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SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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: https://www.tek.com/ Vol.9, No.7; July 1996 Contents FEATURES 4 SPECIAL FEATURE: Installing A Dual-Boot Windows 95/ Windows 3.1x System on Your PC Want to upgrade to Windows 95 but fear the unknown? A dual-boot system may be the answer. It’s easier to install than you think – by Greg Swain 10 Fuel Injection In Economy Cars Multi-point fuel injection systems are generally too expensive for use in economy cars. The Bosch Mono-Jetronic system cuts costs by using just one injector. Here’s a look at how it works – by Julian Edgar DUAL BOOT WINDOWS 95/ WINDOWS 3.1X SYSTEM FOR YOUR PC – PAGE 4 82 Review: The Tektronix THS720 Tekscope Find out about this powerful new 2-channel 100MHz oscilloscope/4000-count digital multimeter with LCD readout – by Rick Walters PROJECTS TO BUILD 26 Build A VGA Digital Oscilloscope, Pt.1 This digital storage scope features a bandwidth of 100kHz and uses a surplus VGA monitor for the readout– by John Clarke 31 Remote Control Extender For VCRs Simple circuit uses just two ICs and a few sundry bits and pieces. Build it and operate your VCR from another room in the house – by Rick Walters 54 Build A 2A SLA Battery Charger Charge 12V SLA batteries from a car or boat battery – by John Clarke 60 Minilog: An 8-Bit Single-Channel Data Logger Low-cost unit can be read in the field using an LCD or can communicate with a PC – by Anthony Mott VGA DIGITAL OSCILLOSCOPE – PAGE 26 70 A Three-Band Parametric Equaliser Low-noise, low-distortion circuit is ideal for use with musical instruments or public address systems – by Bob Flynn SPECIAL COLUMNS 22 Computer Bits Dressing up the screen in Basic – by Rick Walters 40 Serviceman’s Log Lightning strikes again – by the TV Serviceman REMOTE CONTROL EXTENDER FOR VCRs – PAGE 31 77 Radio Control Multi-channel radio control transmitter; Pt.6 – by Bob Young 86 Vintage Radio Making a few odd repairs – by John Hill DEPARTMENTS 2 Publisher’s Letter 16 Circuit Notebook 65 Order Form 90 Product Showcase 93 Ask Silicon Chip 94 Notes & Errata 95 Market Centre 96 Advertising Index THREE-BAND PARAMETRIC EQUALISER – PAGE 70 July 1996  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Christopher Wilson Phone (02) 9979 5644 Mobile 0419 23 9375 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed John Hill Mike Sheriff, B.Sc, VK2YFK Philip Watson, MIREE, VK2ZPW 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: $54 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. PUBLISHER'S LETTER Appliance repairs are still worthwhile Is your VCR or TV on the blink? Thinking of giving it the flick for a new one? Then think again – you will probably save money. This question often arises in the SILICON CHIP offices as we are asked by readers and friends whether a particular ap­pliance is worth repairing. Thankfully we have not yet reached the situation in the USA where virtually nothing is repaired. It’s a matter of “if it stops working, toss it out and get a new one”. The problem is that this mentality is taking hold in Aus­tralia and I know of several recent instances where people have had TVs, microwave ovens or VCRs fail and they have replaced the items without even thinking about having them repaired. And I’m not talking about old appliances either; in each case, the items junked were less than five years old. Frankly, this attitude gives me the horrors – it is just so wasteful. Most appliances of this age can be repaired economical­ly and they can then be expected, on the balance of probabili­ties, to give another five or ten years of operation. Having talked to our writer of the “Serviceman” pages in this magazine, it appears that an average TV, VCR or microwave oven repair is around $100 to $150 or so. That might make repair of a small microwave oven not worthwhile, depending on the actual job, but it probably makes repairing most TVs and VCRs a good proposition. Think of the advantages. First, you save money by repairing instead of replacing the appliance. Second, you help keep your local repairman in business and off the dole queue. Third, you do your bit to keep Australia’s import bill low. Another point to consider is that you will be helping to maintain electronics repair skills in Australia. And if that isn’t enough, you avoid sending several kilo­grams of workable electronics to your local tip. Call me old-fashioned if you will but this is the approach that I always follow if I possibly can. I have just had my ten-year old Philips 63cm TV set repaired and its performance is still very good; not up to the standard of a 1996 set but per­fectly satisfactory nonetheless. I have also had my VCR and convection/ microwave oven repaired in the last two years or so and they are as good as they ever have been. Perhaps my approach leans too heavily to the “repair rather than replace” approach but surely, if the cost of repair is less than half the replacement cost of the equivalent brand and model appliance, and the item is less than five years old, then the repair should go ahead. Clearly, older appliances are often not worth repairing because parts are unobtainable or too expensive. But most serv­iceman will give a rough quote and then you can make a decision whether to repair or replace the item. Think before you buy when an electronic appliance fails. Your decision will have many consequences. 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 VISIT OUR WEB SITE OUR COMPLETE CATALOGUE IS ON OUR SITE. A “STOP PRESS” SECTION LISTS NEW AND LIMITED PRODUCTS AND SPECIALS. VISIT: https://www.oatleyelectronics.com/ SWITCHED MODE POWER SUPPLY:Compact (50X360X380mm), enclosed in a perforated metal case, 240V AC in, 12V DC/2A and 5VDC/5A out: $17 ...HP POWER SUPPLIES: Compact (120X70X30mm) HP switched mode, power in plastic case, 100-240V AC input, 10.6V/1.32A DC output, slightly soiled: $14 ...LASER MODULE: Very bright (650nM/5mW) focusable module, suit many industrial applications, bright enough for a disco laser light show, good results with the Automatic Laser Light Show: $75 ...AUTOMATIC LASER LIGHT SHOW KIT: 3 motors, mirrors plus PCB and comp. kit, has laser diode reg. cct, could be powered by the above 12V switched mode power supply, produces many different patterns, can be used with the laser module: $70 ...LASER POINTER: Our new metal laser pointer (With keychain) is very bright, with 650nM/5mW diode: $65 ... LEDS SUPER PRICES, INCLUDING A SUPER BRIGHT BLUE!: All the following LEDS are in a 5mm housing ...By far THE BRIGHTEST BLUE EVER OFFERED, superbright at 400mCd: $1.50Ea. or 10 for $10 ... 1C red: 10 for $4 ...300mC green: $1.10Ea. or 10 for $7 .. MAKE WHITE LIGHT BY MIXING THE OUTPUT OF THE PREVIOUS 3 LEDS? ..3Cd Red: $1.10Ea. or 10 for $7 ... 3Cd yellow (Small torch!) also available in 3mm: 10 for $9 ... Superbright flashing LEDS: $1.50 Ea. or 10 for $10 ... PHOTOTRANSISTORS: Enclosed in clear 5mm housing similar to the 5mm LEDS, 30V/3uS/<100nA dark current: $1.30 or 10 for $9 ...CONSTANT VOLTAGE DIODES: 1.52-1.66V <at> 10uA: 10 for $7 ...MASTHEAD AMPLIFIER PLUS PLUGPACK SPECIAL: Our famous MAR-6 based masthead amplifier plus a suitable plupack to power it: $20, Waterproof box: $2.50, bottom box:$2.50 ...17mm MAGNIFIERS: Made in JAPAN by Micro Design these eyepiece style metal enclosed magnifiers will see the grain of most papers, used, limited qty.: $4 Ea. ...HF BALLASTS: Single tube 36W Dimmable high frequency ballasts: $18 Ea. ...12V SLA BATTERY CHARGERS: INTELLIGENT “PLUGPACK” 240V-12V GEL BATTERY CHARGERS, 13.8V / 650mA, proper “switching” design with LED status indicator: $8.80 ...LASER POINTER KIT: A special purchase of some 660nM/5mW laser diode means that we can reduce the price of our Laser Pointer kit, includes everything except the batteries: $29 ...SPECIAL BATTERY AND CHARGER OFFER: When our 7AHr/12V SLA battery ($30) is bought with the SLA battery charger the total price for both is: $33 ...USED BRUSHLESS DC FANS: 4"/12V/0.25A: $8, 24V/6"/17W: $12 ...100,000uF ELECTROLYTIC CAPACITORS: 30V/40Vsurge, used but in exc. cond.:$10 ...12Hr. MECHANICAL TIMERS: 55X48X40mm, 5mm shaft (Knob not supplied), two hours timing per 45deg. rotation, two 25V/16A SPST switches which close at the end of the timing period: $5 ...USED IEC LEADS: Used Australian IEC leads: $2.50 ...STANDARD PIEZO TWEETERS: Square, 85X85mm, 4-40KHz, 35V RMS: $8, Wide dispersion, 67X143mm, 3-30KHz, 35V RMS: $9 ...COMPUTER POWER SUPPLY: Standard large supply as used in large computer towers, +5V/22A, +12V/8.5A, -5V/0.5A, -12V/0.5A, used but in excellent condition, guaranteed: $30 ...MAGNIFIERS: Small eyepiece: $3, 30mm Loupe: $8, 75mm Loupe: $12, 110mm Loupe: $15, a set of one of each of these magnifiers (4): $30 ... NEW NICAD BATTERY BARGAIN: 6 PACK (7.2V) OF 1.2V / 800 mAHr. AA NICAD BATT’s plus 1 X thermal switch, easy to seperate: $4 per pack or 5 packs for $16, FLAT RECTANGULAR 1.2V, 400mAh NI-CAD BATTERIES with thermal switch, easy to seperate, (Each batt: 48x17x6 mm): $4 per pack or 5 packs for $16 ...UV MONEY DETECTOR: Small complete unit with cold cathode UV tube, works from 2 X AA batteries ( Not supplied), Inverter used can dimly light a 4W white fluoro tube: $5Ea. or 5 for $19 ...MISCELLANEOUS USED LENS ASSEMBLIES: Unusual lens assemblies out of industrial equipment: 3 for $22 ...USED PIR MOVEMENT DETECTORS: Commercial quality 10-15M range, used but tested and guaranteed, have O/C transistor (BD139) output and a tamper switch, 12V operation, circuit provided: $10 Ea. or 4 for $32 ...CCD CAMERA WITH BONUS: Tiny (32X32X27mm) CCD camera, 0.1lux, IR responsive (Works in total dark with IR illumination), connects to any standard video input (Eg VCR) or via a modulator to aerial input: $125, BONUS: With each camera you can buy the following at reduced prices: COMMERCIAL UHF TRANSMITTER for $15 (Normally $25), IR ILLUMINATOR KIT with 42 X 880nM LED’s for $25 (Normally $35), REGULATED 10.4V PLUGPACK for $10 (Normally $25) ...PIR CASE FOR CCD CAMERA: Used PIR cases of normal appearance, use to hide the CCD camera, plenty of room inside: $2.50 Ea. or 4 for $8 ...CAMERA-TIME LAPSE VCR RECORDING SYSTEM: Includes PIR movement detector and interface control kit, plus a learning remote control, combination can trigger any VCR to start recording with movement and stop recording a few minutes after the last movement has stops: $90 ...GEIGER COUNTER KIT: Based on a Russian tube, has traditional “click” to indicate each count. Kit includes PCB, all on-board components, a speaker and Yes, the geiger counter tube is included: $30 ...RARE EARTH MAGNETS: Very strong! 7X3mm $2, 10X3mm $4, Torroidal 50mm outer, 35mm inner, 5mm thick: $10 ...IR TESTER: Kit includes a blemished IR converter tube as used in night vision and an EHT power supply kit, excellent for seeing IR sources, price depends on blemishes: $30 / $40 ...ARGON-ION HEADS: Used Argon-Ion heads with 30-100mW output in the blue-green spectrum, power supply circuit provided, size: 350X160X160mm, weight 6Kg, needs 1KW transformer available elsewhere for about $170, head only for: $350 ...DIGITAL RECORDING MODULES: Small digital voice recording modules as used in greeting cards, microphone and a speaker included, 6 sec. recording time: $9 ...WIRED IR REPEATER KIT: Extend the range of existing IR remote controls by up to 15M and/or control equipment in other rooms: $18 ...12V-2.5W SOLAR PANEL KIT: US amorphous glass solar panels, 305X228mm, Vo-c 18-20V, Is/c 200mA: $22 Ea. or 4 for $70 ...MIDI KEYBOARDS: Quality midi keyboard with 49 keys, 2 digit LED display, MIDI out jack, Size: 655115X35mm, computer software included, see review in Feb. 97 EA: $80, 9V DC plugpack: $10, also available is a larger model which has mor features and has touch sensitive response keys: $200 ...STEREO FM TRANSMITTER KIT: 88-108MHz, 6-12V DC supply, 8mA <at> 9V, 25X65mm PCB size, PCB plus all on-board comp’s, plus battery connector and 2 electret mic’s: $25, plastic case to suit: $4 ...WOOFER STOPPER KIT: Stop that dog bark, also works on most animals, refer SC Feb. 96, Kit includes PCB and all on board comp’s, wound transformer, electret mic., and a horn piezo tweeter: $39, extra horn piezo tweeters (drives up to 4) $6 Ea. ...ALCOHOL BREATH TESTER KIT: Based on a thick film alcohol sensor. The kit includes a PCB, all on board comp’s and a meter : $30 ...CENTRAL LOCKING KIT (NEW): A complete central locking kit for a vehicle. The kit is of good quality and actuators are well made, the kit includes 4 actuators, electronic control box, wiring harness, screws, nuts, and other mechanical parts: $60, The actuators only: $9 Ea. ...CODE HOPPING UHF CENTRAL LOCKING KIT PLUS A ONE CHANNEL UHF REMOTE CONTROL: Similar to above but this one is wireless, includes code hoping Tx’s with two buttons (Lock-unlock), an extra relay in the receiver can be used to immobilise the engine, etc., kit includes 4 actuators, control box, two Tx’s, wiring harness, screws, nuts, and other mechanical parts: $109 ...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 ...SECURE IR SWITCH: IR remote controlled switch, both Rx and Tx have Dip switches for coding, kit includes commercial 1 Tx, Rx PCB and parts to operate a relay (not supplied): $22 8A/4KV relay $3 ...FLUORESCENT TAPE: High quality Mitsubishi brand all weather 50mm wide Red reflective tape with self adhesive backing: 3 meters for $5 ...LOW COST IR ILLUMINATOR: Illuminates night viewers or CCD cameras using 42 of our 880nm / 30mW / 12 degrees IR LEDs. Power output is varied using a trimpot., operates from 10 to 15V, current is 5-600mA ...IR LASER DIODE KIT: Barely visible 780nM/5mW (Sharp LT026) laser diode plus constant current driver kit plus collimator lens plus housing plus a suitable detector Pin diode, for medical use, perimeter protection, data transmission, experimentation: $32 ...WIRELESS IR EXTENDER: Converts the output from any IR remote control into a UHF transmission, Tx is self contained and attaches with Velcro strap under the IR transmitter, receiver has 2 IR Led’s and is place near the appliance being controlled, kit includes two PCB’s all components, two plastic boxes, Velcro strap, 9V transmitter battery is not supplied: $35, suitable plugpack for the receiver: $10 ...NEW - LOW COST 2 CHANNEL UHF REMOTE CONTROL: Two channel encoded UHF remote control has a small keyring style assembled transmitter, kit receiver has 5A relay contact output, can be arranged for toggle or momentary operation: $35 for one Tx and one Rx, additional Tx’s $12 Ea. OATLEY ELECTRONICS PO Box 89 Oatley NSW 2223 Phone (02) 9584 3563 Fax (02) 9584 3561 orders by e-mail: branko<at>oatleyelectronics.com major cards with phone and fax orders, P&P typically $6. July 1996  3 SPECIAL COMPUTER FEATURE Dual boot for your PC By Greg Swain Windows 95 or Windows 3.1x? – install a dual-boot system and it’s your choice Want to upgrade to Windows 95 but fear the unknown? A dual boot system may be the answer. Let’s make one thing clear right from the outset: Windows 95 is quite different to Windows 3.11, so don’t expect more of the same. Even an experienced 3.11 user will have to spend some time coming to grips with the new interface. For this reason, many PC users have been reluctant to take the plunge into Windows 95, particularly if they need their computer for work. Another concern for many people is that an important appli­ cation or hardware item might not run properly under Windows 95. That problem can invariably be solved by upgrading Don’t be fooled by the spartan look of the desktop when you first install Windows 95. It’s far more user friendly than the old Windows 3.1x interface and you can easily customise it by adding shortcuts to your drives, programs, and utilities, or even to individual documents. Everything else is normally accessed via the Start button. 4  Silicon Chip the application or, in the case of a hardware item, installing new drivers. The drawback is that you usually only find this out after you’ve installed Windows 95 and that means lost time. The pros & cons Although there are some drawbacks, a dual-boot system has several advantages, especially if you are new to Windows 95. First, it lets you explore the new interface and become familiar with it at your own pace. If you need to produce some useful output during this learning phase, then it’s simply a matter of rebooting to switch back to the more familiar Windows 3.11 terri­tory. Second, you can keep all your 3.11 applications and gradu­ally test each one in turn by installing it under the new operat­ing system. In some cases, it will be necessary to obtain an upgrade to avoid problems, although most software should operate satisfactorily. However, it’s nice to know that you can go back to the old Windows 3.1x interface if a particular application does prove trou­blesome. Finally, you can check that all your peripheral devices (scanners, modems, SCSI controllers, soundcards, etc) operate satisfactorily under Win- The Basic Steps To A Dual-Boot System ❶ dows 95. Most setups will be relatively hassle-free, although it may be necessary to retain the old 16-bit drivers in some cases. We’ll have more to say on this subject a little later on. So should you go for a dual-boot system or not? If you absolutely cannot afford computer downtime and you have lots of hard disc space, the answer is a qualified yes. A dual-boot system is not for everyone though. Opting for Windows 95 as the sole operating system is usually a very safe choice, so weigh up the pros and cons of a dual-boot system carefully before making a decision. Space requirements One important thing to consider before plowing ahead is how much space you have left on your hard disc. The Windows 95 oper­ ating system requires about 50Mb or so of hard disc space. On top of that, you will have to reinstall all your applications to get them to run under Windows 95. This means that, for 32-bit applications at least, you will end up with two versions of the same program on the hard disc – one version for each operating system (note: 16-bit applications can be generally be reinstalled into the same directory as before, to save space). By now, you will be starting to realise that a dual-boot system can quickly gobble up hard disc space. Of course, once a program is up and running under Windows 95, the old Windows 3.1x version can be deleted, so a great deal of that hard disc space can easily be regained. After all, there’s little reason to retain two working versions of the same program. A new hard disc If hard disc space is a little tight, then you should con­sider installing a second hard disc (ie, a D: drive). Windows 95 and your various applications can then be installed on this D: drive. This approach simplifies the installation of a dual-boot system somewhat (see Corrupt Swapfile Work­ around) and is also less confusing since most of the files for the two operating systems are kept well separated. Fig.1: when you install Windows 95, the Setup Wizard takes over and guides you step-bystep through the procedure. ❷ Fig.2: choose Other Directory when this dialog box appears to prevent your old c:\windows directory from being overwritten. ❸ Fig.4: pressing F8 when the “Starting Windows 95” message appears brings up this Startup Menu. Option 1 launches Windows 95, while option 7 launches MS-DOS, after which you can launch Windows 3.1x. Fig.3: enter in the directory where you want Windows 95 installed and then complete the rest of the setup procedure. ❹ Microsoft Windows 95 Startup Menu 1. 2. 3. 4. 5. 6. 7. Normal Logged (\BOOTLOG.TXT) Safe mode Step-by-step confirmation Command prompt only Safe mode command prompt only Previous version of MS-DOS Enter a choice: 7 July 1996  5 Table 1: System File Names MS-DOS Filename Filename Under Win95 Win95 Filename Filename Under "Old DOS" autoexec.bat autoexec.dos autoexec.bat autoexec.w40 command.com command.dos command.com command.w40 config.sys config.dos config.sys config.w40 io.sys io.dos io.sys io.w40 msdos.sys msdos.dos msdos.sys msdos.w40 mode.com mode_dos.dos Big hard disc drives are dirt cheap right now, so this is an option that deserves serious consideration. Spring-clean the disc Before installing Windows 95, your hard disc should be given a good clean-up. (1) Delete all junk files from the disc, including bak files, duplicate files and any programs that are no longer used. An uninstall program is handy here, since it will quickly find duplicates and orphan files (ie, files that are no longer required by the system). There are several around but make sure that it will work under Windows 95 if you plan to buy. (2) Delete the permanent swapfile (assuming that you have one). You do this via the Control Panel – just double-click the Control Panel icon, double-click the 386 En­hanced icon, click the Virtual Memory button, then click the Change button. Now go to New Swapfile Settings, choose None from the Type menu, click OK and reboot the computer for the changes to take effect. This will free up the disc space that was previously allo­cated to the swap­file. (3) Run the Scandisk and Defrag Table 2: MSDOS.SYS Values Entry Description [Paths] section: WinDir= Defines the location of the Windows 95 directory, as specified during setup. WinBootDir= Defines the location of the startup files. HostWinBootDir= Defines the location of the boot drive root directory. [Options] section: BootMulti= Enables/disables dual boot capabilities. The default is 0. Changing this entry to 1 enables the ability to start MS-DOS by pressing F4; alternatively, pressing F8 gives the Windows 95 Startup Menu. BootGUI= Enables automatic graphical startup into Windows 95. BootMenu= Enables/disables automatic display of the Windows 95 Startup Menu. The default is 0. Setting this value to 1 eliminates the need to press F8 to see the menu. BootMenuDefault= Sets the default menu item on the Windows Startup Menu. Set this value to 1 if you normally boot straight to Windows 95, or to 7 (or 8) if you normally boot to MS-DOS. BootMenuDelay= Sets the number of seconds for which the Windows Startup Menu is displayed before running the default menu item. A value of 5-7 seconds is usually suitable. 6  Silicon Chip utilities. What’s that, you’ve never run these utilities? Shame on you. Here’s what to do: exit Windows and, at the c:> prompt, type scandisk c: /autofix Then, when scandisk has finished running, type defrag c: /f For further information on these two utilities, type help scandisk or help defrag at the DOS prompt. (4) Check for viruses (this is most important). To do this job properly, you should use an up-to-date virus checker such as McAfee’s Viruscan, Norton Anti-Virus or ThunderByte. If you don’t have an up-to-date virus checker, then at least run the Microsoft Anti-Virus (MSAV) utility that comes bundled with DOS6.x. It’s better than nothing (if only just) and will at least find some of the older, more common viruses. There’s just one more thing to do before tearing the shrinkwrap off the Windows 95 Upgrade pack – clean up your system files. First, make backup copies of autoexec.bat and config. sys on a floppy disc then, using a text editor, open each file in turn and “rem” out anything that obviously has nothing to do with Windows 95 (eg, Dosshell). You can also “rem” out environment statements and anything to do with memory management but it’s best to leave the device drivers in place unless you know what you are doing. If in doubt, leave it in. When you install Windows 95, it creates its own autoexec.bat and config.sys files based on the originals and these new files can easily be edited later on (see panel). A foot in both camps Setting up a dual-boot system so that you can run either Windows 95 or Windows 3.11 is easier than you think. The best way to achieve this is to first install Windows 3.1x and then install the Windows 95 Upgrade pack. Do not attempt to use the full version or an OEM version of Windows 95, as this will install over the top of your previous DOS and Windows 3.1x directories. The installation procedure is quite straightforward. First, boot your machine to the C:> prompt and run the Windows 95 setup program as described in the manual. The Setup Wizard (see Fig.1) then takes over and guides you step-by-step through the installation. To install a dual-boot system, simply select Other Direc­tory when the Choose Directory dialog box appears, then specify a new directory that does not have your previous version of Windows in it. An obvious choice is c:\win95 or d:\win95 if you have in­ stalled a second hard disc specifically for Windows 95. Make sure that you don’t choose the default c:\windows directory if that is where your old Windows 3.1x resides. If you do, then Windows 95 will overwrite the old Windows installation and you can say goodbye to your dual-boot aspirations. Corrupt Swapfile Workaround On some dual-boot systems, a corrupt swapfile warning mes­sage may appear when Windows 3.1x is started after running Wind­ows 95. The reason for this is that Windows 95 can make changes to the swapfile (386­SPART. PAR) that the previous version of Windows does not recognise. There are several ways of beating this problem. (1) Delete the permanent swapfile and create a temporary one. To do this, first delete the corrupt swapfile when prompted. Next, after Windows 3.1x starts, launch the Control Panel, double-click the 386 Enhanced icon, click virtual Memory, click Change and choose the temporary swapfile setting. (2) Install Windows 95 on a separate hard disc drive, so that it cannot interfere with the Windows 3.1x swapfile. (3) Delete the corrupt swapfile and create a new permanent swap­file in Windows 3.1x, then use a text editor to add the following lines to the [386Enh] section of the Windows 95 SYSTEM.INI file: PagingFile=<Win31xPagingFile> MinPagingFileSize=<SizeInK) where <Win31xPagingFile> is the name of the swapfile (usually C:\386SPART. PAR) and <SizeInK) is the size of swapfile divided by 1024. All you have to do now is continue with the setup procedure as normal. It’s as simple as that – well, almost! There are a few tweaks to be made later on, as we shall see. By specifying a different destina- tion directory, the Wind­ows 95 setup procedure automatically makes all the necessary changes to preserve your existing versions of MS-DOS and Windows 3.1x. This includes retaining your current autoexec.bat, config.sys, Clean Up Those System Files By now, you may have discovered that the new autoexec.w40 and config.w40 files (under “Old Dos”) are modified versions of your original autoexec.bat and config.sys files. Sure, some lines may have been “remmed” out but there will also be quite a lot that haven’t been. What happens is that when you install Windows 95 onto a computer with an existing DOS/Windows 3.1x setup, it’s pretty conservative about getting rid of the old 16-bit drivers for devices such as SCSI controllers, soundcards, scanners and net­work cards – this despite the fact that Windows 95 includes hundreds of 32-bit drivers for common devices. Note that this occurs whether you are installing a dual-boot system or a sole operating system based on Windows 95. The problem here is that those old 16-bit drivers will slow your system down. However, there’s an easy workaround for this – just open your autoexec.w40 and config.w40 files (or autoexec.bat and config.sys files in the case of a sole Win 95 operating system) and REM each driver and environment statement in turn. When this is done, Windows 95 loads its own 32-bit drivers to suit any hardware devices it finds. Test your system after each line has been “remmed” out, to confirm that Windows 95 has found the relevant driver and that the system still works cor­rectly. If there’s a device that Windows 95 doesn’t recognise, try running the Add New Hardware wizard from the Control Panel. If you still don’t get any joy (eg, a soundcard isn’t recognised), go back and remove the REM statement from the relevant device driver or environment setting item. Ideally, you should be able to REM everything out so that you have nothing at all in your autoexec.w40 and config.w40 files, although a PATH statement can be handy if you make fre­quent excursions to the command prompt. Anything to do with memory management (eg, EMM386.EXE and HIMEM.SYS) can certain­ly be removed, as Windows 95 takes care of memory automatically. So why doesn’t Windows 95 get rid of the old drivers in the first place? The answer is that it leaves them there just in case it can’t find a suitable 32-bit driver. By playing safe, it ensures that all your hardware items continue to work after installation. It’s up to you to “clean” the system up if you want maximum performance. If it does prove necessary to leave a 16-bit “real-mode driver” in place, then at least your hardware will continue to operate while you track down a suitable Win95 driver. Suitable drivers can often be downloaded from Internet sites and bulletin boards or obtained from software vendors. July 1996  7 Fig.5: Typical Modified MS-DOS.W40 File [Paths] WinDir=D:\WIN95 WinBootDir=C:\WIN95 HostWinBootDrv=C An automatic menu [Options] BootMulti=1 BootGUI=1 BootMenu=1 BootMenuDefault=1 BootMenuDelay=7 Network=0 ; ;The following lines are required for compatibility with other programs. ;Do not remove them (MSDOS.SYS needs to be >1024 bytes). ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxa ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxb ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxc ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxd ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxe ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxf ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxg ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxh ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxi ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxj ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxk ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxl ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxm ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxn ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxo ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxp ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxq ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxr ;xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxs win.ini, system.ini and other system files. Where necessary, Windows 95 renames these system files for its own use. For example, in a dual-boot system, the Windows 95 equivalent of autoexec.bat is named autoexec. w40 while running “old DOS”. If Windows 95 is launched, the original auto­exec.bat file is renamed autoexec. dos, while autoexec.w40 becomes the new autoexec.bat. Similarly, the equivalent Windows 95 file for config.sys is config.w40 under “old DOS”. Table 1 shows how the various file names change, depending on whether you are running Windows 3.1x or Windows 95. Once the installation is complete, your computer will boot straight into Windows 95 (by default) each time it is turned on. Booting to Windows 3.1x Believe it or not, you now have an operating dual-boot system. So how do 8  Silicon Chip dows 95 in its minimal con­figuration (safe mode), boot with step-by-step confirmation, or boot straight to the Windows 95 command prompt. you load your old operating system? It’s easy – wait until you see the message “Starting Windows 95” appear on the screen (it’s there for about two seconds) and press F4. Your old version of MS-DOS will now load, after which you can remove the “rem” statements from your original autoexec.bat and config.sys files. From here on, you will be able to load MS-DOS and launch Windows 3.1x just as before, simply by pressing F4 at the right moment. Alternatively, you can press F8 when the “Starting Windows 95” message appears to view the Windows 95 Startup Menu – see Fig.4. This typically presents you with a list of seven or eight options. If you do nothing, Windows 95 will automatically boot up after a delay of 30 seconds (this delay can easily be changed). If you want your old DOS, you simply select “Previous version of MS-DOS” and press <enter>. The remaining options boot Win- Having to press F4 or F8 at the correct time to boot “Old DOS” is a bit of pain. Wouldn’t it be nice if the startup menu could be made to appear automatically? Well, in case you haven’t already guessed, it can. All you have to do is modify the Windows 95 menu file. This file lives in the root directory of the hard disc and is called (oddly enough) msdos.w40 under “Old Dos” (or msdos.dos under Windows 95). Note that this is a hidden, read-only, system file so you will have to undo these attributes before modifying the file. Assuming you are running “Old Dos”, go to the root directory command prompt and type: attrib -r -h -s msdos.w40 You can now open the file with a text editor and modify it to make the startup menu appear automatically. This simply invol­ves adding the line: BootMenu=1 to the [Options] section of the file. Table 2 shows a list of some possible settings while Fig.5 shows a typical msdos.w40 file. Let’s take a closer look and analyse the various settings under the [Options] section if Fig.4: (1) BootMulti=1 – enables dual-boot capabilities. (2) BootGUI=1 – enables automatic graphical startup into Windows 95. (3) BootMenu=1 – enables automatic display that the Windows Startup Menu, thereby eliminating the need to press F8. (4) BootMenuDefault=1 – sets the default item on the Windows Startup Menu. In this case, the value is 1 and so “Normal” (ie, Windows 95) is selected. Change this value to 7 if you want “Old DOS” to be the default. (5) BootMenuDelay=7 – sets the delay (in seconds) before the default menu item automatically boots if no further action is taken. In this case, the value is seven seconds. (6) Network=0 – this value should be 0 if no network software components are installed, or 1 if networking is installed. Note that this list is by no means complete. We’ve only listed the settings that are relevant to this article. If you like, you can experiment with other settings from Table 2, to customise your particular setup. And in case you’re wondering, do not removed any of the commented lines (ie lines with a semicolon in front of them) from msdos.w40. This file needs to be greater than 1024 bytes for the system to function correctly. Don’t forget to restore the msdos. w40 file attributes when you have finished; ie, type attrib r h s msdos. w40 at the DOS prompt. Giving old Windows the boot That’s really it – you now have a fully functioning dual boot system that will let you explore and optimise Windows 95 at your leisure. My tip is that once you get used to the new inter­ face and sort out any software hassles, you will eventually give your old DOS/ Windows 3.1x setup the boot. Finally, don’t run your old disc maintenance utilities after you have installed Windows 95 (Scandisk, Defrag, etc), as you could wreck your installation. Windows 95 comes with itys own disc maintenance utilities and these should be used instead. In fact, it’s a good idea to delete the old utilities, to prevent any accidents. SC Setting Up Dual Boot Capabilities After Windows 95 Has Been Installed Let’s say that you’ve taken the plunge and installed Windows 95 over the top of your old system but now also want to be able to boot your old MS-DOS. Fortunately, you can set up a dual-boot MS-DOS/Windows 95 system after Windows 95 has been installed. You will not be able to use your previous version of Windows, however. Although we haven’t tested it, the following procedure should work: (1) On a bootable floppy disc that starts MS-DOS 5.0 or later, rename the IO.SYS and MSDOS.SYS files to IO.DOS and MSDOS.DOS, respectively. Note that these are normally hidden, system, read-only files, so undo these attributes before modifying them; ie, type attrib -r -h -s IO.SYS and attrib --r -h -s MSDOS.SYS. (2) Copy these files to the root directory of your hard disc (ie, to the boot drive). Important: be sure to rename the files as described in step 1 before copying them to the hard disc, other­wise you will wreck your existing Windows 95 installation. (3) Rename the COMMAND.COM file on the bootable floppy to COM­MAND. DOS and copy this to your boot drive. (4) Use a text editor to create suitable CONFIG.DOS and AUTOEXEC.DOS files and store them in the root directory. (5) Edit the MSDOS.SYS file so that the Windows 95 Startup Menu automatically appears during boot-up, as described in the text (see “An Automatic Menu”). July 1996  9 Fuel injection in economy cars While most electronic engine management systems in today’s cars are based around multipoint fuel injection, the Bosch Mono-Jetronic is based on just one injector and no airflow meter or MAP sensor. It is used in the Mazda 121 and some other small economy cars. By JULIAN EDGAR The majority of today's EFI systems use one injector for each of the engine’s cylinders. These so-called multi-point systems have the advantage of allowing the fuel to be added just before the inlet valves, giving benefits in mixture accuracy and overcoming manifold wall wetting. However, the cost of such a system is higher than that of a single-point system which normally uses only one or two injectors. 10  Silicon Chip In the cost-sensitive small, economy car sector, every extra dollar saved is crucial. If the injector count can be more than halved and at the same time the airflow meter or MAP sensor done away with, the cost of the system can be made very low. Unfortunately, the technical compromises implicit in a single point system require complex engineering solutions, if the car is to perform at a level near to that which would be achieved by a more expensive system. This article looks at how Bosch engineers developed a simple, cheap EFI system using just one injector and only four major input sensors. Their approach is also used when aftermarket programmable EFI systems are fitted to very “hot” piston engines and peripheral ported rotary engines. In these cases, a manifold pressure signal is not a reliable indicator of engine load and airflow meters are only rarely used. System layout On paper, the Bosch Mono-Jetronic appears similar to any of the more common EFI systems. Fuel is pressurised by an electric pump, fed through a fuel filter and then fixed at a level above the manifold air pressure by a fuel pressure regulator, before being fed to an electronically-controlled injector. Induction air passes through Fig.1: in the Mono-Jetronic system, many normally-discrete components are integrated into one unit: (1) fuel injector (2) intake air temperature sensor (3) throttle butterfly (4) fuel pressure regulator (5) fuel return (6) fuel inlet (7) throttle position sensor (hidden) (8) idle air bypass motor (Bosch) a filter, is monitored by an intake air temperature sensor and then it passes through the throttle body into the engine. However, as Fig.1 shows, the physical layout of the system is quite unusual. The fuel injector, air temperature sensor, fuel pressure regulator, throttle valve, idle speed control actuator and throttle position sensor are all integrated into one unit. Combining the various components into one package in this way obviously reduces manufacturing and installation costs. The assembly is positioned in a similar location to that used by a carburettor in an old car – on top of a multi-branch intake manifold. Collecting engine data The two major inputs determining the injector pulse width are engine speed and throttle position. Engine speed is easily derived by monitoring the ignition signal but accurate sensing of throttle position is more difficult. When load sensing is derived by monitoring the throttle angle, the relationship between the throttle valve opening and the flow area within the throttle body must be maintained to within very close tolerances on all Fig.2: the single injector is located directly above the throttle butterfly, with the fuel pressure regulator incorporated into the same housing. The rest of the fuel supply system is similar to any other EFI system: (1) fuel tank, (2) electric fuel pump, (3) fuel filter, (4) fuel pressure regulator, (5) fuel injector, (6) throttle butterfly. (Bosch) production units. This is because small throttle movements can make huge changes to the engine load. The first step in developing the system is to subject the engine to accurate dynamometer testing. This is so that the air charge for one intake cycle at various engine speeds and throttle openings can be measured. Fig.3 shows an example of these “air charge” amounts. Several interesting aspects can be noted about Fig.3. First, the amount of air breathed per intake stroke is at its maximum at peak torque, as is shown by the air charge line indicative of full throttle (the butterfly open by 90°). As can be seen, the greatest ingestion per intake stroke occurs on this engine at about 3000 rpm. However, of more importance when attempting to measure the correct amount of fuel to be added are the differences in air charge amount which occur at small throttle openings. At idle and low-load, a change of ±1.5° in throttle opening causes an air-charge difference of ±17%! On the other hand, the same amount of throttle movement at high loads can cause a change of only ±1%. From this, it follows that small throttle openings must be measured with extreme accuracy. In the Mono-Jetronic system this is carried out by an unusual throttle position sensor (TPS). All other EFI sysJuly 1996  11 Fig.3: an ‘air charge’ map is developed on an engine dynamometer to show the amount of air ingested during one cycle at different rpm and throttle openings. Note that at idle and low loads, a change of ±1.5° in the throttle opening causes an air charge difference of ±17%, while the same amount of throttle movement at high loads causes a change of only ±1%. This means that very accurate throttle position sensing is required. (Bosch) Fig.4: schematic diagram of the Mono-Jetronic ECU. (Bosch) 12  Silicon Chip A single point injection system can have major problems with manifold wall-wetting, even with a very finely atomised fuel spray. Mono-Jetronic uses sophisticated techniques to overcome these potential problems. tems also use a TPS but it is often just a two-position switch, with contacts for idle and full throttle. The Mono-Jetronic system uses two potentio-meters in its TPS. Each wiper arm carries four wipers, each of which contacts one of the potentiometer tracks. Track 1 covers the angular range from 0-24°, while Track 2 covers the range from 18-90°. The angle signals from each track are each converted by dedicated analog/ Fig.5: this Lambda Map shows the injection duration which gives a 14.7:1 air/fuel ratio at all loads and engine speeds. This is the actual base map, with the injector pulse widths then modified on the basis of the inputs of the other sensors. (Bosch) digital converter circuits. The ECU also evaluates the voltage ratios, using this data to compensate for wear and temperature fluctuations at the pot. Because the engine load cannot be assessed in this way as accurately as with MAP sensing or airflow metering, the system requires the feedback of an exhaust gas oxygen (EGO) sensor, if it is to comply with emissions legislation. The EGO sensor is the normal type, where the output is a small voltage which changes rapidly either side of the stoichiometric (14.7:1) air/ fuel ratio. Other sensor inputs include coolant, intake air temperature and control signals from the air conditioning and/or automatic transmission. The latter two inputs are used as part of the idle speed control. Processing of input data Fig.4 shows a schematic diagram of the system’s ECU. The inputs from the TPS, EGO, engine temperature and intake air temperature sensors are converted by the analog to digital converter and transmitted to the microprocessor by the data bus. The microprocessor is connected through the data and address bus with the EPROM and RAM. The read memory contains the program code and data for defining the operating parameters. In particular, the RAM stores the adaptation values developed during Fig.6: this graph shows the intake air temperature correction to the injector pulse width. Note that the system is calibrated to work over a 100°C range! (Bosch) self-learning, which occurs on the basis of the EGO sensor input. This memory module remains permanently connected to the vehicle’s battery to maintain the adaptation data whenever the ignition is switched off. A 6MHz quartz oscillator provides the stable basic clock rate needed for arithmetic operations. A number of different output stages are used to generate the control signals for the fuel injector, the idle speed control actuator, the carbon canister purge valve (which allows the burning of stored petrol tank vapour) and the fuel pump relay. The fault lamp warns the driver of sensor or actuator problems and also acts as a diagnostics interface. Mixture control The starting point for the calculation of the fuel injector pulse width is a stored 3-dimensional map derived from dyno test data. This “Lambda Map” (Fig.5) contains the optimum pulse widths to deliver a stoichiometric air/fuel ratio under all operating conditions. It consists of 225 control co-ordinates, made up of 15 reference co-ordinates for throttle position and 15 for engine rpm. Because of the extremely non-linear shape of the air-charge curves, the data points are situated very closely together at the low-load end of the map. The ECU interpolates between the discrete points within the map. If the ECU detects deviations from stoichiometric air/fuel ratios and as Fig.7: because only a single injector is used, manifold wetting can cause major problems during transients. Acceleration enrichment (1) and deceleration lean-off (2) is used, with both based on the speed of throttle movement. (Bosch) July 1996  13 Fig.8: the mixture signal from the exhaust gas oxygen sensor is used as a correction factor. Note that the greater the length of time for which the mixture is rich (or lean), the greater the amount of correction which is applied. (Bosch) a result is forced to correct the basic injection duration for an extended time, it generates mixture correction values and stores them as part of the adaptation process. In this way it can compensate for engine-to-engine variations and engine wear. However, because the Lambda map is designed only for the engine’s normal operating and temperature range, it becomes necessary at times to correct the base injector pulse widths. The first of these is when starting. Because the Mono-Jetronic system uses just one injector, manifold wall wetting through condensation is a much bigger problem than in multi-point systems. As in all EFI systems, injector pulse width is increased when the engine is cold but because Very “hot” engines using radical cam specifications sometimes make use of just engine speed and throttle position inputs to calculate the required fuel addition. Doing so overcomes the problem of the poor vacuum signal at low loads which can occur with high valve overlap. The system described here takes the same approach but for reasons of economy. 14  Silicon Chip condensation of the fuel also depends on the air velocity, the starting injector duration is reduced as engine speed increases. To counteract the possibility of flooding, the longer the engine cranks, the less fuel is injected; it is reduced by as much as 80% after six seconds of cranking. Once the engine has started, the injector opening duration is based on values stored within the Lambda map, suitably modified on both a time and temperature basis by the engine coolant temperature input. As the temperature of the intake air increases, its density is reduced, meaning that at a constant throttle position the cylinder charge reduces with increasing temperature. Fig.7 shows the relative enrichment at different intake air temperatures. Transition compensation While all EFI systems use the equivalent of a carburettor accelerator pump during rapid throttle movements, the single injector of the Mono-Jetronic system makes this a critical aspect. During sudden changes in throttle position, three factors need to be taken into consideration. First, fuel vapour in the central injector unit and intake manifold is transported very quickly, at the same speed as the intake air. Second, fuel droplets are generally transported at the same speed as the intake air but are occasionally flung against the intake manifold walls, where they form a film which then evaporates. Third, liquid fuel is transmitted as a film on the intake manifold walls, reaching the combustion chambers after a time lag. At idle and low loads, the air pressure within the manifold is low (there is a high vacuum) and the fuel is almost entirely vapour with no wall wetting. When the throttle valve is opened, the intake manifold pressure rises and so does the proportion of fuel on the manifold walls. This means that, when the throttle is opened, some form of compensation is necessary to prevent the mixture becoming lean due to the increase in the amount of fuel deposited on the walls. When the throttle is closed, the wall film reduces and without some form of leaning-compensation the mixture would become rich. Rather than basing the transitional compensation on throttle position alone, the system uses the speed with which the throttle is opened or closed as the determining factor. Fig.8 shows this compensation, with the maximum correction occurring when the throttle is opened at more than 260° per second. Also incorporated in these dynamic mixture corrections are inputs from the engine and intake air temperature sensors. 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.telstra.com.au Mixture adaptation The mixture adaptation system uses the EGO sensor input. The system must compensate for air-density changes when driving at high altitudes, for vacuum leaks after the throttle butterfly and individual differences in injector response times. Fig.8 shows the variation in the Lambda correction factor with different EGO sensor output voltages. Updates occur at between 100 milliseconds and one second, depending on engine load and speed. Acknowledgment: thanks to Robert Bosch (Australia) Pty Ltd for providing much of the information used in this article. SC July 1996  15 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. Multi-cell charging with the TEA1100 The Fast Nicad Battery Charger published in the May 1994 issue of SILICON CHIP provided the inspiration for this circuit. While the original circuit was con­ figured to charge two or four cells in series, this modified circuit will charge battery packs of between two and eight cells. This caters for the needs of model aircraft which have 8-cell transmitters and 4-cell receivers. Essentially, the modifications to the circuit include using a higher input voltage of 20VDC, changing the sensing resistor at pin 7 of IC1 (TEA1100) to increase the battery voltage range, and increasing the power rating of the 100Ω resistor on the base of transistor Q2 to 5W. Mark Bishop Kew, Vic. ($30). Random number generator This random number generator is based on IC2, a decade counter/7-segment driver which drives a common cathode 7-segment LED display. When power is applied to the circuit, pins 2 & 3 of IC2 are pulled high and the display is on but there is no increase in the count even though clock pulses are received from IC1b. When S1 is pressed, pins 2 & 3 are pulled low and the IC starts counting. During this time, the display is off. When S1 is released, IC2 stop 16  Silicon Chip counting and the display shows a number. Because of the large number of clock pulses applied to pin 1 (clock input) of IC2, this number is effectively random. An optional switch can be connected to pin 15 of IC2 to provide a manual reset function. M. Downey, Salisbury Park, SA. ($30) 0-16V 15A power supply with current limiting This large power supply will deliver up to 15A and has pushbutton selection for the ammeter range to 25mA, 250mA, 2.5A or 25A. The heart of the circuit is an error amplifier based on IC1. It compares the adjustable reference at its pin 3 with the voltage at the output, fed back to pin 2. IC1 drives a triple Darlington transistor based on Q6, Q7 and four 2N3055s (Q8-Q11) in parallel. These four transistors should be mounted on a large heatsink as they can be expected to dissipate in excess of 300W under worst case conditions. The current limiting circuitry is unusual in that it monitors the level of the unregulated supply voltage rather than monitoring the current drain. Q1, Q2, Q3 & Q4 form a latching circuit that supplies current to relay RLY1 and this feeds the unregulated supply through to the main regulator circuit (ie, IC1 & Q5-Q12). Q3 would switch off Q2 by removing its base voltage were it not for the fact that Q3 gets its base bias from the collector of Q4 and Q4 is normally biased on. Q4 is biased critically so that once the unregulated supply falls below a pre- determined level (as set by VR1), Q4 turns off. This tuns Q3 on and Q2 off, there­by dis­ abling RLY1. VR1 is set by connecting a load which draws 20A and is adjusted to turn off just as this current is reach­ ed, as the output volts pot (VR2) is increased. The ammeter has four current ranges. The normal setting is 25A and if a low range is wanted, the appropriate range button is held down while the reading is taken. J. Mallas, Moonah, Tas. ($45) July 1996  17 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 COMPUTER BITS BY RICK WALTERS Dressing up the screen in Basic Drawing boxes and panels using Basic is easy – when you know how. Here’s a basic primer (pun intended). Several readers, who are just coming to grips with program­ ming in Basic, phoned to ask how we created the opening screens for the Reaction Timer featured in the February issue of SILICON CHIP. Another reader asked how to create an analog clock similar to the one available in Windows. Others have asked how to save data so that it can be recalled and used at a later time. All these problems, which are trivial for the experienced programmer, are major stumbling blocks for beginners, especially as many, who have had no formal training in programming, are teaching themselves. Each time we write a program, there are a number of func­tions which we have used previously, and which we will use again in the future. For example, we often wish to print a string of text in the centre of a line. We can try TAB(10) or TAB(15);PRINT “String of text” until we get it right, or much more easily type: PRINT FNCENTRE$(“String of text”) Inevitably, we will ask for input from the keyboard and require a Y(es) or N(o) answer. Then we find that we expected the input to be in upper case but unfortunately the user typed it in lower case. Sometimes we will want to use the “grey” keys on the keypad, and it is also nice to be able to use the ESC(ape) key to exit from a subroutine back to the main menu. Initialisation subroutine To do all these things, we need to create an initialisation subroutine 22  Silicon Chip which contains all the definitions and functions we will use. This is shown as Listing 1. Each time we start writing a new program, we load “INIT” (you call it what you like), edit lines 5 and 6 to reflect the name of the new program and get cracking. The ,A suffix in lines 5 and 6 saves the program as an ASCII file, allowing you to “Type” it from DOS or read it with a word processor. If you omit the ,A it will be saved in GW Basic format, which appears as garbage to anything but Basic. If you want to be sure that no one can read or alter your code, save it with ,P. This is a protected mode, where the program can be run, but not listed or edited. Make sure you have a non-protected backup copy saved as well. Quick Basic users should omit lines 1-15 as they only apply to GW Basic. If, as you progress, you develop Listing 1 1 GOTO 10 2 GOSUB 1890: LPRINT TAB(55);” Printed on “;TODAY$ 3 LLIST 4 END 5 SAVE “C:\filename”,A ‘Save file on C drive 6 SAVE “B:\filename”,A ‘Save file on B drive for backup purposes 7 END 10 REM Put brief description of your program & date on line 10 11 REM run 2 will print listing on printer 12 REM run 5 will save program to drive C 13 REM run 6 will save program to drive B (change to A if re­quired) 14 REM GOSUB 1900 Will clear from current cursor line to Line 24 15 REM Program starts at line 20 20 GOSUB 1000 ‘Initialise 25 ‘Further GOSUB’s here for your program 30 ‘GOSUB 2000 40 ‘GOSUB 3000 etc. 999 END 1000 ‘*********************** 1010 ‘Initialisation routine. 1020 ‘*********************** 1030 KEY OFF: DEFINT A-Z: DEFSTR D,E,K,U ‘Define A-Z integers, DEKU strings 1040 TODAY = VAL(MID$(DATE$,4,2)) ‘Date of today 1050 ESC = CHR$(27): ENTER = CHR$(13): KSP = CHR$(32) ‘Spacebar 1060 KLA = CHR$(0) + CHR$(75): KRA = CHR$(0) + CHR$(77) ‘Left & right arrows 1070 KUA = CHR$(0) + CHR$(72): KDA = CHR$(0) + CHR$(80) ‘Up & down arrows 1080 KPU = CHR$(0) + CHR$(73): KPD = CHR$(0) + CHR$(81) ‘Page up & down 1090 KHOME = CHR$(0) + CHR$(71): KEND = CHR$(0) + CHR$(79) ‘Home & end Listing 2 Listing 3 30 GOSUB 2000 ‘Draw double surround on screen 2000 ‘******************************* 2010 ‘Draw double surround on screen. 2020 ‘******************************* 2030 LOCATE 1,1: PRINT DLT; ‘Double left top 2040 FOR A = 2 TO 79: PRINT DH;: NEXT ‘Double horizontals 2050 PRINT DRT; ‘Double right top 2060 FOR A = 2 TO 23: PRINT DV;TAB(80);DV;: NEXT ‘Double verti­cals 2070 LOCATE 24,1: PRINT DLB; ‘Double left bottom 2080 FOR A = 2 TO 79: PRINT DH;: NEXT ‘Double horizontals 2090 PRINT DRB; ‘Double right bottom 2100 LOCATE 25,1: PRINT FNCENTRE$(“Surround drawn. Press SPACEBAR to end.”); 2110 K = INPUT$(1) 2999 RETURN 40 GOSUB 3000 ‘Display screen colours 3000 ‘*********************** 3010 ‘Display screen colours. 