Smart AC Upgrade with ESP8266 & Home Assistant

One of my favorite DIY projects was turning a regular air conditioner into a smart one using a transistor and an ESP8266. The goal? Full remote control and climate automation without buying an expensive smart unit.

DIY Smart AC with ESP8266 & Home Assistant: Step-by-Step Guide

Step 1: Capture Your Remote's IR Codes

I won’t go deep into that here since there are plenty of guides online, but the basic idea is:

Set up an IR receiver LED (connected to your ESP8266 running ESPHome).
Put the ESP into "listening" mode and point your AC remote at it.
Press each button and log the output. I used the NEC protocol, but RAW might work depending on your remote.

Step 2: Test the IR Transmission

Once you’ve got your codes, set up an IR transmitting LED to send them back.

Use ESPHome’s remote_transmitter component
Verify that your AC responds as if the remote was used

When the AC beeps and obeys your command — congrats, you've cloned the remote.

Step 3: Wire into the AC’s Internal IR Receiver

Now for the fun part — hardwiring your IR signal into the air conditioner so it doesn’t rely on line-of-sight.

Open your AC’s front panel
- Mine (a Frigidaire) had two screws on either side
Swing the panel open to reveal the control board
Unscrew the control panel to access the IR receiver solder points

You’ll need to identify:

VCC (likely 5V or 3.3V) — powers the ESP
GND
IR signal input pin — where you’ll inject your ESP’s IR output

In my case, the IR receiver had three pins, and I had to test all of them to figure out which one carried the data.

⚠️ Tip: Get IR transmission working through an LED first, before wiring into the AC. It’s way easier to debug.

Step 4: Power the ESP from the AC (Optional)

If you want a clean setup, grab 5V and GND directly from the AC board to power the Wemos D1 Mini.

Note: If you're not 100% sure about the voltage, use a multimeter or add a voltage regulator.

I eventually soldered wires from the control board directly to my ESP and left the ESP sitting on top of the AC for easy access.

Step 5: Connect to ESPHome

At this point:

You’ve captured IR codes
Verified them by sending over an LED
Hardwired your signal into the AC
(Optionally) powered your ESP from the AC

Now configure your ESPHome YAML with remote_transmitter + template buttons. You’ll be able to send commands like:

Power On
Power Off
Temp Up / Down
Set Mode to Cool

Step 6: Create a Home Assistant Switch

Use a template switch in Home Assistant to wrap your ESPHome buttons:

If your AC remote uses a single power toggle, you’ll need to track state manually.
- Option 1: Use an input_boolean to fake the state
- Option 2: Use a power-sensing smart plug to infer ON/OFF via a binary sensor

Step 7: Add a Thermostat

If you have a nearby temperature sensor (like from the ESP or Zigbee), you can create a generic_thermostat entity in Home Assistant:

Target temperature
Auto on/off logic
Feels like magic

ESPHome Configuration

remote_transmitter:
  pin: D2
  carrier_duty_percent: 50%

button:
  - platform: template
    name: Air Conditioner Cool Mode
    id: my_button_ac_cool_mode
    icon: "mdi:emoticon-outline"
    on_press:
      - remote_transmitter.transmit_nec:
          address: 0xF508
          command: 0xF609
          command_repeats: 1

  - platform: template
    name: Air Conditioner On
    id: my_button_ac_on
    icon: "mdi:emoticon-outline"
    on_press:
      - remote_transmitter.transmit_nec:
          address: 0xF508
          command: 0xEE11
          command_repeats: 1
      - delay: 3s
      - remote_transmitter.transmit_nec:
          address: 0xF508
          command: 0xF609
          command_repeats: 1

  - platform: template
    name: Air Conditioner Off
    id: my_button_ac_off
    icon: "mdi:emoticon-outline"
    on_press:
      - remote_transmitter.transmit_nec:
          address: 0xF508
          command: 0xEE11
          command_repeats: 1

  - platform: template
    name: Air Conditioner Up
    id: my_button_ac_up
    icon: "mdi:emoticon-outline"
    on_press:
      - remote_transmitter.transmit_nec:
          address: 0xF508
          command: 0xF10E
          command_repeats: 1

  - platform: template
    name: Air Conditioner Down
    id: my_button_ac_down
    icon: "mdi:emoticon-outline"
    on_press:
      - remote_transmitter.transmit_nec:
          address: 0xF508
          command: 0xF20D
          command_repeats: 1

Home Assistant Configuration

climate:
  - platform: generic_thermostat
    name: Air Conditioner
    heater: switch.air_conditioner
    target_sensor: sensor.nodemcu_temperature
    precision: 0.5
    ac_mode: true
    cold_tolerance: 0.5
    hot_tolerance: 0.5
    min_cycle_duration:
      minutes: 1

switch:
  - platform: template
    switches:
      air_conditioner:
        value_template: "{{ states('binary_sensor.air_conditioner') }}"
        friendly_name: "Air Conditioner"
        icon_template: mdi:air-filter
        turn_on:
          - condition: not
            conditions:
              - condition: state
                entity_id: binary_sensor.air_conditioner
                state: 'on'
          - service: button.press
            data:
              entity_id: button.air_conditioner_on
        turn_off:
          - condition: state
            entity_id: binary_sensor.air_conditioner
            state: 'on'
          - service: button.press
            data:
              entity_id: button.air_conditioner_off

Final Notes

If you made it this far — congrats, your dumb AC is now a smart climate-controlled machine. This is just the beginning — any IR device (TVs, fans, fireplaces) can be tamed in the same way.

Don’t forget to share your own wiring diagram or code if you improve it. This project is weirdly satisfying, and way cheaper than buying a "smart" air conditioner.

saihgupr/Smart-AC-Control