Joule Thief Charger Mod

[sucahyo]

At 200mA under load it drops to 80mA when load is removed.

I see. I think your circuit still can be improved. I hear some joule thief circuit will have less current under load if it run at resonant. My stingo mostly does.

[twofortheroad]

Joule thief circuits are self resonant, essentially they are just a modified blocking oscillator. But I'm always open to suggestions on how to make it more efficient.

[sucahyo]

Joule thief circuits are self resonant, essentially they are just a modified blocking oscillator. But I'm always open to suggestions on how to make it more efficient.

I see. I call it self oscillation. Circuit that can run it self and at frequency influenced by their component.

I consider resonant as the position of potentiometer where the circuit produce the greatest output at the smallest input. The purpose of potentiometer in joule thief circuit is to get that effect.

Reduced consumption with load may not be applicable to all joule thief circuit. I reach it before with my modified joule thief, but this circuit is hard to run and require start up touch:


I am satisfy with stingo now.

[twofortheroad]

I normally tune my circuit to output the most current without generating heat in the transistor or coil. About 200-250mA input. Beyond that too much energy is wasted as heat. The circuit is rather efficient as long as its running cool.

[sucahyo]

I normally tune my circuit to output the most current without generating heat in the transistor or coil. About 200-250mA input. Beyond that too much energy is wasted as heat. The circuit is rather efficient as long as its running cool.

I see. My transistor is generating a lot of heat but since it still do not heat up the battery, I still use it. I usually run it at 700mA input 12V to get 500mA output on two nimh.

[boguslaw]

How to measure output frequency ?

[sucahyo]

How to measure output frequency ?

Easy way is to use computer mic and see it in win amp with fourier transform or something. Some use radio, but the correct way is to use scope.