Project Overview

            As we all know, the world consumes larger amounts of energy everyday, and newer, cleaner forms of energy are required to meet the increasing demand for energy. While many forms of clean energy (e.g. wind, water) exist, our group has decided to harness the power of induction to provide a clean, renewable energy source to power a cellphone. The concept for our design is a coil-magnet system attached to a user where the magnet will be allowed to freely move up and down through the coil as the user walks or runs. As the magnet passes through the coil, a current will be induced in the coil that will be used to charge a cellphone.



            Our Goal

            Our goal is to show how the natural up and down movement of the upper body while running or walking can be converted into a reliable source of energy with relative ease. This charger, powered by a magnet sliding up and down through a coil as the user moves, will generate a current and voltage using induction large enough (approximately .5A and 5V) to charge most smartphones. This current, which is generated as AC current, will then be converted into DC current, which will charge the phone. Major tasks involved include determining where to place the coil-magnet system, determining what material will be most suitable to create the coil, and how the charge will be stored when not in use. Technical challenges to be encountered during the design process are converting the current into DC, generating the current required to charge a phone, and designing a charger that is both comfortable for the user and appealing to the eye. The final design will be an eco-friendly cellphone charger that is both reliable and cost-efficient.

            Technical Activities

In designing a cost-effective motion-powered cell phone charger, many technical tasks were completed. All of these tasks focused on designing a prototype that is capable of producing the required .5mA and 5V needed to charge the device, storing the generated energy, and achieving an acceptable movement-charge ratio.

            Designing the Coil-Magnet System

The voltage generated by a magnet passing through a solenoid is proportional to the number of turns of the coil, the strength of the magnetic field created by the magnet, and the cross-sectional area of the coil that the magnet passes through. One of the major tasks of designing the product when designing a charger that is both comfortable and reliable is taking into account these three factors when building the charger.

The coil of the coil-magnet system is created by wrapping a long wire around a cylinder multiple times. Aluminum-copper wire was used for its high conductivity and low cost. The magnet used in the system was chosen both for its size, which allows it to slide through the entire coil without touching the coil, and its magnetic field strength of .1T, which is strong enough to produce the 5 volts required to charge a smartphone.

Converting the Current into a Usable Form

The current that is induced in the coil-magnet system will be generated as an alternating current. However, for this project a direct current is required. In order to overcome this problem, the current was converted from AC to DC by using a bridge rectifier. This rectifier was constructed using four diodes, two for the incoming AC current from the coil and two for the outgoing DC current.



Used equations through out the project with a diagram of the circuit

            Storing Energy

Since the charger will not constantly be in operation, storing unused charge is a priority in designing an energy-efficient product. To accomplish this, the DC wires from the rectifier are directly wired to two nickel metal hydride, NiMH, batteries that will absorb any charge no matter how much current is present.