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Joule Thief Troubles

I have built several Joule Thieves as seen in this video. None of them worked. Is the schematic wrong? I am sure that I used all the right components, and I wound the transformers right... What could be the problem? Could it be the ferrite core? I used one from an old computer power supply. Any help would be appreciated.

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guyfrom7up9 years ago
I could never get them to work. But I suspect that I always screw the toroid up, like connecting 2 wrong wires together so it doesn't all work right, or solder the wrong part to the transistor, etc.
The bifilar is tricky if you look at the signal with a scope the second winding is 180 out of phase. So the coils need to be reversed similar to the coral castle permanent magnetic holder. Which makes me wonder if the signal is now 360 out of phase and is that what makes the magic happen? The more you learn the less you know.
1up (author) 9 years ago
Hey, I finally got it to work! I guess the problem was the toroid. I used some thinner wire from an old printer cable, and I got on eleven turns. Expect a new Instructable soon!
Goodhart 1up8 years ago
That's great that you got it to work.....it was weird, but when I heard so many having troubles with that (both here and in the MAKE forums) I tried it, and it worked. Dumb luck I guess....seems like I wasted all my luck on that one project since none of mine from that time on has gone without a hitch first time through ;-)
on a project with a coil or a toroid, the problem IS always the toroid or the coil. Always.
I've "fried" a few transistors already, breaking "power contact" without the obligatory diode in place.....not on a Joule Thief, but other projects.....
i never had troubles with frying circuit parts, but almost 9 times out of 10 with toroids.....
I suppose it depends on the amperage being used.....I did a lot of Automobile modding when I had an old used VW....unprotected relays could reak havok on things, believe me :-) 
westfw9 years ago
Did you try reversing the leads on one of your coils? What exactly did you use for your core and how many turns of wire did you use? The recent video used rather fewer turns of wire than Big Clive's original (?) directions. What about your transistor? Are you sure you used the right pins - there are several common pin-outs.
1up (author)  westfw9 years ago
1. No, I didn't think it mattered... 2. I used a core from an old computer power supply, and I wound the wires 7 times. 3. I used a 2N3904 transistor, and I will try different pinouts. How can I tell what the right pinout is? What other transistors can I use?
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