The project involves sensing when a 240VAC motor is running. I would like to do this with maybe a coil wrapped around the motor power wires and feed this to an input on the MC, but not sure how to approach this. Thanks

Sparkfun has cool stuff - Non-Invasive Current Sensor - 30A

Thanks! Would you happen to know how this works? Does the signal need some sort or amplification? Also I'm interested in the physics behind capturing and processing a signal through induction

mag field due to current

Hall Effect Sensor

I don't know how the Sparkfun device works, but if you couple the basic physics of a mag field generated by a current in a wire, along with a Hall sensor, it should be not be too tough to make a current sensor.

Here is a thread on using the Allegro ACS712 Hall Effect Current Sensor. They will do up to 30amps.

Here is a 20 am module I got off ebay. They also have the 30amp module.

These will do DC or AC if you Google the web you will find examples of Arduino projects measuring AC current.

Ralph

Thanks guys! I think I can get something together from that.