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September 1999  1 SPECIAL OFFER: ONLY NORMALLY 269 $ 249 $ Excluding Tax Excluding Tax ( 293 Tax Inc) $ Once oscilloscopes were heavy and clumsy to handle but over the years they have got smaller and smaller. The latest development in this field has just arrived: a digital storage oscilloscope in a handy slim housing, scarcely longer than a pencil and about as thick as your thumb! Despite its small size, its performance can match that of a service oscilloscope. With a sampling rate of up to 20MS/s even signals in microprocessor circuits can be recorded. Using its voltmeter function, numeric AC and DC voltages can be easily measured. The osziFOX has many uses. It can be used for taking measurements in amplifiers, digital circuits, telephone installations, hobby electronics, production-line tests, servicing and on-the-spot measuring. With the supplied software for DOS and Windows (3.1x & Win95) recorded signals can be shown simultaneously on a PC screen using the supplied interface cable. For documentation purposes, the recorded signals can be saved to disk or printed. Technical Specifications Sample rates: 50ns, 100ns, 0.5µs, 1µs, 5µs, 10µs, 50µs, 0.1ms, 0.5ms, 1ms Input ranges: 1V, 10V, 100V No of channels: 1, 1MΩ AC/DC coupled Trigger: Internal, external Resolution: 6 bit Buffer size: Voltmeter Display Supply voltage: PC connection: Accessories: 128 byte AC, DC 16 x 32 backlit LCD 9-13V DC <at> 13mA (cable supplied) D9 to serial port via supplied cable Cables, documentation and software EMONA INSTRUMENTS NSW VIC QLD WA Phone (02) 9519 3933 (03) 9889 0427 (07) 3367 1744 (08) 9361 4200 Fax (02) 9550 1378 (03) 9889 0715 (07) 3367 1497 (08) 9361 4300 ORDER ON LINE: http://www.emona.com.au Contents Vol.12, No.9; September 1999 FEATURES   4  Automatic Addressing On TCP/IP Networks Setting up a DHCP server plus WINS & DNS explained – by Greg Swain & Bob Dyball   9  BreezeNet: Wireless Networking Without The Hassles You simply plug it in and it works – by Greg Swain 42  Internet Access – Reduced Prices NSW (02) VIC (03) QLD (07) WA (08) 9361 4200 3367 1497 9361 4300 No time limits, no download limits, no Phone fine print – and no0427 hassles 9519 3933 9889 3367 1744 Fax 9550 1378 9889 0715 Autonomouse The Robot – Page 18. PROJECTS TO BUILD 18  Autonomouse The Robot Automatically avoids objects and flashes two light chasers to show what it’s doing – by John Clarke 35  Voice Direct Speech Recognition Module Train it to recognise your voice! – by Ross Tester 63  Digital Electrolytic Capacitance Meter Test electrolytic capacitors up to 999,900µF – by Eugene W. Vahle Jr Voice Direct Speech Recognition Module – Page 35 72  An XYZ Table With Stepper Motor Control; Pt.5 Building the power supply and drilling your first board – by Rick Walters 86  A Peltier-Powered Can Cooler Keep your tinnies (or anything else) cool this summer – by Ross Tester SPECIAL COLUMNS 30  Serviceman’s Log Hindsight is a wonderful thing – by the TV Serviceman Digital Electrolytic Capacitance Meter – Page 63. 53  Vintage Radio Vintage hifi stereo AM radio – by Rodney Champness DEPARTMENTS   2  Publisher’s Letter 44  Subscriptions Form 58  Circuit Notebook 80  Product Showcase 81  Electronics Showcase 91  Ask Silicon Chip 93  Notes & Errata 94  Market Centre 96  Advertising Index Peltier-Powered Can Cooler – Page 86. September 1999  1 PUBLISHER’S LETTER www.siliconchip.com.au Publisher & Editor-in-Chief Leo Simpson, B.Bus., FAICD Production Manager Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Ross Tester Rick Walters Reader Services Ann Jenkinson Advertising Enquiries Rick Winkler Phone (02) 9979 5644 Fax (02) 9979 6503 Mobile: 0414 34 6669 Regular Contributors Brendan Akhurst Rodney Champness Garry Cratt, VK2YBX Julian Edgar, Dip.T.(Sec.), B.Ed Mike Sheriff, B.Sc, VK2YFK 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: $69.50 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. E-mail: silchip<at>siliconchip.com.au ISSN 1030-2662 * Recommended and maximum price only. 2  Silicon Chip Email us with your ideas for editorial content Each month as we produce SILICON CHIP we try to give a wide range of projects and articles to keep readers interested and satisfied. It is clear that a large number of you are stimulated and entertained by what you read. But there is always the pos­sibility that we could be doing more to satisfy readers and within the limits of our resources, that is what we want to do. Given that we do have limited resources, could we be making better use of them in producing the articles for this magazine? What do you think? For example, many of the project articles in SILICON CHIP are quite long and detailed. Autonomouse the Robot in this month’s issue is one example and the article will be continued next month. The XYZ Plotter is another example of a very big project that has taken a lot of articles to fully present. And there are a number of significant articles to be featured in the coming months which are similarly detailed and have taken a lot of work for us to develop and describe. Do you as readers appreciate all this detail or would you prefer to see more articles with a lot less detail? Maybe just a PC board and not much else? And would you prefer to have fewer project articles and more articles on technical developments? And what about other areas of electronics? What about solar and renewable energy, electric cars or whatever? In the past, we would have taken the trouble to put a reader survey in the magazine and then hope that enough people would fill it in to make it worthwhile. Even so, it would then take months to obtain and collate the results. And would we be asking the “right” questions? These days so many of you have email that you can respond almost immediately, if you wish to give an opinion. So why not email us with your ideas? Keep them brief and to the point and they will be acknowledged. If you don’t have email, by all means send us a letter but we do find it much quicker to answer email than ordinary letters. Now we are also aware that people who respond to reader surveys are often the “committed” readers but we would also like to hear from readers who only buy SILICON CHIP occasionally. We would like you to buy the magazine every month, without fail. After all, we need as many magazine buyers as possible. The more buyers we have, the more resources we will have to make the magazine bigger and more attractive. So it’s over to you. Please drop us a line by email or letter and you could be doing us a big favour because there might be things which are blindingly obvious to you and which we just haven’t twigged to. I look forward to hearing from you soon. And finally, on a subject related to important magazine resources, Bob Flynn, our esteemed draftsman, has retired. On the one hand I wish Bob a long, happy and fruitful retirement. On the other hand, I regret his departure because it is proving to be difficult to obtain a replacement who can replicate his thorough approach to circuit layout. The position is still vacant as I write – see page 41. Leo Simpson M croGram Computers Internet Router The Internet Router is a high performance all-inone network communication device. It provides a local area network with Internet access, the convenience of remote access, and the power to combine your office networks together using LAN-to-LAN routing (IP routing). Two models are available with two or four WAN ports that can support both analog modems & ISDN terminal adapters. The Internet Router is simple, intuitive, and designed for the SOHO user. Web-Based Training from $9.95 per month* New courses now available! Including Windows 98, Quicken 98, Lotus Notes, Internet Tools (Netscape) and more courses on TCP / IP. 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No. 3159 E & OE Parallel Port EPROM Programmer $399 All prices include sales tax MICROGRAM 0999 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 FreeFax 1 800 625 777 We welcome Bankcard Mastercard VISA Amex Unit 1, 14 Bon Mace Close, Berkeley Vale NSW 2261 Vamtest Pty Ltd trading as MicroGram Computers ACN 003 062 100 Fax: (02) 4389 8388 Web site: www.mgram.com.au FreeFax 1 800 625 777 Computer Networking with TCP/IP Automatic addressing on TCP/IP networks Manually assigning IP addresses to individual computers on a network can quickly become a hassle. The answer is to use DHCP and WINS servers, so that IP addresses are handed out automatically each time a machine boots up. By GREG SWAIN & BOB DYBALL Non-routable networking protocols such as NetBeui are fine for small networks, where you only have a few PCs hooked up to one or more hubs and no routers are involved. In fact, NetBeui is one of the most effective protocols for up to about 20 people. It’s fast and easy to configure because you only have to provide each computer with a name – no network or logical addresses are required. However, it’s not uncommon for a network to be segmented using switch­ es and routers. This can be done for any number of reasons but usually it’s done to filter unnecessary network traffic from certain sections, to increase network performance. Bridges and routers are also often used to couple large networks in adjacent buildings together. And that’s where you run into Fig.1(a): here’s how to manually set up an IP address under Windows 98. Each computer on the network must be given a unique IP address, while the Subnet Mask should be the same for all machines. 4  Silicon Chip problems with NetBeui. Because it’s non-routable, network segments on either side of a router will not be able to “talk” to each other. To overcome this problem, a rout­able protocol such as TCP/IP must be used. Although it might initially appear rather mysterious, TCP/IP isn’t all that hard to get going – at least, in basic form. The first step is to install the TCP/IP protocol (if it hasn’t already been installed) and you do that via the Network utility in Control Panel. The procedure is as follows: load the utility, click the Add button, select Protocol, click Add again, select Microsoft, select TCP/IP and click OK – see Fig.1 You can now set up the IP address for the computer by selecting the TCP/ IP protocol (for the network card, not for a dial-up adapter) and clicking Fig.1(b): this screen grab shows how to manually enter IP addresses under Windows NT. The “Default Gateway” is the router address if it exists (otherwise leave it blank). the Properties button. Note that the IP address set here is “bound” to the network card and is non-routable as far as the Internet is concerned. Basically, there are three groups of IP numbers to choose from for private LANs. These address blocks are as follows: 10.0.0.0  to  10.255.255.255 172.16.0.0  to  172.31.255.255 192.168.0.0  to  192.168.255.255 When you manually assign IP addresses, each machine must be given a unique address but the Subnet Mask must be the same if you want the machines to “see” each other on the network. For most networks, a Subnet Mask of 255.255.255.0 will do just fine but note that, if you use this, all your IP addresses must use the same first three groups of numbers; ie, only the last number can be varied. Note also that it’s not usual to end an IP address in 0 or 255. So, for example, if you use a Subnet Mask of 255.255.255.0, you could use IP addresses ranging from 192.168.1.1 to 192.168.1.254. Each machine must also be given a unique NetBios name (or Computer name), as shown in Fig.2. The Work­ group name should be the same for all machines on the network.. Don’t forget to set up file and printer sharing on each machine, so that you can access the desired resources. The LMHOSTS file PCs on a network running TCP/IP need some mechanism to link the IP address of each machine to its NetBios name. This is known as “name resolution” and is necessary to allow computers on the network to communicate with each other. The reason for this is that users generally attempt to communicate with another computer by selecting its NetBios name. However, before communication can take place, the NetBios name must first be translated into that computer’s IP address. Two common methods for achieving this are “broadcast name resolution” and using an lmhosts file. The first method involves broadcasting a query over the network and asking a named computer to respond with its IP address. This is quite satisfactory if there are only a few machines on the network but generates a lot of unnecessary traffic on larger networks. An lmhosts file eliminates the need Fig.2: each machine on the network must be given a unique name, while the Workgroup name must be the same if you want the machines on a LAN segment to “see” each other. Fig.3: Example lmhosts File # IP Address Computer name # 192.168.1.1 lister 192.168.1.20 rimmer 192.168.1.40 starbug 192.168.1.80 holly and don’t do anything. In practice, all you have to do is create the lmhosts file using a text editor and copy it to all the machines on the network. On Windows 9x systems, this file must be placed in the c:\ windows folder (assuming that that’s where Windows is installed), while in Windows NT the file must be in c:\ winnt\system32\drivers\etc. If you are using Windows 95/98 you must also select the “Enable DNS” option in the TCP/IP properties dialog box (see Fig.4) and enter in a host name (this is usually the same as the computer name). If you don’t do this, the system will automatically resort to broadcast name resolution. Similarly, for Windows NT, you have to select “Enable Lmhosts Lookup”. This is done at the WINS Address tab in the TCP/IP Properties dialog box – see Fig.5. Note that each machine on the network must have the same lmhosts file, otherwise you will run into problems. IP addressing with DHCP for these query broadcasts. This is a simple text file that lists the IP address of each machine on the network and its corresponding NetBios name. Fig.3 shows a sample lmhosts file. Its format is fairly straightforward. The lines starting with “#” are comments Manually assigning IP addresses and maintaining an lmhosts file is fine if you only have a few computers on the network. However, it soon becomes unwieldy if the network is constantly changing or if you have more than about 15 computers to administer. Each time a machine is added to the network, for example, the lmhosts file must be altered and copied to each existing machine. As you can imagine, it’s all too easy to assign a new machine with a dupli- Fig.4: if lmhosts is used, you must also select the “Enable DNS” option in the TCP/IP properties dialog box of a Windows 95/98 client computer, Fig.5: a Windows NT client computer must have “Enable Lmhosts Lookup” selected if you wish to use lmhosts for name resolution. September 1999  5 Fig.6(a): setting up the Scope Properties for a DHCP server. In this example, the server can hand out IP addresses to client computers anywhere in the range from 192.168.1.10 to 192.168.1.200. The lease period is set to one day. cate IP address or to neglect updating the lmhosts file on some machines. In either case, the network will no longer work correctly. Often too, users want to take a laptop computer from one location to another and plug it into the network but this won’t work with static IP addresses if the lmhosts files and/or subnet masks are different. The solution is to use DHCP, or the Dynamic Host Configuration Protocol. This service, which runs on Windows NT Server, is one of the most convenient ways of handing out IP addresses. It initially requires more work because we have to set up a DHCP server but after that, it’s all plain sailing. When you set up the DHCP service, it’s given a range of IP address that can be handed out to client computers. The client computers then request an IP address each time they boot and this is automatically allocated by the DHCP server. Because the server keeps a record of which IP addresses have been allocated to clients, there is no chance of duplication. When a client computer subsequently shuts down, its IP address is returned to the pool of numbers back at the DHCP server for later reuse. This means that there’s no guarantee you’ll be given the same IP address each time your machine boots up but at least you will be the only one with the IP address that is assigned. This scheme has several other advantages. First, you don’t have to manually set a static IP address for each machine on the network. Second, you don’t have to maintain the lmhosts files across the network. And third, it makes it very easy to move a computer from one part of a network to another since it will ask for and be automatically assigned an IP address when it boots. OK, so that’s it in a nutshell. In practice, it’s a bit more complicated than that (it always is). Each time, the DHCP server issues an IP address, it does so for a set “lease” period. This lease period is configured at the server and can last for anything up to several days. During the lease period, the client computer contacts the DHCP server and requests that the lease be extended. If everything is OK, the server then renews the lease on the same IP address and restarts the clock. So what happens if the client computer is shut down and then rebooted during the lease period? In that case, the client remembers that the previous lease hadn’t expired and so it asks for the same IP address again. Because an IP address is reserved for a particular client for the duration of the lease, the DHCP server complies with the request and re-issues the address with the lease starting over again. If the lease expires, a new IP address is issued to the client the next time it boots up. Similarly, if the DHCP server is re­config­ured during the lease, the client’s request for an extension will be rejected and a new address will be issued. Setting up a DHCP server We won’t go into all the details of setting up a DHCP server here, although the procedure is fairly straightforward for a simple network. Basically, you need Windows NT Server or a Linux server to set up the service. This server must be given a static IP address (eg, 192.168.1.1). If you don’t have either of these operating systems, there are several shareware programs that let you set up a Windows 95/98 system as a DHCP server – see panel. In Windows NT Server, you install DHCP by first loading the Network utility in Control Panel, then clicking the Services tab, clicking the Add button and selecting “Microsoft DHCP Server” from the list and clicking OK. Fig.6(b): the DHCP Options dialog boxes let you specify the IP addresses of any other devices on the network, such as routers, WINS servers and DNS servers. In this example, we’ve added a router and specified its IP address as 192.168.1.2. 6  Silicon Chip Fig.7: a Windows 98 system is set up as a DHCP client as shown here. By selecting the option shown, the client will obtain a unique IP address from the DHCP server each time it boots. The installation routine creates a new shortcut labelled “DHCP Manager” in the Administrative Tools folder of the Start menu. Once the DHCP service has been installed, you then specify the Scope Properties. This sets the range of IP addresses that the server can hand out to clients for a particular subnet. Fig.6(a) shows the Scope Properties dialog box from the DHCP Manager on Windows NT Server system. In this case, the range of IP addresses that can be passed out to client computers starts at 192.168.1.10 and ends at 192.168.1.200. The lease duration has been set to one day. Other dialog boxes let you specify the IP addresses of other devices on the network, such as routers or WINS or DNS servers – see Fig6(b). By the way, if network reliability is critical, you need to install more than one DHCP server so that the network will still function if a server fails. In that case, you configure each server with a segment of the range of allowable IP addresses. These segments must not overlap, otherwise the system could issue the same IP address to more than one computer. DHCP client configuration Unlike the server side of things, Windows 95/98 and Windows NT Workstation computers can all be set up as DHCP clients without the need for additional software. Once set up, they will request an IP address from a Fig.8: configuring a DHCP client on a Windows NT system. The gateway address corresponds to a router (if it exists). DHCP server each time they boot. Fig.7 shows how a Windows 98 system is configured, while Fig.8 shows the settings for a Windows NT DHCP client. You get to the Windows 95/98 TCP/IP Properties dialog box by first double-clicking the Network icon in Control Panel, then double-clicking the TCP/IP entry for the network card. Make sure that the “Obtain an IP address automatically” option is selected if you want the machine to request IP addresses from the DHCP server. A Windows NT system is set up in similar fashion. Windows Internet Name Service (WINS) Often used in conjunction with DHCP, WINS is a dynamic database that’s used to translate NetBios names into IP addresses. Without WINS, name resolution takes place either by: (1) broadcasting a query over the network and asking a named computer to respond with its IP address; or (2) checking a local lmhosts file (if one is present). As mentioned previously, the first meth­ od can create a lot of unnecessary traffic and in any case, is limited to a local network segment. The second has all the administrative problems discussed previously. As with DHCP, WINS is provided with Windows NT Server. After set-up, client computers contact the WINS server each time they boot and register their name and allocated IP address. This means that a WINS serv- Getting It Together: The Software Required Windows NT Server will allow you to run any or all of these services; ie, DHCP, WINS and DNS. If you don’t have NT Server, consider Linux as an alternative, as you can run DHCP and DNS with the standard Linux or use WINS under Samba server. Linux is not yet for the faint-hearted, though. Be prepared for a steep learning curve and lots of manual text-mode configuration files. Windows 95/98 users should check out some of the shareware sites on the Internet for suitable software. These sites include www.download.com, www.winfiles.com and www.tucows.com One popular product is WinGate, which runs under Windows 95/98/NT and provides DHCP and DNS server capability. WinGate can also function as a firewall and as a proxy server, to allow multiple users on a network to connect to the Internet via a single modem. To find out more about WinGate, point your web browser to www.jantek.com.au September 1999  7 must select “Enable WINS Resolution” and manually enter the IP address(es) of the WINS server(s) on each client computer. Fig.10 shows how to do this. As with DHCP, it pays to have a more than one WINS server to ensure network reliability. Domain Name Server (DNS) Fig.9: here’s how to set up the WINS configuration on a Windows 95/98 client computer if you have a DHCP server. er automatically updates its database whenever computers are added to or removed from the network. When a client computer needs to resolve a NetBios name, it contacts the WINS server, which then hands out the IP address for that name. In effect, WINS is the dynamic equivalent of an lmhosts file. Because a client computer always attempts to contact a WINS server first for name resolution, the need for query broadcasts or lmhosts file checking is eliminated. Setting up WINS WINS is installed on an NT Server machine in exactly the same way as DHCP. After that, it’s a matter of config­ uring each of the client computers to use WINS for name resolution. If you’re also using DHCP, this can be used to supply the primary (and secondary, if it exists) WINS server address to client computers that ask the DHCP server for an IP address. This saves you from having to type in the WINS server address(es) on each of the client computers. Fig.9 shows how to set up the WINS Configuration on a Windows 98 client Fig.10: if you don’t have a DHCP server, you will have to enter the IP address(es) of the WINS server(s) on each client computer, as shown here. computer if you have a DHCP server. It’s just a matter of selecting the “Use DHCP for WINS Resolution” option. Of course, you must also use the DHCP Manager to supply IP addresses to the WINS servers and to hand these out to the clients. If you don’t have DHCP, then you Fig.11: Example hosts File For Windows 98/NT                127.0.0.1 192.168.1.1 192.168.1.20 192.168.1.40 192.168.1.80 8  Silicon Chip localhost lister.reddwarf.home rimmer.reddwarf.home starbug.reddwarf.home holly.reddwarf.home Oh, no! – not another naming system! Well, yes but this one’s somewhat different from WINS because it allows your system to look up, or “resolve”, a domain name (eg, www. microsoft.com) and translate this to an IP address. Currently, this would give you 207.46.130.14 as the IP address for Microsoft’s web site. In practice, this means that a web site on the Internet can be given a friendly address and you don’t have to worry about typing in its IP address. Instead, a Domain Name Server (DNS) looks up the IP address for you. You don’t have to worry about installing a DNS if you only wish to access the Internet, since this will be taken care of by your Internet Service Provider (ISP). However, you may want to set up a DNS if you wish to run a private intranet. Alternatively, if the network is only small and you are using static IP addresses, you can resolve domain names using a hosts file. This works in a similar manner to an lmhosts file (which resolves computer or NetBios names), except that you list the host names next to the IP address. Fig.11 shows a sample hosts file. Note that, as with lmhosts, you must select the Enable DNS option in the TCP/IP Properties dialog box for Windows 95/98. A similar situation applies to Windows NT. By the way, Windows NT server’s implementation of DNS allows direct look-up of the NetBios names from WINS. If this is enabled, it can make quite a powerful system whereby users are able to find others either by their NetBios name (eg, “Rimmer”) or by their Fully Qualified Domain Name (eg, www.siliconchip.com.au). Finally, this article should only be considered as an introduction to DHCP, WINS and DNS. TCP\IP addressing is really quite a complicated subject and you can buy complete textbooks on this topic. And, of course, it all becomes much more complicated when you throw in a SC dial-up adapter. The BreezeNet demonstration system came with an SA-10D Station Adapt­er, an AP-10D Access Point, an SA-PCR PC Card and several external antennas but you can order individual components to suit your special requirements. The laptop computer came from SILICON CHIP. Wireless networking without the hassles Designed for use in professional installations, the BreezeNET wireless networking system is a cinch to install and get going. You don’t need any special driver files with this system; you just plug it into standard network cards and hubs and it works. By GREG SWAIN Want to network different buildings in a school, a univers­ity campus or a factory? A wireless LAN (local area network) can make the job easy and often costs less than a conventional wired LAN. When you think about it, a wireless LAN has a lot of advan­tages. First and foremost is the fact that you don’t have to install cabling – a job that’s often frustrating and awkward (try running cable under concrete paths and roadways, for example). On the other hand, a wireless LAN can easily bridge the gap between computers, be they in different rooms, on different floors or in different buildings! Second, unlike wired LANs, your computers are no longer tied to a particular point. When you have a wireless LAN, they can be easily moved from one location to another. A wireless LAN even permits “roaming”, which can be very useful if you want to trundle a laptop around a warehouse or factory floor, for exam­ ple. Third, a wireless system makes it easy to connect addi­tional computers to the network, anywhere and at any time. All you have to do is connect the appropriate transceiver to the computer, configure it as for a conventional wired LAN, and you’re in business. BreezeNET PRO.11 The BreezeNET PRO.11 system is intended for professional installations. Unlike some wireless networkSeptember 1999  9 EXISTING WIRED LAN REMOTE WIRELESS LAN SA-40 HUB ACCESS POINT (AP-10) SA-PC SA-10 SA-10 ing systems, it’s easily connected to a conventional wired LAN (Ethernet) and is not restricted for use as a standalone system. This means that you could use BreezeNET to “connect” one or more computers to a conventional wired LAN, or to “connect” several individual wired LANs together. These wired networks could be on different floors of a building or even in different buildings, for example. You can also use BreezeNET to connect several wireless cells together and to connect these to a wired LAN. BreezeNET operates at 3Mb/s (maximum) in the licence-free 2.4GHz band and has a range of 50-200 metres in office environ­ments or about 600 metres in free air using the standard 2dBi external antennas. This increases to about 800 metres in free air using a 6dBi omnidirectional external antenna and to 2.4km with an 18dBi unidirectional antenna. Actually, it’s possible to push the range out to about 30km by employing booster amplifiers and low noise amplifiers (LNAs) to drive separate highgain transmit and receive antennas. These amplifiers and antennas are all part of the BreezeNET equipment lineup. Of course, when you’re talking about this sort of range, the services of WIRED ETHERNET ACCESS POINT 1 ACCESS POINT 2 ACCESS POINT 3 OVERLAPPING CELLS Fig.2: two or more access points can be positioned to create overlapping cells. This allows a workstation (eg, a laptop) to be moved across cells without losing its network connection. It also allows a workstation in an overlap area to communicate with two Access Points for load sharing and, if necessary, to extend network coverage. 