Modeling an Enhanced e- voting system

7/30/2019 Modeling an Enhanced e- voting system

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MODELING AN ENHANCED E-VOTING SYSTEM WITH REALTIME DATA COLLATION

BY

EGUONO, EGUONO E.

2009112000

A PROJECT REPORT SUBMITTED TO THE DEPARTMENT OFELECTRICAL/ELECTRONICS ENGINEERING,

ANAMBRA STATE UNIVERSITY OF SCIENCE ANDTECHNOLOGY, ULI

IN PARTIAL FULFILLMENT OF THE REQUIREMENT FORTHE AWARD OF MASTERS DEGREE IN ELECTRICAL

ENGINEERING

SUPERVISOR

DR. P.I. OKWU

DECEMBER, 2013


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DECLARATION

I hereby declare that this report was written by me and it is a

record of my own research. It has not been presented before in

any previous application for a Masters Degree. Authors whose

works have been referred to and reference made to published

literature have been duly acknowledged.

_________________________ ___________________

EGUONO, EGUONO EGUONO Date

Student

Above declaration is confirmed

____________________ _____________________

DR.P.I. OKWU Date

Project Supervisor


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CERTIFICATION

This project titled: MODELING AN ENHANCED E-VOTINGSYSTEM WITH REAL TIME DATA COLLATION BY EGUONOEGUONO EGUONO meets the regulations governing the awardof Masters Degree in Electrical Engineering at Anambra StateUniversity of Science and Technology, Uli and is approved forits contribution to knowledge and literature presentation.

________________________ ____________________DR. P.I. OKWU DateProject supervisor

_____________________ _____________________PROF. S.S.S. OKEKE DateHead of Department

_____________________ ___________________External Examiner Date

This is to certify that the thesis has been examined and

approved for the award of the degree of masters in

Telecommunication Engineering (M.Eng).


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_____________________ ___________________External Examiner Date

_____________________ _____________________Supervisor Date

_____________________ ___________________Head of Department Date

_____________________ _____________________Dean of Faculty of DateEngineering

_____________________ ___________________Dean of School of DatePostgraduate Studies


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DEDICATION

This project report is dedicated to the Almighty God, whose

boundless mercies and love has made this research project a

huge success.

ACKNOWLEDGEMENTS


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I will always owe my unreserved gratitude to my lecturers: Dr.

P.I. Okwu my Project Supervisor, and Programme Coordinator

who worked relentlessly to make me what I have become

today, and for his readiness to help at all time, despite tight

schedules; Mal. Sanni Abdullahi, my HOD, for his painstaking

efforts towards making the Department one of the best. Special

thanks to Engr. Toyin Taiwo, Abebayo B. Michael, and Ishaya

Hope Joshua for their kind support throughout the period of this

Programme.

I must not forget my mother: Mrs. Eunice Anagwu, and Lady,

Florence Ulasi, whose love and belief in me always soured me

to go for higher achievements. I will not forget my brothers ad

sisters: Joy, Ngozi Anagwu, Mr. and Mrs. Chinedu Anagwu, Mr.

and Mrs. Felix Chikodi Reginald, Mr. and Mrs. Chuwkunonso

Anagwu, Pharm, & Mrs. Chimezie Anagwu, Okwudili, Nnamdi,

your prayers have really been fruitful.

To my friends and colleagues: Obinna Obi, Ikechukwu Igboebisi,

Kelechi Mbagwu, Ya u, Mrs. Gloria Ndubueze and others whose

name I may not be able to mention, know that your memories

shall always remain with me.


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TABLE OF CONTENT

Title . . . . . . . . . i

Declaration . . . . . . . . ii

Certification . . . . . . . .

iii

Acknowledgement . . . . . . .

iv

Dedication . . . . . . . . v

Table of Contents . . . . . . .

Vi-viii

List of Figures . . . . . . . .

ix

List of Tables . . . . . . . .

x

Abstract . . . . . . . . .

xi

CHAPTER ONE: INTRODUCTION

1.1 Project Background . . . . . .

1


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1.2 Aims of Objectives . . . . . .

4

1.3 Significance of the Study . . . . .

5

1.4 Scope of the Work . . . . . .

11

1.5 Block Diagram overview of the Project stages

13

1.6 Project Report Organization . . . .

15

CHAPTER TWO: REVIEW OF RELATED LITERATURES

2.1 Review of work on temperature controllers .. . 17

2.1.1Principle of Operation . . . . 17

2.1.2Technologies available . . . . .

19

2.1.3 New Trends . . . . . . .

22

2.2 Set-up overview . . . . . . 25

2.2.1Temperature Measurement and Sensors . . .

25

2.2.2Microcontroller . . . . . . 32


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2.2.3 Serial Communication RS 232 Technology .

33

CHAPTER THREE: METHODOLOGY AND SYSTEM ANALYSIS

3.1 Methodology. . . . . . .

37

3.1.1Structured Analysis and Design method .. .. ..

.. 37

3.1.2Top-Down Design . . . . . .

41

3.1.3 Bottom Up Design . . . . . .

42

3.1.4 Choice Design Approach . . . . .

42

3.2 Limitations of the existing system .. . .

43

CHAPTER FOUR: SYSTEM DESIGN

4.1 System Specification . . . . . 45

4.2 Hardware Subsystem design . . . .

46

4.2.1Input interface . . . . . . 46


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4.2.2 The Control System design . . . .

51

4.2.3 Interfacing relay drivers to the microcontroller

output port . 55

4.3 Software Subsystem design . . . .

61

4.3.1Program block diagram and Control Algorithm .

61

4.3.2 Configuring the serial port of the microcontroller

63

4.3.3 Configuring the PC serial port . . . .

66

4.4 The input/output arrangement of the Project

68

4.5 The Project Block Diagram . .

69

5.1 Hardware Subsystem Implementation .

70

5.1.1The Input Interface Implementation . 70

5.1.2The Control System Implementation .

72

5.1.3. The Output Interface Implementation .

74

5.2 System Testing . . 75


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5.2.1 Test Plan . . . .

75

5.2.2 Hardware Subsystem Testing .

76

5.2.2 Software Subsystem Testing .

77

5.3 Performance Evaluation . .

77

CHAPTER FIVE: SUMMARY AND CONCLUSION AND

RECOMMENDADTION

5.1 Summary of Achievement . .

79

5.2 Problems Encountered and Solution .

79

5.3 Conclusion . . . . 82

5.4 Recommendation . . 80

5.5 Suggestion for Further Improvement .

81

REFERENCES. . 83

APPENDIX A: Full Schematic Diagram .

84

APPENDIX B: Software Details . .

85

LIST OF FIGURES


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1. Fig. 1.1: Block diagram of a PC-Based temperature

controller

2. Fig. 2.2.1: A 2 wire thermocouple

3. Fig. 2.2.2. A typical picture of a thermistor

4. Fig. 2.2.3 A graph of resistance versus temperature for a

typical thermistor

5. Fig. 3.1.1: A structural approach to system analysis

6. Fig. 3.1.2: A block diagram showing the existing system of

temperature monitoring and control system.

7. Fig. 3.1.3: A block diagram model of a PC based 4 point

temperature monitoring and control.

9. Fig. 3.2.1: Modularized approach to system design

10. Fig. 4.2.1: 5/12 Vdc power supply

11. Fig. 4.2.3: Pin-out diagram of ADC0804.

12. Fig. 4.2.4: Diagram showing a minimum configuration of

89C52 microcontroller.

1.3 Fig. 4.2.5: Relay interface to microcontroller

1.4 Fig. 4.2.6 Diagram showing a MAX232 pin-out.

15. Fig. 4.2.7: Connection arrangement of the microcontroller,

MAX232 and DB-9 connector

16. Fig. 4.2.8: Block diagram showing the operation of the

microcontroller

17. Fig. 4.2.9: Project Block Diagram.

LIST OF TABLES


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1. Table 1: Reference table showing the relationship between

baud rate and length of cable for MAX232.

2. Table 4.1: Vref / 2 relationship with Vin range.

3. Table 5.1: Test result for the analog MUX

ABSTRACT


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This project is aimed at designing a temperature monitoring

and controlling system which can be used to monitor the

temperature of industrial processes. This system relies upon

controller, which is connected to temperature, or set point, and

provides an output to a control element. Mostly the control

element is a heater. The controller is connected to a personal

computer using RS232 protocol. The current temperature can

be seen on the PC. This system offers flexibility to controlling

operations because the temperature set point can also be

changed through the user input. It is believed that this project

will remove rigorous and unnecessary monitoring and

controlling activities and hence ensure cheaper and faster

product output. A temperature monitoring system which can be

used to monitor the temperature of industrial processes has

been designed and implemented in the course of this project.

CHAPTER ONE: INTRODUCTION

1.1 Background of the Project

In a typical manufacturing industry, temperature

monitoring makes use of analog temperature controllers.

Such controllers can accept thermocouple input and offer


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imprecise temperature control over a range such as 75 0C

to 1000C. This seemed to pose no disadvantage to them

since their products still sell in the market. However, this

type of controllers used by these industry, unknowingly,

possess no readable display, lack of sophistication for

more challenging control tasks, and no communication

ability, all of which most often expose the industry to the

following problems:

Non-uniform heating rate for a point that requires more

than one heating element, thus causing delay in start-

up of production.

Wastage of raw materials in test-running the line to

ensure that the temperature had reached the minimum

required value

Poor package outlook because the sealers are not

heated

uniformly.

Extra man-power for each extrusion line- one at the

take- off and another at the panel- to ensure that

machine is stopped immediately there is a sign of poor

quality due to failure of one more of the heaters.


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Frequent damage of heating elements as a result of no

precision in control which often leads to over- heating

the elements beyond upper temperature range.

In view of the above limitations, and more, a pc-based

automatic multipoint temperature monitoring and control is

hereby proposed to remove the limitations of analog controllers

and even add flexibility to the control process.

Today, with the continuous price erosion and performance

increase of pc, industrial control is moving from an expensive,

proprietary hardware base to one with foundation of pc-based

software. Pc-based temperature control runs on personal or

industrial hardened computers and provides answers to

initiatives for lean control program.

With the inherent advantages of a pc-based control include

flexibility, high performance, customization, convenience,

easier development, better integration with existing hard

wares, portability and access, the proposed system should be

able to help manufacturing industries solve their problems by

providing uniform heated, precision in measurement and


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control, self monitoring and extension of usage to remote,

inaccessible locations in the manufacturing floor.

1.2 Aims and Objectives

This project PC- based automatic multipoint temperature

monitoring and control is aimed at designing a temperature

monitoring device which can be used to monitor and control the

temperatures of industrial machines. Thus, the complete work

can be viewed as a system having three main features which

serve as the objectives of the work.

PC- based temperature monitoring and control.

Automation facility, which enables the system to be self

monitoring.

Multi-point approach, a feature that makes it possible

for more than one point to be monitored.

Hence, this project is meant to offer flexibility to

monitoring operations by allowing or providing a PC-

interfacing feature

Which allows an operator to monitor the ongoing

process from his PC location at a more convenient and

easy-accessible place, It is believed that this project will


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be able to remove the rigorous activities of monitoring

temperatures by personnel, and engaged him with

other production activities, all aimed at ensuring

cheaper and fast product output.

1.3 Significance of the Study

The beginning of a sweeping change is upon the control

and instrumentation world with the availability of robust

hardware, open technology and real-time, window-based

operating system. PC-based control is emerging as a new

control paradigm for increasing manufacturing

productivity. PC base automatic multi-point temperature

monitoring and control offers open and more intuitive

traditional solutions at a lower total system cost and

easier migration to future technologies. Easier

development, integration, portability, and access, ensure

a flexible and efficient solution. Some of the inherent

advantages of PC-based automatic multipoint temperature

monitoring and control include the following:

Custom User-Interface for Supervisory Control.


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For low-end PID (Proportional Integral-Derivative)

controllers to high end programmable logic controllers

(PCL) system, visualizing the control application can be

very challenging. Many stand-alone controllers have fixed

digital displays for configuring control set-points and

viewing I/O values. PC-based automatic multipoint

temperature controller, being an advanced system, on the

other hand, has a display and typically requires a separate

software package and human machine interface (HMI) to

view and interact with automation systems.

Easy Integrating with Existing System

One may already have a control system that works well for

most needs but could benefit from additional

measurement or advanced control functionality to

optimize certain specialized tasks. A big advantage to

using data acquisition hardware and an open PC platform

is the number of options you have for connecting to

existing equipment. Whether you are communicating with

process instrument, PLC, or single loop controllers, you


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have a variety of ways to integrate a PC-based control

system with existing hardware, this is exactly what a PC-

based automatic multipoint temperature monitoring and

control does in the case of temperature measurement.

Software-defined Control Flexibility.

A PC-based automatic multipoint control system offers you

complete flexibility in defining system functionality and I/O

operations. In addition, even without prior technical skill in

wiring a temperature controller, PC-based automatic

multipoint control system enables an operator to carry out

initial installation since the system just requires relocating

it to another sight without rewiring process (5). Also such

unskilled operator makes changes in the initial setting

using the window-based control interface.

Multipoint Monitoring and Control for Performance

and Reliability.

Beside single point digital temperature controllers which

can control only one process, multipoint digital

temperature controllers control more than one point,

meaning they can accept more than one input variable.

Generally speaking a multipoint controller can be thought


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of a device with many individual temperature controllers

inside one chassis. These are typically mounted behind

the panel in some industrial applications, as opposed to

the front-to-panel (FTP) (9). Multipoint temperature

controllers provide a compact more modular system that

operates either within a stand alone system or in a PLC

environment. They provide a single point of software to

access all control loops.

Enhance Security

PC-based automatic multipoint temperature monitoring

and control systems also have enhance security such as

not having buttons for a person to use and change critical

settings. By having complete control over the information

being read from or written to the multipoint controller, the

machine builder can limit the information that any given

operator can read or change, preventing undesirable

conditions from occurring, such as setting a set point too

high to a range that may damage products or the

machine.

Today, manufacturers around the world look to PC to play

a bigger role in their control system. PCs are already an


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accepted platform for supervisory control, monitoring and

reporting, as well as off-line data management and

analysis. Manufacturers have already realized the

flexibility of the PC and the easy-to-use open architecture

of window-base software applications for manufacturing

environment.

Following the trend, PC-based automatic multipoint

temperature monitoring and control has emerged to

facilitate efficient monitoring and control process for

manufacturing industries. Such temperature controllers

are used in a wide variety of industries to manage

manufacturing processes or operations. Some common

applications include the following.

Heat Treat/Oven

Temperature controllers are used in ovens and in heat

treating applications within furnace, ceramic kilns, boilers

and heat exchangers.

Packaging


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Temperature controllers must maintain a uniform level at

designated temperatures and process time length. This

helps to ensure a high quality product output.

Plastics

Temperature control in the plastic industry is common on

portable chillers, hoppers and dryers, and molding and

extruding equipment, temperature controllers are mused

to precisely monitor and control temperatures at different

critical points in the production of plastics.

Health Care

Temperature control is required in laboratory and test

equipment, autoclaves, incubators, refrigeration

equipment and crystallization growing chambers and test

chambers where specimens must be kept or test must be

run within specific temperature parameters.

Food and Beverage

Common food processing applications involving

temperature control include: brewing, blending,

sterilization and cooking and baking ovens. Controllers

regulate and/or process time to ensure optimum

performance.


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Cable Manufacturing

Insulation materials require as specific temperature which

must be maintained uniformly throughout the barrel and

nozzle zones to ensure good quality of product. Efficient

temperature monitoring and control systems are required

to achieve this.

Finally, the steps taken to incorporate PC to temperature

monitoring and control is one of the many steps required

for a complete computer automation of industrial

processes. Thus, other parameters such as pressure,

colour, texture and so on, can be computerized, providing

a platform for a unified process control.

