Harbor Freight free flashlight plus joule thief

[dchomak]

We like free flashlights and Joule Thiefs here.
Here is a short discussion on them here at BLF

Experimenting with the Joule Thief circuit

Out of boredom I got interested into the Joule Thief circuit. Yesterday I built two of them using a 2N3904 transistor, 1k resistor, 10mm warm white LED and two different handwound coils. One of the coils is a larger toroid with 10 turns on it, the other one is a smaller one with six turns. So far both of them work just fine. The current draw from an eneloop cell is 40 mA with the larger and 44 mA with the smaller coil. I will make a third one tomorrow with an even smaller toroid with only fou…