Camping Generators

Designing a metal detector system induction by constantly

Designing a metal detector using the system equilibrium in the induction

1 Agaja James 2 Azihar Conelius

Department of Electrical and Electronics Engineering, Federal Polytechnic, Auchi, Edo State in Nigeria,

Phone: +2348053312732, agajojul@yahoo.com

Abstract: A system of logic integrated approach has been used to make metal detecting. The controller is simulated to notice. Three technologies have been used very low frequency (VLF) Pulse induction (PI) Beat-frequency oscillation (BFO), the issue of security and safety were also highlighted.

Keyword: micro-controller, low frequency, detector, security, oscillators, sensors

1.0 INTRODUCTION

In the 19th century, many scientists and engineers have used their growing knowledge of electrical theory in an attempt to develop a machine that point metal. Use as a device to find ore rock to give an advantage to any miner working. The German physicist Heinrich Wilhelm Dove invented the system balance of induction, which has been incorporated into metal detectors later, a hundred years. First came the crude machines, uses a powerful battery, and worked in a very limited extent. Alexander Graham Bell used as a device to try to find a bullet in the chest by U.S. President James Garfield in 1881, the attempt failed because the metal bed Garfield was lying on confused the detector [1].

1.2 Trends

Many manufacturers of these new devices brought their own ideas to market. Oregon Whites Electronics began in the 50s by building a machine called Oremaster Geiger Counter. Another leader in technology Detection was Charles Garrett, who pioneered the BFO (Beat Frequency Oscillator) machine. With the invention and development of the transistor in the 50s and manufacturers Metal 60, designers of the detector is smaller and lighter machines with improved circuitry, running on the small battery packs. The companies were in the U.S. and Britain to meet the growing demand [2].

Older metal detectors are used by archaeologists and search engines treasure to find metal objects such as jewelry, coins, bullets, and other various objects buried in the earth surface [3].

1.3 Methodology

Metal detectors use a three technologies:

• Very low frequency (VLF)
• Pulse Induction (PI)
• Beat-frequency oscillation (BFO)

1. [4]

1.4 VLF Technology

Very low frequency (VLF), also known as the balance of induction is probably the most popular detector technology in use today. In a VLF metal detector, two different coils:

• Transmitting Coil – This is the outer coil circuit. Within it is a coil of wire. Electricity is sent along this thread, first one way then the other, thousands of times every second. The number of times the current direction changes every second establishes the frequency of the unit.
• Receiver coil – This inner coil loop contains a spool of thread. This wire acts as an antenna to pick up and amplify frequencies of target objects on the ground. [5]

The actual movement through the issuance of coil creates an electromagnetic field, which is like what happens in an electric motor. The polarity of the magnetic field is perpendicular to the coil of wire. Every time the sense current changes the polarity of the magnetic field changes. This means that if the cable of the coil is parallel to the ground, the magnetic field is constantly pushing down on the ground and then pulling back from him.

1.5 IP technology

A rarer form of metal detector is based on pulse induction (PI). Unlike VLF, IP systems can use a single coil as the transmitter and receiver, or May, with two or even three coils working together. This technology sends bursts, powerful short (pulses) of current through a coil of wire. Each pulse generates a magnetic field of short duration. When the pulse ends, the magnetic field reverses polarity and collapses suddenly resulting in a peak power grid. This item has a few microseconds (millionths of a second) and causes another current running through coil. This current is called the reflected pulse and is very short, lasting only about 30 microseconds. Another pulse is sent and the process repeats. Detector metal of a standard based on IP sends about 100 pulses per second, but the number can vary greatly depending on manufacturer and model, ranging from a few tens of pulses per second over a mile. Pulse induction detectors are widely used in the construction industry; white PI-150 is an industrial machine that can detect large objects to 10 feet, with a roll of 12 or 15 inches.

2.0 Analysis Module

• DC Power

This unit provides DC voltage required for operation of the circuit

• Reference oscillator coil

This oscillator is the reference coil as part of induction and to set the frequency with which concerns the oscillator of the two.

• Search coil oscillator

This is the second oscillator that contains the search coil as inductive element. The inductance of coil Research rates when locating a metal, which in turn changes the frequency of the oscillator. This frequency is compared with one for the oscillator to produce a note beat.

• Mixer

The pulses produced by each oscillator were blended in mixer unit and the sum leaked to the ground.

• Filter Gain

The gain of the filter process and amplifies the difference of mixed pulses of the mixer unit and a piezoelectric buzzer with him.

• Transducer output (position)

The transducer converts the electrical output signal into sound audible to give an audible indication of the presence of a metal.

