metal detector
TRANSCRIPT
METAL DETECTOR
Submitted By Vineesh A. V.Vimiya Varkey Guided BYViji M. C. M .̂ K. Gnanasheela
Ms^Sumol N. C.Ms. Seena George
ABSTRACT
In security aspects, metal detector isan essential equipment. But, the metal
detector, which is available in the market today, is very costly. Hence this stands as a
problem for hobbyists and for small applications. Hence we have taken an endeavor to bring
out a metal detector of minimum cost.
CONTENTS
□ INTRODUCTION
□ BLOCK DIAGRAM
□ CIRCUIT DIAGRAM
□ CIRCUI DESCRIPTION AND WORKING
□ PCB LAYOUT
□ COMPONENT LAYOUT
□ COST ESTIMATION
□ CONCLUSION
□ REFERENCES
□ DATASHEETS
1. INTRODUCTION
In security aspects, metal detector isan essential equipment.
But, the metal detector, which is available in the market today, is very
costly. Hence this stands as a problem for hobbyists and for small
applications. Hence we have taken an endeavor to : bring out a metal
detector of minimum cost .
The salient features of our project is that the equipment isi , ■ '
compact, simple in design and can be used practically anywhere needs. The
metal detector produces an audible alarm signal when a metall ic part icle
comes
near to the sensor. A visible blinking LED is also there to indicate the
presence of metal .
3
Aivlri,..ir- Ii: iv COMPARATOR ------►
,-----[>.
BUZZER
U
SENSINGCURRENTASTABEE.TRANSFORMERBOOSTERMULTIVIBRATOR
I-MONO Si . ABLE
MULTIVIBRATOR
5 V
detection transformer
LM555
5 V
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B D 1 3 9
2 .
1 K
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o
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0
THR
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JK
5 V
0 . 1 M F
n
5 V
ASTABLE
3
L M 3 2 4
5 V
2 K 2 1 0 0 K 1 0 0 K
5 V
70MF
5 V
I22MF
O
T R >L M 5 5 5 0
D/ST H R Q
LED* 1 0 K
B C 5 4 7 I
>
5 V
NON INV. AMPLIFIER COMPARATOR MONOSTABLE
POWER SU PPLY
4. CIRCUIT DESCRIPTION AND WORKING
The circuit of metal detector is shown in Fig. 1. An astable multi-
vibrator is wired around 1C 555. The free running frequency is selected
as 1.2 KHz.
■ _________________________________
o a: 7 _______1 K
' ' , , / _ 3 T H f i 2 t
*- 1X1 i 0 I M F
In astable operation, the tr igger terminal and the threshold
terminal are connected so that a self-tr igger is formed, operating as a
multivibrator. When the t imer output is high, i ts internal discharging Tr.
turns off and the VC1 increases by exponential function with the t ime
constant (RA+RB)*C.
When the VC1. or the threshold voltage, reaches 2Vce/3.
the comparator output on the tr igger terminal becomes high, resett ing
the F/F and causing the t imer output to become low. This in turn turns
on the discharging Tr. and the C1 discharges through the discharging
channel formed by RB and the discharging 'TV. When the VCI falls
below Vcc/3. the comparator
14
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_______
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output on the tr igger terminal becomes high and the t imer output becomes
high asain. The discharging Tr. turns off and the VC 1 rises aaain.
RESET • ~1
16
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' P. K
THPE:. '>
PL
-----V -OUT
GUI' - 1
—
O.'-NT 5
=k ''-'1
- _ 1' L'
18
ASTABLE OPERATION
This frequency is given to the primary of the detecting
transformer through a transistor. So due to the pulsating current How. a
varying magnetic field will formed in me transformer. A voltage will
normally induce in the secondary coil due to the mutual induction. But the
transformer has no core (air core) and so the magnitude of this induced
emf is very low.
detecting trans former
TO AMPLIFIER K\—-•—\ (■ *.<SV
i >O C J
i BD139
I 2
1K
When a ferri te substance conies near to the winding of the
transformer, an effect of core is produced and the induced emf will be
much grater than former. This voltage is amplified with the help of a
non inverting amplifier build with opamp L.M324.
v,—....
