Synchronizing 3 Relays on Tasmota 4CH Board for 3-Phase Consumer

Hello

hope it’s ok to ask for some Tasmota help/ideas.

Guess everybody knows e.g. the 4ch relay boards available and I like to combine 3 relays at such a board to act as 1 relay for e.g. a 3 phase (3x230V) consumer.

So 3 relays should be switched on/off always synchronised by one gui button or one command sent by mqtt.

I searched for a solution and seems that grouping is a method for this, but the documentation says that only 1 relay can be involved in a device group.

So I tried to map 3 gpios to one relay but this does not work.

Kindly ask for your help
Kind regards and big thanks

Are you really sure that having 3 Relay entries with index "1" does not work? That's strange...

Added after 3 [minutes]:

EDIT: It seems you are right! It only toggles one relay:


Ok it seems we need to use rules?

Added after 2 [minutes]:

Probably Rules can help?
https://tasmota.github.io/docs/Rules
Do something like, when switch 1 is on, turn on switch 2 and switch 3. If switch 1 is off, turn off them...

Thanks for your help.
Do you think that rules are fast and reliable enough for this purpose?
I´m struggling because rules are based on triggers. Just in case one relay becomes different because of boot state or sth like this, this is not synchronized by a rule until a state change of any relay, right?

Guess I have to create rules triggered for the state ON of each relay and rules triggered for the state Off of each relay, right?

I also had a look at the interlock function which is available for shutters. Guess that it is possible to put 3 relays into this interlock group but of course the function of an interlock is different. But from the general idea of usage very similar. So sth not like an interlock more like a sync group would be great but seems not to be available

Device group is for linking with other tasmota devices.
You could use rules with backlog for it

Something like this

Rule1
on power1#state=1 do backlog power2 1;power3 1 endon
on power1#state=0 do backlog power2 0;power3 0 endon

3-phase appliances tend to draw a lot of current. Perhaps the solution would be to use a 3-phase contactor externally.
Alternatively, you could rework the board and connect three relays to one output.
There are devices that are sensitive to missing one phase for a long time. For this reason, controlling 3 independent channels is not a very good solution.

Thank you very much and you are right. I have to test if this is really sth. to be used in practical application.

As you can see the result is clearly sequential and not in parallel, so this should not be a problem for the 3phase device:

https://streamable.com/fqlur3

In addition I added for the gui operation to this:

Rule2
on power1#state=1 do backlog power2 1;power3 1 endon
on power1#state=0 do backlog power2 0;power3 0 endon
on power2#state=1 do backlog power1 1;power3 1 endon
on power2#state=0 do backlog power1 0;power3 0 endon
on power3#state=1 do backlog power1 1;power2 1 endon
on power3#state=0 do backlog power1 0;power2 0 endon
Rule2 1

But it’s possible due to rule execution time and by fast button usage that the rule has not finished the last execution and the result is an endless sequence of relay/light on/off in various combinations.

Only way to stop this is a power shutdown and reboot. In case of a connected 3phase device such behavior is of course unacceptable....