (just about any IBM-compatible kit. They won’t do any harm but they your soldering and component placewill do). In fact, it’s a perfect appliment, put it to one side while we get will drain the battery slightly. cation for that old XT gathering dust Next, fit and solder the three capac- on with the fun bit: the robot! in the back shed! itors (one is an electrolytic, so watch Building the robot its orientation) and then the ceramic Starting construction Unfortunately, the instruction manresonator (not polarised). You can start with either the robot or Both ICs are provided with sockets; ual for the robot is a little disjointed the microcontroller board – but seeing the 8-pin socket for the EEPROM and and some important information is we’re an electronics magazine, we’ll the 18-pin for the PIC processor. Care- unclear. So we will try to cover that start with the controller. fully solder in the sockets, making here. First, verify that all the components sure you do not bridge between the The first step, according to the man- Fig.1: the circuit diagram of the Hexapod’s microcontroller which itself is programmed from a PC via the modular programming port, CN1. While the output header has labels for four servos (0-3), only three are used in the kit. Other pins can be used for microcontroller I/O – RB6 and RB7 can have bumper microswitches fitted if you wish. 86 Silicon Chip The first steps in assembling the Hexapod are the mounting of the servos on the underside of the base panel (Fig.2, left) and the gluing in place of the vertical leg supports and spacer bracket (Fig.3, right). ual, is to centre the servos by applying a 1.5ms pulse every 10-15ms. How? You need to do it via the controller board you have just finished and by running a program on your PC which downloads the appropriate program to the controller board. Great if you’re into BASIC programming; hardly the stuff beginners or even the average kit constructor will get their head around quickly. If you wish to do this correctly, you should jump over to the “programming” section at the end of this article and follow the instructions there. But if you’re like us, in a hurry to get the robot going, you can cheat a lot and centre the servos by eye. Sure, it won’t be exactly correct but our kit worked doing it this way, so what the heck? Screw one of the servo actuators onto the servo arm with the screw provided. Turn the servo actuator all the way clockwise and place a reference mark on the servo arm at the end point. Turn the actuator all the way anti-clockwise and place another ref- erence mark on the servo arm at that end point. Half way between those two marks will be close enough to the midpoint for our purposes. Repeat for the other two servos. Now it’s time to carefully break all of the components from the carrier sheet. We didn’t have any difficulty doing this – just take your time and don’t force any pieces. If necessary, help them a bit by cutting with a knife. The largest piece is, not surprisingly, the robot “body”. There will also be four identical back-and-forward legs, two identical up and down legs, eight leg support brackets, two identical vertical leg supports and a leg support spacer. Smooth any carrier sheet remnants from all the components with sandpaper before continuing. Put all of the legs and support pieces to one side for a moment. Now we have to fit the servos to the robot body with double-sided adhesive foam. First, with a pencil and straight edge, mark a centre line right down the length of the body (there are reference marks each end to help you do this). Then mark one line across the body (exactly at right angles to the first line) 85.5mm from the front and another 25.5mm from the back. Next you will need one of the servos, one of the slim actuator arms (not the circular ones) and the actuator arm retainer and screw. Place the servo on its side with the shaft pointing towards you and the wires emerging from the right end. Keeping the servo shaft in mid position, place the retainer onto the shaft and screw the arms on so the actuator points 90° straight upwards. Tighten the screw holding the actuator arm in place, making sure you don’t move the servo off mid position. Once all servos are in position you won’t have access to this screw, so make sure it is right first! In fact, it’s a good idea to do a “dry run”, placing all the servos without adhesive to make sure you understand how they all fit together. When ready to permanently mount Next comes the mounting of the support brackets (Fig. 4, left) and the fitting of the legs (Fig.5, right). Note the way the holes in the support brackets all face towards the middle legs. JULY 1999 87 Once all the legs are fitted, you need to bend the pushrods from the wire supplied so that the servos can drive the legs. The two diagrams here show how those pushrods are fitted. When you get to this stage, your robot is mechanically complete – all you need to do now is add the electronics and batteries. the first one, attach a couple of adhesive foam tabs to the underside of the servo and fix it exactly to the centre of the robot body so that its back lies along the line you ruled closest to the front of the body. When mounted, its actuator