Final Year Project

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Chapter 1 Introduction
1.1 Problem
It seems these days that everyone has a cellular phone. Whether yours is for business purposes or personal use, you need an efficient way of charging the battery in the phone. But, like most people, you probably don’t like being dependent on the main supply for charging your cell phone battery or you don’t have the time to recharge your cell phone battery. As technology has advanced and made our phones smaller and easier to use, we still have one of the original problems: we must plug the phone into the wall in order to recharge the battery. Most people accept this as something that will never change, so they might as well accept it and carry around either extra batteries with them or a charger. Imagine a system where your cellular phone battery is always charged. No more worrying about forgetting to charge the battery. Sound’s Impossible?

1.2 Objective
The objective of this project is to increase the mobility of cell phones by charging them using the energy present in a part of electromagnetic spectrum, which is present everywhere in the free space, and solar energy without using external AC power source.

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1.3 Intended Approach
We have partitioned our project into three phases on the basis of energy types used for charging purpose:

Phase 1 Charging Using Solar Energy In this phase we will design and test the design of solar energy charger, once successfully tested it will be implemented

Phase 2 Charging Using EM Waves In this phase we will design and test the design of EM Wave energy charger, once successfully tested it will be implemented.

Phase 3 Combinations of the Two Charging Systems After successful completion of phase1 and phase2, both systems will be incorporated in a single unit to build an efficient and powerful charger.

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Chapter 2
Background
This project is based on a very simple concept, capture RF energy using an antenna, input it into a RF Transformer and use this energy to power other circuit. RF energy is transmitted to the RF Transformer which matches the impedance of the antenna with that of the receiving circuit so that maximum energy can be transferred. Solar energy which is a part of this project harvests the solar energy from the sun. This section discusses the concepts and the practical devices regarding the harvesting of the energy. Because the circuits are small, the power required is minimal. Similarly these types of circuits can work well for cell phones because cell phones also need minimal power.

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2.1 RF Transformers:
RF transformers are widely used in low-power electronic circuits for impedance matching to achieve maximum power transfer, for voltage step-up or step-down, and for isolating dc from two circuits while maintaining ac continuity. Essentially, an RF transformer consists of two windings linked by a mutual magnetic field. When one winding, the primary has an ac voltage applied to it, a varying flux is developed; the amplitude of the flux is dependent on the applied voltage and number of turns in the winding. Mutual flux linked to the secondary winding induces a voltage whose amplitude depends on the number of turns in the secondary winding. By designing the number of turns in the primary and secondary windings, any desired step-up or step-down voltage ratio can be realized.

Figure 1: Transformer Basics

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2.2 Electromagnetic Waves
Electromagnetic wave includes radio waves, microwaves, infra- red radiation, visible light, ultraviolet waves, X-rays, and gamma rays. Together they make up the electromagnetic spectrum. They all move at the speed of light (186,000 miles/300 million meters per second). The only difference between them is their wavelength (the distance a wave travels during one complete cycle), which is directly related to the amount of energy the waves carry. The shorter the wavelength, the higher the energy lists the electromagnetic spectrum components according to wavelength and...
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