const int servoPin = 2; // set the pin number for the servo
int angle = 0; // variable for rotation angle

void setup() {
   pinMode(servoPin, OUTPUT); // set servo pin as output
}

void loop() {
   for(angle = 0; angle < 180; angle += 1){ // rotate the servo from 0 to 180 degrees
     digitalWrite(servoPin, HIGH); // send a high signal to the servo pin
     delayMicroseconds(500 + (angle * 2000 / 180)); // set the delay corresponding to the angle of rotation
     digitalWrite(servoPin, LOW); // send low signal to servo pin
     delay(20); // delay to stabilize the servo
   }
   for(angle = 180; angle > 0; angle -= 1){ // rotate the servo from 180 to 0 degrees
     digitalWrite(servoPin, HIGH);
     delayMicroseconds(500 + (angle * 2000 / 180));
     digitalWrite(servoPin, LOW);
     delay(20);
   }
}