Another experiment in the Scribbler wheel encoder project that erco and I are working on.
This slightly dark video is a proof of concept video using the Piezo Film Vibra Tab Mass Sensor as a possible wheel encoder on the Parallax Scribbler. It uses the Scribbler's wheel spokes to trip the Vibra Tab as the wheel rotates. It is like a playing card in the spokes of a bicycle wheel.
The Scribbler's wheel has 8 spokes on each side, actually 8 high spots and 8 low spots. That is 16 positions for one turn of the wheel. The wheels are 3-1/8" in diameter (approximately). The circumference is computed with the formula, circumference = pi times diameter, or C= π d. The circumferece is 9.82" or 9-13/16". For each 16th a turn, the wheel has travelled 0.614" or 5/8".
An issue might be the time the Vibra Tab is bent during contact with each spoke. I don't know yet if it sends one message when it bent or continuous messages.
But, as the video shows it does work (at least in concept).