#include <Servo.h>  

Servo myservo;      

void setup() {
  myservo.attach(9); 
}

void loop() {
  // Sweep from 0° to 180°
  for (int pos = 0; pos <= 180; pos += 1) {
    myservo.write(pos);
    delay(15); 
  }

  // Sweep from 180° back to 0°
  for (int pos = 180; pos >= 0; pos -= 1) {
    myservo.write(pos);
    delay(15);
  }
}