Power and voltage reference for two IoTaWatts using splitters?

Support
1

I’m thinking of bringing online a second IoTaWatt to measure more circuits.

Is it possible to power both and provide the voltage reference for both with splitters? E.g.:

Voltage reference:
3 Ways Daisy Chain Power Cable DC…
Arduino Power Supply Splitter…

microUSB splitter:
MicroUSB female to 2 MicroUSB male splitter…

2

You can split one but not both. My recommendation would be to split the AC ref with a CCTV DC splitter cable and use separate USB power supplies for the two units.

3

Not the OP, but out of curiosity, why can’t you split both? Just want to understand the technical limitation for my potential use case(s).

4

Creates a ground loop

5

Thanks.

Is the ground loop relative the USB V- or USB shield? Some devices bond V- and shield, does the IoTaWatt?

I ask because I’m trying to fit this into a recessed enclosure using a USB receptacle since I’m not sure I can fit the USB adapters. The receptacles generally have a pair of ports with isolated V+/V-, but usually bond USB shield to earth ground.

6

I don’t know. Schematic for ESP8266 is open so you can look it up. USB plugs are for chargers. I recommend actual power supplies. They are pretty small.

7

Just closing the loop on this one. The ESP8266 has a few design variants, but USB shield does get tied to system GND in some of them. Therefore, I agree with you that using a USB receptacle (with USB shield bonded to earth ground) is unwise.

I have switched to a larger enclosure and will be using USB power supplies (though probably will need to get ones with cords exiting vertically, but that shouldn’t be difficult). Thanks for the tips!