const int sonic = 4;
const int shadow = 5;

void setup() {
  
  pinMode(sonic, OUTPUT);
  pinMode(shadow, OUTPUT);

}

void loop() {

  digitalWrite(sonic, HIGH);
  delay(2000);
  
  digitalWrite(shadow, HIGH);
  delay(2000);
  digitalWrite(shadow, LOW);

  digitalWrite(sonic, LOW);
  delay(2000);

  digitalWrite(sonic, HIGH);
  
  digitalWrite(shadow, HIGH);

  digitalWrite(sonic, HIGH);
  delay(2000);
  
  digitalWrite(shadow, HIGH);
  delay(2000);
  digitalWrite(shadow, LOW);

  digitalWrite(sonic, LOW);
  delay(2000);

  

}