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SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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: www.dse.com.au Contents Vol.11, No.6; June 1998 FEATURES 4 Troubleshooting Your PC; Pt.2 Avoiding conflicts when installing internal cards – by Bob Dyball 12 Vantis Synario Starter Software Designing programmable logic devices – by Rick Walters 40 Understanding Electric Lighting; Pt.7 The high-pressure sodium vapour lamp 86 Special Subscriptions Offer Troubleshooting Your PC – Page 4 Buy a subscription before end of June 1998 and get a bonus data wallchart PROJECTS TO BUILD 18 Universal High-Energy Ignition System Versatile design accepts inputs from points, Hall effect and reluctor distributors – by John Clarke 60 The Roadies’ Friend Cable Tester Easy-to-use unit tests male-to-female XLR cables and female XLR-to6.5mm jack cables – by Paul Hoad 74 Universal Stepper Motor Controller Use it to drive stepper motors forwards or backwards for a preset number of revs A front-panel pot. lets you vary the speed – by Rick Walters Universal High-Energy Ignition System – Page 18 82 Command Control For Model Railways; Pt.5 Final article lets you choose between five throttle circuits – by Barry Grieger SPECIAL COLUMNS 28 Serviceman’s Log Variety: the spice of life? – by the TV Serviceman 53 Radio Control Radio-controlled gliders; Pt.2 – by Bob Young 58 Computer Bits The Roadies Friend Cable Tester – Page 60 Should you buy the very latest PC – by Jason Cole 68 Vintage Radio Look Ma, no tuning gang! – by Rodney Champness DEPARTMENTS 2 Publisher’s Letter 33 Order Form 38 Circuit Notebook 90 Ask Silicon Chip 94 Market Centre 96 Advertising Index Universal Stepper Motor Controller – Page 74 June 1998  1 PUBLISHER'S LETTER Saving greenhouse gases Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Rick Walters Reader Services Ann Jenkinson Advertising Manager Brendon Sheridan Phone (03) 9720 9198 Mobile 0416 009 217 Regular Contributors Brendan Akhurst Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK Ross Tester Philip Watson, MIREE, VK2ZPW Bob Young SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $59 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 8, 101 Darley St, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9979 5644. Fax (02) 9979 6503. ISSN 1030-2662 and maximum * Recommended price only. 2  Silicon Chip While it passed with little media comment, Senator Robert Hill recently signed the Kyoto accord which commits Australia to reducing greenhouse gases to 1990 levels by 2015. Senator Hill has stated that it will be difficult for Australia to meet these targets and no doubt he is right, given much of the negative or downright non-thinking which appears to come from Government and industry circles. Well, I have little doubt that we can reduce our greenhouse gases to meet or exceed the targets but we will have to be far more innovative than we have been up until now. I would go fur­ther and state that we can save a lot of money in the process. As I have indicated in the past, Australia is very wasteful in its use of energy and raw materials and merely reducing just some of this waste will reap big dividends. One big problem that faces Australia right now is the huge amount of waste paper and plastic produced by each and everyone of us. While local councils do their best to encourage recycling it seems that the problem will get a whole lot worse before it gets better, if it ever does. Let’s face it, we will continue to waste paper and plastic and there’s little that can be done about it. Greenies may wring their hands but that’s the way that modern economies operate. The problem with waste paper and plastic is that it is generally more expensive to recycle it into new product than to dump it in landfills. Hence there are huge amounts of waste paper that can’t be used now and probably never will be in the future and the same goes for most of the plastic bottles which are now being collected for recycling. It will eventually all rot down and contribute to greenhouse gases. As I see it, the only practical solution is to burn it all and use the energy released to generate electricity. There must be literally millions of tons of waste paper and plastic going into landfills every year. Doesn’t it make sense to burn this rather than going to the trouble of extracting valuable coal to generate electricity? After all, our coal reserves will eventual­ly run out. Of course, there would need to be a lot of investment in pollution control devices to stop noxious gases being released into the atmosphere but we should being doing this now rather than building any more conventional coal-fired power stations. Every city and sizable town should have its own high tem­perature furnace and generators to dispose of waste. It does not make sense to truck it long distances to power stations way out in the middle of nowhere. The sooner the greenies and the popula­tion in general come to that realisation and see to it that waste-fired power stations are the way to go, the better. Leo Simpson    Modem Sharer Compact Keyboard with MCR Share a single modem or plotter, etc with mutiple computers. Modem Share is a powerful, easy-to-use adapter for serial data communication between PC’s & one shared modem. It operates up to 128 kbps over a distance of 460 metres. Cat. No. 8588 UPS / PS (ATX) Int 500VA/300W Cat. No. 8499 UPS / PS Internal RUPS S’ware $399 $99 Cat. No. 17012 19” Rack-Mount Industrial Keyboard $500 Ideal POS keyboard with a fully 19” Rack-mount Industrial Keyboard integrated magnetic card reader stylishly recessed into the keyThis 19" rack mountable 101 key, keyboard meets EIA board above the function keys. 310C standard & can be put in the drawer of a 19" It has a full complement of 101 cabinet, or used on the desktop after the removal of keys including 90 relegendable keys in a layout mounting plates. It is enclosed in a heavy duty steel which only occupies an area of 400mm x 210mm. Cat. No. 11804 Modem /R232 Sharer - Computer End $99 case & features embossed key frame without tactile Cat. No. 11805 Modem /R232 Sharer - Printer End $99 The MCR reads track 1 & 2 (ISO 7811 standard). effect but with buzzer to make sure input is effective. Cat. No. 8300 Compact Keyboard with MCR $599 Hi- Scan Bar Code Readers High resolution CCD scanners feaDual Exhaust Fans turing multi-interface communication with RS-232C, Wand & Keyboard Emulation in one unit. Simply release the RJ-45 jack to change cables! Two products to keep your computer and hard drive Offering optical performance with minium resolution of cool! Dissipate heat with dual exhaust fans attached 0.125 mm & maximum reading distance of 20 mm it to a plenum to exhaust hot air from inside the com- can read high-density, laminated & acrylic bar codes. puter. Reduce the possibility of data loss due to a Cat. No. 8458 Hi Scan Bar Code Reader KB Wedge $699 hard drive overheating with dual fans attached to a Also available, Long Range CCD bar code scanners ventillated face plate. It will dissipate heat from the which offer variable width and depth of field. Cat. No. 8489 CCD Bar Code Scanner Long Range KB $469 HDD & significantly lower internal temperatures. Cat. No. 8564 Hard Drive Cooling Fans $49 As well as our standard range. Cat. No. 8420 Dual Exhaust Fans $45 Ultra DMA HDD IDE Controller Give your existing motherboard Ultra DMA support. This IDE controller for the PCI bus gives Ultra DMA performance to suitable hard drives & CD-ROM drives. Up to 33.6Mb/s. Cat. No. 2632 $169 Simply share 4 printers between up to 40 PC’s. Transmits data up to 460m at 10,000 char/sec over 6 wire telephone cable. A small 4-way switch allows the desired printer to be selected. There is no software so they work under DOS and Windows. Cat. No. 12029 Cat. No. 12030 Printer Share - Computer End Printer Share - Printer End $99 $99 Magnetic Card Reader - KB Wedge A bi-directional magnetic stripe reader designed to be used for credit authorization terminals, POS terminals, PC’s & banking terminals. Features easy keyboard wedge installation & requires no software modification, programming of I/O devices or additional power. Cat. No. 8045 Cat. No. 6332 CD ROM Parallel Port 24x Speed & Case $349 Cat. No. 6319 Ext. Case Parallel Port CD-ROM Drive $209 Ethernet Hub Card 5 Port UTP Industrial Control Cards Cat. No. 11287 Ethernet Hub Card 5 Port UTP $99 55 Key Programmable POS Keyboard Printer Sharers Magnetic Card Reader - KB Wedge $399 An external IDE Bus CD ROM 24x speed drive & case which connects to any parallel port. It includes built-in power supply, pass-through printer port & MS-DOS/Windows 3.1x, Win 95 & OS/2 Warp drivers. Achieve data transfer rates up to 960 KB/sec with an EPP (Enhanced Parallel Port). It can be connected to LPT1, 2 or 3 & has external audio connectors. Daisy chain up to 2 drives plus printer. Cat. No.8196 CCD Bar Code Scanner KB Wedge 80mm $359 Mounts on the backplane of a computer but does not plug into a slot, it only connects to the power supply. No separate case & power supply means reduced costs, plus everything is neat & tidy. HDD Controller PCI Ultra DMA IDE External CD-ROM Drive - Parallel Port We have a range of industrial control cards including relay I/O input, digital I/O and A/D D/A cards. Call to discuss your requirements for your particular application. The ACL7125 is a basic digital I/O card for the ISA bus & provides 8 relay actuators and 8 opto-isolated digital inputs. The ACL8111 is a multi-function, high performance, & general purpose data acquisition card designed to combine all functions, such as A/D, D/A, DIO in a single board. Top of the line POS keyboard featuring very robust construction, compact size, down loadable key assignments, multi-level programming, ability to download Cat. No. ACL7125 Relay Output & Opto Digital Input $239 entire 55 key template into internal non-volatile Cat. No. ACL8111 Data Acquisition Card $495 memory in 7 secs!, keyboard emulation (wedge) interface with optional RS-232 interface & internal Video Conferencing Kit A high performance PCI 2KB non-volatile memory. Cat. No. 8356 55 Key POS Keyboard $429 full-motion video/still image capture solution for video Internal UPS & Power Supply conferencing on the net! The The UPS is actually built into a standard size 300W kit includes video capture power supply & the batteries & front panel occupy a card, CCD camera & VDONet’s 5.25in drive bay. Apart from power failure, the 500VA video conference software. Ideal for applications rated UPS also protects against over voltage, under such as Video Mail, Video Conferencing or Fullvoltage, overload & DC short circuit. Available in two Motion Video Capture to AVI file format. sizes - PS/2 or ATX with optional software for autoCat. No. 3356 Video Conferencing Kit $489 matic shutdown. Cat. No. 8498 UPS / PS (PS/2) Int 500VA/300W $429 E & OE All prices include sales tax Come and visit our online catalogue & shop at www.mgram.com.au Phone: (02) 4389 8444 Dealer Enquiries Welcome sales<at>mgram.com.au info<at>mgram.com.au Australia-Wide Express Courier (To 3kg) $10 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 FreeFax 1 800 625 777 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 MICROGRAM 0698 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 COMPUTERS Troubleshooting Your PC; Pt.2 Installing a new card into your PC can be a satisfying experience and can save you money – provided you know what you are doing. Here’s how to avoid the problems and keep your sanity. By BOB DYBALL Have you been thinking of installing an internal modem only to have a friend advise you to buy an external unit instead, because an internal unit is hard to get working? Getting an internal modem or some other add-on card going can be a frustrat­ing experience but it needn’t be if you follow a few simple rules. In this article, we’ll take a look at how add-on computer cards are installed under DOS, Windows 3.x and Windows 95. Due to the similarities to Windows 95, users of both Windows 98 and Windows NT 4 should also 4  Silicon Chip find this information useful. If you plan on installing a new card, or are already having problems with one, you must approach the job in a logical manner. In particular, it is important to avoid “resource conflicts” with other cards or peripherals. In fact, resource conflicts with other hardware items are one of the most common reasons for a new card not working. Fortunately, there are only a few simple rules to learn and by applying these, it’s likely that your new card will work first time. But first, here’s some background on how your PC handles plug-in cards and what fits where. IRQ, DMA, huh what? Computers collect new words and jargon like a dog collects fleas. You don’t need to be a rocket scientist to get a new add-on card going but you do need to understand some of this jargon. We’ll begin with the “system resources”. The term “system resources” covers a number or resources in your computer, including Interrupt Requests (IRQs), Direct Memory Access (DMA) channels, Input/Output (I/O) Ports and Memory. In general, no two devices can share the same resources; if they do, then either one or both devices will refuse to work. Let’s take a look at this in greater detail. Interrupt Requests: an IRQ or “interrupt request” is usually one of the most important things you need to consider when installing an add-on card into your PC. An IRQ is necessary for the add-on card to gain the attention of the computer. Basically, it inter­rupts it, as the name suggests. For example, a serial mouse is usually connected to serial port COM1 which is normally on IRQ4. Now if the PC were to con­tinually check the serial port for mouse movement, it would waste a lot of time that could be better spent on other tasks. Instead, moving the mouse sends data to the serial port and this in turn generates an “interrupt” signal to tell the CPU to process this new data (when it gets around to it). When the interrupt is processed, the “buffer” (a small memory holding area) is emptied of the mouse data and the computer carries on as before. Usually, the same IRQ is not shared between devices; ie, a device using say IRQ4 will normally expect to be the only device on IRQ4 and may even cease working if it isn’t. There are a couple of exceptions to this rule but these can vary somewhat from one machine to another. For example, although IRQ7 is normally assigned to parallel port LPT1, it can also sometimes be shared with say a sound card or an extra serial port. Usually, this works fine if the parallel port mode is set is SPP (Standard Parallel Port) but it might not work if the parallel port is set to EPP (Enhanced Parallel Port) mode and won’t work at all for ECP (Enhanced Communications Port) mode. In all, your computer has 16 possible IRQs, most of which are already reserved for basic system functions and hardware. Table 1 shows a list of common IRQ assignments, including those IRQs that are free for use with expansion cards. Direct Memory Access (DMA): this resource allows data to be moved between memory and other devices in your system. The DMA con­troller chip receives information on the data to be sent and its location, and allows the CPU to do more useful tasks than repeti­ tive data transfers. Most machines have seven DMA channels and these are usually labelled as DMA 1, DMA 2, DMA 3 and so on. Although DMA channels can sometimes be shared, depending on the hardware and software drivers involved, this is best avoided if possible. Input/Output (I/O) Ports: these Table 1: Standard IRQs IRQ 0 Function System timer 1 Keyboard 2 Cascade from IRQ9; often free to use 3 Serial port COM2 4 Serial port COM1 5 Reserved for printer port LPT2 (if present); commonly used by sound card 6 8 Floppy disc controller Printer port LPT1. If port mode set to SPP, can often be shared with serial port, internal modem or sound card Real time clock 9 VGA card. Often not needed by VGA card and may be free to use 10 May be free to use 11 May be free to use 12 Used by PS/2 mouse in some PCs; may be free to use 13 Co-processor 14 Primary IDE hard disc controller 15 Secondary IDE hard disc controller; usually free in 486 and earlier PC. 7 Note: additional cards should only be set to those IRQs that may be free to use allow the CPU to communicate with other devices (eg, serial and parallel ports, expansion cards, keyboard, etc). I/O ports are given an address in hexadecimal format or “hex” (base 16); eg, 3C0H or 200-20FH can be assigned to an I/O port. I/O ports are not shared. This means that each device must have its own I/O port or range of ports. Random Access Memory (RAM): RAM is where information is temporar­ily stored in your PC and is accessed by referring to its “ad­dress” (every memory location is numbered). Memory address “ranges” (limits) have changed over the years, with newer CPUs allowing more memory to be addressed. The 8088 and 8086 CPUs, for example, could only address 1Mb (1024 x 1024 or 1,048,576 bytes) of RAM, while the 80286-based PC/AT could address 16Mb. Note that the 1Mb and 16Mb limits are re­ferred to as “address space” and don’t mean that you can have 1Mb or 16Mb of free RAM at your disposal. That’s because special areas of memory are allocated to special tasks. Memory addresses cannot be shared with other devices. There would be little point in retrieving information from two differ­ent places with the same address if we don’t know which is cor­rect. OK, with that under our belts, let’s find out how to go about installing expansion cards without causing resource conflicts. We’ll start with the non-PnP (Plug and Play) cards. Legacy cards Although most new cards sold today will be Plug and Play (PnP), there are still a few that aren’t. And, of course, there are still lots of older cards in use, which means that you may have to mix PnP and non-PnP cards in the same machine. If you have a non-PnP card (usually referred to as a “lega­cy” card), you will have to manually set the card so that it uses the available resources, as required. This involves either set­ting hardware jumpers (or DIP switches) on the card or configur­ing the card using the supplied software (or sometimes both). (1). Jumpers are small plastic covered links that are used to short two pins together. Often, you will have to set several such jumpers to hardware configure a legacy card, as described in the manual. The idea here is to allocate “free resources” to the card, to avoid conflicts with existing devices. A system with one or more legacy cards can be difficult to configure if you don’t have the manuals. Each June 1998  5 card designates software control or hardware-jumpered control. Troubleshooting legacy cards Fig.1: Microsoft Diagnostic (MSD) is useful for showing which IRQs might be free to use but note that it may not be 100% accurate. Nor will it show which IRQs have been assigned to any expansion cards that have been added. card needs to be removed, reset and replaced to alter the system resources it uses. However, if a card’s manual has been lost, you won’t know what the jumper settings mean unless a diagram has been silk-screened onto the PC board. The moral here is simple – don’t lose the manuals as you will probably need them again one day. (2). Software configuration allows you to set the card up by running a special utility program. This may be supplied on a floppy disc or on a CD-ROM, or on some other media. Typically, the configuration utility 8-Bit Card will install a special device driver into config.sys or autoexec.bat. This will typically set the resources used by the card at boot up, or may be used to enable and disable various features on the card. The main advantage of software configuration is that you don’t need to remove the card from the mother­ board to change its settings. This means that you can quickly change the settings and try again if you run into problems. (3). Some legacy cards provide both hardware and software configuration. Usually, a jumper position on the 8-Bit Slot Jumpers For Setting IRQs, etc 16-Bit Slot 16-Bit Card The differences between the 8-bit and the wider 16-bit slots and cards is clearly shown in this photograph. A 16-bit card will give you more IRQs to choose from. 6  Silicon Chip (1) Conflicts with other software configured cards: soft­ware control methods for legacy cards vary, as there is no common standard system. Interactions between cards or between a card and the motherboard are not unusual. If you find a card does not respond to the configuration utility, try to configure the card with as few other cards in the PC as possible. Alternatively, try configuring it in a different PC first to reset it. (2) IRQ Conflicts: as mentioned before, shared IRQs should be avoided. If you are short of IRQs, try IRQ 7 after changing the printer port mode to SPP. Alternatively, try IRQ 2 (9) if this hasn’t been used by the VGA card. Don’t be fooled into thinking that a device that’s not currently in use has its assigned IRQ free. For example, if you have nothing connected to COM1 (IRQ 4) and say a mouse on COM2 (IRQ 3), then IRQ 4 is not free to use on COM3. IRQ sharing problems will still appear sooner or later due to the “default interrupt handler” on IRQ 4 for COM1. In other words, don’t be tempted to try setting your new internal modem or extra serial port to COM3 IRQ 4. If you do, it won’t work. COM 1 is already assigned IRQ4 and won’t like having it shared. Instead, you will need to assign COM3 a different free IRQ, such as 2, 5, 7, 9, 10, etc. So how do you know which IRQs are free? Well, you could try using a diagnostic utility such as Microsoft Diagnostic (MSD) or Norton Utilities. The MSD utility is supplied with MS-DOS and most versions of Windows. DOS and Windows 3.x users should look in c:\dos or c:\windows directory for msd.exe. Most releases of Windows 95 also include msd.exe, though you need go to the \other\msd folder on the Windows 95 CD to find it. Don’t assume that the list of IRQs given by a diagnostic utility such as Norton Utilities or Microsoft Diagnostic (MSD) is 100% accurate. These programs guess at what is being used and the guess is based on standard IRQs, like those in Table 1. If MSD or Norton Utilities knew everything, there wouldn’t be any need for Plug and Play! A quick look through config.sys and Fig.4: double clicking on Computer in the System Properties dialog box brings up a list of the IRQs used by the computer and the devices using them. Fig.2: this window is accessed by double clicking the System icon in Control Panel, then clicking the Device Manager tab. It presents you with a list of everything in your computer – as far as your computer is concerned. Double clicking on any item with a “+” symbol reveals the individual devices being controlled. A yellow exclamation mark next to a device indicates a resource conflict. Fig.5: this dialog box shows the I/O address used by the various devices in the PC. Fig.3: selecting a device and then clicking the Properties button and the Resources tab brings up this dialog box. It shows the resources used by the particular device (in this case, a sound card) and also indicates any conflicting devices (none in this case). Fig.6: you can also view the DMA channel assignments. Note that any DMA channel used by legacy cards should be reserved in the system BIOS. June 1998  7 ROM PCI/ISA BIOS (PI55T2P4) PNP AND PCI SETUP AWARD SOFTWARE, INC. Slot1 (RIGHT) IRQ Slot 2 IRQ Slot 3 IRQ Slot 4 (LEFT) IRQ PCI Latency Timer : : : : : Auto Auto Auto Auto 32 PCI Clock DMA 1 Used By ISA : Yes DMA 3 Used By ISA : No/ICU DMA 5 Used By ISA : No/ICU IRQ    3 IRQ    4 IRQ    5 IRQ    7 IRQ    9 IRQ 10 IRQ 11 IRQ 12 IRQ 14 IRQ 15 : : : : : : : : : : No/ICU No/ICU Yes No/ICU No/ICU Yes No/ICU No/ICU No/ICU No/ICU NCR SCSI BIOS USB function Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA ISA MEM Block BASE : No/ICU : AUTO : Disabled ESC : Quit ↑ ↓ → ← : Select Item F1 : Help PU/PD/+/- : Modify F5 : Old Values (Shift)F2 : Color F6 : Load BIOS Defaults F7 : Load BIOS Defaults Fig.7: if you install a non-PnP (legacy) card in your PC, then you must reserve its IRQ assignment in the system BIOS in order to ensure that PnP cards will function correctly. Here, IRQs 5 and 10 have been reserved for legacy cards. autoexec.bat will often tell you what’s free and what’s not. If you cannot recall what a scanner card or a sound card is set to for example, look for the relevant entry in these two files. Often, it will contain someth­ing like /In or /I:n, where n is the IRQ that the card has been set to use. Typing SET at the command prompt will also usually provide the BLASTER environment variable. This line will include In, where n is the IRQ that the sound card is using. Still short of IRQs? If your card is an 8-bit card, check to see if you can obtain a 16-bit card instead (this will offer more IRQs to choose from) or, even better, one that doesn’t require an IRQ setting but can use other re­ sources instead. Check your VGA card as well. Some VGA cards have a jumper to disable IRQ use and this will free up IRQ 9 (IRQ 2). If you have a 16-bit sound card on IRQ 5 and find that IRQ 5 is all you can set your new add-on card to, try changing the sound card to IRQ 7 or IRQ 10 to free up IRQ 5. Although a few older DOS games won’t work on IRQ 10, most games will work fine on IRQ 7 or IRQ 10. What is Plug and Play? Plug and Play is a standard for automatically recognising and configuring 8  Silicon Chip just about everything you may wish to add to your PC (either externally or internally). In use since 1994, “Plug and Play” is often abbreviated to “Plug ‘n Play” or simply “PnP”. PnP standards have been applied to many newer ISA cards, PCI cards and mother­boards, as well as to monitors, joysticks, print­ers, modems and many other devices. The detection system used varies to fit the type of device. For example, video monitors use a serial E2ROM chip that contains all the details of the monitor (its refresh rates and so on). PnP modem detection, on the other hand, relies on the PC sending the modem a range of ATI commands (ATI0, ATI1 and so on) and using the responses it gets to determine the model. PnP cards are automatically detected by the PnP BIOS on your motherboard. The card is then assigned the resources it needs and the operating system kept informed of the cards found in the system and their settings. So why do some people call it Plug ’n Pray? There are a several reasons for this, although none are really the fault of the Plug and Play: (1). The user has a motherboard with a PnP BIOS, a PnP operating system (eg, Windows 95) and one or more older non-PnP cards. With this mix, it’s all too easy to get conflicts between non-PnP (legacy) and PnP cards unless you follow a few simple rules. Basically, you have to “tell” the system about any IRQs that have been assigned to the legacy cards. You do that by using the PnP motherboard’s BIOS to reserve the legacy card IRQs, so that they cannot later be assigned to PnP cards (and thus cause conflicts). This must be done for everything to work reliably, other­wise you may as well “Plug and Pray”. To use PnP correctly, you must remember how it works. By reserving the legacy card IRQs in the system BIOS, you let the operating system know which IRQs have already been assigned (by you manually), thereby leaving it free to assign the remaining IRQs to the PnP cards itself. If you do that, Plug and Play will generally work and work well! This process of locking out IRQs can appear in one of two ways. In some PCs, the BIOS will list all IRQs from 0-15 and will allow you to toggle between PnP or Legacy for each IRQ – see Fig.7. Let’s say, for example, that you are installing a legacy modem on COM3 IRQ 9. In that case, you would toggle IRQ 9 in the list to Legacy, press Escape, F10 and Y to save the settings to CMOS – and that’s it. The other common method of locking out an IRQ is via a list of four or so available IRQs – ie, 1st available, 2nd available, 3rd available and so on. Often, the default is 5, 7, 9 & 10. So if your modem is set to IRQ 9, then you would need to change 3rd available to 10 and 4th available to N/A. If you have to use a legacy card in an otherwise PnP sys­tem, make sure (after you lock out its IRQ in the system BIOS) that you set up the device in Windows 95 using the Add New Hardware wizard (in Control Panel). This done, double-click the System icon in Control Panel, click the Device Manager tab, click the new device and then click the Properties button. You should now confirm that the Automatic settings box is unchecked and that the I/O port, IRQ and other resources used by the card are set correctly. Change the resource allocations so that they agree with the settings on the card if necessary. Sometimes, however, the system won’t let you make any changes. If that happens, the Bus Slots For Those Who Missed The Bus Bus slots allow expansion cards to be plugged into a PC mother­ board. Although some mother­ boards have a proprietary bus or no provision for expansion at all (to reduce the physical size of the unit), most have one or more of the following standard bus systems: (1). 