An –Najah National University
Faculty of Engineering & Information Technology
Telecommunication Engineering Derpartment
Wireless Power Transfer
Submitted by:- Ahmad Mohammad Antari1
Ayham Abdallah Odeh2
Izzeddin Khalil Habbazi1
Submitted to:-Dr. Ahmed Masri
Presented in partial fulfillment of the requirements for Bachelor degree in
Telecommunication1 Engineering and Electrical2 Engineering.
Date:28/4/2015
1
Acknowledgment
We would like to express our gratitude for everyone who helped us during the graduation
project starting with endless thanks for our supervisor Dr. Ahmed Masri who didn’t keep any
effort in encouraging us to do a great job, providing our group with valuable information and
advices to be better each time. Thanks for the continuous support and kind communication
which had a great effect regarding to feel interesting about what we are working on and for
guide us in this project such as improve our searching capabilities and how to write the report.
Thanks are extended to the”Telecommunicationand Electrical Engineering Department” for
the beneficial lectures provided such as Electromagnetic1,2 and circuits lecture which was
what we were looking for and which facilitated many things in our project. Many thanks for
Dr. Falah M. Hussen. Thanks are extended to all instructors and engineers who helped us
during the first stages of our graduation project.
My completion of this project could not have been accomplished without the support of my
class mates thank you for allowing us time away from you to research and write.
Thanks to our parents as well, Mr. and Mrs. Mohammad Antari, Khalil Habbazi and Abdallah
Odeh. The countless times youkept the children during our hectic schedules will not be
forgotten.
2
Contents
1. Abstract.............................................................................................................................................. 6
2. Chapter 1: Introduction ..................................................................................................................... 7
2.1. Goal ............................................................................................................................................ 7
2.2. Overview of wireless charging techniques ................................................................................ 8
2.3. Wireless Charging Techniques ................................................................................................... 8
3. Chapter 2: Constraints, Standards/ Codes and Earlier course work ............................................... 11
1.1. Constraints ............................................................................................................................... 11
4. Chapter 3: Literature Review .......................................................................................................... 12
4.1. Faraday's law ........................................................................................................................... 12
4.2. voltage multiplier ..................................................................................................................... 12
5. Chapter 4: Methodology ................................................................................................................. 15
6. Chapter 5: Results and Analysis ....................................................................................................... 19
7. Chapter 6: Discussion ...................................................................................................................... 20
8. Chapter 7: Conclusions and Recommendation ............................................................................... 25
8.1. Coils:......................................................................................................................................... 25
8.2. Frequency: ............................................................................................................................... 25
9. Chapter 8:Impacts and Engineering solution. ................................................................................. 26
9.1. Economic.................................................................................................................................. 26
9.2. Commercial Prospects ............................................................................................................. 26
9.3. Manufacturability .................................................................................................................... 26
9.4. Sustainability ............................................................................................................................ 26
9.5. Ethical....................................................................................................................................... 26
9.6. Health and Safety..................................................................................................................... 27
9.7. Social and Political ................................................................................................................... 27
9.8. Development ........................................................................................................................... 27
10. Future .............................................................................................................................................. 28
11. References (Refer to Appendix B: guideline) .................................................................................. 29
12. Appendices ...................................................................................................................................... 30
3
List of Figures (LOF)
Figure 1 Wireless Charging Techniques .................................................................................................. 8
Figure 2 Voltage quadrupler circuit diagram. ........................................................................................ 14
Figure 3 Block Diagram of the System. ................................................................................................. 15
Figure 4 Transformer principle of working ............................................................................................ 15
Figure 5 Rectifier and smoothing capacitor. .......................................................................................... 16
Figure 6 Tx coil and Rx coil................................................................................................................... 16
Figure 7 joule thief circuit diagram. ....................................................................................................... 17
Figure 8 Voltage doubler circuit diagram. ............................................................................................. 17
Figure 9 Regulator circuit. ..................................................................................................................... 17
Figure 10 Tx and Rx coils of template copper during the test stage. ..................................................... 20
Figure 11 The output at Rx coil of template copper............................................................................... 21
Figure 12 The output at Rx coil with 22v input voltage. ....................................................................... 22
Figure 13 The output after the doubler................................................................................................... 22
Figure 14 The output after the quadrubler.............................................................................................. 23
Figure 15 Mobile phone while charging. .............................................................................................. 23
Figure 16 First testing oscillator............................................................................................................. 24
Figure 17 ) Receiver side circuit. ........................................................................................................... 24
4
List of Tables (LOT)
Table 1 Wireless charging techniques. ................................................................................................... 10
Table 2 Coils used in the experiments.................................................................................................... 19
5
Abstract
Wireless charging is a technique of transmitting power through an air to an electrical device for
the purpose of power feeding, recently, the wireless charging technology has been
significantly advanced in terms of efficiency and functionality. This report first presents an
overview and fundamentals of wireless charging.
