i

DESIGN AND CONSTRUCTION OF A MICROCONTROLLER-BASED MAINS SWITCH

CONTROL SYSTEM

BY

GWAGWA O. TUBUKARE NAU/ECE/2008366010P

A THESIS PRESENTED TO THE DEPARTMENT OF ELECTRONICS AND COMPUTER ENGINEERING

NNAMDI AZIKIWE UNIVESITY, AWKA IN PARTIAL FULFILMENT FOR THE AWARD OF MASTER OF ENGINEERING DEGREE (M. ENG)

IN ELECTRONICS AND COMPUTER ENGINEERING

SEPTEMBER, 2010

ii

iii

CERTIFICATION

The thesis a microcontroller- based mains switch control system

presented by GWAGWA O. TUBUKARE has been read and certified to

have met requirement of the Department of Electronics and Computer

Engineering in the Faculty of Engineering, in project presentation to acquire

a Masters Degree in Engineering.

GWAGWA O. TUBUKARE ..

NAU/ECE/2008366010P Signature Date

iv

APPROVAL

This thesis titled a microcontroller- based mains switch control

system has been approved for the department of Electronics and Computer

Engineering:

BY - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Engr. Prof. H.C. Inyiama Date Supervisor - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Engr. Dr. V. E. Idigo Date HOD - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Prof. C.C. Osuagwu Date External Examiner - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Prof. O.D.Onukwuli Date Dean of Faculty of Engineering - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Prof. N.O. Anike Date Dean School of Postgraduate

v

DEDICATION

To the Lord God Almighty who is the owner of my life and for His divine

providence, love and care.

vi

ACKNOWLEDGEMENT

My sincere gratitude goes to my supervisor, Engr. Prof. H. C. Inyiama, who

has been so supportive to me throughout the period of this program. Also to

my head of department, Engr. (Dr) V. E. Idigo, for his quick response. My

regards to Engr. Dr. (Mrs.) C. C. Okezie, Engr prof. G.N. Onoh, Engr. (Dr)

Eric Okafor, Engr. C. U. Mezi, Engr. A.C. O. Azubogu, Engr. K Akpado,

Engr. C.O. Ohaneme, Engr. A.N. Isizoh, Mr. T.L. Alumona, Mrs. S.U.

Nnebe, Mr. S.P.C. Ndum, Engr. T.C. Okafor, Engr. O.O. Eze, Engr. H.

Ejiofor, Mr. U.P. Ajakor, Mr. C. Ogu,Mr. J.U. Oguejiofor, Mr. T. Onyeyili,

Engr. V.N. Okorogu, Mr. O.O. Nnaeto and staff of the Department of

Electronics and Computer Engineering. Greetings to all my friends, and

fellow classmates who supported me by their encouragement. May God

bless you all.

Special thanks to the members of my family, especially to my wife Mrs.

Gwagwa Mary and my children, Ufuoma Priscilla Gwagwa, Oghenekevwe

Joy Gwagwa, Ovie Gideon Gwagwa and Oghenetega Goodness Gwagwa

for their good courage and patience. May the LORD bless with you all.

vii

ABSTRACT

Many people tend to enjoy use of facilities without control even when there

are bills to settle to guarantee continuity. This project was born out of the

desire to prevent damages and time wastage on control of industrial

equipment. It is designed to control all the facilities (for example electrical

appliances) not only in the hospitality industry but also in organizations such

as schools, for security, safety and elimination of problems associated with

manual switching. The system is a microcontroller-based mains switch

control project which automatically controls AC loads connected to it

through a serial port interface. The switch control system can range from

simply controlling of light without leaving a seat, to being able to switch on

and off industrial electrical devices through a computer interface, so the

system produced will enable the switches to be controlled from one source

(computer system) by simply issuing a command through the interface on

the computer screen to save the time of going from one switch to another to

put on or off the industrial equipments since the switches can be controlled

from a remote system.

viii

TABLE OF CONTENTS

Title Page ... i

Unizik Logo.ii

Certification............ iii

Approval ... iv

Dedication . v

Acknowledgement .vi

Abstract . . ..vii Table of content viii

Chapter One: Introduction

1. 1 Background 1

1.2 Objective .3

1.3 Significance of the Project...4 1.4The scope of the Project5

1.5 Block diagram Overview of the Project .. 6

Chapter Two: Literature Review

2.1 Introduction........ 8

2.2 Overview of Lighting Controller... 11

ix

2.3 Methods of Control. 13

2.4 Types of Systems. 15

2.5 Manual Switching System... 17

2.6 History of Automation. 19

Chapter Three: Methodology and System Analysis

3.1 Introduction .21

3.1.1 Methodology .22

3.1.2 Prototyping22

3.1.3 Classification of system Prototypes. .23

3.1.4 Steps involved in Prototyping.. .24

3.1.5 Advantages of Prototyping25

3.1.6 Disadvantages of Prototyping....26

3.2 Analysis of the Existing System26

3.2.1Three Features of Existing Switch28

3.3The Problem of the Existing Switch 28

3.4 Overview of the Proposed Solution.29

3.4.1 High level model of the proposed Solution. .30

x

Chapter Four: System Design

4.0 Introduction 32

4.1 The Design Objective .34

4.2 Design Process34

4.3 Control Center .36

4.3.1 The hardware Module...36

4.3.2 Switching Circuit..37

4.3.3 Control Module.38

4.3.4 Transmitting Module.39

4.3.4 Receiving Module ....41

4.4 Relay Section..42

4.4,1 Relay driver Unit43

4.5 Power supply Section (Circuit) 45

4.5.1 Electrical Components Used..47

4.6 Functions...48

4.7 Max 232 serial Interface.....50

4.7.1 Serial Connection to the PC51

4.8 Microcontroller Section..54

4.8.1 Mathematical Specification.57

4.9 System software Algorithm.......57

4.10 Justification and choice of Programming Language60

4.11 Data Dictionary.60

xi

Chapter Five: System Implementation and Testing

5.0 Introduction.62

5.1 Hardware Requirements..63

5.2 The control Subsystem63

5.3 Installation Process.66

5.4 How to open the Software...66

5.5 Hardware Guide..67

5.6 System Testing67

5.6.1 Pre-implementation Testing.68

5.6.2 Post-implementation Testing69

5.7 Program Documentation (Operation)..70

5.8 Maintenance Details..71

5.9 Performance Evaluation72

5.10 Project Costing....72

Chapter Six: Summary and Conclusion

6.0 Summary.74

6.1 Problems Encountered75

6.2 Contribution to the Body of Knowledge.75

6.3 Recommendations...76

6.4 Conclusion..77

References...................................................................................78

Appendices

Appendix i: Source Code.. 81

xii

Appendix ii: Sample Output of the Visual Basic Code101

Appendix iii: Evidence of Completion102

Appendix iv: Operational Guide Manual.103

List of Figures

Figure 1.1 Block Diagram overview of the Digital Control System. 6

Figure 3.1 High-Level Model of the Proposed System 31

Figure 4.1 Project block diagram...33

Figure 4.2 The Design Loop..35

Figure 4.3 Diagram of the Hardware Module...37

Figure 4.4 The Data Circuit Diagram38

Figure 4.5 Circuit Diagram of Relay......43

Figure 4.6 Relay Driver Circuit Diagram..44

Figure 4.7 Block Diagram of a Regulated Power Supply System45

Figure 4.8 Block Diagram of the Power Supply Circuits.47

Figure 4.9 Schematic MAX-232 diagram.........51

Figure 4.10 Serial Connection to the PC......52

Figure 4.11 RS-232 Connections using the MAX232 53

Figure 4.11 Shows the Pin- out of the 8952 Microcontroller 54

Figure 4.12 Circuit Diagram of Quartz Crystal Oscillator..56

Figure 4.13 The Overall program Flow Chart.....59

Figure 5.1: The AT89C52 Implementing the Control Subsystem ......65

Figure 5.2 Overall Circuit Diagram.73

List of Table

Table 5.1 Showing the Operational Status of the System 70

1

CHAPTER ONE: INTRODUCTION

1.1 BACKGROUND

Man has been in a continuous quest to improve his well being through

reactions to problems and challenges posed by his environment. For the past

decades, computer and computer communication had gained so much

attention and grown tremendously, that portable and affordable computers

have become ubiquitous. Statistics have shown that most people spend most

of their time on computers, connected together by a network (locally or

globally). Since much time is spent on computer systems, it becomes

necessary to design a device for controlling switches from computer.

