HUMAN POWERED WIRELESS CHARGER

HUMAN POWERED WIRELESS CHARGER

SEMINAR REPORT

Submitted in partial fullfillment of the requirements for the award of the

Bachelor of Technology Degree in Electrical and Electronics Engineering

of the Cochin University of Science and Technology

Submitted By

JITHIN MATHEW

(19131416)

(7th Semester, B.Tech.)

DEPT. OF ELECTRICAL & ELECTRONICS ENGINEERING

COLLEGE OF ENGINEERING

KIDANGOOR

2015

DEPT. OF ELECTRICAL & ELECTRONICS ENGINEERING

COLLEGE OF ENGINEERING

KIDANGOOR

2015

CERTIFICATE

This is to certify that this seminar report entitled Human Powered Wireless Charger

is a bonafide record of the seminar done by Jithin Mathew (Reg No:19131416) under

our guidance towards the partial fulfillment of the requirements for the award of B.Tech

degree in Electrical and Electronics Engineering of the Cochin University of Science and

Technology during the year 2015 - 2016.

Seminar Coordinator

Mrs. Sonima M P

Assistant Professor

Dept. of Electrical & Electronics

College of Engineering Kidangoor

Seminar Coordinator

Mrs. Salini M Venugopal

Assistant Professor



Seminar Coordinator

Ms. Nimmy Berchmans

Assistant Professor



Head of the Department

Mrs. Binimol.V.K

Assistant Professor



ACKNOWLEDGEMENT

This is the most satisfying, yet most difficult part of the project to present gratifying words

because most often they fail to convey the real influence, others have had on ones Life or

work. First and foremost, I give thanks to Almighty, who gave the inner strength, re-

source and ability to complete the work successfully. I extremely grateful to the Principal

Dr.Roobin V Varghese, College of Engineering Kidangoor, for providing me with best fa-

cilities for this creative work. I wish to thank Mrs. Binimol V.K Head of the Department,

Department of Electrical And Electronics Engineering for her support throughout this

Seminar work. I also thank seminar coordinators Mrs.Sonima M P ,Mrs. Salini M Venu-

gopal, Ms. Nimmy Berchmans for their help and co-operation. I gratefully acknowledge

all the staff members of our department for extending their cooperation during seminar.

Above all, I owe my gratitude to my beloved Parents and relatives who have been pillars

of support and constant encouragement throughout the course of this seminar.

Jithin Mathew

(Reg No:19131416)

Abstract

Human Powered Wireless Charger (HPWC) is a device, which harvests kinetic

energy of human body and transmit it as electrical energy wirelessly. It is designed on the

basis of Faradays electromagnetic induction law. HPWC mainly consists of two units a

Human Power Harvesting (HPH) unit and Receiving Unit (RU). The HPH store human

kinetic energy in magnets and transmits to receiving unit wirelessly using electromagnetic

induction.

Contents

1 INTRODUCTION 3

2 Principle of Human powered Wireless Charger( HPWC) 5

2.1 Human Power Harvesting in HPWC 5

2.2 Wireless Power Transfer in HPWC 6

2.3 Theoretical Analysis of HPWC 7

3 Working of Human Powered Wireless Charger (HPWC) 10

4 Output characteristics HPWC 14

4.1 Output Characteristic of HPWC without A Load 14

4.2 Output Characteristic of HPWC with Loads 15

5 HPWC experiment in cellphone 17

6 Advantages of HPWC 23

7 Limitations 24

8 Future scope 25

9 Conclution 26

1

List of Figures

2.1 The schematic diagram of wireless power transfer in HPWC: (a) Form of

power wireless transfer in HPWC; (b) The structure of the receiver; (c)

