In-Depth: How MQ2 Gas/Smoke Sensor Works? & Interface it with Arduino

The MQ2 gas sensor module is designed to detect the presence of various combustible gases and smoke in the surrounding air. At the core of the sensor is a small heating element paired with a sensitive electrochemical material. When power is applied via the Arduino board, the internal heater warms up the sensor's sensing material to a specific operating temperature. In clean air, the electrical resistance of this material remains quite high. However, when target gases like LPG, smoke, or alcohol come into contact with the heated surface, the gas molecules react and cause the resistance of the sensor to drop significantly. This change in resistance alters the output voltage of the sensor module. The module typically provides both a digital output (via an onboard comparator circuit with an adjustable threshold potentiometer) and an analog output. By connecting the analog output to an analog input pin on the Arduino Uno, the microcontroller can read the continuous voltage fluctuations using the Arduino IDE software. The Arduino reads this incoming analog value, converting the raw voltage into a readable number that corresponds to the concentration of gas present in the environment. Jumper wires are used to supply power and ground to the sensor module while routing the signal lines back to the Arduino for processing.