December 1990 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: The CD/Green Pen Story: getting to the truth of the matter
Feature: Understanding PC Memory by Brian Richards
Feature: The Great Green CD Pen Controversy by Leo Simpson
Project: DC-DC Converter For Car Amplifiers by John Clarke & Greg Swain
Project: The Big Escape by Darren Yates
Serviceman's Log: It sounds like Donald Duck by The TV Serviceman
Project: Wiper Pulser For Rear Windows by John Clarke
Order Form
Vintage Radio: Old radio books & magazines by John Hill
Project: Versatile 4-Digit Combination Lock by Gary Ioppolo
Feature: Computer Bits by Jennifer Bonnitcha
Back Issues
Feature: The Story Of Electrical Energy; Pt.6 by Bryan Maher
Feature: Amateur Radio by Garry Crattm VK2YBX
Feature: Remote Control by Bob Young
Feature: Index to Volume 3
Market Centre
Advertising Index
Outer Back Cover

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UNDERSTANDING COMPUTER MEMORY - $3.50 DECEMBER 1990 NZ S4.95 ~J} - l AUSTRALIA'S .M,, E~~ELECTRONICS MAGAZINE, \ ." \•J·l,,-'J. <1 .. ,, ,.1, .. ,. '" . ~ .. ~ .., ., t . ,, .... > * DC-DC Converter For Car Amplifiers * 4-Digit Combination Lock * 5W Power Amplifier For 6-Metres ,·,, ., ' SELF-IGNITING CORDLESS PYROPEN * HAS SOLDER TIP PLUS HOT BLOW TIP * APPROX. 4 HOURS WITH EACH FILL * USES STANDARD BUTANE GAS * SOLDERING TEMP - 250° to 500°C, HOT BLOW 650°C $169.95 *D.C. VOLTAGE UP TO 1000Volts *A.G. VOLTAGE UP TO 750 Volts *D.C. AMPHERE UP TO 10Amp * DIODE TEST * RESISTANCE UP TO 2Mn INCLUDES TEST LEADS & MANUAL ONLV$39.95 BONUS FREE CAN OF WELLER GAS !! KASPAROV POCKET CHESS COMPUTER HSA4330P WEATHER-PROOF OUTDOOR SPEAKER SYSTEM ~ *8 LEVELS OF SKILL TO ADVANCE FROM BEGINNER TO INTERMEDIATE. "TRULY VERSA TILE, TEACHES CHESS TACTICS, SHOWS THE BEST MOVES, AND WARNS OF DANGER." YOU SET THE LEVEL OF HELP REQUIRED ANDTHEN PLAY AGAINST THE COMPUTER. * 3 WAY ACOUSTIC SUSPENSION * 30 WATTS RMS * COMPLETE WITH MOUNTING BRACKETS * COMPACT DESIGN * 116(W) x 120(0) 106(H)mm WAS$299.00 SAVE $20.00 NOW $149.95/PAIR __ ONLV $49.95 STUDIO 200 CONTROL UNIT KIT * SLIM ONERACK PROFILE * FULLY PUNCHED AND PRINTED $199.00 $359.00 • 240 volts input. • Includes 2.1mm PLUG. "As used on many modems, cordless phones, answering machines, etc'. Suitable for Netcom modems. I A VERY RARE PRODUCT CITIZEN SRP-60 SCIENTIFIC PROGRAMMABLE CALCULATOR " 8 digits plus 2 EXPONENT digits plus 2 negative code digits for scientific and engineering display, or 10 digits plus 1 negative code digit for other case. •? Independent memories. • Program mode capacity is 45 steps. • Mode key for decimal/Hexadecimal/Octal/ Statistical/ Program calaculation selection. • Secientific Function: 1/x, x' , In, e•, 10•, 3 ✓x, ✓ x, Log, sin, Cos, Tan, yx, sin-1, cos·1, tan·1, ><-J y, EXP, sinh, cosh, tanll, sinh·1, cosh·1, tanh·1, nl, e999 )) , »0939 • Statistical functions: Ix, "i,y, Ix', "i,'J', Dy, n, X, Y, ax, ay, SX, SY. 10 metre reel ... only 99 cents JUST ARRIVED!!! 10 VOLT A.C. 1amp PLUG PACK PANELS STUDIO 200 SERIES 1OOW PER CHANNEL AMPLIFIER DIAL CORD We 've got reels of the Stuff!!!!!! ONLY $19.95 NITE-WATCH MOTION DETECTOR with TWIN FLOODLIGHT KIT /, * Coverage: 90° <at>15 Metres * Timing & Sensitivity Adjustment * Lights can be operated manually WAS$99.95 Conversion · in" " cm, lb '"' Kg , °F"" °C, gal «» L • Automatic Power off. • Very low power consumption. ONLV $48 95 • NOW$79.95 (Floodlights not included) DAVID REID ELECTRONICS WOULD LIKE TO WISH YOU OUR VALUED CUSTOMERS A VERY MERRY CHRISTMAS AND A PROSPEROUS NEW YEAR. We also promise to give you, the customer, quality products at the lowest prices along with the best service possible throughout 1991 as we have done so in the past. The team: Des, Jeff, Karen, Shane & Anton. "Great for around the field, property, for the kids, or just for fun. It even hos a morse code function and belt U " * Transmltt1~ distance: 50 100 mts in an open field. * Operated by six (6) "AA batteries (not included) * DOC approved (27. 145 mHz). Y $19.95 /pair M Presenting the "How to Operate a Computer" course from MasterTech (TM) Computer Products International. In a matter of hours, you can learn how to easily and confidently operate a personal computer (PC) with the ... "How to Operate a Computer" ... from MasterTech !!! * Step-by-step instruction. * Built-in Instructor. THIS HANDY TOOL KIT COMES COMPLETE WITH: 1 X SPHERICAL MILLING CUTTER. 1 X CONICAL MILLING CUTTER. 1 XTAPERED CUTTER. 1 XWIRE BRUSH . 1 X GRINDING WHEEL. 4 X DRILL BITS - 0.6, 0.8, 1.0, 1.2MM. SET OF 5 CHUCK COLLETTS. 6 X ERASER STICKS 10,000 RPM DRILL & POWER SUPPLYTO SUIT 'ALL IN A HANDY CARRY CASE'. ONLV$99.00 Ours is Only $62.50 5.25 or 3.5 Disk Versions. IBM Compatible. Colour/Mono FUJI NICAD BATTERIES- Made in Japan Ideal for watching a video in the bedroom, kitchen etc. without having to move your comlete VCR system or having long extension cal:>es running from one end of the house to Ille other. "D" size 1.2 volt 4Ah was $29.95/pr Now $19.95/pr "C" size 1.2 volt 1.8Ah was $19.90/pr Now $14.95/pr "AA" size 1.2 volt SOOmAh was$4.95ea Now$2.95ea • Output channel: UHF 30 • Transmitting distance: 10mtr. • Complete with power supply and connecting cables. ONLV$89.95 NOWIN STOCK MULTI FUNCTION CAR ALARM WITH WIRELESS REMOTE LIMITED STOCKS ! ·$ CITIZEN SR-30 SCIENTIFIC CALCULATOR ni;:J · · Protects Vehicle from: ~• Bumping of car body. IC• * Towing. ,__ I ·. c.-····-·· * Window breaking. --~;,-"' -·· ' I{I~:----·* Forced entry of Doors, , {~ ·, - - ~- · ~ = ==:·::::: Bonnet or Bonnet. FEATURES: • Display: 8 digit liquid crystal with 3 sign symbols • Capacity: 8-diglt mantissa with sign, and 2-diglt exponent with sign. • One independent accumulating memory. • Scientific notation with a wide range of 200 decade (-99 to 99) • Degree/Radian/Gradian one key operate for trigonometric. • Mixed chain calculation. • Algebraic operation for arithmatic functions. • Scientific functions: sin, cos, tan, sin·•, cos·•, tarr' , log, 10', In, e•, y•, •Of,0, x', [ ], EXP, 1/x. • The minus sign of the matissa is floating minus. • Automatic power tum off - about 7-8 minutes. • Statistical functions: X, orr', (on)', DATA. DEL. • 3 level parentheses. ,, Recharges 2 or 4 'AA' size nicad ba Two charging Rates: • Quick charge - 4 Hours * Normal Charge - 15 Hours ONLV$21.95 ARLEC - 9 VOLT NICAD CHARGER 9 Volt 11 OmAH ONLV $18.95ea GOING OVERSEAS ??? Travel Adaptors are just what you need! Converts Australian style 3 pin 240 volt plugs ThdiKorjo "British" plug. Great Britian, Ireland, Singapore. Parts of the Middle East, Africia, Asia and Hong Kong. The Korjo "European" plug. Europe, Noumea, Tahiti, Parts of the Middle East, Asia, and South America. For Japan and Hong Kong, use with local adaptors. ALL ONE PRICE $7.SOEACH Also available: Multi reverse adaptor which converts British, European and U.S.A. plugs to Australian style 3 pin plug. ONLY $7.50 $19.95 COMPUTER DISKETTES ARLEC - COMPACT 'AA' NIC includes 2 x ~ ' nicad's FREE!!! NOWONLY 5.25" DSDD $5.95 PKT 10 5.25" DSHD 1.2Mb .... $12.95 PKT 10 -~ 3.5"DSDD $14.95 PKT 10 3.5" DSHD 1.4Mb .... $31.50 PKT 10 a LT AC FILTER CAPACITORS volt AC 0.1 uF and 2 x 0.005uF ·.· 1! It #2 250 volt AC 0.47uF NORMALLY $4.95 NOW$1.95ea 10+ $1.75ea 100+ $1.SOea WAS$3.95 NOW$1.80ea 10+ $1.60 100+ $1.40ea December 1990 THIS DC-DC CONVERTER provides split supply rails of up to ±50Vfrom a +12V supply so that you can run a high power audio amplifier in your car. Details page 24 FEATURES 4 Understanding PC Memory by Brian Richards How to make the best use of the options 14 The Great Green CD Pen Controversy by Leo Simpson We've done the tests to bring you the facts 98 The Story Of Electrical Energy, Pt.6 by Bryan Maher Rebuilding old alternators to better than new PROJECTS TO BUILD 24 DC-DC Converter For Car Amplifiers by John Clarke Can be built to give supply rails from ±35V to ±50V CAN YOU MAKE the big escape by getting safely through the tunnel? This clever game will test your skill. Turn to page 38. 38 The Big Escape by Darren Yates Can you escape from the remote prison camp? 54 Wiper Pulser For Rear Windows by John Clarke Pulses the wiper on at the press of a button 70 Versatile 4-Digit Combination Lock by Gary Ioppolo Easy-to-build circuit uses DIP switches for programming SPECIAL COLUMNS 48 Serviceman's Log by the TV Serviceman It sounds like Donald Duck 66 Vintage Radio by John Hill Old radio books & magazines 82 Computer Bits by Jennifer Bonnitcha Talk to the world: modem mysteries revealed 104 Amateur Radio by Garry Cratt A 5W power amplifier for the 6-metre FM transmitter RECENTLY, THERE HA VE been claims that applying green dye to the edges of compact discs can improve their sound quality. We've done the tests to bring you the facts. See page 14. 110 Remote Control by Bob Young Radio control receivers using amplitude modulation DEPARTMENTS 3 Publisher's Letter 7 Mailbag 65 Subscription Page 80 Circuit Notebook 86 Product Showcase 93 Bookshelf 2 SILICON CHIP 96 Back Issues Ask Silicon Chip Index To Volume 3 Market Centre Advertising Index 114 116 118 120 HERE'S A 4-DIGIT LOCK that will prove useful in many security applications. It's easy to build & is programmed by setting four on-bo~rd DIP switches. Details page 70. PUBLISHER'S LETTER Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates Reader Services Ann Jenkinson Advertising Manager Paul Buchtmann (02) 979 5644 Mobile: (018) 28 5532 Victorian Representative McDonald Woodside & Associates Pty Ltd, 143a Como Parade East, Parkdale, Victoria 3194. Phone (03) 587 5155. Contact: Cameron McDonald. The CD/Green Pen Story: getting to the truth of the matter This month, we lift the lid on a story which has been brewing for some months now and which we had tended to ignore: using green pens to improve the sound of compact discs. At first it sounded too stupid for words and a procedure which any informed CD listener would merely laugh off. But then we heard a little of the theory behind why the green pens are claimed to work and it began to seem as though the story may have some basis in fact. Some audio writers have claimed that they can hear the difference brought about by the pens while others have preferred to sit on the fence. Well, the trouble with letting a concept like this go without any informed comment is that it starts to build up momentum. If enough people - audio dealers, writers and keen enthusiasts - claim to notice a difference, the concept becomes vested with authenticity, despite never being put to objective tests. Besides which, the more we thought about it, the more intrigued we became with the methodology you would need to prove whether or not the concept really did work. And coming up with a method is no easy matter. You can't do double-blind tests (for reasons which are explained in the article); instead, you must use a CD analyser. So that's what we did in preparation for this month's main story. We went to the only organisation in Australia which has CD analysers - the Disctronics plant in Melbourne. They kindly made their equipment available to use for a day plus one of their Quality Assurance staff to actually do all the tests. And what was the result? Do the pens have any effect on compact discs? Well, I'm not going give away the story - you'll have to read the full article inside the magazine. I'm sure you will find it intriguing. See you next month. Leo Simpson Regular Contributors Brendan Akhurst Jennifer Bonnitcha, B.A. Garry Cratt, VK2YBX John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Jim Yalden, VK2YGY Bob Young Photography Glen Cameron Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW ·, Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. All material copyright©. No part of this publication may be reproduced without prior written consent of the publisher. Printing: Magazine Printers Pty Ltd, Rozelle, NSW 2039; Macquarie Print, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates: $42 per year in Australia. For overseas rates, refer to the subscription page in this issue. Liability: 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. Editorial & advertising offices: Unit 39, 5 Ponderosa Pde, Warriewood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. ISSN 1030-2662 DECEMBER 1990 3 •••••••••••••••••••••• I UNDERSTANDING • • () Memory is one of the most important parts of a personal computer but is probably the least understood. This article will describe how the PC uses memory, what types of memory are available and how to make best use of the options. By BRIAN RICHARDS* Let's start with a little history. IBM introduced the PC in 1981, with the capability of using up to 640 kilobytes (640Kb) of memory. At the time, this was 10 times the memory available in virtually all other personal computers. This was enough for most users for the following 2-3 years, during which the IBM PC developed as the number one personal computer. It also became the standard upon which many other manufacturers would base their own designs. · • Brian Richards is Marketing Manager of Hypertec Pty Ltd, 408 Victoria Road, Gladesville, NSW 2111. 4 SILICON CHIP As PC users became more numerous, the demand increased for more powerful software and with this came the demand for more memory to run this software. Also, more power was demanded by users no longer content with the processing speed of the 8088 chip. This resulted in the development of the 80286, the 80386 and the 80486 processors, each delivering more power and functionality. Added to this was the introduction of networks and the memory hungry software needed to run them, often alongside the operating system and the applications. Today, it is commonplace to buy a PC or PS/2 machine with 1Mb or 2Mb (Mb = megabytes) of memory as standard. However, many business machines are running with 8, 10, 12Mb and more, with the advent of operating systems like OS/2 and Xenix, which need large amounts of memory to load and run individual applications. DOS&memory The original and still the most popular operating system for the PC is DOS. To understand how PC memory works we need to look at how DOS uses memory. Each PC has a set amount of memory that it can address. This includes the ROM (Read Only Memory for controlling the display, the hard disc and the movement of data in and out of the computer); RAM (Random Access Memory for the software to use); and Video Memory (for controlling the display image). The system used by PC designers to address memory through DOS is shown diagramatically in Fig, 1. The total amount of memory available to the PC is 1Mb but only 640Kb is available to the operating system and application programs. This segment is known as system memory. This is normally found installed on the motherboard when you get your PC, unless you have a system with less than 640Kb. This is more common in older PCs, which often came with 256Kb or 512Kb of memory. One of the most cost-effective upgrades for the PC is to install a board which brings it up to the full 640Kb of system memory. Most of the more popular application programs now need at least 640Kb to run, shutting out machines with less memory. For the PC or XT, the Hypertec Hyper 256 and Hyper 512 are examples of boards available for just this purpose. If there is a need to add further serial or parallel ports to the machine, then both of these boards are available with the option of extra ports. If a PC AT needs to be upgraded, then the Hyper 128-16 will give an extra 128Kb of memory. All of these products come with easy to understand instructions for installation and a comprehensive manual. Expanded Memory Expanded memory came about because program developers became frustrated with the fact that DOS could only make 640Kb available to them to work in. So three major companies in the PC industry, Lotus, Intel and Microsoft, got together and developed LIM EMS (Lotus-Intel-Microsoft Expanded Memory Specification). What this in effect did was to use a 64Kb window of memory on the "free" area of addressable memory (see Fig.1) to access a much larger region of expanded memory. In EMS version 3.2, there can be up to 8Mb and in version 4.0, up to 32Mb. Now, because DOS came before EMS, it does not know it exists. So to use an expanded memory board, an expanded memory device driver is required. This is loaded from the CONFIG.SYS file during the boot process. Once the hardware and software drivers have been installed, application programs use the expanded memory by making a request to the driver, and must therefore be written specifically for EMS 3.2, 4.0 or both. The driver translates the requests into the correct commands to the EMS memory board, to move the window to the correct position in the expanded memory to retrieve the page requested STANDARD MEMORY SYSTEM BIOS VIDEO ROM EXPANDED MEMORY Fig.1: this diagram shows the system used by the PC to address memory through DOS. The first 640Kb is reserved for system memory, with the space above that used for video memory & B1OS ROM. If expanded memory is used, this is accessed via a "free" area of addressable memory (the EMS window). NORMAL MEMORY T EXTENDED MEMORY Fig.2: unlike the earlier XT machines (8086 & 8088 processors), the 80286 & 80386 processors can address up to 16MB of memory. The memory above 1Mb is called extended memory and is accessed via the "protected mode" of the processor. (see Fig.2). Each page is 16Kb in size. The window is divided into 16Kb sections, so a number of pages can be accessed at one time. EMS Version 3.2 has been out for some time now and all expanded memory boards on the market should support it. Version 4.0, which is rapidly becoming the new standard, is a radical upgrade to the capabilities of EMS. Version 4.0 does everything 3.2 does and more. The enhancements of Version 4.0 open the way to new applications, such as the multi-tasking capabilities of Microsoft Windows. Hypertec's Hyperam 286 and Hyperam MC 32/ 16 Expanded/Extended memory boards offer Version 4.0 support. How much memory It is also important to be clear about how much memory you will need. If the multi-tasking capabilities of Version 4.0 are to be used, then it is advisable to specify at least 2Mb. However, if EMS is to be used only to allow larger spreadsheets, it should be remembered spreadsheets can only use about 1Mb of expanded memory. This is because most spreadsheet applications store information in system memory about the information stored in expanded memory. Typically, a spreadsheet runs out of system memory when about 1Mb of expanded memory has been used. This is, of course, just a rule of thumb. This principle applies to all application programs that use expanded memory, not just spreadsheets. However, it is also possible to use expanded memory for utilities such as RAM discs and print spooling. A RAM disc will improve the performance of disc intensive processes, while a print spooler can significantly reduce the amount of machine time you waste while waiting for a print job to finish. Hypertec boards are supplied with some of these utilities as standard. Extended memory boards Extended memory is memory in the address space above 1Mb, the maximum addressable by the PC. The 80286 processor on the AT bus can address 16Mb of memory. The region between 1Mb and 16Mb is called extended memory, and is accessed via the "protected mode"of the 80286 processor. The 80286 can run in two modes: real and protected. In real mode it behaves like a faster 8088, while in protected mode it allows access to all the extra facilities of the 80286, including the 16Mb of memory. The 80386 also has protected and real modes, as well as a third mode called virtual, in which it operates like a number of 8088 processors, so it can run a number of different programs simultaneously. Extended memory cannot be used in a PC or any maDECEMBER 1990 5 machine. The only difference is that when installed in a 286 machine, it can be configured as extended memory as well as system or expanded memory. A multi-function version is also available with one serial and parallel port. 80386 (32-hit) machines AT-style machines with an 80386 or 80486 processor sometimes have a proprietary 32-bit slot for add-in memory boards. The advantage of this is higher performance for the memory; the disadvantage is that the addin memory boards are typically supplied by the machine manufacturer, at substantial -extra cost. It is worth remembering that 16-bit memory can still be used in the AT bus, at greatly reduced cost, and the performance difference may not be noticeable. MCA machines The Hyperam MC 32/16 can be used to provide extended memory in virtually any MCA (Micro Channel Architecture) machine and can act either as a 32-hit or 16-hit board. It can he supplied as a multifunction version and offers EMS Version 4.0 support. chine with an 8088 or 8086 processor. No device driver No device driver is needed for, extended memory as it is assumed that programs needing this amount of space will be able to control it themselves. There are, however, special programs such as IBM's VDISK driver, which provides an extended memory RAM disc. VDISK puts the processor into real mode and returns control to DOS. Extended memory becomes particularly important with the new generation of operating systems, such as OS/ 2 and Xenix. OS/2 Standard Edition requires at least 1Mb of extended memory to be able to boot and, for satisfactory performance, at least 4Mb is likely to be needed. A rule of thumb for estimating the memory needed to run Xenix is 1Mb to start plus 512Kb 6 SILICON CHIP for each user on the system. As with OS/2, the more extended memory available, the faster the system will run. The right memory board The PC (ie, a machine using the original PC bus) can only use system or expanded memory. Expanding the system memory to the 640Kb limit is the first step in upgrading, as mentioned previously. If expanded memory is required above the system memory, then a board such as the Hyperam 286 is the answer. The Hyperam 286 is a 16-bit board but has been designed so that it also runs in 8-bit PC slots. It supplies 2, 4 or 8Mb of memory which can be used iri PCs as system or expanded memory. As a 16-bit board, Hyperam 286, may also be used to offer the same memory upgrades to a 286 or AT-bus Roughly the same considerations apply to the PS/2 range as for the AT. A PS/2 MCA (Micro Channel Architecture) machine has at least 1Mb already installed, which supplies 640Kb of system memory and 384Kb of extended memory. Some of these machines allow you to place more memory on the motherboard but this will not necessarily provide expanded memory capability. A more flexible and cost effective solution may be a memory board and in the case of MCA machines, there are 32-bit boards available from third party manufacturers. The Hyperam MC 32/16 is one such board and it may be used in any MCA machine. It acts as a 32-bit board in the Models 70-386, 70-486, P70 and 80, while also acting as a 16-bit board in the Models 50, 50z, 60 and 65SX. It can come in a multifunction version and offers EMS Version 4.0 support. So, before purchasing a memory upgrade for your particular machine, think carefully about what you are currently using it for and what you may wish to use it for in the future . This much determined, use the guidelines above to ascertain how much and what type of memory you require. Remember, applications are getting more and more memory hungry with each new release. You are probably going to be using your PC for some years yet, so a little forethought should ensure fewer problems ih the long term. MAILBAG Booster for MiniMitter not permissible A few months ago I purchased and built a "MiniMitter". This unit has proved to be very good and in a city or surburban area would be quite adequate. However, I live in a relatively remote area of Queensland and have a property which covers considerably more than the average suburban territory and consequently require a greater coverage. Consequently, I would therefore be pleased if you could provide me with circuitry for a wideband RF amplifier to boost the output of the MiniMitter, or failing that perhaps you could advise me where I could obtain the necessary design details. R. E. B. Wisher, Biggenden, Qld. Comment: unfortunately we can't provide a booster circuit for the MiniMitter as that would undoubtedly contravene DOTC regulations and would possibly lead to people deliberately attempting to interfere with FM services. Modellers are often supplied battery packs as sealed 2-terminal units. Attempting to rebalance a battery without access to individual cells could cause reverse charging or overcharging of some cells. Perhaps there could be some advantage in following full-size practice. Access to individual cells might be obtained by sliding pins through and beneath the plastic sheath to contact the outside of each cell. For interest, I am obtaining excellent results from recharged alkaline dry cells. They cost less, give more capacity per charge, and are more predictable in service. It would appear that the manufacturers discourage this more for commercial than technical reasons. Special techniques are required for best results. I refer interested parties to articles in the June and July 1986 issues of the English magazine Practical Electronics, on which my experiments have been based. D. MacMillan, Yorkeys Knob, Qld. Balancing ofnicad cells is important For those interested in vintage radio I am an aeromodeller and a LAME whose duties include the servicing of nickel-cadmium aircraft batteries. I have enjoyed Bob Young's excellent series of articles and so wish to mention a characteristic of nicads that may be of interest. When nicad cells are assembled into a battery, the cells can, due to the level voltage characteristic, drift into different states of charge. On discharge, the low cells bottom out first, causing terminal voltage drops in discrete steps of 1.2 volts. If discharge continues, the low cells are driven to reverse polarity, which is harmful. A battery with zero terminal voltage may have a spread of plus and minus voltages across its individual cells. To restore full capacity, aircraft batteries are withdrawn from service at set intervals for rebalancing. This involves individually monitoring and discharging each cell to zero volts, followed by a full recharge. The Historical Radio Society of Australia was formed on the 17th April, 1982 to cater for the needs of those interested in preserving the equipment and records of past times in radio and wireless telegraphy, especially in this country. It is a nonprofit society with members in every state of Australia. A quarterly newsletter is distributed to members, who are encouraged to contribute items such as tips on restoration of equipment, information on early equipment and memories of the days when radio was the wonder of the world. The activities of the society and its members also form subject matter for the newsletter, while a free advertising service is available for purposes in line with the society's aims, such as the sale or exchange or vintage equipment. Meetings are held in Melbourne on the third Sunday of each odd month and the third Thursday of each even SILICON CHIP, PO Box 139, Collaroy Beach 2097. month, except December. Meetings have also been held in Sydney and Brisbane but at present, not on a regular basis. The annual membership fee is $15 per year and new members receive copies of all newsletters issued during that year. Membership enquiries should be addressed to the Membership Secretary, J. R. Wales, PO Box 283, Mt Waverley, 3149. The society is collecting a library of circuit information and at present circuits are available for Astor from C1930; Healing from C1932; AWA for 1930, 31, 33 and 1936 onwards; plus most other makes from 193 7 to about 1954. A charge is made to cover the cost of copying and postage. Address enquiries to Ray Kelly, 49 Sharon Road, Springvale, 3172. J. R. Wales, Mt Waverley, Vic. Wants early issues May I take this opportunity to express my thanks for such a top quality magazine. Congratulations on your success so far. I would like to refer to a letter published in the September 1990 issue about early reprints. I hope other readers will contact you concerning their interest in these back issues. I am in a.· situation where my original copies of January and February 1988 have been lost. I can order the February issue but the January issue poses a problem. My immediate need for this issue is the UHF bow-tie antenna which contained a 300Q to 75Q balun. If perhaps you could inform me about the details of this balun, it would be appreciated. I will still try to obtain the January 1988 issue, as I would like to have a complete collection. M. Dobbins, VK2XQJ, Kotara, NSW. Comment: unfortunately, our stocks of February 1988 are now also sold out, as well as those for April and June 1988. However, where we no longer have back issues available, we can supply a photostat copy of any article for $5.00 including the postage. DECEMBER 1990 7 The next step. Learn how to solder and use printed circuits. Another 20 projects to build. Cat B-2605 S695 Start with the absolute basics and learn to build 20 fascinating projects. Cat B-2600 s49s Complete these 10 projects and you'll be able to tackle any of our electronics kits. Cat B-2610 S695 _....-:: . NEWI PHYSICS FOR KIDS BOOKS ~ \.\~'f.P,.~• . -.. ' • .. u•M•'\~ 1.C;,.-" •' ·~·>~:·. . :·_ ·_._•. w E. UP-TO-DATE WORLD TRANSISTOR COMPARISON TABLE '995 Description and equivalents of every transistor known. Cat B-4760 This book demonstrates just how much fun ~..,_____...___ Physics can be, offering young scientists an introduction to electricity and magnetism. It includes 49 fun filled experiments suitable for junior high school students. Cat 8_1820 LINEAR IC EQUIVALENTS Descriptions, equivalents, & pin connections for linear ICs. Cat B-4761 s199s DIGITAL IC EQUIVALENTS Descriptions, eqmvalents, and pin connections for digital ICs. Cat B-4762 INTERNATIONAL DIODES EQUIVALENTS Equivalents for Zener diodes, Thyristors, Triacs, Diacs, & LEDs. Cat B-4763 1 1895 s 1495 YOIJR WORLD CAN BE AN ELECTRONIC WORLD! QUARTZ STOPWATCH • LCD display • Split lap times • Time & date Cat Y-1051 J Bargain Pries! Only s99s THE AMAZING FLOATING PEN CLOCK • See it appear to defy gravity before your very eyes! • A perfectly balanced gift! Cat Y-1001 NEGATIVE ION GENERATOR • This could be your solution to air-borne pollution such as cigarette smoke and photo copier chemicals • Combats the Ion Imbalance produced by air conditioners Cat Y-9000 56995 Replacement pins available $4.95 s349s MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: 1 ~r:i·~~~\ti:: ~:r~~~~&~~~~P!t!:iu~tfu: re.~=1Lb~iiti~ Coifs twllouf Eiecmcs 525684 DENIUQUIN: Deni Electronics 813672 D\JBBO: Chris's Hi R 828711 FOOSTER: Forster Village Elec1ronlcs 545006 GI.EN INNES: John Sommer1ad Electronics 323661 GRAFTON: Repairs and Soares 421911 GRIR'ITH: Miatronics 624534 INVERELL: lnverell Elecironics 221821 LEETON: lJletun Audiotronic 532000 LIGHTNING RIDGE: CVcle & Sound 290579 UTHGOW: Oouroy PholDJIJal)hics 513173 USMORE: Oecro Electronic Services 214137 MOREE: Mo,.. 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Eyre Electronics 454764 WA: ALBANY: Micro Electronics 412077 BUN8URY: Micro Elecironics 216222 GERALDTON: Batavia l..iQlrting & Electrical 211966 KARRATHA: Daves ll!citmnic 854836 MANDRAH: Micro Electronics 5812206 PalT HEOLAND: Ivan Tomek the Elect 732531 8 SILICON CHIP at ons low pric cat Y-7819 ,,sges 00 ~ ~ --.i ;:;:; r BEDSIDE ALARM CLOCK • The inexpensive way to get to work on time! • Large LED display • Alarm with Snooze Control Cat Y-1005 SAVE OVER 30% ON 5watt WIRE-WOUND RESISTORS Just 45c each or 25c each on bulk purchases of 10 or more! R-1600 R-1603 R-1601 R-1602 R-1604 R-1606 R-1610 R-1614 R-1618 R-1620 R-1622 R-1624 R-1626 R-1628 R-1630 R-1632 R-1634 R-1636 R-1638 R-1640 0.1· 0.22· 0.47" 1· 1.2· 1_5· 2.2· 3_3· 4.7" 5.6· 6.8· 8.210· 12· 15· 15· 22· 27" 33· 39· R-1642 R-1644 R-1646 R-1648 R-1650 R-1652 R-1654 R-1656 R-1658 R-1660 R-1662 R-1664 R-1666 R-1668 R-1670 R-1672 R-1674 R-1676 R-1678 R-1680 POLYSWITCH PROTECTORS (••• = Ohm symbol) 2.2k. 2.7k. 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SPOIL YOURSELF! With a CS Radio or Shortwave Receiver from Dick Smith Electronics. Bring the World Into Your Home! 10 BAND SHORTWAVE RECEIVER These stylish two-way radios will bring hours of fun to the kids. They are 0.O.T.C approved and no license is required. Cat 0-1075 Only s199s/pair • Receive your local AM/FM stations plus 8 shortwave bands • Includes soft carry case . • Battery operated with sockets for an AC adaptor and headphones (not supplied) SANGEAN MULTIBAND RECEIVER • AM/FM plus Long Wave, Medium Wave & Short Wave (150kHz to 30MHz) • Digital display with keyboard frequency entry or dial tuning • 24 hour clock with sleep timer • Plus a host of other features Cat 0-2831 With Electronic Tuning! SLIMLINE AM CB The style of this Dick Smith Electronics CB will compliment your dashboard. At just 140 x 30 x 130mm, It fits exactly where you want it. • Touch control electronic tuning • LED signal strength and power output display • Built-in noise limiter • External speaker jack • Complete with Mic and Mounting Kit sa9 Cat D-1200 DOTC Approved Extra Features... Extra Value! 'SUPER LION' AM SSB CB At this price you weren't expecting all these quality features, but here they are! • Inbuilt SWR meter • Emergency channel 9 switch • Squelch, Mic gain, and Clarifier controls • LED channel display Cat D-1711 DOTC Approved 1.5m CB ANTENNA PACK . Only s199 • High performance Whip Antenna • Includes cable and base plus mounting instructions Cal 0-4076 s199s BENELEC 10 SILICON CHIP 81047/MS ·UtT ....•u~:-❖ ~ With Built-in Logic Tester! ~ With Easy to Read Bar Graph/ PROBETYPE DIGITAL MULTIMETER DIGITAL MULTIMETER A full function Digital Multimeter with Transistor, Capacitance, Diode & Continuity testing - 34 ranges in alll • 200mV to 750V range • 200uA to 20A currant range • 200 to 20M Ohms • 2nF to 20uf capacitance range • Carry case Included This would have to be the smallest, handiest DMM you'll ever have the chance to buy! It features Data Hold, fixed and auto Ranging, plus a full 3½ digit LCD display. • 200mV to 500V range • 0 to 20M Ohms • Auto Polarity indication • Diode and continuity testing • AC/DC Current up to 200mA • Soft carry pouch ;1291!<at>{.i Cat Q-1560 -s599s , A real time-saver! TRI-STATE LOGIC PROBE No need to tie up your CRO or Multimeter for logic testing. Your new logic probe can detect high, low, and pulse states; needs no batteries; and has a tip fine enough to easily contact individual IC legs. • Adjustable threshold for DTL, TTL & CMOS circuits • Pulse and memory modes • Pulse detection to 12.6MHz Cat Q-1272 $3595 DIGITAL CAPACITANCE METER Battery operated, this meter is lightweight and comes with a handy carry case and highly flexible leads. With its 9 ranges and 3.5 digit display, it represents great value for a great price! • 200pF to 20,000uF range • 3.5 digit display • Pushbutton range selection The RC Oscillator you can take anywhere! Great features like continuously variable amplitude, 23 ranges of sine and square wave, plus remote sync, are packed Into a unit no bigger than a digital multimeter. · • 20Hz to 150kHz range 3% Accuracy 20Hz to 100kHz 5% above 100KHz) • 0 to -20dB output control • 0.3% maximum distortion •+ -(+ Cat Q-1220 $119 Budget Priced! 6.5 MHzCRO This is what you need on your workbench at home! It's the perfect CRO for the classroom too, with more going for it than just a tiny price tag. Retrace blanking, internal or external sync, low drift, and quick warm-up all add up to value for money. • 1/1, 1/10, 1/100 attenuatlo ·• 10Hz to 100kHz timebase • 2~0mV/div $ honzontal sensitivity 399 Cat Q-1222 $129 81047/M2 Now that its Cltrisbttas... SPOIL YOURSELF! These handy kits will bring hours of fun to you or your children A low cost project thafs high on safety value. This circuit monitors your brake circuit each time the pedal Is pressed and warns you with an Indicator light If your broke lights have tolled. Comes with a case and all components. Cat K-4500 <at> Apr11•s9 s199s ,.,.. 7,;lf. 1111 ~LE~ ~ GOOGIE EGG TIMER Q VEHICLE CABIN LIGHT DELAY Q The egg that keeps time - from around 3 minutes to 17 minutes! This entire clrt::ult Is designed to flt Inside a Pavlova Mix 'egg shell' pack. It even ticks while counting and gives a musical chime when your eggs are done. This Is a short fonn kit and excludes This circuit will keep your car's cabin light on for 20 seconds oner you close the door - enough time to find the Ignition and strap your self In. Includes a dimmer control for mop reading and comes with case, hardware, and components. c.ase and. b a t t e ~ . ~ Cat K-3590 M1Jiia .• ~ Nov'90 Cat K-4002 -<at>July'89 s249s tdeU1s199s With lnfrared remote control! TELETEXT DECODER MKII QQQ [z] The most Inexpensive way to receive all the advantages of Teletext. Includes remote control, case, silk screen pre-punched front panel, and mains tronsfonner - everything you'll need to assemble a complete unit. Cat K~360 -<at> June/July '89 KEY Mains [1] TELETEXT MKII TUNER MODULE QQ Kits marked with this symbol Involve mains power wiring. Take extreme care when working with this equipment. Even If you don't have a VCR you can still use the Teletext MKII. Simply odd this tuner to your Teletext kit. It enables up to 6 UHF and VHF stations to be pre-tuned and selected from the remote control. ---------------------· <at> Degree Of Simplicity Cat K~361 QQ QQQ 12 Aug'89 Simple Intermediate Detailed SILICON CHIP B1047/M1 COAXIA CABLE STRIPPER • Will cut and strip both RG58 and RG59 cable • Sophisticated design with fully adjustable and replaceable blades Cat T-3635 s14ss HELPING HANDS CABLE TIE GUN ~Sl 495 Neat cabling used to take hours. A Cable Tie Gun like this can make all the difference. It tightens and cuts cable ties in one simply action. Cat T-3560 For fine solder work you really need 2 pair of hands - so here they are! Helping Hands is a PCB holder with magnifying lens that can hold your work at just the right angle and let you see in close without risking soldering your nose to the circuit board! sges CatT-5715 \ UnbB/lsvablsLUG COUNTERSINK TOOL Low Pries/ ~ Cat T-4925 NIBBLING TOOL 1 ~ There's nothing to beat the clean smooth cut of a Nibbling tool. There are no metal filin9s to play havoc on circuit boards and holes m panels and cases can be cut to exact sizes without reaming. s14ss Cat T-4945 RIMPING TOOL For quick and reliable connections, rimping beats solder any time! This ghtweigh1 crimper can cut, strip, and rimp your cable quickly and reliably. tT-3525 s495 DELUXE CRIMPING TOOL 4\ t'£ s3995 This robust crimper has a ratchet drive for accurate control; variable pressure adjustment and double jaws for single action crimping. Cat T-3535 HOBBY KNIFE SET 8 PIECE IC INSERTION & EXTRACTION TOOL KIT • • • • 3 knives in a solid plastic case with magnetic blade holder. Includes 10 blades - each a different shape for a different purpose. Cat T-3618 s 1595 6 IC inserters for all the common OIL packages OIL IC extractor Square IC extractor Zippered vinyl case CatT-4848 ~ s39es ~ DECEMBER 1990 13 The great CD green pen controversy Compact discs are supposedly unimprovable, aren't they? Well, to the average user that is virtually true. Which is why claims for improvement after the application of a green paint or dye to the outside of a compact disc are intriguing to say the least. Well, we've done the tests and we reckon it's a load of garbage. By LEO SIMPSON Want to improve the sound of your compact discs? Of course you do. After all, no matter how good your hifi system, you will always be keen to improve the sound quality, particularly if it can be done for only a small outlay. 14 SILICON CHIP And so what would your reaction be if I told you that you could improve the sound of your compact discs for an outlay of only $10 or perhaps a little more, say $39.95? If it gave an audible improvement to a system costing a thousand or more dollars, it would be well worthwhile wouldn't it? The modification is that you apply a green dye from a special felt tip marker pen, to the inside and outside edge of your compact discs. This is claimed to give real sonic improvements. In fact, I'll quote directly from the literature for the "CD Stop Light" pen: "... will improve sound in all areas - depth, imaging, better bass, smoother mids and highs, less graininess and more musicality. When it's applied to a well recorded Compact Disc the difference can be detected immediately. The first dynamic note will be tighter and crisper than before". There is a lot more along these lines from the distributor of this product. -.·· ·1 This idealised diagram shows the optical system of a compact disc and the laser pickup. Invisible infrared light from the semiconductor laser at bottom is focussed by a lens system onto the disc's recorded surface. Light reflected from the disc passes back through the lens and is diverted by the prism and into the photodiode. Some of the laser light will be scattered and will reflect from the disc edges back to the photodiode. But will that cause any additional errors? So why is it supposed to work? The literature for these pens is not absolutely clear on this point, but let me quote directly from the CD Stop Light literature again: "A laser reads light, if it reads any light other than a direct reflection of its own transmitted light it will read it as a distortion. Also if its own transmitted light is reflected around the disc and it is then read by the laser it will also be interpreted as a distortion." Are you any the wiser? What I interpret this to mean is that some of the light from the laser in your CD player is scattered once it passes through the clear plastic on the underside of the disc. That scattered light will travel out to the shiny edge of the disc and be reflected back, whereupon it will add in a spurious way to the light reflected from the aluminium recorded layer of the disc. In so doing, it will degrade the signal from the optical detector (which is not a laser but an infrared detector diode) and therefore make it more prone to give errors in the data signal. If you accept that concept, then you should have no problems accepting the next part. The light from a CD laser is infrared and therefore invisible. It will be absorbed by a green paint or dye. So if any stray light from the laser is absorbed by the green dye, that should make the data signal from the CD that much cleaner. In other words, there should be less errors in the data and that should, ultimately, mean cleaner sound. OK, so if this interpretation is correct (and what other interpretation can there be?), then it should be possible to test for the reduction of errors off a CD, once it is coated on the edges with one of these green pens. How do you test for data errors from a compact disc? We're not talking here about steady state distortion of an analog signal by the way. We are talking about errors in the digital data stream. Data errors, if they occur, and are not corrected, will not show up as steady harmonic distortion. Instead they will be momentary imperfections in the signal which will be virtually impossible for any analog instrument to measure. So, we need a compact disc analyser to do the tests. Compact disc analyser The only organisation in Australia that we know of which has a compact disc analyser is Disctronics Ltd, in Melbourne. They are the only manufacturer of compact discs in this country. So we approached them with a view to using their compact disc analyser to do a whole series of tests to prove conclusively whether or not the CD Stop Light and other green pens actually work. Disctronics Ltd has four compact disc analysers in their Quality Assurance laboratory but they are not portable and so we could not borrow one. We would have to go to them. And so, on 16th October this year, I visited Disctronics for the whole day. I was armed with a selection of compact discs both good and faulty, a number of green dye pens and various cameras. I also had the full-time assistance of Disctronics' Quality Assurance staff member, Bill Dines, without whom these tests would not have been possible. Projected tests I had planned a number of tests. The first of these was fairly simple and involved looking at the signal waveform from the optical detector (the infrared detector diode) before it is processed by the decoder circuitry. Contrary to what you might think, this is not a simple "squared up" digital signal. Rather, it is rounded, because the laser light is being reflected Since the laser pickup is a mechanical system, it will be subject to variations in the way it tracks the disc surface. This makes it extremely difficult, if not impossible, to detect any variation caused by the marker pens. DECEMBER1990 15 the effect of signal hash due to scattering of the laser light by scratches on the underside of the disc. The photo of Fig.1 is from an absolutely pristine disc which is also from a very good master. It has an almost ideal "eye pattern". Fig.2 is from an average quality CD with not very many scratches or surface defects. Fig.3 is from a CD which is very badly scratched and virtually unplayable in parts. Hash on the digital signal Our objective tests of the CD stop light pens was done in the quality assurance laboratory of Disctronics Ltd, in Melbourne. The author is on the right, decked out in clean room gear, while QA technician Bill Dines is on the left. Between them is one of the Sony CD analysers. from pits in the CD metallisation which are not perfect (ie, they don't have vertical walls) and because the laser spot diameter is not extremely small with respect to the pit diameter. The signal I looked at is known as the "eye pattern" and reveals, to the practised observer, the depth of the pits and the general quality of the pressing from the master. Further- more, because it is an unsynchronised signal (ie, not stationary on the oscilloscope screen) and one which is hard to photograph, I looked at the signal from the lead-in track of a number of CDs. Three photographs of eye patterns from three separate CDs are featured in this article - see Figs.1, 2 and 3. Not only do these photos show the pressing quality but they also show Badly scratched discs such as this abused example do cause the laser to produce a lot of errors, as was clearly shown in our tests. However, even badly scratched discs like this can be played on most CD machines. A worse problem is scratches on the label which make the disc unplayable. 16 SILICON CHIP Notice how there is a lot of "hash" on the signal of Fig.3 compared with the very clean pattern in Fig.1. If you're not sure what I'm talking about, the hash is the blurring at the top and bottom of the signal pattern. This is a clear demonstration that laser light is scattered by scratches and surface defects on a CD and that the resultant waveform from the optical detector is noisy. Noisy signals like these are bound to have more errors than clean signals. Just for the exercise I compared the eye patterns of the same discs when they were treated with the CD pens but if there was any effect there was no way you could see a difference in the patterns. Clean signals stayed clean; dirty signals stayed dirty. Measuring error signals So far, I had confirmed that laser light can be scattered by surface imperfections on CDs and that this scat- Applying the CD Stop Light pen is a little easier because it has a groove in the tip. It's still a messy job, though. FIG.1 FIG.2 These three "eye" patterns show the signal directly from the laser photodiode of the CD player. Fig.1 is from a first quality disc with an almost ideal "eye" pattern. Fig.2 is from an average good quality disc, while Fig,3 is from the very badly scratched disc shown in a photo on the facing page. These photos clearly demonstrate that scratches (and presumably internal reflections) can degrade the signal from the photodetector. But the CD pen did nothing to improve matters in this regard. tering caused distortion (ie, noise and hash) of the recovered digital signal. So the first part of the claim for the CD Stop Light pen is undoubtedly true. Now I had to test whether the green dye treatment had any effect. Measuring errors in the data stream from compact discs can be done in a number of ways. Disctronics has two types of CD analyser in their QA lab, three made by Sony and one made by Shape, a US company. The Sony machines, type CDP-5000, can give a printout of every block error and interpolation on a disc. And this is where I came to the first hurdle. The printout for a typical good disc with an average block error rate might easily run to 100 to 200 pages, with 66 lines per page. For a bad disc, a complete printout would run to thousands of pages! Comparing two such printouts, before and after treatment with the green pens, was clearly going to be impossible. I had quite a few discs to do, so I had to compromise. I decided that for each disc I would only do an analysis of the innermost track (track one) and the outermost track. Because these were closest to the inner and outermost edges of the CD, they would be the most likely to benefit from the green pen treatment, if it worked. I wanted to do at least four discs to begin with. Two of these would be pristine, first quality discs. Two would be really rubbishy, with lots of scratches. After all, if scratches cause light scattering, then the green pens should have an even more beneficial effect. I also wanted to test whether the pens worked better on moulded or pressed compact discs. Those pressed by Disctronics have a clear centre section you can see through and a sharp outer edge. By contrast, those made by PDO (Philips Dupont Optics) and used for many of the Philips and European labels have the metallisation right across to the centre of the disc and a somewhat more rounded outer edge. So I had to test at least four discs. I started with a very good quality PDQ disc. As expected, it had a very low block error rate right through the disc but right at the end it suddenly had a bunch of interpolation errors. Interpolation errors are those that the compact disc player cannot correct by using the standard CIRC (Cross Interleave Reed Solomon Code) method developed by Sony. Instead, it virtually "guesses" what the data should be, from the data immediately before and after the interruption in the signal. Interpolation errors are serious because they represent a definite departure from the original signal and therefore they are distortion. In serious cases, as on badly scratched discs, interpolation errors become audible the disc sounds distorted. Block errors are corrected And that brings me to a most important point. All compact discs have block errors, lots of them. There are 7350 blocks (ie, parcels of serial data) per second and therefore around 30 million blocks on a disc. The average block error rate on a really good disc FIG.3 is likely to be about 20 in every 10second period. Therefore, such a disc is going to have around 9000 block errors. And that's a good disc! For a badly scratched disc, the average block error rate can be 400 to 500 in every 10-second period. This disc is going to have between one and two million block errors over the hour or so of its playing period! But the good news is that block errors are not only detected but that they are all corrected. The resultant data is exactly the same as ifno block errors had occured in the system at all. Many people have trouble with this concept of data correction. It means exactly what it says - data is corrected to precisely the same value as it would have been if the error had never occurred. So good is the CIRC error correction that it can completely correct for data interruptions of up to 4000 bits that's equivalent to a spot on the disc of 2.5mm in diameter. Most CD players cannot track over such a large interruption by the way, but the error correction can cope with it. However, the story becomes even more complicated. Never twice the same The trouble with measuring and comparing block error rates read off discs is that the errors will be different for each disc each time it is played! Why? Because the laser tracking mechffnism just cannot track the disc the same way each time it is played. It is a servo-mechanical system. It can no more track a disc identically each time it is played than you can drive down a road in an identical way each time. Your car will always take a slightly different track than before - and so will the laser. And therefore the block errors are bound to be different, even though the block DECEMBER 1990 17 01:00:13:00 NOISE B.E.R 01:00:13:14 NOISE B.E.R 01:00:13:30 NOISE B . E.R 01:00:13 : 44 NOISE B.E.R 01:00:13:59 NOISE B.E.R 01:00:13:74 NOISE B. E . R 01:00:13:74 NOISE INTER 01:00:14:14 NOISE B . E.R 01:00:1,4:29 NOISE B.E.R 01:00:14:44 NOISE B.E . R 01:00:14:59 NOISE B.E . R 01:00:14:74 NOISE B.E.R 01:00:14:74 NOISE INTER 01:00:15:14 NOISE B.E.R BLOCK ERROR RATE THRESHOLD INTER POLATION THRESHOLD BLOCK ERROR RATE (MEAN) BLOCK ERROR RATE (MAX.) 01:00:13:06 01:00:13:21 01:00:13:21 01:00:13:36 01:00:13:51 01:00:13:66 01:00:14:06 01:00:14:21 01 : 00:14:22 01:00:14:36 01:00:14:51 01:00:14:67 01:00:15:06 01:00:15:22 BLOCK INTER BLOCK BLOCK ERROR RATE POLATION ERROR RATE ERROR RATE NOISE NOISE NOISE NOISE NOISE NOISE NOISE NOISE NOISE NOISE NOISE NOISE NOISE NOISE POLATION POLATION B901001300033703710984 B901001314033903200848 B9010013300353039908F7 B901001344032703230869 B901001359033403290891 B9010013740306017408C7 C003060174020040 B901001414031202230925 B9010014290292024508DA B9010014440289021508BC B9010014590281020908BD B9010014740294020908EB C002940209020063 B901001514027701010866 0070 0071 0072 0073 0074 0075 0076 0077 0078 0079 0080 0081 0082 0083 B901001306031102150806 B901001321033002150840 C00330021502000C B90100133603290324085E B901001351033403220882 B90100136603060217085D B90100140603250217081D C002930217020070 B9010014220293021708A6 B901001436028401080 89 B B901001451025700030883 B9010014670276000308B8 B901001506025500030837 B90100152202800003097F :0200 :0100 :327 . 5 :0479 B.E.R B.E . R INTER POLATION B.E.R B.E.R B.E.R B.E.R INTER POLATION B . E.R B.E . R B.E.R B. E.R B.E.R B.E . R THRESHOLD THRESHOLD (MEAN) (MAX.) 0069 0070 0071 0072 0073 0074 0075 0076 0077 0078 0079 0080 0081 0082 : 0200 :0100 :325 . 2 :0479 Shown here are two CD analyser printouts of a scratched compact disc. Both printouts are for the same compact disc, played twice in succession on the same machine, without any treatment or even being removed from the machine. Note how none of the tracking errors are the same! Clearly, our tests showed that not only does the green dye treatment not work but there is no way that anyone could claim that it does! error rates will be much the same. I had not thought about this before but it was brought home to me strongly when I tried to compare two printouts for a CD, before and after treatment. I expected to find that many, if not all, block errors would be much the same. They're not. For example, I compared a scratched disc at time 01:00:02, before and after treatment with the green pen. In this very short time interval 18 SILICON CHIP (one hundredth of a second), there were two block errors, followed by an interpolation, followed by another three block errors. But while the block error rate was identical for both readouts, none of the block errors or the interpolation were the same. Now I can't say this for sure, but having carefully examined and compared dozens of pages of block error printouts, I don't think there is much likelihood of any given block error occuring twice in succession, for two successive playings of a disc. Think about it: each time your car goes over a pot-hole, it will respond in a slightly different way each time. And so, when the laser encounters an interruption in the data of a CD, the error is detected (and corrected) in a slightly different way each time. Comparing the printouts After doing a series of printout comparisons, I concluded that not only did the green pens not appear to have any measurable effect on the block error rate but they had no effect on the number of interpolations either. Still, I had to pursue the corn- parisons for at least the four discs I mentioned above. So for the remainder of the tests done on the Sony CD analyser, I just took the printout summary. This gives the maximum and average block error rates for the disc. As I have just stated, the differences between the before and after treatment results were negligible. There was one anomaly though. You might remember that I mentioned measuring a very good PDO disc which had a bunch of interpolations at the end, printed out on the summary. Since this was early in the process and I had not thought enough about the difficulties of the test, I decided to see if the green pen had any effect on this bunch of interpolations. The trouble was, I did not think to carefully examine the disc for dust or fingerprints at that stage. Messy business I then applied the green pen to the outer and inner edges of the disc according to the instructions. Now this is a tricky process. If you are not absolutely careful and do not have a steady hand, it is quite easy for the pen to wander over onto the label or the playing surface. On this occasion I made rather a mess of things, so I cleaned it off thoroughly with isopropyl alcohol and then reapplied the green pen. On the subsequent test, the disc went through with no interpolation errors at all. Voila! The pen really worked! Or did it? I then thought that perhaps there was a fingerprint on the disc for the first test and when I had subsequently cleaned the disc, after smudging it with the pen, I had removed it. So I thoroughly removed all the green dye from the disc, made sure it was spotlessly clean and then put it through the same test again. And what do you think? Not only were the interpolations still absent but the maximum block error rate for the disc was now slightly lower. The pen had had no effect at all! But cleaning the disc thoroughly had made a big difference to the interpolations. Block error histograms Just in case the Sony CD Analyser was not giving the full picture, I decided to do some discs on the Shape CD Analyser. This unit uses a Revox According to the instructions which come with the pens, the green dye must also be applied to the inner edge of the compact disc and to any grooves that may also be present in the central area. CD player linked to a special card in an IBM PSZ computer. As well as giving block error summaries, this gives a histogram of the block errors on a disk. Two of these histograms are shown with this article. They show that even though the maximum and average block errors may be similar, the actual histograms, showing a 10-second moving average of block errors, are slightly different. But that is what you would expect, knowing that the laser cannot track the disc identically in each case. We also did some bi-refringence tests on the discs before and after treatment. These tests, performed with red light from a helium-neon laser, show the stresses and strains in a compact disc. Since this test is certainly affected by laser light reflections inside the plastic of the disc, we thought that it might just show the effect of the green dye. But you guessed it, there was no measurable effect. Conclusions So what are the conclusions? You might say that the green pen treat- ment is a load of old rubbish and you'd be correct but let's take it a bit further than that. I started by accepting the theory that internal reflections of laser light might distort the signal coming off the disc. Certainly, a badly scratched disc gave a lot more hash on the signal than that from a clean disc. But digital systems are designed to be largely immune to superimposed noise and so should not be affected in the subsequent decoding. Even so, I still went along with the theory, considering the possibility that, at times, noise on the digital signal from the disc might just cause more errors. I did all the comparison tests and could find no significant difference in the block errors and no difference at all in the number of interpolations. As stated above, block errors are all corrected so even if there had been a difference in their number, there still would have been no difference at all in the final sound quality. There was no difference in the number of interpolations, so the sound quality could not be improved DECEMBER1990 19 due to this source either. It really is a load of garbage. What about listening tests? Some hifi writers have stated that they can clearly hear the difference of 11..0CK ERROR HISTOGRAM 70- rn10- the green pen. Now we regard this as straight out self-delusion. How do you do a fair test? You can't just listen to a disc, treat it with a pen and then listen to it again. It takes a couple of minutes to apply the green pen and 16/10/90 ID: BEACH BOYS LINE: "BAD" STAMP:BEFORE RUN: IRK ONE NI T_HOLD: 1 BURST T_HOLD: 7 NI ERROR:0 BURST ERROR:0 AUG BLER: 48 MAX BLER: 54 30- *iHHHtPASS***** i0- 10- Minutes: BLOCK ERROR RATE (1 0 sec. ave~ages> BLOCK ERROR HISTOGRA M 16 / 10/90 I D: BEACH BOYS LINE: "BAD " STAMP:AFTER RUN: IRK. 1 70- '9-- 50-- 10- rn-- NI T_HOLD: 1 BURST T_HOLD: 7 NI ERROR:0 BURST ERROR:0 AUG BLER: 48 MAX BLER: 56 *****PASS***** 20-- 10- Minutes: I 160 I 7 ~1 then another five minutes to let it dry. And you have to be absolutely sure that you have not put any fingerprints or dust on the disc in the process because that will definitely change the number of errors. The time difference between your two listening tests is likely to be around 10 minutes. With that sort of time gap, how can you be sure of anything? Nor can you directly compare two identical discs, one treated and one untreated, in two identical players. For a start, no two players are absolutely identical and neither are two CDs, even if they are from the same batch. And as we have already said, the same disc is never played through in exactly the same way by the laser, even though the resultant sound quality is the same. Are you getting the picture? Not only does this process not work but the people who are promoting it don't have the evidence to support their claims. If the process really did work, it would be supported by experimental evidence from some official testing organisation. These pens have no such supporting data, just a lot of uncorroborated statements. Our advice to people wanting the best sound quality from their CDs is this: (1) Buy a good quality CD player with a well known brand. Avoid the cheapies - they're an unknown quantity. (2) Take great care with your CDs. Always keep them in their cases when not in use. When handling them, take care not to touch the playing surface the less fingerprints and dust you get on them, the less you have to clean them. (3) Keep the discs as clean as possible. Fingerprints cause interpolation errors - they are worse then scratches in this respect. (4) Take even greater care not to damage the label in any way. Never write on it with any sort of pen or pencil. The screen printed label and the surface immediately under it is the only protection for the metallisation layer. BLOCK ERROR Rfi YE ( 10 sec . a ve~ages ) These two block error histograms show the first track of a <:ompact disc before (top) and after treatment with a CD green dye pen. In this case, the histogram after treatment is slightly worse but this can easily be caused by a fingerprint or a slightly different tracking error in the mechanism. 20 SILICON CHIP Acknowledgement Our thanks to the staff of Disctronics Ltd for their assistance in the preparation of this article and specifically to Alan Bremner and Bill Dines. Laptops for around half the price of the opposition!! A 20MB hard disk notebook laptop for under $2,000 Electronic Solutions has smashed the price barrier on laptop computing yet again with its Model 101 Notebook Computer. This powerful laptop has features previously only found on laptops costing over $4,000. The LPX10 is light (3.5kg) and compact (only 47mm thick) yet packs a 20MB hard disk and a 720K floppy drive. A super-twist LCD screen provides excellent viewing under all lighting conditions. Battery life, even with the hard disk operating, is over 2 hours. Specifications: • Weight: 3.5kG • Hard disk: 20MB • Processor: 80C86 4.77110MHz • Floppy disk: 720K, 3.5" • Battery: 12V 4.0aH NiCad rechargeable • AC power: 115/230V autoswitching • Dimensions: 315(W) x 252(D) x 49(H)mm • Memory: 640K expandable to 1MB. EMS driver supplied • Ports: Dual RS232, Parallel port, external CGA port CAT LPX10 • Display: Supertwist LCD 640x200 pixels , CGA Electronic Solutions releases the Power Laptop at an affordable price! Electronic Solutions does it again, with a power portable that smashes the $4,000 barrier. Up to now, if you needed a powerful, battery powered laptop, you had to really fork out big bucks. Many people have been looking for a hard disk AT class machine with a VGA screen and a fast hard disk. Prices of most machines have been in the $6.p oo to $8,000 class. Electronic Solutions Laptop comes fully equipped for an all up price of $3495 inc tax, including a carry case. The use of the latest CMOS CPU and a very efficient hard disk with auto shutdown saves battery life. Battery life is 3 hours, very good for this type of machine. Features include: • Superior VGA (640x480) backlit display • 1.44MB/720K 3.5MB floppy drive • Optional co-processor • Lightning fast (25msec) 40MB hard disk • Serial, Parallel, VGA output ports • Optional 2400bps modem • Optione.l external floppy drive (5.2 5" 360K/1.2MB or 3.5" 720K/1.44MB) • 12V Ni-Cad battery pack, power supply and charger • Fast, low power 80L286 running at 12MHz • 1MB of RAM, upgradeable to 5MB. Memory mapping can be adjusted to extended, expanded and shadow RAM. Expanded memory support is built-in. Upgrades use conventional SIMM modules, not proprietary memory cards , so upgrade cost is low • The power supply is an autoswitching 240/115V type, so it can be used anywhere in the world without being reconfigured. • The display uses the latest supertwist technology and provides excellent viewing in bright or dim light. The VGA colours can be mapped to 10 different grey scales for best viewing results. CAT. LP212 Electronic Solutions. 5 Waltham Street Artarmon 2064. PO Box 426 Gladesville 2111. Phone (02) 906 6666, Fax (02) 906 5222. DC-DC for car This DC-DC converter will allow you to use a hifi power audio amplifier in your car to provide good quality sound. It provides split supply rails which can be adjusted to suit your amplifier. 22 SILICON CHIP H igh power amplifiers have become very popular for use in automobiles and for good reason. If you want hifi sound in your car, then high power is the only way to go. That's because of the high ambient noise level that's present inside your car - noise which must be masked out by the music. The idea behind this project is to give you an alternative to buying an expensive commercial car power amplifier. It can be used to power virtually any amplifier module with an output of up to 100 watts which means that you can now build your own. In fact, the power amplifiers described in SILICON CHIP in December 1987 should do the job quite nicely. As it stands, the circuit can be used to power twin 50W amplifier modules or a single 100 watt amplifier module, the latter possibly being used to drive a sub-woofer loudspeaker. Of course, you can also use the circuit to power amplifiers with lower power outputs, provided you tailor the supply rails accordingly. That's done simply by adjusting the number of By JOHN CLARKE & GREG SWAIN turns on the secondary of a transformer which you wind during construction. Basic principle The converter circuit is designed to convert the 12V DC supply from your car's battery to give supply rails of up to ±50V. It does this by alternately switching the 12V supply to each half of a centre-tapped transformer primary. The resulting AC waveform is then stepped up by the transformer secondary (because of the turns ratio) and then rectified and filtered to provide the plus and minus supply rails. To obtain high efficiency and reduce the number of bulky components, the converter operates at a switching frequency of about 22kHz. This high frequency allows us to use a ferrite transformer rather than an iron cored type. The circuit also uses high speed power Mosfets to switch the transformer and fast recovery diodes for the rectifiers. Power Mosfets were used because they are very fast and have low switching losses. In addition, the "on resistance" of a power Mosfet has a positive temperature coefficient, which means that they can be paralleled without the need for current sharing resistors. The complete circuit is housed in a diecast metal case to provide the necessary heatsinking and the ruggedness required for automotive use. Typically, it would be mounted in the boot (under the rear parcel shelf) or under one of the seats, along with the power amplifier modules. Specifications Output Voltage .................................................. ±35 to ±50V (adjustable) Input Voltage ............................................................................ 10-13.BV Power Output ................................................................ 100W continuous No Load Current .................. ,............................ ..... 100mA at 13.8V input Efficiency .. .. .. .. .. .. .... .. .. .. .. .. .. .. ... .. ... .. .. .. .. .. .. ... .. ... .. .. .. 80% at 100W output Line Regulation ........... ,. .. .. . .. .. .. ... . .. .. .. .. .. .. .. ... ... .. .. .. .. .. 2% from 11-13.BV Load Regulation ............................................ 2% from no load to full load Output Ripple .......................................................... 30mV p-p at all loads Operating Frequency .... .. ........................................ ...... .. 22kHz (approx.) Temperature Cutout ...................................... ................ 80°C (adjustable) Low Voltage Cutout . ... .. . ..... .. .. . ..... .. .. ... ...... ... ... .... .. .. .. .. ... .... .. .. . ... .. .. .. 10V Current Cutout ..... .......... .... . .. .. ........ ...... .. 15A primary, 1.15A secondary low, the Mosfet will not fully conduct and this can lead to excessive power dissipation and failure of the device. In addition, the converter circuit also features temperature and overload (or short circuit) protection. The temperature cutout is necessary due to the very high temperatures that can occur in a vehicle during the summer months. If the interior temperature reaches 65°C for example, the Mosfet devices do not need to heat up very much before they are likely to be damaged. The temperature cutout switches off the converter at a preset temperature to guard against this possibility. The overload protection circuitry operates at two levels. First, there is a 15A fuse in the supply line which will blow if there is a drastic fault in the converter itself. Second, the positive and negative output rails are fitted with Polyswitches (these are positive temperature coefficient thermistors) which go open circuit when the current through them exceeds about 1.15A. These protect the converter against output short circuits (eg, if a fault occurs in the amplifier) and automatically return to their low resistance state when the fault is cleared. Protection circuitry What's one of the most frustrating things that can go wrong with a car? The answer is a flat battery, particularly if it's been flattened by the hifi system. To guard against this possibility, the converter includes under-voltage protection. In effect, the converter monitors the battery voltage and if it drops below a certain level, the converter switches itself off. This not only protects you from the inconvenience of a flat battery but is also necessary to protect the Mosfets from possible destruction. To explain, a Mosfet is triggered into conduction by applying a voltage to its gate. If this voltage is too A metal diecast case is used to house the circuitry of the DC-DC Converter. This not only provides the necessary heatsinking but also makes the assembly very rugged for automotive use. DECEMBER1990 23 > Q The accompanying specifications panel shows the performance of the converter. Note that it achieves an efficiency of about 80% at 100W output. It also has excellent voltage regulation and low output ripple. > Q i Circuit details I· Q "' "' "' ~!,------- 0; a: w 1- ffi > z 0 u > C It) tl ~ C .... J--+ .,; + I At the heart of the circuit (see Fig.1) is a dedicated switchmode IC from Texas Instruments - the TL494. This device contains all the necessary circuitry to generate complementary square wave pulses at its pin 9 and pin 10 outputs to drive the switching circuitry. It also contains control circuitry to provide output voltage regulation and low voltage dropout. Fig.2 shows the internal workings of the TL494. It is a fixed frequency pulse width modulation (PWM) controller and contains a sawtooth osciliator, an error amplifier and a PWM comparator. It also includes an extra error amplifier, a "dead time control" comparator, a precision 5V reference and output control logic so that the device can be set for push-pull or single ended operation. The PWM comparator generates the variable width output pulses. It does this by comparing the sawtooth oscillator waveform with the outputs of the two error amplifiers. In practice, the error amplifier with the highest output voltage sets the pulse width. The dead time comparator inside the TL494 prevents the push-pull outputs from rising and falling at the same time. In other words, it ensures that there is a brief time delay between one output swinging high and the other output swinging low. This time is called the "dead time" and accounts for about 5% of the total output time. Error amplifiers tl II :::;11 ll In our circuit, one of the error amplifiers is used to provide the low Fig. 1: the circuit is based on the TL494 switchmode IC from Texas Instruments. Depending on the feedback signal applied to its E2 input, this device generates complementary variable width pulses to drive Mosfet switching transistors Q6-Q9. These then drive transformer Tl which steps up the voltage & drives bridge rectifier D1-D4 to produce the supply rails. 24 SILICON CHIP ~ STEERING INPUT Tl495 ONLY I I 7 L________ J Ar-----1 r-------7 I I I I I 1 OUTPUT CONTROL I I I 1 16 FEED BACK J 14 4 1J NONINV INPUT}ERROR INV INPUT AMP 2 REF OUT OUTPUT CON T RO L 12 11 Vee C2 DEAD -TI ME CONTROL L _ _ _ _ _ _ _ _,I 1 -L_ _ _J cr - - ERROR{ NQN INV IN PU T AMP 1 INV INPUT er , c, RT GND 6 E1 DEAD TIME ~~~7 CONTROL - C2 PULSE -STEER ING NONl ~~~~TING _ _ _~ 1 E2 Fig.2: block diagram & pinout details for the TL494 pulse width modulation control IC. The device generates a FLIP-FLOP INyi;~~NG ___--1 r--1 NONll~~~~TING 7: r-------7 ERROR ----t.,,.._ I INVERTING ~I_ _-----, INPUT L _ _l!:_42! rcUR NONINVERTING J A !NPUT -cl_:..;:.c.:...::::-=-j INVERTING INPUT variable width pulse train at the PWM I I I I .-R-EF-ER...E-NC_E.., I REGULATOR 1 - - - - - - - - - - - V RE I I I ~---.---' I I I l _ - l_'c~~~L!_ _J voltage dropout feature. This is done by connecting the 12V rail to pin 2 (inverting input) via a voltage divider consisting of two lOkQ resistors. The other input at pin 1 (non-inverting) is connected to the internal 5V reference (VREF) via a 4.7kQ resistor. When the voltage at pin 2 drops below 5V (ie, when the battery voltage goes below 10V), the output of this error amplifier switches high and reduces the pulse width to zero, thus effectively shutting the circuit down. Note the lMQ resistor between pin 1 and the error amplifier output at pin 3. This provides a small amount of hysteresis so that this particular error amplifier operates as a comparator. The second error amplifier, with inputs at pins 15 (inverting) and 16 (non-inverting), is used to control the output voltage of the converter. In operation, a sample of the output voltage is tapped off by trim pot VRl and fed to the non-inverting input of the error amplifier at pin 16. This voltage is also compared to the internal 5V reference which in this case is applied to the inverting input at pin 15. Thus, if the output voltage rises above its preset value, the output of the error amplifier also rises and this reduces the output pulse width from IC1. Conversely, if the output voltage falls, the error amplifier output also falls and the pulse width increases. The gain of this amplifier is set by the lMQ feedback resistor between pins 3 and 15 for frequencies below This oscilloscope photograph shows the PWM waveforms at the E1 & E2 (pins 9 & 10) outputs of the TL494. The duty cycle here is only slightly less than 50% but, if the error voltage goes up, the pulses become narrower. comparator output by comparing the signal from a sawtooth oscillator with two error amplifier outputs. The following logic circuitry is then used to derive the out-of-phase output signals which drive transistors Qt & Q2. about 33Hz. For higher frequencies, the gain is set to a lower value by the 47kQ feedback resistor in series with the O. lµF capacitor. This is done to prevent the error amplifier from responding to high frequency hash on the supply lines. The 27kQ resistor and .OOlµF capacitor on pins 6 & 5 set the internal oscillator to a frequency of about 44kHz. Because the TL494 is operated in push-pull inode, this means the switching frequency for the output transistors is about 22kHz. Dead time control The dead time control input is at pin 4. When this input is at the VREF voltage, the output transistors are off and as the voltage drops to ground, The top trace in this photograph shows the El (pin 9) output of the TL494 at low duty cycle while the bottom trace shows the corresponding sawtooth oscillator waveform at pin 5. DECEMBER 1990 25 TO BATTERY + TERMINAL TO Sl TO BATTERY - TERMINAL OR CHASSIS \ CORO GRIP GROMMET SOLDER LUG t , - OUTSIDE CASE ~ .....- SOLDER LUG sistors when a preset temperature is exceeded. IC4, an LM334 adjustable current source, functions as the temperature sensor. It produces an output current which is directly proportional to temperature and this current flows through the series 10kQ resistor. The resultant voltage across the resistor (approximately 14.5mV per °K) is then applied to the inverting input (pin 2) of IC3 where it is compared with the reference voltage. When the voltage across the 10kQ resistor reaches +5V (ie, at 85°C), pin 6 of IC3 switches low and turns on Q5 via D7 and the serie~)-kQ resistor. Q5 now effectively conne cts the dead time input (pin 4) to VREF (pin 14) and this shuts down the output transistors inside ICl. VR2 allows the cutout temperature to be set to the required value. D7 is necessary because the output of IC3 can swing much higher than VREF, to almost the +12V rail. Without the diode, Q5's base would be pulled higher than its emitter and this could damage the transistor. Complementary outputs HINKS REQUIRED IF TH1, TH2 NOT USED Fig.3: take care to ensure that all polarised parts are correctly oriented when installing them on the PC board. The two thermistors are optional and can be replaced by wire links if not required. Note that transistors Q6-Q9 must be correctly isolated from the case (see Fig.4). the dead time decreases to a minimum. The dead time input is used to control the duty cycle of the output driver tran,,istors in two ways. First, at initial switch on, the l0µF capacitor across transistor Q5 pulls the dead time input (pin 4) to VREF and thus prevents the output transistors inside ICl from switching on. 26 SILICON CHIP The lOµF capacitor then charges to VREF and as it does so, the duty cycle of the output transistors increases until full control is gained by the error amplifiers. Temperature cutout The second use for the dead time input is to shut down the output tran- Pins 9 and 10 (El & E2) are the complementary transistor outputs for !Cl. These transistors are uncommitted within the IC which means that both the collector and emitter of each transistor are connected to external pins of the IC, so the circuit designer can arrange tham as needed. The collectors at pins 8 and 11 are connected to the +12V supply rail while the emitters are tied to ground via l0kQ resistors. IC2a, IC2b & IC2c (4050) buffer the emitter 2 output at pin 10, while IC2d, IC2e & IC2f buffer the emitter 1 output at pin 9. These non-inverting buffer stages then drive transistors Ql & Q2 on one phase of the output waveform and Q3 & Q4 on the other. Thus, when pin 10 of !Cl goes high, Ql turns on and turns Mosfets Q6 & Q7 on. When pin 10 goes low again, Ql switches off and Q2 turns on and pulls the gates of Q6 & Q7 low again. Q6 & Q7 now turn off again while Q3 switches on Q8 & Q9 to drive the other half of the transformer primary. Ql, Q2, Q3 & Q4 have been included to ensure that the Mosfet transistors are switched on and off as quickly as possible. The idea here is to minimise the time that the Mosfets spend in the linear region where they of turns on the transformer secondary. If the values shown on the circuit are used, the converter will produce supply rails of ±50V. Fast recovery diodes The four Mosfet transistors are bolted to the side of the case using TO-220 insulating kits and their leads soldered to PC stakes on the board. Make sure that the mounting surfaces are free of metal swarf before installing the devices. dissipate high power. In addition, the gates of the Mosfets are driven via ion resistors to ensure that parallel devices switch on simultaneously. D5, D6, ZD2 & ZD3 protect the Mosfets by suppressing any switching spikes genMICA INSULATING BUSH WAS!HER w,}j ~ SCREW r ~ -----CASE ' T0220 DEVICE Fig.4: mounting details for the four Mosfet transistors (Q6-Q9). Smear all mating surfaces with heatsink compound before bolting each assembly together. After each device is mounted, use a multimeter to check that the metal tab of the device & the case are correctly isolated. erated by the transformer. In summary then, the power Mosfets in each phase of the circuit alternately switch the Sl and F2 terminals of the transformer primary to ground, so that the transformer is driven in push-pull mode. For example, when Q6 & Q7 are on, the 12V supply is connected between Fl and Sl. By transformer action, 12V appears across the other half the transformer primary which means that there is a total of 24V across the whole transformer primary (ie, F2 at 24V, Sl at ground). Conversely, when QB & Q9 are on, F2 is connected to ground while Sl goes to 24V. This alternating voltage is stepped up by the transformer secondary and applied to bridge rectifier Dl-D4 which produces positive and negative supply rails with respect to the secondary centre tap. Note that the actual DC voltages produced will depend on the number As mentioned before, Dl-D4 are fast recovery diodes and are necessary to minimise switching losses. Because they operate at high speed, each has been paralleled with a 470pF capacitor to suppress switching hash. At the outputs of the bridge rectifier, the supply rails are filtered using inductors 12, 13 and four lO00µF electrolytic capacitors. From there, the supply rails go to the (optional) Polyswitches THl and TH2 which provide output short circuit protection. The lOkQ resistors across the output rails set the minimum load current, while the parallel .0lµF capacitors provide further filtering of RF components. Voltage regulation To provide the voltage regulation feature, the positive . supply rail is sampled at the junction of 12 and THl and fed to a voltage divider consisting of a 47kQ resistor and VRl. The divided output voltage is then taken from the wiper of VRl and fed to the E2 (pin 16) input of one of the error amplifiers inside ICl. Thus, dependi:µg on this error voltage, ICl adjusts the duty cycle of its PWM output as described previously. Power for the converter is derived CAPACITOR CODES 0 0 0 Value IEC Code EIA Code 0.1µF 470pF 100n 470p 104 471 RESISTOR CODES 0 0 0 0 0 0 0 0 0 No. Value 4-Band Code {5%) 5-Band Code {1%) 2 1MQ 47kQ 27kQ 10kQ 4.7kQ 1kQ 47g 10n brown black green gold yellow violet orange gold red violet orange gold brown black orange gold yellow violet red gold brown black red gold yellow violet black gold brown black black gold brown black black yellow brown yellow violet black red brown red violet black red brown brown black black red brown yellow violet black brown brown brown black black brown brown yellow violet black gold brown brown black black gold brown 3 1 8 2 1 3 4 DECEMBER 1990 27 This close-up view shows how the face of the LM334Z temperature sensor sits against the end of the threaded metal specer. Smear the mating surfaces with heatsink compound before installing the PC board to ensure efficient heat transfer from the case to the sensor. from the car's battery via a 15A fuse and fed to the transformer primary via inductor Ll. This inductor, together with the 0. lµF capacitor at the input, prevents the converter from radiating RF hash from the supply lead. Switch Sl supplies power to the low-current part of the circuit. This supply path is decoupled using 16V zener diode ZDl, a 47Q resistor and a S1 S2 F1 F2 PRIMARY S3 S4 F3 F4 SECONDARY T1 WINDINGS Fig.5: when winding the transformer, be sure to terminate the windings exactly as shown here. Step-by-step winding details for the transformer are given in the text. 47µF capacitor to prevent voltage spikes from elsewhere in the car's electrical system from destroying the !Cs or transistors. Construction Virtually all the parts for the ±50V DC Converter are mounted on a PC board coded SC05111901 and measuring 177 x 100mm. Fig.3 shows the assembly details. Before actually mounting any of the components though, take a few minutes to thoroughly examine the copper side of the PC board. It's far easier to locate and repair any defects before any of the parts are installed. This done, check that the board will fit inside the recommended diecast case and file the edges if necessary. Now you can begin the board assembly. The first step is to install PC pins at all external wiring points and at the Mosfet (Q6-Q9) pin locations. Once these are in position, install the 21 wire links on the board. You don't have to follow any particular sequence when installing the Winding Details For Transformer T1 Output Voltage No. of Secondary Turns Wire Gauge ±50V ±45V ±40V ±35V 47.5 turns 42.5 turns 38.5 turns 33.5 turns 0.5mm 0.6mm 0.6mm 0.6mm bifilar bifilar bifilar bifilar I 28 SILICON CHIP ECW ECW ECW ECW remaining parts, although it's best to install the smaller components first. Check the orientation of the !Cs, diodes and transistors carefully when installing them on the board, since polarity is important here. Similarly, take care to ensure correct polarity of the electrolytic capacitors. Note particularly that Dl & D3 are oriented differently to DZ & D4, so don't be caught here (see Fig.1 for the pinout details). The two thermistors can be regarded as optional and should be replaced with wire links if not used. We strongly recommend them but some readers may prefer to leave them out. It's a good idea to check all resistor values with a digital multimeter before installing them on the board. You can also refer to the accompanying tables for the resistor and capacitor codes, if you're not familiar with these. Don't mount the four Mosfet transistors at this stage - that step comes later. The LM334 temperature sensor should be installed at full lead length. Winding the transformer This is a job that most people hate but it's really quite straightforward provided you follow the step-by-step procedure set out below. First, you will have to decide what voltage you need at the output of your converter, then check the accompanying table for the winding details. This gives winding information fof voltages ranging from ±35V up to ±50V in 5V steps (note: only the secondary winding changes). The transformer is supplied as a bobbin with two E cores, one for the top and another for the bottom. These cores are held together with a Ushaped clamp which is installed after the transformer is wound. Take a look now at Fig.5; this shows how the primary and secondary windings are terminated on the transformer bobbin. Note that the 4-pin side of the bobbin terminates the primary leads while the 5-pin side is for the secondary. To wind the primary, you will need 1-metre of 1.25mm enamelled copper wire (ECW). First, strip off the insulation from one end and solder it to the S1 pin. Now, starting from the bottom, wind on 8.5 turns, with the windings laid side by side as you progress up the bobbin. Once you have wound on the 8.5 turns, run the lead directly down the side of the bobbin (ie, at right angles to the winding), trim to size and terminate the end on the Fl pin. Wrap a layer on insulating tape tightly around the winding to secure the turns firmly in place. The other half of the primary winding starts at S2 and is wound directly over the top of the first winding and in the same direction as the first. Wind on 8.5 turns as before and terminate at the F2 pin. Another layer of insulating tape should then be used to secure this winding. That completes the primary; now for the secondary. First, check the table for the number of turns required and the gauge of wire to be used. You will need a 7-metre length of 0.5mm or 0.6mm enamelled copper wire. Fold the 7-metre length of wire in half and clamp the folded end in the chuck of a hand drill. The other end of the wire should now be clamped in a vyce, the wires pulled taut, and the drill handle turned to twist the wires together. Continue turning the drill handle until there is about one twist every 10mm. Next, cut the wire at the fold, strip the ends of enamel and tin them with solder. Connect these to the S3 and S4 terminals (ie, the two starts). Wind the appropriate number of turns evenly onto the bobbin in the same direction as the primary winding (note: there should be several layers which fill the entire length of the bobbin), then use your multimeter to determine which winding end is F3 and which is F4 (ie, check for on between S3 & F3 and on between S4 & F4). The secondary winding can now be completed by connecting these two leads to F3 & F4 and winding on another layer of insulation tape. This done, fit the top and bottom cores to the bobbin and clamp the transformer assembly to the PC board as shown in Fig.3. Tighten the clamp nuts firmly but don't overtighten them, otherwise you'll crack the ferrite cores. Finally, solder the various transformer pins to the PC pattern. Inductors The three inductors, Ll-L3, are all wound on Neosid iron powder toroids. Inductor Ll is wound using 38 turns of 1.25mm enamelled cop- PARTS LIST 1 PC board, code SC05111901, 177 x 100mm 1 Dynamark label, 170mm x 100mm 1 diecast case, 190 x 120 x 63mm 1 Neosid 17-745-10 iron powder toroid (L 1) 2 Neosid 17-742-1 0 iron powder toroids (L2,L3) 1 Siemens EC-41 N27 ferrite transformer core, bobbin and clamp 4 T0-220 mica washers and insulating mounting bushes 1 panel mount 3AG fuse holder 1 15A 3AG fuse 2 cord grip grommets 1 2.5-metre length 1.25mm enamelled copper wire 1 1-metre length 1.25mm enamelled copper wire 1 2.5-metre length 0.8mm enamelled copper wire 1 ?-metre length 0.6mm enamelled copper wire (see table) 1 ?-metre length 0.5mm enamelled copper wire (see table) 1 500mm length 0.5mm tinned copper wire 2 solder lugs 19 PC stakes 4 6mm standoffs 1 tapped 6mm standoff 2 RN3415 Polyswitches (optional) 1 10kQ miniature horizontal trimpot 1 500Q miniature vertical trimpot Semiconductors 1 TL494 switchmode controller (IC1) per wire on the larger 17-745-10 core. Begin with a 2.5-metre length of wire and feed half of this length through the centre of the core and wind on about half the number of turns. The remaining turns can then be wound on using the other end of the wire. L2 and L3 are wound in identical fashion using 28 turns of 0.8mm wire. You will need about 1.2 metres of wire for each of these inductors. Once the inductors have all been wound, they can be mounted on the PC board at the locations shown. Note that each inductor is strapped firmly to the PC board using a tinned copper wire loop that passes through the 1 4050 hex buffer (IC2) 1 LF351, TL071 op amp (IC3) 1 LM334Z adjustable current source (IC4) 2 BC338 NPN transistors (01 ,Q3) 3 BC328 PNP transistors (Q2,Q4,Q5) 4 MTP3055, BUZ71 Mosfets (Q6-Q9) 4 MUR1550, BYW29 fast recovery diodes (D1 -D4) 2 1N4002 1A diodes (D5,D6) 1 1N4148 signal diode (D7) 1 16V 1W zener diode (2D1) 2 30V 1W zener diodes (2D2,2D3) Capacitors 1 2200µF 25VW PC electrolytic 4 1000µF 63VW PC electrolytic 1 47µF 16VW PC electrolytic 1 10µF 16VW PC electrolytic 1 0.1µF disc ceramic (near S1) 2 0.1 µF monolithic ceramic 3 0.1 µF metallised polyester 2 .01µF ceramic 1 .001 µF metallised polyester 4 470pF ceramic Resistors (0.25W, 5%) 21Mn 24.?kn 3 47kn 1 1kQ 1 27kn 3 47Q 2 10kn 0.5W 410n 610kn Miscellaneous Screws, nuts, heatsink compound, heavy-duty automotive wire for 12V input, 3-way heavy-duty wire for output voltage leads centre of the core. The ends of these loops are soldered to adjacent pads on the PC board (not shown in Fig.3). Make sure that you don't confuse these holes with the holes for the inductor leads. By the way, if you intend using the unit in your car, it would be a good idea to further secure the inductors using a generous amount of silicone sealant. Run it around each inductor to "glue it" to the PC board. This will prevent the inductors from vibrating and eventually breaking their leads. 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These holes should be located 25mm down from the top edge of the case and directly in line with the PC stakes for each device. After drilling, carefully deburr each hole using an oversize drill. If you leave any metal swarf here, it can punch through a mica insulating washer (see Fig.4) and short the case of the device to chassis. You will also have to mark out and drill holes in the case for the fuse holder, the cord entry grommets and the solder lug mounting screw (see Fig.3). A further mounting hole is also necessary to secure the tapped spacer. This is located directly opposite the LM334Z temperature sensor and is positioned so that it sits flush against the face of the sensor (see photo). The four Mosfet transistors (Q6-Q9) must be insulated from the case using mica washers and insulating bushes. Fig.4 shows the mounting details. 