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DiscoverCircuits.com -- Hobby Corner
"Hobby Circuits for your Hobby
Projects"
Last Updated on:
06/19/2009 03:19:11 PM
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Ultra Low Power LED Flasher
December 18, 2008
designed by David A. Johnson, P.E.
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| The efficiency of some newer
LEDs is amazing. Some of the latest green LEDs can launch blinding light with just
one milliamp of current. I take advantage of one of these newer devices in the
circuit below. The flashing circuit uses a classic multivibrator oscillator, made from a
tiny National Semiconductor’s LMC7215 low power voltage comparator. The circuit
produces a short 10ms pulse every two seconds, drawing power from a 3v supply. I
suggest using a surface mounted green LED from Kingbright. Although the LED peak current
is restricted to just one milliamp, this part generates a very bright flash of light. The
circuit draws and average DC current of only 6 microamps from a 3v supply. When
powered by a small lithium coin cell with a 100ma-hour rating, it will flash for about two
years. This flasher might be a great add-on circuit for a flashlight, a key chain or
even attached to a cell phone, so the thing can be found in the dark. Another
application might be for a fake car alarm indicator. The circuit might also be used
in conjunction with some other battery powered product, to let the user know when it is in
operation. The small 6uA current drain would not tax even the most stingy power
budget. |
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Schematic below to view PDF version of this Circuit |
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