Silicon ChipOctober 1997 - Silicon Chip Online SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: Corrosion problems can be minimised
  4. Feature: Have Disc, WiIl Travel by Ross Tester
  5. Book Store
  6. Project: Build A 5-Digit Tachometer by John Clarke
  7. Serviceman's Log: Smoke, fire & confusion by The TV Serviceman
  8. Order Form
  9. Feature: Reprogramming The Holden ECU by Julian Edgar
  10. Project: Add Central Locking To Your Car by Leo Simpson
  11. Feature: Computer Bits by Jason Cole
  12. Project: PC Controlled 6-Channel Voltmeter by Mark Roberts
  13. Project: The Flickering Flame For Stage Work by Ross Tester
  14. Project: Building The 500W Audio Power Amplifier; Pt.3 by Leo Simpson & Bob Flynn
  15. Feature: Radio Control by Bob Young
  16. Back Issues
  17. Product Showcase
  18. Vintage Radio: Wave-traps: another look at this useful accessory by John Hill
  19. Notes & Errata: Colour TV Pattern Generator, June & July 1997; Flexible Interface Card for PCs, July 1997
  20. Market Centre
  21. Advertising Index
  22. Outer Back Cover

This is only a preview of the October 1997 issue of Silicon Chip.

You can view 28 of the 96 pages in the full issue, including the advertisments.

For full access, purchase the issue for $10.00 or subscribe for access to the latest issues.

Items relevant to "Build A 5-Digit Tachometer":
  • 5-digit Tachometer PCB patterns (PDF download) [04310971/2] (Free)
Articles in this series:
  • Computer Bits (July 1989)
  • Computer Bits (August 1989)
  • Computer Bits (September 1989)
  • Computer Bits (October 1989)
  • Computer Bits (November 1989)
  • Computer Bits (January 1990)
  • Computer Bits (April 1990)
  • Computer Bits (October 1990)
  • Computer Bits (November 1990)
  • Computer Bits (December 1990)
  • Computer Bits (January 1991)
  • Computer Bits (February 1991)
  • Computer Bits (March 1991)
  • Computer Bits (April 1991)
  • Computer Bits (May 1991)
  • Computer Bits (June 1991)
  • Computer Bits (July 1991)
  • Computer Bits (August 1991)
  • Computer Bits (September 1991)
  • Computer Bits (October 1991)
  • Computer Bits (November 1991)
  • Computer Bits (December 1991)
  • Computer Bits (January 1992)
  • Computer Bits (February 1992)
  • Computer Bits (March 1992)
  • Computer Bits (May 1992)
  • Computer Bits (June 1992)
  • Computer Bits (July 1992)
  • Computer Bits (September 1992)
  • Computer Bits (October 1992)
  • Computer Bits (November 1992)
  • Computer Bits (December 1992)
  • Computer Bits (February 1993)
  • Computer Bits (April 1993)
  • Computer Bits (May 1993)
  • Computer Bits (June 1993)
  • Computer Bits (October 1993)
  • Computer Bits (March 1994)
  • Computer Bits (May 1994)
  • Computer Bits (June 1994)
  • Computer Bits (July 1994)
  • Computer Bits (October 1994)
  • Computer Bits (November 1994)
  • Computer Bits (December 1994)
  • Computer Bits (January 1995)
  • Computer Bits (February 1995)
  • Computer Bits (March 1995)
  • Computer Bits (April 1995)
  • CMOS Memory Settings - What To Do When The Battery Goes Flat (May 1995)
  • Computer Bits (July 1995)
  • Computer Bits (September 1995)
  • Computer Bits: Connecting To The Internet With WIndows 95 (October 1995)
  • Computer Bits (December 1995)
  • Computer Bits (January 1996)
  • Computer Bits (February 1996)
  • Computer Bits (March 1996)
  • Computer Bits (May 1996)
  • Computer Bits (June 1996)
  • Computer Bits (July 1996)
  • Computer Bits (August 1996)
  • Computer Bits (January 1997)
  • Computer Bits (April 1997)
  • Windows 95: The Hardware That's Required (May 1997)
  • Turning Up Your Hard Disc Drive (June 1997)
  • Computer Bits (July 1997)
  • Computer Bits: The Ins & Outs Of Sound Cards (August 1997)
  • Computer Bits (September 1997)
  • Computer Bits (October 1997)
  • Computer Bits (November 1997)
  • Computer Bits (April 1998)
  • Computer Bits (June 1998)
  • Computer Bits (July 1998)
  • Computer Bits (November 1998)
  • Computer Bits (December 1998)
  • Control Your World Using Linux (July 2011)
Items relevant to "PC Controlled 6-Channel Voltmeter":
  • PC-controlled 6-channel Voltmeter PCB patterns (PDF download) [07110971/2] (Free)
Items relevant to "The Flickering Flame For Stage Work":
  • Flickering Flame PCB [11410971] (AUD $3.00)
  • Flickering Flame PCB pattern (PDF download) [11410971] (Free)
Items relevant to "Building The 500W Audio Power Amplifier; Pt.3":
  • 500W Audio Power Amplifier PCB pattern (PDF download) [01208971] (Free)
  • 500W Audio Power Amplifier panel artwork (PDF download) (Free)
Articles in this series:
  • A 500 Watt Audio Power Amplifier Module (August 1997)
  • Building The 500W Audio Power Amplifier; Pt.2 (September 1997)
  • Building The 500W Audio Power Amplifier; Pt.3 (October 1997)
Articles in this series:
  • Radio Control (August 1997)
  • Radio Control (October 1997)

Purchase a printed copy of this issue for $10.00.
Arranging Your Win95 Start Menus SILICON CHIP OCTOBER 1997 $5.50* NZ $6.50 INCL GST C I M A N Y D 'S A I L A AUSTR E N I Z A G A M S C I ELECTRON SERVICING - VINTAGE RADIO - COMPUTERS - SATELLITE TV - PROJECTS TO BUILD Have Disc, Will Travel PRINT POST APPROVED - PP255003/01272 Slide-out carrier makes it easy to remove & transport hard disc drives 5-Digit Tachometer Building the 500W Audio Amplifier PC-CONTROLLED 6-CHANNEL VOLTMETER FLICKERING FLAME: A SIMPLE LIGHT SHOW ISSN 1030-2662 10 9 771030 266001 Build It For Your Car: Remote-Controlled Central Locking October 1997  1 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au Contents Vol.10, No.10; October 1997 FEATURES   4  Have Disc, Will Travel Slide-out carrier makes it easy to remove and transport hard disc drives from one computer to another – by Ross Tester 37  Reprogramming The Holden ECU A clever software package takes the guesswork out of program changes if engine modifications are made – by Julian Edgar PROJECTS TO BUILD 16  Build A 5-Digit Tachometer This versatile design can cope with virtually any engine or rotating machinery and features 1 rpm resolution and leading zero blanking – by John Clarke Slide-Out Carrier For Hard Disc Drives – Page 4 41  Add Central Locking To Your Car You build a simple receiver and install the actuators and wiring in the doors. The transmitter comes ready-made – by Leo Simpson 56  PC Controlled 6-Channel Voltmeter Simple project uses just one chip & plugs into your PC’s parallel port. The companion software generates the on-screen display – by Mark Roberts 60  The Flickering Flame For Stage Work Here’s a simple prop that you can make for stage work. It’s easy to build and from a distance, gives a convincing imitation of fire – by Ross Tester Build A 5-Digit Tachometer – Page 16 66  Building The 500W Audio Power Amplifier; Pt.3 Final article details the loudspeaker protector and the thermal switch for the fan – by Leo Simpson & Bob Flynn SPECIAL COLUMNS 28  Serviceman’s Log Smoke, fire & confusion – by the TV Serviceman 53  Computer Bits Customising the Windows 95 start menus – by Jason Cole Add Central Locking To Your Car – Page 41 74  Radio Control The philosophy of R/C transmitter programming; Pt.2 – by Bob Young 88  Vintage Radio Wave-traps: another look at this useful accessory – by John Hill DEPARTMENTS   2  Publisher’s Letter 33  Order Form 64  Circuit Notebook 80  Product Showcase 92  Ask Silicon Chip 93  Notes & Errata 94  Market Centre 96  Advertising Index PC Controlled 6-Channel Voltmeter – Page 80 October 1997  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Brendon Sheridan Phone (03) 9720 9198 Mobile 0416 009 217 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Mike Sheriff, B.Sc, VK2YFK Ross Tester Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $54 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Corrosion problems can be minimised Ever thought about corrosion and how much it costs you each year? Most people, when they think about corrosion, think about rust in their car and that is serious enough. After all, rust is the main reason why most cars are finally pensioned off, at least in those Australian states where annual registration inspections are required. But I am thinking of the problem of corrosion in electronic and electrical installations. Perhaps the most glaring of these are involved in domestic TV antenna installations. At one time, a TV antenna installation could be expected to last 20 years or more but with more people doing their own installations, the antenna life might only be a few years and that amounts to a big waste of time and money. A large part of the problem now is that fixtures and fit­tings which used to be hot dip galvanised are now very lightly zinc plated or worse, cadmium plated and passivated. Steel fit­tings that are zinc plated have a blue-white shiny appearance while those that a cad-plated and passivated have a yellowy golden appearance. Now while cadmium plated and passivated steel may be OK for the chassis of electrical equipment used indoors it is pretty useless outdoors. In coastal areas and areas with industrial fallout, such fittings will rust heavily within 12 months. Bright zinc plated fittings are not much better. The same can be said of screws, bolts and nuts which are zinc plated - they rust out quickly. This tendency to install cheap metal fittings is now very widespread, partly because many stores, particularly hardware stores and supermarkets, only stock the cheap rubbish. Have a look around your own home and where you work and note how many of the metal fixtures and fittings are rusting or corroded. You might be quite surprised at how things are deteriorating right before your eyes. Anodised or powder-coated aluminium fittings also often fare poorly in coastal districts and areas of high fallout and are also to be avoided. In the long run, it is much better to use steel fittings which are hot dip galvanised. And if you live within say, two or three kilometres of the coast, use only stainless steel. Stain­less steel hardware is a lot more expensive but you will never have to replace it. When you consider how much corrosion there is in all the buildings across Australia, the cost runs into bil­lions of dollars each year. With a little thought and slight extra initial cost, much of this can be avoided. Leo Simpson ISSN 1030-2662 WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 2  Silicon Chip BARGAIN CORNER See our WEB SITE or “Poll” (02) 9570 7910 for BARGAIN CORNER and NEW PRODUCTS. The WEB SITE has much, much more information and a catalogue. Many more items than the following sample of our “BARGAIN CORNER”. Note that we have LIMITED STOCK of some of the items. 109701.USED GEARED 24V DC MOTORS, metal gears and gear casing, very STRONG!. Approx 28RPM<at>24V, 14RPM<at>12V, starts turning at a few volts, 0.12A <at> 12V N/L, 0.16A <at> 24V N/L, motor itself is 40mm dia., 60mm long: $20. 109702. 115Vac “MUFFIN” FANS, new, 50/60Hz, 0.20A, shaded pole motor, metal frame, plastic blade, 40mm thickness: $4. 109714. INDUCTIVE PROXIMITY SWITCHES, LINK NO30MB-2AL, 30mm dia., 90mm long, two wire, 40 to 250Vac, 0.5A: $5 ea. 99710. CAR CIGARETTE LIGHTER LEADS, good quality, new, fused plug with 2A fuse, curly cord that stretches to 3 metres, terminated in 2.1mm DC plug: 3 for $5. 99711. CAR CIGARETTE LIGHTER LEADS, good quality, new, fused plug with 8A fuse, heavy duty 1.5m long 18 A.W.G. (8A rating) cable, terminated in 2.1mm DC plug: 3 for $7. 99712. UNIDIRECTIONAL ELECTRET MICROPHONE, good quality, fitted with alligator clamp for use as lapel mic and 2.8m long shielded cable terminated in jack plug: $4 ea. 99713. WIRING LOOMS, new, contains 3m each of yellow and blue stranded (0.5mm square C.S.A.) cable, 4m each of red and black heavy duty (1.5mm square C.S.A) stranded cable, also includes some automotive fuses/holders and matching spade connectors: 5 lots (70m wire) for $9. 99715. CAR COMMUNICATIONS SPEAKER IN BOX, parcel shelf mounting bracket, swivel mount, speaker is 4-ohm, 3W nom, 5W max, 50mm diameter, 1.5m cable terminated in jack plug: $6 ea. 99717. MYSTERY BOX OF ELECTRONICS, something to do with hands free phone equipment for cars, 85 x 30 x 120mm plastic box, most bits are surface mount but there are two useful power MOSFETs that could be recovered from the PCB inside, IRF9530 (P-channel, case: TO-220AB, 100V, 0.30-ohm on-resistance, 12A max) & IRF530 (N-channel, 100V, 0.16ohm, 14A): 2 boxes for $4. 79716. PCB WITH SEVEN SEGMENT DISPLAYS: PCBs from poker machines, have 5 x 7.6mm (digit height) and 4 x 20mm 7 segment LED displays which are soldered to the board : 2 boards for $6. 79717. VALVES: 6J6, 6J7, 6AV6, 6D4; new, any mixture of 10 for $20. QUANTITY 79748. HEWLETT PACKARD SWITCH MODE POWER SUPPLY- WORLDWIDE, works at any voltage 100 to 240Vac, 10.6V / 1.32A DC out, used, in plastic box 115 x 70 x 30mm with lead and DC plug. $10 79784. USED TO3 DEVICES: 1kg bag (Approx 80) of used TO3 devices, mostly transistors, some voltage regulators/ diodes/mosfets, wide variety, badly stored, most have bent pins: 1kg bag for $6. COLOUR MONITOR New 12V DC-1A 6" colour monitor, ready for enclosing, no box, just the tube and driver PCBs, digital RGB inputs (CGA?), we may have more information: $65. CALLER ID See the phone no. of your incoming calls displayed on a LCD screen while the telephone is ringing. Has 80 call memory, dialler etc. We should have an approved unit available during the month of publication. Price will be around $50! 650nm VISIBLE LASER POINTER KIT YES, NEW 650nM kit!!! Very bright! Complete laser pointer that works from 3-4V DC. Includes 650nm/5mW laser diode, new handheld case 125 x 39 x 25mm, adjustable collimator lens, PCB battery holder: $30. DISCO LASER LIGHT SHOW PACK The above 5mW/650nm kit plus our AUTOMATIC LASER LIGHT SHOW: $99. 650nm LASER POINTER SPECIAL Light weight (2 x AAA) pen sized pointer with 5mW/650nm laser diode, 140mm long, 18mm diameter: $55. 650nm LASER MODULE Our new module is fitted with a 650nM laser diode! Very small, 35mm long, 10mm diameter, 3 to 4.5V operation: $50. DC MOTOR SPEED CONTROL- EXPERIMENTERS PACK One 20A motor speed controller kit (similar to SC June 97) $18, plus two small new 12VDC motors (40mm dia., 40mm length) plus one used car windscreen wiper motor (which have internal gear reduction) for: $32. VISIBLE LASER DIODE MODULE KIT This kit has the same circuit as our “visible laser diode kit” but has a smaller printed circuit board that allows it to be fitted into a piece of tubing. Dimensions of the board are less than 25mm wide and 50mm long. 650nm/5mW laser diode. 3V operation $29. THREE STAGE IMAGE INTENSIFIER TUBES Back in stock. Make a high resolution night scope that will work in starlight! Three tubes plus the inverter kit plus a suitable eyepiece. The housing and the front lens are not supplied: $250. 32mm AUDIO AMPLIFIER: An LM386 based $9 audio power amplifier which can directly drive a speaker - needs the 32mm preamplifier. WHAT IS 32mm? All boards are 32mm, so you can house these kits in a plastic 32mm joiner: cheap plumbing part. COMPUTER POWER SUPPLY New PCB assembly only, 45 x 108 x 200mm, 120/230V AC IN, +5V-6A/12V-1A/-12V-1A/-5V-1A OUT. Circuit provided, RU approval. Modern design. Not for the inexperienced! Be quick: $16 ea. or 4 for $56. WOOFER STOPPER MkII Works on dogs and most animals, ref SC Feb 96. PCB and all on-board components, transformer, electret mic & horn piezo tweeter: ON SPECIAL $33, extra tweeters (drives 4): $7 ea. Approved 13.8V/1A DC plugpack (PP6) $10. SUPER BRIGHT BLUE LEDS BY FAR THE BRIGHTEST BLUE EVER OFFERED, super bright at 400mCd: $1.50 ea. or 10 for $10. 5mm LEDS AT SUPER PRICES 1Cd red: 10 for $4 300mCd green: $1.10 ea. or 10 for $7 (make white light by mixing the output of red green and blue) 3Cd red: $1.10 ea. or 10 for $7 3Cd yellow (small torch!) also available in 3mm: 10 for $9 Super bright flashing LEDs: $1.50 ea. or 10 for $10 PC POCKET SAMPLER KIT Ref EA Aug 96. Data logger/sampler, connects to PC parallel port, samples over a 0-2V or 0-20V range at intervals of one/ hour to one/100us. Monitor battery charging, make a 5kHz scope etc! Kit includes on-board components, PCB, plastic box and software (3.5" disk): (K90) $30. BOSSMAN ELECTRONICS This new company is a subsidiary of OATLEY ELECTRONICS, for the purpose of giving TAX EXEMPT PRICES to entitled organisations. The product range will that will be included on this list will increase rapidly. For enquiries call BOSSMAN ELECTRONICS on 02 9584 3562 or fax 02 9584 1031. NEW SEMICONDUCTOR BARGAINS 2SK2175 - MOSFETS 15A, TO220, 60V, 30W: 10 for $15, CA3140 - MOSFET input op amp : 5 for $5, TL494 - switchmode power supply IC : 5 for $5, NE555 - timer IC : 10 for $5, ICL7106 - LCD display driver : $5, ICL7107 - LED display driver: $5, IRFZ44 MOSFETS 60V,0.028-ohm on resistance,50A: 10 for $30 C8050 and C8550 transistors: 20 for $5, CMOS ICs 4001/11/13/16/17/20/24/28/40/46/6 0/66/69/93: Any mixture 10 for $8. 12V/7Ah GEL BATTERY BARGAIN Fresh stock standard plus one GEL/LEAD-ACID BATTERY CHARGER for $30. HELIUM NEON LASER BARGAINS Large 2-3mW He-Ne laser head plus a compact potted US made laser power supply. The head plugs into the supply, and two wires are connected to 240V mains. Needs 3-6V/5mA DC to enable: $100. Also 5mW tubes plus a 12V inverter kit: $80. USED ARGON - ION LASER HEADS The cheapest way to get a BLUE-GREEN LASER beam! A power supply design for these is based on a transformer with 80V <at> 10A and 3V <at> 20A secondaries. Ring or Email for more information. Head only: $250. AUDIO - VIDEO MONITOR Compact high resolution 5" screen B/W audio and video monitor. Has two way audio, built in microphone, audio amplifier, speaker and pushbutton “talk” switch. Needs a pre-amplifier and microphone for remote audio monitoring (our 32mm audio preamplifier is ideal). Has two camera inputs to allow manual or auto switching (adjustable speed) between each camera. Needs 12V DC 1A (our switched mode supply is ideal), size 160 x 190 x 150mm, has audio and video outputs for connecting to a VCR etc. Monitor and 6-way mini input connector only $125. BEST “VALUE FOR MONEY” CCD CAMERA The best “value for money” CCD camera on the market! Tiny CCD camera, 0.1 lux, IR responsive, high resolution. This camera has a metal lens housing (not plastic) and performs better than many cheaper models. The pinhole lensed version of this camera is also available for the same price: $105. KITS FOR CCD CAMERA SECURITY New INTERFACE KIT FOR TIME LAPSE RECORDING: now has relay contact outputs! Can be directly connected to a VCR or via a learning remote control: $25 for PCB and all on-board components, used PIR to suit: $12. 32mm 10 LED IR ILLUMINATOR new IR (880nm) LEDs have an output about equal to our old 42 LED IR illuminator: $14. 32mm AUDIO PREAMPLIFIER. An $8 kit that produces a “line level” signal from an electret microphone, connect the output to our . . . UHF VIDEO TRANSMITTER ($30) or $20 when bought with the camera for a complete Audio-Video link. MASTHEAD AMPLIFIER KIT Our famous MAR-6 based masthead amplifier. 2-section PCB (so power supply section can be indoors) and components kit (KO3) $15. Suitable plugpack (PP2): $6 Weatherproof box: (HB4) $2.50. Box for power supply: (HB1) $2.50 Rabbit-ears antenna (RF2) $7 (MAR-6 available separately). NICAD CHARGER & DISCHARGER High quality commercial 7.2V Nicad charger and discharger PCB assembly only. Switched mode design professional, fully assembled and tested fast NICAD battery charger and discharger PCB assembly. Switch mode circuit, surfaced mounted on a double-sided PCB. Nominal unregulated input 13.7V DC, 900mA charge current. Appears to use voltage slope detection for charge terminating, also has a timer (4060) to terminate the charge. We supply a thermistor for temperature sensing. For fast-charging 7.2V AA nicads. Basic information provided, Incredible pricing: $9 ea. or 3 for $21. VERY EFFICIENT WHITE LIGHT - LCD DISPLAY New “second grade” (few missing pixels) Sharp 640 x 480 LCD display (LM64P722). Features a very efficient long life cold cathode BL fluorescent lamp (5mm diam., 150mm long), very easy to remove! Produces useful white light at only about 1-3W AC input! Removing the display will reveal a very uniformly lit backplane with an overall size of 150 x 200mm. Complete display plus BL inverter kit: (Needs 12V-150mA): $17. Data sheets (11pages) for a similar display: $2. NICAD BATTERY SPECIAL New 1.2V-400mAhr cells wired in packs of 6, each pack has a thermal cutout switch, each cell is 16 x 45 x 5mm, as used in mobile phones, 5 packs (30 batteries) for: $10. SOLAR REGULATOR Ref: EA Nov/Dec 94 (intelligent battery charger). Efficiently charge 12-24V batteries from solar panels but can also be used with simple car battery chargers to prevent overcharging. Extremely high efficiency due to the very efficient MOSFET switch and Shottky isolation diode. We now offer a 7.5A or 15A kit: $26/$29 (K09). MORE KITS Geiger counter: $40, Breath tester: $40, 12V DC inverter for driving compact fluoro lamps plus one CFL lamp: $35, Music box: $11, Ding dong doorbell: $3.50, Siren using a 10cm speaker: $14, Electric fence using used car coil: $25 AMPLIFIER - PREAMPLIFIER AND MORE! A professional mostly SM PCB that contains a 5W amplifier based on a TDA1905 IC and a separate audio preamplifier section. We also provide a prewired high quality unidirectional electret microphone that has a wind filter and a mounting clip. A small speaker and basic hook up information is also included. Appears to have been designed for a communications system. Great for many applications including a two way intercom (2 required) that does not require switching! Available at less than the cost of the electret microphone: $15 ea., 2 for $24. OATLEY ELECTRONICS PO Box 89, Oatley NSW 2223 Phone (02) 9584 3563 Fax (02) 9584 3561 orders by e-mail: oatley<at>world.net WEB SITE: http://www.ozemail.com.au/~oatley Major cards with phone and fax orders, P&P typically $6. October 1997  3 Have Disc, Do you have an old hard disc drive lying in a cupboard somewhere, unused and unloved? Here’s a way to put it to good use for next to nothing and perhaps give you the flexibility you’ve always dreamed about! By ROSS TESTER A RECENT JAYCAR advertise- ment in SILICON CHIP caught our eye be­ cause it appeared that it might solve a couple of problems we were having transporting very large files between two remote computers. And it did! But first, our problem. As you probably realise, SILICON CHIP and its sister magazine ZOOM are produced entirely on com­puter. The first time the printer sees any part of these maga­ zines is as finished computer files. Unfortunately, those files, particularly a colour page, can easily be fifty megabytes (50Mb) or more. We have used a number of methods to transport these files to the printers. We’ve “modemed” them (is there such a word?) but that’s really only feasible The “Mobile Rack” comes in two versions, one for IDE drives and the other for SCSI drives. It’s just the shot for transferring large amounts of data from one computer to another, or for taking a backup copy of valuable office data home with you at night. 4  Silicon Chip for relatively small files – large files simply take too much time. The most usual method is to copy the files to 88Mb Syquest discs and to send these to the printer. However, after years of faithful service our Syquest drive was starting to become less than 100% reliable and, in any case, 88Mb is no longer really big enough. It needed replacement. Will Travel Step 1: remove the faceplate covering a spare drive bay. But which way to go? Take a look at a typical computer products catalog and you’ll see that a myriad of portable storage devices is now available. Along with Syquest drives (themselves now available in at least four different configurations), there are high capacity floppies, magneto-optical drives, Zip drives, Jaz drives, Syjet drives and recordable CD-ROM drives (some now re-writable) – to name but a few. Would you believe that there’s even one called a Shark? Each has its own advantages and disadvantages. We’ll look at a few. Zip drives are now quite popular. The discs are cheap but they only hold 100Mb – not much more than our old Syquest discs. The Jaz drive, the Zip’s “big brother”, is much better in this regard – up to a gigabyte per disc. However, the drives and discs are still relatively expensive and not, as yet, particularly common. And of course, both Zip and Jaz discs (like Syquests) can be erased by stray magnetic fields – so that’s a negative. Step 2: plug the data cable into the socket on the frame. High capacity (120Mb) floppy disc drives are now available. Backward-compatible with the old faithful but now-almost-useless 3.5-inch floppy disc, they will probably catch on but as yet they’re almost unheard of. They’re also pretty expensive (about $350 for the drive and $70 for the discs compared to about $40-$50 for a 1.44Mb floppy drive and cents for the discs!). Magneto-optical drives looked like a pretty good bet for a while. Robust and unaffected by magnetic fields, the discs hold up to 640Mb but they are also expensive and much less common than most other storage devices. Alas, we bought an MO drive some time ago but very few others did. It’s an orphan! How about CD-ROM – both the recordable variety and the new re-recordable units? Yes, they’re very attractively priced (the drives and the CDs themselves have dropped dramatically in price in the past year, perhaps due to supply and demand but just as likely because a new standard – DVD – has arrived). Of course, there is no problem in anyone else reading a CD because just about every PC made in the last couple of years has a CD-ROM drive built in. CDs are also quite robust and unaffected by magnetic fields. We also purchased a CD-ROM writer and have used this very successfully. The one big drawback is time: you can’t easily add files to a CD-ROM as you can, say, to a hard disc or a Syquest disc. And where large amounts of data are involved, it can take more than an hour to test, write and verify the CD. Sometimes that’s an hour we can’t spare when the presses are waiting! So you can see, the decision is not at all simple. Or at least it wasn’t until we spotted a rather interesting item in the aforementioned Jaycar advert. Mobile rack The item advertised was a “Mobile Rack”, or removable hard disc carrier and frame for $39.95. As the name sugOctober 1997  5 Step 3: plug a spare power cable into the power socket. Use a Y-adaptor if you don’t have any spare power cables. manded!). What was a perfectly good hard disc drive a couple of years ago, with a capacity of 100Mb or 200Mb, has become today’s paperweight. A quick search soon turned up a couple of old IDE hard discs sitting in the bottom drawer of a filing cabinet (mainly ‘cos no-one had the heart to throw out a perfectly good hard disc! But then again, I still have my first-ever 20Mb MFM drive in a cupboard at home. Call me a sentimentalist if you will). Anyway, we reasoned, what if we resurrected one of these IDE discs and used it one of these frames? For less than forty bucks, our problems could be solved. (Naturally, we would also have to convince our printers to make the same huge investment). Knowing only too well our file transfer problems, which of course were also their problems, they baulked at spending such a princely sum for only a millisecond or two. And then our file transfer problems were over! Here’s how we did it, how they did it, and how you can do it too. Even if it’s only to take work home at night that you should have finished during the day, this little device is a gem! Fitting the disc drive Step 4: carefully slide the frame into the drive bay. gests, the device is designed to allow any standard size 3.5-inch or 2.5-inch disc drive (half height or less), which would normally be mounted inside a computer, to be made removable. The frame comes in two types, one to suit standard IDE hard disc drives and the other to suit SCSI drives. There are two very obvious uses for such a device. The first is file security and we’ll have more to say on this a little later. The second is to allow 6  Silicon Chip the computer’s hard disc drive to be transported from one computer to another, allowing files, programs and so on to be transported. Aha! Exactly what we were looking for! But did we really have to use one of the hard disc drives in our computers? Why not another one altogether? Like most computer users, we have upgraded our hard disc drives many times as our needs increased (no, make that read as the programs we use de- Before doing anything with the drawer, have a good look at your disc drive. Make a note of its type number and any informa­tion printed on it – especially such information as its size and the number of cylinders, heads, sectors, landing zones, precom­press­ ion and so on. If this information isn’t printed on your drive (and on many older drives it may not be), you will need to find it out – either from the manufacturer’s data sheet which