2.1 OBJECTIVE

The project aims to alleviate the pain of trying to locate an object or a metal useful in a given environment. As the tender eye pain is considerably reduced when the metal detector is used in small workshop in which metal parts can be easily moved. Also at the stations of the search of persons and their luggage.

= P / 2R = IV = V 2 / R

The three equations are equivalent. The first is derived from Joule's law, and the other two are referred to by the Ohm's law.

The total amount of heat energy released is the integral of the power in the Time:

W =? V (t) i (t) dt.

If the average power dissipated exceeds the power of resistance, resistance can be distinguished from its nominal resistance, and may be damaged by overheating. The dissipation excessive power in May to raise the temperature of the resistance to a point at which it burns, which could cause fire in adjacent areas and materials.

2.2 series and parallel circuits

• Parallel circuit

Resistances in a parallel cooperation nfiguration everyone has the same potential difference (voltage). To find their total equivalent resistance (Req):

1/Req = 1/R1 +1 / R2 … .. + .. 1 / Rn

The parallel property can be represented in the equations of two vertical lines "| |" (as in geometry) to simplify the equations. For two resistors,

Req = R1 / / R2 = R1R2 / (R1 + R2)

• Circuit in series

The current in the resistors in series is the same but the voltage across each resistor can be different. The sum of potential differences (voltage) is equal to the total stress. To find the total resistance:

Req = R1 + R2 + … .. + R2

 

Red parallel and serial

A network of resistance that is a combination of parallel and series can sometimes be divided into smaller parts that are one or the other. For example,

Req = (R1 / / R2) + R3 = (R1R2) / (R1 + R2) + R3

However, resistance networks many can be divided in this way. Consider a title = "Cube"> cube, each edge has been replaced by a resistor. For example, the determination of the resistance between two opposite vertices requires matrix methods for the general case. However, if the twelve resistors are equal, the resistance to the corner of corner is 5? 6, either.

2.3 Electric circuits

When a capacitor is connected to a source energy, the charge is transferred between the plates at a rate I (t) = dq (t) / dt. As the tension between the plates is proportional to the load, it follows that

V (t) = 1/cq (t) = 1 / c? I (?) D?

Conversely, if a capacitor is connected to a voltage source, the resulting displacement of current is given by

I (t) APV (t) / dt

For example, if we connect a capacitor of 1000 uF with a voltage source, increase the voltage source at a rate of 2.5 volt per second, the current through the capacitor

I = CDV / dt = (1000 x10-6F) (2.5 V / s) = 2.5 mA

Ø DC sources

A circuit containing only a resistor, capacitor, switch and a constant (DC) source vsrc tension (t) = V0 in series is known as a load circuit. Voltage Law Kirchhoff, it follows that

Vo = VR (t) + Vc (t) = I (t) IR / C? i (?) d?

where T (RV) and VC (t) are the stresses in the resistor and capacitor, respectively. This reduces to a first-order differential equation

Assuming the capacitor is initially loaded, no internal electric field and the initial current is I0 = V0 / R This condition allows the initial solution as the differential equation

. i = Vo / Ans (-t/RC)

The corresponding voltage drop through the condenser is

V (t) = Vo [1-exp (-t/RC)]

Therefore, as the increased load of the capacitor plates, the voltage across the capacitor increases until it reaches a steady state value of V0, and the current drops to zero. The current and the difference between the source and strain of capacitor decreases exponentially with time. The decay time constant is given by? = RC.

2.4 serial or parallel arrangements

• circuits in parallel

Capacitors in a parallel configuration each have the same potential difference (voltage). Total capacity (CEQ) is given by:

C eq = C1 + C2 + … … .. + Cn

The reason for putting capacitors in parallel to increase the amount of charge stored. In other words, increasing the capacity also increases the amount of energy it can store. Its expression is:

Estore = ½ CV2

• Series Circuit

The current series capacitors remains the same but the voltage across each capacitor can be different. The sum of potential differences (voltage) is equal to the total stress. Its total capacity is equal to:

1 / Ceq = 1 / C1 + 1 / C2 + … … .. + 1 / Cn

In parallel, the effective area of the total capacity has increased at a higher total capacity. However, in series, the distance between the plaques has actually increased, thereby reducing the total capacity.

Ø noise filters, motor starters and stamps

When an inductive circuit is opened, the current in the inductance collapses quickly, creating significant tension open-circuit switch or relay. If the inductance is large enough, energy will generate a spark, causing contact points to oxidize, or deteriorate, sometimes, welding, or the destruction of a solid state switch. A capacitor in the damper open circuit has recently created a step of this impulse to bypass the contact points, thus preserving their lives, are commonly found in switching ignition, for example. Similarly, in the circuits on a smaller scale, the spark may not be enough to damage the switch, but will still radiate undesirable radio frequency interference (RFI), which removes a filter capacitor. damper capacitors are employees with a low value resistor in series to dissipate energy and minimize RFI. This resistor capacitor combinations are available in one package.

