Microcontroller-Based Digital Peak Flow Meter System

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Microcontroller-Based Digital Peak Flow Meter System

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A Thesis Topic Proposal

Presented to the Faculty of the

Department of Electronics & Communication Engineering

College of Engineering, De La Salle University

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In Partial Fulfillment of

The Requirements for the Degree of

Bachelor of Science in Electronics & Communication Engineering

--------------------------

CO, Jan Christian H.

GACUSAN, Bryan Gabriel D.

HONG, Bible T.

JUANSON, Joseph Anthony C.

October, 2010



CHAPTER 1

Introduction

1.1 Background of the Study

Changes brought about by the modern world are undeniable. Together with the

advancement of technology come new diseases that continue to challenge human

existence. There is an increase in the number of respiratory-related illnesses brought

about by the world’s continuous growth. There are developments in the field of

electronics that aims to provide sensors and components that could lead to portable, user-

friendly and improved lung capacity measuring devices [1]

. Spirometry is a physiological

test that measures how an individual inhales or exhales volumes of air as a function of

time. The primary signal measured in spirometry may be volume or flow. There are

numerous parameters obtained during a spirometry test. It varies depending on the nature

of the procedure, may it be for diagnosis or monitoring. One of particular parameter used

in monitoring lung capacity is called Peak Expiratory Flow (PEF). It is the highest flow

achieved from a maximum forced expiratory test from a maximum lung inflation[9]

It is

used to monitor lung conditions, one of which is asthma. Chronic Obstructive Pulmonary

Diseases (COPD) is a type of disease commonly associated with the lungs[2]

. The most

common types of this respiratory ailment are emphysema, chronic bronchitis, and asthma.

According to a study done by the World Health Organization (World Health Statistics

2008), they estimated that 210 million people have COPD, 23 million died from it over

the past year [8]

. They also predicted that at this rate, it would be the 3rd

leading cause of



death worldwide. The study focuses on developing a microcontroller based digital peak

flow meter system. It provides an alternative to lung capacity testing and monitoring that

are currently done in local hospitals. The system also provides features that are

convenient with regards to monitoring a patient’s lung condition since the device can be

interfaced to a computer to view the results. The data can be viewed by the doctor

through a website obtained from its database.

1.2 Statement of the Problem

In an era when heart disease and cancer are declining, COPD is on the rise in

developing countries such as the Philippines[8]

. Spirometry is the most common test that

is used to measure the lung capacity and the volume of a person’s lung through inhalation

and exhalation of air. It includes different types of tests that doctors use either to diagnose

or to monitor the patient’s lung condition. Since asthma is one of the main causes of

absences during school. It can be caused by a lot of factors that are not yet fully

understood by researchers. It is one of the important chronic respiratory diseases

requiring daily monitoring at home[10]

.

For monitoring the lung condition of a patient, a peak flow meter is used. Peak

expiratory flow (PEF) meter is a portable device widely used by asthmatic patients,

providing the peak expiratory flow (PEF) by a simple self-test[10]

. A peak flow meter is

used to help monitor the medical situation of a patient, asthma being one of this. The

most common type of peak flow meters available in the market is the spring type peak

flow meter. It is an analog device commonly used in local hospitals today to determine

the lung capacity of the patient. An indicator will provide a gauge of how well the



patient's lung functions. This is being determined by reading graduations on the device.

The acceptability of the result is subject to the proper interpretation of the user. Thus, the

data is subject to human error. The data is manually plotted, afterwards presented to a

doctor for assessment. The prototype aims to provide an alternative to this method by

providing a digital output in the evaluation process and remote monitoring of the patient.

The group’s prototype aims to provide assistance to the doctor by allowing the

results of the test to be sent to a computer with use of the Bluetooth technology as its

medium. The information can be then sent to a database that can be viewed by the doctor.

This functionality will allow the doctors to monitor the data through a website that

contains the patient’s information from the server and will allow them to have a better

way of gathering data from the patients.

1.3 Significance of the Study

In numerous occasions, chronic pulmonary medical conditions are often

misinterpreted as minor lung ailments. Disregarding COPD ailments can lead to major

complications in the lung passageways. This study aims to integrate the field of

electronics to the medical world in monitoring pulmonary medical condition by providing

patients with a device that can assess lung air capacity and send them to the computer to

be further viewed and analyzed. Lung obstructions and restrictions can be easily

monitored by the electronic peak flow meter by acquiring the accurate peak expiratory

flow measurements.

The group’s prototype is a digital peak flow meter that would assess the lung

functionality of a patient. The prototype would determine the flow rate. Peak flow meters



available in hospitals and clinics are not digital and is prone to parallax error since the

results depends on proper human interpretation. The device is also portable, allowing

ease of use whenever the patient has to perform the tests required for a day. The LCD

screen would display the results obtained from the test. The push buttons will be used for

the operation of the device. It can be interfaced to a computer through Bluetooth

technology allowing wireless capability. The prototype that the group is proposing can

also provide remote data access through web based feature. The doctors can view the

results remotely; make their recommendations as soon as they get the results from the

database.

1.4 Objectives

1.4.1 General Objective

1.4.1.1 Develop a microcontroller-based digital peak flow meter that would

measure lung capacity and send the obtained data to a computer wirelessly.

1.4.2 Specific Objectives

1.4.2.1 To use a flow sensing circuit to determine lung air flow

1.4.2.2 To program the microcontroller to output flow rate and send the data to a

computer by adapting Bluetooth technology.

1.4.2.3 To display the test result through the LCD.

1.4.2.4 To build the device with an accuracy of 90% as compared to a Mechanical

Peak Flow Meter



1.4.2.5 To use a Graphic User Interface (GUI) that would display the data sent to

the computer.

1.4.2.6 To view the data in a Website that can be accessed by the doctor to view

the data obtained by the system.

1.5 Scope and Delimitation

The patient should be able to understand the procedure therefore he/she cannot

be; unconscious, heavily sedated, incapable of understanding the instructions and/or

incapable of forcibly exhaling through the tube. The group would consult a medical

physician regarding the data gathering method to be used and results obtained. The

consultation would also provide us knowledge, guiding us suppose an error occurs. The

system shall focus only on obtaining the peak expiratory flow (PEF) that is used to

monitor asthmatic condition through lung response. The system will not diagnose the

type of lung illness. Data shall be sent to the computer through the Bluetooth interface

and the results shall be listed and compiled as well as its graph for data gathering

purposes. The computer will be the master, the device which initiates the connection, and

the hand-held device will be the slave with regards to the use of the Bluetooth interface.

The patient should have a Bluetooth-enabled personal computer together with the

software that would display the output of the device. The computer used by the doctor

should contain the graphical user interface (GUI) that would be used to access the

database. The patient should also have the GUI in order to input his or her data and

perform the test. With accordance to the pulmonologist, a test per day should be

sufficient to follow the monitoring of the patient’s lung condition. The device is intended



for home use. The system, specifically the website for the doctor, is only accessible

through local area network using a router since the proponents will be using DLSU-M’s

internet connection for the development of the system. The setup with the router is for

demo purposes only.

1.6 Description of the Project

The block diagram of the prototype is shown below:

Figure 1.1:Block Diagram of the System



1.6.1 Sensor Block

The sensor block will be used to gather the data from the patient’s lungs as

he breathes into the tube. The output obtained from the sensor will be sent to the

microcontroller for processing.

1.6.2 Push Button and LCD Block

The Push buttons and LCD would serve as the input/output (I/O) devices

of the prototype. The LCD will be used to display the test results. On the other

hand, the push buttons will enable the user to operate the device. The push buttons

will serve as the reset button for the MCU and Bluetooth, while switches will be

used to turn the MCU and Bluetooth on and off

1.6.3 Microcontroller Unit

The microcontroller will process and utilize the data obtained from the

sensor. It would perform the operations needed to determine the flow rate of air

from the patient’s lungs. Using these data, it would output the lung capacity

parameters for monitoring purposes. The data gathered can be then sent to the

computer through the Bluetooth feature. A graphical representation of the test can

be viewed and further analyzed by the user.



1.6.4 GUI (client and server)

Two key GUI’s will be used for the system; one will be used for the

client’s computer , another will be used for the server which contains the patient’s

information.

1.6.5 Website

The website will provide the means by which the doctor can view the

results. It contains the patient’s information, allowing the doctor to view the

results over a network

1.7 Methodology

In this thesis, the group shall be responsible in performing tests on the hardware.

The group shall perform 20 tests per patient (see Appendix A for calculation). The data

that would be used as reference for the operation of the device will be the spring type

PEF available in the local market. The group would consult a specialist in lung

functionality in order to gain more knowledge about Peak Expiratory Flow. In

constructing the prototype, the group would also be responsible in studying the

specifications of the microcontroller and Bluetooth technology through the use of their

respective datasheets. Also, the group would study the algorithm of programming the

microcontroller so that it would follow the algorithm of the thesis project. The group

would also study the software necessary to gather data from the microcontroller unit and

transfer it to the computer. The group would create a database for the doctor’s reference

on each patient. In building the peak flow meter, the group shall search for resources to



aid them in constructing the hardware of the system which includes the flow tube,

calculating system for the flow rate which is determined through the use of sensors, and

the LCD to display results.

