I am designing a centralised home automation system.


Switch / Control

  • Lighting
  • HVAC

Take inputs from

  • Sensors (temperature, occupancy, etc)
  • Physical Inputs (Switch/Buttons)
  • Mobile Inputs

The rough design is that there is a controller in the electrical room some where in the building. For more basic devices such as light build, relays can be connected to controller to control electrical supply to the devices. For more complicated devices such as HVAC system, communications protocol of system manufacturer is probably required.

Now I am having problem with determining communication methods for sensors and physical inputs. I am currently exploring wired protocol as an options as sensors require powers anyway so the network can be wired alongside the power delivery (or included in the protocol preferably). As for physical inputs for switches and buttons, they can be rudimentary like power lines running through the switches then the controller detects the voltage at return line. But this does not work for more complex inputs such as rotary dials (like light dimmer), or other complex devices such as screen. Also if the input devices were complex, they may require power (similar to sensors).

The reason for not going for wireless protocol is due to the very thick walls which may not yield good signals. (There are a lot of problems with wifi, so I'd imagine wireless protocols may not be a good option).

So currently, I would like to learn about possible wired communication methods for communicating for sensors or physical inputs.

Nice to have:

  • daisy chained or line/common bus topology to reduce wiring length
  • devices not reliant on specific manufacturer (possibly custom design)


  • Power over Ethernet (PoE) as they have both power delivery and data, as well as dynamic IP for easily adding/removing devices, but not sure of the wiring length limitations, power consumptions, and heating of wires/devices. Not sure if can be daisy chained or line.

  • CANBus as it allows line/common bus topology, but no protocol on dynamic ID and no standards on power delivery.

  • RS485 specifies physical layer but no data link and onward and no power delivery.

  • 1
    There are quite a few building automation systems like KNX, DALI, BACnet, LonTalk, and more. You may want to look into those.
    – jcaron
    May 15, 2023 at 20:13


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