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Vol.8, No.11; November 1995 Contents ▲ FEATURES 4 LANsmart: A LAN For Home Or A Small Office If you have more than one computer, a local area network may be just what you need. LANsmart is one networking system that’s easy to install & get going – by Bob Flynn 16 Programmable Fuel Injection Control New software now makes it easy to quickly program engine management control units. We take a look at how it’s done – by Julian Edgar PROJECTS TO BUILD 22 A Mixture Display For Fuel Injected Cars This simple circuit can be used to monitor the behaviour of the engine control module in your car. It uses just one IC, 10 LEDs and a few minor parts – by Julian Edgar 28 A CB Transverter For The 80M Amateur Band It converts a 40-channel AM/SSB CB radio to the popular 80-metre amateur band – by Leon Williams, VK2DOB 44 Build A Low-Cost PIR Movement Detector Based on a universal PIR chip, this design is easy to build and can be adjusted for sensitivity and output duration. It can also be set so that it triggers only when it gets dark – by Conrad Marder MIXTURE DISPLAY FOR FUEL INJECTED CARS – PAGE 22 60 Dolby Pro Logic Surround Sound Decoder, Mk.2 This fully-featured design includes three power amplifiers, an effects facility and a 2-digit LED display to indicate the delay time. Build it for big movie sound in your own home – by John Clarke 79 Digital Speedometer & Fuel Gauge For Cars, Pt.2 Update your car’s dashboard to a fancy electronic display. Part 2 has the full constructional and calibration details – by Jeff Monegal 90 Build A PC-Controlled Robot From Surplus Parts This cheap and cheerful introduction to robotics uses surplus stepper motors plus two SILICON CHIP stepper motor control boards – by Tony Mercer SPECIAL COLUMNS BUILD THIS CB TRANSVERTER FOR THE 80-METRE AMATEUR BAND– PAGE 22 41 Remote Control Are R/C transmitters a health hazard? ­by Bob Young 69 Serviceman’s Log How friendly is “user friendly”? – by the TV Serviceman 86 Vintage Radio How good are TRF receivers? – by John Hill DEPARTMENTS 2 Publisher’s Letter 8 Circuit Notebook 10 Mailbag 27 Order Form 57 Product Showcase 100 Ask Silicon Chip 102 Market Centre 104 Advertising Index DOLBY PRO LOGIC SURROUND SOUND DECODER, MK.2 – PAGE 60 November 1995  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson Phone (02) 9979 5644 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman, VK2ZLZ Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Jim Lawler, MTETIA Philip Watson, MIREE, VK2ZPW Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $49 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Have you had your house wiring checked? Let’s face it, because we are all familiar with electricity, we take it for granted. We seldom think about the safety aspects of electricity. This thought was prompted by a recent change of home that I have made. My “new” house is older than my previous home, having been built prior to 1950. With this in mind, I made a cursory check of the switchboard before I purchased the house. I was encouraged by what I saw. Instead of the old fuseholders, there was a bank of modern circuit breakers which had evidently been fitted in recent years. And the cables behind the board were in double sheathed plastic so I thought everything was apples. How wrong can you be. The first event to shake my equanimity occurred when I attempted to change over a light fitting. This was to be a straightforward job one Saturday afternoon, requiring no modifications to the wiring; just whip out the old fitting, connect the new one and the job should be finished in under 10 minutes. Ha ha! Two minutes after I started I discovered that the wiring to the light fitting was old, very old. It was the original “tough rubber” insulation and it had long ago perished and then gone crumbly. Even undisturbed, it was in a dangerous state. To cut a long story short, I now have an electrician replacing most of the wiring in the house. To say that I had been deluded is to understate the case. That was bad enough. Having discovered one booby-trap, I instructed the electrician to check every light fitting, switch and power point and rewire/ replace as necessary. I naturally thought that he would just find dicky switches and old wiring. I did not expect that he would find original wiring which was downright illegal and dangerous. But that is just what he found. And this very afternoon he found that the power point in my study had been wired without any earth. The earth had not become disconnected – there was no earth wire at all and never had been! It is the same power point that my computer is connected to. If one of the mains interference suppression capacitors in the computer’s switchmode power supply had shorted to chassis I would have had no way of knowing and the computer would continue to work, only its case would have been live and lethal! Now perhaps you live in a new house and you think “This can’t happen to me because all my wiring is new.” Well perhaps you should think again. Was your house wiring thoroughly checked by an electricity authority inspector when the dwelling was completed? Of course, it wasn’t. From my observations of the wiring in many houses under construction, at least some of the wiring will be suspect. If you are completely certain that all your wiring is new and safe, then sleep well. If not, do what I have done – call an electrician in and prepare to spend some money to make your home safe. It will be money well spent. Leo Simpson ISSN 1030-2662 WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 2  Silicon Chip HEWLETT PACKARD 334A Distortion Analyser HEWLETT PACKARD 200CD Audio Oscillator • measures distortion 5Hz600kHz • harmonics up to 3MHz • auto nulling mode • high pass filter • high impedance AM detector HEWLETT PACKARD HEWLETT PACKARD 3400A RMS Voltmeter 5328A Universal Counter • voltage range 1mV to 300V full scale 12 ranges • dB range -72dBm to +52dBm • frequency range 10Hz to 10MHz • responds to rms value of input signal • 5Hz to 600kHz • 5 ranges • 10V out • balanced output HEWLETT PACKARD 5340A Microwave Counter • allows frequency measurements to 500MHz • HPIB interface • 100ns time interval • T.I. averaging to 10 ps resolution • channel C <at> 50ohms • single input 10Hz - 18GHz • automatic amplitude discrimination • high sensitivity -35dBm • high AM & FM tolerance • exceptional reliability $1050 $79 $475 $695 $1950 BALLANTINE 6310A Test Oscillator BALLANTINE 3440A Millivoltmeter AWA F240 Distortion & Noise Meter ...................... $425 AWA G231 Low Distortion Oscillator ...................... $595 EATON 2075 Noise Gain Analyser ...................$6500(ex) EUROCARD 6 Slot Frames ........................................ $40 GR 1381 Random Noise Generator ........................ $295 HP 180/HP1810 Sampl CRO to 1GHz ................... $1350 HP 400EL AC Voltmeter .......................................... $195 HP 432A Power Meter C/W Head & Cable .............. $825 HP 652A Test Oscillator .......................................... $375 HP 1222A Oscilloscope DC-15MHz ........................ $410 HP 3406A Broadband Sampling Voltmeter ................................................................ $575 HP 5245L/5253/5255 Elect Counter ....................... $550 HP 5300/5302A Univ Counter to 50MHz ................ $195 HP 5326B Universal Timer/Counter/DVM ............... $295 HP 8005A Pulse Generator 20MHz 3 Channel ........ $350 HP 8405A Vector Voltmeter (with cal. cert.) ......... $1100 HP 8690B/8698/8699 400KHz-4GHz Sweep Osc ............................................................ $2450 MARCONI TF2300A FM/AM Mod Meter 500kHz-1000MHz ................................................... $450 MARCONI TF2500 AF Power/Volt Meter ................. $180 SD 6054B Microwave Freq Counter 20Hz-18GHz ......................................................... $2500 SD 6054C Microwave Freq Counter 1-18GHz ............................................................... $2000 TEKTRONIX 465 Scope DC-100MHz .................... $1190 TEKTRONIX 475 Scope DC-200MHz .................... $1550 TEKTRONIX 7904 Scope DC-500MHz .................. $2800 WAVETEK 143 Function Gen 20MHz ...................... $475 FLUKE 8840A Multimeter RACAL DANA 9500 Universal Timer/Counter • true RMS response to 30mV • frequency coverage 10kHz1.2GHz • measurement from 100µV to 300V • stable measurement • accuracy ±1% full scale to 150MHz • list price elsewhere over $5500 • 2Hz-1MHz frequency range • digital counter with 5 digit LED display • output impedance switch selectable • output terminals fuse protected $350 $795 HEWLETT PACKARD 1740A Oscilloscope RADIO COMMUNICATIONS TEST SETS: IFR500A ............................................................... $8250 IFR1500 .............................................................. $12000 MARCONI 2955A .................................................. $8500 SCHLUMBERGER 4040 ........................................ $7500 TEKTRONIX 475A Oscilloscope TEKTRONIX 7603 Oscilloscope (military) • frequency range to 100MHz • auto trigger • A & B input controls • resolution 0.1Hz to 1MHz • 9-digit LED display • IEEE • high stability timebase • C channel at 50 ohms • fully programmable 5½ digit multimeter • 0 to 1000V DC voltage • 0.005% basic accuracy • high reliability/self test • vacuum fluoro display • current list $1780 $695 $350 TEKTRONIX FG504/TM503 40MHz Function Generator TEKTRONIX CF/CD SERIES CFC250 Frequency Counter: $270 • DC-100MHz bandwidth • 2-channel display mode • trigger - main/delay sweep • coupling AC, DC, LF rej, HF rej $990 • 250MHz bandwidth • 2-channel display mode • trigger - main/delay sweep • coupling AC, DC, LF rej, HF rej • mil spec AN/USM 281-C • triggers to 100MHz • dual trace • dual timebase • large screen $1690 $650 The name that means quality CFG250 2MHz Function Generator $375 • 0.001Hz-40MHz • 3 basic waveforms • built-in attenuator • phase lock mode $1290 CDC250 Universal Counter: $405 NEW EQUIPMENT Affordable Laboratory Instruments PS305 Single Output Supply SSI-2360 60MHz Dual Trace Dual Timebase CRO • 60MHz dual trace, dual trigger • Vertical sens. 1mV/div. • Maximum sweep rate 5ns/div. • Built-in component tester • With delay sweep, single sweep • Two high quality probes $1110 + Tax Frequency Counter 1000MHz High Resolution Microprocessor Design CN3165 • 8 digit LED display • Gate time cont. variable • At least 7 digits/ second readout • Uses reciprocal techniques for low frequency resolution $330 + Tax Function Generator 2/5MHz High Stability FG1617 & FG 1627 • • • • • • Multiple waveforms 1Hz to 10MHz Counter Output 20V open VCF input Var sweep lin/log Pulse output TTL/CMOS FG1617 $340 + Tax FG1627 $390 + Tax PS303D Dual Output Supply • 0-30V & 0-3A • Four output meters • Independent or Tracking modes • Low ripple output $420 + Tax • PS305D Dual Output Supply 0-30V and 0-5A $470 + Tax PS303 Single Output Supply • 0-30V & 0-3A • Two output meters • Constant I/V $265 + Tax Audio Generator AG2601A • 10Hz-1MHz 5 bands • High frequency stability • Sine/Square output $245 + Tax • 0-30V & 0-5A $300 + Tax PS8112 Single Output Supply • 0-60V & 0-5A $490 + Tax Pattern Generator CPG1367A • Colour pattern to test PAL system TV circuit • Dot, cross hatch, vertical, horizontal, raster, colour $275 + Tax MACSERVICE PTY LTD Australia’s Largest Remarketer of Test & Measurement Equipment 20 Fulton Street, Oakleigh Sth, Vic., 3167   Tel: (03) 9562 9500 Fax: (03) 9562 9590 **Illustrations are representative only LANsmart: a LAN for home or a small office If you have an office or a home with more than one computer and often need to transfer files from one computer to another or share available resources, then a Local Area Net­work (LAN) such as LANsmart could be just what you need. By BOB FLYNN Most people, if they think about Local Area Networks (or LANs) at all, think that they only used in large organisations with lots of computers which need to be linked together. LANsmart, on the other hand, is designed as a very small network, where as little as three and maybe up to 10 com­puters need to be hooked together. 4  Silicon Chip These days, this can easily happen in the home. Maybe the teenage children have one or more older computers while the parents have a more up-to-date machine and perhaps a laptop. But there may only be one inkjet printer and perhaps just one CD-ROM drive. Wouldn’t it be nice if all the computers could access the printer or CD-ROM drive at any time without the need to undo cables and all that hassle? This is a situation made for LANs­mart. LANsmart can operate with all programs working under Windows or DOS and machines can log onto or leave the network at will, without disrupting operations on any of the other machines. Naturally, it can copy or move files between computers and disc access on individual computers in the network can be restricted to certain directories or sub-directories. Computers in a network also have the ability to send messages to one or all members of the group. The ability of all the computers on the network to access one printer has obvious advantages in terms of hardware investment. The cost of setting up the network system, however, must be offset against any potential savings. The LANsmart system is available as a three, six or 10-user package. All packs come with a D-Link LANsmart network card for each computer; BNC terminated, 5-metre long coaxial connector cables; a BNC T-piece for each card; and two BNC 50-ohm line termi­ nators. Software is supplied with the package on a 3.5-inch floppy disc but can be provided on a 5.25-inch floppy on request. Three user manuals are also provided with the system: LANs­ mart Quick Operation Guide, LANsmart for Windows User’s Manual and LAN­ smart User’s Reference. The package also contains a 20-minute step-by-step installation videotape (VHS), a printed sheet of last minute information and hints and tips regarding the program. A sample network planning sheet is also provided to help you plan your network – a big help, we found. LANsmart may be installed on any IBM or IBM compatible computer. Minimum recommended memory sizes are 640Kb of RAM for file servers and 384Kb for workstations. MS-DOS/ PC-DOS 3.1 or above is required to run LANsmart. For those not familiar with the jargon, a file server is the hub of the network and usually has the printer and most of the key software programs. On the other hand, it could be a slower machine handling just the print­er. A workstation is just one of the individual machines connect­ ed to a LAN. As a single picture is worth a thousand words, it is well worth watching the video that comes with LANsmart A D-Link network card must be installed in each machine on the network. The machines are linked together in daisy-chain fashion using coax cables and T-connectors. The network transfers data at 10 megabits/second. before install­ing the program. Once you have seen the video, setting up the network should be quite straightforward. Installing LANsmart You commence installing LANsmart by inserting a D-Link network card in a slot in each of the computers to be networked. These cards have no switches to set or jumpers to select; setup of the card can be done (if required) from the software. With the cards installed, the machines are connected daisy chain fashion using the coax cables and T-connectors supplied. The first and last machine on the chain must have the open side of its T-connector terminated with a loading resistor. This Fig.1: the resource to be shared is selected by typing “Net” at the C:> prompt, then choosing “Share Your Resources” from the resulting menu and hitting the “Insert” key. The resource type is then selected using the arrow keys and pressing “Enter”. takes the form of a dummy male BNC plug with an internal 50-ohm resistor. Proper termination of the cables is essential if the data transfer rate of 10 megabits/second is to be achieved. In fact, the system won’t work at all and you get an on-screen error message if you don’t have these terminating resistors fitted. The next step is to make a copy of the LANsmart program disc and use this to install the program on each of the comput­ers. Installation can be made direct to DOS or into Windows. If installing to DOS, place the floppy in the drive and at the DOS prompt type A: EASY and installation of the program will commence. While the program is being installed from the DOS prompt you will be given Fig.2: after selecting the resource type, you choose the resource to be shared by repeatedly hitting the “F1” key and using the arrow keys. Hitting “Enter” twice then allocates the selection to the net. This can be done repeatedly; eg to allocate a number of directories. November 1995  5 now follow the prompts to make the resources of your computer avail­able to the network. Access rights Three manuals are provided with the LANsmart system: a Quick Operation Guide, a LANsmart for Windows User’s Manual and a User’s Reference. The package also contains a 20-minute step-by-step installation videotape (VHS). the opportunity to install to Windows if the program discovers Windows on your computer. If you wish to install directly into Windows from Program Manager, choose File, Run and type A: EASY. When the message “Do you want to set up your LANsmart net­work card?” appears, follow the prompts and choose “Set up Con­figuration”. Note that the number you choose for the I/O Base Address and the Interrupt Number may clash with other cards in your computers. This did not happen for us using the default settings or those shown in the video. Save these settings by pressing the Enter key. You can then test the configuration by running Diagnostics, the second field on the Set up Card menu. After the program files are installed and you have entered your company name and the serial number of the program, you will be asked for a name for the station. This can be any name, such as the computer user’s. You are then asked “What type of computer is this?” and you are given the choice of (A) Workstation, (B) Print Server or (C) File/Print Server. Choose the one you want and press Enter. You are then asked to enter the number of computers on the network. Then follows the message “Would you like to reboot your computer to make LANsmart active?” “Y”. Press Enter and your computer will reboot and the LANsmart logo will appear followed by the message “LANsmart Workstation (Server) Installed Successfully”. All computers on the network should have the program installed as above. The next step is to allocate the resources of the server computers on the network. At the DOS prompt type NET, Enter. The main menu will appear and if you move to the line “Share your resources” and press enter, the “Share Your Resources” screen will appear. Press the Insert key and a “Resource Type” window pops up. You can Fig.3: this screen allows you to alter the configuration of your computer. It can be set up as a file/print server, a print server or as a workstation. 6  Silicon Chip Access rights to your directories can be set to one of five levels with LAN­smart: Read-Write-Create, ReadWrite, Read-Only, Write-Create and Write-Only. To restrict access to certain files in a directory (but not all), those files that you wish to share should be moved to a separate directory and access then given to that directory. Use of the F1 (Help) key during this last procedure is of great benefit and will save you from frustration. If you do not use the F1 key while completing “Share Your Resources” and the following “Connecting To Resources” section, remember to move down from one line to the next using the down arrow key. Do not press enter after each line or error messages will appear. Enter can only be used after the “Resource to be shared” and the “Status” lines are filled (“Resource name” and “Password” are optional lines). After completing “Share your resources” and returning to the Main Menu, highlight the “Connect to network resources” field and press the enter key. Follow the prompts as before to choose the network resources you wish to use. If you are going to make use of the C: drive of another server on the network, give it some other drive letter, say D:. Complete the “Connect to network resources”, return to the Main Menu, key down to “Save network setup” and press enter. Press the “Y” key to save the settings and return to the DOS prompt. If everything has gone according to plan, go to the C:\ prompt, type D: and press Enter. Your computer will now be switched to the C: drive of the network computer that you called D:. Computer functions During the installation of the program, you are asked to choose a function for your computer: Workstation, Print Server or File/Print Server. Just what are these functions? A machine set up as a File/Print server allows that computer to share its resources – eg, discs, directo­ries, files and printers – with the rest of the network . Set up as a Print Server, a computer can share its printer(s) with the network. And set Fig.4: these two screen grabs show the opening menus for Network Basic and Network Management when running LANsmart in Windows. up as a work­station, a computer can access the resources of the network but none of the other stations can access a workstation’s resources. LANsmart uses about 100Kb of memory as a File/Print Server, about 90Kb as a Print Server and about 60Kb as a Work­station. For the purpose of this review we set up LANsmart on two of our own computers and it was generally straightforward. We did have trouble with one of the programs on the server computer not booting after LANsmart was installed but it would boot as normal with LANsmart disabled. This lead to much editing of the Config.Sys and Autoexec.Bat files but nothing cured the problem. As a last resort, the program that didn’t want to boot was reinstalled in the computer and that fixed it. You tell me why; I don’t know. We found the system as installed did all it is supposed to do. Files can be transferred from one computer to another with ease and printing from the remote station through the print server is straightforward. The printer server in our setup is used most of the time as a CAD machine. When a large file is being printed in the background, the CAD program runs below its normal speed. However, background printing has no noticeable effect on speed when Fig.5: this Windows screen grab shows the network print queue manager. Files can be deleted or held, or the print order can be altered. the print server is running a word processor program. The lesson here is obvious: connect the printer to a computer that is used mainly as a word processor and any slowdown effects will be negligible. Price & availability At the time of writing this review, LANsmart prices are as follows: three users, $599; six users, $999; and 10 users, $1599.00. A single user add-on card is $169. All these prices include sales tax. LANsmart is available from Smart­ NET Distribution Pty Ltd, 66-76 Dick­ son Ave, Artarmon, NSW 2064 and all SC Harvey Norman stores. Fig.6: this window allows open files on the network to be managed. Among other things, it allows servers to close files that have inadvertently been left open. SC November 1995  7 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. Weekly rubbish reminder This circuit operates a buzzer once a week to remind you to take out the rubbish bin. IC1 is a 4521 oscillator and 24-stage divider which is clocked at 32.768kHz. Its output has a period of 8.53 minutes – 256 seconds high and 256 seconds low. This is fed to IC2, a 4040 12-stage binary coun­ter. Six of IC2’s outputs are fed to a diode AND gate to give a division of 1181. The same diode network provides the reset pulse for both counters. At reset, all the counter outputs are pulled low, including pin 15 of IC2 which momentarily pulls the trigger pin of IC3 low. IC3’s output then goes high for a period of 45 minutes, as set by the 10MΩ resistor and 220µF capacitor at pins 6 & 7. The buzzer therefore sounds for 45 minutes unless the timer is reset manual­ly by the pushbutton at pin 4. The normally-closed pushbutton S1 must be pressed to set the alarm to sound exactly one week later. Manfred Schmidt, Edgewater, WA. ($30) Q2, Q4 & Q6 are turned on, causing the motor to rotate clock­wise. With both comparator outputs high, the situation is re­versed and the motor rotates anticlockwise. When the output of comparator A is high and comparator B is low, the motor is not energised. This occurs in the “dead zone” when the difference in sunlight falling on the LDRs is not suffi­cient to trip the comparators and this threshold is adjusted by VR1. R. Josey, Elizabeth Downs, SA. ($30) Simple solar tracker This solar tracker circuit is an alternative approach to the unit described in the January 1995 issue. It uses two light dependent resistors (LDRs) and a screen which, as the earth rotates, causes more sunlight to fall on one sensor. This turns on a comparator which causes a motor to rotate the solar panel until both sensors receive similar amounts of sun­light. A voltage divider consisting of two 2.2kΩ resistors provides a +6V reference to the comparators. The other two inputs are provided by LDR1, LDR2 and VR1. When both comparator outputs are low, transistors Q1, Q3 & Q5 are turned off, while 8  Silicon Chip Multi-way switching for 240VAC lighting Many homes and offices have a requirement for two-way switching of 240VAC lights, at the top and bottom of stairways, at different entrances to large rooms and so on. The circuit for two-way switching uses two SPDT toggle switches, as shown in the accompa­ nying circuit. It can be implemented using standard architrave switches available from lighting supply and hardware stores. However, when a 3-way or multi-way switching system is required, the circuit is somewhat more complicated – see circuit. The switches at the end of the loop are SPDT types as before but the socalled intermediate switch­ es are DPDT types. These are often only available from electrical whole­ salers or to special order from hardware stores. Note: 240VAC wiring in homes, offices and industry should only be installed by a licensed electrician. SILICON CHIP Ignition coil/ condenser tester We had an enquiry recently from a reader asking for an ignition coil/ condenser tester. While it might appear that our circuit for the Jacob’s Ladder, as featured in the September 1995 issue and based on a standard ignition coil, would do the job, it is not so. The high voltage transistor does not exactly simulate the action of the points and it does not use a shunt capacitor, or condenser, as it is called in automotive parlance. To simulate the switching action of the points, we have used a 12V relay with 10-amp 240VAC contacts. The heavy duty contacts are necessary to reliably switch the coil current. The high voltage capacitor (0.47µF 250VAC) shunting the relay con­tacts does the same job as the condenser shunting the points inside the distributor in a Kettering ignition system. To test a condenser, install it in place of the suggested capacitor. The 555 timer pulses the relay at around 10Hz which is about the maximum rate at which the relay will reliably switch on and off. When the contacts are closed current builds up in the coil. When the relay contacts open the field collapses and a spark will occur at the secondary. Before you apply power to the coil, you must provide a safe spark gap otherwise it may flash over inside and be permanently damaged. The gap can be made with a wire paper clip ex­tended to provide a hook at each end. Fit one end into the EHT socket on the coil and bend the other end so that it is less than 5mm from the negative primary connection of the coil. This becomes the spark gap. If the spark won’t jump across this gap, the coil or the condenser is defective. SILICON CHIP November 1995  9 MAILBAG Thanks for vibrator help I’d like to thank you for publishing my letter regarding a solid state vibrator in the “Ask SILICON CHIP” pages of the August 1995 issue. Secondly, I’d like to thank those readers whose time and effort and offers of help were greatly appreciat­ed, especially Norm Bush of Canterbury who sent a complete radio and Philip Watson of Como for vibrators, technical data and advice. Eric Phillis, Dareton, NSW. Cellullar phone controversy (1) I was amazed at the airy attitude expressed in your Septem­ ber 1995 Publisher’s Letter regarding the concern about cellular aerials overlooking a school yard. As the Editor of a technical journal, I would have expected you to support your argument with some facts on measured field strengths, international standards, etc. After all, mobile phone users have a choice of time and place denied to children in a school yard. I believe that, in the long run, these little brain cookers will, as with cigarettes and asbestos fibres, be found to be just as lethal. Have a nice day. Bill Jolly, Tranmere, SA. Cellullar phone controversy (2) It isn’t often I get mad enough to take to task such a personage as the editor of a major publication but enough is enough. Your editorial in the September issue really does take advantage of the Gentle Reader’s goodwill and tolerance. Yes, I know that in a democracy civilised people can claim the right to free speech, and indeed I would expect that here in Australia everybody would exercise that right. The words the editor of a respected technical journal might choose would normally be expected to be tempered with some toler­ ance though. I am referring of course to your editorial, “Igno­rance and hysteria often carry the day...” in the Sept. 1995 issue. Probably the whingeing wimps, the hypocritical pollies and the hysterical and ignorant parents of Harbord’s little darlings are desperately trying to fath10  Silicon Chip om out why you have singled them out to attack for not being as technically informed as your good self! In my humble opinion, if there is ignorance, hysteria (and yes, intolerance) in the world, it is often because somebody, somewhere, leapt to their feet and clouded the issue with in­ temperate language. Please, do take a moment to reflect before going to print, so as to avoid being taken to task by your read­er. E. Miller, Kyeemagh, NSW. Comment: the politicians are certainly hypocritical and the parents were hysterical. Moreover, Telstra could have provided the measurements of field strength in the preschool yard if asked. If the parents had not wanted Telstra’s information, they could have easily commissioned an independent survey. So could any of the news organisations reporting the melee. They were not about to let a few facts spoil a “good story”. Ignorance and hysteria did carry the day. Telstra backed down and turned off the offending transmitter antennas. MMIC makes a better masthead amplifier In regard to the letter concerning the OM350 (August 1995 issue), I should like to offer my experience with homemade TV masthead amplifiers (MHA). I live in an area poorly serviced by TV (channels 2 & 9 only) and also in the lee of a steep hill. Without an MHA there was only a snowy black and white picture on channel 9. So I built an MHA using a commercially available kit based on an OM350 and had essentially the same problem that was described by your contributor in February. Sometimes the picture was acceptable but at other times, for no apparent reason, it completely degenerated as though the circuit had gone into oscil­lation. The amplifier was powered from a multi-voltage plugpack and I found that switching the output voltage from its nominal 12 volt position down one or more positions would sometimes cure the problem, but not always. Often it would be necessary to drop the voltage so low that the amplifier ceased to work altogether! I tried replacing the original OM350 with another one but this made no appreciable difference. In desperation, I constructed a completely new MHA based on the MAR-6 IC. This is quoted as having a gain of 20dB, a noise figure of 2.8dB, a bandwidth of 2GHz and, most appealingly, is said to be unconditionally stable. It is also very cheap. This MHA has worked perfectly ever since and provides an exceptionally good picture. A. Stockwell, Denmark, WA. Microsoft Network is not the Internet Interesting to see the article by Geoff Cohen on the subject of the Internet in the October 1995 issue. I think it unfair of you not to warn readers that MSN is two-way. While connecting to MSN your hard drive appears as if it is attached to Microsoft’s central computer and can be accessed as if it were, just like any network. Kiss goodbye to your privacy. At least you make the point (only just) that MSN is not the Internet. It is unfair not to advise people of much cheaper ways to connect to the Inter­net. It can be accessed (text mode) using an XT class computer and a 2400 baud modem. This is only slightly slower than a 486DX2-66 and a 28,800 baud modem. As for access charges, well perhaps that’s the biggest joke of all. For text mode access I pay $180 per year for 140 minutes per day (off peak)! At the MSN rate of $5 per hour this would cost me $4258. David Dorling Buderim Qld. Comment: you are confusing MSN with general dial-in IP networking. MSN in Australia does not facilitate network file or device sharing. Note however, that when connecting to the Internet via a TCP/IP connection, care must be taken with file sharing as it is theoretically possible for someone to make their disc viewable to the entire network. The Microsoft Explorer warns about possible file sharing problems when it is activated. SC SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Australian Defence Force – Navy SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Most programmable systems use a MAP sensor as the main determinant of engine load and allow complete control over injector pulse widths. However, specifying a wide pulse width at high RPM may lead to a 100% duty cycle, necessitating the use of larger injectors (above). A look at programmable fuel injection control Australia leads the world in the production of cheap, fully-programmable engine management units. Used in both racing and high-performance road applications, these ECUs can be pro­ grammed to control both ignition advance angle and fuel injector pulse width. By JULIAN EDGAR The ease with which changes to injector pulse width can now be made means that air/fuel ratios can be exactly as desired in any part of the load and engine speed spectrum. But what ratios should be used? The complexity of injector flow rates and the duty cycle implications mean that there are traps present for the unwary! The proportion of air and fuel that is mixed together to form the combustible mixture is generally referred to as the air/fuel ratio. In practice, approximately 14.7kg of air is required for the complete combustion of 1kg of petrol. Another way of expressing this 16  Silicon Chip relationship is to say that about 10,000 litres of air is needed to burn just one litre of petrol! However, this so-called “stoichio­ metric ratio” is not main­tained under all engine operating conditions. The maximum torque and the smoothest operating conditions are experienced when a rich mixture of around 13:1 is used – an air/fuel ratio charac­terised by excessive exhaust emissions and high fuel consumption! Taking this further, the extreme rich mixture limit for a petrol spark ignition engine is about 7.5:1, while the lean limit for conventional engines is about 19:1. In order that catalytic converters can work with maximum effectiveness, current engines use a stoichio­metric mixture for most of the time. This is accurately achieved by the use of