#include <Servo.h>
int servoPin = 9;
Servo servo;
int angle = 0;  // servo position in degrees
void setup() {
    servo.attach(servoPin);
}
void loop() {
    // scan from 0 to 180 degrees
    for(angle = 0; angle < 180; angle++) {
     servo.write(angle);
     delay(15);
    }
      // now scan back from 180 to 0 degrees
    for(angle = 180; angle > 0; angle--) {
        servo.write(angle);
        delay(15);
    }
}