NON INVERT ING AMPLIFIER
The amplified signal is given to the input of a voltage
comparator. The reference voltage is set to a value below the magnitude
of induced emf without any core. So. when the ferri te body is near to the
transformer, the input of comparator is more then thai of reference pin.
Then the output of the comparator goes low.
>
1 O K
COMPARATOR
20
This low pulse is given to the tr iggering input of
monostable multi-vibrator build around 555. The t ime is selected to 2.5
seconds and so the output will high for 2.5 seconds. The transistor
BC547 starts conducting and the buzzer beeps to indicate the presence
of metal . Also the LED turned off for this t ime.
rROiVT COMPARATOR '»
r r • r Tt><
' TP 10
THPEv- *
x -oui
PI
'>N[> -
1 -
[17
MO NOSTA B1 .If . OPERATION
In this mode, the t imer generates a fixed pulse whenever
the tr igger voltage falls below Vcc/3. When the tr igger pulse voltage
applied to the #2 pin falls below Vcc/3 while the t imer output is low;
the t imer 's internal f l ip-flop turns the discharging Tr. off and causes the
t imer output to become high by charging the external capacitor C I and
sett ing the fl ip-flop output at the same time.
The voltage across the external capacitor C L VC 1
increases exponentially with the t ime constant t= :RA*C and reaches
2Vcc/3 at td=l. 1 RA*C. Hence, capacitor C1 is charged through resistor
RA. The greater the t ime constant RAC. the longer i t takes for the VC1
to reach 2Vcc/3. In other words, the t ime constant RAC controls the
output pulse width. When the applied voltage to the capacitor C I
reaches 2Vcc/3, the comparator on the tr igger terminal resets the fl ip-
flop, turning the dischi ir t i i im 1 r . on. At t ins t ime, C I begins to
discharge and the t imer output converts to low. In this way. the t imer
operating in monostable repeats the above process.
The output of monostable is given to base of transistor
BC547 and a buzzer is connected to the colector. So when the
monostable Iriggeres, the transistor will conduct and hence the buzzer
will be on and i t produce a tone to indicate the presence of metal .
After the t ime over, the device will be read) ' for next detection.
5. WINDING DETAILS OF DETECTING
TRANSFORMER
The detecting trams former has a 1:1 winding (the primary
and secondary has the same number of turns). The primary is wound
over a 1cm diameter plastic former with 35 SWG enamaled copper wire.
The primary winding has 210 turns and is wound very closely. An
insulating coating is applied over the primary for isolation. Then the
secondary is wounded over the primary with 40 SWG copper wire and
has also 210 turns. The whole assemly is covered with a well insulator
and apply warnish to allow the winding to set . The leads are taken from
the primary and the secondary.
6. IMLB LAYOUT
7. COMPONENT LAYOUT
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8. COST ESTIMATION
COMPONENTS QTY RATE COSTLM324 1 14.00 14.00LM555 2 10.00 20.00BD139 1 3.00 3.00BUZZER 1 40.00 40.00DETECTING TRANSFORMER 1 300.00 300.003mm LED 2 . LOO 2.001/4W RESISTOR 10 0.25 2.5047K PRESET 5.00 10.00BC547 2 2.50 5.0012-0-12/1A TRANSFORMER 1 100.00 100.001N4007 2 1.00 2.004700MFD/30V CAPACITOR 1 25.00 25.0010MFD/25V CAPACITOR 4 2.50 10.000.1 MFD DISC CAPACITOR 5 1.00 5.0014PIN IC BASE 1 2.00 2.008P1N IC BASE 2 1.00 2.00LM7805 1 10.00 10.00PCB 1 150.00 150.00 •W I R E l O M i
r5.00 50.00
HANDLE 75.00 75.00SOLDERING IRON (25W) 1 200.00 200.00SOLDER & FLUX 1 50.00 50.00EXTRA 350.00TOTAL 1427.50
9. CONCLUSION
This project has been developed considering the need for
" ' intell igent" low cost and longer last ing lamp. With this purpose in
mind, a study has been conducted to understand about the electronic
components available in the market. The equipment is compact, simple
in design and can be used practically anywhere needs.