1.4 Scope of the Work

This work covers the following areas:

Temperature Measurement

Temperature sensors are reviewed and choice made on

the most applicable sensors. The sensor measures the

temperature of the points and converts the reading to a

voltage value. This value is then sent to the


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microcontroller which compares it with the set-point value,

takes appropriate action in order to restore tolerable

limits.

Hardware Programming

High level C-programming language is used to develop

codes for the microcontroller to enable it read the values

sent by the sensors and take appropriate actions. The

Visual Basic Window-based software will be used to

communicate with the PC operating system and the C-

program running on the hardware in order to read the

user set-point values and current temperatures.

Window-based Software Programming

Communication between the hardware and the PC (serial

communication) is facilitated by programming the PC to

be able to communicate with the serial port. The Visual

Basic Window-based software will be used to

communicate with the PC operating system and the C-

program running on the hardware in order to read the

user set-point values and current temperatures.

Level Conversion


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In order to ensure a compatible voltage level between the

hardware and the PC, the MAX 232 technology is

employed. This converts the hardware voltage level to a

voltage which can be handled by the serial port in the PC.

1.5 Block Diagram Overview of the Project Stages

Fig.1.2: Block diagram of a PC-based temperature

controller

A temperature control system relies upon a controller,

which is connected to a temperature sensor. It compares

the actual temperature to the desired control

temperature, or set-point, and provides an output to a

RS232 Interface

PC-based application

MicrocontrollerUnit

Temperature

Sensors

Analog to Digital

Interface

Liquid CrystalDisplay Keypad


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control element. Mostly the control element is a heater.

The controller is connected to a Personal Computer using

RS232 protocol. The Current Temperature can be on the

PC, whereas the Temperature Set-point can also be

changed through the PC or embedded buttons. The

different sections of this project are:

1. Microcontroller

2. Analog to Digital Converter (ADC)

3. Temperature Sensor

4. Relay

5. MAX 232

Microcontroller:

It is the heart of the unit. It performs all the functions like

getting data from ADC, comparing the current

temperature to set-temperature, turning ON/OFF the relay

and communicating with the PC.

Analog to Digital Converter:

The ADC converts the Analog voltage received from the

Temperature Sensor into digital format and gives it to the

microcontroller.

Temperature Sensor:


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The temperature sensor measures the current

temperature and sends value in for of voltage to the

microcontroller. Some IC (e.g. LM35) sensors have output

proportional to the input temperatures.

MAX 232:

Communication with the PC is done through the SERIAL

PORT. The protocol of serial port is RS-232, for interfacing

the controller to the PC using RS-232 protocol, we require

MAX 232 IC.

1.6 Project Report Organization

The design and simulation of the project, PC-based

automatic multipoint temperature monitoring and control

system, followed a systematic approach which reveals a

step-by-step analysis of an existing system, until a

realizable, better system is arrived at. This report covers

the entire steps followed to arrive at the complete

envisaged system. Diagrams and tables are employed,

where necessary, to illustrate facts and results.

Chapter one of this report is an introduction to the project.

It covers the following areas: the project background, aims


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and objectives of the work, justification and scope of the

work and the block diagram overview of the project

stages.

Chapter two is a literature review of related works. In this

chapter, the general concept of temperature control is x-

rayed; different technologies of relevant components are

also reviewed.

In the third chapter, the temperature control technique as

used in an industry is analyzed and shortcomings of the

existing system outlined. Different methods of achieving a

better system are also explored. Then, choice is made

among all the available options. The option chosen is

basically dependent on the nature of the envisaged

system.

Chapter four describes the proper system design. The

input, output and software interfaces are systematically

modularized and designed. The block diagram of the

modules (put together) is also towards the end of this

chapter.


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The whole of chapter five is concerned with the

implementation of the designed system. This involves the

wiring schedules, full schematic diagram and integration

of the different modular designs and schematics,

simulation, testing and performance evaluation, costing

and deployment of the achieved work.

Finally, the last chapter deals with the summary of

achievement, problems encountered during the project

design and implementation stages and the solution

proffered. Recommendations and suggestions for further

improvement are also included.

CHAPTER TWO

REVIEW OF RELATED LITERATURES

2.1 Review of work on Temperature Controllers

2.1.1 . Principle

A temperature controller is a device used to hold a desired

temperature value (2). The simplest example of a temperature

is common thermostat found in homes. All controllers, from the

basic to the most complex, work on the same way. There are


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two variables required by the controller; actual input and

desired set-point value. The input signal is also known as the

process value. The input to the controller is sampled many

times per second, depending on the controller. This input or

process value is then compared with the setpoint value, if the

actual value does not match with the set point, the controller

generates an output signal change based on the difference

between the set-point and the process value, and whether or

not the process value is approaching the set-point or deviating

farther from the set-point. This output signal then initiates

some type of response to correct the actual value so that it

matches the set-point. Usually the control algorithm updates

power value which is then applied to the output.

The control action depends on the type of controller. For

instance, if the controller is an ON/OFF control. The controller

decides if the output needs to be turned on, turned off, or left

in its present state. A temperature controller set control the

temperature inside a room may have its set-point at 68oC and

the actual temperature 67oC. The controller would then send a

signal to increase the applied heat to raise the temperature

back to the set-point of 68oC.


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When analog output is used, the output driver is proportional to

the output power value.

However, if the output is binary output type such as a relay,

SSR driver, or triac, then the output must be time proportioned

to obtain an analog representation.

A time proportioned system uses a cycle time to proportion the

output value. If the cycle time is set to 8 seconds, a system

calling for 50% power will have the output ON for the 4 seconds

and OFF for 4 seconds, while one for 25% power for the same 8

seconds cycle time, will be ON for seconds and OFF for 6

seconds. All things being equal, a shorter cycle time is

desirable because the controller can react quickly and change

the state of the ouput for a given changes on the process. Due

to the mechanics of a relay, a shorter cycle time can shorten

the life of a relay, and is not recommended to be less than 8

seconds. For solid switching devices like SSR driver or triac,

faster switching times are better. The general rule is that, only

if the process will allow it, when a relay ouput is used, a longer

cycle time is desired. (2).


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Typically, all controllers have input and ouput parts. In the case

of a temperature controller, the measured input variable is the

temperature. Temperature controller can have several types of

inputs. The type of input sensors include thermocouples,

resistive thermal devices (RTDs) and integrated circuits (e.g.

LM35). Sensors are treated later in this chapter.

In addition to inputs, every controller also have an output.

Typical outputs provides with temperature controllers include

relay outputs, solid state relay (SSR) drivers, triac and linear

analog outputs. In some cases, the output signal may be

required to retransmit the process to a programmable logic

controller (PLC), recorded or personal computer (PC). In the

case of a PC- based temperature controller, the controller is

connected to a personal computer using the RS 232 protocol. A

software program running on the PC can be used to display the

values on the PC while the set-point can still be changed using

the PC.

2.1.2 Technologies Available

Temperature controllers come in different styles with a vast

array of features and capabilities. There is also plenty of ways


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of categorize controllers according to their functionality. In

general, temperature controllers and either single loop or multi-

loop. Single loop controllers have one input and one or more

outputs to control a thermal system. On the hand, multi-loop

controllers have multiple inputs and outputs, ad capable of

controlling several loops in a process. More control loops permit

controlling more process system functions. Thus, major

development in control technology revolves around increasing

the control capabilities of the controllers.

Reliable single loop controllers range from basic devices that

requires single manual set point changes to sophisticated

profiler that can automatically execute up to eight set-point

changes over time period (2), (9).

The simplest basic controller type is analog controller. Analog

controllers are low cost, simple controllers that are versatile

enough for rugged, reliable process control in harsh industrial

environments including those with significant electrical noise.

Controller display is typically a knob dial. Analog controllers are

synonymous to relay controllers which emerged in the early

60s (9).


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Basic analog controllers are used mostly in non-critical or

unsophisticated thermal systems to provide simple ON/OFF

temperature control for direct or reverse acting application.

