CircuitPlanning:

Arduino UNO R3 --> MQ2 Sensor

Pins--> Vin-->Vcc

Pins--> GND --> GND

Pins--> A0 --> A0

Code:

//Coded and tested by :
// Sheekar Banejee, AI-ML-IOT Solution Engineer and Researcher
int smokeA0 = A0;
// Your threshold value
int sensorThres = 700;
void setup() {
    pinMode(smokeA0, INPUT);
    Serial.begin(9600); //Streaming 9600 bits of Sensor Data per Second
}
void loop() {
    int analogSensor = analogRead(smokeA0);
    Serial.println("Sensor Value: ");
    Serial.println(analogSensor);
    // Checks if it has reached the threshold value
    if (analogSensor > sensorThres)
    {
        Serial.println("Alert! Smoke Detected!");
    }
    else
    {
        Serial.println("Normal...");
    }
    delay(3000);
} 

Results:

Serialmonitor:

EXPANDED TECHNICAL DETAILS

Electrochemical Gas Detection

The MQ-2 is a versatile sensor for detecting LPG, smoke, alcohol, propane, and hydrogen.

• Heating Element Management: The sensor requires a "pre-heat" phase (typically 24 hours for first use, 60 seconds for daily use) to stabilize the internal heater before readings are accurate.
• Sensitivity Calibration: Features an onboard potentiometer to adjust the baseline trigger level. The Arduino reads the analog output voltage; higher concentrations of gas result in lower resistance and higher output voltage.

Safety Alert Logic

• Visual & Audible Warnings: When the gas concentration exceeds a safe limit, the Arduino triggers a Piezo Buzzer and a high-intensity blinking LED.
• Emergency Action: This setup is often expanded with a relay to automatically shut off gas valves or activate emergency ventilation.