Switches are so essential that one cannot avoid using them on a daily basis

for putting on or turning off electrical devices, and as a result of these, many

devices have been designed by man to help him conquer these problems and

challenges posed by physical contact with electricity [1]. The switch control

system can range from simply controlling of light without leaving a seat, to

being able to switch on industrial electrical devices through a computer.

There has to be an interface between industrial electrical devices and a

controller, the personal computer (PC) in this case. Interface is required so

2

that the PC can communicate with other devices. The interface used in this

work is the computer port interface [2]. The microcontroller-based mains

switch control system is made up of several devices connected together;

keypads that transmit commands to the device, the controller that is

programmed to put on or off the appliances automatically via a computer

system [9].

It has been observed that the manual switching of the industrial equipment

in the industrial sector has many problems associated with it, which

includes:

Life of the switch operator might be at risk.

Damage of the industrial equipment.

Dissatisfaction of customers due to damaged equipment.

Time wastage.

As a result of the outlined problems associated with manual switching, the

design of a device that will be able to control switches via a computer

system is intended. The system is aimed at solving the associated problems.

3

1.2 OBJECTIVES

This research work is aimed at constructing effective software and

hardware for microcontroller-based mains switch control system.

Specifically the objectives are to produce a device that:

Saves the time of going from one switch to another to put on or

off the industrial equipments since the switches can be

controlled from a remote place (computer system).

Has program control switch, which will help to reduce the use of

manual switches, if not eliminating it completely.

To create a system that ensure integrity of the complete

microcontroller system during all forms of environmental stress

(shock, transient noise) etc.

Removes friction with the use of the program control switch.

4

1.3 SIGNIFICANCE OF THE PROJECT

The significance of this research work is that the system is designed to show

that it can be useful in the industrial sector, large or small organization such

as schools, hotels and business centers and governments. The system

produced will enable the switches to be controlled from one source

(computer system) by simply issuing a command through the interface on

the computer screen. This work can also create job opportunities.

Time: This work will be able to save the time it takes to manually go

from one device point to another to ensure that proper measures are

taken.

Safety: This will prevent human physical contact with the manual

switches, which we know has taken many lives due to power

instability.

Cost: The system reduces the cost of buying switches, which will

easily wear out due to frequent use.

Home device: This system can equally reduce stress at home

especially when everybody at home is off to work. So it can be used

5

when the system in which it is installed is on line by making it a

web- based.

This work can be used for academic purpose.

Generation of fund: When an organization makes greater profit, they

tend to pay larger tax to the government.

1.4 THE SCOPE OF THE PROJECT

This project is limited to the control of electrical devices from a standalone

computer system. This prototype is achieved through the serial port and

expected to control up to three devices, which will be demonstrated with

three bulbs via three relays. This is achieved through an interface with a

microcontroller, an integrated circuit that contains the entire central

processing unit of a computer on a single chip. It can interpret and execute

program instructions as well as handle arithmetic operations [1]. Their

development in the late 1970s enabled computer engineers to develop

microcomputers. Microprocessors led to "intelligent" terminals, such as

bank ATMs and point-of-sale devices, and to automatic control of much

industrial instrumentation and hospital equipment, programmable

microwave ovens, and electronic games. Many automobiles use

6

microprocessor-controlled ignition and fuel systems. In essence, the

microprocessor contains the core elements of a computer system, its

computation and control engine.

1.5 BLOCK DIAGRAM OVERVIEW OF THE PROJECT

Figure1.1: Block diagram overview of the centralized

digital control system

BRIEF STUDY AND

BACKGROUND

MICROPROCESSOR SWITCH

CONTROL SYSTEM

SUMMARY, ACHIEVEMENTS

RECOMMENDATION,

SUGGESTION AND CONCLUSION

SYSTEM IMPLEMENTATION

AND TESTING

REVIEW ON

MICROPROCESSOR-BASED

SWITCH CONTROL SYSTEM

SYSTEM DESIGN

RESEARCH METHODOLOGY

AND ANALYSIS

7

To ensure clarity as well as understanding of this project work, this report is

presented in six chapters. Chapter one deals on the introduction with some

basic definitions necessary for proper understanding of the project topic.

Chapter two embodies the review of related works while chapter three

describes the methodology and system analysis. Chapter four showcases the

system design a description of the performance analysis. Chapter five

discussed the system implementation. The last chapter chapter six

summarizes the research work and states conclusion. References and

appendices follow immediately after chapter six.

8

CHAPTER TWO: LITERATURE REVIEW

2.1 INTRODUUCTION

A control system is a device or set of devices used to manage, command,

direct or regulate the behaviour of other devices or system. The term control

system may be applied to the essentially manual controls that allow an

operator to, for example close and open a hydraulic press, where the logic

requires that it cannot be moved unless safety guards are in place.

There are two common classes of control systems with many variations and

combinations: logic or sequential controls and feedback or linear controls.

There is also fuzzy logic, which attempts to combine some of the design

simplicity of logic (the study of the principles of valid inference and

demonstration) with the utility of linear control. Some devices or systems

are not controllable. An automatic sequential control may trigger a series of

mechanical actuators (mechanical device form ring or controlling a

mechanism or system) in the correct sequence to perform a task. In the case

of linear feedback systems, a control loop, including sensors (a device that

measures a physical quantity and converts it into a signal which can be read

9

by an observer or by an instrument), control algorithms and actuators, is

arranged in such a fashion as to try to regulate a variable at a reference value

or set point. An example of this may be to increase the fuel supply to a

furnace when a measured temperature drops. As Wikipedia cited, PID

controllers (proportional- integral- derivative controller) is a generic control

loop feedback mechanism widely used in industrial control system, attempts

to correct the error between a measured process variable and a desired

setpoint by calculating and then outputting a corrective action that can adjust

the process accordingly to keep the error minimal. Open loop control

systems do not directly make use of feedback, but run only in pre-arranged

ways. Pure logic control systems were historically implemented by

electricians with network relays and designed with a notation called Ladder

logic [3].

Today, most of such systems are constructed with programmable logic

devices. ON OFF control, for example a switch control is a simple

negative- feedback, when light goes below a setpoint (SP), the light is

switched OFF but when it goes above a setpoint, the light is switched ON,

logic controllers may respond to switches, light sensor and pressure switches

10

and cause the machinery to perform some operation. They are used to

sequence mechanical operations in many applications. Some techniques are

used in control system like the Derivative action which is a part concerned

with the rate of change of the error with time. This action makes control

system behave much more intelligently. The microcontroller- based switch

control system uses specialized equipment to control the switching of

electrical devices. Through the interface on the computer, one can switch

on/off electrical appliances from remote places. Sayers et al. (1991) noted

that technological advances in Digital Signal processor (DSPS), networking,

microprocessors, and programmable logic devices (PLDS) have empowered

designers with entirely new techniques and methodologies that were

economically unthinkable two decades ago. These advances, along with

increased performance demands, have fueled the push of digital technology

deeper into the controlled devices. The justification often quoted for this

push to digital control includes reproductively, increased stability, increased

resolution and decreased infrastructure costs (networks replace control

wiring) [4].

11

2.2 OVERVIEW OF LIGHTING CONTROLLER

A switch is a device that opens or closes a circuit. Switch is a device that

causes the operation of a circuit between discrete specified levels. The

technology of the automation evolves from a manually switching of devices

on or off. This automation can be illustrated with a control system that

uses a computer system to control the state (on/off) of appliances.

Advanced English Dictionary, defines control to mean the authority, or

the power to influence or guide something. It can also be defined as the

levers, switches and other instruments for operating a machine or other

devices. Lighting Controller here can be defined as responsible for directing

or controlling the light automatically whether remotely or locally in contrast

with the manual control where people need to go to the located switch to

turn on or off the light. This reflects the evolution from Energy Management

Systems in which a central computer was used to control the lamps in a

building. A lighting automation technology can enable the person by

assisting in daily routines and enabling the individual to achieve tasks, they

might not have previously been able to achieve. Tasks can range in levels of

complexity from simple tasks such as turning on or off lights through to

12

fully automating the majority of electrical systems within the building.

