The joule thief is a simple electronic circuit made up of only three components, a transistor, a resistor and a basic transformer and can be used to drive small loads such as LED’s which can be supplied from a single AA cell. The joule thief will keep the LED’s glowing when the cell voltage is down as low as 0.5 volts, even though the forward voltage of an LED is over 2.5 volts, which means that more of the cells capacity can be used. For more information Google ‘The Joule Thief Circuit’.
This cache contains a modified joule thief circuit which drives a single LED that flashes at a fixed rate. It is powered by a single AA battery and is designed to run for well over a year.
Optional confirmation in logs, that the LED is still flashing, would be useful to determine the actual battery life.