DEVELOPMENT OF POWER SUPPLY FOR WIRELESS
VIDEO CAPSULE ENDOSCOPY
A Thesis Submitted to the
Department of Electrical and Electronic Engineering
In partial fulfillment of the requirements for the degree of
Bachelor of Science in
Electrical and Electronic Engineering
Of
Bangladesh Army International University of Science and Technology
By
Adwaita Chandra Paul
1201018
Mosiur Rahman Sabbir
1201015
Wasiful Rahman Pavel
1201020
Fahmid Hasan
1201006
Supervised by
Dr. Umma Hany
Associate professor and
Head of the dept. of
Electrical and Electronic Engineering, BAIUST
DECLARATION
We hereby declare that the thesis titled “Wireless Power Transfer of Video Capsule Endoscopy”, a
thesis submitted to the Department of Electrical and Electronic Engineering of Bangladesh Army
International University of Science and Technology in partial fulfillment of the requirements for the
degree of Bachelor of Science in Electrical and Electronics Engineering. The work has not been
presented elsewhere for assessment. The material that are used from other sources it has been
properly acknowledged/referred .
Signature of Students
Adwaita Chandra Paul
ID: 1201018
Fahmid Hasan
ID: 1201006
Mosiur Rahman Sabbir
ID: 1201015
Wasiful Rahman
ID: 1201020
Signature of Supervisor
Dr. Umma Hany
Head of the Dept., Electrical and Electronics Engineering,
BAIUST
ACKNOWLEDGEMENT
First of all, we would like to thank all the people who contributed in some way to the work
described in this thesis. First and foremost, we thank our academic advisor, Dr. Umma Hany, (Head
of the dept. EEE) for accepting us into her group. During our tenure, she contributed to a rewarding
graduate school experience by giving us intellectual freedom in our work, supporting our attendance
at various conferences, engaging us in new ideas, and demanding a high quality of work in all our
endeavors. Additionally, we would like to thank our group mates and collaborators. Every result
described in this thesis was accomplished with the help and support of fellow group mates and
collaborators. We worked together on different phases of the self-assembled lab projects, and
without their efforts this job would have undoubtedly been more difficult. We greatly benefited from
the keen scientific insight, knack, of them, for solving seemingly intractable practical difficulties,
and ability of them to put complex ideas into simple terms. We were fortunate to have the chance to
work with Dr. Umma Hany personally, who patiently taught her student her method for synthesizing
wireless power transfer, in addition to a number of other laboratory techniques, and who worked
closely in the synthesis of different sections that are present in this thesis. She was an extremely
reliable four long weeks in march 2019. We would like to thank the various members of our
university lab assistant with whom we had the opportunity to work and have not already mentioned.
Mr. Aziz, Mr. Sazzad, Mr. Jamal, they provided a friendly and cooperative atmosphere at work and
also useful feedback and insightful comments on my work. We would be remiss if we did not thank
Dr. Sharif Hossain, respected faculty member who deserves credit for providing much needed
assistance with administrative tasks, reminding us of impending deadlines and keeping our work
running smoothly. Additionally, Mr. Shahed provided immediate support for any technical problems
we encountered. Our graduate experience benefitted greatly from the courses we took, the
opportunities we had under Mr. Rakib Hassan, respected faculty and, asst. professor Monjurul
Ahsan respected faculty to serve as a mentor, and the high-quality seminars that the department
organized. Finally, we would like to acknowledge friends and family who supported us during our
time here. First and foremost, we would like to thank mom, dad for their constant love and support.
We are lucky to have met asst. professor Shah Md. Salimullah here, and we thank him for his
mentorship, love, and unyielding support. We owe a debt of gratitude to all the members of the
BAIUST EEE Club of which we were a member for over four years.
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ABSTRACT
Wireless video capsule endoscopy is a procedure used to record internal images of the
gastrointestinal tract for the use of medical diagnosis. The capsule is similar in shape to a standard
pharmaceutical capsule, although a little larger and contains a tiny camera and an array of LED's
powered by a battery. While the capsule provides the best means of observing the inside of the small
intestine, there are many inherent limitations. The key limitation is covered up by the battery. At
times, the capsule transit is so slow that the capsule examines only part of the small intestine before
the battery fails. In maximum cases the lifetime of the battery fails down before the completion of
whole diagnosis process. Hence the entire system can’t able to come up with proper result .so in this
case, we have to keep in mind that the battery does not soon come to an end while the entire process
is going on. The best way to increase the life time of the battery is to supply power externally. Here
we are designing a wireless power transfer system which will be able to transfer the power from
outside to the system inside. Firstly, we came upon an idea to use the body heat temperature for the
input supply. Hence, there is used a TEG (thermoelectric generator) to convert the body temperature
into electric energy. With the result, approximately 0.7 to 1.2 voltage can be found in the output of
TEG using above 25-degree temperature difference. Then boosting this output voltage, we have got
nearly 4.7 volts with the help of a Boost converter. Based on the fundamental principle of Ampere’s
law and Faraday’s law, the wireless power transfer system has been developed here with the
outcome of magnetic coupling resonance here. Mainly the transferred voltage will charge the battery
up and therefore, whole procedure of the video capsule endoscopy may come up with the proper
result. Assiduously the problem with the excellent method would be come to an end.
4|Page
LIST OF CONTENTS
ACKNOWLEDGEMENT .......................................................................................................... 3
ABSTRACT ................................................................................................................................ 4
LIST OF CONTENTS ................................................................................................................ 5
LIST OF FIGURES ..................................................................................................................... 8
ACRONYMS .............................................................................................................................. 9
CHAPTER 1.............................................................................................................................. 10
Introduction ............................................................................................................................... 10
1.1 Introduction ......................................................................................................................... 10
1.2 Challenges ........................................................................................................................... 10
1.3 Background ......................................................................................................................... 11
1.4 Motivation ........................................................................................................................... 15
1.5 Objective ............................................................................................................................. 17
1.6 Outcome .............................................................................................................................. 17
1.7 Organization of thesis.......................................................................................................... 18
CHAPTER 2.............................................................................................................................. 19
SYSTEM AND DEVELOPMENT ........................................................................................... 19
2.1 Video capsule endoscopy .................................................................................................... 19
2.2 Design and development of the system ............................................................................... 20
2.3 Thermoelectric Generator (TEG) ........................................................................................ 21
2.5 Advantages of WPT ............................................................................................................ 24
2.6 Block diagram of a wireless power system ......................................................................... 26
2.7 Coupling coefficient ............................................................................................................ 26
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2.8 Fundamental Principle of Magnetic Coupling Resonance Wireless Energy Transference 27
2.9 Circuit Model and Equivalent Circuit Diagram ..................................................................
27
2.10 Mutual Inductance between Coils ...................................... Error! Bookmark not defined.
2.11 Mutual Induction ................................................................ Error! Bookmark not defined.
2.12 Coupling Coefficient .........................................................................................................
30
2.13 Coupling Factor between Coils .........................................................................................
31
CHAPTER 3 ..............................................................................................................................
33
Theoretical Analysis and Derivation .........................................................................................
33
3.1 Diagram of boost converter .................................................. Error! Bookmark not defined.
3.2 Required appratus ................................................................................................................
23
3.4 Voltage and Current’s relationship .....................................................................................
34
3.5 The basic principle of a Boost Converter development ....... Error! Bookmark not defined.
3.6 Boost Converter Operating in Continuous Mode ................................................................
37
3.7 Boost Converter in Discontinuous mode ............................................................................
38
3.8 Wireless Power Transfer .....................................................................................................
39
3.9 Circuit diagram ....................................................................................................................
24
3.10 Required apparatus ............................................................................................................
24
3.11 Process of WPT .................................................................................................................
41
3.12 Rectifier .............................................................................. Error! Bookmark not defined.
3.13 circuit diagram of bridge rectifier .....................................................................................
43
3.14 Required Apparatus ...........................................................................................................
32
3.15 Working method of a bridge rectifier ................................................................................
