Dimmer Phase Control

Discussion in 'The Projects Forum' started by everythingRF, May 21, 2013.

  1. everythingRF

    Thread Starter New Member

    May 20, 2013

    I wish to build a "universal light dimmer" meaning the dimmer will be able to support both leading and trailing edge phase control of mains 120V/60Hz. Ideally, i would like the circuit to be able to auto-detect the load type (RLC) and select the appropriate phase control scheme to handle the load.

    I know there are commercial dimmers that do this. Does anyone have suggestions? It seems like it would be hard to determine based on the voltage-current phase relationship given that the current will be distorted relative to the line voltage.

  2. aws505


    Mar 11, 2013
    Hmm... Does it need to be able to do both? Perhaps you could just use a random phase dimmer, made of a triac and an opto-coupler, to dim nearly any load. Perhaps I'm overestimating such a circuit's abilities, but I believe that with a PWM you can control brightness pretty well.
  3. LDC3

    Active Member

    Apr 27, 2013
    I don't think you can dim fluorescence lights this way. If you cut the power before the maximum voltage is obtained, you reduce the voltage to the light. When the voltage has been reduced far enough, the light goes out. It may only dim a little when it goes out.
    See this page on "How Fluorescent Dimmers Work"
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    There are several mains dimmer circuits if you search for them.