February 2005 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Tsunami warning system must be built for Indian Ocean
Feature: Border Surveillance In The 21st Century by Barrie Smith
Project: Build A USB-Controlled Electrocardiograph by Jim Rowe
Project: TwinTen Stereo Amplifier by Jim Rowe & Peter Smith
Project: Inductance & Q-Factor Meter by Leonid Lerner
Project: A Real Yagi Antenna For UHF CB by Stan Swan
Feature: School Electronics: Putting The Picaxe To Work by Ross Tester
Salvage It: Build a $2 battery charger by Julian Edgar
Vintage Radio: Converting a 240VAC set to 32V DC operation by Rodney Champness
Book Store
Feature: Build Yourself A Windmill Generator, Pt.3 by Glenn Littleford
Advertising Index
Outer Back Cover

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SILICON CHIP Australia’s World-Class Electronics Magazine! FEBRUARY 2005 7 $ 90* INC GST NZ $ 8 75 INC GST PRINT POST APPROVED - PP255003/01272 ISSN 1030-2662 02 9 771030 266001 Build this USB-controlled ELECTROCARDIOGRAPH BORDER SURVEILLANCE: Detecting smugglers and intruders in the 21st Century! ELECTRONICS IN EDUCATION: East Hills Girls Technology High and their PED-X PICAXE project MORE RANGE ON UHF CB: How to build a dirt-cheap Yagi antenna siliconchip.com.au PLUS TWIN TEN AMPLIFIER INDUCTANCE METER February 2005 1 $2 CHARGER AND MORE! SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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 Contents Vol.18, No.2; February 2005 www.siliconchip.com.au FEATURES 8 Border Surveillance In The 21st Century New technology is on the hunt for contraband, arms and illegal immigrants – by Barrie Smith 79 School Electronics: Putting The Picaxe To Work All the fun at the Picaxe fair and first prize to East Hills Girls Technology High School for an ingenious Picaxe-based pedestrian crossing – by Ross Tester 88 Satellite C-Band TV: Death By Overload, Pt.2 Some practical ideas to minimise (or even eliminate) interference to C-band satellite signals from wireless broadband signals – by Garry Cratt 100 Build Yourself A Windmill Generator, Pt.3 USB-Controlled Electrocardiograph – Page 14. Third article shows you how to build the platform and install the stator, drive shaft and front bearing fitting – by Glenn Littleford PROJECTS TO BUILD 14 Build A USB-Controlled Electrocardiograph It’s controlled by a USB port on your PC or laptop and displays a person’s electrocardiogram (ECG) on the monitor or LCD screen – by Jim Rowe 32 TwinTen Stereo Amplifier Build this gutsy little amplifier for your Discman, MP3 player or games machine – by Jim Rowe & Peter Smith TwinTen Stereo Amplifier – Page 32. 64 Inductance & Q-Factor Meter Compact unit measures inductors from 200nH - 10mH, checks Q-factor from 1-120 and displays the results on an LCD – by Leonid Lerner 72 A Real Yagi Antenna For UHF CB Are you good at scrounging? All it takes is some plastic conduit and a couple of wire coat hangers to build this really effective antenna – by Stan Swan Inductance & Q-Factor Meter – Page 64. SPECIAL COLUMNS 44 Circuit Notebook (1) Laser-Guided Parking Aid; (2) Novel White LED Torch; (3) Electronic Thermostat For Plug-In Heaters; (4) ESR & Low Resistance Test Meter 48 Serviceman’s Log Life at the end of the food chain – by the TV Serviceman 90 Salvage It! Low-Cost Yagi Antenna For UHF CB – Page 72. Build a $2 battery charger – by Julian Edgar 92 Vintage Radio Converting a 240VAC set to 32V DC operation – by Rodney Champness DEPARTMENTS 2 4 43 61 Publisher’s Letter Mailbag Order Form Product Showcase siliconchip.com.au 105 108 109 111 Ask Silicon Chip Notes & Errata Market Centre Ad Index February 2005 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 Editor Peter Smith Technical Staff John Clarke, B.E.(Elec.) Ross Tester Jim Rowe, B.A., B.Sc, VK2ZLO Reader Services Ann Jenkinson Advertising Enquiries Phil Benedictus, Laurence Smith Benedictus Smith Pty Ltd Phone (02) 9211 9792 Fax: (02) 9211 0068 info<at>benedictus-smith.com Regular Contributors Brendan Akhurst Rodney Champness, VK3UG Julian Edgar, Dip.T.(Sec.), B.Ed, Grad.Dip.Jnl Mike Sheriff, B.Sc, VK2YFK Stan Swan SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 003 205 490. ABN 49 003 205 490 All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Hannanprint, Noble Park, Victoria. Distribution: Network Distribution Company. Subscription rates: $83.00 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 Tsunami warning system must be built for Indian Ocean The enormous undersea earthquake and tsunami which occurred on December 26th (Boxing day) will have enormous consequences in Asia and all countries bordering the Indian Ocean for decades to come. The huge death toll, widespread injuries and utter destruction have been truly horrifying. Yet how much of it could have been avoided if there had been an effective warning system? If only. With a system similar to that operating in Hawaii, Japan and for countries bordering the Pacific Ocean, it is probable that much of the death toll and the injuries could have largely been avoided. The economic destruction would still have occurred but buildings and infrastructure can always be rebuilt. Even now, there are plans afoot to build such a warning system and while some people will inevitably say that this is closing the door after the horse has bolted, there will always be more earthquakes and tsunamis to come in the future. Perhaps such events may not be very far into the future, since they are entirely unpredictable. The last major tsunamis killed thousands of people in New Guinea (1998) and Indonesia (Flores, 1992). In fact, since there are probably tens of millions more people living in countries bordering the Indian Ocean, it is arguable that the proposed warning system should be much more precise and comprehensive than the system used in the Pacific. There need to be many more ocean level sensors relaying to satellites and the resultant warnings broadcast much more quickly. After all, when you consider that typical tsunamis travel at around 900km/h across deep oceans – faster than a jet airliner – the earlier the warning, the better. The present system in Japan can generate a tsunami warning within three minutes of a major earthquake and such a system could potentially have saved thousands of lives in Sumatra, even though this was very close to the undersea quake. When you think about it, there is no reason why such warnings could not be relayed automatically to virtually everyone in the population, whether by TV, radio or phone. In fact, in Asia, the mobile phone network could be the key. In the event of a tsunami warning, every person with a mobile phone could have an immediate SMS (text message). The same message could go out to fixed line phones as voice-mail. Of course the internet could have a substantial part to play in any warning system as well, so that people logged onto their computers, including at hotels and resorts, would get immediate warnings via email or internet browser. Ultimately, for such warnings to be effective, there would have to be well published procedures. mustering points and so on, as there are in Hawaii and Japan. Such a comprehensive warning system is feasible right now although it will possibly take many millions of dollars to implement right through the affected countries. But tragically, as we have seen, the cost of having no warning system at all is just too high to contemplate. Fortunately, just as we were going to press, Germany has announced that they want to take a leading role in setting up a warning system and have drawn up a plan to cost an initial 40 million euros. Let us hope that it proceeds without delay. Leo Simpson siliconchip.com.au hotnewproducts <at>hotlowprices MicroGram NEW! Cable Tracer Single or multi-tone signal, two test leads and a 4-conductor modular cable. Cat 11520-7 $129 SMS I/O Controller Simply send an SMS from any mobile phone to turn any electrical equipment on or off. Has 8 inputs & 4 outputs. Cat 17087-7 $1029 Laser Barcode Scanner This stylish laser scanner out performs many higher priced models. Cat 1008039-7 $399 NEW! Internet Security Router with VPN Server Provide secure connections to your travelling salesmen or wireless users with up to 100 VPN tunnels Our intelligent Internet security router provides a VPN Server to enable secure communication over the wired or wireless internet. It features stateful inspection firewall, NAT, active intrusion detection, VPN Server, traffic management, and policy-based network management functions in a single unit. It helps users to create a secure IP-based VPN solution to protect communications via the Internet in addition to offering the ability to prioritize network traffic to guarantee bandwidth requirements for real time applications. NOTE: When VPN is being used, Traffic Shaping and Firewall will not function. Please call for more details. Cat 10164-7 $849 Serial over Bluetooth External HD Case 2.5" Turn any serial device into a wireless device using Bluetooth technology. Cat 11908-7 $459 Turn any 2.5" laptop HD into a portable storage devcie with this USB 2.0 case. Cat 6710-7 $59 Infrared Adapter Digital I/O Card Provides 48 digital I/O lines on a PnP PCI interface. Cat 17053-7 $249 NEW! This USB adapter can be used to communicate with many devices that use Ir e.g. mobile phones. Cat 8923-7 $99 Mini 88 key keyboard Programmable Keypad Comes with a laptop style touchpad making it a great space saving solution. Cat 8751-7 $139 Store multiple keystrokes or complex commands under one key. Cat 8904-7 $319 SATA RAID 4 port Posiflex Receipt Printer NEW! Heavy Duty LCD Arm 8 Way KVM This rack mountable KVM allows one keyboard, monitor, and mouse to control up to 8 PCs. Cat 11656-7 $499 Magnetic Card Readers Many models available to read a variety of magnetic cards. Cat 8768-7 $259 These LCD monitor arms use standard VESA mounts and hold up to 15kg. Cat 4703-7 $179 Optical AV Switch Switch between three inputs and one output. Has S-VHS, RCA, and Optical audio. Cat 23023-7 $149 Attach up to four SATA HDs, can be configured as RAID 0, 1, 5, 10 and JBOD. Cat 2906-7 $249 Robust, reliable docket printer, suitable for common POS applications. Cat 5849-7 $499 802.11g PCI Card Wireless IP Camera Windows Based Terminal PCI TV Tuner USB Serial Port Front Access Video Capture Attach this surveillance camera to your LAN or wLAN and access it anywhere from a standard web browser. Cat 3475-7 $849 This tiny WBT attaches to the VESA mounts on an LCD monitor. It also emulates SCO, DEC, Wyse etc. Cat 1239-7 $649 Watch and capture TV on your PC. Also has a FM radio tuner and S-Video, RCA inputs. Cat 3508-7 $129 No serial port on your new laptop? This mini USB to serial adapter is the answer! Also in 2, 4 & 8 port. Cat 2920-7 $54 Capture analogue (RCA, SVideo) and digital (Firewire) video signals. Comes with a handy front access bay. Cat 23027-7 $349 Compatible with 32 and 64bit PCI slots. A higher gain antenna can be attached. Cat 11443-7 $129 Wireless LAN Equipment! We’ve got the lot - antennas, cards, pigtails, converters, cables! MicroGram Computers Ph: (02) 4389 8444 FreeFax: 1800 625 777 Vamtest Pty Ltd trading as MicroGram Computers ABN 60 003 062 100, info<at>mgram.com.au 1/14 Bon Mace Close, Berkeley Vale NSW 2261 All prices subject to change without notice. For current pricing visit our website. Pictures are indicative only. See all these products & more on our website...www.mgram.com.au siliconchip.com.au F 2005 3 ebruary SHORE AD/MGRM0205 Dealer inquiries welcome MAILBAG DVD player features pitch control I’m still buying cheapo DVD players and continue to be dumbfounded by both what we’re getting and for how much! Some months ago, I was at Lake Cathie (just south of Port Macquarie), where they had just opened a new Woolworths supermarket, and they had some door-buster opening specials. Among other things they had “NuTec” DVD players for $69. They had every possible signal output configuration, vacuum fluorescent display, two Karaoke Mic inputs, electronic echo and tone controls AND variable pitch playback that works on both DVD and CD! I really don’t understand how this works. With DVDs, the audio pitch can be changed dramatically but the frame rate remains rock-steady and artefactfree at 25 fps. The first DVD I tried it on was “2001: A Space Odyssey” and through my big stereo system, all the big orchestral numbers pitched up and down faultlessly. There wasn’t a trace of the irritating whistling and chirping that used to plague the expensive studio pitch-altering devices of a generation ago when you tried to process more than one voice or instrument at a time. There must be some damned clever DCT manipulation software in there. (It would certainly settle those perennial 24 frame film/25 frame video arguments). All for $69 and with a great picture too; clean as a whistle. It works the same with CDs, flawlessly changing the pitch but not the actual speed of the music. The echo is a bit basic; it only works on the microphone inputs and you can only alter the delay, not the actual echo level, but what do you want for that price? In normal Karaoke use (if there is such a thing), it’s actually quite effective. I managed to steam off the “warranty void if removed” label and take a peek inside. The assortment of PC boards is interesting. The main DVD player board is beautifully made, screen printed/green lacquered with platedthrough holes and an assortment of SMD chips, a 27MHz crystal and not 4 Silicon Chip much else. How the hell do they get the 4.43361875MHz and 3.579545MHz colour/color subcarriers out of the same 27MHz? The mains power supply module is a more humble TV-set-like brown phenolic non-SMD job, the vacuum fluoro and front control button PC board is very much Big-W Chinese clock radio standard, while the Karaoke mic input and level pot board looks more like something out of a 1970s Hong Kong pocket radio! Actually, my Aldi player still wins on two points: (1) it remembers where you were up to on a disk even after the power has been switched off; and (2) they supplied the two AAA cells for the remote! Keith Walters, via email. TV interference may have a simple cure I am writing regarding the item on a TV signal strength meter on page 88 of the December 2004 issue. It reminds me of a problem I had with Channel 10 in Melbourne some 10 years ago which has probably been covered in SILICON CHIP before but here goes. I have multiple home outlets and at some time I noticed annoying herringbone patterns across the screen but no audio interference. I started down the path of antenna checking (testing others before actually buying) and balun and cable replacement (not always easy). Having run out of options, I called on Mr Antenna (before he became famous). He told me it was just interference from the FM radio transmitter coexisting on the TV station’s transmitter at Mount Dandenong. The fix was an FM trap at about four dollars. Do you think I wasn’t annoyed? The TV station’s sympathetic chief engineer said they were aware of the problem but management didn’t want to publicise it or the fix. S. K. should check that he is not experiencing some similar phenomenon. Peter Brett, Melbourne, Vic. USB-controlled power switch I have just built the USB-Controlled Power switch published in the November 2004 edition with the modified PC board from the Notes and Errata in the December 2004 edition. Congratulations to Jim Rowe on a very simple idea put to great use. Referring to the problems with some PCs always having power on the USB port to power such devices as USB mouse chargers, I had this exact problem. All you need to get around this problem is a spare PCI slot and a cheap $20 USB add-on card. Run the power switch from this card. When you turn your PC off, the 12V power is removed from the USB ports and the Power Switch shuts down. This now gives me 11 USB ports on my PC and no glowing peripheral in the corner of the room at night. James Deland, Old Reynella, SA. Wind power is cube of the speed In the December 2004 article entitled “Build Yourself a Windmill Generator”, it mentioned that the power in the wind is proportional to the square of speed. In fact, the power is proportional to the cube of the wind speed so that when the speed of the wind doubles, the energy and thus the power is increased eight-fold (2 x 2 x 2 = 8). Consider this: the kinetic energy from the wind is E = 1/2 x mass x wind velocity2. The mass of the air is equal to the density x volume of passing the area swept by the blades or, wind mass flow = density x pr2 x wind siliconchip.com.au velocity. So the energy in the wind is P = 1/2 x pro x pr2 x wind velocity3. This means it is important to protect the windmill structure in gusty places as the energy in the wind varies with the cube of the wind speed. Imagine an energy level which is 27 times more than the one you designed it for when the wind speed triples, which is what usually happens in typhoons. Demetrio Chuasieng, Tsing Yi, Hong Kong Video cameras can check IR remote controls For those who don’t need the completeness of the Remote Control Checker kit featured in the January 2005 issue, a digital video camera will do the same job. Simply point the video camera towards the IR LED in a dimly lit area and you can see the LED flash. The camera receives the IR signal and converts it to a white light on the LCD display. I presume the video camera supports IR reception for Night View camera modes. This is cheaper if you already have a video camera, more expensive if you don’t. A friend mentioned this to me some time ago when I was building a IR controller to turn things on/off from my computer and I wondered if it was transmitting the wrong codes or nothing at all. David Robinson, Alstonville, NSW. Editor’s comment: good point. When I was editing this article I made a mental note to include a panel mentioning that you could check IR remotes with a video camera. As you can see, I forgot. Short life from CFLs I couldn’t agree more with Leo Simpson’s write-up in the August 2004 issue on compact fluorescent lights and with what other Mailbag writers have had to say on the subject to date. We have tried a couple of the CFLs to replace normal incandescent bulbs and they didn’t last as long as the original incandescents. However, on reflection, we really didn’t give any thought as to where one could “properly” replace incandescent bulbs with CFLs. In reality, CFLs are just miniaturised standard fluorescent lights with elecsiliconchip.com.au tronic control thrown in. And where does one usually find standard fluoros used the most? Generally, they are used in areas where they are turned on and left on for several hours at a time; eg, supermarkets, shops, car parks, hospitals, factories, street lights and so on. The way the CFLs are packaged and advertised, one can only believe that you could save heaps of money if you were to replace all the incandescent bulbs in your house with CFLs. I feel that advertising for CFL products should include a recommended minimum operating period per day to achieve the advertised lifetime. Rod Josey, Killarney, Qld. Cheap components and inaudible beepers I wish to express my concern about three matters that no one but me seems to find worth raising. No 1. Never mind about fancy hifi low loss cables. When are manufacturers going to produce flexible flex? Years ago, we used to be able to put our soldering iron down and it would stay where we put it. No 2. When are manufacturers going to produce RCA and similar plugs and sockets that do not get distorted when you try to make a good soldered joint to them? No 3. When are designers who put beepers into equipment finally realise that people of my age cannot hear a sound when the beeper is operated? This can be quite critical when beepers are used in household alarm systems. Evan Prout, Wellington, New Zealand. Extra low voltage limit is 50V AC I note the letter from Brian Clancy in the Mailbag pages of the January 2005 issue, quoting 32V AC as “extra low voltage” That information is four years out of date. The following is an extract from AS/ NZS 3000. 2000 Wiring Rules. Note that the DC voltage limit for ELV is higher than for AC volts. 1.4.90 Voltage Difference of potential normally existing between conductors and Atmel’s AVR, from JED in Australia JED has designed a range of single board computers and modules as a way of using the AVR without SMT board design The AVR570 module (above) is a way of using an ATmega128 CPU on a user base board without having to lay out the intricate, surface-mounted surrounds of the CPU, and then having to manufacture your board on an SMT robot line. Instead you simply layout a square for four 0.1” spaced socket strips and plug in our pre-tested module. The module has the crystal, resetter, AVR-ISP programming header (and an optional JTAG ICE pad), as well as programming signal switching. For a little extra, we load a DS1305 RTC, crystal and Li battery underneath, which uses SPI and port G. See JED’s www site for a datasheet. AVR573 Single Board Computer This board uses the AVR570 module and adds 20 An./Dig. inputs, 12 FET outs, LCD/ Kbd, 2xRS232, 1xRS485, 1-Wire, power reg. etc. See www.jedmicro.com.au/avr.htm $330 PC-PROM Programmer This programmer plugs into a PC printer port and reads, writes and edits any 28 or 32-pin PROM. Comes with plug-pack, cable and software. Also available is a multi-PROM UV eraser with timer, and a 32/32 PLCC converter. JED Microprocessors Pty Ltd 173 Boronia Rd, Boronia, Victoria, 3155 Ph. 03 9762 3588, Fax 03 9762 5499 www.jedmicro.com.au February 2005 5 Mailbag: continued between conductors and earth as follows: (a) Extra-low voltage not exceeding 50V AC or 120 V ripple free DC. (b) Low voltage exceeding extra-low voltage, but not exceeding 1000 V AC or 1500 V DC. (c) High voltage exceeding low voltage. Reg Brownjohn, Charlton, Vic. Energy Meter calibration queries I recently built the DSE version of your Energy Meter (July & August 2004). While the kit appears to work very well, I have a few minor suggestions and observations. (1) Firstly, may I suggest that a better location for the VR1 contrast trimpot is on the solder side of the display PC board where it remains accessible after assembly. (2) In my opinion, the design of the battery backup circuit should include an enable/disable switch so that the meter can be stored without having to first open it and disconnect the battery. (3) The function of R2 is rather obscure. It appears to be there for noise cancellation but what kind of noise? The LPF at the inputs to the op amp should reject RF noise, so as far as I can see, the only other possible noise source is radiated AF. If R2 is intended to cancel the hum from T1, then I would think that R1 and R2 would need to be located symmetrically with respect to the transformer body. As it is now, R1 is about twice as far away as R2. (4) The power calibration procedure is somewhat questionable. My feeling is that the level of accuracy (using a radiator) leaves a lot to be desired. The primary factors affecting the meter’s accuracy are the internal reference voltage of IC1 (2.4V ±200mV) and the tolerances of the scaling and sensing resistors. Rather than use the 2.2MW 400V 5% resistors supplied in the DSE kit, I would use DSE’s 2.2MW 600mW 1% Cat. R0258 resistors. I would then match the actual measured values of 6 Silicon Chip the resistances on each leg of the amp so that the ratio of 2.2MW to 1kW is as close as possible on each side. After assembling the meter, I would carefully measure the reference voltage on pin 9 of IC1 and use this alone to calibrate the meter. My Vref was 2.41V which suggests that no calibration should be necessary in my case. If on the other hand, the measured value was 2.50V, say, then I would think that the power reading should be increased by a calibration factor of (2.50/2.40)2 = 1.085. Having said this, I am puzzled as to why the default power calibration setting is -600 counts. Why not zero? Franc Zabkar, via email. Comment: as with all types of meters, calibration is required. In particular, the Energy Meter needs calibrating to compensate for tolerance in IC1’s voltage reference, the voltage division and current sense resistors and so on. The initial calibration of -600 was to prevent constructors having to calibrate any more than necessary. The tolerance of IC1’s internal reference is the main reason for calibration. Using 1% 2.2MW resistors would not alter this. The balanced current lines using R2 actually works well even though the circuit looks strange with a 0.01W resistor in series with 1kW. Calibration using the radiator is accurate if the procedure is followed carefully. Warnings on 240VAC not too cautious I must agree with Brian Shirley (Mailbag, December 2004) that “Warnings on 240VAC (are) not too cautious.” The casual attitude many people have to the potentially lethal mains supply is almost unbelievable. His story of his misadventures with the lighting fixtures and cables illustrate errors and methods of testing that are all too common, even these days. In the 1960s, the broadcasting station where I worked purchased an AC appliance tester. Not only would this test for wiring transpositions or disconnections on the power outlets, it also tested appliances for leakage to ground and for integrity of the appliance’s earth connection. From memory (now rather hazy after so long), the leakage test used a neon lamp feeding the linked Active and Neutral legs of the power input, which would glow if the leakage to ground exceeded a few milliamps. The earth integrity test used a lowvoltage source to measure the resistance between the appliance’s earthed metal parts and the earth pin on its power cord, on a “good/bad” meter. From memory, the meter would indicate in the “good” part of the scale for a resistance of 3W or less. I have not seem any similar testers either “in the flesh” or in advertisements. Maybe they rejected too many appliances that people judged to be “safe enough.” Greg Mayman, Adelaide, SA. Keep up the high voltage warnings In regards to the issue of high voltage warnings for certain projects, keep doing it! I have had many accidents through complacency and have survived, fortunately. It cannot be expressed more strongly, high voltage IS dangerous and all care MUST be exercised. I haven’t had any misfortunes with high voltage for a few years but that is only because I try to be very aware of the dangers and I do exercise utmost caution. But one day, I may again become complacent and I’ll get bitten again, perhaps fatally next time. Always beware of high voltage. If it doesn’t kill you, it’ll hurt like hell and leaves you feeling very unwell, possibly for some days. It is also possible that you’ll suffer some cardiac damage that may not show up for some time. Ian Dempsey, Dubbo, NSW. Atlas LCR meter a thrill What a thrill to open the August 2004 issue of SILICON CHIP and see my circuit idea published. An added thrill was to have won the Atlas LCR meter. It arrived a few days ago and I have had fun using it. Thanks for a great magazine and thanks for my prize. Robert Gatt, Port Fairy, Vic. siliconchip.com.au siliconchip.com.au February 2005 7 BORDER SURVEILLANCE in the 21st century by Barrie Smith Detecting contraband, armaments and illegal immigrants as they cross borders has been likened to looking for that proverbial needle in the haystack. But that is changing, with amazing new technology already in use and even more just be around the corner. . . 8 Silicon Chip siliconchip.com.au A s the gap between the developing and developed countries continues to grow, there are millions of people wanting a better life in the USA, Canada, UK, Australia and Europe. A spokesman for Canada’s Royal Mounted Police claims at any one time, 18 million people are poised to make a covert voyage to one country or another. These poor (in every meaning of the word) people are willing to borrow, beg and shell out huge amounts of currency to get to the land of their hopes. And there are lot of criminals willing to take their hard-won savings. In 2000, 58 illegal Chinese immigrants died in an airtight truck container at the port of Dover, having been transported across the continent, then across the Channel. The driver and a London-based accomplice were sentenced to 14 and 6 years imprisonment respectively. French Customs in 2001 intercepted a 7.5m truck on a Channel ferry packed with rags and fabric – and 24 Indian nationals loaded in Paris and close to asphyxiation. At the UK end of the Channel Tunnel Customs examined a tanker, laden with sand and 35 Indian ‘illegals’ who had been on the road from Belgium for 4-5 hours. Nine more were found sitting on a load of frozen chickens in a freezer truck chilled to -9°C. Although they were wrapped in thermals the solid-sided vehicle had no exit mechanism and no way for them to leave the vehicle in an emergency. Eight Turkish Kurds, including two children, were found dead in Wexford, Ireland having hidden in a metal container they believed was headed The Chinese developed NUCTECH X-ray scanner now operating in Melbourne, Sydney and Brisbane. It can detect a 1.5mm metal wire hidden behind 10cm of steel. to Dover. A body was found in the wheel well of a US Airways jet at San Francisco International Airport. The unidentified man was discovered a few minutes after landing. Solutions US border authorities believe they have an effective stopper for ‘kamikaze smugglers’ — cars packed with illegal immigrants and drugs that zip across the US-Mexican border. Called a Vehicle Stopping System (VSS), the device snares smugglers in high-tech nets; it stops suspects from fleeing by wrapping around the doors of the vehicle. Road spikes were not “a good solution” because the vehicles lost control and anyway, it was believed, smugglers could drive over the spikes by filling their tyres with silicone. Every year, 16 million containers move through America’s 361 ports, while only 4% of them are scanned — a big hole in the nation’s ‘terrorist shield’. The West Coast ports of Los Angeles-Long Beach, Oakland and Seattle currently process 11,000 containers per day. While people smuggling is a serious problem worldwide, the US itself is People smuggling by road is big (illegal) business, particularly in the US and Europe. Here’s a “load” of illegal immigrants attempting to enter the US hidden deep inside a cargo truck. But modern surveillance equipment can penetrate the steel walls of the truck. siliconchip.com.au also on high alert for illegal terrorist material imports — bombs, nuclear devices and so on. As detection techniques forge ahead, a number of approaches are now being either considered or taken up by authorities in their battle against smugglers. Some methods are claimed to offer comprehensive success in discovery of contraband — human and otherwise — while others are only partially successful. From the Air An Israeli company supplied two Hermes-450 aerial drones to monitor the Arizona border patrol and secure a 560km stretch of the US-Mexican border — known to be the most popular corridor for illegal immigrants. The remotely piloted vehicles can fly up to 145km/h, detect movement from 25km away and transmit live pictures day and night. Melbourne X-ray scanner A Chinese-developed X-ray scanner now operates at Swanson Dock in the Port of Melbourne, scanning steel shipping containers for drugs, armaments, explosives and other materials – and people. Measuring 35 x 15 metres, the scanner is driven by a six million electronvolt linear accelerator that projects a narrow vertical beam, able to penetrate 260mm of steel. It can detect a 1.5mm metal wire hidden behind 10cm of steel. However the level of radiation around the scanner is less than that of a standard hospital chest X-ray machine. Broadly, the container scanner is a very large version of the machines used to check luggage at airports. Trucks carrying up to three 6-metre containers are driven into the scanner shed and parked under a rolling gantry carrying the beam projector. Drivers step down into a waiting room insulated against radiation while the February 2005 9 scanner, riding on a set of rails, runs the length of the truck. The gantry travels at 10 metres a minute, scanning a semi-trailer load of three six-metre containers in about 2.5 minutes. A receptor on the far side of the gantry gathers data produced by the X-ray beam and projects a digital image of each container’s contents on to computer screens in a control room where they are analysed by customs examiners. The whole process takes a little more than 10 minutes per truck. The facility handles about 100 containers a day. Analysis of the images on monitoring screens takes another 10 minutes or so; the operator looks for ‘anomalies’, so if something does not fit the description of the cargo supposed to be inside, the container is manually examined in a nearby shed. Illegal drugs are among the most common seizures. Humans are rarely discovered — but sometimes they are found dead, asphyxiated in an airtight container. The Melbourne container scanner is the first of four bought by customs from NUCTECH Company Limited, the Chinese enterprise which is the largest producer of container and vehicle X-ray inspection systems in the world. Similar facilities are being built at Sydney, Brisbane and Fremantle. Texas Rays At checkpoints on Highways 77 and 281 in Texas, mobile truck-mounted X/gamma ray machines, costing half a million US dollars, are reported to scan a truck’s cargo in seconds in the search for ‘illegals’. TV and radio campaigns warn Latin American viewers of the dangers involved in people smuggling, while a bi-lingual campaign informs truck drivers of the penalties involved in smuggling illegal aliens. Neutron Scanner Examples of NUCTECH scans. 10 Silicon Chip To date, industrial X-ray scanners are unable to reliably detect nuclear or fissionable materials transported in cargo containers due to the latter’s mass (some weigh up to 27 tonnes) and the mix of their cargo — food, sports gear, liquids — all of which may provide frustrating shielding. Over the last few decades, several industries have begun to use thermal, or low-energy, neutron imaging as a complementary technique to X-ray imaging for inspecting objects. Neusiliconchip.com.au Livermore Laboratory design for a high energy neutron imaging system, consisting of a powerful neutron source, multi axis staging platform to hold and manipulate an object and an effective imaging detector (CCD). Livermore Laboratory physicist James Hall with imaging scintillator (light source) of neutron scanner. trons are electrically neutral particles similar in mass to a proton and present in the nuclei of all elements — except hydrogen. The drawback to these lowenergy systems is that they are generally limited to inspection of objects only a few centimetres thick. Now Lawrence Livermore National Laboratory (University of California) researchers has demonstrated the power of using high-energy neutrons as a non-destructive inspection tool for evaluating the integrity of thick objects such as nuclear warheads and their components. In non-destructive surveillance Xrays are adequate for inspecting the condition of high-Z (high-atomic-number) materials such as lead, tungsten and uranium. But X-rays are not always effective in revealing cavities, cracks or other defects in low-Z (low-atomicnumber) materials such as plastics, ceramics, lubricants and explosives when these materials are heavily shielded by thick, high-Z parts. High-energy neutron imaging offers unique advantages over conventional X-ray and thermal neutron imaging, particularly for inspecting light low-Z elements that are shielded by high-Z elements. High-energy neutrons have greater penetrating power through high-Z materials and, compared to X-rays, much stronger interaction in low-Z materials, so yielding more detailed images of the latter. siliconchip.com.au This imaging detector consists of a 60cm diameter transparent plastic scintillator (a component that gives off light when a charged particle passes through it), viewed indirectly by a camera with a high-resolution (2048x2048 pixels) CCD. A thin turning mirror made of aluminised glass reflects the brief flashes of light, generated by neutrons interacting in the scintillator, into the CCD camera. The camera has a fast f/1.0 aperture lens to enhance its sensitivity and is cooled with liquid nitrogen gas to -120° C to minimise dark current noise (to which CCDs are prone). Exposures can be as long as 30 minutes per capture. The final Livermore detector would work by firing a neutron beam through a cargo container as it rolls along a conveyor belt between two large, flat arrays of detectors (jokingly called a ‘nuclear car wash’). The high-speed neutrons would split atoms within concealed uranium or plutonium. The atoms would exhibit their presence by emitting their own telltale electromagnetic radiation (gamma rays) and neutrons, which could be sensed by the detector arrays. Scientists want to be able to detect at least one kilogram of plutonium, significantly less than is required to make a bomb — but some terrorists might try to evade security scanners by bringing fissionable materials into the country in small pieces for later assembly. There are some problems ahead: for example the enriched uranium or plutonium may be shielded with lead, (absorbs gamma rays) or with materials rich in hydrogen (water, wax or wood), which absorb neutrons. Another difficulty is how to pick up Hall and co-workers set up the scanner test. February 2005 11 Bales of marijuana (1) hidden behind a false wall (2) in the rear of a truck, with more bales hidden under a load of hay. the signal of bomb materials against the background noise of cosmic rays in the environment. And the neutrons have to be intense enough to detect fissionable materials without being severe enough to harm human stowaways. The Neutron Race There is an Australian research neutron X/gamma ray research venture being piloted by Dr Brian Sowerby, Project Leader and Chief Scientist, with his team at the CSIRO Minerals unit, based at the Lucas Heights, NSW reactor. Is there a race? Possibly, as the unit is discouraging publicity prior to the official launch and images of the scanner cannot be released. The Australian Government has allocated $8.4 million to the Customs Service to develop a contraband scanner that can quickly and accurately detect illegal drugs and explosives. Using the CSIRO approach the aim is to construct a commercial scale scanner and facility in Brisbane, to trial the technology in 2005. Whereas the US Livermore device is known to be slow in operation at this stage of its development, the Australian venture should have speed on its side and be less intrusive commercially – scanning an air-freight container should take less than two minutes. The Australian scanner combines Xray scanning and the neutron method. It is expected to be around a quarter the cost of the Livermore device, so there should be considerable market interest in it. Customs and CSIRO have already 12 Silicon Chip successfully prototyped, tested and patented the device, thanks to the building of a full-scale prototype at Lucas Heights. In tests it scanned standard air cargo containers and correctly identified a wide range of concealed contraband. In a press release from the CSIRO Dr Nick Cutmore, Program Manager at CSIRO Minerals explains that the main advantage of the scanner, over current and potential new scanners, “is its ability to accurately and rapidly detect and predict the composition, shape and density of an object — in real-time on the tarmac.” Conventional X-ray scanners can detect objects based on their density and shape — but not their composition. X-rays and their variations fall down when there is a need to detecting materials like drugs and explosives, plastics and organics. Dr Cutmore believes the scanner is unique in the way it uses gamma rays and neutron analysis to construct an image and the composition of the object being scanned. The CSIRO scanner is able to distinguish varying classes of compounds; organic materials can be detected, even when hidden behind heavyweight objects. One example is that drugs have been detected in tests, even when placed inside concrete blocks. While keeping a tight rein on information on how the scanner actually works, Dr Sowerby has been quoted in an ABC Radio interview as explaining that a combination of commercially available components were used — but that the key component is the detector ray itself. The principle harks back to some years of earlier research in on-line This contraband detection X-ray system has civil libertarians in a real tizz as it is capable of revealing quite intimate body details (as you can see), along with contraband secreted both on and inside the body. One would have to ask if this is any more intrusive of civil liberty than a full body search of a suspect? siliconchip.com.au low doses of radiation to make an image of the freight, via a highly sensitive detector array system. It moves along the whole length of the vehicle and typically takes a few minutes to produce an image. The scanning equipment uses low exposure high-energy X/gamma radiation systems, linked to a detector array sysDr Brian Soweby with an air cargo container tem, which images the standing on the prototype scanner platform. contents of the vehicles analysis instrumentation for the minand/or freight. eral and coal industries. This used The shielded driver’s cab and operaneutron X/gamma ray techniques to tors cabin form an integral part of the measure the value content of minerals, scanning vehicle and are intended to coal ash and other materials. be occupied throughout the examinaTo apply practical experience to the tion, (which takes up to 50 seconds prototype scanner a quantity of guns, for a 12-metre container and truck). grenades and explosives were taken The tightly collimated X/gamma into Lucas Heights to be stowed into radiation beam scans the vehicle and/ actual airline containers for the tests. or freight either as a ‘flying spot’, scanOne can only imagine the security ning down the vehicle and/or freight headache this must have caused the from top to bottom, or as a fan beam. reactor’s security staff! There are questions about the level Airline and sea containers have a of radiation in order to protect the similar maximum width of a little public, scanner operators and truck more than two metres, so the CSIRO drivers. It is understood the radiascanner is believed to be able to ‘look tion level is not high enough to affect into’ both types. Smaller objects are foodstuffs contained within the trucks well within its ‘view’, possibly right and insufficient to affect humans. down to parcel-shaped objects; in this There is no radiological impact on the case, lower energy neutrons would be environment from using the scanner, employed. as it contains no radioactive material. The report concluded that people UK findings who may fly to the UK to claim asylum The British Immigration Service could well be exposed to a higher dose commissioned a report to determine from cosmic radiation than if they whether the use of “mobile X/gamma were subjected to a scan in a vehicle. ray radiation scanners is justified in In a heartbeat the detection of people seeking to circumvent UK immigration controls.” There have also been trials of heartThe rate of clandestine entry by people beat sensors at Dover and Coquelles concealed in vehicles and/or freight at (in France), respective ends of the ferry ports and the Channel Tunnel is Channel Tunnel. stated to be “very high”. This works by placing up to four Current measures in use include carbon dioxide sensors, which give rapid and generally reliable indications of concealed humans and animals. However, certain types of freight emit CO2, which masks detection. Also, some containers prevent examination by CO2 sensors. The Immigration Service plans to deploy X/gamma radiation scanners at UK ports and control zones as a follow up to the CO2 scanners. The X/gamma ray scanners emit siliconchip.com.au brass sensors, connected to a simple touch screen computer, on the frame of a stationary vehicle. The system is capable of detecting a heartbeat (human, animal, bird etc) by measuring minute vibrations in the vehicle structure and matching them against the known sonic pattern of a human heartbeat. Analysis of this passive millimetric wave imaging uses thermal imaging techniques to detect radiation naturally emitted from objects. Although it can only be used for soft-sided vehicles, it works when the vehicle is moving. Eurotunnel currently uses the system at Coquelles while the British are “looking at it.” Coincidentally, the Ford/Volvo car combine has trialled ‘SecureCar’ in a Volvo S80, using an electronic microaccelerometer, a microprocessor and sophisticated software to detect heartbeats anywhere within the vehicle. The latter also contains two additional systems, designed to aid an individual trapped in the trunk: a CO2 sensor scans the trunk for signs of trapped occupants and a touch-sensitive pad inside the trunk can open