MQ-4 Natural Gas Sensor Experiment Base on Arduino


About: I am a electrical student,like DIY and travel and reading.Recently I am interested in arduino proejct

This project uses sensors to monitor indoor natural gas on the basis of Arduino, and will make alarm if the natural gas leak exceeds the limit.


1.MQ-4 Natural Gas Sensor

2.Arduino Uno with Network Screening

3.Bread board

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As a natural gas sensor,the MQ-4 Natural Gas Sensor is a fast and reliable sensor with a high sensitivity to natural gas and methane, also good sensitivity to propane and butane. This natural gas sensor has a long life and low cost and is widely used for gas leak detection. At the same time, two LED lights are used in the project to display the gas concentration:

Green light: it means the natural gas concentration is below the critical value.

Red light: alert! The natural gas concentration has exceeded the critical value.

The MQ-4 Arduino sensor has four pins:

1. Positive Vcc (+5V)

2. Ground GND

3. Digital output

4. Analog output

Above picture is the wiring diagram:

In the
schematic, there are two resistors connected to the Arduino digital pins and LEDs. The resistance is 220 Ohm

Here is the code:

int pinRedLed = 11;

int pinGreenLed = 8;

int pinSensor = A5;

int THRESHOLD = 250;

void setup() {

pinMode(pinRedLed, OUTPUT);

pinMode(pinGreenLed, OUTPUT);

pinMode(pinSensor, INPUT);



void loop() {

int analogValue = analogRead(pinSensor);

Serial.println("Val: " + analogValue);

digitalWrite(pinGreenLed, HIGH);

if (analogValue >= THRESHOLD) {

digitalWrite(pinGreenLed, LOW);

digitalWrite(pinRedLed, HIGH);


else {

digitalWrite(pinRedLed, LOW);




The green LED remains light up unless the natural gas concentration exceeds the threshold, the red LED will lights up.



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