MH-Z19B ESP32 Library

Overview

This library provides an easy-to-use interface for the MH-Z19B CO₂ sensor on the ESP32, utilizing hardware UART for communication. The library supports flexible pin selection and includes functions to read CO₂ concentration, calibrate the sensor, enable/disable auto-calibration, and configure the detection range.

Features

• Uses ESP32 hardware UART (no SoftwareSerial required)

• Allows custom UART pins

• Supports the following MH-Z19B commands:

  • Read CO₂ concentration (0x86)

  • Zero point calibration (0x87)

  • Span calibration (0x88)

  • Auto-calibration on/off (0x79)

  • Set detection range (0x99)

• Automatic checksum calculation for data integrity

Installation

1. Download the library files (MHZ19B_ESP32.h and MHZ19B_ESP32.cpp).

2. Place them in your Arduino project's src/ directory.

3. Include the header in your code:

   #include "MHZ19B_ESP32.h"

Usage

Basic Example

#include "MHZ19B\_ESP32.h"

MHZ19B sensor(Serial2, 16, 17); // Use UART2 with GPIO16 (RX) & GPIO17 (TX)
  

void setup() {

    Serial.begin(115200);
    
    sensor.begin();

}

  

void loop() {

    int co2 = sensor.readCO2();
    
    Serial.print("CO2 Concentration: ");
    
    Serial.println(co2);
    
    delay(2000);

}

Available Functions

void begin(int baudRate = 9600)

Initializes the sensor with the specified baud rate.

int readCO2()

Reads and returns the CO₂ concentration in ppm. Returns -1 if reading fails.

void calibrateZero()

Performs a zero point calibration (sensor must be in a 400ppm CO₂ environment for at least 20 minutes before execution).

void calibrateSpan()

Performs a span calibration (used for setting a known reference CO₂ level).

void setAutoCalibration(bool enable)

Enables (true) or disables (false) automatic baseline calibration.

void setDetectionRange(uint16_t range)

Sets the sensor detection range (e.g., 2000 ppm or 5000 ppm).

Notes

• Ensure correct wiring: The sensor operates at 3.3V UART level, so direct connection to ESP32 pins is fine.

• Preheat Time: The sensor requires 3 minutes to warm up before stable readings.

• Zero Calibration: Run sensor.calibrateZero(); in fresh air (~400 ppm) and wait 20 minutes before execution.

License

This library is open-source and free to use in personal and commercial projects.

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For issues and contributions, feel free to create a pull request or open an issue.