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How to Use MQ137: Examples, Pinouts, and Specs

Image of MQ137
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Introduction

The MQ137 is a gas sensor designed to detect hydrogen sulfide (H₂S) concentrations in the air. It operates on the principle of resistive change, where the sensor's resistance varies in response to the presence of H₂S gas. The sensor outputs an analog signal proportional to the gas concentration, making it suitable for integration into a wide range of systems.

Explore Projects Built with MQ137

Use Cirkit Designer to design, explore, and prototype these projects online. Some projects support real-time simulation. Click "Open Project" to start designing instantly!
Battery-Powered Emergency Alert System with NUCLEO-F072RB, SIM800L, and GPS NEO 6M
Image of women safety: A project utilizing MQ137 in a practical application
This circuit is an emergency alert system that uses a NUCLEO-F072RB microcontroller to send SMS alerts and make calls via a SIM800L GSM module, while obtaining location data from a GPS NEO 6M module. The system is powered by a Li-ion battery and includes a TP4056 module for battery charging and protection, with a rocker switch to control power to the microcontroller.
Cirkit Designer LogoOpen Project in Cirkit Designer
Arduino UNO Based Air Quality Monitoring and GSM Notification System
Image of Arduino wild: A project utilizing MQ137 in a practical application
This circuit features an Arduino UNO microcontroller interfaced with an MQ135 air quality sensor, an MPU-6050 accelerometer/gyroscope, a SIM900A GSM communication module, and a buzzer. The Arduino reads analog data from the MQ135 sensor and communicates with the MPU-6050 via I2C, while also controlling the buzzer and handling serial communication with the SIM900A module. The purpose of this circuit is likely to monitor air quality and motion, provide alerts through the buzzer, and enable remote communication via GSM.
Cirkit Designer LogoOpen Project in Cirkit Designer
Arduino-Based Air Quality Monitoring System with Multiple Gas Sensors and GSM Module
Image of AIRMS: A project utilizing MQ137 in a practical application
This circuit is an air quality monitoring system that uses an Arduino UNO to read data from various sensors, including the MQ-7 for CO detection, MQ131 for ozone detection, MQ-135 for general air quality, and a DHT11 for temperature and humidity. The Arduino processes the sensor data and can communicate the results via a SIM800L module for remote monitoring.
Cirkit Designer LogoOpen Project in Cirkit Designer
Solar-Powered Environmental Monitoring Station with ESP32 and Gas Sensors
Image of AIR QUALITY MONITORING: A project utilizing MQ137 in a practical application
This circuit is designed to monitor various gas levels and air quality using a set of sensors (MQ-136, MQ-6, MQ-137, MQ-7, and PMS5003) interfaced with an ESP32 microcontroller. The ESP32 collects sensor data and can control a relay module potentially for activating systems like fans or alarms based on the sensor readings. Additional components include a DHT22 for temperature and humidity readings, a power supply with a step-down converter, and safety features like resettable fuses and an LVD (Low Voltage Disconnect) to protect the battery and circuit.
Cirkit Designer LogoOpen Project in Cirkit Designer

Explore Projects Built with MQ137

Use Cirkit Designer to design, explore, and prototype these projects online. Some projects support real-time simulation. Click "Open Project" to start designing instantly!
Image of women safety: A project utilizing MQ137 in a practical application
Battery-Powered Emergency Alert System with NUCLEO-F072RB, SIM800L, and GPS NEO 6M
This circuit is an emergency alert system that uses a NUCLEO-F072RB microcontroller to send SMS alerts and make calls via a SIM800L GSM module, while obtaining location data from a GPS NEO 6M module. The system is powered by a Li-ion battery and includes a TP4056 module for battery charging and protection, with a rocker switch to control power to the microcontroller.
Cirkit Designer LogoOpen Project in Cirkit Designer
Image of Arduino wild: A project utilizing MQ137 in a practical application
Arduino UNO Based Air Quality Monitoring and GSM Notification System
This circuit features an Arduino UNO microcontroller interfaced with an MQ135 air quality sensor, an MPU-6050 accelerometer/gyroscope, a SIM900A GSM communication module, and a buzzer. The Arduino reads analog data from the MQ135 sensor and communicates with the MPU-6050 via I2C, while also controlling the buzzer and handling serial communication with the SIM900A module. The purpose of this circuit is likely to monitor air quality and motion, provide alerts through the buzzer, and enable remote communication via GSM.
Cirkit Designer LogoOpen Project in Cirkit Designer
Image of AIRMS: A project utilizing MQ137 in a practical application
Arduino-Based Air Quality Monitoring System with Multiple Gas Sensors and GSM Module
This circuit is an air quality monitoring system that uses an Arduino UNO to read data from various sensors, including the MQ-7 for CO detection, MQ131 for ozone detection, MQ-135 for general air quality, and a DHT11 for temperature and humidity. The Arduino processes the sensor data and can communicate the results via a SIM800L module for remote monitoring.
Cirkit Designer LogoOpen Project in Cirkit Designer
Image of AIR QUALITY MONITORING: A project utilizing MQ137 in a practical application
Solar-Powered Environmental Monitoring Station with ESP32 and Gas Sensors
This circuit is designed to monitor various gas levels and air quality using a set of sensors (MQ-136, MQ-6, MQ-137, MQ-7, and PMS5003) interfaced with an ESP32 microcontroller. The ESP32 collects sensor data and can control a relay module potentially for activating systems like fans or alarms based on the sensor readings. Additional components include a DHT22 for temperature and humidity readings, a power supply with a step-down converter, and safety features like resettable fuses and an LVD (Low Voltage Disconnect) to protect the battery and circuit.
Cirkit Designer LogoOpen Project in Cirkit Designer

