Phenakistiscope

Challenge: To design a motorized adjustable rotating paper illustration (Phenakistiscope) using a small DC motor and nichrome wire.

Parameters: The motor’s rotational speed must be able to be adjusted using a nichrome wire as a variable resistor. It should be able to rotate your disc in front of a mirror at a rate that a viewer can easily see the illusion. Also, there should be a simple explanation of how the illusion works, written at a junior science level. For me include with your device a ray diagram, drawn to scale, and a circuit diagram with typical current and voltage readings, and corresponding resistance and power calculations for all components.

Scoring: Your system will be scored partly based on marks given by a visiting class of junior science students. They will grade you using a four-point rubric with the following criteria:

Smoothness of image animation, Ease of viewing (ergonomics)

Clarity and brightness of image, Overall quality

My evaluation will be on the engineering of your device and the quality of your ray diagram and circuit analysis. Your rank will on this project will be based on their evaluation, plus my evaluations as follows:

Guest viewers: 50%, Ray Diagram: 25%, Circuit Analysis: 25%

Physics: Images are formed when light enters the eye. If those images are entering at a particular rate, and they are slightly changing each time, you will perceive motion. This is an early form of animation. The path of light can be represented with a ray diagram, and it can show you where your brain thinks the animation is compared to where the physical object actually is. Your disk will be spun by a small DC motor with an adaptor as power supply and a nichrome wire as variable resistor. Current and voltage can be measured, while resistance and power can be calculated.

Extensions: Optical illusions and early animation devices are fascinating to research. Look up zoetropes as an example. Ray diagrams for images produced by mirrors can help you understand why your image in the mirror is “backwards”. (The reason it appears backwards is that it is NOT inverted!). The number of slits in your disk, the size of them, the number of images, and the rate of rotation are all important. Stereoscopic and 3D ones are not impossible!

Help/Hints: Lots of images, just slightly different and “cycling” from one edge to another, will make the best animation. A viewing tube might help viewers get their eyes in the right place. Extra illumination of your drawings might also help.

Quiz Topics: Ray diagrams and image formation for plane mirrors, simple circuitry.

Online Text: 9.3, 16.1, 19