#include <LiquidCrystal_I2C.h>

#define TRIGGERPIN 2
#define ECHOPIN    1

LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup() {
  pinMode (3, OUTPUT);
  pinMode (4, OUTPUT);
  pinMode (5, OUTPUT);
  lcd.init();
  lcd.print("Start"); 
  lcd.setCursor(0, 1); 
  lcd.print("SecuiHome system"); 
  delay(3000); 
  lcd.clear(); 

  pinMode(TRIGGERPIN, OUTPUT);
  pinMode(ECHOPIN, INPUT);
}

void loop() {
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Distance");
  long duration, distance;
  digitalWrite(TRIGGERPIN, LOW);  
  delayMicroseconds(3); 
  
  digitalWrite(TRIGGERPIN, HIGH);
  delayMicroseconds(12); 
  
  digitalWrite(TRIGGERPIN, LOW);
  duration = pulseIn(ECHOPIN, HIGH);
  distance = (duration/2) / 29.1;
  Serial.print(distance);
  Serial.println("Cm");
  lcd.setCursor(9,0);
  lcd.print(distance);
  delay(1000);

  if(distance < 100){
    lcd.setCursor(0,1);
    lcd.print("Trespass");
    tone(3, 500, 1000);
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    delay(500);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    delay(500);
  }
  else{
    lcd.clear();
    lcd.setCursor(0,0);
    lcd.print("Distance");
    lcd.setCursor(9,0);
    lcd.print(distance);
    lcd.setCursor(0,1);
    lcd.print("Not found");
    delay(1000);
  }
}