Hands on: Sonoff POW R2

What can you do with Sonoff POW

I went shopping! Ok, I opened the internet, and the combination of the mouse movement and keyboard keystrokes got the Sonoff POW R2 into my house. I thought I would share a couple of thoughts before I nuke the original software and use it in my upcoming projects [link1, link2].

Why Sonoff POW R2

I already own Sonoff Basics, so what’s so different about its bigger sibling the Sonoff POW R2? The Sonoff POW can turn ON|OFF (I see what you did there Mr S(witch)ON|OFF) but it can also monitor the power sent through the device itself.

That ability makes the Sonoff POW R2 a little more expensive. Is it worth it? That depends on what are you going to do with this information. Before I connected everything, I opened the Sonoff POW R2 up.

Sonoff POW R2
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Inside Sonoff POW R2

The layout is slightly changed, as both Input and Output feed the box from the same side. I’m not a fan of this solution, the way the live wires has to be connected is not ideal. You will end up crossing the live and neutral lines to make the connection.

GPIO Pins

It’s nice to see ITEAD exposing the dev pins once again for tinkering. The following pins are accessible directly from the PCB:

  • RX, TX (serial communication)
  • GPIO 04, 05 (general purpose)
  • Vcc, GND (power)

The GPIO00 which is needed for the flash is not exposed on the PCB, but investigating the ESP8266EX pinout, it appears to be mapped with the button. Even better!

There is enough space in the enclosure to add custom female headers. The case comes with a hole on that side too, so you can route the cables out. I cannot think of any other reason for this hole to exist.

New connectors

The change in the design also introduces spring loaded connectors. The cables have to be pushed back a bit before the spring locks it. It’s much more comfortable in use. I hope it locks the wires in place properly otherwise that cross between the neutral and live wire is going to get messy.

PCB layout

There is a clear separation between the mains and internal, lower voltage. The ESP8266EX is located far away from the mains traces, with antenna poking to the side of the PCB. The board has physical gaps in the PCB to separate the high voltage from each other.

There push button has been redesigned too. The utterly rubbish one from the Sonoff Basic has been replaced by a much stronger version. I have no doubt that this one will last.

eWeLink app

When it works, the app is great. The problem is, the app makes it nearly impossible to pair the sonoff devices on Android 9.0 devices. I had to use Android 8.0 (or app like Bluestacks) to actually get it to work.

I got a message on YouTube that disabling data connection might help. So give it a go if you are struggling to pair your Sonoff. I already flashed mine, so I won’t be testing this.

This is probably the main reason why the eWeLink app comes with 3k 1 star reviews at the time of the writing. The app collects a fair amount of data here are the most useful features:

  • overvoltage/overcurrnet protection (software only*)
  • power cost calc
  • power use in W, A or V
  • timers and schedules
  • Extended graphs

*the protection is implemented by software. Sonoff POW will pass through the current/voltage for a short time (under 1 sec) before turning itself off. Use with caution as this is not how you should protect your devices.

While cost calculator doesn’t include night tariffs, it’s nice to see the estimated price for the electricity used. I also liked the overcurrent and overvoltage protections option. I’m not 100% sure how good these are. I might test it in the hackspace where I have the equipment for such scenarios.

Conclusion

We all know what will happen next. The Sonoff POW R2 will be stripped to the bones, new header installed and tasmota software flashed. This will enable such cool options if the same set of data is available via custom firmware. I already have 2 projects in mind. I will keep it hush for now, but I promise to share it as soon the write-ups are ready. If you have any questions join the discussion on Reddit.

Sonoff POW R2
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Control a power outlet and monitor the power use at the same time
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