#include <Servo.h> //declare to insert Servo.h library
Servo myservo; //create servo object to control a servo
int pos = 0; //variable pos to store position of servo
void setup() {
 myservo.attach(9); //attach the servo to digital pin 9.
}
void loop() {
 for(pos = 0; pos < 180; pos += 1){ //servo turns from 0 to 180 in steps of 1 degree
 myservo.write(pos); //tell servo to go to position in variable 'pos'
 delay(15); //wts 15ms for the servo to reach the position
}
 for(pos = 180; pos>=1; pos-=1) { // servo turns from 180 to 0 in steps of 1 degree
 myservo.write(pos); //tell servo to go to position in variable 'pos'
 delay(15); //waits 15ms for the servo to reach the position
 }
}