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Sonoff Mini Not detecting physical switch


I've installed a sonoff mini and connected the signal wires to 3 3 way wall switches.

If I try to switch ON/OFF the sonoff using the app, there is no problem, it works like a charm always, but when I do it using the wall switches it just works "sometimes".

For what reasson can it be caused?

Is there any maximum length for the wires?

Should I activate any flag in the app?

5 people have this problem

I have measured with a multimeter. Neutral voltage (should be zero) increases up to 3 V when dimmer is dimming. This can make Sonoff to detect a Voltage variation in the S1-S2 pins causing it to switch without any action (it does happen sometimes) or to not detect S1-S2 change enough Voltage.
I think so.
Maybe it was solved by using a shielded cable for s1 and s2.

c'est pas une solution le cable blindé, leurs produits ne sont pas au point ...

J'ai remplacé le sonoff mini par un QUBINO ZMNHND1 et ca fonctionne très bien, une force de vouloir vendre des produits à bas prix, ont négligé la qualité et le Sav.

I too am having this problem in a set-up with two 3-way switches. Sometime flipping one of the physical switches flips the light state, sometimes it does not. Using the eWeLink app, it always works.

At first I thought I had made a mistake with the S1 and S2 connections. So I disconnected the wires from S1 and S2 and attaches the wires to a multimeter to do a set of continuity checks, and it's working correctly -- flipping either switch flips the continuity, so all four combinations (up/up, up/down, down/down, down/up) work correctly.

Clearly the Mini is at fault and given other reports of people who've ordered multiples and have had some work and some fail is disheartening. This is clearly a buggy product and is not ready for market. And I was so excited when mine arrived....

I think it's a software problem. at the time they update it will be fixed
Solved: Issue Is dependent by old Wall mounted deviator because After years of usage internal contacts are ossidate , Just replace deviators and work fine.
This does not solve the issue with the Sonoff mini. This solves the issue with your old switches. But in my case, even connecting/disconnecting a 10 cm long wire between S1-S2 , the problem still exists.

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I'm not an electrical engineer, but I believe this problem is fundamental to the design, and I'll be returning my Sonoff Mini. They chose to send the board voltage through the S1/S2 circuit, which is only 3.3 volts. As such, it's apparently susceptible to interference. They very similar Shelly line of products instead uses the line voltage through the switching circuit -- 110 volts or 220 volts. And that seems the more robust solution when it comes to unshielded house wiring.

But this issue has been on this message board for 4 months, and no one from Sonoff has bothered to respond. They really need to be part of the discussion.

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@Federico: Totalmente desacuerdo. No veo sentido en lo que dices. Está demostrado que es causado por la configuración (Dos conmutadores o dos conmutadores y un cruzamiento) y por la longitud de los cables. Mis conmutadores son nuevos y funcionaban perfectamente y el problema se manifiesta intempestivamente y perdura por horas o minutos y puede dejar de manifestarse durante semanas o meses. Creo que puede estar relacionado con corrientes armónicas y tal vez pueda corregirse con una actualización de firmware, si se puede filtrar la señal que provoca el mal funcionamiento. Lo que es increíble es que no de la cara aquí (en el foro oficial) alguien de la marca y tengamos que estar nosotros haciendo especulaciones. Saludos!

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Hi, same problem here, but I've a Little difference: only 1 Switch fail to work, The others Switches works very well! And the Switch that don't work IS were Sonoff is Connected!
I've noticed that, when a click fail, if you use any other Switch in the House under The same Master breaker, The sonoff restart to work fine. I'd Like to Mount an capacitor (maybe 10 uf) between s1 and s2.
After looking at my videos, Itead recomends to install a 100 nF electrodeless capacitor between S1-S2. I will share the results.
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