3020 ‘*********************** 3030 FOR FOREGROUND = 0 TO 15 3040 FOR BACKGROUND = 0 TO 15 3050 COLOR FOREGROUND,BACKGROUND: CLS 3060 LOCATE 10,10: PRINT “Foreground colour is “;FOREGROUND 3070 LOCATE 12,10: PRINT “Background colour is “;BACKGROUND 3080 LOCATE 25,1: PRINT FNCENTRE$(“Press a key to pause, SPACEBAR to continue”); 3090 K = INKEY$: IF K = "" THEN 3110 3100 K = INKEY$: WHILE K = "": K = INKEY$: WEND 3110 A$ = RIGHT$(TIME$,1): WHILE A$ = RIGHT$(TIME$,1): WEND 3120 NEXT: NEXT ' BACKGROUND, FOREGROUND 3999 RETURN other definitions or requirements, make sure you add them to your INIT file. Now after that lengthy introduction, how do we draw a fancy screen? As you are probably aware, the Basic screen consists of 25 lines with 80 characters on each line. Using our INIT tem­plate, line 30 will be GOSUB 2000 ‘Draw screen. The subroutine will start by moving the cursor to the top left hand corner of the screen (LOCATE 1100 KINS = CHR$(0) + CHR$(82): KDEL = CHR$(0) + CHR$(83): KBS = CHR$(8) 1105 ‘Insert, Delete & Backspace keys 1110 DATA January, February, March, April, May, June, July 1120 DATA August, September, October, November, December 1130 DIM MONTH$(12): FOR A = 1 TO 12: READ A$: MONTH$(A) = A$: NEXT 1140 MONTH$ = MONTH$(VAL(LEFT$(DATE$,2))) ‘Current month 1150 DEF FNCENTRE$(M$) = SPACE$((79 - LEN(M$))/2) + M$ ‘Centre text 1160 DEF FNCEOL$ = STRING$(79 - POS(Q),” “) ‘Clear to end of line 1170 DEF FNYN = INSTR((“ YyNn”) + ENTER + ESC,INKEY$) ‘A = FNYN If A = 1175 ‘0 or 1 - no key, 2 or 3 - Y, 4 or 5 - N, 6 - enter, 7 - escape 1180 ULT = CHR$(218): DLT = CHR$(201): URT = CHR$(191): DRT = CHR$(187) 1185 ‘Singe & Double Left & Right top corners 1190 ULB = CHR$(192): DLB = CHR$(200): URB = CHR$(217): DRB = CHR$(188) 1195 ‘Singe & Double Left & Right bottom corners 1200 UH = CHR$(196): DH = CHR$(205): UV = CHR$(179): DV = CHR$(186) 1205 ‘Single & Double Horizontal & vertical lines 1210 ULI = CHR$(195): DLI = CHR$(204): URI = CHR$(180): DRI = CHR$(185) 1215 ‘Single & Double Left & Right intersections 1220 UTI = CHR$(194): DTI = CHR$(203): UBI = CHR$(193): DBI = CHR$(202) 1225 ‘Single & Double Top & Bottom intersections 1230 UCI = CHR$(197): DCI = CHR$(202) ‘Single & Double Centre intersection 1235 ‘Add your additional initialisation routines here. 1890 TODAY$ = MID$(DATE$,4,2) + “-” + LEFT$(DATE$,2) + “-” + RIGHT$(DATE$,2) 1895 ‘Don’t move or change line 1890 unless you change line 2 1899 RETURN 1900 ‘********************************** 1910 ‘Clear to end of screen subroutine. 1920 ‘********************************** 1930 VIEW PRINT CSRLIN TO 24: CLS: VIEW PRINT 1999 RETURN 1,1). We then want to draw a double left top corner (DLT), 78 double horizontal lines (DH) then a double right top corner (DRT). OK, that’s the top line. Now we want 22 double vertical lines placed on the left and right hand sides of the screen and finally we want the top line repeated at the bottom but using bottom left and right corners. Simple isn’t it? By defining the graphics symbols as simple acronyms (all computer people use acronyms), it makes it easy for us to remem­ber the definitions. We also write the program quicker, as we don’t have to keep looking up the definitions (double left top corner = CHR$(201)) in a list. One other benefit, by defining D as a string, we don’t have to keep typing the $ sign after each definition. It all saves time and reduces errors. So load Listing 1, change lines 5, 6 and 10 to reflect your new program name, add line 30 and subroutine 2000 and run it. Now experiment by adding additional lines to subroutine 2000 to draw smaller single line boxes on the screen. Once you have the program running, you can change the colors from boring white on black. The command is color fore­ground, background. Enter and run Listing 3 to see the range of colours available. Next time we will see if we can write a program to create the analog SC clock. July 1996  23 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. Macservice 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. Macservice Pty Ltd Build a VGA digital oscilloscope How would you like a digital scope with a large screen? This one is based on a VGA monitor and displays two channels, one with a red trace and one with a green trace. At the same time, there is an electronically generated blue screen graticule to make measurements easy. PART 1: By JOHN CLARKE Many readers would like to have an oscilloscope but can’t quite raise the $1000 or so you need for a fairly basic scope these days. However, many readers do have a spare VGA monitor and this can be pressed into useful service with our new VGA Oscilloscope. Apart 26  Silicon Chip from the need for a VGA monitor, it’s a self-contained unit that doesn’t tie up your computer. No modifications are required to the VGA monitor itself – it just plugs into the VGA output on the test instrument which we’ll call the Scope Adaptor for convenience. When you turn both the VGA monitor and the Scope Adaptor on, the screen displays a large blue graticule with seven divisions horizontally and eight verti­ cally. Two traces are also displayed, one red and one green, for the two channel inputs. The Scope Adaptor has knobs for vertical sensitivity & trace position on both channels, plus timebase and trigger level controls. There are also toggle switches for trigger source selection, AC/DC cou­pling, timebase magnification and a few others which we will discuss later. Most importantly, the Scope Adaptor has two BNC sockets for the two channel inputs. These will accept normal 1:1 and 10:1 scope probes. Specifications Bandwidth ......................................useful up to 100kHz Timebase .......................................0.1s to 50µs per division in 11 ranges Sensitivity .......................................10V to 50mV per division in 8 ranges Resolution ......................................8-bit or 256 steps with 224 visible Linearity .........................................±1 LSB Calibration Accuracy ���������������������vertical <5%; horizontal <10% (50µs position uncalibrated) Input impedance .............................1MΩ This photo shows the unit displaying a sinewave in one channel and a square wave in the other. Timebase speeds range from 100ms to 50µs/ division. Using the VGA Oscilloscope is just like using any other scope. First, you connect the scope probes to the circuit to be measured and then adjust the vertical sensitivity controls on both channels to fill the screen. This done, you adjust the timebase control to give a reasonable number of signal cycles on the screen. Finally, you adjust the vertical position controls so that the two traces are comfortably separated (or overlapping if you wish). To obtain a stable display, you will probably need to adjust the trigger level control and also select positive or negative edge triggering with the Slope switch. Or you can select between a triggered or free-running display. As we said above, driving the VGA Oscilloscope is little different from any other scope – up to a point. Where the new VGA Oscilloscope does differ is that it also offers waveform storage, just like a digital storage oscilloscope – and that is exactly what it is. It works in much the same way as typical modern digital instruments such as the Hewlett-Packard HP 54600 series scopes or the Tektronix TDS 300 series. It con­verts the incoming analog signals into digital data and then stores them in RAM. The digital data is then processed in such a way as to generate a raster display on the VGA monitor. Mind you, this VGA Oscilloscope does not have the extremely wide bandwidth of the commercial oscilloscopes mentioned above; nor does it have their price. However, it can be used to monitor signals up to 100kHz, making it a useful instrument for lots of applications. And unlike the commercial scopes, it does have that large VGA screen. To top it off, the display is in full colour! Few commercial scopes can boast a colour screen. Some normal oscilloscope controls are not provided on the Scope Adaptor. No brightness controls are provided since these are on the VGA monitor. Focus is unnecessary since the trace thickness is set by the circuitry. A MAGnification control expands the trace out by either a factor of two or four. This feature can be useful for high fre­quency signals above 20kHz where it is difficult to see each waveform cycle in the x1 magnification. The screen is redrawn at a rate set by the UPDATE switch. The normal setting redraws the trace every second and this is seen on the screen as a momentary trace blanking. The other two positions of the switch are slow and fast. These are provided for low frequency signals and for displaying real time audio signals (music, speech, etc) respectively. Waveform storage A very useful feature of the VGA Oscilloscope is its ability to store a waveform and then display it indefinitely. This ena­ bles viewing of waveforms which cannot be readily seen on a normal oscilloscope. With the storage facility, you can capture momentary pulses in a circuit and view them at your leisure. As noted above, the VGA Oscilloscope does not tie up your computer Features • VGA display (no computer required) • • • Dual trace • Timebase magnification (x2, x4) • • • Free run and triggered display • • • Trigger level control 7 x 8 graticule Calibrated timebase and volts/ division Storage facility Triggering on + or - slope and Channel 1 or Channel 2 Vertical position for each trace AC/DC/GND input coupling July 1996  27 Fig.1: this block diagram shows the various signal processes inside the VGA Oscilloscope. since it directly drives the VGA monitor. It oper­ates best on a multisync monitor. With a standard VGA monitor, the extreme right hand graticule line may not displayed. This is, however, of little consequence. Block diagram Fig.1 shows the block diagram for the VGA Oscilloscope. In essence, signals for Channel 1 run along the top of the diagram while signals for Channel 2 run along the bottom of the diagram. Let’s talk about Channel 1, on the assumption that all operations will be duplicated in Channel 2. Channel 1 input signals are first passed into a switchable attenuator and amplifier (S1, S2, Q1, IC1 & IC2) which sets the amplitude to suit the following circuitry. The signals are then passed to an analog-to-digital (A-D) converter (IC3) which produc28  Silicon Chip es 8-bit data which is then stored in memory. Initially, the A-D conversion operation is triggered either by the free run oscillator which periodically retriggers the oscilloscope or by a trigger signal from CH1 or CH2. After each A-D conversion the new digital value is stored in the next memory address. The A-D conversion rate and memory address is under the control of the timebase oscillator (S5, 1C13, IC14, IC15) which clocks the 8-bit counter via the record switch in IC16. This counter increments the memory address. 256 memory locations are used to store all the data for one screen display. When all memory locations have been filled, the end of count signal (IC17, IC18) changes the chip select, read/ write block to switch the memory to read mode. It also deselects the A-D converter and switches IC16. During this conversion time the display trace is blanked. Note that the timebase oscillator frequency sets the rate of A-D conversions. At fast rates, high frequencies can be observed, while at slow conversion rates low frequency signals are accurately traced. If we want to store and view one complete cycle of the input waveform, the timebase must operate 256 times faster than the input frequency. If the timebase is slower than this then more cycles will be seen. Conversely, if the timebase is faster, then only a portion of the full waveform will be observed. When the memory is in the read mode, the 8-bit counter is clocked from the oscillator and line counter of the VGA timebase circuit. The display/ record switch, IC16, performs this function. This clocking rate is exactly what is required for the memory contents to be displayed on the screen. Screen display In order to understand how the information stored in memory is displayed on the VGA screen, let us look at Fig.2. The display on a VGA monitor is made up of 480 horizontal lines which are scanned by the red, green and blue electron beams. A dot will appear each time one of the beams is is turned on for an in­stant. The respective beams are turned on by the R, G or B signals on the VGA connector. For simplicity, Fig.2 only shows 11 horizontal scan lines instead of 480 but you get the general picture. The position of any dot on the screen is dependent upon how long after the line sync pulse the red, green or blue gun is turned on and on what line is being scanned at the time. Each horizontal line begins with a sync pulse and an entire set of lines is preceded by a frame sync pulse. This must be of sufficient duration for the electron beam to return from the bottom of the screen to the beginning of line 1. The time to scan one line is 32µs and to scan all 480 lines is 16.6ms. Thus, the horizontal scanning frequency is 31.25kHz and the frame rate is 60Hz. This last frequency is called the refresh rate. Making a picture So how do we get the dots on the screen in order to make a picture which means something? We have already stated that we have 256 memory locations which are scanned for each line of the screen. Each of these memory locations is 8-bits and therefore we can have a value stored in each location which ranges from 00000000 to 11111111; ie, 256 values. Let us consider that the top of the screen corresponds to 11111111 and the bottom of the screen is 00000000. So as each line is scanned by the beam of the VGA monitor, simultaneously the 256 memory locations are being scanned. Now imagine that the top line is being scanned and we come to memory location 6 (actually address 00000101 when scanned from left to right) and the value stored just happens to be 11111111. Yippee, we get a dot on the screen which corresponds to that memory location (or address). Next, consider line 2 and we scan across to memory location 5 and the value stored just happens to be 11111110. Again, we get a dot at that Fig.2: this diagram demonstrates the process of writing dots to the screen. There are 256 bytes of memory for each channel and each of the 256 lines on the screen corresponds to one of the possible values stored in each memory location. position. Further, as we scan further across the same line we come to location 7 and the value is also 11111110. Again, we got a dot on the screen. Now we could go on and on with this process and talk about all 256 lines and 256 memory locations but you should be starting to get the picture. This is shown in abbreviated form in Fig.2. This shows only 11 lines and 21 memory locations but the princi­ple is the same: if the value stored in a memory location corre­sponds with the line value we get a dot on the screen. That’s the principle but how is it done? Two magnitude comparators, IC5 & IC6, actually compare the data from each memory location with the line being scanned and its screen value; ie, the screen’s 8-bit address which comes from the line counter. If the line value equals the data value then a short pulse is produced from the output of the comparator and this is applied to the buffer (Q3, Q4 & Q5) which drives the green gun, for the Channel 1 trace. Exactly the same process occurs for Channel 2 input signals except that they are stored in another 256 byte (8July 1996  29 Most of the componentry inside the VGA Oscilloscope adaptor is readily available. The circuitry is mounted on three PC boards, with two small satellite boards used to accommodate the RAM chips. bit) memory. As the Channel 2 memory is clocked out, its values are compared by magnitude comparators IC11 and IC12 and dot signals are generat­ ed for the red gun, corresponding to the Channel 2 trace. To recap, the analog input signals are converted to digital data and clock­ ed into memory at a rate which is set by the timebase switch. The data is then read out of memory at a fixed rate, to suit the requirements of the VGA monitor. The remainder of Fig.1 is devoted to the generation of VGA timebase signals (ie, line and frame sync pulses) and the grati­cule signal which drives the blue gun. Next month The VGA Oscilloscope adaptor has most of the controls you would expect to find on a conventional oscilloscope. Vertical input sensitivity ranges from 50mV/div to 10V/div. 30  Silicon Chip So far, we’ve given you the overall picture of how the VGA Oscilloscope works. The circuit details are just a teensy bit more complicated, as you might expect. We will discuss these next month and also publish the SC parts list. This simple device lets you operate your VCR using its remote control from another room in the house. It picks up the signal from the handpiece and sends it via a 2-wire cable to an IR LED located close to the VCR. Remote control extender for VCRs By RICK WALTERS have two or more TV sets which M are linked (via antenna cable) to a single VCR. The problem is, you can’t directly control the VCR from another room in the house. ANY HOUSEHOLDS NOW For example, you might want to watch a video on a second set in the bedroom but if you want to stop, fast forward or freeze-frame the action, you have to “walk” the remote control to the room where the VCR lives. Wouldn’t it be great if you could control the VCR directly from your bedroom? Well, the answer is you can – by building this simple Remote Control Extender circuit. It packs into a small plastic zippy case and should only take you half an hour to assemble. In use, the device sits on top of the remote TV set (or in some other convenient location in the room) and picks up the signals from the VCR’s remote control. It then converts these signals into electrical impulses and feeds them down a thin 2-wire cable to an IR (infrared) LED placed in front of the VCR. Because the IR pulses from this LED mimic the IR pulses from the remote control handpiece, the VCR responds in exactly the same fashion. It’s as though the handpiece was being operated in the same room as the VCR. Fig.1 shows the basic scheme. It’s been done before OK, we confess that the idea is not new – designs for remote control extenders have been published before. Our last unit was described in April 1994 and was very popular. However, the SL486 IR preamplifier IC used in that design is no longer available and so this circuit is now obsolete. July 1996  31 Fortunately, a new IC which can do the job has recently appeared. This device, from Dick Smith Electronics, carries a Z1954 type designation and is actually a complete IR receiver subsystem. An equivalent part, designated PIC12043, is available from Oatley Electronics. In both cases, the device comes in a TO-220 style package with an integrated plastic lens on one side. This lens sits in front of an integral IR receiver diode. As well, the device includes amplifier, limiter and bandpass filter stages, plus a demodulator. Its on-axis reception distance is quoted as eight metres but this will obviously depend on the intensity of the light output from the remote control. Circuit details Because so much circuitry is packed into the Z1954, the final circuit of the extender is much simpler than previous designs – see Fig.2. Apart from the Z1954, there’s just one low-cost CMOS IC, a transistor, an IR LED and a few sundry bits and pieces. Each time the VCR’s remote control is operated, it sends out bursts of pulsed IR radiation. These bursts are picked up by the IR photodiode inside IC1, converted to electrical signals and fed to the internal amplifier and filter stages. The demodulated output appears at pin 1 and is fed to pin 2 of NOR gate IC2a (note: this gate is actually wired in parallel with IC2d but Fig.1: the unit picks up infrared (IR) light from the VCR’s remote control and converts it to an electrical signal. This signal is then sent down a 2-wire cable and drives an IR LED located in the same room as the VCR. wave oscillator stage based on NOR gates IC2b and IC2c. The output from this stage appears at pin 10 of IC2c and is fed to pin 3 of IC2a, where it is gated by the signal from IC1. The output from IC2a is depicted by the bottom waveform in Fig.3. This signal drives transistor Q1 via a 2.2kΩ resistor. Q1 in turn drives IRLED1 which is at the end of the 2-wire cable and is positioned where it can be “seen” by the sensor in the VCR. Because the signal drive to IRLED1 mimics the transmitted signal, the VCR will obey all the remote control functions. Trimpot VR1 allows the oscillator frequency to be adjusted to suit your VCR (or whatever piece of equipment you are control­ling). The frequency is usually not all that critical and will typically be somewhere around 30-40kHz. Power for the circuit is derived from a 9V DC plugpack supply via reverse-polarity protection diode D1. The resulting supply rail is filtered using a 470µF capacitor and regulated to 5.1V using ZD1 and a 470Ω resistor. Finally, an acknowledge Fig.2: the circuit is based on IC1 which is a complete IR receiver subsystem. When IR LED is connected in series light is received, IC1’s output switches high and low. This signal is applied to NOR with a 1kΩ resistor between gate IC2a,d and gates an oscillator signal generated by IC2b and IC2c. The gated the positive supply rail and signal then drives transistor Q1 which in turn drives infrared LED IRLED1. 32  Silicon Chip we’ll just talk about IC2a to simplify the circuit description). The top two waveforms in Fig.3 depict the transmitted signal and the signal at pin 1 of IC1. Note that the latter waveform has been stripped of the carrier and that it is inverted compared to the transmitted signal. Unfortunately, we don’t want to lose the carrier but we don’t have a choice with IC1. To overcome this, a suitable carri­er is regenerated using a square- lead will be the longer of the two. The IR sensor (IC1) should be installed so that it sits about 5mm above the board surface. The IR LED (IRLED1) is connected via a suitable length of figure-8 cable. This is wired as follows: (1) slide a 50mm length of 5mm-diameter heatshrink tubing over one end of the cable; (2) separate the leads at this end and slide a 30mm length of 2mm-diameter heatshrink tubing over each lead; (3) strip the ends of the leads and solder them to the LED. Con­nect the black trace lead to the cathode and the plain lead to the anode. (4) Push the 2mm heatshink tubing over each soldered joint and shrink it down using a hot-air gun. This done, cover both leads with the 5mm tubing and shrink it down as well. The other end of the cable goes to the jack plug. Connect the black trace lead to the centre pin – ie, to the tip terminal. The plain lead goes to the outer pin. Fig.3: this diagram show the waveforms at various points in the circuit. The output waveform is obtained by gating the middle two waveforms together using parallel NOR gates IC2a and IC2d. Testing Fig.4: install the parts on the PC board as shown in this diagram, taking care to ensure that all polarised parts are correctly oriented. the output of IC1. Normally, IC1’s output is high and LED 1 is off. When the remote control is operated, IC1’s output pulses low and LED 1 lights to indicate that the code is being received. Putting it together The circuit is built on a small PC board coded 15107961. This should be carefully checked for etching faults before you begin assembly. Fig.4 shows where the parts go. Fit the two wire links first, then the six resistors and the two diodes. This done, install the trimpot, transistor Q1, both jack sockets and the ca­ pacitors. Make sure that the diodes and the electrolytic capaci­ tors are correctly oriented. Next, install the acknowledge LED so that it sits about 12mm proud of the PC board. Again, make sure that the LED polari­ty is correct – the anode The unit can now be bench tested to check that it is work­ing properly. Before applying power, check that the centre pin on the 2.5mm power plug is positive. If it is, plug it into the power socket and plug the IRLED lead into the other socket. Now aim the remote control at the IR sensor, press a button and check that the acknowledge LED flashes. If it doesn’t, check the supply voltage to IC1 and IC2 (it should be 5.1V). If everything is OK so far, place the IR LED in front of the VCR and position the Remote Control Extender in another room. Operate the remote control and check to see if the VCR responds. If it doesn’t, hold down a button on the remote control and slowly adjust VR1 until it does. SILICON CHIP Fig.5: check your board carefully against this full-size etching pattern before mounting any of the parts. Fig.6 (right) shows the full-size front panel artwork. REMOTE CONTROL EXTENDER July 1996  33 PARTS LIST 1 PC board, code 15107961, 78 x 33mm 1 plastic utility case, 28 x 54 x 83mm 1 9V DC plugpack with 2.5mm plug 1 3.5mm PC-mounting socket 1 2.5mm PC-mounting socket 1 3.5mm line plug 2.5mm 1 50mm length 5mm-dia. heatshrink tubing 1 60mm length 2mm-dia heatshrink tubing 1 length of figure-8 light duty speaker cable to suit 1 10kΩ horizontal mount trimpot (VR1) The assembled PC board fits neatly inside a standard plastic case and is held in place by the collars of the jack sockets and by the acknowledge LED. Once the VCR operates, find the minimum and maximum trimpot settings and adjust it to the mean position. If it doesn’t work, go over the PC board carefully and check for missing or bad solder joints. You should also check that all polarised parts (ICs, transistor, LED, diodes and elec­ trolytic capacitors) have been correctly oriented and that all resistor values are correct. Once testing has been completed, the PC board can be in­stalled in the case. Note that you will have to drill four holes (two at each end) to accept the jack sockets, the acknowledge LED and the lens of IC1. The PC board is then pushed down into the case so that the collars of the sockets protrude through their respective holes. After that, it’s simply a matter of pushing the acknowledge LED into its hole and aligning the lens of IC1 with its hole, so that it can “see” the IR pulses from the remote control. Finally, if you find a plugpack sup- Semiconductors 1 IR subsystem (IC1); DSE Z1954 or Oatley Electronics PIC12043 1 74HC02 quad NOR gate (IC2) 1 BC548 NPN transistor (Q1) 1 1N4004 power diode (D1) 1 5.1V 400mW or 1W zener diode (ZD1) 1 IR LED, 940nm, Oatley 600D or equivalent (IRLED1) 1 5mm red LED Capacitors 1 470µF 16VW PC electrolytic 1 100µF 16VW PC electrolytic 1 680pF 100VW MKT polyester Resistors (0.25W, 1%) 1 100kΩ 1 1kΩ 1 8.2kΩ 1 470Ω 1 2.2kΩ 1 220Ω Top: the lens of the IR sensor (IC1) must be aligned with a hole in the end of the case, so that it can “see” the pulses from the remote control. Above is a close-up view of the IR LED. ply inconvenient, the unit can be run from a 9V battery. Its current consumption is around 8mA under quiescent conditions and around 25mA when puls­ing. Don’t forget to turn it off when you are finished as the battery will not last very long if the unit is left on SC continu­ously. RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 1 1 1 1 1 1 34  Silicon Chip Value 100kΩ 8.2kΩ 2.2kΩ 1kΩ 470Ω 220Ω 4-Band Code (1%) brown black yellow brown grey red red brown red red red brown brown black red brown yellow violet brown brown red red brown brown 5-Band Code (1%) brown black black orange brown grey red black brown brown red red black brown brown brown black black brown brown yellow violet black black brown red red black black brown 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 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 SERVICEMAN'S LOG Lightning strikes again In the May notes, I told of the havoc caused to a TV set by one of a series of thunderstorms which struck in my area some months ago. There were other casualties from those same thunder­storms as well and this is about one of them. This time, it wasn’t a TV set but rather a portable stereo CD player. And it was another National Panasonic product, a model RX-DT610. The complaint was typical: “it doesn’t go. It wouldn’t go after the blackout when we had that thunder- 40  Silicon Chip storm”. I wasn’t sure which thunderstorm “that” one was but it didn’t really matter; the obvious conclusion was that unit had suffered a strike or power surge, with disastrous results. The RX-DT610 is a very nice looking unit. This one was probably around three years old and would have cost between $300 and $400. It features detachable speakers, twin tape decks, a CD player, a radio tuner covering the broadcast band and the FM band, and a full digital LCD readout. It operates from either mains power or internal batteries. In fact, the unit uses two sets of batteries: a main power supply pack consisting of 10 “D” cells (15V) and a memory backup battery consisting of four “AA” cells (6V). There were no “D” cells in it when it came in and the “AA” memory cells had long since died (they were probably the originals). It looked as though the owner had never used the set on batteries. The set