Sudden 'floating input pin' problem with my Leonardo. What the heck is this?

Projects General Guidance
1

My Leonardo has worked fine for the month or so I've had it.
Until today, when I hooked it up to two push buttons that each type a key on the keyboard. The code was correct , but it randomly fired the keys without me touching anything.

So I loaded the basic 'Button' sketch to begin troubleshooting and noticed that just moving my finger near the Digital 02 wire (which isn't connected to anything else but the Arduino) makes the on board LED turn on. :o

This forum post leads me to believe that what I am experiencing is a 'floating input pin': Digital In too sensitive - Installation & Troubleshooting - Arduino Forum

How could this have suddenly happened? It didn't used to do this and now it appears to be the issue with every digital input on the board.

Additionally, how do I make it go back to the way it used to be?

I've been using Arduino for maybe two months now, so please have mercy.

Thank your for your time.

2

It's quite normal to face this issue if you don't either pull up or down your inputs.
Depending on your electronics and your sketch, most easy way is to use INPUT_PULLUP instead of INPUT as pinMode.

See https://www.arduino.cc/en/Tutorial/InputPullupSerial for more information and a good example.

3

Guess I was just lucky all this time. :grinning: Pullup inputs from now on, it is. Thanks for your thoughts.