came with the drive, from the distributor, a friendly computer techie (who will probably have one of those handy programs which list hard disc drive parameters) or – if you have access to it - the manufactur­er’s web site on the Internet. And while you’re about it, you will also need to find out about the various jumper settings that are applicable to the drive. The jumpers are normally changed by moving a small header onto various sets of pins. These may be mounted on the disc drive PC board itself or they may be elsewhere on the drive. You may or may not need to change a jumper: if this is the only drive in your computer and you are simply making it port­able, you won’t have to bother. It would have been set as a “master” – keep it that way. However, if you are adding another IDE drive to your com­puter, it will probably need to be set as a “slave”. Each drive brand and even types within a brand differ in the way this is done. Finally, if fitting a SCSI drive, you really do need to refer to the manufacturer’s data for the correct settings (see separate panel). Once the jumpers are selected or checked, put the drive aside for a moment. Slide the drawer from the frame and remove its top and bottom metal covers. At first glance, there appears to be no easy way to do this because there are no screws but all you have to do is gently prise the cover off the drawer (even a fingernail will do it). Inside the drawer, you will find a little bag of screws, the front lock keys and a bag of silica gel which says “do not eat” (so don’t – but remember to dispose of it where the littlies won’t get at it either!). You will also see two cables – a flat ribbon data cable and a 4-pin power cable. In 99.9% of circum­stances, they are the only connections needed. Connect the cables to the drive before placing the drive into the drawer – it’s much easier. You will note a red stripe along one edge of the data cable – this is pin 1 (usually, but not always, marked on the disc drive PC board). In nearly all cases, the drive will mount the right way up (ie, PC board to the bottom), with the data cable the right way around. Next, fit the power cable. It is usual for the red lead of the power cable to be closest to the red lead of the data cable; in any case, the plug and socket are keyed which make getting it the wrong way around quite difficult. (Note that we said diffi­cult, not impossible: forcing the cable in the wrong way around will have a briefly spectacular effect as your drive makes its way to hard disc heaven with a puff of smoke and that rather horrible smell of money burning!). Now ease your hard disc drive into the drawer. Older style half height drives are a tight fit, newer low profile drives are easier. Move the drive backwards and forwards until its mounting holes line up with the Step 5: secure the frame in the drive bay using the mounting screws supplied. mounting holes in the drawer. Using the screws supplied secure the drive to the drawer. Finally, pop the top and bottom covers back on – and that part is finished. Mounting the carrier frame This step is virtually identical to fitting a standard hard disc drive to a PC. If you haven’t done that before, the steps are as follows (obviously we don’t have to tell you to turn off your computer and remove its cover!): • Select a suitable drive bay. It will need to accept a stan­dard 5-25-inch half-height disc drive and it will need to be close enough to the first, or master, disc drive to connect to the second socket on the data cable. If you find your data cable has only one socket, you’re up for a new data cable. Don’t worry, they’re cheap! Also note that either socket can be used for either hard disc drive, so if you have to swap the connector over to make it reach, no problem. • Remove the faceplate covering the chosen drive bay. This faceplate Should you use an old hard disc drive? W HILE WE HAVE talked about resurrecting an old drive, there are a few points to keep in mind. Old drives are quite possibly poorer performers than to­ d ay’s drives, so you might find that disc-intensive tasks take a little longer to do. However, we don’t see that as too much of a problem. We’ve already mentioned possible incompatibility problems. That’s for you to discover all for yourself (lucky you!). The area of most concern is that the drive might be worn out (or close to it). With the price of hard discs today a tiny fraction of what they were a few years ago, you might find that it is a lesser risk to invest in a new drive, particularly if important information is to be stored on it. There are some real bargain drives around – one or two gigabyte drives for just a couple of hundred dollars or so! Having said that, there is still a case for using an old drive. If it spins up properly when it’s turned on (ie, the bear­ings aren’t shot), if it doesn’t report loads of bad sectors, if it doesn’t make a ghastly scratching sound when you turn it on or off (ie, the heads aren’t contacting the disc surface), and if you can run Scandisk or Checkdisk and get a clean bill of health after the full surface scan, then go ahead and use it. Perhaps, though, there is even more of a case for updating your current drive to a new higher-capacity model and using the old one as the transportable! October 1997  7 Step 6: fit the disc drive to the drawer and fit the top and bottom covers. You can leave the covers off if they foul the drive – see text. Step 7: slide the drawer with the disc into the frame and push it all the way home so that it mates with the socket on the carrier. is usually plastic (occasionally metal) and either pops out or has screws holding it in place. Sometimes, though, there is a metal plate which needs to be unscrewed or broken away from the main case (the latter is occasionally used on “tower” cases which have a separate, removable front panel). • Check to see if you have a spare power cable fitted with a large 4-pin white plastic plug. If you don’t, you will need to buy a “Y” adaptor – a 8  Silicon Chip power cable with a socket and two plugs. These are readily available but prices vary enormously. We nor­ mally pay about $5 for these but some stores have asked us, unsuccessfully of course, for $24.95 each! To fit this, simply remove the same type of power plug from some other device (eg, a floppy drive), plug this into the Y adaptor socket and push one of the plugs back into the device you just took it from. The other plug, naturally, goes to the mobile rack frame. • Carefully push the data cable socket onto its mating plug on the frame. Remember that the red stripe goes to pin 1 (clearly marked on the back of the frame). Check that you have the socket cor­rectly mated otherwise the drive won’t work. • Now it’s time to slide the frame into its correct position in the drive bay, so that the front of the frame is flush with the front of the computer case or with other drives. Most drive bays have long slots in them to allow you to accurately position the frame. Install two screws on each side to hold it in place and nip the screws up firmly. It is important that you don’t skimp on the screws here because the sides of the frame need to be held rigidly in position so that the drawer slides in and out proper­ly. If your drive bay is the type that uses sliders which clip into place (as on one of our computers), you have no choice but to use them but these can cause a bit of a problem. The pressure of the spring clips causes the edges of the frame to flex in­wards, making it difficult to fit the drawer. However, the drawer will slide in with a little jiggling and juggling! • Slide the drawer containing the disc drive into the bay to check that it fits correctly. If you find that it is too tight a fit, perhaps because you are using an older drive which is a tight fit in the drawer, it is perfectly acceptable to use the drive without its top and bottom covers. You might be sacrificing a little disc protection when it is outside the computer but you will save the vertical space. The drive would probably be happier working without covers anyway – it would stay cooler, although the covers are well ventilated. • Make a final check to ensure you haven’t dislodged any other cables – it’s very easy to do, particularly when working in confined spaces and especially so with easily removed cables such as on floppy drives. Setting up the drive If you are simply making the only drive in your machine removable then you won’t have any setting-up to do, because electrically nothing’s chang­ed. But if you’re adding another drive, as we did, it’s a slightly different story. And it also depends on the age of your computer. On a modern computer with a “Plug‘n’Play” BIOS and Windows 95, you may find that the disc is auto detected when you turn the computer on. Watch the screen carefully before the Windows 95 sign-on screen appears. Even if that doesn’t work, many new computers have an option in the CMOS Setup to auto detect hard discs (see below). Try it! On an older computer (eg, a 486 or older), you’re going to have to tell it that you’ve changed the disc by going into the CMOS setup just after you turn the machine on. With most ma­ chines, you will probably get a message such as “Press DEL to enter setup” not too long after the machine is turned on. Even older machines such as 386s and earlier (what – you’re still using one?) were not quite so standardised. Watch the screen or refer to your manual to see which keys you need to press to enter setup. Control +, Alt +, Control Escape and Alt Escape were often used but there were others! When you enter Setup you are usually presented with a range of options. The one you want is typically the first one: “Stan­dard CMOS Setup”. Press enter and next you will see a warning screen threatening you with mortal injuries if you dare to make any adjustments. Ignore it! The next screen shows you what the computer believes is fitted – for example, a 3.5-inch “A” drive, a 5.5inch “B” drive and a 980Mb “C” drive (hard disc) but with nothing listed for hard drive “D” (the new removable drive). You must manually change the “D” drive parameters to that of the hard disc you’ve just fit­ted. Where do you get those parameters? That’s why we had you write them down before! Note that the arrow keys get you to where you want on the screen, while page up and page down modify the parameters. You will need to change drive “D” to a type 47, the option which allows you to manually enter parameters. Enter the parameters asked for, except for the size. Setup works this out for you and you should check this to confirm that you listed everything else correctly. This done, follow any instructions on the screen to leave the setup area (you typically press the “Escape” key) and return to the opening CMOS setup screen. This time, select the option which writes SCSI – What Does It Mean? as “scuzzi”) SCSI (pronounced stands for Small Com- puter Systems Interface and is a very popular method of connecting peripherals to a PC. Apart from its speed (the latest SCSI disc drives are very fast), it has the advantage of being device independent – you can connect up to seven SCSI devices on the one cable without having to worry about what those devices are. You could have a scanner, tape backup, a hard disc or two, CDROM reader or writer and so on in the chain. As long as each device has its own unique identification, the system can cope with it. The devices can be internal or external and are simply “daisy chained” from one to the next. External devices have the luxury of being removable. As long as the cabling is properly terminated at either end, you can remove SCSI devices from the system at will. One advantage SCSI drives have over standard (IDE) drives is that it is very easy to assign new drive letters to the drives, particularly under Windows 95 and Windows NT. If you have a Plug‘n’Play BIOS , your PC won’t tie itself in knots when you remove an IDE drive. However, it can be mentally flexing, to say the least, to try to remember what drive is what because the operating system automatically assigns the next letter of the alphabet to the next drive it finds. With SCSI drives, though, you can change the drive letter to any letter of the alphabet (except, of course, those already is use). If you make your SCSI disc drive “X”, for example, it will stay drive X. You set the drive letter through the setup to CMOS memory (probably something like “Write to CMOS and exit”). You will need to reboot the computer for the changes to take effect. Once done, check to see that everything works as intended. (If you enter the CMOS setup again, just for a “looksee”, you should find that “D” drive the Control Panel. To do this, double-click System, select Device Manager, click on the hard disc you want to change and check the “removable drive” box. The system will now allow you to change the drive letter by entering the same (wanted) drive letter in the start and end reserved drive letter boxes. When you reboot, the drive will have that drive letter. That’s one of the advantages. The downside is that most SCSI devices, especially hard disc drives, are significantly more expensive than equiv­alent IDE drives. One point to note about SCSI is that it requires proper termination: the devices on the ends of the chain need to be terminated, either physically with a terminator or via a DIP switch on the device PC board (some devices may use software termination). If they aren’t terminated, operation is at best unreliable (usually it won’t work at all) and if the wrong devic­es are terminated, those following on the chain have little chance of working. Just remember that the SCSI controller card is itself a SCSI device and if it is at the end of the SCSI cable (eg, if you have all internal or all external SCSI devices), it must be terminated just like the SCSI device at the other end of the cable. If you have a mixture of internal and external SCSI devic­es, the card is simply another SCSI device on the cable and must not be terminated. SCSI devices have a reputation (only partially deserved) for requiring more setting up than, say, IDE disc drives. Typi­cally, a SCSI controller card needs to be fitted and drivers loaded to run that card. Once installed, though, a SCSI system is very reliable and easy to use. is now listed. You can then exit the CMOS setup without changing anything by selecting the “Do Not Write to CMOS and Exit” option. It sounds like double dutch but that’s the one you want). What if it doesn’t work? Woops! Something’s wrong – an October 1997  9 How Many Drives Can you Fit? O N OLDER (most 486 or earlier) machines, only two IDE drives can be fitted – one as a primary, the other as a slave. If your computer is a modern type (ie, Pentium or equivalent), you can normally run up to four IDE hard discs. Two can be run in the normal “master/slave” arrangement we have talked about here on the “Primary IDE Port” and another two can be similarly run on the “Secondary IDE Port”. On a Pentium, the portable drive could be fitted as either the Primary Master (if it is the only drive) or, error message such as “HDD or controller failure” usually means that the parameters are incor­rect or that the cable or jumper is wrong. Try going back into the CMOS Setup and telling the computer you don’t have a “D” drive and see if that removes the error message. If it does, you have a problem with the drive. Check its connections or jumpers and if these are OK, check the drive parameters. If you don’t get any joy, tell CMOS you have no hard disc drives and try booting from a bootable floppy - just to start eliminating possibilities. You might have accidentally dislodged the floppy disc cable for example, or replaced the cable incor­rectly if you had to temporarily remove it. If your computer used to work with one hard disc but now doesn’t work with two, restore it to what it was (ie, disconnect the new drive) and try booting again. If it doesn’t work, the chances are pretty good that you have dislodged a cable. Go back over all the cables and the changes you’ve made – a common fault is when power cables are not pushed in far enough, especially a plug and socket (eg, the ”Y” adaptor). Systematically eliminate possibilities and you should find the fault. If a known good drive simply refuses to work, you could have incompatibility problems. This mainly occurs with older drives. There have been many cases when a drive will not work with a certain model (or models) of another brand and yet will work with other models or brands. 10  Silicon Chip assuming a two drive system, the Primary Slave OR the Secondary Master. Note that most CD-ROM drives these days are also an IDE device and may take the place of a hard disc drive. They are jumpered as master or slave in exactly the same way as a hard disc. If you have an older machine and wish to run two disc drives and a CD-ROM drive, the easiest way to do it is to buy a sound card with an IDE CD-ROM driver. They cost very little (from about $50) and give you sound capability as well as freeing up one of your IDE ports. In some cases, a drive combination might not work on one computer but the same setup will work fine on another computer. Fortunately, disc drive incompatibilites are fairly rare these days but it can occasionally be a problem if using an old drive! What if you want to use the computer and the drive is elsewhere? In a modern computer, this won’t matter unless, of course, the drive is the only one in which case you’re up the proverbial creek! Yes, it will probably give you an error message saying that the drive is not there – just say thank you very much and keep working! In the case of computers which auto detect, it will auto detect that there is nothing there and continue on its merry way. Next time you plug the drive in, it will auto detect that it is back again (naturally, you’d never think of removing or inserting the drive with the computer power on, would you?). Note that these comments only apply if the disc drive is the same type, master or slave, on both computers. If you want to change from being a master drive on one computer to a slave drive on another, you will almost definitely have to change the jumper to suit. Security Using the mobile rack also has major pluses as far as security of information is concerned. If you handle sensitive or valuable information, you would be aware of the problems in ensuring that only your eyes see it! Even worse, industrial espionage is on the increase and we’ve all heard the horror stories about hackers getting in to company information. With the Mobile Rack, when you go home at night, the whole hard disc can go home with you. No-one, not even the world’s best hacker, can open up your files if they aren’t there! Even if you don’t have this type of problem, you should have a backup copy of your company data off site. The mobile rack makes it delightfully simple because as far as the computer is concerned, the hard disc it contains is just that – another hard disc that can be copied to. When the backup is done you simply remove it for safe storage. Looking at the other side of the coin for a moment, what about the security of the hard disc itself? Doesn’t making it removable make it easier to steal? Thankfully, the makers of the mobile rack are one step ahead: they’ve included a keyed lock which holds the frame (and therefore the disc drive) firmly in place. To remove, simply turn the key and withdraw it. Be warned, though – just like all those millions of disc boxes out there which secretaries around the world dutifully lock up each night, it would appear that one key fits all. So if you have a really determined thief . . . (nah, forget it: if he’s that determined he’d simply knock off the whole damn SC computer, anyway!). Where To Buy the HDD Carrier & Frame The “Mobile Rack” (or removable hard disc carrier & frame) is available from any Jaycar Electronics store. It comes in two versions: (1) Cat. XC-4670 for IDE drives; and (2) Cat. XC-4671 for SCSI drives. Both versions cost $39.95. For further information, contact Jaycar Electronics, 8-10 Leeds St, Rhodes, NSW 2130. Phone (02) 9743 5222; fax (02) 9743 2066. Silicon Chip Bookshop Understanding Telephone Electronics NOW IN STOCK By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. This is a very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $49.95 (please note price rise). Newnes Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Guide to TV & Video Technology By Eugene Trundle. First pub­lished 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $49.95. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $59.00. Power Electronics Handbook Components, Circuits & Applica­tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Surface Mount Technology By Rudolph Strauss. First pub­lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Radio Frequency Transistors Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order  ❏ Bankcard  ❏ Visa Card  ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $85.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semi­-custom electronics & data communications. 63 chapters, soft cover at $115.00. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $52.95. ✓ Title Price ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ Guide to Satellite TV $55.00 Servicing Personal Computers $90.00 Video Scrambling & Descrambling $50.00 The Ar t Of Linear Electronics $70.00 Digital Audio & Compact Disc Technology $90.00 Surface Mount Technology $99.00 Radio Frequency Transistors $95.00 Guide to TV & Video Technology $55.00 Electronic Engineer's Reference Book $160.00 Audio Electronics $75.00 Understanding Telephone Electronics $55.00 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ add $10.00 per book; elsewhere add $15 per book. TOTAL $A October 1997  11 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au Keep tabs on engine revolutions with this: 5-Digit Tachometer You asked for it and here it is: a highly flexible tachometer circuit that should cope with virtually any engine or rotating machinery. It has a crystal timebase and a resolution of one revolution per minute (1 rpm). Let’s face it, everyone loves those large tachometers with 270 degree movements. There is a strong temptation to make the needle sweep around the dial as you push down on the GO pedal. But while they look the part, traditional analog tachome­ters are not particularly accurate and have a very poor resolu­tion which means that you can’t precisely measure a particular 16  Silicon Chip engine speed such as 1450 rpm. For this reason, they cannot be used for accurately tuning an engine for correct mixture (done by adjusting for maximum idle speed) or procedures like setting the throttle switch for EFI engines. So there is a need for a digital tacho with much greater accuracy and resolution. Our new digital tachometer is Main Features   5-digit read out   1 rpm reso lution   crystal tim ebase   presettabl e digital mul tiplier for calibration   0.25 second update    facility fo r last digit to be locked on “0”   display ca n be dimmed for night time use   leading ze ro blanking mounted in a relatively large low profile case, measuring 225mm wide, 165mm deep and 40mm high. This is not the sort of project which could be easily integrated into your car’s dash By JOHN CLARKE board unless the small PC board with the 7-segment displays is mounted separately. But we’re getting way ahead of ourselves . . . Why such a large case? The answer is that a 5-digit tachometer is quite complex and no off-the-shelf ICs will do the job required. A custom microprocessor could but our previous experience with these sorts of projects indicates that our read­ers much prefer circuits with readily available ICs. Just to give an example of an IC that is relatively avail­able and could do most of the job, consider the National Semicon­ductor 74C926. This is a 4-digit counter with a multiplexed display. But we need five digits (or rather, you the readers, appear to want five digits) and the 74C926 does not have leading zero blanking. A tachometer without leading zero blanking looks pretty silly so that rules the 74C926 out of the picture. Sure, we could have added in leading zero blanking but then the advan­tages of a single chip 4-digit counter go out the window. So we have ended up with a relatively large PC board with quite a few ICs on it. Er, just how many are there? Well, 16 to be precise, not counting the 3-terminal regulator. But all the ICs are cheap and readily available. Above: this close-up view shows the board assembly mounted in the case before the front panel is fitted. Take care to ensure that the 7-segment LED displays are mounted correctly (decimal points to bottom right). OK, so we’ve been up-front about the size of the 5-Digit Tachometer and all its ICs, let’s describe its features. Features The SILICON CHIP 5-Digit Tacho­ meter will accurately read the revs of an engine or any rotating shaft with a resolution of 1 rpm and it will read high shaft speeds up to 60,000 rpm. The accuracy is a function of the crystal controlled timebase and the usual counter accuracy of ±1 digit. For example, a reading of 12,000 rpm would have an accuracy of ±1 rpm plus the timebase accuracy of say, Fig.1: the block diagram of the 5-Digit Tachometer. The main feature is the use of a phase lock loop and a programmable divider to frequency multiply the input signal. October 1997  17 18  Silicon Chip Fig.2 (left): the tachometer uses five decade counters to provide a 5-digit display. The diode OR gates provide leading zero blanking for the four most significant digits. less than 50 parts per million, which is negligible in this application. Making a tachometer to suit a wide range of engines is a real problem because you have to cater for so many cylinder, coil and 2-stroke/4-stroke combinations. Just to give you an idea of the complexity involved, we have had to cater for 1, 2, 3, 4, 5, 6, 8, 10 and 12-cylinder engines with single and multi-ignition coil combinations and 2-stroke and 4-stroke engines. Doubtless there’ll be some engines we have omitted but we can’t think of any. Catering for all these possibilities is provided by DIP switches and two links on the PC board. The new tacho’s input circuitry can accept high voltage from the primary winding of an ignition coil or small signals from a shaft position sensor or engine management tachometer output. And if you have a TAI or CDI system, you would also feed the low-voltage signal from the points, Hall effect sensor or reluctor pickup to the low-signal input. The tachometer can also be set to allow for one pulse per shaft revolution to a maximum of 60. The rpm measurement update time is one quarter of a second so there will be a new reading four times each second. In cases where the machine or engine rotation is not stable, the last display digit can fluctuate widely which makes it difficult to take a sensible reading. To cope with this situa­tion, we have provided a facility to lock the last digit to 0 if required. In this case the reading resolution will be reduced to 10 rpm. Frequency multiplication Measuring shaft rpm with a high resolution can be difficult since most motors rotate rather slowly, in electronic terms. For example, a shaft turning at 1000 rpm with one trigger pulse per revolution will provide a signal frequency of 1000/60 Hz or 16.67Hz to the tachometer. A normal frequency counter circuit with a 1-second count period will simply display a read­ing of 16 or 17. This is equivalent to 1Hz or only 60 rpm October 1997  19 Fig.3: these oscilloscope waveforms show the frequency multiplier action of the PLL (IC2). At top (Ch1) is the input waveform at pin 14. Ch2 is the VCO output while the Ref1 waveform is the comparator input at pin 3. Note that the input and comparator signals are in phase and at the same frequency. The VCO is shown multiplying by 10. The lowest trace (Ref2) is the error signal at pin 9. resolu­tion. If it was to display in rpm rather than Hz, then the count period would need to be one minute which is clearly not practi­cal. To obtain a tachometer with an update time of less than one second, the measured pulse signal frequency would need to be at least 60 times greater. This can be done in one of two ways. Firstly, we could sense the shaft rotation with a slotted vane which provides many pulses per revolution but this is not really an easy option. The second option is to multiply the pulse signal electron­ ically and this method is used in the SILICON CHIP 5-Digit Tachometer. Since our tacho­meter has an update time of one quar­ter of a second (250ms) and an actual counting period of 125ms, the multiplication factor for one pulse per shaft revolution is 60 x 8 or 480. Where there are more pulses per shaft rotation (eg, two for a 4-cylinder 4-stroke), then the multiplication factor can be reduced. Fig.1 shows the block diagram of the 5-Digit Tachometer. The input signal is conditioned by filtering to prevent false triggering on noisy signals and then squared up with a Schmitt trigger. The resulting signal is passed to a frequency multiplier consisting of a phase lock loop and a programmable divider. The oscillator output from the phase lock loop is fed through the programmable divider and the divided output is compared in the phase lock loop against the input signal. Hence the phase lock loop “locks” the multiplied frequency output to the input signal. The multiplied frequency is fed to the 5-digit counter and a crystal oscillator provides the “housekeeping”; ie, reset and latch enable signals. The phase lock loop signal is counted over a 125ms period, latched and then reset, ready for the next count sequence. The latched count is shown on the five digit display. Display dimming is included for night-time use. Circuit details Fig.4: timing waveforms for the counter circuitry. When Q13 of IC14 is low, NAND gate IC15d inverts this and enables the clock on IC5b. Thus counting in IC5b and following counters can start. When Q13 of IC14 goes high, the enable input to IC5b goes low and counting stops. IC15c inverts this to produce a low signal to the latch enable inputs on IC8 to IC12 via the .001µF capacitor. The value counted by IC5b to IC7b is then latched and displayed. 