the lid if it touches any part of a living being. Ion scanner At Montreal (Canada) Dorval airport ion scanners are used by the Mounties to detect the explosives or drugs inside closed containers, such as packages or luggage. Already ion scanners are heavily used by Canadian customs officers. Deep Scans So, next time you use your desktop scanner to capture the surface of a printed A4 page, spare a thought for the scientists working with X/gamma ray technology and the like as they peer into the contents of a 27 tonne container! SC Ford/Volvo has trialled ‘SecureCar’ in a Volvo S80, using an electronic microaccelerometer, a small microprocessor and sophisticated software to detect heartbeats anywhere within the vehicle. February 2005 13 BUILD THIS USB ELEC Here’s an easy-to-build project which will let you take your own electrocardiogram (ECG) and display it on a PC. You can read, display, save to disk and print the electrical waveform generated by your heart – or anyone else’s. It connects to your PC via a standard USB cable which also provides the low power it needs to operate. A n Electrocardiograph is a piece of medical equipment used to measure and record the voltages (ECG) produced as a result of heart muscle activity. By attaching electrodes (or ‘leads’ as they are known in the trade) to the skin of your wrists, ankle or chest, our PC-Driven ECG project can display, record or print out the same kind of ECG waveform on your personal computer. Why would you want to build one? Well, looking at the waveforms generated by your heart can be both fun and educational. You can monitor changes to your heart under various conditions, as your heart is affected by many factors such as emotions, mental and physical activity – even breathing. All of these things have a demonstrable effect on the heart’s ECG waveform. Being able to show this 14 Silicon Chip easily, safely and at low cost is an added bonus. Professional ECG machines can cost anything from $4000 up, and while this project is not intended to be used as a diagnostic device, the displayed, recorded and printed waveforms are of a quality approaching that of professional machines. Our new PC-based electrocardiogram is smarter than previous models because its operation is under the control of an inbuilt PIC microcontroller. It’s also faster and compatible with modern PCs, because it’s linked to the PC via a standard USB cable – thanks to the use of an Elexol USBMOD3 interface module. And finally it’s easier to use, because all functions are controlled using a By JIM ROWE Windows-based GUI program, written in Visual Basic. Both the PIC microcontroller’s firmware program and the Visual Basic PC program will be available on the SILICON CHIP website (www.siliconchip. com.au). The PIC program (ECGSAMPL. HEX) is in hex code form ready for PIC programming, while the VB program (ECGCONTR.ZIP) is in the form of a zipped-up installation package. We imagine that kit suppliers will have already programmed the PIC for you. You’ll also need a special USB virtual COM port driver which the PC needs to communicate with the ECG via a USB cable. This will also be available on the SILICON CHIP website, as R9052154.ZIP. Both the latter items can be installed directly on a PC running Win98SE or newer USBcompatible operating systems. Note siliconchip.com.au CTROCARDIOGRAPH PLEASE NO TE: This project has Correct interp not been designed for m edical diagn retation of E osis. CG waveform complex and s and tracing skilled proce s dure and req is a ing. The USB uires medica /ECG is pres l trainented here a educational s an instructi device only. ve and If you are c health of you o ncerned abo r heart, cons ut the ult your GP o r a heart spe cialist. that it won’t work with Win NT-based systems – not through any shortcoming in the design but the simple fact that NT doesn’t recognise the USB port. How it works The muscles of your body are controlled by electrochemical impulses. These impulses are distributed to the muscles by the nervous system. On reaching their destination, the nerve impulses cause the muscles to contract and produce much larger electrical voltages. A small proportion of these voltages is conducted out through to the surface of the skin where they can be detected using sensitive equipment like an ECG (often also called EKG). Because the heart is a large and rather complex group of muscles which contract cyclically in a preset sequence (see sidebar), it is possible to study the overall condition of the heart by measuring the amplitude, timing and waveform of the heart muscle voltage components found on the skin. This is the reason for capturing ECG waveforms, which are obtained using two or more electrodes (pads) attached to the skin via conductive saline gels or paste. siliconchip.com.au A “screen grab” using this project on a live human. We make no comment on the condition of his/her heart from this graph: perhaps a cardiologist out there might care to? February 2005 15 the ECG amplifier, we can cancel out most of the common-mode 50Hz hum before the differential ECG voltages are amplified. By the way, the connections between the electrodes and your skin play an important role in this hum cancellation, because if one connection is poor this can upset the balance of the input amplifier. Most of the remaining 50Hz signals are removed by low-pass filtering in the later stages of the amplifier. As a result the output of the amplifier provides relatively clean amplified ECG signals, with very little 50Hz hum. We then use a simple PIC-driven ADC (analog to digital converter) to sample the amplified signals to be sent to the PC for display and recording. Circuit description Let’s see how the circuit works. It is shown in Fig.1. The shielded electrode leads are brought into the Electrocardiograph via connectors CON1 and CON2 and fed through 1mF coupling capacitors and series 3.9kW resistors to the inputs of IC1. This is an Analog Devices AD623AN device, a specialised instrumentation amplifier offering precision balanced differential inputs and hence very high common-mode signal rejection, combined with high gain. A simplified version of the circuitry The complete ECG setup using our new Electrocardiograph, a laptop PC (with inside the AD623 is shown in Fig.2. USB) and home-made electrodes. You can also use commercial ECG pads. It is essentially three op amps in one: Capturing ECG waveforms is really picked up by the electrodes is virtually two matched-gain input stages feeding quite a challenge, because the voltage the same regardless of their position a balanced ‘subtractor’ output stage. components found on the surface of on the body. In other words the 50Hz The overall AD623 gain for differthe skin are quite small in amplitude: hum is a ‘common mode’ signal, while ential-mode signals is set by the single around 1mV peak to peak, depend- the tiny ECG voltages are ‘differential external resistor Rg (between pins 1 & ing on the positions of the electrodes mode’ signals. 8), which gives a gain of 1000 times and the resistance between them and By using a highly balanced differ- (60dB) using a value of 100W. the skin. ential amplifier as the input stage of Returning to the main circuit, to So to display or record ensure that IC1 can deliver these voltages we need to INVERTING maximum undistorted output INPUT feed them through a high level and also that the ADC 50kΩ 50kΩ 2 A1 gain amplifier. used for sampling the amplified To make the job that much signals can handle the largest harder, the tiny voltages we signal swing, we connect IC1’s 1 50kΩ want to measure are usureference signal input (pin 5) to 6 A3 Vout ally completely swamped Rg a low impedance source of +2.5V 50kΩ by 50Hz hum, picked up by DC (ie, half the supply voltage). 8 our bodies from the fields This is provided by the voltage surrounding the AC wiring NONOUTPUT divider formed by the two 3.0kW 50kΩ 50kΩ REF in our homes and offices, etc. INVERTING resistors and it thereby sets the A2 INPUT 5 Luckily we are only inzero-signal output level of IC1 3 AD623 INSTRUMENTATION AMP terested in the voltage difto +2.5V DC. The two 220kW ferences between the two Fig.2: a simplified look inside the heart of the input bias resistors for IC1 are electrodes being used at any project, an Analog Devices AD623 instrumentation also returned to the same +2.5V time, whereas the 50Hz hum amplifier. It’s essentially three op amps in one. point, as you can see. 16 Silicon Chip siliconchip.com.au siliconchip.com.au February 2005 17 1 µF 1 µF SC 1nF 220k 100Ω 10 µF A K D1,D2: 1N4148 3.0k +2.5V INSULATED RCA PLUGS 5 6 3.0k 100nF 10k HI LO 8.2k TO CON2 TO CON1 usb ELECTROCARDIOGRAPH A K 4 100nF ELECTRODE LEAD WIRING NOTE: SHIELDED LEADS SHOULD BE OF EQUAL LENGTH SHIELDED LEADS 7 IC1 AD623AN 220k 2 1 8 3 IMPORTANT: INSULATE ELECTRODE ENDS OF LEAD SHIELD BRAIDS 1nF 3.9k 47nF 3.9k BALANCED INPUT AMPLIFIER Fig.1: the complete ECG circuit. It uses a preassembled module from Elexol to connect to the USB port on your PC. 2005 LEDS ELECTRODE 2 ELECTRODE 1 CON2 CON1 ELECTRODE LEADS D1 A K K A 20k 10k 10k 10k 10k LADDER DAC 10k 10k 10k 20k D2 220 µF 1 µF LP FILTER 1.8k GAIN S1 100 µF 82Ω 20k IC2a 8 2 3 20k 20k 20k 20k 20k 20k 20k 20k 5 2 3 4 5 6 7 8 9 1,4 IC3 8 1 20 DIR 1 10 18 17 16 15 14 13 12 11 100nF 1.2k OE 19 IC4 74HC245 6 7 LM311 COMPARATOR 2 3 2X/4X AMPLIFIER RB2 RB3 RB4 RB5 RB6 RB7 1k 6 RB0 7 RB1 8 9 10 11 12 13 10k 6.8 µF NP 11k IC2: LM358 5 Vss 100k OSC2 OSC1 RA0 RA1 RA2 RA3 15 16 17 18 1 2 7 14 X1 4MHz 28 27 26 25 4,13 RSTI 8 PCTL 100nF 1,2,16, 29,32 GND EP RXLD TXLD RSTO USB-MOD3 INTERFACE MODULE 33pF TxD RxD RTS CTS SLEEP VIO 100 µF 'DIGITAL' +5V +VBUS 100nF 12 100nF 33pF 4 IC2b 100nF 6 5 14 Vdd 4 MCLR IC5 PIC16F84 -04 3 RA4 1 µF 2.7k LP FILTER 'ANALOG' +5V 18 10 9 15 17 K λ A CASE USB CABLE TO PC 220Ω 220Ω LED 1 LED λ 2 33k K A RFC1 1mH 18 Silicon Chip Looking straight down on the completed PC board, mounted inside the bottom of the case. Note the earth connection on the right-hand side of the box. RECEIVE COMMAND SEND DATA USB CONNECTOR 33pF 33pF RSTI EP* 5002 © 15020170 RSTO 3V3 Din RTS* o CTS* i SLEEP IC5 DTR* o DSR* i 1 DCD* i VIO* * +V RI* i PEN* o PCTL RXLED TXLED 11k 100 µF + IC1 AD623 1 LL 220 µF 100nF 74HC245 1.0 µF SIDE OF BOX 100nF 10 µF 33k 1.0 µF 47nF + 100nF + 3.9k 3.9k 1.0 µF 1.8k 1nF 1nF 20k 3.0k 3.0k 1 IC4 1 100nF 220k 100Ω 1.2k IC2 LM358 8.2k 220k 82Ω 100nF Fig.3: and here’s the matching overlay diagram to help you place the components correctly. Between this and the photo above, you should have no problems in construction. 1k 100nF 1 10k 4148 D1 D2 4148 100 µF 6.8 µF NP 100k IC3 LM311 RFC1 1mH 2.7k PIC16F84A 100nF TXENo GND 1.0 µF X1 4MHz 20k 20k 20k 20k 20k 20k 20k 20k EDAT Dout 220Ω 220Ω ECLK + ECS 100nF B+ +V ELEXOL USBMOD3 V5+ LED2 (TXD) LED1 (RXD) G 20k 10k 10k 10k 10k 10k 10k 10k 1 + 10k 20k As IC1 is being operated with such a high gain, we also need to prevent it from amplifying any stray RF signals which may be picked up by the electrode leads (or the subject’s body). This is the purpose of the 1nF bypass capacitors on each input of IC1 and also the 47nF capacitor between the two inputs. All three capacitors form a balanced low-pass filter, in conjunction with the two 3.9kW input series resistors. The rest of the Electrocardiograph’s amplifier and filter circuitry is based around IC2, an LM358 dual low-power op amp. The output from IC1 is fed to the input of IC2a via a passive RC low-pass filter formed by the series 8.2kW and 1.8kW resistors and the 1.0mF capacitor, which give a corner frequency (-3dB point) of about 17Hz and an attenuation of about -9dB at 50Hz. IC2a is used to give additional fixed amplification to the ECG signals, of either two or four times as set by switch S1, which determines the negative feedback ratio. So in the LO position of the switch the amplification in IC2a is 2, while in the HI position it gives a gain of 4. The overall ECG signal gain for the two switch positions is therefore 2000 and 4000, respectively. IC2b is used to provide additional low-pass filtering, to further reduce any remaining 50Hz hum. With the R and C values shown this filter stage has a corner frequency of about 15Hz, providing further attenuation of about -21dB at 50Hz. At the same time it has unity gain for the low frequency ECG signals. So at the output of IC2b (pin 7) we end up with relatively clean and hum-free ECG signals, amplified by either 2000 or 4000 times depending on the setting of switch S1. The rest of the circuit is involved in performing analog-to-digital conversion (ADC) of these signals, and sending them back to the PC via the USB cable and port. Both of these functions are controlled using IC5, a PIC16F84A microcontroller operating at 4MHz. Analog-to-digital conversion is done using comparator IC3 to compare the amplified ECG signals with a programmed reference voltage generated by IC5 and IC4, an octal transceiver containing eight digital buffers. IC4 drives the binary ladder network formed by the 10kW and 20kW resistors. The combination of IC4 and the ladder network forms a simple digital- CON2 CON1 S1 GAIN HI LO LEAD2 LEAD1 M3 x 9mm CSK HEAD SCREW WITH SOLDER LUG, NUT & 2 x STAR LOCKWASHERS siliconchip.com.au to-analog converter (DAC), whereby IC5 can generate any of 256 different voltage levels between 0V and 5V at the positive input (pin 2) of IC3, by providing 8-bit values on the outputs of its I/O port B (pins 6-13). The output of comparator IC3 is connected to pin 3 of IC5 which is bit 4 of the micro’s I/O port A, configured here as an input. This allows the micro to monitor the output of IC3 and perform a simple ‘successive approximation’ ADC algorithm. It generates a sequence of voltages at pin 2 of IC3 and changes the sequence according to the comparator output (which indicates whether the DAC voltage is higher or lower than the ECG voltage on pin 3). As a result, the micro can quickly ‘zero in’ on the ECG voltage during each sampling sequence, arriving at its 8-bit digital equivalent in only 48ms. When each digital sample has been taken, the micro then sends it out in serial format (38,400bps) from bit 1 of its I/O port A1 (pin 18) to pin 27 (RxD) of the USB-MOD3 interface module. This module then reformats the sample and sends it back to the PC via the USB cable and port. The micro is programmed in firmware to take a sequence of 8192 of these samples at a time, at any of three rates: 500, 1000 or 2000 per second. The rate is controlled by the Visual Basic software running in the PC, which sends a control code out to the micro when you click on the ‘Start Sampling’ button. The control code is sent out via the USB cable, is received by the USBMOD3 module and then sent to the micro via the module’s pin 28 (TxD), connected to bit 0 of the micro’s I/O port A. Two inverse-parallel connected diodes (D1 and D2) at the inputs of IC3 are used to limit the voltage swing between the comparator inputs to +/0.6V, regardless of the real difference between the amplified ECG and DAC reference voltages. This limiting prevents the comparator from being saturated and allows it to respond faster when the difference voltage changes in polarity. The USB-MOD3 module is powered from the PC via the USB cable and it provides +5V DC from its +VBUS pins (pins 4 and 13), to power the rest of the circuitry. IC3, IC4 and IC5 are powered from it directly, while IC1, IC2 and the siliconchip.com.au Your Heart & Its Electrical Activity R T P Q S ONE HEART BEAT/PUMPING CYCLE Most people are aware that your heart is basically a pump, which pushes your blood around your body via your arteries and veins. The typical human adult heart is about the size of a clenched fist, and weighs about 300 grams. It is a popular misconception that the heart is located in the left side of the chest. It’s not: the heart is located near the centre (although its apex points to the left) and is virtually surrounded above and at the sides by the lungs. In a normal adult it pumps about once per second although this can vary dramatically due to a large number of causes (age, fitness, current activity and health/disease being just four). The pumping action is triggered mainly by a nerve centre inside the heart, called the sino-atrial or ‘SA’ node. Each pumping cycle is initiated by a nerve impulse which starts at the SA node and spreads downwards through the heart via preset pathways. The heart itself is made up of millions of bundles of microscopic R muscle cells, which contract when triggered. The muscle cells are electrically polarised, like tiny electrolytic capacitors (positive outside, negative inside), and as the trigger pulse from the SA node passes through them, they depolarise briefly and contract. So with each beat of the heart, a ‘wave’ of depolarisation sweeps from the top of the heart to the bottom. Weak voltages produced by this wave appear on the outside surface of your skin, and can be picked up using electrodes strapped to your wrists, angles and the front of your chest. It’s these voltages (about 1mV peak to peak) which are captured and recorded as an electrocardiogram or ‘ECG’. The actual shape and amplitude of the ECG waveform depends upon the individual being examined and the positioning of the electrodes but the general waveform is shown above. The initial ‘P’ wave is due to the heart’s atria (upper input chambers) depolarising, while the relatively larger and narrower ‘QRS complex’ section is due to the much stronger ventricles (lower output chambers) depolarising. Finally the ‘T’ wave is due to repolarisation of the ventricles, ready for another cycle. Doctors are able to evaluate a number of heart problems by measuring the timing of these wave components, and their relative heights. They can also diagnose problems by comparing the way the wave components change with the various standard electrode and lead connections (as shown below). L V1 V2 V3 V4 CHEST CROSS-SECTION V5 V6 SINO-ATRIAL (SA) NODE HEART STANDARD CONNECTION POINTS V6 V5 V1 F V2 V3 V4 LEAD NAME ELECTRODE 1 ELECTRODE 2 LIMB LEAD 1 L R LIMB LEAD II F R LIMB LEAD III F L LEAD aVR R L+F R+F LEAD aVL L LEAD aVF F R+L PRECORDIAL (x6) V1 — V6 R+L+F February 2005 19 standard diecast aluminium box measuring 119 x 93 x 34mm. The box is used upside down, with the PC board assembly mounted component-side down inside the main part of the box via four 6mm long M3 tapped Nylon spacers, with eight 6mm long M3 machine screws (four of them with countersink heads, passing through matching holes in the box). The two RCA Here’s the bottom of the case, which has become the top... connectors used for showing the end cutouts for the electrode leads and the the ECG electrode switch. Below right is the top of the case, which has leads are accessed become the bottom, showing the end LED and USB connector cutouts... Confused? All is explained in the text! through two 12mm diameter holes in analog circuitry are fed via a low-pass one end of the box, with miniature filter formed by RF choke RFC1 and the slider switch S1 mounted in a 5 x 100mF bypass capacitor. These remove 10mm rectangular hole at the same any digital switching noise from the end, fixed in the case via two 6mm ‘analog’ 5V rail. long M2 machine screws. When it is transmitting or receiving At the other end of the case are two data via the TxD or RxD lines, the 3.5mm holes for the indicator LEDs, USB-MOD3 interface module pulls plus a 13 x 11.5mm rectangular hole down its TXLD (pin 17) or RXLD (pin for access to the USB connector. 15) pins. LED1 and LED2 indicate bus Assembling the components on the activity. PC board is quite straightforward, as Although the complete Electrocar- the only surface-mount parts used diograph is housed in a metal box to are in the Elexol USB-MOD3 module, provide shielding, the metal box is not which comes prebuilt and tested. connected directly to the signal earth It’s in the form of a 32-pin DIL as you might expect. package with machined pins on Instead, it’s connected via a parallel standard 0.6” x 0.1” spacing, which combination of a 33kW resistor and a drop straight into matching holes 100nF capacitor, to provide current on the main PC board and are then limiting in the (unlikely) event of the soldered. earth connection of your PC becoming To protect it from broken and the signal earth of your possible damage computer and the Electrocardiograph however, the modbecoming ‘live’. ule shouldn’t be Even if you are touching a good earth mounted on the and the Electrocardiograph box at the board until you’ve same time in this situation, you should fitted all of the othbe safely protected from receiving er components. The anything more than a small ‘tingle’. component overlay diagram for the PC Construction board is shown in All of the Electrocardiograph Fig.3. circuitry except slider switch S1 You can begin is mounted on a PC board which assembly by fitting measures 107 x 81mm and coded the single wire link, 07102051. which goes in the The board assembly fits inside a centre of the board 20 Silicon Chip just above the location for IC3. Then fit the PC pins: two for the connections to switch S1 and one for the wire to the metal box itself. Then fit the two board-mounting RCA connectors CON1 and CON2. You may need to enlarge the slots in the board pads with a small jeweller’s needle file, before the connector lugs will pass through them to allow the connectors to mount down against the top of the board. Then the lugs are soldered to the board copper underneath to hold them securely in place. Next, fit the 18-pin IC socket for the PIC (IC5) which should be fitted with its notch end facing to the left, where the USB-MOD3 module will ultimately be fitted. Use a socket with machined pins, for higher reliability. Fit the resistors next, taking care to fit each one to the board in its correct position as shown in the overlay diagram. Then fit the multilayer monolithic and ceramic capacitors, again using the overlay diagram as a guide. The MKT capacitors and the 6.8mF nonpolarised electrolytic capacitor and the 4MHz crystal can be installed either way around. The remaining electrolytic capacitors are polarised, so make sure that you fit these with the orientation shown in the overlay diagram. Note that the 220mF electrolytic at the lower left corner of the PC board should be a low leakage type (RBLL). The two 1N4148 diodes (D1 & D2) go in almost the exact centre of the board, with opposite polarities. Then fit IC2, IC3 and IC4, all of which solder directly into the board. Make sure you fit them the correct way around, as shown in the overlay diagram. Then fit IC1, taking even more care, as it’s siliconchip.com.au rather more expensive. The two LEDs are fitted next. Their leads are left straight, and introduced to the PC board holes with the longer anode leads towards the right (as seen in the overlay diagram) and the ‘flat’ side of the LED bodies towards the left. The leads are then soldered to the pads under the board with the LED bodies held directly above and about 15mm above the board. This allows them to be bent outwards by 90° afterwards, so the bodies will protrude out through the matching holes in the box. Finally, you can drop the USBMOD3 module into place and solder its pins to the pads underneath. You don’t have to solder all of its pins; just those where the main PC board pad is connected to a track or the earth copper. These will be sufficient to make all necessary connections and hold the module securely in place. Preparing the box There aren’t very many holes to cut in the aluminium box, but those there are should be located and cut accurately so that the PC board assembly and slider switch S1 will mount inside it without problems and the complete assembly can be connected easily to the ECG electrode leads and the USB cable. The location and size of all holes needed in the box are shown in the drilling diagram of Fig.4. Final assembly Use four countersink-head M3 screws to attach the four M3-tapped Nylon spacers to the inside of the box. Tighten these screws fairly tightly, because their heads become inaccessible when the dress front panel is attached later. Now fit the PC board assembly into the box. You’ll find it necessary to push the RCA connectors further through their box holes than their final position, to allow you to swing the USB module/LEDs end of the board down into the box. Once the board is sitting on the spacers you can slide the board back until its mounting holes are correctly aligned over the spacers. Then fit the four remaining M3 x 6mm screws, to attach the board assembly securely inside the box. Once this is done you should be able to push the two indicator LEDs out through their matching 3.5mm holes, so they’ll be visible when the box is closed. siliconchip.com.au Parts List – USB Electrocardiograph 1 PC board, code 07102051, 107 x 81mm 1 diecast aluminium box, 119 x 93 x 34mm 1 Elexol USBMOD3 USB interface module (www.elexol.com) 2 RCA sockets, PC board mounting (CON1,2) 1 1mH choke (RFC1) 1 4MHz crystal (X1) 1 miniature DPDT slider switch (S1) 1 18-pin DIL socket, with machined pins 2 6mm x M2 machine screws, round head 4 6mm x M3 tapped Nylon spacers 4 6mm x M3 machine screws, countersink head 4 6mm x M3 machine screws, round head 1 9mm x M3 machine screw, countersink head 1 M3 nut with two star lockwashers 1 solder lug 3 1mm PC pins Semiconductors 1 AD623 instrumentation op amp (IC1) 1 LM358 dual op amp (IC2) 1 LM311 comparator (IC3) 1 74HC245 octal transceiver (IC4) 1 PIC16F84A microcontroller (IC5) programmed with ECGSAMPL.hex 1 3mm green LED (LED1) 1 3mm red LED (LED2) 2 1N4148 diodes (D1,D2) Capacitors 1 220mF 50V RBLL low leakage electrolytic 2 100mF 16V PC electrolytic 1 10mF 16V PC electrolytic 1 6.8mF NP electrolytic 4 1.0mF MKT polyester 8 100nF multilayer monolithic 1 47nF multilayer monolithic 2 1nF NPO disc ceramic 2 33pF NPO disc ceramic Resistors (0.25W 1% metal film) 2 220kW 1 100kW 1 33kW 1 11kW 9 10kW 1 8.2kW 2 3.0kW 1 2.7kW 1 1.8kW 1 1kW 2 220W 1 100W 11 20kW 2 3.9kW 1 1.2kW 1 82W For making two ECG electrodes: 2 insulated RCA plugs (1 red, 1 black) 3 metres of figure-8 shielded stereo cable 2 50 x 30mm rectangles of blank PC board (see text) 4 Nylon cable ties 2 40mm lengths of 20mm wide Velcro hook strip 2 350mm lengths of 20mm wide Velcro felt strip 2 25mm lengths of 4mm diameter heatshrink sleeving The next step is to prepare the box ‘earthing’ connection. This is done by passing a 9mm x M3 countersink-head machine screw through the single hole on the side of the box, close to the terminal pin on that side of the mounted PC board. Then to the inside of the screw fit a star lockwasher, a solder lug, another star lockwasher and finally an M3 nut. The screw and nut should then be tightened up very firmly, so the solder lug becomes a good and reliable electrical connection to the box metalwork. The lug is then connected to the nearby PC pin, using a February 2005 21 6.25 16 NOTE: ALL DIMENSIONS IN MILLIMETRES B CASE OUTSIDE DIMENSIONS 92 x 119 x 35 INCLUDING LID 11.5 B 6.5 18 11.25 36.75 36.75 A 13 A A: B: C: D: 43.25 HOLE DETAILS: 3.5mm diam (CSK) 3.5mm diam 12mm diam 2.5mm diam L 43.25 34 C 10 A A A 9 17.5 8.5 19 D D C 13 12 C 10 16 Fig.4: drilling details for the diecast aluminium box. The hole and cutout positions must be accurate to accommodate the PC board. Inset below: a pair of commercial ECG pads as supplied by First Aid Plus. These are self-adhesive and really, really stick! (LID) L C short length of tinned copper wire or a resistor lead offcut. Make sure both ends are soldered properly. Then mount slider switch S1 in the end of the box, using two M2 x 6mm screws and connect the centre and leftmost switch lugs to the PC pins immediately behind them, using short 22 Silicon Chip lengths of tinned copper wire or resistor lead offcuts. Now plug your programmed PIC micro IC5 carefully into its socket up near the top of the board and then attach the box lid via the four screws provided. The final step is to apply the front panel to the bottom of the box, which then becomes the top. The artwork for the dress front panel is reproduced in this article, actual size (see Fig.5). It can be photocopied onto a sheet of A4 self-adhesive label paper and then covered with clear ‘Contact’ or siliconchip.com.au similar adhesive film, before being cut out along the outline border. Then the backing paper on the back of the label can be peeled off, allowing the dress panel to be stuck on the top of the Electrocardiograph box. The adhesive film covering will protect the panel from finger grease and dirt. If you want the colour version and don’t have access to a colour copier, the file can be downloaded from www. siliconchip.com.au and printed on a colour inkjet or similar, then applied as above. You might also want to fit four small adhesive rubber feet to the lid/base of the box, so it won’t scratch any surface it’s placed on. The electrodes: buy or make? It goes without saying that the best electrodes you can use with this device are those intended for the purpose. Unlike the adhesive electrode pads made for TENS machines, ECG pads are disposable items and are therefore relatively cheap (only a couple of dollars or so each) but like TENS pads, are fairly difficult to find and usually have high minimum order quantities (eg, 50 minimum). We’ve managed to track down one source from a first aid supplies company in Sydney, First Aid Plus, who will sell them by mail order in small quantities – six pads for $10 including postage. ECG pads are almost always removable from their leads – they usually use a press-snap type of fitting. We suggest you obtain pads with the male snap on them, as this gives you a convenient “nipple” on which to clip a small alligator connector. First Aid Plus will assume you want male snaps and supply those unless specifically asked for female. Contact First Aid Plus at PO Box 37, Harbord, NSW 2096. (Phone 02 9905 0155); website www.firstaidplus. com.au If you don’t want to buy pads, or find it inconvenient, there is an alternative “pad” or electrode which you can make yourself. It’s not as efficient nor convenient but once made, should last perhaps indefinitely. Its made from a small rectangular piece of blank PC board. The details are shown in Fig.7. Note that the shield braid wires of each lead are bent back away from the centre conductor and then insulated with a sleeve of 4mm OD heatshrink sleeving so they can’t come into contact with either the centre wire or the human subject. Then the centre wire is passed through the small hole in the electrode and soldered to the copper underneath, after which the end of the lead is firmly secured to the electrode using two small Nylon cable ties, each of which passes through one of the 3mm holes on the side. As you can see from the circuit of Fig.1, the electrode leads are made from shielded microphone cable. The two leads should be of equal length, to maintain the balance of the ECG Electrocardiograph’s input stage. The home-made electrodes are held SAFETY WARNING The circuit of this USB ECG is directly connected to the PC which controls it, via the USB cable. Although no optical isolation is fitted, the electrodes which connect to the skin of the human subject are capacitively coupled and also have significant resistance connected in series with them. This means that even if the PC’s earth connection becomes broken and its power supply also develops a direct short circuit to active 240VAC (a very unlikely chain of events), the potential current which could flow through the body between the electrodes is very small and highly unlikely to cause injury. However if you are concerned about this small safety risk, there are two steps you can take to ensure that the USB/ECG project is used with virtually complete safety: (1). Always ensure that the human subject to which the ECG electrodes are connected is insulated from earth and unable to contact any earthed (or ‘live’) metalwork. (2). If insulation of the subject can not be achieved, connect and use the USB ECG only with a laptop computer running from batteries – rather than a desktop or laptop PC running from 240V AC. As used in the ECG project in this issue . . . Elexol’s USBMOD3 USB Interface Here’s some more of our range of USB and MP3 modules: 2nd Generation USB Plug and Play Need to get data into serial development module or out of a USB port? Try this second generation, Low Cost USB Data I/O Module 24 independently programmable Input/Output pins grouped into 3 ports. Single module high-speed digital Input/Output solution. Up to 128 modules can be connected to a single PC with capabilities of further expansion. Easy to connect by 0.1” pitch headers to suit standard IDC connectors. Integrated Type-B USB connector. On-board unique serial number in EEPROM and custom programmable FLASH microcontroller. Both USB enumeration information & microcontroller can be re-programmed to suit customer needs. Module powered by the USB from the PC. USB MOD1 - 100k baud (RS232) 300k baud (RS422/RS485) USB MOD2 - USB MOD4 - USB Plug and Play USB Plug and Play Parallel USB Plug and Play Parallel 8-Bit FIFO 8-Bit FIFO Serial Development Development Module. Development Module (2nd Module. Up to 920k baud Gen). Up to 8 Million bits (RS232) and 2000k baud Up to 8 Million bit (1 Megabyte) per sec. (1Megabyte) per second. (RS422/RS485). MP3 MOD4 - VS1001 chip. Converts clocked serial data (MP3) to stereo audio out. Suitable for driving headphones. Visit our web shop <at> www.elexol.com Elexol Pty Ltd Ph: (07) 5574 3988 Fax: (07) 5574 3833 (PO Box 5972, Bundall, Qld 4217) siliconchip.com.au February 2005 23 against the subject’s skin with Velcro strips. A 40mm length of 20mm wide Velcro hook strip is attached to the top of each electrode using a small amount of epoxy adhesive (eg, Araldite). One end of a 350mm length of the matching felt strap is attached to one half of the hook strip. The strap can be run around the subject’s forearm or ankle, pulled reasonably tight and then pressed into the ‘other half’ of the hook strip to hold the electrode in place. It’s very simple but it works surprisingly well. By the way, you need to make sure that the copper side of the electrodes is kept clean and bright, so it can form a good electrical contact with the skin. Each time the electrodes are applied to a subject you also need to apply some conductive liquid or paste to both the electrode copper and the skin underneath – again to ensure a good contact. This normally applies to commercial pads too. A convenient liquid to use is sodium chloride or saline solution, which is available at low cost from most pharmacists. Just wet a small piece of cotton wool with this and use it to apply a fairly generous amount to both the RECEIVE TRIGGER SEND DATA electrode and the subject’s skin where it’s being placed. Installing the software As mentioned earlier, there are two pieces of software which need to be installed on your PC before it will be able to communicate with and control the Electrocardiograph. There’s the Electrocardiograph control program itself, written in Visual Basic 6. There’s also a special ‘USB virtual COM port driver’ which allows Windows and the control program to communicate with the Electrocardiograph via its USB-MOD3 interface module and one of the PC’s USB ports. The VCP driver has been written by the makers of the main USB interface controller chip in the Elexol USB-MOD3 module, an FT232BM device made by Scottish firm Future Technology Device International (FTDI). A copy of FTDI’s VCP driver will be available for downloading on the SILICON CHIP website (www.siliconchip. com.au). It’s also available directly from the FTDI website (www.ftdichip. com) and updated versions of it may be available there as well in the future. The actual driver file is included in the download file (R9052154.ZIP) which also contains a PDF document explaining how to install and configure it. Basically the procedure is to download the ZIP file and unpack it using Winzip or PKUnzip onto a suitable subdirectory on your PC’s hard disk. Then when you first connect the hardware box up to your PC via a USB cable, and Windows comes up with its ‘Found New Hardware Wizard’ dialog box, you direct the wizard to the subdirectory where the driver package was unpacked, and tell it to refer to the file FTDIBUS.INF. It will then install the VCP driver for you. After this is done it’s a good idea to open up the Device Manager panel to set the port settings. The method is different for different versions of Windows. As we mentioned before, Windows NT is a no-go, as is Win95 (for the same reason). Under Windows 98SE, open Control Panel (-> System Properties -> Device Manager), where you’ll find a USB Serial Port device listed under USB High Speed Serial Converter. Select this port device, and click on Properties. Then under the Port Settings tab select 38,400 bits per second, 8 data bits, None for parity, 1 stop bit and USB TO PC +5V LEAD 1 C 2005 07102051 + ELE R A C O R T C H P A R DIOG SILICON CHIP GAIN LEAD 2 LOW HIGH Fig.5, the full-size front panel, along with, along with Fig.6, the PC board pattern (also full size). If you don’t have access to a colour photocopier, download the panel from www.siliconchip.com.au and print it on a colour inkjet. 24 Silicon Chip siliconchip.com.au Taking an ECG Apart from the gain - which is set to either LOW (2000) or HIGH (4000) using slider switch S1, all other functions of the Electrocardiograph are controlled using the ECGSampler program. This is very easy to use because when you fire it up, it provides a GUI window (see screen grab) which allows you to set the configuration or to start it taking an ECG recording and then displaying, saving and printing it. There are three drop-down menus at the top, with the labels ‘File’, ‘Settings’ and ‘About’. The first menu is for saving, reloading or printing ECG records, while the second is for changing various USB port and settings: the virtual COM port, the COM port settings (bit rate, parity, stop bits etc.), the sampling rate (500, 1000 or 2000 samples/second) and also for advising the software on which position the gain switch has been set (Low/2000 or High/4000). siliconchip.com.au 5 A BLANK PC BOARD LAMINATE (COPPER SIDE DOWN) 50 B 26 Fig.7 if you want to make your own electrodes (pads) here’s how to do it from a couple of scraps of PC board. The advantage – they’re dirt cheap. The disadvantage: they get dirty (tarnished) very easily and need to be cleaned before use. 3. SOLDER CENTRE CONDUCTOR TO COPPER (UNDERNEATH) 1. REMOVE 10mm OF OUTER INSULATION & BEND SHIELD BRAID BACK 2. FIT HEAT SHRINK TO COVER BRAID 4. SECURE CABLE USING NYLON CABLE TIES B 10 Xon/Xoff for flow control. Finally click on the Advanced button, and select COM5 as the port number. This forces the VCP driver to make its USB virtual COM port COM5, so there shouldn’t be any clashes with any existing COM ports. If you’re using XP, go to Control Panel, ->System -> Hardware ->Device Manager, -> Ports (COM & LPT) where you should find the “USB Serial Port” (probably set to COM4). Click on this and then “Port Settings” and proceed as per Win98 (including the Advanced tab). Now let’s turn to the Visual Basic control program for the USB Electrocardiograph. This is available for downloading from the SILICON CHIP website as a zipped-up installation package called ECGCONTR.ZIP. Inside this package are the CAB files for the program and its various support components and an installation program Setup.exe together with its ‘instruction sheet’ SETUP.LST. Download the package and unpack it on a TEMP directory. Then doubleclick on the Setup.exe file so that it installs everything, on a suitable subdirectory of your Program Files directory. If you wish you can also create a shortcut on your Desktop, called SILICON CHIP ECG or similar. The shortcut simply needs to be linked to the installed VB program itself, called ECGSampler.exe. 15 30 ALL DIMENSIONS IN MILLIMETRES CABLE TO RCA PLUG & ECG SAMPLER HOLE A: 1mm DIA. HOLES B: 3mm DIA. The third drop-down menu displays a small dialog box showing the version number of the software itself. Once you have made sure that the software is set up correctly to suit the USB port and the Electrocardiograph, taking an ECG is then simply a matter of choosing which lead configuration you want, applying the electrodes to your subject (or yourself), and then clicking on the ‘Start Sampling’ button on the left-hand side of the GUI window. A graphical ‘progress bar’ will then appear along the bottom of the GUI beneath the main display window, to show you the progress as the ECG samples are taken. When all of the 8192 samples are received back from the Electrocardiograph, the progress bar will display again more briefly, as the ECG record is plotted in the display window. The display window is calibrated in terms of both ECG voltage and time, as shown in the screen grab. The same calibrations are reproduced when the record is printed out, along with the date and time – and when you save the record to your hard disk (or a floppy), the calibration info is saved with it as well. So once you’ve taken an ECG record, it’s easy to work out such things as the subject’s current heart rate or other aspects of the ECG waveform. Lead configurations Finally, which lead configuration should you use, just to take a basic look at your own ECG or that of someone else? We suggest you use the ‘Lead II’ limb configuration, with lead 1 connected to the subject’s left ankle and lead 2 connected to their right wrist or inside forearm. This usually gives the largest waveform amplitude, providing your electrode-skin connections are good. (See the diagram in the sidebar, “Your heart and its electrical activity.”) If you get weak waveforms with a relatively large amount of hum, this is usually a sign of poor electrode contact. So take them off, apply a bit more saline solution and try again. The exact positioning of the limb electrodes is not critical, as the limbs are really being used as convenient ‘conductors’ joined to the four ‘corners’ of the subject’s trunk. The main thing is to get the best possible contact to the skin. If you want to try some of the chest positions for the lead 1 electrode, the electrode positions are then fairly critical. You really need medical knowledge to know the right chest electrode positions, so it’s best to leave these to the professionals. Note that when lead 1 is being used with a chest electrode, lead 2 should be connected to electrodes in all three of the limb positions so that it provides a ‘whole body’ reference signal. So you’ll need to make up at least two more electrodes, and connect these all in parallel – by connecting them to the Electrocardiograph’s CON2 input socket via leads of the same length as the original two electrode leads. If you really want to play around with all of the lead configurations, or you’re a medico who wants to use the USB Electrocardiograph for serious diagnostic work, you might want to make up a set of nine electrodes and leads, plus a small switch box to allow you to select any of the standard lead configurations at will. SC February 2005 25 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Build The TwinTen . . . a gutsy little stereo amplifier with surprisingly good performance by JIM ROWE & PETER SMITH Want a compact amplifier to team with your Discman, MP3 player, games machine or whatever? This tiny stereo amplifier puts out a surprising amount of power, considering that it runs from a 16VAC 1.5A plugpack. N OT ONLY IS THIS a gutsy little amplifier, it is an ideal learnwhile-you-build-it project for high school and tech college students. It all fits onto a single largish PC board with no 240VAC mains voltages present – that’s taken care of by the 16VAC plugpack. The TwinTen has inputs for three stereo program sources such as CD player, MP3 player and FM/AM tuner and has front-panel LEDs to indicate which source has been selected. The other controls are Bass, Treble, Volume and Balance. At the rear, there are RCA line inputs, binding posts for the speaker connections, a finned heatsink and a socket for the plugpack supply jack. As part of the final checking of this 32 Silicon Chip amplifier, one of our staff members took it home for a blast on his large stereo system. His daughter was so impressed with the performance from such a tiny package that she wanted it straight away. We thought that was a pretty good endorsement. The reason why it packs such a punch is that it can deliver around 17 watts music power per channel into 4-ohm loudspeakers. In a typical room with reasonably efficient speakers, that’s enough to blast you out of your seat. And did we say it’s tiny? It measures just 225mm wide, 40mm high and 165mm deep, including the knobs and rear heatsink. It’s also pretty quiet and its other performance parameters are pretty good as well, considering that we have kept a very tight rein on the overall cost of the design. One reason it performs so well is that it is based on the same National Semiconductor LM1875T 20W audio amplifier IC used in the Schoolies’ Amplifier, published in the December 2004 issue. This IC has inbuilt thermal protection so that even if you abuse it or short out its output, it won’t be damaged. The power amplifier circuits are very close to the Schoolies’ Amplifier circuit but inevitably there are component differences to provide different gain and so on. How it works As you can see from the circuit diagram, the amplifier is quite straightforward. The left and right channels are identical, with an input preamp stage followed by a tone control stage and finally a power amplifier stage. We’ll follow the signal path through the left (upper) channel in detail but the right (lower) channel is exactly the same. Source selector switch S1a allows the user to select input signals from any one of three sources. These are labelled CD, MP3 and TUNER but any siliconchip.com.au The new amplifier is built into a low-profile ABS instrument case measuring just 225 x 165 x 40mm. Construction is straightforward, since all the parts except for the loudspeaker terminals are mounted on a single PC board. Power comes from an external 16VAC 1.25A plugpack supply. of these inputs can be used for line level audio signals from sources such as a DVD player, a MiniDisc player, games console or a VCR. From the switch, the selected signal passes through a simple low-pass filter formed by a 2.7kW resistor and 680pF capacitor. This filters out any RF (radio frequency) signals or noise that may be present with the incoming audio signals, to prevent them from causing trouble. After this, the signals are applied directly to volume control potentiometer VR1a. From the wiper of VR1a, the signals pass through a 220nF coupling capacitor to the input of IC1a, which is one half of a TL072 dual FET-input op amp IC. IC1a is used as an input preamplifier stage, with its voltage gain set to 3, using negative feedback provided by the 5.6kW and 2.7kW resistors. The amplified signals from IC1a’s pin 1 output are then fed to this channel’s tone control stage, which is based on IC2a – half of a second TL072 dual op amp. IC2a is connected in what is known as a Baxandall negative feedback tone control circuit, where the op amp’s negative input is connected siliconchip.com.au to the wipers of both the bass and treble control pots (VR2a and VR3a). As shown, the incoming signals from IC1a are fed to one end of each pot’s filter circuit, while the feedback signals from IC2a’s output (pin 1) are connected to the other end of each filter circuit. As a result, when both VR2a and VR3a are set to the middle of their ranges, the tone control stage provides the same gain (ie, unity or 1) for signals of all audio frequencies. This gives the amplifier a flat frequency response. However, if VR2a is turned clockwise (towards input preamp IC1a), the stage provides more gain for frequencies lower than about 500Hz, thus giving SPECIFI CATION S Power Output Both channels driven into 8W ........................................................... 