Referring to Bill Gates (2000), We will be able to control our entertainment

systems in simple but elegant ways, use any TV in the house to monitor

inexpensive outdoor surveillance cameras and connect to the Internet from

multiple locations [23]. Some of these tasks will not require a PC, but in the

end it will make sense to have a computer to quietly orchestrate the

operations of the systems in a house.

Most of the todays lighting automation technologies requires computer to

operate them. Even the stand alone designs need computer to be initialized.

The existence of computer technology had driven the lighting automation

technology into the right path. The capability of the lighting automation

technology has transformed the environment to be an intelligent

environment or smart environment (Heimer, 1995) [23].

13

2.3 METHODS OF CONTROL

There are many options available for controlling the lighting system. In

order to operate all the mechanical and electrical devices, it requires either a

very large or a very complex remote control keypad. There are several

options of the lighting control method that can be identified and these are:

Computer

Control systems can be completely computerized. This capability

allows us to perform complete control and monitoring functions from

any personal computer.

Hand Held Remote Control

Similar to a standard universal remote control that we use for the

television, DVD player, VCR, or any other electronic equipment, a

Hand-Held Remote Control is used to provide portable, in home,

control of any function available in the home automation system.

14

Timed Events

Employing a computer-controlled system typically includes software

that can be programmed to initiate activities. This capability provides

the ability to trigger, or initiate, pre-defined events at pre-scheduled

times or under predefined conditions. For example, the system can be

programmed to turn off all room lights, turn on fan, and turn on gate

lamps.

Keypad

A keypad is the least costly method to control light fixtures, lighting

scenes, audio/video (AV) equipment, or other devices. These are wall

plates, similar to a regular wall switch plate with 2 to 8 buttons on

them. Simply press a button to initiate the desired action. A single

button press may activate only one light fixture, many fixtures

located anywhere in the home, or lighting with AV events

simultaneously. Each plate has an engraved description as to what

each button will activate. Buttons can be illuminated for locating

them in the dark.

15

Liquid Crystal Display

A LCD Touch Screen controls everything a keypad does plus it can

display an array of additional information. The display may include

such things as video camera shots, email, weather, and stock quotes.

These can be presented on a greyscale screen or on full colour

screens. In addition, the information is presented in real-time.

Essential for Heat, ventilation and air conditioner (HVAC) and

monitoring, LCD screens provide enhanced control of the lighting,

AV systems, security, and the capability to control the entire home

from any room.

2.4 TYPES OF SYSTEMS

There are several types of systems, or commonly called system protocols,

that perform light control to suit occupant needs and budget. All of these

various types of control systems should have the capability for interfacing

with other systems in the building.

16

Power Line Carrier (PLC)

This technology or protocol has existed for over 20 years and used

for existing homes and expanding existing systems. A command

signal is transmitted over our existing 230 volt home wiring.

Wireless Protocols

Wireless technology, sometimes referred to as RF, or radio

frequency, control systems, have existed for over 10 years. RF

components are used in the construction of wireless devices. However,

RF is more commonly used for existing homes and for expanding existing

hardwired systems. A command signal is transmitted by radio waves to the

controller. Systems using this technology have been experiencing

increasing reliability and dependability.

Hardwired Systems

This technology has existed for over 40 years. Hardwired systems

create a communications network within the home that is impervious

to the problems that are sometimes suffered by the other protocols

described above. This technology is most always used in new

construction due to the extremely reliable communication by a data

17

path over wire placed in the walls before they are covered. This is

known as pre-wiring the home for control. This system can also be

used during major home remodels and controlling other sections of

the home not being remodeled with one of the wireless methods

described above.

2.5 MANUAL SWITCHING SYSTEM.

The operation of manual switching system is by controlling the switching

by hands. One can switch something off: to turn off electric bulb or

industrial equipment or appliance with a switch or one can switch on: to turn

on electricity with a switch. A switch is a device for completing or breaking

a circuit [1]. In a Multi- throw switch, there are two possible transient

behaviour as you move from one position to another. In some switch

designs, the new contact is made before the old contact is broken. This is

known as make-before- break and ensures that the moving contact never

sees an open circuit. The alternative is break-before-make, where the old

contact is broken before the new one is made. This ensures that the two

contacts are never shorted to each other.

18

The two types of designs are in common use for different applications.

According to Leo Martins, placing parenthesis around all position rather

than the resting position can modify the on-off notation; for example, on

(on) - off- (on) switch can be switched on by moving the actuator in either

direction away from the center but returns to the control off position when

the actuator is released [24].

Push-to-make switch makes contact when the button is pressed and breaks

when the button is released. A push to break switch breaks contact when

the button is pressed and makes contact when it is released. An example of

push-to-break switch is a button used to release a door hold open by an

electromagnetic system. According to Chris Kotoroski, the word toggle is a

reference to the kind of mechanism or joint consisting of two arms, which

are almost in line with each other, connected with an elbow- like pivot.

Toggle switch is a generic class of electrical switch that uses a mechanical

lever, handle or rocking mechanism to activate it [7].

19

2.6 HISTORY OF AUTOMATION.

The first industrial robot, used in 1965 was controlled by a computer and

worked in an automobile assembly plant. Since 1980s, the use of computer

machines has greatly stimulated development. Stephanie (2002), IBM in

1981, introduced its personal computer (PC) for use in home, offices and

schools [25]. Prior to the time there had been several MS-DOS compatible

personal computers that ran DOS programs. As smaller computers became

more powerful, they could be linked or networked to share memory space,

software and information and also communicate with others. Organizations

have come a long way in using technology over the past years. From the

early 1980 through the mid- 1990s, Organizations for the most part used PC

based automated system to boost efficiency and cut cost. Many roles for

human industrial processes presently lie beyond the scope of automation.

Automated control systems have reduced the need for a client to use his

hand in controlling electrical appliances in a hotel. In general, automation

has been responsible for the shift in the world economy to industries in the

19th century and from industrial to services in the 20th century [3].

20

James Watt (1787), a Scottish engineer constructed a device called a flyball

governor to regulate the speed of a steam engine [22]. The use of the flyball

governor marked the first industrial application of automation. These days,

technology and automation have advanced to the stage of controlling some

of the electrical appliances (equipment) at home, office, industries, hotels etc

through a personal computer (PC). This led to the design of this project

microcontroller- based mains switch control system.

21

CHAPTER THREE: METHODOLOGY AND SYSTEM ANALYSIS

3.1 INTRODUCTION:

System Analysis means the procedural study of the operation of a system

with an attempt to discover its problem areas i.e. to know why the system is

not functioning properly and what can be done to restructure the system.

This chapter is concerned with investigation and analysis of the existing

system with a view to understanding how it works including the problems

and limitations. The characteristic attributes of a problem situation where

system analysis is required are complexity of the issue and uncertainty of the

outcome of any course of action that might reasonably be taken. System

analysis usually has some combination of the following: Identification and

re- Identification of objectives, constrains, and alternative course of action;

examination of the probable consequences of the alternative in terms of

costs, benefits and risk; presentation of the results in a comparative

framework so that the decision maker can make an informed choice from

among the alternatives.

This chapter also deals with the methodology, considering the advantages of

each and the justification of the need for the proposed system.

22

3.1.1 METHODOLOGY

Internationally Software Engineering has accepted standards for

transforming ideas in software. They include:

The structured system Analysis and Design methodology

(SSADM)

Prototyping

Experts system methodology

Usability engineering methodologies, etc.

The methodology applied in the system is prototyping and is discussed

below.

3.1.2 PROTOTYPING

The prototyping methodology is applied in the development of this

project. Prototyping is the process of building a model of a system. It

is a model of a system, built to show off certain features or to get a

working model before refining other parts of the design or just to

evaluate the feasibility of the system development. A system

prototype is a working system built to test ideas and assumptions

23

about the proposed system. Prototyping is an iterative process that is

part of the analysis phase of the system development life cycle. It

helps the analyst develop an initial set of system requirements.

In electronics, prototyping means building an actual circuit to a design

to verify that it works, and to provide a physical platform for

debugging it, if it does not work. Prototyping sometimes converts

intangible specifications into a tangible but limited working model of

the desired information system.

3.1.3 CLASSIFICATION OF SYSTEM PROTOTYPES

System prototypes could be classified into:

I. Evolutionary prototype: This design is adapted for permanent use

after the ideas are clarified and must be built using the program tools

that will be used for the final system.

