Circuit Project: 0.3 to 1.5V LED Flashlight

It’s a little wisp of a circuit that allows you to drive a blue or white LED from a low voltage. Normally, if you want to light up a blue or white LED
you need to provide it with 3 – 3.5 V, like from a 3 V lithium coin
cell. But a 1.5 V battery like a AA cell simply will not work. But using
the Joule Thief, it works like a charm. Not only does it work with a
brand new battery, but it works until the battery is nearly dead— down
to 0.3 V. That’s well below the point where your other toys will tell
you the battery is dead, so it can steal every last joule of energy from
the battery (hence the name). To learn how to make one, watch the
video, which is available in a variety of formats. [via]

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