115V/230V synchronization signal for phase control

[cyberblak]

Hi,

Does anyone know a good synchronization circuit for digital phase control of an AC motor?

The circuit needs to generate a pulse (or an edge) at each zero-crossing of the mains voltage, and it needs to be isolated.

I should add that I need a circuit that is less power-hungry than a simple resistor with an optoisolator (the resistor dissipates a lot of heat!)

Any idea?

Thanks,

cyberblak

 

[IanP]

Take a look at the circuit below ..
Part of it, build around H11L1 and Q1, is an example of an optically isolated zero-crossing circuit .. (The H11L1 can be replaced by any similar opto-coupler, D1-D4 should be 1N4004 or any other diodes rated for 400V) ..

Regards,
IanP