Piezoelectric Energy Harvester - Capstone Design

1 Introduction
1.1 Problem Statement
Now a days the cost of the energy is increasing day by day, and the supplies of
the fossil fuels or the traditional sources start decreasing , beside the environ-
mental problems and issues that start aggravated and creating many problems.
Therefore sustainable forms of energy have become very important. The high
priority was to find another sources of energy that are clean and efficient. So
the renewable sources of energy like solar, wind, waterfalls and etc was the ideal
and perfect solution to wean ourselves off of most of the problems. One of the
renewable energy sources that can be used and converted into useful energy is
the vibration or the kinetic energy that cased by the motion of the objects, like
the motion of the vehicles on roads or the footsteps of peoples around us, this
kinetic energy can be captured and converted into electrical energy by using
piezoelectric technology.
Figure 1: footsteps causing a vibration [?]
In small experiment we counts the cars that are passing al ain- abu dhabi
road coming from al ain in 10 minutes at 7:30 on 1st-may-2014 am more than
650 cars passed the road, which has 4 ways. All these cars can create a huge
useless vibration energy in 10 minutes so can we imagine how much vibration
energy can be created in one day.
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Figure 2: counting numbers of cars that are passing abu-dhabi al ain road
Also for example in abu-dhabi university in 2013 the number o under grad-
uated students was 4965 students [?]. If we just consider 25Our objective and
goal in our project is to convert parasitic energy loss into a beneficial gain in
other words convert the vibration energy into electrical energy and have an ef-
ficient, clean and sustainable parasitic energy harvesting system. The parasitic
energy or the vibration energy on congested roads is harvested using piezoelec-
tric devices which use the mechanical strain that is generated by the vehicles
and convert, it into electrical energy. This energy is used to run many systems
like street lights, speed detectors, radars, house lights, or for example entering
or attending card checking system and also it can be fed back to the grid.
1.2 Motivation
in fact converting this useless kinetic energy into useful form of energy is a
greatest solution, for many energy problems, as we know the main problem with
renewable energy is that it is inconsistent due to the instability of the sources
like the wind, sunlight, or lack of water pressure. For example harvesting energy
from the sun or the solar rays is only possible during the day time, or if there is
clouds that will make harvesting the solar energy very difficult. But this problem
does not apply in piezoelectric energy harvesting system. This energy is solely
driven on the mechanical strain created by the vehicles and the piezoelectric
system is constantly generating and storing this energy during the day and
night regardless of low or high traffic. Also this technology is environmentally
friendly, it is not noisy like the wind mail it is also don’t causes any increase
in the carbon footprint, moreover it is don’t need a large places to be exist
and it is not affect the natural views because it can be constructed under the
construction, such as streets 3. It is also safety and no risks associated with this
technology so it will not affect safety in the buildings and constructions. The
installation of the piezo ceramics will be under the streets or floors so cars or
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people will not be able to know that this technology is there. .this novel idea is
not only clean but it is also renewable.
Figure 3: piezoelectric ceramics can be constructed under the construction [?]
The maintenance cost is very small and minimal due to the long life cycle
of the piezo ceramic ,although the initial cost can be high but it may reduced
just as solar power which has spread all over the world and the high initial costs
which was very high at the beginning have started reducing. this technology
has the ability to produce up to 44 mw of electricity every year from one-single
lane, which is stretched through 1 km or roadway which can supply electricity
up to 30,800 homes. 30,800 households can have clean and free energy for a
duration of one year that cuts down a lot of bills, maintenance cost of a plant,
carbon footprint, fossil fuels or other resources [?] .
Such idea can fit well in an airport, train stations, malls, streets or any
crowded places. Like schools or hospitals. It can light up streets, households,
automatic doors, or anything that can have thermal or mechanical strain.
2 Literature Review
This technology, once successful, would be able to provide power for the street
lights. Moreover, this power costs less, it is clean and highly efficient (20-70%
efficiency) [?]It is applied in places like: Tokyo Railway Station in Japan where
, where the floors where a piezoelectric sheet is placed people pass by electrical
energy is harvested from the mechanical stress applied on the sheets by the
footsteps of passersby.This also this powers the ticket gates. [?].When crystals
gain a charge under mechanical pressure, distortion, or stress, it is said to be
piezoelectric. A few of the materials that exhibit this form of energy are: Quartz
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crystals, Barium titanate, lead zirconate, and lead titanate. Excluding quartz,
all of these materials are ceramic. When these materials are under mechani-
cal stress, the lattice structure gets deformed and this causes piezoelectricity.
The piezoelectric devices generate electricity due to the special sheet which is
composed of two thin metal sheets enclosing a thin layer of quartz crystals or
any other crystal exhibiting piezoelectric characteristics. Under pressure, these
crystals deform and cause piezoelectricity. The Energy harvester circuit will
harvest this energy and convert it to electrical energy. The mechanical energy
is transformed into electrical energy using transducers. [?]
Figure 4: Lattice structure of Lead Zirconate Titanate (PZT) and Barium Ti-
tanate after mechanical stress
Lead Zirconate Titanate (PZT) is a widely used ceramic material for piezo
technology. This material is made up of elements, namely lead, zirconium com-
bined with titanate. This material is made under very high temperatures. It can
operate under high temperatures and it also has greater sensitivity than most of
the other piezo ceramics. This material has a perovskite crystal structure and
each of its unit consists of a small tetravalent metal ion and a large divalent;
the small tetravalent ion in the lattice is either titanium or zirconium and the
large one is lead. Each of these crystals has a dipole moment depending on
its symmetry: Either tetragonal or rhombohedral. [?] When mechanical stress
is applied the molecular dipole moments are altered or reconfiguration occurs.
Piezoelectricity will then accumulate due to three factors: Orientation of po-
larization or dipole density P within crystal, crystal symmetry, and mechanical
stress applied. [?] The crystalline materials have to operate at 50% of the Curie
Temperature.
Piezoelectric materials can be affected strongly by temperature due to the
fact that magnetic materials have a limited value for temperature known as
the Curie temperature. Curie temperature is the temperature at which mag-
netic materials change sharply in their magnetic properties. [?] The piezoelectric
material has the following to abide by in terms of temperature:
Temperature dependence of the coefficients are shown below:
ˆ Materials: PIC151, PIC255, PIC155 graphs on the left
ˆ Materials: PIC181, PIC241, PIC300 graphs on the right
Temperature curve of piezoelectric charge coefficient
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[?]
Figure 5: Stress Strain Graph for PZT
In Figure 5 Curve 1 is with the nominal operating voltage on the electrodes,
Curve 2 is with the electrodes shorted (showing ceramics after depolarization)
The PZT material can withstand pressure up to 250MPa without breaking and
this value should not be approached under normal conditions because depolar-
ization occurs at 20-30% of the mechanical limit. [?]
This energy harvesting circuit will help in converting the piezoelectric energy
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Figure 6: Energy Harvesting Circuit [?]
into electrical energy in order to be stored in a battery to power up the street
lights or traﬃc lights. This chip is used particularly for the piezoelectric sheet.
The minimal possible circuit is used, as anything complex will consume or cause
loss of energy which in this case we need to store.The Energy harvester Circuit
