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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Tuesday, June 01, 2021 03:06 PM
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More
Indicator Circuits
Micropower Circuits
Light Flashers |
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3v Low Battery Voltage Flasher
Circuit
designed
by David Johnson, P.E. |
| 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. |
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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
Flasher circuit in the January 2 issue of EDN magazine in 1997. |
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Click on Circuit Below to view PDF of Schematic |
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eMail David A.
Johnson, P.E. about this circuit |
