I would like to move my current heating thermostat to another room and have it wirelessly close the circuit at the original thermostat location.
Thermostat switch would be wired to a transmitting (Tx) arduino which would transmit a signal when the thermostat state changed.
Wires to heating system (originally connected to thermostat) would be connected to a second receiving (Rx) arduino with a receiver and the Rx Arduino would open/close the heating circuit when receiving the signal.
I would think there should be non-Arduino solutions as well -- basically I just want to remotely operate a relay connected to the heating wires triggered by a circuit (on the thermostat) being open or closed, but I haven't been able to find a model project explaining how. And I have two Arduino Uno boards anyway in case that makes it simpler.
Tx and Rx would be in adjacent rooms max 30 feet apart and separated by one wall. Wifi is an option but I would prefer to use Rf or Bluetooth. I was looking at Simple nRF24L01+ 2.4GHz transceiver demo as a potential option.
Voltage for heating system wires is 24V AC. I'm not sure if I could wire that circuit directly to output pins on the Arduino or if I would need to add something in addition to the receiver to operate that circuit.
ok -- suggestions on specific options? And does it sound reasonable to use the two arduinos with Rf transmitter/receiver pair like nRF24L01+ module pin connection?
You still have a problem powering the old thermostat in the new position. Unless it is REALLY old and uses a bimetalic switch, which requires no power to operate.
@Idahowalker Are you using bluetooth for any of the pi connections to the ESP32s, or just wifi? Are you using ESP32s for both temp sensors and for the heating circuits? (where are your temp sensors)?
5 of the ESP32's have temperature sensors that transmit the temperature to the MQTT Broker on the RPi and are processed by the Python program to determine operational parameters for heating, cooling, humidity, and fresh air exchange (I maintain a C02 PPM of less then 400PPM). Also, the ESP32's take color pictures and infrared images that are processed on the RPi.
For temperature sensors I use BME 688's and BME280's.
I guess all of this is because you've figured that the thermostat is in the wrong place for your needs but you want to keep the features of the device (display, programming) without having to pull new wires from the heating system.
If i were going to do something like this, I'd go the @Idahowalker route and have multiple sensors. That's mostly because my bedroom can get very cold overnight but my thermostat is perfectly happy with what it's reading in the dining room. I think just turning the HVAC fan on would help me a lot.
As to relays, you will need something that will have a decent lifetime - from the price of the typical Arduino relay modules, I have a suspicion that those relays aren't intended for long term service, more like temporary hobby projects.
I'd take a look at your thermostat and see what relays it's using - you'll want something at least that good.
One precaution I've seen on other projects like this is to add an old school bimetallic strip thermostat in parallel with the Arduino controller. Set it to ten above freezing to protect your pipes if the Arduino solution fails.
And I have old hot water baseboard heating so no fan to turn on independently (though I could put a small doorway fan in to circulate air between the adjacent rooms). Thanks for the advice on quality of relays and backup in case the Arduino solution fails.
@Idahowalker How are you powering the ESP32 connected to the thermostat? This may be a dealbreaker for me unless I can siphon some power from my heating circuit (which has no common wire). I can't run cord to the original thermostat location, and batteries will probably not last long enough.
And reading more about thermostats, my initial test for whether the switch in the thermostat was run by the thermostat's batteries might have been misleading: the thermostat might be recharging by siphoning power from the heating circuit, in which case I would have to provide additional power to the thermostat. But that should be do-able since I can run a wire to the relocated thermostat.