DESIGN AND CONSTRUCTION OF AUTOMATIC METAL DETECTOR FOR SECURITY GUARDS

i DESIGN AND CONSTRUCTION OF AUTOMATIC METAL DETECTOR FOR SECURITY GUARDS BY WILSON, KUFRE ARCHIBONG 19050200018 DEPARTMENT OF ELECTRICAL/ELECTRONICS ENGINEERING GREGORY UNIVERSITY , UTURU ABIA STATE NOVEMBER, 2023 ii DESIGN AND CONSTRUCTION OF AUTOMATIC METAL DETECTOR FOR SECURITY GUARDS BY WILSON, KUFRE ARCHIBONG 19050200018 BEING A PROJECT SUBMITTED TO THE DEPARTMENT OF ELECTRICAL/ELECTRONICS ENGINEERING GREGORY UNIVERSITY, UTURU ABIA STATE IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF BACHELOR DEGREE (B.Eng) IN ELECTRICAL/ELECTRONICS ENGINEERING NOVEMBER, 2023 iii APPROVAL PAGE This project ‘DESIGN AND CONSTRUCTION OF AUTOMATIC METAL DETECTOR FOR SECURITY GUARDS’ was carried out by WILSON, KUFRE ARCHIBONG (1905020018) of the department of Electrical and Electronics Engineering, Gregory University Uturu,. Having met the requirement for the award of Bachelor Degree (B.Eng). Engr. Eti-ini Robson , B.Eng., M.Eng., MNSE ……………… ……………………. (Supervisor) Date/ Signature Engr. Samuel Effiong , B.Eng., M.Eng., MNSE ……………………………………. (Head of Department ) Date/ Signature Engr. Dr. Nseobong Okpura ……………………………………. (External Supervisor ) Date/ Signature iv CERTIFICATION This is to certify that this research project is an authentic record of work carried out by WILSON, KUFRE ARCHIBONG with Registration number (18050408005) under my supervision. It has been read and approved as having met the requirements of the Department of Electrical and Electronics Engineering, Gregory University Uturu, Abia State, Ibom Metropolitan Polytechnic Study Centre, Atan Offot, Uyo, for the award of Bachelor Degree (B.Eng) in Electrical and Electronics Engineering. Engr. Eti-ini Robson, B.Eng., M.Eng., MNSE ……………………………………. (Supervisor) Date/ Signature Engr. Samuel Effiong , B.Eng., M.Eng., MNSE ……………………………………. (Head of Department) Date/ Signature Wilson, Kufre Archibong ………………………………. (Student) Date/ Signature v DECLARATION I hereby declare that this project entitled ‘Design And Construction of Automatic Metal Detector for Security Guards’ has been written by me and that it is the record of my own research work. It has not been presented in any previous application for a higher degree. All sources of information are specifically acknowledged using references. WILSON, KUFRE ARCHIBONG NOVEMBER, 2023 vi DEDICATION This project is dedicated to God Almighty who granted me favour before Him and men . vii ACKNOWLEDGEMENTS I wish to acknowledged myself for finding time to further my academic. In carrying out this work, i have been assisted directly or indirectly by a number of people. Though it will be impossible to mention all of them, few deserve to be singled out. I appreciate my able and capable supervisor Engr. Eti-ini Robson who despite his tight schedule made out time to read through the manuscript at different stages and provided all the necessary corrections in this write up. Also his direction, constructive criticism and useful suggestions made this research work a reality. I wish to acknowledge the of Head of Department in person of Engr. Samuel Effiong, in his effort to pilot the affairs of the Department of Electrical/ Electronics Engineering Technology. My profound appreciation also goes to my amiable and caring parent, for laying this foundation. I also acknowledge my Lecturer, friends and colleague for their support and prayer. viii ABSTRACT A battery in the top of the metal detector activates the transmitter circuit (red) that passes electricity down through a cable in the handle to the transmitter coil(red) at the bottom. When electricity flows through the transmitter coil, it creates a magnetic field all around it. If you sweep the detector above a metal object (such as this old gray spanner), the magnetic field penetrates right through it. The magnetic field makes an electric current flow inside the metal object. This flowing electric current creates another magnetic field all around the object. The magnetic field cuts through the receiver coil (blue) moving about up above it. The magnetic field makes electricity flow around the receiver coil and up into the receiver circuit (blue) at the top, making a loudspeaker buzz and alerting you you've found something. ix TABLE OF CONTENT Cover page - - - - - - - - - - -i Title page - - - - - - - - - - -ii Approval Page - - - - - - - - - -iii Certification - - - - - - - - - - -iv Declaration - - - - - - - - - - -v Dedication- - - - - - - - - - - -vi Acknowledgment - - - - - - - - - -vii Abstract - - - - - - - - - - -viii Table of Content - - - - - - - - - -ix List of Figure - - - - - - - - - - -xii List of Table - - - - - - - - - - -xiii CHAPTER ONE : INTRODUCTION 1.0 Background of the Study - - - - - - - -1 1.1 Statement of Research Problem - - - - - - - -2 1.2 Objective of the Study - - - - - - - - -2 1.3 Research Question - - - - - - - - -3 1.4 Scope of the Study - - - - - - - - -3 1.5 Justification/ Relevance of the Research - - - - - - -3 1.6 Limitation of the Project Research - - - - - - -4 CHAPTER TWO :REVIEW OF RELATED LITERATURE 2.0 555 Timer - - - - - - - - - -5 2.1 Integrated Circuit (IC) - - - - - - - - -5 x 2.2 Internal Schematic - - - - - - - - -7 2.3 Electronic Oscillator - - - - - - - - -8 2.4 Relaxation Oscillator - - - - - - - - -9 2.5 Pin Configuration - - - - - - - - -11 2.6 Operating Modes of 555 Timer - - - - - - - -12 2.7 555 Timer Circuits - - - - - - - - -15 2.8 Flip Flop - - - - - - - - - -15 2.9 Resistor - - - - - - - - - - -16 2.10 Resistor Colour Code - - - - - - - - -17 2.11 Capacitor - - - - - - - - - -19 2.12 Types of Capacitor - - - - - - - - -22 2.13 Coil - - - - - - - - - - -23 2.14 Application of Coil - - - - - - - - -24 2.15 Sound Transducers - - - - - - - - -25 2.16 The Loudspeaker Output Transducer - - - - - - -26 CHAPTER THREE : DESIGN METHODOLOGY 3.0 555 Timer Design - - - - - - - - -30 3.1 Design Calculation - - - - - - - - -32 3.2 Design Materials of Automatic Metal Detector - - - - - -33 3.3 Design Algorithms - - - - - - - - -34 3.4 Block Diagram of the Design - - - - - - - -35 3.5 Design Working Principle of Automatic Metal Detector System - - -35 xi CHAPTER FOUR: TESTING, PACKAGING AND EVALUATION 4.1 Research and Construction Result - - - - - - -38 4.2 Installation Result - - - - - - - - -38 4.3 Interfacing Operation - - - - - - - - -38 