Arduino 11 - servo jednoducho

int pulz;

void setup() {

  pinMode(2, OUTPUT);
  pulz = 1500;
  Serial.begin(9600);

}

void loop() {

 if (Serial.available())
 {
   char c = Serial.read();
   if (c == 'a') pulz += 5;
   if (c == 'z') pulz -= 5;
   Serial.println(pulz);
 }
 digitalWrite(2, HIGH);
 delayMicroseconds(pulz);
 digitalWrite(2, LOW);
 delay(18);

}