int pos = 0;   
void setup() {
  pinMode(9, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
}
void loop() {
  pwm_ms(500);
  digitalWrite(11, HIGH);
  delay(2000);
  digitalWrite(11, LOW);

  pwm_ms(1470);
  digitalWrite(12, HIGH);
  delay(2000);
  digitalWrite(12, LOW);
  pwm_ms(2400);
  digitalWrite(13, HIGH);
  delay(2000);
  digitalWrite(13, LOW);
}
void pwm_ms(int time){
  digitalWrite(9, HIGH);
  delayMicroseconds(time);
  digitalWrite(9, LOW);
  delayMicroseconds(20000-time);
}