Gold - Gold Mining Terminology - Business - Business Ideas

Gold Mining Terminology

With years of experience in mining industry, Rachana Global is a dominant player in providing services for Gold mining and Fluorite mining. Rachana Global is one such exploration and mining services provider whose name can best be associated with all the gold mining terminology as stated below:Flour Gold/Gold Dust: Gold that is so fine that it looks and feels like flour or dust is called flour gold or gold dust.

Hard Rock Mine: A hard rock mine is a tunnel that is dug into solid rock for the sole purpose of finding valuable or precious rocks, minerals, or metals. Gold originates deep within the earth in places called Pockets. The pockets are filled with gold, heavy ore, and quartz.Hard Rock Mining: Hard rock mining refers to the underground mining techniques used to excavate hard minerals, mainly those minerals containing metals such as ore containing gold, copper, zinc, nickel and lead.Placer Mining: Placer Mining is the most common form of mining, it involves mining gold that has been washed away from it's source and deposited in small cracks, holes, or sand bars in the mainstream of a river.. It almost always involves the use of water in some way or another. Placer mining tools generally include the rocker box, sluice, dredge, highbanker, shaker table, drywasher, and always the pan.

Electronic prospecting: Electronic prospecting is a method for detecting gold, silver or other types of precious metals using a metal detector. The most known of electronic prospecting is done when nuggets are searched for.Ground Balancing: Ground balancing is the ability a metal detector has in order to ignore or get rid of the effect of detection of iron minerals or salt that is wet. Ground balancing is very important when it comes to searching for gold.

Gold Panning: The process of locating the richest gold bearing ground with the help of detecting equipments like gold pans and dredges.Wet Panning: Wet panning is the action that is done for gold with water that is used to create the state of suspension that allows the gravity to make the gold flakes sink into the riffles of a gold pan.Gold Metallurgy: The process of recovering gold from its ores, refining it and preparing it for commercial use is known as Gold Metallurgy.

Gold Mining: The technical and mechanical way of removing gold from its ores using various mining methods is known as Gold mining.Gold Refining: The mechanical process of separating valuable gold from the other waste materials from its ore using gold refining equipment is called gold refining.

Smelting: Smelting is the purifying process of heating the gold with a chemical substance called flux. The flux bonds with the contaminants and floats on top of the melted gold. The gold is then cooled and allowed to harden in molds, and the flux-contaminant mixture (slag) is hauled away as a solid waste.Gold dredging: The process of extracting gold from sand, gravel and dirt using water and mechanical methods and placer mining equipments like gold dredge is called as gold dredging.

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The Secret to Cleaning Your Metal Detecting Finds - Hobbies

In general, larger searchcoils will give better depth with larger targets and better ground coverage. However, sensitivity to smaller objects may be sacrificed. Smaller searchcoils will offer greater sensitivity to smaller objects and improved target separation in trashy soil. There are certain features needed for certain places the device is going to be used for. If you intend to use it on the beach, the terrain wont be that rigorous. But you are going to need waterproof protection.

A recent study proves that hand-held metal detectors are just as accurate as x-rays in finding coins and other metallic objects swallowed by children. They are cheaper and radiation-free, are usually lightweight, highly sensitive and require little maintenance. The special shape of the sensitive surface makes operation of the device easy, unlike portable metal detectors with ring transducers.

In 1881, Alexander Graham Bell constructed one of the worldos first metal detectors in an attempt to find an assassin's bullet in President James Garfield. Fischer patented a portable version in 1931.

The Secret to Cleaning Your Metal Detecting Finds

Metal detecting is considered to be one of today's most sought-after hobbies. In fact, nearly 80% of people who are into treasure hunting love metal detecting as well. Many people have tried metal detecting, but only those who know what it takes to become successful in metal detecting accomplish something. People who persevere the most tend to find more treasures than any other person does, even if they have been doing metal detecting for many years.

This goes to show that metal detecting is not just any "finder's keepers, losers weepers" game. The valuables that people find are not appraised just because they are rare. Most importantly, their values depend on the perseverance people use when finding metals.

However, metal detecting is not just plain what you see is what you get activity. Since most of the treasures are buried beneath the earth, you can expect layers upon layers of sand, mud, or dirt on the items. Now, the question is: Is it safe to clean these items?

