/*
Voltaat learn (http://learn.voltaat.com)
Link for full tutorial:

Tutorial: Arduino Smoke Level Detector using MQ-135 Sensor with Alarm!

 LiquidCrystal I2C Library: https://learn.voltaat.com/wp-content/uploads/2023/08/LiquidCrystal_I2C-1.1.2.zip

The purpose of this sketch is to detect smoke, display the smoke level on the LCD, and emit an alarm sound when the smoke levels reaches a certain value.


Connections from the Arduino to the breadboard:

• Arduino GND pin → Breadboard ground line

• Arduino 5V pin → Breadboard 5V line


Connection from the LCD with I2C Module:

• VCC pin → breadboard 5v line

• GND pin → breadboard GND line

• SDA pin → Arduino analog pin A4

• SCL pin → Arduino analog pin A5


Connections from the MQ-135 sensor:

• MQ-135 sensor VCC pin → Breadboard 5V line

• MQ-135 sensor GND pin → Breadboard ground line

• MQ-135 sensor A0 pin → Arduino pin A0



Connections from the Arduino to the passive buzzer:

• Arduino GND pin → buzzer GND pin (- pin)

• Arduino pin 3 → buzzer VCC pin (+ pin)


*/

#include "Wire.h"
#include "LiquidCrystal_I2C.h"

// Initialize the LCD with the I2C address
LiquidCrystal_I2C lcd(0x27, 16, 2);  // Change the I2C address if necessary

int buzzer = 3;
int smokeA0 = A0;
// Your threshold value
int sensorThres = 200;

void setup() {
 pinMode(buzzer, OUTPUT);
 pinMode(smokeA0, INPUT);
 Serial.begin(9600);
 lcd.init(); // Initialize the LCD
 lcd.backlight(); // Turn on the LCD backlight
}

void loop() {
 int analogSensor = analogRead(smokeA0);

 Serial.print("Pin A0: ");
 Serial.println(analogSensor);
 lcd.setCursor(0, 0);  // Set the cursor to the first position of the first line
 lcd.print("Smoke Level:");
 lcd.setCursor(12, 0);  // Set the cursor to the first position of the second line
 lcd.print(analogSensor-50);
 
 // Checks if it has reached the threshold value
 if (analogSensor-50 > sensorThres) {
   lcd.setCursor(0, 1);  // Set the cursor to the first position of the third line
   lcd.print("Alert....!!!    ");
   tone(buzzer, 1000, 200);
   
 } else {
   lcd.setCursor(0, 1);  // Set the cursor to the first position of the third line
   lcd.print(".....Normal.....");

   noTone(buzzer);
 }
 
 delay(500);
 lcd.clear();
}