1.8 Gantt Chart

Activity May June July Aug Sept Oct Nov Dec Jan Feb March April

Brainstorming of Proposal

Preparation of Proposal

Preparation of Materials

Purchasing of MaterialsBuilding of Project Prototype

Programming of Microcontroller

Integration of Prototype

Testing

Evaluation of Results

Recommendation of Adviser

2009 2010

1.9 Estimated Budget

Mouthpiece and tubing P100

Bluetooth P1500

LCD Display P300

Flow sensing Circuit P5000

Miscellaneous P7000

Total: P13,900



CHAPTER2

Review of Related Literature

2.1 A Differential Pressure Approach to Spirometry

(Flow Rate Measurement)

In developing the prototype, it is imperative that we understand the flow

measurement part of the design. In order to meet the requirements of the PEF test, we

must choose carefully the sensors to be used to obtain the best results. In our work, we

are to take into consideration the different aspects of flow measurement to determine the

flow rate needed. We are to obtain a, volumetric flow rate for our thesis so one of the

options that we could consider is the use of differential pressure sensing.

In this particular article describes a possible implementation of the prototype. This

follows the theory set forth by Bernoulli in his equation. The main principle which

underlies differential pressure flow measurements is the mathematical expression of

Bernoulli’s theorem which states that introducing a constriction within a tube would

generate a difference in pressure. The equation shown below can describe the relationship

between the parameters needed.



In this equation Cd is described as the coefficient of dispersion, typically 0.97. A2 and

A1 are the area of the inner and outer parts of the tube, while (p1-p2) is the pressure

difference across the tube. Rho is the fluid density of air expressed in kg/m^3. The choice

of the sensor is crucial for the performance. The device has to cope with flow rates up to

14 L/s with an accuracy of 0.2 L/s. Due to the non linear relation between pressure and

flux, the very large range of 3500 Pa with an accuracy of 0.12 Pa must be achieved. To

match these specifications, they used sensors: a large dynamic range sensor and a low

dynamic range sensor, but with high accuracy, were coupled. The first one (Honeywell

24PCEFA6D) is able to measure up to 3449 Pa whereas the second sensor (AllSensor

1mbar D-4V 6M67) has a maximum range of 100 Pa and an accuracy of 0.1 Pa suitable

for the requirements.

In our groups design, however, we are concerned only on the PEF reading so we

don’t have to couple a low range sensor since it may not be able to read the maximum

expiration of the patient since it will saturate at a lower level.

2.2 Peak expiratory flow meter capable of Spirometric

test for asthma monitoring

Asthma is one of the important chronic respiratory diseases requiring daily

monitoring at home. Peak expiratory flow meter (PEFM) is a portable device widely used

by asthmatic patients, providing the peak expiratory flow (PEF) by a simple self-test.

Commercial PEFM produces displacement of a spring connected plate by the force

generated on the plate by patient's expiratory flow. The patient reads the maximum

displacement position on scale of the marker moving with the plate during increased flow



period In developing the prototype, we should be able to understand the principles behind

PEF measurement as well as the electronic components used in the design. There are

various ways on achieving a flow measurement with regards to the flow sensor to be

used. In this particular article, the proponents used a differential pressure sensing device.

Air chamber pressure signal was sensed by 3 differential pressure transducer (MPX2010,

Motorola, U.S.A.), amplified and filtered appropriately. A digital circuit was followed for

ADC conversion and data output with the RS232C serial communication protocol.

2.3 Spirometry (Peak Expiratory Flow or PEF Test

Guidelines and Equipment Specifications)

Spirometry is a test in which lung ailments and diseases such as Chronic

Obstructive Pulmonary Disease can be easily diagnosed. Spirometry is a physiological

test that measures how an individual inhales or exhales volumes of air as a function of

time. The primary signal measured in spirometry may be volume or flow. It is invaluable

as a screening test of general respiratory health in the same way that blood pressure

provides important information about general cardiovascular health. However, on its

own, spirometry does not lead clinicians directly to an aetiological diagnosis.

Spirometry can be undertaken with many different types of equipment, and

requires cooperation between the subject and the examiner, and the results obtained will

depend on the factors varying with each patient. Test performed are either used to

diagnose a certain ailment, or monitor a patients lung condition over a certain time

period. It can be performed at home as instructed by the physician.



In monitoring a patient’s lung condition, for example an asthma patient, he or she

can perform a Peak Expiratory Flow test. PEF is the highest flow achieved from a

maximum forced expiratory maneuver started without hesitation from a position of

maximal lung inflation. When it is obtained from flow – volume curve data, it is expressed

at BTPS in liters/sec. The defining characteristics of the flow – time curve, in relation to

PEF, are the time taken for flow to rise from 10% of PEF to 90% of PEF, i.e. the rise time

(RT), and the duration that flow is .90% of PEF, called the dwell time (DT). When PEF is

obtained with portable monitoring instruments, it is expressed in liters/min.

Ideally, PEF should be recorded by an instrument that primarily records flow.

Measuring PEF requires an instrument that has a flat frequency response (5%) up to 15

Hz.Although there is evidence of significant frequency content in PEF up to 20 Hz, it is

recommended, at this stage, that manufacturers achieve a goal of recording fidelity up to

15 Hz.The PEF must be measured with an accuracy of 10% or 0.3 liters/sec (20 L/min),

whichever is the greater.

PEF is dependent on effort and lung volume, with subject cooperation being

essential. PEF must be achieved as rapidly as possible and at as high a lung volume as

possible, in order to obtain the maximum value. The subject must be encouraged to blow

as vigorously as possible. The neck should be in a neutral position, not flexed or

extended, and the subject must not cough. A nose clip is not necessary. After the point of

full lung inflation, the subject must deliver the blow without any delay. Hesitating for as

little as 2 s or flexing the neck allows the tracheal visco-elastic properties to relax and

PEF to drop by as much as 10%. Tonguing,spitting or coughing at the start of the blow

may falsely raise the recorded PEF in some devices.In the laboratory, the subject must



perform a minimum of three PEF manoeuvres. When PEF is a self-administered

recording, it is important that the subject has been adequately taught how to perform the

test, when to perform it and what action to take depending on the resting value obtained.

Regular checks of the patient’s PEF technique and meter are an important part of the

follow-up.

2.4 Development of a Prototype Digital Spirometer

(Sensors)

The growing world comes at a price. We have become more exposed to hazardous

elements that prove to be a challenge to the human body. There are developments in the

field of electronics that can provide user friendly, portable and improved spiromety

systems. In the work of Chin-Wann Lin, Di-Ho Wang, and Hao-Chien Wang entitled

“Prototype development of a digital Spirometer”, they studied the development of a

prototype digital spirometer. Specifically, their work discussed design principles,

including sensors that could be used in the development of a portable model. They've

stated that the basic spirometer design falls down into two categories, flow-sensing and

volume-sensing. Yet, for most modern designs, flow-sensing would prove to be practical

not only from developments brought about by advancements in modern electronics, but

because of its compact size compared to volume-sensing models. It is a suitable

component to use in designing portable spirometers. They gave four examples of

transducers that the developer can use in their model: 1. a pneumotachometer for pressure

difference, 2. a hot wire anemometer for any temperature difference across the valve, 3.

turbinometer for revolutions per unit time of a certain propeller of a turbine, 4. ultrasound



for transient time across the lumen. In the design of their prototype, they used a used a

hotwire sensor with an end connected to a Whetstone bridge and then excited with a

constant voltage level without a negative feedback. Their thermal bridge is then

connected to an analog to digital converter (ADC) and a microprocessor to process the

data. Their prototype also included the use of a keyboard, LCD, audio components, 32K

EPROM for the algorithm, 32K SRAM that is used to process the data, and a UART for

serial communication. From the flow-time curve, volume-time curve and the flow-

volume curve gathered, and then the pulmonary parameters that are used in spirometry

(FEV1, FVC, FEV1/FVC) are computed and compared accordingly from the these

curves.

2.5. Bluetooth in Wireless Communication

In 1994, L. M. Ericsson of Sweden just invented the future of wireless

communication. Named after the king of Denmark in 940 A.D., Bluetooth technology

was introduced. Competing with IrDA and HomeRF, Bluetooth took wireless

communication to much greater heights. Improving IrDA’s 1 meter separation for

transmission and its line-of-sight propagation requirements, Bluetooth has 10 meters of

range and can be further increased depending on the strength of the receiver. It does not

require line-of-sight propagation which will be suitable for our thesis, a portable

spirometer. It is clearly a better tool for PC-to-peripheral connection compared to IrDA

for our thesis because the thesis aims to be portable, thus it can and must be located

slightly away from the PC and must not use line-of-sight propagation to give the doctors

and patients flexibility while testing.



With the help of the journal, we will be able to further understand Bluetooth

technology as we aim to implement our thesis using the technology. The journal includes

details about Bluetooth such as the basic configurations, frame formats, hardware and

software implementation and protocols together with the architecture and network

topology of Bluetooth, which is very helpful for our thesis. With the increase of

companies taking part in the Bluetooth Special Interest Group (SIG), the implementation

of our thesis using Bluetooth only makes sense in order to keep in pace with today’s

technology.