The idea of our project is based on converting power from AC to DC using the transformer,
and then entered to the oscillator circuit in order to get a current with high-frequency and then
to the transmitter coil, At the receiver side, due to changes in the magnetic field the receiver
coil receives the signal and generates an inductive current relatively weak, enters directly into
a circuit in order to double the voltage, then to the rectifying stage and then the regulator to
get a 5 volts which is what we are interested in.
6
Chapter 1: Introduction
Wireless power transmission (WPT) is an efficient way for the transmission of electric power
from one point to another through vacuum or atmosphere without the use of wire or any
substance. By using WPT, power can be transmitted using inductive coupling for short range,
resonant induction for mid-range and Electromagnetic wave power transfer. By using this
technology, it is possible to supply power to places, which is hard to do using conventional
wires. Currently, the use of inductive coupling is in development and research phases. The most
common wireless power transfer technologies are the electromagnetic induction and the
microwave power transfer. For efficient midrange power transfer, the wireless power transfer
system must satisfy three conditions: (a) high efficiency, (b) large air gap, (c) high power. The
microwave power transfer has a low efficiency. For near field power transfer this method may
be inefficient, since it involves radiation of electromagnetic waves. Wireless power transfer can
be done via electric field coupling, but electric field coupling provides an inductively loaded
electrical dipole that is an open capacitor or dielectric disk. Extraneous objects may provide a
relatively strong influence on electric field coupling. Magnetic field coupling may be preferred,
since extraneous objects in a magnetic field have the same magnetic properties as empty space.
Electromagnetic induction method has short range. Since magnetic field coupling is a nonradioactive power transfer method, it has higher efficiency. However, power transfer range can
be increased by applying magnetic coupling with resonance phenomenon applied on. A
magnetic field is generated when electric charge moves through space or within an electrical
conductor. The geometric shapes of the magnetic flux lines produced by moving charge
(electric current) are similar to the shapes of the flux lines in an electrostatic field.
Goal
The aim of this project is to create the wireless power transfer system that will allow future
systems to wirelessly charge phones. The goal is to obtain a good efficiency regardless of the
distance, because we are dealing with small dimensions. 60% is the minimum requirement for
the quality factor (Q) low power standard, and a 5 cm would give sufficient range for user
interaction. The Q low power standard is a set of wireless power specifications that companies
have to follow in order to gain the recognition of the Wireless Power Consortium [9].
Overall, these goals would make it possible for a charging system to be efficient, and also give
the system a good charging radius. A product that uses this technology would be a working
system where someone can sit in their car and have their phone charge requiring a conscious
effort to initiate the charging.
7
Overview of wireless charging techniques
Nikola Tesla, the founder of alternating current electricity, was the first to conduct
experiment of wireless charging. He achieved a major breakthrough in 1899 by transmitting
108 volts of high-frequency electric power over a distance of 25 miles to light 200 bulbs and
run an electric motor. In 1901, Tesla constructed the Wardenclyffe Tower to transfer electrical
energy globally without cords through the Ionosphere. However, due to technology limitation
(e.g., low system efficiency), the idea has not been widely further developed and
commercialized. Later, during 1920s and 1930s, magnetrons were invented to convert
electricity into microwaves, which enables wireless power transfer over long distance.
However, there was no method to convert microwaves back to electricity until 1964, when W.
