July 2000 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: 42V electrical systems in cars
Feature: Say Bye-Bye To Your 12V Car Battery by Julian Edgar
Project: A Home Satellite TV System by Garry Cratt & Ross Tester
Project: A Moving Message Display by Atilla Aknar & Ross Tester
Project: Compact Fluorescent Lamp Driver by John Clarke
Project: El-Cheapo Musicians' Lead Tester by John Clarke
Order Form
Project: Li'l Powerhouse Switchmode Power Supply; Pt.2 by Peter Smith & Leo Simpson
Review: Motech MT-4080A LCR Meter by Leo Simpson
Product Showcase
Review: ADEM Compac II Security System by Ross Tester
Vintage Radio: The AWA P1 portable 11-inch B/W TV set by Rodney Champness
Book Store
Back Issues
Notes & Errata
Product Showcase
Market Centre
Outer Back Cover

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The Future: High Voltage Car Electrical Systems SILICON CHIP JULY 2000 6 6 $ 00* $ 60* UNTIL 30/6/00 INC GST ISSN 1030-2662 NZ $ 7 50 07 INC GST PRINT POST APPROVED - PP255003/01272 9 771030 266001 www.siliconchip.com.au PROJECTS TO BUILD - SERVICING - COMPUTERS - VINTAGE RADIO - RADIO CONTROL Moving Message Display To Build Simple to construct o Simple to program! A Home Satellite TV System for under $50! FREE THIS ISSUE: ALTRONICS 2000 CATALOG Quickie Project: Muso’s Test Box SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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.premierbatteries.com.au Contents Vol.13, No.7; July 2000 FEATURES 4 Say Bye-Bye To Your 12V Car Battery The days of 12V car electrical systems are numbered. Radical changes are just around the corner – by Julian Edgar 72 Review: Motech MT-4080A LCR Meter Versatile instrument can also check a raft of parameters, including Quality factor, phase angle, dissipation factor and ESR – by Leo Simpson 80 Review: ADEM Compac II Security System Is there an intruder on your premises? This clever system lets you know then lets you listen in – by Ross Tester Home Satellite TV System For Less Than $50 – Page 10. PROJECTS TO BUILD 10 A Home Satellite TV System For Less Than 50 Bucks Tune into TV signals on the Optus B1 satellite with this surplus gear. $50 buys you all the bits – by Ross Tester & Garry Cratt 18 A Moving Message Display It’s easy to build, easy to program, easy on the pocket and easy on the eye – by Atilla Aknar & Ross Tester 30 Compact Fluorescent Lamp Driver Moving Message Display – Page 18. Operates from a 12V DC supply and can drive up to four 9W CFLs at full brightness. Use it as part of a solar power installation or anywhere you require good lighting without mains power – by John Clarke 42 El-Cheapo Musicians’ Lead Tester Checking leads is a snap with this handy tester – by John Clarke 60 Li’l PowerHouse Switchmode Power Supply; Pt.2 Second article has all the construction details. And we’ve improved the output filtering for even better performance – by Peter Smith & Leo Simpson SPECIAL COLUMNS 54 Serviceman’s Log Big is not always beautiful – by the TV Serviceman Compact Fluorescent Lamp Driver – Page 30. 82 Vintage Radio The AWA P1 portable 11-inch B/W TV set – by Rodney Champness DEPARTMENTS 2 53 59 70 74 Publisher’s Letter Subscriptions Form Mailbag Circuit Notebook Product Showcase 90 92 93 94 96 Ask Silicon Chip Notes & Errata Electronics Showcase Market Centre Advertising Index Musicians’ Lead Tester – Page 42 JULY 2000 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.) Peter Smith Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0414 34 6669 Regular Contributors Brendan Akhurst Louis Challis 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. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $69.50 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 42V electrical systems in cars Most people would agree that there have been radical changes in the design of automobiles in the last 15 years or so. Not only do computer chips now control the entire operation of car engines these days, they also control the automatic transmission, brakes (ABS), the air-bags, cruise control, traction control, air-conditioning (climate control) and even suspension. But as radical as those changes are, they are just for openers. We’re going to see a lot more changes in the next few years as designers work out how to make cars perform a lot better while using less fuel and providing more safety. A fundamental part of this next raft of changes will be the electrical system itself. The old faithful 12V system will be superseded by 42V systems, based on a 36V battery but acknowledging the fact that the actual DC voltage will be maintained at around 42V. This is equivalent to 14V from an existing 12V battery system. The proposed 42V system is described this month in an article starting on page 4. The main reason for going to the higher voltage is that the electrical load in cars is getting higher all the time. Increasing the voltage by a factor of three reduces the current by the same factor and this greatly reduces voltage losses as well as enabling the wiring harness to be reduced in weight. However, some of the changes envisaged for cars involve such things as electric power steering, electric blower super-charging and even solenoid-operated valve trains. These really do involve quite high peak powers but they are better done electrically rather than driven by the engine. They would not be really feasible at 12V but they become a whole lot easier at 42V. The most exciting concept has to be computer-controlled valve trains. These could bring about quite startling increases to engine power and responsiveness, as well as completely eliminating all the drawbacks of existing camshaft and valve lifter systems. In fact, this would make existing variable valve timing schemes such as Honda’s VTEC and Toyota’s VVT seem crude in the extreme. Instead of bringing a more aggressive cam profile above a certain engine speed like these mechanical systems, a computer-controlled valve train could apply infinitely variable valve timing, from cylinder to cylinder if necessary. So if you suddenly wanted heaps of power, not only would the fuel charge increase but the inlet valves could be wide open to accept that charge, instantaneously. Possibly the system might end up being so effective that it would make super-charging or turbo-charging obsolete. You could have car engines that were completely docile and very economical most of the time, only to change to fire-breathing monsters in the blink of an eye. Now maybe we could have roads where we could use all this extra performance. Energy crisis? What energy crisis? Leo Simpson Desktop Dual Speed Hubs All the dual speed hubs are designed with an "extension port". When all the connected devices are running at 100Mbps, the last port of 8/16-port dual speed hub can be set as a distance extender that overcomes the 5 meters uplink restriction for typical Class II Fast Ethernet hubs. You can uplink to any 100Mbps Fast Ethernet hub as far as 100 meters away. For the 5-port dual speed hub, the 5th port is a truly "10/100Mbps auto-sensing switching port". Low cost & supremely easy to install, the 5/8/16-Port Dual Speed Hubs are the best choice for your office network. Mobile Racks *Affordable Web-Based Training Removable storA whole range of courses are available! Including age modules are WIN 2000, Lotus Notes R5, Home Business, the perfect soluMotivation, Internet Information Server 4 and tion for protecting Microsoft Certified Systems Engineer Series. your valuable data. Features include an easy pull-out handle, auto-close door design, *Full details at www.tol.com.au LED indicators for power & hard disk drive as well Ethernet 100Base-TX to Fibre SC Cat. 11325 $338 as an internal cooling fan. Also available is a IDE Ethernet 100Base-TX to Fibre ST Cat. 11326 $338 hot-swap model. Pressure Sensitive Pen Tablet At last an affordable pressure sensitive pad with an active area of 146 x 108mm. Two buttons on the stylus pen enable you to simulate clicking on the right, left or middle button of a Five Port Desktop 10/100Mbps Hub Cat. 11336 $160 3-button mouse. It is sensitive to Eight Port Desktop 10/100Mbps Hub Cat. 11337 $208 512 pressure levels which allows Sixteen Port Desktop 10/100Mbps Hub $407 you to vary line width according to pressure using your Cat. 11338 8 Relay Output & Isolated Digital Input - PCI favourite application software (Photo Impact 4 Light software included). The tablet has a default resolution of A PCI interface card that 508 lpi, but can be set up to 4064 lpi. features 8 opto isolated Pressure Sensitive Pen Tablet Cat. 8896 $158 digital input channels with 5 - 24 volt AC or DC and a Smart Card Reader/Writer - Serial withstand voltage of 1000V. Identical in size and feel to credit cards, Eight reed relays are also included on the card and smart cards store information on an intehave a contact rating of 120V AC 0.5A or 30VDC grated microprocessor chip located with1A, breakdown voltage is 300V AC/DC min. LEDs in the body of the card. The Smart Card indicate energised relays. A daughter board, Cat reader/writer connects to the PC via a 17069, is available to allow expansion to 16 CH serial port and takes power from the keyinput and 16 CH output. board port with a T type cable. The Cat. 17068 8 Relay Output & Isolated Digital Input Cat. 17069 Expansion Daughter Board $413 $301 Printer Servers There's no need for a computer just to operate as a printer server, or you can avoid slowing down a work station when a print job is running by installing this small print server. It connects directly to the printer and a UTP cable. Suitable for Windows 95, Windows NT, Novell, TCP/IP & Unix. reader is compliant with ISO7816/3 with T=0,T=1 and APDU protocols. A software library for DOS, Win95/98 and WinNT4.0/2000 is included. Cat. 8899 Cat. 8901 Smart Card Reader/Writer - Serial Smart Card / Mag. Card Reader OEM Windows Terminal $160 $689 Cat. 6610 Cat. 6611 Cat. 6614 Cat. 6615 Cat. 6612 Cat. 6613 Mobile Rack HDD Frame Kit IDE $66 Mobile Rack Tray Only for IDE $37.25 Mobile Rack HDD Frame Kit IDE Hot Swap $151 Mobile Rack HDD Frame Kit IDE 66 $84 Mobile Rack HDD Frame Kit SCSI $75 Mobile Rack HDD Frame Kit SCSI Wide $122 TV Display on PC Monitor An easy-to-use external unit to enable you to watch full screen high quality TV on your PC monitor. It features one-touch key between your PC and TV, built-in infra-red receiver input for IR remote control and supports channel auto scan and memory. TV Display on PC Monitor Cat. 3372 $311 FireWire to PCI Host Adapter Connect a digital video camera to your PC. Our Firewire card allows IEEE 1394 FireWire devices to connect to a PC at speeds up to 400Mbps. Three external & one internal IEEE 1394 ports allow connections to hard drives, scanners, VCRs, HDTV, printers etc. Editing your videos is simplified with bundled Ulead Video Studio DV SE software. Upgrade software* is available at the time of purchase. A PCMCIA FireWire adapter also available. FireWire to PCI Host Adapter Cat. 2621 $197 This windows based terminal is MediaStudioPro V6.0 VE Cat. 70406 *M $219 suitable for NT Terminal Server & PCMCIA to FireWire Adapter Cat. 2821 $312 Citrix Metaframe. It supports External Case for CD via USB Port Microsoft's RDP and Citrix ICA3 This external case protocols. Ports are DB25 parallel, two DB9 serial, two Cat. 11288 Printer Server 1 Parallel Port 10MB/s $198 will support standard Also available, auto-sensing dual speed USB, VGA DB 15, PS/2 mouse & keyboard ports & audio in IDE Bus CD-ROM & out. Just add a monitor, keyboard & mouse. 10/100MB/s print servers. drives and connects Windows Terminal $923 Cat. 11312 Printer Server 1 Parallel Port 10/100MB/s $272 Cat. 1214 to a USB port. It Cat. 11293 Printer Server 3 Parallel Port 10/100 MB/s $367 Serial and TCP/IP Ethernet LAN terminals. includes built-in power supply and support for Serial Terminal 460Kbps Cat. 1133 $475 Fast Ethernet Media Converters TCP/IP Ethernet LAN Terminal Cat. 1134 $498 Windows 98 /2000. Convert from Fibre to MII (Media Independent External Case for CD USB Port Cat. 6622 $187 External Case ffor CD Parallel Port $131 Cat. 6319 Interface) or 100Base-TX. Available with SC or ST ISA VGA Cards Cat. 6632 CD ROM Parallel Port 48xSpeed & Case $303 ISA VGA cards for your legacy systems. fibre connectors. Cat. 11327 Cat. 11328 Ethernet MII to 100Mbps Fibre SC Ethernet MII to 100Mbps Fibre ST $329 $329 Cat. 2223 ISA VGA Card 16-bit TR8900D 1MB $71.50 E & OE All prices include sales tax MICROGRAM 0700 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 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 The days of 12 volt systems and conventional air-cooled alternators for cars are numbered – radical changes are just around the corner! By Julian Edgar D uring the last 15 years or so there has been a major change in the electronic architecture of cars. The introduction of engine management, anti-lock brakes, traction control, climate control, automatic stability control and similar systems has meant that some cars have as many as 10 electronic control units. These frequently communicate with one another via Controller Area Network or CAN buses and all have full self-diagnostic ability. But while all of these electronic changes have been occurring, the power generation and distribution system of cars has remained static. An air-cooled alternator charging a single 12V battery, with a running-car voltage of about 14V distributed by copper cables, has been the system employed in all cars. However, even this has now started to change – water-cooled alternators are being fitted to some vehicles, combined starter/alternators are being developed and a standardised 42V electrical system is imminent. New Electrical Loads The electrical loads of modern cars have increased dramatically over the 4 Silicon Chip last 10 or 15 years. Luxury cars – especially – are voracious consumers of electrical power. Fig.1 shows the maximum electrical loads of the current model BMW 750iL, which can reach a staggering 428 amps (5.9kW)! So what on earth draws so much electrical power? In this car over half of the maximum power load is from the short-term electrical heating of the catalytic converters. Because this single load is so great, it’s worth looking at in a little detail. Catalytic converters function most efficiently at cleaning the exhaust when they reach a temperature of about 600°C. This heating is normally provided by the passage of the hot exhaust gases through them. However, in cold start conditions, it takes some time for the catalytic Power Consumers Maximum Consumption (Amps) Electric catalytic converter heating element (30 seconds)............................ 240 Engine.............................................................................................................. 23 Suspension......................................................................................................... 4 Body.................................................................................................................. 3 Secondary air pump......................................................................................... 30 Low beam light................................................................................................ 13 High beam light................................................................................................. 9 Fog light............................................................................................................. 9 Brake light......................................................................................................... 4 Reading light...................................................................................................... 1 Fan blower...................................................................................................... 29 Rear compartment fan blower........................................................................ 16 Airconditioning ................................................................................................. 3 Audio systems and telephone.......................................................................... 10 Wiper stage II.................................................................................................... 9 Auxiliary fan..................................................................................................... 25 Total Maximum Consumption.................................................................. 428 Fig. 1: the maximum current consumption of the BMW 750iL is a staggering 428 amps! The short-term load placed by the two catalytic converter heating elements makes up much of this. [BMW] Luxury cars like this BMW 7-series have huge electrical power loads. This requires the use of a water-cooled alternator and twin batteries. [BMW] battery services other loads. Two redundant temperature sensors monitor the temperature of the starter battery; if it falls below 0°C, the electric cat converters are not heated. (Incidentally, US authorities require the use of the two temperature sensors to reduce the possibility of malfunction.) ENGINE CONTROL UNIT ELECTRIC CATALYTIC CONVERTER CONTROL UNIT ELEC.CATALYTIC CONV. PROG TIME CONTROL POWER OUTPUT SWITCH TEMPERATURE CONTROL SECONDARY AIR PROGRAM CAN CAN RECORD. OF MEAS. VALUE DIAGNOSIS DIAGNOSIS SECONDARY AIR SECONDARY AIR PUMP VALVE SECONDARY AIR VALVE * BATTERY TEMPERATURE SENSORS * * BATTERY ISOLATOR SWITCH STARTER BATTERY ELECTRIC CATALYTIC CONVERTER 2 Fig.2: a schematic diagram of the BMW catalytic converter electric heating system. [BMW] h 0A 11 STARTER MOTOR ELECTRIC CATALYTIC CONVERTER 1 LIQUID COOLED ALTERNATOR VEHICLE CIRCUIT LOAD converter to reach operating temperature – in the meantime, emissions are high. Manufacturers strive to reduce cat converter warm-up time by placing the converter close to the engine and by using exhaust pipes prior to the cat converter that have little thermal mass, eg, double skin pipes. However, under high engine loads, these approaches can result in cat converter overheating, with the resultant destruction of the ceramic matrix within the converter. Electric heating of the cat converter results in reduced cold-start emissions, while still allowing it to be placed sufficiently far from the engine to ensure durability. In the BMW 750iL, two catalytic converters are used, both electrically heated for a maximum of 30 seconds. The heating starts once the engine speed exceeds 400 RPM (ie, as soon as the engine is started). A dedicated electric cat converter control unit is used, linked to the engine control unit via a CAN bus. The vehicle uses a two-battery electrical system – a 110Ah battery is used to start the vehicle and provide cat converter heating current, while a second smaller (55Ah) VEHICLE CIRCUIT BATTERY Ah 55 JULY 2000 5 A current car has a wiring loom that in some cases stretches for 2000 metres. Using a higher system operating voltage could reduce the mass of the loom significantly. [DaimlerChrysler] The electric cat converter control system has full self-diagnostic ability, with up to 14 error messages able to be recalled. Fig.2 shows a schematic diagram of the BMW system. While cat converter heating is one of the greatest of the new electrical loads, automotive technology being developed also involves substantially increased electrical demands. These include: • electromagnetic solenoid operation of the valvetrain; • electrically assisted power steering in large vehicles; • brake-by-wire; • ride control systems. In fact, US automotive supplier Delphi predicts that within 20 years, the electrical power consumption of a typical car will have reached 10kW without any form of electrical propulsion being employed and more than double this if the electrical power is used to aid vehicle motive power. Given that 10kW represents a current flow of 725A at 13.8V, it is not surprising that moves are afoot to raise the standard voltage of car electrical systems! 42V Systems About 40 years ago automotive electrical systems moved from a 6V standard to 12V. Now a change to 42V systems is being proposed. While called a 42V system, this uses a 36V battery and 42V alternator output, much like the current system uses a 12V battery but a 14V rail (actually 13.8V) and alternator output. 6 Silicon Chip Two multi-company committees are working on the new standard. At the Massachusetts Institute of Technology, the Consortium on Advanced Automotive Electrical/Electronic Components and Systems includes General Motors, Ford, Daimler-Chrysler, BMW, PSA-Peugeot/Citroen, Renault, Volvo and automotive electronics suppliers Delphi, Bosch and Siemens. In Europe, Sican – an organisation in Hanover, Germany – is working with major German carmakers and component suppliers to formulate the new 42V standard. The commitment to the new standard is high. For example, the French automotive component company Valeo has eight of its nine component divisions working on products using 42V technology. The commercial risks to a car manufacturer of embracing 42V technology and at the same time undertaking a major redesign of all the electronics in the car means that, initially, dual 12V/42V systems are likely to be introduced first. As Delphi state, “The increase in voltage means rethinking and possibly redesigning everything from light bulbs to major components”. Says Daimler-Chrysler: “We have decided to retain a 12V supply so that components in standard use today can remain operable.” The major benefit of the higher voltage is in the reduced current flows that are then possible for the same power consumption. Wiring bundles could be as much as 20% smaller, in turn reducing cable mass and so benefiting fuel consumption and emissions. One need only attempt to pick up the wiring loom of a modern car (which can stretch to a combined length of 2000 metres) to realise that the mass of copper used is considerable. DaimlerChrysler again: “We see the development of a 42V net not only as a technological necessity, but as a contribution to lessening the environmental burden.” A number of approaches to the introduction of 12V/42V architecture are proposed: • Single voltage generation and single voltage energy storage – a 42V alternator charges a 36V battery which services 36V loads, with a DC/DC converter to charge a 12V battery that services 12V loads; • Single voltage generation and dual voltage energy storage – a 42V alternator charges the 36V side of a dual 12V/36V battery, with a DC/DC converter to charge the 12V portion of the battery; • Dual voltage generation and single voltage energy storage – where a dual 14V/42V alternator charges two separate systems, one 12V and the other 36V; • Dual voltage generation and dual voltage energy storage – where a dual 14V/42V alternator charges a dual 12V/36V battery. Each of these approaches is shown in Fig.3. The current and future technologies which would benefit from the introduction of a 42V architecture are shown in Figs.4 & 5. New Alternator Designs The very high electrical power demand of modern cars is also resulting in the development of more efficient alternator designs. One approach is to water-cool the alternator, circulating engine coolant through passages cast in the alternator housing. In some cases, the alternator may be entirely surrounded by a water jacket. A liquid-cooled alternator design was first introduced (in very small numbers) in passenger cars in 1995. That design used two conventional Lundell-type alternators axially mounted on the one shaft and developed 14V/220A with low noise levels. Subsequently, BMW has introduced (on cars such as the 750iL cited above) a water-cooled alternator that uses a single Lundell brushless design developing 14V/150A. The BMW alternator uses liquid cooling for two major reasons: to reduce the alternator noise associated with normal fan-cooling by up to 3dB and to increase electrical performance. Other advantages of the design include: • rapid engine warm-up due to the utilisation of alternator waste heat; • packaging advantages due to the absence of an alternator aircooling duct; • a longer alternator life; • good fording ability for the car. DC-DC CONVERTER However, I am sure that the last advantage is of theoretical nature only – how many owners would drive a $272,000 BMW 750iL through a river!? When high temperatures are present in the engine bay, air-cooled alternators experience elevated temperatures through heat-soak. As a result, air-cooled alternators are normally significantly de-rated in capacity in order that their temperature rise is not excessive when there are combined high electrical loads and high heat-soak thermal loads. A water–cooled alternator is comparatively insulated from engine bay heat variations and so temperature increases from heat soak do not need to be taken into design consideration. This results in more power being obtainable from the same sized package. The durability of a water-cooled alternator is improved by the reduction in the degree of thermal cycling that the alternator undergoes. Air-cooled alternators experience a rapid increase in temperature immediately following start-up. As the alternator speed then increases, the forced-air cooling system becomes more effective and so the temperature decreases. With water cooling, marked temperature peaks no longer occur, especially in the 2500 – 4000 RPM alternator speed ranges most often used. The possibility of using short-term boosting of the alternator output DC-DC CONVERTER 14V 14V 12V BATTERY 12V LOADS 42V 12V/36V BATTERY 12V LOADS 42V ALTERNATOR ALTERNATOR STARTING MOTOR 36V BATTERY STARTING MOTOR 36V LOADS Single-voltage generation and single-voltage energy storage Single-voltage generation and dual-voltage energy storage 12V LOADS 12V BATTERY 14V 12V/36V BATTERY 14V ALTERNATOR 42V 36V LOADS 12V LOADS ALTERNATOR 42V 36V BATTERY STARTING MOTOR 36V LOADS Dual-voltage generation and single-voltage energy storage STARTING MOTOR 36V LOADS Dual-voltage generation and dual-voltage energy storage Fig. 3: the different approaches that could be taken to adopting 14/42 volt architecture in automotive applications. [Delphi] JULY 2000 7 Current Technology Benefits of 42V Architecture Electric power steering More power, improved fuel economy Electric brakes Redundant power supplies Power windows, power seats, Reduced size and mass of motors; more efficient operation power hatchback lifts Heated catalytic converter Lower emissions; quicker light-off time Heating, ventilation, airconditioning Greater efficiency; smaller/lighter units; flexible packaging blower motors and cooling fans Mobile multimedia More power available for video, phones, navigation systems, audio amps, fax machines Water pumps Improved efficiency; longer service life Selected engine management system Reduced size and mass; increased performance components (eg exhaust gas recirculation valves, ignition systems, control actuators) Fuel pumps Reduced size and mass Heated seats Faster heating, more efficient operation; increased power Fig.4: the benefits to current automotive electrical technology of adopting a 42V system. [Delphi] Future Technology Ride control systems Brake by wire Steer by wire Electromagnetic valve control Integrated starter/generator Benefits of 42V Architecture Improve ride, handling and vehicle stability Improved vehicle packaging and vehicle performance Enhanced performance; improved packaging; improved passive and active safety Lower emissions; optimal power; individual cylinder control; lower cost Faster starts; quicker charging; design flexibility; low noise & vibration; improved fuel economy Fig.5: the benefits to proposed automotive technology able to be realised with a 42V system. [Delphi] reveals another potential advantage of water-cooling. The output of an alternator can be increased by a number of means: • feeding the excitation circuit with an increased voltage supplied by a DC/DC converter; • using a higher amount of excitation by employing an excitation winding layout with lower resistance; • operating the alternator in self-excitation at higher terminal voltage. Since these methods are all limited by heat build-up considerations, the greater thermal mass of a water-cooled alternator has inherent advantages when any of these approaches is taken. 8 Silicon Chip Each of these short-term boost techniques is being actively considered for automotive use. Lundell alternators are also being supplemented by water-cooled hybrid permanent magnet/Lundell designs. Delphi produces one such design, capable of developing 13.5V/150A at 6000 RPM alternator speed. The alternator requires a minimum of two litres/ minute coolant flow at a maximum temperature of 130°C. Fig.6 shows a drawing of the Delphi design, with the coolant connection pipes prominent. Probably the most dramatic development in alternator technology, however, is the Integrated Starter Alternator Damper (ISAD) being developed by German company Continental ISAD Electronic Systems GmbH & Co. The ISAD combines the function of a starter motor and alternator into one assembly, located between the engine and gearbox. Fig.6: a drawing of a Delphi 13.5V/150A water-cooled hybrid permanent magnet/ Lundell alternator. Note the water pipe connections. [Delphi] ISAD is able to generate output voltages of 12, 24, or – significantly – 42V. The device eliminates: • the conventional starter motor and solenoid; the flywheel; • the conventional alternator; • the alternator pulley and belt drive • system; • and in some cases, the harmonic balancer. Both BMW and Citroen have shown vehicle prototypes using 42V ISAD systems. In a car equipped with a 42V ISAD system, each normally belt-driven device could be replaced with an electric motor. In some cases this would have significant advantages – the aircon-ditioning compressor could be located close to the cabin instead of at the front of the engine, for example. Conclusion Cars featuring water-cooled alternators or combined starter/alternators, 42V wiring and much higher electrical loads are likely to be appear in the next few years. No longer will “12V” be synonymous with cars… SC SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au Believe it or not . . . A $49 Satellite TV System Have you ever looked at those satellite dishes which have sprung up on pubs, clubs and even private homes and thought “Gee, I wonder what they’re watching?” Have you ever wished that you too could get into satellite TV reception – but have been scared off by the $$$$$? Wish no longer! By Ross Tester and Garry Cratt* 10 Silicon Chip H ere is a full satellite TV system which you can set up in your own backyard for a tad under fifty dollars. No, not five thousand and fifty dollars, not even five hundred and fifty dollars. Just fifty measly dollars. For that, you get a satellite dish, the mounting hardware, a LNB (low noise block converter) and an analog satellite receiver which you can plug directly into most TV sets (or video recorders). And yes, the price even includes the Generally Silly Tax. Point the dish in the right direction (we’ll tell you how later), tune the receiver (we’ll tell you how later) and start watching satellite feeds. If you’re into amateur television (or would like to be), this would be a great system to get you going. How is this possible? One of the consequences of rapidly changing technology is the huge amount of equipment made obsolete in just a few years. Thousands of still-operating ’386 and ’486 computers have no doubt gone to the junkyard or dump, replaced by the latest higher speed processor models. Most of us regard this as a terrible waste of manpower and money. But that’s “progress” (or is it marketing?) for you. Satellite TV has enjoyed as similarly short a lifespan as the personal computer and the amount of obsolete equipment destined as landfill is rap- Here’s what you get in the hardware department: the 90cm dish, the mounting plate, three mounting struts, the main mounting bracket (right) plus the LNB and its mounting bracket (bottom). Below is the Scientific Atlanta 9600 series receiver plus the 125VA enclosed 240/110 transformer. Not bad for $49.95, eh? idly increasing. It was a case of being “in the right place at the right time”. Garry Cratt, from the satellite reception specialists Av-Comm Pty Ltd, found a huge quantity of surplus satellite TV equipment sitting in one of his supplier’s warehouses, just a day or so away from being picked up by a metal recycler. The systems were obviously used (in some cases very used) but had all been nevertheless working perfectly when replaced a few months previously. Instead of the local dump or metal recycler’s, the whole lot – pallets and pallets of it – found their way to Av-Comm’s warehouse instead. And the price was what the metal recycler had offered! JULY 2000 11 These two shots show how the mounting bracket bolts to the mounting plate which in turn bolts onto the rear of the dish. The whole assembly is designed to slip over a 2-inch water pipe. Rotating the dish on the pipe allows you to set the azimuth, or direction, while adjusting the threaded rod on the right of the bracket (with the black cover on the end) lets you set the elevation, or distance above the horizon. Being an “offset” dish, it is more vertical than a “prime focus” dish. When the truckloads of equipment arrived, Garry took a closer look at his bargain purchase. The dishes were all in quite good nick, even if somewhat “shop soiled” (Garry used a slightly different expression but decorum prevents us quoting him verbatim). They were 90cm offset dishes, the type recommended by most K-band broadcasters because of their good sidelobe performance and no aperture blockage. Because an offset dish is actually only a section of a larger “prime focus” antenna, the offset angle means that the actual angle of the reflector FOCAL POINT FOCAL POINT OFFSET DISH PRIME FOCUS DISH Fig.1: the difference between a “prime focus” dish and an “offset” dish. In reality, an offset dish is a portion of a prime focus dish, having the same focal point as if it were the prime focus dish. This can best be illustrated by the diagram at right where the offset dish above is superimposed over the prime focus dish. As an offset dish is it mounts more vertically in higher latitudes, there is less pooling of water or build-up of snow and ice. They also have good side-lobe performance and, because the feedhorn doesn’t “get in the way” of incoming signals, no “aperture blockage”. 