Home Assistant control of Mitsubishi MCFZ-A24 WV A/C - Part 2

In part 1 I described how I decoded the IR signal from the original remote and modified Tasmota to send commands the A/C unit was happy with. As IR is one way, I also wanted to read the room temperature so I wanted to add a BME280 module. These are quite nice as they can read temperature, pressure and humidity over an I2C connection.

The whole point of this project was to try out new things and building a circuit with perf board isn't something I'd done before. My first attempt was bit messy but the second was OK and fitted nicely into a small project box. I used a standard 2N2222A transistor to drive the LEDs, which are just generic 940nm ones from eBay.

The ESP-01S modules that I used doesn't break out many GPIO pins to the header but Tasmota let's you re-assign pins. The ESP chip has a few constraints and won't boot if certain pins are pulled low at power-on but with a bit of trial and error (although it is well documented) I found a working combination of pins.

Originally I put the BME280 into the same enclosure but I didn't take into account how much heat the ESP8266 and AMS1117 3.3v voltage regulator give off, which skewed the readings. To mitigate this I put the sensor into it's own box (with some small vent holes) and added an interconnect cable. I2C is really meant for short PCB connections but a 30cm cable seemed to work OK. There are better enclosures for temperature sensors but this will have to do for now. I'm also experimenting with MP1584EN voltage regulators as they should run cooler.

I'd already generated a custom firmware build for the IR sender so I re-compiled it again to add in support for the sensor. Usually it's included in to the tasmota-sensors binary but that is separate to the tasmota-ir binary due to the limitations of the ESP module.

Once all fitted together it looks quite neat, although it does need a reasonable view of the A/C in order to reliably send commands.

In part 3 I'll show the Home Assistant configuration.