An Arduino is a microcontroller — a single board designed to control something ... an accelerometer for detecting motion, or a Piezo sensor on a door, it can notify you when someone knocks ...

[mircemk] shows how to create a simple non-contact proximity sensor using little more than an Arduino Nano board, and a convenient software library intended to measure the value of capacitors.

Inside [Klaus]’ device is an Arduino ... sensor used a small TFT to display the distance to an object, but after a few revisions, [Klaus] redesigned the device to speak the current distance ...