#include <Servo.h>

Servo Servo;

int pos = 0;

void setup() {

Servo.attach(9);

}

void loop() {

for (pos <=0; pos <= 90; pos += 1){

// in steps of 1 degree

Servo.write(pos);

delay(10);

}

for (pos = 180; pos >= 0; pos -= 1) {

Servo.write(pos);

delay(10);

}  
}