as well as the Charge control circuit is shown below:
Figure 7: Charge Controller Circuit [?]
The charge controller circuit will rectify the AC current as we might either
need AC or DC according to the needs of the devices. Later on, it will also
include a charge monitoring system in order to detect whether the battery is
full or not and, accordingly, proceed to charge up the battery or stop. The ﬁrst
application of a piezoelectric material was that created by Dr. Ville Kaajakari
who put a tiny piezoelectric generator in order to convert the energy generated
from walking in order to power mobile phones, GPS, mp3 players etc. [?]
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Figure 8: Piezoelectric generator in shoe [?]
This next application is that of an everyday common device: the gas lighter.
Here the application of piezoelectric is used in order to generate a spark which
ignites the gases by generating a current. So, two piezoelectric materials are
put in such a way that their polarization is reversed. As more stress is applied
more polarization occurs. In order to light the lighter the two materials are
faced towards each other on the same charged side to light it up. They are
connected in a circuit with a spark gap for the lighter to ignite the spark, there-
by pressing the two piezoelectric materials together. This creates a charge that
travels through the circuit to the device. The charges neutralize a spark which
goes through the gap which in turn will burn the gas to create fire. [?]
Figure 9: Lighter application of piezoelectric [?]
Another application is when piezoelectric energy is harvested from human
movement. To be precise this is applied in Tokyo, Japan by the East Japan
Railway Company. The flooring is embedded with piezoelectric materials at the
ticket gates. This is powered by the stepping pressure on the sheets at the gate
to power up the lights in the station or the automatic ticket gates. [?]
There are many different types of renewable energy such as solar, wind,
geothermal, bio fuels, hydroelectric and more. The problem with most of these
renewable energy sources is that they are natural resources and most of them
need to be used or consumed in order to produce energy. Some are taken back
into the environment but, if contaminated, are hazardous to the environment.
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The other problem is all these renewable energy sources need a staffed plant to
function and produce electricity. It comes with expensive machinery: turbines,
generators, propellers, protection devices, etc. Most need maintenance for both
the plant and the machinery. The plant uses electricity, too, so the cost is high
and is constant throughout production. Whereas parasitic energy is a form of
energy that is taken from wasted energy or from loss of energy and converted to
electricity. The initial cost is the only cost incurred besides some maintenance
cost. Other than that, it poses no threat to the environment. The other benefits
are zero carbon footprint emission, no harmful materials used in production, no
plant required, no staffing.
2.1 Applications
Piezo technology can be found in all areas of the market such as medical field
,mechanical or automotive engineering, and semiconductor technologies. This
technology exists in our daily lives such as generator of ultrasonic vibrations
which are applications in cleaning bath for glass and jewelry and also in medi-
cal tooth cleaning. Piezo technology is used in metrology where the ultrasonic
sensors give off a high-frequency sound pulses which surpasses the human hear-
ing capacity and then it receives signals from the objects that reflect the pulses.
Here piezo force sensors are used. In ultrasonic technology the piezoceramics
are used to generate ultrasonic waves in frequency which ranges from 20 to 800
kHz. This can be used for diagnosis an therapeutic application such as tartar
removal or lithotripsy. Its used for scientific instrumentation pumping and dos-
ing, medical technology, and harvesting energy [?] Piezoceramic devices fit into
four categories: piezo generators,sensors,piezo actuators, and transducers.
2.1.1 Piezoelectric Generators
Piezoelectric ceramics will give output voltages which is sufficient to spark across
an electrode gap and this is used as ignitors in the following: fuel lighters, gas
stoves, welding instrumentation’s, and other devices. Piezoelectric systems are
simple and small and they are advantageous over other systems which include
permanent magnets, transformers and capacitors. Piezoelectric energy can be
stored as they resemble solid state batteries for electronic circuits.
2.1.2 Sensors
A piezoelectric sensors which transform a physical parameter like acceleration
or pressure into an electrical signal. Some sensors are acted upon for gener-
ating vibrations to convert to electrical energy and some apparatuses have an
acoustical signal which will create the vibration and these are in turn converted.
Piezoelectric system can have a visual, audible, or physical output to the input
given from the piezo sensors.
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2.1.3 Piezo actuators: Multilayer, Stack, Bending, Stripe
The piezo actuator will take the electrical signal into a exact but controlled
physical displacement in order to regulate exactitude machining tools, lenses,
or mirrors. These actuators are also used for control of hydraulic valves, act like
small-volume pumps or special purpose motors or others. Piezoelectric devices
have an advantage and that is that they are unaffected by energy efficiency losses
which will not let them use the miniaturization of electromagnetic motors which
limits them to sizes less than 1cm3
. These devices also lack electromagnetic
noise. There are different types of piezo actuators: Stack actuators which is
made in on of two ways such as discrete stacking or co-firing, this all depends
on the user’s requirements. Another type is stripe actuator or the bending
actuator which has thin layers of the piezoelectric ceramics which are bonded
together.
2.1.4 Transducers
Piezoelectric transducers will transform electrical energy to vibrational mechan-
ical energy which is usually sound or ultrasound in order to carry out a task.
These devices will generate sounds that is heard and has several advantages
either relative or as an alternative to electromagnetic devices- these devices are
very compact,simple, and very reliable, with minimal energy that can output
very high level of sound. This a matches criteria of the the needs of batter-
powered devices. Piezoelectric effect is know as reversible so a transducer can
both generate an ultrasound signal from the electrical energy and change incom-
ing sound to electrical energy. In certain devices for measurements of different
units a single transducer is use for signaling and receiving in other cases two
transducers are use for separate roles. These transducers are also used in order
to generate ultrasonic vibrations for cleaning,atomizing liquids, drilling, milling
ceramics, or other materials, welding plastics, medical instrumentation, or other
reasons. [?]
A piezoelectric circuit is used worldwide for a variety of reasons. The circuit
used to test the bulbs is modified in a way that can use any suitable high voltage
source as the substitute for piezoelectric crystal. This circuit can be put in shoe
insoles,fishing lure, toys, or other applications that needs a light source. In
other applications by placing capacitors that are parallel with the crystal and
the light source, the capacitor is charged by applying pressure to the crystal.
This can be useful by placement of piezo discs on the pedal of a bicycle to light
up the flashlight in rural areas where electricity is scarce.
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Figure 10: Applications of Piezoelectric ceramics [?]
In figure 1 the piezoelectric circuit is used for a light tester that will makeup
a first embodiment of the present invention, figure 1A shows that the light tester
is using an alternative high voltage source and figure 2 shows the schematic of
the circuit which has been altered in order to include the light sources.
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Figure 3 shows the ﬁshing lure that uses a piezoelectric circuit. Figure 4 and
5 shows how toys use piezoelectric circuit and in a industrial scale.
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Figure 6 shows how a shoe using a piezoelectric circuit can light up an LED.
Figure 7 shows the schematic for another use of the present invention that
includes a storage capacitor. Fire 8 shows how a crank mechanism is used for
the circuit to operate in ﬁgure 7.
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Figure 9 uses a camera which combines the circuit of ﬁgure 7 in order to