There are some manufacturers of cleaning solutions that suggest you clean your items. However, if your metal detector finds include coins of high value, it is best not to clean them.

Metal detectors work on the principal of electromagnetics and their effects on conductive metals. There are actually two separate elements in the coil of a typical unit. One is a high-powered coil of metal which uses the battery power to generate a penetrating magnetic field.

Will smaller children be using this detector? If this is to be a family detector then it is critical that you consider the size of the detector including how short the pole can be. Any place there is construction and the ground is being cleared, that is a great place to start treasure hunting. Successfull treasure hunting starts with having the right metal detector. But which type of metal detector should you get? Complete info on metal detectors and treasure hunting at detect-metal.info.

In older parks check in front of bandstands or areas where people would sit, to listen to bands playing in the summer. Another good place is baseball diamonds. Check the infield and the area where the players would wait to play. Also look in the area that the families and fans would watch the game from. As with other electronic equipments, innovations seems to always happen overnight. If you are going to buy a metal detector today, try to know that technologies are currently employed. You do not want to be behind the technology line, right?

Metal detectors using PI (Pulse Induction) technology often makes use of a single coil or even a series of coils that works as a receiver and the transmitter. The short bursts of electricity are allowed to pass through a coil or wire which causes magnetism. This means that coins classified as "key collector's items" should never be cleaned. This is to preserve the mint mark and the date on the coins.

If you have found non-key collector's items, or those with the typical "face values," you can clean them using mild solution. However, the cleaning process will depend on the kind of coin you have found. For example, copper and nickel can both be cleaned with the same process. Other coins are cleaned using a different cleaning process and techniques.

Here are also some tips on eliminating stains on your coins. You can try using the salt and vinegar solution. This will remove stubborn stains or those that were not removed with the usual cleaning solution. The key here is to evaluate, analyze, and appraise your metal detector finds before you start cleaning them. This way you will be able to detect if a certain item is more valuable when preserved and kept the way you have found it, or if it has to undergo a special cleaning process to make it more appealing and presentable.

Indeed, cleaning metal detecting finds may or may not be advantageous, depending on the kind of items that you have. So to ensure quality, always evaluate your items first. There are many different types of metal detectors, some are more complicated then others. Find out how you can go treasure hunting today!

Hand-held Metal Detectors are designed to safeguard security-sensitive areas like schools, courtrooms, corrections facilities, sports events, businesses, nightclubs, bars and other public areas and events. They are used along with walk-through metal detectors. It is responsible for receiving frequencies that bounce back from the object that the coil detects. This type of detector is best for identifying different types of metals.

It does, however, have its own downsides. Some say that the knobs of the Pro XL are quite loose and when adjusting it, you have to be careful not to hit it with your arms. It is quite sensitive and bumping it may require you to start or reset the adjustments. Some users put a rubber band around the knobs to keep them from moving or becoming loose. Most metal detector companies also offer supplementary services like designing, material sourcing, prototyping, short run manufacturing, upgrading or re-designing, assembly services and specialty packaging.

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Metal Detecting Enthusiasts to Metal Detecting Professionals - Hobbies

You would be surprised what people are willing to buy if they like one particular thing you own or if they are interested in collecting certain things. Below is a list of things that you might find in your home and could sell, but this is by no means a complete list. Use your imagination and have a good look around the cupboard under the stairs and the garage! First, you'll need something to house your treasure. It could be a plastic tub or a cardboard box. Decorate it, if you wish. It can be as simple or elaborate as you like.

An old Native American we met at a hot spring in Arizona showed us how to find arrowheads and metates (used for grinding corn or mesquite beans) in the desert. They're hundreds of years old. He sold one of his metates for $200 during a yard sale, but for non-Native Americans this may be illegal. Check with authorities on this one.

The next question is how can you Treasure Hunt and will it make you money?? In answer to this the answer must be that 'yes' it can make you money but only to a few hard working and lucky hunters.

