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rowan · 03-08-2007, 03:19 PM

LEDs can certainly be dimmed, just vary the current. That's why I asked earlier about the value of the resistor you used and whether you were satisfied with the light output.

Looks like you're using 240 ohms, which at 2 x 3.5V forward drop would work out to roughly 8mA of current. Check the specs to be sure, but it's likely the ones you have can tolerate more than double that. To limit the current to 20mA for the two LEDs in series with a 9V source you'd use a 100 ohm resistor.

To add dimming to your existing light just put a wire wound potentiometer in the "+" line between the battery and the array, say 1000 ohms. It needs to be wire wound (5 watts) because I don't think a standard pot would handle that current.

03-08-2007, 03:19 PM
rowan Too lazy to set a custom title Join Date: Mar 2002 Location: Australia Posts: 17,393	LEDs can certainly be dimmed, just vary the current. That's why I asked earlier about the value of the resistor you used and whether you were satisfied with the light output. Looks like you're using 240 ohms, which at 2 x 3.5V forward drop would work out to roughly 8mA of current. Check the specs to be sure, but it's likely the ones you have can tolerate more than double that. To limit the current to 20mA for the two LEDs in series with a 9V source you'd use a 100 ohm resistor. To add dimming to your existing light just put a wire wound potentiometer in the "+" line between the battery and the array, say 1000 ohms. It needs to be wire wound (5 watts) because I don't think a standard pot would handle that current.