operate the ﬂash. Figure 10 shows the piezoelectric circuit in a bike pedal.
Figure 11 shows and emergency light signal that uses a piezoelectric circuit. [?]
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2.2 Report Outline
The remaining chapters in this report are the following: design, implementation,
project management, results and discussions, summary of entire report.
3 design
The main design for us was implementing a prototype for a street with piezo
materials installed in the design to harvest the energy from the motions of car
model, but during our researches we found that building a prototype is very
diﬃcult, ﬁrst of all the piezo materials was very expensive, where each piece of
2 in2
is worth more than 400 dhs more over the current that coming out from
the piezo was very small (the maximum output power was less than 2.5mw)
and we need more than one piece to generate enough power for our system .
So we make up our mind to build a simple design that can generate a power
from piezo materials, then we have to store it , measure it and then supply it
to the load which will be a small led. The design contains three main systems
electrical system, mechanical system and programming system.
3.1 electrical system
Electrical system this system is divided into three stages14:
1. generating electrical power
2. storing the electrical power
3. supplying the electrical power to the load and the smart system.
Figure 14: the three stages for the electrical system
3.1.1 generating the electrical power
In this stage we have to extract the power from the piezo materials. The energy
generation stage has a mechanical structure that is built in order to generate
enough power for the system to function and produce electricity to power the
other subsystems. The mechanical structure have an array of piezoelectric discs
that are connected to produce maximum amount of voltage and current. The
mechanical structure is designed in a way to apply enough pressure without
breaking or damaging the piezo discs. The structure has two layers: one lower
layer with the piezo disc, a second layer has a bolts that transfer the pressure
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that applied on the upper layer onto the discs. The next pictures showing the
generating stage .
For our design we used 12 piezo buzzers as shown in the next picture 15.
Figure 15: piezo material buzzer
These components can supply us with a voltage between zero and thirty or
more depending on the pressure that we apply in other words, when we apply
a stress on the piezoelectric material, an electrical field is induced this what
we called the piezoelectric effect . Those buzzers have two poles , positive and
negative( the covered part or the white color is the anode, the metal part is the
cathode) when we feed them with electrical voltage they start vibrating we used
them in our design because they were cheaper and available for us.
3.1.2 storing the electrical power
In this stage we have to store the energy that is generated in storing unit, there
is two methods to store the power, the first method is using piezo harvesting kit,
boost converter ,charge controller and a battery. The second method is to build
a normal circuit that convert ac current to dc current and store it in supper
capacitor.
3.1.3 method 1
: In this method we need to use the following:
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3.1.4 piezo harvesting kit eh300/30116
.: This device converts the ac power output from a piezoelectric discs to a dc
power output, it construct of
1. a full-wave rectiﬁer bridge which convert the ac current that reverse it
direction into one direction current and
2. charge management and dc-dc conversion ic that control the input power
and produce a stable dc current
3. some storage capacitors for storing and smoothing the power.
Figure 16: piezo harvesting kit eh300/301 [?]
Figure 17: piezo harvesting kit eh300/301 main parts [?]
3.1.5 boost converter
: This part is depend on the size of the battery that we are we going to charge,
since the output from the harvesting kit are 1.8v, 2.5v, 3.3v, and 3.6v we may
need to charge more than 3.6 v battery , in this case we need to boost the output
voltage from the harvesting kit to the needed voltage using boost converter that
can step up the dc voltage
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Figure 18: boost converter [?]
3.1.6 method 2
: In this method we need to design a simple circuit that contain
1. bridge rectifier which convert the ac current that reverse it direction into
one direction dc current.
2. smoothing capacitor to smooth the output of the rectifier
3. voltage regulator to generate a fixed output voltage
4. super capacitor to store the power.
It was very difficult to chose the most suitable method for us, method 1 was
good but very expensive, method 2 was cheep but we can’t guaranty the results.
So method 2 was our first choice. How bridge rectifier work19
Figure 19: bridge rectifier work [?]
A diodes bridge rectifier is construct of four diodes connected as shown in
19. Points a and c are the inputs, during positive cycle of the voltage diodes
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d1 and d3 are forward biased so they conduct the current or the voltage but
d2 and d4 are reverse biased so they operating like an open circuit. So current
flows as shown in part1 . During negative half cycle, the diodes d2 and d4 are
forward biased and the diodes d1 and d3 are reverse biased so the current will
flow as shown in part 2 in both cases current flows through the resistor in the
same direction, but increasing and decreasing so we get ripple current in the
resistor or the output [?].
Calculations for the smoothing capacitors: The output from the rectifier on
its own would be a cycles of half sine waves and the voltage varying between
zero and 30v. So to smooth the output of the rectifier we use a capacitor which
placed across the rectifier output , the rectifier will charge the capacitor then
when the voltage from the rectifier drop down the capacitor will provides the
voltage that it store it.
Figure 20: the bridge current and smoothing capacitor current [?]
The diagram 20 shows the output from the bridge and the capacitor smooth-
ing voltage. The best capacitor should match the next condition
R * c ¿ 1 / f R = the resistance of the load c = value of capacitor in f f =
the frequency - this will be two times the frequency of a bridge [?] . If we are
going to use about 500 and the maximum frequency is 4 hz then the required
capacitor is more than 125f Picture21 is showing the method2 simulation:
In this picture 21 we chose a power source as piezo because there is no piezo
elements in the multism program the storing unit will be a super capacitor
In this picture 22 we can see the simulated output voltage from the bridge
diodes and how it is ripple, to construct the bridge diode we will use a schottky
diodes those diodes are perfect for our project since they are consuming very
less power. See ******
In this picture 23 we can see the simulated output voltage from the smooth-
ing capacitor and the regulator, the yellow line is the smoothing capacitor out-
put, the blue line is the regulator output
3.1.7 supplying the electrical power to the load and the smart sys-
tem
Our load should be very simple because the output power from our system is
very small we chose to use leds and rheostat as a load connected in series with
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Figure 21: multism simulation for storing energy stage
Figure 22: the output voltage simulation from the diodes bridge
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Figure 23: the output voltage from the smoothing capacitor and the regulator
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a switch, the aim of the switch is to control the supply of the energy . We can
adjust the rheostat to change the brightness of the leds24.
Figure 24: supplying the electrical power to the load stage
In this picture24we can see the simulated circuit for the load where the led
is connected in series with the rheostat and the switch.
3.1.8 Arduino Part
In this part of the report the description of the problem that we face and the
objectives we are trying to achieve will be explained. FSM models, flow charts,
architecture figures are put in order to describe to the reader exactly what
we are trying to solve. Description of the whole design is explained in details
here about every component used and every connection made between each
component and system and the flow through the systems. The tools that are
used for the components are used in FSM models and through flow charts and
Multisim and/or Eagle PCB circuit connections.
Description of the mechanical system is described in detail and how it con-
