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Optimal way to turn off a triac

  1. May 25, 2015 #1
    I'm trying to use a triac to turn on mains power (fused) with and opto-isolator but what is a good method to turn it off, high on low off, I'm not trying to short the mains or use a bjt on high power ac. if someone could give me a hint i'll figure it out from there.


    edit: no relays
  2. jcsd
  3. May 25, 2015 #2


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    You are asking how to make a solid state relay.


    Just google "triac light switch" and look at the images to find one that looks like what you want to do.
  4. May 25, 2015 #3
  5. May 25, 2015 #4


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    I was just illustrating the concept. It helps if you don't keep secrets in the original post.

    Did you look at figure 5,6, or 7 in the moc3020 datsheet you linked to?

    Or, try figure 12 in the datasheet for the part you just posted a circuit for.

    It shows how to use the optically isolated driver to drive a power triac, which is what you need to do.

    Have you read anything about triacs? Maybe this will help.

    Here is a "make your own solid state relay" tutorial.
    http://letsmakerobots.com/node/38000 [Broken]
    Last edited by a moderator: May 7, 2017
  6. May 25, 2015 #5
    although I haven't read about triacs in a while I know their not what I want to use, half conduction was not what I was looking for, plus theirs still the problem with turning them off and just briefly looking at the datasheets and tuts about them they come with to many problems that I just don't feel like dealing with right now. this may be a dumb question but what do those figures have to do with anything?
  7. May 25, 2015 #6

    jim hardy

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    ???? half conduction ? turn them off ?

    maybe you need to read a little about triacs.
    They're bidirectional.
    They turn themselves off, just remove drive and wait for next sinewave zero crossing.

    If you want to turn it off mid-cycle you'll have to add a commutating circuit.
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