Problems using the dimmer behind a 3-way toggle switch configuration

Hello people.

I am having problem with the 3-way setup of the shelly dimmer.

I have identified the cable that goes from the last commuted switch to the set of 3 dimmable leds and installed the dimmer following carefully the installation diagram, the cable that comes from the toggle switch to I1 and the cable that goes to the lights to the O.

The shelly dimmer works fine when using only the app but if i use any of the wall switches for going from power off to power on, the lights starts blinking (by changing their intensity) indefinetely (when using the edge mode) or they only work for going from off to on once (when using the toggle Mode).

It seems somehow that the shelly is having problems to detect the status of the physical switch, i have noticed too that the blinking speed is higher when the light are set to lower light intensity values.

Tried to use the multimeter to get any additional insights without luck, i just see some jumping voltage values (from 10 to 30 volts between I1 and O and similar oscillations comparing O to N) when the physical switch goes from off to on.

Thanks you a lot for your help

Having just install three of these in the last week in configurations that have 3-way switches tied to the I1 input that have the toggle configuration set does work. Based on what you are saying though, it really sounds as if your the output (O) line is powering the 3-way switch chain, as well as the lights. So the lights are on and you flip a switch and the power to I1 goes from off to on. The Dimmer sees the change and then turns off the lights, but now the Dimmer sees the change on I1 again and turns them back on. and it just gets suck in this loop.

The 3-way switches should be connected between the I1 input and line power that is also tied to the L connection.

Thanks for the help,

I did the installation after check which one of the 3 switches is supposedly the last one of the chain. The first one receives the power with a black cable from there all the rest uses the tipical white cable for light lines.

Well the thing is after supposedly identifying the last switch (3 white cables) of the commuted chain i cut the exit cable that is supposedly going to the load, the lights, and from there the end that comes from the switch it's currently connected to the I1 and the other end that supposedly goes to the light is connected to the O. I did all the installation on a big junction box at the entrance of the room.

But yeah now if find myself thinking if my suppositions were right even if i made those based on the output of a multimeter, it could be loop like the one you are saying, will that match with a diferent behaviour when changing from edge to toggle mode?

One more question the line that powers the switch chain need to be exactly the same cable that goes into L, i always thought L is just to feed the device so It doesnt matter from where i take it. Is the input I1 of the shelly active or pasive? On the shelly1 is active in the sense that works with a 220v powered switch, am i right?

Thanks you a lot for the help

Well, I am in the US so this is all done 120V, but that should not matter. The 3-way wiring can drive one crazy if you are in a box with a other switches, etc. I have not studied the edge modes much at all, so I can't answer how those would work in this case.

As for the power source for the I1 input, I would suspect that it would not matter if it came from a different circuit to make things work and I came close to needed that in my setup because I had the power coming in on one end of my 3-way switches and the lights connected at that other end of those switches, but I don't think that would have been considered safe to do and would have gone against our our National Electric Code, because in some failure case one circuit could be back-powering another circuit even if the breaker was off.

Yeah i get the point about the isolation of the circuits, but as you said many times is not viable to use the same branch unless you use a lot of additional cable and have space enough for that in the tubes.

I am going to do a similar dimmer install on another room (again with 3 switches), let see how that ones goes, this time i'll check cafefully all the switch boxes at the same time to be perfectly sure i am installing it correctly, if i get that one to work i'll review the other install and maybe even try switching the dimmers in case that could be the problem.

Another reason that could be related with the problem is if somehow residual current can fool the shelly into thinking the status of the switch is not the real one.