Project idea: Convert any switch to a smart switch

Hi everyone,

I m relatively new to the whole smart home thing but have some technical skill. I’m currently running OpenHab2 and Zigbee2mqtt on a RaspberryPi 4 for my setup of lights addressed by Aquara Sensors and Buttons.

However as many a smart home enthusiast before me I have run into the issue of lights being switch of by physical buttons and then not being able to turn on via the smart system, and vice versa (depending on the power-on behavior of the light in question i guess).

So I set out looking for smart switches to replace the existing ones in my flat. However it is a rented flat, and I don’t want to start out replacing everything with expensive EnOcean equipment, or pulling of the switch covers to replace them with cheap-looking often too large Chinese Buttons.

What I was looking for was basically a small “Sensor” to attach to my existing switch that would send a message to the zigbee2mqtt server whenever the switch changed state. I would then bridge through the existing wires to my lights and have everything smart (I guess this would even work for people without neutral in their switch boxes).

So my first question would be if this actually exists and I just didn’t find it?

Failing that I have a left over Aqara door sensor. So my idea is to simply remove the “magnet detecting” reed switch in those, and solder in my existing switches. Thereby transforming them to (battery powered) smart switches.

Additionally I thought I might combine this with a mini power supply like
this, to get rid of the need for battery-replacements.

I would welcome any advice on a “as small as possible” 230V to 3-3.3V powersupply to fit to the Sensor.

I also welcome any thoughts on how to do this better, or why not to do this at all xD

I just thought I d ask the community, maybe we can come up with something together :slight_smile:

The Qubino Zwave switches will do this, they can be wired behind the original light switch, and be used to both sense the light being on/off, they will also allow you to continue to use the original switch.

Tho they are z-wave and not zigbee. I did a look for a similar zigbee item but did not find any off hand. I have used these myself and been very happy with them. I use them for my fireplace, and some vintage items I wanted to be smart, but not change their physical look.

Shelly or Homematic would be other options you could look into

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Thanks for your suggestions,
the Qubino aswell as the Homematic solution are a bit too expensive to install in every switch, they would also require additional hubs. The homematic also relies on a battery, which for that price seems odd.

I have also thought about the Shelly 1 as a solution, but I think I would prefer Zigbee over Wifi. Additionally I really struggled, last time I wanted to fit a Shelly behind a switch, there just isnt enough space…

I agree, you can use a zwave dongle or hat (if using a pi), no hub needed. But I understand not wanting another tech. I also fully agree over not going Wifi. Every single wifi smart home device I’ve bought in the last 10 years has ended up dead. And a few were found to have foreign backdoors that gave access to my network. Wifi suffers from problems of lifespan. either are no longer supported, or the company went belly up, etc. At least with ZWave/Zigbee. They will always work regardless of any company/cloud closing.

Ok so I just went ahead and did it today (see pictures).
And besides my very poorly positioned cable holes that I had to re-drill everything is working great. I stuck with battery power for now, mainly for safety reasons, so lets see what the battery-life is on these.

I glued the door sensor to the back of my Berker switch using the pre-attached pads and had easily enough space in the switch box.

All in all very easy to do. I have already order 4 more door-sensors to do the rest of the flat :wink:

With this solution you now know the state your switches are in, but what about controlling them as well , to be able to turn them on and off remotely ?

Since the connected lights are smart themself I dont need a smart relay to turn them on and off.

Do you mean you’re using smart bulbs? This is quite a clever idea!

Well yes,
bulbs, full ceiling lights and LED-Strips with a Zigbee-Controller. That s actually another reason I cant use a zigbee-relay or zigbee-dimmer. The LED-Strips aren’t connected to the switch but are permanently powered. This way I can control whatever lights I want with the switch.

Just to chime in that the Fibaro z-wave relays work sort of co-operatively with a physical switch. That is, you flick the switch on, and the relays comes on as well. Flick the switch off, and the relay turns off. In either state, the zwave can turn the switch on or off too (to sort of override the physical switch). If say the physical is on, but the zwave is off, then you just have to switch the physical off and back on to turn the lights on. They’re also designed to fit inside the back-box behind the physical switch (but even still, do need a fair amount of space), or you can put them in the ceiling rose (if you’ve got a pendant light) - no battery required.

Pretty cool, if maybe a bit too expensive for every single light around the house:

And here comes Philips doing the exact same thing, but charging 40€ for what is essentialy a 10€ door switch witch cables sticking out