#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

void setup() {
  lcd.begin(16,2);
  lcd.print("Alarma activada!");
  delay(1000);
  pinMode(5, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(3, INPUT);
  digitalWrite(5, LOW);
  digitalWrite(4, HIGH);

}

int alerta=0;

void loop() {
  if (digitalRead(3)==HIGH){
    if (alerta==0){
      alerta=1;
      lcd.clear();
      lcd.print("Intruso!");
      digitalWrite(5, HIGH);
      digitalWrite(4, LOW);
    }
    
  }
  else{
     if (alerta==1){
      alerta=0;
      lcd.clear();
      lcd.begin(16,2);
      lcd.print("Alarma activada!");
      digitalWrite(5, LOW);
      digitalWrite(4, HIGH);
     }
  }

}