10  Silicon Chip Fig.1: BreezeNet can be used to create a stand-alone wireless network or to link a wireless network to an existing wired LAN, as shown here. Each Station Adapter (SA-10, SA-40) plugs into a conventional network card which makes the system easy to set up. an RF engineer are required to ensure correct installation and compliance with regulations. In its most basic form, the Breeze­ NET system consists of an SA-10 PRO.11 Station Adapter, an AP-10 PRO.11 Wireless Access Point and the necessary antennas. You don’t have to open up the computers to install either of these units – they both plug into the existing Ethernet “backbone” using Cat.5 cable. In practice, this means that the PCs to be networked must be equipped with conventional network interface cards (NICs), exactly as for conventional wired LANs. And of course, it’s also necessary to install the relevant networking protocols (eg, NetBEUI, TCP/IP, etc), set up workgroups and computer names, and share drives and printers in the conventional manner. For laptops, you need the SA-PCR PRO.11 Wireless PC Card Adapter. This clever little device features twin retractable antennas and plugs into a PCMCIA Type II expansion slot on the laptop to provide mobile network access. Unlike the SA-10 station adapter, which connects to an existing network card, this device is the network card, as well as a radio transmitter. Connecting it up The SA-10 Station Adapter is connected to the PC’s network interface card (NIC) via a standard Cat.5 network cable. You can use one station adapter for each PC but if you have several machines close together, it makes more sense to use the SA-40 adapter. This is similar to the SA10 but it has four ports on the back, which means that it also functions as a conventional 4-port hub. Basically, the SA-40 allows up to four PCs to be connected to the hub to form a small wired LAN. It then provides these four stations with wireless access to a remote wired LAN and/or to other wireless stations. Wireless access points Each wireless network must have at least one AP-10 Wireless Access Point within its coverage area. The AP-10 manages the wireless LAN and is really the “brains” of the system. It keeps a list of known “wireless” stations and it deals with any messages it receives in several different ways (depending on the sources and destination of those messages). First, if a message that’s destined for a wireless station is received from the wired LAN, the AP-10 relays the message to that station. However, if the message has a destination address that it doesn’t recognise (eg, if the message is intended for another wired station), the AP-10 ignores the message. On the receiving side, if the AP-10 receives a wireless message that’s addressed to another wireless unit, it relays the message to that station without forwarding it to the wired LAN. And if it hears a message whose address it doesn’t recognise, it assumes that the message is for a station on the wired LAN and forwards it on accordingly. This might all seem unnecessarily complicated but it serves a very useful purpose: it minimises broadcast traffic, both on the wired LAN and at an RF level, and that means faster network operation. In operation, the AP-10 Access Point keeps a single address for each SA-10 station adapter and up to four addresses for each SA-40. These addresses are registered with the AP-10 when the very first messages are transmitted from the adapters. This means that the SA-10 won’t work properly if you attempt to connect it to more than one PC (eg, via a hub) or, in the case of the SA-40, to more than four PCs. In any case, the station adapters are not designed to plug into hubs; instead, they must be connected directly AP-10D WB-10D SA-40 SA-10 AP-10 AP-10 SA-PC SA-10 SA-PC Fig.3: the WB-10 PRO.11 wireless bridge allows LAN segments in adjacent buildings to be connected. These segments can be either wireless or wired, or a mixture of both. Ranges of up to several kilometres are possible, depending on the antenna system used. to the NICs in the PCs. By contrast, the AP-10 is designed to plug into a network hub. It can also be connected directly to a single PC but in that case you must use a Cat.5 crossover cable. By adding extra access points, the range of the wireless LAN can be greatly extended. Each access point covers a certain area (or cell) and by overlapping adjacent cells, the user is free to roam between them without network interruptions – see Fig.2. In operation, the stations within the cells choose the best Access Point to communicate with. They then automatically switch from one access point to the next as the user moves between cells. It’s also possible to co-locate several AP-10s to share the network traffic in heavily congested locations. The stations inside the common coverage area are automatically equally divided between the Access Points, so that the load is shared equally. Workgroup bridge What if you want to connect wired networks located in sepa­rate buildings or on separate floors? BreezeCOM have that covered too, in the form of the WB-10 PRO.11 Workgroup Bridge. This device plugs into the local network and transmits traffic to the second remote network via an AP-10 Access Point. In this way, a central LAN could be connected to one or more remote LANs; eg, on a university campus. Technical details By now, it’s obvious that a lot of technology is built into this system to ensure reliable and efficient wireless For laptops, the SA-PCR wireless PC card functions as both a network card and a radio transmitter. It features twin antennas which can be retracted when not in use, to prevent damage. September 1999  11 Both the SA-10 Station Adapter (left) and AP-10 Access Point can be fitted with dual-diversity antennas to ensure reliable radio communications. The receiver circuitry monitors the relative signal stengths from the two antennas and automatically switches to the antenna with the best signal. networking. So let’s take a brief look at some of the other technical details of this system. First, both the SA-10/40 and AP10 units are equipped with dual-diversity antennas. In operation, the receiver monitors the relative signal stengths from the two antennas and automatically switches to the antenna with the best signal. This technique effectively combats problems due to multipath propaga­tion and changing signal conditions (eg, when a user with a laptop computer moves about). BreezeNet also uses “Frequency Hopping Spread Spectrum” (FHSS) technology to eliminate interference from other equipment using this band and between adjacent units. The technology makes it virtually impossible for someone else to eavesdrop or to access an existing network using similar wireless LAN equipment. In addition, the system complies with the IEEE 802.11 Wire­less LAN standard which means that it can operate with other wireless LAN products which comply with this standard. Software setup The rear panel of the SA-10 Station Adapter has a single RJ-45 socket (the SA-40 has four). This connects via a standard Cat.5 cable to the network card in the computer. The monitor (MON.) socket allows the unit to be connected to the serial port of a PC so that it can be configured using the embedded SNMP (Simple Network Management Protocol) software. 12  Silicon Chip Although the BreezeNet PRO.11 wireless networking system operates immediately after installation, it’s best to change some of the internal settings. This is done for security reasons, as much as any thing else. In summary, you configure the Station Adapters and Access Points using the embedded SNMP (Simple Network Management Proto­col) software. This involves connecting the MON jack on the rear panel of each item to the COM port on the PC using the supplied cable and then running a terminal emulation program such as HyperTerminal. Each AP-10 Access Point on the Brief Technical Details Wired LAN Interface Compliant with: Physical Interface: Ethernet/IEEE 802.3 CSMA/CD standard. 10BaseT for AP-10 Access Point, SA-10/40 Station Adapters & WB-10 Wireless Bridge; PC Card Type II/ PCMCIA 2.1 for SA-PCR/PCD PC Card Adapters Wireless LAN Interface Compliant with: IEEE 802.11 CSMA/CA wireless LAN standard Radio Specifications Type: Frequency hopping spread spectrum (FHSS) Frequency Range: 2.4-2.4835GHz Antenna Diversity: Two antennas selected on a per packet basis Range 2dBi External Antennas: 50-200 metres from Access Point to Station Adapter in an office environment; about 600 metres in free air Other Antennas: 2.4km with 18dBi unidirectional antenna; up to 30km depending on external antenna and regulations Data Rate Over the air 3Mb/s, 2Mb/s & 1Mbs; 15Mb/s aggregate with overlapped cells (maximum number of co-located Access Points = 15) network must be given the same “network identifier” (ESS ID) or password. This prevents unauthorised access by third parties, unless they happen to know what the password is. Alternatively, you might want to separate two adjacent wireless networks by deliberately giving the Access Points dif­ferent passwords. In addition, you can set different frequency hopping se­quences for each Access Point, to minimise channel collisions, and configure a range of other parameters such as whether to use one or both antennas. Unfortunately, we didn’t get the chance to evaluate this aspect of the BreezeNET system, since we were supplied with a demonstration system only. This included an SA-10D Station Adapt­er, an AP-10D Access Point, an SA-PCR PC Card (for laptops), several external antennas, two plugpack power supplies and a manual. We plugged it in as directed and it all worked, just like that! The manual, by the way, is quite comprehensive and includes sections on Planning & Installing Wireless LANs (including multi­ ple-hop installations), Accessory Installation, Wireless LAN Concepts and Radio Signal Propagation. There are also tables showing the various antennas available and the expected ranges for various data rates (3Mb/s, 2Mb/s & 1Mb/s). Where to get it This 8.5dBi unidirectional external antenna gives a range of about 2.4km in free air. The price of all this technology doesn’t come cheaply but as previously pointed out, this equipment is intended for profes­sional installa- A comprehensive range of external antennas is available for use with the BreezeNet wireless networking system. This 6dBi omnidirectional antenna gives a range of about 800 metres in free air. tions. And in many situations, it will be far cheaper to install a wireless network (eg, to link buildings) than a wired network. You can expect to pay around $2030 for the SA-10 Station Adapter, $3010 for the SA-40 Station Adapter and $3640 for the AP-10 Access Point. For further information on the BreezeNet PRO.11 wireless networking system, point your web browser to: www.breezecom.com The equipment is sold locally by Namlea Data Systems, 22 Cleg St, Artarmon, NSW 2064. Phone (02) 9439 6966; fax (02) 9439 6965 or email: SC ndson­line<at>namlea.com.au September 1999  13 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.dse.com.au AUTONOMOUSE HEROBOT T   Pt 1: By JOHN CLARKE This clever little robot runs around the floor and stops if it finds anything in its way. It then turns to one side or the other and moves forward again. Light chasers run in one direction or another, depending on what it’s doing. 18  Silicon Chip Fig.1: the block diagram comprises three main sections: light sensing, forward/reverse motor control and the light chas­ers. A UTONOMOUSE THE ROBOT is autonomous – it runs around by itself without any need for its controller (you) to direct it in any way. It will “see” objects in its way and can turn away from them or reverse to avoid collisions. It also has a variety of light displays which vary according to its actions. Its features include: •  Forward and reverse light chaser. •  Clockwise and anticlockwise turning light chaser. •  Rear flashing light. •  Steers away from objects. •  Reverses from potential collisions. •  Adjustable speed. •  Adjustable sensitivity of object detection range. •  Object sensing immune to effects of normal ambient light. •  Automatic slowing before reversing to prevent motor/gear damage. Autonomouse the Robot moves on three wheels, with two at the front and a swivelling castor at the rear. The side wheels are independently driven to allow the robot to steer and reverse. Autonomouse is built as a basic shell using several PC boards soldered together. The two “eyes” are located on the front of the case and provide the robot with straight-ahead and periph­eral vision. It is dressed with red transparent acrylic on its front, top and rear. Autonomouse will steer away from an obstacle it detects with its peripheral vision. If this is not effective in avoiding the object, the robot will stop, reverse up and turn around. An object directly in front of the robot will cause it to reverse up and turn directly. When Autonomouse travels forward, a row of eight LEDs at the front flash sequentially from top to bottom to show the direction of travel. If Autonomouse reverses, the LEDs chase from bottom to top. At the top of the robot are eight LEDs arranged in a circle which sequentially chase clockwise or anticlockwise whenever it turns left or right. This chaser does not operate if the robot is going forwards or in reverse. Fig.1 shows the block diagram of the Robot. It comprises three main sections: light sensing, motor control and the light chasers. The light sensing section has a 38kHz driver which modu­lates infrared LEDs. There is an IRLED and sensor associated with each sensor, one for the right, one for the centre and one for the left. The IR sensors will detect infrared signals at 38kHz and reject any other light signals. This makes them much less sensi­tive to natural light or other September 1999  19 Fig.2: the circuit has several sections which are duplicated, such as the left and right motor drivers, the two 8-LED chasers and the left and right timers (IC2, IC4). 20  Silicon Chip September 1999  21 Fig.3: these waveforms show the operation of the 38kHz drive to the infrared LEDs. The top trace is the output at pin 3 of IC1 at 4V peak-to-peak. The lower trace is the voltage at the base of transistor Q1. Fig.4: these waveforms show the operation of the infrared detec­tors. The top trace shows the output from one of the infrared detectors in the presence of a relatively strong 38kHz IR signal. The output is low for most of the time. The lower trace is the infrared detector output in the presence of a weaker 38kHz sign­al. It is low for only some of the time. Fig.5 (left): these oscilloscope waveforms show the operation of IC8a which produces the pulse width drive for the H-bridge drive circuits to the motors. The lower trace is the triangle waveform at around 400Hz. This triangle waveform is compared with the voltage at pin 2, shown by the straight line. The output is the top trace which goes high whenever the triangle waveform is above the voltage at pin 2. light sources such as incandescent or fluorescent lights which produce a 100Hz modulated signal. When a sensor detects a 38kHz signal, it will produce an output to indicate that there is an obstruction in the way. The robot will steer left if it detects a relatively weak signal from the right detector and steer right if it detects a weak signal from the left sensor. If any of the detectors receive a strong reflected signal, the robot will reverse to avoid the obstacle. Output from the left sensor is used to trigger right timer IC2 and reverse timer IC3. Similarly, the right sensor output triggers the left timer IC4 and also reverse timer IC3. When a weak signal is received by the left infrared detec­tor, the right timer is triggered but there is insuf22  Silicon Chip ficient signal to trigger the reverse timer. A strong signal received by the left infrared detector will also trigger the reverse timer. Similarly a weak signal to the right detector will only trigger the left timer, but a strong signal will trigger the reverse timer as well. The right timer drives the forward/ reverse circuitry which controls the right motor. If the right timer is not triggered by the left infrared detector then the motor is driven in the for­ ward direction. The motor reverses whenever the right timer is triggered. The two LED chasers each comprise an up/down counter (IC10 or IC12) which drives a one-of-10 decoder (IC11 or IC13) which then drives eight LEDs. Reverse timer IC3 makes the counters count down rather than count up and this changes the direction of the LED chaser. Circuit description Fig.2 shows the full circuit details. IC1 is powered from a 6V battery via switch S1a while the other ICs are powered at 5V via low dropout regulator REG1. The motors are powered from a separate 6V battery and switch­ ed via S1b. We use two battery packs so that the heavy load drawn from the motors does not have any effect on the control circuitry. IC1 is separately powered from 6V to prevent its oscillation entering the 5V supply rail and being injected into the very sensitive infrared detectors IRD1 & IRD2. IC1 is a 555 timer running at 38kHz to drive the IR LEDs. The 38kHz output at pin 3 is clamped to an am- plitude of 0.6V by diode D1. This is done to maintain a constant signal level re­gardless of the battery voltage. Following D1, the signal is lightly filtered with the 3.3kΩ resistor and .0033µF capacitor and fed to trimpot VR2 which sets the signal level to transistor Q1 which functions as an emitter follower to drive the three IRLEDs via separate 470Ω resistors. The oscilloscope waveforms in Fig.3 show the operation of the 38kHz drive to the infrared LEDs. The top trace is the output at pin 3 of IC1 at 4V peak-to-peak. The lower trace is the voltage at the base of transistor Q1. Note that the vol­tage is nominally at +2.6V with a 360mV 38kHz modulation swing. Note that each IRLEDs is driven at a nominal 1.2mA which is then modulated at 38kHz. This is to make sure that the 38kHz signal from each LED is about the same. The infrared light from the three IR LEDs is picked up by infrared detectors IRD1 and IRD2. These comprise an infrared optotransistor, preamp­ lifier and 38kHz filter circuitry. A strong 38kHz infrared signal will cause the IRD output to go low. This is shown in the waveforms of Fig.4. The top trace shows the output from one of the infrared detectors in the presence of a relatively strong 38kHz IR signal. The output is low for most of the time. The lower trace is the in­frared detector output in the presence of a weaker 38kHz signal. It is low for only some of the time. The output from IRD1 triggers the right timer IC2 via the 27kΩ resistor and diode D2. Pin 2 of IC2 needs to be pulled below about +1.7V in order to switch the timer output at pin 3 to a high level. This means that the output from IRD1 must be low for more than 2/3rds of the time. IC2’s output stays high until pins 2 & 6 reach about +3.3V and then pin 3 goes low. The 1µF capacitor at pins 2 & 6 effectively integrates the output of IRD1. So pins 2 & 6 are pulled down by IRD1 and pulled up by the 390kΩ resistor. The output from IRD1 also triggers reverse timer IC3 via diode D3 but here the filter components at pins 2 & 6 are a 10µF capacitor and a 100kΩ resistor. These components mean that the output from IRD1 must be low most of the time in order to trigger IC3. In fact, if IRD1’s output were permanently low, the voltage at pin 2 Parts List 1 PC board, code 08409991, 114 x 145mm (Board 1) 1 PC board, code 08409992, 114 x 128mm (Board 2) 1 PC board, code 08409993, 114 x 72mm (Board 3) 2 motor/gearbox drives (Jaycar YG-2725) 2 4 x AA cell holders and battery snaps 8 AA alkaline cells 1 DPDT miniature toggle switch (S1) 1 plastic panel, 75 x 110 (battery support panel) 1 piece of double sided PC board, 114 x 69mm (rear panel) 1 piece of single sided PC board, 45 x 105mm (castor bracket) 2 35 x 20mm pieces of PC board (motor/gearbox mounting) 3 pieces of red transparent acrylic, 60 x 90mm, 60 x 140mm and 60 x 60mm 2 64mm diameter wheels (see text) 1 30mm furniture castor 12 15mm long tapped spacers (Perspex or Acrylic mounting) 6 9mm long tapped spacers (rear Perspex panel and motor mountings at motor end) 4 6mm long tapped spacers (motor mounts gear end) 26 M3 x 6mm screws 4 M3 x 15mm screws 5 M3 Nylon insulating washers (to insulate PC tracks for some screws and spacers) 1 5mm LED bezel 1 20mm length of 5mm black plastic tubing (IRLED1 & IRLED3 1 70mm length of 5 x 0.75mm sheet brass or equivalent (rear panel support) 1 500mm length of red hookup wire 1 500mm length of black hookup wire 1 300mm length of yellow hookup wire 1 300mm length of green hookup wire 1 300mm length of blue hookup wire would be +1.5V, just below the 1.67V threshold. This means the IRD1 must detect a very strong signal in order to stay low long enough to trigger IC3. 1 600mm length of 0.8mm tinned copper wire (links) 29 PC stakes 3 50kΩ (503) horizontal trimpots (VR1,VR3,VR4) 1 10kΩ (103) horizontal trimpot (VR2) Semiconductors 2 IRLED receivers (IRD1-IRD2) (Jaycar ZD-1952 or equival­ent) 3 5mm infrared LEDs (IRLED1IRLED3) 6 555 timers (IC1-IC4,IC7,IC14) 2 4030 quad 2-input XOR gates (IC5,IC9) 1 4081 quad 2-input AND gate (IC6) 1 LM393 dual comparator (IC8) 2 4029 4-bit up/down counters (IC10,IC12) 2 4028 1-of-10 decoders (IC11,IC13) 16 3mm red LEDs (LEDs1-LED16) 1 5mm red flashing LED (LED17) 1 LM2940-T5 low dropout 5V regulator (REG1) 4 BC640 PNP transistors (Q2,Q3, Q10,Q11) 4 BC639 NPN transistors (Q4,Q5, Q12,Q13) 10 BC338 NPN transistors (Q1, Q6-Q9,Q14-Q17,Q18) 14 1N914, 1N4148 diodes (D1D14) Capacitors 1 2200µF 25VW PC electrolytic 2 470µF 25VW PC electrolytic 14 10µF 16VW PC electrolytic 4 1µF 16VW PC electrolytic 4 0.1µF MKT polyester 1 .039µF MKT polyester 1 .0033µF MKT polyester 1 330pF ceramic or MKT polyester Resistors (1%, 0.25W) 3 390kΩ 8 2.2kΩ 3 100kΩ 3 1kΩ 2 27kΩ 3 470Ω 3 22kΩ 4 56Ω 22 10kΩ 4 22Ω 1 3.3kΩ Miscellaneous Double-sided adhesive tape. The timeout period for IC3 is 2.9 seconds and this sets the reversing time for the robot. The triggering time is also signif­icant; it takes one September 1999  23 Table 2: Capacitor Codes  Value  0.1µF  .039µF  .0033µF  330pF IEC 104 393 332 331 EIA 100n 39n 3n3 330p tied high, pin 12 must be low for pin 11 to go high and so IC5a operates as an inverter. With pin 8 tied low, if pin 9 goes high, so will pin 10 and so IC5b operates as a buffer or non-inverter. IC5c is set up as a timer. When its pin 5 goes high, pin 6 stays low until the 10µF capacitor charges via the 10kΩ resistor. Thus the output goes high for this period then goes low. Similar­ly, when pin 5 input is taken low, the output goes high again until the 10µF capacitor discharges via the 10kΩ resistor. This output controls the motor speed voltage at pin 2 of comparator IC8a via diode D10. It does this by momentarily pulling the 1µF capacitor voltage high whenever the output of IC2 changes. Pulse width modulation Comparator IC8a provides the pulse width modulation signal to drive the right motor. It compares the speed voltage at its pin 2 with the triangle waveform at its pin 3. The triangle waveform is generated by 555 timer IC7, operating at around 400Hz. If the voltage at pin 2 is low, the resulting pulses from the output of IC8a will be high most of the time (ie, wide puls­es) and the motor will run at full speed. By pulling pin 2 of IC8a high whenever the output of IC2 changes we effectively stop the motor before applying a reverse voltage. Fig.6: this is the component overlay for board 2. Note that the IRLEDs and IR detectors will be angled to optimise collision avoidance. second for the timer to be triggered due to the 100kΩ resistor and 10µF capacitor time constant. The reverse timer is activated when the robot encounters a solid obstruction that it has not been able to avoid by simple steering manoeuvres. IRD2 and IC4 operate in the same way as IRD1 and IC2. IRD2 also triggers IC3 via diode D4. IC2 drives IC5a, IC5b & IC5c via diode D6. IC5a, IC5b and IC5c are 2-input exclusive OR (XOR) gates. The gate outputs only go high when one input is at a different logic level to the other. Thus, with pin 13 of IC5a Table 1: Resistor Colour Codes  No.    3    3    2    3  22    1    8    3    3    4    4 24  Silicon Chip Value 390kΩ 100kΩ 27kΩ 22kΩ 10kΩ 3.3kΩ 2.2kΩ 1kΩ 470Ω 56Ω 22Ω 4-Band Code (1%) orange white yellow brown brown black yellow brown red violet orange brown red red orange brown brown black orange brown orange orange red brown red red red brown brown black red brown yellow violet brown brown green blue black brown red red black brown 5-Band Code (1%) orange white black orange brown brown black black orange brown red violet black red brown red red black red brown brown black black red brown orange orange black brown brown red red black brown brown brown black black brown brown yellow violet black black brown green blue black gold brown red red black gold brown SMART FASTCHARGERS® 2 NEW MODELS WITH OPTIONS TO SUIT YOUR NEEDS & BUDGET Now with 240V AC + 12V DC operation PLUS fully automatic voltage detection Use these REFLEX® chargers for all your Nicads and NIMH batteries: Power tools  Torches  Radio equip.  Mobile phones  Video cameras  Field test instruments  RC models incl. indoor flight  Laptops  Photographic equip.  Toys  Others  Rugged, compact and very portable. Designed for maximum battery capacity and longest battery life. AVOIDS THE WELL KNOWN MEMORY EFFECT. SAVES MONEY & TIME: Restore most Nicads with memory effect to capacity. Recover batteries with very low remaining voltage. CHARGES VERY FAST plus ELIMINATES THE NEED TO DISCHARGE: charge standard batteries in minimum 3 min., max. 1 to 4 hrs, depending on mA/h rating. Partially empty batteries are just topped up. Batteries always remain cool; this increases the total battery life and also the battery’s reliability. DESIGNED AND MADE IN AUSTRALIA For a FREE, detailed technical description please Ph (03) 6492 1368; Fax (03) 6492 1329; or email smartfastchargers<at>bigpond.com 2567 Wilmot Rd., Devonport, TAS 7310 The oscilloscope waveforms of Fig.5 show the operation of IC8a. The lower trace is the triangle waveform at around 400Hz. This triangle waveform is compared with the voltage at pin 2, shown by the straight line. The output is the top trace which goes high whenever the triangle waveform is above the voltage at pin 2. The left motor circuitry, comprising IC9a, IC9b, IC9c and IC8b, operates in the same way as just described and IC8b is fed with the triangle waveform from IC7. IC6a and IC6b are AND gates which have the pulse signal connected to one of their inputs; they control the right motor H-bridge circuit, depending on the outputs from IC5b & IC5c. The H-bridge for the right motor comprises transistors Q2-Q9. When IC6a’s output is high, Q6 and Q9 are on and they turn on Q2 and Q5 which drive the motor in one direction while transistors Q3 & Q4 are off. When IC6b’s output goes high, Q7 & Q8 are turned on and they turn on Q3 and Q4 to drive the motor in the opposite direc­tion. The lefthand motor H-drive circuit is the same as for the right and uses transistors Q10-Q17 controlled by IC6c & IC6d. Both H-drive circuits are powered from the 6V supply reserved for the motor drive and they are each decoupled with 470µF capacitors to suppress the voltage spikes which can occur with the pulsing of the motors. LED17, a flashing LED, is connected across the battery supply to provide further visual activity. LED chasers The forward/reverse chaser comprises IC10, IC11 & IC14 and LEDs 1-8. IC14 is a 555 timer operating at •  RESELLER FOR MAJOR KIT RETAILERS •  PROTOTYPING EQUIPMENT •  CB RADIO SALES AND ACCESSORIES •  FULL ON-SITE SERVICE AND REPAIR FACILITIES •  LARGE RANGE OF ELECTRONIC DISPOSALS (COME IN AND BROWSE) Ph (03) 9723 3860 Fax (03) 9725 9443 Come In & See Our New Store M W OR A EL D IL C ER O M E Board 2 sits on top of the unit, while board 1 sits beneath it and forms the base of the chassis. Board 3 is mounted vertically, at the front. ELECTRONIC COMPONENTS & ACCESSORIES Truscott’s ELECTRONIC WORLD Pty Ltd ACN 069 935 397 27 The Mall, South Croydon, Vic 3136 email: truscott<at>acepia.net.au www.electronicworld.aus.as September 1999  25 Fig.7: this diagram shows the component layouts for boards 1 & 3. Take care to ensure that the correct part is used at each location. about 16Hz to clock IC10 which is a 4029 4-bit up/down counter. This has its pin 9 connected to ground to select binary coded decimal (BCD) mode so 26  Silicon Chip that it counts up to 10 only. The up/ down input at pin 10 connects to pin 3 of IC3 which goes high when the robot is in reverse. Thus, IC10 counts down when the robot is going forward and counts up when reversing. The 4-bit outputs from IC10 connect to IC11, the BCD-to-decimal decoder, and it drives the eight LEDs in sequence. Why only eight LEDs when IC11 has 10 outputs available? Well, we have to let the bean counters have their way on some occasions so they got to eliminate two LEDs! The turning chaser comprises counter IC12, decoder IC13 and LEDs 9-16. The circuit is very similar to the forward/reverse chaser but there are some differences incorporated to enable the LEDs to be switched off and also to ensure that during the chase sequence, at least one LED is always lit. IC14 clocks IC12 which is set up as a binary counter with pin 9 tied high. Thus IC12 counts in a binary sequence from 1-8 and we use only three out­puts. The Q4 output from IC4 is not connected but we play around with the D input (pin 11) of IC13 to make it do what we want. Taking the D input high prevents any of the eight LEDs from lighting. This is because a high D input represents a count beyond 8 and we are only decoding the first 8 counts; any count over 8 will not be decoded and the LEDs will be off. So the D input is pulled high by the two 10kΩ resistors associated with transistor Q18. Q18 is turned on via diode D12 or D13 when either the left or right motor timers (IC2 or IC4) have a high output at pin 3 and so pin 11 of IC13 is pulled low. This starts the LED chaser sequence, because the low D input means that the robot is turning left or right. The direction of the chaser depends on the voltage at the up/down input at pin 10 of IC12. It counts up whenever the right motor timer (IC2) output is high. In this case, the up count means a clockwise rotation of the chaser since the LEDs are in a circle. If Q18 is turned on via the left timer output, then the up/down input is low and the counter counts down and gives an anticlockwise direction for the chaser. If the reverse timer, IC3, has a high output, then the D input to IC13 is pulled high via diode D14 and the LEDs go out. Construction Autonomouse is built on three PC boards: Board 1 is coded 08409991 and measures 114 x 145mm; Board 2 is coded 08409992 and measures 114 x 128mm and board 3 is coded 08409993 and measures 114 x 72mm. A piece of double-sided PC board (114 x 69mm) forms the rear panel. Fig.8: these are the full-size etching patterns for boards 1 and 3. Check your boards carefully before installing any of the parts. The three PC boards and rear panel board are soldered to­gether to form the robot body. The front, top and a section of the rear are covered in red transparent Acrylic or Perspex to house the LED chasers and flasher and are mounted on tapped brass spacers. The 6V batteries each consist of a September 1999  27 This view shows how Autonomouse goes together. The motor/gearbox assembly is mounted on board 3 (details next month). Fig.9: actual size artwork for board 2. 28  Silicon Chip 4-AA cell holder and these are mounted on a platform panel measuring 75 x 110 x 2mm which attaches to board 1 on tapped spacers. The battery holders are held in place with double-sided adhesive tape. The two motor/gearbox sets are located on board 3. They are located with metal standoffs and held with brackets made from pieces of PC board measuring 35 x 20mm. You can start construction by checking the three PC boards for defects such as shorts or broken tracks. Repair these if necessary before assembly. Note that board 1 requires a couple of notches in its front edge nearest transistors Q4 & Q12. The shape of the notches is marked out in the copper pattern and is necessary to allow clearance for the screws for the spacers on board 3. Figs.6 & 7 show the component layouts for the three boards. Insert and solder in all the wire links and PC stakes on the three boards. The resistors can be installed next, and you can use Table 1 as a guide to the resistor colour codes. Next, install the ICs, taking care to mount each in its correct position and with the correct orientation. Trimpots VR3 & VR4 should be mounted on the copper side of board 1 to allow adjustment when the robot is assembled. VR1 & VR2 are mounted on the top side of board 2 in the normal manner. The transistors and diodes can follow, again taking care with their orientation; don’t get the BC338s, BD639s and BD640s mixed up. The capacitors can be mounted next and note that the elec­trolytic types must be placed with the polarity as shown. Table 2 shows the relevant capacitor codes. All the red LEDs should be mounted with their tops about 12mm above the board. This will allow clearance for the red acrylic which is supported on 15mm spacers. The three infrared LEDs are mounted at right angles to the PC board by bending their leads over in a gentle arc (not with pliers). The two infrared detectors, IRD1 & IRD2, are mounted with 1mm of lead protruding from the copper side of the PC board; don’t shorten their leads. That’s all we have room for this month. In Pt.2, we shall complete the construction and tell you how to test SC your Autonomouse. Oatley Electronics Shop Now Open Fridays 1pm-4:30pm & Saturdays LOOK AT THIS 10am-4pm during September and October as a trial. On sale RG11 75ohm 250M rolls will be surplus and special sale items only. All regular advertised, E x t r e m e l y h i g h q u a l i t y catalogue stock and kits must be ordered in advance by Phone, COMMSCOPE brand. P/N Fax or E-mail and can be paid for and picked up at the shop. RG11QD. 13mm VERY low loss JUNE SALE!!! Did you miss it? Well you were not the only one!!! coaxial cable with 4 cores (2 pair) The ads were so small that most people missed them So we are going to run it again attached. Band-width better than as the Much BIGGER September Sale. To see just what’s on sale just check out the September Sale link on our new web page or if you have a polling fax you can 1Ghz. $60 per 300M roll see our text list of sale items on 02 95707910. But don’t forget our web page USA IEC MAINS LEADS $2 NEW SUPER LOW PRICE + LASER AUTOMATIC LASER LIGHT SHOW KIT: MKIII. Automatically changes every 5 - 60 secs. Countless great displays from single to multiple flowers, collapsing circles, rotating single and multiple ellipses, stars, etc. Easy mirror alignment with “Allen Key”. Kit inc. PCB, all on board components, three small DC motors, mirrors, precision adjustable mirror mounts: (K115) + very bright 650nM laser (LM2) module. Kit with laser module $55 Kit + laser module + plug-pack + instument style case all at a special price of $70 BARGAIN CORNER where we sell all of our regular specials like run out end of stock & special one or few of items like A portable medical X-Ray machine for $1500. SOLAR PANELS ARE BACK Quality SEIMENS brand Polycrystalline cells. Voc Isc 1W output. 