Low battery indicator

Posted on Jul 30, 2012

The indicator flashes an LED when the battery voltage drops below a certain threshold. 2N4274 emitter-base junction serves as a zener which establishes about 6V on the L161`s positive input. As the battery drops, the L161 output goes high. This turns on the Darlington, which discharges Cl through the LED

Low battery indicator
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The interval between flashes is roughly two seconds and gives a low battery warning with only 10 µ A average power drain.

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