nects to the other subsystems which is the electrical and the arduino system.
Here the design of the mechanical system along with every components descrip-
tion and circuit connections withing is described. The description is in the
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Figure 25: the final design for the circuit
form of pictures, circuits, and useful information. The electrical circuits and
connections are drawn on multisim and EAGLE for PCB printing and circuit
connections to be clear and concise. The arudino connections with the system
and the LCD are in the form of circuit and the additional code is written and
explained in details.
3.1.9 Implementation
In this section the implementation of our system is described. Every components
purposed using connections or code is described..The circuits, codes, and figures
from software are explained and shown as well as the progress from the progress
presentation model to the current and final model is shown along with the
description of all the problems faced and the changes made to the model. List
of components, circuits, models, circuits, and softwares used and changed are
all corrected and explained in details.
3.1.10 Project Management
In this part of the report the members explain about their background as well as
the progress that has occurred is shown on the Gantt chart and compared to the
one made in the proposal presentation. The software elements and the planning
involved is described as well as the communications between team members and
the professors is shown as proof via emails.Weekly report, minutes of meetings,
supervisor meetings are all arranged and put in the report.
3.1.11 Results and Discussions
This part of the report will show all the evidence we have gathered throughout
the whole period of time that our system works and is fully functional. The tests
that needed to be carried out are shown as evidence along with the results. Any
changes made is discussed and explained in details.
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3.1.12 Conclusion and Future Work
Concluding with the summary of the entire report and what we have learned
from the design building process technically and about working as a team. What
we found out about the system about the materials over the whole time. Sug-
gestions of how the system can be improved and what to expect in the future.
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4 Design
The circuit that will be connected at the end of the piezoelectric and electric
systems will be the power monitoring system previously the control system. The
circuit which is after the energy harvesting system and storage will be monitored
using the Arduino Uno Rev-3 and display on the liquid Crystal Display. The
circuit and connections are drawn on Eagle CAD and the schematic diagram as
well as the Board is shown below:
4.0.13 PCB
Figure 26: Schematic diagram for the power monitoring system
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Connections between components and details:
ˆ Materials needed:
Liquid Crystal Display 16x2
Arduino Uno Rev-3
10k potentiometer
1 MΩ, 100K Ω, and 330 Ω resi resistors(Voltage divider)
Breadboard
Pin headers
ACS 712 Current Sensor
LED
ˆ Arduino connections to LCD:
The pin headers are ﬁrst soldered onto the 16 pins of the 16x2 Liquid
Crystal Display. The connections between the two components are revised
and the connections are made. The connections between the two are as
follows: Pin 1(GND) of the LCd is grounded by connecting to the ground
of the arduino at Gnd Pin. Pin 2(Vcc) of LCD is connected to the 5V pin
on the Arduino. The LCd is now powered up and grounded for displaying
output from the Arduino. Pin 12 and Pin 11 are connected to pin 4(RS)
and Pin 6(Enable) pins respectively. Register Select(RS) pin will control
the location of the LCD’s memory that data is being written to and this
connects to Pin 12 (MISO) and this is the SPI communication medium for
the LCD to display/write data onto the display that the Arduino outputs
through pin 12(MISO). Pin 11 is also for SPI communication(MOSI)to
device which connects to the Enable pin for writing to the registers. The
data being displayed comes from here where the Arduino through pin
11 enables the registers for writing on the LCD and the LCD outputs
the location of the registers that data will be written to. Next is the
connection from the LCD D4 pin to digital pin 5: D4 pin is a data pin
and there are 8 data pin D0-D7, these pins depending on their states being
high or low the bits are being written to a register when writing or the
values being read when you read from it and it is connected to digital
pin5 which is with output of analogWrite() function hence the arduino
will send analogWrite() function and D4 pin writes to the registers the
depending on the state. LCD D5 pin to digital pin 4 which can have these
functions digitalWrite() digitalRead()and so data is either being read or
written. LCD D6 pin to digital pin 3 holds the same as D4 and the same
in this case LCD D7 pin to digital pin 2. [?,?]
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ˆ Arduino connections to Voltage Divider:
Arduino Uno-R3 is connected to a voltage divider so as to measure the
Voltage to output onto the LCD. The voltage divider takes the input which
is going to be very high for the Arduino to takes since it takes a maximum
voltage of 5V and 3.3V. So the Current that we have has a maximum
of 50V and through the voltage divider of 1MΩ and 100kΩ and this will
bring down the voltage for input to the arduino to 5V. The middle of the
voltage divider is connected to the analog A2 pin on the arduino as this
will take the analog value and using the code it will display the how much
voltage is running in the circuit. The circuit is connected to R1 which is
1MΩ resistor and 100kΩ resistor is grounded. The A2 pin is carrying out
functions of analogRead() so it reads the voltages that is being inputted
to the Arduino to be read. [?]
ˆ LCD connections to potentiometer:
The potentiometer is used in order to adjust the brightness and contrast
of the LCD and the connections are as such : The outer legs one of them is
grounded and one of them is connected to 5V. The middle pin is connected
to the Vo Pin 3 of the LCD which is responsible for the display contrast. [?]
ˆ Current sensor connections to LED:
The current sensor is used in order to detect the current that ﬂows through
the circuit and the LCD displays the voltage, current, power, and watt-
hour on the display. In order to do this the current sensor’s GND is
connected to the ground on the arduino and the 5V is connected to the
5V of the Arduino, the middle pin is connected to the analog A3 pin this
pin is for the current readings to be sampled and is inputted to the arduino
which using the function analogRead() and is processed in the Arduino
and and sent to the LCD. [?]
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Figure 27: Schematic diagram on board for the power monitoring system
In this circuit diagram: The components used are Arduino Uno, 16x2 LCD
character display, 10k potentiometer, resistors, LED, and ACS712 current sen-
sor. The following has it’s own purpose in the design and it’s use is explained
in the following few pages:
Arduino Uno:
The Arduino Uno is a board which has a microcontroller base on the AT-
mega328. This board has 14 digital input/output pins,6 analog input, 16 Hz
ceramic resonator, a USB connection, a power jack, an ICSP header and a reset
button. Ithas everything necessary for the microcontroller to function by just
connecting it to the computer via USB cable or by power it up using AC-to-DC
adapter or a battery. Previous boards use FTDI USB-to-serial driver and the
current model does not;on the other hand, it uses an ATmega16U2 which is
programmed as the USB-to-serial converter. Some of the key features of the
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Figure 28: Arduino Uno Rev3
Arduino are listed below: [?]
ˆ Microcontroller - ATmega 328
ˆ Operating Voltage - 5V
ˆ Input Voltage(recommended) 7-12V
ˆ Input Voltage(limits) - 6-20V
ˆ Digital I/O pins - 14
ˆ Analog Input Pins - 6
ˆ DC Current per I/O Pin - 40 mA
ˆ DC Current for 3.3V Pin - 50 mA
ˆ Flash Memory 32 KB (ATmega328) of which 0.5 KB used by bootloader
ˆ SRAM 2 KB (ATmega328)
ˆ EEPROM 1 KB (ATmega328)
ˆ Clock Speed 16 MHz
[?]
16x2 LCD character display
A liquid Crystal display screen is an electronic device via which many devices
can have diﬀerent applications. A 16x2 LCD display is the most commonly used
LCd in electronic devices. This LCD is 16x2 which means it has 16 characters
with 2 lines. and each characters resolution is 5x7 pixels. Command and Data
registers are present in this LCD. The command register will store the commands
28

