Design And Construction Of A Metal Detector Using 555 Timer

Metal detector is designed to meet up with security demand in our society such as in our financial institution, churches, homes, schools etc. A metal detector is a device which responds to metal that may not be readily apparent.

This system detects metals of different types and also electronics gadgets such as cell phone, bombs etc. it work in such a way that when such devices are brought close to it, it detects it by giving out a beep. The metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced in the metal, and this produces an alternating electric field of its own.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• PROBLEM STATEMENT
• AIM OF THE PROJECT
• OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• LIMITATION OF THE PROJECT
• USES AND APPLICATION OF THE PROJECT
• SCOPE OF THE PROJECT
• PURPOSE OF THE PROJECT
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• HISTORICAL BACKGROUND AND DEVELOPMENT OF METAL DETECTOR
• REVIEW OF AN COLPITTS OSCILLATOR

CHAPTER THREE

3.0     CONSTRUCTION METHODOLOGY

3.1     BLOCK DIAGRAM OF METAL DETECTOR

3.2     MAIN COMPONENTS IN METAL DETECTOR CIRCUIT

3.3     METAL DETECTOR CIRCUIT DIAGRAM USING IC555

3.4     CIRCUIT DESCRIPTION

3.6   LIST OF COMPONENTS USED

3.7     OPERATION OF METAL DETECTOR

3.7     POWER SUPPLY UNIT

CHAPTER FOUR

4.0      TESTING AND RESULTS

• CONSTRUCTION PROCEDURE AND TESTING
• INSTALLATION OF THE COMPLET DESIGN
• ASSEMBLING OF SECTIONS
• CASING AND PACKAGING
• TESTING OF SYSTEM OPERATION
• COST ANALYSIS

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                             INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

A metal detector is described as an electronic instrument which detects the presence of metal nearby. Metal detectors are useful for finding metal inclusions hidden within objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe which can be swept over the ground or other objects. If the sensor comes near a piece of metal this is indicated by a changing tone in earphones, or a needle moving on an indicator. Usually the device gives some indication of distance; the closer the metal is, the higher the tone in the earphone or the higher the needle goes. Another common type are stationary “walk through” metal detectors used for security screening at access points in prisons, courthouses, and airports to detect concealed metal weapons on a person’s body [1][2].

Metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced in the metal, and this produces a magnetic field of its own. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metallic object can be detected [2].

Nowadays, the metal detector is used to identify metallic devices such as bombs, guns for security purpose. To avoid any illegal or unauthorized entry of metallic objects, bombs, knives, guns within the luggage bags of the person carrying them in public places like theatres, shopping malls, parks, airports, hotels, railway stations. A security system is developed by using proximity sensor which is named as a metal detector. So, a metal detector is used in many robotic or electronics projects  to detect any present metals which are nearby or the existence of hidden items within objects. This article gives an overview of metal detector working principle and applications [2][3].

1.2                                                         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 e.g. 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 e.t.c 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.

1.3                                                   AIM OF THE PROJECT

The objective of the project is to build a device which detects the presence of metal nearby, hidden within objects, or metal objects buried underground.

1.4                                             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.

1.5                                         SIGNIFICANCE 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 [3].

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.

With the help of a hand held detector, security personnel can physically detect if a person is carrying a metallic object. On the other hand, walk through metal detectors are much quicker, and they alert the security personnel of dangerous objects such as knives or weapons [3].

Metal detectors are able to deter potential would-be criminals because the would-be criminal will think twice before walking through a security check point [3].

1.6                                           LIMITATION OF THE PROJECT

As for the limitation of using any type of metal detector, they cause privacy concerns. A lot of people can find it uncomfortable while passing through a detector scanning them for  potentially dangerous metallic objects. In some cases it is possible that they ask to be manually searched when the rules of safety allow such actions [4].