II. The throwaway prototype: This design is to be discarded after

utilization; basically it is to test ideas and is especially useful for

comparing alternative designs for part of a system.

24

3.1.4 STEP INVOLVED IN PROTOTYPING

I. Identify the users known information requirements and features

needed in the system.

II. Develop a working prototype.

III. Use the prototype, noting need enhancements and changes; this

expands the list of known system requirements.

IV. Revise the prototype based on information gained through user

experience.

V. Repeat these steps as needed to achieve a satisfactory system.

When both user and analyst decide that sufficient information has been

collected for the prototyping process, they determine how to meet the

requirements they have identified using one of the following

alternatives.

a. The prototype is redeveloped

b. The prototype is implemented as the completed system.

25

c. The project is abandoned; in this case the prototype has been

provided to meet the desired objectives within existing

technology or economic or operational guidelines

d. Another prototype series is begun: The information gained

through the current experience may suggest an entirely different

approach or contrasting features.

3.1.5 ADVANTAGES OF PROTOTYPING

I. Requires user involvement.

II. It helps to refine the potential risks associated with the delivery of the

system being developed.

III. Prototyping facilitates system implementation since users know what

to expect and exposed developers to potential future system

enhancements.

IV. User can point to features they like or dislike and so indicate

shortcomings in an existing and working system more easily, and then

they can describe them in a theoretical or proposed system.

26

3.1.6 DISADVANTAGES OF PROTOTYPING.

I. The process of developing a prototype can cause systems to be left

unfinished or implemented before they are ready.

II. Prototyping can sometimes lead to incomplete documentation and

insufficient analysis.

III. The process of developing a prototype may require greater

involvement and commitment by key users who are already busy with

their regular work.

IV. If sophisticated software prototypes are employed, the time saving

benefit of prototyping can be lost.

V. In prototyping, structure of system can be damaged since many

changes could be made and it is not suitable for large applications.

Our prototype in this project is constructed using a microprocessor to

control electrical appliances.

3.2 ANALYSIS OF THE EXISTING SYSTEM

The present procedure involves a manual control of the power switch

by the industrial electrician. The power control switch is operated

with hand by pushing the switch lever to on position if its intended to

27

be turned on or off position if its intended to be turned off. Basically,

during the analysis of this procedure, it is discovered that the

operators is at high risk of been electrocuted. Manually, switches have

been existing for many years in every home, industry, company,

schools and colleges.

These switches are in different standards such as:

1. ON- OFF e.g. toggle switches it is used to switch the power

supply of a circuit. When used with mains electricity, this type

of switch must be in the lives wires.

2. (ON OFF) push- to- make switch is for doorbell.

3. (ON OFF) push- to- break switch is also for doorbell. This

switch can be ON in both positions, switching on a separate

device. In each case, it is often called a change over switch

example; a SPOT switch can be used to switch ON red lamp in

one position and a green lamp in another position.

Reed switch:

The contacts of a reed switch are closed by bringing a small

magnet near the switch. They are used in security circuits, for

28

example to check the doors and close. Standard reed switches

are SPST (simple ON/ OFF)

3.2.1 THREE FEATURES OF EXISTING SWITCH

Contacts (example single pole, double throw)

Rating (maximum voltage and current)

Methods of operation (toggle, slide, key) etc.

3.3 THE PROBEM OF THE EXISTING SWITCHES (SYSTEM)

Electrocution: Those switches claim a lot of lives as a result of

direct contact of the operator with them for example; the

operator might be electrocuted in the process of carrying out

power change over.

Time wastage: it takes time to go from one switch to the other

to ON or OFF them whenever there is power failure.

Friction: friction is applied in operating these switches. Worn

out switches can lead to the damage of the electrical devices

which it is controlling.

29

Frequent touching of the switch causes the damage of the switch

circuit.

Bad switch control might result to serious inferno to industrial

equipment and other valuables.

3.4 OVERVIEW OF THE PROPOSED SOLUTION:

Now that the shortcomings of the present system have been

identified, it becomes necessary to specify what the new system

will achieve:

The new system must eliminate direct contact with switch by

providing an interface on the computer screen through which

the electrical devices will be controlled.

The new system will save the time it takes the device and

operator in going from one switch to another.

The new system must be able to turn ON or OFF the

selected electrical devices anytime any day. To implement an

efficient system integrated with software and hardware

components for the purpose of creating a microcontroller- based

mains switch control system for electrical appliances.

30

The new system must respond in real- time.

There must be a (new) system that is efficient in controlling

power switch without causing any sparking. This help to avoid

interference which may affect any mobile devices.

The new system will have program controlled switching, which

will help to reduce the use of manual switches in the industry.

The new system reduces the movement of the user in switching

ON or OFF the appliances and would be an advantage to the

physically challenged.

3.4.1 HIGH LEVEL MODEL OF THE PROPOSED

SOLUTION.

The High Level model (HLM) is a top- down design

specification of those modules and sub modules identified for

automation. This high level model comprises the power supply

section, MAX- 232, microprocessor, GUI (computer system),

the relay, and the appliances. It is this HLM that is taken to the

system design chapter as the control center, decomposed,

exploded, analyzed, programmed and finally a cohesion is

achieved at the end to bring a system into existence.

31

APPLIANCE 1 APPLIANCE 2 ... APPLIANCE n

Figure 3.1: High-level model of the proposed system

COMPUTER

MAX - 232

MICROCONTROLLER POWER CIRCUIT

RELAY 1 RELAY 2 RELAY n

32

CHAPTER FOUR: SYSTEM DESIGN

4.0 INTRODUCTION:

In this chapter, the design of a switch control system is described for

controlling appliances such as bulbs using a computer system through a

serial port. The Graphical user interface (GUI) through which command is

given to the switch controller circuit is achieved with visual basic. The

system can control other appliances such as Television, Refrigerator, Ceiling

fan etc. This design is a prototype of a switch control system which can be

used in a large organization to control several electrical appliances

connected to it. There is an interface provided by visual basic programming

language, which contains ON buttons and OFF buttons through which

control command is sent to electrical devices. Therefore when any command

button is clicked to switch on or off, device signals go from the control

module through the serial port, serial cable to the Max- 232 interface which

amplifies the signals. The signal goes to the microcontroller and from the

microcontroller the signal gets to the relay through the transistor down to the

bulbs which are the receiving module. The design consists of two modules:

the hardware and the software modules both working together to achieve the

33

desired result. In the hardware module, the power source supplies current to

all the hardware component of the control box. Max 232 acts as buffer that

amplifies the signals coming from the computer. The 8051 microprocessor

used is the controller that controls the relay and makes it function like a

switch.

Figure 4.1 Project Block Diagram

34

4.1 THE DESIGN OBJECTIVE

The objective of the design is to implement a system (prototype) that will

turn ON or OFF three electric bulbs through a computer system. With

this system an operator will not move from one switch point to another in

order to control the appliances as with the case of manual system.

4.2 DESIGN PROCESS

The design process is a basic step by step sequence of tasks that are

performed in various situations. The first step assumes we have an initial

concept about what should be achieved in the design process to generate an

initial design. This often requires a lot of manual effort because most designs

have some specific goals that can be reached only through the designers

skillful knowledge. The next step is the simulation of the design at hand. The

Computer Aided Design (CAD) tools can be helpful in this step. Adequate

input conditions that can be applied to the design that is being simulated and

later to the final product that has to be tested is necessary. By applying these

input conditions, the simulator tries to verify that the designed product will

perform as required under the original product specifications. If the

simulation reveals some errors, then the design must be changed to

35

overcome the errors. Simulation efforts are necessary because errors are

typically much harder to fix if they are discovered late in the design process.

Simulation of redesigned version is to determine whether the errors have

disappeared. Figure 4.1 below is a design sequence. The loop is repeated

until the simulation indicates design successful.

Design Concept

Initial Design

Simulation

Design Correct?

Design Successful

Redesign

No

Yes

Figure 4.2: The Design Loop

36

4.3 CONTROL CENTER.

To bring the system into existence, the high level model or the control center

in chapter three is analyzed and divided into modules. The different modules

or sections include: the hardware module (control module, relay section,

power supply section and microcontroller control section). The control

centre activates the module of interest at any time.