Ø tuned circuits

In a tuned circuit like a radio receiver, the selected frequency is a function of the inductance (L) and capacitance (C) in series, and is given by:

. f = 1 / 2? SC

This is the resonant frequency that occurs in an LC circuit.

2.5 IC

An inductor is a passive electrical component with a large coil. The inductors are implemented by a spiral winding conductor May around a ferromagnetic core. Large inductors used at low frequencies may have thousands of laps around an iron core at very high frequencies of a piece of wire (ie – with the towers and the core is reduced to zero) has significant inductance.

Inductance "ideal" is the induction, but not the strength or capacity, and not dissipate energy. A real inductor is equivalent to a combination of an ideal inductor extent, some resistance and capacitance, usually small. Resistance, a necessary property of a superconducting cable, except at temperatures may contribute significantly to the impedance, and can dissipate significant in certain applications. At a some frequency, usually much larger than the stress of work, a real inductor behaves as a resonant circuit, and can cause parasitic oscillations.

3.0 IC CIRCUIT

Parallel circuit ·

Inductors in a parallel configuration each have the same potential difference (voltage). To find their total equivalent inductance (Leq):

1/Leq = 1/L1 + 1/L2 + … … + 1/ln

series circuit

The current in the inductors in series is the same but the voltage in each coil may be different. The sum of the potential differences (voltage) is equal to the total stress. To find their total inductance:

Leq = L1 + L2 + …. + N L

These simple relations valid only if there is mutual coupling between the magnetic fields of individual drivers.

 

4.0 Introduction

This chapter discusses the design and analysis methods used in the design of the electronic metal detector. These tests are needed to make the correct choice of component values for effective performance.

 

4.1 Specifications design

Power Source:
Any PP3 two 9V batteries are ideal.

Capacitors:
2 off 220UF 16V electrolytic.
5 off of polyester .01 UF.
5 off of polyester .1 UF.

Connectors:
All resistors 1 / 4 W 5%
6 off 10k
1 off 1K
1 OFF 2.2M
2 off 39k

Transistors:
All BC 337b. Almost any NPN small signal with a gain of 250 + will. There are hundreds of choices.

Output audio:
A 2.5 inch 8 Ohm Speaker works, but a helmet or headphones that vibrate are better than the impedance, the better.

Del 4.2 Fuel System

The main circuit power supply is provided by two 9V batteries in series to get 18v regulated and maintained at 12V through voltage regulator 7812.

FUEL SYSTEM

The input buffer 7812 is calculated as

Connecting batteries in series is given by PT = P1 + P2 + P3 + …

Therefore, the input power regulator is pt = P1 + P2

pt = 9 +9 = 18V

3.1.2 Oscillator Circuit

The oscillator circuit consists of two oscillators are different sensor oscillator and local oscillator or reference. Their oscillation frequencies 124khz down in order to be able to operate in the same frequency. The two circuits are series LC oscillator circuit comprising an NPN transistor BC 337 for each swing so effective.

• The sensor oscillator

To calculate the inductance of the coil of the formula of the resonant frequency used

F = (2? (LC) 1 / 2) -1

Where F = frequency in Hertz, which is set at 124khz

L = inductance of the coil

C = capacitor

L = 1 / (4 2CF2)

L = 1 / (4 x (3,142) 2 x 6-x0.1×10 (124 x 103) 2)

L = 16.47μH

Then, to calculate the number of turns, a formula for coils applies Wheeler

L = N2 R2 / 9R + 10l

Where N = number of turns

r = outer radius of coil (cm)

l = physical length of coil (cm)

16.47outer L = radius of coil (cm)

L = physical length of coil (cm)

L = 16.47μH

r = C / 2? where C = circumference of the coil former

r = 3.6 cm / 2? = 0.57cm

Converting to inches

2.54 to 1 inch

0.57cm -?

0.57 / 2.54 = 0.23inches

L = 2.36 inches

N2 = L (9r + 10l) / R2

= 16.47 (10×2.36 + 9×0.23) / 0232

N2 = 89 laps

Applying formula to calculate the resonant frequency of the coil here, we have:

L = 1 / (4 2CF2)

Where f = 124khz, C = 0.1μF

L = 1 / (4 x (3.142) 2 x0.1×10-6 x (124 x 103) 2)

L = 16.47μH

Then, using Wheeler's formula to determine the number of turns

L = N2 R2 / 9R + 10l

Where r = C / 2? = 52 / 2?