20  Silicon Chip The full circuit for the 5-Digit Tachometer is shown in Fig.2. Starting at the top lefthand corner of the circuit, the signal from an ignition coil is divided down with 22kΩ and 10kΩ resistors. The .056µF capacitor rolls off signals above about 400Hz and the filtered signal is then AC-coupled to the base of Q1. The 10kΩ resistor between base and emitter holds Q1 off in the absence of a voltage on the ignition coil input. The 1.2kΩ resis­tor at Q1’s base is there to provide a low voltage signal input point which can drive the transistor with as little as 1V peak-to-peak. The collector of Q1 is pulled to the 8V supply via a 10kΩ resistor and its output is filtered with another .056µF capacitor. IC1 is an LM393 dual comparator with only one section used in our circuit. The comparator is connected as a Schmitt trigger with hysteresis set by positive feedback between the output at pin 7 and the non-inverting input at pin 5. The pin 7 output is an open collector transistor and when it is off, the 1.2kΩ resis­tor pulls it high. A voltage divider at the non-inverting input (pin 5), formed by the two 10kΩ resistors across the supply and the 10kΩ feedback resistor, sets this input at +5.23V. The signal from Q1’s collector must go higher than this to drive the comparator output at pin 7 low. When the output is low, the same voltage divider action sets the non-inverting input at +2.77V and so the collector of Q1 must go below this voltage before IC1’s output will again go high. The wide hysteresis (about 2.5V) on IC1 ensures that any noise on Q1’s collector will be ignored. Phase lock loop Following IC1 is the phase lock loop (PLL), IC2. This oscillates at a maximum frequency set by the 100pF capacitor and resistor at pin 11. The actual frequency is controlled by the input voltage at pin 9. When pin 9 is at the full supply voltage, the oscillator runs at the maximum rate. When pin 9 is close to 0V, the oscillator runs at its slowest speed. This is nominally more than 100 times slower than the maximum rate. The PLL’s oscillator output at pin 4 is fed to program­mable dividers IC3 and IC4. IC3 divides from 1 to 15, depending on the switch settings on DIP1-DIP4. If only DIP1 is set high, the IC divides by 1. When all switches are closed, the IC divides by 15. IC4 divides by 16 when only DIP5 is closed and this increases to 255 when DIP5-DIP8 are all closed. Thus, when IC3 and IC4 are used together, we can divide from 1 up to 255 + 15, or a total of up to 270 in steps of 1. Fig.5: these oscilloscope waveforms show the timebase circuitry in action. The top trace shows the enable signal to pin 10 of IC5b. The second trace is the clock signal (pin 9) which is counted when pin 10 is high. The low pulse on the third trace latches the counted data into IC8, IC9, IC10 and IC11. The posi­tive edge of the pulse clocks D-flipflop IC16. The reset pulse on the fourth trace resets counters IC5b-IC7b. The output from the programmable dividers is passed to the enable input of IC5a. This is a binary coded decimal (BCD) coun­ter which divides by 10 at its Q4 output. With the inclusion of IC5a, the overall division can be up to 2700. There are two link options, with LK1 selecting divide by 10 and LK2 selecting divide by 1. Following IC5a, the divided signal is applied to the com­parator input of the PLL at pin 3 and this is compared with the tacho input signal at pin 14. The PLL produces an error signal at pin 13 which after filtering is applied to the voltage controlled oscillator input at pin 9. The rate at which the PLL tracks the incoming signal is set by the filter components at pin 9. The 6.8µF capacitor in con­junction with the 180kΩ resistor sets the lowest frequency for Specifications Readout range ������������������������������ >100 to 1 Maximum reading �������������������������� nominal 60,000 rpm with 0.25 second update Multiplier settings �������������������������� from x1 to x270 in steps of 1; x270 to x2700 in steps of 10 Resolution ������������������������������������� 1 rpm maximum or 10 rpm if last digit locked on 0 Accuracy ��������������������������������������� ±1 digit (crystal locked) Count period ��������������������������������� 0.125s (1/8s) Update period ������������������������������� 0.25s (1/4s) Input sensitivity ������������������������������ 3V p-p on ignition coil input and 1V p-p on low signal input Maximum Input Voltage ����������������� 600V on ignition coil input, 120V on low signal input October 1997  21 Parts List For 5-Digit Tachometer 1 PC board, code 04310971, 198 x 155mm 1 PC board, code 04310972, 104 x 24mm 1 front panel label, 215 x 32mm 1 plastic case, 225 x 165 x 40mm 1 clear red plastic sheet, 74 x 19 x 2mm 1 mini TO-220 heatsink, 20 x 20 x 9.5mm 1 3mm screw and nut for heatsink 4 12G x 10mm self-tapping screws 4 6mm metal spacers 1 small cordgrip grommet 5 PC stakes 2 4-way DIP switches (DIP1DIP4 & DIP5-DIP6) 1 2m length of 0.8mm tinned copper wire 1 32.768kHz crystal (X1) Semiconductors 5 HDSP5303 common cathode 12.5mm LED displays (DISP1-DISP5) 1 7808 8V positive regulator (REG1) 1 LM393 dual comparator (IC1) 1 4046 phase lock loop (IC2) 2 4526 programmable binary dividers (IC3, IC4) 3 4518 dual BCD counters (IC5IC7) which it will lock, while the 4.7kΩ resistor in series with the 6.8µF capacitor improves the response time when the circuit locks. The oscilloscope waveforms in Fig.3 show the PLL (IC2) in action. At top (Ch1) is the input waveform at pin 14. Ch2 is the VCO output while the Ref1 waveform is the comparator input at pin 3. Note that the input and comparator signals are in phase and at the same frequency. The VCO is shown multiplying by 10. The lowest trace (Ref2) is the error signal at pin 9. 4-bit counters The VCO output from IC2 clocks the second 4-bit BCD counter in IC5; ie, IC5b. Its outputs at Q1-Q4 are decoded by IC8 which is a 4511 BCD to 7-seg22  Silicon Chip 5 4511 BCD to 7-segment LED decoders (IC8-IC12) 1 4071 quad OR gate (IC13) 1 4060 binary counter (IC14) 1 4093 quad Schmitt NAND gate (IC15) 1 4076 quad flipflop (IC16) 3 BC338 NPN transistors (Q1Q3) 2 1N4004 1A diodes (D1,D21) 19 1N914, 1N4148 switching diodes (D2-D20) 1 16V 1W zener diode (ZD1) Capacitors 1 1000µF 16VW PC electrolytic 2 100µF 16VW PC electrolytic 1 6.8µF 16VW PC electrolytic 1 1µF MKT polyester 9 0.1µF MKT polyester 2 .056µF MKT polyester 3 .001µF MKT polyester 1 100pF MKT polyester or NP0 ceramic 2 22pF NP0 ceramic Resistors (0.25W 1%) 1 10MΩ 1 4.7kΩ 1 180kΩ 3 1.2kΩ 1 150kΩ 35 680Ω 1 22kΩ 1W 1 1.2Ω 25 10kΩ Miscellaneous Hookup wire, connectors, solder, etc. ment LED display driver. Thus, the LED display shows the count value from IC5b. The divide-by-10 output at Q4 of IC5b clocks the following IC6a counter at its enable input, pin 2. Similarly, IC6b, IC7a and IC7b are clocked from the Q4 outputs of the previous counter stage. Each of these counters drives its own 7-segment decoder (IC10-IC12). Leading zero blanking Diodes D2-D17, IC13 and IC16 provide leading zero blanking for the LED displays. This means that instead of the display indicating 00651, for example, it will only show 651, with the leading two zeros unlit. This makes the display far easier to read. The leading zero blanking works by monitoring the Q1-Q4 count outputs of the 4518 counters (ie, IC6a-IC7b) via the diodes which are connected as OR gates. If the BCD output from IC7b is zero (ie, outputs Q1-Q4 low), then the common cathode connection of diodes D14 -D17 will be held low via the 10kΩ resistor connecting this point to ground. This low level is applied to data input DD of quad D flipflop IC16. The corresponding QD output when clocked at pin 7 applies a low to the blanking input of IC12 at pin 4 to turn off the display. IC13b is a 2-input OR gate which monitors the diode OR gate D10-D13 for IC7a and the D14-D17 diode OR gate signal via IC13a. If both inputs to IC13b are low, then its pin 11 is low. This low output is applied to the DA input of IC16 and is clocked to the QA output and thence to the blanking input of IC11. If there is other than a zero count at least one diode will pull an input of IC13b high to prevent blanking. A similar scenario occurs with IC6b, IC6a and the associated diodes driving IC13c and IC13d. Note that the blanking circuit relies on the information from the most significant digits. If for example, IC13a’s output is high due to a count higher than zero for IC7b, the IC13b, IC13a and IC13d OR gates will have high outputs and no blanking will occur. Thus as soon as a more sig­nificant digit has a count more than 1, the following less sig­nificant digits cannot be blanked. IC16 is used to latch in the leading zero blanking after the IC6a to IC7b counters have counted the signal from IC2. If these blanking signals were not latched, then the leading zero feature would be lost as the counters made their next count from zero. Timing A 32.768kHz crystal oscillator is formed across the invert­er at pins 10 and 11 of IC14. The 10MΩ resistor biases the invert­er while the 150kΩ resistor and the 22pF capacitors across the crystal prevent it from oscillating in a faster spurious mode. The Q12 and Q13 outputs of IC14 produce 4Hz and 2Hz respectively. Fig.4 shows the timing waveforms for the counter circuitry. When Q13 of IC14 is low, NAND gate IC15d inverts this and enables the clock on IC5b. Thus counting in IC5b and the This view shows how the board assembly mounts inside the case. The two 4-way DIP switches are used to set the PLL multi­plication ratio so that the unit can be made to work with virtually any 2-stroke or 4-stroke engine. following counters can start. When Q13 of IC14 goes high, the enable input to IC5b goes low and counting stops. IC15c inverts this to produce a low signal to the latch enable inputs on IC8-IC12 via the .001µF capacitor. The value counted by IC5b-IC7b is then latched and displayed. The .001µF capacitor charges via the 10kΩ resistor to the positive supply and the rising edge clocks the leading zero data on DA-DD on IC16 to the QA-QD outputs. Diode D19 prevents the pin 7 input of IC16 going above the positive supply when IC15c’s output goes high again. When both Q12 and Q13 of IC14 go high, the pin 3 output of NAND gate IC15a goes low. The resulting high on the pin 4 output of IC15b resets the 4518 counters via the .001µF capacitor. Diode D18 prevents excursions below ground when IC15b goes low. The 10kΩ resistor and .001µF capac- itor between the output of IC15a and the input to IC15b produce a short delay to prevent unwanted resets as Q12 goes low and Q13 goes high at the end of the count se­quence. The oscilloscope waveforms of Fig.5 show the timebase cir­ cuitry in action. The top trace shows the enable signal to pin 10 of IC5b. The second trace is the clock signal (pin 9) which is counted when pin 10 is high. The low pulse on the third trace latches the counted data into IC8, IC9, IC10 and IC11. The posi­tive edge of the pulse clocks D-flipflop IC16. The reset pulse on the fourth trace resets counters IC5b-IC7b. Display dimming The 7-segment displays DISP1 to DISP5 have their common cathodes connected to the collector of Q3. If transistor Q2 is off, then Q3 is turned on via the 1.2kΩ base resistor. This provides the full brightness to the displays via their 680Ω anode resistors. Diode D20 and transistor Q2 provide the dimming control feature. Diode D20 feeds a 1024Hz signal from pin 5 of IC14 to the input of Q2. When the Q5 output of IC14 is low, the base of Q2 is momentarily pulled low via the 0.1µF capacitor, switching off the transistor and allowing Q3 to turn on and light the display. The 0.1µF capacitor charges up via the 10kΩ base resistor on Q2 and so the transistor turns on again, turning Q3 and the displays off. Since the displays are turned on and off at 1024Hz there is no apparent flicker and the proportion that Q3 is on sets the brightness. This is determined by the 0.1µF capacitor value and this can be increased for a brighter display. Power for the circuit comes from the 12V battery in a car or a 12V DC 500mA plugpack. Diode D21 prevents a reversed polari­ty connection from damaging the circuit. A 1000µF capacitor filters the supply, while a October 1997  23 1.2Ω resistor decouples the supply from transients which are shunted using 16V 1W zener diode ZD1. The 7808 regulator provides the 8V supply for the circuit. Two 100µF capacitors decouple the input and output for the regulator and nine 0.1µF capacitors help bypass the supply lines on the PC board. housed in a plastic instrument case measuring 225 x 165 x 40mm. You can begin construction by checking the PC boards for etching defects such as shorts between tracks and undrilled holes. These should be fixed before inserting any compo- Table 1: Capacitor Codes Construction The 5-Digit Tachometer is constructed on two PC boards. The main PC board is coded 04310971 and measures 198 x 155mm, while the display PC board is coded 04310972 and measures 104 x 24mm. The display is designed to attach at rightangles to the main PC board. As already noted, the tachometer is nents. Then insert and solder in all the links as shown on the component overlay diagram of Fig.6. Next, insert and solder in all the resistors. You can use the accompanying resistor colour codes in Table 2 as a guide to selecting the correct values. Better still, check each value with your digital multimeter before soldering it in. The ICs and DIP switches can be installed next, taking care with their orienta­tion. Be sure to put the correct IC in each position. When soldering in the diodes, note that D21 and D1 (both 1N4004) are larger bodied than the others (1N914s). Take care with their orientation. Insert the capacitors and note that the electrolytic capacitors need to be inserted with the polarity ❏ ❏ ❏ ❏ ❏ ❏ ❏ Value IEC Code EIA Code 1µF    1u  105 0.1µF   100n   104 .056µF   56n  563 .001µF    1n  102 100pF   100p   101 22pF   22p   22 Table 2: Resistor Colour Codes ❏ No. ❏  1 ❏  1 ❏  1 ❏  1 ❏ 25 ❏  1 ❏  3 ❏ 35 ❏  1 24  Silicon Chip Value 10MΩ 180kΩ 150kΩ 22kΩ 10kΩ 4.7kΩ 1.2kΩ 680Ω 1.2Ω 4-Band Code (1%) brown black blue brown brown grey yellow brown brown green yellow brown red red orange brown brown black orange brown yellow violet red brown brown red red brown blue grey brown brown brown red gold brown 5-Band Code (1%) brown black black green brown brown grey black orange brown brown green black orange brown red red black red brown brown black black red brown yellow violet black brown brown brown red black brown brown blue grey black black brown brown red black silver brown Fig.6: this diagram shows the component layout on the main and display PC boards. When mounting the LED displays on the small board, make sure that the decimal points are located in the bottom righthand corner. shown. Table 1 shows the codes which will be shown on MKT and ceramic capacitors. The 3-terminal regulator REG1 is mounted horizontally with its metal face towards the PC board and a small heatsink beneath it. Bend the leads before inserting it into place. It is secured with a screw and nut. Next, insert the PC stakes, transistors and the crystal. When inserting the displays on the smaller PC board be sure that the decimal point is located in the bottom righthand corner. Note that the decimal points are not used in this circuit. Case work Attention can now be turned to the case. First, temporarily place the main board in position and check October 1997  25 96 Testing times 12 6 80 - 8 60 - 10 48 - 12 40 Checked all your work carefully against the wiring diagram? If so, apply 12V to the board and check that the display shows a 0 or 1 on the righthand digit. If not, immediately disconnect power and check for errors such as reverse polarity connection of power or incorrectly placed components. When the circuit is operating, the supply to each IC should be 8V. You can check this by connecting one side of your multimeter to the ground PC stake and measuring pin 16 on IC2-12, IC14 & IC16; pin 14 on IC13 & IC15; and pin 8 on IC1. You can set the DIP switches according to Tables 3 & 4 to suit your application. Note that at least one switch must be set to ON or the programmable divider will not operate. Note also that either LK1 or LK2 must be present on the board (but not both), otherwise IC5a will malfunction. You can check that the tachometer operates by applying a signal from a function generator to the input. You may need to use the low signal input for this. Alternatively, simply pulling pin 9 of IC2 to 8V will cause the PLL oscillator to run at maxi­mum and so display a reading. Test that the display dims when the dimming input is connected to 12V. 0.5 960 2 1 480 3 1.5 320 4 2 240 5 2.5 192 6 3 160 Table 4: Switch & Link Settings (LK1 = 10x, LK2 = 1x) Multiplier DIP 87654321 LK1, LK2 x960 01100000 yes, no x480 00110000 yes, no x320 00100000 yes, no x240 00011000 yes, no x192 11000000 no, yes x160 10100000 no, yes x160 00010000 yes, no x120 00001100 yes, no x96 01100000 no, yes x80 01010000 no, yes x80 00001000 yes, no x60 00000110 yes, no x48 00110000 no, yes x40 00000100 yes, no the location of the display PC board. Now, using a drill larger than 10mm, remove the two integral mounting pillars in the base of the case which would otherwise foul the display PC board when it is placed in position. Place the main PC board in position over the integral standoffs, using 6mm spacers to raise it, Secure it with self-tapping screws. Now place the display PC board vertically in position and mark the rear of this board where the main PC board makes contact. Remove both PC boards and tack solder them togeth­er at the large copper areas. Make sure they are at 26  Silicon Chip Vehicle installation The tachometer can be installed into a vehicle using auto­ m otive connectors to make the connections to the ignition posi­tive supply, the lights circuit for dimming and the coil terminal. The ground connection can be made to the chassis with an eyelet and self-tapping screw. Where access to the coil primary is impossible with the modern style of combined coil and transistor, you Fig.7: this full-size front panel artwork can be used as a template to make the cutout for the LED displays. 120 5 1 RPM 4 10 4-stroke: Multiplier Pulses Per Number Of (0.125s count Shaft Rotation Cylinders/Coil period) DIGITAL TACHOMETER 8 right angles and check the positioning by placing into the box again. If correct, solder all matching copper tracks. Apply a liberal fillet of solder to the large copper areas to improve mechanical strength. Next, drill the rear panel for the cordgrip grommet. The front panel requires a rectangular cutout for the display window and this can be made by making a series of holes around the hole perimeter and then filing it to shape, so that the red plastic window fits tightly in place. Table 3: Muliplier Ratio For Various Engines & Shaft Pickups can pick up a suitable signal from the tachometer output lead of your engine management computer. The signal connects to the low signal input. It is calibrated as normal, taking the number of engine cylinders into account. Fig.8: this is the full-size etching pattern for the two PC boards. In some installations, it may be eas­ ier to keep the main PC board separate from the display board and connect with multi-way cable. This will allow the display to be mounted in a confined space. If the tachometer is to be used on stationary machinery, a suitable shaft rotation sensor may be required. These are normal­ly a metal vane with several notches which trigger a Hall effect switch or optical pickup. Last digit lock If you wish to lock the last digit on zero to prevent it continuously fluctuating, the PC board will require a small modification. Pins 3 & 4 of IC8 should be disconnected from the +8V supply using a knife to break the track in the thinned out section. Then make a solder bridge from the track leading to pins 3 & 4 to the ground at pin 8. Finally, break the track leading to the “g” segment of DISP1 in the thinned section under the seven 680Ω SC resistors. October 1997  27 SERVICEMAN'S LOG Smoke, fire & confusion Yes, that is the only way I can describe the happenings which inspired this month’s notes. More to the point, some of these “happenings” were of my own creation; in hindsight, I should have done better. But, it’s easy to be wise after the event. In the continuous pursuit of brownie points, in the con­stant hope of a financial reward, or gratuity, I grasped the opportunity to repair one of SILICON CHIP’s monitors. Until now, my copy book wasn’t looking too good with them. One of their previous 21-inch monitors had the infuriating habit of dying at their premises but working constantly in my workshop. In the end, I concluded that my workshop was either drier or less polluted than their office. Or was it the other way round? Any­way, there didn’t seem to be any way of even starting the repair on that monitor. This time, it was a 1993 MAG MX17F 17-inch monitor with two distinct problems. First, there was an intermittent vertical jitter and height size problem and then, after about half an hour, the set would pulsate on and 28  Silicon Chip off in hiccup fashion (oh no! – more intermittents). Removing the case and metal covers gave fairly good access to the main printed circuit carrying the deflection circuits. The power supply, small signal and RGB circuitry boards turned out to be less accessible, in roughly that order. On examining the main board it didn’t take a mental giant to see that there were quite a few suspicious-looking solder joints. So out came the soldering iron and an hour later I had reworked almost the entire board. When I reconnected it, every­thing looked good – the vertical problem had vanished and the set was still running perfectly an hour later. I reboxed it and put it aside for a soak test, thinking that that was that. It was still working at closing time and half way through the next day but that was as far as it went. There was no longer any vertical jitter but by lunchtime, it had started to hiccup again. During the soldering procedure, I had noticed a dark spot around Q506, a 2SD799 low-voltage high-current TO-220 transistor. Thinking that maybe this transistor had become damaged due to high temperature from the dry joints, I decided to remove it for testing and possible replacement. The only problem was that I didn’t have a replacement or even a substitute. Fortunately, the set employed another one in a different circuit location and so I swapped them over (this wasn’t easy, as access was just under the yoke). But the swap made no difference – an hour or two later, it was hiccuping again. The scientific approach Next, I removed and reworked the power supply and small signal boards but the set still hiccuped. The brute force ap­proach was over; now for the scientific one! First, I summoned Mrs Serviceman to get on the blower and track down a circuit diagram – I always give her the easy tasks – while I dusted off the multimeter and warmed up the CRO. As it happened, she quickly traced the agency but that was as far as it went – the company wasn’t prepared to supply a circuit diagram which meant that I was on my own unless I could score one from somewhere else. But for now, I decided to let it ride while I delved deeper into the monitor. I was waiting for it to warm up when the phone rang and I had to deal with an elderly lady trying to book in a TV repair at home. It took some time to get all her details, the type of set, the fault, the likely costs involved and make an appointment. By the time I finished, there were two people queuing at the coun­ter. And then the phone rang again. All in all, by the time I dealt with everything it was over half an hour and when I went back into the workshop, the monitor was well and truly hiccuping. More precisely, this show­ed up on the supply rails which were pulsating in sympathy. In particular, I wanted to measure the 185V rail (the only voltage that wasn’t fluctuating was the 325V to the main electrolytic from the bridge rectifier). I also needed to figure out whether the hiccuping was due to an abnormal load, a safety circuit, or an excessively high voltage rail. I let everything cool and tried again and, as luck would have it, the fault was now permanent – it was hiccuping whether it was hot or cold and regardless as to how long the set had been running. Next, I shorted the horizontal output transistor’s base to its emitter and hung a 100W load on the 185V rail. It was still hiccuping. I then tried varying the input voltage with the Variac but it was a switchmode power supply that gave all or nothing. However, there was one thing – as the analog multimeter was swinging up and down, I noticed that the needle seemed to overshoot past 200V, although this might have been due to lack of damping in the meter. I marked the position of the 185V setup pot (VR303) and then ad­justed it. Interestingly, the set stopped hiccuping when I reached the lower end stop of VR303. Bingo! – it meant that this rail had to be too high. Circuit tracing My next step was to trace out the control feedback circuit – see Fig.1. This showed that VR303 was fed from the 185V rail via R331. The voltage on the wiper of VR303 then biased Fig.1: the voltage control feed­ back circuit in the MAG MX17F computer monitor. regulator IC303 which in turn fed optocoupler IC302 in the switchmode power supply primary. Resistor R331 was a 1W unit and, when I removed the brown glue that was covering it, I found that it was slightly disco­ loured. So, were its colour markings correct? It was now nearing closing time and I was about to shut the shop but I was eager to prove that I was on the right track. I read from left to right – brown, red, black = 12Ω and quickly fitted a new one. Big mis­take! The set tried to start, there was a crack – a puff of smoke – and WHOOPS! It was too late to investigate further. I had to leave it; there was some (supposedly) important engagement or other for which I had to be on time – a wedding anniversary or something. It wasn’t until next day that I realised my folly. Initial­ly, I had noted only the first three bands but there were actual­ ly five equally spaced bands – which I read as brown, red, black, brown and white. And the multimeter read 118kΩ. So was it really a 120kΩ resistor and had I misread the third colour, or had it been changed due to the brown goo or heat? But this didn’t make sense either. It was the white band that shook me out of my lethargy. As I had read it, the white band would be in the tolerance position. But there is no white tolerance band in the resistor scale. I had read the colours in the wrong order – the correct sequence was white, brown, black, red, brown. And that worked out to 91kΩ, 1%. So the multimeter reading of 118kΩ was correct; the resistor was originally a 91kΩ device but had gone high, to 118kΩ. This meant that the 12Ω resistor I had fitted was singular­ly inappropriate; as testified by the fate of IC303, which now consisted of just three legs sticking up out of the board. It took some time to find the rest of it in order to determine its type number. It turned out to be a TL431. I fitted a 91kΩ resistor for R331, replaced IC303, reset the pot to the mark I had made, connected a digital multimeter to the 185V rail, and gingerly switched on. The set functioned correctly and the rail was almost spot on 185V. Finally, I rehoused the chassis and put it aside for a long soak test, while trying to ignore the “was it ready?” October 1997  29 Serviceman’s Log – continued was marked. After such major surgery, I felt that it should have been checked. Anyway, at least it per­formed well after a prolonged soak test. The Magtron was made by AVAT, which stands for Advanced Video and Audio Technology Co. It