【Two-way Control】By installing ZBMINI-L in one of your existing two- or multi-way control junction boxes to make the connected light smart.
Checked the manual and nothing is said about wiring for a three way circuit other than this diagram illustrating what looks to be a three way circuit but nothing is connected to the other circuit.
The standard ZBMINI toggles the output relay every time the input switch changes state. If the switch circuit is wired as shown, flipping either of the 3-way switches will change the state of the switch circuit and will cause the relay to toggle.
I would wire it like the diagram but it doesn’t show both three way switches. I am more comfortable around 12 volts DC
Without ripping out the walls I am only guessing. I do know there is a black wire and a white wire at the light and both switches have a black, a white, and a red wire.
Should I power down the circuit and do a continuity test of each wire?
It does show the switches, just not in a user-friendly format. See below. I've outlined each switch in a black box and labeled the "common" terminals with a C and the travelers with a Tr.
When we moved to our home in 1982 the basement was 4 concrete walls with a furnace and water heater in the middle. I must have bought 100 2x4s, lots of drywall, 200 feet of 14/3 with ground, loads of can lights, wall outlets, and switches. Had no qualms about any of that. My weakness is three way switches. Thankfully I don’t have any 4 way switches.
Don't feel bad about that part. Those pictures I shared above...I have them bookmarked. Every time I mess with a three way switch I need to match my circuit to one of the pictures before i feel confident enough to start pulling off wire nuts and loosening screws.
There may still be 120 volts somewhere in the same box, but you are correct that neither switch is connected to the main voltage. There is likely some low voltage control power that the zbmini uses on the switch circuit, but I've never measured it.
A momentary switch might work with a quick tap (fast as you can), otherwise it will see both the close AND open of the momentary switch and will toggle the output for each of those events.
Here are two photos of the other three way switch. Black white and red. Ignore the other black and white wires. Those connect to another Sonoff switch for the exhaust fan.
Once both switches are out, I will power the circuit up and check voltages at the wires.
This is more me thinking out loud.
With all the wires disconnected at one switch the voltage tester shows voltage across the black and white wires and also the black and red wires.
At the other switch there is no voltage from the white to the black nor from the white to the red nor from the white to the red.
Now I’m stuck. Wire nuts on all the exposed wires and no light in the bathroom.
Really don’t want to fry one of these Sonoff switches.
Going to disconnect the light fixture and run continuity tests and build my own wiring diagram. But first off to take my wife out for early Mother’s Day.
Update. Connected the black to the white at each switch and the light came on with no sparks.
As a retired auto mechanic I used complex schematics like this with hundreds of circuits
This is a good time to dig out the non-contact voltage tester. I would normally shut off the breaker, disconnect all the switch and fixture wires, wire-nut the ends and then turn the breaker back on. The non-contact tester will beep when you find the hot wire. Knowing where the power enters the circuit is a big help. If you don't have a non-contact tester, check voltage with each one compared to ground. Once you know where the hot is at, you can start to reconnect wires one box at a time and see how it travels through the circuit. There are a couple other items that might be helpful.
Do any of the white or red wires have black tape on them, or another sort of marking that would identify them as "hot?"
You should be able to see all 3 or 4 wires that are part of the same cable. Are there any wires that are wire-nutted together and do not land on a switch or fixture terminal? THese will typically be either a neutral or a hot which simply passes through the box on it's way to the next device.
And I'm not sure if you saw this, but wanted to point it out...
At some point this switch shorted out on the ground conductor. Always a good idea to push the ground conductors as far back as possible and "fold" the wires neatly behind any switches or receptacles to try and prevent this kind of thing.
And here are two more variations of 3-way circuits. Combined with the two I shared earlier, that's all that I am aware of.
I noticed that also. We had the bathroom remodeled about 20 years ago. They moved the switches from the wall to the side of a cabinet. The circuit must have been live and the hot touched the ground. I replaced the box with a plastic quick box and am tidying up the mess.
The switch in the other location is the source.
Need to revisit your edited diagram and get both switch locations controlling the light.
I can connect the white and black at one location and control the light by opening and closing a switch connected to the other back and white wires. The red wire is not connected to anything and appears to be the traveler. I currently have a two way circuit.
Need to take the quick box back out and enlarge the opening some more because the right side is pinched . The old metal box was a bit smaller.
I have an older home with 100 amp service and a fuse panel with 10 fuses and no neutrals.
My father had issues installing ceiling fixtures in my childhood home. It was built in 1890. There was a gas pipe at each fixture that he had to work around.