Possessed Arduino.

So my Arduino Uno has gone mad. Long story short, If i upload the example sketch for a button with an LED and have no button connected, whenever my hand comes within 8" or so to the arduino the light goes on. BUT there has to be a wire in the PIN for the button (but the other end doesn't have to be connected to anything).

All that is connected to the arduino is an LED in PIN 13 to ground and a wire in pin 2 but not connected to anything.

Ive used multiple arduinos (two unos and a mega), computers (mac and PC), wires, LED's, i even wrote my own code to see if that was it and had the same outcome.

Anyone have any ideas?

If the pin is floating, you may trigger it very easily.

Put in a pull down resistor or, turn on the internal pullup.

When nothing is connected to an input, it is open or floating. The input impedance is very high, almost indefinitely high. So it will pick up any static electricity or noise or whatever. I think you hand introduces the mains 50/60Hz into the circuit.

There are a few projects that do something like that. Search for : arduino theremin capsense