Update on power level threshold flow-triggering

In case anyone is interested, I thought I would provide an update to this thread.

In summary, my goal was to find a device that could quickly communicate to my Node Red instance when power consumption on an outlet passed a threshold (one message for above and a separate message for below). I had found 2 smart outlets that do this, but each was too slow, and one only worked in an IoT ecosystem that I don't use or want to add:

  • Currant
  • Sonoff S31 15A

The Currant outlet was about a second faster than Sonoff, but is tied to Samsung SmartThings. I could get an iOS notification, but I couldn't tie in Node Red. The Sonoff tied into Node Red (when I flashed tasmota on it), but whether I used MQTT or webhooks, there was still a 2-3 second delay. I studied the tasmota code extensively and learned that the hardware simply doesn't have the accuracy or response time. It wasn't engineered to be quick and it wasn't engineered to provide accuracy below 5 watts (or was it 0.5 watts? - I don't recall. I think 5).

I bought another less-smart outlet that works nearly instantaneously. It sends a 915Mhz signal when power is cut and a separate signal when power starts flowing, and I've been in contact with the designer and given our discussions, he and his engineer are not developing a dev kit USB dongle that can report on the signals. This has the following drawbacks:

  • I cannot set my own thresholds
  • There is an upper limit on the number of devices (8)
  • It can only detect power changes on the outlet it's plugged into - not power changes on what's plugged into it, so I can't (as I imagined) turn any dumb device into a semi-smart-reporting device

It's pretty cool how it works. It uses the strategy I'd envisioned for such an outlet. It does an extremely quick boot when turned on and sends the on signal. When turned off, it uses charge stored in a capacitor to send the off signal (which is does repeatedly until the charge is exhausted). And it has a fallback/slower repeated signal it sends intermittently while on so that in case, the dying off signal doesn't make it, the receiving device(s) will turn off if it misses that heartbeat a few times in a row.

I've been really impressed with how fast it is. I suppose that if I wanted to have any dumb device be able to trigger it, I'd have to splice the wire and insert a plug I could plug it into. Or, perhaps there is a weird wall-wart that puts 2 plugs on the same circuit - like the splice, but without having to cut the wires. That would be perfect, actually.

I'm really looking forward to having that dev kit. I ping the designer now and again to see where they're at with it.