Ryan writes – “Capacitive sensors have historically been regarded with fear and hostility among hobbyists. They’re notoriously flaky, unreliable, and difficult to design. Further, they traditionally fall in the “analog domain” which is something the casual microcontroller hobbyist can sometimes wince at. They usually require fancy shielding, and are unsettlingly sensitive to changes in things like temperature, humidity, air pressure, cosmic radition, my girlfriends feelings, and the mushroom kingdom stock market index.
I’ve found lately though that capacitive detection doesn’t have to be so scary. With a few simple design rules and a little signal processing, you can do some immensely cool stuff with basically no effort at all. (And as many parts!) This project is just one simple example. There are all sorts of ways you could couple a theremin-like antenna set up with some signal processing to produce fun results. I hope to try more of them!” – Link.