points down (away from the robot body). The other two servos are prepared and mounted in a similar way, except that when mounted, the servo actuators point straight up with the servos back-to-back along the centre line. Their back edges follow the line you ruled towards the back of the robot body. This means the adhesive foam pads actually stick to opposite sides of the servos. Now you have to make the vertical leg supports, using the two support pieces with their central spacer. Before gluing, place the two vertical legs in position with their two Nylon nuts & bolts. It’s vital that you don’t get any glue on the legs themselves, otherwise they won’t be able to move. When this assembly is dry, glue it to the TOP side of the robot body (it fits into notches on the body). Again, keep glue away from the legs. Next come the horizontal leg support “hinges” which are glued directly to their respective legs. You will note that there are two holes on the hinges – these holes must be aligned in the same direction for each hinge. The hinges on the front legs have their holes to the rear; the hinges on the back legs have their holes to the front. It’s also important that the hinges 88 Silicon Chip are assembled exactly in line with each other – placing the Nylon bolt through each will line them up for you. Finger-tighten all of the Nylon nuts and bolts and glue the hinges to the legs, making sure you don’t get glue on the faces of the hinges or on the base. Now all the legs and their fittings are assembled, it’s time to make the pushrods which connect the legs and their respective servos together. This is done with the tinned copper wire. Be careful here: there is just enough supplied to do the job. Before using the wire, it’s a good idea to straighten it by nipping one end in a vice and pulling the other end hard with a pair of pliers. The legs can be mounted at 90° to the body, which is most efficient, or they can be mounted at, say, 10 degrees offset – which looks more like a bug! It’s up to you which way you go. Cut two 200mm lengths and mark them (with a Texta or similar) at 30, 80, 130 and 180mm. Bend the wire at 90° at 30mm and push the longer end through the two holes in the centre leg brackets. Push the other end right through one of the pair of holes in a front leg hinge set and bend it back to make it captive in the hinge set. Bend the wire at the 80mm and 130mm marks about 15° in a horizontal direction, with the mark at 180mm at 90° in the vertical direction. The free end then passes through a pair of holes in the rear hinge set and is bent over underneath to make captive. Snip the ends off the wire to make sure they don’t foul anything as the legs are moved backward and forward. The other piece of wire, for the opposite side, is prepared the same way. Exact angles are less important than making the two pieces of wire symmetrical. The rear legs connect to their respective servos with short (83mm) lengths of the same wire. These go through the other holes in the rear hinges and connect to one of the holes in the servo actuators. We used the second hole from the top which seemed to work pretty well. The centre legs connect to the centre hole in the remaining servo with the remaining length of wire. It must be bent in an elongated “S” shape as per the diagram. Naturally, you will have to thread the wire through some of the holes before bending – the angles are too acute to allow it to pass through otherwise. Now see if you can move the front legs by gently pushing on the rear legs and vice versa. Don’t push too hard because you’re also turning the servo. Wiring the beast It really is starting to look like a beast, isn’t it? The controller PC board and 4 x AA cell holder are glued to the top side of the body with the same adhesive foam we used to glue the servos in place (lucky there were 32 foam tabs in the pack!). The 9V battery holder is glued to the underside of the body in front of the vertical leg servo. Now we have to run the wiring from the servos to the controller – and here’s where you can come unstuck. We believe the instructions are not clear enough in telling you which way around the 3-pin servo plugs go on the header pins. The circuit diagram in the “First Step” manual has the wire colours shown but doesn't tell you which way around they go on the socket – and they could be placed either way around. The wiring diagram in the kit manual is not 100% clear, either. It would be too easy for anyone not familiar with electronics to get it back to front. And then there is the dire warning about not getting it back to front . . . In all cases, the black wires in the servo connectors go to the header pins closest to the edge of the PC board. This makes the red wires go to the middle pins while the yellow wires, the ones which receive direction information from the controller, connect to the pins closest to the controller IC. It is also possible to get the wrong servo on the wrong set of header pins. The left servo goes to the pins labelled Servo-0, the right to the pins labelled Servo-1 and the middle to the pins labelled Servo-2. When mounted, both their actuators point up, alongside the body. The servos are taken care of, now for the power wiring. In