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. 1 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. 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. 3 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 4 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 frequency (the number of complete cycles per second). A portion of the spectrum which is used for HF, VHF, and UHF radio communication has been expanded to show more detail. Figure 2: Electromagnetic Spectrum 5 2. 3 Antenna Fundamentals
All radios, whether transmitting or receiving, require some sort of antenna. The antenna accepts power from the transmitter and launches it into space as an electromagnetic or radio wave. At the receiving end of the circuit, a similar antenna collects energy from the passing electromagnetic wave and converts it into an alternating electric current or signal that the receiver can detect. How well antennas launch and collect electromagnetic waves directly influences communications reliability and quality. The function of an antenna depends on whether it is transmitting or receiving.
A transmitting antenna transforms the output radio frequency (RF) energy produced by a radio transmitter (RF output power) into an electromagnetic field that is radiated through space. The transmitting antenna converts energy from one form to another form. The receiving antenna reverses this process. It transforms the electro- magnetic field into RF energy that is delivered to a radio receiver. We will be using receiving antenna in our project. To select the right antennas for a radio circuit, certain concepts and terms must be understood.
These include: radiation fields and patterns, directionality, resonance, reception, reciprocity, impedance, bandwidth and gain. 6 2. 3. 1 Radiation Fields The electric and magnetic fields (components) radiated from an antenna form the electromagnetic field. The electromagnetic field transmits and receives electromagnetic energy through free space. A radio wave is a moving electromagnetic field that has velocity in the direction of travel and components of electric intensity and magnetic intensity arranged at right angles to each other. 2. . 2 Radiation Patterns The radio signals radiated by an antenna form an electromagnetic field with a definite pattern, depending on the type of antenna used. This radiation pattern shows the antenna’s directional characteristics. A vertical antenna radiates energy equally in all directions (Omni directional), a horizontal antenna is mainly bidirectional, and a unidirectional antenna radiates energy in one direction. Figure 3: Omni directional Pattern Figure 4: Bidirectional Pattern 7 Figure 5: Unidirectional Pattern 2. 3. 3 Directionality
Vertical receiving antennas accept radio signals equally from all horizontal directions, just as vertical transmitting antennas radiate equally in all horizontal directions. Because of this characteristic, other stations operating on the same or nearby frequencies may interfere with the desired signal and make reception difficult or impossible. However, reception of a desired signal can be improved by using directional antennas. Horizontal half-wave antennas accept radio signals from all directions. The strongest reception is received in a line perpendicular to the antenna (i. e. broadside and the weakest reception is received from the direction of the ends of the antenna). Interfering signals can be eliminated or reduced by changing the antenna installation so that either end of the antenna points directly at the interfering station. 8 2. 3. 4 Resonance Antennas can be classified as either resonant or non resonant, depending on their design. In a resonant antenna, almost the entire radio signal fed to the antenna is radiated. If the antenna is fed with a frequency other than the one for which it is resonant, much of the fed signal will be lost and will not be radiated.
The same is for the receiving antenna in which resonant antennas will receive the entire signal for which it is resonant. 2. 3. 5 Reception The radio waves that leave the transmitting antenna will have an influence on and will be influenced by any electrons in their path. For example, as an HF wave enters the ionosphere, it is refracted back to earth by the action of free electrons in this region of the atmosphere. When the radio wave encounters the wire or metallic conductors of the receiving antenna, the radio wave’s electric field will cause the electrons in the antenna to oscillate back and forth in step with the wave as it passes.
The movement of these electrons within the antenna is the small alternating electrical current which is detected by the radio receiver. When radio waves encounter electrons which are free to move under the influence of the wave’s electric field, the free electrons oscillate in symphony with the wave. This generates electric currents which then create waves of their own. These new waves are reflected or scattered waves. This process is electromagnetic scattering. All materials that are good electrical conductors reflect or scatter RF energy.