which are given to the LCD and this is done by things like : initializing screen,
clearing screen, setting cursor position etc. The data into the LCD is the ASCII
value of the character. The pin diagram is shown below for an LCD [?]
Figure 29: LCD pin diagram
29

Figure 30: LCD pin diagram connections
10k potentiometer
Figure 31: 10kΩ Potentiometer
The Rotary potentiometer standing at 10kΩ is and adjustable potentiometer
and the pot is turned in order for the resistances to changes. The VCC connec-
tions are connected to the outer pin whilst the ground is connected to the other
one and the center pin is connected to have a voltage from 0 to VCC which de-
pends upon the rotation of the pot. This can be connected to a mcrocontroller
on an ADC to get varying inputs from the user. Int this case the potentiometer
was connected between pin Vo of the LCD and ground and 5V ont he Arduino
for changes in the contrast of the LCD. [?]
30

Resistors
Resistors are electronic coponents which usually have a certain, non-alternating
electrical resistance. The resistor’s resistance blocks the ﬂow of the electrons
that go through a circuit. These components are passive which is that it will
only consume power and will never generate power. These components are
added to circuits where it will work alongside the active components such as
LEDs, microcontrollers, or other integrated circuits. Resistors limit the current,
are used as voltage dividers and pull-up I/O lines. [?]
LED:
LED also knows as Light emitting diode is a special diode that will give oﬀ
light when the electric voltage is give to it. It is a common electronic equipment
that is used in a lot of devices. An LED has two heads that is used on order
to give input voltage the longer head is the positive head called Post and the
smaller one is negative head called Anvil. [?]
31

ACCS 712 current sensor:
Figure 34: ACS712 -Current Sensor
The ACS712 provides economical and the exact solutions that are needed for
AC or Dc current sensing devices in industrial , and communications system.
Sine we are establishing a power monitoring system we need to measure the
current from the output of the system in order to calculate the power that the
system generates and in order to do that a current sensing break out board is
needed hence, we have used the ACS712. [?]
32

4.0.14 Flow Chart
chart.JPG
Figure 35: Flow chart of design system
The piezoelectric discs are arranged in the mechanical system which upon
force produces electricity which goes through the energy harvesting circuit and
stores the electricity in a supercapacitor which in turn will light an LED. The
output from energy harvesting system will go into the power monitoring system
through the voltage divider circuit and through the current sensing module back
to be read into the Arduino Uno Rev-3 which in turn will send the data to the
LCd for displaying to output the voltage, current, power in W and Wh.
33