Such controllers accept thermocouple or RTD as input sensors,

and they offer imprecise measurement.

Limit controller is another type of controller. It provides safety

limit control over process temperature. They have no ability to

control temperature on their own. Put simply, limit controllers

are independent safety to be alongside an existing control loop.

Limit control is latching and part of redundant control circuitry

to positively shut a thermal system down in output must be

reset by an operator, it will not reset by itself once the limit

condition does not exist.

By early 70s (9), the programmable Logic Controller emerged

with a promising higher control capability. The PLC belongs to

the general- purpose temperature controller and is used to

control most typical processes in industries. Typical, they come

in a range of DIN sizes; have multiple outputs and


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programmable output function. These controllers can also

perform PID control for excellent general control situations.

They are traditionally placed in the front panel with the display

for easy operator accessibility.

Value Motor Drive temperature controllers are specifically

designed to control valve motors used in manufacturing

applications such as gas burner control on a production line.

Special tuning algorithms give accurate control and fast output

reaction without the need for slide ware feedback or excessive

knowledge of three-term PID tuning algorithms-proportional

derivative. Valve motor drive digital controllers are used to

control the position of the valve, somewhere between 0% open

to 0% open, depending on the energy needs of the process at

any given time. They use of ON/OFF Duplex function which is a

very simple algorithm and like its counterpart, ON/OFF control,

is another low cost controller with fast output reaction but low

accuracy.

2.1.3 New Trends


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Modern temperature controllers came out as the need for

automatic calculation of PID parameters for optimal thermal

system performance arose. The PC-based controllers followed

the introduction of MMI/SCADA in the mid 80s (8), replaces the

traditional and proprietary controllers such as PLC, with

standard PC-based hardware and software. PC-based control

runs on personal or industrial hardened computers and

provides answers to initiatives for lean control program. This

PC-based control approach provides end-users and machine

builders with a platform to dramatically reduce control system

design time and maintenance cost by reducing down-time with

built in diagnostic, real time simulation, and consolidation of

data into a single database. Some estimates indicate the PC-

based control market is growing at a rate of over 70 percent a year!

(8).

The PC and desktop software industries are also participating in

this evolution of control with the evolution of window NT.

Window NT version 4.0 is the first Window-based operation

system (6) that provides a truly deterministic, real time

operating system. The advent of many software OS lends PC-

based control more facilities for developing better functionality.


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For example, even without any prior programming experience,

you can use NI LabVIEW graphical development environment to

define custom control functionality and meet your unique

needs. You can build onto the basic LabVIEW application to add

features (6) such as

- Signal processing functions like filtering and averaging;

- Configurable dead banding and hysteresis;

- Data Collection and report generations; and

- Additional input and output channels.

Some manufacturers of temperature controllers have extended

the advantages of PC-based control in designing more

sophisticated controllers such as the profiling digital controllers

or profilers. Profiling digital controllers, also called Ramp-Soak

controllers are controllers that will allow the operator to

program a number of setpoints and the time to sit at each set-

point. The changing of the setpoint is called Ramp and the

time to sit at each set point is called Soak or Dwell. One

remp and one soak are considered to be one segment. A

profiler offers the ability to enter a number of segments to

allow complex temperature profiles. There are many

applications for a profiling controller. The profiles are often


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referred to as recipes by the operator and are often kept on a

computer and downloaded via a communications channel

directly into the controller as needed. Most profilers allow

storage of multiple recipes for later use. Smaller profilers may

allow for 4 recipes with 16 segments each while more

advanced profilers would allow for more. Profile temperature

controllers are able to execute ramp-and-soak profiles such as

temperature changes over time, along with hold and soak/cycle

duration, all the while being unattended by an operator,

allowing the operator to perform other tasks. Typical

applications for profile temperature controllers include heat

treating, annealing, environmental chambers, and in complex

process furnaces.

2.2 Set-up Overview

In this section, the different technologies of the major

components used in this project are explored.

2.2.1 Temperature Measurement and Sensors

Temperature monitoring is central to the majority of data

acquisition systems, be it to save energy costs, increase safety,


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testing time whatever your reasons, you will need a device to

measure the temperature a sensor. Thermocouples,

resistance temperature device (RTDs), thermistors and infrared

thermometers are all types of temperature sensor. Which can

choose depends on factors like your expected maximum and

minimum temperatures, the accuracy you need and your

environmental conditions. The most popular sensors are

thermocouples, RTDs, thermistors and ICs. These are discussed

below, pointing at potential problems when using some of them

in computerized temperature measurement.

Thermocouples

Thermocouples are popular temperature sensors because they

are cheap, versatile and sturdy. They consist of two dissimilar

metals joined together, making a continuous circuit. If one

junction has a different temperature to the other, an

electromotive force (voltage) is set up. This voltage varies with

the temperature difference between the junctions. If the

temperature at one junction is known, the temperature at the

other junction can be calculated.


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Types of Thermocouple

There are several types of thermocouple, labeled with letters

according to their constituent metals. A K-type thermocouple,

for example, is made up of chrome and Alumel. The metals give

the thermocouples differing properties, such as temperature

ranges and accuracy.

Figure 2.2-1: A 2 wire thermocouple

Potential Pitfalls in a Computerized Thermocouple

System

The Cold Junction Reference Measurement. The

system depends on knowing the temperature of one of the

thermocouple junctions (the cold junction). Housing this

junction in an isothermal box will keep the temperature

constant, and a cold junction sensor in the box will tell the

system the temperature. In our plug-in card example, the

VoltmeterCopper wire

Thermocouple

Wires (2 Types)

SensingJunction

ReferenceTemperature


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isothermal box sits outside the computer. You would

connect the thermocouple wires to screw terminals in the

box, and connect the terminals to the card with a ribbon

cable.

Attaching the Thermocouples to Metal Surfaces. if

the thermocouples are directly to a metal surface,

particularly one carrying its own voltage such as heating

element, you need to isolate the signals. This will prevent

high voltages in the monitored item damaging the data

acquisition equipment. It will also make the

measurements floating, letting you record the small

thermocouple voltage in the presence of high voltages.

Linearization. The voltage produced by a thermocouple

does not change linearly with temperature presenting a

problem for the data acquisition system. A good solution is

to use software (7) to obtain the correct temperature in,

say, 0C or 0F. Some custom-made software kits, e.g.

Windmill, can do this automatically for B, E, J, K, N, R, S

and T type thermocouples.

Using the Wrong Type of Thermocouple Lead.


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You need to connect the thermocouple to the data

acquisition equipment using the correct type of extension

or compensation lead. This is made of either the same

material as the thermocouple metals, or material with

similar characteristics.

Long Thermocouple Leads Noisy Signals and

Added Wiring Costs.

Thermocouple leads are often many metres long, and

have a higher resistance than normal copper wire. This

means that the lead can act as aerials, picking up

environmental electrical noise that contaminates the

voltage signal. It might also mean expensive wiring costs.

In this case you need either to take precautions against

nose, or distribute data acquisition units placing them

close to the thermocouples on Modubus, RS485 or

Ethernet networks for example.

RESISTANCE TEMPERATURE DEVICES (RTDs)

Resistance temperature devices (or detectors) rely on the

principle that the resistance of a metal increases with

temperature. When made a platinum, they may be known as


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platinum resistance thermometers (PRTs), and when specified

to have a resistance of 100 ohm at 00C, as Pt 100.

Potential Pitfalls in a Computerized RTD System

Errors Arising from Lead Resistance.

When the resistance to be measured in small, the

resistance in the leads to the RTD can significantly affect

accuracy. Several methods exist for monitoring RTDs,

which address the problems associated with lead

resistance. These methods include balanced bridges and

constant current sources.

Constant current source measurements give

excellent results for all wiring configurations,

including 2-wire, 3 wire, 4-wire and 4 wire

compensated.

The most accurate results are obtained using a 4 wire

arrangement. Each RTD requires the data acquisition

hardware to provide a constant current source. The

current flows through the RTD and the voltage drop the

RTD is measured. Using Ohms law the value of the

resistance of the RTD can be calculated.

