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DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Tuesday, June 01, 2021 03:06 PM
Hobby Circuits List
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Blinkers & Flashers |
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HIGH INTENSITY LINE POWERED LED
FLASHER (Dec 8, 2008)
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There are times when you would like
to generate an intensely bright flash of light using electrical power from the AC
line. This hobby circuit below can drive a one to three watt power LED with
about 350ma of peak current. Since the circuit drives the LED with a constant
current, any LED color can be used. I have also shown how you could use an
array of 7 LEDs, wired in parallel. This array may not produce as much light
as the single power LED but the array would be cheaper to build.
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The circuit uses a classic Schmitt trigger oscillator,
which drives a constant current switch circuit. The components are selected so
the circuit produces a short 20ms flash with a flash rate of about 0.5Hz. A
high voltage capacitor in series with a bridge rectifier limits the current drawn
from the power line to about 5ma. A 47 ohm metal oxide resistor is used as a
fuse. Since the LED current pulse packs quite
a bit of energy, a fairly large 2,200uF capacitor is used to collect and store
energy from the power line between flashes. The capacitor voltage is limited
by a zener diode to 7.5v. A diode and capacitor circuit isolates the
oscillator voltage from the main energy storage capacitor. This isolation
insures that the oscillator frequency and pulse width remain fairly constant. |
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Click on Circuit Below to view PDF of Schematic |
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Blinkers & Flashers
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eMail David A.
Johnson, P.E. about this circuit |
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