Looking for *CHEAP* source of spit core transformers

There are many cheap split core chokes that are designed to be clamped over cables. You could use those and wind your own transformer !

I made one out of a 20mm ring core by cutting it in half with a Dremel and abrasive disk. 50 turns of fine enamel wire wound on one half of the core works fine with my digital multimeter.

Its important to get the mating faces of the cut core as flat as possible so that they make good contact over the full area. I found that the hardest part to achieve ! I ended up using fine valve grinding paste on a sheet of plate glass to get good mating faces.

I made a mount from two strips of wood held by a single nut and bolt to hold the two core halfs together. Hot met glue was used to hold the core halfs to the wood.

HTH

Sounds good... I may give that a shot. Appreciate the advise. Jim

You're welcome. Report how you get on !

Why can't you just remove the wire from the breaker, slide a toroid over it, then reconnect the wire to the circuit breaker? The other problem; power is a lot more difficult to monitor than current. Mike

I've got a board that can do that, for exactly the same purpose:

I've got a prototype working (although on the bench, not in the box) but have yet to send out for my first batch of boards.

I'm planning on using non-split transformers, and just disconnecting the wires long enough to slip the transformers over them. Digikey has them for under $9 each, or $6.50/ea if you buy 25+.

Go to your local surplus shop and get a bunch of wall-warts for a buck apiece. Get an EXACT turns count by measuring, cut out the low-voltage secondary, and slip the wire under test through the winding window left by the secondary.

BE SURE and use the proper burden resistor, or you could electrocute yourself or start a fire.

Have Fun! Rich