performs very well when it is working. But it wasn’t working now and a quick check with the ohmmeter indi­cated at least one reason; the mains input was open circuit. I was not familiar with this model and, because units like this are so physically cramped, I needed a manual before doing any serious work on it. Fortunately, one was available although it wasn’t cheap. Before ordering it, I decided on a brief visual inspection. This revealed that there was no fuse in the transformer primary circuit although there was one in the secondary circuit. Just why this was so I cannot imagine. The transformer primary is in the most vulnerable position and the transformer is an expensive component. Having confirmed that it was the transformer which was open circuit, the replacement cost was the next thing I had to consid­er. This was over $100 and I hadn’t even checked for whatever other faults there might be. Was I justified in pressing on? Ordinarily, the answer would be not. But it transpired that the damage was covered by the owner’s house and contents in­surance policy, so that wasn’t any real worry. In any case, the owner wanted it fixed regardless. So I ordered a new transformer and a YOU CAN AFFORD AN INTERNATIONAL SATELLITE TV SYSTEM SATELLITE ENTHUSIASTS STARTER KIT YOUR OWN INTERNATIONAL SYSTEM FROM ONLY: FREE RECEPTION FROM Fig.1: part of the Panasonic RX-DT610 portable stereo unit. IC305 is at top, IC306 at lower right and D310 at bottom left. IC306 is a multiple supply rail device. Asiasat II, Gorizont, Palapa, Panamsat, Intelsat HERE'S WHAT YOU GET: ● manual and put the unit aside until they arrived. When they did, I set to and replaced the transformer. And I say “set to” advisedly. This model – and a lot more like it – is a right proper swine to service. In this case, access is only through the front of the cabinet and, need I spell it out, the power supply board is right at the back, behind all the other boards. And that means that all the other boards have to be pulled out of the way, involving the removal of countless screws and clips. Anyway, the transformer was duly fitted and I replaced the other boards, at least to the point where I could safely switch on. This produced some signs of life but not much. The LCD read­out came on and there was a loud hum from both speakers. And that was it. That meant that I had to pull everything out again and start searching for faults. This wasn’t easy because I had to work on the various boards while they were half hanging out of the cabinet, on leads which were not designed to aid servicing. Nevertheless, I managed to make a series of voltage checks and I found several voltages which were quite wrong. These were mainly around two ICs – IC306 and IC305. IC306 is a rather unu­sual device, best described as a multiple supply rail source. IC305 is, basically, the audio amplifier. But it also appears to perform a supply rail function, delivering 9V at pin 4. Well, it should have been but it wasn’t. Cooked ICs At this point, I could only conclude that at least one of these ICs had taken a wallop when the trans­former was destroyed. To cut the losses in time and effort, I decided to order and replace both ICs without further mucking about. As it transpired, this was a wiser move than I imagined. I later learned from a colleague that failure of one of these ICs can destroy the other, so replacing them one at a time can lead to further destruction. ● ● ● ● ● 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 July 1996  41 Serviceman’s Log – continued So the two replacement ICs were duly obtained and fitted. Now, I hoped, the thing should work. And it did. There was sound in the speak­ers, the tape was working and there was some life in the radio. The latter was not fully operational, however, due to the failure of the memory backup batteries. The radio is pushbutton operated, the wanted channels being selected and stored in the memory. Since this had failed, new cells had to be fitted and the radio reprogrammed. But when this was done it worked perfectly. So we had the two tape decks and the radio working. The only thing I hadn’t checked was the CD player. This was awkward, because the physical location of the board and the length of the leads was such that it was not possible to check it until every­thing was back in place. I reassembled the unit (a somewhat lengthy and tedious procedure), cross­ ed my fingers and pushed a CD in. Nothing happened; the drive spindle simply didn’t work. Which meant, of course, that the whole thing had to come apart again. Troubleshooting guide I thought I’d pull a swifty here. The service manual con­tains a troubleshooting guide – one of those flowchart arrange­ments using a “yes/ no” sequence to direct the user from section to section in the hope that it will eventually pinpoint the faulty one. It started with the assumption of no CD playback and asked: “does the disc rotate?” A “no” response instructs you to remove the disc and open and close switch S790. I wasted a lot of time looking in vain for S790 and finally concluded that they probably meant either S822 or S823 on the leaf switch board (board “D”). This achieved nothing. The next questions on the flowchart were directed to the optical pickup; whether it moved and what was its position. These checks achieved nothing either and I seemed to be getting nowhere. I decided it was time to abandon the scientific and resort to the primitive –well, basics anyway. When in doubt, check the supply rails. My first inclination was to go directly into the CD player and look for supply rails but I soon realised that this was not practical. The lid to the CD player operates two interlock switches (the previously mentioned S822 and S823) and so this section is effectively disabled while the lid is open. Any meas­urements could thus be meaningless. The nearest point to the player itself is the leaf switch board (board “D”) which carries the two interlock switches. And this is fed by two plug/ socket assemblies, W302, sections “B” and “F”. It was section “B” which attracted my attention because it connects to the main circuit board and carries two supply rails – 8V and 5V (pins 3 and 4). The 8V on pin 3 was OK but there was no 5V on pin 4. From there, I moved back to the main board to trace out the path. This was easy enough on the circuit, which indicated that the 5V came from pin 6 of the previously replaced IC306 via fuse ICP5. This, however, is not a conventional clipin glass fuse. Instead, it is more like a small transistor encapsulation and is wired directly into the board. Fuse ICP5 was intact but there was no sign of the 5V right back at pin 6 of the IC. So was the new IC306 faulty? That was too horrible an idea but the only logical alternative was a short circuit on this rail. And there was, a check from pin 6 to chassis confirming this. But where? Somewhere in the CD player seemed to be the most likely so I disconnected this by unplugging board “D”. This made no difference, which meant that the short was on the main board. Was it in the IC? I sucked the solder Especially For Model Railway Enthusiasts Available only from Silicon Chip Price: $7.95 (plus $3 for postage). Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 42  Silicon Chip off pin 6 but the short remained. Well, thankfully, that cleared the IC. I moved along the rail and removed fuse ICP5. Ah! A result – of a kind – at last. The short was on the side of the fuse remote from pin 6 of the IC. So why had the fuse not blown in this situation? That puzzle aside, I still had to find the fault. Fortunately by now, there weren’t many likely places left and I eventually traced it to zener diode D310, from the 5V rail to chassis. And that was the final step. A new zener diode restored the 5V rail and the CD player came to life. So, after a day’s soak test, it went back to a happy customer. But it is not a very satisfactory episode in my long love/hate relationship with fuses. There was no fuse where it would probably done the most good and saved the power transform­er. And the one fuse which was where it could have done some good didn’t work. Same thing again My next story is about a video recorder and the awkward situation which can arise when a service job bounces – when the customer returns the device with the complaint that “it’s doing the same thing again”. It seldom is the same thing of course but some customers take a lot of convincing. This set was an Akai model VS-8, an older machine but one which in its day was in the top range, with lots of features. These included stereo sound (with Dolby), long play, slow motion, insert sound dub, and so on. In short, it was a very nice ma­chine. I had first serviced it about five years ago but had not seen it since until it came in a few weeks ago. And the complaint now was that it was chewing tapes when they were ejected. When I opened it, it was clear that, apart from the specif­ic problem, it needed a fair amount of work. A common problem with these machines is failure of the memory backup battery, which then leaks onto the power supply board and attacks the copper tracks. This had happened to this set but, fortunately, only to a minor degree and I had caught it before any major damage had been done. It also needed a new set of belts and tyres and a set of brake pads. And it was these latter items which were the cause of the complaint. When in the eject mode, the system is supposed to pull the tape tight, against the brake pads, before the cassette is actu­ally ejected. This wasn’t happening properly, or at least not every time. As a result, a small amount of tape was left protrud­ing from the cassette and this was fouling on the way out. So it was a major overhaul job: clean up the battery area and fit new batteries; fit new belts, tyres and brake pads; replace the pinch wheel (which had become hard and shiny; and clean the heads and the tape path generally. I also changed the sensing lamp, something which I do as a matter of course in a major overhaul. After that the machine behaved like new and the new brake pads were obviously doing their job. I returned it to the cus­tomer and thought no more about it. The same thing? Until about three months later, that is. Then the customer was back with the machine, complaining that it was doing the same thing. The first thing to do in such cases is to check the ma­chine, in front of the customer, and see whether it really is doing the same thing. In fact, it wasn’t. The fault now was that the cassette wasn’t being accepted properly and it wouldn’t play. And this was intermittent. The situation was a little dicey at this stage. While it clearly was not the same fault – and I made sure that the customer understood this – I couldn’t rule out the possibili­ty that I might have done something wrong during reassembly. So I said leave it with me and I would check it out. The reason the cassette wasn’t always accepted wasn’t hard to find. It was due to a faulty leaf switch which senses the cassette’s position and activates a sensing light and the indica­tor light on the front panel. In fact, the cassette was in posi­tion; it was just that the system didn’t know this and the indi­cator said it wasn’t. And, of course, it could not be played. Well, that was easily fixed, and I assumed that that would solve July 1996  43 Serviceman’s Log – continued Fig.2: the motor drive circuitry in the Akai VS-8 VCR. IC6 drives the “Rell” (reel) motor (M903), while IC5 above it drives the “Lowding” (loading) motor (M902). which is described as the “Lowding Motor”). Anyway, spelling problems aside, I had to find out why the “Rell Motor” wasn’t working in the fast forward mode, even though it was working in the play and record modes. Unfortunately, access to the mecca drive board is very awkward. It is necessary to remove the top cover, take out the loading cage, and remove the front control panel. And the board is behind the front panel but so mounted that it is almost impos­sible to remove it; any work has to be done with it in situ. Each of the aforesaid motors is driven from its own IC – IC5 for the loading motor and IC6 for the reel motor. Naturally, I was interested in IC6, which is shown as a BA6109. But it wasn’t a BA6109 on the board. This IC had obviously been replaced at some time with a new IC designated BA6209. Unfortunately, I had no idea whether this was a legitimate replacement, or how significant the change was in regard to this problem. More to the point, a voltage check on this IC, in various modes, left little doubt that it was faulty. And as a BA6109 was available, it seemed logical to fit it. Unhappy customer the whole problem. But it didn’t; a routine check showed that there was obviously something else wrong. And it was very funny “wrong” as it turned out. No fast forward When I’d fixed the leaf switch, I pushed a test cassette into the machine and put it through its paces. And at first all seemed well; it played, it recorded and it rewound. But then I discovered that it wouldn’t fast forward. And from this emerged another problem. When the tape was fully rewound, it wouldn’t play. However, if it was only partially rewound – as it was when I made my initial test – it would play, record and rewind as normal –until it was fully rewound again, that is. I pulled the cassette out and checked it and could see immediately why it would not play; it had rewound completely so that only the clear section of tape was visible at the take-up reel. Normally the end sensor, when 44  Silicon Chip it sees the clear tape, initiates a reset (forward wind) function, which brings the active tape up to, or close to, the take-up reel. This cancels the end sensor signal, which otherwise disables the system. That was only an intermediate explanation, of course. So why wouldn’t it reset? My first reaction was to suspect the end sensor. This consists of phototransistor TR2 (PN202S), lamp 1N901 (fed from terminals 15 & 16), and some associated circuitry. But no, the end sensor system was working correctly in all respects. Two faults; one problem Then the penny dropped. The two failures had to be related because it is the fast forward mode which is activated by the end sensor to provide the short burst of reset action, as described above. So solve the fast forward problem and all should be well. This meant delving into the “mecca drive” board, which provides the drive for reel motor M903 (described as the “Rell Motor”, as distinct from M902 But first I contacted the customer and explained what I had found, what would need to be done, and what it would cost. This worked out at around $67, involving $12 (cost price) for the IC and the rest for labour. Even then, this did not nearly cover the time taken to track down the fault and fix it. The customer wasn’t particularly happy about this charge, even though I did my best to convince him that this was a com­pletely separate fault in no way connected with the first service call. Anyway, after some show of protest he agreed to meet the cost and for me to go ahead. Which I did, and everything worked out as expected (I’m not sure what I would have done had another fault turned up). But it was a classic example, not only of an unusual technical fault, but of the problem facing any serviceman when a second, complete­ ly unrelated, fault occurs shortly after any service work. And, of course, it’s always, “... doing the same thing again”. But that’s life SC in this game. 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 electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semicustom electronics & data communications. 63 chapters, in hard cover at $120.00. Silicon Chip Bookshop Radio Frequency Transistors Newnes Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Guide to TV & Video Technology By Eugene Trundle. First pub­lish-­ ed 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $39.95. Servicing Personal Computers By Michael Tooley. First published 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. 336 pages, in paperback at $49.95. 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. Digital Audio & Compact Disc Technology Electronics Engineer’s Reference Book Hard cove 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 Power Electronics Handbook Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order r Edited by F. F. Mazda. version now available First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, ❏ 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. Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering, impedance matching & CAD. 235 pages, in hard cover at $85.00. Surface Mount Technology By Rudolph Strauss. First pub­ lished 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. Audio Electronics By John Linsley Hood. Pub­lished 1995. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. Covers tape recording, tuners & radio receivers, preamplifiers, voltage amplifiers, power amplifiers, the compact disc & digital audio, test & measurement, loudspeaker crossover systems and power supplies. 351 pages, in soft cover at $52.95.   Title  Newnes Guide to Satellite TV  Guide to TV & Video Technology  Servicing Personal Computers  The Art Of Linear Electronics  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Electronic Engineer's Reference Book  Radio Frequency Transistors  Surface Mount Technology  Audio Electronics 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 Price $55.95 $39.95 $59.95 $49.95 $55.95 $59.95 $120.00 $85.00 $99.00 $52.95 Charge SLA batteries away from the mains Want to charge a sealed lead acid (SLA) battery away from home? This simple project lets you use your car or boat battery to automatically – and safely – charge 12V SLA batteries. By JOHN CLARKE Sealed Lead Acid (SLA) batteries are used in a host of devices: cam­ corders, spotlights, toys, portable TVs, communications equipment and even go-anywhere vacuum cleaners . . . and these are only a few applications which spring to mind. SLA batteries are great when you’re at home or close to a power outlet and charger. But charging them when you’re miles (or even kilometres) from home? – that’s a different matter! 54  Silicon Chip Despite what many people believe, you cannot simply connect a 12V SLA battery to your car or boat battery via a current limiting resistor and expect it to charge properly. The reason for this is that there is insufficient potential difference between the two batteries to fully charge the SLA battery. What’s more, even when such a system is used to partially charge an SLA battery, it requires constant monitoring to ensure that the battery isn’t cooked by too high a charging current. Main Features • Powered from 12V battery • 2A average current limit • Suitable for 12V 6.5A.h & greater capacity SLA batteries • Efficient switchmode desig n • Fuse protected • Reverse polarity protectio n • Power indication Many readers have asked for a safe, reliable means of charging SLA batteries from vehicle or boat batteries, which is the reason this project was developed. Whether camping, boating, travelling or off-roading, this charger will come in handy. Fig.2: inside the Motorola MC34063 DC-DC converter IC which forms the heart of the circuit. Fig.1: the basic operation of the DC-DC converter. It connects to the car or boat battery and directly charges any SLA battery with a capacity of 6.5Ah or more to an endpoint of 13.8V, without the need for constant monitoring. The charger will initially supply over 2A to a discharged battery and this current will gradually decrease as the battery voltage reaches 13.8V. Another application is as a solar battery charger, using 12V panels. The circuit will step-up the voltage from the panels when it drops below 12V and thereby improve overall effic­ iency. This design effectively super­cedes the design published in Nov­ember 1991. Basic operation In operation, the SLA battery charg­er steps up the voltage from the battery using a DC-to-DC converter. Fig.1 shows the basic principle of the step-up circuit. When switch S1 is closed, current I1 flows through inductor L1. When S1 opens, the field collapses and an induced current, I2, flows through the load via D2. C1 is also charged at this time and discharges through the load when S1 is closed. By using a transistor or Mosfet in place of S1 and by monitoring the output voltage across the load, we can adjust the on and off times for the switching so as to provide a constant voltage output. A Motorola MC34063 DC-DC converter IC has been used to control this operation. This IC contains all the necessary circuitry to produce either step-up, step down or an inverting DC converter. Its principal sections are a 1.25V reference, comparator, oscillator, RS flipflop and a Darlington transistor pair (Q1 and Q2) – see Fig.2. The frequency of operation is set by a capacitor on pin 3. A 0.001µF cap­ acitor, for example, will set it running at about 30kHz. The oscillator drives the flipflop which in turn drives the Darlington transistor. Excess current is sensed at the current peak input (pin 7) and this switches off the flipflop and Darling­ton transistor, to bring the current under control. The on time for the Darlington transistor is set by the comparator. This is used to monitor the output voltage. When the pin 5 comparator input exceeds the 1.25V reference, the comparator goes low to keep the flipflop from setting and thus holds the Darl­ing­ton off. Conversely, if the output voltage is too low, the inverting input of the comparator will be below the 1.25V reference and so the Darlington can be toggled by the RS flipflop at the rate set by the oscillator. The complete circuit Fig.3 shows the full circuit diagram. The Darlington emitter at pin 2 drives the gate of Mosfet Q1 while the 120Ω resistor turns off the gate whenever the Darlington is off. Note that the Darlington collectors at pins 1 and 8 are connected to the positive supply (pin 8 via a 47Ω resistor). A 0.1Ω resistor between pins 6 & 7 sets the peak current delivered to the Fig.3: The similarities between the complete circuit and that of Fig. 1 are obvious, with the IC and Q1 effectively replacing the switch and its functions. July 1996  55 This view inside the assembled SLA charger shows how the PC board clips into place using the integral side pillars. Note that inductor L1 is secured to the board with cable ties ­– don't rely on its leads to hold it in place. inductor to 0.3V/0.1Ω, or 3A peak. The average current supplied to the load via D2 is limited to a little under 2A. A 0.68µF capacitor at the output filters the voltage before it is applied to the SLA battery. Voltage regulation is provided by the 22kΩ and 2.2kΩ voltage divider resistors connected to pin 5. When the output voltage is 13.8V, the voltage at pin 5 is 1.25V. Since this is the reference voltage on the internal comparator (see Fig.2) the IC will maintain 13.8V at the output. The 0.1µF capacitor at pin 5 removes transient voltages which could cause the IC to behave erratically. Diode D1 has two purposes. First, it provides reverse polarity protection for the circuit. This may be of no consequence if a cigarette-lighter plug is used to obtain the battery voltage. However, if clip leads are used, then reverse polarity is a distinct possibility and protection is useful. The second purpose for D1 is to prevent overcharging. This can happen with a step-up circuit when the input voltage rises above about 14V. At this point, the FET will be permanently turned off and so there is a direct path to the batter via D1, L1 and D2. However, the resulting drop across 56  Silicon Chip D1 and D2 (approx. 1.2V) will limit the voltage applied to the SLA battery. Finally, fuse and zener diode protection has been included to limit the short circuit current and prevent transient voltages damaging IC1. LED1 provides power indication. Construction The Silicon Chip 2A SLA Battery Charger is housed in a plastic case measuring 130 x 68 x 42mm. The components are mounted onto a PC board coded 04305961 and measuring 103 x 60mm. A front panel label measuring 62 x 126mm affixes to the top lid. Begin construction by checking the Both power diodes and the Mosfet are mounted on finned heatsinks. There is no need for insulating bushes or washers but make sure that the leads do not contact the heatsink. PC board for shorted tracks or small breaks, then insert all the PC stakes. These are located at the four external wiring points on the PC board. Next, insert and solder in all the resistors, using the accompanying table as a guide to the colour codes. This done, insert the IC and zener diode. The capacitors are next: there are no polarity-conscious capacitors in this circuit so their orientation is unimportant. However, the fuseholder clips must be inserted correctly, otherwise the fuse will not clip in. It is best to fit the fuse into the clips before inserting them into the PC board. D1, D2 and Q1 are each mounted horizontally on the PC board with a heatsink and secured with a screw and nut. Bend the leads for each component at right angles before mounting these devices. LED1 is mounted on the end of its leads so that it will later protrude through the front panel. Inductor L1 is wound with 1mm enamelled copper wire on a ferrite toroid. Draw half the length of wire through the centre of the core and wind on 22 turns neatly side by side. The direction is unimportant. Now, using the other end of the wire, wind on another 22 turns so that the toroid has 44 turns neatly wound around the core. The windings are terminated into the PC board holes as shown on Fig.4. Make sure that the wire ends are stripped of insulation before soldering. The insulation can be scraped off with a knife or melted off with a hot soldering iron. L1 is secured in place with two cable ties which loop through holes in the PC board and around opposite sides of the toroid. Final assembly The assembled PC board can now be installed in the case. First, affix the label to the front panel and drill out the holes for the LED and switch S1. You will also need to drill out holes in the top and bottom of the base of the case to accept the cable grommets. This done, place the PC board in the case and test the lid to check that the LED passes through its front panel hole. Adjust the height of the LED if necessary, so that it just protrudes through the lid. Next, connect the lighter plug to a length of twin automotive wire or heavy-duty figure-8 cable. This done, Fig.4: install the parts on the PC board as shown on this wiring diagram. Fig.5: check your board against this fullsize pattern before installing the parts. pass the other end of the lead through a grommet and terminate the wires to the PC board and S1 as shown. Similarly, connect the battery clips to one end of the second length of twin automotive wire, pass this wire through the second grommet and connect the leads to the output terminals on the PC board. You are now ready to test the unit. Apply power from a 12V supply (or battery) and check that the LED lights. If it doesn’t, check that the LED is oriented correctly and that the supply is connected with the correct polarity. Now measure the voltages on IC1 with a multimeter. There should be about 12V across pins 4 and 6. Now connect a 470Ω resistor (or there­ abouts) in parallel with a 100µF 16VW (or larger) electrolytic capacitor across the output terminals (positive of capacitor to positive terminal, negative to negative) and check that the output voltage is about 13.8V. Note that some power supplies will not cope well with the battery charger since it draws high RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ No. 1 2 1 1 Value 22kΩ 2.2kΩ 120Ω 47Ω 4-Band Code (1%) red red orange brown red red red brown brown red brown brown yellow violet black brown 5-Band Code (1%) red red black red brown red red black brown brown brown red black black brown yellow violet black gold brown July 1996  57 PARTS LIST 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 Semiconductors 1 MC34063 DC-DC controller (IC1) 1 MTP3055E, BUZ71 60V Mosfet (Q1) 2 BY229 fast recovery diodes (D1,D2) 1 16V 1W zener diode (ZD1) 1 5mm red LED (LED1) 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 Capacitors 2 100µF 16VW electrolytic (for testing) 2 0.68µF 250VDC MKT polyester 1 0.1µF 63VW MKT polyester 1 .001µF 63VW MKT polyester Resistors (0.25W, 1%) 1 22kΩ1  120Ω 1W 2 2.2kΩ 1 47Ω 1 470Ω (for testing) 1 0.1Ω 5W POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc 1 PC board, code 14305961, 103 x 60mm 1 plastic case, 130 x 68 x 42mm 1 front-panel label, 62 x 126mm 1 SPDT toggle switch (S1) 3 TO-220 mini heatsinks (19 x 19 x 9.5mm) 3 3mm screws and nuts 2 M205 PC board fuse clips 1 3A M205 fuse 1 battery clip, red 1 battery clip, black 1 cigarette lighter plug (or two more battery clips) 2 cable ties 2 cord grip grommets 1 Neosid 17-742-22 iron powder ring core 4 PC stakes 1 1.5-metre length of 1mm enamelled copper wire 1 3-metre length of 5A twin red/ black automotive cable 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 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). 