The Pocket Bolt started with a concept from physics class: Faraday’s Law states that a changing magnetic field produces electric current. This is how mechanical motion can charge up a phone.

I first built a prototype to get a tangible sense of the device. I thought about using raw materials, such as a magnet placed within a coil of wire. But after doing some research, I found that such a simple device would not produce enough current due to electrical resistance. To charge an iPhone requires 5 watts of power, whereas this configuration would only generate 1.2 watts at best.

Instead of using raw magnets and wires, I decided to create a generator from a motor. From Faraday’s Law, spinning the magnets within a motor would generate electricity. I began testing the voltage and current of various motors to get as close to the necessary 5 watts as possible. Finally, I ended up using a 5V DC motor stripped from an electric pencil sharpener.

Further research led me to discover critical electrical components to make the circuit work. It needed a full-wave voltage rectifier, which would convert negative voltages from spinning the motor in the opposite direction to positive voltage. A voltage regulator would maintain the voltage at 5 volts, bumping up and down as needed. Lastly, a diode would prevent backflow of charge from leaking back to the motor.

With a tight time frame, I decided to use a similar electric board from another portable charger that came with 2000 mAh rechargeable batteries. I wired my motor into the circuit and attached a wheel to the motor using a 3D printout piece. The last thing to do was to put everything together in a comfortable, handheld 3D printed case. The prototype worked, and I received a lot of great feedback from the community at the EXPO.