DESIGN AND CONSTRUCTION OF A METAL DETECTOR

By

ENWENEABURU ORONDA

Presented To

Department of Electrical/Electronic Engineering

ABSTRACT

The project work titled Design and construction of a metal detector. When fully design and implemented would be able to detect any metallic material that is passing or coming close. This function would serve as a security check for dangerous metallic material as an alarm. Going by the sophisticated means of armed rubbers adopt these days in the breaking into bank supermarkets offices and highly secured area. No security system will be optimized or complete without the installation of metal detector. This will stop or reduce to the bearest minimum the activities of men of the underworld. The device we then build we function as a metal detector that can scout out metal objects, such as coins, nails, keys such as car keys you may not be able to fine, and even gold if you're looking for it in a beach (through this one may not have industrial strength). This metal detector can detect certain kinds of metal- especially iron -containing metals, which are called ferrous meat, even if under a half-inch of dry well or sand.

TABLE OF CONTENT

Title Page - - - - - - - - - - i

Approval Page - - - - - - - - - ii

Certification - - - - - - - - - iii

Dedication - - - - - - - - - iv

Acknowledgement - - - - - - - - v

Abstract - - - - - - - - - - vii

Table of Content - - - - - - - - viii

List of Figures - - - - - - - - - xii

CHAPTER ONE: INTRODUCTION

11 Background of Study - - - - - - 1

12 Problem Statement - - - -- - - - 2

13 Objective of the Project - - - - - - 3

14 Significant of the Project - - - - - - 3

15 Methodology - - - - - - - - 4

16 Scope of the Project - - - - - - - 4

17 Project Outline - - - - - - - - 5

CHAPTER TWO: LITERATURE REVIEW

21 What a Metal Detector Is - - - - - - 7

211 Brief History of Metal Detector Evolution - - 8

22 Types of Metal Detectors Available - - - - 11

221 Pulse Induction (PI) Metal Detector - - - - 12

222 Industrial Metal (IM) Detector - - - - - 14

2221 Basic operation of an IM Detector - - - 15

223 Coin/Treasure Metal Detector - - - - 16

23 Uses of Metal detectors - - - - - - 18

24 Principles Applied in the Project - - - - 19

241 Magnetism - - - - - - - - 19

2411 Paramagnetism - - - - - - - 22

2412 Ferromagnetism - - - - - - - 23

2413 Diamagnetism - - - - - - - 26

2414 Antiferromagnetism - - - - - - 27

2415 Ferrimagnetism - - - - - - - 28

2416 Superparamagnetism - - - - - - 29

2417 Electromagnet - - - - - - - 29

25 Electromagnetism - - - - - - - 30

26 Brief Description of the Electronic Components Used - 33

261 Resistor - - - - - - - - - 33

26 2 Inductors - - - - - - -- - 35

263 Capacitors - - - - - - - - 36

264 Transistors - - - - - - - - 37

265 TDA0161 - - - - - - - - - 37

CHAPTER THREE

31 Design of a Metal Detector Circuit - - - - 39

32 How this Metal Detector Works - - - - 39

33 Component Use for Design - - - - - 40

34 Metal Detector Schematic - - - - - 43

35 Explanation of Circuit - - - - - - 43

36 TDA0161 Proximity Detector IC - - - - 44

37 Resistor R1 and Potentiometer R2 - - - - 44

38 How to Use Metal Detector - - - - - 47

39 Power Supply Unit - - - - - - - 49

310 Principle of Operation of the Metal Detector - - 49

311 Calculations Involving Choice of Component and

their Functions - - - - - - - - 51

CHAPTER FOUR: SYSTEM IMPLEMENTATION

41 Testing - - - - - - - - - 56

42 Performance Evaluation - - - - - - 57

43 Project Packaging - - - - - - - 58

44 Bill of Engineering Measurement and Evaluation - 58

CHAPTER FIVE: SUMMARY AND CONCLUSION

51 Summary of Achievements - - - - - 60

52 Problems Encountered and Solutions Adopted - 61

53 Contribution to Knowledge - - - - - - 63

54 Suggestions for Further Improvement - - - 63

56 Recommendation - - - - - - - 65

55 Conclusions - - - - - - - - 66

References - - - - - - - - - 68

Appendix - -- - - - - - - - 70

LIST OF FIGURES

Fig 20: Magnetic domains in ferromagnetic material - 24

Fig 21: Effect of a magnet on the domains - - - 25

Fig 22: Antiferromagnetic ordering - - - - 27

Fig 23: Ferromagnetic ordering - - - - - 29

Fig 24: A simple demonstration of Electromagnetism

Field - - - - - - - - - 32

CHAPTER ONE

INTRODUCTION

11 Background of Study

It has been observed that the rapid growth in the technological knowledge across the world has been accompanied by a rapid rise in crime rate These criminal acts takes the form of breaking of private and official homes and making away with a huge sum of money, valuable and in most cases hosts of lives The background of this project work comes into play for the removal or minimization of the above criminal act by a way of a METAL DETECTOR, which will be handly or connected to a strategic position in our homes and offices

