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Which is more efficient: fan controller or inline resistor?

watdahel

watdahel

Limp Gawd
Joined
Dec 8, 2010
Messages
456
I looked at the circuitry of bay fan controllers and noticed how elaborate they are with rheostats, chips and transistors, capacitors and what have you, and they use heatsinks to cool it all down. Why do they use heatsinks? Is heat given off because they are inefficient? Are they using pulse width modulation by chance to slow the fan?

I am looking to silence some case fans and it looks to me a simple inline rheostat would do just as well without the extra circuitry. My main question is what are the advantages/disadvantages of a fan controller over a rheostat?
 
Fan controllers are voltage based. Rheostats are essentially variable resistors, and when they're handling up to 50 watts going through them, they need some sort of heatsink. So no, no PWM in most fan controllers, that requires even more elaborate hardware.

Chips and transistors are required for displaying RPM and other info for models with an LCD screen.

An inline rheostat would probably work, but you probably can't control much more than one or two fans with one rheostat. Of course, this depends on how many amps the rheostat is rated to handle.
 
If your fans will run off 7V it is really easy to use a Molex-Fan header adapter and just swap the 5V and ground lines to get 7V to the fan. A lot simpler than wiring in a resistor.
 
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