complies with a newish Swedish safety standard (MPRII) for levels of magnetic and electrical radiation, which it proudly boasted on the front. Anyway, this was severely corroded by, of all things, coffee being poured into it. However, the damage was localised and it didn’t take much to clean up the mess. The reason it was dead was because D515 was short circuit and C527 had exploded. Apart from that, it worked well when the work had been completed. The ancient Sanyo pleas from SILICON CHIP – I wanted to thoroughly test it. It went back a few days later and hasn’t missed a beat since. Now, about that, er, possible emolument arising from pre­viously mentioned brownie points. No? I thought not. Oh, well. Two more monitors Surprisingly, the same week I had two other monitors in for repair. They were similar but dissimilar, if that makes sense. One was a 1993 MAG LX1564 and the other was a Magtron BMC-14SV4. They were similar in that the badges were the same font, size, and colour. The other similarity was that they were both dead due to corrosion. However, their chassis were completely different. The MAG came from a location near the beaches, was corroded by salt air and in serious trouble. The power supply was blown and had to be rebuilt component by component. The faulty items were: F301, 3.15AT fuse; Q301, 2SK955 FET; IC301, CS3842A IC controller; and ZD307, 18V zener. Once 30  Silicon Chip the power supply was working, it went into hiccup mode – like the previous MAG moni­tor. Interestingly, it used the same main rail regulation circuit and the same resistor but in this case the cause was a short circuit horizontal output transistor (2SC4747). By the time I found this, R153, a 1Ω resistor, had expired from the current flow. I also replaced a leaky electrolytic capacitor (C330, 1000µF 35V). It was a bit like me: old, haggard and worn out, but still functional – just! I was still not out of the woods. There was no picture and there appeared to be sparking inside the CRT socket. This monitor was fitted with a lot of internal metal mesh electrostatic screens which makes access difficult. I had to move several before I could get to the problem area. And yes, it was the CRT socket – it was corroded and sparking across its own internal spark gap. A new socket fixed that and it behaved like a new one. I haven’t been able to track down a circuit for this model either. I would have liked to have known how to set up the HT and EHT rails, as nothing Now for a change of scene – TV sets. Mr Woods is a long standing customer of mine who owns a number of sets in a large rambling 2-storey house. Unfortunately, the house is on the side of a hill; worse still, all his sets are 63cm models. The one he wanted me to look at was an ancient Sanyo CTP8631N employing a B7PJ chassis, though this is probably irrel­evant for this story. He said his grandchildren had come down for the weekend and jumbled up all the stations. What’s more, the video would not work. He implied that all that was needed was a retune. Quick and easy – now where have I heard that before? I arrived that afternoon and climbed, thankfully, only two flights of stairs to their rumpus room. The TV set sat in a rather dark, damp-looking corner. I switched it on and noticed that the touch sensors wouldn’t change channel nor was there any picture. In fact, I was just pointing this out when there was loud banging from the rear and bright flashes of green raster on the screen. I switched off immediately and asked Mr Woods if this the simple fault about which he was complaining? Well, actually it was – except it hadn’t made that banging noise before! I turned the set around and carefully removed the back. One has to be very careful with some Sanyo models; the heavy back can fall and take the neck off the tube in one quick guillotine action. This model was OK SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏  3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________  Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ and once inside I could see that it was very damp and obviously tracking from the ultor cap. As my CRC 2-26 contact cleaner/ lubricant was in the car way down the street, I asked if he had anything similar handy. The best he could suggest was some WD40. Close enough, I thought – it would do. I sprayed the touch sensors, ultor cap, EHT transformer and tripler, then wiped up the excess where I could. When I switched on again, the channel selector worked and there was no more banging. But there was still no picture and I could hear hissing and spluttering noises from around the EHT transformer. I turned the set off and sprayed more WD40 in that area. Another big mistake: I switched on again and stuck my head in the back, trying to pinpoint the sparking which I could still hear. Then there was a loud clicking noise and a flashover near the EHT transformer connections. The WD40 ignited in huge ball of fire and I nearly lost my eyebrows and what hair I have left. The area had been fairly saturated with WD40 and it con­tinued to burn with 30cm long yellow flames which showed no signs of extinguishing. I realised I had only a few seconds before the wooden case might start to burn too and cause a major disaster. I switched the set off quickly. There was nothing to hand except a large rag which I grabbed and attempted to smother the flames. In what seemed like an eternity, I finally put the fire out and then turned around aghast to see that Mr Woods had watched the whole saga. He was far less concerned about it than I was. I think many people would have abandoned the situation there and then but I figured that if I did that I would be let­ting Mr Woods down as well as myself – like falling off a horse, you should get back on immediately to restore your self-con­fidence. Or so I’m told. In practice, I play it safe; I don’t get on horses. The trick was to pretend that it was all quite normal. The melee had lasted, perhaps, only 10 seconds but I had at least seen where the fire started. I pulled the chassis out and unscrewed the EHT transformer. This transformer is fitted with terminal pins (or “posts”), which protrude vertically in a semi­circular array from a plastic support above the main winding assembly. October 1997  31 Serviceman’s Log – continued These terminals are supply points for the various voltage leads leading to other parts of the circuit. They are fed, in turn, by short bare wires emanating from within the transformer. And one of these short wires – the one connected to the G2 (screen) terminal – had corroded and broken, creating a gap across which some 500V was producing a spark. And it was this spark which had ignited the WD40. With some difficulty, due to the short length of wire and the restricted space, I managed to solder a jumper across the gap. There was now no need to wipe away excess WD40 because the heat had evaporated it along with any moisture and I was confid­ent there were no more sparks to ignite it in any case. Neverthe­less, I was nervous when I switched the set on again. It was all an anticlimax – both picture and sound were fully restored, much to my relief. The various stations could now be tuned in correct­ly with their corresponding touch button numbers and even the video functioned. 32  Silicon Chip The fire area looked rather messy, with molten plastic leads and fittings, but I checked that their insulation was still OK and nothing was likely to short. After I had replaced the covers and put the set back, I explained the situation as best I could. I advised him that this damp corner was not the best place for it, that he shouldn’t leave the set on unattended, and that he should have some sort of fire appliances inside his house anyway (smoke detectors, fire extinguishers, etc). Finally, I emphasised that the set was old and corroded and really should be replaced. I didn’t dwell too much on the flamma­ble qualities of WD40 and left while the going was good and my reputation still intact. My final faux pas My final faux pas for this week – did I really need that many? – involved a Sony SLV-X57AS video recorder which came in with the fault “too fast”. More exactly, when playing a tape the horizontal hold was off speed and speech was fast, rather like slow Donald Duck. Both the capstan and drum motors were running fast and the auto-tracking was not working. I removed all the covers and the front panel and examined the set carefully all over. It looked fairly new and in good condition. I refitted the control knobs and switched on. According to the service manual, all the pulses in and out of the servo/system control (IC501) were at incorrect speed. These included the drum FG, PG and capstan FGs, as well as the control pulses from the ACE head and the outputs to the motors. I noticed that when I touched pins 7 and 6 of IC403, the drum motor could be slowed until the picture was locked. IC403 is the error integrator. I checked all the supply rails and “scoped” them for ripple, in case some of the electrolytics had gone in the power supply. All were present and correct. I then changed IC403, IC406, IC407 and was about to change IC405 before even trying to change IC501, a 100-pin surface-mounted high-density microprocessor. But by now I was beginning to smell a rat. The machine was in good condition and no-one had fiddled with it – or so I was assured. What drastic action could have caused this? Well, I had to order these two ICs and they were expensive. In the meantime, I would have to put the machine aside and so, rather than risk losing the screws, I decided to reassemble the whole thing. Fitting the front panel is a little fiddly, especially with the toggle control knobs and switches, but at least I had the whole thing back together. I was checking it to make sure I had done it all properly when I noticed a switch under the front panel, marked “Color System NTSC PB on PAL TV”. It was in the wrong position but I didn’t put any significance on this; it can easily happen when refitting the front panel. Instead, I simply moved the switch to its correct position and switched on for a check. However, when I pressed play, the picture from the tape came up perfect in all respects. Suddenly all was clear. This recorder is a dual-standard machine; it will play either an NTSC tape or a PAL tape into a PAL receiver and someone had inadvertently moved the switch into the wrong position. So much for my high-tech approach. I had found the fault and fixed it unwittingly – if only it hadn’t taken so long for me to wake up to it! SC ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. TOTAL $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  GIFT SUBSCRIPTION DETAILS RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia October 1997  33 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au The connection to the modified ECU is made by fitting this BNC socket. The “BAAM VP Auto” label refers to the car (a VP Commodore with automatic transmission) and the unique broadcast code of this MemCal (BAAM). By JULIAN EDGAR Reprogramming the Holden ECU Real-time reprogramming of Holden’s ECU (electronic control unit) is now possible thanks to a very clever software package. It takes the guesswork out of optimising performance if engine modifications are made. No major car company provides software that allows its engine management system to be reprogrammed. This means that anyone who is capable of reprogramming the main chip in the ECU has previously been involved in some clever detective work, to find out how it works! Some aftermarket companies make chip changes on an experi­ mental basis, altering a byte and then observing how the engine responds to that change. In that way, they gradually build up a picture as to which parts of the program control which aspects of the engine behaviour. A radically different approach has been adopted by Ken Young, the programmer behind the Kalmaker (former­ly DynoCal) package. Ken has identified the function of each byte within the dozen or so programs used by Holden in its various ECUs and has written a software editing package to suit. Basically, the Kalmaker software runs on a portable PC and allows real-time reprogramming of the Holden ECUs. As indicated in the July 1997 issue, the Holden ECU is based on a MemCal. This is a plug-in module that contains an EPROM (for program and engine data) plus DIP resistor packs to provide engine fuel backup values. The rest of the electronics within the ECU module includes the injector drivers plus various counters, timers and so on, as required in any engine management system. The EPROM in the MemCal is not amenable to byte-by-byte reprogramming. To get around this problem and to allow data changes “on the fly”, the MemCal is replaced with a new PC board dubbed a “Real Time Board” October 1997  37 GMH 16K ECM Programs H35 Base program used on 1.8l TBI Camira H54A H54B 1.6l TBI + 1.8l PFI Pulsar/Astra 2.0l PFI Camira H5D Late 1.6l TBI + 1.8l MPI Pulsar/Astra? Late 2.0l PFI Camira, also VL Walkinshaw & VN V6 & V8 FVA FVB FVC FVD Series of programs for Formula Brabham V6 HA5 Used on later VN V6 only HB1 Minor change used on VN V6 & Group A V8 HDB Group A V8 & HSV HFB Used on all late VP V6 & V8 H03 V6 LPG GMH 32K ECM Programs H12A H12B VR 3.8l V6 & 5.0l Manual Transmission H3C VR 5.7l V8 Manual Transmission H5B VS 5.7l V8 Manual Transmission H5A VS 5.0l V8 Manual Transmission GMH 64K PCM Programs H11A H11B H11C VR 3.8l V6 & 5.0l V8 with 4L60E H2A VR 3.8l V6 LPG H3D VR 5.7l V8 with 4L60E H59 VS 5.7l V8 with 4L60E H84 VS 5.7l V8 with 4L60E 96 transmission update H58 VS 5.0l V8 with 4L60E H83 VS 5.0l V8 with 4L60E 96 transmission update Fig.1: a number of different ECU programs have been used by Holden over the years. Each of these needs a script containing data ad­dresses and other information purpose-written for it. 38  Silicon Chip (RTB). This contains a static RAM and a series of resistors. The resistors calibrate the engine’s fuel backup values and also tell the ECU how many cylinders the engine has (the latter is done in both the hardware and software). The static RAM contains both the program and the engine management maps and it is the latter that are changed during reprogramming. Connecting up A coaxial cable is used to connect the PC to the ECU. One conductor is a ground while the other connects to the data port already present on the ECU. This port is normally used to read sensor data for fault diagnosis and several commercially-available tools are available to do this. One aspect of the Holden system that makes it amenable to program manipulation is that the data port is bidirectional. It is used by diagnostic tools to temporarily disable the input of a sensor, allowing easy fault diagnosis. If, for example, a coolant temperature sensor is suspected of having an open circuit in its wiring loom, it can be software-disabled and the resulting engine change studied. This bidirectional port has its origins in the US On-Board Diagnostics (OBD) legislation, which requires that vehicle emissions be kept within certain parameters for long periods. The Kalmaker software modifies this facility, using it to write the transmitted data to the static RAM rather than just using it to disable a particular input sensor. The program addresses are contained within the individual Kalmaker scripts. The Kalmaker program itself is just a general purpose editor; it’s the scripts that contain all the intel­ ligence and a script has been written for each of the different Holden MemCal programs. Fig.1 shows the different MemCals that have been produced over the years. Note that there are often update MemCals within the one model. However, these only change the program data (rather than programming technique) so they don’t need a new script. Using the bidirectional port to write directly to the static RAM gives seamless changes in real time. This is important as sudden mixture or timing changes can be dangerous if the engine is being run under load on a dyno during the reprogram­ming. The MemCal is replaced with a Real Time Board which contains a static RAM chip (the empty socket) and resistors that configure the backup fuel maps. Another approach used in some systems is to use an EPROM emulator in conjunction with a standard EPROM. Each time a data change is made by the emulator, the ECU toggles to the standard EPROM, covering up the data gap, so to speak. This can cause hiccups as the engine is momentarily run by a program that is no longer ideal for the operating conditions. It’s for this reason that the Kalmaker program avoids this approach. The serial data cable connects the PC’s parallel port to the ECU via an interface board. The interface is needed because the ECU high speed serial data link does not conform to RS232 specifications and its baud rate is 8192, not the standard 9600. The interface board allows bidirectional communications via the PC’s parallel port status lines. The PC can then poll the paral­lel port for incoming data in a similar fashion to Laplink’s PC-to-PC communications software. Reprogramming a Holden A development ECU is used during the real-time reprogramming. Once the program is correct, it is burnt into a normal MemCal’s EPROM which is then re-inserted into the standard ECU. If the engine has been modified or its operating parameters changed (eg, if premium unleaded fuel is always used), changes can normally be made October 1997  39 SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. SUNSHINE DEVICE PROGRAMMERS Power 100 Universal Programmer 48-pin Textool Socket para I/F ............$1371 Hep 101 Value for Money 8MB E(E)PROM - 1 slave socket ...................$283 Hep 808 High Speed 8MB E(E)PROM programmer 1 master 8 slave sockets .. $790 Jet 08 Production Series E(E)PROM Programmer Stand alone or PC (para) .$1590 PEP01 Portable 8MB E(E)PROM series Programmer, Parallel Port ....................$295 EML2M EPROM Emulator ....................$480 Picker 20 Stand Alone IC Dram CMOS Portable Tester ......................................$199 RU20IT 16 Piece UV EPROM Eraser with timer .............................................$187 Plus converters, adapters & eproms. Contact us for other spe­cialised development tools or data acquisition, industrial elec­tronics, computer and electronic parts and service. Available from: D.G.E. Systems; Nucleus Computer; Stewart Electronics; TECS; X-ON. SUNSHINE ELECTRONICS 9b Morton Ave, Carnegie, Vic, 3163 TEL: (03) 9569 1388 FAX: (03) 9569 1540 Email: nucleus<at>ozemail.com.au 40  Silicon Chip Effective engine management reprogramming must be done in real-time on an engine or chassis dynamometer, as shown here. to the engine management program to improve performance. However, for this to be done efficiently, real-time reprogramming while the vehicle is tested on a dynamometer is a necessity. While it would be possible to remove the MemCal, reprogram it on the bench and then plug it back into the car, this approach is very time consuming because the changes are unlikely to give the optimum performance “first go”. Instead, the complete ECU is removed and temporarily replaced with the development ECU con­taining the serial cable plug and Real Time Board. Changes can then be made in real time while the car is under load. Typically, the air/fuel ratio is sensed by a high-speed heated oxygen sensor placed in the exhaust and the engine power checked on the dynamometer at full-load for air/fuel ratios ranging from 13:1 to as rich as 12:1. Both the Commodore V6 and V8 engines develop maximum power at an air/fuel ratio of about 12.5:1. Ignition timing changes are normally made by holding the car at a certain MAP setting (ie, at a constant load) and RPM and then advancing the timing until the rate of the measured power increase slows or stops, or detonation intrudes. The timing is then generally retarded a few degrees from this point. Note that in some cars, no power gain at all can be made by remapping in this manner. Once the new program has been devised, the original program can be erased by removing the protective sticker and exposing the MemCal to UV light. The new program can then be burnt into the EPROM of the MemCal and the MemCal re-inserted in the standard ECU. Contacts (1) KAL Software (Brad Host) – phone 0412 266 758. (2) Awesome Automotive – phone SC (08) 8277 3927. This is what you need for remote control of a central locking system. The two-button transmitter provides the lock and unlock functions and a relay on the receiver board can power up a sepa­rate car alarm. By LEO SIMPSON Add central locking to your car Don’t you just envy those swaggering motorists who just park their car, get out and then walk away without having to lock the doors. They just blip their little key remote and the doors all lock themselves automatically. It’s even better for them when it’s raining. None of this fumbling with keys while you get drenched. A S YOU CAN SEE, I get frustrated by motoring’s little tribulations. It’s even worse if you regularly drive two cars, one with central locking and one without (no, I don’t mean at the same time). When driving the car without central locking, it’s all too easy to walk away without locking the car. And then there are the times when you go to open the rear doors to get something off the back seat and the doors are still locked. All of which is a pretty strong incentive to install remote central locking. It’s stops you getting wetter in wet weather and avoids the possibility of strained fingers when trying to open locked doors. Actually, adding central locking to a car doesn’t require any electronics at all. All you need is a set of central door locking solenoids, a wiring diagram, a screwdriver, a free after­noon and a fair bit of patience. The tricky bit is where you have to thread the wires for the solenoids through the door pillars and so on. But simply having central locking is not good enough be­cause you still have to lock and unlock your car with a key. To be truly up to date you need one of those nifty keyring doodads and that’s what this project is all about. In essence, this project provides the UHF remote link; a keyring transmitter with two buttons and a UHF receiver board which operates the central door-locking solenoids. Actually, we should note that they are not solenoids but motor-driven actua­tors. You don’t need to assemble the circuitry of the keyring transmitter. It October 1997  41 Fig.1: the 2-channel transmitter uses diodes to pull pins 12 or 13 low when the pushbuttons are pressed. The result is a 100kHz burst of pulses at 304MHz. button S1 or S2 on the transmitter is pressed, IC1 will detect a valid code at pin 12 or 13 which is signified by that line going low for as long as the transmitter button is pressed. The receiver module also drives Q6, an emitter follower which turns on LED5 whenever a signal is being received. Note that any received signal will be indicated by LED5, whether it is a valid code or not. At other times, LED5 may flicker on or off due to random noise being received. If pin 12 goes low, its output is inverted by gate IC2c to drive transistor Q4 via LED3 and a 3.3kΩ resistor. When Q4 turns on it provides the “unlock” function on the central locking module. If pin 13 goes low, its output is inverted by gate IC2d to drive transistor Q3 via LED4 and a 3.3kΩ resistor. Q3 provides the “lock” function on the central locking module. Alarm switching comes fully assembled. All you need to build is a small PC board with a preassembled UHF receiver module and a handful of other parts. Transmitter circuit Now while you don’t have to build the transmitter since it comes ready built, it is useful to have a look at the circuit in order to understand how it functions. The transmitter circuit is shown in Fig.1. It shows an 18-pin trinary encoder chip, IC1, an A5884, It drives a single transistor connected as an oscillator which runs at 304MHz whenever pin 17 of IC1 goes high. The result is a 100kHz burst of encoded pulses at 304MHz which is radiated by the inductor L2, which is actually just a single loop of track on the PC board. IC1 can deliver two separate encoded pulse trains, depend­ing on which button is pressed. When either button is pressed, power is applied to IC1 via diode D3 or D4 while the encoding option is selected by D2 or D1 respectively. Note that there are many thousands of codes available depending on whether the ad­dress lines are tied high, low or left open circuit. That’s where the word “trinary” applies, because there are three separate encoding options for each address line. LED1 provides a visual indication that the transmitter is operating, a 42  Silicon Chip handy feature if you suspect that battery is dying. A number of the components on the transmitter board are surface mount types so if you do pull it apart you will find that they are rather hard to see and identify unless you have a magni­fying glass. Receiver circuit Fig.2 shows the circuit of the receiver board. This uses a small UHF receiver module to detect the pulses of 304MHz and turn them into a pulse stream which is fed into pin 14 of the matching trinary decoder chip, IC1, an A5885M. Depending on whether Gates IC2a and IC2b are connected together as an RS flip­flop. When pin 13 of IC1 goes low, corresponding to button S1 on the transmitter being pressed, the flipflop is set, with pin 3 of IC2 going high. Being a flipflop, pin 3 stays high even after button S1 is no longer being pressed and it drives transistor Q5 via LED2 and the associated 3.3kΩ current limiting resistor. Q5 operates the relay to supply power to a car alarm, if you have one fitted. Hence this circuit can operate central locking and a car alarm if you wish. When pin 12 of IC1 goes low, corresponding to button S2 on the transmitter being pressed, the flipflop is reset, with pin 3 of IC2 going low. This turns off Q5 and the relay, so that the car alarm is turned off. Operating either of the buttons will cause diode D2 or D3 to conduct and turn on transistor Q2 which operates a buzzer. The buzzer is optional and probably not necessary for most applica­tions. Board assembly This is what the transmitter looks like when you pull it apart. You will need to tweak the trimmer capacitor at the top of the board to set it to 304MHz. Fig. 3 shows the component layout on the PC board. The board assembly is pretty straightforward but we would suggest that the PC stakes and links be installed first. Then insert the resistors, diodes, LEDs and electrolytic capacitors. Make sure that the polarised components are installed the right way around. Then insert the transistors and Fig.2: a UHF receiver module drives the trinary decoder to oper­ate transistors for the lock and unlock functions. The relay can be used to switch a car alarm, if desired. note that there is a trap for young (and old) players at this point. We have seen these C8050 transistors supplied with varying pinouts. The board is designed to take transistors with the conventional EBC pin sequence, as shown on Fig.2. However they can sometimes be supplied with the ECB pinout sequence, so you should always check the labelling on the plastic encapsulation. If it is dif­ferent, you will need to bend the transistors’ pins to match the PC board. Next, install the two ICs and then the receiver module. Do not solder the address pins of IC1; ie, pins 1-8 and 10 & 11. These may be soldered later when you custom code the transmitter and decoder. Check your work carefully against Fig.2 and Fig.3. Test & alignment Now apply power from a 12V DC source and operate the but­ tons on the transmitter. Each time a button is The central locking kit comes with two master and two slave actuators, a control unit, the loom and mounting brackets for the actuators. The control unit is linked up to the decoder board for full remote control. pressed, LED5 (orange) should come on brightly. LED3 should light when button S1 is pressed and LED4 should light when button S2 is pressed. Fur- thermore, LED2 should light when S1 is pressed and go out when S2 is pressed, showing that the alarm functions are correct. October 1997  43 Fig.3: the component overlay for the PC board. Install the UHF receiver module as the last step in assembly. If these functions are not operating correctly, go back and double-check all your work. The most common problems are missed solder joints or a component installed at the wrong position. You are not likely to have damaged an IC unless you installed it the wrong way around. Speaking of missed solder connections, 10 pins on the decoder IC should not have been soldered at this stage. If you accidentally tied one or more of these pins to the adjacent positive or negative bus-bars, even by a solder splash, then it will not acknowledge the transmitter even though LED5 may light each time one of the buttons is pressed. Supposing that everything is working so far, the tasks of alignment and coding still remain to be done. Alignment? What alignment? It works, doesn’t it? Well we stated earlier that the UHF transmitter and the receiver module operate at 304MHz. We lied. They are supposed to operate at 304MHz but as supplied they operate at 318MHz. To obtain the correct frequency, you need to tweak the adjustable capacitor in the transmitter and add a capacitor across the coil on the receiver board. To do both of these tasks, you will need super duper eyes with microscopic vision or at least, good lighting, a very good magnifying glass and a steady hand. Let’s do the receiver modification first. You need to iden­tify the 10pF Parts List 1 keyring transmitter with two buttons and LED indicator 1 PC board, 117 x 48mm 1 UHF receiver module 1 12V relay with SPDT contacts 6 PC pins 1 buzzer (optional; see text) 3 100µF 16VW electrolytic Semiconductors 1 A5885 trinary decoder (IC1) 1 4093 quad 2-input NAND Schmitt trigger (IC2) 5 C8050 NPN transistors (Q1-Q5) 2 1N4148 small signal diodes (D2,D3) 3 GIG power diodes (D1,D4,D5) 1 6.2V zener diode (ZD1) 3 green LEDs (LED1, LED3) 3 orange LEDs (LED2,LED4,LED5) Resistors (0.25W, 1%) 1 100kΩ 2 1kΩ 7 3.3kΩ 1 82Ω Where To Buy The Parts The PC board and other parts for this design are avail­able from Oatley Electronics who own the design copyright. Their address is PO Box 89, Oatley, NSW 2223. Phone (02) 9584 3563; fax (02) 9584 3561. The prices are as follows: UHF remote control with two-button transmitter.....................................