void setup() {
  // put your setup code here, to 
  pinMode(21, OUTPUT);
  pinMode(22, OUTPUT);
  pinMode(23, OUTPUT);
}

void loop() {
  analogWrite(21,1023);
  analogWrite(22,0);
  analogWrite(23,0);
  delay(1000);
  
  
  analogWrite(21,0);
  analogWrite(22,1023);
  analogWrite(23,0);
  delay(1000);


  analogWrite(21,0);
  analogWrite(22,0);
  analogWrite(23,1023);
  delay(1000);


  analogWrite(21,1023);
  analogWrite(22,1023);
  analogWrite(23,0);
  delay(1000);


  analogWrite(21,1023);
  analogWrite(22,0);
  analogWrite(23,1023);
  delay(1000);  
}