The journal also talks about essential components in order to establish a Bluetooth

connection such as devices that will serve as the master and slave, host controller

interface, the establishment of connection of each layer, link manager and how to

disconnect or end the connection. With this information the group will able to have a

grasp of the technology. This part of the thesis is essential as it will be the one to transfer

the data from the spirometer to the computer, which is monitored by the doctor, so proper

knowledge of Bluetooth will be imperative. This journal will be a great help to the group

as they try to learn and understand the different components that comprises their thesis to

be able to properly integrate them.



CHAPTER 3

Theoretical Considerations

3.1 Flow Measurement

3.1.1 Differential Pressure Sensor

Figure 3.1 Inside a differential pressure sensor (MP3V5004DP Datasheet)

Figure 3.2 Differential pressure sensor (MP3V5004DP Datasheet)

A silicon chip acts as the pressure-sensitive element on micromechanical

piezoresistive pressure sensor which is etched on the chip which forms a cavity.

At the high stress points on the membrane atoms that are locally implanted in the

silicon crystal, zones with an altered conductivity are formed which electrically



function as a resistor. In the moment an external pressure is applied, the molecular

structure of the silicon crystal will be deformed when the silicon membrane dents.

In the resistor areas the piezo effect is observed. When the mechanicl crystal

shifts it creates a measurable change in their electric value and if the said resistors

are connected up as a Wheatstone Bridge, when there is an impressed current or

voltage, a differential signal in volts will be generated.

Differential pressure can be defined as the pressure difference between

two distinct points and so, when measuring differential pressure, two pressures

are compared. With most pressure sensors, it is often the case that only one

pressure ratio, namely P1/P2 ≥1 or P1/P2 ≤ 1, can be evaluated and the

measurement of pressure under the said condition is referred to as "differential

pressure measurement".

Differential Pressure sensors can only determine a specific range of

pressure and is only suitable in the pressure range they are relevant. It applies to

most that P1-P2 ≤ Pmax or P2-P1 ≤ Pmax, where Pmax is determined by the

technical conditions and is specified. Two conditions can be observed about

pressure sensors when it reaches a certain pressure, the proof and burst pressure.

The proof pressure is the maximum pressure which may be applied without

causing durable shifts of the electrical parameters of the sensing element while the

burst pressure is the maximum pressure which may be applied without causing

damage to the sensing element or leaks from the housing. These conditions must

be taken into account when the user connects up the pressure to the sensing

element. Overall, pressure can be measured due to the amount of dent the



membrane exerts on the silicon crystal. When there is no dent, there is no pressure

exerted and when the dent gradually increases, the pressure measured also

increases.

3.1.2 Bernoulli’s Equation

In measuring the volumetric flow rate of fluids, one of the most commonly

used methods is differential pressure measurement. By having a constriction

across, a tube would have a change in pressure. This change in pressure can be

translated into flow rate by computation. There are different flow tubes that are

used for different differential pressure measurement systems but they all follow

the Bernoulli equation. Bernoulli’s equation, named after Daniel Bernoulli, states

that an increase in flow speed of a fluid denotes a corresponding decrease in

pressure.

Equation 3.1. Bernoulli’s Equation

Where: h h h

h

h h h h



Since flow rate is constant all throughout the tube, furthermore, the volumetric

flow rate is expressed as, , and , at initial and throat point

respectively, we have

Equation 3.2. Relationship between volumetric flow rate at initial and throat sections

Where is the cross sectional area of the initial section and is the

cross sectional area of the throat section. In order to solve for the constant that is

to be used for the programming of the microcontroller to output the corresponding

volumetric flow rate from the sensor reading, we must first determine Q1 which is

the volumetric flow rate. Simplifying Bernoulli’s equation to get Q1 we must first

solve for V1 from Equation 3.1.

Assuming that the altitude is constant in the equation, we can use

equation 3.2 to equation 3.1, we can now isolate to get,

Equation 3.3

By isolating and , we can simplify the equation since .

denotes the fluid density of the fluid in.



Equation 3.4

Equation 3.5

Where the diameter of the initial is section and is the diameter of the throat. With

cancellation of similar terms we get,

Equation 3.6

We now have a value for V1 given the venturi tube diameter at the opening and at

the throat. In determining the volumetric flow rate Q, we can multiply V1 and the

cross sectional area of the corresponding section of the tube.

From this equation, we can now determine the volumetric flow rate needed.



3.1.3 Flow Tubes

The following are the different types of flow tubes that follow

Bernoulli’s Equation. They are described below.

3.1.3.1 Orifice Plate

Figure 3.3 Orifice Plate Diagram

An orifice tube is a type of flow tube that introduces a constriction

to the inner section of the pipe through an element known as an orifice

plate. An orifice plate is a circular plate inserted in the flow tube that has a

hole in the middle. This hole introduces a constriction in the middle which

pushes the fluid flowing to converge. This in turn, increases the fluid

velocity of the fluid with a corresponding decrease in pressure. The

pressure difference is measured before and after the orifice plate.



3.1.3.2 Pitot Tube

Figure 3.4 Pitot Tube Diagram

A Pitot tube is another type of flow tube used for flow rate

measurement. In this flow tube however, instead of an orifice

plate, an impact probe is inserted in the tube. This impact probe is

faced directly to the flow. A pressure difference can be measured

as fluid flows through the probe.

3.1.3.3 Venturi Tube

Figure 3.5 Venturi Tube Diagram

The venturi tube is a flow tube that has a larger pipe

diameter at the ends then gradually constricts in the middle. The



constriction in the middle is known as the throat. As the fluid flows

through the tube and into the converging section, it increases its

velocity as the cross sectional area decreases. This corresponds

also to a drop in pressure from the wider section. A difference in

pressure is obtained across the pressure taps located at the throat

and the initial section. This can be measured by a u-tube or by a

differential pressure sensor.

3.2 Microcontroller Unit

A microcontroller unit (MCU) is a circuitry that involves the use of a

microcontroller that serves as the brain of a system. It has a single chip that contains the

central processor (CPU), non-volatile memory for the program, read-only memory

(ROM) as an example, and volatile memory for the input and output, like random access

memory (RAM). Microcontrollers come in different sizes and architectures that choosing

the right type of microcontroller greatly depends on the application.

Figure 3.6 Basic Microcontroller

Microcontrollers are designed for embedded applications, which is why the group

decide to consider using it for the project. Microcontrollers are commonly used in

automated systems to control the system with respect to all the inputs and outputs. The



MCU is a very critical part of the system because it will send out the necessary

information to the whole system so that it will work the way it should be.

3.2.1 Microcontroller SpecificationsA critical part of selection of microcontrollers is the specification

and computing power that the microcontroller can provide.

Microcontrollers are usually classified according to their arithmetic

registers and index registers. This groups are more commonly known as 8-

, 16-, 18-, 32- bit groups. The cost of each group is also proportional to its

features, capabilities and limitations.

3.2.1.1 Microcontroller Resources

Microcontroller units have an on-chip resource that allows

it to attain higher level of integration and reliability. An on-chip

resource is defined as a block built inside the MCU so that it can

perform different functions that can be used by the microcontroller.

Since these resources are built-in, it increases the overall reliability

of the MCU because external circuitry will be unnecessary to be

able to use the said functions. Popular on-chip resources that are

commonly used are memory devices, which include random access

memory (RAM), read only memory (ROM), erasable

programmable read only memory (EPROM), Electrically Erasable

Programmable Read-Only Memory (EEPROM), and flash

memory, timers, system clock, oscillator, and I/O.



3.3 Bluetooth

Bluetooth is one of the newest networking technology that use a low transmission

power setting, typically 1 milliwatt. Bluetooth technology is ideal for mobile battery

operated devices and systems. Bluetooth can also instantly connect, detect and

communicate to other Bluetooth devices without relying on a user input. Bluetooth

technology primarily relies on two important things; a radio frequency technology that

will allow the communication between two devices, and software with a set of protocols

that will enable and control traffic between two devices in transmitting and receiving data

to each other.

3.3.1 Radio Frequency Properties

The principal transmission system used in Bluetooth technology is low

energy radio waves. The frequency of operation of Bluetooth devices are typically

2.40 GHz to 2.48 GHz, which is a radio frequency reserved for medical, industrial

and scientific devices.

3.3.2 Bluetooth Connection

Bluetooth devices can interact with one or more Bluetooth devices. When

there are only two devices connected with each other, wherein one acts as the

master and the other the slave, the connection made is called point to point. But

when Bluetooth devices connected together where in one acts as a master and the

others act as the slaves, this ad-hoc network is usually called as a Bluetooth

piconet. There can be a maximum of 7 active slaves in a piconet. Bluetooth



devices in a piconet integrate and synchronize their frequency-hopping to keep in

touch with each other. Finally, a scatternet is a group of Bluetooth piconets

interconnected together.

Figure 3.7 Bluetooth Connections: (a)Point to Point (b) Piconet (c) Scatternet

Since every device in a Bluetooth piconet is synchronized in frequency-

hopping there is minimal risk of two Bluetooth piconets interfering with each

other. Piconets also change frequencies 1600 times per second making a collision

between two piconets to last only a fraction of a second.

3.3.3 Bluetooth Power Classes

There are 3 types of power classification when using Bluetooth

technology.

These are the following:

Type Power Level Operating Range

Class 3 Devices 100mW Up to 100 meters

Class 2 Devices 10mW Up to 10 meters

Class 1 Devices 1mW 0.1-10 metersTable 3.1 Bluetooth Power Classes



3.3.4 Bluetooth Interfacing

There are a lot of ways to implement Bluetooth technology in a system.