the kit we built, two power switches were included which make it very easy to turn power on and off. The alternative is to whip a battery out but that is sometimes not quite so easy with the thing going walkabout! Wiring the battery connectors to the switches is the easy part. Connecting the switches and negative supplies to the PC board – well, that wasn’t quite so simple. We could only find two header connectors supplied in the kit – one red, one black. And there are four connections to make: +9V, 0V, +6V and 0V. What to do? We cheated. We cut the header connector leads to a suitable length, giving us four header connectors. These we soldered to suitable lengths of insulated hookup wire and connected those to the switches and battery holders. Of course we also insulated the soldered joins. We’ve been assured by the suppliers that more connectors will be supplied in future kits so this problem should not occur. The switches themselves are the standard mini toggle switches, complete with nuts and washers. However, we found that they were such The battery holders and the microcontroller PC board are attached using doublesided foam tape. Be careful to keep wiring away from the pushrods or legs. a snug fit into the two holes right at the back of the robot that no nuts or washers were required. That bit is up to you. Finally, we used a couple of cable ties to tidy up all the wiring. Because the servo leads can’t easily be shortened, there is a fair amount of excess wire around. And the last thing you want is a wire dragging along the pushrods as they move back and forward, back and forward . . . The penultimate step is to check your wiring and all clearances, making sure that the legs move in unison with each other. If all is OK, insert the 9V battery and the four AA batteries and switch on. Hopefully, nothing at all will happen! Programming it That’s because you haven’t programmed the Stamp controller yet, so the beast hasn’t got a brain to tell it what to do. The first thing to do is to load the supplied software into a directory on your hard disk drive (it will work from floppy if you must!). Make a directory called stamp1 and copy all the files from both the “stamp1” and “Hexapod” directories on the supplied floppy disk to that directory. Connect the supplied cable to your computer’s parallel (printer) port and the RJ-11 socket on your robot. You OK, How Does Hexapod Walk? The principle behind walking with the 3-servo robot is simple. One of the servos is used to provide vertical lift to legs 1,3,5 or 2,4,6. The other servos provide the horizontal shift for the left legs, 1 & 3, or the right legs, 4 & 6. By cycling through the sequences to the right the robot can walk forward, reverse or turn left or right. To walk forward, follow the sequence 1,2,3,4 then repeat. To walk backwards, follow the sequence 4,3,2,1 then repeat. The same rule applies to turning sequences. You can experiment with the amount of throw for the servos and the type of feet with different floors. JULY 1999 89 These are the screens you should see on your PC: above, we have loaded stamp1.exe and then pressed “ALT-L” to list the available PBASIC programs. Selecting “WALK.BAS” loads the program to make Hexapod walk. This is displayed in the screen top right. Pressing “ALT-R” will download this to your Hexapod, as shown bottom right (assuming, of course, that the cable is connected AND the 9V supply is turned on). Turning on the 6V supply should start Hexapod walking. It’s wise to disconnect the cable first, though! Turning off the power switch or even removing the batteries will not alter the program: it will stay in the robot’s memory for at least 40 years or until it is replaced, which ever comes first . . . will need to turn the 9V supply on but the 6V supply doesn’t need to be on yet (in fact, it’s more convenient not to have it on unless you want to be chasing the little beast all over the place!). Run the stamp1.exe program. This brings up the screen shown above. Load the appropriate BASIC program. Alt-L will list the available files for you; Alt-H will give you a list of valid commands. After loading the program, press Alt-R to download it to the controller on your Hexapod. It will begin running automatically – as soon as you turn the 6V supply on, the legs should start to move. If it doesn’t, you will probably already have received a “hardware not found” error on your screen. Check that the 9V battery is OK, that it is turned on and that there is power getting to the board. You can also check that the on-board regulator is working by measuring the voltage between pin 6 and pin 8 on header H1 – you should get very close to 5V. If this doesn’t work, make sure that the cable is properly plugged into both your parallel socket and the RJ11 socket on the robot. If all else fails, go over your soldering once again and check the placement and polarity of the components on the board. Assuming that everything is now working properly, disconnect the programming cable. Next time you turn Hexapod on, he/she/it will go 90 Silicon Chip lumbering away again, exactly as before. That’s because the program stays in memory until erased (or another program is loaded, which is effectively the