4 panels req. $10ea. or 4 for $36 to charge 12V batteries. Specifications: Open circuit voltage: 5.7v...Short circuit current: 0.22A...Peak Power: 1.0W <at> 100mW/ sq cm...Dimensions: 160mm x 55mm x 5mm...Flying lead: Dual cable 25cm long. Should be placed under glass for outdoor use. NEW ULTRA-SONIC RADAR KIT + Just like the top European cars you can fit a reversing radar that will sound a buzzer or flash a + 4093 light on your dash to let you know when your car is + near another car or object. Inc. adjustable range + upto1M output to drive relay or buzzer. kit includes PCB plus all on-board components including MOBILE PHONE ANTENNA Ultra-sonic transducers and buzzer for $16 This antenna kit includes 4 meter terminated coaxial cable and external OVER $100,000 WORTH OF OFFICE NOW TRY OUR PROFESSIONAL PIC capasitively coupled on glass antenna SUPPLIES FOR ABOUT 1/4 OF RETAIL. MICRO PROGRAMER Complete installation kit with glass cleaner. Folders, binders, directory boards + Programs up to 39 different types of PIC lettering, cork boards, white boards large & chips, Software works under DOS, WIN 340mm long. $5 small, fabric boards, bulletin boards, notice 3.xx and WIN 95, Quick Easy construction, 12V Automotive Relays with 30A SPDT Contacts (73 ohm relay boards, instant signs, desk signs, flip Connects to Pc’s parallel port. Download coil). RRP $7. our price $3 ea. 4 for $10 charts + easels and more, Mostly quality fully functional evaluation software from ***NEW***WHITE LED 5mm 3500mcd. Quartet brand products. Sale to be held on the Internet Very bright Ideal for mini torch etc.... $4 our web site 14 Oct. & at a location to be register for a announced on 15 &16 Oct. in the small fee. More ***NEW*** Peakhurst / Mortdale area. Do your details on our web page 35-140 LED IR company / school a favour & tell your MASTHEAD AMPLIFIER KIT SPECIAL ILLUMINATOR KIT Purchasing Officer NOW!!! Based on a low noise (2.8dB noise figure) Switches on when it gets 240-110 ISOLATION TRANSFORMERS & wide bandwidth (2GHz) amp IC (MARdark or can be controlled by 500 VA, COMPACT METAL CASE, 6), this kit can be used as an active TV alarm system. Kit includes FUSED, MAINS LEAD. ONLY$80 antenna. The PCB is divided into two mount ing tray & universal sections. The PCB can be cut so that the swivel mount.35 LEDs $25. NEW MOSFET STEPPER DRIVER Extra 35 LED pack (3extra This kit is designed to work below 5V & supply board can be indoors. The MAR-6 packs max) $14 per pack. greater than 35V (higher voltage available separately $4. The amp140 LED kit:$67 Ideal for MOSFETS avail.)Very efficient (very little lifier produces good results with use with our monochrome heat) & work with software like DANCAD any two metal wires or strips actcameras to see in the dark. etc.(for step/dir-ection signals) & is ideal ing for the antenna. It should for CNC projects. It works well with the even work with a coatKEY-CHAIN LASER POINTER hanger! Basic kit with both in a presentation box. Quality stepper motors in our the PCBs & all on-board metal housing + 3X LR44 famous German parts (K03) $15 ...Basic Kit + /AG13 bats. FREE. printer $45 or$35 2 Weather-proof Plastic Extra bats. 50c Ea. with new or previous printer purchase Boxes + plug-pack: $24 Line lens+$0.80...X-hair lens N E W . . . P C M O T H E R B O A R D (ask for your free case with this item) +$0.80...Module (no case) only $8 UMC-486 CACHE ISA SX 40Mhz. Pointer not for sale in NSW. IRFZ-44...$2.50 Original package, 486-40Mhz CPU, book NICAD BATTERY PACK 60V/50A/0.028 ohm inc..., 5 X 16 bit & 1 X 8 bit slots, 4 X 30 pin Removed from equipIRF-540...$2.50 & 1 X 72 pin Mem. slots 220 X 170mm $18 ment for routine 100V/28A/0.077 ohm BUILD YOUR OWN COMPUTER maintenance. We can’t fault them. Some 4 IRFP460...$2.50 CONTROLLED 2/3 AXIS MACHINE some 6 cell. $0.20 / cell. Guaranteed! 500V/20A/0.27ohm using parts of our now famous $46 surplus CHARGER PCB (to suit above 6 cell IRF-820...$5 GERMAN PRINTER & CNC shareware packs) 7.2V trickle charger add $5 500V/2.5A/3.0 ohm (DANCAD) The printer is full of steppers, 16 X 2 LINE LCD CHARACTER toothed belts, pulleys, bearings etc (EA NEW AUSTRALIAN DISPLAY June 99). we have plans/notes for $9 (on PLUG PACKS AT BELOW + 1M IDC floppy) & links to find lots of info on the net . WHOLESALE PRICES ext. cable, TWO MOTOR LASER LIGHTSHOW KIT GENERAL ELECTRIC 20VA LED, buzzer Kit includes motors, mirrors, reversing 14VDC <at> 700mA..... & switch on $12 or 3 for $30 switch and all electronic components. Can AUDIOVOX 9V a PCB. be controlled with a variable DC input.Lots <at> 500mA TOLL FREE PHONE NUMBER of patterns, flowers, stars etc. $16 AUDIOVOX 12V <at> 400mA.... Sorry but we don’t have one but if Laser module to suit $8 you call 02-95843564 24hrs & (NEW) 12V / 2.3Ah AUDIOVOX LEAD $5 Ea. or 5 for $20 KIT SPECIAL leave a message & your number ACID BATTERY (Model BTR-1900). FM FM Priced at a fraction of their real value (as TRANSMITTER TRANSMITTER FM TRANSMITTER MKII we will call you back ASAP at our used in video cameras & older mobile MKII KIT / RADIO MIC. Has cost. (ORDERS ONLY) phones - same as Panasonic batteries we good range & stability & sold before). 180 (L) x 60 (H) x 22 (W) mm, can be con-figured as a 0.67Kg, made in Japan. The contacts hand held mic, lapel mic PO Box 89 Oatley NSW 2223 (which are easily solderable) are at one or musical instrument Ph ( 02 ) 9584 3563 Fax 9584 3561 end of the battery. 2 batteries + suitable transmitter. Kit includes orders by e-mail: oatley<at>world.net 500mA float PCB, all onboard com88-108MHz 88-108MHz www.oatleyelectronics.com charger. ponent, suitable small major cards with ph. & fax orders, case & lapel microOATLEY OATLEY Post & Pack typically $6 ELECTRONICS ELECTRONICS (02)-95843563 (02)-95843563 phone with clip. just $17 Prices subject to change without notice $16 $55 $25 $25 MOSFET BARGAINS $10 OATLEY ELECTRONICS $20 OATLEY ELECTRONICS OATLEY ELECTRONICS ***SUPER SPECIAL*** B R A N D N E W PA C K A R D B E L L KEYBOARDS. Top quality Packard Bell computer keyboards for just $12 Ea. We don’t have enough space here for all of our kits. Most of our old kits are still active. Just check our web site to see our full range of kits & products. *** FANTASTIC BARGAIN *** COMPUTER POWER SUPPLY PCB: New PCB assembly. Dimensions are 45 x 108 x 200mm. Switchable 120/230V AC input. DC outputs are +5V<at> 6A,+ 12V <at> 1A,-12V<at>1A,-5V<at>1A. Data Inc.RU approval. Mains input . Be Quick: (Ps6) . 4 for $20 U S 11 0 - 9 V D C P L U G PA C K S UL listed, In a Screw together case that could be used for other projects, with rectifier and electrolytic cap. 5 for $4 PELTIER EFFECT DEVICES Make a solid state food cooler / warmer for the car etc. with 2 heatsinks, a fan and one of the following. Could be used for cooling overclocked PC CPUs. All 40 X 40mm. 4A T 65deg. Qmax 42W $25 6A T 65deg. Qmax 60W $27.50 8A T 65deg. Qmax 75W $30 Comes with info to build cooler / heater plus data. Some used heatsinks avail. BASIC PIC MICRO PROGRAMER JUST Learn program your own 16F83 /16F84 /16C84 micro-controllers the easy way with this simple kit that just plugs in to your Pc’s printer port and uses these small, cheap but powerful chips. Kit inc. program examples and notes PCBs, all on-board components, Db25 connector and a PIC chip ready to program. An incredible bargain at just $29 Software available free to Download From our web page ***NEW***NEW***NEW*** DING DONG DOOR BELL KIT Kit inc. Chip on-board type PCB plus speaker, push button, (( ((( ))) )) ) ( Battery holder, enough wire up (((((( )))))) to run 24 Meters & new surplus case. Ideal for commercial or domestic extension bell $10 UHF AUDIO / VIDEO TRANSMITTER KIT Kit includes all components needed...... PCB plus all on-board components, connectors, switch, metal case, telescopic antenna, twin RCA A/V lead, all that is needed to complete the full kit. 12Vdc <at>10mA operation. Ideal for transmitting audio and video around you home.. Complete suitable Kit for just $25 plugcack $5 AT LAST! A COLOUR CMOS CAMERA WITH GOOD RESOLUTION + BUILT IN AUDIO + FREE PLUG PACK + F R E E V H F M O D U L AT O R . Available with swivel mount or dome mount housing. $29 ( DIN ) (( DI DING NG G )) ( O ) ((D NG DONG N G)) DO DOOR BELL OATLEY ELECTRONICS $160 No Audio $160 BNC connector (video), DC connector (power), RCA connector (audio). 330000 pixel. 330 TV line res. 7-12Vdc 55mA max. INTRO PRICE $160 ** CCD CAMERA SPECIAL ** WITH A FREE VHF MODULATOR The best "value for money" CCD camera on the market! 0.1 lux, High IR response & hi-res. Better than most cheaper models. 32 X 32mm $99... With 1of these lenses pinhole (60deg.), 92 deg.; 120 deg. or for (150 deg) add $10 SC-SEP-99 SERVICEMAN'S LOG Hindsight is a wonderful thing When it comes to servicing equipment, it’s sometimes all too easy to accidentally create an additional fault – one that often doesn’t appear until after the job has gone back to the customer. Such was the case with two of my stories this month. It is a chastening fact that despite doing everything one can possibly do to get something absolutely 100% right, it lets you down at the critical moment. A friend’s wife, Patricia, had 30  Silicon Chip picked up what looked like a bargain in a garage sale. It was a white Sharp R-2A55 Carousel microwave oven with touch controls and a cooking sensor – all for only $70. Unfortunate- ly – and inevitably – there turned out to be a catch . . . it didn’t work! I was called in to check it. When I removed the covers it was all too obvious that this wasn’t the bargain of the century. The whole thing was a mass of panicking cockroaches. Fortunately, I was able to get the whole thing outside before too many had fled into the workshop. There then followed an unpleasant half hour of spraying insecticide and cleaning up the damage their excreta had caused. The fuse was blown and the protection diode and capacitor were short circuit but the death knell for the viability of this oven was the touch switch pad (key unit) which didn’t work eith­er. I discovered this only after I had to purchased the service manual ($35.50) and established which of two connectors needed to be joined to reset/clear the flashing display. My reasoning was that if I could operate the oven without the touch pad, I could eliminate the microprocessor as the cause of the trouble. But the switch pad was the stumbling block; it would cost $65 and what with all the other items, including a missing plate and display window, the estimated cost (trade) came to a shade over $200. On this basis, the project had to be abandoned, which left Pat without an oven. Luckily, I had an old but otherwise immaculate Toshiba ER-562ETA oven, surplus to requirements. This somewhat more modest oven hadn’t been used for years but after checking it out, it proved to be in good working order. And so I offered it to Pat with a 12-month warranty for $70 (at least that would partly cover me for the expenses involved in working on the other one). Her husband picked it up and said he could install it and I thought no more about it – at least not until he casually men­tioned at a social gathering a week later that when he got it home, it didn’t work. Of course, I was rather embarrassed about this, espe­cially as this was a trigger for the other members of our group to voice their shonky secondhand technician stories. There was nothing for it but to eat humble-pie until I had it back in the workshop to investigate what had gone wrong. What’s cooking As I said earlier, this was a very simple oven consisting of a heat/defrost switch, a rotary timer and a start button. And sure enough, everything was dead. The cook light didn’t illu­ minate when the start button was depressed and neither did a fluorescent tube (with the end connectors removed) or a glass of water indicate any microwave activity. I removed the cover and examined it. Everything looked in order. The fuse was OK, the oven light came on and, with it disconnected and the capacitor discharged, the diode measured OK. Interestingly, the start switch is not a simple switch; it is a spring loaded plastic lever connected to a lower door interlock relay and at first, I couldn’t quite understand how the magnetron circuit is switched on. The fundamental circuit of a microwave oven is very simple. It consists of a 240V power transformer which has a filament winding and high voltage secondaries which feed the magnetron. The cathode is connected to the high voltage via a capacitor and an asymmetric rectifier diode. The whole lot is switched fully on or off via the timer, by applying 240V to the primary. From this, I not only found out how the oven was switched on but in the process, why it had failed. The lower interlock lever on the oven door depresses the relay to the “on” position, when the start lever allows it to do so. Or that was what was supposed to happen. However, this oven hadn’t been used for a very long time and the lower Items Covered This Month •  Toshiba ER-562ETA Microwave Oven •  Akai CT2105A TV Set •  Mitsubishi HS-M54(A) VCR •  Panasonic NV-HD100 VCR •  Akai CT-2868 TV Set lever, which is spring-loaded, wasn’t returning to its normal position. And it wasn’t doing so because its lubricat­ing grease had hardened. A small squirt of CRC 2-26 on its axle and a little working back and forth restored its function imme­diately. I returned the oven and demonstrated it to Pat that same afternoon. However, I don’t think that this is the last of the innuendo I will cop from my “mates”! Blue Akai Jim Makim is a 68-year old retiree and a nicer man it would be hard to find – intelligent and articulate. In his younger days, mainly during the valve era, Jim was an electronics engineer and so could understand a lot about his set and its symptoms. His Akai CT2105A decided to go all blue and so Jim asked me to call. He would have delivered it himself but he was due to have an operation shortly and so decided against it. It was obvious that the voltage on the blue cathode of the CRT was low, causing it to go blue, but was it due to a heater cathode short or to a problem on the video output? The easiest way to check this was to remove the blue drive transistor (C505, 2SC2482). If there was no blue with no transistor in (which was what happened) the problem was unlikely to be heater cathode. Next, I swapped this transistor with the one from the red amplifier (C503) but no change. I then disconnected the drive from the main board to the blue output transistor on the CRT socket and no blue was displayed. I now felt sure that the prob­lem was not on the CRT socket but on the motherboard, mainly the drive from IC301 AN5601K. Rather than take the whole set back to the workshop, I removed the motherboard and CRT board and took them with me. I then checked all the components associated with the blue amplifi­er. There was a lot of silicone rubber compound on the board which may have corroded them but they all measured OK. The only thing that I couldn’t check was IC301 on the moth­erboard, which I now felt was the most likely culprit. I ordered a new one and made another visit when it was ready. I plugged it all back together, fully confident that I had fixed the problem but no such luck. I was mortified (again!) to find that the fault was still there. There was September 1999  31 Serviceman’s Log – continued Fig.1: the CRT board circuit for the Akai CT-2105A colour TV set. The blue drive transistor (Q505) is at extreme right, while the red transistor, Q503, is at extreme left. The blue signal comes in on pin 3 of connector CN301. Resistor R513 is circled in red. nothing for it but to return to the workshop with the whole set. Fortunately, another identical model set had just come in for a different problem, so I removed the CRT board and swapped it over. This fixed the fault, restoring the blue function completely. So what had I overlooked? Well, ridiculously enough, I have had this fault before, on early Samsung models. But because of the way I had tackled the problem, I had forgotten the cause. The component that was faulty was R513, a 12kΩ 2W resistor feeding C505’s collector from the high-voltage rail, which had gone very high. So when the blue transistor was turned on, the collector voltage dropped too low and turned the blue gun hard on. If I had checked the base voltage of the blue output tran­sistor after swapping it with the red output transistor, I would have found it to be correct. However, this wouldn’t have picked up the fault in the collector circuit. Jim was most understanding of my faux pas. The leftover part I have recently taken on a young casual assistant, Tom. He is doing 32  Silicon Chip a technical course and is seeking as much practical experience as he can get. He is getting on very well and although he has been mainly involved with audio repairs, he also dabbles with video equipment. In my experience, audio technicians often make better VCR technicians than those with exclusive backgrounds in television. They tend to have a better understanding of electromechanical interfacing. I was out doing a service call when Mrs Thomas brought in the family Mitsubishi HS-M54(A) VCR with the tape jammed inside. It was fairly urgent as Mrs Thomas needed to return the tape to the rental store as soon as possible to avoid late fees. Tom obliged by removing the tape for her but Mrs Thomas brought the VCR back a day or two later complaining that it wouldn’t rewind. This time the job fell to me, as Tom was at college that day. There was a note in Tom’s writing taped on top of the VCR, saying that it wouldn’t rewind, together with a piece of white plastic that had been found inside the machine. I removed the covers and examined the video deck which is a Mitsubishi Fo chassis Series 3. There appeared to be nothing untoward and I could see that the main pinch roller assembly had already been replaced. I made sure that the shaft was well lubri­cated and that all the other functions were working. I did notice, however, that the tape cassette was intermit­tently catching on the lefthand side as it went in and down but I didn’t put much store on that. The deck could fast-forward nor­ mally, so why wouldn’t it rewind? The idler looked fine and I confirmed that it could rewind with a dummy test cassette in the machine. The supply reel had lots of torque, the brakes were off and the take-up reel was free. Yet when a proper tape was inserted, it wouldn’t rewind at all. There was no friction worth writing about from the opposite reel, nor was there any along the tape path, with the tape wrapped around the head drum. So the problem only occurred when a real tape was used but it worked fine with the dummy. It had to be something to do with friction between the cassette and the driving wheel hub. Why is it catching? By this time, I was becoming infuriated with the cassette catching on the lefthand side as it went down and so I decided to take a closer look. The only way to find out what was causing this was to remove the ejector and run it in and down by hand, so that’s what I did. But I could find no reason at all why the ejector should be sticking. There was no friction that I could feel and so, ex­asperated by all this, I decided to fit the ejector back in the deck. This isn’t nearly as easy as taking it out and requires a bit of a deft hand and experience to install it. Basically, one has to angle it down slightly at the front, to engage two tongues with locating lugs on each side, and then push it down and forward at the same time, using a long thin screwdriver to locate the loading gear into its well. If all goes well, the ejector will line up with the screw mounting holes at the rear. The first time I did this, I used a lot of force to line up the holes and when I tried loading a cassette it was still catching and not rewinding as before. It still worked OK with the dummy tape cassette, though. By now, I was beginning to get an idea as to what was caus­ing this, so I took an old tape, unscrewed the case, removed the two spools inside and reassembled it. When I loaded this, it was easy to see what was happening. The cassette went in easily but when I looked at it from the top, I could see that the spool wasn’t in the centre of the hole in the cassette housing. Instead, it was displaced towards the rear but it could turn on engaging rewind. I removed the doctored cassette and removed the ejector again. This time, I reinstalled the ejector more carefully, without using any force, ensuring in the process that all four anchor points were lined up as well as the loading gears – as per the service manual. Now when I put the tape cassette in, it lined up exactly in the centre of the hole. And that solved the problem. When I tested it with a real cassette, I found that it would now go in and rewind properly. It wasn’t until Tom came back the next day that the mystery was completely solved; only then did I learn that he had removed the cassette housing to remove the faulty tape. I tested the machine thoroughly to make sure it wasn’t responsible for damaging the hire tape but it performed fault­lessly through many operations, with different tapes. Finally, one might ask where did the piece of white plastic come from? Unfortunately, I haven’t a clue – I couldn’t find any gears broken or chipped and can only conclude that it came from the hire tape. The Panasonic VCR And now for a couple of less traumatic episodes. I thought Mrs Laruso’s VCR was going to be a doddle. She described her Panasonic NV-HD100 VCR as having an intermittent problem in which the mechanism would stick between various play functions. The common cause of this problem is the loading motor coupling. This coupling splits, then slips on the shaft on which it is normally a press fit. It was one of those busy days and my mind was preoccupied with other things, so I worked on it in a sort of automaton mode. I had done a few of these so it wasn’t difficult. It involved completely removing and replacing the deck and loading motor assembly but I soon had the job completed. The machine performed like a bought one and I handed it back to a suitably grateful Mrs Laruso after demonstrating it performing its tricks. I thought nothing more of it for a couple of weeks until Mrs Laruso brought it back in. This time, she was complaining that the eject mechanism was going back and forth and turning the VCR off without fully accepting the tape. She could insert the tapes but they were spat out again almost straight away. This was different. In order to accept the tape, the cas­sette pushes a lever across the right­ hand photocoupler and the mech­ a nism senses that it is down when both end sensors see light from the centre LED source. By maintaining an even pressure with my hand, I could push a cassette to the bottom of the ejector assembly and get the deck to load the tape around the head. All play functions worked but I noticed when the tape came to the end that the machine did not stop immediately, implying that the end sensor wasn’t working. When I rewound it to the beginning of the tape, it also didn’t stop immediately. As it was unlikely that both end sensors were faulty, my suspicions turned towards the centre LED. With the tape in fast forward, I could cause it to stop and rewind by shining a torch onto the left end sensor and, similar­ly, stop it by shining the torch on the right sensor. I removed the deck once more and checked the LED sender. It was OK and activated a remote control infrared tester. And by very carefully suspending the deck upside down, while still connected to the rest of the VCR, I measured the voltage across the LED – there was nothing. With an incredible amount of patience and a lot of time, I traced (without a circuit) the power source to the LED through the connectors and onto the main PC board, until finally it came to an unmarked surface mounted resistor alongside a screw near the front – and then the whole mystery fell into place. When I repaired the original fault, I had replaced the original Panaso­nic screws, including one which has a head with a flange on it. This screw did not belong there; the diameter of the flange was oversized for this location. And I had carelessly fitted it so that it hit this resistor and cracked it, thus breaking the voltage supply for the LED. Fortunately, I could read 211 on one part of the resistor, which I interpreted as 210Ω but I measured it to be 200Ω. I fitted two 100Ω resistors and the correct screw to get me back to where I’d been two weeks earlier. The moral of the story is to place the screws into contain­ers, so that one reassembles them in the exact reverse order to which they were removed. Anyway, I wasn’t about to admit to Mrs Laruso that my carelessness had wiped out all the profit I had made out of the original repair – and then some. One just has to put it down to experience. The Akai TV set Mrs Clyde’s Akai CT-2868 AT TV set was still under warranty and because it was 72cm set, it required a service call. The problem was that it had a vertical hold that wouldn’t lock – intermittently! As there is no external vertical hold control, I was fairly sure it was just faulty reception. If there is serious ghosting and it is spaced at the appro­priate distance apart, it can confuse the set so that September 1999  33 Looking for an old valve? Serviceman’s Log – continued or a new valve? BUYING - SELLING - TRADING Australasia's biggest selection Also valve audio & guitar amp. books SSAE DL size for CATALOGUE ELECTRONIC VALVE & TUBE COMPANY PO Box 381 Chadstone Centre VIC 3148 Tel: (03) 9571 1160 Fax: (03) 9505 6209 Mob: 0411 856 171 email: evatco<at>mira.net 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 it doesn’t know which vertical sync pulses to lock onto. Some earlier sets had additional modules that could be fitted, to help the set decide which pulses to select. Of course, when I arrived her set was going fine and I confirmed that the reception was ghost free. It was 34  Silicon Chip only then that she told me that it took up to a couple of hours before it misbehaved. Why didn’t she switch it on much earlier? I told her there was nothing I could do then and there but I would call back later after my next job a few streets away. In the meantime, I asked her to leave the set running. Fortunately, it was faulty when I returned but the only clue I had was that it was probably a temperature sensitive component. But it was not a job I could do in the home – it would have to come back to the workshop. When the set was finally plonked on the bench, I tackled it with an array of hairdryers and freezers. Gradually I managed to isolate the problem to several components near IC302, especially two tantalum capacitors C331 (pin 34) and C333 (pin 33), but replacing these made no difference. I also replaced electrolytic capacitors C340 and C341 on the 12V feed (pin 29) to the IC but there was still no difference. The preset vertical hold (VR303), zener ZD301, capacitor C332 and diode D306 were also all ul­timately cleared of guilt. I was beginning to feel unhappy about R351 (180kΩ), as it was very sensitive to heat and cold – but that could have been due to the frost and moisture condensing on the outside. First, I measured it in circuit with a Philips PM2505 multimeter and it read high. I then measured it again and it checked OK. By now I was thoroughly suspicious, so I unsoldered one leg and remeasured it more carefully just in case diode D308 was affecting it. When I put my prods on it, it measured exactly 180kΩ but when I re­peated the measurement a short time later, it read 250kΩ. How could this be? I repeated the procedure several times using crocodile clips (so that my fingers didn’t affect the measurement) and amazingly it measured 180kΩ one way and 250kΩ the other way. I won’t attempt to explain this phenomenon but enough was enough. I fitted a real resistor – one that measured 180kΩ both ways – and that fixed the fault. I can only surmise the resistor had gone high – for whatever reason – and the heat from the iron had made it good again but I leave all the speculation to you, and yes, I was SC sober when it happened. Teach it to recognise YOUR voice! VOICE DIRECT Speech Recognition By Ross Tester As you are reading this, a spacecraft is speeding towards Mars. It will make a “soft” landing in just a few weeks. One of its scientific experiments will be to listen for, and learn any sounds made on the planet. That task will be undertaken by a very similar chip to that used in this project! September 1999  35 SEPTEMBER 1999  35 S ome projects appear so simple, yet the underlying technology is not only state-of-the-art, it’s difficult to believe. This is one such project: a voice recognition module which actually learns words, in your voice, and then recognises them when asked to do so. Think about that for a moment. The chip is not simply recognising an inbuilt vocabulary, though that is no mean feat in itself. It’s actually recognising words which YOU teach it. The words don’t have to be English. In fact, the words don’t have to be words in the true sense at all. They can be sounds. They can even be complete gibberish, just so long as the chip can recognise them and learn them. That’s one of the reasons it was chosen for the Mars project. Just imagine if they do find little green men up there – they’re not likely to have learnt the Queen’s English, are they? Seriously, though, if there are sounds to be heard, the chip will learn them. (If you’d like to know more about the Mars Microphone probe, check out the website www.sensoryinc.com/ html/mars.htm). Now, back to this amazing technology and our project. It’s all done with a purpose-designed module from Sensory, Inc, of the USA. This module, measuring just 50 x 50mm and containing a couple of ICs and a few surface-mount devices, is capable of learning, and then recognising, virtually any word – with Front (left) and rear (right) of the Sensory Inc. “Voice Direct” module, shown actual size. a few provisos such as the words not being too similar. For instance, it shouldn’t have a great deal of trouble with cat and cart but cat and mat might give it some angst. But more on this later. All that is required is the connection of power (5V DC), an electret microphone, a speaker and three switches and the module is ready for operation. In this mode, shown in Fig.1, it will ask you to say a word and then repeat it. If you say the word the same way twice, it will then ask you for the next word, and so on, up to 15 words in total. If you only want, say, three words, you simply do not respond when it asks for the fourth word and the learning mode is then terminated. When you push the “recognise” switch, it asks you to say a word. If your word is in its vocabulary, it responds by sending one of its outputs high. What you do with that output is entirely up to you. Fig.1: Sensory Inc’s suggested circuit which will recognise three words and flash a LED. We used this as a starting point for our experimenter's board. 