6W RMS Both channels driven into 4W ........................................................... 6W RMS One channel driven into 4W ............................................................ 10W RMS IHF Burst Peak Output (Music Power) Both channels driven into 8W ..............................................................13.5W Both channels driven into 4W...............................................................17.1W General Distortion at 1W continuous into 8W..............................................0.04% THD Frequency response (-3dB points).............................................. 10Hz - 72kHz Signal-to-noise ratio <at> 10W RMS into 4W ..............................................-80dB Input impedance, all channels................................................... 12kW//600pF Treble tone control range at 20kHz............................................ +11dB/-12dB Bass tone control range at 50Hz............................................... +12dB/-13dB February 2005 33 Par t s Lis t – TwinTen Amplifier 1 PC board, code 01102051, 215 x 156mm 1 low-profile ABS instrument case (225 x 165 x 40mm) with prepunched front and rear panels (see text) 1 16VAC 1.25A plugpack 1 3-pole 3/4-position rotary switch 2 M205 PC-mount fuse clips 1 M205 2A slow-blow fuse 1 finned heatsink, 84 x 24mm (Altronics H 0668) 3 PC-mount dual RCA sockets 1 PC-mount 2.5mm concentric power socket 4 binding posts, 2 red & 2 black 5 20mm skirted instrument knobs 1 knob actuator, 40 x 30 x 2.5mm (see text) 4 6G x 6mm self-tapping screws 3 6G x 9mm self-tapping screws 2 M3 x 16mm screws, nuts & flat washers 2 TO-220 insulating washers and nylon bush sets 1 small tube of heatsink compound 1 300mm length of 0.7mm tinned copper wire 1 200mm length figure-8 speaker cable Semiconductors 2 TL072 dual op amps (IC1,IC2) 2 LM1875T audio amplifiers (IC3, IC4) 2 12V 1W zener diodes (ZD1,ZD2) bass boost. On the other hand, if VR2a is turned anticlockwise (towards the output of IC2a), the stage provides lower gain for frequencies below 500Hz, thereby giving bass cut. In the same way, VR3a can be used to give a variable amount of boost or cut to frequencies above 2kHz; ie, treble boost or cut. And as both of these tone controls are part of a negative feedback circuit connected around IC2a, the boost or cut action is achieved without causing any significant distortion or increase in signal noise level. Balance control The output signals from IC2a are then fed via a 4.7kW series resistor and 1mF non-polarised (NP) capacitor to the positive input of IC3, which 34 Silicon Chip 1 3mm green LED (LED1) 1 3mm red LED (LED2) 1 3mm orange LED (LED3) 4 1N5404 3A diodes (D1-D4) Capacitors 4 2200mF 25V electrolytic 2 470mF 16V electrolytic 4 220mF 25V electrolytic 2 4.7mF 16V NP electrolytic 2 1mF 16V NP electrolytic 4 220nF 50V MKT polyester 8 100nF 50V MKT polyester 2 10nF 50V MKT polyester 4 1.5nF 50V MKT polyester 2 680pF 50V disc ceramic 2 330pF 50V disc ceramic 2 33pF 50V disc ceramic Resistors (0.25W 1%) 2 270kW 4 4.7kW 4 82kW 4 2.7kW 2 56kW 3 1kW 6 27kW 2 470W 4 10kW 2 100W 2 5.6kW 2 10W 2 2.7W Potentiometers 1 PC-mount 16mm dual 10kW log. pot (VR1) 1 PC-mount 16mm dual 100kW linear pot (VR2) 1 PC-mount 16mm dual 50kW linear pot (VR3) 1 PC-mount 16mm 50kW linear pot (VR4) is the power amplifier IC for the left channel. We’ll look at this in a moment but first note that one end of pot VR4 (the Balance control) is connected to the junction of the 4.7kW resistor and 1mF NP capacitor. Because the moving wiper of VR4 is connected to ground, this means that the 4.7kW resistor and the associated “half” of VR4 form a variable voltage divider, while the other “half” of VR4 forms a similar voltage divider with the 4.7kW resistor in the right channel. In addition, because the two dividers share VR4, their division ratios vary in opposite fashion; when the wiper is turned one way from the centre position, the gain is reduced in the left channel but increased in the right channel, and vice-versa. Fig.1 (right): the circuit consists of identical input preamp stages (IC1a & IC1b), followed by a tone control stage (IC2a & IC2b) and finally power amplifier stages IC3 & IC4. Switch S1 selects the input signal, with LEDs1-3 indicating the selected signal source. So VR4 provides a “see-saw” or differential adjustment of the gain in the two channels, allowing them to be matched or balanced (to compensate for any difference in the incoming signal levels). Power amplifier IC IC3 is an LM1875 power amplifier IC, which comes in a TO-220 package with five connection leads and a metal tab for connection to a heatsink. It’s connected as a basic amplifier stage, with a voltage gain of about 18 times, as set by the 82kW and 4.7kW negative feedback resistors (ie, 1 + 82k/4.7k). The 4.7mF capacitor in series with the 4.7kW resistor is used to give the amplifier full DC negative feedback, for maximum thermal stability. In addition, the series 220nF capacitor and 2.7W resistor connected between IC3’s output and ground form a Zobel filter network, to ensure that the amplifier is stable at high frequencies with varying loudspeaker loads. Power supply Both IC3 and IC4 operate from dual supply rails of ±22V DC. This gives a total DC supply of 44V – necessary for the power amplifier stages to develop the power we want into 8W loudspeakers, with low distortion. We generate the +22V and -22V supply rails from the external plugpack’s supply voltage of 16VAC using four half-wave rectifier circuits, one each for the positive and negative rails for IC3 and IC4. Each rectifier circuit uses a single 1N5404 diode and a 2200mF reservoir capacitor and they’re all kept separate to minimise crosstalk between the two channels. The input preamp and tone control stages around IC1 and IC2 don’t need to operate from the same high voltage rails, because the signals they handle are at a much lower level. IC1 and IC2 are therefore operated from +12V and -12V rails, derived from one of each pair of high voltage rails using 470W series resistors and 12V zener diodes ZD1 and ZD2. There’s also a 470mF siliconchip.com.au siliconchip.com.au February 2005 35 Fig.2: the frequency response curves for the left and right channels of the amplifier. The response is 3dB down at 10Hz and 72kHz. capacitor across each zener diode for added filtering and decoupling, while the supply lines to IC1 are also given a small amount of extra decoupling via the 100W resistors and 100nF capacitors. Finally, note that the selector switch has three poles. Two of these (S1a & S1b) select the input signals for the left and right channels as described previously, while the third (S1c) pole is used to switch about 10mA DC to one of three LEDs, to show which input source has been selected. The LEDs have different colours, so they’re easily identified from a distance. Construction The new amplifier is very easy to build, with all components apart from the four loudspeaker terminals mounting directly on a single PC board. This board is coded 01102051 and measures 215 x 156mm. It’s designed to fit inside a low-profile plastic instrument case measuring 225 x 165 x 40mm. The box is fitted with a rear panel cut from 2mm thick sheet aluminium which acts as the heatsink for the two output amplifier ICs (IC3 and IC4). However, by itself, the heatsinking provided by the rear panel is insufficient. Therefore, an external finned heatsink is bolted to the rear panel, to help keep the power amplifier ICs cool. As shown in the photos, the front panel on the prototype was also made from aluminium but a standard plastic panel could also be used. To reduce off-board wiring to a minimum, we have mounted input selector 36 Silicon Chip Fig.3: this plot shows how the noise and distortion (THD) varies with frequency for a power output of 1W into 8W. It’s better than .05% from 20Hz to 20kHz. switch S1 directly on the PC board with its control spindle vertical. The only complication arising from this is that you need to convert a standard 20mm knob into a custom side actuator lever knob, to allow the switch to be operated via a lever which emerges through a matching slot in the front panel. It’s not hard to make this special knob, as we shall see later. Board assembly Before installing any of the parts, it’s a good idea to carefully inspect the copper side of the PC board for manufacturing defects. In particular, make sure that there are no bridges between pads or tracks or breaks in the tracks and make sure that all the holes have been drilled. If everything checks out OK, you’re ready to start the assembly. Fig.6 shows where all the parts go. Begin by fitting the six wire links to the board, followed by the resistors and the MKT and ceramic capacitors. Table 2 shows the resistor colour codes, although it’s a good idea to also check each value using a digital multimeter before it is installed on the board. That’s because some of the colours can be difficult to read. Next, install the four rectifier diodes (D1-D4), zener diodes ZD1 & ZD2 and the two TL072 ICs (IC1 & IC2). These parts are all polarised so make sure they go in the right way around. By the way, don’t fit the rectifier diodes with their bodies right down against the board – instead, mount them so that each diode body is about 4mm above the board. This provides better ventilation and also reduces any interference coupling to the signal track which passes underneath them. That done, fit the electrolytic capacitors, again taking care to ensure that they go in with the correct polarity. The only exceptions here are the 1mF and 4.7mF electrolytic capacitors which are non-polarised. It’s now simply a matter of completing the board assembly by fitting the large hardware items. These parts include the DC power socket, the three dual RCA connectors and the control pots. Before fitting the control pots, you will probably need to shorten their spindles, so that the knobs sit close to the front panel when the amplifier is finally assembled. This job can be done using a small hacksaw – cut each spindle at a point 9mm from the threaded bush and remove any burrs with a small file. Each pot mounts directly on the PC board. Be sure to fit each dual pot (VR1, VR2 & VR3) in its correct position, as they all have different values. Each pot should be pushed down onto the board as far as it will go before soldering its pins. Once all four pots have been mounted on the board, cut a 160mm length of 0.7mm tinned copper wire and pass one end down through the small hole in the left front corner of the board just to the left of VR4. Solder it to the copper underneath, then run the free end across the top of all four pots (see Fig.6 and photo). It’s then soldered to the metal body of each pot, to make sure siliconchip.com.au Fig.4: THD + noise vs. output power into 4W. The right channel (red) has higher distortion at the lower power levels due to noise from the power supply circuitry. that all four (and also the metal front panel, when it’s fitted) are connected to the amplifier’s signal earth. Note that you will need to scrape away a small area of the anodising on each pot body using sandpaper, to ensure that the solder properly bonds to the metal. The rotary switch is fitted next but this also needs its spindle cut short. In this case, cut the spindle at a point just 6mm from the threaded bush and again remove any burrs using a small file. There’s another operation to be performed on the switch before it’s mounted. This is to make sure that it Fig.5: THD + noise vs. output power into 8W loads. Once again, the right channel is worse due to power supply noise but it’s still generally substantially less than 0.1%. is set for only three positions. This is done by first unscrewing the mounting nut and removing the star lockwasher underneath. That done, prise up the switch’s stop washer and turn the switch spindle anticlockwise with your fingers until it won’t turn any further. After this, refit the stop washer with its cranked locating pin passing down into the second hole from the anticlockwise end of the series moulded into the switch body (the hole between the moulded “3” and “4”). Finally, refit the star lockwasher and nut, threading the nut down against the star lockwasher just hard enough to fasten everything in place. If you now try turning the switch spindle by hand, you should find that it has only three positions. The switch can now be fitted to the PC board. It must be orientated so that the round spigot moulded into the top/front of its body is directly behind the spindle, as indicated in the wiring diagram (Fig.6). The pins on the rear of the switch can then be pushed down through the corresponding holes in the board, until the moulded black lugs that hold the switch body together are resting on the board. Finally, the pins can all be soldered to the copper pads. The rear panel carries three pairs of RCA input sockets (Tuner, MP3 & CD), the heatsink, and the left and right channel speaker terminals. There’s also an access hole for the power socket. siliconchip.com.au February 2005 37 Fig.6: install the parts on the PC board as shown here but refer to the text before mounting the audio amplifier ICs (IC3 & IC4) and switch S1. The three source indicator LEDs can now be installed. These mount vertically at the very front of the board, immediately in front of rotary switch S1. All three are orientated so the flat 38 Silicon Chip on the side of the body is towards the right. First, solder their leads to the pads underneath so the underside of each LED’s body is just 12mm above the board. After that, it’s just a matter of bending each pair of leads forward by 90° at a point 3mm below the LED body, so that the LEDs will later protrude through the matching holes in siliconchip.com.au This is the view inside the completed unit. Take care to ensure that all polarised parts are correctly oriented – ie, the ICs, LEDs, diodes, zener diodes and the electrolytic capacitors. the front panel of the amplifier. At this stage, the PC board assembly should be complete except for the two LM1875 audio output amplifiers (IC3 and IC4). Don’t install these yet – that step comes later, after they have been bolted to the rear panel. Side actuator knob With the board assembly now complete, you can make the special side actuator knob for the selector switch. This is made by first modifying a standard knob by cutting off its top and bottom. This is then fitted with an actuator lever cut from a small piece of 3mm Perspex or acrylic sheet (the accompanying diagram gives you a siliconchip.com.au template). The two are then cemented together using epoxy adhesive. First, cut out the actuator paddle from a small piece of 3mm-thick Perspex using a hacksaw and then smooth it all around using a small file. Lightly sand one side as well using fine garnet paper, so it has a matt surface. Next, cut off the top and bottom of a 20mm skirted knob at the positions marked in Fig.7. This should leave only the knob section immediately around the brass insert. It’s a good idea to smooth both cut surfaces (top and bottom) with fine garnet paper, so they’re flat and free from burrs. Finally, mix up a small amount of Araldite (or similar) epoxy adhesive and cement the lower surface of the knob to the matt surface of the Perspex actuator paddle. This should be done with the knob positioned as close as possible to the centre of the round hole in the paddle and with the knob orientated so its grub-screw hole is pointing at “12 o’clock” when the paddle arm is positioned at “5 o’clock” – see Fig.7. Make sure that you have a layer of epoxy adhesive between the two surfaces, as well as a fillet all around the lower circumference of the knob. The assembly should then be left untouched for 24 hours so the adhesive can cure. Once it has cured, attach the side actuator knob to the rotary switch by pushing it down onto the spindle as far as it will go. Check that the grubscrew is in the centre of the spindle’s February 2005 39 a photocopy of the panel artworks as a template. The small rectangular slot in the front panel for the input switch paddle is best cut by drilling a row of 2.5mm holes fairly close together and then opening them into the slot using jeweller’s needle files. The larger round holes for the input sockets and the control pot spindles are best made by first drilling a small hole in the centre of each position. It’s then simply a matter of opening each hole out to the correct diameter using a hand-held tapered reamer. Finally, remove any burrs from the holes using a countersink bit. Once both panels have been prepared, you can prepare dress labels by photocopying the artworks onto adhesive-backed A4 label paper. The stickers can then be given a protective coating using wide clear cellulose packaging tape, before cutting them to size. After that, you just peel of the backing, carefully affix each one to its panel and cut out the various holes using a sharp hobby knife. How To Make The Switch Actuator Fig.7: follow this diagram to make the side actuator knob. The actuator paddle is made from 3mm-thick Perspex and must be glued to the modified knob exactly as shown in the diagram at right – ie, in the 5 o’clock position. flat, then tighten the grub-screw using an Allen key and move the actuator lever to the centre position. Preparing the case The next step is to remove 12 of the Table 1: Capacitor Codes Value 220nF 100nF 10nF 1.5nF 680pF 330pF 33pF μF Code 0.22µF 0.1µF 0.01µF .0015µF NA NA NA EIA Code 224 104 103 152 680 330 33 IEC Code 220n 100n 10n 1n5 680p 330p 33p integral mounting pillars in the bottom of the case, so that they don’t foul the PC board assembly. Leave only the four pillars that line up with the corner mounting holes in the PC board itself. You can use an oversize drill to remove the unwanted pillars. Front & rear panel assembly Now for the rear panel assembly. Begin by installing the four binding posts used for the loudspeaker terminals (red to the top, black to the bottom), then slide the rear panel into position in the bottom half of the case. That done, slip the front panel over the pot shafts, LEDs and switch actuator and slide this assembly into the case. The PC board can now be temporarily secured by installing four 6G x 6mm screws at the corner positions. Follow this by fastening the three dual Drilling the panels If you buy a complete kit of parts, you won’t have to worry about this next step – the panels will come precut, drilled and screen printed. Alternatively, if you’re building the amplifier from scratch, you’ll have to first cut the front and rear panels to size (219 x 34.5mm) from 2mm sheet aluminium. That done, you can drill the various holes in each panel, using Table 2: Resistor Colour Codes o o o o o o o o o o o o o o No. 2 4 2 6 4 2 4 4 3 2 2 2 2 40 Silicon Chip Value 270kW 82kW 56kW 27kW 10kW 5.6kW 4.7kW 2.7kW 1kW 470W 100W 10W 2.7W 4-Band Code (1%) red violet yellow brown grey red orange brown green blue orange brown red violet orange brown brown black orange brown green blue red brown yellow violet red brown red violet red brown brown black red brown yellow violet brown brown brown black brown brown brown black black brown red violet gold brown 5-Band Code (1%) red violet black orange brown grey red black red brown green blue black red brown red violet black red brown brown black black red brown green blue black brown brown yellow violet black brown brown red violet black brown brown brown black black brown brown yellow violet black black brown brown black black black brown brown black black gold brown red violet black silver brown siliconchip.com.au Above and right: these two close-up views clearly show the construction of the side actuator knob. Note that it’s vital to glue the actuator paddle to the knob in the correct position; ie, with the arm at 5 o’clock to the grub screw – see text and Fig.7. RCA connectors to the rear panel using three 6G x 9mm screws, then secure the pots to the front panel using the supplied nuts and washers. You are now ready to bolt the two LM1875 audio output devices (IC3 & IC4) to the rear panel, along with the finned heatsink. Fig.9 shows the mounting details. First, check that the area around the mounting holes is smooth and free of any burrs. That done, apply thermal grease to the various mating surfaces (see Fig.9), then slip the two LM1875 devices into position on the PC board. Finally, bolt them to the rear panel along with the heatsink using two M3 x 16mm screws. Don’t leave out the insulating bushes that go through the device tabs and make sure that the mica washers are properly aligned before tightening the mounting screws. Tighten both mounting screws so that the tab of each IC is clamped flat against its mica washer and the rear panel. Once that’s been done, set your multimeter to a low ohms range and use it to confirm that the device tabs siliconchip.com.au Fig.8: these full-size artworks can be photocopied and used as drilling templates for the front and rear panels, if necessary. They can also be copied onto adhesive-back paper and used to make the final dress panels – see text. February 2005 41 Rear Panel & Heatsink Assembly Fig.9: follow this diagram to mount the heatsink and audio amplifier ICs (IC3 & IC4) on the rear panel. Note that the amplifier tabs must be isolated from the panel metalwork using mica washers and insulating bushes. are indeed electrically isolated from the rear panel. If either device tab shows a short to the rear panel, the assembly must be dismantled and the fault located. Assuming everything is OK, remove the PC board and panel assembly from the case and solder the pins of each LM1875 device. The internal wiring can now be completed by running figure-8 speaker cable between the loudspeaker terminals and the PC board. Finally, refit the assembly to the case and fit the knobs to the pot spindles. You are now ready for the smoke test. Checkout time OK – connect a 16VAC plugpack to the input socket and apply power. If all is well, the centre red LED on the front panel should light (assuming the Source switch is in that position). The other two LEDs should light when the switch actuator is moved to their respective positions. If the LEDs do light correctly, the supply voltages are probably OK. However, if you’d like to make sure, you can check the DC supply voltages using a multimeter. The simplest way to do this is to connect one lead of the multimeter to the tinned copper wire that connects the bodies of the control pots and then use the other lead to touch various supply voltage points. As a guide, several convenient voltage test points are marked on the PC board overlay diagram (Fig.6). For example, near the ends of the two 470W resistors near the centre of the board, you should be able to measure -22V, +22V, -12V, and +12V as shown. Similarly, you should be able to measure -22V on the anode of diode D3 and +22V on the cathode of diode D1. If all of these voltages measure correctly (ie, within ±0.5V), your amplifier is probably working correctly. To confirm this, switch off, connect suitable loudspeakers and connect a suitable audio source (eg, a CD player or AM/FM tuner) to a pair of input sockets. Finally, apply power and check that the unit is working properly by varying all the front-panel controls. All that remains now is to finish the assembly by fitting the top half of the case and fastening it all together using the four 25mm-long M3 machine screws provided. Your new TwinTen Stereo Amplifier is now ready for use. Happy SC listening! The finished amplifier is quite compact and is ideal for use in a rumpus room or study. 42 Silicon Chip siliconchip.com.au SILICON CHIP Order Form/Tax Invoice Silicon Chip Publications Pty Ltd ABN 49 003 205 490 www.siliconchip.com.au PRICE GUIDE: SUBSCRIPTIONS YOUR DETAILS (Note: all subscription prices include P&P). (Aust. prices include GST) Your Name________________________________________________________ (PLEASE PRINT) Organisation (if applicable)___________________________________________ Please state month to start. 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SUBSCRIBERS QUALIFY FOR 10% DISCOUNT ON ALL SILICON CHIP PRODUCTS* * except subscriptions/renewals Qty Item Price Item Description Subscribe to SILICON CHIP on-line at: www.siliconchip.com.au Both printed and on-line versions available Total TO PLACE YOUR ORDER siliconchip.com.au P&P if extra Total Price BUY MOR 10 OR ISSU E BACK ES A 1 0 & G ET DISC % OUN T $A Phone (02) 9979 5644 9am-5pm Mon-Fri Please have your credit card details ready OR Fax this form to (02) 9979 6503 with your credit card details 24 hours 7 days a week OR Mail this form, with your cheque/money order, to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy, NSW, February 2005 43 Australia 2097 02-05 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. Laser guided parking Most people have a reasonably small garage and it is most annoying when the car is left just far enough in to close the door but not far enough to squeeze past without knocking off your kneecaps! There are lots of gizmos out there to help with parking in tight spaces but all are expensive. This unit works well and costs peanuts! All up, it shouldn’t set you back more than about $10 and will let you park the car within 1mm in both axes. The main working part is a lowcost laser pointer and a simple timer circuit. The laser starts operating when the remote-controlled garage door opens and then stays on for about three minutes after the door is closed. If your garage door lacks a remote controller then a limit switch can be used to control the circuit when the door is opened manually. The circuit operation is straightforward. An existing door controller or a 9-12V DC plugpack can power the circuit. A 3-terminal regulator (REG1) reduces this to +5V to power the electronics in the laser module. The anode of diode D1 is connected to the positive side of the motor circuit or a manual limit switch (S1), so that the gate of Mosfet Q1 is pulled high when the door begins to open. This switches on the Mosfet and powers the laser. A 100mF capacitor in the gate circuit holds Q1 on for a short period after the motor stops or the switch opens, giving plenty of time for parking. The desired “hold on” time is adjustable with trimpot VR1. The laser is mounted inside an adjustable light fitting scavenged from a floodlight. After removing the redundant light and socket, it is fixed to the ceiling of the garage CONTRIBUTE AND WIN! As you can see, we pay good money for each of the “Circuit Notebook” contributions published in SILICON CHIP. But now there’s an even better reason to send in your circuit idea: each month, the best contribution published will win a superb Peak Atlas LCR Meter valued at $195.00. So don’t keep that brilliant circuit secret any more: send it to SILICON CHIP and you could be a winner! 44 Silicon Chip at a location that will allow it to be aimed at the dash of the vehicle. To set up the system, first park the car in the optimum position and then aim the laser at a fixed point on the dash. I chose a position just behind the steering wheel where the dash begins. The car is then moved away and the point at which the laser hits the concrete floor is clearly marked with a bullseye about 100mm in diameter. A permanent marker or paint is best used for the job. The result must be visible from inside the vehicle and provides assurance that the laser has not moved since you left home (kids can do amazing things with balls and such!) Now as you drive into the garage, the point of laser light can be seen immediately, moving progressively up the car's bonnet and (hopefully) through the windscreen and onto the exact spot on your dash! Ron Russo, Kirwan, Qld. ($50) siliconchip.com.au Novel white LED torch Although this design is reproduced directly from the manufacturer’s datasheets, its use in this application is rather novel. Originally intended for high-visibility LED bargraph readouts, here the LM3914 is used as the basis of a 10-step variable brightness currentregulated white LED torch! The circuit has only four components in the control and regulation circuit: R1, R2, VR1 and the LM3914. The circuit can be built directly on the pins of the LM3914 to produce a package not much bigger than the LM3914 itself. The LM3914 is set to operate in bargraph mode so that the LEDs light progressively as its input signal increases. This signal comes from the wiper of VR1, which provides a variable voltage between 0V and the supply voltage to pin 5 of the LM3914. The internal resistor ladder network of the LM3914 has its low end (pin 4) connected to ground and the high end (pin 6) connected to the supply voltage via R2. The purpose of R2 is to give LED 10 a clear turn-on zone. Resistor R1 (620W) on pin 7 of IC1 sets the current through each LED to about 20mA. As VR1 is rotated from the 0V position (all LEDs off) to the supply voltage position (all LEDs on), the LEDs will progressively light. With all LEDs off, the circuit will draw about 5mA. With all LEDs illuminated, it will draw about 205mA and dissipate 307mW with a 4.5V supply. (Editors note: these are nominal figures only. Actual device dissipation will depend entirely on the input voltage and LED forward voltage. In use, we recommend that a resistor (R3) be inserted in series with the positive supply, chosen so that the LM3914’s dissipation is limited to about 500mW. Typically, this would be needed for supply voltages of 6V and higher. The inclusion of the resistor necessitates a 10mF decoupling capacitor across the supply rails.) By carefully selecting the LEDs, this torch can be as bright as 15,0000mCd while costing less than $20. Mick Stuart, Lambton, NSW. ($30) Electronic thermostat for plug-in heaters Most room heaters with a temperature control work by controlling the duty cycle of the heater, which in turn controls the energy output. However, without temperature feedback, it’s up to the user to continually adjust the heater for maximum comfort. A plug-in thermostat would seem to be the simplest add-on solution. However, these are not commonly available, hence the impetus for this project idea. It is based on a battery-operated thermostat from Jaycar and a plug-in electronic timer switch of the type typically available from hardware stores and supermarkets. The need for an electronic timer switch is twofold. First, it contains a mains-rated relay that can be used to switch the maximum allowable load current (ie, 10A). And second, it also contains a timer and this can be used in addition to the thermosiliconchip.com.au static function if desired. All that is required is to (carefully) determine the control voltage for the relay in the timer, find a supply source for this voltage in the timer circuit and use the thermostat to control the timer relay from this source. Alternatively, if the timer still works, the thermostat could just be wired in series with the timer relay coil. As shown in the accompanying diagram, two wires connect the thermostat to the timer circuit. It can be hard-wired with the thermostat mounted permanently to the timer or connected with a longer wire and plug/socket at the timer. This would allow the thermostat to be mounted separately to better sense room temperature. If the timer control signal to the timer relay is cut, the timer is disabled. Alternatively, the timer could be used in series with the thermostat (eg, the thermostat controls a heater under the control of the timer). A socket mounted in the timer will allow the timer to be used without the thermostat and the thermostat can be plugged in when required. In practice, the thermostat does quite a good job of controlling room temperature. Ian Hood, Woden, ACT. ($30) February 2005 45 Silicon Chip Binders Circuit Notebook – Continued REAL VALUE AT $12.95 PLUS P & P These binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a dis tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. H 80mm internal width H SILICON CHIP logo printed in gold-coloured lettering on spine & cover H Buy five and get them postage free! Price: $A12.95 plus $A7 p&p per order. Available only in Aust. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my  Bankcard  Visa  Mastercard Card No: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Card Expiry Date ____/____ Signature ________________________ Name ____________________________ Address__________________________ 46 S ilicon Chip __________________ P/code_______ siliconchip.com.au ESR & low resistance test meter Len C is this m ox o winner nth’s o Peak At f the las LCR Meter As electrolytic capacitors age, their internal resistance, also known as “equivalent series resistance” (ESR), gradually increases. This can eventually lead to equipment failure. Using this design, you can measure the ESR of suspect capacitors as well as other small resistances. Basically, the circuit generates a low-voltage 100kHz test signal, which is applied to the capacitor via a pair of probes. An op amp then amplifies the voltage dropped across the capacitor’s series resistance and this can be displayed on a standard multimeter. In more detail, inverter IC1d is configured as a 200kHz oscillator. Its output drives a 4027 J-K flipflop, which divides the oscillator signal in half to ensure an equal mark/space ratio. Two elements of a 4066 quad bilateral switch (IC3c & IC3d) are alternately switched on by the complementary outputs of the J-K flipflop. One switch input (pin 11) is connected to +5V, whereas the other (pin 8) is connected to -5V. The outputs (pins 9 & 10) of these two switches are connected together, with the result being a ±5V 100kHz square wave. Series resistance is included to current-limit the signal before it is applied to the capacitor under test via a pair of test probes. Diodes D1 and D2 limit the signal swing and protect the 4066 outputs in case the capacitor is charged. A second pair of leads sense the signal developed across the probe tips. Once again, the signal is limited by diodes (D3 & D4) before begin applied to the remaining two inputs of the 4066 switch (pins 2 & 3 of IC3a & IC3b). These switches direct alternate half cycles to two 1mF capacitors, removing most of the AC component of the signal and providing a simple “sample and hold” mechanism. The 1mF capacitors charge to a DC level that is proportional to the test capacitor’s ESR. This is differentially amplified by op amp IC4 so that it can be displayed on a digital multimeter – 10W will be represented by 100mV, 1W by 10mV, etc. To calibrate the circuit, first adjust VR1 to obtain 100kHz at TP3. Next, momentarily short the test probes together and adjust VR4 for 0mV at pin 6 of IC4. That done, set your meter to read milliamps and connect it between TP4 and the negative (-) DMM output. Apply -5V to TP2 and note the current flow, which should be around 2.1mA. Transfer the -5V from TP2 to TP1 and adjust VR2 until the same current (ignore sign) is obtained. Remove the -5V from TP1. Again, set to your meter to read volts and connect it to the DMM outputs. Apply the probes to a 10W resistor and adjust VR3 for a reading of 100mV. Finally, ensure that all capacitors to be tested are always fully discharged before connecting the probes. Len Cox, siliconchip.com.au Forest Hill, Vic. Tektronix TPS2000 The New Isolated Channel Battery Operated Scope. Do you face these Power Measurement Challenges? • Make multi-channel floating measurements • Measure current and voltage distortion and their spectral content • Measure harmonics, instantaneous power, power factor, switching loss to characterise power electronics circuitry • Measure 3-phase currents & voltages • Validate compliance to regulatory standards • Work in an environment without AC Power • Document and Save your measurement results For more information about the TPS2000 family... Talk to NewTek Instruments: Ph: 02 9888 0100 email: info<at>newtekinstruments.com NewTek Instruments Pty Ltd - Sydney - Melbourne www.newtekinstruments.com SERVICEMAN'S LOG Life at the end of the food chain Getting lumbered with a set that other technicians have looked at beforehand usually spells trouble. But that’s life – all you can do is look as happy as you can and get on with the job of fixing it. Over the years, I have seen many Panasonic M16 TV chassis with a wide variety of faults. This doesn’t mean that it is an unreliable series – on the contrary, it is just that it is such a popular set and with good reason. It 48 Silicon Chip is very well built, reliable and a good performer, although the remote control is a bit over-complex. The first models were released in 1991 and then a second series called “The One Up” was released in 1994. The latter had a lot of small changes to almost every part of the set which regretfully meant that the modules and their PC boards were not interchangeable between the two models. Even the cabinet detail is different. Recently, I had an 80cm TX33V30X (M16MV30 chassis) come in which was dead. This set had already been looked at by other technicians and I wasn’t too happy at being the bunny at the end of the food chain. In this situation, you not only have to fix the original faults but also any introduced along the way. And of course, the client expects to pay less than he’s already been charged. Anyway, I quickly established that the main switchmode power supply board (D PCB – value $593.26) was severely damaged, with 4A fuse F801 and resistor R809 (3.3W 15W) having also failed on two other boards. So was this due to a power surge and if so, was it a possible insurance claim? I really wasn’t sure. Repairing these power supplies is always rather tricky, as there are about 25 components that need to be checked, tested and replaced where necessary before switching on and doing voltage checks. If you miss any or make any mistakes, you can be in for an expensive repeat failure of everything. From the soldering, I could see someone had already been down this path and a lot of parts had already been replaced. Nevertheless, I found three transistors that had failed – Q801 (2SC4706F137) which is the main 130W power chopper transistor and drivers Q802 & Q803. I also found the 6.2V zener diode that’s in parallel with the two emitter resistors (1W and 0.82W) to be short circuit. I ordered original parts and replaced these, along with R809 and capacitor C580 (220mF 200V), which was looking dodgy. I then connected a Variac to the supply input, disconnected R560 on the “X” board and clipped a 100W dummy load globe across the 140V rail (TPD1). I also disconnected protection diode D560. When I wound the Variac up, the power supply started working at about 90V and at 110V I was getting a steady 140V output with no stress. I then checked the 5V output from IC803 and the 12V rail to the primary of the remote control power supply. The output from regulator IC802 was high at 15V (with no load) but after swapping the device, I realised that there was a parallel resistor (R817, 5.6W) across it, which accounted for the discrepancy. By now, I was feeling pretty happy that all was going well and that the power supply was working. So, feeling confident, I wound my ancient Variac up to firstly 200V and then up to 240V. Well, it reached the first part OK but at 240V there was a spark and a smell from the Variac – and then all was silent. B<at>#$%&r!! It took a while to work out was happening. The Variac fortunately wasn’t damaged but because the wiper contact was old, worn and tarnished, it couldn’t handle the increased current. As a result, I stripped it down and cleaned and polished the copper windings. The 3.3W 15W resistor (R809) had failed in the set too and this convinced me that the power supply had blown again. I checked everything in the power supply again but surprise, surprise – nothing else had failed and after siliconchip.com.au replacing R809, it was still giving a +140V output from 90V AC input. Being a little too dumb, I tried turning up the Variac again very carefully. It got to 220V without problems but as I increased it past this, the 4A mains fuse suddenly blew. Well, something was seriously wrong to blow a 4A fuse and damage a 3.3W 15W resistor but not damage the switchmode supply. Obviously, there was something amiss with the input from the N board. This board receives 240V AC from the mains filter S Board and includes a full-wave rectifier which provides around 300V for the chopper transistor. But hello, hello, what about all the extra circuitry on this board? I suddenly realised that this set is designed to work from 110VAC to 240VAC 50/60Hz and the N Board has a Triac (Q812) which switches power to C809 (330mF). Its gate is controlled by transistors Q811 and Q814 which are in turn switched by a voltage detector circuit. This latter circuit ensures that Q814 is only on when the mains voltage exceeds 120V. siliconchip.com.au In addition, there is also an overvoltage protection circuit. This includes SCR D813 which is also controlled by the Triac Q812. Anyway, I decided to fire this N Board up via the Variac and monitor its output with the power supply D Board disconnected. And just in case, I fitted the 100W globe in place of the mains fuse (F601). As I turned up the Variac, I noticed Items Covered This Month • Panasonic TX33V30X TV set, M16MV30 chassis • Panasonic TX80P300A TV set, EURO 7A chassis • Panasonic TC-68P22A TV set, MX8 chassis • Panasonic TC-15PM50A TV set, (MX-7Z chassis) • Creek Audio CD43Mk2 CD Player • Sony TCD-D7 DAT Walkman Want cheap, really bright LEDs? We have the best value, brightest LEDs available in Australia! Check these out: Luxeon 1, 3 and 5 watt All colours available, with or without attached optics, as low as $10 each Low-cost 1 watt Like the Luxeons, but much lower cost. •Red, amber, green, blue and white: Just $6 each! Lumileds Superflux These are 7.6mm square and can be driven at up to 50mA continuously. •Red and amber: $2 each •Blue, green and cyan: $3 each Asian Superflux Same as above, but much lower cost. •Red and amber: Just 50 cents each! •Blue, green, aqua and white: $1 each. Go to www.ata.org.au or call us on (03)9419 2440. February 2005 49 Serviceman’s Log – continued that the globe started to glow at just 50V and that as I went up to 240V, it became very bright indeed. What’s more, the measured output rose to nearly 500V DC. The voltage detector circuit was obviously not working and it didn’t take much to track the culprit down – R843, a 324kW resistor, was open circuit. Not having a replacement, I disabled the circuit by shorting Q814’s collector to its emitter. This set the output to the correct 300V but it didn’t stop the globe from lighting when there should have been virtually no load – or so I thought. I disconnected the protection circuit and other circuit sections but nothing made any difference until I removed dual posistors D825 and D826 (these are near the input to the board and are for the degaussing circuit). I then realised that these could easily be the cause of the 0.5A that was required to make the globe light up. I refitted the 4A fuse and wound the Variac right up. All was OK, so I reconnected the power supply and again wound the Variac up to find everything was still working. 