HomeHome AutomationSonoff DUALR3 has a hidden secret

Sonoff DUALR3 has a hidden secret

I'd like to say, that no Sonoffs were harmed in making this video, but I can't

Another month, another product from ITEAD. This time, Sonoff people decided to marry Sonoff Mini (review) with Sonoff Dual and then use it to make babies with Sonoff POWR2 (review)- to create Sonoff DUALR3. A switch that is small enough to sit behind the wall switch and powerful enough to tackle multiple gangs individually. As the name suggests, two is the magic number! Let’s see what else can we do with it.

Sonoff DualR3

It’s only slightly bigger than it’s older brother Sonoff Mini (review), which should fit comfortably behind the wall switch. It’s WiFi-based and as usual with Sonoff devices, you can link it up with eWeLink devices and take the advantage of smart assistant integration: Google Home and Alexa.

Upon closer inspection, Sonoff DualR3 has fewer terminals than I would like. It can operate 2 switches and 2 gangs, but the number of terminals smaller than the number of cables required to pull it off. You’ll have to splice the cable to make it work. It’s worth noting that Sonoff DualR3 required Live and Neutral access to work, so you will have to settle on ceiling fixture or amount behind the wall switch based on your location and wiring standard.

Terminals are made of metal and look sturdy, to accommodate the lighting wires. The smart switch comes with the following specification:

  • Input 100-240V AC 50/60Hz 15A
  • Output 100 -240V AC 10A per gang (15A total)
  • Motor Load 240W max at 1A (inductive)
  • WiFi 2.4GHz 802.11 b/g/n
  • per channel power measurements

As you can see the despite being small, it packs a punch, as long as you stay clear of high inductive loads as wiring schematics include instructions to connect a motor. This could be an ideal device to use for the garage door opener.

Sonoff DUALR3 comes with a small bracket that can be used to mount on a DIN rail or on walls with 2 screws. It’s easy to clip the device in and out.

Pairing and eWeLink

Here is a hint to the incoming surprise. Pairing is done over Bluetooth instead of the traditional AP point. It pairs in the instant and eWeLink walks you through the setup process. Sonoff DUALR3 can be used as:

  • switch for lights
  • motor controller
  • inline power meter with 2 channels

Sonoff DualR3 and eWeLink app offer 3 switch modes for detection. There is a pulse, edge and follow mode available to be set separately for each switch. This should cover all switches that you use to toggle your lights.

Unlike Sonoff Mini, switches added to Sonoff DUALR3 use mains power to connect. These have to be connected to the Live wire in order to work. If you planning on replacing Sonoff Mini, make sure that your wall switch is compatible as Mini used 3.3V switching logic.

Power measurement

Power consumption measurements explain why there are 2 power lines in, as the device uses this to measure power use across each channel. I have to say, I like this, as the eWeLink app not only allows you to monitor the consumption of the device but also set values at which Sonoff DUALR3 will turn itself off thanks to OPS function.

Both channels can measure the following values:

  • Current draw
  • Voltage
  • Real Power
  • Reactive Power
  • Apparent Power
  • Daily Consumption

And draw nice charts of the power use. In addition to this, there is an option to measure the power use “real time” by specifying start and stop time of the measurement.

Motor controller

Another use case would be to control a small motor with Sonoff DUALR3. This could be a roller blinds mechanism, shutters or even garage door providing that motor falls within the specification.

LAN and DIY Mode

The LAN option is available, but there is no indication of DIY mode as of yet. Something I will be asking about ITEAD soon. I would love to see this available on the device that has power metering enabled.

The surprise lies inside

Obviously, the next step was to poke inside and take a closer look at the PCB, available pads for hacking and whatever else there is. And here comes the big surprise. Unlike anything else from sonoff I played with before, Sonoff DualR3 isn’t ESP8266/ESP8285 based.

I believe Sonoff DUALR3 is the first Sonoff Switch with ESP32 inside. It’s quite the departure from experiments with other microcontrollers. Will we see more Sonoff boards that are ESP32 based? It’s a question I’ll get to ask ITEAD after New Year’s break in China. For now, I can toy around with the idea of ESP32 being inside new Sonoff products.


My attention drifts next to dev pads. After all, you know what I’ll do next. Flash Tasmota and try to figure out this thing in NodeRED. I’m pleased to see the usual suspects present on the PCB: GND, 3V3, TX, RX but GPIO00 isn’t exposed. There are RX2 and TX2 pads as well probably responsible for 2nd switch/gang combo. I will prod this thing further in my hacking attempt.

Mapping ESP32 will be the most difficult task, as I expect I have to remove the ESP from the pain PCB to investigate the traces. Since I already killed my Sonoff DualR3, it will be used as a sacrificial goat while I’m waiting for a new one to arrive.

No Sonoff were harmed in making this….

If you haven’t seen the video, and you still want to know what happened to my unit, read on. I made 2 mistakes. I was in rush (to make the video ready for today) and I took a quick look at the wiring diagram. It’s not my 1st rodeo, I knew enough about how to connect these (at least that what I thought). I used a multimeter to confirm that there is no DC voltage on S1 and S2 pins like on Sonoff Mini. That was my 2nd mistake – ignoring the readouts.

When I connected the switch, I wired it between S1 and Neutral, which was incorrect. – it should be wired to Live. Flipping the switch shorted 240V and fried the Sonoff DUALR3. Don’t be me, take your time connecting things.

The post mortem brings some good news. ITEAD was kind enough to label all pins on the extension board making the identification a breeze and confirming that GPIO00 is exposed. And for our convenience, it is connected to the physical button on Sonoff DUALR3. Looks like we have all pads to try to hack this thing, except I don’t have a working device.

Buy Sonoff Dual R3

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Final thoughts

It’s a nifty device that enables me to control multiple gangs independently. It will be fun to hack but I will have to wait for the new one to arrive! It was completely my fault and I’m so angry with myself. On the other hand, it proves that everything terminated well without causing a fire. I will ask for the new one and this time I will try not to kill it. Wish me luck! If you want to see how that turned out, pick one of the options to follow me. Got any questions? Leave it in this Reddit thread.


This product has been sponsored by itead.cc, but I reserve the rights to a honest and unbiased opinion about the product..

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