🚨 Smart Gas Leak Detector with NodeMCU & Servo Motor

September 27, 2025

🚨 Smart Gas Leak Detector with NodeMCU & Servo Motor

Student Project – IoT Based Gas Cylinder Safety System

This project detects gas leaks using an MQ-2 sensor, alerts the user, and allows remote control of the gas cylinder valve using a servo motor. The system hosts a colorful animated webserver for monitoring and control.

Components Required

Component	Quantity	Description
NodeMCU ESP8266	1	Wi-Fi enabled microcontroller
MQ-2 Gas Sensor	1	Detects LPG, Butane, Methane
Servo Motor (SG90)	1	Rotates valve knob to OFF position
Jumper Wires	Several	For connections
Breadboard	1	Prototyping
USB Cable	1	Power + Programming

Circuit Connections

NodeMCU Pin	Component
D0 (GPIO16)	Servo Signal (Orange wire)
3.3V	MQ-2 VCC
GND	MQ-2 GND & Servo GND
A0	MQ-2 Analog Output
Vin (5V)	Servo VCC

💻 Arduino Code (NodeMCU)

#include <ESP8266WiFi.h>

#include <ESP8266WebServer.h>

#include <Servo.h>

// Wi-Fi Credentials

const char* ssid = "YOUR_WIFI_NAME";

const char* password = "YOUR_WIFI_PASSWORD";

// Web server on port 80

ESP8266WebServer server(80);

// MQ-2 Sensor

int mq2Pin = A0;

int gasValue = 0;

bool gasLeak = false;

// Servo

Servo gasServo;

int servoPin = D0;

// HTML Page

String webpage = R"rawliteral(

<!DOCTYPE html>

<html>

<head>

<title>Smart Gas Leak Detector</title>

<style>

body { font-family: Arial, sans-serif; text-align: center;

background: linear-gradient(to right, #00c6ff, #0072ff); color:white; }

h1 { font-size: 30px; }

h2 { font-size: 20px; }

.cylinder { width: 150px; animation: bounce 2s infinite; }

@keyframes bounce { 0%,100%{transform:translateY(0);} 50%{transform:translateY(-10px);} }

.status { margin:20px; padding:10px; border-radius:10px; font-size:18px; }

.safe { background: #4CAF50; }

.leak { background: #f44336; animation: blink 1s infinite; }

@keyframes blink { 0%,100%{opacity:1;} 50%{opacity:0.5;} }

button { padding:15px 30px; margin:10px; font-size:16px; border:none; border-radius:10px; cursor:pointer; }

.on { background:#4CAF50; color:white; }

.off { background:#f44336; color:white; }

</style>

</head>

<body>

<h1>Smart Gas Leak Detector</h1>

<h2>Student Name</h2>

<div id="status" class="status safe">Gas Status: SAFE</div>

<div>

</div>

setInterval(()=>{ fetch('/gas').then(r=>r.text()).then(data=>{

let st=document.getElementById('status');

if(data.includes('LEAK')){

st.innerHTML='Gas Status: LEAK DETECTED!';

st.className='status leak';

} else {

st.innerHTML='Gas Status: SAFE';

st.className='status safe';

}

})}, 2000);

</script>

</body>

</html>

)rawliteral";

// Handle Root

void handleRoot() {

server.send(200, "text/html", webpage);

}

// Servo ON

void handleOn() {

gasServo.write(90); // Open valve

server.send(200, "text/html", "<h1>Gas Turned ON</h1><a href='/'>Back</a>");

}

// Servo OFF

void handleOff() {

gasServo.write(0); // Close valve

server.send(200, "text/html", "<h1>Gas Turned OFF</h1><a href='/'>Back</a>");

}

// Gas Sensor Data

void handleGas() {

gasValue = analogRead(mq2Pin);

if (gasValue > 400) { gasLeak = true; server.send(200, "text/plain", "LEAK"); }

else { gasLeak = false; server.send(200, "text/plain", "SAFE"); }

}

void setup() {

Serial.begin(115200);

WiFi.begin(ssid, password);

Serial.print("Connecting");

while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); }

Serial.println("Connected!");

Serial.println(WiFi.localIP());

gasServo.attach(servoPin);

gasServo.write(90); // Default ON

server.on("/", handleRoot);

server.on("/on", handleOn);

server.on("/off", handleOff);

server.on("/gas", handleGas);

server.begin();

}

void loop() {

server.handleClient();

}

1)Detects LPG / Butane leaks with MQ-2 sensor
2)Webserver with animation (works on PC & Mobile)
3)Live gas status (SAFE / LEAK DETECTED)
4)Remote ON/OFF gas control using servo motor
5)Colorful UI with bouncing cylinder animation

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