10. REFERENCE
□ OP-AMPS and Linear Integrated Circuits by Ramakant A .
Gayakwad.
□ vvww.national.com
□ www. fa irchild.c om
□ www.google.com
F=/\IROHII_D
29
LM555/NE555/SA555Single Timer
31
Features• High Current Drive Capability (200mA)• Adjustable Duty Cycle• Temperature Stability of 0.005WC• Timing From p.Sec to Hours• Turn off Time Less Than 2u.Sec
Applications• Precision Timing• Pulse Generation• Time Delay Generation• Sequential Timing
DescriptionThe LM555/NE555/SA555 is a highly stable controller capable of producing
accurate timing pulses. With monostable operation, the time delay is controlled by one external resistor and one capacitor. With astable operation, the frequency and duty cycle are accurately controlled with two external resistors and one capacitor.
WvV
Discharging Tr.
Internal Block Diagram
33
GND 0-------------WW -AVA—0 Vcc
0DischTrigger (2 arge
Output0— m0Threshold
ControlReset 0
Voltage
©2002 Fairchild Semiconductor Corporation
Rev. 1.0.2
LM555/NE555/SA555
Application InformationTable 1 below is the basic operating table of 555 timer:
Table 1. Basic Operating Table
Threshold Voltage (VthMPIN 6)
Trigger Voltage (VtrXPIN 2)
Reset(PIN 4) Output(PIN 3) Discharging Tr. (PIN 7)
Don't care Don't care Low Low ONVth > 2Vcc / 3 Vth > 2Vcc / 3 High ' Low ON
Vcc / 3 < Vth < 2 Vcc / 3 Vcc / 3 < Vth < 2 Vcc / 3 High - -
Vth < Vcc / 3 Vth < Vcc / 3 High High OFFWhen the low signal input is applied to the reset terminal, the timer output remains low regardless of the threshold voltage or-the trigger voltage. Only w hen the high signal is applied to the reset terminal, timer's output changes according to threshold voltage and trigger voltage.When the threshold voltage exceeds 2/3 of the supply voltage while the timer output is high, the timer's internal discharge TV. turns on. lowering the threshold voltage to below |/3 of the supply voltage. During this time, the timer output is.maintained low. Later, if a low signal is applied to the trigger voltage so that it becomes I/3 of the supply voltage, the timer's internal discharge Tr. turns off. increasing the threshold voltage and driving the timer output again at high.
1. Monostable Operation
Figure I illustrates a monostable circuit. In this mode, the timer generates a fixed pulse whenever the nigger voltage falls below Vcc/3. When the trigger pulse voltage applied to the #2 pin falls below Vcc/3 while the timer output is low. the timer's internal flip-flop turns the discharging Tr. off and causes the timer output to become high by charging the external capacitor CI and setting the flip-flop output at the same time.The voltage across the external capacitor C1. Vci increases exponentially with the time constant 1=Ra*C and reaches 2Vce/3at ld=l. I Ra*C. Hence, capacitor CI is charged through resistor Ra. The greater the time constant RaC. the longer it lakesfor the Vci to reach 2Vcc/3. In other words, the lime constant RaC controls the output pulse w idth.When the applied voltage lo the capacitor C1 reaches 2Vcc/3. the comparator on the trigger terminal resets the Hip-flop.turning the discharging Tr. on. Al this time. CI begins lo discharge and the timer output converts to low.In this way. the timer operating in monostable repeals the above process, figure 2 shows the time constant relationship basedon Ra and C. figure 3 shows the general waveforms during monostable operation.It must be noted that, for normal operation, the trigger pulse voltage needs to maintain a minimum of Vcc/3 before the timer output turns low. That is. although the output remains unallected even if a different nigger pulse is applied while the output is high, it ma\ he affected and the waveform not operate properly if the trigger pulse voltage al the end of the output pulse remains al below Vcc/3. I'igure -I shows such timer oulpul abnormality.
