HomeAssistant - perfect one.

It's been a while of hard work for me with reading about the electrical wires installation etc.

I've landed with a small plan, which I would like to discuss

1. for sure KNX is too expensive for me to consider at this moment, although method I chose will be KNX-proof for future.
2. the only way to meet the requirements of: easy external (not by me) service, work even without computer/domoticz hang etc./future-proof is to run wires from every switch and socket I want to control to central cabinet and switch it from there.
3. run LAN/cat5e cable to each socket for future KNX proof installation or running any arduino there instead of typical wall switch.

So if I enter room and want to switch light, I just press a doorbell-type switch on wall, which will put an impulse to central cabinet (using 230V) and switch there will turn the proper light on. It is both: easy to service for external serviceguy if I would be away and some module is dead and also it will be able to work without ANY automation software/hardware further.

Also, doorbell-type cabinet switches are possible to control externally.
Every doorbell-type switch connected to them will release 'turn on/off' action same as a button pressed on a wall, so I can use one of these:
https://www.aliexpress.com/item/DIN-Rail-Mount-16-SPDT-Power-Relay-Interface-Module-OMRON-10A-Relay-5V-Coil/1986473508.html
to securely control bistable switches I want, with optoisolation using ie. MQTT and HomeAssistant.

The only question left is: how to know what is the status of each light/socket managed by bistable relays?
If I turn on something via homeautomation and turn it off by hand on wall-switch, how to monitor them?

The only way I manage to consider is using stairway-like switch (so managed from both sides of power line) instead of doorbell bistable one. But then switch on wall would be once on, once off in different positions.

Any other thoughts? What do you guys think about the idea described above?

Loxone and KNX/EIB are considered 'expensive' by me.
I'm looking more for a way to use system like this but without complicated expensive installations.

For now on I've found on OpenHardware project for in-wall WiFi ESP relays, with MQTT it could be it. But WiFi can be interrupted so not for security use tho...
I'm looking also for some other ways to control everything without using loxone/knx.

Hi!

I'd be looking for a new home and could have possibility to change some in cabling hopefully.

Currently I'm thinking what to go for in broad field of home automation.
I'd like to choose a way that can act on lights and switches, but also be independent from 'smart' insallation, so when I remove it everything works fine (or if something with domoticz or antyhing else is broken, lights and manual switches would still work).

Also I'd totally love not to use WiFi/other radios in places I can have cables in, so it can't be intercepted and disabled with stronger signal.

Do you have any ideas on what to choose?

@kimot so the only thing that's left is TCP/IP and MQTT...

@TimO this small W5100 module: http://www.aliexpress.com/item/TOP-Mini-W5100-LAN-Ethernet-Shield-Network-Module-board-Best/32457200047.html with step-down dc converter.
Cheaper than the PoE standard version.

TOP Mini W5100 LAN Ethernet Shield Network Module board Be

$5.80

@kimot what has to be done to prepare MySensors to use CAN?
I'm thinking about ordering some modules for tests.

@pjr I'm aware of that
Still struggling with decision either to use the CAT5e just as a loooong cable to (doorbell) switch or use it to PoE small nanos all over the place and run i.e. MQTT on each wall-switch separate.
In second option the RS485 protocol would be the best, because of small form factor (smaller than ethernet port inside switch) and possibility to use MySensors too

@LeoDesigner I will put cat5e for 'LAN' purposes to proper socket, but I also want to control my lights not via connecting/disconnecting 230V in-wall, but in central control panel.
I was planning to use doorbell push buttons on walls just to give signal to automation and then MCU will set proper relays/dimmers on/off etc.

That's why I was thinking about putting cat5e also to on-wall switches, then on 1 pair make the +/-12V signal, another pair for data bus etc. And now I'm looking for most efficient way to connect it everything together.
Each room will have temperature sensor for sure (in the switch), some may have dimmers etc. Last idea was to put mini arduinos inside the hole in wall, but I'm afraid of resetting them every once in a while, just because arduino likes to hang itself...

@kimot Thank you for the information - your english is good enough to understand.

I'm just looking for more simple protocol than ethernet to send data from various places - wired.
And it seems that, for longer distance and cat5e cable in-wall, ethernet is the only choice