Converting the Resistance to a Temperature.


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Software like Windmill automatically converts the resistance

measurement to a temperature in your choice of engineering

units (7).

Thermistors

Thermistors are inexpensive, easily-obtainable temperature

sensors. They are easy to use and adaptable. Circuits with

thermistors can have reasonable output voltages not the

millivolt outputs thermocouples have. Because of these

qualities, thermistors are widely used for simple temperature

measurements. Theyre not used for high temperatures, but in

the temperature ranges where they work they are widely used.

Thermistoers are temperature sensitive resistors. All resistors

vary with temperature, but thermistors are constructed of

semiconductor material with a resistivity that is especially

sensitive to temperature. However, unlike most other resistive

devices, the resistance of a thermistor decreases with

increasing temperature. Thats due to the properties of the

semiconductor material that the thermistor is made from.

Figure 2.2-3 is a graph of resistance as a function of

temperature for a typical thermistor. Notice how the resistance

drops from 100000 ohms, to a very small value in a range


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around room temperature. Not only is the resistance change in

the opposite direction from what you expect, but the

magnitude of the percentage resistance change is substantial.

R

104

102

0 100 200 300 400 500 T (0K)

Fig 2.2-3 Graph of resistance versus temperature for a typical

thermistor.

Sensor (LM 35)

The LM 35 is an integrated circuit sensor that can be used to

measure temperature with an electrical output signal

Fig 2.2-2: A typical picture of a thermistor


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proportional to the temperature in degree Celsisu. Actually IC

temperature sensors consist of integrated temperature

dependent resistors whose output voltage increases

proportionally with increase in temperature due to increased

output resistance. A brief summary of its advantages over

other sensors include:

- more accurate and precise temperature measurement;

- scaled sensor circuitry so that it is not subject to oxidation

and other environmental factors;

- output conditioning of LM35 is simpler when compared to

that of thermocouples, thermistors, etc.

The above inherent properties of IC temperature have made

the more desirable in computerized applications.

2.2.2 Microcontroller

A microcontroller is a single chip microprocessor system which

contains data and program memory, serial and parallel 1/O,

timers, and internal interrupts, all integrated into a single chip.

First microcontrollers were developed in the mid 70s (4). These

were basically calculator-based processors with small ROM

program memories, very limited RAM data memories, and a


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handful of input/output ports. More powerful 8 bit

microcontrollers were later developed. In addition to their

improved instruction sets, these microcontrollers included on-

chi counters/timers, interrupt, 1/O, on-chip ultra-violet erasable

EPROM memory.

The 8051 family was introduced in the early 80s by Intel.

Currently this family of microcontroller has many versions and

some types of included on-chip analog-to-digital converters. In

the 90s, the recent microcontroller, Intel 8951 evolved with all

the features and instruction set of the other trends to

microprocessors. This gives it the ability to be used more easily

with minimum cascading, or even without additional memory

devices. Still in this twenty first century, another Intel 8952,

which is an advanced form of Intel 8951, has been introduced.

Today, microcontrollers have moved into other more powerful,

16 bit market. They are high performance processors that find

application in real-time and computer intensive fields (e.g. in

digital signal processing or real-time control).

2.2.3 Serial Communication


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Communication is essential in electronics system. It can be in

the form or wired or wireless, serial or parallel. The main idea is

to transfer information from one system to another system,

communication in one direction is call a simplex communication

system, and duplex means communication is in both direction

at the same time. Half duplex means that communication is

taking place in both direction but only one direction

communication is taking place at any one time.

Communication between electronics devices usually deals with

logic Is and 0s. a typical electronic system uses the concept of

voltage or frequency. The choice of signal varies.

Voltage/frequency changes can be produced and detected

using simple electronics, so it is relative a easier type of signal

to implement. The information from the sender can be in the

form of voltage. By detecting the voltage, the receiving device

is able to interpret the information. The common understanding

or interpretation of both the sending and receiving device is

known as the communication protocol. The information

conversion to a suitable transmission signal is also known as

encoding. Decoding is the other way round.


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In todays wired communication system, there are a wide

variety of serial communication standard from RS232, RS485,

USB, CAN, and many more. They are simply the standard

defined for communication hardware. Today, various serial

communication interface USART are present. They are TTL

version of the serial communication, represented by 5V/0V. It is

similar to RS232 physical format represented by -/+IOV in the

voltage.

USART is not design for distance communication. To enable

longer communication distance, USART signal will need further

encoding into RS232 signal format before transmission. Other

common names for USART (Universal Synchronous

Asynchronous Receiver Transmitter) are UART or SCI (Serial

Communications Interface). Serial data in TTL format is the very

basic serial communication interface to understand. RS232 is

the encoded version of USART. The encoded signal allows the

data to be deployed for longer communication distance. Some

article may have defined a maximum communication distance

of 15m for RS232 signal. You can try pulling the

communication distance further, it should still works actually.

15rn is only a general guideline.


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If the data transmission rate is low, the distance can even go

further. There have been reports from the internet that some

users have achieved 50m to 200m without any problem. In this

project, I have tried baud rate of 9600bps over 100m without

any problem. Baud-rate is presented in bps (data bits per

second). The higher the value the more the data can be

transmitted in a given time period. The higher the speed, the

shorter the communicationdistance.

The data transmission length of the cable can be determined

by many factors. The factors include the following:

- Data transmission speed

- Quality of the cable, noise (unwanted signal)

- Transmitted voltage '

- Receiver sensitivity

- Etc.

Communication distance using RS232 can be increased further

if the cable is of better quality, a shield or coaxial cable for

example.

The most significant factor is the data transmission speed. The

following is a reference diagram showing regarding the

relationship between data baud rate and cable length.


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Baud-rate Length (distance)

19200bps 15m

9600bps 150m

4800bps . 300m

2400bps . 900m

Table 1: Reference table showing relationship between

baud-rate and length of cable, for MAX232.

1C chip maker has come up with the integrated circuit for

interfacing RS232 with TTL logic (5V for logic 1, 0V for logic 0),

making the interfacing work very simple. MAX232 is one of the

many 1C in the market which helps to convert betweenRS232

-/+10V and TTL +/-5V. The charge pump design allows the

circuit to generate +/-10V from a 5V supply. (See fig. 4.2.7).


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CHAPTER THREE:

METHODOLOGY AND SYSTEM ANALYSIS

3.1

Methodology

Before the inception of the idea that a PC-based system can be

employed to facilitate efficient monitoring and control of

temperatures of industrial processes, a number of steps was

explored in arriving at a conceptual model of the new system.

3.1.1 Structured analysis and design

The steps began with investing and understanding the

current/existing physical system.

The various steps are summarized the diagram below.

EXISTING PHYSICAL SYSTEM

EXISTING LOGICAL SYSTEM

REQUIRED LOGICAL SYSTEM


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REQUIRED PHYSICAL SYSTEM

Figure 3.1-1: Astructured approach to system analysis

Existing Physical/Logical System

As earlier mentioned, Cutix Pic Nnewi, like most other

manufacturing industries, make use of analog temperature

controllers with thermocouple sensors as Inputs. The

concept/logical model of the existing system can be viewed as

shown below:

POWER SUPPLY

CONTROLLER 1

ON/OFF

R1

HEATER1

SENSOR1

HEATER2

HEATER4

HEATER3

SENSOR2

SENSOR3

SENSOR4

R2 R3 R4

CONTROLLER 2

ON/OFF

CONTROLLER 3

ON/OFF

CONTROLLER 4

ON/OFF


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Figure 3.1-2: Existing physical system of temperature

control

and monitoring system.

Considering a four-point temperature control and monitoring

requirement which already was implemented using a separate,

stand alone temperature controllers. Such control can be

achieved using analog controllers or even stand alone PLC.

Each control unit is independent of the other. A problem

statement was formulated after attempting to provide answers

to the following questions:

1. How can the temperature be measured more accurately so

that quality control can be optimized?