I\7iliv. fllus/div
Figure 1. (Vlonoalable Circuit
lY«iv.*An*/Jiv
LU 'J. II.U. K, I M.„\ ( I D.IM.il-. \ n- M
Figure 3. Waveforms of Monostable Operation
Figure 2. Resistance and Capacitance vs. Time delay(td)
LM555/NE555/SA555
K^'Alkll UL-lkQ, ('l=II.OIul'°. \'n-5\
Figure 4. Waveforms of Monostable Operation
(abnormal) 2. Astable Operation
Figure 5. Astable Circuit Figure 6. Capacitance and Resistance vs. Frequency
wjt LM124kT#@ LM224 - LM324
LOW POWER QUAD OPERATIONAL AMPLIFIERS
■ WIDE GAIN BANDWIDTH : 1.3MHz
■ INPUT COMMON-MODE VOLTAGE RANGE INCLUDES GROUND
■ LARGE VOLTAGE GAIN : 100dB
9 VERY LOW SUPPLY CURRENT/AMPLI : 375|iA
■ LOW INPUT BIAS CURRENT : 20nA
■ LOW INPUT OFFSET VOLTAGE : 5mV max. (for more accurate applications, use the equiv-alent parts LM124A-LM224A-LM324A which feature 3mV max.)
■ LOW INPUT OFFSET CURRENT : 2nA
■ WIDE POWER SUPPLY RANGE : SINGLE SUPPLY : +3V TO +30V
■ DUAL SUPPLIES : ±1.5V TO ±15V
DESCRIPTION
These circuits consist of four independent, high
gain, internally frequency compensated operation-
al amplifiers. They operate from a single power
supply over a wide range of voltages. Operation
from split power supplies is also possible and the
low power supply current drain is
independent of the magnitude of the
power supply voltage.D
S014
(Plastic Micropackage)
PTSSOP14
(Thin Shrink Small Outline Package)
PIN CONNECTIONS (top view)
Output 1 1 CInverting Inpul 1 2
[]
Non-inverting Input 1 3
vfcc* 'I CNon-inverting Input 2 5
£ \t
Inverting Input 2 6 L~
NDIP14
(Plastic Package)
3 14 OwipuM
] 13 Inverting Inpul -1
*■ ] 12 Non-inverting
Inpul 4
] n Vcc
l 3 10 Non-irivtrting
Input 3
"2 1 Inverting Input
Part NumberTemperature RangePackage
NDPLM124-55X, + 125X•••LM224-40°C, +105X•••LM324OX, + 70X••mExample : LM224N
ORDER CODE
N = Dual in Line Package (DIP)D = Small Outline Package (SO) - also available in Tape & Reei (DT) P = Thin Shrink Small Outline Package (TSSOP) - only available in Tape &Reel (PT)
December 2001
1/13
LM124-LM224-LM324
SCHEMATIC DIAGRAM (1/4 LM124)
LJ
!
LM124-LM224-LM324
T :6MAlOOt'A
LM124-LM224-LM324
05 ./ V
[ 0 6
LM124-LM224-LM324
Inverting .input
Non-inverting ; ; input .
777,
•-- ^Q2 Q3
Q4j- •
777,
•
27?• - |Q11
Q7
Output
LM124-LM224-LM324
X
Q8 |" |Q9
557 ~777
foiO * | Q12
' 50MA
777, 777, ^777, 777, 777, GND
LM124-LM224-LM324
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter LM124 LM224 LM324 UnitVcc Supply voltage ±16 or 32 VVi Input Voltage -0.3 to +32 V
Vid Differential Input Voltage 1' + 32 V
PlotPower Dissipation N SuffixD Suffix
500 500 400 500 400 mW mW
Output Short-circuit Duration z) Infinite'in Input Current 3' 50 50 50 mA
^oper Opearting Free-air Temperature Range -55 to +125
-40 to +105
0 to +70 °C
Tstg Storage Temperature Range -65 to +150 XEither or both input voltages must not exceed the magnitude of
Vcc* or Vcc".