43
3.16 The Smoothing Capacitor .................................................. Error! Bookmark not defined.
CHAPTER 4 ............................................................................................................................. 48
Simulation and Result analysis ................................................................................................. 48
6|Page
4.1 Simulation analysis ............................................................................................................. 48
4.2 Result................................................................................................................................... 51
CHAPTER 5.............................................................................................................................. 52
Summary ................................................................................................................................... 52
Conclusion................................................................................................................................. 52
Future work ............................................................................................................................... 52
References .................................................................................................................................... 53
7|Page
LIST OF FIGURES
Fig1 Capsule endoscope ………………………………………………………………………… ..... 15
Fig 2.1Video capsule Endoscopy ………………………………………………………………… .. 18
Fig2.2Block diagram of entire system………………...……... ...............................................................20
Fig 2.3 Thermo Electric Generator on human …………… ...................................................................... 23
Fig 2.4 Block diagram of an wireless power system……………………… ................................… ...... 24
Fig 2.5 Magnetic coupling between two coils…………………………………………………… ...... 28
Fig 2.6 Mutual induction …………………………………………………………….… .................... 29
Fig 3.1 Boost converter………………………………………………………... .................................... 30
Fig 3.2The two currents path of a boost converter……………………………………………… ...... 34
Fig 3.3 Waveforms of current and voltage in a boost………………………………………………..35
Fig 3.4 Waveforms of current and voltage in a boost converter ………….... ....................................... 37
Fig 3.5 Wireless power transfer design …………………………………….... ..................................... 38
Fig 3.6 Pin diagram of NE 555 timer IC……………………………………... ..................................... 39
Fig 3.7 Wireless power transfer system…………………………………………………...……… .. 42
Fig 3.8 Wireless power transfer system with T equivalent circuit……………………...……….… .. 43
Fig 3.9 Bridge rectifier………………………………………………………………………….... ….44
Fig 3.10 Input sine wave……………………………………………………………………………..45
Fig 3.11 Pulsating DC output………………………………………………….................................... 46
Fig 3.12 Average DC voltage for a full wave rectifier……………………..………………………..47
Fig 3.13 Load voltage waveform for the full-wave rectifier with filter capacitor ................... 48
Fig 4.1 Breadboard design of the boost converter …………………………………………………..50
Fig 4.2 Multimeter output of the boost converter ……………………………………………....… . 50
Fig 4.3 Wireless power transfer breadboard design ………………………………………....………51
Fig 4.4 Distance vs output DC voltage graph ……………………………………………………….53
8|Page
ACRONYMS
WPT
Wireless Power Transfer
AC
Alternating Current
DC
Direct Current
RMS
Root Mean Square
LED
Light Emitting Diode
GI
Gastrointestinal tract
WCE
Wireless capsule endoscopy
PILLCAM
Pill and camera
WPT
Wireless power transfer
VCE
Video capsule endoscopy
TEG
Thermoelectric generator
CE
Capsule endoscopy
9|Page
CHAPTER 1
INTRODUCTION
1.1 Introduction
Capsule endoscopy is a method that uses a tiny wireless camera to take pictures of the digestive tract
of a patient. As a capsule travel through the digestive tract, the camera takes thousands of pictures
that are transmitted to a recorder of patient wearing on a belt around the waist. Video capsule
endoscopy is a powerful diagnostic tool that has proved especially useful in imaging the small
intestine. In video capsule endoscopy now a days the primary question lies in the short battery life
existing in it.
Capsule endoscopy commonly described to as “pill cam” – is a diagnostic process that enables the
gastroenterologist to ask three portions of our small intestine using a tiny camera the size of a large
vitamin pill. The video capsule is swallowed and as it travels through the body, images are sent to a
data recorder worn on a waist belt(capsuleEndoscopy)[1].
As the battery placed in video capsule endoscopy has a certain life time of 6 to 8 hours and while it
is done then the whole system became disable. The full digestion system requires approximately 12
hours to complete its action. So, in this case if there is any suitable sort of external source which will
provide sufficient amount of supply or provide power to the system then it can surpass the
complication of battery. Principally we are using the body temperature of 25 degree Celsius to 28
degree Celsius to generate approximately 1.2 volts using TEG. Then methodically it is given the
output to the dc to dc boost converter which will boost the input 1.2 voltage to a output of
approximately 4.7 volts which will be fed further to the system by wireless power transfer.
1.2 Challenges
To make this procedure video capsule endoscopy (VCE) more robust, it should make the battery
longer lasting than the previous time. That’s why to enhance the lifetime of the battery, have come
up with a new invention which is included with using the TEG where the body temperature
transformed into electrical energy. Further, it will be used to enhance the lifetime of the battery.
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In recent studies related with Thermo Electric Generator (TEG), is seen that in approximately 23-25degree temperature difference TEG is capable of converting into mostly 1.2V dc in the output.
According to our project the voltage will be boosted to nearly 5V. Eventually, by a wireless power
system, the 5V dc will be transferred in the battery to increase the lifetime of it.
1.3 Background
Video capsule endoscopy (VCE) is a powerful diagnostic tool that has proved especially useful in
imaging the small intestine. VCE technology offers greater magnification than traditional endoscopy
while also providing excellent resolution. It is a clinically useful tool for detecting occult bleeding
and superficial lesions that are not radio graphically observed. It may also provide functional
information as the capsule moves passively through the small intestine.
The development of endoscopy enabled direct visualization of the esophagus, stomach, proximal
small bowel, and colon. However, even with these technologic advances, certain limitations
remained in the noninvasive diagnosis of gastrointestinal (GI) tract pathology. Much of the small
bowel is not accessible with traditional endoscopy or even push endoscopy (which allows imaging
up to 80-120 cm beyond the ligament of Treitz) but can be visualized with capsule endoscopy.
Technical advances in many areas (optical design, light-emitting electrodes, and image sensors)
were essential to the development of VCE and the design was accomplished in 1997. In 1999, the
first volunteer studies were performed, and high-quality images from volunteers were published in
the literature shortly thereafter. In 2001, VCE was approved by the US Food and Drug
Administration (FDA) for use in patients in the United States and by 2003, capsule endoscopy had
already been used in more than 4000 patients(Capsule Endoscopy)[2].
Research is being done on magnetically guided capsule endoscopy (MGCE), which makes use of
extracorporeal magnetic fields to guide, orient, power, and operate the capsule and its mechanisms.
Video capsule endoscopy (VCE) is a powerful diagnostic instrument which has proved basically
useful in imaging the slender intestine. VCE technology payoffs greater magnification than
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conventional endoscopy while in addition providing excellent resolution. It is a clinically adjuvant
tool for track out occult bleeding and superficial lesions which are not radio graphically
accomplished, it may also transfer functional information since the capsule drifts passively through
the slender intestine.
After proclamation of the first wireless capsule endoscopy (WCE) method in 2000, produced the
very first commercial WCE product scheme M2A in Yoqneam, Israel. The capsule endoscope (CE),
of the system which is 11mm in diameter and 26mm in long, which is diminutive enough to be
swallowed for the patient. The CE is comprises of 7 main models as for example optical dome,
RF(radio frequency) transmitter, short-focus lens, CMOS (complementary metal oxide
semiconductor) image sensor, LED (light emission diode) lighting, MCU (micro control unit) and
Cell battery. Since the CE is devoured by patients, it will run throughout the exhaustive GI tract
along with the ingenuous peristalsis. During this approach, the optical dome can agitate the intestine
wall in the absence of air inflation. In the meanwhile, the micro CMOS image sensor
Imaging the GI tract and the RF model disseminates the images outwards of the patient’s body at
frame rate of 2 f/s (frames per second). The images are accepted by the receiving box outward and
demonstrated in PC workstation. Following the examination, the CE is vented out inherently. The
CE is energized by a cell battery that allows in excess of 6 hours of uninterrupted operating. The
initial human clinical trial was executed in 2001, and the FDA was granted to M2A in august 2001.
Such WCE proposes a convenient inspection with deficient preparation and instantaneous recovery.
