this is a simple aurduino distance sensor I built. It uses the Aurduino Uno R3 as a microcontroller It uses the HC-SR04 as an ultrasonic device (Sender and Reiceiver) It uses 5 5mm LEDs and 1k resistors for each. It could have a buzzer atached to it for proximity sounds, or atached and played with I dont know i just thought it was cool.