int i = 50;
void setup() {
pinMode(9, OUTPUT);
Serial.begin(9600);
}

void loop() {
for( i =400; i <= 3000; i+= 2){
  speedo();
  delay(90);
}
void speedo(){
  i+= 3;
  digitalWrite(9, HIGH);
delayMicroseconds(i);
digitalWrite(9, LOW);
delayMicroseconds(700);
Serial.println(i);
}
}

void variableDelay(unsigned int us){
    unsigned int i;
    for( i = us; i > 0; i-- ){
        delayMicroseconds(1);
    }
}

 void variableDelay(unsigned int us){     unsigned int i;     for( i = us; i > 0; i-- ){         delayMicroseconds(1);     } }