// LCD1602 to Arduino Uno connection example

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 10, 9, 8, 7);
int a=2;

void setup() {
  lcd.begin(16,2);
  pinMode (a,INPUT);
  pinMode (1,OUTPUT);
}

void loop() {
  int b=digitalRead(a);
  lcd. setCursor(0,1);
  lcd.print (b);
  if (b==0);
  {
    lcd.print("human not detach");
    digitalWrite( 1, LOW);
  }
{
  lcd.print("human detach");
  digitalWrite(1, HIGH);
}
  // ...
}