#include <Servo.h>

Servo myservo; 

int pos = 90;    

void setup() {
  myservo.attach(11);  
}

void loop() {
  for (pos = 90; pos <= 180; pos += 1) {
  
    myservo.write(pos);             
    delay(15);                     
  }
  for (pos = 180; pos >= 90; pos -= 1) {
    myservo.write(pos);             
    delay(15);        
  }
}