Inside [Klaus]’ device is an Arduino Uno, an HC-SR04 ultrasonic distance sensor, and an Adafruit Wave Shield.

Makers, developers and enthusiasts building distance related projects may be interested to know that the HC-SR04 ultrasonic sonar distance sensor is now available to purchase directly from the ...

With a standard old HC-SR04 ultrasonic sensor, an audio module and a servo to drive a custom gauge needle he’s made a device which can warn people around you if they’re too close for comfort.