Dimming white leds

Thread Starter

boatsman

Joined Jan 17, 2008
186
I have an array of 12 white leds powered by three AAA batteries. The light they emit is bright. I want to be able to adjust the intensity of the array from off to full brightness. If I just use a potentiometer the leds are either on or off. How can I make a simple dimmer?
 

wayneh

Joined Sep 9, 2010
16,398
There are several simpler circuits that folks use, but PWM as recommended by Bertus is the best, especially if you want a nice full range of control.

The second best approach is probably the LM317 based circuits.

Last choice is what you already tried. It could be made to work, but a potentiometer that can handle the power will be more expensive.
 

LDC3

Joined Apr 27, 2013
924
There are several simpler circuits that folks use, but PWM as recommended by Bertus is the best, especially if you want a nice full range of control.

The second best approach is probably the LM317 based circuits.

Last choice is what you already tried. It could be made to work, but a potentiometer that can handle the power will be more expensive.
Did you notice that the power is coming from 3 AAA cells? The voltage is about 4.5 V and probably has a current less than 100 mA. A 1/2 watt potentiometer is probably cheaper than building any circuit.
 

DickCappels

Joined Aug 21, 2008
6,459
It sounds like your basic problem is that your pot (actually used as a rheostat in this case) has too high of a resistance. Try a lower resistance part, such as 10k, 5k, or 1k and you will not see the on/off effect.
 

THE_RB

Joined Feb 11, 2008
5,438
The PWM solution will be a lot more energy efficient (ie give longer battery life) than just using a resistor (or large pot).

It will also give a better light quality when dimmed.

That makes it a better option, even though it takes more effort to build.
 
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