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1

Hello there,

The project i am looking at in a nut shell:
Nest has a 24v DC output that can be switched on or off via the app.
Nest is located downstairs.

A thermostat / water heater is upstairs runs on 220v AC.

I want to be able to switch on the 24v on the nest via app on demand and that switches on the thermostat/hot water heater, i cannot run cables as its too messy and boring.

The plan is to get 2 arduinos 2 wifi modules, some step down modules etc.
I like to get 1 arduino & wifi downstairs and one upstairs and have them send a signal to each other.
As soon as downstairs is switched on it will Wireless send a signal upstairs and switch on hot water thermostat. As soon as its off i like to have it off upstairs, or send an on and off signal at current detection downstairs.

Would this approach be feasible?
Could i use step down 24v each time to power it / boot it or would i be better with a constant power supply 5-12v?
Any other recommendations or things i haven't thought off?

Thanks for your time, much appreciated!

2

You could consider 2 Wemos boards. Only $4 each, and small. The Wemos' regulator can only handle 5V, so you will need a mini DC-DC convertor to supply it with 3.3V.

How much current can the 24V output supply? The Wemos connected to it might need around 80mA @3.3V, so only around 15mA @24V. This Wemos would simply transmit a "switch on" signal every minute to the other Wemos.

The other Wemos could be run from an inexpensive USB phone charger and have an output connected to a high-current solid state relay (immersion heaters use a lot of current). If it does not receive a "switch on" message, it switches off the relay after 2 minutes.

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A simpler solution would be to bypass the Nest and just have a single Wemos controlling the immersion heater. You could use the Blynk app to control it.