It is not necessary to know what you are looking for when you begin the search. This process allows your hearts desire in your subconscious mind to speak to you. As you look through the pictures, notice which ones resonate strongly inside you

Graduating from Metal Detecting Enthusiasts to Metal Detecting Professionals

There's no question about your enthusiasm for metal detecting but there's everything to doubt about your metal detecting skills. If you want to transform your enthusiasm into something more productive, visible, and concrete - such as obtaining real honest-to-goodness finds - here are some simple tips to upgrade your metal detecting abilities to the next level:

On Using Metal Detectors

In order to prevent losing depth, always remember to keep your metal detector low and flat to the ground. Don't neglect to use headphones, no matter how keen your hearing is. Take your time sweeping grounds; if you're after valuable finds rather than beating the record on who finds something the fastest, sweep the ground slowly and with painstaking care. Make several sweeps on the same area to ensure that you missed nothing. Lastly, take the time reading your metal detector's user guide, if any has been provided.

Always practice. It's not impossible that you'll find nothing on your metal detecting skills you wish to improve.

On Other Metal Detecting Equipment

Always have extra batteries and a charger with you. Make sure that your charger has the necessary connectors so you can use it in the car during emergencies. Never forget to take a flashlight with you. Before leaving home, make sure that the flashlight's in good working order.

Have you ever wished for the Publishers Clearing House to come to your door one bright and early morning? Or perhaps you bought a lottery ticket, feeling the anticipation of being sent a substantial check every week for the rest of your life.

Talk to friends and find out where their favorite swimming holes are on the local creeks. What about their favorite fishing spots? Any place where people gather along a creek is a potential good metal detecting spot.

Our city collects large junk for free during a week each spring. We see good bicycles, furniture, games, toys, chairs, and more, in front of almost every house. Several people come with trucks and trailers to pick out things to sell at flea markets or auctions. It's a regular source of income for some of them. I'm sure this happens in other cities too.

Corporate teams will spend the entire day in wandering to every possible locations and comparing the sites with the given photographs. In this event, each team has to take photographs, which should be similar to the given photographs.

Where can you find hidden treasure? Almost anywhere. How can you find it? Here are some new ideas on that.

On Comfort and Safety

Either have a backpack with you at all times or wear a shirt or pants that has lots of pockets. This will not only make certain tools and equipment more accessible, but it will also allow you to pocket small finds quickly in order to resume sweeping immediately. Wear gloves, elbow and knee pads to protect yourself from dirt and injury. Always have an insect and bug repellent with you to enjoy nonstop metal detecting. Don't forget to have a bottle of drinking water handy so you can refresh yourself at regular intervals.

On Metal Detecting Sites With metal detecting, older is always better. Any land rich with history is surely rich with metal detecting finds as well. The question is where these old lands are.

Avail yourself of all the resources available to you such as the Internet and the library in order to look up old maps.

Befriend old-timers of your area as they can probably point you to a place or two that can't be found on any of the local maps you've so far unearthed.

You are now merely metal detecting enthusiasts, but with a bit of practice and luck, all of you will surely be on your way to becoming successful metal detecting professionals.

From this we can see that it is a hobby or job that involves hunting for precious metals, gems etc. So we call assume that any job or hobby involving hunting for such items has an element of 'Treasure Hunting' involved in it.

I hope you find this technique useful and that you recover more treasure because of it. As I know it has increased the number of targets that I have been able to recover greatly.

A dresser without knobs only needs new knobs but a dresser without a drawer is going to take some more work. Could you replace the dresser with a wicker basket you pull in and out? The basic metal detectors are easy to get used to, with less features and buttons. Find out more about gold metal detectors today! Recognizing that your own treasure chest of positive memories and capacities are more precious to you than any winnings is what THE ENCHANTED SELF is all about. When we begin to acknowledge that we ourselves are our own messengers of enchantment, then we can begin to brighten our lives and the lives around us.

Metal detecting, be it relic or treasure hunting, is appealing whether as a work or a hobby. There are several ideal places where we can go detecting to enjoy using our metal detector. It might be on a beach, near a gold prospecting site, or in an area that has many old relics and artifacts in it.

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Metal Detecting in the UK - Hobbies

A third style, the Printed Spiral, is made only by Tesoro for use with pulse induction circuitry. It offers good sensitivity to a broader range of target sizes and improved sensitivity to less conductive targets such as fine gold chains. All searchcoils are electrostatically shielded and waterproof. There are certain features needed for certain places the device is going to be used for. If you intend to use it on the beach, the terrain wont be that rigorous. But you are going to need waterproof protection.