8-bit ISA slots: released in 1981, the original IBM PC, featured an 8-bit bus. This ran at the (then) blindingly fast speed of 4.77MHz and later became known as the ISA (Industry Standard Architec­ ture) bus. Early models of the PC had a separate fixed IRQ allocated to each slot. This meant that a card set to IRQ 7, for example, had to go into the last slot (the IRQs were numbered 0-7). This was soon changed to allow any of the IRQs to be available at each slot. (2). 16-bit ISA slots: in 1984, when the 80286-based PC/AT was introduced, the ISA slot grew from 8 to 16 bits, the number of IRQs increased to 16 (0-15), and the bus speed increased from 4.77MHz to 8MHz. 16-bit ISA slots are backwards compatible; ie, a 16-bit slot can accept an 8-bit card, with one section of the slot simply left unused. trick is to change the “Setting based on” option from “Basic configuration 0” to some other setting (eg, “Basic configuration 5”) and then try again. You may have to try several settings before you find one that will let you make changes. Usually, the first one or two “basic settings” are preset and cannot be changed. (2). The user has an old non-PnP motherboard and wishes to add new PnP expansion cards. Older mother­ boards with BIOS dates before 1994 or so won’t have PnP BIOS extensions. This means that you won’t be able to reserve IRQs for legacy cards in the system BIOS, because there is simply no provision to do so. The way around this is to configure any PnP cards in these older PCs as if they were “software configured cards”. Usually, there will be a DOS (3). MCA or Micro-Channel Architecture: introduced in 1987 by IBM, MCA had no backward compatibility but featured a 32-bit data bus, a 10MHz clock and auto-configuration of cards. Although technically brilliant, it flopped. IBM made MCA proprietary, thereby forcing prices up, choices down and users off to EISA bus or VLB bus instead. (4). EISA bus: the EISA bus was in­ troduced by Compaq to compete with MCA. Though not widely accepted by home users, it did have a following in the server market. It featured a 32bit data bus, a clock speed of 8MHz, bus mastering, auto-configura­tion of cards and backwards compatibility with ISA. EISA systems tended to be expensive. The add-on cards were also expensive and are now about as rare as MCA cards. (5). VESA Local Bus, or VLB: the Video Electronics Stan­dards Associ­ ation (VESA) introduced the VLB in 1992. It provided two or three slots with a 32-bit data bus directly con­ nected to the CPU. It was clocked at the same speed as the CPU, usually 25MHz, 33MHz or 40MHz. Although bus mastering and automat­ ic con­ figuration weren’t supported, it was backwards compatible with 8-bit and 16 bit ISA bus slots. PnP manager or software setup utility sup­plied, so that you can configure the card manually. Sometimes, problems can arise with older motherboards that have early PnP BIOS extensions. An update to the ROM BIOS can usually correct this. This will require a visit to your supplier (provided they can do the job), or you might try Mr BIOS on www.mrbios.com for a third party update. (3). The user has a motherboard with a PnP BIOS and is using PnP expansion cards but is still running DOS and Windows 3.x. Neither DOS nor Windows 3.x support PnP (unlike Windows 95, Windows 98 and, to some extent, Windows NT 4). If you need to keep using your older nonPnP operating system, you will need to use the DOS PnP manager supplied The VESA bus was popular in 486-based computers for video and hard disc controller cards, being ef­ fective in reducing data bottlenecks in the system. (6). PCI - Peripheral Component Interconnect: this was de­signed after Intel and others got together in 1991 and offers automatic configuration (PnP) and high-speed operation. PCI first appeared in some late-model 486 machines and is still the stan­dard bus used in nearly all PCs today. 64 bits of data are pushed through a 32-bit bus which is clocked at 33MHz. PCI can also pump data in burst mode to 133MHz, with newer versions offering even more. (7). Universal Serial Bus, or USB: although it’s still too soon for wide choices and low prices, USB is set to make quite an impact on the market. With transfer rates up to 12Mb/s, up to 127 USB devices can be daisy chained together and “hot swapped” (no need to turn the PC off first), all with Plug and Play recogni­tion. A large number of companies are getting into USB, with a whole host of new devices set to come onto the market. USB re­ quires at least Windows 95b (version 4.00950B or later) and a recent motherboard with USB support. with the card and treat any PnP cards in your system as if they were plain software-configured cards. In order for Plug and Play to work, it needs to be all or nothing; ie, you must have a PnP BIOS and a PnP operating system. (4). PnP motherboard BIOS, expansion cards all PnP, PnP operating system. This is my favourite – you simply plug in the cards and turn it on. And that’s pretty well all there is to it! If you are adding a PnP modem, for example, you let the auto-detection kick in, then insert the modem “driver” disc when instructed and the PnP system does the rest. You don’t have to worry about setting or reserving IRQs. Next month, we’ll take a look at some common modem problems and SC tell you how to fix them. June 1998  9 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SOFTWARE: Logic array design Vantis Synario Starter Software Fancy designing a project which incorporates a program­mable logic device? Now you can do it at low cost with this new kit from Vantis. It contains sample PLDs, all the software on CDROM & can be implemented on a standard PC. By RICK WALTERS Over the last 10 years or so, many new programmable IC devices have been released which have been incorporated into electronic equipment without much fanfare. They were initially available as PLAs which is the acronym for Programmable Logic Arrays. PLAs were an IC which consisted of a programmable array of logic AND gates followed by a pro12  Silicon Chip grammable OR array, which could be programmed by the manufacturers of many types of elec­tronic equipment, to perform a specific function. This was done by fusing (melting) various links inside the device to obtain the required result. PLAs were followed by PALs which had a fixed OR structure and programmable AND devices. Although this made them slightly less flexible than the PLA they were cheaper and faster. PALs gradually evolved into SPLDs (simple programmable logic devices), and FPLAs (field programmable logic arrays), which are re-programmable, while the fused link types were not. Now we have CPLDs, which instead of being simple, are com­plex. All these latter devices are similar to EEPROMs (electri­cally erasable programmable read only memory) in that they can be erased and reprogrammed in a test jig. The latest CPLDs from Vantis are designated ISP, which stands for “in system programmable”. The advantages of PLDs for a designer or manufacturer of modern electronic equipment are many. These include their small size and high packaging density which allows a lot of functions to be crammed into one chip. They also give excellent protection from unauthorised copying of the product and they can often reduce inventory because one type of PLD may be programmed to provide a whole range of circuit functions in different products in a manufacturer’s range. What has created all this interest in PLDs? To find out, we recently took a look at the Vantis MACH starter kit, which consists of a CD-ROM, a programming kit which includes two devices and a print­ed ISP manual. The CD-ROM runs under Windows 95 or Windows NT4.0 and contains all the programming software, the data sheets for all MACH (macro array CMOS high density) devices and a copy of the MACH ISP manual. The programming kit consists of a small PC board with a 44-pin zero insertion force (ZIF) socket and a 2-metre cable which connects to the parallel port of a PC. This lets you program either of the supplied devices, which are a MACH111SP-5JC and a MACH211SP-7JC, to come to grips with the concept. The 111SP-5 is a 44-pin PLCC device containing 32 macro­cells (1250 PLD gates) with 32 I/O pins, two dedicated inputs and eight output en­ables. It can operate at up 167MHz and draws 40mA. The 211SP-7 has 44 pins, 64 macro­ cells (2500 gates), similar I/O pinouts and operates at up to 133MHz, drawing a similar current. Naturally the kit is capable of programming other devices in the Vantis range, as well as these two. Fig.1: here, the source is listed as “test”, while the virtual device is listed as flipflop (Flipflop.sch). a simple example of how to create a project. Creating the schematic We obviously needed a circuit for our project which we’ll called “test” – highly original we admit but you’ve got to start somewhere. To keep it simple, we decided on a clocked flipflop made from a few gates and we named it “flipflop”. Fig.1 shows this progress, with the source listed as “test” and the virtual device as a flipflop (flipflop.sch). The next step would seem to be to draw the flipflop circuit. Clicking on Window brings up a list of editors. We chose schematic and the window of Fig.2, without the symbol libraries or circuit appeared. A description of the drawing symbols is shown in a separate panel. Clicking on the gate symbol brought up the symbol libraries window. From the top we selected the gates library and then scrolled down until we found a 2-input AND gate. Two of these were placed, then an OR gate, and these The software The software requires a Pentium PC or equivalent with 16Mb of memory and is loaded in the normal manner. Adequate instructions are given inside the CD cover and we had no trouble loading it into one of our machines. Once you click on the Vantis icon a window opens. It is titled Vantis Synario software project navigator, with the in­ struction: “select new project or open project”. Naturally we selected a new one as we didn’t have any existing projects saved. At this stage, you feel the need for an on-screen tutorial or a at least few pages of text to take you through This close-up view shows the programming board which carries the 44-pin PLCC socket. It is connected via a cable to a PC’s parallel port. June 1998  13 Fig.2: the next step is to draw the circuit in the Schematic Editor. The Symbol Libraries dialog box lets you select devices and place them on the schematic. were connected by select­ing the line symbol. As you can see from Fig.2 we have just placed an inverter. Once the layout is completed and the I/O lines (inputs and outputs) labelled, the file is saved and the window closed. We Fig.3: this dialog box shows the processes that are available when the flipflop device is selected. 14  Silicon Chip are then returned to the screen of Fig.1. Fig.3 shows the processes available when we click on flipflop, while Fig.4 shows those available when Virtual Device is selected. Double-clicking on flipflop will take you straight into that schematic in the editor. This would be handy if you were drawing a large circuit over several sessions, as the project you were last working on is presented each time the Vantis software is loaded. Once your circuit is finalised, the schematic has to be compiled. If this step is successful you move on to reducing the schematic logic. If there are problems with the compilation then error messages are generated and logged. When all is well with the circuit you click virtual device, then update all schematic files. This is necessary as a large device can consist of several, or indeed many, pages of circuits. The main page may only be a block diagram of a concept, with each sub-circuit representing one block, or maybe only part of a block (top down hierarchy). 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. The advertiser, BBS Electronics, is no longer in business. June 1998  15 that when the dot on the IC faces towards P2 you can push it down into the socket. Pushing the socket down ejects the chip. The MACHPRO software has to be separately installed from the CD into its own directory on the C: drive. The readme.txt file in the MACHPRO subdirectory on the CD gives full instructions on how to set it up for Windows 95 or NT4.0 and which files have to be copied and unzipped. This is the time to read chapter 3 and appendix B of the Mach ISP manual. These gives a good insight into the steps you must now take. Once read, from Start – Programs – MACHPRO for WIN, run MACHJTAG-ISP TOOL. This opens a window entitled JTAG chain editor and MACH programmer. Clicking on the file menu brings up two chain files which are demonstration programs and selecting Chain1 brings up the screen shown in Fig.5. If project is selected, one of the options available is to program the device. Fig.4: different processes are available when Virtual Device is selected. Summing up Fig.5: two demonstration programs are included with the software: Chain1.wch and Chain2.wch Vantis assigns and labels interconnections between all the blocks and if one block or circuit is altered it can effect the interconnections right through them all. The last step is to combine all the individual blocks into one larger logic block. You can specify the particular device you wish to use or let the software tell you the device type it can fit everything in. Programming the device Now comes the relatively easy part – actually programming the chip. One of the photos (on page 13) shows the programming board with the 44-pin PLCC socket and the cable which connects it to the compu­ter’s parallel 16  Silicon Chip port. A +5V supply is needed and this can be obtained from a separate power supply or from the computer’s games port on pin 1. Surprisingly, the socket has no indication of which way the IC fits into it. On the fourth try we found Drawing Symbol Table Symbol Instance Name Pin Attrib Wire Net Name Net Name I/O Pin Symbol Attrib Net Attrib Duplicate Move Drag - - Delete Text Li ne Rectangle Arc Circle Highlight Net While the time available did not allow us to program a device to match a complex circuit function, we saw enough of the program and the comprehensive literature on the CD-ROM to get some feel for its capabilities. Inevitably though, just as with any other complex software package, there will be a steep learn­ing curve for anyone diving in at the deep end. The lack of a tutorial for beginners, either printed or on the CD, is a little disappointing though and would make the initial hurdles a lot easier. To really come to grips with the program, you will have to plough through the 347-page manual and print out the bits that you need, so that you can refer to them until you become more familiar with the software. Having said that, the Vantis Mach Starter Kit will be a good investment for any designer who is not yet into using these devices. The keen price of the development kit and the reasonable cost of the devices won’t place much of a burden on the bank balance. The Mach Starter Kit costs $89 and is available from BBS Electronics Australia Pty Ltd, PO Box 6686, Baulkham Hills, NSW 2153. Phone (02) 9894 5244; fax (02) 9894 5266; or email to SC bbsaust<at>bbsaust.com.au. MAILBAG Programmable ignition software modifications The Programmable Ignition originally presented in the March & September 1996 issues of SILICON CHIP has proven to be a very popular design. There are now a great many units on the road across Australia and overseas. Almost on a daily basis, enquiries have been made to see if any modifications can be made to the project to make it suitable for a particular application. There have been efforts made in some cases to accommodate these changes but on the whole, it is a very difficult and time-consuming process to cater for the needs of all. One modification enquiry stood out more than most and this was to give the module the ability to retard the ignition timing after a certain RPM rather than to keep advancing it. If this could be achieved, then the unit would be more suited to vehicles that were turbo-charged or that ran on gas. If the timing is continually advanced in some of these vehicles, damage to the engine may occur due to pinging at high RPM. Unfortunately, no immediate solutions to the problem could be found as it required a major revamp of the software. The PIC 16F84 only has 1K of ROM in which to squeeze the code and as it stands, it’s a testament to the RISC-based design of the PIC processor that the software could be squeezed into the chip at all, considering what it has to do. As such there was not much hope of cramming anything else into a chip that was already bulging at the sides. One thing about writing software is that the more you do it the more efficient your code becomes. It was time to at least have a go at the changes needed. After a lot of groaning, moan­ ing, changing and squeezing, the code was eventually remodelled to accommodate the new advance function. As a bonus, the chip even has 25 extra ROM locations available, although I seriously doubt that anything else could be implemented without reinforcing the plastic casing of the chip! The result is that the user can now program the chip so that the timing can be retarded or advanced after the Stage 2 RPM. There are no changes to the software as far as user program­ming is concerned and there is no change to the hardware. The PIC 16F84 is a Flash-based device and as such, can be reprogrammed. If anyone is interested in upgrading to the new software, a reprogramming service is available by sending the chip to the author, along with $5.00 to cover costs. The chip needs to be properly packaged to avoid both physical damage and damage caused by static. Anthony Nixon, 8 Westminster Court, Somerville, Vic 3912. Phone (03) 5977 5792. 1kW stereo system is a work of art As you can see from the photo, my stereo version of the 500W amplifier, published in August, September & October 1998, is well under way. You were right when you said the amps were big and they’re heavy. I’m 16 stone and I can’t lift my stereo ver­sion of this amplifier! The toroidal transformers are 1kVA each (made by Tortech). These include an electrostatic shield between primary and second­ary (wound copper flat strip) which is connected to the star earth point on the chassis, as well as other earths. The 8 x 10,000µF capac- itors per channel are of the highest quality and are screw-terminal types. The capacitors are connected by “frog” plates, made from silver-plated copper sheet. Unfortunately, I could not source the 0.15µF 275VAC (Philips MKP2222-336-10154) capacitors in the Zobel network. I substituted 1500VDC poly­propylene types, one as 0.1µF and the other as three .047µF in parallel. I hope this is OK? The heatsinks are of copper construction and the case (welded) is of 2mm mild steel, having removable panels under the PC boards. I have also used .01µF 1500VDC poly­propylene capaci­tors for the suppression capacitors across the transformer prima­ries. I hope this is also OK? It also has the speaker protectors, fans and the thermal cutouts. The unit is divided into three separate sections, by 2mm shield plates. It is of dual mono construction and has separate fuses and power switches. After only having partly built this unit, I have many enjoyable hours yet to go to complete it. I can’t even imagine how many hours you guys must have spent. R. Lewellin, Somerville, Vic. Comment: We are impressed with the amplifier and we love the timber plinth even more. Your capacitor substitutions should be satisfactory but we would like to see covers over the main filter capacitor banks. June 1998  17 Universal High Energy Ignition System Versatile design accepts inputs from points, Hall Effect and reluctor distributors By JOHN CLARKE 18  Silicon Chip T HIS HIGH ENERGY electronic ignition system will boost performance and greatly reduce the need for tune-ups in cars with points or it can be used to replace the ignition module in cars with Hall effect and reluctor distributors. You could also re­place your points with a Hall effect sensor to forever eliminate ignition timing adjustments. Over the past years at SILICON CHIP we have published a series of ignition systems all based on the Motorola MC3334P integrated circuit. This was first featured in the High Energy Ignition for cars using points in May 1988 and this is still available as a kit 10 years later. In June 1988 we featured a version for Hall effect distributors and in May 1990, a version for reluctor distributors. Also very popular was the Programmable Ignition system featured in March 1996. This was used in conjunction with our High Energy Ignition circuit to provide electronic advance. It used a microprocessor to perform the advance calculations and there have been several updates to the program since the publica­tion date. Because of this Programmable Ignition, there have been many requests for variations and so we have finally decided to tie all the versions together in an update of the original circuit. Accordingly, it has provision for points, Hall effect or reluctor triggering and connection terminals for the Programmable Igni­tion. In addition, the circuit has been revised to include op­tional current limiting for the ignition coil, has a tachometer output signal and uses a new high voltage Darlington output transistor which has a TO-218 plastic package. The plastic high voltage transistor is easy to mount and can be fitted inside the case. In contrast, the TO-3 transistor used in our previous designs needed to be mounted on the Main Features • High energy coil output at high RPM • Operates on reluctor, points or Hall effect signals • Twin points input for twin coil engines • • Fixed 0.9ms spark duration Coil current limiting when fully charged • Coil primary voltage limited to 300V • • Separate tachometer output • 4-22V operating voltage 400mV RMS reluctor circuit sensitivity outside of the case. The plastic high voltage transistor results in a safer installation. The full range of features of the new circuit is shown in an accompanying panel. Readers who are familiar with the previous High Energy Ignition circuits will see that it is quite similar in overall configuration but with the refinements listed above. Current control The High Energy Ignition is socalled because it provides maximum The finished High Energy Ignition module should be mounted in a well-ventilated spot in the engine bay, well away from the exhaust manifold. To ensure good circuit earthing, the case has a separate earth lead which should be bolted to a good earth point inside the engine bay. June 1998  19 Fig.1: the circuit has three alternative input circuits for triggering from points, Hall effect or magnetic reluctor pickups. Other refinements include current limiting for the ignition coil and a separate tachometer output. energy storage in the ignition coil by including dwell extension. What this means is that the coil current is allowed to flow for most of the time instead of simply while the points are closed (the dwell time). Dwell extension means that the high voltage switching transistor is off for a fixed 0.9ms and this sets the spark duration. This is particularly important at high rpm when there is less time for the coil current to build up. Most car ignition systems incorporate a ballast resistor which is connected in series with the coil primary and limits the maximum current. In effect, the voltage applied to the coil is never more than about 7V. During starting, the ballast resistor is switched out so that the full battery voltage is applied to the coil. This 20  Silicon Chip compensates for the drop in battery voltage when the starter motor is cranking the engine. While this is necessary to ensure an easy start, the bat­tery may not be particularly low when cranking the engine and, considering that this circuit also incorporates dwell extension, the coil current may become excessive. This can cause the igni­tion coil to run considerably hotter than it otherwise would and also means that the battery drain is higher than it needs to be. With these thoughts in mind, we have incorporated current limiting to prevent the coil current rising above 5A. Now let’s have a look at the circuit of Fig.1. As already indicated, the heart of the circuit is the Motorola MC3334P integrated circuit which is especially designed for this applica­tion and has an operating temperature range up to 125°C. This lets it operate comfortably inside the engine bay of a car. Circuit description Fig.1 shows the MC3334P IC controlling a high voltage tran­sistor Q1. There are three trigger circuits, catering for cars with points, Hall effect or magnetic reluctor pickups in the distributor. Q1 has a high voltage rating to allow it to withstand the voltages developed across the primary winding of the ignition coil and it is a Darlington type (effectively two transistors in cascade) to give a high current gain. When Q1 is turned on to feed current through the ignition coil primary, its base current is supplied via a 100Ω 5W pullup resistor at pin 7 of IC1. Q1 is turned off when IC1 pulls its output at pin 7 to ground (0V). The string of 75V zener diodes (ZD1-ZD4) limits the voltage at Q1’s collector to 300V when the coil fires. This prevents damage to the transistor and also prevents damage to the coil itself if one of the spark plug leads becomes detached, allowing the secondary voltage to rise to an excessive value. Q1’s emitter connects to ground via two parallel connected 0.1Ω 5W resistors. The voltage across them is monitored by IC1’s pin 8 input via trimpot VR1 and the 33Ω resistor. The 100Ω resis­tor from pin 8 to ground forms a voltage divider with the 33Ω resistor and VR1, to allow adjustment of the current limit. This current limit occurs when pin 8 is at +160mV (nominal). This causes IC1 to reduce the base drive to Q1 to maintain the coil current at the set value. The positive supply for IC1 is fed via a 330Ω dropping resistor and is decoupled with a 0.1µF capacitor. This provides a measure of filtering for voltage transients. The IC clamps tran­ sient voltages above 90V and shuts down if the steady-state supply reaches 30V. The trigger signal drives the bases of transistors Q2 & Q3. When the trigger signal is high, Q2 is switched on and so its collector is low. This pulls pin 5 of IC1 low via the .01µF capacitor and causes pin 7 to go low, to turn off transistor Q1. Pin 7 is an open collector output, meaning that it needs an external pullup resistor (100Ω 5W in this case) so that it can go high when the internal transistor turns off. The .01µF capacitor at the collector of Q2 now begins to charge via the 470kΩ resistor and after about 0.9ms, the voltage at pin 5 reaches the threshold of the comparator inside IC1. This causes pin 7 of IC1 to go open circuit again, allowing the 100Ω resistor at the base of Q1 to turn it on again. When the trigger signal to Q2 goes low, the .01µF capacitor at its collector is discharged via the 2.2kΩ and 470kΩ resistors. Thus the .01µF capacitor provides the dwell extension by turning Q1 on immediately after the coil has fired. The 0.9ms period has been set to suit the majority of ignition coils in cars with single coil installations. Transistor Q3 switches on and off in sympathy with the trigger signal applied to its base. The resulting 12V square wave at its collector is suitable for driving most tachometers. If you are using an impulse tachometer, Fig.2: these oscilloscope waveforms show the performance of the ignition circuit with reluctor triggering. The lower trace is the reluctor signal while the top trace is the coil primary voltage waveform. The coil primary voltage is limited to 312V peak-to-peak. Note that the coil is fired on the negative slope of the reluctor waveform. then a circuit to drive this is shown in Fig.8. Trigger circuits Fig.1 shows the alternative circuits for points, Hall effect and reluctor triggering. Provision for all of these is included on the PC board. The points trigger circuit provides for distributors with one or two sets of points. Each set of points has current sup­plied to it via a 47Ω 5W resistor. This relatively high current of about 250mA is necessary to keep the points clean. It acts to burn off oxidation and oil residues which would otherwise eventu­ally stop the points from working at all. Diode D1 provides the trigger signal for Q2. Each time the points open, its anode is pulled high via a 47Ω 5W resis­tor. This turns on Q2 and IC1 turns Q1 off, as described previously. The second set of points (Points 2) is used with 2-stroke twin cylinder engines where the two plugs can be fired simultane­ously. The Hall effect trigger circuit is based on a Siemens HKZ101 ignition sensor. Power is fed to the sensor via a 100Ω resistor. This limits the transient current which is clamped by the Hall effect sensor’s internal circuitry. The 820Ω resistor is the pullup for the internal open collector transistor. Its output