58  Silicon Chip ✂ ✂ Street ___________________________________________________________ current pulses. However, a 100µF capacitor connected to the power supply terminals will usually prevent the supply from going into overload. If this fails, use a 12V battery instead. Now you can test the charger on an SLA battery. Connect the charger to the lighter socket in your car and to the SLA battery and check that the battery charges to 13.8V. Check the temperature of D1, D2 and Q1. They SC should run warm. S ONI2C3 R T C 2 ELE SW 2 7910 y, N EY OATL ox 89, OatleFax (02) 570 C a rd reflective tape with self-adhesive backing. Other motorists will see you better at night if this is stuck to chromed or unpainted car bumpers or on bicycles: 3 metres for $5. Visa PO B 579 4985 fax a rd , ) C 2 0 SOUND FOR CCD CAMERAS / UNIVERSAL ( r ne & rs: e e o t n s h o a p h AMPLIFIER P , M ith rde d o w r a d d c e Uses an LM386 audio amplifier IC and a e B a n k x accept most mix 0. Orders BC548 pre-amp. Signals picked up from e r 1 an electret microphone are amplified and & Am . P & P fo (airmail) $ drive a speaker. Intended for use for s order 4-$10; NZ world.net listening to sound in the location of a $ <at> . y t CCD camera installation, but this kit atle Aus o : L could also be used as a simple utility I A M amplifier. Very high audio gain (adjustable) makes this by E unit suitable for use with directional parabolic reflectors etc. PCB: 63 x 37mm: $10 (K64). 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. Some models include a dimming option which requires either an external 100kΩ 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 B: 1 x 16W tube, dimmable, filter used, 43 x 4 x 3cm: $16. Type F: 1 x 32W or 36W tube, dimmable, no filter, 34 x 4 x 3cm: $18 (Cat G09, specify type). 27MHz RECEIVER CLEARANCE Soiled 27MHz telemetry receivers. Enclosed in waterproof die cast metal boxes, telescopic antenna supplied. 270 x 145 x 65mm. 2.8kg. Two separate PCBs. Receiver PCB has audio output. Signal filter/squelch PCB is used to detect various tones. Circuit provided: $12. 40-CHANNEL FM MICROPHONE A hand held crystal locked 40-channel FM transmitter with LCD display: 88-92MHz in 100kHz steps, 50m transmission range. Perfect for use with synthesized FM receivers: $50. SPEED CONTROLLED GEARED MOTOR Experiment with powering small vehicles, large children’s cars, garage door openers, electric wheelchairs, rotisseries, etc. etc. We supply a speed control PCB and components kit, A 25A MOSFET and a 30A diode (flyback), and a used 12V geared windscreen wiper motor for a total price of: $30. CHARACTER DISPLAYS We are offering three types of liquid crystal character displays at bargain prices. The 40 x 2 character display (SED1300F) is similar to the Hitachi 44780 type but is not directly compatible. We will also have similar displays - data available for a 16 x 4 and 32 x 4 display. Any mixture of these displays is available for a crazy price of $22 each or 4 for $70. IR TESTER USING IR CONVERTER TUBE Convert infra red into visible light with this kit. Useful for testing infra red remote controls and infra red laser diodes. We supply a badly blemished IR converter tube with either 25 or 40mm diameter fibre optically coupled input and output windows and our night vision high voltage power supply kit, which can be powered from a 9V battery. These tubes respond to IR and visible light. A very cheap IR scope could be made with the addition of a suitable casing and objective lens and eyepiece. $30. MISCELLANEOUS ITEMS 2708 EEPROMS: $1 each; 4164 MEMORY ICs: 16 for $10: AC MOTOR, 1RPM Geared 24V-5W Synchronous motor plus a 0.1 to 1RPM driver kit to vary speed, works from 12V DC: $12 K38 + M30; SPRING REVERB, 30cm long with three springs: $30 A10; MICROSONIC MICRO RECORD PLAYER, Includes amplifier: $4 A11; LARGE METER MOVEMENTS: moving iron, 150 x 150mm square face, with mounting hardware: $10. REFLECTIVE TAPE High quality Mitsubishi brand all weather 50mm wide red VHF MODULATOR KIT For 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). ‘MIRACLE’ ACTIVE AM ANTENNA KIT Available soon. To be published in EA. After the popularity of our Miracle UHF/VHF antenna kits we have produced this AM version for our ‘Miracle’ series. Large antennas are not the most attractive inside a house but sometimes this is needed to receive a weak radio signal. This kit will connect to a remote loop of wire, preferably outside where reception is good, via coax cable and allow it to be tuned from inside via varactor diodes. Radio reception is greatly improved and it can even pickup remote stations that a radio can’t receive with its ferrite rod antenna. No connections are required to the existing radio as the receiving end is coupled to the ferrite rod in the radio with a loop of wire around the radio. Excellent kit for remote country areas where radio reception isn’t very good, or where a large antenna is not possible. Great for caravanners, boats that venture far out to sea, etc. 2 x PCBs and all on-board components. BATTERY CHARGER WITH MECHANICAL TIMER Simple kit which is based on a commercial 12 hour mechanical timer switch which sets the battery charging period from 0 to 12 hrs. Employs a power transistor and five additional components. Can easily be “hard wired”. Information that shows how to select the charging current is included. We supply information, circuit and wiring diagram, a hobby box with aluminium cover that doubles up as a heatsink, a timer switch with knob, a power transistor and a few other small components to give you a wide 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. Or you could use it in your car. No current is drawn at the end of the charging period: $15. AUTOMATIC LASER LIGHT SHOW KIT Kit as published in Silicon Chip May 96 issue. The display changes every 5 - 60 seconds, and the time is manually adjustable. For each of the new displays there are 8 different possible speeds for each of the 3 motors, one of the motors can be reversed in rotation direction, and one of the motors can be stopped. There are countless possible interesting displays which vary from single to multiple flowers, collapsing circles, rotating single and multiple ellipses, stars, etc. etc. Kit makes an excellent addition to any lightshow and all these patterns are enhanced by the use of a fog machine. Kit includes PCB, all on board components, three small DC motors, 3 high quality/low loss dichroic mirrors: $90. Suitable 12V DC plugpack: $14. LASER LIGHTSHOW PACKAGE Our 12V Universal inverter kit plus a used 5mW+ helium-neon laser tube head plus a used Wang power supply plus an automatic laser light show kit with dichroic mirrors (as above): $200. ARGON-ION HEADS Used Argon - Ion heads with 30-100mW output in the blue - green spectrum. Head only supplied. Needs 3Vac <at> 15A for the filament and approx 100Vdc <at> 10A into the driver circuitry that is built into the head. We provide a circuit for a suitable power supply the main cost of which is for the large transformer required: $170 from the mentioned supplier. Basic information on power supply provided. Dimensions: 35 x 16 x 16cm. Weight: 5.9kg. 1 year guarantee on head. Price graded according to hours on the hour meter: We have had no serious problems with any of these heads as they were used at a very low current in their original application. Argon heads only: $300. SIREN USING SPEAKER Uses the same siren driver circuit as in the “Protect anything alarm kit”. 4-inch cone / 8-ohm speaker is included. Generates a very loud and irritating sound with penetrating high and low frequency components. Output has frequency components 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. DC MOTORS We have good stocks of the following high quality DC motors. These should suit many industrial, hobby, robotics and other applications. Types: Type M9 : 12V. I no load = 0.52A <at> 15800 RPM at 12V. Weight: 150g. Main body is 36mm diameter. 67mm long: $7 (Cat M9) Type M14 : Made for slot cars. 4 to 8V. I no load = 0.84A at 6V. At max. efficiency I = 5.7A <at> 7500 RPM. Weight: 220g. Main body diameter is 30mm. 57mm long: $7 (Cat M14). ULTRASONIC COMMUNICATOR KIT Ref: EA Sep/Oct 93. Signals picked up by an electret microphone are modulated onto an oscillator which drives a 40kHz ultrasonic transducer. This is received by a 40kHz ultrasonic receiving transducer and is amplified and detected. The detected signal is amplified by a simple three transistor amplifier to drive a speaker. This makes a communications link using ultrasound which can transmit over a few metres. The quality of the sound is limited by the narrow bandwidth of the transducers but this is an interesting experiment. Both transmitter and receiver PCBs are 63 x 33mm: $16 (K45). BOG DEPTH SOUNDER KIT Detect the presence and depth of any body filler on your car. This simple circuit uses an oscillator which is oscillating weakly. When steel is placed near the small search coil the inductance shifts and the oscillator components are arranged so the oscillator will stop running. The remainder of the circuit simply detects when the oscillator stops and gives a visual or audible indication of this. The circuit is arranged so that the change in inductance needed to stop the oscillator can be varied. This allows variable depth of filler sensing, between 0 and about 3mm. Large areas of body filler over 3mm thick are generally considered undesirable as the filler may lift or crack. Kit supplied includes pre-wound search coil (33 x 22 x 10mm). A LED is supplied in the kit as the visual indication. An audible indication can be obtained by using a low power piezo buzzer, which is recommended but not supplied with the kit: $12 (K62). $2 for optional low power piezo buzzer. HIGH VOLTAGE AC DRIVER This kit produces a high frequency high voltage AC output that is suitable for ionizing most gas filled tubes up to 1.2m long. It will partially light standard fluorescent tubes up to 1.2m long with just 2 connections being made, and produce useful white light output whilst drawing less than 200mA from a 12V battery. Great for experimenting with energy efficient lighting and high voltage gas ionization. PCB plus all on board components, including high voltage transformer: $18. PC CONTROLLED PROGRAMMABLE POWER SWITCH MODULE This module is a four-channel programmable on/off timer switch for high power relays. The timer software application is included with the module. Using this software the operator can program the on/off status of four independent devices in a period of a week within a resolution of 10 minutes. The module can be controlled through the Centronics or RS232 port. The computer is opto-isolated from the unit. Although the high power relays included are designed for 240V operation, they have not been approved by the electrical authorities for attachment to the mains. Main module: 146 x 53 x 40mm. Display panel: 146 x 15mm. We supply: two fully assembled and tested PCBs (main plus control panel), four relays (each with 3 x 10A / 240V AC relay contacts), and software on 3.5-inch disk. We do not supply a casing or front panels: $92 (Cat G20). July 1996  59 The Minilog can be used with a companion liquid crystal display so that its recorded data can be read or it can be connected to a PC to download its data. Build the Minilog: an 8-bit data logger The Minilog is a tiny, single channel, 8-bit, 0-5V data logger. It can be read in the field or it can communicate with a PC. The logging configuration can be easily altered by the user to suit any application because a BASIC STAMP ll is used in the design. By ANTHONY MOTT This project was developed from a more complicated applica­tion that required the collection of four or five sample readings from an air speed sensor in a model aircraft. In that application it was necessary to be able to launch the logger remotely and be able to read the recorded data in the field. While retaining the operational benefits developed in the model air60  Silicon Chip craft unit, only the bare essentials of hardware are used in this mini logger. The heart of the unit is a BASIC STAMP II (BS2) chip and an ADC0831 serial output analog to digital converter (ADC). The BS2 is a complete computer module built on a 24-pin DIL header. It uses a PIC16C57 microcontroller, 24LC16 EEPROM, voltage regulator, power down controller, serial I/F and a 20MHz resona­tor. The PIC16C57 is pre-programmed with a PBASIC interpreter – similar to other BASICs but with controller specific commands. BS2’s instruction set can be used on any of its 16 I/O lines. Program and data are stored in the 2048 byte 24LC16 EEPROM. The EEPROM ensures that program and data are retained indefinitely, power or no power. A handheld readout unit is describ­ ed for field use. This has a 40- character 2-line liquid crystal display unit controlled by a serial input LCD managing “backpack” and two push buttons. Current drain is so low that a separate battery is not fitted; rather the display unit steals some power from the logger’s battery. The display unit connects to a 5-pin block on the Mini­log board. It is possible to use a PC to read and display the Mini­log’s stored data Fig.1: the Minilog is based on the Basic STAMP II module togeth­er with IC1, the analog to digital converter. by using a terminal program. Using capture features available in most terminal programs allows a user to store and display the Minilog’s data and use that data in a spreadsheet or other data analysis programs. An additional mode of operation is “direct read”. With the display unit connected, the data present at the logger input is presented on the display and updated five times each second. Minilog’s logging program is written, developed and stored on an IBM compatible PC, using the BS2 software supplied in the Stamp development kit. A copy of three heavily commented programs to configure the Minilog (for the three basic roles outlined above) will be available on disc and printout. Note that the remarks are not stored in the BS2 but are kept in the PC file so there is no excuse for not making clear and detailed notes about your program. The program is loaded into the BS2 from the PC’s COMn port (“n” is autosensed) and takes about one second to load, making “write and try” much more convenient than conventional CPU/EPROM combinations. The 4-pin connector on the Minilog is used for loading the program from the PC. The same connector is used when reading data from the Minilog to the PC with a terminal program. Circuit details The circuit of the Minilog is shown in Fig.1. The ADC0831 ADC chip used in Minilog has two pins, Vref and Vin, allowing range and span setting. However, to keep Minilog simple, these pins are connected with Vref to +5V and Vin to ground. This arrangement gives a 0-5V input range. An additional resistor can be fitted to act as a voltage divider to increase the input voltage range (see later). A 1MΩ resistor and a .01µF capacitor are fitted at pin 2 to filter noise. The resistor will also help protect the ADC0831 from “over voltage” inputs. Each input reading will be converted to a single byte value in the range 0 to 255. An input of +3.2V will be converted to 163 (256/5*3.2=163.84) and stored as this value. Note that the deci­mal portion of the calculation is ignored. The highest speed of Minilog is better than ten samples per second; ie, one every 100 milliseconds. This can decrease to one per minute in 1ms steps. The sampling rate is determined by the software and can be any value that you may require, from milli­seconds to hours. Comments in the software explain how changes can be made. Battery drain from the 216-style 9V battery whilst logging at five samples per second is about 15mA without the display connected. If using very slow sample rates, using the BS2 SLEEP command rather than PAUSE will put the BS2 into a power down state between readings and this will reduce the current drain considerably. Data storage space depends on program length. With 2048 bytes available for program and data, the shorter the program, the greater the data storage space. With each of the three pro­grams supplied, there is room to hold at least 1000 samples. Using Minilog The following describes how the MINILOGL.BS 2 program sup­ p lied with a Minilog kit works. It is simple to change the pro­gram to suit your purpose – there are ample comments in the software to make changes easy. Once the program is loaded, the Minilog can be connected to the data source, powered up and when the event to be logged is ready, it is started by momentarily closing the “launch” switch contacts. The first closure trips July 1996  61 Believe it or not this teeny little board (shown here larger than life) is a single channel data logger which can store up to 1000 events. It uses the Basic STAMP module (a PIC processor with on-board Basic interpreter) and an analog to digital converter with an input range of 0-5V. the Minilog into its data collection routine – subsequent closures will be ignored. The display need not be connected at this time. Minilog will take samples and store them until the avail­able memory is full and then halt. If Minilog is powered down before the memory is full, it will simply stop – all data col­lected will be retained. Powering up Minilog again will allow the data to be read, however launching Minilog again at this time will result in the stored data being overwritten from the begin­ning. If the display is connected before Minilog is powered up, a prompt to start will be displayed and if a launch switch closure happens, the display will report that logging is under way. Mini­ log will report via the display when it has filled the data memory. The display may be disconnected once logging is under way without interfering with the program. However, connecting the display unit after turning the Minilog on will cause the display to malfunction as the initial62  Silicon Chip ising data that the Minilog sends to the LCD backpack at turn-on will not have been processed. To read the data collected, connect the display unit, power up Minilog and follow the display prompts which provide for displaying the data or erasing the data memory by using the two pushbuttons “A” and “B”. The Minilog software handles brief pushbutton closures and holding a button down continually may produce strange results. An exception to this is when scrolling through the “pages” of data – holding button “A” down will scroll through at about two pages per second. Provision has been made in the software for each sample to use up to four character spaces. This means that 12 samples plus page identification can be displayed as a “page” using the 40character 2-line LCD unit. A logging session recording 250 samples would be displayed over 21 “pages”. The reason that four spaces are provided for a 3-digit sample is that a formula may be incorporated in the program so that raw data fed into the ADC is actually processed and displayed in a meaningful format. Remember that the BS2 uses only integer arithmetic – no decimals please. If you want data with decimal places, you will need to multiply by 10 or 100 and read an inferred decimal point. There are comments in the software showing how to use formulas and how to change the page display format. Two additional programs, MINI­ LOGP.BS2 and MINILOGD.BS2 (see listing), are available. MINILOGP. BS2 provides for logging of data and unload­ing the stored data to a PC using a terminal program. When Mini­log is used in this manner, the display unit can be used to keep track of what is happening but it is not essential. Comments in the software explain how to use this program. MINILOGD.BS2 is used with the display unit and provides an instant readout of the data present at the ADC input, with the display being updated about five times per second. Again, formu­las can be included between the data and the display, making this program useful for testing or calibrating instruments. Precautions Fig.2: wiring diagram for Minilog. The STAMP module plugs into a 24-pin header on the PC board. The BS2’s on-chip regulator will be destroyed if the power supply is reversed, overvoltage is applied or if too much current passes through the regulator. The maximum input voltage should be limited to 12V. Mini­log uses the on-chip regulator for the ADC0831, display unit (when connected) and the BS2 itself. A total load current of 18mA has been measured and provided the regulator thermal dissipation is kept low (by not exceeding 9V), up to 50mA drain is possible. The ADC0831 span and reference pins are connected to +5V and ground in Minilog. This means that the ADC input should not exceed +5.3V or -0.3V. To help protect the input of the ADC, a 1MΩ resistor and a .01µF capacitor are provided, as noted above. These work as a noise filter and help limit possibly destructive currents. Limiting diodes are not recommended because they could rectify stray RF signals and create odd voltages at the ADC input pin. Where the voltage input range would exceed the 0-5V ADC0831 input limit, provision has been made on the Minilog PCB to install an additional resistor to act as a voltage divider. This would change the allowable raw input range according to the following table: Input Range Resistor Value 0-5V Not required 0-7.5V 2MΩ 0-10V 1MΩ 0-15V 500kΩ 0-20V 333kΩ Construction As can be seen from the photos, there is very little to assemble with this project. Use sockets for both ICs –you will probably want to use the BS2 module in another project. Be sure to fit the two resistors, capacitor and link before fitting the 24-pin socket. Take care with the power lead polarity and orient the sockets and ICs correctly. There is no need for a power switch, as the polarised plug and socket is cheaper and easier. The arrangements for the launch switch will depend on your appli­cation – a short lead with a microswitch is suggested. Two leads are required: one of four conductors to connect the Minilog to your PC for programming the BS2 and to “unload” data when using a terminal program. This lead requires a link between pins 6 and 7 on the DB9 to allow the BS2 software to sense which COM port is being used to program the BS2 module. The second lead of five conductors is used to connect the Minilog “remote” pins to the display unit. As these connectors are not polarised to the Minilog board, both the pin header and socket for each connector should be marked clearly to aid correct connection – a dab of liquid paper fluid is effective for this purpose. Listing For Direct LCD Readout ‘ MINILOGD.BS2 ‘ ‘ MINILOG OPERATING PROGRAM. (Anthony Mott, April 1996). ‘ ‘ (SERIES 2.2 PROGRAM.) ‘ ‘ FOR INSTANT (OR DIRECT) DISPLAY OF DATA INPUT, TO LCD DISPLAY IN ‘ REMOTE UNIT. ‘ ‘ USES BS2 CHIP AND ADC0831, PLUS A 40 X 2 LCD DISPLAY REMOTE UNIT. ‘ THE REMOTE UNIT PUSH BUTTONS HAVE NO EFFECT WITH THIS PROGRAM. ‘ (USES VERSION 3A LCD SERIAL BACKPACK.) ‘ ‘ IN LISTING, NOTE DIFFERENCE BETWEEN 0 (ZERO) AND O (CAPITAL “o”). ‘ ‘ I CON 254 ‘ LCD INSTRUCTION VALUE CONSTANT. B CON $4054 ‘ SERIAL BAUD RATE CONSTANT FOR ‘ 9600 BAUD; = $4000 HEX + 84 DECIMAL = ‘ $4000 + $54 = $4054. ($ = HEX.) FOR 9600 ‘ NEED TO FIT JUMPERS ON BACKPACK BOARD AT ‘ “BPS” AND FOR 40 X 2 DISPLAY, AT “LINES”. ‘ (SEE SERIAL BACKPACK INSTRUCTION MANUAL.) S CON 11 ‘ SERIAL DATA OUT, BS2 I/O PIN 11. SAMP VAR WORD ‘ VARIABLE FROM ADC SAMPLING FUNCTION. DISP VAR WORD ‘ CALCULATED VARIABLE FOR DISPLAY ON LCD. ‘ ** NOTE THAT BS2 I/O PIN NUMBERS ARE NOT ‘ THE SAME AS BS2 I.C. PIN NUMBERS ! LOW S PAUSE 1000 ‘ ONE SECOND DELAY FOR LCD TO “WAKE-UP”. SEROUT S,B,[I,1] PAUSE 5 ‘ CLEAR DISPLAY, 1 = CLEAR. ‘ PROCESS OF CLEARING DISPLAY TAKES TIME, ‘ THIS SHORT DELAY FOLLOWING “CLEAR” ‘ IS NECESSARY TO AVOID MISSING SUBSEQUENT ‘ CONTROL CODES OR DISPLAY DATA. IT IS ‘ REQ,D AFTER EACH “CLEAR SCREEN”. SEROUT S,B,[“MINILOG DATA LOGGER...”] ‘ PRINT “HEADER”. SEROUT S,B,[I,194,”DIRECT READ FUNCTION: VALUE =”] ‘ FIXED PORTION OF SECOND LINE; ‘ I = LCD INSTRUCTION CONSTANT (254), 194 ‘ IS LOCATION TO COMMENCE TEXT DISPLAY. ‘ FIRST LINE IS 128-167, SECOND IS 192-231. SAMP = 0 ‘ ZERO VARIABLE. SAMPLE: LOW 3 SHIFTIN 5,6,2,[SAMP\9] ‘ READ ADC AND DISPLAY VALUE ROUTINE. ‘ SELECT ADC AND INIATE CONVERSION. BS2 I/O ‘ PIN 3 IS CONNECTED TO ADC “CHIP SELECT”. ‘ TRANSFER DATA FROM ADC0831 TO BS2: ‘ DATA IN I/O PIN 5, CLOCK OUT I/O PIN 6, ‘ DATA INPUT FORMAT MODE 2, VARIABLE = ‘ SAMP, 9 DATA BITS (AS REQ,D BY ADC0831). continued on page 64 July 1996  63 Continued from page 63 HIGH 3 PARTS LIST ‘ DESELECT ADC. DISP = SAMP * 1 ‘ ENTER MANIPULATION FORMULA HERE. WITH ‘ A MAXIUMUM STORED VALUE OF 255, AND A MAXIMUM DISPLAY CAPACITY (FOR THE ‘ PROGRAM AS WRITTEN), OF 65,530, THE MAXIMUM MULTIPLIER HERE IS LIMITED ‘ TO 65530/256=256. NOTE THAT BS2 WORKS WITH INTEGERS (WHOLE NUMBERS) ONLY. ‘ “10 * 3.2” WOULD GIVE A RESULT OF 30, THE .2 BEING IGNORED. ALSO ‘ “32 / 10” WOULD GIVE 3, (BUT THE .2 CAN BE RECOVERED IN THIS CASE - READ ‘ BS1 AND BS2 MANUALS.) ‘ EXAMPLE 1: INPUT TO ADC IS 0 TO 5 VOLTS, AND WANT THE DISPLAY TO SHOW THIS ‘ VALUE TO 3 DECIMAL PLACES. 5 VOLTS WILL EQUAL A COUNT OF 255. ‘ 5/255=0.0196078, SO MULTIPLY STORED VALUE BY 196 AND DIVIDE BY 10 WILL ‘ GIVE A DISPLAY VALUE OF 4998 FOR 5 VOLTS INPUT. HAVE TO INFER DECIMAL ‘ POINT POSITION TO GET 4.998. REPLACE “DISP=SAMP*1” WITH “DISP=SAMP*196/10”. ‘ EXAMPLE 2: INPUT TO ADC IS 0 TO 10 VOLTS, VIA VOLTAGE DIVIDER. WANT ‘ DISPLAY TO READ 0 TO 10 VOLTS FROM 0 TO 255 “SAMP”. 10/255=0.03921568. ‘ IGNOR LAST FIVE DECIMAL PLACES, AND MULTIPLY “SAMP” BY 39. SO FOR 6 VOLTS ‘ INPUT, HALVED BY VOLTAGE DIVIDER, IS CONVERTED TO 255/5*3=153. ‘ (5= 0-5V ADC INPUT RANGE, 3= 6V INPUT/2). ‘ 153*39=5967, SO HAVE TO INFER DECIMAL POINT TO READ AS 5.967 VOLTS, ‘ REPLACE “DISP=SAMP*1” WITH “DISP=SAMP*39”. NOTE CALCULATION SCRATCH-PAD ‘ LIMITATION OF 65,025, OTHERWISE WOULD USE *392/10 TO IMPROVE RESOLUTION. ‘ COULD ALSO DIVIDE RESULT BY 10 TO GIVE A SHORTER, AND SIMPLER ‘ DISPLAY: 5.96 VOLTS, “DISP=SAMP*39/10”). NOTE THAT BS2 ARITHMETIC IS ‘ DONE STRICTLY IN LEFT-TO-RIGHT ORDER. SEROUT S,B,[I,225,DEC DISP] ‘ DISPLAY DISP, COMMENCING AT LCD LOCATION ‘ 220, IN DECIMAL FORMAT. PAUSE 200 ‘ 1/5th SECOND DELAY BETWEEN SAMPLE READINGS. ‘ THIS CAN BE ALTERED, BUT MAKING DELAY TOO ‘ SHORT MAY RESULT IN BLINKING/ILLEGIBLE ‘ DISPLAY. SEROUT S,B,[I,225,” “] ‘ BLANKS OUT OLD VALUE ON DISPLAY BEFORE ‘ READING AND DISPLAYING NEXT ONE. GOTO SAMPLE ‘ START READ/DISPLAY PROCESS AGAIN. A bridging socket is required for the remote pins when using the MINILOGP.BS2 software without the display unit. Construction details of the display backpack and LCD unit are covered in detail in the backpack kit. Testing Minilog’s performance is best done with a linear potentiometer connected across the 5V supply, with the wiper to the Minilog input. Connection of a slide or rotary potentiometer in this way would also allow logging of the mechanical position of an actuator, wind vane, doorway, gearwheel, control lever, etc. Software The Basic Stamp development kit 64  Silicon Chip includes a disc with an editor/programmer – a:\STAMP2\STAMP2\.EXE. This program is used to create, edit, debug and load programs for the BS2 module. The STAMP2 editor is best accessed from DOS (or DOSSHELL), because Windows will interfere with port assignment (Windows 95 is OK). There are three versions of the Minilog program provided on the disc – MINILOGL.BS2 talks to the LCD backpack and MINILOGP.BS2 talks to a PC. A shareware copy of a terminal commu­nication program, set up for 9600 baud, COM2 and auto LF is included so that you can set up PC communication quickly. MINILOGD.BS2 provides an instant readout on the LCD of the data pres- Minilog module 1 Minilog 2.2 PC board 3 22kΩ 0.25W or 0.125W resistors 1 1MΩ 0.25W or 0.125W resistor 1 1µF tantalum electrolytic capacitor 1 0.1µF ceramic capacitor 1 .01µF ceramic capacitor 1 9V battery and snap connector 1 24-pin DIL socket 1 8-pin DIL socket 4 5-pin socket shells (one is cut down to 4 pins) 1 3-pin polarised socket shell 1 3-pin polarised header 14 crimp fitting sockets for shells 1 11-pin length of single header strip (to make one 2-pin, one 4-pin & one 5-pin) 1 DB9 socket, with solder tails 1 Basic Stamp II module 1 Basic Stamp II development kit 1 Minilog software Light duty hook-up wire for leads Display unit 1 Hitachi LM018XML (or equivalent) 40 character 2-line LCD (Farnell Cat No 491-640) LCD serial backpack, (includes hardware to connect to display) available as a kit or assembled and tested (from MicroZed) 2 pushbutton switches, normally open contacts Case to house display and push buttons (210 x 50 x 30mm) Kit availability A kit for both the Minilog unit and the display unit will be available from Microzed Computers, PO Box 634, Armidale, NSW 2350. Phone (067) 722 777. ent at the input (see example listing included with this article). All three programs have notes and comments about the way Minilog works and ideas for making changes to suit your particular application. Acknowledgement: The author would like to acknow­ ledge the encouragement and support given by Bob Nicol of MicroZed Computers in preparing this article SC for publication. ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL 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. $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS  New subscription – month to start­­____________________________  Renewal – Sub. No.________________    Gift subscription  RATES (please tick one) 2 years (24 issues) 1 year (12 issues) Australia (incl. GST)  $A135  $A69.50 Australia with binder(s) (incl. 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Please have your credit card details ready OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail order form to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia July 1996  65 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 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 Build a three-band parametric equaliser If you are interested in musical instruments, public address systems or any application where you need fine control of the audio spectrum, then this three-band parametric equaliser could be just what you want. It is a very quiet, low-distortion circuit that is easy to use. Design by BOB FLYNN T HERE ARE many audio appli- cations where simple tone con­trols or graphic equalisers just can’t do the job. For the most precise control of the audio spectrum, a onethird octave graphic equaliser is the best but it is a complex unit. Such a graphic equaliser will have 30 or more sliders to cover the full audio range but its capabilities may be wasted in many situations. For example, you may only have two or three troublesome peaks or dips in the response and these could possibly be fixed by nudging only three of the sliders – all the rest would be unnecessary. 70  Silicon Chip By contrast, a three-band parametric equaliser can do many of the tasks of a graphic equaliser and it is a much simpler unit with considerably less active circuitry. Our parametric equaliser has three frequency bands, with their centre frequency adjustable over the nominal ranges from 40Hz to 160Hz, 320Hz to 1.3kHz and 2.2kHz to 5kHz. While they do not overlap, these ranges have been selected as a good compromise between overall circuit complexity, minimum interaction between ranges, ease of use and audible effectiveness. We could have added more bands but since each band needs a minimum of three potentiometers, the number of knobs on the control panel rapidly gets out of hand. With three bands we end up with 10 controls in all. The controls for each band are frequency, boost/cut and Q. The frequency control is self-explanatory – it tunes the centre frequency for each band; ie, the frequency at which the boost or cut setting is at a maxi­mum. The boost/cut control is same as a bass or treble control. In its centre setting the frequency response for the band is flat; when rotated clockwise, boost is applied and when rotated anticlockwise, the frequencies are cut. The third control is labelled “Q” and this knob determines whether the boost will be applied as a sharp peak or over a much broader range of frequencies. Similarly, when cut is applied, the Q control determines whether the cut will result in a deep notch or a much broader “valley” in the response. Let’s look at a few examples to see how the parametric equaliser works in practice. Have a look at the response curves in Fig.1. There are actually three response curves, all with the Q control set for maximum. The top AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz) 15.000 17 MAY 96 11:21:36 AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz) 15.000 10.000 10.000 5.0000 5.0000 0.0 0.0 -5.000 -5.000 -10.00 -10.00 -15.00 17 MAY 96 12:37:47 -15.00 20 100 1k 10k 20k 20 100 1k 10k 20k Fig.1: these boost and cut response curves were taken with the Q control set for maximum. The top curve shows the effect when maximum boost is applied in all three bands. This results in three sharp peaks centred at about 64Hz, 490Hz and 3.3kHz. Each one of those peaks can be moved back or forward within its respective frequency band, by rotating the relevant frequency control. Fig.2: this set of response curves was taken with the Q controls set for a medium value; ie, with the control centred. The first curve shows the low band set for medium cut while the other two bands have medium boost applied. The second is the reverse, with medium boost applied in the low band and medium cut applied in the middle and top bands. AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz) 15.000 AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz) 15.000 17 MAY 96 11:29:54 10.000 10.000 5.0000 5.0000 0.0 0.0 -5.000 -5.000 -10.00 -10.00 -15.00 17 MAY 96 11:33:38 -15.00 20 100 1k 10k 20k Fig.3: one of these curves shows the low and top bands boosted while the centre channel is cut. The other curve shows the low and top bands cut and the centre channel boosted. curve shows the effect when maximum boost is applied in all three bands. This results in three sharp peaks as you can see, centred at about 64Hz, 490Hz and 3.3kHz. Each one of those peaks could be moved back or forward within its respective frequency band, by rotating the relevant frequency control. The bottom curve shows the same frequency and Q settings as for the top curve except that the boost/cut control is now set to maximum cut. Meanwhile, the third curve which is between the top and bottom traces shows the overall flatness of response 20 100 1k 10k 20k Fig.4: this pair of frequency plots shows the low band set for a flat response, while the centre and top bands have either modest boost or cut. when the boost/cut controls are all centred. The response is less than 1dB down at 20Hz and 20kHz. As shown by the above curves, the maximum boost and cut which can be obtained at any frequency within the band ranges is ±10dB. Note that you can have any combination of boost & cut, frequency and Q settings so the number of response curves you could obtain is virtually infinite. It means you can compen­ sate or “equalise” the frequency response for many “real world” applications. Fig.2 gives another set of response curves, this time with the Q controls set for a medium value; ie, with the controls centred. The first curve shows the low band set for medium cut while the other two bands have medium boost applied. The second is the reverse, with medium boost applied in the low band and medium cut applied in the middle and top bands. Fig.3 is another variation on the theme, this time with the low and top bands boosted while the centre channel is cut and then with the low and top bands cut while the centre channel is boosted. Finally, Fig.4 is a pair of frequency plots with the low band flat while the July 1996  71 AUDIO PRECISION SCTHD-HZ THD+N(%) vs FREQ(Hz) 5 17 MAY 96 12:42:53 1 AUDIO PRECISION SCTHD-HZ THD+N(%) vs FREQ(Hz) 5 17 MAY 96 13:36:10 1 0.1 0.1 0.010 0.010 0.001 0.001 .0005 .0005 20 100 1k 10k 20k Fig.5: total harmonic distortion versus frequency with all the boost/cut controls centred (ie, with a flat response), at a level of 1.5V RMS. AUDIO PRECISION SCFREQRE AMPL(dBr) vs FREQ(Hz) 15.000 20 100 1k 10k 20k Fig.6: total harmonic distortion versus frequency, taken with the three bands set for maximum boost and high Q, as in Fig.7. 17 MAY 96 12:54:11 Performance Frequency response ............... (see graphs) 10.000 Signal-to-noise ratio ............... 99dB unweighted (22Hz to 22kHz); -103dB A-weighted, with respect to 1V RMS (with boost/cut controls centred) 5.0000 0.0 Harmonic distortion ................ see graphs -5.000 Maximum output level ............ 9.3V RMS Maximum boost & cut ............. ±10dB -10.00 Range of Q ............................. 0.45 to 5 -15.00 20 100 1k 10k 20k Fig.7: response curve with all bands boosted; this is the test condition for the distortion measurement of Fig.6. other two bands have modest boost or cut. Fig.5 is a plot of total harmonic distortion versus fre­quency with all the boost/cut controls centred (ie, with a flat response), at a level of 1.5V RMS. As can be seen the distor­tion is very low, averaging about .002%. Fig.6 is another plot of total harmonic distortion but this time with the three bands set for maximum boost and high Q, as in Fig.7. This time the distortion is somewhat higher but still satisfactory for the applications in which the circuit is likely to be used. Circuit description Fig.8 shows the complete circuit of the three band paramet­ric equaliser. It is based on three “state variable” filters, one for each of the bands. Each of the state variable filters is identical 72  Silicon Chip Supply current ........................ 30mA (typical) at ±15V apart from the capacitors which determine their fre­quency ranges. All the op amps are LM833 dual low noise types. Eleven op amps out the total of 12 are used and IC2b is unused. To simplify the discussion of the state variable filters, let’s confine ourselves to band 1, the low frequency band. It employs IC1a, IC1b and IC2a. The latter two op amps are integra­tors with their frequency cutoff determined by the 0.12µF ca­ pacitors and their tuning controlled by the 25kΩ dualganged pot VR3a & VR3b. State variable filters have three useable outputs: high-pass, low-pass and bandpass (ie, low-pass and high-pass in combi­nation). The bandpass output is the one we want and this is taken from the output of IC1b, via the 6.8µF non-polarised (NP) capaci­tor. The Q of the filter is controlled by IC1a, in conjunction with the 100kΩ dual-ganged pot VR2a & VR2b. VR2a is in the input to IC1a while VR2b is in the feedback loop from IC1b to IC1a. Both pot sections are wired as variable resistors. Notice that the wipers of VR2a & VR2b are shown with an arrow to show clock­wise rotation of the knob; maximum clockwise rotation gives maximum resistance for VR2a & VR2b and this corresponds to the maximum Q condition. The three state variable filters are Fig.8 (right): the parametric equaliser is based on three “state vari­able” filters, one for each of the bands. Each of the state variable filters is identical apart from the capacitors which determine their frequency ranges. July 1996  73 Fig.9: follow this layout diagram when installing the parts on the PC board. In particular, check that the ICs are correctly oriented and don’t get the pot values confused. 74  Silicon Chip Fig.10: check your board carefully for etching defects before installing any of the parts by comparing it against this full-size pattern. There are quite a few links on the board and these should be installed before any other components are soldered in. Take care to ensure that all polarised parts are correctly oriented and note that the ICs all face in the same direction. effectively in paral­lel and connected into the feedback network of op amp IC6b on the input side and into the input circuit of op amp IC4b on the output side. When all the boost/cut controls are centred, the gain of the circuit is unity over the whole audio frequency range. When one of the boost/cut controls is set to boost, the signal from the accompanying state variable filter is increased to IC4b, while the feedback to IC6b is reduced. Hence, the gain is boosted for that particular band. VR1 provides an input volume control for the whole circuit. We assume that for most applications it will be set for maximum input signal to the circuit and thereby give an overall gain of unity; ie, 1V in gives 1V out. The circuit is designed to run from TABLE 1: CAPACITOR CODES ❏ ❏ ❏ ❏ ❏ Value IEC Code EIA Code 0.12µF   120n   124 0.1µF   100n   104 .015µF   15n   153 .0022µF   2n2   222 ±15V supply rails and these will normally be supplied by 3-terminal 15V regulators in the main amplifier or mixer. The rails are heavily bypassed with 100µF and 0.1µF capacitors to ensure good stability. Assembly We are presenting this project as a PC board which can be installed in a case together with a suitable power supply or incorporated into a larger piece of equipment. The PC board measures 230 x 72mm and is coded 01107961. To make the board size manageable it has been designed around 16mm diameter pots. Actually, we could have made the board a good deal smaller but in practice, the knobs need to be spaced so that typical male fingers can operate them comfortably. By itself, the PC board is difficult to use unless you also have the control panel; otherwise you don’t know where the pots are set. We have designed a control panel which measures 249 x 59mm. The completed PC board and control panel have been designed to fit neatly into a plastic    TABLE 2: RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 1 6 10 6 3 1 Value 100kΩ 20kΩ 10kΩ 8.2kΩ 4.3kΩ 100Ω 4-Band Code (1%) brown black yellow brown red black orange brown brown black orange brown grey red red brown yellow orange red brown brown black brown brown PARTS LIST 1 PC board, code 01107961, 72mm x 230mm 1 front panel label, 249 x 59mm 10 knobs to suit 16mm pots, 15mm in diameter 2 metres 0.71mm dia. tinned copper wire (for links) 7 PC pins 6 LM833 low noise dual op amps (IC1-1C6) Potentiometers (all 16mm dia.) 3 100kΩ linear dual-ganged pots (VR2,5,8) 3 25kΩ linear dual-ganged pots (VR3,6,9) 3 10kΩ linear pots (VR4,7,10) 1 50kΩ logarithmic pot (VR1) Capacitors 4 100µF 16VW electrolytic 4 6.8µF non-polarised electrolytic 1 2.2µF non-polarised electrolytic 2 0.12µF 63V MKT polyester 6 0.1µF 63V MKT polyester 2 .015 63V MKT polyester 2 .0022 63V MKT polyester Resistors (0.25W, 1%) 1 100kΩ 6 8.2kΩ 6 20kΩ 3 4.3kΩ 10 10kΩ 1 100Ω 5-Band Code (1%) brown black black orange brown red black black red brown brown black black red brown grey red black brown brown yellow orange black brown brown brown black black black brown July 1996  75 Running The Circuit From A 12V Supply Fig.11: this full-size artwork can be used as a drilling template for the front panel. Fig.12: use this power supply arrangement if you wish to run the parametric equaliser from the 12V supply in a car. 76  Silicon Chip While the parametric equaliser has been specifically de­ signed to run from balanced ±15V rails, it is also possible to run the whole circuit from a single 12V supply, as would be the case if the unit was used in a car. The distortion, signal han­ dling and signal-to-noise ratio will not be as good but for car applications its performance would still be more than adequate. To run from 12V it will be necessary to split the supply to effectively give ±6V rails. This can be done by wiring two 4.7kΩ instrument case measuring 259 x 65 x 180mm (W x H x D). This has space for a power supply and is available from Jaycar Electronics with plastic front and rear panels (Cat. HB-5974) or with aluminium panels (Cat. HB-5984). The full wiring details for the PC board are shown in Fig.9. Start construction by checking the PC board against Fig.10. Fix any shorts or broken tracks that may be evident. There should not be any of these faults but if they are present it is better to fix them before any parts are soldered in. There are quite a few links shown in Fig.9 and these should all be installed before the other components. This done, fit the resis­tors. Table 2 shows the colour codes for all the resistor values specified. Use your multimeter to check the resistor values if you are not sure of the colour codes. Next, fit all the capacitors, making sure that the electro­lytics are correctly polarised; ie, connected the right way around. Now fit all resistors across the 12V supply, as shown in Fig.12. However, the input and output signal earths will no longer be tied to the centre rail; instead, they go to the 0V rail. This means that input earth, the grounded side of the input pot VR1 and the output earth must all be isolated from the earth system (supply centre tap) and connected instead to the 0V line of the incoming 12V supply. If this is not done correctly, there will be a short across the -6V rail and the circuit will malfunction. six ICs; they are all oriented in the same direction. Last, fit the pots and make sure you don’t get the 25kΩ and 100kΩ pots swapped around. Check your work carefully against the wiring diagram when you are finished. Power up When the board is complete, connect a DC supply set to ±15V and check the voltages. +15V should be present at pin 8 of each LM833 while -15V should be at pin 4 of each IC. Then, if you check the output of each op amp, pins 1 or 7, the voltage should be close to 0V. The exception is pin 7 of IC2b (unused) which is likely to be at -15V; this does not matter. Further testing cannot be done until you make input and output connections to the board via shielded cable. You can then use an audio oscillator and an oscilloscope (or an AC milli­voltmeter or DVM with a wide frequency re­sponse) to check the effect of SC each control. RADIO CONTROL BY BOB YOUNG Multi-channel radio control transmitter; Pt.6 This month, we deal with the assembly of the Mk.22 transmitter case and the sub-assembly interwiring. The unit is housed in a sturdy welded steel case with a powder coat finish. The steel case helps in maintaining the very good 3rd order inter­modulation performance. Before we start on the mechanical assembly, there are a few details which have arisen in regard to the PC modules as a result of experience gained over the past few weeks. Firstly, I blew the power tracks clean off an RF module because I forgot to insert the insulator under the FET in one of the modules. When I checked the RF module assembly instructions, I found to my horror that I did not stress the importance of this insulator. In fact, I did not mention it at all. The insulator is supplied in the kit and is of the type that does not need thermal goo to work properly. Please make sure it is correctly in place because if it isn’t the 10V rail is shorted directly to the ground plane and let me tell you, those tracks really glow in the dark; for a while anyway, at least until they vaporise. Also do not fit or remove the RF module while the power is applied in case the FET accidentally touches the earth. For added safety, always remove the power socket before removing or fitting the module. Secondly, TB29 is shown in the encoder PC overlay (Fig.2, page 61 in the June 1996 issue) as a non-polarised 2-pin connec­tor. It should be a polarised connector, inserted with the polar­ising keyway towards the edge of the PC board. Finally, TB30 was shown incorrectly as a 3-pin connector (Fig.4, page 62 in the June 1996 issue) for the encoder/decoder patch cord. The amended drawing is shown in Fig.2(a). Also TB10 was incorrectly referred to as TB30 in the captions in the same issue. Mechanical assembly Let us start with the case. You can begin by cleaning up the powder coating edges and overspray. The cases sit flat on a tray during powder coating and may pick up some black swarf or rubbish along the rims of the two halves during the process. July 1996  77 Fig.1: details of the fixed wiring in the transmitter. Using a sharp utility knife, trim off any excess material and foreign matter. Check that the components all fit easily into their respective holes or slots. The powder coating goes on very thickly to achieve the ripple finish and this tends to close up any openings in the case. Remove any overspray or coating where electrical contact with the case is required; for example, the mounting brackets for the RF module, top of the threaded inserts (PC standoffs) etc. Once the case halves are prepared, mount the charge socket into the hole provided at the bottom righthand corner of the front panel. Now we can begin gluing down all the sticky bits. The battery pack is first. Using the double-sided self adhesive foam-backed tape provided, apply two strips along cells 2 and 7. The battery goes in with the positive 78  Silicon Chip terminal on the right as viewed from the back of the case. It is a good idea to remove any greasy residue from the case and components to be glued down by wiping them with a tissue soaked in metho. Do not use strong solvents on the front of the case as they may damage the surface sheen. Press the battery pack firmly into place about 1mm to the right of the charge socket hole, with the battery sitting against the case bottom. Next, prepare the meter by applying a very thin strip of ordinary contact cement around the edge of the concealed face. Care is needed here to ensure excess glue does not ooze into the meter adjustment screw. This glue strip is only to stop the meter moving in the mounting brackets which will be fitted later, so the glue can be applied quite sparingly. Press the meter into place and then remove it immed­iately. Check that the glue has not migrated under pressure and leave until the glue is dry to touch. Then press the meter firmly into place. Remember here that contact cement works best when the sol­vents have evaporated and the glue feels dry to touch. Now very carefully apply a strip of glue around the inside lips of the control stick escutcheons and a matching strip of glue around the corresponding edges of the large square holes for the control sticks, taking care to stay inside the boundary of the escutcheon. The bond must be good here for the glue provides the only fixing for the escutcheon. I find that some of the exotic modell­ing contact cements such as “Zapadapagoo” work very well in this application. Again, wait until dry and press the escutcheon firmly into place, ensuring that the parallel sides of the escut­cheon are vertical and the scollops (curves) are at the top and bottom of the case. Finally, using contact cement, fit the antenna insulator into the top of the case. Any excess contact cement should be wiped off immediately with metho (do not use thinners or anything stronger). Mount the slide switch, next ensuring the cover plate is mounted correctly. There is a small pip which indicates ON. This goes towards the bottom of the case. Remember we are assembling an Australian designed set and in Australia, down is ON. Wiring details It is now time to fit the few hardwired links in the transmitter. Fig.1 shows the layout of the interwiring. The hook-up wire provided is single strand 21/008, (21 conductors x 0.008mm, unplated, various colours and red and black 14/0.01mm, tin plated). Always twist the wires into a cable form wherever possible for neatness and minimisation of RF pick-up. The tin plated wire minimises the “black wire syndrome” and must be used for all positive and negative power runs. Begin by wiring the 6-pin and 10pin power sockets. The 10-pin socket uses five pairs of two pins in parallel, so gently bend each pair together as shown in Fig.1. Tin and solder the appropriate leads and then cover each pin pair with the 3mm heatshrink supplied. Twist the red/yellow/black leads into a cable. Do not include the white antenna lead in this cable. It remains separate and goes directly to the antenna tag. The 6-pin socket is quite straightforward. Just block off pin 2 to match the missing header pin on TB7 (on the encoder module). The 10-pin socket is plugged into the 10-pin header on the RF module and a dot of paint is placed on the right hand side of both the socket and header. Just make sure you get it right in the first place. Next, wire the battery to the charge socket. Note that the location of the battery positive lead is important. It must go to the terminal shown in Fig.1 as this is the terminal that mates with the tip of the charge plug. When wiring the switch, strip the leads long enough so that the tinned lead can be pushed through both switch lugs as shown in Fig 1. This connects the two switch poles in parallel for added reliability. Connect the meter as shown and the wiring is virtually complete. The remaining wiring consists of wander leads which simply plug onto the appropriate header pins on the PC boards. We will deal with the final programming next month. Fit the handle, toggle switches and auxiliary control potentiometers. It is a good idea to wire these items before mounting them – see Fig.2. Three-core ribbon cable (blue/white/blue) is supplied for this task. At this stage of assembly, most of the hardware is in place and the transmitter and encoder modules have yet to be installed. Auxiliary control pots Wiring the auxiliary control pots is a little tricky. In order to maintain servo reversing and channel allocation on these pots, it is necessary to solder the 4.7kΩ limiting resistors to the pot terminals as shown in Fig.2(d). Insulate the pot back cover with a small piece of tape. Once wired, coat the resistors with contact cement and leave to dry overnight. Finally, lash the wires to the pot body with the small cable tie supplied. There is no polarity on these leads as the plug is revers­ible. It is a good idea to paint a dot on the right hand side of the plug/socket as an aid to visually determining if the plug is reversed or normal. Also a small self- adhesive label wrapped around the leads just above the socket can be a great aid in identifying each lead, as all control Kit Availability Kits for the Mk.22 transmitter are available in several differ­ent forms, as follows: Fully assembled transmitter module......................................................$125.00 Basic transmitter kit (less crystal)............................................................$89.00 Transmitter PC board...............................................................................$29.50 Crystal (29MHz).........................................................................................$8.50 Fully assembled encoder module..........................................................$159.00 Encoder kit.............................................................................................$110.00 Encoder PC board...................................................................................$29.50 Transmitter case kit................................................................................$395.00 Full transmitter kit (includes all the above).............................................