If this is your first metal detector purchase, consider getting some professional and expert advice to make sure that you have making the right choice. Metal detectors usually come with a complete control box containing the controls, circuitry, batteries, microprocessor, and the speaker. Metal detectors also include a search shaft that connects it to the coil and the control box. Metal detectors come with a control box that contains the circuitry, controls, speaker, batteries and the microprocessor; a shaft that connects the control box and the coil; a search coil that actually senses the metal; and a stabilizer that keeps the unit steady as it is moved. The basic metal detectors are easy to get used to, with less features and buttons. Find out more about bounty hunter metal detector today!

Metal Detecting in the UK

Metal detecting is a hobby that is not just popular in the United States. In the United Kingdom, metal detecting is also a rather popular activity enjoyed by many. Clubs, organizations and groups abound, along with many popular locations that are perfect for metal detecting enthusiasts.

Metal detecting actually has a long and rich history in the United Kingdom. Interestingly enough, the invention of metal detectors sprung not from a recreational or leisurely need: on the contrary, it came from the need to detect the locations of dangerous mines, so that they might be disarmed. By the end of the Second World War, metal detectors had become considerably sophisticated and effective. Soon after, some archaeologists began using mine detectors in their digs and excavations, in search for ancient metal artifacts.

By the 1950s, metal detectors began to be used to recover small items like coins in England. The brothers Caiger-Smith used what were previously mine detectors to recover modern as well as Roman coins in the fields surrounding the town where they lived, in the Newbury area. They even wrote and published their experience with metal detectors and what these nifty gadgets could possibly accomplish in the future. The paper sparked interest in metal detectors that would continue to grow until the present time.

Go to your local " do it yourself " coin operated car wash. Look for the place where they dump the contents of the 25 cent vacuum cleaners. Search the piles and see what a gold mine they are for coins and rings. Any place there is construction and the ground is being cleared, that is a great place to start treasure hunting. Successfull treasure hunting starts with having the right metal detector. But which type of metal detector should you get? Complete info on metal detectors and treasure hunting at detect-metal.info.

ome detectors have more ways of adjusting the "fit" to the person. Some of the other ways that detectors adjust are that the arm cup can be raised or lowered, and the box containing the board and controls can be taken off of the pole and mounted in a small pouch. Many people say to us "I have always wanted to do this!" As with other electronic equipments, innovations seems to always happen overnight. If you are going to buy a metal detector today, try to know that technologies are currently employed. You do not want to be behind the technology line, right?

If you are planning to buy a metal detector, you should check out the features of each before buying one. Metal detecting is a fun hobby but having the wrong equipment can cost you time and money. Mention the words metal detector and you'll get completely different reactions from different people. For instance, some people think of combing a beach in search of coins or buried treasure.

As in most other countries, laws govern metal detecting in the UK. A metal detecting enthusiast should be granted permission to go metal detecting on all lands except those that are open to the public such as parks and beaches that are not privately-owned. Otherwise, in the case of fields and farms that are privately owned, you must ask permission first before you search, and usually an agreement between the property owner and the metal detecting enthusiast is made regarding any items of value that may be found in the area.

There is also a Treasure Act and Code of Practice in the UK that every metal detecting enthusiast should read and remember; as there are certain items, such as coins that are older than three hundred years old, that must be reported to the authorities when they are found. Metal detecting is so popular in the United Kingdom that a national body has been set up for the hobby. The national body is called the National Council for Metal Detecting, or NCMD, and you can visit their site on , where you can find some very useful information on metal detecting in the UK. A recent study proves that hand-held metal detectors are just as accurate as x-rays in finding coins and other metallic objects swallowed by children.

Now that you have learned the three different types of metal detector, itos up to you to make your choice as to what type of detector you wish to use for your searches.

Some users put a rubber band around the knobs to keep them from moving or becoming loose. You should buy a metal detector that is light weight. This is important when you are detecting things on a riverbank or body of water.

The Garrett Enforcer G-2 is the smallest body scanner and sensitive enough to detect even the smallest of knives or guns.

The most popular one is the Super Scanner. It can detect hatpins as small as one inch.

