Needing help with Electrical question

[Rickster]

I understand that most incandescent dimmer switches are actually choppers, and just chop the AC utilizing a diac or a triac.

Simple schematic found here: clicky

Which functionally does this:

What is the difference in the incandescent dimmer switches and the fan control switches?

What's the schematic look like for one of these fan control switches that look exactly like the incandescent dimmer switches? Specifically, I want to know what the Lutron fully variable fan control does functionally.

(example part found here: Clicky )

 

[Rob]

Holly crap. I thought I was bored.

 

[Scoobyvroom]

A AC fan is normally spun by a induction motor, where current is applied to a winding and the winding creates magnetic force inside the rotor, even thought there are no permanent magnets. Using your standard dimmer like you said it chops the juice creating a duty cycle. The problem I think lies in the fact that there is not enought time to allow enought juice to create a stong enought field to spin the motor. It makes it either on or off. I could be wrong maybe an EE will pipe up. It dosen't vary the speed but it will vary the amount of torque the motor puts out.

 

[0Face]

:dntknw:

 

[Geezer]

I tried a light dimmer on a fan. The dimmer worked fine but heated up more than one would in a light circuit. I just assumed it was a variable resistor, like the fuel sending unit for your fuel guage, (so now this thread has a tie in to FJRs ) and wasn't made for the extra current that a fan draws.

 

[Rickster]

FWIW -- I took apart a light dimmer, and a fan controller.

Both use a triac and some circuitry to chop the AC.

The only difference is the values of the resistors and capacitors (the potentiometer is the same), so I conclude that the only difference is in the timing of how the signal is chopped. I don't have an o-scope handy, but I would guess that the signal for the fan control chops at the peak of the AC waveform to deliver 120 VAC as opposed to the dimmer that will chop anywhere along the waveform.

If anyone knows for sure -- I'd like to know.