How to Use MQ-136: Examples, Pinouts, and Specs

Introduction

The MQ-136 Gas Sensor Module by DIYmore is an electronic device designed to detect the presence of hydrogen sulfide (H2S) in the air. This sensor is widely used in industrial applications, environmental monitoring systems, and by hobbyists for safety and air quality projects. The MQ-136 sensor is sensitive to H2S gas concentrations and can be used to alert users to hazardous conditions.

Explore Projects Built with MQ-136

Use Cirkit Designer to design, explore, and prototype these projects online. Some projects support real-time simulation. Click "Open Project" to start designing instantly!

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.

Open Project in Cirkit Designer

Battery-Powered MQ-2 Gas Sensor with Alert Buzzer

This is a simple gas detection alarm system that uses an MQ-2 sensor to detect gas presence and sound a buzzer when gas is detected. It is powered by a rechargeable 18650 battery, with a TP4056 module for battery management and charging. A rocker switch is used to control the power to the system.

Open Project in Cirkit Designer

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.

Open Project in Cirkit Designer

Arduino UNO Based Gas Detection and GSM Alert System

This circuit is designed to monitor air quality using an MQ135 sensor and provide visual and audible alerts. It features an Arduino UNO microcontroller interfaced with a GSM module for communication, an I2C LCD for display, and LEDs and a buzzer for local alerts. The Arduino runs embedded code to read the MQ135 sensor data, display air quality index (AQI) on the LCD, and trigger SMS and call alerts via the GSM module when gas is detected above a certain threshold.

Open Project in Cirkit Designer

Common Applications

• Industrial safety systems
• Environmental air quality monitoring
• Gas leak detection in residential and commercial premises
• DIY projects involving air quality measurements

Technical Specifications

Key Technical Details

• Target Gas: Hydrogen sulfide (H2S)
• Detection Range: 1 ppm to 10 ppm H2S
• Preheat Duration: 20 minutes (minimum)
• Supply Voltage: 5V ± 0.1V
• Heater Voltage: 5V ± 0.1V
• Heater Current: 150mA (typical)
• Heater Power Consumption: 0.75W (typical)
• Load Resistance: Adjustable via onboard potentiometer
• Operating Temperature: -20°C to 50°C

Pin Configuration and Descriptions

Usage Instructions

Integration with a Circuit

1. Power Supply: Connect the VCC pin to a 5V power source and the GND pin to the ground.
2. Signal Output: The MQ-136 provides two types of outputs:
   • Digital Output (DOUT): Connect to a digital input pin on a microcontroller. The sensor outputs a low level when the H2S concentration reaches or exceeds a certain threshold, which can be adjusted using the onboard potentiometer.
   • Analog Output (AOUT): Connect to an analog input pin on a microcontroller to get a variable voltage that is proportional to the H2S concentration.

Important Considerations and Best Practices

• Preheating: Allow the sensor to preheat for at least 20 minutes to stabilize its readings.
• Calibration: Calibrate the sensor in an environment with a known H2S concentration or in fresh air for baseline readings.
• Ventilation: Ensure proper ventilation around the sensor to prevent saturation and to allow for accurate readings.
• Avoid Harsh Conditions: Protect the sensor from exposure to high concentrations of corrosive gases, high humidity, and extreme temperatures.

Example Code for Arduino UNO

// MQ-136 Gas Sensor Example Code for Arduino UNO

int analogPin = A0; // Analog input pin connected to AOUT on the sensor
int digitalPin = 2; // Digital input pin connected to DOUT on the sensor
int sensorValue = 0; // Variable to store the sensor value

void setup() {
  pinMode(digitalPin, INPUT); // Set the digital pin as input
  Serial.begin(9600); // Start serial communication at 9600 baud
}

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

  if (digitalRead(digitalPin) == LOW) { // Check if the digital output is LOW
    Serial.println("H2S threshold exceeded!");
  }
  delay(1000); // Wait for 1 second before the next loop
}

Troubleshooting and FAQs

Common Issues

• Inaccurate Readings: If the sensor provides inconsistent or inaccurate readings, ensure that it has been properly preheated and calibrated. Also, check for any environmental factors that may affect the sensor's performance.
• No Response to Gas: Verify that the sensor is receiving the correct operating voltage and that the pins are connected properly. Additionally, check if the sensor has been exposed to high concentrations of gas, which may have caused sensor poisoning.

Solutions and Tips

• Preheating: Always preheat the sensor before use to ensure accurate readings.
• Calibration: Regularly calibrate the sensor to maintain its accuracy over time.
• Sensor Replacement: The MQ-136 sensor has a limited lifespan. If the sensor fails to respond after troubleshooting, consider replacing it.

FAQs

Q: How often should I calibrate the MQ-136 sensor? A: Calibration frequency depends on the usage and the environment. It is recommended to calibrate the sensor before initial use and periodically during its lifetime.

Q: Can the MQ-136 sensor detect other gases besides H2S? A: The MQ-136 is specifically designed to detect hydrogen sulfide. While it may show some response to other gases, it is not recommended to use it for detecting gases other than H2S.

Q: What is the expected lifespan of the MQ-136 sensor? A: The lifespan of the sensor can vary based on usage and environmental conditions. Typically, these sensors can last for several months to a couple of years with proper maintenance and calibration.