The treat in question is detected by an SR-04 ultrasonic distance sensor connected to an Arduino Nano. All in all this was a highly successful build as far as neighborhood entertainment value goes.

This is an Arduino-based Proximity Sensor circuit wired using the popular HC-SR04 Ultrasonic ranging module,used here for non-contact object detection purpose. The HC-SR04 module includes ultrasonic ...

[Klaus] wanted some sort of aid for parking his car, and after running across a $4 ultrasonic sensor, decided to build his own speaking distance sensor (.de, Google Translation). Inside [Klaus]&#82… ...