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MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP FOR SALE 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 tronixlabs.com - Australia’s best value for hobbyist and enthusiast electronics from adafruit, DFRobot, Freetronics, Raspberry Pi, Seeedstudio and more, with same-day shipping. PCBs & Micros: SILICON CHIP can supply PCBs and programmed microcontrollers and other specialist parts for recent projects and some not so recent projects: www.siliconchip.com.au or phone (02) 9939 3295. KIT ASSEMBLY & REPAIR LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience 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 bigal radioshack<at>gmail.com PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191. sesame<at>sesame.com.au www.sesame.com.au DAVE THOMPSON (the Serviceman from SILICON CHIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Phone NZ (+64 3) 366 6588 or email dave<at> davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith 0409 662 794. keith.rippon<at>gmail.com 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 94 similar to those used in Triac-based light dimmers and while they can vary the speed over quite a wide range, they can also produce quite a lot of interference to AM radio reception. To cope with the radio interference problem, we produced a linear (ie, non-switching) design in the May 2014 project, a Deluxe 230VAC Fan Speed Controller. Essentially, this circuit rectifies the 230VAC mains and the fluctuating DC is then varied by a series Mosfet. You can see a 2-page preview at www.siliconchip.com.au/Issue/2014/ siliconchip.com.au May/Deluxe+230VAC+Fan+Speed+ Controller Finally, the most common motor used where high power is required is the induction motor which has no brushes, commutator or slip-rings and relies on an induced rotating magnetic field to drive the rotor. This type of motor is essentially constant in speed as it is locked to the 50Hz mains frequency. These are commonly used in pumps, refrigerators, air-conditioners and so on. The only practical way to control the speed of such a motor is to produce a circuit which varies its operating frequency and voltage. We have produced one such design, along with a number of revisions and additions which can all be found on our website if you search for “induction motor speed controller”. However, the main design was featured in the April & May 2012 issues and was revised in the December 2012 issue. You can see a 2-page preview of the April 2012 issue at www. siliconchip.com.au/Issue/2012/April/ 1.5kW+Induction+Motor+Speed+Co SC ntroller%2C+Pt.1 Next Issue The February 2016 issue of SILICON CHIP is due on sale in newsagents by Monday 25th January. Expect postal delivery of subscription copies in Australia between January 25th and February 5th. January 2016  95