int pinservo = A0;
void setup() {
  // put your setup code here, to run once:

  pinMode(pinservo, OUTPUT);


}

void loop() {
 
  for (int i=400;i<2500;i++){   // 400 micro-second for 0 degree, 2500 micro-seconds for 180 degree
      digitalWrite(pinservo,HIGH);
      delayMicroseconds(i);
      digitalWrite(pinservo,LOW);
      delayMicroseconds(20000-(i));
  }

  delay(3000);
}