As well as recording the current temperature, one of the more important abilities of any thermostat system is the ability to turn the turn the boiler on and off as required.

Now I’ve played with a few “off the shelf” thermostats and really didn’t like any of them!

Therefore the obvious thing to do is create my own 🙂

I tried a few times to get my current SSR to turn my boiler on / off, but I wasn’t getting anywhere with it. It turns out that’s because I was using a zero-cross sensing SSR, which just wouldn’t work.

Therefore I looked into buying another SSR to test on my system.

Wemos D1 Mini

And then I came across the Wemos D1 Mini. This is a nice little ESP-8266EX unit, built into a stackable system. It’s much smaller than the NodeMCU boards, but still contains everything to program the board via microUSB (so no serial adapters, etc.)

miniYou can see the board above, and more details can be found here: http://www.wemos.cc/Products/d1_mini.html The board is available for just under £3, which is nice and cheap for me.

Wemos D1 Mini Relay Shield

However, what I liked about this board, was that I could buy a Relay Shield to sit on top of the ESP board.

relay

You can see the board above, and more details can be found here: http://www.wemos.cc/Products/relay_shield.html

Combined together, you have a MQTT based 240v relay switch for £4.18

There might be cheaper options out there, but I do like the the look of this one. It’s easy to build, cheap enough, and stackable (which I can’t see me needing any more than the relay switch at the moment).

Boiler Switch Circuit

The circuit for this is simple enough. Just plug in a microUSB to power the board and connect the relay pins to the required pins / cables on your boiler. This will of course be different for different boilers.

BE VERY CAREFUL AROUND 240 / 120V LIVE WIRES. I’M NOT RESPONSIBLE IF YOU’RE STUPID ENOUGH TO KILL YOURSELF BY NOT KNOWING WHAT YOUR DOING!!!

Without that out of the way, the code is simple enough and is available in my Github project folder, under “Boiler Switch”. This can be found here: https://github.com/nerobot/Home-Automation/tree/master/ESP8266%20boiler%20switch

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