$35 Additional two-button transmitter............................................................$15 Central locking kit, two masters, two slaves plus loom ..........................$60 Please add $5 for postage and packing. 44  Silicon Chip ceramic capacitor which is connected in parallel with a slug-tuned coil. It and the coil are surrounded by wax so you will need to look very closely. Now solder a 2pF ceramic capacitor across the 10pF capacitor. Set the transmitter and receiver board close to each other and apply power to the receiver board. Press one of the transmit­ter buttons and slowly rotate the trimmer capacitor anticlockwise until LED5 comes on brightly. You will need to use a metal-tipped alignment tool when doing this adjustment, to minimise the ef­fects of stray capacitance. Do not use a small screwdriver – it is just not workable. You will need to do this adjustment repeatedly, to get maximum range. Each time you do the adjustment, the transmitter should be moved further away from the receiver. You will need an assistant to note when the various LEDs on the receiver board light. Ultimately, you should be able to get a range of more than 10 metres and while the system is capable of more range than that, there is not a great deal of point in doing so. After all, do you really want your central locking operable from more than 10 metres? Coding the system The final step in the electronic work for this project is to code the transmitter and receiver. Both must be coded exactly the same way otherwise the system cannot work. If you connect pin 2 of the transmitter chip to 0V, then pin 2 on the decoder chip must also be connected to 0V. Note that while the circuit of Fig.1 shows both positive and negative busbars for coding, and the same on Fig.2, the transmitter board actually only has the 0V track available for easy coding. If you want to tie some pins high, you will need to wire a small link on the back of the PC board. If you take this approach, you must be careful that the board can still sit flush in the bottom of its case. If it does not, you will not be able to close the case up without having one of the but­tons permanently pressed. Once the system is coded and operating as it should, it can be fitted into a case or a large piece of heatshrink tubing and installed underneath the dash panel of your car. Make sure the central locking system is working exactly as it should before hooking it up to the remote control receiver. 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.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au COMPUTER BITS BY JASON COLE Customising the Windows 95 Start Menus You don’t have to put up with your Start Menu the way it is. It’s easy to rearrange it just the way you want, so that it’s more convenient to use. We show you how. In Windows 95, the Start Menu is the focus point for launching programs. As you probably know, Windows 95 utilises shortcuts extensively. These shortcuts aren’t the actual program but a street sign for the computer so that it knows where to go to run the program. We usually put our own shortcuts on the Desktop along with often-used files but you can’t overdo it otherwise the Desktop can get a bit crowded. A better and less confusing approach is to launch lesser-used pro- grams from the Start button. This is located on the lefthand side of the Taskbar which itself is usually located at the bottom of the screen. You don’t have to have it at the bottom of the screen, by the way. If you want it at the top of the screen instead (or along one side), just drag it to its new location using the mouse. But back the Start button and its associated menus. One of the problems here is that as each new program is installed, it adds one or more new shortcuts to the Programs section of the Start Menu. Sometimes, even shortcuts to “readme” files are added which means that, over a period of time, your Start Menu can become quite cluttered. I’ve even seen cases where a Start Menu occupied virtually the entire screen when the wanted program was buried several layers deep. And that’s another problem. Often, it would be more con­venient to have a particular program near the front of the Start Menu so that you don’t have to drill down to get at it. Equally, it would be better if other less-used programs were further up the back, so that they were out of the way, Well, the good news is that you don’t have to put up with your Start Menu the way it is. You can easily rearrange it and even delete unwanted shortcuts from it, so that it is less clut­ tered and easier to use. Those “readme” file shortcuts are prime candidates for the Recycle Bin, for example. Let’s rearrange things Fig.1: you get to this dialog box by clicking Start, Settings, Taskbar. Alternatively, you can right click the Taskbar and select Properties. Fig.2: select the Start Menu Programs tab and then click the Advanced button to open an Explorer like window of the Start Menu folder. Before starting, the first thing to realise is that the entries in the Start Menus simply mirror the shortcuts in the Start Menu folder and its sub-folders. The Start Menu folder, by the way, is automatically created when Windows 95 is installed. You can rearrange the Start Menu by using Explorer but the correct method is to use the Start Menu Wizard. To get to the Wizard, click the Start button, then go to Settings and select Taskbar. This will bring up the Taskbar Properties dialog box – see Fig.1. Select the Start Menu Programs tab, October 1997  53 cuts around. Don’t do this in a haphazard manner though – instead, the Start Menu folder should be organised so that it makes sense to you and so that it is more convenient to use. If you use a particular program quite often, then don’t put it six folders down. Feel free to experiment because you are not going to lose any programs or the Start button. At worse, you can only lose the shortcut to a program and new shortcuts are easy to create. To move a shortcut or folder, just left click on what you want to move, drag it to where you want it to go, and let go of the mouse button. And that’s it – the next time you click the Start button and go through the various menus, the item will appear in its new location. Fig.3: once the Explorer window of the Start Menu is open, you can rearrange the various menus simply by dragging the shortcuts around. Fig.4: you can create a new folder or shortcut by first selecting the folder that will hold it in the lefthand pane of the Explorer, then right clicking the righthand pane. It is then a matter of selecting either Folder or Shortcut from the drop-down menus. Tip: Old Programs & Long File Names When installing an old Windows 3.1x program in Windows 95, you may find that it cannot find or accept “Program Files” as a folder name. That is because the old programs do not understand anything other than the 8.3 character format. To overcome this, you have to use the 8.3 name for Program Files which then click the Advanced button (Fig.2). You will now see an Explorer-style window as shown in Fig.3. However, unlike a standard Explorer window, 54  Silicon Chip is “Progra~1”. Any Windows 95 long file names will be seen as xxxxxx~1. exe, xxxxxx~.txt or xxxxxx~.doc, etc. Note that the prefix is the same but the beginning is only the first six char­acters then ~1 or ~2 or ~3, etc, depending on how many programs start with the same first six characters. this only shows the Start Menu folder which is exactly what we want. You can now rearrange your Start Menus by simply moving the short- Adding new folders Creating new folders is a little different. If you want to create a folder called “Games” in the “Programs” folder, for example, you first click on the “Programs” folder in the lefthand panel. This selects the folder that you want to create the new folder in. You now go to the righthand pane (which lists the contents of the Programs folder) and click the right mouse button on a vacant space. This brings up a small options panel. Go to the New option and then select the Folder option from the drop-down list – see Fig.4. A new folder will now appear at the bottom of the list of files. The first thing you do to this folder is change its name from “New Folder” to “Games” (or whatever name you want). The new folder is already set up to have its name changed so just start typing and press enter to accept the new name. You can now move any shortcuts or even other folders into this new folder, or just the games you like to play the most. If necessary, you can create your own shortcuts and place them in this folder. These shortcuts are created in exactly the same way as for a standard Explorer box or on the Desktop. To create a new shortcut in the Start Menu, first go to the left window and select the folder that will hold the new short­cut. This done, right click in the right window as before and then select New and Shortcut from the resulting drop-down menus. A new window will then appear asking for a command – see Fig.5. Fig.5: when you create a new shortcut, this window appears and you have to type in the command line for the program. Note that you must include the path. The command line that you enter here is simply the program that you want the shortcut to point to. Note that you must in­clude the path; eg, c:\games\doom2\doom2.exe (for the games program Doom 2). You then press the Next button to bring up the window shown in Fig.6, into which you can type the name of the shortcut. Note that this window will come up with a default which shows the name of the program, in this case doom2. exe. You can change this to whatever you want (eg, DOOM II the Awesome Game), as this is only the name of the shortcut and in no way affects the program itself. Now press the Next button and your next task will be to choose an icon. Finally, press Finish to make the Fig.6: the next window lets you type in a name for the shortcut. You can type in any name you like to replace the default which will be the name of the program. Fig.7: arrange your menus in a logical fashion so that they are convenient to use. Shortcuts to readme files are logical candidates for the Recycle Bin. new shortcut appear in the folder. If it appears in the wrong place, don’t worry – all you have to do select it and drag it into the correct folder. And that’s all you need to know to rearrange your Start Menu. The best way to learn is to have a go, so why SC not get started? THE “HIGH” THAT LASTS IS MADE IN THE U.S.A. Model KSN 1141 The new Powerline series of Motorola’s 2kHz Horn speakers incorporate protection circuitry which allows them to be used safely with amplifiers rated as high as 400 watts. This results in a product that is practically blowout proof. Based upon extensive testing, Motorola is offering a 36 month money back guarantee on this product should it burn out. Frequency Response: 1.8kHz - 30kHz Av. Sens: 92dB <at> 1m/2.83v (1 watt <at> 8Ω) Max. Power Handling Capacity: 400W Max. Temperature: 80°C Typ. Imp: appears as a 0.3µF capacitor Typical Frequency Response MOTOROLA PIEZO TWEETERS AVAILABLE FROM: DICK SMITH, JAYCAR, ALTRONICS AND OTHER GOOD AUDIO OUTLETS. IMPORTING DISTRIBUTOR: Freedman Electronics Pty Ltd, PO Box 3, Rydalmere NSW 2116. Phone: (02) 9638 6666. October 1997  55 The circuit is built on a small PC board and connects to the parallel port of the computer. Note the resistor array (RN1) adjacent to the IC. PC-controlled 6-channel voltmeter Consisting of just a handful of parts, this simple project plugs into your PC’s parallel port to provide a 6-channel voltmeter. The companion software generates an on-screen display which shows the readings in both analog and digital format. By MARK ROBERTS Two versions of this project are being presented here, the first based on the Motorola MC145041 8-bit analog-to-digital (A/D) converter. This version features three 0-6V input channels and three 0-20V channels and provides 20mV resolution. The second version uses either the 10-bit MAX192 A/D con­verter or the 56  Silicon Chip 12-bit MAX186 chip. It has the same voltage ranges as before but the resolution is improved to 4mV for the 10-bit chip and 1mV for the 12-bit chip. The downside of this version is that the Maxim devices are considerably more expensive than the 8-bit Motorola device. As a guide, the Motorola MC145041 device and the equivalent TLC542CN device from Texas Instruments can be obtained for around $5. By contrast, the MAX192 and MAX186 devices cost around $20 and $55 respectively, so consider carefully whether you really need the extra resolution before opting for the Maxim chips. Note also that the software differs between the two ver­sions. The same software is used for the 10-bit and 12bit Maxim chips, however. As shown in the photos, all the parts are accommodated on a single PC board which also includes the DB25M connector. This connector plugs directly into either LPT1 or (provided that your computer has two parallel ports) into LPT2. The circuit is pow­ ered directly from the parallel port, so no external power supply is required. Fig.1 shows the on-screen display generated by the soft­ware. As can be seen, there are separate “metered” (analog) and digital displays for each input channel. In addition, there is a “button” to toggle the power on or off (just click with the mouse), plus two smaller buttons that let you select the computer port (either LPT1 or LPT2). Finally, there are two digital output buttons and these may be manually toggled on or off using the mouse. When an output is toggled on, it sends its corresponding output on the circuit board high and this can be used to remotely control an external device, either via an optocoupler or some other suitable inter­face circuit. Note that this interface circuit should be suitably buf­fered or isolated to avoid damage to the parallel port. Applications So what are the applications for such a device? A few that spring to mind include: (1) multi-channel analog acquisition; (2) testing or monitoring digital and analog circuits; (3) monitoring security systems; (4) industrial process control; and (5) battery management. In short, you can use this device wherever it is necessary to monitor multiple DC voltages and have them all displayed on a computer monitor. Depending on the readings, you can also elect to remotely control one or two external devices at the click of a mouse button. The 0-6V and 0-20V voltage ranges can be easily altered if necessary, to accommodate higher voltages. This is Fig.1: this is the on-screen display generated by the software. Note that the Channel 0 bezel has changed to red here, indicating an overrange condition. done by changing the voltage divider resistors at the inputs. This does not alter the voltage ranges shown on the “meters” however, so you will have to scale the readings yourself. Circuit details Refer now to Fig.2 – this shows the circuit details of the 8-bit version based on the Motorola MC145041 (or the TLC542) ADC (IC1). IC1 is basically an 8-bit A/D converter with 11 analog input channels, although only six channels (0-5) are used here. The incoming data on each channel is fed to an internal multi­ plexer which selects each channel in turn, depending on the data fed to an internal address latch. The multiplexer output in turn drives the A/D converter section of the chip. The resulting digital data for each channel is then shuf­fled out in serial fashion on the Dout line (pin 15) and fed to pin 13 of the parallel port. It is then displayed on the screen under software control – see Fig.1. Pin 17 of IC1 is the serial data input Fig.2: the 8-bit version is based on the Motorola MC145041 A/D converter (IC1). October 1997  57 Fig.3: the 10/12-bit version is based on the MAX186 and MAX192 chips. The circuit is similar to the 8-bit version. the readings for the 8-bit version will depend on the accuracy and stability of the 5V rail from the computer. By contrast, the Maxim devices feature an internal +4.096V reference so if accuracy and resolution are important, these are the devices to go for. Second, the input impedance is only 156kΩ for the 0-6V channels and 490kΩ for the 0-20V channels. Depending on the circuit being measured, these relatively low input impedances may cause reading inaccuracies due to loading effects. Construction Fig.4: the parts layout for the 8-bit version. Fig.5: the parts layout for the 10/12-bit version. (DIN). This input is driven from pin 2 of the parallel port and feeds data to the internal multiplexer address latch via an 8-bit data register to select the input channels. For example, Ch 0 is selected by loading $0 into DIN, Ch 1 by loading $1, Ch 2 by loading $2 and so on. The remaining pins connected to the parallel port are VDD (pin 20), SCLK (pin 18), CS-bar (pin 15) and EOC (pin 19). VDD is the supply pin and this is fed from pin 9 of the parallel port which supplies a +5V rail. This +5V rail is also fed to the VREF input at pin 14 to provide a reference voltage. SCLK is the clock input, CS-bar is the chip select input and EOC is the end of conversion output. The incoming voltage signals are fed to the CH0-CH5 inputs via voltage di- vider networks. In the case of the 0-6V channels, the voltage divider networks use 56kΩ and 100kΩ resistors, while the 0-20V channels use 390kΩ and 100kΩ resistors. Finally, the digital outputs are made available at pins 14 and 16 of the parallel port and are fed to the output terminals on the board via 1kΩ isolating resistors. Fig.3 shows the circuit for the 10/12bit version. It is virtually identical to the 8-bit version, the main difference being that the Maxim chips do not provide an EOC output. 58  Silicon Chip Design limitations Before moving on to the construction, we should first point out that this simple design does have a few limitations. First of all, the accuracy of The 8-bit version of the Multi-Channel Voltmeter is built on a PC board coded 07110971, while the 10/12-bit version is built on a board coded 07110972. Figs.4 & 5 shows the wiring details for the two versions. Begin the assembly by fitting PC stakes to the Output 1 and Output 2 terminals and to the adjacent GND terminal. This done, install the wire links, then fit the remaining components. Note that the eight 100kΩ resistors are all contained in a single in-line package which is designated RN1 (for resistor network). Be sure to install this package the right way around; ie, with the common “earth” pin adjacent to pin 10 of IC1. The remaining resistors in the voltage divider networks are installed end-on to minimise board space. Take care to ensure that the IC is correctly oriented. We used an IC socket on the 8-bit version but this Parts List 8-Bit Version 1 PC board, code 07110971, 53 x 42mm 1 DB25M PC-mount connector 3 PC stakes 1 400mm-length 7-way rainbow cable 8 miniature hook connectors 1 MC145041 or TLC542CN 8-bit A/D converter IC 1 22µF 16VW electrolytic capacitor 1 0.1µF MKT capacitor 3 390kΩ resistors 1 8 x 100kΩ resistor network (RN1) 3 56kΩ resistors 2 1kΩ resistors The PC board can be plugged directly into the parallel port or connected to the port via an extender cable fitted with DB25 connectors. Fig.6: the full-size artwork for the 8-bit version. can be considered optional. Complete the board assembly by soldering the DB25M connector into place. The seven input leads (one for each input channel plus ground) can be run using rainbow cable. On the prototype, the ends of these leads were terminated in miniature hook connectors. It’s a good idea to label each lead with the number corresponding to its input channel. Software The software comes on three floppy discs and runs under Windows 3.1x, Windows 95 and Windows NT. It’s easy to install – all you have to do is run the setup.exe file on the first disc (within Windows) and follow the onscreen instructions. In Wind­ows 95, you click Start, Run and then type A:\setup.exe in the space provided Fig.6: the full-zize artwork for the 10/12-bit version. 10/12-Bit Version 1 PC board, code 07110972, 53 x 42mm 1 DB25M PC-mount connector 3 PC stakes 1 400mm-length 7-way rainbow cable 8 miniature hook connectors 1 MAX186 (12-bit) or MAX192 (10-bit) A/D converter IC 1 4.7µF 16VW electrolytic capacitor 1 0.1µF MKT capacitor 1 .01µF MKT capacitor 3 390kΩ resistors 1 8 x 100kΩ resistor network (RN1) 3 56kΩ resistors 2 1kΩ resistors Where To Buy Parts & Software Parts and software for this design are available as fol­lows: (1). MC145041 (TLC542) 8-bit A/D converter ................................................$4 (2). MAX192 10-bit A/D converter ................................................................$20 (3). MAX186 12-bit A/D converter ................................................................Call (4). Software for 8-bit A/D converter (three discs) ........................................$20 (5). Software for 10-bit & 12-bit A/D converters (three discs) ......................$25 (6). Optional LPT2 card for PC .....................................................................$15 Please add $5 for postage. Payment by cheque or money order only to: Mr Softmark, PO Box 1609, Hornsby, NSW 2077. Ph/fax (02) 9482 1565. Note: the software associated with this design is copyright to Mr Softmark. (assuming that the floppy disc is in the A: drive). In Windows 3.1x, you click File, Run and type in A:\setup.exe. Alternatively, you can double-click the setup. exe file from the File Manager or, in Win95, from the Explorer. When you boot the software, you get the screen display shown in Fig.1. Note that the meters and digital readouts will all overrange if the device is unplugged from the parallel port. If any channel overranges, its channel SC number button turns red. October 1997  59 By ROSS TESTER T This little lighting gimmick was used at a recent school eisteddfod. It uses a 12V 20W halogen lamp/reflec­tor fitting mounted in a plastic drink bottle filled with orange/red cellophane. It gives a convincing imitation of fire, hence the name “Flickering Flame”. Why not set your next performance on fire? 60  Silicon Chip HEATRICAL PRODUCTIONS often call for flaming torches and similar lighting effects. The problem is that for fairly obvious safety reasons most theatres and halls have very strict rules regarding the use of naked flames on stage. In fact, in most halls, naked flames are taboo. We had just this situation recently when our local high school needed some props for its Rock Eisteddfod act. One scene was a castle wall lit by flaming torches – except they couldn’t have flames! Also they (and the Rock Eisteddfod itself) had a couple of other curly requirements which made life just that much harder! For example, mains power was not an option because the props on which the flaming torches were placed were to be moved to various positions on the stage. And the lights themselves needed to be completely portable because the props were stored offstage and assembled in a rush! One other request was that they had to cost as close to nothing as possible and be reasonably sized – not too big to get in the way but conversely not too small either. And they had to look realistic! For those not familiar with the Rock Eisteddfod, perhaps a word or two of explanation is in order. The challenge is open to all secondary schools and entails an act of dance and drama set to contemporary recorded music. The act itself can be no more than eight minutes and most importantly, any set or props used must be capable of being brought onto stage and set in less than four minutes (and con­versely, removed in the same time). There are strict limits on the amount of money a school can spend and there are also limits on the number of LEFT: it mightn’t look too spectacular up close and as a still photo but from an audience viewpoint it looks just like the real thing when it is working. backstage crew allowed to assist the “perform­ers”. Those who have never seen a Rock Eisteddfod performance before marvel at the spectacle, the professionalism, the choreog­raphy, the costumes and the props. Ah, the props. This is where we came in, with a request to help out with those flaming torches (no pun intended!). The props people at the school had come up with the basic design for the torch (and as you will see, it’s amazing what you can get away with from a distance!). What they wanted was something to make them flicker. “Easy”, we thought. First of all we looked at a real flick­ering flame (a candle, to be precise). Effectively, the “light” was on all the time but every now and then it dimmed a bit as the flame was caught by a breeze. All we needed to do was emulate that. A microprocessor could easily be programmed to do the job nicely. “Whooaa! Too expensive”, they said. OK then, how about a 555 timer configured as an astable multivibrator driving a cheap power Mosfet? You couldn’t get much cheaper than that! The problem with that idea was that while it certainly flickered the lights, it was far too regular: looked more like a flamin’ lighthouse than a flaming torch! What about two 555 timers running at different, unrelated frequencies? Would this give the random effect we wanted? We tried this idea and . . . sure would! Calculating values gave us roughly the right oscillation rates, trial and error gave us the effect we wanted. Fig.1 shows the final circuit. The duty cycle (on time to off time) is set by the ratios of R1 to R2 and the oscillation rate is set by R1 and R2 in conjunction with C1. The duty cycles were set very high – around 10:1. Any longer than this and the lights actually went right off – not very realistic at all! The oscillation rate was set at about 1Hz or longer. The values of R1 & R2 are significantly higher than one might “normally” expect to be used in 555 circuits. The reason for this is that high values of resistance allow low values of capacitance. A high value resistor costs the same as a low value resistor while a high value capacitor costs significantly more than a low value unit. We used the same values for R1 The 20W halogen lamp can be directly soldered to the PC board as shown here, or connected via flying leads. The component at top right of the PC board is a pair of header pins with a shorting link – this formed our on/off switch. Fig.1: the circuit employs a 556 dual timer to drive a Mosfet. The two oscillators run at different rates to give a random flickering effect from the halogen lamp. & R2 in the two oscillator circuits but picked different capacitor values to ensure that the operating frequencies were not too close together. While on the subject of costs, we looked at the lolly shop catalogs and found that a 556 (two 555s in one package) was a few cents cheaper than a pair of 555s, so we went this route. The outputs of both astable oscillators are fed to a diode “OR” gate and these feed the gate of the Mosfet. In effect, the difference between the two oscillators is fed to the Mosfet gate. What happens is that when either of the oscillator outputs goes low, one of the diodes is forward biased, taking the Mosfet’s gate low. When the gate is taken high, which will be most of the time, the Mosfet is turned hard on and is a very low resistance. Therefore, the lamp lights at full brilliance. When the Mosfet gate is pulled low by either of the oscil­lator outputs, the Mosfet turns off, turning off the lamp. But because of the very short “off” time and the thermal inertia of the lamp filament, it doesn’t actually turn off but flickers. So we have random flickering of the lamp, which is just what we want. Viewed up close, it doesn’t look all that impressive. From more than a few metres away though, the