same thing). In fact, the manufacturers of the BASIC Stamp say that if you come back in 40 years time and turn the Hexapod on, it will still have the program in memory. We think you might need some fresh batteries, though! What to do next Once you are completely satisfied with Hexapod’s operation, we suggest once again tightening up the Nylon Where To Get It: Our Hexapod Robot Walker Kit came from the Australian distributors of Lynxmotion products, RobotOz, 7 Felgate Place, Warwick, WA 6024. Phone 08 9243 4842; fax 08 9246 1563, email kits<at> robotoz.com.au Recommended retail price of the kit, including the BASIC Stamp microcontroller, is $320. The optional infrared proximity detector sells for $65 and the programming cable $10. For more information, visit the RobotOz website www.robotOz. com.au The kit is manufactured in the USA. Assembly drawings in this article courtesy Lynxmotion, Inc. nuts & bolts (finger tight), then melting them slightly with your soldering iron. We found in operation the nuts continually working loose – and every now and then poor old Hexapod would “throw a leg”. An alternative to melting (and therefore damaging) the nuts and bolts would be a tiny dab of glue. There are quite a few programs to try out on the disk which make the robot do various things. Or if you have web access you can try downloading others from the manufacturer’s website, www.lynxmotion.com You can also add other hardware to your robot: an optional infrared sensor is available which stops the robot hitting objects. A cheaper option is to fit a couple of microswitches to the front of the robot as bumper switches, connected to I/O pins 6 and 7 of the header socket. If the robot hits anything, the switches tell the legs to stop walking. In this case, those two resistors (R4, R5) we said to leave out at the beginning, need to be fitted! Remember, too, that the controller on the robot is a full-blown PBASIC Stamp microcontroller, not dissimilar to that we used in the article “Getting Going With BASIC Stamp” in the January 1999 issue of SILICON CHIP. You can write PBASIC programs or download loads of them from websites to do a whole lot of things apart from SC move your robot’s legs! 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. Drift in digital voltmeter I built the Car Digital Voltmeter from the June 1993 issue but have experienced drift with the readout. I recently checked the construction and can’t find anything wrong. If I let the meter stabilise overnight and then re-calibrate it, I find that it still drifts high. Can you suggest a fix for this problem? The 7805 heatsink runs hotter than I expected even though you make mention of this in the construction details. (T. W., via email). • There are two components most likely to cause a temperature drift: trimpot VR1 and transistor Q1. Try changing these. Questions on electronic ballast design Recently I undertook to assemble the “fluorescent driver” part of the project that you published in October 1994 with the intention of powering 40W fluoro lamps. I have not been able to obtain the saturable transformer toroids (part no RCC 12.5/7.5/5 3F3). However, I managed to obtain some Small DC-DC converter wanted I have been looking through SILICON CHIP to see if there have been any projects that could fill my requirements: a DC-DC converter, as small as possible, the input to be from 6-9V DC and with an output of 24-26V at 150-180mA. The load is a light bulb rated at 24V and 150mA. The source of input power is a from D cell batteries. I came across the item the April 1993 issue called a “High Voltage Converter”. Do you feel that this circuit would be suit able? What alternation would I need to make if it is OK? And could I use a pot similar sized cores from some PC switchmode power supplies. These plastic coated cores were separately coloured as green, grey, white and yellow. I assume that the colouring refers to a code of some sort. The green and grey toroids worked but quickly became very hot. At switch-on, the circuits operated at 85-90kHz and increased in frequency up to 130kHz as the cores became hot. I have experimented with the turns ratio of T2 to try to reduce the operating frequency and the heating but the output current decreases at the same time. The only way that I have found to reduce the operating frequency is to close the gap in the inductor in series with the fluoro tube but then the output current decreases again. It seems to be a catch-22 situation. Since constructing the circuit (and putting it on hold) I have reverse-engineered a commercial unit which proved to be very similar except that it used bipolar transistors instead of Mosfets. This unit drives a 21W U-shaped fluoro tube and runs at 30kHz. The driving toroid does not heat up though the whole unit gets warm while in operation. The resonating capacitor in series in place of RA1 and RA2 so that I could adjust the output voltage to the lamp? The variable arm of the pot could go to the connection joining the two 470µF capacitors. Or would it be much more efficient to use a pot core transformer with a couple of power transistors? (R. B., Miranda, NSW). • The April 1993 design is the one that comes closest to your application. You need