drives the base of Q2. The reluctor trigger circuit employs a 10kΩ load across the reluctor coil and a 470pF noise suppression capacitor. From there, the reluctor signal is fed via 10kΩ and 47kΩ resistors to the base of Q4. This transistor is initially biased on using a 5.1V zener which supplies a stable offset even if the battery supply varies. The circuit is designed to trigger each time the reluctor signal swings negative. The 2.2kΩ pullup resistor at Q4’s collector provides the trigger signal to the base of Q2. The oscilloscope waveforms of Fig.2 show the performance of the reluctor trigger circuit. The lower trace is the reluctor signal while the top trace is the coil primary voltage waveform. The peak-to-peak coil primary voltage is limited to 312V. Note that the coil is fired on the negative slope of the reluctor waveform. Construction The High Energy Ignition system is constructed on a PC board which measures 102 x 82mm and is coded 05305981. It is housed in a diecast aluminium case measuring 119 x 93 x 57mm. The case must not have internal ribbing, to allow the high voltage June 1998  21 Fig.3: the component overlay for the points version. Note that while provision is made for two sets of points, this will only be required on twin-cylinder motors where the plugs can be fired simultaneously. Fig.4: the component overlay for Hall effect triggering. Darlington transistor to be mounted inside it. Before you install any parts on the PC board, check it thoroughly against the published pattern of Fig.10 and make sure that all holes have been drilled. There should not be any shorts or breaks between tracks. If there are, repair these as neces­sary. There are several component overlays for the PC board and you should 22  Silicon Chip choose the one which applies to the version you wish to build. Fig.3 shows the component overlay for the points ver­sion, Fig.4 is the version for Hall effect triggering while Fig.5 is for reluctor triggering. Fig.6 shows how to connect up the Programmable Ignition described in March 1996. Start construction by inserting the PC stakes at the exter­nal wiring connection points on the PC board and the link (for the Hall effect version). This done, install the resistors. You can use the accompanying table (Table 2) as a guide to the colour codes. When inserting the diodes and zeners, take care with their orientation and be sure to place each type in its correct place. Once these are in, install the IC and transistors, taking care to orient them as shown. Transistor Q1 is oriented with its metal flange towards Fig.5: the component overlay for reluctor triggering. Fig.6: this component layout shows how to connect the Programmable Ignition described in March 1996. the edge of the PC board. Do not cut its leads short as you will need the full length to enable the tab to be bolted to the case. The capacitors can be installed next. The accompanying capacitor table can be used as a guide to the codes. Insert the PC board into the case and mark out the posi­tions for the four 3mm corner mounting holes. Drill these out and then fit 9mm standoffs using 15mm long 3mm screws. Place the PC board onto the screws and hard down on the standoffs. Now Table 1: Capacitor Codes ❏ ❏ ❏ Value 0.1µF 470pF IEC Code EIA code 100nF   104 470p   471 June 1998  23 Fig.7: this diagram shows how to mount the high voltage Darling­ton transistor. Fig.8: this circuit uses the primary winding of a small 12VAC transformer (type 2851 or equivalent) to produce a high voltage pulse to drive impulse tachometers. mark out the mounting hole positions for Q1, the earth screw on the side of the case and two holes at each end for the cordgrip grommets. Remove the PC board and drill and file these out to shape. The hole for Q1’s mounting must be deburred with a larger drill to prevent punch-through of the insulating washer. Fig.9: this diagram shows how the Siemens Hall sensor should be installed to provide reliable triggering. The vane needs to penetrate the sensor by between 8mm and 11.5mm. The triggering point is between 0.1mm and 1.8mm from the centre line of the unit. Secure the PC board to the case with star washers and nuts. Q1 is mounted as shown in Fig.7. Secure Q1 to the case with a screw, nut, insulating washer and insulating bush. If you are using mica washer insulators we recommend using two to obtain an adequate voltage rating. You should also apply a smear of heatsink com- pound to the mating surfaces before assembly. The silicone impregnated glass fibre washers do not require heatsink compound. Check that the metal tab of Q1 is indeed isolated from the case by measuring the resistance with a multimeter. Attach the wires for the +12V supply and trigger input connections Table 2: Resistor Colour Codes ❏ No. ❏  1 ❏  1 ❏  2 ❏  1 ❏  4 ❏  1 ❏  3 ❏  1 ❏  1 ❏  1 ❏  2 ❏  1 24  Silicon Chip Value 470kΩ 56kΩ 47kΩ 22kΩ 10kΩ 4.7kΩ 2.2kΩ 820Ω 390Ω 330Ω 100Ω 33Ω 4-Band Code (1%) yellow violet yellow brown green blue orange brown yellow violet orange brown red red orange brown brown black orange brown yellow violet red brown red red red brown grey red brown gold orange white brown gold orange orange brown brown brown black brown brown orange orange black brown 5-Band Code (1%) yellow violet black orange brown green blue black red brown yellow violet black red brown red red black red brown brown black black red brown yellow violet black brown brown red red black brown brown (NA) (NA) orange orange black black brown brown black black black brown orange orange black gold brown The PC board caters for points, Hall effect or reluctor trigger­ing. Note the plastic high voltage Darlington transistor which is easy to mount. and tachometer output, if used, and secure with the cordgrip grommet. The coil output has its own cordgrip grommet to separate this wire from the trigger inputs. Wire up the earth connection to the solder lug and secure to the case. Note that a second solder lug attaches to the outside of the case and is attached with the same screw. The wire from this is secured to the car chassis with another lug and self-tapping screw. Installation If you are using the existing points or reluctor trigger, the ignition unit can be installed directly into the car’s engine bay. Locate the case in a position where air flows over it and away from the exhaust side of the engine. It can be secured in the engine bay with angle brackets attached to the side of the case and secured with self-tapping screws to the chassis. Wire up the positive connection to the positive 12V igni­tion, the negative wire to the chassis and the trigger input to the points or reluctor. The High Energy Ignition Or CDI? Some readers will be wondering about the pros and cons of this circuit versus the Multi-Spark CDI system published in the September 1997 issue of SILICON CHIP. Briefly, we recommend this revised High Energy Ignition circuit for most cars, including those with Hall effect reluctor distributors, when the existing ignition module has failed and is very expensive to replace. We do not recommend using this system to replace or modify the ignition system in any unmodified car with fuel injection and electronic engine management. We take the view that the car manufacturers do know best, having spent many millions of dollars in optimising their systems. On the other hand, if you have a highly modified late model car which has been supercharged or turbocharged, you may re­quire an ignition which delivers more spark energy than the existing original equipment. In this case, you may want to con­sider the Multi-Spark CDI system. Su­ percharged and turbocharged engines have considerably higher cylinder pressures, meaning that the existing ignition system may not have enough energy to reli­ably fire the spark plugs. Of course, we also recommend the Multi-Spark CDI design for 2-stroke and 4-stroke engines in motorbikes, outboards and Go-karts, in racing applications and in older cars (pre-1975) which do not have lean mixtures. By the way, if you wish to use the High Energy Ignition with a rotary engine, you will need to build two complete systems; one to fire the first set of plugs and one to fire the second set. June 1998  25 This photo shows how the high-voltage Darlington transistor is mounted on the end of the case with a silicone heatsink washer (see also Fig.7). reluctor requires the correct polari­ ty connection in order to fire at the correct position. However, this is best determined by testing the engine. If it does not fire immediately, reverse the reluctor leads and try again. Hall effect trigger While readers may prefer to use the existing points in their initial installation, Hall effect triggering is a far better proposition since it has no contacts and is unaffected by dirt. It also does not bounce and cause erratic triggering nor does it require constant readjustment for correct engine timing. The Hall effect sensor recommended is the Siemens HKZ101 (available from Jaycar Electronics). You must also obtain a rotating vane assembly to suit your distributor. These are available from automotive aftermarket retailers selling Bosch ignition systems (eg, Repco). Make sure that you have one of these before purchasing the Hall sensor. Fig.10: this is the full-size etching pattern for the PC board. 26  Silicon Chip Fig.9 shows how the Siemens Hall sensor should be installed to provide reliable triggering. The vane needs to penetrate the sensor by between 8mm and 11.5mm. The triggering point is between 0.1mm and 1.8mm from the centre line of the unit. To install the sensor, you must remove the distributor from the vehicle. To do this, rotate the engine until cylinder number 1 is at the firing point and this is seen by the rotor button roughly lining up with the number 1 firing position, usually marked with a notch on the edge of the distributor housing. You should also note the direction of distributor rotation as the engine is rotated. With the distributor out of the engine, find the position where the points just open for the number 1 cylinder and mark the position on the distributor where the centre of the rotor is now positioned. This is the point where the Hall Effect sensors’ output should go high. Now remove the rotor, points and capacitor. The Hall sensor should be mounted near where the points were located so that there is sufficient lead length to exit from the distributor. The exact location for the Hall sensor can be determined as follows. Fit the vane assembly to the distributor and align the rotor with the firing point marked. The Hall effect sensor should now be positioned so that the leading edge of one of the metal vanes is about halfway through the slot. Mark the position for the sensor taking care to ensure that the vane will pass through the gap without fouling. Note that Fig.9 shows the configuration for a counter clockwise rotating distributor. Clockwise rotating distributors are timed as the vane enters the Hall sensor from the other side. A suitable mounting plate can now be made to fit the Hall sensor to the distributor advance plate. This mounting plate must be positioned so that the vane penetrates by 8-11.5mm, as stated above. The Hall sensor should be pop riveted to the adaptor plate through 3.5mm holes which are countersunk beneath the plate. The adaptor plate can then be secured to the advance plate using machine screws, nuts and washers. Try to take advantage of any existing holes left when the points were removed. The leads from the Hall effect sen- sor should pass through the existing points lead grommet. Check that the vanes pass through the gap in the sensor without fouling and that the lead dress allows the full movement of the distributor advance plate. Reinstall the distributor in the engine, with the rotor pointing towards the number 1 cylinder firing point. Do a static timing check so that the engine is set to fire when the vane is central to the Hall sensor. Connect the Hall sensor leads to the ignition unit using suitable automotive connectors. Finally, start the engine and correctly tune it with a timing light. Current limit adjustment The current limit adjustment is done by measuring the vol­tage across the 0.1Ω resistors and adjusting VR1 for a reading of 250mV when the engine is stationary. Connect your multimeter (set to read 0-2V) across the 0.1Ω resistor and set trimpot VR1 fully clockwise. Now short out the ballast resistor and switch on the ignition. Adjust VR1 for a meter reading of 0.25V. This will give current limiting at 5A. Switch off the ignition. Note that some cars have the ballast incorporated as re­sistance wire into the main wiring harness. In this case, the easiest way to bypass the ballast is to take the +12V feed to the circuit directly from the battery via a 10A fuse or from a convenient point on the fuse panel. Tachometer connection The tachometer output signal is a 12V square wave which should be sufficient to trigger most electronic tachometers. For example, the digital tachometers featured in the August 1991 and October 1997 issues of SILICON CHIP can be directly triggered without modification. Impulse type tachometers will require a much higher vol­tage. You may find that the tachometer will operate when connect­ed to the collector (coil) connection of Q1 but if not, the auxiliary circuit shown in Fig.8 should solve the problem. As shown, this uses the primary winding of a small 12VAC transformer (type 2851 or equivalent) to produce a high voltage pulse when switched via transistors Q1 and Q2. The coil voltage is limited by the .033µF ca- Parts List 1 PC board, code 05305981, 102 x 82mm 1 diecast aluminium case, 119 x 93 x 57mm (with no internal ribs) 2 cordgrip grommets 1 transistor insulating bush 1 TO-218 insulating washer (silicone type rated at 3kV) 2 solder lugs 4 3mm x 15mm screws 2 3mm x 9mm screws 4 9mm tapped brass spacers 6 3mm nuts 6 3mm star washers 5 PC stakes 1 2m length of red automotive wire 1 2m length of black or green automotive wire 1 100Ω horizontal trimpot (VR1) Semiconductors 1 MC3334P electronic ignition (IC1) 1 MJH10012 TO-218 10A 400V Darlington transistor (Q1) 2 BC337 NPN transistors (Q2, Q3) 4 75V 3W zener diodes (ZD1ZD4) 1 1N4004 1A 400V diode (D3) Capacitors 2 0.1µF 63VW MKT polyester 1 .01µF 63VW MKT polyester Resistors (0.25W, 1%) 1 470kΩ 1 330Ω 1 56kΩ 1 100Ω 5W 1 22kΩ 1 100Ω 2 10kΩ 1 33Ω 1 4.7kΩ 2 0.1Ω 5W 2 2.2kΩ Miscellaneous Angle brackets and screws for pacitor connected between collector and emitter of Q2. Programmable ignition connection If you are building the Programmable Ignition system de­scribed in March 1996 (or its later variants), mounting case, automotive connectors, cable ties, solder Reluctor trigger circuit 1 5.1V 1W zener diode (ZD5) 1 BC337 NPN transistor (Q4) 1 .0022µF 63VW MKT polyester capacitor 1 470pF 63VW MKT polyester capacitor or 100°C rated ceramic 2 47kΩ 0.25W 1% resistors 2 10kΩ 0.25W 1% resistors 1 2.2kΩ 0.25W 1% resistor 1 390Ω 1W 5% resistor 1 PC stake Points trigger circuit 1 1N4004 1A 400V diode (D1) 1 1N4004 1A 400V diode (D2) (optional; see text) 1 .01µF 63VW MKT polyester capacitor 1 47Ω 5W resistor 1 47Ω 5W resistor (optional; see text) 1 PC stake (optional; see text) Hall effect trigger circuit 1 Bosch rotating vane assembly to suit distributor 1 Siemens HKZ101 Hall effect sensor (available from Jaycar Elec­tronics) 1 820Ω 0.5W 5% resistor 1 100Ω 0.25W 1% resistor 2 PC stakes Programmable Ignition interface 5 PC stakes Delete 1 0.01µF 63VW MKT polyester capacitor 1 470kΩ 0.25W 1% resistor 1 22kΩ 0.25W 1% resistor 1 330Ω 0.25W 1% resistor the circuit of Fig.1 shows asterisks at the connection points for the +12V, ground and points input and the +5V and coil output. The compon­ ents marked with a cross are to be removed. This is shown in the overlay diagram for the Programmable Ignition installation – see Fig.6. SC June 1998  27 SERVICEMAN'S LOG Variety – the spice of life? It has been an assorted month with lots of minor faults. They ranged from a dead garage door controller to a whis­tling TV set, a crook notebook computer and a couple of trouble­ some VCRs – including one that bounced. My first story concerns a Blaupunkt stereo TV set with a dead remote control. The main drama with most remote controls is opening them without breaking or damaging them. Most are clipped together but which way? Is the lower half of the case on the inside or vice versa? And are the clips on the outside or the inside? Having opened this one, I confirmed a flat battery and cleaned away the obvious corrosion due to the coffee (or was it lemonade?) which had been spilt over the unit and which had leaked onto the PC board. After that, I quickly tracked the problem down to a fracture on the crystal leg. While I was on a winning streak, I tackled a Sharp remote control which wouldn’t select programs 1-14, although the rest were OK. I suspected that part of the multilayered PC board had corroded but when I finally opened it, I found it was remarkably clean. It was only by chance that, under a strong light, I caught sight of a fine 50mm-long crack! This surprised me, as I was sure that no-one else had been inside this unit since it was first manufactured some eight years ago. What’s more, there was no indication of any damage to the outside, yet there it was; a 50mm crack cutting off the return path to the IC from these buttons. Not only that, but the fracture was not from one edge to the other but in the middle of the board. I can only surmise some stress had been applied to it during manufacture and it had main­tained continuity until just recently. Anyway, the repair was simple – a little solder over the cracked track soon had the unit going again. Garage door controller My next job was a garage door opener. The unit in question was a B&D Controll-A-Door, and the LED on the remote control transmitter wasn’t even lighting. Access to the inside was via just one screw but unlike the last remote, it was very dirty inside. I brushed out the dust and cleaned the board with metho and a toothbrush. When I tried it again, the LED was just begin­ning to glow intermittently. 28  Silicon Chip I first suspected poor contacts on a plug that’s fitted to set the frequency but they proved to be OK. The problem with small assemblies like these is holding them steady while you attach two meter probes and push a button simultaneously. First, I determined there was continuity from the 9V battery to the circuit board, via the switch. I then checked the board and crystal for dry joints and fractures. I tried freezing the parts and noticed that the intensity of the LED varied but without pinpointing the cause. There was an old style .0068pF styroseal capacitor (a type which has problems with internal connections) so I replaced that but to no avail. Similarly, I made sure that there was no dirt or shorts between the vanes of the preset tuning capacitor. When in doubt, it always a good idea to check the supply rail to various parts of the circuit. To do this, I soldered a pigtail to the negative side of the PC board 9V battery connec­tion and followed the trail with the positive probe. It didn’t take long to find the culprit, there being a substantial voltage drop across the microswitch. A few squirts of contact cleaner between the cracks of the switch shell restored its function completely but I would be a lot happier if I could find a re­placement. I checked that it was actually transmitting by listening for noise in a shortwave radio and it seemed OK. Most similar remote controllers can be checked like this but it is better to use one of the remote checkers available on the market. However, many of these won’t prove that the correct waveform or frequency is being produced. They only prove that the unit is transmitting. Sanyo colour TV set My next customer brought in a Sanyo SS Plus CPP6012-00 TV set (A3A20 chassis series). He described the fault as what amounted to intermittent line tearing and rolling but only on some channels and when the set was cold. I began to worry when he told me that another company had tried to fix it but had given up and suggested he bring it to me. I asked him straight out who this obliging company was and made a mental note to return the favour. However, they did tell him what a “good chap” I was and so, with my ego suitably stroked, I took on the challenge. I began the job by phoning the other service company to find out what they had actually tried, so as not to repeat the exercise and waste time, effort and money. Their general consensus was that the problem was due to the AGC circuits crushing the sync pulses. A large scale integrated IC (IC101, LA7680) which contains all the IF and RF stages (including the AGC) had already been changed, so it appeared that a peripheral component was to blame. I removed the covers and connected the set to a colour bar generator. I first fed the signal in as RF and then via the AV sockets at the rear. When the AV input was selected, the picture was sharp and clear. Conversely, when the RF input was selected, the fault was very pronounced when cold but improved when hot. As the temperature seemed critical, I tried freezing and heating and noticed that the fault varied quite dramatically when I was close to Q110. This transistor is an NPN power regulator that supplies 9V to IC101 and to the front end. I measured the rail to find it a little low at 8.8V but not unduly so. A common problem with many manufacturers is that rail vol­ tages are not always accurately shown on the circuit. The circuit – if you are lucky enough to have one – is really only a guide. Anyway, I exhausted my investigations around the AGC cir­cuit and on Sanyo’s advice replaced D801 (1N­ 4148), which comes off the IF AGC line, as well as C115 (0.47µF). This made no difference and so I came back to the 9V rail. This rail starts from pin 15 of the switchmode power supply chopper transformer as B5 (15V) on the cathode of D554. It is then switched by Q554 (2SB764) from the remote microprocessor CPU (IC701) and Q792, Q552 and D562, before going through IC551 to become B6, a 12V rail. This 12V is then applied to the collector of Q110 which produces 9V, courtesy of R110 and D110. June 1998  29 Serviceman’s Log – continued All this was working as expected and there was no unusual noise on the rails themselves, as shown by the CRO. I replaced electrolytic capacitor C117 just in case but was still going nowhere. My next step was to connect an isolated variable power supply to the emitter of Q110 and chassis. When I varied the level, the symptoms were quite obvious below 9V but the set be­haved perfectly at this voltage and above. The ridiculous thing here is that we are only talking about 0.2V but it was enough to make the difference. Since there are only about five components in this simple circuit, I removed and checked each one but could not fault any of them. Finally, I replaced them one at a time with new ones and only when I replaced D110, a 10V zener diode, did the fault clear. Now it might appear that this is what I should have done as soon as I suspected the 9V rail but the spooky thing is that when I tested it across a current limited power supply, the zener worked out exactly on 10V, 30  Silicon Chip as indeed did a new one. So I put it down to a dodgy zener. I don’t have the luxury of unlimited time to make exhaustive tests as to why that part didn’t work properly when cold – it was enough to track it down. Anyway, it fixed the problem and the set was still working when the owner called to pick it up a week later. Both he and I were on cloud nine. Resurrecting Sam The next customer was a lady who complained that her Sam­sung Winner VB306 VCR was dead. And she was right. The mains fuse hadn’t actually failed but to all intents and purposes nothing was working. Fortunately for me, I have a service manual for this model, which was a great help. I decided to start with the power supply but quickly dis­covered that it is very difficult to access the circuit anywhere in this machine to measure voltages. In the end, I removed the switchmode power supply, removed its covers and soldered pigtails to each of the secondary voltage rails, before plugging it back into the motherboard. I soon discovered that the 5V rail was down to 3.5V. By replacing a 470µF capacitor (C3), the 5V was restored and the machine began to operate. However, the panel display was still non-existent. I delved back into the power supply to find that the 5.8V rail which goes to the filament of the fluorescent display was down to only 1V. Replacing a 100µF capacitor (C38) fixed that problem but since two of the electrolytics had failed, I decided to replace all the secondary electro­ lytics to improve reliability. The lady agreed and is now happily reunited with her Winner. The notebook computer For a change of scene, the next customer produced a little notebook computer. It was an early KTX 386SX16 monochrome LCD notebook and not much was happening that gave anyone any con­ fidence. The green power LED would come on and the other LEDs would flicker but there was no display. Worse still, there were thumping noises from inside, probably from the hard disc drive. In short, it rather seemed as though it was “cactus”. Still, I volunteered to look at it, especially as I own the very same model. I proposed to compare them and swap parts if neces­sary, to find the cause of the problem. The weakest part of this early notebook is the 12V battery pack. These never last long due to problems of charging and discharging them properly. In this case, the battery was missing so I dug out my old KTX and connected it to his AC power adaptor so that I could see what was supposed to happen on boot-up, with regard to LEDs lighting, etc. To my surprise, my KTX machine misbehaved in exactly the same manner as his. Initially, I suspected that my computer had also given up the ghost. Then it slowly dawned on me that per­haps I was looking at this the wrong way round – it might not be the computer that was at fault but the power supply instead. I couldn’t wait to dig out my power adaptor and plug it into the customer’s notebook. Bingo! – it booted up perfectly. The AC adaptor supplied with the KTX notebook uses a gener­ic “Go Forward” GS-30 A-18 switchmode power supply, designed to deliver 18V at up to 2A. I rigged up a dummy load of 20Ω and measured the voltage across the primary input filter capacitor following the bridge rectifier as 340V, which is correct. On the secondary side of the circuit, however, there was only 9V. A quick inspection revealed a number of electrolytics on the output voltage rail that were beginning to leak. I replaced both 1000µF 35V capacitors with equivalents but this didn’t fix the problem. I then replaced a 100µF 63V unit which restored the voltage completely. I then reworked the soldering and reassembled everything before returning it to the owner with a bill that was much less than expected. and the voltage varies, according to the light, on pins 42 and 43 of IC601 on the central processing unit. These light sensitive devices are notorious for being intermittent and so I fitted two new ones. Interestingly, the replacement PN268 looks like a clear LED while the original is dark violet or black. The two pigtails are designated emitter and collector and not anode and cathode respectively. These devices can be tested on an ohmmeter, on the 10x range (or greater), with the red probe (battery negative) on the long pigtail and the black probe on the short one (ie, the opposite polarity to a LED, which also conducts on the x1 range). The last thing to check is that the chassis return for the mode motor and the sensor is good. This involves tightening the screw which connects the lead to the chassis. It was now all systems go each and every time. The bouncing VCR The next VCR I had to deal with was Mr Young’s Panasonic NV-J11A, which had bounced back with a vengeance. It had come in a few weeks earlier, the customer complaining that it gave a rolling pattern with intermittent noise bars. What was not no­ticed by Mr Young at that time was that there was no counter – or rather, I should say that the counter didn’t count. The cause turned out to be dirt on the ACE head which pre­vented control pulses from reaching the tracking circuits and the real time clock. Cleaning fixed that problem. Complex assembly The next beast The next beast to repair was another VCR, this time an overseas JVC HRD211EM (Middle East Multi System version). This customer’s problem was that the video was intermittently not accepting his tapes properly. First, I checked the 5V and 12V rails from the IC regulator (STK5481) and looked for any lurking brown goo on the PC boards. So far, everything was OK. The cassette housing is controlled by light sensors (PN268R-NC) This time, the complaint was slightly different; it rolled only at the beginning of a tape. Inspection confirmed that the counter was working but the rolling problem was intermittent as described. With the covers off, I could see that the tape was intermittently spilling due to poor take-up torque. A new Play