4.0.15 FSM
Figure 36: Finite State Machine for System
The state machine describes how the system will work from each state to
state and each subsystem to subsystem. The idle state is the Piezo mechanical
system and this given pressure will act as output 1 and send the signal to the
harvesting system which will get input 1 if input is 0 the idle state will be
actuated again. From the energy harvesting system output of 1 is given the the
battery in our case the capacitor if input is zero the system will be actuated
again for output of 1 to capacitor which gives output of 1 to the LED.
34

4.1 Arduin Code
#include <LiquidCrystal.h>
double PinV = 2;
double PinI = 3;
int time;
double Voltage;
double Current;
double Power;
double PowerWh;
LiquidCrystal lcd(12,11,5,4,3,2);
void setup(){
Serial.begin(9600);
lcd.begin(16,2);
time = 0;
Voltage =0;
Current =0;
Power =0;
PowerWh = 0;
}
void loop(){
Voltage = (analogRead(PinV)*12.764)/218;
if(Voltage <0){
Voltage = 0;
}
Current = ((514-analogRead(PinI))*27.03/1023);
if (Current <0){
Current = 0;
}
Power = Voltage *Current;
PowerWh = (Power /3600) +PowerWh;
Serial.print("VOLTAGE : ");
Serial.print(Voltage);
Serial.println("Volt");
Serial.print("CURRENT :");
Serial.print(Current);
Serial.println("Amps");
Serial.print("POWER :");
35

Serial.print(Power);
Serial.println("Watt");
Serial.print("ENERGY CONSUMED :");
Serial.print(PowerWh);
Serial.println("Watt-Hour");
Serial.println(""); // print the next sets of parameter after a blank line
delay(2000);
lcd.setCursor(0,0);
lcd.print(" ");
lcd.setCursor(0,0);
lcd.print(Voltage);
lcd.print("V");
lcd.setCursor(8,0);
lcd.print(Current);
lcd.print("A");
lcd.setCursor(0,1);
lcd.print(" ");
lcd.setCursor(0,1);
lcd.print(Power);
lcd.print("W");
lcd.setCursor(8,1);
lcd.print(PowerWh);
lcd.print("Wh");
delay(1000);
}
ˆ # include< LiquidCrystal.h > - This code will include the library for the
Liquid Crystal because we are using an LCD for displaying the voltage,
current, and power.
ˆ double PinV = 2;
double PinI = 3;
int time;
double Voltage;
double Current;
double Power;
36

double PowerWh;
This will initialize all our variables. PinV which will be connected on the
arduino to Analog A2 and PinI to analog A3 pin and these are the pins
for reading the voltage and current from the circuit.
ˆ LiquidCrystal lcd(12,11,5,4,3,2); - This line will prepare the arduino to
know the pin connections :12,11,5,4,3,2 are the ones the lcd will connect
to and initialize.
ˆ void setup(){
Serial.begin(9600);
lcd.begin(16,2);
time = 0;
Voltage =0;
Current =0;
Power =0;
PowerWh = 0;
}
void loop(){
if(Voltage <0){
Voltage = 0;
}
if (Current <0){
Current = 0;
}
Here the code is ready for startup with the funciton void setup() and the
lcd is initialized where it will begin and where the display will output data.
lcd.begin(16,2); The variables are all initialized to 0.
ˆ
void loop(){
if(Voltage <0){
Voltage = 0;
}
if (Current <0){
Current = 0;
37

}
Here the code runs into a loop where the Voltage and Current are initial-
ized and will be displaying these two variables constantlt with a delay of
2 second
ˆ
ˆ
This equation is for outputting the power values in W and Wh from the
Votlage and Current values onto the display.
ˆ
delay(2000);
This is the code for outputting the values onto the serial monitor.
lcd.setCursor(0,0);
lcd.print(" ");
lcd.setCursor(0,0);
lcd.print(Voltage);
lcd.print("V");
lcd.setCursor(8,0);
lcd.print(Current);
lcd.print("A");
lcd.setCursor(0,1);
lcd.print(" ");
lcd.setCursor(0,1);
38

lcd.print(Power);
lcd.print("W");
lcd.setCursor(8,1);
lcd.print(PowerWh);
lcd.print("Wh");
delay(1000);
}
This code will print onto the LCd the values of the Voltage, Current,
Power in W and Wh. The calculations and readings are taken from the
arduino and the LCD reads this part of the code and outputs it onto the
LCD.
4.1.1 Calculations
Calculations for the Arduino part are as follows:
Since the voltage input fromt he piezo electric system ranges from 0-50V the
voltage needs to be stepped down in order to be inputed to the Arduino which
takes only 5V maximum. Hence,
A voltage divider calculation is needed for 50V to be converted to 5V.
Figure 37: Voltage Divider circuit
R1 R2 = R1∗R2
R1+R2 =
1MΩ∗100KΩ
100KΩ+1MΩ = 90909.09090909091 Ω
The analog reading needs to be converted to digital and this is done by mul-
tiplying the voltage divider output by the ration which is from the A2 input
and the R1 resistor which comes up to around 12.764 and this is divided by 218
because 1023/5 = 204.6 and the closest approximation is 218 because we need
a digital output of 5V.
For the current sensing part calculations need to be done for analog to digital
conversion:
39

Current = ((514-analogRead(PinI))*27.03/1023); The calculation is done of
514-analogRead(PinI) because when the input is 0 the current sensor gives an
output of 2.55V and in digital half of 5V needs to be subtracted so it is 514. It
is multiplie by 27.03 since the sensitivity is 0.185 V as per the datasheet 5V is
divided by 0.185V and this gives 27.03 and the whole thing is divided by 5V for
a digital output to be given out.
40