to use a bigger toroid and change the feedback to obtain 24V. To do this, use just one value for RA and change it to 18kΩ. By the way, have you thought of just using a 6V lamp in stead, to eliminate the need for a DC-DC converter? with the fluoro tube heaters was temporarily increased to .0025µF (to try to reduce the running frequency), with the result that the circuit tries to start but just keeps blinking. The same happens when a 1000pF capacitor is placed in parallel with the 680pF snubber network capacitor. Could I ask a number questions in order to get this circuit operating? (1). What are the required magnetic properties of T2 (the saturable transformer) to assure correct and reliable operation? (2). What other (if any) toroids can be used as substitutes for T2? (3). What other means have I of reducing the operating frequency while still maintaining sufficient output current? (4). What formulas can I use to calculate the inductances and resonant frequencies for various operating powers? (5). What formulas can I use to calculate the values of the capacitor and resistor in the snubber network? (6). What components are supposed to run hot (if any)? It seems to me that the electronic ballasts don’t seem to be any more efficient (judging by the amount of heat produced) than the normal iron-cored ballasts. (L. Z., Kilburn, SA). • The saturation properties of the Philips RCC12.5/7.5/5 ferrite ring core used for transformer T2 are critical for correct operation of the circuit. Using a different core from a switchmode supply will not necessarily provide the correct oscillation frequency to drive the fluorescent tube at its rated current. The nearest available core is the RCC13.25/7.35/5.7 which is available from Farnell Electronics (Cat. 178-504). Its cross sectional area and Al value are almost identical to the recommended type. Also, as you have discovered, you cannot simply change the number of turns on T2 and obtain the correct frequency. The frequency is obtained by reaching the point of saturation for the T2 core, by adjusting the turns for N2 and N3 which drive the gates of JULY 1999 91 4Ω operation for class-A amplifier I have built your 15W class-A amplifier as described in the July and August 1998 issues and was wanting to know a few things. If the amplifier has a power output of 15W into 8-ohm loads with a quiescent current of 1A then at a guess it will only have the same into 4-ohm loads and the head room will be the quiescent current and not the supply rail voltage. So if I wanted to double the output power into 4Ω I would need to double the quiescent current. Is this correct? I have Electronic Workbench 5 at home and have played with this Q2 and Q3 respectively. Note that the N1 winding on T2 is in series with inductor L3 and forms part of the series inductance with the fluorescent tube. The N2 and N3 windings drive the 330Ω resistors at the gates of the Mosfets and these provide a load to produce the saturation in the core. Calculating the turns for T2 is an iterative process. We shall show how the circuit values were calculated but of course you will see that some of the values that are needed to be used are calculated later. The RCC12.5/7.5/5 core begins to saturate at about 450mT and its cross-sectional area is 12.2µm2. From this we can calculate the approximate number of turns required for N2 and N3. The formula is T (number of turns) = V (voltage)/ (4.44 x frequency x A (cross sectional area) x B (saturation in Tesla). This works out to be 6.65 turns using 21.6V for the voltage across the windings and at 100kHz. (We assume we can approach 600mT for a sine wave before the saturation produces a flux collapse. The 21.6V is obtained as follows. The number of turns required for N1 is found by ensuring that the voltage across this winding will produce more than 12V into N2 and N3 so that they can drive the 12V zener via the 330Ω resistors in parallel and the 330Ω resistor across the zener. Analysis of the resistive divider reveals that we need at least 18V across N2 and N3 to begin driving the zener. The voltage is calculated using the inductance 92 Silicon Chip circuit a lot and would like to know how practical this idea would be in practice. (Raymond – via email). • The answer to your letter is not simple. First, you can operate the amplifier as it is into 4-ohm loads but at the quiescent current of 1A it will not stay in class-A if you drive it to full power. This would be about 25-30W, depending on the power supply. The result would be higher distortion than if the system was operating in class A at all times but it will still be pretty good. To obtain class-A operation at all power levels up to clip ping into 4-ohm loads, the quiescent current would have to be increased of winding N1 and the divider ratio formed by inductor L3. The inductance formula is: L = N2 x Al (nH) Al for the T2 core is 900nH and thus with 14 turns on N1 we have an inductance of 176µH. Now at 100kHz, 176µH has an impedance of 110Ω. The impedance of the 900µH inductor L3 is 565.5Ω. Assuming we have 310V across both L3 and N1 at the time of saturation with about 90V across the fluorescent tube, the voltage across the 14 turns in N1 will be (110/675.5) x 300 = 50.4V. The