It is a realistic surrogate to traditional wire transfer invasive endoscopy and metamorphosing the
techniques of supervision the GI tract. The appellation of M2A was modified to PillCam (means Pill
and Camera) later. In 2005, Imaging formulates into two diverse WCE systems: PillCam ESO
precisely for the esophagus and PillCam SB precisely for the small intestine. The two sorts of CEs
possess the identical architecture and the uniform working principle to M2A. PillCam SB owns
outline of 11 × 26mm and weights lower than 4 g, and its uninterrupted operational time is 7 ± 1
hours. PillCam ESO possess the corresponding dimensions to PillCam SB and is equipping with
miniature cameras one as well as the other ends. Within the five-minute ascertainment of fleeting
down the esophagus, PillCam ESO contains the proficiency of capturing 18 images each second,
and which also possess continuous functional time is 20 ± 5 minutes. PillCam SB and PillCam ESO
are supplanted now by the
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second generations, that integrate advanced optics and automated light controls as to provide most
optimum image attribute and illumination.
PillCam COLON is one more product of Imaging, that particularly look for visualization of the
colon mucosa and detecting polyps. While FDA repudiated PillCam Colon application at USA in
2008, Given Imaging flourished the second-generation PillCam COLON 2 and acquired a CE Mark
in 2009 and was available at commercial terms in Europe in 2010. PillCam COLON 2 is arrayed
with double image sensors to the both ends and produces an around 360◦ view of the colon. It
measures of 11 × 31 mm. The most prominent nature of PillCam Colon 2 is the bidirectional
Communication within the CE and the data recorder. Consequently, the image capture rate which
can be regulate in real time in between 4 f/s to 35 f/s to diminish colon tissue coverage and can keep
working nearly around 10 hours. Besides those Olympus Optical Company is one more prime
vendor of WCE. Olympus got their very first major patents in 1981 and revealed its WCE named
Endo-Capsule in Hamburg, Germany in 2005, that measures 11 × 26 mm. Unlike M2A, this CE is
prepared on six white LEDs with a supersensitive CCD (charge-coupled device) image Sensor, so it
is reported to produce high-resolution images also the working period in the GI tract be allowed to
be 8 hours. The advance capsule endoscope from Olympus was stated to have the Capability to
activate and deactivate itself, but such kind of capsule endoscope is not candidly available on the
market. With the initial launch of M2A numerous kinds of WCE were advanced and they all were
operated in the same principle. OMOM was manufactured by Chinese Chongqing Jingshan
Company and obtained its FDA in March 2005. The CE size is about 11 × 25.4mm possessing a
field of view of 140◦. The frame rate is 2 f/s and the highest operating time is 6 to 8 hours.
Nowadays, it’s been extensively used in Chinese hospital. Micro Cam was produced by Intro Medic
Company, in Korea, in april 2007. The CE size is 11 × 24mm having a field of view of 150◦.The
topmost frame rate can be 3 f/s, and the highest operating time reaches in excess of 11 hours. In
2001 RF System Lab proposed an optimum CE model of Norikas. In the proposed model Norika is
9 × 23mm of outline and is arrayed with CCD image sensor along with the frame rate of 30 f/s.
Which four illumination LEDs owns different light wavelengths that can produce simulative 3D
images. The focal point of the camera lens that can be regulated for obtaining more clear images.
The most noteworthy
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attribute of Norika is the in vivo drug delivery also sample extraction. To deal with the power
demand, Norika is energized wirelessly.
The development of endoscopy accredited unswerving visualization of the esophagus, stomach,
proximal small bowel, and colon. Nevertheless, even with these technologic headways, certain
constraints remained in the inviolable diagnosis of gastrointestinal tract (GI) pathology. Much of the
tiny bowel is untrodden with traditional or even push endoscopy (which enables imaging up to 80120 cm afar the ligament of Treitz) but can be envisaged with capsule endoscopy. Capsule
endoscopy is high-caliber to radiographic techniques in the unearthing of mucosal disease and
angiodysplasia. Investigators have bankrolled on the edge of this approach, unveiling an expanding
docket of clinical indications(SwallowableWireless Capsule Endoscopy)[3].
The abstraction of dispatching power without wires was inaugurated in the late 1890s.The name,
Nikola Tesla is mostly famed in case of wireless power relocation. Nikola Tesla flourishingly
illuminated electric bulbs wirelessly at his Colorado Springs Lab. In his experiment, he utilized
electrodynamics induction which is also acquainted as resonant inductive coupling. While he was
making his own experimentation in the lab, he innovated an electrical resonating transformer in the
year 1891.
Nikola Tesla was remained optimistic that his transformer would convey power unaccompanied by
the connection of wires. At the Pikes Peak, North America the weather was a bit tempestuous.
Lightning squall was day-to-day there. Tesla perceived the natural lightning and scrutinized how it
proceeded. He also appraised how the lightning navigated to the ground. He detected that just after
the lightning air persists charged for some moments. Then he examined with his transformer and
remarked how the charges were bounced back. He literally endowed an astonishing sequel even with
a miniature tesla coil. Notwithstanding he was not only doing trial with the miniature one, but also,
he assembled one of the vastest coils ever forged. The enthralling matter is the excretion from the
gigantic coil in Colorado Spring Lab could be glimpsed from a prolonged interspaced.
Later Nikola Tesla had initiated the idea of wireless power transfer, and test for connected
technology patent in 1902. Since then, multiple scientists have done experiment on it. Few of them
were efficient to acquire some feat in induction power transmission at near range. In our case, the
main aim of our thesis paper was to gain a good output and thus avail to the
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transmission of wireless power transfer. In order to placement pace with the ultra-modern
technologies, the idea of wireless power transfer is essential to be arrived to light which was
different cause behind select this concept.
In modern era, no one wants to use the wire or cable in case of charging any device and there comes
the essentiality of WPT. According to the IMF, Bangladesh's economy is the second quick thriving
major economy of 2016. With the first enhancement of economy, the value of breathing is receipt
higher day by day. In that case, the uses of good devices are getting very well-known now days. The
smart devices have different features but the transfer of the power into them wirelessly in one of the
presentable features in current times. People are numerous interested of using devices that does not
call for the connection with the help of wires or cords. It has been written above previously that, to
get rid of the boring wires, WPT is the perfect solution. This paper narrated about the performance
and design of wireless power transfer using Tesla coil technique. Recently in Bangladesh, there are
some producers who have invented electric motorcycles (also E-Cycles). There are easy bikes
(known as Electric Rickshaw) which usually exchange within a permanent area. These vehicles run
by rechargeable batteries. To recharge them, wires are needed to be connected from the wall socket
to the batteries. WPT can be a promoted recharging system in this regard(WIRELESS POWER
TRANSFER)[4].
1.4 Motivation
Video capsule endoscopy is largely applied to diagnose wound in the digestive track operating
painless endoscopic imaging of the overall small bowel. The video capsule endoscopy transmits
images of total gastrointestinal GI tract so as to perceive the abnormalities in the slender intestine by
dint of a wireless communication link among endoscopic capsule and a wireless device settled
outward of the body. The capsule moves through the digestive tract, camera captures thousands of
pictures those are transferred to a recorder that wear on a belt around the waist. To observe the inner
side of the tiny intestine capsule endoscopy favors the doctors an area where it is quite difficult to
reached by means of more-traditional endoscopy procedures. Traditional endoscopy provides
passing a long, flexible tube arranged along with a video camera down the throat or through the
rectum.
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Figure1 Capsule Endoscope
Capsule endoscopy (CE) is appointed with various parts, for example the ingestible video capsule,
the source of light (white LED), the camera (recording device), the antenna, the complementary
metal oxide semi-conductor, batteries that run for 8 h and a transmitter with an application-specific
integrated circuit. The measurement of the capsule applied for the slender intestine is nearly the size
of an extensive pill (26 × 11 mm), and about 3.4 g of weighs. The CE is providing 140° of viewing
field.