Arm (type VXL1861) underneath the reel pulley fixed this but I noticed that there was too much noise on reverse search and the back tension arm was not being cleared from touch­ing the tape. A slight touch with a pair of long nose pliers bent the lever closer to the plastic lever underneath, so that it pulled away further on review mode. I was beginning to think I was jinxed on this repair when I discovered that, though the noise was much reduced, it was still excessive in the review mode. When I unsoldered the heads (VEH0532) and measured their Q factor (VEH0532), all three read zero out of six on the video head tester. This meant that the heads were far too worn and it was amazing that they were still giving any sort of a picture (new ones read typically five out of six and anything better than three for an old machine is good). I conveyed the bad news to the customer and understandably, it didn’t go down too well. However, he agreed to let me fit new heads. This went off without any hitches and everything worked perfectly afterwards. However, I did have to explain to the now incredulous Mr Young that the first few seconds of recording on any machine have a slight colour patterning, as the tape has to go from the bulk erase head to the ACE head before it is norma­lised. Fig.1: this diagram gives some idea of the compact nature of Orion 10/VR combination VCR/TV set. The VCR “block” sits in the bottom of the cabinet, with the TV “block” above it. The next repair was an Orion 10/VR VCR and TV set combina­tion which was dead. This repair would have been quite routine had it not been for the complex way in which the set was assem­bled. The unit had been dropped and, as a result, the tracking control was now missing and one of the feet was broken on the outside. The major difficulty was coping with the VCR and TV assemblies on the inside; there literally was no access to eith­er. It wasn’t so bad removing both the TV and VCR together from the front June 1998  31 Serviceman’s Log – continued ble the set – you should have seen the fun and games I had getting the loose tracking control sub-assembly back into the front of the case. I then put it aside to soak test while it waited for the PRF-1600-F003 IC protector to arrive. The set was still working a week later but the main thing I learnt from the exercise was to steer clear of this model unless you have plenty of time and patience. Whistling Panasonic shell. The real problem comes after that because the TV motherboard is held in a metal frame above the VCR (which is in a metal box underneath) and both are connected together by a dozen or so leads. The next drama I found from the service manual was that the TV set and VCR had separate mains transformers and bridge recti­ f iers but shared some of the regulators and secondary power supply rails. It was all very tortured and maze like. After a lot of trouble, I discovered that a 12V rail de­rived from the VCR wasn’t reaching the TV set on plug CP7004. This was eventually traced to a fuse F7002 3.15AT in the VCR transformer secondary (T7001). However, there was still no 11.5V on TP501 in the TV section, which was still dead. Gaining access to the TV circuitry meant unplugging it from the VCR and unscrewing it from the metal frame, after which I was able to perform some continuity tests along the PC board. Eventu­ally, I found a 3.9Ω 0.5W fusible resistor (ICP501) that 32  Silicon Chip had gone open circuit. This resistor was wired in series with a 4.2Ω 18W resistor (R501) and connected in parallel with power regulator Q503. I was rather puzzled by this arrangement on two counts. First, connecting a 0.5W resistor in series with one rated at 18W seems rather strange. Second, the fusible resistor was in fact marked in the service manual as a PRF-1600-F003 IC protector, whatever that was (my guess is that this is a circuit protector chip fuse rated at 1.6A but it doesn’t appear in any of my gener­ic parts catalogs). As a temporary measure, I decided to fit another 3.9Ω 0.5W resistor while I waited for the correct replacement part to ar­ rive. Unfortunately, that didn’t cure the problem – the TV set was still dead. It didn’t take long to spot the remaining problem, however. Now that I had the whole TV section in my hot little hands, I could see that the drop had fractured the solder connection to the horizontal output transformer. I repaired this and the set came good. It took quite some time to reassem- My last repair concerns a Panasonic TC-68A61 68cm stereo TV set which came in with a loud whistling vibration from the rear. The owner had finally decided he just couldn’t take it any more. With the rear cover removed, it was obvious that the noise was coming directly from the deflection yoke assembly on the neck of the tube. The question was, what to do about it. A new yoke (TLY15912F) would probably be rather expensive and time-consuming to fit. The “singing” noise was caused by the copper wire vibrating against the ferrite core and the only way to stop this is by securing the winding and the ferrite together. I decided that the cheapest and most effective way was to use superglue and additional rubber wedges. I gingerly emptied the contents of five tubes of glue so that it flowed down the wire and hopefully onto the ferrite. As it happened, this was quite successful and the first application reduced the noise by 75%. The remainder was cured by adding thinner wedges to the ones already fitted (which align the purity and dynamic convergence of the yoke). The aim here was to push the wire harder onto the ferrite former without disturbing the settings. I was relieved when this worked as I didn’t fancy removing the yoke, sealing it and then realigning everything. No-one can be as accurate as the manufacturer in installing modern TV yokes, many of which are actually cemented to the tube. Unfortunately, the cure proved to be short-lived. After about a week of soak testing, the glue broke down under the heat and the whistling returned as bad as ever. So it looks like the repair will be expensive – that’s if the owner decides to go ahead with it. Oh well, you win some, you lose SC some! 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. 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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 June 1998  33 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au Silicon Chip Bookshop SUBSCRIBE AND GET 10% OFF SEE PAGE 86 Guide to Satellite TV Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1997 (4th 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. 383 pages, in hard cover at $55.00. 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 $90.00. Video Scrambling & Descrambling For Satellite & Cable TV By Rudolf F. Graf & William Sheets. First pub­lished 1987. This is an easy-to-understand book for those who want to scramble and unscramble video signals for their own use or just want to learn about the techniques involved. It begins with the basic techniques, then details the theory of video encryption and decryption. It also provides schematics and details for several encoder and decoder projects, has a chapter of relevant semiconductor data sheets, covers three relevant US patents on the subject of scrambling and concludes with a chapter of technical data. 246 pages, in soft cover at $50.00. 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 inter­ ested in audio design. 336 pages, in paperback at $70.00. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $90.00. Surface Mount Technology By Rudolph Strauss. First pub­lished 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Radio Frequency Transistors Principles & Practical Applications. By Norm Dye & Helge Granberg. Published 1993. This book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF 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 $95.00. Guide to TV & Video Technology By Eugene Trundle. First pub­lished 1988. Second edition 1996. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 382 pages, in paperback, at $55.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First published 1989. 6th edition. This just has to be the best refer­ ence book available for electronics engineers. Provides expert coverage of Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. Prices valid until 30th June, 1998 all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, semi­-custom electronics & data communications. 63 chapters, soft cover at $160.00. 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 $75.00. Understanding Telephone Electronics By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. This is a very useful text for anyone wanting to become familiar with the basics of telephone technology. The 10 chapters explore telephone fundamentals, speech signal processing, telephone line interfacing, tone and pulse generation, ringers, digital transmission techniques (modems & fax machines) and much more. Ideal for students. 367 pages, in soft cover at $55.00. ✓ Title Price ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ Guide to Satellite TV $55.00 Servicing Personal Computers $90.00 Video Scrambling & Descrambling $50.00 The Ar t Of Linear Electronics $70.00 Digital Audio & Compact Disc Technology $90.00 Surface Mount Technology $99.00 Radio Frequency Transistors $95.00 Guide to TV & Video Technology $55.00 Electronic Engineer's Reference Book $160.00 Audio Electronics $75.00 Understanding Telephone Electronics $55.00 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ add $10.00 per book; elsewhere add $15 per book. TOTAL $A June 1998  37 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Current indicator for 12V battery chargers This charge rate indicator was designed to replace a defec­tive ammeter on a 12V 5A battery charger. It connects in series between the charger and the battery being charged and uses three LEDs to indicate the charge current. REG1 and its associated components provide a smooth 5.6V supply as the battery voltage rises, ensuring stable operation and accurate reference voltages. Most of the work in this circuit is done by IC1, an LM324 quad op amp. Current sensing is achieved by measuring the voltage developed across R1, a .01Ω wirewound resistor. This extra low value is used to reduce the forward voltage drop at higher cur­rents. R1 is made by cutting a 300mm length of 0.8mm enamelled copper wire and forming it into a coil on a pencil. IC1a is configured as a non-inverting DC amplifier with a maximum gain over 100 and this is adjustable by trimpot VR2. The voltage developed across R1, (10mV per amp), is fed to this op amp and results in a corresponding output of 1V per amp. The remaining three op amps of IC1 are wired as comparators, with their outputs driving LEDs corresponding to the rate of charge. The first (trickle) Charging lithium ion cells We have had a number of requests from readers who wish to charge Lithium-Ion batteries, using the Multi-Purpose Battery Charger published in the February & March 1998 issues. This can be accomplished in the following way. The divider applied to the Vbat input at pin 19 must be altered to suit the fully charged voltage of the cell at 4.1V. 38  Silicon Chip LED lights if more than about 30mA is flowing, showing that the battery is connected and fully charged. LED2 (medium), lights at 1A, indicating a medium rate of charge and LED3 (high) is lit while the charge current exceeds 3A. The charger is set to the SLA position during charge. The divider resistors required between the 100kΩ resistor and ground via switch S5b are as tabled. The resistors can be connected between position 6 of S5b and the No. of Cells Divider Resistors 1 82k in parallel with 330k 2 33k in parallel with 100k 3 18k in parallel with 100k The current consumption of this circuit is negligible com­ pared with the charging currents involved and is about 30mA when all three LEDs are alight. Steve Carroll, Timmsvale, NSW. ($40) TP Cell test point on the PC board. You will need to adjust the locking washer on switch S5 so that the sixth position can be used. Also, the sixth position on the front panel can be labelled to indicate the LiIon position. This position is for one LiIon cell or battery voltage only. If you need to charge differ­ ent voltage LiIon batteries, then a different switching method will need to be devised. John Clarke, SILICON CHIP Code access control This combination lock circuit uses just one IC but it is not a keyboard encoder such as the 74C922. Instead, it uses a 4022 4-stage divide-by-8 counter with eight decoded outputs. The user must push the 10 buttons in the correct sequence in order to make the door strike operate for about four seconds. When power is first applied, IC1 is reset by virtue of the capacitor at pin 15. This sets the Q0 output (pin 2) high. Pushbutton 6 must then be pressed to cause FET Q1 to turn on and clock IC1. This causes the Q1 output (pin 1) of IC1 to go high and then button 2 is pressed to deliver the next clock pulse. This process must be repeated for IC1 to count through until its Q7 output goes high to turn on Q2 and operate the door strike solenoid. Each button must be pressed within a certain time or the counter will reset, forcing the user to start again. Battery capacity meter circuit This circuit was added to the Automatic Discharger for Nicad batteries, as published in the September 1994 issue of SILICON CHIP. It involves the addition of a quartz clock movement which can be used to provide an estimate of the battery capacity. An analog quartz clock movement typically uses an AA bat­tery of about 1Ah capacity that lasts for one year. A simple calculation shows that the average consumption is about 130µA. In fact, the CMOS drive consumes much less and every second the solenoid giving the impulse consumes a few milliamps for less than 50ms. LED1, in the Automatic Discharger, has a current through it which varies with the setting. For example, when a 3.6V battery drops to 3.3V the LED current is about 2mA and on the highest setting it is about 14mA. The voltage across LED1 can be expected to vary between 1.8V and 2V. Typically, an analog clock movement works on 1.5V and keeps going until the battery drops to about 1V. We can drive the clock from the voltage across the LED but we need to drop the nominal 1.8V by about 0.45V and have a substantial capacitor to average As can be seen, some of the buttons are connected to 0V and pressing any of these or any of the low outputs of IC1 will not cause the counter to advance. The code as shown in the diagram is 6247027, although any other 7-digit code can be used by wiring the Q outputs sequentially to the pushbuttons, with the unused numbers having the “free” side of the pushbutton connected to the 0V rail. S. Williamson, Hamilton, NZ. ($35) the current and supply the solenoid impulse. This is shown in the accompanying circuit. The Schottky diodes (D1, D2) have a forward voltage drop of 0.22V each and are available from Dick Smith Electronics (Cat. Z-3250). The 2200µF capacitor should be checked for leakage current but can be expected to be less than 100µA at 2V. The resulting supply to the clock will vary between about 1.4 and 1.6V from the lowest to the highest battery setting. When using the circuit, the procedure would be to set the clock at 12 o’clock, press the discharge button and return at leisure when the clock has stopped. Since the nominal discharge rate is 200mA, the battery capacity can then be calculated. V. Erdstein, Highett, Vic. ($30) June 1998  39 Pt.7: The High-Pressure Sodium Vapour Lamp Electric Lighting The high pressure sodium vapour lamp is widely used in industrial and commercial applications and in road lighting. Unlike the monochromatic yellow low pressure sodium vapour lamp discussed in Pt.6, the high pressure version produces light across a wide spectrum. By JULIAN EDGAR It was recognised quite early in the development of the Low Pressure Sodium (LPS) lamp that its colour appearance and render­ing would be improved with little loss of luminous efficacy if the internal pressure could be greatly increased. But before this could occur, a suitable material had to found for the arc tube. It had to 40  Silicon Chip transmit light, be resistant to the highly reactive sodium and be stable at high temperatures. The degree of difficulty in developing this material was enormous. LPS lamps were widely used by the 1930s but it was another 25 years before research into High Pressure Sodium (HPS) lamp yielded good results! The breakthrough came in 1959 with the development of a special ceramic material, polycrystalline translucent alumina (PCA), which transmits 92% of light and lacks the minute pores that would allow active sodium to pass through. The PCA material is also chemically resistant to sodium and can withstand the central arc temperature of 1500K. The first commercial lamp appeared in 1965 and was rated at 400 watts, 42,000 lumens and had a life of 6,000 hours. Today, a typical 400 watt HPS lamp has a luminous flux of 47,000 lumens and a life of 24,000 hours. Construction Fig.1 shows the construction of an HPS lamp. The inner PCA tube is translucent (not transparent) and is Fig.1 (left): a high pressure sodium vapour lamp uses an arc discharge tube made from polycrystalline translucent alumina. The tube contains sodium, mercury and xenon and is mounted within a glass envelope. (Murdoch, B; Illumination Engineering). Fig.2: the luminous efficacy of sodium vapour lamps varies with the internal pressure. At the left of the diagram is a low pres­sure sodium vapour (SOX) lamp while the SON plus, standard SON, SON Comfort and White SON are all high pressure sodium vapour lamps. (Philips Lighting Manual). held in place by a system of springs and support wires. The end nearer to the lamp cap is a sliding fit over the tube support, with a flexible electrical connector allowing the tube to expand when hot. The discharge tube contains an excess of sodium to give saturated vapour conditions when the lamp is running. Some mer­cury is present within the tube to act as a buffer gas. The tube also contains xenon gas to aid starting and to limit heat conduc­tion from the discharge arc to the tube wall. Feed conductors are made from niobium, which has a coeffi­cient of expansion close to PCA. The electrodes consist of rods of tungsten with tungsten coils wound around them. These are mounted at each end of the discharge tube, which is in turn housed within an evacuated protective glass bulb. The bulb is evacuated to reduce heat loss from the discharge tube and to eliminate corrosion of the niobium by air. Where the lamp is to be used with specially designed opti­ cal systems (eg, in a floodlight), the outer bulb Fig.3: as sodium vapour pressure increases, the colour rendering index (Ra) improves. It’s unfortunate, because as Fig.2 shows, luminous efficacy is reduced at higher pressures. (Philips Light­ing Manual). is tubular in shape. General purpose HPS lamps use an ovoid bulb. Some ovoid lamps have a diffusing coating of calcium pyrophosphate on the inside of the bulb which is designed to reduce glare. Note that this coating does not flu- oresce like the coating on a mercury lamp. As Fig.4 shows, the output from an HPS discharge tube con­tains almost no UV radiation. Lamp performance The performance of a HPS lamp is These are Sylvania High Pressure Sodium vapour lamps. The coating used on the inside of some of the bulbs is for diffusing purposes only. (Sylvania). June 1998  41 Fig.4: this piechart shows the energy balance of a typical 400W high pressure sodium vapour lamp. Of the 400 watts input power, 118 watts of visible radiation is produced. (Philips Lighting Manual). very dependent on the sodium vapour pressure in the discharge tube. Fig.2 shows the variation in luminous efficacy at various sodium vapour pressures, with the performance of four different Philips lamps indicat- Fig.5: initial current (I) is high while lamp power (P), lamp voltage (V) and luminous flux (φ) take around nine minutes to reach normal operating values. (Philips Lighting Manual). ed. The SOX lamp is a Low Pressure Sodium lamp and as can be seen, its luminous efficacy is very high. The four High Pressure Sodium lamps shown on the diagram are the standard SON and SON Plus, the SON Comfort Fig.6: on start up, the spectral output of the lamp is very red. This changes to the yellow of a low pressure sodium vapour lamp after about 10 seconds, then changes to the golden-yellow of a high pressure lamp. (de Groot, J & van Vliet, J; The High Pres­sure Sodium Lamp). 42  Silicon Chip and the White SON. It can be seen that the White SON has a lower luminous efficacy than the standard SON. As an example, the standard Philips SON50 (50W) High Pressure Sodium lamp has a luminous flux of 3300 lumens, while the 50W White SON has a luminous flux of just 2300 lumens. So why would anyone specify a White SON rather than a standard SON lamp? The answer is that the colour rendering of the White SON at Ra 83 is far better than the Ra 20 of the standard SON. High Pressure Sodium lamps that use lower pressure (are you following?) have a “golden yellow” appearance that correlates to a colour temperature of 1950K. The higher pressure lamps have a warm-white colour appearance, correlating to a colour temperature of 2500K. The relationship between sodium vapour pressure and colour rendering index (Ra) can be seen in Fig.3. Since luminous efficacy decreases with improved colour rendering, this must be taken into account when selecting the most appropriate HPS lamp for a given application. Is colour rendering or luminous efficacy more important? Fig.4 shows the energy balance of a 400W Philips SON-T lamp. Of the input power of 400 watts, 118 watts of visible radiation is produced. Interestingly, the spectral power distribution of a HPS coincides well with the plant sensitivity curve for photosynthe­ sis, meaning that there are horticultural applications for the lamp. Starting The HPS lamp is ignited by a high voltage pulse of 1.8 - 5kV, depending on the lamp type and wattage. Once ignition has occurred, it takes about 9 minutes before the lamp reaches stable operating conditions. Fig.5 shows the changes that take place in lamp current, power, voltage and luminous flux in the 12 minutes following ignition. What this diagram doesn’t show is the changing spectral output during this period. Fig.6 shows the characteristic changes in the spectrum with the increase in sodium vapour pressure that follows ignition. Initially, the lamp exhibits the red spectrum of xenon, the starting gas. This is followed within 10 seconds by the characteristic yellow spectrum of an LPS vapour lamp, which then gradually changes into an HPS discharge spectrum. If the mains supply is broken, the lamp has to cool down before re-ignition can occur. This takes about a This Philips floodlight is fitted with a tubular 150W high pressure sodium lamp and uses integral control gear. (Philips). minute. Where constant lamp operation is crucial for safety, a HPS lamp con­ taining two identical discharge tubes can be used. When one tube is operating, the other is off. If a mo- mentary power failure extinguishes the lamp, the non-operating tube will be ignited as soon as power returns, avoiding the normal one-minute cooldown delay. Some types of High Pressure Sodium vapour lamps have sufficiently good colour rendering to be used indoors in commer­cial lighting. (Philips). June 1998  43 Fig.7: to overcome the problem of delayed re-ignition of the lamp, the Sylvania 250 Standby (dotted line) uses two arc tubes within the one envelope. Only one tube is used at a time, allow­ing immediate ignition following a power cut. (Sylvania Lighting Solutions). Fig.8: a typical HPS lamp starter circuit (inside dotted lines). It uses a semiconductor switch to close a resonance circuit which generates a train of ignition pulses. These pulses are stepped up to the desired amplitude by a transformer which also forms part of the starter. Once the lamp has ignited, the starter automati­cally stops functioning. (Philips Lighting Manual). Fig.9: in this circuit, the electronic starter is connected to a tapping point on the ballast which acts as a step-up auto-transformer. (Philips Lighting Manual). This luminaire is suitable for mounting on low ceilings and can be used to illuminate food preparation areas, loading docks and the like. It can be fitted with High Pressure Sodium vapour lamps ranging from 150 to 400W. (Sylvania). Fig.7 shows the operation of this type of dual tube lamp. Control circuits Most HPS lamps are operated with a choke ballast and have an external 44  Silicon Chip starter. A series type of circuit is shown in Fig.8. In this circuit, a semiconductor switch closes a resonance circuit which generates a train of ignition pulses. These pulses are stepped up to the desired amplitude by a transformer which forms part of the start­er. Once the lamp has ignited, the starter automatically stops functioning. Note that the starter circuit must be located with 0.5 metres of the lamp otherwise the ignition pulses will be absorbed due to capacitive losses in the wiring. A so-called semi-parallel control circuit is shown in Fig.9. Here the electronic starter is connected to a tapping point on the ballast which acts as a step-up auto-transformer. HPS lamps with good colour rendering use a stabilisation unit that prevents colour shifts occurring as a result of mains voltage fluctuations or lamp aging. The distance between this type of control unit and the lamp must be kept to less than 0.3 metres. Next month, we’ll take a look at SC metal halide lamps 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 RADIO CONTROL BY BOB YOUNG Radio-controlled gliders: Pt.2 This month we will look at some of the factors to be taken into account when designing a 2-metre glider and see how these were applied in the Silvertone Stingray, an unconventional 2-metre design. The concept of the MAAA sanctioned 2-metre class was to provide a simple entry level model on which to learn the craft of R/C glider flying. This model was to place few demands on the radio equipment and the model builder’s skills. The main parameters call for rudder and elevator only (no ailerons, camber changing preset flaps or releasable tow hooks) and a span not exceeding two metres. “V” tails are allowed. Wing loading is to be in the range of 12-75g/dm2. For those inter­ested in the complete rules, see the MAAA Official Rules and Instructions Handbook (Chapter 3, Provisional Rules. pp2-41). As a result, the typical 2-metre glider has evolved along rather old fashioned, conventional lines with a polyhedral wing, a simple (lightweight) structure, and rudder and elevator controls. This is typified by the yellow and red glider This is a typical 2-metre glider showing the polyhedral wing and a simple structure. It has just two controls, elevator and rudder. pictured in this article. Sometimes the designs include a butterfly (“V”) tail with mixing on the rudder/elevators. In the thinking of most design­ ers, the rudder-only design dictates that large amounts of dihe­dral (ie, wings sloping upwards) are required in order to induce the model to turn. To my mind, this is wrong as the dihedral can fight the rudder. True, dihedral is required to initiate the turn but it then tends to pull the model out of the turn and the net result is a model that is difficult to hold in a constant rate turn, a most important point in thermal soaring. But 2-metre gliders do not have to look like models out of the 1930s. The design we will be discussing this month does not follow the current trend and had its genesis during the 1970s when I was producing models for the military. While I had often visited glider fields in the past and flown the odd glider, I had never been interested enough to undertake a glider design of my own and fly seriously in competi­ tions. In the good old days, if models did not make a noise and go fast they held no interest for me. Nowadays, if they make a noise I cannot hear them and if they go fast I cannot see them. Much has changed since I was 30 years old. During the early 1980s, Harold Stephenson, a very keen glider flyer, became a regular customer and finally convinced me to design a model for the new 2-metre class just gaining popular­ity at the time. He even offered to help me build it, an offer too good to refuse. I finally relented and drew up the plans on a strip of brown paper from my roll in the shop. Fig.1 shows the finished design, redrawn recently on June 1998  53 In contrast with conventional 2-metre gliders, the Silvertone Stingray has swept-back wings, a “V” rudder and most important, a blended wing/fuselage junction to keep turbulence to a minimum. a computer using a CAD program. Harold built the wing and I built the fuselage and there it sat for the next 15 years or so (in the tradition of all good models). That is until another friend, Barry Ming, incensed that such an interesting model should sit unfinished for so long, offered to take it and finish it. So in 1996 