12 Silicon Chip FOCAL POINT with respect to the horizontal plane is much higher than that of a prime focus dish, ensuring that rain, ice and snow cannot pool on the dish surface. In simple words, the dishes are much more vertical. The “offset” part also means that the LNB is not mounted at the apparent focus of the parabola of the dish but is offset. Despite the age of the dishes and LNBs (probably a decade or so old), he was surprised to find they were capable of providing a result at least comparable with a brand new dish and LNBF combination, when used on the new Optus B3 satellite Aurora digital system (used to deliver ABC and SBS across Australia). Of course the system performance margin is less due to the higher noise figure of the LNB, typically 1.1dB. The satellite receivers are of similar vintage to the dishes and LNBs and, as such, are also a little soiled. But a few minutes with a rag and some metho does absolute wonders – we’re sure you could do the same too. The receivers, by the way, are Scientific Atlanta Model 9600 series, a brand very highly respected in the satellite TV world as offering superb quality. Designed to fit in a 19-inch rack, they’re also quite happy in a stand-alone mode. There are a couple of different models within the series but we’re not The feedhorn and its attached LNB first mounts in its own bracket (shown below) which allows it to rotate, thus setting polarisation. As shown (label up), the polarity is vertical. The feedhorn bracket is bolted to the three mounting struts which in turn bolt onto the dish. This shot also shows the RG-6/U cable connected and secured to the bottom strut with cable ties. Note the “drip loop” in the cable. high-performing receiver especially considering its age – and even more so considering the price. What’s it perform like? going to expand on the differences. What you get for your $49.95 is what you get! With 20-channel memory and a wide rage of user functions accessible from the front panel, they’re quite simple to use (unfortunately, there are no instruction manuals but the labelling is pretty much self-explanatory). On the rear panel are inputs from the LNB, vertical and horizontal inputs, IF out/IF in sockets (usually connected), video output and composite baseband outputs plus a range of connectors for audio output (stereo if available), remote control, presets for audio level, switches to invert and/or clamp video and so on. We won’t bother with many of these but they are there for you if you want to experiment. Most of the receivers operate on 110V AC but even here you’re not on your own. Included in the price is a 240/110V 125VA Ferguson transformer, housed in its own steel case, complete with 3-pin socket and mains lead. The replacement cost of this transformer on its own is about $90… but it’s included in the $49 deal. All in all it’s a very comprehensive, We’re not pretending that it has the performance of a modern system utilising a digital receiver and smartcard arrangement – but such a system costs just a little more than this system – well over $1500 in fact. This system is much cheaper yet is capable of providing more-than-watchable results. For under $50, it’s great value even for experimenters. Garry tells us that many have already been sold to amateur operators for ATV experiments – without any publicity at all. Word of a bargain soon gets around! This is an analog system – which is one of the reasons for its withdrawal from use. It is not capable of tuning digital signals but there are still plenty of analog signals to play with – for example, all of the network “interchange” signals currently being transmitted on the Optus B1 satellite. Using a small dish (90cm is considered small!) doesn’t give you the picture quality of a larger dish (say 1.8 or 2.5m) but the pictures are still perfectly watchable. The bigger the dish (within reason), the better the results. Also, modern LNBs have a lower noise figure than the LNB used in this system – replacing the LNB with a unit of more recent vintage would also improve the reception. Again, though – don’t look at the quality. Look at the price! By the way, the format of the re- ceived signal doesn’t change in the receiver: if you pick up a PAL signal from the bird, you get a PAL signal out. If it’s NTSC, you get NTSC out. Contrary to popular belief, you can watch an NTSC picture on a PAL TV – it’s just that glorious living Technicolor becomes glorious boring black and white. If you have a multi-standard TV set... lucky you! And before we get onto building and erecting the dish, a word on legalities. It will pay you to get in touch with your local council or building authority to check on their rules. Our local council, for example, allows a single dish up to 1.5m in diameter, ground or building mounted, to be erected without a permit. Anything larger, or more than one in your backyard, or mounted up high, requires a development application. Building the system First of all, check that you have all the bits. You should receive the 90cm dish, a mounting plate, three LNB mounting arms, the LNB itself, an LNB mounting bracket and the dish assembly mounting bracket which probably (but not definitely) has U-bolts still attached. Of course, you also get one of the Scientific Atlanta 9600 series receivers (ours was a 9630) and the Ferguson TS115/125B transformer, if required (for 110V receivers). You will also get many of the nuts and bolts needed to put it together – perhaps not all of them but for $49.95, what’s a couple of bolts between friends? What you don’t get is any coax JULY 2000 13 cable, mainly because every location needs a different length of cable, nor the “F” connectors which are essential to connect the LNB to the receiver. The first step is to give the whole lot a clean. Dust off the cobwebs (no, we’re not kidding!) and give the whole thing a bit of TLC. You might like to give any exposed or corroded parts a spray with some WD40. Even though the dish “reflector” is one piece, there are a quiet a few other bits of hardware involved, hence the most logical assembly sequence is outlined here. Bolt the mounting plate to the mounting bracket – when the recess in the mounting plate points up, the mounting bracket sits on top of this. The holes in the mounting plate are threaded so no nuts are needed Bolt this assembly to the back of the dish. There are four bolt holes in the dish which correspond to the four bolt holes in the plate. To ensure there are no protrusions onto the reflector surface (reducing the dish efficiency), the bolts are countersunk. Simply bolt the backing plate assembly to the back of the reflector with the bolts going from front to back (ie, through the dish then through the mounting plate), ensuring the mounting pole entry point faces towards the bottom of the dish. A feedstrut mounting hole helps to identify the bottom of the dish. Make sure these are well and truly tight – these bolts stop the dish vibrating in the wind which in turn helps ensure picture stability. Put the dish assembly aside for a moment while you get the LNB assembly ready. Its bracket grips to the throat of the horn with two nuts and bolts (see photo opposite). Just finger-tighten the nuts for the moment. There are three struts which hold the LNB assembly in place – two the same length and one shorter. The two longer ones are horizontal struts while the shorter one is the bottom strut. Each strut has a square end and a rounded end. The left-hand and And here’s what it should look like when it’s all finished and ready to go. Compare this photo with the side-on shot on page ??? and you should have no problems working out what goes where. (The knee bone’s connected to the thigh bone, the thigh bone's connected...) The tropical-looking setting, by the way, is in the suburbs of Sydney! 14 Silicon Chip Table 1: ANALOG CHANNEL LIST K BAND (viewable with this [90cm] dish) FREQ USER POLARITY VIDEO AUDIO OPTUS B1 (160 degrees east) 12386 Network 7 Horizontal EPAL 7.38/7.56 12451 Herbalife Horizontal PAL 6.60 12458 Network 10 Vertical PAL 7.38/7.56 12480 Network 10 Vertical EPAL 7.38/7.56 12488 Network 9 Horizontal EPAL 7.38/7.56 12728 Network 9 Vertical PAL 6.60 12739 Herbalife Vertical PAL 6.60 C BAND FREE TO AIR IF FREQ 1086 MHz 1151 MHz 1158 MHz 1180 MHz 1188 MHz 1428 MHz 1439 MHz (viewable with a larger [>2.2m] dish) APSTAR 2R 76.5E 3750 VATSA (India) Vertical PAL 6.2/6.8 1400 MHz THAICOM 3 78.5E 3507 Raj TV 3535 ATN 3649 Thaicom test 3649 VTV Vietnam 3685 MRTV Vertical Vertical Horizontal Horizontal Horizontal PAL 6.60 PAL 6.60 PAL 6.60 PAL 6.60 NTSC 6.60 1643 MHz 1615 MHz 1500 MHz 1500 MHz 1465 MHz INSAT 2E 82E 3557 Vijay TV 3579 Jaya TV 3655 Asianet 3809 DD5 Tamil TV 3850 DD1 Metro 3930 DD2 National 4089 DD7 W Bengal Vertical Vertical Vertical Vertical Vertical Vertical Vertical PAL PAL PAL PAL PAL PAL PAL 1593 MHz 1548 MHz 1495 MHz 1341 MHz 1300 MHz 1220 MHz 1061 MHz ASIASAT 2 100.5E 3885 Worldnet USA 3960 CCTV 4 China 3980 RTPi Portugal Horizontal Horizontal Vertical PAL 6.60 PAL 6.60 PAL 6.6/7.2 1265 MHz 1190 MHz 1170 MHz GORIZONT 25 103E *** (Inclined orbit) 3675 RTR RHCP SECAM7.02 1475 MHz ASIASAT 3 105.5E 3650 Marathi 3760 Now TV 3800 Star Sports 3840 Channel V 3900 Punjabi TV 3920 Phoenix 3940 Zee News 3960 Star World 3980 Zee TV 4100 PTV 4120 CCTV4 4140 Bangla TV Vertical Horizontal Horizontal Horizontal Vertical Horizontal Vertical Horizontal Vertical Vertical Horizontal Vertical PAL 6.60 PAL 6.60 NTSC 5.9/6.2 NTSC 6.2 PAL 6.60 NTSC 6.20 PAL 6.80 NTSC 5.76 PAL 6.80 PAL 6.65 NTSC 6.20 PAL 6.60 1500 MHz 1390 MHz 1350 MHz 1310 MHz 1250 MHz 1230 MHz 1210 MHz 1190 MHz 1170 MHz 1050 MHz 1030 MHz 1010 MHz PALAPA C2 113 E 4180 TPI Indonesia 4160 TV5 France 4140 TV Brunei 4140 SITV Singapore 4120 MTV Asia 4060 IVM Indonesia 4040 CNBC Asia 3980 CNN Int 3900 TV3 Malaysia 3880 ATVI Aust 3840 TVRI Indonesia 3840 TPI Indonesia 3745 RCTI Indonesia Vertical Horizontal Vertical Vertical Horizontal Vertical Horizontal Vertical Vertical Horizontal Horizontal Horizontal Vertical PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL PAL 970 MHz 990 MHz 1010 MHz 1010 MHz 1030 MHz 1090 MHz 1110 MHz 1177 MHz 1250 MHz 1270 MHz 1310 MHz 1310 MHz 1405 MHz 6.60 6.60 6.60 5.50 5.50 5.50 5.50 6.60 6.60 6.80 6.80 6.80 6.60 6.60 6.80 6.80 6.80 6.80 6.2/6.8 6.60 right-hand struts have an “L” and “R” punched into the rounded end. We’ll leave you to work out which of these is the left and which is the right. Fit the two horizontal struts first. In all cases the square end goes to the reflector and the round end to the appropriate holes on the feedhorn bracket. Finally, bolt the bottom strut to the dish (again, the square end). The top end of this strut also connects to the feedhorn bracket but it goes to a tapped mounting hole at the bottom of the bracket. Some of the smaller nuts and bolts required may not be supplied – you may find them in your junk box or in worst case, spend a few cents at your local hardware store. The assembly of the dish is basically complete but you will obviously need some form of secure, rigid mounting post or mast. Keep in mind the wind loading of a 90cm dish not too far off vertical! Ideally, you want a 2-inch (50mm) OD galvanised pipe, about 3.5 – 4 metres long. The bottom end of this should be either cemented into the ground (at least 500mm or so) or securely bolted or clamped to some very firm support structure. The distance off the ground is not critical but if it is at all high off the ground, it should be quite high: high enough so that even a superleague basketballer can walk under it without cracking open his skull! For the moment, tighten the U-bolt nuts only enough to allow the whole assembly to stay in position on the mast but be rotatable. Later, when you finally tighten the U-bolts they should be very tight so that the dish is secured very firmly. The dish will want to swing away from the wind like a weather vane so these bolts must ensure that it cannot! Don’t worry just yet about any adjustment to the dish – just aim it in a basic east/northeast direction before you partially tighten the U-bolts. The feedhorn/LNB bracket bolts are still only finger tight – that makes it easier to adjust polarity if necessary later. The dish assembly is now complete but you may wish to cover any gal-plated bolts in silicone sealant for more protection against rust. Don’t seal the U-bolts or feedhorn bracket bolts; you need to aim the dish first. Connecting it up We’ll assume you have made up a suitable length of high quality, 75-ohm coax. RG-6/U is normally used for satellite installations – normal RG-59 TV cable has too much attenuation at the very high frequencies involved. The length should be enough to easily reach from the dish to where the receiver will be placed, without any “trip traps” (ie, lengths running above the ground where they can be tripped over!). F connectors are used on both the feedhorn and receiver so you’ll need three of these. F connectors are available in screw-on or crimp-type (which require a special crimping tool). All of these items are available at most electronics stores or satellite specialists. F-male to RCA-female adaptors are also available if you want to use a standard video-type lead. (Av-Comm Pty Ltd has RG-6/U coax for $1.00 per metre and F connectors for $1.39 each, both inc GST). Screw one end of the F connector into the receiver “RF in” socket and the other end into the LNB socket (on the back). LNB power, by the way, is supplied by the receiver down the coax. JULY 2000 15 Elevation angles (in degrees) of a prime focus dish to the 160°E Optus B1 satellite from Australia. If your town isn’t on the map, you will need to extrapolate a little. You’ll also need to calculate the angle for the 18° offset dish we’re using (subtract 18 from your location’s true elevation angle). In the final event, though, trial and error can be used to get the best result. 75 70 65 60 55 50 45 25 Because the output of the receiver is video and audio, your TV receiver will need video and audio inputs (most modern ones do). Alternatively, connect the receiver via the video-in and audio-in sockets on your video cassette recorder. You could also buy or build an RF modulator. Dish alignment Aligning the dish involves a bit of knowledge which you may or may not have yet! Basically, there are just a few of things you need to know. First, the output of the LNB occupies a band of frequencies between 950MHz and 1450MHz. Second, the polarity of the signal from the satellite can be either horizontal or vertical (sometimes both) and the way to adjust this is simply to rotate the feed horn/LNB in its bracket through 90°. Finally, the dish needs to be aimed quite precisely in the direction of the satellite. This involves two adjustments which themselves depend on where the dish is installed – the direction itself (also called the azimuth) and also the elevation of the satellite above the horizon. Azimuth is set by simply rotating the dish on the pole; elevation is set by adjusting the large screw thread on the mounting bracket so that the correct angle of elevation is achieved. (The type of mounting bracket fitted to the dish is called an Az-El bracket because it allows adjustment of both). There is another slight wrinkle: remember we said before that this is an offset dish. Normally a dish is aimed directly at the “bird” along its parabolic axis but an offset dish needs to be aimed as if were part of a larger dish (which in theory it is). For example, we want to aim at the 16 Silicon Chip 30 35 40 Optus B1 satellite (the one with most analog signals on it!) located at 160° east. The calculated angle of elevation for Sydney is 49.5° (this is derived mathematically). As the offset angle of the dish is 18°, the actual elevation of the dish is 31.5° (the angle between the vertical backing plate and true vertical). A large protractor and plumb bob is handy to get this angle right. If you’re in Woop Woop, make the appropriate adjustments to this angle. (Oh, Woop Woop isn’t on the map? Choose a nearby town or city and use that. You may need to extrapolate slightly). Firing it up Knowing all this, it’s time to aim the dish. We’re going to cheat a bit by using the receiver as a signal strength indicator. The signal level meter reads from 0 to 99, with the higher the figure the more signal being received. By tuning the receiver to a known frequency (see table 1), and setting the LNB polarity we can adjust the dish for correct alignment. The LNB has a label attached to one side – when this label faces up, the LNB is vertically polarised. The digital frequency readout on the receiver (accessed when you press the “tune” button) is a 3-digit figure which is actually the frequency in MHz or, if that figure is between 000 and 450, the frequency without a “1” in front of it – eg, if the readout says 955 it is 955MHz; if it says 245 it is 1245MHz. Set the elevation as detailed above and aim the dish as close as you can to where the satellite should be. This may require a compass and an accurate local map to get the angle correct but in general, close enough should be good enough to find some sort of signal. Once a signal has been found the dish can be aimed properly. This can take some time for the first time user but then that’s part of learning about satellite TV. For those who find the job a bit too time consuming, a simple signal strength meter can be purchased, as can an elevation meter, used for setting the dish elevation. Of course a plumbob and a protractor can also be used for this purpose. Once the elevation has been set, all that is necessary is to pan the dish around towards magnetic north until some sort of image is seen. Mounting the dish on a ground-mounted pole makes this procedure much easier. When a signal is received the dish azimuth, elevation and the LNB polarity can be peaked for best picture. At the same time the channel can be entered into the receiver’s memory by pressing the “channel” button, selecting an unused channel and then pressing “store”. Next time you want that satellite signal, it should still be there. So now you’ve made your first, albeit small (and low cost – especially low cost!) steps into the fascinating world of satellite TV. You’ll agree – it’s SC out of this world! WHERE DO YOU GET IT? This system is only available from Av-Comm Pty Ltd, 24/9 Powells Rd, Brookvale NSW 2100, (phone 02 9939 4377) for $49.95 including GST. Freight is additional (due to the size of the dish the goods would normally be sent by road). All dishes and hardware are as described and photographed; receivers are from the Scientific Atlanta 9600 series with minor differences between models. Orders will be filled on an “as received” basis until stocks are exhausted; specific receiver models cannot be requested nor can you order individual components from these systems. If you want only the dish, for example, it will still cost you $49.95 – and you're going to get a bonus receiver and LNB! The systems are all used and are sold “as is”, and there is no guarantee (although all systems were working at time of withdrawal from service). * Garry Cratt is the Technical Director of Av-Comm Pty Ltd. Want the very latest in security? YOUR OPTIONS ARE BLACK AND WHITE! ,QWURGXFLQJ 0LFUR $GHP $QG QRZ $GHP &RPSDF ,, Adem Compac II takes this unique concept even further! It looks just like a smoke detector... but it’s not! This remarkable device contains a PIR movement detector as well as a micro which dials your phone when it senses an intruder. It even gives you a voice message to tell you what’s happening. Then you can enter your code and listen in via an inbuilt microphone, just like the Micro Adem, and take any appropriate action. Shown approx. same size! But there’s more: you can actually talk back to anyone on the premises. 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JULY 2000 17 Phone (02) 9649-5065; Fax (02) 9649-4324. email: sales<at>4dsystems.com.au website:www.4dsystems.com.au Flexible, attractive There’s nothing particularly new about moving message displays – except this one. Not only is it easy to build, it's easy to program, it looks good. . . and the price is right. Design by Atilla Aknar* Article by Ross Tester A great deal of time and effort has gone into the design of this moving message display. And the end result is a very attractive proposition – in all senses of the word. For a start, the kit price is significantly less than any commercial product which could be classed as equivalent. That’s a welcome change – we all know that these days building a kit can often cost as much as buying a finished product (or even more). Second, the display looks good. It’s housed in a clear acrylic tube with a red acrylic filter and black backing and end caps. This method means the display is suitable for placing on a shelf or desk, hanging from a wall or even hanging from a ceiling (see inset box). Third, it is flexible. We have shown a “double” display – that is, two PC boards linked together to form an 8-unit display. However, there’s nothing to stop you making a mini version with only one PC board and a 4-unit display. Finally (and perhaps most importantly), the system is incredibly easy to use. No special PC software is required – just a “dumb terminal” capable of sending and receiving via the RS232 (serial) output. Almost certainly your computer already has just such software built in; in some cases (eg, Windows 2000 users) you may need to download some freeware from the ’net. Basically, all you have to do is type your text into the PC, it sends the text on through the RS232 port to the message board’s EEPROM message store and the text stays in memory until another message is written, even if power is cut. A somewhat similar Moving Message Display was published in the February 1997 issue of SILICON CHIP. However, when we say “somewhat similar” any comparison between that project and this is just about limited to the name! The major difference is that the earlier project was totally controlled by a PC and had to remain connected to it. This one is fully self-contained: once the message is programmed in via the computer, the display runs independently. The other big difference is in the number and type of LEDs: the earlier one used 336 individual LEDs in a 48x7 matrix. This one uses eight integrated LED displays, each with a 5 x 7 matrix, making 280 LEDs in total. This is what your Moving Message Dispay should look like before it is placed in its tube “case”. Of course, there’s nothing to stop you using it just like this if you want to but the red Acrylic filter in front makes it look much better. 18 Silicon Chip So instead of 672 soldered LED joints you make just 112 (28 per display). The circuit The circuit, shown in Fig.1 (overleaf), is reasonably standard for this type of equipment. Most of the clever work is done inside the PIC micro-controller! Power is provided by a nominal 12V DC plugpack capable of supplying about 350mA. This is regulated to about 5.6V by a 7805 5V regulator with a silicon diode between its “ground” input and the circuit ground. This diode effectively lifts the normal 5V output of the regulator by the voltage drop across the junction, around 0.5-0.7V. A MAX202CPE communications chip (IC3) accepts data from the serial port of the computer in a 9600,8,N,1 format (ie 9600 baud, 8 data bits, no parity bits, 1 stop bit). This is fed into the TX and RX inputs of IC1, a PIC16C63A. PIC Ports RA0-RA3 connect to the message store IC, a 93LC46B EEPROM, (IC2) which can store up to 125 characters. This is non-volatile memory, meaning the contents of the ROM are not lost when power is removed. The contents will in fact stay in memory for many, many years (around 40 years guaranteed) which makes the message board ideal for very occasional warning messages. The OSC inputs are connected to a 3.58MHz crystal oscillator circuit which provides timing for the entire circuit. This particular frequency crystal is used because they’re made in the hundreds of millions for NTSC TV sets – so they’re really cheap! The microcontroller’s output ports, RB0-RB7, RA4, RA5, RA2 (which does double duty) and RC0-RC4 are all used in the multiplexing and driving circuitry for the 7 x 5 matrix of LEDs, each housed in a single TC20-11SWRA display (DISP1-4). Interposed between the LEDs and PIC are three ULN2003AN high current buffers (IC5, 6 and 7) connected to the LED columns, along with LED row driver transistors Q4-Q10. As there are eight of the LED displays each with five columns, there are 40 columns to drive. The PIC allocates 40-byte buffers corresponding to the message and proceeds to drive column 1 with the first part of the first letter of that message. For example, if the message begins with the letter B, D, E, F, H, K, L, M, N, P or R, the whole first column of LEDs (on the right) is lit. This is then moved to column 2, then column 3, and so on. In the meantime the PIC has told And here it is inside the case, complete with filter. The cable in front is all that is required to program it from virtually any PC running a terminal program. JULY 2000 19 20 Silicon Chip JULY 2000 21 Note the groove down the middle of the boards: if the “mini” version is constructed, the boards snap apart along this line. For the “maxi” version, the two boards require seven inter-connecting links as shown here and in the illustration below. column 2 to light in the pattern corresponding to the next part of the first letter: for example, if it were a B, D or E the top and bottom LEDs in the column would be lit. When column 2 empties into column 3, the contents of column 1 are moved to column 2 and column 1 lights with the next portion of the letter. This process happens continuously and the eyes, with their persistence of vision, are fooled into believing that they are seeing a full word, indeed a full message, whereas at any particular instant in time, all that would be seen is a series of LEDs. To prove the point that it is indeed an optical illusion, try getting so close to a moving message display that you can no longer read words. Or fix your gaze on either the start or the end of the message. All you will see is a mess of flashing LEDs! Mini or full version? What we have been describing so far is only half the circuit. We mentioned before that it could be built in a “mini” version using only half the LEDs. The full version consists of two nearly identical PC boards, the second board missing a few components and with a few links across the back of the boards. Note that the PIC chip is programmed slightly differently in the second board so don’t mix the PICs up when constructing. It won’t work! Data output is taken from the RC3, RC4, RC2, RC1 and RC0 ports of one Components are mounted on both sides of the PC board. Most are on the “bottom” side (Fig.2 above – note only one board shown) but the LED displays mount on the top side (Fig.3 below), along with the seven links between the Part 1 and Part 2 boards. 22 Silicon Chip The completed “maxi” version of the moving message display with two near-identical PC boards connected together to form an eight-letter display. We say “near identical” because there are differences – not the least being the PIC chips themselves which are are certainly not interchangeable. Each contains different code. PIC and fed into the RC7, RC6, RA3, RA2, RA1 and RA0 inputs of the second PIC. On the second board, the MAX202 RS232 communications chip (IC3), the 93LC46 EEPROM message store (IC2) and associated capacitors (C7 to C11) are not used. The housing Apart from the fact that it works so well, one of this project’s biggest assets is that it looks great! The entire project (with the obvious exception of the RS232 lead) is housed in a 305mm length of 65mm (OD) clear acrylic tube with black end caps glued in place. A 300 x 53mm length of 3mm red acrylic is used as a filter in front of the LED displays, effectively hiding all but the lit LEDs. The LED displays mount on one side of the PC board(s) while all components mount on the other. A 305 x 110mm piece of dark window-tinting film wraps around the rear of the acrylic tube, hiding everything inside except the LED displays. – how long you want the cable to be!). Connections We will assume you are making the “maxi” version (ie, eight LED displays) because that’s the way the kit is supplied (including the case length). If you only want the “mini” version (four LED displays), the two PC boards will need to be snapped apart at the V-groove between them. You’ll also need to cut the acrylic tube to the right length (and that’s not an easy task!). Before we start on the electronics side we’re going to work on the “case”, which consists of an acrylic tube, a red acrylic filter, two end caps and a sheet of dark window-tinting film. The reason for this cart-before-thehorse approach is that the filter must be glued inside the tube and the film fixed to the outside of the tube. The latter takes several hours to dry, so while that’s happening you can get on with the electronics. First, though, there are two holes needed for the DC power socket and the 3.5mm stereo socket (serial data) in one end of the tube. Exact position isn’t important – as a guide ours were 25mm and 45mm from one end. We rebated the hole for the 3.5mm socket so the nut would be recessed. Secure the length of red acrylic inside the tube, opposite the drilled holes, with a drop of acrylic glue (available at hobby shops) on each corner (super glue shouldn’t be used because it leaves a white residue on the acrylic). The sheet of window tinting film should be just the right length to wrap around the outside back of the tube from one edge of the red acrylic filter to the other. A standard 2.1mm DC socket is mounted through the rear of the tube to allow connection to power. That part was easy. The harder part was mounting a standard 9-pin “D” serial connector on the curved surface. In the end Atilla came up with an elegant solution: drop the D connector and use a 3.5mm stereo audio socket instead! Only three connections are required from the computer’s serial port so a 3.5mm stereo jack plug and socket was ideal. And it allows a very neat connection – the only slight hiccup is that you’ll need to make up your own serial cable because, as far as we know, no-one has ever made or used a 9-pin D to 3.5mm stereo cable or adaptor before now. Fortunately, that part is really easy (and you can choose – within reason Construction JULY 2000 23 (Left): It's a good idea to solder only two LED displays in place to test it – if these two work, the odds are that it will all work. If they don't work, you only have two displays to unsolder! Dunk the tube in water containing a small amount of mild detergent. Peel off the protective backing sheet from the film and carefully dunk that as well (the detergent makes the water wetter!) Remove both and shake off excess water, then place one end of film on the outside of the tube, adhesive side in, right along the line of the red acrylic filter inside the tube. Slowly wrap the film right around back of the tube, removing any air bubbles as you go with a cloth used as a squeegee. When you get to the other end of the film it should be a perfect line-up with the other side of the red acrylic filter inside. The detergent water means you have a bit of “slip” available if you need to The acrylic filter is marginally narrower than the PC board (though exactly the same length). This is to account for the curvature of the tube: the PC board mounts right in the middle but the filter sits closer to the side. move the film; indeed, it will allow you to remove it completely and start again if necessary. When satisfied that you have a perfectly placed film, put the tube aside to dry for several hours (overnight is ideal if the tube is left in a reasonably warm [not hot] place). Now, back to the electronics assembly. First check the PC board for obvious defects (remember it is double sided). Most components, with the exception of some wire links and the LED displays, mount on one side of the board. You can easily identify which side the links and displays mount on by the words “DISP4” through “DISP1” printed on it. Proceed as you would with any project assembly: mount all the low profile, non-active components (resistors, crystal and capacitors, taking due care with electrolytic capacitor polarity) followed by the smaller active components (diodes and transistors). Note that the main filter capacitor (C14) needs to be pretty small, otherwise the assembled board may not fit properly in the tube (it may foul the power or serial sockets). The kit will have small capacitors but if you source your own they may need to be mounted about 10mm above the board and then bent over at right angles, lying on top of D1, C12, etc. All ICs except the PIC are soldered directly into the board; again, check the polarity! Solder the PIC’s socket in Parts List – for “mini” version* 1 x PC board coded M4399 (two boards attached together) 1 x clear acrylic tube, 305mm long, 57.5mm ID, 63.5mm OD (case) 1 x red acrylic sheet, 305mm long, 50mm wide, 3mm thick (filter) 2 x black end caps to suit tube (glue on type) 1 x 305mm x 110mm sheet self adhesive dark window tint film 1 x 3.5mm stereo phone socket 1 x 2.1mm DC socket 1 x 10-way PCB header plug Semiconductors 1x 1N4001 silicon diode 1 x Pre-Programmed PIC16C63A (IC1)# 1 x 93LC468 (IC2) 1 x MAX202 RS-23 communication chip (IC3) 1 x 7805 regulator (REG1/IC4) 3 x ULN2003A high current drivers (IC5,6,7) 4 x TC20-11SRWA 7x5 LED displays (DISP1-4) 7 x BC327 PNP transistors 3 x BC337 NPN transistors 24 Silicon