Slowing down the ceiling fan with a incandescent light bulb as a resistor

Discussion in 'The Projects Forum' started by umetnic, Jul 18, 2015.

  1. umetnic

    Thread Starter New Member

    Jul 18, 2015
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    Hello 2 All! :D

    I have this ceiling fan, that is a 'little' 2 fast for my needs. It has 4 speeds. Off, 4,3,2,1.
    Sometime in the past I managed to successfully (no hum) slow it down with a help of incandescent light bulb, that added extra resistance.
    I forgot How I wired it, so I would like to check that part with You all.

    Should I wire it before or after the switch?

    Thank You & one Pleasant Day 2 all!
     
  2. #12

    Expert

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    All parts of a series circuit can be interchanged in any combination and the circuit is still the same circuit.

    However, I would place the resistance after the wall switch and before the speed switch if you want it to affect all 4 speeds. I'm having some difficulty imagining how to pick off one speed only because I'm thinking about the tapped inductor in my fan speed switches. I would have to get inside the selector to do that.
     
    Last edited: Jul 18, 2015
  3. crutschow

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    Mar 14, 2008
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    I have used a series capacitor to slow down a fan with no power loss or heat generation (or buzz).
    The capacitor size to get the desired speed reduction would likely be around 0.5 to 1 μF, non-polarized (such as speaker crossover capacitors), with a voltage rating higher than the peak power line voltage.
     
  4. DickCappels

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    Aug 21, 2008
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    As #12 stated, which side of the switch the resistor/capacitor is placed is unimportant electrically. There might be a slight safety advantage to putting it after the switch since it would be disconnected from the line most of the time.


    Edit: Corrected spelling of #12's name.
     
    Last edited: Jul 19, 2015
  5. Alec_t

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    Beware, if you try that trick, that the cap capacitance doesn't resonate with the motor coil inductance at the mains frequency or a harmonic; otherwise excessive voltage can occur across the coil.
     
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  6. crutschow

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    Have you observed that to be a problem?
     
  7. Alec_t

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    Yes. I once tried running a circulation pump with a series cap to reduce pump speed. The pump had a short life. On stripping it down and doing an autopsy I found charring around the coil terminations, suggesting arcing between them. Simulation of the pump + cap combo indicated a resonance with coil voltages around 900V. Mains voltage here is 240V.
     
  8. #12

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    You spelled my name wrong.:mad:

    :D
     
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  9. cmartinez

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    Could've been worse... could've been spelled #13 ... :p
     
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  10. Hypatia's Protege

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    Assuming a non-resonant condition: At 60Hz, 1uF will exhibit an Xc of > 2.6K thus limiting (240V) 'power availability' to a mere Ca. 22W!? --- Granted - If it works, it works! --- Though I'm bound to wonder if resonance is 'coming into play' after all...

    FWIW I'd just use a diode...:)

    Best regards
    HP

    PS: Then again, maybe not -- Some induction motors 'object' to 'mutilated' waveforms:(
     
    Last edited: Jul 18, 2015
  11. #12

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    I would certainly expect an AC induction motor to be irritated by monopolar excitation.
     
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  12. Hypatia's Protege

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    Indeed, perhaps an inductive reactor would be the safest route...
     
  13. #12

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    That's probably why all the fan speed controls in my house contain a tapped inductor for speed control. (They arrived in the boxes with the fans.)
     
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  14. cmartinez

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    I'd really like to see a schematic for that arrangement.
     
  15. #12

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    It's really quite simple. Power->SP5T switch->tapped inductor->fan motor.

    or did you mean to ask about an inductive nuclear reactor? :confused:

    Don't worry. It's just that HP uses different words than what we are familiar with. I can understand most of him because English is my first language and I have experience back to the 1950's when I was reading literature from the 1920's. A lot of changes in American have to be translated to/from British.
     
  16. cmartinez

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    That simple uh?... bit I'd like to understand how it works... gonna google it and find out, see if I can find some sort of animation
     
  17. #12

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    Xl = 2 Pi F L
    An inductor in series with a motor winding adds to the impedance of the winding without allowing all the magnetic flux (in the inductor) to act on the rotor. A capacitor brings in options for reduced impedance in a series circuit and/or series resonance. A resistance interferes with the phase relationships in the motor, but you can get away with it in small doses.

    If you want to see pandemonium, try limiting the current in an arc lamp (Hg, HPS, Metal Halide) with a capacitor instead of an inductor! :eek:
     
    Last edited: Jul 18, 2015
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  18. Hypatia's Protege

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    Reactors react and, hence, exhibit reactance -- seems plain enough?:cool:

    On the other hand, a 'nuclear reactor' would better be termed a 'crucible' -- Aye! 'Convention'! More formidable than 'City Hall' and infinitely better tolerated!:(;)

    FWIW I expect the cited lexical disparity owes to an abstract -- as opposed to empirical -- background...

    Best Regards
    HP:)

    PS: Non-inclusive pronoun use? Tsk Tsk Tsk! ;););)
     
    Last edited: Jul 18, 2015
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  19. #12

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    I didn't get any of that after the second sentence, even after checking a dictionary for 3 of the words. :eek::confused:
     
  20. cmartinez

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    If that's the way you feel... imagine how I feel with my limited english diction... :confused::oops:
     
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