I recently had to build an infrared close proximity sensor that could tell if something was dropped in a parcel delivery drop box. After some searching, I ended up using a microcontroller and a piece ...

[url=http://arstechnica.com/civis/viewtopic.php?p=31622763#p31622763:2qs83ys1 said: You do some PCB stuff? I'm dying to go into basic electronics & circuits, but I ...