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I purchased a ceiling fan a while back which is one of those fancy ones that is operated with a remote control. However, for some reason, the remote broke, and the fan is stuck on maximum speed, I can turn it on/off by the wall switch and that's it.

Is it possible to manually control the fan speed by installing a light dimmer switch?

migrated from electronics.stackexchange.com Feb 6 '16 at 22:05

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Light dimmers use triac based phase control for dimming purpose. It chops the sine wave somewhere in between depending upon the knob position, which produces a signal like this:

Phase control

(a) is pure sine wave. (b) and (c) represent modified sine wave going to the appliance depending upon dimmer knob position. This works well for dimming an incandescent bulb because they give off light based on heating of the filament.

However when you give this waveform to a ceiling fan, it won't behave very well. Most obvious issue will be a humming sound specially at a lower speed (corresponding to signal (b)). Lesser obvious issues might be increased energy loss in the coil.

Nowadays companies have started using a series capacitor to reduce the voltage while maintaining a sine wave which eliminates humming while reducing the fan speed.

  • Actually many motor speed controls work the same way - you are right that it doesn't work well at extreme speed reduction but it can still be useful. The trick is that the a motor-drive Triac circuit is protected against the inductive load, unlike a lamp dimmer which usually isn't. – Chris Stratton Feb 6 '16 at 17:00
  • waveform above is obviously wrong, (hint: plot motor current), – Jasen Feb 6 '16 at 20:07
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Always best to get the word directly from the manufacturer, as some newer fans are implementing DC motors.

The common incandescent/halogen dimmer is not designed to work with the typical induction motor ceiling fan. However, induction dimmers commonly referred to as low voltage magnetic dimmers, are sometimes reported to work with induction ceilings fans. But, best advice is to use what the manufacturer has tested and supports.

  • @Jasen. Although it does not solve the OP's problem or answer his question, just because you have not seen it doesn't make it reality, ever. There have been belt-driven ceiling fans for years and years, do an internet search. Antique ceiling fans were belt driven by necessity, sometimes several were linked together with drive belts. Speed control was accomplished with different sized pulleys. – Jimmy Fix-it Feb 7 '16 at 6:28
  • steam powered fans, cool! – Jasen Feb 7 '16 at 6:38
  • @JimmyFix-it Kris changed his answer soon after my comment - it now says "DC" – Jasen Feb 7 '16 at 6:40
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yes, but it works better if you use a fan speed controller, lamp dimmers have the wrong switching profile and cause excess heating a low speeds

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    This misses that a while you can run a motor or a lamp from the same conceptual sort of TRIAC circuit, a "lamp" dimmer generally will not have a drive circuit sufficiently protected against the reaction of an inductive load like a motor. It might fail immediately, or it might fail at some random point in the future, but there's a quite good chance that it will fail - and it may fail "on". – Chris Stratton Feb 6 '16 at 16:58
  • this, is strue a different triac circuit is needed. eg:cache.freescale.com/files/microcontrollers/doc/app_note/… – Jasen Feb 6 '16 at 20:07
  • this is not new technology, they were available on the 1990s, and are all over the web now: search buy electronic fan speed control – Jasen Feb 6 '16 at 20:55

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