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TULSIRAMJI GAIKWAD PATIL COLLEGE OF ENGINEERING AND TECHNOLOGY, MOHGAO,NAGPUR AND TECHNOLOGY, MOHGAO,NAGPUR

“ELECTRONICS AND COMMUNICATION DEPARTMENT”

SIMPLE METAL DETECTOR

PRSENTED BY: PRATIK MANKAR BHAGESHREE RATHOD DIPALI MOHITE GUIDED BY:

Mrs. R.D. POCHHI

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Introduction

Principle of operation

Circuit diagram

Parts list

Picture of components

Information about transistor

BFO detector design

Advantages and Disadvantages of circuit

Application

Conclusion

Reffernce

TABLE OF CONTENTS

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Metal detector is a device that can detect metal,the basics can make a sound when it is nearsome metal.

Active detector uses the coil to transmit a pulseor a continually waveform.

when some metals are coming close to the coilthe amplitude of the reflective pulse is gettinglittle lower and a duration of the pulse a littlelonger.

INTRODUCTION

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• When some metal is moving close to a coilthe magnetic field around the coil ischanged and the coil inducts some energy,called Eddie current.

• If there is measured on the speaker andpushes a little to the membrane, the speakergenerates some energy.

• The need for detection is very clear toprotect our self from any kind of danger.

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In our circuit oscillator will produce a shift infrequency. The end result is a detector thatoperates like two-transistor circuit.

Metal passing through the set of coils creates animbalance which the internal circuitry senses asa signal of finite amplitude and definite phaseangle with respect to a reference signal suppliedby the oscillator.

In our metal detector circuit two variablecapacitors and loop are used to generateoscillation in the circuit.

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pRINCIPLE OF OPERATION

• Increasing the value of the variablecapacitor will lower the oscillator’sfrequency and decrease the value withincrease the frequency.

• Here in our metal detector circuittransistor is used as a colpitts oscillator.

• If we increase L1’s inductance it will causethe decrease in frequency and if wedecrease this L1’s inductance it will causethe increase in frequency.

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CIRCUIT DIAGRAM

1.Capacitors- c1= .01uf, c2= .0001uf, c3= .005uf,c5= 4-34pf, c6= 12-100pf, c4= .1uf

2. Transistor- Q1(2N3904) 3. Resistances- R1= 1K, R2= 270K 4. Power source- 9V 5. Switch- S1 6.Loop- L1 7.Wires- single pin

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PARTS LIST

VARIABLE

CAPACITOR

PICTURE OF COPONENTS

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1K RESISTOR270K RESISTOR

RESISTORS

CONSTANT

CAPACITOR

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This 2N3904 transistor is called NPN switching transistor.> Features:

Low current (max 200 max)Low voltage(max 40 v)

>Applications:(1) High speed switching.(2) Well suitable for TV

and Home appliance equipment.(3)Small load switch

transistor with high gain and low saturation voltage.

INFORMATION ABOUT TRANSISTOR

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The basic way the beat frequency oscillator(BFO) works, when a detector coil is abovesome metal, it will change the frequency inthe detector oscillator, which has the detectorcoil in the frequency dependent circuit. Thisrelative simple metal detector is not a realBFO, but it is the closest group of detectors.When the metal is near the detector coil thesignal is send to a timer pin. Internally thecalculation is made, and showed on the LEDand some different sounds are made.

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“BFO” DETCTOR DESIGN

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Advantages- (1) Circuit diagram is very simple. (2) We can easily measure the

oscillation frequency of this circuit. (3) It has some sensitivity through

which it can sense the metal easily. Disadvantages- (1) It has less sensitivity. (3) Instead of variable capacitor we

cannot use any other capacitor for tuning purposes.

ADVANTAGES AND DISADVANTAGES

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Airport and Building SecurityMetal detectors are used for airport and

building security to determine whether guns, knives, or other weapons are being transported onto aircraft or into public buildings.

APPLICATION

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In Civil Engineering, metal detector are used tolocate rebar (strengthen steel used as rod inconcrete) .Rebar detectors are lesssophisticated. Detectors can only locatemetallic objects below the surface.

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Land mine detector can sense as little as 0.5 grams of metal. So, now-a-days militaries are using land mine detector to identify the land mine. Military has used metal detector to pinpoint buried land mines since world war1.

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Metal detectors are also used in the constructionindustry to locate steel reinforcement barsembedded in concrete, and to pinpoint metal pipesand wires in floors and walls. This is useful inavoiding unnecessary damage when replacingplumbing or wiring in a building or house.

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This project has been developed considering the need

for low cost.

The equipment is compact, simple in design and can be

used practically anywhere needs.

This circuit may also be constructed by using chip and

the chip is CS209A.

conclusion

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• Even the detectors with good coil compensation could not always detect the smaller target to the required depth in all lanes.

• The metal detector gives a respectable range for beat frequency operation (BFO) up to 90mm .

• In our circuit oscillator will produce a shift in frequency. The end result is a detector that operates like two-transistor circuit.

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WEB SOURCE- (Access Date: 08/04/2015) References: (1) http://www.principle.htm (2)http://www.freesimpleelectroniccircuitdia

gra m.htm (3)http://www.simplemetaldetectorcircuitdi

agram.htm (4) www.wikipedia.com

REFFRENCE

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THANK YOU

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