Since a receiving antenna is a good conductor, it too acts as a scatterer. Only a portion of the energy which comes in contact with the antenna is converted into received electrical power. If a receiving antenna is in close proximity to wires, it is possible for the reflected energy to cancel the energy received directly from the desired signal path. 9 When this condition exists, the receiving antenna should be moved to another location within the room where the reflected and direct signals may rein- force rather than cancel each other. 2. 3. Reciprocity The various properties of an antenna apply equally, regardless of whether the antenna is used for transmitting or receiving. This is what is meant by reciprocity of antennas. For example, the more efficient a certain antenna is for transmitting, the more efficient it will be for receiving the same frequency. If antenna is used as a receiving antenna, it receives best in the same directions in which the same antenna produced maximum radiation. Maximum Radiation Minimum Radiation Figure 6: Reciprocity Of Antenna 2. 3. 7 Impedance
Impedance is the relationship between voltage and current at any point in an alternating current circuit. The impedance of an antenna is equal to the ratio of the voltage to the current at the point on the antenna where the feed is connected (feed point). If the feed point is located at a point of maximum current, the antenna impedance is 20 to 100 ohms. If the feed point is moved to a maximum voltage point, the impedance is as much as 500 to 10,000 ohms. 10 The input impedance of an antenna depends on the conductivity or impedance of the ground.
For example, if the ground is a simple stake driven about a meter into earth of average conductivity, the impedance of the monopole may be double or even triple the quoted values. Because this additional resistance occurs at a point on the antenna circuit where the current is high, a large amount of transmitter power will dissipate as heat into the ground rather than radiated as intended. Therefore, it is essential to provide as good a ground or artificial ground (counterpoise) connection as possible when using a vertical whip or monopole. The amount of power an antenna radiates depends on the amount of current which flows in it.
Maximum power is radiated when there is maximum current flowing. Maximum current flows when the impedance is minimized. 2. 3. 8 Bandwidth The bandwidth of an antenna is that frequency range over which it will perform within certain specified limits. These limits are with respect to impedance match, gain, and/or radiation pattern characteristics. 2. 3. 9 Gain The antenna’s gain depends on its design. Transmitting antennas are designed for high efficiency in radiating energy, and receiving antennas are designed for high efficiency in picking up (gaining) energy.
Directional receiving antennas increase the energy gain in the favored direction and reduce the reception of unwanted noise and signals from other directions. Receiving antennas should have small energy losses and should be efficient as receptor. 11 2. 4 Antenna Types 2. 4. 1 Half Wave Dipole The horizontal half-wave dipole antenna is used on short- and medium-length sky wave paths up to approximately 1,200 miles. Since it is relatively easy to design and construct, it is the most commonly used field expedient wire antenna.
It is a very versatile antenna; by adjusting the antenna’s height above ground, the maximum gain can vary. This antenna is a bidirectional antenna i. e. , the maximum gain is at right angles to the wire. The half-wave dipole is a balanced resonant antenna. It produces its maximum gain for a very narrow range of frequencies, normally 2 % above or below the design frequency. Since frequency assignments are usually several megahertz apart, it is necessary to construct a separate dipole for each frequency assigned. Figure 7: Half wave Dipole Antenna 12 2. 4. 2 Inverted Vee
The inverted vee, or drooping dipole, is similar to a dipole but uses only a single center support. Like a dipole, it is designed and cut for a specific frequency and has a bandwidth of 2% above or below the design frequency. Because of the inclined sides, the inverted vee antenna produces a combination of horizontal and vertical radiation vertical off the ends and horizontal broadside to the antenna. All the construction factors for a dipole also apply for the inverted vee. The inverted vee has less gain than a dipole. Figure 8: Inverted Vee Antenna 2. 4. 3 Long Wire
A long wire antenna is one that is long compared to a wavelength. A minimum length is one-half wave- length. However, antennas that are at least several wavelengths long are needed to obtain good gain and directional characteristics. Constructing long wire antennas is simple, and there are no critical dimensions or adjustments. A long wire antenna will accept power and radiate it well on any frequency for which its overall length is not less than one-half wavelength. The gain of a long wire antenna depends on the antenna’s length. The longer the antenna, the more gain.
