I want to combine a wireless 3-way switch with a manual 3-way switch, and want my server at home to know when my light is on or off (this is the tricky part). And when I say wireless 3-way switch, I mean something M2M, not a manual wireless switch.

For example I could do that with a "dual pow" from Sonoff, but this device does not exist.

There is a “pow” switch, that can tell me if the current is flowing, but it’s not 3-way, so I cannot combine it with a manual 3-way switch. There is also a dual relay from sonoff, and with that I can do a 3-way switch but it won’t tell me if the light is on or off.

I can do that myself on the breadboard with something like ESP8266 for the wireless + ACS712 for the current detection + 2 switches for the 3-way switch but I want something safe and reliable and I don’t have the tools and the knowledge to do so.

I also don’t want to replace all my manual switches by wireless switches, it would be a cool solution but I have way too many manual switches and I’m looking for something cheap.

Do you have any idea how I can do that ? This is what I have so far :

  • Dual pow from sonoff => does not exists
  • Dual switch from sonoff + current detector => didn’t find any good out-of-the-box 220V wireless cheap current detector
  • Two pow switch from sonoff => too big and too expensive

As a current detector to know if my light is on or off I could simply use an ESP8266 chip powered on 220V and plugged just behind my lamp : when I ping it that's ON and when I don't that's OFF but I didn't find any cheap device powered in 220V with esp8266. I can find some on aliexpress but there is no plastic case around it.

I hope I’m clear ^^ if you know any hardware that can help me, either a 3-way wifi switch with a current detector on it or even just a 220V powered wireless cheap current detector please tell me about it ! Also if you know any other solution I can use to manage what I want to do I would be very glad to hear about it.

Thanks and happy home automation !


  • What sort of control and status protocols do you have at your disposal? Do you have the capability to add contact-closure type inputs to your system? How is the existing wiring run, or is this all new wiring? Is wirelessness a requirement for this setup? – ThreePhaseEel Jul 21 '18 at 21:31
  • Also, where are you on this planet? – ThreePhaseEel Jul 21 '18 at 21:34
  • 1
    It’s hard to tell which of your requirements are actual requirements for your project, and which are requirements because you envision that in order to have Y, must use X. For example, I use off-the-shelf products and can control any switch in my house from anywhere in the world, and I can tell whether it’s on or off. On or off isn’t done via current detection, it just the status of the switch, whether it’s been operated manually or remotely. So which are actual requirements? – Tyson Jul 21 '18 at 23:27
  • This might be better asked on the Internet of Things stack. – Harper - Reinstate Monica Jul 22 '18 at 4:41
  • Hi, thank you for your answers ! I will try to answer everything : I'm from France, my home automation system run on HomeAssistant and I have a RFXCom to manage the wireless as well as Wifi. My installation is not a new installation, hence the wirelessness. I think my requirements are OK : I want a system that just add the capability of turning ON/OFF my lights (and knowing its state), without changing the manual switches and still able to operate when my home automation system is down. The only way I see is to add a 3-way switch that knows when the current flows. I can be wrong though :) – DBCL Jul 29 '18 at 10:10

This should be easily handled by better smart switches, because of how they work.

There is a "master" smart switch which accepts supply, neutral and the switched-hot line to the light. That master is the only switch which decides the lamp state. It communicates directly with the central control system, meaning the master switch can both set and report on/off. It knows because it is the only one doing it.

How is 2/3/n way switching accomplished? The master smart switch then communicates with other switches one of two ways.

  • with "smart remote switches", which communicate with the master via a communication wire, radio, or powerline signaling. In that case the remote requests the master to change the light to on vs off, and the master does so.
  • A plain old 1-way switch, that either energizes a single messenger line, or does not. Using traditional 3-way techniques, this can be extended to any number of switches. When the smart master sees the messenger line change, it knows someone has thrown a switch, and it voluntarily flips the light on/off.

Again, the smart master is doing all the flipping, so it itself knows whether the light is on or off.

If you are using smart 3-way switches that do not work that way, get ones that do.

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  • Thank you for your time and detailed answer, this is a good solution but I cannot accept it since it's out of the question scope : I don't want to replace any manual switches. The installation should work even if all my home automation system is down, which happens from time to time :) – DBCL Jul 29 '18 at 10:00

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