5 implementation
5.1 implementing the electrical system:
5.1.1 implementing the power generating stage:
On the mechanical structure we place 12 buzzers on the lower layer upon the
holes, each disk has another disk replaced opposite to it to make it easy when we
want to connect them in series by connecting the positive side of each buzzers
to the negative side of the other buzzer then we connect the groups in parallel
as shown in38. The negative side of each piezo will be the negative output from
the bridge and the positive side will be the positive side of the bridge rectifier
since we are going to connect each buzzer to diodes bridge. When we apply a
pressure on the upper layer the bolts press the piezo discs at the same time, the
piezo disks will convert the pressure to electrical power.
Figure 38: replacing the piezo discs on the lower side of the mechanical system
In picture 38 we can see the piezo discs replaced on the lower layer and
each disk is connected to diodes bridge rectifier . And in order to increase the
output voltage from the buzzers we connect each two disks in series but the
output current from the piezo was very small so to increase the output current
we connect the groups in parallel . Picture39 showing the mechanical system of
the power generating stage. Picture 40 showing the lower layer with the piezo
disks placed on it and the upper layer with the bolts fixed on it also we can see
the springs between the upper and the lower layers. Picture38 showing when we
apply the pressure on the upper layer we can see how the all bolts are pressing
the piezo discs.
41

Figure 39: the mechanical system of the power generating stage
Figure 40: the lower and the upper layers of the mechanical system
42

Figure 41: applying pressure on the mechanical system
5.1.2 implementing the power storing stage:
5.1.3 build bridge rectifier
Instead of connecting the all the piezo buzzers directly together then connect to
one diode bridge it was better Idea to connect each buzzer to bridge so we need
12 bridges, otherwise the output from each piezo may cancel the output from
the another piezo (the output from the piezo is sine wave so may the positive
cycle may canceled by the negative cycle of the other piezo). The piezo buzzers
provide us with very small power, so we use schottky diodes 42 that consume
very small voltage to build our bridge rectifier we will need 4 diodes and connect
them as following:
1. for each two diodes connect the negative side of one of them to the positive
side for the another one. This will be the input side of the bridge
2. now the free unconnected positive side for one diode connect it to the
other free unconnected positive side to the opposite diode, this will be the
positive side of the bridge.
3. finally the free unconnected negative side for one diode connect it to the
other free unconnected negative side to the opposite diode, this will be
the negative side of the bridge.
Picture42 showing the bridge rectifier that we built for each diode the side
with line is the negative side
5.2 connect the piezo discs to the bridge
After we built our bridge rectifier we have to connect the piezo discs to it and
that can be done by connecting the negative side and the positive side to the
input side of the bridge, as shown in picture 44 , we can see the red wire of the
43

Figure 42: schottky diodes [?]
Figure 43: diode bridge
44

piezo (positive wire) connected to the input side of the bridge the same thing
to the black wire(negative wire).
Figure 44: connect the piezo discs to the diode bridge
5.2.1 connecting the piezo discs in parallel and series
For each two piezo discs connect their one positive side of the bridge to the one
negative side to the second bridge, this will be the series connection between
the piezo buzzers and that will increase the output voltage, then connect the
free unconnected positive sides of the all diode bridges together and the free
unconnected negative sides of the all diode bridges together this will be the
parallel connection, tha aim of the parallel connection is to increase the output
current. See picture45
5.2.2 connecting the smoothing capacitor , regulator and the storing
super capacitor
Finally to finish the storing stage we have to connect smoothing capacitor 100f (
to smooth the output rippled voltage from the bridge rectifier) a cross the bridge
rectifier and connect the positive side to the input of the regulator the output
45

Figure 45: connecting the piezo discs in parallel and series
of the regulator is connected to another 100f capacitor the aim of the second
capacitor is to filter and remove any noise or ac frequency in the regulator
output. The middle pin of the regulator is grounded, finally we connect the
super capacitor to store the output voltage, picture46 is showing the connected
component for the storing stage.
Figure 46: power storing circuit
5.2.3 implementing the load circuit:
We used a LED as a load, this led is connected in series with a rheostat and
switch. The aim of the rheostat is to adjust and control the flowing voltage to
46

the LED, and the switch is used to turn oﬀ and on the circuit. Picture 47 is
showing the load circuit.
Figure 47: power storing circuit
#include <LiquidCrystal.h>
double PinV = 2;
double PinI = 3;
int time;
double Voltage;
double Current;
double Power;
double PowerWh;
LiquidCrystal lcd(12,11,5,4,3,2);
void setup(){
Serial.begin(9600);
lcd.begin(16,2);
time = 0;
Voltage =0;
Current =0;
Power =0;
PowerWh = 0;
}
void loop(){
47

if(Voltage <0){
Voltage = 0;
}
if (Current <0){
Current = 0;
}
delay(2000);
lcd.setCursor(0,0);
lcd.print(" ");
lcd.setCursor(0,0);
lcd.print(Voltage);
lcd.print("V");
lcd.setCursor(8,0);
lcd.print(Current);
lcd.print("A");
lcd.setCursor(0,1);
lcd.print(" ");
lcd.setCursor(0,1);
lcd.print(Power);
lcd.print("W");
48

lcd.setCursor(8,1);
lcd.print(PowerWh);
lcd.print("Wh");
delay(1000);
}
Figure 48: Arduino circuit for Displaying values
The implementation of this code and connecting the circuit altogether gave
a lot of problems. The problems starts with input voltage since it is varying
and not a constant voltage obtain a voltage divider suitable for the system was
critical. The other issue was due to the voltage problem one of our LCD’s had
burnt out and would not display the correct values or characters on the screen.
The code gave a lot of errors during compiling, there were problems uploading
the code due to conﬁguration of the ports. But the code and connections after
revision gave us the results we needed for our system as a whole to work.
49

Figure 49: Software implementation
Figure 50: Software implementation
50

5.3 Project Management
Figure 51: Gantt chart progress for system
As can be seen from the Gantt chart the only change from the progress
report to the ﬁnal design report is the added timing for testing for a duration
of about 30 days from 27 September to November 10.
51

5.3.1 Assembling the all systems:
Finally we connect the all systems together, we connect the mechanical part
with the piezo ceramics to the storing circuit, the storing circuit is connected
to the load circuit as shown in pictures 52 refb13.
Figure 52: Assembling the all systems
5.3.2 Problems that we face during the work
1. before getting the piezo buzzers we ordered a square shape piezo material
54, those piezo was very expensive about 400dh for each54, when we test
it we shocked that the output from it is less than 0.1mw, so we need more
piezo sheets , also it is only can generate power when we vibrate it, and
that is not consistent with our project, where we need to generate power
when we press the sheets, this mistake teach us to be very careful in the
future when we want to order anything.
2. in the first time we built our rectifier bridge from normal diodes , and
when we connect it to the piezo disks , the output voltage dropped to
zero, that’s why we used the schottky diodes that have very small voltage
drop.
6 results
6.1 results of testing circuit
Before we build the final demo we built a simple design testing circuit to test
the properties of the piezo elements and check it if they are able to generate
52

