// www.ProgettiArduino.com
  
  #define LED 11             
  #define SWITCH 5

  bool OnOff = false;
  int Premuto = LOW;

void setup() {  
  pinMode(LED, OUTPUT);
  pinMode(SWITCH, INPUT);
}  
  
void loop() { 
  int puls = digitalRead(SWITCH);
  if (!Premuto && puls)
  {
    OnOff = !OnOff;
  } 
  
  Premuto = puls;

  if (OnOff)
  {
      digitalWrite(LED, HIGH);
  }
  else
  {
    digitalWrite(LED, LOW);
  }
}