voltage induced in the 6 turns used for N2 and N3 will be 21.6V. The inductance of L3 is calculated to limit the power delivered to the tube, when running at 100kHz, to 36W. As mentioned, the impedance of L3 and N1 totals 675.5Ω at 100kHz and the 310V across this means that there is 0.46A flowing. This current times the 90V across the tube produces 41W. The .001µF capacitor across C3 is to produce a striking voltage for the tube when kick-started via the Diac circuit before oscillation begins. It oscillates in conjunction with L3 and N1. Its value does not affect the oscillation frequency once Q2 and Q3 have begun oscillation. Changing the value will reduce the striking voltage. The 680pF capacitor is used to compensate the inductance of N1 and L3 for the gate capacitance of Q2 and Q3. Changing this value will not overly affect normal operation but will to around 2A. This raises a number of problems. First, the heatsinks would have to be increased in size to be able to dissipate double the power. Second, the heatsink for the regulat ed power supply would need to be greatly increased to take a substantial increase in dissipation and if you are building a stereo version you would need a substantially bigger power trans former as well. Finally, the BC327,337 transistors (Q11,Q13) would have to be upgraded and there is no suitable pin-for-pin substitute. However, provided you are willing to bend the pins, you could use BC639 and BC640. affect the tube strike voltage when the Diac is pulsing Q3. The 680pF capacitor will damp oscillations in the .001µF capacitor and series L3 and N1 inductance. The T2 core is designed to run hot because it is operating up to saturation point where losses are high. The wattage loss, however, is small and the overall efficiency of such an inverter is very high, at above 90%. This is much greater than a normal ballast circuit. Having stated all this, are you sorry you asked? Over the years quite a few readers have asked questions about design of inverters and switchmode power supplies. As the above answers demonstrate, the design of switchmode circuitry is not a simple task. Inevitably, after all the theoretical design is done, there is a great deal of trial and error to optimise the design. Pink noise source has high output I recently constructed the Pink Noise Source as de scribed in the January 1997 issue of SILICON CHIP. Initially its sound output was cyclically intermittent (squegging) after the startup delay but this was corrected by changing the noise source transistor (Q1) to a BC548B. After a startup delay of about seven seconds, the output sounds OK but measured on a DVM it is around 5.25V RMS on the 0dB range instead of 60mV as specified. All components have been measured and checked well within tolerances. Notes & Errata Sustain Unit for Electric Guitars, March 1998: the BFR84 dual gate Mosfet (Q1) is no longer available. The solution is to substitute a 2N5484 N-channel FET, as shown on the accompanying overlay diagram. An extra 22kΩ resistor is required to alter the level control voltage range from VR3 and this can be connected between pins 2 & 4 of IC2a, on the back of the PC board. Also the 0.1µF capacitor between pins 8 & 9 of IC1c should be changed to .001µF. Have I missed something? (Doug – via email). • The 5.25V RMS that you are obtaining at the 0dB output of the pink noise source must be a measurement error. This is because the circuit is powered from a 9V battery and even if IC1b is being over-driven, it could only deliver about 3V RMS. Perhaps you are measuring the DC voltage at the output of IC1b which should be sitting at around half supply. Check the 10µF capacitor at this output to see if it is short circuited. Improving the ignition on a Honda I have a 1994 Honda Integra VTIr and was wondering if I could use the Multi-Spark Capacitor Discharge Ignition kit (September 1997) on it. I have seen similar products on the market such as the Crane Hi6 ignition amplifier so I figure that this kit would do the same thing but at a fraction of the cost. I have provided a portion of the installation of the Crane Hi6 for you to read, as it looks similar to your kit. (Thanh – via email). • Since your car already has a very comprehensive engine management system which includes solid state ignition, we cannot see the point of fitting the Multi-Spark CDI or any commercial aftermarket system. The only possible justification for fitting a higher output ignition system would be if the engine has been substantially modified to either increase its rev limit or its compression ratio. In our opinion, since you already have a highly developed engine, you would be wise to leave it alone. Identifying an unknown PC board I have a kit with a PC board number SC09111931 which has a missing output transistor (the big one with the heatsink). I was wondering if you can tell me what the transistor is or where to get information on this kit. (Michael – via email). • If you search in the projects index on our website you can identify any project from the board number. This board was a simple low voltage speed controller featured in the January 1994 issue. The transistor is a BD679 and can be obtained from Jaycar, DSE, etc. 