Pedal-Powered Generator
One day, I was using a bicycle exercise machine for nearly an hour without any distractions from a TV or a music player. I concentrated on verifying every stroke produced effective power in the crank. I began pondering where all the energy I produced went. After a little investigation, it turns out that the exercise machine uses a small portion of that energy to power the electronics that control the resistance in the pedal, as well as to display various gauges about the exercise session, while the rest of the energy is wasted as heat produced by Eddie currents. As I generally don't like to waste anything valuable, I brainstormed ideas for harnessing this energy.
Pedal-powered generator with an electric blender plugged in.
I spent a few days designing and constructing a wooden frame for the apparatus while gathering devices and materials (such as an automotive alternator, a bicycle, a belt, and electrical components) I would need. When I acquired all the components, I spent a few more days assembling, calibrating, and testing the apparatus.
The complete project consists of
  • a bicycle with the rear axle mounted to the wooden frame and the rear tire removed from the wheel;
  • an automotive alternator mounted to the wooden frame, which is adjustable (to alter the belt tension) by tightening or loosening a rope;
  • a belt connecting the rear wheel to the alternator;
  • an inverter, to convert the 12 volts of DC current from the alternator into household 120 volts AC current; and
  • an electrical control panel mounted to the handlebar.
Control panel (including inverter) mounted to handlebar.
Alternators do not contain any permanent magnets. Instead, they consist of a series of coiled wire on both the rotor and the stator. Therefore, alternators require an initial input voltage to jump-start the magnetic fields before they can begin producing electrical current. This control panel (pictured on the right) satisfies this requirement using a 9-volt battery to excite the alternator. Once the alternator begins producing power, it sustains the magnetic field on its own without help from the 9-volt battery, so it is immediately disconnected using a "push-on, release-off"-style ignitor switch. A green LED indicator light indicates whether the 9V battery is delivering power to the alternator, and another light indicates whether the alternator has a voltage across its terminals. I later added an excitor regulator that bypasses the indicator light, because the light's resistance prevented the battery from delivering sufficient power to excite the alternator. A large capacitor (located at top-right, in blue) is used to dampen irregularities in the power supply.