code:

// Sweep
// by BARRAGAN <http://barraganstudio.com>
// This example code is in the public domain.

#include <Servo.h>

Servo myservo;  // create servo object to control a servo
// a maximum of eight servo objects can be created

int pos = 0;    // variable to store the servo position

void setup()
{
myservo.attach(9);  // attaches the servo on pin 9 to the servo object
}

void loop()
{
for(pos = 0; pos < 90; pos += 1)  // goes from 0 degrees to 180 degrees
{                                  // in steps of 1 degree
myservo.write(pos);              // tell servo to go to position in variable ‘pos’
delay(10);                       // waits 15ms for the servo to reach the position
}
for(pos = 90; pos>=1; pos-=1)     // goes from 180 degrees to 0 degrees
{
myservo.write(pos);              // tell servo to go to position in variable ‘pos’
delay(10);                       // waits 15ms for the servo to reach the position
}
}