MQ2 Gas Sensor Circuit with Arduino

The MQ2 Gas Sensor Circuit with Arduino is a low-cost sensor.

It can catch bad gas in air very quickly.

When we connect it with Arduino, we make small gas alarm system.

It reads gas level, show number on LCD and buzzer make sound when gas goes high.

This circuit is very simple to make and easy to learn.

It is good project for basic gas detection using Arduino.

Arduino Coding:

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2);

int sensorPin = A0;
int buzzerPin = 8;
int gasValue = 0;
int limitValue = 300;

void setup() {
lcd.init();
lcd.backlight();
pinMode(buzzerPin, OUTPUT);
}

void loop() {
gasValue = analogRead(sensorPin);
lcd.setCursor(0,0);
lcd.print("Gas: ");
lcd.print(gasValue);

if(gasValue > limitValue){
digitalWrite(buzzerPin, HIGH);
lcd.setCursor(0,1);
lcd.print("Gas High! ");
} else {
digitalWrite(buzzerPin, LOW);
lcd.setCursor(0,1);
lcd.print("Safe ");
}
delay(300);
}

Coding Explanation:

• LCD library works with I2C LCD.
• SensorPin reads analog gas value from MQ2.
• BuzzerPin becomes HIGH when gasValue is more than limitValue.
• LCD shows gasValue and warning message.
• Delay slows loop to read clearly.

Circuit Working:

Parts List:

MQ2 has heater and sensor resistor.

When gas increases, sensor resistance falls.

Arduino reads this as higher analog value.

Code checks value.

If value is high then buzzer turns ON and LCD shows alert.

Formulas:

Below is the formula for MQ2 Gas Sensor Circuit with Arduino:

MQ2 output = voltage across load resistor RL.

Vout = (RL / (RL + RS)) * VCC

where,

• RL is the load resistor which is a fixed resistor on the sensor.
• RS is the sensor resistance which changes when gas level changes.
• VCC is the supply voltage of 5V.

When gas level rises, RS becomes small so Vout becomes high.

How to Build:

To build a MQ2 Gas Sensor Circuit with Arduino follow the below steps:

• Take all the parts as shown in circuit diagram.
• MQ2 VCC pin connect to Arduino 5V
• MQ2 GND pin connect to Arduino GND
• MQ2 AO pin connect to Arduino A0
• MQ2 DO pin connect to Arduino digital pin D7
• Buzzer positive connect to Arduino pin 8
• Buzzer negative connect to GND
• I2C LCD VCC pin connect to 5V
• I2C LCD GND pin connect to GND
• I2C LCD SDA pin connect to Arduino A4
• I2C LCD SCL pin connect to Arduino A5

Conclusion:

This is simple project for MQ2 Gas Sensor Circuit with Arduino.

Arduino read sensor value and give warning by buzzer and LCD.

This project is good for safety and for basic learning.

References:

MQ2 gas sensor has high default sensor value