post #11 of 11
Originally Posted by Xazen;12813368 
PWM is by far the best way to control the speed of a fan. There is no way that you will be able to tell that the fan is running on PWN from seeing it 'pulse'. The period of the waveform is way to small to be noticed by human senses. It simply supplies full voltage to the fan for a certain percentage of the period, call the duty cycle. But with the period being so small it keeps the fan at a constant speed.

PWM is pretty much the standard for powering DC motors of any kind. Its even used to control the brightness of LEDs by making them pulse, however its so fast that our eyes just see them as being dimmer.
It is an audible difference, not a visual one. It is very obvious when fans are running PWM rather than voltage reduced.