32 SILICON CHIP Smear heatsink compound on each of the mating surfaces before screwing each assembly together and note how the leads of the devices are bent to mate with the PC stakes on the board. As each device is mounted, use your multimeter to confirm that its tab is indeed correctly isolated from the case. If you do get a short circuit, be sure to clear the problem before proceeding further. Heatsink compound should also be smeared over the mating surfaces of the tapped spacer and the LM334Z temperature sensor to ensure good thermal transfer. This done, the external wiring can be hooked up and the board permanently installed in the case. Use heavy-duty automotive cable (or 240V AC cable) for all external leads. Testing To test the converter, you will need a 12V DC supply with a current rating of at least 0.5A and a multimeter. Set the multimeter to the 100V DC range and connect it between the positive and negative output rails. Trimpots VRl and VRZ should initially be set to their midpoint positions. Connect up the power supply, switch on and check that you obtain a voltage above ±35V (ie, above 70V). If not, switch off immediate! y and check your work for wiring errors. Assuming an output voltage is obtained, adjust VRl to give the desired value. If you have a variable power supply, check that the output remains rock steady for supply variations over the range 10-13.BV. Below lOV, the converter should be switched off uy the low voltage dropout circuit. To set the temperature cutout, connect a multimeter across the lOkQ resistor at pin 2 of IC3 and adjust VR2 for 4.2V at room temperature; ie, at 25°C. Add or subtract 14.5mV/°C for temperatures above or below this figure. This sets the sensor to give the required 5V across the l0kQ resistor at 80°C - the point of temperature cutout. Installation Finally, make sure that you install the unit in a professional manner. 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Times 100; 2KHz to 150 KHz. 23 Position Pre~selected Range Switch • Sino/Squ are Wave Output Pocket Size Autoranging Multimeter • 3.5 Digit LCD • Automatic Ranging • DC Voltage; 1OOUV to 750V • AC Voltage ; 1 mV to 500V • Resistance; 2000 to 20MO • Continuity Tester • Comes in Folding Wallet Laboratory Quality Electronic FET Volt/Ohm Meter with Center Zero • Output Attenuator : 2 Position 0dB and - 20dB with Fine Adjust Control • Output Impedance : 6000 • • • • • Slnewave : 1.2V RMS Max (No Load) Squarowavo: 8V PTP Max (On Load) Sync Pulse: 1.2V RMS (No Load). Impedance: 1KO Compact Size : 820 x2 10 x 21mm • Battery Indicator $65.00 01060 Fantastic for the glovebox, too/kit and, of course, your top pocket. Excellent for mobile field worlc. A great gift idea for your budding genius student Great New Inductance Capacitance Digital Multimeter NEW FOR CHRISTMAS Terrific New 18 Range Digital Multimeter From World Famous Labtech Instruments • • ' • • • 3.5 Digit LCD • Compact Design 128 x 75 x 24mm • DC Voltage 5 Ranges: 1OOuV to 1000V" Input Impedanc e: 1MO • DC Current 6 Ranges; 0.1 uA to 1OA • O verload Protection • Resistance Measurement 5 Rang es ; 0.10 to 2000k0 • Cent re Zero Scale • O verload Protectio n Q 1050 Multimeter a 1054 Multimeter $39.95 Another Altronics Price Breakthrough Great For The Christmas Stocking! voltage and roslslanco meas1.111Hr1ents, and safe to use. Th• large LCD digits mak• laklng mea5Ur• menls quick and e/llclent. e 3.5 Digi t LCD e Bar Graph Displ ay • Conti nu ity Check With Buzzer • Tilt Stand on Desktop • Data Hol d Function • Minus Memory to Nullify • DC VolVAC Volt, 1OOuV- $99• 00 ~ This trully fantastic bonch Digital Multim eter+ LC R, w tth capacitance and. Inductance ranges , enables you to test a ., ,::, .· wide variety of compone nts. lndlspenslble for the design engineer, technic ia n and enthusiast allke. e 3.5 Oigil LCD e Tillslond on Desktop • • • • • e • • • • DC Voltage 5 Ranges 10OuV to 1OO0V DC Curren t 6 Rangea 100nA to 20A AC Voltage 5 Ranges 10OuV to 750V AC Curren! 6 Ranges 100nA to 20A A esislance 7 Rang es 100mO to 200Mn Inpu t Im pedance 10MO C apacitance 5 Rang es 1pF to 20u F Inductance 5 Ranges , uH to 20 H Diode Test • Continui ty Test Wi th Buz.zer Tran sista- Test (hFE ) Q 1062 Multimeter $149.00 Includes Deluxe Carrying Case 1000V e t OMO Input Impedance • Low 1 : :~e~(e R~~~a+:i:e Per Second e DC/AC Curr en t 100uA- 10A • Resistance: 0 .10 to 20 Mn • Transistor Gain hFE Comes With Free Carrying Case Worth $12.50 A Great New Instrument Which Combines Digital Ease With Analogue ~ Sensitivity. 1f\lJ!o1~G Great New Digital Multimeter With Bar Graph Display This popular 3.5 digit This Month Each Meter At Last! A True Rms Analog Digital Multimeter At A Very Competitive Pries Q 1057 Carry Case $12.50 Mu/1/molH Is slmpllclty Itself. Full autoranglng on 4.5" MirroN>d Scale. Knife Edged Poi nter A CIDC Voltage; 7 Ranges 0.3 to 1200V Input Impeda nce; AC 1MO, DC 10MO A C/ DC Curre nt ; 6 Ranges 0.01uA to 12A Peak-to-Peak Scale e Diode Chocker e True RMS AC e dB Meter •45d8 to + 5 Im pedance • 3.5 Digital Display • 4.s• Anal AC Volt t0OuV-tOOOV e DC Amp/AC Am p • Resistance 0.10 •20Mn • Diode Ch eck • Buzzer • Au tomati c Polarity Rever sal • L NewProdu ~HIGH TECH Company Collapse Brings Fantastic Bargains for the Electronic Enthusiast *''V.1a te I'' (now D1scovery") · SENSATION! 11 l• '·' } . ;_ . ~- ... ,. ·· :·' ' . UNBELIEVABLE VALUEI Around $250.00 value for as low as $24.00! Altronics has recently purchased this quality stock from the liquidator of DTX AUSTRALIA LTD. You can use this equipment to gain limited access to the ·· viatel" information system_ Each unit contains a Telecom approved modem and information decoding circuits. The single PCB is a goldmine of quality components for the enthusiast, Including the fantastically valuable SAA 5020 AND SAA 5050 chips. ALL STOCK BRAND NEW PREMIUM QUALITY INDIVIDUALLY TESTED BY THE MANUFACTURER (in our rush to get this amazing SCOOP PURCHASE to you we have not had time to check each unit so we cannot offer any warranty) "VIATEL" - Now known as "DISCOVERY" What is "DISCOVERY"? Worth well over $1 50.00 for the salvage value of the 11 bits" alone! Look at this list of component parts ! • Mains Transformer. 240-9/15/24V 300mA • Line Isolation Transformer . Telecom approved 600/600 Ohm or 600/1 SO Ohm impedance. • Video/RF Modulator (Channel 0) e Low profile 12V SA SPOT Relay e Capacitor· 2,0uF 440V AC • Crystals • 6MHz and 4.43MHz e TTL, CMOS, Linear and LSI ICs · SAA 5020, SAA 5050, 2516 and many more • Voltage regulators • Bridge rectifiers • Trimpots and capacitors • Filter capacitors • Flatpack heatsink I Plus much, much more! Telecom "DISCOVERY" is a sophisticated information service whereby subscribers may access essential business and leisure information and transaction services, With the "VIA TEL" Videotex Modem Decoder and your own TV receiver or computer monitor, you can look up any telephone number in Australia Via the electronic w hite and yellow pages; .connect up to news services; check airline sched ules; pay bills or go shopping, You can even go to the bank without leaving th e comfort of your own horre, At the push of a button, you can check the weather or plaoe a bet VIATEL VIDEOTEX MODEM DECODER Four models to choose from; Each with a numeric keypad. X 1000 WITH RF OUTPUT X 1002 WITH RF OUTPUT AND TELEPHONE HANDSET X 1004 X 1006 WITH RF AND RGB VIDEO OUTPUT 1 to 5 each 6 or more each $29.95 $34.95 $34.95 $23.95 $27.95 $27.95 $39.95 $31.95 WITH RF AND RGB VIDEO OUTPUT AND TELEPHONE HANDSET SENSATIONAL LA■TECH SOLDERING STATION MICRON T 2440 Full 12 Months Warranty 20MHZ DUAL TRACE OSCILLOSOPE e.c1n1n1c r....,.._ eon--.1o1-1111 r - i u .. Slallon No,r .,._ le - , quaHty and-tHltyt ::i:.::.~'°:fc':m~ con- soldsing o11..... "'""·'" in -po,alure, hand ooldoring. Simply rolalo delaMd rotary Milch tNly ID Nlectable lixed - " " · " " " of: 320'C (eo&'f), 350'C (662'f), 380'C (716'f). 410'C tnO'f). 440'C (824'fl without ch""9inll hMllr or tip. Pacud wtlll • - : Tempo,aue readout a oonRI :Z•o vdta99 ' ...,;tct,;ng; GrOl.lld tip; .__ . . . . Chrome ptalod, iron clad tip $100 Q 0155 LAITECH DUAL TRACE FREE BONUS OFFER OSCILLOSCOPE COMPUTE WITH TWO Uh 1 PROBE KITS ONLY $799.00 NORMALLY $899.00 ·.......,tT ;2440 Normally S 159.95 Dual tracking :t 50V power supplyts111oonai1pApruoi Features: Coffl)Onent Tester. Wide bandwidth and high sensitivity. Very low power oonsu~tion. High sensitivity X-Y mode. Z axis (intensity modulation). Front panel electrical trace rotator. Regulated power supply circuit for accuracy. Description: This model is a dual trace 20MHz Oscilloscope using a high brightness CRT. The vertical ~lijiers have high sensitivity of 5mV/div and a frequency characteristic response with smooth roll off exceeding 20MHz. The highest triggering sweep speed is 0.2uSecldiv. For coffl)Onent tests, a special circuit is designed, with which a single COffl)Onent or COffl)Onents in or out of actual circuit board can be easily tested, requiring no power to drive the circuit. The display shows fault of COffl)Onent value, characteristics of COffl)Onent, and haK-dead COffl)Onents under Audio Oscillator & Function Generator Fantastic Hi Tech - Hi Soec Thi• ultra low dlatortlon oaclllator fa comparable with the If.at laboratory lllandard alne wave oaclllatora.. Aa well a• having very low dlatortlon It haa excellent envelope atabilitj, aquare wave output and output metering. K3380 Spadftcadono Type: Dual Ucking wilh owitch mode pre-regul•- far high efficiency OUtput V--: 0 ID ±SOY OUtputCU...nt 1.7A ~om Oto p;N: 1.5A 8191V: IA at IOOVTrocklng Accuracy:Wilhin±1% ~:!:r!':i.=t~ps:-.::::..±tso~:~:!:.':=•~:~:-!tor ±5mV flan far mojno i:..11y protoctad agalnet output ohort clrculla and forward and - - vollagH oonMClod to Iha outpu~ lu• prot0<:tlon for Iha lnnoformar. AVIATION HEADPll>NES Normally $155 This month only $105.00 Why pay $400 or more for a David Clark set? WITH OIL FILLED EAR CUSHIONS • High performance, noise attenuating earphones. • Noise cancelling microphone • Cushlonecf head pad • Super sturdy• Great performance • Superb, professional pilot's headset will last a lifetime with reasonable treatment. • Includes standard aircraft jacks. x. adjustable • Attenuator Ocl:, •1 Odb, • unbalane&d ngle PCB. Kit comes complete wilh e1. K2540 assive Infra-Kell Lite Guard Floodlight Control C9070 ONLY $189.00 Now available from Altronlcs Dealers How often haw you thought there could be I prowter outside your door? ln•tall a Life Guard and (once onned) any "gueor wtll be floodlit when detoclod by thlo highly eenoldva Infra-Rad Deloctor. Spaclftcadono: • Raintight. outdoor, all-wealher operation• Operation Time: adjustable 5 aecondo to 18 minute&• Sensitivity: aqustable 20' to 50', 30 beams I Aimable to desired drection with 2 bal joints• Switching capabilily: 300W max. incandeoc:onl • Operation modH: OFF. AUTO, TEST, ON. le<:overage 18x 12metres. s53so · WAS $135.00 High Energy Siren with Swivel Bracket Absolutely ear splitting SPL CHRISTMAS SPECIAL ONLY $99.00 SAVE $36.00 Feature■: Lens simply 'snaps' to either wide angle (range 410ft) for normal use or nonnal angle (range 80ft plus) for corridor applieation5. • Snazzy integral mounting brackets allow comer 90 deg. mounting as well aa normal surface mount• •Pulee counr circuit to eliminate false triggering • tamper• contact• 12VOC powered e Built-in test lamp e alarm out put SPOT 30V 1A. s 5301 This month $79.00 BUY 3 FOR & 180.00 AND SAVE $50.00 Uniden 27 MHz 40 Channel Hand-Held Transceiver '° The Uniden V MHz HandHeld io a completely Nilcontained channel CB tranceiver built into a miaophone. AH of tie moat desirable featurN are right on the miaophone induding LED dilplay, instant Channel 9, channel up/down keys and volume and equelch control. '° And ito onap-on battery p,id< 120db. Handy bracket for wall mounting etc. 12V 300mA. $29.95 gives you full CB power · 'Nhenever and wherever you nMd it A wlNCOpic magnetic mount ant.ma, 1&• coax.al cable and carr)'ng caH complete lho p,id<age. lncludeo lwo-yeer warranty. C 9615 ! 1! h? L? .:~ 2 One Klllogram. Ideal For Buahwalklng, C.nolat and Trallblaara.. (See SC Feb'88) LARM SYSTEM This refined car burglar alarm has about every feature you could possibly want to keep would be thieves away. FEATURES: e Internal & External Sirens • Dash lamp flasher• Battery back up • Delayed & Non delayed inputs • Ignition killer • Easy to build and install. K4370 • Easy to operate Simplicity itself - just select the switch to Home, Off or Away as desired. A 45 second exiVentry delay allows you to vacate and/or re-enter your premises and disarm the system. • No key switches or code buttons to push. Thus the system is ideal for families - even the kids can operate this system. • Facil~y for external siren • Battery back-up (batt9ry S'C'cells not included) System Contents • Master Control Unit• Front Door Bell Sw~ch • Panic/Emergency Switch • Three Window/Door Reed Sw~ches • Mounting Hardware• 20 Metres Wire • Instruction Manual · FANTASTIC VALUE Complete System S 5465 Normally $129.00 THIS MONTH ONLY $99.00 NORMALLY $129.00 THIS MONTH ONLY $119.00 Earns its cost hunderds of times over In cleaning connectort1, PCB's, switches, jewellery, glsBBes, watches, drafting pens, etc. Awarded the Good Product Design Awsrd for CETDC in 1987 With Wireless Remote Control HIGH POWER CAR ALARM lOA/F USE Pas. +Plugs into fuse box ~ In Just 3 minutes you wtll be amazed at the difference! r - - - - - ~ Headlights BLUE TOP VALUE Door switch circuit Doors, trunk, , hood etc. ((rm<at> Remote control NORMALLY $199.00, ONLY $174.OOTHIS MONTH Ao100 'kev' This alarm system will be triggered by unauthorised entrance through the car doors, boot, bonnet or removal of the car sound unit. The siren will sound and the headlights flash for 60 seconds. Simple wiring, wire it yourself without professional assistance. FOUR DIGIT COMBO LOCK Automatic Reset High Perform ance s 5220 ONLY $99 .00 ULTRASONIC CLEANER W cm 't scratch or damage - uses ordinary tap water and creates millions of super-penetrating bubbles. Hospital tests show that Ultrasonic cleaning produces better results safer than ccmventional methods. _B_L_A_a _ _ _ _ _ _ ~ Earth YELLOW Pin Point WIii even clean your teeth! RADIO RED MULTI FUNCTION CAR ALARM WITH * WIRELESS REMOTE r FANTASTIC! SOLENOID OPERATED DOORLOCK DESIGNED BY 8-12V DC AL TRON/CS OPERATION Yesl Thars right, this four digit combination lock was de5igned from the ground up by the ALTRONICS R&D DEPARTMENT to exactly satisfy your 6ecurity requirement6. lds11f for use In alarm systems, solenoid operated doors and all systems requiring security •ccsss. Feature ■: • Single PCB con6truction • Fit6 into standard GPO wall box• Over 14 000 possible combinations• 5 second combination entry time • Code easily changed via OlP swilches • Latched or momenlary output• Optional battery back-up K 1925 $39.95 lncrea6es home security and garden privacy. Control your front door from lounge, kitdien or bedroom or anyv..t,ere you like. Comes complete with two face plates for either concealed or visible fitting . S4390 Build your own security Wireless remote activate/de-activate alarm system system (where fitted) . Horn sounds to confirm armed. Light flashes to indicate dis•med. Compreh1n1lve eyetem protect• from: • Bum ping of car body • Towing • Window breaking • Forced entry of door boot or bonnet. and central door locking VERY COMPREHENSIVE s 5225 $129.00 Direct Import Price! AMAZING SAVINGS ON 48A SPACERS AND SCREWS!!! ftem R/HD SCREW R/HDSCREW R/HD SCREW R/HD SCREW SPACER TAPPED SPACER TAPPED SPACER TAPPED SPACER TAPPED SPACER TAPPED Size 6mm 6mm 10mm 10mm 10mm Oty per pack 25 100 25 100 8 100 8 100 100 <at>m> Clear ou t Price $1.20 $2.30 $1.30 $2.30 $1.20 $6.00 $1.20 $6.50 $10.00 $39.95 21 st Century entertainment - fascinate your friends this Christmas! PLASMA LAMP DISPLAY <at>rmD ~ CZ) Normally SAVE $10.00 t 10 or mo re $1.00 $2.00 $1.20 $2.00 $1.00 $5.00 $1.00 $5.50 $9.00 Amazing I Pulsating high voltage plasma discharge continually changes shape and direction. Mode Gelectable to either fingertip control or sound activated. For example, from voice or sound system. Provides endless fascination as it sizzle6 and arcs. Supplied complete with AC mains adaptor. Imagine getting one for Christmas/ A 0120 Normally $199 SAVE $50.00 Up till now similar lamps have sold for $1000 and more!! THISMONTHO WANTMOREPOWERFROMYOUR AMPLIFIER? - LOOK AT THIS!! BRIDGE ADAPTOR FOR STEREO AMPLIFIERS (SeeEAJune"85) Many combinations to choose from 300 Watt Inverter with Auto Start Operates from 12V Car Battery Auto start draws power from your battery only when appliance is plugged in and •tumed on• , that is battery can be left permanently connected if required. • Voltage reg_ u lated • Current regulated• Current Overload unit self limits. Complete kit K 6750 $279.00 Fully built and tested K 6755 $379.00 100's of uses at home and away. POWERHOUSE 600W INVERTER (See EA Dec "87) NEW THIS MONTHI This nverter has the capacity to produce 600 watts od mains power which will run a fantastic array of appliances. Ideally suited to running power tools, lighting (including fturos) electric motors and much more. It can be used as a portable or permanent fixture. • Manual or Auto Start facilities • Low battery cut-out. This simple circuit makes it possible for any stereo amplifier lo deliver four times the single channel power into the same aingle load. Frequency response is 10Hz.1o 300kHz. and harmonic dist«tion is leu than 0.001% at8V RMS. K5565 Kit Version K 6770 $425.00 Fully built and t ested 12V Input K 6774 24V Input K 6775 $525.00 GREAT SAVINGS ff f DISCOLITE (See SIiicon Chip July/Aug "88) BANKCARD Add some life to your next party Great for parties, shop displays and special lighting effects The DISCOLITE flashes party lights on and off in beat with the music from your sound system. • 4 light channels contrUed by 4 seoarate audioe channels • Forward, reverse & auto-reversing chaser patterns• Simultaneous strobe on all 4 channels • Alternating light patterns • Music modulation available on chaser strobe and alternate patterns • inbuilt microphone for beat triggering or audio modulation of lights • Direct inputs • Sensitivity control • Presettable sensitivity levels for each channel • Front panel LEDs mimic light display • Altronics kit prepunched and screened. e VISA e VALUE Beat Triggered Strobe (SeeAEMJuly11115) • • • K 5805 e $15.95 $159.50 MASTERCARD e Designed by Au•tralian Electronica Monthly. Flalhea in time to your music plu• it will work as a normal strobe. E,cclu•ively customi•ed by Altronic• inlo our H 0480 instrument caH, making conatruction a breeze and improving stability and overall appearance. Include• silk screened panel. K 5790 Was $79.95 Now $70.00 SAVE $10.00 For Increased power two tube option K 5795 $16.50 PHONE TOLL FREE 008 999 007 e NEXT DAY JETSERVICE DELIVERY Country clients please allow an additional 48-72 hours MORE AL TRONICS DEALERS WANTED If you have a Retail Shop, you could increase your income significantly by becoming an Altronics Dealer, Phone Chris Campbell (09) 328 2199 for Details. 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Stirling Street Excl'lange Perth W.A.6000 AL TRONICS RESELLERS Chances are there is en Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. PIHH Note: Resellers have to pay the cost of freight and insuranc_e and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - 1n many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. Don"t forget our E1prn1 Mall and Phone Order Service -for lhe coat of a local call, Bankcard, Vlaa or M•tercard holder, can phone order for aame day deapatch. Blue Ribbon Daalera are highlighted with a ■. These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. WA STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg $8 over 1Kg AUSTRALIA WIDE - We proce..- your order the day received and despatch via. Australia Post. Allow approx 9 days from day you post order to when you receive goods OVERNIGHT JETSERVICE Up to 3 Kg is $8.00- 3Kg to 5Kg is $20.00- We process your order the day received and despatch via. Overnight Jellervlce Courier for delivery next day Country areas please allow additional 24-48 hours. HEAVY HEAVY SERVICE -All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. $12.00 to 10Kgs, $15.00 over 10Kgs. INSURANCE - As with virtually every other Australian supplier, we send 11oods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1). When phone ordering please request "Insurance". TOLL FREE PHONE ORDER - Bankcard.Visa. Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight Jetnrvlce we deliver next day. C OUNTRY ALBANY BP Electronics !I 412681 ESPERANCE Esperance Communications 713344 GERALDTON Bird Electronics 641631 KALGOORLIE Todays Electronics ■ 212777 PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Farmer Electronlca 522388 DARWIN Ventronics 853622 ACT CANBERRA Bennett Commercial Electronics 805359 VICTORIA C ITY All Electronic Components 6623506 The Electronic Component Shop ■ 6706474 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics ■ 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 SHEPPARTON Tattersal Sounds 8212892 MILDURA McWilliam Electronics 236410 WARRNAMBAL Kovoit Electronics 627417 QUEENSLAND CITY Delsound P/L 8396155 SUBURBAN CAPALABAKingsway Electronics 3902399 WOODRIDGE David Hall Electronics 8082777 C OUNTRY BUNDABERG Bob Elkins Electronics 721785 GLADSTONE Superlronics 724459 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 7724466 MAROOCHYDOREMals Electronics 436119 SA CIT Y Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIES BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LONSDALE Force Electronics ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764. T ASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878BLACKTOWN Sheridan Electronics 621 1494 COU NTRY COFFS HARBOUR Coifs Habour Electronics 525684GOSFORD Tomorrows Electronics 247246 GRAFTON East Coast Electronic 431250 NEWCASTLE Novocastrian Elect.Supplies 621358 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 WAGGA WAGGA Phillips Electronics 216558 Can you n1ake the big escape? You've been incarcerated for six months in a remote prison camp and the escape tunnel has just been completed. Try to make it through the tunnel without being caught by the guards. By DARREN YATES "It is the sworn duty of every officer to try and escape. If he cannot, it is his sworn duty to make the enemy use an inordinant number of troops to guard him." These are the words that continually flow through your mind as you stare at what was once the shower block drainage outlet. Now, it's just a big hole in the ground that you hope will take you to freedom. "The Tunnel King" sits at the other end of the tunnel, just below the surface with only the top soil above him. The fat candles that line the tunnel are blown out as he starts to gently break through the loose ground. Expecting to be on the edge of the tree line east of the prison camp, he quietly pulls himself up through the hole. Behind him, is the prison camp and more importantly, the 5-metre barbed wire fence and the guards. He turns around and sees the trees nearly 10 metres away from him! "Big X", head of the Escape Committee and still in the tunnel, tries to figure out a way around the problem. An order comes back to you through the tunnel. "Send down 20 metres of rope". You're the next to go down the tunnel mouth. You hope that some- Block diagram 2-PHASE i - - - - - - t COMPARATOR 1 - - - - - - 1 COMPARATOR OSCIL!.ATOR CHAIN c~i1~gl LEDS D3 LOW FREQUENCY OSCIL!.ATOR IC3 R 270k Fig.1: block diagram of the Big Escape. If the switch is pressed while the output of the low frequency oscillator is high, capacitor C will charge via the 270kQ resistor. The voltage on the capacitor is then fed to a chain of 10 comparators inside IC3 and this in turn drives the LEDs. The 2-phase oscillator & the comparator control logic doubles the range ofIC3, so that it can drive 19 LEDs. 38 SILICON CHIP thing hasn't gone wrong and then word comes back that the tunnel is 10 metres short! You're told that there has been a change of plans. The electric lights through the tunnel have been linked to a common switch in "Hut 5". When the Senior Officer flicks the switch, you can move through the tunnel and follow the rope out of the tunnel to the trees - but only when the light is on. If you keep moving when the light is out, you push the men further up the tunnel to be discovered by the guards patrolling the perimeter fence and the escape bid is blown. Good luck. As "Big X" said, this is a situation where you need skill and patience, and a touch of luck! To play the game, when the green GO LED is on, you press the MOVE button to make your way through the tunnel. If you hold on for too long, you blow the escape for everyone and the guards round you up at the tunnel mouth. You can also change the difficulty level to make the game as easy or as hard as you like. All the circuitry, including the LEDs, is built on a single PC board, so there's no matrix wiring to be done. All you have to do is wire in the power switch, hook up four 1.5V cells and you're away. While the idea of this circuit is not new, what is new is the way it's been designed. If you look at the block diagram in Fig.1, what we have is a lowfrequency oscillator, with a switch in series between it and a storage capacitor. This is the pushbutton switch on the lid of the zippy box. When the output of the low frequency oscillator is high and the switch is pressed, the capacitor is charged up via the 270kQ resistor. If the switch is still down when the output goes low, the capacitor dis- range; ie, from Oto 0.625V in 62.5mV steps. If we now move the 10kQ resistor from pin 6 to between pin 4 and ground and tie pin 6 to the voltage reference, the comparators now respond to the upper half of the range; ie, from 0.625V to 1.25V in 62.5mV steps. So, in total, we now get 20 steps. Display multiplexing To make this work in the circuit, PARTS LIST The Big Escape is built into a plastic zippy case. Whenever a LED flashes on, you can press the switch & move along the escape tunnel. But press the switch while the LED is out and you quickly move back to your starting point. charges much faster though the diode (D3). The capacitor is also linked to a series of 10 comparators, in IC3. As the capacitor voltage rises above the preset reference voltage for each comparator, that particular comparator's output goes low, lighting the corresponding LED. However, we have 19 LEDs in our "tunnel" and only 10 comparators! That problem is easily solved. By using some switching logic, we can make those 10 comparators do double the work and cover double the range. The LM3914 Refer now to Fig.2 which shows the internal block diagram of the LM3914 (IC3). This IC contains a string of 10 comparators which respond to a voltage on the input at pin 5. Each of the non-inverting pins is connected to a point in a lkQ resistor string, which divides the reference voltage at pin 7 into tenths. So with a 1.25V reference, the lowest comparator responds to a voltage above 125mV, the next comparator to a voltage above 250mV and so on. The ends of the resistor string are brought out to pin 6 (RHI) and pin 4 (RLO). Looking now at Fig.3 which is a simplified version of the internal diagram of Fig.2, if we put in a 10kn resistor between pin 6 and the voltage reference (VREF), and tie pin 4 to ground, the string of comparators will now respond to the lower half of the Features Of The Game * Press the Go button only when the green light is on; otherwise you will slip back and possibly be recaptured. * The variable knob sets the degree of difficulty. Set it fully anticlockwise for kiddies and Kingswood drivers; fully clockwise for BMW drivers and video games fanatics. * There are 19 LEDs denoting 19 steps to freedom; escape while you can. * If you escape, an alarm will sound, so hightail it out of there. * Turn the unit off to reset the game. After all, why should the next player have an easy run? * Battery operation, with low current drain. Use alkaline cells for long life. 1 plastic case, 158 x 95 x 50mm 1 PC board, code SC08112901, 81 x 132mm 1 front panel label, 152 x 91 mm 1 100kQ linear potentiometer 1 knob to suit 1 flat 4 x AA battery holder 3 PC pins 1 DPDT toggle switch 1 momentary pushbutton switch 1 transducer (Jaycar Cat. AB3440 or equivalent) 6 25mm x 3mm machine screws 6 3mm nuts 6 3mm washers 4 10 x 3mm tapped spacers 1 9-volt battery snap connector Semiconductors 2 4093 Schmitt NANO gates (IC1 ,IC4) 1 4066 quad CMOS analog switch (IC2) 1 LM3914 LED driver (IC3) 2 BC558 PNP transistors (01 ,2) 1 3mm green LED (LED 1) 18 3mm red LEDs (LEDs 2-19) 1 3mm yellow LED (LED 20) 4 1N914 signal diodes (D1-D4) Capacitors 1 33µF 10VW PC electrolytic 1 22µF 25VW tantalum 3 0.1 µF metallised polyester 2 .018µF metallised polyester Resistors (0.25W, 5%) 1 4.7MQ 1 100kQ 1 1.2MQ 3 10kQ 1 1MQ 1 9.1kQ 1% 1 270kQ 2 4. 7kQ 1 220kQ 2 2.2kQ 1 150kQ 1 1.8kQ 1 120kQ 1 820Q Miscellaneous Hookup wire, solder, etc DECEMBER 1990 39 VREF V EF r-- - - - - LMJsa- - - - - , I _ COMPARATOR 1 OF 10 I IC3 ;1./ 10 ;1./ lk 11 I I 10x1k I 10x1k I I I I ;1./ lk 12 lk 13 ;1./ I (a) ;1./ 1k ml OUT 14 ;1./ lk 7 + THIS LOAD DETERMINES LEO BRIGHTNESS 15 REFERENCE VOLTAGE SOURCE 1.25V lk 16 ':' REF I ADJ ;1./ I ;1./ 8 1k ;1./ 11 ;1./ lk 1k y• FROM PIN 11 MOOE SELECT AWLIFIER 9 I TYPE CONTROLS OF DISPLAY, BAR OR SINGLE I LEO I y-~ IN I I -=- 5 I L- I I _-=-_ _ - - - - - ___ ..J Fig.2: the LM3914 contains a string of 10 comparators. These compare the voltage at the pin 5 input with a voltage derived from a 1.25V reference and a string of tlcQ divider resistors. we only need to use the old "handfaster-than-eye" trick; ie, we rapidly switch the lOkO resistor between the two pins. Because our eyes cannot react to high-frequency switching, the LEDs will appear to be on at a constant brightness. What we end up with is a string of comparators that for half the time test 40 SILICON CHIP .• . (b) Fig.3: this diagram shows how the LM3914 can be made to work over two ranges. If a 10kn resistor is connected between pin 6 and VREF, the comparators will respond to the lower half of the voltage range. Similarly, if the resistor is connected between pin 4 & ground, the comparators respond to the upper half of the range. 17 lk SIG I the lower half of the voltage range, and for the other half, test the upper half of the range. If you go back to the block diagram in Fig.1, you can see we also have a 2phase clock, which produces two "out-of-phase" waveforms; ie, when one output is high, the other is low and vice versa These signals are fed into our control logic which consists of a 4066 quad analog switch and a couple of transistors. The 4066 switches the inputs to the comparators while the transistors switch two rows of LEDs to the outputs of the comparators. The idea of the control logic is to make sure the correct LEDs turn on in the right sequence. In effect, the 10 comparators are multiplexed to two sets of LEDs. The circuit Now let's take a look at the circuit diagram of Fig.4. The circuit uses two 4093 quad Schmitt trigger NAND gates (ICl and IC4), one 4066 quad analog switch (ICZ) and the LM3914 LED driver (IC3). NAND gates ICla and IClb form the 2-phase clock oscillator which has a frequency of about 90Hz. ICla is connected as a standard Schmitt RC oscillator while IClb simply inverts the Fig.4: the final circuit contains all the • elements shown in Fig.4. IC1a,1b form the 2-phase oscillator, ICtc is the low frequency oscillator, & IC2a,2b form the comparator control logic which switches IC3 between the upper & lower ranges. Also included on the circuit is a 2-tone chime circuit made up ofIC4a-d & a piezo buzzer. ~ .... 0 cc cc ..... t?J :t:I ~ to t?J (") t?J t:l I G\ 01 1N914 25VWr TANT° GREEN 2.2k K ,. "'F~r 01! 0 4.7M .,. :, IC2b 12 • 101Mr 33 82001 1 I I 'K"YI LE03 ~ I LED12~ I LED4~LED~ ,CYI LED~ISiKI L E D ~ THE BIG ESCAPE I 1 IC3 LM3914 L. I I J ~1 I 9.1 1'/o 1 4 .,. +6V 0.1+ ,. 220kS ~- .,. o.1I .l I I .... l!! .l V B 4 .018 I .011! I VIEWED FROM BELOW eOc ~ _J WINNER~ LED19 1-. YELLOW K 150k 120k 1 ...I- &V 'I T + VPIEZO BUUER S2a -~f When installing the capacitors, bend their leads so that they lie parallel to the PC board to provide sufficient clearance for the lid. The LEDs should all be installed so that there is 20mm between the board & the bottom of each LED body. Take care with component orientation. output to give the second of the 2phase signals. These two signals are fed to the control inputs of two analog switches, ICZa and ICZb, as well as to transistors Ql and QZ. •The analog switches are used to short out the lOkQ and 9. lkn resistors from pins 4 and 6 of the LM3914. For their part, transistors Ql and QZ switch the two strings of LEDs. The reason for the 9. lkQ resistor is that to make the circuit work prop- erly, we can't use comparator 10 in the usual way. This is due to the fact that when the input voltage is higher than the voltage at the non-inverting input of comparator 10, its output goes low and the LED naturally turns on. Because this is the last comparator, the LED would then remain on as the input voltage increased for the top half of the range. The 9. lkQ resistor overcomes that problem by allowing the first LED of the upper range to The potentiometer is installed with its back cover resting on the PC board & its terminals soldered to three PC stakes. Trim the pot shaft to suit the control knob before installing it on the PC board. 42 SILICON CHIP turn on just as the ninth LED of the lower range is going out. Basically, we need to allow lkQ for each comparator. Since we only need the first nine comparators in the lower range, we only need 9kQ (9. lkQ is the closest value). We can still use comparator 10 on the upper voltage range but this requires some extra circuitry, which we will come to shortly. The input voltage comes from the 33µF storage capacitor connected to pin 5 of the LM3914. This capacitor is also connected via a momentary contact pushbutton switch to an RC oscillator built around IClc. The frequency of IClc is about 1Hz. (This is the low frequency oscillator shown in Fig.1). When the output of IClc is high and the switch is depressed, the 33µF capacitor charges up via the 270kQ resistor. If the button is depressed when the output is low, the capacitor will rapidly discharge through diode D3. The green LED at the output of IClc turns on when it goes high, indicating that it is alright to move. The 4. 7MQ resistor in parallel with the 33µF capacitor slowly bleeds off the voltage. This is to stop people from sitting at one level for hours on end; the longer you wait to make your next move, the further back you slip! Each 30 seconds or so, you slip back one position. Reset to start The second pole of the on/off switch (SZb) is used to reset the game, when a player has either just won or wants to start again. Diode D3 can only allow the 33µF capacitor to discharge down to +0.6V (ie, the voltage drop of a diode), so when the power is turned off, S2b shorts out the capacitor. This way, when the game is switched back on again, the capacitor has no voltage across it and the game is ready to go. Potentiometer VRl changes the rate at which the ZZµF timing capacitor on the inputs of IClc is charged and discharged. This sets the time for which the output is high and low, and so becomes our DIFFICULTLY control. With the pot rotated fully anticlockwise, the game is set at its most difficult level. Note that this control only changes the mark/space ratio, not the frequency. To give the storage capacitor a wider Fig.5: you can install the parts on the PC board in any order although it's best to start with the wire links & PC stakes (for mounting VRl). Note particularly that the LEDs don't all face in the same direction so watch your step here. Check Fig.4 for the pinout details of the LEDs & transistors when mounting these components. voltage range to work with, we have increased the reference voltage of the LM3914 from 1.25V to 2 volts. This is done by adding the 1.8kQ and 8200 resistors to pins 7 and 8 of IC3. As mentioned earlier, the 2-phase clock also controls PNP transistors Ql and Q2. These are switched on and off at a rate of 90Hz and they give the LEDs the appearance of being on continuously. The transistors are wired so that when IC2a switches on due to a high voltage to pin 5 from ICla, transistor Q2 remains off and Ql is turned on via the out-of-phase signal coming from IClb. Thus Ql controls the lower nine LEDs and Q2 controls the upper nine, but what about the 19th LED? As we mentioned earlier, the last LED requires some extra circuitry because of the problem we face with comparator 10. Normally, the voltage at pin 10 is switching from the positive rail to ground at 90Hz. However, once the input voltage at pin 5 of IC3 rises above the threshold level of comparator 10, the output at piri 10 goes low. Double inversion Diode D4 half-wave rectifies the switching waveform and dumps the resulting charge into a 0.lµF capacitor. The voltage across the capacitor is also fed to the control input (pin 12) of IC2c, which is connected to function as an inverter. When pin 12 of IC2c is high, the analog switch turns on and pulls the output at pin 11 low. Pin 11 is connected to the input of ICld, which is also connected as an inverter to drive the 19th LED. Some of you may be wondering why bother with a double inversion and why not just wire the LED in series with IC2c? The problem here is that CMOS analog switches don't like high currents, whereas the NANO gate can easily handle the current demand of the LED. The output of IC2c drives a 2-tone alarm to indicate that an escape has been made. The alarm comprises all four gates in IC4, which is a quad 2input Schmitt trigger IC. Three of these gates are wired as oscillators while the fourth, IC4c, functions as an inverter. Sounding the alarm IC4a is· connected as an RC oscillator, operating at about 10Hz. When its pin 1 is high, it oscillates and when pin 1 is low, the output at pin 3 is kept high. Pin 3 is connected to pins 8 and 9 of IC4c which functions as an inverter to enable oscillator IC4d. IC4d therefore oscillates when IC4a's output is high, and it stops oscillating when IC4a's output is low. The third oscillator in the trio, IC4b, TABLE 1: RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 D No Value 4-Band Code (5%) 5-Band Code (1%) 1 4.7MQ 1.2MQ 1MQ 270kQ 220kQ 150kQ 120kQ 100kQ 10kQ 9.1kQ 4.7kQ 2.2kQ 1.8kQ 820Q yellow violet green gold brown red green gold brown black green gold red violet yellow gold red red yellow gold brown green yellow gold brown red yellow gold brown black yellow gold brown black orange gold not applicable yellow violet red gold red red red gold brown grey red gold grey brown brown gold yellow violet black yellow brown brown red black yellow brown brown black black yellow brown red violet black orange brown red red black orange brown brown green black orange brown brown red black orange brown brown black black orange brown brown black black red brown white brown black brown brown yellow violet black brown brown red red black brown brown· brown grey black brown brown grey brown black black brown 1 1 3 1 2 2 DECEMBER 1990 43 ~tlt)t° + 0 0 ~~ii,, -~ ~o • 0 I ~---1-0 . . . . . ... .. . . . ..' . ...... .. .. . . .. . .. . ...... . ...' ......... .. .. .. .. ...... . . . .. :::::::::::::::::+::::::::: ........... ... . .... . .. . . . ' . ' ' .. . .' ... . . ............ ......... .. . ' . .. 0 ' ' •••I • I • o • o • ' . oscillates at roughly the same frequency as IC4d but since IC4b's pin 5 is also connected to pin 11 of IC,Zc, it oscillates whenever IC4d is muted. Just · to make it interesting, the piezo buzzer is connected between the outputs of oscillators IC4b and IC4d. That way, both oscillators contribute to give the 2-tone sound. The current drain of the circuit is about 13mA, so the four "AA" cells should last quite a long time. Construction Most of the components fit on a single PC board. This carries the code number SC08112901 and measures 81 x 132mm. Before you begin soldering in anything, check the board carefully for breaks or shorts in the tracks. These should be touched up now. 44 SILICON CHIP . . .:.·.:: . .. .. .......... . .. . -:.:..: . .- 0 ' .' 0 SC08112901 0 Fig.6: here are full size artworks for the front panel & the PC hoard. Compare your PC hoard to the artwork shown above & repair any damaged tracks before installing any of the parts. Fig.5 shows how all the parts are mounted on the board. Begin the assembly by installing three PC pins for the potentiometer, then install the wire links and resistors. The 5% resistor values should be easy to distinguish (see Table 1) but if you're not sure, use your multimeter to double check, especially the 9. lkQ 1 % resistor. Now insert the capacitors. Because there is little clearance between the zippy box lid and the PC board, you'll need to lay the capacitors over on their sides. This includes the electrolytics as well. Make sure that all polarised capacitors are correctly oriented. Once you've completed this, solder in the diodes and transistors. Again, make sure they are correctly oriented on the board. Now you're ready to solder in the 20 LEDs. When you do this , make sure that you leave a lead length of 10mm from the base of the LED to the PC board. Since they have to poke through the front panel, you need to keep them as straight as possible. Again, use the overlay diagram to make sure they are each installed correctly. Ne~t. solder in the four ICs. Again, check that they are the right way around. Finally, the pushbutton switch and the potentiometer can be soldered into place. The switch should sit flush on the board, while the tabs of the potentiometer are soldered to the three PC pins (see photo). Now for the front panel artwork. If 111• comp,,t.,- •nd .i.ctronlc ,,.,,,. joyatlclt ,. c/a119t1y dnlgMd for two handH ,,,_,.lion. Tiu not only he/,,. :o Iner.- control and accuracy but •l• o prolong. pl•ylng tlma by rwluclng hand fatl(lw th•t can be ...ocl•lad with nonnlll a/ngle hand o,,.r• IIBd unll& JSC-$ fa a/ff de•lgnad iMJ Iha hmd(lrl,- can eully be on• tabla or oth.,- /fat ~~>==;;;:-- • urf•ce for .i.b/1/zlng Iha 111lt during ,-, It la compatlb# lli#th moat computets lncludng ~.-+-~Atn.trad,Awf, Commodore n. ,..,lid •nd ~ ELECTRONICS SOUND AUSTRALIA Your P.A. Accessory Specialist STEEL SPEAKER GRILLES CHROME CATCHES 5·. $ 8.95 6"- $ 9.95 Large Lockable $9.95 8"- $11.95 10"- $15.95 Small Lockable $4.95 12"- $19.95 15"- $23.95 STEEL SPEAKER 18"- $34:95 Clamps for GRILLES Grilles Pk4- $2.95 5" $8.95 STEEL DISHES The PC board is mounted on the lid of the case on 10mm spacers & secured using 25 x 3mm machine screws & nuts. Check that the tops of the LEDs sit flush with the surface of the lid & adjust the LED lead lengths if necessary. The 4 x AAA battery holder sits in the bottom of the case, beneath the PC board, and can be either glued in place or secured using foam rubber. you are making your own Scotchcal panel, we suggest you use an aluminium-backed panel as they are much easier to work with. Once it is ready, peel off the backing and carefully place it on the zippy box lid. Remember this is sticky stuff and once it's on, it stays on, so make sure you get it right first go. Once it's on, you can drill the holes for the pot, switch, mounting screws and the 20 LEDs. The crossmarks on the front panel artwork show where the holes are to be drilled. The holes for the LEDs and the screws should be 3mm in diameter, the switch hole 7mm and the hole for the potentiometer should be 8mm in diameter. Note that the two larger holes (for the switch and pot) are best made by drilling small pilot holes and then ehlarging them with a reamer. The next step now is to wire up the 2-pole power switch, the battery and the transducer. The transducer itself is secured to the right wall of the box with two 25 x 3mm machine screws. Don't forget to drill a 7mm diameter hole to allow the sound to escape. The last step is to mount the board on the lid using four 10mm spacers and another four 25 x 3mm machine screws and nuts. To do this, first slide the lid over the potentiometer shaft and the pushbutton switch, then carefully line up the LEDs with the holes. You may need to tilt the outer LEDs towards the middle of the board to get them to fit but this should not be by very much. Once everything is lined up, you can slide the spacers into position between the board and the lid and install the mounting screws. You should end_up with the pushbutton switch sitting flush with the lid and the 20 LEDs just poking through their holes. Adjust the LEDs if necessary. 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If it doesn't, first check that there are no solder splashes shorting out any of the tracks on the board. If that doesn't help, check that you have the power switch correctly wired up. Lastly, check again that all components are correctly installed, particularly the LEDs, by comparing your work with the parts layout diagram. Now you're ready to see if you have the patience and skill to escape the prison camp! At Last!!! Public Address & Hi Fi Combined Now you can Mlf9 Hi R qu•lty audio anywhe,.. n. ) SP352L T .,,.• •,. haw thalr Jown on board 100 wit IIM 'x'former• to o IIWV:Offlfl lofl(I, ·crowded cab/a tuM. 111- speakers t:1tn I» connected up to •ny 100 'IIO/t line output on mo• t mono public llddrfla ampllfiflta. If true ste,.o is required they can ew,n be hooktld up to • domastic Hi R •mpllfler with II• •Id of •NY to ins,.// •tep up tr• nsfonne,.. Ideal for office •nd warehoUN aetupa or nen If you almply want HI R • udio piped through to your •wlmmlng pool •nd beckyard. 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RS232· 2 way ......... ............ $39 2155 l'.50 $3.85 13.50 P12170 S1.30m $1.-1 W12672 · C _;/ / Jt you have 2 or 4 compal1ble devices that need to s hare a thi rd or fifth , then these inexpencivedata !ranter will save youthe time and hassle of constantly changing c·ables and leads around. 100 • . 0 82 5P 25 pin ~ug The perfec t solulion! 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It BNC MALE PLUG 1-9 TY CO~ HEATSINK coMPouNo Heatsi nk comPound applted to the baseIsand -J ~ ~~Ii~ T 115V 31 741 1·9 $0.50 $0.50 $0.50 $0.60 $0.60 $0.60 $0.40 SQ.40 $1.CIC) $0.40 $0.50 10+ $0.45 $0.45 $0.45 $0.55 $0.55 $0.55 90.30 $0.30 so:eo $0.38 $0.45 MAIL ORDER & CORRESPONDENCE P.O. Box 620, Cloylon, 3168 Order Hotline: 008 33 5757 fToll FrN Sb1cdy ordare only) POSTAGE RATES $1 • $ 9.99 ... .. .. ...$ 3.00 $ 10 • 24. 00 ... ... . .$3.50 $25 • $ 49.99 ...... $ 4 .50 $50 • $ 99.99 ... .. .