clamp on or tongs current meter

[BruceM]

Thanks for your good work and update on parts prices, 12gauge.

I also have the expresspcb files available for this homebrew AVR project- so those that would rather have a PCB can do that; but as 12gauge found, the mini transformers (pcb mount) parts were no longer available, so alternates would have to be found and the pcb layout adjusted for them.  ExpressPCB software is free, and the miniboard size of double sided board is about $61 including second day shipping in the US.

The circuit is simple  enough that hand wired on perf board is practical, and that does give you a lot more flexibility on parts.

For a 240V version, using a 300VA-500VA step down (to 120VAC) transformer for excitation is a good way to go.  It would be best if the line voltage sense transformer was 240V primary coil- it would then see line voltage independent of the load of on the step down transformer, but it will work either way.