Gain has a simple relationship to length; however. A long wire antenna radiates a cone of energy around the tie wire. 13 Figure 9: Long Wire Antenna 2. 4. 4 Sloping Vee The sloping vee is a medium to long-range sky wave antenna that is simple to construct in the field. Antenna gain and directivity depend on the leg length. For reasonable performance, the antenna should be at least one wavelength long, but preferably several wavelengths long. Figure 10: Sloping Vee Antenna 14 2. 4. 5 Patch & Micro strip Antenna Other types of antennas to consider are patches, micro strips.
The patch antenna has two major problems when being used with a research project like this. The first is that it also needs to be relatively large. The second reason is that it is highly directional, meaning that it only radiates, and accepts radiation, in one direction, i. e. , it does not have a good coverage area. These reasons rule out this option. A micro strip antenna can be any type of antenna discussed previously, but what makes it unique is that it is “painted” on to a surface so that it is in the same plane as the printed circuit board.
This means that it can be patch, a dipole, as long as all the metal is in the same plane. The main problems with this antenna are its gain and its directionality. 2. 4. 6 Helical Antenna A helical antenna is an antenna consisting of a conducting wire wound in the form of a helix. In most cases, helical antennas are mounted over a ground plane. Helical antennas can operate in one of two principal modes: normal (broadside) mode or axial (or end-fire) mode. In the normal mode, the dimensions of the helix are small compared with the wavelength. The field radiation is similar to an electrically short dipole or monopole.
Broadside Helical Radiating at 90 degrees from the vertical or horizontal plane this design is efficient as a practical reduced-length radiator when compared with the operation of other types such as base-loaded, top-loaded or center-loaded whips. These are usually wound in a linear spiroidal pattern (constant parallel spaced turns) providing consistent uniform radiation as a reduced sized equivalent in respect to the standard 1/4 wave antenna. 15 They are typically used for mobile communications applications where reduced size is a critical operational factor.
An effect of this type of ‘reduced size 1/4 wave’ is that the matching impedance is reduced from the nominal 50 ohms to between 25 to 35 ohms base impedance. This does not seem to be adverse to operation and matching with a normal 50 ohm transmission line, provided the connecting feed is the electrical equivalent of a 1/2 wave at the frequency of operation. Another example of the type as used in mobile communications is “spaced constant turn” in which two or more different linear windings are wound on a single former and spaced so as to provide an efficient balance etween capacitance and inductance for the radiating element at a particular resonant frequency. 2. 5 The Solar Cell A solar cell or photovoltaic cell is an electronic device that converts solar energy into electricity by the photovoltaic effect. Sometimes the term solar cell is reserved for devices intended specifically to capture energy from sunlight, while the term photovoltaic cell is used when the source is unspecified. Assemblies of cells are used to make solar modules, or photovoltaic arrays. Photovoltaic’s is the field of technology and research related to the application of solar cells for solar energy.
Solar cells are used for powering small devices such as electronic calculators. Photovoltaic arrays generate a form of renewable electricity, particularly useful in situations where electrical power from the grid is unavailable such as in remote area power systems. Solar Cells are classified into three generations which indicates the order of which each became prominent. 16 2. 5. 1 First Generation First generation cells consist of large-area, high quality and single junction devices. First Generation technologies involve high energy and labor inputs which prevent any significant progress in reducing production costs.
Single junction silicon devices are approaching the theoretical limiting efficiency of 33%. 2. 5. 2 Second Generation Second generation materials have been developed to address energy requirements and production costs of solar cells. Because of the defects inherent in the lower quality processing methods, second generation has much reduced efficiencies compared to First Generation. 2. 5. 3 Third Generation Third generation technologies aim to enhance poor electrical performance of second generation (thin-film technologies) while maintaining very low production costs.
Current research is targeting conversion efficiencies of 30-60% while retaining low cost materials and manufacturing techniques. They can exceed the theoretical solar conversion efficiency limit for a single energy threshold material. 2. 5. 4 High efficiency cells High efficiency solar cells are a class of solar cells that can generate electricity at higher efficiencies than conventional solar cells. High efficiency solar cells are more efficient in terms of electrical output. For the testing purpose of our project we have used second generation solar cell, however we are also evaluating high efficiency cells and first generation cells. 7 Chapter 3 Literature Review Since this is a relatively new concept there has been a less amount of research done in wireless mobile charging, however much importance has been given to the research in the field of the wireless energy transfer or wireless power transmission. We have learned valuable lessons from the research done in the field of wireless energy transfer. 3. 1 Wireless Energy Transmission Wireless energy transmission is the process that takes place in any system where electrical energy is transmitted from a power source to an electrical load, without interconnecting wires in an electrical grid.
