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The original was posted on /r/homeassistant by /u/DiggingForDinos on 2025-06-30 13:44:07+00:00.

One of my favorite DIY projects was turning a regular air conditioner into a smart one using a transistor and an ESP8266. I started by using an infrared receiver to capture all the remote control codes (power, mode, up, down). Next, I tapped into the air conditioner’s internal IR receiver and wired it up so I could send those codes directly—essentially, I was transmitting IR commands over a wire.

For power, I grabbed 5V and ground from the unit to feed the Wemos D1 Mini. Then, I set up ESPhome to create virtual buttons that would fire off the codes. The cherry on top was adding a generic thermostat in Home Assistant, so now the A/C has full climate control. Honestly, I thought it was a pretty cool upgrade.