closed-loop control based on an exhaust gas oxygen sensor. However, maintaining stoichio­ metric mixtures at all times would limit power, prevent adequate cold engine performance, increase emissions and reduce fuel economy. Because of this, mixtures other than stoichiometric are used at large throttle openings, during warm-up and during over-run conditions. The air/fuel ratio which gives best results is influenced more by engine load than any other factor. Adam Allan (of Adelai­de’s Allan Engineering) is very experienced in tuning programm­ a­ble engine management units for both race and road use. Taking the example of a turbocharged 2-litre engine, he suggests that the appropriate air/fuel ratio would be about 16-14:1 at the extremely low load of -50kPa manifold pressure, 14-12:1 (depend­ing on the Fig.1: the maximum pulse width that can be specified is dependent on the engine speed, if duty cycles of 100% are to be avoided. If there is one injector pulse per rev (the most common configura­tion), the pulse width cannot exceed 10ms at 6000 RPM. torque output of the engine) at 0kPa , and about 12:1 at full load of +50kPa boost. Other factors influence this relationship, with a standard VL Commodore Turbo using an extremely rich mixture of 10:1 at full throttle. The ECU has been programmed in this way probably so that there is a safety margin if the injectors become partial­ly blocked or poor fuel is used, etc. Injector control Notwithstanding the changing air/ fuel ratios and differing engine efficiencies at different loads, the amount of fuel used increases in proportion with the power output. In this respect, a fuel injected engine and one equipped with a carburettor are similar – more power means more fuel. However, a carby engine uses a continuous flow mechanism, whereby the fuel and air are being constantly mixed. On the other hand, in an electronically fuel injected engine, the fuel and air are mixed in the intake ports in a series of spurts; ie, the fuel is added to the air only when the injector is open. The pulse width – or time that the injector is open – is measured in milliseconds. This determines the amount of fuel which flows from the constant-pressure injector. In practice, the injectors must operate quite rapidly. At 6000 RPM, for example, the engine’s crankshaft is rotating at 100 times per second. This means that the maximum time available for the injection operation to occur during a single crankshaft revolution is 0.01 seconds, or 10 milliseconds. If the pulse width is 8 milliseconds – and the injector fires once per engine revolution – then the injector will be open for 8/10ths of the available time. This ratio is expressed as an 80% duty cycle. If the duty cycle reaches 100%, as it would with an injector pulse width of 10ms at 6000 RPM, then the injector will be held open continuously. Fig.1 shows the relationship between a 100% duty cycle, the engine speed and the firing frequency of the injector. Once a duty cycle of 100% is reached, no further fuel can be added to the engine by the injectors (at least, not without changing the fuel pressure!). A further increase in the engine load would then result in an increase in the air/fuel ratio, giving rise to a possibly damaging lean-mixture condition. In this situation, larger injectors would need to be fitted. However, the use of large injectors means that the preci­sion with which fuel can be added at low loads suffers. A large injector will not be able to respond to very small pulse widths as accurately as a smaller injector, with inaccurate metering at low loads resulting in poor driveability and exhaust emissions. As a result of this, manufacturers often specify injectors which reach an 80-90% duty cycle figure during full power operation. Note that while the duty cycle reaches its peak at the high­est power output, the same is not true of injector pulse width. The greatest pulse width applied to the injectors is usually achieved at peak torque. Fig.2: the Haltech E6 injector pulse width QuickMAP is config­ured in 500 RPM increments over the engine speed range using just four input figures. Further tuning is then necessary to obtain ideal air/ fuel ratios. November 1995  17 Fig.3: while the injector duty cycle is greatest at peak power output, the maximum injector pulse width normally occurs at peak torque, where the greatest amount of air and fuel is ingested in one stroke. This graph shows the injector pulse width for a tur­bocharged 2-litre engine in which the peak torque occurs at 4000 RPM. To explain, the peak torque figure of an engine is reached when the greatest force on the piston is realised. This is asso­ciated with the maximum ingestion of air, which in turn requires the maximum amount of fuel per engine cycle. In a conventional piston engine, the peak torque value often occurs over only a very small portion of the wideopen throttle engine speed range. It is here that the maximum injector pulse width is required. Programming fuel maps BASE FUEL DELIVERY As with its ignition advance angle system, Haltech – a major manufacturer of programmable ECUs – uses a proprietary QuickMAP approach to programming. This allows the very quick production of rough fuel maps for the whole load and RPM range. The QuickMAP process requires the input of the following parame­ters: (1). Idle injection pulse width; (2). Full load injection pulse width; (3). Fuel percentage decrease at 2000 RPM; and (4). RPM at which peak torque occurs. From this data, the software calculates approximate fuel maps for all loads at 500RPM increments throughout the engine’s speed range. Fig.2 shows an example of a fuel map for a turbocharged engine which has been calculated by this QuickMAP approach. Note that this map is for different loads (the horizontal axis shows manifold pressure) at a constant engine speed, and so injector pulse width increases in proportion to increasing load. Fig.3 shows the injector pulse width necessary for full load at different engine speeds. These figures were devised for an engine which had peak torque occurring at 4000 RPM. As a result, the maximum injector pulse width occurs at that engine speed. While the QuickMAP approach allows the speedy production of approximate fuel maps, fine tuning is vital for optimal engine performance. Fig.4 shows a modified 3500 RPM QuickMAP which was produced by Paul Keen of Adelaide’s Darlington Auto Tune for a Nissan FJ20 turbo­ charged engine. On this particular car, the maximum boost pressure was 50kPa (the position of the ‘active’ black bar), making it unnecessary to tune for loads greater than this figure. Note the subtle variations in injector pulse widths which have been made, especially at loads around -50kPa. These low manifold pressures are obtained in cruise conditions around urban areas. The fine tuning is necessary because poor driveability at these throttle openings is very noticeable. Fig.5 shows a fuel map for a Ford 289 V8 which uses Autro­nic engine LOAD RPM Fig.4: the fuel map for a 50kPa boost turbocharged engine. Note the small variations in the injector pulse widths at light load (-50kPa) conditions. This is necessary to ensure good driveabili­ty at light loads. 18  Silicon Chip Fig.5: this fuel map for a Ford 289 V8 was drawn from Autronic tabular data using Microsoft Excel® software. The peaks and troughs are due mainly to resonances in the intake and exhaust manifolding. Fig.6: a coolant temperature correction chart. It can be regarded as equivalent to the choke in a carburettor engine. Note that the mixture is leaned as the coolant temperature rises. Fig.7: the air temperature is also used to modify the fuel map, with ±15% correction available. Notice how the mixture is en­riched at the lower temperatures and is leaned as the intake air temperature rises. Fig.8: the fuel injectors react more slowly as the battery vol­tage declines and this is countered by increasing the injector pulse width. Fig.9: the control screen for the Haltech E6 closed-loop oxygen sensor feedback system. The times at which the system works in closed-loop, the amount of correction, and the speed at which it operates are set by the user. management. This engine was tuned on an engine dy­namometer equipped with extensive data gathering equipment and the resulting fuel map shows a number of “peaks” and “valleys”. These occur mainly because of reson­anc­es in the exhaust and intake manifolds, which reduce the effective restriction at certain engine speeds and gas flows. Note also that the pulse width values do not markedly de­cline past peak torque. This may be due to the use of relatively rich air/fuel ratios at high loads for this particular engine. Injection correction maps In addition to the base injector timing which is mapped using load and engine speed, a series of pulse width correction charts are also usually employed by programmable ECUs. The Haltech fuel coolant chart The Haltech engine management ECU. It can be programmed to compensate for coolant temperature, air temperature and the battery voltage, and has optional closed-loop oxygen sensor feedback control. November 1995  19 sumption. This map can be adjusted to give fuel economy benefits when the air inlet temperature is high. (Of course, the maximum realisable power will be decreased at high inlet air temperatures.) Battery voltage correction Chassis or engine dynamometers and exhaust gas analysers are required to set up programmable fuel injection ECUs. shown in Fig.6 is an exam­ple. Effectively this map provides the equivalent of the carbur­ ettor choke. It shows temperature on the horizontal axis, while the percentage enrichment is shown on the vertical axis. By the way, the Australian-produced Haltech system is sold around the world, which is why it can correct mixtures with temperature inputs down to -40°C! Each of the bars can be adjusted for height, depending on whether the engine requires warmup mixtures richer or leaner than the normal setting shown here. Mixture modification according to air temperature is also carried out – see Fig.7. At cold inlet air temperatures, the fuel atomises less easily, while the converse is true for warm inlet air temperatures. During testing of their Formula 1 turbocharged V6, Honda found that an inlet air temperature of 70°C gave the best specific fuel con- Rally cars can use extensive correction maps in addition to the usual base fuel and ignition charts. Examples include enrichment of the mixture at times of low and high engine coolant temper­atures, RPM limiting via fuel and/or ignition modification, and the correction of injector opening time on the basis of battery voltage. 20  Silicon Chip As battery voltage decreases, the response time of the injectors increases and so a correction map is used to negate this potentially deleterious effect – see Fig.8. Most, if not all, engine management systems have voltage compensation but not very many of them allow the user to manipulate the amount of correction. In a rally or long distance race car, for example, injector opening time compensation could be programmed in for voltages lower than the 9V limit of the standard map. This could be of benefit if the battery was slowly discharging due to an alternator problem, for example. Along with a few other programmable systems, the Haltech E6 can be set up to use the feedback input of an exhaust gas oxygen sensor – see Fig.9. Used only at light throttle openings, the system monitors the output voltage signal from the oxygen sensor. This is normally about 1V when the mixture is rich and close to 0V when it is lean. The sensor is designed to change its response very quickly as the mixture passes through the stoichiometric ratio. Closed loop control is user-optional with the Haltech system and can be disabled if, for example, the vehicle is to be used in a pure race application. The lowest engine speed at which closed loop control will become functional is user-specified, with this a requirement because some engines will not idle satis­factorily with stoich­ io­metric air/fuel ratios. The number of cycles through which the engine passes before correcting the mixture can be set in the range from 4-10, with the default being eight. The throttle opening angle after which the system will go into open loop is also definable, with a 30% figure being the default. Finally, the oxygen sensor reference voltage can be set, with the vast majority of sensors having a 600mV output at the stoichiometric air/fuel ratio. Acknowledgements: thanks to Allan Engineering (08 522 1901) and to Darlington Auto Tune (08 277 4222). SC SILICON CHIP BOOK SHOP Newnes Guide to Satellite TV 336 pages, in paperback at $49.95. Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Servicing Personal Computers By Michael Tooley. First pub­ lished 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. Optoelectronics: An Introduction By J. C. A. Chaimowicz. First published 1989, reprinted 1992. This particular field is about to explode and it is most important for engineers and technicians to bring themselves up to date. The subject is comprehensively covered, starting with optics and then moving into all aspects of fibre optic communications. 361 pages, in paperback at $55.95. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. Power Electronics Handbook Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Surface Mount Technology By Rudolph Strauss. First pub­ lish-ed 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First pub­ lished 1989. 6th edition 1994. This just has to be the best reference book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. semicustom electronics & data communications. 63 chapters, in paperback at $140.00. Radio Frequency Transistors Principles & Practical Appli­ cations. By Norm Dye & Helge Granberg. Published 1993. This timely book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering techniques, impedance matching & CAD. 235 pages, in hard cover at $85.00. Newnes Guide to TV & Video Technology By Eugene Trundle. First pub­ lish-ed 1988, reprinted 1990, 1992. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 432 pages, in paperback, at $39.95.  Title Price  Newnes Guide to Satellite TV  Servicing Personal Computers  The Art Of Linear Electronics  Optoelectronics: An Introduction  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Surface Mount Technology  Electronic Engineer's Reference Book  Radio Frequency Transistors  Newnes Guide to TV & Video Technology $55.95 $59.95 $49.95 $55.95 $55.95 $59.95 $99.00 $140.00 $85.00 $39.95 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ & PNG add $10.00 per book, elsewhere add $15 per book. TOTAL $A November 1995  21 A mixture display for fuel injected cars This simple project allows you to monitor the fuel mixtures being run by your car. You can use it as a tuning tool, to help in vehicle modification, or simply to see the behaviour of the engine control module. It is based on an LM3914 chip and 10 LEDs. By JULIAN EDGAR One aspect which makes engine-managed cars very different to their earlier carby brethren is the use of a number of sensors to measure various engine parameters. For example, inlet airflow, coolant temperature and throttle position all have sensors to measure their values. One of the most interesting sensors is the exhaust gas oxygen (EGO) sensor. As the name suggests, this sensor is mounted in the exhaust flow, usually in the ex­haust manifold. Specifically, it measures the oxygen content in the exhaust gas (relative 22  Silicon Chip to air) and generates a voltage which is dependent on the air-fuel mixture. It does this to deter­mine whether the air-fuel ratio is rich, stoichiometric, or lean. The most commonly used EGO sensor generates its own voltage output which varies between zero and 1 volt. In round terms, if the sensor output is about 200mV or less the mixture is lean and if the output voltage is over 800mV it is rich. However, the precise value of the output voltage is less important than its relative value. In other words, ‘rich’ and ‘lean’ are only mean­ ingful terms when compared with stoichiometric ratios and the sensor has been designed so that its output changes very rapidly around this point. Fig.6 shows the response curve of a typical oxygen sensor. Monitoring the sensor output can be done with a digital multimeter but the response time of the typical multimeter is too slow to keep up with mixture fluctuations. The mixtures fluctuate in a rapid rich-lean-rich-lean sequence as the ECM responds to the EGO sensor’s output. Depending on the particular EFI system (and the health of the EGO sensor), this can occur at frequencies as high as 10Hz. The rapidly varying output of the EGO sensor means that it is easiest to read on a bargraph. Hence this project uses 10 coloured LEDs in a bargraph. Two red LEDs are used to indicate lean mixtures, six green LEDs to show mixtures in a normal range and two yellow LEDs to show rich Fig.1: the signal from the oxygen sensor is monitored by an LM3914 dot/bar display driver in dot mode. Different coloured LEDs are used to highlight the signal changes. Above: the Mixture Meter uses just a single IC and three other compon­ents, in addition to the 10 LEDs. The two LEDs at the extreme left are red, the two on the far right are yellow and the middle six are green. Make sure that no solder bridges are formed between the tracks, especially at the IC and LED connections. mixtures. Incidentally, depend­ing on the application of the Mixture Display, you may wish to reduce the number of green LEDs and substitute more red and yellow ones. It is important that coloured LEDs be used (as opposed to an all-red bargraph display, for example), because it is far easier to see at a glance the mixture strength by simply looking at the LED colour, rather than its position in the dis­play. Circuit details The circuit presented here is iden- tical to that featured in “Electronic Engine Management: Pt.5” on oxygen sensors, in the February 1994 issue of SILICON CHIP. It is based on a National Semiconductor LM3914 dot/bar display driver. In dot mode, it drives the LEDs so that as the input voltage to its pin 5 is increased, it turns on progressively higher LEDs. For example, at the lowest input voltage, LED1 is alight; at midrange voltages, LED4 or LED5 may be lit; and at the highest input voltage, LED10 will be lit. In bar mode, the LM3914 operates as a bargraph display driver, turning on more LEDs for higher input voltages. Hence, for the lowest input voltage, only LED1 will be lit; for midrange voltages all LEDs up to LED4 or LED5 may be lit; and for the highest input voltage, all 10 LEDs will be lit. The circuit is shown in Fig.1 and as Fig.2: the parts layout for the PC board. Note that you can use the 680Ω resistor and a 6V or 9V battery to check the LEDs before they are installed. you can see, there is the LM3914, the 10 LEDs and little else. The 680Ω resistor connected to pin 7 (the internal 1.25V voltage reference) sets the current through the LEDs, while trimpot VR1 acts as a sen­sitivity control. Not shown on the circuit is pin 9 which is left open circuit to operate in dot mode or connected to the +12V line for bargraph mode. Construction The Mixture Display is built on a small PC board measuring 74 x 36 mm and coded 05111951. The component layout is shown in Fig.2. Start the construction process by making sure that you can identify all the components and then check the PC board to ensure that there aren’t any breaks in the copper pattern or unwanted bridges between the tracks. Fig.3: this is the full-size etching pattern for the PC board. Check the board carefully before installing any of the parts. November 1995  23 PARTS LIST 1 PC board, 74 x 36mm, code 05111951 1 LM3914 dot/bar display driver (IC1) 1 18-pin IC socket 2 red LEDs (LED1,2) 6 green LEDs (LED3-8) 2 yellow LEDs (LED9-10) 1 680Ω 1% 0.25W resistor 1 5kΩ trimpot (VR1) 1 10µF 16VW PC electrolytic capacitor Miscellaneous Hook-up wire, solder, PC stakes The LEDs should be oriented so that their internals look like this. If their connections are reversed they won’t work! This is a Nissan 3-wire oxygen sensor. In this type of sensor, two wires provide power for an internal heating element, while the third wire is the signal output. If any are found, they should be fixed before proceeding further. Before installing any components, it is a good idea to check all the LEDs because some may be non-standard. Normally, one lead of a LED is longer than the other and this is the anode (marked with an “A” on the circuit). To check the LEDs, you will need a 6V or 9V battery and the 680Ω resistor which will later be soldered into the PC board. Connect the resistor to the positive battery terminal and the longer (anode) lead of the LED to the free end of the resistor. The other LED lead goes to the battery negative. If the 24  Silicon Chip LED lights, it is a standard type; if it does­n’t, reverse the LED leads. If it now lights, cut a few millimetres off the longer lead, making it the shorter one. This way, all the LEDs will be similar (and correct) when you come to install them. If a LED still doesn’t light, it is a dud and should be tossed out. Now install the 680Ω resistor, followed by trimpot VR1 and the 10µF electrolytic capacitor which must be installed with correct polarity; ie, negative lead furthest from the LEDs. The LEDs are also polarised and so must be soldered in the correct way around if they’re to work. With the board orientated so that the LEDs are at the top and the PC tracks are facing downwards, the LEDs are inserted with their longest wire on the right. Start by inserting the two red LEDs, which go at the lefthand end of the board (when viewed with the LEDs at the top). When soldering the LEDs into place make sure that a solder bridge isn’t formed between the two leads, as their solder pads are quite close together. Continue with the six green LEDs and then the two yellow LEDs. Making them line up neatly will be easier if their leads are bent so that the LED bodies are hard up against the edge of the PC board. With all the LEDs in place, hold the board up to the light and check that the internals of the LEDs show that they are all lined up the same way. Next solder in the IC socket. The socket has a small cutout at one end which shows the correct orientation to insert the IC. The notch in the socket should be at the opposite end to the 680Ω resistor. Make sure that bridges aren’t formed between the IC socket pins during the soldering. Insert PC stakes into the holes marked I/P, GND and +12V and solder them into place. Finally, insert the IC into its socket, making sure that it is in the correct way around. Now double check for solder bridges and make sure that the orientation of the LEDs, IC and capacitor are correct. Connecting the board The Mixture Display is powered from an ignition-switched +12V rail How does an EGO sensor work? There are two types of oxygen sensor in general use, one based on Zirconium Oxide (also known as Zirconia, ZrO2) and the other based on Titanium Oxide (TiO2). The Zirconium Oxide type is the most common as it generates a voltage directly and does not need to be connected in a bridge circuit. By the way, EGO sensors are also often referred to as Lambda sensors, from the Greek symbol λ which is used in the equation: λ = air-fuel ratio/air-fuel ratio at stoichiometry When the air-fuel mixture has too much air (ie, lean), λ is greater than one (λ > 1). Conversely, when the air-fuel mixture has too much fuel (ie, rich), λ is less than one (λ < 1). Fig.4 shows the cross-section of a typical zirconia EGO sensor. In essence, this uses a thimble-shaped section of zirco­nia (a ceramic-like material) with platinum electrodes on the inside and outside. The EGO sensor actually generates a voltage due to the vastly different concentrations of oxygen ions at either elec­ trode. Oxygen ions are negatively charged. The zircon­ i a has a tendency to attract the oxygen ions and they accumulate on the surface just inside the platinum electrodes. The platinum elec­ t rode exposed to air has a much higher concentration of oxy­gen than the exhaust electrode and therefore it which could be accessed from the fuse panel or another switched device (like the radio). Connect this rail to the +12V pin on the board and connect the GND pin to chassis. Make sure that these wires are connected the right way around otherwise you will damage the IC and possibly the LEDs too. The Fig.4: cross-section of a typical zirconia EGO sensor. Fig.5: the inside platinum electrode is exposed to air while the outside is exposed to the hot exhaust gas, via a porous protec­tive layer. becomes electrically negative. In practice, the air electrode is connected to chassis and so the exhaust electrode is positive. The magnitude of the voltage depends on the concentration of oxygen ions in the ex­haust gas and the temperature of the sensor. Fig.6 shows the sharp response of a typical EGO sensor as the air-fuel mixture varies from rich to lean and back again. Note that the response is slightly different from rich to lean than from lean to rich. The difference is the hysteresis of the sensor. Fig.6: the voltage output of the sensor changes very quickly around the stoichiometric mixture point. This means that mixtures which are only a little rich or lean can be easily seen. This sensor response is obtained at operating temperatures of 360°C and above. final connec­tion is to the signal output of the oxygen sensor. Oxygen sensors are commonly available in single or 3-wire configurations. If your car is fitted with a single-wire sensor, simply connect the signal lead from the Mixture Display to this wire. Don’t disconnect the oxygen sensor output from the vehicle ECM; instead wire the Mixture Display in parallel. The easiest way of doing this is to access the EGO sensor wiring near to the sensor itself. Push a pin right through the centre of the lead and bend it over and twist the leads together. This way, the integrity of the oxygen November 1995  25 connected the Mixture Display, buy another IC and try again! If one or two LEDs fail to light, check for solder bridges between their leads. Using the mixture display This is single-wire oxygen sensor. This wire connects directly to the Mixture Display’s I/P lead. If you want to be really fancy, the Mixture Display can be integrated into the dash of the car. Here the LEDs have been positioned so that their layout reflects the shape of the re­sponse curve of the oxygen sensor. The panel replaced one of the dash vents and the LEDs have been connected to the PC board by flying leads. sensor lead is preserved. Now solder the Mixture Display signal lead to the pin, making sure that you don’t damage the lead’s insulation. Wrap the join with good quality insulation tape. If your car’s sensor is the 3-wire type, then a little more detective work will be needed. The extra wires found in this type of sensor are to power an internal heater, which brings the sensor up to temperature faster than solely by heat trans­fer from the exhaust gas. With the car running and up to operat­ing temperature, one wire will be +12V, another 0V and the final wire 0.4-0.6V. It is the latter which is the EGO sensor output and this must be connected to the I/P terminal on the Mixture Dis­play board. Incidentally, if yours is a 3-wire type, you can also access the other 26  Silicon Chip two EGO sensor wires for the power supply to the Mixture Display, running three wires to the PC board from the oxygen sensor, rather than just the single signal wire. With the car running, the Mixture Display should light some of its LEDs. If the EGO sensor is still cold, the ‘lean’ red LED may be the only one to light but as the sensor comes up to tem­perature, other LEDs will also light. With the sensor up to temperature, a blip on the throttle should cause the lit LED to run up and down the scale. If all the LEDs light at once – and there is a burning smell coming from the display – switch off the ignition immediately and check the orientation of the IC. If no LEDs light, check the polarity of the power supply wiring and if you find that you had wrongly There are two ways of calibrating the Mixture Display: (1) on the road; and (2) on a chassis dyno. The easiest is on the road, although note that this won’t be appropriate in a car which has already been highly modified. With an assistant in the passenger seat and with the engine up to operating temperature, drive at a constant speed, say 60km/h, with a steady throttle opening. The lit LED should start oscillating up and down the display, as the ECM makes the mix­tures alternately rich and lean in closed loop operation. Adjust trimpot VR1 so that the oscillations in either direction are symmetrical around the middle LED. Now, use full throttle and watch what happens to the Mix­ture Display. It should instantly show a rich mixture (either of the two yellow LEDs lit) and this mixture should be constantly held. Lift the throttle abruptly and the display should blank, as the injectors reduce their flow on the overrun – and so the mixture goes full lean. At idle, the Mixture Display should again show the closed loop oscillations. If you’re installing the Mixture Display on a highly modi­fied engine then in-car calibration can still be done –but with the proviso that the mixtures may be all wrong to start with. The safest approach with this type of car is to use a chassis dyno and an exhaust gas analyser so that the Mixture Display can be calibrated according to the gas analyser’s readout. Whether to help in tuning, to allow intelligent modifica­tion, or simply so that you can see the way in which the EFI computer is working, the Mixture Display is a cheap and effective tool. No oxygen sensor? Note that if you have an engine which runs on leaded petrol (either carby or EFI), it will not have a factory installed exhaust gas oxygen sensor. The way around this is to source a sensor from a wrecker and install it in the exhaust manifold yourself. However, running leaded petrol will soon poison the sensor and so this approach should be used only for tuning purposes, with the sensor then SC removed for everyday use. ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. TOTAL $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS ❏ New subscription – month to start­­___________________________ ❏ Renewal – Sub. 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Please have your credit card details ready ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail coupon to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia November 1995  27 A CB transverter for the 80-metre amateur band Looking for an inexpensive way to get on the amateur bands? Do you have a 40-channel AM/SSB CB radio lying around? If so, you can build this transverter to convert the CB to the popular 80-metre (3.5MHz) amateur band. PART 1 – By LEON WILLIAMS, VK2DOB Many prospective amateur radio operators quickly lose interest when they look at the prices of modern amateur-band transceivers. Often, however, they already own an AM/ SSB 27MHz CB radio which they no longer use. These old CB radios have a number of features which make them ideal for use on the amateur bands. The obvious exception to this is, of course, their frequen­cy range. This is where a transverter can be employed. It’s a device that converts transmitted and received RF signals from one 28  Silicon Chip band to another. Coupled to a CB radio, it can provide an effec­tive and inexpensive way of getting on to the amateur bands. In this case, the transverter takes the 27MHz transmitter signal from the CB and converts it to a 12-watt signal on 3.5MHz. Conversely, on receive, it takes the incoming 3.5MHz signals from the antenna and converts them to 27MHz for the CB. A major advantage of this scheme is that there are no modi­fications to the CB – the transverter simply plugs in between the antenna socket and the antenna itself. Operation is simply a matter of selecting a channel and talking, as the transverter has an automatic transmit/receive changeover circuit (this can be overridden). The transverter to be described has an output power of 12W PEP, which is ample during normal conditions on the 80-metre band. It is housed in a neat instrument case with aluminium front and rear panels and runs off 13.8V DC. Inside the case, there are three easy-to-build PC boards and common inexpensive components are used throughout. The potential problem of ordering an expensive crystal for the mixing frequency has been eliminated by using a novel phase locked loop (PLL) circuit. CB channels are spaced 10kHz apart and the PLL has a ±5kHz fine tune control so that the space between the channels can be used. This provides continuous coverage from 3.500MHz Fig.1: block diagram of the CB to 80-metre transverter. During transmit, the 27MHz signal is attenuated and mixed (in the Tx mixer) with the signal from a PLL frequency generator to produce a difference signal of 3.5MHz. Conversely, in receive mode, the incoming 3.5MHz signal is mixed with the PLL signal in the Rx mixer to produce a difference signal of 27MHz. TABLE 1 Fig.2: block diagram of the PLL frequency generator section. The output of a 10MHz crystal oscillator is divided by 54 to give a nominal frequency of 185kHz. This signal is then compared in a phase detector with the divided output from a voltage controlled oscillator (VCO) to produce an error signal. to 3.700MHz. Working out what frequency you are on is simple. When the CB channel selector is in the 20s, the frequency is between 3.5MHz and 3.6MHz. Similarly, when the channel selector is in the 30s, the frequency is between 3.6MHz and 3.7MHz. This is shown in the channel table (Table 1). Apart from a mix-up in channels 23, 24 and 25, the scheme works well. From 3.560MHz, the channels remain in sequence to 3.700MHz, with the second channel digit being the 10kHz indica­tor. Note that 18 and 23-channel CBs transceivers are not suit­able because of their limited frequency range. Block diagram Fig.1 shows the block diagram of the transverter. When the CB radio starts to transmit, the relays are energised by an RF detector circuit. This directs the 27MHz transmitted signal of about 12W to a dummy load/attenuator. A small amount of the signal is then tapped off by the drive control and fed to a mixer stage. This mixer stage also accepts a 23.705MHz signal from a PLL fre­ quency generator, giving a difference frequency of 3.5MHz on the output. Finally, this signal is amplified and the resulting 12W output fed via a second relay to the antenna. When the CB changes back to receive mode, the RF detector de-energises the relays and the 3.5MHz signals from the antenna pass through the second relay contacts to the receive mixer. The PLL signal is also applied to this mixer, however the output frequency this time is 27MHz. This signal then passes via the first relay and into the CB radio. How it works PLL board: Fig.2 shows the block diagram of the PLL sec­tion. A 10MHz crystal oscillator has its output divided by 54 to give a nominal frequency of 185kHz and this is applied to one input of a phase detector. This is the reference frequency for the PLL. In Frequency Channel 3.50MHz 20 3.51MHz 21 3.52MHz 22 3.53MHz 24 3.54MHz 25 3.55MHz 23 3.56MHz 26 3.57MHz 27 3.58MHz 28 3.59MHz 29 3.60MHz 30 3.61MHz 31 3.62MHz 32 3.63MHz 33 3.64MHz 34 3.65MHz 35 3.66MHz 36 3.67MHz 37 3.68MHz 38 3.69MHz 39 3.70MHz 40 addition, a voltage controlled oscillator (VCO) generates a nominal 23.705MHz signal which is buffered November 1995  29 30  Silicon Chip Fig.3: the complete circuit diagram for the transverter. Q10 and X1 form the 10MHz oscillator, while IC2 is the divide-by-54 stage. IC3 is the VCO, while IC4 divides the VCO output by 128. T4, D6D9 and T5 form the transmit mixer and this drives Q4, Q5 and the two output FETs (Q8 & Q9). IC1 is the receive mixer, while Q1-Q3 provide automatic relay switching. and ap­plied to the receive and transmit mixers. The VCO signal is also tapped off and divided by 128 to provide the other input of the phase detector. When there is a difference between the two phase detector inputs, an error signal is produced. This error signal is passed through a low-pass filter to obtain a DC voltage to change the frequency of the VCO, so that the divided frequency equals the reference frequency. In practice, the VCO frequency needs to vary from 23.700MHz to 23.710MHz to cover the 10kHz spacing between CB channels. To accomplish this, the 10MHz reference frequency is varied between 9.9984MHz and 10.0027MHz by a series variable capacitor. Let’s have a closer look at how it works – see Fig.3. Q10 and its asso­ciated components form the reference oscillator. Feedback is provided by the 220pF and 330pF capacitors, while the 60pF variable capacitor (VC1) trims the 10MHz crystal frequency. The nominal 10MHz signal is taken from Q10’s emitter via a 47pF capacitor and amplified by Q11 to provide a 4.5V p-p clock signal for IC2. This IC, a 4040 12-stage binary counter, divides the 10MHz signal by 54. Diodes D11-14 and their associated 4.7kΩ resistor November 1995  31 PARTS LIST 1 plastic instrument case (Jaybox), 250 x 170 x 75mm 2 binding posts – 1 red, 1 black 1 1-2mm thick aluminium sheet, 240mm x 155mm 2 SO239 panel mount sockets 14 No. 4 x 12mm self-tapper screws 10 6mm long brass spacers 1 SPDT toggle switch (S1) 2 TO-220 insulating washers and bushes 1 in-line fuse holder 1 3A fuse 1 knob PLL BOARD 1 PLL PC board 1 10MHz crystal (X1) 3 PC pins 1 25mm brass spacer 1 5mm former and F29 slug 1 plastic tuning gang (160pF + 60pF) Semiconductors 2 74HC4040 12-stage binary counters (IC2,IC4) 1 4046 phase lock loop (IC3) 2 78L05 3-terminal regulators (REG1,REG2) 7 BC548 NPN transistors (Q10-Q16) 4 1N4148 diodes (D11-D14) 1 BB119 varicap diode (VC2) Capacitors 1 100µF 25V electrolytic 1 100µF 16V electrolytic 7 0.1µF monolithic 1 330pF polystyrene 1 220pF polystyrene 2 150pF ceramic form an AND gate. In operation, the diode anodes remain low until the count reaches 54. At this point, the anodes go high, the counter is reset and the process starts again. IC3 is a 4046 PLL but only its phase detector section is used. This is an edge-triggered type, which is important because the signal from pin 2 of IC2 does not have an equal mark/ space ratio. Pin 3 is the other input to the phase comparator, while the output is at pin 32  Silicon Chip 2 100pF ceramic 3 47pF ceramic 1 22pF ceramic Resistors (0.25W, 5%) 3 47kΩ 1 1kΩ 2 22kΩ 2 560Ω 3 10kΩ 2 470Ω 3 4.7kΩ 3 220Ω 1 2.2kΩ 1 150Ω 1 1.5kΩ 1 100Ω MIXER BOARD 1 mixer PC board 1 SPDT 12V relay (RLY1) 5 5mm coil assemblies with F16 slugs 3 2-hole F14 ferrite balun formers 11 PC pins 1 100Ω horizontal trimpot (VR1) Semiconductors 1 NE602 mixer IC (IC1) 2 BC548 NPN transistors (Q1,Q2) 1 BC337 NPN transistor (Q3) 2 BD139 NPN transistors (Q4,Q5) 8 1N4148 diodes (D1,D2,D4,D5,D6-D9) 1 1N4004 diode (D3) 2 6.2V zener diodes (ZD1,ZD2) Capacitors 1 4.7µF 63V electrolytic 13 0.1 monolithic 4 470pF ceramic 1 220pF ceramic 2 47pF ceramic 2 22pF ceramic 1 10pF ceramic Resistors (0.25W, 5%) 1 22kΩ 2 470Ω 1 10kΩ 2 330Ω 13. This output pulses low or high, depending on which way the following VCO stage needs to be directed. Note that the output pulses from IC3 are low-pass filtered to produce the DC control voltage. The filter values were deter­mined during development and ensure quick locking and low phase noise. When the loop is in lock, the steady-state DC voltage across the 100µF capacitor is 2.5V. This DC control voltage is applied to varicap diode VC2 via a 47kΩ resistor. 