effect is quite convinc­ing – there’s fire in that thing! In the end, we made quite of few of these torches, varying the timing capacitors in each to ensure they never flickered “in sync”. Making the torch You would be surprised at how much you can get away with in designing props! Looking at the photograph, you’ll see that our torch appears exactly what it is: crumpled cellophane in a plas­tic drink bottle, fitted to a length of cardboard tube. But to the audience, it looks just like October 1997  61 Fig.2: the halogen lamp was soldered directly to the PC board but it would be easier if you used a standard halogen lamp socket base. a flaming torch! We cut the bottom off a PET 1.25l Coke bottle with a sharp serrated knife. Did we forget to mention that we drank the cont­ents first? Next, we cut some thin strips, about 15-20mm wide, of red cellophane and laid these down the inside of the bottle. About five or six strips seemed to work best but you can experi­ment for the desired effect. Then we crumpled a sheet of orange cellophane and placed this inside the red strips. Presto, a torch! By the way, PET stands for Polyethylene Terephthalate, which is the long-winded moniker for polyester. Now you know. The other end of the bottle was removed to suit the lamps used. We mentioned safety before as this was a major concern. The lamp we used was especially chosen for the job: a 12V 50mm dia­ meter halogen type with dichroic reflector, normally used in low voltage downlights or shop display lights. However, we used a specific type. Most 12V downlights have a 50 watt rating; we used a 20 watt type to keep heat to a minimum. And to ensure that the hot halogen lamp would not be able to ignite the cellophane (we’ve seen that happen before!) we chose a lamp with an integral clear glass cover. Should these lamps not be available at your normal shop Jaycar stores have them (Cat No SL-2732). They are coded “BAB” on the reflector, indicating that they have a beam width of 38 degrees which is pretty well optimum for this job. Their price is right, too at $4.95 each (we were quoted $15 each at a 62  Silicon Chip Fig.4: this is the full-size etching pattern for the PC board. lighting store!) Incidentally, Jaycar have a similar 12V/20W lamp just 35mm in diameter if space is a problem. They also have bases to suit these lamps but at $2.95 each we decided to forego these to keep cost to a minimum and solder directly to the lamp pins. In retrospect, that may not have been such a brilliant idea. The reasons will follow shortly . . . The lamps were fitted to the neck end of the bottle, shin­ing upwards through the cellophane. To do this, we cut the neck off, leaving an opening about 25mm in diameter. What you want to achieve is an opening not too large for the lamp to slip through. We used contact adhesive to hold the lamp in place. Yes, the lamp does get rather hot; in fact, enough to distort the PET bottle but we were able to operate our torches for half an hour or more without any problems. Allow the adhesive to dry completely. While this is happen­ing, you can fashion the mounting hardware. We used 100mm card­board tube long enough to take the battery pack (see below) and the lamp itself. Eight slots were cut in the tube, about 40mm down from the top, which allowed the lamp to be simply pushed into place. It is quite important that the tube be made deep enough to ensure that no white light can be seen by the audience – this ruins the effect completely. We said before that our idea was to solder the pins of the lamp directly to the PC board. This is not quite as simple as it seems the pins simply did not want to solder! They’re probably nickel plated or similar which is certainly not designed for ease of soldering. Eventually, after much scraping of the pins and with a very hot iron we were able to make a soldered joint but this was definitely the weakest link in the chain. If you can afford to invest another couple of dollars in the bases, they would make life much easier. The circuit is designed to operate from 12V DC. The elec­tronics drain is negligible but the lamp itself draws the best part of 2A (ie, 20W/12V). We used a battery pack made of six 2.5A SLA rechargeable cells (mainly ‘cos the school had these on hand), giving an operating time of more than an hour. As the whole Rock Eisteddfod performance was over in eight minutes, this was more than enough. If you need longer times, you will need a suitably larger battery. Assembling the PC board This view shows the 20W halogen lamp and its integral reflector. We designed a PC board to suit the project. It is coded 11410971 and measures 58 x 38mm. This is quite straightforward to assemble as the only polarised parts are the IC, Parts List 1 PC board, code 11410971, 58 x 38mm 2 PC Stakes 1 SPST switch (optional) 1 12V 20W sealed halogen reflector lamp (see text) 12V battery capable of supplying 2A Semiconductors 1 556 dual timer 1 MTP3055E power Mosfet 2 1N914 diodes Fig.3: this diagram shows the overall scheme. The battery and PC board/lamp assembly is mounted in a cardboard tube with the lamp illuminating a PET soft drink bottle filled with crumpled cel­lophane. Mosfet and diodes. Make sure you get these right, along with the battery connections Therefore, construction is very simple – apart from solder­ing the lamp, as mentioned above. We made provision for an on/off switch on the board or you could simply connect and disconnect the battery as required. Before you solder in the Mosfet and the lamp, you can check the operation of your circuit with an analog multi-meter. Apply 12V and check the voltage at pins 5 & 9 of the IC using a multimeter (set to measure 12V DC). At both pins, you should see the meter dipping regularly – but not down to zero volts, unless you have chosen a much higher value resistor for R2. When you measure at the junction of the two diode anodes, you should see the meter dipping more or less randomly, indicat­ ing that the two outputs are being added, or rather Capacitors 1 0.1µF MKT polyester or ceramic 1 .039µF MKT polyester or ceramic 2 .01µF MKT polyester or ceramic Resistors (0.25W, 1%) 2 10MΩ 1 100kΩ 2 1MΩ subtracted, through the diodes. With the 20W lamp suggested, a heatsink for the FET is not really necessary. It does get reasonably warm to touch but should be quite happy at this level. Do not use a 50W lamp. There is no doubt that it will melt the PET bottle and it could well set fire to the SC cellophane. October 1997  63 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. 3-aspect signalling for model railways This circuit uses one 74139 dual 2-to-4 decoder, six PNP transistors and four diodes to drive two sets of 3-aspect (red, yellow, green) colour signals. Lamps are used in the circuit and dropping resistors will be required if LEDs (red, orange, green) are substituted. Considering the lefthand side of the circuit, the chip is enabled with the G1 input, pin 1, grounded. It then treats the A1 and B1 inputs as a 2-bit binary number in the range 0-3 and sets the corresponding output pin low Pin 2 (A1) Pin 3 (B1) Pin 4 (1Y0) Pin 5 (1Y1) Pin 6 (1Y2) Pin 7 (1Y3) Colour Low Low Low High High High Green High Low High Low High High Red Low High High High Low High Yellow High High High High High Low Red and the others high. If we assume that A1 is high when the next track block is occupied and low when clear and B1 is high when the track block is occupied and low when clear, the above table shows the outputs for the four possible input combinations and the required signal colour. The 1Y1 and 1Y3 outputs are ORed by diodes D1 & D2 to drive transistor Q3 and the red lamp. The righthand side of the circuit based on IC1b works in exactly the same way. D. Nowlan, East Hawthorn, Vic. ($35) Low dropout 5V regulator This regulator has been designed to run 5V circuits from 9V dry batteries. These batteries exhibit a gradual voltage reduc­tion during their useful life, from just above 9V when fresh to about 5.5V at the endpoint. This circuit has a dropout of just 0.6V, enabling the full battery life to be obtained for a maximum load current of 100mA. Common features of all low-dropout regulators are that the main series transistor works as a common-emitter amplifier (as opposed 64  Silicon Chip Q1 works as a common emitter amplifier and is driven by error amplifier Q2. Using the 12/24V speed controller as a dimmer A number of readers have requested modifications to allow the 12V/24V motor speed controller published in the June 1997 issue to be used as a dimmer. This is easily accomplished by a modification to the “soft start” feature in the original circuit, involving the Inhibit input, pin 4. If pin 4 is held high, the output drive signals at pins 9 & 10 are inhibited. In the original (June 1997) circuit, a 10µF capacitor (C2) initially holds pin 4 high and as it charges, pin 4 drops to zero and gradually allows the output pulse width at pins 9 & 10 to increase to the required width. In this modified circuit, we have omitted C2 and instead connected a 220µF capacitor at pin 4 to give a controlled “dim up” or “dim down” function, as selected by switch S1. When switch S1 is off, pin 4 is held high (ie, at +VREF) by the 100kΩ resis­tor. When the switch is moved to on, the 100kΩ resistor discharg­ es the 220µF capacitor at pin 4. The lamp load is then dimmed up to the setting selected by trimpot VR1. Longer dimming times can be obtained by increasing the value of the 220µF capacitor. Note that if power applied to the circuit with switch S1 in the on position, the full load voltage will be applied to the lamps, with no soft start. SILICON CHIP to emitter follower configuration in standard regulators) and the load current is only a fraction of its maximum collector current. Because of this, transistor Q1’s collector-to-emitter saturation voltage is very low. Q1 is driven by Q2 working as an error amplifier. R6 en­sures that its collector current doesn’t fall below 100µA. It uses metal film base bias resistors (4.7kΩ) in order keep the output noise voltage low. The reference zener diode ZD1 is connected between the output and emitter of Q2. Q2 compares a sample of the output voltage at its base with the zener reference voltage at its emitter. Because of the low amplification factor of the error ampli­ fier and additional losses due to the zener diode’s internal resistance, the positive feedback resistor Rf has been included. A startup resistor (Rs) is also necessary to deliver initial base current to Q2. The values of resistors Rs and Rf had to be found empiri­cally, with Rs being the minimum value at which the regulator would power up with the maximum load connected to it and when supplied by the lowest designed input voltage. Rf must be such as not to give the regulator a negative output resistance (ie, an increase of output current causing any increase of output vol­tage) over any part of its output current range. The prototype has been tested and gave the following results: minimum dropout voltage 0.6V <at> Iout = 100mA (100mV <at> Iout = 10mA); line regulation below 20mV <at> Vin + 5.6-9V, Iout = 100mA; load regulation below 5mV <at> Iout = 5-100mA. Note that the regulator does not have overload protection. M. Frankowski, Warsaw, Poland. ($35) October 1997  65 Part 3: building the 500W Audio Power Amplifier In this final article on the 500W audio power amplifier, we present the details of the loudspeaker protector module and the thermal switch for the fan. By LEO SIMPSON & BOB FLYNN As we left the power amplifier last month, supposing you were building it, you had just had the module on “heat soak” for about an hour to check the quiescent current setting. This is set by adjusting trimpot VR2 so that the voltage across the 390Ω 5W resistors (temporarily installed across fuses F1 and F2) is 30V. After the initial 66  Silicon Chip setting, the voltage will creep up quite a bit, perhaps to 45V or more, so it is necessary, to readjust trimpot VR1 to bring the voltage back to 30V. It is important to note that the thermal compensation provided by the Vbe multiplier transistor (Q9) does not give perfect compensation for the drift in quiescent current. Even after you have tweaked it a number of times, it will still drift about. Of course, if the thermal compensation wasn’t included in the circuit, the quiescent current would rapidly go out of con­trol as soon as the amplifier was called upon to deliver signifi­cant power. Having set the quiescent current to your satisfaction, you can now set the DC offset current at the output, by adjusting trimpot VR1. You need a digital multimeter for this test. Set it to the lowest available DC voltage range, probably 200mV, and connect it directly across the output terminals on the PC board. Adjust VR1 to obtain zero volts. You should be able to get it to within ±1mV although again, it will tend to drift about. Fig.1: the circuit of the Loudspeaker Protector is changed from that presented in the April 1997 issue and employs a thermal cutout to operate the relay if the heatsink temperature exceeds 80°C. In practice, the DC offset voltage or its drift is not important if you are driving a 4Ω or 8Ω load. Even if the DC output offset went as high as ±50mV, the current would still be less than 20mA through a 4Ω loudspeaker and that is negligible in the overall scheme of things. The main reason we have included the offset adjustment trimpot (VR1) is so that the amplifier can be used to drive one or more 100V line transformers. Because such transformers have a very low primary resistance, the resulting DC offset current from a 50mV DC offset being present at the output could be consider­ able. The current could lead to substantial power dissipation in the amplifier and could lead to premature saturation of the transformer itself, resulting in less power delivered and higher distortion. Loudspeaker protector Now that we have come this far, we can turn our attention to the Loudspeaker Protector PC board. The circuit of this is shown in Fig.1. This is based on the Universal Loudspeaker Pro­tector we presented in the April 1997 issue but inevitably, we have modified it. The original circuit was designed to suit a stereo amplifier and since this is a mono amplifier we have omitted three transistors and the other components needed for the second channel. Second, we have changed the method of powering the board. The method we had intended using involved run- ning the module from the +80V DC rail via a 470Ω 10W wire­wound resistor and using the on-board regulator circuit to obtain 12V for the relay and so on. This method works but there is a problem with the time delay between the amplifier being turned off and the relay actually disconnecting the loudspeakers. This problem arises because of the large amount of ca­pacitance in the filter bank – 40,000µF on each rail. This ca­pacitance takes quite a long time to discharge, particularly if the Warning! The 160V DC supply across the capacitor bank in the power supply is potentially lethal. As well, high voltages exist on the bridge rectifier and on many components in the amplifier module, including the fuse­ holders. The following rules should be observed: (1). Do not operate the amplifier without the Perspex shield covering the filter capacitors. (2). Disconnect the mains plug and allow the filter capacitors time to fully discharge before working on the circuit. The LEDs will go out when the capacitors have discharged to a few volts. amplifier is not delivering any power at the time it is turned off. The solution is to power the Loudspeaker Protector module from the 57VAC supply via a 270Ω 10W wire­ wound resistor. This feeds the AC supply to the PC board and to a diode and 470µF filter capacitor to provide a DC supply. This is shown on Fig.1. With this arrangement, the derived DC supply drops rapidly to zero as soon as the amplifier is turned off and so the speaker is disconnected almost immediately. The other difference between the circuit presented here and the original circuits shown in the April 1997 issue is that we use a thermal cutout switch to control the relay. This is a different arrangement to that shown on the proto­type amplifier module in the photograph on pages 24 & 25 of the August 1997 issue. That showed the thermal cutout switch mounted on the heatsink and connected in series with the loudspeaker output. Having the thermal cutout in series with the amplifier’s output would be appropriate if the Loudspeaker Protector module was not being used but we don’t want two sets of contacts in series with the loudspeaker; ie, the thermal cutout and the relay contacts. Therefore we connect the thermal cutout so that it operates the relay and that means that only the relay contacts are in series with the loudspeaker circuit. Note that the thermal cutout switch has a pair of “normally closed” conOctober 1997  67 Fig.2: the component overlay for the Loudspeaker Protector PC board. Note that some component positions are vacant. tacts. When the temperature of its mounting base (ie, the heatsink in this case) rises above 80°C, the contacts open and interrupt the base current to transistor Q4 on the Loudspeaker Protector module. For the sake of completeness, let’s now give a brief de­scription of the Loudspeaker Protector circuit in Fig.1. The amplifier’s output is connected to the three-transistor monitoring circuit via two 22kΩ series resistors and two 47µF bipolar capacitors. This network is a low-pass filter which removes virtually all audio signal. From there, any DC signal is fed directly to the emitter of transistor Q1 and the base of Q3. If a positive DC signal of more than 0.6V is present (indi­cating an amplifier fault), Q3 will turn on. In the same way, if a negative DC signal Capacitor Codes ❏ ❏ ❏ ❏ ❏ ❏ Value IEC Code EIA Code 0.15µF   150n   154 0.1µF   100n   104 .01µF   10n  103 820pF   820p   821 100pF   100p   101 of more than 0.6V is present (again, an amplifier fault condition), Q1 will turn on and this will turn on Q2. Q2 & Q3 have a common 56kΩ load resistor and this normally feeds base current to Q4. Q4 feeds base current to Q5 and so both of these transistors and the relay are on. But when an amplifier DC fault occurs, either Q2 or Q3 is turned on to shunt the base current away from Q4. Thus Q5 and the relay are turned off and the speaker is disconnected. Because we are dealing with such a high power amplifier, both sets of relay contacts are connected in parallel, to handle the high currents involved. To give some idea of the size of the fault current, that can occur, consider what happens if one of the output transistors suffers a “punch-through” failure and goes short circuit. This connects the 80V rail directly to the loudspeaker and if it is a nominal 4Ω speaker it will have a voice coil resistance of about 3Ω. Thus, a peak current of around 25 amps or more will initially flow. With any luck, the relevant supply fuse will blow but then the amplifier is likely to “latch” in the opposite direction and connect the other 80V rail across the speaker, to give it a double whammy, if it hasn’t already been burnt out by the peak dissipation of more than two kilowatts! As you can see, it is important for the relay to disconnect the speaker very rapidly, before it is damaged. These very high fault currents will form an arc across the relay as it tries to break the circuit. For this reason, the moving contacts of the relay are shorted to the loudspeaker ground lines. Thus the current is shunted away from the speaker and the fuse(s) blow. As already noted, the DC supply rail for the Loudspeaker Protector circuit is derived from one of the 57V AC lines from the power transform­ er. This feeds diode D2 via the 270Ω 10W resistor. The resulting DC rail from the 470µF filter capacitor is fed to transistor Q9 which functions as a voltage regulator to provide +12V to the circuit. Resistor Colour Codes: Loudspeaker Protector Module ❏ ❏ ❏ ❏ ❏ ❏ No. 1 2 2 1 1 68  Silicon Chip Value 220kΩ 56kΩ 22kΩ 2.7kΩ 2.2kΩ 4-Band Code (1%) red red yellow brown green blue orange brown red red orange brown red violet red brown red red red brown 5-Band Code (1%) red red black orange brown green blue black red brown red red black red brown red violet black brown brown red red black brown brown This view inside the chassis shows the thermal switch for the fan (right) and the thermal cutout (left) which interrupts the load. The fan operates when the heatsink temperature reaches 60°C, while the load is disconnected at 80°C. Note that while the relay is off, for example, just after power is applied, the voltage across the 470µF filter capacitor will rise to +80V. That is why we have specified a rating of 100V for this capacitor. In addition to monitoring DC faults in the power amplifier, the Loudspeaker Protector also provides a turn-on delay for the loudspeaker. This prevents audible turn-on thumps from the ampli­fier itself or any preamplifier circuitry preceding it. This is achieved with resistors R1 & R3 and capacitor C1. When power is first applied, C1 is discharged and no base current can flow via the 56kΩ resistor R1 and so Q4 & Q5 and the relay are held off. C1 then charges via the 220kΩ resistor R3 and eventually sufficient voltage is present to allow resistor R1 to bias on Q4. This turns on transistor Q5 and the relay and so the loudspeaker is connected to the amplifier. The delay is several seconds. PC board assembly All the parts, with the exception of the 270Ω 10W resistor, are mounted on the PC board which is coded 01104971. The wiring diagram is shown in Fig.2. Note that some transistor and other component positions are vacant. Fit the PC pins first and then the resistors. The two 47µF electrolytic capacitors can go in either way around since they are non-polarised (NP or BP). The other electrolytics are polar­ ised and must be inserted the correct way around. Next insert the transistors, diodes and zener diode and make sure that you put the correct type in each position. Finally, the relay can be installed. We mounted ours by soldering short lengths of stout tinned copper wire to each relay pin. These wire leads are then pushed through the relay mounting holes on the board and soldered. We understand that some kitset suppliers may provide a PC board with slotted holes so that the tinned copper wire may not be necessary. When the board is complete, check your work carefully and then install it in the case. The chassis wiring diagram of Fig.3 shows the details. Make the connections for the power supply and the thermal cutout but do not make the speaker connections yet. Resistor Colour Codes: Power Amplifier Module ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 4 2 1 1 1 1 2 4 2 1 1 5 2 3 Value 22kΩ 18kΩ 8.2kΩ 1.2kΩ 560Ω 470Ω 330Ω 270Ω 220Ω 180Ω 120Ω 100Ω 30Ω 18Ω 4-Band Code (1%) red red orange brown brown grey orange brown grey red red brown brown red red brown green blue brown brown yellow violet brown brown orange orange brown brown red violet brown brown red red brown brown brown grey brown brown brown red brown brown b brown black brown brown orange black black brown brown grey black brown 5-Band Code (1%) red red black red brown brown grey black red brown grey red black brown brown brown red black brown brown green blue black black brown yellow violet black black brown orange orange black black brown red violet black black brown red red black black brown brown grey black black brown rown red black black brown brown black black black brown orange black black gold brown brown grey black gold brown October 1997  69 Fig.3: this is the complete wiring diagram for the 500W power amplifier. Note that it differs in detail from that presented last month. Note also that the full DC supply is potentially lethal and that high DC voltages exist on the amplifier supply rails and on may components, including the fuseholders. 70  Silicon Chip Fig.4: actual size artwork for the Loudspeaker Protector PC board. DANGER! High Voltage Switch off and allow the filter capacitors to completely discharge before working on the circuit. Fig.7: this diagram shows how the fan is wired to the mains via the optional thermal switch. Apply power and the relay should operate after about two seconds. Next, try simulating an amplifier fault condition with a 6V or 9V battery. Connect the battery across the inputs, first with one polarity and then the other way around. In each case, the relay should immediately open and then close again as soon as the battery is removed. Fig.8 (below): this is the artwork for the amplifier PC board, reduced to 0.707 times actual size. To bring it up to full size, you will need a photocopier which can enlarge by a factor of 1.414. Fig.5: this warning label should be affixed to the Perspex cover over the filter capacitors in the power supply. October 1997  71 Parts List 1 500W amplifier module (see parts list, August 1997) 1 toroidal transformer, 2 x 57V, 800VA 1 240VAC 17W 140mm fan 1 3AG panel mount fuseholder 1 5A slow-blow 3AG fuse 1 15A, 2-pole mains rocker switch with neon indicator 1 3-way mains terminal strip 1 80°C thermal cutout (TH1) (Altronics S-5610) 1 60°C thermal switch (TH2; for fan switching) 1 Perspex sheet, 332 x 100mm 4 100mm-long brackets plus machine screws & nuts (to mount Perspex cover) 1 metre, 1mm dia. tinned copper wire 1 metre, 14 x 0.2mm hook-up wire, red 1 metre, 14 x 0.2mm hook-up wire, black 2 metres, 32 x 0.2mm hook-up wire, red 2 metres, 32 x 0.2mm hook-up wire, black 0.5 metre, 32 x 0.2mm hook-up wire, white 8 capacitor mounting clips 24 3M x 10mm CSK screws 24 3M nuts 24 3mm shake proof washers 1 4M x 20mm CSK screw 1 4M nut 1 4mm steel washer Semiconductors 1 KBPC3504 400V 35A bridge rectifier 2 red LEDs If these checks are OK, you are ready to complete the wir­ing. If not, check the circuit for errors. Now make the speaker and amplifier connections to the Loud­speaker Protector board, using heavy duty hookup wire. This should be twisted and oriented as shown in the photos. Fan wiring With that done, it is time to wire in the fan. This is switched by a thermal switch similar to that used for controlling the Loudspeaker Protector. However, the thermal switch used to 72  Silicon Chip Capacitors 8 10,000µF 100VW electrolytic 1 .01µF 275VAC polypropylene Resistors 6 15kΩ 1W Loudspeaker Protector 1 PC board, code 01104971, 107 x 55mm 8 PC pins 1 relay with 240VAC 10A DPDT contact, 12V coil <at> 75mA, Jaycar SY-4065 or similar 4 3mm x 20mm screws 4 3mm nuts 4 6mm spacers 1 U-shaped heatsink (Altronics Cat H-0502 or equivalent) Semiconductors 3 BC547 NPN transistors (Q1, Q3, Q4) 1 BC557 PNP transistor (Q2) 1 BC327 PNP transistor (Q5) 1 BD649 NPN Darlington transistor (Q6) 1 13V 500mW zener diode (ZD1) 2 1N4004 silicon diodes (D1,D2) Capacitors 1 470µF 100VW electrolytic 1 470µF 25VW electrolytic 1 220µF 16VW electrolytic 2 47µF 50VW NP (non-polarised) electrolytic Resistors (0.25W, 1%) 1 220kΩ 1 2.2kΩ 2 56kΩ 1 2.7kΩ 1 22kΩ 1W 2 22kΩ 1 270Ω 10W wirewound control the fan has “normally open” contacts and operates at a temperature of 60°C. Hence, until the heatsink rises to that temperature, the fan does not operate. When the heatsink tempera­ ture does rise above 60°C, the thermal switch will operate and its contacts will stay closed until the temperature drops below 35°C. The 240VAC supply to the fan comes from the same insulated terminal block which is used to connect the transformer primary winding. The wiring to the thermal switch and the fan should be run in 250VAC-rated hook­up wire. It should be twisted as shown in the photos. Fit heatshrink tubing over the terminals of the thermal switch, to avoid the possibility of accidental contact with the 240VAC mains supply. When all the wiring is complete, apply power and recheck the voltages in the amplifier. Assuming everything is OK, disconnect the power and wait until the filter capacitors in the power supply have completely discharged (ie, when the LEDs go out). Now unsolder the 390Ω 5W resistors across the fuses, F1 & F2, and fit the fuses. These should be 5A for an 8Ω load and 7.5A for a 4Ω load. Do not make the mistake of leaving the 390Ω resistors on the board. If the amplifier does blow the fuses at some stage, the resistors will be back in circuit and may contribute to further damage in the amplifier, before they themselves burn out. You are now ready for a listening test. Connect a loud­ s peaker and This internal view of the completed prototype shows the finalised wiring to the Loudspeaker Protector and the thermal switches on the heatsink. Note that these details are different to the chassis photo in last month’s issue. The transparent Perspex shield over the bank of filter capacitors is a worth­while safety measure in view of the high supply voltage – 160V in total. program source and prepare to be impressed. Finally, a few omissions and errors crept into the parts list published for the amplifier module, on page 32 of the August 1997 issue. Two 300Ω 0.25W resistors were omitted, a 6.8kΩ 1W resistor was specified instead of 8.2kΩ 1W and only five 0.1µF MKT polyester capacitors were specified while 11 are required. Also, the 100pF 500V ceramic capacitor should be an NPO type, Philips 2222 650 10101. Note that on the PC board component overlay diagram on page 57 of the September 1997 issue, the unlabelled transistor adjacent to trimpot VR1 is SC Q3, a BC556. October 1997  73 RADIO CONTROL BY BOB YOUNG The philosophy of R/C transmitter programming; Pt.2 This month, we will look at some of the broader issues governing the design and programming of comput­er transmitters. Last month we covered some of the fundamental aspects in regard to model design and their influence on successful program­ ming. Perhaps I should point out that this series of articles is not intended to be a stepby-step programming guide. There are far too many different brands of transmitters, each using a dif­ferent programming technique, for that approach to be successful. Instead, I want to establish the fundamental principles upon which programming is based and show how an understanding of these principles can help simplify the programming process and improve safety. Transmitter design This is a fine example of a modern computer controlled 6-channel R/C transmitter. It has memory to cater for up to four different models and host of programming options. 