C. Brown realized this through a rectenna. Brown demonstrated the practicality of microwave
power transfer by powering a model helicopter, which inspired a series of research in
microwave-powered airplanes during 1980s and 1990s in Japan and Canada . More recently,
different consortiums, e.g., Wireless Power Consortium [2], Power Matters Alliance, and
Alliance for Wireless Power, have been established to develop international standards for
wireless charging. Nowadays, the standards are adopted in many products in the market.
Wireless Charging Techniques
Three major techniques for wireless charging are magnetic inductive coupling, magnetic
resonance coupling, and microwave radiation. The magnetic inductive and magnetic
resonance coupling work on near field, where the generated electromagnetic field dominates
the region close to the transmitter or scattering object. The near-field power is attenuated
according to the cube of the reciprocal of the distance. Alternatively, the microwave radiation
works on far field at a greater distance. The far-field power decreases according to the
reciprocal of the distance. Moreover, for the far-field technique, the absorption of radiation
does not affect the transmitter. By contrast, for the near-field techniques, the absorption of
radiation influences the load on the transmitter.
Figure 1 Wireless Charging Techniques
8
1) Magnetic Inductive Coupling: Magnetic inductive coupling is based on magnetic field
induction that delivers electrical energy between two coils [2]. Figure 1a shows the reference
model. Magnetic inductive coupling happens when a primary coil of an energy transmitter
generates predominant varying magnetic field across the secondary coil of the energy receiver
within the field, generally less than the wavelength. The near-field power then induces
voltage/current across the secondary coil of the energy receiver within the field. This voltage
can be used by a wireless device. The energy efficiency depends on the tightness of coupling
between two coils and their quality factor. The tightness of coupling is determined by the
alignment and distance, the ratio of diameters, and the shape of two coils. The quality factor
mainly depends on the materials, given the shape and size of the coils as well as the operating
frequency. The advantages of magnetic inductive coupling include ease of implementation,
convenient operation, high efficiency in close distance (typically less than a coil diameter) and
safety. Therefore, it is applicable and popular for mobile devices. Very recently, MIT
scientists have announced the invention of a novel wireless charging technology, called
MagMIMO , which manages to charge a wireless device from up to 30 centimeters away. It is
claimed that MagMIMO can detect and cast a cone of energy towards a phone, even when the
phone is put inside the pocket.
2) Magnetic Resonant Coupling: Magnetic resonance coupling, as shown in Fig. 1b, is based
on evanescent-wave coupling which generates and transfers electrical energy between two
resonant coils through varying or oscillating magnetic fields. As the resonant coils, operating
at the same resonant frequency, are strongly coupled, high energy transfer efficiency can be
achieved with small leakage to non-resonant externalities. This property also provides the
advantage of immunity to neighboring environment and line-of-sight transfer requirement.
Compared to magnetic inductive coupling, another advantage of magnetic resonance charging
is longer effective charging distance. Additionally, magnetic resonant coupling can be applied
between one transmitting resonator and many receiving resonators, which enables concurrent
charging of multiple devices. In 2007, MIT scientists proposed a high-efficient mid-range
wireless power transfer technology, i.e., Witricity, based on strongly coupled magnetic
resonance. It was reported that wireless power transmission can light a 60W bulb in more than
two meters with transmission efficiency around 40% [6]. The efficiency increased up to 90%
when the transmission distance is one meter. However, it is difficult to reduce the size of a
Witricity receiver because it requires a distributed capacitive of coil to operate. This poses big
challenge in implementing Witricity technology in portable devices. Resonant magnetic
coupling can charge multiple devices concurrently by tuning coupled resonators of multiple
receiving coils [7]. This has been shown to achieve improved overall efficiency. However,
mutual coupling of receiving coils can result in interference, and thus proper tuning is
required.
