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Timer on reduced-frequency circuit

Discussion in 'General Electronics' started by Lacustral, Aug 1, 2007.

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  1. Lacustral

    Lacustral Guest

    I'm thinking of using a variable speed control and a timer in series.
    Would a timer have trouble with the lowered frequency electricity from the
    speed control? WOuld an electronic timer run OK that way?

  2. Jasen Betts

    Jasen Betts Guest

    maybe, but the easy fix is to put the timer before the speed control.
    you don't need to power the speed control when not using the fan.

  3. Arfa Daily

    Arfa Daily Guest

    Firstly, a variable speed control does not affect the 'frequency' of the
    supply current. It does, however, have a profound effect on the waveshape,
    if it is electronic rather than passive, and this may well affect an
    electronic timer's ability to work correctly, as opposed to keeping time,
    which I presume is your reason for asking about frequency. If you put the
    timer ahead of the speed control, there will be no such issues, as the timer
    will only be fed with 'standard' line power, which it will then pass thru'
    to the speed control during one of its 'on' periods.

  4. I assume you mean a common thyristor phase control, not one that actually
    changes the frequency of the power, though the same comments apply.

    If you mean put the timer first which plugs into a wall socket and then the
    switched output of the timer goes to a variable speed control, there should
    be no problem. The timer will run off the unmodified power.

    However, if it is an electronic timer that is in series with the load ONLY
    then this is probably not a good idea unless the timer manufacturer
    specicially states that it is permissible.

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  5. Lacustral

    Lacustral Guest

    Probably. A guy at an electric store said it changes the frequency, which
    sounded weird to me. But no, it would be an ordinary speed control. I
    vaguely remember reading about phase affecting power delivery in a physics
    I see - that makes sense.

  6. Jasen Betts

    Jasen Betts Guest

    Some speed controls do (a device called a variable frequency drive),
    but that is for large industrial motors, small fan speed controllers
    just reduce the voltage that the fan gets.

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