Chip Capacitors 1x 470µF 25VW PC mounting electrolytic(C14) 1x 100µF 16VW PC mounting electrolytic (C15) 8 x 0.1µF polyester (C3, C7-C13) 2 x 39pF ceramic (C1, C2) Message Board Programming 1 length (as required) 3-conductor (or twin shielded) cable 1 x 3.5mm stereo phone plug 1 x 9-pin D plug (to suit computer serial port) Suitable PC terminal program ** Resistors (1%, 0.1W) 15 x 4.7kΩ (R1-R8, R12-R18) 3 x 1kΩ (R10,R19,R20) 8 x 22Ω (R21-R27) NOTES: * All of above semiconductor, resistor, capacitor and crystal lists must be doubled for maxi version, with exception of IC2, IC3, C7, C8, C10 & C11 – only one of each required. The tube, filter and tint film specifed are for the “maxi” version. Crystal 1 3.579545MHz Miscellaneous 7 lengths approx 150mm long very thin insulated hookup wire (for links in maxi version) 5 lengths approx 50mm long thin insulated hookup wire (for PC board to two sockets connections) 1 x plugpack supply, 12V DC <at> 500mA output Acrylic glue Foam plastic, bubble wrap, etc for packing #IC1 requires different code for each half of display. R11, C4-C6 are not included in either version nor is any position shown on PC board **Term90 software may be downloaded free of charge from www.siliconchip.com.au How the display fits in the tube: this photo and drawing should reveal all! The one thing we haven’t shown is how to put the window tinting film on the outside of the tube but this is fully explained in the text. The packing material behind the PC board stops any movement – it can be just about anything nonconductive. Foam rubber/plastic is ideal. PC BOARD LED DISPLAYS 58mm (ID) CLEAR ACRYLIC TUBE (notch to top) but don’t fit the PIC yet. You can also solder in the regulator; it lies flat down on the PC board with its legs bent down at 90°. Before commencing work on the opposite side of the board, check your soldering carefully. Remember most of your soldering will be covered by the displays so if you’ve made a dry or suspect solder joint or a bridge, now’s the time to discover it! We suggest you use a magnifying glass to inspect the whole of the boards thoroughly. PACKING MATERIAL POWER AND PROGRAMMING SOCKETS RED ACRYLIC FILTER the inside with nuts on the outside. If your sockets are the type which mount from the outside with the nut on the inside, you’ll need to unsolder the wires before final assembly. At this stage you don't need to connect the serial input but you can solder the wires on now if you wish. It’s best to use a black wire for the ground connection; please yourself which other colours you use. Now solder in just two of the LED Links The full or “maxi” version requires seven long links between the two (joined) boards using fine insulated hookup wire. Five are for data, two for power. Place these links on the LED display (ie opposite) side of the boards where shown before continuing. Testing If you’re satisfied with your workmanship, it’s time to put it to the test. The reason we do this now, before completion, is that it is very much harder later on, once all eight LED displays are in place and even harder once the message board is mounted inside its case. First, solder two wires (red and black are good choices) to the “PWR” inputs – 50mm is ample. Solder these to the DC socket, matching the polarity of the plugpack. Usually, plus (red) is the centre pin but don’t bank on it. If in doubt, check it with a multimeter first. By the way, it is preferable to use sockets which mount through from COMPONENTS The DC power socket (left) and the 3.5mm stereo “programming” socket (right). With 20/20 hindsight, we would have swapped these around... displays into each half of the board – say one in DISP1 position on the right board and one in DISP 4 position on the left board. Note that the soldering is (obviously!) done on the component side of the PC board. You may note that they can go in either way – but one way won’t work! The type number and other writing along one edge of the display is the bottom of the device. When you hold the PC board so that you can read the writing on it (eg, DISP4, DISP3 etc), the display is DARK WINDOW TINT inserted so that the writing on it goes to the bottom. Finally, insert the PICs into their sockets – again, check the polarity. It would be a real shame to see the most expensive component go up in a puff of smoke with that awful, acrid smell! Now connect the plugpack to the DC input socket and apply power. If all is well, you should see first of all the righthand display LEDs flashing and then shortly after the lefthand display LEDs should do likewise. You probably won’t be able to make out any meaningful message – just the LEDs flashing is a good sign. If the LEDs don’t flash, you’ll need to go hunting for the reason. It’s almost certain to be an incorrectly placed component or a bad solder joint. With components on both sides of the board, it’s difficult to remove anything to trouble-shoot. That’s why we suggested you examine the board with a magnifying glass before soldering in the displays. You could check that you get about 5.6V between the output of the 7805 and the negative supply. If you have an oscilloscope you could also check that the crystal is oscillating. Apart from that, the only other easy check to make is that the PIC microcontroller is not only inserted correctly but also that all its pins are actually in their respective holes (it’s easy to bend a pin out of position). Finishing off If you did get flashing LEDs, you can now insert and solder the rest of JULY 2000 25 Programming it: as easy as 2-1-3! We mentioned before that programming the Moving Message Display is one of its best features: it’s easy! You can use just about any dumb terminal program and communicate with the Message Board in 9600,8,N,1 format. Because we use Windows 2000 (which doesn’t include a suitable terminal program) we used a freeware program called Term90 which can operate in a DOS box under Windows anything. The following is a guide to using this program which can be downloaded free of charge from the SILICON CHIP website, www.siliconchip.com.au Install the software as normal under Windows 95, 98, NT or 2000. SETTING UP THE SIGN PROGRAMMING 1. Plug the data cable into serial port COM2 on your PC. The Menu displayed is as follows. To setup your message on the Moving Message Display, use the following commands: 2. Plug the stereo jack into the back of the Moving Message Display. 3. Plug the power connector into the back of the Moving Message Display and the power pack into the power point. DO NOT turn on the power at this stage. 4. Start the TERM90 terminal program. When it starts you will see a blank screen with some menus. DO NOT change any of these menus. 5. Now turn on the power to your Moving Message Display. The display should read “MINI DISPLAY” and you should see a MENU displayed on your computer screen. You are now ready to start programming your message. 1. 2. 3. 4. 5. 6. Type new message Delete existing message Program message Message scroll speed = FAST Message scroll speed = MEDIUM Message scroll speed = SLOW The CAPS LOCK key must be pressed to enable your text to be sent to the Moving Message Display 1. Press 2 to delete any existing message. 2. Press 1 and a sub menu will be displayed to enable you to type your message – in normal, BOLD or REVERSE text if required. Press CTRL+B to display the text following in BOLD (this will display a smiley face symbol). CTRL+R REVERSES the text following (this will display an up & down arrow symbol). Note – reversed text is much harder to read. CTRL+E ends the text enhancements. 3. Adjust the scroll speed by selecting option 4, 5 or 6 from the main menu. Type in your text and you will see this displayed in real time on the Moving Message Display. 4. DO NOT use the arrow keys to cursor up, down, left or right. This will corrupt the displayed text and you will have to start again. Use the backspace key to move over the text you want to change and retype your text. 5. After your message is complete press ESC; you will see a prompt MESSAGE ACCEPTED. Now press 3 to program the Moving Message Display. You will see a prompt MESSAGE PROGRAMMED. Press ESC to clear the screen and re-display the main menu. 6. If you want to change your message simply follow the steps under SETTING UP THE SIGN and then press 2 to delete your message and then follow the steps under Programming. 7. Finally select FILE, EXIT and OK to close the terminal program, unplug your data cable and place the Moving Message Display in the appropriate location. The TERM90 screen, run either under DOS or in a Windows DOS box. It’s as simple as 2-1-3: The top part of the screen comes on when you turn on the Moving Message Display. Pressing 2 deletes any existing message, pressing 1 readies the terminal for your new message. Pressing 3 programs the new message into the unit, where it will stay until deleted. 26 Silicon Chip A really nifty method of mounting . . . Just imagine the visual impact of this Moving Message Display apparently floating in space with no visible signs of support and or power wires… We’ve seen this done before by professional display companies – all it takes is two lengths of some very fine, black insulated wire (such as one of the four conductors from telephone cable). The wires not only support the unit, they provide the power connections. The idea is to wrap the wires tightly around the unit right the LED displays. It’s probably a good idea to carefully remove the PICs and store them back in their anti-static packaging before soldering. As you place each display, make sure the labels all go the same way – down! If you didn’t do it before, solder in the three serial input wires and connect them to their socket. Fig.2 shows the wiring for both the sockets. up close to the end caps, with the power connections made by running the wires along the back of the unit, following the edge of the tint film. You could even dispense with the DC socket and wire directly to the PC board. Done right, the wires are almost invisible. The opposite ends are secured to what ever you want to hang it from. The one thing to watch is that as both wires are black, you have to be careful with polarity. The result looks fantastic – especially if the room is just a little dark and the wires cannot easily be spotted. tube: it should be a reasonably snug, but not too tight, fit. Slide it all out again, taking care not to scratch the acrylic. You will need to cut or pierce the tinting film with a very sharp knife or scalpel to give access to the two holes you drilled before. Be careful – it’s easy to damage the film. Now slide the assembled PC 3.5mm STEREO PLIUG 5 1 5 2 3 6 DB-9 FEMALE CONNECTOR (SOLDER SIDE) 9 Finally, carefully re-insert the PIC chips and the electronics side is complete. Now when you connect power you should see the complete message which is programmed into the new PIC chip: “MINI DISPLAY”. If you get this message, it’s a fair bet that your unit is working properly and ready to program. You might like to skip to the “programming” section and type in a message just to make sure! You may have noticed that there are quite a number of apparently empty holes on the finished board. These are not component holes as such, but “vias” or plated-throughholes which connect the tracks together where required on opposite sides of the board. Providing you have components wherever shown on the component overlay (fig.2), you’re ready to get your display up and running. Final Assembly First step is to make sure it all fits! Slide the whole shebang into the inside and fit the appropriate nuts. We mentioned before that some DC power sockets mount from the outside with the nut on the inside. If yours is one of these (as will be supplied in the kit), you will need to unsolder the wires, mount the socket and then very carefully resolder, taking care not to get the iron too close to the acrylic. It melts! RING BODY TIP Here's how to make up the programming cable to operate from the serial port on your PC. The length can be as long as you like (within reason!). This cable is shown in the photo on page 19. board(s) into the tube, wires and connectors end first, about three quarters into the tube. The assembly goes on the side of the red acrylic closest to the drilled holes. Before sliding all the way in, push the two sockets (3.5mm and DC power) through their holes from the Where do you get it? The Moving Message Display was designed by 4D Systems Pty Ltd, who hold copyright on the design and on the program residing in the PICs. A complete kit of parts is available from 4D Systems for $189 (including GST) plus pack and post. Contact 4D Systems at Suite 2, 3-5 Station Road, Auburn NSW 2144. Phone (02) 9649 5065; fax (02) 9649 4324 Email: sales<at>4dsystems.com. au Web Site: www.4dsystems. com.au * Atilla Aknar is Managing Director of 4D Systems Pty Ltd. (While we mounted our 3.5mm socket closest to the outside edge of the tube, it may be better to swap the two sockets around and mount the DC socket closest to the edge to make soldering easier). The assembled PC board is a reasonably good fit inside the case but it was able to move. We didn’t want this, so we pushed some scraps of foam rubber in behind the board (ie, component side) to stop it rattling. You might need to do similar. Before gluing on the two end caps, connect power and check that everything still works. If so, a couple of dobs of acrylic glue on the end caps will secure them in place. And that’s just about all there is to it. By now, you’re starting to agree with us that the Moving Message Display is the equal of any commercial unit – and you’ve saved money building it. Now, what are you going to tell the world about with your new Moving Message Display? SC JULY 2000 27 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.rockby.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.rockby.com.au Compact Fluorescent Lamp Driver Although our photo shows a single CFL in a loose bayonet fitting, the unit is designed to be wired as a permanent installation with fixed bayonet sockets. Compact fluorescent lamps (CFLs) are far more efficient than their incandescent counterparts. This inverter circuit is ideal for driving 240VAC CFLs from a 12V battery, up to a total load of about 40W. It can be used anywhere you require good lighting when there is no mains power, or as part of a solar-powered lighting system. By JOHN CLARKE O BTAINING GOOD LIGHTING from battery power has never been easy unless fluorescent lamps are used. This is because fluorescent lamps produce far more light output than incandescent lamps for a given power input. In practice, this means that you can burn your lights for longer before the battery goes flat – up to five or six times longer, in fact! This “Compact Fluorescent Driver” is built into a sturdy metal case and is specifically designed to drive 30 Silicon Chip CFLs. It delivers a 240V (340V peak) waveform that’s approximately sinusoidal in shape, which means that it’s capable of driving CFLs with a high power factor, as well as earlier designs with low power factor. Note that, in general, this circuit is not designed to power other mains-operated equipment. Background Fluorescent lighting which operates from 12VDC is not new and there are many commercial 12V fluorescent lights available which use the “long-tube” style of lamp. Of course, the tube itself doesn’t operate from 12VDC but rather via a DC-DC converter circuit built into the fitting. In fact, SILICON CHIP published a high-efficiency inverter for 18W and 36W fluorescent tubes in the November 1993 issue and this was designed to fit inside the lamp batten. Because of their large size and light dispersion characteristics, this type of lamp is mainly used for mounting on the ceiling of a caravan or for emergency lighting. However, they are somewhat less than ideal for camping or outdoor use because of their bulk and rather awkward shape. Compact fluorescent lamps on the other hand provide lighting similar to a gas-powered camping lantern and are ideal for mounting on a picnic table, on the ground or even in a caravan ceiling. They will fit into standard mains-style bayonet or Edison screw (ES) fittings and consequently are easy to replace. They are typically rated at 9-25W which means that you can run up to four lamps using this circuit, depending on their rating. Physically, a CFL consists of a small folded fluorescent lamp attached to a base which contains the driver (inverter) circuit. The internal driver circuit for the tube is basically an “electronic ballast”. This typically produces a high-frequency drive waveform and includes inbuilt current limiting for the tube. The high frequency prevents flicker and also improves the light output. What this all means is that the CFL’s internal driver circuit assumes that it will be supplied with a 50Hz sinewave at 240VAC, which is close to 340V peak. Any or all of these features of the supply may be used by the electronic ballast to drive the fluorescent tube. Any external circuit which drives the CFL from a different supply (such as 12VDC) must take these requirements into consideration. Fig.1: a typical power supply circuit as used in many older compact fluorescent lamps. Its main disadvantage is the fact that it draws current over only a small part of each mains cycle. Note that the tube is powered from 340V DC. Fig.2: this circuit is used in the newer CFLs and offers a much improved power factor compared to the circuit shown in Fig.1. The tube is no longer powered from 340V DC but from the full-wave rectified mains waveform. Basic circuits Fig.1 shows a typical power supply circuit as used for some CFL electronic ballasts. It uses a low value resistor in series with a full-wave bridge rectifier. Filter capacitor C1 charges up to the peak voltage of the 240VAC waveform to give a 340VDC supply which is then applied to the electronic ballast circuit. The ballast circuit in turn drives the fluorescent tube. Based on this power supply, you would expect that CFLs can also be driven from a 340VDC supply. After all, if 340VDC is applied to the Active (A) and Neutral (N) terminals, the voltage across C1 would still be 340VDC (neglecting the voltage drops across the diodes in the bridge rectifier) and the electronic ballast would be none the wiser. This may be true for those CFLs that use this particular power supply but not for all CFLs. Some CFLs derive their supply in a different manner and cannot be directly powered from 340V DC, as we shall see. Power factor correction A big disadvantage of the circuit shown in Fig.1 is that it only draws current from the 240VAC mains near the crest of the waveform, where the voltage is at or near its peak of about 340V. This occurs because capacitor C1 is topped up to the peak mains voltage and the rectifier diodes do not conduct below this peak voltage. So this is a rather crude supply because current is only drawn for a brief interval during each mains half-cycle. What’s more, the current pulses will be quite high in value. This leads to poor power utilisation and results in considerable power losses, which reduces the efficiency. A better approach is to use a circuit that draws current over the greater WARNING! The output voltage produced by this CFL Driver circuit is potentially lethal! Do not build it unless you are experienced and know what you are doing. In particular, make sure that you do not touch the output leads and check that they are securely connected to an approved mains lighting socket in a fixed installation before connecting 12V DC power. Treat these wires as though they are at mains potential. Finally, be sure to keep your hands away from the PC board components associated with the output terminals, diodes D7-D10 and the 470kΩ and 1MΩ resistors in the feedback path. part of the waveform and this is what CFL designers are now beginning to do. The newer electronic ballasts effectively draw current over most of the mains waveform, thus reducing the peak current and also improving the power factor. This also creates less of a problem for the supply utilities. By the way, the term “power factor” in this case refers to the extent to which the sinusoidal mains waveform is utilised. A low power factor of around 0.5 means that current is only drawn over a part of the mains waveform while a high power factor (greater than 0.95) means that the waveform is almost fully utilised. Fig.2 shows how these “improved” electronic ballasts derive their supply from the mains to improve the power factor. The circuit looks similar to Fig.1, with C1 charging to 340VDC as before. However, there is a major difference and that is that the fluorescent tube is no longer simply powered from 340VDC but from the full-wave rectified mains waveform. The supply for the electronic ballast is still derived from the 340VDC across C1 but this is now isolated from the rectifier output using diode D1. An LC filter on the mains input prevents the high-frequency switching noise produced by the electronic ballast from being fed back into the mains supply. JULY 2000 31 Fig.3 (left): this scope shot shows the mains waveform, along with the current waveform for a non-power factor corrected CFL. Note that the current waveform is quite “peaky”. The flattening at the top of the mains waveform is not caused by the circuit but is present in many industrial areas due to switchmode power supplies in PCs and gas discharge lighting. Fig.4 at right shows the mains wave-form and the corresponding current waveform from a power factor corrected CFL. Note how the current is far less “peaky” than before. Using this circuit, the current drawn by the fluorescent tube is much more sinusoidal in shape compared to that from Fig.1 (see Figs.3 & 4). The peak current is substantial ly reduced and the current peak lasts much longer. By the way, you might expect that this circuit would produce a flickering effect similar to that produced by standard fluorescent long-tube lamps which are driven from the mains. This is because the current through the lamp is varying at a 100Hz rate. In fact, the light output is modulated by a small amount but the effect is not noticeable due to the use of longpersistence phosphors and because the tube is driven at a high frequency by the electronic ballast. Now for the million-dollar question: What would happen if we were to drive a CFL which uses the circuit of Fig.2 from a 340VDC supply? Well, initially, not much. The fluor escent tube would be quite bright but would otherwise appear to be operating correctly. In practice, however, it would be severely over-driven. That’s because it is being driven from 340VDC rather than a 340V peak fullwave rectified waveform which has a DC equivalent (RMS) of 240V. As a result, the life expectancy of the CFL would be severely compromised. 32 Silicon Chip So how do we produce a circuit which will comfortably drive all types of CFLs? The obvious answer is to use a sinewave inverter which produces a 50Hz 240VAC waveform. In this way, all CFLs would be powered correctly. However, this type of inverter is fairly complicated and requires a fair number of power devices to produce a clean 240V sinewave. Fortunately, a pure sinewave inverter is overkill and we don’t need to do this. The alternative approach is to take into account the fact that CFLs actually fullwave rectify the mains waveform before doing anything else. If we use an inverter that provides a fullwave rectified sinewave output rather than a genuine sinewave, the CFL circuit would be none the wiser. And that’s just what we have done here. Of course, only two diodes in the CFL’s fullwave bridge rectifier are now used, since we now have a pulsating DC supply rather than AC, but this is of no consequence. Block diagram Fig.5 shows the general arrangement of our CFL driver circuit. It’s powered from a 12V battery which supplies a switchmode controller IC, the push-pull outputs of the controller in turn driving transformer T1 via buffer stages and Mosfets Q1 & Q2. In operation, the Mosfets switch the primary windings of transformer T1 in an alternate fashion at a high frequency and the resulting waveform is stepped up to a higher voltage in the secondary winding. The secondary output of T1 is then full-wave rectified and filtered to produce pulsating DC with a peak voltage of about 340V. The exact voltage at the output is controlled via the feedback from the A+ terminal to the switchmode controller, in this case via a “half sinewave shaper” circuit. In a conventional switchmode circuit, this feedback is simply a voltage divider which is set to provide the required DC output voltage. It adjusts the pulse width applied to the transformer so that the output voltage is maintained regardless of variations in load current or input voltage. In this circuit, however, we have to produce a half sinew ave shape. This is done by rapidly switching in different voltage divider resistors in sequence to simulate the half sinewave shape. This job is performed by the “shaper” circuit. Circuit details Refer now to Fig.6 for the final circuit details. It uses just six lowcost ICs, two Mosfets, a transformer and a handful of transistors, diodes, resistors and capacitors. At the heart of the circuit is a TL494 pulse width modulation (PWM) controller (IC1). It contains a sawtooth oscillator, two error amplifiers and a PWM comparator. Also crammed onto the chip are a “dead-time” control comparator, a 5V reference and output control options for push-pull or single-ended operation. The RC oscillator components at pins 5 & 6 set the operating frequency to about 50kHz. The PWM outputs from the error amplifiers appear at pins 9 & 10 (E1 & E2) and drive paralleled buffer stages IC2d-IC2f and IC2a-IC2c respectively. In turn, these drive Mosfets Q1 & Q2. Q1 & Q2 drive the centre-tapped primary winding of transformer T1 in push-pull mode; ie, when Q1 is on, Q2 is off and vice versa. As shown, the centre tap of the transformer connects to the +12V rail, while each side of the primary winding is connected to the drain of its corresponding Mosfet. When Q1 is on, 12V is applied across the top half of the primary winding. Because of transformer action, the lower half of the primary winding also has 12V impressed across it which means that Q2’s drain is at 24V. Similarly, when Q2 is on, the bottom of the transformer primary goes to 0V and the top goes to 24V. The resulting 24V peak-to-peak waveform on the primary is then stepped up by the secondary winding. High speed diodes D7-D10 rectify the resulting AC output from the secondary and this is then filtered using two paralleled 0.1µF 250VAC capacitors. Note that Mosfets Q1 & Q2 are protected from over-voltage excursions on the drains using 16V zener diodes ZD1 & ZD2, togeth er with series diodes D1 & D2. The series diodes prevent each of the zener diodes from conducting when its associated Mosfet is switched on. In addition, any reverse voltages that would otherwise be applied to Parts List 1 PC board, code 11107001, 143 x 112mm (302 holes) 1 diecast box, 171 x 121 x 55mm 1 front-panel label, 167 x 117mm 1 M205 fuseholder 1 M205 5A fuse 1 25-28mm diameter iron powdered toroid (L1) (Jaycar LO-1244 or similar) 1 E30 transformer assembly (T1) 1 SPDT 10A toggle switch with integral LED and resistor (S1) 2 M3 x 10mm screws 2 M3 nuts 2 M3 flat washers 1 M4 sized solder lug 2 transistor insulating bushes 2 TO-220 silicone insulating washers 2 cordgrip grommets 3 100mm cable ties 1 200mm cable tie to secure ferrite cores on T1 1 2m length of heavy duty automotive figure-8 wire 1 2m length of 240VAC 7.5A figure-8 wire 1 12m length of 0.25mm ENCU wire 1 1200mm length of 1mm ENCU wire 1 500mm length of 0.8mm tinned copper wire 4 PC stakes Semiconductors 1 TL494 switchmode controller (IC1) 1 4050 hex buffer (IC2) 1 7555, LMC555CN, TLC555, CMOS timer (IC3) 1 4029 4-bit counter (IC4) 2 4051 8-channel analog multiplexers (IC5, IC6) 2 MTP3055 60V Mosfets (Q1, Q2) 2 BC547 NPN transistors (Q3, Q4) 2 16V 1W zener diodes (ZD1, ZD2) 5 1N914, 1N4148 diodes (D1-D4, D6) 1 1N4004 1A diode (D5) 4 1N4936 500V high-speed diodes (D7-D10) Capacitors 2 4700µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 2 0.1µF 250VAC MKT X-Class 5 0.1µF MKT polyester 1 .039µF MKT polyester 1 .001µF MKT polyester 1 560pF ceramic 2 220pF ceramic Resistors (0.25W, 1%) 2 1MΩ 1 12kΩ 1 470kΩ 4 10kΩ 1 270kΩ 2 4.7kΩ 1 75kΩ 1 3.3kΩ 1 47kΩ 1 3kΩ 1 33kΩ 2 2.2kΩ 1 27kΩ 2 1kΩ 1 24kΩ 1 470Ω 4 22kΩ 2 10Ω Miscellaneous CFLs, bayonet or ES lamp holders. Fig.5: the CFL Driver uses a switchmode controller to drive Mosfets Q1 & Q2. These in turn drive centre-tapped transformer T1 which steps up the voltage across the primary. The transformer output is then rectified and fed to the CFL. The half sinewave shaper circuit in the feedback path ensures that the output waveform approximates a sinewave. JULY 2000 33 MAIN FEATURES • • • • • • Suitable for driving compact fluorescent lamps (CFLs). Can drive loads up to 40W for CFLs with a power factor of 0.95. Can drive loads up to 33W for CFLs with a low power factor. Output voltage (and thus lamp brilliance) remains constant for 11-14.4V DC input. Reverse polarity protection. Built-in electric shock protection between high voltage output and battery terminals. the gates of Q1 & Q2 due to capacitive effects are shunted to ground via diodes D3 & D4. Feedback The feedback signal for the PWM controller (IC1) is derived from the high-voltage output at the A+ terminal. This is sampled using a voltage divider consisting of series 470kΩ and 1MΩ resistors and a resistance value switched in by the 16-step half sinewave shaper circuit. The resulting feedback signal is then applied to the pin 16 input of IC1. Pin 16 is the non-inverting input of one of the internal error amplifiers in IC1. A 1MΩ feedback resistor between pins 3 & 15 and the 4.7kΩ resistor between pins 3 and 14 (VREF = 5V) sets the gain of this error amplifier to 213. Also included in the negative feedback loop is a 1kΩ resistor and series 0.1µF capacitor and these set the low frequency rolloff for the error amplifier. In operation, IC1 continually adjusts the pulse width drive to the Mosfets so that the voltage on pin 16 is maintained at 5V. The duty cycle and thus the output voltage on the A+ terminal at any instant depends on the resistor values switched in by the sinewave shaper circuit to form the bottom leg of the voltage divider in the feedback path. For example, if a 22kΩ resistor is switched in, the ratio is 22kΩ divided by (470kΩ + 1MΩ + 22kΩ), or .0147. As a result, the A+ output will be at 5V/.0147 = 340V. Lower output voltages are selected by switching in higher value resistors. Half-sinewave generator In operation, the shaper circuit sequentially switches in various resistor values to give an approximate half 34 Silicon Chip sinewave at the A+ output. IC3, IC4, IC5 & IC6 make up the shaper circuit. IC3 is a CMOS 7555 timer which produces a 1.6kHz square wave at its pin 3 output, as set by the RC timing components on pins 2 & 6. This signal is applied to the clock input of IC4, a 4029B 4-bit counter, via a 2.2kΩ resistor. This resistor and its associated 220pF capacitor increase the risetime of the pin 3 output of IC3 to suit the operation of the counter. The Q1-Q2 outputs of IC4 are applied to the A, B & C inputs respectively of both IC5 & IC6. These ICs are basically single-pole 8-way switches, with the position of the switch selected by the count value on the A, B & C inputs. As IC4 counts up from 0 to 7, the Y0-Y7 outputs of IC5 & IC6 are each selected in succession and so different resistor values are sequentially connected to the common terminal at pin 3 (and thus to pin 16 of IC1). As a result, the divider ratio is constantly being altered and this means that the feedback voltage also alters each time a different resistor is selected. As shown on Fig.6, the Y0-Y7 outputs of IC5 and IC6 are connected together in reverse order; ie, Y0 of IC5 goes to Y7 of IC6, Y1 goes to Y6, Y2 goes to Y5 and so on. The reason for this is that we use IC5 to progressively select lower-value resistors (starting at 270kΩ) for the rising part of the output waveform and then use IC6 to select the resistors in reverse order for the falling part of the waveform. In this way, IC5 and IC6 use the same set of resistors. They just use them in reverse order to each other! The Q3 output from IC4 is used to decide whether IC5 or IC6 is selected. This output connects directly to the inhibit input (INH, pin 6) of IC5 and also drives transistor Q3 via a 10kΩ resistor. Transistor Q3 functions as an inverter and controls the inhibit input of IC6. In practice, the inhibit input must be low for the IC to be selected. As a result, IC5 is selected while IC4 counts from 0-8, while IC6 is selected for the 8-16 count, after which the cycle repeats. Dead-time So how do we stop the circuit from producing glitches in the output each time IC5 or IC6 selects a different voltage divider resistor? The answer to this is transistor Q4 which is connected between the dead-time (DT) input of IC1 (pin 4) and the VREF terminal (pin 14). This transistor is driven by the pin 3 output of IC3 via a 3.3kΩ resistor and a 220pF capacitor. Each time pin 3 goes high, Q4’s base goes high for about 2µs (as set by the 22kΩ resistor to ground) and so Q4 briefly turns on and connects the DT input to +5V (ie, to VREF). This effectively shuts the PWM controller down for 2µs on each clock pulse, which is ample time for IC5 or IC6 to select the next resistor value. When Q4 switches off at the end of the 2µs period, a 4.7kΩ resistor pulls the DT input low and the PWM controller begins operating again. High voltage protection The high voltage output at the A+ terminal is potentially lethal since it produces 240V RMS and can provide well over 150mA of current. For this reason, it is important that you don’t simultaneously come into contact with the A+ and N terminals. Any contact between a battery terminal and the N terminal will not cause a shock since the N terminal is tied to