3) Microwave Radiation: Microwave radiation utilizes [8] microwave as a medium to carry
radiant energy. Microwaves propagate over space at the speed of light, normally in line-ofsight. Figure 1c shows the architecture of a microwave power transmission system. The power
transmission starts with the ACto-DC conversion, followed by a DC-to-RF conversion
through magnetron at the transmitter side. After propagated through the air, the microwaves
captured by the receiver rectenna are rectified into electricity again. The typical frequency of
9
microwaves ranges from 300MHz to 300GHz. The energy transfer can use other
electromagnetic waves such as infrared and X-rays. However, due to safety issue, they are not
widely used. The microwave energy can be radiated isotropically or towards some direction
through beam forming.
Table 1 Wireless charging techniques.
Wireless
charging
technique
Inductive
coupling
Magnetic
resonance
coupling
Microwave
radiation
10
Advantage
Safe for human,
simple
implementation
Disadvantage
Short charging
distance, heating
effect, Not
suitable for
mobile
applications,
needs tight
alignment
between chargers
and charging
devices
Not suitable for
mobile
applications,
Limited charging
distance, Complex
implementation
Effective
charging distance
From a few
millimeters to a
few centimeters
Loose alignment
From a few
between chargers
centimeters to a
and charging
few meters
devices, charging
multiple devices
simultaneously on
different power,
High charging
efficiency,
Nonline-of-sight
charging
Long effective
Not safe when
Typically within
charging distance, the RF density
several tens of
Suitable for
exposure is high,
meters, up to
mobile
Low charging
several kilometers
applications
efficiency, Lineof-sight charging
Applications
Mobile
electronics (e.g.,
smart phones and
tablets),
toothbrush, RFID
tags, contactless
smart cards
Mobile
electronics,
home appliances
(e.g., TV and
desktop), electric
vehicle charging
RFID cards,
wireless sensors,
implanted body
devices, LEDs
Chapter 2: Constraints, Standards/ Codes and Earlier course work
Constraints
Our major constraint was the size the coils compared with the size of smart phones which is the
target for charging, the receiving coil could not be larger than the size of the Phone, so it must
be made combatable to the phone size. The coil size was the main cause of the efficiency
losses and this point will be solved in the future by using on-chip inductors like spiral inductor.
Wireless power transfer concepts forced us to use AC with high frequency, working with AC
made the project more difficult by introducing main component to the circuit which is
oscillator. The second one is the possibility of obtaining sufficient amount of the voltage when
we keep in mind that the phone is the receiver side , so the output voltage must be greater than
5V, the third challenge is the parasitic resistance which comes from inductors (coils) we can
face it by using parallel capacitor to eliminate the real part and achieve the resonant frequency
which is a round 1MHz , and the last challenge is the efficiency that will get it at the receiver
side we got about 25% efficiency compare to the input voltage and it decreases with distance ,
we used a voltage multiplier to rise the amount of efficiency .
11
Chapter 3: Literature Review
Faraday's law
Faraday's law of induction makes use of the magnetic flux ΦB through a hypothetical surface Σ
whose boundary is a wire loop. Since the wire loop may be moving, we write Σ(t) for the
surface. The magnetic flux is defined by a surface integral:
Where dA is an element of surface area of the moving surface Σ(t), B is the magnetic field (also
called "magnetic flux density"), and B·dA is a vector dot product (the infinitesimal amount of
magnetic flux through the infinitesimal area element dA). In more visual terms, the magnetic
flux through the wire loop is proportional to the number of magnetic flux lines that pass through
the loop.
When the flux changes—because B changes, or because the wire loop is moved or deformed, or
both—Faraday's law of induction says that the wire loop acquires an EMF, , defined as the
energy available from a unit charge that has travelled once around the wire loop.Equivalently, it
is the voltage that would be measured by cutting the wire to create an open circuit, and
attaching voltmeter to the leads. Faraday's law states that the EMF is also given by the rate of
change of the magnetic flux:
,
Where is the electromotive force (EMF) and ΦB is the magnetic flux. The direction of the
electromotive force is given by Lenz's law.
For a tightly wound coil of wire, composed of N identical turns, each with the same ΦB
Faraday's law of induction states that
Where N is the number of turns of wire and ΦB is the magnetic flux through
a single loop.
voltage multiplier
How does voltage multiplier work?
