Finally not always using Arduinos:
Every time i nearly finished a project, I'm annoyed about using an arduino again, which uses a lot of space and isn't really necessary. A small stand-alone-controller would totally be enough. While prototyping the Arduino-PCB is a cool thing, but afterwards, when everything is finally assambled, the arduino needs a lot of space, which could be used for other things, like less case.

The idea to build an EMF-Detector came while i fucked up my last project partially. While i was soldering the pcb i did a mistake while connecting a wire. This gave me a broken signal of a buttonstate (switching from 0 to 1) switching back and forth. I fixed that, but wanted to know exactly why this happens.

Result: When you don't connect the input of the controller to ground, you are not able to set a solid state and the µController starts to interpret everything what he gets. In this case it reads electromagnetic fields. So why not digging further into this and build a gauge to have a look on which devices are having a nice electromagnetic party?