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

void loop() {
  // put your main code here, to run repeatedly:

  for(int i=0; i<= 255; i+=20){
    analogWrite(5,i);
    delay(50);
  }
  for(int i=255; i>=0; i-=20){
    analogWrite(5,i);
    delay(50);
  }

}