The circuit shows a half wave voltage doubler. During the negative half cycle of the sinusoidal
input waveform, diode D1 is forward biased and conducts charging up the pump
12
capacitor, C1 to the peak value of the input voltage, (Vp). Because there is no path for
capacitor C1to discharge into, it remains fully charged and acts as a storage device in series
with the voltage supply. At the same time, diode D2 conducts via D1 charging up
capacitor, C2[10].
During the positive half cycle, diode D1 is reverse biased blocking the discharging of C1 while
diodeD2 is forward biased charging up capacitor C2. But because there is a voltage across
capacitor C1already equal to the peak input voltage, capacitor C2 charges to twice the peak
voltage value of the input signal.
In other words, V(positive peak) + V(negative peak) as on the negative halfcycle, D1 charges C1 toVp and on the positive half-cycle D2 adds the AC peak voltage
to Vp onC1 and transfers it all to C2. The voltage across capacitor, C2 discharges through the
load ready for the next half cycle.
Then the voltage across capacitor, C2 can be calculated as: Vout = 2Vp, (minus of course the
voltage drops across the diodes used) where Vp is the peak value of the input voltage. Note that
this double output voltage is not instantaneous but increases slowly on each input cycle,
eventually settling to 2Vp.
As capacitor C2 only charges up during one half cycle of the input waveform, the resulting
output voltage discharged into the load has a ripple frequency equal to the supply frequency,
hence the name half wave voltage doubler. The disadvantage of this is that it can be difficult to
smooth out this large ripple frequency in much the same way as for a half wave rectifier circuit.
Also, capacitorC2 must have a DC voltage rating at least twice the value of the peak input
voltage. [10]
The advantage of “Voltage Multiplier Circuits” is that it allows higher voltages to be created
from a low voltage power source without a need for an expensive high voltage transformer as
the voltage doubler circuit makes it possible to use a transformer with a lower step up ratio than
would be need if an ordinary full wave supply were used. However, while voltage multipliers
can boost the voltage, they can only supply low currents to a high-resistance (+100kΩ) load
because the generated output voltage quickly drops-off as load current increases.
By reversing the direction of the diodes and capacitors in the circuit we can also reverse the
direction of the output voltage creating a negative voltage output. Also, if we connected the
output of one multiplying circuit onto the input of another (cascading), we can continue to
increase the DC output voltage in integer steps to produce voltage triplers, or voltage
quadruplers circuits, etc[10].
13
Voltage Quadrupler
Circuit Diagram
Figure 2 Voltage quadrupler circuit diagram.
Parts list








D1 - Rectifier Diode
D2 - Rectifier Diode
D3 - Rectifier Diode
D4 - Rectifier Diode
C1 - Capacitor, electrolytic
C2 - Capacitor, electrolytic
C3 - Capacitor, electrolytic
C4 - Capacitor, electrolytic
How a Voltage Quadrupler Works
If you have seen the Voltage Doubler, Two-Diode Circuit and the Voltage Tripler
Circuit featured in this site, you can easily recognize that the Voltage Quadrupler Circuit above
is a mere extension of the said two circuits. You will observe that you can infinitely multiply
the input voltage by following the pattern of repeatedly adding a series-connected rectifiercapacitor combination. It's up to you to experiment on adding more diodes and capacitor to
achieve the desired output voltage. [5]
The above voltage quadrupler circuit uses minimum components to approximately multiply
(quadrupler) the AC voltage (Vin) across the input terminals. The resulting output voltage is
DC (Direct Current). Capacitors, C2 and C3, charges to double the value of Vin. The series
combination of C2 and C3 produces a DC voltage equivalent to two batteries connected in
series. The result is an output DC voltage that is four times the value of Vin. The voltage rating
of the diodes and capacitors used should be within safe level, preferably, double the value of the
input voltage. You may use capacitance values of 1000mF or higher. The higher the value of
the capacitance, the smoother (non-fluctuating) the resulting output DC voltage.[5]
14
Chapter 4: Methodology
The design of the project is to take the energy from a power source and allow it to be
transferred wirelessly. The receiving AC will then be converted to DC for charging. The main
part that the design needed is the capability to transfer the power wirelessly.
Figure 3 Block Diagram of the System.
