Joule thief

Electronics Club

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I’ve been running an electronics club as an extra mural activity for students at my2013-11-14 09.10.38 school for several years now. We started off building simple kits such as Velleman, Kemo and RSE who are based in JHB (rse.apexmedia.co.za) but we have now started to branch out and build our own circuits. Students have built LED signs, radios and recently started to use Arduinos (www.robotics.org.za) to build more complex projects such as a tweeting weather station (www.twitter.com/ridgewayweather). One circuit I really want to get the new students to build is the joule thief. I’d never heard of it before I came across it on hackaday.com. The joule thief works in a very simple way. Basically take a used battery and the joule thief will build up a store of electrical energy in its toroid and release it as a pulse at a much higher voltage than the dead battery could – perfect for lighting up LEDs. At 40,000 times a second your eye can’t see the pulses, you simply see a working LED. I built a messy working version to test it out and have ordered all the parts of ebay. Let’s see if the students can build it – watch this space…


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