50 Silicon Chip Finally, I reconnected resistors R560 and D560 and removed the Variac and switched on. This time the set came on properly with everything working except the OSD and Teletext. I was about to get very technical when I realised it was because diode D8, which supplies 14V to the PIP (Picture-In-Picture) H board wasn’t connected. The 324kW resistor (R843) is on back order. However, as this set is extremely unlikely to ever leave Australia, it could stay permanently switched to the 240V position. Oh dear, how sad, never mind Barbara M went on and on about how disgraceful it was that her Panasonic TV had broken down after only four years – “I mean”, she said, “if you spend that sort of money you should get better than that”. She was talking to the wrong guy – frankly, I think it is a miracle that these sophisticated appliances last so long without breaking down. It’s because of this reliability, that 50% of the service industry has gone forever and the rest of us are struggling to survive. It only seems like yesterday that black and white TVs broke down three times a year and as a percentage of the average income, cost a “helluva” lot more to purchase. I listened to her politely, agreeing with every word, and suggested she complain to the people who sold her the set – if she is good at whinging (sorry, complaining), perhaps she could get a new TV set. She liked this idea and said she would try. Of course, I wasn’t surprised when she phoned back an hour later to book a service call. The set was a Panasonic TX80P300A, employing a EURO 7A chassis and the fault was intermittent no sound. This was a type of problem that could only be fixed in the workshop, so in due course a swap was made – she had a loaner and I had her Panasonic. The fault was extremely intermittent and only really occurred at switch-on from cold. I entered the service mode but there were no error messages recorded and the option codes were set correctly. I then spent a lot of fruitless time checking the amplifiers, power supplies, time-control preamplifiers, etc but got nowhere. Because the fault was more prevalent when cold, I then thought I might get some clues if I attacked it with a can of freezer. I used up virtually a full can of this expensive stuff but eventually narrowed the problem down to the sealed digital processor panel (DP-PCB). Suitably encouraged, I removed the metal covers from the module and tried again with the freezer. And this time, I was able to pinpoint the problem to IC2510, a MR27V401D ROM. Before going further, I discussed the fault with a Panasonic technician. I was told that there can be a problem with the soldering to this device and that it can often be fixed simply by removing and resoldering the IC. The only trouble is this isn’t as simple as it sounds. This particular IC is surface mounted, with two rows of incredibly fine legs. Even so, I decided to give it a go as a new module costs around $300. I started by removing the metal frame which holds the screen covers to get better access. I then soldered all the pins on one side together with excessive solder so that I could heat all that side at the same time. Next, I applied heat to the centre siliconchip.com.au of the IC to loosen the glue and then reheated the pins that had been soldered together while lifting the device slightly with the blade of a knife. The idea here is that once one side has lifted, the same procedure can be applied to the other side. After removing it, the area around it was cleaned up using solderwick and electronic circuit board cleaner (or metho). Any excess solder was also carefully removed from the IC pins. That done, the IC was replaced by first soldering two pins at opposite ends, before flow soldering the rest. The excess solder was then removed using solderwick and the results checked with a microscope. Unfortunately, in this case, the IC itself was faulty and I had to order a new one (Part No: C3ZBK0000011 – sub 16). My second attempt fixed the problem completely. Oh, goodie I had another Panasonic TC-68P22A with an MX8 chassis come in with an intermittent dark or no picture, “Oh, goodie”, I thought, “I know what the trouble is here!” Why was I so confident? Well, early production TC-68P22A sets have a problem with their EEPROM software and Panasonic issued a fix which says: “MPU Firmware Upgrade for unstable white balance. Due to the early firmware settings, it is possible for the customer to access cut off and sub-brightness without knowledge of doing so”. The fix is to put the set into Market CHK1 mode and change the IO memory address data according a to a table supplied. Unfortunately for me, this modification had already been done – so much for my initial exuberance! And the picture wasn’t just dark – the width and height were a little low as well. It was then that I had a little luck – another identical model came in with identical fault symptoms. This too had had the firmware upgrade done but the fault could be varied by tapping the chassis. As a result, I worked on this set first and despite finding several dry joints (plug A22 pins 13, 14, 15 and 16), the real culprit turned out to be IC3001, a surface-mounted IC on the rear AV switch board (H-PCB). Having got one set working, it was easier to roughly locate the fault in the other one by substituting the boards. Surprisingly, the board that made the most difference was the CRT socket (L PCB) but it almost confused me completely because when I swapped it over, the picture became excessively bright. It wasn’t until I remembered that I had turned the screen voltage up before swapping the module that I realised what was going on. Resetting it restored a perfect picture. So what was wrong with the CRT socket assembly? After all, there isn’t all that much circuitry on it. I checked all the voltages and did all the usual DC checks but couldn’t find anything wrong with it. I then decided to swap components from one board to the other. It was only when I transferred C370, a 1000pF 2kV capacitor, that the picture was fixed completely. This ceramic capacitor is between the screen (G2) grid of the picture tube and ground. It measured perfectly with every meter you care to mention. Its capacitance was spot on and there was no leakage, yet when I refitted it to the board, it recreated the fault exactly. I Superbright Lumileds - Indoor & Outdoor LED light fitting range D HIGH BRIGHTNESS D LONG LIFE D FULLY DIMMABLE D ENERGY EFFICIENT The range of LUMILED downlight fittings shown here have been designed for domestic, display, marine, mobile home and caravan applications. All fittings use Lumileds, which are: - Long life (typical 100,000 hours) - High efficiency, low power, low voltage - Vibration proof The OPLLGW series White powder coated. This series is a ceiling type gimballed fitting and require a 57mm diameter cutout (MR11 size). 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Email us: sales<at>prime-electronics.com.au BRISBANE SHOWROOM 22 Campbell Street Bowen Hills QLD 4006 Telephone: (07) 3252 3762 Facsimile: (07) 3252 5778 SOUTHPORT SHOWROOM 11 Brickworks Cntr, Warehouse Rd Southport QLD 4215 Telephone: (07) 5531 2599 Facsimile: (07) 5571 0543 SYDNEY 185 Parramatta Road Homebush NSW 2140 Telephone: (02) 9704 9000 Facsimile: (02) 9746 1197 February 2005 51 Serviceman’s Log – continued can only surmise that it was breaking down internally under load. Creaky sound I had a Creek Audio CD43Mk2 CD Player from come in with the complaint that “the sound distorts and after a while it disappears completely”. I began by checking all the power supply voltages and then got stuck into it using the freezer. Eventually, I noticed that the output waveform from the 16.93MHz crystal (CM1) was distorted and came good when frozen. I ordered and replaced both this and IC4 but it made no difference. Even putting the CRO onto the crystal would clear the fault. I checked for corrupt data going into the DAC but it was OK. In desperation, I went back to the agents who contacted Mike Creek. He emailed us to tell me that this was an early production model and that there was a crystal on the servo PC board as well as the clock oscillator on the DAC board. The servo uses a frequency that’s half the master clock but isn’t synchronised to it. Inevitably, after time, the frequencies drift out of lock. Replacing the other 8MHz crystal fixed the problem but a modification is on its way to get rid of this 8MHz crystal altogether. Walk, don’t skip We had a DAT Walkman (Sony TCD-D7) brought in with the sound skipping, an error display and a blank display on cue and review when cold. As well, the client insisted that the sound was too low. The first two problems were due to incorrect operation of the rotary encoder switch due to a defective cam gear (and the switch can become dirty also). This has now been replaced with an improved type (Part No: X-3344966-3). The cue and review problem was tricky, especially as fast forward and rewind were OK. It searches slowly, then at high speed and then loses the data signal. The reason was due to the take-up reel sticking. It had to be removed and the shaft cleaned and lubricated. Finally, the low level sound problem was tackled. I traced this down 52 Silicon Chip to C131 and C231, both 10mF 4V surface-mounted electros at the inputs of amplifier IC308. After that, it was like new! Corrupted data An LG rear DLP projector (model RT-44SZ21RB) came in with the picture shifted to the left. In addition, one-third of the picture on the right was missing and skin colour tones were green. I put the set into the service mode using a special remote control supplied by LG. This has to be pointed at the centre of the screen where the remote control receiver sensor is. You press the menu for five seconds until the EZ IN-START mode display comes on. Unfortunately, because the picture was off centre, it wasn’t possible to read all the data options. I managed to select “No.2 ddp1010” and then noticed H-position = 340 (up one end), so I lowered it to 78. This centred the picture and adjusting CW1 – which was set at 1112 – down to 115 fixed the colour. Why the data had become corrupted I don’t know – perhaps it was due to a power surge? We then found that using the video to switch channels caused the projector to roll once each time. To fix this, we replaced the digital optical driver CCT board which is under the “engine”. This is big job, as mentioned in a previous column. Storm damage I recently had to service a Panasonic TC-15PM50A (MX-7Z chassis) which had been hit during an electrical storm. As shown in the accompanying photo, the mess on its main PC board was incredible, covering about 30cm2. Washing the PC board in detergent and hot water and then using a variety of circuit board cleaners soon revealed the real damage. Large chunks of the PC pattern – especially the spark gaps – had vaporised, taking out the 4A fuse (F801), VDR D806 and R809, the latter a 2.2W 5W resistor in the negative return from the bridge rectifier. It also left a large area of black “soot”, not only on the PC board but also on the cabinet and tube (see above photo). This view shows the sooty mess left on the back of the main board of the Panasonic TC-15PM50A TV when the PC tracks vaporised. This is the same area of the PC board after it had been cleaned. Note the missing track sections in the bottom centre of the picture. I repaired the PC tracks with left over wire tags from high-power components (such as axial power diodes) and fashioned new spark gaps for C845 and C846 using aluminium foil cut to shape and liberal quantities of flux plus a hot iron. I also used generous quantities of solder to give them rigidity. Actually, I’m a bit surprised that Panasonic don’t supply replacement spark gaps, as the PC board (and circuit) are marked, drilled and punched for such components. However, they are not shown in the parts list. This also applies to their other products (eg, VCRs) which employ similar protection. Despite the mess, it was amazing that the rest of the set wasn’t damaged and it is a testimony to its design that it withstood such a large strike without further damage. However, cleaning this set to pristine condition is uneconomic, considering the price of new TVs that are the same size. Its long-term reliability must also be SC questionable. siliconchip.com.au FEBRUARY BARGAINS USB 2.0 DVD Maker 149 Alcohol Breath Tester with LCD Readout Stay safe and under the limit on the roads. This unit is very compact & features an integrated LCD to give you an actual readout of your blood alcohol content.. 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AR-1833 Was $69 $24.05 Cat. AR-1833 SAVE $ .95 2 x 40 Channel Transceivers Cat. DC-1010 Need to charge fast? How about half an hour! It charges 2 x AAA or 4 x AA, Ni-MH or Ni-Cd batteries. Automatic switching to trickle charge with a microprocessor keeping an eye on things. An array of safety features are included Cat. MB-3538 $ .95 & mains plugpack is supplied. KIT OF THE MONTH World Renowned Media Cat. XC-4701 $ .75 PK IR Remote Control Tester Kit 9 69 Cat. XC-4707 $ .65 EA 30 Min Super Fast AA/AAA Battery Charger INTERNET> www.jaycar.com.au $19.05 Cat. AR-1830 $ .95 94 February 2005 Store your video memories forever! Don’t worry about the fading quality of your old VHS or Betamax tapes. Transfer them to DVD directly through your PC. You can then use the powerful editing software to add colour and transition Cat. XC-4809 .00 effects, as well as adding sound tracks to $ your masterpiece. The tiny capture box is just 35(W) x 95(D) x 15(H)mm, and is powered by the USB connection. See our website for full details. 49 Rechargeable 5W Luxeon LED Hand Torch Won’t chew through batteries! It includes 4 x Panasonic sub C rechargeable batteries, charged with the included mains adaptor. It features a strong metal, water resistant housing, and includes a nylon belt pouch and carry strap. Measures 227(L) x 37(Dia)mm. Cat. ST-3339 $ .00 159 Don’t forget your February discount coupon! You can find it in the back of your 2004 Catalogue! Marvin the Auto-Scan FM Radio Robot A great radio! Lift his left arm to control volume, or his right arm to scan for stations! Stands 140mm tall. Requires 4 x AA batteries. Cat. AR-1772 $ .95 19 Cat. AR-1831 $ .95 69 1 300k Pixel SurfCam USB Web Camera Wi Fi Hot Spot and RF Bug Detector Video conferencing and more! It uses a 300k pixel colour CMOS sensor with auto exposure and white balance for optimum performance. Software included for creating Cat. QC-3223 greeting cards and $ .00 photo albums. Quickly check for wireless network access, or wireless devices! Now you can check for wireless connectivity without having to boot up your laptop! It measures just Cat. XC-4885 75 x 37 x 10mm with $ .95 an LED strength meter. 5.1 Multimedia Speakers Image Media Player 35 39 Compact, stylish, and functional! This unit will accept a stereo signal, or decoded AC-3 inputs & distribute it to produce a wonderfully presented sound stage. 2.5" satellite speakers, and a 6.5" woofer. 55WRMS system power. Digital slide shows on your TV! Just insert your memory card and plug it into the composite input on your TV! Cat. XC-4857 It also acts as a card reader when $ .00 connected to your PC. 149 TOO HOT TO PRINT! Cat. XC-5169 $ .95 99 Drastic Reductions on Media Prices! See in store for details, here are just two: High Definition Digital Terrestrial TV Card for PCs HDTV on your computer! Watch either high or standard definition TV on your PC! It supports wide-screen (16:9) and standard (4:3) aspect ratios. 512MB SD Card 179 USB 2.0 Video Capture Box Streaming full resolution video on your PC! Preview, record and playback video, or burn to CD or DVD. This is a great way of making DVDs if you own an analogue video camera. Includes capture and editing software, supports MPEG1 and MPEG2. 4 Speed 4X Cat. XC-4733 SAVE $2 Business Card Scanner Cat. QV-3090 $ .00 99 69 2 Port Auto KVM Switch Simple switching! This KVM (keyboard, video, mouse) switch allows you to connect two PCs to the one set of peripherals. You then switch operation between the computers with the use of "hot keys". It has 1.2m moulded cables, Cat. YN-8095 so no extra cables $ .00 SAVE are required. $14 Was $89 75 19 Was $4.50 Now $2.50 No more data entry! Just slip a business card through the scanner, and it automatically detects the information, stores it in a database, or prepares it for export to popular software. Was $169 Cat. XC-4842 $ .95 Utilise USB power and take the strain off your eyes. A 50mm diameter glass lens provides great magnification while a built in lamp lights your Cat. ST-2809 work. $ .95 Was $199 Now $129 Fortis DVD+R Cat. XC-4819 $ .00 Simple PC security! Keep the small transmitter with you, and when you are out of range (around 2m), it puts your PC into "lock mode". When you return, it resumes normal operation. Transmitter, receiver, software and drivers supplied. USB Magnifier Lamp SAVE $70 Cat. XC-4798 USB Wireless PC Security Lock USB Radio and Remote Control Cat. XC-4960 $ .00 SAVE $30 139 Radio on your PC! Receive, play, and record FM radio stations through an ultra-stable phaselocked-loop (PLL) tuning system for superior reception. Includes an IR remote control which can also be used with software such as MS PowerPoint. Cat. XC-4880 $ .95 79 SUMMER IS IN ITS LAST WEEKS - ENJOY IT WHILE IT STILL LASTS! Digital Map Distance Calculator Laptech Personal Swim Coach Just like having your own personal trainer! It can mount above or below the water, and you simply touch the face at the end of each lap. It records and reports lap times, total distance, and more! Cat. XC-0210 SAVE Was $ .95 $10 $59.95 How far is the next turn off? Automatically convert a map’s scale distance to real distance by rolling the small wheel along the desired route. It works with any map scale and displays in kilometres or miles. 49 Cat. XC-0375 $ .95 19 A great backup torch! Wind the handle for about a minute, and you get about 30 minutes of superbright light. Selectable 1 or 3 LED operation, water resistant. Cat. ST-3337 $ .95 29 12V Portable Stove 12VDC Cooler / Warmers Keep your pies hot, or your beers cold! A solid state thermoelectric device cools to -25°C, or heats to +65°C relative to ambient temperature. Perfect transport for hot or cold food and drinks over long distances without trouble. They are powered from your car’s cigarette lighter socket or a mains plugpack (not included). 4L RED Cat. GH-1376 4L Versions $ .95 4L SILVER Cat. GH-1377 each Holds 6 x 375mL cans SAVE 8L Version Was $44.95 $5ea $ .95 8L RED Cat. GH-1378 each Holds 12 x 375mL cans Was $79.95 Mains plugpack available to suit - GH-1379 $39.95. 39 74 2 Wind Up Dynamo LED Torch 12V Camping Shower Great for cooking or keeping food warm! It heats up to 140°C, and draws up to around 10A. Heating oven inside measures approx 225(L) x Cat. YS-2808 120(W) x 90(H)mm. $ .95 49 Digital Compass with Clock and Thermometer Stay on the right track! Don’t mess around with mechanical compasses. Includes suction cup mounts and lanyard. Was Cat. QM-7262 SAVE $ .95 $59.95 $10 49 A touch of luxury! Wash away the cares of the day no matter how far from civilisation you are! The camping shower allows you to take a shower wherever you are. Cat. YS-2800 Powered by your $ .95 vehicle’s 12V battery. 19 8L Collapsible Bucket No need for wasted storage space! This bucket collapses down to just 255 x 35mm when not in use. Measures 255 x 230mm Cat. GH-1260 $ .95 open with an 8 litre capacity. 14 FOR INFORMATION AND ORDERING TELEPHONE> 1800 022 888 INTERNET> www.jaycar.com.au IP Addressable Camera CCD Colour Dome Camera with Pan / Tilt Function Versatile monitoring! Few surveillance devices can match the versatility of a pan/tilt camera. Wether you want to concentrate on particular areas, or have a large area to cover, the control is at your fingertips. This camera is integrated into a weatherproof dome housing, suitable for ceiling mounting. Just use the remote control to follow the action. It uses a 1/3" Panasonic Colour CCD Sensor to provide quality 420TV line Cat. QC-3497 resolution $ .00 video. 499 Wireless Doorbell / Intercom with Door Strike Control Open the door from anywhere! This great unit acts as an intercom, with a wireless receiver. Take it out the back, or around the house. It also has electronic door strike control, so you can let your visitors SAVE in too! Was $129 $20 Cat. AI-5510 $ .00 109 Cat. AS-3190 $ .95 34 Standard Mount 7" Monitor SAVE $100 Headrest Bracket to Suit Great versatile mounting option. Cat. QM-3757 $ .95 14 SAVE $40 Roof Mount 7" Monitor Ideal for rear seat viewing! It has integrated dome lights in the console, so you can replace your factory interior light. Was $419 Cat. QM-3751 $ .00 Dash Mount 7" Monitor 399 2004 Cat Price $199 Buy an additional B&W camera (QC-3257) for just $50 more! Save $219 total. Buy an additional colour camera (QC-3262) for just $60 more! Save $239 total. Cat. QC-3255 $ .00 89 SAVE $120 Cat. QC-3260 $ .00 109 In Wall Speakers A great mounting solution! If space is limited, or you simply don’t want free standing speakers, then these are a great option for you. 8 ohm impedance allows them to be used in an array of applications. Supplied with attractive white baffle covers. 2 Way Cat. CS-2440 $99.00 3 Way Cat. CS-2442 $149.00 SAVE $50 Buy an additional camera 89.00 Cat. QC-3271 for just $ SAVE $40 249 INTERNET> www.jaycar.com.au SAVE $100 Wireless Colour CMOS Camera with Infrared Illumination Night vision! The camera features 12 IR LEDs that automatically switch on in low light conditions. The strong metal construction offers durability, and the camera can be mains powered using the supplied adaptor, or with a 9V battery. Ltd qty. Was $299 Buy an additional camera 119.00 Cat. QC-3275 for just $ Cat. QC-3274 $ .00 199 SAVE $60 2.4GHz B&W CMOS Wireless Camera and Monitor Set SAVE $80 Simple surveillance! Consisting of a wireless camera with a 5.5" monitor, with a transmission distance of up to 100m, it is ideal for monitoring in a shopfront, home, or office. The camera also has QC-3254 built in IR LEDs for night viewing. Cat. $ .00 Ltd qty. Was $279 199 Discountinued Speaker Clearance! Limited stock and no rainchecks on all items. Not available in all stores, or from techstore. Stock cannot be transferred between stores. Please check your local store for availability. Was Product Description CM2090 100W 8-Ohm Mylar Dome Midrange Speakers $46.50 CS2246 12" 200W Carbon 2 Way Ceiling Speakers Fibre Response Subwoofer $159.00 Two Way Car Speakers Great quality sound! Most ceiling CS2250 4" 20W $24.95 speakers are just simple single CS2254 5" 25W $29.95 speaker designs. These dual cone CS2258 6" 40W $34.95 speakers are superior, suitable for a Three Way Car Speakers CS2262 6" 50W $59.95 wide range of applications. Supplied CS2268 6" x 9" 65W $89.95 with attractive white baffle covers. $62.95 Two way 6.5" drivers Cat. CS-2446 $89.95 CS2280 4" 40W High Quality CS2282 5" 50W High Quality $72.95 Two way 8" drivers Cat. CS-2448 $119.95 CS2288 6.5" 75W High Quality $82.95 CS2290 6" x 9" 80W High Quality $95.00 Subwoofers 12" Double Magnet CS2270 10" 200W XL-Series Subwoofer Response Subwoofer $169.00 CS2274 10" 125W Titanium $89.00 Top quality, excellent CS2276 12" 150W Titanium $129.00 performance! CS2297 6.5" 40W Split This extreme subwoofer is Speaker System $79.50 built to exceed today’s high quality CS2360 10" 200W Polycone Subwoofer $139.00 competition standards. It features a CS2454 10" Subwoofer with large double magnet, dual voice coils, 120W Amp and Enclosure $499.00 and up to 250WRMS power handling. Cat. CS-2228 Tweeters Ltd qty. $ .00 CT1907 Economy Piezo Bullet $11.95 SAVE Was $279 CT1908 Economy Piezo Horn $22.95 $40 CT1920 KSN1151 400W Horn $95.00 CT1924 KSN1165A Piezo Bullet $49.95 2 x 150WRMS MOSFET Car Amplifier CT2000 70mm 75W Cone $18.00 Power to spare! CT2008 1" 20W Dome $19.95 CT2022 1" 100W Vifa D26 Get all the power you need to Screened Tweeter $39.95 run your speakers or subs. CW2103 3" 15W 8-Ohm It will give you 150WRMS Response Screened Tweeter $27.95 x 2 into 4 ohms, 230WRMS CT1955 KSN1196A x 2 into 2 ohms, or 450WRMS x 1 into Exponential Horn $85.00 CW2101 5" 40W 8-Ohm 1 ohm. Quality gold connections for maximum Response Woofer $45.00 conductivity. Ltd qty. SAVE Cat. AA-0434 CW2105 6" 20W 8-Ohm Paper Was $289 $40 $ .00 Cone Woofer $23.50 FOR INFORMATION AND ORDERING TELEPHONE> 1800 022 888 SAVE $110 239 379 Retractable! This unit folds down to store into a single DIN space (standard car stereo space) so it will go Cat. QM-3753 unnoticed. $ .00 Was $449 2.4GHz Wireless Camera Systems Hassle free installation! Just apply power, and the camera will transmit video and audio to the awaiting receiver. The multi-channel receiver can be used with up to 3 cameras, and even scan between them. RCA outputs for video and audio, and a mains plugpack & connecting cables are supplied. Ltd qty. 2004 Cat Price $229 See our website for full features & specs 299 169 249 Colour Wireless Camera / Receiver 7” Widescreen TFT LCD Monitors for Cars Great versatility! It offers wide viewing angles, image reverse, and more! Was Cat. QM-3752 $399 $ .00 $80 Covert surveillance made easy! You can monitor the transmitting camera from up to 100m away, complete with audio. The camera can be mains powered using the supplied adaptor, or with a 9V battery. Cat. QC-3270 Ltd qty. .00 Was $249 $ B&W Wireless Camera / Receiver 5 x 8" Horn Speaker Ideal for alarms! This attractive unit in high impact white plastic features a special bracket for maximum flexibility in mounting. Ideal for any outdoor application including marine. 20WRMS power handling with 8 ohm impedance. Mini Wireless CMOS Colour Camera with Audio SAVE Remote surveillance? No worries! SAVE This internet addressable $100 camera features an integrated web server, so there is no need for a computer! Also has a local composite video output. Cat. QC-3390 Was $349 $ .00 Now Save $19.95 $26.55 $119.00 $40.00 $14.95 $10.00 $17.95 $12.00 $19.95 $15.00 $29.95 $49.95 $34.95 $49.95 $54.95 $52.95 $30.00 $40.00 $28.00 $23.00 $28.00 $42.05 $99.95 $69.05 $49.00 $40.00 $59.95 $69.05 $49.95 $29.55 $59.95 $79.05 $289.95 $209.05 $6.95 $9.95 $74.95 $37.95 $9.95 $9.95 $5.00 $13.00 $20.05 $12.00 $8.05 $10.00 $16.95 $23.00 $11.95 $16.00 $45.95 $39.05 $19.95 $25.05 $9.95 $13.55 3 40 Channel UHF Transceiver New model, better features! Due to the outstanding success of our DC-1010 model, we have introduced this new version which is more compact, and has some great new features. It has a compact rechargeable battery pack, and is supplied with a charging cradle that can charge up to two transceivers at once. If the battery pack runs flat, you can still use AAA batteries. It also has a four step scrambling function for private communications. •Transceiver measures 53(W) x 95(H) x 32(D)mm. 1x Transceiver with Charging Cradle Extra Transceiver Cat. DC-1025 Cat. DC-1028 69.95 89 $ $ .95 Spare Rechargeable Battery Packs Cat. DC-1029 9.95 $ Lithium Batteries for Top Performance AAA Pk2 You can be sure you are buying at a competitive price at Jaycar Cat. SB-2372 11 $ .98 AA Pk2 Cat. SB-2375 CR123 Cat. SB-2377 CR2 14.95 $ Cat. GT-3280 14 $ .95 Air Powered Rocket Launcher and Pump Novelty Buzzing Mosquito Box Love to hate it! It sounds just like a mosquito when hidden in a dark spot. It will infuriate someone while they try and find it, only for it to stop when exposed to light again! Cat. GT-3282 14 $ .95 Photo Album with Voice Recorder Ever lasting memories! You can record up to a 10 second voice message to accompany each photo. It is great for keeping memories alive, or sending to a distant relative. Holds 24 - 6” x 4" photos Cat. XC-0288 Holds 36 - 6” x 4" photos Cat. XC-0288 Cat. XC-0289 15.95 $ Cat. XC-0289 59.95 $ 7.95 $ Great on the dash! They will keep small items in place such as mobile phones or sunglasses. The uses are endless, and they are washable. Measures 170 x 100mm, supplied as a pair. SAVE $5 Cat. GG-2250 5.95 $ No more parking fines! It can be set up to 19hr 59mins in 1 min increments. It also features a clock and keychain. Weighing only 21g, it is a great addition to your keyring. Cat. XC-0121 9.95 $ Negative Ion Generator for Cars Desk Clock with Alarm and Calendar SAVE $3 Small, sleek, and stylish. A unique rubber stand moulds to any shape to suit all surfaces. Clock face size is Cat. XC-0216 81(H) x 55(W)mm. $ .95 Was $17.95 Cat. GG-2268 12.95 $ No more scalding! Get your shower just right to avoid it being too hot or cold. It connects inline with your hand shower displaying the actual water temp between 0 and 50°C. Was $14.95 SAVE $5 Cat. GH-1350 9.95 $ No candles required! It uses a lamp to heat the oils, with Lemongrass, Sandalwood, and Lavender fragrances supplied. It looks great, and removes the hazard of candles from traditional Cat. GH-1045 oil burners. SAVE $ .95 Was $39.95 $10 SAVE $15 Learns IR commands! Turn on your air conditioner at a preset time, or your TV when you wake up. Works with most IR Cat. AR-1732 $ .95 remote controls. Limited qty Was $29.95 29 14 3kg Digital Nutrition Scales Disco Alarm Clock An alarm with a difference! Wake up to upbeat disco tunes instead of the usual screeching that we all know and love. Measures 155 x 130 x 125mm. Limited qty SAVE Was $29.95 $15 No flat batteries, no sore muscles! Charge your mobile phone from your USB port, or ease away the stress of the day. It suits Nokia, Siemens, Samsung, and Sony Ericsson phones. Aromatherapy Table Lamp 14 Alarm Clock with IR Remote Control 24 Hand Shower Thermometer 9 Car Parking Timer Cleaner air! Negative ions bond with smoke and dust particles that are airborne in the cabin of your car. It leaves the air clean and fresh, and even reduces the Cat. YX-2900 $ .95 smell of heavy smog. SAVE $10 For every basketball fan! Throw it at the wall to turn the alarm off! You can’t play ball with it, but it is fun to wake up to. 100mm diameter Cat. XC-0159 Was $14.95 $ .95 Non-Slip Dashboard Mats No more cold coffee! This great little unit will ensure that your hot beverages won’t go cold throughout the day. Cat. GH-1365 $ .95 75mm dia. heating coaster. USB Phone Charger / Mini Massager Great savings on Clocks Basketball Action Clock Multi Purpose Ear Thermometer A simple way of taking temperature! No thermometers in mouths and squirming kids, just take a quick check with our ear thermometer. Supplied with 20 disposable covers. Cat. QM-7227 USB Powered Coffee Mug 49 Ever misplaced your keys? Now you can find them in a flash with ease. Just whistle, and the key finder will beep so you can track it down. It also has a handy light. Cat. XC-0350 29 49.95 Stay safe this summer. It displays blood alcohol concentration between 0.00% and 0.05%. It provides a good result, but should not be relied upon to produce precise Cat. QM-7292 results. $ .95 Was $59.95 Cat. SB-2378 Great fun for the whole family! The missiles launch spectacularly into the air with the use of the hand pump. They launch Cat. GT-3006 over 30m into $ .95 the air! $ Alcohol Breath Tester with Readout 13.95 $ Key Finder with Light 4 Great fun! There name is quite a mouthful, but are actually quite simple. They are fun to play with, and are supplied as a pair. Cat. LM-1650 44.95 .98 24 Select your victim! Just hide it in a dark spot, and it will make a sound like a dripping tap until it is exposed to light. It sounds authentic, and is sure to entertain you while they try and find it. $ 11 $ Oblique-Spheroid Haematite Magnets Novelty Dripping Sound Box Cat. XC-0160 14.95 $ Count your calories! This scale gives you the calories, kilojoules, cholesterol, protein, fat, and carbohydrates for over 470 common foods based on the weight. It acts as a regular scale too. SAVE Was $79.95 $20 Cat. QM-7240 59.95 $ FOR INFORMATION AND ORDERING TELEPHONE> 1800 022 888 INTERNET> www.jaycar.com.au Electric Shock Reaction Game Electronic Toy Safes Ideal protection against… siblings! Features an illuminated keypad and programmable combination, with voice or sound effects. Pink Cat. GH-1310 Blue Cat. GH-1311 BOTH COLOURS •185(H) x 135(W) x 125(D)mm. $ .95 How quick are you? Wait for the light to change from red to green, then hit the button. If you are the last, you will receive a mild shock, but don’t jump the gun or you will get one too! 19 ea As seen on Channel 9’s Merrick and Rosso Unplanned, dubbed... The Pain Machine! Cat. GH-1095 49.95 $ The Amazing Flygun! Keep the kids entertained! The Amazing Flygun is a safe, fun, and effective method of killing flies and mosquitoes. Launch the spring powered swatter at your target! It is safe, fun and really does work! 7 $ .95 199 Wide Angle 4x Binoculars Keyring Laser Pointer Wide 16° angle viewing! Great for a day at the races, or simply enjoying a view. Weighs just 167g. Bright, long distance beam. Ideal for lecturers, or just for fun, it features a 1mW laser module with a chrome finished housing. Measures 73(L) x 15(dia)mm. Was $12.95 Cat. GG-2126 3 LED Head Torch 29 $ SAVE Weighs just 62 grams! $5 So light, you would barely know it is there. It runs for hours on the 3 x AAA batteries, and is suitable for many Cat. ST-3058 applications. $ .95 Was $29.95 SAVE $20 Waterproof to 30m! The ultra bright light is great for many applications, while the waterproof housing allows you to take it just about anywhere. Selectable use of 4 or 8 LEDs to Cat. ST-3074 conserve power when the maximum $ .95 light is not required. Was $69.95 49 Aluminium Keychain Torch 17 Super Bright Xenon Aluminium Hand Torch CCFL / Xenon Hand Torch Cat. ST-3326 19.00 $ SAVE $5 A torch and lamp in one! Use the bright Xenon globe to find you way in the dark, and the CCFL lamp to illuminate a small area or table. It has a weatherproof housing, so you can take Cat. ST-3078 $ .95 it anywhere and know it will work. Was $24.95 Fantastic 8x magnification binoculars. They have an integrated camera to take photos from a distance. Up to 100 seconds of video can also be recorded. Measures 110 x 90 x 46mm. Was $74.95 19.95 Cat. QC-3198 64.95 $ S! Animated Pen Stand Your Grandmother won't like it, but you will! It lets out a series of amusing sounds and lifts its head when you insert a pen into the rearfacing rectal receptacle. Flashing LED Tie Pin Stand out from the crowd! Everyone will notice you with this flashing pin. It has a magnetic back, so you can also attach it to your fridge. It flashes multiple colours in sequence, and measures around 10mm dia. Cat. ST-3099 SAVE Was $3.95 $ .95 $2 24.95 IOU HILAR ted! A must for Austin Powers fans! The Scottish-accented, repulsive character from the movie is a barrel of laughs. He will belch, fart, or say one of eight hilarious Cat. GT-3106 phrases. $ .95 29 Novelty Animated Farting Man Endless fun for practical jokers! He turns his head and lets out farting noises when someone passes by. •250mm tall. Cat. GT-3100 24.95 $ 1 Farting Salt n Pepper Shakers A great gag for all occasions. They make a fart sound when tipped upside down. Great for parties! Cat. GH-1080 19.95 $ R-Ra INTERNET> www.jaycar.com.au 9.95 $ $ Musical Bathtub Novelty FOR INFORMATION AND ORDERING TELEPHONE> 1800 022 888 SAVE $10 Your heart will go shala-la-la-la! Sing along with these sound activated, animated characters enjoying a vigorous bathtub romp. Sure to put a smile on everyone’s face. Cat. GH-1090 19 Cat. ST-3102 All the noise without the spit! Just press the button for a loud 120dB whistle sound. Great for personal safety and Cat. YS-2812 sporting events. Cat. GT-3110 19.95 $ Hand Held Farting Keyring Novelty Animated "Fat Bastard" Doll SAVE $5.95 SAVE $3 Hygienic Electronic Whistle $ Great Titanium look finish! Made from polished Aluminium, it is rugged and compact. It has a single LED which is focused through a magnifier lens for a more powerful beam. The 4 button cells have an operating time of Cat. ST-3322 SAVE $ .95 around 15 hours. $5 Was $22.95 High output Xenon globe! It has a strong aluminium body with a rubber grip. You can adjust the beam from spot to flood, which makes it versatile in various situations. Powered by 3 x AAA batteries (incl). Limited qty. Was $24.95 .95 Binoculars with 300k Digital Camera 24 8 LED Waterproof Head Torch SAVE $5 Relax! It has a soothing vibration with attachments for use on the head or joints. Great after a hard day at work. Cat. GG-2260 Was $19.95 $ .95 14 KILLS COCKROACHES TOO! Cat. YS-5545 Vibrating Head and Joint Massager Mini Digital Video Camera Fantastic price! This easy to use camera fits in the palm of your hand! The recorded video can be transferred to a computer for editing, or simply viewed directly on any TV with AV inputs. Supplied with camera bag, cables and software. •3.1 mega pixel software resolution for stills. •1.5" colour LCD screen. •5 layer glass lens. •32MB internal memory •SD/MMC expansion slot •4x digital zoom •Internal microphone and lots more! New Was $249 SAVE improved model $50 Cat. QC-3230 with 32MB $ .00 internal memory Every practical joker should have one! Cat. GH-1082 $ .95 Makes a great farting sound when the button is pressed. 9 Remote Controlled Secret Farter The new millennium’s whoopee cushion! Activated by a remote control, it has three realistic fart sounds. Cat. GH-1088 19.95 $ 5 Back to School Bargains! Get Set Up in Electronics! We have three great deals for the budding enthusiast to get the tools you need to get started. See website for individual product specifications. Basic Start-Up Pack Intermediate Start-Up Pack If you will only be doing light soldering and a little handy-work, then this is for you. It includes: Low Cost Multimeter Cat. QM-1500 $9.95 Soldering Kit Includes a 25W Duratech soldering iron, quality metal stand, and desolder wick) Cat. TS-1650 $24.95 7Pc 1000V Screwdrivers Cat. TD-2022 $19.95 4.5" S/S Cutters Cat. TH-1882 $9.50 4.5" S/S Long Nose Pliers SAVE Cat. TH-1884 $9.50 This pack will help you tackle bigger jobs, and includes a high quality Japanese made soldering iron. Auto Ranging Multimeter Cat. QM-1530 $49.95 46W GOOT Soldering Iron Cat. TS-1430 $59.95 Deluxe Soldering Iron Stand Cat. TS-1507 $13.95 Vacuum Desolder Tool Cat. TH-1860 $11.25 200g Roll of 0.71mm Solder Cat. NS-3005 $6.95 7Pc 1000V Screwdrivers Cat. TD-2022 $19.95 4.5" S/S Side Cutters Cat. TH-1890 $12.95 4.5" S/S Long Nose Pliers SAVE Cat. TH-1893 $13.50 $13.90 TOTAL: $73.85 GET ALL THIS FOR JUST $59.95 Advanced Start-Up Pack $38.50 TOTAL: $188.45 To give you an even better start, GET ALL THIS FOR JUST $149.95 when you purchase one of these Mains Powered Glue Guns start-up packs, you can buy any other Great for hobby work! Ideal for low stress repairs and Hardcore Electronics product* bonding on all sorts of materials. with a 5% discount at the time of See website for details. purchase (excluding sale items). Two types available. Ltd qty. *Hardcore Electronics refers to products within pages 7 – 200 of our 2004 catalogue. 4A Car Battery Charger Keep your batteries in top shape! It delivers up to 4A, reducing as the battery comes up to charge. Minimum battery capacity is 20Ah, mains Cat. MB-3520 powered. Ltd qty. $ .95 Was $39.95 SAVE $20 19 8A Car Battery Charger Great for big batteries! The four stage LED scale indicates charging status, and you can select from heavy or trickle charging. Suitable for 6 and 12V batteries. Ltd qty. Cat. MB-3522 $ .95 Was $69.95 29 SAVE $40 Cat. AM-4210 $ .00 Protect your equipment! It uses fast acting MOVs to neutralise spikes and surges. Cat. MS-4026 Ltd qty. $ .95 Was $22.95 14 6 SAVE $$$ $22 Cat. MB-3580 $ .95 4 PAR Automatic KVM Switch 49 Mains Surge Protector Protect your mains appliances! Metal Oxide Varistor (MOV) protection on all three lines. Ltd qty. Cat. MS-4008 SAVE Was $ .95 $5 $14.95 9 GET ALL THIS FOR JUST $299 1600W Heat / Strip Gun A must have for the toolbox! If can run at 400°C or 600°C, and is great for heatshrinking, quick drying parts, making plastic maleable, Cat. TH-1600 SAVE and more! Ltd qty. $ .95 $30 Was $79.95 49 Colour Wheel for PAR 36 Lights A great way to enhance party lighting! It works well with mirror balls, or just on its own. The rotating wheel changes the colour of the light shining from behind. Ltd qty. Was $31.50 Cat. SL-2961 SAVE $ .95 $11.55 19 Just like the real thing! It uses a 12V 20W MR11 SAVE halogen globe. It includes a $15 mains plugpack, and four different coloured filters Cat. SL-2967 .95 for a great effect. Ltd qty. $ Was $29.95 14 Twin Underwater Halogen Lamps Great as a spare! Keep one at home, and one at the office. It has an output of 6.8VDC at 700mA, which is required for Nokia phone charging. Ltd qty. SAVE Was $29.95 Ideal for multiple PCs! It swaps the keyboard, monitor, and mouse, between each PC with the use of “Hot Keys”. Ideal for several rooms etc. Ltd qty. Was $129.95 TOTAL: $384.65 12VDC Mini PAR Halogen Light Stock up now! They feature a “safe socket”, which has a flange around it, so kids can’t slide a knife in and hurt themselves. Ltd qty. 3m Cat. PS-4125 Was $4.95 now $2.95 5m Cat. PS-4130 Was $5.95 now $3.50 99 Walk around the room with no wires! The reproduction is clear, and does not suffer from RF interference like radiobased units. 7 metres operating distance. Cat. AA-2051 Ltd qty. SAVE $ .95 Was $79.95 $30 SAVE $8 SAVE $$$ They look great! They have a max load rating of 2400W, with a safety overload & reset switch. A 1m mains lead is attached & there are two sizes. Ltd qty. 4 Way Cat. MS-4041 Was $5.95 NOW $2.95 6 Way Cat. MS-4046 Was $8.25 NOW $4.95 Charger for Nokia Phones Wireless IR Headphones Mains / Telephone Surge Protector iMac® Blue Powerboards SAVE $$$ Mains Extension Leads 5 Input Mains Powered Stereo DJ Mixer Mix up a storm! Now you can be the DJ at your next party. It has great functionality including crossfade, talk over, LED level indication and more. SAVE Ltd qty. Was $169 $70 7.4mm stick glue gun Cat. TH-1990 Was $16.95 NOW $9.95 11mm stick glue gun Cat. TH-1992 Was $17.95 NOW $11.95 This pack includes high quality tools, and a professional anti-static soldering station for precise soldering and desoldering. True RMS Multimeter Cat. QM-1536 $79.00 Duratech Soldering Station Cat. TS-1380 $159.00 GOOT Vacuum Desolder Tool Cat. TH-1856 $24.95 Soldering Iron Tip Cleaner Cat. TS-1510 $12.95 1kg Roll of 0.71mm Solder Cat. NS-3002 $28.95 7Pc 1000V Screwdrivers Cat. TD-2022 $19.95 Angled Micro Nippers Cat. TH-1894 $16.95 6" 1000V Side Cutters Cat. TH-1985 $18.95 7" 1000V Bull Nose Pliers SAVE Cat. TH-1984 $23.95 $85.65 Cat. YN-8096 $ .95 59 7 SAVE $70 Light up your fishpond! This set comprises of two 10W halogen lamps that are powered by the included mains transformer. 2m total lead length. Ltd qty. Cat. SL-2765 Was $19.95 $ .95 SAVE $10 6V Rechargeable Halogen Torch SAVE $28 9 Super bright! It will run for up to 2hrs on a full charge, and features an integrated stand in the base. Includes mains charger. Ltd qty. Cat. ST-3086 $ .95 Was $47.95 19 Mains Double Adaptor Economy Soldering Iron Sellout! Handy around the house! Stock up now! Ltd qty. Was $3.65 SAVE $1.65 Cat. PP-4032 $ .00 2 Get them before they’re gone! They are great for someone just starting out, or as a backup iron to keep in the toolbox. Two types available. Ltd qty. 25W Cat. TS-1410 Was $9.95 NOW $6.95 80W Cat. TS-1420 Was $17.95 NOW $9.95 FOR INFORMATION AND ORDERING TELEPHONE> 1800 022 888 INTERNET> www.jaycar.com.au NEW HARDCORE ELECTRONICS! Temperature Controlled Soldering Station It features a high quality ceramic heating element for accurate temperature control, adjustable between 200 and 480°C. The soldering pencil is lightweight, (45g excluding cable), so it is comfortable for long periods. It is a great station, so check out our website for details Arriving Mid Feb! Cat. TS-1560 $ .00 TDA1905 5W Audio Amp IC BARGAIN SCOOP PURCHASE! It is a 5W audio amplifier with an internal muting facility. 16 DIP package, data sheets are available on our website and are included with the 100 pack. Cat. ZL-3600 $ .95 ea 3 99 Complete SMD working at your fingertips! This robust unit features a soldering pencil, and hot blower for all rework applications. The soldering pencil and hot blower have individual temperature Cat. TS-1570 $ .00 adjustment, and the air flow can also be varied. It is ESD safe for sensitive components, and is ready to tackle a Arriving myriad of tasks. See our website Mid Feb! for details. 