2 4.7kΩ 2 1kΩ 1 680Ω 14 680Ω 1W 1 560Ω 2 100Ω 1W 2 22Ω 2 15Ω 2 10Ω PA BOARD 1 PA PC board 1 SPDT 12V relay (RLY2) 1 6-hole ferrite bead 2 2-hole F14 ferrite balun formers 3 T-50-2 Amidon toroid core 10 PC pins 1 1kΩ horizontal trimpot (VR2) Semiconductors 1 BD140 PNP transistor (Q6) 1 BC327 PNP transistor (Q7) 2 IRF510 power FETs (Q8,Q9) 1 1N4004 diode (D10) 1 6.2V zener diode (ZD3) Capacitors 1 470µF 25V electrolytic 5 0.1µF monolithic 6 820pF polystyrene Resistors (0.25W, 5%) 1 22kΩ 1 390Ω 2 4.7kΩ 1 100Ω 1 1kΩ 2 10Ω Miscellaneous Medium-duty & light-duty hook-up wire; 0.7mm, 0.4mm and 0.2mm enamelled copper wire (ECW) for winding coils & transformers; tinplate for metal shields; 2mm screws and nuts; 3mm screws and nuts; heatsink compound; min­iature 50-ohm coax; coax braid (for winding T9) Q12 is the 23.705MHz VCO and its frequency of operation is determined by L5, VC2 and several associated capacitors. The output of the VCO is fed to emitter follower Q13 and then goes in two directions: (1) to the output buffer (Q14 & Q15) which sup­plies around 15mW to the mixers; and (2) via a 47pF capacitor to Q16. Q16 amplifies the VCO signal to around 4V p-p to drive the clock input of IC4. This IC divides the VCO frequency by 128. The output appears it can develop the output power required. In summary, the PLL frequency generator circuit effectively multiplies the 10MHz crystal oscillator frequency by the ratio of the two dividers – ie, 128/54 or 2.37037 – to obtain the output frequency of 23.705MHz. There are two points to note about this. First, to obtain the required 10kHz shift in the VCO frequency, we only need to move the oscillator frequency by 4.2kHz. Second, any drift in the reference oscillator will be multiplied by 2.37037 in the VCO. That is Fig.4: the parts layout for the mixer board (groundplane not shown for clarity). The 12 why polystyrene capacitors 680Ω resistors are mounted vertically on the board and need about 5mm of lead left are speci­fied in the 10MHz above the ground­plane so that they can be soldered to the top and the bottom. The tops oscillator circuit. of these resistors are then soldered to a small piece of blank PC board and a lead run Mixer board: Let’s now from this board back to the main mixer board – see photo. take a look at the mixer board circuitry. In the reat pin 4 and is applied to the second +5V to the logic circuits, while REG2 ceive mode, the signals from the antenphase detector input of IC3. Note is “jacked up” to 8.5V to power the na are first passed via the NC (normally that IC2 and IC4 must be high-speed VCO and it’s Q13 buffer. closed) contacts of RLY2 to a band­pass CMOS (HC) types because of the clock The output buffer stage (Q14 & Q15) filter stage based on T3 and T2. These frequencies involved. REG1 provides is fed directly from +13.8V so that reject strong out-of-band signals and Fig.5: the parts layout for the PLL board (groundplane not shown). Be sure to solder component leads to the groundplane where the copper comes right up to the edge of the hole. Fig.6: the parts layout for the power amplifier board (groundplane not shown). Make sure that the two power FETs (Q8 & Q9) are correctly oriented. November 1995  33 Fig.7: here are the winding details for the various transformers and coils. Further details on the winding procedures are given in the text. are tuned to provide a flat passband across the 80-metre band. The secondary winding of T2 is connected to the balanced input pins of the receive mixer. This stage is based on IC1, an NE602 mixer IC. A 10pF capacitor limits the VCO signal to around 500mV p-p at the external oscillator input (pin 6). The output of the mixer appears at pins 4 & 5 and is tuned to 27MHz by T1 and its parallel 22pF capacitor. The secondary winding of T1 then couples this signal via a 220pF capacitor and the NC contacts of RLY1 to the CB radio socket. Diodes D5 and This close-up view shows what’s inside the shielded section on the mixer PC board. The 12 680Ω attenuator resistors are at the far left, while relay RLY1 is at the centre. Note that this shielded area is normally fitted with a metal lid. 34  Silicon Chip D6 are included to protect IC1 from high-level RF as the relay changes from receive to transmit. Let’s now consider what happens in the transmit mode. During a transmission, about 12W PEP is present at the CB socket and a small portion of this is passed to the RF detector (D1 & D2) via a 10pF capacitor. This RF detector in turn charges the 0.1µF and 4.7µF capacitors, thereby turning Q1 on and Q2 off. As a result, Q2’s collector voltage, which is normally at about 2V, goes high. When Q2’s collector reaches about 7V, ZD1 conducts and provides base current for Q3 which turns on and energises the two relays (RLY1 & RLY2). D3 is there to protect Q3 from any voltage spikes that may be generated by the relay coils. When there is no RF, the 4.7µF capacitor discharges via the 22kΩ resistor and the base of Q1. This produces a delay in the relay releasing and eliminates relay chatter in between words. If the delay needs to be increased, it’s simply a matter of increasing the 22kΩ resistor. Conversely, the 22kΩ resistor should be decreased if the delay proves to be too long. Switch S1 is the Rx/Tx switch. In the Rx/Auto position, the circuit automatically switches to transmit mode in the manner described above. Conversely, in the Tx position, the circuit remains in transmit mode at all times and this can be used to prevent the relays from switching if there are long pauses between sentences or words. When RLY1 energises (ie, its normally open contacts close), the signal from the CB is applied to a resistive Pi attenuator. This dissipates the bulk of the power in the 12 680Ω 1W resistors wired in parallel. The two other arms of the attenuator are made up of two parallel 680Ω resistors and a 100Ω resistor in parallel with a 100Ω trimpot (VR1). This trimpot is used as the drive control and varies the power delivered to the transmit mixer. Note that a 100Ω 1W resistor is also connected across the relay contacts. While this may seem odd, it is included for a very specific reason. It was found during development that some CBs produced a spurious signal if the relay de-energised while the push-to-talk (PTT) button was held down (ie, if there was no speech input). This caused the RF detector to energise the relay again and if the This view shows how the three PC boards are arranged inside the case. The power amplifier board is at top right, the PLL board at bottom right and the mixer board at left. Note that the lid has been removed from the shield at top left on the mixer board, so that the attenuator components can be seen PTT was not released, the relay would chatter. The 100Ω resistor across the relay contacts eliminates this problem by maintaining a resistive load for the CB. On the downside, there is some attenuation of the received signal but this is of little consequence. The transmit mixer is a balanced ring type made up of transformers T4 and T5 and diodes D6-D9. It was chosen because of its strong signal performance and the fact that we do not re­quire gain at this point. The PLL signal at 23.705MHz is injected into the centre tap of T5 via a 0.1µF capacitor, where it is mixed with the 27MHz drive frequency. The resulting 3.5MHz difference frequency is then fed to a double-tuned filter circuit based on T5 and T6, which is similar to the receive filter (T2 and T3). The filtered low-level 3.5MHz signal is then amplified by two identical broad­ band amplifiers based on Q4 and Q5. These two stages have consid­erable negative feedback to ensure stable and predictable perfor­ mance. They deliver around 100mW to the final amplifier stage. Power amplifier board: The remainder of the circuitry is accommo­dated on the power amplifier board. Transistors Q6 & Q7 provide the transmit/ receive switching. When the TX-bar line from Q3 is high (ie, Q3 is off), Q6 is turned off and so Q7 turns on. Q7 then supplies power to the receive mixer (IC1) on the mixer board. Conversely, when the TX-bar line goes low, transistor Q6 turns on and Q7 turns off. Q6 now supplies power to the transmit driver stages (Q4 & Q5) and to bias trimpot VR2. Zener diode ZD3 is includ­ed to ensure that the bias voltage does not vary during transmit. The output devices consist of power FETs Q8 and Q9, which are connected in parallel. Their gates are DC biased to around 3.8V by VR2 and this results in a typical quiescent current of 200mA per device. A 10Ω resistor is placed in each gate lead to prevent instability. Immediately following the output pair, transformer T9 cou­ples the signal to a low-pass filter consisting of L2, L3, L4 and six 820pF capacitors. When viewed on a spectrum analyser, all harmonics and spurious components were at least 55dB below the wanted signal. Relay RLY2 switches the antenna between the re­ c eive mixer (during receive mode) and the output low pass filter (during transmit mode). Power for the circuit is derived directly from a suitable 13.8V supply. A 3A fuse is included in the supply lead as a precaution against short circuits. Construction This design is built on three double-sided PC boards. On each of these, the top side carries a continuous copper ground­plane except for clearances around most of the component holes. However, some component leads must be soldered directly to the ground­ plane. These leads will be obvious since the groundplane copper will come right up to the edge of the holes. The exceptions here are the electrocontinued on page 39 November 1995  35 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au The rear of the transverter carries the antenna socket, two power supply binding posts and the input socket (which connects to the CB radio). Note that the three boards are mounted on a metal baseplate. lytic capacitors which get their earth connections via the leads of adjacent components, which are themselves sol­ dered on the top and bottom of the board. Fig.4 shows the parts layout on the mixer board. Install the resistors and PC pins first. The 12 680Ω resistors that make up the dummy load are soldered vertically and need about 5mm of lead left above the ground­plane so that they can be soldered to the top and the bottom. A small piece of scrap PC board is cut out and drilled to fit over the top of the resistors – see photo. The leads are soldered to this piece and a wire is soldered from it to the track under the board. The other 1W resistors are also mounted vertically on the board, as shown on Fig.4. The capacitors can be soldered in next. Make sure that their leads are kept short and be careful not to short any leads to the groundplane as they pass through the holes. Now solder in the relay, followed by the coils and transformers. Fig.7 shows the coil winding details. The tuned transformers are made up of a 6-pin base and former, a metal can and a ferrite slug. Transformers T1, T2, T3 and T6 each consist of two windings soldered to the relevant pins. The larger winding is wound first, with the second winding wound over it towards the bottom of the former. T7 and T8 are bifilar wound on F14 ferrite balun formers. Two wires, each 400mm long, are twisted together until there are about five twists per centimetre. The combined wires are then wound six times through the centre of the balun former – ie, up one hole and down the other. The ends all appear at the same end of the former. Scrape the enamel off the ends of the wires and identify the windings with a continuity tester. The start of one winding and the end of the other winding forms the centre tap. Transformer T4 is similar except that it is trifilar wound (ie, it uses three twisted wires). Two of the wind­ ings are con­ nected as before, while the third winding becomes the primary. Tuned transformer T5 is a hybrid combination of a standard sec­ ondary winding with a bifilar primary winding wound around the top of the secondary. Fig.3 indicates the phasing of the windings with black dots. In each case, this phasing must be correct, otherwise the circuits will perform poorly or not at all. The tuned winding cans are soldered directly to the ground­ plane, while the balun formers mount vertically with the winding ends facing the PC board. When this is complete, install the semiconductors, making sure that they are correctly oriented. Note that the diodes in the transmit mixer (D6-D9) should be a matched set. This involves measuring the forward November 1995  39 YOU CAN AFFORD AN INTERNATIONAL SATELLITE TV SYSTEM SATELLITE ENTHUSIASTS STARTER KIT YOUR OWN INTERNATIONAL SYSTEM FROM ONLY: FREE RECEPTION FROM Asiasat II, Gorizont, Palapa, Panamsat, Intelsat HERE'S WHAT YOU GET: ● ● ● ● ● ● 400 channel dual input receiver preprogrammed for all viewable satellites 1.8m solid ground mount dish 20°K LNBF 25m coaxial cable easy set up instructions regular customer newsletters BEWARE OF IMITATORS Direct Importer: AV-COMM PTY. LTD. PO BOX 225, Balgowlah NSW 2093 Tel: (02) 9949 7417 / 9948 2667 Fax: (02) 9949 7095 VISIT OUR INTERNET SITE http://www.avcomm.com.au YES GARRY, please send me more information on international band satellite systems. Name: __________________________________ Address: ________________________________ ____________________P'code: __________ Phone: (_______) ________________________ ACN 002 174 478 40  Silicon Chip resistance of a batch of 1N4148 diodes with a multimeter. Choose the four that have the closest readings. As can be seen in the photographs, the dummy load area has a 30mm high metal screen installed around it. This is necessary to ensure that the 27MHz signals do not get radiated. A cover needs to be soldered on top, however this should be left until after the board has been mounted in the case and testing has been completed. The screen can be made from copper, brass shim or tinplate (as used in the prototype). It measures 35 x 70mm and is soldered to the groundplane. Before it is mounted, holes need to be drilled to match the SO239 socket. This socket needs to be offset to allow the centre pin to pass by the side of the relay. A wire is then soldered from the centre pin to the PC board at the rear of the relay. PLL board The PLL board can be assembled next – see Fig.5. Begin by installing the resistors and PC pins. This done, install the capacitors, diodes, transistors, ICs and the crystal. The VCO coil (L5) is wound on a former without a base or can. A hole needs to be enlarged carefully in the PC board so that the former is a tight fit. A drop of Super Glue® will ensure that it stays there. Wind the coil tightly onto the former and coat it with silicone adhesive or similar to ensure that the winding does not move, to avoid microphonics. A 30mm high screen is soldered around this PC board about 1-2mm in from the edge. In addition, a separate 30mm high L-shaped piece (48 x 25mm) is soldered around the VCO section. A top cover is not required for this board. Before the outer screen is soldered on, it is necessary to drill mounting holes for the variable capacitor (VC1). This variable capacitor mounts with its side resting on the board and its leads pointing towards the crystal. Once the holes have been drilled, install the shield, then mount VC1 in position. Two wires can now be soldered between VC1’s leads and the board – one from the top lead to the crystal and the other from the middle to the groundplance. A shaft extension needs to be manufactured for VC1. The technique finally adopted is to carefully solder a 25mm-long brass spacer at 90° to the centre of a piece of tinplate measuring 20 x 35mm. Two holes are then drilled in the tinplate (one on either side of the spacer) and the flat plastic knob that comes with VC1. Finally, the tinplate piece, with the shaft extension attached, is fastened to the plastic knob using 2mm screws and nuts. PA board The PA board is the easiest of the three to construct – see Fig.6. Start as before with the resistors and PC pins, then in­stall the capacitors. The 820pF polystyrene capacitors used in the prototype were single-ended types. If you can only get axial types, you will need to bend one lead down the side of the body so that they mount vertically. Mount the relay next, followed by coils L1-L4 and transformer T9. Fig.7 shows how the coils are made. The output transformer (T9) requires special mention as it is a bit un­usual. It is made by placing two balun formers end-to-end. The primary consists of a piece of good quality coax braid which is first threaded through the holes to form a single turn. A scriber or similar implement is then used to poke a hole in the braid at each of the four exit points. Finally, a secondary winding of three turns of hook-up wire is wound from the other end of the formers, with the turns fed through these holes and passing up and down inside the centre of the braid. Care is required during this procedure to avoid shorts between the windings, because when power is applied the primary is at +13.8V and the secondary is at ground potential. This is the main reason why enamelled copper wire is not used. Teflon coated wire would be preferable, although normal hook-up wire has proven successful. Use the largest size of wire possible. The holes in the board for the primary winding will need to be enlarged to pass the braid. Make sure that none of the braid can touch the ground­plane. Finally, solder in the semiconductors, with the two output FETs (Q8 & Q9) mounted about 5mm above the board. This makes it easier to solder their source leads to the top of the board. That’s all we have space for this month. Next month, we shall complete the wiring and give the test and SC alignment procedures. REMOTE CONTROL BY BOB YOUNG Are R/C transmitters a health hazard? In the light of current concerns over cellular phones and a possible link with brain tumours, is there a health hazard for R/C modellers? Let’s have a good look at the topic and see if there are reasons for concern. I have been holding R/C transmitters close to my body for the past 45 years and I must admit this issue concerns me. On the other hand, R/C transmitters are fairly low in power and so they prob­ably don’t pose much of a hazard – or do they? The radiation we are concerned with is NIR or non-ionising electromagnetic radiation – radiation in the electromagnetic spectrum that does not have sufficient energy to produce ionisa­ tion in matter. This radiation has an energy per photon of less than 12.4eV, wavelengths longer than 100nm and frequencies less than 3000THz. Included in the NIR part of the spectrum are magnetic fields, static electric fields, extremely low frequencies (ELF), radio frequencies (RF) up to and including microwaves, visible infrared (IR), lasers and ultraviolet (UV) – see Fig.1. From Fig.1, it can be seen that the energy per photon is related to frequency. The higher the frequency, the greater the energy in the photons. This is good news for modellers in regard to the relatively low radio frequencies we use but bad news for those who operate models in direct sunlight. Let’s have the bad news first. The key factor in assessing the effects of radiation is the exposure level and this is usual­ly related to time and the power density. The rate at which RF electromagnetic energy is imparted to a biological body is de­fined as the SAR (specific absorption rate) and is expressed in watts per kilogram (W/kg). For optical radiation (UV, visible and IR), two systems of quantities and units are used: the photometric and radiometric systems. The photometric system covers only the visible portion of the EM spectrum whilst the radiometric system is used for all optical radiations. When RF energy is absorbed in a medium, the most obvious effect is heating, so the radiation intensity can be determined calorifically. In SI terminology, the radiant intensity, irra­diance or more commonly “power density” is expressed in watts per square metre. It is also valid to express radiant energy flow in the associated electric (E) and magnetic (H) field strengths. The units are volts per metre (V/m) and amperes per metre (A/m). One further point which is impor- Table 1: Injuries to Humans Exposed to Optical Radiation Radiation Skin Damage Eye Damage UV Erythema, aging, skin cancer, photosensitive reactions Photokeratitis, conjunctivitis, cataract, corneal oedema Visible Photosensitive reactions, burns Retinal injury Near Infrared Burns, heat stress Cataract, retinal injury, corneal injury Far Infrared Burns, heat stress Corneal injury tant to grasp is the dif­ference between the “far field” and “near field” measurements and their effects. In the far field (more than one wavelength from the source), either V/m or A/m can be used to describe the intens­ity of energy flow as there is a constant phase relationship between them (E/H = 120π). The source can be regarded as a point where the inverse square law holds. However, in the near field, at points normally less than one wavelength from the source, there is not a constant phase relationship between E and H and so both the electric and magnet­ic field strengths must be given to properly express the intensi­ty of the field. In the near field, the inverse square law does not hold. Keep in mind here that the near field for ELF can be measured in hundreds or thousands of kilometres so you are almost always in the near field. The near field for R/C transmitters is in the range 7-10 metres. In the case of sunlight, we are very definitely in the far field and the inverse square law applies. Yet from a distance of 148 million kilometres, there is still enough power in the radia­tion to quite literally burn the skin off your body. The biological effects of exposure to all optical radiations are mainly to the skin and eyes and can be divided into three major categories: thermal (including thermo-mechanical), photo­ chem­ ical and direct electric field effects, the last being a special case. Most damage is thermal and photochemical (athermal). The ability of optical radiation to damage the skin and eyes depends on their transmission and the absorption in the critical organ. Figs 2 & 3 give various absorption levels of optical radiations in the skin and eyes. For modellers, this has serious ramifications and for professional flyers such November 1995  41 Fig.1: as can be seen from this diagram, the photon energy of radiation is directly proportional to the wavelength. as myself, very serious consequences. At times, particularly when flying for the military, test flying new radios, practising for contests or on contract work, I would spend 5-6 hours daily, staring up at the sky. I did this for over 20 years. The result is that my face is now a mass of blotches and I need to have skin cancers removed regularly. In my early days, sunscreens were almost unheard of and by the time they were in common use, the damage had been done. The skin specialist I attend recommends applying blockout daily and yet I still find myself reluctant to apply gooey creams for everyday wear. UV damage Table 1 shows the principle injuries to the skin and eyes from the various optical radiations. The wavelength significantly affects the final outcome when considering eye damage. The ef­fects of UV are generally photochemical on the lens and cornea. Because of the imaging characteristic of the cornea, UV-A is the greatest hazard. UV-B and UV-C are absorbed in the cornea and conjunctiva and at sufficiently high doses will cause kerato­ conjunctivitis. UV causes damage to the epithelial cells which would normally be repaired in a day or so. If the dose is high enough however, scaring, giving a milky appearance, may result. Sometimes, it can induce an invasion of blood cells in the cornea or cause long term damage. Chronic exposure to sunlight, especially the UV-B compon­ent, accelerates the skin aging process and increases the risk of skin cancer. Exact quantitative and dose-response relationships have not been established although fair-skinned individuals, especially of Celtic origin, are much more prone to develop skin cancer. Work populations exposed to artificial sources of UV-B have not been studied in detail to ascertain the risk 42  Silicon Chip of cancer from this source. However, be careful of the UV light boxes used in PC board manufacture. Squamous cell carcinoma is the most common cancer associated with UV-B. There is also a wide range of drugs which increase sen­sitivity to UV. These include sulphurs, diuretics, some antibiot­ics, estrogens and many others. Cosmetic ingredients (in per­ fumes, deodorants and soaps) may react with UV to produce photo-allergenic or photo­toxic effects which can include redness, itching, hives, blistering or uneven pigmentation, so do not use them before going out in the sun. Compared to the foregoing, what is to follow on RF radiation pales into insignificance. Do yourself a favour and buy the best sunglasses you can afford, use blockout daily or at least when out modelling and generally follow the “slip, slop, slap” rou­tine. Finally, there are good aspects of sun­ light. Rickets, a disease long thought to be banished from modern society, has suddenly become a menace once more. This is caused by people avoiding sunlight so much that they are now not producing enough vitamin D to protect them from the disease. RF exposure When a biological organism is exposed to RF or microwave radiation, electric and magnetic fields are induced within it. A perfect dielectric absorbs no energy from the electromagnetic field and the field is propagated through the medium unattenuat­ ed. However, the human body is a lossy dielectric and there is, as a result, a motion of free ions (conduction loss) and molecular rotation (dielectric loss). The nett result is an energy transfer from the field to the human body. This absorbed energy will be the source of work and a temperature rise will occur. This work may be electrical, mechanical or chemical. It is difficult to measure the exact absorption in a com­plex shape such as a human body or animal and the distribution of the energy within the body will vary by several orders of magni­ tude depending on the size of the body, irradiation frequency and orientation. To complicate matters further, the RF spectrum can be divided into four ranges as far as absorption is concerned. These are the sub-resonance range, the resonance range, the hot spot range and surface heating range. By far the greatest influence is frequency. The critical frequencies for humans in the resonance range peak at 70MHz and will vary between 30MHz and 300MHz depending on size and on whether a ground plane is present. Between 400MHz and 3GHz, sig­nificant localised energy absorption occurs, giving rise to hot spots. Depending on frequency, these may vary in size from 1cm in cross section to several centimetres. At frequencies over 2GHz, the effects are mainly confined to surface heating. Testing on animals is difficult because of the differences in size and the heat transfer characteristics of fur bearing animals. Frequency scaling is one approach used, where the fre­quency is increased or reduced to match the size of the animal. Exposure of tissues to RF results in a temperature rise when the rate of energy absorption exceeds the rate of dissipa­tion. Heat dissipation mechanisms include active and passive thermo-regulatory mechanisms. Passive mechanisms include heat radiation, conduction, convection and evap­or­ ative cooling. Active mechanisms include blood circulation and cutaneous vasodilation to shift the internal heat to the skin so that passive mechanisms can dissipate the heat into the environment. A good stiff breeze adds a chill factor which aids cooling. The possibility of local hot spots exists where the rate of absorption is high compared to the vascular heat Fig.2: this diagram shows that UV-B frequencies around 700nm have the deepest penetration into your skin. transfer mechan­ism or where pooling occurs. Among these spots are the lens of the eye, the necrotic centre of tumours, the splan­chnic region and above the spinal cord. Exposure of animals to high levels of radiation has caused various injuries ranging from local lesions and necrosis (death of tissue) to gross thermal stress from hyperthermia. Death from overheating has been induced with power densities of a few hundred to several thousand watts per square metre. Some animals died of hot spots due to non-uniform energy absorption and some of these died showing no signs of distress. I can recall an accident in which a technician left off an inspec­ tion panel from a radar waveguide and sat in front of the opening during a prolonged test. He died as a result of his kidneys overheating. The kidneys have poor heat dissipation due to the fat around them. The cornea and crystalline lens are very susceptible to injury within the range of 1-300GHz; the cornea between 10-300GHz and the lens between 1-10GHz. Exposure within the range of 1.5-2kW/m2 lasting from one hour to 24 hours, or for a few hours per day repeated for a few days per week, can result in cataracts. The formation of retinal lesions is also possible. Behavioural changes One of the most obvious effects are behavioural changes and some small animals have been observed showing signs of decreased endurance and convulsive activity. Both ANSI (1982) and INIRC/IRPA (1984) considered this behavioural sensitivity to be the lower limit of harm from exposure to RF fields and have based their exposure limits on these effects. Studies on the health effects in humans have been inade­quate, for various reasons. The most obvious is that it is not wise to use human guinea pigs. Fig.3: your eyes are very susceptible to optical radiation, particularly ultraviolet. Excessive exposure can lead to the formation of cataracts. Surveys of personnel exposed to RF accidentally have been conducted but since the exposure levels and times are not known accurately, the results are inconclusive. Early studies conducted in Czechoslovakia, Poland and the Soviet Union reported that some subjective complaints such as headaches, irritability, sleep disturbances, weakness, decreased sexual activity (libido) and generally poorly defined feelings of ill health were experienced. However later studies conducted in the USA and Poland with better controls indicated there was no relationship between exposure up to 60W/m2 and the incidence of functional disturbances, morbidity, reproductive performance and the health of children. Power densities required for the formation of cataracts appears to be above 1kW/m2 which agrees with the experimental data for rabbits. Following a detailed study of all factors involved in RF exposure, the International Non-Ionising Radiation Committee of IRPA has published guidelines on limits of exposure to RF fields. The health risk assessment and exposure limits can be found in INIRC/ IRPA (1984). Australian Standard AS 2772.1-1988 was based on this standard. Now for the good news. AS 2772.1 does not concern itself with transmitters below 7W and 1GHz and sets the maximum occupa­tional exposure at 10W/m2 for transmitters in the range 30MHz-300GHz. In addition, the SAR is related to watts per kilogram, so the more kilograms you have, the more watts you can safely absorb. The non-occupational long term exposure rate is set at 0.4W/kg. As most R/C transmitters run around 0.5W into a very inef­ficient antenna and most of us weigh more than 1.25kg there is little likelihood of any real danger. Here again, the truth is that nobody really knows. Keeping in mind Murphy’s Law 743 which states that all things that are fun are bad for you, I am sure somebody will eventually come up with the proof that we should not use R/C transmitters at all. However, be that as it may, probably the