The purpose of applying a video capsule is to capture the largest possible number of images along
with the GI tract. For example, the capsule for the slender intestine can capture two images every
second that can produce nearly 55,000 images throughout the test. To imaging the small intestine
video capsule endoscopy is a robust diagnostic instrument. In the entire arrangement recently, the
primary question arises in the limited battery life. The battery possesses an absolute life time of 6 to
8 hours. As the battery is done comprehensively the overall system become in capacitive. In video
capsule endoscopic system as the final image taken by the capsule assist the doctor to detect when
the capsule reaches to the colon. Mostly the capsule transfers through the digestive system readily
and is expectedly to pass through the stool. Despite of that, if the doctor detects the capsule stacks in
the slender intestine yet to create any symptoms. Might wait more time for the capsules so as to
leave from the body. If it is not observed that the capsule pass within the stool, for making surety
doctor might demand for an abdominal X-ray that is gone of the body. If there is any symptom it is
commonly not needed. Bowel obstacle must be eliminated if the capsule creating signs and
symptoms, either by surgery or by dint of an endoscopy process,
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relying on the place capsule is stack. Such things are so, problematic nowadays to overcome that
difficulty the battery life lifetime must have to extend so that the capsule can get ample operation
time and cover the total intestine. Entire digestion system demands approximately 12hrs to fulfill its
operation. To recover some of those complication and limitation like short time battery life the
process is running on (WEIGHTED CENTROID BASED LOCALIZATION )[5].
1.5 Objective
•
To design and development 5v dc supply using body temperature.
•
To design wireless power supply.
•
To simulate the developed system and analyze the system.
1.6 Outcome
Small bowel capsule endoscopy is non-invasive means of measuring the small bowel mucosa for
many indications such as vague gastrointestinal bleeding small bowel crohn’s disease, celiac disease
and polyposis syndrome. While it offers excellent diagnostic utility comparing other imaging
modalities, a key limitation of the technology is the limited battery life which ranges from 4 to 12
hours rely on the system used. Capsule endoscopy is not complete exactly 16.5% of the cases,
defined as the failure of capsule access into the cecum subsequent to cessation of battery life, which
thus leaves a section of the distal small bowel unexamined. Fortunately with the progresses in
technology, newer generations of capsule endoscopy commit longer battery life without sacrificing
image quality. PillCam SB2U is a newer generation capsule endoscopy that commits 12 hour of
operating time comparing 8 hours of its predecessor, SB2. The expanded battery life is performed
while maintaining identical physical dimensions (26 mm*11 mm). It is conceivable that completion
rate would promote with longer capsule endoscopy operating time, but to date there has not been
any study that examined particularly the influence of battery life on capsule endoscopy completion
rate. With therefore investigated to established the clinical influence of longer battery life on capsule
endoscopy in terms of completion rate and rate of positive findings. At times, transit is so slow that
the capsule examines only part of the small intestine before the failure of the battery. The developed
power supply will enhance the life time of the wireless video capsule endoscopy which will help the
completion of diagnosis.
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1.7 Organization of thesis
This thesis is divided into four chapters. Following this introductory part is chapter 1, which
presents background information of wireless power transfer of video capsule endoscopy the. Chapter
2 describes the system and development of the circuit, also describe the block diagram of the
system, about wireless power transfer, coupling co efficient, mathematical analysis of mutual
induction, about boost converter, rectifier.
Chapter 3 describes the theoretical analysis of boost converter and diagram of boost converter,
required appratus, voltage and current’s relationship, boost converter operating in continuous mode,
boost converter in discontinuous mode, wireless power transfer, circuit diagram, required apparatus
process of WPT, rectifier circuit diagram of bridge rectifier, required apparatus, working method of
a bridge rectifier.
Chapter 4 describes the simulation and analysis of the crucial parts, result.
Chapter 5 includes the conclusion following by future work.
Eventually the references of the used articles are given.
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CHAPTER 2
SYSTEM DEVELOPMENT
This chapter is all about of entire system development.
2.1 Video capsule endoscopy
Capsule endoscopy is a technology that uses a swallowed video capsule to take photographs of the
inside of the esophagus, stomach, and small intestine. The capsule contains one or two video chips
(cameras), a light bulb, a battery, and a radio transmitter. As the capsule travels through the
esophagus, stomach, and small intestine, it takes photographs rapidly. The photographs are
transmitted by the radio transmitter to a small receiver that is worn on the waist of the patient who is
undergoing the capsule endoscopy. At the end of the procedure, approximately 8 hours later, the
photographs are downloaded from the receiver into a computer, and the images are reviewed by a
physician. The capsule is passed by the patient into the toilet and flushed away. There is no need to
retrieve the capsule.
Figure 2.1 Video capsule endoscopy
While the capsule provides the best means of viewing the inside of the small intestine, there are
many inherent limitations and problems with its use, the most important limitation lies in battery by
which the whole system runs at.
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The lifetime of the battery used in the video capsule endoscopy is 6 to 8 hours. Entire
gastrointestinal tracks need at least 12 hours. That's why the life time of the battery should be
increased. It is possible to increase the battery life in two ways.
•
One is by increasing the size of the battery, the capacity of the battery is increased resulting
in the enhancement of lifetime.
•
Another is transferring power wirelessly it is possible to recharge the battery which will help
to increase its lifetime.
At approximately 25-degree Celsius temperature difference, Thermoelectric Generator is able to
convert 0.7 to 1.2 volts.
2.2 Design and development of the system
1.2V
TEG
DC
Boost
converter
4.7V
4.9V
WPT
DC
AC
4.7V
LOAD
Rectifier
DC
Figure 2.2 Block diagram of entire system
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The circuit diagrams and required explanation of different blocks are described in below
2.2.1 Thermoelectric Generator (TEG)
Thermoelectric generators are the devices are able to convert temperature differences into electrical
energy, using a phenomenon which is called the "Seebeck effect". Their typical efficiencies are
approximately 8%. TEGs are the solid-state devices, and they have no moving parts. A
thermoelectric generator (TEG) may be used to harvest electrical power from human body heat with
the objective of powering wearable electronics. At the NSF Advanced Self-Powered Systems of
Integrated Sensors and Technologies (ASSIST), Thermo Electric Generators are one of the owning
technologies being researched to advance the center’s mission of generating wearable, self-powered,
health and environmental monitoring systems. As part of this effort, an exploration of the relevant
parameters for maximizing the wearable TEG power output from the body heat and maintaining the
body comfort is particularly important. For this purpose, the heat from the body must be directed
into TEG with minimal loss, the generator must be designed for maintaining a high temperature
differential across the thermoelectric material and the generator must have a small form factor to
maintain the body comfort. In order to address these requirements, an optimum TEG design was
developed and experiments were conducted both on a temperature-controlled hot plate and on
different body locations including the wrist, upper arm, and chest. The TEG was further fabricated
into a T-shirt and the power was recorded for different human activities. Comparison of the
experiments on various body locations and on the T-shirt yielded the highest to lowest power
generated on the upper arm, wrist, chest and T-shirt, respectively. The prospect of powering a
wearable electrocardiogram sensor by a TEG on the upper arm is discussed (Wearable
thermoelectric generators for human body heat harvesting)[6].
Thermoelectric energy conversion of human body heat illustrates a promising substitute as it
is hugely independent of external factors. Lossecet al. used a theoretic access to optimize the
thermal method of TEG worn on the human body. In the authors indicated on a wearable
medical system which is launched by body heat and finds if a patient falls down. Leonov et al.
presented a thermal harvester worn on the human wrist that may be used to launch a pulse
oximeter. The authors brought out that in more indoor scenarios, the average power
harvested per square centimeter is greater using the thermal harvester
21 | P a g e
comparing to a equally sized solar cell. Nevertheless, the generated voltage is used to
directly charge up a super capacitor as an energy buffer and the device is only operational if the
ambient temperature is lower than 25–27 C(Human body heat for powering wearable devices: From
thermal energy)[7].
Figure 2.3 Thermoelectric generator on human body
While the capsule provides the best means of viewing the inside of the small intestine, there are
many inherent limitations and problems with its use, the most important limitation lies in battery by
which the whole system runs at.
The lifetime of the battery used in the video capsule endoscopy is 6 to 8 hours. Entire
gastrointestinal tracks need at least 12 hours. That's why the life time of the battery should be
increased. It is possible to increase the battery life in two ways.
•
One is by increasing the size of the battery, the capacity of the battery is increased resulting
in the enhancement of lifetime.
•
Another is transferring power wirelessly it is possible to recharge the battery which will help
to increase its lifetime.
At approximately 25-degree Celsius temperature difference, thermoelectric generator is able to
convert 0.7 to 1.2 volts.
