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Circuits designed by David Johnson, P.E.
Last Updated on:
Friday, March 23, 2012 06:11 AM
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More
LED Circuits, Flashers |
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Wireless LED
Flasher -- January 9, 2011 |
| There are times when you
would like to flash a LED through a thick plastic case without wires. The
circuit below performs this feat. It can be powered from a supply ranging from
3v to 6v. It draws about 300ua of average current at 5v. It uses a low power op amp as
a pulse generator. A negative going pulse from that generator gates a power
oscillator on for about 20ma. That oscillator is connected to a series resonant
circuit, which drives a small coil. |
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Feedback from the coil insures that the oscillator runs at the LC network’s resonant
frequency. A similar coil, located some distance away, collects some of the magnetic
field produced by the oscillator’s coil and uses it to drive a LED. A separation of
about 1/2 inch is about the limit for this circuit. |
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Click
on Drawing Below to view PDF version of Schematic |
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