4.4 Packaging/ Casing - - - - - - - - -38 4.5 Testing and Result - - - - - - - - -39 4.6 Precautions Taken During Construction - - - - - - -39 4.7 Repairs and Maintenance - - - - - - - -40 4.8 Bill of Material - - - - - - - - - -40 4.9 Schematic Detail - - - - - - - - - -41 CHAPTER FIVE : SUMMARY, CONCLUSION AND RECOMMENDATION 5.0 Summary - - - - - - - - - -42 5.2 Conclusion - - - - - - - - - -42 5.3 Recommendation - - - - - - - - - -42 REFERENCE - - - - - - - - - - -44 xii LIST OF FIGURE FIGURE PAGES 2.1 NE555 in 8-pin DIP package - - - - - - -5 2.2: Internal Block Diagram of 555 Timer - - - - - -8 2.3: 1 MHz Electronic Oscillator Circuit Which Uses the Resonant Properties -10 2.4: 555 Timer Pin Configurations I - - - - - - -11 2.5: 555 Timer Pin Configurations II - - - - - - -12 2.6: Duty Cycle for 555 Timer - - - - - - - -13 2.7 : An SR latch, constructed from a pair of cross-coupled NOR gates - -16 2.8: Resistor Electronic Symbol - - - - - - -17 2.9: Symbol of Colour Code - - - - - - - -18 2.10: Parallel plate Capacitor - - - - - - - -21 2.11: Physical Image of a Capacitor - - - - - - -21 2.12: Fixed, Polarized and Variable Capacitor - - - - - -22 2.13: Image of an Inductive Coil - - - - - - - -24 2.14: Sound Transducer - - - - - - - - -26 2.15: Loudspeaker Transducer - - - - - - - -27 2.16: The Moving Coil Loudspeaker - - - - - - -28 3.1: Schematic Diagram of Automatic Metal Detector System - - - -35 4.1: Design Packaging - - - - - - - - -39 xiii LIST OF TABLE TABLE PAGE 2.1: 555 Timer Pin Configuration and it Function - - - 14 4.1: Bill of Material - - - - - - - 40 1 CHAPTER ONE INTRODUCTION 1.0 Background of the Study A metal detector is 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 ( Andrew, 1994). The simplest form of a 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 ( Tylor, 2016). The first industrial metal detectors were developed in the 1960s and were used extensively for mineral prospecting and other industrial applications. Uses include detecting land mines, the detection of weapons such as knives and guns (especially in airport security), geophysical 2 prospecting, archaeology and treasure hunting. Metal detectors are also used to detect foreign bodies in food, and in the construction industry to detect steel reinforcing bars in concrete and pipes and wires buried in walls and floors. Metal detector system is constructed to meet the requirement for both domestic and industrial operations. This help to reduce the stress of manual search of bags and cloths of visitors entering a building and the system can automatically detect the density of metal in the possession of someone who is carrying harmful substance and easily alert, the security personnel . The system consist of 9v dc supply, an RLC Circuit and a 555 timer ( George and Carl. 2012). 1.1 Statement of Research Problem Due to the high rate of insecurity in our society today. The need for constructing metal detector is paramount. Crime is due to poverty, family condition, peer pressure, the society, drug, unemployment, polities, deprivation, Religion, unfair judicial system . Crime is a breach of law or rule, an illegal act of annoyance or resentment brought about by a perceived insult or disregard for oneself. People tend to carry weapon secretly to public places unauthorized. Automatic metal detector help to detect hidden weapon. 1.2 Objective of the Study The primary aim and objective of this project is to construct a metal detector which detects metal object of different sizes mainly used as a security gadget for fishing out persons with weapons in an establishment. The aim of constructing this project were to : i. Solve both private and industrial security challenge ii. To fish out culprit with weapons 3 iii. To reduce the rate of crime exhibition 1.3 Research Question At what range will the automatic metal detect dangerous crime weapon? 1.4 Scope of the Study The project is based on a simplified design using a dc supply of 9 volt battery for the entire circuitry. The IC ( integrated Circuit) is a 555 timer which generate a pulses with frequencies audible to human hearing aid, the RLC circuit ( Resistance, inductance and capacitance circuit) is the metal detection part of the system and it send the signal to the IC which finally generate pulse to the speaker that gives the output signal. Therefore, the project is made to detect metal objects at different frequency at ease, without the use of expensive modules. 1.5 Justification/ Relevance of the Research The relevance of this system is on the operation of the gadget in both domestic and industrial outfit such as Churches, hospitals, airports, banks, industries etc. Metal detector system is of great importance due to the fact that they solve the problem of manpower and high rate of embarrassment between security personnel and the individual involved. The project wil also helped to reduced crime rate, because at the entering point , the culprit most have been apprehended. 4 1.6 Limitation of the Project Research This project construction is made of component that is locally manufacture, and it is design specifically to detect metal substance in a place where metal substance of any kind is not needed. 5 CHAPTER TWO REVIEW OF RELATED LITERATURE 2.0 555 Timer The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide two or four timing circuits in one package. Figure 2.1 NE555 in 8-pin DIP package ( John , 2003). 2.1 Integrated Circuit (IC) An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, normally silicon. The integration of large numbers of tiny transistors into a small chip resulted in circuits that are orders of magnitude smaller, cheaper, and faster than those constructed of discrete electronic components. The IC's mass production capability, reliability 6 and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other digital home appliances are now inextricable parts of the structure of modern societies, made possible by the small size and low cost of ICs ( John , 2003). ICs were made possible by experimental discoveries showing that semiconductor devices could perform the functions of vacuum tubes, and by mid-20th-century technology advancements in semiconductor device fabrication. Since their origins in the 1960s, the size, speed, and capacity of chips have progressed enormously, driven by technical advances that allow more and more transistors on chips of the same size - a modern chip may have several billion transistors in an area the size of a human fingernail. These advances, roughly following Moore's law, allow a computer chip of today to have millions of times the capacity and thousands of times the speed of the computer chips of the early 1970s. ICs have two main advantages over discrete circuits: cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time. Furthermore, packaged ICs use much less material than discrete circuits. Performance is high because the IC's components switch quickly and consume little power (compared to their discrete counterparts) because of their small size and close proximity. The main disadvantage of ICs is the high cost to design them and fabricate the required photo masks. This high initial cost means ICs are only practical when high production volumes are anticipated ( John , 2003). 