74  Silicon Chip As noted last month, modern transmitter design has been driven largely by the requirements of the international class competitor allied with the need for mass production and market­ing. The smaller the number of models any one manufacturer can produce to capture the largest market share, the more efficient the operation. This development has crept up slowly and probably began with Phil Kraft when he introduced his Signature Series. This radio had settings for throw in different directions and dual rates. I recall one of the Australian Kraft factory team crashing on one occasion during an aerobatic contest. He hit the ground inverted at the bottom of an outside loop. When I questioned him about what caused the crash, he informed me that he had the dual rate switch set to low instead of high and the loop diameter was too great for the height available. Fig.1: this is the configuration for a “flaperon” wing, showing the direction of servo rotation to achieve (a) flaps or (b) ailerons. I had been flirting with dual rate at the time and after that I dropped it as I had also found that learning two complete sets of control responses detracted from the purely instinctive response so necessary for high level performance. I am not a great fan of gadgetry for this reason. As a manufacturer I have to play the game and provide these gadgets but personally I like simplicity and prefer to rely on my own physical dexterity. Soon after, Futaba introduced their “J” series with FM transmission and a few mixers for elevator to flaps and rudder coupling. Both these radios used potentiometer adjustments, no channel allocation and no model memory. Flying a different model meant readjusting the pots if the models were not correctly set up, a situation we dealt with last month. R/C system designers eventually found a better way and that was the computer encoder. Now models of all types could be flown, the sky literally being the limit. This has lead to the overly complex computer transmitter, designed to be all things to all people, which in many instances has so many features that it just simply overwhelms the beginner and sports flyer. Basic requirements Let’s look at what a modeller really needs from a transmit­ter. To begin, it is essential that you have a clear understand­ing of what your requirements are. At the most fundamental lev­ e l, this may involve deciding that the transmitter is to be used for cars, boats, aircraft or helicopters. This may involve choos­ing the ideal physical layout such as wheel or stick transmitter, or the ideal program configuration such as the helicopter specif­ic transmitters now available. This may seem pretty obvious but what is not so obvious is the next step. That is to decide what is the best system for your branch of the hobby. Fixed wing flyers, for example, fall into broad categories such as beginner, sport, glider, scale, aerobat­ ic, pylon, ducted fan, etc and each cate- gory places different demands on the R/C system. Sport flyers have the minimum requirements in regard to auxiliary features. Scale may call for a relatively large number of channels with few mixing features. F3B gliders place the most stringent demands on the R/C system in regards to complexity of programming. It is in trying to produce a radio that will cover all of these requirements that has lead the R/C manufacturers to produce the very complex transmitters we now see in the model shops and the computer makes it all possible. Manufacturers claim that the key to this flexibility is model memory. Some transmitters now offer up to one hundred model memories, a mind bending figure. In view of the fact that many modellers have taken off with the wrong program loaded, such a large number of memories certainly ups the odds in this area. Last month, we looked at model memory and decided that for modelOctober 1997  75 Fig.2: this is a glider in “crow” landing configuration, sometimes referred to as “butterfly” mode. Flaps are down and the ailerons are up but still providing aileron function. Elevator trim compensation is sometimes applied. lers flying fixed wing sport models, model memory presented more of a danger than an advantage. If the models are basically the same type and correctly set up, then model memory is a rela­tively unimportant feature. Having said that, there are several aspects of fixed wing aircraft operations whereby model memory may become very import­ant. Such is the case of a modeller who specialises in F3B (multi-task gliders) for example. F3B models use variable geometry with each configuration stored in a separate model memory. These memories are switched in flight so that with the flick of a single switch, the entire aircraft geometry may be reconfig­ ured. One F3B model may use as many as six or seven memories. Under these circumstances one hundred memories suddenly shrinks to about fifteen models. However, here we are talking about the most specialised, highest level competition flying that exists in this sport. The average club flyer has no need for anything remotely like the sort of R/C system called for in F3B. Futaba, for example, in their Super 7 transmitters originally had all three model types, powered fixed-wing aircraft, helicopters and sailplanes, however the sailplane features were lacking. They then released (1993) a sailplane specific system, the 7UGFS, which had to relinquish the helicopter features to make way for the complicated F3B program­ming. So the crux of the matter comes back to choosing the cor­rect system for your needs, remembering not to get too ambitious with your first radio. Since 1993, computers and memory chips have made enormous strides and the very latest transmitters on 76  Silicon Chip offer have covered all of the gaps, albeit at a mighty price. Choosing a system So what sort of radio should you choose? Can the potential dangers of model memory be minimised while still holding on to the advantages? I believe there is a way to have the best of both worlds but it involves thinking outside the square. So let us proceed with a more detailed examination. For example, take a modeller who regularly flies sport, aerobatic (F3A) and glider (F3B) models. This would be most unusual modeller I might add, for most modellers specialise in only one or two branches as a rule. For this particular examina­tion we will use the programming manual for the Futaba Super 7 system (7UAPS and 7UAFS), as written in good English by Don Edberg and published by Dynamic Modelling, Irvine CA. This is as excellent publication which not only gives the programming steps but also the aerodynamic theory behind why such steps are necessary. There are other manuals rewritten for other systems and if they are not available in your area, then as a last resort you should fall back to the factory manual. Unless that is, you have an American system such as the Ace Radio Micro­pro 8000 system which has an excellent factory manual. Before we start, it is necessary to look at some of the innovations that have crept into modern transmitters. First is channel allocation, which is the ability to assign each front panel control to a particular channel number in the data trans­ mission sequence. This is a very useful feature but should be used with the greatest of care. Not all transmitters have this function but when it is used it should be used with as much consistency as possible from model to model. If the wrong memory is loaded accidentally, coping with a reversed control is one thing but if ailerons became elevator, for example, then all hell would break loose. This becomes increasingly difficult as we move into the more complex programming systems which are made possible by another trend in model design and that is two independent servos for each control which are electronically but not mechanically cou­pled – see Fig.1. This trend has been accelerated by the increasing size of models, the need for some degree of fail-safe servos on these very large models, the falling cost of servos and finally the ability to mix two different functions into one control. The more obvious configurations such as elevons and V-tail have always called for two servos with mixing on each servo. However, such configurations as the airbraking system desig­nated CROW (both ailerons UP and flaps DOWN), ailerons mixed into flaps, and the ultra weird “ailevator” configuration where ailerons are mixed into elevators on a standard fixed wing model, all demand two independent servos for their functioning. So the very first thing we notice in the Futaba manual is the attempted consistency applied to channel allocation through­out the programming descriptions. In the first instance, the channel allocation given in the Super 7 manual for setting up a sports model is ch1 – aileron; ch2 – elevator; ch3 – throttle; and ch4 - rudder. This is the traditional Futaba channel allocation which is still used on their non-programmable transmitters. The F3A model will follow similar lines with perhaps ch5 allocated to retracts and ch6 allocated to flaps, if these are used. There would be no problem running these two types of models from the one 6-channel transmitter without model memory, using the techniques discussed last month. However, when we change to F3B mode the problems begin. Channel allocation suddenly becomes a very different matter. In the F3B model we are dealing with the multi-servo wing as a mandatory item. The F3B model The F3B model is a multi-task model which calls for a very high level of aerodynamic sophistication. Variable camber wings are a must for this type of model in order that the launch, speed, cruise, endurance and landing tasks are all carried out in the most efficient aerodynamic configuration. Thus, the ailerons and flaps are called upon to perform multiple roles, with the ailerons performing the functions of flaps, ailerons or speed brakes in the one flight, often with any two simultaneously engaged. Flaps likewise may be called upon to perform as flaps, reflexed trailing edges to increase speed or even ailerons in some models. In the CROW (landing) con­figura­tion, the ailerons are both moved UP to provide airbrakes (whilst still performing as ailerons) and the flaps are at maximum droop. Elevator trim is mixed in to compensate for the trim shift caused by the flaps and ailerons and coupled aileron/rudder may be engaged to compensate for the loss of aileron efficiency in the UP position – see Fig.2. To add to the programming confusion, glider wings may be two, three or four servo types, depending on the complexity of the design. Added to this are additional problems of complex mixing of elevators with flaps, flaps with elevators and rudder with ailerons. The F3B glider is the most complex program of all model types and I believe the prime driving force shaping devel­opment of the modern computer transmitter. Yet when I had completed the F3B module for the Mk.22 TX and I needed to run the final testing, I looked around for someone with a four servo wing and could not find one in an easily accessible location. The best I could find at short notice was a two-servo wing. In all of Syd- ney there is not a handful of these complex models yet they dominate transmitter development the world over. As I stated previously, in trying to cater for the handful, the transmitter designers have made life really tedious for the average flyer. The channel allocation for the F3B model called for in the Futaba UAFS/ PS system is ch1 – right aileron, connected to the aileron stick; ch7 – left aileron, not connected to any front panel control but slaved through an inverting mixer from ch1 to provide the equal and opposite drive signal. Ch3 is right flap and ch6 is left flap, both connected in parallel with ch3 con­nected to the throttle stick to provide flaps. Ch2 is elevator and ch4 is rudder. Ch5 is left unused. From the above it would appear at first glance that there is no possibility of flying sport and F3A models from this trans­mitter configuration without model memory, which is oddly enough quite wrong. We still have a throttle stick, aileron stick, elevator stick and rudder stick all in the correct locations. So long as all models are fitted with seven channel receiv­ers and absolute consistency is adhered to in regard to channel allocation and servo directions, there is still no danger of model memory causing a catastrophic result if the wrong memory is accidentally loaded. Even if the sport program is loaded for the F3B model, at least one half of each control will work in the correct sense and direction, although one half of the flaps working would certainly raise the adrenalin levels for a while. However, problems could arise if the channel allocation was changed to squeeze in a 6-channel receiver in one or more models in your fleet. So as a general rule, the larger the number of channels available in your system the easier and safer programming becomes. One final point: many manufacturers make a big deal about their trim memory function. This function stores the trim offsets for each model. Here is one function that you could well do without. Make sure that all servos are correctly neutralised and that all trims are in neutral for all models, when the final trimming of each model is complete. That is the only approach if you want to avoid a nasty surprise one day. SC The answers! to 260,000 questions, ALL in one book! The largest range of replacement semiconductors in the industry! Call now to get your new NTE cross reference book for just $25. Stewart Electronic Components P/L P.O. Box 281 Oakleigh 3166 phone (03)9543-3733 fax (03)9543-7238 P.C.B. Makers ! If you need: •  P.C.B. High Speed Drill •  P.C.B. Guillotine •  P.C.B. Material – Negative or Positive acting •  Light Box – Single or Double Sided – Large or Small •  Etch Tank – Bubble or Circulating – Large or Small •  U.V. Sensitive film for Negatives •  Electronic Components and •  •  Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE Prompt and Economical Delivery KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 •  ALL MAJOR CREDIT CARDS ACCEPTED October 1997  77 Silicon Chip Back Issues September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Operating an R/C Transmitter; Index to Vol. 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. 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. 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. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2; The Snowy Mountains Hydro Scheme. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band; the Bose Lifestyle Music System; The Care & Feeding Of Battery Packs; How To Make Dynamark Labels. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. April 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. 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. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car; Fitting A Fax Card To A Computer. 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. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; MIDI Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. ORDER FORM Please send me the following back issues: _____________________________________________________________________ _____________________________________________________________________________________________________________ _____________________________________________________________________________________________________________ Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ PLEASE PRINT Street ______________________________________________________ Suburb/town _______________________________ Postcode ___________ 78  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503.  Card No. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; A Windows-Based Logic Analyser. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. November 1993: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. December 1993: Remote Controller For Garage Doors; LED Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags – How They Work. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. 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; Passive Rebroadcasting For TV Signals. 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; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. 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. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Cruise Control – How It Works; Remote Control System for Models, Pt.1; Index to Vol.7. 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 Pre­a mp­lifier;The Latest Trends In Car Sound; Pt.1. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark­rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. May 1995: What To Do When the Battery On Your PC’s Mother­b oard Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder (Uses Pressure Sensing); Adding RAM To A Computer. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. September 1995: Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­v erter 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; Use your PC As A Reaction Timer. 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 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; Build A High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. 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 Fluores­c ent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. September 1996: VGA Oscilloscope, Pt.3; Infrared Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­ grammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; Infrared Stereo Headphone Link, Pt.2; Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. November 1996: Adding An Extra Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. December 1996: CD Recorders –­ The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. January 1997: How To Network Your PC; Using An Auto­ transformer To Save Light Bulbs; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (for Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. February 1997: Computer Problems: Sorting Out What’s At Fault; Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Audible Continuity Tester; Cathode Ray Oscilloscopes, Pt.7. April 1997: Avoiding Windows 95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; Installing A PC-Compatible Floppy Drive In An Amiga 500; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. May 1997: Windows 95 – The Hardware Required; Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. 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; How Holden’s Electronic Control Unit works, Pt.1. 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; How Holden’s Electronic Control Unit Works, Pt.2. September 1997: Multi-Spark Capacitor Discharge Ignition; Build The 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. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc for $10 including p&p. October 1997  79 PRODUCT SHOWCASE Electromagnetic compatibility test system The Schaffner BEST 96 EMC test system combines all neces­sary functions for full compliance testing of residential, com­ mercial and light industrial electrical and electronic products. The BEST 96 system comprises a multi-function generator providing burst, electromagnetic discharge (ESD), surge and power quality pulses (for single-phase power line and data line compliance), a ground plane, cables, ground strap, grounding resistor and cou­pling clamp for data line testing and a step-by-step instruction manual. BEST 96 provides a universal interface/coupler into which the product-under-test is plugged in and preprogrammed tests using “built-in” test pulses are then run. The testing procedure has all signal functions controlled from the BEST 96 front panel or alternatively, from a PC using Windows-based software. For further information, contact Westek Industrial Products Pty Ltd, Unit 2, 6-10 Maria St, Laverton North, Victoria 3026. Phone (03)9369 8802 or Fax, (03)9369 8006. 1GHz RF spectrum analyser The new Laplace SA1000 1GHz Spectrum Analyser is control­lable by any PC capable of running under Windows and is suitable for in-house EMC testing. Frequency coverage is from 20kHz to 1.1GHz with selectable start and stop frequencies and logarithmic or linear scaling. The single frequency mode of the instrument permits true averaging and quasi-peak measurements which can be plotted against time to enable the monitoring of trends and excursions as required by EMC standards for fluctuating emis­sions. The software package (EMC En80  Silicon Chip gineer) also provides other important capabilities including antenna factor compensation; background nulling; multiple trace comparison; and limit line display for common EMC standards. The SA1000 has very high sensitivity to low field strengths down to less then 17dBµV/m (when used with the Laplace broadband antenna). An inbuilt calibration source confirms the operation and accuracy of the analyser. An audio modulator and internal loudspeaker are also provided. The demodulation technique is suitable for both FM and AM signals. For further information, contact Nilsen Technologies, 150 Oxford St, Collingwood, Vic 3066. Phone (03) 9419 9999; fax (02) 9419 1312. STEPDOWN TRANSFORMERS 60VA to 3KVA encased toroids Westcode power semiconductors A broad range of Westcode Semiconductors (UK) Ltd’s devices is now available in Australia. They include thyristors, distrib­uted gate (fast turn off) thyristors, high frequency thy­ ristors, diodes and fast recovery diodes. These devices can be supplied, mounted within insulated base modules such as the WK250 series and are available in double thyristor, thyristor/diode, diode/thyristor and double diode arrangements. Westcode semiconductor assemblies feature a choice of integral water-cooled and air-cooled packages. The compression mounting technology in conjunction with ceramic device packaging ensures excellent hermeticity and heat conduction properties while maintaining high electrical isolation (withstanding voltage of 2.5kV RMS). Devices available have peak reverse voltage ratings ranging from 500V to 1700V at a junction op- Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 erating temperature of 130°C. Air-cooled devices can operate at typically 300A (thyris­tors) and 250A (diodes) as measured on half-cycle sinewave average basis and at an ambient temperature of 85°C. Water-cooled devices (eg, an AC diode switch) can operate at 750A RMS (inlet water at 25°C and flow rate of 4.5 litres/min) October 1997  81 Hioki single-phase power meter The new Hioki Model 3330 Power meter covers the range from 30W to 18kW and has an energy range to 999,999 MWhr. The 3330 measures current to 30A without the need for a current transform­ er or shunt. Voltage is measured over three ranges: 150, 300 and 600V. The instrument caters for power measurement on inverters and switchmode power supplies, having a bandwidth from 10Hz to 50kHz. The unit also measures frequency up to 50kHz. An inbuilt comparator function permits adaptation to assembly line operations and automatic testing (ATE) together with optional RS232 and GPIB interfaces. Basic accuracy is ±0.3% and compared to an air-cooled equivalent of 555A RMS at an ambient temperature of 85°C. For further information, contact Westek Industrial Products Pty Ltd, Unit 2, 6-10 Maria St, Laverton North, Vic 3026. Phone (03) 9369 8802; fax (03) 9369 8006. Variable speed motor control ICs Two new ICs from GEC Plessey Semiconductors (GPS) are tar­geted at variable speed motor control applications in white goods, such as washing machines, fan drives in air conditioning systems, water pumps and general purpose industrial inverters. The SA828 3-phase PWM generator IC is designed for use in AC induction motor drive systems. Switching carrier frequencies up to 24kHz allow ultrasonic operation of inverter power switch­es. The power waveform is stored in an on-chip ROM. Two standard waveform options are available: sine plus third harmonic (a means of increasing motor power output for a given line supply voltage to the inverter) or pure sine. Other waveforms can be provided to customer order. The SA828 operates as a standalone microprocessor periph­eral imposing just a small processing overhead on the micropro­cessor as it requires attention 82  Silicon Chip fast response time is 0.4 seconds, making the instrument suitable for transient measurements. For further information contact only if the frequency or ampli­ tude of the output waveform needs to be changed. Any of the popular 4 or 8-bit microprocessor and micro­con­troll­ers can be inter­faced with the SA828. The SA838 is a single phase variant and is available for applications such as uninterruptible power supplies or single phase induction motor drives. For further information, contact GEC Electronics Division, Unit 1, 38 South St, Rydalmere NSW 2116. Phone (02) 9638 1888. Nilsen Technologies, 150 Oxford Street, Collingwood, Vic, 3066. Phone (03) 9419 9999; fax (03) 9416 1312. New instrumentation catalog from Fluke Charger conditioner for nicads Premier Batteries has introduced a single module charger conditioner which uses negative pulse technology to charge and condition nickel cadmium and nickel metal hydride batteries. The charger is supplied with dedicated cup modules to cater for Motorola Saber, Visar, MTS2000, HT600, GP300 and the Bendix King Radio. It has the added advantage of a 12V charger for in-car use. It will charge batteries in approximately one hour and the negative pulse conditioning will maintain the peak charge indefi­nitely, without shortening battery life. For further information, contact Premier Batteries Pty Ltd, 9/15 Childs Road, Chipping Norton, NSW 2170. Phone (02) 9755 1845. Philips Test & Measurement has released the 1997/98 Fluke instrumentation catalog. The 242-page catalog describes the complete range of more than 400 Fluke products including selec­tion guides, accessories and customer support information. It features 19 sections for product categories such as Scope­meters, multi­meters, bench oscilloscopes, timer/counters, generators and network test tools. The catalog is available from Philips Test & Measurement. Phone (02) 9888 SC 0416; fax (02) 9888 0440. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. SILICON CHIP This page is blank because it contained advertising which is now out of date and the page has been removed to prevent misunderstandings. VINTAGE RADIO By JOHN HILL Wave-traps: another look A versatile wave-trap can be a useful accessory in any area where there is a strong local station. A wave-trap can make a big difference when it comes to tuning other stations and all my vintage receivers, superhets included, perform better when used with a wave-trap. As the crow flies, 3CV Central Victoria on 1071kHz is about six kilometres from where I live. Its 5kW output belts out 24 hours a day and to a vintage radio enthusiast such as myself, my local station is a complete pain in the neck – so to speak! When it comes to crystal sets, simple regeneratives and TRF receivers, 3CV dominates the dial. When listening to a simple crystal set, the local station can be heard over the full tuning range. TRF receivers handle the situation a little better but the amount of interference can still be very annoying. Even superhets with their superior selectivity are not immune to the problem and splatter from 3CV can be heard some distance either side of the 1071kHz position on the dial. My local radio station has not always caused such frustra­tion. Some years ago, 3CV ceased transmission at 11pm every night, thus providing a good opportunity to listen beyond the usual veil of interference. Using a simple crystal set, I was amazed to find other stations out there just waiting to be heard. These included 3BO Bendigo, 3BA Ballarat, 3LO Melbourne, and even 5AN Adelaide on odd good nights. However, those exciting late-night Only a few components are required to build an effec­tive wave-trap. Shown is an old variable capacitor, a reel of enamel covered wire & a cardboard former. 