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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