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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP FOR SALE tronixlabs.com – Australia’s best prices on a growing range of hobbyist and enthusiast electronics from adafruit, DFRobot, Freetronics, Raspberry Pi, Seeedstudio and more, with same-day shipping. Audio + Video: Professional quality Quest AV brand equipment is made and sold in Australia exclusively by Quest Electronics. Ph 0431 920 667. 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 LEDs: BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, tritium markers. We can order almost anything in! www. ledsales.com.au PCBs & Micros: SILICON CHIP Publications can supply PCBs and programmed microcontrollers for all recent projects. Order from our Online Shop at www. siliconchip.com.au or phone (02) 9939 3295. PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191. sesame<at>sesame.com.au www.sesame.com.au NIXIE CLOCK KITS SILICON CHIP July-Aug 2007 Full kits & spare tubes still available (For a limited time only) Phone 0403 055 374; Email glesstron<at>msn.com KIT ASSEMBLY & REPAIR 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 bigalradioshack<at> gmail.com KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith 0409 662 794. keith.rippon<at>gmail.com 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 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. Ask SILICON CHIP . . . continued from page 101 sinewave generator which will work with your computer’s sound card. Just do a Google search. Ultra-low-power LED driver wanted I need to drive a LED from a very low power source (1-1.2V with 200µA). siliconchip.com.au I’m less than a beginner at this stage and have built a ‘Joule Thief’ which won’t run that low. I have read about a Mosfet-based one that may do it and charge pumps etc (but they are such small chips and it looks very difficult to solder them without a microscope). Do you know of any circuits you could point me towards? (G. A., via email). • It depends on what you want from the LED. If you are saying that you only have a 1.2V supply and only want to draw 200µA, then the LED will not show much past a very dim glow. That is after the voltage is stepped up to sufficient voltage to drive the LED. Typically, indicator LEDs are barely visible at currents below 1mA. A Joule Thief will not be able to supply any more power than is available from the supply. If you want the LED to flash, then that might be achievable since the overall current will be low but LED current will be higher during the flash continued page 104 September 2014  103