How to make a Gas and Smoke leakage warning system using Arduino

Hello and welcome back. In this project, we will learn how to make a gas and smoke leakage warning system using Arduino. For this, I mainly used an MQ2 sensor to detect gas and smoke in the environment. This system is only for demonstration and educational purposes, so you can easily modify and improve it as you like. If you want to know more info about the MQ2 sensor, please use this link.

For this, I added buzzers and LEDs to give both sound and visual indications. In addition, I included an automatic control door in this project. When gas leakage is detected, the door will open automatically. For this mechanism, I used an SG90 servo motor. Specially, I designed a custom PCB for this project using JLCPCB to make the circuit more compact, reliable, and professional.

Ok, let’s do this project step by step. The required components are given below.

Arduino Nano board x 1 — Our Store / Amazon
MQ2 sensor x 1 — Our Store /Amazon
SG90 servo motor x 1 — Our store / Amazon
Female header x 1 — Our Store / Amazon
Male header x 1 — Our Store / Amazon
5V Active buzzer x 2 — Our store / Amazon
10k Resistor x 1 — Our store / Amazon
5mm Red LED x 2 — Our store / Amazon
5mm Green LED x 2 — Our store / Amazon
180 ohm Resistor x 2 — Our store / Amazon
Tactile Push button x 1 — Our store / Amazon
Barrel jack socket x 1 — Our store / Amazon

Disclosure: These Amazon links are Affiliate links. As an Amazon Associate, I earn from qualifying purchases.

Step 1

Firstly, identify these components.

Step 2

Secondly, let’s order PCBs for this project.

First, go to the JLCPCB official website and log in to your account. If you are a new customer, please use my link here to register and claim $123 in new user coupons.

How to make an analog and digital real-time clock with an OLED display

Click the “Instant Quote” button and upload the Gerber file, which you can download from the link below.

Gerber file – Download
For this project, I ordered five Blue PCBs. Next, select the build time and shipping method. Finally, click “Save to Cart” and complete the payment.

Step 3

Thirdly, let’s unbox the PCB package for this project.

Step 4

Next, solder all the components onto the PCB.

Step 5

Afterward, connect the Arduino Nano board and the MQ2 sensor to the PCB. Then, connect the Arduino board to your computer.

Step 6

Now, copy and paste the following program into the Arduino IDE.

Program — Download

#define RLED 4
#define GLED 5
#define Buzzer1 6
#define Buzzer2 7
#define Button 8
#define MQ2 A0

#include <Servo.h>

Servo myServo;

int gasValue = 0;
int threshold = 300;

bool alarmState = false;
bool doorOpened = false;

void setup() {
  pinMode(RLED, OUTPUT);
  pinMode(GLED, OUTPUT);
  pinMode(Buzzer1, OUTPUT);
  pinMode(Buzzer2, OUTPUT);
  pinMode(Button, INPUT_PULLUP);

  myServo.attach(3);

  // ⭐ Normal startup condition
  digitalWrite(RLED, LOW);
  digitalWrite(GLED, HIGH);
  digitalWrite(Buzzer1, LOW);
  digitalWrite(Buzzer2, LOW);

  myServo.write(0);  // Door closed

  Serial.begin(9600);
}

void loop() {

  gasValue = analogRead(MQ2);
  Serial.println(gasValue);

  // Gas detected
  if (gasValue > threshold && alarmState == false) {
    alarmState = true;
  }

  // 🔥 ALARM MODE
  while (alarmState == true) {

    if (digitalRead(Button) == LOW) {
      resetSystem();
      break;
    }

    digitalWrite(RLED, HIGH);
    digitalWrite(GLED, LOW);

    // Loud pulses
    for (int i = 0; i < 3; i++) {

      if (digitalRead(Button) == LOW) {
        resetSystem();
        return;
      }

      digitalWrite(Buzzer1, HIGH);
      digitalWrite(Buzzer2, HIGH);
      delay(200);

      digitalWrite(Buzzer1, LOW);
      digitalWrite(Buzzer2, LOW);
      delay(150);
    }

    delay(300);

    // Open door once
    if (doorOpened == false) {
      for (int pos = 0; pos <= 90; pos++) {

        if (digitalRead(Button) == LOW) {
          resetSystem();
          return;
        }

        myServo.write(pos);
        delay(15);
      }
      doorOpened = true;
    }
  }

  delay(100);
}


// Reset function
void resetSystem() {

  alarmState = false;

  digitalWrite(RLED, LOW);
  digitalWrite(GLED, HIGH);
  digitalWrite(Buzzer1, LOW);
  digitalWrite(Buzzer2, LOW);

  // Close door
  for (int pos = 90; pos >= 0; pos--) {
    myServo.write(pos);
    delay(15);
  }

  doorOpened = false;
  delay(300);
}