#include <LiquidCrystal.h>
int state = LOW; //LOW or 0 ===> Flag
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

void setup() 
{
  pinMode(4, OUTPUT);
  pinMode(13, INPUT);
  lcd.begin(16,2);
  lcd.println("No Motion!");
}

void loop() 
{
  if (digitalRead(13)==HIGH)
  {
    digitalWrite(4, HIGH);
    if (state == LOW)
    {
      lcd.clear();
      lcd.println("Motion Detected!");
      state = HIGH;
    }
  }
  else
  {
    digitalWrite(4, LOW);
    if (state == HIGH)
    {
      lcd.clear();
      lcd.println("Motion Ended!");
      state = LOW;
    }
  }
}