Gas Alert System Using Arduino UNO – Step by Step Tutorial (MQ-2 Gas Sensor)

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Intermediate Project

Gas Alert System
Using Arduino

Detect LPG, methane & smoke with an MQ-2 sensor. Triggers buzzer + LED on gas leak. Includes circuit diagram, code, and Tinkercad simulation.

⏱ 30 min build 🔌 Arduino UNO 💡 MQ-2 Sensor 🧪 Tinkercad Sim

🔥 Why this project? Gas leaks from LPG cylinders cause thousands of home fires every year. This simple Arduino circuit gives you an instant audible + visual alarm — easy to build, cheap, and potentially life-saving.

01

Objectives

• ✓ Detect harmful gases — LPG, methane, and smoke
• ✓ Trigger dual alert: buzzer (audible) + LED (visual)
• ✓ Build a low-cost, real-world safety system
• ✓ Learn MQ-2 sensor interfacing with Arduino

02

Components Required

🔵

Arduino UNO

🟡

MQ-2 Gas Sensor

🔴

Red LED

⚫

Buzzer

🟢

220Ω Resistor

🟣

Breadboard

🟠

Jumper Wires

03

Circuit Diagram

gas_alert_circuit.json

5V Power GND Analog A0 Digital D7 (LED) Digital D8 (Buzzer)

04

Step-by-Step Wiring

STEP 1

Connect MQ-2 Gas Sensor

VCC → 5V (Arduino) GND → GND (Arduino) A0 → Analog Pin A0

STEP 2

Connect Red LED

Long leg (+) → D7 via 220Ω resistor Short leg (−) → GND

STEP 3

Connect Buzzer

Positive (+) → Digital Pin D8 Negative (−) → GND

💡 Pro Tip Always connect the 220Ω resistor in series with the LED to prevent burning it out. Without the resistor, excess current will destroy the LED.

05

Working Principle

06

Arduino Code

gas_alert.ino

// ── Gas Alert System | MakeMindz.com ──────────────
// Detects LPG, methane, smoke via MQ-2 sensor
// Triggers buzzer + LED when gas exceeds threshold

// ── Pin Definitions ──────────────────────────────
int gasSensor = A0;   // MQ-2 analog output → A0
int led       = 7;    // Red LED → Digital Pin 7
int buzzer    = 8;    // Buzzer  → Digital Pin 8
int threshold = 300;  // Adjust based on sensor sensitivity

// ── Setup ────────────────────────────────────────
void setup() {
  pinMode(led, OUTPUT);
  pinMode(buzzer, OUTPUT);
  Serial.begin(9600);  // Open Serial Monitor for live readings
  Serial.println("Gas Alert System Ready!");
}

// ── Main Loop ────────────────────────────────────
void loop() {
  int gasValue = analogRead(gasSensor);  // 0–1023
  Serial.print("Gas Level: ");
  Serial.println(gasValue);

  if (gasValue > threshold) {
    // ⚠ Gas detected — activate alerts
    digitalWrite(led, HIGH);
    digitalWrite(buzzer, HIGH);
    Serial.println("⚠ WARNING: Gas Detected!");
  } else {
    // ✓ Air is clean — keep quiet
    digitalWrite(led, LOW);
    digitalWrite(buzzer, LOW);
  }

  delay(500);  // Check every 500 milliseconds
}

⚙️ Calibration Tip The default threshold is 300. Open the Serial Monitor (9600 baud) and check the readings in clean air vs. near a gas source. Set your threshold 20–30% above the clean-air reading for reliable detection.

07

Tinkercad Simulation

🧪 Try it in Tinkercad

No hardware? Run the complete circuit simulation online — drag the MQ-2 sensor slider to trigger the alert.

Open Simulation

How to run the simulation:

1

Open Tinkercad

Click the simulation button above to open the pre-built circuit

2

Click "Start Simulation"

The green Start button at the top right of the Tinkercad editor

3

Open Serial Monitor

Click "Serial Monitor" (bottom panel) to see live gas readings

4

Adjust Sensor Slider

Click on the MQ-2 sensor and drag the gas concentration slider above 300 — the LED lights up and buzzer activates

5

Test & Modify

Change the threshold value in the code and re-simulate to see the difference

08

Real-World Applications

🍳

Home Kitchen Monitoring

🏭

Industrial Safety

🧪

Laboratory Safety

🏠

Smart Home Systems

📡

IoT Gas Monitoring

🚗

Parking Garages

🚀 Level Up This Project Add a GSM module (SIM800L) to send SMS alerts when gas is detected. Connect an LCD display to show real-time gas readings. Or integrate with a relay to automatically cut off gas supply.

⚡

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