I get so much email about this circuit that I’m going to post it here as jpg. Here are the files, schematic and PCB, in Kicad.
If you use these files, please turn the silkscreen layer on because I didn’t and so my boards didn’t have any. Also, please credit me for the design work. Don’t be pissed off at me if you can’t get what you want out of this design. It detects a voltage potential from 8′ away. The QFN is a PITA to solder but you can get free samples from Analog Devices. I got pretty good at soldering these after I blew up 6 of them.
Finally, use these and make it better!