Wireless transmission is ideal in cases where instantaneous or continuous energy transfer is needed, but interconnecting wires are inconvenient, hazardous, or impossible. Though the physics of both are related, the wireless energy transmission is distinct from wireless transmission for the purpose of transferring data, where the percentage of the power that is received is only important if it becomes too low to successfully recover the signal. While in wireless energy transfer, the efficiency is a more critical parameter and this creates important differences in these two technologies.
There have been many concepts which have been identified and tested few of which are: 3. 1. 1 Inductive Coupling The action of an electrical transformer is the simplest instance of wireless energy transfer. The primary and secondary circuits of a transformer are not directly 18 connected. The transfer of energy takes place by electromagnetic coupling through a process known as mutual induction. 3. 1. 2 Resonant Induction Electromagnetic induction works on the principle of a primary coil generating a predominantly magnetic field and a secondary coil being within that field so a current is induced within its coils.
This causes the relatively short range due to the amount of power required to produce an electromagnetic field. Over greater distances the non-resonant induction method is inefficient and wastes much of the transmitted energy just to increase range. This is where the resonance comes in and helps efficiency dramatically by “tunneling” the magnetic field to a receiver coil that resonates at the same frequency. 3. 1. 3 Radio and Microwave Power Transmission The work in the area of wireless transmission via radio waves was performed by Heinrich Rudolf Hertz.
A later Galileo Marconi worked with a modified form of Hertz’s transmitter. Nikola Tesla also investigated power transmission and reception using radio waves. A rectenna may be used to convert the microwave energy back into electricity. Rectenna conversion efficiencies exceeding 95% have been realized. These are however far fielding transmission unlike the induction and the resonant induction. 19 Chapter 4 Method of Investigation Start Antenna Solar Cell Rectifier Charging Unit Filter Voltage Regulator Battery Voltage Indicator Stop Figure 11: Flow Chart 20 4. 1.
Description of Project Design The work on the project has been done following three phase strategy. In the First phase we designed and implemented the solar powered charging system after successful validation of the parameters of the design, we moved to the second phase which involved the charging cell phone using RF energy. After successful completion of the second phase, we moved to the final phase of the project in which we combined both the sources of energy to provide the cell phone with the maximum amount of current for charging. 4. 2. Cell Phone Requirements
This project has been designed keeping in mind the most commonly used cell phones which accordingly belongs to Nokia brand. The specification of the nokia’s 2626 cell phone, which we are going to use as a testing phone, is 3. 7V with 1020mAh. It takes approx. 2hrs to charge the battery of the cell phone with a normal charger meaning, the power required by the cell phone is: P = 3. 7V*1020mA P = 3. 774W Hence Energy = 3. 774 j in one second The energy required for 2hrs of charging is: E = 3. 774j/s * 7200sec E = 27172. 8 Joules This is the amount of energy required by the Nokia 2626 cell phone for complete charging. 1 4. 3. Block Diagram Electromagnetic Waves Rectifier & Filters Figure 12: Block Diagram Combiner Battery Charging Unit Battery 22 Cell Phone Charging Unit Solar Panel 4. 4 Circuit Diagram Figure 13: Circuit Diagram 23 Chapter 5 System Hardware 5. 1 Rectifiers and Filters Rectifier is a device which converts the AC input signal to pulsating DC signal. Rectifiers can be of two types either half wave rectifier or full wave rectifier. Half wave rectifiers convert the AC input signal to pulsating DC signal with only one output pulse for a complete cycle. Figure 14: Half Wave Rectifier
Full wave rectifiers convert the AC input signal to pulsating DC signal with two rectifiers output pulses for each cycle. 24 Full wave rectifiers are of two types: • Center-Tapped Full Tapped Full-Wave Rectifier Figure 15: Center-Tapped Full wave Rectifier • Bridge Full Full-Wave Rectifier Figure 16: Bridge Full Wave Rectifier Filters are used to convert pulsating DC to a pure DC signal and to remove ripples from the DC signal. For this purpose a simple capacitor is used. 25 Figure 17: Filtered Wave This figure shows the voltage decreases exponentially. This is due to the RC time constant.
