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The circuit below will
flash any LED color with fixed current pulses powered by a 3v battery. It
uses a charge pump approach, which routes a constant current pulse through
the LED, regardless of the LED voltage requirement. Using this approach,
white and blue LEDs, which normally require about 3.6v can be flashed with a
3v battery. With the component values selected, the LED is hit with 15ma
current pulses lasting about 10ms every two seconds. This keeps the average
current draw from a 3v battery to about 200uA. |