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Tuesday, June 01, 2021 03:06 PM
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Low Power Sequential Flasher using 10 LEDs -
April 17, 2011 |
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A
while back I posted a flasher circuit which flashed 10 LEDs sequentially. That
circuit was powered by four AA alkaline cells. The circuit below operates much
the same way but has been modified to run from a single 3v CR2032 lithium coin cell.
The average battery current drain is a low 400uA. |
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Yet, by using
some super bright green surface mounted LEDs from King Bright, the effect is quite
impressive even if each LED is driven with only 2ma of current.
The circuit
completes a cycle of the 10 LEDs once each second. A LMC7215 low power voltage
comparator is configured as a 10Hz 20ms pulse generator. This 10Hz clock is
fed to a 74HC4017 decade counter. The 4017 is unique in that it has 10 outputs
which turn on sequentially with each leading edge of the clock input. The LEDs
are all ganged together and connected to a constant 2ma sinking current circuit.
As the battery voltage drops, the circuit will maintain a constant 2ma of current. |
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The 10 LEDs can
be configured into a loop or a line. A loop display might be handy for dog
collars. A line mode can convey a right or left pointing direction. |
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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 |
