Trying the Joule Thief

I found a circuit at a website called the Joule Thief. It's a nifty LED driver circuit that can allow an LED to be driven from a nearly dead battery. I figured it would work to boost the voltage from the generators I had but I couldn't get it to work with my limited knowledge (and lack of caring to figure out how the circuit really worked.) I suspect it relies on the nature of LED's to oscillate properly.

I got a couple bigger 12-volt motors from the electric cars for kids to drive around in — all from the trash. The smaller one can source 8A at 0.5V or 4 watts, and the larger can source 9A at 0.6V or 5.4 watts … both at 3,100 RPM.