How to turn a basic minisplit into a real thermostat

I am the founder of Integrated House. In my own home, and in several we have automated in Medellín, the minisplit already cooled well. What was missing was not a new unit with factory Wi‑Fi. What was missing was a real thermostat: something that sends the command, confirms the AC responded, and adjusts to the room temperature—not the sensor stuck on the evaporator.

If you only want the short version of why it is worth it, start with smart air conditioning without replacing your minisplit. Here I go into how we do it when the goal is to close the full loop.

Electrical safety note. Anything that touches the minisplit board, the buzzer, the supply, or 110/220 V wiring must be done by an experienced technician. A badly built voltage divider or optocoupler can damage the equipment or, worse, put the installer at risk. This guide orients the design; it does not replace a professional install or local codes.

1. ESP32, infrared, and a room thermometer

The base is an ESP32 with infrared LEDs aimed at the indoor unit, an IR receiver to learn the original remote, and a temperature sensor (and sometimes humidity) placed where you actually are: near the bed or sofa, not next to the air outlet.

The flow is simple:

1. Aim the remote at the receiver and capture on, off, modes, temperatures, and fan speeds.
2. Store those signals on the ESP32.
3. When the home decides to change something, the ESP32 “replays” the same IR packet the remote would have sent.

From the minisplit’s point of view it still receives an infrared command. You do not need to void the manufacturer’s warranty for basic control. The room sensor is what changes the game: without it, you only have a networked remote.

2. Zigbee coordinator on a small computer

The ESP32 speaks Zigbee (or joins the home’s Zigbee ecosystem). In practice we put a Zigbee coordinator on a small computer: a mini PC or a Raspberry Pi with Home Assistant and Zigbee2MQTT, wired to the home router.

That gives three concrete things:

• Control from the local network and from the phone, without depending on the AC brand’s app.
• One logic for lights, blinds, climate, and scenes.
• Less drama when the building’s internet fails: the brain stays at home.

The coordinator does not have to be bulky. What matters is that it stays stable, with reliable power and the Zigbee antenna where the sensor mesh has good reach.

3. One step further: air that comes out and a display that changes

When you want certainty, not just “I sent IR and hope,” we add two discreet Zigbee sensors:

• Temperature at the minisplit outlet. A sensor on the grille or near the airflow confirms cold air is coming out (or that it stopped). If you commanded cool and the outlet does not drop, something failed: emitter battery, line of sight, or the unit did not get the command.
• Light on the digital display. Many minisplits show the setpoint or mode on a display. A light sensor (or a well-placed phototransistor) detects brightness or digit changes. It does not “read” the number like a human, but it tells you the screen reacted after the command.

With that you stop flying blind. The system does not only command; it observes.

4. The buzzer beep as acknowledgment

I discovered this on my own minisplit. The buzzer beep annoyed me at night, so I disconnected it. Later I realized that same beep is the clearest signal that the unit received and accepted the remote’s command.

That buzzer line can go to an ESP32 input, always with proper conditioning: a well-calculated voltage divider or, better in many cases, an optocoupler that isolates the ESP32 from the AC electronics. Without that, do not do it. Wrong voltages burn pins or, in the worst case, put whoever is measuring at risk.

When the buzzer “sounds” (even if you silenced it in the room), the ESP32 marks acknowledgment. If you sent IR and there was no beep within a reasonable time, you retry or alert. It is a cheap hardware detail and it changes control reliability.

5. The result: a thermostat that closes the loop

With learned IR, room temperature, Zigbee network, and—if you want—outlet air, display, and buzzer, you no longer have a minisplit with an app. You have a thermostat:

• You measure the room where you are.
• You send the command over IR.
• You confirm the unit reacted.
• You adjust again if temperature leaves the range.

That is closing the loop. Fixed schedules and “leave it at 22 all night” become unnecessary when the home reacts to what is actually happening.

How we do it at Integrated House

At Integrated House we do this upgrade on the equipment you already have. It costs less than throwing away a minisplit that cools well just to buy one with factory Wi‑Fi, and it ends up integrated with the rest of the home—not a stray brand app.

Every home is different: AC brand, line of sight, whether the buzzer can be touched, where to put the thermometer. That is why we start with a visit and design to fit.

If you want to turn your minisplit into real smart control, write to us from the site. We review your case and propose the cleanest path for your home.