MPR121 Capacitive Touch Breakout

The MPR121 is a capacitive touch sensor controller chip that you can find in different pieces of hardware. In class, I used the breakout board made by Sparkfun. The diagram below is from the Sparkfun’s hookup guide and the same circuit I demoed in class. The 12 electrodes in the demoed example were CNC blade cut pieces of conductive fabric. You can connect anything that can conduct electricity. 

Sparkfun Guide

Although Sparkfun discontinued this component, their hookup guide explaining how it works applies to most hardware using this chip and still offers up information on how it communicates to your Arduino board.

Adafruit Guide

The new MPR121 breakout you can purchase is made by Adafruit. They also have a comprehensive guide

Arduino Library for MPR121

You need to download and install an Arduino library to program the MPR121 chip. You can download it here. This will also work with the Sparkfun board. 

Example Code

Once the library is installed navigate to Examples > MPR121 Library > MPR121test

This example reads all 12 electrodes. Connect conductive fabric, foil, thread or a banana, open the Serial monitor and watch your touches and releases print as you touch your conductive material.