   digitalWrite(motorB_brake, LOW);   // Disengage the Brake for Channel B
   
   
+  batteryLevel();
+  
   // Turn in place constantly.
   digitalWrite(motorA_direction, HIGH); // Channel A forward
   digitalWrite(motorB_direction, LOW); // Channel B backward

    sonar_last = millis_now;
  
    unsigned int cm = sonar.ping_cm(); // Send a ping, get ping time in microseconds (uS).
    Serial.print("Ping: ");
    Serial.print(cm);
    Serial.println("cm");
  }
  
  // Check to see if it's time for another melody.

    melody_last = millis_now;
    playMelody();
    
    batteryLevel();
  }
  
}

void playMelody() 
{
  // iterate over the notes of the melody:
  for (int thisNote = 0; thisNote < 8; thisNote++) {