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Design of metal detector using the induction balance system application

Design of metal detector using the induction balance system application

1 James agajo 2 Azih Conelius

Dept. of Electrical and Electronics Engineering, Federal Polytechnic, Auchi, Edo state Nigeria

Phone: +2348053312732 ,

ABSTRACT: An embedded system logic approach was used to achieve metal detection,. The controller is simulated to realize this. Three technologies were used Very low frequency (VLF) Pulse induction (PI) Beat-frequency oscillation (BFO) , The issue of safety and security were also emphasized.

Keyword: Microcontroller, low frequency, detector, security, oscillators, sensors

1.0 INTRODUCTION

Towards the end of the 19th century, many scientists and engineers used their growing knowledge of electrical theory in an attempt to devise a machine which would pinpoint metal. The use of such a device to find ore-bearing rocks would give a huge advantage to any miner who employed it. The German physicist Heinrich Wilhelm Dove invented the induction balance system, which was incorporated into metal detectors a hundred years later. Early machines were crude, used a lot of battery power, and worked only to a very limited degree. Alexander Graham Bell used such a device to attempt to locate a bullet lodged in the chest of American President James Garfield in 1881; the attempt was unsuccessful because the metal bed Garfield was lying on confused the detector.[1]

Many manufacturers of these new devices brought their own ideas to the market. Whites Electronics of Oregon began in the 50's by building a machine called the Oremaster Geiger Counter. Another leader in detector technology was Charles Garrett, who pioneered the BFO (Beat Frequency Oscillator) machine. With the invention and development of the transistor in the 50's and 60's, metal detector manufacturers and designers made smaller lighter machines with improved circuitry, running on small battery packs. Companies sprang up all over the USA and Britain to supply the growing demand.[2]

Larger portable metal detectors are used by archaeologists and treasure hunters to locate metallic items, such as jewelry, coins, bullets, and other various artifacts buried shallowly underground.[3]

1.3 METHODOLOGY

Metal detectors use one of three technologies:

Before going to my own design technique which is beat-frequency oscillation let me briefly introduce the other technologies. [4]

1.4 VLF Technology

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

The current moving through the transmitter 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. Each time the current changes direction, the polarity of the magnetic field changes. This means that if the coil of wire is parallel to the ground, the magnetic field is constantly pushing down into the ground and then pulling back out of it.

1.5 PI Technology

A less common form of metal detector is based on pulse induction (PI). Unlike VLF, PI systems may use a single coil as both transmitter and receiver, or they may have two or even three coils working together. This technology sends powerful, short bursts (pulses) of current through a coil of wire. Each pulse generates a brief magnetic field. When the pulse ends, the magnetic field reverses polarity and collapses very suddenly, resulting in a sharp electrical spike. This spike lasts a few microseconds (millionths of a second) and causes another current to run through the coil. This current is called the reflected pulse and is extremely short, lasting only about 30 microseconds. Another pulse is then sent and the process repeats. A typical PI-based metal detector sends about 100 pulses per second, but the number can vary greatly based on the manufacturer and model, ranging from a couple of dozen pulses per second to over a thousand. Pulse Induction detectors are now widely us ed in the construction industry; the Whites PI-150 is an industrial machine which can detect large objects to 10 feet, using a 12 or 15 inch coil.

2.0 MODULE ANALYSIS

This unit supplies the necessary d.c voltages for the circuit operation

This oscillator contains the reference coil as the inductive element and set the frequency to which that from the oscillator two is referred to.

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

The pulses produced by each oscillator are mixed in the mixer unit and the sum filtered to ground.

The gain filter processes and amplifies the difference of the mixed pulses from the mixer and drives a piezo buzzer with it.

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

2.1 OBJECTIVE

The aim of the project is to ease the trouble of trying to locate a useful metallic object in a particular or specified environment. As the trouble of straining the eyes is drastically reduced when the metal detector is used in the workshop where small metallic components could be easily misplaced. Also at security posts for searching people and their luggage.

P=I2R= IV= V2/R

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

The total amount of heat energy released is the integral of the power over time:

W= v(t)i(t)dt.

If the average power dissipated exceeds the power rating of the resistor, the resistor may depart from its nominal resistance, and may be damaged by overheating. Excessive power dissipation may raise the temperature of the resistor to a point where it burns out, which could cause a fire in adjacent components and materials.