22 | P a g e
2.2.2 Boost converter
Diagram of boost converter
Figure 2.4 Boost converter
Required appratus
•
MAX 756 IC
•
Capacitor (150 microfarad)
•
Ceramic Capacitor (100 nF)
•
Capacitor (100 microfarad)
•
Inductor (22 micro-henry)
•
Resistor(470 ohm)
•
Zener diode
•
LED
The boost converter is used to "step-up" an input voltage to some higher level, required by a load.
This unique capability is achieved by storing energy in an inductor and releasing it to the load at a
higher voltage. Because of the ease with which boost converters can supply large over voltages, they
will almost constantly comprise a few regulations to control the output voltage and there are many
I.Cs. manufactured for this purpose. A typical example of an I.C. boost converter
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is designed for use in low power systems such as PDAs, cameras, mobile phones, and GPS devices.
We are using it for powering wireless video capsule endoscopy (Boost converter) [9].
In this section, we have used the boost converter with the purpose of boosting the output of
thermoelectric generator. In case of this, there is found nearly 4.9 volts in the output of boost
converter.
2.2.3 Wireless Power Transfer
Circuit diagram
Figure 2.5 Wireless Power Transfer design
Required apparatus
•
555 timer IC.
•
1.2k resistor.
•
10k resistor.
•
Capacitor (3300 pF).
•
Capacitor (10nF).
•
Transistor (BD 139).
•
Resistor 47ohms (1 watt).
•
Capacitor (100nF).
Here power transmission system is used for wireless video capsule endoscopy. The system will be
employed by using resonant coil to transmit power from a 5-volt DC supply to the output which is
resulted in the AC form. The major purpose is to achieve Wireless power transfer the
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overall objective of this intent is to design and successfully accomplish a wireless through resonant
inductive coupling within the transmitting and receiving coils in the nearby field. The advantages of
wireless power transfer are too many to be described. Some of them are mentioned below:
•
First of all, Wireless Power Transfer is a protected, certain, impermeable and durable
form of transmission of power. It assists us from using annoying wire connections.
•
It allows power transfer system to become bearable.
•
WPT really allows a network to attain locations that could not be acquired by using a
network cable. The worth of transmission and distribution becomes deficient
•
The failure of power because of short circuit and fault on cables will never stand in
the power transmission system and power theft will be impossible at all.
•
Wastage during transmission is at negligible level in the WPT. Therefore, the
efficiency of this system is very much higher than the wired transmission.
•
One of the major benefits is, wireless power allows a highly expandable power
range.
•
WPT increases the product life of a device.
•
Elimination of cords on the ground that make tripping hazards. Allows no wire
installation
•
A necessary step towards consumer wireless power
25 | P a g e
Block diagram of a wireless power transference system in VCE
DC
source
Primary
coil
Seconda
ry coil
Ac
source
Rectifi
er
Load
Dc
source
with
noise
Regulator
Figure 2.6 Block diagram of wireless power system
The output we got from the boost converter was 4.9 V dc and that is fed to the primary side of the
wireless power system. Here, in each side (primary and secondary) 300 turns copper solenoid is
applied. Resulting this, because of magnetic induction we get that identical voltage in ac form.
sequentially the output voltage is now rectified and supplied to the load through regulator.
The different terms related to wireless power transfer are discussed in details as below
2.2.3.1 Coupling coefficient
Wireless power transfer through magnetic resonance coupling procedure has opened a new
probability to the electric vehicle method. It assumes many kinds of the wireless charging
applications. Nevertheless, though the effectively of power transference is relatively high, the
efficiency only depends on displacement of coils. There have been a lot of research on procedures to
preserve power transmission at the highest efficiency. Nevertheless, in such methods, the
information on system parameter especially coupling coefficients is essential, and in the charging
applications, such information is unlikely to be available without communication methods. Hence, it
has been come to attention that parameter estimation is very crucial factor to be applied in a
charging lane system. Here it was presented with derivations of equations for
26 | P a g e
estimating coupling coefficients in several configurations of wireless power transfer system, using
information from only one side, either in the transmission side or in the receiving side, of the
system. An experimental system of the coupling coefficient estimation system is constructed for
estimation from the receiving side using a dc/dc converter (Coupling Coefficients Estimation of
Wireless Power Transfer System via Magnetic Resonance Coupling Using Information From Either
Side of the System)[8].
2.2.3.2 Fundamental Principle of Magnetic Coupling Resonance Wireless
Energy Transference
The technology of wireless energy transference founded on magnetic coupling and resonance takes
convenience of two electromagnetic systems with same appointed resonance frequency, which can
excite resonance created by electromagnetic coupling, to transfer energy in a particular distance.
Usually two electromagnetic systems in a certain distance is weakly coupled. However, if the two
system’s natural resonant frequency are equal, they are able to excite strong magnetic resonance. If
one of them provides energy for the system continuously at a same rate and the other side consumes
energy simultaneously, the energy transmission could be realized.
2.2.3.3 Mutual Inductance between Coils
Mutual inductance is the fundamental operating principal of the transformer, motors, generators and
any other electrical equipment that interacts with another magnetic field. Then we can identify
mutual induction as the current flowing in one coil that induces a voltage in an adjoining coil. The
quantity of mutual inductance that links one coil to another relies very much on the relative
positioning of the two coils. If one coil is positioned next to the other coil so that their physical
distance is small, then nearly all of the magnetic flux produced by the first coil will interact with the
coil turns of the second coil inducing relatively large voltage and therefore generating a large mutual
inductance value.
27 | P a g e
Figure 2.7 Magnetic coupling between two coils
The mutual inductance that lie between the two coils can be greatly raised by positioning them on a
common soft iron core or by enhancing the number of turns of either coil as would be found in a
transformer.
If the two coils are compactly wound one on top of the other over a common soft iron core unity
coupling is said to lie between them as any losses due to the leakage of flux will be extremely
inconsiderable. Then considering a perfect flux linkage between the two coils the mutual inductance
that lies between them can be given as.
M
=(μoμrN1N2A)
Where:
µo = Permeability of free space (4.π.10-7)
µr = Relative permeability of the soft iron core
N = Number of coils turns
A = Cross-sectional area in m2
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L = Coils length in meters
Figure 2.8 Mutual induction
Because of the current flow in coil one, L1 sets up a magnetic field surrounding it with some of these
magnetic field lines moving through coil two, L2 giving us mutual inductance. Coil one has
a
current of I1 and N1 turns where the coil two has N2 turns. Hence, the mutual inductance, M12 of
coil two that remains with respect to coil one relies on their position with respect to each other and is
given as:
M12 = N2ᴓ12
I1
similarly, the flux linking coil one, L1 when a current flow in coil two, L2 is exactly the same as the
flux linking coil two when the same current flows around coil one above, then the mutual inductance
of coil one with respect of coil two is defined as M21. This mutual inductance is true irrespective of
the size, number of turns, and relative position of the two coils. Because of this, the mutual
inductance between the two coils as: M12 = M21 = M.
Now we can observe that self-inductance characterizes an inductor as a single circuit element, where
mutual inductance shows some form of magnetic coupling between two inductors or coils, relying
on their distance and arrangement, we know that the self-inductance of each individual coil is given
as:
L1 =( μOμrN12A)
L2 =( μOμrN2²A)
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By cross-multiplying the two equations above, the mutual inductance, M that exists between the
two coils can be showed in terms of the self-inductance of each coil.
M²= L1L2
Now,
Mutual Inductance between Coils
M = H √L1L2
Still, according to the above equation, zero flux leakage and 100% magnetic coupling between the
two coils, L1 and L2. Practically there will always be some loss because of leakage and position, so
the magnetic coupling between the two coils can never reach or exceed 100%, but can become very
close to this value in some special inductive coils.
If some of the total magnetic flux links with the two coils, this quantity of flux linkage can be
defined as a fraction of the total possible flux linkage between the coils. This small part of value is
called the coefficient of coupling and is defined by k.