449 High Quality CAT III Multimeter Probes A must for the professional! They are made from strong silicon rubber for durability and flexibility, with adequate strain relief and finger guards. Rated at CAT III to pass 15A of current. 900mm Cat. WT-5335 Cat. WT-5335 120mm Cat. WT-5337 $ .95 24 Cat. WT-5337 $ .95 29 Keyring Voltage and Leakage Tester Very clever! This great device will flash when voltage, static radiation, or microwave radiation is detected. Also features a small integrated Cat. QP-2278 $ .95 torch. Cat. ZL-3604 Versatile attachments! Suitable for drilling, polishing, engraving, grinding, sanding and cutting. Housed in an 8 compartment mini storage case it includes many parts to get the job done. Cat. TD-2404 $ .95 19 Economy Brand 1W LEDs 1W Luxeon LED’s •Up to 25 Lumens per LED! •Fully dimmable. •100,000 hours life expectancy. Red Cat. ZD-0400 Orange Cat. ZD-0401 Green Cat. ZD-0402 Royal Blue Cat. ZD-0406 White Cat. ZD-0404 Cat. ZD-0400/01 Cat. ZD-0402-06 $ .95 $ .95 14 16 •Up to 80 Lumens per LED! •Fully dimmable. •100,000 hours life expectancy. White Cat. ZD-0430 Red Cat. ZD-0432 Orange Cat. ZD-0434 Green Cat. ZD-0436 Blue Cat. ZD-0438 Protect from the hazards of CO! Carbon monoxide is a silent killer that can be generated by any household appliance running on gas, kerosene or heating oil and internal combustion engines. This meter detects concentrations as low as 1ppm up to 1000ppm with a Cat. QM-1665 $ .00 5% accuracy. SAVE Was $229 $30 199 1000V 7 Piece Screwdriver Set GS and VDE tested and approved. Soft rubber grip handles, with insulation right to the tip. Cat. TD-2022 $ .95 19 90 - 300VAC / DC Voltage Tester A quick go / no go indication. Great for simply testing to see if a wire is live. High quality insulated probes, neon indication. Cat. QP-2240 $ .95 3 29 Wide and narrow beams! These lenses are used to evenly distribute light in the desired way. Wide beam lens Cat. ZD-0420 Narrow beam lens Cat. ZD-0422 Cat. ZD-0420 $ .95 9 Quality Rechargeable Cordless Screwdriver Belden RG6 Heavy Duty Coax Cable Cat. WB-2028 $ .95/M 0 Great price! Made in the USA, this cable is no less than the quality you have come to expect from Belden. Roll length is 305m. Ltd qty. Cat. WB-2008 Was $1.75/M $ .75/M SAVE $1/M 0 Rotary Coax Cable Stripper A Long Lost Treasure! HKZ-101 Hall Effect Vane Jaycar has it back! Previously obsolete, the HKZ-101 has been commonly requested, but difficult to find since Siemens deleted it in 1998. This copy is almost identical, and works very well. See our website for data. SAVE $30 139 Solid Core Cat 6 Network Cable $1/M 9 A great selection of tools. Contains a crimp tool with 5 interchangeable dies, cable cutter, coax stripper, screwdriver, all in a handy case. Cat. TH-1878 Was $ .00 $169 19 High performance! This UTP cable will operate well above 200MHz, exceeding the most critical Cat 6 and Gigabit requirements. Roll length is 305m. Ltd qty. SAVE Was $1.95/M Cat. ZD-0422 $ .95 Coax Crimping Tool Kit Top quality! This unit features a high torque motor, to drive screws harder and faster than those cheap units. Beware of inferior lower priced units - Cat. TD-2495 $ .95 they do not have the same power as this unit. INTERNET> www.jaycar.com.au 29 Luxeon LED Lenses 5W White Luxeon LED’s FOR INFORMATION AND ORDERING Versatile mounting! These LEDs emit light at a 360° radius parallel to their base, allowing for various mounting and lighting possibilities. 1W Cat. ZD-0407 3W Cat. ZD-0439 Cat. ZD-0439 Cat. ZD-0407 $ .95 $ .95 17 All Types - each $ .95 69 Carbon Monoxide Meter Cost effective alternative! We believe our in-house brand economy LEDs are just as bright as the Luxeon counterparts at a much cheaper price. See website for data. Red Cat. ZD-0410 $10.95 Green Cat. ZD-0412 $12.95 Blue Cat. ZD-0414 $12.95 White Cat. ZD-0416 $12.95 White Side Emitting Luxeon LEDs 3W Luxeon LED’s •Up to 120 Lumens per LED! •Fully dimmable. •100,000 hours life expectancy. Cat. ZD-0440 $ .95 9 TELEPHONE> 1800 022 888 Cat. ZL-3602 34.50 pk 10 $200 pk 100 $ 60Pc Drill Accessories Set EXPANDED RANGE OF HIGH FLUX LED’S Multi Function ESD Safe SMD Rework Station CHECK THE GREAT PRICE! This section is dedicated to what’s new for the Hardcore Enthusiast. Cat. ZD-1900 $ .95 19 The easiest way to strip coax! It will strip the outside jacket and inner conductor in one operation. Suitable for RG58/59/62/6 and 3C2V 75 ohm cable. A quality stripper. SAVE Was $22 $5 Cat. TH-1820 $ .00 17 7 EXCLUSIVE TO JAYCAR! Ref: Silicon Chip Nov 2004. Automatically open your electronic gates or automatic garage door as you approach in your vehicle, without the use of remote controls! It uses a large coil sensor to detect moving metal (eg a car chassis), which reduces false alarms from animals and people etc. Kit supplied with PCB, silk screened machined case, pre-wound and Cat. KC-5402 $ .00 insulated 5000 turn coil, and all electronic components. 179 20W "Schoolies Amp" Kit A great low cost amplifier! Ref: SC Dec 2004. It uses a simple but effective design to give 20WRMS into a four or eight ohm load. Kit supplied with PCB, and all electronic components. Requires +/- 25V power supply, use KC-5347. Cat. KC-5403 .95 Heatsink not included. $ A must for car enthusiasts! Ref: SC Jan 2005. Be the envy of you mates as they hear the rumble when they press your doorbell. You may have seen commercially available units, but nothing like this. It sounds just like a V8, and has variable background noise for tappets and valves etc, for an even more realistic effect. 2 versions available: Full V8 Doorbell Kit USB Mains Board Switch Kit Supplied with PCBs, silk-screened & machined case, push button bell switch, speaker, hook-up wire, & all electronic components. Includes the Cat. KC-5405 optional 120mm length of 100mm $ .95 diameter pipe for that extra rumble! Automatic peripheral switching! Ref: Silicon Chip Nov 2004. This project allows you to have your peripheral devices switch automatically when you switch on your USB equipped PC. It will fit INSIDE many power boards, so you won’t even know it’s there! Kit includes PCB & all Cat. KC-5401 $ .95 electronic components. Requires a mains powerboard. Contains the working electronics only. Supplied with PCBs, and all electronic Cat. KC-5406 $ .95 components. No case, speaker, or pushbutton etc supplied. 49 19 10A Motor Speed Controller Kit Cat. KC-5390 $ .95 99 Very versatile! Ref: SC June 1997. Control DC motors or dim incandescent lights. It can handle up to 10A, or 20A with an extra MOSFET transistor. Kit includes PCB, and all electronic components. Extra MOSFET – ZT-2450 $7.80. YOUR LOCAL JAYCAR STORE Regulated Voltage Adaptor Kit 8 49 Short Form V8 Doorbell Kit Dr Video Kit Mk II NEW SOUTH WALES Albury Ph (02) 6021 6788 Bankstown Ph (02) 9709 2822 Bondi Junction Ph (02) 9369 3899 Brookvale Ph (02) 9905 4130 Campbelltown Ph (02) 4620 7155 Erina Ph (02) 4365 3433 Hornsby Ph (02) 9476 6221 Newcastle Ph (02) 4965 3799 Parramatta Ph (02) 9683 3377 Penrith Ph (02) 4721 8337 Silverwater Ph (02) 9741 8557 St. Leonards Ph (02) 9439 4799 Sydney City Ph (02) 9267 1614 Taren Point Ph (02) 9531 7033 Wollongong Ph (02) 4226 7089 VICTORIA Coburg Ph (03) 9384 1811 Frankston Ph (03) 9781 4100 Geelong Ph (03) 5221 5800 Melbourne Ph (03) 9663 2030 Ringwood Ph (03) 9870 9053 Springvale Ph (03) 9547 1022 QUEENSLAND Aspley Ph (07) 3863 0099 Brisbane - Woolloongabba Ph (07) 3393 0777 Gold Coast - Mermaid Beach Ph (07) 5526 6722 Townsville Ph (07) 4772 5022 Underwood Ph (07) 3841 4888 AUSTRALIAN CAPITAL TERRITORY Canberra Ph (02) 6239 1801 TASMANIA Hobart Ph (03) 6272 9955 SOUTH AUSTRALIA Adelaide Ph (08) 8231 7355 Clovelly Park Ph (08) 8276 6901 WESTERN AUSTRALIA Perth Ph (08) 9328 8252 NORTHERN TERRITORY Darwin Ph (08) 8948 4043 NEW ZEALAND Newmarket - Auckland Ph (09) 377 6421 Glenfield - Auckland Ph (09) 444 4628 Wellington Ph (04) 801 9005 Christchurch Ph (03) 379 1662 Freecall Orders Ph 0800 452 9227 Control appliances from anywhere! Ref: Silicon Chip Nov 2004. The SMS controller kit works with Nokia 3210, 3310, 5110, and 6110 models to control electronic outputs, and gives you a host of control options. The possible uses are almost endless! Kit includes PCB, preCat. KC-5400 programmed micro, and all electronic $ .50 components. Requires Nokia data cable. A Jaycar Exclusive 79 19 Top video stabilisation! Ref: SC June 2004. Get the picture you paid for and strip out piggyback carrier signals. It works with composite and S-Video. Kit includes PCB, case, panels, and all electronic components. SMS Controller Kit V8 Sounding Doorbell Kit Driveway Automatic Entry Sensor Kit Very versatile! Ref: EA Aug ’97. Get a regulated 3 to 15VDC voltage at up to 1.5A from a car battery or ATX power supply. Includes PCB and components. Luxeon Star LED Driver Kit Power 1W, 3W, and 5W Luxeon LEDs from a 12V source! Ref: Silicon Chip May ‘04. Save $$$ off purchasing pre-built drivers. Kit includes PCB, and all electronic components. Cat. KC-5225 $ .95 23 Cat. KC-5389 $ .95 29 The SHORT CIRCUITS LEARNING SYSTEM The Short Circuits learning system is a great way to learn electronics. It is fun, informative, and you build great projects along the way. Here is just one from Short Circuits 2… FM Radio Kit with Electronic Tuning Cat. KA-1797 $ .95 6 Includes a powerful amplifier! This is a true state-of-the-art 88-108MHz FM radio with electronic station tuning. It has a voltage regulated power Cat. KJ-8238 $ .95 supply and works really well! Includes PCB and electronic components. Instructions are in the Short Circuits 2 book. 29 AC/DC Current Clamp Meter Kit 12VDC Relay Card Kit for DMMs Low current trigger! A cheap alternative! Ref: SC Sept ’03. It works with your DMM just like a professional clamp meter. Kit includes PCB, case, hall Cat. KC-5368 $ .95 effect sensor, pre-cut core, and electronic components. 34 The "Flexitimer" Kit A must have! Ref: EA March ’91. Using just a handful of components, it can accurately time intervals to trip the relay. Cat. KA-1732 $ .95 Includes PCB and all electronic components. 18 IR Remote Control Extender Kit A low cost solution! Ref: SC July ’96. It receives the IR signal, then re-transmits it in another room. Much cheaper than commercial units. Includes PCB, case, and electronic Cat. KC-5209 $ .95 components. This kit will close the relay contacts with just 5mA as a trigger. Great for use with a kit using an LED trigger. Includes PCB and electronic Cat. KG-9142 components. $ .95 7 22 Three Stage FM Transmitter Kit PC Infrared Transceiver Kit Up to 1km range! Quick and easy! Ref: SC Dec ’01. From our Short Circuits 2 range. Powered from 6 to 12V, it is only 70(L) x 17(W)mm. Includes PCB, electret microphone, battery Cat. KJ-8750 snap, and electronic $ .95 components. Adapts to PC motherboards that have provisions for on-board IR support. Includes PCB and all Cat. KC-5323 $ .95 electronic components. 19 Performance Electronics for Cars Book 21 Dual 12V Battery Controller Kit Over 160 pages! The Performance Electronics for Cars Book from Silicon Chip publications has chapters on modification and theory, as well as the 16 projects. Here is just one… Cat. BS-5080 $19.80 Nitrous Fuel Mixture / Motor Speed Controller Kit Save a fortune over pre-built units! Use it with an injector to fire nitrous fuel into your engine, or control an electronic water pump etc. Hundreds of uses! Kit includes PCB and all electronic components. PRICES VALID TO END FEBRUARY 2005 Cat. KC-5382 $ .95 24 No more flat batteries! Ref: EA Feb ’96. It disconnects the auxiliary battery from the system when the engine is off, so you won’t run your primary flat. Kit includes PCB, case, Cat. KA-1782 $ .95 and all electronic components. 49 FOR INFORMATION AND ORDERING TELEPHONE> 1800 022 888 INTERNET> www.jaycar.com.au PRODUCT SHOWCASE XGameStation Micro Edition can turn you into a games programmer! The SX52 generates the sync pulses and well as the raster data. XGS Micro Studio Imagine understanding how video game systems are designed and developed at an engineer’s level. Imagine writing your own games for a piece of hardware you’re personally capable of building. This isn’t a field trip to the factory – this is decades of video game hardware development “boot camp” compressed into a single product designed to upgrade your brain and take you to the next level of skill and understanding. It was estimated that only 100-200 people on the entire planet understood the workings of the legendary Atari 2600 and its design. What if you could design machines like this and beyond? The XGS Micro Edition’s graphics hardware was inspired by retro designs such as the Atari 2600, Atari 800, and Apple II to give the system the most flexibility possible while at the same time keeping the hardware complexity to a minimum so users can understand the system. Therefore, the graphics are generated via a software / hardware combination without a dedicated frame buffer or sprite system. The SX52 core is responsible for general control of the raster timing and video signals generated via controlling a special D/A converter that generates a TV level signal and mixes Luma and Chroma to generate composite video. siliconchip.com.au Developing for the XGS ME is a snap thanks to XGS Micro Studio! This fullfeatured Windows IDE brings the look and feel of modern development environments to the lowlevel world of the XGameStation Micro Edition. XGS Micro Studio is a completely unified, graphical interface for SX Assembly Language development, covering everything from writing code to programming assembled binaries to the XGS ME hardware. With numerous built-in utilities and a completely configurable look and feel, your potential will be limited by your imagination, not by your toolset. • Write Assembly Language, configure the hardware, and program assembled binaries to the flash memory, all from a single program! • Built-in Instruction Browser provides an instant summary of every supported instruction, including syntax, clock cycles, program words required, and more! • The Real-Time SX Interface encapsulates complete control over the SX52 chip in a single tool, allowing you to read and write program memory, alter configuration registers, and more in a single place. • User-configurable environment settings. • Note: Currently only supports Assembly Language development. How are all those Xmas toy batteries? If you’re typical of most people, you have collected a box or drawer full of batteries that you’ve removed from something or other because they were going flat . . . but you’re loathe to throw out because they could have some life left in them! That’s where this new LCD battery tester from Dick Smith Electronics comes in really handy. In just a couple of seconds it gives you a visual indication of just how good (or how crook!) those batteries are. It tests most 1.5V and button cell batteries including N and AAA types and has an LCD bargraph scale. Unfortunately, it doesn’t do 9V types. Ah well, back to the tongue test . . . Retail price is $9.97 (Cat Q1462) from all DSE stores, PowerHouse, website, etc. Contact: Dick Smith Electronics (all stores) Reply Paid 500, PO Box 500, Regents Park DC NSW 2143. Tel: 1300 366 644 Fax: (02) 9642 9155 Website: www.dse.com.au AUDIO MODULES broadcast quality Contact: Nurve Networks 402 Camino Arroyo West, Danville, CA US 94506 Tel: 0111 1 952 736 2098 Fax: 0011 1 952 736 2128 Website: www.xgamestation.com Manufactured in Australia Harbuch Electronics Pty Ltd 9/40 Leighton Pl. HORNSBY 2077 Ph (02) 9476-5854 Fx (02) 9476-3231 February 2005 61 Ozitronics www.ozitronics.com Tel: (03) 9434 3806 Fax: (03) 9011 6220 Email: sales2004<at>ozitronics.com K32 - Two Stage FM Transmitter. . . $15.40 K74 - 8-Channel PC Relay Board . . . $53.90 K142 - 12-Channel IR Relay Board . . $92.40 K145 - Temperature Logger . . . . . . . . $37.95 K153 - DTMF Tone Grabber Mk2 . . . $40.15 K154 - 4-Digit Preset Down Counter. . $32.45 K157 - 2-Channel UHF Remote. . . . . $71.50 APR9301 30 Sec Voice Recorder IC . . . $5.50 DS18S20 Temperature Sensor . . . . . $13.20 Prices include GST – shipping extra. Full documentation available from website. Over 130 kits available – check website. Fingerprint security for your PC Worried about prying eyes when you’re away from your computer? This fingerprint ID unit from Microgram could solve this (and many other) security problems. The user simply places the finger inside the unit. It operates via (and is powered by) the USB port (under Windows 98SE/ME/2000/ XP) and authenticates a fingerprint in less than a second. It has logon protection, screen saver protection, time limit control and comes complete with software. Size is 80 x 45 x 35mm Recommended retail price is $199.00 Contact: Microgram Computers 1/14 Bon Mace Cl, Berkeley Vale 2261 Tel: (02) 4389 8444 Fax: (02) 4389 8388 Website: www.microgram.com.au Powered mini speakers from Jaycar Let’s face it: the speakers fitted to most portable devices are not exactly hifi. Most wouldn’t even make it to fi! Jaycar Electronics have released these nifty little powered extension speakers which go at least part of the way towards hifi – probably midfi! Perhaps that’s a bit cruel. They gave a surprisingly good account for themselves, especially considering the size of the four speakers (at 1.5in – they call them micro drivers) themselves. Designed to cradle an Ipod or similar in the centre, they can handle the output of most small audio devices (Ipods, MP3s, CD/tape players and even laptop/notebook computers) for a much better sound than the original Contact: Jaycar Electronics PO Box 6424, Silverwater NSW 1811. Tel: 1800 022 888 Fax: (02) 9741 8500 Website: www.jaycar.com.au MedicAlert medical data now on USB flash disk The MedicAlert Personal HealthKey, worn by the consumer, enables secure storage, maintenance and communication of personal health information and will allow first responders immediate access to emergency and personal health information. The MedicAlert Personal HealthKey uses USB flash drives from SanDisk. Updates to the personal health record can by provided by both the patient and those authorised by the patient such as a physician, specialist or pharmacist. Critical emergency information can be SILICON CHIP WebLINK How many times have you wanted to access a company’s website but cannot remember their site name? Here's an exciting new concept from SILICON CHIP: you can access any of these organisations instantly by going to the SILICON CHIP website (siliconchip.com.au), clicking on WebLINK and then on the website graphic of the company you’re looking for. It’s that simple. 62 Silicon 62 S ilicon C Chip hip device offers. A volume control and power switch on the unit itself is an added bonus. Operating from 4 x AAA batteries, or mains plugpack (included), the output power is 4W RMS. They measure 230 x 81.5 x 110mm (fold to just 230 x 37 x 61mm) and weigh only 286g. A standard 3.5mm stereo plug is supplied. Recommended retail price is $89.95, from all Jaycar stores and website. easily accessed by simply inserting the SanDisk USB drive into any computer equipped with a USB port. In the event that a patient is unconscious, the HealthKey is designed to display select critical medical information as previously authorised by the patient. Contact: SanDisk Corporation 140 Caspian Ct, Sunnyvale, CA USA 94089 Tel: 0111 408 5420500 Website: www.sandisk.com JED designs and manufactures a range of single board computers (based on Wilke Tiger and Atmel AVR), as well as LCD displays and analog and digital I/O for PCs and controllers. JED also makes a PC PROM programmer and RS232/RS485 converters. Jed Microprocessors Pty Ltd Tel: (03) 9762 3588 Fax: (03) 9762 5499 WebLINK: jedmicro.com.au A 100% Australian owned company supplying frequency control products to the highest international standards: filters, DIL’s, voltage, temperature compensated and oven controlled oscillators, monolithic and discrete filters and ceramic filters and resonators. Hy-Q International Pty Ltd Tel:(03) 9562-8222 Fax: (03) 9562 9009 WebLINK: www.hy-q.com.au siliconchip.com.au Manage contacts via their business cards Altech computers has a neat system for managing the piles of business card we all seem to collect over the years. With the WorldCard Color business card scanner you simply scan the card in and manage the collected data in your database management system. If you wish, you can then export that data to your PDA, mobile phone etc. The lightweight (216g) colour scanner has an A6 capacity (175 x 75 x 45mm) for larger images and 600dpi resolution. It operates via the USB interface on your laptop, notebook or desktop PC. Contact: Altech Computers Unit 37. 401 Holker St Silverwater 2128 Tel: (02) 9735 5655 Fax: (02) 9735 5656 Website: www.altech.com.au View RF signal instabilities and transients you never knew existed! The Tektronix RSA3408A, a new high performance DC to 8GHz RealTime Spectrum Analyser provides 36MHz-wide real-time triggering and capture capabilities and enhanced resolution yielding a 2000-fold improvement in the analysis of power and frequency changes over time. With the RSA3408A, engineers will be able to view RF signal instabilities and transients that they never knew existed. Consumer and industrial applications such as RFID tags, keyless entry and satellite radio systems, wireless game controllers, GPS receivers and wireless LANs are resulting in RF signals that are becoming increasingly complex and transient in nature, generating problems that are harder than ever to find and identify. More than ever, RF signals carry complex modulation and change from one instant to the next, hopping frequencies, spiking briefly and then disappearing. These transient and time-varying transmission techniques help RF devices avoid interference, maximize peak power and, oftentimes, evade detection. Conventional spectrum analysers Sound Awards in their respective price points. Each model supports many of today’s advanced home theatre surround sound formats, including Dolby Digital Surround EX, DTS, DTS 96/24 5.1 for DVD video, DTS ES (Discrete 6.1 and Matrix 6.1), and NEO:6 Cinema & Music modes. New A/V receivers from Denon Denon’s new AVR2105 provides seven channels of 90 watts into 8 ohms to drive all speakers in a 7.1 home theatre surround system, while the AVR1905 provides seven channels of 80 watts. Both received the UK’s “What HiFi” 2004 are often inadequate to meet many of the new demands. The RSA3408A Real-Time Spectrum Analyser dramatically improves the ability to troubleshoot RF – for example, triggering on RF anomalies that can’t be detected by other instruments, capturing a truly seamless record of spans up to 36MHz over a long period of time and analysing time-correlated multi-domain views of their signals. Contact: NewTek Sales 11 Lyon Park Rd, North Ryde, NSW 2113 Tel: (02) 9888 0100 Fax: (02) 9888 0125 Website: www.newteksales.com For added utility and flexibility, both feature Dolby Pro-Logic IIX decoding, the first technology to offer users the choice of processing traditional stereo music and movie content into a room-filling 6.1 or 7.1 channel listening experience. Contact: Audio Products Group Tel: 1300 134 400 Website: www.audioproduct.com.au This valuable WebLINK Space for Rent! Our website is updated daily, with over 5,500 products available through our secure online ordering facility. Features include semiconductor data sheets, media releases, software downloads, and much more. JAYCAR JAYCAR ELECTRONICS ELECTRONICS Tel: 1800 022 888 Tel: 1800 022 888 WebLINK: WebLINK: www.jaycar.com.au www.jaycar.com.au siliconchip.com.au We specialise in providing a range of Low Power Radio solutions for OEM’s to incorporate in their wireless technology based products. The innovative range includes products from MK Consultants, the world-renowned specialist manufacturer. TeleLink Communications Tel:(07) 4934 0413 Fax: (07) 4934 0311 WebLINK: telelink.com.au Want to be NOTICED? Without costing you a fortune? To reserve your place in SILICON CHIP WebLINK, email BENEDICTUS SMITH Pty Ltd info<at>benedictus-smith.com DFecember 2004 63 F ebruary 2005 63 ebruary 2005 63 This unique project demonstrates what can be achieved with a relatively simple circuit and some clever programming. With only a microcontroller and a handful of components, it functions as a wide-ranging, multi-frequency inductance and Q-factor meter. Inductance & Q-Factor Meter Pt.1: By LEONID LERNER I NDUCTORS ARE UBIQUITOUS, being indispensable in circuits such as loudspeaker crossover networks, switchmode power supplies and RF amplifiers. Unlike other components, inductors are often handmade, particularly when prototyping or assembling a do-it-yourself project. At a minimum, this suggests the need for a meter to check inductance values prior to use in circuit. But that is not the end of the story. Of all the passive components, inductors typically show the greatest deviation from ideal behaviour. This is due primarily to coil resistance and the hysteresis of the core material. The picture is further complicated 64 Silicon Chip by the fact that the losses are frequency dependent. The skin effect in copper wire and the complicated frequency characteristics of magnetic materials both come into play and are apparent even at audio frequencies. To provide a more informative picture of inductor performance then, this new meter allows you to measure the Q factor of a prospective resonant circuit at the operating frequency. If you’ve never heard of Q factor, then read on . . . Measuring L & Q There are several basic methods of measuring the inductance (L) and the Q-factor of a tuned circuit, the most common being “temporal” (time domain) and “spectral” (frequency domain). The spectral method was described in the “Poor Man’s Q-Meter” article in the July 2004 issue of SILICON CHIP. It consists of applying a sinusoidal voltage of varying frequency to a resonant circuit and measuring the circuit response as a function of applied frequency. The response of such a circuit will generally follow that shown in Fig.1, with a peak at a given frequency, dropping away on both sides in a bell-shaped curve. Circuit theory demonstrates that the peak angular frequency squared is just the inverse of the inductance (L) times the capacisiliconchip.com.au Specifications Range Inductance: 200nH - 999μH Q-Factor: 1-120 (approx.) Power Supply 9V DC 300mA plugpack Features (1) Internal or external tank capacitance facility for accurate Q measurements (2) Measurement frequency autoranging up to 20MHz tance (C). So if we know C, inductance can be found. On the other hand, the Q factor is the ratio of the peak frequency to the width of the bell-shaped curve at half-power. This is how the Q is manifest experimentally. Theoretically, it is defined as the ratio of the circuit reactance to its resistance at resonance. It should be emphasised that the preceding definitions are only approximations but give excellent results provided Q is greater than 2 or so. For heavily damped resonant circuits, the relationships between waveform and circuit parameters are more complicated. However, we are not interested in such circuits here. Fig.1: the spectral response of a resonant circuit reveals a peak at a given frequency, dropping away on both sides in a bell-shaped curve. The Q factor is manifest as the ratio of the peak frequency to the width of the bell-shaped curve at half-power. Temporal method The temporal method of inductance measurement is adopted in this design. It is based on the fact that when a rectangular pulse is applied to a resonant LCR circuit, such as that shown in Fig.2, decaying oscillations give rise to a ringing waveform. These oscillations continue until all energy is dissipated in the circuit resistance, with their frequency the same as that at which the peak occurred in the spectral response. The Q factor in the temporal response manifests itself as the ratio of the oscillation coefficient (the angular frequency) to twice the decay coefficient. We can use this information to measure the L and Q of a parallelresonant circuit with a square wave generator and a scope. The generator is connected to the tuned circuit through a large resistor, so as not to appreciably load the circuit and thereby alter the Q. This resistance should be larger than the series resistance multiplied by Q2. siliconchip.com.au Fig.2: the temporal method used in this design relies on decaying oscillations after a rectangular pulse is applied to the resonant circuit. The Q factor manifests as the ratio of the oscillation coefficient (the angular frequency) to twice the decay coefficient. A typical oscilloscope trace of a ringing waveform set up in a resonant circuit by such a generator is shown in Fig.3. The period is the time required for the signal to undergo N oscillations, divided by N. The Q factor is the number of oscillations required for the peak amplitude (starting at some convenient peak) to drop to about 0.043 of its initial value. In practice, one can get better accuracy by counting the number of oscillations for the amplitude to drop to one fifth, and multiplying this number by two. The above procedure is the basis for this project, with an AT90S2313 microcontroller performing the multiple functions of generator, scope and calculator. A liquid crystal display (LCD) and keypad are also included to provide a convenient means of setting basic parameters and observing the measurement results. Fourier transformed It is interesting that one can get from the ringing waveform of the temporal response to the bell-shaped curve of the spectral response by a technique called the Fourier Transform, or its numerically useful form, the Fast Fourier Transform (FFT). This means one February 2005 65 Fig.3: this scope shot shows the response of an LCR circuit to an applied pulse. Decaying oscillations give rise to a ringing waveform, which continues until all energy supplied by the pulse is dissipated in the circuit resistance. The frequency of oscillation is the same as would occur at the peak in the spectral response. does not actually have to make spectral measurements in order to obtain the spectral response. This is useful because it is much easier to extract the parameters of interest from the spectral plot than from the temporal plot. The former involves just finding a peak in the data, while the latter requires establishing and then counting the zero-crossings. Another advantage in using FFTs is that the effects of the inevitable analog noise, as well digitising distortions, are minimised, as they are separated from the signal in the Fourier analysis. Depending on circuit Q, our meter can measure inductances as low as 200nH and as high as 10mH. The range of Q measured varies from about 1 to 120. Circuit basics Before looking at circuit operation in some detail, it is instructive to consider the block diagram in Fig.4. The central component of the system is an Atmel AT90S2313 microcontroller. This particular micro was chosen because it is relatively cheap yet includes all of the features needed to minimise the total component count. The micro controls a “pulser”, which is used to excite a tank circuit. The tank circuit consists of the in- ductor under test and a paralleled capacitor. The capacitor can be selected by the user and connected externally. Alternatively, one of three internal capacitor values can be chosen from the keypad. To minimise loading and compensate for circuit losses, the waveform from the tank circuit is buffered and amplified by an op amp. Following this, it is fed into a sample-and-hold (S/H) circuit and then into an analogto-digital converter (ADC). The ADC functions are contained mostly within the micro so they do not appear on the diagram. A ramp converter was chosen for its simplicity and low cost. For readers not already familiar with this type of converter, its operation can be summarised as follows: A conversion cycle begins with the charging of a capacitor from a constant-current source. As the capacitor begins to charge, a binary counter starts counting from zero. The increasing capacitor voltage (the “ramp”) is Fig.5 (right): complete circuit diagram (minus power supply) for the meter. A high-speed sample and hold circuit made up of a simple counter (IC2), analog switch (IC3) and some clever programming allows the meter to measure resonant circuits at frequencies up to 20MHz. Fig.4: the AT90S2313 microcontroller forms the heart of this design. After stimulating the tank circuit, it digitises the resulting waveform and displays the results on an LCD. 66 Silicon Chip siliconchip.com.au siliconchip.com.au February 2005 67 ing port bits PD3 and PD4 (IC5, pins 7 & 8). Signals from these pins are fed through isolating diodes D6 and D7 to current amplifiers Q3 and Q6 and from there to switching transistors Q4/ Q5 and Q7/Q8. Two medium-current transistors are used in parallel to reduce the dynamic collector-emitter resistance and hence its influence on the circuit Q. Even so, the transistors contribute about 0.5W series resistance and the influence of this on the Q should be borne in mind. Relays could have been used to reduce the series resistance further. However, these are slow, prone to failure and not really in accord with our solid-state approach. In addition, the use of high-current audio transistors is precluded by their high output capacitance. If there is some concern about the contribution of the internal circuitry to the Q factor then you can leave out the link and use an external tank capacitor. This is the view inside the completed prototype. The full construction details will be published in Pt.2, next month. continually compared with the input voltage. When the two voltages are equal, the comparator stops the counter, whose count is then proportional to the input voltage. Although simple, ramp converters have a comparatively long conversion time and a somewhat reduced precision. In this application, precision is not of particular concern since it is the time characteristics of the signal that are of paramount importance. However, conversion time is important. Inductors in the order of a few hundred nanohenries require measurement frequencies of tens of megahertz to achieve a sufficiently large Q and so an accurate measurement. This is clearly well beyond the capabilities of our simple ramp converter. Even if the design was to use a dedicated high-speed (20MHz or better) ADC, the micro would not be fast enough to store the results of each conversion. All this overlooks the fact that the ringing waveform is repetitive. It can therefore be digitised at low speed by repeatedly stimulating the tank circuit and measuring each waveform at progressively larger offsets from time zero. 68 Silicon Chip To achieve the desired 20MHz sampling rate, measurements must be made at 25ns intervals. This is achieved with the aid of a programmable sample-and-hold block which holds each measurement long enough for the low-speed ramp converter to complete its task. Detailed operation The circuit diagram for the majority of the L/Q Meter appears in Fig.5. Let’s start at the test terminals, where the inductor under test and capacitor(s) are connected to form the tank circuit. Transistor Q1 is used to pulse the tank circuit. It is driven via a 100W current limiting resistor from output port bit PD5 (IC5, pin 9). A second 100W resistor in the emitter circuit limits peak pulse current to about 50mA. Diode D2 provides isolation between the tank circuit and the driver so as not to dampen the oscillations. Installing a shorting link between the “A” and “B” terminals links the inductor under test with an internal set of capacitors. A 1nF capacitor across the terminals fixes the minimum capacitance. Two other capacitor values (10nF and 100nF) can be switched into the circuit under program control us- Fast op amp needed So as not to load the tank circuit, the output signal is buffered by an op amp (IC4), which is connected in a non-inverting configuration for high input impedance. An AD8055 op amp was chosen for the task as it has high gain-bandwidth product and high slew rate and is stable when driving capacitive loads at low gains. Lower spec op amps are not suitable here, as they would severely limit the frequency range of the meter. Ideally, the output from the op amp should swing between about 0-4V maximum, which is the maximum input range of the comparator. To this end, op amp gain is set to about 1.8 by the 1.2kW and 1kW resistors, counteracting losses in the circuit. To maximise dynamic range and minimise the influence of noise and digitisation errors, the AD8055 and analog switch (IC3) are powered from ±5V supplies. Furthermore, the inverting input of the op amp is biased at -1.8V, meaning that the output (pin 6) will swing either side of +1.8V. This scheme makes the most of available headroom, which is limited to about 3.7V. Note that the micro is programmed to reject the initial part of the ringing should saturation occur. Hold it a moment The output of the op amp drives a siliconchip.com.au Fig.6: the power supply section. A conventional +5V regulator (REG2) powers the entire circuit, while a switchmode inverter (IC6) generates -5V for some of the analog circuitry. An LM337 negative regulator (REG3) is used only to generate a bias voltage for op amp IC4. high-speed sample-and-hold circuit ahead of the comparator (ADC) input on pin 12 of the microcontroller. The S/H circuit consists primarily of an analog switch (IC3c) and 680pF storage capacitor. As mentioned earlier, the micro digitises a measurement by repetitively sampling successive waveforms. Samples are taken at incremental offsets from time zero to build a complete and accurate digitisation of the ringing waveform. Sampling begins by closing the analog switch (IC3c) at time zero. After the programmed delay, the switch is opened, leaving the 680pF storage capacitor charged to the waveform voltage at that instant. Our slow ADC then has sufficient time to digitise the voltage, after which it is stored and the cycle repeats. This is represented graphically in the scope shots of Figs.7(a)-7(d). Unfortunately, the 100ns cycle time of the micro means that it is too slow to directly control the analog switch (IC3c). With a maximum 20MHz sampling rate, we need 25ns resolution. This is provided by external logic, consisting of a 40MHz oscillator module (OSC1), timing circuits (IC1 & IC2) and a level converter (Q2, D1, IC3d, siliconchip.com.au etc), all under control of the Atmel microcontroller (IC5). Level conversion Let’s look at the level converter circuit first. It consists mainly of transistor Q2, diode D1 and analog switch IC3d. The sole purpose of this circuit is to convert the 0-5V levels from the NAND gate output (IC1a) to ±5V levels to control the S/H switch (IC3c). Since the minimum sample time is only 25ns, Q2 is required to switch in nanoseconds and have a slew rate in the order of 1000V/ms. This is achieved with the use of a high beta transistor and 100W resistors in the base-emitter circuits, as well as the germanium diode (D1) between the collector and base. The results can be seen in the oscilloscope trace of Fig.7(a). Q2 inverts the control signal from IC1a, so a spare analog switch (IC3d) is used to invert it again before it is fed to the control pin of the S/H switch. Timing secrets The two divide-by-2 sections of a dual decade counter (IC2) are cascaded to divide the 40MHz clock down to 10MHz for the micro’s clock input on pin 5. The divide-by-5 section of the second half of the decade counter (IC2b) is used to derive two out-ofphase 8MHz timing signals. Output 3 (bit 2) of the counter (pin 9) is used by the micro as an 8MHz synchronisation signal. It is high during only one state of the five states of the counter, allowing precise determination of the instantaneous state of the 8MHz clock with respect to the 10MHz clock. Output 2 (bit 1) of the counter is NANDed with port bit PD0 (pin 2) of the micro via IC1a to generate the “hold” signal for the S/H circuit. As the micro’s port outputs are synchronised to its 10MHz clock, the difference between the rising edges of the two signals on IC1a’s inputs allows generation of 0ns, 25ns, 50ns and 75ns delays under program control. This can be seen in the simplified timing diagram of Fig.8. Output 2 is also NANDed with port bit PD1 via IC1d so that the micro can freeze the counter. Note that Output 2 is used here instead of Output 1 as it goes high earlier in the counting cycle, thus allowing for the propagation delay through gates IC1c-IC1d and IC2b. Digitising The micro program performs analog February 2005 69 How The Ringing Waveform Is Digitised Fig.7(a): the following series of scope shots were captured at progressively longer timebase settings and provide an insight into how the ringing waveform is digitised. Here, the green trace shows the waveform at the S/H output (pin 9 of IC3c), while the red trace shows the control signal on pin 6. Note the very fast transitions of the latter, which for the all-important trailing edge (hold) constitutes 7ns, or 1400V/ms. The waveform is oscillating at a 1.8MHz rate and its instantaneous value is captured when the control signal goes low. Also, note that the voltage at the S/H output doesn’t decay noticeably during the hold period (red trace low), when the analog to digital conversion takes place. Fig.7(c): with a timebase of 200ms/div, the sample-and-hold control signal is now just a succession of spikes and is not shown. At this time scale, the sequence of flat plateaus reproduces a digitised version of the original ringing waveform of Fig.7(a), occurring at a rate almost 1000 times faster. to digital conversions by using the AT90S2313’s internal comparator in a ramp converter. This requires a voltage rising at a constant rate to be produced at the inverting input of 70 Silicon Chip Fig.7(b): a waveform is acquired by continuously stepping the delay between the pulse applied to the tank circuit and the hold signal. The rising plateaus generated by successively greater delays capture the rising edge of a particular sinusoidal cycle and show how a repetitive 1.8MHz signal is effectively frozen and reproduced on a much larger time scale. Note that the hold period or the time interval between successive pulses, reflected in the length of the plateaus, increases with increasing voltage. This is because the conversion time of the ramp converter is proportional to the sampled voltage. Fig.7(d): this final shot is at the longest timebase setting (2ms/div). Each bunch of oscillations is the digitised ringing waveform in the previous figure. Between acquisitions the micro performs calculations, so the S/H circuit is idle and the charge on the 680pF capacitor decays. comparator IC5 (pin 13). This is produced by an LM334 constant current source (REG1) which is used to charge a 4.7nF capacitor. The LM334 provides temperature compensation in this time-critical part of the circuit. The input signal (via the S/H circuit) is applied to the non-inverting input of the comparator (pin 12). The output siliconchip.com.au New VAF speakers not just for audio perfectionists VAF Speakers have a legendary reputation for providing the best accuracy and value. Fig.8: the time difference between the rising edges of 8MHz and 10MHz clock signals are exploited to enable high-speed sampling. The micro latches a high on PD1 (pin 3) on the rising edge of its 10MHz clock and after a 0, 25, 50 or 75ns delay, the rising edge of the 8MHz clock freezes the input voltage at that instant. of the comparator is programmed to trigger a counter interrupt inside the AT90S2313 when the ramp voltage exceeds the input voltage. Note that the LM334 is rather slow compared to the speed of the rest of the circuit, so current is not switched at its input terminal. Instead, switching is performed at pin 13 of the micro, which is connected to an internal pulldown transistor. This shunts current from the LM334 until the conversion commences. Once enough of the waveform is acquired, the microcontroller performs an FFT of the sample and finds the spectral peak. The FFT is a complicated mathematical procedure and is quite computationally intensive. It is therefore usually performed on highspeed floating-point processors such as Intel’s Pentium class and above. However, speed is not of paramount importance in this application. More importantly, the results must be accurate and this was confirmed by comparing the results of two FFTs, one performed on a Pentium and the other on an AT90S2313. Display and keypad A 2-line x 16-character LCD module, keypad and ISP (in-system programming) interface to the micro via port B (PB2 - PB7) and one bit of port D (PD6). A number of port B lines are shared between devices. The LCD module is interfaced in 4-bit rather than 8-bit mode, so only its upper data lines (DB4 - DB7) are connected. The keypad has 12 keys, organised siliconchip.com.au in a matrix of 4 rows x 3 columns. The micro pulses each row in turn and polls the columns to determine which key is being pressed. Note that 4.7kW resistors are included in series with all the keypad lines to protect the port pins. This means that if a key is pressed while the micro is updating the LCD, no harm is done. Power supply The power supply section of the L/Q Meter appears in Fig.6. Starting at the DC input socket, diode D9 provides reverse polarity protection ahead of a 7805 positive voltage regulator (REG2). This regulator provides +5V for the entire board. As explained earlier, -5V is also needed for op amp IC4 and the analog switch (IC3), and this is generated from the +5V rail by a MAX635 switchmode voltage inverter (IC6). As shown, this device requires only a diode (D8), inductor (L1) and filter capacitor to function as complete switchmode inverter. The -5V rail is reduced to -1.8V by an LM337 negative voltage regulator (REG3). The 120W and 56W resistors between the “GND” and “OUT” terminals set the output voltage to -1.8V, to be used as a bias voltage in the op amp circuit. Next month They are also available as kits because we know that’s the way enthusiasts like them. VAF’s brand new Generation 4 DC-Series is now available and offers extreme levels of accuracy at incredible prices. They go very deep so they can be used for Home Theatre without a subwoofer in many rooms. They are very sensitive so they don’t need big expensive amps to drive them. They can take high power so if you have a huge room or simply want to play loud, you can. They also work well close to walls so you can use them in small rooms too. VAF Speakers are used by the ABC, Parliament House in Canberra, and in preparation of many international DVD titles in Australia.... You can use them too. Buy direct from the people who make them, and for less than you may think. 