Figure 53: piezo layer with storing and load circuits
Figure 54: piezo material that we order
53

enough power and understand the relation between the pressure, voltage, and
the size of the piezo. The next pictures is showing the results of the testing
circuit
Picture 55 showing the testing circuit are connected in parallel to one rectiﬁer
bridge.
Figure 55: testing circuit
Picture 56 is showing the output from the testing circuit, the piezo buzzers
was new so they were able to give us 54.6v with one press.
Picture 57 showing the testing circuit while it charging the capacitor. In one
minute we were able to charge the capacitor to 10.06v
6.2 results from the main demo
After we implement and built our demo we were able to generate electrical power
and store it in super capacitor then supply it to the load, in other words the
project was very successful and meet the objects. The next pictures are showing
the results of our demo
We test the piezo elements to see how much voltage we can get from it
picture59and ?? showing the output voltage from the ceramics:
Picture 59 showing the output from the piezo squared ceramic, we can notice
how is the output is sin wave and very small output power , and we need to
vibrate the sheet to get the output.
Picture ?? showing the output waves on the oscilloscope from the piezo
buzzer discs, the output is sin wave and the maximum voltage was about 10 v
this volt we get it by clicking the discs continuously.
Picture?? showing the output voltage on the oscilloscope when we apply
pressure on the mechanical system, this improve that we were able to generate
54

Figure 56: output from the testing circuit
Figure 57: testing circuit while it charging the capacitor
55

Figure 58: output from the piezo squared ceramic
Figure 59: output waves on the oscilloscope from the piezo buzzer discs
56

a power from the piezo sheet.
Figure 60: output voltage on the oscilloscope when we apply pressure on the
mechanical system
Picture61is showing the rectified output from the bridge rectifier in the me-
chanical system, here we can see how the current has one direction only after it
rectified.
Picture62 is showing the output that is charging the super capacitor, this is
output is coming from smoothing circuit.
Picture63 is showing the multimeter value before the system start charging
the capacitor here we can see the capacitor is discharge
Picture64 is showing the multimeter value after the system start charging
the capacitor here we can see the capacitor is charged tell 10.22v this picture
improve that we were able to charge a super capacitor.
Picture 65 showing the super capacitor is discharging and supplying the
voltage to the load , the multimeter value is dropped from 10.22 to 9.33.
Picture66 shows the led glows after we turn on the switch. The lime of
glowing depend on the rheostat value when it zero the led only sparks one time
and then turned off, but when we increase the value of the resistance, the led
works for long time but with low brightness.
57

Figure 61: output from the piezo squared ceramic
Figure 62: output that is charging the super capacitor
58

Figure 63: multimeter value before the system start charging
Figure 64: showing the multimeter value after the system start charging
59

Figure 65: super capacitor is discharging and supplying the voltage to the load
Figure 66: led glows after we turn on the switch
60

Figure 67: Arduino Code
Figure 68: Arduino Code
61

Figure 69: Arduino Code output on serial monitor
Figure 70: Complete system working and displaying output
62

Figure 71: 3V at end of discharge completely and also voltage at which LED
lights up
Figure 72: 2minutes 22 seconds body weight on mechanical structure to charge
capacitor to 10V
63

Figure 73: 4 minutes 2 seconds to charge capacitor to 10 V by hand
Figure 74: 2 minutes 8 seconds to discharge from 10 V to 3V
The final systems as shown in Figure is what we had by the end. We con-
nected the input which is at the voltage divider and ground the negative part
and this gives us output. The arduino is powered up by the USB cable to the
laptop and the Arduino code is compile and uploaded to the microcontroller.
Once the input from the system was given the output is shown on both the
serial monitor and the LCD display. The input from the mechanical structure
goes through a circuit as shown in Figure ?? The circuit goes through a rectifier
circuit from each of the peizos in an array and it then goes into the energy har-
vesting circuit where it is parallel with a capacitor for smoothing the voltages
out and then a voltage regulator in order to a fixed voltage and then through a
parallel capacitor network for smoothing out more and remove the noise. At the
end of it it will go to another separate board which will have a rheostat which
plays with the resistance which in turn will be a brightness meter for the LED
and this capacitor will light up the LED. We managed to charge the capacitor
64

up to 10 V with the body’s weigh typically 60kgs for 2 minutes 22 seconds as
shown in Figure 72 and by hand it takes 4 minutes 2 seconds as shown in Figure
73. The discharge time is 2 minutes 8 seconds to drop from 10 V to 3.5 volts as
shown in Figure 74, 71
7 Conclusion and Future Work
The conclusion of this report is that the proposed design system that was to
light up a bulb through the use of piezoelectric discs with the pressure from
vehicles on the roads was down scaled to a mechanical system with an array of
piezo discs to receive pressure through ones body weight successfully charged a
capacitor and lit up and LED. The project has worked in terms of the technical
stages of charging up a battery and lighting a lamp just the source of pressure
is a human not a vehicle and instead of piezo discs we proposed a piezo sheet
implemented on roads. It could not be implemented on roads as we do not have
enough resources are available to do so also more research is needed regarding
road implementation. American piezo and other industries gave us a red ﬂag
for the use of piezo sheets on roads and other suppliers would not supply a few
sheets to our group. With team coordination this design system has been a
success. With the appropriate design made and division of work between the
team members the design has been successfully carried out as each subsystem
works perfectly and gives the readings and outputs that is needed for evidence
of work. The problems is piezo is a new technology and the resources are not
always readily available the other issue is the ouput is not a steady source of
voltage or current hence, we have very low power. The power is in mJ because
we have very low current output as it is not a stable source of energy they are
peaks of energy which needs to be sampled and harvested and then outputted.
Due to the lack of times, resources,a a ﬂexible budget this could not be achieved.
The future thought is to use a linear booster in order to step up the voltage and
a voltage sampler in order to have a constant output not peaks of output which
needs a lot of time to store. The application then for the future can be used for
charging phones with every footstep, road implementation but these areas need
a lot of research.
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