Poles distribution of magnet; (d) Relative position of two claw-type poles in

receiver. 7

3.1 The structure diagram of HPWC: (a) The overall structure of HPWC; (b)

The mounting position of each part of HPWC. 11

3.2 Open circuit performance testing of HPWC 13

3.3 Performance testing of HPWC with a load. 13

4.1 Changes of open-circuit voltage of HPWC with Coil when hand crank re-

volving frequencies are 0.5Hz, 1Hz and 1.5Hz, respectively. 15

4.2 Coil with a load of 62, output performances of HPWC change with time

when working frequency of hand crank is 0.5Hz, 1Hz and 1.5Hz, respectively. 16

5.1 The structure of the experimental setup. 18

5.2 The schematic diagram of HPH and RU. 19

5.3 The structure of the receiver and transmitter: (a) The receiver; (b) The

transmitter. 20

5.4 The circuit diagram of the converter in RU 22

2

INTRODUCTION

Recent years statistics shown that the energy consumption in power grid steeply in-

creased. Of the reasons analyzed increase in usage of portable devices like cellphone, Music

player, laptop, Power Banks subjected to be the one. As an alternative, human power with

green and sustainable features has attracted an increasing interest in the last few years. In

fact, human power is rich enough to support the low-power mobile electronic devices.

With the introduction of ultra-low power IC and advancement in electronics power con-

sumption in mobile devices considerably reduced. There by human power gradually be-

comes an important alternative to supply electricity. In fact, such energy is strong enough

to power most of the mobile electric devices. According to measurement, more than 60W

electricity can be easily generated by arm motion from an adult. Many successful human

power generators (HPG) have thus been developed such as: shoe mounted magnetic gener-

ator, boot mounted dielectric elastomer generator, shoe mounted piezoelectric generator,

backpack mounted generator, knee mounted magnetic generator, tube magnetic genera-

tor, liquid metal magnetohydrodynamics generator, thermoelectric generator and so on.

Therefore, HPGs can be well suited for powering the wearable and implantable devices,

such as cellphone, LED, MP4, computer, power banks and so on.

Even though human energy harvesters are successfully experimented, the need of wires to

supply or huge charge storing devices make them inconvenient in usage. In order to meet

the demand of frequent, fast and instant charging for mobile electronic products by con-

sumers, wireless charging is now drawing a great deal of attention. The technology of the

wireless electric energy transmission (WEET) can deliver electricity power from one point

3

HUMAN POWERED WIRELESS CHARGER 4

to another through atmosphere or vacuum via an inductive coupled device without using

wires or connectors. More than comfort problems wires and connectors used in traditional

human powered systems can leads to many hazardous accidents for human being.

Considering comfort and safety facts, design and development of a system that can har-

vest human energy instantly and transmit electricity wirelessly become a need. A Human

Powered Wireless Charger is such a system that is being capable to generate electricity

from human power and transmit instantly to low power mobile devices. Human Powered

wireless charger (HPWC) is the perfect power delivery approach in the dangerous environ-

ment such as humidity, dust, underwater, gas, mining; it is also highly appropriate for the

mobile electronic devices such as mobile phone, electric shavers, and electric toothbrushes.

Department of Electrical & Electronics 2015 College of Engineering,Kidangoor

Principle of Human powered Wireless

Charger( HPWC)

2.1 Human Power Harvesting in HPWC

Human power is well suited to provide energy to mobile electronic products. HPWC

mainly harvests the kinetic energy of human body, which is produced by the muscle of

body parts such as hand, arm, finger, leg and so on. In detail, muscle converts metabolism

energy into kinetic energy with the maximum conversion efficiency of 25% . In HPWC,

using a hand crank, the kinetic energy of hand rotary motion can be collected and then

delivered to magnet via transmission mechanism. In order to increase the revolving speed

of magnet, four gears meshing with each other were employed as the transmission mecha-

nism. According to the definition of transmission ratio, one has:

i1 = n1/n2 = z2/z1 (1)

i2 = n2/n3 = z3/z2 (2)

i3 = n3/n4 = z4/z3 (3)

where,i1, i2and i3 are the transmission ratios of the first and second gear, the second

and third gear, and the third and fourth respectively. n1, n2, n3 and n4 are the revolving

speed of the first, second, third and fourth gear. z1, z2, z3and z4 are the teeth number of the

5


first, second, third and fourth gear, respectively. Combining (1), (2) and (3), the revolving

speed of the fourth gear can be expressed as:

n4= n1/[(z2/z1).(z3/z2).(z4/z3)] (4)

Therefore, when the teeth number of each gear is known, the revolving speed of the fourth

gear is proportional to the first gear.

