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parth kothiya
parth kothiya
Associate III
May 5, 2019 12:06 PM UTC
Solved

Zero crossing detector which gives exact result op-amp or optocoupler ?

i want to control AC voltage using firing angle control for this which ic gives rising edge at exactly zero crossing point of ac sine wave op-amp or optocoupler?

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    Vangelis Fortounas
    Vangelis FortounasBest answer
    Associate II
    May 6, 2019 5:55 PM UTC

    Hi

    You used word "exactly" . The winner is op-amp.

    Optocouplers use LEDs. LED's "ON" forward voltage to is several hundreds of millivolts.

    Optocouplers also need to connect to a rectifier bridge to give ZC signal every zero crossing that adds some extra hundreds of millivolts to "ON" forward voltage that means extra hysteresis.

    In practice for 220/110V AC solutions the optocoupler is widely used, is cheaper, low BOM, and works fine for TRIAC controlled AC motors (washing machines) , resistive loads, etc.

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    1 reply

    Vangelis Fortounas
    Vangelis FortounasBest answer
    Associate II
    May 6, 2019 5:55 PM UTC

    Hi

    You used word "exactly" . The winner is op-amp.

    Optocouplers use LEDs. LED's "ON" forward voltage to is several hundreds of millivolts.

    Optocouplers also need to connect to a rectifier bridge to give ZC signal every zero crossing that adds some extra hundreds of millivolts to "ON" forward voltage that means extra hysteresis.

    In practice for 220/110V AC solutions the optocoupler is widely used, is cheaper, low BOM, and works fine for TRIAC controlled AC motors (washing machines) , resistive loads, etc.

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