unasolavoltaquandorestabassoilpin

int led = 13;

int presenza =8;
int presenzastate =0;

void setup (){
  pinMode (led,OUTPUT);
  pinMode (presenza,INPUT);




  }
  void loop (){


    presenzastate=digitalRead(presenza);
     bool fallingEdge = false;
if(presenzastate == LOW && !fallingEdge){
fallingEdge = true;
digitalWrite (led,HIGH);
delay(3000);
digitalWrite(led,LOW);
delay(3000);
}
if(presenzastate) fallingEdge = false;

  }