Short-circuits from the output lo VCC can cause excessive healing if VgC > 15V. The maximum output current is approximately 40mA independentThis input current only exists when the voltage at any of the input leads is driven negative. It is due to the collector-base junction of the input PNP transistor becoming forward biased and thereby acting as input diodes clamps. In addition to this diode action, there is also NPN parasitic action on the IC chip, this transistor action can cause the output voltages of the Op-amps to go lo the Vcc voltage level (or to ground for a large overdrive) for the time duration than an inpul is driven negative.This is not destructive and normal output will set up again for input voltage higher than -0.3V.
dnuii-LiiLuu^ iFuui me uuipui iu v^*^ lchi LdUbe excessive neduny u vpc > ov. i ne maximum uuipui currer of the magnitude of Vcc. Destructive dissipation can result from simultaneous short-circuit on all amplifiers.
LM124-LM224-LM324
2/13 L1I
LM124-LM224-LM324
TYPICAL SINGLE - SUPPLY APPLICATIONS
LM124-LM224-LM324
HIGH INPUT Z ADJUSTABLE GAIN DC INSTRUMENTATION AMPLIFIER
DC SUMMING AMPLIFIERe - 100k______________' . :LM124eo - • oe2 100k i Io f ^ • i- LIe3 100ko—f |---- r^r100ke4 100k
o i re0 = e, +e2 -e, -e4 Where (e, te?) > (e3 *e4) to keep e0 > Ov
LOW DRIFT PEAK DETECTOR
10k(As shown Av = 101)1 1/4 ! LM124eo +5V- 1 ]| RlR2 1M> /■y-■ ►e, (rnV)
NON-INVERTING DC GAIN
LM124-LM224-LM324
Rl 100k
t? J 1/4iLM124
R3 100k
R4 100k
R2 2k
I T o R5 100k ■ 1/4 <V. .LM124
1/4:|_M124
R6 100k
R7 100k• !!
if Rl - R5 and R3 - R4 = R6
= R7
e0 =
' ' •£(e2 -e,) - ■
1As shown e0 = 101
(e2-.en).
e ' ° ■ ♦
i.N W «a,.uin t
-<\ ^J< K _____
1M"___________ Inpul cunenl
' pDlyt.'fittM'HiniK oi |>nlyt?Ehyleritt
LM124-LM224-LM324
8/13
MOTOROLASEMICONDUCTOR TECHNICAL DATA
Order this document by BC546/D
Amplifier TransistorsNPN Silicon
EMITTER
BC546, BBC547, A, B, CBC548, A, B, C
CASE 29-04, STYLE 17 TO-92 (TO-226AA)
BAS
RatingSymbolBC 546BC 547BC 548UnitCollector-Emitter
VoltagevCEO654530VdcCollector- Base VoltagevCBO805030VdcEmitter-Base
VoltagevEBO6.0VdcCollector Current — Continuousic100mAdcTotal Device Dissipation @
T/\ = 25=C Derate above 25°Cpd625 5.0mW mW/XTotal Device Dissipation @ Jq = 25~C
Derate above 25°CPd1.5 12Watt mW/cCOperating and Storage Junction Temperature RangeTj. Tstg-
55 to +150XTHERMAL CHARACTERISTICSCharacteristicSymbolMaxU
nitThermal Resistance, Junction to AmbientRHJA200°c/wThermal Resistance,
Junction to CaseR0JC83.3cc/w
MAXIMUM RATINGS
REV 1
—------------------------------------------— (M) MOTOROLA
© Motorola. Inc. 1996
CharacteristicSymbolMinTypMaxUnitOFF CHARACTERISTICSCollector-Emitter Breakdown VoltageBC546v(BR)CEO65——V(IC = 1.0 mA, Ib = 0)BC54745——BC54830——Collector-Base Breakdown VoltageBC546v(BR)CBO80——V(IC = lOOuAdc)BC54750