2.2 Wireless Power Transfer in HPWC

In HPWC,human power is transferred to a receiver coil wirelessly based on electro-

magnetic induction through a magnetic field, which would be setup in the mobile

As Fig. i(a) shows, a receiver is placed above the magnet with four pairs of poles dis-

tributed in the circumference. In addition, the coil in the receiver is sandwiched between

two pieces of claw-type poles by rivet, which is shown in Fig. i(b). In order to meet the

poles distribution of magnet, each piece of claw-type pole has four claws. And the rela-

tive position of two claw-type poles in the receiver is revealed as Fig. i(d). When these

two pieces of poles are placed in magnetic field of the magnet, they would be magnetized.

Based on the structure of the claw-type poles and magnet, when the magnet is rotated by

human power along one direction at a fixed frequency, the polarity of claw-type pole would

change periodically. In detail, when the magnet makes one turn, the polarity of claw-type

pole would change four times. In that case, a cyclically changing magnetic field could be

produced around the coil in the receiver. As a result, a voltage would be produced at the

two ends of the coil, which also changes periodically as the claw-type pole does. Finally,

driven by human power, HPWC can provide power to electronic devices without the use

of conventional wires or cables.



Figure 2.1: The schematic diagram of wireless power transfer in HPWC: (a) Form of

power wireless transfer in HPWC; (b) The structure of the receiver; (c) Poles distribution

of magnet; (d) Relative position of two claw-type poles in receiver.

2.3 Theoretical Analysis of HPWC

Based on the Faradays electromagnetic induction law, the induced voltage of the

receiver coil is mathematically expressed by Lenzs Law

E= N./t (5)

where, E is the induced voltage of coil in receiver, is the magnetic flux through the

coil, N is the number of coil turns and /t is the changing rate of magnetic flux. To

maximize /t should be close to zero. In addition, because of the short distance be-

tween two claw-type poles, the magnetic field around the coil is assumed as uniform, so

the maximum value of induced voltage of coil in the receiver can be written as:



Em= N.B.S.2piF (6)

where, B is the magnetic induction intensity, S is the area of coil, and f is the chang-

ing frequency of magnet field. Based on the principle of wireless power transfer in HPWC

as mentioned above, the output voltage of HPWC changes periodically, which is analogous

to a single-phase alternator. Therefore, when the magnet rotates at a frequency, the output

voltage of the receiver coil in HPWC can also be mathematically expressed as:

u = Umsin(2pift+) (7)

where, u is the output voltage of coil in the receiver, Um is the maximum value of output

voltage of the coil, t is time, 0 is the starting phase angle of u . Changing Um into

Em=N.B.S.2piF, then (7) can be transformed as:

u = Emsin(2pift+)

= N.B.S.2piF.sin(2pift+0) (8)

For HPWC, f depends on the revolving speed of magnet and the number of the mag-

net poles, which can be expressed as:

f = n4p

u = N.B.S.2piF.sin(2pift+0)

= N.B.S.2pin4p.sin(2pift+0) (10)

Combining (4) and (10), the output voltage of the receiver coil in HPWC can be defined as:



N.B.S.2pin1/[(z2/z1).(z3/z2).(z4/z3)].p. sin(2pin1.pt/[(z2/z1).(z3/z2).(z4/z3)]+0 (11)

From (11) one can see that the maximum value of output voltage depends on the num-

ber of coil turns, the magnetic induction of magnetic field, area of the coil, the revolving

speed of hand crank, transmission ratios of the gear train and the pole number of magnet.

When the magnet and the transmission mechanism are fixed, dimensions of coil in the

receiver and the revolving speed of hand crank are two important factors to influence the

performance of HPWC. Therefore, in the following experiment, the influences on HPWC

by these two elements will be presented respectively.


