Ian’s Spoke POV

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" POV stands for Persistence Of Vision. It’s a term that's been applied to devices that rely on the eye's tendency to continue to "see" an image for a short time after it has disappered. This is also what causes the apparent blurring of objects that are in motion (like an airplane propeller).

This project consists of three circuit boards with a row of 32 LEDs on each (actually 64 LEDs because they’re double sided). The circuit boards are mounted radially in the spokes of a bicycle wheel and batteries near the hub supply power to them. The LEDs are controlled by a microcontroller that measures the rotational speed of the wheel by way of a hall effect (magnetic) sensor. As the wheel rotates, the microcontroller turns the individual LEDs on and off in such a way that a static image appears to float inside the wheel."

http://www.ianpaterson.org/projects/spokepov20050704/index.htm