For our thesis, the group has decided to make use of a Bluetooth module that will

connect with the universal asynchronous receiver/transmitter (UART) pin of the

microcontroller unit. This type of interface will make use of the Bluetooth module

as the bridge to connect the MCU to the computer for data interpretation. The

Bluetooth will incorporate the serial port profile (SPP) that will emulate a serial

cable connection so that it could be interfaced with the UART of the

microcontroller unit.

3.3.4.1 Bluetooth Serial Port Profile

The EGBT 9830 incorporate a Bluetooth Serial Port Profile (SPP)

that allows it to communicate to the PIC16F877a’s serial port module. The

SPP defines how to set-up virtual serial ports on two devices and

connecting them with Bluetooth technology. When the two devices

connect, the Bluetooth units emulate a serial cable using Recommended

Standard 232 (RS-232) control signaling. RS-232 is a common interface

standard for data communications equipment; primarily used on the serial

port of a personal computer. The profile ensures that data transmission can

speed up to 128 kbit/sec. The profile defines the roles of the two devices;

who will take the initiative to connect (Master) and another who will wait

for a connection to be requested (Slave) The whole profile emulates serial

port communication and the figure below will show how it is being

emulated.



Figure 3.8 Figure showing serial port emulation

From the figure, the baseband, Link Management Protocol (LMP)

and Logical Link Control Adaptation Protocol (L2CAP) are the Open

Systems Interconnection (OSI) layer 1 and 2 Bluetooth protocols. Radio

Frequency Communication (RFCOMM) is a Bluetooth adaptation that

provides a transport protocol for serial port.

3.4 TCP/IP

3.4.1 TCP/IP Model

Prior to the development of the 7 OSI Layer, there existed an earlier model

called the Transmission Control Protocol/Internet Protocol (TCP/IP). It is the

basic communication language or protocol of the Internet. The TCP/IP model

involves a set of general design guidelines and implementations of specific

networking protocols to allow communication of computers over a network.



TCP/IP provides an end-to-end connection which specifies the matter at which

data should be formatted, addressed, transmitted, routed and received at the

destination. When setting up a direct access to the Internet, every computer is

provided with a copy of the TCP/IP program. TCP/IP is a two-layer program. The

higher layer, Transmission Control Protocol, handles the encoding or assembling

of a message or file into smaller packets that is sent over the Internet. A receiving

unit, which also has a copy of the TCP/IP program, decodes or disassembles the

message or file to its original form. The lower layer called the Internet Protocol

handles the address of each packet to ensure that the message arrive at its rightful

destination.

TCP/IP uses a client/server model of communication in which a user

(client) requests and is provided a service by another computer (server) in the

network. TCP/IP communication is point-to-point. TCP/IP and the higher-level

applications that use it are collectively said to be "stateless" because each client

request is considered a new request unrelated to any previous one and by stateless

it means that it frees the network paths so that anyone can use it continuously.

Taking note however that the TCP layer is not stateless until all the packets in a

message are received by the requesting client.

TCP/IP is sometimes referred to as the Internet model. It has

four abstraction layers as defined in RFC 1122. Shown below is the TCP/IP’s

corresponding layers used at each hop.





3.4.2 The Link Layer

The Link Layer is practically the scope in networking of the local

connection in which a host is attached. The Link Layer is used to move

packets of two different hosts on the same link between each of their

Internet Layer. It is under this layer that the process of transmitting and

receiving packets can be controlled in the software device driver for the

network card, firmware or specialized chipsets. These perform data link

functions such as adding a frame header to prepare it for transmission over

a physical medium. It is also under this layer that the process of sending

can be chosen whether it would be over a virtual private network or

networking tunnel.

3.4.3 The Internet Layer

The Internet Layer answers the problem about sending packets

across one or more networks. Internetworking requires sending data from

a source network to a specific destination. This process is called routing.

The Internet Protocol has two basic functions. First is the Host Addressing

and Identification and this is accomplished through the use of IP address.

The second function is the Packet Routing which is the basic task of

getting packets of data (datagrams) from a source to a destination by

sending the packets to the next network node (routing) closest to the

destination.



3.4.4 The Transport Layer

The Transport Layer is the one responsible for the end-to-end

message transfer capabilities regardless of underlying network along with

error control, flow control, congestion control, and application addressing

(port numbers). End-to-end messaging or connecting application at the

transport layer can be categorized as either connection-oriented, such as in

Transmission Control Protocol (TCP), or connectionless, such as in User

Datagram Protocol (UDP).

In layman’s term, the transport layer can be thought of as a

transport mechanism such as a vehicle responsible to ensure the safe

arrival of its goods/passengers to the destination. It is practically safe to

say that the Transport Layer is the first stack of the TCP/IP to offer

reliability. Protocols above transport also offer reliability.

3.4.5 The Application Layer

The Application Layer is the higher-level protocol that is

commonly used by most applications for networking communication.

Some examples of the application layer protocols are the File Transfer

Protocol (FTP) and the Simple Mail Transfer Protocol

(SMTP).Application Layer generally treat the transport layer and lower

protocols as “black boxes” which provide a stable network connection

across the device to which it communicates. Transport and lower level



layers are largely unconcerned with the specifics of application layer

protocols.

3.5 Programming Software and Languages

3.5.1 C# Language

Microsoft C# is a new programming language designed for wide range

applications that run on the .NET framework. It is considered as an evolved

version of the Microsoft C and Microsoft C++. It is mostly simple, modern, type

safe, and object oriented. C# codes are compiled as managed codes which benefits

from the services offered by common language runtime. It is designed to work as

an integration of the capabilities of both Microsoft C++ and the Visual Basic

along with Java programs. The services available include language operability,

garbage collection, enhanced security, and improved versioning support. The

library for Visual C# programming is the .NET Framework.

3.5.2 Microsoft SQL 2008

Figure 3.11 Microsoft SQL server 2008

Structured Query Language (SQL) is a computer language used as

database management for relational database management system (RDBMS). Its

scope comprises of data insert, query, update and delete, schema creation and



modification and data access control. It is practically used to manipulate database

information with the help of programming languages such as Visual C# by

establishing connection strings to the SQL Manager.

3.5.3 ASP.NET Programming

Figure 3.12 ASP.Net

ASP.NET is a web application tool developed by Microsoft to allow users

to develop dynamic web sites, web applications, and web services. ASP.NET is

the next generation of ASP. However, it is a misnomer to say that ASP.NET is the

upgraded version of ASP. ASP.NET is a completely new technology for server-

side scripting. ASP.NET is a part of the Microsoft .NET Framework and it is a

powerful scripting tool for creating dynamic and interactive pages. It is built on

the Common Language Runtime (CLR) which allows programmers to write

ASP.NET code using any supported .NET Language.

3.5.4 Internet Information Services (IIS)

IIS, formerly called Internet Information Server, is a web server

application created by Microsoft to support web publishing. IIS is a group of

Internet servers (including a Web or Hypertext Transfer Protocol server and File

Transfer Protocol server) with additional capabilities for Microsoft's Windows

NT and Windows 2000 Server operating systems. It is a Windows component that



comes along with Windows Operating System. IIS allows web pages developed to

be published either on local area network, wide area network or internet based

network. This web application is accomplished by creating virtual directories

wherein requested pages by users are directed to that virtual directory.

3.5.5 Browser

A browser is a web application used for retrieving, presenting and

traversing information resources on the World Wide Web. A protocol is used to

establish an understanding between the requesting party and the browser. This

protocol is called the Hyper Text Transfer Protocol (HTTP).

A browser understands HyperText Markup Language (HTML) codes only.

Usually, upon typing the URL in the browser, we easily see the webpage that we

wish to view. However, behind that, a lot of processes occur before we are able

to view the page. When a URL, also called a domain name, is typed in the

browser, the domain name is analyzed in the Domain Name System. The Domain

Name System (DNS) handles all the public IP addresses and the corresponding

domain names of each and every website available in the web. When the DNS

finds the corresponding IP address, it returns the value to the browser and the

browser directs a request to the web server with the IP address. The web server

processes the request then sends the requested page back to the browser in HTML

format. Finally, the received page is then displayed to the user.



3.6 Human Lungs

Figure 3.13 Anatomy of the human lungs

The lungs are responsible for breathing. It is a machine in our body that supplies

oxygen to the blood that transports it to all of the cells of the body for sustaining the

processes each of them are performing. It moves out CO2 out of the lungs, which is the

byproduct of the metabolic process performed by the cells. The lungs under normal

conditions of rest normally breathe in 500ml of air per inhalation. On the average, a

person takes 12 breathes per minute. This translates to 6L/min during one breathing

cycle.

3.7 Peak Expiratory Flow

Peak Expiratory Flow or PEF is defined as the maximum forced expiration made

after maximal lung inhalation. It should be performed without hesitation to achieve the

best possible maneuver. The patient should be at rest. The test is usually performed

sitting upright or standing up straight. Either way the patient should be as relaxed as



possible to be able to perform his best exhalation through the PEF device. It is expressed

in terms of volumetric flow rate (Liters/min). PEF is ideally recorded by a device that

determines flow rate. It is a lung function exam usually taken at home to monitor the

patient’s response to medication and lung condition.