88  Silicon Chip long distance DX sessions with crystal sets came to an abrupt end when 3CV changed to 24-hour nonstop broadcasting. It was much the same when I was a lad living in Bendigo. Back then, 3BO swamped my crystal sets and little regenerative receivers. So local radio stations have been an annoyance to me for most of my life. It is not surprising, therefore, that I have spent some time experimenting with wave-traps. The basic function of such a device is to block out any unwanted frequency (the strong local) yet, at the same time, let all the other frequencies through. It sounds good but there are trade-offs as you will see later on. Different designs Wave-traps (or rejector circuits as they are correctly termed) are nothing new and many old wireless magazines published details on how to build them. I have tried several different types over the years and have found that they all have advantages and disadvantages. Finally, I have come up with a fairly good compromise. There are quite a few different designs of wave-trap but three in particular are applicable to vintage radio receivers. The first one to be discussed is the common parallel tuned trap (Fig.1). As can be seen from Fig.1, this type of trap is connected in series with the aerial lead. When tuned to resonance with the strong local station, it blocks (or rejects) that frequency while allowing other frequencies to pass through it (apart from those close to the resonant signal). This type of wave-trap works very well on superhet receiv­ers and the Fig.1: the parallel tuned wave-trap is easy to build. It uses just a coil and a variable capacitor. Fig.2: by connecting the aerial to different points on the coil, the effectiveness of the trap can be varied. This is the author’s “Super Wave-Trap”. It can be changed from a parallel-tuned configuration to a secondary-tuned configu­ration at the flick of a switch. What’s more, in secondary-tuned mode, the aerial can be switched to any of the four taps on the primary winding. previously mentioned splatter either side of 3CV is reduced to nothing. But this benefit is not without a small cost. Other nearby stations are reduced in volume a little as a result of using the trap and there is also some degree of atten­uation over the rest of the dial. So what the trap giveth with one hand, it taketh away with the other. But any good 5-valver can make up for any losses the paral­lel-tuned, series-connected wave-trap may in- troduce. Lesser receivers are not so tolerant, namely crystal sets and small regenerative receivers. The effect of a parallel-tuned trap on a crystal set is interesting. However, before going into details, mention should be made of another powerful local station. Some 145km away at Horsham, the 50kW transmitter used by 3WV on 594kHz is powerful enough to be considered a strong local station. In crystal set terms, it supplies quite Fig.3: the tuned secondary wave-trap works well with crystal sets and simple regenerative receivers. good listening volume and is the second most powerful station in my listening area. Now when a parallel tuned wavetrap is used with a crystal set and is tuned to reject 3CV, there are two noticeable effects. First, it is so effective it blocks out 3CV as though it doesn’t exist. Second, it broadens the tuning of 3WV to such an extent it can be heard over the entire range of the dial. When trying to tune in 3WV, the tuning never peaks on the station. It’s every­where but nowhere in particular. In this case, the wave-trap not only filters out 3CV, it also disrupts the receiver’s tuning circuitry. As far as crystal sets are concerned, a parallel tuned trap is much too severe and a more compatible trap is required. Simple regenerative receives do not perform that well on a parallel tuned trap either. The trap is effective as far as controlling the local station is concerned but there is a tenden­cy to block out a sizeable band of frequencies on either side of the resonant frequency. So this type of trap is by no means suitable for use with all vintage receivers. Tapping the coil The trap shown in Fig.2 is a variation of the parallel tuned trap and incorporates a tapped coil. By tapping the aerial into the coil at different connection points, the effectiveness of the trap can be altered. Perhaps the best setup would be to have a sliding contact so that the aerial can be connected to any part of the coil. October 1997  89 A tuned secondary wave-trap with a 6-turn primary is the ideal wave-trap for the author’s crystal set (shown here) and the prevailing reception conditions. Although I have never used this type of trap, it seems to have very good possibilities. Tuned-secondary wave-trap At this stage of our story it is time to discuss the third type of trap. This is known as the tuned secondary wavetrap and is shown in Fig.3. There are some significant differences between this design and the previous ones. The most obvious is that there are now two windings and the tuned section is inductively cou- pled to the primary through which the aerial is connected. In this design, the effectiveness of the trap depends to a large extent on the number of turns on the primary. These turns are wound directly over the secondary winding and the greater the number of primary turns, the more effective the trap. Experiments with crystal sets have indicated that about six turns on the primary winding are just about right for my recep­tion conditions (and for the type of crystal set being used). And This 2-valve regenerative receiver’s performance is greatly improved when using a secondary tuned wave-trap with a 24-turn primary. 90  Silicon Chip with so few turns, there are no adverse effects. No longer is 3WV spread across the entire dial, nor is there a void near the resonant frequency as previously mentioned. The tuned secondary trap only moderately suppresses 3CV and allows sufficient signal to pass through to enable the station to be heard at a normal listening level. Without the trap, the headphones are too loud for comfortable listening and when they are laying on the bench they can be heard “barking” away from anywhere in the room. However, a 6-turn primary is not sufficient for a 1-valve regenerative receiver as the local station is still quite unre­strained and swamps half the tuning range. Instead, simple regen­erative receivers seem to work better with about 20 or more turns on the primary. Even then, 3CV is still fairly broad in its tuning but it is not a bad compromise considering the type of receiver and the close proximity of the station. A point worth mentioning is the fact that two secondary tuned wavetraps can be used in series to trap out two strong local stations without greatly affecting the signal strengths of other stations. The super wave-trap Each type of vintage radio requires its own special wave-trap setup. This could lead to a situation where one has half a dozen or so different traps in order to obtain optimum results from a number of receivers. To remedy this situation, the “Super Wave-Trap” has been built. The Super Wave-Trap incorporates the best of both designs and can be changed from parallel-tuned to secondary-tuned at the flick of a switch. In addition, when switched to secondary mode, the tapped primary can be switched from six to 24 turns in incre­ments of six turns at a time. Wiring up the trap was a bit of a nightmare and two switch­es (a rotary and a double-throw multi-pole) were used to sort out the problem. Now some experts may suggest that, in theory, the last thing a low-performance receiver such as a crystal set needs in its aerial system is a network of tapped coils and switches. The theory is that RF currents are impeded by such things and, there­fore, the Super Wave-Trap may defeat its own Silicon Chip Binders REAL VALUE AT $11.95 PLUS P &P 1920s receivers such as the “three-valver” lack selectivity and are easily over­ powered by local transmissions. A wave-trap can help overcome this problem. purpose by having too much high-frequency impedance. This theory did not hold up in practice and while there might be losses, in practice they are too small to detect. The advantage of using the trap far outweighs any disadvantages. The Super Wave-Trap has what some may consider an odd addi­tion – an earth terminal. It’s not that a trap actually needs one but it can be convenient to have both aerial and earth leads coming from the same part of the bench. The earth lead simply passes through the cabinet of the trap. While such a setup is unnecessary, it’s OK as far as I’m concerned. Talking about earth leads, it is a good idea to use an earth on any re- Crystal set DX’ing Back in my boyhood days, the term “wave-trap” meant nothing to me. Yet, if I had known then what I know now, my crystal set listening may not have been restricted to one sta­tion. DX’ing with a crystal set is a lot more practical today than it ever was in the past. Transmitters operate at much higher wattages now and effective crystal set range has increased ac­cordingly. But although increased power can be an advantage, it can also be a disadvantage if a powerful transmitter is in your neighbourhood. Simple regenerative receivers and crystal sets, in particular, bene­fit from such a device because these receivers lack selectivity. A wave-trap helps to reject the stronger signals these simple receivers cannot cope with. If you are having reception problems due to a nearby transmitter, then a wave-trap may help solve or at least SC reduce your problem. ★  Hold up to 14 issues ★  80mm internal width ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A11.95 plus $A3 p&p in Australia; or $A11.95 plus $A8 p&p in NZ & PNG. Not available elsewhere. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form  Even superhets can have some minor problems with nearby trans­mitters and, in some cases, a wave-trap can be of assistance. Shown is a dualwave AWA Radiolette. ceiver that’s connected to a wave-trap. Although the trap works without the receiver being earthed, it seems to be more effective if it is. In a very strong local signal area, the lead from the wave-trap to the receiver’s aerial terminal should be as short as possible. If living under the shadow of a transmission tower, a long lead from the trap to the aerial terminal will only pick up unwanted RF signal. If the lead has to be long, it’s advisable to use coaxial cable to make the connection. These binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. Enclosed is my cheque/money order for $________ or please debit my ❏ Bankcard  ❏  Visa   ❏ Mastercard Card No: ________________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ October 1997  91 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. Drill speed controller has insufficient range I purchased the Drill Speed Controller on the advice that this unit would give a full 235-240VAC output when in the maximum position. I have assembled the kit only to see that the output (measured under load using a DVM) reads 128V when using with a drill, yet it varies beautifully to very low and no internal adjustment will change this. Of course, the drill is noticeably slower but has plenty of torque. Can you please tell me if this is the normal characteristic for this kit? (J. C., Rydalmere, NSW). • Your drill speed controller is working exactly as it should. Since they effectively half-wave rectify the 240VAC mains sine waveform, by virtue of their use of an SCR (silicon controlled rectifier) or in this case, a Triac which triggers only on posi­ tive half-waves, the maximum voltage output is reduced to about 160V RMS. As you have found, this leads to a significant reduc­ tion in maximum speed of your drill. It is not possible to design an SCR or Triac speed control to give full speed Interference problem with car antenna I am experiencing AM interference with the Car Antenna Adaptor featured in the December 1988 issue of SILICON CHIP. It appears that the interference problem relates to overhead power lines as the interference increases in relation to the proximity and number of power lines. No nearby power lines, no interference. The adaptor setup picks up very much more inter­ference than the original, conventional antenna. Is there anything I can do to stop this interference? I have tried running the 75Ω coaxial cable to 92  Silicon Chip range and still have good speed regulation and low-down torque. However, we are presently doing some development work on a Mosfet speed control which we hope will have a greatly increased output range. High resolution voltmeter I want to build a voltmeter to read 0 to 5V DC but with a better resolution than a typical 41/2-digit LCD and I want to use LED displays. I see you published a circuit in June 1993 for a car voltmeter but it does not have the resolution required. I also need a peak-hold function. I want to hold the high­est reading for two minutes so I can write it down. Can you help? (L. S., Sydney, NSW). • We do not have such a circuit on file and it is our opinion that because of the very high accuracy required, typically around .02%, such a project is beyond the scope of a magazine article. From your requirements it appears as though you need a 5-digit benchtop instrument. Such instruments are made by Fluke, Blackstar and Thurl- within two to four inches (50 to 100mm) of the actual rear window demister, the closest I could get without perhaps damaging the demister terminals. (P. P., Klemzig, SA). • Unfortunately, there is no way of eliminating this problem with the Car Antenna Adaptor. The problem may well be worse than with the original antenna since the main axis of the antenna is horizontal. In fact, the only way of effectively eliminating or reduc­ing interference from power lines is to use a large loop antenna. This is very effective in a fixed installation but is clearly not practical at all in a car. by-Thandar. You can expect to pay over $1000. Alternatively, you could adapt a standard 4000-count digital multimeter and use a fixed DC offset to improve upon the basic resolution of your readings. For example by applying a precise 3V offset, you could at least measure your 5V readings with 4-digit resolution. Depending on the range selected, you may only get 4-digit resolution from a 5-digit multimeter in any case. 6V regulator for cars I am interested in trying to adapt the circuit shown on page 97 of your publication “20 Electronic Projects For Cars”. It is for an automotive voltage regulator. I would like to adapt this to work from a generator rather than an alternator for a 6V system as used in classic English motorcycles. The electro-mechanical regulator normally used provides around 8.5V at up to 6 amps to charge the battery. Any help you could give me would be greatly appreciated. (J. W., North Balwyn, Vic). • It should be possible to adapt your enclosed circuit by simply changing the zener diode from 12.8V to around 5.6V so that the regulator cuts out at a charging voltage of around 7.7V; ie, half the equivalent voltage for a 12V lead-acid battery. We would be wary of a circuit that allowed the generator to deliver 8.5V because that would lead to overcharging of the battery. Vader voice vanquished Recently I built the Vader Voice, as shown in your Septem­ber 1995 issue. At the moment, I get no sound at all from the unit and while most of the tests come out correctly, I find that instead of getting +4.5V at pins 2 & 5, of IC1 and pins 1 & 2 of IC2, I am only getting readings of +1V. Are you able to make any suggestions as to the source of my problem? I have double checked the positioning, polarity and correctness of all components, and replaced ICs 1 & 2 but still have 1V at these positions. (B. M., Wellington, NZ). • The fact that points which should measure +4.5V have only 1V present suggests that the voltage divider consisting of two 220kΩ resistors includes a resistor with the wrong value or the asso­ciated 10µF capacitor is the wrong way around. Our bet is that one of the resistors is 27kΩ instead of 220kΩ. We assume that your 9V battery is fresh and is delivering 9V. Query on TV sound Can you please tell me if the TV stereo sound format is the same used for FM broadcasting apart from the different deviation and perhaps different pre-emphasis? I am wondering if the same stereo decoder chips can be used. (P. C., Glenhuntly, Vic). • While both FM radio and TV sound are frequency modulation systems, their deviation and de-emphasis are different. However the major difference is in how the stereo channels are encoded. FM radio uses a multiplex method with the modulation switched between left and right channels at a rate of 38kHz. By contrast, stereo TV uses two separate subcarrier frequencies, at 5.5MHz and 5.742MHz above the vision carrier. Hence, the methods of decoding stereo TV are quite differ­ ent from FM multiplex stereo and different IC decoders are re­quired. TV pattern generator programming I have purchased your new Colour Television Pattern Genera­ t or and wonder if you could explain the addressing of the EPROM (IC1) via the four 74HC193 counters. It appears unusual and I wonder if it makes programming easier. The least significant bit of the counter is connected to A1 on the EPROM but the most significant bit goes to A10 instead of A15. Is the software available now from SILICON CHIP? (C. M., Salisbury, SA). • This project used unusual addressing to the EPROM to simpli­fy the PC board design. Since the EPROM would be programmed and run with the same addresses then it is not important which order the address lines are ac- Guitar/PA amplifier wanted I wish to obtain information on the building of a guitar/PA amplifier. I have long been impressed with the tonal reproduction of valve amplifiers. My requirement is an amplifier with a 100W capacity and some (or all) of the features of the Fender amps of the 60s era (reverb, echo, etc). I would most appreciate any advice you can offer me with regard to circuit diagrams, sources of supply of valves, power transformers, audio transformers and speaker enclosure dimensions. (J. S., Isle of Capri, Qld). • We have not published any circuits for valve power amplifi­ ers and nor do we think they are a practical or economic alterna­tive to a well-designed solid state amplifier. For a high perfor­mance guitar/ PA amplifier, we strongly suggest the 175W module presented in the March 1997 issue of SILICON CHIP. You might also consider building the Digital Effects Unit published in the February 1995 issue, to provide effects such as reverberation, echo, vibrato, etc. cessed as long as it is consistent. After all, the address labelling on the EPROM is only arbitrary anyway. The software is available from SILICON CHIP for $10.00, including postage and packing. 4Ω loudspeaker. The only way to get the full power would be to use a DC-DC inverter. We published a suitable project along these lines in the December 1990 issue. When do you change the filter? Notes & Errata I have a water purifier but I never know when to change the filter. Can you design a project to detect when the filter needs changing? (D. S., Miller, NSW). • Unless the conductivity of the filtered water changes over time, as the filter deteriorates, we cannot think of any elec­tronic method which could tell you when to change the filter. Perhaps one of our readers can suggest a method. Amplifier module needs DC-DC inverter I am enquiring about details of the 50W amplifier module described in the March 1994 issue of SILICON CHIP. The kit runs on 25VAC and I was wondering if the circuit can be changed so that the amplifier can be run off a car battery with the same power output. Also, I was wondering how to change a stereo signal to a mono signal. Do you simply join the left and right channels to make one channel? (N. B, Gladesville, NSW). • In order to deliver the full 50W, this module needs a DC supply rail of ±35V or 70V in total. If it was to be run di­rectly from 12V DC, the power output would be less than 4W into a Colour TV Pattern Generator, June & July 1997: the patterns produced by the TV Pattern Generator are slightly off-centre on the TV screen due to a slight displacement in the line sync signal. In most cases, the normal over­ scanning of each line on the TV screen will mask out this small shift. It can be corrected by adding an RC network to delay the line sync by the requisite 1.5µs. This involves adding a 4.7kΩ resistor between the D7 output of IC1 at pin 11 and the sync input of IC10 at pin 16. The pin 16 input of IC10 is bypassed to ground with a 270pF capacitor. The resistor is best placed instead of the link on the PC board above the three 330Ω resistors near IC10. Note that IC10 has an incorrect pin 1 labelling on the PC board. The position shown for pin 1 is actually pin 16. The capacitor can connect from pin 16 to pin 1 of IC10 on the underside of the PC board. Flexible Interface Card For PCs; July, 1997: there are two errors in the Basic listing shown on page 28. Line 90 should read: B$ = RIGHT$(TIME$,2): WHILE RIGHT$(TIME$,2) = B$: WEND ‘wait one second. Line 220 should read: LOCATE 24,20: PRINT “Line”;LIN; ‘print it. Note: do not put full stops at the ends of the lines. SC October 1997  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES FOR SALE Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. C COMPILERS: Ever ything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086 or 8096: $140.00 each. Macro Cross Assemblers for these CPUs + 6800/01/03/05 and 6502: $140.00 for the set. Debug monitors: $70 for 6 CPUs. All compilers inc ‘HC12, XASMs and monitors: $480. 8051/52 or 80C320 Simulator (fast): $70. Disassemblers for 12 CPUs only $75. Try the new C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo disk: FREE. All prices + $5 p&p. GRAN­ T RONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph/Fax (02) 9631 1236 or Internet: http://www.mpx.com.au/~lgrant. To run your classified ad, print it clearly on a separate sheet of paper, fill out the form below & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________  Bankcard    Visa Card    Master Card Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my Signature­­­­­­­­­­­­__________________________  Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip MICROCRAFT IS NOW ON THE WEB: Dunfield (DDS) products are now available ex-stock at a new low price; please ask for our catalogue. Micro C, the affordable “C” compiler for embedded applications. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $139.95 each + $3 p&h • EMILY52 is a PC based 8051/52 high speed simulator $69.95 + $3 p&h • DDS demo disks $7 + $3 p&h • VHS VIDEO from the USA (PAL) “CNC X-Y-Z using car alter­nators” (uses car alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Fixed price electronic design and PCB layout • Credit cards accepted • All goods sent registered mail • Call Bob for more de­ t ails. MICRO­CRAFT, PO Box 514, Concord NSW 2137. Phone (02) 9744 5440 or fax (02) 9744 9280. http://www.micro.com.au email sales<at>micro.com.au MicroZed have 8-pin 6 I/O 12C508 at $3.66 ea. 1 off price quartz window version $24.40. KIT ASSEMBLY AND TESTING: free quotes, fast service. Phone Brian (03) 6266 4438 or 017 150514. ELECTRONIC ENGINEERING SOLUTIONS: No matter what problem what industry we will find you a solution that meets your needs. Specialising in schematic & PCB design, custom Windows based software, embedded control, Windows/PC based test equipment, turnkey solutions. Fast turn around with competitive rates. DAMUE PTY LTD, 46 Whitby Road, Kings Langley NSW 2147. Phone (02) 9624 2802. Fax (02) 9624 2651 or E-mail alovell<at>ibm.net $69 VIDEO CAMERAS $69 TOP QUALITY MODULES & ONLY $69! with Ja­p anese Optical GLASS (not plastic) Lens Elements, And... Light­ weight... Trouble-Free FRP Lens Holders! ALSO Optional MicroFine Zero Backlash Focus, 13 Optional Lenses 2.1mm to 12mm, PLUS Infra-Red Cut, Pass & Polarising Filters, IR Illuminators & 74mW LEDs. DISCREET TINY 36mm SQUARE Metal Cased & DOME CEILING Cam­e ras with 3.6mm Lens ONLY $99, Options for both include 10 Lens­e s, MicroFine Focus, IR Cut, Pass & Polarising Filters. Teeny Weeny 28mm Square Modules. 420 & 460 line 0.05 lux PCB Modules. 420 line Colour Modules & Cameras from $329. Hi-Res 570/450 line Mono/Colour Cameras. Simplify cabling & reduce cost of CCTV installations, use our VERSATILE SINGLE-CABLE MULTI-CHANNEL POWER-up-COAX System. For Monochrome, Colour & Audio Cameras. Use just ONE low cost 75 ohm antenna coax cable in a DAISY-CHAIN with 1 to 15+ Cameras & any number of output devices connected any­w here in Chain. Basic single channel system only $99, extra channels & output devices easily added. We have a WIDE RANGE of CCTV Equipment PLUS many UNIQUE items unobtainable elsewhere. Before you buy Ask for our Illustrated Detailed Price List with Application Notes. Allthings Sales & Services 08 9349 9413 Fax 08 9344 5905. HOMEMADE GENERATORS: how to instructions. Eight pages free text and colour photos on the Internet at: http://www.onekw.co.nz/ PCBs MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics, Ph/Fax (02) 9554 9760. sesame<at>nettrade.com.au MicroZed Computers BASIC STAMPS & PIC Tools With third party supporting products, all in stock. Easy to learn, easy to use sophisticated CPU based controllers. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (067) 72 2777 – may time out to Mobile 014 036775 Fax (067) 72 8987 http://www.microzed.com.au/~microzed Credit cards OK. Send two 45c stamps for info 651 Forest Rd, Bexley 2207 68HC11 & 68HC05 DEVELOPMENT SYSTEMS: Oztechnics, PO Box 38, Illawong, NSW 2234. Phone (02) 9541 0310, fax (02) 9541 0734. http://www.oztechnics.com.au/ makes all the project PCBs published in SILICON CHIP and other Australian magazines Tel +61 2 9587 3491 Fax 9587 5385 E-mail rcsradio<at>cia.com.au WEBSITE WITH FREE CIRCUITS http://www.airborn.com.au Also: Programmers for 89C2051 and 89C51: $188 Eval. Kit: $233 Romem: Free! ELECTRONICS (02) 9925 0325 MicroZed have 5V UPS. Uses 2 x AA nickel cadmium cells. AirBorn VARIAC: Zenith brand 0-270V 3A $80 (063) 51 4368. SIGNAL GENERATOR: Marconi model 2019 80KHz to 1040MHz AM/ FM Synthesized with Calibrated output 13dbm to -127dbm, GPI Bus Connector, Service Manual, Recalibrated in August 1997, in Excel­lent Condition. $4000.00. Phone (03) 5134 4275. Microprocessor For Digital Effects Unit This is the 68HC705-C8P pro­ gramm­ed micro­pro­cessor IC for the Digital Effects Unit (see Feb­. 1995). Price: $45 + $6 p+p WANTED WANTED – CIRCUIT IDEAS: If you have a good circuit idea, why not send it to us for publication in Circuit Notebook? We pay up to $60 for a good circuit but don’t make it too big please. Payment by cheque, money order or credit card to: Silicon Chip Pub­ lica­ tions, PO Box 139 Collaroy 2097. Phone (02) 9979 5644; Fax (02) 9979 6503. Silicon Chip Binders ★  Heavy board covers with 2-tone green vinyl covering REAL VALUE AT $11.95 PLUS P &P ★  Each binder holds up to 14 issues ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A11.95 plus $A3 p&p each (NZ $A8 p&p). Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. October 1997  95 14 Model Railway Projects Shop soiled but HALF PRICE! Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemishes. Otherwise, they're undamaged and in good condition. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) This book will not be reprinted Yes! Please send me _____ copies of 14 Model Railway Projects at the special price of $A3.95 + $A3 p&p (p&p outside Aust. & NZ $A6). Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏  Visa Card   ❏ MasterCard Card No. Street AirBorn Electronics......................95 Altronics................................. 34-36 Daycom.......................................77 Dick Smith Electronics........... 12-15 Emona.........................................81 Freedman Electronics..................55 Harbuch Electronics....................81 Instant PCBs................................95 Jaycar ............................IFC, 45-52 Kalex............................................77 Rola Australia..............................95 MicroZed Computers...................95 Model Railways Book..................96 Oatley Electronics..........................3 RCS Radio...................................95 Signature­­­­­­­­­­­­___________________________  Card expiry date______/______ Name Advertising Index ______________________________________________________ PLEASE PRINT ______________________________________________________ Suburb/town_________________________________ Postcode_________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). 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