How to Use MQ-135 to Detect Gases

In this tutorial, you will learn how to detect gas with an MQ-135 sensor and an Arduino.

Parts Required

  • Arduino
  • MQ-135 Gas Sensor
  • Jumper wires
  • Breadboard


MQ-135 Air Quality Sensor Tutorial | Microcontroller Tutorials

To use the LED connect it to digital pin 13.


int sensorValue;
int digitalValue;
void setup()

Serial.begin(9600); // sets the serial port to 9600
pinMode(13, OUTPUT);
pinMode( 3, INPUT);


void loop()


sensorValue = analogRead(0); // read analog input pin 0

digitalValue = digitalRead(2); 
digitalWrite(13, HIGH);
digitalWrite(13, LOW);
Serial.println(sensorValue, DEC); // prints the value read
Serial.println(digitalValue, DEC);

delay(1000); // wait 100ms for next reading




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