ground. However, the A+ terminal could cause an electric shock if you connect yourself between it and a battery terminal. As a safeguard, we have added a leakage-to-ground detector circuit Fig.6 (right): the final circuit uses IC1 to drive Mosfets Q1 & Q2 via parallel buffer stages . IC3-IC6 form the half sinewave shaper circuit. It constantly changes the feedback so that IC1 varies its PWM output to produce a half sinewave shape. JULY 2000 35 Fig.7: install the parts on the PC board and complete the wiring as shown here. Fig.8: this diagram shows the mounting details for Mosfets Q1 & Q2. Use your multi-meter to check that the device tabs are correctly isolated from the case. 36 Silicon Chip which will switch off the PWM controller if the current between the A+ terminal and one of the battery terminals exceeds 224µA. Let’s see how this circuit works. As shown, the N terminal is tied to ground via a 1kΩ resistor and a parallel 0.1µF capacitor which is used as a filter. Normally, this terminal will be at ground unless there is leakage between the A+ terminal and ground (or battery +). If there is leakage, the voltage across the 1kΩ resistor rises by 100mV for every 100µA of leakage current. This voltage is monitored by the pin 1 input of IC1 which is the non-inverting input to the second error amplifier. The inverting input at pin 2 is connected to a voltage divider across the 5V reference and sits at 224mV. If the voltage at pin 1 reaches this 224mV limit, the PWM controller shuts down the high voltage step-up operation and limits the current to 224µA. Power Power for the circuit is derived from a 12V DC source (eg, a battery). This is applied to the ICs via reverse-polarity protection diode D5 and to the centre tap of transformer T1 via inductor L1. Two 4700µF capacitors decouple the supply for the transformer and are bypassed with a 0.1µF capacitor. Reverse polarity protection for the Mosfets is provided by fuse F1. If the supply is connected the wrong way around, the internal drain-source protection diodes in the Mosfets conduct heavily and the fuse blows before any damage occurs. Building it The CFL Driver circuit is built on a PC board coded 11107001 and measuring 143 x 112mm. This fits inside a The PC board fits neatly into a standard metal diecast case which also serves as a heatsink for Q1 and Q2. Be sure to use 240VAC-rated cable for the output lead and make sure that this has been correctly terminated before applying power. standard diecast case measuring 171 x 121 x 55mm. Alternatively, the PC board could be fitted into a plastic case with 6021-type flag heatsinks (29.5 x 25 x 12.5mm) used for each Mosfet. The PC board includes solder mounting points for these heatsinks if the diecast case is not used. Begin construction by checking the PC board for shorts between tracks and for any breaks in the copper pattern. Also, check to ensure that the hole sizes are correct. You will need 1mm holes for the transformer pins, diode D5 and the zener diodes. Next, check that the PC board fits neatly into the case. The PC pattern (Fig.11) shows the profile required. In particular, the half-moon “cutouts” (to clear the central mounting posts) and the small rectangular cutouts (to clear internal ribs) may need filing to shape so that the board fits. It is also necessary to round the corners of the board as shown, to clear the corner posts of the case. Fig.7 shows the wiring details. Begin the PC board assembly by installing the links and resistors. Table 2 shows the resistor colour codes but you should also use a digital multimeter to check each value, just to be sure. The ICs can be mounted next, taking care with their orientation. Make sure also that each IC is placed in its correct position. Now for the capacitors. The electrolytic types are polarised and must be oriented with the polarity shown. The MKT and ceramic types usually include a value code and these can be deciphered using Table 1. Table 1: Capacitor Codes       Value IEC code EIA code 0.1µF 100n 104 .039µF 39n 393 .001µF 1n0 102 560pF 560p 561 220pF 220p 221 Fig.9: here are the winding details for transformer T1. The secondary is wound on first, with each successive layer covered with insulating tape. The primary is then bifilar wound (ie, two wires at once) over the secondary. JULY 2000 37 What’s Inside A Compact Fluorescent Lamp? While CFLs are a throw away item once the fluorescent tube has burnt out, they have relatively complex circuit, as shown in the photo and Fig.10. This is a typical circuit for an electronic ballast without the power supply (ie, rectifier diodes, filter capacitor, etc). The circuit operates in two separate modes, one to start the tube and the second mode for normal running. There are two Mosfets (Q1 & Q2), transformer T1 and a number of associated components which make up an oscillator. The fluorescent tube is driven via inductor L1 and winding N1 of the transformer. T1 also drives the gates of Q1 & Q2 via windings N2 & N3 which are connected in antiphase. Tube starting When power is first applied, the .022µF capacitor connected to Diac 1 charges via the 560kΩ resistor. When the voltage reaches about 30V, the Diac fires (breaks down) and discharges the capacitor voltage into the gate of Q2. Zener diode ZD2 protects the gate from over-voltage. Mosfet Q2 is now switched on and current flows from the positive supply via the .047µF capacitor, the fluorescent tube top filament, the .0033µF capacitor, the second tube filament, inductor L1 and transformer T1’s N1 winding. This current flow in N1 then applies gate drive to Q1 via N2 and switches off gate drive to Q2 via N3 due to the antiphase connection of this winding. If oscillation doesn’t occur, the process starts all over again with the .022µF capacitor charging again to fire the Diac to turn on Q2. When oscillation does occur, Mosfets Q1 and Q2 rapidly switch on and off in alternate fashion. The frequency of operation is set by the combined inductance of L1 and the N1 winding, together with the .0033µF capacitor across the tube. The startup circuit comprising the .022µF capacitor and the Diac is now prevented from operating by diode D1. This diode discharges the 38 Silicon Chip Fig.10: typical circuit for a CFL electronic ballast, minus the power supply components. It’s basically an oscillator circuit that operates in two different modes – one for starting and the other for normal running. .022µF capacitor every time Q2 is switched on. The oscillator current now flows through the filaments of the fluorescent tube and allows the normal mercury discharge to take place. This means that the fluorescent tube will light up. When this happens, the .0033µF capacitor is effectively shunted by the mercury discharge and the voltage across the tube is now at about 100V peak. Normal running The frequency of oscillation is now determined by the properties of the core used for transformer T1. As the current builds up in winding N1, the core begins to saturate. When this happens, the flux in the core stops changing and gate drive to Q1 or Q2 ceases. The flux now collapses to drive the opposite Mosfet and this process continues to maintain oscillation. The current through the tube is limited by the current at which T1’s core saturates and by L1’s inductance. The two 10Ω resistors, together with zener diodes ZD1 & ZD2, limit the gate drive to Q1 & Q2, while the .0022µF capacitor at the cathode of D1 forms a snubber network to suppress commutation in the opposing Mosfet at switch on. This considerably reduces the switching losses in each Mos fet. The 330kΩ resistor in parallel with this capacitor keeps diode D1 reverse biased at start-up. Finally, the .047µF capacitor in series with one of the tube filaments ensures that the tube is driven by AC. This prevents mercury migration to the tube ends which would cause black ening and shorten the tube life. The diodes, zener diodes and transistors can now all be installed, followed by Mosfets Q1 & Q2. The latter should be mounted at full lead length, with only 1-2mm of each pin protruding below the PC board to allow for soldering. This enables their metal tabs to be bolted to the side of the case later on. Inductor L1 can now be wound and installed. It comprises a 25-28mm iron powdered toroid with 20 turns of 1mm enamelled copper wire wound around it. The wiring diagram and photographs show how it is wound. Keep each turn tight around the toroid and space the windings evenly. Clean and tin the ends of the winding before mounting it on the PC board. After mounting, the toroid is secured using two plastic cable ties which are fed through adjacent holes in the PC board. Winding the transformer Fig.9 shows the winding details for transformer T1. Begin by soldering one end of a 12-metre length of 0.25mm enamelled copper wire to pin 4, then wind the turns on neatly side-by-side. Wrap a layer of insulating tape around each layer as it is completed before winding on the next layer. After completing 200 turns, terminate the wire at pin 7 and secure the windings with another layer of insulating tape. The centre-tapped primary wind ings are wound together (ie, bifilar) Fig.11: check your PC board against this full-size etching pattern before mounting any of the parts. Table 2: Resistor Colour Codes  No.  2  1  1  1  1  1  1  1  4  1  4  2  1  1  2  2  1  2 Value 1MΩ 470kΩ 270kΩ 75kΩ 47kΩ 33kΩ 27kΩ 24kΩ 22kΩ 12kΩ 10kΩ 4.7kΩ 3.3kΩ 3kΩ 2.2kΩ 1kΩ 470Ω 10Ω 4-Band Code (1%) brown black green brown yellow violet yellow brown red violet yellow brown violet green orange brown yellow violet orange brown orange orange orange brown red violet orange brown red yellow orange brown red red orange brown brown red orange brown brown black orange brown yellow violet red brown orange orange red brown orange black red brown red red red brown brown black red brown yellow violet brown brown brown black black brown 5-Band Code (1%) brown black black yellow brown yellow violet black orange brown red violet black orange brown violet green black red brown yellow violet black red brown orange orange black red brown red violet black red brown red yellow black red brown red red black red brown brown red black red brown brown black black red brown yellow violet black brown brown orange orange black brown brown orange black black brown brown red red black brown brown brown black black brown brown yellow violet black black brown brown black black gold brown JULY 2000 39 Fig.12: this is the front panel, reproduced here two-thirds actual size. A full-size reproduction can be obtained by scanning it at 150% on a flatbed scanner or by enlarging it on a photostat machine. using 1mm enamelled copper wire terminated on pins 1 & 2 and finishing on pins 10 and 9 respectively, as shown. Make sure that there are 6-turns for each winding. Finish with a layer of insulating tape. The transformer can now be completed by inserting each core half of the transformer into the bobbin and clamping them with clips or a 200mm cable tie. This done, the transformer can be mounted on the PC board with pin 1 orientated as shown on Fig.7. Finally, complete the board assembly by installing four PC stakes at the supply input and A+ and N terminals. Final assembly Now for the final assembly. First, temporarily fit the PC board into the case and mark out the mounting holes for Mosfets Q1 & Q2. This done, remove the board and drill the holes for these, taking care to remove any metal swarf with an oversize drill. You also need to drill holes in the case ends for the input and output cordgrip grommets and for the fuse holder. A hole is also required in the lid for the power switch. The on/off switch mounts on the case lid, adjacent to the 12V DC supply cable and the fuse. An integral LED acts as a power on/off indicator. 40 Silicon Chip Once all the holes have been drilled, secure the PC board to the corner pillars of the case using the supplied screws. Note that a solder lug must be placed under one of these screws – this solders to an adjacent PC stake and is used to earth the negative supply rail to the case (see Fig.7). The two Mosfets can now be bolted to the side of the case. First, check that the mounting areas are perfectly smooth and free of metal swarf, then mount each device using a TO-220 insu lating kit as shown in Fig.8. After each device is mounted, use a multimeter to check that its metal tab is electrically isolated from the case. If the meter indicates a short, the device will have to be removed and the cause of the problem determined. Finally, wire up the connections to the fuse, switch and PC board as shown using automotive wire for the 12V side and 240VAC rated cable for the output. This 240VAC output cable can then be connected into one or more bayonet or ES lamp holders. Make sure that the output cable is actually connected to a socket, since the wires should be treated as you would any mains outlet. The voltage produced could prove fatal if you are careless enough to connect yourself across the output leads while the unit is running. Testing Before doing anything, check that the output leads have been correctly terminated. This done, connect a 12V DC supply (rated at 1A or more) and check that the switch LED lights when the switch is “on”. If the LED doesn’t light, check that you have installed the 5A fuse in the fuseholder. Now check the supply rails to the ICs. There should be 11.5V on pin 12 of IC1, pin 1 of IC2, pin 8 of IC3 and pin 16 of IC4, IC5 & IC6. Next, carefully check the output voltage across the PC stakes on the board, using a multimeter set to measure up to 340V DC. Assuming no load is connected, the meter should indicate a value close to 340V DC (not 240V) due to the storage effect of the capacitors across the output. For the final test, you will need a 12V lead-acid battery capable of supplying several amps. Plug in a load such as a 15W 240V filament lamp or CFL and check that the output voltage SC is now around 240V DC. Vamtest Pty Ltd trading as MicroGram Computers ABN 60 003 062 100 If you’re a Muso, it’s pounds to peanuts that you have a collection of leads which need testing on a regular basis. This is a bit of chore if you use a multimeter but it’s a snap with this handy Musicians’ Lead Tester. By JOHN CLARKE EL Cheapo Musicians' Lead Tester L ET’S FACE IT, the various audio leads owned by musos do not have an easy life. Microphone and guitar leads are often damaged in transit from one gig to another or while setting up. They can become intermittent and cause nasty crackling noises in the sound or heavily attenuate the signal level due to shorts or breaks in the cable itself or in the connectors. Yes, you can check leads using a multimeter; probing each terminal to measure continuity from one end to another and to check for possible shorts. But you only have to do it a few times to know that the results are usually not very reliable. This is because you are never sure whether the multimeter probe has made good contact or if it has shorted to an adjacent pin or to the shell of the plug. There has to be an easier way. Of course, commercial cable testers are available. They usually comprise an XLR (eXtension Line Return) panel plug and panel socket plus 6.35mm jack sockets in a small box. You just plug the lead into the relevant sockets, then an array of LEDs and pushbuttons allow the cable to be tested. They check for shorts and correct intercon42 Silicon Chip nections and give you the result. Some even tell where the break or short is in the lead. Such testers are not cheap. But our Musicians’ Lead Tester is cheap. It should only take a couple of hours to build and will save many hours of frustration with leads. It indicates shorts, open circuits and how the lead is connected. You can even wobble the lead under test to verify an intermittent connection. And guess what? It is so cheap that it does not have a PC board and only a few components. Sadly, it won’t tell you where the fault is in a bad cable but what do you want? A cheap tester or an expensive one? This one’s cheap. The tester comprises an XLR panel socket connected in parallel with a stereo 6.35mm panel jack socket and an XLR panel socket plug connected in parallel with a stereo 6.35mm panel jack socket. This will allow testing of cables with XLR plug to XLR socket, XLR plug to jack plug, XLR socket to jack plug and jack to jack termina- Parts List 1 plastic Jiffy box 158 x 95 x 53mm, or sealed ABS box 115 x 90 x 55mm 1 front panel label 1 metal shell XLR panel socket 1 metal shell XLR panel plug 2 stereo 6.35mm panel mount jack sockets 1 single pole 12-position or 3-pole 4-position rotary switch (S1) 1 knob to suit S1 1 momentary pushbutton switch (S2) 4 5mm high-brightness red LEDs (LED1-LED4) 4 5mm LED bezels 4 1N4004 1A diodes (D1-D4) 4 1kΩ 0.25W resistors 1 9V battery 1 9V battery clip 4 M3 x 10mm screws and nuts 1 200mm length of green hookup wire 1 200mm length of red hookup wire 1 200mm length of black hookup wire 1 200mm length of blue hookup wire 1 100mm length of 0.8mm tinned copper wire incorrect LED will light compared to the switch selection. Jack plug test Fig.1: the circuit uses an XLR plug and socket pair, two jack sockets, two switches and a number of LED indicators. tions. Mono or stereo jack plugs are catered for. The circuit comprises four LEDs which are used to test the four possible connections in an XLR lead. These are the shell (case) connection, the pin 1 earth (shield) and pins 2 & 3 signal leads. The ground for the 6.35mm jack socket connects to pin 1, the tip to pin 3 and the ring to pin 2. A rotary switch (S1) selects each of the four connections in turn and the LEDs light according to the connection made. The circuit is powered via a single 9V battery and there is a 1kΩ current limiting resistor for each LED. A battery test switch (S2) lights the four LEDs. XLR to XLR test In a good XLR-XLR lead, there will be continuity between pin 1 on the socket and pin 1 on the plug and so LED2 will light up when switch S1 is in position 2. Similarly, a good pin 2 connection on the XLR lead will allow LED4 to light when S1 is in position 3. LED3 will light when S1 is in position 4. LED1 may or may not light depending on whether the shell is connected. If the shell is connected to the pin 1 shield, then both LED1 and LED2 will light in positions 1 and 2 of switch S1. Note that it is wise for microphone leads to have the plug and socket shells connected to pin 1 to ensure effective shielding. However, some XLR leads may not have the shell connected, to prevent hum loops when connecting from an earthed instrument to an amplifier which has XLR inputs. A faulty lead will show some difference from the above LED conditions. Shorts between pins will light up more than one LED for selections of S1 and breaks will not light up any LED. Transposed leads will be shown as the Jack to XLR lead tests are trickier since there are many variants in the wiring for these. For a standard XLR to stereo jack lead, LEDs 1, 2 & 4 should light for positions 2, 3 & 4 of the switch. You may find that pins 2 & 3 are transposed which means that the tip and ring terminals on the jack plug connect to pins 2 & 3 respectively. This still means that the lead is good. Again, shorts are indicated with more than one LED alight and breaks are indicated with no LED alight. The shell LED lights if connected to pin 1. Mono jack to mono jack leads (guitar lead) will show a short between pins 1 and pins 2, corresponding to the ring connecting to ground. Finally, XLR to mono leads will need to be carefully interpreted. It is common for the unused pin on the XLR end to be connected to ground (pin 1) to provide for an unbalanced connection to a balanced input. This means there may be a short shown between pins 1 & 2 or between pins 1 & 3. For a good lead there will be a connection between the tip and either pin 3 or pin 2. To find this connection, firstly push the jack plug into the socket fully to make contact with the tip. If there is a connection between pin 3 and the tip then LED3 will light for position 4 of the switch. If the tip is connected to pin 2, you will find that the tester shows a short between all three connections since the tip will be at ground and pin 2 will be grounded via the ring connection contacting the ground on the mono jack. You will need to pull the jack plug out one notch so that the tip of the jack plug is contacting the ring contact on the socket. The tester should then show a connection between pins 2 and tip without shorts between the other terminals. If you are uncertain about the indications from the tester, you can always try a known good lead to check how the tester performs and compare this with the suspect lead. Putting it together We built our unit into a sealed ABS box measuring 115 x 90 x 55mm. Alternatively, you could use a plastic Jiffy box measuring 158 x 95 x 53mm. Use a metal shell XLR panel socket and plug JULY 2000 43 Fig.3: this is the full-size front panel artwork. Fig.2: follow this wiring diagram to build your lead tester. The photo below shows the finished unit. Our prototype only used one stereo jack socket but you can easily add a second socket if you wish. 44 Silicon Chip and stereo 6.35mm panel mount jack sockets. The rotary switch can be a 3-pole 4-position type or a single pole 12-way type with the locking tab set so that it only rotates through four positions. The LEDs can be general purpose types but preferably high brightness, so that the Tester can be used in bright light. All the components mount on the lid with the exception of the 9V battery. Use the front panel artwork as a guide to placement of the components and drill out the holes required for these. The cutouts for the XLR socket and plug can be made by drilling a series of holes around the required cutout perimeter and knocking this piece out. Then file to shape. Mount each XLR and jack socket pair on either side of the box lid. The LEDs are arranged above the rotary switch so that the pointer on the knob indicates which LED is selected. By the way, our prototype used only one jack socket but the circuit shows two. Cut the switch shaft to a suitable length for the knob and attach the components to the box lid. Wire it all up according to the diagram of Fig.2. The anode lead for each LED is soldered to a strip of tinned copper wire and this becomes the positive connection for the battery clip lead. The cathode ends of the LEDs connect to the shell, pin 1, pin 2 & pin 3 of the XLR socket via 1kΩ resistors as shown. Connect the anodes of diodes D1-D4 to the shell and to pin 1, pin 2 & pin 3 of the XLR socket. Now common the cathodes and connect this point to switch S2. The other terminal of S2 connects to the wiper of S1. The battery can be held in place using a strap or clip on the bottom of the case. Battery life should be extra long and you can even use a “dead” battery from a smoke alarm, since SC the low voltage will not matter for this circuit. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. 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SUBSCRIBERS QUALIFY FOR 10% DISCOUNT ON ALL SILICON CHIP PRODUCTS AND SERVICES* *except subscriptions/renewals and Internet access Item Price Qty Item Description P&P if extra Total Price Spec i SUB al Offer SCR IBE & COM PUTE GET R OM FO N Aust R FREE! IBUS ralia Only* Total $A TO PLACE YOUR ORDER Phone (02) 9979 5644 9am-5pm Mon-Fri Please have your credit card details ready OR Fax this form to (02) 9979 6503 with your credit card details 24 hours 7 days a week OR Mail this form, with your cheque/money order, to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy, NSW, MARCH 2001 53 Australia 2097 * Special offer applies while stocks last. 07-00 SERVICEMAN'S LOG Big is not always beautiful I had two Compaq computers to repair this month, one of them proving quite expensive to fix. At the more routine level, there is the growing problem of how best to handle large TV sets – in the home or in the workshop? Both computers were brought in by Mr Galvin. The first was a slightly ancient 1996 Presario 4704 computer (series PSB220C/3590 Pentium) that was dead. The second was a 1998 Armada 1573D series 2920D notebook, which looked as though it had a faulty hard disk. I started with the Presario PC, which had a faulty power supply. Unfortunately, being a Compaq, a generic power supply could not be fitted and exchange units were not really a viable economic proposition. The only option was to try to repair the existing one. I removed and disassembled it on the workshop bench. When it was finally in pieces, the major clue to its demise was plainly visible, namely a large female cockroach, complete with egg sac, which had managed to electrocute itself on the track side of the board. Removing the corpse and cleaning up its corrosion was probably all that was needed (the mains fuse hadn’t blown) but I also replaced all three of the small electros (1µF to 4.7µF) on the supply plugs. I also checked the high-value resistors. I didn’t want to refit the supply to the computer only to find it was still faulty, so I fitted a 12V 36W car globe to the 5V rail as a dummy load and turned on the power. The fan started and the globe lit. Satisfied that all was OK, I then refitted the unit and found that the machine was now working normally. So one set down and one to go. I now turned my attention to the Armada 2920D notebook which was fitted with an Intel Pentium 233MMX 54 Silicon Chip microprocessor. Its problem was that it wouldn’t boot up. Instead, it was displaying a “1720 Intelli-Safe Hard Drive Detects Imminent Failure” error message, followed by a “Non-System Disk or Disk Error” message. The next problem was that the computer belonged to Mr Gal vin’s son. This probably accounted for its failure and also for the complete loss of instruction books and utility disks. However, all was not lost and a few hours on the Compaq web site produced a nearly complete set. One of the utilities I downloaded is a diagnostics program (PC Diagnostics). This reported no diagnostic partition and a password protected hard disk lock. The latter proved not to be the case. A more precise message was, “1799-08 failed cable test and buffer compare”. I then ran Fdisk and this said that there was no partition. However, it wouldn’t save the instructions when I tried to create a new partition. Norton Diagnostics found no problem but Disk Doctor found “Invalid Signature in Partition Table” and “Bootable Par- Items Covered This Month • Compaq Presario 4704 computer. • Compaq Armada 1573D notebook. • Panasonic TC29V26A TV set. • Grundig ST70-75S TV set. • Philips 33FL1880/75R Matchline • • TV set. AWA SC6341 (AS630) TV set. Panasonic TC-29V50A MX-2A TV set. tition cannot be booted from”. All the above seemed to indicate a faulty hard disk but to confirm this, I contacted Compaq Technical Support who also thought it was a hard disk problem. However, I decided to take one more precaution – I took the notebook to a local computer specialist and ask him to fix it. He also diagnosed a faulty hard drive and quoted to replace the 3.2Gb IDE IBM hard drive with a 6.4Gb IBM Travelstream hard drive. After getting the quote accepted by Mr Galvin, the new hard disk drive was ordered and duly fitted. But guess what – we still had the same error messages. This meant that the fault had to be on the motherboard, most probably in the IDE controller section. Unfortunately, a new motherboard would cost over $1200 and I was beginning to feel that I was out of my depth. After consulting Mr Galvin, we agreed to take it to one of their official agents and invest $50 in a quote. Not surprisingly, the official diagnosis was the system board but, fortunately, they offered a repaired/exchange board with a three-month warranty for only $550 fitted. We agreed on this and a few days later I picked up the repaired computer and reinstalled the original software. I tested it thoroughly but no more problems were found. I subsequently quizzed the service department as to what had caused the problem but I drew a blank. Because it was an exchange unit, no one knew the answers – perhaps Mr Galvin’s son might. Large TV sets Now about those large TV sets – and they are getting larger. Though I try to look calm on the exterior, I always panic inside when I agree to repair a large TV set with what could be a nasty problem in the home. By and large it is much more sensible to take the set to the workshop rather than the workshop to the set. However, the public perception seems to be that all faults are simple enough to be dealt with in the lounge room. After all, it can’t be very serious, they reason . . . the fuse, the on/off switch or a bad connection. And bad connections are easy to find; so easy that some customers consider they shouldn’t even have to pay for them! It’s the same with VCRs. I had a case recently when an ancient VCR had come into the workshop because it was chewing tapes. It was duly fixed and the customer took it home. Hours later I received an irate call from the same individual who was furious that I had ruined his VCR and he wanted his money back. I tried to calm him down and work out what the problem was. Very heatedly, he said that the set was dead and nothing worked. This was hard to believe, so I asked whether the clock was working. “Intermittently”, was his response. Asked to explain this, he came back with “well, its on now, its off now, its on now, its off now”. It took 10 minutes of patient talking before he learnt how to switch the VCR on and set the clock . . . and he had only owned the unit for 10 years! Panasonic TC29V26A But back to the present. There were several large TV sets in the workshop but at least these were in a controllable environment (mine). The first off the rank was a Panasonic TC29V26A, an M16MV30 chassis. This 8-year old set had had a tough life, lived near the sea and was badly corroded. The set came in dead, which turned out to be a faulty horizontal output transformer and horizontal output transistor. This was a straightforward routine type fault and the set was left on test afterwards. When Mr Rose called to pick it up he asked whether I checked the tuning – implying that he had mentioned it when he had brought it in. Well, I didn’t recall that and I don’t think he did. But, anyway, I hadn’t – the set appeared to be working with most stations. It didn’t occur to me to check them all as I wasn’t aware of any problem. Of course, when I tried it out in front of him, the problem confronted us. The automatic search certainly tuned in the stations but just wouldn’t stop and be memorised. Considering the corrosion of the motherboard, it was a wonder the set was working at all. In addition to the usual 5V and 12V rails, the tuning system required a 30V rail. These were all available on the tuner/IF module B. The tuning voltage was derived from pin 46 of microprocessor IC1213 (MN1872432TW1) on the E board and applied to Q1202. This then varied the voltage applied to the tuning pin of the tuner. The IF from the tuner goes through Q110, Q101 and Q105 to pins 20, 21 & 23 of IC101. The AFC output is at pin 12 and feeds the tuner, as well as the microprocessor (pin 10) via IC102 (pins 3 and 4) and Q102 (TP891). The microprocessor detects, controls and stores the data in the EEPROM (IC1211). The problem was where to start looking. I reasoned that as the corrosion was worst around the microprocessor, I had only to check the tracks running to it and any small components around it. The prime suspect was diode D1203 from the AFC input (pin 10) to 12V. As it happened, this was a bullseye; substituting a new 1N4148 for the MA700 fixed the prob lem. From experience, I know that Panasonic small diodes do not like corrosion! Dead Grundig The next set was a dead Grundig ST70-75S using a CUC 6360 chassis. This, too, had a short circuit horizontal output transistor (BU508AG, T568.) Whenever I see a horizontal output transistor that’s gone short circuit, the question is “why did it fail”? In this case, I felt sure that the horizontal output transformer was to blame even though it looked good. Most Grundig transformers have a clear plastic outer cover and when they fail they sometimes leave a dark colour or shade on the inside. Unfortunately, there were no such clues here. The question was, should I risk simply fitting another transistor or should I also change the transformer at the same time? I decided on the latter course, as I didn’t want any recalls at a later stage. I duly ordered and fitted replacements for both, only to be disappointed by the immediate failure of the Introducing direct from USA “Test-Um” TEST GEAR TM From the company that brought you the world-famous ’Lil’ Buttie’ comes an outstanding range of phone and data test equipment... TP100 TELL-ALL TESTER r Identifies phone/data lines r 10Base-T, Token Ring, 100MBit Systems r Built-in battery TT100 TONE TRACER r High sensitivity r With volume control r Headset jack included TG100 TONE GENERATOR r Multi-function - 3 tones r Auto-Off function r Separate “talk” battery Available exclusively through: Call now for more info! Distributor enquiries welcome! Telephone Technical Services Tel (07) 3286 6388, Fax (07) 3286 6399 Shop 2, 55 Shore St West, Cleveland Qld 4163 www.ttservices.com.au JULY 2000 55 new transistor (the manufacturers had substituted a 2SD1884). I thought I was into one of my usual messes when I noticed C511, a blue rectangular 9nF 1600V capacitor in the collector circuit of the horizontal output transistor (T568). This capacitor was no longer perfectly shaped but had a bulge in it. This value is not available off the shelf and its part number is 8515-911-695. Its replacement turned out to be a green 9.5nF capacitor, which, I was assured, is now the default value for 66cm versions of this chassis. Replacing it finally fixed the fault but left the geometry needing a slight adjustment. This is one of those irritating sets that cannot be serviced without its remote control. To get into the service mode, one has to press I, select special functions