7 2.2 Internal Schematic The internal block diagram and schematic of the 555 timer are highlighted with the same color across all three drawings to clarify how the chip is implemented: i. Green - Between the positive supply voltage VCC and the ground GND is a voltage divider consisting of three identical resistors which create two reference voltages at 1⁄3 VCC and 2⁄3 VCC. The latter is connected to the "Control Voltage" pin. ii. Yellow and Orange - Two comparators are each connected to one of the reference voltages, while the other two inputs are fed directly from the "Trigger" and "Threshold" pins. iii. . The "Reset" pin overrides the other two inputs, thus the flip-flop (and therefore the entire timer) can be reset at any time. iv. Pink - The output of the flip-flop is followed by an output stage with totem-pole drivers that can load the "Output" pin with up to 200 mA (varies by device). v. Cyan- Also, the output of the flip-flop turns on a transistor which connects the "Discharge" pin to ground 8 Figure 2.2: Internal Block Diagram of 555 Timer ( John , 2003). 2.3 Electronic Oscillator Electronic Oscillator is an electronic circuit that produces a periodic, oscillating electronic signal, often a sine wave or a square wave. Oscillators convert direct current (DC) from a power supply to an alternating current (AC) signal. They are widely used in many electronic devices. Common examples of signals generated by oscillators include signals broadcast by radio and television transmitters, clock signals that regulate computers and quartz clocks, and the sounds produced by electronic beepers and video games. Oscillators are often characterized by the frequency of their output signal: 9 i. A low-frequency oscillator (LFO) is an electronic oscillator that generates a frequency below approximately 20 Hz. This term is typically used in the field of audio synthesizers, to distinguish it from an audio frequency oscillator. ii. An audio oscillator produces frequencies in the audio range, about 16 Hz to 20 kHz. iii. An RF oscillator produces signals in the radio frequency (RF) range of about 100 kHz to 100 GHz. Oscillators designed to produce a high-power AC output from a DC supply are usually called inverters. There are two main types of electronic oscillator — the linear or harmonic oscillator and the nonlinear or relaxation oscillator ( John , 2003). 2.4 Relaxation Oscillator In electronics a relaxation oscillator is a nonlinear electronic oscillator circuit that produces a non sinusoidal repetitive output signal, such as a triangle wave or square wave. The circuit consists of a feedback loop containing a switching device such as a transistor, comparator, relay, op amp, or a negative resistance device like a tunnel diode, that repetitively charges a capacitor or inductor through a resistance until it reaches a threshold level, then discharges it again. The period of the oscillator depends on the time constant of the capacitor or inductor circuit. The active device switches abruptly between charging and discharging modes, and thus produces a discontinuously changing repetitive waveform. This contrasts with the other type of electronic oscillator, the harmonic or linear oscillator, which uses an amplifier with feedback to excite resonant oscillations in a resonator, producing a sine wave. Relaxation oscillators are used to produce low frequency signals for applications such as blinking lights and electronic beeper sand in voltage controlled oscillator (VCOs), inverters and switching power supplies, dual-slope analog to digital converters, and function generators ( Meddow, 1997). 10 The term relaxation oscillator is also applied to dynamical systems in many diverse areas of science that produce nonlinear oscillations and can be analyzed using the same mathematical model as electronic relaxation oscillators. For example, geothermal geysers, networks of firing nerve cells, thermostat controlled heating systems, coupled chemical reactions, the beating human heart, earthquakes, the squeaking of chalk on a blackboard, the cyclic populations of predator and prey animals, and gene activation systems have been modeled as relaxation oscillators. Relaxation oscillations are characterized by two alternating processes on different time scales: a long relaxation period during which the system approaches an equilibrium point, alternating with a short impulsive period in which the equilibrium point shifts. The period of a relaxation oscillator is mainly determined by the relaxation time constant. Relaxation oscillations are a type of limit cycle and are studied in nonlinear control theory( Meddow, 1997). Figure 2.3: 1 MHz Electronic Oscillator Circuit Which Uses The Resonant Properties 1 MHz electronic oscillator circuit which uses the resonant properties of an internal quartz crystal to control the frequency. Provides the clock signal for digital devices such as computers. 11 2.5 Pin Configuration This means it has 8 different pins, each of which have different functions for the IC. The chart below gives the identities of each of the pins and what function they play in a circuit. Figure 2.4: 555 Timer Pin Configurations I ( Meddow, 1997). 12 Figure 2.5: 555 Timer Pin Configurations II ( Meddow, 1997). 