I want to make a joule thief to power a 10W LED (833ma @ 12v) from ~2 AA batteries, suggestions on toroid ? # of turns ?

My transistor inventory:

Part #          Package
TIP122       TO-220
TIP32          TO-220
2N2222      SMD
2N3904      TO-92
2N3906      TO-92
C1815        TO-92
BC546        TO-92

-max-2 years ago

Use a boost converter. Joule thieves are inefficient and cannot deliver much current. If you are determined to make one, use the TIP32 or the TIP122. They can handle higher currents and are more robust.

Nighter3D2 years ago

I doubt a joule thief is gonna work here. Joule-thieves are simply miniature Boost-converters and their ability is very low.

Even if you use a larger converter like a MC34063 based converter you would have to deal with a 9A current peak (according to calculations) which goes way beyond the rating of pretty much most if possibly all common transitor or inductors out there.

Sorry but you are asking for a very improbable circuit here.

More to the point, the internal resistance of an AA cell is not going to like letting you have 9A current peaks. There is, incidentally, no problem with 9A for a common transistor, or inductor.

The MC34063 is ONLY for low loads, unless you add an external switch etc etc. .

Never going to happen. A joule thief can't possibley provide that much power.