Working of Human Powered Wireless Charger

(HPWC)

Human Powered wireless charger consists of a Human Power Harvester (HPH), a re-

ceiver and a supporting system.HPH collects human kinetic energy firstly through a hand

crank and transfers it to the magnet through a transmission system. HPH is comprised

of a hand crank, gears,axes, a clutch, a magnet seat and a magnet. Among them, the

magnet made of ferrite has eight poles in periphery direction. The operating principle

of HPH is that when the hand crank is rotated by hand, the first gear which is fixed to

the hand crank starts to turn. The rotation movement of the first gear could revolve the

second gear which meshes with the first one. Based on the same argument, the second gear

transmits the kinetic energy to the third gear and then to the fourth one. After that, the

clutch which is fixed to the fourth gear begins to work. At that moment, the magnet seat

driven by the clutch starts to rotate in one direction. Finally, fixed in the magnet seat,

the magnet begins to revolve. Now, through transmission mechanism, the human kinetic

energy is transferred to magnet successfully. It is worth to note that the magnet in HPWC

revolves under the same revolving speed as the fourth gear through the function of a clutch

set in the magnet seat.

From Fig.3.1 one can also see the mounting position of the receiver in HPWC. In this

experiment, the receiver was placed on the outside surface of the top housing, which is

also above the magnet during the whole experimental process. Through measurement, the

10


Figure 3.1: The structure diagram of HPWC: (a) The overall structure of HPWC; (b) The

mounting position of each part of HPWC.



distance between receiver and magnet was 3mm. As Fig. 2.1 and 3.1 show, the face with

claw-type pole B of the receiver is close to magnet.The mounting position of the copper

coil is illustrated as Fig.2.1. Moreover, the two claw-type poles and rivet are made of

electrical pure iron. As Fig. 3.1 shows, the supporting system of HPWC mainly contains a

bearing, top and bottom housings, which are employed to fix and support the other parts

of HPWC. All of the parts in the supporting system are made of organic glass.

Fig. 3.2 and fig. 3.3 is the photograph of the experimental prototype. The dimension of

the equipment is 90mm50mm28mm. In detail, the testing chart of open-circuit HPWC

and HPWC with a load are shown as Fig. 3.2 and 3.3, respectively. All the voltage data

in this experiment were collected by oscilloscope.



Figure 3.2: Open circuit performance testing of HPWC

Figure 3.3: Performance testing of HPWC with a load.


Output characteristics HPWC

4.1 Output Characteristic of HPWC without A Load

Fig. 4.1 shows the open-circuit voltage change of HPWC with copper Coil in the

receiver when a male test subject twirls the hand crank at frequencies of 0.5Hz, 1Hz and

1.5Hz respectively. From this chart, one can see that the open-circuit voltage of HPWC

with Coil A changes like a sinusoidal wave when the revolving speeds of hand crank are

30r/min, 60r/min and 90r/min, which agrees well with the theoretical analysis.

the maximum open-circuit voltage of HPWC with Coil( No of turns, N= 600, Wire di-

ameter of coil= 0.12mm, outer diameter of coil D1 = 20, Inner diameter of coil D2 =

6mm,Resistance of coil = 56.6 ) is aboutis about 1000mV, 700mV and 370mV when the

hand crank rotation frequencies are 1.5Hz, 1Hz and 0.5 Hz respectively Furthermore, it

can be observed that the maximum open-circuit voltage of HPWC with Coil increases with

the working frequency of hand crank. Thus, when the dimension of copper coil and the

configuration of magnet are fixed, the maximum open-circuit voltage of HPWC increases

only with the working frequency of hand crank,

14


Figure 4.1: Changes of open-circuit voltage of HPWC with Coil when hand crank revolving

frequencies are 0.5Hz, 1Hz and 1.5Hz, respectively.

