Is there such a thing as a latching relay, preferrably din rail compatable, that could be controlled through home assistant via an esp or the like. ideally it could be added on to one end of a 3/4 way light switch circut, and act as one of the switches. the latching part is so that if home assistant shuts down or loses power for some reason, it doesn't turn the lights on, as it could be in the on or off state for the lights to be on. sorry if that was a ramble, not sure how to explain it.
#Latching Relay???
warm patio
crystal linden
I'm not sure if this would do exactly what you need, but Shelly's relays have a mode they call "edge" which allows them to go into an N-way circuit.
You wire the output of the switches into the relay's switch terminal as normal, but the operating mode means the output flips when the input flips, irrespective of either being on or off at that point in time.
I've got one wired into a 2-way like this, and it's been working great.
I found someone's wiring diagram (UK colours; blue neutral / brown phase), which has an error (the phase definitely doesn't go to the side contact of an ES bulb), but otherwise is fine.
glossy arrow
yeah having a shelly towards the lighht in the cirtuit and treating all the switches as the switch input means if the shelly is set to the switch being toggle then the switches will work if HA is offline
but a latching relay does exist in electronics so if you wanted to build something you could. they usually have 2 input signals which are "set" and "reset" for basically on/off
crystal linden
Sometimes though only two contacts, and you have to give them 12V/GND for on, and GND/12V for off, which increases the difficulty a smidge (but far from an insurmountable challenge).
glossy arrow
Sometimes though only two contacts, and you have to give them 12V/GND for on, an...
oh yeah, there's loads of variations on the latching relay.