36  Silicon Chip Just think of the applications: do you want the TV set on, or the channel changed? You can TELL the module which channel you want! Or you walk into a lift and instead of pressing a button, you tell the lift which floor you want. The lift then whisks you to your floor! The possibilities of such a system are endless! How about a robot which comes out to serve you in the restaurant, recognising your order by what you say? Gee, you could even send a system into space and land on another planet – Mars, for example. It could listen for sounds, learn them, recognise them – and maybe turn on a transmitter and tell us back on earth. . . Oh, someone has thought of that one already? Yes, it really is out of this world! The experimenter’s board As you can see from the photographs and main circuit, we have developed an experimenter’s PC board to go with the speech module. Let’s explain why. The user manual which accompanies the module suggests a circuit which lights LEDs when it recognises a word. However, they only suggested three LEDs. But we thought “there are 15 words, so why not 15 outputs?” It isn’t quite that simple, because only eight of the word outputs have their own output pins. The last seven require decoding, using combinations of the other outputs. So we added a couple of low-cost AND gates to provide all 15 word outputs. The manual also suggested a 4.5V power supply using three 1.5V batteries. But it also says that low battery levels will degrade performance. For the sake of a cheap 5V regulator and a couple of capacitors, we sidestepped that problem. You can use a 12V plug- pack supply without worries. Now that we had 12V available, we thought it would be a good idea to provide a relay output and driver, just in case you had something you wanted to control. Naturally, this (just like the extra decoding) is entirely optional – if you want to save a little money, you can leave them off. Some parts which aren’t optional, though, are the microphone, the speaker and the three pushbutton switches. These are, as you might expect, essential for setting the mode, teaching the module and recognising the words. Because we had now decided to put all this on a printed circuit board, we decided to mount the speaker and mic on-board and use PC board-mounting switches as well, making the whole thing self-contained. Now, how to mount the module itself? Sensory suggest using standard 0.1in header pins to make connection, as all connections to the module are brought out to holes on a standard 0.1in grid. We took advantage of this to mount the board by duplicating the rows of holes, allowing the module to simply drop over rows of header pins mounted on our PC board. From there, it was a simple matter to solder the pins to their appropriate connections – it’s impossible to get the connections wrong. (But you can bridge between adjacent pins so you have to be very careful and use a clean, fine-tipped soldering iron). As you can see, we also added two extra rows of header pins to enable connection between the word 1-8 outputs and the decoding circuitry. As output 8 is always part of the decoding, this was wired directly on the PC board. One other pair of header pins was installed on two pads which are actually shorted out. This might seem a little strange but these pins can be used to select a “slave” mode of operation if the copper between them is cut. Again, you may care to leave these pins out. All of the electronics are on a PC board measuring 160 x 118mm. Power connection to the board is made via a 2.1mm DC power socket (so it will suit most plug packs). Polarity is the “standard” centre positive but Above: the SILICON CHIP experimenter’s board ready for theVoice Direct module. The lower row of LEDs light when words 1-8 are recognised. With suitable connections the upper row of LEDs light with words 9-15. Below: with the Voice Direct module fitted. because there really is no standard, a series diode will prevent catastrophes if power is connected with the wrong polarity. A resistor and LED between +12V and 0V will show that power is on and also connected the right way around! Construction Start with the resistors. Once these are soldered in place (particularly the ones in series with LEDs), the chances of making an error in placing other components are significantly reduced. Next, solder the 9 PC pins in place. The two power diodes, small (bypass) capacitors and the two wire links complete most of the low profile components. Now move on to the semiconductors: all of the LEDs except the “power on” LED are oriented with their cathodes (marked by a flat on the body and a shorter lead) towards the edge of the board. How far down you mount the LEDs is up to you – we left about 5mm between the top of the board and the LED body. September 1999  37 You could solder them in anywhere from flat down on the board to standing full length upright (the latter has the advantage of being able to be used again in another project). The 5V regulator is mounted with its flat side towards the edge of the board and both electrolytic capacitors have their negative sides towards the edge also. The two ICs have their notched end (or the dot marking pin 1) towards the middle of the board. When mounting the switches, ensure that their flat sides also go towards the edge of the board, like the LEDs. The relay cannot mount incorrectly – it has eight pins and they only fit one way. Likewise, the DC power socket must be correct with its three pins in a triangular pattern and the opening towards the outside of the board. About all that are left are the microphone and speaker, along with the header pins which mount the module. First, the electret microphone insert. Take a look at the two pins on the rear: one of the two is connected to the case and this pin goes into the hole closest to the regulator. The speaker is mounted by two short lengths of tinned copper wire connecting the speaker terminals to the appropriate PC pins. We made our speaker more secure by putting a dab of super glue gel on the back of the speaker, securely holding it to the PC board (double-sided adhesive foam tabs would be just as effective). Finally, we come to the header pins which are used to mount the Voice Direct module. We used two 25-pin headers which gives 50 pins – exactly the number required to fill all the holes on the board. In truth, this is a bit of an overkill because in this application only 22 of the pins are actually needed to connect to the board. However, we filled all 50 holes on the base PC board with header pins and soldered only those required – 19 along one edge and three adjacent. Because the header pins come in 25-pin strips, you will have to cut them (a pair of sharp sidecutters is fine). Cut a 19-pin length from one strip and an 18-pin length from the other – these are for the parallel rows. You will have a 6-pin and a 7-pin length left from each strip; by sheer fluke there are 13 pins required to complete the set! Push the short length of the header pin block through the PC board and very carefully solder the required pins underneath using a fine-tipped iron with a clean tip. Regularly clean the tip on a wet sponge as you work and don’t overheat the solder joint as the pads are very small and could easily lift. Check, and check again, that you haven’t bridged solder between any two pins. We didn’t bother soldering all 50 pins in place on the board, only the required pins (ie, all 19 in one strip and the three adjacent) and also the end pins of each of the other header pin sets, just to hold them in place. An 8-pin length and a 7-pin length of header pins are also needed to connect the chip outputs and decoding lines. We also used a 2-pin set on the pads connected to the “stand alone” pins but this is not necessary in this application (we happened to have a Fig. 2: our final experimenter’s board circuit. You can see the similarities between this circuit and the basic circuit overleaf. We have added a power supply, outputs for all words and also some decoding for words 9 through 15. 38  Silicon Chip HEADER PIN SET JP3 – PINS 12-14 CONNECTED HEADER PIN SET JP1 – NO CONNECTION HEADER PIN SET JP2 – ALL CONNECTED EXCEPT 8 & 9 Fig 3: Here's how it all goes together on the printed circuit board. The bottom row of LEDs represents words one to eight while the top row will decode nine to fifteen. The word output pins 1-7 need to be connected to the appropriate word 9-15 input pins for decoding – see the separate logic table. 2-pin set spare, so why not?) You could use a single header pin (instead of a PC stake) in the base circuit of the relay driver if you wish. Before mounting the Voice Direct module on the PC board, you might like to confirm that the everything is working correctly. Plug in a 12V supply and ensure that the power LED lights. Measure the voltage between pins 4 and 5 of header pin set JP2 of the voice module (counting from the end closest to the supply) and confirm it is 5V (pin 4 +5V, pin 5 0V). Temporarily solder a length of insulated hookup wire to a point on the +5V rail under the board and touch the other end of this lead on each of the header pins in the 8-pin set (word 1-8 outputs). Each of the LEDs should light in turn. Do the same with the 7-pin row (word 9-15 inputs) and each of those LEDs should also light. Finally, touch the lead on the PC stake (or header pin) connected to the base circuit of the relay driver and you should hear the relay click in. If all is OK, disconnect power and unsolder the wire. If all is not OK, you’ll need to track down the fault before proceeding. There are four holes on the board (above the switches) which at this stage we’ll leave unfilled. They’re for a more difficult learning mode, which we’ll cover shortly. Mounting the module With the header pins in place, it is simply a matter of dropping the Voice Direct module over the pins and sliding it down. Because the holes on the module are all plated through, it is quite possible that the module won’t even need to be soldered in place (especially useful if you wish to use the module elsewhere). But . . . Murphy’s law being what it is, there is always a chance that one or more pins won’t make contact so we took the safe way out and soldered the 22 required header pins to the module. Again, a very fine, clean iron is essential. The project is now finished: now’s the time to teach it some words! Voice “training” Apply power to the board and press the “train” button. You should hear a voice say “Say word 1”. Speak your chosen word clearly into the microphone. The voice will say “repeat”. Make sure you speak the same way – that is, don’t change inflections or emphasis because the module may think you are saying a different word. If it understands the word, it will say “accepted” and ask you to “say word 2”. You keep on repeating the process until all 15 words are trained or you have trained the number of words required. If you want to train six words, for example, simply do nothing when it asks you for word seven and it will respond with the September 1999  39 Parts List 1 PC board, code 07109991, 160 x 118mm 1 Sensory Inc. “Voice Direct” speech recognition module 1 2.1mm PCB mounting DC power socket 3 25-pin 0.1in header pin sets 3 momentary action push button switches, PC board mounting 1 PC board mounting 12V relay, DPDT contacts 1 electret microphone insert 1 8Ω speaker, 57mm Semiconductors 16 5mm LEDs (any colour) 2 4081 quad AND gate ICs 1 BC337 NPN transistor 1 7805 voltage regulator 2 1N4004 power diodes Capacitors 1 1000µF 25VW PC electrolytic 1 10µF 12VW PC electrolytic 2 0.1µF MKT polyester, monolithic or ceramic Resistors (0.25W, 5%) 2 10kΩ   1 1kΩ 15 560Ω Miscellaneous 9 PC stakes, hookup wire for links, header cables for connecting module outputs to decoder inputs words “training complete”. If a chosen word is too close to another word, it will tell you. You should try to avoid similar sounding words. There is a way to ensure stricter training and recognition which we will cover shortly. If you have any difficulty getting the module to recognise words, a few tips: •  Keep the same distance from the microphone with the same voice level when training and saying words. •  Use a natural voice – while the module will remember accents and strange voices, you might not! •  The physical and emotional state of the voice matters. For example, if you’ve just run up a flight of steps and are out of breath, your voice will sound different than when you are relaxed. •  In either training or recognition, 40  Silicon Chip background noise may be a problem – the module doesn’t know that the background noise is not part of the word! So take this into account. Voice recognition Press the “recognise” button and you will be asked to say a word. Say the word clearly. If the module recognises the word it will respond with the appropriate word number and light the LED corresponding to that number. If it cannot recognise the word because of incorrect pronunciation, inflection or accent, it will say “word not recognised”. If you say the word too softly it will ask you to speak up. If you say the word too quickly it will tell you so! As described, the module is set up for “relaxed” training – it will recognise more words but may not be able to differentiate between some words. Another mode, called “strict” training and recognition, is also available. In this mode, where the train and recognise lines are permanently pulled to ground via a 100kΩ resistor, the module is harder to train, it accepts less words but has better accuracy in recognising words. Provision has been made on the PC board for these 100kΩ resistors – they’re the empty holes we referred to earlier above the train and recognise switches. For most purposes, the relaxed mode is easier to use – in this case, simply leave the 100kΩ resistors out. Decoding As mentioned before, words 1-8 cause a single output to go high for about a second, lighting the appropriate LED. Words 9-15 need to be decoded because they send two outputs high – output 8 and another of the 1-7 outputs, depending on the word. Table 1 shows the output table. In order to differentiate between words 1-8 and 9-15, decoding is required. We have provided two 4081 quad AND gates on the board with the module output 8 permanently connected to one input from each gate. Decoding, then, is simply a matter of connecting a wire between the appropriate 1-7 output header pin and the required decoder header pin. This will cause a single LED to light for outputs 9-15. Logically, word 9 would be the LED closest to the PC board corner and word 15 would be the LED closest to the speaker. Relay output A relay circuit is also provided to give a “real world” output, with two sets of changeover contacts. Usage is simple: connect the relay driver input to any of the required word outputs and when that word is recognised, as well as its LED lighting the relay will pull in for the same time. This is about a second which should be long enough to initiate some further action. If not long enough, a simple time delay can be added. Note that we have not provided any latching circuitry on the PC board – if you want this, it can easily be achieved by using one of the sets of relay contacts to hold the relay on once it is triggered. TABLE 1: WORD RECOGNITION LOGIC Word 1 Word 2 Word 3 Word 4 Word 5 Word 6 Word 7 Word 8 Word 9 Word 10 Word 11 Word 12 Word 13 Word 14 Word 15 Output 1 (header pin set JP2 - pin 12) Output 2 (pin 13) Output 3 (pin 14) Output 4 (pin 15) Output 5 (pin 16) Output 6 (pin 17) Output 7 (pin 18) Output 8 (pin 19) Output 8 (pin 19) AND Output 1 (pin 12) Output 8 (pin 19) AND Output 2 (pin 13) Output 8 (pin 19) AND Output 3 (pin 14) Output 8 (pin 19) AND Output 4 (pin 15) Output 8 (pin 19) AND Output 5 (pin 16) Output 8 (pin 19) AND Output 6 (pin 17) Output 8 (pin 19) AND Output 7 (pin 18) Where do you get the Voice Direct Module? At the time of going to press, we were unable to determine if distribution has been arranged in Australia. It is possible that some suppliers will have stock shortly. These days, though, there is no great problem as it is possible to buy the module direct from the USA using the Internet. Sensory Inc. distributors Jameco Electronic Components (www.jameco.com) or JDR Computer Products (www.jdr. com) have a kit available for $US49.95 plus postage and handling. This kit includes three tiny pushbutton switches (not the same as the Jaycar ones we used but they will fit the PC board), a speaker, microphone insert and of course the pre-assembled module itself. Apart from the PC board, all the components on our experimenter's board are commonly available. The PC board should be available from the usual PC board suppliers such as RCS Radio in Sydney. For more information on the Voice Direct module, including detailed data in Acrobat format (PDF), visit the Sensory Inc website: SC www.sensoryinc.com Following the retirement of our technical draftsman (who has been with SILICON CHIP since the first issue), we are looking for someone with the right qualifications and experience to take his place. The person we are looking for must be able to maintain the outstanding “look and feel” of the circuit diagrams, PC board overlays, drawings and diagrams which have become synonymous with SILICON CHIP and have contributed very much to its success and respect in the marketplace. Essential requirements for this position: •  An understanding of electronics, to at least advanced hobbyist level – the function, operation and requirements of components and electronic circuitry. •  Practical experience in one or more of the PC-based CAD, engineering or drawing packages used today (we use Generic CAD but other software experience will be acceptable). •  The ability to interpret a variety of original material and turn it into clear, lucid diagrams. •  The ability to handle sometimes very tight deadlines with accuracy, clarity and thoroughness. •  The ability to work as part of a small, busy team. •  The ability to commence yesterday! Other qualifications and experience which would be well regarded: •  Experience in Internet web page design and construction. •  The ability to design and produce electronic projects of the type which appear in SILICON CHIP. •  Possibly technical writing expertise. SILICON CHIP offices are located at Mona Vale on Sydney’s Northern Beaches. This is the full-size PC board pattern for the project. Because of the close spacing of tracks (especially around the header pin sockets) copying this from the magazine is not really a proposition. Use it instead to check commercially obtained boards. Of course, the PC board pattern is available from the SILICON CHIP website, www.siliconchip.com.au If you can satisfy all, or most of these requirements, please contact Leo Simpson, Publisher, SILICON CHIP with your CV as soon as possible in one of the following ways: email: silchip<at>siliconchip.com.au Fax: (02) 9979 5644 Mail: PO Box 139, Collaroy NSW 2097. September 1999  41 NOW EVEN BETTER! Even 42  Silicon Chip LOWER cost Internet access IT'S AS EASY AS A-B-C TO GET CONNECTED! (a) Fill in this form and either post it or fax it to SILICON CHIP – (02) 9979 6503; or (b) Call SILICON CHIP on (02) 9979 5644; 9am-4pm Mon-Fri and we'll guide you through it! (c) WE WILL THEN FAX YOU OR POST YOU your password and EASY setup details. 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Please have your credit card details ready 44  Silicon Chip 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 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. 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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 VINTAGE RADIO By RODNEY CHAMPNESS, VK3UG Vintage Hifi Stereo AM Radio Most of our readers would probably be aware that many AM stations broadcast in stereo but apart from some car radios, few people have the facility to receive stereo AM broadcasts which are of potentially very good quality. But did you know that stereo AM broadcasts began in the late 1950s, long before FM stereo broadcasts began? People used to set up two AM radios to listen to the occasional broadcasts from the ABC and some commercial stations. But we’re getting ahead of ourselves. True, AM as received on the average domestic receiver is rather poor in regard to quality, often only having a frequency reproduction range of 150Hz to around 3.5kHz. The IF (Interme­diate Frequency) bandwidth is usually quite narrow and the audio response of the audio amplifier in small radios is rather re­stricted as well. No wonder that AM radio has a reputation of being low fidelity. The transmitters, however, do have a much wider frequency response, being nominally flat from 50Hz to 10kHz or 12kHz, and often a lot wider than that. And the Motorola CQUAM stereo modulation which has been used by Australian AM stations since 1985 is a high quality system. Hence, with a good-quality stereo AM receiver and a low noise antenna system, it can be very difficult to tell the difference between AM stereo and FM stereo broad­casts. Early AM stereo As mentioned above, stereo AM broadcasting was introduced in Australia on an experimental basis around about the late 1950s and ran through to the mid 1960s. But if you weren’t an ABC listener you may not have been aware of it. In most capital cities the ABC had two 50 kilowatt co-located AM broadcast trans­mitters just out of the metropolitan area, fed from studios in the city. BELOW: two dial scales, two tuning knobs and two magic eyes made this Pioneer stereo AM receiver a knob-twiddler’s delight at the time of its production in about 1964. The bass and treble controls used concentric knobs, as did the volume control. There was no balance control. September 1999  53 The top of the chassis was neat and well laid out. Note the two tuning gangs, one at the front and one at the rear, near one of the output transformers. The two magic eye tubes are mounted horizontally at each end of the front panel. In New South Wales, these two stations were (and still are) 2BL and 2FC while in Victoria, they were 3AR (now 3RN) and 3LO. Every so often the stereo broadcasts took place and anyone with two radios could tune one set to 3AR and the other to 3LO and receive “stereo”. My parents and family lived on the South Aus­tralian border so what with selective fading at night and very ordinary radios the expected “stereo” was something none of us were convinced had really occurred! But stereo AM did occur and no doubt in the metropolitan areas the stereo was well received. Setting up the receivers was a bit of a problem, and overall it was a messy way of receiving stereo AM. Some of our entrepreneurial Japanese manufacturers could see a lucrative market for hifi stereo AM receivers and commenced to build them. There were not too many models but there was at least one built by Pioneer, as featured here, and one by Kenwood. 54  Silicon Chip But double AM stereo wasn’t a commercially successful ex­periment. People found it too tricky for them to get the hang of, even though it did work quite well. You would not think it would be hard to properly tune radios to different stations but there you are. Hence there are very few of these early stereo receivers around. I recently had the pleasure of restoring a Pioneer SM-B161 AM (circa 1964) stereo receiver. What is immediately different about this receiver compared to the run of the mill sets of the era in that it has two complete independent AM receivers in the one case. It had two slide-rule AM dials and two tuning knobs. The audio amplifiers are typical high quality of the era, with a pushpull class AB1 amplifier in each channel, putting out around 8-10 watts RMS. The output transformers for the audio stages are quite large – about the size of a small power transformer in a typical 1950s mantle receiver. They are certainly not called speaker transformers in such a set! Preamplifiers are provided for low level magnetic phono cartridges, as well as ceramic (crystal) cartridges. Considerable care has been taken to shield the inputs and the cables to the 12AX7 stages which functioned as preamplifiers. The earth leads go to various points around the chassis to minimise hum loops and the heaters of the valves are balanced to earth by preset potentiometers to minimise any residual hum. Pioneer have been very successful in reducing hum to such a level that it is inaudible at full volume and no input. Could that be said of many of the radios that we restore? Certainly not! The attention to detail to achieve high quality performance is obvious. One of the photos in this article shows the front panel layout which has the two dial scales. One is purely the AM broad­cast band while the other is the broadcast band plus a shortwave band from 3.8 to 12MHz. Magic eye tuning The converter in each receiver is the ubiquitous 6BE6, feeding a single IF stage using a 6BA6 which then goes to a germanium diode detector (OA81). From the AGC line of each re­ceiver a 6E5 “magic eye” is used to assist tuning of each receiv­er independently. The 6E5 is also handy for aligning the receiv­er, as it is only necessary to observe the fluorescent screen of the appropriate 6E5 while the RF and IF tuning adjustments are made. The output of each receiver then goes into a large switch which combines, separates or selects the receiver, record pick ups or auxiliary inputs; this is a large and busy switch. From this switch, the signals are either separated or combined go to the respective tone control network and audio amplifiers and thence to the speakers. Fig.1 is a block diagram showing how the receivers and amplifiers are interconnected. Servicing the SM-B161 The top and bottom covers of the receiver come off easily, allowing ready access to the componentry. It is a complex piece of equipment with 14 valves, including the rectifier and the two magic-eye tuning devices. From the under-chassis view it can be seen that there are a lot of passive components. I had to replace around 30 leaky electrolytic capacitors and a few out of tolerance resistors. Care is needed in replacing the components. I replaced them one at a time so as to not get any in the wrong spots. When I first opened up the set I This photograph shows the great handful of components which had to be replaced. As can be seen, most of the electrolytics were faulty. found that wax had been dripping out of one of the audio output transformers. This sug­ gested that it had overheated for some reason or another. I then checked the capacitors around the particular twin 6BM8 output stage and found that the cathode bypass electrolytic capacitor had emptied its insides out. This almost certainly means that the valves had been drawing a lot of current. The grid capacitors were then found to be quite leaky so that was likely to be the reason for the high current through the 6BM8s and the cathode resistor. It was also obvious at this stage that a few other capaci­ tors had spilled their insides around the underside of the chas­sis, as can be seen in one of the photos. The set was designed for 115V or 230V AC operation and there were three ordinary paper capacitors of 400V rating from mains to earth – depending on which way the mains supply was connected. For 230/240VAC operation this is The under-chassis view shows the crowded point-to-point wiring of the era. Access is good though and replacing parts is straightforward provided you do just one at a time. September 1999  55 Fig.1: block diagram of the Pioneer SM-B161 AM stereo receiver. It uses two AM tuner stages, each of which was tuned to a different frequency to pick up one channel of the stereo signal. 6E5 6BE6 CONVERTER MAGNETIC PICKUP 6BBA6 IF AMP 12AX7 PREAMP OA81 DETECTOR 12AX7 PREAMP AM MONO AUX PICK-UP AUXILIARY 12AX7 PREAMP 12AX7 PREAMP SWITCHING NETWORK CRYSTAL PICKUP 6BE6 CONVERTER PREAMP ½ x 6BM8 TRIODE PHASE SPLITTER ½ x 6BM8 TRIODE AM STEREO CRYSTAL PICKUP MAGNETIC PICKUP TONE ½ x 12AX7 AUX 6BBA6 IF AMP OA81 DETECTOR RECORD RECORD TONE ½ x 12AX7 PREAMP ½ x 6BM8 TRIODE PHASE SPLITTER ½ x 6BM8 TRIODE OUTPUT ½ x 6BM8 PENTODE HT OUTPUT ½ x 6BM8 PENTODE OUTPUT ½ x 6BM8 PENTODE HT OUTPUT ½ x 6BM8 PENTODE 5AR4 RECTIFIER 6E5 a dangerous practice as the ratings of the capacitors will be exceeded often, due to spikes and surges on the mains, even though the peak voltage on 240VAC mains is only around 340V. Even a 600V DC rating capacitor is insufficient as the spikes are often greater than 1000V and there can be problems with corona discharge with­ in the dielec­tric. So while DC-rated capacitors were often used in this appli­cation, only capacitors rated for 250VAC operation are safe. However, as it turned out, the fitting of suitable capacitors in these locations made no improvement in noise suppression so they were left out of the set. It was found also that the mains plug had been wired so that the power switch was in the Neutral lead rather than the Active. This was corrected! It is always wise to check the wiring of mains leads to make sure that in the past no-one has put mains Active to chassis or some other equally dangerous thing. The top of chassis view shows a set which is easy to access with major components well labelled. While the photo may not show it well, the valve types and similar pieces of information 56  Silicon Chip are stamped onto the chassis. This would have been most useful if any of the valves were missing. When the set was at last turned on, the voltages were moni­tored carefully around the set, particularly in the power supply and in the audio output stage where wax had dripped from the transformer. All was well and several hours of operation showed no further trouble in that stage. As was common practice at the time, each channel has one of the 6BM8 triodes used as a phase splitter for the following pentode output stages. The 47kΩ resistors used for plate and cathode loads in this stage were way out of tolerance. This would mean that the drive to the output pentodes was unequal and hence the fidelity of the output would be adversely affected. So these resistors were replaced too, to solve this problem. The RF alignments were touched up using the magic eyes to show peak alignment. The performance was quite satisfactory. For best performance, each tuner must be used with its own aerial as connecting both receivers to the one aerial causes signal “suck out” and other undesirable effects. This is a bit of a nuisance and probably was another reason why the product concept didn’t really catch on. Summary Pioneer produced a very good twin AM tuner cum stereo amplifier, of high quality for the era of its construction. It is a bit crowded under the chassis but every­thing can be got at. The received audio quality on radio stations is excellent. On the down-side the bandwidth is so good that 9kHz inter-station heterodyne whistles are quite obvious at night. 