4 new kits from $449pr to $1,999pr. If you want instant results, fully assembled versions are also available. For Info or to Order FreeCall 1 8 0 0 8 1 8 8 8 2 email vaf<at>vaf.com.au www.vaf.com.au That’s all we have room for this month. Next month, we will give the full construction details and describe how the new Inductance & Q-Factor SC Meter is used. February 2005 71 Building a real Yagi Antenna for UHF CB Can you scrounge a bit of plastic electrician’s ducting and a few wire coat hangers? If so, in a couple of hours you can build yourself a really cheap, really effective antenna for your UHF CB or PRS hand-held and enjoy significantly increased range! 72 Silicon Chip 72 Silicon Chip siliconchip.com.au siliconchip.com.au cheap by Stan Swan R emember those Christmas-stocking-filler walkie-talkie radios you had as a kid? The sort that you and your mates played spies with – before their batteries gave out on Boxing Day? Operating in the 27MHz band (CB channel 14 being most common) most of these flea-power sets had just two controls: on/off and push-to-talk. Many didn’t even rate a volume control! Not only did they have mediocre “lucky to get next door” range but lack of noise-killing squelch revealed your broom cupboard hideaway. Naturally your allowance didn’t stretch to costly 9V battery replacement every few days either. Untold numbers of such sets probably now lie discarded in those very broom cupboards. Such cheap wireless toys rightly lead to most hand-held two-way radios being dismissed as kids stuff. Serious communications surely justifies professional equipment, perhaps larger 27MHz CB, VHF marine or even (another) mobile phone? Allow hundreds of dollars. Anyway, today’s kids would probably organise their spy ring by mobile phones or text messages, to their (and their parent’s!) lament when the bills arrive. PRS = Potent Radio Surprise Surprise! The walkie-talkie has grown up, and modern 2 way-radios are now the cat’s whiskers. In most countries, evolving from an attempt to tidy 27MHz CB abuse, generous slices of the radio spectrum around 450MHz were assigned in the 1990s for licence free, low power (0.5W) UHF CB voice communications. New Zealand and much of Asia calls this the Personal Radio Service (PRS) but in Australia it’s simply referred to as UHF CB. It covers 40 FM analog channels between 476.425 and 477.400MHz, with specific limits on power and so on. In Australia, conventions have been established as to which channels are simplex and which are for repeater inputs and outputs, which channels are for emergencies, which channels truckies and travellers use, and so on. Two channels are even reserved for “non voice” data communication – more of this in a later article! The US Family Radio Service (FRS) and European Personal Mobile Radio (PMR) are similar, but with slightly different frequencies (PMR = 446MHz siliconchip.com.au siliconchip.com.au February 2005 73 February 2005 73 The simplest UHF CB antenna? A quarter-wave whip! Perhaps the simplest external UHF CB antenna is a quarter-wavelength whip, which can conveniently be rustled up at this UHF frequency with an old telescopic aerial or welding rod offcut. With one 477MHz wavelength = 628mm, then 1/4 wave = 157mm. The telescopic version allows VERY convenient tweaking of course and even extension to a desirable 5/8 of wavelength (here 392mm) when a more squashed radiation pattern emerges. Verticals give an omnidirectional pattern, so won’t have the potential gain of a Yagi but lend themselves to elevated mounting if an artificial ground can be provided. Such a ground is often configured as a few sloping radials, each themselves 1/4 wavelength long but it’s not usually too critical. A 2-way radio in fact uses loose coupling to your body itself as the ground and vehicle mounted whips employ the metalwork of the car. Although cheap TV grade “F” connectors are fine at UHF, BNC are more rugged and reliable. One simple DIY design uses an emptied plastic CD spindle as the connector holder, with an aluminium “disk” inside as a simple ground plane. Thermally conductive aluminium will be a soldering nightmare, so bolt a solder tag from the coax shield to it instead. The disk ground should be larger (usually 1/2 wavelength across = 314mm) but this could be enhanced if placed on a car roof top or the like. For antenna security it’s suggested that several strong magnets be placed inside the plastic case to grip nearby iron work, although maybe the plastic container could be filled with pebbles or sand for stability when on a platform or stationary vehicle. But don’t forget to take it down before you drive off . . . Even a simple vertical antenna can greatly enhance reception, especially if signals are otherwise weakened by nearby shielding metalwork. Assorted F and BNC connectors and adaptors allow designs to suit your application. Use heat shrink or sleeving to prevent the main antenna conductor shorting. 74 Silicon Chip In Australia, conventions have been established as to which channels are simplex and which are for repeater inputs and outputs, which channels are for emergencies, which channels truckies and travellers use, and so on. Two channels are even reserved for “non voice” data communication – more of this in a later article! The US Family Radio Service (FRS) and European Personal Mobile Radio (PMR) are similar, but with slightly different frequencies (PMR = 446MHz over 8 channels) and local regulations. In all cases however, operation is totally licence free, with no ongoing running costs. There’s no privacy (so don’t broadcast your Swiss bank account details…) and, despite some businesses in the bush trying to claim “their channel” no-one has the right to use a channel over anyone else (except the emergency channel which is backed by regulation). When first offered back in the 1990s, and even as recently as the SILICON CHIP March 2001 review, UHF CB radio sets were costly and largely appealed to commercial and events users. Such is now not the case, since mass production has lead to insanely cheap global prices. In NZ and Australia, UHF sets now flood electronic retailers and discount stores at such throw-away prices that customers may not in fact take them seriously. Even electronic gurus often consider them as glorified toys until they try one out! Perhaps because of such “cheapness”, uptake seems very modest here in larger NZ cities, no doubt also reflecting the now nearautomatic tendency to reach for one’s mobile phone. But remote regions, group bush hikes or vehicle convoys may suffer cellular flakiness. If you’re passing through Snake Gully and require group broadcasts for a comfort stop ahead, then mobile phone calls may be futile and are limited to 1:1 of course, even if coverage improves. Ranges of the modern UHF CB sets are rather more line-of-sight than 27MHz CB, although reduced atmospheric noise at the higher frequencies mean receivers can be very sensitive indeed, with quality FM audio as well. City block coverage is typical (ideal shopping!) with bush conditions perhaps a kilometre or so. Unobstructed links (eg, over water) can allow clear siliconchip.com.au wonderland of microelectronics but most importantly two generous solder pads beside the clamped spring antenna. Yay! It’s the work of moments to solder (perhaps with 1mm holes drilled for header pins) a flexible coax lead to these and direct it out via the nowempty rubber ducky space. Strictly speaking, UHF grade coax and BNC connectors should be used, but for convenience even a short length of thin flexible shielded audio coax and cheap RCA sockets are tolerable, especially while you experiment. Avoid transmitting without an antenna of course, since you may damage the set with the signal that’s now got nowhere to go! Antenna basics Jaycar’s Digitech DC-1030 is typical of modern UHF CB/PRS transceivers which sport a huge range of features. Opening the case reveals a couple of nice large pads to which we can solder an external antenna. The existing antenna is the spring-like coil (shown with its cover removed, top left of opened-up transceiver). reception at even 10km or more. Signals will penetrate buildings and vegetation to a certain extent, as 477MHz propagation is not as picky as 2.4GHz WiFi, where at times it seems even a shadow will threaten to throttle coverage! Battery life is much enhanced and most units now capable of using rechargeable NiMH AA or AAA cells, further reducing ongoing costs. Docking stations and mains chargers can make a group’s wireless operations almost seamless – particularly appealing perhaps to a sports or school group short on expertise (and $$$) but needing reliable equipment. Even budget $40 models feature near-bewildering control options, such as scanning, voice operated transmission (VOX), duplex repeater and subaudible tone calling. If you intend buying a UHF CB family pack for an outing or sports event then ensure you choose a model that’s ergonomic, else granny may waste half the day trying to deactivate dual watch and CTCSS calling, or annoy the group with VOX transmissions every time she coughs! Before Christmas, Australian discount department stores were flogging siliconchip.com.au four-packs of UHF CB transceivers for less than $100 – (that’s just $25 per set!). However, we cannot make any comment as to their “mod-ability” which follows in this article using the Jaycar DC-1030. External antenna mod Most 2004-era UHF CB sets use a traditional rubber ducky antenna, involving a coiled wire “spring” radiator inside a short flexible rubber sleeve. Radio regulations, common to both NZ (RSM) and Australia (ACA), specify that external antennas are permitted, so it’s naturally tempting to replace this rubber ducky with something more effective. At the very least perhaps an antenna can be placed higher on a building for better coverage. Naturally, opening and modifying a transceiver may void your warranty but at their bargain prices this may be incidental. Courtesy of Jaycar Electronics (which fortunately stocks largely the same range both sides of the Tasman) a pair of their DC-1030 handhelds was obtained. This model readily unscrewed (joy of joys – a Philips head, not a tamperproof screw!) to reveal a not only a In spite of white-hot changes in electronics, antennas remain near timeless devices, with designs dating back decades ripe for hands-on experimentation. Considerable design and simulation software now exists, ranging from the broadcast professional’s Numerical Electromagnetics Code (NEC) to (gasp!) DOS-based programs such as Yagi Optimizer (yo.zip). Perhaps the most complete repository is that of a Canadian ham, VE3SQB, whose web site, www.qsl.net/ve3sqb/ is justifiably praised for its Visual Basic antenna simulations. Taking 477MHz as the midpoint of the UHF CB band, radio waves at this frequency will have a wavelength (L) (in metres [=1000mm]) of: L = 3 x 108 477MHz, or some 628mm, a length convenient for “plumbers delight” designs, especially classic Yagi-Uda’s. The Yagi The “Yagi” antenna (fellow inventor Uda is usually now neglected) dates from 1929. It is probably best known as a TV or FM radio antenna but lends itself to easy home-built use. Amateur radio operators love ’em! As with theoretically all antennas, the Yagi can be used to transmit or receive electromagnetic energy (in the form of radio waves). Here we’ll describe it as a receiving antenna. It consists of at least two elements (although a minimum of three is more February 2005 75 A typical antenna design and simulation program screen. Note the slight dimensional variations from the version used in this article. It’s probably best to use such software as a guide and optimise performance by field trimming. common) and theoretically there is no upper limit. All elements are (again normally) aligned in the same plane. The most important one is the driven element (DE) – the one that connects to your transmitter and/or receiver. Behind the driven element is (usually) one reflector (R), slightly longer than the driven element. As its name suggests, its job is to reflect electromagnetic energy back towards the driven element. In front of the driven element is one or more directors, each slightly shorter than the driven element. Again, as the name suggests they direct energy towards the driven element. The more directors a Yagi has, the more directional it becomes. The Yagi is most effective when the boom (on which all the elements mount) points directly at the signal source (transmitter), with the directors towards the front. It will normally work “back-tofront” (ie, with the reflector pointing towards the transmitter) but nowhere near as well. As you turn the Yagi boom away from the antenna, performance drops off, to the point where at rightangles to the transmitter, there may be little or no signal at all. These are called “nulls”. Antenna textbook theory assigns the driven element (DE) as a half wavelength across. The actual physical length reduces somewhat by a factor relating to the elements diameter and frequency in use (typically 0.94). Thus, for 477MHz it’s 628mm x 0.5 x 0.94 = 295mm wide – about 1½ handspans. 76 Silicon Chip A birds eye view of the expected radiation from a 4-element Yagi such as ours. Note the large broad frontal lobe - this could be sharpened with even more directive elements. The rear reflector (R) is usually 1.05 times this (=310mm) and front directors (D) 0.95 times (=280mm). Tradeoffs between bandwidth, gain and feed impedance govern element spacings, with L/8 to L/3 gaps (here 78–209mm) common. Practical needs to compact the design arise as well – ours in fact follows this. Confused by the maths? Try a simulation program instead. Typically these may make all sorts of assumptions and their recommendations may be just a guide to the actual best design for your application. Measurements to just the nearest millimetre will do as well, since it’s hard for the average home constructor to cut and drill better than that. Experiment – you’ll learn by doing! Cotanger and ducting Yagi You could drill holes in a broom handle to mount Yagi elements but for flexibility a mount such the one that follows may appeal! This uses a very special type of wire called cotanger – if you haven’t heard of this before, go into your bedroom, open up you wardrobe and remove a shirt from what’s holding it up. Unless you’re unlucky (or upmarket You don’t have to label which element is which – but it might help you eliminate misteaks mstakes misstakes errors! You can see the “raw materials” at right: a length of electrical ducting and a few wire coathangers. siliconchip.com.au REFLECTOR (R) = 310mm DRIVEN ELEMENT (D) = 295mm* 120mm DIRECTOR 1 (D1) = 280mm DIRECTOR 2 (D2) = 280mm 110mm 160mm 477MHz 4-ELEMENT YAGI -- (~6dB GAIN) * BREAK DE AT CENTRE AND BEND 90° INTO TERMINAL BLOCK (90° BENT SECTIONS NOT INCLUDED IN 295mm LENGTH) ALL ELEMENT LENGTHS ARE END TO END ELEMENTS #10 GAL WIRE (2.5mm DIAM) CUT FROM COATHANGERS KEEP AS SHORT AS POSSIBLE ~450mm LENGTH 2-PART (SNAP FIT) PVC ELECTRICAL DUCTING 2-WAY MAINS TERMINAL BLOCK (MOUNTED ALONG CONDUIT) COAX CABLE (TO TRANSCEIVER) 3x 2-WAY MAINS TERMINAL BLOCKS (MOUNTED ACROSS CONDUIT) This scale diagram should help you construct the 477MHz Yagi antenna. Element lengths shown here were theoretical and may benefit from slight trimming. Spacings can readily be adjusted by drilling extra holes in the ducting walls. with wood or plastic models) you have in your hand a cotanger. (Whoops, we forgot who we are talking to. if y ou don’t hang your shirts up . . . you might have to surreptitiously raid someone else’s wardrobe). OK, so it’s made of galvanised wire about 2.5mm in diameter and when cut to appropriate lengths, is just stiff enough to make an antenna from. In our antenna, the wire elements are supported by terminal blocks that neatly fit inside a length of plastic electrical 2-part ducting (the kind which has a “lid” which snaps onto the “base”). The split driven element (DE) is secured by connectors turned through 90o. Doubling the connectors allows back ups should brass screws strip their threads on the tough iron wire and the connectors easily slide to test element positions. Thicker elements are in fact more desirable than thin, since radiation resistance and bandwidth is improved. Construction The length of the ducting and the distance from its end to the first elesiliconchip.com.au ment is not important (as long as it is long enough!). We have said around 450mm would be an adequate length; you may like to make yours longer if you want to be able to either mount it on a mast or hold it in the hand. In both cases, any extra length should be at the reflector end. First of all, you’ll almost certainly have to straighten the coathangers out first. Cut the elements to the dimensions shown from your coathangers using heavy-duty plier blades or even a hacksaw (don’t use your good sidecutters – you’ll either break them or notch them!). Using the diagram and photo as a guide, mark out the position of the driven elements on the ducting and drill all the appropriate holes. All elements pass through the sides of the ducting. The reflector and two directors are continuous lengths of wire, while the driven element is divided in two and the very end (say last 10mm) is bent at 90° to go into their respective places in the terminal block. The reflector and directors pass right through the terminal block and are held captive by the screws. One side of each of those terminal blocks is unused but you need two-way blocks to be able to mount them with a suit- Parts List – 477MHz UHF CB Yagi 1 boom made from a 450mm length 2-part electric cable ducting, of a size you can scrounge (typically ~30mm wide) 1 310mm length 2.5mm galvanised steel wire (from coathangers) – “R” 2 280mm lengths 2.5mm galvanised steel wire (from coathangers) – “D1, D2” 2 ~160mm lengths 2.5mm galvanised steel wire (from coathangers) – both for “D”. 4 2-way mains terminal blocks 4 nuts, bolts and washers (to mount terminal blocks on duct) 1 length (to suit) coax cable (preferably mini 75W low-loss) 1 plug to connect to socket you fit to your transceiver February 2005 77 With a home-brew field strength meter and a good pair of binoculars, you can do some quick performance checks of your new antenna – and compare the readings to the “rubber duck” antenna that the UHF transceivers come with. able bolt, washer and nut. To find the right spot for the reflector and director terminal blocks, poke the elements through the hole just drilled in one wall of ducting, slide the block on, the poke the element though the opposite wall and slide it out until it is roughly in position. Place the terminal block in the exact middle of the ducting (either by eye or by measure). Mark the terminal block mounting hole and drill it, then secure it with its bolt, nut and screw. Very carefully find the half-way point of each of the elements and make sure it is in the exact centre of the block. Tighten up the grub screws in the terminal block and your three elements are in the right spot. The driven elements are similar except that there are two of them and they have the 90° bend in their ends. Their terminal block mounts along the duct, rather than across it, so that the 90° ends turn into the terminals. It’s pretty important to have the ends of the driven elements mounted tight up to the terminal block. Strip off a couple of centimetres of coax cable and connect it, nice and DMM ON LOW DC RANGE (eg 200mV) GERMANIUM DIODE (eg OA91) 1λ WIRE LOOP (APPROX 628mm) 78 Silicon Chip 200mV close, to the terminal block. It doesn’t matter which way around the braid and inner conductor go. The coax can run along the ducting and out the reflector end. Give your antenna a final check, then snap the ducting cover on – and its finished. Performance Performance of this 4 element design was most satisfactory – we estimate around 6–8dB of gain, which translates into range doubling and improved signals in marginal areas. Modest direction finding was also possible, allowing homing in on a remote “lost in the bush” transmitter. This could be educational “fox hunting” fun for a scout group and may even stimulate a youthful interest in electronics or ham radio. Field testing Since classic transmitter testing equipment (usually SWR meters and antenna noise bridges) may be unavailable, it’s suggested you initially use a “Poor Man’s Field Strength Meter” (FSM). Our “poor man’s field strength meter” merely consists of a loop of wire, a germanium diode and a digital multimeter. Ideally the loop should be 628mm from multimeter terminal to terminal. But it’s not a particularly exact science: near enough will usually be good enough. The multimeter leads themselves (usually about 750mm each) will be a tad too long because that will be about 1500mm. Simply connect a germanium diode (such as an OA91 or 95) in series with a length of wire, ideally one wavelength long (628mm), and plug into a DMM switched to sensitive (200mV?) DC range. The wire loop picks up the radio signal, and the diode rectifies this to DC, much in the style of a classic crystal set. If it’s a clear diode (and most modern ones are) make sure it is well covered, or it may act as a tiny solar cell and generate a few millivolts when sunshine strikes it! Such a simple FSM may respond to all manner of passing transmitters, especially if powerful UHF TV stations, mobile phone towers and so on are nearby. Since it’s the relative “far field” readings that are of interest, these are readily determined by placing your FSM on a wooden chair some 20m away while trimming or rotating your antenna – maybe supported on a kitchen Lazy Susan – and reading the result via either a second person, or a pair of good binoculars. Meter readings from a directed antenna of some 20mV were noted at 20m distance – about as far apart as even good binnies can read on a DMM with even large LCDs. The proof of the idea of course is in performance. Since virtually all radio receivers incorporate automatic gain control (AGC) to amplify weaker signals more and attenuate strong ones, audible checks at some distance may be biased, although background “hiss” may be a good measure. With a test over an unobstructed 11km link, deep nulls – that is, drops in signal – were found much as predicted near 90o as the handheld Yagi was rotated and frontal radiation improvements were very significant. The Yagi reception was almost “arm chair quality” beside an unmodified set at the same time, and it’s feasible that Yagis at both ends would have allowed line of sight ranges of 30-50km. Mmm – just the ticket for that outback farm, off shore island or mega shopping mall! Ultimately the earth’s curvature may be the limiting factor, even if both ends are elevated. SC References www.manuka.orcon.net.nz/prs.htm hosts direct web links and pointers to simulation software. siliconchip.com.au The PICAXE in Education . . . In the January issue we briefly mentioned the success of the PICAXE Fair and the display by students from East Hills Girls Technology High School. With the 2005 school year commencing even as this issue of SILICON CHIP goes on sale, we thought it timely to have a more detailed look at the achievements of the girls and where it is hoped this will lead in the future. W hile many schools and colleges will have finished organising their 2005 subject and course offerings and indeed various curriculum options, a lot don’t really set them in concrete until the second or third week of the new year – ie, right about now! We’re hoping that this feature might prompt or shape some of the choices schools and colleges make – as in, “we could do that too!” And even if it is too late for this semester or even this year, maybe we might be able to “sow the seeds” for 2006. OK, enough preamble: let’s go back to where this all started: the PICAXE siliconchip.com.au fair – and where we went from there. In the lead-up to the PICAXE fair, PICAXE enthusiasts and groups were invited to bring their projects and/or designs along for all to see and evaluate – including the “father” of the PICAXE, Clive Seager, Technical Director of Revolution Electronics (UK). Clive made the trip to Australia specifically for the PICAXE fair and to further preach the PICAXE gospel. Incidentally, it was acknowledged at the fair that Australia has probably the highest per-capita interests and usages by Ross Tester of PICAXEs in the world. That’s due in no small part to the infectious enthusiasm of SILICON CHIP’s regular contributor, Stan Swan and his incredibly popular PICAXE column in the magazine. If Clive Seager is the father of the PICAXE, Stan Swan must be regarded as Professor PICAXE in this part of the world. You might expect that Stan has a financial interest in promoting the PICAXE – the truth is, Stan is another educator: a lecturer at Massey University in Wellington, NZ and his interest stems (at least in part) from getting his students as keen about this technology February 2005 79 With teachers Steve Sharp (left) and Anthony Rotondo, the girls from East Hills Girls Technology High School are holding their pride and joy, along with the extensive documentation they prepared for it. Pictured are Samantha, Alisha, Fiona, Eleanor, Kim-Anh, Jessica and (back row) Victoria and Sarah. as he is. (As well as in the pages of SILICON CHIP you’ll find Stan on his website, www.picaxe.orcon.net.nz). Back, though, to the PICAXE fair: IT students from East Hills Girls Technology High School entered their PICAXE project and were awarded first prize for their efforts. Ped-X As soon as Leo Simpson and I walked into the PICAXE fair, Stan dragged us across the room to the East Hills Girls Technology High School display and their “PED-X – the new generation of technology”. “You’ve gotta see thus,” he said. (Remember, he’s a Kiwi). As its name suggests, PED-X has something to do with pedestrian crossings. Something to do with? PED-X is a fully automated pedestrian crossing control system driven, surprise surprise, by a PICAXE (in this case, an 18X). The girls, all from classes which sit either the School Certificate or the 80 Silicon Chip Higher School Certificate later this year, had made a model of a pedestrian crossing, complete with LED traffic and pedestrian lights. First, it automatically sensed the presence of a pedestrian, checked to see if it was one of those “push button and run” nuisances we’ve all experienced (the ones who delight in stopping traffic because they can!). If the person was still at the crossing the traffic control phase was started with the usual amber then red light, then green pedestrian “walk” light. At the same time it sensed whether it was day or night and if the latter, also activated road-mounted indicator lights ahead of and at the crossing to give drivers more visual notice that a crossing was being used. As Tim Shaw would say “but wait, there’s more . . .”. Their crossing also had sensors embedded in the crossing itself to ensure that older pedestrians had in fact completed the crossing, before switching the traffic control lights back to green. For good measure, they also included an initialisation or POST (power on, self test) routine to make sure the crossing lights always came up they way they should after a power failure. In the case of the model, it is of course powered by battery – but there is nothing to stop this type of control system being implemented in full-size, fair-dinkum pedestrian crossings. If you used LED arrays for the traffic control lights, all you’d need would be a few driver transistors and it would work exactly the same as the model. In fact, one of the design features was that a full-sized system could have battery backup and so keep working during a power failure. So it was, a few days after the fair (and just before the school holidays) we arranged a visit to East Hills Girls Technology High School. The challenge The girls embarked on the project as a challenge to broaden their learning experience, in keeping with the siliconchip.com.au A close-up of the model PED-X researched and created by the girls in year nine. The overall design and programming was done by year 11 IT students. It is completely automatic and changes its operation depending on speed of pedestrians and time of day. About East Hills Girls Technology High School philosophy of the school. Their challenge: not to build a better mousetrap but design and build a better, safer pedestrian crossing. Under the guidance of Steve Sharp, Head Teacher IT, Anthony Rotondo, IT teacher and Lesley Kaye, the girls took on the challenge and came up with a project which has many elements which could influence design in the “real thing.” With limited-to-zero experience in programming, electronics and modelmaking, students were divided into two teams: the (then) Year 9 Computing Studies class were to research the subject in depth and create the model, while the (then) Year 11 Software Design and Development set the parameters for their better pedestrian crossing and then developed the software to run it. Steve Sharp assisted them with the electronics. Their research found that about one in six road deaths were pedestrians and that of the 290 fatalities in 2001, 93 were people aged 65 or over – or one eighth of the population contributed to one third of pedestrian fatalities. The girls concluded that with an ageing population, by the year 2041 if other factors remain unchanged, statistically one third of the fatalities will be of pedestrians 85 years of age and over. Clearly, that was an unacceptable prospect. embedded lights on the median strip and on the crossing itself as a warning to drivers. (3) Sensors on the road which check to see if cars are driving by, to keep the pedestrian lights on red. (4) Sound augmentation for the vision-impaired. (5) Crossing time to be customised to pedestrians. (6) Sensors to detect the amount of light (ie night/dusk/bad weather etc) The Ped-X was designed to give particularly older people but also visually impaired pedestrians a much safer way of crossing the road. The team’s observations suggested that many of these people do not have enough time to safely cross the road. The Ped-X overcomes this by sensing the progress of people on the crossing itself. Whether you are an Olympic athlete or a person on a walking frame, it will not return the traffic control lights to green before crossing is completed. In the model, this was achieved by the use of magnets tripping reed switches embedded in the pavement. The girls were first to acknowledge that this was not a “real world” situation but also suggested that there were a number of ways to sense the location of people on the crossing – passive infrared, microwave and other methods were suggested. The project “How much difficulty was there writing the code,” I asked. The software creators, Eleanor, Fiona, Jessica and Kim, replied that they found it quite difficult to start off but once they had the basic knowledge (no pun intended!) it got easier and easier. In the end, they told me, they were really enjoying writing and refining With the research behind them, the girls brain-stormed the requirements for a better crossing. They came up with key design factors: (1) No buttons to press – the crossing would be completely automatic. (2) Not only the “normal” pedestrian and traffic control lights but also siliconchip.com.au Coding Principals, leading teachers and administrators looking to expand their school’s subject choices and the depth of their curricula could well look at the example of East Hills Girls Technology High School. While it is a “technology” school, many of the Key Learning Areas and programs set up at the school should be adaptable into mainstream or comprehensive high schools and colleges, with significant advantages for both teachers and students. East Hills Girls Technology High School is located in the south-western suburbs of Sydney and is believed to be the sole girls-only technology high school in the country (while located across the road from East Hills Boys Technology High School, the two schools are independent of one another). At the end of 2004, there were more than 950 girls enrolled at the school with over half travelling from outside its “normal” catchment area. Fortunately the school is within a few hundred metres of Panania railway station. Computing Studies is a compulsory subject for all students in years nine and ten and the Specialist Information Technology faculty has five full-time staff. As well as offering a broad range of subject choices in Information Technology in the senior school, it also teaches the district Gifted and Talented class in IT – year eleven students are able to complete Certificate II in Information Technology and the HSC in one year. The school has five computer classrooms, a video production unit, darkroom and specialist rooms for technological studies, sciences, creative arts and drama. Industrial Technology – Electronics is offered as a course for years nine and ten students, teaching basic electronics, robotics, computer systems and components. February 2005 81 INITIALIZATION Sets lights and reads analog sensor. Go to Sees if sensor 0 or 7 is on. If it is, go to sensor check, if off then loop. LOOP If 0 or 7 on SENSOR CHECK Waits. Checks sensors 0 and 7 again (to see if pedestrians have run away). Checks amount of light. ANALOG SENSOR If less than original lighting then low cross. If higher If lower LOW CROSS CROSS The future Changes traffic light to red, crossing to green. Low cross has median strip lights. Go to If crossing is active CROSS CHECK If no-one is on crossing 2 and 6 then delay 2 seconds. If sensors 2 and 6 ON then loop to cross check again. If no-one is on crossing DELAY 2 Waits 10 seconds and then goes to crossing Go to CROSSING Red on. Amber off. Green off. Crossing green off. Flashes green, flashes red. Go to INITIALIZATION This flowchart shows the operation of PED-X. 82 Silicon Chip the software, getting it to do exactly what they wanted it to do. That’s one of the beauties of the PICAXE, of course: coding is very easy to learn, even for a beginner. It also doesn’t require any dedicated programmer – as readers who have been following Stan Swan’s PICAXE project know, all you need are two resistors and you code direct from your PC. It could hardly be simpler! As for the PED-X project, Steve Sharp said that the PICAXE is a superb system for students to gain knowledge in both programming and mecatronics. With very simple, low cost components, the girls have proven it possible to build solutions to quite complex problems. “Since the model is totally controlled by software, the program can be easily erased and the PICAXE made available to the next group of enterprising software engineers,” he said. “Imagine what type of solution they might come up with!” The knowledge and skills gained by the students at East Hills Girls Technology High School in the preparation of PED-X has been excellent. Simply by actually building models such as this allows students to bridge the gap between programs they create on the computer to how those programs actually work in real life. In addition, the hands-on experience has allowed them to develop excellent problem-solving skills – skills which will be invaluable for their School Certificate and Higher School Certificate later in the year and into their future careers. Many of the girls involved in the project plan to make their careers in some aspect of information technology, whether through further study at University/TAFE or by directly entering the workforce. In addition to the skills learned in the PICAXE project, their studies have introduced them to a wide variety of topics in the IT area – everything from basic word processing and spreadsheets right through to animation and graphic design. As Stan Swan rightly points out overleaf, “It’s my view that Picaxes are truly an educator’s dream.” Now all we have to do is convince the hundreds of other schools and colleges teaching technology to take up that dream! siliconchip.com.au Stan’s Corner . . . You can perhaps thank Google for the Australasian Picaxe takeoff! It was only mid 2002, while helping a NZ high school battle with budgets and boredom in an electronics class project, that I’d reflected “there’s just got to be a better way – especially for today’s PlayStation/text message/web page generation!” Although microcontrollers had become well established in the electronics industry, their costs or steep learning curves meant both staff and students dismissed them as unsuitable for the average student (or stressed teacher!), especially given limited class instruction time and tight resources. When a lengthy Google session unearthed the (then) little-known Revolution Education’s Picaxe offerings, I’d initially thought their $5 prices were a misprint, since at even $50 each they’d have been good value! But $5 they were and they’ve since “just worked” as absurdly cheap, versatile and powerful (yet easy to use) engines, amply justifying my 2003 “New Millenium 555” reflections and enthusiasm. It’s my view that Picaxes are truly an educator’s dream, especially given the reduced component needs a project now requires. Suitable capacitors out of stock for a 555 R-C timer? Wrong value thermistors purchased? Budget cleaned out for a year-end technology project? Want the siliconchip.com.au kids to take something home to show off or work on? With a Picaxe, only trivial components may be needed, with desired circuit alterations made via the program editor, perhaps even reusing earlier hardware! It’s a triumph of key strokes over components. Aside from the bargain prices, educationally where the Picaxe family really shine is perhaps as a liberator from normal hard-wired circuits that can only really be tested when finally assembled and powered up. The resulting puff of smoke and associated agony of defeat that crushes many new electronics students is almost alien to Picaxe designs, as ideas can often be incrementally developed and verified as one goes – rather like doing a crossword puzzle. This rapid reinforcement, combined with extremely supportive internet resources, serves to stimulate new learners and provide almost a 3-D aerial view of an electronic design. It’s akin to a General flying high over a battle field for a campaign overview. Such self-directed learning can encourage rank beginners to explore possibilities. But it especially empowers lateral thinkers who may be continually pushing “what if” design boundaries anyway, hopefully as a stimulus for more powerful controllers and even an electronics career. Under such a learning scheme students may need less initial formal theoretical instruction and instead largely “learn by doing”, correcting mistakes and expanding ideas as they go, much as word processing now empowers writers. Hence seductive LED patterns, CRC data massaging or even memoryhungry musical tunes might call for maths algorithms that’d normally be considered very tedious if taught as stand-alone theory. Given the high level commands employed, it’s even tempting to speculate Picaxes may appeal to foreign students keen to enhance their English language skills. Late teen Asian students introduced to them here in NZ show an enthusiasm that perhaps relates to the simultaneous English and Electronics benefits arising! SC February 2005 83 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au/ Practical ideas to minimise, if not eliminate, interference to C-band satellite reception from wireless broadband signals. Death by Ove Part 2 – by Garry Cratt* In December, we explained how the new Unwired wireless broadband service uses a band which had previously been used to receive C-band satellite TV, with obvious results. Here we present several methods of reducing various of levels interference affecting existing systems. O bviously, you will know when your satellite signal is being interfered with. But is it interference from Unwired or from another source? Remember how difficult it was to align your dish to receive the miniscule amount of signal in the first place? And then how often the signal was interefered with – before the days of wireless broadband? You may be jumping to conclusions and blaming the wrong source. However, if the interference has only been apparent since about last August, the chances are it is Unwired causing your problems – either Unwired itself (in which case the interference would be pretty-much constant), or a local Unwired user (in which case the interference could be intermittent, especially if the user turns his/her computer off at times). Even if the source of interference is not Unwired, many of the suggestions made in this second article may well assist you. Something is getting in – so why not eliminate all possibilities! It’s always best to try the easiest (and usually cheapest!) solutions first. Remember, though, this is an imperfect science and there are few cheap cures. However, every problem that can be eliminated will contribute to the overall success in improving performance. For existing systems, if it is possible to still receive some satellite channels, it is likely that some of the economical fixes suggested here will cure the problem to the extent that normal viewing will be restored. Note, though, that this only applies to signals in the C band above 3.7MHz – it will probably not be possible to view any channel in the extended section of C band. Any channel falling between 3.4 and 3.7GHz will probably be lost, affecting users of Telstar 10, Thaicom3, Insat 3a, Insat 2e, Asiasat 3 and Palapa C2. For existing systems suffering in- Spectrum analyser screen showing the interfering signal – the huge “spike” halfway up the screen. And here’s the interfering signal after the combiner – it’s dramatically attenuated. 