4.2 Output Characteristic of HPWC with Loads

When the resistance of 62 is connected to the Coil, the changes of output voltage

of HPWC are indicated in Fig. 6, wherein the test revolving frequencies of hand crank are

0.5Hz, 1Hz and 1.5Hz respectively. From Fig.4.2 one can see that the output voltage also

changes as a sine wave and the change periods of the output voltage at different revolving

speeds of hand crank are coincident with the calculated ones. Moreover the maximum

output voltage of HPWC with a load of 62 is about 370mV, 300 mV and 200 mV, when

the revolving frequencies of hand crank are 1.5 Hz, 1 Hz and 0.5Hz. It also can be observed

that the maximum output voltage of HPWC with a load increases with the revolving fre-

quency of hand crank when the magnet and coil are fixed.



Figure 4.2: Coil with a load of 62, output performances of HPWC change with time when

working frequency of hand crank is 0.5Hz, 1Hz and 1.5Hz, respectively.

In addition, based on the computing method of effective value of alternating voltage,

the effective value of output voltage of HPWC can be written as:

U = Um/

2 (13)

where, U is the effective value of output voltage of HPWC. The output effective power

of HPWC can be calculated as:

P = (Um)2/2RL (14)

where, P is the effective value of output power of HPWC and R is the resistance of the

load.


HPWC experiment in cellphone

In order to demonstrate the availability of the HCCC, an experimental prototype is fabri-

cated and tested. The structure of the system is shown as Fig.5.1. From this picture, one

can see that the HCCC mainly contains a human power harvester (HPH) and a receiving

unit (RU). In addition, the RU is fixed to the cellphone as a part. For this experimental

prototype, the RU is placed at one lateral side of the cellphone. However, the RU can

be mounted into other places of the cellphone. When the HCCC is used to charge the

cellphone, it just needs to put the cellphone on the surface of the HPH. For the HCCC,

the upper surface of the HPH is designed with a groove, which is exactly matched with the

location of RU in the cellphone. Therefore, in order to make the HCCC work effectively,

it is necessary to insure that the RU is coupled with the HPH when placing the cellphone

on the HPH.

The main function of the HPH is to collect the human power, and then transfer it to

the RU part. As Fig.5.2 shows, the HPH mainly contains human power transmission parts,

a transmitter and supporting components. In addition, human power transmission parts

are comprised of a hand crank, four gears, a clutch and four axes. The operation principle

of these transmission parts is that when a hand turns the hand crank, the first gear which

is fixed to the hand crank begins to move, then the human kinetic energy is transferred to

the clutch through the four gears which mesh with each other orderly. It is worthy to note

that the transmission ratio of the first gear unit is i1=12:35=0.34, while for the second one

the

17


Figure 5.1: The structure of the experimental setup.

transmission ratio is i2=10:35=0.28 and the third one is i3=12:81 =0.15. Hence, the re-

lationship between the revolving speed of hand crank and the magnet seat can be written as

nms = nhc/(i1.i2.i3) (15)

(where nhc ,nms are the revolving speed of the hand crank and magnet seat respectively).

Moreover, the transmitter is comprised of a magnet seat and eight magnets, which is also

shown in Fig.5.3. When the clutch moves, the magnet seat driven by the clutch starts to

rotate in one direction. At the same time, inlaid in the magnet seat, the eight magnets be-

gin to revolve with the magnet seat synchronously. The rotation of these magnets produces

a time-varying magnetic field around them. Finally, through the transmission mechanism

and the transmitter, the human kinetic energy is converted into a kind of time-varying

magnetic field energy successfully. The supporting components which are employed to

support and fix the other parts of the HPH consist of a bearing, a top housing and a



Figure 5.2: The schematic diagram of HPH and RU.



bottom housing. All the parts of the supporting components are made of organic glass.

trans.JPG

Figure 5.3: The structure of the receiver and transmitter: (a) The receiver; (b) The

transmitter.