9kHz notch filt­ers would no doubt eliminate this problem. We had 10kHz station spacing at the time this set would have come to Australia and perhaps the 10kHz whistles may not have been so obvious. Some high performance AM sets did have these filters, however. Certainly it is an interesting instrument which the Japanese entrepreneurs hoped would suit the stereo system that appeared might take on in Australia. There would be very few of this style of twin AM stereo receiver in Australia so they are well worthwhile collect­ing. It would be worth keeping an eye out for one in your local branch of Cash Converters. SC September 1999  57 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. Dry cell battery checking This simple, easy-to-use tester was developed to check 9V batteries in radio microphones. Used by non-technical staff, it gives a definite Go/NoGo indication that means that useable batteries are not discarded. The advantage of the device is that, unlike a conventional DMM, there is no need to switch it on, select the appropriate range, handle probes, interpret the read­ ing and then switch off. The circuit is based on ICL7665 under/over voltage detector chip in an 8-pin package. The chip draws its power from the battery being tested and it will work down to around 2V. It has two internal comparators which use the same 1.3V reference vol­tage (1.3V). Each comparator has effectively two outputs which change state, depending on the actual voltage being measured. Trimpots VR1 & VR2 set the upper and lower voltage thresholds, respec- tively, for the circuit. For example, you could set trimpot VR1 so that batteries delivering 8V or more were given a pass, indicated by LED1 turning on. Similarly, you could set trimpot VR2 to fail any batteries which deliver less than 7.5V, turning on LED3. The third output of the circuit is used to drive LED2 and this comes on for batteries delivering more than 7.5V but less than 8V. The three LEDs should be high brightness types. R3 should be chosen to provide a suitable load for the battery. With a value of 470Ω, the nominal load current will be 20mA. For many applications this will not be adequate and R3 will need to be reduced in value. Brian Critchley, Elanora Heights, NSW. ($20) Foolproof audio compressor This circuit was developed for an application where foolproof compression was needed with no user-adjustable controls. Accordingly, the attack time is pre-set, with the release time being automatically determined, by the instantaneous amplitude of the input signal. In operation, the op amp functions with a maximum gain of around 470, as set by the 470kΩ and 1kΩ feedback resistors. Transistor Q1 buffers the output to feed diode D1 which rectifies the signal and produces a DC voltage which is proportional to the signal. When the output from the diode is above 0.6V, it turns on transistor Q2 which shunts the input signal, depending on how hard it is turned on. The noise-gate feature is useful for eliminating quiet passages during 58  Silicon Chip program material. This is achieved by connecting the .01uF capacitor across Q2 via switch S1. This forms a low-pass filter in conjunction with the 1MΩ and 220kΩ resistors, with the cut-off frequency dependent on the base current of the BC549. The op amp is an LF357, which gives the circuit a good frequency response from around 20Hz to 40kHz. The single voltage rail enables it to be powered from a 9V battery. S. Williamson, Hamilton, NZ. ($30) WARNING: The whole of this circuit operates at mains potential and is therefore dangerous. It MUST be housed in a case which gives suitable insulation. Do NOT work on this circuit when power is applied. Surveillance lights with buzzer This security lighting system was devised after thieves visited a residential property and stole some equipment from the backyard during the night. The basis of the security light was a 12V PIR module sourced from Oatley Electronics. This unit has an output which switches high whenever movement is sensed. Unfortunately though, in its original form it would turn on a light at any time of the day or night. The solution was to connect an LDR circuit across the output of the PIR. The resistance of the LDR is low during daylight hours and it, together with series 18kΩ resistor and 20kΩ trimpot VR1, hold the PIR’s output low. At night the LDR’s resistance rises to several megohms, allowing the PIR’s output to swing high whenever movment is sensed. The output of the timer is used to control two timers. One turns on a floodlight for five minutes while the other sounds a piezo buzzer (with inbuilt oscillator) ten seconds inside the house. The complete circuit, including the PIR module, is directly powered from the 240VAC mains supply. This type of supply must only be used where there are no user controls accessible, as the whole circuit is at mains potential. The wiring from the control unit to the PIR module must also be 240VAC mains-rated. Do not attempt to construct this circuit if you are not experienced in 240V mains projects. The circuit works as follows: The incoming mains voltage is fed via a 100Ω 1W resistor and 0.68µF 250VAC capacitor to diodes D1 & D2. On positive half-cycles, diode D1 conducts and charges the 470µF capacitor C1. On negative half-cycles, D2 conducts to discharge the 0.68µF capacitor, ready for next half-cycle. The 12V 1W zener diode limits the voltage across C1 and the resulting 12V supply rail powers IC1, IC2, Q1, the relay and buzzer and the PIR module. IC1 is a 4060 binary divider which has one inverter connected as an oscillator to provide a source of clock pulses. These are divided by a factor of 214 to provide the 5-minute period for which the floodlight is turned on. Normally the output Q14 of IC2 is high, preventing the oscillator from working. When the PIR’s output goes high, the output of IC1a will go low and the outputs of IC1b & IC1c will go high, resetting IC2 and allowing the oscillator to run. While IC2 is being clocked, the waveform at pin 10 is fed via diode D3 to continually charge the 0.1µF capacitor C2, at the gate of FET Q1. This causes Q1 to turn on and energise the relay and this connects the floodlight to the 240VAC supply. The relay is a 12V unit with a 400Ω coil (Altronics S-4160). After 214 counts, when Q14 of IC2 goes high, diode D4 holds pin 11 high preventing the oscillator from working. The 22MΩ at Q1’s gate will discharge capacitor C2 and the relay will drop out, turning the floodlight off after about five minutes. The outputs of IC1a and IC1b also feed the buzzer B1 through diode D7. Pin 12 of IC1d is connected to pin 9 of IC2 while pin 13 of IC1d goes to pin 5 of IC2. The resultant output from pin 11 of IC1d is fed to the buzzer which only sounds when the outputs of IC1b and IC1c are high. When they are low diode D7 is reverse biased and no sound will be produced. The buzzer is a low-current type such as Altronics Cat S-6109. The buzzer will only sound while the PIR output is high. If the intruder stays in the PIR range and moves around, the buzzer will keep sounding and the floodlight will stay on, as the timer will be reset each time movement is detected. If the buzzer does not sound for long enough, it can be extended by increasing the value of capacitor C3 at the inputs of IC1b and IC1c. SILICON CHIP September 1999  59 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 Design by EUGENE W. VAHLE JR.* Digital electrolytic capacitance meter Do you need to check large value electrolytic capacitors? Unfortunately, you can’t do it with the capacitance ranges on your digital multimeter or even with most capacitance meters. You need this special purpose instrument which can measure electrolytic capacitors ranging from around 10mF up to as high as 999,900mF – yep, almost 1 Farad. The problem with electrolytic capacitors is threefold. First is the sheer value of capacitance which typically ranges from around 1µF to many thousands of microfarads. Normal measur­ ing techniques which essentially measure the capacitor’s im­ pedance at a particular frequency just don’t work. Because the capacitance is so high, the impedance is just too low to measure unless you use quite low test frequencies or resort to special circuit techniques. Second, electrolytic capacitors need to be charged (or polarised) to present a reliable and consistent capacitance value. Third, compared with every other type of capacitor, elec­ trolytics can have quite a high leakage current and this can confuse a normal capacitance measuring instrument. So how does this instrument get around these problems? Instead of trying to measure impedance with a test frequency, this circuit measures the time taken to charge the capacitor to a particular voltage. It is based on the following formula for capacitance: C = Q/V where C is capacitance in Farads, V is the voltage applied to the capacitor and Q stands for charge in Coulombs. Without getting too technical, if we pump charge into a capacitor at a September 1999  63 CLOCK IC2 CONSTANT CURRENT SOURCE Q9 4-DIGIT COUNTER IC1 7-SEGMENT LED DISPLAYS COMPARATOR Q5, Q6 Constant-current source CUT Fig.1: the block diagram of the Electrolytic Capacitance Meter shows a constant current source to the charge the capacitor under test (CUT), a comparator and the 4-digit counter. The meter measures the time period to charge the test capacitor to 4V. known rate, the time taken to reach a certain voltage is directly proportional to the capacitance. We could write this as an equation too but suffice to say that pumping charge into a capacitor at a known or fixed rate is exactly the same as charging it with a constant current source. And that is exactly what this circuit does, as shown in the block diagram of Fig.1. The constant current source charges the capacitor under test (CUT) while the counter is clocked. When the capacitor reaches a particular voltage, a comparator stops the counter and the displayed value is the capacitance. Pretty simple, eh? Our Electrolytic Capacitance Meter is quite simple. It has a 4-digit 7-segment LED display, a 4-position range switch, a toggle switch with Test and Discharge positions and the terminals for the capacitor. So let’s test a capacitor. First, turn the unit on, connect a capacitor to the terminals, making sure that the negative lead goes to the black terminal and flip the toggle switch to the discharge setting. If the capacitor has some charge in it, the red LED will come on briefly and then go out, to signify that the capacitor is now discharged. Now flip the toggle switch to the test position and the 4-digit display will start counting up from zero. Depending on the value of the capacitor, the count will stop after a few seconds and the value shown is the capacitance in microfarads. What about the range switch? It has four settings: x0.1, x1, x10 and 100. So if the displayed value is 1500, for example, and the range switch is set to x1, then the value is 1500µF. Most electrolytic capacitors have large tolerances, ranging from -20% 64  Silicon Chip DC (Vcc). This voltage is applied to the two 5V regulators (REG1 & REG2). REG1 is wired in convention­al fashion and produces a +5V output. REG2, on the other hand, is wired in an unconventional manner which we’ll explain shortly. to +80%, meaning that a capacitor specified as 1000µF might have an actual capacitance of as little as 800µF (-20%) or as much as 1800µF (+80%). Other capacitor types have a lower tolerance (±10%). For capacitors with substantial series resistance (such as double layer capacitors used in memory backups), the formulas provided later on in Table 1 can be used to find the actual capacitance and series resistance. About the circuit Refer now to Fig.2 for the complete circuit of the Electro­lytic Capacitance Meter. As shown, it uses two integrated cir­cuits: IC1, a 74C926 4-digit counter/multiplexed 7-segment dis­ play driver and IC2, a 7555 CMOS oscillator/timer. In addition, there are 10 transistors (Q1-Q10), two 5V regulators (REG1 & REG2), a bridge rectifier (D1-D4), two light-emitting diodes (LED1 & LED2) and four 7-segment LED displays. Power for the device comes from a 12V AC plugpack. Its output is rectified by diodes D1-D4 and filtered by a 470µF capacitor to give about 18V Special Notice *This project and article has been adapted with permission from an article in the May 1999 issue of the American magazine Popular Electronics. The original design did not have a PC board and this has been produced by SILICON CHIP staff. The Popular Electronics design was also based on the 74C925 instead of the 74C926 used here since it is more readily available. The output from the bridge rectifier is also applied to a range-select resistor network via S2a and then to the emitter of transistor Q9. These components, in company with REG2, form a rather odd-looking constant-current source. Let’s see how it works. REG2 is a 7905 -5V regulator. Usually, the GND terminal of a 3-terminal regulator is referenced to GND or the 0V rail in a circuit but in this case, the input (IN) is grounded while the GND terminal is jacked up to +18V by connecting it to the bridge rectifier output. Because the regulator delivers a -5V rail with respect to the GND terminal, this means that the output will be at +13V (ie, Vcc - 5V). As a result, Q9’s base is held at a constant 5V below the Vcc rail and so its emitter maintains a constant voltage across the selected range resistor. This causes Q9 to function as a constant current source. After subtracting the 0.6V developed across the base-emit­ter junction of Q9, the voltage across the selected range resis­tor will be approximately 4.4V. This means that the current through the selected range resistor will be 44µA for the x0.1 range, 440µA for the x1 range, 4.4mA for the x10 range and 44mA for the x100 range. A 1µF capacitor is included to filter the output of REG2, while the parallel 2.2kΩ resistor sets the minimum load on REG2’s output. This is done because on the 44µA (x0.1) range, the base current needed for Q9 is very small (around 0.4µA). Comparator stage Let’s now take a look at the comparator circuit which is based on Q5 & Q6. First, a +4.5V reference voltage is derived from a 220Ω/2kΩ voltage-divider network across the output of REG1. This reference voltage is applied to the base of Q10 (which means that Q10’s emitter will be at +5.1V) and also to the emit­ter of Q6. The comparator is used to halt the count when the voltage across the test capacitor reaches 4V. It works as follows: when S1 is in the discharge position, +5.1V is applied to the base of Q6 via a 2.2MΩ resistor. Since the emitter of PNP transistor Q6 is at +4.5V, it is biased off and it removes base drive to Q5 so Q5 is off as well. With Q6 turned off, pin 5 of IC1 is pulled low via a 1MΩ resistor (between Q6’s collector and ground), thus latching the count into IC1 and transferring the latched data to the display. At the same time, with Q5 off, pin 13 goes high and resets IC1’s internal counter to 0000 (resetting the counter has no effect on the latched data). If S1 is now set to the TEST position, the base of Q6 is pulled low via the test capacitor (which initially acts as a short-circuit), thus turning it on. This pulls pin 5 of IC1 high, turning the internal latch off. At the same time, Q5 turns on and a low is applied to pin 13 of IC1 to release the reset on the counter. The test capacitor now charges via constant current source Q9. The rate at which it charges is determined by the selected range resistor and during this time, IC1 is clocked by IC2. When the voltage across the test capacitor reaches about 4V, Q6 turns off again, latching the final count into the display and reset­ting the counter again. The charge on the test capacitor then continues to increase until it reaches a level that’s sufficient to forward-bias Q10, at which point Q10 turns on and clamps the voltage to about 5.1V. The .01µF capacitor at Q6’s collector is included to prev­ ent the 2-transistor comparator from false triggering, while the 0.1µF capacitor at pin 13 of IC1 ensures that there is a short delay between the latching and resetting operations. The 1µF capacitor at Q9’s collector is also necessary to prevent false triggering of the comparator. Discharge indicator When S1 is subsequently switched to the DISCHARGE position, the test Fig.2 (left): the circuit shows a bridge rectifier at the power input so a 12V AC or DC plugpack can be used. Don’t try using a 555 for IC2 in­stead of the 7555 specified because it won’t work as well. September 1999  65 capacitor discharges through the parallel-connected 100Ω resistor. As the capacitor discharges, the voltage across this resistor turns on transistor Q8. This turns on Q7 and lights LED2. When the voltage across the 100Ω resistor drops below 0.6V, Q8 & Q7 turn off and LED2 extinguishes, indicating that the unknown capacitor has been safely discharged. Counter circuit There’s plenty of room left inside the case, since most of the circuitry is on the vertically-mounted PC board. Note how the 7-segment LED displays are mounted – see text. 66  Silicon Chip IC1 is a 74C926 4-digit counter/ display driver and is clocked by IC2, a 7555 CMOS oscillator/timer. The reason that the CMOS version of the 555 was chosen was because it has a cleaner output than the standard 555. IC2 is wired in astable mode and has an output frequency of 105Hz, as set by the RC timing compon­ents on pins 6 & 7. VR1 allows the output frequency to be adjust­ed so that the unit can be calibrated. The output from IC2 clocks pin 12 of IC1 and it does this while the test capacitor charges to 4V. When IC1’s latch enable (LE) pin is subsequently pulled low, the value in the counter is latched and transferred to the segment driver outputs. The digit driver outputs of IC1 are at pins 7, 8, 10 & 11. These multiplex the common-cathode displays via driver transis­ tors Q1-Q4 at a rate determined by IC1’s internal clock. While that’s going on, IC1’s segment-driver outputs (pins 1-4 and 15-17) activate the appropriate display segments. The 47Ω resistors connected in series with IC1’s segment-driver outputs provide current-limiting, while the 390Ω resistor in series with S2b’s wiper limits the current to the selected decimal point. The decimal points are controlled via S2b (part of the range switch). When S2b is in the x1 position, DISP4’s decimal point turns on. Similarly, when S2b is in the x0.1 position, DISP3’s decimal point lights. The other two displays do not need a decimal point. Construction All the components for the Electrolytic Capacitance Meter are assembled on one PC board, with the Range selector switch (S2) and the 7-segment LED displays mounted on the copper side. This allows access to the components and to the frequency preset trimpot (VR1) when the PC board is mounted on the front panel. The first step, as always, is to check the board for un­ drilled holes and etching faults. While these are uncommon, it is far easier to check for them before beginning the assembly, rather than getting half-way though and then finding it necessary to drill a hole. Fig.3 shows the assembly details. The 23 links are best fitted first, although if you use resistor pigtails as jumpers you will naturally have to fit them before the links. The diodes and preset potentiometer come next, followed by the eight PC stakes (these mount at the external wiring positions). Note that two of these PC stakes are inserted directly adjacent to the wiper pads for switch S2. Fig.4 shows the loca­tion of these two stakes. Next, install the transistors, diodes, capacitors (includ­ing the electrolytics) and the two 3-terminal regulators. Lie the 470µF electrolytic capacitor (adjacent to the 7805 5V regulator) flat against the PC board to keep it away from the regulator’s heatsink. Note that the four diodes have their cathode bands all facing in the same direction. Parts List 1 PC board, code 04109991, 195 x 62mm 1 plastic case, 200 x 70 x 160mm, Jaycar HB5912 or equivalent 1 Perspex window, red or smoked grey, 57 x 23mm 1 12V AC or DC plugpack 1 panel-mount socket to suit plugpack 1 2-pole 6-position PC-mounting rotary switch with indexing lug, 2 nuts & toothed washer 1 SPDT toggle switch 1 binding post terminal (red) 1 binding post terminal (black) 1 TO-220 heatsink 2 20-way pin strips, Jaycar PI6743 or equivalent 1 knob to suit rotary switch 9 PC board stakes 1 3mm x 18mm threaded spacer 1 3mm x 6mm CSK head machine screw 1 3mm x 6mm machine screw 2 3mm solder lugs 1 20kΩ horizontal PC-mount trimpot (VR1) Semiconductors 1 74C926 4-digit counter/display driver (IC1) 1 7555 CMOS timer (IC2) 1 7805 5V regulator (REG1) 1 7905 -5V regulator (REG2) Take care to ensure that the electrolytic capacitors are all correctly oriented. Also, be sure to use the 7805 device for REG1 and the 7905 for REG2 (don’t get them mixed up). NOTE: the PC board has been laid out to suit 2N2222 tran­sistors in the TO-18 metal can package but they are also avail­able as TO-92 plastic packs. Unfortunately, the pinouts for the two packages are different (see Fig.2). If you have TO-92 tran­sistors, the trick is to bend the base (centre) lead of each transistor towards the flat on its body. The transistor will then slot straight into the board. Make sure that the transistor lead connections are correct; the circuit won’t work if you get them mixed up. Rotary switch mounting The rotary switch is inserted from the copper side of the PC board. Before 4 2N2222 NPN transistors (Q1-Q4) 2 2N3904 NPN transistors (Q5,Q8) 2 2N3906 PNP transistors (Q6,Q7) 2 2N2905/2N2907 PNP transistors (Q9,Q10) 4 1N4001/4004 1A diodes (D1-D4) 4 7-segment common cathode displays (DISP1-DISP4) 1 5mm green LED (LED1) 1 5mm red LED (LED2) Capacitors 1 470µF 25VW PC electrolytic 3 100µF 16VW PC electrolytic 2 1µF 50V PC electrolytic 2 0.1µF MKT polyester 2 0.1µF monolithic ceramic 2 .01µF MKT polyester Resistors (0.25W, 1%) 1 2.2MΩ 1 2.2kΩ 2 1MΩ 1 2kΩ 1 100kΩ 2 1kΩ 1 47kΩ 1 390Ω 1 39kΩ 1 220Ω 1 22kΩ 1 150Ω 1 15kΩ 2 100Ω 1 10kΩ 7 47Ω 1 4.7kΩ Miscellaneous Tinned copper wire for links, light duty hook-up wire mounting it, solder 25mm lengths of tinned wire to the two common pins. This done, push the switch pins and wires through the board holes until the 12 outside pins are just pro­truding through on the component side. The outside pins can now all be soldered on the copper side of the board. You will need a soldering iron with a small tip for this job. It’s best to solder a couple of diagonally opposite pins first, as this will make it easier to ensure that the switch is square with the board. Once the switch soldering has been completed, connect the wire leads from the common pins to the adjacent PC stakes (see Fig.4). Regulator REG1 must be fitted with a small finned heatsink to keep it cool. You will need to drill another hole in this heatsink, towards one side, so that it can be offset to clear the lid of the September 1999  67 Fig.4: two short wires from PC stakes are used to connect the wipers of the rotary switch. 7-segment LED displays can be made by first drilling a series of small holes around the inside perimet­ er, then knocking out the centre piece and filing the cutout to a smooth finish. The indicator LEDs, toggle switch (S1) and the two test terminals (red to the wiper of S1, black for earth) can now be installed. The terminals used in the prototype had locating lugs which meant that matching holes had to be filed in the front panel after the centre holes were drilled. These locating lugs stop the terminals from rotating when the binding posts are tightened or undone. Once the terminals are mounted on the front panel and the solder lugs fitted, the excess lengths must be cut off so that they don’t foul the PC board. As long as they are shorter than the switch terminals, they will be OK. Final assembly Fig.3(a): take care when installing the 2N2222 transistors because their pin­outs are different depending on whether you have the metal TO-18 type or the plastic TO-92s (see text). Fig.3(b) at right shows the full-size PC board artwork. case (see photo). Smear some thermal grease on the mating surfaces before bolting REG1 to the heatsink. Case preparation The plastic case must have the five lugs at the front of the bottom and the two at the front of the lid removed, to 68  Silicon Chip allow the PC board to sit in position. This is easily done by drilling them out or using a sharp chisel and a small hammer. Next, use the front panel label as a template to mark out and drill the holes for the various items of hardware. The rec­tangular cutout for the The wiring between the front panel and the PC board is straightforward. Use light, flexible leads to allow the panel to fit close to the PC board without jamming or straining the wires but leave these wires long enough to be able to access the PC tracks if you fold down the front panel. The power leads from the back panel can be soldered in later. The anode leads for the two LEDs are wired to their respec­tive stakes on the PC board, while their cathodes are connect­ed together and wired back to the EARTH stake. The black test terminal also connects to the EARTH stake, while the red terminal goes to the wiper of switch S1. The other two The 7-segment LED displays and the rotary switch (S1) are mounted on the copper side of the PC board. Note that we modified the connections to S1’s wipers after this photo was taken (they now connect to PC stakes; see Fig.4). terminals on the switch go to the TEST and DISCH stakes on the board. The indexing lug on the rotary switch should be set to allow for four positions from the fully anticlockwise direction then a nut fitted to hold it in place (ie, three clicks, four positions). The toothed washer should be fitted behind the front panel but don’t attach the front panel just yet. Now plug the four displays into the 20-way pin strips, making sure that all the decimal points are at bottom right. This done, push the 40 pins through the PC board holes, then fit the front panel and secure it at one end with a second nut on the rotary switch. The other end of the front panel is secured to the board using an 18mm threaded spacer and two screws. Countersink the hole on the front panel so that the bolt head will not be visible when you fit the label. Fig.6 shows the dimensions of the window for the LED dis­plays. This can be made from either red or smoked Perspex and should be about 3mm thick. The 2 x 3mm rebate around the outside can be made using an engraving tool (ask your local engraver), a small router or even a flat file. Fit the window from the back and secure it with a couple of drops of super glue. This done, push the pin strips forwards until the displays touch the window, then tack solder the four corner pins. Check that the alignment is satisfactory before soldering the remaining 36 pins. Next, slide the front panel into the plastic case guides and check that the lid fits properly and does not foul the heat­sink. You can then fit the plugpack socket to the rear panel and connect it to the two PC stakes near the diodes. Testing To test the unit, first apply power and check that the power LED lights. If it doesn’t, you’ve probably got the LED wired the wrong way around. Next, use your multimeter to check for about 18V on the cathodes of D2 and D3 (the actual voltage measured will depend on the plugpack used). You should be able to measure the same vol­tage on one end of the 2.2kΩ resistor near REG2 and 5V less (ie, about 13V) at the other end. Pin 18 of IC1 should measure +5V. If all voltages are correct (within ±10%), connect a multimeter set to read a DC current of 50mA (probably Resistor Colour Codes  No.   1   2   1   1   1   1   1   1   1   1   1   2   1   1   1   2   7 Value 2.2MΩ 1MΩ 100kΩ 47kΩ 39kΩ 22kΩ 15kΩ 10kΩ 4.7kΩ 2.2kΩ 2kΩ 1kΩ 390Ω 220Ω 150Ω 100Ω 47Ω 4-Band Code (1%) red red green brown brown black green brown brown black yellow brown yellow violet orange brown orange white orange brown red red orange brown brown green orange brown brown black orange brown yellow violet red brown red red red brown red black red brown brown black red brown orange white brown brown red red brown brown brown green brown brown brown black brown brown yellow violet black brown 5-Band Code (1%) red red black yellow brown brown black black yellow brown brown black black orange brown yellow violet black red brown orange white black red brown red red black red brown brown green black red brown brown black black red brown yellow violet black brown brown red red black brown brown red black black brown brown brown black black brown brown orange white black black brown red red black black brown brown green black black brown brown black black black brown yellow violet black gold brown September 1999  69 SILICON CHIP + 3 TEST ELECTROLYTIC CAPACITANCE METER + x10 x1 x0.1 RANGE x100 -+ + POWER + + + + DISCHARGE DISCHARGING 17 Fig.5: actual size artwork for the front panel label. the 200mA range on most digital meters) across the capacitor terminals and read the value with the Range switch set to the x100 range. This should be around 44mA. Now, stepping anticlockwise, check that the other ranges measure close to 4.4mA, 440µA and 44µA. This is deter­mined by the actual output voltage of REG2 70  Silicon Chip 23 51 57 2 Fig.6: dimensions of the window for the LED displays. This can be made from either red or smoked Perspex and should be about 3mm thick. The 2 x 3mm rebate around the outside can be made using an engraving tool (ask your local engraver), a small router or even a flat file. and the exact value of the selected range resistor. Next, connect a 2200µF or 4700µF capacitor across the termi­nals, set S2 to the x10 range and set the toggle switch (S1) to TEST. The display should start counting up. Wait for five sec­onds, then flick the toggle switch to DISCHARGE. The Discharge LED should come on briefly, then extinguish, while the count should remain fixed on the LED displays. Calibration If you have an electrolytic capacitor with an accurately known value (say 10,000µF or more), connect it across the test terminals and check its value on the x10 range. Now adjust VR1 until the correct value is displayed. This will have to be done on a trial and error basis, with the capacitor re-tested after each adjustment. On our unit, VR1 had to be adjusted until it was almost against the clockwise stop. If you find you need more adjustment, reduce the 39kΩ resistor which goes to pin 7 of IC2 to 33kΩ. If you don’t have a known capacitor, then get several capacitors of the same nominal value (say 10,000µF or more) and test each one. You can then select a unit from the middle of the range and use this as the standard. Note that the overall accuracy is better on the x10 range. Using the meter Normally, a quick check is all that is needed to find a bad capacitor. For example, there will be times when the meter won’t stop counting. As illustrated by Table 1, this indicates that the capacitor has excessive leakage or an internal short. Note that when using the x100 range (44mA), you should let the meter warm up for a couple of minutes to allow the circuit to stabilise. That’s because Q9’s base-emitter junction voltage varies slightly as the transistor warms up. This doesn’t pose a major problem but it can decrease the accuracy until the circuit stabilises. Computer-grade electrolytic capacitors are designed to have a low equivalent series resistance (ESR) while memory backup capacitors have a fairly high ESR. When testing a capacitor that has a high ESR, use the formulas in Table 1 to find the correct capacitance and ESR. The formulas aren’t perfect but they’ll get you close enough. The meter can be allowed to roll over (count to 9999 and continue) if desired. That comes in handy when it’s necessary to test a larger capacitor on a lower range. If you suspect, for instance, that the capacitor being tested has high ESR, testing it on a lower range gives better accuracy because of the lower test current. It is also possible to test a capacitor larger than 1F on the x100 range using that method. Let’s look at a couple of examples: Example 1: while testing a 300,000µF computer-grade capaci­ tor on the x100 range, the meter’s readout displayed 3855. In that case, the actual measured capacitance is 3855 x 100 = 385,500µF. On the x10 range, the meter was allowed to roll over three times, producing a finished count of 9556. The x10-range capacitance would then be 39,556 x 10 = 395,560µF. Both readings are high compared with the capacitor’s specified value and both readings are within 10% of each other. The regulator heatsink must be offset as shown in this close-up photo, to clear the lid of the case on the x100 range. In such cases, you could just accept the reading obtained on the x10 range or use the formula in Table 1 to find the cor­rect capacitance and ESR. Here, the high-range reading is too low and the low-range reading is too high. Table 1 indicates that the capacitor has either leakage or series resistance and should be tested with an ohmmeter. Since we’re checking a memory-backup capacitor, it becomes obvious that the erroneous reading is probably due to series resistance. In such cases, we’d use the lowrange reading of 47,020µF. Using the formulas for ESR and capacitance: (1). ESR = (47,020 - 30,100)/(.011 x 47,020) = 32.7Ω. (2). C = ((11 x 47,020) - 30,100)/10 = 48,712µF. The test terminals, indicator LEDs and test switch are wired back to PC stakes on the board. Referring to Table 1, note that some leakage is indicated but the capacitor is otherwise OK and that the highrange reading is correct (the higher range reading is not the same as the high reading). This means that this capacitor is actually about 385,500µF which is about 29% higher than the manufacturer’s specifications – but well within tolerance. Example 2: while testing a memory backup capacitor (speci­fied as 0.047F) on the x100 range, the meter produced a readout of 30,100µF. On the x 10 range, the meter displayed 47,020µF. The two readings, of course, are not within 10% of each other. It is not difficult to recognise that the reading on the x10 range is closer to the correct value because the series resistance of memory backup capacitors can cause erroneous readings Example 3: while testing a 2200µF capacitor on the x10 range, the display produced a readout of 1610µF. On the x1 range, the reading was 1636µF. Both readings are low and within 10% of each other. Table 1 indicates that the capacitor has low ca­pacitance and to take the high-range reading (1610µF) as the cor­rect value. As it turned out, the capacitor was low by 27% and unusable! Finally, the accuracy of the meter can be increased using several approaches. For example, the CO (carry out) output (pin 14) of the counter/ display driver could be used to clock another counter driving another 7-segment display. This would allow you to see the rollover, instead of counting the number of rollovers. Anoth­er approach would be to divide the 105Hz clock frequency by 10 (when you know there will be roll over), to provide an SC additional x1000 range. September 1999  71 YZ TABLE WITH STEPPER MOTOR CONTROL Part.5: Power Supply & Software This power supply has been specifically designed to power the controller cards and the stepper motors used in the X-Y-Z Table, as presented in last month’s issue. In addition, we show you how to drill your first PC board. By RICK WALTERS The software which controls the three motors energises the Z-axis motor continuously. Conversely, the X and Y motors have the power removed when they are not stepping. This allows us to use a 15V supply for the X and Y motor driver stages, to ensure that at least 12V is fed to the motors after the voltage drop across the driver transistors is taken into account. By contrast, the Z-axis motor driver stages are powered from a +12V rail. The resulting lower voltage applied to the Z-axis motor ensures that it doesn’t overheat during the long periods for which it may be energised. Keeping the voltage constant on the X and Y stepper motors allows us to consistently step them at their maximum speed, regardless as to whether one or both motors are driven. If the voltage varied (as it would with an unregulated supply), we would have to reduce the maximum stepping rate. Fig.30 shows the circuit of the power supply. This is simi­lar to the Stepper Power Supply described in the December 1997 issue. The previous unit provided unregulated +18V & +12V rails, along with a regulated +5V rail. The revised unit described here does away with the +18V rail and provides a regulated +15V rail instead. It also uses a larger power transformer. This was done because the output of the original supply varied quite a bit, depending on whether one, two or three motors were being driven at any given time. Circuit details The circuit is built into a standard plastic case, with binding post terminals used for the supply outputs. A LED provides power on/off indication. 