4.3.1 THE HARDWARE MODULE

The hardware module is the main switch controller. It takes power from the

main switch control. There is also a serial cable meant to be connected to the

serial port of a computer system. A USB to Serial (DB-9) adapter could also

be used to connect the serial port to the computer system. The program

which controls the hardware module is written in Assembly and Visual

Basic Programming Language. The assembly language converts the high-

level language which is the VB programming language to machine language

of Zeros (0) and Ones (1).

37

Figure 4.3: Diagram of the Hardware Module

The hardware module is made up of the three circuits

The data circuit

The switching circuit and

The power supply circuit.

4.3.2 SWITCHING CIRCUIT

The switching circuit is made up of BC 337 transistor switching circuit; each

circuit is connected to a relay, a transistor and diode. The relay when

activated, ON or OFF any appliance connected to it. The three lines from the

38

microcontroller are each connected respectively to the BASE pin of the three

corresponding transistor

Figure 4.4: The data circuit diagram

The circuit is the heart of this module. It comprises of 9-pin Dip-male

connector, Max-232, 8952 microcontroller, crystal oscillator. The circuit

connects directly to the computer serial port through a pin cable. The MAX-

232 amplifies signal (VS) that goes into the microcontroller from the

computer system through the serial cables. Serial data is transmitted from

the PC as a series of positive and negative voltage on a single wire, which

serial data occurred at a pre-determined time established by the base wire.

39

The 11-0597MHZ crystal oscillator determines the speed of the 8952

microcontroller used. The microcontroller is connected to the three BC 337A

transistors that operate the relays. Pin 2 and 3 of the serial port are connected

to line 14 and 13 of the MAX- 232.

4.3.3 CONTROL MODULE

The control module consists of the graphical user interface (GUI) and the

software, which controls the hardware and are based on the computer

system. A user interface that is graphical in nature; that is, the user can enter

commands by using a mouse, icons and windows.

4.3.4 TRANSMITTING MODULE

This module consists of the software and some parts of hardware. On

clicking a device button (Command button) on the GUI (graphical user

interface) depending on the previous state of the device, the software should

determine whether to turn ON or OFF the device. The term

transmitter means an electronic device, which with the antenna propagates

an electromagnetic signal such as radio, television or other

40

telecommunications. A transmitter usually has a power supply, an oscillator,

a modulator and amplifiers for audio frequency, intermediate frequency (IF)

and radio frequency (RF). Sometimes a device, e.g. a cell phone contains

both a transmitter and a radio receiver or transceiver. The modulator is the

device which modulates the signal information onto the carrier frequency

which is then broadcasted.

In industrial process, control transmitter is any device which converts

measurement from a sensor into a signal to be received usually sent through

wires by some display or control device located a distance away. Some

transmitter require excellent frequency stability, there are usually several

amplifier stages between oscillator and antenna. Special standard frequency

transmitters use frequency synthesis referenced is to a very stable atomic

clock. This is generated from the oscillators output, filtered with

combination of inductors and capacitors and then amplified.

41

4.3.5 RECEIVING MODULE

This is where the processes are to command and control the desires device.

A receiver is a device whose main function is the reception of signals. It is

designed to perform the task of low and high frequency reception. Receiver

is useful in appliances such as the detection of signals from high-frequency

impendence bridges, signal strength measurement, frequency measurement

and even detection and display of individual component of high frequency

wave. It selects the desired signal from all unwanted signal, amplifying and

demodulating it and displaying it in the desired manner. Then receiver tunes

to the desired signal and converts the incoming signals to an intermediate

frequency is the same for all received signals, regard less of the original

frequency of the signals. Therefore, once the signal has been translated to

the intermediate frequency, circuitry optimized to perform the critical

receiver function at this signal. A Receiver converts all signals to IF value

and then performs the steps needed to fully receive the modulated

information.

42

4.4 RELAY SECTION

A relay is an electrically operated switch that makes or breaks one or more

of the contacts between its terminals [1]. Current flowing through the coil of

the relay creates a magnetic field which attracts a lever and changes the

switch contacts. The coil current can be ON or OFF so relays have two

switch positions and they are double throw (change over) switches. The coil

of a relay passes a relatively large current, typically 10VDC for a 12v relay,

but it can be as much as 10mA for relay designed to operate from lower

voltages.

Three electromagnetic relays are connected to the po (port) of the

microprocessor/microcontroller one of the relay switch is to be connected to

the individual Diode and also has its own separate transistor all connected to

MAX-232. The Diode is located at the back of the circuit board. The circuit

is ON when the relay coil is on and the contact closes. When the coil is off

the circuit is OFF and the contact opens.

43

Figure 4.5: Circuit diagram of relay.

NO- Normally Open: Com is connected to this when the relay coil is on.

COM- Common always connects to this, (NO) it is the moving part of the

switch

NC- Normally closed: Com is connected to this when the relay coil is off.

4.4.1 RELAY DRIVER UNIT

The Relay diver circuit show in figure 4.6 below is designed to control three

different electrically operated appliances. Relay contacts are normally open

and therefore devices are not working at the beginning until energized

through proper order by the micro controller or microprocessor. The relay

output is simply a pull down transistor or open collector output. It can

connect to a power flash with ease. In this design, we employed the BC 337

RL3OMIH-SH-124D

44

transistor. The transistor is used to establish the current necessary to

energize the relay in the collector circuit. With no inputs at the base of the

transistor, the base current, collector current and the coil current are

essentially zero and the relay sits in the un-energized states.

However, when a positive pulse is applied to the base, the transistor turns

on, establishing sufficient current through the coil of the electromagnet to

close the relay. Ideally, the current through the coil and transistor will

quickly drop to zero, the arm of the relay will be released and the relay will

simply remain dormant until the next on signal.

1K MICRO CONTROLLER

1K

1K

BC337

+5V+5V IN4001

RELAY 1 RELAY 2 RELAY 3

IN4001 +5V IN4001

BC337 BC337

Figure 4.6: Relay driver circuit diagram

45

The characteristics of BC337 transistor used is as follows

Lead current is 5mA 10mA

Max voltage 7volts

PD (max) 100mw at 250C

To calculate for the limiting Resistor

R1= Vin = 5

I 5 x 10 3

Therefore a value of 1k is used as the limiting resistor.

4.5 POWER SUPPLY SECTION (CIRCUIT)

There are many types of power supply. The one used for this project is

designed to convert high voltage AC mains electricity to a suitable low

voltage supply for electronic circuits and other devices. The power supply is

broken down into a series of blocks, each of which performs a particular

function.

240AC MAINS

Regulated 5VDC

Figure 4.7: Block Diagram of a Regulated Power Supply System

TRA NSFORMER RECTIFIER

CIRCUIT

SMOOT

HING

VOLTAGE

REGULATOR

46

Transformer: steps down high voltage AC main to low voltage AC.

Rectifier: converts AC to DC, but the DC output is varying Smoothing:

Smoothes the DC from varying greatly to a smaller ripple Regulator:

Eliminates ripple by setting DC output to a fixed voltage. The power

supplies made from these blocks are described below with a circuit diagram.

It consists of 12v 350mA transformer, a rectifier, a 100 out capacitor for

smoothing and a 5v regulator. The 12v transformer input is connected

directly to the 240Vac mains to give a 12Vac. The 12VAC output from the

transformer is passed through four Diodes connected as a bridge rectifier to

rectify the 12Vac voltage to 12VDC which powers and derives the

transistor, 12Vv relay switching after passing through the smoothing

circuits. It also powers a 5v regulator, which converts the 12v dc, which now

drives the ICS.

47

Figure 4.8: Block diagram of the power supply circuit

4.5.1 ELECTRICAL COMPONENTS USED

Other components used for the design are:

1. Resistor (1000)

2. Transistors (BC 337A- NPN configuration)

3. Capacitors

4. Diodes

5. LED (red)

6. Crystal oscillation (11.0592MHZ)

7. Relay (12v)

8. The microcontroller (Intel 8952)

9. The serial port

10. Serial cable

11. Max- 232

In 7812 out

In 7805 out

To relay

To other ICs

48

4.6 FUNCTIONS

In this design, a resistor (1000) is placed in series with each of the

transistors and one with a light- emitting diode (LED) to limit the current

passing through the Transistor and the LED respectively. The NPN transistor

(BC 337A) is used in the design of this project. This semiconductor device

provides current amplification. A small current of I mA flowing between

base and emitter can produce as large as 100MA or more in the collector

emitter circuit. Transistors are therefore widely used as current amplifiers

and as relay drivers. Transistor amplify current, they are used to amplify the

small output current from a logic chip so that it can operate a lamp (bulb) in

relay or other high current device. The B 337A NPN, which are low power

transistors are used to switch the relays coils. A transistor may be sued as

switch (either fully ON with maximum current, or fully OFF with no

current) and as an amplifier (always partly ON).

