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DiscoverCircuits.com
-- Hobby Corner
Last Updated on:
03/19/2008 06:54:11 AM |
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3v Low Battery Voltage Flasher |
| Many battery powered devices use two AA alkaline cells. Often you will not
know when it is time to replace the batteries until the device powered by them actually stops operating. The hobby circuit below can be
connected to a 3v battery, to give you some warning when the battery is nearing its end of life. It will flash a LED when the battery
voltage drops to about 2.4 volts. The electronic circuit draws only 1ua of current in standby mode and jumps to only 20ua when flashing,
so it can safely be included without depleting the battery energy. A voltage detector IC from Panasonic (Microchip also makes similar
devices) is used to monitor the battery voltage. The device’s open drain output swings low, when the battery voltage is below 2.4 to 2.5
volts. This action turns on the two transistor oscillator circuit, which drives the LED with short current pulses lasting only 2ms.
I published this circuit in the January 2 issue of EDN magazine in 1997. |
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Click on Drawing to view PDF |
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