Relay for 4 way-switch


I have a “4-way” switch installed in my bedroom. 4-way means that I can switch the light from 3 places (near the entrance, from either side of the bed).

I would like to add that setup to HA via the relay behind the switch, however, I cannot figure out what relay can support this. Maybe someone here has already done a similar thing.

My constraints are that I can neither change the switches nor the wires.

P.S. I have successfully retrofitted “3-way” switch with this relay , however cannot figure out how to do that with “4-way”

Ewelink have a 4 channel relay available on Aliexpres for about $20
Tested as working by me :slight_smile:

Thanks for the suggestion, though it looks like it serves a different purpose. The relay in your link can control 4 separate lights, while I’m looking for the relay that needs to control one light from 3 different switches.

Basically this is my setup : image

Which location are you trying to replace? one of the ends or in the middle?
For the one in the middle you will need a cross switch.

You can make a 4 way with just 1 relay, just need the correct type.

I do have a cross switch in the middle, and ideally would like to put a relay there

Just need 1 relay with 2 switch contacts (excuse the crappy drawing :smiley: )

wouldn’t you just add a shelly relay to just one switch?

Hi im in the same boat , but in the uk, assume wiring is the same. So a shelly or a sonoff mini will do the job? I will only need 1?


I am just looking at this and have some thoughts.

If you try to replace one of the switches with a relay it has to have 3 output terminals and will require power of its own so in that diagram it would have to be behind the first switch plate in the chain. A Sonoff MINI I don’t think will do that job because it doesn’t have normally closed and normally open 3 terminal output.

However, this approach is not great because you will only be able to schedule “toggle”. If you want to go away and want to be able to predict a definition of “on” e.g. for timed security lighting then you must ensure the other two switches are in a known configuration before you go on vacation otherwise On will be Off and vice versa.

A better approach might be to try to get an extra cable run above the ceiling to the lights, taken from the same circuit (Or I guess another one if you know what you are doing). Then use that to insert a sonoff mini (for example) above the ceiling. This is likely very easy above the ceiling if this is a top floor because the rest of that light circuit will be present in the roof space. But if you don’t have a roof space it will be harder. Then convert the switch network to be just a loop, that starts above the ceiling and comes back - by making a modification behind the first switch. This loop just connects across the switching input on a sonoff mini for example.

An attempt at explaining this with text:

Today :-

LIVE- > BLAH (switch network) → LAMP
NEUTRAL(thru switches) → LAMP

Tomorrow :-

LIVE (new one, same circuit, above ceiling) → MINIR2 → LAMP → NEUTRAL (new one above ceiling)

LOOP (disconnect power and neutral at the first switch , wire the neutral that went to the lights to the old live input of the switch network, to make the network into a voltage-free loop… ) → BLAH (switch network) → BOTH MINIR2 SWITCH INPUTS

Critical to ensure the miniR2 switch is in the live. So when it is off you can change bulbs and what not without cutting the power. And after this change I guess the light switches are just across the miniR2 switch terminals.

This would be much nicer because then “turn on” from automation is ALWAYS turn on regardless of the state you have left your switches in. The switches would just toggle the relay I think.

Would be interesting to hear any better ideas ???

Be sure to read the wiring regulations and adhere to them.

Another one is installing sonoff basic r4 on the light fixture using the magic switch mode

It turns out that after debugging this is not my setup. In my setup the power comes into the top most switch from the ceiling and the switch network is a loop that goes down to ground floor and back up to the lamps. Therefore it appears that a single sonoff ZBMINIL2 (or similar) can just be put behind the top most switch and I am done. Switch network just goes across S1/S2 and ZBMINIL2 takes the live + lamp return.

Edit : Confirmed , a single ZBMINIL2 behind the top most switch was all I needed, using the switch network across the 2 inputs. It just fitted in there.

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oh that’s cool