Also, in this advantageous medical era, we can find a lot of medical reasons why some person might have metal on his/hers body. Sometimes, metal devices can be surgically installed inside the person’s body which will cause the alarm to be set off each time that person walks through a metal detector. In many cases it is possible for the security personnel to see on their computers that the metal object that caused the alarm is actually a harmless tool and not a weapon [4].

As already said, metal detectors create electromagnetic fields. This can cause electrical interference to electronic devices that one person might have in its possession. This includes medical devices such as pacemakers. Some metal detectors can harm pacemakers because they have a very strong electromagnetic field. In this case, such detectors can be fatal for those people, and it is strongly advised that they avoid passing through them [4].

In many situations, metal detectors can give a false alarm if people are wearing some kind of jewelry, watch, phone, loose change or similar. This can make some people feel embarrassed and can cause panic for no reason. A false alarm caused by detectors can be inconvenient both for the security personnel and the person to whom the alarm turned on [4].

1.7                               USES AND APPLICATION OF THE PROJECT

Metal detectors are used for:

Treasure Hunting

• Different types of treasure hunting that use metal detector technology include “coin shooting” or coin hunting, prospecting for gold and/or silver, historical artifact hunting, and beach combing for valuables lost on the beach. Serious coin and relic hunters will do an enormous amount of research beforehand to determine where specific, potentially valuable sites are located. The depth to which a metal detector can pinpoint a buried metal object depends largely on the strength (and expense) of the model. The typical amateur treasure-hunting metal detector can only detect metal objects one or two feet below the surface [4].
• Airport and Building Security

Metal detectors are used for airport and building security to determine whether guns, knives, or other weapons are being transported onto aircraft or into public buildings. The technology and efficiency of a security metal detector is much more advanced than that of an amateur treasure-hunting detector. There are two types of security metal detectors: the walk-through detector, and the wand detector [4].

A walk-through metal detector consists of a metal-detecting arch or “gate” through which an individual passes to be screened. If an alarm sounds, an operator stops the individual from walking past the checkpoint, and proceeds to investigate the cause and the source of the alarm.

A wand detector is slightly more laborious to use, but it is a much less expensive alternative to a walk-through detector. Security personnel pass the wand slowly over all sides of the body of the individual being screened, with an alarm within the wand sounding when metal is detected [4].

Land Mine Detection

The military has used metal detection to pinpoint buried land mines since World War I. Of the two types of landmines used in warfare, antipersonnel and antitank, antipersonnel mines are harder for metal detectors to locate because they are often made of plastic. Both types of mines are typically buried close to the surface, making detection of metal-based mines relatively easy, though intensely nerve-wracking, as the slightest contact with a mine will easily detonate it.

Construction Industry

Metal detectors are also used in the construction industry to locate steel reinforcement bars embedded in concrete, and to pinpoint metal pipes and wires in floors and walls. This is useful in avoiding unnecessary damage when replacing plumbing or wiring in a building or house. Some models of metal detector used for construction industry purposes bear a resemblance to the wand detector used for security purposes, while others more closely resemble those used for treasure hunting [5].

1.8                                                 SCOPE OF THE PROJECT

Metal detectors are made up of an oscillator that produces an alternating current that passes through a coil, which creates an alternating magnetic field. This means that when an electronically conductive metal is near the detector, it creates eddies of air, which causes a change in the magnetic field, which enables the operator to see where the metal is [5].

The metal detector designed in this project will make use of technology called Beat Frequency Oscillator (B.F.O). 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 [6].

1.9                                         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.

To achieve the aim and objectives of this work, the following are the steps involved:

1. Study of the previous work on the project so as to improve it efficiency.
2. Draw a block diagram.

• Test for continuity of components and devices,

1. Design and calculation for the device was carried out.
2. Studying of various component used in circuit.
3. Construction of the circuit was carried out.

• Finally, the whole device was cased and final test was carried out.

1.10                        PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to Metal detector. In this chapter, the background, significance, objective limitation and problem of Metal detector were discussed.

Chapter two is on literature review of Metal detector. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.