2. Can there be a possibility of bringing the control under the

supervision of only one hardware so that easy supervision

an4 surveillance can be made on the process?

3. Can there be a means of establishing a common

communication interface and display so that monitoring can

be done more effectively and abnormality noticed on time

before having 'any damaging effect on the machine or


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product. For instance, when a thermocouple or controller

fails, how can we get a timely notice for its replacement?\

4. How can more security be implemented so that somebody

does not tamper with the set-point on the controller and reset

the knob at a wrong setting.

5. How can the installation process be simplified so that much

time is not devoted to mounting the system in a new place of

interest?

The problem statement can now be formulated: "a need to

design and construct an automatic multipoint temperature

monitoring and control system". Such systemshould have the

following features:

- ability to provide precise and accurate temperature

measurement.

- ability to handle the control of all the four temperatures

that need

to be controlled.

- communication user interface with dip hardware for

monitoring and

controlling the four points almost simultaneously.

- ease of installation without requiring the whole production


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process

be shut down.

- room for integration with other systems if need be.

The Proposed Logical/Physical System

Looking at the deficiencies of the existing system and the

features required of the required system,, a PC-based approach

to system control seems to meet the requirements for the new

system. A physical representation of the proposed model is as

shown below.

CPU

R1

HEATER1

SENSOR1

HEATER2

HEATER4

HEATER3

SENSOR2

SENSOR3

SENSOR4

R2 R3 R4

SINGLE CONTROLLER HARDWARE

SCREEN

POWER SUPPLY


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Figure 3. 1-3: A Block Diagram model of a pc-based 4-

point temperature monitoring and control3.1.2 Top-down Design

Top-down design is the technique of beginning with a complex

project and breaking it down into its constituents. For a supra

system which consists oF several systems and subsystems, a

top-down design approach of such system can be represented

as follows:

SUPRA SYSTEM

SYSTEM

SUBSYSTEM

PROGRAM MODULES

Hence, the project "PC-based automatic multipoint

temperature monitoring and control" is a supra system with

components system as

- temperature controller system, made up of data acquisition


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(or temperature measurement.) unit and control unit; and

- temperature monitoring system, made up of hardware inlet-

facing with PC and user program (Window-base program)

development.

Each of the individual system has its other subsystem and

program modules.

3.1.3 Bottom-up Design

This is a situation where one starts with simple subsystem or

program modules and proceeds to constitute the main system

and subsequently supra system, as the case may be.

3.1.4 Choice Design Approach

The design approach used in this project design is the top-down

design. The whole system is broken down into different smaller

modules.

MODULE 1: Design of the data acquisition system.

This comprises wiring and interconnecting tlic sensors, ADC,

and multiplexers to the microcontroller.

MODULE 2: Configuration of the microcontroller 89C52 and its

control program using C programming language. The MAX232

protocol is also configured at this stage.


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MODULE 3: Design of the PC monitoring Window-based

interface. Here, the Visual Basic (VB 6.0) programming

languagc.is used to write a program that will enable the PC to

communicate with the hardware (controller).

Fig.3.2-1: Modularized approach to the project systemdesign

The final step is integration of the different modules to form the

system required. It is important to note that any of the above

modules can be tackled first and important information that

can be used for the other recorded appropriately for reference

purpose.

3.2 Limitations of the Existing System

It seems appropriate at this point to explicitly enumerate the

major deficiencies of the existing system, which prompted the

MODULE 1

MODULE 2

MODULE3


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design of the new system. From the on-going discussions and

the analysis carried out ab initio, it will be discovered that;

- the old system does not provide a precise temperature

measurement due to the inherent characteristics of the

sensors used;

- monitoring and controlling the temperatures of more than

one point at the same time, using the old system is more

cumbersome and demanding since there are different

controller for each temperature;

- with the old system, a staff should always go round to

observe the controllers at all time to know the one which

is malfunctioning or not functioning at all. This task would

be made easier using a PC-based multipoint temperature

monitoring and control where all events are observed at

a time from one point PC screen.

- Also, there is the possibility of all point being interfered

with by an intruder thereby distorting normal production

parameter settings. Such is minimized with PC-based

system.


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CHAPTER FOUR

SYSTEM DESIGN, SIMULATION AND PERFORMANCE

EVALUATION

4.1 System Specification


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The PC-based automatic multipoint temperature monitoring

and control system is a system that helps users to continuously

monitor the temperaturesof different points of interest at the

same time with the help of a personal computer (PC). The

system will be able to maintain a desired temperature set by

the user at a stable value.

During operation, the maximum value is keyed in by the user.

The current value of the point being monitored must not go

above the maximum set-point. A stable set-point range is

maintained by the microcontroller-based hardware which turns

ON a respective heater for each point whenever the current

temperature reading tends to go below the maximum set-point,

and turns OFF the heater whenever the maximum set- point is

reached. Thus the required temperature is maintained by the

hardware for optimum production operation.

For this project, the range of temperature measurable by the

system is from OC to 100C;

i.e. the maximum set-point must not be any value outside the

range of 0 - 100,


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(0oC < Tmax < 100oC). This system is capable of monitoring

and controlling up to four different points of interest

concurrently but independently.

4.2 Hardware Subsystem

4.2.1 Input Interface

MODULE 1: Design of the data acquisition system. Mere, the

following parts of the project are designed and configured.

- Power supply

- Sensor configuration with the ADC.

Power Supply Design

The power supply requirement for all the components used in

this falls within the 5VDC and 12VDC supplies. Therefore, a

suitable 5V/12DC supply is designed using the following

components: 240/12VAC step-down transformer, a bridge

rectifier 1C, 7505-5V and IN4742 12V voltage regulators and

capacitors of varying specification.


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Fig. 4.1.1: A 5V/12VDc Power Supply Circuit.

The input voltage to the power is to be within the range of 7 to

20 VAC. Here a step-down (240/15VAC) transformer is used to

supply 15VAC to the circuit. The MC7505 5-V regulator and

zener diode 1N4742 are used in the circuit to provide a fixed

5vDcand 12vDc outputs respectively for the system

components. The power supply circuit can handle up to 1A of

current, provided that the transformer can handle the current.

The voltage regulator is provided with heat-sink for easy heat

dissipation.


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Sensor (LM 35)

The LM 35 is an integrated circuit sensor that can be used to

measure temperature with an electrical output signal

proportional to the temperature in degree Celsius. The

summary of its advantages over other sensors have been

discussed in chapter two.

The operational characteristics ofLM35 temperature sensor

includes the following:

- Output voltage that is proportional to the Celsius

temperature;

- accuracy of about +/- 0.4C at room temperature and +/-

0.8C over a range 0C to 100C;

- It draws only about 60uA from its supply and possesses

allow self-heating capability (the sensor self-heating

causes less than 0.1C temperature rise in still air.

Calibrating the LM35 with respect to ADC step output


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The ADC0808 has 8-bit resolution with a maximum of 256 steps

and the LM35 produces l0mV for every degree rise of

temperature. The calibration of LM35 sensor will be such that

for output of 0C to 100C, the input to the ADC ranges from 0to

256 x l0mV, i.e, 0 - 2560mV or 0 - 2.56V.

ADC CONFIGURATIONThe ADC used is ADC0808. It has the frequency

F = 1 HzI.IRC

Where R = 10K, C = 150pF

F = 606 KHz.

Fig 4.2.3: Pin-out diagram of ADC0808


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Vcc: this is +5V power supply pin or a reference voltage pin

when Vref/2 input pin is open.

Vin(+) is used as the only input to be converted when Vin (-) is

connected to the ground.

WR (start conversion) is used to signal the ADC0808 to start

converting the analog input of Vin to an 8-bit digital number,

whenever the pin makes a low-to-high transition.

CS is an active low input used to activate the ADC808.

RD (output enable): A high-to-low RD pulse is used to read the

converted data output of the ADC.

Another parameter to consider in configuring the ADC is the

Vref/2. This determines the step-size of the ADC and

subsequently the digital output of the ADC. The following table

shows Vref/2 relation to Vin range.