2.6 Operating Modes of 555 Timer 555 timer has three operating modes, namely astable mode, monostable mode & bistable mode. Astable Mode In this mode, 555 timer can work as an oscillator. Uses contain LED & lamp flashers, logic clocks, pulse generation, security alarms, tone generation and PPM and so on. The 555 timer IC can be used as a simple analog to digital converter. For example, selecting a thermistor as a timing resistor permits the use of the 555 timer IC in a temperature sensor, the o/p pulse period is determined by the temperature. Monostable Mode In this mode, 555 timer IC works as a one shot pulse generator. Applications mainly include bounce free switches, timers, touch switches, missing pulse detection, frequency divider, pulse- width modulation (PWM), capacitance measurement, and so on ( Meddow, 1997). 13 Bistable Mode In this mode, the 555 timer IC can work as a flip-flop, if the DIS-pin is not connected & no capacitor is used. It is used in bounce-free latched switches. The Important Features of the 555 Timer i. 555 timer IC works from a wide range of power supplies ranging from +5V to +18V. ii. Sourcing or sinking load current is 200mA. iii. The external components must be selected correctly, so that the timing intervals can be completed in several minutes along with the frequencies beyond several hundred kHz. iv. The o/p of a 555 timer IC can drive TTl due to its high current o/p. v. It takes a temperature stability of 50 ppm/oC change in temperature (ppm means parts per million) vi. The timer’s duty cycle is adjustable. vii. The max power dissipation per package is 600 milliwatts & its reset and trigger i/ps has logic compatibility Figure 2.6: Duty Cycle for 555 Timer ( Meddow, 1997). 14 Table 2.1: 555 Timer Pin Configuration and it function ( Meddow, 1997). Pin Number Pin Name Pin Function 1 Ground Pin 1 connects the 555 timer chip to ground. 2 Trigger Pin 2 is the trigger pin. It works like a starter pistol to start the 555 timer running. The trigger is an active low trigger, which means that the timer starts when voltage on pin 2 drops to below 1/3 of the supply voltage. When the 555 is triggered via pin 2, the output on pin 3 goes high. 3 Output Pin 3 is the output pin. 555 timer's output is digital in nature. It is either high or low. The output is either low, which is very close to 0V, or high, which is close to the supply voltage that's placed on pin 8. The output pin is where you would connect the load that you want the 555 timer to power. This may be an LED, in the case of a 555 timer LED flasher circuit. 4 Reset Pin 4 is the reset pin. This pin can be used to restart the 555 timer's timing operation. This is an active low input, just like the trigger input. Thus, pin 4 must be connected to the supply voltage of the 555 timer to operate. If it is momentarily grounded, the 555 timer's operation is interrupted and won't start again until it's triggered again via pin 2. 5 Control Voltage Pin 5 is the control pin. In most 555 timer circuits, this pin is simply connected to ground, usually through a small capacitor, about 0.01 μF capacitor. This capacitor serves to level out any fluctuations in the power supply voltage that might affect the operation of the timer. Some circuits (though rare) do use a resistor between the control pin and Vcc to apply a small voltage to pin 5. This voltage alters the threshold voltage, which in turn changes the timing interval. Most circuits do not use this capability, though. 6 Threshold Pin 6 is the threshold pin. The purpose of this pin is to monitor the voltage across the capacitor that's discharged by pin 7. When this voltage reaches 2/3 of the supply voltage (Vcc), the timing cycle ends, and the output on pin 3 goes low. 7 Discharge Pin 7 is the discharge pin. This pin is used to discharge an external capacitor that works in conjunction with a resistor to control the timing interval. In most circuits, pin 7 is connected to the supply voltage through a resistor and to ground through a capacitor. 8 Power Supply (Vcc) Pin 8 is connected to the positive power supply voltage. 555 timer ICs need DC voltage in order to operate. This is the pin 15 which connects to the DC voltage to power the 555 chip. The voltage must be at least 4.5V and no greater than 15V. It's common to run 555 timer circuits using 4 AA or AAA batteries for 6V or a single 9V battery. Connecting the pins in different ways, we can put the 555 timer in astable mode, bistable mode, or monostable mode. The 555 timer can be used for basic timing functions, create warning lights that flash on and off, produce musical notes of varying frequencies, and even control the control position of a servo motor. 2.7 555 Timer Circuits The 555 timer ICs are used to generate a precise square wave form and that is used in many circuits. This circuit is designed with transistors, diodes, resistors and flip flops, and this circuit can be worked in the range of 4.5-15V DC supply. The 555 timer circuit consists of three functional parts, namely flip-flops, a comparator and a voltage divider. The main function of the comparator is to compare 2-i/p voltage levels such as inverting (-) and non-inverting (+) terminals. If the ‘V’ is high at the non inverting terminal, then the o/p is high. 2.8 Flip Flop Flip-flop or latch is a circuit that has two stable states and can be used to store state information. A flip-flop is a bistable multivibrator. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic. Flip-flops and latches are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems. Flip-flops and latches are used as data storage elements. A flip-flop stores a single bit (binary digit) of data; one of its two states represents a "one" and the other represents a "zero". Such data 16 storage can be used for storage of state, and such a circuit is described as sequential logic. When used in a finite-state machine, the output and next state depend not only on its current input, but also on its current state (and hence, previous inputs). It can also be used for counting of pulses, and for synchronizing variably-timed input signals to some reference timing signal (Snelgrove, 2 011). Figure 2.7: An SR latch, constructed from a pair of cross-coupled NOR gates (Snelgrove, 2 011). 2.9 Resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. Resistors act to reduce current flow, and, at the same time, act to lower voltage levels within circuits. Resistors are common elements of electrical networks and electronic circuits and are ubiquitous in electronic equipment. Practical resistors as discrete components can be composed of various compounds and forms. Resistors are also implemented within integrated circuits . 