For my project I wanted to create a PWM sensor that tracked pressure and could send that information to an LED. I built a pressure system that used two pieces of conductive tape separated by a piece of Velostat. When I would apply pressure to the system, the strength of the pressure would translate to the color of the LED.
Here is a picture of the pressure sensor:
I used an RGB LED that would change from Blue to Green based on the pressure applied to the sensor. The system was very responsive and the pressure strength was easily manipulated.
Here is a video of the system in action:
Here is the code I used for the system: