Setting up multiple IoTaWatts

I am installing two colocated IoTaWatts. One on a main panel and one on an adjacent direct fed sub-panel. I have three somewhat related questions:

  1. Can the two (or three) IoTaWatts share a single voltage reference transformer without causing problems? I.e. use a splitter cable.
  2. Can the IoTaWatts be powered from a single multi-port charger of sufficient capacity?
  3. I have an UPS nearby. Does powering the IoTaWatt monitors when the voltage reference goes away cause any problems?

Thanks again to this wonderful community.

Moved from OEM Community at request of Robert Wall

Yes. It’s important to maintain the same polarity however. That’s easy if you just use a standard splitter like those offered by suppliers of CCTV equipment.

Not a good idea. Actually, you shouldn’t use a charger at all to power an IoTaWatt. Chargers can’t be relied upon to provide the clean power needed. Using individual 1A USB power supplies is recommended. There are plenty of inexpensive units sold for Raspberry Pi that will work fine.

No, recent releases of the IoTaWatt firmware do not need the voltage reference to operate. It’s not advisable, however, to connect the VT to a UPS.

Thanks again Bob, you and this group are great.

In #3 above, I was not planning on putting the voltage ref on the UPS, just the power supply so I can get a clean indication of how often my power drops. Subject of a long ongoing “discussion” with my supplier.


I have two instances of IoTaWatt running. One for the house, one for my shop.
Both devices identify themself as “IoTaWatt Power Monitor” on the web page and as the page title. The device names are different. I would find it very useful if the page title included the configured device name instead of the generic “IoTaWatt.”

I would also find it useful if the configured device name could include special characters like “_” or “-” and be longer than 8 characters. This would let me id the devices as “iotawatt_shop” instead of “iotawat2”.

Neither of these devices seem to reply to “device_name”/local but work fine with IP_address/local or bare IP_address. This is with both Chrome & Firefox clients on Win_10, Android and Linux. Didn’t try either IE or Edge or other Android browsers.

I also recently noticed that the newer device shows a faint blue glow near the power plug when the room is dark. The older device shows nothing.


Good suggestion Mike. Now that you mention it, as you might guess I have a lot of them running and that would be helpful.

So this is an open software project. The configuration app is right there in the root directory index.htm. If you run the file manager and editor, it is actually the file that gets teed up for editing. ctrlS will save it and then reload the app and try out your changes. I’d save a copy of the original just in case.

I’ll entertain a pull request to do what you need. Otherwise, I’ll look at it next time I’m doing work on that app.

This has become more of a problem lately with two browsers having done something to inhibit mDNS. I’ve been looking into it but not making a lot of progress. mDNS is an outgrowth of Apple’s Bonjour printer locating service, and it still works great on an iDevice with safari, which I carry around in my pocket. So I tend to minimize the impact this is having on other users. It is a problem and I’d like to come up with a better solution. Ideas are always welcome.

I know something is going right when this is the kind of problem folks are reporting. The ESP8266 nodeMCUs are sourced from various manufacturers. The blue led is part of that component and the location/brightness can vary. If it bothers you, you could always seal the edge of the power plug opening with some tape.

Thanks again,
None of these issues are impacting the WONDERFUL product’s use or performance. Just gilding on the edges. The “blue glow” was simply an observation and wondering if it meant something I should be aware of.


It was a one-liner.

I think I solved this. Will be in the next ALPHA release.

Longer than eight causes problems. How about iotashop?

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