For 0 to 100 %  speed variation you need a frequency variator and not a
dimmer.
Ac motors ( rotor in short circuit, squirell type ) can't be controlled
more than 10...15% near full speed by controlling voltage supply.
Alternatives: use a DC motor ( or an AC with brushes ) and a dimmer
style circuit; use a slow PWM ( on-off) to get a medium speed control
between 50...100%.

best regards, Vasile



On Wed, 27 Feb 2002, Lee McLaren wrote:

> I am trying to find a circuit to control a mains (240v) AC fan motor. I need
> to control the fan speed from 0 to 100% so I dont think I can get away with
> a dimmer type triac controller. Does any one have any links or sugestions?
> Preferably the controller can be controlled by a PIC chip but an analog
> circuit would do for a start. The motor will only be around 50watts.
>
> Regards
>
>
> Lee McLaren
>
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