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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP NIXIE CLOCK KITS KIT ASSEMBLY & REPAIR SILICON CHIP July-Aug 2007 Full kits & spare tubes still available (For a limited time only) KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith 0409 662 794. keith.rippon<at>gmail.com VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years experience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $10 inspection fee plus charges for parts and labour as required. Labour fees $35 p/h. Pensioner discounts available on application. Contact Alan on 0425 122 415 or email bigal007<at> internode.on.net FOR SALE questronix.com.au – audiovisual experts solve home, corporate security and devotional installation & editing woes. QuestAV CYP, Kramer TVone (02) 4343 1970 or sales<at>questronix. com.au PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au PCBs & Micros: Silicon Chip Pub­ lications can supply PCBs and pro- Phone 0403 055 374; Email glesstron<at>msn.com Television Replacements Your one-stop shop for all your electronic parts from aerials to zener diodes. 134a Ayr Street, Doncaster 3108 03 9850 4144 sales<at>tvr.com.au This month’s special: grammed micros for all recent (and some not so recent) projects described in the magazine. Order online or phone (02) 9939 3295. Log periodic aerials and digital set-top boxes. SOLAR PANELS LOW COST: full range 5W to 250W, eg: 40W/12V Poly $69, 130W/12V $169, 190W/24V $165, 200W/12V $225, 250W/24V $225, 230W Poly $190. AGM Batteries: 7AH $19.50, 9AH $24.50, 20AH $52.50, 55AH $129, 105AH $199, 220AH $399. (03) 94705851 or (03) 9478 0080 chris<at>lowenergydevelopments.com.au www.lowenergydevelopments.com.au 544 High St, Preston 3072, Melbourne. PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191. sesame<at>sesame.com.au www.sesame.com.au LEDs! Nichia, Cree and other brand name LEDs at excellent prices. LED drivers, including ultra-reliable linear driver options. Many other interesting and hard-to-find electronic items! www.ledsales.com.au Call or email for details GET INTO HAM RADIO AND SPEAK TO THE WORLD. Look at www. gscott. com.au for the best Australian books that cover the standard and the advanced licences. WANTED SILICON CHIP pays up to $60 for Circut Notebook items or you could win a $150 gift voucher from Hare & Forbes. See the Circuit Notebook pages in this issue for details. ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words plus 95 cents for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. to circulate. But the dissipation of the Mosfet at 20A is only about 0.5W and a bit over 1W at 30A. The real question with regards to how hot the PCB will get is how much additional dissipation there will be in the PCB itself, the wirsiliconchip.com.au ing and the solder joints etc. You would have to push it really hard to get the comparator beyond 85°C and even then it would be unlikely to fail. The ‘E’ versions probably come off the same production line as the ‘I’ versions but undergo more extensive testing to ensure their parameters don’t go out of spec between 85°C and 125°C. So there shouldn’t be any real problems with the circuit even continued on page 104 January 2014  103 Advertising Index Altronics.................................. 72-75 Core Electronics............................. 7 Emona Instruments...................... 43 Freetronics................................... 45 Gless Audio................................ 103 Hare & Forbes.......................... OBC Icom Australia................................ 5 Involve Audio.................................. 6 Jaycar .............................. IFC,49-56 Keith Rippon .............................. 103 Ask SILICON CHIP . . . continued from page 103 if the parameters did get a bit worse than specified (higher leakage, etc). It may shift the cut-off point a bit but that would be it. As for the diode clamp, you are right but luckily it isn’t critical. The divider resistors limit any current that might flow into the comparator’s input clamp diode to a safe level. Li’l Pulser controller is unresponsive I am currently building the Li’l Pulser Train Tontroller kit (SILICON CHIP, July 2013). However, the pot doesn’t seem to dial the voltage up or down and the brake & inertia switches don’t work. It powers up though and will go into reverse and shows 12V on the tracks. I am using a 12V switchmode power supply out of a PC, if that helps. I have cleaned all flux off and checked for dry joints/solder bridges/broken tracks and all seems good. I am just wondering what I should do? (A. C., via email). • The Li’l Pulser is designed to be powered from a pulsating 12V DC rail (that means the voltage swings up to around 16V) or from 15-17VDC. Running it from 12V DC will not necessarily work successfully and the regulator’s output will only be 10V or so instead of 12V. That may well affect the speed setting range. The fact that you can select forward and reverse suggests that pin 5 of IC3b is at a low voltage. The output of IC3b, however, is possibly high or the Mosfet is switched on continuously for some other reason. 104  Silicon Chip DOWNLOAD OUR CATALOG at www.iinet.net.au/~worcom WORLDWIDE ELECTRONIC COMPONENTS PO Box 631, Hillarys, WA 6923 Ph: (08) 9307 7305 Fax: (08) 9307 7309 Email: worcom<at>iinet.net.au One possibility is that transistor Q6 is the wrong type and/or diode D7 is the wrong way around. You will need to check that all components are placed correctly and orientated as shown on the overlay diagram. Footnote: the reader subsequently discovered that a 470kΩ resistor had been installed in series with VR2 & VR3 instead of 470Ω. KitStop.......................................... 93 LD Electronics............................ 103 LED Sales.................................. 103 Low Energy Developments........ 103 Master Instruments.................... 103 Microchip Technology..................... 3 Mikroelektronika......................... IBC Micro Engines................................ 6 Ocean Controls............................ 11 PicoKit.......................................... 10 Quest Electronics....................... 103 Radio, TV & Hobbies DVD............ 93 RF Modules................................ 104 Sesame Electronics................... 103 Silicon Chip Binders................ 11,78 Misleading power ratings on LED lights Silicon Chip Bookshop................. 81 I recently purchased four 27W LED floodlights from a local (Perth) eBay store. On testing them on a workshop power supply, I found they only drew 1.25A at 12V. They were rated at 1224V so I went up to 24V and the current dropped. The power was actually about 15W. On contacting the supplier, I had to teach him how to use his multimeter and Ohm’s Law when he tested one on his car battery. He agreed that they were not drawing 27W as advertised and offered a refund. I said that I would be happy at half the price and he agreed. The money was refunded quickly into my account. He then contacted his supplier and questioned the power rating. The supplier said that they were 27W as they were fitted with nine 3W LEDs. My supplier left his advertisement as 27W but changed the current draw to 1.25A. The current regulator Silicon Chip Subscriptions........... 19 Silicon Chip Online Shop............. 67 Television Replacements........... 103 Wiltronics........................................ 9 Worldwide Elect. Components... 104 xLogic............................................. 8 in the light prevents the rated power from being achieved. These lights are common on eBay and I am curious to know if others think that selling them as 27W with only a 15W power draw is misleading. (C. C., Mosman Park, WA). • A lot of products sold on the internet have misleading descriptions. Short of asking for a refund or a price reduction, as you did, there is not much else that can be done since any overseas seller is not subject to Australian consumer protection laws. In your case, the seller is subject to Australian law and is legally required to SC provide a correct description. siliconchip.com.au