The amount of current amplification is called the current gain, hFE. When

transistor is saturated the collector current IC is determined by the voltage

and the external resistance in the collector circuit, not by the transistor

current gain.

49

Therefore, the ratio of IC/IB for saturated transistor is tested. Where IB =

Base current, IE = Emitter current. The emitter current IE = IC +IB, but IC

(collector current) is larger than IB, so roughly IE =IC.

Diodes allow electric current to flow in only one direction. The purpose of

the diode in this design is to prevent spikes from the relay coil from

damaging the transistor and the computer on which the circuit is connected

to. It protects the serial port against voltage higher than +5v signal and

against wrong polarity signals. Diodes are used to protect transistor and

integrated circuits from the brief high voltage produced when the relay coil

is switched off. The protection diode is connected across the relay; it is

connected so that it will normally not conduct. Conduction only occurs when

the relay coil is switched off, at this moment current tries to continue

flowing through the coil and it is harmlessly diverted through the diode.

Without the diode no current could flow and the coil would produce a

damaging voltage spike in its attempt to keep the current flowing. The

Crystal oscillator determines the speed of the microprocessor in the

hardware module.

50

4.7 MAX 232 SERIAL INTERFACE

For communication between the personal computer and the

microprocessor an interface is needed. The Max-232 serial converter IC

is connected between computer and the microprocessor. It works with

voltages =15V to +15V. Modern low power consumption logic operates

in the range of 0V and +3.3V or even lower. To receive serial data from

the interface the voltage has to be reduced. Also the low and high voltage

level has to be inverted. This level converter uses a Max232 and five

capacitors. The MAX232 from Maxim was the first IC which in one

package contains the necessary drivers and receivers to adapt the RS-232

signal voltage levels to TTL logic [18].

51

Figure 4.9: Schematic Max-232 diagram

4.7.1 SERIAL CONNECTION TO THE PC

The expanded drawing below shows the actual connections to a PC from the

MAX 232A in the circuit above. T1 OUT, pin#14 on the MAX232A goes to

pin#2 on the DB9 attached to the PC serial port. Pin# 13, R1 IN on the

MAX232A goes to pin# 3 of the DB9 connector attached to a PC serial

port. Make sure to connect pin#5 from the DB9 connector to the circuit

GND. Below is a quick hookup diagram showing (only) the connections to

the DB9 serial connector without the capacitors. Make these last three

52

connections after building the circuit above to connect the programmer to

your PCs serial port.[18]

Figure 4.10: Serial connection to the PC

Here's an expanded drawing showing the actual connections to your PC

from the MAX232A in the circuit above. T1 OUT, pin#14 on the

MAX232A goes to pin#2 on the DB9 attached to the PC serial port. Pin#

13, R1 IN on the MAX232A goes to pin# 3 of the DB9 connector attached

to your PC serial port. Make sure to connect pin#5 from the DB9 connector

to your circuit GND. Below is a quick hookup diagram showing (only) the

connections to the DB9 serial connector without the capacitors. Make these

53

last three connections after you have built the circuit above to connect your

programmer to your PCs serial port.[18]

Figure 4.11: RS-232 Connections using the Max-232

Five capacitors are normally required for the MAX232A. If you don't mind

the added expense, or you want to conserve board space, you can use the

MAX233 that doesn't require the 5 external capacitors; however the

MAX233 is considerably more expensive so I chose to use the 232 to keep

the project costs to a minimum [18].

54

4.8 MICROCONTROLLER SECTION The 8051 microprocessor is a low- power, high performance CMOS 8- bit

microprocessor with 4KB of flash Erasable and programmable read only

memory (EPROM). This devices is compatible with the industry standard

8051 instruction set and pin configuration. The on-chip flash allows the

program memory to be quickly reprogrammed using non-volatile memory

programmer such as PG302.

Figure 4.12: Shows the pin- out of the 8952 Microcontroller.

55

The 8952 microcontroller has 40 pins functioning 1/0 port lines. Each pin

can operate as a control line or pin of the address or data bus. Each line can

operate independently in interfacing to single- bit devices like switches,

LEDS, transistors, speakers etc.

Port 0: port 0 is a dual-purpose port on pins 32-39 of the 8952 IC. It is use as

a general- purpose 1/0 port.

Port 1: port 1 pin is available for interfacing to external devices required. No

alternate function are assigned for port 1 pins, thus they are for interfacing to

external devices.

Port 2: Port 2 is a dual-purpose port as well as general-purpose 1/0 design

with external code memory or more than 256bytes of external memory.

Port 3: These pins are multifunctional with each having an alternate purpose

related to special features of the 8051.

RESET: This is on pin 9 of the 8952-microcontroller audio used for

resetting the device. The circuit is shown in the figure below;

GND: The on pin 20. It is an input pin and is used for the circuit ground of

the system.

ALE: This is on pin 30. It means Address Latch Enable. It is an output

function pin for latching the low byte of the address during access to

external memory.

EA: This is on pin 31. It is an input function pin for external access enables

it must be strapped to GND to enable the device to fetch code from external

program memory.

56

XTAL1: XTAL1 is on pin 18.It is an input function to the inverting

oscillator amplifier (crystal) and to the internal clock operating

circuit.XTAL2 is on pin 19 and is an output function pin from the inverting

oscillator amplifier. Also two capacitors is connected of 30 PF value is also

connected where one side of the capacitor is connected to the ground as

shown below in fig 4.7

Figure 4.13: Circuit diagram of quartz Crystal Oscillator

The essence of the crystal oscillator is to control the speed of the

microcontroller. Here, the speed of the microcontroller refers to the

maximum oscillator frequency connected to XTAL1; in this case a crystal

with 11.059MHZ frequency was used. The frequency can be observed on the

XTAL2 pin using the oscilloscope.

30F

30F

57

4.8.1 MATHEMATICAL SPECIFICATION

CALCULATION ON MICROCONTROLLER

Mathematically; the 8952 microcontroller operate at a maximum frequency

of 24MHZ. Any crystal oscillator frequency within this range will operate

the controller effectively. However, we chose to use an 11.059 MHZ crystal

12 crystal pulses make 1 cycle (instruction line), so using an 11.059MHZ

crystal oscillator i.e. 11.059,000 crystals pulses/sec => 11.059,000. Then the

controller executes approximately 1,000,000 instructions every seconds.

Thus the time it takes to execute a single instruction is =1/1000,000 =1s

which implies that it takes 1 micro second to execute a single instructions.

1 s= 1000,000.

4.9 SYSTEM SOFTWARE ALGORITHM

After building the hardware, the chip is as good as nothing if there is no

software program to direct the actions of the microcontroller. The sequence

of operation used to solve a problem is often called ALGORITHM. It is this

sequence of operation that constitutes the action of the microcontroller chip.

A very simply way of representing these sequence of actions is by the use of

58

flow charts. This is a guide in writing the assembly language program that

runs the microcontroller. A program is an orderly sequence of machine

instructions that can be obtained using a high level or low level

programming language statement. The written program is burn in

microcontroller using EEPROM programmer. Shown below is a flow chart

that describes the action of this project.

59

Figure 4.14: The overall program flow chart

IS THE

APPLIANCE

ON?

START

SWITCH ON THE

APPLIANCE

SWITCH OFF THE

APPLIANCE

NO YES

MAX-232

MICROPROCESSOR

RELAY 1 RELAY 2 RELAY n

APPLIANCE 1 APPLIANCE 2 APPLIANCE n

60

4.10 JUSTIFICATION AND CHOICE OF PROGRAMMING LANGUAGE

For this project, assembly language was chosen because it is hardware

driven i.e. language that is close to the hardware than the high level or other

languages. Assembly language is a language which is one step above

machine, where abbreviations called mnemonics substitute for the

machine code. Unlike other programming languages, assembly language is

not a single language, but a group of languages. Each processor family has

its own assembly language.

4.11 DATA DICTIONARY

Data dictionary contains the list and meaning of all the variables to be used

in the development of the application including alias names:

Mov it is used to move the content of a register to another register.

Org it is used to initialize the assembler

Clr it is used for clearing a port or a register

Cancel it is a name use for representing the port for the cancel button.

61

Jnb it is a short form of jump on bit. It checks if its first variable is set and

if true, it executes the second variable

Call it is a name used for calling a function

Scan it is used as a label in a program

Ret it is used for returning to a call from a subroutine.

Setb it is used for sending a 1 to a register or to a port.

62

CHAPTER FIVE: SYSTEM IMPLEMENTATION AND TESTING

5.0 INTRODUCTION

The various units of the microcontroller- based mains switch control system

(both the hardware and software subsystems) are implemented using

different circuitry formulations that satisfy the aim of the design, and

software coding using a specific software language that provide appropriate

control as specified in the design

Concerning the implementation of this system the hardware part of the

design; that is, the wired diagram of the system is shown. In chapter four the

design of the system was shown to be consisting of three circuits, the power

supply circuit, switching circuit and the data circuit. This chapter also states

the system operation of the device. Brief attention was given to the issue of

programming and the other constructions carried out during the design

process. The chapter five of this work will deal with the implementation of

the hardware and software designs, testing the system, and performance

evaluation.

63

5.1 HARDWARE REQUIREMENTS

Microcontroller

Transistors

Relays

AC bulbs

Capacitors

LEDS

Switches

Diodes

Resistors

5.2 THE CONTROL SUBSYSTEM

The implementation of the control subsystem is done using a single

microcontroller chip. This chip, the AT89C52WD belong to the 8051 family

of chips and comes as a 40pin integrated circuit (IC). The AT89C52WD is a

low power; high-performance CMOS 8-bit microcontroller (microcomputer)

with 20K byte of flash programmable and erasable read only memory

(ROM). Manufactured using Atmels high density nonvolatile memory

technology this device is compatible with the industry standard 80C51

instruction set and pin out. The on-chip flash allows the program memory to

be reprogrammed in system or by a conventional non-volatile memory

64

programmer. By combining a versatile 8-bit CPU with Flash on a monolithic

chip, the Atmel AT89C52 is a powerful microcontroller which provides a

highly flexible and cost effective solution to many embedded control

applications [19, 20].

This microcontroller chip runs on a clock frequency of up to 33MHZ and

has a 256 x 8bit internal RAM, with 32 programmable I/O lines including

other features making it very suitable for output application. The

programmable 32 I/O lines are grouped into four ports each having 8 pins.

These ports labeled P0 to P3 can be used as an 8 bit data bus with the port

address or single bit data each using the particular pin address [20]. The

connection of the controller for our application is as shown figure 5.1.

65

Figure 5.1: The AT89C52 Implementing the control Subsystem

The specification sheet of the AT89C52 shows that the reset (RST) input

voltage is 0.7Vmin to (Vcc + 0.5)Vmax. Meaning the microcontroller will

reset at an input voltages of - 0.7V to Vcc + 0.5V. This implies that the chip

will run only when the reset input is below 0.7V down to 0V. It is required

that the chip reset to start the execution of internal program from the origin

XTAL218

XTAL119

ALE30

EA31

PSEN29

RST9

P0.0/AD0 39

P0.1/AD1 38

P0.2/AD2 37

P0.3/AD3 36

P0.4/AD4 35

P0.5/AD5 34

P0.6/AD6 33

P0.7/AD7 32

P1.0/T21

P1.1/T2EX2

P1.23

P1.34

P1.45

P1.56

P1.67

P1.78

P3.0/RXD 10

P3.1/TXD 11

P3.2/INT0 12

P3.3/INT1 13

P3.4/T0 14

P3.7/RD 17P3.6/WR 16

P3.5/T1 15

P2.7/A15 28

P2.0/A8 21

P2.1/A9 22

P2.2/A10 23

P2.3/A11 24

P2.4/A12 25

P2.5/A13 26

P2.6/A14 27

U1

AT89C55

33pf

33pf

CRYSTAL

10u

10k

TO LC

D D

ATA LIN

ES

TO K

EYP

AD

CO

NTROL S

IGN

AL OU

T

TO D

EVIC

E I/

O

66

at startup. The differentiator circuit connected to the reset input ensures a

good startup at about 0.04V in 0.5s when powered. As earlier stated, the

essence of the crystal oscillator is to control the speed of the microcontroller.

Here, the speed of the microcontroller refers to the maximum oscillator

frequency connected to crystal; in this case a crystal with 11.059MHZ

frequency was used. Higher crystal value may be used in order to meet with

speed demand of most logic chips if high speed systems are to be developed.

5.3 INSTALLATION PROCESS

The set up program prepares your computer to stall the software from the

CD.

To install the program;

Insert the CD in the CD Drive;

Double click on My computer on the Desktop

Double click on CD drive icon

Double click on setup icon

Follow the screen instructions to complete installation.

5.4 HOW TO OPEN THE SOFTWARE

Click to view start menu

Click on all program

Click on control

Finally click on control

67

The interface will appear:

Check the ON/ OFF box and click on desired relay button

When the status is B or D or F the relays are ON, but when the status

is A or C or E then the relays are OFF.

5.5 HARDWARE GUIDE

The switch controller must be connected to the system unit. The guides on

how to connect it to the computer are:

Insert the serial cable female port into D- shape male 9- pins serial

port at the back of system unit and screw.

Connect the power cable into any power source of 240V

Ensure the computer system cables are properly fixed.

5.6 SYSTEM TESTING

The importance of the testing stages in the development of any new product

or repair of existing ones cannot be over emphasized. Tracing of faults is

very difficult in a finished work, especially when the work to be tested is too

complex. Therefore, Software or hardware testing is very important element

68

of assurance and it represents the ultimate view of specification, design and

coding. Two stages of testing are involved for the purpose of this project.

The objectives of embarking on new software and hardware project through

testing are to ensure that it meets the requirements in the specification. The

two stages are:

i. Pre-implementation testing.

ii. Post-implementation testing.

5.6.1 PRE-IMPLEMENTATION TESTING

Pre-implementation testing is carried out on the components before they

are soldered to the veroboard. This is to ensure that each component is in

good working condition on board. The components used in this design

can be grouped into:

Discrete components e.g. resistors, light emitting diodes, capacitors,

transistors. Etc.

Integrated circuit components. The discrete components are tested

with a multimeter by switching the meter to the required value and

69

range corresponding to each discrete component to check for

continuity.

5.6.2 POST-IMPLEMENTATION TESTING

After implementing the circuit on a project board, the different sections of

the complete system were tested to ensure that they were in good operating

condition. The continuity test carried out is to ensure that the circuit or

components are properly linked together. This test was carried out before the

circuit was powered.

After the testing stages and troubleshooting has been done on the whole

circuit, it was powered. Visual troubleshooting was also carried out at this

stage to ensure that the components do not burn out. Different load was

added or connected to the power outlet ranging from 25 watts to 200 watts

of power to check if the circuit can carry it without any effect to the circuit.

After all the test and observation as explained above, the project was now

certified ready for packaging.

70

Table 5.1 Showing the operational status of the system

RELAY NO STATE STATUS APPLIANCE

1 ON B Bulb

OFF A Bulb

2 ON D Bulb

OFF C Bulb

3 ON F Bulb

OFF E Bulb

5.7 PROGRAM DOCUMENTATION (OPERATION) The microprocessor/microcontroller- based main switch control system is a

system consisting of software and hardware module. The hardware module

is the controller circuit, which must be connected to the system unit and the

software module is in a CD-ROM and needed to be installed in the system

unit (hard disk). This takes effect only when the controller is properly

connected to the computer system through the serial port and to the power

source. Any electrical device connected to it can be switch ON or OFF

through the interface provided by the software. Depending on the previous

71

state ON or OFF bulbs, when the command button of any relay is clicked,

signals goes from there to desirable bulb.

When relay 1 is off the status will display A but when it is ON, the status

will display B.

Also when relay 2 is off the status will display C, when it is ON the status

will display D.

Finally when relay 3 is off the status will display E but the relay is ON the

status will display F.

5.8 MAINTENANCE DETAILS Maintenance involves the preventing the development of faults and even its

correction when it occurs. Things to do to effect this are:

Ensure that proper connections are done with accurate power voltage.

Ensure that the points of connection or joining on the wires are firmly

soldered to avoid exposure of the circuits inside the casing.

