[Bird603568] sent in this sweet little LED hack that’ll drive a white LED from just 1.5 volts. The circuit consists of a pair of coils wound on a ferrite core, a resistor and a NPN transistor. He notes that the circuit still functions even at .35v. The version pictured is even small enough to fit inside a normal flashlight bulb base.
Joule thief LED driver
October 10, 2007 By 30 Comments