2.2.3.4 Coupling Coefficient
Generally, coupling is the interaction between two devices or circuits. The coupling between two
wires can be increased by winding them into coils and putting them close together on a common
axis, so the magnetic field of one coil move through the other coil. The mutual inductance of two
conductor is used to measure the amount of inductive coupling between them. The coupling between
two wires can be increased by winding them into coils and putting them close together over a
common axis, so the magnetic field of one coil move through the other coil. The two coils may be
physically contained a single unit, as in the primary and secondary windings of a transformer, or
may be divided. It can be intentional or unintentional. Unintentional inductive coupling can create
signals from one circuit to be induced into a neighboring circuit, this is called cross-talk, and is a
form of electromagnetic interference. The amount of inductive coupling that lies between the two
coils is exposed as a fractional number between 0 and 1 instead of a percentage (%) value, where
0indicates zero or no inductive coupling, and 1 indicating full or Highest inductive coupling.
30 | P a g e
Now, if k = 1 the two coils are fully coupled, if k > 0.5 the two coils are said to be tightly coupled
and if k < 0.5 the two coils are said to be randomly coupled. Now the equation which assumes a
perfect coupling can be modified into this coupling coefficient, k and is given as:
2.2.3.5 Coupling Factor between Coils
Here,
K=
M=
M
√L1L2
k
√L1L2
When the coupling coefficient, k is equal to 1, (unity) then all the lines of flux of one coil cuts all of
the turns of the second coil, then two coils are closely coupled together, the result of mutual
inductance will be equal to the geometric mean of two individual inductances of the coils.
Also when the inductances of the two coils are the equal, then L1 is equal to L2, the mutual
inductance that lies between the two coils that will equal the value of one single coil as the square
root of two equal values which is same as one single value as:
M=√L1L2=L
2.2.4 Rectifier
We are here using rectifier with the purpose of converting the AC into DC. Hence after wireless
transference the output we got that was AC.
31 | P a g e
circuit diagram of bridge rectifier
Figure 2.9 Bridge rectifier
Required Apparatus
•
4 Diode (1NI4004)
•
Capacitor (100 F)
•
Resistor (100 ohms)
•
Bread board
The working method of the bridge rectifier is discussed broadly in the theoretical analysis of it.
32 | P a g e
CHAPTER 3
THEORETICAL AND ANALYTICAL APPROACH OF DEVELOPMENT
This chapter include the theoretical and analytical approach of the system
3.1 Boost converter
Here in this part of the chapter we will discuss about the theoretical and analytical explanation
of the boost converter
3.1.1 Theoretical approach of boost converter
A boost converter, the output voltage is higher than the input voltage. The boost converter is a
highly efficient step-up dc/dc switching converter. A transistor switch is used in this converter.
The voltage is modulated by pulse width into an inductor. Rectangular pulses of voltage into an
inductor result in a triangular current waveform. Various equations will be derived for the
current and voltage for a boost converter. We can assume that the converter is in the continuous
mode, that means the inductor's current never goes to zero.
The basic definition and notation are included in below
Peak inductor current
ipk
Min inductor current
io
Ripple Current
∆i
Ripple Current Ratio to Average Current
R =
Off Duty Cycle
1-D =
Switch Off Time
Toff
=
Average and Load Current
Iavg
=
=
(ipk-io)
∆i /iavg
Toff / T
(1-D) / f
∆i / 2 = I load
33 | P a g e
Figure 3.1 Boost converter
Voltage and Current’s relationship
Voltage and current’s relationship of the inductive coupling:
I = (1L)∫01 V dt + i0
V = L dtdi
For a constant rectangular pulse:
I = VtL + io
From this, that current shows a linear ramp, when constant pulse is given by the voltage.
the value of current is (When the transistor switches on):
or
Ipk = (Vin – Vtrans)Ton
L+io
∆I = (Vin – Vtrans)Ton
L
the value of current is (When the transistor switches off):
or
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Io= ipk -(Vout – Vin + VD)Toff
∆I = (Vout – Vin + VD)Toff
VD = Voltage drop across the diode.
Vrms =Voltage drop across the transistor.
Noted that, when io is zero, the continuous/discontinuous boundary occurs.
By equating through delta i, we can solve for Vout:
(Vin – Vtrans)Ton= (Vout – Vin + VD)Toff
VinTon = VonToff -VinToff
Vin Ton + VonToff =VoutToff + VTrans Ton + VDToff
Vin -VTransD = ( Vout + VD) ( 1 – D)
Vout = {(Vin – VtransD)
(1–D)}−VD
We can also solve for the duty cycle as follows,
Vout – Vin + VD= Vout – Vin + VD
D=
(Vout – Vin + VD)
(Vout + VD – Vtrans)
The neglected voltage drops across the transistor and diode then:
Vout =
Vin
(1–D)
Now it’s clear that the output voltage is related presently to the duty cycle of the pulses.
35 | P a g e
3.1.2 Analytical approach of boost converter
Observing figure, no 3.1 we see
(a) When the switch is closed, current runs through the inductor in clockwise direction. The
inductor reserve energy by producing a magnetic field. The left side’s polarity of the inductor is
positive.
(b) Current will be decreased as the impedance is higher When the switch is opened. The magnetic
field prior created will be destroyed maintaining the current to the load. So, the polarity will be
turned over and two sources will be in series. For that a higher voltage should remain here to charge
the capacitor by the diode D.
If the switch is cycled in fast rate, it is not possible for the inductor to discharge fully in between
charging stages, and the load will always monitor a voltage greater than that of the input source by
itself when the switch is opened. Also, while the switch is opened, the capacitor arranged in parallel
with the load is charged to this combined voltage. When the switch is then closed and it shorted out
the right-hand side from the left-hand side, the capacitor is therefore able to supply the voltage and
energy to the load. By this time, the blocking diode restrain the capacitor from discharging by the
switch. The switch must be opened again fastly to restrain the capacitor from discharging too much
that consists of 2 distinct states
•
When the On-state, the switch S is closed, then the inductor current is increased.
•
When the Off-state, the switch is open and the only path of the inductor current is flowing
through the diode D and the capacitor C also the load R. This is the results for transferring
the energy which accumulated during the On-state into the capacitor.
•
Inductor current is the same as the input current as we can seen in the figure 3.1 So it's not a
discontinuous.
36 | P a g e
Boost Converter Operating in Continuous Mode
Figure 3.2 Waveforms of current and voltage in a boost converter.
Here
Vo = Output voltage
Vi= Input voltage
IL= Current through the inductor
When a boost converter runs in the continuous mode, the current flows through the inductor which
never falls to zero. In the Figure we show the typical waveforms of currents and voltages in a
converter operating in this mode. The output voltage can be measured as follows, in the case of an
ideal converter operating in the steady conditions.
By the On-state, the switch S is closed, which makes the input voltage occurs across the inductor,
which makes a change in current moving through the inductor during the time period.
Where
•
L is the inductor value.
•
D is the duty cycle.
37 | P a g e
It illustrates the fraction of the commutation period which is the time, T at which the switch is on.
Therefore, D ranges between 0 (S is never on) and 1 (S is always on).
When it is Off-state, the switch S is open and therefore the inductor current flows through the load.
If we consider 0 voltage drop in the diode, and a capacitor large enough for its voltage to remain
unchanged.
As we consider that the converter runs in steady-state conditions, the amount of energy stored in
each of its equipment has to be equal at the beginning and at the end of a commutation cycle.
So, the inductor current has to be equal at the beginning and end of the commutation cycle. This
means the overall differences in the current is zero.
the output voltage is always more than the input voltage (as the duty cycle goes from 0 to 1), and
that it increases with D, theoretically to α as D approaches 1. This is why this converter is
sometimes described to as a step-up converter. Rearranging the equation reveals the duty cycle to
be:
Boost Converter in Discontinuous mode
Figure 3.3 Waveforms of current and voltage in a boost converter operating in discontinuous mode.
If the ripple amplitude of the current is too much, the inductor can be completely discharged before
the end of a full commutation cycle. This commonly happens under light loads. In this
38 | P a g e
case, the current flow through the inductor falls to zero during part of the period. Though the change
is slight, it has a strong effect on the output voltage.
3.2 Wireless Power Transfer
Here it has been discussed about the theoretical and analytical approach of wireless power transfer
system
3.2.1 Theoretical approach wireless power transfer
Wireless power transfer is the process where electric energy is transmitted from power source to an
electrical load without any wire connection. Wireless power transfer is based on the magnetic
resonance and near field coupling of two loop resonators was reported by Nicola tesla a century ago.