most serious health risk from R/C transmitters is getting poked in the eye SC by your mate’s antenna! November 1995  43 Build A LowCost PIR Movement Detector This low-cost circuit is based on a universal PIR chip. It is easy to build, can be adjusted for sensitivity and output duration, and is suitable for use in alarm and surveillance applications. P By CONRAD MARDER ASSIVE INFRARED (PIR) de- tectors are one of the most common sensors used in security systems. Typically, they are mounted high on a wall and are used to turn on lights or to activate burglar alarm systems. The circuit described here uses a sensitive dual-element PIR sensor and has a range of about 12 metres. This range can be adjusted by means of a single sensitivity control. In addition, there is a day/night sensor control and this can be set to dis­able the output during daylight hours; eg, so that security lights only turn on at night. Alternatively, the day/night sensor can be effectively disabled simply by setting the control to one extreme (ie, anti­clockwise). The PIR sensor will 44  Silicon Chip then operate at all times, re­gardless of the ambient light conditions. Another very worthwhile feature of the unit is that the output “on” time can be adjusted from 3 to 30 seconds. It also features very low quiescent current (less than 500µA), making it suitable for long-term battery operation. By contrast, most commercial units have much higher quiescent currents and so can only be battery operated for short periods of time. Apart from its obvious security applications, this PIR detector is ideal for controlling garden and path lights. Typi­cally, these path lights would be low voltage types powered from a battery and a solar panel – see Fig.3. By adding the PIR detec­tor and setting the day/night sensor, the lights could be made to operate only during the hours of darkness, when ever movement was detected. How it works Refer now to Fig.1 for the full circuit details. As shown, the circuit is based on IC1, an MPCC device which is specially designed for use in PIR detectors. This device contains the necessary gain blocks and filters, plus an internal oscillator and counter stages for the output timing function. Its pin func­tions are shown in Table 1. The other important component is the PIR sensor (Murata IRA-E100S1). This is a dual element type that combines a window filter, two heat-sensitive crystals and a FET buffer stage in one 3-pin package. It is combined with an external plastic Fresnel lens, which focuses the IR energy onto the PIR sensor and provides additional filtering. Note that the external Fresnel lens is white-coloured and is almost opaque to visible light. However, it is transparent to the wavelengths associated with body heat in the range 8-10µm. The FET inside the PIR sensor is Fig.1: the circuit is based on IC1, an MPCC device which is specially designed for use in PIR detectors. It operates in conjunction with a dual-element PIR sensor. VR1 sets the sensitivity, VR2 sets the output “on” time, and VR3 sets the sensitivity of the daylight sensor. wired as a source-follow­er, with its source connected to pin 2. This output is, in turn, coupled to pin 8 of IC1 via a voltage divider consisting of R12 and R4. This voltage divider is necessary because the PIR sensor used is far more sensitive than other types that can be used with the MPCC IC. In addition, the sensitivity of the unit is adjusted using VR1. This pot samples the drain reference voltage on pin 7 and applies an offset voltage to pin 2. Each time movement is detected and a signal is applied to pin 8, the output at pin 16 goes high. This then turns on power Mosfet Q4 and so the output goes low for a preset “on” time. VR2, R7 and C10 allow this time to be set anywhere from 3-30 seconds. If you require longer times, just increase the size of C10. Pin 11 of IC1 is the “daylight adjust” pin and is connected to the wiper of VR3. This pot is wired in series with LDR1 and R8 and controls the gain of an internal daylight sense amplifier and hence the sensitivity of the daylight detector. It is adjusted so that the output (ie, the drain of Q4) toggles only when the ambient light falls below a certain level. During daylight hours, the resistance of LDR1 (a light dependent resistor) is low and pin 11 of IC1 is pulled towards Vcc (ie, towards the +5V rail). As night falls, however, the resistance of LDR1 rises (ultimately to several megohms) and so the bias on pin 11 progressively shifts towards ground. When it reaches a critical level, the output can toggle in the normal manner. Pin 17 of IC1 is used to flash a LED indicator (LED 1) each time movement is detected. This LED operates while ever movement occurs, even when the output has been disabled by the day/ night sensor. As an optional extra, the circuit also includes an output toggle facility. This is based on the circuitry connected to pin 15. Normally, the toggle input is Main Features • • • • • • • Optional day/night setting with variable sensitivity. • Optional toggle output (output can change from on to off or from off to on). • Compact size (83 x 54 x 28mm). Output “on” time adjustable from 3-30 seconds. Very low quiescent current: < 500µA. Activated operating current < 5mA. Sensitivity adjustment for PIR sensor. LED output to show sensor has been activated. Open drain Mosfet output able to switch 12V at currents up to several amps. November 1995  45 This is what the top of the board looks like when all the parts have been installed. Note particularly the orientation of Q4 (ie, metal face towards D1). open circuit, Q1 is off and IC1 operates in the normal manner. However, if the toggle input is pulled to +5V, Q1 turns on and pin 15 goes low. This, in turn toggles the output of Q4; ie, if the output was high it switches low and remains there until the toggle input is released, and vice versa. Fig.2: install the parts as shown here, noting that the PIR, LDR and LED 1 are installed on the track side of the PC board (see photo). Note also that pin 2 of the PIR sensor is connected to the top of the adjacent 22kΩ resistor. 46  Silicon Chip The PIR sensor, the LDR and LED 1 are mounted on the track side of the PC board. The plastic Fresnel lens is simply clipped into position. Power for the circuit is derived from a 9-20V DC supply (eg, from a 9V battery or from an alarm control panel). This supply rail is filtered using C1 and regulated to about 5.9V using diode D1 and transistors Q1, Q2 & Q3. A discrete regulator was chosen in preference to a 78L05 because of its very low current consumption (a 78L05 would typically draw around 2mA). Diode D1 sets the voltage on Q1’s emitter to about 0.6V, which in turn means that its base voltage is about 1.2V. The output voltage of the regulator is set by R2 and R3, which form a voltage divider on the base of Q3. Basically, Q3 functions as an error amplifier, while Q2 & Q1 are wired as a Darlington pair. If the output voltage rises above 5.9V, Q3 turns on harder and starves the base of Q2 to throttle the voltage back. Conversely, if the output voltage drops below 5.9V, Q3’s collector voltage rises and Q2 & Q1 are driven harder to bring the output back up again. Construction Construction is straightforward, with all the parts in­stalled on a small PC board (45 x 68mm) – see Fig.2. This board carries a screen-printed overlay pattern to simply the job of assembly. Begin construction by installing the two wire links (one near VR1 and the other near the LDR). This done, install the resistors and capacitors, followed by the three trimpots. VR1 & VR3 are both miniature horizontal mount types, while VR2 is a larger vertical mount type. It is also a good idea to check the resistor values using a digital multimeter, as some of the colours can be difficult to decipher. The capacitor codes are shown in the parts list. Make sure that the five electrolytic capacitors are correctly oriented. IC1, D1 and the transistors (Q1-Q5) can be installed next. The prototype used an IC socket but this is not really necessary and the IC can be soldered directly to the board. Make sure that it’s oriented correctly, though – pin 1 is adjacent to a notch in one end of the IC body and this goes towards Q5. Note that transistor Q4 (the P222 Mosfet) must be installed with its metal face towards diode D1. The remaining transistors are oriented as indicated on the layout diagram. The PIR sensor, the LDR and the LED are all installed on the copper side of PARTS LIST Fig.3: the PIR detector could be married with a solar panel and a 12V battery and used to control low-voltage globes for garden and path lights. By suitably setting the day/night sensor, the lights could be made to operate only during the hours of darkness, when ever movement was detected. Fig.4: this diagram shows how to wire the output to switch a relay. Note that the relay should be powered from the 9-15V source, not from the regulated output at the emitter of Q1. Table 1: Pin Functions for IC1 Pin No. Name Description 1 Vcc Supply voltage (5V nominal) 2 Sens. adjust PIR motion sensitivity input 3 Offset filter PIR motion offset filter 4 Anti-alias PIR anti-alias filter 5 DC cap PIR gain stabilisation filter 6 Vreg Voltage regulator output 7 Pyro (D) Pyro drain voltage reference 8 Pyro (S) Pyro source input signal 9 Gnd (A) Analog circuitry ground 10 Gnd (D) Digital circuitry ground 11 Daylight adjust Daylight adjustment & CdS input 12 Daylight sense Silicon photodiode input 13 Gain select PIR gain select input 14 On/Auto/Off Mode select tri-state input 15 Toggle Mode select toggle input 16 Out Load on/off output 17 LED PIR motion indicator output 18 C Off timer oscillator input 19 R Off timer oscillator output 20 Fref Frequency reference oscillator the board – see photo. Install the LDR and the LED first and note that the LDR can go in either way around. It is mounted slightly proud of the board so that its leads can be soldered (note: you can leave the LDR out if the daylight detec­tion feature is not required). The LED is installed with its top about 10mm above the board. It must be oriented so that its anode lead goes 1 PC board, 45 x 68mm (Oatley Electronics) 1 plastic zippy case, 83 x 54 x 28mm 1 plastic Fresnel lens 1 light dependant resistor (LDR1) 2 500kΩ horizontal mount trimpots (VR1,VR3) 1 1MΩ vertical mount trimpot (VR2) Semiconductors 1 Murata IRA-E100S1 PIR sensor 1 MPCC IC (IC1) 4 BC548 NPN transistors (Q1Q3,Q5) 1 P222 N-channel Mosfet (Q4) 1 1N4148 silicon diode (D1) 1 red LED (LED1) Capacitors 2 100µF 16VW PC electrolytic 3 10µF 16VW PC electrolytic 1 0.47µF monolithic – code 474 3 0.1µF monolithic – code 104 1 .0047µF polyester – code 472 1 220pF ceramic – code 221 Resistors (0.25W, 5%) 1 390kΩ 1 22kΩ 1 150kΩ 4 10kΩ 1 100kΩ 1 3.9kΩ 1 56kΩ 1 22Ω 1 47kΩ Where to buy parts A kit of parts for the PIR Movement Detector is available for $20 plus $3.50 p&p. The case is an extra $3.00. Contact Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985 or fax (02) 570 7910. Note: copyright of the PC board asso­ ciated with this design is retained by Oatley Electronics. to pin 17 of IC1 (the anode lead is the longer of the two – see Fig.1). The PIR sensor is next. Do not touch its IR window, as this will seriously degrade its sensitivity. This device is positioned flat against the PC board and its pin 1 and pin 3 leads then looped back through adjacent holes to the copper side of the board for soldering. The pin 2 lead is soldered to the top of the adjacent 22kΩ resistor. November 1995  47 The plastic Fresnel lens covers both the PIR sensor and the LDR. If necessary, it can be secured to the PC board by applying epoxy resin to its clips. If a fingerprint does find its way onto the IR window, remove it using pure alcohol and a soft lint-free cloth. Finally, the board assembly is completed by clipping the plastic Fresnel lens into its four mounting holes. This lens covers both the PIR sensor and the LDR and can be secured using epoxy resin applied to its mounting clips if necessary. The assembly should now be carefully checked for wiring errors. Testing To test the unit, first set VR1 to mid-posi­tion and set VR2 & VR3 fully anticlockwise. This done, apply power and check that the LED flashes briefly when a hand is waved in front of the sensor. If it doesn’t, switch off immediately and locate the problem before proceeding. The LED may be oriented incorrectly, for example. Assuming that all is well, temporarily connect a LED in series with a 1kΩ resistor between the output (O/P) and the 5.9V rail. Now wave a hand in front of the sensor and check that this LED lights for about three seconds. VR2 can then be adjusted to set the required output “on” time (3-30s). 48  Silicon Chip The completed PC boards fits neatly into a small plastic case with the Fresnel lens protrud­ing through a 24mmdiameter clearance hole. The output toggle function can now be checked by connecting the I/P terminal on the PC board to the +5.9V rail. The output indicator LED that was connected in the previous step should immediately change state; ie, if it was on it should turn off, and if was off it should turn on. Final assembly The prototype was housed in a standard plastic zippy case measuring 83 x 54 x 28mm (eg, DSE Cat. H-2855). As shown in the photos, the board sits on the base with the Fresnel lens protrud­ ing through a 24mmdiameter clearance hole. A second, smaller hole located immediately beneath the lens is used for LED 1 (the movement indicator). The power supply, output and output toggle leads exit through a hole drilled in the lid. Alternatively, they can be connected to a screw terminal strip. VR1 (sensitivity) and VR3 (day/ night adjust) can be set after the unit has been finally installed in position. As a general rule, advance the sensitivity control (VR1) only as far as necessary for reliable triggering. VR3 can be set so that the output operates only in low-light conditions. The best way to do this is to initially set VR3 fully clockwise, then slowly turn it anticlockwise (while waving a hand in front of the sensor) until the output indicator LED (not LED 1) just comes on in daylight conditions. VR3 can then be backed off slightly, so that the output is disabled in daylight (ie, the output indicator LED stays off when movement is detected). There’s just one wrinkle here – each time the output indi­cator LED comes on and VR3 is adjusted, there must be a no-trig­ger period of at least eight seconds before the circuit can be re-tested. That’s because the output at pin 16 of IC1 will continue to toggle if fur­ther movement is detected within this period, regardless of the setting of VR3. If you later find that the lights come on too early or too late, then it’s simply a matter of tweaking VR3. Rotate it clockwise to make the lights come on later, or anti­clockwise to make them come on earlier. Alternatively, if you want the unit to operate at all times (eg, if it is to be used as an alarm sensor), simply set SC VR3 fully anticlockwise. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au PRODUCT SHOWCASE Low-cost inkjet plotters from HP Hewlett-Packard has introduced two large-format inkjet plotters, the DesignJet 250C colour model and the DesignJet 230 monochrome unit. The 250C plotter is HP’s first large-format colour device designed specifically for the low end of the computer-aided design (CAD) market, while the 230 plotter replaces the model 220. The 250C offers colour output in three different print modes. The plotter’s four ink cartridges, cyan, yellow, magenta and black (CYMK), let users create a full range of colours with 300 dots-per-inch (dpi) resolution. It takes only six minutes for the HP 250C to print a typical A1 size colour CAD drawing in normal mode. The 230 plotter also features three print modes. It uses the same black print cartridge as the model 250C and both models produce black output in 600-dpi resolution. A black-only A1 size plot takes only five minutes on either plotter in normal mode (600 dpi). Commonly available media, includ- ing plain paper, vellum, translucent and polyester film, may be used for black-only plot­ting. For colour plotting, HP’s special inkjet paper must be used; it is readily available through drafting-supply stores and outlets where plotters are sold. The plotters come with Centronics/ Bi-tronics and RS-232 serial ports and may be connected to a LAN through an HP JetDi­rect EX external connection. The plotters come with HP-developed drivers for AutoCAD Release 11, 12 Power supply for train controller For those who need a robust power supply for the train controller published in the September & October 1995 issues, this unit from CIL Distributors should fill the bill. Based on a 120VA toroidal power transformer, it has two 15V AC outputs, each with a capacity of 4A. The unit is double insulated and housed in a high impact plastic case with soft rubber feet. It is fitted with a 2-metre power cord and has and 13, and Microsoft Windows 3.1. The plotters can switch automatically between HP-GL, HP-GL/2 and HP RTL modes. The HP DesignJet 250C plotter is $5440 for A1 size and $7408 for A0. The DesignJet 230 model is $4341 for A1 size and $5903 for A0 size. All prices include sales tax. Readers may obtain further information on HP products and services, Australia-wide, by calling 131 347 (toll free, no STD area-code required). slow-blow fuse protection. Fully approved to AS31081990, the new supply is priced at $125.00. For further information, contact CIL Distributors Pty Ltd, PO Box 236, Castle Hill, NSW 2154. Phone (02) 634 3475. The supply is also available from Anton’s Trains, Cnr Prince & Mary Sts, North Parra­matta, NSW 2151. Phone (02) 683 3858. November 1995  57 Tektronix TVS600 VXI waveform analysers The new TVS600 series VXI waveform analysers from Tektronix offer the fastest available waveform acquisition performance in the VXI format. At five Gigasamples/second on four channels simultaneously, with a 1GHz bandwidth and eight bits of vertical resolution, the TVS600 series sets new performance benchmarks in VXIbased waveform analysis for advanced research and characteri­sation – and is fully VXI plug and play compliant. The TVS621 and TVS641 analysers are C-size VXI cards with two or four input channels respectively. Both modules incorporate digital real-time signal acquisition, derived from the TDS600 benchtop DSO, and have 250MHz bandwidth, simultaneous 1GS/s sample rates and 15K record length. The instruments’ trigger system discriminates on both edge transitions and pulse width, and responds to triggers on any of the 10 available back­plane trigger lines. The TVS625 and TVS645 are C-size VXI cards and feature a 5GS/s sample rate, 1 GHz bandwidth and 15K record length. Employ­ ing a digital real-time signal acquisition engine similar to that of the TVS621 and TVS641, these VXI modules can capture signals on all channels simultaneously with 200ps/point time resolution. For further information, contact Tektronix Australia Pty Ltd, 80 Waterloo Rd, North Ryde, NSW 2113. Phone (02) 888 7066. KITS-R-US PO Box 314 Blackwood SA 5051 Ph 018 806794 TRANSMITTER KITS $49: a simple to build 2.5 watt free running CD level input, FM band runs from 12-24VDC. •• FMTX1 FMTX2B $49: the best transmitter on the market, FM-Band XTAL locked on 100MHz. CD level input 3 stage design, very stable up to 30mW RF output. $49: a universal digital stereo encoder for use on either of our transmitters. XTAL locked. •• FMTX2A FMTX5 $99: both FMTX2A & FMTX2B on one PCB. FMTX10 $599: a complete FMTX5 built and tested, enclosed in a quality case with plugpack, DIN input •connector for audio and a 1/2mtr internal antenna, also available in 1U rack mount with balanced cannon input sockets, dual VU meter and BNC RF $1299. Ideal for cable FM or broadcast transmission over distances of up to 300 mtrs, i.e. drive-in theatres, sports arenas, football grounds up to 50mW RF out. FMTX10B $2599: same as rack mount version but also includes dual SCA coder with 67 & 92KHz subcarriers. • AUDIO Audio Power Amp: this has been the most popular kit of all time with some 24,000 PCBs being •soldDIGI-125 since 1987. Easy to build, small in size, high power, clever design, uses KISS principle. Manufacturing rights available with full technical support and PCB CAD artwork available to companies for a small royalty. 200 Watt Kit $29, PCB only $4.95. AEM 35 Watt Single Chip Audio Power Amp $19.95: this is an ideal amp for the beginner to construct; uses an LM1875 chip and a few parts on a 1 inch square PCB. Low Distortion Balanced Line Audio Oscillator Kit $69: designed to pump out line up tone around studio complexes at 400Hz or any other audio frequency you wish to us. Maximum output +21dBm. MONO Audio DA Amp Kit, 15 splits: $69. Universal BALUN Balanced Line Converter Kit $69: converts what you have to what you want, unbalanced to balanced or vice versa. Adjustable gain. Stereo. • • •• COMPUTERS I/O Card for PCs Kit $169: originally published in Silicon Chip, this is a real low cost way to interface •to Max the outside world from your PC, 7 relays, 8 TTL inputs, ADC & DAC, stepper motor drive/open collector 1 amp outputs. Sample software in basic supplied on disk. PC 8255 24 Line I/O Card Kit $69, PCB $39: described in ETI, this board is easy to construct with •onlyIBM3 chips and a double sided plated through hole PCB. Any of the 24 lines can be used as an input or output. Good value. 19" Rack Mount PC Case: $999. •• Professional All-In-One 486SLC-33 CPU Board $799: includes dual serial, games, printer floppy & IDE hard disk drive interface, up to 4mb RAM 1/2 size card. PC104 486SLC CPU Board with 2Mb RAM included: 2 serial, printer, floppy & IDE hard disk $999; VGA •PC104 card $399. KIT WARRANTY – CHECK THIS OUT!!! If your kit does not work, provided good workmanship has been applied in assembly and all original parts have been correctly assembled, we will repair your kit FREE if returned within 14 days of purchase. Your only cost is postage both ways. Now, that’s a WARRANTY! KITS-R-US sell the entire range of designs by Graham Dicker. The designer has not extended his agreement with the previous distributor, PC Computers, in Adelaide. All products can be purchased with Visa/Bankcard by phone and shipped overnight via Australia EXPRESS POST for $6.80 per order. You can speak to the designer Mon-Fri direct from 6-7pm or place orders 24 hours a day on: PH 018 80 6794; FAX 08 270 3175. 58  Silicon Chip Lightweight scope from Yokogawa Yokogawa’s new replacement for their popular DL1200A and DL1300A Digital Oscilloscopes is smaller in size yet more power­ful. The DL1540 weights just 5kg and has a footprint smaller than an A4 sheet. The DL1540 is a long record length, 150MHz, 4-channel digi­ tal oscilloscope with a maximum sample rate of 200MS/s. It has a high speed update rate irrespective of the number of channels in use. It also acts as a recorder capable of capturing very fast RF current immunity tester The investigation and assurance of electromagnetic compa­tibility of equipment under the effects of radiated HF-fields, as specified by standards such as IEC 8013, involves the use of highly complex test facilities that are mostly to be found only in specialised test laboratories. Such tests can prove to be expensive if items have to be tested many times. The palm sized, battery-operated NSG 420 RF Current Immuni­ty Tester can help to minimise such costs. By using a substitu­tion method, involving the injection of HF-energy into power feed and interconnecting cables, valuable information regarding the interference immunity of a test object can be obtained, allowing the appropriate countermeasures to be incorporated at an early stage in the development work. The simplicity of operation and low cost also makes the NSG 420 a valuable tool on the production line to check the consist­ency of the EMC measures incorporated in a product. For further information, contact Westinghouse Industrial Products, 175-189 Normanby Rd, South Melbourne, Vic 3205. Phone (03) 676 8888 or fax (03) 676 8777. SATELLITE SUPPLIES Rod Irving Electronics 1995-96 catalog Rod Irving Electronics has just released its annual catalog for 1995-1996. Its 196 pages include over 10,000 line items available from RIE, ranging from customised computer systems, computer accessories, electronic accessories and components, solar products and hard-to-find products. All 10,000 line items are available from RIE’s outlets in the Melbourne, Northcote, Oakleigh, Box Hill, Vermont, Adelaide and Sydney. The mail order number is 1-800 33 5757. In keeping with the current trend of shopping on the Internet, RIE also now has an e-mail address: rie<at>ozemail.com.au. surge signals. Pulses as small as 20ns can be recorded in real time on an optional built-in printer. In single shot applica­tions, up to 120K word length is available and since the signal is first stored in memory, a fast sampling speed can be used, enabling signals of tens of MHz to be printed out. For slower signals, the DL1540 shows a waveform on its 7-inch CRT similar to a recorder, with a Roll mode allowing information equivalent to two pages (20K word) to be kept. The DL1540 has a built in 3.5-inch floppy drive that is MS-DOS compatible. This allows waveform data, panel settings and display to be saved and later included in a word processor docu­ment. A History Memory function stores the last 100 displays, any one of which may be recalled and magnified quickly and easily with the instrument’s Zoom function. For further information, contact Audio Lab Aussat systems from under $850 SATELLITE RECEIVERS FROM .$280 LNB’s Ku FROM ..............................$229 LNB’s C FROM .................................$330 FEEDHORNS Ku BAND FROM ......$45 FEEDHORNS C.BAND FROM .........$95 DISHES 60m to 3.7m FROM ...........$130 Yokogawa Australia, 25-27 Paul St North, North Ryde, NSW 2113. Phone (02) 805 0699. AUDIO MODULES broadcast quality Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 476-5854 Fx (02) 476-3231 R.S.K. Electronics Pty. Ltd. Complete Audio Lab kit with PCBs, 1% resistors, PTH screened PCBs, IC sockets, boot Eprom, screen printed case, 8K RAM, 8031 processor and all ICs. Includes calibration and Audio Lab V5.1 software 10 VAC 1A plugpack plus socket $18. 2-Metre serial cable $9. $330 inc. tax. Processor test kit $15. Freight $9. Fully assembled & calibrated complete with plugpack (1-year warranty) $450 5 Ludwig Place, Duncraig, Perth WA 6023 Phone (09) 448 3787 LOTS OF OTHER ITEMS FROM COAXIAL CABLE, DECODERS, ANGLE METERS, IN-LINE COAX AMPS, PAY-TV DECODER FOR JAPANESE, NTSC TO PAL TRANSCODERS, E-PAL DECODERS, PLUS MANY MORE For a free catalogue, fill in & mail or fax this coupon. ✍     Please send me a free catalog on your satellite systems. Name:____________________________ Street:____________________________ Suburb:_________________________ P/code________Phone_____________ L&M Satellite Supplies 33-35 Wickham Rd, Moorabin 3189 Ph (03) 9553 1763; Fax (03) 9532 2957 November 1995  59 Dolby Pro Logic Surround Sound Decoder, Mk.2 Set yourself up with movie sound in your living room, using this Dolby* Pro Logic Surround Sound and Effects Unit. It includes a microprocessor for delay control plus power amplifi­ers. Fully approved and tested by Dolby Laboratories Licensing Corporation in the USA, it will provide you with a new standard of listening pleasure. By JOHN CLARKE 60  Silicon Chip Main Features • • • • • • • • • • • • • D OLBY PRO LOGIC Surround Sound provides an extra dimension to the sound of movies in your home and makes them so much more enjoyable. For big movie sound, you don’t have to go to the cinema; you can now have it all at home. Not only will the SILICON CHIP Surround Sound Unit decode Pro Logic sound but it includes an effects facility which adds depth to unencoded sources. These include music from CDs, records and tapes. Once you have listened to music via the effects unit you may find it difficult to go back to standard stereo sound. The delay time between the front channels and rear surround loudspeaker outputs can be adjusted to suit your personal prefer­ence. We first published a basic Pro Logic Surround Sound Decoder in the December 1994 and January 1995 issues of SILICON CHIP. Since then we have had many requests for a deluxe version with power amplifiers and adjustable delay. Here is the result. Housed in a low profile case, it includes three power amplifiers, one for the centre channel and two for the rear surround speakers. Line outputs are provided to drive a standard stereo Genuine Dolby* Pro Logic active surround sound decoding Meets all Dolby specifications Stereo, 3-stereo, surround and effects modes Normal, wideband (full range) or phantom centre channel Noise sequencer to set up balance between channels Trim control for centre and surround channels Master volume control for all channels Subwoofer output Line outputs to left and right channels (to external stereo amplifier) 20W amplifiers for centre, surround left and surround right outputs Effects selection for simulated surround sound Adjustable delay from 15ms to 30ms Presettable power-up delay time amplifier for the left and right front channels. And for those who like lots of bass, there is a subwoofer output which can be connected to a separate power amplifier and subwoofer loudspeaker. On the front panel are the on/off switch, up and down delay and noise sequencer buttons, mode and centre channel selection switches, the centre and surround trim controls plus the main volume, Dolby/Effects switch and effects level controls. At the rear are six RCA sockets for stereo inputs and the left, right and subwoofer outputs. Six binding post terminals are provided for the left and right surround and centre loudspeaker outputs. The 2-digit display on the front panel indicates the selected delay time for the surround channel. This can be varied from 15ms to 30ms in 1ms steps. An initial delay value is set whenever the unit is switched on. This can be preset to any value between 15ms and 30ms by DIP switches inside the unit. Noise sequencer The noise sequencer is used to set the balance between channels. When switched on, the sequencer LED lights and a noise signal is sent to each channel in turn for about two seconds. The LED display shows which channel has the noise signal by displaying L, C, R or S. Thus, the centre and surround channel outputs can be adjusted to match the sound levels from the front left and right channels. The mode control selects stereo, 3-stereo or surround sound. Stereo selection simply passes the signal without any processing. “3-stereo” adds the centre channel, while “Surround” adds the surround output, as you would expect. Note that during noise sequencer operation only the channels selected will be fed with noise signal. The centre switch controls the centre channel mode. In Normal position, frequencies below 100Hz are attenuated so that a wide range loudspeaker is not required. The signal below 100Hz is added to the left and right channels at a -3dB level to restore the bass balance. In Wideband mode, the centre channel receives the full frequency range and a wide range speaker will be required. Final­ly, in Phantom mode, no centre channel speaker is required as the centre channel signal is fed equally to the left and right front speakers. Note that the subwoofer output is only available when Normal or Phantom modes are selected. The Dolby/Effects switch selects between the Pro Logic decoding and the Effects operation. When in effects mode, the centre channel is simply the left plus right signal, while the November 1995  61 Fig.1: the block diagram for the Surround Sound Decoder. Most of the decoding work is done by IC1 and IC2, while IC6 controls the delay times and noise sequencer operation. surround channel is the left minus right signal. The surround channel is also delayed by the value set on the display and the surround volume is set by the effects level control. Block diagram Fig.1 shows the block diagram for the SILICON CHIP Surround Sound Decoder. Most of the decoding work is done by IC1 and IC2, while IC6 controls the delay times and noise sequencer operation. The left and right channel encoded signals (Lt and Rt) are initially processed by an automatic balance control within IC1. This de­tects any difference between the left and right channels and adjusts the gain in each channel until the difference is nulled out. Precise balance between the left and right channels is im­portant for obtaining the best separation between each of the four channels. 