2.2 Series and parallel circuits

Resistors in a parallel co nfiguration each have 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 equations by two vertical lines "||" (as in geometry) to simplify equations. For two resistors,

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

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

Req= R1 + R2 +..+ R2

Parallel and series network

A resistor network that is a combination of parallel and series can sometimes be broken up into smaller parts that are either one or the other. For instance,

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

However, many resistor networks cannot be split up in this way. Consider a cube, each edge of which has been replaced by a resistor. For example, determining the resistance between two opposite vertices requires matrix methods for the general case. However, if all twelve resistors are equal, the corner-to-corner resistance is 56 of any one of them.

2.3 Electric circuits

When a capacitor is connected to a current source, charge is transfered between its plates at a rate i(t) = dq(t) / dt. As the voltage between the plates is proportional to the charge, it follows that

V(t) = 1/c q(t) = 1/ci()d

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

I(t)Cdv(t)/dt

For example, if one were to connect a 1000 F capacitor to a voltage source, then increase the sourced voltage at a rate of 2.5 Volts per second, the current flowing through the capacitor would be

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

A circuit containing only a resistor, a capacitor, a switch and a constant (DC) voltage source vsrc(t) = V0 in series is known as a charging circuit. From Kirchhoff's voltage law it follows that

Vo=Vr(t) + Vc(t) = i(t)R I/C i()d

where vr(t) and vc(t) are the voltages across the resistor and capacitor respectively. This reduces to a first order differential equation

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

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

The corresponding voltage drop across the capacitor is

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

Therefore, as charge increases on the capacitor plates, the voltage across the capacitor increases, until it reaches a steady-state value of V0, and the current drops to zero. Both the current, and the difference between the source and capacitor voltage decay exponentially with respect to time. The time constant of the decay is given by = RC.

Capacitors in a parallel configuration each have the same potential difference (voltage). Their total capacitance (Ceq) is given by:

Ceq =C1 +C2 + ..+Cn

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

Estored = CV2

The current through capacitors in series stays the same, but the voltage across each capacitor can be different. The sum of the potential differences (voltage) is equal to the total voltage. Their total capacitance is given by:

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

In parallel, the effective area of the combined capacitor has increased, increasing the overall capacitance. However, in series, the distance between the plates has effectively been increased, reducing the overall capacitance.

When an inductive circuit is opened, the current through the inductance collapses quickly, creating a large voltage across the open circuit of the switch or relay. If the inductance is large enough, the energy will generate a spark, causing the contact points to oxidize, deteriorate, or sometimes weld together, or destroying a solid-state switch. A snubber capacitor across the newly opened circuit creates a path for this impulse to bypass the contact points, thereby preserving their life; these were commonly found in contact breaker ignition systems, for instance. Similarly, in smaller scale circuits, the spark may not be enough to damage the switch but will still radiate undesirable radio frequency interference (RFI), which a filter capacitor absorbs. Snubber capacitors are usually employed with a low-value resistor in series, to dissipate energy and minimize RFI. Such resistor-capacitor combinations are available in a single package.

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

.f = 1/2LC

This is the frequency at which resonance occurs in an LC circuit.

2.5 INDUCTOR

An inductor is a passive electrical component with significant inductance. Inductors are implemented by some sort of coiled conductive winding which may surround a ferromagnetic core. Large inductors used at low frequencies may have thousands of turns around an iron core; at very high frequencies a straight piece of wire (i.e., with turns and core reduced to zero) has significant inductance.

An "ideal inductor" has inductance, but no resistance or capacitance, and does not dissipate energy. A real inductor is equivalent to a combination of a significant ideal inductance, some resistance, and capacitance, usually small. The resistance, a necessary property of a wire except at superconducting temperatures, may contribute significantly to the impedance, and may dissipate significant power in some applications. At some frequency, usually much higher than the working voltage, a real inductor behaves as a resonant circuit, and can cause parasitic oscillation.

3.0 INDUCTOR CIRCUIT ARRANGEMENT

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 through inductors in series stays the same, but the voltage across each inductor can be different. The sum of the potential differences (voltage) is equal to the total voltage. To find their total inductance:

Leq = L1 + L2 + .+Ln

These simple relationships hold true only when there is no mutual coupling of magnetic fields between individual inductors.