8.27cm == 3.26inches

L = 0.6 cm == 0.24inches

N2 = L (9r + 10l) / R2

N2 = 16.47 (9×3.26 + 10×0.24) / 3262

N = 7 Tours

4.3 Circuit amplifier

A common-emitter (CE) transistor amplifier was used because its features include:

• Its output resistance is fairly large (50k or so)
• His current gain (?) Is tall (50 – 300)
• It's high voltage gain of the order of 1500 and above
• It produces very high power gain of 10,000 times or 40 dB.

The transistor used is a BC337 NPN transistor.

In a design appropriate amplifier circuit works normally when

VCE = VCC ½

As a setting for the EC

VCE = VCC – ICRL

HFE = IC / IB

When VCE = collector emitter voltage

HFE = absolute minimum gain for the selected transistor is 100

IC = collector current

Base current IB =

Therefore, RL = (VCC – VCE) / IC

The voltage gain is given by

AV = r / re

When ro = resistance of leaving the scene

Re = the emitter resistance

25mV / IE.

4.4 Beat Frequency Oscillator Technology

The circuit uses two radio frequency oscillators called research and oscillators reference and is listening to the same frequency. the oscillator output is introduced into a blender, producing a signal that contains the sum and difference of the components of frequency of two input signals.

1. The mixer output is fed into a low pass (gain) where the harmonic filter is removed, leaving the component frequency difference, but theoretically 0 Hz, after the output is no difference. However, when the metal is introduced near the search coil, the oscillator frequency changes are a little research, then there is a difference frequency, which is within the range of audio frequencies, appearing at the output of filter. This output is amplified by an audio amplifier and fed to a loudspeaker that produces sound output which indicates the presence of metal

5.0 TESTING AND ANALYSIS

The next test was conducted in the proposed tour to know the state of the scene and proposed different sets:

Test Short Circuit

The connections were checked with a multimeter set to continuity to ensure no short circuit occurs. The test was short circuit and was not found.

Open Circuit Test

Different connections have been checked for open circuit and not found using several meters.

Functional tests

The value of the voltage and current value were measured at each stage and all is at confirmation with the design specifications.

Insulation test

Insulation test was conducted in all units units that require particular circuit properly insulated. For example, the coils used in oscillators.

SYSTEM PERFORMANCE AND TEST RESULT

The metal detector was used to test different sizes of metal on different remote search coil and The following results were obtained.

(i) Beer of metal, the speaker output healthier and more metal, the sound output of the speaker – but this also depends on the size of the search coil.

(ii) The greater the distance between the head of research and more metal speaker output Audio and down, the lower the sound output through the loudspeaker, so that die in a critical distance, where theoretically the magnetic field due to the height Search is zero.

6.0 CONCLUSION

Beat Frequency Oscillator (BFO), the principle is a series of simple principles reliable and efficient place to build a metal detector. Although some money is paid these benefits, and apparently are.

(i) Low sensitivity

(ii) short-range detection. Although it depends on the size of the search coil.

(iii) not be able to discriminate between metals

All this is nothing, it is interesting to know the design and construction of metal detector is a success. Since the project during the test produces the desired effect. In particular, This research has made the principle of electromagnetic induction very clear to me and to any literate person on average about me. In general, the invention metal detectors, the effort to participate in the localization of components in a metal workshop drastically reduced. Also the banks of the shame and any another facility so that customers had resolved that some metal detectors are mounted on the front door to trigger an alarm when it detects metal in person s trying to enter.

REFERENCES

1 Edeka, FP, "electronic circuitry design Hardware "2008

2 A textbook of electrical technology by BL Theraja and AK Theraja, S. Chard and Company, 2005.

3 Studio J. electronic components Smith (2nd edition), 1999

4 circuit electronic design and analysis of Donald A. Neumann, Mc GrawHill Book Company, USA 1996.

5 amps for comparison and special functions, Texas Instruments, the data volume of product B, Custom Printing Company, 1997.

About the Author

James Agajo is into a P.H.D programme in digital signal processing related area, he has a Master Degree in Electronics and telecommunication Engineering and also possesses a Bachelor degree in Electronics and Computer Engineering from the Federal University of Technology Minna Nigeria. To he’s record he has carried out researches in various areas as it concern telecommunication with particular emphasis on wirless communication network. His interest is in intelligent system development with a high flare for Engineering and Scientific research.He has Designed and implemented the most resent computer controlled robotic arm with a working grip mechanism 2006 which was aired on a national television , he has carried out work on using blue tooth technology to communicate with microcontroller. Has also worked on thumb print technology to develop high tech security systems with many more He is presently on secondment with UNESCO TVE as a supervisor and a resource person. James is presently registered with the Nigeria Society of Engineers.

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