88 Silicon Chip terference, start by trying to identify the possible source. It will most likely be on a nearby mobile phone tower, high-rise building rooftop, or communications site. Use the ACA website to search for your location, It will show if there is a transmitter nearby (http://www.aca. gov.au/pls/radcom/spectrum_search. cat_listing). If the satellite dish is rooftop mounted, consider relocating it to ground level, where buildings can be used to shield the dish from the local source. Check that cabling is RG/6 quad shielded, check the fitting of connectors, and replace crimp types with compression connectors. Bury any cabling that is lying on the ground (preferably in conduit), and shield long vertical runs of cable by using metal tubing or pipe. For those equipped with a signal generator and spectrum analyser covering 1400-2000MHz, there is the option of building a stub filter. These can be made by obtaining a pre-terminated length of small diameter 75W cable, cutting the length in half, and adding an open circuit quarter wavelength stub at the joining point. Best results are obtained if small diameter hardline is used for the stub. From practical experience, we have found that a stub length of 30mm will give the stub a resonant frequency of * Technical Director, Av-Comm Pty Ltd siliconchip.com.au leg of a dual input combiner. Replacing the LNB with one rated from 3.7-4.2GHz will definitely help, although to date we have not found any dual-polarity models that effectively eliminate the problem. This may change with time as manufacturers are persuaded to produce models with inbuilt filtering. Replacing a dualpolarity type with a single-polarity model (as shown below) is a huge step in the right direction, as long as single polarity reception is acceptable. Many satellite systems have been sold for the viewing of ethnic channels. Fortunately these tend to all be of the same polarity. If interference is severe, locate a reputable installer who uses a spectrum analyser. Remember the interfering signal may be 70dB stronger than the satellite signal in severe cases, so some instrumentation is necessary to be able erload 1500MHz and that this frequency increases by approximately 90MHz for every 1mm that is removed from the stub length. The photo shows single and dual stub filters. The dual stub filter achieves around 70dB of rejection when the two stubs are separated by half a wavelength. Use the same formula to calculate the half wavelength, which should also be made from miniature hardline. The filters can be constructed on a strip of blank circuit board, and covered in heatshrink tubing after “alignment”. Alignment is achieved by very carefully trimming the length of the stub using a sharp knife or scalpel. If you are building a two-stage filter, trim each stub by the same amount. Do not include the amount of hardline stripped for termination in the above calculation. They apply only to the coaxial section of the line. As these filters must be power passing, ensure there are no remnants of shielding that can accidentally short against the centre conductor at the open circuit end of the stub. Unfortunately, this type of stub has a lopsided frequency response and achieves only 10dB of rejection per octave. This means the filter is quite broad. Those with less construction experience can try inserting a 10dB attenuator in the feed line to the receiver. If that doesn’t work, try inserting the “bypass” Single-polarity feed horn. to observe improvements. Interference is likely to be more severe when watching satellites having a low look angle, although this does not mean that dishes set to high elevation values are immune. Use a single polarity PLL LNB and, if necessary, purchase a waveguide filter for additional protection. Waveguide filters are designed with different loading on input and output ports. While they might appear cosFreq (MHz) 1500 1590 1680 1770 1/4λ Stub 30mm 29mm 28mm 27mm 1/2λ Stub 60mm 59mm 58mm 57mm At top is a single open-circuit stub filter while at the bottom is a twin version. Once tweaked, they should be sealed in heatshrink or similar for protection. siliconchip.com.au Waveguide filter offers 70dB rejection. metically to be symmetrical, it is important to observe the port markings. Using a waveguide filter in reverse provides very poor filtering. As a general rule, the grooved flange, designed to accept a gasket, must be mated with the feedhorn. Vendors warn that the use of sealant on the mating surfaces will substantially reduce the performance of the filter. Commercial installations requiring operation of both polarities will require two PLL LNBs and two waveguide filters, fitted to an ortho-mode coupler. There is a world of difference between ortho mode couplers. The type which work well have the LNBs mounted at right angles to each other. Those with LNBs mounted in the same plane are likely to suffer bad interference. In some early commercial installations, orthomode feedhorn was used but as only one signal polarity signal is being utilised, only one port had an LNB fitted. This curious attempt at economy has the effect of providing a perfect conduit for the interfering signal to enter the LNB. Any unused port should be loaded with another LNB (there will be plenty of surplus 3.4-4.2GHz models lying around soon!). The recommended “kit” for C band installers seeking to rectify this interference is as follows: Av-Comm interference buster kit: X1415 10dB line attenuator X1751 PLL combiner L1511 C band single polarity DRO LNB with filter L1515 C band PLL LNB F1300 single polarity feedhorn F1750 C band orthomode coupler F4000 Waveguide filter SC February 2005 89 Salvage It! BY JULIAN EDGAR Build a $2 battery charger Battery chargers needn’t cost a fortune. Here’s one you can build for a couple of bucks – or even less if you’re a good scrounger! R ECENTLY, WE’VE described a very sophisticated lead-acid battery charger in SILICON CHIP – in fact, perhaps one of the most sophisticated DIY designs in the world. But hey, it might be good but it also costs a lot more than a few dollars. This design? Well, it’s right at the other end of the scale – the $2 trickle battery charger! Sure, it takes a bit of fiddling to initially set up but after that you’re laughing. The components This battery charger comprises just a plugpack, a resistor and a fuse. For charging a 12V battery, a plugpack with a nominal rating of around 13-14V and a current capacity of about one amp (1A) is fine. Low-cost plugpacks matching these specs can be found wherever consumer goods are being thrown away or being sold cheaply secondhand. Those with the required ratings were often used to power printers and older scanners. Make sure when selecting the plugpack it has a DC (direct current) output. Some higher-powered plugpacks have an AC (alternating current) output as they’re designed for garden lights and so don’t need to rectify the AC to DC. The plugpack shown here was sourced from a shop at the local tip – half a dozen of them for $5. The resistor needs to be a high power design (eg, 5W) with a resistance around 5Ω. Lots of junked goods use high power resistors so always keep an eye out for these components – they’re amongst the few individual electronic components always worth collecting. Chassis-mount fuseholders can be found in amplifiers and in-line fuseholders in the supply wiring to A 1A 13.5V plugpack makes an ideal foundation for a trickle battery charger. Plugpacks like this can be picked up for nearly nothing at the tip and where secondhand electrical goods are sold. 90 Silicon Chip A high-power resistor limits the charging current flow, especially when the battery is well down in voltage. Always be on the lookout for high power resistors – they’re amongst the few individual electronic components always worth salvaging. car radios and amplifiers. The fuses themselves? Well, they’re in nearly all goods – and like high power resistors, fuses are always worth salvaging, sorting and storing. Building it Fig.1 shows the trickle charger circuit. It’s really very simple. An unregulated 13-14V DC plugpack has a no-load output of up to 18V. Connect that straight to a flat battery and more current will flow than is healthy for the plugpack – hence the need for the resistor. To set up the system (a once-only event), you’ll need your multimeter, a fairly flat 12V battery, the plugpack and a resistor with a rating of around 5Ω 5W. Cut off the original low-voltage plug and use the multimeter to work out the polarity of the output – mark the positive lead. Then wire the plugpack to the battery as shown in Fig.2 – don’t forget to include the resistor! Switch on and use the multimeter to check the current flow. If for example the plugpack is rated at 1A (the rating will be written on siliconchip.com.au Silicon Chip Binders REAL VALUE AT $14.95 PLUS P & Fig.1: the charger circuit is simplicity itself. The plugpack charges the battery through a high-power resistor, with a fuse providing additional protection. Fig.2: the required value of the resistor is found by measuring the current flow when charging a fairly flat battery. The measured current in this situation should be less than the rating of the plugpack. P These binders will protect your copies of S ILICON CHIP. They feature heavy-board covers & are made from a dis tinctive 2-tone green vinyl. They hold 12 issues & will look great on your bookshelf. H 80mm internal width it) and in this test condition the flat battery is drawing more than 1A, increase the value of the resistor. If the current is a lot less than the maximum the plugpack is capable of, reduce the value of the resistor. If you find that there’s no current flow, even with the resistor completely removed, you need a better plugpack. Once an appropriate amount if current is flowing, leave the system charging for a few minutes and then feel the temperature of the resistor. Careful: it may be very hot! If it is too hot to touch, increase the resistor’s power dissipation. For example, if you are using a 5Ω 5W resistor, you could try two 10Ω 5W resistors in parallel (resulting in a 5Ω 10W combination). Size the value of the fuse to match the peak current flow that you’ve measured – eg, a 1A fuse if you’ve measured a maximum of 1A. If you don’t have any fuses of that value, go smaller rather than larger. Using it In practice, the trickle charger works very well. Feeling the temperature of the resistor gives an immediate indication of battery voltage – if the resistor is warm, the battery’s voltage is still low and so charging can continue. If it is cold, measure the voltage of the battery to see how high it is. After a few charging events it’s easy to get a good feel (groan) for what’s happening SC in the system. Rat It Before You Chuck It! Whenever you throw away an old TV (or VCR or washing machine or dishwasher or printer) do you always think that surely there must be some good salvageable components inside? Well, this column is for you! (And it’s also for people without a lot of dough.) Each month we’ll use bits and pieces sourced from discards, sometimes in mini-projects and other times as an ideas smorgasbord. And you can contribute as well. If you have a use for specific parts which can siliconchip.com.au easily be salvaged from goods commonly being thrown away, we’d love to hear from you. Perhaps you use the pressure switch from a washing machine to control a pump. Or maybe you salvage the highquality bearings from VCR heads. Or perhaps you’ve found how the guts of a cassette player can be easily turned into a metal detector. (Well, we made the last one up but you get the idea . . .) If you have some practical ideas, write in and tell us! H SILICON CHIP logo printed in gold-coloured lettering on spine & cover H Buy five and get them postage free! Price: $A14.95 plus $A10.00 p&p per order. Available only in Aust. Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or call (02) 9939 3295; or fax (02) 9939 2648 & quote your credit card number. Use this handy form Enclosed is my cheque/money order for $________ or please debit my  Visa  Mastercard Card No: _________________________________ Card Expiry Date ____/____ Signature ________________________ Name ____________________________ Address__________________________ __________________ P/code_______ February 2005 91 Vintage Radio By RODNEY CHAMPNESS, VK3UG Converting a 240VAC set to 32V DC operation A 240VAC to 32V DC conversion? You must be kidding? Well, no – this project was undertaken to discover the differences in design and performance between sets using a “normal” 200-250V high tension (HT) supply and those with just 32V HT. Converting a 240VAC set to 32V DC operation is really doing things backwards these days. After all, how many people have a 32V DC supply available to power such a set? However, as well as checking out the performance dif- ferences after the conversion, I also wanted to determine which valves worked best with low HT voltages, particularly in the audio section. A redundant 240VAC mantel set was chosen as the guinea pig for this task. It proved to be an extremely interesting project, with some unusual challenges in design. A set with only 32V HT is not as “tame” as many might think. It ended up being a really hot performer – better, in fact, than the original set and still with only five valves. Ho-hum circuitry The design of typical 4/5 valve mains-operated receivers is rather “ho-hum” to most restorers. Typically, they include a 6BE6/6AN7 converter, 6BA6/6N8 IF amplifiers, a 6AV6/6BD7 detector/first audio stage, a 6AQ5/6M5 audio output stage and a 6X4/6V4 rectifier. The circuitry is all fairly predictable, with 200-250V HT on the plates and about 85V on the screens of the RF valves. The bias is usually obtained from a back-bias network. Of course, there can be quite a lot of variations in the circuitry and valves used but it’s usually nothing out of the ordinary. 32V DC sets This view shows the chassis layout of the converted 32V receiver, with the white arrow (top left) indicating the new 6BA6 RF stage. A chassis photo of a similar main-powered version of this set is on page 81 of the September 2004 issue. 92 Silicon Chip During the years between the 1930s and the 1950s, many radios were designed to operate from 32V DC lighting plants. That’s because many country areas did not have access to 240V AC mains until the early 1960s. There were two ways of supplying power to a set connected to a 32V lighting plant. The first method was to wire the valve heaters (sometimes filaments) in series parallel across the 32V supply (to keep the current drain down) and to supply the plate and screen voltages from batteries or later on, from genemotors (small motor generators) or vibrator power supplies. siliconchip.com.au Above: rear chassis view of the converted 32V receiver, with the bias battery taped to the second IF transformer. Note that the 12DQ6A audio output valve is sitting where the power transformer was originally fitted. This meant that only minor modifications had to be made to a normal AC mains-powered set as far as the amplifying circuitry was concerned. Instead, the only section that required major alterations was the power supply. This scheme worked quite well, with many fine highly sensitive 32V sets produced. In fact, they had to be good performers, as the average 32V set was located well out in “the sticks”. The second method of supplying HT power to the set was quite different to the first, with the HT being taken directly from the 32V. This meant that a fair amount of redesign was needed to get reasonable performance, since there was now just 32V on the plates of the valves compared to 250V for Bias 32V HT mains-operated sets. Radio Corporation, in particular, produced a number of quite highperformance sets with 32V HT. However, a set with 32V HT required eight valves to achieve the same performance as a 5-valve vibrator-powered set. Radio Corporation sets typically used an RF stage, a converter, two 455kHz IF stages and three audio stages – the latter using two valves in push pull – to get the performance desired. Even then, only around 300mW of audio output was obtained from a pair of 25L6GT valves operating in push-pull. structing a set with 32V HT, I decided to convert a typical 240VAC mantle set. A run-down HMV 61-51 mantle set was selected to be the guinea pig. I had no less than seven of these and I really wouldn’t miss one if the project was a flop! The first step in the conversion involved removing the power transformer and rectifier valve, which were now redundant. However, the most critical sections of the set are the IF and the audio output stages. Initially, several valve data books were consulted to find out which output valves The conversion In order to simplify the task of con- 36V HT 40V HT 44V HT 35L6GT 12DQ6A 35L6GT 12DQ6A 35L6GT 12DQ6A 35L6GT 12DQ6A -1.5V 10mA 30mA 13mA 35mA 18mA 45mA 21mA 50mA -3.0V - 16mA - - - - - 23mA Table 1: plate current for the 35L6GT and 12DQ6A valves at different HT voltages. siliconchip.com.au February 2005 93 Fig.1: the HMV 61-51 a fairly conventional 5-valve superhet. This diagram shows the circuit before the conversion was carried out. would draw the most current with a HT supply of 32V. 25L6GT and 35L6GT valves have commonly been used in push-pull in the audio output stages of these sets but I wanted to carry out some tests before committing myself. In 94 Silicon Chip the end, a test set-up something like a simple valve tester was constructed to measure the current drawn by various valves with 30-45V on the plates and screens and with various control grid bias voltages. Comparative tests were run on the 35L6GT and 6DQ6A/12DQ6A valve types and as shown in Table 1, the 12DQ6A draws more current at low voltages which was the characteristic sought. Using just one audio output valve (12DQ6A) would also eliminate the need to use a couple of audio transformers – after all, I wanted to keep it as near as practical to the original circuitry. To maximise the voltage across the valve, cathode bias was eliminated and the local oscillator was originally used to provide bias. This wasn’t successful and so another method had to be devised. The impedance of the audio output transformer also had to be altered from my original calculation – more on these two problems later. Initially, I also thought that the first audio stage would need a lower value for the plate resistor, since the voltage across it would be lower. This was tried but when the amplifier was fed with audio, the output was very distorted. R7 – a 10MW grid resistor – was used to develop contact potential bias. This was too high in this instance, so this resistor was reduced to 1MW, the valve now running on virtually zero bias. In addition, plate resistor R8 was increased to 330kW and the audio from this stage was then quite satisfactory, an oscilloscope showing little distortion. It was now time now to get the output stage working properly. This had a few problems, as mentioned earlier. I had expected to be able to use a bias of -1.5V, plus a 600W speaker transformer (the nearest I had to 1kW) which had an output of 3.5W to suit the speaker. Unfortunately, the output was still distorted. I tried substituting my 16W workshop loudspeaker for the set’s speaker to see if that was causing the problem and the audio improved considerably. I also experimented with the bias on the 12DQ6A and found that -3V also produced better audio quality – both from listening tests and as observed on the oscilloscope. Because the valve was now drawing less current, the speaker transformer impedance was recalculated and now came out at around 2kW. As a result, a new transformer was installed and this then gave good results with the set’s original loudspeaker. I had expected to be able to tap off -3V from the local oscillator’s grid resiliconchip.com.au Fig.2: this is the circuit of the HMV 61-51 after conversion to 32V operation. Note the added 6BA6 RF stage and the modified audio output stage which is now based on a 12DQ6A. There are lots of other changes as well, including additional RF filtering, a modified AGC circuit and bias changes to the 6BA6 IF stage. sistor, to bias the 12DQ6A. However, due to the low level of oscillator activity, there was insufficient voltage available to bias the output valve. I then tried increasing the oscillator activity but that caused other problems, so the oscillator circuit was left as it was. Another approach is to use cathode bias with the 12DQ6A. However, the audio output would drop by about 20% when the 32V battery was down to 28V and there is only just enough audio output as it is. Some 32V sets actually used a battery to provide the bias and in the end, this is what I elected to do. It should last for years – in fact, those in some sets are 10-20 years old. Parasitic oscillation Although the audio quality was now much better, the oscilloscope showed that the output valve was going into parasitic oscillation over part of the audio signal, thus causing distortion. This was cured by connecting a 3300pF capacitor (C34) between the plate of the 12DQ6A and earth. It’s worth noting that the 6DQ6/12DQ6 valves are quite high performance valves and have to be treated with care to prevent spurious oscillation. When the set was subsequently tested at 45V (which some lighting plants developed when at the end of the battery charge), the audio once again distorted on the peaks. I then remembered that some of these high-performance valves require a screen stopper to overcome such problems and in this case, a 100W resistor (R27) completely cured the audio distortion. Once this was all done, the 12DQ6A really worked well and the audio output was more than adequate. When it comes to doing design work and finding weird and wonderful faults, an oscilloscope is an invaluable piece of equipment! IF filtering Another worthwhile improvement involved fitting additional IF filters in siliconchip.com.au February 2005 95 Photo Gallery: AWA Radiola 120 Manufactured in 1933, the Radiola 120 (and its table model companion the 120) were AWA’s first AC-powered superheterodyne models. The set was one of the few AWA designs to use an autodyne mixer, the company reverting to conventional mixer/ oscillator circuits for all subsequent designs. Another unusual aspect of the design involved mounting the 8-inch (20cm) electrodynamic speaker above the chassis, in the upper section of the cabinet. The valves fitted were: 57 autodyne mixer; 58 175kHz IF amplifier; 57 anode bend detector; 59 audio output; and 280 rectifier. Photo: Historical Radio Society of Australia, Inc. the audio stages. This prevents 455kHz IF signals from being amplified and then re-radiated back into the front end of the set where they can cause instability. The extra components involved here are C33, C35 and R26. Some sets have these components installed as standard but many manufacturers decided they could get away without them. This usually didn’t cause any problems but some sets do have instability problems due to this lack of IF filtering. Once again, the oscilloscope was handy here. It was able to show the amount of IF signal getting through each audio stage and indicate the ef96 Silicon Chip fectiveness of the additional filtering components. The converter and IF stages were treated as a single unit and the only modification involved shorting out the screen dropping resistors (R5 and R6). The set was then turned on and although it actually worked, the 6BA6 was found to be faulty and was replaced. That done, the set was aligned and although the sensitivity was fair, it was hardly adequate for remote country areas. And that meant that some further work would have to be done to solve this problem. Because most 32V radios have an RF stage, I decided to fit one to this set. However, since there is only a 2-gang tuning capacitor, any RF stage would need to be untuned – unless a 3-gang capacitor and an RF coil could be fitted. Once again, I didn’t feel like carrying out major surgery, so I opted to install an untuned RF stage. The design of this RF amplifier is similar to the video amplifier stages used in old valve TV receivers. In this case, I designed the untuned amplifier to have a cut-off frequency of around 2MHz (note: the 1948 Philips portable model 111 used this technique as well). As shown in Fig.2, a 6BA6 was selected as the RF amplifier and the “video” circuit was designed to couple the 6BA6 to the following 6BE6. These untuned amplifiers are rather different in design to a “normal” tuned amplifier. They aren’t particularly complex and require no tuning but their total gain is lower because the circuit is broadband. Once installed, the RF amplifier stage boosted the performance of the set such that it now equals almost any other 32V set with an RF stage. The components forming the matching and peaking network between the RF amplifier and the converter are R21, R22, L4, L5 and C31. AGC tweaks By now, the set was beginning to show real promise. However, further testing revealed that the sound distorted on strong stations. This is a sign of problems with the AGC system and with such a low HT voltage, the IF stage(s) are particularly sensitive to too much or too little bias voltage. The IF stage was overloading so to overcome this problem, the AGC was removed from this stage and contact potential bias was obtained using a 10MW resistor (R24) in the grid lead. Capacitor C9 functions as the RF bypass for the IF transformer. In addition, by taking the signal for the AGC diode from the plate of the 6BA6 IF valve, a higher AGC voltage was obtained. This meant that the IF valve was no longer overloaded, even when high signal levels were encountered. As before, the oscilloscope was very useful for determining where the overload was occurring, which made it easier to find a solution. Power supply The power supply circuit for a set siliconchip.com.au An under-chassis view of the converted receiver, with the RF inter-stage coupling components visible near the tuning drive. The 12DQ6A audio output stage wiring is at the lefthand end of the photograph. that uses 32V DC as the HT voltage is very simple. The voltage supplied from a 32V electric lighting plant is nominally 32V but does vary widely, depending on the state of charge of the battery bank. Typically, with 16 cells, it will vary between about 28V with a flat battery bank (allowing for voltage drop in the power cables) to around 40V (ie, 2.5V per cell) at the end of charging. In some cases, to overcome the voltage drop in the power cables under load, one or two additional cells were added to the bank. This meant that the voltage would rise to 45V at the end of a charge. This variation is really too much for the valve heaters, so the on/off switch in most 32V sets is a 3-position switch, with the third position labelled “charge”. The switch positions in order are “off”, “charge” and “on”. In the “charge” position, a resistor is placed in series with the heaters and dial lamps to limit the voltage applied to them when the battery bank is on charge (in this set, S1 performs that function). Note that in many vibratorpowered sets, the current to all sections of the set is usually fed through a 10W resistor to drop the voltage to around 32V when the batteries are on charge. To minimise electrical noise (interference) entering the set and causing problems, a filter consisting of capacitor C36 and a 10mH choke is installed. The audio ripple on the 32V line when charging is taking place is removed by capacitors C17 and C21. Finally, note that decoupling resistor R10 is quite low in value, to minimise the HT voltage drop. Summary Several main points have emerged from this very useful exercise: (1) A set with only 32V HT on the plates and screens of the valves can perform as well as a set with a HT voltage of 250V. (2) To achieve good sensitivity, five stages are needed compared to four stages in a normal mains-operated receiver. (3) Care is needed to ensure minimum voltage losses, particularly in the plate and screen circuits. (4) Only minimal RF bypassing is required. The sets are remarkably stable, due largely to the relatively low gain per stage. (5) The AGC circuit needs to be carefully designed, to avoid overloading the IF stage(s). (6) A valve which draws reasonable currents on low voltages is required for the audio output stage. (7) Careful design is requited in some sections of the circuit to achieve good results on low voltages. That’s it – a fun project just to show what the differences are between sets running on normal HT voltages and SC those running on low voltages. Issues Getting Dog-Eared? Keep your copies safe with these handy binders. REAL VALUE AT $12.95 PLUS P & P Available Aust, only. Price: $A12.95 plus $7 p&p per order (includes GST). Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. siliconchip.com.au February 2005 97 ALL S ILICON C HIP SUBSCRIBERS – PRINT, OR BOTH – AUTOMATICALLY QUALIFY FOR A REFERENCE $ave 10%ONLINE DISCOUNT ON ALL BOOK OR PARTSHOP PURCHASES. CHIP BOOKSHOP 10% (Does not apply to subscriptions) SILICON For the latest titles and information, please refer to our website books page: www.siliconchip.com.au/Shop/Books PIC MICROCONTROLLERS: know it all SELF ON AUDIO Multiple authors $85.00 The best of subjects Newnes authors have written over the past few years, combined in a one-stop maxi reference. Covers introduction to PICs and their programming in Assembly, PICBASIC, MBASIC & C. 900+ pages. PROGRAMMING and CUSTOMIZING THE PICAXE By David Lincoln (2nd Ed, 2011) $65.00* A great aid when wrestling with applications for the PICAXE See series of microcontrollers, at beginner, intermediate and Review April advanced levels. Every electronics class, school and library should have a copy, along with anyone who works with PICAXEs. 300 pages in paperback. 2011 PIC IN PRACTICE by D W Smith. 2nd Edition - published 2006 $60.00* Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcontrollers. 255 pages in paperback. PIC MICROCONTROLLER – your personal introductory course By John Morton 3rd edition 2005. $60.00* A unique and practical guide to getting up and running with the PIC. It assumes no knowledge of microcontrollers – ideal introduction for students, teachers, technicians and electronics enthusiasts. Revised 3rd edition focuses entirely on re-programmable flash PICs such as 16F54, 16F84 12F508 and 12F675. 226 pages in paperback. by Douglas Self 2nd Edition 2006 $69.00* A collection of 35 classic magazine articles offering a dependable methodology for designing audio power amplifiers to improve performance at every point without significantly increasing cost. Includes compressors/limiters, hybrid bipolar/FET amps, electronic switching and more. 467 pages in paperback. SMALL SIGNAL AUDIO DESIGN By Douglas Self – First Edition 2010 $95.00* The latest from the Guru of audio. Explains audio concepts in easy-to-understand language with plenty of examples and reasoning. Inspiration for audio designers, superb background for audio enthusiasts and especially where it comes to component peculiarities and limitations. Expensive? Yes. Value for money? YES! Highly recommended. 558 pages in paperback. AUDIO POWER AMPLIFIER DESIGN HANDBOOK by Douglas Self – 5th Edition 2009 $85.00* "The Bible" on audio power amplifiers. Many revisions and updates to the previous edition and now has an extra three chapters covering Class XD, Power Amp Input Systems and Input Processing and Auxiliarly Subsystems. Not cheap and not a book for the beginner but if you want the best reference on Audio Power Amps, you want this one! 463 pages in paperback. DVD PLAYERS AND DRIVES by K.F. Ibrahim. Published 2003. $71.00* OP AMPS FOR EVERYONE By Bruce Carter – 4th Edition 2013 $83.00* This is the bible for anyone designing op amp circuits and you don't have to be an engineer to get the most out of it. It is written in simple language but gives lots of in-depth info, bridging the gap between the theoretical and the practical. 281 pages, A guide to DVD technology and applications, with particular focus on design issues and pitfalls, maintenance and repair. Ideal for engineers, technicians, students of consumer electronics and sales and installation staff. 319 pages in paperback. by Sanjaya Maniktala, Published April 2012. $83.00 Thoroughly revised! The most comprehensive study available of theoretical and practical aspects of controlling and measuring EMI in switching power supplies. Subtitled Exploring the PIC32, a Microchip insider tells all on this powerful PIC! Focuses on examples and exercises that show how to solve common, real-world design problems quickly. Includes handy checklists. FREE CD-ROM includes source code in C, the Microchip C30 compiler, and MPLAB SIM. 400 pages paperback. By Garry Cratt – Latest (7th) Edition 2008 $49.00 Written in Australia, for Australian conditions by one of Australia's foremost satellite TV experts. If there is anything you wanted to know about setting up a satellite TV system, (including what you can't do!) it's sure to be covered in this 176-page paperback book. See Review Feb 2004 SWITCHING POWER SUPPLIES A-Z PROGRAMMING 32-bit MICROCONTROLLERS IN C By Luci di Jasio (2008) $79.00* PRACTICAL GUIDE TO SATELLITE TV See Review March 2010 ELECTRIC MOTORS AND DRIVES By Austin Hughes & Bill Drury - 4th edition 2013 $59.00* This is a very easy to read book with very little mathematics or formulas. It covers the basics of all the main motor types, DC permanent magnet and wound field, AC induction and steppers and gives a very good description of how speed control circuits work with these motors. Soft covers, 444 pages. NEWNES GUIDE TO TV & VIDEO TECHNOLOGY By KF Ibrahim 4th Edition (Published 2007) $49.00 It's back! Provides a full and comprehensive coverage of video and television technology including HDTV and DVD. Starts with fundamentals so is ideal for students but covers in-depth technologies such as Blu-ray, DLP, Digital TV, etc so is also perfect for engineers. 600+ pages in paperback. RF CIRCUIT DESIGN by Chris Bowick, Second Edition, 2008. $63.00* The classic RF circuit design book. RF circuit design is now more important that ever in the wireless world. In most of the wireless devices that we use there is an RF component – this book tells how to design and integrate in a very practical fashion. 244 pages in paperback. PRACTICAL RF HANDBOOK AC MACHINES By Jim Lowe Published 2006 $66.00* Applicable to Australian trades-level courses including NE10 AC Machines, NE12 Synchronous Machines and the AC part of NE30 Electric Motor Control and Protection. Covering polyphase induction motors, singlephase motors, synchronous machines and polyphase motor starting. 160 pages in paperback. PRACTICAL VARIABLE SPEED DRIVES & POWER ELECTRONICS Se e by Malcolm Barnes. 1st Ed, Feb 2003. $73.00* Review An essential reference for engineers and anyone who wishes to design or use variable speed drives for induction motors. 286 pages in soft cover. Feb 2003 BUILD YOUR OWN ELECTRIC MOTORCYCLE by Carl Vogel. Published 2009. $40.00* by Ian Hickman. 4th edition 2007 $61.00* Alternative fuel expert Carl Vogel gives you a hands-on guide with A guide to RF design for engineers, technicians, students and enthusiasts. the latest technical information and easy-to-follow instructions Covers key topics in RF: analog design principles, transmission lines, for building a two-wheeled electric vehicle – from a streamlined couplers, transformers, amplifiers, oscillators, modulation, transmitters and scooter to a full-sized motorcycle. 384 pages in soft cover. receivers, propagation and antennas. 279 pages in paperback. *NOTE: ALL PRICES ARE PLUS P&P – AUSTRALIA ONLY: $10.00 per order; NZ – $AU12.00 PER BOOK; REST OF WORLD $AU18.00 PER BOOK To Place Your Order: INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) www.siliconchip. com.au/Shop/Books Use your PayPal account silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au with order & credit card details FAX (24/7) MAIL (24/7) Your order and card details to Your order to PO Box 139 Collaroy NSW 2097 (02) 9939 2648 with all details PHONE – (9-5, Mon-Fri) Call (02) 9939 3295 with with order & credit card details You can also order and pay for books by cheque/money order (Mail Only). Make cheques payable to Silicon Chip Publications. ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. ALL PRICES INCLUDE GST ALL S ILICON C HIP SUBSCRIBERS – PRINT, OR BOTH – AUTOMATICALLY QUALIFY FOR A REFERENCE $ave 10%ONLINE DISCOUNT ON ALL BOOK OR PARTSHOP PURCHASES. CHIP BOOKSHOP 10% (Does not apply to subscriptions) SILICON For the latest titles and information, please refer to our website books page: www.siliconchip.com.au/Shop/Books PIC MICROCONTROLLERS: know it all SELF ON AUDIO Multiple authors $85.00 The best of subjects Newnes authors have written over the past few years, combined in a one-stop maxi reference. Covers introduction to PICs and their programming in Assembly, PICBASIC, MBASIC & C. 900+ pages. PROGRAMMING and CUSTOMIZING THE PICAXE By David Lincoln (2nd Ed, 2011) $65.00* A great aid when wrestling with applications for the PICAXE See series of microcontrollers, at beginner, intermediate and Review April advanced levels. Every electronics class, school and library should have a copy, along with anyone who works with PICAXEs. 300 pages in paperback. 2011 PIC IN PRACTICE by D W Smith. 2nd Edition - published 2006 $60.00* Based on popular short courses on the PIC, for professionals, students and teachers. Can be used at a variety of levels. An ideal introduction to the world of microcontrollers. 255 pages in paperback. PIC MICROCONTROLLER – your personal introductory course By John Morton 3rd edition 2005. $60.00* A unique and practical guide to getting up and running with the PIC. It assumes no knowledge of microcontrollers – ideal introduction for students, teachers, technicians and electronics enthusiasts. Revised 3rd edition focuses entirely on re-programmable flash PICs such as 16F54, 16F84 12F508 and 12F675. 226 pages in paperback. by Douglas Self 2nd Edition 2006 $69.00* A collection of 35 classic magazine articles offering a dependable methodology for designing audio power amplifiers to improve performance at every point without significantly increasing cost. Includes compressors/limiters, hybrid bipolar/FET amps, electronic switching and more. 467 pages in paperback. SMALL SIGNAL AUDIO DESIGN By Douglas Self – First Edition 2010 $95.00* The latest from the Guru of audio. Explains audio concepts in easy-to-understand language with plenty of examples and reasoning. Inspiration for audio designers, superb background for audio enthusiasts and especially where it comes to component peculiarities and limitations. Expensive? Yes. Value for money? YES! Highly recommended. 558 pages in paperback. AUDIO POWER AMPLIFIER DESIGN HANDBOOK by Douglas Self – 5th Edition 2009 $85.00* "The Bible" on audio power amplifiers. Many revisions and updates to the previous edition and now has an extra three chapters covering Class XD, Power Amp Input Systems and Input Processing and Auxiliarly Subsystems. Not cheap and not a book for the beginner but if you want the best reference on Audio Power Amps, you want this one! 463 pages in paperback. DVD PLAYERS AND DRIVES by K.F. Ibrahim. Published 2003. $71.00* OP AMPS FOR EVERYONE By Bruce Carter – 4th Edition 2013 $83.00* This is the bible for anyone designing op amp circuits and you don't have to be an engineer to get the most out of it. It is written in simple language but gives lots of in-depth info, bridging the gap between the theoretical and the practical. 281 pages, A guide to DVD technology and applications, with particular focus on design issues and pitfalls, maintenance and repair. Ideal for engineers, technicians, students of consumer electronics and sales and installation staff. 319 pages in paperback. by Sanjaya Maniktala, Published April 2012. $83.00 Thoroughly revised! The most comprehensive study available of theoretical and practical aspects of controlling and measuring EMI in switching power supplies. Subtitled Exploring the PIC32, a Microchip insider tells all on this powerful PIC! Focuses on examples and exercises that show how to solve common, real-world design problems quickly. Includes handy checklists. FREE CD-ROM includes source code in C, the Microchip C30 compiler, and MPLAB SIM. 400 pages paperback. By Garry Cratt – Latest (7th) Edition 2008 $49.00 Written in Australia, for Australian conditions by one of Australia's foremost satellite TV experts. If there is anything you wanted to know about setting up a satellite TV system, (including what you can't do!) it's sure to be covered in this 176-page paperback book. See Review Feb 2004 SWITCHING POWER SUPPLIES A-Z PROGRAMMING 32-bit MICROCONTROLLERS IN C By Luci di Jasio (2008) $79.00* PRACTICAL GUIDE TO SATELLITE TV See Review March 2010 ELECTRIC MOTORS AND DRIVES By Austin Hughes & Bill Drury - 4th edition 2013 $59.00* This is a very easy to read book with very little mathematics or formulas. It covers the basics of all the main motor types, DC permanent magnet and wound field, AC induction and steppers and gives a very good description of how speed control circuits work with these motors. Soft covers, 444 pages. NEWNES GUIDE TO TV & VIDEO TECHNOLOGY By KF Ibrahim 4th Edition (Published 2007) $49.00 It's back! Provides a full and comprehensive coverage of video and television technology including HDTV and DVD. Starts with fundamentals so is ideal for students but covers in-depth technologies such as Blu-ray, DLP, Digital TV, etc so is also perfect for engineers. 600+ pages in paperback. RF CIRCUIT DESIGN by Chris Bowick, Second Edition, 2008. $63.00* The classic RF circuit design book. RF circuit design is now more important that ever in the wireless world. In most of the wireless devices that we use there is an RF component – this book tells how to design and integrate in a very practical fashion. 244 pages in paperback. PRACTICAL RF HANDBOOK AC MACHINES By Jim Lowe Published 2006 $66.00* Applicable to Australian trades-level courses including NE10 AC Machines, NE12 Synchronous Machines and the AC part of NE30 Electric Motor Control and Protection. Covering polyphase induction motors, singlephase motors, synchronous machines and polyphase motor starting. 160 pages in paperback. PRACTICAL VARIABLE SPEED DRIVES & POWER ELECTRONICS Se e by Malcolm Barnes. 1st Ed, Feb 2003. $73.00* Review An essential reference for engineers and anyone who wishes to design or use variable speed drives for induction motors. 286 pages in soft cover. Feb 2003 BUILD YOUR OWN ELECTRIC MOTORCYCLE by Carl Vogel. Published 2009. $40.00* by Ian Hickman. 4th edition 2007 $61.00* Alternative fuel expert Carl Vogel gives you a hands-on guide with A guide to RF design for engineers, technicians, students and enthusiasts. the latest technical information and easy-to-follow instructions Covers key topics in RF: analog design principles, transmission lines, for building a two-wheeled electric vehicle – from a streamlined couplers, transformers, amplifiers, oscillators, modulation, transmitters and scooter to a full-sized motorcycle. 384 pages in soft cover. receivers, propagation and antennas. 279 pages in paperback. *NOTE: ALL PRICES ARE PLUS P&P – AUSTRALIA ONLY: $10.00 per order; NZ – $AU12.00 PER BOOK; REST OF WORLD $AU18.00 PER BOOK To Place Your Order: INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) www.siliconchip. com.au/Shop/Books Use your PayPal account silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au with order & credit card details FAX (24/7) MAIL (24/7) Your order and card details to Your order to PO Box 139 Collaroy NSW 2097 (02) 9939 2648 with all details PHONE – (9-5, Mon-Fri) Call (02) 9939 3295 with with order & credit card details You can also order and pay for books by cheque/money order (Mail Only). Make cheques payable to Silicon Chip Publications. ALL TITLES SUBJECT TO AVAILABILITY. PRICES VALID FOR MONTH OF MAGAZINE ISSUE ONLY. ALL PRICES INCLUDE GST BUILD YOURSELF A WINDMILL GENERATOR Part 3: the windmill platform – by Glenn Littleford* The windmill platform has to perform several tasks. It must support the thrust and weight of a propeller, support the alternator and drive shaft from the propeller, include some sort of tail furling system, provide a mounting point to the tower, be strong enough to survive high winds and it must be easily maintained and modified. If possible, it should also allow some means of getting the generated current from the alternator to the ground without the power leads becoming twisted, stressed or breaking. 