1 Reference VT 2 IoTaWatts


Power points are at a premium here (along with space).

Can I put a Y cable on a single reference transformer (In this case the MP3027) and run it to both IoTaWatts to let them figure out their references? Or do I really need one reference per unit?


You can split the AC, but I strongly recommend buying one as maintaining polarity is very important. Also, the units cannot share a common USB power supply when sharing the AC. They must each have their own independent supply to avoid ground loops which can damage the units.

Interesting, what’s the mechanism for the ground loop over the AC?

Can I live without AC all together if I only care to get amps, not watts?

The AC signal rides on a DC bias.

No, you must have an AC reference. How about using a power strip?

yeh doh, that makes perfect sense, you’d think with all the eevblog I watch I’d have thought of that.

It was meant to live in a panel in the wall - one per panel under the main panels, there just wasn’t room for 2 outlets, now I’m looking for a cad drawing of the case (I could just go unplug one but… they’re in use now lol) so I can make a custom mounting plate to go on the outside of the panel that’ll let me get two transformers in the wall and keep it somewhat ‘wife friendly’

This is how I solved it.

I have two panels on each side of a stud with the iotawatt installed below in an enclosure.

A little time in fusion360 and 7 hours on the printer, now I have a room for a double adapter and a mp3027 (which btw is a massive transformer compared to the other 9v ac adapter I have)