Conversely a PWM controller for PWM fans – such as the one featured in this article – doesn’t modulate the 12V supply line but instead sends a PWM signal along a different supply line (the magic “fourth wire”) to a more advanced 12 VDC motor, leaving the 12 V supply line uninterrupted.

There are PWM controllers and there are PWM fans, but the way in which PWM is implemented in each differs greatly: a standard PWM controller modulates the 12 V supply line of an “ordinary” 12 VDC motor. The image below shows how different pulse widths affect the resulting power of the PWM signal: Three different PWM signals showing average voltage PWM Controllers vs. These on-off pulses are delivered to the motor several thousand times per second, and because the intensity (or width) of each pulse can be changed, so the speed at which the motor turns can be changed. Rather than being powered by a continuous supply of power (which would ordinarily be the case) our DC fan motor is being fed with pulses of power it is essentially being switched on and off very rapidly. Think of a PWM signal as if it were a beating heart.

Although you don’t need to understand the ins and outs of PWM, it helps to have a rough idea about how PWM works, so here’s a very quick explanation. PWM stands for Pulse Width Modulation and is, among other things, a very clever means of controlling power to electrical devices: in our case a DC (direct current) fan motor.

Fortunately, this neat fan controller project requires only a little time, expense, and commitment, and the circuit is relatively easy to build and very satisfying to use! First Things First…What is PWM? However, when it comes to building parts of your computer from scratch, the tally of enthusiasts who can claim this prestige most certainly diminishes. I’m sure that most hardware enthusiasts are no strangers to dalliances with DIY, whether it be case modding, component modding, or custom cooling.

Computer fan control