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Controllic Triacs (using optocouplers)

Discussion in 'Electronic Design' started by jodleren, Jun 25, 2007.

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  1. jodleren

    jodleren Guest

    Hi all!

    I am educated within eletronics, but that is 10 years ago. I have been
    working on a simple controller, which should turn on/off a 12VAC/1A
    (10W) line. For that I use an optocoupler and and a TRIAC. (before
    anyone asks - the 12VAC is not my call).
    It has to open 5 (1-9) times per second.

    I found this:

    My german is rusty too, so here it goes:

    I simply have a 1K resistor instead of those 2 and that is all.
    Could anyone explain me the idea of:
    a) the RC on the right?
    b) the 47nF condensator?
    Noise reduction?

    Next, I have a question regarding the optocouplers:
    Currently I use IL420 (IL4208) from Infineon. Using that it works.

    But S21ME4 from Sharp does not - it turns slightly on. Then again, the
    datasheets (from says "For triggering medium/high power
    As much as I read about it, the S21ME4 is cheaper, and may be able to
    drive the line alone, though I am not sure. It is also ~4 times
    cheaper than IL420. Maybe the ME3 (without zerocross detector may
    I am wondering whether it does not work @ 12V.

    But using a IL420 and BTA06 triac it works.

    I have a solution, I just want to know why it works as it does :)

    Sonnich Jensen
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