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. JULY 1999 93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FRWEEBE YES! Place your classified advertisement in SILICON CHIP Market Centre and your advert will also appear FREE in the Classifieds-on-the-Web page of the SILICON CHIP website, www.siliconchip.com.au And if you include an email address or your website URL in you classified advert, the links will be LIVE in your classified-on-the-web! S! D E I F I S C LAS EXCLUSIVE TO SILICON CHIP! FOR SALE C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $155.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 and 68HC12 for $78. Debug monitors: $78 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 Simulator (fast, now incl. 80C320): $78. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, the 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $199, $37 tax, $10 p&p. SOIC adaptors: 20-pin $90, 14-pin Need prototype PC boards? Positions At Jaycar Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. We are often looking for enthusiastic staff for positions in our retail stores and head office at Rhodes in Sydney. A genuine interest in electronics is a necessity. Phone 02 9743 5222 for current vacancies. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. AV-COMM P/L, 198 Condamine St, Balgowlah, NSW 2093. Tel: 02 9949 7417 or 9948 2667. Fax: 9949 7095; www.avcomm.com.au 94 Silicon Chip KITS-R-US PO Box 314 Blackwood S.A. Ph/fax 08 8270 3175 FMTX2A Universal Stereo Coder $49 FMTX2B 30mW Xtal Locked 100MHz Transmitter $49 FMTX1 1-3 Watt Free Running Transmitter $49 FMX1 200mW Full Broadcast Transmitter, built & tested $499 FM220 10-18 Watt FM BGY133 Philips Linear $499 FM1525 25 Watt Discrete Linear FM Band $499 FM2100 110 Watt Discrete Linear FM Band $699 FM3000 300 Watt Discrete Linear FM Band $1499 Philips 828E/A VHF Receiver Boards (6 metres) $9 AWA 721 VHF Receiver Boards (2 metres) $9 AWA 721 VHF transmitter boards 1 watt (2 metres) $19 Philips 323 UHF transmitter boards 500mW (70cm) $19 AEM 35 Watt Little Brick Audio Power Amp $15 Digi-125 200W RMS Audio Power Amp $39 CA Clipper Compiler, new in box $49 6dBd Gain Colinear FM Band Antenna $999 Roll Smart-1 FM Station Audio Processor $999 Free catalog on disk of discounted surplus components Same day shipping, credit cards OK, circuits supplied. SPECIAL STEAM BOAT KITS $14 We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. $85, 8-pin $80. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; Fax (02) 9631 1236; or Internet: http://www.grantronics.com.au WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. $420.00 complete plus sales tax if appli cable. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/Ecowatch ph: (03) 5968 4863 fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. SPEAKERWORKS: specialist in speaker repairs and parts. DIY refoam kits: 31/2", 4", 5", 6", 7", 8", 9", 10", 11", 12" and 15" $39.95. Includes shims, dustcaps and adhesive. Largest inventory of cones, surrounds, gaskets, spiders, dustcaps, grilles, foam and cloth and 4,700 custom voice coils. Phone 02 9420 8121, Fax 9420 8131. TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. $190. MAGNETIC CARD READER, SC January 1996. Holds up to 8 cards. Use as a door lock. $65. Melbourne 9806 0110. PHILIPS SCOPE PM3217 $755; Goould Scope OS300 $650; Racal Dana Counter 9916 DFM $480; Racal Dana Counter 9903 $220. Phone Steve 07 3890 1259, 0418 800974. TEST EQUIPMENT: Spectrum Analyser Hewlett Packard 8559A with 182T mainframe .01-21GHz. Immaculate. Complete with all manuals. $10,000 neg. (07) 3269 6647. THE LOGIC ANALYSER KIT will stay at $750 ($800 - NZ). Ph 02 9878 4715. peter.baxter<at>tantau.com.au www.tantau.com.au VIDEO CAMERAS & CCTV ! UP to 2¼ YEARS WARRANTY! PIR MOVEMENT DETECTOR with inbuilt concealed PINHOLE Mono or DSP COLOUR Camera, Microphone & Timer/Controller for VCR - Lights - Etc from $139 * BULLET Camera just 22 mm dia 480 Line 0.05 lux SONY CCD or DSP COLOUR from $132 * 32 x 32 PINHOLE PCB Modules with On-Board Microphone from $85 * COLOUR DSP 32 x 32 Pinhole Module with On-Board MICROPHONE from $155 * MINI 36 x 36 Cameras from $85 - SONY CCD $102 - COLOUR DSP $162 * DOME Cameras from $88 - SONY CCD $105 - COLOUR DSP $164 * SINGLE-CABLE-SOLUTIONS 5 mm dia for Video, Audio & Power Supply from 40 c/m * BALUNS use Telephone or LAN cable for Video & Power Supply ONLY $15 ! DIY PAKS: FOUR Cameras, Switcher & Power Supply from $499 - with 14 Inch Monitor from $637 with MULTIPLEXER for FULL-FRAME FULL-RESOLUTION RECORDING from $1198 * FOUR COLOUR CAMERAS, SWITCHER & POWER SUPPLY from $812 - with COLOUR QUAD 4 Pix 1 Screen from $1207 * With MULTIPLEXER $2039 * HIGH RESOLUTION QUADS 720 x 576 (Better than SUPER-VHS Quality) Time & Date from $284 * COLOUR QUADS from $503 * COLOUR DUPLEX MULTIPLEXERS from $1329 * 14 Inch MONITORS from $218 - with Inbuilt 4 Ch SWITCHER from $256 * SEE-in-the-DARK with our Combination CAMERA INFRARED ILLUMINATOR Kit from $160 * 50 LED DIY Infra Red Kits only $19 * Plus full range of ANCILLARY EQUIPMENT * DISCOUNTS: Based on ORDER VALUE, BUYING HISTORY, for CASH / CHEQUE & NZ BUYERS ! BEFORE YOU BUY Ask about New Enquiry Offer & visit our Web Site at www.allthings. com.au