The voltage decreases in relation to the inverse of the resistance of the load, R, multiplied by the capacitance C. 26 5. 2 Battery Charg Charging Circuit Figure 18: Battery Charging Circuit The LM 317 is an adjustable 3-treminal positive voltage regulator capable of supplying in excess of 1. 5A over an output voltage range of 1. 2V to 37V From 37V. the datasheet of LM 317 we get the following formula: ? R ? Vout = 1. 25 ? ?1 + 2 ? + I adj ? R 2 ? R1 ? ? ? From datasheet we know that the maximum value of Iadj is 100 µ A. For Vout = 6 Volts let us find the values of resistors R1 and R2.
Volts, Let R1= 1K ? Therefore: R ? ? 6 = 1. 25 ? ?1 + 2 ? + 100µ ? R2 ? 1K ? 6 = 1. 25 + 1. 25 ? R2 + 100µ ? R2 1K 6 ? 1 . 25 = (1 . 25 m + 100 µ ) ? R 2 4 . 75 = 1 . 35 m ? R 2 R2 = 4. 75 1. 35m 27 R 2 = 3 . 518 K ? ? 4 K ? D1 is a schottky diode used to protect LM 317 from reverse current. D1 also prevents discharging of battery when the source is removed. 28 5. 3 Hybrid Battery Charging Circuit Figure 19: Hybrid Charging Circuit Name R1, R4 R2 R3 R5 R6 C1 C2 D1 D2, D3 D5, D6 D4 Q1 IC1, IC2 T1 B1 Description 1K 4K 220 F, Current limiting resistor for LED 3K 1. 470 F, Filtering Capacitor 1000 F, Filtering Capacitor Schottky Diode to safe solar panel from reverse current Schottky Diodes making a center tapped full-wave rectifier Schottky Diodes to safe LM 317 and to prevent discharging of Battery LED, shows the charging of Lead acid battery BD139 LM 317, adjustable positive voltage regulator RF center tap transformer (Adjustable turns), For impedance matching 6 Volts, 4. 5 Ah Lead acid battery Table 1: Hybrid Component 29 5. 4 Cell Phone Charging Circuit Figure 20: Cell Phone Charging Circuit 30 From the datasheet of LM 317 we get the following formula: ? R ? Vout = 1. 5 ? ?1 + 2 ? + I adj ? R 2 ? R1 ? ? ? From datasheet we know that the maximum value of Iadj is 100 µ A. We need the following Voltage and current value for charging cell phone: For Nokia we need: 15 Volts and 350m A (For new cell phones chargers with thin pins, for example N Series, E Series. ) 2- 5. 7 Volts and 700m A (For older cell phones model chargers with thick pins, for example 3310, 1100 series, 2626 and others. ) For Samsung we need: 3- 5 Volts and 700m A For Sony Ericson we need: 4- 4. 9 Volts and 450m A Now Calculating for For Vout = 5 Volts and 350m A, let us find the values of resistors R1 and R2.
Let R1= 1K ? Therefore: R ? ? 5 = 1. 25 ? ?1 + 2 ? + 100µ ? R2 ? 1K ? 5 = 1. 25 + 1. 25 ? R2 + 100µ ? R2 1K 5 ? 1 . 25 = (1 . 25 m + 100 µ ) ? R 2 3 . 75 = 1 . 35 m ? R 2 31 R2 = 3. 75 1. 35m R 2 = 2 . 77 K ? ? 3 K ? Now let us calculate the value of R6. We know that VBE = 0. 7 Volts Therefore VR3 = 0. 7 Volts Iout = VR3 R3 Iout = 0. 7 R3 0. 7 I out R3 = For Iout = 350mA R3 = 0. 7 350m R3 = 2 ? Similarly For 5. 7 Volts and 700m A we obtain: R4 = 3. 29k ? ? 3 . 3 k ? R5=1 ? For 5 Volts and 700m A we obtain: R6 = 3k ? R7=1 ? For 4. 9 Volts and 450m A we obtain: R8 = 2. 7k ?