In the first phase of the project by the addressee, the source would be 220 volts and 50 hertz,
the first step is to turn it into a constant voltage using the following steps.
A-
Transformer:
Figure 4 Transformer principle of working
15
As described in the previous figure, the first block which is the presence of transformer we need
a step down transformer because the output voltages smaller than the input voltage. If the
secondary coil has half as many turns of wire then the output voltage will be half the input
voltage. Decreasing the voltage does not decrease the power. As the voltage goes down,
the current goes up [12].
B-
Rectifier and smoothing capacitor
Figure 5 Rectifier and smoothing capacitor.
A full-wave rectifier converts the whole of the input waveform to one of constant polarity
(positive or negative) at its output. Full-wave rectification converts both polarities of the input
waveform to pulsating DC (direct current), and yields a higher average output voltage. Then we
use a smoothing capacitor to reduce the ripple and convert it to constant as much as possible
[13].
COscillator
DTransmitting coil and Receiving coil:
Figure 6 Tx coil and Rx coil.
Transmitting and receiving coils is considered the heart of the project, but how the power
transfer from, to each secret in the Faraday's law.
16
E-Voltage Multiplier
Based on the amount of efficiency in such circuits, and based on the measurements that we
have had in the lab, we found that the amount of the final voltage that we get is 4.2 dc volts
and is inadequate to charge Mobile or other devices such as the Lap Tops. Based on the
research we got the following solutions:
1) Joule thief: it has some disadvantages which areunstable and the amount of gain
voltage was small compared with the second point.
2) DC Voltage Doubler Circuit: which we have adopted in the receiver circuit.
Figure 7 joule thief circuit diagram.
Figure 8 Voltage doubler circuit diagram.
F-Rectifier :( as in transmitter)
G-Regulator:
Figure 9 Regulator circuit.
17
A voltage regulator is a device that maintains a relatively constant output voltage even though
its input voltage may be highly variable. There are a variety of specific types of voltage
regulators based on the particular method they use to control the voltage in a circuit. In general,
a voltage regulator functions by comparing its output voltage to a fixed reference and
minimizing this difference with a negative feedback loop.
H-Output (phone)
18
Chapter 5: Results and Analysis
In lab, the coils did not test as well as expected. It was especially noticeable when pairing the
transmitting coils with the receiving coils, where the efficiency dipped greatly. Even the highest
efficiency obtained was less than the standard 70%, obtaining only up to 50%. Although the
insulated wrapping wire provided good results, and had potential to give good quality factors,
the material felt too fragile and thin. It doesn’t seem to be smart to use it, especially in higher
power situations. Either way, the copper hook up wire provided better results under the same
conditions. The tinned copper bus wire also had slightly better L and R values than the hookup
wire, but didn’t seem to work to transfer wireless energy. The four-coil system also did not live
up to its name, testing worse than the hookup wire coils. This could have also been caused by
the material, since the similar configurations of magnet wire coils also tested worse than the
hook up wire coils.
During the testing process, we experience many coils, and took readings and found that the best
pair of them was the coil number (1) as a transmitter and the coil number (2) as a receiver
which we considered it as a final decision.
Table 2 Coils used in the experiments.
Coils
19
Radius (cm)
Number of turns
Thickness (mm)
6.5
2
1
6
10
0.5
3.8
8
0.3
4.5
5
0.8
Chapter 6: Discussion
At the beginning, We have used the template coil of copper as shown in the fig(10), but the
voltage obtained were very low, so we connect the voltage multiplier with it but the voltage we
got still low as shown in fig(11) and the results obtained in the first experiments were better so
we do not use it.
Figure 10 Tx and Rx coils of template copper during the test stage.
20
Figure 11 The output at Rx coil of template copper.
After that, we've connected transmitting coil directly with the function generator and we have
connected the receiver coil with a capacitor and with led, but we have about 15v input voltage
for the led to be Light and we get 1.3v. Therefore, we used Joule thief to amplify the received
voltage and got 5v, but the voltage that we got stayed small (low value of amplification) and
unstable, so we've removed the Joule Thief and we amendment on the circuit and increase the
input voltage to 22 volts, so we got a 17.8-volt peak to peak at the receiving coil, as shown in
figure (12), but the voltage after the rectifier was very small.
