Circuit - Universal 3v LED Flasher - Circuits designed by David A. Johnson, P.E.

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Circuits designed by David Johnson, P.E.

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Last Updated on: 06/18/2009 07:22:24 AM

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Universal 3v LED Flasher #1
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.

The circuit relies on a cheap 74HC14 hex Schmitt trigger inverter IC. One inverter forms a pulse generating oscillator. Other inverters are ganged together to increase the drive current. A two transistor circuit forms a constant sinking current controller.

Master Schematic Category List - David A. Johnson, P.E.