Two way switch, no space behind ideal switch

  • I`m trying to install a shelly one in a two-way switch configuration. My switch setup matches this configuration:

    ar768_Wechselschaltung.png


    My problem is that the switch`s box into which I`m supposed to install the shelly(left on the picture) is full of wires and there is no space for it. The others box, however (the right one) has plenty of space. I also have access to neutral in booth locations.


    So my question is, is there a way for me to install a shelly 1, or maybe a shelly 1 l (I don`t have one of those but if it would work I`d be willing to buy one) in my less ideal switches box?


    I was thinking about connecting one of the wires connecting the two switches directly to the light in the left box and connecting a phase to the switch itself with the remaining wire attached to it, I would then install a shelly 1 l into the right box and use one of the wires coming from the left switch, which I connected directly to the lights, bypassing the switch, as the output of the relay and the other wire as one of the switch inputs, I would connect the right switch to phase also and to the other switch input. I`m not sure however whether a shelly one l could work with this.

  • Hello IIEMC,


    WELCOME TO THE FORUM


    If you have "L" AND in the right switch box AND the "L" comes from the same phase/circuit breaker as for the left switch then you can do it as suggested. You only need to change to momentary contacts within your switches, either by exchanging them or by adding a spring (if available) to both switches.

    Grüße Bernd


    Mein "Smarthome":

    FHEM als "Master"(Cloud-Free :))mit 89 Shellys(1,1PM,2,2.5,4Pro,RGBW2,PlugS,Uni, alle mit Original-FW),13x Sonoff (Tasmota-FW),12x Blitzwolf/Gosund(Tasmota-FW),85x One-Wire Temp-Sensoren(16x D1-Mini mit Tasmota-FW),51x Modbus(Hutschienenzähler),31x Intertechno 433MHz(Rolladen-Aktoren),16x FBDECT(8 Heizkörperthermostate,8 Schaltsteckdosen),21x Homematic(16 Raumthermostate,3 FB-Heizungsaktoren,2 Repeater),1x Loxone MiniserverGo,etc

    Neues von Print Worth 3D: ==> Marktplatz

  • Thanks for your reply.


    I don't fully understand why momentary contacts are necessary, is it because the shelly shouldn't be exposed to phase on the switch inputs for an extended period of time? Also, wouldn't the shelly detect a momentary switch press as two separate changes in the switch's state turning the light on when I press it and off when I release it?

  • No, the Shelly has no problem with permanent voltage at the "SW". The point is that you like to connect two switches in parallel. This is only possible with momentary contacts. How should the Shelly detect ON/OFF if e.g. one of the switches is permanent ON. Nothing will happe if you put the second one to ON. Even nothing will happen if you put it OFF again.

    Grüße Bernd


    Mein "Smarthome":

    FHEM als "Master"(Cloud-Free :))mit 89 Shellys(1,1PM,2,2.5,4Pro,RGBW2,PlugS,Uni, alle mit Original-FW),13x Sonoff (Tasmota-FW),12x Blitzwolf/Gosund(Tasmota-FW),85x One-Wire Temp-Sensoren(16x D1-Mini mit Tasmota-FW),51x Modbus(Hutschienenzähler),31x Intertechno 433MHz(Rolladen-Aktoren),16x FBDECT(8 Heizkörperthermostate,8 Schaltsteckdosen),21x Homematic(16 Raumthermostate,3 FB-Heizungsaktoren,2 Repeater),1x Loxone MiniserverGo,etc

    Neues von Print Worth 3D: ==> Marktplatz

  • In other words: You have 2 available wires between the switches. The 2-way-switch circuit needs both.


    But if you want to put the Shelly behind the switch „far“ from the one, where the line to the lamp leaves, you need an additional line from box 1 to 2. That‘s why you use momentary switches, which need only one switching pulse line. You have the other line available as lamp line.

  • Oh, I get it now, that is how I would do It with a shelly one, but the shelly one L has two switch inputs, so can I do something like this?shelly one.png

    (sorry for the quality, I only had ms paint)

    This way the two switches are independent, so normal switches should work. I may have drawn the wires connecting to the switches to the wrong place, please ignore that, I would correct that with a multimeter.


    What I`m not sure about is whether leaving the Sx terminals empty is a problem or not, looking at it now I see that the right switch could be wired to Sx instead of "L", but I can't do this with the left one, as I only have 2 wires connecting the boxes.

  • I did some research and it seems like I cannot connect the switch from "L" to Sx on the 1 L, so I`ll have to go with the momentary switch config, I have one final question though.


    Is there a way to tell the shelly one in software that it is connected to a momentary switch? I may be wrong but the way I see it is the shelly toggles the relays state when the switches state change, so when I turn a regular switch on it toggles it once, when I turn it off it toggles it again, so if I connect a momentary switch to it I expect it to toggle once I press and once I release ending up in the same state as it started in.


    I could just set the switch input as detached and set up the toggling behavior externally, in node-red for example, I`m just curious whether or not this is needed.