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airspirit · 12-03-2002, 10:36 AM

I learned a good lesson last night/this morning:

Ceiling fan controllers DO NOT work right for controlling AC fans. Neither do dimmers. Not potentiometers or rheostats. You cannot cheaply control fan speed without creating crazy fan noise (obnoxious buzzing that is louder than the fan itself).

The only thing that will do this correctly is a Variac Transformer. The ceiling fan controllers and such are Triac based just chop off a portion of the sine wave causing all sorts of chaos and you risk burning your fan up and possibly your house down. A Variac transformer with the correct W load rating can provide a smooth transition from 0-X VAC while keeping the integrity of the the AC sine wave (no chopping). The downside of these controllers is that they are expensive (120 VAC/3A 0-130VAC output at Allelectronics is $45 + s/h).

For all of you considering AC fans to cool your machines, keep this in mind. While there is a solution that will work, it is not a cheap one. Going with a cheaper method such as a dimmer will cause more noise than it will prevent.

12-03-2002, 10:36 AM	#1
airspirit Been /.'d... have you? Join Date: Jul 2002 Location: Moscow, ID Posts: 1,986	Lesson: AC Fan Controllers I learned a good lesson last night/this morning: Ceiling fan controllers DO NOT work right for controlling AC fans. Neither do dimmers. Not potentiometers or rheostats. You cannot cheaply control fan speed without creating crazy fan noise (obnoxious buzzing that is louder than the fan itself). The only thing that will do this correctly is a Variac Transformer. The ceiling fan controllers and such are Triac based just chop off a portion of the sine wave causing all sorts of chaos and you risk burning your fan up and possibly your house down. A Variac transformer with the correct W load rating can provide a smooth transition from 0-X VAC while keeping the integrity of the the AC sine wave (no chopping). The downside of these controllers is that they are expensive (120 VAC/3A 0-130VAC output at Allelectronics is $45 + s/h). For all of you considering AC fans to cool your machines, keep this in mind. While there is a solution that will work, it is not a cheap one. Going with a cheaper method such as a dimmer will cause more noise than it will prevent. __________________ #!/bin/sh {who;} {last;} {pause;} {grep;} {touch;} {unzip;} mount /dev/girl -t {wet;} {fsck;} {fsck;} {fsck;} {fsck;} echo yes yes yes {yes;} umount {/dev/girl;zip;} rm -rf {wet.spot;} {sleep;} finger: permission denied