a finished model, painted all over in black, rolled into my workshop. Barry then informed me that the original plan had disintegrated due to age and my only record of the design was gone. It took me another 12 months to apply the colour trim and plug in the radio (one cannot hurry these things) and finally, in late 1997, the model turned out for its test flight. This I might add was on the day of the contest. Why 54  Silicon Chip is it that I sense a lack of surprise at this last statement? Old hands know exactly what I mean. The model still looks quite modern 16 years on and is quite eye-catching in style. Since then the model has flown in four contests, winning several rounds and maxing in several others and has attracted a good deal of interest, largely as result of its excellent flying characteristics and pleasing appearance. The weak link is my piloting, for I simply do not have the finesse necessary to read the subtle signs required for good thermal flying and my spot landings are appalling; with no throt­ tle to adjust the final approach I tend to undershoot all the time. Thus I would be very interested to see this design in the hands of a good flyer, part of my reason for publishing it here. With the addition of ailerons the model would make a great slope soarer and the addition of flaps and ailerons would convert it into an interesting open class sailplane. I am currently working on an F3B version which is scaled up approximately 1.5 times with flaps, ailerons and 2.5° of dihedral and a much better wing section. I must point out that this is not intended as a full con­struction article as it is a difficult model to build and only for experienced modellers. The design lends itself well to fibre­glass but the original is all wood with a built-up wing using 1/2" x 1/8" spruce spars in a “H” girder arrangement enclosed in a 1/16" “D” box leading edge. The plug-in wing dowels for the wings are 1/4" steel rods in brass tubes. The wing stubs are laminated out of 1/2" sheet balsa and hand shaped. Note that the large American influence in modelling tends to favour the Imperi­ al system of measurements in some components. Finished weight is 1.05kg, quite heavy by 2-metre stan­dards, whereas a very simple lightweight can come in at 0.5kg, ready to fly. Even so, the wing loading is still only 33.8g/dm2 (7.9oz/sq ft) due to the large wing. There is some evidence to suggest that this loading is too light for the Eppler 205 section used on this model and the next round of trimming will concen­trate on the effects of ballast and elevator trim on performance. The model certainly likes to fly fast and I feel that I have been flying it too slowly in the last two contests. The original model pictured has several shortcomings. Firstly, the nose is too short and this has been corrected on the drawing presented in Fig.1. The plastic film was also a mistake as it goes slack in the heat. A better approach is a fully sheeted wing covered with silk or Oz Cover and painted all over. Finally, the wing section is over 20 years old and now completely outclassed by the modern thinner sections. However the overall design shows promise and I believe it could be developed into a potent per­former. Design fundamentals There is a fundamental rule in glider design that all glid­ers eventually come down and that little gliders June 1998  55 Fig.1: this 17-year old design has recently been redrawn with a CAD program. The nose has been lengthened slightly to correct an original design shortcoming. The plug-in wing dowels for the wings are 1/4" steel rods in brass tubes. The wing stubs are laminated out of 1/2" sheet balsa and hand shaped. This photo shows the high degree of blending between the wing and fuselage. The fuselage height has been kept to a minimum by laying the servos on their sides. come down more quickly than big ones. Which is just a cute way of saying that one of the key factors in glider design is Reynolds numbers. We examined Reynolds numbers in the recent articles on jet turbines and concluded then that the bigger the chord (width) of the wing, the more efficient it will be. Now there is a fundamental conflict in glider design that arises out of this simple statement. One major source of losses in the wing is the induced drag which arises at the wing tips. Allied to this is the problem of interference drag which arises at the junction of the wing and fuselage. Thus the turbulence from the induced drag extends inwards along the wing panel from the tips and the turbulence from the interference drag 56  Silicon Chip extends outwards from the wing/ fuselage junc­tion. The traditional answer to this problem in sailplanes is to increase the aspect ratio of the wing (ratio of wingspan to wing chord or width), thus increasing the clear span (free of tur­bulence) panel size on each wing half. A good example of this is the 3-metre F3B glider featured in one of the photos in this article. Unfortunately, in doing this we immediately reduce wing chord and thus the Reynolds numbers on the wing and to some extent defeat the purpose of improving the overall efficiency. On full size sailplanes, this is not quite as important as on small models, for there is strong evidence to suggest that a wing section with a chord of less than 200mm falls into the very low Reynolds numbers and ceases to work effectively as an airfoil section at model speeds. A quick glance at the data panel in Fig.1 will show that the mean aerodynamic chord on the Stingray-2M is only 184.5mm, a figure somewhat short of that minimum, so the overall wing effi­ciency is not going to be anywhere near as high as on the F3B version or larger models in general. This applies to all 2-metre gliders and small models. So what to do? I have kept the aspect ratio as low as I could on the Stingray to keep the spar depth and Reynolds numbers as high as possible and yet I have still fallen below the recom­ mended minimum chord. There is little we can do on tip drag (winglets on the tips may offer some help here) but we can do something about wing/ fuselage interference drag. There was a lot of work done during the 1930s and 1940s on wing junction drag and the Vought Corsair F4U was one result. This work showed that wing/fuselage junction angles of 90° or less gave rise to a marked increase in interference drag. The crank­ ed wing of the Corsair was one method of increasing the wing/fuselage junction angle to above 90°. The results were spectacular and the Corsair was one of the fastest piston engine aeroplanes of WWII. The McDonnell XP-67 experimental twin-engined fighter in 1942 was an even more interesting example and the fuselage, nacelles and wing in this design were an almost seamless blend of aerodynamic styling. Thus, by blending the wing/fuselage junction and increasing the junction angles to above 90°, we can substantially minimise the junction turbulence and thereby increase the clear span panel size without reducing the chord. The cross-section at BB on Fig.1 shows just how close the junction angle approaches 180° on the Stingray-2M. One of the photos shows even more detail of the blending. To achieve these angles, the height of the fuselage has been reduced by laying the servos on their side. If we could completely eliminate the wing/fuselage junction we could almost double the effective aspect ratio of the wing without a reduction in chord. Flying wings do just this and the result is a very efficient flying machine indeed. ELECTRONIC COMPONENTS & ACCESSORIES • RESELLER FOR MAJOR KIT RETAILERS • • PROTOTYPING EQUIPMENT • FULL ON-SITE SERVICE AND REPAIR FACILITIES • LARGE RANGE OF ELECTRONIC DISPOSALS (COME IN AND BROWSE) CB RADIO SALES AND ACCESSORIES M W OR A EL D IL C ER O M E Croydon Ph (03) 9723 3860 Fax (03) 9725 9443 Mildura Ph (03) 5023 8138 Fax (03) 5023 8511 Truscott’s ELECTRONIC WORLD Pty Ltd ACN 069 935 397 30 Lacey St Croydon Vic 3136 24 Langtree Ave Mildura Vic 3500 P.C.B. Makers ! • • • • • Bruce Curl with “Calypso” a 3-metre F3B glider. Note the high aspect ratio of the wing, the traditional answer to minimising induced drag and interference drag. So the essence of the Silvertone Stingray-2M is the blended wing/ fuselage. But the design is more complex than this for there are many other factors which can be incorporated into this blend­ed junction. The strakes down the fuselage sides serve a dual purpose. At low or zero angles of attack they serve merely as flow separators, inducing the airflow into a smooth separation at the wing junction. At high angles of attack, when combined with the swept-back wing, they serve as turbulators, inducing the wing to stall at the centre section, well before the tips begin to stall. With the centre of gravity (CG) well back from this point, the nose begins to settle first during a stall, a very handy outcome. The net result is to reduce the need for washout on the wing tips, further increasing the efficiency of the wing overall. An additional minor benefit of the blended fuselage is an im­provement in fuselage lift which can be quite significant in some aircraft. The Grum­man Panther, another blended fuselage aircraft, produced 30% of its SC overall lift from the fuselage. • • • • If you need: P.C.B. High Speed Drill P.C.B. Guillotine P.C.B. Material – Negative or Positive acting Light Box – Single or Double Sided – Large or Small Etch Tank – Bubble or Circulating – Large or Small U.V. Sensitive film for Negatives Electronic Components and Equipment for TAFEs, Colleges and Schools FREE ADVICE ON ANY OF OUR PRODUCTS FROM DEDICATED PEOPLE WITH HANDS-ON EXPERIENCE Prompt and Economical Delivery KALEX 40 Wallis Ave E. Ivanhoe 3079 Ph (03) 9497 3422 FAX (03) 9499 2381 • ALL MAJOR CREDIT CARDS ACCEPTED June 1998  57 COMPUTER BITS BY JASON COLE Should you buy the very latest PC? Unless you’re a “techno-junkie” who really must have the latest and greatest, it often pays to hold back when it comes to new computer hardware. The latest and greatest may not be the most reliable if you buy on the cheap. When is the best time to buy computer hardware? Should you buy the very latest technology or should you opt for something that’s been around for awhile? In my opinion, you should definitely go for the latter option. There are two reasons for this. First, you will usually get much better value for your money (or more bang for your buck) if you buy behind the leading edge. Second, unless you buy good quality gear in the first place, the older tech­ nology will generally have less bugs and will be more reliable. By way of example, when the Pentium processor was first introduced, it was available in 60MHz and 75MHz versions. Due to its internal architecture, it was faster than the 486 (even the DX4-100) but because it still ran at 5V, it generated a lot of heat. Eventually, the Pentium processor was redesigned to run at 3.3V which reduced the amount of heat generated for a given clock frequency. Now as we all know, the faster a CPU runs the hotter it gets. One way of overcoming this problem is to reduce the operat­ing voltage of the processor. However, there’s a limit to how low we can go before we start getting logic errors. The alternative is to dissipate the heat generated by fit­ting a heatsink to the processor. However, a CPU is only so big and the heatsink fitted to it is generally too small to dissipate sufficient heat by itself. For this reason, a small fan is now integrated with the heatsink to provide forcedair cooling. However, integrated fan/heatsinks were not universally used by PC vendors until about the time that Pentium 100 machines were released. Consequently, there are some earlier machines out there with inadequate CPU cooling and these can suffer reliability problems. On a hot day, such machines will crash far more often and, in extreme cases, the CPU can be damaged. If you have a Pentium 60/75MHz machine, then its a good idea to check the processor. If necessary, purchase and fit an integrated fan/ heatsink – the CPU will run much cooler if you do. The same goes for many 486 machines. Imagine how hot a DX2-66 or DX4-100 processor gets when it is working at 60 or 100 million instructions per second. There are many such processors that don’t even have a heatsink to keep them cool and again some suffered from reliability problems because they ran too hot. This problem is well sorted out in the later Pentium (and equivalent) machines, which invariably have adequate cooling. Higher bus speeds An integrated fan/heatsink should be fitted to the CPU to ensure reliability. If necessary, you can buy and fit one yourself. 58  Silicon Chip Until recently, the fastest bus clock speed was 66MHz but that’s now been upped to 75MHz. Unfortunately, some 75MHz bus motherboards initially displayed a few quirks when used with a 233MHz processor. Generally, the motherboards that caused prob­lems Tip Of The Month were the cheaper brands; the more expensive motherboards were usually OK and worked well. Some time ago, an acquaintance of mine bought a new comput­er based on the latest Intel Pentium II processor. Unfortunately, to cut costs, he went for the cheapest motherboard, the cheapest video card and the cheapest sound card he could find. He ended up with a system that would only work on alternate resets – the rest of the time, it would lock up. This took place about two weeks after the Pentium II was released. As it turned out, the CPU itself worked fine but the combination motherboard, video card and sound card did not. In my opinion, it is never a good idea to buy cheap if you want the very latest technology. If you do, you are more likely to strike problems than if the technology has been around for awhile. You should also buy from a reputable dealer who is rea­ sonably close to your home, so that you can get the machine fixed if there are problems. So the message is this: if you want the latest technology, be prepared pay a premium for top quality components from a reputable dealer. If you want to buy on the cheap, it’s best to go for something that’s been around awhile. It’s a bit like buying a new car. How many times have you heard someone say that it’s best to wait for six months after a new model is released, so that SC the bugs have been ironed out? 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. Notes & Errata: this file lets you quickly check out the Notes & Errata 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 any item. 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. OR D ER FOR M PRICE ❏ Fl oppy Index (i ncl . fi l e vi ewer): $A7 ❏ Notes & Errata (i ncl . fi l e vi ewer): $A7 ❏ Al phanumeri c LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Control l er Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Ni cad Battery Moni tor, June 1994): $A7 ❏ Di ski nfo.exe (Identi fi es IDE Hard Di sc Parameters, August 1995): $A7 ❏ Computer Control l ed Power Suppl y Software (Jan/Feb. 1997): $A7 ❏ Spacewri .exe & Spacewri .bas (for Spacewri ter, May 1997): $A7 ❏ I/O Card (Jul y 1997) + Stepper Motor Software (1997 seri es): $A7 ❏ Random Number Generator/Chook Raffl e (Apri l 1998): $7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my Bankcard   ❏ Visa Card   ❏ MasterCard ❏ Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ The Desktop is a wonderful place too have Shortcuts so that you can quickly start programs but remember that it is still a folder. It is generally located in C:\ Windows\Desktop and like any other folder you can place small programs in there and have them run. That means that if you delete the item from the Desk­top, you will delete the actual file; not the short­ cut to it. So be careful because not all items on the Desktop are necessarilyshortcuts. How do you identify a shortcut? Just look for the little shortcut ar­ row associated with the icon. June 1998  59 The Roadies’ Fr A tester for XLR and jack plug cables As the name suggests, this tester is designed for anyone who regularly has to check cables fitted with XLR plugs and/or 6.35mm jack plugs. Coloured LEDs on the tester clearly indicate good cables and bad, making cable checking a simple task. Design by PAUL HOAD I ONCE THOUGHT THAT the first choice in test gear when fault finding must surely be a multimeter. To test something as basic as a microphone cable, one would only need to use the multimeter’s inbuilt continuity tester and listen for tone or no tone. Purpose built testers were for “laypersons” who could not properly use a multimeter or interpret the test results! Then one evening my brother asked me to “come over for dinner and, while you’re here, sort out some crook microphone leads”. George is the administrator of the New Theatre in Sydney and so he has a few cables to check, as you might expect. “No problem!”, I thought. “As long as I remember to bring my multi­ meter, most of the time will be spent eating and drinking a few glasses of red”. The first thing I wished I’d brought were some small alli­gator leads to clip onto the pins of the male XLR plugs. Even so, there would still be a risk of shorting adjacent pins. My other problem was getting reliable contact between the meter probes and the female XLR pins. They are physically larger than the ends of standard meter probes and when inserted, result in a sloppy fit. Using an extra set of hands (George’s) was essential to ensure that one meter probe was held in contact with the male XLR pins. LEFT: the Roadies’ Friend tests all aspects of male XLR to female XLR cables and also male and female XLR to 6.5mm jack cables. Various LEDs show the condition of the cable, whether it is functional or where faults lie. Note the flush-mounted pushbuttons which insure that no damage will occur if it is stepped on! 60  Silicon Chip riend Sounds easy, doesn’t it? Well, not really. You see the pin numbering for male and female XLR sockets is mirror-imaged. So you have to keep an eye on both ends and get your numbers right. Oh yes! I almost forgot: pin 1 is the shield and is usually always wired correctly but this is not always the case with pins 2 and 3. These connect the balanced pair of wires which carry the music. So long as they are correctly soldered, the lead will work fine, even if 2 and 3 are swapped. Of course this results in functional leads that have unknown phase characteristics. Therefore, when testing a cable, you have to test each conductor against every other in order to locate out-ofphase leads. Short circuits also need to be checked in this fashion. I can’t remember if I found the crook leads and if I did, chances are the faults would not have been intermittent since any attempt to flex the cable near the connectors would have caused the meter probes to fall out or short other pins. What a hassle! This all became the inspiration behind the Roadies’ Friend Lead Check­ er and a significant mind shift on my part about the virtues of multimeters versus purpose-built testers. The Roadies’ Friend tests all aspects of male XLR to female XLR cables and also male and female XLR to 6.5mm jack cables. Various LEDs show the condition of the cable, whether it is functional or where faults lie. Since the Roadies’ Friend can be expected to be used in rough and tumble situations, it had to be designed to be rugged and difficult to damage. It had to be possible to walk on it without causing any damage, apart from incidental scratches! That meant that it had to have a strong case, no protruding switches and no on/off switch. There’s no point in having Fig.1: this is the basic concept of the cable tester, with one LED associated with each pin of the two XLR sockets and two others to show shorts to the XLR shells. an instrument like this if it can be accidentally turned on and then stay on to flatten its battery. The photos show one of the later prototypes and as you can see, it’s a pretty basic instrument with no bells and whistles. The front panel LEDs and arrows make it virtually self-explanatory. If you plug in a good XLR male to XLR female cable, for example, and then press the SCAN button, six LEDs will come on, one for each pin in each connector. If there is a short from a pin to the XLR shell, another LED, associated with the particu­lar socket, will come on. Alternatively, you can use the STEP button to individually test each conductor in the cable. Circuit description No fancy microprocessor controlled circuitry is used in this project and nor are there any special purpose or hard-to-get ICs. There are just three garden-variety CMOS ICs and not a lot else. The cleverness of the design lies not so much in the cir­cuit but in the front panel design and the use of LEDs to indicate the various cable conditions. The basic operating principle is shown in Fig.1. A 3-position switch (IC2) is used to pass current via LED6, LED7 or LED8 through a pin at one end of the cable. These three LEDs are the ‘send’ LEDs. At the other end of the cable, we monitor the currents through all pins, including the connector housing. Five ‘receive’ LEDs (LEDs 1-5) are wired to do this monitoring. If pin 1 is to be checked then LED6 will receive a low from IC2 and current will flow through R8, LED1 and R1 from the positive supply. Both ‘pin 1’ green LEDs will be on and all others will be off. The current drain is about 10mA and will cause a voltage drop of about 4V across ZD1. As ZD1 is a 5.1V type, it will not conduct. Open circuits & transposed wires If the cable is open-circuit, no current will flow through R8, so LED1 will be off (open pin 1). ZD1 conducts across the open circuit and lights LED6. If ZD1 was not included, LED6 Where To Buy The Roadies’ Friend The copyright for this project is owned by the designer, Paul Hoad. The Roadies’ Friend is priced at $115 for the fully assembled and tested version and $65 for the full kit. Payment may be made by cheque or postal money order to Hoad Electronics, Box 19, 314A Pennant Hills Rd, Carlingford NSW 2118. Phone/fax (02) 9871 3686. June 1998  61 Fig.2 (left): the complete circuit of the Roadies’ Friend. Counter IC1 is cycled through three possible outputs by oscillator IC3c to drive currents through the cable under test. Good and bad cables are then indicated by the eight LEDs. would also be off and we would not know which pin was being checked. Because the corresponding ‘send’ and ‘receive’ LEDs have the same colour, it is easy to detect transposed wires. These faults result in different coloured ‘send’ and ‘receive’ LEDs being lit. Short circuits If pins 1 & 2 of the XLR plug were to touch, then the cur­rent would increase through LED6 due to R8 and R9 being in paral­lel and this current would be equally shared between LED1 & LED2. These two ‘receive’ LEDs would both be ‘on’, indicating the short circuit. R8 and R9 increase the dynamic resistance of LED1 and LED2. If they were not included, then the LED with the lowest turn-on voltage would light and the other LED may be off. A worst case short-circuit in a cable (all wires shorted together) would see all the receive LEDs sharing the current from a single ‘send’ LED. This equates to only 3.5mA per receive LED and 17mA for the send LED. Surprisingly, this does not cause the big difference in brightness between LEDs that you might expect. The 3mm receive LEDs are physically smaller and appear subjec­tively brighter at lower currents than do the larger 5mm types used for the send LEDs. There is also little apparent difference in brightness in the larger LEDs operating at 10mA or 17mA. The relative values of resistors R8-R12 and R1 ensures that LED intensity is largely independent of the number of short circuits in a cable. For example, if the values of R8R12 are very large compared to R1, then the total current will change significantly for each additional short circuit, hence the send LED would vary in brightness compared to the receive LEDs. The reverse is true when R1 is large compared to R8, etc. The send LED would then have a constant brightness while the receive LEDs would dim in 62  Silicon Chip bright­ness with each additional short circuit. The values chosen repre­sent a good compromise. Plugs and sockets Let’s now have a look at the full circuit of Fig.2. There are six panel-mounted sockets in the tester. Each XLR socket is paralleled with its associated stereo 6.35mm jack socket: sleeve to pin 1, ring to pin 3 and tip to pin 2. The tip and sleeve of the mono receive socket is also paralleled. The ‘send’ mono socket (SK3) is a little different though, as will be explained in a moment. The circuit can be conveniently split into two parts. The part we’ll describe first does the actual testing of each wire in the cable. Whenever the output of paralleled inverters IC2e & IC2f goes low, it sends a ‘test’ signal via diode D8 to SK3 to see if a mono plug has been inserted. If this socket is empty and there­fore the integral switch contact is closed, Q2 is biased on via diode D8 and resistor R7. Q2 turns on LED8 and current can now flow to either the ring of the stereo jack socket or pin 3 of the XLR socket. Diode D7 isolates this ‘test’ signal from pin 2 on the XLR socket and the tip of the stereo socket. Plugging into the mono socket (SK3) opens the integral switch contacts and stops the bias to Q2 which turns off LED8 and the abovementioned pins. As a result, only two send LEDs (LED6 & LED7) are available when a mono plug is inserted. This avoids confusion when checking unbalanced leads, such as guitar, which only use two conductors. Also, the user can plug RCA, BNC or other unbalanced adaptors at this point. A stereo/mono panel switch is also avoided! The digital bit So much for the testing side of things. The rest of the circuit controls the low signals which are passed via the three ‘send’ LEDs. The heart of this section of the circuit is the 4017 counter IC1. It receives clock pulses from IC3c and it counts so that pins 3, 2 & 4 go high, in sequence. Each of these three outputs is inverted and buffered by IC2 to become the low signals fed via the three send LEDs. The inverters are paralleled to increase output current. You need to create a wiring harness in the box, as shown in this photograph. Start by in­stalling the two XLR sockets and then run the wires as shown. Install the jack sockets, wire them up and then remove them to dangle like this so that the PC board can be fitted. NAND gates IC3a & IC3b are connected together to work as an RS flipflop which is controlled by switches S1 & S2. If S1 is pressed, pin 11 of IC3 will be low and diode D1 will not conduct. Under these conditions, IC3c will oscillate at a frequency deter­mined by resistors R2 & R3 and capacitor C1, at pins 5 & 6. All three ‘send’ LEDs will be strobed and appear to be on continually. This is the ‘scan’ mode which tests the cable au­tomatically. If S2 is pressed, pin 13 of IC3b will be pulled low via diode D3. This will cause pin 11 to go high and D1 will June 1998  63 Fig.3: make sure you follow the steps in the text when assembling the cable tester. The PC board must be temporarily installed in the box when the LEDs are soldered in place. conduct, disabling oscillator IC3c. Pressing S2 also causes diode D6 to conduct and pull pins 5 & 6 low. IC3c now functions as a switch debouncer for S2. Each press of S2 results in a clean, debounced pulse which clocks IC1. This is the ‘step’ mode. Therefore, the user uses switch S2 to ‘step’ through each conductor in a cable. Whenever switches S1 or S2 are pressed, diodes D2 or D5 will conduct to charge the 10µF capacitor C2. This biases on FET Q1 which supplies voltage to the rest of the tester circuit. If no more buttons are pressed, C2 discharges via R6 and so Q1 turns off. This provides the automatic switchoff feature for the circuit. The turn-off delay, after the last button is pressed, is about 20 seconds, long enough to assess the condition of any cable. Diodes D3 and D4 prevent current flowing via the internal diodes of the NAND gates to ground (0V). Without these diodes, Q1 will not turn off as it should. Assembly procedure The Roadies’ Friend is housed in a UB3 plastic zippy box from Dick Smith Electronics. Made of ABS plastic and with heavy internal ribs, this is a very sturdy enclosure. Similar looking enclosures from other sources were not so good. As a guide, if the box can be twisted or easily flexed then it won’t do. So why is nothing mounted on the lid? Plugs get stuck for all sorts of reasons; eg, different tolerances, not pushing the release mechanism properly and so on. Repeated ‘struggles’ to remove recalcitrant plugs (good word that, recalcitrant) would quickly weak­en the threads of the self-tapping screws and buckle or crack the plastic lid. Therefore everything is mounted in the base of the box for greater strength. Also, the XLR sockets are mounted inside the box to provide further mechanical support when pulling stuck plugs. 