$6.00 $ 1 00 • $199 .. ..... $7.00 $200 • $ 500 .. .....fREE; $500 Plus .... ... .. FREE 10• fans (m11ed) only S,0.15 each OD IRVING ELECTRONICS CITY: 48 A ' BECKETT ST, MELBOURNE .c NORTHCOTE: 42S HIGH ST. NORTH COTE ~ SYDNE Y: 74 PARRAMATTA RD. STANMORF ~ORDER: S6 RENVER RD. CLAYTON PH: PH: PH: PH : (03) (03) (02) (03) 663 489 S19 §43 61Sl 8866 3134 7877 rl Ind wholeule inquiries to: illTRONICS WHOLESALE 56 Renver Road. Clayton Phone (03) 543 21 66 (3 llnes) (03) 543 2648 Errors and om1ssrons excepted. Prices and specif,catKJi1s subject 10 change. IBM' PC' .. , . AT · 1,1 ,eg,11eftdllaotm11•sol lnl~ "IONl BuslnHs Mech"'" · ~ ,s I r19111n1d rradolffltr1, •Oef,oru 119s11red n.....,.s ol l"-••spec"ve o,r,nto II.-' \ \ • SERVICEMAN'S LOG It sounds like Donald Duck Poor old Donald! He takes the blame for a multitude of problems, not the least of which is the way people use him to describe a multitude of distortion effects. So much so that I sometimes wonder what they would do without him. Perhaps he should charge for this service. Truth to tell, not many forms of distortion really do sound like Donald Duck. And that's not surprising I suppose, because I imagine that the true Donald Duck sound is a lot more complex than most common forms of distortion. Anyway, to get down to business, the problem involved another National NV-G7 video recorder, at which I recoiled slightly after recounting last month's notes. However, one has to take the good with the bad. The customer - one of my regulars simply dumped it on the counter and came out with the above heading; "It sounds like Donald Duck". "Any problem with the picture?" "No - picture's perfect. But the sound's just like Donald Duck". And that was about it, as far as the customer was concerned. He was obviously convinced that all I had to do was wave my magic screwdriver and all would be well. I find such faith quite touching. When most people use the Donald Duck analogy they mean a recording that is running fast, even though this is not strictly accurate - at least from Donald's point of view. But I couldn't reconcile such an effect with the fact that the picture was supposedly perfect. If the tape was running that fast the picture would also be running fast - assuming that it remained locked. So I set the machine up and pushed in a test tape. And the result was quite surprising. Yes, the sound was funny and it did seem to be some kind of speed abnormality, although I couldn't define it initially. And, yes, the picture was perfect; normal speed, no noise bars, rock steady. So what was happening to the sound? I listened to it long and carefully a number of times before I came to any conclusion. Finally, it seemed to me that the sound would run at normal speed for one period, then hesitate briefly as though the tape had stopped or slowed significantly, then resume normal speed, then hesitate, and so on. I also judged that the normal period was longer than the hesitant one, while the whole process was happening quite rapidly, producing a high speed chopping effect. The end result was certainly strange, though I doubt whether Donald would have been flattered by the comparison. But Donald's sensitivities aside, I had a problem to solve; what was the most likely cause of such an effect which I had certainly never encountered before - and how was I going to track it down? Transport problem This is the stator from the capstan motor in the National NV-G7 video recorder. It consi!!ts of 6 flat windings on a PC board, together with three small surfacemounted solid state devices at the centre of three of these windings. 48 SILICON CHIP Well, it had to be a transport problem of some kind: the capstan drive, the drum drive or, more specifically, the servo systems associated with them. But which or what? And why was it not affecting the picture? I sat down and had a good long THIS TESTER CAN PAY FOR ITSELF IN LESS THAN ONE DAY <at>Dlliu CHECK,. 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A variation of tape speed will affect the sound directly. So it was conceivable that we had a capstan speed variation which was upsetting the sound, but was within the capture range of the drum servo system. In short, a capstan motor fault. It was all pure theory, of course, but I felt it was strong enough to justify checking the capstan motor and replacing it if that was the only way to prove the point. And at that point I had no knowledge of just what kind of motor was involved. Nor was there much about it in the manual. But when I delved into the innards of the machine I found a capstan motor like no other I had ever seen before. Not that I'm knocking it; on the contrary, it is a robust, well designed component, much larger than the usual run , easy to get at and take apart and, in this case anyway, economical to repair. The two main parts are the rotor and stator. The rotor is simply a metal disc, about 75mm in diameter, which runs in close proximity to the stator. Being such a simple device, I felt it was unlikely to be at fault and turned my attention to the stator. The accompanying photograph gives a good idea of the stator construction. As can be seen, it consists of six flat windings mounted on a PC board. A circle enclosing the windings would have a diameter of about 75mm, matching the rotor diameter. The stator board itself is about 90mm across. In the centre of three of the coils is a solid state device, the purpose of which is not clear. The external connections to these devices and to the coils run via a flexible copper pattern which mates with an edge connector. $1499.00 Plus Tax BONUS - SINGLE CHIP ADAPTER FOR TESTING 64K x 1, 256K x 1, IM x 1, and 4M x 1 DRAM chips PACIFIC MICROELETRONICS PTY LTD 'CENTRAL PARK' UNIT A20, 4 CENTRAL AVENUE THORNLEIGH, NSW, 2120 Telephone: (02) 481 0065 Fax: (02) 484 4460 Australian Representative FUJITSU MICROELECTRONICS PACIFIC ASIA LTD. o) FUJITSU DECEMBER1990 49 SERVICEMAN'S LOG - CTD "' ~ '6> .,.· + _y,. Jl . • .., • .· .,. As encountered in the machine, the stator is the other way up to that shown in the photo. It is held by three screws, the holes for which can be seen, and across the back of the board is a bar, held by two screws, which carries one bearing for the rotor shaft. So undoing five screws takes the whole thing apart. But before I took it apart, I gave it a physical check-out. In particular, I checked for free movement of the rotor, adjustment of the bearings, etc. As far as I could tell there was nothing wrong here, which really left only the stator assembly. That led me to another pleasant surprise; a replacement stator was available for around $30 which is quite a modest figure considering that some capstan motors are well over the $100 mark. On that basis I decided on a replacement rotor. Even if I was wrong (and I felt pretty sure I was right), it wasn't a great deal to risk. 50 SILICON CHIP But I was right; the new rotor fixed it and Donald was sent packing. And the final cost was quite reasonable, partly because of the modest replacement cost, plus the relative ease of fitting. So I finally had another satisfied customer. Two Donald's While on the subject of Donald and his mutilation of the English language, I had another video recorder recently against which the same accusation was levelled. In some respects, the cases were similar, in others quite different. It was one of those sameonly-differnt situations. For a start, it was a completely different brand of recorder; a Sharp VC381X. It was also intermittent and, probably as a by-product of this, had something of a history to it. The customer was a stranger, having recently moved into my area from the Orange district. And that was where the fault first appeared and was tackled by a local serviceman. Judging from what I found later, he had tackled the problem logically, had obviously gone to a lot of trouble, and had done everything in a thoroughly professional manner. And, according to the customer, he seemed to have fixed it. It ran for a couple of months before they moved and apparently survived the move, for a few weeks at least! But then suddenly the old fault was back. And the nature of the fault? "It goes Donald Duck. Y'know, everything speeds up. But only sometimes; usually after it's been on for about 20 minutes". The speed-up included the picture which, he explained, was still visible but running fast, with lines across it. "Y'know, like in fast forward, only with Donald Duck sound" . All of which was a pretty good fault description; better than I get from most customers. That, and the history I related above, at least gave me a head start. In fact, I had already mentally .registered that it sounded very much like a capstan fault; possibly in the capstan servo system. At first switch-on, the machine behaved normally and I let it run with a test tape. Then, just as the owner had predicted, after about 20 minutes it suddenly ran amok, with speeded up picture and sound. I switched it off and let it rest for half an hour or so, then tried again. But it was still faulty. I removed the top cover, then lifted the top board, which is hinged at the back, thus gaining access to the mechanical area. The machine performed in the same faulty manner while I looked over this section but there was nothing obvious. I turned the machine off, turned it on its side, removed the bottom cover, and swung out the bottom board, which also hinges at the back. This carries the capstan and drum servo circuits, although it was the capstan system that I suspected. As I explained in the first story, incorrect capstan speed can normally be accommodated by the head drum, which is locked to the reference pulses on the tape. The picture speed will be incorrect and it may display cross-over lines, but it should remain locked. The sound speed will likewise be incorrect. completely aimless exercise. I turned it off in disgust. Later, I switched the machine on again, only to find that all the faults had vanished; it was working perfectly. So what had I done during my aimless probing. I didn't wake up immediately, but at that stage the machine was on its side, with the top and bottom boards folded out at right angles. In order to turn the machine over and get a better look from the top, I closed the bottom board. Whereupon it shut down. I swung the board out again and it was working. I immediately suspected a hairline crack in one of the tracks, and went through the routine of twisting, prodding, and generally abusing the board in an effort to get a lead on it. All of which proved completely fruitless. Suddenly, I woke up to the fact that it was the position of the board that was critical. Swing it in from the open position and all would be well until it was within about 50mm of fully closed, whereupon the machine would suddenly shut down. Open this gap ever so slightly and it would work; close it again and it would stop. But then, when the board was fully Closer inspection of the bottom board around the relevant servo IC, IC706, revealed that the previous serviceman had had the same idea. The IC had obviously been removed and no doubt replaced, along with several other components in this section. And, as I said earlier, it had all been very neatly done. At this point, I turned the machine on again. And lo and behold, it was back to normal. But not for long. Its next trick was to really run amok, displaying not only the high speed fault, but a swag of other faults as well. A revolting development Pressing the PLAY button could send it into the fast forward wind function. Or rewind the tape. Then the dew light came up and the machine shut down completely. As another cartoon character is wont to exclaim, "What a revolting development"! Yes, revolting it was because, right then, I didn't have a clue where to look next. I went through the motions of going over all the components, prodding and poking, but it was a CROSSOVER FOR BETTER PERFORMANCE TO BRIDGE STATIC RAM DYNAMIC RAM 4164-10 41256-8 4464-10 41C1000-8 44C256-8 64k x 1 100NS 256K X 1 SONS 64K x 4 100NS 1M x 1 SONS 256K X 4 SONS EPROMS 2716 2732 27C64 27C256 $9.95 7.95 6.50 7 .50 $2.60 3.00 3.00 9.50 9.50 61161 6264L 622561 2k X 8 BK x 8 32K x 8 100NS 100NS 100NS $2.50 3.80 9.95 FD 55BR 360K FD235F 720K FD55GFR 1.2M 235HF 1.44M TEAC TEAC TEAC TEAC 5.25" 5.25" 5.25" 3.5" $126.00 126.00 130.00 140.00 (AUSTRALIAN MADE) 12 Months Warranty SHORTED TURNS TESTER Built-in Meter to check EHT transformers including split diode type, yokes and drive transformers. Built-in meter reads positive or negative 050kV. For checking EHT and focus as well as any other Hi-tension voltages. $98.00 + $5.00 p&p LOW VOLT AGE PROBE Ideal for checking microwave ovens and TVs. The ranges are from O to 5kV Negative and from Oto 10kV Positive. Double insulated fo r safety. MOTHERBOARD 80286-12/16MHz BABY AT MOTHER BOARD TV TEST EQUIPMENT THAT WILL EARN YOU MORE MONEY $78.00 + $3.00 p&p HI-VOLTAGE PROBE FLOPPY DISK DRIVES FDD FDD FDD FDD closed, it would work again. I left the board fully closed and went over it again; prodding, twisting, bashing (yes , and calling it names), but all to no avail. I couldn't fault it. But I did latch on to something. Running from the back of the bottom board, and soldered to the copper tracks, are two ribbon cables, about 100mm long. These run up into the mechanism area and terminate in suitable plugs in this section. One ribbon is designated AB and the other AN. I left the bottom board closed and lay the machine flat, under which conditions it was working normally. And, with the top board swung out, I had ready access to the ribbons and plugs. I wiggled the plugs, without any effect, then started poking at the ribbons. This was where I struck oil, though not immediately. After several tries, I happened to move the AN (12-conductor) cable a certain way and the dew light came on and the machine shut down. The necessary movement was quite critical but, with care, also quite predictable. So, after putting it $180.00 $8 4 INPUT / OUTPUT CARDS AT 1/0 CARD 1 SERIAL, 1 PARALLEL, 1 GRAPHIC AT 1/0 CARD 2 SERIAL, 1 PARALLEL, 1 GRAPHIC $45.00 55 .00 .oo + $5 .oo p&p · ·. TO ORDER PLEASE RING (02)369 2745 WITH YOUR CREDIT CARD DETAILS - WE WILL SHIP THE GOODS THE SAME DAY. If you need any computer product not listed here, please give us a call. . , $75.00 + !_~.DO p&p_ '(~-..... ,"°_. .. ~ Prices include 20% Sales Tax. Delivery $4.00 anywhere in Australia REMOTE CONTROL TESTER " n ¼,, . ) ;) $85.00 + $4.00 p&p l2.,.......,.....,._.....i.....,.,. i;:10 [D)<at>Dll BRIDGE ELECTRONICS ~ PO Box 272, BONDI, .. NSW 2026 ~ j ;(•l: ' (02) 369 2745 FAX (02) 389 2063 PHONE ! :(3i He£: DEGAUSSING WAND 7,700 apere turns. Strong magnetic field , larger than usual coi l with multicore centre. Double insulated for safety with momentary on/off switch. 240V AIC 2.2 amps. This one is just about as important as having a soldering iron in your toolbox! (INFARED OR ULTRASONIC) Designed to test any lnfared or Ultrasonic control units. With the extension lead you can also test infared units which cannot be placed in front of the testing unit. Requires a 9V battery. Output is via the LED diode and piezo speaker. TUNER REPAIRS trom only $11.00 + p&p Chekque,dMonMey Qtrder,d 8 an car or as erca~ 11JNERS1\216 Canterbury Road, Revesby, • ~ NSW, 2212, Australia Telephone (02) 774 1154 We also repair most tuners on an exchange basis. TV -.,• DECEMBER 1990 51 SERVICEMAN'S LOG - CTD through the go/no-go cycle several times, I knew I was close. After the first failure I imagined that the plug and socket assembly would be the most likely culprit but, after several of the above cycles, I changed my mind. The fault was definitely close to the bottom board end of the cable, where it was soldered directly to the copper tracks. So it was either a break in one of the conductors, or a dry joint at the board. Now I reckon, after all these years, I can pick a suspect joint with the best of them; which is not the same as claiming to be infallible. Nevertheless, if there was a dry joint there I felt sure a close examination would reveal it. So I turned the machine over, reached for the jeweller's loupe, and went over each of the 12 connections from every angle and with every lighting angle. And I would have passed every one of them as a perfect joint; there was absolutely nothing I could see to arouse any suspicion. On the other hand, a broken lead was a long shot. There is no flexing of the cable, apart from servicing activities, so why should it fail. In any case, the easiest thing to try was the soldering. I reached for the iron, unsoldered each joint, examined it, and carefully remade it. And this exercise did nothing to change my mind; I found no evidence of any fault. I was convinced that I would have to replace the cable. But I was wrong; when I put the recorder back into operation it came good immediately, and nothing I could do with the bottom board would create the fault. I was only partly convinced, of course; I've been caught like that before. I closed both boards, refitted the covers, set the machine up on the end of the bench, and put it through a number of cycles for the rest of the .1.m.,.;. r..1;;,:•.;: RCS Radio Pty Ltd is t he only compar,y which manufactures and sel ls every PCB & front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. 52 SILICON CHIP TETIA TV TIP Hitachi CTP-229 (NP8CA Chassis) Symptom: excessive brightness and not enough control to bring it down. A "sort of" picture could be obtained by reducing the screen voltage but this revealed heavy shading on the left hand side of the screen. Cure: C719, a 4. 7µF 250V electro, open circuit. This capacitor is a bypass on the 180V rail feeding the video output transistors. This fault is rather like a screen-voltage problem but the clue is that with this one there are no retrace lines visible. TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015. day. It never missed a beat. Dew sensor At the end of the day I disconnected it completely from the mains and let it cool over night. But when I switched it on next morning we were in trouble again. No, it didn't Donald Duck but the dew sensor came up. My first reaction was to rip everything apart and start again. Fortunately, second thoughts prevailed. I simply left it on with the dew sensor flashing. After about an hour, the sensor shut down and the machine came good and stayed that way for the rest of the day. I shut it down again that night, and the dew sensor came on again next morning, clearing itself after an hour. And the same thing happened the next day. By which time I was more than a little suspicious of the dew sensor itself. So much so that I ripped it out and fitted a new one. And that really fixed everything. Many days of testing, under all conditions, failed to reveal any problems. So Donald had been sent packing again, and everyone was happy. But I make it a practice in all cases involving intermittent faults to warn the customer that it might recur, and to come back immediately if it does. W~OD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR: C '1::;::=======~====-===================================~===~~~==-~~~ t r a label? , - - - - - - - - - - - - -- SerialTest serial ~: ~ ~ ~ Cl C C ~ TakeacloselookatAPPA multimeters. Look familiar? That's because they're sold under different brand names. And that means you could ~ay a lot more than you need to. We ve seen the top of the line model selling at around $150 more than our price. So you're paying that much extra just for the branij label! Lookltth,t11tur,sLarg, high contrast display. n,, 96 and 98 har, analog bar graphs loo Colourcod,d inputt,nnlnals and function switch tor ,asy 1111/ng Prob, ,torag, clips bultt In for ,asy two handed m,asur,m,nb Tilt Mi 1, water r,1/slanc, for Industrial us, • Shockproof/or, drop of 1.5ml • Buin-,n tin stand • :ri:'!'iigc;i;rt,r;:!,1 ~#~'if 1• nt1ants forandut, : 0 ◄ od 193 1999 count • Large 20mm high contrast LCD readout • 8 Functions • Vdc, Vac, Ade, Aac, Ohms, Diode, Frequency, Capacitance 0.5% de accuracy Ranges Vdc 200mV, 2V, 20V, 200V, 1000V Vac 2oomv, 2~2ov, 2oovoo7sov Ad~l,~· 2 , 20mA, 2 mA, Aa~l.~· 2mA, 20mA, 200mA, Ohms 2000, 2kn, 20kn, 200kn, 2Mn, 20Mn Frequency 2kHz 20kHz, 200kHz ca~acltance 2n~. 20nF, 200nF, 2µF, Also°Fvailable with transistor tester in place of capacitance ran_ges $142.80 ◄ od 19 3 1/2 digit plus 41 segment analog bar graph Autoranging or manual selection 6 functions • Vdc, Vac, Ade, Aac, Ohms, Diode Water resistant Data hold Memory offset Ranges ~ ~ Q: C Ii.. Cl C ~ Vdc 200mV, 2V, 20V, 200V, 1000V Vac 200mV, 2V, 20V, 200V,J50V Ade 200uA, 2mA. 20niA, 2wmA, 2A. 20A Aac 200uA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200n, 2kn, 20kn, 200kn, 2M!l,20Mn $166.80 ode/ 98 • 3 1/2 digit pius 41 segment analog bar graph • Autoranging or manual selection • 8 Functions • Vdc, Vac, Ade, Aac, · Ohms, Diode, Frequency, Capacitance Data hold ◄ Memory offset Ran11es Vdc 200mV, 2V, 20V, 200V, 1000V Vac 200mV, 2V, 20V, 200V.J50V Ade 200uA. 2mA, 20mA, 2wmA. 2A, 20A Aac 2~, 2mA, 20mA, 200mA, ~Jn. oh~s 2kn, 2011n, 200kn, 2Mn, 20M!l Frequency 2kHz 20kHz, 200kHz Ca~acitance 2n~. 20nF, 200nF, 2µF, OµF $21UO le ~ Q: C Ii.. Cl C ~ !e ~ Q: I 76 Component ester Does the things your multimeter doesn't! Capacitance 200pF to 20uf Resistance 200n to 20Mn • Transistor hfe and lceo • Diode displays Vf at 1mA LED displays VI at 2Ma and 1OmA • Battery tests 9V and 1.5V cells • SCA Pass/Fail test $142.80 MEMOREX - . ~ GENUINE PREM IUM GRADE DISKS 5 1/4 $16 • 95 per 1o 2S/2D 5 1/4 2S/HD $24 ■ 95 per 10 3 1/2 2S/2D $24. 95 per 10 3 1 /2 2S/HD $49 95 per 1O .__ _ _ _ _ _ _ _ _ _ _ _ _•_ _ _ _ _ _ __ Fan PrI .ices Blown AWay ■ n s $15• 95 Variable Transformers This month onlv they're all 15 _95 instead of $24.95. Save! 120mm 240V, 120mm 110V, 80mm 240V, 80mm 110V. 120mm 12V. 90mm 12V, 60mm 12V ~- A great way to "adjust" the mains! tt • • ··,. you're suffering from over or under · mains voltages or you want_ to ---"11 observe the effect of changing mains conditions on equipment, then here's the answerEnclosed SA 59.60 7A 87.30 13A 14.65 Open 1.2A $97.70 2.5A $122.20 Allow $20 P&P, they are big and heavy! ... ~ 0 ~~ae~~mi ~rs&cl~i~ii;mulate !~!i~~~n~1t~o~es~~f:t~ ~~~~~t~ or terminatemonitoringsequences. Handles baud rates up to 115.2kbaud. • View each byte in ASCII or EBCDIC, decoded to hex, decimal, binary or octal · . ., , .:, • Writes captured data directlv to disk to allow maximum capfure li e aveadded another room for our test Instruments and data books. We carry one of the best selections of technical data in Sydney. Availability changes daily so give us a call to check that we have what you want In stock! DIC-5000 Desoldering Tool The SC-5000 gun incorporates a motorised diaphragm pump. There are no tubes or separate compressors. A built-in thermosensor circuit controls the GOW ceramic heater to ensure rapid warm-up . Exact temperature control prevents damage to sensitive circuitry. The gun can also be used as a hot blow fool. $399.00extax ($479.50 inc tax) Stand $42.50 Need to Run 240Vac Equipment Off 12V Batteries?~. Depending on capacity _you can run your microwave oven, T.V., Electric Drill etc from a 12V battery with these handy inverter kits ... • ~~ie~hecksum calculations • Auto-configuration to any of the comms ports 1 to 4 • Time-stamping (absolute and relative) including delta time calculafions • Split line DTE over DCE display $395 plus sales tax Send $10 for a demo disk, refundable on purchase. Save $400! on Xcelite Tool Kit The serviceman's dream is here in this h1!9e assortment of Xcellte hand tools. ~ase is covered in posh tan leather grain vinyl and has remova le tool pallets in lid and bottom plus solid brass hardware. And we've chopped the price from $1295 to only $895!! Contains Nuldriwrs: 8, 10 11 13mm So/d,ring Iron: 25Wplus solder lnt,rchang,abl, Smwdrir,rs: Handle, extension, 9 Allen hexsocket blades, 7 Hex-nut blades, 2 slotted screw blades, 2 Phillips blades, reamer Pliers ,tc: Seizer, ad·ustable wrench na/s, electronic and Powerhouse 600W • Runs lighting (Including fluoros) motors etc up to 2.SA . • can be configured for 12/24V de • Easy to Assemble • Manual or Auto-start • Low Batte_ry cut-out • Compact Toroidal Transformer • Tough Steel case with industrial powder coat finish Complete Kit $425.DD · tied, 1Phillips, 5 set nu/driver ,. ro-P,nG11 x127mm 5 Powerhouse 300W • Very compact • 260x190x80mm • High efficiency toroidal tranny • Aulo start • only draws current when appliance Is on • Voltage & Current Regulated • Current overload protection Cof11plete Kit $279.0D Built & Tested $379.0D ~ GEOFF WOOD ELECTRONICS PTY LTD C t, 229 Burns Bay Road, (Corner Beatrice St.) 1Nc 1N Nsw Lane Cove West, N.S.W. P.O. Box 671, Lane Cove N.S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $5.00 to cover postal charges. Next day delivery in Sydney add $5.00. ~ Q ··"'"·· Cl C This is an MS-DOS software and cabling package which enables technicians and engineers to pertorm serial data comms analysis. n offers SOP.histlcated problem solving facilities at a fraction of the cost of dedicated hardware systems. SerialTest provides a window onto RS232 lines operating either as.a passive observer or actively sending 't "' ~ -- · C Ii.. g b ::0 data PC analysis on your . .,, 0 :1) C) ........, All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA. CHEQUES OR CASH CHEERFULLY ACCEPTED l: ~ Wiper pulser for rear windows Does your car or van have a wiper attached to the rear windscreen? If so, this device will be useful. It allows you to push a switch and have the wiper automatically operate for one or two wipes before parking itself off. By JOHN CLARKE Rear screen wipers are a good idea for vehicles which do not have a protruding boot to protect the rear windscreen from road grime when the roads are wet. Vehicles such as hatchbacks, station wagons and vans all suffer from road grime on the rear windscreen and a wiper is virtually a necessity for maintaining clear vision. However, many rear screen wiper controls have only a single on/off switch and this can be a nuisance in light drizzle conditions. Essentially, you've got two choices: either you leave the wiper running continuously whether it is needed or not, or you manually switch the wipers on and off to clear the windscreen as required. The first option causes excessive wear of the wiper blade, while the second is distracting for the driver. This simple wiper controller solves both those problems. To activate the wipers, all the driver has to do is press a pushbutton switch. The controller then takes over and automati- All the parts, including the relay, are installed on a small PC board which can be mounted out of sight under the dashboard. The external wiring leads connect to power, to the existing wiper switch & to the new wipe switch. 54 SILICON CHIP cally switches off the wiper after one or two wipes. That way, the driver doesn't have to worry about switching the wiper off again and can concentrate on the task at hand. Unlike many automotive projects, this project is easy to install. All you have to do is assemble a small PC board and fit a pushbutton switch to your dashboard. There are just six wires to run: two for the power supply (+12V & GND), two to the contacts of the existing wiper switch, and two to the new pushbutton switch .. You don't need to run any wiring to the rear wiper itself; instead, all wiring is concentrated at the front of the vehicle. How it works Refer now to Fig.1 which shows all the circuit details. ICl is a 555 timer which is connected as a monostable, with Cl (22µF) and Rl (lOOkQ) as the timing components. Initially, Cl is held discharged by a transistor inside ICl, pin 3 is low, and Ql and the relay are off. Assume now that the wipe button (S1) is pressed. When this happens, ICl's pin 2 trigger input is pulled low and this both releases the internal short circuit across Cl and drives the output (pin 3) high. This high turns on Ql which in turn switches on the relay and closes the relay contacts. Because the relay contacts are wired in parallel with the rear wiper switch, power is now applied to the wiper motor. Capacitor Cl now charges via Rl towards the positive supply rail (Vee). After about 2.4 seconds, the voltage across Cl reaches 2/3 Vee (ie, 2/3 of the supply rail) and this switches pin 3 low again and turns off the relay. At the same time, the internal transistor in ICl switches on and discharges Cl so that the timer is ready for the next cycle. +12V FROM IGNITION SWITCH I 01 1N4002 PARTS LIST TO EXISTING REAR WIPER SWITCH 10!l v--- R1 100k 15k mJ 100 16VW 1W c- 4 0.1 + IC1 555 - B WIPEI S1 C1 22 16VW EOc VIEWED FROM BELOW + - TO CHASSIS SINGLE WIPE FOR AUTOMOTIVE REAR SCREEN WIPER Fig.1: the circuit uses a 555 timer IC which is wired for monostable operation. When the wipe switch (S1) is pressed, pin 3 goes high & turns on Ql & the relay to activate the wiper. Timing capacitor Cl then charges via Rl and, when it reaches 2/3 of the supply voltage, the relay turns off again. The 2.4 second monostable period will be quite sufficient to pulse the rear screen wiper to give one or two wipes, depending on the speed of the wiper. At the end of the monostable period (ie, when the relay contacts open), the wiper will auto-park in the conventional manner. The 15kQ resistor pulls pin 2 of ICl high and thus disables the timer circuit when Sl is open. The parallel 0. lµF capacitor is included to prevent noise from triggering the 555, while DZ protects Ql by quenching the back EMF that is generated when the relay turns off. Power for the circuit is derived from the car battery via the ignition switch. Dl and its associated lOQ resistor and lO0µF capacitor provide supply decoupling to prevent ICl from false triggering on voltage transients, while zener diode ZDl protects ICl against any high voltage spikes that might be present on the supply line. As a further precaution against false triggering, the relay is separately powered from the 12V supply to isolate it from the supply to ICl. Construction There's nothing at all complicated about the construction. All the parts (including the relay) are mounted on a small PC board coded SC 05211901 and measuring just 78 x 23mm. This in turn slots into a small plastic zippy box to give a compact arrangement that can be hidden out of sight under the dashboard. Note that the case specified is the Dick Smith Electronics HL-2855 , since this is the one that contains the internal mounting slots. Alternatively, you could use a case from one of the other retailers and simply wedge the board in position using foam rubber. Before installing any parts on the board, first check that it slides neatly into the case and that the lid can be fitted. If you strike problems here, file the edges of the board carefully until you do get a neat fit. This done, fit PC stakes to the five external wir- 1 plastic case, 28 x 54 x 83mm (DSE H-2855) 1 PC board, code SC05211901 , 23 x 78mm 1 DPDT 12V PCB-mounting relay 1 momentary contact push-on switch 7 PC stakes 2 rubber grommets Semiconductors 1 555 timer IC (IC1) 1 BC337 NPN transistor (01) 2 1N4002 1A diodes (D1 ,D2) 1 16V 1W zener diode (ZD1) Capacitors 1 100µF 16VW PC electrolytic 1 22µF 16VW PC electrolytic 1 0.1µF metallised polyester 1 .01 µF metallised polyester Resistors (0.25W, 5%) 1 100kQ 1 15kQ 1 1kn 1 10n Miscellaneous Solder, hookup wire, etc. ing points (see Fig.2). Refer to Fig.2 when mounting the parts on the PCB. Install all the low profile parts first and push them down onto the board as far as they will go before soldering their leads. Be sure to orient the polarised parts correctly. These include the IC, transistor, diodes and electrolytic capacitors. The resistor values can all be checked using a digital multimeter before installing them into circuit. Alternatively, refer to Table 1 for the colour codes. SC05211901 Fig.3: here is a full-size artwork for the PC board. +12V FROM IGNITION SWITCH S1 Fig.2 (left): you can install the parts on the PC board in any order, although it's best to leave the relay until last. Use automotive connectors to terminate the external wiring leads. DECEMBER1990 55 the case to accept rubber grommets (see photo). These two holes accept the external wiring leads. Testing The PC board is designed to slot neatly into a small plastic zippy case as shown here. Alternatively, you could use a case without slots & secure the board using foam rubber. Use rubber grommets at the wiring exit points. To test the unit, first connect the external wiring leads and temporarily wire in the pushbutton switch (S1). Now apply power to the circuit and check that the relay switches on for about 2.4 seconds when the switch is pressed (note: the relay will remain on if the switch is held down). If you strike problems, switch off immediately and carefully check the wiring. Does pin 3 of IC1 go high (ie, to +12V) when S1 is pressed? If not, the 555 circuit isn't working correctly. If pin 3 does go high but the relay doesn't turn on, check the circuit around Q1. In particular, check the back of the board carefully for shorts or missed solder joints. Most project problems are caused by faulty soldering. Installation Be sure to disconnect the battery before installing the wiper controller in the vehicle. The wipe switch can be mounted at any convenient point on the dashboard. Finally, install the relay on the board. The relay used in the prototype was a DSE P-8012 but equivalent relays from other retailers will do the job just as well (eg, Jaycar Cat. SY-4052; Altronics Cat. S-4190). Push the relay right down onto the board before soldering the leads. Once the board has been completed, drill a couple of holes in the side of Assuming everything checks out OK, the unit can now be installed in the vehicle. Be sure to disconnect the battery before connecting the wiring to prevent short circuits. Also, make sure that the +12V supply from the ignition switch is derived from the fused side of the fuse box. The ground lead can be connected to a suitable chassis location using a self-tapping screw and solder lug. The leads to the existing rear wiper switch can either be soldered directly to the switch lugs or spliced to the existing leads using automotive crimp connectors. Be sure to install the wiring in a professional manner and cover any exposed connections with insulation tape. Finally, re-connect the battery and check that the circuit operates the wiper correctly. If you want to increase the number of wipes, just increase the value of Cl. Similarly, reduce the value of Cl if you want to reduce the number of wipes. ~ TABLE 1: RESISTOR COLOUR CODES 0 0 0 0 0 56 No Value 4-Band Code (5%) 5-Band Code (1%) 1 100kO 15kO 1kO 100 brown brown brown brown brown black black orange gold brown green black red gold brown black black brown gold brown black black gold gold 1 SILICON CHIP black yellow gold green orange gold black red gold black black gold I I I I I ORDER FORM 1 USE THIS FORM FOR ALL YOUR SILICON CHIP ORDERS SUBSCRIPTION: Q Q RATES: NEW SUBSCRIPTION: Month To Start_ _ _ _ _ _ __ (PLEASE TICK ONE) 2 YEARS (24 ISSUES) 1 YEAR (12 ISSUES) RENEWAL: Sub No., _ _ _ _ _ _ Start In,_ _ _ _ __ Australia Australia With Binder NZ & PNG (Airmail) Overseas Surface Mail Overseas Airmail □$A84 □$A1O5 □$A13O □$A13O □$A24O □$A4 2 □$A53 □$A65 □$A62 □$A1 2O QGIFT SUBSCRIPTION : Month To Star.__ _ _ _ _ __ . GIFT SUBSCRIPTION DETAILS ~ Mr/Mrs/Ms: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ a n Address: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ 0 SPORTS SHIRT -4 Please send me, _ _ _ _ _ Sports Shirt(s) <at>$A24.95 l z ; .,. _ _ _ _ _ _ _ _ _ Postcode,_ _ _ _ _ _ _ __ 0 :I SLOPPY JOE ~ Yes! Please send me,_ _ _ SILICON CHIP binder(s) at $A14.95 each C Cl 0 (including postage) TOTAL$_ _ _ _ _ _ _ _ _ _ _ __ z .:j (Overseas Orders add $A3 each for postage) •i BACK ISSUES: a ISSUE including postage (NZ add $A3) Size :. _ _ _ _s, M, L, XL, XXL Total$"'----- •=ii SILICON CHIP BINDERS Please send me; _ _ _ _ _ Sloppy Joe{s) <at>$A27.95 including postage (NZ add $A3) Size:_ _ _ _ S, M, L, XL, XXL Total$,....___ __ $A5.00 each (includes postage). Overseas orders add $A 1.00 per issue for postage. YEAR ISSUE YEAR ISSUE YEAR ISSUE YEAR n C -4 -4 z Ill I: g = i Ill TOTAL $A ,Enclosed is my cheque/money order for$, _ _ _ _ _ __ or please debit my Card No. ■. ri. ii VISA L,.I l r . [~ .Lw.l ] Mr/Mrs/Ms: _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Address:_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Card expiry date Signature_ _ _ _ _ _ _ __ _ _ __ _ _ _ _ Postcod e:_ _ _ _ _ _ __ 24 Hour Fax Service Subscription Hotline (02) 979 6503 Send the coupon with your Credit Card Details. 24 Hours, 7 Days a week. Telephone (02) 979 5644 9am-5pm Mon-Fri and quote your Bankcard, Visa Card or MasterCard No. and expiry date. · ~ Detach and Mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 No stamp required in Australia DECEMBER1990 65 VINTAGE RADIO By JOHN HILL Old radio books & magazines As a vintage radio enthusiast, I have amassed a good collection of old receivers, ancient loudspeakers and a considerable quantity of assorted bits and pieces. But while the basic aim of most collectors would be to collect radio receivers and associated equipment, literature from the early days of radio is also a valuable and collectable item. Old radio books and magazines contain a wealth of knowledge from the past. When dealing with a bygone era, such as valve radio, one needs all the facts and figures that are available and old radio books are crammed full of useful information. In perhaps just 20 or 30 years from now, these old books and magazines will be the only permanent source of information regarding valve technology. All those who knew first hand will have either passed on or forgotten the details. There are surprisingly few people around today who have a sound knowledge of valve technology. Although valves were starting to be phased out only 25-30 years ago, the solid state revolution was so totally overwhelming that, almost overnight, valves became obsolete. Even currently practising technicians who started out when valve television was at its peak would probably now have trouble remembering some of the finer points of valve technology. The accumulated knowledge of 5060 years of valve development has been largely forgotten in a very short period of time. Many of those involved in vintage radio have had no previous electronics experience. They can be doctors, plumbers, office workers, students or whatever. These people have found an interest in early radio and have a pressing need to find out more about it, hence the value they place on old radio books of any kind. In many instances, reading from the past is their only way of finding solutions to the problems they encounter with their hobby today. There is plenty of information around on modern electronics but very little on the valve era. The only way one can get onto old electronics magazines and valve radio books, in particular, is to look and keep looking until they are found. The Sunday morning "trash and treasure" market is one such place to find old pre-loved books. Likewise with secondhand dealers and book exchanges. Ask and keep looking! Scrounging takes time but it can be very exciting when an interesting book is found. Valve specifications Valve specification manuals are about the most valuable old books the vintage radio collector can have. In fact, they can be considered essential for the vintage radio repairman as they contain such vital information as operating voltages. 66 SILICON CHIP One of the most valuable books is a valve specification manual. Without a valve manual, the vintage radio repairer is working in the dark with one hand tied behind his back. If he cannot determine which valve socket connection is what, then he will be greatly disadvantaged as far as any checking or repair work is concerned. A valve manual should be high on one's list of book priorities for it contains much useful information. These old radio and television theory books were bought for $10. Written in technical jargon, they are fairly difficult for the lay person to understand. Valve equivalents manuals are also very handy to have. These useful books list valves of similar characteristics, many of which are completely interchangeable without having to modify the circuit. They can save you both time & expense. Australian service manuals contain the circuits used by Australian manufacturers for a particular year. The manual shown here contains 1938 circuits. If only there were more such manuals around today. Even better is to have several valve manuals from different valve manufacturers. The reason for suggesting this is simple: European type valves are not listed in the American RCA valve catalog but they are all there in the Philips manual. Radio was a compelling hobby from the early 1920s through to the postwar period until about the television era. The radio magazines of those days presented an almost endless array of radio and audio projects for both the beginner and the more experienced alike. Old radio magazines, especially those directed at the hobbyist, contain a great deal of useful know-how about valve radio. Many of these magazines, especially "Radio and Hobbies", can still be found today and they always supply informative reading. The television era began in Australia at the time of the 1956 Olympic Games. From about that time on, radio began to take a back seat as far as electronics magazines were concerned and has remained there ever since. Only on odd occasions is there an article or project that is radio oriented. Developments in modern solid state electronics over the past 20 years or so and, in particular, the intense interest in personal computers and other state of the art "high-tech" pieces of equipment, have generally made radio a fairly tame and uninteresting subject. Just about gone are the days when enthusiasts built their own receivers and audio systems. Likewise with the true radio amateur who constructed his own transmitter and receiver. Today's attitude seems to be: "if it can't be bought, it can't be made". But we're getting off the track a bit here - back to the books! As mentioned earlier, if you are looking for simple,, basic, understandable information relating to valve radio, then search out old radio books and magazines from the 1920s through to the mid 1950s. These publications are crammed full of all the things the up and coming vintage radio enthusiast is wanting to know about. Of special interest in some old magazines is the questions and answers section, where readers queries are answered. Also of great interest is the never ending saga of the "Serviceman Who Tells". Much can be learnt from his .stories. Early radio magazines were considered so valuable that some enthusiasts had them bound and covered. I was fortunate recently to obtain a bound set of "Radio and Hobbies" magazines, ranging from 1939 to 1947. These were kindly given to me by a lady who thought that I might have some use for them. DECEMBER 1990 67 which goes to show that old George had an interest in radio quite some time before broadcasting began here in Australia. Somewhere around 1924, George built himself a 5-valve receiver (which is now part of my collection) and he was one of the first in the Nhill district of Victoria to have a radio. Hidden costs More dusty old books on the subject of early radio. There is something to be learnt in each one. Keep your eyes out for old books - a vintage radio library is part of the hobby. Many hard cover books published in the 1920s were not far removed from the radio magazine format. Some of these publications were practical books on building and repairing the radios of the day. Most of these books were written for those who knew absolutely nothing about radio and after reading them for a while, one feels as though they were prepared for kindergarten children, not adults thirsting for scientific knowledge. Some of these early radio publications appear fairly amateurish in their presentation of a technical subject but it is all very well to be knowledgeabJe some 60 years further down the track. Only a few months ago, I had the opportunity of sorting through some old radio "junk" which included half a dozen or so old books. The late owner of the books was thoughtful enough to write his name and the purchase date on each one, which is a great help if there is no publication date inside. One of these books was dated 1919 Only old radio books will reveal what early radio was all about, although terms such as "note magnifier" often leave the reader a little puzzled. 