62  Silicon Chip At this point, either the balanced left and right outputs or noise sequen­cer signals are passed through to the following stages. This is selected by the Noise Sequencer input signals (E, A and B) under control from IC6. When the noise sequencer is selected, a noise signal is passed in turn to the Left, Centre, Right and Surround outputs. The channel mode switch (S4) sends a signal to IC6 so that it is aware of the switch position. In the stereo mode, noise is sent to only the left and right channels, while in 3-stereo, the centre channel also receives a noise signal. When the noise sequencer is off, an L-R and L+R signal is produced from the left and right balanced outputs. In its most simple form the L+R signal becomes the centre channel and the L-R signal becomes the Surround channel. These outputs are used for the effects selection while the Pro Logic outputs include further processing to improve channel separation, channel dominance and directional accuracy in each channel. Effects or Pro Logic decod­ing is selected by switch S2aS2f. The surround output (designated S’) or the L-R signal is sent to an anti-alias filter within IC2 prior to delay process­ing. This filter removes frequencies above 7kHz. Without this anti-alias filter, extraneous signals can occur at the output of the delay unit and these would cause distortion plus a variety of spurious beat effects. The delay time is adjusted by IC6 (the microprocessor). A 7kHz low pass filter also follows the delay to limit the signal to the same bandwidth as the originally recorded surround signal. This reduces noise and improves the surround sound repro­duction. A modified Dolby B-type noise reduction within IC1 restores the signal to its original flat response. The L, C, R & S signals from S2a-S2d PARTS LIST 1 folded metal case, 436 x 50 x 260mm, with screened front panel 1 input/output socket label, 65 x 40mm 1 loudspeaker terminal label, 75 x 40mm 1 Dolby licence label, 145 x 7mm 1 heatsink, 180 x 42 x 26mm 1 2 x 18V 160VA toroidal transformer (T1) 1 IEC mains male socket 1 3-core mains lead with moulded 3-pin plug & IEC female plug 1 M205 panel mount fuseholder (F1) plus 3A fuse 1 6-way RCA panel sockets 6 banana sockets – 3 red, 3 black 1 SPST miniature rocker switch (Altronics Cat S 3210) (S1) 1 6-pole 2-position break before make rotary switch (S2) 2 DPDT centre off switches (S3,S4) 1 5kΩ linear pot (VR1) 2 50kΩ log pots (VR2,VR3) 1 10kΩ log pot (VR4) 1 6m length of shielded audio cable 1 500mm length of 7.5A brown mains rated wire 1 100mm length of 7.5A blue mains rated wire 4 500mm lengths of hookup wire – red, green, yellow & black 1 800mm length of 3-way rainbow cable 1 300mm length of 0.8mm tinned copper wire 1 2-way mains terminal block 5 22mm black anodised knobs 1 solder lug 4 12mm tapped spacers plus 8 screws 8 9mm tapped spacers plus 16 screws 7 6mm standoffs plus 7 screws & nuts 20 100mm long cable ties 100 PC stakes 1 0.47µF MKT polyester capacitor 1 0.1µF 3kV ceramic capacitor 1 S14K 275V metal oxide varistor Decoder PC Board 1 PC board, code 01409951, 160 x 165mm 1 2MHz crystal (X1) 4 5V reed relays, Jaycar Cat. SY-4036 (RLY1-RLY4) Semiconductors 1 M69032P Mitsubishi Dolby Pro Logic Surround Decoder (IC1) 1 M65830P Mitsubishi Digital Delay (IC2) 1 TDA1074A quad VCA (IC3) 2 LF347 quad op amp (IC4,IC5) 1 BC338 NPN transistor (Q1) 1 1N4004 1A 400V diode (D11) Capacitors 5 100µF 16VW PC electrolytic 1 47µF 16VW PC electrolytic 1 22µF 16VW PC electrolytic 5 10µF 16VW PC electrolytic 1 10µF 25VW PC electrolytic 1 10µF 16VW RBLL electrolytic 2 4.7µF 16VW PC electrolytic 11 1µF 16VW PC electrolytic 1 0.68µF MKT polyester 1 0.33µF MKT polyester 5 0.22µF MKT polyester 1 0.18µF MKT polyester 15 0.1µF MKT polyester 2 .068µF MKT polyester 1 .056µF MKT polyester 3 .047µF MKT polyester 2 .022µF MKT polyester 3 .0056µF MKT polyester 1 .0047µF MKT polyester 1 .0033µF MKT polyester 1 .0022µF MKT polyester 2 680pF ceramic 3 470pF ceramic 4 180pF ceramic 2 100pF ceramic Resistors (0.25W 1%) 3 10MΩ 1 8.2kΩ 1 1MΩ 6 7.5kΩ 1 330kΩ 1 5.6kΩ 1 150kΩ 3 4.7kΩ 6 100kΩ 1 2.7kΩ 4 68kΩ 1 1kΩ 7 47kΩ 1 470Ω 1 33kΩ 7 100Ω 7 22kΩ 1 30Ω 2 18kΩ 2 10Ω 14 15kΩ Power Supply PC Board 1 PC board, code 01409952, 105 x 140mm 1 TO-220 heatsink, 30 x 25 x 13mm Semiconductors 1 7815 15V 3-terminal regulator (REG1) 1 7915 15V 3-terminal regulator (REG2) 1 7812 12V regulator (REG3) 1 317T adjustable regulator (REG4) 1 7805 5V regulator (REG5) 4 1N5404 3A diodes (D1-D4) 6 1N4004 1A diodes (D5-D10) 1 PO4 1A bridge (BR1) Capacitors 2 10,000µF 25VW PC electrolytic 1 4700µF 25VW PC electrolytic 1 1000µF 25VW PC electrolytic 2 470µF 25VW PC electrolytic 1 47µF 25VW PC electrolytic 7 10µF 25VW PC electrolytic Resistors (0.25W 1%) 1 10kΩ 1 120Ω 1 1.8kΩ 1 100Ω 5W 1 680Ω 5W Amplifier PC Board 1 PC board, code 01409953, 200 x 50mm 12 M205 PC mounting fuse clips 6 3A M205 fuses 3 TO220 insulating bushes & washers 3 LM1875 20W amplifiers (IC7-IC9) Capacitors 6 100µF 25VW PC electrolytic 3 22µF 25VW PC electrolytic 3 2.2µF bipolar electrolytic 3 0.22µF 63V MKT polyester 6 0.1µF MKT Resistors (0.25W 1%) 3 22kΩ 3 1kΩ 3 18kΩ 3 1Ω Microcontroller & Display PC boards 1 PC board, code 01409954, 76 x 90mm 1 PC board, code 01409955, 26 x 115mm 1 4MHz crystal (X2) 1 4-way DIP switch 3 momentary PC switches (S5-S7) 1 6-way PC board header plug 1 6-way PC board header plug Semiconductors 1 MC68HC705C8P programmed microprocessor (IC6) 2 HDSP5301 common anode 7segment displays (DISP1, DISP2) 3 1N914 diodes (D12-D14) 1 3mm red LED (LED1) Capacitors 1 10µF 16VW PC electrolytic 2 0.1µF MKT polyester 2 39pF ceramic Resistors (0.25W, 1%) 1 1MΩ 1 1kΩ 4 47kΩ 14 330Ω 6 10kΩ Miscellaneous Heatshrink tubing, solder, machine screws & nuts. November 1995  63 +12V LEFT INPUT 37 10 10  15 L AB IN 22k +4V 18 0.1 +4V 7.5k 0.1 15k 6 47k 7 10 10  22 1 L OUT 32 2 C OUT R AB OUT L BPF OUT R BUFFER IN L BPF IN R OUT IC1 M69032P R AB IN 16 L BUFFER IN 17 L+R L BUFFER OUT 680pF RIGHT INPUT 100 L AB OUT 34 1 38 2 22k 1 S2b 22k 1 S2c 22k 1 S2d 22k 1 20 1 33 2 29 0.1 0.1 7.5k 47k 9 10 R BPF OUT VREF 680pF 15k 10 LL 14 AB HOLD TC 0.1 100k .0047 2 R RECT O/P FILTER 0.1 1 C RECT O/P FILTER 22 26 22k 0.33 +4V 100 NOISE HPF 0.1 1 5 4 50 51 0.22 52 0.22 55 4.7 53 4.7 54 470pF 18k 15k .0033 S' OUT IREF 0.68 S2e 8.2k 1 100k 14 LPF IN2 3 NOISE TEST B NOISE TEST A NOISE TEST E VCSTC 7.5k 18k 470pF 5.6k GND 12 IC2 M65830P REF 0.1 17 0.1 18 0.1 19 47 OP 20 IN1 22 4 REQ 5 SCK 6 DATA GND LPF OUT1 7 9 10 11 12 23 VLRTC MODE 100 CC1 23 LPF IN1 +5V 10M 1 1 CENTRE 2 S3a VLRTC 0.1 25 24 VCSTC CENTRE MODE 1k .068 OP 21 30  OUT1 .0056 10 VCSTC 22k CC2 X OUT S RTC VLRTC 2.7k VOLUME VR1 5K LIN 100pF .0056 40 C RTC VC1 VC2 VREF 9 10 8 1 24 VCC VDD .068 16 OP IN2 15 OP OUT2 2 X IN X1 1M 2MHz 1 LPF OUT2 13 15k .0022 2 16 17 VCA OUT 1 15k 15k 39 3 2 15 VCA VCA OUT IN +5V 15k 35 VP 11 10 100pF L-R 13 12 4 VCA VCA OUT IN IC3 TDA1074A DECOUPLE 1 100 +20V +4V NR 49 TC 330k NOISE REF 6 7 14 VCA VCA OUT IN EFFECTS VOLUME VR4 10k LOG .047 NR 45 WT 11 R RTC .022 0.22 18 NR 41 .0056 VCF 8 L RTC .022 0.22 12 28 NOISE LPF .047 .047 44 LPF 47 -IN 470pF LPF 46 OUT 42 NR IN 0.1 56 S RECT O/P FILTER 27 5 VCA IN +4V LPF 48 +IN 3 L RECT O/P FILTER 0.1 10 43 100 10M +4V IC5d CENTRE 30 CONTROL R BPF IN 68k 47k 13 14 R BUFFER OUT VREF 68k 150k 100  19 68k 2 22k +4V 68k 21 1 S OUT S2a 36 31 0.18 3 MODE S4a 2 10M 1 2 B +4V A K MODE S4b 3 E C VIEWED FROM BELOW 3 DOLBY PROLOGIC SURROUND SOUND DECODER 64  Silicon Chip 10k 0.1 Fig.2: the circuit for the Surround Sound Decoder. Note that some of the power supply components pertaining to amplifiers IC7, IC8 & IC9, are shown on the power supply circuit of Fig.3. 15k 180pF 1 15k 9 10 1 15k IC4a LF347 RLY1 8 LEFT OUTPUT 100  100k +15V 0.1 15V 1 15k 0.1 -15V 1 15k 4.7k 33k 47k CENTRE TRIM VR3 50k LOG -15V 6 180pF 5 47k CENTRE S3b 1 2 S2: 1: EFFECTS 2: DOLBY PROLOGIC S3: 1: WIDEBAND 2: PHANTOM 3: NORMAL S4: 1: SURROUND 2: 3-STEREO 3: STEREO RLY2 RLY3 14 IC4c 22 5 1k K PD1 10k PB5 39pF 7 IC4d 100  10 7 1 2 4 6 g a e d c b a f g e 18 1 e 3,8 PB4 2 4 10 9 7 6 d c g f a b a b f g e DISP1 2xHDSP5301 d 10k b 1 IC9 2 LM1875 22k D14 17 D13 +25V 470  RLY4 SURROUND RIGHT SPEAKER 0.22 63V 22 2.2 BP RLY1 RLY3 D11 1N4004 1 1k NOISE SEQ ON/ OFF S7 UP SET S6 4 18k D12 100k 1 IC8 2 LM1875 22k 4 1 RLY2 18k B 10 DISP2 10k 3x1N4148 4.7k c 100  1 2.2 BP 19 IRQ 2 PC0 28 10 11 12 13 14 15 16 c d PB3 PA2 9 PB2 PA3 8 PB1 PA4 7 PB0 PA5 6 PA0 PA6 5 PA1 PA7 4 2 1 S2f 10k DOWN S5 25 PC3 33 PD4 39pF RLY4 +5V PB6 X2 4MHz 0.22 63V SEE POWER SUPPLY DIAGRAM FOR SUPPLY DETAILS OF IC7, 8 AND 9 IC5a 3 LF347 11 PD0 PD3 PD2 32 31 30 29 IC6 MC68HC705C8P CENTRE SPEAKER 2 -15V 36 PD7 13x 330  1 47k 180pF  39 20 4 1k SURROUND TRIM VR2 50k LOG A 27 PC1 26 PC2 IC7 2 LM1875 22k 4.7k PB7 1M 1 22 6 PC6 38 2.2 BP 47k 40 37 34 3 SUBWOOFER OUTPUT -15V RIGHT OUTPUT 100  330  R 3 100k 10k 24 PC4 23 PC5 IC5c 10 100  11 2 100k +5V DELAY TIME DIP1 4x47k 21 PC7 8 18k 0.1 1 4 180pF 12 NOISE SEQ LED1 9 0.22 100  15k 13 10 .056 7.5k 1 IC4b 3 15k 7.5k 7.5k 7 IC5b C Q1 BC338 SURROUND LEFT SPEAKER 0.22 63V 1k E 22 3,8 +5V November 1995  65 Fig.3: the power supply has five separate regulators and is driven by 160VA mains transformer. pass to a 4-way volume control, IC3. Adjustment of VR1 controls all four channels simul­taneously. IC7, IC8 and IC9 are the power amplifiers for the centre and rear surround channels respectively. IC9 is sent an inverted surround signal when S2f is in the Effects position and a non-in­verted signal when S2f is in the Dolby Pro Logic position. The subwoofer output is fed via a 100Hz low pass filter which obtains a mixed signal from the left and right 66  Silicon Chip channels, after the volume control. This means that the subwoofer level will be controlled by the master volume control. The low pass filter is controlled by S3 so that in the wide­ band position of the centre mode, the filter is off. Circuit operation The complete circuit for the Surround Sound Decoder Unit is shown in Fig.2. The left and right channel inputs are applied to IC1 at the auto balance input (pins 15 and 22) via 10µF coupling ca­ pacitors and 10Ω resistors. The 22kΩ resistor at each pin biases the inputs to a 4V reference while the 10Ω resistors are RF stoppers. The auto balance time constant at pin 14, comprising a 10µF low leakage capacitor and a parallel 10MΩ resistor, prevents the auto balance control signal from modulating the audio signal. The outputs from the left and right Inside the Dolby Pro Logic Decoder unit. It has three power amplifiers to serve the centre and rear surround channels. Despite the circuit complexity, the construction is straightforward, with most of the parts mounted on five PC boards. buffers at pins 18 and 19 connect internally to voltage controlled amplifier circuits. These outputs also each connect to bandpass filters at pins 6 and 7 and pins 9 and 10 respectively which roll off signals above 5kHz and below 200Hz. The signal is subsequently applied to the full wave rectifier circuitry and the L+R and L-R networks. Output filter capacitors for the full wave rectifiers on the Left, Right, Centre and Surround channels connect to pins 3, 2, 1 and 56 respectively. The Rectifier Time Constant (RTC) capaci­tors within the log difference amplifiers for these channels are at pins 8, 11, 5 and 4. The time constant capacitors which control the rate at which the sounds can move from one channel to another are at pins 50-55. The rate control time constants are important since they prevent the system becoming lost and plac­ing sounds in the incorrect channel if subject to sudden tran­sients or loss of signal due to dropouts. The noise source in IC1 is filtered at pins 27 and 28 so that the output signal for the sequencer is centred around 500Hz. The noise sequencer is controlled at its A, B and E inputs from IC6. S’ output The surround signal before the delay is labelled S’ to differentiate it from the surround signal after delay. The S’ output at pin 39 of IC1 is filtered by an 8.5kHz low pass anti-alias filter formed by the op amp at pins 22 and 23 of IC2 and the associated resistors and capacitors. IC2 is clocked by a 2MHz crystal to accurately set the delay. The two 0.1µF capacitors at pins 17 and 18 are for the delta modulation circuit in the analog to digital conversion and the digital to analog conversion respectively. The 30Ω resistor and .068µF capacitor between pins 20 and 21 determine the re­sponse rate of the op amp used for delta modulation. The demodulated delayed signal appears at pin 15 while the op amp between pins 13 and 14 is connected to form a second order 7kHz low pass filter. Another 7kHz second order filter is provid­ed by the op amp between pins 46 and 47 in IC1. This feeds the modified Dolby B-type noise reduction unit within IC1. The output from the noise reduction unit is internally connected to the operation and combining network circuit block. The four output channels from this combining network appear at pins 32, 38, 33 and 29, representing the left, centre, right and surround signals. The above signals from IC1 are selected when switch S2 is in the Pro Logic position. When S2 is in the Effects position, the automatic balance left and right channels are selected as well as L+R for the centre channel and the output from IC5d for the surround signal. Signals from S2a-S2d are applied to IC3, a TDA1074A quad voltage controlled amplifier. It can provide a 110dB control range with 80dB separation and excellent volume tracking between channels. Distortion is better than .005% at 300mV for signals between 20Hz and 20kHz. The gain is adjusted by varying the con­trol voltage inputs at pins 9 and 10 using VR1. VR1’s voltage range is set by the 1kΩ resistor to Vref, the 22kΩ resistor to VR1’s wiper and the 2.7kΩ resistor from the top of VR1 to the 20V supply. Minimum volume occurs when the wiper of VR1 is set at ground. The output from each VCA at pins 7, 12, 2 and 17 is coupled via 10µF capacitors to quad op amp IC4. IC4a November 1995  67 *Trademarks & Program Requirements Note 1: “Dolby”, “Pro Logic” and the Double-D symbols are trademarks of Dolby Laboratories Licensing Corporation, San Francisco CA94103-4813 USA.) Note 2: this Dolby Pro Logic surround sound decoder requires a program source such as a stereo TV set or hifi stereo VCR. The program must be Dolby Surround encoded as depicted in the movie credits by the Dolby double-D surround symbol. For unencoded stereo signals, the Dolby 3-stereo selection will provide the centre front channel. Effects selection will provide surround sound from any stereo signal source. The decoder will not operate from a mono signal. and IC4c provide a nominal gain of -1 for the left and right channels respectively. The 180pF capacitor across the feedback resistors provides a high frequency roll-off at about 40kHz. IC4b and IC4d have a variable gain between -10dB and +10dB, as set by the 50kΩ potentiometers, VR2 and VR3. Relays RLY1-RLY4 are used to isolate the left, centre, right and surround outputs at power up to prevent audible thumps in the loudspeak­ers. The subwoofer signal is derived by mixing the left and right channel signals in op amp IC5b which feeds the second order Butterworth low pass filter based on IC5c. Note that switch S3b grounds the signal applied to the filter when it is set in the wideband centre mode position. IC5a is a unity gain inverter for the right channel sur­round amplifier which is used when switch S2f is in the effects position. The three power amplifiers (IC7IC9) for the centre and rear surround channels are National Semiconductor LM1875 20W devices. They come in a 5-pin TO-220 package. Their gain is set by the 18kΩ feedback resistor between pins 2 & 4 and a 1kΩ resistor to ground via a 22µF capacitor. A 2.2µF bipolar capacitor couples signal into the non-inverting input at pin 1. The output at pin 4 is connected to a Zobel network comprising a 1Ω resistor and 0.22µF capacitor. This prevents high frequency instability when driving inductive loads such as loudspeakers. Microprocessor control IC6 is a 68HC705C8P microprocessor. It sets the delay value in IC2, controls the noise sequencer operation, drives the 2-digit display 68  Silicon Chip and operates relays RLY1-RLY4 via transistor Q1. Initially, when power is first applied, the relays are off since the PC0 output of IC6, pin 28, is low. After a delay of about five seconds, PC0 goes high which turns on transistor Q1. The relay coils are then powered in series from the 25V supply via a 47Ω dropping resistor. Before PC0 goes high, IC6 checks the switch positions of DIP1 and sets the IC2 delay with this value. The 2-digit display is driven accordingly. Once PC0 goes high, the microprocessor goes into stop mode where it draws low power and produces minimum noise. This is desirable, to keep noise out of the audio circui­try. If a switch is pressed, the interrupt input at pin 2 goes low via one of the diodes D12-D14. The microprocessor wakes up and responds accordingly. If the up switch is pressed, then the delay value will increment on the display and will also be updat­ed in IC2. Similarly, if the down switch is press­ed, the delay value will decrease. If the noise sequencer switch is pressed, it will set IC1 to produce noise in each channel and drive LED1. The PD4 input at pin 33 monitors the mode switch so that the noise sequenc­er will Kit Availability Kits will be available from all Jaycar Electronics stores. Our thanks to Jaycar Electronics for their assistance in the development of this project and for their liaison with Dolby Laboratories who have approved the design. Jaycar Electronics is the licensee for the design which was developed in our labora­tory. function only on the channels selected. After performing these functions, the microprocessor again goes into sleep mode. Finally, IC6 is clocked by a 4MHz crystal oscillator at pins 38 and 39. The 10µF capacitor and the 10kΩ resistor connected to the reset pin (pin1) provide a power-on reset. Power supply The power supply is quite complex and has five separate regulators, as shown in the circuit of Fig.3. The mains trans­former is a 160VA toroidal unit with two 18V secondaries. The primary side of the transformer is protected with a 3A fuse while switch-off transients caused by switching S1 are suppressed with a .01µF/3kV capacitor and a metal oxide varistor (MOV) across the transformer primary. The two 18V windings are connected in series to drive a full wave bridge rectifier (diodes D1-D4) and two 10,000µF capacitors to derive the ±25V supply rails for the power amplifiers. Each power amplifier has its supply rail decoupled with 100µF and 0.1µF capacitors. The 18V windings also drive three pairs of diodes to derive other supply rails. First, D5 and D6 and a 47µF capacitor provide the +25V rail for the relays. Using such a small reservoir ca­pacitor ensures that the voltage will fall quickly once power is removed. The relays must switch off quickly to decouple the outputs of IC4 and thus prevent switch off thumps. A separate bridge rectifier (BR1) and two 470µF capacitors feeding 3-terminal regulators REG1 and REG2 are used for the ±15V rails for the op amps. Diodes D7 and D8 and a 4700µF capacitor drive two 3-terminal regulators, REG3 and REG4, to produce a +12V rail for IC1 (the Pro Logic decoder) and a +20V rail for IC3 (the quad VCA chip). Finally, diodes D9 and D10 feed a 1000µF capacitor. Again, this produces raw DC of about +25V and this is fed via a 100Ω 5W resistor to 3-terminal regulator REG5, to produce a +5V rail for IC3 and IC6. That’s all we have space for this month. Next month, we will complete the description of the Dolby Pro Logic Decoder by giving the full construction details and the performance specifiSC cations. SERVICEMAN'S LOG How friendly is “user friendly”? How friendly is “user friendly”? That question was prompted by recent cases of customer confusion, caused mainly by technologies that were supposedly designed to overcome user difficulties with earlier designs. One product that causes a great deal of user difficulty is the VCR. They’ve been around for many years now but a surprising percentage of users still have trouble programming the timer. They can manage to record a program if they are present when it is being broadcast but setting it up for a late night movie, or for a favourite sitcom that clashes with a dental appointment, is completely beyond them. As a result, one of the major features of the VCR – and for which they paid good money – is lost. Unfortunately, efforts to overcome these problems don’t always help. On the contrary, they often seem to make things worse. And on top of this, makers keep loading on more and more features, most of which will never be used anyway and which only add further confusion to the scene. Of course it is easy enough to sneer at “user ineptitude”. But is this fair? The average user doesn’t have a degree in electronics or even a smattering of the discipline. Nor should they have to. It is time we stopped building confusion into these appliances. What started all this? The sudden realisation that, as a serviceman, I am being called on more and more to Fig.1: this circuit shows the controller IC (IC001) in the Sony KV-2183AS colour TV set. This receives instructions from the IF unit (IF201) via pins 10 & 11 (AFTD, AFTU). solve problems which don’t involve any mechanical or electronic failure. In­ stead, they are simply problems caused by user confusion. The largest area where these problems occur involves chan­nel selection and remote control. Let’s look at a couple of typical cases. The first one involved a Sony TV set, a KV-2183AS, owned by one of my lady customers. Her complaint was that, since her grandson had come to stay with her she couldn’t receive channel 9 any more and when she tried to restore it, she lost channel 7 as well. The Sony, like most modern sets, uses an automatic search system to set it up for the wanted channels. The user puts it into the search mode and it scans the band(s) until it finds a channel. The user then has the option of putting that channel into memory or bypassing it. Either way, the system then scans for the next channel and presents the same option. This procedure is repeated until all the wanted channels have been memorised and are ready to be recalled at the touch of a button. Willie did it Well, there are no prizes for guessing what had happened in this case and the lady had been honest enough to admit to it, which is more than I can say for some customers. Little Willie had had a bit of a fiddle and made a mess of things. Anyway, I didn’t imagine it would be anything more than a routine job. How wrong can you be! I pressed the programming buttons and the system went into search mode. But, instead of stopping as it reached each channel, it shot straight through and just kept on searching, repeatedly going around and around through all the bands. However, in a seeming contradiction, the remaining channels – 2, 10 and SBS) were still locked in mem­ory and could be called up. I wasn’t quite sure where to start, a November 1995  69 Fig.2: the IF unit in the Sony KV-2183AS drives the controller IC (IC001) from pins 5 (AFT DN) and 4 (AFT UP). factor not helped by the fact that access to the appropriate PC boards leaves a lot to be desired. But the circuit suggested two suspects: (1) the con­troller IC (IC001 – M50431-611SP), which controls most of the set’s operational functions; and (2) the IF board (IF201 – IFB-368), which supplies some of the information to the controller. I picked the IF board as my first choice, if only because it was the easier option. The controller IC is a 42-pin device, whereas the IF board has only 12 pins. But, more than that, the IC was a relatively low risk device, while this IF board has something of a reputation. The complete assembly, in a metal can, carries a Mitsumi brandname and is used in several makes of sets. No circuit is available and it is described as being non-serviceable. Three of its terminals – 4 (AFT UP), 5 (AFT-DN) and 1 (RF AGC) – feed data to the controller. The works consist of a small PC board carrying an IC, coils, ceramic filters and some transistors. And the reputation, as you might have guessed, is for dry joints. Well, at least that aspect of it is serviceable, so I pulled it out and examined it. There were several obvious dry joints around the filters, which I fixed first. I then reworked the rest of the board. After all, once you get that far, there’s not much point in mucking about. Having done that, I refitted it and tried again. And that was it; it worked perfectly, stopping at every station. I repro­grammed it for the missing channels and the job was done. So everyone was happy. Well, more or less. While the lady was happy to have the set going again, it had cost her a service call and she must have wished that Little Willie had kept his fingers to himself. I hope the error of his ways was pointed out to him. OK, so there was a genuine technical failure, although it wouldn’t have mattered if Little Willie had left things alone. But the episode shows that making it easy to select and store channels can make it just as easy, or even easier, to foul things up. Remember the turret tuners in the early TV sets? The user couldn’t muck about with those. Granted, they were expensive and mechanically vulnerable and nobody really mourned their replace­ment with electronic tuning. But I wonder if the electronic systems could be made a bit more secure? The complicated NAD That Sony episode was really just a minor hiccup compared with the next story, which occurred shortly afterwards. The customer was a Greek gentleman who, unfortunately, had only a limited command of English. Even so, his command of English was far better than my command of Greek. Which made communication somewhat difficult. And we needed all the communications skills we could muster because his problem was a difficult one – a lot more difficult than he realised, in fact. However, with patience, the story eventually evolved. It transpired that he had purchased a NAD stereo TV set and VCR in a knockdown/job-lot deal from a highly respected company that was closing down after 30 odd years trading in Australia. And he wanted me to come around to his house and sort out some problems. 70  Silicon Chip In greater detail, the TV set was a NAD Monitor, which is really a rebadged ITT-Nokia 7163VT. These sets are made by Nokia Consumer Electronics, a very large Finnish company, which also makes sets under the Akai, ITT, Luxor and Salora labels. They also make mobile telephones and other electronic appliances. So what did I have to sort out? There were two problems really. One was that the set had been programmed for some sta­tions but not all, and the owner had no idea of how to go about doing this job himself. The other problem was harder to pin down initially but, by gestures, he indicated that the top of the picture was flicking back and forth; ie, flag-waving. However, this apparently only occurred when the set was working from a VCR, an important point as it turned out. My experience with European sets in general, and the Nokia family in particular, has been strictly limited; little more than secondhand from colleagues. But I had learned enough to know that they can be significantly different from the American and Asian designs with which we are most familiar. I was also aware that this was an upmarket model, featuring a whole host of features, But just how many I wasn’t to realise fully until much later. In fact, it is a multi-standard type –PAL, SECAM, NTSC – with provision for all the minor variations of these standards which occur from country to country. It also features stereo sound/dual language facilities (again with variations to suit different standards), digital sound (NICAM), Videotext and Teletext (with a wide range of options). And, in addition to the usual video recorder facili­ties, it can also handle a video disc player, video games, a pay TV decoder, a video camera, a computer and tape recorders. And so on. No instruction book Of course, the owner didn’t have an instruction book and that settled it; there was no way I was going to tackle a problem like that in-house. From what little I do know about European sets, I can’t escape the impression that, if there is a hard way to do something, they’ll find it. Anyway, I managed to explain that he would have to bring the set to the shop and that I might need it for some time. And so it eventually landed on my bench. But where should I start? There were no controls on the set, as everything was done via the control unit. And it was a control unit the like of which I had never seen before, though I’d previously heard about it. It is called a “TV Mouse” control – a supposedly impressive term obviously derived from the computer scene. So the first thing I had to do was learn how to use this device. My knowledge of mouses – er, these devices – is limited but I imagined there would be a ball on the underside, the kind of thing that is used to move a cursor around a computer screen. But there was nothing like this; it looked like a fairly standard control unit, though with a lot more buttons than most. The accompanying drawing will give the reader some idea (I only acquired this diagram much later). OK, let’s suppose I could work out how to use it. This should allow me to program in all the local channels and solve that problem. But what about the flag waving? In the normal way of things, flag waving suggests a fault in the ANOTHER GREAT DEAL FROM MACSERVICE 100MHz Tektronix 465M Oscilloscope 2-Channel, Delayed Timebase VERTICAL SYSTEM Bandwidth & Rise Time: DC to 100MHz (-3dB) and 3.5ns or less for DC coupling and -15°C to +55°C. Bandwidth Limit Mode: Bandwidth limited to 20MHz. Deflection Factor: 5mV/div to 5V/div in 10 steps (1-2-5 sequence). DC accuracy: ±2% 0-40°C; ±3% -15-0°C, 40-55°C. Uncalibrated, continuously variable between settings, and to at least 12.5V/div. Common-Mode Rejection Ratio: 25:1 to 10MHz; 10:1 from 10-50MHz, 6cm sinewave. (ADD Mode with Ch 2 inverted.) Display Modes: Ch 1, Ch 2 (normal or inverted), alternate, chopped (250kHz rate), added, X-Y. Input R and C: 1MΩ ±2%; approx 20pF. Max Input Voltage: DC or AC coupled ±250VDC + peak AC at 50kHz, derated above 50KHz. HORIZONTAL DEFLECTION Timebase A: 0.5s/div to 0.05µs/div in 22 steps (1-2-5 sequence). X10 mag extends fastest sweep rate to 5ns/div. Timebase B: 50ms/div to 0.05µs/div in 19 steps (1-2-5 sequence). X10 mag extends maximum sweep rate to 5ns/div. Horizontal Display Modes: A, A Intensified by B, B delayed by A, and mixed. CALIBRATED SWEEP DELAY Calibrated Delay Time: Continuous from 0.1µs to at least 5s after the start of the delaying A sweep. Differential Time Measurement Accuracy: for measurements $900 of two or more major dial divisions: +15°C to +35°C 1% + 0.1% of full scale; 0°C to +55°C additional 1% allowed. TRIGGERING A & B A Trigger Modes: Normal Sweep is triggered by an internal vertical amplifier signal, external signal, or internal power line signal. A bright baseline is provided only in presence of trigger signal. Automatic: a bright baseline is displayed in the absence of input signals. Triggering is the same as normal-mode above 40Hz. Single (main time base only). The sweep occurs once with the same triggering as normal. The capability to re-arm the sweep and illuminate the reset lamp is provided. The sweep activates when the next trigger is applied for rearming. A Trigger Holdoff: Increases A sweep holdoff time to at least 10X the TIME/DIV settings, except at 0.2s and 0.5s. Trigger View: View external and internal trigger signals; Ext X1, 100mV/div, Ext -: 10, 1V/div. Level and Slope: Internal, permits triggering at any point on the positive or negative slopes of the displayed waveform. External, permits continuously variable triggering on any level between +1.0V and -1.0V on either slope of the trigger signal. A Sources: Ch 1, Ch 2, NORM (all display modes triggered by the combined waveforms from Ch 1 and 2), LINE, EXT, EXT :-10. B Sources: B starts after delay time; Ch 1, Ch 2, NORM, EXT, EXT :-10. Optional cover for CRT screen – $35 through the vertical system. Continuously variable between steps and to at least 12.5V/div. X Axis Bandwidth: DC to at least 4MHz; Y Axis Bandwidth: DC to 100MHz; X-Y Phase: Less than 3° from DC to 50kHz. DISPLAY CRT: 5-inch, rectangular tube; 8 x 10cm display; P31 phosX-Y OPERATION phor. Graticule: Internal, non-parallax; illuminated. 8 x 10cm Sensitivity: 5mV/div to 5V/div in 10 steps (1-2-5 sequence) markings with horizontal and vertical centerlines further marked in 0.2cm increments. 10% and 90% for rise time measurements. Australia’s Largest Remarketer of markings Graticule Illumination: variable. Beam Test & Measurement Equipment Finder: Limits the display to within the graticule area and provides a visible 3167. Tel: (03) 9562 9500; Fax: (03) 9562 9590 display when pushed. MACSERVICE PTY LTD 20 Fulton Street, Oakleigh Sth, Vic., **Illustrations are representative only. Products listed are refurbished unless otherwise stated. November 1995  71 Fig.3: this diagram shows the front panel of the “mouse” remote control unit used with the Nokia 7163 colour TV set. The mouse function was not immediately obvious and the use of symbols and colours for some of the buttons didn’t offer much help when it came to using the device. horizontal flywheel sync system, particularly involving the flywheel time constant. So one might be tempted to pull the chassis out, find the appropriate section, and start trou­bleshooting – all this without the benefit of a circuit, at least initially. But, as I hinted earlier, European 72  Silicon Chip sets are different. Apparently, they find it necessary to provide a choice of fly­wheel time constants: long for off-air operation (particularly in fringe area situations) and short for VCR operation. I have no idea why this is so, particularly as American and Asian designs seem able to achieve a compromise setting which is quite satis­factory for both conditions. But that’s the way it is. And it meant that this set almost certainly would have this facility. And there was, therefore, little point in assuming a fault and pulling the set apart, if it was just a matter of resetting this adjustment. But, once again, I was at the mercy of the control unit, because any such adjust­ment would have to be made through it. As readers can imagine, with nothing more than an array of buttons on a control unit, and no other data, it was a formidable situation. And, to make matters worse, not all the buttons are clearly identified. While most are marked with words or numbers, the top four carry symbols and the four beneath them have both symbols and colours (the colour sequence, from left to right, is red, green, yellow and blue). Three other buttons, two below the numerical buttons and the other in the bottom righthand corner, also carry symbols only. Talk about starting from behind scratch! I switched the set on and it came up on one of the channels to which it had already been preset. I took a punt and pressed the menu button. This brought up a selection of menus and, after a lot of trial and error (read muckin’ about), I realised that all the menus –and there is a swag of them – can be presented in no less than nine languages. Unfortunately, Greek is not among them but, fortunately, the system had already been programmed for English. Pressing the video button brought up a menu offering colour (saturation), brightness, contrast and sharpness functions. Similarly, the audio button produced a menu offering stereo, hypersonic on, bass, treble, balance and volume – each with its own bargraph display for reference. The menus are presented as white characters on a black background, similar to some computer presentations. The exception here is the item that’s currently selected, which will have the reverse presentation; ie, black charac- ters on a white background (typically referred to as the “cursor”). All that was fine as far as it went. But how did one move the cursor to change the selection and, having changed it, acti­vate it? I found the answer quite by accident. I noticed that moving the control unit sometimes produced a sound from inside it and, at the same time, I realised that the cursor on the menu had changed. So this was their version of a mouse; a loaded contact ball inside the control which moved when the control was pointed up or down, or banked to the right or left. And, logically, the cursor moved up when the front of the control was lifted and down when it was depressed. For example, when in the audio menu, one could select, say, volume and then vary the volume up or down by rotating or banking the control to the left or right. Or one could select, say, brightness in the video menu and vary it in a similar manner. I was starting to get the hang of the thing now. But it was only the beginning; it was to take a lot more “muckin’ about” before the job was done. And it would be virtually impossible to set out all the things that can be done with this system or, indeed, how I worked out how to do them. We’d be here forever. In any case, I doubt whether the reader could follow it all, without the benefit of a hands-on approach. But I did make some notes as I worked out what I needed to do, just in case I had to do it again. These will give the reader some idea of what is involved. First, the tuning. Press the MENU button, then the blue button, to bring up MENU 1. Move the cursor to TV-PROGR and call up MENU 2 by rotating the mouse control. This gives a choice of tuning approaches: (1). The channel number mode. A number of frequencies are pre-programmed into the set – useful only if a list of channel frequencies is available. Enter a channel number – assuming that one is available to suit an Australian transmission. No channel list available. Resorted to search mode. (2). The search mode. Press the green button to change from channel mode to frequency mode. Press the MENU button and rotate the mouse to search for stations. When a station is found, revert to the channel mode to What about the user? And one has to admit that it is all extremely clever and ingenious. But how does it sit with the average user? Is he or she really expected to program such a complicated device? Among other things, they would have to select the appropriate TV system, find and store all the TV channels, consult and use the video adjustments and options, and carry out the sound adjustment options. In most cases, of course, a dealer would have already made the adjustments and the set would be ready to go on installation. The catch comes if the system has to be reprogrammed for any reason (eg, if the user moves to a different