The function of RU is to generate electricity by the induction effectiveness in the time-

varying magnetic field produced by the transmitter, and then convert the electricity power

into a stable DC to meet the requirement of the cellphone lithium battery. In order to

achieve this function, RU is comprised of a receiver and a converter, which is revealed as

Fig.5.2. When using the HCCC to charge a cellphone, it should make sure that the receiver

is put above the transmitter so that it can couple with the transmitter closely. In this case,

the gap between the receiver and transmitter is 3mm which is comprised of the thickness

of RU (1mm), three air layers (1mm) and the thickness of HPH (1mm). The output port

of receiver is connected to the input port of the converter directly. The output end of the



converter is connected to the cellphones power interface directly.

In addition, the structure of the receiver is shown in Fig. 5.3(a). This figure shows that

the receiver is built up by four parts: claw-type pole A, copper coil, claw-type pole B and

a rivet. The copper coil is working as a conductor in the rotating magnetic field, which

is winded by copper wire with a diameter of 0.3mm. With 500 turns in total, the copper

coil resistance is 4.27. And the rivet, claw-type pole A and B are all made of permalloy.

Besides, in order to reduce the electromagnetic induction in laminations, the claw-type

pole A and B are made of three pieces of permalloy sheets with a thickness of 0.1mm for

each piece. These three pieces of permalloy sheets are glued together into one piece by

silicon rubber. Whats more, for the transmitter, the eight cylindrical magnets made of

neodymium iron boron (NdFeB) are 6mm in diameter and 6mm in height. The magnetic

field formed by such eight magnets is along the axial direction. These magnets are embed-

ded in the magnet seat in which there are eight holes distributed along the circumference

direction for the eight magnets. It is worthy to note that every two adjacent magnets

must be arranged with opposite magnetic poles on one side, which is shown as Fig. 5.3(b).

Therefore, when the magnet seat rotates the magnetic field direction changes four times in a

cycle.According to the relationship between nhc ,nms the rotation speed can be expressed as

nmf= nhc/(i1.i2.i3) = 280nhc (16)

Thus the changing frequency of the induced voltage produced by the receiver is

fv= 280nhc (17)

In order to meet the charging requirement of the lithium battery in the cellphone, a

converter is used to transform the electricity generated by the copper coil. This power

converter is mainly comprised of a diode, a capacitor (100 F /10V), a resistance (460),

a zener diode (Z6V) and a triode, which is shown as the circuit diagram in Fig.5.4. Through

rectification, filtering, stabilivolt and amplification, the input alternating voltage can be



changed into a stable direct voltage of 6V. In Fig.5.4, the input voltage of the converter Uin

is the output voltage of the receiverUR, and the Uout is the output voltage of the converter

Uc.

Figure 5.4: The circuit diagram of the converter in RU

In the experiment, all voltage data of the receiver were collected by oscilloscope.


Advantages of HPWC

No traditional plug ,jack and wire.

Utilises human power more conveniently.

No batteries required.

Safety from short circuiting.

Easily portable and low cost.

Green and sustainable charger.

Energy conservation and environmental protection.

Instant charging solution in travelling, work site, critical situations etc.

Generation is absolutely free from effects of climatic conditions.

23

Limitations

Transmitter and receiver need to be very powerful as the distance increases.

Slower charging.

Wireless transmission of energy causes drastic effects to human body due to radia-tions.

Strong magnetic material need to be used in HPH transmssion unit.

Low transmission efficiency.

24

Future scope

1. Besides half wave rectification in converters full wave rectification can be implemented

for high output voltage.

2. It is shown that transmission efficiency depends on the revolving speed of the magnet,

from this inference the revolving speed of the proposed system can be improved by

enabling rotation of coil in receiving unit in opposite direction of rotation of magnet

in HPH unit.

3. Pedal powered laptops can be implemented in remote areas where power supply is

not much available.

25

Conclution

The vast possibilities of human powered wireless charger studied and analyzed. I found

that human power harvesting is a vast area in which a lot of researches are undertaking.

Presently the system is in the stage of development and it is effectively experimented

in cell phone charging unit. Improving the revolving speed and strength of magnet in

transmitting device transmission efficiency can be improved. implementation of suitable

rectification units also can considerably improve overall system efficiency.

26

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HUMAN POWERED WIRELESS CHARGER