Gas Leak Monitor 4.0
Note
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Kit purchase
Looking for parts? Check out our all-in-one kits below — packed with components, beginner-friendly guides, and tons of fun.
Name |
Includes Arduino board |
PURCHASE LINK |
|---|---|---|
Ultimate Sensor Kit |
Arduino Uno R4 Minima |
|
Universal Maker Sensor Kit |
× |
Course Introduction
This Arduino project uses an MQ-2 gas sensor, LEDs, and a buzzer to detect gas concentration in real time.
Note
If this is your first time working with an Arduino project, we recommend downloading and reviewing the basic materials first.
Required Components
In this project, we need the following components:
SN |
COMPONENT INTRODUCTION |
QUANTITY |
PURCHASE LINK |
|---|---|---|---|
1 |
Arduino UNO R4 WIFI |
1 |
|
2 |
USB Type-C cable |
1 |
|
3 |
Breadboard |
1 |
|
4 |
Wires |
Several |
|
5 |
Buzzer Modudle |
1 |
|
6 |
LED |
Several |
|
7 |
MQ-2 Gas Sensor Module |
1 |
|
8 |
1kΩ resistor |
Several |
Wiring
Common Connections:
MQ-2 Gas Sensor Module
A0: Connect to A0 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.
Buzzer Modudle
I/O: Connect to 2 on the Arduino.
GND: Connect to breadboard’s negative power bus.
VCC: Connect to breadboard’s red power bus.
LED
Connect the LEDs cathode to the negative power bus on the breadboard, and the LEDs anode to 1kΩ resistor then to 4 to 11 on the Arduino.
Writing the Code
Note
You can copy this code into Arduino IDE.
Don’t forget to select the board(Arduino UNO R4 WIFI) and the correct port before clicking the Upload button.
// -------- Pin definitions --------
#define PIN_SMOKE A0 // MQ-2 smoke sensor
#define PIN_BUZZER 2 // Buzzer
int ledPins[] = {4, 5, 6, 7, 8, 9, 10, 11}; // LED bar
const int LED_COUNT = 8;
// -------- Thresholds --------
#define LED_START_TH 50 // LED starts lighting
#define LED_STEP 50 // One LED per 50
#define WARN_TH 100 // Warning threshold
#define ALARM_TH 300 // Alarm threshold (same as traffic light project)
// -------- Setup --------
void setup() {
pinMode(PIN_BUZZER, OUTPUT);
for (int i = 0; i < LED_COUNT; i++) {
pinMode(ledPins[i], OUTPUT);
digitalWrite(ledPins[i], LOW);
}
Serial.begin(9600);
}
// -------- Main loop --------
void loop() {
int smokeValue = analogRead(PIN_SMOKE); // Read smoke value
ledBarDisplay(smokeValue); // LED display
buzzerService(smokeValue); // Buzzer (same behavior as before)
Serial.print("Smoke value: ");
Serial.println(smokeValue);
}
// -------- LED bar display --------
// 50 -> D11
// 100 -> D11, D10
// 150 -> D11, D10, D9 ...
void ledBarDisplay(int value) {
int ledCount = 0;
if (value >= LED_START_TH) {
ledCount = (value - LED_START_TH) / LED_STEP + 1;
}
if (ledCount > LED_COUNT) {
ledCount = LED_COUNT;
}
// Light LEDs from D11 to D4
for (int i = 0; i < LED_COUNT; i++) {
int index = LED_COUNT - 1 - i;
digitalWrite(ledPins[index], (i < ledCount) ? HIGH : LOW);
}
}
// -------- Buzzer behavior --------
// WARN (100–299): short beep every 1 second (same as yellow)
// ALERT (>=300): fast alarm beep (same as red)
void buzzerService(int value) {
unsigned long now = millis();
// -------- ALERT mode --------
if (value >= ALARM_TH) {
const unsigned long period = 250;
unsigned long phase = now % period;
if (phase < 120) {
tone(PIN_BUZZER, 2000); // Alarm ON
} else {
noTone(PIN_BUZZER); // Alarm OFF
}
return;
}
// -------- WARN mode --------
if (value >= WARN_TH) {
const unsigned long period = 1000;
unsigned long phase = now % period;
if (phase < 80) {
tone(PIN_BUZZER, 1200); // Short reminder beep
} else {
noTone(PIN_BUZZER);
}
return;
}
// -------- SAFE mode --------
noTone(PIN_BUZZER);
}