LED Brightness

[W-L]

I got a roll of these LED light strips and wanted to use it for some desk lighting but it's be nice if I could add a dimmer. I saw that my local hardware store had potentiometers and wanted to know if that's be a good solution or if it'd need another method to dim the light.

 

 

LED light strip:

http://i.ebayimg.com/00/s/NTAwWDUwMA==/$(KGrHqV,!nMFBkEtlQgiBQclCWj))!~~60_12.JPG

 

 

Potentiometer:

http://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Potentiometer.jpg/225px-Potentiometer.jpg

 

[Oisin Maguire]

NO just nonononononononono

 

sorry leds are not an ohmic device simply placing a smaller voltage across them makes no difference {unless you want to break them}. what you need to do is decrease the current, the 'standard' voltage drop across a led is 1.5 volts and is very bright with a current of 0.5 amps.

what you should do is buy an op-amp{id go with an 8-pin 411} and 5 resistors and a potentiometer and set them up as a constant current source. the potentiometer in this way is used as to set a variable current by varying the resistance.

[W-L]

Hmm seems a little complicated, I did read that LED's work well with PWM voltage controls, would that be a simpler solution if i were to purchase one of those?

[Oisin Maguire]

Hmm seems a little complicated, I did read that LED's work well with PWM voltage controls, would that be a simpler solution if i were to purchase one of those?

Well no its not the voltage you want to regulate its the current you want to change but you want to keep the voltage across the leds constant.

 

{that being said you could use a PWM as the controller but what your doing there is effectively turning the leds fully on and off again fast enough that it looks like the light is dimmer, if thats what you want, its not going to be that the leds are less bright its that there on for less time}

 

[its really to do with the eye and ccds having an integration period or integration time(image a strobe light)] we dont see each photon by photon we see the averaged photons over integration period.

[W-L]

Ok cool I'm probably going to try it with PWM controller first then thanks for the advice (: