DESIGN AND CONSTRUCTION OF A OVER VOLTAGE AND UNDER VOLTAGE PROTECTOR OF SPECIFICATION

ABSTRACT

Under and Over voltage protection are provided for electronic circuits by disposing one or more ground bars for diverting harmful currents away from the sensitive electronic circuit elements. The ground bars are each associated with a row of contact portions of the electronic circuit. Microgaps between each contact portion and the corresponding ground bar are designed to provide an electrical conduct from the contact portion to the ground bar when normal operating voltages are exceeded, thereby channeling excess current harmlessly to ground. Under normal operating conditions, however, the microgaps act as electrical barriers, insulating the contact portions from ground. The microgaps may be filled with any combination of air, vacuum or known variable voltage material.

TABLE OF CONTENTS

Title Page                                                                                                     

Certification                                                                                                  i

Dedication                                                                                                     ii

Acknowledgement                                                                                         iii

Notation                                                                                                        vii

Abstract                                                                                                        iv

Chapter One                                                                                                1

Introduction                                                                                                  1

Block Diagram                                                                                              1

Design Specification                                                                                     2                                                                                                                                                                                                                                           

Chapter Two

Literature Review                                                                                          3

Transformation unit                                                                                      4

Principle of action of a transformer                                                              6

Equation of a transformer and calculation                                                    8

Rectification unit                                                                                           10

Full wave bridge rectifier                                                                              11

Simple operation of full wave bridge rectifier                                               11

Filtration unit                                                                                                13

Capacitor type of filter                                                                                 14

Stabilization unit                                                                                           15

Zener diode                                                                                                   16

Zener diode as voltage stabilizer                                                                   17

Amplification unit                                                                                         18

Operational amplifier (comparator)                                                              19

Transistor as an amplifier                                                                             21

Electromechanical switch or Relay unit & its operation                               22

Advantages of relay over a simple mechanical switch                                  23

Electromechanical or Relay characteristics                                                   24

Chapter Three                                                                                             25                                                                                                                     

Constructor and Description                                                                        25

Chapter Four                                                                                               29

Conclusion and Recommendation                                                                 29

Appendices                                                                                                   30

Schematic diagram of the work                                                                     30

Layout of components on vero board                                                           31

Well – labelled exploded view of the work                                                   32

          Bill of Materials                                                                                            33

          References                                                                                                     34

                                                Abbreviations and meaning

            i                 RMS                                                          Root Mean Square

            ii                LED                                                          Light Emitting Diode

            iii                     PS                                                        Power Supply

            iv                     IC                                                        Intergrated Circuit     

            v                      PIV                                                     Peak Inverse Value

            vi                     EMF                                                    Electromotive Force

            vii                    R-C                                                     Resistor Capacitor

            viii                   R_L                                                                          Load Resistor

             ix                    Vm                                                      Maximum Value

             x                     Vz                                                       Zener Voltage

                                    Electricity and Magnetism

                                    Quantity                                             Quantity Symbols                  Units Symbol

                 i                  Capacitance                                                               C                                           F

                 ii                 Frequency                                                                   F                                              Hz

                iii                 Magnetic Flux                                                            f                                      Wb, mWb

                iv                 Power                                                                          P                                              W

                v                  Resistance                                                                   R                                             W

                vi                 Voltage                                                                       V                                             V

                vii                Current                                                                        I                                               A

Section of graphical symbols

                             Description                                                          Symbols

                Alternating                                                                                 

                Positive polarity

                Negative polarity