and dial 8500 to get into the service adjustments. Also, supposedly, one needs the remote control to switch the set on because I was informed that an “S” 56 Silicon Chip connector on the motherboard had been disconnected. However, I couldn’t find this and as the set was now working properly and the customer had money in his hands, I resisted the temptation to take it further. This reminded me of a small AWA C3426 with a Daewoo chassis that was also dead. After spending a lot of time checking out the TV set, I found out it was the remote control that was the problem. The batteries had been left in too long and corroded the PC board tracks but only for the power on/off and volume functions. Linking the corroded tracks restored these two functions and let me switch the set on. Big Phil Next were two large Philips TV sets, one of which was a 33FL1880/75R Matchline using an FL1.1-S AA chassis. This 84cm set was a “top-ofthe-range” unit about eight years ago but this one was nearly dead. All that was showing were the mute, stereo and power front panel displays and these were all pulsating. The service manual refers to code 99, and there is a sort of fault-finding tree chart in Section 8. Following this, I put the set into the Service Default Mode by shorting S24 to S25 and found test point TP56 was at 4V (“set power on” should be 17.5V and “set power off” should be 0V). There was no 141V on TP57. I really wasn’t any the wiser for all this and suspected that I could diagnose this better by using commonsense rather than their error codes. The set uses a SOPS or Self Oscillating Power Supply (the output voltage is controlled by the frequency). I noticed that TP60 measured 18V and I was getting a feeling that the problem wasn’t in the power supply but probably in the horizontal output stage. This 84cm set actually uses two output transistors in parallel and these are designated ON4673A (or BU508AF). One of them, Q7504, was a dead short. Access to the underside of this set is really difficult and in the end I decided that the best course would be to unplug everything and pull it right out. Muggins also decided it would n’t be necessary to mark where each lead should go back, as logic and the service manual would easily sort this out. That was a BIG mistake. After many hours, I still couldn’t work out where all the plugs went back – especially the 26V supply to the SCAVEM (Scan Velocity Modulation) board on the neck of the tube. It was only after Philips had very kindly sorted me out that I discovered that there is an error in the service manual. In fact, the lead is connected to 28V and the two leads plug onto IL62 and IL63. They also told me that the main causes of failure of this transistor are due to C2504 and C2523, which are 8200pF and 470pF respectively. I replaced both of these, reconnected the board and switched on. Everything now worked well except that it was stuck in the service mode, which gives a row of figures on the screen. The manual states that to exit this mode, you press the personal preference button on the front panel of the set. In reality, I found that this would only happen if I switched the set off using the remote control. The second Philips set was a current model 34PT5793/79R A8.0A AA, still under warranty. Its problem was a bright uncontrollable white raster before the set cut out. I measured the cathode voltages on the tube but found nothing. I could see that R3840, which supplies 200V to IC7830, was badly burnt. I then checked IC7830 to find that it was totally short circuit. The circuit diagram had it marked as a TDA6103 but the spare parts list had it as TDA6107Q; the same as was fitted in the set. I ordered a new IC and fitted it along with a new 100Ω resistor, which was all that was needed to restore the picture. I suspect that the IC failure may have been due to a CRT flashover. PLUG IN AND MEASURE NEW 500mV -- 400V 0 -- 20MHz 8-bit RTN: S R 20 YEA NCE EXPERIE TRONIC IN ELECTROL CON AWA stereo TV set Mr Staples wanted a house call to his 15-year old AWA SC6341 (AS630) TV set. This is a large stereo console lowboy and his complaint was that the “sound was unclear”. I don’t know how I was persuaded to attend such an old set but there I was in his dark and dingy sitting room with the set, plus his VCR and a book rack of cassettes on top, while Mr and Mrs Staples were having a meal and watching me. The “sound unclear” was actually a distorted left channel. Access to the back of the set was appalling and access to the boards inside the set wasn’t much better. It would mean lying full length on the floor to work on it. I reasoned that, as it was only one channel, it was probably the sound output IC or preamplifier – I would order one and return later. This was an overconfident assumption on my part because on the next visit, after I had replaced IC3A2 AN7158N and IC3P0 M515236, it still had the fault. Using an audio probe, I eventually traced the problem back to the TDA3800G stereo decoder (IC302). Replacing this didn’t fix the fault either. It was then that I remembered fixing the same model some years ago for the same fault. In that case, the problem was that the three subminiature pots that are used to set up the stereo decoder were badly corroded. Replacing them is the easy part but aligning them in the home without the correct equipment (a stereo generator, etc) is just too difficult. I offered the Staples a short-term partial solution – just turn the balance control to the right, which would mute the distorting left channel. This would have been fine except for the even more ancient National NV450 VCR connected to it. Being mono, the left and right channels were both muted. Not being a quitter, I suggested connecting the VCR via the AV leads and settle for dual-mono. However, for some unknown reason, the audio output of the VCR was much lower than that required by the TV set and the result was still unsatisfactory – besides which, they had lost the VCR remote control and wouldn’t be able to change the channels while they ate their meals. Mr Staples was clearly totally unimpressed with my efforts and claimed that I had made the set worse. I was finally shown the door and the last I heard was they bought a new TV set. I only wish that they had done this before calling me. set – a Mitsubishi 2SC6343 AS631 with lack of height, rolling when cold, and a white vertical bar on the lefthand side. I was, I was told, the first technician to attend this set in 15 years, which says a lot for Mitsubishi. After spending an uncomfortable half-hour resoldering suspect joints, I concluded that the problems were probably due to dried out electrolytics on the motherboard and possibly in the power supply. Unfortunately, I didn’t have my ESR meter with me so I decided to measure all the supply rails in the set and compare them with the circuit. Everything measured OK until I reached the 14V rail input to Q552, which was very low. Replacing C562 (100µF EXR 35) fixed all three symptoms at once, except for a touch of poor linearity and top retrace lines. This turned out to be a very sick C454 (10µF EXR 100) in the vertical output stage. I really should stop repairing sets that are over 10 years old. They always lead to trouble. Another ancient set Another house call Not to be outdone, fate determined that stupidity would rule the day. I accepted another call for another ancient Another house call was initiated by a Mrs Hayes. She wanted me to fix her dead Panasonic TC-29V50A MX-2A STORAGE OSCILLOSCOPE SPECTRUM ANALYSER VOLTMETER TRANSIENT RECORDER RTN introduces the TiePie HANDYPROBE HP2 a powerful, 8-bit 20MHz virtual measuring instrument for the PC. Convince yourself: download the demo software from www.tiepie.nl Other fine products from RTN include: Genuine PARALLAX BASIC Stamps PHYTEC Rapid Development Tools ELAB Application Specific Chips All BASIC Stamps stocked: BS1, BS2 & the new BS2-SX. OEM chipsets for high volume applications. OZ-made BS Development board for all the BASIC Stamps also available thru Jaycar nationwide (25 convenient locations) RobotOz in WA (08) 9243 4842 New Serial port driven LCD modules. 2*16 and 2*40 types available. Software control over backlit, etc... FREE CD-ROM catalog now available - includes 85MB of data on our products (03) 9338 3306 email: nollet<at>mail.enternet.com.au http://people.enternet.com.au/~nollet RTN Phone/Fax JULY 2000 57 TV set in her home. I was envisaging all sorts of major problems like horizontal output transformers or worse, blown switchmode power supplies. Some of the modern power supplies these days are fairly complicated and difficult to diagnose. Fortunately, this circuit was reasonably straightforward and conventional, using an optocoupler feedback between the hot and cold sides of the chopper transformer to control the output and standby/on positions. There was voltage on the primary side but only a little on the secondary side and the standby LED was off. Further checks showed that the cathode of D808 was at 15V but there was nothing on the emitter of Q802 due to R833 22Ω being open circuit. At this point, I had a quick interlude for a prayer – please, please, let this be the only fault in the set. My prayers were answered; replacing the resistor restored all the functions on the set. Sometimes a faulty Q802 can be the cause of the resistor failing and sometimes the whole circuit can be destroyed. I was lucky this time. Well, almost. The set was sitting Fig.1: part of the power supply circuitry in the Panasonic TC-29V50A. The chopper transformer is at left, with the optocoupler immediately below it. 58 Silicon Chip on a very attractive stand with a companion Panasonic hifi VCR on lovely polished floorboards. When I had rotated the set to get access to the back, I had needed to lift the corner of a mat to allow the castors to roll past. And of course, I had to do the same when putting it back into its normal position. Unfortunately, as I was putting it back, the castor caught the edge of the mat and required just a tiny, tiny shove to push it free. But when I did this, the whole stand suddenly collapsed like a deck of cards and the 50kg TV set landed right on top of me. I was in shock – I thought an earthquake had occurred. I just couldn’t believe it; I hadn’t pushed the stand very hard and it had collapsed right on top of me. The noise was also deafening in the otherwise quiet house and it certainly attracted Mrs Hayes’ attention. Fortunately there was no real damage; I had taken the weight of the TV set which was unmarked by the incident. When I started to reassemble the stand, it quickly became obvious why it had collapsed. It is held together by plastic studs and some of these were missing while others had broken. The whole thing was just holding together. It was fine if left untouched but if pushed laterally, it all came tumbling down. I was a little bruised and my ego was somewhat dented by the need to explain all this to the astonished Mrs Hayes. But really it wasn’t my fault – there was no way of telling how poorly the stand was constructed. Anyway, I managed to get it all back together and it still worked properly. SC So maybe I was lucky after all. MAILBAG Monkeys in charge of the kingdom I would like to bring your readers’ attention to an appalling state of affairs in our industry. How would most of the service people and hobbyists respond to the fact that most if not all are practising electronics outside the law, in Queensland anyway? You see in Queensland we have a statutory authority called “The Electrical Workers Board”. This official sounding group is the body which determines who can and cannot do electrical work in this state (each state has a similar body). “Fine” you say, “We don’t do electrical work”. But you do! You repair equipment and some (many) even make kits. Now this solely industry-protecting monopoly will gladly tell you that this is electrical work and is solely the realm of qualified electrical workers (electricians) and they are fully intent on prosecuting anyone who breaches their rules. I, for one, am a holder of one of their restricted licences which allows me to legally repair the power cord on a mains-powered item. Sounds good. Well, I can’t build a kit legally, certainly not one with a mains outlet (such as a light chaser). I have been a TAFE-qualified technical officer for 14 years and I have a BOCP which is a federal licence to work on broadcast equipment, including the no-break power supplies, but I can’t build a kit within the law. It is about time our industry started to lobby our governments to put pressure on these people. It is a fact that as far as knowledge of electricity is concerned, electricians live at the bottom of the food chain! Yet through what is arguably one of the most powerful unions in this country they have our lawmakers bluffed. There is even an advert on TV up here about electrical safety that says if you spill something in your TV, turn it off and call an electrician! If this is not brought back to some state of sanity, it will not be long before you need to be a licensed electrician to start your car! All the while if you take a large pay cut and have half your brain removed, you can drag cable around a cottage for four years and become a member of this elite club – it’s an electrical apprenticeship! You might say that I am being too harsh but I have had to repair too many devices to mention, that were left in a state so poor by one of these masters of electricity as to require rewiring (yes, I broke the law). The general exemption thought to be enjoyed by electrical engineers only covers work done in the course of your practice as an engineer – you can’t build a kit legally either! “What field do I work in?” Answer: Medical Electronics. Our standards of electrical safety far exceed that of a normal electrical installation. I hope you will investigate this and maybe we could start some sane discussion in our industry. Please do not publish my name or I may lose my licence. Name supplied and withheld at request. Comment: this is yet another case of over government by people who have no idea of what unintended impact their regulations will have. While quite a few electricians do have some knowledge of electronics, it is fair to say that most would not be able to build the average project described in this magazine, let alone repair any electronic appliance. Hot wire cutter works well The article on the hot wire cutter by Leo Simpson in the April 2000 edition was excellent. Several months ago we needed a small foam cutter. After many hours of searching the WWW (not much info found) I decided to have a try at making one myself. Using the Dick Smith Electronics resistance wire I experimented to find the right current to get the wire to the correct temperature (about 2.5A). The resulting cutter gets used almost daily and the pieces of foam that it has cut have been sent to all corners of the globe. After reading the April 2000 article on the GlowPlug Driver circuit, I will build one of these to control the current. At the moment I am using a 12V 4A supply with a couple of 1Ω 10W resistors to achieve the correct series resistance. Gareth Hassall, Quest Electronic Developments Pty Ltd. Class A amplifier has excellent sound I’ve just recently built your Class A amplifier design from the July & August 1998 issues. It’s excellent – I’ve never heard an ampli fier this good. I immediately noticed a big improvement in the sound compared to my previous amplifier. It has a more transpar ent sound with substantially better bass, in part I suspect to the regulated power supply and partly due to less masking of the bass frequencies from the smoother high frequencies. A top design – well done guys. The whole project cost me about $400 in the end but I hate to think how much a commercial amplifier of this quality would cost. David Snoswell, Adelaide. JULY 2000 59 Li’l PowerHouse Since preparing the first article for the Li’l PowerHouse we could not let well enough alone. Having seen how good this little switchmode power supply is, we could not avoid the temptation to improve it and so it now has even better regulation, and better residual hum and noise. How did we do it? Read on. By PETER SMITH & LEO SIMPSON As with any high-performance circuit, half the magic is in the “core” ICs and most of the rest lies in the PC board layout and associated wiring. And so it is with the Li’l PowerHouse. Having produced the prototype, confirmed that it all worked and prepared the first article for publication, somebody (who shall remain nameless) realised that there were a few tweaks that could be done to the circuit board and output filter network. Could the changes be made? Chief bean counter/publisher: “No! You’ve already changed the PC board 60 Silicon Chip from the one that’s shown in the first article”. Nameless one: “But it’ll be much better!” CBC & P: “No, you’re talking about a new PC board, a complete rewire, more photography, egg on collective editorial faces, pushing the deadlines...” Nameless one: “But I’ll work evenings, weekends, come in early in the mornings, make your morning tea...” CBC & P: “You’re on!” And it came to pass. The new PC board looks vaguely similar to the one Part 2 shown on page 61 of the June 2000 issue but in many respects it has been a complete revamp. As often happens, you change one aspect, which leads to another few changes and before you know it the PC board is looking radically different. Not only has the copper track layout for much of the PC board been changed, the output filter network is now quite different. The second toroid filter now has two windings on the same core but we have managed to do without one 470µF 63VW filter capacitor and that is a worthwhile saving. Why didn’t we do it this way the first time? Answer: we’re not perfect . . . yet. Amended circuit Fig.5 shows the portion of the circuit which has been changed to incorporate the 2-winding version of toroid L2. These two windings are phased so that flux developed by L2a is cancelled by the flux developed in Despite the relatively minor circuit changes, the final PC board assembly differs quite markedly from the prototype shown last month. Please note: Some constructors have not been able to calibrate the current reading successfully, finding that the current reading is too high and cannot be adjusted low enough with VR2. If you encounter this problem, try reducing the value of the 15kΩ resistor connected to pin 2 of IC2. We suggest a value of 7.5kΩ. L2b. This effectively cancels the DC component of the flux and prevents core saturation. The two inductors on the one core effectively filter any common mode signals. Apart from this change, the circuit is otherwise identical to that published last month but the changed circuit board has also led to significant performance improvements. mounting holes which mate up with three of the integral pillars in the base. Fig.6 shows the complete wiring diagram and includes the component overlay for the PC board. Begin by checking the PC board for any etching defects and undrilled holes. If everything is OK, start by installing the PC stakes at all external wiring points. You will need 21 PC stakes, not 22 as listed last month. Note that the stakes should be a tight fit into their respective holes, before they are soldered. It is no use having PC stakes which fit loosely as they will tend to come away from the PC board when you attempt to solder wires to them. Next, install the resistors and wire links. Table 1 shows all the resistor values and their respective colour codes but you should also use your Building the Li’l PowerHouse The Li’l PowerHouse was built into a folded metal case measuring 200 x 162 x 67mm. Alternatively, it can be built into a standard plastic case measuring 200 x 155 x 65mm, with metal front and rear panels. All the circuitry, apart from the front panel components and the digital panel meter, is mounted on a PC board measuring 126 x 113mm and coded 04106001. If you are using the plastic case, you will find that the PC board has corner Fig.5: this diagram shows the amended output filter circuit. The main change involves the second toroid filter which now has two windings on its core instead of one. These winding effectively filter any common mode signals and together prevent core saturation. JULY 2000 61 Fig.6: install the parts on the PC board and complete the wiring exactly as shown here. Be sure to use 250VAC-rated cable for all mains wiring and sleeve all exposed terminals with heatshrink tubing to avoid the possibility of accidental contact. Note that the earthing details differ from the arrangement shown here if you use are using a plastic case with metal front & rear panels – see text. 62 Silicon Chip multimeter to check each value before it is installed. Resistor R1, the current sensing resistor, is a length of 0.4mm enamelled copper wire, installed as shown. Make sure you tin each end of the wire (scrape off the enamel at each end first) before soldering it to the PC board. By the way, don’t use anything other than 0.4mm enamelled copper wire for this job, otherwise you may have trouble calibrating the supply later on. Note also that the 680Ω 5W resistor should be mounted with its body about 2mm above the PC board because it will get quite hot when the supply is set to deliver close to 40V DC. Next, install the ICs, the diodes and zener diode, REF1 and the trimpots. Solder only the two outside pins of IC1 at this stage (do not trim the leads) so it can be easily adjusted to line up with the mounting hole in the rear panel. Note that while we have specified the 1A LM2575HVT-Adj device, you may be supplied with the higher-rated LM2576HVT-Adj which will work just as well (and also has the advantage of being a little more rugged). Make sure that the ICs and diodes are correctly oriented and be sure to use the correct device at each location on the board. IC sockets are optional (we used two as part of our prototype testing). Zener diode ZD1 should be mounted with a small loop at one end to provide thermal stress relief. The capacitors can be installed next and make sure that all the electrolytics are installed the right way around otherwise there could be pyrotechnics when you first turn it on. Winding the inductors Both the inductors were specified as prewound types in the parts list in last month’s issue but we include the details here for those who want to make them. To make L1 you will need to tightly wind 60 turns of 21 B&S (0.71mm) enamelled copper wire onto a Neosid 33mm diameter powered iron toroid (Neosid 17-742-22; Altronics L-5120). The turns are made side by side – do not overlap. A total of 210cm of wire is required. Scrape the enamel off the ends of the winding, tin them with solder and then solder the inductor into the PC board. Fig.7: the winding details for inductor L2. Two windings are required, each consisting of 13 turns of 22 B&S (0.63mm) enamelled copper wire. Once it is soldered in place, the toroid can be secured to the PC board with two ‘blobs’ of hot-melt glue or non-corrosive silicone sealant. For L2, two windings are required. Each winding is 13 turns of 22 B&S (0.63mm) enamelled copper wire wound tightly onto a 14.8mm Neosid powered iron toroid (Neosid 17-73222; Altronics L-5110). Again, the turns are made side by side – do not overlap. Two 40cm lengths of wire are required and they must be wound exactly as shown in Fig.7 to ensure correct phasing. Case preparation If you have purchased a kit with a pre-punched case and silk-screened front panel, you don’t need to worry about these next few steps. But if you are starting with a plastic instrument case with blank metal front and rear panels, you have some work ahead of you. For a start, some of the integral pillars on the base of the case must be removed in order to accommodate the PC board. To do this, first sit the board in the base, against the back panel, and use a felt-tipped pen to mark three mounting pillars (ie, the three directly beneath the board mounting holes). This done, remove the PC board and remove all the unused pillars using an oversize drill. Note that you will also need to remove any pillars which will be underneath the transformer when it is mounted. Next, the various holes and cutouts in the front and rear panels need to be made. A hole needs to be drilled in each panel to mount an earth lug with a screw, nut and star washer (note: use a countersunk dress screw if the front panel is supplied screen printed). Choose a convenient point on the far lefthand side of the front panel for a common earth point and drill for a 3mm countersunk bolt. Drill a second 3mm hole in the rear panel in a roughly complementary position and run a length of wire from there to the common earth point on the front panel. Secure all four earth lugs to this point. The front panel label can now be fitted and used as a drilling template for the various holes. It’s always best to drill small pilot holes first and then carefully enlarge them to size using a tapered reamer. The square cutouts for the LCD panel meter and for switch S1 can be made by first drilling a series of small holes around the inside perimeter of the marked areas, then knocking out the centre pieces and filing each cutout to shape. Both the switch and panel meter clip into place with their integral retaining lugs. On the rear panel, you will need to drill holes to accept the mains fuse (F1), the cordgrip grommet and three solder lugs. Refer to the photos for the locations of these holes. In addition, Fig.8: the mounting details for IC1. Its metal tab must be electrically isolated from the metal case using an insulating pad and bush. JULY 2000 63 Table 1: Resistor Colour Codes  No.  3  6  1  1  1  1  2  1  1  2 Value 1MΩ 100kΩ 27kΩ 15kΩ 4.7kΩ 1.5kΩ 1kΩ 470Ω 300Ω 100Ω you will also have to drill a mounting hole for IC1. The location of this mounting hole can be determined by fitting the PC board inside the case and sliding the rear panel into position. Mark out and drill the hole, then carefully deburr it using an oversize drill so that the surface is perfectly smooth. Finally, refit the rear panel and adjust IC1 as necessary before soldering its three remaining pins to the PC board. Fig.8 shows how IC1 is isolated from the rear panel using a mica washer and insulating bush. Smear all surfaces with heatsink compound before bolting the assembly together (note: heatsink compound is unnecessary if you use a silicone impregnated wash er). Finally, check that the metal tab of IC1 is indeed isolated from the rear panel using a multimeter switched to a low ohms range. Note that the legs of IC1 should not be under any stress when it is finally bolted into position. The PC board assembly can now be attached to the base of the case and the hardware items mounted on the front and rear panels. Before mounting the potentiometers, cut the shafts to a length to suit the knobs. Note that we have installed a 10-turn pot for the Voltage Adjust control (VR1) in our prototype but this is an optional feature. It is worthwhile having though. Final wiring Fig.6 also shows the wiring details. Begin this work by stripping back the outer insulation of the mains cord by 170mm, so that the leads can reach the mains switch (S1) on the front panel. This done, push the mains cord through its entry hole and clamp it 64 Silicon Chip 4-Band Code (1%) brown black green brown brown black yellow brown red violet orange brown brown green orange brown yellow violet red brown brown green red brown brown black red brown yellow violet brown brown orange black brown brown brown black brown brown securely to the rear panel using the cordgrip grommet. The Neutral (blue) mains lead goes directly to switch S1, while the Active (brown) lead goes to S1 via the fuse. Slide some heatshrink tubing over the leads before soldering the connec tions. After the connections have been made, the tubing is shrunk over the switch contacts and fuse to prevent accidental contact with the mains. Our prototype was built into a folded metal case and the earthing details are as shown in Fig.6 and the photos. We chose a point just in front of the power transformer. Use a 3mm bolt and star washers to secure the three earth lugs as per the wiring diagram. Make sure that you scrape away the paint from underneath these lugs and from under the transformer mounting bolts, to ensure a good earth connection. If you are using a plastic case with metal front and rear panels, the earthing details are different. In this case, the green/yellow striped lead from the mains cord connects directly to an earth lug terminal which must be securely bolted to the front panel. Additional green/yellow earth wires are then run from the front panel earth to the rear panel and from the front panel to the power transformer frame. Important: if the aluminium panels are anodised, you will need to scrape away the anodising from around the earth lug holes to ensure good electrical contact. All switches and pots are wired with light duty (1.5A or less) hook-up wire. Load switch S2 and transformer T1 should be wired with medium duty (5A or more) hook-up wire. The 0.33µF capacitor at the output is wired 5-Band Code (1%) brown black black yellow brown brown black black orange brown red violet black red brown brown green black red brown yellow violet black brown brown brown green black brown brown brown black black brown brown yellow violet black black brown orange black black black brown brown black black black brown directly across the backs of the output terminals (see Fig.6). The connections to the digital panel meter are made using a 13-way SIL connector and ribbon cable. You can cut down a larger socket strip or glue two smaller ones together. Note that the two wires running from pot VR1 to the rear of the board near IC1 are twisted and routed along the bottom of the case, hard up against the side (see photos). The idea here is to reduce noise pickup from inductor L1 as much as possible while minimising wire length. In addition, use several plastic cable ties to lace the mains wires together. This is an important safety measure as it prevents any wire that may come adrift from making accidental contact with any part of the metalwork or vulnerable low-voltage circuitry. Be warned that the wiring to pushbutton switch S4 (Set Current) may present a few problems if the switch specified in the parts list is not used. This is because some momentary pushbutton switches have their common (C) terminals in the middle and their normally open (NO) and normally closed (NC) contacts on the outside, whereas the switch we used has its common terminals at one end. If your switch has its common terminals in the middle, the wiring shown in Fig.6 will no longer be relevant and you will have to work out the connections from the circuit diagram published last month (Fig.4). The common, NO and NC terminals will usually be marked somewhere on the body of the switch. Note that the wire connecting the pole of S4b to the PC board (and to Keep all wiring neat and tidy and use plastic cable ties to bind the mains wiring. Note that a separate earth lead must be run to the transformer frame if you are using a plastic case, rather than the metal case shown here. the 100kΩ resistor at pin 2 of IC4) should be omitted at this stage. It will be connected later. Testing Before applying power, carefully check your work for any wiring errors. This done, wind VR1 fully anticlockwise and set VR2, VR3, VR4 and VR5 to their centre positions. Switch on the supply and check that the voltage across ZD1 is about 5.1V. If so, check the reading on the digital display. It should show about .000 for both positions of S3, the meter switch. Now adjust VR5 for a reading of exactly .000 on the panel meter. If everything is OK at this stage, you can check the supply voltages to each IC. Connect your multimeter negative lead to the cathode of ZD1 and check the voltage at pin 7 of IC2 and IC4, pin 8 of IC3 and pin 8 of IC5. These should all be at +5.1V. Pin 4 of IC2 should be at about -5V. If at any stage the voltages are incorrect, switch off immediately and correct the problem before proceeding. Voltage calibration Now turn off the supply and connect the missing wire from the pole of switch S4b to the PC board. This done, set the meter switch to the Volts position, turn the power supply on again and check that the output voltage is adjustable from 1.23V up to about 42V (depending on the mains voltage at your location). Connect a digital multimeter to the output terminals and with no load connected, set the Load switch (2) on. Now set the output voltage to read 39V on the digital multimeter (DMM) using the Voltage Adjust control VR1. Connect your DMM between pin 6 of IC4 (marked TP1 on Fig.6) and 0V (marked GND) and set the DMM to read millivolts. Adjust VR4 for a reading of 390mV on the DMM. Check the reading on the digital panel meter. If it is not 39.0, JULY 2000 65 Photo A: taken at an output of 12V and 160mA, this scope photo shows the high frequency ripple of about 2mV peak to peak. Note that the ripple and noise is now about 10 times better than we specified last month. Photo C: taken with the same output settings as photo A, the scope timebase has now been switched down to 5ms/ div to show the 100Hz ripple. This time the noise on the waveform is the residual 52kHz ripple shown in photo B. Photo B: taken at an output of 12V and just over 1A, this scope photo shows that the high-frequency ripple is not much higher than for the lower current condition and is 3mV peak to peak. The noise on the waveform is actually jitter caused by superimposed 100Hz ripple. Photo D: again taken with an output setting of 12V and 1A, these scope waveforms demonstrate the switchmode and filter operation. The top trace is taken from the input to L1 while the lower is the waveform at the input to L2. After passing through L2 the waveform becomes the same as shown in photo B. adjust the trimpot at the rear of the DPM for the correct reading. Current calibration Rotate the Current Limit pot (VR2) fully clockwise and set the meter switch (S3) to the Current position. Now connect a 4.7Ω 5W resistor across the output terminals, set the Load switch (S2) on and connect your DMM across the 4.7Ω resistor. Power up and adjust the output voltage to read 4.7V on the DMM using the Voltage Adjust control (VR1). Adjust trimpot VR3 for a reading of 1.000A on the DPM. Note that the 66 Silicon Chip 4.7Ω resistor will get very hot during this procedure – don’t burn yourself or singe your dining room table! Note: the DPM will read somewhere around .010 with no load connected. This is normal and is the result of the input offset of op amp IC2. This offset also results in a small difference between the current set reading and the actual current limit value although in most circumstances this small error should be of not consequence. Switch off the Load switch and press the Current set switch and check that the display reading can be varied from .010 up to at least 1.100A by adjusting the Current Limit control. Note that the overload LED may light when the control is fully anti clock wise. This is normal and the LED will extinguish when the current limit reaches about 10mA (0.01 on the display). Check the current limiting The current limiting feature should now be checked for correct operation. To do this, leave the 4.7Ω resistor in circuit and switch on the Load switch. Rotate the Current Limit control anticlockwise until the overload LED lights. This should initially occur at These digital scope plots show the same waveforms as in photo D. Note the remnant switching spikes in the lower trace. These are completely removed by the second stage of filtering in L2. Fig.10: this full-size artwork can be used as a drilling template for the front panel. The cutouts can be made by drilling a series of small holes and knocking out the centre piece. Fig.9: this is the full-size etching pattern for the PC board. can observe the output ripple and noise. Right; it’s all finished and set to use. 1A but you should now be able to set lower current limits by further reducing the control setting. The power supply will “squeal” during current Footnote: kits for this project will be available shortly from Altronics in Perth. You can order on their toll-free number SC 1800 999007. limiting but this is quite normal. Finally, you can check the power supply on various loads and if you have access to an oscilloscope, you JULY 2000 67 S RONIC Y OATLE ELECT S ELECT S RONIC RONIC Y OATLE Y OATLE ELECT S RONIC Y OATLE ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE 1st FOR AUSTRALIAN MADE KITS DEVELOPED IN AUSTRALIA!!! S RONIC Y OATLE ELECT ICS CTRON Y ELE OATLE COMPUTER POWER SUPPLY: New complete PCB assembly only. Overall ICS CTRON dimensions are Y ELE E L T A O 45 x 108 x 200mm. Switchable 120/ ICS CTRON 230V Y ELE AC input. E L T A O DC outputs are +5V<at> 6A, +12V<at>1A, -12V<at>1A, ICS -5V<at>1A. 