R9=1. 5 ? 32 Component List Components R1 R2 R3 R4 R5 R6 R7 R8 R9 D1 IC 1k ? 3k ? 2? 3. 3k ? 1? 3k ? 1? 2. 7k ? 1. 5 ? Schottky Diode for safety purpose LM317T Table 2: Cell Charging Components 33 5. 5 Selector and User Interface Circuit Figure 21: Selector and User Interface Circuit : 34 This circuit uses AT89C51 micro controller is used for two purposes. 1. First and the main purpose is the selection of desired mobile phone charging circuit. 2. Secondary purpose is to interface 16×2 lines LCD with the circuit. 5. 6 Charge Pump Circuit Figure 22: Charge Pump Circuit
Components List Component Capacitor Diode 15nf / 12 / 12 Table 3: Charge Pump Components Rating / Quantity 35 5. 6 Solar Cell Specifications Figure 23: Solar Cell Power Rating Pmax = 5 Watts Voc = 19. 2 Volts Isc = 0. 3 Amp Size Length = 13. 4 inches Breadth = 5. 7 inches Height = 1. 4 inches 5. 7 Antenna Specification Gain = 3 dB Diameter = 1cm Height = 1ft Weight = 50gms Impedance = 58ohms Figure 24: Antenna 36 Chapter 6 System Software 6. 1 Selector and User Interface Code RS EN BIT BIT P2. 0 P2. 2 LCD ;main EQU P1 ORG 00H MOV A,#0FFH MOV R1,#00H MOV P0,#0 MOV P3,A ;R1=0 ;MAKING PORT 0 ZERO MAKING PORT3 INPUT ;R5=FFH CALL CALL CALL LCDINIT GO_2_LINE1 PRJ_MESSAGE1 OUTER: MOV A,P3 ;GETTING DATA FROM P3 ACALL DELAY CJNE A,#0FFH,INNER LJMP OUTER ;JUMP IF A! =FFH 37 INNER: CJNE R1,#2,INNER1 ;JUMP IF R1! =2 ;P0=04H MOV P0,#04H CALL CALL CALL LJMP RET1 LCDINIT GO_2_LINE1 PRJ_MESSAGE2 INNER1: CJNE R1,#1,INNER0 ;JUMP IF R1! =1 ;P0=02H MOV P0,#02H CALL CALL CALL LJMP RET1 LCDINIT GO_2_LINE1 PRJ_MESSAGE3 INNER0: CALL CALL CALL MOV P0,#01H LCDINIT GO_2_LINE1 ;P0=01H PRJ_MESSAGE4 LJMP RET1 RET1: INC R1 CJNE R1,#3,NEXT MOV R1,#00H ;R1=0 ;R1=R1+1 ;JUMP IF R1! =3 NEXT: LJMP OUTER ;GOTO OUTER ===================================================== DSPLYMSG: 38 MOV MOVC CJNE A,#00H A,@A+DPTR A,#’~’,SND_DATA RET SND_DATA: CALL CALL INC JMP DATAWRT DELAY1 DPTR DSPLYMSG ;==================================================== LCDINIT: MOV NXTINST: MOV MOVC CJNE DPTR,#INITMSG A,#00H A,@A+DPTR A,#’~’,SND_CMND RET SND_CMND: CALL CALL INC JMP COMNWRT DELAY1 DPTR NXTINST ;==================================================== 39 COMNWRT: MOV CLR SETB CLR LCD,A RS EN EN ;CLR RS FOR COMM ;SET AND CLR EN RET ;==================================================== ;==================================================== GO_2_LINE1:
MOV CALL CALL A,#80H COMNWRT DELAY1 RET ;==================================================== ;==================================================== DATAWRT: MOV SETB SETB CLR LCD,A RS EN EN ;SET RS FOR DATA ;SET AND CLR EN RET ;==================================================== ;==================================================== 40 DELAY1: MOV MOV DJNZ DJNZ R3,#50 R4,#255 R4,$ R3,$-4 RET ;==================================================== ;===================================================== PRJ_MESSAGE1: MOV CALL DPTR,#PRJMSG1 DSPLYMSG RET ==================================================== ;===================================================== PRJ_MESSAGE2: MOV CALL DPTR,#PRJMSG2 DSPLYMSG RET ;==================================================== ;===================================================== 41 PRJ_MESSAGE3: MOV CALL DPTR,#PRJMSG3 DSPLYMSG RET ;==================================================== ;===================================================== PRJ_MESSAGE4: MOV CALL DPTR,#PRJMSG4 DSPLYMSG RET ;==================================================== INITMSG: DB 01H,02H,3CH,0CH,’~’ PRJMSG1: DB ‘ Select Charger ‘,’~’ PRJMSG2: DB ‘ NOKIA ,’~’ PRJMSG3: DB ‘ SAMSUNG ‘,’~’ PRJMSG4: DB ‘ SONYERICSSON ‘,’~’ 42 DELAY: HERE2: MOV R3,#255 MOV R4,#255 HERE: DJNZ R4,HERE DJNZ R3,HERE2 RET END 43 Chapter 7 Results and Discussion This project has been successfully implemented and is in working condition. It has been tested by charging three mobiles and a USB device; however they are to be charged consecutively not simultaneously. Each charging port has been customized for different cell phone vendors, namely Nokia, Samsung and Sony Ericsson. Theoretically each output given for Nokia, Samsung and Sony Ericsson was 5Volts and 350m A, 5 Volts and 700m A, 4. Volts and 450m A respectively. However practically we are getting 5Volts and 350m A, 5 Volts and 700m A, 4. 9 Volts and 450m A respectively. It takes an average of approximately 5 hours to charge a cell phone, and approximately 2 hours to charge using USB device. 44 Chapter 8 Conclusion and Future Work This project is a milestone in achieving independence from the AC power source. Even though this project is comparatively larger than the cell phone in size and dimensions, however it will eventually be quite smaller in size due to the advent of efficient and smaller solar cells and high gain antennas.
The future work on this project would be introduced by miniaturization of the components used; so that the entire project will be integrated inside a cell phone, utilizing the existing cell phone antenna for harvesting energy to charge battery, and the microprocessor in the cell phones to replace the external microcontroller. Another advancement in this project will be the development of an artificially intelligent program, which will monitor the power level of the battery and stops charging when the maximum voltage level is reached, and will start charging when the power level of the battery fall below the threshold level.
The program would also ensure the selection of the maximum strength signal from among those present in the vicinity of cell phone. 45 Figure 25: Project 46 References   C. Balanis, Wiley “Antenna Theory” (3rd edition), 2005 W. Stutzman and G. Thiele” Antenna Theory and Design”, Wiley, 1997.  J. Kraus and R. Marhefka “Antennas (3rd edition)” McGraw-Hill, 2001.    Hecht, Eugene “Optics”, Pearson Education, 2001. Serway, Raymond A,Jewett, John W “Physics for Scientists and Engineers”, Brooks/Cole, 2004. Tipler, Paul “Physics for Scientists and Engineers: Electricity, Magnetism, Light, and Elementary Modern Physics”, W.
H. Freeman, 2004. Reitz, John; Milford, Frederick; Christy, Robert “Foundations of Electromagnetic Theory”, Addison Wesley, 1992. Jackson, John David “Classical Electrodynamics”, John Wiley & Sons, 1975. UNSW School for Photovoltaic Engineering. “Third Generation Photovoltaics”. Retrieved on 2008-06-20. M. Andreev, M. B. Kagan, I. I. Protasov, and V. G. Trofim, ”Solarenergy converters based on p-n AlxGa12xAs-GaAs heterojunctions”, Fiz Tekh Poluprovodn, 1970 www. compoundsemiconductor. net www. howstuffworks. com       47 Data Sheets 48