#define LED 11
int fade;
void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:
  for(fade=0;fade<=255;fade++){
    analogWrite(LED,fade);
    delay(100);
  }
  
  for(fade=255;fade>=0;fade--){
    analogWrite(LED,fade);
    delay(100);
  }
}