Joule Thief Efficiency Testing

145

03:21:58

Just seeing where I can push a 20-turn JT circuit and maintain a relatively stable output.  Currently set to power a 3v LED with 0.9VDC.

published 10 years ago

thebugger

10 years ago

Usually joule thiefs can be made to work with as low as 200-300mV, as long as you use a germanium transistor. The only condition is that the Vcc must be enough to enable the transistor (that is the base voltage Vbe). For Si transistors the Vbe is 0.6-0.7V for Ge it is 0.2-0.3V

thebugger

10 years ago

And by the way 10H at 20 turns is an impossible transformer. Maybe not impossible but unfeasible

thebugger

10 years ago

The lowest i got to, was 670mV with EC's transistors, which simulate Si transistors. I bet i can get it to work at 200mV with Ge transistors. Whether it'll work in reality i can't tell

Khombhat

9 years ago

You're right about that transformer. Forgot that I had played with that parameter at all, actually. I had also never heard of a germanium transistor before. Going to have to look into that one. I know this circuit isn't very efficient at all and I really just built it to test out different cap, diode, and resistor setups. Transistors are fun little buggers.

Khombhat

9 years ago

Oh and I have actually physically built a joule thief using a Si transistor that worked at 400mV. It wasn't your typical winding though, not a 20/20 kind of thing.

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