How to Use MQ 135: Examples, Pinouts, and Specs

Introduction

The MQ-135 is a versatile gas sensor designed to detect a wide range of gases, including ammonia, nitrogen, oxygen, alcohols, aromatic compounds, sulfide, and smoke. It is widely used in air quality monitoring systems, industrial applications, and safety systems to ensure a healthy and safe environment. The sensor provides an analog output that can be easily interfaced with microcontrollers like the Arduino UNO for real-time monitoring and data logging.

Explore Projects Built with MQ 135

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

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.

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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.

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Arduino UNO Air Quality Monitor with LED Indicator and Piezo Speaker

This circuit uses an Arduino UNO to monitor air quality via an MQ 135 sensor and provides visual and auditory feedback using an LED and a piezo speaker. The Arduino is powered by a MAHIR 7.0 power supply, and the LED and speaker are controlled through digital pins D13 and D12, respectively.

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ESP32-Based Air Quality Monitoring System with Multiple Sensors

This circuit is an air quality monitoring system that uses an ESP32 microcontroller to collect data from various sensors, including the MQ135 and MQ-2 gas sensors, a DHT11 temperature and humidity sensor, and a PMS5003 PM2.5 air quality sensor. The ESP32 processes the sensor data and can potentially transmit it for further analysis or display.

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Technical Specifications

Key Technical Details

Pin Configuration and Descriptions

Usage Instructions

How to Use the Component in a Circuit

1. Power Supply: Connect the VCC pin to a 5V DC power supply and the GND pin to the ground.
2. Analog Output: Connect the AOUT pin to an analog input pin on your microcontroller (e.g., A0 on Arduino UNO).
3. Digital Output: Optionally, connect the DOUT pin to a digital input pin on your microcontroller if you want to use the threshold-based digital output.

Important Considerations and Best Practices

• Preheat Time: The sensor requires a preheat time of at least 24 hours for optimal performance. Ensure the sensor is powered on for this duration before taking any measurements.
• Calibration: Calibrate the sensor in a clean air environment to establish a baseline reading. This helps in accurately detecting gas concentrations.
• Ventilation: Ensure proper ventilation around the sensor to avoid saturation and ensure accurate readings.
• Avoid Contaminants: Keep the sensor away from water, oil, and other contaminants that could affect its performance.

Sample Arduino Code

// MQ-135 Gas Sensor - Arduino UNO Example Code

const int analogPin = A0; // Analog input pin connected to AOUT
const int digitalPin = 2; // Digital input pin connected to DOUT (optional)
int sensorValue = 0;      // Variable to store the analog value

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

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

  // Optional: Read the digital output
  int digitalValue = digitalRead(digitalPin);
  Serial.print("Digital Value: ");
  Serial.println(digitalValue); // Print the digital value to the serial monitor

  delay(1000); // Wait for 1 second before taking the next reading
}

Troubleshooting and FAQs

Common Issues Users Might Face

1. No Output or Incorrect Readings:

   • Solution: Ensure the sensor is properly connected to the power supply and ground. Check for loose connections and ensure the preheat time is met.

2. Fluctuating Readings:

   • Solution: Ensure the sensor is in a stable environment with consistent airflow. Avoid placing the sensor near sources of interference or contaminants.

3. Slow Response Time:

   • Solution: Verify that the sensor is not saturated with high concentrations of gas. Allow the sensor to recover in clean air if necessary.

FAQs

1. How long does the sensor last?

   • The MQ-135 sensor has a lifespan of approximately 2 years under normal operating conditions.

2. Can the sensor detect multiple gases simultaneously?

   • Yes, the sensor can detect a range of gases, but it provides a combined output. Specific gas concentration detection requires calibration and additional processing.

3. Is the sensor waterproof?

   • No, the MQ-135 sensor is not waterproof. Avoid exposure to water and other liquids.

By following this documentation, users can effectively integrate the MQ-135 gas sensor into their projects, ensuring accurate and reliable gas detection for various applications.