Detection and clearance are still very often carried out in humanitarian demining ways using manual methods or computer as primary procedure When operating in this way, detection phase still relies heavily on metal detectors, whereby, each alarm needs to be carefully checked until it has been fully understood or its source removed This is normally done visually and prodding or excavating the ground Metal detectors are probably going to remain in use for some time

12 Problem Statement

Going by the sophisticated means armed robbers adopt these days in breaking into banks, super markets and highly secured areas or the activities of assassins in conference hall, airport, hospital eg there are every indication that they are out for the worst and a better way of lessening the harshness of these menace is to get highly alerted security wise No security system will be optimized or complete without the installation of metal detector This will stop or reduce barest minimum, the cases of men of the underworld breaking into banks, hotels, conference hall, homes, hospital etc systematically undetected

The exigency of Metal detector involvement in security outfits whether national, sub-national and domestic level cannot be over emphasized

The researcher was motivated to design a project which will demonstrate the undisputable wide use of transistors in field of electronics to produce the kind of sound that should be able to alert people for special attention, and serves as a danger signal in a nutshell

13 Objective of the Project

1 To construct a walk through metal detector that is capable of detecting the presence of a metallic device

2 To the walk through metal detector world also incorporate the functionality of metallic object

3 The walk through metal detector will be capable of producing an alarm on reception of a metallic object

14 Significant of the Project

The significant of this project is to construct a functional electronic detector security system, which will be beneficial technology to human beings This project will also bring technology nearer home especially to the student, and to me as the designer, and the contribution in the advancement of technology, thus helping them to assemble, design and construct projects based on simple component and material locally or foreign

Again, this project will encourage indigenous technology and discourage the large expense being made on foreign security systems All these were born in mind during the assembling, designing construction and casing of this project

15 Methodology

This system is developed using several electrical and electronic principles The principle of electromagnetism is a major principle applied When the coil which serves as the sensor is placed over a metal and the system is switched ON, the electric current passing through the coil makes it magnetic and being placed over a metal, the metal generates a very small voltage (in micro volts) in form of eddy currents This generated eddy current is received by the sensors and thus it causes a disturbance to the main current flow The difference is harnessed by electronics and connected to an amplifier from where it is fed into the audio output which serves as the transducer to the system

16 Scope of the Project

The metal detector designed in this project will make use of technology called Beat Frequency Oscillator (BFO) this technology employs two oscillators at resonance and a variation of the frequency of oscillation of one of the oscillators due to the presence of a metallic object would be picked up by a tiny receiver within the control box which creates an audible series of tones (beats) based on the difference between the frequencies

17 Project Outline

The first chapter of this project write up gives an introduction to the work intended It discusses a short background of the project work The specific objectives of the project are also clearly stated The problem the system is to solve and its significance is also highlighted The scope of the work is stated here in terms of the parameters to be achieved in the design

The second chapter of this write up reviews the related literature of the work It gives basic insight as to principle of operation of the system It also reviews past design in this field and the results obtained

The third chapter show cases the design methodology and on the explanation of each method employed

The fourth discusses the actual design of the work The analysis, assumptions an mathematical models involved in achieving a complete system design is discussed

The chapter five deals on the procedures observed in the coupling of the different designs and modules of the work Also the result of the finished project after test and evaluation and conclusion made are stated

The last chapter contains the conclusion and recommendations made It also contains the Bill of Engineering Measurement and Evaluation (BEME)