4.0 INTRODUCTION

This chapter deals with the design methods and the analysis employed in the design of the electronic metal detector system. These analyses are required to make the correct choice of component values for effective performance.

4.1 DESIGN SPECIFICATION

Power source:Any two 9v battery PP3 is ideal.

Capacitors:2 off 220uF 16v electrolytic.5 off .01uF polyester.5 off .1uF polyester.

Resistors:All resistors 1/4 watt 5%6 off 10k1 off 1K1 off 2.2M2 off 39k

Transistors:All BC 337B. Just about any small signal NPN with a gain of 250+ will do. There are hundreds to choose from.

Audio output:A 2.5 inch 8 ohm speaker will work but headphones, buzzer or earpiece are preferable, the higher the impedance the better.

4.2 Power supply Circuit

The main power supply to the circuit is from two 9v batteries connected in series to produce 18v and then regulated and maintained at 12v by using a 7812 voltage regulator.

power supply circuit

The input to the 7812 regulator is calculated thus

Series connection of batteries is given by pt = p1 + p2 + p3 +

Therefore the power input to the regulator is pt = p1 + p2

pt = 9+9 =18v

3.1.2 Oscillator Circuit

The oscillator circuit are made up of two different oscillators which are the sensor oscillator and the local or reference oscillator. Their frequencies of oscillation are set at 124khz since they are to operate at the same frequency. The two oscillator circuits are series LC circuit comprising of a BC 337 NPN transistors each for effective oscillation.

To calculate the inductance of the inductor the resonance frequency formula is used

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

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

L = inductance of the inductor

C = capacitance of the capacitor

L = 1/ ( 42CF2 )

L = 1/ ( 4 x (3.142)2 x0.1x10-6 x (124 x 103 )2 )

L = 16.47H

Then to calculate the number of turns, Wheelers formula for coils is applied

L = N2 r2/ 9r + 10l

Where N = number of turns

r = outer radius of coil (inches)

l = physical length of coil (inches)

L = 16.47outer radius of coil (inches)

l = physical length of coil (inches)

L = 16.47H

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

r= 3.6cm/2 =0.57cm

Converting to inches we have

2.54cm 1inch

0.57cm - ?

0.57 / 2.54 = 0.23inches

L = 2.36 inches

N2 =L( 9r + 10l) / r2

= 16.47( 9x0.23 + 10x2.36 ) / 0.232

N2 = 89 Turns

Applying the resonant frequency formula to calculate the inductance here we have:

L = 1/ ( 42CF2 )

Where F = 124khz , C = 0.1F

L = 1/ ( 4 x (3.142)2 x0.1x10-6 x (124 x 103 )2 )

L = 16.47H

Then using the Wheelers formula to find 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 ( 9x3.26 + 10x0.24 ) / 3.262

N = 7 Turns

4.3 Amplifier Circuit

A common emitter (CE) transistor amplifier was used because of its characteristics which include:

The transistor used is a BC337 NPN transistor.

In a proper design the amplifier circuit operates normally when

VCE = VCC

Also for a CE configuration

VCE = VCC ICRL

hfe = IC / IB

Where VCE = collector emitter voltage

hfe = absolute minimum gain for the selected transistor which is 100

IC = collector current

IB = base current

Therefore RL = (VCC VCE) / IC

The Voltage gain is given by

AV = ro / re

Where ro = output resistance of the stage

re = emitter junction resistance

25Mv / IE.

4.4 Beat Frequency Oscillator Technology

The circuit employs two radio frequency oscillators called the search and the reference oscillators and is tuned at the same frequency. the output of the oscillator is fed into a mixer, which produce a signal that contains the sum and difference frequency components of the two input signals.

The output from the mixer is fed into a low-pass(gain) filter where the harmonic is removed leaving the difference frequency component to subsist, though at theoretically 0Hz , as a result the output will have no difference. However, when metal is brought into the vicinity of the search coil, the frequency of search oscillators shifts slightly, then a there is a frequency difference, which is within the audio frequency range, appears at the output of the filter. This output is amplified by an audio amplifiers and fed to a loud speaker which produces sound output thus indicating the presence of metal

5.0 TESTING AND ANALYSIS

The following test was performed on the project circuit to ascertain the condition of the different stage and the project as a whole:

Short Circuit Test

The connections were checked with a multimeter set in continuity to ensure no short circuit occurs. The test was done and no short circuit was found.

