Arduino GSM Gas Leakage Alert System

 

1. Introduction

Gas leakage detection becomes much more powerful when combined with real-time alerts. In this project, we enhance the basic MQ-2 gas detector by integrating a GSM module (SIM800L) to send an SMS alert when gas leakage is detected.

This system is highly useful for:

• Homes and kitchens
• Laboratories
• Industrial safety systems

It ensures that even if you are not nearby, you will still receive a warning message instantly.

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2. Components

• Arduino UNO
• MQ-2 Gas Sensor Module
• SIM800L GSM Module
• Buzzer
• LED
• 220Ω Resistor
• Resistors (10kΩ & 20kΩ for voltage divider)
• Breadboard
• Jumper Wires
• 3.7V Li-ion Battery (for SIM800L)

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3. Circuit and Connections

Arduino Uno Pinout Diagram

Pinout Diagram of MQ-2 Sensor

Pinout Diagram SIM800L GSM Module

Arduino Pin interfacing to SIM800L GSM Module

Pinout Diagram of Buzzer

🔌 Connections:

MQ-2 Sensor → Arduino

• VCC → 5V
• GND → GND
• A0 → A0

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SIM800L → Arduino

• VCC → 3.7V Battery ⚠️ (DO NOT connect to 5V)
• GND → GND (common ground with Arduino)
• GSM TX → Pin 10 (Arduino RX)
• GSM RX → Pin 11 (Arduino TX) (voltage divider required since GSM is 3.3V and Arduino in 5V)

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🔽 Voltage Divider (IMPORTANT)

• Arduino TX (Pin 11) → 1kΩ → SIM800L RX
• SIM800L RX → 5.6kΩ → GND

(This reduces 5V to ~3.3V safe for SIM800L)

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Buzzer → Arduino

• Positive → Pin 8
• Negative → GND

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LED → Arduino

• Anode → Pin 7 (via 220Ω resistor)
• Cathode → GND

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4. Detailed Step-by-Step Circuit Working

1. MQ-2 sensor continuously monitors gas levels.
2. Arduino reads analog values from the sensor.
3. When gas exceeds threshold:
   • Buzzer turns ON
   • LED glows
4. Arduino sends AT commands to SIM800L module.
5. GSM module sends SMS alert to predefined number.
6. User receives warning message instantly 📩

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5. Code

#include <SoftwareSerial.h>

SoftwareSerial gsm(10, 11); // RX, TX

int gasSensor = A0;
int buzzer = 8;
int led = 7;

int threshold = 300;

void setup() {
  pinMode(buzzer, OUTPUT);
  pinMode(led, OUTPUT);
  
  Serial.begin(9600);
  gsm.begin(9600);

  delay(2000);
  gsm.println("AT");
  delay(1000);
  gsm.println("AT+CMGF=1"); // SMS mode
  delay(1000);
}

void loop() {
  int gasValue = analogRead(gasSensor);
  Serial.println(gasValue);

  if (gasValue > threshold) {
    digitalWrite(buzzer, HIGH);
    digitalWrite(led, HIGH);

    sendSMS();
    delay(10000); // avoid repeated SMS
  } else {
    digitalWrite(buzzer, LOW);
    digitalWrite(led, LOW);
  }

  delay(500);
}

void sendSMS() {
  gsm.println("AT+CMGS=\"+91XXXXXXXXXX\""); // Replace with your number
  delay(1000);
  gsm.println("⚠️ Gas Leakage Detected!");
  delay(100);
  gsm.write(26); // CTRL+Z
  delay(5000);
}

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6. Detailed Step-by-Step Code Working

• SoftwareSerial creates communication with GSM module
• analogRead() reads MQ-2 values
• Threshold defines danger level
• When exceeded:
  • Alarm activates
  • sendSMS() function is called
• AT commands used:
  • AT → check module
  • AT+CMGF=1 → text mode
  • AT+CMGS → send SMS

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7. Tips

• SIM800L requires stable 3.7V (high current) ⚠️
• Use Li-ion battery (recommended)
• Ensure proper network signal
• Add capacitor (1000µF) across power for stability
• Avoid continuous SMS sending (use delay)
• Test GSM separately before integrating

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8. Uses

• Smart kitchen safety system
• Industrial gas monitoring
• LPG leakage alert system
• Remote safety monitoring

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9. Conclusion

This project demonstrates a real-world IoT-ready safety system using Arduino. By combining gas sensing with GSM communication, you can monitor hazardous situations remotely. It is a powerful upgrade from basic detection systems.

Note: Follow the below given link for detailed GSM Interface and Commands

https://simplebasicelectronics.blogspot.com/2026/04/arduino-gsm-sim800l-interfacing.html

Note: Follow the below given link for detailed MQ-2 Interface

https://simplebasicelectronics.blogspot.com/2026/03/arduino-gas-leak-detector-using-mq-2.html