light dimmer using triac-bt151

Discussion in 'General Electronics Chat' started by Kaiser Ed Bayawa, Jan 26, 2016.

  1. Kaiser Ed Bayawa

    Thread Starter Member

    Mar 19, 2015
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    is it okey to use a triac as light dimmer without a diac on its gate?
     
  2. Sensacell

    Well-Known Member

    Jun 19, 2012
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    You need something to control the triggering of the triac to effect dimming.
    Triac dimmers operating on AC use phase control to adjust the power delivered to the load,
    that's what the diac does in the circuit, along with the RC network.

    So no, it won't work without a diac.
     
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  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    A diac is just two 30V zener diodes back to back, it ensures that the capacitor charges upto approx 27V then it fires the triac.
     
  4. Lestraveled

    Well-Known Member

    May 19, 2014
    1,957
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    This is an incorrect statement. While it is true they both will not conduct until a breakdown voltage is reached, this is where the similarities end. A zener diode will stay at the breakdown voltage, the Diacs voltage will drop. It kind of acts like a spark plug.

    https://en.wikipedia.org/wiki/DIAC
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    In the past i made i dimmer using two zeners and it worked just as well, its better to use it with the diac as its designed for that purpose.
     
  6. Kaiser Ed Bayawa

    Thread Starter Member

    Mar 19, 2015
    60
    6
    Thank you sir. Can you please show me a diagram using zener diode instead of diac so that I can perform it easily.
     
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