Again Dimmer :)

Discussion in 'The Projects Forum' started by denissoncs, Mar 9, 2012.

  1. denissoncs

    Thread Starter New Member

    Nov 8, 2011
    Hi guys!

    I'm trying to implement a dimmer to my bedroom. I was looking this projet from this site: <snip>, as far as I understood, the power sent to the lamp would be controlled by the potenciometer, and the DIAC is there to reduce the harmonics. I simulated this circuit first ou Multisim 11 and the values I suposed was right didn't work. Can anyone help me on how to correctly calculate these values?

    Last edited by a moderator: Mar 10, 2012
  2. jimkeith

    Well-Known Member

    Oct 26, 2011
    Actually, the DIAC is the triggering device--the harmonics are caused by the distorted waveform that is applied to the load. To reduce RFI, a small inductor is connected in series with the TRIAC that takes the edge off the current rise time thus attenuating high frequency harmonics. In dimmers, the low frequency harmonics are considered insignificant when compared with the total residential load--easy for the utility to handle--only in large industrial systems is harmonic reduction a serious goal.
  3. denissoncs

    Thread Starter New Member

    Nov 8, 2011
    Thanks for the help, I understood what you said. I found lots of dimmer circuits but all of them don't explain how they chose the values of the elements of the circuit.

    Someone know some reference that explain how to calculate each resistor, capacitor... or I must find by trial and error?

  4. wayneh


    Sep 9, 2010
    Ummm... Isn't this a mains-powered project and therefore an off-limits topic here?

    Either way, I recommend the OP proceed with extreme caution. So easy to get hurt.
  5. Georacer


    Nov 25, 2009
    The initial circuit was censored, since it was mains powered and therefore prohibited, according to the ToS.

    Please post an isolated circuit or the discussion can't continue.