Sam Tandy recently joined Matrix Technology Solutions, and after the requisite shadowing of other employees, he was given the task of building a Rott’s pendulum. Since this implementation would involve electrical work, firmware, and constructing the device mechanically, it seemed like a great project with which to get his feet wet.
How this type of pendulum works is that a central beam is attached to a rigid structure via a bearing in the middle allowing it to rotate. At either end of this beam, another beam is attached — one fixed at a right angle, and one that is free to rotate. When pushed, the device’s central member and free member create rather unpredictable gyrations. In order to record the speed, Tandy hooked up an RGB LED module and an accelerometer to the outer spinning member, and used a PIC16F88 microcontroller to modify the light’s color according to how fast it was going.
As seen in the video below, the results do appear quite chaotic, with both free members speeding up and slowing down at times in a frenzy of motion. Besides video, the speed also recorded in a long-exposure photograph, which records the LED’s path and the light color to indicate speed. Firmware and CAD files are available in the project’s writeup.