This Joule Thief uses three SS8050 high current transistors, each having a 333 ohm bias resistor (actually three 1k resistors in parallel). At less than a half volt, it gobbles battery current, 49 mA at 0.42 volts. That is a lot more than the typical JT, which drops to a very low current as the voltage drops below 1V. The JT will draw excessive current if the supply voltage rises above 3/4 volt. This circuit might do well on a single solar cell in broad daylight. It will work on two solar cells in series, which should give nearly a volt in broad daylight. But the solar cells should be matched to the circuit so that the current will not exceed the circuit’s maximum.
2013-04-21 Triple Transistor Low Voltage Joule Thief
good idea, but im confused a bout dtail of toroid!
I think I used a piece of cat5 cable for the wires. Three wires were wound trifilar, at the same time. Two were twisted together on both ends and used for the primary from the collectors to +1.5V. The third wire was used as the feedback winding, with one end connected to the +1.5V and the other end to the three 333 ohm resistors. This winding has to be connected opposite the others, just like every Joule Thief. If it doesn’t light up, you may have to swap the ends of only this winding.