With more and more gadgets coming out every day that utilize USB for charging, it’s almost necessary to have a USB port available at all times. This DIYer decided to create a 5V generator using his bike and a modified USB car charger. The 5V USB plugs are situated under his seat and he has a carrying rack for cellphones, GPS, or MP3 players on the go.
The USB bike generator works by placing a rotating wheel perpendicular to the rear wheel of the bike with a heavy spring. The mini-wheel turns a stepper motor to generate a charge that is then smoothed out by an in-line rectifier.[Link]