Tuesday, 20 May 2008

LED dimmer circuit


Using the circuit from the Renewable Energy UK website I breadboarded an LED dimmer. Again, if I could draw a circuit diagram on the computer I would.

I used just one "string" of three LEDs with a 140 ohm resistor in series. Apart from the 555 timer IC (59p (I think) from Maplin) all the components came from my drawers (ooer, missus). It worked extremely well: the LEDs not dimming completely, as predicted, but at "full" brightness they looked bright enough.

Measuring the voltage at "full" I found:

10.2V across the three LEDs in series, i.e. 3.4V across each LED.

And a lot less power was consumed by the electronics - I used a (small) BC546 transistor which didn't even get warm.

An interesting side effect of taking the photo: when pointing the digital camera at the LEDs the camera's CCD sensor shows you the mark/space ratio on the screen!

There's more to do, as I now want to combine the voltage regulator with the dimmer.

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