Open Circuit Test

The various connections were checked for open circuit and none was found using multi meter.

Functional Test

The different voltage value and current value were measured at each stages and all were found in confirmation with the design specifications.

Insulation Test

Insulator test was carried out in all units of the circuit especially those units that require adequate insulation. Example, coil used in the oscillators.

SYSTEM PERFORMANCE AND TEST RESULT

The metal detector was used to test for various sizes of metal at various distance from the search coil and the following result were obtained.

(i) The lager the metal, the louder the sound output from the loud speaker and smaller the metal , the lower the sound output from the loud speaker though this also dependent on the size of the search coil.

(ii) The closer the distance between the search head and the metal, the greater the sound output from the loud speaker and the farther the distance the fainter the sound output from the loud speaker, to extent the sound die off at some critical distance where theoretically the magnetic field due to the search head is zero.

6.0 CONCLUSION

The beat frequency oscillator (BFO) principle is one of the reliable simple and cast effective principles of building a metal detector .though some price are paid for these seemingly advantages and they includes.

(i) Low sensitivity

(ii) Short range of detection. Though depended on the size of search coil.

(iii) Not be able to discriminate metals

All these is nothing at all,It is interesting to know that the design and construction of metal detector is a success. This is because the project when tested produced the desired effect. In particular, this research work had made the principle of electromagnetic induction very clear to me as well as to any average literate person around me. In general, with the invention of metal detectors, the stress of one indulging in locating metallic components in a workshop has been reduced drastically. Also the embarrassment banks and other establishment cause their customers has been solved as some of the metal detectors are mounted on door entrances so as to trigger up an alarm when a metal is detected on s person trying to enter.

REFERENCES

1 Edeko, F.O, Electronics circuit design material 2008

2 A textbook of electrical technology by B.L. Theraja and A.K. Theraja, S. Chard and company, 2005.

3 Study of electronic components by J.A. Smith (2nd edition) , 1999

4 Electronic circuit analysis and design by Donald A. Neumann, Mc Grawhill Book Company, USA 1996.

5 Amplifiers comparators and special functions, Texas instrument, Data book volume B, Custom Printing Companys,1997.

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Common Metal Detector Products

Metal detectors are used to detect metals. Metal detectors have a control box with speakers, batteries, microprocessor, circuit and controls. The unit must also have a stabilizer to keep it steady when it is moved. It needs a search coil to sense the metal and a shaft to connect the control box to the coil.

These are the different brands of metal detectors available in the market:

Tesoro Golden Max This is a metal detector that weighs less than 2 and a half pounds. It has great sensitivity and is the lightest in the market. It allows you to control what you need to find.

Tesoro DeLeon This is a metal detector named after Ponce de Leon, who went to Florida looking for treasure. It is easy to use. It is a target identification detector. However, it is not as light as the Tesoro Golden Max.

Whites E-Series This is a complete series of metal detectors for use. This series of metal detectors have the following models:

1. DFX .

This metal processor combines microprocessor technology and turn-and-go simplicity.

2. XLT

This metal detector is simple and versatile. It has 5 programs and 10 adjustments that can be made.

3. MXT

This metal detector has three completely different operating modes. These modes are the gold prospecting, coin and jewelry and relic.

Prizm Series This series of detectors includes the following:

1. Prizm II

2. Prizm III

3. Prizm IV

4. Prizm V

All these show exactly when and where to hunt.

Fisher These metal detectors are named after a German called Fisher. They have an 8-inch center spider coil, instruction manual and 5 year warranty.

Garrett This is a hand-held detector that can detect a medium sized pistol or a small piece of jewelry from a distance of 9". It is simple. This detector is the most popular one. The Garrett Scanner PD 6500 Walk is a unique one that has special features.

Bounty Hunter It is streamlined and has two operating controls and a mode selection switch. It is user friendly and gives great performance too.

Minelab These metal detectors cost approximately $1395. They have an operating frequency of 1.5 to 100 kHz. One model is made primarily for use in parks, beaches and on the battlefield. The Minelab's FBS provides excellent technology to work on saltwater beaches.

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