The set-up process is very simple, and best understood by referring the wiring diagram. If everything goes right,you should see the burning eye of the red LED when there is no object in the safe-zone ...

Buy arduino, buy sound shield, buy distance sensor shield, plug into each other, burn example code, stuff components inside box. Not only is this not a hack but he might as well have just bought a ...

Instead, it relies on an ultrasonic distance sensor to detect a hand (or foot) waved in front of the door. An Arduino Leonardo runs the show, sounding a buzzer when the ultrasonic sensor is triggered.

In this mode, you can interface the HC-SR04 ultrasonic ping sensor with a servo motor and the main board (Only some reward tiers include the extra servo motor PCB and servo motor kit).