72  Silicon Chip As shown in Fig.30, the 30V centre-tapped secondary of the power transformer is full-wave rectified by diodes D1 & D2. The output from the rectifiers is then filtered using a 4700µF ca­pacitor to give around 2022V, depending on the load. This rail is then fed to 3-terminal regulator REG2, which provides a +15V regulated rail to power the X-axis and Y-axis stepper motors. This adjustable regulator is rated at 3A, since the X and Y motors will draw a total current of 1.5A when they are both stepping. The output voltage can be trimmed by changing the 150Ω resistor. A 470µF capacitor and a parallel 0.1µF capacitor are used to filter the output from REG2. The second regulator, REG1, provides a stable +5V rail for the logic circuits on the controller cards. Its output is fil­ tered using 10µF and 0.1µF capacitors. This bypassing of the regulator outputs is a precaution to prevent the regulators from oscillating if we have long leads between the power supply and the controller cards and motors. The +12V rail for the Z-axis stepper motor is derived from D3. This diode half-wave rectifies the output from a 24V tap on the transformer, while a 4700µF capacitor filters the output. The unloaded output voltage is around 13.5V but this drops to around 11V as soon as the motor is energised. For this reason, the software drives this motor at a slower stepping rate than the X & Y motors, so that it operates reliably with the lower voltage. Assembly Most of the parts are mounted on a PC board coded 10108993. Fig.31(a) shows the assembly details. Fig.30: the circuit provides regulated +5V & +15V supply rails, plus an unregulated +12V rail. Begin by installing eight PC stakes at the external wiring points, then install the resistors, diodes D1-D3 and 3-terminal regulator REG1 (7805). Note that D1 & D2 are both 1N5404 types, while D3 is a 1N4004. Next, install the capacitors, taking care to ensure that the electrolytics are correctly oriented. Don’t install REG2 at this stage, as it’s not mounted directly on the board. The completed PC board is housed Fig.31(a): follow this parts layout diagram to assemble the PC board. in standard plastic case, along with the power transformer. The front panel carries four banana sockets (0V, +5V, +12V and +15V) and the power indicator LED, while the rear panel carries the cordgrip grommet, safety fuse and mains switch. Both the transformer and the PC board are mounted on an aluminium baseplate (see Fig.32), which is earthed to ensure electrical safety. Drill out all the mounting holes in the Fig.31(b): this is the full-size etching pattern for the PC board. September 1999  73 This close-up view shows the completed PC board and the front-panel wiring. Note that regulator REG2 is mounted on the copper side of the board and has its metal tab bolted to the baseplate for heatsinking – see Fig.33. Fig.32: this diagram shows the drilling details for the aluminium baseplate. 74  Silicon Chip base­plate, then mount the transformer and earth lug as shown in Fig.34. The transformer is secured using 4mm screws, nuts and lockwashers, while the earth lug is mounted using a 3mm screw nut and lockwasher. It’s also a good idea to fit a second nut to the earth lug, so that the first nut is locked into place. Make sure that this assembly is tight. Regulator REG2 is mounted on the baseplate, beneath the PC board. This is necessary to ensure adequate heat­ sinking. Fig.33 shows the mounting details for this device. It must be electri­ cally isolated from the baseplate using an insulating pad and bush. Make sure that the mounting area is smooth and free of any metal swarf (which could puncture the insulating pad) before bolting the device down. Flying leads are used to connect REG2’s terminals back to its copper tracks on the PC board. Take care to ensure that these connections are all correct (a pinout diagram for the LM317 is shown on Fig.30) and keep the leads as short as possible. It’s a good idea to use a multimeter to confirm that the metal tab of the Fig.33: the mounting details for regulator REG2. Be sure to isolate its metal tab from the baseplate using an insulating washer and bush. regulator is properly isolated from the base­ plate. This done, the PC board can be mounted on 5mm-long stand­offs and secured using 3mm screws, nuts and lockwashers. The front and rear panels of the case can now be drilled to accept the various hardware items. The front panel is best drilled after attaching the label. Four holes are required to accept the banana sockets, plus a small hole in the middle for the LED bezel. The rear panel hardware can be positioned as shown in the photos. Use a small file to carefully profile the hole for the cordgrip grommet so that it is a precise fit. A slight problem here is that the plastic end panel is a bit too thick to suit the grommet. This means that you will need to chamfer the top and bottom of the hole on the inside of the panel to make sure that the grommet locks in properly (ie, the top and bottom slots in the grommet must engage the panel). We chamfered the prototype’s panel using a Stanley knife and a small file. Take your time with this job and make sure that the grommet is a neat (tight) fit. The hole for the mains switch can be made by first drilling a series of small holes around the inside perimeter of the marked area and then knocking out the centre piece and filing the hole to shape. Once again, make sure that the mains switch is a tight fit so that it’s secured properly when pushed into the mounting hole. The baseplate assembly sits directly on four standoffs moulded into the base of the case. You will have to drill 3mm holes through the centre of each standoff, so that 3mm mounting screws can be passed through from outside the case. Once this has been done, the baseplate assembly can be mounted in position and firmly secured. Wiring Now for the internal wiring. The mains cord Fig.34: the wiring details for the Stepper Power Supply. September 1999  75 Once the mains wiring has been completed, the rear panel can be slipped into position. After that, it’s simply a matter of completing the wiring from the PC board to the front panel and to the secondary terminals of the transformer. Use medium-duty hookup wire for this job. LED1 is wired by connecting it in series with a 330Ω resis­tor across the +5V and 0V output terminals. Its cathode (K) lead must go to the 0V terminal and this lead will be adjacent to a flat surface on the LED body (it’s also the shorter of the two leads). Testing Before applying power, check your wiring carefully and use a multimeter to confirm a good connection between the transformer metalwork and the earth terminal of the mains plug. This done, attach the lid, apply power and check that the indicator LED comes on. Finally, use your multimeter to check the voltages on the front panel sockets. You should get readings of around +15V, +13.5V and +5V with respect to the 0V terminal. Modifying the original supply The rear panel carries the on/off switch, the safety fuseholder and the cord clamp grommet. Make sure that the mains cord is properly secured and that all mains wiring is installed in a professional manner. must be secure­ly clamped by the cordgrip grommet and the Active (brown) wire connected directly to the fuseholder. The Neutral (blue) lead goes directly to switch S1, while the Earth lead (green/yellow) is soldered to the earth lug on the baseplate. Make the Earth lead somewhat longer than the other two leads, so that it will be the last to come adrift if the mains cord is reefed out by brute force. The two primary leads of the power transformer go to the bottom of S1, while the remaining terminal on S1 is 76  Silicon Chip connected back to the second terminal on the fuseholder. Be sure to sleeve all terminals on the mains switch and fuseholder with heatshrink tubing. This is done by pushing a short length of heatshrink tubing over each lead before it is soldered. After soldering, the heatshrink is then pushed over the exposed terminal and shrunk down using a hot-air gun. Be sure to use 250VAC-rated cable for all mains wiring. This includes the wiring to the fuseholder and to switch S1. If you built the supply described in the December 1997 issue, the diodes, 5V regulator and capacitors can be salvaged for the new PC board. You will need to purchase the LM317 adjust­able regulator plus a few extra capacitors and the four resis­tors. Unfortunately, the old transformer doesn’t have a high enough secondary voltage and we had to use a different type. The good news is that the new transformer fits on the old baseplate and you can use the same case. Although we haven’t tested it, it may be worthwhile trying the old transformer if you already have the previous supply. We suggest that you connect the +18V rail to the LM317 input and then adjust the 150Ω resistor to give a regulated +14V output. The existing +12V output can be used for the Z-axis card. Check this voltage under load and if it is much above +12V, fit a 5W series resistor to drop the voltage to around +12V when the motor is energised. Because the motor draws 0.6A, each 1Ω of resistance will drop about 0.6V. The indicator LED can be added to the existing +5V rail, as shown in this article. Drilling A PC Board Right, all systems should now be go. You have built and tested the power supply and stepper motor driver cards and wired them to the stepper motors. The XY table is running smoothly and you are just itching to drill the PC board for your latest pro­ject. Well, hopefully, you soon will be able to. There are just a few more checks to be made before you get into the nitty gritty. We will step back a little for a moment and cover the ground for those of you who may be a little hesitant to plough ahead without guidance. First, if you have already obtained the XY table software and followed the wiring in last month’s issue, you will find that the X arrow keys move the table in the Y direction and vice versa. In the XY table software, the first four terminals at the rear are for the Y motor and the next four are for the X motor. However, for all other software the sequence is X, Y then Z. To keep all the wiring consistent, we have modified XYREAD and XYTABLE to conform to this pattern. The new files are named XYREADM and XYTABLEM (Modified) to allow you to distinguish them from the previous versions. If you wish to modify your BAS files, all you need to do is edit line 3140 in each to read FOR A = 1 TO 4: STP(A) = STX(A) * 16 + STY(A): NEXT. Now you can swap your X and Y motor connections to conform to those shown last month. Pressing R while running the XYTABLE software allows you to select the stepping rate for the motors. This is very dependent on the processor in your computer. We used a 386 for this project and running under GW Basic a value of 50 gave good results. When using the EXE files a value of 2400 gave excellent results. To get a feel for your machine, start with these values and set new X and Y values an inch larger (or smaller) and listen to the motors step. Keep increasing the value until they begin to step smoothly. You will soon know from the “clunking” noise they make when they are mis-stepping, or not stepping at all, compared to the smooth steps they make once the stepping rate value is large enough. Set the count value so that you can move over the entire table area without any problems. Remember this number as you will need it shortly. We have mentioned previously that the BAS files are too slow and would take far too long to carry out any task but they are fine for experimenting. This is especially if you wish to alter the software to suit your needs. The seven files we mentioned in the July issue were DRLSE­ TUP. BAS, DRLSETUP.EXE, DRLSETUP. FIL, DRLTEST.BAS, DRLTEST.EXE, PCBDRILL.BAS and PCBDRILL.EXE. We glossed over them briefly then, as the power supply and new driver boards were not available at that stage. We shall now describe the func­tion of each of these BAS files in a little more detail. Setting up The first (DRLSETUP) is the program to set up the drill parameters. This simply asks for the maximum X dimension for your table in inches, the maximum Y dimension again in inches, then the stepping rate. Here’s where you enter that value you had to remember. The DRLSETUP.FIL has initial values loaded which you can accept by pressing the Enter key. Next the card number (ie, jumper setting) for the dual stepper motor card is requested, followed by the card number for the single stepper card. Then you are asked whether you want to display Imperial or metric values. As we have said in a previous article, the system was actually designed for steps of one thou­sandth of an inch, as all PC board layouts are in these measure­ ments. The metric display is only a conversion of the Imperial value to the closest equivalent. The next decisions you have to make are how many fast down and slow down steps the drill should make. When a PC board is drilled, the Z axis motor moves the drill down until it is a little above the board and holds it there. When a hole is to be drilled it just makes a small movement down and up, thus drilling the hole. The initial movement is the number of fast down steps; the latter is the number of slow down steps. The sum Power Supply Parts List 1 240V-15/0/15V power transformer, DSE M1991 or equivalent 1 plastic case with plastic end panels, 190 x 100 x 80mm 4 adhesive rubber feet 1 PC board, code 10108993, 75 x 60mm 1 front panel label, 83 x 67mm 1 240VAC 2-pole mains rocker switch, Altronics S3212 (or equival­ent) 3 red panel mount banana sockets 1 black panel mount banana socket 1 cord grip grommet 1 mains lead with moulded 3-pin plug 1 M205 safety 240VAC screw type fuseholder Altronics S5992 (or equivalent) 1 500mA M205 fuse 1 solder lug 8 PC stakes 4 5mm pillars 1 3mm x 10mm bolt 4 3mm x 15mm bolt 5 3mm nuts 5 3mm star washers 4 3mm flat washers 2 4mm x 12mm bolts 2 4mm star washers 2 4mm flat washers Semiconductors 1 7805 5V regulator (REG1) 1 LM350T variable output regulator (REG2) 2 1N5401/5404 power diodes (D1,D2) 1 1N4001/4004 power diode (D3) Capacitors 2 4700µF 25VW RB electrolytic 1 470µF 25VW RB electrolytic 1 10µF 16VW RB electrolytic 2 0.1µF monolithic ceramic Resistors (1%, 0.25W) 1 1.2kΩ 1 150Ω 1 120Ω Miscellaneous Hookup wire, 12mm-diameter heat­shrink tubing, 4mm-diameter heat­sh­rink tubing. September 1999  77 Fig.35: this is the test PC board pattern included with the software. When you drill a test board following the procedure in the text, its pattern of holes should match this artwork. of these two values cannot exceed 25 as this represents half a revolution of the motor. Pick 10 and 5 for these for the moment; you will get another chance later. The penultimate question is which parallel port you wish to use. If it is your workshop machine you probably don’t have a printer connected and in this case it will be LPT1. The last (ultimate) question is whether you wish to re-drill the PC board. If you answer no, it means that you fit an 0.8mm drill and only drill all the holes to this size, then drill the larger ones by hand later. To redrill means you want all the holes drilled with the smallest size drill. The table then returns to home and asks for the next size drill to be fitted in the chuck. It then drills all these and so on, until all the holes on the board are the correct size. Calibrating the drill depths The next program, DRLTEST, is used to confirm and adjust the drill fast down and slow down settings. The values given previously were just starting values. This program moves the drill to the fast down position, then allows you to move it up or down until it sits the distance you desire above the PC board. Once this is done, it then moves the drill down the number of slow steps you set in DRLSETUP. If this is unsatisfactory you can decrease or increase the number, which moves the drill up or down to the new position. When you exit the program, the new values are saved and used in PCBDRILL. Obviously it is wise to make sure that there is no PC board in the way each time you carry out this test, as the drill will break when it hits the board unless you have the drill motor running. If you look closely at the picture on page 72 of the July 1999 issue, you will see two clamps on the drill support bar, one towards the table base and one at the other end. These allow you to readily set the stand position for plotting or drilling a PC board. We fabricated these clamps but two automotive hose clamps from the nearest auto parts outlet would be a lot cheaper. Once you get the drill in position and moving correctly, slide the clamp up to the drill support and tighten it. Next time you plan to drill a PC board you can just slide the support down until it touches the clamp, then tighten the support knob. Drilling a test board The remaining program is PCBDRILL which should indicate its purpose. If you don’t yet have Protel or are not familiar enough with it to lay out a PC board, we have included a file called LCOSW.PCB, available both from our website (www.silicon­chip.com.au) and on the floppy we supply with this software. The two files generated by Protel (LCOSW.TOL and LCOSW.TXT) are also included. 78  Silicon Chip LCOSW.PCB is just a small board 100 x 20mm with 61 holes, including 14 for an IC, which will let you play around with the program and confirm the motor stepping rate and general operation of the XYZ table. PCBDRILL asks for the name of the PC board file to drill. In this case you type LCOSW in upper or lower case. If you add the .PCB suffix it will be accepted; if you omit it, the program will add it. Computers are supposed to save us time so why should we type any more characters than necessary? You will then be asked whether you want to flip the art­work. Normally, you lay out a PC board from the top (called the laminate or component) side and that is the side you would drill from. But as we plan to plot our boards then drill them, we will be working from the copper side and this is why it will be neces­sary to flip the layout. Pressing Enter or Y will flip it, while N maintains the view from the component side. Just to make things awkward, LCOSW.PCB was drawn looking at the copper side and does not need to be flipped. If you only plan to drill boards this could be a reason to alter the software to make Enter the no flip default. You now have to set up your computer with a directory named PROTEL, then two subdirectories below this named TRAXEDIT and TRAXPLOT. The software looks for LCOSW.TXT and LCOSW.TOL in the TRAXPLOT subdirectory. If you don’t follow this setup, the software won’t work. Setting up directories All software accessing output ports (printer) directly should be run from DOS, so if you run Windows select START, SHUTDOWN, then click “Restart in MSDOS Mode” and click OK. You will be dumped in the WINDOWS directory. Then Type CD\ and press Enter, which will place you in the root directory of your hard disk. To make a directory, type MD PROTEL and press Enter, then type MD PROTEL\TRAXPLOT and press Enter. Next, type MD PROTEL\TRAXEDIT and press Enter. Now you must copy the files to the TRAXPLOT directory. Type COPY A:LCOSW.TXT C:\PROTEL\ TRAXPLOT (press Enter), then type COPY A:LCOSW.TOL C:\ PROTEL\TRAXPLOT (press Enter). This assumes you have obtained a floppy from SILICON CHIP. Alternatively, if you download the files from our website, you must also place the two LCOSW files in the TRAXPLOT subdirectory. LCOSW.PCB must be copied to the TRAXEDIT directory (COPY A:LCOSW.PCB C:\ PROTEL\ TRAXEDIT). The other seven files should be placed in the BAS directory. If you haven’t yet created one, from the root directory (where you should still be), type MD BAS (press Enter). Then COPY A:P*.* \BAS (press Enter), then COPY A:D*.* \BAS (press Enter). The messages should read 2 files copied, then 5 files copied. When you want to run the programs, load DOS as described above, then when C:\WINDOWS shows, type CD\BAS (press Enter) and you will be placed in the BAS directory, from where you can run any BASIC or EXE program. Setting up Protel Once you have laid out a PC board using Protel and saved it, you have to create the TXT and TOL files we have just talked about. To do this, change to the PROTEL TRAXPLOT directory and type TRAXPLOT. Press the spacebar to access the first menu and the FILE menu will be highlighted. Press ENTER, then use the down arrow key to move to LOAD and then press ENTER again. If the entry does not read C:\PROTEL\TRAX­EDIT\*. PCB, then type this and press ENTER. You should now see LCOSW.PCB highlighted and pressing ENTER will load this file then return you to the FILE menu. Pressing ESC will get you back to the TRAXPLOT menu. Move down to SETUP, press ENTER, then move down to NC DRILL and press ENTER again. The box should read: OUTPUT FILE : C:<at>LCOSW X OFFSET 0.000 inches Y OFFSET 0.000 inches METHOD : GENERATE TOOL TABLE C:<at>LCOSW MATCH OVERSIZE: 0 MATCH UNDERSIZE: 0. If all these entries are correct, press ESC twice to get back to the main menu. If these entries aren’t all correct, move to the line(s) with the incor­rect entry and press ENTER to allow you to edit the value. Move the cursor down to NC DRILL and press ENTER. You will be asked CONFIRM PROCEED WITH NC DRILL (press Y). The box will show: TOOL FILE GENERATED LCOSW.TOL Press any key to continue When you do this, the next message will be: DRILL FILES GENERATED C:\PROTEL\TRAXPLOT\LCOSW.DRL C:<at>LCOSW.TXT Press any key to continue Pressing a key will get you back to the main menu after which you press ENTER as FILE is highlighted, move to QUIT (press ENTER) then enter Y to exit to DOS. This probably all sounds quite daunting if you have not done it before but believe me, it is heaps easier to actually do it than to describe how to do it. In any case, the reason we supply the LCOSW files is to save you these initial hassles. By the way, if you have downloaded Easytrax or if you have Autotrax, you will have to save all the EDIT files to the PROTEL\TRAXEDIT directory and all the PLOT files to the PROTEL\TRAXPLOT directory. If you don’t do this, you won’t be able to set up the files using Protel as described above. Note also that if you have Easytrax, you should type EASYPLOT and EASYEDIT instead of TRAXPLOT and TRAXEDIT. Next month we will describe the pen holder and the software for plotting a pattern directly onto the copper of a PC board. This will allow you to make your own PC SC boards, provided you have etching facilities. September 1999  79 PRODUCT SHOWCASE Altronic’s Aussie Maxi Mount bracket gets world-wide sales Designed and manufactured in Australia by Altronic Distributors, this high capacity speaker swivel mount is being exported in significant quantities to North America and Europe, where it is very popular with professional speaker installers. The bracket is designed for quick and easy installation, requiring no special tools and can handle a payload of up to 15kg, making it suitable for most small to medium speakers. It also suits a wide variety of other uses such as security lights, CCTV cameras and so on. It can be swivelled up to 50° in either the vertical or horizontal plane and with optional hardware can mount to brick/ masonry, timber or plaster walls. Retail price is $59 per pair. For more information contact Altronic Distributors, Perth, Tel (08) 9328 2199, Fax (08) 9328 4459. Kenwood Power Supplies from Nilsen Nilsen Technologies have released two new power supplies, the Kenwood PAC series DC (top) and the Kenwood PDS series of EMC compliant lab models (bottom). The PAC series is available in outputs from 0-20V to 0-60V (3A) with load regulation of 4-8mV max. The PDS series are equipped with active smoothing filters and have very low output noise. Outputs available are 0-20V (18A) up to 0-120V (6A). For more information contact Nilsen Technologies, Freecall 1800 623 350, Feefax 1800 067 263. High Accuracy, Rugged Instrumentation Amp The Linear Technology LT1920 amplifier from REC Electronics is capable of withstanding input faults of +/-100V DC and spikes of over 8kV, yet is accurate to 30 parts per million. With industry-standard pinout and compact SO-8 package, it is suitable for a wide range of precision data acquisition. Contact REC ELectronics on (02) 9638 1888 or via www.rec.com.au Hobbyist/Handyman Bit Set Do you have devices or appliances that need fixing – but you can't find the right bit to undo the screws? Dick Smith Electronics has released a 101-piece bit set that has just about everything the hobbyist, handyman and the technician could want. It features a magnetised bit holder along with flat and Philips, square, hex, Torx, Security Torx, Tri-wing and more, all in a handy storage case. The bits should fit a cordless drill or power screwdriver, too. With a recommended retail price of $36.80, the Bit Set (Cat. T-4513) is available at all Dick Smith Electronics stores or from their mail order service on 1300 366 644. 80  Silicon Chip Jands’ Studio Microphone Clinic Jands Electronics, an Australian professional audio, lighting and staging manufacturer and distributor hosts regular ‘Industry Nights’ for the audio and lighting industry. Course notes, demos and guest speakers are all provided free. The next Industry Night, on 7 September at The Globe in Newtown covers the selection and placement of studio microphones. Presenter Nick Orsatti said that the topics will include close miking and ambient techniques, stereo miking and techniques for multi-channel surround recording. To register or for more information, please contact Jands Electronics on 02 9582 0909. FOR SALE Audio Service Business + 25 Acre Bush Property NSW South Coast – 10mins from Moruya, 20mins from Bateman's Bay. Business established 20 years. Great potential for expansion into TV/VCR if required. Large 3-4 bedroom passive solar stone house – many features. Large workshop. Phone (02) 4474 2985 or email brunnion<at>sci.net.au L LECTRONICSHOWCASELEC SPEAKER SALE For the very first time we are having a sale of selected loudspeaker drivers from the prestige MOREL line. On sale are two drivers: UNIVERSAL WIRELESS DEVELOPMENT SYSTEM Linx RF modules from Clarke & Severn Electronics offer a simple, efficient and cost-effective method of making a product wireless. Want to know more? Contact CLARKE & SEVERN ELECTRONICS PO Box 1, Hornsby NSW 1630 Ph (02) 9482 1944 Fx 9482 1309 email: sales<at>clarke.com.au www.clarke.com.au MW 265 EMC Technologies' internationally recognised Electromagnetic Compatibility (EMC) test facilities are fully accredited for emissions, immunity and safety standards. 222mm Shielded Woofer, Fs 30Hz ,Vas 88.6L Qts 0.44 Power 150W Hexatech voice coil Normally $190 EMC Technologies DMS 30S Melbourne: (03) 9335 3333 Sydney: (02) 9899 4599 NOW $130 27mm Shielded Dome Tweeter, 94mm dia. Fs 650Hz Power 200W Hexatech voice coil Double chambered Sens 90dB Normally $129 NOW $75 All other MOREL products available – many ex-stock We are sole Australian Distributors for: •  CLIO Electro-Acoustic Measurements •  SOFIA Vacuum Tube Curve Tracer •  JASPER Power Router Circle Jigs Australian Audio Consultants Web site: Email: www.mgram.com.au info<at>mgram.com.au BUSINESS FOR SALE: Vamtest Pty Ltd trading as Microgram Computers A.C.N. 003 062 100 Unit 1, 14 Bon Mace Close Berkeley Vale NSW 2261 Phone: (02) 4389 8444 Fax: (02) 4389 8388 SWITCHMODE POWER SUPPLIES 25W500W Extensive Range Escape to the sun in beautiful Coffs Harbour! • • • • •   • • •   • Stable electronic retail business Easily run by husband and wife team. Agent for GSM carrier Access to large electronics suppliers (niche market). Very strong customer base inc Government depts and schools etc. Five year rental option on current highway premises. Full figures available. Current owners (12 years) are moving to a new business. Price only $55,000 + SAV. Enquiries: Hunter & Associates (02) 6651 6818 R.T.N • Basic Stamps, SX chips and tools. • OZ-made boards and development tools • Best pricing on temp, a/d, rtc kits • New Xilinx PLCC44 development system • New OZ made serial LCD module 2*16 • Stepper and R/C servo motor chips • New super catalog on CD Rom with 40 meg of  Stamp related data. Now available via SAE and  our cost $4.50, or free with orders over $125 Phone/Fax 03-9338-3306 HTTP://people.enternet.com.au/~nollet Email: nollet<at>mail.enternet.com.au PO Box 11, Stockport SA 5410 Phone / Fax 08-85-282-201 E-mail aac<at>rbe.net.au MicroZed Computers GENUINE STAMP PRODUCTS FROM Scott Edwards Electronics microEngineering Labs & others Easy to learn, easy to use, sophisticated CPU based controllers & peripherals. PO Box 634, ARMIDALE 2350 (296 Cook’s Rd) 6 Sarich Court, Technology Park, Bentley WA 6102 Ph: 08 9470 1177 Fax 08 9470 2844 web: www.computronics.com NEW FROM QUESTRONIX DVS5 Video & Audio Distribution Amplifier Ph (02) 6772 2777 – may time out to Mobile 0409 036 775 Fax (02) 6772 8987 http://www.microzed.com.au Most Credit Cards OK DVS5 Video & Audio Distribution Amplifier VGS2 Graphics Splitter Five identical Video and Stereo outputs plus h/phone & monitor out. S-Video & Composite versions available. Professional quality. VGS2 Graphics Splitter High resolution 1in/2out VGA splitter. Comes with 1.5m HQ cable and 12V supply. Custom-length HQ VGA cables also available. Check our NEW website for latest prices and MONTHLY SPECIALS www.questronix.com.au Email - questav<at>questronix.com.au Video Processors, Colour Correctors, Stabilisers, TBC's, Converters, etc. QUESTRONIX All mail: PO BoxS548, Wahroonga NSW 2076 eptember 1999  81 Ph (02) 9477 3596 Fax (02) 9477 3681 Visitors by appointment only TECHNICAL LOOK: TEN NEW NEW! TCP/IP EXPLAINED By Philip Miller. Published 1997. $ 90 This concise and practical book offers readers an in-depth understanding of the Internet Protocol suite. It assumes no prior knowledge of TCP/IP, only a basic understanding of LAN access protocols, explaining all the elements and alternatives. It leads the reader through the Internet protocols, combining study questions with reference material. Examples of network designs and implementations are given. 518 pages, in paperback, at $90.00. LOCAL AREA NETWORKS: An Introduction to the Technology NEW! SETTING UP A WEB SERVER A complete reference for anyone setting up a web server. Covers all major platforms, software, links and web techniques. It details each step required to choose, install and configure the hardware and software elements, create an effective site and promote it successfully. The book covers the main web server software applications, how they differ, and which work best in each environment. 273 pages, in paperback, at $65.00. NEW! 65 NEW! By Tim Williams. First published 1991 (reprinted 1997). THE CIRCUIT DESIGNER’S COMPANION By PK McBride & Nat McBride. Published 1999. $ O R D E R H E R E 29 95 If you want to create web pages for your business or your own home site, but don't know where to start . . . or if you have some experience of Web page design and now need to master all aspects of HTML form then “HTML4.0 Made Simple” is for you. it uses a combination of tutorial approach, carefully focussed examples and quick reference guides. 