I am looking at transforming my existing light switches to zigbee enabled switches by adding an in-wall module (I cannot replace my physical switches with new ones).
My goal is to have electricity going through my zigbee light bulbs 100% of the time and the switch action being a trigger in home assistant (no action on a relay or anything like that).
From my research the only existing module which operates this way is the Philips Hue wall switch which is battery operated and quite pricey (~40€ per switch).
Is there no alternative?
An idea I had was to use a module like the sonoff ZBMINI-L2 in parallel to the light bulb (see image), but this is completely out of recommended usage. Has anybody ever tried this ?
Do not use it that way. You will create a short between the fase and neutral.
You will want to search for a switch coupler. The others like the one you linked are meant to be used with a light and wont have a connection for fase and neutral but will get their power from through whatever you hook up.
Don’t know where you are, but in the UK you can get mountings for the Hue switches that clip over standard wall switches, so the existing switch can stay always on.
I’ve got several of these and they work really well, besides being quick to fit and causing no damage. I’ve found Hue batteries last about two years, so not a problem. You’re right about the cost, though.
For that consider a Shelly L1 (wifi not ZigBee though) as they can be configured in “Detached” mode so they trigger a virtual switch, but not the relay. It may be possible that the ZBMINI-L2 will do the same, but I’ve no experience of them.
Then you can have the relay permanently on, and the physical switch toggles the virtual switch you can use to toggle your bulbs.
I have used the detached mode on the Shelly L1 in a few places in my system and it’s been flawless.
The L1 also allows for 2 switches, so only one relay needed for a 2 gang switch.
use a module like the sonoff ZBMINI-L2 in parallel to the light bulb (see image)
What you’re suggesting there is full-on shorting the L-in to the N wire. I would suggest you don’t
The ZBMINIL2 hardware can actually be hacked to work much like a mains-powered Hue Wall Switch - all it takes is a single PCB trace cut to incapacitate the control circuit’s ability to trigger the relay’s set (“ON”) state.
Just pry open the plastic case - there are two top-bound U-shaped tabs on the right and one on the left. Take the PCB out, flip it and identify the +5V trace between the control circuit and the relay’s “set” coil. Cut the trace in a way to be sure that its two ends are properly isolated (I just fat-fingered mine with a screwdriver )
It would be a good idea to have a load (e.g. a bulb) on the L-out terminal when first powering the device up just in case the relay was left in the set state. It will happily enter the reset (“OFF”) state with a push of the onboard button and will hold it henceforth, thus the L-out terminal can subsequently be treated as a direct N-in.
Although my unit continues to perform well and even OTA-updated its firmware (1.0.10 → 1.0.14) since the modification, please understand that there could be serious issues. If there’s even the slightest doubt in your mind as to your qualification to do this, do seek professional help. Since we’re dealing with a mains-powered device to begin with, the obvious loss of warranty is the least of your concerns. Don’t lose your house to a fire, or even your life, over this! You have been warned.
In case anyone stumbles upon thus topic: I tried to add the S-Mate 2 to Z2M but was unsuccessful, it does not appear to use Zigbee (nor does any of the documentation suggest so). I tried all sorts of things to get it into pairing mode but without success.