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S IC ICS N O R As used in some garage CT CTRON Y ELE Y ELE E L T A O OATLE safety lights CALL OR E-MAIL ”BRANKO” VERY COMPETITIVE PRICES Made in Japan: (ZA0031) 4 for $5 ICS NICS FOR CTRON ECTRO MORE DETAILS ON THESE AND MORE KITS SEE OUR WEB SITE Y EL68 S Y ELE ilicon Chip OATLE www.oatleyelectronics.com OATLE Orders: Ph ( 02 ) 9584 3563 or 64, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box 89 Oatley NSW 2223 major cards with ph. & fax orders, Post & Pack typically $6 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081 BARGAIN CORNER PCB DESIGN AND PRODUCTION SERVICE S ICS ICS ICS ICS ICS ICS ICS ICS ICS S ICS TRONIC CTRON CTRON CTRON CTRON CTRON CTRON CTRON CTRON CTRON CSC_JLY_00 CTRON Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE E OATLE OATLE OATLE OATLE OATLE OATLE OATLE OATLE OATLE OATLE L T A O RONIC Y OATLE ELECT S RONIC Y OATLE ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT ICS WEIGH STATION TRANSDUCERS: CTRON Y ELE OATLEThese bridge configured strain Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE AMBIENT TEMPERATURE CONTROLLER KIT: Use this kit as an electric hot water bottle, an aquarium heater, incubator, beer brew heater, heater for your pets' "pad" etc. Features LED indicators, adjustable temperature, approximately 0.5 degree hysteresis and a 30W heater. The mosfet included is used as the heater. Requires 12V AC or DC supply <at> approximately 2.5A. Kit uses 3 new recovered surplus parts which makes possible the bargain price. Kit includes PCB and all on-board components, mosfet, thermistor and a suitable box: (K145) $18 (a suitable surplus mains transformer is available for $9 extra mains wiring experience necessary). gauge transducers are all made by Transducers Inc. (USA). ICS CTRON Y ELE OATLEAll are brand new but may be slightly soiled around the mounting ICSscrew sockets: CTRON Y ELE (ZA0008) OATLE Model # U62H-1K-10P1: 2mV/V <at> 1,000LBs, approx N90mm dia. 110mm long. Approx. 2.8Kg: ICS CTRO $89 Y ELE each (1 only) E L T A O Model # U42-5K-10P1: 2mV/V <at> 5,000LBs, approx. IC90mm dia. 140mm long. Approx. 3Kg: S CTRON $99 Y ELE each (1 only) E L T A O Model # U42-50K-10P1: 3mV/V <at> 50,000LBs, approx. 170mm dia. 280mm long. Approx. 20Kg: ICS CTRON $165 Y ELE each (1 only) OATLEModel # U42-100K-10P1: 3mV/V <at> 100,000LBs, approx. 170mm dia. 280mm long. Approx. 20Kg: S RONIC (1 only) $199 IR TESTER KIT: CTeach Y ELE OATLE This simple kit can be used to test remote 200A R/C MODEL SPEED CONTROLLER KIT: controls. If the remote control is S IC designed to work direct from a standard operating, the LED on the tester will This RONis CTkit Y ELE OATLE1-2ms pulse from a radio control receiver to flash. Circuit is based around control an electric motor in one direction only. our HC312 IR Receiver ICS Features CTRON inc. brake. Kit inc. PCB and all on-board Module & operates from Y ELE OATLEcomponents including 5 high power MOSFETs a 9V battery (not supplied). Kit is supplied with PCB and a small (26 x 64 x 38mm) case: (K152) $35 ICS and all on-board components N O R T C Y ELE + a surplus case, label & battery holder: (K125) $8 OATLE ICS CTRON Y ELE OATLE S TRONIC C Y ELE SQUARE FANS: 240V Limited quantity. These Sunon Brand fans are ICS CTRON brand Y ELE new and operate OATLE from 240V AC <at> 0.125A. They measure 120 x 120 x ONICS 38mm: LECTR E Y E OATL (MF2) $14 each or 3 for $35 OATLE ICS CTRON PC Y ELE CONTROLLED OATLEDISPLAY KIT: MOVING MESSAGE LED Ref: SC Feb. 97. 336 LED's and control circuitry ONICS (413 x 110mm) solder masked / silk onELEaCTRlarge Y OATLEscreened / through-hole plated PCB. Requires Software, a 12V / 1A Plugpack, Acrylic Casing, S and TRONIC Parallel Port Computer Cable. CDB25 Y ELE OATLEPCB & Software on 3.5" disk: (K100B) $75 PCB, Software on 3.5" disk, 336 Bright Red LED'S, All ICS on-board CTRON components & a suitable surplus power Y ELE OATLEsupply: (K100) $165 ICS CTRON Y ELE OATLE ICS CTRON Y ELE OATLENEODYMIUM RARE EARTH MAGNETS. S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT Y OATLE S RONIC ELECT ICS (NEW) PHILIPS Active Speaker System: CTRON Y ELE These compact pair of speakers contain a built-in OATLE amplifier and bass reflex port. Designed in Europe. Frequency range 100 - 18kHz, 2.25" full TRONICS C Y ELE range speakers with 4W PMPO output. Stylish, OATLE easily portable and click together to form a single ICS CTRON Y ELE package. Requires OATLE 4 x 1.5V AA batteries (not supplied) ICS CTRON and has socket for Y ELE OATLE operation with a plugpack. Has 3.5mm ICS CTRON stereo plug to connect Y ELE OATLE to source: (SBCBA100) $12 ICS RON 12V DC - 240 AC INVERTER KIT: ELECT TLEY OAauto Features inc. modified square wave output & start with load sensing, easily modified to accept ONICS 24V DC input. Uses Mosfets with minimal LECTR LEY E T A O heatsinking required. Requires a 240V to 8V-0-8V transformer. 200-600 Watt output dependant on transformer. To save money you can wind yourELECTRONICS EY OATLonown transformer. Basic kit includes PCB & all board components including 4 x 60A Mosfets: Basic kit including PCB & all on- board LECTRONICS E TLEY components: (K127) $39 Basic kit includingOAPCB & all on- board components ICS with a suitable 300VA CTRON Y ELE Torroidal Transformer OATLE (weighs 5kg) and a large ICS GET ONE WHILE YOU STILL CAN!!! filter capacitor. This transCTRON Y ELE THE LAST OF OUR FAMOUS GERMAN-BUILT former is robust and is the OATLE size of many similar 500VA PRINTER / SCANNER MECHANISMS ICS Worth $1800!! These heavy duty printer models: (K127T) $92 CTRON Y ELE mechanisms. We have constructed a Plotter and OATLE a CNC machine bed (could mount a cutter, router, HOSE REELS: drill etc). from parts that were mainly recovered Self retracting compressed Air hose reels with a TRONICS C AC Y ELE from these printer. The main parts that were not swivel inlet connection. Powered by a 24V OATLE geared motor assembly which is attached to the recovered from the printer were some chipboard and two pieces of 1" aluminium angles. You would reel. The whole assembly is mounted on a frame RONICS CT has Y ELE also require a Stepper Motor driver kit (K142) for that needs to be bolted to a firm surface. Reel OATLE is a diameter of 350mm and is 115mm high. Hose each Stepper Motor. Parts inc.SIX MINEBEA STEPPER MOTORS: manually extended, pulling the hose sharply ICS theELECTRON 2x4 wire type 23LM-C355-38V 50x55mm 3x4 actuates a reversing mechanism that retracts TLEY A O wire type 17PM-H303-04V 37x 42mm 1x4 wire hose. A matching enclosed type 17PM-M007-02, 42x33mm A PCB WITH 240-24V torroidal transICS CTRON SGS STEPPER DRIVER IC'S. A POWERFUL & former is included. Made Y ELE OATLE in SWEDEN by Winler & COMPACT SWITCH MODE POWER SUPPLY WITH FAN. Features 240V input and outputs of Sundberg: (ZA0005) There S RONIC 5V/8A, -12V/1.5A, +12V/1A & +32V/4A. A 24 PIN are a few different units availELECT TLEY A O able ranging from $150 to $300 PRINT HEAD, OPTICAL SCANNER, CPU, EPROM, matching BELTS & PULLEYS, two Call for more details and prices. ICS GEARED MOTOR ASSEMBLIES with micro CTRON Y ELE (NEW) STAINBRITE ELECTRONIC CLEANER: OATLE switches and a MAINS FILTER. We have the enclosed Arlec transformers (main UNBELIEVABLE unit) but we don't have the leads, electrode & acid CTRONICS PRICE OF ONLY LE LEY E req. Has three output terminals; Common,OATLow $49 and High. Low output delivers 28V AC at 13A, NOTE WEIGHS High output delivers 38V <at>13A. The output RONICS OVER 20kg & SO CT Y ELE terminals similar to the ones used on arc welders. WE ARE UNABLE OATLE The unit can obviously deliver much higher TO POST IT TO currents, has a 10A fuse in the 240V ICS OTHER CTRON AC primary. (supplied with Y ELE COUNTRIES INC. OATLE mains lead) in an industrial NEW ZEALAND. strength box which measures Plans / notes on ICS CTRON approx. 300 x 200 x 200mm. Y ELE floppy for an A3 OATLE Unit & instruction booklet only. plotter & a 2/3 approx. 13kg: (ZA0026) $120 axis mill: $9 ONICS Very strong!!! You will S be able to separate two of these by NICnot CTROthem pulling apart directly away from each other. Y ELE OATLE Zinc coated. CYLINDRICAL 7 mm diameter x 3 S TRONIC (G37) $2.50 CYLINDRICAL ELECthick: mm Y E L T OA 10mm diameter x 3 mm thick: (G38) $5 TOROIDAL S 50mm outer, 35mm inner, RONIC R 5mm ELECTthick: (G39) $12 ROD 10mm long, ELECT Y E L T ATLEY OA 4mm diameter: (G54) $2.50 CYLINDRICAL 3mm USED) POCKET PAGERS: Check out our “new look” web site for Omore Small modern pagers, brands products. Amazing cheap super bargains in diameter xS 1.5mm thick: (G58) 2 for $1 S IC include LINK, PHILIPS, RTC. our bargain corner & many other items that weELECTRONIC CTRON E L E Y Y Condition “unknown”, all have OATLELAPTOP COMPUTER MEMORY: OATLE can not fit on this page This memory is brand new and still in it's original two small (grain of wheat) 1.5V ICS (static bags). All modules are the lamps and lots of other parts. Some of our prices have changed as aELECTRONICS packaging CTRON Y ELE LEY OATLEHypertec brand and we are selling them for a All are powered by one AA cell. (089910) 5 for $5 result of GST & some as a result ofOATthe fraction of their retail price. See our website for A limited number of these have very small 1.5Vdc poor performance of the Australian motors. 13mm long X 10mm dia. for $5 ea. ICS NICS dollar... further CTROinfo. CTRON Y ELE Y ELE ULY 2000 69 OATLE www.oatleyelectronics.com Orders: Ph ( 02 ) 9584 3563 or 64, Fax 9584 3561, sales<at>oatleyelectronics.com, PO Box J89 OATLE Oatley NSW 2223 major cards with ph. & fax orders, Post & Pack typically $6 Prices subject to change without notice ACN 068 740 081 ABN18068 740 081 S ICS ICS ICS ICS ICS ICS ICS ICS ICS S ICS TRONIC CTRON CTRON CTRON CTRON CTRON CTRON CTRON CTRON CTRON CSC_JLY_00 CTRON Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE Y ELE E OATLE OATLE OATLE OATLE OATLE OATLE OATLE OATLE OATLE OATLE L T A O RONIC Y OATLE ELECT 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. 4-wire milliohm tester for DMMs Based on a Maxim IC application note, this simple battery-powered adaptor converts an ordinary digital multimeter (DMM) into a 4-wire milliohmmeter that accurately measures the resistance of wiring, motor coils, solenoids, high current inductors and meter shunts. It could also be used to locate shorts on a PC board. The circuit is essentially a constant current source which applies 1A, WANTED! YOUR CIRCUITS AND PROJECTS! If you have a scathingly brilliant, original circuit that you'd like to share with the world – and make some money as well – send it in to us. We’ll pay up to $100 for a really good idea: • • • It must be your own work It must not have been published or submitted elsewhere It must be something other SILICON CHIP readers would find interesting. Send to: The Publisher, SILICON CHIP, PO Box 139, Collaroy, NSW 2097. email: silchip<at>siliconchip.com.au Phone: (02) 9979 5644 70 Silicon Chip 100mA or 10mA to the unknown resistance via two test leads, according to the range switch (S2) setting. In use, you set your DMM to the 2V range and connect it across the resistance being measured. This forms a 4-wire connection to the resistance being measured. This method of connection avoids the problems of resistance in the test leads. Pressing switch S1 passes the selected current through the resistance being measured. With 1A selected, the DMM reading will be in Ohms. A 1Ω resistance, for example, will read 1.000. With 100mA selected by range switch S2, you have to multiply the multimeter readings by 10 to get a value in Ohms or by switching the DMM to 200mV, the reading will once again be in Ohms. Finally, if the 10mA range is selected, the DMM should be set at 200mV and the reading will need to be multiplied by 10 to give the correct value in Ohms. The overall accuracy will depend on that of the DMM, the op amp’s input offset voltage (±70µV maximum) and the tolerances of resistors R1, R2, R3, R4, R5 & R6. These resistors could be trimmed to improve the accuracy if you have suitable standards. The constant current source works as follows: The LM336 provides a 2.5V reference to the non-inverting input (pin 3) of op amp IC2 and this is compared with the voltage developed by the Mosfet (Q1) current through resistors R4, R5 and R6. Note that S1 disconnects the 9V battery when it is not pressed and this means that there is no current drain from the 1.5V battery either. If you use a D cell here it should produce thousands of measurements. The current drain from the 9V battery when S1 is pressed is only about 30µA so it should last for years. SILICON CHIP. Fine & coarse power supply control Often a circuit calls for a multi-turn potentiometer in order to be able to give sufficiently fine control. However, 10-turn potentiometers are not cheap. This circuit idea is an eco nomical alternative. It uses a dual gang 50kΩ linear potentiome ter as the coarse control and a 500Ω linear potent iometer as the fine control. A portion of both the 50kΩ pot elements are effectively connected in series with the 500Ω potent iometer between them. However, because of the method of connection, the total resistance in circuit 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. Designed for maximum battery capacity and longest battery life. Constant voltage charger uses LM317 The ability to adjust the output voltage of the LM317 3-terminal regulator makes it ideal as the basis for a simple constant voltage charger. These two circuits, taken from the National Semiconductor Linear Brief 35, have the advantage of no filter capacitors and the final voltage from the charger is adjusted by potentiometer R3. In the top circuit, R1 defines the charger output impedance and enables a “taper” charge characteristic to be obtained. In the lower circuit, transistor Q1 provides control of the peak charging current, an important point with smaller batteries. Note that the transformer secondary voltage will need to cater for the voltage drop across the regulator and depending on the charging current, the LM317 will need to be mounted on a heatsink. AVOIDS THE WELL KNOWN MEMORY EFFECT. SAVES MONEY & TIME: Restore most Nicads with memory effect to capacity. Recover batteries with very low remaining voltage. CHARGES VERY FAST plus ELIMINATES THE NEED TO DISCHARGE: charge standard batteries in minimum 3 min., max. 1 to 4 hrs, depending on mA/h rating. Partially empty batteries are just topped up. Batteries always remain cool; this increases the total battery life and also the battery’s reliability. DESIGNED AND MADE IN AUSTRALIA For a FREE, detailed technical description please Ph (03) 6492 1368; Fax (03) 6492 1329; or email smartfastchargers<at>bigpond.com 2567 Wilmot Rd., Devonport, TAS 7310 Truscott’s • RESELLER FOR MAJOR KIT RETAILERS • PROTOTYPING EQUIPMENT • COMPLETE CB RADIO SUPPLY HOUSE • TV ANTENNA ON SPECIAL (DIGITAL READY) • LARGE RANGE OF ELECTRONIC COMPONENTS Professional Mail Order Service is always constant and is equal to 50kΩ + 500Ω = 50,500Ω. As you can see, as the coarse 50kΩ control is wound up, less of the top element is in circuit while more of the bottom element comes in, thus keeping the overall resistance constant. The result is a very consistent fine and coarse control operation. The circuit could be used with the constant current load featured in Circuit Notebook in the February 2000 issue. It is also equally applicable to the Li’l PowerHouse 40V 1A Power Supply described in June 2000 and in this month’s issue. Karl Sundberg, Ashfield, NSW. ($25) Truscott’s Amidon Stockist ELECTRONIC WORLD Pty Ltd ACN 069 935 397 Ph (03) 9723 3860 Fax (03) 9725 9443 27 The Mall, South Croydon, Vic 3136 (Melway Map 50 G7) email: truscott<at>acepia.net.au www.electronicworld.aus.as JULY 2000 71 Motech MT-4080A LCR meter Some digital multimeters have facilities for testing inductance, capacitance and resistance but none really do a good job for all three, particularly as far as inductance is concerned. This is where the Motech MT-4080A LCR meter comes into its own. T HE MT-4080A is a multimetersized instrument with a large liquid crystal display and eight pushbuttons on its control panel. As well, there is a three-way socket with large contacts to take the measurement adaptors. Of course, some components with suitable leads can be plugged straight in but most component measurements will be taken using one of the adaptors. All told, up to 10 component par ameters can be measured: AC impedance and DC resistance from zero up to 9999MΩ; serial and parallel inductance from 0.000µH up to 9999H; serial and parallel capacitance from 0.000pF to 9999F; equivalent series resistance (ESR) from zero to 9999Ω; Dissipation factor (for capacitors) from 0 to 9999; Quality factor (for inductors) from 0 to 9999; and phase angle from -180° to + 180°. 72 Silicon Chip Not only can all these parameters be measured but you can also use one of five test frequencies: 100Hz, 120Hz, 1kHz, 10kHz and 100kHz. The two lower frequencies are important when measuring ESR of electrolytic capacitors while 100kHz is important when measuring small inductors and dissipation factor in the smaller capacitors. At most times though, the chosen test frequency is likely to be 1kHz. The test voltage level is also select able, at 1V, 250mV or 50mV RMS or 1V DC (for DC resistance measurements). Furthermore, if you are making measurements on a component that is varying, you can select fast or slow measurement speeds: 2.5 or 4.5 meas urements/second. The LCD panel will show two par ameters for each measurement, plus the signal level and frequency. For example, when measuring a capacitor it will display the capacitance in pF, nF, µF or F (Farads) plus the Dissipation factor or ESR. Similarly, for an inductor, it will display the inductance in µH, mH or H (Henries) plus the Q or ESR. Accuracy of the MT-4080A is quoted as ±0.2%. The instrument also has a range hold and relative modes which can be handy when selecting components against a standard value. Two adaptors are available for measurements plus a shorting bar attachment. The first adaptor is a 4-wire probe for surface mount components while the second is a 4-wire probe for testing standard leaded components. Power comes from two AA cells which may either be alkaline or rechargeable NiMH. A constant current charger is also supplied. All told then, the Motech MT-4080A is a well-thought out instrument that is very straightforward to use. We used it in our laboratory for several weeks and found it a very reliable unit. The MT-4080A is priced at $1142 plus GST. For further information, contact Westek Industrial Pro ducts, Unit 2, 6-10 Maria Street, Laverton North, 3026. Ph (03) 9369 8802; fax SC (03) 9369 8006. JULY 2000 73 PRODUCT SHOWCASE Altronics’ “Jenny Craiged” plugpacks Once you have a plugpack in a double power point, it’s often difficult (and sometimes impossible) to get anything else into the other outlet – let alone a second plugpack. Altronics Distributors claim they placed their new super-slim plugpacks on a strict diet to overcome this problem – and the results are plain to see. Two of the “PowerTran” 12V/ 500mA DC plugpacks (model M 9272) can easily fit side-by-side in a standard double outlet while the larger 16V/1.5A AC plugpack (model M 9332) still leaves enough space for another 3-pin plug to be inserted into the other socket. The M 9272 plugpacks, by the way, measure 43 x 86 x 60mm (w x h x d). All are Energy Authority approved and are designed for vertical mounting. These sell for $14.95 (pre GST). One point we did notice is that unlike most plugpacks (which are welded or glued), these are held together with tamper-proof screws. Of course we couldn’t resist the temptation to undo a tamper-proof screw so we opened one up… revealing the 16V AC model has plenty of space inside for a rectifier/filter/regulator if you so wished. This would also make them extremely attractive to the OEM market. There are several models in the range covering the vast majority of applications – DC and AC models of various output voltages and capacities, a couple of switchable models and even a regulated supply or two. For more information contact Alt-ronics on 1800 999 007 (Perth (08) 9328 1599), or visit their website www. altronics.com.au Toroidal transformers for recent SILICON CHIP audio projects Amongst their extensive range of transformers, Harbuch Electronics have available a number of toroidal models specifically made to suit recent SILICON CHIP audio projects. Of particular interest is the transformer to suit the recent 100W per channel stereo amplifier featured in the March and May issues. This transformer is rated at 300VA and has two 35V<at>2.25A + two 50V<at>0.1A windings as specified in the article and sells for $60.45. Harbuch also have 80VA and 160VA models with two 21V<at>1.9A (or 3.8A) to suit the ultra low distor74 Silicon Chip tion class-A amplifier featured in the July and August 1998 issues. These transformers sell for $35.45 and $42.50 respectively or a 160VA low flux model with flux band sells for $65.90. Finally, a whopping 800VA model with two 57 V<at> 7A windings to suit the 500W mono amplifier (August-Oct ober 1997) sells for $134.50. Harbuch Electronics may be contacted on (02) 9476 5854; fax (02) 9476 3231. All prices quoted above are pre-GST so you will need to contact Harbuch for latest GST-inclusive pricing. Security screwdriver set from Jaycar More often than not these days, manufacturers try to make life difficult when we want to remove screws. They use a variety of tamper-proof and tamper-resistant models to try to keep the lid on – when we want it off. In service work, making modifications or just because we want to see what’s inside, there have been many occasions in the past when we’ve been stymied by security screws. Not any more! That’s where this screwdriver set from Jaycar comes in incredibly handy. It contains bits which will fit most of the commonly-used security screws found today. There are Torx and tamper-proof Torx, Tri-Wing, pin-drive, hex (allen), security hex and pin drive, along with half a dozen standard sockets from 4 to 8mm, a magnetic bit holder and a screwdriver handle, all housed in a plastic case with see-through lid so you can instantly check to see if any bits have gone west. The case itself is only 120 x 50 x 90mm so it won’t take up a lot of room in your tool box. But it could save your bacon one day! All of the bits and sockets can also be used in power screwdrivers or drills. It’s one very handy set (we used it to remove the tamper-proof screws in the plugpacks elsewhere on these pages!) The “Royal Flush” set is just one of the specialised bit sets stocked in Jaycar stores. This one (Cat TD2037) sells for $18.95 (inc GST) and is also available by mail order or via Jaycar’s website, www.jaycar.com.au Questronix computer-to-video conversion and computer video switching units Quest Electronics have many video editing, titling, processing and conversion products but there is one that will gladden the heart of anyone who has ever had to make a presentation using computer-based information. . . only to find that they cannot display such information on large screen or projection TV systems. While many of the high performance (read high price!) video projectors will accept graphics or images from a PC, a significant proportion won’t. That’s where the fully imported CORIOscan Connect will help out. Not only will it convert a PC or Mac video output to a variety of TV-type formats (composite video, S-Video and RGB, switchable between NTSC and PAL) it as flicker reduction for a super-stable image on TV, has quick adjustment for overscan and freeze, allows 2x zooming and panning and works up to a resolution of 1600 x 1200 (although 1024 x 768 is recommended). Automatic or manual control is available. A full-function remote control is included which gives you control over all of these functions and many more, while a loop-back port is provided so you can still use your computer’s VGA monitor. No special driver software is required – you simply connect the system up, select the required mode and you’re ready to start the display. The CORIOscan Connect is housed in an attractive plastic case measuring 100 x 200 x 30mm. The rear panel houses the power input socket (12V DC <at> 300mA; plugpack included), the PC input socket, PC loop output socket and the RGB, S-Video and Composite Video output sockets. And while on the subject of video processing equipment Quest Electronics have also released a locally designed and manufactured Multimedia Switcher which will not only switch the video graphics (VGA/SVGA/XGA etc) from three personal computers to a single monitor or projector but also their stereo audio outputs to a single pair of speakers or stereo power amplifier. Housed in a one-unit 19-inch rack mounting aluminium case, the unit is designed to handle large presentations Affordable digital camera Last month we told you about the $4600 Sony digital camcorder/still camera. If that one is a bit out of your price range (it is out of ours!) then this little digital camera from Dick Smith Electronics might be more to your liking! At just $147 (pre GST price) the D-CAM digital camera has 256 x 256 pixel resolution, 24bit true colour image quality and the ability to store up to 15 pictures. It weighs just 100g and comes with Arcsoft Photostu-dio software, compatible with Windows 95/98. The camera is ideal for students who want to include colour pics in their school assignments or for anyone who wants to send images over the Internet. It is available from all Dick Smith Electronics stores (includi n g P o w e rHouse stores), via DSE Direct Link mail orders (1300 366 644) or via the Dick Smith webs i t e , w w w. dse.com.au or productions where the inputs can come from a variety of sources. Four push-button switches with indicator LEDS on the front panel select either standby or the computer source, or a remote control can be used with a D-socket on the rear panel provided for the purpose. In the standby mode the sync from input one is sent to the output but the R,G and B signals are blanked, resulting in a stable, black screen. Audio is also disconnected in standby mode. Each computer input can be separately monitored at the same time as the buffered main output carries the selected input. This output can drive long 75W cables without ringing or smearing. The unit is mains powered For more information on these, or any of the large range of video processing products available through Quest Electronics, contact them on (02) 9477 3596; fax 02 9477 3681 or visit their website at www.questronix. com.au/~questav TOROIDAL TRANSFORMERS FOR SILICON CHIP AMPLIFIERS 15W CLASS A AMPLIFIER 80VA for single channel monoblock 240:2x21V/1.9A 160VA for amplifier as published 240:2x21V/3.8A 160VA low flux design + flux band 240:2x21V/3.8A 160VA low flux design + flux band 240:2x42Vct/1.9A ULTRA LOW THD 100W AMPLIFIER 160VA for single channel monoblock 240:2x35V/2.25A + 2x50V/0.1A 300VA for dual channel amplifier 240:2x35V/4.5A + 2x50V/0.1A $35.45 $42.50 $65.90 $74.40 $50.70 $60.45 500W MONO AMPLIFIER, as published 800VA 240:2x57V/7A $134.50 All prices include WST. Freight extra. HARBUCH ELECTRONICS PTY LTD Ph 02 9476 5854 Fx 02 9476 3231 JULY 2000 75 Hotter Hot Chips : new micro development board Back in the February 2000 issue we reviewed the “Hot Chip” starter kit, an easy way to get into playing with microcontrollers. Now there’s a new Hot Chips starter kit from the same people – Investment Technologies Pty Ltd – and they haven’t been sitting on their hands for six months! For a start, the new model (reproduced same-size below) is much more “user friendly”. The original (ABC Mini) was a tiny PC board which basically had to be hardwired to a development board. The ABC Maxi is much larger (120 x 72.5mm) with many new features. There’s not only tons of room for mounting components or “breadboarding” (a 20 x 12 matrix of plated-through holes at one end of the board), there are several PC-mounting sockets for the 20mA (sinking) I/O connections, (bi-directional with internal pullup resistors), a number of header pin sets for programming, a socket to suit an LCD display, a 3.5mm speaker socket for sound output and four output MOSFETs capable of driving 8A loads each and 4 opto-isolated ouputs. And that’s not all! Physically the board is rather different, not the least because the Atmel AVT AT90S8535 chip is changed from a 44-pin SMD device to a 40-pin PDIP package in a socket. Clock speed is still 8MHz but the new model is said to have slightly faster capabilities than the old. There is also extensive software included although you can use your own software if you wish. A serial (RS232) connector is provided to allow interfacing to any PC via a standard 9-way “straight through” cable. RTS and CTS is available. There is also a programming connector which connects to the parallel port and on-board RS485 circuit with 4-pin screw terminal connection. Also included is easily programmable software: a True Basic Compiler, Assembler, Programming with on-screen results and a communications package. The software runs on Windows 3.11 to Windows ’98. A DOS version compiler and assembler is also supplied for diehard DOS fans. This user friendly software inter- “Real flat” monitor from Philips The new Philips 109P 19-inch “real flat” monitor is claimed to deliver a more natural, comfortable view with no distortion and drastically reduced reflection. The monitor incorporates Philips’ proprietary “Image Clear Enhancement” technology which is said to have several technological innovations, including a flat aperture grille tube and aspecial inner surface on the tube, designed so that the screen appears flat from a distance of 75100cm. The tube also incorporates an ex76 Silicon Chip tremely high contrast coating for enhanced colours and whiter whites. Maximum resolution of the screen is 1920 x 1440 with a flicker-free display of 1280 x 1024 at up to 103Hz. The screen has an actual viewing area of 18 inches diagonal. An Auto Calibrate function is said to extend the life of the monitor by up to 32%. It is available through authorised Philips resellers. For more information contact Philips Electronics, freecall 1800 658 086 or their website at www.philips.com.au/ pcperipherals faces with all of the required tools on either this or the earlier board to enable you to get going quickly. Included in the software is a Basic Compiler - Optimised for the AVR Boards; Assembler - With C like mathematics; Programming With on screen results and help; a Comms Package; a full help system with the option of modifying and adding your own notes; a DOS Version Assembler and Basic Compiler The Basic Compiler can also be purchased separately or a trialware version is downloadable from the ‘net. Like the earlier version, the new board is available from Dick Smith Electronics stores throughout Australia, PowerHouse stores and mail order service. Price is $293 inc GST (Cat K-1432). Yokogawa SignalExplorer: 500MHz, 1GS/sec The new SignalExplorer DL7100 from Yokogawa is specifically designed for high-speed extraction and screen display of desired information from large volumes of captured data. It has 4 channels, a 500MHz bandwidth and a large TFT colour display and with its sampling rate of 1GS/sec and up to 2M words (or 8M words) of memory a faster sampling rate and complete waveform acquisition is assured. The DL7100 also features a new Data Stream Engine (DSE) IC, also designed to handle large amounts of data and provide fast screen update rates. This new DSE, combined with enhanced triggering functions and an “all points display” technique which plots all data points without compression, makes it easy to capture abnormal signals such as high-speed surges. The display is updated 30 times per second even when using 1M word of memory and the all-points display. The oscilloscope also has four analog inputs plus an additional 16 logic inputs available as an option. Its history memory function can save up to 2000 previous acquisitions, making it possible to store waveforms with events not even covered by trigger settings. An optional built-in printer records waveforms and other data and the ’scope will also output data to a colour printer or PC via its comms port. Data viewing and reporting is made simple with the Yokogawa Waveform Viewer software supplied. For more information contact Yokogawa Australia Pty Ltd on (02) 9805 0699; fax (02) 9888 1844 or email measurement<at>yokogawa. com.au New Tacho and Voltmeter kits from DSE According to Dick Smith Electronics, projects for cars are always among the most popular in their stores. So when SILICON CHIP published a digital voltmeter (February 2000) and a digital tacho (April 2000) specifically for in-car use, they were delighted. Recently they were telling us how good their kits had turned out, promising to send over a couple of built-up version for us to have a look at. Now we know why they are so happy with them. The kits are every bit as good as the originals. No, that’s wrong. They’re better! They look very smart with their silk-screened front panels – we’re just a bit jealous that it’s not viable to silk-screen our prototypes. Inside, the kits are also very professionally prepared with screened and masked PC boards. The instructions, too, have been re-written with the novice in mind. OK, DSE Kit Department, we’re impressed! The kits are available at all DSE stores, Power-House stores or via mail order or their website: www.dse. com.au 3Com’s AirConnect: 11Mbps wireless LAN 3Com has announced the availability of its new AirConnect wireless LAN system, offering speeds of up to 11Mbps without a physical (ie, wired) connection. Wireless LANs have been around for some time now. While significantly more expensive than their cable-based counterparts they offer some significant advantages. For example, in old buildings cabling can prove difficult, if not impossible. A wireless LAN eliminates the need for cabling. Large institutions which may be spread over several buildings or even several areas – universities and colleges, schools, hospitals and the like – can also benefit from a wireless LAN system. And of course with more and more people using notebook com- puters instead of a fixed workstation, being able to stay connected to the LAN wherever they are situated makes a lot of sense. 