location). The reality is that they usually have to call in the likes of yours truly to do the job for them. And that costs money. Finally, there is the vulnerability of these systems by reason of all adjustments being accessible via the remote control. A careless user, or an inquisitive Little Willie, can wreck a long and complex programming sequence in a few seconds. Again, that costs money. So what’s the answer? I don’t know – I can only see the problem. And it’s a SC very real one. SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ allocate a number for it. It can also be given a name, if desired; eg, “Channel 7”, or “SBS”, etc. Save by pressing the red button. So, by this process, all the local channels were eventually located, stored, numbered and named. Then it was to the flag- waving problem. This was fixed as follows: Press MENU button. Brings up INDEX menu. Press blue button. Brings up sub-menu listing SAT-PROGR, TV-PROGR, EXT-PROGR. Select EXT-PROGR. Brings up sub-program listing, among other functions, SYNCHR-VCR. Select the latter. Rotate control to switch to long time constant. And that was it; problem solved. It sounds easy when you say it quickly but it wasn’t easy, of course. It took many hours – and much colourful language – before the two above routines were worked out and completed. But by the time I had done it all, I realised that I was beginning to enjoy the challenge; that, in fact, I was being sucked in by the technology and the ingenuity behind it – much as I suspect the engineers who designed it were sucked in. November 1995  73 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: Rod Irving Electronics Pty Ltd Design By JEFF MONEGAL Digital speedometer & fuel gauge; Pt.2 Despite the circuit complexity, the digital speedometer and fuel gauge is straightforward to assemble. This month, we give the construction and calibration details. All the parts for the main circuit and the A/D converter mount on a single main PC board, while the display module is built on two smaller boards which are mounted back to back on 12mm spacers. As indicated in an accompanying panel, a complete kit of parts for this design (minus the case) is being offered by CTOAN Electron­ ics. No special assembly techniques are required apart from the use of a good quality fine-tipped soldering iron. The PC boards are all solder masked to help stop solder runs and carry screened printing to show the parts placement. Fig.4 shows the parts layout on the main PC board. Note that a few minor changes were made to the circuit after the board design was finalised. As a result, the following changes should be made: (1). the positions indicated for resistor R1 and diodes D1 & D2 should be left vacant; (2). Q1 should be omitted and a wire link connected between what were its collector and emitter terminals; and (3) R2 should be increased to 1.5kΩ. Begin by installing PC stakes at the external wiring points and 10-way IDC pin headers at the CON1 and CON2 positions. This done, install the resistors, capacitors and diodes, taking care to ensure that all polarised parts are correctly oriented. There are also a number of wire links on November 1995  79 Fig.4: install the parts on the main PC board exactly as shown here but note that the 100µF capacitor (C18) to the right of Q7 should be left out until after the calibration is completed. Note also that a few minor changes will be necessary if the car has a “positive” sender – see text. the board and these should also be installed at this stage (the prototype used 0Ω resistors). If your car has a conventional sender (ie, one that has minimum resistance when the fuel tank is full), install the parts exactly as shown in Fig.4. Make sure that R19 is 470Ω (not 820Ω as marked on the PC board). Both R20A and the adjacent wire link should be omitted. Alternatively, if your car has a “positive” sender (ie, one that has maximum resistance when the tank is full), then you will need to make the following changes: (1) change R19 to 820Ω; (2) omit R20; and (3) install R20A (33kΩ) and the adjacent wire link. Do not install C18 (100µF) at this stage. That step comes later, following the calibration procedure. The IC sockets can be installed next. A 28-pin IC socket must be used for the microprocessor, as CTOAN Electronics will not accept chips for testing or reprogramming that have solder on their pins. The use of IC sockets for the remaining ICs can be considered optional, although they were used in the prototype. Once the IC sockets are in, the remaining parts can all be installed. Note particularly the arrangement for LED 1 (red) and the LDR. The leads of the LED must be bent at right angles before installing it, so that it sits against the LDR as shown in the photo. Take care with the LED polarity – its anode lead will be the longer of the two. The yellow LED (LED 2) is mounted on the board in the con­ventional manner, as shown. A small heatsink is required for the 7805 3-terminal regu­lator and this is bolted to the board as shown in the photo. Smear the metal tab of the regulator with heatsink compound before bolting the assembly together. Display modules This close-up view shows the mounting details for LED1 and the LDR. Note how the LED is bent over so that it directly faces the surface of the LDR, so that its resistance reduces to just a few hundred ohms when power is first applied. 80  Silicon Chip Fig.5 shows the parts layout on the display module PC boards. As indicated earlier, you will have to build two such display modules – one for the speed display and the other for the fuel display. Install the parts on the PC boards as shown, taking care to ensure that the displays are all oriented with their decimal points at bottom right. Note that resistors R1-R7 & R9 on the IC board Fig.5: install the parts on the display boards as shown in this diagram. Note that the two ICs face in opposite directions and don’t forget to install the insulated wire link (shown dotted) on the board at left. are all mounted end-on to conserve space. In addition, an insulated wire link must be installed on the back of this board (shown dotted). Once the board assemblies have been completed, they can be mounted back-to-back on 12mm spacers and secured using machine screws and nuts. Finally, the two boards in the assembly are wired together by installing 13 wire links between them along one edge. The completed display modules are connected to the main board via 10-way ribbon cables fitted with IDC connectors. These cables are supplied pre-assembled in 1-metre lengths. Testing The unit can now be tested by following this step-by-step procedure: (1). Connect a link across the fuel sensor inputs; (2). Connect a display module to the speed connector (CON1) on the main board using one of the supplied 10way ribbon cables. The photos show the connector orientations (no damage will result if you do plug the cable in the wrong way around – the display just won’t work). (3). Install all the ICs except for the microprocessor (IC2) on the main board. (3). Connect a 12V DC power supply to the power input terminals and use a multimeter to check that there is +5V TABLE 1: CAPACITOR CODES ❏ ❏ ❏ ❏ ❏ ❏ Value 0.47µF 0.1µF .01µF .001µF 27pF The two boards that make up the display module are mounted back-to-back on 12mm-long spacers and the assembly secured using machine screws and nuts. IEC Code 470n 100n 10n 1n0 27p EIA Code 474 104 103 102 27 on pin 3 of the microprocessor socket. (4). Short pin 1 of IC3 to the +5V rail using a clip lead and check that the buzzer pulses on and off. (5). If all these checks are OK, switch off and install the microprocessor (make sure that it is correctly oriented). (6). Reapply power and check that the display shows 00 after a few seconds. If it does, switch off and connect an oscillator to the speed input (labelled “SIG” on the PC board). Set the oscil­lator frequency to about 50Hz and the signal amplitude to 5V (make sure that the amplitude in not greater than 5V, otherwise you could damage IC2). (7). Reapply power – the display should now show a reading. Check that this reading can be varied by adjusting the oscillator frequency. Check also that the reading can be varied by adjusting VR1 on the main board. (8). Test the various speed alarm settings. If you haven’t alrea­dy wired up switch S1, you can select a speed setting simply by shorting its pin to +5V. Begin by selecting 62, then adjust the oscillator so that the reading goes higher than 62. The buzzer should immediately sound and the display should flash on and off. Now press the mute button. The buzzer should stop but the display should continue to flash. Now check the other speed settings in turn. (9). If everything checks OK so far, adjust VR1 so that the speed display shows the incoming oscillator frequency. This is not the final calibration but is a good starting point. This view shows the rear of the completed display module. Note the direction from which the cable enters the pin header on this board. November 1995  81 are not as stated, go back over your work carefully for possible faults. In particular, check that all parts are in their correct locations, have the correct value or type number, and are correctly orient­ed. The microprocessor is easy to check if you have an oscillo­scope or a logic probe. If the microprocessor is operating cor­rectly, pin 18 will have short positive pulses occurring every 0.75-2 seconds. You should also see various pulses on pins 9, 10 and 11. If these pulses are there, then the microprocessor is operating correctly. Installation This close-up view shows two stages in the speed sensor assembly. The unit at top shows what the sensor looks like after the parts have been mounted on the Veroboard, while at bottom is the finished sensor after it has been covered in heatshrink tubing and sealed with silicone sealant. (10). Connect the second display module to the fuel socket (CON2 on the main board). With the shorting link still in place, the display should show some figure above 30. Adjust VR2 and confirm that the display reading varies, then do the same with VR3. (11). Replace the shorting link with a 1kΩ resistor and check that the display now shows a reading of less than 20. If not, try adjusting VR2. (12). Adjust VR2 so that the display reads less than 10. After a few seconds, the low fuel lamp should start to increase in bril­liance. Troubleshooting If all is correct so far, then the project is operational and fuel gauge calibration can take place. If things Where To Buy A Kit Of Parts Kits for this project will be available from CTOAN Elec­tronics. The details are as follows: Kit 1 is for the speedometer section only and includes a screened and solder-masked main PC board, the on-board components (including a programmed microprocessor but not the parts for the fuel gauge A-D converter), the buzzer, S1 and S2, a Hall Effect sensor and two button magnets. This kit also includes all the parts for a single display module (PC boards plus on-board com­ponents. The cost of this kit is $73.00. Kit 2 includes the additional components required to build the fuel gauge, including a display module and the parts for the A-D converter. The cost of this kit is $20. Additional display modules are available for $13 each. In addition to the above kits, CTOAN Electronics is also offering fully built and tested main PC boards for $130.00 ($140 if the fuel gauge A-D converter is required), plus fully tested dis­play modules for $20.00 each. A repair service is also available for a minimum cost of $20.00 (does not include replacement of the microprocessor). Kits can be ordered over the phone using a credit card (Bankcard, MasterCard or Visa), or by sending a cheque or money order to: CTOAN Electronics, PO Box 211, Jimboomba 4280, Qld. Phone (07) 297 5421. Please add $5.00 for postage and packing with each order. Note: copyright of the PC boards associated with this design is retained by CTOAN Electronics. 82  Silicon Chip It is important that this unit be installed in a profes­sional manner, so as not to compromise the reliability of the car’s existing wiring. In particular, make sure that any power supply connections are run via suitable fuses. The +12V supply to D3 must be derived via the ignition switch and the fusebox is probably the best place to make this connection. Be sure to connect to the fused side of the switched supply. Similarly, the connection to the car’s lights (from D8) can also be made at the fusebox (eg, to the supply for the tail lights). The connection to the fuel sender can be made by discon­ necting the appropriate lead to the existing fuel gauge and connecting it to the main PC board instead (ie, your existing fuel gauge must be disconnected). Alternatively, you can install a switch, so that you can select between the two. This switch should be a break before make type. If you have trouble identifying the sender lead, check its colour code by referring to the wiring diagram in the car’s manual. Alternatively, you can check the colour of the lead at the sender itself. Initially, the unit should be installed so that you have easy access to the trimpots on the main PC board. This is neces­sary to allow final calibration later on. The two display modules should be positioned on the dash­board where they can be easily read. They can either be mounted in separate cases or mounted side-by-side in a single case, with red Perspex used for the display windows. Be sure to mount the low-fuel warning lamp in a conspicuous location. Fig.6: the Hall Effect sensor, along with R36 (10kΩ), is mounted on a piece of Vero­board. This assembly is then waterproofed by covering it in heatshrink tubing and applying silicone sealant to any gaps. Fig.7: the mounting details for the Hall Effect sensor and its companion magnets. Note that the magnets must be oriented so that alternate poles pass by the sensor; ie, one magnet is mounted with its north pole closest to the sensor while the other is mounted with its south pole closest to the sensor. The speed alarm selection switch (S1) and the alarm mute pushbutton (S2) should be mounted in locations where they are easy to use. Hall effect sensor The Hall Effect sensor, along with resistor R36 (10kΩ), is mounted on a small piece of Vero­board (Fig.6). This assembly is then waterproofed by covering it in heatshrink tubing and applying silicone sealant to any gaps. Fig.7 shows the mounting details for the Hall Effect sensor and its companion magnets. Note that the magnets are mounted on the tailshaft (or on a driveshaft in a front-wheel drive car) and are oriented so that alternate poles pass by the sensor; ie, one magnet is mounted with its north pole closest to the sensor while the other is mounted with its south pole closest to the sensor. Calibration Calibration of the speed display is best carried out with the help of a second person. The procedure is straightforward – simply drive along a road at a known steady speed and have the other person adjust VR1 until the display reads the same as the existing speedometer. Calibration of the fuel display is also quite straightfor­ward. The easiest way is to use a sender that’s been obtained from a wrecking yard. Note that this sender must be the same type as the one used in the car. To calibrate the display, temporarily connect this second sender to the main PC board (disconnect the sender in the car), set it to the “empty” position, and adjust VR2 so that the dis­play reads “00”. If the display cannot be zeroed, try adjusting the value of R19 (this should rarely be necessary). This done, set the sender to the “full’ position and adjust VR3 to obtain the correct reading (ie, 100% or the capacity of the tank in litres or gallons). For example, if the car has a 65-litre tank, adjust VR3 so that the fuel display reads “65” (sender at “full”). Alternative­ly, adjust VR3 so that the display reads “100” for 100%. The above procedure should now be repeated two or three times to obtain the final calibration. This is necessary because there is some interaction between the two adjustments. Note that, in some cars, the engine may cut out due to fuel starvation before the sender actually quite reaches minimum resistance. However, the above procedure should be accurate enough for all practical purposes. In any case, it’s not a good idea to let the fuel run out completely, as this can lead to rubbish clogging the fuel injectors or the jets in the carbur­ettor. If you are unable to obtain a sender from a wrecking yard, then it may be possible to remove the sender from the fuel tank and use this for calibration instead. Be warned, however, that disturbing the existing sender might cause the tank to leak later on (even if you replace the gasket) and this could mean a new fuel tank. We don’t recommend this option unless you know exactly what you are doing. Another way of calibrating the fuel display is to calibrate it against the existing fuel gauge. However, this method is only viable if you have installed a switch to select between the two. Note that the two units cannot be operated in parallel as this will lead to wildly incorrect readings. Once calibration has been completed, install C18 (100µF) on the main PC board and complete the installation. Don’t forget to reconnect the fuel gauge sender if you calibrated the unit using SC a second external unit. November 1995  83 NICS O R T 2223 LEC PC CONTROLLED PROGRAMMABLE POWER SWITCH MODULE This module is a four channel programmable W 0 S 1 N 9 , driver for high power relays. It can be used in 7 y le 70 any application which requires algorithm control 9, Oat Fax (02) 5 rd 8 a x C o for high power switching. This module can work Visa PO B 579 4985 as a programmable power on/off switch to limit fax a rd , ) & C 2 0 e ( r unauthorised access to equipment where the n e e o t n s h : o s a p r h P access to use or change parameters is critical. , M ith rde d o w r a d d c e This module can also be used as a universal B a n k x accepte most mix 0. Orders timer. The timer software application is ine r 1 o m $ f A ) cluded with the module. Using this software l i P a & & m r the operator can program the on/off status (ai s. P t r Z e e N n d . r ; of four independent devices in a period of o rld $10 o w 4 $ <at> a week within an accuracy of 10 minutes. . tley a Aust o : The module can be controlled through L I A M the Centronics or RS232 port. The computer is opto by E isolated from the unit, to ensure no damage can occur to the computer. Although the relays included are designed for 240V operation, they have not been approved by the electrical LEARNING - UNIVERSAL REMOTE CONTROL authorities for attachment to the mains. Power consumption These Learning IR Remote Controls can be used to replace is 7W. Main module: 146 x 53 x 40mm. Display panel: 146 up to eight dedicated IR Remote Controls: $45 x 15mm. We supply: two fully assembled and tested PCBs (main plus control panel), four relays (each with 3 x 10A / NEW CATALOGUE AT OUR WEB SITE 240V AC relay contacts), and software on 3.5" disk. We do We have combined efforts with DIY ELECTRONICS (a Hong not supply a casing or front panels. Kong based company) in producing a WEB SITE on the $92 (Cat G20) INTERNET. At this site you can view and download a text version of both of our latest catalogues and other up to date 3.5 DIGIT LCD PANEL METER information. Email orders can also be placed through here. 200mV full scale input sensitivity, “1999” count, 9 to 12V The combined effort means that you get offered an extensive <at> 1mA operation, decimal point selectable (with jumper range of over 200 high quality, good value kits, and many wire), 13mm figure height, auto polarity indicator, overrange more interesting components and items. The range of kits indication, 100Mohm input resistance, 0.5% accuracy, 2 to offered includes simple to more advanced kits, and they cover 3 readings per second. With bezel and faceplate. Dimensions: a very wide field of applications: educational, experimental, 68 x 44mm. Use in instrumentation projects. EPROM, microprocessor, computer, remote control, high $27 (Cat D01) voltage, gas and diode lasers, night vision etc. We’ll leave it to you to do the exploring at: CCD CAMERA-VCR SECURITY SYSTEM http://www.hk.super.net/~diykit This kit plus ready made PIR detector module and “learning You can also request us to send you a copy of our FREE remote control” combination can trigger any domestic IR catalogue with your next order. remote controlled VCR to RECORD human activity within a 6M range and with an 180 deg. angle of view!. Starts HELIUM-NEON LASER BARGAIN VCR recording at first movement and ceases recording Helium neon 633nM red laser heads (ie tubes sealed in a few minutes after the last movement has stopped; just a tubular metal case with an inbuilt ballast resistor) that like commercial CCD-VIDEO RECORDING systems costing were removed from equipment that is less than 5 years thousands of dollars!! CCD camera not supplied. No conold. These are suitable for light shows. Output power is in nection is required to your existing domestic VCR as the the range of 2.5-7.5mW. Heads are grouped according to system employs an “IR learning remote control”: $90 for output power range. Dimensions of the head are 380mm an PIR detector module, plus control kit, plus a suitable long and 45mm diameter. Weight: 0.6kg. A special high “lR learning remote” control and instructions: $65 when voltage supply is required to operate these heads. With purchased in conjunction with our CCD camera. Previous each tube we will include our 12V universal laser power CCD camera purchasers may claim the reduced price with supply kit MkIV (our new transformers don’t fail). Warning: proof of purchase. involves high voltage operation at a very dangerous energy level. SUPER SPECIAL: FLUORESCENT LIGHTING SPECIAL $80 for a 2.5-4.0mW tube and supply. (Cat L01) A 12V-350V DC-DC converter (with larger MOSFETS) plus a $130 for a 4.0-6.5mW tube and supply. (Cat L02) dimmable mains operated HF ballast. This pair will operate a This combination will require a source of 12V <at> at least 32-40W fluorescent tube from a 12V battery: very efficient. 2.0A. A 12V gel battery or car battery is suitable, or if 240V See June 95 EA: $36 for the kit plus the ballast. operation is required our Wang computer power supply (cat number P01) is ideal. Our SPECIAL PRICE for the Wang power STEREO SPEAKER SETS supply when purchased with matching laser head/inverter A total of four speakers to suit the making of two 2-way kit is an additional $10. speakers (stereo). The bass-midrange speakers are of good quality, European made, with cloth surround, as used in LASER WARNINGS: upmarket stereo televisions, rectangular, 80 x 200mm. The 1. Do not stare into laser beams; eye damage will result. tweeters are good quality cone types, square, 85 x 85mm. 2. Laser tubes use high voltage at dangerous energy levels; Two woofers and two tweeters: $16. be aware of the dangers. 3. Some lasers may require licensing. NEW: PHOTOGRAPHIC KITS SLAVE FLASH: very small, very simple, very effective. ARGON-ION HEADS Triggers remote flashes from camera’s own flash to fill in Used Argon-Ion heads with 30-100mW output in the blueshadows. Does not false trigger and it is very sensitive. Can green spectrum. Head only supplied. Needs 3Vac <at> 15A even be used in large rooms. PCB and components kit: $7. for the filament and approx 100Vdc <at> 10A into the driver SOUND ACTIVATED FLASH: adapted from ETI Project circuitry that is built into the head. We provide a circuit for a 514. Adjustable sensitivity & delay enable the creation suitable power supply the main cost of which is for the large of some fascinating photographs. Has LED indicator that transformer required: $170 from the mentioned supplier. makes setting up much easier. PCB, components, plus Basic information on power supply provided. Dimensions: microphone: $13. 35 x 16 x 16cm. Weight: 5.9kg. 1 year guarantee on head. Price graded according to hours on the hour meter. SINGLE CHANNEL UHF WITH CENTRAL LOCKING Argon heads only, 4-8 thousand hours: $350 (Cat L04) Our single channel UHF receiver kit has been updated to Argon heads only, 8-13 thousand hours: $250 (Cat L05) provide provision for central locking!! Key chain Tx has SAW resonator locked, see SC Dec 92. Compact receiver GEIGER COUNTER AND GEIGER TUBES has prebuilt UHF receiver module, and has provision for two These ready made Geiger counters detect dangerous Beta and extra relays for vehicle central locking function. Kit comes Gamma rays, with energy levels between 30keV and 1.2MeV. with two relays. $36. Additional relays for central locking $3 Audible counts output, also a red LED flashes. Geiger tube ea. Single ch transmitter kit $18. unplugs from main unit. To measure and record the value of nuclear radiation level the operator may employ a PC which is MASTHEAD AMPLIFIER SPECIAL connected to the detector through the RS232 interface. This High performance low noise masthead amplifier covers gives a readout, after every 8 counts, of the time between each VHF-FM UHF and is based on a MAR-6 IC. Includes two count. Main unit is 70 x 52 x 35 mm. Geiger tube housing PCBs, all on-board components. For a limited time we will unit is 135mm long and is 20mm diameter. Power from 12 also include a suitable plugpack to power the amplifier from to 14V AC or DC. mains for a total price of: $75 (Cat G17) $25 EY OATL E 84  Silicon Chip CCD CAMERA Very small PCB CCD Camera including auto iris lens: 0.1Lux, 320K pixels, IR responsive, has 6 IR LEDs on PCB. Slightly bigger than a box of matches!: $180 VISIBLE LASER DIODE KIT A 5mW/670nM visible laser diode plus a collimating lens, plus a housing, plus an APC driver kit (Sept 94 EA). UNBELIEVABLE PRICE: $40 Suitable case and battery holder to make pointer as in EA Nov 95 $5 extra. 12V-2.5 WATT SOLAR PANEL KITS These US made amorphous glass solar panels only need terminating and weather proofing. We provide clips and backing glass. Very easy to complete. Dimensions: 305 x 228mm, Vo-c: 18-20V, Is-c: 250mA. SPECIAL REDUCED PRICE: $20 ea. or 4 for $60 A very efficient switching regulator kit is available: Suits 12-24V batteries, 0.1-16A panels, $27. Also available is a simple and efficient shunt regulator kit, $5. SOLID STATE “PELTIER EFFECT” DEVICES We have reduced the price of our peltiers! These can be used to make a solid state thermoelectric cooler/heater. Basic information supplied: 12V-4.4A PELTIER: $25 We can also provide two thermal cut-out switches, and a 12V DC fan to suit either of the above, for an additional price of $10. BATTERY CHARGER Simple kit which is based on a commercial 12 hour mechanical timer switch which sets the battery charging period from 0 to 12 hrs. Timer clock mechanism is wound-up and started by turning the knob to the desired time setting. Linear dial with 2 hrs timing per 45 degrees of rotation, eg, 270 deg. rotation for 12 hr. setting. The contacts on the timer are used to switch on a simple constant current source. Employs a power transistor and 5 additional components. Can easily be “hard wired”. We supply a circuit, a wiring diagram, and tables showing how to select the charging current: changing one resistor value. Ideal for most rechargeable batteries. As an example most gel cells can be charged at a current which is equal to the battery capacity rating divided by 5-10. Therefore if you have a discharged gel cell that has 5Ah capacity and are using a charge current of 0.5A, the timer should be set for about 10 hours: Or 5hrs. <at> 500mA. This circuit is suitable for up to approximately 5A, but additional heatsinking would be required at currents greater than 2A. Parts and instructions only are supplied in this kit. Includes a T-03 mini fin heatsink, timer switch, power transistor and a few other small components to give you a limited selection of charge current. You will also need a DC supply with an output voltage which is greater by about 2V than the highest battery voltage you need to charge. As an example a cheap standard car battery charger could be used as the power source to charge any chargeable battery with a voltage range of 0-15V: $12 (K72) COMPUTER CONTROLLED STEPPER MOTOR DRIVER KIT This kit will drive two 4, 5, 6 or 8 wire stepper motors from an IBM computer parallel port. The motors require a separate power supply (not included). A detailed manual on the computer control of motors plus circuit diagrams and descriptions are provided. Software is also supplied, on a 3.5" disk. PCB: 153 x 45mm. Great low cost educational kit. We provide the PCB and all on-board components kit, manual, disk with software, plus two stepper motors of your choice for a special price. Choose motors from M17/M18/M35. $44 (K21) Kit without motors is also available: $32 MOTOR SPEED CONTROLLER PCB Simple circuit controls small DC powered motors which take up to around 2 amps. Uses variable duty cycle oscillator controlled by trimpot. Duty cycle is adjustable from almost 0-100%. Oscillator switches P222 MOSFET. PCB: 46 x 28mm. $11 (K67) For larger power motors use a BUZ11A MOSFET: $3. FM TX MK 3 This kit has the most range of our kits (to around 200m). Uses a pre-wound RF coil. The design limits the deviation, so the volume control on the receiver will have to be set higher than normal. 6V operation only, at approx 20mA. PCB: 46 x 33mm: $18 (K33) LOW COST IR ILLUMINATOR Illuminates night viewers or CCD cameras using 42 of our 880nm/30mW/12 degrees IR LEDs. Power output (and power consumption) is variable, using a trimpotentiometer. Operates from 10 to 15V and consumes from 5mA up to 0.6A (at maximum power). The LEDs are arranged into 6 strings of 7 series LEDs with each string controlled by an adjustable constant current source. PCB: 83 x 52mm: $40 (K36) VHF MODULATOR FOR B/W CAMERAS (To be published, EA) Simple modulator which can be adjusted to operate between about channels 7 and 11 in the VHF TV band. This is designed for use in conjunction with monochrome CCD cameras to give adequate results with a cheap TV. The incoming video simply directly modulates the VHF oscillator. This allows operation with a TV without the necessity of connecting up wires, if not desired, by simply placing the modulator within about 50cm from the TV antenna. Suits PAL and NTSC systems. PCB: 63 x 37mm: $12 (K63) SOUND FOR CCD CAMERAS/UNIVERSAL AMPLIFIER (To be published, EA). Uses an LM386 audio amplifier IC and a BC548 pre-amp. Signals picked up from an electret microphone are amplified and drives a speaker. Intended for use for listening to sound in the location of a CCD camera installation, but this kit could be used as a simple utility amplifier. Very high audio gain (adjustable) makes this unit suitable for use with directional parabolic reflectors etc. PCB: 63 x 37mm: $10 (K64) LOW COST 1 to 2 CHANNEL UHF REMOTE CONTROL (To be published, SC) A single channel 304MHz UHF remote control with over 1/2 million code combinations, which also makes provision for a second channel expansion. The low cost design has a 2A relay contact output. The 1ch transmitter (K41) can be used to control one channel of the receiver. To access the second channel when another transmitter is purchased, the other transmitter is coded differently. Alternatively, the 3ch transmitter kit (K40) as used with the 4ch receiver kit is compatible with this receiver and allows access to both channels from the one transmitter. Note that the receiver uses two separate decoder ICs. This receiver operates from 10 to 15Vdc. Range is up to about 40m. 1ch Rx kit: $22 (K26) Expansion components (to convert the receiver to 2 channel operation; extra decoder IC and relay): $6 ONE CHANNEL UHF TRANSMITTER AX5326 encoder. Transmit frequency adjustable by trimcap. Centred around 304MHz. Powered from 12V lighter battery. LED flashes when transmitting. Size of transmitter case: 67 x 30 x 13 mm. This kit is trickier to assemble than the 3ch UHF transmitter: $11 (K41) THREE CHANNEL UHF TRANSMITTER The same basic circuit as the 1ch transmitter. Two buttons, allows up to 3 channel operation. Easier to assemble than the 1ch transmitter and has slightly greater range. Size of transmitter case: 54 x 36 x 15mm: $18 (K40) ULTRASONIC RADAR Ref: EA Oct 94. This unit is designed to sound a buzzer and/or operate a relay when there is an object at a preset distance (or less) away. The distance is adjustable from 200mm to around 2.5 metres. Intended as a parking aid in a car or truck, also may be used as an aid for the sight impaired, warning device when someone approaches a danger zone, door entry sensor. PCB: 92 x 52mm. PCB, all on-board components kit plus ultrasonic transducers (relay included): $22 (K25) Optional: buzzer $3, plastic box $4. SIREN USING SPEAKER Uses the same siren driver circuit as in the “Protect anything alarm kit”, kit number K18. 4" cone/8 ohm speaker is included. Generates a really irritating sound at a sound pressure level of 95dB <at> 1m. Based around a 40106 hex Schmitt trigger inverter IC. One oscillator modulates at 1Hz another oscillator, between 500Hz and 4KHz. Current consumption is about 0.5A at 12V. PCB: 46 x 40mm. As a bonus, we include all the extra PCBs as used in the “Protect anything alarm kit”. $12 (K71) PLASMA BALL Ref: EA Jan 94. This kit will produce a fascinating colourful changing high voltage discharge in a standard domestic light bulb. The EHT circuit is powered from a 12V to 15V supply and draws a low 0.7A. Output is about 10kV AC peak. PCB: 130 x 32mm. PCB and all the on-board components (flyback transformer included), and the instructions: $28 (K16) We do not supply the standard light bulb or any casing. The prototype supply was housed in a large coffee jar, with the lamp mounted on the lid. Hint: connect the AC output to one of the pins on a fluorescent tube or a non-functional but gassed laser tube. Large non-functional laser tube or tube head: $10 ELECTROCARDIOGRAM PCB + DISK The software disk and a silk screened and solder masked PCB (PCB size: 105 x 53mm) for the ECG kit published in EA July 95. No further components supplied: $10 (K47) TOMINON HIGH POWER LENS These 230mm (1:4.5) lens have never been used. They contain six coated glass lenses, symmetric, housed in a black aluminium case. Scale range is from 1:10 through to 1:1 to 10:1. Weight: 1.6kg. Applications include high quality image projection at macro scales, and portrait photography in large formats: $45 (Cat O14) PROJECTION LENS Brand new, precision angled projection lens. Overall size is 210 x 136mm. Weight: 1.3kg. High-impact lexan housing with focal length adjustment lever. When disassembled, this lens assembly yields three 4" diameter lenses (concave, convex-concave, convex-convex). Limited quantity: $35 (Cat O15) INTENSIFIED NIGHT VIEWER KIT Reference article: Silicon Chip Sept 94. See in the dark! Make your own 3 stage first generation night scope that will produce good vision in starlight illumination! Uses 3 of the above fibre optic tubes bonded together. These tubes have superior gain and resolution to Russian viewers. 