17 Figure 2.8: Resistor Electronic Symbol (Snelgrove, 2 011). 2.10 Resistor Colour Code Components and wires are coded are with colours to identify their value and function. The colours brown, red, green, blue, and violet are used as tolerance codes on 5-band resistors only. All 5-band resistors use a colored tolerance band . To distinguish left from right there is a gap between the C and D bands. i. band A is the first significant figure of component value (left side) ii. band B is the second significant figure (some precision resistors have a third significant figure, and thus five bands). iii. band C is the decimal multiplier iv. band D if present, indicates tolerance of value in percent (no band means 20%) For example, a resistor with bands of yellow, violet, red, and gold has first digit 4 (yellow in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms. 18 Figure 2.9 : Symbol of Colour Code . Table 2.2: Colour Code composition (Snelgrove, 2011). The colors brown, red, green, blue, and violet are used as tolerance codes on 5-band resistors only. All 5-band resistors use a colored tolerance band. The blank (20%) “band” is only used with the “4-band” code (3 colored bands + a blank “band”) . 19 2.11 Capacitor A capacitor is a passive two-terminal electrical component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance. While capacitance exists between any two electrical conductors of a circuit in sufficiently close proximity, a capacitor is specifically designed to provide and enhance this effect for a variety of practical applications by consideration of size, shape, and positioning of closely spaced conductors, and the intervening dielectric material. A capacitor was therefore historically first known as an electric condenser (Theraja and Theraja, 2003). The physical form and construction of practical capacitors vary widely and many capacitor types are in common use. Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The non conducting dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, and oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy(Theraja and Theraja, 2003). Capacitance is defined as the ratio of the electric charge on each conductor to the potential difference between them. The unit of capacitance in the International System of Units (SI) is the farad (F), defined as one coulomb per volt (1 C/V). Capacitance values of typical capacitors for use in general electronics range from about 1 pF (10−12 F) to about 1 mF (10−3 F). The capacitance of a capacitor is proportional to the surface area of the plates (conductors) and inversely related to the gap between them. In practice, the dielectric between the plates passes a 20 small amount of leakage current. It has an electric field strength limit, known as the breakdown voltage. The conductors and leads introduce an undesired inductance and resistance. Capacitors are widely used in electronic circuits for blocking direct current while allowing alternating current to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits they tune radios to particular frequencies. In electric power transmission systems, they stabilize voltage and power flow. The property of energy storage in capacitors was exploited as dynamic memory in early digital computers. Charge separation in a parallel-plate capacitor causes an internal electric field. A dielectric (orange) reduces the field and increases the capacitance. A capacitor consists of two conductors separated by a non-conductive region. The non- conductive region can either be a vacuum or an electrical insulator material known as a dielectric. Examples of dielectric media are glass, air, paper, and even a semiconductor depletion region chemically identical to the conductors. A capacitor is assumed to be self-contained and isolated, with no net electric charge and no influence from any external electric field. The conductors thus hold equal and opposite charges on their facing surfaces, and the dielectric develops an electric field. In SI units, a capacitance of one farad means that one coulomb of charge on each conductor causes a voltage of one volt across the device. An ideal capacitor is sufficiently characterized by a constant capacitance C, defined as the ratio of a positive or negative charge Q on each conductor to the voltage V between them: = 21 Because the conductors (or plates) are close together, the opposite charges on the conductors attract one another due to their electric fields, allowing the capacitor to store more charge for a given voltage than when the conductors are separated, yielding a larger capacitance. In practical devices, charge build-up sometimes affects the capacitor mechanically, causing its capacitance to vary. In this case, capacitance is defined in terms of incremental changes: Figure 2.10: Parallel plate Capacitor (Theraja and Theraja, 2003). Figure 2.11: Physical Image of a Capacitor (Theraja and Theraja, 2003). 22 2.12 Types of Capacitor i. Fixed Capacitor A fixed capacitor is constructed in such manner that it possesses a fixed value of capacitance which cannot be adjusted. A fixed capacitor is classified according to the type of material used as its dielectric, such as paper, oil, mica, or electrolyte. ii. Polarized Capacitor All electrolytic capacitors (e-caps) are polarized capacitorswhose anode (+) is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the electrolytic capacitor. iii Variable Capacitor A variable capacitor is a capacitor whose capacitance may be intentionally and repeatedly changed mechanically or electronically. Variable capacitors are often used in L/C circuits to set the resonance frequency, e.g. to tune a radio (therefore it is sometimes called a tuning capacitor or tuning condenser), or as a variable reactance,e.g. for impedance matching in antenna tuners. Figure 2.12: Fixed, Polarized and Variable Capacitor (Theraja and Theraja, 2003). 23 2.13 Coil An inductor, also called a coil or reactor, is a passive two-terminal electrical component that stores electrical energy in a magnetic field when electric current is flowing through it.