Common Applications and Use Cases

  • Air quality monitoring systems
  • Industrial safety systems for detecting H₂S leaks
  • Environmental monitoring
  • Gas detection in confined spaces
  • Research and development projects involving gas sensing

Technical Specifications

The MQ137 sensor is a versatile and reliable component. Below are its key technical details:

Parameter Value
Target Gas Hydrogen Sulfide (H₂S)
Operating Voltage 5V DC
Load Resistance (RL) Adjustable (typically 10kΩ–47kΩ)
Heater Voltage (VH) 5V ± 0.2V
Heater Power Consumption ≤ 800mW
Detection Range 5 ppm to 500 ppm
Preheat Time ≥ 24 hours
Operating Temperature -20°C to 50°C
Humidity Range 35% to 95% RH
Analog Output Voltage proportional to gas level

Pin Configuration and Descriptions

The MQ137 sensor module typically has 4 or 6 pins, depending on the breakout board. Below is the pin configuration:

Pin Label Description
1 VCC Power supply input (5V DC)
2 GND Ground connection
3 AOUT Analog output voltage proportional to gas level
4 DOUT Digital output (threshold-based, optional)
5 H1 Heater pin 1 (used internally, not user-accessible)
6 H2 Heater pin 2 (used internally, not user-accessible)

Note: Pins H1 and H2 are typically pre-wired on breakout boards and do not require user interaction.

Usage Instructions

How to Use the MQ137 in a Circuit

  1. Power the Sensor:

    • Connect the VCC pin to a 5V DC power source.
    • Connect the GND pin to the ground of your circuit.
  2. Read the Output:

    • Use the AOUT pin to read the analog voltage output. This voltage corresponds to the H₂S gas concentration.
    • Optionally, use the DOUT pin for a digital signal if the module includes a comparator circuit.
  3. Calibrate the Sensor:

    • Allow the sensor to preheat for at least 24 hours before taking measurements.
    • Use a known H₂S concentration to calibrate the sensor and determine the relationship between the analog output voltage and gas concentration.
  4. Connect to a Microcontroller:

    • The MQ137 can be interfaced with microcontrollers like the Arduino UNO. Use the AOUT pin to connect to an analog input pin on the Arduino.

Important Considerations and Best Practices

  • Preheating: The sensor requires a preheating period of at least 24 hours for accurate readings.
  • Ventilation: Ensure proper ventilation around the sensor to avoid saturation or false readings.
  • Load Resistor: Adjust the load resistor (RL) value to optimize the sensor's sensitivity and range.
  • Environmental Factors: Avoid exposing the sensor to high humidity or temperatures outside its operating range.
  • Calibration: Regularly calibrate the sensor to maintain accuracy, especially in environments with fluctuating gas concentrations.

Example Code for Arduino UNO

Below is an example of how to interface the MQ137 with an Arduino UNO to read the analog output:

// MQ137 Gas Sensor Example Code for Arduino UNO
// This code reads the analog output of the MQ137 sensor and prints the value
// to the Serial Monitor. Ensure the sensor is properly preheated before use.

const int analogPin = A0; // Connect the AOUT pin of MQ137 to Arduino A0
int sensorValue = 0;      // Variable to store the analog reading

void setup() {
  Serial.begin(9600); // Initialize serial communication at 9600 baud
  Serial.println("MQ137 Gas Sensor Test");
  delay(1000); // Wait for 1 second before starting
}

void loop() {
  sensorValue = analogRead(analogPin); // Read the analog value from the sensor
  Serial.print("Analog Value: ");
  Serial.println(sensorValue); // Print the value to the Serial Monitor

  // Add a delay to avoid flooding the Serial Monitor
  delay(1000); // Wait for 1 second before the next reading
}

Note: The analog value read from the sensor must be converted to a gas concentration (ppm) using a calibration curve or formula specific to the MQ137.

Troubleshooting and FAQs

Common Issues and Solutions

  1. No Output or Incorrect Readings:

    • Cause: Insufficient preheating time.
    • Solution: Ensure the sensor has been preheated for at least 24 hours before use.
  2. Fluctuating Readings:

    • Cause: Unstable power supply or environmental interference.
    • Solution: Use a stable 5V power source and avoid placing the sensor near strong air currents or high humidity.
  3. Low Sensitivity:

    • Cause: Incorrect load resistor value.
    • Solution: Adjust the load resistor (RL) to optimize sensitivity for your application.
  4. Sensor Saturation:

    • Cause: Exposure to high concentrations of H₂S for extended periods.
    • Solution: Allow the sensor to recover in clean air before reuse.

FAQs

Q1: Can the MQ137 detect gases other than H₂S?
A1: While the MQ137 is optimized for H₂S detection, it may respond to other gases. However, its sensitivity and accuracy for non-H₂S gases are not guaranteed.

Q2: How do I convert the analog output to ppm?
A2: Use the sensor's datasheet to obtain the calibration curve or formula. This typically involves plotting the analog output voltage against known gas concentrations.

Q3: Can I use the MQ137 outdoors?
A3: The MQ137 can be used outdoors, but ensure it is protected from extreme weather conditions and high humidity.

Q4: How long does the sensor last?
A4: The sensor's lifespan depends on usage and environmental conditions. Under normal conditions, it can last several years with proper care.

By following this documentation, you can effectively integrate the MQ137 gas sensor into your projects and ensure reliable performance.