[Dave Holmes]

Originally Posted by Luke Planemaker

Thanks Dave, I agree with RB, Magnifico!
So no problem running AC or DC motors, within the dimmer wattage rating then?

That is a qualified 'yes', or a definate 'maybe'.

You see, when the triac fires, it is part way into the half cycle of the sinusoidal AC waveform, so the current ramps up VERY sharply (in contrast to its normal rate.) Depending on the type of motor, it can run just fine (Like my Dremel motor tool without a built in speed controller) or it may just burn up, like some other motors I have toasted. I have found that certain inexpensive model train power transformers don't like it. They overheat and burn out.

Like I said, it is really best with a resistive load like a lamp, heater, soldering iron or such. When you get to fooling around with inductive loads like motors or transformers, it often works just great, but sometimes it smokes 'em.

I'll dig around and see if I have any figures that illustrate what is happening with the current if anyone really is interested. It should clarify it even more.

[Luke Planemaker]

So the lower the dimmer setting, the later the triac fires, and the less wave half=less power? I'm guessing because the current isn't a smooth sine wave, but more "spikey", windings heat up more?

The install manual states flourescent lights should not be used with these dimmers. In regards to motors, I guess it's try it and see if the magic smoke gets released!

[Dave Holmes]

Exactly!!

[uk.expat]

on the subject of fluorescent lights, dimmer switches will not work with fluorescents as they require a high voltage to strike up the gas in the tube,they get the high voltage when the starter breaks the circuit and induces a high voltage across.Dimmer switches should work with universal motors ie ac/dc motor which are brushed series wound,am I right in stating this.Been a while since I was at school.