[1] An inductor typically consists of an electric conductor, such as a wire, that is wound into a coil. When the current flowing through an inductor changes, the time-varying magnetic field induces a voltage in the conductor, described by Faraday's law of induction. According to Lenz's law, the direction of induced electromotive force (e.m.f.) opposes the change in current that created it. As a result, inductors oppose any changes in current through them. An inductor is characterized by its inductance, which is the ratio of the voltage to the rate of change of current. In the International System of Units (SI), the unit of inductance is the henry (H). Inductors have values that typically range from 1 μH (10−6H) to 1 H. Many inductors have a magnetic core made of iron or ferrite inside the coil, which serves to increase the magnetic field and thus the inductance. Along with capacitors and resistors, inductors are one of the three passive linear circuit elements that make up electronic circuits. Inductors are widely used in alternating current (AC) electronic equipment, particularly in radio equipment. They are used to block AC while allowing DC to pass; inductors designed for this purpose are called chokes. They are also used in electronic filters to separate signals of different frequencies, and in combination with capacitors to make tuned circuits, used to tune radio and TV receivers. 24 Figure 2.13 Image of an Inductive Coil (Theraja and Theraja, 2003). 2.14 Application of Coil Inductors are used extensively in analog circuits and signal processing. Applications range from the use of large inductors in power supplies, which in conjunction with filter capacitors remove residual hums known as the mains hum or other fluctuations from the direct current output, to the small inductance of the ferrite bead or torus installed around a cable to prevent radio frequency interference from being transmitted down the wire. Inductors are used as the energy storage device in many switched-mode power supplies to produce DC current. The inductor supplies energy to the circuit to keep current flowing during the "off" switching periods. An inductor connected to a capacitor forms a tuned circuit, which acts as a resonator for oscillating current. Tuned circuits are widely used in radio frequency equipment such as radio transmitters and receivers, as narrow band pass filters to select a single frequency from a composite signal, and in electronic oscillators to generate sinusoidal signals. 25 Two (or more) inductors in proximity that have coupled magnetic flux (mutual inductance) form a transformer, which is a fundamental component of every electric utility power grid. The efficiency of a transformer may decrease as the frequency increases due to eddy currents in the core material and skin effect on the windings. The size of the core can be decreased at higher frequencies. For this reason, aircraft use 400 hertz alternating current rather than the usual 50 or 60 hertz, allowing a great saving in weight from the use of smaller transformers. Inductors are also employed in electrical transmission systems, where they are used to limit switching currents and fault currents. In this field, they are more commonly referred to as reactors (Theraja and Theraja, 2003). Because inductors have complicated side effects (detailed below) which cause them to depart from ideal behavior, because they can radiate electromagnetic interference (EMI), and most of all because of their bulk which prevents them from being integrated on semiconductor chips, the use of inductors is declining in modern electronic devices, particularly compact portable devices. Real inductors are increasingly being replaced by active circuits such as the gyrator which can synthesize inductance using capacitors. 2.15 Sound Transducers Sound is the generalised name given to acoustic waves. These acoustic waves have frequencies ranging from just 1Hz up to many tens of thousands of Hertz with the upper limit of human hearing being around the 20 kHz, (20,000Hz) range. The sound that we hear is basically made up from mechanical vibrations produced by an Audio Sound Transducer used to generate the acoustic waves, and for sound to be “heard” it requires a medium for transmission either through the air, a liquid, or a solid. 26 Figure 2.14: Sound Transducer ( Horowitz and Hill, 1987) 2.16 The Loudspeaker Output Transducer Sound can also be used as an output device to produce an alert noise or act as an alarm, and loudspeakers, buzzers, horns and sounders are all types of sound transducer that can be used for this purpose with the most commonly used audible type output sound actuator being the Loudspeaker ( Bishop, Anyawu , Olapade and Morris, 2012). Loudspeakers are audio sound transducers that are classed as “sound actuators” and are the exact opposite of microphone. Their job is to convert complex electrical analogue signals into sound waves being as close to the original input signal as possible( Horowitz and Hill, 1987). Loudspeakers are available in all shapes, sizes and frequency ranges with the more common types being moving coil, electrostatic, and piezo-electric. Moving coil type loudspeakers are by far the most commonly used speaker in electronic circuits, kits and toys, and as such it is this type of sound transducer we will examine below ( Bishop et al, 2012). The principle of operation of the Moving Coil Loudspeaker is the exact opposite to that of the “Dynamic Microphone” we look at above. A coil of fine wire, called the “speech or voice coil”, 27 is suspended within a very strong magnetic field, and is attached to a paper or Mylar cone, called a “diaphragm” which itself is suspended at its edges to a metal frame or chassis. Then unlike the microphone which is pressure sensitive input device, this type of sound transducer can be classed as a pressure generating output device ( Bishop et al, 2012). Figure 2.15: Loudspeaker Transducer ( Horowitz and Hill, 1987). 