3.7.1 Test Procedure

The accuracy of the test is entirely dependent on the patient’s

understanding of the procedure. After full lung inhalation, the subject must

be able to blow out without any delay or obstruction to the PEF device.

Variables such as improper lip fitting, incorrect posture, and hesitation can

render the test null and therefore should be repeated again. Hesitating for a

moment, even for as little as 2 seconds, or flexing the neck may affect the

results. Tonguing, spitting or coughing at the start of expiration can falsely

raise the value of the PEF. It is important that the subject is briefed

accordingly as to the conditions of peak flow measurements. Before home

use, the doctor shall instruct and patient regarding the proper measures

taken before the test. Commonly, the PEF test is repeated 3 times during a

trial. The acceptable values are noted during tests and the highest value is

recorded on the PEF monitoring sheet provided by the doctor. The patient

writes down the time and day that they took the test. They chart also

contains zones. These zones are namely green, yellow and red. These

zones indicate the performance of the patient’s tests, usually based on the

best reading. Green is 100%-80% of the best reading. Yellow is 80%-50%

of the best reading. And lastly, red is 50% or below of the best reading.



3.7.2 Peak Flow Meter Device

Figure 3.14 Mechanical Peak Flow Meter Device

The typical peak flow meter device is a mechanical device that has

a spring or a thin metal plate that pushes the cursor as it receives the air

coming from the patient’s lungs. This cursor moves along the graduations.

On the average, these devices measure from 50 to 700 L/min. PEF devices

can be used at the doctor’s office or at home depending on the treatment

plan prescribed by the doctor. In most cases, is device is used at home for

lung condition monitoring. It comes with a PEF test chart that is used to

record the value, time and date of each PEF test. This chart is then brought

back to the doctor to be reviewed.



Chapter 4

Design Considerations

4.1 General System Block Diagram

The figure below is the general system block diagram:

Figure 4.1 General Block Diagram of the System

This figure gives a description of the whole system, including the different

components it contains. The Peak Flow Meter System includes a flow sensing circuit that

is responsible for obtaining the Peak Expiratory Flow. The data is processed to the MCU

and it performs the necessary operations that translate the signal coming from the sensor

into a digital output that can be displayed to the LCD. The Bluetooth module is

responsible for sending the data to the computer. In the computer, a GUI handles the data

coming from the Bluetooth module. Two key GUIs would be needed for the whole



system; one would be the GUI for the computer receiving the data directly from the

device and the other for the computer handling the server. The third part would be the

Website. The website allows the doctor to view the test results obtained by the device

remotely. The website obtains the data from the server.

4.2 Flow Measurement

Here is the block diagram of the Flow Sensing Block:

Figure 4.2 Block Diagram of the Flow Measurement Block

4.2.1Differential Pressure Sensor

Pressure Sensor Schematic Diagram and Board Design:

Figure 4.3 Sensor Circuit for MP3V5004DP



For our pressure sensor, the group used the MP3V5004DP Differential

pressure sensor. It has a pressure rating of 3.9KPa and has an output of 0.6 to 3V.

The output voltage of the sensor responds to variations in pressure difference

introduced in it. It has a wide range of applications, moslty revolving around

microcontroller and microprocessor based systems since its output pin can be

directly coupled to the ADC input of the MCU. The sensor also has compensation

for temperature variations within it operating temperature (0 to 85 degrees

celsius) . This is important since changes in temperature is directly proportional to

the pressure introduced to the sensor. For minimizing the effects of noise in the

silicon pressure sensor, an effective general approach would be a low pass filter.

The low pass filter with a cutoff frequency of 650 Hz is recommended for the

system. A 470 pF ceramic capacitor have been determined to give the best results

since it provides a decent output to the ADC of the microcontroller. From the

noise point of view, adequate decoupling is also important. A 1.0 mF ceramic

capacitor in parallel with a 0.01 mF ceramic capacitor works well for this

purpose. Also, with respect to noise, it is preferable to use a linear regulator rather

than a relatively noisier dc regulated power supply 5 volt output.

Figure 4.4 Differential Pressure Sensor PCB (MP3V5004DP)



4.2.2 Venturi Tube

In the group’s thesis, the concept of differential pressure measurement was

used. This was chosen since it provides higher accuracy as compared to other

flow measurement techniques. This is done by measuring the pressure difference

across a tube that in which fluids flow in. This method employs different types of

tubes as discussed in the previous chapter.

Considering the application however, the proponents used Venturi Tube.

This device is a hollow tube that is wider at the ends then gradually constricts in

the middle. As the fluid flows inside the tube, it would gain velocity as the cross

sectional area of the tube decreases as it reaches the middle. An increase in the

velocity is accompanied by a change in pressure. This pressure difference

translates into volumetric flow rate through the use of Bernoulli’s equation. The

group used a Venturi Tube since it has has no mechanical or movable parts inside.

This would make the cleaning of the device to be easier as compared to the other

flow tubes. It also offers minimum head loss, as compared to other flow tubes

using differential pressure flow measurement. Also, they can be very accurate. A

well calibrated tube can measure with high accuracy, having readings within

5%.



Figure 4.5 Venturi Tube of the Prototype

The dimensions of the device are given below:

D1 (initial Diameter) = 27mm

D2 (throat Diameter) = 13.5mm

The opening of the tube was chosen to conform to standard peak flow

meter mouth pieces. The throat diameter of the device, which is 13.5mm, was

used to follow the specifications of a Venturi Tube. The common ratio of the

throat diameter and Inner diameter is given below:

The converging and diverging angles of the device are 21º and 15 º

respectively. These are optimal values for the said sections since they make the

device less expensive by making the tube generally shorter. Solving for the

constant to be used in the programming of the Microcontroller, we have to use the

equation in the previous chapter regarding volumetric flow rate and substitute the

dimensions of the device.



Recall that,

And,

We now substitute the values which are 27mm and 13.5mm, representing the D1,

and D2 respectively. In order to get the constant for the program of the MCU,

assume a pressure difference of 1PA (P1-P2 = 1) and substitute:

Equation. 4.1

To solve for Q1 (Volumetric Flow Rate) (Eq.3. 3)

Converting to L/min



x 0.97 (Cd)

A dispersion coefficient Cd is assumed to be .97 for smaller tubes as

provided for Venturi tube specifications.

Finally we get,

For a pressure difference of 1Pa, the group obtained a value

of .

Equation 4.2

By relating the constant derived from equation 4.2, which is 10.77592772,

to the voltage level per pressure difference of the sensor, we can now output the

value of the volumetric flow rate. Using the equation from the sensor’s datasheet,

we can determine the corresponding pressure difference per voltage output. Let P

be the pressure difference,

Equation 4.3

But

Equation 4.4

Simplifying 4.3 we get

Equation 4.5



Isolating P we get,

Equation 4.6

Equation 4.7

Dividing both sides by 0.2 to isolate P we get,

Equation 4.8

By using the value of P, solved from determining the flow sensing

circuit’s Vout and Vs, the value of Q can now be outputted.

4.3 Microcontroller Unit

The microcontroller unit (MCU) serves as the intelligence of the whole system. It

processes all inputs and produce corresponding outputs according to the specification

made by the user, which is the program burned to the microcontroller. Selection of proper

microcontroller is imperative for the success of the system. Several factors must be

considered such price, availability, manufacturer support, development tools and

specifications. It is a must to be able to determine the needs of the system before

selecting a microcontroller. For the system, the group selected to PIC16F877a



Microcontroller because its features fits the system. The pin diagram of PIC16F877a is

show in the figure below.

Figure 4.6 Microcontroller Pin Diagram from Datasheet

4.3.1 PIC16F877a Specifications

It is important to understand the specifications of PIC16F877a to be able

to see if it fits perfectly to the system. Coming from the datasheet, PIC16F877a

has the following specifications that can be used for the system: 8K x 14 words of

Flash Program memory, 368 x 8 bytes of Data Memory (RAM), Synchronous

Serial Port (SSP) with SPI™ (Master Mode) and I2C™ (Master/Slave), Universal

Synchronous Asynchronous Receiver Transmitter with 9-bit address detection,

and up to 8-bit Analog to Digital converter (ADC).



4.3.1.1 Universal Synchronous Asynchronous

Receiver Transmitter

PIC16F877a has two serial I/O modules, one of which is the

USART module. The USART module of PIC16F877a can be configured

as a full-duplex asynchronous system or as a half-duplex synchronous

system that can communicate with peripheral devices such as a personal

computer.

4.3.1.2 Analog to Digital Converter

PIC16F877a analog to digital conversion results in a corresponding

10-bit digital number and has the ability to be able to operate even when

the device is in sleep mode. The A/D converter is very critical as it will

convert the pressure reading, in terms of analog voltage, of the sensor and

then it will proceed to different arithmetic process in order to compute for

the correct value.

4.3.2 Microcontroller Algorithm

For the system to run properly, a proper algorithm must be implemented.

The flowchart below summarizes the algorithm that can be implemented to the

microcontroller in order process and compute for the parameters needed by the

system. One of the advantages of using PIC16F877a, which is manufactured by

Microchip Technology Inc., is the abundance of compilers and different

programming languages available that can be used in order to program it. For the



system, the group incorporated the program in the C language and used MikroC

as the compiler. Below is a summary of different commands that can be used for

the system that can be found in the help of MikroC.

