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DiscoverCircuits.com -- Hobby Corner
"Hobby Circuits for
your Hobby Projects"
Last Updated on:
06/19/2009 03:16:10 PM
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Ramping LED Driver
designed by David A. Johnson, P.E. |
Ramping LED Driver
The circuit below was designed to drive a LED with an intensity ramping mode.
Two 555 timers generate two different triangle waveforms. The upper device
generates a 10KHz signal while the lower unit produces a 1Hz signal. The two
signals are fed to a voltage comparator. The result is a pulse width modulation
(PWM) signal, which with the aid of the FET, drives the LED in such a way that its
average light output slowly ramps from about zero light to maximum and then slowly dims
back down. The circuit should operate over a supply voltage ranging from 3v to 12v. You
can easily vary the ramping time by changing the value of the 1M resistor. For an
interesting effect, you can place a 1N4148 diode in parallel with the 1M resistor, with
the cathode (banded end) side connected to pin 3. |
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Click on Schematic below to view PDF
version of this Circuit |
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