int LED1=5;
void setup() {
  // put your setup code here, to run once:
pinMode(LED1, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
for(int brightness=0; brightness<=255;brightness++){
  analogWrite(LED1,brightness);
  delay(10);
}
for(int brightness=255; brightness>=0;brightness--){
  analogWrite(LED1,brightness);
  delay(10);
}
}