This project allows you to have capacitive touch keyboard input. Which means you can touch a wire or any conductor with your finger and it will input as a USB keyboard key into any Computer, Raspberry Pi, etc.
I've searched and searched how to do this, but ended up figuring it out my self, now I'm excited to share it.
To do the USB keyboard emulation you will need a ATmega32U4 based Arduino such as the Leonardo. The ATmega328P based ones, such as the UNO don't support this. Also it uses the analog pins. Leonardo and clones have 6 inputs. Smaller ATmega32U4 boards have 4 or 3.
You can get a ATmega32U4 board for about $3 to $8 on AliExpress
Having touch keyboard input can be usefull for many projects including making a cheap Makey Makey.
Step 1: Arduino Sketch
My sketch has keys useful for navigating Kodi media player.
You will need to install the ADCTouch library to compile the TouchKeyboard sketch.
In Arduino IDE, choose Sketch | Include Library | Manage Libraries. Search for "ADCTouch" by martin2250 and install
Make sure you have the following settings under Tools:
Board: Arduino Leonardo
Step 2: Easy to Use in a Project
It's easy to put in a project. In this example I just used some alligator jumpers and screws to make a Kodi controller.