28 Figure 2.16: The Moving Coil Loudspeaker ( Horowitz and Hill, 1987). When an analogue signal passes through the voice coil of the speaker, an electro-magnetic field is produced and whose strength is determined by the current flowing through the “voice” coil, which in turn is determined by the volume control setting of the driving amplifier or moving coil driver. The electro-magnetic force produced by this field opposes the main permanent magnetic field around it and tries to push the coil in one direction or the other depending upon the interaction between the north and south poles. As the voice coil is permanently attached to the cone/diaphragm this also moves in tandem and its movement causes a disturbance in the air around it thus producing a sound or note. If the input signal is a continuous sine wave then the cone will move in and out acting like a piston pushing and pulling the air as it moves and a continuous single tone will be heard representing the frequency of the signal. The strength and therefore its velocity, by which the cone moves and pushes the surrounding air produces the loudness of the sound. 29 As the speech or voice coil is essentially a coil of wire it has, like an inductor an impedance value. This value for most loudspeakers is between 4 and 16Ω’s and is called the “nominal impedance” value of the speaker measured at 0Hz, or DC. Remember that it is important to always match the output impedance of the amplifier with the nominal impedance of the speaker to obtain maximum power transfer between the amplifier and speaker. Most amplifier-speaker combinations have an efficiency rating as low as 1 or 2%. Although disputed by some, the selection of good speaker cable is also an important factor in the efficiency of the speaker, as the internal capacitance and magnetic flux characteristics of the cable change with the signal frequency, thereby causing both frequency and phase distortion. This has the effect of attenuating the signal. Also, with high power amplifiers large currents are flowing through these cables so small thin bell wire type cables can overheat during extended periods of use, again reducing efficiency ( Horowitz and Hill, 1987). The human ear can generally hear sounds from between 20Hz to 20kHz, and the frequency response of modern loudspeakers called general purpose speakers are tailored to operate within this frequency range as well as headphones, earphones and other types of commercially available headsets used as sound transducers. 30 CHAPTER THREE DESIGN METHODOLOGY 3.0 555 Timer Design The 555 timer is capable of being used in astable and monostable circuits. In an astable circuit, the output voltage alternates between and 0 volts on a continual basis. By selecting values for R1, R2 and C we can determine the period/frequency and the duty cycle. There are so many metal detector designs but most of them are complex in design so here we are going to design a simple metal detector circuit using 555 Timer IC. 3.1 Design Calculation i. 555 Timer Design Calculation Formulas and equations for 555 Timer Frequency f = 1 { {2} {1+22 }} Frequency f = 1.44 { {1+22 }} Where 1 {2} = 1.44 = {2} 2 = 0.693 x C x (1 + 2 ) {2} = 0.693 = {2} 2 = 0.693 2 Where C = Value of Capacitor in Farads 1 and 22 = Value of the input Resistance F = frequency in kHz 31 = Positive or High Time from each pulse = Negative or low Time from each pulse ii. For duty cycle (Voltage across Capacitor) = Vcc x (1- e-t / (R*C)) this equation describes the time it takes to charge a capacitor of capacitance C when it is in series with a resistor of resistance R . I am interested in the time it takes for the voltage across the capacitor to equal 2/3Vcc, or: 2/3xVcc = Vcc x (1- e^-t / (R*C)) which can be rearranged to: 2/3 = 1- e-t / (R*C) e-t / (R*C) = 1/3 -t / (R*C) = ln(1/3) t = 1.1xRxC seconds To connect an indicator LED to the output pin of the 555 and pick some arbitrary values for R and C to make sure that this really work In the last step we calculated the duration of the pulse output from the 555 in monostable mode to be: t = 1.1xRxC seconds where R and C are the resistor and capacitor in series if we choose R = 10Kohms and C = 470uF t = 1.1x10000x0.00047 t = 5.17 sec 32 iii Inductance of Coil Calculation The inductance of an air core coil inductor formular is given as = + μH Where N= Number of turns of wire d = Inductor Coil Diameter l = Inductor Coil length L= Inductance in μH 3.2 Design Materials of Automatic Metal Detector 33 Parts: - 555 - 47 kΩ resistor - two 2μ2 F capacitor - 9 V battery, switch, battery cable and some wires - buzzer - 100 m of copper wire, 0,2 mm in diameter - gaffer tape and wood glue 10 μF capacitor and speaker (8 Ω impendence). Tools: - breadboard and wires - pliers, tweezers, pliers for making holes - soldering iron and soldering wire - sharp knife, ruler, pencil and pair of compasses - hot glue Coil 34 The most difficult part is making coil. I calculated that with coil 90 mm width I need about 150 windings and with diameter 70 mm 290 windings that inductance can be 10 mH. I made coils core from cardboard. Coil is made from lacquered copper wire which is 0,2 mm in diameter. I did 150 turns. Before soldering, you must clean up both ends of coil with the help of sandpaper. 3.3 Design Algorithms 35 3.4 Block Diagram of the Design Figure 3.1: Schematic Diagram of Automatic Metal Detector System 3.5 Design Working Principle of Automatic Metal Detector System The 555 timer IC is an integral part of electronics projects. Be it a simple project involving a single 8 bit micro-controller and some peripherals or a complex one involving system on chips, 36 555 timer working is involved. These provide time delays, as an oscillator and as a flip-flop element among other applications. The 555 timer act as a wave generator and it generate pulse with frequencies audible to human hearing through the capacitor between pin 1 and pin 2. The generate configuration is made of resistive, inductive and capacitive circuit formed by a 47kΩ resistor and 2-2 μf capacitor and a turns of coil 150 inductor coil. RLC circuit is the metal detector part. The coil wound is an air core inductor suddenly increase the inductance of the overall reactive or impedance. When there is no metal piece, the signal fed to the speaker causes some audible sound and when there is a reactive change around the circuit, the system sent signal to the transducer speaker at different tone. But whenever a metal is brought near the coil, the impedance of the resistance inductance circuit RLC changes making the system to increase, resulting to variation of sound generated. The output of transducer speaker is 8ohms. In summary on how metal detector work i. A battery in the top of the metal detector activates the transmitter circuit (red) that passes electricity down through a cable in the handle to the transmitter coil(red) at the bottom. ii. When electricity flows through the transmitter coil, it creates a magnetic field all around it. iii. If you sweep the detector above a metal object (such as this old gray spanner), the magnetic field penetrates right through it. iv. The magnetic field makes an electric current flow inside the metal object. v. This flowing electric current creates another magnetic field all around the object. The magnetic field cuts through the receiver coil (blue) moving about up above it. The magnetic field makes electricity flow around the receiver coil and up into the receiver 37 circuit (blue) at the top, making a loudspeaker buzz and alerting you you've found something. . 