Command Name Type Description

Lcd_Init Void

Initializes LCD to a specific port with default

pin settings

Lcd_Cmd Void

Sends command to LCD. Predefined LCD

commands can be found in the MikroC Help.

Usart_Init Void

Initializes USART module with the desired

baud rate.

Usart_Write Void Sends a data byte via USART module

Usart_Data_Ready Unsigned short

A function used to test if data in the receive

buffer is ready for reading.

Adc_Read Unsigned

Initializes PIC’s internal Analog to Digital

Converter module to work with RC clock.

Table 4.1 Key commands for the MCU algorithm



Figure 4.7 Microcontroller Flow Process Chart

YES

NO

START

Blow in the tube

Compute for the flow

rate and initialize

variables

NO

YES

Is the flowrate greater

than

previous

Display result in LCD

and initialize Bluetooth

Is

Bluetooth

module

ready?

Send Data to PC via

Bluetooth

END



4.3.3 Microcontroller Interfacing

4.3.3.1 LCD

The device used a 2x16 SC162A3 LCD. Since the group is using

PIC16F877A, the group has adapted the schematic diagram for LCD

configuration as provided by MikroC, which serves as the compiler of the

MCU. The LCD will be used to display the results, informing the user of

his Peak Expiratory Flow. From the schematic diagram we made a board

design.

Figure 4.8 MikroC LCD interfacing configuration,



Figure 4.9 LCD Schematic diagram

Figure 4.10 Microcontroller PCB with LCD



4.3.3.2 Bluetooth

The system involves the transmission of data wirelessly through

Bluetooth technology. The group decided to use the EGBT 9830

Bluetooth module due to its availability. The Bluetooth module allows the

microcontroller unit to send the data obtained from the test wirelessly

using the Bluetooth Serial Port Profile (SPP) and be connected directly to

the Universal Synchronous/Asynchronous Receiver/Transmitter (USART)

port of a microcontroller. The product manual provided by the supplier has

given the group the basic design and pin configuration to interface the

module to the MCU. The interfacing of the EGBT 9830 module to the

microcontroller unit is shown below:

Figure 4.11 EGBT

9830

Figure 4.12 Bluetooth Module PCB



4.3.3.2.1 Bluetooth Initialization

The module is initialized by default at baud rate of 9600, 8

data bit, 1 stop bit and no parity. In order to use the Bluetooth

module, the device must be initialized with correct Bluetooth

address by sending 13 bytes to the module before it becomes

operational. The sequence of the bytes is as follows:

02 52 27 06 00 7F XX XX XX XX XX XX 03

The six “XX” bytes represent the address that you will

assign to the module. After initializing a valid Bluetooth address,

the Bluetooth core of the module needs to be activated to be able

for the module be operational. The following 7 bytes must be sent:

02 52 66 00 00 B8 03

All the bytes are sent by the microcontroller after it has

been physically connected and powered up. The flowchart below

summarizes the whole design in order to use the module.



Figure 4.13 Bluetooth Flow Process Chart

NO

YES

NO

YES

START

Initialize

Bluetooth

Address: Send

13 bytes

Is the

address

valid?

Start Bluetooth

Core: Send 7

bytes

Is the

core

ready?

END



4.4 Graphic User Interface

The Graphical User Interface (GUI) shall be constructed using Microsoft Visual

Studio C# Language. C# Language was used in this thesis to take advantage of its

networking capabilities along with its ability to use both Microsoft C++ programming

and Visual Basic. The data from the device is sent to the GUI (called the Chat Client) and

the GUI shall act as a path in which data could be sent to the server over Internet through

TCP/IP. The server computer is another GUI (called the Chat Server) that monitors for

connections and online users. The server acts as a storage for the database of all the

patients and doctor. The layout and design of the 2 GUIs are shown below:

Figure 4.14 Patient Login Interface



Figure 4.15 Patient Sample Data Interface

Figure 4.16 Chat Server Interface



Figure 4.17 Chat Server Interface detects a client to be online

Figure 4.18 Chat Server Interface detects a client has logout.

4.4.1 Chat Client

Field Name/Method Name Type Description

InitializeConnection VoidInitialize parameters to enable the user to

connect to the server

CloseConnection Void

Disconnects the thread connection of the

user from the server.

ReceiveMessages Void

Called for every time a new message is

received from the thread.

SetsUpdate Void

Updates the set number if changes occur

in the database.



FillData VoidFills a table with PEF values that serves

as the data source for plotting.

Registration VoidA method called to inform user that

registration was unsuccessful.

Complete Void

A method called to inform user that

registration was successful.

UpdateLog Void

Called when the status textbox needs to

be updated with new message.

PatientData VoidCalled to enable user interface when

login is successful.

RegistrationDetails Void

Called to fill the combo box with

registered doctors’ names in the database.

Append Void

Called to append username and password

to be sent to the server for checking.

AppendRegister Void

Called to append registration details to be

added to the server database

InitializeLog VoidInitializes sending of username and

password to the server to check validity.

CloseLog Void

Disconnects the user from the server and

disables patient interface.

WrongData Void

Called when the input username or

password is not valid.

PEFData VoidSets the value of the label box equal to

the obtained PEF value.

Table 4.2 Variables and methods used in the lines of codes of the Chat Client

4.4.2 Chat Server


StatusChangedEventArgs ClassHandles the method that updates the server

text box when changes occur.

ChatServer Class

Class that handles the methods for database

manipulation.

AddUser Void

Adds a user to the database when

registration requirements are met.

AddUsertoDoctorsComment VoidAdds the username of the user to the Doctors

Comments database.

AddUsertoPEFData Void

Adds the username of the user to the

PEFData database.

RetrievedataUser String

Retrieves the data of the user when login is

successful.

RetrieveComment StringRetrieves the comments of the doctor for the

specific user.



RetrievePEF StringRetrieves the PEF values of the user for the

specific set number.

RetrieveDoctors StringRetrieves the names of the doctors registered

in the database.

RetrieveSets String

Retrieves the number of set as listed in the

database for the specific user

UpdatePEF String

Updates the PEF data of the patient when

new value is received by the server

OnStatusChanged VoidMethod that changes the status text box of

the server when changes occur.

StartListening Void

Method that opens a thread to listen for

connection requests.

KeepListening Void

Method that continuously allows the server

to listen for connection.

Connection Class

Class which handles the method that

receives the requests

Connection VoidMethod which opens a thread for each

requesting user

CloseConnection Void

Closes the thread, stream sender and stream

receiver when the user disconnects.

AcceptClient Void

Method which handles all received messages

from the user.

Table 4.3 Variables and methods used in the lines of codes of the Chat Server

4.4.3 Database

Database Description

PatientData

Database which stores the

personal information of each

patient registered.

PEFDataDatabase which stores the

PEF values of each specific

patient.

DoctorsComments

Database which stores

comments made by the

doctor over the website.

Table 4.4 Database used in the Chat Server code



Figure 4.19 Flow Process Chart of the GUI



4.5 Website

Figure 4.20 General Process Flow of the Website



The website is constructed using ASP.NET programming. Unlike the previous

generation called ASP, ASP.NET allows call functions which lessens the usual tedious

programming. Moreover, ASP.NET supports dynamic and interactive communication

with the server. Since the thesis has login functions and data retrieval, it needs to be

constructed dynamically. SQL statements are again used to retrieve the data from the

database. The server used for the website’s server is the same server used by the patients

to allow consistency with the data. This website shall only be accessible within a Local

Area Network. Shown below is the simplified structure of the system.

Figure 4.21 Structure of the System


DoctorsName String Retrieves the doctor’s information in theDoctorsData database.

Login Void

Retrieves the information of those patients

registered to the user

User StringRetrieves the username of the patients

registered to the doctor

View Void

Retrieves the information of the selected

patient and displays the plot menu.





Figure 4.22 Voltage Regulator PCB

Figure 4.23 Voltage Regulator

Board Schematic Diagram

4.6.2 Battery

The device is supplied by an 8.6V 2100mAh battery. It is to supply the

Microcontroller, Differential Pressure Sensor, and Bluetooth Module that requires

5V, 3.3V and another 3.3V respectively. When these components are connected

together, they draw 210mA of current. With the current rating of the battery, it

can power up the prototype sufficiently.

Figure 4.24 8.6V 2100mAh Battery



Chapter 5

Data and Results

5.1 System Testing

In the testing setup, the device was tested both in patients and in controlled

air. There are 4 patients with 20 tests each. In testing the device using controlled air,

the group used 4 different pressure readings. The transmission accuracy was likewise

tested by sending 90 varying data points in the Chat Client. Lastly, the theoretical

Bluetooth range for class 2 radios was likewise tested in order to find out the

maximum range at which the device is capable of transmitting data to the computer.

The following tests were done to meet the objectives of this thesis.

Figure 5.1 Mechanical Peak Flow Meter Figure 5.2 Digital Peak Flow Meter

5.1.1 Peak Flow Meter Device (Patient Testing)

5.1.1.1 Objectives

5.1.1.1.1 To use a flow sensing circuit to determine lung air flow.

5.1.1.1.2 To display the test result through the LCD.



5.1.1.1.3 To build the device with an accuracy of 90% as compared

to a Mechanical Peak Flow Meter.

