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i need to regulate the speed of a noisy kitchen FAN from a microcontroller (arduino board), i have been looking around and checked a lot of websites and schematics, and i think the solution should goes to a TRIAC regulator I think...

The point is that i have no knowledge in power electronics and i don't know witch circuit is going to be good and reliable. I have seen some circuits that use only a TRIAC and others that uses a TRIAC and a DIAC... Why is the difference? and the DIAC function?

Could you provide me with some good schematics or recommendation form my situation?

thanks you very much :)

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Word or warning - TRIAC control will generate noise in the windings of the motor (fan) coils. This can be almost as annoying as a fan running fast. The problem is the TRIAC switching on part way though the cycle gives a current surge and the winding will physically move (not damaging) which makes the deep hum.

Also you need to check that you fan is a true AC fan and not what we call in the industry a EC fan. These are supplied by AC mains but have a internal PSU and then drive a DC fan - TRIAC control will not work on these fans.

However AC fans run very quiet if you run them of a step down transform, auto transformer which is good if you want a fixed speed.

I would suggest looking at getting a replacement fan if you want quiet operation. DC fans are easy to speed control with either a PWM input or by voltage regulating them (DO NOT voltage chop a fan - its kills them). Or look of a fan with speed control inputs, two speed AC or EC fan.

Just worth considering as a option from the start that all.

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