Gallerythumb 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.