38 CHAPTER FOUR TESTING, PACKAGING AND EVALUATION 4.1 Research and Construction Result After a close examination and research on the design and construction of this project work,it has been derived that automatic metal detector system allow criminal weapon to be detected easily before the culprit intended to commit the crime. 4.2 Installation Result The system here are typically chosen for simple installations, and it prevent a variety of security threat safety and meet a particular needs that product assistance to help in choosing the best crime free environment. 4.3 Interfacing Operation Since automatic metal detector system involved security personnel to other person ( visitor or intruder). The interfacing operation requires: i. In a public place it need the operation of a large security personnel ii. At the entering point, it need coordination of equipment by security personnel iii. A redundant backup path is required 4.4 Packaging/ Casing All electronics devices are designed such that the casing can be opened and the inside components can be easily accessed. Therefore after , the complete design of my work, it was package to avoid dust and moisture. This is mainly to protect the circuit from damage and to make the whole project presentation portable. 39 Figure 4.1: Design Packaging 4.5 Testing and Result After the construction, the complete design was tested absolutely good. This was made possible by putting different electronics component together which after full rectification give in effective supply to the LED which illuminate bright light. 4.6 Precautions Taken During Construction i. I tested all the electronics component for effectiveness confirmation before using it for connection. ii. I measure the value of the components with the use of a multimeter and ohm- meter before connections. iii. The circuit was connected in it respective stage as shown in the schematic diagram. 40 iv. I tested each components after soldering to know when any of it is blown or not working. v. I ensured , the circuit was properly built, tested and verified for the desired output result 4.7 Repairs and Maintenance In Engineering concept, no electronics or machine is hundred percent efficiency, therefore the gadget most be properly maintained to avoid unexpected faults that often require costly emergency repair. This project research work have a replacement component in stock for extension, repairs and maintenance. The essence of repairs and maintenance is to provide an ongoing support to keep the system running for a reliable and convenient security networking. 4.8 Bill of Material Bill of materials (BOM) should be selected by analyzing the maximum operating voltages and current levels of each node of the circuit while consider tolerance with electrically satisfactory components. Each component should be reconsidered base on available budget and size. The BOM must be kept up to date with the schematic diagram. Table 4.1: Bill of Material S/N ITEM RATE QUANTITY AMOUNT ₦ 555 Timer 1500 1 1500 2. Speaker 8 ohms 1000 1 1000 3. Capacitor • 2 μf • 10μf 100 100 1 1 100 100 4. Resistor 47K 100 1 100 5. Coil 1500 1 1500 6. Battery 9V 1500 1 1500 7. Packaging 4000 4000 Total 8900 41 4.9 Schematic Detail The schematic design detail control the project implementation, so accuracy and completeness are critical for success. They include information that is necessary for the proper operation of the circuit. The schematic include adequate design detail of the 555timer pin configuration and actual rated voltage to be supply to the system. 42 CHAPTER FIVE SUMMARY, CONCLUSION AND RECOMMENDATION 5.0 Summary The simplest form of a 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. A metal detector is 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. 5.2 Conclusion Security is the degree of resistance to, or protection from, harm. It applies to any vulnerable and/or valuable asset, such as a person, dwelling, community, item, nation, or organization. Security gadget is the material used to ensure safety, crime prevention e.t.c. Metal detector aid this duty at the point of entry. 5.3 Recommendation I strongly recommend that government should set up industries for production of basic electronic component locally and establish research centers in each university/Polytechnic to enable student have good sound practical knowledge on electronics component and their operation. 43 Secondly, I will also want the school management to procured Standard Electrical equipment for practical has enshrined in NTBE standard of establishing a Polytechnic. 44 REFERENCE Andrew, P. (1994). The Metal Detector. Second Edition. John Wiley and Son, New York, USA. Pp. 34-40 Bishop, O.N.,Anyawu, I.J., Olapade, O.L. and Morris, N.M. (2002). Basic Electronics. 1st Edition. Macmillan Introduction to Technology Series. Pp. 113-115. George, O.and Carl, M. (2012). Inside the Metal Detector. S.K Kataria & Son Publisher, New Delhi, India Pp. 45- 53. Horowitz, P. and Hill, W. (1987). Art of Electronics. Low Price Edition. Cambridge University Press.pp. 167-169. John, B. (2003). Electrical and Electronic Principles and Technology. Second Edition, Jordan Hill, Oxford. pp. 15-20. Meadow, R.G. (1997). Technician Electronics 2. Low Price Edition. pp.276-270. Snelgrove, M. (2011). Oscillator .McGraw-Hill Encyclopedia of Science and Technology, 10th Edition , Science Access online service. McGraw-Hill Theraja, B.L. and Theraja, A.K. (2003). Electrical Technology. 21st Edition Nirja Construction and Development Company, New Delhi. pp. 206- 230. Tyler J. K. (2016). "Archaeologists and Metal Detectors . The New York Times Retrieved Proceeding. USA.