New building: parallel low-voltage network for esphome?

we are about to build a house (new building) and I am thinking a lot about smarthome.
The most obvious would be KNX, but that is also a question of cost and I also like to tinker :wink:

I would therefore be interested in your opinion on the following idea:
One small control cabinet per floor, where the power cables are connected as a star network and are mostly connected to relays. Parallel to this, I lay a low-voltage network to the (light) switches and other sockets for signaling (similar to KNX, but not as a BUS). At first I thought about 5V, but I was told that there would be problems with external voltage, etc. So it would probably end up with 12/24V.
The switch signals only control the relays at the beginning and that’s it. So much for the new building and the doing for the electrician.

Why the whole thing: I have the possibility to hang an esp32 or similar in between with minimal effort and make the whole thing “smart” with ESPHome (step by step).

What do you think? Interesting or the wrong path? Is there a smarter option? How would you go about it?

Thanks for the constructive feedback :blush:

First ideas:
PCF8574 I2C 8CH optocoupler for button detection (10€)

8CH SSR or MOSFET boards (preferably with I2C) to control the relays with 12/24V (30€). However, I have not yet found any suitable boards for this…

You are not very clear about your wanted wiring… If power, do current/voltage drop calculations between your voltage, current, wire diameter and length.
If signal, higher voltage is better for interferences but it’s giving you a big hassle to connect to low voltage MCUs. If you are willing to go with esp32, take care of your signals with wifi, ble, and short shielded 3v3 wiring.

If no one is doing low voltage wiring in house there is a good reason :wink: You can’t get low voltage like 5/12V to travel far unhappy :frowning:

If you’re already planning to run LAN cables through the house, you can use PoE (Power over Ethernet) to get DC power to any of those LAN points. I believe the standard voltage for PoE is 48v, and you could step down from there.

EDIT: I think there are ESP modules that support PoE, so you’d be killing two birds with one stone. You’ll have power for the device, as well as hard-wired communication, which will always beat WiFi.

1 Like

That’s what they were telling 25 years ago, during first boom of internet and concept of iot. We were installing ethernet all over the houses with an idea that tomorrow every fridge and laundry machine is online with ethernet. Every room also had telephone jack and pre wiring for alarm systems.

It never happened. Everything went wireless.Because it’s more convenient and because 99% of old houses didn’t have all those wirings, so it was missing the mass adoption.

1 Like

By the way, think of all the loads that we have in our houses nowadays. All electronics use DC, led lightning use DC, new motors are DC, new air conditioners are DC, resistive loads don’t care if it’s AC or DC. I’m sure that I have hundreds of AC/DC converters in my house
For efficiency we should have DC in our houses instead of AC. But it’s not gonna happen (any time soon).

1 Like

I would draw an utp cable with every power cable to every power socket, switch… Doing that you have multiple options: you can use only power cable and connect old way ( disregarding utp or using it later when needed), you can use POE, you can use it for 12/24V system (if you choose to use it), you can use it to trigger relays directly… just make sure to install deep “wall base” so you’ll be able to squeeze a module inside, behind a switch/socket.
5V is a no-go, that’s for sure. You’d get only 3-4V at the end of longer cable. Higher voltage = lower current = less loss in cables.
Then you use these switching PSU modules at the end for 12/24V, or these ones for POE step-down.

1 Like

Ok, thanks for the answers.

karosum: actually signaling, i.e. tapping button signals, possibly also temperature, humidity, movement.
The esp should then also control the 230v relays (but would then be 12v/24v control voltage).
Ideally, I can then also operate an esp with the mains.

vincen: ok, that means it should be 24v… I think knx uses it too…

dzerovibe: yes, I’ve already seen some, but they only drew power via poe, everything else continued to run via ble/WiFi

karosum: I agree with you, it definitely won’t work without WiFi, but I would like to do without battery-powered iot devices wherever possible… I don’t think it’s sustainable or ecological, and as I hope to have the opportunity to build a new home soon, I want to cover as many cases as possible…

I’ve also read in an article that DC grids for the home would be much more effective nowadays, but the different voltages are a massive problem.

protoncek pavel: so you would lay 3 utp cables in a room with 2 light-switches? 2 to the switches, one for the LAN?

Thank you for the tips :blush:

(Sorry I couldn’t link you, because of forum restrictions)

How could that be the problem? At the moment we have different voltages from 120/240/400V to 3V but from AC to DC.
Problem is complexity of change, old devices not being compatible. So may be year 2100.
Anyway, to build specific wiring for future, for my experience, is going to be mistake. Build what you need now and install big/extra conduits wherever you can.

Yes, one utp togehter with each power cable where you plan to install switch, power outlet etc… So you can first install totally classic “dumb” lights/power outlets/switches, but later when you decide to add smart system to any electric device, you already have utp there waiting, and you just add esp module.
Lay power cables normally to where fuses will be, while you lay all utp’s to a place where you’ll have your router, switch, poe, internet, server… let’s say “server room” :slight_smile:

Having all utp’s in one place (like server room) has a lot of benefits - for one you can later program VLAN’s, etc… just don’t forget ot mark them :stuck_out_tongue_winking_eye:

Oh… perhaps it’ would be better to use ftp (shielded) cable, since they will go beside power cables.