So I have this old baseboard heater in my mobile home that I'd really like to hook up to the internet. The only issue is smart thermostats are expensive and rarely run on line voltage, so I figured I'd make my own. I have an electrical conduit running two wires with 240v potential from my heater to the spot I'd like to mount the thermostat. Both wires are independently charged with 120v of opposite polarities, and when the two wires are connected the circuit closes and the heater comes on. (I'm sure most of you understand line voltage heaters but I wanted to be thorough.)
Controlling the heater is easy. I found a great Solid State Relay that is more than capable of handling the voltage and current to power the heater. What isn't as easy (at least for me) has been finding a way to power the arduino, no other power wires are nearby and I know enough about electronics, to know I don't know enough about electronics to mess around with 240V AC power without talking someone considerably more knowledgeable than myself about electrical. Would just a normal 240v AC to 12vdc power supply be fine regardless of the fact that both wires are electrically charged? Would the power supply close the circuit, rendering the relay useless?
Another option considering my lack of experience working with AC power, is a 2 in one Relay/transformer like this one on amazon. https://amzn.to/2FUgnwR I'd be fine paying extra to make sure I don't die/burn my house down due to my ignorance. But the electrical for this confuses me more than the two wire setup above. Units like this output 24VAC R.C.W. power intended for smart thermostats. How would I go about powering the microcontroller and controlling the heater? Is it the exact same setup as before just with idiot friendly voltages? Thanks for reading and any and all safety tips would be greatly appreciated, there’s no such thing as too thorough.