21
Figure 12 The output at Rx coil with 22v input voltage.
So we use voltage multiplier between them, the first experiment was the voltage doubler, the
output before the rectifier was 2.02 volt, as shown in the figure(13)
Figure 13 The output after the doubler.
Which is not enough for charging the mobile phone. So, we moved to the second experiment
which is the voltage quadrupler, we got 7.21 volt, as shown in the figure(14), which is a good
value to be rectified and stayed above 5 volts in order to have a constant 5 volts DC after the
regulator.
22
Figure 14 The output after the quadrubler.
Then we connect the regulator, which fixed the voltage at 5volt, and we reached the goal that
needed, which is charging mobile buttery, as shown in figure(15).
Figure 15 Mobile phone while charging.
When we made sure that the phone is charging, we fixed the receiving circuit and moved to
transmitter circuit and amended it. We used the transformer to convert the voltage coming from
the source which is 220 volts, 60 Hz to 30 volts DC and we have entered this voltage into
23
oscillator to get AC current with high frequency about 1 MHz, and we connect the oscillator
with the coil, but the oscillator circuit did not work well so we have to replace it with more than
one oscillator circuit,we started with the oscillator shown in figure(16), but we were not able to
get a circuit with good output, so we leave it to second graduation project.
Figure 16 First testing oscillator.
Finally, we adopted the final receiver side circuit , which our project was based on it, and it has
been implemented using proteus shown in figure (17).
Figure 17 ) Receiver side circuit.
24
Chapter 7: Conclusions and Recommendation
From the experiments performed on the transfer of power wirelessly we were able to charge the
phone without the use of wires, where we were able to charge the phone at a distance of 10 cm
using the following specifications:
Coils:
Inductor is the primary key for whole system which is will generate a magnetic field that will
generate a voltage on the receiver inductor. We've found that the only positive outcome of using
a larger transmitting coils is to get a greater distance, but with the preservation of a small value
for parasitic resistance, we should have a transmitter inductor and receiver inductor that
communicate well together, as well as the distance between each two laps must be appropriate
to maintain the good efficiency of the system.
Frequency:
To get the best value for the frequency the magnetic resonance must be satisfy, which means
that inductor and capacitor power must be equal and thus were sending energy together and at
the same strength, leading to the delivery of energy to longer distances, and the values of L and
C at the sender must be equal to the values of L and C at the receiver, to receive the same
frequency and greater value of energy [4]. When the value of the frequency increase the value
of the receiving energy will increase, we found that the best frequency to receive the energy
required is 1MHz.
25
Chapter 8:Impacts and Engineering solution.
Economic
The original estimated cost of component parts was 25$, which was actually higher than the
actual final cost of the parts which was 15$. This was mostly due to the fact that some of the
materials, that were originally planned to be used, were not needed. Some additional
equipment costs were needed for wireless power transfer coil testing, which helped find the
best coil material.
Commercial Prospects
If a wireless power transfer mobile charger was manufactured on a commercial basis, the
expected number of devices sold per year would be high units since it is a luxury item. The
estimated manufacturing cost for each device would be about 9$, and could sell for 15$ per
device.
Manufacturability
The manufacturing of wireless coils should be a relatively easy process, aswell as soldering the
wires of the circuits together. The whole process can be doneeither manually or mechanically.
Most of the rest of the process of putting the systemwhere it is needed is done by the user [11].
Sustainability
Since a completed device only serves to charge a phone, there are very few issues to worry
about when maintaining it. The only concerns come from errors in the circuit that can be
remedied by an electronic devices repair shop. The sustainability of this system is lower, since
this is a system for charging, which depends on efficiency for sustainability. The efficiency of
this system is sacrificed for practicality, and so it is not as sustainable as a 100% efficient
charging system. Any upgrades in the efficiency of the coils or inverters/converters will
improve the sustainability of the project. The only problems with upgrading the design are the
limits of the technology [11].