68 SILICON CHIP Another of those old books is titled "Boys Book of Wireless" and it contains some very detailed instructions on how to build a crystal set for the extraordinary low cost of three shillings and sixpence. The humorous part about this incredibly low-priced wireless receiver was all of the additional extras that the author, for some reason or other, did not consider to be part of the overall expense of setting up such a receiver. Yet he warned not to settle for less than what he suggested. These incidental extras were: 15 shillings for headphones, 10 shillings for a listener's licence, 100 feet of aerial wire, a substantial 2-piece wooden aerial mast with suitable guy wires and insulators, a combined lightning arrestor and knife switch, plus a 3ft square sheet of copper deeply buried in the ground for an earth. All up, it probably came to more This back page magazine advertisement from 1949 helped the author to accurately date three of his vintage radios. Vintage Radio Service Tips Mullard Models 61 & 69 Weak reception and loss of sensitivity in these models can often be traced to the ½W 1OOk.Q resistor in the screen of the IF stage and the ½W 150kQ resistor in the converter screen. Either or both of these resistors frequently go high in resistance. Replace with 1W resistors. The symptoms and causes referred to above frequently occur in other makes of radio using high value screen resistors. If you don't have access to a circuit diagram with valve voltages, a check of the resistors using a good quality multimeter should suffice. For the sake of an extra few cents, always use 1W resistors when replacing ½W types that go high. Peter Pan Model BKL There are still quite a few of these mantel sets to be found and they like a couple of week's wages rather than the claimed three and sixpence. Likewise with some of the advertisements for early radios. People were encouraged to buy budget priced radios with items such as valves, batteries and loudspeakers being optional extras. Talk about hidden costs! Prices and wages in the 1920s are things that we cannot comprehend today. I remember my mother making the comment just after World War 2 that the pound didn't buy much any more. It bought even less in a 1920s radio shop. Radios and radio parts and accessories were very expensive, as old books and magazines so readily reveal. (I wonder what Mum thinks of the dollar these days?) look quite attractive when restored . Oscillator stability can be improved by installing a 50pF mica capacitor in series with the 6A8 oscillator grid. The capacitor should be connected between the grid end of the oscillator coil and the oscillator grid leak. Faulty Tracking If stations are received above or below their dial markings, the high frequencies being OK but the low frequencies being out and sensitivity poor, check the oscillator tracking capacitor. The readings will be high or low depending on whether the capacitor is open or short-circuited or whether it has reduced or increased in capacity. Vintage Radio Service Tips are supplied by Resurrection Radio, 51 Chapel St, Windsor, Vic 3181. Phone (03) 529 5639. fact , a valve suitable for audio work. This term was only in vogue for a short period and seems to be peculiar to early English publications. One set of books that are well worth having if you can obtain them are the "Australian Radio Service Manuals". These books were published at yearly intervals and contained all the circuits that Australian manufacturers used during the previous year. Any book with circuits in it is a very handy thing to have. I have only one of these service Early terminology When reading these old books, some of the early terminology takes a bit of coming to grips with, too. A couple of mid 1920s books frequently mention the term "note magnifier". There are note magnifier valves and note magnifier stages. Could this be an early version of a guitar amplifier? No - but close! It would appear that the term note magnifier describes the audio section of a radio. A note magnifier valve was, in Radio books from the 1920s and 1930s are usually written in simple terms with numerous illustrations and explanations. They are ideal for those just starting out in vintage radio. Resurrection Radio Vintage Wireless Specialists Re airs - Restoration - Sales Our skil ed technicians offer QUALITY repairs and restoration. We also have a large stock of Bakelite and Timber radios fully restored and for SALE. Parts are available for the enthusiasts including over 900 valve types, high voltage capacitors, transformers, dial gliisses, knobs, grille cloth etc. Circuit diagrams for most Australian makes and models. Send SAE for our catalogue. WANTED - Valves, Radios, etc. purchased for CASH Call in to our Showroom at: 51 Chapel Street, Windsor,Vic 3181 PO Box 1116 Telephone: (03) 529 5639 manuals and it covers 1938 circuits. It has not only helped out with the right circuit from time to time but has also established an accurate manufacturing date for a couple of recflivers. If the model number matches up with a circuit in the book, then it's not hard to guess the year in which the set was made. Books on radio theory are also worth collecting and delving into. These can help solve the mysteries of automatic gain control, grid bias, high tension supplies and numerous other aspects of valve radio. However, some radio theory books can be heavy going and obviously weren't intended for the layman. Yes, there is a lot of interesting reading to be found in old radio books. Every vintage radio collector should also have his vintage radio library for not only do these books look back into early electronic h istory but there is so much to be learnt from them. Old radio books also give an insight into the advances electronics has made since the turn of the century. The only word to describe that progress is "incredible"! DECEMBER1990 69 Versatile 4-digit coIDhination lock Here's a 4-digit lock that will prove useful in many security applications. It's easy to build and can be quickly programmed by setting four on-board DIP switches. By GARY IOPPOLO Keypad locks are often far more convenient to use for accessing secured areas or systems than conventional keys. They can provide better security too and offer far greater flexibility if the security system needs changing. We all know about the disadvantages of conventional keys. They are cumbersome to carry around, can be 70 SILICON CHIP easily lost and are easily copied. By contrast, this electronic lock only requires the user to remember a 4digit code. It's based on three lowcost ICs and is bound to prove useful in applications such as burglar alarms, security doors and gates, computer systems, ignition killers and a host of other areas. So let's get on with it and take a look at some of the features of this versatile circuit. The design considerations were straightforward: the circuit had to be low in cost, yet extremely versatile; the PC board was to fit inside a standard GPO (general purpose outlet) wall box; and the code was to be entered via a keypad. The keypad is a standard 3 x 4 decimal keypad as used in some telephone diallers. A 4-digit code is used to .unlock the the unit and all the digits from 0-9 plus the"*" key can be used to make up the combination. This gives you 14,641 possible combi11ations, which should be more than enough for most applications. The remaining key oa the keypad, the "#" key, is used to reset the circuit if you make a mistake entering the code. The 4-digit code is set using four PARTS LIST 1 decimal keypad (Altronics Cat. S-5380) 1 PC board, Altronics Cat K1925 4 4-way DIP switches 8 PC pins 1 9V battery snap 1 7-pin male transit connector 1 7-pin female transit connector 8 AAA 1.2V nicad cells or one 9V nicad battery (not included in kit; see text) 1 2MQ miniature vertical trimpot The keypad of the 4-digit combination lock is mounted on a blank mains wall plate, while the electronic circuitry & backup battery fits inside the wall box. The 4-digit code is programmed in by setting four 4-way DIP switches. on-board 4-way DIP switches. Each switch is used to set a binary code and this code is compared to the code from the keypad decoder. Because DIP switches are used, rather than wire links, the code can be easily changed at any time. The DIP switches also guarantee that the code is retained even if power is removed from the circuit. In addition, you can wire the circuit for momentary or latched operation and there is provision for battery back-up so that you're not locked out during a mains failure. A single wire link is used to determine whether the circuit operates in latched or momentary output mode. The time interval for momentary output is adjustable from about 0.5 to 20 seconds by means of an on-board trimpot. In latched mode, the output remains on (unlocked) after the correct code is entered until the # (reset) key is pressed. The output of the combination lock is an open-collector transistor that can switch load currents of up to 0.6A and voltages up to 30V. When the transistor turns on, it also lights a LED to indicate the unlocked condition. This LED is located on the front panel, to the lower left of the keypad (see photo) No tricks There's no way that you can trick this keypad. For starters, the circuit is designed to automatically reset if any key is pressed out of sequence. Also, only one key can be registered at any one time, so you can't fool the circuit by pushing all keys at once. Keys that are pressed too quickly in sequence will also be ignored. To register, each key must be held down for longer than the debounce period. Finally, the 4-digit code must be entered within a 5-second period, otherwise the lock will reset regardless as to whether the correct code was entered or not. Backup power Any mains-derived DC power supply capable of delivering 11-30V DC can be used to power the circuit, and there is provision to recharge a nicad back-up battery. This backup battery can consist of either a single 9V nicad battery or 8 AAA (1.ZV) nicad batteries. The current consumption in standby mode is about 400µA which means that AAA 180mAh nicads will Semiconductors 1 4017 decade counter (IC1) 1 7 4C922 keypad decoder (IC2) 1 4030 quad XOR gate (IC3) 2 BD681 Darlington transistors (01 ,03) 1 BC549 NPN transistor (02) 3 1N4002 diodes (D1 ,D2,D30) 33 1N914 diodes (D3-D29, D31-D36) 1 11 V 400mW zener diode (ZD1) 1 6.8V 400mW zener diode (ZD2) 1 red LED (LED 1) Capacitors 1 47µF 35VW PC electrolytic 1 47µF 16VW PC electrolytic 3 10µF 19VW PC electrolytics 1 4.7µF 1'6VW PC electrolytic 1 1µF 16VW electrolytic 1 0.1 µF monolithic 1 .01 µF monolithic Resistors (0.25W, 5%) 1 10MQ 3 10kn 10 1MQ 1 3.3kQ 2 100kQ 1 4700 1 47kQ 1 R1 (see text) Miscellaneous Hookup wire, tinned copper wire for links, solder, etc. last about 18 days from full charge. We'll talk more about backup batteries later on, in the constructional notes. How it works Take a look now at the circuit of Fig.1. It can be broken down into four main sections: a power supply, the keypad and its associated decoder (ICZ), a sequencer (ICl), and a comparator stage (IC3 & D31-34). Each DECEMBER 1990 71 Although IC sockets were used on the prototype, these can be considered . optional. The keyboard is affixed to the mounting plate by gluing the corners with 5-minute Araldite. section will be discussed in quite a bit of detail, as this detail will be beneficial if it comes to troubleshooting. We'll start with the power supply which is at the top of the diagram. A regulated power supply with a low standby current consumption is necessary for this circuit. This meant that 3-terminal regulators such as the 7805 were out of the question, since these have a standby current of around 5mA - too much for a battery backup supply. It was time to try a transistor regulator circuit but it was soon found that a couple milliamps were needed for the transistor base current and its associated zener diode in order to obtain an adequate output current. This problem was solved by using a high gain Darlington transistor (Ql) . The Darlington used is a BD681 and this operates in conjunction with ZD2 which sets the regulator output to about 6V. The final circuit consumes only about 200µA with no load, making it ideal for use with a back-up battery. It will also regulate any DC input voltage between 11-30V. Normally, the backup batteries are trickle charged from the main supply rail via Rl. The value of this resistor is dependent on the supply voltage 72 SILICON CHIP and can be obtained from Table 1. It sets the charging current to somewhere between 1.5mA and 2.5mA while ever the main supply is active. If the main supply fails for any reason, D2 becomes forward biased and the backup batteries supply power to the circuit via the regulator. ZDl prevents the batteries from overcharging, while Dl prevents the batteries from discharging back through the supply if the supply voltage drops to a low value. It also provides reverse polarity protection for the circuit. Keypad decoding A single integrated circuit (IC2) is used to provide the keypad decoding logic. IC2 is a 74C922 hex keypad decoder from National Semiconductor. It is designed to scan a 4 x 4 (4 columns, 4 rows) keypad and output a binary value on. pins 14-17 which corresponds to the value of the keypress. In this design, we are using a 3 x 4 keypad but this is no problem since we just ignore one of the column outputs which the 74C922 normally uses to scan the keypad. In this case, the Xl output at pin 11 is not used. As a result, the binary value at the ABCD outputs (pins 17-14) does not match the value of the keypress but in this circuit that's of no consequence. All you have to do is to set each DIP switch as shown in Table 2 to obtain the required key value. A "1" in the binary code means that the corresponding switch is on and vice versa. Note that each DIP switch has four switch settings, with the leftmost switch corresponding to the most significant bit. Only a few other components are used in the keypad decoder circuitry. These include a 4. 7µF debounce capacitor on pin 6 and a lµF oscillator capacitor on pin 5. These set the debounce period to about 50ms and the keyscan oscillator frequency to about 60Hz. The only other connections to IC2 are at the Data Available (D/ A) output (pin 12) and the Output Enable (OE) input (pin 13). Both these connections are used to interface the 74C922 to the sequencer circuitry. The DI A output goes high during a keypress and returns to the low state when the key is released. The OE input enables the outputs when low and returns them to a high impedance state when high. Sequencer The sequencer circuit is based on a very busy 4017 CMOS decade counter. It is reponsible for driving the DIP switches, triggering the output transistor (Q3), maintaining the code sequence and responding to various reset conditions. Briefly, this part of the circuit operates as follows. The Q0-Q4 outputs of ICl drive DIP switches Sl-S4 respectively and the outputs of these switches are applied to one set of inputs of XOR (exclusive-OR) gates IC3a-lC3d via diode OR gates D6-D21. Fig.1: the circuit uses keypad decoder • IC2 to scan the decimal keypad. When a key is pressed, this IC outputs a 4-bit binary code on pins 17-14 (A-D) & also clocks decade counter ICl which drives the DIP switches. XOR gates IC3a-d then compare the 4-bit code from IC2 with the corresponding DIP switch setting and generate a reset pulse if the wrong key is pressed. If no reset pulse is generated, Q4 of ICl goes high on the fourth keypress and turns on transistor Q3 to switch the load. PRE-REGULATED SUPPLY 01 BD681 + ~ - - + - - - ---1r---.-+6V + 10 16VWJ 10k VIN 11-30V EXT. SUPPLY +5-30V 47 t ··-r .,. .,. ':" +6V 100k 4.7 + 16VW! 5.6k .,. 1N91 4 10 I + 16VW! t +6V 15 10M o.1I .,. 04 10 RST IC1 4017 .,. 03 +6V 13 EN CLK 4 1M . .,. +V 1M 1M . .,. D24 1N91 4 + 47 16VW: D29 1N91 4 .,. 1 DE 12 D/A 1 Y1 +6V 1M .01J B 18 +6V D26 D27 4x1N914 D 14 3 Y3 IC2 74C922 C 15 B 6 4 7 17 Y4 X4 DSC KB 6 ·~ t 6V\\' ~ ECB 1 16VW 1M 1M .,. 4.7 B X3 10 X2 5 eOc VIEWED FROM BELOW .,. Y2 D25 1M .,. 1M .,. .,. 4-DIGIT COMBINATION LOCK .~. DECEMBER 1990 73 0/C OUTPUT :LED1 ~~!--"-GND BATTERY+ VIN +11-30V ~ :.,,..--GND .'>.~ ""-Mif--PRE-REGULATED SUPPLY Fig.2: to save space, all the resistors on the PC board are mounted end-on, with the eight lMQ resistors made into two 4-way single in-line packages (see Fig.3). Refer to Fig.1 for the pinout details when mounting transistors Ql, Q2 & Q3 on the board. As shown here, the DIP switches are set for a code of 1879 but you should choose your own code. The other inputs of the XOR gates are connected to the binary output lines from the keypad decoder, IC2. Thus, each time a key is pressed, the XOR gates compare the binary output from IC2 with the corresponding DIP switch setting. If the values match, the XOR gate outputs all remain low. However, if the values don't match (ie, a wrong key is pressed), one or more of the XOR gate outputs goes high. The XOR outputs are then OR'ed using diodes D31-34. Let's now look at what happens in a bit more detail. Since Q0 is connected to the Output Enable on IC2, the latter's output lines (pins 17-14) will all be in the high impedance state during standby mode. These lines are pulled low by four lMQ resistors and thus place a logic 0 on pins 2, 6, 8 & 12 of the XOR gates (IC3a-d). At the same time, Q1Q9 ofICl are also all low and thus the DIP switch outputs will all be low. So, in standby mode, all inputs to the XOR gates are low and thus their outputs are also low. This means that D5 will be forward biased and so D36's anode will be held low. Now let's take a look what happens when a key is pressed. When this happens, the DI A output of IC2 goes high and clocks ICl. Ql of ICl now switches high and this high is applied to the first DIP switch (Sl). Depending on the setting of the DIP switch, this will apply a high or low to the remaining inputs of the XOR gates via diodes D6-D9. For example, let's say that Sl is set to 0101. This means that pins 6 & 8 of Sl will switch high when Ql of ICl goes high and so pin 5 of IC3b & pin 9 of IC3c will be pulled high. If this binary pattern matches the setting of the first DIP switch, each XOR gate will have the same logic level on its two inputs. Thus, the XOR gate outputs will remain low and no reset pulse will be generated. If the next key in the seqvence is now pressed, IC2's DIA output goes high again and clocks ICl to Q2. This output drives DIP switch S2 and its setting is again compared with the binary output from IC2. If all four keys are pressed in the correct sequence, Q4 of ICl switches high and turns on the Darlington output transistor, Q3. Q3 is used to switch the load (eg, a relay or solenoid-operated door strike). LED 1 provides visual indication of the unlocked condition (ie, it lights when Q3 is on), while D30 quenches any back EMF which may be generated by inductive loads. Wrong key Let's now consider the situation if we hit a wrong key during the code entry. When this happens, the output code from IC2 will no longer match CAPACITOR CODES o 0 0 Value 0.1µF .01µF IEC Code EIA Code 100n 10n 104 103 RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 74 No. Value 4-Band Code (5%) 5-Band Code (1%) 1 10 2 1 3 10MQ 1MQ 100kQ 47kQ 10kQ 3.3kQ 470Q brown black blue gola brown black green gold brown black yellow gold yellow violet orange gold brown black orange gold orange orange red gold yellow violet brown gold brown black black green brown brown black black yellow brown brown black black orange brown yellow violet black red brown brown black black red brown orange orange black brown brown yellow violet black black brown 1 SILICON CHIP and no reset pulse will be generated. However, if the output code goes to 1111 (ie, the # key is pressed), D29's anode will be pulled high by the lMO resistor and a reset pulse will be applied to pin 15 of ICl. Because the "#" key is used as a reset key, it cannot be used as part of the combination. All the other keys, including the "*" key, can be used, however. Code entry period , This close-up view shows one of the 4 x 1MQ SIP resistor assemblies (see also Fig.3). The other SIP assembly can be seen adjacent to IC2 at the back of the PC board. Note the 4-way DIP switches which are used to set the code. the corresponding DIP switch setting and so different logic levels will be applied to the inputs of one or more of the XOR gates. The outputs of these XOR gates will thus switch high and D5 will cease conducting. The reset line is now pulled high via the associated 100kO resistor and diode D36. This high resets ICl, so that we're now back where we started from, with Q0 high. Momentary operation VRl, D35 and the associated 47kO resistor and l0µF capacitor provide the time-out period when the circuit is wired for momentary operation. When the output is enabled (ie, the correct code has been entered), ICl's Q4 output charges the toµF capacitor via the 47kO resistor and VRl. Eventually (after one time constant), the voltage on the capacitor pulls the reset line high via D3 and this resets IC1, thus switching off the output transistor. VR1 allows this time period to be set anywhere between 0.5 and 20 seconds. For latched operation, the toµF capacitor is simply shorted out so that it cannot charge by installing a wire link (shown dotted on Fig.1) across its terminals. The 0. lµF capacitor on pin 15 of IC1 is used to decouple the reset line to prevent false triggering. As a further precaution, when the output is enabled, the clock enable (pin 13) input of IC1 is taken high after a small delay produced by the 5.6k0 resistor and 4.7µF capacitor on the Q4 output. This prevents further clocking of ICl until it has been reset and prevents the output transistor (Q3) from switching on if an incorrect entry is made on the fourth keypress. Also, when Darlington transistor Q3 turns on, it disables the comparator output by pulling the anode of D36 low via D4 to prevent any reset pulses from being generated by additional key presses. The only way to reset the unit when the output is enabled is to press the "#" key, or to wait for it to time out if it is in momentary mode. The "#" key is detected by ANDing the four data lines from IC2, since the output code when this key is pressed is 1111. This AND gate function is performed by diodes D25-28 and the associated lMO resistor. Normally, at least one of the output lines from IC2 will be low and so the anode of D29 will be pulled low by one or more of the diodes in the AND gate Table 1: Charging Resistor Volts (VtN) 12-15 15-18 18-24 24-30 R1 Value 2.2kO 3.9kO 6.8kO 10k0 Transistor Q2 and its associated components set the code entry period (ie, the period of time during which the code must be entered on the keypad). In standby or output enabled mode, Q0 or Q4 of ICl is high, and so transistor Q2 is turned on via D22 or D23. While ever Q2 is on, the 47µF capacitor across its output is discharged and D24 is reverse biased. However, while the user is part way through the code, Q0 and Q4 of ICl are both low, transistor Q2 is off and the 47µF capacitor charges towards the supply rail via a 100kO resistor. If the code in not entered within the period set by this RC time constant (about 5 seconds), the voltage across the capacitor will eventually go high enough to reset ICl. So you've got just 5 seconds to enter the code. If an incorrect number is pressed during code entry, Q0 ofICl switches high and Q2 turns on and discharges the 47µF capacitor. This ensures that you get the full 5 seconds to enter the code on each attempt. Construction The PC board for this project is fairly compact and consists of many fine tracks. Before starting assembly, it's a good idea to check the board for any shorts or discontinuites in the trackwork. It might also pay to check the hole sizes for the DIP switches and the PC pins and enlarge them if necessary. You will need a fine, clean soldering tip for this job and plenty of light, as there is not a great deal of space to work in on the board. Also, try not to spend too long soldering a joint, as these fine tracks have a tendency to lift if they get too hot. Be especially careful with solder bridges and splashes as well, as it's not hard to short tracks on this board. Fig.2 shows the parts layout on the PC board. Begin the assembly by mounting all the diodes and wire DECEMBER1990 75 box, it's best to mount the PC pins on the copper side of the board. Back-up battery If you mount the keypad on a mains wall plate as shown here, the PC board is best attached via matching 7-pin transit connectors. If the keypad is mounted away from the board, the two can be wired together using ribbon cable. If you intend using the unit to control a door strike, you will have to make up a suitable battery pack. Unfortunately, you cannot use a l00mAh 9V nicad battery here as it will have insufficient current capacity to ensure reliable operation. The best approach is to make a battery pack of 8 x AAA nicad cells. These have a current rating of about 180mAh (nearly twice that of the 9V nicads), so they will operate door strikes easily. They should all be connected in series by soldering leads to their positive and negative terminals, and then taped up so that they cannot short against the wall box or to the underside of the PC board. Be careful not to get the batteries too hot during soldering and don't spend too long on any one joint. Check the completed assembly by measuring the output voltage. You should get a reading of about 9.6V. 4R Testing "' N Fig.3: here's how to make the two 4 x 1MQ resistor SIP assemblies. Begin each assembly by soldering the four resistors to the PCB. Fig.4 (right) shows the cutout details for the blank wall plate. 3 DIA. 57 N "' 24 DIMENSIONS IN MILLIMETRES links. If you intend using IC sockets, mount these now as well. Now it's time to make some home-made resistor SIPs (Single Inline Packages). If you haven't already noticed, all the resistors on this PC board are mounted vertically. This was done to save space and thus give a more compact board. You may also have noticed that two groups of 4 x lMQ pull-down resistors all share a common earth, so each group is made into a 4-resistor SIP pack. Fig.3 shows how this is done. It's best to start off by soldering one end of each resistor in the SIP arrangement to the PC board. The top lead of the resistor furthest from the earth pad is then bent across the other three resistors as shown in Fig.3, and 76 SILICON CHIP then down to the earth pad. Finally, the top leads from the other resistors are all soldered to this earth lead. The rest ofthe resistors can now be installed, followed by the trimpot, capacitors and transistors. Make sure you get all polarities correct on the capacitors and transistors as any mistakes here could fuse the tracks on this board. The 47µF capacitor adjacent to QZ is the one rated at 16VW. The other 47µF capacitor must be rated at 35VW and goes next to the pre-regulated output terminal see Fig.2). You can now complete the PC board assembly by installing the multi-pin connector, DIP switches and PC pins at all external wiring points. If you intend mounting the unit in a wall Now that the board is completed and the battery back-up organised, we can test the circuit for correct operation. Connect the keypad to the PC board temporarily for the moment via a length of ribbon cable, as this makes testing and troubleshooting a bit easier (just tack the ribbon cable to the solder side of each PC board). With that done, let's give it a work out. Begin by connecting an appropriate DC supply to the main input terminals or just connect a 9V battery to the back-up battery terminals. This done, check the regulator output - it should be around 6V. If not switch off immediately and find the fault. If it's OK, check the supply pins on all the ICs to make sure they are getting power. Before we proceed any further, you will need to set up a combination. This is done via the DIP switches and Table 2 shows the switch settings for each key value. Before setting the switches, orient the board so that it faces towards you with the DIP switches along the bottom. The leftmost DIP switch represents the first digit of the code and so on to the right. Remember that you can use any key on the keypad except the"#" key, as this is the reset key. the "#" key during the time-out period and check that the unit resets. Finally, check that the circuit is reset by an invalid key entry (ie, pin 3 of ICl switches high) . OK, you now have a working combination lock, so let's put it to work. Installation The eight AAA nicad batteries are first soldered in series and then wrapped in plastic insulation tape. They sit in the bottom of the wall box, below the PC board, and are connected via flying leads to the PC stakes. Initially, when first switched on, the unit will be in an unknown state but after about 5 seconds will be reset by the time-out circuit. You may also reset it during this time by pushing the"#" key. After resetting, check that pin 3 of ICl is high (ie, at +6V) and that pins 14-17 of IC2 are all low. If everything is OK, enter the first digit of the code on the keypad and check that pin 2 of ICl is now high. Wait for 5 seconds and check that pin 3 switches high again. If so, you can assume that the entry period circuitry is working. If not, check transistor Q2 and its associated components. Made it this far? Now try entering the complete 4-digit code correctly. As soon as the fourth digit is entered, the LED should light. Assuming that the unit is wired for momentary output (link open), the LED should then extinguish after the time-out period set by VRl. Verify this and then enter the code correctly once again. Push any key but the "#" key and check that the LED remains on. Now press Table 2: DIP Switch Settings Key DIP Value 1 2 3 4 5 6 7 8 9 0001 0010 0011 0101 0110 0111 1001 1010 1011 1101 1110 1111 . 0 # Where to buy the kit A complete kit of parts for this project is available from Altronics Pty Ltd, 174 Roe St, Perth, WA 6000. You can also order by calling toll free on (008) 99 9007 and quoting your credit card number or by mail order from PO Box 8350, Stirling Street Exchange, Perth 6000. Prices are as follows: Kit of parts (Cat. K-1925) .............................................................. $39.95 Door strike (Cat. S-4390) ........................................................... ... $39.95 Blank mains wall plate ... ................................................................. $4.00 Eight AAA 1.2V nicad cells (Cat S-5021) ............................ .......... $28.00 12V DC 300mA plugpack ... ........................................................... $15.95 Note: copyright© of the PC board is retained by Altronics Pty Ltd. Before installing the unit, you first have to choose between momentary or latched operation. For momentary output, just leave the board exactly as shown in Fig.2. For latched operation, either remove the lOµF capacitor immediately adjacent to VRl and replace it with a wire link, or simply bridge its pads on the solder side of the PC board. Remember that if you opt for a latched output, the only way to reset the unit is to press the "#" key. If the load is polarised, connect its negative terminal to Q3's open-collector output terminal and the positive to an external power supply. This external supply can be the pre-regulated output from Dl, the main supply to the keypad, or a completely different external supply. In most cases, you can simply connect the positive of the load to the pre-regulated supply terminal (see Fig.2). This scheme will give you the advantage of battery back-up should the main supply fail. If a totally different external supply is used, it must share a common earth with the keypad circuitry. If you intend using a door strike with the unit, the S-4390 from Altronics is suitable. This is a 12V 400mA unit and is ideal for the ·purpose. Finally, you need to decide how the keypad is to be mounted. You have two choices here: fix the board directly to the keypad or connect it via a length of ribbon cable. If the unit is to be installed in a wallbox, it's best to mount the keypad via a 7pin transit connector (see photo). The recommended wall box is the Clipsal NO157 which measures 95 x 54mm and has a depth of 37mm. Note that other types of wall boxes may not have sufficient depth to accommodate the batteries. Fig.4 shows the dimensions of the cutout for mounting the keypad on a blank mains wall plate. The keypad and LED can be secured to the mounting plate using 5-minute Araldite. DECEMBER1990 77 I ~Sl#td4- EASTER BARGAINS IN DECEMBER! I BOARD SOLUTIONS Pty Ltd J 3C87-33MHz (equiv 80387/33) SIMM Module, 1MB sons SIPP Module, 1MB sons MOTHERBOARDS 10MHz XT, (640K) OK RAM 10MHz XT, (1 MB) OK RAM 31 MHz XT286 OK RAM Baby 286 12MHz OK RAM Baby 286 12MHz OK RAM VLSI Baby 286, 12MHz VLSI OK Neat 286, all-in-one, OK RAM 20MHz 286 OK RAM 16MHz NEAT 286 OK RAM 16MHz 386SX, OK RAM 20MHz 386SX, OK RAM 20MHz 386 NEAT, OK RAM 25MHz 386 NEAT, OK RAM 25MHz 386, 32K Cache, OK Neat 33MHz 386, 32K Cache, OK I M1010 115.00 M1000 149.00 M1020 199.00 M2015 299.00 M2030 449.00 M2020 499.00 M2010 545.00 M2045 545.00 M2040 599.00 M3000 845.00 M3005 895.00 M3002 1645.00 M3004 1795.00 M3010 1995.00 M3020 2395.00 CHIPS 1M RAM Chip - 1OOnS 1M RAM Chip - sons 256K RAM Chip - 1OOnS 256K RAM Chip - sons 4 X 256K RAM Chip, 100nS 4 X 64K RAM Chip, 120nS For VGA card 64K RAM Chip - 120nS NEC V20Chip NEC V20 Chip, 10MHz NEC V30 Chip, 10MHz 80387SX 16MHz Co-Processor 8087-2, 8MHz Co-Processor 2C87-8MHz (equiv 80287/8) 2C87-10MHz (equiv 80287/10) 2C87-12MHz (equiv 80287/12) 2C87-20MHz 3C87-16MHz (equiv 80387/16) 3C87-20MHz (equiv 80387/20) 3C87-25MHz (equiv 80387/25) I 19.95 21.95 6.95 7.95 22.95 29212 29112 29000 29010 29020 29540 29500 29550 29555 29560 29565 29570 29575 29580 9.95 4.95 24.95 39.95 49.95 795.00 275.00 449.00 495.00 549.00 649.00 649.00 749.00 949.00 1099.00 225.00 225.00 INTERN. FLOPPY DISK DRIVES YE-Data 360K YE-Data, 720K/1.44M 03000 drive Plus Frame YE-Data, 1.2MB 05500 03000 03010 05510 NEC 42MB, 28mS 3.5in 08000 plus Frame WO 42MB 28ms + controller Add M'Scribe 85MB 19ms + controller Kalok 20MB 40mS 08000 08010 08020 08030 08100 I 745.00 775.00 795.00 1395.00 399.00 EXTERNAL FLOPPY DISK DRIVES For Amiga 500, 1000, 2000, 3.5in 880K For Amiga 500, 1000, 2000, 5.25in 360/BSOK For Commodore PC1, 5.25in 360/720K 40/80 track For Atari ST series, 3.5in 720K For Atari ST series, 5.25in 360ll20K 40/80 track For Amstrad PC1512/1640, 3.5in 720K For IBM XT, 3.5in 720K XT For IBM AT, 3.5in 1.44MB For IBM XT, 5.25in 360K For IBM AT, 5.25in 1.2MB For TOSHIBA laptop series, 5.25in 360K For TOSHIBA laptop series, 5.25in 1.2MB I 149.00 184.95 199.00 175.00 INTERNAL HARD DISK DRIVES II 29300 29380 29400 29480 29200 29585 29680 29690 I D9500 249.00 09510 299.00 D9520 D9530 299.00 299.00 D9540 299.00 D9550 09560 D9570 09580 D9590 269.00 299.00 329.00 299.00 329.00 D9600 349.00 09610 399.00 MICE & JOYSTICKS Joystick PC/XT/AT 3 Button Serial, Champ & Mat Mouse Mat 34.95 99.95 7.50 J1000 J1030 J1040 MONITORS Monitor, 14in TTL, Amber Monitor, 14in TTL, Green Monitor, 14in TTL, Paper White Monitor, 14in EGA Monitor, 14in VGA 640 x 480 Monitor 14in VGA 1024 x 768 Monitor, 14in Multisync I M9000 M9010 M9020 M9030 M9040 M9060 M~OSO 249 .00 249 .00 249 .00 599.00 749 .00 799.00 899.00 1/0 CARDS 2 Ser. 1 Parallel Games, Parallel & 2 x Serial Chip Set & Cable suit 11040 Multi 1/0 Card XT only Multi 1/0 Card, 2 Ports all 4 drive types supported (XT Only) Parallel Printer Card (XT/AT) Serial PortCard X 1 (XT/AT) Serial PortCard X 2 (XT/AT) 1/0 Plus Card - XT Only Serial/Parallel Card - XT/AT 2 Serial , 2 Parallel, AT Multi-Serial Card, 4P-AT 69.95 74.95 24.95 i1080 i1110 i1041 i1000 129.00 i1010 i1020 i1030 i1040 i1050 i1060 i1070 i1090 164.95 29.95 54.95 64.95 99.00 64.95 84.95 245.00 VIDEO CARDS VGA Card, 800 x 600 (256K) VGA Card, 1024 x 768 (512K) Magic Combo CGA Card EGA Card Mono Hercules Card, 16MHz operation + Parallel Port V1000 V1010 V1020 V1035 199.00 299.00 V1040 89.95 129.00 179.00 DEALERS FOR BUil T-UP SYSTEMS REQUIRED IN ALL AREAS. PHONE OR FAX FOR DETAILS! 2400BPS INT. MODEM BARGAIN You won't believe the price! Hayes Smartmodem compatible internal modem, full or half duplex with auto dial and auto answer ready to plug straight into your PC (half size card) for instant world-wide computer communications. Note: Not Telecom Approved BONUS! FREE COMMUNICATIONS SOFTWARE, FULL 12 MONTHS WARRANTY, Package Includes: * Modem * Two phone leads * Software * Detailed instructions ALL FOR ONLY s295 We've seen similar modems advertised elsewhere on "special" for $399 & more! BOARD SOLUTIONS IS YOUR ONE-STOP PC Others have Chrisbnas "sales" about now ... Board Solutions is so far ahead of the opposition we're already well into 1991 Get your Easter Bargains now and avoid the rush! P.S. Have a Happy Chrisbnas & New Year anyway! I I POWER SUPPLIES 200 Watt PSU Suit Tower Case 200 Watt PSU Suit Baby T Case 150W PSU, Circuit Board 150W Switching PSU - XT 200W Switch PSU - Baby AT 200W PSU, Baby AT, L Type 220W Switching PSU - AT 200W PSU With Battery Backup 150W PSU Cap. 220nF/200V P2020 P2030 P1500 P1510 P2000 P2010 P2200 P2040 P9000 195.00 149.00 85.00 124.00 149.00 149.00 195.00 695.00 3.95 KEYBOARDS 101 Key Keyboard, XT/AT 101 Key Keyboard + TrackBall K1010 K1020 99.95 174.95 Hinged, Baby AT Full Size Hinged AT Case Hinged Baby ATw/200W PSU Slimline 'XT' or 'AT' with PSU 3.5in Hard Disk Ext.+ Cable 5.25in Floppy Disk Ext. + Cable 5.25in Full Height Ext. + Cable Baby Tower Case AT Baby Tower Case+ 200W PSU Tower for 6 Dev. (4 front, 2 rear) Tower for 6 Dev. (4 front, 2 rear) & 200W PSU Tower for 6 Devices, (6 front) Tower for 6 Devices, (6 front) + 200W PSU Case, hinged XT C1000 C1005 C1010 C1020 C1030 C1040 C1050 C1070 C1080 C1090 C1100 C1120 C1130 C1140 I ___IN_T_E_R_FA_C_E_C_A_R_D_;S_ . - - - -- R-A_M_C_A_R_D_S_ ______,I .... RAM Card, OK RAM, XT only 2MB RAM Cd, OK LIM/EEMS AT 2MB RAM Cd, OK LIM/EEMS XT 6MB RAM Card, -OK RAM 8MB Fast Card Suit 20MHz +SX 32 Bit RAM Card 25 + 33MHz R1000 R1010 R1020 R1030 R1040 R1050 99 .00 265.00 245.00 295 .00 299.00 349.00 DISK CONTROLLER CARDS Floppy Disk Card, 4 Ports 360K Disk Cont 4 port, 21n 2Ex or 41n Floppy Disk Card All Drives ESDI Hard Disk Cont Card -AT ESDI HOD/FOO Card -AT Hard Disk Cont, 1 :1 lnt. AT HOD/FOO Cont, 1 :1 lnt. AT Hard Disk Cont, 1 :1 lnt. RLL, AT HDD/FDD Cont, 1:1 int, RLL, AT SCSI HOD/FOO for AT Hard Disk Controller, XT Hard Disk Controller, RLL-XT E1000 E1030 E1010 E1040 E1050 E1060 E1070 E1080 E1090 E1105 E1110 E1120 55.00 134.95 99.00 349.00 425.00 245.00 275.00 249.00 285.00 275.00 134.95 154.95 CASES 48 Line 1/0 Card F1130 Serial RS-422 Adaptor F1140 Industrial 1/0 Card F1150 Universal Wire-wrap Card F1030 Dual Serial RS-422 Card F1040 80286 Speed-up Card F1050 IEEE 488 Interface Card F1060 IEEE 488 Interface Card- National Compatible F1070 A-0/0-A Converter, 12 bit, 1 Ch. F1080 Clock Card - XT F1100 EPROM Writer Card F111 O Games Card- 'XT'& 'AT' F1120 125.00 199.00 249.00 295.00 99.00 134.95 125.00 189.00 325.00 399.00 499.00 399.00 499.00 95.00 ____J 110.00 135.00 445.00 125.00 195.00 495.00 445.00 595.00 199.00 49.95 245.00 35.00 NETWORK 8K Ethernet 8 bit with 'l' Adaptor 16K Ethernet 16 bit with 'T' Adaptor Ethernet 50 Ohm Terminator Thin Ethernet Cable, 25 feet Thin Ethernet Cable, 50 feet Thin Ethernet Cable, 75 feet Auto Boot ROM for NEE1 N1000 399.00 N1017 N1020 N1030 N1040 N1050 N1060 499.00 12.75 35.00 55.00 75.00 39.95 CALL (02) 906 5696 FOR THE DEALER NEAREST YOU! PRINTERS! FAMOUS BRAND PANASONIC PRINTERS If you're looking for the ultimate in quality, reliability and value,look no further than these outstanding models from Panasonic - a brand to trust! 144cps 192cps 240cps 330cps 192cps 192cps 240cps 9 pin 9 pin 9 pin 9 pin 24 pin 24 pin 24 pin 80 col 80 col 80 col 132 col 80 col 132 col 132 col PS000 $349 P5010 $449 P5020 $499 P5030 $949 P5040 $649 P5050 $1099 P5060 $1249 • 14 day money-back guarantee (except software) • 12 months warranty on all our products • Mail orders are our speciality • Road Freight on normal size items $9.00 • Insurance $1.00 per $100 of order value • All prices INCLUDE sales tax • We accept Visa, Bankcard, Mastercard and Post Office COD • Call for very latest products and prices • Special prices apply for month of publication, or while stocks last • Leasing facilities available: Just ask! • Government pricing available on request. • KEY for products on these pages: BOLD products are new products, BOLD prices are new low prices. ENHANCEMENT COMPANY ······································- HIGH QUALITY JSE SYSTEMS BUILT, TESTED AND FULLY GUARANTEED! 286 12MHz SYSTEM Includes • • • • • • • 8112MHz (Landmark 16MHz) 1 MB RAM on board 1.2MB (5-1 /4in) Floppy Disk Drive Serial, Parallel and Games Ports Floppy Controller Enhanced 101 Key Keyboard Hinged "Baby AT" case and 200W power supply • 14in Paper White Monitor & Mono Hercules Card $1195 X2859 All this for only Add $695 for 42MB 28ms + controller 386SX 16MHz SYSTEM Includes • • • • • • • • • 8116MHz (Landmark 21 MHz) 1MB RAM on board 1.2MB (5-1/4in) Floppy Disk Drive Hard/Floppy Controller 42MB 28ms Voice Coil Hard Disk Drive 2 Serial, 1 Parallel Ports 16 Bit256K VGA Card (exp to 512K) Enhanced 101 Key Keyboard Mini Tower case with LED display and 200W power supply • 14in Super VGA 1024 x 768 Colour Monitor, 0.28mm dot pitch X3862 All this for only $ 2995 386 25MHz SYSTEM Includes • • • • • • • • • • 8125MHz (Landmark Speed of 47MHz) 32K SAAM Cache 1 MB RAM on board 1.2MB (5-1 /4in) Floppy Disk Drive Hard/Floppy Controller 42MB 28ms Voice Coil Hard Disk Drive 2 Serial, 1 Parallel Ports 16 Bit 256K VGA Card (exp to 512K) Enhanced 101 Key Keyboard Midi Tower case with LED display and 200W power supply • 14in Super VGA 1024 x 768 Colour Monitor , 0.28mm dot pitch $ 4195 X3865 All this for only FOR DOS 4.01 please add $100 ALL SYSTEMS INCLUDE A 12 MONTH "BACK TO BASE" WARRANTY ••••••••••••••••••••••••••••••••••••• J ~SHU/4:,, BOARD SOLUTIONS Ply Ltd PO BOX 1120, LANE COVE NSW 2066 TEL (02) 906 5696 FAX (02) 906 4592 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. Current limiter for 240VAC lamps This circuit was designed in response to a letter from a reader who was having trouble with photo lamps used with the Datek PCB system. The lamps were blowing after only a few minutes of intermittent use. The cold resistance of these expensive globes is about 7.5Q, so it is easy to see why there is trouble with inrush currents at turn on. Here is a solution to the problem. The circuit consists of two identical current limiters set up so that each works on the opposite half of the mains cycle. It works like this. When the mains active input is positive with respect to the neutral, the collectors of Ql and QZ are positively biased with respect to their emitters via the lamp and DZ . A lO0Q lW resistor supplies base current for Ql and QZ (which are connected as a Darlington pair) and turns them on. Climate controller for a greenhouse This circuit will control a heater, fan and a cooler in a greenhouse. It uses the fact that the forward voltage across a silicon diode varies linearly with temperature. The diode in question is a 1N914 (D1) which is connected in a bridge circuit and monitored by a differential amplifier consisting of transistors Ql and Q2. The variable output voltage from the differential amplifier is parallel connected to four op amps, ICla-d. Each of these op amps then drives the non-inverting(+) input of an LM339 quad comparator; ie, ICla drives comparator IC2a and so on. The inverting input(-) of each comparator is connected to a trimpot which sets the temperature at which the output device will be turned on (or off). For example, ICZ is controlled by lOkQ trimpot VR3. 80 SILICON CHIP D1 1N5404 0.22!1 5W 24DVAC INPUT 02 1N5404 04 01 MJE13007 MJE13007 100!1 1W 0.22!1 5W 1000 1W LOAD AO--------------------------The emitter current from Ql passes through the associated o.zzn 5 watt resistor which is used to set the current limit. If the voltage drop across the 0.22Q resistor exceeds about 0.7 volts, Q3 begins to conduct and robs base current from Ql and Q2, turning them off. The net result is that turn on current is limited to less than five amps and this gives much longer bulb life. On the other half cycle, Dl is forward biased and current limiting is provided by Q4, Q5 and Q6. On the construction side of things, Ql and Q4 should each be on a small heatsink and all normal precautions taken for a mains-powered design. Many different power transistors can be used but they should have a Vce of at least 400 volts and be able to carry at least 4 amps. The transistor beta is also important and should be at least 10-15 in the current range of interest. David Eather, Brisbane, Qld. ($30) IC2a's output is used to control the heater. When the output of IC2a goes low, meaning that the temperature has dropped below the setting of VR3 , PNP transistor Q3 is turned on. This turns on the associated relay and therefore the heater. The outputs of IC2b and ICZc can be used to control a fan and an evaporative cooler. These comparators drive NPN transistors, Q4 and Q5. These are turned on when their associated comparator outputs go high. The relay contacts should be rated for mains voltage. The neon indicators show whether the respective outputs are on or off. The fourth output, associated with IC2d and Q6, is optional. Calibration is not difficult. All that is needed are two bowls, a digital multimeter, a thermometer of reasonable accuracy and some hot and cold water. First, put some ice-water into a bowl, place the thermometer into the ice-water, and insert the sensor diode so that it is only half submerged. While you are waiting for the temperature to stabilise, connect your digital multimeter to the bridge outputs (collectors of Ql and QZ ). When the thermometer has reached 0°C, adjust multiturn trimpot VRl to obtain 0.00V on the DVM. Next, take the thermometer to the other bowl and by gradually adding hot or cold water, raise the temperature to 30°C. Now immerse the sensor diode in the water and watch the voltage on the DVM rise. Adjust trimpot VRZ to read 0.50V on the DVM. When this is done go back to the ice-water to make sure it is still OK - a small tweak may be required. Now you can calibrate dials for trimpots VR3, VR4, VR5 and VR6, so that the threshold temperatures can be set anywhere between 0°C and 30°C. Roy Raines, Doonside, NSW. ($45) ~ = '""" 0 co co ..... !:x:l 1:1:1 I:>:! Es:: R A 1k 240VAC .,. N 1 E 21551 .,. + .,. .,. '" W..." 0.1 ! +12V LED1 .,. ':" 10k 10 1811 10k .,. .,. 68!l 4.7k .,. 10k TEMP SEJ~~Tf 10k TEMP S~LJjTI• • • ,d J 100k 100!! 