Wall Switch for Shelly
A momentary wall switch that nobody sells, made by fitting micro switches behind the rocker arms of an Elko RS-16 — safe on 240 VAC with a diode, resistor and zener holding the switches inside their ratings.
I’ve search everywhere for a wall switch with 2 or 4 momentary spring loaded switches, but they don’t seem to exist, so decided to make my own. a DPST switch type (on)-Off-(on).
I use Elko RS-16 wall switches throughout my house, so had to find a way of modifying one and it turned out not to be too hard. The Elko switch uses rocker arms at the back that I could use to push on micro switches.
Adding a diode, resistor and a zener to limit voltage and current to within the micro switches max ratings, makes this work at mains 240VAC. The Sw inputs of the Shelly i3 that I use for this, only needs a tiny current relative to its L input and I suppose this goes for most other Shellys when powered from mains. So far, I’ve only used this with the i3, so when having two buttons, I need two i3’s. Unfortunately Shelly decided to make the i3 instead of an i4, wich in my opinion would have made a lot more sense.
The only micro switches I found that are small enough, Omron D2MQ, are unfortunately quite expensive at around €2 a pc so total parts cost apr. €12, excluding the wall switch :-(.
Assembled PCB with modified Elko switch rockers
PCB made to snap into Elko socket
Screw terminals accessible
Two button version with 4 microswitches. For one button, only two micro switches are needed.