——BC54830——Emitter-Base Breakdown VoltageBC546v(BR)EBO6.0——V(lE = 10 uA, IC = 0)BC5476.0——BC5486.0——Collector Cutoff Current'CES(VCE = 70V,VBE = 0)BC546—0.215nA(VCE = 50V. VBE = 0)BC547—0.215(VCE = 35 V, VBE = 0)BC548—0.215(VCE = 30 V,
TA = 125°C)BC546/547/548——4.0uA
ELECTRICAL CHARACTERISTICS (TA = 25°C unless otherwise noted)
F=/\IROHIL-D
SEMICONDUCTOR TU
BD135/137/139
F=/\IROHIL-D
Medium Power Linear and Switching Applications• Complement to BD136, BD138 and BD140 respectively
F=/\IROHIL-D
1 TO-126
1. Emitter 2.Collector 3.Base
NPN Epitaxial Silicon Transistor
Absolute Maximum Ratings TC=25°C unless otherwise noted
Symbol Parameter Value UnitsVCBO Collector-Base Voltage : BD135 45 V
BD137 60 V
BD139 80 V
VfJEO Collector-Emitter Voltage BD135 45 VBD137 60 V
BD139 80 V
VEBO Emitter-Base Voltage 5 Vlc Collector Current (DC) 1.5 A'CP Collector Current (Pulse) 3.0 AlB Base Current 0.5 APc Collector Dissipation (TC=25°C) 12.5 WPc Collector Dissipation (Ta=25°C) 1.25 wTj Junction Temperature 150 cTSTG Storage Temperature - 55 - 150 ■ =c
Electrical Characteristics Tc=25°C unless otherwise noted
Symbol Parameter Test Condition Min. Typ. Max. UnitsVCE0(sus) Collector-Emitter Sustaining Voltage :
BD135 : BD137 : BD139
lc = 30mA, lB = 0 45 60 80
V V V
'CBO Collector Cut-off Current VCB = 30V, lE = 0 0.1 uA
'EBO Emitter Cut-off Current VEB = 5V. Ic = 0 10 pA
hFE1 nFE2 hFE3
DC Current Gain : ALL DEVICE : ALL DEVICE : BD135: BD137, BD139
VCE = 2V, lc = 5mA VCE = 2V, lc = 0.5A VCE = 2V, lc = 150mA
2525 40
40
250 160
VCE(sat) Collector-Emitter Saturation Voltage lc = 500mA, lB = 50mA 0.5 V
VBE(on) Base-Emitter ON Voltage VCE = 2V, lc = 0.5A 1 V
hFE Classification
Classification'61016nFE340 - 10063 - 160100 - 250
t-2000 Fawchild Semiconductor International
Rev. A, Feb'uaiy 2000
(—/-VI t-t l_» Ml 11_ L/
KA78XX/KA78XXA3 -Terminal 1 A Positive Voltage Regulator
(—/-VI t-t l_» Ml 11_ L/
FeaturesOutput Current up to IAOutput Voltages of 5. 6. 8. 9. 10. 12. 15. 18. 24 V Thermal Overload Protection Short Circuit ProtectionOutput Transistor Sale Operating Area Protection
Description
The KA78XX/KA78XXA series of tin 'ce-tcrminul positive regulator are available in the TO-220/D-PAK package and with several fixed output voltages, making them useful in a wide range of applications. Each type employs internal current limiting, thermal shut down and safe operating area protection, making it essentially indestructible. If adequate heal sinking is provided. the\ can deliver over IA output cunenl. Although designed primarily as fixed voltage regulators, these devices can be used with external components lo obtain adjustable \oltages and currents.
(—/-VI t-t l_» Ml 11_ L/
TO-220
D-PAK
1
1. Input 2. GND 3.
Internal Block Digram
(—/-VI t-t l_» Ml 11_ L/
INPUT SEHlbSPASSE l.EMKN T
(—/-VI t-t l_» Ml 11_ L/
©2001 Fairchild Semiconductor Corporation
GND
Rev. 1.0.0