VrcI/2(V)

Vin(V) Stepsize(mV)

1

Not 0 to 5 5/256 -19.53


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connected

2.0 0 to 4 4/256=15.62

.i.5 0 to 3 3/256-11.71

1.28 0 to2.56

2.56/256=10.0

1.0 0 to 2 2/256 = 7.81

0.5 0 to 1 1/256 = 3.90

Table 4.1:Vref/2 relationship with Vin range

From the table above, to get a l0.0mV stepsize of the LM35

Vref/2 of value 1.28 is required. This value is achieved by

connecting potentiometer to fix the voltage across the 10K pot

at 25 volts. This should overcome any fluctuations in the power

supply.

Digital output of the ADC is given by;

Dout = VinStepsize


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For example, when the LM35 inputs 250mV to the ADC, the

digital output, from the ADC after conversion should be

Dout = 250mVl0mV

= 25C as temperature reading.

4.2.2 The Control System Design

MODULE 2: The microcontroller is the central control unit in

this project. The microcontroller used in 89C52. The diagram

below shows the pin-out of 89C52.


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Fig. 4.2.4: Pin-out diagram of 89C52 with minimum

configuration

RST: This is the reset input. This input should normally be at

logic 0. A reset is accomplished by holding the RST pin high for

at least two machine cycles.

Power on-reset is normally performed by connecting an

external capacitor and a resistor to this pin. (See fig...)

XTAL1 and XTAL2; These pins are where an external crystal

should be connected for the operation of internal oscillation

device.

P3.0(bit 0 of port 3): This is a bi-directional 1/0 pin with an

internal pull-up resistor. It is also used as the data receive

input (RXD) when the device is used as an asynchronous UART

to receive serial data.

P3.1 (bit 1 of port 3):This is also a bi-directional 1/0 pin with

an internal pull-up resistor. This pin also acts as the data

transmit output (DXT) on the 8051 family when the device is

used as an asynchronous UART to transmit serial data.


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P3.2 (bit 2 of port 3): This is a bi-directional 1/0 pin with an

internal pull-up resistor. This pin is also the external interrupt 0

(INTO) pin.

P3.3 (pin 3 of port 3): This is a bi-directional 1/0 pin with an

internal pull-up resistor. This pin is also the interrupt (1NT1)

pin.

P3.4 (bit 4 of port 3): This is a bi-directional 1/0 pin with an

internal pull-up resistor. This is also the counter 0 input (TO)

pin.

P3.5 (bit 5 of port 3): This is a bi-directional 1/O pin with an

internal pull-up resistor. This pin is also the counter 1 input (TI)

Pin.

GND: This is the ground Pin.

P3.6 (bit 6 of port 3): This is a bi-directional 1/O pin. This pin

is not available on the 89C2025. It is also the external data

memory write (WR) pin.

P3.7 (bit 7 of port 3): This is a bi-directional/1/O pin. On the

standard 8951, this pin is also the external data memory read

(RD) pin.

P1.0 (bit 0 of Port 1): This is also bi-directional 1/O pin. This


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pin has no internal pull-up resistor on the 20 pin devices. It is

also used as the positive input of the analog comparator (AIN0)

on the 20-pin device.

P1.1 (bit 1 of Port 1): This is a bi-directional 1/O pin. This pin

has no internal pull-up resistor on the 20-pin devices. It is also

used as the positive input of the analog comparator (AINI) on

the 20-pin device.

P1.1 (bit 1 of port 1): This is a bi-directional 1/O pin. This pin

has no internal pull-up resistor on the 20-pin devices. It is also

used as the positive input of the analog comparator (AINI) on

the 20-pin device.

P1.2 to P1.7: These are the remaining bi-directional 1/O pins

of port 1. These pins have internal pull-up resistors.

Vcc: This is the voltage supply pin.

Fig.4.2.4 shows that the following external components are

required to have a working microcontroller.

XI-. Crystal (e.g. 12MHz)

Cl.C2:33pF capacitor


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C3; l0uF / 10V electrolytic

capacitor R1:8.2K,0.125W

resistor.

Programming requirement

The microcontroller used in this project was programmed

using the following:

1. Suitable C compiler which generates machine codes for the

microcontroller. The M1DE-51 editor software was used in

this project due to its wide compatibility with C compilers.

4.2.3 Interfacing relay driver to the microcontroller

output port.

The four points being monitored by this system, each has a

sensor and a heater. When the maximum temperature is

exceeded or the minimum temperature more than the current

temperature, a control signal is sent to the respective output

port of the microcontroller for switching ON or OFF a

corresponding heater-as the case may be. Four separate output

pins (P2.0 to P2.3) are used as output to the relay drivers. A


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typical design for interfacing a relay to a microcontroller is

done here.

Fig. 4.2.6: design of relay interface to a microcontroller.

The function of the relay driver is to provide the necessary

current typically 25 to 70mA to energize the relay coil. AN NPN

is used to drive the relay. The transistor is driven to saturation


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(turned ON) when logic 1 is written on the port pin thus turning

ON the relay. The relay is turned OFF by writing logic 0 on the

port.

A diode is connected across the relay coil to protect the

transistor from damage due to back emf generated in the

relay's inductive coil when the transistor is turned OFF. When

the transistor is switched off, the energy stored in the inductor

is dissipated through the diode and the internal resistance of

the relay coil. A pull-up resistor is used at the base of the

transistor. The microcontroller 8052 has an internal pull up

resistor of 10K, so when the pin is pulled high (logic 1), the

current flows through tins resistor. The maximum output

current is

5V = 0.5mA10K

BC547 has a DC current gain of 100, so the maximum collector

current is

0.5x100-50mA

This value is not enough to turn the transistor to saturation.

Therefore, an external pull-up resistor is used. When the

controller pin is high, current flows through the controller pin as

well as through the pull-up resistor. For the circuit shown, a


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4.7K pull-up resistor is used; so the current added to the base

current is

5V = 1.1mA4.7K

Hence, the total base current is (0.5+1.1) mA = 1.6mA.

The maximum collector current is I.6mAxlOO = 160mA, which

is enough to turn ON the relay driver- BC547.

NB: The same arrangement is connected to each of the four

output pins connected to the four different heaters,

Interfacing aMAX232 technology to a Microcontroller

The MAX232 diagram below shows that it has two sets of line

drivers: Rl, Tl and R2,T2. The communication cable from the

hardware through the MAX232 is connected to the PC port

using the DB-9 connector.


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Fig. 4.2.7: Diagram showing a MAX232 pin-out

The diagram below shows the pin connections(pin-outs) of a 9-

way serial port. Each pin has a two of three letter mnemonic as

follows:

GND 5

DTR 4 RI 9

TXD 3 CTS 8

RXD 2 RTS 7

CD 1 DSR 6


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Pin # Mnemonic Meaning

1 CD - Carrier

Detect

2 RXD -

Receive Data

3 TXD - Transmit

Data

4 DTR - Data Terminal Ready

5 GND - Ground

6 DSR - Data Set Ready

7 RTS - Request To Send

8 CTS - Clear To Send

9 RI - Ring Indicator

For a simple serial communication there are three pins that are

important. Data is transmitted over one pin (Transmit Data or

TXD for short) and received over another pin (Receive Data or

RXD). The third wire that's needed is the Ground wire (GND) -

serving as a return path for the electrical signal. It is important

to ensure that the TXD and RXD of the two computers are


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interchanged during wiring. That is, the RXD pin of one port

must be connected to the TXD pin of the second and so on. This

means that when COMI transmits data (on TXD) controller

hardware will receive data on RXD, and vise versa. The

complete wiring between the two connectors looks like this:

COMI CONTROLLER

RXD 2 TXD 3

TXD 3 RXD 2

GND 5 GND 5

Also, in order to allow data transfer between the PC and a

microcontroller- based system without any error, there is need

to make sure that the baud rate of the PCs COM port matches

the baud rate of the microcontroller. This should be taken care

of during software programming.