Ethical
This system does not interfere with any ethics since the project will behave in safe and
professional manner. The ethics of “stealing” the idea of wireless power transferis fine, since
people are allowed to use basic ideas to carry out their project [3].
26
Health and Safety
Using magnetic fields to transfer power wirelessly is safe to most people, as magnetic fields
have no known interference to the normal human body. MRI (Magnetic resonance imaging)
machines use32, 32much stronger magnetic fields on people with no problems. The magnetic
field that the coils create pales in comparison to a MRI scan. People with other materials inside
them, such as pacemakers, on the other hand may have a problem though, so there would be
some sort of safety check to go through before you buy this product so nobody is harmed.
Social and Political
This would have an excellent social impact on our world. The use of this system in our life will
get people questioning what it is, and more people will learn more about wireless power and
how practical it is. There aren't that many political viewpoints about this system, since wireless
power transfer is a relatively new technology on the market.
Development
While creating the project, the amount of knowledge on the internet greatly helped with
learning new technologies. Coupled with the basic knowledgeof circuits, it was only a matter of
combining various technologies to create a final concept [12].
27
Future
In this report we have been able to charge the mobile phone in a wireless method from an
electrical source, where any a charger can charge any mobile phone. If anyone wants to add
any improvements to our project, we advise him to improve the efficiency and try to reach
farther distance from which we have obtained. In the second graduation project we will work
to charge the mobile phone from another mobile phone, then we will get rid of the problem
that faced a lot of people, which is the empty of battery when the charger does not exist.
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References (Refer to Appendix B: guideline)
[1] URL: “http://electronics.stackexchange.com/questions/64297/how-is-current-lowered-asvoltage-is-increased-in-ac-power-transmission”, accessed onJan 10, 2015.
[2] URL: “http://www.wirelesspowerconsortium.com” .
[3] URL:
“ http://www.fcc.gov/document/information-needs-communities”. [Accessed:
April3, 2015]
[4]URL:”http://www.mpoweruk.com/history.htm”.
[5]URL:”http://www.electronic-circuits-for-hobbyists.com/voltage-quadrupler-circuit.php”.
[6] A. Kurs, A. Karalis, R. Moffatt, J. D. Joannopoulos, P. Fisher, and M. Soljacic, “Wireless
power transfer via strongly coupled magneticresonances,” Science, vol. 317, no. 5834,
pp. 83-86, June 2007.
[7] A. Kurs, R. Moffatt, and M. Soljacic, “Simultaneous mid-range power transfer to multiple
devices,” Appl. Phys. Lett., vol. 96, pp.044102-1 - 044102-3, January 2010.
[8] X. Lu, P. Wang, D. Niyato, and Z. Han, ”Resource allocation in wireless networks with
RF energy harvesting and transfer,” to appearin IEEE Network.
[9] Wireless Power Consortium, Creating the Standard for Wireless Charging,
Wireless Power Consortium, March 15, 2011. [Online]. Available:
http://www.wirelesspowerconsortium.com.[Accessed: march20, 2015]
[10]URL:” http://classroom.synonym.com/voltage-regulator-theory-operation-2451.html”.
[11]URL:”http://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1136&context=eesp
”
[12]URL:”http://electrical4u.com/what-is-transformer-definition-working-principle-of-transformer/”.
[13]URL:”http://www.electronics-tutorials.ws/diode/diode_6.html”.
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Appendices
Appendix A
Equations

DC Power:𝑷 = 𝑽 × 𝑰

AC Power:𝑷𝒂𝒗𝒈 = 𝑽𝒓𝒎𝒔 × 𝑰𝒓𝒎𝒔

𝑽𝒑𝒑
⁄ 𝟐
𝟐 √𝟐
𝑷𝒐𝒖𝒕
Power Efficiency:
⁄𝑷𝒊𝒏 × 𝟏𝟎𝟎%
Frequency:𝟏⁄
𝟐
𝟐𝝅 × √𝑳𝑪
𝑽𝒓𝒎𝒔 =


Capacitance:𝟏⁄ 𝟐 𝟐
𝟒𝝅 𝒇 𝑳

ElectroMotive Force (EMF)

Magnetic Flux
30