100 Silicon Chip siliconchip.com.au T his windmill platform is available as a kit consisting of laser-cut steel parts, stainless steel nuts and bolts and a set of new bearings. The steel sections are grade 250 mild steel, 8mm thick, and designed to fit together easily. Also included are the 4mm steel propeller hub plates, machined propeller adapter, a 200mm length of steel rod and a 100mm length of steel tube (these form part of the propeller hub and tail assembly). Not included with the kit is the tail boom, a 1000mm length of 22mm steel tube, or tail. Why aren’t they included? Well, the whole kit packs into a 350mm square box for delivery. If the tail boom and tail was included, a much larger package would be needed and the extra delivery costs would far outweigh the cost of the tail parts themselves. You can pick up a length of 22mm steel tube for less than $10 new (or from the local scrap metal yard for a couple of dollars) and the tail fin can be made from a small sheet of scrap plywood or steel. The tail boom and tail fin (3mm aluminium, approx 600mm by 500mm) can be included with the windmill kit if requested. If you decide to make your own tail fin (and I recommend you do), why not get creative with your design? I’ve seen tail fins shaped and painted like chickens, pigs and cattle dogs. Fig.1 shows the windmill platform parts. The platform is designed to be easily assembled. You will need only some basic tools and access to a welder. There are two new bearings included with the kit: a 6005 (which is the same one F&P use in their washing machines); and a heavy duty 56205 bearing and F205 carrier to support the weight and thrust of the propeller. The windmill platform is designed to be bolted onto a car wheel hub at the top of your mast. We are using a car Tack and weld the hinge tube and tail boom to the tail brace. *www.thebackshed.com siliconchip.com.au Fig. 1: view of all the laser-cut steel parts making up the windmill platform. hub for strength and reliability. Car hubs are designed to carry over a ton so you will never need to worry about this bearing failing, But there is a disadvantage: because we use a car bearing our drop wire needs to feed down the side of the windmill Mount the base plate in a vise, fit and tack-weld the front and rear bearing supports. Check they are square before fully welding. February 2005 101 Fig. 2: alternative to using a car hub bearing. If the wind in your area changes direction several times a day you might need to use a yaw bearing like this. Fig.3: top view of the windmill platform showing the stator and bearings placement. and mast, not down the middle of it. So after a few wind changes (a windmill changing direction to face the wind is called a “yaw”) you may find your drop wire wrapped around the mast. On my windmill I have a rope tied to the tail with a tennis ball attached to the end that I can reach from the ground. About once a week I grab the tennis ball and walk the windmill around to unwind the drop wire. The rope is also handy to point the windmill in one direction by tying the rope to a tower guy wire. If you are in a location where the wind changes direction several times a day, you might want to look at another option (see Fig.2). Using this design you can feed the drop wire down the middle of the mast, allowing the windmill to spin around several times before the twist in the drop wire becomes a problem. Occasionally you would still need to untwist the wire. This approach is not as strong and reliable as the car bearing. A better option still would be to use the car hub and bore a 10mm hole down the center of the stub axle. Doing so shouldn’t weaken the hub enough to be a concern, but you will need access to a good lathe and some sharp drill bits as stub axles are very hard! Fit the hinge rod, short and long hinge plates and tail stop plate, tack and fully weld. Once the weld has cooled, clean up the metal work with a wire brush, then apply a few coats of paint to prevent rust. 102 Silicon Chip siliconchip.com.au Commercial windmills overcome the yaw problem by using a set of slip rings and brushes to connect the drop wire to the windmill. This is a little complicated to explain here but it has been done by windmill enthusiasts. I’ve chosen the common Holden hub pattern for this windmill as these are readily available from trailer supply outlets. If you have another hub pattern that you want to use, the kit can be supplied to suit at no extra charge, providing the hub diameter does not exceed 140mm. The tail used on our windmill is of the self furling type, which means the tail is designed to turn the windmill out of the wind if the wind speed or load on the windmill blades exceeds a safe point. So how does it work? You will notice the windmill propeller is offset to one side of the mast by exactly 100mm. So as the wind blows against the propeller, the whole windmill will want to turn away from the wind. Our tail is on a hinge of sorts, angled back and angled out to the opposite side of the propeller. This angle means the tail wants to turn downward and out (just like when you are asked to move a mate’s fridge, as soon as you lean the fridge back the door opens and gets in the way ). We have placed a stop on the hinge, so the tail will stop when it is pointing directly back from the windmill. When the windmill in running in normal winds, the weight of the tail is enough to keep the tail against this stop and therefore keep the propeller facing the wind (remember the tail will always be downwind). As the wind speeds up the force against the propeller will reach a point where it exceeds the weight of the tail. The propeller will start to turn out off the wind and the tail will turn upward on the hinge. While gravity wants to pull the tail back down, the force of the wind keeps the tail downwind, where it balances against the force of the propeller trying to turn the windmill around. As the wind picks up the tail will lift higher, until it reaches the top hinge stop. At this stop the tail is almost in line with the propeller, which is almost at right angles to the wind. The furling is adjusted by adding or removing weight The bearing, bearing plate and spacer plate fit into the stator as shown. The gap in the spacer plate is to clear the welding on the rear bearing support. siliconchip.com.au from the tail or changing the tail boom length. If you find your windmill is turning out of the wind too early, try adding some weight to the tail, or move the tail further out (and vice-versa if the tail doesn’t furl early enough). This method of furling is very simple and reliable and has been in use for hundreds of years. Putting it all together. Included with the windmill kit is a full set of detailed instructions but I’ll show you the basics here to give you an idea of how the windmill is assembled. All the steel parts in the kit are laser cut. Laser cutting leaves a loose flaky edge on the steel, and this needs to be removed – easily done with a wire brush or coarse sand paper. Also check that the 6005 bearing fits into the bearing plate. As this part is laser cut it should be a nice fit but sometimes parts are a little too tight. If so, grab a metal file and file off any excess metal until the bearing slides snugly into the adapter. Secure the base plate in a vise and slide on the front and read bearing supports, then tack-weld together. Check all is square before fully welding (either stick or mig welding is fine). Allow to cool before proceeding. Next fit the tail stop, short and long hinge plates and hinge rod to the base plate and weld together, making sure you have the tail stop plate the right way around (see Fig.1). You will also need to weld the tail brace to the hinge tube and tail boom. If you use a length of galvanised pipe for your tail boom, be warned that welding galvanised steel gives off some very toxic fumes, so use a gas mask with suitable filter and weld in a well ventilated area. Once the parts have cooled down give them a going over with a wire brush to remove any welding splatter and slag, Then paint them with a good metal paint, such as “Killrust” or engine enamel. Press the 6005 bearing into the bearing plate. It will sit flush on one side but on the other side, the side which fits into the F&P stator, it will poke out 4mm. Using the four 6mm bolts, fit the stator retaining plates, stator, bearing plate and sparer plate to the rear bearing Almost finished: the stator, drive shaft and front bearing fitted. February 2005 103 support on the windmill platform (see Fig.3). Now slide in the drive shaft from the front until it pokes out the back of the stator, screw on and tighten the drive shaft retaining nut, and then tap the drive shaft forward until the retaining nut is home. Add a drop of Loctite to the retaining nut, being careful not to get any on the bearing. Next slide on and secure the front bearing using the four 12mm bolts. The front bearing has a grease nipple, so pump in some bearing grease to fully lubricate the bearing, then tighten the two grub screws onto the drive shaft. Check that the drive shaft spins freely. If there is any resistance, loosen and re-tension the stator bolts. Now screw on the magnet hub. The hub is designed to mesh with the shaft spline while the plastic retaining nut will slowly feed the hub over the stator as it is tightened. Try rotating the hub to check that the hub is not binding against the stator. You should feel a distinct cogging as the hub rotates – this is normal. Be aware that the stator will be generating electricity as you rotate the hub, so treat the connections as live and possibly shocking! Mount the windmill level. I use a “test stand” for this. It’s basically a mast about 1.5m high. Apply a little grease to the tail rod and slide on the tail boom, making sure it can rotate freely. If it’s a little tight, remove any burs or seams inside the tail hinge tube with a round file. Now with the windmill level and the tail pointing directly out the back of the windmill, position the tail fin on the tail boom, clamp with a couple of G-clamps and check that it is straight up and down. Then mark and drill the tail fin bolt holes. It’s not critical that the tail fin is vertical but it definitely looks better. cool breeze, plus you only need to run two wires from the windmill to your battery’s positive and 0V terminals. If you place your rectifier near your batteries, you will need to run three wires from the windmill (or six if you plan to experiment with delta/star configurations) but you won’t have to worry about water ingress into the rectifier or taking your windmill down if the rectifier fails. The windmill base plate includes a few extra bolt holes for mounting the rectifier, and a 20mm hole to suit the supplied cable retainer to support the drop wire. The kit The windmill kit is available via my website, www. thebackshed.com The web site includes detailed instructions, a bunch of photos of my windmill creations, and other windmill projects including a “Mini-Mill” using a stepper motor from an old PC floppy drive. SC Next month In the final part to this series, we will look at a couple of propeller options, basic propeller blade designs, and some options for a mast. Mounting the rectifier As we mentioned last month, the output of the windmill is AC and you need to rectify that to DC before using to charge batteries, etc. You can mount your rectifier either on the windmill (at the top of your mast), or at your battery bank. One advantage of mounting on the windmill is that the rectifier is up in a Screw on the magnet hub and check that there is no binding or scraping. Remember the stator terminals will be live while the hub is rotating. 104 Silicon Chip With the windmill mounted level, fit the tail boom and align the fin vertically, then drill and bolt to the tail boom. siliconchip.com.au 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; or send an email to silchip<at>siliconchip.com.au Compressor for PA system On your PortaPAL PA system (SILICON CHIP, February & March 2003) that uses the TDA1562Q Philips IC, do you have a companion audio compressor/ limiter circuit or an audio bandpass input filter so as to limit the input for voice passband only and to avoid clipping/over-modulation? (B. M., Minneapolis, USA). • We published a single chip compressor for microphones and guitar in March 1999. The signal would need to be connected after the initial balanced microphone preamplifier. A CD compressor was published in June 2000. Antenna connection for FM tuner Can FM radios that only have a “flying lead” as an FM antenna (ie, they have no 75-ohm coax input) be connected or matched to a 75-ohm TV/ FM antenna wall outlet? If so, how is this done? TDK has released a wonderful slimline CD/tuner system (NX-03CD) but unfortunately it doesn’t have a coax antenna input. I’d like to be able to connect this system to my rooftop TV/ FM antenna, as reception is marginal on some FM stations with only the “flying lead” antenna that’s provided with this system. (R. B., via email). • You can connect the tuner’s flying lead to the centre pin of a coax wall socket. It won’t be as good as a full coax connection but it will be better than nothing. Polystyrene foam cutter I have a faint memory of seeing an article on constructing a polystyrene foam cutter in an electronics magazine. Have you ever published such an article and if so is it still available for purchase? (D. G., Bicton, WA). • A hot wire cutter was described in the April 2000 issue of SILICON CHIP. The back issue is available for $8.80 including GST and p&p (Australia). Modifying PC ATX supplies In the July 2004 article outlining how to modify a switchmode power supply to provide 700V, the schematic shows T2 as a transformer that drives the primary switching transistors. The text and photos don’t seem to show any thing about this transformer. I was just wondering how that part of the circuit works. Also is there any difference in modifying old PC supplies vs ATX supplies? (A. L., Mosgiel, NZ). • Not shown on the circuit are several components used to bias the bases of Q1 & Q2 ahead of the transformer (T2) secondary inputs. A transformer is used here is to isolate the primary side from the secondary side control circuits, as well as to “level shift” the drive signals to the switching transistors. As this part of the circuit varies between supplies, and also because it wasn’t part of the modifications, we omitted that sort of detail to make the circuit easier to follow. ATX supplies can be modified but are significantly more difficult to work with unless you have SMPS experience. They include an additional (+3.3V) high-current rail and a dedicated standby power circuit. You’ll find an example of an ATX power supply circuit on this page: www.pavouk.comp.cz/hw/en_atxps. html Sensitivity reduction for Dog Silencer I have just built the “Shut that Mutt” kit featured in the April 2004 issue. Video Enhancer & Y/C Separator Burst Problem I’m having a problem with the Video Enhancer & Y/C Separator project described in the August 2004 issue. In short, what should the “amplified bursts” at D1 look like? At first I wound too few turns on L1 and got the peak burst with the slug right in. Then I wound too many and the peak was with the slug right out. I now have the right number of turns, as I’m getting the peak with the slug part way in. However, the amplitude is only about 1.7V p-p. The top of the burst is at about 1V, siliconchip.com.au which is not enough to switch IC4d, whose output is always high. Consequently, I’m not getting any “PLL error signal” either. The “trimmed BG pulses” are good and IC10c is gating the burst onto the base of Q1, at about 0.3V p-p. What sort of amplitude should I be getting for the “amplified bursts” going into IC4d? What could be wrong? (R. S., via email). • The amplified gated bursts at D1 should look like a short burst of reasonably constant amplitude sinewaves (at 4.433MHz), with a tapering start and finish. They should have an amplitude of about 2.5V peak to peak, with the negative peaks at roughly 0V (because of the action of D1). As a result, the output at pin 11 of IC4 should be essentially a square wave version of the bursts, with a peak-peak amplitude of almost 5V. Perhaps your coil L1 is still not peaking properly at 4.43MHz, as this would give most of the symptoms you describe. Either that or perhaps Q1 is faulty and has very low gain. February 2005 105 High-Power Ultrasonic Amplifier I am interested in building an ultrasonic cavitation unit and need some help selecting a suitable amplifier to power the transducer. I am going to use the DSE K2802 kit or the low cost 10MHz function generator detailed in the May 2003 issue of SILICON CHIP. The frequencies I am interested in amplifying are from 20-120kHz at around 100150W power. The transducer has a 10-ohm impedance. Could you please suggest a suitable amplifier and the modifications required for operation in this frequency range? (A. W., Tenterfield, NSW). • We have no power amplifier design suitable for continuous power delivery at 120kHz – virtually no audio power amplifier is suitable as the power dissipation in the output and driver stages will be very much higher at ultrasonic frequencies The device really does seem to work on our dogs but I have a problem. It appears to be triggering all the time and I have no adjustment on the sensitivity control; its either off or on. Any ideas please? (G. L., Thebarton, SA). • You may want to try reducing the gain of Q2 or Q1. Try connecting a 470W resistor in series with the emitter of Q1. Larger toroid for auto ammeter I wonder if you can give me some advice on the 0-80A Auto Ammeter described in the June 2002 issue. I bought the kit from Jaycar but the ferrite core suppressor only takes cables up to 1012mm diameter. My car has two main cables off each terminal, along with a couple of smaller ones. The two main ones are about 8 or 9mm each (ie, two big cables off each terminal). These will not fit inside the ferrite core. Can you suggest what I should do? Also with the Smart Fuel Mixture Display kit for EFI cars, I put in high brightness LEDs instead of standard ones. Can I put a potentiometer in the circuit to adjust the brightness independently of the LDR? If so, where and 106 Silicon Chip than in the audio range. This is despite the fact that many audio amplifiers have a frequency response well beyond 100kHz. However, this is usually measured at only 1W and any attempt to up the measured power at 100kHz would have the immediate effect of burning out any Zobel network or similar filter in the output, as well as causing the output and driver stages to seriously overheat. The cavitation transducer is also likely to be a piezoelectric type which means that it will present a highly capacitive load to the amplifier and this means its impedance at 120kHz is likely to be very low. Your quoted figure of 10W probably applies to much lower frequencies. It may be possible to modify a high-power Mosfet amplifier to do the job but there could be a lot of work in doing so. what value? (D. A., via email). • You can use a toroidal core such as the Jaycar LO-1238 instead of the suppression core. The toroid will need to be split in half for the Hall effect sensor to be placed in the gap. Score the toroid so it can be split in half. The brightness of the Smart Fuel Mixture Display can be varied by altering the 680W resistor at Q1’s emitter. A larger value will reduce brightness. Use a 2kW trimpot to adjust to the required level. Substituting ignition coils in a Fuego I own a 1985 Renault Fuego with an electronic ignition unit that can no longer be replaced. I have diagnosed that the HT coil secondary is open-circuit, resulting in no HT spark, although the unit provides the timed pulse correctly, as verified by a lamp test across the primary. The data shows that the primary should be 0.4-0.6W and the secondary 2-12kW. To my thinking, this represents roughly a 12,000:1 ratio delivering around 144kV for the HT, although my research shows that most systems tend to be 15-60kV. Wouldn’t I be able to use a common automotive coil instead of trying to match this rare and expensive Renault item? I know there are Renault owners all over the country that would love to explore this. (F. G., via email). • The resistance ratios do not indicate the turns ratio of the coil. However it we would certainly be inclined to give a conventional ignition coil a try – not a sports coil. 12V traffic lights I was wondering if you would have any idea how to make a set of simple traffic lights. It needs to be biggish, start on red by default, then yellow, then green and run from 12V. (A. T., Griffith, Vic). • We published a LED traffic light design for a model railway layout in the May 1997 issue. This could be extended to a larger system with incandescent lamps instead of LEDs but you would have to upgrade the power supply and the switching transistors. Solar battery charger question I have a question about the solar battery charger published in March 1993. I am using this to charge a battery for a weather station data logger (based on the PICAXE logger) and I am concerned that the LEDs on the charger display may drain the battery. Can I somehow leave them out? (E. P., via email). • The LEDs are isolated from the battery by diode D2 so they don’t drain the battery when it is not being charged. So there is no need to leave them out. 50V speed controller wanted Some time ago, you published a design for a motor speed controller for a wheelchair and it was rated to 50V. Is a reprint available? (M. R., via email). • We have not published a speed control of any sort to work at 50V. Nor have we published a design suitable for forward/reverse which you would need for a wheelchair. About the most suitable design that could be adapted would be our Railpower Train Controller from October, November and December 1999. siliconchip.com.au It could be used at up to 24V without modification, apart from a bigger heatsink for the output stage. It would be limited to less than 10A though. Alternatively, you could have a look at the 50A controller for models, published in the May 2000 issue. It would need a high power changeover relay for reversing. However, a 50V 5kW speed controller was published in the October 1994 issue of “Electronics Australia”. This is very high power for a wheelchair and was claimed in the article to be enough to do “wheelies”! We’re not surprised. It also requires a relay for reversing but it would need to have a very high rating. We can supply a copy of this article for $8.80 including postage and packing within Australia. Turbo timer help needed I bought a Turbo Timer kit from Jaycar Electronics and can’t get it to work properly. The reset works, the thermostat works, the time-out works but the relay cuts in as soon as the switch wire is powered up which should only happen when the power is removed from it. Please help. (P. H., via email). • The fact that your timer immediately starts operating when power is applied suggests a mistake in the trigger circuit involving the 2.2mF capacitor. Check all the components around it. Our prime suspect is the 1.8kW resistor. Check that it is connected properly. Multi-Spark CDI makes squealing sound I have just built the Multi-Spark CDI system and notice on the test bench that it makes a fair bit of highfrequency semi-random audible noise from the inverter. I don’t have a coil or trigger connected at this point in time but is this normal for a no-load condition? Could it be just that the circuit is regulating the 300V? This voltage is correct as well. I’m just checking all is well before I assemble the unit into the case. (A. H., Dunedin, NZ). • You get a sort of squealing/squelch noise as the circuit regulates – it is normal. However, once you get it installed on the motor, you will also find that siliconchip.com.au Tone Controls For The SC480 Amplifier First of all, I would like to thank you for an excellent magazine, which I think is possibly the best of its kind on the planet. I recently built two SC480 modules (SILICON CHIP, January & February 2003) and have housed them in a nice rackmount case purchased from Jaycar. It all went very smoothly until the moment of the real test. I connected a set of speakers and tried to drive it using a mixer. Unfortunately, a worn out cable of the right speaker shorted out and bang, there goes my right module. Not only fuse F1 went but my beautiful Motorola transistors Q11 and Q12 went, much to my disappointment. I would have thought that you have built in enough protection via the Polyswitch PTC and fuses F1 and F2 so disasters like this could not possibly happen. After this little drama and all my the squealing is modulated each time the coil fires. Switchmode power supplies for amplifiers I enquired some time ago about supplying a car-style audio amplifier from 240V AC. As you commented at the time, a high power 13.5V supply would be both expensive, weighty and cumbersome, given that the quality of the average auto amplifier was minimal anyway. Well and good but still having the amplifier on hand, I decided to experiment a little. I tested the output of the switchmode power supply of the amplifier and found that it supplied ±35V DC to the output stages. I therefore tapped into the circuit at this point and supplied the amplifier from a separate power supply consisting of a 500VA transformer, four 10,000mF electros, 35A bridge rectifier, etc. I mounted the lot together with a couple of cooling fans in an old AT computer case and had myself a usable amplifier of around 80 watts RMS per channel, all with a built in subwoofer filter/ decoder. It is not very hifi but a useful adjunct when a bit of extra grunt was called for neat work revisited, finally the unit was switched on and I must say the performance is very impressive. Now how about a nice preamplifier with tone, balance and volume controls, to drive this little beast? (P. T., via email). • We are really surprised that you blew the output stage. We would have expected the PTC to protect things. As far as tone controls, etc are concerned, you might want to have a look at the 50W/channel amplifier described in the March & April 1995 issues. This had a separate tone control board which you might want to use. Alternatively, have a look at the remote volume control board published in the July 2002 issue. This did not have tone controls (you don’t need ’em anyway – the amplifier is so good) but does have a remote motorised volume control. in a PA situation. The supply still cost something like $300 to put together which still made for an expensive amplifier. Which brings me to my question. Why do all or most amplifier designs use large, expensive iron-cored transformers and lots of large (expensive) filter capacitors, etc, while switchmode power supplies are a lot less expensive and lighter? They are used in audio circuits (computers for one), so why not for power amplifiers? (T. C., via email). • Quite a lot of cheap home-theatre systems now use digital amplifiers and switchmode power supplies. And while some higher quality amplifiers do use switchmode power supplies they have not become popular with most manufacturers, possibly because of concerns about radiated hash. Light control for greenhouse I am looking for a way to turn on and off five 250W lights with a light sensor; one sensor to turn lights on and another one to turn them off. It is for an indoor greenhouse and I want to augment natural light with artificial light so they get 12 hours of light a day. February 2005 107 Fuel Consumption Meter For Diesels I drive a diesel vehicle and would like to be able to observe my fuel consumption while driving, displayed digitally in litres/minute to two decimal places. The idea is so I can learn what combination of speed/load/gears/etc gives the best economy. Being diesel, there is fuel going into the injectors but fuel not used returns to the tank (bypass line). Do you know of a product on the market or a kit I could build to do this job for less than $500. The engine uses a maximum of 1 litre/ minute. (G. D., Gibson, WA). • One possibility might be to adapt the August 1995 Fuel Injector Monitor. This provides a bargraph indication of the injector duty cycle up to 100%. It does not show the consumption but fuel consumption will be directly proportional to injector duty cycle. It can be used on any motor, diesel or petrol, which uses solenoid injectors. A better design might be the Duty Cycle Meter that was described in our new book “Performance Electronics For Cars”. This displayed the injector duty cycle on a 2-digit LED readout. The artificial lights will have to adjust to the schedule of the Sun. Any ideas would be greatly appreciated. (B. T., Edmonton, Canada). • Have a look at the Sunset Switch described in our June 2003 issue. This is available on our website or we can send you the printed issue for $10.00 (Australian dollars) airmail. shooting. For example, is there voltage at the emitter of Q4? If not, you may have a problem with IC2b or Q4. Our bet is that you have a solder splash on the board or an open-circuit connection. Troubleshooting the Speed Alert I need to measure the current through a wire providing 240V AC with an upper limit of 10A. I would like to use a 10A DC panel meter as they are readily available from local electronic outlets such as Jaycar. I suspect that by using a parallel circuit of two diode paths, one with the meter in line, that this might do the job. I am reluctant to try this idea as it might at least blow up the meter and at worst do other damage. Will my idea work or is there a better solution? (D. W., Spence, (ACT). I built a Speed Alert kit (SILICON CHIP, November & December 1999) a few months ago. I have doublechecked everything and everything is correct. The LEDs light up but I get no display; no numbers at all. I have tested them with a multimeter and everything seems to be OK. Have you any idea what could be wrong? (S. W., Moss Vale, NSW). • You will need to do some trouble- How to measure 240VAC current • EXTREME DANGER: do not even think of using a 10A DC panel meter to measure 240V AC current. Instead, have a look at the Current Clamp Adaptor for multimeters published in the September 2003 issue of SILICON CHIP. Theremin volume control not progressive I’ve assembled the Theremin from the August 2000 issue. The pitch antenna works fine but I have a problem with the volume plate. When my hand gets near the plate, the sound is cut off but it should do some kind of fade-out I guess. So it’s quite impossible to get the volume louder and softer – it’s loud or cut. I’ve tried the suggestions described in the manual. Is there anything else I can do? (S. M., Ingolstadt, Germany). • Try using a smaller value of resistance between pins 1 and 2 of IC2b. A value of 220kW should decrease the sensitivity of the volume control. Notes & Errata RGB to Component Video Converter, October 2004: the feedback resistor for IC2a should have a value of 1kW, not 510W. This resistor is located just in front of IC2 but on the top of the PC board. 4-Wire Stepper Motor Driver, March 2004 (Circuit Notebook, page 37): the text states that “The original circuit’s IRRZ44Ns can be replaced with IRF9530s”. This should read “The original IRFZ44Ns can be replaced with IRF530s”. 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. 108 Silicon Chip siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $22.00 (incl. GST) for up to 20 words plus 66 cents for each additional word. Display ads: $36.00 (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. Alternatively, fax the details to (02) 9979 6503 or send an email to silchip<at>siliconchip.com.au 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______________ Phone:_____________ Fax:_____________ Email:__________________ siliconchip.com.au FOR SALE Penguin temperature and humidity dataloggers N1500 universal process indicator. Displays thermocouple, RTD, 4-20mA and 0-5V readings Labjack USB Data Acquisition Module features 8 12bit analog inputs, 20 digital I/O, 2 analog outputs and high speed counter. Free software, Labview driver and ActiveX component. UHF 433MHz and Infra Red remote relay controller cards Serial and Parallel port relay controller cards Pump and Alarm Controller card. Programmers for Atmel and PIC microcontrollers. sPlan Windows electronic schematic software and Sprint Layout Windows PCB layout software are feature packed but low in price DAS005 Parallel Port Data Acquisition Module features 8 12bit Analog inputs, 4 Digital I/Ps & 4 Digital O/Ps. Free windows software and source code. Pixel Programmable Controller with 4 analog inputs, 8 digital inputs and 8 relay outputs. Uses a 28X Picaxe. Programmed in basic or Flow chart. 2, 4 & 8 Relay Cards suitable for TTL and Open Collector Outputs Stepper Motor and Servo Motor controller kits Switch Mode and Linear Power Supplies and DC-DC converters. Full details and credit card ordering available at www.oceancontrols. com.au PICAXE PROJECT PCB KIT for hobbyist and home automation, POWERMATE energy meter, thermochron temperature logger, ibutton accessories ULN2803A driver, Luxeon Star LEDs, LED optics. info<at>techbits.com.au www.techbits.com.au ELECTRONIC ENGINEERING CONSULTANTS: Electronic Hardware and Embedded Software for Industrial Control and Commercial Communications. www.furzy.com.au February 2005 109 ELNEC IC PROGRAMMERS Universal and specialised models High quality Realistic prices Large range of adaptors Free regular software updates Windows 95/98/Me/NT/2k/XP GRANTRONICS PTY LTD PO Box 275, Wentworthville. 2145. Ph: 02 9896 7150 New New New Foam surrounds,voice coils,cones and more Original parts for Dynaudio,Tannoy and others Expert speaker repairs – 20 years experience Australian agents for products Trade welcome – email for your user ID Phone (03) 9647 7000 Mark22-SM Slimline Mini FM R/C Receiver speakerbits.com.au www.grantronics.com.au TAIG MACHINERY Micro Mini Lathes and Mills From $489.00 • • • • • 6 Channels 10kHz frequency separation Size: 55 x 23 x 20mm Weight: 25gm Modular Construction Price: $A129.50 with crystal Electronics Silicon Chip Circuit Ideas Wanted Do you have a good circuit idea? If so, sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We pay up to $60 for a good circuit so send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. NOW AVAILABLE FROM Stepper motors: 200 oz in $89.00, 330 oz in $110.00 Digital verniers: 150mm $55.00, 200mm $65.00 59 Gilmore Crescent (02) 6281 5660 Garran ACT 2605 0412269707 PO Box 580, Riverwood, NSW 2210. Ph/Fax (02) 9533 3517 email: youngbob<at>silvertone.com.au Website: www.silvertone.com.au RCS RADIO/DESIGN is at 41 Arlewis St, Chester Hill 2162, NSW Australia and has all the published PC boards from SC, EA, ETI, HE, AEM & others. Ph (02) 9738 0330. sales<at>rcsradio. com.au, www.rcsradio.com.au meter, I/O Relay Card. Also available: Digital Oscilloscope, Temperature Loggers, VHF Receivers and USB ActiveX (and USBDOS.exe file) to control our kits from your own application. www. ar.com.au/~softmark S-Video . . . Video . . . Audio . . . VGA distribution amps, splitters, standards converters, tbc’s, switchers, cables, etc, & price list: www.questronix.com.au NIXIE TUBES, SEVERAL TYPES. Nixie clock kit just $140 including tubes. 74141 nixie driver chips. Superbright LEDs from 35 cents. 5mm superbright warm white LEDs. Other great stuff and more coming soon! www.ledsales.com.au USB KITS: GPIB Interface, Thermostat Tester, LCD Module Interface, Stepper Motor Controller, PIO Interface, DTMF Transceiver, Thermometer, DDS HF Generator, Compass, 4 Channel Volt- www.siliconchip.com.au Project Reprints Limited Back Issues Limited One-Shots If you’re looking for a project from ELECTRONICS AUSTRALIA, you’ll find it at SILICON CHIP! We can now offer reprints of all projects which have appeared in Electronics Australia, EAT, Electronics Today, ETI or Radio, TV & Hobbies. First search the EA website indexes for the project you want and then call, fax or email us with the details and your credit card details. Reprint cost is $8.80 per article (ie, 2-part projects cost $17.60). SILICON CHIP subscribers receive a 10% discount. We also have limited numbers of EA back issues and special publications. Call for details! visit www.siliconchip.com.au or www.electronicsaustralia.com.au 110 Silicon Chip EXPERIMENTER PLATFORM for PICAXE/AVR/BS2 low cost yet provides incremental encoder, piezo, three pushbuttons, three LEDs, serial port, PSU, 830 Breadboard and PC GUI. www. rhombus-tek.com PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone (02) 9593 1025. sesame<at>sesame.com.au www.sesame.com.au CENTRAL COAST FIELD DAY, Sunday 20th February. Don’t miss Australia’s biggest Amateur Radio exhibition and sale of new and used radio and communication equipment at Wyong Race Course, just 1 hour north from Sydney. Gates open 8.30 a.m. Special Field Day bargains from traders and tons of siliconchip.com.au Do You Eat, Breathe and Sleep TECHNOLOGY? Opportunities for full-time and part-time positions all over Australia & New Zealand Jaycar Electronics is a rapidly growing, Australian owned, international retailer with more than 39 stores in Australia and New Zealand. Our aggressive expansion programme has resulted in the need for dedicated individuals to join our team to assist us in achieving our goals. We pride ourselves on the technical knowledge of our staff. Do you think that the following statements describe you? Please put a tick in the boxes that do: Knowledge of electronics, particularly at component level. Assemble projects or kits yourself for car, computer, audio, etc. Have empathy with others who have the same interest as you. May have worked in some retail already (not obligatory). Have energy, enthusiasm and a personality that enjoys helping people. Appreciates an opportunity for future advancement. Have an eye for detail. Why not do something you love and get paid for it? Please write or email us with your details, along with your C.V. and any qualifications you may have. We pay a competitive salary, sales commissions and have great benefits like a liberal staff purchase policy. Advertising Index Amateur Scientist CD (House).OBC Acetronics..................................111 Send to: Retail Operations Manager - Jaycar Electronics Pty Ltd P.O. Box 6424 Silverwater NSW 1811 Email: jobs<at>jaycar.com.au Alternative Technology Assoc......49 Jaycar Electronics is an equal opportunity employer and actively promotes staff from within the organisation. Av-Comm...................................111 Altronics................................. 84-87 Dick Smith Electronics........... 26-31 Eco Watch..................................111 Elexol...........................................23 Satellite TV Reception disposals gear in the flea market. Exhibits by clubs and groups with interests ranging from vintage radio, packet radio, scanning, amateur TV and satellite. www.ccarc.org.au. Ph (02) 4340 2500. STOCK REDUCTION SALE: Every Friday 12pm to 5pm. Electronic components, switches, LEDs, displays, enclosures, connectors, crystals, relays, neons and many more. At Switches Plus Components, Unit 1 - 2 Sibthorpe Street, Braeside, Victoria. Phone (03) 9587 4044. ImageCraft C Compilers: 32-bit Windows IDE and compiler. For AVR, 68HC08, 68HC11, 68HC12, 68HC16. from $330.00 Atmel Flash CPU Programmer: Handles the 89Cx051, 89C5x, 89Sxx in both DIP and PLCC44 and some AVR’s, most 8-pin EEPROMS. Includes socket for serial ISP cable. $220, $11 p&p. SOIC adaptors: 20 pin $132.00, 14 pin $126.50, 8 pin $121.00. Full details on web site. Credit cards accepted. GRANTRONICS PTY LTD, PO Box 275, Wentworthville 2145. (02) 9896 7150 or http://www.grantronics.com.au WEATHER STATIONS: windspeed & direction, inside temperature, outside temperature & windchill. Records highs & lows with time and date as they occur. Optional rainfall and PC interface. Used by government departments, farmers, pilots and weather enthusiasts. Other models with barometric pressure, husiliconchip.com.au 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°. AV-COMM P/L, 24/9 Powells Rd, Brookvale, NSW 2100. Tel: 02 9939 4377 or 9939 4378. Fax: 9939 4376; www.avcomm.com.au Grantronics.................................111 Harbuch Electronics.....................61 Hy-Q International........................63 Instant PCBs..............................111 Jaycar ..................63-60,63,111,IFC JED Microprocessors................5,63 Microgram Computers....................3 MicroZed Computers....................83 Ozitronics.....................................62 NewTek Instruments.....................47 Nurve Networks...........................49 & MADE TO ORDER PCBs For more details: www.acetronics.com.au Phone (02) 9600 6832 email: acetronics<at>acetronics.com.au Prime Electronics.........................51 Quest Electronics..................63,110 RCS Radio.................................110 RF Probes....................................93 midity, dew point, solar radiation, UV, leaf wetness, etc. Just phone, fax or write for our FREE catalog and price list. Eco Watch phone: (03) 9761 7040; fax: (03) 9761 7050; Unit 5, 17 Southfork Drive, Kilsyth, Vic. 3137. ABN 63 006 399 480. THE PIC CLUB meets 6pm, 2nd Tuesday each month. We discuss PIC programming and project design. 1st Floor, Sydney Mechanics School of Arts, 280 Pitt Street, Sydney. Phone: 9593 1025. KIT ASSEMBLY NEVILLE WALKER KIT ASSEMBLY & REPAIR: • Australia wide service • Small production runs • Specialist “one-off” applications Phone Neville Walker (07) 3857 2752 Email: flashdog<at>optusnet.com.au Silicon Chip Binders.....................46 Silicon Chip Bookshop............98,99 SC Car Projects Book....................7 Perf. Electronics For Cars....112,IBC Silicon Chip Subscriptions...........43 Silvertone Electronics................110 Speakerbits................................110 Taig Machinery...........................110 VAF Australia................................71 ____________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: RCS Radio Pty Ltd. Phone (02) 9738 0330. Fax (02) 9738 0334. February 2005 111 From the publishers of The Lat SILICON s t n e t n o C UND TECH BACKGRO Intelligent turbo timer I SBN 095852294 - 4 TURBO BOOST & nitrous fuel controllers 9 780958 522946 $19.80 (inc GST) NZ $22.00 (inc GST) How engine management works We’ll let the contents speak for themselves: Not a reprint – new projects and articles not published before Learn how engine management works Build projects to control nitrous, fuel injection and turbo boost systems Switch devices on and off on the basis of signal frequency, temperature and voltage Build test instruments to check fuel injector duty cycle, fuel mixture and brake and coolant temperatures P L U S L O T S MORE 112 Silicon Chip t Managemen ng Engine stems work di an st er R 1: Und engine sy 6 CHAPTEhandle on how the various Getting a ement ine Manag anced Eng r ECU functions dv A : 2 R TE he 14 CHAP yond spark and fuel – ot Going be c Systems lled systems in a car er Electroni th O : 3 nically-contro R tro TE 20 CHAP rundown on the other elec A quick Systems pensive as Electronic ex odifying Carstems is not as difficult or M : 4 R TE electronic sy 26 CHAP Understa Systems ur car’s Modifying yo ink you might th n Modificatio Electronic right wires IY D : 5 R TE e 30 CHAP multimeter and finding th Using a ct Kits c circuits ronic Proje lding Elect successfully build electroni ui B : 6 R TE to basic skills 36 CHAP You only need a few , voltage er A Multimet – here’s how to measure eter TER 7: Using 40 CHAP make do without a multim can’t You resistance current and INSTRUMENTS Meter modes art Mixtureal time, see the operating TER 8: Sm 42 CHAP ur car’s fuel mixtures in re -load “lean-out” occurs if a high Track yo d be warned of the ECU an Cycle Meter devices o jector Duty cycles or use it to switch In : 9 R TE P ty 50 CHA monitor fuel injector du Digitally ads nt engine lo ometer off at differe igital Therm perature D to an incredible 1200°C m Te h ig H TER 10: D readout, can measure rature 58 CHAP mpe or LE D et te It uses an LC off at a pres vices on or can switch de SWITCHES AND TIMERS g rnal triggerin Auto Timer : Versatile er with lots of uses and exte 1 1 R TE P A le tim 66 CH se adjustab A multipurpo h – lots r the bonnet ltage Switc : Simple Vog the sensors already unde switching 2 1 R TE P A e in id 72 CH on and off us to nitrous ox es rol Switch devic and fan cont water-spray of uses from y up to ture Switch rk all the wa 3: Temperajustable design that can wo 1 R TE P A H ad 77 C ral-purpose A cheap gene C 5° 24 4 RS ICS FOR CA E ELECTRON PERFORMANC siliconchip.com.au S M test From CHIP off witch equency Syou switch devices on and TER 14: Fr 82 CHAP eap adjustable design lets This ch speed according to Timer ta Throttle on and off, based on how es TER 15: Del 86 CHAP tricky way of turning devic A really iving ally you’re dr enthusiastic ne anding Engi s – p.6 ONTROLLERS MODIFIERS & C Controller LCD Hand – p.105 r rrecto Speedo Co – p.129 r se Adjuste to reduce t : Digital Pul noids in your car – use it extra fuel in 6 1 R TE P A le an l d so ro lse nt 92 CH pu co e or th control of g assistance t Managemen Take eerin ge power st boost, chan r d Controlle Adjuster, Dig 7: LCD Hanprogram the Digital Pulse rcuits 1 R TE P A H r ci r to lle lle ro ro nt nt 105 C Co co t tronic Boos e this plug-in Us t Elec Independen Adjuster and daptor d Injector A u need this 8: Peak-Hold fuel injectors? – if so, yolse Adjuster 1 R TE P A H Pu -hol l ak ta gi pe Di 108 C ve , er ha your car Cycle Met Does e Duty tor to use th roller simple adap c Boost Cont ni tro ec El t en nd pe de In or el Adjustered to adjust air/fuel rat 9: Digital Fu 1 be us R -loop TE P A th H r to at can ange closed 112 C ltage intercep or swaps and even ch vo t an illi br A inject or er et m allow air-flow acteristics running char t will get – this projec Corrector 0: Speedo n or altered the diff ratio? 2 R TE P A H io 129 C ped out the transmiss rately again Swap reading accu r nic speedo st Controlle your electro ctronic Booost maps at the flick of le E t en nd depe rbo bo tween two tu PTER 21: In 134 CHAine being able to change be just that do u yo Imag ts is project le a switch – th troller even just to s Fuel Con el supply or R 22: Nitrouinjector for the nitrous fu TE P A H C 149 ntrol an extra Use it to co fan speeds vary pump or Timer rd you’ve gent Turbo atch how ha R 23: Intelliengine idle-down time to m TE P A H C 154 er set the This turbo tim been driving Engine Advanced t – p.14 Managemen ture Smart Mix Meter – p.42 Capacitor : Resistor & ENDUM 160 ADD Codes om Jaycar The Kits available fr and. See Ze Where To Buyoject described in this Abousoktralariae an d New al ery pr l over details. Kits for ev d dealers al for further s stores an ck covers ba e id Electronic ts ou front and the inside p.50 cle Meter – or Duty Cy Fuel Inject om.au siliconchip.c r t Controlle Turbo Boos – p.134 Turbo Intelligent 4 Timer – p.15 om.au siliconchip.c Order direct from SILICON CHIP Publications Price: Aust. $A22.50 (inc. GST & p&p); Overseas $A26.00 (inc. p&p via airmail). Silicon Chip Publications Pty Ltd, PO Box 139 Collaroy, NSW, Australia 2097. Phone (02) 9939 3295; Fax (02) 9939 2649. Email silchip<at>siliconchip.com.au siliconchip.com.au February 2005 113