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4.3: Software Subsystem Design

4.3.1 Program Block Diagram and Control Algorithm

Program Block Diagram:

Various steps taken in programming the microcontroller using C

programming language are shown in the following block

diagram.

Initialize ADC

InitializeSerial-port

Update threshold

Controller Addresschange

Start Conversion

ReceiveTemperature

Monitor and ControlTemp.

Send temperature


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Fig. 4.2.8: Block diagram showing the operation of themicrocontrollerThe Control Algorithm

The control algorithm is implemented in the control sub-

program and is used by the microcontroller to control the entire

system when the temperatures (Tmax) are sensed, converted

to volts, digitized and displayed by the microcontroller.

BEGIN

DO

GET Tmax

IF T < Tmax THEN

Turn ON heater

ELSE

TURN OFF HEATER

LOOP

4.3.2: Configuring the serial ports

Before the microcontroller serial port can be used it is

necessary to set various registers.


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SCON: this is the serial port control register. It should be set to

hexadecimal 0x50 for 8-bit data mode.

TMOD: This register controls the timers for baud rate

generation, and it should be set to hexadecimal 0x20 to enable

timer 1 to operate in 8-bit auto-reload mode.

TH1: This register should be loaded with a constant so that the

required baud rate can be generated. A method for determining

the values to be loaded into THI is discussed later.

TR1: This register starts/stops the timer and it should be set to

1 to start timer 1. T1: This register should be set 1 to indicate

ready to transmit signal.

Determining TH1 value

The value of be loaded into the TH1 register is dependent on

the crystal oscillator value and the required baud rate. Dividing

1/12 of the crystal frequency by 32 gives the default value

upon activation of the 8052 RESET pin. With XTAL = 12.00MHz,

we can determine the TH1 value needed to have 9600 baud

rate as follows

XTALOSCILLATOR

12 32 BAUDRATE

TH1VALUE


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Give a machine cycle frequency of 8052 as 12.00MHz. We

determine the TH1 value:

12.00MHz/12 = 1000 KHz;

1000 KHz/32 = 31250: the freq. of UART to timer 1 to

set baud rate.

31250.9600 = 3.255: TH1 value

Hence, setting TH1 value to 3(=FD hex) gives an error of 7%

In programming the 8952 to transfer character byte serially;

1. TMOD register is loaded with the value 20H, indicating the

use of timer 1 in mode 2 (8-bit auto-reload to set baud

rate).

2. The TH1 is loaded with the value 0xFD to set baud rate for

serial data transfer.

3. The SCON register is loaded with the value 50H, indicating

serial mode 1, where an 8-bit data is framed with start and

stop bits.

4. TR1 is set to 1 to start timer 1

5. T1 is cleared by CLR T1 instruction.

6. The character byte to be transferred serially is written into

SBUF register.


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7. The T1 flag bit is monitored with the use of instruction JNB

T1, xx to see if the character has been transferred

completely.

8. To transfer the next byte, go to step 5.

Steps 1-4 indicate how to initialize the serial port for 9600 baud

rate. Using C programming language, steps 1-4 are shown

below.

Void serial init0

SCON = 0x50;

TMOD = 0x20.

TH1 = 0xFD;

TR1 = 1;

T1 = 1;

Also, in programming the 89C52 to receive character byte

serially, the same steps 1-4, except step 5, are to be followed.

At step 5, R1 register is cleared by CLR R1 instruction. The

same R1 flag bit is monitored with the use of JNB R1, xx

instruction to see if an entire character has been received yet.

When R1 is raised, SBUF has the byte. Its contents are moved

into a safe place.

4.3.3 Configuring the PC Serial port using Visual Basic


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MODULE 3:

Visual Basic (VB) comes with a ready-made component for

handling communication ports, the MsComm control. MsComm

is a simplification of the underlying API call for controlling a

communication port. In programming for serial communication

using MsComm in VB, one has to initialize button that opens the

ports and configure the settings for baud rate, parity, data bits

and stop bits and sets off a polling loop. Here I have used baud

rate of 9600, data bits of 8, no parity, i.e. parity (none) and one

stop bit. One can initially set COM1 (and COM2) up with both

RTS and DTR set off:

With MSComm 1

.MsComm1-settings = 9600, 8, N, 1

.DTREnable = False

.RTSEnable = False

.CommPort = 1

.PortOpen = True

End With

One set up the program just polls for input and rest of the

program can be written as shown below. The complete program

is attached as part of appendix B.


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Do While MSComm1. PortOpen

S1 = MSComm 1. Input

(Program body)

:

:

:

Else

DoEvents

End If

Loop

Program Description

When microcontroller changes address and send address code

to the PC serial port, the Vb program understands it to mean

ready and it activates the object, say Temperature 1, and it

sends the Tmax for the object. The microcontroller receives the

value and stores in SBUF of the microcontroller. Then it

initializes the ADC to start conversion. After, it reads and sends

the value of PC as Current temperature. The VB obtains the

value and displays it in the TEMP box. The microcontroller

performs control operation with the current temperature,

comparing it with Tmax. It then takes the required action


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depending on the outcome of the comparison. After the control

operation, the microcontroller changes address and sends code

to the Vb on the PC to activate another object, say

Temperature 2. It then repeats the whole steps taken for

temperature 1. Such steps are also taken for the Temperatures

3 and 4, and cycle repeats continuously.

4.4 The Input / Output arrangement

The whole system, made up of the microcontroller-based data

acquisition hardware, the PC-interface and the relay outputs, is

arranged having the microcontroller-based hardware as the

central system. This system receives inputs from both the

temperature sensors and the PC interface. The outputs that go

out of the microcontroller include the following:

- Current temperature for display

- Control signal to the relay drivers to switch ON or OFF

the respective heaters.

- Control signal to ADC to start conversion of the next

temperature after processing the previous reading.

- Control address bits to the MUX to switch to next

sensor.

4.5 Project Block Diagram

Liquid

POWER SUPPLY

ANALOGTO

DIGITALCONVERTER

SENSOR 1

SENSOR 2

SENSOR 3

SENSOR 4

RELAY

MICRO-CONTROLLER

MAX232

PC


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Fig.4.2.9: Block diagram of the project

4.6 SIMULATION OF THE SYSTEM

Having successfully completed the designs, the block diagram,

system specification and design, the actual implementation

was done using simulation software. Proteus ISIS is a suitable

simulation tool for microcontroller based designs. So the

microcontroller hardware is implemented with proteus

application software. This involves integration of different

components of the system to achieve a complete working

system.

4.6.1 Input interface implementation


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The input interface, with respect to the microcontroller-

based hardware, is made up of:

1. temperature sensor circuitry

2. 4-channel analog-to-digital converter (ADC)

Temperature sensor circuitry

Four LM35 temperature sensors are connected to four input

channels of the ADC0808. The diagram below illustrates the

wiring diagram of the sensors and the ADC.

Fig. 5.1.2: Circuit diagram showing the wiring schedule

of the input interface to the Microcontroller.

4.6.2 The Control System Implementation


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The microcontroller is configured for normal operation, i.e.

connecting the power-on-reset, the crystal oscillator.

Then, the controller is connected to the input interface of

figure 5.1.2.

4.6.3 The Output Interface Implementation

The output of the system includes the signal that triggers

the relay drivers to switch a corresponding heater ON or

OFF. This signal comes from the output port 1 (p1.0 - p1.3)

of the 8952 microcontroller. The implementation of the

output interface connected to the input section is shown in

the diagram below.


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Fig. 5.1.4: Diagram showing output and input interfaces

to microcontroller

4.7 System simulation test

The PC-based automatic multipoint temperature

monitoring and control system essentially comprises two

basic parts, namely: the hardware and the software parts.

So far, the hardware has been implemented. A systematic

test of the hardware on proteus is to be done. At this

point, the embedded software is loaded to the

microcontroller and every aspect of the hardware tested.


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The temperature inputs are simulated while the variation

in the temperature is observed on the LCD. The serial

virtual tool is used to view what the m

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