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Thread: Dimmer Switch Question

  1. #1
    Automated Home Lurker
    Join Date
    Sep 2005

    Default Dimmer Switch Question

    When you have a dimmer switch on aything less than full power, does it consume proportionally less electricity?

    I mean, if you have the dimmer on 50% brightness, is it only consuming 50% of the electricity?


  2. #2
    Automated Home Sr Member jon00's Avatar
    Join Date
    Jan 2004
    Bromley, UK

    Default Re: Dimmer Switch Question

    In simple terms, yes. A standard household dimmer chops the AC waveform to reduce the brightness. They are not 100% efficient which is why they still get hot. Now the technical explanation:

    A light dimmer normally uses a semiconductor device called a triac which is placed in series with the light. Because mains supplies use alternating current at 50 or 60 Hz, the triac has an interesting characteristic in that it will turn its self off when the AC sinusoidal waveform reaches zero (i.e swinging between positive and negative at 100 times a sec with 50 Hz supply, 120 times with a 60 Hz supply). The circuitry of the dimmer allows you to adjust the delay before the triac will turn back on. The longer this delay, the dimmer the bulb will be. Because it is switching the light on/off (very fast) rather than just resisting the flow of current ( i.e by using a variable resistor), this is very efficient.

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