#include <Servo.h>
Servo servo;
const byte SRV = 11;

void setup() {
    servo.attach(SRV);
    servo.write(0);
}

void loop() {
 /*   servo.write(90);
    delay(1000);
    servo.write(180);
    delay(1000);
    servo.write(90);
    delay(1000);
    servo.write(0);
    delay(1000);
*/
    int i;
    for (i=0; i<180; i++) {
        servo.write(i);
        delay(50);
    }
    for (i=180; i>0; i--) {
        servo.write(i);
        delay(50);   
    }
}