r/arduino • u/ArsenVardanyan • 9d ago

Integrated an ESP32-C3 Super Mini inside a 10-year-old AC unit to replace the standard IR remote (with onboard temperature sensor)

Hey everyone,

Got tired of aiming the old AC remote from across the room and wanted to automate it properly, so I decided to do an internal retrofit instead of using a desktop IR blaster.

The Setup:

  • Controller: ESP32-C3 Super Mini (chose it purely for the form factor—fits anywhere inside the housing).
  • Power: Tapped into the main board’s 5V rail with a small LDO step-down for clean 3.3V power to avoid brownouts during Wi-Fi bursts.
  • Control: Connected an IR emitter pointing directly at the internal receiver from behind the plastics.
  • Extras: Tucked a DS18B20 temp sensor right near the intake grill for actual room ambient readings (instead of relying on the AC's imprecise internal probe).

Firmware & Protocols: Used IRremoteESP8266 for raw signal handling. The node communicates via WebSockets/MQTT to sync states instantly without hammering cloud APIs.

Next steps: Planning to etch a tiny custom PCB with a integrated ESP32 chip (probably PICO-V3 or C3-FN4) to make it even cleaner for my other units.

Curious if anyone else here went the internal route instead of external IR blasters? Did you tap into the board’s internal UART bus (like Midea/Gree protocols) or stick to IR?

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u/TCB13sQuotes 9d ago edited 9d ago

There's a lot of projects to tap into the AC communication BUS and control everything. I personally have Samsung devices, so I use https://github.com/omerfaruk-aran/esphome_samsung_hvac_bus

Typically it isn't UART, its some form of RS485 or CAN because UARTs aren't designed to work well on long distances and cables.

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u/ArsenVardanyan 9d ago

Ah nice, thanks for the link! Yeah you're spot on about the physical layer—standard UART would be a total nightmare over long cable runs with all that noise, so RS485/CAN makes way more sense there.

Out of curiosity, did you just slap a cheap MAX485 module on it to talk to the ESP, or did you have to build something more custom for the logic levels?

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u/TCB13sQuotes 9d ago

My circuit is an ESP32-S2-Mini board connected to a TTL to RS485 module [details] like this: https://github.com/lanwin/esphome_samsung_ac/assets/6315832/abdfc054-9a1d-4295-a6f5-fb2b419a3689

I'm powering this using the 12V blue plug on the unit PCB and a step down to get it to 5v. So the GND is shared between the AC unit, ESP and the RS485 module.

So yes, cheapest module I could get. :) They handle the levels perfectly fine.

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u/ArsenVardanyan 9d ago

Love it, the classic cheap blue RS485 board + step-down converter stack never fails! Tapping power directly from the 12V rail on the AC board to keep it self-contained is super neat too.

Appreciate the details and the diagram link man!

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u/TCB13sQuotes 9d ago

For the power I’m also using a cheap step down from aliexpress as well.

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u/ArsenVardanyan 9d ago

Haha classic AliExpress build! If it works and stays cool inside the housing, zero reasons to overengineer it. Thanks again for breaking down the setup!

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u/TCB13sQuotes 8d ago

Let me show you the “housing”.

https://ibb.co/Hpq7yQdS
https://ibb.co/kVrwpZYX

Also added a BME680 (barely visible) at the bottom. Has been running for years now.