Ensure that the system is kept on a safe place.

Proper connection especially the circuit should be done orderly to

ensure continuity in the circuit.

72

The management of any organization using this project should employ

a computer literate who will be able to operate it to avoid damage due

to carelessness.

5.9 PERFORMANCE EVALUATION

This project work or prototype by evaluation, perform up to 98% of its

proportion. 100 % performance can still be achieved by way of adjustment

of error noticed.

5.10 PROJECT COSTING

(a) Cost of prototype = N39,000.00

(b) Cost of commercial Production = N25,000.00

(c) Average Cost of conventional type = N60,000.00

73

Figure 5.2 Overall Circuit Diagram

1K

12V

RELAY

1K

12V

RELAY

1K

12V

RELAY

11.0592MHZ

Vcc

18 19

20

40

1K

10F

30F 30F

8952

39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

74

CHAPTER SIX: SUMMARY AND CONCLUSION

6.0 SUMMARY

In summary, the project work (A microcontroller-based mains switch control

system) was introduced in chapter one giving us an insight that it was a

microcontroller- based mains switch control system interfaced to a personal

computer through which appliances could be switched ON or OFF without

leaving ones seat. In chapter two of the research work, various literatures on

the topic under study were reviewed analyzing the invention, operations,

function of microcontroller to control appliances. Chapter three provides an

analysis of the existing system and proposed system as well as the

methodology. Chapter four was based on the system design. Chapter five

dealt with the system implementation and testing of the entire

microcontroller- based mains switch control system. Finally this project is

able to switch ON or OFF a device using computer system via serial port.

The system was designed in such a way that maintenance and repairs are

easily done in case of any faults. Soldering techniques and practical

75

electronic were carefully studied and the experience gained from it was

instrumental to the success of this project

6.1 PROBLEMS ENCOUNTERED

Some problems were encountered in the cause of developing the prototype

of this system. Most prominent is the issue of frequent power failure from

the public power supply. This prolonged the wiring time. Secondly, the

problem of some components initially tested okay not functioning on circuit

board during testing.

6.2 CONTRIBUTION TO THE BODY OF KNOWLEDGE

The microcontroller based controlled system approach is an automated

switching of appliances that leads to:

The elimination of direct contact with switch by providing an

interface on the computer screen through which the electrical devices

will be controlled.

The saving of the time it takes the operator going from one switch to

another is a delight to the Operator.

76

The ability to turn ON or OFF the selected electrical devices

anytime any day (e.g. in the hotel room, childrens room etc) is a plus

to the system.

Real- time response.

System reliability in controlling power switch.

The elimination of users movement in switching ON or OFF the

appliances is an advantage to the physically challenged.

6.3 RECOMMENDATIONS

(a) Before going ahead to wire components on the circuit board ensure

that you test the hardware properly and simulate the design. This

will enable you make all necessary adjustments to reduce mistakes

and design errors.

(b) For better implementation use the same family of chips if possible

(i.e only TTL or only CMOS). This will ensure compatibility of

components.

(c) Ensure to keep within specified values; because exceeding any of

these values may cause a permanent damage to either the clips in

particular or the entire system as a whole.

77

(d) It is recommended that this work be used in industries such as

hotels, schools to provide easy and safe use of the electrical

devices. The management of any organization using this work

should employ a computer literate person to operate the system.

6.4 CONCLUSION

The result achieved in the design and construction of the microcontroller-

based mains switch control system is actually a move away from manual

mode of switching to that of automation. For the fact that the materials used

are locally sourced make room for cost effectiveness of design and economic

application viable.

The system was designed in such a way that maintenance and repairs are

easily done in case of any faults.

78

REFERENCES

[1]. IEEE Std 610.10-1994, IEEE Standard Glossary of Computer Hardware

Terminology (Computer Hardware Dictionary)

[2]. Osinuga and Oresotu (2001) Description of a Computer Port Interface

(2001).

[3]. Wikipedia the free encyclopedia (2008). History of Modern computing

(http://www.wiki.com/histroy/mordencomputing).

[4]. Sayers, A.P. Robson, A.E. Adams and G.E.Chester,(1991) Principles of

Microprocessor, Hewlett-Packard Journal.

[5]. Ismail, and V.M Rooney, (1987) Microprocessor Hardware and

Software Concepts IT Press, Chicago.

[6]. Takashi (1990) Observed the increase in processing capacity of evolving

Microprocessors.

[7]. Chris Kotoroski, (2008) A push to break breaks word toggle switch.

[8]. Tendler,J.M. Dobson, S. Field, S. LE and Sinharoy, B. (2002) Power for

system micro architecture, IBM Journal of Research and Development.

[9]. Addison, Wesley k. and Takashi 9 (1990) Power electronics for the

79

microprocessor Age, Oxford University Press.

[10]. Alluwalia. A and Yeralan: Programming and interfacing the Beyond

Logic (2008), Interfacing the serial RS-232 Port,

(http//www.Interface com/ MAX-232/html)

[11]. Boylston, R.L.,and L Nashalsky. Electronic Devices and Circuit

Theory, edition, Prentice Hal/ of India private Ltd., New Delhi, 8th

edition, 2004

[12]. Douglas, V.H; Microprocessor and Interfacing .Tata McGraw-Hill,

New Delhi; 2nd Edition Electrical Technology, ELBS and Longman

group,

[13]. Hennessy, J,L and Patterson D.A (2002), Interfacing the serial RS-232

Port. (http//www.interface.com/Max-232/html).

[14]. Hughes Edward; 4thEdition, 1972 8951 micro controller adhesion_

Wesley, 1995.

[15]. Kassakian, John G. Martin, F. Schechter, and George C. Varghese,

(1991). Principles of power Electronic Microprocessor and Computer

(http://www.electronic org/microcomputer/kit/html).

[16]. Kerrville, Gregg (1998) Practice guide to the low voltage directive

Oxford, Boston Newness, vll, 203p.

[17]. Kingenstein (1996) Switch power control circuit in practice Willy,

80

338p.ISBN047692005 2nd Edition, Osborne McGraw Hill, Berkley

California, ISBNO-93 1988- 34-9 PG1-1

[18]. Max-232 Serial Converter. (http://www. sodoityourself.com)

[19]. B. RAM: Fundamentals of Microprocessor and Microcomputers, 6th

edition, Dhanpat Rai 2008.

[20]. Microchip AT89C51, Micro controller datasheet

http://www.microchip.com, copyright 2000-2004 pg 5-10.

[21].Thomas L. Floyd, Digital Fundamentals, 10th Edition, Prentice Hall

2009.

[22]. James Watt, Related Articles, Microsoft Encarta Premium 2009.

[23]. Hermiza Binti Abdullah Sani, Project on Lighting Controller-Based On

PC Serial Port, Mara University of Technology, Shah Alam 2006.

Pg 8.

[24]. http://www. Linkedin.com/pub/dir/martin/leo

[25]. Stephanie (2002), International Business Machine Corporation,

Microsoft Encarta 2009.

81

APPENDIX I: SOURCE CODE

PROJECT: A MICROCONTROLLER-BASED MAINS SWITCH CONTROL SYSTEM.

AUTHOR: GWAGWA O. TUBUKARE

PROCESSOR: AT89C52WD

DATE: 03/06/2010

org 00h

mov SCON,#01010000b

mov TMOD,#00100000b

mov a,PCON

setb acc.7

mov PCON,a

mov TH1,#250 ;baud rate = 9,600

setb TR1

relay1 equ p0.0

relay2 equ p0.1

relay3 equ p0.2

CPU EQU 40

CPUIN EQU 41

clr RI

clr TI

mov p0, #00h

CLR P2.0

82

MOV 40, #00H

MOV 41, #00H

SCL BIT P1.0 ;SCL BIT IS PORT 1, BIT 0

SDA BIT P1.1 ;SDA BIT IS PORT 1, BIT 1

SLV_ADDR EQU 0101B ;FIXED SLAVE ADDRESS BITS

DATAOUT EQU R5 ;DATA READ FROM DEVICE

ACK_READ EQU 10000101B ;READ FOR ACK POLLING 18

DSEG

ORG 006EH

PAGE_DATA: DS 1

BLK_ADDR: DS 1

BYTE_ADDR: DS 1

BYTE_DATA: DS 1

CSEG

ORG 0040H

C