25mm size tube only weighs 390g. 40mm size tube only weighs 1.1kg. We supply a three stage fibre optically coupled image intensifier tube, EHT power supply kit which operates from 6 to 12V, and sufficient plastics to make a monocular scope. The three tubes are already bonded together: $270 for the 25mm version (Cat N04) $300 for the 40mm version (Cat N05) We can also supply a quality Peak brand 10x “plalupe” for use as an eyepiece which suits all the above 25 and 40mm windowed tubes well: $18 35mm camera lenses or either of the Russian objective lenses detailed under “Optical” suit these tubes quite well. IR “TANK” TUBE/SUPPLY KIT These components can be the basis of a very responsive infra red night viewer; the exact construction of which we leave up to you. The new IR tube is as used in older style military tank viewers. The tube employed is probably the most sensitive IR responsive tube we have ever supplied. Responds well even to 940nm LED illumination. The resultant viewer requires IR illumination, as without this it will otherwise only “see” a little bit better than the naked eye. Single tube, first generation. Screen diameter: 18mm. Tube length 95mm. Diameter: 55mm. Weight: 100g. Tube can be operated up to about 15kV. Our miniature night viewer power supply (kit number K52) is supplied with its instructions included. Only very basic ideas for construction of viewer is provided. Tube and the power supply kit only: $80 (Cat N06) RUSSIAN SCOPE KIT Our hybrid Russian/Oatley kit design makes this the pick of the Russian scopes in this price range! We supply a fully assembled Russian compact scope housing containing the intensifier tube, adjustable eyepiece and objective lens. Housing is made from aluminium. The objective lens is fixed in focus, but it is adjustable after loosening a grub screw. We also include the night viewer power supply kit (kit number K52) and a small (84 x 55 x 32mm) jiffy box to house the supply in. The box must be attached by you to the scope housing. Operates from a 9V battery. This scope has a useful visible gain but is difficult to IR illuminate satisfactorily. Length of scope is 155mm: $290 (Cat N07) LASER POINTER A complete brand new 5mW/670nM pointer in a compact plastic case (75 x 42 x 18mm) with a key chain. Features an automatic power control circuit (APC) which is similar to our kit number K35 & our laser diode module’s circuit. Battery life: 10 hours of operation. Powered by two 1.5V N type batteries (included). This item may require licensing: $80 (Cat L08) MAGNETIC CARD READER Commercial cased unit that will read some information from most plastic cards, needs 8 to 12V DC supply such as a plugpack. Draws about 400mA. Power input socket is 2.5mm DC power type. Weight: 850g. 220 x 160 x 45mm: $70 (Cat G05) 400 x 128 LCD DISPLAY MODULE - HITACHI These are silver grey Hitachi LM215 dot matrix displays. They are installed in an attractive housing. Housing dimensions: 340 x 125 x 30mm. Weight: 1.3kg. Effective display size is 65 x 235mm. Basic data for the display is provided. Driver ICs are fitted but require an external controller. New, unused units. $25 ea. (Cat D02) 3 for $60 VISIBLE LASER DIODE MODULES Industrial quality 5mW/670nM laser diode modules. Consists of a visible laser diode, diode housing, driver circuit, and collimation lens all factory assembled in one small module. Features an automatic power control circuit (APC) driver, so brightness varies little with changes in supply voltage or temperature. Requires 3 to 5V to operate and consumes approx 50mA. Note: 5V must not be exceeded and there must be no ripple on the power supply, or the module may be instantly destroyed. These items may require licensing. We have two types: 1. Overall dimensions: 11mm diameter by 40mm long. Driver board is heatshrinked onto the laser housing assembly. Collimating lens is the same as used in the above laser pointer, and our visible laser diode kit: $55 (Cat L09) 2. Overall dimensions: 12mm diameter by 43mm long. Assembled into an anodised aluminium casing. This module has a superior collimating optic. Divergence angle is less than 1milliradian. Spot size is typically 20mm in diameter at 30 metres: $65 (Cat L10) This unit may also be available with a 635nm Laser Diode fitted. FLUORESCENT LIGHT HIGH FREQUENCY BALLASTS European made, new, “slim line” cased, high frequency (HF) electronic ballasts. They feature flicker free starting, extended tube life, improved efficiency, no visual flicker during operation (as high frequency operation), reduced chance of strobing with rotating machinery, generate no audible noise and generate much reduced radio frequency interference compared to conventional ballasts. The design of these appears to be similar to the one published in the October 1994 issue of Silicon Chip magazine, in that a high frequency sine wave is used, although these are much more complex. Some models include a dimming option which requires either an external 100K potentiometer or a 0-10V DC source. Some models require the use of a separate filter choke (with dimensions of 16 x 4 x 3.2cm); this is supplied where required. We have a limited stock of these and are offering them at fraction of the cost of the parts used in them! Type A: 1 x 16W tube, not dimmable, no filter, 44 x 4 x 3.5cm: $20 Type B: 1 x 16W tube, dimmable, filter used, 43 x 4 x 3cm: $26 Type C: 1 x 18W tube, not dimmable, no filter, 28 x 4 x 3cm: $20 Type D: 2 x 32W or 36W tubes, dimmable, no filter, 43 x 4 x 3cm: $26 Type E: 2 x 32W tubes, not dimmable, no filter, 44 x 4 x 3.5cm: $22 Type F: 1 x 32W or 36W tube, not dimmable, no filter, 34 x 4 x 3cm: $20 Type G: 1 x 36W tube, not dimmable, filter used, 28 x 4 x 3cm: $20 Type H: 1 x 32W or 36W tube, dimmable, filter used, 44 x 4 x 3.5cm: $20 (Cat G09, specify type). CYCLE/VEHICLE COMPUTERS BRAND NEW SOLAR POWERED MODEL! Intended for bicycles, but with some ingenuity these could be adapted to any moving vehicle that has a rotating wheel. Could also be used with an old bicycle wheel to make a distance measuring wheel. Top of the range model. Weather and shock resistant. Functions: speedometer, average speed, maximum speed, tripmeter, odometer, auto trip timer, scan, freeze frame memory, clock. Programmable to allow operation with almost any wheel diameter. Uses a small spoke-mounted magnet, with a Hall effect switch fixed to the forks which detects each time the magnet passes. Hall effect switch is linked to the small main unit mounted on the handlebars via a cable. Readout at main unit is via an LCD display. Main unit can be unclipped from the handlebar mounting to prevent it being stolen, and weighs only 30g. Max speed reading: 160km/h. Max odometer reading: 9999km. Maximum tripmeter reading: 999.9km. Dimensions of main unit: 64 x 50 x 19mm: $32 (Cat G16) November 1995  85 VINTAGE RADIO By JOHN HILL How good are TRF receivers? In the early days of broadcasting, the TRF or tuned radio frequency receiver reigned supreme. Although there were odd superhets around from about 1924 onwards, they did not become really popular until a decade later. The reluctance of buyers to go the way of the superhet has always puzzled me as there is little doubt that the superhet was by far the better receiver. But price often dictates terms and it was perhaps for this reason that the TRF remained popular for so long. Another factor may have been that selectivity – the super­het’s main claim to fame – was less important This stylish looking Radiola 45E console is a 5-valve TRF receiver of 1930 vintage. Most 5-valve TRFs were reasonably selective because of their three tuned circuits but the cheaper 4-valve types had selectivity problems. 86  Silicon Chip while there were only a few stations on the air. As the number of stations in­ creased, better selectivity became more and more important. Nevertheless, in recent months I have restored a number of TRF receivers and, as a result, I have come to look upon them more favourably than I had in the past. Compared to super­hets of the same era, some TRFs were very good receivers – and still are! Back in those distant days of the early 1930s, the TRF receiver had reached the peak of its development, whereas the superhet was still in the developmental stage. Those early superhet designs were unduly complex and expensive, and there were problems with double spotting and the choice of a suitable IF. It also needed an extra valve for the local oscillator which, ac­cording to super­het opponents, “didn’t do anything”. This initial criticism created a marketing problem and it wasn’t until the mid to late 1930s that an acceptable design compromise was reached and the superhet came into its own. Let’s take a look at some of those old TRF receivers and try to ascertain just how good (or bad) they really were. The TRF receiver A TRF receiver must have at least one stage of radio fre­quency amplification ahead of the detector, typically a leaky grid or anode bend type. Those two stages alone constitute a TRF re- ceiver and a 2-valve set of this type is practical although it would be suitable for headphone use only. However, such a simple receiver can be greatly improved on. More valves and tuned circuits can be added to the front end to increase amplification and selectivity, while extra valves can be added after the detector to give increased amplification and more power output for the audio signal. These additions have their limitations, however, and three RF stages and three AF stages was about as far as most manufac­turers were prepared to go. Exceeding these limits could lead to instability unless special precautions were followed. Some of the cheaper TRFs had Another 5-valve TRF receiver. This set is typical of many early 1930s receivers that were made for a price. While the front looks good with its attractive walnut veneers, the sides were just very plain plywood. A 4-valve “el-cheapo” TRF receiver. This unit has been left unrestored and does not inspire much enthusiasm. It lacks aes­thetic appeal and its performance is poor to say the least. only 4-valves, including the rectifier. With just two tuned circuits, these simple budget-priced receivers were not very selective or sensitive. They did not perform as well as a 4-valve receiver with a regenerative detector, for example. Regeneration was, however, incorporated into some of the low priced TRFs which was perhaps a mixed blessing in a radio of this type. Positive feedback (regeneration) improves both sen­sitivity and selectivity quite dramatically but it can also introduce distortion and alter the tuning of the detector stage. Most TRF receivers did not use regeneration. still another tuned circuit. In fact, up to five tuned stages were used in a few of the really up-market receivers such as some of the American Majestics. Short wiring and well shielded stages allowed such receivers to be quite stable. They were very selective, extremely powerful and boasted a huge complement of valves. They also had a loudspeaker that could handle the power. The speaker alone in an old Majestic receiver weighs close to 10kg and the fully assembled sets were big and heavy to say the least. Perhaps one problem with some early TRF receivers was the fact that the ganged tuning capacitors used in the late 1920s and early 1930s were not manufactured to the precision standards that were to follow in later years. The same can be said for the RF coils used in these receivers. Component variations like this make perfect multi-stage alignment a difficult, if not impossible, process because, unless the tuned stages track together in near perfect unison, the set’s performance will be only mediocre. TRF receivers need to be well aligned. Valve limitations TRF receivers were first developed in the days when the triode valve was the only type available. However, there are two distinct disadvantages when using triodes as RF amplifiers. First, a triode valve does not have This mediocre 4-valve TRF receiver at least looks a bit different from the usual console. Actually, this Radiola 34E is a large table model that was sold with optional legs (circa 1931). a very high amplifica­tion factor and many valves are needed if high gain is to be obtained. Second, the internal capacitance between the grid and plate of a triode valve provides an unwanted positive RF feedback path between the plate circuit and the grid circuit. In an RF amplifier stage, with the plate circuit and the grid circuit The 5-valve TRF The standard 5-valve TRF was a better compromise, as it allowed three tuned circuits which gave more selective tuning. Even so, if such a set is operated in close proximity to a strong local broadcasting station, then that station will occupy a considerable portion of the dial. This clearly indicates the lack of selectivity of the basic TRF design. However, where the average TRF had a 3-gang tuning capaci­tor and limited selectivity, some of the better sets had 4-gang capacitors which added This 8-valve Apex receiver with its push-pull output stage performs rather well for an old TRF. Many budget-priced TRF receivers from the late 1920s were housed in pressed steel cabinets. November 1995  87 TRF receivers were at their peak when this unit was made. With its three 24As and 47 output pentode, it is quite a reasonable radio set. The chassis cleaned up quite well. both tuned to the same frequency, this feedback will cause instabili­ty, whereby the set bursts into uncontrollable oscillation. The triode’s feedback problem was overcome by a process known as neutralization and receivers using this technique were known as “Neutro­ dynes”, a registered trade name at the time. Neutrodynes have very stable RF amplifiers when the neutralizing capacitors are correctly adjusted. Unfortunately, the adjustment can be quite critical. The RF tetrode Neutralizing suddenly became history with the advent of the radio frequency tetrode, or screen grid valve. The tetrode val­ve’s screen grid, between the control grid and the plate, elimi­nated the positive feedback problem of the old triode. The screen grid valve had another advantage apart from better RF stability. It had a much higher amplification factor than the triode and this provided a significant boost to the performance of TRF receivers using screen grid valves. Speaking from my own experience, 88  Silicon Chip I believe that a tetrode TRF with two RF stages is roughly equivalent, in gain, to a triode TRF with three RF stages. The last of the TRFs went one better and used the first generation radio frequency pentodes. A TRF using these valves and using diode detection and automatic gain control could be quite an interesting receiver – if such a thing actually exists. (It most unlikely that such a commercial set was ever made, if only because there was no real mass demand. There was also a technical problem in that the tuned circuit feeding the detector had to be earthy on one side, which does not suit a conventional diode detector circuit. This problem could be overcome, with some difficulty, and home construction designs were published. Ed.) All of the mains-powered TRF receivers I have encountered use American-designed valves. The triodes are nearly always type 27, while the tetrode types have been 24, 24A and 35. No doubt there are a lot of sets around with other valves in them (26s for example, as well as European types) but the majority are these old faithfuls from the early AC era. Speaking of old faithfuls, the output valves seem to be either 71As, 45s or 47s. These old warriors are direct heated types with a rather heavy filament for thermal stability. Many of the better TRF receivers had twin output valves in push-pull. Such a setup can produce quite a few watts of output power and a set of this type can sound surprisingly healthy for such an ancient radio receiver. I have a 1929 Apex, an 8-valve set with two 45s in push-pull, and it really can make that speak­er cone rattle back and forth. Interestingly, only a few years earlier, around 1926-27, nearly all radio receivers were battery powered with outputs that were considerably less than half a watt. What was the latest thing in 1927 was completely obsolete by 1930. The radio scene changed rapidly during that period. Collecting TRF receivers From a collector’s point of view, any TRF receiver is a good find but they are few and far between. As far as mains-powered receivers are concerned, I have found only two in 10 years of collecting. On the other hand, I know a collector who has located about 10 in the past 12 months, so I ELECTRONIC VALVE & TUBE COMPANY VALVE SPECIALS! NEW SOVTEK SHIPMENT A typical layout for a TRF receiver – a tuning section with three valves, three coils and a three-gang tuning capacitor, all neatly arranged side by side. In addition, this receiver employs an output valve and a rectifier valve, giving five valves in total. 6L6GC 10.00 5Y3GT 12.00 EL34G 20.00 6V6GT 10.00 6CA7 5881 24.00 18.00 5AR4/GZ34 22.00 12AX7WA/7025 9.00 EL84/6BQ5 10.00 Matching at $1 per valve Prices valid until 31.12.95 Send SSAE for catalogue PO Box 381 Chadstone Centre Vic 3148 Tel/Fax (03) 9571 1160 or mobile 018 557 380 Silicon Chip Binders Buy subsc a & get a ription discou nt on the binder This old Apex chassis has an impressive line-up of valves. The rectifier is out of sight behind the transformer cover. The old style valves really look the part on this chassis. guess I must be looking in the wrong places. I do have a few battery-powered TRFs which I have yet to restore. Some are multi-dial types in which the tuning capacitors are not ganged but are individually controlled by separate dials. There is also another old battery operated Neutrodyne in the shed which has single knob tuning and it should make an interesting story one day. All I need is a little more time! Radio collectors are a funny lot with some specialising in receivers of specific types. Personally, I like to diversify and have a little bit of everything and that includes a few TRF receivers to maintain some kind of balance in my collection. As I stated earlier, I have come to look upon them more favourably than I had previously. So how good were those early TRF radios of the pre-superhet days? Well, they varied from poor to very good, with several categories in between. Then, as now, price dictated the quality of an item and if you paid out enough of that crinkly folding stuff, then you bought yourself a good radio SC receiver. These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a dis­tinctive 2-tone green vinyl & will look great on your bookshelf. Price: $A11.95 plus $3 p&p each (NZ $8 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. November 1995  89 Showing its turntable origins, this robot has two stepper motors mounted on the mast to operate the shoulder and elbow. The plat­ter is turned by a third stepper motor in place of the original belt drive. Build a PC-controlled robot from surplus parts What looks like a pile of timber and electronic scrap yet can be controlled by a computer? Answer: a robot based on the stepper motor drivers described in the January 1994 issue of SILICON CHIP. It is a cheap and cheerful introduction to robotics using readily available parts and surplus stepper motors. By TONY MERCER* Designed as a practical exercise in robotics and PC control for TAFE students, this robot uses software written in Visual BASIC. It is interfaced to a PC’s printer port and, using on-screen menus, is controlled with the keyboard and mouse. 90  Silicon Chip The robot presented here is a demonstration unit only, as an example of what is possible. It is a 3-axis device with a waist, a shoulder and an elbow which has an attached gripper. The waist is made from a record turntable which can be cheaply ob­tained from a secondhand shop. The shoulder and elbow driver arms are made from discs of customwood 300mm in diameter and belt-driven by two servos. The gripper mechanism is made from 24-gauge galvanised steel scrap and is powered by a small geared motor. The stepper motor article in the January 1994 issue of SILICON CHIP was quite comprehensive, particularly in regards to stepper motor technology (back issues are available at $7 includ­ ing postage.) Kits for the stepper motor board are currently available from Altronics in Perth – ­ phone (09) 328 1599. This project makes use of two of these boards, one to drive two stepper motors and the other to handle a third stepper motor and up to four solenoids. You can also opt to use just one step­per board to drive two stepper motors or one stepper motor and four solenoids. Depending on what approach you take, some changes will be required, as detailed in the section headed “Solenoid Test”. Apart from being able to actuate motors and solenoids, it is also possible to connect up to five different sense lines. Four sense lines are used in this project. An individual sensor line will have a 10kΩ resistor pulling it to the +5V rail on the driver board – see Fig.1. In this case, the line will normally be high or a “1”. If the line is brought to ground, it will be low or a “0”. This can be done using a switch or an open-collector transistor, as shown in Fig.2. We can not only step the motors, and be confident of their final positions, but can also sense the result of these actions or any other sensory input we might be interested in. It may be that we are using the robot to lift something from the flat car of a model train, for example, but not until the flat car is in position. The robot software can be programmed to wait until this happens and then to proceed from there. We can also use the solenoid outputs to turn a DC motor on in either direction and use the sensors to sense when an action has been completed. The boards are connected in daisy chain fashion via a length of 25-way ribbon cable. A 25-pin IDC male plug is used for the computer connection and two 25-pin IDC female plugs for the stepper drivers. The plugs are attached to the cable as shown in Fig.3. Software The software handles the operation of the robot and in­cludes diagnostic This is one of seven screens used by the software to control the robot. The different levels add program features in a way which makes it less confusing for the novice (level 5 shown). This is the final screen (level 7) used to control the robot and it adds the AND/ OR function. The various levels are stepped through by clicking on the level box at the bottom righthand corner of the screen. screens for testing the stepper boards’ operation, as an aid to debugging the system. Fig.1: individual sensor lines will have a 10kΩ resistor pulling them to the +5V rail on the driver board. In this case, the line will normally be high or a “1” As pointed out in the January 1994 article, a stepper motor is designed to rotate a specified distance when a Fig.2: the sensor lines can be pulled low using a switch or an open-collector transistor, as shown here. November 1995  91 Fig.3: the stepper boards are connected in daisy chain fashion via a length of 25-way ribbon cable. A 25-pin IDC male plug is used for the computer connection and two 25-pin IDC female plugs for the stepper drivers. Fig.4: the waist of the robot uses a toothed belt driven by a stepper motor. Since the platter will not need to rotate any more than 270° or so, the belt will not need to wrap around the entire circumference but can be attached at two points with screws. pair of wires has current sent through them. This step (usually in the range of 1.8° to 7.5°) is determined solely by the mechanical char­acteristics of the motor and not by any voltage level or rate of application. Once the step has taken place and provided the voltage is still applied, the motor will be locked in position. To obtain another step from the motor, a voltage has to be applied to 92  Silicon Chip another set of wires and then another set, and so on. Stepper motors come in a variety of types – 4-wire, 6-wire and 8-wire – and how these are connected to the driver boards is explained in the January 1994 article. The software moves the robot arms by pulsing the stepper motors a certain number of times. Provided that there is no slippage, the arms should go to the position required. However, stepper motors do have inertia. If a loaded motor is presented with a pulse sequence that is too fast, it will just hunt back and forth. Similarly, if a motor running at maximum speed is suddenly deprived of its pulse train, it will tend to run on. While no damage is likely, the program will lose vital positional data and think that the arm is somewhere other than where it actually is. The software needs to take care of this. The way to control the speed of a stepper motor is to vary the rate of its driving pulses. To accelerate the motor to its final running speed, the pulse rate is slow at first and then increases. Deceleration is the reverse procedure. If the software is instructed to move an arm to a specified position, it needs to know where it is and where it is to go to. To achieve this, the software uses two registers, called the current position and the programmed position. The software com­pares these two resisters and computes a difference. It will then issue a number of pulses to the designated stepper motor. Once done, it will look at other current and programmed positions and repeat this operation until there are no more differences. The current register contains only stepper motor positions and solenoid and sensor status. The program position is a 2-dimensional array, one dimension holding the new required position (which when done will become the new current position) and the other dimension a list of all the future positions. When the software is run, it starts by comparing the cont­ents of its current register with the register contents of the first location in the array. It will look at stepper motor one and if it sees a difference it will take action to reduce this difference to zero. If the current content is a number less than the programmed position, a positive difference results and the current motor counter will increment to the new number. If the current motor content is a number greater than the programmed content, then the difference will be negative and the current motor counter will decrement to the new number. When this is done the next motor is interrogated and so forth. When all the motors are positioned, the software will look at the solenoids. As the so- lenoids can only be on or off, it will merely turn on those that are required and turn off those that are not. Next, the input sensors are interrogated. By now it should be clear that the program is running a set of positional data contained in the 2-dimensional array. Each new program position contains a complete set of positional requirements for each of the stepper motors and solenoids. There’s a great deal more in the programs, as will become apparent later in this article. Teaching the robot to move As noted above, the control program has a series of seven on-screen menus (Level 1-7) and you control the actions of the robot with the keyboard and mouse. When the robot starts, the screen will be in Level 1. From this screen you will be able to manually move the motors, select motor speed, select a higher level, observe the current motor position, set the base motor timing and Exit the program. Before setting the position of any of the motors, you first need to set the speed. Because stepper motors are critical of pulse rate, it needs to be carefully set. Each pulse is a result of a series of internal program steps, updating the screen, etc. Howev­ er, computers operate at different speeds depending on whether they have a 286, 386, 486 or other processor and if they have the turbo facility on or not. To overcome this variation in computing speed, we need to set a variable in the program. As you view the main program screen you will see a “set timing” button in the upper right-hand corner. Clicking on this will cause the program to test its internal timing and produce a number unique to this configura­tion. When the motors are now actuated you should see a fairly consistent speed. When the program is started it will automatically set the base speed. You need only alter it if you have changed the status of the turbo facility. You can also change the speed in five increments with the button at the bottom righthand corner. Clicking on it will increment it up to 5 (fastest) and then back to 1 (slowest). To position a particular stepper motor, click on the one you want and the screen will change to provide further instruc­tions. Briefly, the left mouse button is pressed to move the Three diagnostic screens are featured in the software. This one is used to check the operation of the stepper motor driver boards which were described in the January 1994 issue of SILICON CHIP. The operation of up to five sensors is checked using this diagnostic screen. A third screen is used to check the operation of the solenoids. motor clockwise while the right mouse button is pressed to move in the other direction. Pressing any key on the keyboard will return you to the main menu. While the motor is moving you will see a counter incrementing or decrementing, depending on which direction you are moving. If the motor movement is erratic, the speed you are using might be too high. Select a slower speed and try again. You may also experience erratic motor operation because the load is too high, the voltage applied to the motor too low or the current limiting resistors (if used) on the stepper board are too large. Once back in the main menu you can either select another motor or you can exit. To leave the program, click on the Exit button and you will return to the beginning menu. To exit alto­gether, select Exit and you will be returned to the DOS prompt. Level 2 adds more functions to the screen: four solenoids, four sensor inputs and Clear facilities for the current step motor locations. If you require a solenoid to actuate, just click on the one that you want. If you want to disable a particular solenoid, click on the solenoid button and you will see it toggle off. Home position To the right of the stepper motor button is the CLR button which will clear the contents of the current November 1995  93 Fig.5: the mast is attached to the turntable platter using two pieces of 25 x 50mm dressed pine 450mm long using four angle brackets. Two steppers are mounted on the mast to operate the shoulder and elbow discs via toothed belts. 94  Silicon Chip register for this motor to zero. When you first start to use the program you must “home” the actuated arms. You do this by moving the arms to the midpoint of each arm’s travel. For repeatability, you should mark this “home” position with a pencil. On return to the main menu, you press the clear button and this current location will be “home” or zero. Be careful that you do not clear the register after this as you will confuse the program logic. Because of this, the clear function is hidden from view until the level control (bottom righthand corner) is incremented to 2 . This is done so that you do not accidentally click on it. Level 3 adds the facility to store settings in memory. The new buttons are AddMem, NewPg, Run, SetStep and StpPg. NewPg clears the memory prior to a new program. SetStep sets the step number to 1 so that the program can start from here. Stp Pg stops the program but only after all the individual locations have been interrogated and Run commences operations. You can add the new location(s) to memory, which is what the new positional array is called, by clicking on the AddMem button. The speed information is also loaded. You will see the step number and program end labels increment and the program location change to the current value. Repeat this as often as you need with this and the other motors. Before writing a new program you should list on a piece of paper the moves you want to take place and include on this the actual numbers for each position, the solenoid and sensor status and branch and wait conditions. Once the program is being run and you are debugging it there may be changes that you will want to make. Level 4 has several development tools for this. These comprise six new but­ tons, as follows: Single Step (Sglstep) allows the program to execute one complete step and then you will see the contents of the next position that the program will go to; the new stepper motor positions, solenoid and sensor requirements and Branch and Wait Until. Pressing the button again will cause the program to per­form these operations and you will be presented with the contents for the next step. If you want to change any of this, use the Change button. Clicking on this button brings up a screen that tells you to click on the function that you want to change. The select­ed function will not alter its state but merely load the new state into the current program step. Move Forward increments the step number and displays the next lot of contents. No other action will take place. Move Backward does the same thing, only in the reverse direction. The Insert button allows you to insert new locations into the program. In this case, the program end counter and step number will increment and the insertion will assume the current step number. Save program When you want to save the program click on the SaveP button and a copy of the program array will be loaded onto the default disc. Level 5 adds the Wait Until facility. With this you can stop program execution until a selected condition is sensed. You need to click on the sense input that you want ‘high’ for the program to continue. At this level you can ‘OR’ up to four sense lines. The program will advance when any of them become high. Level 6 adds the Branch function. You will see the current step number appear in the box below the BR button. Click on the UP or DN buttons to tell the software where you want the program to branch to and the Unco button for conditional or unconditional branch. As for the Wait Until function, the conditional branch will occur when any of the sense lines you have selected goes high. Level 7 adds the AND/OR facility. In the AND case, the Wait Until or Branch will not occur unless all the selected sense lines go high. In order to help in the debugging of the electronics there are three diagnostic screens: Stepper Motor Test, Solenoid Test and Sensor Test. Making the robot As noted previously, the waist is made from a record turnt­able which can be cheaply obtained from a secondhand shop. Remove the tone arm mechanism and the drive motor which is replaced with a stepper motor. The stepper can be coupled to the platter using a toothed belt, as depicted in Fig.4. Fig.6: the shoulder arm and elbow driver arm are made from discs of customwood 300mm in diameter. These are driven by steppers and toothed belts. Since the platter will not need to rotate any more than 270° or so, the belt will not need to wrap around the entire circumference but can be attached at two points with screws. The stepper motor will need a November 1995  95 Made of sheet metal, the gripper is similar in principle to a bicycle’s brake calliper. Note the elastic bands which provide tensioning. toothed pulley to match the belt. The 6-wire motor supplied by Oatley Electronics is an unusual size (pitch 2.07mm). R & I Instrument and Gear Co Pty Ltd, Box 1302, South East Mail Centre, Vic 3176, can supply a belt of the right length and almost the right pitch (2.03mm). Alternatively, the prototype was driven by the origi­nal turntable rubber belt using a stepper motor giving 1.8° per step. Mast For the mast, attach two pieces of 25 x 50mm dressed pine 450mm long to the turntable, using four angle brackets as shown in the diagram of Fig.5. Drill a 6mm hole through the top of the mast to accept a 6mm bolt 150mm in length. The shoulder arm and elbow driver arm are made from discs of customwood 300mm in diameter. Fasten these so that they are free to rotate alongside each other. Fasten another stepper motor to the mast and connect it to the shoulder in the manner shown in Fig.6. The resulting movement of the shoulder will be something less than 180° but this was not found to be a problem. Again the mechanical connection to this will need to be deter­ mined by you. Note that there will 96  Silicon Chip Fig.7: the gripper is similar to a bicycle brake calliper in concept and is actuated by a geared motor pulling a string against tension provided by rubber bands. Fig.8: two relays connected to the solenoid outputs provide for control of the gripper motor. RLY2 connects voltage to the DC motor while RLY1 controls the motor direction. be more load on this axis than on the waist, considering that we are actually going to lift something. To this 300mm disc attach a piece of 25 x 50mm dressed pine so that the reach is extended by 150mm. This is power­ed by a stepper motor in the same manner as for the shoulder. From 150mm pieces of light timber construct a box section as shown and connect the driving arms at right angles. The distance between the outer points and the axis will need to be the same as the dimensions on the 300mm disc. Now, using light dressed timber, make two driving arms and fasten them to the box section. The driving arm lengths need to be the same as the distance between the centre of the 300mm half and the pivot point of the elbow. Other methods could be used to mechanically attach the stepper motor to the arm. For instance, a length of threaded rod can be connected to the stepper motor shaft and the arm connected to this via a threaded nut. Gripper The gripper was made from 24 gauge galvanised steel sheet. It is similar to a bicycle brake calliper in concept and is actu­ated by a geared motor pulling a string against tension provided by rubber bands – see Fig.7. The mass of the gripper and its motor are counterbalanced by weights at the other ends of the arms. Using a piece of Veroboard and two relays build the circuit of Fig.8. One of the relays, RLY2, is actuated by the solenoid 2 output and will connect a voltage to the DC motor. The other relay, RLY1, is driven by the solenoid 1 output so that the motor direction can be forward or reversed. Two switches will be attached to the first two sensor in­puts; the closed switch to sensor input 1 and the other to sensor 2. One will be ‘high’ when the gripper is open and when it is closed the other will be ‘high’. Once the robot is completed, you are ready to program it to pick up something by using the manual position and remembering buttons. To use the gripper, the following sequence may be of help. (1). Select the sensor being used to determine grip closure. (2). Click on the Wait Until and OR control. (3). Select the solenoid that governs the direction of motor move­ ment. Whether or not this is set or reset depends on how you have wired the relays and the polarity of the motor drive supply. (4). Select the solenoid that turns the gripper motor on. The motor should start to move. You may like to wait until the sensor indicating the gripper is closed goes high and then turn the power off to the motor. This should prevent any damage to the mechanism if you are not quick enough to add this to memory and then turn the solenoid off. (5). Add to Memory. (6). When the the sensor for gripper closure comes on (goes high), the gripper is closed. De-select the solenoid that turns the gripper motor on. The gripper motor should stop. Reapply power again if you had already disconnected it. (7). Add to Memory. Position the gripper and load to where you want it to be, using the methods as described before. Open gripper To open the gripper the following may prove useful. (1). Select the sensor that indicates that the gripper is open. Make sure that you de-select the sensor that indicates gripper closure and the other two sensors. Failure to do this will result in no operation when the Wait Until function is set, as you can not have the gripper open and closed at the same time. (2). Click the Wait Until and OR operation. (3). Select the solenoid that governs gripper motor direction. (4). Select the solenoid that causes the gripper motor to oper­ate. The gripper motor should now be running and allowing the gripper to open. Again, you may want to disconnect power as for the closing sequence. (5). Add to Memory. (6). When the indicator that shows the gripper has opened comes on de-select the solenoid that powers the gripper motor. Reapply power if you went down this path. (7). Add to Memory. Position the gripper for another operation or branch back to repeat the sequence. A simple gripper open/close function is included in the registered This photo shows a stepper motor mounted in place of the origi­nal belt drive motor, to provide movement for the waist. A geared 12VDC motor operates the gripper, against tension provided by two elastic bands. version of the software (see below). Further reading (1). Robot Builders’ Bonanza, by Gordon McCombs. Published by Tab Books. Software availability Shareware versions of this software can be obtained by sending $8 to NewTech Education Resources, PO Box 61, Ferntree Gully, Vic 3156. Details of the registered version of the soft­ware will SC be on the disc. * Tony Mercer is a lecturer in technology studies at the Hawthorn Institute of Technology and can be contacted during office hours by phoning (03) 9810 3279. November 1995  97 Silicon Chip Supply For Burglar Alarms; Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; Using The NE602 In Home-Brew Converter Circuits. BACK ISSUES September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; All About Electrolytic Cap­acitors. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages); UHF Remote Switch; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Index to Volume 2. November 1990: How To Connect Two TV Sets To One VCR; A Really Snazzy Egg Timer; Low-Cost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Simple 6-Metre Amateur Transmitter. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speed­ing Up Your PC; Phone Patch For Radio Amateurs; Active Antenna Kit; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape – A Game Of Skill; Wiper Pulser For Rear Windows; A 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. 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. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. March 1990: 6/12V Charger For Sealed Lead-Acid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception; How To Find Vintage Receivers From The 1920s. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Fitting A Fax Card To A Computer. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2. September 1990: Remote Control Extender For VCRs; Power June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. July 1991: Battery Discharge Pacer For Electric Vehicles; Loudspeaker Protector For Stereo Amplifiers; 4-Channel ORDER FORM Please send me a back issue for: ❏ July 1989 ❏ September 1989 ❏ January 1990 ❏ February 1990 ❏ July 1990 ❏ August 1990 ❏ December 1990 ❏ January 1991 ❏ May 1991 ❏ June 1991 ❏ October 1991 ❏ November 1991 ❏ March 1992 ❏ April 1992 ❏ August 1992 ❏ September 1992 ❏ March 1993 ❏ April 1993 ❏ August 1993 ❏ September 1993 ❏ January 1994 ❏ February 1994 ❏ June 1994 ❏ July 1994 ❏ November 1994 ❏ December 1994 ❏ April 1995 ❏ May 1995 ❏ September 1995 ❏ October 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ September 1988 October 1989 March 1990 September 1990 February 1991 July 1991 December 1991 May 1992 October 1992 May 1993 October 1993 March 1994 August 1994 January 1995 June 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ April 1989 November 1989 April 1990 October 1990 March 1991 August 1991 January 1992 June 1992 January 1993 June 1993 November 1993 April 1994 September 1994 February 1995 July 1995 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ May 1989 December 1989 June 1990 November 1990 April 1991 September 1991 February 1992 July 1992 February 1993 July 1993 December 1993 May 1994 October 1994 March 1995 August 1995 Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ____________________________ Card expiry date_____ /______ Name _______________________________ Phone No (___) ____________ PLEASE PRINT Street ________________________________________________________ Suburb/town ________________________________ Postcode ___________ 98  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 979 5644 & quote your credit card details or fax the details to (02) 979 6503. ✂ Card No. Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Step-By-Step Vintage Radio Repairs. September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & Ultralights, Pt.1; The Basics Of A/D & D/A Conversion; Windows 3 Swapfiles, Program Groups & Icons. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Alti­meter For Gliders & Ultralights, Pt.2; Getting To Know The Windows PIF Editor. November 1991: Colour TV Pattern Generator, Pt.1; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Solid-State Laser Pointer; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Automatic Controller For Car Headlights; Experiments For Your Games Card; Restoring An AWA Radiolette. Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Step-Up Voltage Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Remote Volume Control For Hifi Systems, Pt.1; Alphanumeric LCD Demonstration Board; The Micro­soft Windows Sound System. June 1993: Windows-Based Digital Logic Analyser, Pt.1; Build An AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Remote Volume Control For Hifi Systems, Pt.2 July 1993: Build a Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Windows Based Digital Logic Analyser; Pt.2; Quiz Game Adjudicator; Programming The Motorola 68HC705C8 Micro­controller – Lesson 1; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; A Microprocessor-Based Sidereal Clock; The Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Aircraft Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Electronic Engine Management, Pt.12. October 1994: Dolby Surround Sound – How It Works; Dual Rail Variable Power Supply (±1.25V to ±15V); Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuv­enator; A Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Cruise Control – How It Works; Remote Control System for Models, Pt.1; Index to Vol.7. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Preamplifier; The Latest Trends In Car Sound; Pt.1. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. February 1992: Compact Digital Voice Recorder; 50-Watt/ Channel Stereo Power Amplifier; 12VDC/240VAC 40-Watt Inverter; Adjustable 0-45V 8A Power Supply, Pt.2; Designing A Speed Controller For Electric Models. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1; Programming The Motorola 68HC705C8 Micro­controller – Lesson 2. March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty Stereo Amplifier, Pt.1; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Direct­ories; Valve Substitution In Vintage Radios. November 1993: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Electronic Engine Management, Pt.2; Experiments For Games Cards. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. December 1993: Remote Controller For Garage Doors; Low-Voltage LED Stroboscope; Low-Cost 25W Amplifier Module; Build A 1-Chip Melody Generator; Electronic Engine Management, Pt.3; Index To Volume 6. May 1992: Build A Telephone Intercom; Low-Cost Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Electronic Engine Management, Pt.4. May 1995: Introduction To Satellite TV; CMOS Memory Settings – What To Do When the Battery On Your Mother­ board Goes Flat; Mains Music Transmitter & Receiver; Guitar Headphone Amplifier For Practice Sessions; Build An FM Radio Trainer, Pt.2; Low Cost Transistor & Mosfet Tester For DMMs; 16-Channel Decoder For Radio Remote Control. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; Infrared Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. February 1994: 90-Second Message Recorder; Compact & Efficient 12-240VAC 200W Inverter; Single Chip 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Electronic Engine Management, Pt.5; Airbags – How They Work. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; A 1W Audio Amplifier Trainer; Low-Cost Video Security System; A Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Multi-Station Headset Intercom, Pt.2; Electronics Workbench For Home Or Laboratory. March 1994: Intelligent IR Remote Controller; Build A 50W Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Electronic Engine Management, Pt.6. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; Dummy Load Box For Large Audio Amplifiers; Internal Combustion Engines For Model Aircraft; Troubleshooting Vintage Radio Receivers. April 1994: Remote Control Extender For VCRs; Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Low-Noise Universal Stereo Preamplifier; Build A Digital Water Tank Gauge; Electronic Engine Management, Pt.7. July 1995: Low-Power Electric Fence Controller; How To Run Two Trains On A Single Track (Plus Level Crossing Lights & Sound Effects); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder; Adding RAM To Your Computer; Philips’ CDI-210 Interactive CD Player. September 1992: Multi-Sector Home Burglar Alarm; Heavy-Duty 5A Drill speed Controller (see errata Nov. 1992); General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads; Build A Relative Field Strength Meter. October 1992: 2kW 24VDC To 240VAC Sine­wave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Regulated Lead-Acid Battery Charger. January 1993: Peerless PSK60/2 2-Way Hifi Loudspeakers; Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; MAL-4 Micro­controller Board, Pt.3; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.5. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Two Simple Servo Driver Circuits; Electronic Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; An 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; A PC-Based Nicad Battery Monitor; Electronic Engine Management, Pt.9 July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. March 1993: Build A Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Low-Cost Audio Mixer for Camcorders;A 24-Hour Sidereal Clock For Astronomers. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Build a Nicad Zapper; Simple Crystal Checker; Electronic Engine Management, Pt.11. April 1993: Solar-Powered Electric Fence; Build An Audio September 1994: Automatic Discharger For Nicad Battery March 1995: 50W/Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. April 1995: Build An FM Radio Trainer, Pt.1; Photographic Timer For Darkrooms; Balanced Microphone Preamplifier & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. August 1995: Vifa JV-60 2-Way Bass Reflex Loudspeaker System; A Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; The Audio Lab PC Controlled Test Instrument, Pt.1; The Mighty-Mite Powered Loudspeaker; An Easy Way To Identify IDE Hard Disc Drive Parameters. September 1995: Build A Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walk-Around Throttle For Model Railways, Pt.1; Build A Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2; Automotive Ignition Timing, Pt.1; Running MemMaker & Avoiding Memory Conflicts. October 1995: Build A Compact Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walk-Around Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1; Automotive Ignition Timing, Pt.2. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, Aug­ust 1989, May 1990, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear­sheets) at $7.00 per article (includes. p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. November 1995  99 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. How to stack bow-tie arrays I live in a very poor TV reception area. We have four local channels on UHF from a translator which is not line of sight and not supposed to cover our area anyway. VHF is a complete no-go. I was using a 20-odd element Yagi with a masthead amplifier which gave a fair picture on two channels and a lousy picture on the other two. I then built the 4-Bay Bow-Tie Antenna, featured in the July 1994 issue, with great success. I now have a good picture on two channels most of the time and just OK on the other two. Ever searching for a better picture, my questions are: (1) How do I phase another bow-tie array with this one for more gain? (2) Can you give the theoretical measurements for the feed lines, and what would the output impedance be? (3) Could the reflective elements be made of heavy gauge “wire netting” like some cheaper bow-ties that are around and would this result in reduced gain? In the July 1995 issue you had a questions from I. M. of Schofields about his soldering iron station. I built Sermons via FM radio I wonder if you can help me with a problem experienced in my local church. A few of the congregation have poor hearing and have trouble following the service. I wonder if it would be practical to provide and inductive loop around the church and feed the audio from the PA amplifier to it. Or would it be more practical to invest in a number of infrared headphones and the necessary infrared transmitter? (A. P., Bundaberg, Qld). • Either approach could probably be made to work, depending on the size of the church. However, 100  Silicon Chip the solder­ing station and experienced the same problem; eg, not heating unless I force the Triac to conduct with a potential on its gate. After replacing IC2, I found the current through LED2 and there­fore through the internal LED of IC2 was not enough to make its Triac conduct. I therefore decreased the 1kΩ resistor in series with LED2 to 510Ω. This seems to be working OK for some months now. I also found the quoted voltages around IC1b to be nothing like mine. Ohm’s Law says they should be as you say, but not in my example, even though it’s working fine. (P. M., Toormina, NSW). • We have not published any information on the topic of stack­ing antennas and can only comment in general. Firstly, hori­zontal or vertical stacking will give essentially the same signal pickup. Horizontal stacking is to be preferred if you want to cancel ghost reception while vertical stacking will narrow the vertical acceptance angle and suppress aircraft induced interfer­ ence (eg, picture rolling). As far as signal pickup is concerned, the spacing is not critical but the cables from each array should be short and equal in length. The reflector can an easier approach, which would work in churches large or small, would be to feed the audio signal to the miniature FM stereo transmitter featured in the October 1988 issue. With the signal being radiat­ed in the FM band between 88 and 108MHz, people in the congrega­ tion could then just bring their own Walkman-style receivers to be able to listen in comfort using unobtrusive earpieces. Any member of the congregation found listening to the wrong program could be asked to double their weekly donation! A kit for the FM transmitter is readily available from all kitset suppliers and we can supply photostat copies of the original article for $7 including postage. be made of wire netting and this will have no effect on the gain or front-toback ratio. Woofer stopper should be triggered by barking Since my last letter on this subject, I have since tried out a commercially available device, American made, called a “Barker Breaker”, intended to be placed near to where the problem dog might be. It is triggered by the sound of the dog’s bark and I guess by other loud noises but the sensitivity of the microphone is adjustable and maximum pick up range seems to be about 6-8 metres and fairly directional. It is suggested that it be mounted under the eaves of the house and the claim is that its use over a period will condition the dog not to bark, at least in that vicinity. There is also a manual trigger control, to enable the unit to be carried in your pocket and used to frighten off at­tacking stray dogs. Two drawbacks with this unit stopped me buying it. First, the price, about $150, is rather more than a Woofer Stopper. Second and, more importantly, its sound output is well within the range of human hearing and is loud enough to likely cause more annoyance to the neighbours than the dog’s bark. It also seems to have little deterrent effect on our dog, which simply gives a slightly irritated glance it its direc­tion, as if to say “and who’s making that unseemly racket?”. The Woofer Stopper, similarly triggered, would seem to offer a far more practical solution. Please reconsider? (J. P., Kaleen, ACT). • This project has certainly touched a sensitive chord in many people. Some people are so troubled with barking dogs that they would seem to be on the edge of a nervous breakdown. In some cases, the dogs concerned have been so far away that no electronic device could possibly solve the problem. Selfish and unthinking dog owners can certainly cause a lot of anguish for other people. Info on 250VAC capacitors enclosed which is a cir­cuit card from a range hood sold on the Australian market – see photo. You will note the resistor (lead broken in handling) and the capaci­tor used to drop the voltage. In this case the capacitor is rated at 250VAC. The burn marks appear to have been sufficient to start a fire had there been combustible material around. Fortunately, this was enclosed entirely in metal and the range hood was only about 1 year old and had no grease as would typically accumulate with use. I am not sure of the exact function of the PC board. Resis­tors R7 & R8 (thermistors?) stick out on opposite sides of the grease filter and I presume it shuts off the fan if insufficient air flow exists or perhaps shuts off the fan I refer to your answer to J. K on page 92 of the August 1995 issue in which you state, “provided these capacitors do have the correct 250VAC rating and also a suitably rated limiting resistor is placed in the circuit, such circuits should be safe”. I would like to hear further comment on this practice as it applies to the making and use of mains filters used in the supply leads to computers and hifi sets. The use of a sacrificial resistor in series with the capacitors would appear to reduce their effectiveness as a filter, so should we use, in this case, a series fuse rated just above the load current of the appliance? (B. P., Port Macquarie, NSW). • Generally, the ca- This photo shows the faulty 260VAC circuits. The PC pacitors used in filters board controls the fan in a range hood. are much smaller than in circuits used to derive low voltage on temperature. The active lead is red, rails from the mains. We agree that neutral blue, and the white lead feeds series resistors would prejudice their the switch to the fan motor. This was removed from a new apartoperation but fuses would be a problem too since they may be subject to ment in a complex of ap­proximately nuisance tripping. In any case, such 100 units. The tenant advised that mains rated capacitors are now very several of their neighbours had said their range hoods didn’t work as well. I widely used in switchmode power supplies in computers, TV sets and would be very interested in your ideas other equipment and they appear to on what the sequence of failure was on both items. (D. H., Annandale, NSW). be quite reliable. • In the circuit with insulation tape around it, it is clear that the capacitor More info on 250VAC has had a catastrophic short circuit capacitors which led to the fire. As far as we can I wrote to “Ask SILICON CHIP” in tell, the capacitor in the fan control is April 1994 and I told of my bad ex- intact. Without being able to refer to perience using capacitors to reduce the circuit, it is difficult to know just mains voltage to electronic circuits. I what has failed in the unit. We should point out that today’s am enclosing the original component­ 250VAC capacitors are supposed to be ry which caught fire. Note that the tape is fibreglass made by 3M as high tem- self-quenching in the event of a short perature insulating tape from the USA. and there­fore should not give rise to SC flames and smoke. This brings me to the second item AVICO POWER PRODUCTS APPROVED I E C CONNECTORS Avico Electronics now have available, a range of NSW Dept. of Energy approved “IEC” 3 PIN connectors. Features Include: • Rated at 240Vac 50Hz <at> 10A • 5mm wide solder or spade terminals • Clip or screw mounts • Integral fuse holder MODELS AVAILABLE IEC1 - Standard panel “clip mount” 3 pin Male socket......... RRP $1.45 IEC2 - Panel “screw mount” 3 pin Male socket............... RRP $1.45 IEC3 - Standard panel “clip mount” 3 pin male socket with fuse holder......... RRP $4.45 IEC4 - Panel “screw mount” 3 pin Male socket with fuse holder............... RRP $4.45 IEC5 - Standard panel “clip mount” 3 pin Female socket...... RRP$1.45 IEC6 - Panel “screw mount” 3 pin Female socket............ RRP $1.45 IEC7 - Dual socket panel “clip mount” 3 pin Male/Female......... RRP $4.95 IEC14 - Right angle plug screw terminating 10A 240Vac 3 pin Female plug.... RRP $2.95 IEC15 - Inline plug screw terminating 10A 240Vac 3 pin Female plug........ RRP $2.45 Imported and distributed by AVICO ELECTRONIC PTY LTD PHONE: (02) 624-7977 FAX: (02) 624-7143 Trade Enquiries Only ASK FOR AVICO PRODUCTS AT YOUR FAVOURITE ELECTRONICS RETAIL STORE We still think that having the Woofer Stopper automatically triggered by the sound of a dog barking is not practical. However, we will reconsider the concept and perhaps produce a higher-powered device. No promises, though. November 1995  101 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES FOR SALE Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 979 6503. INVERTERS 12V-230VAC 90% EFFICIENCY. Modified Sine Wave. Compact 55 x 160 x 98mm. Light 800gm. Standby 50mA/0.6W. 100 Watt Continuous $99. 200 Watt $149. A.S.S. (09) 349 9413, fax (09) 344 5905. _____________ _____________ _____________ _____________ _____________ INFRA-RED CORDLESS RECHARG­ EABLE STEREO HEADPHONES. 20Hz-20kHz. Lightweight. $69. A.S.S. (09) 349 9413, fax (09) 344 5905. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ TINY 2/3 MATCHBOX SIZE VIDEO CAMERA MODULES $169. RF MODULATOR $30. Patch these into your TV Antenna System Display and/or Record on all TVs & VCRs. VERY FLEXIBLE & PRACTICAL VIDEO SUR­VEILLANCE PACKAGE only $199. Camera 400+ TVL, 35 x 35 x 25mm incl Lens, Auto Iris, Infra-Red & Low Light Sensitive. IR LEDs 50mW pkt/30 $15 SEE IN TOTAL DARKNESS. A.S.S. (09) 349 9413, fax (09) 344 5905. D.I.Y. PACKAGED CCTV SYSTEMS. $699. 10" Monitor 4 Ch Switcher, Camera, 20M Cable & Stand PLUG-IN & GO! Features Two-Way Inter­com, Alarm I/Ps, VCR I/O, 400 TVL 0.2 Lux Low Light & IR Sensi­tive Camera. A.S.S. (09) 349 9413, fax (09) 344 5905. CLOSED CIRCUIT VIDEO EQUIPMENT. Mono & Colour Cameras incl. Lens from $249. 32 x 32 x 15mm Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Card No. ✂ ❏ Bankcard   ❏ Visa Card   ❏ Master Card Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 102  Silicon Chip RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 CONCEALED PINHOLE Modules from $239. 4 & 8 Ch Quad & Freeze Screen Splitters & Switchers from $239. Combination Modulator/Antenna Boosters to Display/Record Video on TV/VCR. Video Microscopes 10X to 1000X. Discounts 10% - 37.5%. A.S.S. (09) 349 9413, fax (09) 344 5905. EDUCATIONAL ELECTRONIC KITS: easy to build. Good quality. Up-to-date technology. Cheap. Guaranteed to work. Wide range selection. Send $2.00 in stamps for catalogue and price list. Or log onto our BBS FREE for full details of every kit. DIY ELECTRONICS, 22 McGregor Street, Numurkah, Vic 3636. Ph/Fax (058) 62 1915. Ph/BBS (24hr) (058) 62 3303. BasicMicro-1 Kit programs in Basic from LPT1 $65. New fast low-power PIC16C84 Micro $15 and Programmer $20. Erase: 2 secs. Burn In-Circuit: 2010 secs. 18/28 pin PIC proto PCB $20. Free promo disc covers all kits. <finger donmck<at>tbsa.com.au> 68HC705 DEVELOPMENT SYSTEM: Editor, assembler, In Circuit Simula­tor and Programmer board. Oztechnics, PO Box 38, Illawong, NSW 2234. Phone (02) 541 0310. Fax (02) 541 0734. email:OZTEC<at>OZE­MAIL.COM.AU. YOUR UNUSUAL PARTS source: UCN5804B, DS1620, DS1202, DS­ 2401, DS1215, DS1232, UGN3503U, UDN2998W, UDN2993B, MAX038, MAX691, ISD2590, IR LEDs, PCB mounted switches, latest remote control decoder chip & more. With data sheets. DIY Electronics, tel/fax: (058) 62 1915. MONITOR STAND $3.00; Ethernet adaptor $49.00, diskette box $4.00. Right Technology. Ph: (02) 638 1059. Fax: (02) 684 4892. MicroZed are supplying BS2 upgrade kits free with purchase of BS2 and carrier, regardless of where you bought your legit BS1. Proof of purchase required. 486 DX4 100MHz AMD CPU on a VLB motherboard with 256 cache. $475 plus 5% S/H. Prices are in Canadian dollars. Other items are available. Please write for details. Send Money Orders to Renato Zannese, 615 Roding Street, Downsview, Ontario, Canada M3M 2A6. MEMORY * DRIVES * MODEMS LASER PRINTER MEMORY HP 2MB UPGRADE $158 CO-PROCESSORS 80387SX/DX to 40MHz $90 SIMMS (Parity/No Parity) COMPAQ 4MB 30 PIN-70 $210 $196 8MB CONTURA AERO $480 4MB 72 PIN-70 $221 $196 TOSHIBA 8MB 72 PIN-70 $445 $386 2100/50 8MB $546 16MB 72 PIN-70 $834 $728 DRIVES SEAGATE 32MB 72 PIN-70 $1665 $1475 545MB EIDE 14ms 3yr $266 EDO SIMMS 850MB EIDE 11ms 3yr $326 4MB (1Mbx32)-70ns $235 1080MB EIDE 11ms 3yr $344 8MB (2Mbx32)-70ns $463 2150MB SCSI 9ms 5yr $1250 MAC MODEMS (Includes Sales Tax) 8MB P’BOOK $445 14,400 BANKSIA 5yr W $283 VIDEO MEMORY 14,400 SPIRIT 2yr W $230 256KX16 70ns (SOJ) $38 28,800 BANKSIA V.FC $366 256KX16 70ns (ZIP) $57 28,800 SPIRIT V.34/V.FC $413 Authorised VIKING COMPONENTS agents. America’s fastest growing computer memory manufacturer. EX TAX PRICING AS AT OCTOBER ‘95 Sales Tax 22%, O/Night Delivery $8. Ring For Latest Prices. Credit Cards Welcome. We Also Buy And Trade-In Memory. SPECIAL! (Incl Tax) 1Mbx9 – 70ns Simm $52 1Mbx9 – 80ns Simm $38 ‘Counterfeit’ Dev. Kit 8 I/O (low-cost second source Stamp) FBASIC TICkit 21 I/O (uses 16C57) MicroZed Computers PO Box 634 (296 Cook’s Rd), ARMIDALE 2350 V (067) 722 777 F (067) 728 987 Mobile (014) 036 775 Parallax Basic Stamp 1 & Now 2 Here at last: 16 I/O Stamp PELHAM Ph: (02) 980 6988 Fax: (02) 980 6991 Suite 6, 2 Hillcrest Rd, Pennant Hills, 2120. WEATHER FAX PROGRAMS for IBM compatibles *** “RADFAX2” $35 is a high resolution, shortwave weather fax, Morse & Rtty receiving program. Needs SSB HF radio & Radfax decoder. *** “MAXISAT” Version 2.3 $75 is a NOAA, Meteor & GMS weather satellite picture receiving program, lots of features, needs WEATHERFAX card, 2Mb of EMS memory & 1024 x 768 SVGA card. Programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 for postage. Only from Michael Delahunty, 42 Villiers St, New Farm, Qld 4005. Phone (07) 358 2785. MICROCRAFT PRESENTS: Dunfield (DDS) products are now available in Australia. Micro C, the affordable “C” compiler for embedded applications. More memory, more commands, faster Old commands improved too Range of accessories stocked. Phone support for all products. Send 2 x 45c postage stamps for information. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $149.95 each + $3 p&h • Now on special is the SDK, a package of ALL the DDS “C” compilers for $410 + $6 p&h (save $139) • EMILY52 is a PC based 8051/52 high speed simulator $69.95 + $3 p&h •DDS demo disks $7 + $3 p&h • VHS VIDEO from the USA (PAL) “CNC X-Y-Z using car alter­nators” (uses alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Device programming EPROMs/PALs etc from $1.50 (inc SILICON CHIP FLOPPY INDEX WITH FILE VIEWER Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. Price $7.00 each + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 9979 5644 & quote your credit card number; or fax the details to (02) 9979 6503. Please specify 3.5-inch or 5.25-inch disc. November 1995  103 Microprocessors For Silicon Chip Circuits We have stocks of the 68HC705-C8P pre-programmed micro­pro­cessor ICs for the Digital Effects Unit (Feb­ruary 1995) and the Remote Controlled Stereo Preamplifier (Sept.-Oct. 1993). Also available is the pre-programmed Z86E08 microprocessor for the Railpower Mk.2 Model Railway Controller. Price: 68HC705-C8P – $45 ea; Z86E08 $18 ea The above prices include postage. Payment by cheque, money order or credit card to: Silicon Chip Pub­lica­tions, PO Box 139, Collaroy, NSW 2097. Phone (02) 9979 5644; Fax (02) 9979 6503. label). We use and recommend the HILO ALL-07 Universal Programmer • Fixed price PCB layout & photoplots. We use and recommend PROTEL For Windows EDA tools • Credit cards accepted • Call Bob for more de­tails. MICROCRAFT, PO Box 514, Concord 2137. Phone (02) 744 5440 or Fax (02) 744 9280. C COMPILERS: Dunfield compilers are now even better value. Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC16, 8051/52, 8080/85, 8086 or 8096: $140.00 each. Macro Cross Assemblers for these CPUs + 6800/01/03/05 and 6502: $140 for the set. Debug monitors: $70 for 6 CPUs. All compilers, XASMs and monitors: $400. 8051/52 or 80C320 simulator (fast): $70. Demo disk: FREE. All prices + $5 p&p. GRANTRONICS PTY LTD, PO Box 275, Wentworth­ville 2145. Ph/Fax (02) 631 1236 or Internet: lgrant<at>mpx.com.au. COMPLETE WORKSHOP PROGRAM: suit IBM compatible 386 or better computer. Handles: Stock Control, Sales, Service Records, Debits, Credits, Faults, Service Manuals and Phone Directory. Full price $399.00. For demo disk, phone or fax your details to (045) 71 1640. Circuit Ideas Wanted Do you have a good circuit idea. If so, why not sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We’ll pay up to $60 for a really good circuit but don’t make them too big please. Send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 104  Silicon Chip Advertising Index Altronics ................................ 36-38 Av-Comm.....................................40 Avico Electronics.......................101 Car Projects Book....................OBC Defence Force Recruiting............11 Dick Smith Electronics........... 12-15 Electronic Valve & Tube Co..........89 Harbuch Electronics....................59 Instant PCBs..............................104 Jack Albers Electronics & Software Development. MicroZed have PIC Source book. Gives code for Stamp routines to be used in your own PIC programs. $70 plus $8 courier delivery. NEW SPRINKLER CONTROLLER KITS: RAIN BRAIN version uses ‘C8 and switch mode supply. Features galore!! Contact Mantis Micro Pro­ducts, 38 Garnet St, Niddrie 3042. Phone/fax (03) 337 1917. SATELLITE DISHES: international reception of Intelsat, Panamsat, Gorizont, Rimsat. Warehouse Sale – 4.6m Dish & Pole $1499; LNB $50; Feed $75. All accessories available. Videosat, 2/28 Salisbury Rd, Hornsby. Phone (02) 482 3100 8.30-5.00 M-F. EVERYTHING FOR PIC16Cxx CHIPS: affordable “starter kit” $89, includes data and EEPROM chip, assember, simulator. Latest programmer, WARP-3 $70 and 20% off “flawed overlay” PP1 programmers. For demo disc send business size SSAE and a $2 coin to: NEWFOUND ELECTRONICS, 14 Maitland St, Geelong West 3218. Ph (052) 24 1833 newfound<at>ne.com.au BC, MC, Visa. WANTED WINDOWS ACCELERATOR board for EPOCH LB motherboard. This board has full AT size sockets for local bus. Contact Bob on (067) 72 2777 or (014) 03 6755. Jaycar ................................... 49-56 Kits-R-US.....................................58 L & M Satellite Supplies...............59 Macservice...............................3,71 MicroZed Computers.................103 Oatley Electronics.................. 84-85 Pelham......................................103 RCS Radio ................................102 Rod Irving Electronics .......... 74-78 R.S.K. Electronics........................59 Scan Audio................................104 Silicon Chip Back Issues....... 98-99 Silicon Chip Bookshop.................21 Silicon Chip Software..................73 Silicon Chip Walchart.................IBC _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730.