Power is wirelessly transfer when magnetic field is transferred over short distance. The magnetic
field is created using inductive coupling between coils of wire or electric fields using capacitive
coupling between electrodes. The concept of inductive coupling and magnetic field comes from the
following principles.
Wireless power transfer is a generic term for a number of different technologies for transmitting
energy by means of electromagnetic fields. The technologies differing in the distance over which
they can transfer power efficiently, whether the transmitter must be aimed(directed)at the receiver,
and in the type of electromagnetic energy they use.
In this project, we have used 5V input in lieu of 3V input in the primary circuit and the output
generated in the secondary circuit is 5V ac.
Generating various types of output waveform in addition of an external RC circuit using a NE555P
timer IC. It is Very inexpensive, useful and popular device which may be used not only a simple
timer to generated a single pulse but also long-time delays, or as a relaxation oscillator generating
waveform of altering duty cycle from 50 - 100%. Mainly, 555 timers are immensely robust and
static 8-pin device that can be conducted either as a very perfect monostable, bistable or a stable
multivibrator to generate different kind of applications. The single 555 timer chip in its fundamental
form is a bipolar 8-pin mini bi-inline package comprising of few 25 transistors, 2
39 | P a g e
diodes and 16 resistors designed to form two comparators, a flip-flop and a high current output
stage.
Figure 3.4 Pin diagram of NE 555 timer IC.
●Pin 1 - Ground: The ground pin is connected with the 555-timer chip to the negative(0V) terminal
of the input supply.
● Pin 2 - Trigger: That’s the negative input connected to the comparator no.1 in which a negative
pulse the internal flip-flop while dropping the voltage below ⅓ Vcc making the output to switch
from a “LOW” to a “HIGH” state.
● Pin 3 - Output: The output is added to the output driver which is connected to that flip-flop and
the base of the NPN transistor and this pin is able to drive any TTL circuit which has the capability
to source up to 200mA of current at an output voltage that is same to Vcc - 1.5V approximately.
● Pin 4 -Reset: This is used here to “reset” the internal flip-flop to control the state of the output at
pin 3 hence it is connected to the flip-flop. It is an active-low input and is usually connected to
a logic “1” when it is not used to prevent any unwanted resetting of the output.
● Pin 5 - Control Voltage: This pin is used to control the timing of the 555 by over riding the ⅔
Vcc level of the voltage divider network. Using the voltage, the width of the output signal may be
changed independently of the RC timing network. When not used it is connected to ground via a 10
nF capacitor to can extract any noise.
40 | P a g e
● Pin 6 - Threshold: This pin is connected in the positive input of the 2nd comparator and when the
voltage is applied to it exceeds ⅔ Vcc causing the output to switch from “HIGH” to “LOW”
state, this pin is used to reset the flip-flop. It connects directly to the RC timing circuit.
● Pin 7 - Discharge: This discharge pin is directly added to the collector of an internal NPN
transistor that is used to discharge the timing capacitor to ground when the output at pin 3 switches
is “LOW”.
● Pin 8 - Supply +Vcc: the power supply pin is used for general purpose TTl555 timer is between
4.5V and 15V.
Here our output voltage is approximately 5V ac.
Wireless power transfer runs on the inductive power transfer fundamental principle, as found in the
traditional transformers. The only difference is that when in the transformer the two coils are in very
close together proximity and carries ferrite material to enhance the coupling, inductive chargers
have an air gap between the coils.
3.2.2 Analytical approach of wireless power transfer
The process follows the following steps:
•
The main voltage is transferred into alternating current, preferably, high-frequency AC.
•
This current is converted to the coil through transmitter circuit. This AC produces a magnetic
field in the transmitter coil.
•
The induced magnetic field produces a current in the close to the receiver coil.
Wireless power transfer with inductive coupling is mainly using an air core transformer where the
primary and the secondary are not adjusted together like in a typical transformer. Such power
transfer procedures are largely used for passive RFID powering [3]-[7], where the needed power is
smaller with respect to external power. The schematic of the inductively coupled system used for
wireless power transfer. It consists of a primary and a secondary coil. At the primary side, through
which the power is transferred as a power supply (US, RS) and a coil (L1). The
41 | P a g e
secondary side is formed by resonant circuit (L2 and C2) followed by rectifier and resistive load R
load representing power consumption of external power in the battery.
Figure 3.5 Wireless power transfer system
The power X-fer is realized by inductively coupled coils that are L1 and L2 forming loosely coupled
air core transformer, whose mathematical formulation is given in (1) and (2) for the purpose of
mathematical analysis the air core transformer is replaced with T equivalent circuit Resistors R1 and
R2 are resistive parts of L1 and L2 coils.
U1=
U2=
L1
L2
±
±
M
di1/ dt
di2/dt
di2/dt
di1/dt
M
For the purpose of mathematical analysis, the air core transformer is placed with T equivalent
circuit. Resistors R1 and R2 the, resistive parts of L1 and L2 coils.
Figure 3.6 Wireless power transfer system with T equivalent circuit
42 | P a g e
The values X1, X2, XM and XC2 in equivalent circuit are as given in (3)-(6), one by one. This
assemble to a phasor analysis. The object is to replace the wireless power transfer system with
Thevenin voltage and Thevenin impedance. So, doing the mathematical formulation of the WPT can
be evaluated.
X1 = jꙍ (L1 - M)
X2 = jꙍ (L2 - M)
XM = jꙍM
1
Xc2 =
jꙍc2
Equations (7) and (8) give the calculated values for Thevenin voltage UT and impedance ZT, for system operating at resonant frequency, ꙍ=√L2C21
UT = UsC2M (R2 (Rs + R1) + ꙍ2 M2- jꙍL1R2)/
(R2 (Rs + R1) + ꙍ2 M2)2 + (ꙍL1R2)2
2
2
2
Zr= ꙍ L2 (ꙍ (L12 R2 + M2 (Rs + R1)) + R2 (Rs + R1)2
(R2(Rs + R1) + ꙍ2 M2)2 + (ꙍL1R2)2
/
3.3 Bridge rectifier
In this section we will explain about the theoretical and analytical approach of a bridge rectifier.
3.3.1 Theoretical approach of a bridge rectifier
•
When it is the positive half cycle of secondary voltage, the diodes D2 and D3 become
forward biased and the diodes D1 and D4 turned into reverse biased. The current flows in
this time through D2 to load and then load to D3.
43 | P a g e
•
While it is the negative half cycle of the secondary voltage, the diodes D1 and D4 are
forward biased and the rectifier diodes D2 and D3 turn into reverse bias. By this time the
current flows through D4 to load and load to D1.
•
It is found here that in both of the cycles, the load current flows in the same direction. Here
we get a pulsating DC voltage.
Figure 3.7 Input sine wave
Figure 3.8 Pulsating DC output
•
Adding a capacitor at the output making the conversion of the pulsating dc voltage to fixed
dc voltage.
•
Till a time period of t=1s input voltage is gradually increasing and hence the capacitor
becomes charged up to the peak value of the input. After a time period t=1s input starts
44 | P a g e
decreasing, at that time the voltage across the capacitor makes the diodes D2 and D4 reverse
bias and because of that this will not conduct. Now capacitor starts discharging through the
load, then voltage across the capacitor decreases gradually.
•
When the peak voltage overcomes the capacitor voltage, diodes D2 or D4 become forward
biased and therefore capacitor again charges to the peak value. This process continues. As a
result, a smooth dc voltage is found.
3.3.2 Analytical approach of the bridge rectifier
Peak inverse voltage when one of these diodes in a full-wave rectifier is in the state of reverse bias,
the peak voltage across that diode will be such kind of that is approximately equal to V m. Diode D1
is conducting and D2 is in reverse bias mode. Thus, the cathode of D1 will be at Vm. As this point is
added directly to the cathode of D2, its cathode will also be Vm. With Vm applied to the anode of
D2, the sum of voltage across the diode D2 is then 2Vm. Hence, the maximum reverse voltage across
either diode will be approximately twice the peak load voltage.