3Com’s AirConnect system is made up of wireless access points, PC cards and the software and firmware to drive it. Access points are fixed to a ceiling or wall and act as a bridge between the wired network and up to 63 simultaneous wireless PC or laptop/ notebook users. AirConnect also lets users switch between the LAN, modem and wireless environments based on where they are situated. Users can also choose different network resources such as printers, etc. A number of features make AirConnect unique. Its Site Survey utility, for example, enables IT professionals to identify dead spots and address them before installation. Its Dynamic Access Mobile Connection Manager is a set of tools which simplifies wireless connectivity to monitor strength, signal quality and data rate, while the PowerBASE-T module powers the access points via the installed Ethernet cable, eliminating the need for power supply wiring. AirConnect has a starter pack which includes an access point, three PC cards and the management software for around $2700. For more information, contact any 3Com distributor or 3Com Australia Pty Ltd, Level 13, 65 Berry St North Sydney NSW 2060. Freecall 1800 644 606, or visit the website www.3com.com SC JULY 2000 77 DON’T UTER COMP MISS OMNIBUS THE ’BUS! www.siliconchip.com.au SILICON CHIP’S 132 Pages $ 95 * 9 ISBN 0 95852291 X 9780958522910 09 9 780958 522910 IN LINCLUDES FEA U TUR X E A collection of computer features from the pages of SILICON CHIP magazine Hints o Tips o Upgrades o Fixes Covers DOS, Windows 3.1, 95, 98, NT o RT Do you feel a little “left behind” by the latest advances and developments in computer hardware and software? Don’t miss the bus: get the ’bus! THIS IS IT: The computer reference you’ve been asking for! SILICON CHIP's Computer Omnibus is a valuable compendium of the most-requested computer hardware and software features from recent issues of SILICON CHIP magazine - all in one handy volume. Here's just a sample of the contents: Troubleshooting your PC: what to do when things go wrong NO Choosing, installing and taming computer networks AVA W Upgrading and overclocking CPUs DIRE ILABLE C Hard disk drive upgrades, tune-ups and tips SILIC T FROM Windows 3.1, 95, 98 and NT tips and tricks ON just $ CHIP The Y2K Bug - and how to swat it 125O* INC All about Linux GST & P& P And much more!!! ORDER NOW: Use the handy order form in this issue or call (02) 9979 5644, 9-5 Mon-Fri with your credit card details. * Price includes GST 09 VIDEO PROCESSING MADE EASY... Whether you’re an exhibition or display specialist, a Government department, a school or religious body, a corporate A/V department or even an advanced video enthusiast, you’ll find plenty to choose from in the huge range of quality QUESTRONIX video and audio processing equipment. It will make your life a lot easier and your work a lot smarter, a lot more professional . . . W! ! NE W NE CDM-830T Auto Video Standards Converter GFX3 Multimedia Switcher (VGA) VCC3020 Hi Res Video Processor/Corrector CORIOSCAN Connect Converter At last! Convert anything to anything - with 2 inputs, Y/C & CV, AGC, bars, timebase correction, picture adjustments, Genlockable. Professional Unit. For presentations, displays, etc. Takes any of three VGA/SVGA/XGA + audio inputs (each with own monitor), switches via front panel or remote control. 1U rack mount. 4 video (Y/C & CV) and stereo audio inputs. 2 sets of outputs. Adjustable R,G,B, colour, brightness, detail. Also fade, neg image, split screen and more! High quality automatic scan converter from PC monitor output (VGA/SVGA/XGA) with own monitor output to PAL or NTSC format (CV, Y/C or RGB output). Audio isolators, interfaces, distribution amps VGA splitters, amplifiers, switchers & converters Video distribution Amplifiers Video Switchers Video Editors Video Titlers Video Processors Video Stabilisers Video Mixers Video Timebase Correctors Video Standards Converters Video Adaptors Video Isolators VCRs and Tvs A/V Cables Long VGA Cables VISIT OUR WEBSITE -- www.questronix.com.au -- MONTHLY SPECIALS Quest Electronics Pty Limited, ABN 83003501282, trading as QUESTRONIX Showroom: Postal: Phone: email: 2/1 Leonard St Hornsby NSW (by appt. only) PO Box 548, Wahroonga NSW 2076 (02) 9477 3596 Fax: (02) 9477 3681 questav<at>questronix.com.au ADEM Compac II – A Very Smart Security System Product Review by Ross Tester D espite “everyone knowing someone” who has suffered the misfortune of a home or business burglary – often the someone is themselves – fitting a security system is still not one of life’s priorities to many people. If you did want to fit a system, until now, there have been two basic choices: do-it-yourself or pay a security company to do it for you. The first method scares many people, especially the non-technical, because of the difficulty of installation, particularly retro-fitting an existing building. All those cables to run and more particularly hide, sensors to fit, power to connect . . . it’s no wonder that people are scared off. And that’s before we start to consider renters who aren’t permitted to install security systems. The second method scares many people simply because of the cost. Sure, a lot of security companies heavily subsidise the alarm capital cost and the installation. But they get you in the end with the on-going costs: back-to-base monitoring is often expensive ($10-20 per week is not uncommon) and the charges for action after an alarm (and most likely a false alarm) can really hurt. Sending a patrolman around to inspect the premises is often not included in the basic monitoring price. Now there’s a new security product on the market, easily fitted and operated by even the most non-technical of people, which combines the best features of both the above methods at a fraction of the cost of either. It puts you back in control of the situation – monitoring the alarm and what action to take when you have checked it out. It’s called the ADEM Compac II and it comes from another company in the group which developed the Moving Message Display (see elsewhere in 80 Silicon Chip this issue) – 4D Systems Pty Ltd. In fact, we only discovered it by accident when we were talking to them about the display. We were so intrigued we just had to have a closer look … We’re talking about an alarm system which is completely free-standing and self-powered (though it can be run from a plugpack supply). The only installation you need to do is fix a couple of mounting screws to the ceiling, attach the unit and then plug a (supplied) phone plug into a phone socket. OK so far, but what does it do? The ADEM Compac II has a built-in Passive Infrared (PIR) detector which senses movement just like the PIR sensors used in most alarm systems these days. However, that is where the similarity ends. Instead of sounding an alarm, it then dials one of two pre-programmed phone numbers and delivers a message – one you record yourself. It could be along the lines of “This is 27 Smith Street. An intruder may be on the premises”. When the phone is answered (or the second phone, if it cannot get through to the first) the system delivers that message and then waits for a security ID number (which, of course, you program yourself!) to be entered via the phone dial pad. Then the really tricky bit starts! An inbuilt microphone listens for any sound being made at the premises – all without the possible intruder knowing about it. Now if you watch the movies, you’ll know that every good crook sneaks around without making a sound “…a fly’s foot-fall would be distinctly heard…” and all that (with apologies to Messrs Gilbert and Sullivan). In real life, crooks aren’t that clever. With rare exception, they reef out draws, pull contents out of cupboards, turn over furniture – in fact, they make quite a racket. And that’s what you can listen in on.You can remotely set the sensitivity of the unit to pick up even the faintest sound – say from a room or so away. You can even mask background sounds. And if you don’t like what you hear, you can do one of three things. (1) You can cut the call off and summon help – the Police, a neighbour, the 120kg guy down the street with the baseball bat . . . (2) You can remotely set off a siren within the ADEM Compac II which hopefully will scare the pants off the crook (or at least force a hasty retreat), or … (3) You can actually talk back, via the phone, to whoever is in the premises. Just imagine the impact of that on the poor crook. He (perhaps she) could be told anything you like. I seem to remember a movie some time ago where a burglar was startled by a voice from the dark (was it a parrot?): “Stay where you are and put your hands up,” it said. “Jesus is watching you.” “As if I care,” said the crook, starting to get brave. “You should,” said the voice. “Jesus is that dirty great big hungry Rottweiler standing in the doorway . . .” Enough friviolity – because this product is anything but frivolous. Each ADEM Compac II comes with its own coded infrared controller which is used to arm or disarm the system. Or if you wish, you can call the unit from any phone, fixed or mobile, anywhere in the world to enter your code and arm or disarm it. Just the shot if you’ve flown to Vladivostok and thought “damn, I forgot to turn on the alarm.” Not only that, you can remotely pro- The ADEM Compac II looks a lot like a smoke detector. But it’s a very clever alarm system in a similarsized package. It’s shown here with its remote control unit but it can also be armed and disarmed via any phone - from anywhere in the world! gram the unit, including change your code, change your message, adjust the audio sensitivity, change the numbers it will dial to and so on. Incidentally, there is no restriction on the type of phone it will call – mobile or fixed, local/STD or even international, with a number up to 18 digits long. (Seeing most mobile numbers are only 10 digits long and even the longest direct dial overseas numbers are only 15-16 digits that gives it pretty wide scope). Hey, it will even call you and tell you that the batteries are getting flat! All this, by the way, is housed in an attractive package which looks and mounts a lot like a smoke detector. At 180 x 180 x 35 mm, it’s about the same size, too. A comprehensive instruction manual is included as is the previously mentioned keyring-sized remote control. The system carries a 12 month warranty. At $699 (inc gst) it might sound expensive. But when you consider what you’re getting for your money (a complete system!) AND how much it will save you in the future (possibly even a big loss of property!) we think it’s a bargain; even more so when you consider not only the convenience (especially for those in rental properties) but also the technology involved. As you’ve probably gathered by now, we’re pretty impressed by the ADEM Compac II. It’s a great example of where technology and a worthwhile application marry perfectly. The ADEM Compac II is available through security specialists or direct from 4D Systems Pty Ltd, Suite 2, 3-5 Station Rd, Auburn NSW 2144. Phone (02) 9649-5065; Fax (02) 9649-4324. Their website is at www.4dsystems. com.au SC JULY 2000 81 VINTAGE TELEVISION By RODNEY CHAMPNESS, VK3UG The AWA P1 portable 11-inch B/W television set This month we have changed the heading on this article to reflect the change in subject material to television as we deal with one of the early portable TV sets from the valve era. Portable valve TVs are good collectables because they don’t take up a lot of space. Back in the valve black and white TV days, most sets were great lumbering beasts which often needed two hefty chaps to lift and shift them from place to place. Some were just moveable with one person providing they didn’t mind the risk of getting a hernia. As time went by a few small portable sets made their appearance in Australia. One was a General Electric – a set modified slightly from American standards and powered by an external 240V to 110V transformer. It was a beast to get at and as a result I took quite a dislike to servicing them. On the other hand, AWA produced a similar-sized set in the P1 series of the late 60s. It was easy to disassemble and get at, and with practice it was possible to replace a picture tube in just 15 minutes. It was a nice set to work on and it worked well too. I had one of these for quite a few years – in fact it was our one and only set. The drawback was that you needed binoculars to see the screen if you sat too far away! I sold it and a few years later bought it back again when I got interested in vintage radio and television. I also managed to get four more defunct units, so restoring at least one to working order was a good bet. As I suggested back in the November 1999 issue, if you intend to restore valve black and white television sets to work ing order it is desirable to have more than one available. The reason for this is that picture tubes, horizontal output transformers and deflection yokes in particular are virtually unobtainable. Restoration of television sets to working order is a rather different task to restoring valve radios but with care, there is no reason why this should not be just as successful. Restoring the P1 The AWA P1 before restoration. It is a good candidate for restoration since it does not take up a lot of space. 82 Silicon Chip Removing the cabinet back is a snap. The set was tipped onto its front with a blanket on the workbench protecting the front. The four Nylon screws securing the back were removed and the cabinet lifted upwards. The aerial terminal board was This rear view of set shows how the PC board swings out, allowing easy access to most items for service. unclipped from the turret tuner and the whole of the set was exposed; five minutes work at most. The set was sat upright and three screws around the edge of the printed circuit board were removed. The coaxial cable was unclipped from near the picture tube and the board swung out to gain access to most of the set, which can be seen in one of the photographs. A general clean-up and dusting out were in order. TV sets attract lots of dust due to the high voltage used on the picture tube; 11kV in this case. A number of grubby sections responded well to washing with a kerosene-soaked rag and now look good. I removed the valves and washed them in soapy water, then rinsed them in plain water. They come up well. I keep the bases of octal valves out of the water as it will get into the base and take some time to dry or may make a conductive path inside the base between pins; a good way to ruin a valve. The turret tuner was likely to need some attention on the channel change contacts, just as wave-change contacts in dual-wave radios often do. Two self-tapping screws hold the side panel/shield of the tuner in place and these were removed. With a rag soaked in contact cleaner I rubbed each of the exposed coil terminations along each channel biscuit to clean any muck off. All 13 biscuits were cleaned. Then CRC (or similar) lubricant/ cleaner was used to free up the small screw at the righthand end of each tuner biscuit. This screw is adjusted to set the fine tuning on each channel, so it needs to be free – they get rather tight when the grease congeals on them. Having cleaned up the turret tuner biscuit contacts, the shield was put back on the side of the tuner. I’ve never really found out why the coil assemblies used in the tuners for each channel are called biscuits. However, the early ones do look like small rectangular brown biscuits. (That’s why . . . Ed). I found that the speaker cloth had The AWA P1 rear view with the cabinet removed and the track side of the PC board exposed. been pushed back from the grille so I had to take the speaker out to gain access to it. This wasn’t the easiest job as the tuner had to be taken out too. It is attached to the set frame with three self-tappers, of which only two were easily accessible. The chassis/frame or whatever you call the metalwork supporting the set had to be separated from the front escutcheon and picture JULY 2000 83 This side view shows the turret tuner with its metal shield removed to give access to tuner channel change contacts and the biscuits. tube. Only two self-tappers hold the two sections together and these were removed. The channel-change knob was removed and the set moved back away from the picture tube a few centimetres – as far as the EHT lead would allow. The tuner screws were now all exposed and were undone and the tuner removed, to give access to the speaker mounting screws. They were removed and the speaker pulled back. The cloth was pushed back into place; just a few seconds work. I decided that the control potentiometers which are mounted in front of the speaker could do with a squirt of contact cleaner while I had all that section apart. Reassembling it all was the reverse of the disassembly procedure. However, before doing that I cleaned around the sections of the set now exposed, so that all sections ended up being clean. Circuit diagram It is most desirable to have a circuit diagram and any other information pertaining to the set. I am fortunate to have a reasonable supply of black and white TV circuits and information so I was able to look up and find all the necessary information on the P1 which covered four foolscap pages. This included the circuit with oscilloscope waveforms, a circuit of the 84 Silicon Chip tuner, parts list, a PC board layout and a description of how to go about various servicing activities. J & R Publications put out a series of loose leaf manuals over a period of several years from around 1960. These cover television sets, valve radios and Australian and overseas origin transistor receivers, in several different volumes. Careful inspection of the set did not reveal anything looking out of place or overheated. Most of the set uses polyester capacitors and knowing their reliability, it was not thought any problems should arise through them being faulty. Power was applied to the set with the cabinet back still removed. A raster came up on the screen, and then a weak picture appeared on the screen when I held one of the aerial/antenna terminals. But there was no sound except a low level buzzing noise. These are VHF-only sets so if there are no VHF TV stations nearby, a down converter or a VCR with a VHF output channel will be necessary if any TV signals are to be seen. Troubleshooting Now where do you start to look for troubles in a TV set with 13 valves? One of the good things about TV sets is that they are easier to sectionalise than a radio, just by observing what the set does or does not do. The fact that I could get a picture on the screen indicated that the power supply, tuner, video IF, video amplifier, picture tube, and the vertical and horizontal deflection circuits and the extra high voltage (EHT) were all working. What was left? The AGC circuit could have been faulty but the signal level I had was too weak to actuate it anyway. However, the likely culprits were the sound IF which comes off the output of the video amplifier and possibly the audio amplifier. I was able to inject some audio into the grid of the audio stage and got output, so it seemed likely the sound IF was faulty. I tried a fresh 6CS6 but with no improvement. Ah well, I’d better get serious about this. I looked at the circuit around the sound IF stage and noted the voltages I could expect to find. I looked at the PC board pattern in the information I had and started tracing where the various pins of the valve appear on the track side of the board. Most voltages appeared within the normal expected range but the plate showed a big fat zero. Testing the other side of the plate feed resistor revealed 180V, which is normal. The 470kΩ plate resistor had gone open circuit. This was replaced and the set tried again. Off-station we had glorious hiss and on-station, once a good antenna was connected and the fine tuning adjusted, we had good clean sound. In reality this was the only electronic fault in the set. Lucky me. I adjusted the fine tuning on the only VHF channel available and the video recorder output channel, check ed the vertical hold and the other controls, and the set worked just as it should. I have a suspicion that the 6GK5 triode RF amplifier may be a little weak, and when I get hold of a spare I’ll try it, but at the moment it is quite satisfactory. Note that did say a triode RF amplifier. These caused many problems for early radio experimenters and here they are being used successfully at VHF from 45-222MHz. Triodes are low noise so work much better as an RF amplifier at VHF but they do have to be neutralised. Luckily, the picture tube was in good order with no sign of flaring and overall the set worked like it had years ago The rabbit ears telescopic antenna was broken in the set, so the easiest method of replacing it was to swap the back off another set which had an intact antenna. This certainly was an easy job. The cabinet was a bit grubby too so a dose of detergent, warm water, a small scrubbing brush, a cloth and some elbow grease had the cabinet looking quite good. Scuff marks and other marks in the plastic are not easily removed regrettably, but it can be clean. (Editor’s hint: try car polish). Once scrubbed up, a wipe of with a clean wet rag will leave the cabinet free of detergent and dirt. Set summary The AWA P1 series of small portable valve receivers were well thought out, relatively easy to service (picture tube change in 15 minutes), gave good pictures and were reliable. The only criticism of them is the sound IF system used – ie, the quad-rature detector. The limiter type After restoration, the set produced a good black and white picture. IF amplifier followed by the FM ratio detector was a far superior IF system in my opinion but a bit more expensive to put into the set. That said, the quality of the audio with the quadrature detector was quite OK as long as the signal coming SC in was of good quality. Restoration Tips For B&W TV Sets These tips are just a few to help you get into black and white TV restoration. There are not many of these sets left, so now is the time to start collecting even if restoration is not contemplated for a while. By taking it carefully and asking for help if needed, the restoration of our early TV history can be just as much fun as our radio restorations. (1) Try to obtain more than one example of the same chassis set. (2) Obtain a circuit diagram and any other information available on the receiver. (3) If this is your first go at restoring a TV set, enlist the aid of a fellow restorer or perhaps a retired TV serviceman for advice. (4) Providing the picture tube, deflection yoke and horizontal output transformer (and maybe the vertical output transformer too) are OK, the set should be quite restorable. If any of these three are faulty, another old set with these as good components will be necessary – otherwise it will be suitable as a static restoration (cabinet and general clean inside). (5) Replace all paper capacitors, taking particular note of the voltage ratings. Some values are critical, others non-critical as in radio receivers. (6) Check all resistor values (within reason) as many of them can be expected to go high or open-circuit. (7) When replacing components, particularly in the video IF and video amplifier sections, pay particular attention to maintaining the same lead dress, as this may affect picture quality. (8) Have a reasonable supply of valves on hand. Sometimes a valve won’t work in one circuit position but will work in another position. (9) Mark the chassis with the valve type alongside each socket, so that valves are not plugged into the wrong sockets. (10) If you are confident all has been done that can be done in the way of replacing faulty components, the set can be turned on. It is necessary to observe the HT line and the horizontal output valve. The rectifiers plates can glow red if they are thermionic types as can the horizontal output valve if things are not right. MOST IMPORTANT (11) DO NOT adjust IF and tuner tuning slugs unless you know exactly what you are doing and have suitable test equipment. TV receiver IF and tuner sections can tolerate quite a bit of drift without giving a bad picture due to the broadband nature of the tuned circuits. The tuner and video IF stages have a bandwidth of at least 7MHz, not 10kHz like the AM radio IF bandwidth. (12) Treat old picture tubes like un exploded bombs, particularly the larger ones. If handling a picture tube, wear a leather apron, gloves and safety glasses for complete safety. (13) NEVER pick up a picture tube by the neck; this is a weak area where the glass is thinnest. Tubes can implode, doing enormous damage. It is rare but it does happen. JULY 2000 85 REFERENCE GREAT BOOKS FOR NEW NEW NEW NEW AUDIO POWER AMP DESIGN HANDBOOK INDUSTRIAL BRUSHLESS SERVOMOTORS From one of the world’s most respected audio authorities. The new 2nd edition is even more comprehensive, includes sections on load-invariant power amps, distortion residuals, diagnosis of amplifier problems, and much more. 368 pages in paperback. Designed as a guide for professionals and a module text for electrical and mechanical engineering students. A step-by-step approach covering construction, how they work, how the motor behaves and how it is rated and selected. It may only be a small book but it has outstanding content! 186 pages in hardback. By Douglas Self. 2nd Edition Published 2000 By Peter Moreton. Publ. 2000 85 $ VIDEO SCRAMBLING AND DESCRAMBLING for Satellite & Cable TV by Graf & Sheets SETTING UP A WEB SERVER If you've ever wondered how they scramble video on cable and satellite TV, this book tells you! Encoding/decoding systems (analog and digital systems), encryption, even schematics and details of several encoder and decoder circuits for experimentation. Intended for both the hobbyist and the professional. 290 pages in paperback. NEW 2nd By Simon Collin. Published 1997. 65 $ Edition 1998 TCP/IP EXPLAINED 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. 273 pages, in paperback. 99 Assumes no prior knowledge of TCP/IP, only a basic understanding of LAN access protocols, explaining all the elements and alternatives. Combines study questions with reference material. Examples of network designs and implementations are given. 518 pages, in paperback. THE CIRCUIT DESIGNER’S COMPANION $ 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. 302 pages, in paperback. 65 LOCAL AREA NETWORKS: An Introduction to the Technology ELECTRIC MOTORS AND DRIVES Want to become more familiar with local area networks (LANs) without facing the challenge of a 400-page text? . Gives familiarity with the concepts involved and provides a start for reading more detailed texts. 191 pages, in paperback. For non-specialist users – explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction, stepping, synchronous and reluctance motors. 339 pages, in paperback. By Austin Hughes. Second edition published 1993 (reprinted 1997). By John E. McNamara. 2nd edition 1996. O R D E R H E R E 69 $ By Tim Williams. First published 1991 (reprinted 1997). By Philip Miller. Published 1997. $ 99 $ NEW NEW NEW NEW 69 $  AUDIO POWER AMPLIFIER DESIGN...............................$85.00  INDUSTRIAL BRUSHLESS SERVO MOTORS..................$99.00  VIDEO SCRAMBLING/DESCRAMBLING..........................$65.00  TCP/IP EXPLAINED.........................................................$99.00  LOCAL AREA NETWORKS...............................................$69.00  SETTING UP A WEB SERVER..........................................$69.00  THE CIRCUIT DESIGNER’S COMPANION........................$65.00  ELECTRIC MOTORS AND DRIVES...................................$65.00  UNDERSTANDING TELEPHONE ELECTRONICS.................$59.00  AUDIO ELECTRONICS.....................................................$85.00  GUIDE TO TV & VIDEO TECHNOLOGY............................$59.00  EMC FOR PRODUCT DESIGNERS...................................$99.00  THE ART OF LINEAR ELECTRONICS...............................$88.00  INTERNET HOME PAGES MADE SIMPLE........................$27.00  DIGITAL ELECTRONICS ..................................................$65.00  ESSENTIAL LINUX..........................................................$85.00 ORDER TOTAL: $...................... TAX INVOICE 65 $ Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ____________________________________ Postcode_____________ Daytime Phone No. (______) __________________________________ STD Email___________________<at>_________________________________  Cheque/Money Order enclosed OR  Charge my credit card –  Bankcard  Visa Card  MasterCard No: Signature_________________________Card expiry date______/______ PLUS P&P (if applic): $.............. TOTAL$ AU.................... ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. ALL PRICES INCLUDE GST BOOKSHOP WANT TO SAVE 10%? SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL BOOK PURCHASES! ENQUIRING MINDS! (To subscribe, see page 53) ALL PRICES INCLUDE GST UNDERSTANDING TELEPHONE ELECTRONICS THE ART OF LINEAR ELECTRONICS By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. $ 59 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. AUDIO ELECTRONICS $ 88 By Lilian Hobbs. First published 1996. Second edition 1999. 85 $ 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. DIGITAL ELECTRONICS – A PRACTICAL APPROACH GUIDE TO TV & VIDEO TECHNOLOGY 59 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. EMC FOR PRODUCT DESIGNERS By Tim Williams. First pub lished 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. P&P AUST: Add $A5.50 per book – Orders over $100 P&P free in Australia. NZ: Add $A10 per book, $A15 elsewhere 27 $ By Richard Monk. Published 1998. By Eugene Trundle. First published 1988. Second edition 1996. $ 00 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. 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. By John Linsley Hood. First published 1993. NEW SECOND EDITION 1998. $ 65 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 ESSENTIAL LINUX By Steve Heath. Published 1997. 99 $ 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. 85 $ 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 Silicon Chip Back Issues April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; Amtrak Passenger Services. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Build A Windows-Based Logic Analyser. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. June 1991: A Corner Reflector Antenna For UHF TV; Build A 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +5V to ±15V DC Converter; Remote-Controlled Cockroach. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. December 1993: Remote Controller For Garage Doors; Build A LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Car Speed Alarm. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple Electronic Die; A Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: A Low-Cost 3-Digit Counter Module; Build A Simple Shortwave Converter For The 2-Metre Band; The Bose Lifestyle Music System (Review); The Care & Feeding Of Nicad Battery Packs (Getting The Most From Nicad Batteries). October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. November 1990: Connecting Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; 6-Metre Amateur Transmitter. December 1990: 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. ORDER FORM Please send thethe following back issues: Please send following back issues: December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; The MIDI Interface Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags In Cars – How They Work. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Engine Management, Pt.6. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Po August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Build A Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. ____________________________________________________________ Enclosed is my cheque/money order for $______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 88 Silicon Chip Note: prices include postage & packing Australia ....................... $A7.70 (incl. GST) Overseas (airmail) ............................ $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. Email: silchip<at>siliconchip.com.au November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); How To Plot Patterns Direct to PC Boards. December 1996: Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote Control System for Models, Pt.1; Index to Vol.7. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (For Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Preamplifier. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; Remote Control System For Models, Pt.2. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Cathode Ray Oscilloscopes, Pt.7. April 1997: Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. December 1998: Protect Your Car With The Engine Immobiliser Mk.2; Thermocouple Adaptor For DMMs; A Regulated 12V DC Plugpack; Build Your Own Poker Machine, Pt.2; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Glider Operations. January 1999: The Y2K Bug & A Few Other Worries; High-Voltage Megohm Tester; Getting Going With BASIC Stamp; LED Bargraph Ammeter For Cars; Keypad Engine Immobiliser; Improving AM Radio Reception, Pt.3; Electric Lighting, Pt.10 February 1999: Installing A Computer Network (Network Types, Hubs, Switches & Routers); Making Front Panels For Your Projects; Low Distortion Audio Signal Generator, Pt.1; Command Control Decoder For Model Railways; Build A Digital Capacitance Meter; Remote Control Tester; Electric Lighting, Pt.11. March 1999: Getting Started With Linux; Pt.1; Build A Digital Anemometer; 3-Channel Current Monitor With Data Logging; Simple DIY PIC Programmer; Easy-To-Build Audio Compressor; Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12. May 1997: Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. April 1999: Getting Started With Linux; Pt.2; High-Power Electric Fence Controller; Bass Cube Subwoofer; Programmable Thermostat/Thermometer; Build An Infrared Sentry; Rev Limiter For Cars; Electric Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft. May 1995: Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1997: PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Cathode Ray Oscilloscopes, Pt.10. May 1999: The Line Dancer Robot; An X-Y Table With Stepper Motor Control, Pt.1; Three Electric Fence Testers; Heart Of LEDs; Build A Carbon Monoxide Alarm; Getting Started With Linux; Pt.3. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/ Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; How To Identify IDE Hard Disk Drive Parameters. September 1995: Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Keypad Combination Lock; The Vader Voice; Jacob’s Ladder Display; Audio Lab PC-Controlled Test Instrument, Pt.2. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Transverter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2. March 1996: Programmable Electronic Ignition System; Zener Diode Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Audio Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. May 1996: Upgrading The CPU In Your PC; High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluorescent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: Adding A Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. June 1999: FM Radio Tuner Card For PCs; X-Y Table With Stepper Motor Control, Pt.2; Programmable Ignition Timing Module For Cars, Pt.1; Hard Disk Drive Upgrades Without Reinstalling Software; What Is A Groundplane Antenna?; Getting Started With Linux; Pt.4. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home. July 1999: Build The Dog Silencer; A 10µH to 19.99mH Inductance Meter; Build An Audio-Video Transmitter; Programmable Ignition Timing Module For Cars, Pt.2; XYZ Table With Stepper Motor Control, Pt.3; The Hexapod Robot. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget; Win95, MSDOS.SYS & The Registry. August 1999: Remote Modem Controller; Daytime Running Lights For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting, Pt.14; DOS & Windows Utilities For Reversing Protel PC Board Files. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Build A Musical Doorbell; Relocating Your CD-ROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1997: Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. September 1999: Automatic Addressing On TCP/IP Networks; Wireless Networking Without The Hassles; Autonomouse The Robot, Pt.1; Voice Direct Speech Recognition Module; Digital Electrolytic Capacitance Meter; XYZ Table With Stepper Motor Control, Pt.5; Peltier-Powered Can Cooler. October 1999: Sharing A Modem For Internet & Email Access (WinGate); Build The Railpower Model Train Controller, Pt.1; Semiconductor Curve Tracer; Autonomouse The Robot, Pt.2; XYZ Table With Stepper Motor Control, Pt.6; Introducing Home Theatre. November 1999: USB – Hassle-Free Connections TO Your PC; Electric Lighting, Pt.15; Setting Up An Email Server; Speed Alarm For Cars, Pt.1; Multi-Colour LED Christmas Tree; Build An Intercom Station Expander; Foldback Loudspeaker System For Musicians; Railpower Model Train Controller, Pt.2. February 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. December 1999: Internet Connection Sharing Using Hardware; Electric Lighting, Pt.16; Index To Volume 12; Build A Solar Panel Regulator; The PC Powerhouse (gives fixed +12V, +9V, +6V & +5V rails); The Fortune Finder Metal Locator; Speed Alarm For Cars, Pt.2; Railpower Model Train Controller, Pt.3. April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Adjustable Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator; Build A Laser Light Show; Understanding Electric Lighting; Pt.6; Jet Engines In Model Aircraft. January 2000: Spring Reverberation Module; An Audio-Video Test Generator; Build The Picman Programmable Robot; A Parallel Port Interface Card; Off-Hook Indicator For Telephone Lines; B&W Nautilus 801 Monitor Loudspeakers (Review). May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. February 2000: Build A Multi-Sector Sprinkler Controller; A Digital Voltmeter For Your Car; An Ultrasonic Parking Radar; Build A Safety Switch Checker; A Sine/Square Wave Oscillator For Your Workbench; Marantz SR-18 Home Theatre Receiver (Review); The “Hot Chip” Starter Kit (Review). June 1998: Troubleshooting Your PC, Pt.2; Understanding Electric Lighting, Pt.7; Universal High Energy Ignition System; The Roadies’ Friend Cable Tester; Universal Stepper Motor Controller; Command Control For Model Railways, Pt.5. July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem And Sorting Out Problems); Build A Heat Controller; 15-Watt Class-A Audio Amplifier Module; Simple Charger For 6V & 12V SLA Batteries; Automatic Semiconductor Analyser; Understanding Electric Lighting, Pt.8. August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory); Build The Opus One Loudspeaker System; Simple I/O Card With Automatic Data Logging; Build A Beat Triggered Strobe; A 15-Watt Per Channel Class-A Stereo Amplifier. September 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A WaaWaa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. October 1998: CPU Upgrades & Overclocking; Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. November 1998: The Christmas Star (Microprocessor-Controlled Christmas Decoration); A Turbo Timer For Cars; Build A Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Setting Up A LAN Using TCP/IP; Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. March 2000: Doing A Lazarus On An Old Computer; Ultra Low Distortion 100W Amplifier Module, Pt.1; Electronic Wind Vane With 16-LED Display; Glowplug Driver For Powered Models; The OzTrip Car Computer, Pt.1; Multisim Circuit Design & Simulation Package (Review). April 2000: A Digital Tachometer For Your Car; RoomGuard – A Low-Cost Intruder Alarm; Build A Hot wire Cutter; The OzTrip Car Computer, Pt.2; Build A Temperature Logger; Atmel’s ICE 200 In-Circuit Emulator; How To Run A 3-Phase Induction Motor From 240VAC. May 2000: Building the Ultra-LD Stereo Amplifier, Pt.2; Build A LED Dice (With PIC Microcontroller); A Low-Cost AT Keyboard Translator (Converts IBM Scan-Codes To ASCII); 50A Motor Speed Controller For Models; Dolby Headphone – Five Channels Of Surround Sound; What’s Inside A Furby. PLEASE NOTE: November 1987 to March 1989, June 1989, August 1989, December 1989, May 1990, February 1991, June 1991, August 1991, February 1992, July 1992, September 1992, November 1992, December 1992, May 1993, February 1996 and March 1998 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disk for $10 including p&p, or can be downloaded free from our web site: www.siliconchip.com.au JULY 2000 89 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Volume control for Plastic Power amplifier I have brought a kit from Jaycar Electronics for the Plastic Power amplifier which featured in the April 1996 issue of SILICON CHIP. It is rated at 175W into 4Ω loads. I want to put a volume control on this unit. I have been told to remove the 1kΩ input resistor from the board and replace it with a 1kΩ logarithmic pot. Can you let me know where the pot is to be installed? (G. T., via email). • The 1kΩ resistor should be left on the PC board and you should use a 50kΩ pot (not 1kΩ). Connect it the same way as we have in the Ultra-LD amplifier in the May 2000 issue. Erratic readings on PIC tachometer I’ve built the tachometer project in the April 2000 issue. It works fine when connected to my power supply and sinewave generator but when connected to my car’s ignition coil, the reading was not accurate and the least significant digit (100s) is always jumping a few digits. For example, the reading might be Engine immobiliser flattens the battery I bought the Engine Immobiliser kit as published in the December 1998 issue of SILICON CHIP and connected it to my 1997 Barina Swing. All voltages/currents were as per the article and the operation was OK after wiring. However, the car battery went flat overnight. I put in a new battery and that was discharged too. Otherwise the engine immobiliser seems to work OK. On the workbench, it draws only about 150mA intermittently. The car wiring was done by a qualified electrician (cost me $200 for the $30 kit!) and is very thor90 Silicon Chip 1200 RPM but it will jump to 1700, then 1300 then 1200 RPM; not stable at all. The reading is also higher than the actual RPM. The length of the wires connected to the tachometer has been reduced to only 15cm long. Can you advise? (T. V., via email). • You could try increasing the value of the .056µF capacitor following the 22kΩ ignition coil input resistor. This will damp down any oscillations from the ignition coil which may be causing the high count on the display. Try a 0.1µF capacitor as a first attempt. Reducing the value of the 47kΩ resistor between pins 3 of IC2a and pin 6 of IC1 to 22kΩ may also help. IR remote control with 30 keys I was reading about the remote controller for trains in the April 1992 issue (I know it’s ancient) and I would love to use the chips you used for infrared transmission/reception. These are the MV500, MV601 and the SL486 but I can’t find them anywhere. I am guessing they have been outdated, so could you please tell me the chips you would use for this same type of application today. I need to have about 30 keys oughly done. Are there any errors in the kit? (G. K., Wollstonecraft, NSW). • Almost certainly, your Engine Immobiliser is incorrectly wired to your vehicle. This is because the circuit should not draw current from the battery until the ignition is switched on. Your current measurements indicate that it is working correctly. Check that the supply to the hidden switch, S1, is from the fused side of the ignition supply and not from the battery side. In this way, when you set the ignition immobiliser, current will only be drawn from the battery when the ignition is switched on. on the keypad of the transmitter. (P. K., via email). • Have you seen our more recent design from the October, November & December 1999 issues? This uses a cheap remote from Oatley Electronics and has eight buttons in all. We don’t know of any chipset which will allow you to use 30 keys. Temperature control for vacuum forming I want some information on your 240V 5A motor controller kit published in September & November 1992 and also on your heater controller kit published in the July 1998 issue. I want to control the temperature on the heating elements in my home-made vacuum forming machine. Or do you have something more suitable? (S. A., via email). • We’re not sure how you wish to control the heating elements and whether they run from 240VAC or not? If they do, the heater controller described in July 1998, a zero-voltage switching design, is the right choice. If you are using a vacuum cleaner motor to produce the vacuum, the 5A motor controller is suitable; you can use it for any 240VAC brush-type motor. Load requirements for the Ultra-LD amplifier In your write-up on the ultra low distortion amp project in the March & May 2000 issues you recommend not using low impedance speaker loads because of increased distortion caused by current sharing imbalances in the output transistors. One fact you can be sure of in audio amplifier design is that the output load will be highly reactive over the audio frequency range. Even good speaker designs like the Vaf DC-7 provide a widely varying load, ranging between 4-17Ω with a nominal impedance of 6Ω. Have a look at http://www.vaf. com.au/dc7_spec.html How can we expect your amplifier design to behave when connected to such loads? Will distortion be the only issue or will there be other problems as well? (M. D., ANU, via email). • The Ultra-LD will handle nominal 6Ω and 8Ω loads OK but we don’t recommend 4Ω loads because as you point out, loudspeaker loads are highly reactive and they can dip to very low values. We wouldn’t recommend driving electrostatics either. Avoid stupidity with 240V speed controller I seek your advice concerning the 10A 240VAC speed con troller described in the November 1997 issue of SILICON CHIP. I have blown several BUP213s (usually owing to my own stupidity) and have noticed the aforementioned semiconductor usually fails before or at the same time as the 10A fuse blows. Consequently, I have wondered whether an IGBT upgrade might be the best option (as my stupidity is probably a permanent, but fortunately intermittent, factor!). Since the price of higher rated IGBTs appears to rise exponentially with their current ratings, would it not be feasible to connect two BUP213s in parallel? Of course, some physical modifications to the layout would be required, but nothing too challenging. Would any other component modification be required? (J. B., Burragate NSW). • We are intrigued as to what particular form of stupidity causes the BUP213 IGBT to blow. If you are intermittently stalling the power tool in question, we would expect the over-current limiting to take care of the situation. Perhaps you should check the circuit at low voltage, as described in the article. On the other hand, if you are making some sort of connection to the circuit while it is powered up, there is always the risk of blowing the BUP213 and other parts. Having said that, the BUP213 can be upgraded to a BUP314 which is a larger TO-218 package and has a current rating of 52A rather than 32A for the BUP213. These are available from Farnell Components; phone 1300 361 005. We don’t recommend parallel connection of IGBTs since they will not share the current equally. In an overload situation this might mean Insufficient signal from reluctor I have one problem with the Multi-Spark CDI system described in the September 1997 issue. I connected it up to a reluctor from a Chrysler and there is no output from the coil. Then I shorted out the wires for the pickup and got a spark from the coil. I then tried it on a Falcon XF with reluctor and it worked perfectly. The resistance on the Chrysler pickup is about 460Ω and on the XF it is about 1.2kΩ. I looked at the trigger input for the ignition system featured in the June 1998 issue and noticed there was a 2.2kΩ resistor in it but the equivalent resistor in the September 1997 circuit was 10kΩ. I made the change anyway but still no go. There doesn’t seem to be enough pulse from the Chrysler pickup. Can I modify the circuit so that it will work properly? (M. K., via email). • The reluctor signal is usually quite substantial at around 30V peak-to-peak and so the circuit that you blow one and then the other, within milliseconds of each other. Coolant alarm query I have built the Coolant Level Alarm from the June 1994 issue of SILICON CHIP and I feel that there is a problem with the connection of the “hot” side of the indicator lamp. Fig.1 has the connection between the 33Ω resistor and the anode of diode D2 but Fig.2 has the 12V and the lamp commoned. Which one is right? (D. H., via email). • Fig.2 is right; Fig.1 is wrong. This was noted in the Errata we published in the February 1995 issue. Multipurpose fast battery charger I’ve built the Multi-Purpose Battery Charger described in the February and March 1998 issues and it is not quite up to spec. I’ve tried it on a couple of 2.3A.h 12V SLA batteries and the charger only stays on FAST for about three seconds before switching to 100% should operate. The actual resistance of the reluctor coil does not indicate much since the output is dependent upon the strength of the magnet associated with the reluctor, the number of turns on the coil and the reluctor gap, as well as the rotational speed. The sensitivity of the reluctor trigger circuit can be increased by reducing the value of the 47kΩ resistor at the cathode of ZD5. This will reduce the level of current holding Q8 on when there is no signal from the reluctor. You could try using a 220kΩ trimpot and adjusting it until the circuit works or try various values from 68kΩ to 220kΩ. The 2.2kΩ resistor you refer to is used in the collector of the transistor and will not affect the sensitivity of the reluctor circuit. Either value could be used here. By the way, Chryslers are pretty old now; it is possible that the reluctor is faulty or you are using reversed connections to the circuit. Try swapping the reluctor leads. even though the battery voltage does not correspond to the “full” voltage. At a battery terminal starting voltage of 11.3V, the voltage across TP CELL and TP GND is 0.97V/cell but ramps up quickly during the initial 3-second period to about 1.8V, before stepping back to a steady 1.65V during the 100% stage. The charge terminates some time later but I’m guessing this issue relates to time-out rather than the batteries reaching full charge. Admittedly, they are older batteries so this might well be the problem. Do you know why the TP CELL voltage for a 12V SLA battery is not equal to the terminal voltage divided by six cells? I read something about scaling it back to a NiCd equivalent. I’ve downloaded a copy of the application notes from the Philips semiconductor site and this reading has prompted a couple of questions: (1) Given a 27kΩ Rref resistor on pin 20 and an 820pF capacitor on OSC/pin 14, I read from the chart that the oscillator frequency will be about 50kHz. This is consistent with your notes. However, reading across the chart, I get time-out periods of JULY 2000 91 600W DC-DC converter questions A few years back, I bought the 600W DC-DC converter kit from Jaycar in Perth and I didn’t have the time to start on it until recently. Before I start, I have some questions: (1) Do I need to upgrade the car’s alternator to a higher capacity? My present car is a 1600cc Toyota Corolla CSI. I think the output of the alternator is about 70A. (2) Will there be a surge that will destroy any of the car’s electronics if I wired the converter to come on as the ignition is switched on? (3) Is there 45/90/180 minutes or three times the values that you arrived at. When I ran the SLA battery described above I had the switch on 30-minute time-out but am sure that it was reasonably longer than this. Am I misinterpreting the chart? (2) Given Rb of 3.3kΩ, Rsense of 0.05Ω and Rref of 27kΩ, I calculate an Ifast of 3A rather than the 6A quoted in the article. Am I overlooking something here? (P. J., via email). • Voltage regulation at Vbat (pin 19) is 1.63V for an SLA battery. Since the end-point for a 12V SLA battery is 14.6V, the 0.111 division by the resistors for the 12V position on S5b will give 1.6V for the cut-off voltage. The fact that the voltage on your SLA batteries reaches 1.8V before dropping to 1.65V suggests that either the divider resistors for the 12V position on S5b are incorrect or the batteries are high impedance and so faulty. The timeout period is also set by the POD voltage at pin 6. This is actually tied low via a 33kΩ resistor (see over- any requirement for a slow start circuit? (4) Do I need to increase the capacity of my present battery? (A. W., via email). • You will not need to upgrade your alternator unless you are expecting to drive your amplifiers at full power when all the headlights and accessories are on. You can switch the inverter on via the ignition and this was shown on the circuit. The car battery should not need changing since the circuit is intended to operate only when the engine is running, so as to keep the battery topped up. lay diagram) for a divide by 1 selection and so the 15-minute timeout is set to about 22 minutes. The timeout is 226 x tosc x POD x PTD. PTD is set to divide by 1, 2 or 4 by the selection at pin 7 via switch S2. The charging current does not follow the formula detailed in the data sheets because we are using an unfilt ered DC voltage to charge the battery. Problem with TENs unit I recently built one of your TENS units (SILICON CHIP, August 1997) and found it terrific for pain relief for an inoperable spinal injury I suffered about 10 years ago. The problem is it was working fine one day then the next day it just would not work. I am in my first year of a diploma in electronics course in which I have passed my hand soldering with a 97% pass mark. I have checked all resistors, capacitors and diodes and they are fine, so I was just wondering if there LE have been any problems with the units after they had gone into production? Alternatively, could you advise me on where to look for any possible faults? (J. C., via email). • The TENS Unit does not appear to have any particular problems. The problem with your particular unit could be with the transformer (T1) or any other component such as IC1 or IC2, or the Mosfets Q1 and Q2. Or simply, the batteries may be “flat”. We suggest you check the operation of each part of the circuit to isolate the problem. First, check the voltage at the drain of Q1 – you should get a reading of 80V. If this is not present, check the supply to IC1 at pin 6 (6V). If this is OK, the windings in T1 may be shorted or open circuit. If you do measure 80V, check the supply to IC2 which should be around 15V. You should also check the output voltage at the electrodes – this should give readings up to 40V (as measured with a DC-reading multi meter), depending on the pulse width setting. Lack of output voltage may mean that IC2 is not operating or that Q1 or Q2 are short circuited. Further checking can be made with an oscilloscope. You should obtain similar displays to those published. Notes & Errata RoomGuard Intruder Alarm, April 2000: the 100kΩ resistor at the junction of D1, D2, D4 and pin 9 of IC1 on the circuit on page 31 should be 10kΩ. The wiring diagram on page 32 is correct. LED Dice, May 2000: LED6 is shown back to front on the PC board component overlay on page 60. Its cathode (the flat side) should go towards the top of the page. The circuit diagram on page 58 is correct. SC 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. 92 Silicon Chip ECTRONICSHOWCASELECT at CHEAP CHEAP CHEAP PRICES! ICs, LCD Displays,Transistors, Diodes, Leds, Books, Connectors, Switches, Transformers, Fans, Relays, Speakers,Terminals, Resistors, Buzzers, Leads, Knobs, Batteries, Computer Accs. etc. FOR A FREE MONTHLY MAILER PLEASE CONTACT ROCOM ELECTRONICS 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 Email: sales<at>rocom.com.au 3990 FULL RANGE $ ELECTROSTATIC Now you can afford the legendary clarity, transparency, depth and precision of an electrostatic speaker. 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Here are two from the wide range available: PowerQwest Zapcatcher PowerQwest Teleswitch Suppresses power line surges and spikes to huge 6500A pk (8x 20s) plus 40dB of mains noise suppression Suppression plus music muting system which cuts power on one outlet (eg to an amplifier) when phone rings. SURPLUS 4x 10A protected outlets 10A thermal circuit breaker Visual warning indication lights PowerQwest Technologies products are available from better computer stores, office products suppliers and department stores. Reseller enquiries to: 4x 10A protected outlets RJ-12 protected phone sockets 10A thermal circuit breaker Phone (02) 9979 4811 Fax (02) 9979 4833 Engineers, technicians, electronics enthusiasts, What can make your job easier? Freezer Spray, Dust Off, Circuit Board Cleaner, Heat Sink Compound... Chemical Technology Contact us for your products guide and distributors list Richard Foot Pty Ltd PO Box 245, Terrey Hills NSW 2084. Tel 02 9979 8311 Fax 02 9979 6098 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! CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12 words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $__________ or please debit my ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ________________________ Card expiry date______/______ Name _____________________________________________________ Street _____________________________________________________ Suburb/town _________________________ Postcode______________ 94 Silicon Chip FOR SALE RAIN BRAIN AND DIGI-TEMP KITS: 8-station sprinkler controllers. New Digi-temp and Moni-temp use DS1820 sensors. 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Atmel Flash CPU Programmer: Handles the 89Cx051, 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 $85, 8-pin $80. Credit cards accepted. GRAN TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; Fax (02) 9631 1236; or Internet: http://www.grantronics.com.au VIDEO CAMERAS: DOME COLOUR only $90 ! Mono only $63 ! BULLET only $110 ! with 2 YEAR WARRANTY * DOME: 480 Line 0.05 Lux with SONY CCD & ChipSet only $95 * 380 Line $92 * 450 Line $117 with 5 YEAR WARRANTY & BLEMISH FREE CCD * COLOUR DOME: 400 Line DSP $177 * BETTER THAN SUPER-VHS Resolution 600 + Line DSP $192 * 450 Line $186 * 440 Line $215 with 5 YEAR WARRANTY & BLEMISH FREE CCD * PINHOLE IN PIR DETECTOR $144 * COLOUR DSP PIN in PIR CASE $189 * MINI CAM: $87 * 420 Line $108 with 5 YEAR WARRANTY & BLEMISH FREE CCD * DSP COLOUR $172 * 4 Ch Switcher $101 * QUAD 1024 H-Pixels $226 * COLOUR QUAD $521 * Auto Scanner $147 * REMOTE PAN & TILT $312 * TX BOOSTER 1 Watt $189 * DIGITAL PC VIDEO RECORDER SOFTWARE & PCI CARD from $119 * MULTIPLEXER 4 Ch $832 * REMOTE DIAL-UP, PAGING, WEB-CAM S/W & PCI CARD $239 * PINHOLE MODULES $77 * COLOUR DSP $165 * DIY PLUG-IN 20 metre AV Cable Sets only $30 ! UP TO 5 YEARS WARRANTY * DISCOUNTS * www.allthings.com. au * 08 9349 9413 SOLAR PANELS: 120 watt $995.00, 80 watt $650.00, 60 watt $510.00, 40 watt $395.00 (all with 25 year guarantee). UNBREAKABLE PANELS: 64 watt $550.00, 42 watt $420.00, 32 watt $340.00, 11 watt $190.00, 5 watt $120.00, 1.25 watt $80.00. WIND ROLA Australia (08) 8270 3175 www.bettanet.net.au/GTD Silvertone’s RC Receiver Still the best little performer available! MP3-CD Player: $699 Plays standard CDs & MP3s as well. Plays MP3 CDs made with a CD writer. Up to 2200 songs per CD. Car adapter available. ROLA 15U & 15UX: $325 Size: 15" (380mm). Freqency response: 30-3,000Hz (15U); 30-12,000Hz (15UX). Power handling: 250 watts RMS. SPL: 97db/1 metre. FS (resonant frequency) 30Hz. 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°. 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 AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au 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. 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. GENERATORS: 400 watt $950.00. INVERTERS: sinewave inverters, inverter/chargers, mod. Sinewave inverters, call with requirements. AUSTRALIA WIDE DELIVERY (Free on orders over $500.00). TASMAN ENERGY: (03) 6362 3050 Fax (03) 6362 3054. TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test equipment without the cost of telephone lines. Melbourne 9806 0110. RCS HAS MOVED to 41 Arlewis St, Chester Hill 2162 and is now open, with full production soon. Tel 9738 0330; Circuit Ideas Wanted Do you have a good circuit idea? We pay up to $60 for contributions to Circuit Notebook. Silicon Chip Publications, PO Box 139, Collaroy, 2097. Positions At Jaycar 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. Fax 9738 0334. rcsradio<at>cia.com.au; www.cia.com.au/rcsradio DIY CCTV PAKS 4 Cameras & Switcher $315 as above COLOUR $419 4 Cams, Switcher/Monitor $433 as above 14" Monitor $461 4 Cams, QUAD & Monitor $602 as above 14" Monitor $630 4 COLOUR & QUAD $797 MORE at: allthings.com.au Also Fully Plug-In DIY Paks with all Cables & Power Supplies PLUS PC Digital Motion / Sound detection & activated Video / Audio Recording systems 08 9349 9413. WANTED PERSON WITH EXPERIENCE / APTITUDE able to fault find & repair PCBs – without diagrams. GENEROUS PKG NEG. Tel John<at>AER (03) 9482 4958 0415 305 470. JULY 2000 95 Silicon Chip Binders Keep your copies safe, secure and always available with SILICON CHIP binders: they’re cheap insurance! Advertising Index Altronics.........................................9 REAL VALUE AT $12.95 PLUS P &P  Heavy board covers with 2-tone green vinyl covering Av-Comm Pty Ltd.........................95 EMC Technologies.......................93 4D Systems.................................17 Harbuch Electronics....................75  Each binder holds up to 14 issues so that you can include catalogs Instant PCBs................................95  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Kits-R-Us.....................................95 Price: $12.95 (includes GST) plus $5 p&p each (available Aust. only). Price includes GST. MicroZed Computers...................93 Jaycar ................................... 45-52 Microgram Computers..............3,41 Oatley Electronics.................. 68-69 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. PowerQwest ...............................93 Premier Batteries.......................IFC Printed Electronics...................... 95 Questronix...................................79 DON’T MISS THE ’BUS Do you feel left behind by the latest advances in computer technology? Don’t miss the bus: get the ’bus! Includes articles on troubleshooting your PC, installing and setting up computer networks, hard disk drive upgrades, clean installing Windows 98, CPU upgrades, a basic introduction to Linux plus much more. Rall Electronics............................93 Rockby Electronics................ 28-29 www.siliconchip.com.au SILICON CHIP’S 132 Pages $ 95 * 9 ISBN 0 95852291 X 9780958522910 09 09 9 780958 522910 COMPUTER OMNIBUS Rocom Electronics.......................93 R.T.N............................................57 Silicon Chip Back Issues....... 88-89 Silicon Chip Binders....................96 IN LI CLUDE FEA NU S TUR X E Silicon Chip Bookshop........... 86-87 SC Computer Omnibus...............78 A collection of computer features from the pages of SILICON CHIP magazine Silicon Chip Subscriptions...........53 o Hints o Tips o Upgrades o Fixes Covers DOS, Windows 3.1, 95, 98, NT NO W AVA DIRE ILABLE C SILIC T FROM ON just $ CHIP 125 ORDER NOW: Use the handy order form in this issue or call (02) 9979 5644, 8.30-5.30 Mon-Fri with your credit card details. RT INC O P&P Note: price includes the GST. SC EFI Tech Special..................IBC Silvertone Electronics..................95 Smart Fastchargers.....................43 Solar Flair/Ecowatch....................94 Telephone Technical Services.....55 Truscott’s Electronic World...........43 Vass Electronics..........................93 HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. Email: tpeters<at>pip.elm.mq.edu.au 96 Silicon Chip Wiltronics.....................................73 Yokogawa....................................79 _____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd. Phone 0408- 613-300. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. Own an EFI car? Want to get the best from it? Youll find all you need to know in this publication