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DiscoverCircuits.com -- Hobby Corner
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Tuesday, June 01, 2021 03:06 PM
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LEDs
Flasher |
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High Power
LED Flasher
August 3, 2008
, Circuit designed by David A. Johnson, P.E. |
| Power
LEDs are becoming more popular these days. The DC input power to these devices
ranges from 1 watt to 5 watts. Normal LEDs only receive about 0.05 watts.
At this higher power, these devices can emit a lot of light.
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You can
buy them in just about any color in the rainbow but white seems to be the most popular.
One application for these devices is a flashing light. If the flash duration and
flash rate is kept low, the average current can be low enough that even a small battery
can last quite a while. |
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The
circuit below is designed
to power any 1 to 5 watt power LED. It is designed
to run from a +3v supply, which includes two standard alkaline or NiMH
AA cells.
It uses a charge pump method to provide the higher voltage needed by white and blue
LEDs. It also has an active current liming circuit, set for 250ma. This
is sufficient current to produce an intense light flash.
The
circuit uses a classic two transistor oscillator to produce the pulse train.
With the components shown, the circuit generates a 20ms pulse at a frequency of
about 0.5Hz. The 2.7 ohm resistor sets the LED pulse current at about 250ma.
The average battery current is only 1.3ma, so a pair of standard AA cells should
power the flasher for about one month. This intensely bright flasher might
find uses in warning lights and might be great for those who ride their bicycle at
night. The intense bright flashes are impossible to miss at night.
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Click on Circuit Below to view PDF of Schematic |
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Flasher
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eMail David A.
Johnson, P.E. about this circuit |
