/* This is a Gas leakage dectector. 
It reads the current gas level, if it exceeds the pre-defined threshold level,
the LED and Buzzer is triggered. In case of any gas leakage, it automatically 
shutts the valve of the gas. */

#include <LiquidCrystal.h>

#define GasSensor A0
#define LedPin 13
#define BuzzerPin 7 
#define RelayPin 8

// Initialize the leakage as negative 
bool gasLeak = false;

// Initialize the LCD with the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  Serial.begin(9600); 
  //Set the output pins
  pinMode(LedPin, OUTPUT);
  pinMode(BuzzerPin, OUTPUT);
  pinMode(RelayPin, OUTPUT);

  // Set up the number of columns and rows on the LCD
  lcd.begin(20, 4);
}

void loop() {
  // Read gas level from the sensor
  int gasLevel = analogRead(GasSensor);

  // Set a threshold value
  int GasThres = 500;

  // Check if gas level is above threshold
  if (gasLevel > GasThres) {
    // If gas leak detected, activate LED and buzzer
    digitalWrite(LedPin, HIGH);
    digitalWrite(BuzzerPin, HIGH);
    tone(7, 262, 250); // Controls the buzzer sound
    digitalWrite(RelayPin, HIGH); // Activate relay to close the valve
    gasLeak = true;
  } else {
    // Otherwise, turn off LED and buzzer
    digitalWrite(LedPin, LOW);
    digitalWrite(BuzzerPin, LOW);
    digitalWrite(RelayPin, LOW); // Deactivate relay to open the valve
    gasLeak= false;
  }

  // Display gas valve status and current gas level on LCD
  PrintOnLCD(gasLevel);

  delay(1000); 
}

void PrintOnLCD(int gasLevel) {
  // Print a message on the LCD display based on gas leak status
  lcd.clear(); 
  lcd.setCursor(0, 0); 
  // Print current gas level value on the LCD
  lcd.print("Gas Level : ");
  lcd.print(gasLevel); 
  
  //Print the condition on the screen
  lcd.setCursor(0, 2);
  if (gasLeak) {
    lcd.print("Gas Leak Detected!");
    lcd.setCursor(0, 3); 
    lcd.print("Shutting off valve");
  } else {
    lcd.print("Gas Level in Control");
    lcd.setCursor(0, 3); 
    lcd.print("Valve is Open");
  }
}