detecting a c motor run


Does anyone have any thoughts on the easiest way to detect whether or not an AC motor is running?

I would like to end up with a 5 v max. signal, and all I am interested in is whether or not it is running.

The main objective is the ease of installation, as I would like to be able to just "stick" it on the motor itself without getting into the wiring.

Do you suppose there would be any kind of magnetic field sufficient to operate a magnetic reed switch or hall effect sensor or something of that nature?
I can't remember what it's called, but there is a device that simply encircles an electrical cord and senses when current is being drawn through it. Check out the HS site - I remember it being discussed there a while ago.
Digger said:
Current Sensor

Would this help? Its an ac output of 1 V peak to peak for every amp drawn. Its also just a plug in module.
thanks. I appreciate it.. .. that would be the cat's anus, but the stuff is going to be hardwired, probably with flexible conduit instead of plug and cord connected.

You'd think there would be some magnetic field around the motor that could be detected with something.

I have one hooked up with a 120v ac to 5 vdc solid state relay.
I'd really like to try to find something that didn't require disturbing the wiring, and could be just "stuck" on the side of the motor or something.
I like your original thought about a typical magnetic contact from an alarm system stuck on the motor - I meant to give this a try this afternoon out in the shop but it slipped my mind - happens often after 60. If you try it I would be interested to know how it works.
This seems to be the sort of thing I had in mind.

I think I'll look into cooking one of these jaspers up.

thanks all for your input