The microcontroller-based concept was chosen because I wanted to scale the sensor system later to suit other applications. Here is the diagram of my Arduino infrared close proximity sensor ... the D13 ...

Instead of measuring light, we measure the ambient voltage field on pin ... our Arduino. A5 is used as a “floating input”, but unfortunately it is very noisy. The usual solution is to use some sort of ...

[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.