198 pages, in paperback, at $29.95.      TCP/IP EXPLAINED.............................................$90.00  LOCAL AREA NETWORKS..................................$65.00  HTML 4.0 MADE SIMPLE...................................$29.95  SETTING UP A WEB SERVER.............................$65.00  THE CIRCUIT DESIGNER’S COMPANION...........$59.95  ELECTRIC MOTORS AND DRIVES......................$59.95  UNDERSTANDING TELEPHONE ELECTRONICS....$55.00  AUDIO ELECTRONICS........................................$79.00  GUIDE TO TV & VIDEO TECHNOLOGY...............$55.00  EMC FOR PRODUCT DESIGNERS.......................$95.00  THE ART OF LINEAR ELECTRONICS..................$80.00  INTERNET HOME PAGES MADE SIMPLE...........$24.95  DIGITAL ELECTRONICS .....................................$59.95  ESSENTIAL LINUX..............................................$85.00               ORDER TOTAL: $............. 82  Silicon Chip Includes grounding, printed circuit design and layout, the characteristics of practical active and passive components, cables, linear ICs, logic circuits and their interfaces, power supplies, electromagnetic compatibility, safety and thermal management. Aimed at the practising designer who needs straightforward, easy-to-follow advice. 302 pages, in paperback, at $59.95. $ HTML 4.0 MADE SIMPLE 65 $ By John E. McNamara. 2nd edition 1996. Intended for those who want to become more familiar with local area networks (LANs) without facing the challenge of a 400-page text. The goals of the book are to give prospective LAN users or purchasers familiarity with the concepts involved and to provide a head start for reading more detailed texts. 191 pages, in paperback, at $65.00. NEW! By Simon Collin. Published 1997. $ 59 95 ELECTRIC MOTORS AND DRIVES NEW! By Austin Hughes. Second edition published 1993 (reprinted 1997). This book is for non-specialist users of electric motors and drives. The author explores most of the widely-used modern types of motor and drive, including conventional and brushless DC, induction motors (mains and inverter-fed), stepping motors, synchronous motors (mains and converter-fed) and reluctance motors. 339 pages, in paperback, at $59.95. 59 95 $ Your Name_________________________________________________ PLEASE PRINT Address ___________________________________________________ ___________________________________ Postcode_______________ Daytime Phone No. (______) __________________________________ STD  Cheque/Money Order enclosed OR  Charge my credit card –  Bankcard   Visa Card   MasterCard Signature_________________________ Card expiry date______/______ PLUS P&P (if applic): $.............. TOTAL$ AU.................... ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. BOOKSHOP WANT TO SAVE 10%? SILICON CHIP SUBSCRIBERS AUTOMATICALLY QUALIFY FOR A 10% DISCOUNT ON ALL PURCHASES! TITLES AVAILABLE! $ UNDERSTANDING TELEPHONE ELECTRONICS By Stephen J. Bigelow. Third edition published 1997 by Butterworth-Heinemann. 55 (To subscribe, see page 53) 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. AUDIO ELECTRONICS   GUIDE TO TV & VIDEO TECHNOLOGY $ By John Linsley Hood. First published 1993. NEW SECOND EDITION 1998. 80 All you need to get started. Create and design your own Internet home pages that include both text and graphics, using this practical, easy to follow, jargon free guide. This edition has been enhanced and updated and now covers HTML 4.0. 182 pages, in paperback, at $24.95. 79 $ Eugene Trundle has written for many years in Television magazine and his latest book is right up to date on TV and video technology. The book includes both theory and practical servicing information and is ideal for both students and technicians. 382 pages, in paperback, at $55.00. 55 EMC FOR PRODUCT DESIGNERS NEW! P&P Add $A5.00 per book – Orders over $100 P&P free in Australia. NZ: Add $A10 per book, $A15 elsewhere 24 95 $ DIGITAL ELECTRONICS –  A PRACTICAL APPROACH By Richard Monk. Published 1998. $ 59 95 With this book you can learn the principles and practice of digital electronics without leaving your desk, through the popular simulation applications, EASY-PC Pro XM and Pulsar. Alternatively, if you want to discover the applications through a thoroughly practical exploration of digital electronics, this is the book for you. A free floppy disk is included, featuring limited function versions of EASY-PC Professional XM and Pulsar. 249 pages, in paperback, at $59.95. ESSENTIAL LINUX By Steve Heath. Published 1997. By Tim Williams. First pub­­lished 1992. Second edition 1996. Widely regarded as the standard text on EMC, this book provides all the information necessary to meet the requirements of the EMC Directive. It includes chapters on standards, measurement techniques and design principles, including layout and grounding, digital and analog circuit design, filtering and shielding and interference sources. The four appendices give a design checklist and include useful tables, data and formulae. 299 pages, in soft cover at $95.00. NEW! By Lilian Hobbs. First published 1996. Second edition 1999. By Eugene Trundle. First pub­­lished 1988. Second edition 1996. $ This practical handbook from one of the world’s most prolific audio designers has been updated and amended to make it the leading practical source of information for those interested in linear electronics and its applications, particularly in the world of audio design. 348 pages, in paperback, at $80.00. DESIGNING INTERNET HOME PAGES MADE SIMPLE By John Linsley Hood. First published 1995. Second edition 1999. This book is for anyone involved in designing, adapting and using analog and digital audio equipment. It covers tape recording, tuners and radio receivers, preamplifiers, voltage amplifiers, audio power amplifiers, compact disc technology and digital audio, test and measurement, loudspeaker crossover systems, power supplies and noise reduction systems. 375 pages in soft cover at $79.00. THE ART OF LINEAR ELECTRONICS NEW! 95 $ Provides all the information and software that is necessary for a PC user to install and use the freeware Linux operating system. It details, setp-by-step, how to obtain and configure the operating system and utilities. It also explains all of the key commands. The text is generously illustrated with screen shots and examples that show how the commands work. Includes a CD-ROM containing Linux version 1.3 and including all the interim updates, basic utilities and compilers with their associated documentation. 257 pages, in paperback, at $85.00. 85 $ NEW! POST 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 December 1999  83 Silicon Chip Back Issues September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; The Story Of Amtrak Passenger Services. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; The Burlington Northern Railroad. July 1989: Exhaust Gas Monitor; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; The NSW 86 Class Electrics. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; High Or Low Fluid Level Detector; Studio Series 20-Band Stereo Equaliser, Pt.2. October 1989: FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 2-Chip Portable AM Stereo Radio, Pt.2; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Phone Patch For Radio Amateurs; Active Antenna Kit; Designing UHF Transmitter Stages. February 1990: A 16-Channel Mixing Desk; Build A High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2. March 1990: Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; The Australian VFT Project. 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. June 1990: Multi-Sector Home Burglar Alarm; Build A Low-Noise Universal Stereo Preamplifier; Load Protector For Power Supplies; Speed Alarm For Your Car. July 1990: Digital Sine/Square Generator, Pt.1 (covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Build A Simple Electronic Die; A Low-Cost Dual Power Supply; Inside A Coal Burning Power Station. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes); Horace The Electronic Cricket; Digital Sine/Square Generator, Pt.2. September 1990: A Low-Cost 3-Digit Counter Module; Build A Simple Shortwave Converter For The 2-Metre Band; The Bose Lifestyle Music System (Review); The Care & Feeding Of Nicad Battery Packs (Getting The Most From Nicad Batteries). 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. 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. November 1990: How To Connect Two TV Sets To One VCR; Build An Egg Timer; Low-Cost Model Train Controller; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Build A Simple 6-Metre Amateur Band Transmitter. December 1990: The CD Green Pen Controversy; 100W DC-DC Converter For Car Amplifiers; Wiper Pulser For Rear Windows; 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers of Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Low-Cost Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; A Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateur Radio & TV. April 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. 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. 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, Pt.1. 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. September 1991: Digital Altimeter For Gliders & Ultralights; Ultrasonic Switch For Mains Appliances; The Basics Of A/D & D/A Conversion; Plotting The Course Of Thunderstorms. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Altimeter For Gliders, Pt.2; Military Applications Of R/C Aircraft. November 1991: Build A Colour TV Pattern Generator, Pt.1; A Junkbox 2-Valve Receiver; Flashing Alarm Light For Cars; Digital Altimeter For Gliders, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Build a Turnstile Antenna For Weather Satellite Reception. 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: Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; 1kW Dummy Load Box For Audio Amplifiers; Troubleshooting Vintage Radio Receivers; The MIDI Interface Explained. October 1992: 2kW 24VDC - 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; A Regulated Lead-Acid Battery Charger. January 1993: Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Projects For Model Railroads; Low Fuel Indicator For Cars; Audio Level/VU Meter (LED Readout); An Electronic Cockroach; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5. March 1993: Solar Charger For 12V Batteries; Alarm-Triggered Security Camera; Reaction Trainer; Audio Mixer for Camcorders; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Converter; Digital Clock With Battery Back-Up. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Alphanumeric LCD Demonstration Board; The Story of Aluminium. June 1993: AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Build A Windows-Based Logic Analyser. July 1993: Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Quiz Game Adjudicator; Windows-Based Logic Analyser, Pt.2; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; Microprocessor-Based Sidereal Clock; Southern Cross Z80-Based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; +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. December 1993: Remote Controller For Garage Doors; Build A LED Stroboscope; Build A 25W Audio Amplifier Module; A 1-Chip Melody Generator; Engine Management, Pt.3; Index To Volume 6. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Colour TV Pattern Generator, Pt.2; Index To Volume 4. 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. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Experiments For Your Games Card. 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 In Cars – A Look At How They Work. ORDER FORM Please send me the following back issues: _____________________________________________________________________ _______________________________________________________________________________________________________________ Card No. Signature ___________________________ Card expiry date_____ /______ Name ______________________________ Phone No (___) ____________ Note: all prices include post & packing Australia ....................................................... $A7 NZ & PNG (airmail) ...................................... $A8 Overseas (airmail) ...................................... $A10 Street ______________________________________________________ Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Suburb/town _______________________________ Postcode ___________ Or call (02) 9979 5644 & quote your credit card details or fax the details to (02) 9979 6503. PLEASE PRINT 84  Silicon Chip ✂ Enclosed is my cheque/money order for $­______or please debit my:  ❏ Bankcard  ❏ Visa Card  ❏ Master Card 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. 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. 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. 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. April 1996: Cheap Battery Refills For Mobile Telephones; 125W Audio Power Amplifier Module; Knock Indicator For Leaded Petrol Engines; Multi-Channel Radio Control Transmitter; Pt.3; Cathode Ray Oscilloscopes, Pt.2. 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. 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. 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. May 1996: Upgrading The CPU In Your PC; 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 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. 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 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. 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 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); 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. 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; Remote Control System For Models, Pt.2. March 1995: 50 Watt Per Channel Stereo Amplifier, Pt.1; Subcarrier Decoder For FM Receivers; Wide Range Electrostatic Loudspeakers, Pt.2; IR Illuminator For CCD Cameras; Remote Control System For Models, Pt.3; Simple CW Filter. April 1995: FM Radio Trainer, Pt.1; Photographic Timer For 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. May 1995: What To Do When the Battery On Your PC’s Mother­board Goes Flat; Build A Guitar Headphone Amplifier; FM Radio Trainer, Pt.2; Transistor/Mosfet Tester For DMMs; A 16-Channel Decoder For Radio Remote Control; Introduction to Satellite TV. June 1995: Build A Satellite TV Receiver; Train Detector For Model Railways; 1W Audio Amplifier Trainer; Low-Cost Video Security System; Multi-Channel Radio Control Transmitter For Models, Pt.1; Build A $30 Digital Multimeter. July 1995: Electric Fence Controller; How To Run Two Trains On A Single Track (Incl. Lights & Sound); Setting Up A Satellite TV Ground Station; Build A Reliable Door Minder. August 1995: Fuel Injector Monitor For Cars; Gain Controlled Microphone Preamp; Audio Lab PC-Controlled Test Instrument, Pt.1; Mighty-Mite Powered Loudspeaker; How To Identify IDE Hard Disc Drive Parameters. September 1995: Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.1; Keypad Combination Lock; The Vader Voice; Jacob’s Ladder Display; Audio Lab PC-Controlled Test Instrument, Pt.2. October 1995: Geiger Counter; 3-Way Bass Reflex Loudspeaker System; Railpower Mk.2 Walkaround Throttle For Model Railways, Pt.2; Fast Charger For Nicad Batteries; Digital Speedometer & Fuel Gauge For Cars, Pt.1. November 1995: Mixture Display For Fuel Injected Cars; CB Trans­ verter For The 80M Amateur Band, Pt.1; PIR Movement Detector; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.1; Digital Speedometer & Fuel Gauge For Cars, Pt.2. December 1995: Engine Immobiliser; 5-Band Equaliser; CB Transverter For The 80M Amateur Band, Pt.2; Subwoofer Controller; Dolby Pro Logic Surround Sound Decoder Mk.2, Pt.2; Knock Sensing In Cars; Index To Volume 8. January 1996: Surround Sound Mixer & Decoder, Pt.1; Magnetic Card Reader; Build An Automatic Sprinkler Controller; IR Remote Control For The Railpower Mk.2; Recharging Nicad Batteries For Long Life. February 1996: Three Remote Controls To Build; Woofer Stopper Mk.2; 10-Minute Kill Switch For Smoke Detectors; Basic Logic Trainer; Surround Sound Mixer & Decoder, Pt.2; Use your PC As A Reaction Timer. 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; Build A Multi-Media Sound System, Pt.1; Multi-Channel Radio Control Transmitter, Pt.8. 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; Build A Multi-Media Sound System, Pt.2; 600W DC-DC Converter For Car Hifi Systems, Pt.2. December 1996: CD Recorders –­ The Next Add-On For Your PC; Active Filter Cleans Up CW Reception; Fast Clock For Railway Modellers; Laser Pistol & Electronic Target; Build A Sound Level Meter; 8-Channel Stereo Mixer, Pt.2; Index To Volume 9. January 1997: How To Network Your PC; 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. 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; Jet Engines In Model Aircraft. May 1998: Troubleshooting Your PC, Pt.1; Build A 3-LED Logic Probe; Automatic Garage Door Opener, Pt.2; Command Control For Model Railways, Pt.4; 40V 8A Adjustable Power Supply, Pt.2. June 1998: Troubleshooting Your PC, Pt.2; Understanding Electric Lighting, Pt.7; Universal High Energy Ignition System; The Roadies’ Friend Cable Tester; Universal Stepper Motor Controller; Command Control For Model Railways, Pt.5. July 1998: Troubleshooting Your PC, Pt.3 (Installing A Modem And Sorting Out Any Problems); Build A Heat Controller; 15-Watt Class-A Audio Amplifier Module; Simple Charger For 6V & 12V SLA Batteries; Automatic Semiconductor Analyser; Understanding Electric Lighting, Pt.8. August 1998: Troubleshooting Your PC, Pt.4 (Adding Extra Memory To Your PC); Build The Opus One Loudspeaker System; Simple I/O Card With Automatic Data Logging; Build A Beat Triggered Strobe; A 15-Watt Per Channel Class-A Stereo Amplifier. September 1998: Troubleshooting Your PC, Pt.5 (Software Problems & DOS Games); A Blocked Air-Filter Alarm; A Waa-Waa Pedal For Your Guitar; Build A Plasma Display Or Jacob’s Ladder; Gear Change Indicator For Cars; Capacity Indicator For Rechargeable Batteries. October 1998: CPU Upgrades & Overclocking; Lab Quality AC Millivoltmeter, Pt.1; PC-Controlled Stress-O-Meter; Versatile Electronic Guitar Limiter; 12V Trickle Charger For Float Conditions; Adding An External Battery Pack To Your Flashgun. November 1998: Silicon Chip On The World Wide Web; The Christmas Star (Microprocessor-Controlled Christmas Decoration); A Turbo Timer For Cars; Build Your Own Poker Machine, Pt.1; FM Transmitter For Musicians; Lab Quality AC Millivoltmeter, Pt.2; Beyond The Basic Network (Setting Up A LAN Using TCP/IP); Understanding Electric Lighting, Pt.9; Improving AM Radio Reception, Pt.1. 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. December 1998: Protect Your Car With The Engine Immobiliser Mk.2; Thermocouple Adaptor For DMMs; A Regulated 12V DC Plugpack; Build Your Own Poker Machine, Pt.2; GM’s Advanced Technology Vehicles; Improving AM Radio Reception, Pt.2; Mixer Module For F3B Glider Operations. March 1997: Driving A Computer By Remote Control; Plastic Power PA Amplifier (175W); Signalling & Lighting For Model Railways; Build A Jumbo LED Clock; Cathode Ray Oscilloscopes, Pt.7. January 1999: The Y2K Bug & A Few Other Worries; High-Voltage Megohm Tester; Getting Going With BASIC Stamp; LED Bargraph Ammeter For Cars; Keypad Engine Immobiliser; Improving AM Radio Reception, Pt.3; Electric Lighting, Pt.10 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. May 1997: Teletext Decoder For PCs; Build An NTSC-PAL Converter; Neon Tube Modulator For Light Systems; Traffic Lights For A Model Intersection; The Spacewriter – It Writes Messages In Thin Air; A Look At Signal Tracing; Pt.2; Cathode Ray Oscilloscopes, Pt.9. June 1997: Tuning Up Your Hard Disc Drive; PC-Controlled Thermometer/Thermostat; Colour TV Pattern Generator, Pt.1; Build An Audio/RF Signal Tracer; High-Current Speed Controller For 12V/24V Motors; Manual Control Circuit For A Stepper Motor; Fail-Safe Module For The Throttle Servo; Cathode Ray Oscilloscopes, Pt.10. July 1997: Infrared Remote Volume Control; A Flexible Interface Card For PCs; Points Controller For Model Railways; Simple Square/Triangle Waveform Generator; Colour TV Pattern Generator, Pt.2; An In-Line Mixer For Radio Control Receivers; How Holden’s Electronic Control Unit works, Pt.1. August 1997: The Bass Barrel Subwoofer; 500 Watt Audio Power Amplifier Module; A TENs Unit For Pain Relief; Addressable PC Card For Stepper Motor Control; Remote Controlled Gates For Your Home; How Holden’s Electronic Control Unit Works, Pt.2. September 1997: Multi-Spark Capacitor Discharge Ignition; 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; 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; 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. February 1999: Installing A Computer Network (Network Types, Hubs, Switches & Routers); Making Front Panels For Your Projects; Low Distortion Audio Signal Generator, Pt.1; Command Control Decoder For Model Railways; Build A Digital Capacitance Meter; Remote Control Tester; Electric Lighting, Pt.11. March 1999: Getting Started With Linux; Pt.1; Build A Digital Anemometer; 3-Channel Current Monitor With Data Logging; Simple DIY PIC Programmer; Easy-To-Build Audio Compressor; Low Distortion Audio Signal Generator, Pt.2; Electric Lighting, Pt.12. April 1999: Getting Started With Linux; Pt.2; High-Power Electric Fence Controller; Bass Cube Subwoofer; Programmable Thermostat/ Thermometer; Build An Infrared Sentry; Rev Limiter For Cars; Electric Lighting, Pt.13; Autopilots For Radio-Controlled Model Aircraft. May 1999: The Line Dancer Robot; An X-Y Table With Stepper Motor Control, Pt.1; Three Electric Fence Testers; Heart Of LEDs; Build A Carbon Monoxide Alarm; Getting Started With Linux; Pt.3. June 1999: FM Radio Tuner Card For PCs; X-Y Table With Stepper Motor Control, Pt.2; Programmable Ignition Timing Module For Cars, Pt.1; Hard Disk Drive Upgrades Without Reinstalling Software; What Is A Groundplane Antenna?; Getting Started With Linux; Pt.4. July 1999: Build The Dog Silencer; A 10µH to 19.99mH Inductance Meter; Build An Audio-Video Transmitter; Programmable Ignition Timing Module For Cars, Pt.2; XYZ Table With Stepper Motor Control, Pt.3; The Heapod Robot. August 1999: Remote Modem Controller; Daytime Running Lights For Cars; Build A PC Monitor Checker; Switching Temperature Controller; XYZ Table With Stepper Motor Control, Pt.4; Electric Lighting, Pt.14; DOS & Windows Utilities For Reversing Protel PC Board Files. PLEASE NOTE: November 1987 to August 1988, October 1988 to March 1989, June 1989, August 1989, December 1989, May 1990, August 1991, February 1992, July 1992, September 1992, November 1992, December 1992 and March 1998 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, or can be downloaded free from our web site: www.siliconchip.com.au September 1999  85 Just right for Summer! Last month, we introduced Peltiereffect devices and described an accurate temperature controller. This month, given the fact that those long, hot summer days are just around the corner, we’re putting a Peltier device to the most noble of uses – keeping those tinnies temperate! By Ross Tester A PeltierPeltierA Powered Powered Can Cooler Cooler Can 86  Silicon Chip O K, this project could (and probably would!) be used to keep cold a lot more than a few cans. But hey, we’re realists. We know what most dinkum Aussie blokes use their Eskys for. . . and for the benefit of our readers across the Tasman, that translates to what antipodean gentlemen use their chilly bins for . . . Well, this is one chilly, chilly bin bin! It’s not exactly in the league of most of the electronics projects you see in the pages of SILICON CHIP. Basically, we’re using just one electronic component – a Peltier device – and a bit of hardware. So even if you don’t know a resistor’s anode from its cathode (or maybe if you do?), this project should be right up your alley. Of course, if you enjoy a drop of the amber nectar, it’s even better. Fortunately, the project must be completed before you can cool a can, so there’s little danger of making a mistake due to over-sampling along the way. That’s just as well because if you get the connections wrong, you can actually warm the can instead of cooling it. No, we won’t get into any Aussie vs Pom beer discussions right now, thank you. The Peltier device Just in case you didn’t see last month’s issue where we discussed the Peltier device in detail, a word or two of explanation. It’s quite a simple device, basically a number of P-N junctions sandwiched between two metal plates. Pass current through the junctions one way and they absorb heat – one of the two plates gets very much colder than the other. Reverse the current and the junctions emit heat. This effect can be used to heat or cool. If you thermally bond the plate All you can see on the lid of the cooler is a large heatsink and 12V fan. The Peltier device is sandwiched between this assembly and an internal heatsink. getting cold to another surface, it will “suck” heat from that surface. And that’s exactly what we are doing in this project: we thermally bond a Peltier device to two heatsinks, one of which is inside the cooler. When power is applied the Peltier device cools, dragging the temperature of the heatsink down with it. The heatsink draws heat from its surroundings – the inside of the cooler. Therefore the cooler (and anything in it) cools down. (For a more detailed description of the Peltier device, see page 55 of the August 1999 SILICON CHIP). Peltier devices come in a variety of current ratings. The higher the current, the greater their cooling (or heating) capacity. While this is true up to a point, there are several limitations which stop the device operating at its maximum. Perhaps the most important of these is the ambient temperature – if the air on the “hot” side of the device is itself Reproduced from last month’s issue, this is what the Peltier device looks like. This particular one is rated at 12V, 4A. The side closest to the camera is the “cold” side when 12V DC is connected + to red, - to black. hot then there will not be anywhere near as much heat transfer as if the air was cooler. Linked with this is the amount of heat which can be drawn away from the Peltier device. In this project we use a suitably-sized 12V fan which has a reasonable flow but is certainly not hurricane strength. More airflow means more cooling; more cooling means greater efficiency. The “∆T”, or difference between the hot and cold side of the device, is given as 65°C. This is more-or-less the same for all of the types of Peltier device available in this size range. What this means is that at its rated power, the cold side of the device will be 65°C cooler than the hot side (or, obviously vice versa). In an ideal world, this would be the case – but this is not an ideal world. So don’t expect to get a 65°C difference in your cooler! The main difference you would note between the various devices is not so much in their cooling or heating ability but the time it takes to cool or heat. The higher the current, the faster the device will operate. DC switching? Last month we warned about switching a Peltier device with DC due to the thermal stress and shock which may occur between the two plates due to their difference in temperature. This September 1999  87 can be enough to damage or even destroy a Peltier device with continual usage. For this reason, in temperature control applications it is preferable to switch the Peltier device on and off at a rapid rate (>2kHz) and change the duty cycle (on time to off time) to achieve the appropriate power level. The net result is the same but the stresses are elminated. But guess how we are switching the Peltier device in our cooler? With DC, that’s how! The rationale is that in this application the Peltier device would not be switched on and off repeatedly – rather, it would be turned on and left on, for possibly hours on end. While there would be some thermal shock at each switching, it’s nowhere near as bad as switching on or off every few minutes or so, as happens in temperature control. We want the Peltier to work flat out – and that means staying on until the last tinnie is removed! The circuit The circuit, shown in Fig. 1, could hardly be simpler: the Peltier device is in parallel with a 12V fan – and that’s it. There is no on/off switch (it’s intended to run from your car cigarette lighter socket) and there’s no fuse (the cigarette lighter socket already has one). You just plug ’er in and away + – Fig. 1: the circuit diagram could hardly be simpler – a Peltier device in parallel with a 12V fan, both connected to 12V DC. she goes! Peltier devices are not all that common but Oatley Electronics have 4A, 6A and 8A models for between $25 and $30. They are all 40mm square with a ∆T of 65°C. Construction The Peltier device is mounted through the lid of the cooler and requires a suitable-sized hole to be cut in the lid. Fig.2 shows how this is arranged. The exact method of mounting depends to a large degree on the type of cooler you are fitting the device to. We used a “Willow” brand – it happens to be a 33-litre size but that’s unimportant. What is important is (a) enough clearance under the handle to allow the heatsink/fan assembly to fit and (b) a suitable flat area in the middle of the lid to allow the whole assembly to sit flat. Our cooler also had a The first step is to cut a hole in the lid of the cooler the same size as the aluminium block, then drill the mounting holes through the top heatsink, cooler lid and bottom heatsink, taking care not to foul any heatsink fins. The photo at right shows the aluminium block in the hole – a nice, tight fit. 88  Silicon Chip very handy recess in the underside of the lid which just fitted a large (140x 155mm) heatsink; very handy indeed! The heatsinks we used were preloved units from the junk box – it just so happened we had two on hand which fitted quite nicely. If you have to buy new heatsinks, the Jaycar Cat HH8592 (125 x 125mm) and the Altronics H-0566 (150 x 121mm) would appear to be amongst the most suitable. As we said before, efficient thermal transfer is absolutely vital if the system is to work and this depends on intimate contact between the inside heatsink, the Peltier device and the outside heatsink. Your cooler lid will almost certainly have some thickness, probably made of two sheets of plastic (polycarb-onate?) with either air or another insulator (eg, polystyrene foam) between them. In our case it was about 10mm thick. So you’re probably going to need a block of aluminium, slightly thicker than the lid of the cooler, to occupy the space. Again, refer to Fig.2. Exact size of this block of aluminium is not important as long is it is just larger than the Peltier device (which itself is is 40mm square) – say around 50mm square. As you can see from the photo, it sits inside four screws which hold the asssembly together, sandwiching the Peltier device between the aluminium block and the outside heatsink. Fig. 2: exploded view of all the components in the powered cooler. Not shown are the electrical connections: the Peltier device and fan simply wire in parallel (the wires can be hidden between the fan and outer heatsink and held in place with the cable clamp). To minimise stresses on the Peltier device, a gasket/washer of thin rubber (preferably heat-conductive) is fitted between the Peltier device and the outside heatsink. This has a cutout the same size as the aluminium block and Peltier device, the idea being to give shock protection for the Peltier device while still allowing intimate contact between the elements. The photograph shows this more clearly. The small block of aluminium shouldn’t be too difficult to obtain from either an aluminium merchant or perhaps a non-ferrous scrap yard; the rubber gasket may be a little more difficult. If all else fails, virtually any closecell rubber or foam material will do –believe it or not, we cut our gasket from an old Neoprene mouse mat!   