1. F
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
1
2. 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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3. Metal detector is a device that can detect metal,
the basics can make a sound when it is near
some metal.
Active detector uses the coil to transmit a pulse
or a continually waveform.
when some metals are coming close to the coil
the amplitude of the reflective pulse is getting
little lower and a duration of the pulse a little
longer.
INTRODUCTION
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4. • When some metal is moving close to a coil
the magnetic field around the coil is
changed and the coil inducts some energy,
called Eddie current.
• If there is measured on the speaker and
pushes a little to the membrane, the speaker
generates some energy.
• The need for detection is very clear to
protect our self from any kind of danger.
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5. In our circuit oscillator will produce a shift in
frequency. The end result is a detector that
operates like two-transistor circuit.
Metal passing through the set of coils creates an
imbalance which the internal circuitry senses as
a signal of finite amplitude and definite phase
angle with respect to a reference signal supplied
by the oscillator.
In our metal detector circuit two variable
capacitors and loop are used to generate
oscillation in the circuit.
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pRINCIPLE OF OPERATION
6. • Increasing the value of the variable
capacitor will lower the oscillator’s
frequency and decrease the value with
increase the frequency.
• Here in our metal detector circuit
transistor is used as a colpitts oscillator.
• If we increase L1’s inductance it will cause
the decrease in frequency and if we
decrease this L1’s inductance it will cause
the increase in frequency.
6
11. 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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12. The basic way the beat frequency oscillator
(BFO) works, when a detector coil is above
some metal, it will change the frequency in
the detector oscillator, which has the detector
coil in the frequency dependent circuit. This
relative simple metal detector is not a real
BFO, but it is the closest group of detectors.
When the metal is near the detector coil the
signal is send to a timer pin. Internally the
calculation is made, and showed on the LED
and some different sounds are made.
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“BFO” DETCTOR DESIGN
14. 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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15. Airport and Building Security
Metal detectors are used for airport and
building security to determine whether guns,
knives, or other weapons are being transported
onto aircraft or into public buildings.
APPLICATION
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16. In Civil Engineering, metal detector are used to
locate rebar (strengthen steel used as rod in
concrete) .Rebar detectors are less
sophisticated. Detectors can only locate
metallic objects below the surface.
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17. 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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18. Metal detectors are also used in the construction
industry to locate steel reinforcement bars
embedded in concrete, and to pinpoint metal pipes
and wires in floors and walls. This is useful in
avoiding unnecessary damage when replacing
plumbing or wiring in a building or house.
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19. 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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20. • 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. 20
