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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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LINK to Dave's circuit, but DO NOT COPY any files to your WEB
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AC Powered White LED Strings
May 14, 2007
designed
by David A. Johnson, P.E. |
| A while back a guy by the
name of Ken Schultz sent me a simple drawing of how he connected a string of 30
LEDs, to make a nice under the counter accent light, powered by 120vac. He
wired the strings in two series sections of 15 LED each, but wired in opposite
directions. |
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| He
then used just one capacitor to limit the AC current through the two stings. I
looked at the circuit and decided that it seemed quite reasonable. The only change
I decided to make was to add a metal oxide resistor in series with the capacitor, to act
as fuse and to limit the peak current, should there be a voltage spike on the AC line.
With the two strings of 15, the current is first pumped through one series string, then
as the AC line polarity changes, it flows through the second string. Since the
capacitor acts as a constant current source, you can use other string numbers. The
capacitor value shown keeps the current limited to about 20ma for the LEDs. In Europe
and Australia, where the line frequency is 50Hz, you may see a noticeable strobing of
the LEDs, if there is substantial separation between the two different polarity strings. |
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Soktha from France (soktha@free.fr)
sent me his version of this circuit, using two strings of 14, for a total of 28 white
LEDs. He mounted the LEDs onto a wood stick. When powered up from a 240vac 50Hz
source, the devices provided a nice white light. |
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Click on Circuit Below to view PDF of Schematic |
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