Wall switch with Sonoff and optocoupler

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Hello, I need some advice from the electronics professionals among you.
Unfortunately, I have too little knowledge about it.
The following drawing should represent my circuit.
The optocoupler from Ali.
I would like to use the Sonoff (Tasmota/mqtt) and a wall switch to set up a changeover circuit. The optocoupler sets GPIO14 to low when the wall switch is pressed. Then the Sonoff toggled the signal to the relay.

Basically, my setup is already working. Unfortunately, only for a certain time. Then the circuit begins to spin. Makes his own operations. Sometimes even half an hour is fine.

Lamp on - Lamp off - Lamp on - Lamp off…

I had already tried with an electrolytic capacitor of 0.1mF between GND and OUT. But even this did not improve noticeably. Without a capacitor, the circuit sometimes remains stable for several minutes. But unfortunately not forever.

Can someone tell me what makes this circuit stable?

Currently my test setup is running for just over an hour. I had it all re-clamped and plugged in again.
For my test I use a breadboard and the known cable connections. Could it be that my problem is a connection problem? Or transition resistances?

@thrusty Why didn’t you use the wall switches to directly switch gpio14 and gnd? This should be a much simpler and more compect way than this, but requieres to wall switch to be a pushbutton and not a switch.

Then I’d have to switch some switches. All of them, actually.
With this circuit I can use the wall switch additionally as a change-over switch in the 230V mains.
That’s the problem. 230V must remain.

I think it can help when you put a pulldow resistor between GPIO14 and GND maybee 4,7kOhm. Without a resistor the state of GPIO14 isn’t clear this is allways a problem when you use the GPIO as input and want to controll a switch is closed or open.

You can also set the internal pulldown/pullup resistors of the Arduino with code in the IDE.

You don’t need push button switches, a normal changeover switch workes fine for me.
Do you have one of them running? If you are receiving messages over MQTT this can happen too. So be sure it is the electronics and not caused by software.

Edit:
With this you’ve made a half bridge rectifier so only the positive part of the AC voltage becomes a pulse, then the second half doesn’t activate the optocoupler. So in fact there is a 50Hz pulse coming from the optocoupler, switching it on and off. A delay in the software can prevent this.

I think it was realy a contakt problem. Now, i have delet the breadboard and have close the contakts with screws. It seems to be better. I will look for it for longer time.
Thanks for help.

@thrusty said in Wall switch with Sonoff and optocoupler:

Hello, I need some advice from the electronics professionals among you.
Unfortunately, I have too little knowledge about it.
The following drawing should represent my circuit.
The optocoupler from Ali.
I would like to use the Sonoff (Tasmota/mqtt) and a wall switch to set up a changeover circuit. The optocoupler sets GPIO14 to low when the wall switch is pressed. Then the Sonoff toggled the signal to the relay.

Basically, my setup is already working. Unfortunately, only for a certain time. Then the circuit begins to spin. Makes his own operations. Sometimes even half an hour is fine.

Lamp on - Lamp off - Lamp on - Lamp off…

I had already tried with an electrolytic capacitor of 0.1mF between GND and OUT. But even this did not improve noticeably. Without a capacitor, the circuit sometimes remains stable for several minutes. But unfortunately not forever.

Can someone tell me what makes this circuit stable?

Hello
sorry for refloating this thread so old but it is exactly my question.

@Thrusty how has this circuit worked with time?

Does the connection between the optocoupler need anything else? Did you do it as you have in the diagram?
thanks !!

I can’t help in this specific case, but you should switch the L cable (brown/black) instead of the N (blue) one.

@sagatxxx
Hello, and sorry for the late answer. I think I had contact problems at the beginning. Test circuit, plug contacts, whatever…
After I had screwed all the contacts it worked.
I don’t have this circuit running anywhere yet. But I have run it for a week as a test. It worked without any problems.
The circuit exactly as I had drawn it.
On the Sonoff runs tasmota. Not the original software!
This is how a hardware/software switch works. Only that there is a permanent power consumption, in contrast to a pure hardware change-over switch.

@SaxnPaule
Probably you’re right and it’s the better solution to switch the phase.
And you pinch lamps or other consumers like that. But in this case it’s really uninteresting which side is switched.

But the most important thing is, nobody who doesn’t know anything about it should screw around with 230V.

@thrusty How have you connected the optocoupler? do not connect the vcc output?

@sagatxxx
It‘s the same as the circuit above. Without other components.
VCC is not conected.
OUT —> GPIO 14 (Sonoff)
GND —> GND (Sonoff)
And tasmota on the Sonoff.
That works.

@thrusty thanks!! i´ll try

@sagatxxx
I looked for the picture, and I found it. Only the Lamp is not connected. But the relays and the led of Sonoff switched.