Raspberry Pi-Powered Projector Tells You How Fast You’re Riding Your Bike

Affordable, highly capable, and open-source computing hardware, such as the increasingly popular Raspberry Pi, continues to have its innovative influence on the maker world. Take, for instance, Matt Richardson, the Brooklyn-based maker, video producer, and writer, who hasn't taken the onset of these devices lightly by the looks of all of the crafty gadgets he's built.

This time, Richardson shows off his newly-assembled tech gear that straps onto his mountain bike and projects his real-time riding speed on the ground as he rides around the streets of New York at night.

The device is very much still a working prototype, but its potential for bike-riding glory speaks for itself. To detect the bike's moving speed, a Hall sensor is attached near the front wheel of the bike. Hall sensors vary their output voltage according to changing nearby magnetic fields, and thus can be used for speed detection and proximity sensing applications.

This sensor is wired up to a breadboard that sits on a piece of balsa wood; the wood is strapped between the top, down, and seating tubes of the bike (the middle, triangular section of the bike) with a few pieces of velcro straps to keep it from moving. From the breadboard, another wire is hooked up to a Raspberry Pi that is powered by an onboard USB cellphone battery pack charger. Finally, an HDMI cable runs along the tubes and up onto the bike's handlebars where a small, downward-facing projector is clamped.

The result of Richardson's invention is a high-tech headlight capable of projecting a rider's current speed. Since this is only the first prototype, Richardson (in the video below) says he will be working on packing the components into a single piece rather than laying them out on a piece of balsa wood. He also hints at future iterations that will include GPS integration and the addition of an animated projection mode.

It will be interesting to see what the future iterations of this project will integrate. Fellow makers have already suggested options: using the projector for navigation via Google maps, heart rate monitoring, distance traveled calculations, and strapping on a dynamo to energize the onboard battery charger.

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