PIV = 2 Vm
Using the ideal diode model, the peak load voltage for the full wave rectifier is V m. The full wave
rectifier produces twice as many output pulses as the half wave rectifier. This is the same as saying
that the full wave rectifier has twice the output frequency of a half wave rectifier. For this reason,
the average load voltage (i.e. dc output voltage) is found as
V
avg
=
2Vm
Π
Figure 3.9 Average DC voltage for a full wave rectifier
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We observed that the single-phase half-wave rectifier generates an output wave every half cycle and
it was not effective for using this type of circuit to generates a steady dc supply. The full-wave
bridge rectifier however, provides us a greater mean dc value (0.637 Vmax) with reduced putted on
ripple while the output waveform is twice that of the frequency of the input frequency.
We can enhance the average dc output of the rectifier when at the same time minimizing the ac
changing of the rectified output by using smoothing capacitors to filter the output waveform.
Smoothing or reservoir capacitors added in parallel with the load across the output of the full wave
bridge rectifier circuit enhances the average dc output level even greater as the capacitor acts like a
storage device.
The diagram below shows the unsmoothed varying dc (thin line) and the smoothed dc (thick
line). The capacitor charges quickly near the peak of the varying dc, and then discharges as it
supplies current to the output.
Figure 3.10 Load voltage waveform for the full-wave rectifier with filter capacitor
It is noted that smoothing significantly enhances the average dc voltage to mostly the peak value.
However, smoothing is imperfect because of the capacitor voltage falling a small as it starts
discharging, providing a small ripple voltage. For many of the circuits a ripple which is 10% of the
input voltage is efficient and the equation below provides the required magnitude for the smoothing
capacitor. In the full-wave circuit, the capacitor starts discharging for only a half-
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cycle before being recharged. Therefore, the capacitance needs are only half as much in the fullwave circuit as for the half-wave circuit
C=
Il T
2Vp−p
Here the main benefits of a full-wave bridge rectifier are that having smaller AC ripple value for a
conferred load and a smaller reservoir or smoothing capacitor than an equivalent half-wave rectifier.
Hence, the principle frequency of the ripple voltage is twice that of the AC supply frequency
(100Hz) where there it was for the half-wave rectifier it is exactly equal to the supply frequency
(50Hz).
The quantity of ripple voltage that is putted on top of the dc supply voltage by the diodes may be
virtually reduced by connecting a much improved π-filter (pi-filter) to the output terminals of the
bridge rectifier. This type of low-pass filter comprises of two smoothing capacitors, generally of the
same value and a choke or inductance across them to build up a high impedance way to the
alternating ripple component.
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CHAPTER 4
Simulation and Result analysis
4.1 Simulation analysis
Inially using thermoelectric generator , at 25 degree to 28 degree celcius temperature difference
there is produced nearly 0.7 to 1.2 volts.after that using boost converter ,we have boosted this
voltage into approximately 5 volts.
Figure 4.1 Breadboard design of the Boost Converter
Figure 4.2 Multimeter output of Boost converter(4.98 volts)
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Then we used wireless power transfer circuit to transfer this 4.98 volts in the capsule. Here there
are two parts in the WPT circuit. Primary and secondary circuit. The primary side is called the
transmitter and the secondary circuit is called receiver. Here in both primary and secondary
circuits the number of turns are same ,300. We used solinoid wire which is 38 in measurement.
Figure 4.3 Wireless power transfer broadbread design
The input in the primary circuit is always fixed ,that is 4.98 volts got from the boost converter.
But the output in the receiver end varries with the distance between two coils. The variation of
output voltage with varying distance is given below.
Distance (cm)
AC O/P
DC O/P
0
5.70
6.00
1
5.66
5.74
2
5.4
6.5
3
5.04
5.9
4
4.84
5.81
5
4.70
4.75
6
4.63
4.21
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7
4.57
4.35
8
4.48
4.29
9
4.39
4.13
10
4.33
4.09
11
4.24
4.05
12
4.14
3.92
13
4.08
3.85
14
3.90
3.73
15
3.77
3.68
16
3.54
3.56
17
3.41
3.36
18
3.34
3.24
19
3.23
3.18
20
3.19
3.04
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4.2Result
After this experiment, it is found a relation between distance and output voltage .Here is the relation:
distance vs output voltage :
Figure 4.4 Distance vs output DC voltage graph
In this graph given here,x axis denotes the distance between the primary and secondary circuits as well as y
axis denotes the output voltage in the secondary circuits. we can observe that when the distance is 0, we get
6.0 dc volts. Then, up to 19 inch distance, the voltage curve is almost linear. Then suddenly after 3.7 volts, it
starts decreasing rapidly and at 19. Inch distance,the voltage goes to zero. So, from the overall
discussionandthetableandalsothegraph,we can say the voltage decreases according to the distance .
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CHAPTER 5
Summary
Conclusion
Recent studies over video capsule endoscopy come to a point that the battery is the main obstacle in
the entire process of diagnosis in gastrointestinal tarct in medical science.This obstacle implies the
less lifetime of battery.here in this project , we have tried to solve this problem by increasing the
lifetime through supplying power in a external way.So TEG is used here with a vital role of
converting the body heat temperature difference into electrical powere. But the power provided by
TEG is too less to use it for enhancing the lifetime .hence a boost converter is used to boost the
output voltage given by TEG into approximately 5volts. At the end ,the voltage boosted by the boost
converter is used for wireless power transfer which will charge up the battery to increase the lifetime
to complete the whole video capsule endoscopy in the gastrointestinal tract.
Future work
Throughout the project, we have tried to solve the problem involving lifetime of battery during
diagnosis process. Therefore, we have taken the collaboration of WPT by supplying externally. A lot
of work can be done on this in near future. By using nanotechnology, this part of medical science
can be developed specially. The application can make the life of human more comfortable. In there
are many spaces in this site for investigation. If it is possible to find anything which will be able to
convert the gastrointestinal track temperature into electric power, then it would be a revolutionary in
the VCE method.
1. Harvesting power from the gastrointestinal track can be examined. If it proceeds then video
capsule endoscopy would have been easier technology. The complication may there be reduced
mostly.
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Through back the project the output voltage which was approximately 5v dc was not pure enough.
As it has been generated due to magnetic induction and coupling. There may remain some noise
mixed with it.
2. There may have been develop an improved and simulated wireless power circuit which will
generate power without any noise in the output.
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References
1.Capsule Endoscopy. American Association of Blood Banks, American College of Surgeons, American
Medical Association, Association for Academic Surgery, Massachusetts Medical Society, Society of
Critical Care Medicine, Society of Laparoendoscopic Surgeons, Eastern Association.
2.Coupling Coefficients Estimation of Wireless Power Transfer System via Magnetic Resonance Coupling
Using Information From Either Side of the System. Jiwariyavej, Vissuta, Imura, Takehiro and Hori, Yoichi.
3.Human body heat for powering wearable devices: From thermal energy. Moritz Thielen a, ⇑,1, Lukas Sigrist b,1, Michele Magno c,d, Christofer Hierold a, Luca Benini
c,d.4.https://www.atlantagastro.com/services/capsule-endoscopy/. [Online]5.Capsule Endoscopy.
5.https://www.atlantagastro.com/services/capsule-endoscopy/. [Online]
6.Mutual Inductance. www.electronics-tutorials.ws/inductor/mutual-inductance.html. [Online]
7.SwallowableWireless Capsule Endoscopy. Corporation, Hindawi Publishing.
8.Thermoelectric generator. https://en.wikipedia.org/wiki/Thermoelectric_generator. [Online]
9.Wearable thermoelectric generators for human body heat harvesting. Melissa Hyland, Haywood
Hunter ,JieLiu Elena,Veety Daryoosh ,Vashaee.
10.WEIGHTED CENTROID BASED LOCALIZATION . Hany, Umma.
11.WIRELESS POWER TRANSFER. Tahsin Khandaker, dMD. Mahmudul Alam,Dipta
Chowdhury,M.Sajib Zaheen.
12.https://en.wikipedia.org/wiki/Thermoelectric_generatorhttps://en.wikipedia.org/wiki/Wireless_power_
transferhttps://ieeexplore.ieee.org/abstract/document/6840297
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