12mm PC standoffs ensure that the switches are flush with the face of the tester. They can’t accidentally be turned on. Assembly steps The componentry for this project is really squeezed into the UB3 plastic utility box so it is necessary to do the assembly in a particular sequence. Follow the steps below: (1) Solder all the components, except the LEDs, to the PC board. The component overlay and wiring diagram is shown in Fig.3. Make sure you do not confuse the zener diodes with the ordinary diodes and watch the polarity of all diodes and electro­lytic capacitors. (2) The Mosfet (Q1) needs to be Resistor Colour Codes ❏ No. ❏  1 ❏  2 ❏  3 ❏  1 ❏  5 64  Silicon Chip Value 2.7MΩ 390kΩ 15kΩ 220Ω 180Ω 4-Band Code (1%) red violet green brown orange white yellow brown brown green orange brown red red brown brown brown grey brown brown 5-Band Code (1%) red violet black yellow brown orange white black orange brown brown green black red brown red red black black brown brown grey black black brown ABOVE: your PC board should look like this when it is complete. You will need to temporarily install it in the box when soldering the LEDs in place. LEFT: this is what the assembly looks like with the board installed. Make sure that the jack sockets don’t touch the underside of the board when they are installed. handled carefully to avoid damage from static discharges. It should be supplied packed with its leads stuck into a piece of black conductive foam and it is a good idea to leave this in place while the device is soldered into the PC board. Note that the gate (middle pin) of Q1 must be cranked out to fit in its respective PC hole. The two PC switches are installed with their flat sides facing the 4017 IC, as shown on the component overlay in Fig.3. (2) Attach the three Nylon standoffs to the PC board and insert the LEDs but don’t solder them to the board at this stage. Note that LED5 is reversed in orientation compared to the other seven. (3) Temporarily attach the PC board with its standoffs to the base of the box. Gently push the LEDs through their respective holes so that they are barely proud of the front panel. This sets the LED leads to the correct length for soldering. (4) Remove the PC board from the box and solder the battery snap con- nector to the board. Connect a battery and press the SCAN switch S1. LEDs 6, 7 & 8 should immediately light and then go out after 20 seconds or so. Pressing the STEP switch repeated­ly should then light LEDs 6, 7 and 8 in sequence. If these checks are not OK, you will have to carefully go over your work to find any mistakes. In our experi­ence, most faults are due to missed solder joints or solder splashes shorting between tracks. (5) Install the two XLR sockets from June 1998  65 Parts List 1 PC board, 97 x 73mm 1 UB3 plastic utility box, 130 x 68 x 42mm (DSE Cat H-2853) 1 front panel label 1 male XLR socket (SK1) 1 female XLR socket (SK4) 2 6.35mm stereo jack sockets (SK2,SK5) 2 6.35mm switched mono jack sockets (SK3,SK6) 2 round momentary contact PCB switches (S1,S2) 1 216 9V battery and snap connector 1 10-way IDC connector 3 12mm tapped 3mm Nylon spacers The battery compartment is made by sliding a suitable piece of Veroboard or copper laminate into the vertical slots, as shown here. Line the compartment with foam rubber to prevent the bat­tery from coming into contact with the underside of the PC board. the inside of the box. Don’t install the other sockets at this stage. (6) Make a wiring harness to connect the six connectors via a short length of ribbon cable to an IDC transition plug. Ensure that the wiring loops down to the bottom of the box between the connectors and that it loops outside the XLR connectors and not through them. (7) Temporarily install the four jack sockets and solder the appropriate wires to them. Then remove the sockets from the box, leaving them hanging from the harness. (8) Solder the IDC plug to the PC board. (9) Install the PC board into the box with 3mm screws. Check that 66  Silicon Chip the LEDs are correctly aligned and make sure that the wiring harness is not fouling the PC board and is laying neatly along the sides of the box. (10) Reinstall the jack sockets and check the clearance between each socket and the PC board. (11) Make the battery compartment with a suitable piece of Vero­board, matrix board or PC laminate fitted into the appropriate slots in the case. Then place a piece of thin foam rubber to insulate the PC board and prevent the battery from moving. One of the photos shows this clearly. When everything is complete, connect the battery again and push the SCAN switch. LEDs 6, 7 & 8 should light up as before. Now you should Semiconductors 1 4017 decade counter (IC1) 1 4069 hex inverter (IC2) 1 4093 quad NAND Schmitt trigger (IC3) 1 NDF0610 P-channel Mosfet (Q1) 1 BC558 PNP transistor (Q2) 8 1N914, 1N4148 diodes (D1-D8) 3 BZX79-5V1 5.1V 400mW zener diodes (ZD1,2,3) 3 3mm green LEDs (LED1,4,5) 1 3mm red LED (LED2) 1 3mm yellow LED (LED3) 1 5mm green LED (LED6) 1 5mm red LED (LED7) 1 5mm yellow LED (LED8) Capacitors 1 33µF 25VW PC electrolytic 1 10µF 25VW PC electrolytic 1 0.1µF MKT or greencap metallised polyester Resistors (0.25W, 1% or 5%) 1 2.7MΩ 1 220Ω 2 390kΩ 5 180Ω 3 15kΩ Miscellaneous 3mm mounting screws, nuts and washers, ribbon cable, foam rubber, Veroboard, solder. connect a variety of cables and simulate shorts, transpositions and open circuits to check that all cable faults are detected. Screw the lid onto the case and your SC Roadies’ Friend is complete. VINTAGE RADIO By JOHN HILL Look Ma, no tuning gang! Generally, vintage radios have tuning gangs but that doesn’t apply to all sets. Coming across a set without a tuning gang often throws the restorer into a bit of a tizz. That such sets work quite well is acknowledged but understanding how the circuits work is something else. In the early days of radio, variable inductance tuning was common until good single gang variable capacitors became avail­able. Subsequently, the introduction of multi-ganged variable capacitors almost spelt the death knell of variable inductance tuning. It never died completely, however, being used extensively in transmitters and a few special purpose receivers. It was also often used to tune aerials to resonance. Gradually, iron dust and ferrite cores for radio frequency (RF) coils, aerial coils, oscillator coils and intermediate frequency (IF) transformers became more common for fine adjust­ment of tuned circuits for best performance. It was found that a considerable variation in the inductance of a coil could be achieved by sliding an iron dust or ferrite core in and out of a coil. In fact, a tuned cir- The Astor GPM receiver was housed in a pink plastic cabinet and featured a large tuning dial. This unit had been knocked around somewhat during its history and someone had carried out some rough and ready service work on it. 68  Silicon Chip cuit consisting of a variable inductor with a fixed capacitor across it could be easily made to tune the broadcast band – and other bands as well. The Astor GPM and BNQ In the early 1950s, Radio Corporation started to bring out inductance tuned radios under the brandnames of Astor, Airchief and several other labels. The inductance tuning system really suited car radios as dust tended to block the ganged tuning capacitors previously used. On the domestic front, the Astor GPM and BNQ mains-powered models were produced in 1955 and 1956 respectively. The circuit shown is for the GPM (Fig.1) and I have a BNQ – but no circuit for it. However, the circuits are almost identical, the differences being that the BNQ used a 6X4 rectifier in lieu of the 6V4 and the cathode resistor on the 6BH5 is 47Ω. The BNQ model also has a tone control. One of the unusual features of these sets is the variable inductance tuning. Radio Corporation was one of very few manufac­turers that used inductance tuning in 240V domestic receivers. A number of manufacturers used it in their car radio ranges, howev­er. The circuitry around the 6BE6 in the schematic diagram can be seen to be unusual compared to what is considered to be the norm. Instead of two windings on each coil or a tapping, both coils consist of a single winding. Fig.2 shows the aerial input circuit redrawn to make it a little easier to understand. Amateur radio operators will be quite familiar with this circuit as it is called a pi-coupler. It is commonly used to match the impedance of the transmitter output valve to the aerial circuit and to tune the stage. Fig.1: the circuit for the Astor GPM radio receiver. An unusual feature is the use of variable inductance tuning. In the average set, the aerial connects to a coupling coil of about 400Ω impedance and wound on the same former as the tuned winding. This impedance is the RF “resistance” of the “average” aerial within the broadcast band. The coil is induc­tively coupled to the tuned winding. The signal voltage in the tuned winding is increased due to transformer action and the Q of the tuned circuit. In the pi-coupler tuned circuit, the low impedance input from the aerial is matched by the 650pF capacitor (C63), while the high-impedance input to the grid of the 6BE6 is matched by the combination of C64, C13 and C14. This tuned circuit also increases the signal voltage applied to the grid of the 6BE6 by the action of the circuit’s Q and by the ratio of the values of the capacitors at each end of the coil. So it does exactly the same job as a circuit with a fixed inductance (or fixed inductances) and a variable capacitor. The advantage is that only one winding is used. In addition, the circuit in Fig.2 also acts as a low-pass filter. This means that it lets all frequencies below the design frequency through but pro- gressively blocks higher frequencies. This is a handy feature for broadcast receivers, as it helps to reduce the image response without the need for an RF stage. For example, if the set is tuned to 693kHz, the image for this set (which has a 455kHz IF) is 1603kHz. In this set, I meas­ured the image response as being 35dB down on the wanted signal. This means that a 2mV 1603kHz signal would be required at the aerial to have the same effect in the set as a 30µV signal at 693kHz. Oscillator circuit The oscillator circuit is also con­ figured as a pi-coupler but is really being used as a Colpitts oscillator. The 6BE6 is normally used as a Hartley Fig.2: this diagram shows the aerial input circuit of the GPM receiver, redrawn to make it easier to under-stand. oscillator, whereby the tuning coil is tapped and the cathode goes to that tap. However, in this case there is no physical tap, as can be seen on the circuit diagram. Instead, it is capacitively tapped by capacitors C10, C62 and C65, with the tapping point towards the end going to pin 6 of the 6BE6. The oscillator feedback ratio is controlled by the ratio of the values of C10:(C62 + C65) and remains constant across the broadcast band. As a result, this type of oscillator is more reliable than some others used in vintage radios. As an aside, some sets which use 6A7 converter valves and the like are rather unreliable and may drop out of oscillation on the lower frequencies. This is often due to the actual circuit used for the oscillator, where the actual amount of feedback varies significantly across the band. I’ll talk about this in a later article and describe how it can be largely overcome. The circuit shown in Fig.1 uses no padder. So how did the manufacturer obtain good tracking across the broadcast band, with the resonant frequencies of the aerial and oscillator coils remaining 455kHz apart at all times? Elementary my dear Watson! June 1998  69 The oscillator coil is wound as a solenoid, with each turn right alongside the other. The aerial coil, on the other hand, has its turns wound side-by-side to begin with and then they are variably spaced over the rest of the winding. This can be seen on the photograph of the rear of the unit, which clearly shows the tuning mechanism (the aerial coil is the smaller diameter coil). This is a simple way to do it but no doubt it initially took some experimentation to get the tracking right. A specially made cam would then have been fitted to the winding equipment so that it could easily wind this coil. There were no computers then to make the job easier. Philips on occasions made inductance tuning mechanisms too and two views of a typical Philips unit can be seen in the photo­graphs. It is much smaller than the Astor unit and is shielded, being built into one of their small IF can-sized assemblies. The Philips unit is also gear-driven compared to the metal belt drive on the Astor. A quite compact set could be made with a Philips variable inductance tuner. Restoring the BNQ receiver SILICON CHIP This advertisment is out of date and has been removed to prevent confusion. 70  Silicon Chip I got my BNQ at an auction for a nominal price of $3. The cabinet, like many plastic-cased sets, had faded from its origi­nal pink where it had been exposed to sunlight, so that it now looks a bit mottled. It was a bit knocked around and someone had carried some rough and ready service work on it at some stage during its history. Care is needed when removing this set from its case. The front of the case consists of three plastic sections which are held together by plastic spigots. These go through holes in the mating section and are then melted into one another to hold the sections together. However, this is a very weak system and the front plastic escutcheon plate will break away from the main front section of the case with very little pressure. To make matters worse, the dial lamps are attached to the escutcheon plate with short wires and it is very easy to withdraw the chassis and rip the escutcheon out at the same time. I ex­tended the leads going to the dial lamps to overcome this prob­lem. Another problem occurs if the chas- sis-mounting clamps are not tightened correctly when the set is reinstalled in the cabinet. Unfortunately, it isn’t easy to tighten these clamps as it’s not possible to bear straight down on the screws which are slightly in from the back edge of the cabinet front. If the clamps are loose and you push the knobs on, the chassis slides back and again causes the escutcheon to break away from the front section of the cabinet. It’s great fun having to repair the cabinet for the second time. In this case, it was broken before I even worked on the set, so others had had problems too. Mr Radio Corporation certainly didn’t get this part of the receiver’s design right! Circuit problems Now onto the electronic restoration. There were quite a few minor problems with the set which stopped it from working. First, I discovered that a chassis-mounted electrolytic capacitor had lost its capacitance and someone had simply connected another capacitor across it. This is not really a good move as the faulty unit may have gone short circuit later on. In this case, both capacitors had lost almost all their capacitance, as indicated on a capacitance meter. Further investigations revealed that several resistors had either gone high or open circuit and so these were replaced. I usually check the resistors in circuit with a multimeter and make allowance for any parallel resistances in my assessment. If there is any doubt, one end of the resistor is unsoldered so that it can be checked by itself, with any effect from other parallel components. Paper capacitors in old receivers are quite often leaky, sometimes with a leakage resistance as low as a megohm. I use a high voltage tester across the paper capacitors to see how much leakage there is. Murphy has a great time with paper capacitors! The leakiest ones always seem to be in positions where no dis­cernible leakage can be tolerated, such as the audio coupler between the plate of the first audio stage and the grid of the audio output, or the AGC/AVC bypass. These nominated capacitors were replaced because they were quite leaky, along with several others. The cathode bypass on the 6BH5 was left These two photos show the top and bottom views of a typical Philips inductance tuning mechanism. This unit is much smaller than the unit fitted to the Astor receiver. in position, as it would have to be very leaky to cause a problem. As a general rule, it’s a good idea to replace all paper capacitors with polyester or similar types where leak­ages under about 100MΩ can cause a noticeable alteration in the operating conditions of the valves in the set. Paper capaci­tors become more leaky as the temperature of the set rises. I “rescued” a bagful of paper capacitors from defunct TVs many years ago and decided to test them at about 50°C in the kitchen oven. Before going into the oven, they tested OK on a multimeter but after heating, the multimeter showed almost all of them to be leaky. As a result, they were all consigned to the rubbish bin. 50°C is not an unreasonable temperature, as sets that are running can easily develop a temperature this high or higher inside them. On the other hand, polyester and polystyrene capacitors came out of this test smelling of roses. Radio Corporation had a habit of using a combination of single conductor rubber-insulated hookup wire as well as plastic-covered wire in their sets. I don’t know why they did that as the rubber-covered wiring often has to be replaced – the rubber goes hard and cracks off or goes gooey and behaves a bit like a resis­tor rather than an insulator. Perhaps plastic-covered wire was more expensive than rubber-covered wire in the early 1950s. Anyway quite a bit of the wiring in critical areas had to be replaced. If there are any doubts about the safety of per­ished rubber wiring, it should always be replaced. Switching on Before applying power to the set, the insulation of the power transformer to the set chassis was checked with the high voltage tester. I also checked to make sure no shorts existed from high tension to chassis and tested the speaker transformer to make sure its primary winding was OK. In this case, the speak­er transformer was OK although this component had obviously been replaced at some stage in the past, probably because the primary had gone open circuit. Once these checks had been completed, the set was plugged in, power applied and the high tension (HT) voltage checked using a multimeter. This looked OK and so voltages elsewhere in the set were measured to see if they were as expected. Most were but one wasn’t, so a bit more sleuthing was needed. At this stage, the set was actually working but seemed very low on output and was not very sensitive. I checked the voltages around the set and found that the 6BH5 wasn’t drawing any cur­rent. The reason for this was that there was no screen voltage, due in turn to the fact that one end of the resistor from the HT to the screen had become detached. I resoldered it and that fixed the problem. Alignment The next job was alignment. The IF slugs seemed to be jammed so I couldn’t do anything with the IF. However, checking the IF by tuning the signal generator between 400kHz and 500kHz confirmed that there was only one response peak and that was at 455kHz. As the sensitivity of the set was good, it was assumed the IF was correctly aligned. I had no option anyway! Because it has an inductance-tuned front end, you may wonder how the alignment technique compares to a normal variable-capacity version. Well, the circuit is certainly different but in fact the alignment procedure is just the same as with the more familiar variable-capacitor tuned receiver front ends. The first thing was to check that the oscillator tuning range was correct. It tuned from 530-1700kHz and the station calibrations were quite close to what they should have been so all was OK here. If the range had not been correct, it may have been necessary to adjust the oscillator iron-dust slug (the one in the larger diameter coil; see photograph) so that the set tuned down to 530kHz. Conversely, at the top end of the dial, the oscillator trimmer may have required adjustment so that the signal generator could be heard on 1700kHz. A check at both ends of the dial will show whether the stations appear where they should on the dial. If they don’t line up, the procedure is to first tune to a station at the bottom end of the band; eg, where 3AR is June 1998  71 This inside view of the Astor GPM mantel radio receiver clearly shows the variable inductance tuning mechanism. The aerial coil is the smaller coil (towards the rear of the unit) with the variably spaced winding. marked (this was on 620kHz but is now on 621kHz and renamed 3RN). You then feed in a 620kHz signal from the signal generator and adjust the oscillator slug so that the signal generator is heard. This done, you go to the other end of the dial and tune to the 3AK mark which corresponds to 1500kHz. The signal generator is then set to 1500kHz and the oscillator trimmer adjusted for maximum signal through the set. Having got the oscillator tuning correct, all that remains is to tune to a station at about 600-700kHz and adjust the aerial coil iron-dust slug for best performance. You can either monitor the output by ear on a weak station using a typical aerial or using instruments on a medium to strong station. This done, you then adjust the aerial trimmer for best performance on a frequen­cy between 1400kHz and 1500kHz. Note that it may be necessary to repeat these adjustments as they do interact. Finally, seal the adjustments 72  Silicon Chip with some nail polish or beeswax. I have found that the inductance tuners hold their initial adjustment quite well and only rarely require more than a minor tweak to get the best out of them, as in this case. Performance So what is the set like to work on and what about its build quality and overall performance? The set is a good performer, although there is a tendency for some RF instability at the low-frequency end of the dial. I get the impression that the set was intended for the lower end of the market – the case certainly attests to that. The works are built on a flat sheet of metal with brackets to mount the controls and the speaker, so it could almost be said to have no chassis. The chassis plate is situated half way up the inside of the case, so there is a lot of vacant space under the chassis, although this may not be obvious from the photograph of the back of the set. The photograph of the front of the set shows that it has a large semicircular dial scale, marked with virtually all the stations that were available at the time. On the other hand, a rather small knob is used for tuning which makes the job a little fiddly. Summary The cabinet is poorly designed as previously mentioned and in my set, it has also warped. As a result, the plastic lugs at the top of the cabinet don’t grip and the two sections can easily come apart. The use of rubber-insulated wire when they were also using good plastic-insulated wire in the same set is a back­ward step and the small direct-action tuning knob doesn’t say much for the designer. On the plus side, the performance of the set is quite good and in general the access is quite reasonable. I’m hard to please in this area but so many sets are spoilt just for a little more thought in operational ease (ergonomics), layout and accessibili­ty. I believe that Radio Corporation built many superb sets but seemed to lose the plot in some areas from time to time. However, I am happy to have SC this radio in my collection.   Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication       
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  Universal Stepper Motor Controller This circuit can be used to drive a stepper motor for a preset number of revolutions in the forward or reverse direction at a speed which can be varied. Jumpers on the board allow it to drive steppers with 1.8 or 7.5 degree increments. By RICK WALTERS This circuit is a “grown-up” version of the manual stepper motor driver that we featured in the June 1997 issue of SILICON CHIP. It was very popular but a number of readers asked us how it could be modified to drive larger stepper motors. And they want­ ed 74  Silicon Chip several other features as well. As it turned out, modifying the original circuit was not that straightforward and we decided that rather than “bodgie up” the previous design, we should produce a new version with all the bells and whistles that our readers have been asking for. This new stepper motor driver has a RUN/STOP switch, a FORWARD/ REVERSE switch and a speed control. These functions are similar to those on the previous board but with the addition of four more ICs, a couple of transistors, a few small components and two thumbwheel switches it becomes a motor driver which can be programmed to step a motor for 1-99 revolutions. Jumpers on the board allow you to use steppers with 1.8 degree or 7.5 degree increments. One immediate use which springs to mind for this option is as a coil winder. We looked at adding a third thumbwheel and the associated com- ponents but it would add a fair bit more to the cost and rarely would you ever need to wind 999 turns. How it works? Fig.1 shows the new circuit. The core of the circuit, in­volving IC1a, IC2 & IC3, is similar to that in the June 1997 issue. However, to make the circuit programmable via decade switch­es, we have added four 4510 pre­settable up-down counters. Since many readers may not have seen the previous circuit, we will give a complete circuit description. As before, the circuit can be divided into three sections: one controlling the duration of operation, one controlling the speed and direction of stepping and the third controlling the stepper motor drivers. Let’s look first at the speed section, involving IC1a, a NAND Schmitt trigger configured as a clock pulse generator. With switch S1 in the STOP position, the output of IC1a is held high and there are no clock pulses into IC2, a 4017 decade counter. When S1 is moved to RUN, IC1a is enabled and it will begin to oscillate. Its output will be a square wave, the fre­quency of which is dependent on the value of the capacitor from its input, pin 2, to ground (0V) and the value of the resistance between its output, pin 3, and input, pin 2. By including a 250kΩ potentiometer in this path we can vary the frequency over a wide range. IC1a’s square wave output clocks IC2 and causes each of its outputs (pins 3,2,4,7,10,1) to go high (+5V) in sequence. The output pulses from pins 2 & 7 are fed via diodes D5 and D7 (wired as an AND gate) and inverter IC1b to clock flipflop IC3a, while the outputs from pins 4 and 10 are fed via diodes D6 & D8 (anoth­er AND gate) and through IC1c to clock flipflop IC3b. When IC2’s pin 1 goes high, it resets IC2 via diode D1, after a slight delay introduced by the 10kΩ resistor and .001µF capacitor. Thus one complete cycle of IC2 is actually four motor steps. Parts List 1 PC board, code 10106981, 112mm x 98mm 1 plastic instrument case, Jaycar HB-5910 or equivalent 1 power transformer, Jaycar MM-2002 or equivalent 1 amp (T1) or 1 power transformer, Jaycar MM-2004 or equivalent 2 amp (T1) 2 SPDT toggle switches (S1,S3) 1 SPDT toggle switch (S7, optional) 1 DPDT toggle switch (S2) 2 BCD thumbwheel switches, Altronics S-3300 or equivalent (S4,S5) 1 pair of end plates for above, Altronics S-3305 or equivalent 1 250VAC mains switch (with indicator), Jaycar SK-0985 or equiv­alent (S6) 1 IEC mains input socket (with fuseholder), Jaycar PP-4004 or equivalent 1 0.25A slow-blow 5mm x 20mm fuse 1 IEC mains lead, Jaycar PS4106 or equivalent 1 6-pin connector, Jaycar PP2024 or equivalent Semiconductors 1 4093 quad NAND Schmitt trigger (IC1) 1 4017 decade counter (IC2) 1 4027 dual JK flipflop (IC3) 4 4510 presettable up-down counters (IC4-IC7) 1 78L05 voltage regulator (REG1) 6 BC548 NPN transistors (Q1,Q6,Q7,Q12-Q14) 4 BD680 or BD682 PNP Darlington power transistors (Q2,Q4,Q8,Q10) 4 BD679 or BD681 NPN Darlington power transistors (Q3,Q5,Q9,Q11) 8 1N914 small signal diodes (D1-D8) 1 1N4004 1A power diode (D9) 1 1N4004 1A power diode (D10) or 1 1N5404 3A power diode (D10) 1 BR610 100V 6A bridge rectifier (BR1) Capacitors 1 4700µF 25VW PC electrolytic 1 470µF 25VW PC electrolytic 1 100µF 16VW PC electrolytic 1 10µF 25VW PC electrolytic 1 0.22µF MKT polyester 3 0.1µF monolithic ceramic (MC) 2 0.1µF MKT polyester 1 .01µF MKT polyester 2 .001µF MKT polyester Resistors (0.25W, 1%) 3 100kΩ 15 10kΩ 7 47kΩ 8 4.7kΩ Miscellaneous 1 knob for speed control 1 1.6mm baseplate, 220mm x 150mm 4 6PK x 6mm self-tapping screws 13 PC stakes 1 4mm x 15mm screw 2 4mm x 6mm screws 5 4mm nuts 4 4mm flat washers 4 4mm toothed washers 3 earth lugs 4 3mm x 10mm threaded spacers 11 3mm x 6mm screws 1 3mm x 12mm screw 3 3mm flat washers 3 3mm star washers 4 3mm nuts 100mm rainbow cable red & black hookup wire tinned copper wire Note. While the Jaycar MM2004 power transformer is shown in their catalog as having identical output voltages to the MM2002, the one we were supplied with only had 6V, 9V, 12V and 15V taps. These voltage taps are probably satisfac­ tory for this project. Bridge drivers Before we describe the logic operations any further, let’s have a look at the stepper drivers. The type of stepper motor specified has two windings, designated here as MA and MB. Each winding is connected across a bridge of four transistors (ie, like a bridge rectifier in re­verse) comprising Q2, Q3, Q4 & Q5 and Q8, Q9, Q10 & Q11. We will first describe how winding MA is driven; the drive to MB is identical. Assume pin 1 of IC3a is high and therefore its complement, pin 2, will June 1998  75 76  Silicon Chip Fig.1 (facing page): the heart of the circuit is formed by oscillator IC1a, decade counter IC2 and dual JK flipflop IC3 and these control the direction and speed of the stepper motor. Counters IC4, IC5, IC6 and IC7 control the number of steps. be low. Pin 1 will turn Q1 & Q5 on, and Q2 will be turned on, as well. Q6, Q3 & Q4 will be turned off. Therefore current will flow through motor winding MA via Q2 & Q5. When IC3a is toggled, pin 1 will go low and pin 2 will go high. This will turn off those transistors which were on and turn Q3, Q4 and Q6 on. Current will now flow through MA in the other direction, via Q4 & Q3. A similar sequence occurs with flipflop IC3b and the motor winding MB. This sequence of voltage and current reversals causes the motor to step. The reversing switch, S2, is wired to the MB wind­ing and reverses the direction of the current relative to MA, causing the motor to change its direction of rotation. The resistor and capacitor from pins 4 & 12 of IC3 reset these flipflops at power-up, ensuring the motor will always rotate in a known direction. To recap so far, the motor is started by S1, the speed is varied by VR1 and the direction (selected while the motor is stopped) is set by S2. Revolution counter To count the number of revolutions of the motor we first need to know whether we are driving a 1.8 or 7.5 degrees per step unit. A 7.5 degree motor takes 48 steps per revolution while a 1.8 degree unit has to make 200 steps. The steps are counted by IC4 and IC5 which are arranged as presettable dividers. Each time IC2 completes one cycle and resets itself via its pin 1 output (as previously described) this pulse also clocks the dividers. But we are getting slightly ahead of ourselves. When S1 is moved to RUN, the low to high voltage transition on its common pin is coupled through the .01µF capacitor to the preset enable inputs (pin 1) of IC6 & IC7 and via diode D4 to IC4 & IC5. This loads the BCD value which is present at the “P” inputs into each counter. IC4 has P1 (bit 1) tied high and a jumper to pull P3 (bit 4) high. This Fig.2: this is the component layout for the PC board. It also shows the wiring for the optional switch (S7) to take the place of jumpers J1 & J2. This will allow easy switching between 1.8 and 7.5 degree steppers. will give a division of 10 or 50. Similarly, IC5 is able to divide by 0 or 2. By using the appropriate link we can divide by 12 (10+2) or 50 (50+0). This, together with the four steps provided by IC2, makes up one complete revolution for each type of motor. So each time counters IC4 and IC5 count down to zero, pin 7 of IC4, which is normally high, will go low, momentarily turning Q13 off. This transistor is normally held on by the 47kΩ resistor at its base. The positive-going pulse at its collector reloads the preset count into IC4 and IC5 through diode D3 and also applies a clock (count down) pulse to IC6 and IC7. Thumbwheel setting Thus, IC4 and IC5 continuously count down and after each full revo- lution of the motor they are preset by transistor Q13 which also clocks IC6 and IC7. These are also presettable down counters. When S1 is moved to RUN, they are loaded with the value set on the thumbwheel switches as described earlier. After the preset number of revolutions has occurred, pin 7 of IC6 will go low, turning transistor Q14 off. This allows its collector to go high, holding IC2 reset through D2. With no drive pulses from IC2 the motor will stop. To make the controller as flexible as possible we have added a MODE switch, S3, which we have called the PRESET/CONTinu­ous switch. In the CONT position, the motor will run continuously while S1 is set to RUN. Conversely, in the PRESET position, the motor will turn for the number of revolutions set on the thumbwheels June 1998  77 Fig.3: use this diagram to complete the wiring from the PC board to the front and rear panels and to the mains transformer. and then stop. Switching to STOP then RUN will rotate the motor again for the same number of preset revolutions. Thus, by setting the thumbwheels to 75 and running the motor for three cycles, it would rotate it for 225 rev78  Silicon Chip olutions. Assembling the PC board The circuitry for the new Stepper Motor Controller is accommodated on a PC board which measures 113 x 99mm and is coded 10106981. The component layout for the board is shown in Fig.2. The first step in assembly is to inspect the board for etching faults or open circuit tracks. The tracks between IC pads should be checked with a multimeter to ensure they are not shorting to the pads. Begin by inserting and soldering the 15 links. Then contin­ue by fitting the This view inside the case shows the wiring to the PC board and to the mains transformer and front-panel. Note the rainbow cable that’s used to wire the decade switches. resistors, capacitors, diodes, transistors and ICs. Add the components a few at a time, soldering and cutting the leads as you go. Double check the direction of diodes and capacitors before you solder them in. We have specified a choice of two types for diode D10 in the parts list. If you are using a low current motor you can use a 1N4004 diode type but if the motor coils are going to draw around 1A or more then the type 1N5404 should be fitted. The power transformer we have specified will readily supply the higher current. Once the PC board assembly is complete, it’s time to drill the front and rear panels as well as the baseplate. The easiest way to cut the required rectangular holes in the plastic panels is to mark the cutout on the rear with a scriber, then using a hammer and a sharp chisel, outline them from the back. When the panel is turned over you can see the hole outline and it can be readily chiselled from the front. After mounting all the hardware you can begin the wiring, as shown in the diagram of Fig.3. You will see that there are four wires shown dotted on the PC board. These are run under the PC board to keep the heavy motor currents away from the digital circuitry. We used a short length of rainbow cable to wire the thumb­ wheels as there are nine wires and it is easy to get them mixed up if they are all the same colour. The wires from the tens switch (S4) go to IC6, while those from the units switch (S5) go to IC7. The diagram of Fig.3 shows the wiring details. Make sure you sleeve and heatshrink all the connections to the mains switch (S6), power transformer and the mains input socket. A large sleeve should also be fitted right over the IEC socket for added safety. Note that the leads to the mains switch should also be sleeved in heatshrink tubing for some distance as shown in the above photo, so that the mains wiring cannot possibly come adrift. Alternatively, you can use cable ties to securely bind the mains wiring. We also recommend that the case of the pot be earthed to the baseplate – see Fig.3. We have made the mains connections to the transformer fairly inaccessible, as they are quite difficult to sleeve adequately. We have used a power transformer with a multi-tapped sec­ ondary to cater for the wide range of stepper motors which are available. The 6.3V or 7.5V tap should be suitable for most 5V single winding motors and the 8.5V or 9.5V tap will drive 5V centre-tapped motors (where the tap is not being used), or 12V motors without tapped windings. The higher voltage taps will allow you to add a resistor in series with each winding to obtain higher torque June 1998  79 The rear panel carries the IEC mains input socket (with fuseholder) plus a 6-pin output connector for the stepper motors. without exces­ sive current flowing, or even run the somewhat rare 24V steppers. Testing It is wise to check the 240VAC mains wiring with a multi­meter before applying power. You should read zero ohms from the earth pin on the IEC socket to the metal base plate. When the mains switch is off there should be an extremely high resistance between the Active and Neutral pins but when the switch is turned on, the reading should drop to around 60-70Ω which represents the resistance of the trans- You can use this Universal Stepper Motor Controller to drive a range of stepper motors for a preset number of revolu­tions in the forward or reverse direction at a speed which can be varied 80  Silicon Chip former primary winding. A reading of around 1-2Ω is bad news. Fix the problem! If the reading stays very high you have either mixed up the switch wires or forgotten to fit the fuse. You will have to determine the voltage necessary for the motor you plan to use and connect the bridge rectifier to the appropriate tap on the power transformer. Leave the motor un­ plugged at this stage. Plug the mains lead into the IEC socket, turn on the front panel POWER switch and then plug the 3-pin mains plug into a power point. Turn the mains on, checking that the power indicator in the front panel switch lights. If not, turn the mains off immediate­ly, remove the 3-pin plug from the power point and recheck all your mains wiring. Once the indicator is working you should measure the vol­ tage at the 4700µF capacitor. It should be roughly 1.5 times the AC tap voltage you selected. Next, measure the voltage between pins 7 and 14 of IC1. This should be 5V ±5%. This voltage should also be present at pin 16 of each of the other ICs, while keeping the meter’s negative lead on pin 7 of IC1. The phasing for 1.8 degree steppers appears to be black to pin 1 on the rear connector, red to pin 2, white to Fig.4: above is the full-size etching pattern for the PC board, while at right is the full-size front panel artwork. pin 5 and green to pin 6. This will rotate the motor to agree with the front panel switch. If your stepper has different colours, use your multimeter (switched to Ohms) to find the wire pairs and connect one pair to pins 1 & 2. Poke the other wires into pins 5 & 6 and swap them if the motor runs in the wrong direction. Once they are correct you can fit the pins and push them into the plug. Mineba stepper motors (available from Jaycar) are 7.5 de­grees per step and are wired with brown - pin 1, red - pin 2, yellow pin 5 and orange - pin 6. If you want to run different steppers at different times, you will need a wired plug for each one. Alternatively, you could wire the stepper up to a 4-way insulated terminal block (as shown in one the photos) and then wire that up to the 6-way plug. If you want to frequently change between 1.8 or 7.5 degree steppers, it may be desirable to wire up a switch to take the place of jumpers J1 & J2. We have shown the wiring for this optional switch (S7) in the PC board layout diagram of Fig.2. Fault finding If you are careful with your assembly and check thoroughly as you proceed, everything should work, but if bad luck inter­ venes, you will have do some fault-finding with your multimeter. If you turn the speed control to minimum and trace the clock pulses through the circuit an analog or digital multimeter set to read 5V will jump around if the clock pulses are present, but give a steady reading if no clock is present. Pin 3 of IC3 should continuously alternate between ground (0V) and +5V. IC2 pins 2, 4, 7 & 10 should sit at ground and swing to +5V sequentially. Pins 1, 2, 3, 13, 14 & 15 of IC3 should alternate SC between ground and +5V. June 1998  81 Part 5: the throttles & control panel In this concluding article in the series on the Proto­power 16 Command Control system we describe the wiring of the handheld throttles and the control panel. The handheld throttles may be wired with or without inertia and may have provision for “double-heading”. Design by BARRY GRIEGER The circuit of the basic handheld throttle is very simple and is shown in Fig.1 on the facing page. It uses a single-pole double-throw (SPDT) switch (S1), a 10kΩ linear potentiometer and requires just four wire connections back to the control panel. Three of those connections come, via the control panel, from the terminal strip on the encoder board: Forward (+1.2V), Reverse (+8.8V) and Stop (+5V). The fourth wire is the Output (wiper) connection from the 10kΩ linear potentiometer. The Forward and Reverse wires go to the outside terminals of the SPDT switch. Our prototype handheld throttles used minia­ture slide switches but they could just as easily have been miniature toggle or rocker switches instead. The moving contact of the SPDT switch is connected to one side of the 10kΩ poten­tiometer. The prototype throttles were wired up in the smallest prac­tical plastic boxes using 6-core flexible cable. Don’t use telephone cable here by the way because each of the six wires is solid core and with the amount of flexing that can be expected on throttle cables, you can expect wire breakages. Any cable you use to wire up the handheld throttles must have multi-strand cores, to allow it to flex. You can use 4 or 6-core cable, shielded or unshielded, just as long as it can take a lot of flexing. Ignore this point and Run your model railway with Command 82  Silicon Chip you will be giving yourself a lot of headaches in the future. Make the throttle cables as long as seems necessary but typically, a length of about 1.5 metres or so will probably be adequate; any longer and it will be prone to tangling or tripping you up. Terminate the free end of the cable in a 5-pin DIN plug. You can use whatever method of termination to the DIN plug you like but it must be consistent for all plugs and sockets. We suggest using pins 1 & 3 for the Forward and Reverse connections, pin 2 for the Stop connection and pin 4 for the output connection. The number of throttles you will need depends on the number of people who are expected to operate the layout at any one time. Typically, we expect that most layouts will need three or four handheld throttles but you could have up to 16, one for each channel on the system. In practice though, we think that having any more than about six people operating locomotives on the layout at one time would be unwieldy. Inertia throttle While the simple throttle of Fig.1 will suffice for many users, some readers will want a handheld throttle with built-in inertia, or momentum, as it is sometimes referred to in model railway magazines. In effect, the inertia circuit simulates the enormous mass of a real train and therefore only allows the train to accelerate or decelerate very gradually. Fortunately, inertia can be incorporated very simply with the addition of two capacitors and a resistor, as shown in the circuit of Fig.2. As you can see, the voltage from the potentio­meter’s wiper connection is fed through a 10kΩ resistor to a pair of 470µF electrolytic capacitors con- nected back to back. This gives a resultant capacitance of 235µF and this provides a delay whenever the throttle setting is increased or decreased. The two electrolytic capacitors are connected back to back to provide a bipolar capacitor, which is necessary because the forward/reverse switch can cause the voltage polarity across the composite capacitor to be either positive or negative. By the way, if you find that the amount of inertia provided is not enough, you can increase it by doubling both capacitors, from 470µF to 1000µF. Alternatively, you can get a similar result by increasing the 10kΩ resistor to 22kΩ. In other respects the wiring of the inertia throttle is exactly the same as for the simple throttle of Fig.1. Switchable inertia & braking While inertia adds realism to operation, it can be a draw­back in shunting manoeuvres so it is worth having a switch to switch the inertia in or out. The circuit to do this is shown in Fig.3 and the inertia switch is S2. Note the 470kΩ resistor across S2. This is to keep the inertia capacitor charged to the current throttle setting so that if you inadvertently switch inertia in while running, there is less of a change to the train velocity. And yes, we reckon that some people will want locomotive braking as well and this is just a further refinement on the circuit – see Fig.4. Here, we switch a 2.2kΩ resistor across the back-to-back 470µF capacitors using a pushbutton switch, S3. Each time the pushbutton is pressed, the capacitors are discharged via the 2.2kΩ resistor and the train comes to a stop. The value of 2.2kΩ is chosen as a compromise between real­ism and safety. In reality, trains just cannot Fig.1: this is the basic throttle circuit providing just speed (VR1) and direction (S1). Fig.2: this throttle incorporates inertia with the two back-toback electrolytic capacitors. come to a rapid stop but in model practice, when you apply the brake you may want the train to come to a stop in a short distance to avoid a colli­ sion or over-running points, etc. Naturally, you can increase the severity of braking by reducing the value of the 2.2kΩ resistor. Note that if you apply the brake and leave the throttle setting unchanged, the loco will not come to a full stop. In effect, it would be like applying the brakes on a real locomotive but still keeping the engine going – not very realistic! So for the train to come to a full stop, you need to apply the brake and reduce the throttle setting to zero. In normal operation, if the greatest realism is to be achieved, we expect that the brake will only be used in an emer­gency stop. At other times, the Control June 1998  83 Fig.3: adding switch S2 and a 470kΩ resistor to Fig.2 allows the inertia to be switched out which can be handy when you are doing shunting manoeuvres. train will be accelerated or decelerated to a stop with the inertia circuit switched in. Double-heading throttle Double-heading of locomotives pre­sents a problem for a Command Control system since effectively you need a handheld throttle for each locomotive. That becomes a little tricky, as you might imagine trying to juggle two controls, and is doubly inconvenient (pun intended) if you want one of the loco­motives to run in reverse. How do you do it? Fortunately, it is quite easy and all you need is a “double-heading” throttle which uses Fig.4: switch S3 adds braking. When S3 is pressed it discharges the inertia capacitors but the throttle (VR1) should be wound back to allow the locomotive to come to a full stop. a dual-ganged 10kΩ linear potentio­ meter. This throttle circuit is shown in Fig.5. You will notice that it is essentially a doubled-up version of Fig.1 but the slide switch reverses the voltage to the second section of the pot, VR1b. Essentially, we send a forward and reverse command to the locos simultaneously, from a single throttle. Why reverse the loco? Old hands at railway modelling will probably be puzzled by the need to reverse one locomotive of the pair when double-heading, so it needs some explanation. First, we should comment This throttle has been wired for double heading a pair of loco­motives and uses the circuit of Fig.5. 84  Silicon Chip that if you are double heading you can run both locomotives head-to-tail, in which case both will be running in the same direction and there is no reason to reverse one of the locos. But if you want to run the pair of locomotives “tail to tail” as is often done in “full size” trains, then the second locomotive of the pair must run in reverse and it must receive a throttle signal to tell it to do so. This is where the old hands may be puzzled because they will be aware that if you pick up a model locomotive off the track, swap it end for end and then put it down on the track again, it will continue to run in the same direction as before. That is because, in a conventionally wired layout, the track polarity determines the direction of motion; swap the track polarity and the loco will reverse. However, in a Command Control system the track polarity is con­stant and the track voltage does not vary either. The only way that the locomotive can change direction is for it to get an appropriate throttle forward/ reverse signal. So if you pick up a locomotive in a Command Control system, swap it end for end and then place it down on the track again, it will head off in the opposite direction! So now you should be clear as to why a “double-heading” throttle needs a dual-ganged pot and is wired as shown in Fig.5. Note that the forward/reverse switch is now a double-pole type (ie, DPDT) but most slide switches tend to be this variety anyway. When you are wiring the 5-pin DIN plugs for the This prototype control panel has eight DIN sockets to let eight single or double-heading handheld throttles to be used simultaneously. The row of RCA sockets along the bottom corre­sponds to the 16 channels of the system. Associated with each DIN socket are two RCA sockets wired to pins 4 & 5. The DIN sockets are connected via patch cords to the wanted RCA input channel. double-heading handheld throttle, we suggest an extension of the conven­ tion outlined above: Pin 1, Forward; Pin 3, Reverse; Pin 2, Stop; Pin 4, Forward Output (lead loco) and Pin 5, Reverse Output (trailing loco). Naturally, the refinements of inertia and braking can be added to the circuit of Fig.5 but the wiring does tend to become a little busy. The photos of the wiring in one of the handheld prototype throttles actually shows the “double heading” circuit used in Fig.5. Finally, if you are going to run a permanent double-heading locomotive lash-up, then the easiest way is to set both locomo­tive decoders to the same channel and then you can use a simple throttle as per Fig.1 or its variants. Note that in any double-heading locomotive lash-up, both locos should ideally be the same and have the same motors, gearing and so on, so that their speeds will always be matched for any given throttle setting. Control panel The above photo shows a blue con­ trol panel with two handheld throttles plugged in. The prototype control panel has eight DIN sockets to let eight single or dou­ ble-heading handheld throttles to be used simultaneously. If you want more, the panel will have to be extended or the DIN sockets squash­ed more closely together. Also arrayed on the control panel is a large number of RCA sockets. Along the bottom of the panel is a row of 16 RCA sockets and these correspond to the 16 channels of the Protopower 16 Command Control system. Each one of these RCA sockets is wired to the 16-way cable connecting to the encoder board. Then you will notice that there are two RCA sockets asso­ciated with each Fig.5: a dual-ganged potentio­meter (VR1a/VR1b) and a DPDT switch (S1a/S1b) allow two locos to be controlled in a double-heading lash-up. of the eight DIN sockets. Each pair of RCA sockets is wired to pins 4 & 5 of the associated DIN socket so they represent the throttle outputs for the handheld control. Now, here is the big question: how is the connection made between each of the RCA throttle outputs and the 16 RCA throttle inputs to the encoder board? The answer is quite simple: you need RCA to RCA plug patch cords. So the way each handheld throttle is assigned to a particu­ lar channel is merely to connect a patch cord between the throt­tle output and the wanted input channel. Simple! If you want to run eight throttles and have them all with the possibility of double-heading, then you will need at least 16 RCA to RCA patch cords and they will need to be long enough to reach from one end of the control panel to the other, in order to provide for any throttle to go to any channel. Or you could make things a little tidier by making some patch cords long and some short although that will probably limit your flexibility. As well as the 16-way ribbon cable to the encoder PC board, the control panel will need three wires going back from the DIN sockets to the Forward (+1.2V), Reverse (+8.8V) and Stop (+5V) connections on the encoder board. Since each layout will have its own features, we have not provided a wiring diagram. Depending on your preferences, the control panel could be combined with the other control gear for your layout – lighting, points switching and so on. Have fun! SC June 1998  85 3 1 2 GREAT REASO SUBSCRIBE NO Every new or renewing subscriber* between now and June 30 gets a FREE copy of the superb SILICON CHIP/JAYCAR Wall Data Chart. THAT’S WORTH $10.95 ALONE! 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November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. September 1990: Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band; the Bose Lifestyle Music System; The Care & Feeding Of Battery Packs; How To Make Dynamark Labels. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1990: The Dangers of PCBs; Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; NE602 Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. December 1989: Digital Voice Board; UHF Remote Switch; Balanced Input & Output Stages; Operating an R/C Transmitter; Index to Vol. 2. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. March 1992: TV Transmitter For VHF VCRs; Thermostatic Switch For Car Radiator Fans; Coping With Damaged Computer Directories; Guide Valve Substitution In Vintage Radios. April 1992: IR Remote Control For Model Railroads; Differential Input Buffer For CROs; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; IR Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. August 1992: An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; MIDI Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; 16-Channel Mixing Desk, Pt.3; Active CW Filter; Servicing Your Microwave Oven. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. June 1991: A Corner Reflector Antenna For UHF TV; Build A 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers, Pt.2; Active Filter For CW Reception; Tuning In To Satellite TV. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Microsoft Windows Sound System; The Story of Aluminium. July 1990: Digital Sine/Square Generator, Pt.1 (0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. July 1991: Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; A Windows-Based Logic Analyser. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. 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Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. ✂ Card No. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. May 1995: What To Do When the Battery On Your PC’s Mother­ board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. January 1997: How To Network Your PC; Control Panel For Multiple Smoke Alarms, Pt.1; Build A Pink Noise Source (For Sound Level Meter Calibration); Computer Controlled Dual Power Supply, Pt.1; Digi-Temp Monitors Eight Temperatures. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80Based Computer; A Look At Satellites & Their Orbits. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. February 1997: Cathode Ray Oscilloscopes, Pt.6; PC-Controlled Moving Message Display; Computer Controlled Dual Power Supply, Pt.2; Alert-A-Phone Loud Sounding Alarm; Control Panel For Multiple Smoke Alarms, Pt.2. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder (Uses Pressure Sensing); Adding RAM To A Computer. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Audible Continuity Tester; Cathode Ray Oscilloscopes, Pt.7. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. April 1997: Avoiding Win95 Hassles With Motherboard Upgrades; Simple Timer With No ICs; Digital Voltmeter For Cars; Loudspeaker Protector For Stereo Amplifiers; Model Train Controller; A Look At Signal Tracing; Pt.1; Cathode Ray Oscilloscopes, Pt.8. December 1993: Remote Controller For Garage Doors; LED Stroboscope; 25W Amplifier Module; 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. September 1995: Keypad Combination Lock; The Incredible Vader Voice; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Jacob’s Ladder Display; The Audio Lab PC Controlled Test Instrument, Pt.2. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design; Engine Management, Pt.4. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. May 1997: Windows 95 – The Hardware Required; Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. February 1994: Build A 90-Second Message Recorder; 12-240VAC 200W Inverter; 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Engine Management, Pt.5; Airbags – How They Work. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1. November 1993: High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Engine Management, Pt.2; Experiments For Games Cards. March 1994: Intelligent IR Remote Controller; 50W (LM3876) Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Engine Management, Pt.6. April 1994: Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Universal Stereo Preamplifier; Digital Water Tank Gauge; Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Simple Servo Driver Circuits; Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; 80-Metre AM/CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; PC-Based Nicad Battery Monitor; Engine Management, Pt.9. July 1994: Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Nicad Zapper; Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Engine Management, Pt.12. October 1994: How Dolby Surround Sound Works; Dual Rail Variable Power Supply; Build A Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Build A Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuvenator; Novel Alphanumeric Clock; 80-Metre DSB Amateur Transmitter; Twin-Cell Nicad Discharger (See May 1993); Anti-Lock Braking Systems; How To Plot Patterns Direct To PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Remote Control System for Models, Pt.1; Index to Vol.7. January 1995: Sun Tracker For Solar Panels; Battery Saver For Torches; Dolby Pro-Logic Surround Sound Decoder, Pt.2; Dual Channel UHF Remote Control; Stereo Microphone Pre­amp­lifier;The Latest Trends In Car Sound; Pt.1. February 1995: 50-Watt/Channel Stereo Amplifier Module; Digital Effects Unit For Musicians; 6-Channel Thermometer With LCD Readout; Wide Range Electrostatic Loudspeakers, Pt.1; Oil Change Timer For Cars; The Latest Trends In Car Sound; Pt.2; Remote Control System For Models, Pt.2. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. March 1996: Programmable Electronic Ignition System; Zener Diode Tester For DMMs; Automatic Level Control For PA Systems; 20ms Delay For Surround Sound Decoders; Multi-Channel Radio Control Transmitter; Pt.2; Cathode Ray Oscilloscopes, Pt.1. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. May 1996: Upgrading The CPU In Your PC; Build A High Voltage Insulation Tester; Knightrider Bi-Directional LED Chaser; Simple Duplex Intercom Using Fibre Optic Cable; Cathode Ray Oscilloscopes, Pt.3. June 1996: BassBox CAD Loudspeaker Software Reviewed; Stereo Simulator (uses delay chip); Rope Light Chaser; Low Ohms Tester For Your DMM; Automatic 10A Battery Charger. July 1996: Installing a Dual Boot Windows System On Your PC; Build A VGA Digital Oscilloscope, Pt.1; Remote Control Extender For VCRs; 2A SLA Battery Charger; 3-Band Parametric Equaliser; Single Channel 8-bit Data Logger. August 1996: Electronics on the Internet; Customising the Windows Desktop; Introduction to IGBTs; Electronic Starter For Fluores­cent Lamps; VGA Oscilloscope, Pt.2; 350W Amplifier Module; Masthead Amplifier For TV & FM; Cathode Ray Oscilloscopes, Pt.4. September 1996: VGA Oscilloscope, Pt.3; IR Stereo Headphone Link, Pt.1; High Quality PA Loudspeaker; 3-Band HF Amateur Radio Receiver; Feedback On Pro­g rammable Ignition (see March 1996); Cathode Ray Oscilloscopes, Pt.5. October 1996: Send Video Signals Over Twisted Pair Cable; Power Control With A Light Dimmer; 600W DC-DC Converter For Car Hifi Systems, Pt.1; IR Stereo Headphone Link, Pt.2; Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. November 1996: Adding A Parallel Port To Your Computer; 8-Channel Stereo Mixer, Pt.1; Low-Cost Fluorescent Light Inverter; How To Repair Domestic Light Dimmers; Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For Dark­ rooms; Balanced Microphone Preamp. & Line Filter; 50W/Channel Stereo Amplifier, Pt.2; Wide Range Electrostatic Loudspeakers, Pt.3; 8-Channel Decoder For Radio Remote Control. December 1996: CD Recorders ­– The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/ RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/ Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How Holden’s Electronic Control Unit works, Pt.1. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home; How Holden’s Electronic Control Unit Works, Pt.2. September 1997: Multi-Spark Capacitor Discharge Ignition; 500W Audio Power Amplifier, Pt.2; A Video Security System For Your Home; PC Card For Controlling Two Stepper Motors; HiFi On A Budget; Win95, MSDOS.SYS & The Registry. October 1997: Build A 5-Digit Tachometer; Add Central Locking To Your Car; PC-Controlled 6-Channel Voltmeter; The Flickering Flame Stage Prop; 500W Audio Power Amplifier, Pt.3; Customising The Windows 95 Start Menu. November 1997: Heavy Duty 10A 240VAC Motor Speed Controller; Easy-To-Use Cable & Wiring Tester; Regulated Supply For Darkroom Lamps; Build A Musical Doorbell; Relocating Your CD-ROM Drive; Replacing Foam Speaker Surrounds; Understanding Electric Lighting Pt.1. December 1997: A Heart Transplant For An Aging Computer; Build A Speed Alarm For Your Car; Two-Axis Robot With Gripper; Loudness Control For Car Hifi Systems; Stepper Motor Driver With Onboard Buffer; Power Supply For Stepper Motor Cards; Understanding Electric Lighting Pt.2; Index To Volume 10. January 1998: Build Your Own 4-Channel Lightshow, Pt.1 (runs off 12VDC or 12VAC); Command Control System For Model Railways, Pt.1; Pan Controller For CCD Cameras; Build A One Or Two-Lamp Flasher; Understanding Electric Lighting, Pt.3. February 1998: Hot Web Sites For Surplus Bits; Multi-Purpose Fast Battery Charger, Pt.1; Telephone Exchange Simulator For Testing; Command Control System For Model Railways, Pt.2; Demonstration Board For Liquid Crystal Displays; Build Your Own 4-Channel Lightshow, Pt.2; Understanding Electric Lighting, Pt.4. March 1998: Sustain Unit For Electric Guitars; Inverter For Compact Fluorescent Lamps; Build A 5-Element FM Antenna; Multi-Purpose Fast Battery Charger, Pt.2; Command Control System For Model Railways, Pt.3; PC-Controlled LCD Demonstration Board; Feedback On The 500W Power Amplifier; Understanding Electric Lighting, Pt.5; Auto-detect & Hard Disc Drive Parameters. April 1998: Automatic Garage Door Opener, Pt.1; 40V 8A Adjustable Power Supply, Pt.1; PC-Controlled 0-30kHz Sinewave Generator; Build A Laser Light show; Understanding Electric Lighting, Pt.6; Philips DVD840 Digital Vide Disc Player (Review). May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; A Detector For Metal Objects; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992 and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear sheets) at $7.00 per article (includes p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. A complete index to all articles published to date is available on floppy disc for $10 including p&p. June 1998  89 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. UV water cleaner inverter I am interested in employing the High Efficiency Inverter for Fluorescent Tubes as described in the November 1993 issue. I want to operate an ultraviolet water cleaner outdoors from 12V rather than 240VAC. The device as supplied is wired as a conventional fluores­cent light with ballast and starter and is quoted as having a power consumption of 8W. Your inverter circuit however, is de­ signed to operate tubes no smaller than 18W and so I need to modify the number of turns on T2 to alter the frequency of the driver circuit or perhaps alter the value of L2 so that the current is limited to a value that does not allow the 8W limit of the UV tube to be exceeded. A comparison of the 18W and 36W designs suggests that increasing N1 from 24 to 32 turns and decreasing N2 and N3 from 3 to 1.5 turns might be the solution. I assume that there could be some trial and error required since frequency of operation and current limiting of the circuit is determined by the characteristics of toroid T2. Presumably the current drawn by the tube should be measured in some Multiple outputs from headphone amplifier I am interested in a small distribution amplifier which would give my portable mixer’s “headphone out” the ability to have three or four jacks with individual volume adjustments. Are there any kits available or would there be enough usefulness in the idea for it to be a future project? (P. S., Clifton Hill, Vic). • Since your mixer’s 90  Silicon Chip way to ensure that it is not over-dissipating. What would you suggest? (R. B., Wellington, NZ). • As it stands the design has been optimised for 36W and 18W fluorescent tubes. To alter the circuit for an 8W tube does involve changing windings on the T2 toroid, however the process is not as simple as interpolating the published winding details. What happens when changing the N1 winding to a larger number of turns is that the core of T2 saturates with a lower current. Thus as the current builds up through the fluorescent tube and induc­tor L2, the core saturates earlier and so the frequency of oscil­ lator operation is higher. This oscillator comprises Mosfets Q3 & Q4 and their gates are switched via the N2 and N3 windings. A higher operating frequency also means lower current through the fluorescent tube because the impedance of inductor L2 is higher. So what we have is lower current through the fluorescent tube but we also have a higher operating frequency. In the case of changing the windings on T2 to suit an 8W tube, the frequency would be well above 200kHz. This is rather high for our circuit and would increase the Mosfet switching losses. headphone output will have a low output impedance, it can easily drive half a dozen 10kΩ potentiometers, all in parallel, to provide multiple volume outputs. The accompa­nying circuit shows how this can be done. An alternative approach would be to increase the inductance of L2 to 1.8mH by increasing the number of turns by a factor of 1.414. This means that L2 should have 85 turns rather than the original 60 turns. The increased inductance reduces the fluor­ es­cent tube current. The windings for T2 should be initially kept the same as for the 18W circuit. Now the circuit will operate at a lower frequency but be more current-limited with the added induc­tance of L2. Since the N1 winding also forms part of the overall inductance in series with the fluorescent tube, the current should be checked to make sure the tube is not overdriven. The windings on T2 should then be altered to obtain the correct current. Use a 1Ω resistor in series with the tube and measure the RMS voltage across it with an oscilloscope or RMS reading meter. Note that the multi­ meter must have sufficient bandwidth for the measurement. If using an oscilloscope, you will need to make an estimate of the current. Since the current waveform is reasonably sinusoi­dal, a meter measuring average voltage may provide a satisfactory reading. Assuming the conduction voltage across the 8W fluorescent tube is 56V, the RMS current should be 0.145A, corresponding to 0.145V RMS across the 1Ω resistor. Multi-charger modifications wanted I am an aeromodeller and at the moment I am putting togeth­er another field box that will travel easier. To save space I would like to construct the battery charger that you have fea­ tured in the February and March 1998 issues of the magazine but have struck a problem. I use three different batteries: a 12V 7A sealed lead acid, 9.6V AA NiCd packs in the transmitters and 4.8V AA NiCd packs in the receivers in the models. Is there any way of making some simple changes to the charger to cater Robot control via UHF I am attempting to build a robot as one of my spare-time projects and plan to control movement by sending serial data from my PC to the robot (which is controlled by an old XT motherboard) via a radio link. I was hoping you could offer some advice as to the best way to go about this. I thought about modifying the Central Locking kit from the October 1997 edition or the Remote Control Gate unit, using the Oatley transmitter and receiver, from the August 1997 issue. Would modifications be possible to give reliable operation? Also I am hoping to put a CCD camera on the robot to send video/audio to a TV and I was wondering if you have published any suitable circuits. (D. M., Bayswater, Vic). • While we haven’t tried it, it should be possible to use the UHF transmitter section (without the encoder chip) of the Central Locking kit, together with the matching receiver, to serve as a data link. The range would only be a few metres but it could be extended by using bigger transmitting and receiving antennas. If you elected to put a video link on the robot, you could probably use the UHF modulator and transmitter section from the project featured in the December 1991 and March 1992 issues. The signal will be able to be received by any conventional TV set with a UHF tuner. for these ranges as they are not shown in the article. (D. P., Lathlain, WA). • The charger can be used with your 12V SLA battery and the 9.6V nicads. To charge the 4.8V battery you will require a change in the voltage divider resistors from the battery to Vbat (pin 19 of IC1) and ground. Use 18kΩ in parallel with 12kΩ to replace the 100kΩ and 10kΩ resistors used in the 14.4V switch position. This will give you a 4.8V setting. Woofer starter wanted Recently, I was reading about your Woofer Stopper, pub­ lished in the February 1996 issue. I have never had this problem with my dog because he never barks – or only occasionally when something annoys him. What I would like to know is this: is there something that would make him bark, like a “woofer stopper in reverse”, because when strangers come in he just wags his tail. I don’t want him to bite anybody but just to bark and maybe growl a bit. I can have it switch on when somebody comes into my yard. I thought if a frequency can stop a dog from barking, maybe a certain frequency can make him bark. If this is possible I would certainly be interested in building one. (K. L., Tweed Heads South, NSW). • Your dog sounds like the ideal pet. We cannot suggest any electronic way to make him bark. Enjoy his company AUDIO TRANSFORMERS Manufactured in Australia Comprehensive data available Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 June 1998  91 Building the 2kW sinewave inverter What level of skill is required to build the 2kW 24V DC/240VAC inverter described in a 5-part series from October 1992? What instruments would be required? What is the cost of the five sets of transcripts? Also, I have a standard 15W high effi­ciency fluoro with a standard socket (ie, bayonet) for my 240VAC 50Hz supply. However, when I sell this house I will take these costly fluoros with me and I will move to a house with a 12V DC system. Is there an article to describe the construction of a small dedicated inverter for this 15W fluoro and also a 10W fluoro? Do you have plans for a voltage regulator/rectifier that can be used with a standard 12V car alternator. I intend to make a wind generator from a spare alternator. The input will probably be around 350W and and get a PIR detector or a sensor on your gate to indicate when people arrive. Assembler wanted for speed control I would love to own the full range speed control published in the November 1997 issue but unfortunately I am not able to assemble a kit myself. Can you nominate a qualified person to do this job for me? (W. S., East Wollongong, NSW). • This type of request is very common and if anyone wanted to set up to provide this sort of service on a continuous basis they would probably find the output about 100-150W. (R. O., Gidgegannup, WA). • The 2kW sinewave inverter is a project for very experienced constructors only. You need to wind the large inverter transform­er or have it made by Harbuch Transformers Pty Ltd. There is a considerable amount of metalwork in the project. We can supply the relevant back issues or photostat copies of the articles for a total of $35.00 including postage. We can also program the EPROM (supplied by you) for the project at a cost of $10.00. As far as we can recall, the original kit price for the project was over $1500 and you may be wise to check the prices of equivalent commercial sinewave inverters available today. At the very least, you will need a good multimeter and access to an oscilloscope. With regard to your 15W fluorescent lamps, have a look at the inverter for CFLs in the March 1998 issue of SILICON CHIP. there is plenty of work. If any reader is able to assemble and fully test the full range speed control, please contact us here at SILICON CHIP, together with the price for this service. Hates waking up in the morning Like everyone, I hate waking up in the morning but espe­cially to the sound of an alarm clock or radio. I’d like a cir­cuit that connects in-line with the bedside lamp. It would have an electronic timer that turns the lamp on at a particular time, then brings the lamp to full brilliance over, say, a 10 minute period. This would be a much more civilised way to wake up. (S. P., Bicton, WA). • We love waking up in the morning because it means we’re not dead yet but some of us do have problems getting out of bed once we are awake. Having said that, we have not published a circuit which meets your requirements but it would be possible to take the audio signal from a clock radio and use it to control a bedside lamp. This is not a project that we would normally consider but we wonder if any of our readers has designed a circuit to perform the task. Speakerphone sounds boomy I read with interest your answer concerning the Speaker­ phone (May 1988) problem in “Ask Silicon Chip” March 1998. I recently constructed a Speakerphone myself and while my unit works OK, people say my voice sounds “echoey” or like I am talk­ing down a pipe; volume is OK and apparently legible. I have tried various methods to cure the problem to no avail. I have tried mounting the electret in a block of rubber, sealing the back and mounting the block to the front panel. I would be most interested to hear your answer to my problem. (H. S., Bairnsdale, Vic). • Your complaint about sounding like speaking down a pipe is commonplace with any “hands free” phone apart from those used for mobile phones in cars. The problem is that the voice pickup includes a lot of room echo. You can help minimise the problem by speaking as close to the microphone as possible (not practical in many situations, we agree) and by placing the whole unit on a cushion or piece of carpet. Sitting the unit on a hard SC surface makes things worse. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 92  Silicon Chip MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086 or 8096: $145.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 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 centi­ metre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly on a separate sheet of paper, fill out the form below & send it with your cheque or credit card details to: Silicon Chip Clas­ sifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ ____________ ____________ ___________ ___________ ___________ Enclosed is my cheque/money order for $­__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip and 68HC12 now combined at the new low price of $75. Debug monitors: $75 for 6 CPUs. All compilers, XASMs and monitors: $480. 8051/52 Simula­ tor (fast, now incl. 80C320): $75. Try the C-FLEA Virtual Machine for small CPUs, build a “C-Stamp”. Demo desk: FREE. All prices + $5 p&p. Atmel Flash CPU Programmer: Handles the 89Cx051, the 89C5x and 89Sxx series, and the new AVRs in both DIP and PLCC44. Also does most 8-pin EEPROMs. Includes socket for serial ISP cable. $189, $35 tax, $10 p&p. 20-pin SOIC adaptor only $70. Credit cards accepted. GRAN­TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150 or Internet: http://www.grantronics.com.au TELEPHONE EXCHANGE SIMULATOR, SC February 1998. Test all sorts of equipment without the cost of extra telephone lines. Melbourne 9806 0110. AWA C1070 Modulated Oscillator (1936) $75. (02) 9603 8763 Camp­ belltown. ELECTRONIC ENGINEERING SOLUTIONS: No matter what problem what industry we will find you a solution that meets your needs. Specialising in schematic & PCB design, custom Windows based software, embed­ ded control, Windows/PC based test equipment, turnkey solutions. Fast turn around with competitive rates. DAM­ UE PTY LTD, 46 Whitby Road, Kings Langley NSW 2147. Phone (02) 9624 2802. Fax (02) 9624 2651 or E-mail alovell<at>ibm.net OSCILLOSCOPE HP 54501A with probes & trolly 100MHz digital $2200 ono Tek 7904 with plug ins 500MHz main frame $1200 ono Ph 08 9291 7646 Fax 08 9291 4070. SIMPLE PIC84 PROGRAMMER: var ious models available. Also PIC-driven moving message and digital displays. EST (02) 9789 3616. www.nettrade.com.au/sesame/ LOGIC ANALYSER: As new Philips PM3585/61 Dual Analyser, 200MHz timing and 50MHz state acquisition, 2K sample memory, 190mm x 130mm display, 64 signal inputs, remotely controllable. Also included: manuals, pod cables, system software, H8/330 disassem­bler with adapter pod, H8/500 adapter pod. Contact Smart Silicon Systems (02) 9901 3598. 4 DIGIT RED LED DISPLAYS: common cathode 0.24 inch. Data sheets availa­ ble. $3.00 each or $2.80 per 100. Phone Col (02) 9608 3313. R.T.N. Parallax AUS/NZ distributor. Special on till July 98, a complete StampBus motherboard which holds the Basic Stamp1 chip­set a serial LCD driver module and a 2*8 LCD module. Ideal ex­pandable starter kit for $110.00 includes tax. and postage to any location in AUS/NZ. Programming software and examples supplied also. Now also carry the FerretTronics range of R/C servo KITS-R-US PO Box 314 Blackwood S.A. Ph/fax 08 8270 3175 FMTX2A Universal Stereo Coder $49 FMTX2B 30mW Xtal Locked 100MHz Transmitter $49 FMTX1 1-3 Watt Free Running Transmitter $49 FMX1 200mW Full Broadcast Transmitter, built & tested $499 FM220 10-18 Watt FM BGY133 Philips Linear $499 FM1525 25 Watt Discrete Linear FM Band $499 FM2100 110 Watt Discrete Linear FM Band $699 FM3000 300 Watt Discrete Linear FM Band $1499 Philips 828E/A VHF Receiver Boards (6 metres) $9 AWA 721 VHF Receiver Boards (2 metres) $9 AWA 721 VHF transmitter boards 1 watt (2 metres) $19 Philips 323 UHF transmitter boards 500mW (70cm) $19 AEM 35 Watt Little Brick Audio Power Amp $15 Digi-125 200W RMS Audio Power Amp $39 CA Clipper Compiler, new in box $49 6dBd Gain Colinear FM Band Antenna $999 Roll Smart-1 FM Station Audio Processor $999 Free catalog on disk of discounted surplus components Same day shipping, credit cards OK, circuits supplied. Need prototype PC boards? We have the solutions – we print electronics! Four-day turnaround, less if urgent; Artwork from your own positive or file; Through hole plating; Prompt postal service; 29 years technical experience; Inexpensive; Superb quality. Printed Electronics, 12A Aristoc Rd, Glen Waverley, Vic 3150. SPECIAL STEAM BOAT KITS $14 VIDEO CAMERAS & ANCILLARY EQUIPMENT - OUR PRICES ARE DOWN AGAIN! Ask for latest Illus­ trated Catalogue/Price List. Following now available from.. 380 x 0.2 PCB Module $69. SONY Chipset 400 x 0.05 lux PCB $89. 36 x 36 Mini Cam $85. DOME Ceiling $89. COLOUR DSP 32 X 32 PCB $182. COLOUR DSP 330 TVL PCB $212. COLOUR DSP 450 TVL PCB $326. DUMMY CEILING DOME Tiny 32 x 32 PCB modules could be fitted inside these $19. COL­ OUR DSP 380 TVL C/CS Mount Cam­ era with Audio $270. COLOUR DSP 450 TVL C/CS Mount with Audio $367. QUAD 4 pix - 1 Screen $254. QUAD/ Multiplexer Full Frame Full Resolution Recording $748. PACKAGED SETS! QUAD + FOUR CAMERAS + Power Supplies $645 just add cabling! CCTV - TV/VCR RF Module $14. Infra-Red 50 LED 52mm Round Illuminators $28. Wireless Video/Audio Transmit­ ter - Receiver Module/PCB pairs Last Chance! Sellout! These will never be available again $28. GREENCELL Battery Regenerator 4 x AA or AAA suit Alkaline, Heavy/Super Duty Zinc Chloride & Nicads with Mains Plug Pack $14. UPT TO 2 Year WARRAN­ TY on most items! DISCOUNTS are available based on ORDER VALUE, BUYING HISTORY and for CASH! Allthings Sales & Services 08 9349 9413 Fax 08 9344 5905. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. TRUE RMS DMM Includes Capacitance Frequency Min/Max reading Bargraph Auto range PRESTON ELECTRONIC COMPONENTS Now at 172 HIGH STREET, PRESTON, VIC (Corner of Bell and High Streets) Phone: (03) 9484 0191 Specialising in a wide range of: TV Antennas – Resistors – Cables – Cir­ cuit Boards – Capacitors – Sprays – PCB Artwork – Instrument Cases – Relays – Kit Sets – Semiconductors (all types) – Trimpots – Photo Sensitive – Transformers – Switches – Alarm/Security Equipment – CB Radios & Accessories. We are approved resellers for Altronics, DSE and RPG Products! $98.00x ex ta Computronics Corporation Ltd 6 Sarich Way, Technology Park, Bentley, WA, 6102 Ph. 08 9470 1177 Fax 08 9470 2844 Specifications at www.computronics.com.au Silicon Chip Binders ★ Heavy board covers with 2-tone green vinyl covering ★ Each binder holds up to 14 issues REAL VALUE AT $12.95 PLUS P &P ★ SILICON CHIP logo printed in goldcoloured lettering on spine & cover Price: $12.95 plus $5 p&p each (Aust. only) Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. control chips. Email: nollet<at>mail.enternet.com.au http://people.enternet.com.au/~nollet Ph/fax/ans (03) 9338 3306. HOMEBUILT DYNAMO, engineering dreams into reality. “An absolutely marvellous book for the true ex­ perimentalist!” Elektor Electronics. (www.onekw.co.nz) WANTED SERVICE INFORMATION: DOES ANYONE HAVE service information on a Nordmende colour 3675 TV chassis ICC4 that I can have a copy of? Reply to J. Dench, PO Box 40-317, Glenfield, Auckland 1310, New Zealand. Fax 09 4446542. June 1998  95 14 Model Railway Projects Shop soiled but HALF PRICE! Our stocks of this book are now limited. All we have left are newsagents’ returns which means that they may be slightly shop soiled or have minor cover blemish­ es. Otherwise, they're undamaged and in good condition. SPECIAL CLEARANCE PRICE: $3.95 + $3 P&P (Aust. & NZ) This book will not be reprinted Advertising Index Altronics................................. 34-36 Bainbridge Technologies..............91 BBS Electronics...........................15 Computronics..............................95 Dick Smith Electronics..................... ................................ IFC,OBC,10-11 Harbuch Electronics....................91 Instant PCBs................................95 Jaycar ................................... 45-52 Kalex............................................57 Microgram Computers...................3 Oatley Electronics........................67 Yes! Please send me _____ copies of 14 Model Railway Projects at the special price of $A3.95 + $A3 p&p (p&p outside Aust. & NZ $A6). Enclosed is my cheque/money order for $­A__________ or please debit my Preston Electronics......................95 ❏ Procon Technology......................95 Bankcard   ❏ Visa Card   ❏ MasterCard Printed Electronics.......................95 Card No. Quest Electronics........................70 Signature­­­­­­­­­­­­___________________________ Card expiry date______/______ Scan Audio..................................70 Name Silicon Chip Back Issues....... 88-89 ______________________________________________________ PLEASE PRINT ______________________________________________________ Silicon Chip Bookshop.................37 Suburb/town_________________________________ Postcode_________ Silicon Chip Binders/Wallcht........93 Street 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). Silicon Chip Software..................59 Silicon Chip Subscriptions..... 86-87 Truscott’s Electronic World...........57 Valve Electronics.........................91 Circuit Ideas Wanted Do you have a good circuit idea. If so, why not sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We pay up to $60 for a good circuit but don’t make it too big please. Send your idea to: Silicon Chip Publications, PO Box 139, Col­ laroy, 2097. 96  Silicon Chip Microprocessor For Digital Effects Unit This is the 68HC705-C8P pro­ gramm­ed micro­pro­cessor IC for the Digital Effects Unit (see Feb­. 1995). Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Pub­ lica­tions, PO Box 139 Collaroy 2097. Phone (02) 9979 5644; Fax (02) 9979 6503. Zoom EFI Special........................73 Zoom Magazine.........................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) 9587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. R AUSTRALIA’S BEST AUTO TECH MAGAZINE It’s a great mag... but could you be disappointed? If you’re looking for a magazine just filled with lots of beautiful cars, you could be disappointed. Sure, ZOOM has plenty of outstanding pictorials of superb cars, but it’s much more than that. If you’re looking for a magazine just filled with “how to” features, you could be disappointed. Sure, ZOOM has probably more “how to” features than any other car magazine, but it’s much more than that. If you’re looking for a magazine just filled with technical descriptions in layman’s language, you could be disappointed. Sure, ZOOM tells it in language you can understand . . . but it’s much more than that. If you’re looking for a magazine just filled with no-punches-pulled product comparisons, you could be disappointed . Sure, ZOOM has Australia’s best car-related comparisons . . . but it’s much more than that If you’re looking for a magazine just filled with car sound that you can afford, you could be disappointed. Sure, ZOOM has car hifi that will make your hair stand on end for low $$$$ . . . but it’s much more than that. If you’re looking for a magazine just filled with great products, ideas and sources for bits and pieces you’d only dreamed about, you could be disappointed. Sure, ZOOM has all these . . . but it’s much more than that. But if you’re looking for one magazine that has all this and much, much more crammed between the covers every issue, there is no way you’re going to be disappointed with ZOOM. Look for the June/July 1998 issue in your newsagent From the publishers of “SILICON CHIP”