$594.00 Post and packing of the above kits is $3.00. Payment may be made by Bank­­ card, cheque or money order payable to Silvertone Electronics. Send orders to Silvertone Electronics, PO Box 580, Riverwood, NSW 2210. Phone (02) 533 3517. July 1996  79 at any time, all with no fuss. So the leads must be long enough to reach around the transmitter sides. Fig.2(b) shows the leads for the toggle switches and control pots at the top of the case and their suggested length is 350mm. All the other leads can be 270mm long. This applies particularly when we come to the configuration modules and more especially when we use the CROW configuration module. Because the toggle jumpers have sockets at each end, it is easy enough to make these in various lengths to suit your application. The length shown in Fig.2(e) is a suggestion only. The knobs, toggle boots and Silver­ tone label can be fitted at this point. Control mode choice Fig.2: details of the various wander leads used in the transmit­ter. elements use the same type of lead as shown in Fig.2(b). There are far too many leads and all with variable functions for colour coding to work successful­ ly, so I settled on blue/ white/blue ribbon cable with ID tags. Fig.2(c) shows the details of the toggle switch jumper lead. Fig.2(e) shows the small patch cord for the toggle switch programming. These are required only if you intend to configure one or more channels as a toggle switch channel. You need one lead for 80  Silicon Chip each channel. It is a good idea to make all of these leads at the one time. Fig.2(f) shows the details of the control stick wiring. Use heatshrink sleev­ing where appropriate to protect the solder joins. You can tailor the length of each lead to suit each control stick/slider/toggle/ pot location and thus minimise the amount of loose wire hanging about. However, the versatility of the Mk.22 lies in the fact that any lead can go to any plug anywhere in the transmitter Now comes decision time. As supplied, the control sticks are arranged to provide Mode I (Throttle/Aileron on the right stick). If you require Mode II (Aileron/Elevator on the right stick) then do the mode change on the sticks before fitting them into the case. Note well that the trims are on the outside of the case contrary to normal practice. This makes them much more readily accessible in flight than the normal layout. As before, it is a good idea to wire the pots before mounting the sticks. Use leads as per Fig.2(f). Lash the wiring to the pot body using a small cable tie and secure with a couple of drops of contact cement. Mount the sticks with the two outside sets of screws (6BA x 6mm), making sure that the correct stick location is observed for the mode chosen. It is very easy to get confused when working from the back of the case. Next comes the preparation of the antenna/RF module brack­ et. First, mount the antenna attachment screw and insulating washers in the 6mm hole provided. The screw protrudes into the “U” and the antenna solder tag goes under the nut on the inside of the “U”. Solder the white antenna wire to the solder tag and don’t forget to fit the 3mm heatshrink tubing. The two meter clamps and the RF module bracket are fitted at this point. The meter clamps simply go under the stick mount­ing screws adjacent to the meter. The RF mounting bracket uses the two stick mounting screws adjacent to the switch. Do not over tighten the stick hold down screws as you can crack the mounting lugs on the control sticks. Drop the antenna down through the insulating grommet and screw it fully home onto the antenna mounting screw. Do not overtighten the antenna for you may want to remove it from time to time. Mount the encoder module using the 6BA x 6mm screws provid­ed. Do not over tighten as these screws are slightly undersized to allow them to pass through the corner holes. The transmitter was originally designed around 6BA screws but nutserts were not available in these sizes. The corner holes of the encoder module should not be drilled out as they are plated through. A small drop of contact cement or nail polish will serve to lock all of the screws into place and prevent them from unscrewing with use. If you lose one of these screws make sure the replacement is no longer than 6mm. Finally, mount the RF module using the 3 x 6mm screws pro­vided, taking care to ensure that the mating surfaces of the PC board and mounting brackets are clean, bare metal. This is the heat­ sink for the output FET and the earth connection for the RF module and so the surfaces must make good contact. This is what your transmitter should look like when all the wiring is complete. Voltage checks Disconnect any leads connected to the PC boards. Switch the ON-OFF switch to ON and check that the volt­ ages are correct at the terminals on the main power connectors for the RF and encoder modules. If all is correct, switch off and plug the two power connectors onto their respective mates, observing polarity. Make sure the crystal is in place and that the RF module is programmed for AM modulation. Extend the antenna and, with a sniffer probe held near the antenna, switch on. You should see a modulated RF signal on the scope’s screen. If not, check the RF module programming and repeat the tuning sequence published previously. Check the signal pin on the RF module to ensure that a data pulse train is present. (Note: to make a sniffer probe, just ground the tip of the scope probe – the resulting loop works just fine). Once you have the modulated RF signal on the screen you may relax. Congratulations you now have a working Mk.22 transmitter. Next month we will show you how to align the system and how to get the best out of it. SC Close-up detail of one of the sticks and the power switch which is partly obscured by the antenna. Note that both poles of the switch are wired in parallel for increased reliability. July 1996  81 TEST EQUIPMENT REVIEW The Tektronix THS720 is a lightweight, portable instrument which combines a powerful 2-channel 100MHz oscilloscope and a 4000-count digital multimeter in one convenient package. It has a liquid crystal display and is very easy to drive. By RICK WALTERS The Tektronix THS720 TekScope This go-anywhere measuring system operates continuously from the mains via a plugpack or for around two hours from an inbuilt battery. A spare 2.8 ampere-hour battery and a battery charger which is capable of recharging the battery in 1.5 hours are also supplied. The TekScope, as well as the charger, will operate from the mains or from a 12V cigarette lighter sock­et, which is an excellent idea for a portable instrument. The number of different functions packed into this tiny package, which measures 180 x 220 x 50mm (W x H x D) and weighs only 1.5kg, is quite amazing. The major features of the oscilloscope are: 82  Silicon Chip • 100MHz bandwidth with 20MHz selectable; • 500MS/s sample rate and 2500-point record length; • Separate digitisers for each channel; • Waveform averaging and enveloping with hardware peak detection; • Digital Real Time digitising (up to 5X oversampling), sin(x)/x interpolation and peak detect acquisition to limit the possibili­ty of aliasing; • Independently isolated input channels measuring up to 1000V RMS and floating at 600V RMS (using P5102 probes); • Cursors and up to 21 measurements continuously updated; • Simultaneous oscilloscope and me- ter operation on the same or different signals; and • Pulse and video triggering capability. The DMM features are: • True RMS AC volts, DC volts, Ohms, continuity and diode check functions; • Auto or manual ranging; • Data logger plot of meter measurements; • Maximum, minimum, delta maxmin, relative delta and average statistics selectable; • Bargraph indication for “analog meter” style indication; • Input can float to 600V RMS; • Input over-voltage indicator. It is apparent that great amount of design effort has gone into this unit as exemplified by the case support assembly (see Fig.1). It normally lies flat against the back of the case but can be flipped out with a finger. By swinging it up, the TekScope can be hung on a hook. If the hinged centre piece is pushed out, it can be used to hang the unit on the rung of a ladder or, if this centre piece is clipped into a slot on the rear of the case, it can support the TekScope for bench use. Pressing the on/off button, located at the bottom left of the front panel, causes the THS720 to do a self-check of all functions. After a few seconds, the message “Power-On self check. PASSED . Press the CLEAR MENU button” appears on the screen. When the menu is cleared the instrument is ready for use. The unit initialises to the same mode and settings as when it was turned off. Pressing the SCOPE or METER button will select that function. Let’s look at the scope features first. An internal 1.2kHz square wave output (its connections are located under a flap on the righthand side of the meter) is provided to allow you to properly compensate the input probes. This waveform is shown in Fig.2 with the VERTICAL MENU displayed across the bottom. Pressing the button below the menu item pops all the options up. Another useful feature is the AUTORANGE button. When any waveform is fed to the TekScope, instead of having to adjust the vertical sensitivity, the horizontal sweep rate and the synchro­nising trigger point, a press of the autorange button will usual­ly give you a rock steady trace at a suitable amplitude. As previously explained, the change­over from SCOPE to multi­meter is just a matter of pressing the METER button. The meter can be connected to one circuit and the scope to another and you can readily switch between them. What is even more useful is the ability to display the SCOPE function on a full screen and (for instance) a DC voltage which appears in the top right corner next to the meter face. As a practical example, you could monitor the output fre­ quency of a VCO (voltage controlled oscillator) Fig.1: a built-in tilt stand folds out and snaps into place when not in use. For benchtop operation the tilt stand locks in place with the hinged flap. It is hinged up to hang from a nail or extended to hang on the rung of a ladder. using the SCOPE probe and display the waveform, with the frequency readout on the righthand side of the display. The VCO input voltage can then be monitored using the DMM and displayed at the top righthand side of the readout (see Fig.3). As mentioned in the specifications, the meter circuitry and the SCOPE inputs are each isolated from ground. This allows you to monitor, for example, the mains voltage with the DMM, while the SCOPE probe could be looking at the ripple on a 5V supply referenced to ground. Controls While the AUTORANGE button is useful in obtaining a stable display, it may not be quite what you require. The auto setup can be overridden by pressing the VOLTS/DIV, SEC/DIV or TRIGGER LEVEL controls. The VERTICAL controls consist of a sensitivity rocker switch, a position rocker and a menu selector. The VOLTS/DIV switch has a large sine­ wave at the top and a smaller one at the bottom. Pressing the top increases the displayed amplitude; pressing the bottom reduces it. Similarly, pressing the top of the POSITION rocker moves the trace upwards while pressing the bottom moves it down; all quite logical and intuitive. As you would expect, provision is made for both channels, the stored references and the Math display to be turned on or off. Display selection is effected by pressing the required button. The display is turned off by selecting it, then pressing the WAVEFORM OFF button. The MENU button produces screens similar to Windows “drop down” menus, with the menu screen options depending on the wave­form selected. For the input channels (CH1 and CH2), you have the choice of selecting the input coupling method (AC, DC or ground), inverting the waveform, setting the bandwidth and selecting the type of probe (voltage or current) as shown in Fig.2. Using the Math function, you can add both channels, subtract CH2 from CH1, subtract CH1 from CH2, or multiply the two inputs. If one channel was measuring voltage and the other current, then the resultant waveform would represent the power being dissipated in the component being measured. If either reference channel (A or B) is selected, you have the option to save CH1, CH2 or math July 1996  83 Fig.2: this is the 1.2kHz waveform used to calibrate the 10:1 voltage probes. The Vertical MENU button has been pressed to show the choices available. The previous menu selection was the probe type and this is shown in inverse lettering. Fig.3: the VCO output waveform and frequency are shown on the display, the input voltage to the VCO is shown next to the meter. Fig.4: a plot of the output of a regulated power supply over a 4-minute period. The trace moves from right to left, so the small negative spike that appears around 2.8 minutes actually happened 1.2 minutes after we started the test. The readout on the RHS shows that the voltage dipped to 26.44V at this time. The plateau which begins at 2.6 minutes was actually 28.48V. The slight difference in the two average figures is prob­ably due to the fact that the run was stopped before the full four minutes and the figures were updated at different times. Fig.5: a one Farad capacitor was charged to 3.96 volts and dis­charged through a 1kΩ resistor. This time constant is 1000 sec­onds, or 16.66 minutes. As near as I can calculate from an en­larged graph, this shows a time constant of 16.25 minutes. This indicates that the capacitor was about 2.5% below its nominal value. waveform to a location from 1-10; ie, 60 locations in all. The HORIZONTAL controls operate in a similar manner to the VERTICAL controls although instead of rocking vertically they rock horizontally. Pressing the right or left POSITION arrow moves the trace in that direction. The right side of the SEC/DIV button with the expanded sinewave expands the displayed waveform, while the left side with the compressed sinewave increases the number of cycles displayed on the screen. The MAG button expands the display by a factor of 10. The MENU button allows you to se84  Silicon Chip lect the main or delayed timebase and set the delay time. The main timebase trigger has three preset positions at 10, 50 or 90% of the waveform period or by using the TOGGLE button any period from 0-100% can be select­ed. The delayed timebase can be set to start any time from 2 nanoseconds to 50 seconds after the main sweep. Trigger controls The trigger controls, while they appear simple, have a vast range of options. The TRIGGER LEVEL toggle moves the trigger point up and down the waveform from 100% to 0%. The SET LEVEL TO 50% button does just that. All the other functions are accessed via the MENU button. There are three trigger types you can select from: Edge, Pulse and Video, all of which can be from the CH1 or CH2 waveform. For edge triggering you can select DC, HF reject, LF reject or noise reject (DC low sensitivity) coupling. The slope of the trigger can be selected for a positive going or a negative going edge. For pulses, you can select either the positive going or the negative going edge, as well as setting a pulse width with the TOGGLE rocker. Once this width is set, you can then elect to trigger when the incoming pulse is less than the set width, greater than the set width, equal to the set width (with a toler­ance) or not equal to the set width (with a tolerance). For the video mode, you can select any field, field 1, field 2 or lines. You can also select scan rates between 15kHz and 65kHz with the TOGGLE button. With all these options it is hard to imagine a waveform that could not be triggered. While the controls we have covered so far exist in some form on all analog scopes, the following are mostly peculiar to the newer digital scopes: The DISPLAY button lets you set the screen display for dots or continuous lines, set the contrast, turn the “T” (which indi­cates the trigger point) on and off, and show an XY or YT format on the screen. It also allows you to have a full graticule, a grid, crosshairs or a frame for the display. The CURSOR menu lets you move vertical and horizontal reference lines around on the waveform and these can be used for the system to calculate things like propagation delay. Perhaps the most comprehensive of all the menus is the MEAS(ure) menu. This contains 21 different definitions for the measurement of the displayed waveform. These include, peak-topeak amplitude, true RMS over the first cycle, frequency, duty cycle and true RMS over the entire waveform. If you need to carry out a particular measurement on a routine basis, you can set up the TekScope to make the measure­ment and then save the setup in one of 10 non-volatile memory locations. This setup may be recalled at any time using the location number that it was saved in. If you have a suitable printer, the screen display can be sent to it via the supplied RS232 cable when ever the HARD COPY button is pressed. Naturally any previously stored waveforms can be recalled and printed in this manner. The printers supported are Thinkjet, Deskjet, Laserjet and Epson 9 & 24-pin. Using the Windows terminal program, the screen display or stored waveforms can be transferred to an IBM compatible PC. The formats supported are IMG, TIFF, PCX, BMP, EPS and DPU411/412 So much for the oscilloscope; let’s now look at the digital multimeter specifications. First, the five DC voltage ranges cover from 400mV to 880V with an accuracy of ±(0.5% reading + 5 counts), while the five true RMS AC voltage ranges cover from 400mV Above: BNC sockets are provided at the top of the TekScope for the two oscilloscope inputs. These inputs are completely isolated from each other and can be connected to sources at different potentials. The multimeter jack sockets (see photo below) are mounted at the side of the instrument, together with the serial input connector and probe compensation signal output (under the flap). to 640V, with an accuracy of ±(2.0% reading + 5 counts). The six resistance ranges are 400Ω to 40MΩ with an accuracy of ±(0.5% reading + 2 counts), except on the 40MΩ range where it is ±(2.0% reading + 5 counts). The DMM also features a diode test function and a continui­ty tester which emits a tone when the measured resistance is below 50Ω. Once you have become familiar with the SCOPE functions, the meter operation will be a breeze. When you press the METER button, the five functions listed above are available for selection. By pressing DC and AUTORANGE the meter will display the voltage. The same selection procedure is applicable to AC and Ohms. A vertical analog bargraph (with solid bars), situated at the righthand side of the display, moves up and down in sympathy with the signal level, with open bars to indicate the maximum and minimum values recorded. The maximum open bar can be seen in Fig.4; the minimum open bar is directly below it and is filled in by the bargraph. The data logger function could be a very useful feature for many users. It records the meter measurement over a period of time just like a chart recorder. This period can be set from four minutes to eight days. Two uses that immediately spring to mind are monitoring variations in the mains voltage and checking the stability of DC power supplies. To this end we set up a power supply on the bench and monitored its output voltage for four minutes. The result can be seen in Fig.4. The MEAS(ure) menu was set to store the MAX, AVERAGE and MIN voltage over that time. From this graph, you can see where the voltage dipped to the minimum value of 26.44V at about 2¾ minutes. The maximum voltage plateau is from 1-1½ minutes. continued on page 93 July 1996  85 VINTAGE RADIO By JOHN HILL Making a few odd repairs It often only takes a few simple repairs to keep an old vintage radio in working order. It helps if the valves are in their correct sockets, though. About five years ago, I had a visit from my sister-in-law, Doris, who fell in love with – no, not me – my radio collection. She just had to have an old radio and wouldn’t take no for an answer. What’s more, it wasn’t just any old radio she wanted; it had to be a nice big console model. So we went to my storage shed and I dragged out a few likely contenders. Doris chose one that appealed to her and she seemed pleased with her choice because, even at that unrestored stage, the receiver was working and it sounded rather good. I was to restore the radio part while Doris’ friend, Shirl, would refurbish the timber cabinet. It was not long before the fully-restored receiver was the pride and joy of the lounge room. Being a 1940 model (unbranded), it was made at a time when super­het development had reached its peak and this dual-wave set was indeed a very good radio. In fact, as far as 5-valve receivers go, this particular one gives exceptional performance and it is really well designed. Its 10-inch (250mm) electrodynamic loudspeaker produces This little 5-valve Philips receiver has been operating on a Silastic repaired speaker cone for the past seven years. 86  Silicon Chip a good sound and Doris was more than pleased with her old radio. However, what I didn’t know for quite some time was that the old 5-valver was turned on at around 7.30 most mornings and was on all day until the TV news at night. When I heard about that I nearly had a heart attack! I just couldn’t help worrying about that half-century old power trans­former running for 10 hours a day, not to mention the fine wind­ing of the field coil and the valves which were only good second­hand units at the time of the restoration. Well, to cut a long story short, the old receiver eventual­ly packed it in and had a minor relapse. So after about five years of daily use, it found itself once again on my workbench for repairs. What I found was most interesting and well worth reporting. Weak sound The main problem with the receiver was weak and distorted sound, which was quickly traced to an open screen resistor. Once the defective component was replaced the set fired up as it had always done and the ailment was completely cured. When I originally restored this receiver, I had marked the valve test readings on the valves. Despite the heat of the recti­fier and output valves, the Texta pen markings were still there to read, as though they were written only yesterday. The interesting aspect of this is that when the valves were tested again, they all gave much the same readings as five years ago. The 6V6 output valve had dropped from 80 to 75, the 6B6 first audio was down by a similar amount and the other valves were much the same as before. This gives a good practical indica- Dow Corning’s Silastic is ideal for speaker cone repairs. It is tough, flexible and adheres to the paper cone very well. tion of how long a radio valve can be expected to last, especially when it operates in a receiver that is working properly. The original restoration saw the replacement all the paper and electrolytic capacitors. The resistor values were all OK and, as a result, the set has been working as it was designed to work. It was only the failure of a screen resistor that brought this good run to a halt. Loudspeaker repairs The console receiver that Doris “adopted” is a 1940, 5-valve, dual-wave unit with good performance. Shirl’s cabi­net restoration was a top job! This particular speaker cone was split from rim to centre. The repair has not had any apparent adverse effect on its perfor­mance. Another point of interest is the loudspeaker. Five years ago the speaker cone was starting to split at the outer edge and these splits were repaired using Dow Corning “Silastic”. The type used was the automotive gasket formula – the one that smells like vinegar. In this instance, the repair was still intact and looked as though it would remain that way for quite some time to come. When applying Silastic to a speaker cone, it needs to be rubbed well into the paper for good adhesion and used as thinly as possible. Whilst this repair method has been mentioned before in this column, it was comforting to see a repair which has been in service for many years and showing no signs of lifting or cracking. The speaker in our kitchen radio (a late 1950s 5-valve Philips) was also “bogged up” with Silastic about seven years ago. Although this repair has not been checked since, the set is still working OK so it is, presumably, another successful speaker cone repair. Once again, the little Philips receiver is on for at least four hours a day and gets constant use. I recently received a letter from July 1996  87 This Radiola console chassis was sent to me for repair by someone in Queensland. Unfortunately, it was sent in without its loudspeaker and output transformer, which complicated the troubleshooting procedure. a reader seeking informa­ tion about speaker cone repairs. In this case the speakers be­longed to an old Hammond valve organ (drool!) and the inquiry sought my advice on a suitable repair method. Cigarette paper and shellac had been recommended but the person concerned was hoping I could suggest something better. Once again, I recommended the Silastic treatment but what a test it will be in an organ. A nice loud 16 foot bass note will just about shake anything loose and that could include a smear of silicone rubber. Only time will tell? According to some old repair men, speaker cones were tradi­ t ionally repaired with paper and nail polish or paper and shel­lac. As far as I’m concerned, such a repair should be sat­isfac­tory on the main conical part but not on the outer edge or rim where the paper actually flexes. Quite often the outer edge of the cone simply wears out and the rim starts to separate from the cone. This area needs to be mended with something strong and flexible and I have yet to find anything better than Silastic to do the job. If the Silastic repair can be done before the rim starts to separate, it will be a better job than if the rim has already split. If the rim has split half way around the cone, then it is more difficult to do a neat repair job. 88  Silicon Chip Incidentally, a wet finger will smooth out the Silastic and help to finish off the job more neatly. The old Radiola Quite recently, someone I have never met sent a radio for me to repair all the way from sunny Queensland. This person assumed that there must be a repair man asso­ciated with the “Orpheus” Radio Museum in Ballarat who could fix his valve radio. So he sent the set to his brother in Ballarat who, in turn, eventually brought it to me. In a letter to see if I would be interested in doing the job, it was stated that others had already looked at the receiver and the “expert” opinion was that it needed two new valves, a 6SQ7 and a 6V6 (apparently on the basis that these valves did not light up). If I could supply these valves, it should be all that was needed to fire up the old receiver once again. I agreed to at least look at the radio and arranged a time. The set arrived and much to my dismay it was just a chassis without its loudspeaker. The chassis was from an early postwar Radiola console, being a large dual-wave type with GT octal valves. A speaker lead wired directly into the chassis had a 5-pin socket on the end of it which connected to a 5-pin plug fixed to the speaker frame – a typical Radiola set up of that era. As anyone who tinkers around with valve radios would know, one likely cause of failure in these receivers is the output transformer which is, more often than not, attached to the loud­speaker. My immediate thought was, “I bet it is the output trans­former that is at fault”. But as it was interstate, I had no way of knowing! I suggested that the chassis be left with me while I tried to work out the problem of the missing loudspeaker, the two valves that supposedly wouldn’t light up, and anything else that might ail the non-functioning receiver. When I finally found time to work on the old 5-valver, I was able to work through some of the mysteries quite easily. First, there were only three connections to the 5-pin speaker socket, with one of them going to chassis. This imme­diately indicated a permag speaker and not an electrodynamic type, as first thought. And a high tension filter choke mounted on the chassis confirmed this. It is amazing what you fail to notice until you have time to quietly check things out, without having some concerned person present suggesting what might be wrong. The main problem was solved when it was discovered that the 6SQ7 and the 6V6 valves failed to light up because some “expert” along the way had put them into the wrong sockets. And yes, you guessed correctly! When the valves were changed over and a speaker and output transformer substituted, the set burst into life without replacing a single component. So, once again, that left the output transformer as the number one sus­pect. Now it is very difficult dealing with someone you don’t know through a third person who may not be all that enthusiastic about being involved. Even so, I requested through the third party that the loudspeaker be sent to me so that I could check it out and fit another output transformer, assuming that my assump­tion was correct. In the meantime, I would go ahead with the repair and re­place the remaining paper capacitors, test the valves, renew the wiring that had perished natural rubber insulation, give it a tune up, a new dial cord and whatever else the old Radiola may require. A rear view of the Radiola chassis. The old receiver wasn’t working because two of its valves (the 6V6 and 6SQ7) had been transposed in their sockets. Once the valve problems were sorted out, it worked quite well, even with its original paper capacitors. Several weeks went by before I was made aware that the owner was reluctant to send the speaker because he was sure that there was nothing wrong with it. The chassis was to be picked up that afternoon and returned to Queensland. The Radiola was set up on the workbench for a final run so that it could be demonstrated when picked up later in the day. It was working OK sometime later when I left the workshop for morning tea but it was not working when I returned. What’s more, there was a smell in the air that suggested something was cooking at a fairly high temperature. I was right! It was wax that was cooking and it was bubbling out of the high tension filter choke very nicely. A high tension short was suspected – what else could it be? A likely suspect was the electrolytic capacitor on the output side of the filter choke. It checked out OK! After eliminating a number of other possibilities, the fault turned out to be in the filter choke itself. While the winding was still intact, it was short­ ing to the core laminations which was most undesirable to say the least. A replacement choke solved the problem and the Radiola chassis was on its way to Queensland that afternoon. I asked to be informed as to whether the loudspeaker worked when the time came to try things out. Eventually, I will find out if my original diagnosis was correct. No guarantees Wasn’t it a stroke of luck for all concerned that the faulty filter choke croaked while it was still on my workbench? My reputation could have been ruined! The choke failure is also a good reason why it is unreason­able to expect a guarantee with vintage radio repairs unless one replaces all suspect and likely-to-fail components and charges accordingly. Few are prepared to pay the price. I work on a standard kerbside warranty. Once the owner’s vehicle leaves SC the kerb, it’s out of warranty! EVATCO Music Retailers Musicians Radio Collectors Hobbyists Industrial Users Contact us for the BEST prices for valves/tubes We stock SVETLANA, SOVTEK & TESLA Also a large range of vintage & NOS tubes Plus Valve SOCKETS & BOOKS Send SSAE for catalogue ELECTRONIC VALVE & TUBE COY PO Box 381 Chadstone Centre 3148 Tel/fax (03) 9571 1160 Mob: 0411 856 171 Email: evatco<at>werple.net.au July 1996  89 PRODUCT SHOWCASE