5.1.1.2 Materials

5.1.1.2.1 Digital Peak Flow Meter Device

5.1.1.2.2 Mechanical Peak Flow Meter

5.1.1.3 Procedures

1. Turn on the power supply for the Digital Peak Flow Meter Device.

2. Latch the first push button to turn on the microcontroller.

3. Have the patient hold the Venturi Tube at a horizontal position

perpendicular to him/her.

4. Have the patient stand firm or sit upright and inhale at his/her

maximum breathing capacity.

5. Have the patient empty out the air in his/her lungs in the Venturi

Tube.

6. Record the resulting flow rate as seen in the LCD.

7. Repeat steps 3-6 using the Mechanical Peak Flow Meter.

8. Repeat the procedures to 4 patients.



5.1.1.4 Data and Results

Figure 5.3 LCD with PEF Result

Figure 5.4 Flow Sensing Circuit

5.1.1.4.1 Patient 1

Trial Flow Rate

(Mechanical) L/min

Flow Rate

(Digital) L/min

%difference Accuracy

1 600 608 1.33333333 98.66667

2 370 358 3.243243243 96.75676

3 690 717 3.913043478 96.08696

4640 677 5.78125

94.218755 670 621 7.313432836 92.68657

6 680 694 2.058823529 97.94118

7 660 656 0.606060606 99.39394

8 690 748 8.405797101 91.5942

9 550 578 5.0909090901 94.90909

10 690 694 0.579710145 99.42029

11 630 662 5.079365079 94.92063



12 650 652 0.307692308 99.69231

13 630 623 1.111111111 98.88889

14 670 728 8.656716418 91.34328

15 690 753 9.130434783 90.86957

16 620 675.8 9 91

17 660 720 9.090909091 90.9090918 650 703 8.153846154 91.84615

19 690 755 9.420289855 90.57971

20 670 690 2.985074627 97.01493

Table 5.1 PEF Results for Patient 1

5.1.1.4.2 Patient 2

Trial Flow Rate

(Mechanical) L/min

Flow Rate

(Digital) L/min


1 550 588 6.909090909 93.090912 650 612.19 5.816923077 94.18308

3 570 563 1.228070175 98.77193

4 510 503 1.37254902 98.62745

5 520 524.45 0.855769231 99.14423

6 450 485 7.777777778 92.22222

7 640 605 5.46875 94.53125

8 610 605 0.819672131 99.18033

9 430 402 6.511627907 93.48837

10 610 671 10 90

11 620 653 5.322580645 94.67742

12 690 727 5.362318841 94.63768

13 490 523.9 6.918367347 93.08163

14 510 469.7 7.901960784 92.09804

15 550 580 5.454545455 94.54545

16 530 554 4.528301887 95.4717

17 520 497 4.423076923 95.57692

18 570 601 5.438596491 94.5614

19 690 755 1.951219512 98.04878

20 540 563 4.259259259 95.74074




5.1.1.4.3 Patient 3

Trial Flow Rate

(Mechanical) L/min

Flow Rate

(Digital) L/min


1 400 396.23 0.9425 99.0575

2 370 403 8.918918919 91.081083 370 341 7.837837838 92.16216

4 490 537 9.591836735 90.40816

5 410 433 5.609756098 94.39024

6 370 402 8.648648649 91.35135

7 390 394 1.025641026 98.97436

8 386 370 4.14507772 95.85492

9 440 400 9.090909091 90.90909

10 440 423 3.863636364 96.13636

11 360 380 5.555555556 94.44444

12 380 412 8.421052632 91.57895

13 360 328 8.888888889 91.11111

14 460 502 9.130434783 90.86957

15 440 423 3.863636364 96.13636

16 410 444 8.292682927 91.70732

17 390 417 6.923076923 93.07692

18 360 385 6.944444444 93.05556

19 370 383 3.513513514 96.48646

20 390 424 8.7179 91.28205


5.1.1.4.4 Patient 4

Trial Flow Rate

(Mechanical) L/min

Flow Rate

(Digital) L/min


1 650 607 6.615384615 93.38462

2 700 768 9.714285714 90.28571

3 650 633 2.615384615 97.38462

4 670 676 0.895522388 99.10448

5 640 601 6.09375 93.90625

6 630 626 0.634920635 99.36508

7 650 682 4.923076923 95.076928 660 689 4.393939394 95.60606

9 690 758 9.855072464 90.14493

10 680 702 3.235294118 96.76471

11 680 721 6.029411765 93.97059

12 670 657 1.940298507 98.0597

13 690 667 3.333333333 96.66667

14 690 754 9.275362319 90.72464



15 680 644 5.294117646 94.70588

16 670 697 4.029850746 95.97015

17 690 747 8.260869565 91.73913

18 660 644 2.424242424 97.57576

19 670 720 7.462686567 92.53731

20 660 636 3.636363636 96.36364Table 5.4 PEF Results for Patient 4

5.1.2 Peak Flow Meter Device (Controlled Air Testing)

5.1.2.1 Objectives

5.1.2.1.1 To test the Peak Flow Meter Device using controlled air.

5.1.2.1.2 To determine the accuracy of the device under controlled air

condition.

5.1.2.2 Materials

5.1.2.2.1 Digital Peak Flow Meter

5.1.2.2.2 Mechanical Peak Flow Meter

5.1.2.3 Procedures

1. Turn on the power supply for the Digital Peak Flow Meter Device.

2. Latch the first push button to turn on the microcontroller.

3. Set the value of the pressurize container to an initial value.

4. Place the nozzle at the center of the Venturi Tube’s entrance.

5. Record the flow rate as shown in the LCD.

6. Repeat steps 3-5 using the Mechanical Peak Flow Meter.

7. Repeat the procedures to 4 different pressures.




5.1.2.4.1 Pressure of 10 psi

Trial Flow Rate (Mechanical) L/min Flow Rate (Digital) L/min

1 185 1862 200 195

3 190 201.92

4 195 157.706

5 190 186.16

6 185 172.52

7 190 192.62

8 190 165.27

9 185 168.94

10 190 157

11 190 182.85

12 185 172.52

13 200 172.52

14 185 172.52

15 200 157.7

16 200 198.87

17 200 176.03

18 190 179.47

19 200 168.94

20 200 186.16

Average 192.5 177.5358

Table 5.5 PEF Results for Pressure of 10 psi

%22639.92%7736104.7%100%%100

%7736104.71005.192

5358.1775.192100%

difference Accuracy

l Theoretica

al Experiment l Theoreticadifference


Trial Flow Rate (Mechanical) L/min Flow Rate (Digital) L/min1 350 343

2 340 375

3 350 343

4 340 408

5 330 377

6 345 383



7 345 383

8 340 388

9 330 323

10 340 360

11 360 336

12 320 37713 350 326

14 350 358

15 350 365

16 350 367

17 340 323

18 355 382

19 345 350

20 335 365

Average 343.25 361.6

Table 5.6 PEF Results for Pressure of 20 psi.

%65404.94%345957757.5%100%%100

%345957757.510035.343

6.36135.343100%

difference Accuracy

l Theoretica



Trial Flow Rate (Mechanical) L/min Flow Rate (Digital) L/min1 400 415

2 450 397

3 430 365

4 460 373

5 430 396

6 430 367

7 410 455

8 450 417

9 440 430

10 400 415

11 440 40012 400 425

13 460 385

14 440 445

15 470 408

16 450 440

17 440 380



18 460 412

19 500 425

20 470 409

Average 441.5 407.95

Table 5.7 PEF Results for Pressure of 30 psi

%04784.98%952161.1%100%%100

%952161.1100509

0635.499509100%

difference Accuracy

l Theoretica



Trial Flow Rate (Mechanical) L/min Flow Rate (Digital) L/min

1 500 461.82

2 550 457.833 530 464.46

4 530 513.26

5 540 522.71

6 500 485.08

7 550 513.26

8 450 504.85

9 460 512.07

10 540 492.59

11 550 445.64

12 520 502.4213 500 474.88

14 440 503.64

15 500 492.59

16 570 530.84

17 450 569.75

18 460 481.28

19 490 534.29

20 550 518.01

Average 509 499.0635

Table 5.8 PEF Results for Pressure of 40 psi.

%40091.92%599093998.7%100%%100

%599093998.71005.441

95.4075.441100%

difference Accuracy

l Theoretica




5.1.3 GUI and Website

5.1.3.1 Objectives

5.1.3.1.1 To program the microcontroller to output flow rate and send

the data to a computer by adapting Bluetooth technology.

5.1.3.1.2 To use a Graphical User Interface (GUI) that would display the

data sent to the computer.

5.1.3.1.3 To develop a website that can be accessed by a doctor to view

the data obtained by the system.

5.1.3.2 Materials

5.1.3.2.1 Laptop

5.1.3.2.2 Bluetooth

5.1.3.2.3 Chat Client

5.1.3.2.4 Chat Server

5.1.3.2.5 Router

5.1.3.3 Procedures

5.1.3.3.1 Graphical User Interface (GUI)

1. Input the IP Address of the web server to connect to.



Figure5.5 GUI: Inputting Server IP

2. Input the registered username and password of the user.

Figure 5.6 GUI: Inputting Username Password



3. If the user is not yet registered, he/she could register by clicking

the register button.

