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).

As the servo rotates, the returns from the ultrasonic sensor are plotted on a screen run by a Raspberry Pi. If an object is detected in the 180-degree field of view of the sweeping sensor, a ...