Kia ora @etec , I am using the Shelly relays as you describe. I have three controlling water pumps, two for irrigation and one for household water (we are off grid in every respect). The irrigation pumps have timers so they turn on and off at fixed times, plus a timeout in case I turn them on manually and forget to turn them off. If the power goes off and back on again, the pumps stay off to prevent startup power draw pushing a low battery back over the edge. All this works without any network traffic at all; they do send status information out, and will change their behaviour if told to by Node-red and MQTT; but if the network is down they will still do all their pre-programmed stuff.
There are also Shellies that switch 2-4 relay outputs.
The point I am making is that a few Shellies and a single SBC running Node-RED (or HomeAssistant, whatever) will probably do all you need. Modern Shellies (more recent than Shelly 1) can also act as WiFi range extenders, particularly nice if you have a wide area or some nice Faraday cages to block signal.
Shellies draw power to stay alive from the wire feeding the socket outlet. You don’t need more than one SBC, making power supply overall much simpler. Logic is split between the SBC and the Shellies, but in a sensible way that helps a lot if the WiFi is at all loose. The Shellies are individually programmed via a web interface, and in my case the simple automations onboard the Shellies contribute all the ‘mandatory’ features, with the SBC just providing a nice web UI to check status and ‘future expansion’.
1 Like