A renter sought to automate their apartment's analog AC unit without compromising their security deposit. Standard smart home solutions were impractical due to the AC's unit-mounted, knob-based controls and the lack of available smart plugs for its NEMA 5-20P outlet.

Instead, the author opted for a DIY approach, employing an ESP32 microcontroller and a stepper motor. This setup was mechanically coupled to the AC's temperature control knob. The stepper motor, controlled by the ESP32, rotates the knob to adjust the temperature, effectively turning the AC on or off by setting it to extreme hot or cold. This solution cost approximately $15 in parts.

The contraption is affixed to the AC unit using L-brackets and binder clips, avoiding permanent modifications. It communicates with a Home Assistant instance via MQTT, allowing the AC to be controlled based on room temperature sensor data. This 'janky' yet functional solution frees the user from manually adjusting the AC, demonstrating a creative workaround for limited smart home integration in rental properties.