100k .,. .,. I +12V +12V N I I '1 L,, , +12V I• 240V NEON_ .,. ~ COMPUTER BITS BY JENNIFER BONNITCHA Talk to the world: modem mysteries revealed Have you been curious about modems but did not know what questions to ask? Like a lot of computer hardware, they are pretty inscrutable devices but very useful nonetheless. In this article, we give some interesting background on the subject and dispel some of the mysteries of Hayes-compatible modems. at least one COM port is standard on personal computers, this simple connection method opens up world-wide communication opportunities. Macintosh users will note that a special port on the rear of the computer has been set aside for a modem. Much like the personal computer, a special cable is required to attach the modem to the port. Most computer users are aware that a modem is a device which enables a computer to connect via a telephone line to similar equipment across town or across the world. The name Modem comes from the terms MOdulation and DEModulation. Modulation (the regulation, adjustment or varying of tone or pitch, amplitude or frequency of a wave by a wave of a lower frequency to convey a signal) is used because some signals cannot be directly sent over some transmission channels. The solution is to modify or modulate a carrier wave to represent the Modem types & connections original digital signal. Demodulation is the reverse process of modulation where the original signal is extracted from the carrier wave. The modem thus modulates digital data into a carrier wave for transmission through an analog system (ie, a telephone line) and then demodulates the carrier wave back to a digital signal at the receiving end for further use by a terminal or computer. The vast majority of modems are external boxes which occupy a small space near your computer. Using the appropriate cable, the modem is connected to a COM or serial port. Since Table 1 : Communications Standards 82 CCITT V21 300 bps full duplex; Australia & Europe CCITTV22 1200 bps full duplex; Australia & Europe CCITT V22bis 2400 bps full duplex; Australia & Europe CCITTV23 75/1200, 1200/75 full duplex; Australia & Europe CCITT V23 1200 bps half duplex; Australia & Europe BELL 103 300 bps full duplex; USA only BELL 212A 1200 bps full duplex; USA only BELL 2400 2400 bps full duplex; USA only SILICON CHIP Modems differ in operating parameters and performance according to their intended application and this can include: (1). Acoustic Couplers: these acoustically connect any telephone handset by cradling the coupler's acoustic transmitter and receiver to the handset. These may be OK for non-critical portable applications but they are now largely superseded by standard modems which are connected directlv to the phone lines. " (2). Modem Eliminators (line drivers): these can substitute for a conventional modem by extending the cable distance between two data terminal equipment devices beyond the 15-metre limitation imposed by the RS-232 interface. (3). "Standard" Modems: These are intended for communication through the public switched telephone network, leased telephone line or both switched and dedicated applications. The acoustic-coupled modem uses the telephone handset and two foam cups into which you insert the earpiece and mouthpiece of the telephone. The main problem with these is that stray sounds in the vicinity of the connecting cups can leak into the Table 2: The Hayes Command Set COMMAND DESCRIPTION A Initiates an answer mode data call Turn carrier off Enable carrier Pause for x seconds (default is usually 2) Forces the modem to re-enter the command state after dialling. Dial the number string "s" Does not echo characters typed when in the command mode Echoes characters typed when in command mode Half-duplex: Echoes characters typed during a data call Full-duplex: Does not echo characters typed during a data call Hangs up Goes off-hook Speaker always off Speaker on until carrier detected Speaker always on Goes back to data (on-line) mode Dials using rotary pulse dialling Enables status messages (Result Codes) Disables or turns off status messages Dials using touch Results Codes as digits Results Codes as words Wait for second dial tone Resets co C1 Ds EO E1 FO F1 HO H1 MO M1 M2 0 p QO 01 T VO V1 w z signal and affect your data. Also, connecting the microphone to the mouthpiece and the speaker to the earpiece is an easy mistake to make and very frustrating. As noted above, this type of modem is now pretty well obsolete. Direct-connect modems plug directly into your telephone or wall jack. Since the acoustic links are eliminated, the signals are cleaner and much more reliable. Auto-answer modems are usually able to auto-dial, thus enabling you to select a phone number or enter it direct from your computer keyboard. This versatile style of modem is the target of most communications software. Data transmission rates The differences between modem types are primarily speed-related. Speed is measured in bits per second (bps) but is generally referred to as baud rate (from Emil Baudot, an early pioneer of telegraphic communication). Originally, the baud described how fast dots and dashes could be sent on telegraph wires. Standardisation exists to the extent that 2400 baud is the most common rate at present. This represents about 230 characters per second. CCITT (International Telegraph and Telephone Consultative Committee) is an international body which establishes and recommends communications standards. The 2400 baud rate is also known as CCITT V22Bis. Other common baud rates are 300 (V21), 1200 (V23) and 9600 (V32). The Bell system has traditionally dominated the US communications industry and while the CCITT standards run parallel to many Bell specifications, the two systems are not fully compatible. Some of the more common standards are listed in Table 1. Low speed modems use bit rates up to 600 bps; medium speed from 1200 to 2400bps; high speed from 3600 to 16K bps and wide band 19.2K bps and faster. The "better" quality modems are capable of accurately sending more data down the phone line. While speed is important, particularly with STD or overseas phone charges to consider, remember that your fast modem needs a modem of equivalent capabilities at the other end to get the most out of it. Where time is money, you could consider a modem with data compression and error detection facilities. The modem analyses the data coming from your computer and sends it out as short sequences of characters to represent a longer information string. Thus, the data is effectively compressed; at the other end a modem which understands the compression method unpacks the compressed data. Communication codes There are three basic communication modes: (1). Simplex: the most elementary approach which provides 1-way communication between two points or transmission in one direction only, thus providing no way of responding - like your radio. (2). Half Duplex: provides transmission in two directions but only in one direction at any one time - like a taxi radio where the driver or controller may both talk but only one at a time. (3). Full Duplex: transmissions can occur in both directions simultaneously - like talking to your mother on the phone. When data is transmitted, it synchronises. or operates in response to the receiving device's clock. Most low to medium speed modems use asynchronous transmission where each information character sent contains one start bit and one or two stop bits to frame the character. Each character or sequence of bits is sent down the line in a strictly-timed rhythm. Thus, both the sending and receiving devices must be "in tune" for the inforDECEMBER 1990 83 if you look is a combination fax and modem. The Sendfax (from Bitzel Products) gives you the best of both worlds with a 2400 baud modem and 4800 baud fax. Load the appropriate software and you are in business. Table 3: Typical Result Codes DIGIT WORD DESCRIPTION 0 OK Command executed 1 CONNECT Connected 2 RING Ringing signal detected 3 NO CARRIER Carrier signal not detected or lost 4 ERROR Illegal command, error in command, command too long, invalid character format 5 CONNECT 1200 Connected at 1200bps 6 NODIALTONE No dial tone so subsequent commands discarded 7 BUSY Busy detected so subsequent commands discarded 8 NOANSWER Silence not detected so subsequent commands discarded 9 CONNECT 1200/75 Connected in 1200/75 mode mation to be received in an intelligible manner. The start and stop bits allow the receiving and transmitting devices to synchronise with each other. Though advantageous at high speed, sophisticated timing circuitry is required at both ends of the transmission. High speed synchronous transmissions also require high cost devices to control the data flow. Using your modem The popularity of bulletin boards, the ability to perform banking transactions and the listing of up-to-date Modem commands share price information, amongst other things, means that today there is virtually no information you can't access with a computer and modem. All kinds ofreally good stuff is available for the asking. A fax machine lets you talk to the world. Basically, it consists of a telephone, scanner, thermal printer and modem. Fax cards are a cost-effective method of sending and receiving information. You can only send the information stored in your computer unless you have access to a scanner, thus this limits to a certain extent the usefulness of these devices. On offer Table 4: Pin Assignments For Connectors PC END D25F 2 3 4 5 6 7 8 12 20 22 84 D9F 3 2 7 8 6 5 1 NA 4 9 SILICON CHIP MODEM END SIGNAL TD RD RTS CTS DSR GND7 CD HS DTR RI DIRECTION To Modem 2 From Modem 3 To Modem 4 From Modem 5 From Modem 6 From Modem 8 From Modem 12 To Modem 20 From Modem 22 D25M Mandatory Mandatory Mandatory Desirable Desirable Modems manufactured by Hayes Microcomputer Products Inc were among the first to employ a modem control language. A modem needs software to "drive" it (much like a fax card requires operating software), providing information via a series of commands to, for example, dial a telephone number, automatically answer a received call and disconnect finished calls. The microprocessor inside the modem enables it to interpret the software commands. As a result, Hayes utilised the term "Smartmodem" and sales boomed. Other vendors subsequently incorporated the same command set into their products and thus helped to give almost total acceptance to one of the few standards in the computer industry. Communications programs were able to be used on modems manufactured by any vendor utilising the "Hayes-compatible" command sets. AT is a mnemonic for ATtention and each command in the Hayescompatible modem must be preceded by the character sequence AT in uppercase notation to gain the modem's attention - thus the AT commands. After the initial AT, the following commands can be in upper or lowercase. Table 2 lists some of the commonly used commands in the Hayes modem command set. Note that it is by no means exhaustive and you should check your modem manual for all the codes it supports. Each command sent to a Hayescompatible modem consists of an attention sequence (uppercase AT), the command and a terminating carriage return. Each command starts with a single letter (eg, Dial, Tone, Pulse) and may have additional characters as well. Some commands use numeric options; if you choose to use just the command letter, the number O (zero) is assumed. You can put more than one modem command on a single line provided any command that dials or answers the phone is last on the line. Secondly, any command which resets the modem also clears the buffer, so no The MegaModem from Avtek obeys the Hayes command set, can run at speeds up to 2400 baud, and features autodialling (tone or pulse) & auto answer. following commands are executed. For example, to command a modem to automatically dial a call, you could enter the following: AT DP9, T1234567 <CR> The AT is the modem attention command while the D tells the modem to initiate dialling using pulse dialling (P). The 9 might be included if the modem's telephone line requires that digit to access an outside line. The comma is useful for making calls through a PABX to ensure sufficient time elapses between tones before continuing. In this example, the command causes the modem to pause for two seconds (the default setting) before continuing to dial. Then the phone number is dialled using tone (T) dialling. Once the number has dialled and your modem connects to another modem, it is said to be in "on-line" mode. The rest of the operation takes place between the two devices. Sometimes you may need to get back to command mode. Depending on the operation in progress, the modem transmits characters and monitors the information. You can interrupt the modem by: (1). a silence of one second or longer; (2). 3 "+" characters - the Escape command; (3). another silence of one second or longer. The modem responds by returning to command mode where you can hang up (ATH), change parameters as required, or return to online mode (ATO). In response to commands, modems can issue result codes. These can be sent as either a single digit or a word code via the V command so they can be interpreted by the operator. You can suppress them altogether via the Q command. As always, check your manual for information appropriate to your modem. Typical Result Codes are shown in Table 3: A table showing the 25-pin serial port pin assignments (IBM/clones) was published in last month's column, while Table 4 shows the pin assignments for the D25M modem end of the serial cable and for the D25F and D9F PC connectors. AT-style PCs using the D9 connector cannot support the HS signal due to insufficient pins on the connector. What next? You can set up your modem to make it answer a phone automatically after a specified number of rings for example. You can learn more about your modem by checking the manual since most manufacturers provide some "extra" features. With patience and practice, you can make your computer talk to the world. Supported & Serviced Australia-wide by Elmeasco Instruments Pty Ltd N S W (02) 736 2888 Vic (03) 879 2322 Old (07) 875 1444 S.A. (08) 344 9000 W.A. (09) 470 1855 You've Gotta Getta Goldstar from: A..C..L John Pope Electrical 80 6576 Y..w. D.G.E. Systems (049) 69 1625 • W.F.Dixon (049) 69 5177 • Macelec (042) 29 1455 • Newtek (042) 27 1620 • Novacastrian Electronic Supply (049) 62 1358 e Obiat Pty Ltd 698 4776 e Digitel 709 6511 e Geoff Wood 427 1676 QUEENSLAND St Lucia Electronics 252 7466 • BAS. Audiotronics 844 7566e The Electronics Shop (075) 32 3632 • Solex (Townsville)(077) 72 4466 • Xanthos Electrical (079) 27 8952 S.AYSTRALIA Force Electronics (08) 212 5505 ~ G.B. Telespares 328 4301 • The Electronic Components Shop 670 6474 e Factory Controls (052) 78 8222 e Mektronics 587 3888 • Truscott Electronics 723 3094 W A!!SJRALIA Atkins Carlyle 481 1233 • Leda Electronics 361 7821 PAPUA NEW GUINEA TE (P.N.G.) Pt Moresby 25 6322 Lae 42 6246 ·Recommended prices only DECEMBER1990 85 I PRODUCT 500V power supply has instrument bus Hewlett Packard Australia has released a range of power supplies with HP-IB, HP's version of the standard Instrument Bus. Known as the 6030 range, it includes the 6035 supply which can deliver 500 volts DC at up to 2 amps (1 kilowatt). Previously, the highest output voltage available from New IIT-3C87 coprocessor A big increase in computing speed can be obtained when running software which can make use of a coprocessor but now, apparently, there are coprocessors and coproces- SHOWCASE an HP supply was 200 volts. The new range of power supplies can be programmed using Standard Commands for Programmable Instruments (SCPI) which is becoming an industry standard for programming test and measurement instruments. For further information on the new range of supplies, contact Hewlett Packard Australia Ltd, 34-41 Joseph St, Blackburn, Vic 3130. sors. The new IIT-3C87 is claimed to be up to three times faster than the standard Intel 80387. Available in 16, 20, 25 and 33MHz versions, the new coprocessor has an 80-bit internal architecture, higher accuracy and copes with the full range of transcendental operations for sine, cosine, tangent, arctangent and logarithms. Device dissipation is typically 0.6 watts. For further information, contact the Australian distributor, CAD Connections, Level 3, 220 Pacific Highway, Crows Nest, NSW 2065. Phone (02) 957 6719. Tuitional electric projects from DSE Just in time for Christmas are these three electric kits which will give an 340W power supply from Setec The model SM340ACI power supply from Setec can deliver 340W of power, with three separate outputs: ±12V at 5A and +5V at a whopping 45A - all this in a package 292 x 127 x 63.5mm. All outputs from the supply are short circuit & overload protected. The supply will shut down if any output is overloaded for more than lOms. It also has soft-start circuitry which limits the inrush current to BOA peak. If, for any reason, the unit overheats (eg, fan failure), the unit will again shut down. Also provided is a TTL-level sense signal which is high when 86 SILICON CHIP the output voltages reach regulation and goes low at least lms before they fall out of regulation, say due to loss of AC power. Line and load regulation is ±0.5% for the 5V supply from 2.3A to 45A and ±0.5% for the ±12V supplies from 0-5A. Output noise I is rated at lO0mV p-p (0 to 20MHz) on the 5V rail and 120mV p-p (0 to 20MHz) for the ±12V rails. For further information on the Setec range of power supplies, contact Setec Pty Ltd, 6 Holloway Drive, Bayswater, Vic 3153. Phone (03) 762 5777. introduction to electricity and electronics for young children. There is a battery operated motorboat, an electric bell and a large kit with 80 experiments described inside. For the motorboat, the constructor has to build a completely disassembled permanent magnet motor and the same goes for the electric bell which is supplied completely disassembled. The BO-experiment kit has a large perforated plastic board into which various modules and components are plugged in. Connections between all the parts are made by pressing bared wires into spring contacts; it's all very simple and, best of all, no soldering is required. Available from all Dick Smith Electronics outlets, the kits are priced as Satellite siren offers high security Intended to be installed on the outside of a home or building, the E48 satellite alarm incorporates a siren and strobe lamp. It has internal monitoring of its input circuitry so that if the wires are cut, the alarm instantly sounds. The unit is of a two-case construction and if the outer or inner cases are tampered with while the alarm is enabled, the siren again sounds. The alarm time can be programmed, up to a maximum of 10 minutes. Normally powered from 12 volts DC, the unit also has its own internal 12V 2.6Ah SLA battery, so that the alarm can sound if it is tampered with. Tough enough to take it, wherever you take it follows: electric bell $16.95, motorboat $16.95 arid 80 experiment kit $69.95. The strobe lamp can be either blue or amber. After the alarm has been triggered and timed out, the strobe remains flashing until the unit is manually reset. The quiescent current drain is 6.5mA, rising to 900mA when the strobe and siren are activated. The price is $199. For further information, contact Force Electronics on (08) 212 5505; or by mail to 203 Wright St, Adelaide, SA 5000. Video RAM DAC for VGA displays A new RAM DAC has been released which is claimed to provide a dramatic increase in image quality from standard PC VGA displays. Produced Fluke 80 Series multimeters come in a rugged, water and dust resistant case. They can handle up to 1000 VAC (RMS)/DC on any terminal and have an "input alert"™ warning if test leads are in the current jacks and a non-current function is selected. They are shielded against electro- · magnetic interference and are protected against shock and vibration. Each Fluke 80 Series multimeter comes in a rugged protective holster, with a unique "Flex-Stand"™, which bends and holds to any shape, allowing the multimeter to be stood or hung almost anywhere. To find out just how tough a Fluke 80 Series multimeter can be ... call your local Fluke distributor today. FLUKE AND PHILIPS- THE T & M ALLIANCE e PHILIPS DECEMBER1990 87 - - --= ... , - - -~ SP~~C1ltli CHRISTMAS OFFER Save50%on thisXTtoAT upgrade Kit. Tired of waiting for you slow old XT to get things done? But you don't want to chuck out a perfectly reliable machine? Well, here's the answer. A complete conversion kit at a special low price. You get a state-of-the-art 20MHz motherboard, fast memory and a fast 16-bit controller for your hard disk - this kit takes you right up to the performance of the best machines costing $4,000 to $5,000! You'll get speed around 20 times that of your old XT! The upgrade includes: A rocket-fast 20MHz "AT" motherboard, complete with 1MB of high speed RAM. Expandable on-board to 2MB. Full LIM EMS 4.0 support built in (no need for expanded memory cards). Normally selling for $745. 1 A fast 1:1 interleave 16-bit disk controller. 2 Data transfer is around 6 times faster than with an XT controller on the 8-bit bus. Normal price is $245.00 Electronic Solutions. 5 Waltham Street Artarmon 2064. PO Box 426 Gladesville 2111. Phone (02) 906 6666. Fax: (02) 906 5222 Multimeters for automotive testing Two n ew multimeters have been released by Fluke and are especially aimed at the automotive electrician who is required to troubleshoot the electronics in modern cars. An extension of the very popular Fluke 80 series, the 86 and 88 have all the basic meter functions such as volts DC and AC, amps DC and AC and resistance. They also have a range of automotive features such as RPM, change alert, frequency, duty cycle and pulse width. An inductive pickup is included for measuring RPM in spark engines and pulse width (on-time) for fuel injectors. The 88 is the top model, having all the features of the 86 which in turn is very similar to the current Fluke 85 m odel. Also featured in the 88 is a low ohms range, with .01n resolution - useful for testing regulator, relay and ignition contacts. Another feature is "Smoothing" which displays the average of eight measurements. This is handy for measuring fluctuating signals such as idle speed (especially in older cars with points and carburettors). For further information contact Philips Test & Measurement, 25-27 Paul St, North Ryde , NSW 2113. Phone (02) 888 8222. by Analog Devices Inc, the new ICs employ a patented algorithm to eliminate jagged edges ("jaggies" or aliasing) in drawn lines, provide photorealistic colours and shading, and show text with resolution comparable to 300 dots per inch laser printers, on existing monitors. Compared with the present VGA standard of 320 x 200 pixels and 256 colours, the new new Analog Devices' chips are claimed to give an apparent resoluticn of 1280 x 1024 and 792,000 colours. For further information, contact the Australian distributors for Analog Devices: NSD, 205 Middleborough Road, Box Hill, Vic 3128. Phone (03) S90 0970. B & W 200 Series loudspeaker system For those searching for a set of high quality speakers at a reasonable price, then these B & W 200 Series systems from Convoy International are worth looking into. There are four models in total, ranging from around $500 for a pair for the 201s to around $1200 a pair for the 204s. The 201s are a 2-way shelf-mounting style, suitable for a small system or extension speakers. The 202s are larger models designed for stand mounting, while 203 and 204s incorporate dual mid/bass drivers. The 204s are 50% larger than the 203s. Common to all models are ferrofl uid tweeter cooling for reliability On the alert, accurate and safe Fluke 80 Series multimeters come with a large number of "alert" functions designed to ensure safe, easy use . The "Input Alert" prevents accidental damage through wrong lead connection . An automatic power cut-off (after 30 minutes idle) extends battery life. This may be overridden in 36 hour record mode. And the readouts couldn't be easier. Fluke's patented "Touch Hold"™ feature, when activated, captures, locks and displays each measurement. yet leaves you both hands free . to position the probes. In the relative mode, measurements can be made relative to your own reference point. And there's a maximum/minimum alert, plus automatic storage of max/m in readings. And there's much more. Why not be alert to all the special features of Fluke 80 Series multimeters ... call your local Fluke distributor today. FLUKE AND PH ILIPS- THE T & M ALLIANCE le) PHILIPS DECEMBER1990 89 Check out these BARGAINS! As a special CHRISTMAS BONUS: FREE PACK AND POST applies to all these items (Aust. only): Including the Battery! BE QUICK TO SECURE YOUR PORTABLE POWERHOUSE BARGAIN Brand NEW INDUSTRIAL GRADE, 6.5Ah sealed lead-acid battery. YES 6.5Ah !! Only a fraction of their real value. More than 5 times the capacity of the standard 1.2Ah battery. Can be used for alarms, commu nications equipment, HeNe laser power supplies, lighting, solar powered systems or as battery backup etc. Excellent low temperature performance as they retain 9a°% of full capacity at 0°. This battery is more commonly called a 12V sealed GEL battery. ONLY $29.90 ea (for 1O+ $26.90). Stocks are limited. Dimensions 150 x 95 x 65mm. Weioght 2.54kg. Don 't forget the FREE postage offer before CHRISTMAS. BRAND NEW 2-3mW HE-NE LASER TUBES. We have made a special purchase on a small quantity of these tubes, and pass on the savings to you. These are long life tubes, of the same size as our 4-5mW tubes: 40mm diameterand 350mm long. Even the ballast resistor and the connecting clips will be included with each tube. Use them for experimenting , Disco effects, Surveying etc. Lasers are fascinating! We are offering these at about 1/3 of their normal pri ce. A SUITABLE 12VOLT D.C. LASER POWER SUPPLY that will power this, and higher powered tubes, will be available. The complete kit of parts including a torroidal transformer with a prewound secondary, will only cost approximately $50 - $60. These supplies will become available in early FEBRUARY SEE IN THE D.AR,K! with our INFRA RED NIGHT VIEWER at a SPECIAL price, TILL THE END OF 1990. We have good stoc k of the 6032A tubes. This is your opportunity to build a product which commercially cost 1000's of dollars at a fraction of the cost. We supply the electronic kit, a 6032A Image Intensifier tube, and the case components for only. . ONLY $339.00 BRAND NEW TUBES The 6032A tubes are BRAND NEW and perform well with a good infra red torch. Torch and Lenses are not supplied STILL ON SPECIAL: Till the end of 199D!: Single Channel UHF Supported & Serviced Australia-wide by Elmeasco Instruments Pty Ltd N S W (02) 736 2888 Vic (03) 879 2322 Old (07) 875 1444 S.A. (08) 344 9000 W. A. (09) 470 1855 You've Gotta Getta Go/dstar from: A.C.T. John Pope Electr':al806576H...S..W,_ D.G.i:. Systems (049) 691625 e W.F.Dixon (049) 69 5177 • Macelec (042) 29 1455 • Newtek (042) 27 1620 • Novacastrian Electronic Supply J049) 62 1358 e Obiat Ptv Ltd 698 4776 e Dioitel 709 6511 e Geoff Wood 427 1676 QUEENSLAND St Lucia Electronics 252 7466 • B.A.S. Audiotronics844-7566e The Electronics Shop (075) 32 3632 • Solex (Townsville)(077) 72 4466 • Xanthos Electrical (079) 27 8952 S.A!ISTIIALIA Force Electronics (08) 212 5505 ll!C.IllfilA G.B. Telespares 328 4301 • The Electronic Components Shop 670 6474 • Factory Controls (052) 78 8222 • Mektronics 587 3888 • Truscott Electronics 723 3094 W AUSTRALIA Atkins Carlyle 481 1233 • Leda Electronics 361 7821 PAPUA NEW GUINEA TE (P.N.G.) Pt Moresby 25 6322 Lae 42 6246 'Recommended p rices only 90 SILICON CHIP Transmitter/ Receiver . . at $49.90, the pair! · PIA detector with commerical case at $39.90, Interface at $7.90! DECEMBER SPECIAL : 1.Svolt to 9volt KIT complete $7.99 OATLEY ELECTRONICS PO BOX 89, OATLEY, NSW 2223 Telephone: (02) 579 4985 Fax No: (02) 570 7910 Certified & $4-$6 Aust. NZ add $2 and glass-reinforced kapton former housing for the bass drivers to reduce the effects of heat buildup at high volume levels. For more details, contact Convoy International on (02) 698 7300. DB9 to DB15 converter plug lishing software. Its features include 132 x 50 line text mode, multifont display of up to 8 concurrent fonts, 6 times faster than standard IBM VGA displays and 8 and 16-bit operation. A large range of application drivers are available including AutoCAD, VersaCAD, Ventura, Windows, Word 5 and Lotus 1-2-3. For further information, contact Electronic Solutions, 5 Waltham Street, Artarmon, NSW 2064. Phone (02) 906 6666. Power analyser for rent This one-piece 9-pin male to 15pin female converter comes with external screws for mounting on existing screw pillars. It is priced at $19.95 and is available from Geoff Wood Electronics, 229 Burns Bay Rd (PO Box 671), Lane Cove, NSW 2066. Phone (02) 428 4111. Super VGA card has increased resolution The new ES VGA Plus card supports up to 1Mb of memory and up to 256 colours at 800 x 600 pixels, as required by the latest CAD and pub- Count on them to measure up 1n more ways ■ Analysing a power supply line for glitches used to be something only for companies with money to spare but now Imagineering Rentals have the PowerScope 4800 power analyser available for rent. The 4800 can detect, capture and analyse power supply disturbances such as surges and sags in voltage, frequency disturbances, high frequency noise, frequency spectrum and total harmonic distortion. It also provides these readings on easy-toread, real-time graphs. It can also be connected to any IBM PC and has its own uninterruptable power supply. For more information, contact lmagineering Rentals, Unit 7, 252 Allambie Rd, French's Forest, NSW 2086; or phone (02) 975 2699. GPIB switch box for up to four computers You've heard of printer sharers and queuers. Now there is a GP-IB version, mainly intended for devices such as plotters and, surprise, surprise, printers (GP-IB types, that is). For further information, contact your local branch of Elmeasco Instruments Pty Ltd, or at 18 Hilly Fluke multimeters are made in the USA, to the highest standards, offering accuracy you can depend on ... and they are guaranteed for 3 years by Ph ilips, the name you can trust. Each measurement Is clearly shown on the display, so you know exactly what you're measuring . . . without having to check connections or switch positions. Fluke Models 83 and 85 have bar graphs fo r analogue read ings, while the Model 87 has a high resolution pointer. The 10-times zoom fac ility lets you enhance resolution. And your Fluke Multimeter comes comp lete with protect ive holster, safety leads, 9V battery and operating instructions. To find out why no other m ul timeter measures up to the Fluke 80 Series ... call your local Fluke distributor today. FLUKE AN D PHILIPS - THE T & M ALLI ANCE Street, Mortlake, NSW 2137. Phone (02) 736 2888. ij PHILIPS DECEMBER 1990 91 'TIN 1183 le • m«llum to ,-vy duly two pl•lfonn mounting br•cut .,,.c11l"11y dnlgMd for ..curlflll -,»•k- •tc to IIMlle Md celllnp, iau• or l»nch to,-. ON» mount/Id 1M brKk•t t:1111 N ,o,.tlld • full -~-...••NIIMI being &fJ or down until tlw required IMWlng or llelffl/ng.,.. • KM#wd. g Both pMtfonM IMve pn,drl/1«1 holH for mounting •nd .ii mo'llng ,,.,,. 1111d Jofn,. .,. ...,lymn.d or locked with M /er~ .ilMI k•y .uppli«J with tlw unlL I AR ELECTRONICS Is Your Product Or Service · Getting The Exposure It Deserves? 25,000 consumers will read this page. They need to see your advertisement if you want them to buy your product. Contact Paul (018) 28 5532 or Cameron (03) 587 5155 to reserve this space. Low cost laser printer Dot matrix near letter quality printers have come down a long way in price recently but so have laser printers. Why have "near letter quality" when you can now have laser quality at 300 dots per inch? This new Okilaser 400 has a printing speed of four pages a minute and emulates the HP Laserjet Series II. Its Low-cost parts storage box Tidy up your stock of small components with this 16-drawer parts storage box. Its overall size is 185(H) x 242(W) x 124(D)mm and the drawers are 110(L) x 50(W) x 34mm(D). You can also divide each drawer into either 2, 3 or 4 sections. At $12.95, it is good value for money from Jaycar Electronics. Low noise FET-input op amp - 92 TM 1185 le• 1-•vy duty two pl•tform mounting br•cbt ia•lgtHld for Ncurlflll •m.11 TV'• •nd -,»aer• to WIIII•, c./1/flll", dem or bench to,-. WhM mounltld It c.n be ,o,.ted • fu/1360 iag,_• u -11 u bt,/flll •wiwli.d up or down to MY .,.wing •·"···•··•··• ,.. or lleten/ng •ngi.. Both pl•t -form. IMve predrllled ho»• :jILICON CHIP data buffer is 512K standard and has optional 1 megabyte or 2 megabyte RAM expansion. The interface is Centronics parallel or RS232C serial. Up to 25 different fonts can be resident. The paper holder will take up to 200 sheets and trays are available for A4, A5, A6, B5, Letter, Legal, Executive and Envelope. The price? Just $1995 from Rod Irving Electronics, 74 Parramatta Rd, Stanmore, NSW. Phone (02) 519 3134. A new 8-pin FET-input op amp in a plastic mini-DIP package is now available with input voltage and noise figures comparable with devices packaged in metal cans. Designated the AD645, from Analog Devices, it has guaranteed maximum input voltage noise of 2.5µV peak to peak from 0.1Hz to 10Hz and 12nVl✓Hz RMS at 1kHz. Typical applications include low noise photodiode and optical circuitry for medical and analytical instrumentation. For applications requiring a high input impedance, the AD645K also guarantees maximum input bias currents of 1.5 picoamps at either differential input over its full ±20V input range. Other guaranteed parameters include 15 femtoamp peak to peak input current noise from 0.1Hz to 10Hz and only 0.8fA/✓ffz RMS from 0.1Hz to 20kHz. The 2MHz unity gain bandwidth AD645K will typically settle to within 0.1 % in 6µs and to within .01 % in 8µs. Slew rate is 2V /µs and minimum open loop gain is 120dB. For further information, contact NSD Australia, 205 Middleborough Rd, Box Hill, Vic 3128. Phone (03) 890 0970. BOOKSHELF A qualified approval for this book Physics for Kids: 49 Easy Experiments With Electricity & Magnetism, by Robert W. Wood. Published 1990 by Tab Books, Blue Ridge Summit, Philadelphia. Soft covers, 235 x 185mm, 134 pages. ISBN 08306 3412 6. $19.95. Ostensibly, this book has the commendable purpose of introducing basic concepts of electricity and magnetism to young children. To that end, it has no less than 49 simple experiments which purport to demonstrate such concepts as static electricity (electroscope, a relay, a compass and so on). Nothing wrong with that you may think and that is true. However, when we first looked at this book our immediate reation was to recommend that this book not be sold . Why? Because a number of the experiments suggest the use of a 2core lamp flex, with mains plug still fitted, as part of the "experiment". For example, one experiment demonstrates how a fuse works - by blowing it. This requires a number of batteries Another blast from the past More Golden Age of Radio, by John W. Stokes. Published 1990 by Craig Printing Co Ltd, Invercargill, New Zealand. Hard covers, 306 x 220mm, 203 pages, packed with photos. ISBN 0 908629 29 X. Price $49.95. Just how many different models of radios (er, wirelesses?) were manufactured in the "golden age of radio"? There must have been many thousands. This book catalogs just some of them. Those people who have seen John Stokes' previous books, "The Golden Age of Radio in the Home" and "70 Years of Radio Tubes and Valves" will be even more enthusiastic about this volume. It covers radios made in NZ, Australia, the US, Canada and Great Britain. It will be of considerable in- in a tube, a 2-wire mains cord with moulded plug, with the wires stripped back, and a short length of fuse wire. The fuse wire is wrapped around the pins of the plug and the bared wires are then connected to each end of the battery stack and then, as you might expect, the fuse blows. What do the youngsters then do with that moulded plug and cord with the wires stripped back? With no adults around to supervise, it's pounds to peanuts that sooner or later it will be plugged into a power point to "charge the batteries" or something equally dangerous. This could easily have fatal consequences. ■ terest to Australians because a lot more Australian radios are featured. There are an immense number of photos but not much on the technical detail of the radios. Still, if more technical detail was to be included the We have discussed this matter with Dick Smith Electronics, the importer of the book. As a result, they have have decided to remove experiments 14 and 15 from the book, before putting it on sale. They will insert a notice in the book to the effect that "experiments 14 and 15 may involve excessive risks to young experimenters. In the interests of safety, these experiments have been removed from this publication". With the relevant pages removed, the book can be recommended to anyone looking for a book of basic experiments in electricity for children. It is available from all Dick Smith Electronics stores. (L.S.) Diode handbook International Diodes Equivalents. Published by Tech Publications, Singapore. Soft covers, 305 x 170mm, 135 pages. ISBN 9971 84 567 9. Our review of this book in last month's issue unfortunately omitted to mention where it came from. It is available from all Dick Smith Electronic stores for $14.95. (L.S.) book would be vast. There is also some information on early valves and components such as capacitors (condensers). I found it fascinating to go through although I must admit to being a little disappointed that I could not find' the old console radio I listened to as an ankle-biter. It was a Stromberg-Carlson (I think) with two moulded vertical windows for the station call signs. At any rate, if you were alive before the coming of television, you are sure to find much of interest in this book. Be aware though, if you read this book you might get bitten by the restoration bug (is that old radio still sitting our in your parents' garage?). The book is available from Resurrection Radio, PO Box 1116, Windsor, Vic 3181. Phone (03) 529 5639. The price is $49.95 plus $10 postage to anywhere in Australia. (L.S.) DECEMBER199U 93 CITIZEN CX-70 PRINTING CALCULATOR A-3000 REMOTE CONTROL SYSTEM "You can control just about anything with this remote control transmitter/receiver. TV's, Stereos, Alarms etc. * Receiver relay output: N.0./N.C. up to 5 amps. * Receiver operating voltage: 12 volts DC * Complete with two (2) remote keys (batteries includedj * Operating Distance: 10 meters * Frequency: 300 - 310 MHz NORMALLY $109.95 NOW$89.95 ~LLY 95 STEREO SOUND FEEDER NOW ONLY $69.95 N 10 BAND SHORTWAVE RECEIV "Play your portable CD player or cassette through your car's FM speaker system in rich stereo sound". Model SG-78 * MW/SW1/SW2-8/FM Bands * Battery or plugpack operation * includes soft carry case. * Simply plug into the lighter socket. No hard wiring required. * Also functions as a power supply (3V, 6V, 9V) for most portables. • Perfect for all vehicles or boats, equipped with 12V gigarette lighter socket and FM radio. AVM-1 AUDIO VIDEO MIXER 10 Digit LCD display emory Function 1/o mark up/ Mark down ate Function epts standard paper (58mm) or mains adaptor operated uded) NOW ONLY $75.00 Due Mid December HDS-90 PROBE TYPE DIGITAL MULTIMETER Now there's a simple and inexpensive way to add narration , sound effects, and background music to your videos alter you have been out in the field and shot them. This easy to use mixer enables one microphone and up to three video inpU1'; to be added to the sound track on the video tape. Ideal for the home movie, sports event or wedding where expensive professional consultants cannot be justified. Each input has its own seperate audio volume control for fading music etc. in and out as well as a master control for ~enuating the overall audio output level. SPECIFICATIONS • Auto and Manual range operation. Mic Input?: 1 x 6.5mm socket • AC/DC ampere measurement. 3 x RCA Line Inputs: sockets • Logic test function (CMOS/TTL) Output Imped: 300mV <at>600 OHM • Data hold and diode test functions. Signal to Noise: 55dB Frequency Resp: * Fast response continuity buzzer. 20Hz to 20KHz +/-2d Output Level: 300mV * Large 3.5 digit LCD display. Power Supply: 0VDC 006P Battery ONLY$69.95 * 12 Months warranty. Convert your Oscilloscope to a Spectrum Monitor with a Bandwidth of 100MHz CH. OSCILLOSCOPE Sweep Modes: Auto, Normal. Display: X-Y operation. Sensitivity: 5mV/DIV to 5V/DIV, DC to 10MHz. * Timebase: 1Oms/DIV to 0.1 us/DIV. • Includes probe. * 12 months Warranty. * * * The SPECTRUM PROBE is a low cost 1OOmHz Spectrum Analyzer in a handheld probe. * Now see the frequency components of signals and noise. • Use it as a sensitive RF detector. • Locate radiated EMI sources. * Check your RF signal generator. • Check for stage gains in amplifiers. Model: VOS 107 ( As Featured in Silicon Chip Nov. '90) NORMALLY $499.00 NOW ONLY $469.00 PLAYMASTER "PRO SERIES ONE" HIGH POWER AMPLIFIER KIT ORMALL Y $599.00 NOW$549.00 SAVE$50.00 Watts RMS into Bohm o4ohm oat 100Watts into Bohm NOW ONLY $55.00 KASPAROV - "CONQUISTADOR" 16K CHESS COMPUTER * 17 Playing Levels • 4 tournment Levels with clock controlled play * 3 Specialist Levels (Problem Solving, Infinite, Analysis and 1Osecond chess) •. 9 Casual Levels (including MAKES A Beginners Levels) GREAT GIFT TRANSLATOR RS-232C Line Booster can more than double your RS-232 cable lengths without a modems all amplifies RS-232 signals and sends them to the receiver. Theseven important lines 2-6, 8 & 20 are amplified and.there is one spare amplifier wich can be connected to any unuse line. Lines support pins: 2-6, 8 & 20 Pin 1, 7 is wired directiy from the male connector to thefemale Connectors: DB25S female to DTE DB25P maleto DCE LED: Power on Size: 80 x 54.5 x 26mm Weight: 60g * Ideal for travellers, students, business people and holiday makers. • Instant word conversion of ENGLISH, FRENCH, GERMAN, SPANISH and ITALIAN. • 1,400 words in each language. • Light and easy to carry. NOWONLY 9.95 WAS $59.95 Save Nearly 50% only $29.95 CB BAND SWR METER/ POWER METER/ AM MODULATION METER/ FM DEVIATION METER AND MATCHER ... ALL IN ONE UNIT! CM100 "On Watch " PORTABLE ELECTRONIC MONITORING SYSTEM • For monitoring infants, the elderly, the sick • Transmits all sounds in the room up to 300ft away. • Battery operated transmitter, receiver complete with AC adaptor. * 1 Watt / 10 Watt / 100 Watt switchable. WAS$99.95 Model: MS-110 NOW$69.95 Normally $89.95 ANGEAN AT5-803A SHOR HSW4230PD SS REFLEX TEM * Coverage from 150KHz to 30 MHz. * AM/CW/SSB, inbuilt RF Gain * 1OOHz - 20kHz • 30 Watts RMS • 82dB/Wm * Black woodgrain cabinet NORMALLY $299.00/pr control, BFO. * PLL synthesised tunning, LCD display. * Scanning, 9 memories, 12 shortwave bands. NOW $160.00/pr 240 volt DE-SOLDERING TOOL - 30 Watt Limited Stocks * Slim Design • One hand operation • Self-contained suction power and heating equipmen • Replaceable tip * Easy Maintenanc NOW $39.95 NOW ONLY $659.00 inc. tax Spare tip to suit $4.95 DELUXE COMPACT DISC CARRYING CASE Now only $14.95 * ARLEC POWER SURGE PROTECTOR • Removable tray. (Holds 20 discs) * Attractive leatherette cover. (Black) * Felt Lined interior. * Locable case with carry handle. ___..,,,,.- <le"··,.... * Holds 8 VHS or BETA tapes. FLUKE 87 TRUE RMS DIGITAL MULTIME• Display: Analog/Digital (4.5 dig~). Back-I~ display. • Ranges: Volts, Ohms, Current (10A AC/DC), mA, uA, Freq., Capacitance & DiodeTest. • Touch hold and relative modes. • Min/M.ooAverage recording mode w~ MirvMax alert. • Input alert and overtoad protection. • 0.1 % basic DC accuracy. • Audible continuey. • Includes probes and holster. Normally $59.95 TOP VALUE! ONLV $21 .95 VIDEO CASSETTE STORAGE CABINET NOW ONLY $289.00 ¥ ~ . :.£~',./ • Surge Capacity: to 4500 Amps * Maximum continual voltage: 275 volts * Reaction time: less than 25 nanoseconds * Clamping voltage: 710 volt, 50 amps. * Energy absorption factor: 75 joules NOW ONLY $22.95 Ideal for computers, TV and videos etc. MORE SPECIALS IN THE FRONT OF THIS MAGAZINE Silicon Chip BACK COPIES March 1988: Remote Switch For Car Alarms; Telephone Line Grabber; Endless Loop Tape Player; Build Your Own Light Box; New Life For Radio-Cassette Players; Old-Time Crystal Radio. April 1988: Walkaround Throttle For Model Railroads, P t . 1 ~ i m m i n g Pools; Slave Flash Amplifier For CD Players; ~__reedback, Pt.1 ; Mobile Antennas For The VHF & UHF Bands. filHi.03~~ May 1988: Optical Tachometer For Aeromodellers; High Energy Ignition For Cars; Ultrasonic Car Burglar Alarm; Walkaround Throttle For Model Railroads, Pt.2; Designing & Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data. em1~ June 1988: Stereo Control Preamplifier (Uses LM833), Pt.1; Breakerles · ion For Cars Using Hall E a-Fast Nicad Battery Charg5 .Mc . t Controller (Uses PIR Det , Sniffer Probe & Preamplifier; What Is Negative Feedback, Pt.2. July 1988: Stereo Control Preamplifier, Pt.2; Fitting A Fuel Cut-Off Solenoid; Booster For TV & FM Signals; The Discolight Light Show, Pt.1; Tone Burst Source For Amplifier Headroom Testing; National Semiconductor LM833 Op Amp Data; What Is Negative Feedback, Pt.3. August 1988: Bui lding A Plasma Display; Universal Power Supply Board; Remote Chime/ Doorbell; High Performance AC Millivoltmeter, Pt.1; Discolight Light Show, Pt.2; Getting The Most Out Of Nicad Batteries; Data On Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Vader Voice; Motorola MC34018 Speakerphone IC Data; National Semiconductor LM12 150W Op Amp Data & Applications; What Is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (Uses Rohm BA1404); High Performance FM An tenna; Matchbox Crystal Set; Electronic House Number; Converting A CB Radio To The 28MHz Band; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone; How To Quieten The Fan In Your Computer; Screws· & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor For Shortwave Receivers; Electronics & Holden's New V6 Engine; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter For Computers ; Ultrasonic Proximity Detector For Cars; Simple Computer Sound Repeater; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System ; LED Flasher For Model Railways (uses LM3909) ; Build A l ,---------------------------------- . --7 Use this handy form to order your back copies Please send me a back issue for: O August 1988 0 September 1988 D January 1989 D February 1989 D June 1989 D July 1989 D November 1989 D December 1989 o April 1990 o May 1990 o September 1990 o October 1990 D March 1988 D October 1988 D March 1989 D August 1989 0 January 1990 D June 1990 D November 1990 D May 1988 D November 1988 D April 1989 D September 1989 D February 1990 O July 1990 Enclosed is my cheque/money order for $_ _ _ ___or please debit my O Bankcard Card No. ~~' '---I'---'---'----'I I'---'---'---'----'II'---'---'---'--- Signature _ _ __ _ _ __ ____ Card expiry date_ _~/ Namn Street Suburb/town Postcode_ _ _ __ D July 1988 D December 1988 D May 1989 D October 1989 O March 1990 O August 1990 I I O Visa Card 0 Master Card $5.00 each (includes p&p). Overseas orders add $1 each for postage. NZ orders are sent air mail. Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 Or call (02) 979 5644 & quote your credit card details. Fax (02) 979 65o3 x I L ______________________ ---------------~'-----96 SILICON CHIP Simple VHF FM Monitor (uses MC3362), Pt.1; Lightning & Electronic Appliances; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1; 32Band Graphic Equaliser, Pt.1; Stereo Compressor For CD Players; Map Reader For Trip Calculations; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Electronics For Everyone - Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; Electronics for Everyone - All About Electroly1ic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Universal Temperature Con- . troller; Understanding CRO Probes; LED Message Board, Pt.3; Coherent CW - A New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm ; NSW 86 Class Electrics; Facts On The PhaxSwitch Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-day Programmable Timer; Introduction To Stepper Motors; GaAsFet Preamplifier For The 2-Metre Band; Modern 3-Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; Alarm-Triggered Telephone Dialler; High Or Low Fiuid Level Detector (uses LM1830N); Simple DTMF Encoder (uses Texas TMC5089); Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669) ; A Guide To Hard Disc Drives. October 1989: Introducing Remote Control ; FM Radio Intercom For Motorbikes (Uses BA 1404 And TOA 7000) Pt.1 ; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super Sensitive FM Bug; Build A Low Cost Analog Multimeter; 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 (Records Up To Four Separate Messages, Uses Texas TMS3477NL and 256K RAMs); UHF Remote Switch; Balanced Input & Output Stages; National Semiconductor LM831 Low Voltage Amplifier IC Data; Install A Clock Card In Your PC; Index to Volume 2. January 1990: Service Tips For Your VCR; Speeding Up Your PC ; Phone Patch For Radio Amateurs; High Quality Sine/Square Oscillator; Active Antenna Kit; The Latest On High Definition TV; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas ; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; Digital Waveform Generation Using a PC; The Controls On A Model Aircraft. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3 ; Simple Service Tips For Your Microwave Oven; Model Aircraft Aerodynamics; Active CW Filter For Weak Signal Reception. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors; The Mazzie CW Transceiver; Waveform Generation Using A PC, Pt.3; 16Channel Mixing Desk, Pt.4 ; What To Do When Your Computer Goes Bung, Pt.1; Electronic Load For Checking Power Supplies. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To Your Computer; What To Do When Your Computer Goes Bung, Pt.2. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; LowCost Dual Power Supply; Inside A Coal Burning Power Station ; What To Do When Your Computer Goes Bung, Pt.3; Digital Waveform Generation Using A Computer, Pt.4. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Appliances; Horace The Electronic Cricket ; Digital Sine/Square Wave Generator, Pt.2; The Tube Vs. The Microchip (Two Shortwave Receivers Compared) ; What To Do When Your Computer Goes Bung, Pt.4. September 1990: Music On Hold For Your Telephone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; LowCost 3-Digit Counter Module; Voice Mail For Your Computer; Simple Shortwave Converter For The 2-Metre Band; How To Make Dynamark Labels. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; The Bose Lifestyle Music System; Using The NE602 In Home-Brew Converter Circuits. November 1990: Low-Cost Model Train Controller; Battery Powered Laser Pointer; A Really Snazzy Egg Timer; 1.5V To 9V DC Converter; How To Connect Two TV Sets To One VCR; Introduction To Digital Electronics ; Simple 6-Metre Amateur Transmitter. PLEASE NOTE: November 1987, December 1987, January 1988, February 1988, April 1988, & June' 1988 are now sold out. All subsequent issues are still available but stocks of March 1988 are now low. Order now if you want this issue. DECEMBER1990 97 TheStory f Electrical Energy, Pt.6 As time passes, all alternators either wear out or fail completely. Now though, instead of scrapping worn out machines, it is often worthwhile rebuilding them to better than new. By BRYAN MAHER All over the world, the picture of electricity generation is undergoing a change in emphasis. Projecting future demands is becoming more difficult and in many countries the number of possible new power station sites is severely restricted. So existing stations are being upgraded and improved. In the USA, Canada and Europe, atomic plants tend to provide the base load. Thus, many fossil fuelled power stations, designed for base load 20 or 30 years ago, are today required to cope with cyclic load duty. The changing economic climate forces generating companies to extend the working life of existing machinery rather than purchase new equipment. All the above factors make the decision to recondition and upgrade old alternators, to extend their life by 20 or more years, a sound financial proposition. No longer does it make sense to scrap a power station after 30 years of service, as was done in Australia and overseas until recently. Very large alt~rnators can be retrofitted to obtain higher output, better efficiency and greater reliability, especially under peak load duty. This giant 970MVA alternator, being lifted by the crane, failed and was rebuilt to a much higher standard. 98 SILICON CHIP The electro/mechanical justification for a 30-year-old alternator retrofit may be summarised as follows: (1). The stator insulation may no longer be reliable; (2). Improved design can today raise the efficiency; (3). Alternators designed for steady base load years ago may well fail if used on cyclic peak duty. Two types of peak load Two forms of peak load duty are used, depending on the requirements: (1). Load cycling means that the turboalternators are run at full speed all the time, the load changing from full power during peak hours to some minimum load at other times. (2). In two-shift operation, the machine may run at full speed between 7am and 7pm daily, carrying the full load during peak times and perhaps 3/ 4 load throughout the day. Between 7pm and 7am, all electrical load may be removed, the steam supply shut down and the turbo-alternators kept revolving slowly. This way, thermal equilibrium is more easily restored before the next shift. Sometimes, electrical shaft turning gear is employed for this purpose. Either of the above two forms of cyclic loading has a bad affect on the alternator. The changing power load causes thermal cycling in the stator with consequent expansion and contraction problems in the insulation of the copper coils. Either the copper coils will expand by sliding with respect to the core slots, or the copper will remain still in the slot and suffer elastic compression. The amount of movement or stress depends on the difference between the no-load and full-load temperatures, and the relative expansion coefficients of core and windings. Minimising these stator stresses requires careful choice of copper and Modern alternators are big brutish machines running with very fine tolerances. The rotor of a big machine (say 1 gigawatt) may weigh as much as 70 tonnes and rotates at 3600rpm (60Hz) or 3000rpm (50Hz). Vibration is a very big problem, particularly at the ends of the stator windings. silicon steel alloys. Also (and most importantly), the full load temperature must be kept as low as possible. The best way to do this is to use water cooling. Rotor stresses In two-shift operation, the rotor winding and core teeth suffer cyclic forces which accelerate metal fatigue. At full speed, centrifugal forces on the rotor winding are so strong that the conductors cannot possibly slide axially under thermal expansion. Therefore, the copper remains under axial compressive stress at full load. In load cycling operation, this thermal compression cycles on and off, fatiguing the copper. In two-shift mode, the centrifugal forces alternately range from maximum to zero, accelerating wear on the winding insulation. Rejuvenation Some alternators are rejuvenated when their reliable lifetime is judged to have ended. In other cases, actual failure precipitates a complete retrofit. In this chapter, we trace the story of a very large alternator from burnout to its complete restoration. In June 1986, a 970MVA 60Hz steam turbo-alternator in Florida, USA suffered a stator winding to earth fault. The machine protection automatically opened the alternator circuit breaker and switched off the excitation. This prevented further power from being generated, preventing the escalation of the short circuit into a possible full scale fire. The steam valve was closed and DECEMBER 1990 99 weeks. While on loan, this spare ·alternator produced 2500GWh of electrical energy. The contract involved complete redesign of the alternator using the original stator casing. This required a new stator core with improved slot geometry and provision of laminated end pressure plates. The original hydrogen cooled stator winding was replaced by a new water cooled coil set and end-winding supports were made flexible to accommodate startup expansion stresses. Improved stator insulation was also incorporated and the rotor winding replaced using coil retaining rings of advanced design. Dismantling During assembly, the laminated stator core of an alternator must be thoroughly compacted to minimise vibration. This is achieved by inductive vibration and massive clamps. half an hour later, the machine was at a standstill. When the 69-tonne rotor was removed, inspection 'showed severe burning of the stator coils deep within the core slots. And removal of the ZZkV coils revealed the iron laminations to be severely burnt. It was a mess. Records showed that this machine .had run for almost 20,000 hours, in- eluding nearly 800 stop/start cycles. In fact, even though it was a very large machine, it had been used mostly for peak load duty. The ABB company was awarded the contract to remove, retrofit and replace the 460-tonne alternator. During the repair, a 730MVA alternator was loaned to the power company, being mounted on the original foundations and brought on line in just 11 With the alternator lifted from its foundations, the old stator windings and laminated core were removed. The remaining 113-tonne stator housing was then shipped by rail to ABB's workshops in Richmond, Virginia for cleaning and modification. Simultaneously, at the company's Birr workshops in Switzerland, new stator coils and iron core segments were designed and manufactured. These were delivered in sections tr. the Richmond shops for assembly. With the stator casing mounted vertically over one end press-plate, the first task was stacking the core into the stator casing. The core is composed of low-loss silicon alloy steel segments, each 119th of a circle. Each lamination was punched, deburred and coated on both sides with heat resistant varnish, then placed on the core stack. For long life, it is important that the core laminations be compacted tightly, otherwise vibrating segments would damage the coil insulation. Therefore the core was periodically compressed using hydraulic rams during the stacking process. The completed core was vibrated by inductive currents, while being squeezed hydraulically to settle and compact all the steel segments. Stator winding This photo shows the stator of a 300MVA 2-pole turbogenerator undergoing testing at ABB's Birr works in Switzerland. The stator is cooled by pumping de-ionised water through the windings and end connections. 100 SILICON CHIP With the casing and its core returned to horizontal attitude and the coil support ring fitted, the new 31,800 amp stator windings were installed. The new stator coils were wound using multiple parallel flat copper wer/ng machine• lesaphone• /ml/ea The mOMI CPEP-1 MWUIN 1/ghtn/n(I, po- .UtflN #Id ap/ltN coally aqulpment by do not reach yi,ur c-lantly monitoring lhe PHONE /Ina and lhe IIAINS po- IIM, Simply conMCt to an exlatln(I po-, point, plllfl In your fllx •tc and• MrlH of lndk:ators a/Iowa lhe atatia of Iha ma/na This close-up photo of a rotor shows some of the detail of the ends of the excitation windings. The windings are subjected to considerable stresses, both from the retaining rings which stop them flying out and the centrifugal forces. bars interleaved with stainless steel tubes for the water cooling. The original coils were hydrogen cooled. Because water has much higher specific heat than any gas, less volume is needed when water does the cooling. Hence, less space in each coil is required for the water tubes (compared with the original larger hydrogen tubes). Thus, more of the coil cross section can be copper, even when slightly smaller coils are used. So compared to the old coils, the new coils are smaller in total cross section yet contain more copper. The new smaller coils naturally require smaller slots to accommodate them. Therefore, more iron volume remains. The result is that for the same total magnetic field , the greater core section means lower flux density. Thus, in the refurbished machine, the excitation losses are lower. As core vibration amplitude is proportional to the square of magnetic flux density, the reworked machine (using lower flux density) also has much less vibration. The coil insulation can therefore be expected to last a lot longer. High voltage insulation Micadur, which exhibits high di- electric and mechanical strength, was used for the stator coil insulation. Developed by ABB specifically for turbo-alternators, Micadur is superior to the insulation used in the original windings. The newly renovated stator, winding end connections and cooling water tubes are shown in the photos. The laminated construction of the end-press plates results in reduced iron losses compared to the original design. The method of supporting the stator end connections is just as important as the slot insulation. This is because coil overhangs can be subject to vibration if not suitably clamped. The clamping support used in the refit is rigidly fixed to the stator core. Therefore, no 120Hz vibration can be transferred from the core to the coil end overhangs. This is a considerable improvement over the original design. A further improvement introduced in the retrofit is that the coil ends are allowed to move in the axial direction, yet are restrained radially and tangentially. Axial flexibility accommodates differential thermal expansions which must occur during changing loads. Therefore, the reworked machine is -~JS11•a po-point. Fully Telecom and O.pt of Mlnarala and .n,a __ ,... Enargyapprowd. ELECTRONICS suitable for cyclic peak load duty as well as steady base load operation, an important consideration for its owners. Provision was also made for retightening the end connections as the winding insulation settles and ages. De-ionised cooling water is pumped through the stator windings and end connections, passed through a cooling heat exchanger and filter, then recirculated. On return from the stator, the circulating water is monitored for temperature rise, flow rate, pressure differential and electrical conductivity. Rotor improvements Alternator rotors are made in one piece from high grade steel, with slots milled to receive the insulated copper excitation winding. The steel teeth between these slots are subject many stresses. At the normal speed of 3600rpm, the copper winding tends to fly out, so must be tightly restrained against the enormous centrifugal forces. Wedges driven into keyways in the slots, along with circumferential steel to anlen exlallng Unique powder -a ret»fvin ehlmen excalhln UHF recapllon compared to ollHlr UHF anlennM of almllar aize and price. Two m""'11a.,. a11allable: TVA14-S.nd Four and TVA15-Band R.,,., Both.,. aupplied with back reflectors to pre'llent ghoalln(I aa _,, .. • Mlerproof entry ,& f t .bolt and a lilt adjua1able ELECTRONICS metal mounting bracket. An Tl.'llllft. .n.&\.li'J DECEMBER 1990 101 ·:r ·- This photo shows the rotor of a reconditioned alternator in the process of being refitted. This is a tricky job since the clearances are tight and because of the tendency for rotors to sag under their own weight. Compared to the original design, the reconditioned machine generates 14% more power. bands, are used to hold the winding in place along the length of the rotor body. Restraining the ends of the rotor windings is a big mechanical problem. The usual practice is to fit a steel retaining ring over the insulated winding ends. On this machine, this had ultimately resulted in cracking of the rotor teeth. This happened because when the machine was stationary, .the retaining rings applied considerable force to the steel teeth. Then, at full speed, centrifugal forces exerted by the winding pushed radially outwards, taking tension off the teeth. This reversal of forces in the rotor teeth each time the machine was run up to speed caused metal fatigue, and hence the cracking. Extensive tests with this method have shown that cracks appear after about 200 starts, while 1000 starts can cause dangerous cracking right through a tooth. As this particular machine had already had about 800 starts in its lifetime, a new approach was needed. This involved using a ring set fixed in place on the rotor using a bayonet locking system. This greatly reduces the stress reversal cycle at start-up. In addition, the new rings are made from a manganese chromium steel alloy that's not sensitive to stress-corrosion cracking. These rings and the rotor modifications to accommodate them are designed for 10,000 starts, ensuring a long life for the rebuilt machine. Uprated alternator After the completed rotor had been overspeed tested, the finished alter- TABLE 1 Output voltage Apparent power Stator volts Power factor Increase in power 102 SILICON CHIP Original 22kV 970MVA 22kV 0.89 Retrofitted 22kV 20kV 1050MVA 1100MVA 20kV 22kV 0.89 0.89 71 .2MW 115.?MW Ii' ·' . -- ·' nator was returned to its original site and coupled to the steam turbine. Tests validated the calculated details used during the retrofit. Because of the changes made in the design of the stator coils, 14% more power (116 megawatts) could be taken from the alternator for the same temperature rise. Even then, this increase in available power is limited not by the alternator but by the ratings of the original exciter. The results are shown in Table 1 for two values of alternator voltage: Z0kV and 22kV. Increased efficiency The modifications made during the retrofit resulted in lower alternator losses and hence increased efficiency. The new stator slot and coil design give lower flux density, thus reducing excitation power loss and stator heating. Compared at the original power output, the rebuilt machine has 600kW less losses which is a fantastic saving in energy. Completed in December 1987, the retrofitted alternator has been operating on load ever since - a much cheaper solution than a completely new machine. Acknowledgement Grateful thanks to ABB staff and to ABB Review for data, photos and permission to publish. MODEM SENSATION! Here's an amazing bargain - if you're quick. An internal modem for your PC giving you world-wide data communication flexibility! • Hayes "Smartmodem" Compatible Internal Modem for MS-DOS PC's • 2400/1200/300 BPS, full or half duplex Access a huge range of data bases and bulletin boards • Bell 103, 212A, CCITT V .22 & V.22bis compatible - anywhere in the world. Communicate with other • Auto dial AND auto answer computers. The possibilities are endless! • Complete with highly detailed Fully guaranteed for 12 months (not 3!) PLUS our instruction manual and BONUS exclusive 21 day satisfaction guarantee! communications software! Completely internal supplied with standard (modular) phone cord. Socket included for standard phone handset · Both touch-tone and pulse dialling included Low Speed Data Format (0-300 bps) - Serial; binary asynchronous: 7 or 8 data bits, 1 or 2 stop bits, odd, even or no parity Built-in two inch speaker with volume control for monitoring purposes High Speed Data Format (120012400 bps) - Serial, binary, asynchronous: 7 data bits, 1 or 2 stop bits, odd, even or fixed parity (8 data bits no panty) NOTE: These modems are not Telecom Approved. Ideal for experimental use. We've seen similar advertised elsewhere at $399+! OUR PRICE: s295 ,.._eOARo Cl~~~b~\\l'l'l:t\~¥~! SOLUTIONS ~'" CALL (02) 906 5696 FAX 906 4592 OR POST TO PO BOX 1120, LANE COVE NSW 2066 ) ,AMATEUR RADIO BY GARRY CRATT, VK2YBX A 5W power amplifier for the 6-metre FM transmitter Last month, we described the construction of the 6-metre summertime special - an FM exciter for the 6-metre band. This month we follow up with a matching power amplifier, designed to provide up to 5 watts of RF power from a one milliwatt source. Designs for RF power amplifiers have been published many times before. Most rely on the use of special power transistors, specifically produced for the low band (70-85MHz) commercial 2-way radio market. Some of these devices allow power levels of up to 50 watts to be achieved but all carry a significant price tag, often around the $30 mark. At such a high price, there certainly is no margin for construction error. The complete amplifier design presented here can be built for less than the cost of one of these devices. CB output transistors Bearing in mind the high cost of power transistors, we decided to opt for a more economical line up. Considering the tens of thousands of 27MHz CB transceivers in service, having an output of similar proportions but at around half our required frequency, we thought it might be possible to use the same configuration. It should simply be a matter of scaling the values of L and C to suit 52MHz, and substituting devices rated at that frequency. Fig.1 shows our circuit. As can be seen, we selected a fairly common Japanese transistor, the 2SC710, as the predriver (Ql). This particular transistor is often found in CB transceivers. The 2SC710 is readily available from several sources as a spare part. We used fixed biasing via 5.6kQ and 1.2kQ resistors to set the operating conditions of this stage. The output is then coupled from the collector of Ql via an impedance "transformer" made using a ferrite balun core and some 25 SWG enamelled copper wire. This ensures a reasonable match to the low impedance input of the second stage. The trimmer capacitor VCl allows the primary winding of the transformer to be resonated at the operating frequency. This approach improves both the efficiency and harmonic suppression compared with an untuned stage. The second stage, Q2, uses a Motorola device, the MRF629, which has minimum gain of 8dB and can easily be driven to 1 watt output. In addition, this transistor, unlike several others we tried (2N3866, 2N4427), is supplied in a grounded emitter TO39 package, which greatly improves grounding and heat dissipation. Also, the price of the device in "one off" quantities is quite reasonable. The output stage (Q3) uses a 2SC1306, the same device used in the a The 6-metre power amplifier is designed to match the FM exciter described last month. Because it works at RF, make sure that all component leads are kept as short as possible. The completed board should be housed in a metal case. 104 SILICON CHIP RFC5 0.65uH 10 + 16VWJ RFC2 5.tik PAIi ff'~•· .,. VC1 5-70pF 1.2k C ELJe ; VIEWED FROM BELOW ECB 6-METRE POWER AMPLIFIER Fig.1: three RF transistors are used in the circuit for the 6-metre power amplifier. Q1 serves as the predriver & this drives Q2 via impedance matching transformer T1. Q2 provides a minimum gain of 8dB & drives output stage Q3 via a tuned circuit consisting ofL1 & RFC4. L2 tunes the output stage for maximum efficiency. INPUT PARTS LIST 1 PC board, code SC06101911, 117 x 80mm, 2 adjustable RF coils (L 1, L2); available from Stewart Electronic Components 5 RF chokes (see winding details) 1 F14 balun core, DSE Cat. L1340 (T1) 2 BNC sockets 1 heatsink for 02, DSE Cat. H3412 1 heatsink for 03, DSE Cat. H3490 Semiconductors Fig.2: the circuit is built on a PC board with a groundplane on the component side to ensure stability. When installing the parts, be sure to solder the leads on both sides of the board if the ground plane comes right up to the edge of the hole. 27MHz version of the power amplifier found in thousands of CB radios. This device is rated to over 100MHz and when driven with the MRF629, provides a level of output power exceeding 4 watts. This is quite sufficient to enable local contacts during the winter months and can be used to significant advantage during the 6-metre season (about the time you read this). Tuning and bypassing Both the input and output circuits of the final stage of amplification are tuned, via Ll and L2, to provide a further improvement in efficiency. Bypassing is especially important in a design such as this, and so exten- sive use has been made of RF chokes and decoupling capacitors in the DC supply line to the three stages to ensure that they remain stable under all conditions. These RF chokes are made by winding a specified number of turns on a 2.2kQ or 2.7kQ resistor. This saves the problem of having to obtain commercial prewound chokes. Construction Construction of the power amplifier is made easy by the use of a double-sided PC board. The top side (component side) of the board forms the groundplane, as with the exciter described last month. Components connected to ground are soldered on 1 2SC710 NPN RF transistor (01) 1 MRF629 NPN RF transistor (02) 1 2SC1306 NPN RF transistor (03) Capacitors 1 10µF 16VW electrolytic 2 .01 µF disc ceramic 1 680pF disc ceramic 1 1SOpF disc ceramic 1 120pF disc ceramic 2 100pF silvered mica 1 82pF disc ceramic 1 5-70pF ceramic trimmer Resistors (0.25W, 5%) 1 5.6kQ 1 1.2kQ 1 68Q 2 47Q 1 22Q Miscellaneous 25 & 30 B&S enamelled copper wire for winding RF chokes DECEMBER 1990 105 ELECTRONICS WORLD DECEMBER SPECIALS USED 'AA' 700mAH NICAD BATTERIES $ 0.50 TEMPERATURE CONTROLLED $135.00 SOLDERING STATION UNIVERSAL NICAD BATTERY $ 29.95 CHARGER Can do 4 at a time (AA, C, D, or 9V Nicads) p-101911 1{ + ae• 0 0 ~ 0 ao'Co ,o-a o L ao 00 v~ p 00-0 ocl» ~ 0 0 40 CHANNEL AM CB RADIO $ 79.00 SMOKE DETECTOR $ 49.95 PIEZO SIREN WITH BACKUP BATTERY $ 59.95 Ideal for Car Alarms DIGITAL DISPLAY AM/FM STEREO CAR RADIO $ 49.95 PORTASOL GAS SOLDERING IRON $ 35.00 ARLEC SUPER TOOL KIT $ 69.50 LOGIC PROBE $ 35.00 SCANNER FANATICS FREQUENCY REGISTER OF VIC. $ 24.95 PHILIPS INFRARED REMOTE CONTROL $ 35.00 COMMON CATHODE 7-SEGMENT DISPLAY $ 1.00 $ 15.95 VIDEO DUBBING KIT ARLEC 2 SPEED CORDLESS DRILL AND SCREWDRIVER $ 69.95 2-CHANNEL FM WIRELESS INTERCOM $ 89.95 SINGLE CHANNEL UHF TRANSMITTER KIT $ 18.00 SINGLE CHANNEL UHF RECEIVER KIT $ 34.90 VULTURE CAR ALARM KIT $ 39.90 INFRA RED NIGHT VIEWER KIT $239.00 TALKING ELECTRONICS ULTIMA FM BUG KIT $ 12.50 Mail Orders Welcome 30 Lacey St, Croydon VIC, 3136. Telephone: Fax: 106 (03) 723 3860 (03) 723 3094 (03) 725 9443 SILICON CHIP ,' 0 ~00 dli c&o 0 8 019 . oo ao SC06101911 0 acmog ·8 0 •ao Fig.3: here are the two full-size artworks for the PC board. the top side of the board, while the remaining circuitry is interconnected by the pattern on the underside of the PC board. This arrangement ensures a good low impedance earth, which is most important for stable operation, especially as some of the components carry significant RF currents. The entire board assembly should be mounted in a metal enclosure and fitted with BNC connectors for input and output terminations. Be sure to use silicone heatsink compound between Q2 ,Q3 and their respective heatsinks, to ensure efficient thermal transfer from the devices. It is quite normal for Q3's heatsink to become hot after extended transmit operation. No doubt larger heatsinking arrangements can be made for the output transistor by constructors with access to metalworking equipment. The current drain of the power amplifier, when fed from a 13.8 volt DC supply, is around 1 amp. Make sure that you have a power supply of sufficient current rating. Apart from the transistors, which are freely available from the sources quoted in this article, most components are standard types and should be available from parts stockists. The two 100pF capacitors in the output (associated with L2) should be silvered mica or other high voltage types, as the RF voltage developed across these components ·can exceed the nominal 50 volt rating of the ceramic capacitors used in the lowerpower stages of the amplifier. Fig.2 shows the component layout of the amplifier. Keep all component leads as short as possible. This is easily achieved as most of them are horizontally mounted on the circuit board. To successfully tin enamelled copper wire, in order to secure the ends of the conductors, first scrape away the enamel with a scalpel or "Stanley" knife. This done, wind a few turns of this bared enamel wire around one lead of the resistor, then apply solder and a reasonably hot iron to the resistor lead. After several seconds, the solder will flow onto the copper wire, and the lead will be secured. It is now a simple matter of wind- ing the prescribed number of turns onto the resistor and terminating the other end in the same manner. The windings of the RF chokes can be held in place by coating them with clear nail polish, prior to insertion into the PC board. Alignment To align the power amplifier, connect a power meter to the output and a current meter in series with the DC supply. Set the ferrite cores of both Ll and L2 so that they are flush with the tops of the formers. It's then just a case of tweaking both cores for maximum RF output power. You will have to repeat this procedure several times to get the best alignment. Neither of our prototypes could be maladjusted to cause deliberate high harmonic content in the output. In fact, all transmitter harmonics were suppressed by 40dB minimum. It should be noted that, due to the high gain of the power amplifier, as little as -10dBm input will generate some output (around 1 watt in fact). However, compression does not occur Winding Details for the Inductors RFC-1 RFC-2 RFC-3 RFC-4 RFC-5 10 turns of 30 35 turns of 30 10 turns of 25 20 turns of 30 20 turns of 30 B&S B&S B&S B&S B&S ECW wound ECW wound ECW wound ECW wound ECW wound on on on on on a 2.2kQ 0.5W a 2.7kQ 0.5W a 2.2kQ 0.5W a 2.2kQ 0.5W a 2.7kQ 0.5W resistor. resistor. resistor. resistor. resistor. Transformer T1 : Primary - 3 turns 25 B&S ECW; Secondary - 2 turns 25 B&S ECW. Balun core is F14 material (DSE Cat. L-1340). Note 1: all resistors must be carbon or composition types. Note 2: ECW stands for "enamelled copper wire". until a level of +3dBm is applied. If using a higher input level, a suitable attenuator should be used to limit the input power to lmW. The RF output can be measured using an inexpensive CB power meter. These meters have a reasonable frequency response up to the region of 70-B0MHz. Parts availability The 2SC710 transistor can be obtained from Benelec Pty Ltd, phone ANTRIM TOROIDAL TRANSFORMERS QUALITY TOROIDAL POWER TRANSFORMERS, MANUFACTURED IN U.K. NOW AVAILABLE EX-STOCK AT REALISTIC PRICES. General Construction UV IIM 1/./SULA ll{lr.l (02) 693 5111. The MRF629 transistor can be obtained from Benelec, VSI Electronics and Dick Smith Electronics. Heatsinks can also be obtained from DSE, Cat H-3412 (Q2), and H3490 (Q3). The adjustable RF coils (Ll, L2) can be purchased from Stewart Electronic Components (phone 03 543 3733), part number CG 105. The output transistor can be obtained from DSE or Benelec, and the toroidal former can be purchased from Dick Smith DSE. E-1 LAMINATED POWER TRANSFORMERS PCB MOUNT STOCK RANGE PCB mount ex-stock in sizes from 2.5V A to 25V A with secondary voltages from 2 x 6V to 2 x 20V. Triple output models also available for logic circuits. Chassis mount manufactured to order in sizes from 2.5VA to 1 KVA in E-1 and C core. CHASSIS MOUNT TO ORDER w,~o•~G ,,.su,,..1,0~ We are the largest ex-stock supplier of toroidal power transformers in Australia. Our standard range consists of the U.K. manufactured ANTRIM range in 10 VA sizes from 15VA to 625VA. All have a single 240V primary and dual secondary windings ranging from 2 x 6V to 2 x 55V. Our local manufacturing facilities supplement this range by manufacturing specials to order. Models are available from stock to suit most project kits. Comprehensive data sheets are available on request. Enquiries from resellers and manufacturers are welcomed. Prices are extremely competitive and generous trade discounts apply for quantity. HARBUCH ELECTRONICS PTY LTD 90 George St .. HORNSBY NSW 2077 Phone (02)476-5854 DECEMBER1990 107 .... I I I ~· I "',/ / ;t ,: ,,,. } :. i rww Z-NX Super Bue Mo,._ I aNowa you to get moat out ol yow compullt' and enhance I your p,oducllvtty. glvN you I abllty to expend the vereltilffy ol your computer through ol I draw gragt,lc aoltware euch • pain~ and CAD programa. The I "-,..,._ 11tow1 you to run progr..,. lka GEM and WlndoThe 2 the ~ the the ,._ - 2 1wlllch makae aN -adorw ol teeter. Many I p o p ueellar l a r ~ -. . . ..,._, the COrnputa' j:I 111d word procneore - other program■ can aao ba "" Super Mo... 2. f1'•------·-----I I! with m mouse. MODELS: ATM- 110 Touch Mouse tor IBM PC/ XT/ AT and comptttlble's, Operate■ under Microsoft I mouse system mode. FEATURES, • User's linger movements on the 58 X 48mm front panel of lhe touch mouse control the ~ on- screen cursor movement • Wilh no ball, the !ouch mouse requires no desk space lor rnovemenl. No pad to get dirty and take up desk space. · One finger can do all the users drawing. Compatible with all existing mouse software. • RS· 232 serial port ~ - Especially suitable tor laptops, the touch mouse saves on desk space. mouse • Microso Mou.eSy • Super hlg 600mmrte • Super hlg 200 O.P.1. ( • Silicon r I • • 100% ~croeoft Compatible • IBM or APPLE Family 1 • 1 _...... Computer Compatible. • FrN Softwa,w with Pop-up ._._ • Ute time Warranty. Aleo eupplled with the Super Bua MouN trt two FREE Ttlepalnt dlako which allo- the ,._r to perform high rHolutlon graphic:. with the mo....Graat Valuol .X19951 .......................$119 HURRY! THIS OFFER CAN'T LAST COMPUTER CASES • Three buttons, user defln-.,e • Silicone coated steel ball • High resolutio~ movement of 195 dots/Inch . Smaller table space and less hand movement required · Optical rotary encoder • M ■ x. tracking speed : 200mlsec • Mouse resident firmware · Size : 116 x 66 11: 34mm , Mouse Driver Software included, allowing you to Install with all popular software packages. Also Included is the handy Pop-up menu software that allows the user to integrate the mouee with the keyboard, DOS, and other popular software- packagH I I I .I •FREE SOTWARE INCLUDED/{! MOUSE ·DRIVER I I·• DEMO TEST PROGRAM PROGRAM I I · HIGH LEVEL LANGUAGE INTERFACE ROUTINE: I IMicroaolt C, Microoolt Fo11ran. Quick Baolc, Turbo C I I • POP-UP MENU I I DR. HALO IN GRAPHICS SOFTWARE x199so ...........................................$149.ool I Paacal .•. etc. X19950 ......... . ;..: I I I BABY AT* STYLE I COMPUTER CASING I key IHC11rity mounting acc..sories II • THECHEAPESTXTTURB MOTHERBOARD IN THE SOLAR SYSTEM I Small lootprint. Features switch, 8 slots and 1r. · · · · · · · · · · · . .: Size: 360(W) x175(H) x405(D)mm ..... ~ ~..-----·- ----- I I -- .. . . ~ II ~1;")~ INCLUDES FREE SOFTWARE! , PC PAINTBRUSH & IMAGE TOOL i , is mighty little XT motherboard has 8 **** expan::.ion slotsand uses 5 low cost RAM chips to provide a full 640K memory. The ASIC chip well known tor its reliability is also used. The CPU is a state- of the art NEC V20 running at 4.7110 MHz (switchable) with zero wait states. Size is just 208 X 161 mm. "GOOD THINGS COME IN SMALL PACKAGEs·· MEMORY SIZE -'I I I I I We are offering to you the FASTEST XT Icompared on 11111 Planet. II features 31 MHz to 4.nMHz on the standard XT. . The board Is fully XT compatible and runs with all standard XT cards. Speed Is swltchable between standard 4.nMHz ,.nd turbo speed .. Up to 1 MB ol RAM can be fitted _ on board • For even taster operation the memory above "' 640K can.be used as "shadow" RAM tor speeding • up BIOS operations or as a RAM disk. The board provides software selection ol wait• state. ~. W I . 128K bytes 256K bytes 384K bytes 512K bytes 640K bytes I I I I I I I Features selectable "spring centring" or "tree floating". Electrical trim adjustments on both axis. 360 degree cursor control $99 DRAM C14205 .................. $49.95 424256 X 1 424256 X 2 424256 X 3 424256 x 4 or 421000 x 4 424256 x 5 or 421000 x 4 + 424256 1 APPLE* COMPATIBLE JOYSTICK Ideal tor games or word processing. Fits most 6502 "compatible" computers. x C14200 ................. $29.95 THE WORLD! For quality and a great price this EGA vid the cheapest in the world. Using advanced paradise chip technology. it reliability and maximum perlormanfe. FEATURES INCLUDE: Full compatibility with XT, AT. 386 Full 256K display memory Completely backward comp. with CGA, MD , Hercules with Intelligent switching software. 480 line extended EGA mode. X18036 ... $199 X18036 IBMXT ISM PS2 MODEL 30 ~ -........- - - - - - - - - - - t 10MHz XT IBMAT 1 ONLY ...... $139 ·----------- ·, RDER HOTLINE FOR CREDIT CARD O ·. .., ' . , \ \ \ \.----"'"" ::::--;,, , ., ") ,c2\ \\ \?"() . -i- \ . . _ 45'!1 _/ J/ - -~ ~ ,I. ·,-·--. l~t> u ' "• "· 2&4WAY RS232 DATA TRANSFER 1B RS232 BREAK OUT BOX CPF The Fortron CPF Filtered Electronic A simple way of monitoring RS232 intertace lead activity. Interface powered, pocket size !or circuit \eos~efria~~::~a reg~a~~~ing . Spike Protector provides a protective electronic barrier for microcomputers. printers, telephone systems and modems electronic typewriters. audio and stereo systems and other sensitive electronic equipment. The CPF provides protection from dangerous electrical sp!kes that can ca1Jse anything from obvious damage (like immediate equipment failure) lo less obvious harm that can drastically 2 spares. 24 swil'?hes enable:> you to break out circuits or reconh~ure and patch any or all the 24 active positions . SPECIFICATIONS: Connectors: 0B25 plug on 80mm ribbon cable and D825 socket. Indicators: Tricolour LED's !or TD . RD, RTS, CTS, DSR. CD. T.C . AC , OTA , (E)TC . Jumper Wlrn: 20 tinned end pieces Power: Interface power. Enclosure: Black. high impact plastic. Dimensions: 85 1t 95 1t 30mm shorten a system·s life. CPFs superior circuitry design and semi conductor technology responds instantly to any potentially damaging over-voltage, ensuring safe trouble free operation . X15700 ............... ....115 THE BUTTON SPIKE PROTECTOR Surges and spi~es are caused not only by lightning strikes and lo.ad switching but also by other equipment being switched on and off. such as fluorescent lights, electric motors. fridge freezers. air conditioners. etc .. For effective protection such spikes must be stopped before they reach ~~i:{o~\~:~~:!~:~~r. ~1~~tect 1 all equipment plugged into adjacent outlets on the same branch circuit. The Button employs unique metal o,cide varister technology and will dissipate 150 jo·ules of electrical energy . (nearly twice that ol comparable surge arresters .) ~~·:~:;~~::Ii~&~ so annoying inter1erence, general hash RIBBONS SPECIFICATIONS: • Elec:trlcll rating: 220·260 volts (AC) 50Hz 10 Amp sheets of 70 gsm bond paper. ~- ~ KEYBOARD ENCLOSED PRINTER STAND g 5 Pin Din plug and socket 1·9 ~ffll\;{iib 10+ $17.95 Erase your EPROMs quickly and. • MX80, FX80, RX80, FX800, MX70, MXBO. LXBOO 1·9 safely. This unll Is the cost effective solution to your problems. It will erase up to 9 x 24 pin devices in complete safety, in about 40 minutes (less time for leas chips) • Chip drawer has conductive foam pad • Mai ns powered • High UV intensity at chip surtace ensures EFROMs are thoroughly erased 10+ • MX100, FX100, RX100.L01000 1·9 10+ C22002 .. ..$19.95 $17.95 • LX80 1·9 C22003 ..$12.95 10+ $11.95 1.9 C22051 .. $13.95 ~~9 PIN TO 25 PIN CONNECTOR ADAPTORS NEW 1The tdeal solul1on 1Features C21058 (80 cotumnt NATIONAL PANASONIC KXM110 PRINTER RIBBON C22034 .................. $19.95 X 1566B 069 Plug to 0B25 Socket X 15669· DB9 Socket 10 0B25 Plug $8.115 qu.i11y ABS pl■ ollc and POCKET AUTO AB SWITCHES •Stationary holder •lnclude1 pull-out 1hell lo, • Pocket size, auto,.1cannlng • Allow, 2 PCs to share one Printer Mouoe 6 PROTECTEO POWER 0\/nETS for p,otectlng porson1I graphic equallNra, c o players etc SPECIFICATIONS: • Ellctrlcll rating: 240V Ill:;, 50Hz. •3 $99.95 JI RIPPER STRIPPER Mital OJ1ide Vartstora (MOV) • Maximum clamplng Votllgo: NCh MOV: 710 votta at 50 amps • Anponw time: Leu than 25 --·· • Adju1t1bte arms allows •••Y LEADS Rem ove ugly paper teed edges quickly and cleanly with this simple 111110 gadget ?"n .,,,~ . • Clamp mounting C21062 .......... .$39.95 •1.8 metres P19029 ..................$14.95 • 3 metres P19030 ..................$19.95 • 10 metres P19034 .................. $39.95 C21085 .................. $14.95 ., ~ ~ 80386-33•••! ! ~...•$~~ SYDNEY :74 Parramana Rd. Stanmore. 2048. Phone (02) 519 3134 Fax (02) 519 3868 IIELBOURNE:48 A'Becken SI. Phone (03) 663 6151 NORTHCOTE:425 High Si Phone (03) 489 8866 .. CLAY°l'ON:56 Ren~ei Rd: Phone (03) 543 7877 IIAILORDERI CORRESPONDENCE: P.O. Box 620, CLAYTON 3168 Order Hotline: 008 33 5757 (Toll tree. strictly alders only) Inquiries: (03) 543 7877 Telex : AA 151938 Fax: (03) 543 2648 IICRODOT 1n •RINGVALE ROAD NUNAWADING. I'll.AN 1251 OREENSBOROOQH COMPUTERS 17 GRIMSHAW ST I-Ho-at) Ph: 434l1N BRISBANE DEALER YRC COMPUTER SERVICE 147 LUTWYCHE RD . LUTWYCHE,4030 IICROTRONi:8 :IOI MOAPHETT ST ADELAIDE, tlOOO RITRONICS WHOLESALE. 56 Renver Road, Clay1on. Phone: (03) 543 2166 (3 lines) Fax: (OJ) 543 2648 COPY HOLDER (YU-H33) • Copy area 9 1~ " ,c 11 .. • Sliding line guide • Flat me1ar base C21060 ---......____ ., ., . ....,. : ,_.,. ' .. ..... ... $39.95 ,,,-....____ ( Errors and omissions excepted. Prices and specihcations subjeet to change. IBM'. PC· . xT·. AT· , ••• r90jjllte<«:llf.o.m.,q gt 1n1em.,,onai eu...... u ~ 'Appa,. • •91111Mf..:tff~·o.not.s,..,.,.....:1 ,,..,....1ol"-•HP1Ctr.re-.. 088 335757 TOLL FREE -MAIL ORDER HOTLINE FOR CREDIT CARD ORDER _:_ . 80388-25•••.!!:l\~'i!!f..... $2,815 All aalOI tax exempt ordet'I and whotfflfe lnqulrlOI to: X10086 .....................$69.95 ~,·~ MIN....__ __ XT3114 S•"I XT 12M STD. SIZE. •••••••••••• 1119 SUNTEC AT 12M.•••••••••••••••$375 ADELAIDE DEALER • Sliding line guide PRINTER LEAD 10A • IBM' compatible • ·0B37 Male 10 34 IOC connec1or • Lenglh 0 ·5 melres s COPYHOLDE? (YU-H32) • Suits IBM• PCIXT, compallbles • 25 pin "O" plug (computer end) to Centron lca 36 pin pluq ~ . vlclooequlpmen1, colour TVs, ■mpftflerw, tuners, 3 112" FLOPPY DISK DRIVE EXTENSION CABLE RS232 MINI TESTER • Male to le~te connec11ons • All pin wired straight through • Dual colour LEO indicates activity and direction on 7 lines • No batteries or power reQutred T.D. Transmit Data D.S.R. Data Set Ready R D Receive Data C .D. Carrier Detect R.T.S. Request 10 Send D.T.A. Data Terminal Ready C .T.S. Clear to Send Cal . X15656 Normally $39.95 positioning • Copy ■ rea 91 12 .. J1 11" Serial model: MS-201 • Host-powered X19150.................. $79.95 Parellel model: MP-201 Protocol transparent X19155 ..................$89.95 5¼" FLOPPY DISK DRIVE EXTENSION CABLE $99.95 XT' Cover Set C21066 ..................$14.95 AT' Cover Set C21068 ..................$16.95 XT 10M RODIRVING ELECTRONICS Keep your computer and accessories free of dual and grime while not In use antl•1tatic rubberlHCf top • IBM. compalible • 0B37 Male lo 34 way edge connector • lenglh 0 ·5 metres SMART DRIVE ADAPTER IDEIFDC •••••••••• $81 SMART DRIVE ADAPTER IDE 1/0 IFDC..•$119 DUST COVER A working bench for your MouH. •High 2 WAY FDD CONT. (360·1 .44M) .•..•..•••••••••••••• $80 CLOCK CARD......••••.•••••• 149 SPECIAL.-ONL Y $32.95 MAGIC STAGE MOTHERBOARDS (3S0-1 . 44M) •.••.•••••..••••...•• lf129 $69.95 ~~ gold plated pins X14955 ................. .. $159 $12.50 ~:g;:;ing GAMES •••••••••..•.••.••...•....•• $29 AT SIP GA MES ................ 135 4 WAY FDD CONT. X14950 ................... $129 With built-in timer 10+ DUST COVERS DELUXE PRINTER STAND VOICE MAIL ••••••••••••••.•••• $245 PRINTER CARD.............. S35 EGA CARD...................... $139 2 WAY FOO CONT. (360K).............................. 149 RS232 SERIAU CARD •.••. ..••••••••••••.•.•.•.•••. 149 Without timer • C ITOH 8510·1550 • Resl ore s order to your work area w1lhout occupying e,ctra space • -=eeds and relolds paper under !he printer automatically • AdJUSlable paper delleclors ensure smoo1h !low ol paper • Made of moulded plastic • Suitable for most printers ;g~~a~~i~~~r • • All 25 pins wired straight through Cat. X 15650 Male to Male Cat. X 15651 Male to Female Cat . X 15652 Female to Female only 49 onlY$59 UV EPROM ERASER P19038 ................... ...15 -- ~ ~ P19046 2wAY1x191301 4 WAY (X 191 35) . C22031 ....$16.95 $15.25 $69.95 P1 9045 ~~ttn,~i~e switches . These data switches support the 36 pin centronic interface used by Centronics. Printronics . Data Products. Epson , Micronics . Star. and many other printer manufacturers . • No power required • Speed and code transparent • Two/Four position rotary switch on front panel • Three/Five inter1ace connections on rear panel • Switch comes standard with lemale connector • Bale locks are standard • CP80. SX80, DP80. BX100, BX100, MB100 C22036 .. $19.95 Only$24.95 lili $49 2&4WAY CENTRONICS DATA TRANSFER SWITCHES EXTENSION LEAD • Keeps your paper and prmt•outs· neal and orderly • Transparent cover makes 1t easy to check on paper supply • Paper can oe led lrom the ·centre or the rear accord1ng to the destgn of the printer • Removable drawer which allows paper to be changed without movmg the printer • Retractable rear basket makes prmt•out cotlect1on fast and convemen1 • Suitable tor mosl pnnters each PRINTER RIBBONS TO SUIT: Cal.C21003 11 x9 112" $41.00 Cal.C21005 15x 11" ... $67.95 ~ / $39 only $ COMPUTER PAPER Quality paper at a low price! 2.000 ~~ '849 CENTRONICS GENDER CHANGERS • Female to Female . • Saves modifying or replacing non-mating Centronics cables. • All 36 pins wired straigh\ through . Cat.X15663MaletoMale Cat. Xt 5661 Male to Female Cat. X15664 Female to Female Normally $33.95, ~~~l:~~~:~~fa~~~~~r JOUies Protection Level : 350V peak cre.ated by small motors. fluorescent lamps, and the like that threaten the perlo,mance and shorten equipment life of unprotected electronic components. ~a~~~~~r20 ·., .. ,r'I, XT HD CONTROLLER $129 AT HO CONTROLLER $199 AS232/ SERIAL/ CLOCK .......................... $511 MONO/ COLOUR CARDO& MULTI 1/0 ..••...........•...... $99 512K RAM •••••••••••••••••••••• $59 DIAGNOSTIC................. TTU PRINTER................ $89 RAM 2M AT EXT/EXP .. $225 SM AT EXT/EXP •••••••••••$325 Save time and hassles of constantly helps eliminate troublesome and $69.95 2 ''::: 4 WAY Cal.X19125 only Voltaie : 240V Nominal $38.95 Spike/RFI Protectton: 4.500 amps for 20mtsecond pulses. Maximum clamplng v ott■ge: 275V differential mode . U you haye two or four compatible devices that need to share a third or fifth. then these inexpensive data transfer switches will save you the lime and hassle of constantly changing cables and leads around. • No power required • Speed and code transparent • Two/Four position rotary switch on front panel • Three/Five inter1ace connections on rear panel • Switch comes standard with SPECIFICATIONS: Additionally. CPF's filtering capability Cat.X10088 .. .. . , , ........ , .. ., SWITCHES CONTINUOUS POWER FILTER SPIKE ARRESTOR J .-.- 1"" REMOTE CONTROL BY BOB YOUNG Radio control receivers using amplitude modulation This month we will look at amplitude modulated receivers for use in R/C models. They have the advantage of being simple, easy to understand, and above all, reliable. Why use amplitude modulation (AM) when all the movers and shakers in the R/C movement talk endlessly about FM (frequency modulation)? There are several very sound reasons for my preference for AM. To begin, this column is written for beginners and sports flyers, and they do not face the demanding situations that the experts face in competition work. Secondly, beginners are never quite sure of whether they will be good at R/C work or even if they will enjoy it, to the level that they wish to stay in the hobby. So expensive equipment is a waste if it is just going to be resold or sit on a shelf. Thirdly, and most importantly, AM still gives the best value for the dollar. FM sets are expensive to purchase, much more expensive to repair and most important of all, much more expensive and sometimes more difficult to change crystals in. This is a very important practical consideration. Many modellers end up with lots of pairs of crystals, as the ability to change frequencies on a crowded field or on a race day is important. All of these disadvantages come for a very slender (if any) performance increase. Narrow band FSK The point to keep in mind here is that FM as used in R/C model equipment is not really true FM. It is more 110 SILICON CHIP correctly defined as Narrow Band Frequency Shift Keying (NBFSK) and believe me, the emphasis is on narrow band. The typical frequency shift range is from 1.5-2.SkHz. Now everybody "knows" that FM is better than AM and this may very well be true. But for it to be true, we are speaking of frequency shifts in excess of ±S0kHz. At this figure, there is a marked improvement in the signal to noise ratios over AM. With frequency shifts down around 1-3kHz, the signal to noise ratios are similiar to, if not worse, than AM and any talk of FM (NBFSK) R/C systems being better than AM systems in this regard is nonsense. NBSK advantages NBFSK systems do have two distinct advantages over AM. The AGC problem in AM receivers can be tricky and the time constants must be carefully set. A model moving very quickly past a Tx can create a lump in the AGC line which will show up as a glitch in the controls. This is particularly true of high speed model aircraft but can apply to boats and cars. Secondly, the frequency spacing can be moved a little closer with NBFSK. Typically, AM receivers operate on 20kHz spacing and are hard pressed to come down to lOkHz. It can be done but it is expensive. As many clubs only allow 20kHz spacing on their fields, this is really not a serious disadvantage. NBFSK disadvantage NBFSK receivers do have one very serious disadvantage. They suffer from "capture", in which an interfering Tx can override the master Tx. Control will thus pass to the interfering Tx if it is strong enough. On the other hand, AM receivers will often fight their way through interference. Even brief snatches of recovered control are sometimes sufficient to keep the model flying until the interference has passed. From a design point of view, the NBFSK system places much more stringent demands on the designer and the components he uses. To begin with, in an AM system, the crystal locks the transmitter oscillator onto frequency. Thus, the problems associated with the design of the supply rails, for example, are minimal. In other words, the crystal stabilises the electronics. The situation in a11 NBFSK transmitter is much more complex. Here the electronics stabilises the crystal; a "cart before the horse" situation if ever I saw one. To achieve the frequency shift required for modulation, the electronics must be able to pull the crystal "off frequency" and herein lies the danger in the NBFSK system. Supply rails to the transmitter oscillator must be well stabilised with regards to voltage and must be heavily decoupled. Also, the temperature stability of the components must be excellent and the oscillator design very precise. The crystals used in AM systems 07 BC548 A 2.2k 0.1+ + ANTENNA 50.I-.,. C B .047I . T1 YELLOW I 01 .0022I 470n • . . .,. 