Luggable PA system from Altronics There are many so-called portable public address systems around, intended for schools, community groups, sporting bodies and the like. Most of these systems are, not to put too fine a point on it, rubbish. So it’s very refreshing to find a system which not only works but works well. The system is the “Black Max” Portable PA Unit from Altronic Distributors, in Perth. It is described as a rugged, heavy duty self-contained PA system and with that we cannot argue. The first thing you notice about the unit, even before taking it out of its carton, is the weight: some 13kg! That’s why we prefer to describe this 90  Silicon Chip system as luggable, as distinct from portable. True, it can be carried from place to place. True, it doesn’t need mains power with the optional field battery pack. True, it is completely self-contained. But just try carrying it over any distance and you’ll agree; it’s portable just like a suitcase full of bricks is portable! Not that we are trying to put this Black Max down. Far from it: that weight all comes because of the features and performance built in. And if you want performance, weight is a small consideration. To be honest, we’re also speaking from experience. This is not the first time we have come across the Black Max. Our first introduction to the unit was when, in another life, we needed a truly portable PA system for use at Surf Carnivals. Like the man who was so impressed with the shaver he bought the company, we were so impressed with the Black Max we purchased one. That was over two years ago and until now, it had done nothing to change that first impression! Now, having seen the new model, we are envious. It’s not only more rugged but sports a range of new features and even better performance. So what do you get for your money? We’ll start with the outside. The Black Max measures 430mm high, 300mm wide and 210mm deep. It’s made from heavy duty MDF covered in a thick crinkle-finish black PVC. All eight corners of the case are protected by heavy duty ribbed speaker box corners, as in professional sound systems, which also double as feet in either vertical or horizontal direction. There is an expanding carry handle on top and a “top hat” mount let into the base so that the unit can be used directly with an optional tripod stand or other mounting system. Almost the entire front of the unit is covered with acoustic foam, behind which (and hidden) is a grille to prevent damage to the speaker. The speak­er itself is a 2-way 200mm coaxial type. Rear panel facilities On the rear panel is the (optional) logic controlled, auto reverse cassette deck. While delightfully easy to use, if we have one criticism of this deck it is that it has no tape counter. Again, from experience, using a cassette deck without a counter in anything but back­ground music situations can be a real drawback. Cuing is very difficult, especially during “events” where various tapes are required. Below the cassette is the inbuilt mixer, offering two microphone channels, both with balanced (XLR) and unbalanced (6.5mm) sockets (3mV sensitivity, 200-600 ohms) plus left and right auxiliary (RCA) inputs (250mV, 100k impedance), which are of course summed to mono. Each input channel has its own level control so full mixing is available. Unfortunately, however, the auxiliary input level control also doubles as the cassette level control, so this can only be used for one or the other. The MIC 1 socket also has a switch which can be set to “wireless mic” where this option is fitted. The wireless microphone itself bears special mention, being a fully professional quality model with performance as good as any we have used, even in stage applications. Unlike some “el cheapo” wireless microphones which transmit in the 88-108MHz FM band, with obvious consequences, these microphone use the “professional” 200MHz band, with a choice of two frequencies to avoid other users in the same area. (We have found the wireless microphone reliable for up to about 100 metres or more line-of-sight, but have experienced breakthrough from a club with a mic on the same frequency almost 1km away!) A 6.5mm socket is provided for an extension speaker. There is a matching speaker available as an option or, the output can be used for other 8-ohm speakers. Indeed, when we are using our (older!) Black Max for beach use, we usually plug in a low impedance horn speaker for dramatically increased coverage. Rounding out the “control panel” is an IEC mains input socket and an on/off master switch. Unfortunately, there is no line level output on this new model, which precludes one of the features we have found most useful on the older model: using it to drive a larger PA system. We have found that the older Black Max, with a wireless microphone, makes a magnificent “front end” for our 350W beach PA system which we use at surf carnivals. BassBox® Design low frequency loudspeaker enclos­ures fast and accurately with BassBox® software. Uses both Thiele-Small and Electro-Mechanical parameters with equal ease. Includes X. Over 2.03 passive cross­over design program. $299.00 Plus $6.00 postage. Pay by cheque, Bankcard, Mastercard, Visacard. EARTHQUAKE AUDIO PH: (02) 9948 3771 FAX: (02) 9948 8040 PO BOX 226 BALGOWLAH NSW 2093 STEPDOWN TRANSFORMERS 60VA to 3kVA encased toroids Field battery pack Below all of the controls and inputs is one of the Black Max’s main features: a “field battery pack”. This option is much more than a collection of cells. Instead, it is a rechargeable pack which automatically charges when ever the mains is connected and can be left float charging indefinitely. It also contains a DC/DC inverter so that completely portable operation is at much the same output level as mains powered. Charging time from flat is approximately 10-12 hours and gives up to eight hours continuous operation. The amplifier itself is naturally hidden from view inside the case. It is rated at 40W RMS, with a frequency response of 50Hz to 20kHz and distortion of less than 0.07%. In use The most immediate reaction is the quality of sound reproduction. For a small “PA”, it’s almost “hifi”! With 40 watts to play with (and a genuine, measured 40 watts RMS, not the figment of someone’s imagination Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 476-5854 Fx (02) 476-3231 in the back blocks of Taipei), the sound level is more than adequate for a quite large hall. We have used the system at the local high school hall on a number of occasions, with excellent results. With the optional extension speaker added on, the sound spread is, as one would expect, even better. It also performs more than acceptably outside, especially when the unit is mounted a metre or so off the ground. For this reason, we think that the optional heavy-duty stand is a must have item! One thing we have found from July 1996  91 experience, and many people have commented on, is the lack of acoustic feedback, even when working very close up and at high levels. There is nothing more annoying that being subjected to a PA system either on the verge of, or actually, breaking into feedback. You really do have to put the mic virtually in front of the speaker to make this one misbehave! For this alone the designers of the Black Max must take top marks! extension speaker, with 20-metre lead, sells for $279; the heavy duty tripod stand $140; and the field battery pack $395 All items are available through Altronics Distributors in Perth (09) 328 2199 or their authorised distributors. (R. T.) Boundary mics for permanent installation How much Performance of this type does not come cheap. But, as the man says, “ya gets what ya pays for”! The Black Max standard system (ie, unit with hard-wired microphone and no cassette player) has a recommended retail price of $595. With the wireless microphone receiver it jumps to $849, and with the cassette recorder as well it retails for $1190. Note that these prices do not include the wireless microphone itself: the hand-held model (as reviewed) sells for $335, guitar transmitters are available for $269 and lavalier (clipon) mics are $379. The other options mentioned: the Amber Technology announces the new Beyerdynamic MPC 22/23 Acoustic Boundary Microphones, designed for permanent installa­tion into table tops or ceilings. With a diameter of only 30mm, the microphones are suitable for recording and sound reinforce­ment applications requiring high quality reproduction of speech, including telephone and video conferencing systems, in board­ rooms, courtrooms and churches. KITS-R-US PO Box 314 Blackwood SA 5051 Ph 018 806794 TRANSMITTER KITS •• FMTX1 $49: a simple to build 2.5 watt free running CD level input, FM band runs from 12-24VDC. 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. •• FMTX2A $49: a universal digital stereo encoder for use on either of our transmitters. XTAL locked. FMTX5 $99: both FMTX2A & FMTX2B on one PCB. •connector FMTX10 $599: a complete FMTX5 built and tested, enclosed in a quality case with plugpack, DIN input 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 •soldDIGI-125 Audio Power Amp: this has been the most popular kit of all time with some 24,000 PCBs being 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 •to Max I/O Card for PCs Kit $169: originally published in Silicon Chip, this is a real low cost way to interface 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. •onlyIBM3 chips PC 8255 24 Line I/O Card Kit $69, PCB $39: described in ETI, this board is easy to construct with and a double sided plated through hole PCB. Any of the 24 lines can be used as an input or output. Good value. •• Professional 19" Rack Mount PC Case: $999. 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 PC104 486SLC CPU Board with 2Mb RAM included: 2 serial, printer, floppy & IDE hard disk $999; VGA 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. 92  Silicon Chip Beyer claim the MPC 22 and 23 produce higher gain before feedback than typical boundary microphone designs. The MPC 22’s semi-cardioid response makes it suitable for multiple microphone installations while its integral low-cut filter eliminates low frequency rumble and unwanted surface-bound noise. The MPC 23’s half-spherical polar pattern offers a uniform pickup pattern and is ideal in single microphone installations. Both models feature an M20 x 1.5 threaded body with mating nut for direct installation into material to a maximum thickness of 57mm and are supplied complete with elastic bearing rings for mechanical isolation from the mounting surface. Termination of the microphones is via a male 3-pin XLR connector fitted in its base. Both models may be run with universal 8-52VDC phantom powering. Beyer MPC 22/23 microphones are available in white or black finish and have a recommended retail price of $375.00. For further information, contact Amber Technology, Unit B, 5 Skyline Place, Frenchs Forest 2086. Phone (02) 9975 1211; fax (02) 9975 1368. Flatbed printer has automatic head gap adjustment The new C-650 flat­ bed printer from C. Itoh is able to iden­tify the thick­ n ess of the paper being used and adjust the print head gap automatically, providing con­sis­t­ent print quality on all types of stationery. Friction feed and push tractors provide accurate feeding of both cut sheet and continuous paper. Unusual paper thickness (from 0.05-2mm) and different sizes can be handled. The C-650 paper feed is suited to special stationery such as multiple forms, labels, prescriptions and passbooks, and is capable of handling stationery sizes ranging from cheque cards to A4 landscape. Paper path handling is straight-through under software control or by 1-key touch operation. Both Centronics parallel and RS232 serial interfaces are standard and an optional serial interface with current loop and RS422 is also available, as is an auto sheet feeder. For further information, contact Anitech, 52/2 Railway Parade, Lidcombe, NSW 2141. Phone (02) 749 1244. 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. Battery capacity meter wanted I have been a regular reader of your magazine for the past 4-5 years and one of my interests involve model aircraft which I regularly fly. As a consequence of this, I have a vested interest in the proper care of nicad batteries which are used in the transmitter and receiver packs. To avoid memory effect, I regularly discharge these packs using a nicad discharger I have built using a circuit from a past issue of your magazine. This works well but it does have some drawbacks. What I would like is an indication of the batteries’ capacity. This would involve a timer in the circuit with a readout display in minutes, showing the time it took the batteries to discharge to the endpoint voltage. A lot of the commercially available nicad chargers/cyclers which are dedicated to modelling have this feature. It would also be nice to have variable discharge currents to suit different capacity batteries; eg, 500mA, 750mA and 1000mA. Does SILICON CHIP plan to publish such a circuit? I am sure that the discharger circuit mentioned above could be modified and expanded to include a timer and variable current discharge circuit. Of course, it would need to have its own supply to power the display when the batteries have discharged. (J. C., Western Gardens, Vic). • We do not have any immediate plans to produce a discharger or cycler with a timer. However, we have published your letter in order to gauge reader interest in the concept. For your reference we did publish a “discharge pacer” for electric vehicle batteries (lead acid) in the July 1991 issue. This was a fairly complex instrument which indicated the percentage ampere-hour capacity remaining in a rechargeable battery as it was discharged. would be a con­siderable development time. Commercial units are complex and involve a variable frequency output to give control over speed. Older speed controls used cyclo-inverters employing SCRs. Howev­ er, just recently an IC has been released which we believe con­ tains most of the control circuitry needed for a variable fre­quency, variable voltage speed control. We will investigate this chip and see if it can be the basis of a speed control suitable for publication in SILICON CHIP. But we are not promising anything at this stage. Variable speed for induction motors Leak amplifier circuit wanted Is there a circuit available for controlling the speed of induction motors? I have a wood lathe with a 2hp motor, and speed control without the laborious rearranging of belts and pulleys would be of great benefit. I’m sure many other machines could also benefit from easier speed control. I believe commercial units are available but at around $1400 to $1700 the control unit often exceeds the price of the complete machine it is meant to control. (W. S., Hallett Cove, SA.) • We have not published a suitable circuit and up until the last week or so, we were not likely to since there I am currently restoring a Leak Delta 70 amplifier. I think the HT rail may be too high (75V). The preamp boards are drawing too much current. I would appreciate it if someone would send me a circuit diagram with these voltages, etc. I will reimburse them for their trouble. As an aside, this is one for the Serviceman. I was given an Ibanez effects unit from a large club in Sydney. No-one could get it to work properly. After much measuring of resistors, capacitors, etc, I took it out in the sunlight and found what looked like a fine piece of wire under the board lacquer. TekScope Review . Encouraged by this, we then charged a one Farad capacitor to 3.96V and discharged it with a 1kΩ resistor. The voltage was chosen to ensure that the DVM would not switch ranges as the capacitor discharged. This graph can be seen in Fig.5. The time constant for this combination is 1000 seconds; ie, the voltage across the capacitor should drop to 37% of the initial value (1.46V) in . . continued from p85 1000 seconds or 16.67 minutes. Similar recording functions are available on the other ranges. By now you must be wondering how much this great little instrument is going to set you back. The prices are as follows: THS710 (60MHz), $3195 + sales tax; THS720 (100MHz), $3795 + sales tax. These prices include the TekScope, carry case, two CRO probes, multimeter leads, two batteries, the charg­er, and RS-232 and power cables. After using the TekScope for a week I probably still have not explored all its capabilities and will be very reluctant to hand it back to Tektronix. I doubt if the vast majority of users would need, or even want, any additional features to be included. I shall have to start working on the boss to buy me one for my SC workbench. July 1996  93 Replacement modules work well Thank you for your help with upgrading my Fisher amplifier (Ask SILICON CHIP, April 1996). I changed the input sensitivity to the LM3876 power amplifier chip as you suggested. The performance is now very clean and very loud, with excellent overall gain – the best Fisher amplifier I have ever heard. I was wondering if the same modification could be made to the 25 watt chip, the LM1875T, as featured in the December 1993 issue of SILICON CHIP. You see, I have another amplifier with the same preamp problem; not enough gain. What would the modifications be? I also want to build two sub­ woofers for my Dolby Pro Logic System. I would like to try using some stormwater piping for the enclosure just as you used in the March 1995 issue. However, that piping is too big for my application as I want them to fit snugly behind the two lounge chairs for that added oomph. I was thinking of using an 8-inch subwoofer supplied by Jaycar (Cat. CW-2136). For a vented enclosure, they say that a 33-litre box with a vent tuning of 39Hz would be a good size. The piece of storm water piping I have is 20cm inside dia­ meter at two metres in length. It is just big enough inside to mount an 8-inch subwoofer. After scraping between the tracks on this very sensitive part of the board it burst into action. After inspecting the so-called wire short it turned out to be a human hair! It sounds far fetched but that is what stopped it from working properly. (M. Chase, 58 Douglas St, Nowra, NSW 2541). Electronic speedo wanted I have a problem with my Ducati and that is that I have changed the size of the front wheel. The speedo was driven from an 18" front wheel which is now 17". There is a commercial unit available but this is just too 94  Silicon Chip Could you please tell me the length of piping I would need to get 33 litres in volume? They also say that the vent needs to be 50mm in diameter and 80mm long, which I would fit at the other end of the piping. Is this correct? Could you please help me with the formula for working out how to calculate internal air volume inside piping as I would also like to do another version using different size piping and woofers for my car subwoofer? I was also very interested in bandpass enclosures and their performance with subwoofers. Is it possible to take a piece of piping and mount the subwoofer driver on a baffle and seal it in the middle of the piping so that there was an enclosure in front of the driver as well as in back, sealed and vented at both ends like a bass cannon? Would this work? I also read in another book just recently that you can now get what they called a “Bass Shaker”. It’s a round device that screws to your walls or floors and it shakes you during heavy bass notes so that you physically feel the action. I would love to hear more about these devices and how they work. Maybe you could publish an article on it and maybe a project on this shaker some time in the future. It seems to be the next logical step towards perfection. (K. S., Morphett Vale, SA). small for viewing quickly in traffic and at high speeds. There were also other problems with this unit; the stated maximum speed was 160km/h but only 100km/h was read. If the unit was left in bright sunshine, the LCD went black then lost some of the display. Now also at night this unit is not backlit so it cannot be seen. What is required is a speedo that works off the wheel via a Hall Effect trigger, with three or four LED sections and a trip­meter so I can calculate the fuel consumption. Also the circuit board area should be as small as possible and run off 12V DC. This of course would not be the only use for the speedo as there are other vehicles around the farm that it could • The method for increasing the gain of the LM1875T module is exactly the same as for the LM3876. To double the gain, simply reduce the 10kΩ resistor at pin to 4.7kΩ. No other changes to the circuit are necessary. To obtain a volume of 33 litres with 20cm ID tubing you would need a length of 105cm. You should also allow for the volume of the loudspeaker itself and so the length should be increased to about 108cm. The formula to use for these calculations is the volume of a cylinder: V = πr2h where r is the radius and h is the height. We cannot give detailed answers concerning vent design or about bandpass systems. To design these you need access to a speaker CAD program, such as BassBox 5.1, reviewed in the June 1996 issue. We have seen references to the Bass Shaker but we can see little to recommend the concept. All that such a unit will do it is to excite various panel resonances around the room so that you will be beset by unwanted buzzes and rattles. It will also disturb your neighbours. If you are using a subwoofer with a response down to 25Hz, it will give you all the physical sensation you could want. You will be able to “feel” the bass – provided the program material does contain really low frequencies. be adapted to. (L. R., Glenorie, NSW). The project which comes closest to your requirements was the digital speedo and fuel gauge described in the October & November 1995 issues of SILICON CHIP. We can supply back issues for $7.00 each, including postage. Kits for this project are available from CTOAN Electronics. Phone (07) 297 5421. • Notes & Errata Digital Voltmeter for Cars, June 1993: the digital readout board has a missing track between pins 12 & 16 of IC3. These must be linked together for the SC circuit to work. MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE SATELLITE DISHES: international reception of Intelsat, Panamsat, Gori­ zont,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. VALVE BANK NOW OPEN: 700 types – many new and hard to get types. Phone (058) 71 1921 or send SAE to Retrieval Radio, 25 Wirbill St, Cobram, Vic 3644. A REAL BARGAIN: Riston type copper clad laminate. Develop cold, no toxic fumes, easy to use. Excellent results. Single sided 610x304 $34; 305 x 304 CLASSIFIED ADVERTISING RATES 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. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. ✂ _____________ _____________ _____________ _____________ _____________ $17.50; 152 x 305 $9.95; 152 x 152 $6.50. Double-sided also available. 2 litre developer mix, worth $2.50, free this month. Add sales tax if applicable. Delivery $6.00. Money back guarantee. Ph (02) 743 9235. Fax (02) 644 2862. RAIN BRAIN 8 STATION SPRINKLER KIT: Ultra reliable & versatile Hi Q kit. Rain switch & LED B/L Free!!! (SC Jan. 1996). Mantis Micro Products, 38 Garnet St, Niddrie, 3042 P/F/A (03) 9337 1917 man­tismp<at>c031.aone.net.au MINILOG KIT available from MicroZed Computers. EDUCATIONAL ELECTRONIC KITS: Best prices. Easy to build. Full details. Latest technology. LESSON PLANS FOR TEACHERS – see our web page. Send $2 stamp for catalog and price list to: DIY Electronics, 22 McGregor St, Num­urkah, Vic. 3636. Ph/fax (058) 62 1915. Or Email laurie.c<at>cnl.com. au and let us send details. Go WWW:http://www.cnl.com.au/~laurie.c or BBS (058) 62 3303. Download details free any­time. C COMPILERS: Dunfield compilers are now even better value. Everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC16, 8051/2, 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 moni- RCS RADIO PTY LTD Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 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 July 1996  95 PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) Ph (067) 722 777 – may time out to Mobile 014 036 775 Fax (067) 728 987    (Credit Cards OK) Specialising in easy-to-get-going hard/software kits with on-board interpreters. Also Assembler tools. Range of support hardware too. Get your project going in hours, not months Send 2 x 45c stamps for information package Microchip Programmers, Simulators and PIC chips ➡ MicroZed Computers Altronics ................................ 66-69 68HC11 F1 boards and now 80535 (up spec 8051) Extra I/O and peripheral plug-ins too Artech Corporation........................9 ingamebo Th Australian made bs NEW Prototype wiring kit NEW Micro Scott Edwards Electronics Accessories for Stamp and second source for Stamp 1 Data Collection Proto Board now in stock BASIC Stamp I and II Macintosh patch now available SPECIAL! (ExTax) 1Mbx9 – 70ns $25 30-pin Simms KITS KITS KITS: PC printer port Relay Board with DOS/WIN drivers $68.50. DC Speed Controller $33.15, 110db Piezo Screamer $19.90. IR Toggle Switch $18.40, CCD cameras $185.00. FM Trans­ mitters, Amplifiers, Power Supplies, Microcontroller kits and more. FREE catalog available. Ozitronics, 24 Ballandr y Crescent, Greens­ borough 3088. (03) 9434 3806. ozitronics<at>c031.aone.net.au http://www.hk.super.net/-diykit/oz.html WEB Search on “DonTronics” for the World’s first PIC Basic Compiler. Basic Interpreters, Stamps, PIC CPUs and Programmers starting at $20 for the PCB and software. You can re-program the EEPROM version of these suckers in-circuit! Ring or fax for free promo disk. 29 Ellesmere Crescent, Tulla­ marine 3043. Phone (03) 9338 6286. Fax (03) 9338 2935. MICROCRAFT PRESENTS: Dunfield (DDS) products are now available exstock at a new low price; please ask for our catalogue. Micro C, the affordable SIMMS (Parity/No Parity) 4Mb 30 PIN-70 $71 $90 4Mb 72 PIN-70 $75 $53 8Mb 72 PIN-70 $133 $100 16Mb 72 PIN-70 $230 $192 32Mb 72 PIN-70 $456 $378 EDO SIMMS 8Mb (1Mbx32) – 60ns $118 16Mb (2Mbx32) – 60ns $210 MAC MEMORY 8Mb P’BOOK 190 $240 VIDEO MEMORY 256K x 16 70ns (SOJ) $17 256K x 16 70ns (ZIP) $48 LASER PRINTER MEMORY 2Mb UPGRADE $140 CO-PROCESSORS 80387SX/DX to 40MHz $100 COMPAQ 8Mb CONTURA AERO $240 All other models available $Call TOSHIBA PORTEGE/SATELLITE 8Mb / 16Mb EDO $294 / $550 All other models available $Call IDE DRIVES: SEAGATE/CONNER 1080Mb EIDE 10.5ms 3yr $283 1620Mb EIDE 14ms 3yr $360 2113Mb EIDE 10.5ms 3yr $384 MODEMS: BANKSIA / SPIRIT 28,800 BANKSIA V.34 $360* 28,800 SPIRIT V.34/V.FC $350* *Plus 14% sales tax on modems Ex Tax Pricing – Delivery $8. Pricing as at 26/6/96. Phone for latest. Sales Tax On Modems 14%. Everything Else 22%. Credit Cards Welcome. We Also Buy And Trade-In Memory. PELHAM Memory Pty Ltd Suite 6, 2 Hillcrest Rd, Ph: (02) 9980 6988 Pennant Hills, 2120. Fax: (02) 9980 6991 Email: pelham1<at>ozemail.com.au “C” compiler for embedded applications. Versions for 8051/52, 8086, 8096, 68HC08, 6809, 68HC11 or 68HC16 $139.95 each + $3 p&h • Now on special is the SDK, a package of ALL the DDS “C” compilers for $399 + $6 p&h • EMILY52 is a PC based 8051/52 high speed simulator $69.95 + $3 p&h • DDS demo disks $7 + $3 p&h • VHS VIDEO from the USA (PAL) “CNC X-Y-Z using car alter­nators” (uses car alternators as cheap power stepper motors!) $49.95 + $6 p&h (includes diagrams) • Device programming EPROMs/PALs etc from $1.50 • Fixed price electronic design and PCB layout • Credit cards accepted • All goods sent certified mail • Call Bob for more de­tails. MICROCRAFT, PO Box 514, Concord NSW 2137. Phone (02) 744 5440 or fax (02) 744 9280. MicroZed HAVE range of PIC chips. OTP and /JW versions available. PIC 16C84 /04 one off price $9.76 incl. S/T. 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. 68HC705-C8P – $45 ea; Z86E08 $18 ea. Prices include p&p. 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. 96  Silicon Chip Av-Comm.....................................41 Car Projects Book....................OBC MEMORY * DRIVES * MODEMS tors: $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. Advertising Index Dick Smith Electronics........... 18-21 Earthquake Audio........................91 Electronic Valve & Tube Co..........89 Harbuch Electronics....................91 Instant PCBs................................96 Jaycar ................................... 45-52 Kits-R-US.....................................92 Macservice............................ 24-25 MicroZed Computers...................96 Model Railway Projects Book......42 Oatley Electronics.....................3,59 Pelham........................................96 RCS Radio ..................................95 Rod Irving Electronics .......... 35-39 Silicon Chip Bookshop.................53 Silicon Chip Software..................58 Tektronix....................................IFC Telstra..........................................15 Zoom.........................................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.