Figure 5.7. GUI: Register Interface

4. Use the control buttons to view the desired operation of the

interface.

Figure 5.8 GUI: Control Buttons



5. Follow the following procedures for reading of data.

a. Establish the connection with the Bluetooth.

Figure 5.9 Icon to connect to Bluetooth Serial Port Function

Figure 5.10 Bluetooth Establishing Serial Port Connection

b. Click the Read Value Details and set it the same as the

value of the Bluetooth’s COM Port.



Figure 5.11 GUI: Setting Bluetooth COM Port

c. Make sure that the patient has already taken the test

before clicking the Read button.

d. Wait for at least 5 seconds after the test before clicking

the Read button.

e. Click the Update button to add the data in the user’s

database.

6. Logout the account after use to avoid wrong data from being

stored in the user’s database.

5.1.3.3.2 Website

1. Join the network of the web server.

2. Access the web server by typing http://(webserverIP) or

http://(webserverName) in the browser.



Figure 5.12 Website: Inputting Web Server Name

3. Input the registered username and password of the doctor.

Figure 5.13 Website: Inputting Username and Password

4. Choose the name of the desired patient information to view.



Figure 5.14 Website: Choosing which Patient Information to view

5. Choose the desired points to plot.

Figure 5.15 Website: Plotting of Data



6. Leaving of comment is optional.

Figure 5.16 Website: Leaving of Doctor’s Comment

7. The Zones are only available for plots with 90 data points.

Figure 5.17 Website: Viewing Zones

8. Logout the account to ensure security.




Figure 5.18. Digital Peak Flow Meter Bluetooth System

Figure 5.19. Intelligence Board of the System.

5.1.3.4.1 Graphical User Interface (Accuracy of Reading)

Trial Device

Reading

Login

Successful

Received

Data

Data

Plotted

Data

Updated

1 364.052 Yes 364.05 Yes Yes

2 383.6865 Yes 383.6865 Yes Yes

3 295.408 Yes 295.40 Yes Yes

4 276.4126 Yes 276.1426 Yes Yes

5 448.3833 Yes 448.3833 Yes Yes6 533.1442 Yes 533.1442 Yes Yes

7 528.5347 Yes 528.53 Yes Yes

8 471.0057 Yes 471.0057 Yes Yes

9 493.8306 Yes 493.8306 Yes Yes

10 332.4328 Yes 332.4328 Yes Yes

11 508.4783 Yes 508.4783 Yes Yes

12 514.4583 Yes 514.4583 Yes Yes



13 543.3727 Yes 543.3727 Yes Yes

14 295.408 Yes 295.408 Yes Yes

15 442.8924 Yes 442.8924 Yes Yes

16 291.237 Yes 291.237 Yes Yes

17 332.4328 Yes 332.4328 Yes Yes


20 451.1036 Yes 451.1036 Yes Yes

21 375.6302 Yes 375.6302 Yes Yes

22 313.4196 Yes 313.4 Yes Yes

23 539.9847 Yes 539.9847 Yes Yes

24 264.8348 Yes 264.8348 Yes Yes

25 291.237 Yes 291.237 Yes Yes

26 269.4149 Yes 269.4149 Yes Yes

27 490.1002 Yes 490.1002 Yes Yes


30 295.408 Yes 295.408 Yes Yes

31 440.1213 Yes 440.1 Yes Yes

32 337.9082 Yes 337.9082 Yes Yes

33 417.2906 Yes 417.2906 Yes Yes

34 317.3703 Yes 317.3103 Yes Yes

35 402.364 Yes 402.3 Yes Yes

36 440.1213 Yes 440.1213 Yes Yes

37 415.822 Yes 415.822 Yes Yes

38 435.9316 Yes 435.9316 Yes Yes


41 408.4001 Yes 408.4 Yes Yes

42 405.3934 Yes 405.3934 Yes Yes

43 373.9981 Yes 373.9981 Yes Yes

44 409.8953 Yes 409.89 Yes Yes

45 467.0931 Yes 467.09 Yes Yes

46 482.5531 Yes 482.55 Yes Yes

47 369.0586 Yes 369.0 Yes Yes

48 276.1426 Yes 276.1426 Yes Yes

49 255.4283 Yes 255 Yes Yes50 299.5209 Yes 299.5209 Yes Yes

51 350.3515 Yes 350.3515 Yes Yes

52 428.8579 Yes 428.8579 Yes Yes

53 502.427 Yes 502.427 Yes Yes

54 352.0932 Yes 352.0932 Yes Yes

55 370.7124 Yes 370.7 Yes Yes

56 474.886 Yes 474.886 Yes Yes



57 492.592 Yes 492.5 Yes Yes

58 544.4978 Yes 544.4 Yes Yes

59 350.3515 Yes 350.35 Yes Yes

60 456.4956 Yes 456.495 Yes Yes

61 449.74 Yes 449.74 Yes Yes


64 552.3057 Yes 552.3057 Yes Yes

65 481.2837 Yes 481.2837 Yes Yes

66 552.3057 Yes 552.3057 Yes Yes

67 386.8621 Yes 386.8621 Yes Yes

68 418.754 Yes 418.754 Yes Yes

69 438.7292 Yes 438.7292 Yes Yes

70 460.4983 Yes 460.498 Yes Yes

71 764.9926 Yes 764.992 Yes Yes


74 415.822 Yes 415.822 Yes Yes

75 534.2904 Yes 534.2904 Yes Yes

76 601.0995 Yes 601.099 Yes Yes

77 534.2904 Yes 534.290 Yes Yes

78 468.401 Yes 468.401 Yes Yes

79 529.6908 Yes 529.6908 Yes Yes

80 468.401 Yes 468.401 Yes Yes

81 607.1749 Yes 607.1749 Yes Yes

82 305.5866 Yes 305.5866 Yes Yes


85 341.5097 Yes 341.5097 Yes Yes

86 478.7349 Yes 478.7349 Yes Yes

87 543.3727 Yes 543.37 Yes Yes

88 341.5097 Yes 341.5097 Yes Yes

89 390.0118 Yes 390.0118 Yes Yes

90 447.0169 Yes 447.016 Yes Yes

Table 5.9 GUI: Accuracy of Reading



Figure 5.20. Website resulting graph after 25 tests

Figure 5.21 GUI resulting Graph after 25 tests



Figure 5.22 Website resulting graph after 50 tests.

Figure 5.23. GUI resulting graph after 50 tests





Figure 5.26. Website resulting Zones after 90 tests

Figure 5.27. GUI resulting Zones after 90 tests





5.1.4.3 Procedures

1. Using the footsteps method, count how many steps are covered for a

certain distance (e.g. 6 steps/ 3 meters). Perform the method for at

least 3 times then take the average. Use this as a reference to measure

distance when performing the test.

2. Power up the Peak Flow Meter Device.

3. Run the Bluetooth application in the Laptop.

4. See if the Bluetooth icon for the Peak Flow Meter Device is shown in

the screen as devices available within the area.

Figure 5.28 Digital Peak Flow Meter Bluetooth Icon

5. If the device is visible, check whether transmission is possible then

increase the distance between the Laptop and the device by a meter

and reset the Bluetooth. Otherwise, stop the test.

6. Repeat Steps 2-5.




5.1.4.4.1 Footstep Method

Trial Number of Steps

1 62 7

3 6

Average 6.33333 ≈ 6

Table 5.11 Average number of steps for every 3 meters

5.1.4.4.1.1 Length of the measuring tape = 3 meters

5.1.4.4.1.2 Steps covered within the length of the measuring tape = 6

5.1.4.4.1.3 meter stepsmeters

stepsmeter Steps /2

3

6/

5.1.4.4.2 Bluetooth Visibility

5.1.4.4.2.1 Theoretical Bluetooth Range for Class 2 radios = 10 meters

Table 5.12. Bluetooth Visibility and Transmission Range

Distance (m) Bluetooth Visibility Transmission Successful

1 Yes Yes

2 Yes Yes3 Yes Yes

4 Yes Yes

5 Yes Yes

6 Yes Yes

7 Yes Yes

8 Yes Yes

9 Yes Yes

10 Yes Yes

11 Yes No



CHAPTER 6

Conclusion and Recommendation

6.1 Conclusion

In reference to the data and results obtained from the testing done on the device

and under the given time frame, the system’s performance met the objectives made

during the early stages of the study. The group was able to use a flow sensing circuit that

measures Peak Expiratory Flow or PEF through the use of differential pressure

measurement. The flow measurements made with the venturi tube, together with the

differential pressure sensor, was able to match the mechanical peak flow meter used

commercially with an accuracy of 90%. The device was able to display the results done

during the tests through the LCD. It was also able to transmit the data wirelessly from the

device to the computer by adapting Bluetooth technology.

A critical part with the development of the thesis was the consultations made to

health care professionals regarding the lung function testing procedures and parameters.

Note that the testing of the PEF values was consulted with a doctor to get the results that

would satisfy the objectives of the study. This gave light to the areas of the system that

needed medical expertise, such as the GUI and Website Layout. For the venturi tube,

consultations made to a mechanical engineer proved to be vital since they gave the

proponents knowledge on the theories regarding flow measurement, specifically

differential pressure flow measurement.





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[13] (Cooney, Biomedical Engineering Principles, 1976)

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Microcontroller-Based Digital Peak Flow Meter System