How to Use MH-Z19D Infrared CO2 Sensor Module: Examples, Pinouts, and Specs

The MH-Z19D is a high-precision infrared sensor module manufactured by Zhengzhou Winsen Electronics Technology Co., Ltd. It is designed to measure carbon dioxide (CO2) concentration in the air using non-dispersive infrared (NDIR) technology. This sensor is known for its accuracy, stability, and ease of integration into various electronic systems.

• Indoor air quality monitoring
• HVAC (Heating, Ventilation, and Air Conditioning) systems
• Greenhouse CO2 monitoring
• Industrial process control
• Smart home and IoT devices

The following table outlines the key technical details of the MH-Z19D sensor module:

The MH-Z19D module has a 7-pin interface. The pinout and descriptions are as follows:

1. Power Supply: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. UART Communication:
   • Connect the UART_TX pin of the sensor to the RX pin of your microcontroller (e.g., Arduino).
   • Connect the UART_RX pin of the sensor to the TX pin of your microcontroller.
3. PWM Output (Optional): If you prefer to use the PWM output for CO2 readings, connect the PWM pin to a digital input pin on your microcontroller.
4. Hardware Reset (Optional): The HD pin can be connected to a GPIO pin for manual reset functionality, but it is not required for normal operation.

• Warm-Up Time: Allow the sensor to warm up for at least 3 minutes after powering it on to ensure accurate readings.
• Calibration: The MH-Z19D supports automatic baseline correction (ABC) to maintain long-term accuracy. Ensure the sensor is exposed to fresh air periodically for proper calibration.
• Voltage Levels: The UART pins operate at 3.3V TTL logic. If your microcontroller uses 5V logic, use a level shifter to avoid damaging the sensor.

Below is an example of how to interface the MH-Z19D with an Arduino UNO using UART communication:

#include <SoftwareSerial.h>

// Define RX and TX pins for SoftwareSerial
SoftwareSerial mySerial(10, 11); // RX = Pin 10, TX = Pin 11

byte cmd_get_concentration[] = {0xFF, 0x01, 0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x79};
unsigned char response[9];

void setup() {
  Serial.begin(9600);         // Initialize hardware serial for debugging
  mySerial.begin(9600);       // Initialize software serial for MH-Z19D
  Serial.println("MH-Z19D CO2 Sensor Initialized");
}

void loop() {
  // Send command to request CO2 concentration
  mySerial.write(cmd_get_concentration, 9);
  delay(100); // Wait for the sensor to respond

  // Read the response
  if (mySerial.available()) {
    for (int i = 0; i < 9; i++) {
      response[i] = mySerial.read();
    }

    // Check if the response is valid
    if (response[0] == 0xFF && response[1] == 0x86) {
      int high = response[2];
      int low = response[3];
      int ppm = (high << 8) + low; // Combine high and low bytes
      Serial.print("CO2 Concentration: ");
      Serial.print(ppm);
      Serial.println(" ppm");
    } else {
      Serial.println("Invalid response from sensor");
    }
  }

  delay(2000); // Wait 2 seconds before the next reading
}

• Replace 10 and 11 in SoftwareSerial mySerial(10, 11) with the pins you want to use for RX and TX on your Arduino.
• Ensure the sensor is connected to the correct pins and powered properly.

1. No Response from the Sensor

   • Cause: Incorrect wiring or insufficient power supply.
   • Solution: Double-check the connections and ensure the sensor is receiving 5V DC.

2. Inaccurate Readings

   • Cause: Sensor not warmed up or improperly calibrated.
   • Solution: Allow the sensor to warm up for at least 3 minutes. Ensure the sensor is exposed to fresh air periodically for automatic baseline correction.

3. UART Communication Issues

   • Cause: Mismatched baud rate or incorrect RX/TX connections.
   • Solution: Verify that the baud rate is set to 9600 and that RX/TX pins are correctly connected.

4. PWM Output Not Working

   • Cause: Incorrect pin configuration or signal interpretation.
   • Solution: Ensure the PWM pin is connected to a digital input pin and use appropriate code to read the PWM signal.

• Q: Can the MH-Z19D measure CO2 concentrations above 5000 ppm?
  A: No, the sensor's maximum measurement range is 5000 ppm.

• Q: How often should I calibrate the sensor?
  A: The sensor supports automatic baseline correction (ABC), which calibrates the sensor automatically when exposed to fresh air. Manual calibration is not typically required.

• Q: Can I use the MH-Z19D with a 3.3V power supply?
  A: No, the sensor requires a 4.5V - 5.5V DC power supply for proper operation.

• Q: Is the sensor suitable for outdoor use?
  A: The sensor is designed for indoor use. It may not perform reliably in extreme environmental conditions or high humidity.

By following this documentation, you can effectively integrate the MH-Z19D sensor into your projects and ensure accurate CO2 measurements.