I would like to replace normal (mechanical) switches at home with Sonoff Touch ones, which I will be able to manage.

Today I have this:

enter image description here

and by adding the Sonoff Touch I will have that (P1 is the WiFi module, the whole dashed box is the Sonoff Touch):

enter image description here

The concern I am having is that the lamp(s) which are in series with the switch will lower the voltage on the switch. I do not know yet by how much.

Are there practical indication on the voltage range required by a Sonoff Touch to function properly? (the documentation mentions 90~250V AC, I am more looking at some experience based cases)

Circuit schematics thanks to CircuitLab

  • your proposed circuit will mean the light is on all the time Mar 23, 2018 at 22:55
  • @JaromandaX: I hope the current drawn by the WiFi module will be very small, probably too small to light the bulb
    – WoJ
    Mar 25, 2018 at 20:23
  • True, didn't consider that Mar 25, 2018 at 22:54

1 Answer 1


Inside the Sonoff, there will be an AC to DC converter like Hi-link HLK-PM03 220V to 3.3V Step-Down Buck Isolated Power Supply Module which is used to power the Wi-Fi module separately. As I have created the same Wi-Fi smart switch using a solid-state relay, ESP-12 generic module and simple LED within an AC-outlet and also created just like sonoff.

If the Sonoff is directly connected to the power supply and at the output of sonoff the Lamps are connected in series, there will be no issue of Power Supply.

And if the Power supply is given simultaneously to both Lamps in series and Sonoff then also there is no problem, I think.

My circuit was like this. For creating a small product as sonoff replace the solid-state relay with generic relays and you will have a small custom product.

  • Thank you for the answer. Would it be possible for you to share your circuit so that I have a look (I was thinking about building the same but my electronics skills are limited)
    – WoJ
    Feb 14, 2020 at 15:08
  • @WoJ Added my simple circuit diagram for reference. You can just google and search for more example with "Controlling Lamps using relay and ESP8266/Arduino"
    – Lucifer
    Feb 17, 2020 at 8:11

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