I have a 4 channel fanbus on my Antec P160. Since the case has 2x 120mm fans there are 2 unused knobs. I was considering using them to control the brightness of some LEDs in my case; 3x in front air intake & 3x in side window. The fanbus is a Noise Isolator 3.5" and uses PWM. I assume that since it uses pulse width modulation I can solder in the correct resistor (for 12V) and this will make sure the 12V pulses become (the appropriate) 4V pulses. Am I correct?
I'd try picking a resistor to run the LED at much less than "normal" current, you'll get a better dimming effect.
I kinda assumed the PWM factor would give a linear drop off regardless of nominal intensity. So then it would be a matter of trial and error to get the resistor value that gives the best effect. Though hopefully not so low that I will have to buy brighter LEDs.
I would see about finding some 100 ohm, trimmer pots,that you can put in series with the resistor, to trim the resistance to exactly what you need.
It's also worth noting that quite a few fanbus PWM controllers operate at a switching frequency of around 20-30Hz, anything below about 85Hz is going to be observable as flickering of the LEDs in a purely resistive circuit. So it's worth checking before you start any major modding.
