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

[parth kothiya]

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?

[Vangelis Fortounas · Accepted solution]

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.