2.2k 2.2k 220k AGC + C 0.47,2.2.:r pF A --------+--......--------+--+------+---♦+4.BV + .047+ 50.r 100k 14 B 100k .,. .,. .,. .,. 13 Fig.1: this is the circuit of a simple AM R/C receiver which has been thoroughly proved over many years. The CMOS ICs provide audio gain and squaring (ICt) and serial to parallel conversion for the 8 channels (IC2). are simple third overtone series mode types which are very cheap to produce at 27-40MHz. However, they cannot be pulled off frequency very easily. This makes it sound like a bad thing when in fact it is a good thing; such is the nature of the AM/FM conflict. Typically, series mode crystals can only be pulled about 1-1.5kHz in our bands. As a result, fundamental crystals are required for NBFSK systems and these can be pulled up to 5kHz off frequency easily. They are, however, much more expensive to produce. In addition, they are even more expensive if cut to 30MHz, which is about the limit of fundamental crystal technology at the moment. Thus, we have an additional problem in that the crystals used in R/C sets are cut to one half of the Tx output frequency and doubled in one of the Tx stages. All of this amounts to much greater complexity and a much higher price. Now the important point here is that 90% of all modellers only require one thing of their R/C systems and that is that the integrity of the radio link must be perfect. In other words, the commands sent must equal the commands received. AM will do this at a much lower cost/complexity factor than FM. The reliability of AM sets is also better than FM sets, mainly due to the simplicity involved. This is not to say that FM is unreliable; far from it. In fact, it is a tribute to the modern component industry that this system works as well as it does. But AM will do the job with less fuss and a much greater cost effectiveness. I always feel sad when I see a beginner stagger out of a hobby shop loaded down with expensive equipment he does not really need, or for that matter, know how to operate to its full potential. Nor is he ever likely to reach this level within the lifetime ... of his first radio. Such is modern merchandising. AM receiver circuit Let us turn now to Fig.1 , which is a typical AM single conversion Rx of the type used throughout the . R/C industry for many, many years. It gave excellent results and a lot of fun to untold thousands of modellers. This type of Rx, incidentally, is still used in the current generation of two channel systems. Even here though, the relentless demand for increased complexity in all things (the "Gingerbread Syndrome", I call it) is forcing the pace on the development of much more complex voltage regulation circuits, for example. In Fig.1 we see a simple superhet Rx using a local oscillator (Q6), mixer (Ql), two IF (intermediate frequency) stages (QZ, Q3) and an active detector (Q4). Audio amplification after the detector is provided by a transistor (Q5) and this is followed by several stages of squaring using a CMOS 74C04 inverting buffer (ICl). The seDECEMBER 1990 111 The circuit of the 8-channel receiver shown in Fig.1 can be built into a very small box as this original Silvertone unit shows. The circuitry was on two small PC boards and there was provision for crystal changing. The slightly larger Futaba receiver at left is a 3-channel unit. rial to parallel conversion and decoding is performed by the 74C164 shift register (ICZ), which gives eight channels of decoded information out. (In R/C work, a control output is referred to as a channel, hence eight channels can control eight separate controls, each giving left and right, up and down, etc). The designer of a receiver for R/C use faces several problems which are relatively unique in Rx design. The overriding factor is that the final unit must be small, light in weight and cheap to produce. In addition to this, it must have good sensitivity and be capable of sustaining crash after crash. Some of these crashes can provide "G" forces that can wrench components completely out of the PC hoard. At all times, the unit is subjected to high levels of engine vibration and high levels of in-flight "G" forces. Thus, all tall components or components with thin leads must be bonded to their neighbours at the top end with contact cement or similar. I have had components fall completely out of the PC board under extreme engine vibration. The salt water hazard The receivers in model cars and boats are regularly immersed in water (salt, brackish or fresh). Salt water can electroplate the copper from the PC board to the plastic Rx case in 10 minutes if the board is not correctly coated. The moral here is get that model out of the water quickly, get the power off pronto, wash it out with fresh water from the bottle you carry espe112 SILICON CHIP cially for this purpose and then flush with methylated spirits to absorb all residual water. The metho comes from the other bottle you carry just for this purpose. The reason you carry these bottles, of course, is that you are operating near water regularly. You do carry these bottles don't you? Another serious problem is that of the Rx coming into extremely close proximity of anything up to 15 or 20 transmitters, all on very close frequencies. The typical frequency spacing on most club fields is 20kHz. The Rx design shown in Fig.1 was one of the first in this country designed specifically for close band spacing. Prior to Silvertone introducing this system in 1969, the band spacing on club fields was 50kHz. While the design is very basic and cheap to build, it gave good performance on 15kHz spacing and revolutionised frequency utilisation in this country. We had to devise a new method of frequency control to handle the number of transmitters on the air at any one time, and this system is now the Australian standard. We also had to pull a few devious little tricks to achieve this spacing from such a simple design and here are a few of them. One of the big problems faced in model transmitters is the "hole" or weak signal area off the tip of the Tx antenna. This can be overcome with more Tx power, greater Rx sensitivity or more effective antennas. This Rx used a bifilar wound antenna coil (11) which was intended for use with a centre-fed antenna. We envisioned self-adhesive burglar alarm tape on the wing leading edges. The.se would have doubled as turbulators to enhance lift. As it turned out, this Rx was sensitive enough not to require such an antenna system but it did work well in practice. Diode D1 across 11 clamps the input signal to 0.6V and helps prevent front end overload. AGC (automatic gain control) was applied to the mixer (Q1) and the two IF stages (Q2, Q3). This was unorthodox but it definitely helped when others stuck their Tx antennas through the covering on your wings. The active detector Q4 gives good AGC and a high level of audio output. This audio is then "sliced" at approximately 1V above ground, thus eliminating the low level noise and adjacent channel interference present in the audio output. There are, of course, more modern and elegant ways to achieve this slicing and op amp slicers are great. The output of Q5 is a straight line with no noise with no carrier present. Filtered audio is applied to pin 9 of IC2 (enable). Thus, with no carrier, IC2 was switched off and this further ensured that there were no spurious servo output signals. The rest of the circuit was fairly straightforward and followed conventional superhet practise. This was a nice little Rx and it stayed in production for 15 years. I can still recommend it to anyone who just wants to fly and fly and fly and not get bogged down in endless discussions about the latest and greatest in the gingerbread line. For those who prefer to roll their own, I have included circuit values. Go and have some fun! SHERIDAN ELECTRONICS MORE ACCESSABLE - MORE STOCK - MORE SPECIALS IEC Socket & Filter with Fuse 9" 12VDC 30Hz TTL GREEN SCREEN Complete with Deflection yoke & Driver Board, as well as Data Yes we still have stock of this P0RUlar line "" PREH MEMBRANE QWERTY KEYBOARD * Alphanumeric * Non-encoded * 30 volt 20mA contact rating. Without housing NORMALLY SELLS FOR $109.00 lus_Tax __ _ NOW ONLY TELEPHONE DOUBLE ADAPTORS $39. Sea PERSONAL SHOPPERS ONLY CAPACITORS Others claim to be the cheapest, think again. OUR PRICE $39.95ea $1.95ea 25,000uF 25 Volt Very useful Electro's $4.S0ea PL 15/40VA FERGUSON TRANSFORMER CANNON 5 PIN MALE & FEMALE Buy the pair $S S0pr and Save • • SCOOP PURCHASE TRANSFORMERS Priced to clear - LESS than cost $12.SOea 12VDC BRUSHLESS FANS 80mm x 80mm You have seen our competitors price - compare this $9.95ea 240 Volt Primary 16 Volt Secondary 5 Amp Continious NORMALLY $34 _00 $5.S0ea DON'T PAY "'~='"'""'"" THERMAL SWITCH 56° 12 volt We have purchased a limited quantity so be quick $1.00ea OUR PRICE $64.95 DISK DRIVE POWER SUPPLY _,,.,.,, NO NAME PLUG PACKS .... 3.5 volt 130mA 17 volt 3.4A, 8.5 volt 6.8A · ONLY $3.95ea 57 PRACTICAL PROGRAMS & GAMES IN BASI ALL ONLY 240 Volt Primary 13.8 volt Secondary 1.5 Am Continious LESS THAN 1/2 PRICE $99.00 OR $80.00 33 CHALLENGING COMPUTER GAMES FOR TRS80/APPLE/PET ALL ABOUT HOME SATELLITE TELEVISION YOU PAY ONLY $13.50 3 IN ONE • DRILL / DRIVER/ SOLDERING IRON TOWERS INTERNATIONAL SELECTOR BOOK 3rd EDITION N.ot $89.95 $15.00ea 1 Copy per Customer . BRAND NEW $19.95 $3.95ea TELEPHONE GOODIES 610 Plugs & Sockets 611 · Plugs & Sockets $2.SOea $2.S0ea OTHER SPECIAL LINES 12Volt 10A Relays DPDT 12Volt SA Relays DPDT 12Volt 1A Relays DPDT $2.SOea $2.00ea $0.95ea D25P D25S $0.70ea10+$0.60ea $0.70ea10+$0.60ea Twisted Hook up Cable (5mm 500 metre Spool) 1N40021 A Diodes $15.00 inc P&P $3.00/100 Rubber Feet 4 for $0. 70 (Get some for your next project) UHF TRANSISTORS 2N59464W 2N594710W 2N613625W $8.00ea $10.00ea $12.00ea SHERIDAN ELECTRONICS, 328 ELIZABETH ST, SHOP HOURS WEWILLBECLOSE0FROM 9 (Cnr Kippax St. opp. Central Station & Dental Hospital) ~frN • FRI 5.30pm ~~~-o~~R¼~~t~~r~~:1 SURRY HILLS, NSW, 2010 TELEPHONE: (Q_2l 281 7727 VISA BANKCA~~o:As~i'tf~ARD .ooam · :EI 1 [g l- l . . ~~:P;u~~~J:::. roALL .__ __. DECEMBER 1990 113 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. The black art of loudspeaker design I am attempting to design a high quality speaker system around Vifa components: D19 tweeter, D75 mid, W13 bass plus subwoofers and I'd like to use passive first order crossovers because if I use separate amplifiers for each speaker, I don't need to make up a separate active crossover board. To this end I've been reading as many articles as I can on crossovers and I'm slowly coming to the conclusion that in many cases either they have not explained themselves clearly enough or they haven't really been thought out sufficiently. It seems to me that too many articles rely on conventional wisdom unquestioningly. I read frequently that it's important not to load a speaker near its resonant frequency(~) because excess cone excursion will destroy it, yet it seems to me that in many cases the box is extremely heavily damped, so much so that this effect is nearly zero. If my (by now, fairly rusty) physics is correct, the impedance of a speaker at resonance is a measure of its cone excursion capabilities (ie, its Q) - so Optoelectronic dizzy for a Renault Virage I have a Renault Virage to which I fitted a transistor assisted ignition system a few years ago. The system works well but I am still troubled by wear of the points. Do you have an optoelectronic circuit to replace in the points? (L. D., Tin Can Bay, Qld). • We have not published a circuit for an optoelectronic ignition system. We do not believe that such a system would be reliable because the oil vapours which are inevitably inside the distributor would eventually be deposited on the op114 SILICON CHIP that if an 8-ohm speaker manages to reach 9-ohm at resonance, then the cone excursion is close to normal. I realise that the energy increases as the frequency decreases but that's not what I'm discussing here; it should be considered separately. Frequency/amplitude graphs of speakers are close to useless unless a frequency/phase graph is included after all, a speaker acts like a filter at various places, particularly at resonance, and designing a crossover without reference to it is wrong. It's surely system amplitude and phase that give the final response graph, not the crossover in isolation. I have seen several articles which discussed a first order crossover and gave idealised graphs showing how good they were, then at a later point in the article mentioning that a speaker had to be phase-reversed, in this instance because of speaker peculiarity. They have completely missed the point. Articles that specify that a speaker must have output at f/2 or 2f in a first order crossover are expressing themselves badly. If a speaker still has considerable output at an octave outside its designed range, why is this a good thing? 4th order crossovers have toelectronic components and prevent them from working. That is why modern cars use reluctor distributors or Hall Effect distributors. We have published two such circuits for reluctor or Hall Effect distributors but, as far as we know, they are not applicable to your car. The only way you could make them work is if you could get a Hall Effect or reluctor distributor from a later model Renault. The relevant articles were in May 1988 (Hall Effect) and May 1990 (reluctor distributor). Back issues are available for $5.00 each including postage. virtually none and they are considered a good thing too! Unless I miss my guess, the article should say that the speaker must have output well outside its range, like it or not, because otherwise the speaker is acting like a filter, and therefore mucking up the idealised design parameters. It seems to me that if you have a midrange driver, for example, that exhibits rolloff above a certain frequency at a measurable rate (eg, 6dB/ octave), then you can use that as a first order crossover built into the speaker. If you want a faster roll off, then use it as one of the elements, so that you add a 1st order rolloff to it and use a 2nd order on the matching tweeter for a combined 2nd order filter. I'd appreciate your thoughts on the subject. Thanks for a first rate magazine. (I. C., Surry Hills, NSW). • You have picked a very complex subject to study. We will attempt to answer or comment on some of your questions in order. As far as loading a speaker near its f (resonant frequency) is concerned, it is normal practice to design the box to provide a good deal of damping, as you have suggested. The impedance of a speaker at resonance is not a measure of its cone excursion capabilities, although it does reflect its Q. The maximum cone excursion of a speaker is purely a function of the length of the voice coil, the suspension system and the length of the magnetic gap. The problem arises if the speaker is excited below its resonance, where a lot of damping is not usually available. In this case, because there is no damping, the cone excursion is out of control and so distortion or speaker damage is the result. The same principle of not exciting the speaker below its resonance applies to tweeters and midrange drivers. You are quite right about frequency amplitude graphs of speakers being useless unless a phase plot is in0 eluded. However, most articles ignore it because the phase characteristics of the speaker driver are well outside the control of the crossover designer it's like burying your head in the sand since you cannot control some aspect. Loudspeakers that have considerable output at an octave outside their design range are generally a problem. This applies particularly to woofers which have considerable high frequency output which is generally very peaky in nature. It's not a good idea to use the speaker's natural high frequency rolloff as part of the crossover design. This is because the speaker's rolloff is generally not well defined and also, if you use it as a signal limiting factor in the design, you are liable to introduce harmonic distortion. Where to buy a 38kHz crystal In your October 1988 issue you published a circuit for a low power stereo FM transmitter. I made the transmitter but when it came to procuring the 38kHz crystal I could not obtain one in this country. Could you advise me as to where I might obtain one from in Australia, preferably in Sydney as I have relatives there? It seems like a good circuit and operates well except of course that it does not transmit stereo without the correct crystal. (G. C., Dunedin, NZ.) • You should be able to get this component as a spare part from Dick Smith Electronics in N(;lw Zealand. They do have this project as a kit. Failing that, you may be able to get it as a spare part from Dick Smith Electronics in Sydney (PO Box 321, North Ryde 2113); or Jaycar Electronics (PO Box 185, Concord 2137). Making the UHF switch work at 2 7MHz Having read your article on the UHF remote switch in the August 1990 issue .just recently, I felt keen enough to build it either by buying a kit from Dick Smith or from components sourced locally. There is, however, a problem. The local authorities allow such devices tc:i be operated at 27MHz only. Would it be possible to modify the existing circuitry to accommodate this Picture in picture TV sets & VCRs I seem to remember that when I was a kid of about 7 years old (and I'm 37 this year so I could have been imagining things). a neighbour had a top of the range black and white Blaupunkt TV that displayed two channels at once - one picture full size with the second picture inset in a 5 or 6-inch frame in the upper right hand corner, the two pictures being interchangeable. Now, more recently, I've seen colour TVs and VCRs capable of PIP (picture in picture). I have an IBM XT clone with a CGA card and run it through an RGBI/PAL encoder/modulator into a 51-cm Rank-Arena C202A TV tuned to Channel 0. The big question is, how can I or how complicated is it to build a black box or convert the TV so that it would be possible to have picture in picture (say Channel 10 picture on the main screen with the computer screen in the corner) and be able to interchange pictures? Even if there is no chance of solving my own problem, is there lower frequency? (E. Foo, Selangor, Malaysia). • It would be possible to make the circuit work at 27MHz but it is unlikely that you could get the finished unit into the same small case. To get sufficient range at 2 7MHz and still keep the unit reasonably small, you would probably need to use a ferrite rod antenna. The only problem is, we have not designed such a circuit and so, for the time being at least, we can't help you. Big power supply occasionally hums I put together a kitset from Dick Smith Electronics for a 20 amp power supply. It operates very well except for intermittent hum; ie, it will operate without hum for 1 or 2 weeks then the hum comes on again. It powers a 2-metre Tx/Rx which is used daily about 4pm to 5pm. Could any chance of doing a kit project and an article on the subject of PIP for Australian TV? (R. B., Port Douglas, Qld). • While it is possible, it is very complicated to convert an existing television set to picture in picture operation. Several companies, such as Fujitsu, have suitable chip sets for processing and switching the video information. The problem is that you need two complete TV tuner and IF strips to provide the two sources of video information. That is what these deluxe picture in picture sets have. If you had a VCR, it would be possible to use it as one source of video and sound but there then would be quite a lot of work in interfacing the PIP chip set to an existing TV set. This would be even more of a problem with today's sets which have floating chassis. Another possibility would be to use two VCRs as the video sources, to feed the PIP chip set and then take the resulting composite PAL video plus audio to feed a modulator. If there is any reader interest, we could have a look at doing it as a project. you give me some idea what to do to overcome the problem? (W. M., Wyoming, NSW). • There are three possibilities for the intermittent hum problem in your power supply. First, you may have loose laminations in the transformer. It's a long shot but it may be worth trying to tighten the clamping screws. Second, the power supply may be intermittently unstable and when this occurs, it is increasing its internal current drain. If this was the case, the power supply would be getting very hot while it was humming. This should be checked out and may be due to poor solder connections. Third, it may not be a fault at all. The hum may be caused by switching tones on the mains and it may be that you are using the power supply when these tones occur. When this occurs you may also hear your fluorescent lamps giving a similar hum. If that's the case, there really is no cure. DECEMBER1990 115 Index to Volume 3: January-December 1990 Features 01/90 4 Checking VCR Tape-Loading Problems 01/90 10 Update On High Definition TV 01/90 82 The Technology Letters 02/90 1O Bose Noise Cancelling Headphones 02/90 78 PC Program for Great Circle Bearings 03/90 96 The Technology Letters 04/90 6 Servicing Your Microwave Oven 04/90 68 Taking The BASF CD Challenge 04/90 83 High Density Data Storage From Philips 05/90 4 Error Correction For Digital Recordings 05/90 16 Fingerscan Personal Identification 06/90 4 Off-Shore Oil Platforms 06/90 76 The Technology Letters 07/90 8 Review: AR950 100-Channel Scanner 08/90 76 Laservision: High Power Communication 08/90 82 The "Tube" vs The Microchip 09/90 6 Voice Mail For Your Computer 09/90 16 How To Make Dynamark Labels 09/90 18 The Fluke 45 Digital Multimeter 09/90 20 The Bose Lifestyle Music System 09/90 60 Kenwood CS-6020 150MHz Oscilloscope · 10/90 4 The Dangers Of Polychlorinated Biphenyls 10/90 38 The Bose Lifestyle Music System 11/90 6 How To Connect Two TVs To One VCR 11 /90 16 Introduction To Digital Electronics 11/90 110 Turn Your CAO Into A Spectrum Analyser 12/90 4 Understanding PC Memory 12/90 14 The Great Green CD Pen Controversy Electric Railways 01/90 86 A Look At Very Fast Trains 02/90 94 The French TGV Fast Trains 03/90 4 The Australian VFT Project Electrical Energy 07/90 52 Pt.1: Coal Burning Power Stations 08/90 32 Pt.2: The Quest For Greater Efficiency 116 SILICON CHIP 09/90 30 Pt.3: How Alternators Are Excited & Cooled 10/90 94 Pt.4: High Voltage Transmission lines 11/90 98 Pt.5: Gas Turbine Power Stations In The NT 12/90 98 Pt.6: Rebuilding Old Alternators Design & Theory 01/90 100 Modifying The Studio 200 Amplifier 03/90 10 The UC3906 SLA Battery Charger IC 06/90 18 Fitting A Fax Card To Your PC Vintage Radio 01 /90 14 Obtaining the Right Spare Parts 02/90 6 Safety With Vintage Radios 03/90 14 Wave Traps -A Useful Vintage Radio Accessory 04/90 16 Finding Receivers From The 1920s 05/90 8 Cleaning up the Chassis 06/90 22 How to Recognise AD/DC Sets 07/90 6 How to Solve Unusual Problems 08/90 6 Tuned Radio Frequency Receivers 09/90 64 The Gentle Art of Scrounging Valves 10/90 16 The Different Types of Radio Valves 11/90 38 Testing Old Radio Valves 12/90 66 Old Radio Books & Magazines TETIA TV Tips 01 /90 62 GEC 2213A 02/90 46 Kriesler 37-104 (Sharp 9C140 chassis) 03/90 38 Pye T30 ChaS$iS 04/90 62 Sony KV-1830AS 05/90 63 Sanyo CTP 7605A 06/90 53 Pye T29 Chassis 07/90 40 Philips 14CT2006 08/90 49 Hitachi CWP139 09/90 74 Philips KT3A-1 Chassis 10/90 53 Philips K9 Chassis 11 /90 48 Kriesler 59-01 12/90 52 Hitachi CTP-229 Serviceman's Log 01 /90 58 Sing It Again Sam(sung) 02/90 44 Another Song About Sam 03/90 34 A Bit of the Snag With The Sausage Machine 04/90 60 It's an Ill Wind, As They Say 05/90 60 Something Old & Something New 06/90 50 You'll Get a Buzz Out Of This One 07/90 40 The Dangers Of A Quick Fix 08/90 46 It Was The Last Thing I Tried 09/90 74 The Risk of Passing The Buck 10/90 52 If Only I'd Known All The Symptoms 11 /90 48 The Customer Takes A Holiday 12/90 48 It $ounds Like Donald Duck Computer Bits 01/90 70 Speeding Up Your PC - The Options 02/90 68 Some Ideas On Computer Interfacing 03/90 80 Digital Waveform Generation Using a PC 04/90 36 Mass Storage Devices 05/90 82 What To Do When Your Computer Goes Bung 06/90 70 What To Do When Your Computer Goes Bung; Pt.2 07/90 72 What To Do When Your Computer Goes Bung; Pt.3 08/90 70 What To Do When Your Computer Goes Bung; Pt.4 09/90 93 What To Do When Your Computer Goes Bung; Pt.5 10/90 87 What's Gone Bung Now? 11 /90 80 Computer Cables & All That Rot 12/90 82 Modem Mysteries Revealed Remote Control 01/90 73 Designing UHF Transmitter Stages 02/90 14 Transmitter Encoders & Black Wire Syndrome 03/90 86 The Controls On A Model Aircraft 04/90 88 Model Aircraft Aerodynamics 05/90 74 Aerodynamics & Stall Conditions 06/90 87 Design Factors For Model Aircraft 08/90 88 Bluff Body Design & Automotive Aerodynamics 09/90 82 The Care & Feeding Of Battery Packs 10/90 110 The Adverse Effects Of Dihedral 11 /90 104 Nicad Cells For High Rate Discharge Projects to Build 01 /90 18 Active Antenna For Shortwave Listening 01/90 26 Phone Patch For Radio Amateurs, Pt.1 01/90 42 A High Quality Audio Oscillator 01/90 63 Speed Controller For Ceiling Fans 02/90 18 16-Channel Mixing Desk, Pt.1 02/90 32 A High Quality Audio Oscillator, Pt.2 02/90 50 The Incredible Hot Canaries 02/90 62 Phone Patch For Radio Amateurs, Pt.2 02/90 74 Random Wire Antenna Tuner For 6 Metres 03/90 20 6/12V Charger For SLA Batteries 03/90 30 Delay Unit For Automatic Antennas 03/90 44 Workout Timer For Aerobics Classes 03/90 60 16-Channel Mixing Desk, Pt.2 04/90 20 Relative Field Strength Meter 04/90 28 Build A VOX With Delayed Audio 04/90 46 Dual Tracking ±50V Power Supply 12/90 11 0 Radio Control Receivers Using Amplitude Modulation Circuit Notebook 01/90 34 Quiz Game With Light Chasers 01 /90 34 High &. Low Boost for PA Loudspeakers 01/90 35 Clipping Indicator for Stereo Amplifiers 02/90 26 Electronic Speedo 02/90 26 Parametric Equaliser 02/90 27 Simple Transistor Beta Tester 02/90 27 30-Second Bilge Pump 03/90 42 100-Sequence LED Chaser 03/90 42 Pulse Width Modulated Signal Compressor 03/90 43 Bilge Pump With 15s Sloshing Delay 04/90 40 Pulse Width Modulated Signal Expander 04/90 40 Low-Cost Alarm Status Indicator 04/90 41 Single Supply Instrumentation Amplifier 05/90 14 Delay Circuit for Intermittent Wipers 05/90 14 24 V Gel-Cell Battery Charger 05/90 15 Adjustable Boxing Timer 05/90 15 2-Phase Oscillator Uses a Flipflop 06/90 56 Antenna Control In Holden Cars 06/90 56 Gutsy 220V Power Supply 06/90 57 40W Bridged Power Amplifier 07/90 60 Driving Stepper Motors from a Parallel Printer Port 07/90 61 Switching Mains With Your Computer 07/90 61 One-Chip DC Volume Control 08/90 42 Electronic Time Delay Switch 04/90 72 16-Channel Mixing Desk, Pt.3 04/90 94 Active CW Filter For Weak Signal Reception 05/90 18 High Energy Ignition For Reluctor Pickups 05/90 30 4-Digit Capacitance Meter 05/90 48 16-Channel Mixing Desk, Pt.4 05/90 66 The Mozzie CW Transceiver 05/90 92 Waveform Generation Using A PC, Pt.3 06/90 30 Multi-Sector Home Burglar Alarm 06/90 40 Universal Stereo Preamplifier 06/90 60 A Speed Alarm For Your Car 06/90 66 Load Protector For Power Supplies 07/90 16 Digital Sine/Square Wave Generator 07/90 28 Alarm Keypad & Combination Lock 07/90 34 Build An Elegant Electronic Die 07/90 64 Waveform Generation Using A PC, Pt.4 07/90 78 Low Cost Dual Power Supply 08/90 16 High-Stability UHF Remote Transmitter 08/90 20 Universal Safety Timer For Appliances 08/90 52 Digital Sine/Square Wave Generator, Pt.2 08/90 66 Horace The Electronic Cricket 09/90 24 Remote Control Extender For VCRs 09/90 40 Music On Hold For Telephones 09/90 48 Alarm Power Supply With Battery Backup 09/90 54 Low Cost 3-Digit Counter Module 10/90 24 Build The Surfsound Simulator 10/90 48 Low Cost Siren For Burglar Alarms 10/90 66 DC Offset For Digital Multi meters 10/90 72 Dimming Controls For The Discolight 11/90 24 Battery Powered Laser Pointer 11/90 42 Low-Cost Model Train Controller 11/90 56 A Really Snazzy Egg Timer 11 /90 72 Build A 1.5V To 9V DC Converter 11/90 75 Modifications To The 16-Channel Mixer 12/90 24 DC-DC Converter For Car Amplifiers 12/90 38 The Big Escape 12/90 54 Wiper Pulser For Rear Windows 12/90 70 Versatile 4-Digit Combination Lock 08/90 42 Effective In-Circuit Battery Tester 08/90 43 Remote Control For Early Rank Arena TVs 08/90 43 Overvoltage Protection For Power Supplies 09/90 90 2.4GHz Prescaler For 1GHz Frequency Meter 09/90 90 Low Cost Battery Minder 09/90 91 Traffic Lights For Model Railways 09/90 92 Electronic Control For Radiator Fan 09/90 92 1 Hz Timebase With Variable Pulse Width 10/90 62 Expanded Scale 11.6-12.6V Voltmeter 10/90 62 Low-Cost Mains Frequency Indicator 10/90 63 Obtaining -5V From A +5V Supply 10/90 63 Digital Staircase Waveform Generator 11/90 32 Low Frequency Sample & Hold Circuit 11 /90 32 Single Chip Low Battery Alarm 11/90 33 FM Stereo Test Tone Transmitter 12/90 80 Current Limiter For 240VAC Lamps 12/90 80 Climate Controller For A Greenhouse 05/90 42 Electronic Load For Checking Power Supplies 06/90 84 Understanding Frequency Modulation 07/90 88 Weather Fax Frequencies 08/90 82 The Old vs The New 09/90 98 Shortwave Converter For 2-M 10/90 82 Using The NE602 In Home-Brew Converter Circuits 11/90 66 The 6-Metre Summertime Special . 12/90 104 A 5W Power Amplifier For The 6-Metre Transmitter Amateur Radio 01/90 66 Yaesu's New FRG-8800 Shortwave Receiver 02/90 74 Random Wire Antenna Tuner For 6-Metres · 03/90 72 Understanding Single Sideband Transmission 04/90 94 Active CW Filter Notes & Errata 03/90 102 Alarm-Triggered Telephone Dialler, September 1989 03/90 102 Simple 40-Metre Receiver, December 1989 04/90 101 Ask Silicon Chip - How Do You Wind Inductors? March 1990 05/90 101 2-Chip AM Stereo Radio, October 1989 05/90 101 Digital Waveform Generation, Computer Bits, March 1990 05/90 101 Active Antenna, January 1990 06/90 102 Radfax Decoder, November 1989 06/90 101 VOX With Delay, April 1990 08/90 108 Phone Patch, January 1990 10/90 118 3-Digit Counter, September 1990 10/90 118 Radfax Decoder, November 1989 10/90 118 VOX With Delay, April 1990 10/90 118 0-1 00V 1.5A Dual Tracking Power Supply, April 1990 10/90 118 16-Channel Mixing Desk, February, March & April 1990 DECEMBER1990 117 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. r-------------------------, FOR SALE CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads - $7.00 for up to 15 words plus 40 cents for each additional word. Display ads (casual rate) - $20 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number you must include your permanent address and phone number for our files: We cannot accept ads submitted without this information. To run your classified ad, print clearly on the lines below or on a separate sheet of paper & send the form together with your cheque or credit card details to : Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" is a high resolution, shortwave weather fax, Morse & RTTY receiving program. Needs CGA, SSB HF radio & Radfax decoder. Also "RF2HERC", "RF2EGA" & "RF2VGA", same as RADFAX2 but suitable for Hercules, EGA & VGA cards respectively. $35. *** "SATFAX" is a NOAA, Meteor & GMS weather satellite picture receiving program. Uses EGA & VGA modes, needs EGA or VGA colour monitor & card, plus "WEATHER FAX" PC card. $45. *** All programs are on 5.25-inch or 3.5-inch discs (state which) & include documentation. Add $3 postage. ONLY from M. Delahunty, 42 Villiers St, New Farm, 4005 Old. Phone (07) 358 2785. MODEL TRAIN CONTROLLER: see SILICON CHIP November 1990, $19.95 plus $2.50 p&p. Plugpack, 12VAC, 1.7A, suitable for above (use rectifier), $29.95 plus $4.00 p&p. Kits built & repaired. Prototype production board supplier to the hobbyist & supplier of SILICON CHIP project PCBs. Electronic Toy Services, PO Box 491, Noarlunga Centre, SA 5168. Phone (08) 382 8919. LASER SALES & service. All types from 30mW to 20 watts, also scanners IIT MATHS Enclosed is my cheque/money order for $_ __ _ or please debit my Cl Bankcard Card No. Cl Visa Card Cl Master Card ~ .______,_____,I '---I.,____.__.__I ~I'----"--.__I ~I '----"--L_____j Signature_ _ _ _ _ _ _ _ _ _ _ Card expiry date._ _ _,/_ __ Name _ _ _ __ _ _ _ __ _ _ __ _ _ _ _ _ _ __ _ COPROCESSORS 2C-08 2C-10 2C-12 2C-20 2C87- 8MHZ 2C87-10MHZ 2C87-12MHZ 2C87-20MHZ 3C-16 3C87-16MHZ $640 3C-20 3C87-20MHZ $680 3C-25 3C87-25MHZ $840 3C-33 3C87-33MHZ $990 These pices include Sales Tax. Stocks are limited at this price, so order early. Street _ _ _ _ __ __ _ _ _ _ _ __ _ _ __ _ _ __ Suburb/town _ _ _ _ _ __ _ ____ Postcode_ __ _ __ L-------------------------J 118 SILICON CHIP PHONE (02)957 67 FAX (02)954 5550 ► ..I (/) D. D. (l) '- -§ ~ c.) Ill - a..o ~ ~ti Cll -~ (1)111 0111 a,.u, ~ -6 W ~ a-~ o: C ~(/) gi ~ 0: ~ ti-c ~ ~ C1l -~ >,..: co "ffi -0 ~o ~ D. ~~(l)Cl)N«l u, jjj?J: -C"ll ·.=·s; t: (/) (l) (l) ~'-OlQJ>...J (/) ..92 e _.cCll ~~ (l) -~ L ©Cl)Q)~~ a>o •e.c ~ c( -~ ~ 0 ~ ~ ;r: u, r 0(1)<((1)0 ►~ IC") E» .c - ~- ·--~~~ a 5i o;.: ~.,... o. (/) m .E ~ Ia, E .!::: ._ m (,) .,... 8 ~ C"ll c.:!= § <i>OlO.Cl)Q+- CD'--o Ol(/)..,....3:o 0 0 Q) >, ....!::: Q) 0 :;: Ol ai (/) «i o.- Cl> 0 .C'cECl)O.o_mc., >.c Lt) en (,) )( ~~o.o._c - co Z LL lli Ill :i -~ 3: t C - ~ o.-oOo, .c · - ~ ~, (l) Ql ·:::; C E §: a.. §: ·u5 oco-"''-'-~c c.) 0 :::, :::, (l) :::, «i ~ ~ cr o !: CHRISTMAS CLEARENCE SALE N C C ...a ~ ~ .J -~ "6> ::, :i C'• ~ w <i: ..2 - en ... w~ ..I Lt) Ill -a 1-~ 0 a; C 0. r:;- ~ ◄ g . a. .c SURPLUS STOCK AT REDUCED PRICES Only Items listed on Special - while stocks last BC548/558 BC547/557 BC549/559 BC107/108 BC327/337 8D139/140 TIP31 C/32C 2N2222 2N3055 MJ2955 $0.09 $0.09 $0.09 $0 .30 $0.20 $0.35 $0.60 $0.33 $1 .30 $1.40 t - - - - -~ - JIFFY Box with lid UB1 50x90x150mm UB3 41x68x130mm UB5 28x54x83mm Money Order or Cheque M. Radvanyi, PO Box 49, Kingswood, NSW, 2749 from basic to animated 3-D images. Special: air-cooled argon 120mW laserhead (8 lines), blue to green. Includes small lightweight switchmode PSU, interlock keyswitch, remote option, $9000.00. PO Box 215, Geelong, Vic 3214. Telephone (052) 48 3503. MS-DOS NOTEBOOK-SIZE computers. Have you been looking at the Atari Portfolio, POQET or PSION computers? Perhaps the "NEW FOR 91" NOTEBOOK TANDY 1100-FD is the one for you. With a built-in 3.5-inch floppy & 640Kb of RAM, this unit is hard to beat. Don't buy one until you have a look at my free brochure. I can save you $100-$260 on this unit. Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. Phone (03) 338 6286. Potentiometer: $ 8.00 555 Timer $0.29 $ 8.00 741 Op Amp $0.35 $ 8.00 CMOS 4000 $0.45 $ 29.00 4001 $0.25 $ 19.00 4011 $0.25 $ 30.00 4017 $0.40 $ 55.00 Reg uA7805 $0.45 $ 29.00 Zener Diodes $120.00 3 to 33 volt $130.00 400mW $0.10 ~ ----, 1 Watt $0.15 SCR C103Y $0.30 $ 2.95 C103B $0.50 $ 2.40 25A C37D $2.00 $ 1.95 Diac ST2 $0.20 24mm Linear 1/4" 50eea 500W, 1K, 5k, 25K, SOK, 100K, 250K, 1M, 2M, TRIMPOTS 10mm vert 12e 250W, 1K,2K,5K, 10K,25K, 250K GREENCAPS 100V: .001 se, .0039 9e, .0047 1oe .033 , 1e .. 22 1se. .33 22e, .47 2se, CERAMIC Caps: 50volt 2.2, 100, 2200, 3300, 4700pF all se. .01, .033, .047uF all 7e 1000/25V 35~ 3.5mm panel sockets 20~ Banana plug/socket 25~ Ferrite rod 106x10mm 40~ Ferrite flat 60x12x6mm 25~ MIXED BAGS - Capacitors plus resistors: $2.00 per 100, $8.00 per 500, $15.00 per 1000. MYSTERY BAGS • broad range all usable (15.00 individual value) for $5.00 per 100. DIGGERMAN ELECTRONICS PO BOX 33 CORAMBA, NSW, 2450 Postage $1.00 minimum or 10% of order value KIT REPAIRS Kits repaired from all magazines. PCs and peripherals also repaired Ring anytime 9am - 9pm EEM ELECTRONICS 1O Bouverie Place Epping Vic. 3076 (03) 401 1393 TOROID POWER TRANSFORMERS From quality UK manufacturers. Available from stock at discount prices, 15VA to 625VA. Send SSAE for data & prices to: Transformer Discounters, PO Box 542, Wahroonga 2076. ACTIVE SHORTWAVE ANTENNA SILICON CHIP, JAN 1990. Complete kit Tested $t19.00, Case $10.00. $59.00, Built and LOOP ANTENNA Improve signal strength & quality wi1h this portable antenna. Kit $44.00, Buitt and Tested $69.00 COMPACT INDOOR FM ANTENNAS Two models to choose from. Terk FM2000 a passive loop FM antenna for $69.95 or the Terk Pl2 powered FM antenna with wideband low noise filter for $199.00. We can a/eo provide ....,,,bly facllltln for 111n11II prodUct/on runa at com,,.,ltlve prk:H VALVES: 6V6G, 3S4, 2X2/879, DF64, IC7G, VR118, 3C45, 12E1, G50/1G, GC10/48, 7583, 2T4C, 1421A.AII Nos. Phone: Hycal Instruments (02) 633 5897 MEDTRON PROGRESSIVE Treatment Unit, with manual; Mullard valve tester with spare parts; BAC221-AC Frequency Set with AC supply in mint con- Popular ICs ELECTROs 16V Upright:220uF 15~, 470uF 20~1000uF 30~. GENERATE YOUR OWN DIGITAL WAVEFORMS As described in SILICON CHIP in March, May, June & July 1990. ALSO suits the design described in Electronics Australia Software and PC Board $39.95 inc. P&P Software only $32.50 inc. P&P 100 TRANSISTORS EACH JILOA (TECHNIKIT DIVISION) PO Box 73, Glenhuntly, VIC 3163. Telephone: (03) 571 6303 dition; offers please. Phone Hycal Instruments (02) 633 5897. CAPACITORS: 2,000µF 25volt, chassis mounting $1.00 each; 0.47 Farad & 0.1 Farad only $5.00 each; slider pots 50k0 linear 45mm travel $1.q0; MC14514BPC $2.00; LM7812 & LM7912 $0.70 each; LM324 $0.75; 9volt battery connectors $0.20; battery DECEMBER 1990 119 MEMORY EXPANSION SIMM & SIP 9 X 256 9x 1MB 8 x 1MB(MAC) 9x4MB -120ns -100ns - 80ns - 70ns - 60ns -100ns - 80ns - ?Ons - sons - 70ns - 80ns N/A 23.00 23.80 24.70 30.00 79.00 81.50 89.50 76.50 82.00 528.00 -100ns - sons - 80ns - 80ns - 80ns 2.10 2.40 2.50 7.65 7.65 Prices At Sept. 13, 1990 CO-PROCESSORS INTEL 8087-2 80287-10 80C287-12 387SX-16 387DX-16 387SX-20 387DX-20 387DX-25 387DX-33 175.00 308.00 390.00 435.00 478.00 490.00 538.00 680.00 835.00 CYRIX 387SX-16 387DX-20 387DX-33 400.00 490.00 750.00 515.00 340.00 340.00 340.00 340.00 570.00 340.00 340.00 2MB 2MB 2MB 2MB 2MB 3MB 2MB 2MB COMPAQ 386-20, 386-25, 386-20E, 386-S, 386-33 680.00 4MB MODULES 4MB BOArds 798.00 IBM PS/2 DRAM/DIP 4164 41256 41464 4 X 256 1MB Advertising Index TOSHIBA LAPTOP T1000SE T1600 T3100E T3100SX T3200SX T3200 T5100 T5200 PELHAM WEITEK 3167-20 3167-33 4167-25 4167-33 820.00 1010.00 1500.00 1780.00 30/286,50 70E61, 121 70A21 2MB 2MB 2MB 250.00 280.00 280.00 Sales Tax 20%. Overnight Delivery. Credit Cards Welcome 1st Floor, 100 Yarrara Road, Pennant Hills, NSW 2120. Tel (02) 980 6988 Fax (02) 980 6991 holder 2 x AA $0.28; 1N5404 $0.30; 1N5819RL $1.00; 1N4742 (12-volt zener) $0.24; 1N752 (5.6-volt zener) $0.18. Minimum order $5.00. All stock is new. Phone Hycal Instruments (02) 633 5897. 1GHz DIGITAL FREQUENCY Meter, AEM July 1986, fully built, calibrated with 12-month warranty. $300.00. Hycal Instruments (02) 633 5897. UHF GaAsFET Preamplifier, EA May 1986. Fully built and tested with 12month warranty. $125.00. Hycal Instruments (02) 633 5897. ANTIQUE RADIO restorations. Your one-stop electronic repair shop. Specialising in restoring vintage radios including chassis rewiring, quality new parts, valves, valve sockets, speakers, transformers, cabinet restoration. Quality secondhand radio dials & parts for most brands & models. About 400 radios in stock for restoration & parts. Every restored wireless is covered by a 2-year warranty on parts & service. French polishing of timber cabinets available. Vintage car radios in valve & transistor types available for restoration. Repairs done on tape decks, amplifiers, TVs & videos. Open Sat. 1Oam-Spm; Sun. 12.30-Spm. 109 Cann St, Bass Hill, 2197. Phone (02) 645 3173 BH or (02) 7261613 AH. r-------------------------, : I I I SILICON CHIP BINDERS To: Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097, Australia. ~ cfib Yes! Please send me _ _ _ SILICON CHIP binder(s) at $A11.95 plus $A3 p&p each (NZ $A6 p&p). Enclosed is my cheque/money order for $_____ or please debit my 0 Bankcard O Visa Card O Master Card Card No. Signature_ _ _ _ _ _ _ _ _ _ __ Card expiry date_ _~/_ __ Name _ _ __ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ __ __ Street _ _ _ _ __ _ _ _ _ _ _ __ _ __ _ __ __ _ __ Suburb/town _ _ _ _ _ _ _ _ _ _ _ __ Postcode_ _ _ _ __ _ ~ - - - - - - - - - - - - - - - - - - - - - - ---J 120 SILICON CHIP Adroit Electronics .................... 119 Altronics .. ..... ..... .................. 33-37 Arista................ ............ 45,92, 101 Back Issues ..................... .. ... 96,97 Bridge Electronics .................... 51 Board Solutions.... ........ 78,79, 103 Cad Connection .. .............. ... ... 118 David Reid Electronics ........ IFC,1 94,95 Dick Smith Electronics .. ........ 8-13 Diggerman Electronics .. .......... 119 EEM Electronics ...................... 119 Electronic Solutions ........... . 21,88 Electronics World .. .. .. ........... . 106 Elmeasco ............................ 85,90 Geoff Wood Electronics .. .. .. .. .. 53 Harbuch Electronics .. ....... .. ... 107 Hycal Instruments .................... 119 Jaycar Electronics ................ 57-64 Jiloa ....... .. ....... .. ............ ... .. .... .. . 119 J.V. Tuners .............................. 51 Oatley Electronics ......... ........... 90 Pacific Microelectronics ..... .. ... 49 PC Marketplace .... ................ IBC Pelham .................................. 120 Philips T&M ... .... ... .......... 87,89,91 RCS Radio ... ... ....... .. .. .. .. .. ..... .. 52 Resurrection Radio .. .. .. .. .. .. .. .. .. 69 Rod Irving Electronics ... ....... 30,31 46,47, 108,109 Sheridan Electronics ................ 113 Silicon Chip Binders .............. OBC Subscriptions .. ... .. .. .... ... ........ .. 65 Sound Australia ...... .. .. .. ............ 45 Transformer Discounters ........ 119 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. Phone (08) 382 8919. • Jemal Products, 5 Forge St, Welshpool, WA 6106. Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. [a lfilllElmlmlllElllElfJDmlllEllttlDIIIDHDltal SAVE ON THESE CHRISTMAS SPECIALS MOUSE- . Mighty Scan X ~-.::,...-.;. ' Eliminate keyboard Input and get a new high In resolution with this 400 DPI scanner. INCLUDING SOFTWARE AND~ MOUSE MAT USUALLY $119.00 • fully utilized memory• VGA, EVGA and 8514/A adapters in 256 color display modes e driver included e Window interface TIFF. PIC. PCX. CUT, HFF, IMG e supports all the main computer publishing programs Specifications: •Scanning length: 305mm • Scanning width: 105mm • Resolution: 200/300/400DPI • Grey scale: 10 le"'91s, 3 dither patterns plus text mode • Scanning speed: 3ms/1ine NOW ONLY $99.00 YOU SAVE $20.00 AND GET A FREE MOUSE COVER AS WELL! MOTHERBOARDS FLOPPY DISK CONTROUERS XT 12MHz TURBO M/BwAsS129.oo NOW ONLY $99.00 SAVE $30.00 286 16MHz NEAT M/B wAs$649.oo NOW ONLY $449.00 SAVE $200.00 31 MHz MOTHERBOARD wAs $225.oo NOW ONLY $200.00 SAVE $25.00 with 1MB memory on board, WAS $395.00 NOW ONLY $320.00 SAVE $75.00 WAS $109 $139 $225 $249 $299 NOW $79 286112MHz: SYSTEM 360/720/1.2/1.4x2 NORMALLY $99.00 BARGAIN AT $59.00 • 1MB on board expandable to 4MB e 1.2MB floppy disk dri""' e 2 seriaV1 parallel ports • 101 keyboard • Baby AT case • Mono monitor and card SAVE $40.00 RIDICULOUS PRICE AT $999.00 360/720/1.2/1.4x4 NORMALLY $129.00 BARGAIN AT$99.00 with 40MB hard drive only $1599.00 SAVE $30.00 DISPLAY CARDS MGA/HERCULES CGA EGA VGA 256K VGA 512K Buy from us for only $379.00 SAVE $20.00 Others sell for $399.00 $89 SAVE $30 $50 $149 $199 $249 $76 $50 $50 Sound Blaster Normally $399.00 Now $349.00 EXTERNAL DRIVES WHERE THERE IS A COMPUTER THERE IS A ROCTEC DRIVE WE HAVE AUSTRALIA'S LARGEST RANGE OF EXTERNAL DRIVES COMPUTER PART# SIZE MACINTOSH AMSTRAD AMSTRAD AMSTRAD AMSTRAD NEW D 2905 D 2910 D 2912 D 2914 D2915 3.5" 3.5" 5.25" 5.25" 5.25" 880K 720K 360K 1.2MB NEW 1.2MB ATARI ATARI AMIGA AMIGA IBM IBM IBM IBM IBM NEW LAPTOPS LAPTOPS D2916 D2918 D 2930 D 2932 D 2946 D 2948 D 2950 D 2952 D2956 VARIOUS VARIOUS 3.5" 5.25'.' 3.5" 5.25" 3.5" 3.5" 5.25" 5.25" PSI/ 720K 3601720K 880K 3601720K 720K 1.44MB 360K 1.2MB 1.2MB 360K 1.2MB COMMENTS CAPACITY DEALER ENQUIRIES WELCOME - FOR PC1512/1640 FOR MODEL PC 2000 SERIES FOR MODEL PC 2000 SERIES FOR AMSTRAD PORTABLE PRICE NEW FOR ATARI ST SERIES FOR 500/1 000/2000 SUITS MOST COMPATIBLES SUITS MOST COMPATIBLES SUITS MOST COMPATIBLES SUITS MOST COMPATIBLES NEW NEW NEW SUIT TOSHIBA, COMPAQ, ZENITH SUIT TOSHIBA, COMPAQ, ZENITH $349 .00 269.00 ...329:00" 249.00 ~ 249.00 399.00 269.00 299.00 .299:00" 199.00 ...299;60 249.00 _.299:ffl) 249.00 __329:00 299.00 __200:eo 249.00 _329:C0 299.00 449.00 349 .00 399.00 WRITE OR PHONE FOR FREE CATALOGUE TRY PC MARKETPLACE SUPERFAST MAILORDER - Pfii{ (jfeeson 's MONITORS 14" WHITE/AMBER NOW $189.00 • text to speech • dignized voice INPUT/OUTPUT• microphone amp and jack • MIDI interface • joystick port• power amp & volume oontrol e bundled software • 11-voice FM music (Ad U, compatible) PERSONAL COMPUTER MARKETPLACE PHONE OR FAX TODAYI PtyLtd FREIGHT CHARGES PHONE (02) 418 6711 Include $10 wrth order for all normal rtems • heavy rtems, e.g. monrtors add $15. FAX (02)418 6713 14 day money back guaramee Mail Order Address: Order by phone (use credrt card), by fax or by mail. P.O. Box 1100 Lane Cove Unless insurance is declined rt will be charged at 1% ofto1al purchase. This is for your pro1ection. NSW2066 PRICES CURRENT FOR MONTH OF PUBLICATION OR WHILE STOCKS LAST. • SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE • SERVICE IS THE DIFFERENCE • SERVICE IS THE DIFFERENCE