Allthings S & S. T 08 9349 9413 F 08 9344 5905 SATELLITE TV RXs * MPEG Digital EPG $499 * COMBINATION Digital / Analog $649 * COMBINATION Digital / Analog / Positioner $799 * www.allthings.com.au * Allthings Sales & Services 08 9349 9413 SOLAR PANELS: buy by mail and save! 75 watt from $590.00, unbreakable s/steel 64 watt $555.00. Largest manufactured: 120 watt $995.00, flexible 32 watt $475.00. All other sizes available, top brands, lowest prices. INVERTERS: budget inverters from $110.00 (12V 140W). High quality pure sine wave inverters from $390.00. Call with your requirements. WIND GENERATORS: wide variety available, call with requirements. TASMAN ENERGY Free call 1800 226626 PRINTED CIRCUIT BOARDS for all magazine projects, then go to http://www.cia.com.au/rcsradio RCS Radio – Bexley (+61 2) 9587 3491. RTN Australia Parallax distributor: Basic Stamps BS1, BS2, BS2-SX all ex stock. Chipsets also available for high volume applications. SX development tools and chips also available. New super BS1/2 development board Oz made now available. Custom I/O extender chips for the Basic Stamps. Serial Led driver kits, a/d kits, temperature kits, etc. FerretTronics servo and stepper motor chips. TiePie HandyScope HS2, Dos and Win software included. Ph/Fax (03) 9338 3306. Email: nollet<at>mail.enternet.com.au Http://people.enternet.com.au/~nollet SILICON CHIP This section contained advertising which is now out of date and it has been removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au JULY 1999 95 CLASSIFIED ADVERTISING RATES Advertising Index 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 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) 9979 6503. Aust. Audio Consultants...............57 Enclosed is my cheque/money order for $__________ or please debit my EMC Technologies.......................56 ❏ Bankcard ❏ Emona Instruments...................IFC Visa Card ❏ Master Card Av-Comm Pty Ltd.........................94 Coffs Harbour Electronics............57 Computronics Corporation..........56 Dick Smith Electronics........... 14-17 Harbuch Electronics....................55 Card No. Instant PCBs................................94 Jaycar .............................. 45-52,95 Signature__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ Kits-R-Us.....................................94 Microgram Computers..............3,57 MicroZed Computers...................56 Nucleus Computer Services........57 Oatley Electronics........................35 Printed Electronics................. 56,94 Questronix...................................56 ELECTRONIC/MECHANICAL DESIGN AND CONSTRUCTION. We offer a complete design service for electronic and mechanical devices. Most work is done in house and you deal directly with the designers. No job is too small and can be to prototype or “turn key” stage, in one offs or for future production. Simply send us an email at vladimir<at>u030.aone.net.au with your questions or requirements and we will get back to you. Silvertone’s RC Receiver Still the best little performer available! RAIN BRAIN AND DIGI-TEMP KITS: 8 station sprinkler controllers, 60 channel temp monitor uses DS1820s over 500 metres. Has PC Data logging. Mantis Micro Products, http://www.home.aone.net.au/mantismp 96 Silicon Chip RobotOz......................................56 Silicon Chip Binders/Wallcht....OBC Silicon Chip Bookshop............... 8-9 Silicon Chip Subscriptions...........67 Silvertone Electronics..................96 Win $500USD cash dontronics.com Smart Fastchargers.....................23 ELECTRONICS FOR BEGINNERS COURSES: including DC & AC principles and operational amplifiers. Community Colleges. Monday evenings from 26 July, Tuesday evenings from 27 July or Saturdays 9-5 from 31 July. Enquiries: 02 9130 7988. Solar Flair/Ecowatch....................94 WORKBOOK FOR SALE: “Electronics for Beginners Stage 1, DC Electrical Principles”. Phone 02 9130 7988. Printed circuit boards for SILICON CHIP projects are made by: A NEW address for Acetronics http://www.acetronics.com.au On-line PCB quotes, free software, DIY PCB supplies plus many other items & services. 02 9743 9235. Still only $129.50 AM or $149.50 FM. May be used with most ppm transmitters. This and many other radio control products available from: Silvertone Electronics, PO Box 580, Riverwood 2210. Phone/Fax (02) 9533 3517. www.silvertone.com.au Resurrection Radio......................69 PCBS MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics (02) 9554 9760 sesame<at>internetezy.com.au; http:// members.tripod.com/~sesame_elec 1A LASER DIODE DRIVER, 3W head laser power monitor, IR laser diode with housing, greatly reduced price, e-mail Truscott’s Electronic World...........23 Vass Electronics..........................55 Zoom EFI Special......................IBC _____________________________ PC Boards • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 9587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. lmatthee<at>perthpcug.org.au for details and pictures KIT ASSEMBLY ANY KITS assembled/repaired: professional, speedy service. Phone Neville Walker (07) 3857 2752. Own an EFI car? Want to get the best from it? Youll find all you need to know in this publication