[dms-discuss] The Joule Thief - A simple maker project

[Bill King]

Today during MakerSpace hours, Julie and I made a Joule Thief. This is a
simple, cheap electronics project that uses a "dead" (well, mostly dead)
battery to power a small LED, which is a neat trick in that an LED needs ~3
volts to turn on and the "dead" battery is well below that. The "magic" is
in the way energy is stored in the coil's magnetic field and then dumped to
the LED at a higher voltage 50K times a second. Because of persistence of
vision, you see it as always on.

The only parts needed are:
1 - 1K resistor
1 - 2N2222 transistor
1 - ferrite core
~2 feet of very fine wire
1 - single cell AA battery case
1 - nearly dead AA cell


We can buy enough supplies to make 30-50 units for about $35.

If you're curious you can google <joule thief> or see Big Clive's version
(which is what we're making):
https://www.youtube.com/watch?v=K53beWYdIpc

This project teaches soldering skills and some basic electronics and gives
the participant something to take home. It takes about 15 minutes to wind
the coil and solder the pieces together. I'll offer it as a workshop, an
opening day project, or both.

This prototype was made from parts salvaged from a compact fluorescent
light bulb. If you have any dead CFLs I'd like to get them to make a couple
more to work out the build process. Some of the parts will come from China
so they're not immediately available.

thanks,
Bill
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