GreatScott! Created a Hand-Cranked Generator That Produces 2mW of Power

Manually generating electrical power can be a rewarding experience. That’s why GreatScott! built a hand crank generator out of a DC motor. He used a 12V 21W light bulb as a load hooked up to an energy meter and the generator. With the help of a hand crank, it only produced 2W of power, which is ideal for emergencies, but it’s not enough to power anything useful. To boost energy production, he decided to try out a mechanical bike setup but abandoned this technique.

Another approach he used involves spinning the shaft with his hand instead, making it possible for testing. An induction motor with two pole pairs and a reduced rotational speed was used for this project. Without modifying the phases of the motor, he discovered that it doesn’t output any voltage. This is because the rotor comes with a squirrel cage that consists of conductors that are shorted to one another and are non-magnetic. When the rotor spins, there is no magnetic field that cuts through the stator coils and creates induced voltages, which could power objects. He added eight neodymium magnets to the induction motor rotor and modified the coil windings of the BLDC motor so that it outputs a high voltage to power certain loads. He also realized the polarity of the magnets needs to alternate constantly.

However, he removed the entire squirrel cage to add a magnet holder on the rotor shaft. The holder was designed in Fusion 360 with 8 square holes for the magnets. He also used proto pasta filament for 3D printing. After the 3D prints were complete, he combined two strong component adhesives, which were used to glue the holder onto the shaft and secure the magnets in their pockets while altering their magnetic orientation.

He inserted the modified rotor after swapping out the rotor. The extra space in the motor was used for the coil windings. It produced nice sine waves and voltage peaks of 4.8V. Next, he hooked up a rectifier, energy meter, and light bulb to the generator coils and ran the rotor, which generated 2mW of power. Changing the load to a 0.5W LED boosted the maximum output power to 9mW.

An induction motor can be transformed into a generator, but it needs more powerful magnets. Otherwise, the motor doesn’t work mechanically or electrically.