Joule thief is not working.

I just made a joule thief and my led is not lighting up. I put a single AA and it wont power. My led does though require 3.6v and i gave it 3.7v for a few seconds and the transistor became extremely hot. Is there something i am doing wrong?

I have a 1k resistor, a 2N2222 transistor, a led that requires 3.6v and 30ma, regular wire 26 awg, and a toroid bead.

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First thing to check: Is the LED backwards, embarrassingly enough I have made this mistake before while making a joule thief.
Second thing to check: The toroid. Is it wired correctly... did you wind it yourself or did you find it prewound. Important to double check. I have also made this mistake before.
Third thing to check: The transistor itself. While building the joule thief (I've built many over the years), I've occasionally run into a faulty transistor. Just replace it with another (You can buy 'em in packs of 15 at radioshack) and see if it works. ALSO make sure it is wired correctly.

These are just some general things to check that I've found to be the most likely reasons why a joule thief doesn't work.

Hope it helps!
Munchys (author)  transistorguy6 years ago
i have 3 different transistors. I have wired the toroid myself and wrapped wire around about 9-11 times. I have everything set up on a breadboard and when i give it 3.0-4.5v the led lights up but with only one 1.5v battery it wont light up.
I have had that problem myself. The easiest solution is that it is just a bad connection with the transistor. Make sure ALL of your breadboard connections are tight and snug! When I breadboard, I don't just push the pieces into the board, but I also use pliers to make sure the connections go all the way down. Double check all of the connections!

Also, I have found that one of the most troubling parts of this type of circuit is the toroid. Check that the toroid connections and winding are not only correct, but connected to the right parts of the circuit. This link may help:


I have found that whenever I make the toroid myself, I usually encounter problems like this. I prefer to buy them, but I can never find them to the specs I want! Ripping them out of old electronics is usually your best bet. If you want to make it yourself, just make sure your windings are correct. Double check them.

Best of luck!
Munchys (author)  transistorguy6 years ago
I believe a problem maybe me using solid wire instead of stranded.
Heres a pic of the circuit i made myself..
Thats a nice looking toroid. Good job. The solid wire shouldn't effect it. When you connect it to the circuit make sure you are using the right wires. What I mean by this is that The top green wire and the bottom blue wire should be connected together and to the battery. The others go to the transistor or resistor. For further clarification.... (if you have been doing so) don't attach both wires coming from one side of the toroid to the battery! You need to alternate sides.

Let me re-explain that:
(I am referring to the picture as I see it, the top part of the picture is the top, the bottom is the bottom.)
The two wires farthest left (The top green wire and the bottom blue wire) go to the battery. The other two go to the transistor or the resistor. Take your pick which goes to which, it doesn't matter much.

Good luck! If you have a breadboard (if you don't, I recommend one) its much easier to try these different configurations without having to solder any connections. All you have to do it plug them into the sockets.
Munchys (author)  transistorguy6 years ago
Thanks its working now!
I have a bread board as well, only i am us a .25" & 1.5" pvc pipe cut of and a 1k variable resistor using the 2 outside pins. Not working, don't have or want metallic cored toroid. Any help is greatly appreciated.
rickharris6 years ago
Too hard to fault find without seeing a) your circuit b) a good quality photograph of what you have built c) some more information about what it is / is not doing.