Sonoff Mini R4 Extreme does not detect button press when bulb is connected to switchwire


I’m using a Sonoff R4 Mini in my bathroom (displayed as a relay). I want my fan (displayed as a motor) to be controlled by the Sonoff relay. The Sonoff relay should be activated both by wifi or by an external switch. For this, I’m using the following layout:

I connected a switchwire from the switch to the S2 input.

However, a light bulb is also connected to the switch wire.

My Sonoff does not register a press on the external switch when the light bulb is connected (sonoff displayed as a relay):

However, when I disconnect the light bulb, the Sonoff does register the press on the external switch (sonoff displayed as a relay):

I have no idea why this is happening. How can I find out the cause? I want the light bulb and S2 to be activated at the same time when I press the external switch.

A “fast thought” about this:
If your “model circuit” is really representing the internal of the MINIR4 (S2 connection) then the light is in parallel to the “solenoid in series to a 4.7kOhm” resistor. If you are using a “normal” light bulb, it has an internal resistance of about 60 Ohm, so the 4.7kOhm of the other branch makes it work almost as an open circuit. If you are using LED lamp, it could even be “stranger”, I am not sure if the modern LED lamps are all wired to use the AC current in both directions or still work as diodes…

Thanks, I was already hoping someone like you with a bit of knowledge on electrical engineering would answer.

The resistors are there just to show that the loop is not short-circuited when the switch closes. I don’t know what the resistance really is.

The light itself is a halogen GU 10 light.

My actual guess is that there is a lot more than that solenoid and resistor… remember that the relay also toggles when S2 is connected to S1 through a switch, no “Lin” there… so there is some electronics in there. So I guess the (relatively) low resistance of the lamp just messes with the detection in S2. Either you put the lamp in parallel with the motor (and both work together) or you use a different R4Mini for the Lamp (and build a Scene so that one of them follows the other)

Thank you very much for your input, I was fearing that something like that might’ve been going on.

Thank you very much for your input, I was already fearing that something like that might’ve been going on.