Use the aluminium block as a template for carefully cutting the hole in the cooler lid. We used a fine-bladed jig saw to cut ours after first drilling a pilot hole. The block should be a snug fit in the hole. When ready for final assembly, this block can be held in place with some silicone sealant if you wish to maintain the cooler’s semi-watertightness. Then again, who ever tips their cooler upside down? If you do use silicone sealant, it’s important NOT to get any on the face of the aluminium block – this could act as a heat insulator. Place the Peltier device in the middle of the aluminium block and mark the position of the two screw holes along the centre line (size to suit the screws) allowing, say, 5-10mm clearance. You may need to look at your heatsinks before determining position to ensure that the holes are not going to line up with the fins of the heatsink. If the size and layout of your heatsink means that a clash is inevitable, you may need to do what we did and use over-length bolts with nuts tight- Upside-down view of the outside heatsink, with the Peltier device wired in and the rubber gasket in situ. The gasket compresses to ensure a good heat transfer between the aluminium block (not shown) and the top heatsink. Note the liberal use of heat transfer compound! September 1999  89 ening down onto washers sitting on top of the heatsink fins. The use of liberal amounts of silicone heat transfer compound is vital – between the inside heatsink and aluminium block, the aluminium block and Peltier device and between the Peltier device and outside heatsink. The name of the game is to transfer as much heat as possible, as efficiently as possible. Mounting the fan Again, this depends on the layout of your heatsink and the mounting holes for the fan. The most usual method of mounting would be to drill some holes through the heatsink and fit the fan with nuts and bolts. It is important that the fan sits directly on the heatsink fins and draws its airflow through the fins. You can check the airflow most easily by connecting the fan to a 12V battery or supply. In some cases, reversing the connections will reverse the fan direction and therefore airflow but some fans will not operate with reversed connections – in this case, simply turn the fan over. If there is a protective finger guard, make sure it is on the outside of the fan. 120mm fans are available from all the usual suppliers. Which way is ­up? The convention is that when the Peltier device is lying flat with its leads pointing towards you and the red lead on the right side, the upper plate is the “cold” side. Needless to say, this is the side which goes on the inside of the cooler. The red lead, as you would expect, connects to +12V and the black to earth. But even if you do manage an up-stuff, no problem. Simply reverse Parts List 1 suitable cooler, preferably with plastic (polystyrene) lid. 1 Peltier-effect device 1 12V fan, 120mm square (or to suit your heatsink) 2 large heatsinks, size to suit cooler 1 aluminium block, approx 50 x 50 x 5mm (see text) 1 close-cell rubber (or similar) gasket, approx 75mm square 1 3m length heavy-duty polarised figure-8 cable 1 car cigarette lighter plug 1 cable clamp 4 assembly bolts, approx 1/8in or 3mm, length to suit heatsinks, with nuts & washers 1 cable clamp bolt, 3mm x 10mm with nut and washer 4 fan mounting bolts, 1/8in or 3mm, length to suit fan and heatsinks the connections and the heating/cooling plates are reversed. The Peltier device and the fan simply connect in parallel and are wired to a cigarette-lighter plug. Airflow of the fan is important: it needs to be wired so that it is sucking air through the heatsink and blowing it away. This gives the most efficient and effective set-up. We used a 3m length of heavy-duty figure-8 cable which came already fitted with a cigarette lighter plug. These are available from Oatley Electronics for $1.00 each or 10 for $4.00 (what a bargain!). The cooler end of the cable was anchored to the outside heatsink with a small cable clamp and the wire ends soldered to the Peltier device and fan leads, all insulated with small lengths The view inside the cooler lid after assembly. As you can see, this heatsink has been around the traps a little but the additional holes don’t cause any concern. Note the two bolts which mount on top of the heatsink fins with suitable load-spreading washers. 90  Silicon Chip of heatshrink tubing. Be careful with the wires connecting to the Peltier device – they are only soldered themselves and can break off (as we found!). Checking it out It is simply a matter of plugging it in and leaving it to run for, say, half an hour. The lid doesn’t even need to be fitted on the cooler. You should find after this time the inside heatsink is quite cool, even cold, to touch. If it is warm to hot and the outside heatsink is cold . . . congratulations – you’ve made a warmer, not a cooler! To cool, reverse the connections to the Peltier device. Incidentally, there is nothing wrong with connecting the cooler “back to front” if you want to keep food warm. It won’t cook it but it certainly will keep it warmer than the outside temperature. If you want to make a “universal” cooler/heater, simply fit a double pole, double throw switch in the power lead to reverse the connections to the Peltier and fan. One warning: don’t leave it connected for too long. Even with the lowest-rated (4A) Peltier, it will flatten your car battery in fairly quick time, especially if your battery isn’t quite up to scratch. This device really is intended for use when the car engine is running! And one last point: Peltier devices should NOT be operated from 12V battery chargers unless there is a battery connected as well. Most battery chargers have little or no smoothing; the output is usually half-wave rectified (50Hz) or full-wave rectified (100Hz) pulsating DC. That’s fine to charge a battery but by itself will effectively switch a Peltier on and off at either 50Hz or 100Hz – much too slow to avoid the mechanical stresses we mentioned before. Connecting a battery is like connecting a giant capacitor across the supply, smoothing it out to nearly SC constant DC. Where to get the parts: Peltier Device: Oatley Electronics Heatsinks: Jaycar, Altronics Fan: Jaycar, Altronics, Dick Smith Electronics Power Lead/Plug: Oatley Electronics Cooler: Big W, KMart, etc. 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. Fan control in a caravan I am in the process of building the “High Current Speed Controller for 12V & 24V DC Motors” from the June 1997 issue of SILICON CHIP. I wish to operate a 12V DC fan in a caravan off the van’s 12V battery with the idea of being able to set the fan speed to suit the conditions and thereby, in cooler conditions, limit the discharge from the battery. I do not know the exact voltage at which the 7812 will drop out of regulation. The worrying aspect to successful operation of this circuit is that when the battery is fully charged at say 13.8V, the 7812 is going to be hard pressed to provide a regulat­ed output as there is little head room and this is going to be worse as the battery voltage starts to fall, as it will in this application. Can I get around this situation by fitting a lower voltage regulator; eg, a 7809? I realise this may not give me the drive to the Mosfets to be fully conducting or is this only going to give me more losses to the heatsink? If this is acceptable, it would allow Fast battery charger squeals I have just completed the Fast Battery Charger from the February & March 1998 issues (the one with the Philips TEA1102 chip) from a Dick Smith Electronics kit. It seems to work OK except that under load of about 1A or more it squeals quite loudly. The noise comes from the inductor. I was wondering if the air gap is a bit wide. The Dick Smith kit supplied two small strips of fibreglass. I haven’t measured it but it could be a little wide. What should be the inductance? Is it critical? I wound it according to instructions (plus or minus half the battery voltage to fall to a lower value before the regulator dropped out. A DP3T selector switch could then be wired to give full speed, off and controlled speed. I would appreciate your comments on the following: (1) How well will the circuit work with a 7809 regulator? (2) How will the fan and more importantly, the electronics, behave when the battery voltage drops to a value where the regulator ceases to function? (3) How can I lower the output voltage of the 7812 to say 10V or would the drop out voltage still remain the same? (P. R., Kingaroy, Qld). •  The regulator was included to ensure that the gates of the FETs were never taken more positive than 12V; ie, when connected to a 28V supply. If you are sure there will be no spikes, etc, on the supply you can remove the regulator but we suggest that you leave it in. When the regulator stops regulating its output will drop but the circuit should continue to function. The criterion for satisfactory operation is “how hot are the heatsinks?” While they remain cool (or not too hot) don’t worry. When their tem- a turn). Any sug­gestions? (S. S, Lily­field, NSW). •  The squealing noise is caused by the windings in the induc­tor moving on the bobbin as the current flow modulates them. You can reduce this noise by winding a layer of insulating tape around them. Alternatively, coat the sticky side of the tape with some epoxy resin and then wrap the windings in the tape. You can expect the noise to be considerably reduced after the resin has set. The actual number of turns is not critical and anywhere between 10 and 20 turns is suitable. The gap spacers supplied by Dick Smith Electronics are correct. perature starts rising, the gate drive to the Mosfets is too low. Your circuit will work fine but the current taken by the controller is negligible and we would leave it connected perma­nently if the initial tests prove OK. CDI on a Kawasaki 250 I am writing in reference to the Multi-Spark CDI kit, which I have purchased for use in my 1980 Kawa­ saki Z250-B. It runs with points, with one coil-point-capacitor-spark plug per cylinder (this is a twin-cylinder bike). I am now unsure if this kit is suitable for my bike. What I really need to know is how can I hook the CDI to my engine when each contact points runs a dedicated (separate) cap/coil/plug system independent of the other cylinder? The instructions assume a distributor of sorts, one which runs a high-tension switching setup, whereas a motorbike engine has an individual isolated switch per cylinder that runs prior to the coil. I cannot see from the circuit diagram how the two coils are to be triggered separately from circuit switching, to correspond to each contact point. Can you give a definite YES or NO as to whether the kit can facilitate dual-isolated CDI switching? Does the circuit board and component setup cater for this or do modi­fications have to be made? (D. S., Ashmore, Qld). •  The circuit is suitable for twin-cylinder engines with two coils as described at the end of page 29 and beginning of page 30 in the September 1997 issue. Both coils are connected in parallel and using the two points facility will fire both coils whenever either of the points open. This means that on a twin engine, one cylinder will fire as required during the compression stroke just before top dead centre for the piston. This will produce a normal firing action September 1999  91 FM transmitter shows drift I have built the FM Stereo Transmitter published in October 1988 and have found it to be unstable – the frequency constantly fluctuates by about 300kHz. I have tried it at 101.3MHz and it fluctuates from 101.1 to 101.3MHz, and at 90.2 it goes from 90.1 to 90.3. It is about 5 metres from the radio. Any ideas why? (J. S., via email). •  The frequency of oscillation should be far more stable than the 300kHz deviation you are measuring. There are a number of comments we can make. Firstly, try the transmitter on an audio signal and check whether it sends a quality stereo signal to the receiver. If it works correctly then perhaps the way you are measuring the oscillator frequency is not accurate. If the transmitter is modulating a signal, then it can be very difficult to measure the carrier since it is while the other cylinder will be at bottom dead centre. Firing a cylinder with the piston at bottom dead centre can do no harm to the engine and in fact nothing will happen since there will be no combustible gases under pressure. The circuit does not fire each spark plug in an alternate fashion with one coil for one cylinder providing a spark as controlled via one set of points and the next cylinder spark controlled by the second set of points for the second coil. Both work together. The only way to have alternate firing of each coil is to use two CDI systems, each firing their own coil and via their respective sets of points. High power guitar amplifier I wish to build a guitar amplifier and I am going to use your 125W Plastic Power Amplifier (SILICON CHIP April 1996) to drive a 150W speaker cabinet using Celestion 12-inch guitar loudspeakers. I am also going to use the Three-Band Parametric Equaliser (SILICON CHIP July 1996) for the EQ section of the preamplifier. Other features I will incorporate are an effects 92  Silicon Chip deviating by up to ±75kHz. This can upset a frequency meter so that it provides a fluctuating reading. Also the resolution in the readings you provide suggest that the meter you are using only has 100kHz resolution for the measurement and so you can expect that the last digit will fluctuate by at least one digit. Finally, the frequency may well be unstable if the coil windings are loose on the former or the slug within the former is loose. The slug can be made more secure with a short length of dental floss placed down the thread. Also a dry solder joint on the oscillator components or IC could produce erratic oscilla­tion. You should also check the 47pF capacitors for value and check whether they are NPO types. NPO capacitors either have this written on the body or a black dot on the top. Also check the cell voltage to make sure it is not below about 1V when powering the transmitter. loop, DI output and valve modelling circuitry for richness of harmonics. I want the best possible performance from the finished product and that brings me to the point of this letter. You state in the power amplifier article that headroom is really a measure of the regulation of the power supply. You then say that the suggested power supply is a “minimum spec” design. Is there another power supply that I could use, which has better regulation and could improve the performance of the amplifier? Are there any other modifications that I could make to the amplifier module so that it will give better performance and tone for musical instrument use? Headroom is very important for me. Also Jaycar specifies 8000µF capacitors for use in the power supply instead of the 10,000µF specified in your article. Which capacitance value should I use? Which fuse rating should I use for the transformer’s prim­ ary winding protection? Will the amplifier offer better perfor­mance if I put the power supply in a separate metal case inside the amplifier rack case? Should the 560Ω 5W resistors wired across the fuse clips be removed after setting the quies­ cent current? What will happen if a signal exceeds the input sensitivity of 1.37V RMS? Are there any modifications I can make to improve perfor­mance and tone of the preamplifier circuitry; eg, mounting the potentiometers off-board? Any other advice on this too? Finally, what fuse rating should I use for a 160VA transformer? (O. N., Canterbury, Vic). •   We assume that your 12-inch speakers will each be 8Ω and wired in parallel so the total load impedance will be 4Ω. In that case, the amplifier will be able to deliver between 175W and 230W, depending on the supply regulation. If that is the case, we would recommend a 300VA transformer with two 10,000µF 63VW elec­trolytic capacitors on each supply rail. You may also need to use a bigger heatsink for the power transistors. The mains fuse should be a 1.5A slow blow type. The 560Ω resistors should be removed from the fuseclips after the quies­cent current has been set. Assuming a 4Ω load, the input sensitivity for maximum power of 175W will be around 1.15V RMS. In fact though, the maximum power refers to the power available just at the onset of clip­ping; ie, audible overload. This power level will depend on the mains voltage and the supply rail voltages at any time. If the input signal is too high, you will get audible distortion. And if you seriously overdrive the amplifier, you will blow the speak­ers. For a guitar amplifier there is little point in having the power supply in a separate case because the only improvement would be in residual noise and that is usually not a problem – the noise level from the performance is so loud that it usually drowns out any noise from the amplifier. We would not recommend mounting the preamplifier potentiom­eters off-board; that will inevitably lead to degraded perfor­mance. VGA to PAL converter wanted Have you ever featured a VGA to TV (PAL) converter project? If so could you please tell me which issue? (Stewart, via email). •  We have not produced a VGA to PAL converter and it would not be a simple project as there would be Notes & Errata Burglar alarm extensions, June 1999: on the circuit on page 83, IC5a adjacent to IC4a should be labelled IC5c. IC6b’s output should be pin 8. The “ZONE 3” label on the line to pin 5 of IC8 should actually be on the line to pin 7 of IC8. In addition, the output of IC8 driving the Zone 1 relay should be pin 12. The second last paragraph of page 84 should read “Pins 4, 10 and 12 of IC3 are connected to the roller door switches”. Audio-Video Transmitter, July 1999: on the overlay diagram on page 38, the .001µF capacitor shown connecting pin 3 of IC1 quite a lot of standards conversion required in that the horizontal and vertical sweep rates for PAL are quite a lot slower than typical VGA. To do the standards conversion, the circuit would require a line or frame store. If you need one, the best approach would be to buy it. Two of our advertisers, Microgram Computers and Namlea Data Systems, should be able to help you. Faulty sensor on speed alarm Back in your December 1997 issue you published a project for a car speed alarm. I am having trouble with this kit. I cannot get the sender to register any speed. It will show a speed when I switch it on and it will show different speeds when the buttons are pushed but it will not show any difference in speeds when the sensor is put into operation. Also, is there any way that I can make the alarm sound louder to ground should be .01µF. The circuit diagram is correct. Daytime Lights for Cars, August 1999: on the overlay dia­gram on page 33, the 470Ω and 1kΩ resistors shown below diode D3 should be 4.7kΩ and 470Ω respectively. The circuit is correct. Line Dancer Robot, May 1999: in the circuit diagram on page 18, the 4.7kΩ collector resistor for Q1 should be labelled R5 instead of R3, while the 1.5MΩ base resistor for Q1 should be labelled R6 not R5. On the PC overlay diagram on page 19, the 470Ω resistor below R14 (270Ω) can be replaced with a link (it is in series with R5). as I am a bit hard of hearing? (K. M., North Booval, Qld). •  We are not sure that you do have a problem with your speed alarm. The display section of the project is operating correctly since it does display the alarm speed and can be changed using the buttons. It will not and is not supposed to show the dif­ference in speed between the set and actual speeds as the car is driven. However, if you are saying that the alarm does not sound when the preset speed is exceeded, then you may have a problem with the sensor circuit. Check that the magnets and sender are located close together when they pass each other. You may find that the sensor operates correctly if the magnet is flipped over so the opposite pole is facing out. Check all wiring from the Hall Effect board to the main PC board. The output level of the speed alarm can be varied by adjusting VR2. This alters the frequency driving the piezo transducer and if adjusted carefully you will find a position where the sound is loudest. This is the resonance point for the transducer. An alternative method of increasing the sound level is to use a powered piezo transducer which will operate at 5V. This can be driven between the collector of transistor Q3 and 0V. Note that for this connection you will always have the siren sounding above the alarm speed setting. A suitable siren could be the Dick Smith Cat L-7024 or Jaycar Cat AB-3462. Transistor brands for class-A amplifier How important to the final performance of the Class-A amplifier July & August 1998) is it to use the speci­fied Philips/Motorola BC547s, 557s, 327s and 337s? I look forward to building it. (S. H., via email). •  In a high performance amplifier such as this, it really is important to go for the “brand-name” transistors. Other transis­tors will certainly work but there is no guarantee that the finished amplifier will have really low distortion. SLA charging information wanted In an issue of SILICON CHIP I read an article on an SLA charger. That article had quite a bit of information on SLA batteries. I am chasing after information on charging techniques and more importantly discharge curves for SLA batteries. Can you pinpoint the issue please? (A. H., via email). •  It seems likely that the article you are referring to was one featuring the UC3906 SLA battery charger IC, published in the March 1990 issue. We can supply this issue for $7 including SC postage. 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. September 1999  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FRWEEBE YES! Place your classified advertisement in SILICON CHIP Market Centre and your advert will also appear FREE in the Classifieds-on-the-Web page of the SILICON CHIP website, www.siliconchip.com.au And if you include an email address or your website URL in you classified advert, the links will be LIVE in your classified-on-the-web! S! D E I F I S C LAS EXCLUSIVE TO SILICON CHIP! CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $11.00 (incl. GST) for up to 12 words plus 55 cents for each additional word. Display ads: $27.50 (incl. GST) per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 9979 6503. Taxation Invoice ABN 49 003 205 490 _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ 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 FOR SALE TELEPHONE EXCHANGE SIMULATOR, SC Feb. 1998. Test equipment without the cost of telephone lines. $190. MAGNETIC CARD READER, SC Jan. 1996. Holds up to 8 cards. Use as a door lock. $65. Melbourne 9806 0110. ELECTRONIC/MECHANICAL DESIGN AND CONSTRUCTION: we offer a complete design service for electronic and mechanical devices. Most work is done in house and you deal directly with the designers. No job is too small and can be to prototype or “turn key” stage, in one offs or for future production. Simply send us an email at vladimir<at>u030.aone.net.au with your questions or requirements and we will get back to you. WEATHER STATIONS: Windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. $420.00 complete plus sales tax if appli­cable. Optional rainfall and PC interface. Used by Government Departments, farmers, pilots, and weather enthusiasts. Other models with barometric pressure, humidity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalogue and price list. Solar Flair/ Ecowatch ph: (03) 5968 4863 fax: (03) 5968 5810, PO Box 18, Emerald, Vic., 3782. ACN 006 399 480. RAIN BRAIN AND DIGI-TEMP KITS: 8 station sprinkler controllers, 60 channel temp monitor uses DS1820s over 500 metres. Has PC Data logging. Mantis Micro Products, http://www.home.aone.net.au/mantismp 1/3 PRICE Heatshrink Tubing 2:1 Ratio 3 mm 55c, 6 75c, 10 90c, 16 $1.25 www.allthings.com.au PRINTED CIRCUIT BOARDS for all magazine projects, then go to http:// www.cia.com.au/rcsradio RCS Radio – Bexley (+61 2) 9587 3491. FREE !! DUMMY DOME with CAMERA orders this month * AV 2.4 GHz TRANSMITTERS from $99 * QUADS 4 Pix 1 screen from $256 HIRES better than SUPER-VHS Quality * Modules 32 x 32 from $76 also with Tiny Hi-Sens On-Board MICROPHONE * PIR MOVEMENT DETECTOR inbuilt concealed PINHOLE Mono or DSP COLOUR Camera, Microphone & Timer/Controller for VCR - Lights - Etc from $139 * BULLET 22 mm dia 480 Line 0.05 lux SONY CCD or DSP COLOUR from $132 * COLOUR DSP 32 x 32 Pinhole Module with MICROPHONE from $155 * MINI 36 x 36 from $85 - SONY CCD $102 - COLOUR DSP $162 * DOME from $88 - SONY CCD $105 - COLOUR DSP $164 * BALUNS use phone or LAN cable for Video & Power Supply from $11 * DIY PAKS: 4 Cameras, Switcher & Power Supply from $499 - with 14" Monitor from $601 with MUX for FULL SCREEN / RESOLUTION RECORDING from $1209 * 4 COLOUR CAMERAS, SWITCHER & POWER SUPPLY from $807 - with COLOUR QUAD 4 Pix 1 Screen from $1211 * With MUX $2033 * COLOUR QUADS from $512 * COLOUR DUPLEX MUX from $1329 * 14" MONITORS from $218 - with Inbuilt 4 Ch SWITCHER from $256 * SEE-in-the-DARK CAMERA INFRA­R ED ILLUMINATOR Kit from $160 * 50 LED DIY Infra Red Kits only $19 * Plus full range of ANCILLARY EQUIPMENT * DISCOUNTS: Based on ORDER VALUE, BUYING HISTORY, for CASH / CHEQUE & NZ BUYERS ! BEFORE YOU BUY Ask about New Enquiry Offer & visit our Web Site at www.allthings.com.au Ph 08 9349 9413; Fax 08 9344 5905. Win $500USD cash dontronics.com C COMPILERS: everything you need to develop C and ASM software for 68HC08, 6809, 68HC11, 68HC12, 68HC16, 8051/52, 8080/85, 8086, 8096 or AVR: $155.00 each. Macro Cross Assemblers and Disassemblers for above CPUs + 6800/01/03/05, 6502 and 68HC12 for $78. Debug monitors: $78 for 6 CPUs. All compilers, XASMs 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. Phone: (03) 9545 3722; Fax: (03) 9545 3561 Call Mike Lynch and check us out! We are the best for low cost, small runs. Satellite TV Reception International satellite TV reception in your home is now affordable. Send for your free info pack containing equipment catalog, satellite lists, etc or call for appointment to view. We can display all satellites from 76.5° to 180°. Positions At Jaycar We are often looking for enthusiastic staff for positions in our retail stores and head office at Rhodes in Sydney. A genuine interest in electronics is a necessity. Phone 02 9743 5222 for current vacancies. 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. SPECIAL STEAM BOAT KITS $14 1A LASER DIODE DRIVER, 3W head laser power monitor, IR laser diode with housing, greatly reduced price, e-mail lmatthee<at>perthpcug.org.au for details and pictures. AV-COMM P/L, 198 Condamine St, Balgowlah, NSW 2093. Tel: 02 9949 7417 or 9948 2667. Fax: 9949 7095; www.avcomm.com.au Silvertone’s RC Receiver Still the best little performer available! Ph: (03) 98306288     Fax: (03) 98306481 and monitors: $480. 8051/52 Simulator (fast, now incl. 80C320): $78. 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. $199, $37 tax, $10 p&p. SOIC adaptors: 20-pin $90, 14-pin $85, 8-pin $80. Credit cards accepted. GRAN­TRONICS PTY LTD, PO Box 275, Wentworthville 2145. Ph (02) 9896 7150; Fax (02) 9631 1236; or Internet: http://www.grantronics.com.au Still only $129.50 AM or $149.50 FM. May be used with most ppm transmitters. This and many other radio control products available from: Silvertone Electronics, PO Box 580, Riverwood 2210. Phone/Fax (02) 9533 3517. www.silvertone.com.au PCBS MADE, ONE OR MANY. Low prices, hobbyists welcome. Sesame Electronics (02) 9554 9760 sesame<at>internetezy.com.au; http:// members.tripod.com/~sesame_elec A NEW address for Acetronics: http:// www.acetronics.com.au On-line PCB quotes, free software, DIY PCB supplies plus many other items & services. 02 9743 9235. September 1999  95 Silicon Chip Binders Keep your copies safe, secure and always available with SILICON CHIP binders: they’re cheap insurance! Altronics................................. 60-62 REAL VALUE AT Aust. Audio Consultants...............81 PLUS P &P Clarke & Severne........................81 $12.95   Heavy board covers with 2-tone green vinyl covering Advertising Index Av-Comm Pty Ltd.........................95 Coffs Harbour Electronics............81 Computronics Corporation..........81   Each binder holds up to 14 issues so that you can include catalogs Dick Smith Electronics........... 14-17 EMC Technologies.......................81  SILICON CHIP logo printed in gold-coloured lettering on spine & cover Emona Instruments...................IFC Evatco..........................................87 Price: $12.95 plus $5 p&p each (available Aust. only) GNP Acoustics............................79 Order by phoning (02) 9979 5644 & quoting your credit card number; or fax the details to (02) 9979 6503; or mail your order with cheque or credit card details to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Harbuch Electronics....................34 Instant PCBs................................95 Jaycar .............................. 45-52,95 Kits-R-Us.....................................95 Microgram Computers..............3,81 SATELLITE TV RXs Digital MPEG-2 FTA EPG DVB CAM for Encryption from $399 www.allthings.com.au SOLAR PANELS: buy by mail and save! 75 watt from $590.00, unbreakable s/ steel 64 watt $555.00. Largest manufactured: 120 watt $995.00, flexible 32 watt $475.00. All other sizes available, top brands, lowest prices. INVERTERS: budget inverters from $110.00 (12V 140W). High quality pure sine wave inverters from $390.00. Call with your requirements. WIND GENERATORS: wide variety available, call with requirements. TASMAN ENERGY Free call 1800 226626 RTN Australia Parallax distributor: Ba­sic Stamps BS1, BS2, BS2-SX all ex stock. Chipsets also available for high volume applications. SX development tools and chips also available. New super BS1/2 develop­ment board Oz made now available. Custom I/O extender chips for the Basic Stamps. Serial Led driver kits, a/d kits, temperature kits, etc. FerretTronics servo and stepper motor chips. TiePie HandyScope HS2, Dos and Win software included. Ph/Fax (03) 9338 3306. Email: nollet<at>mail.enternet.com.au http://people.enternet.com.au/~nollet BITZ 25W Transceivers Sat TV RXs VCRs ABS CROs Yagis Isolation TXs CCTV Equip Gas Detectors 16 mm Projectors Components www.allthings.com.au Namlea Data Systems.............OBC Oatley Electronics........................29 Printed Electronics...................... 95 Procon Technology......................95 Questronix...................................81 RobotOz......................................95 Rosemary Brooks........................80 R.T.N............................................81 Silicon Chip Binders/Wallcht........57 Silicon Chip Bookshop........... 82-83 Silicon Chip Position Vacant........41 KIT ASSEMBLY Silicon Chip Subscriptions...........44 ANY KITS assembled/repaired: professional, speedy service. Phone Nev­ille Walker (07) 3857 2752. Silvertone Electronics..................95 KIT ASSEMBLY: kits assembled/repaired in Sydney. Phone Tess on (02) 9728 6443. Truscott’s Electronic World...........25 HELP SAVE THE NIGHT SKY! We are losing our heritage of starry night skies. Poor, inefficient outdoor lighting is causing glare and “light pollution”. This wastes energy and increases greenhouse gas emissions. You can help by joining SYDNEY OUTDOOR LIGHTING IMPROVEMENT SOCIETY (SOLIS). SOLIS aims to educate and inform about quality outdoor lighting and its benefits. We also lobby councils, government and other bodies to promote good lighting practice. SOLIS meetings are held third Monday night of each month at Sydney Observatory. Individual membership is $20 pa. Donations are also welcome. Cheques payable to “SOLIS c/- NSAS”, PO Box 214, West Ryde 2114. Email: tpeters<at>pip.elm.mq.edu.au 96  Silicon Chip MicroZed Computers...................81 Smart Fastchargers.....................25 Solar Flair/Ecowatch....................94 Zoom EFI Special......................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. MORE FROM YOUR EFI CAR! Own an EFI car? Want to get the best from it? You’ll find all you need to know in this publication EFI TECH SPECIAL Here it is: a valuable collection of the best EFI features from ZOOM magazine, with all the tricks of the trade – and tricks the trade doesn’t know! Plus loads of do-it-yourself information to save you real $$$$ as well . . . HERE ARE JUST SOME OF THE CONTENTS . . . n Making Your EFI Car Go Harder n Building A Mixture Meter n D-I-Y Head Jobs n Fault Finding EFI Systems n $70 Boost Control For 23% More Grunt n All About Engine Management n Modifying Engine Management Systems n Water/Air Intercooling n How To Use A Multimeter n Wiring An Engine Transplant n And Much More including some Awesome Engines! AVAILABLE DIRECT FROM SILICON CHIP PUBLICATIONS PO BOX 139, COLLAROY NSW 2097 - $8.95 Inc GST & P&P To order your copy, call (02) 9979 5644 9-5 Mon-Fri with your credit card details! FROM THE PUBLISHERS OF “SILICON CHIP”