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Metal Detector Circuit
JULY 31, 2017 BY ADMINISTRATOR 25 COMMENTS
Contents [hide]
1 Circuit Diagram
2 Components Required
3 Component Description
4 Metal Detector Circuit Explanation
5 Block Diagram of Metal Detector
6 Working
7 Advantages
8 Disadvantages
9 Applications
10 Related Articles
Metal detector is a very common device that is used for checking persons, luggage or bags in
shopping malls, hotels, cinema halls, etc. to ensure that person is not carrying any metals or
illegal things like guns, bombs etc. Metal Detectors detect the presence of metals.
There are different types of metal detectors like hand held metal detectors, walk through
metal detectors and ground search metal detectors. Metal detectors can be created easily
and the circuit for a basic metal detector is not that complex.
In this project, we have designed a simple DIY type Metal Detector Circuit using very simple
components that can be used in our homes and gardens.
Circuit Diagram
The following image shows the circuit diagram for the metal detector circuit.
Components Required
1 x TDA0161 Proximity Detector IC
2 x 47nF Capacitors (Ceramic Capacitor code 473)
1 x 1 K Resistor (1/4 Watt)
1 x 330 Resistor (1/4 Watt)
1 x 100 Resistor (1/4 Watt)
1 x 5 K Potentiometer
1 x 2N2222A (NPN Transistor)
1 x 5V Buzzer
Coil (copper wire of 26 30 AWG is taken and it is wound in to a coil of diamater 5 6 cm
and 140 150 turns)
Additional Components (for LED)
1 x 220 Resistor (1/4 Watt)
1 x 5mm LED
Component Description
TDA0161 Proximity Detector IC: TDA0161 is a Proximity Detector IC manufactured by
STMicroelectronics. It can be used detect metal objects by detecting the slight changes in the
high frequency Eddy current losses.
The TDA0161 IC acts as an oscillator with the help of externally tuned circuit. The changes in
supply current will determine the output signal i.e. current is high when a metal object is near
and it is low when there is no metal object.
TDA0161 has 8 pins and it comes in Dual in line Package (DIP). The following image shows
the pin diagram of TDA0161 IC.
NOTE: According to STMicroelectronics, TDA0161 Proximity Detector IC is obsolete. If it is
available in the market, go ahead and make this fun project. If it isnt available, try to find a
replacement IC. We will try to update if any similar IC is available. If you find any Proximity
Detector ICs, please mention it in the comments section.
Coil (Inductor): We have taken a 30 AWG Copper wire for this project. It is then wound in to a
coil using a 5.8cm diamater reference. The coil consists of 140 150 turns.
Metal Detector Circuit Explanation
When the LC circuit that is L1 and C1 has got any resonating frequency from any metal
which is near to it, electric field will be created which will lead to induces current in the
coil and changes in the signal flow through the coil.
Variable resistor is used to change the proximity sensor value equal to the LC circuit, it is
better to check the value when there is coil not near to the metal. When the metal is
detected the LC circuit will have changed signal. The changed signal is given to the
proximity detector (TDA 0161), which will detect the change in the signal and react
accordingly. The output of the proximity sensor will be of 1mA when there is no metal
detected and it will be around 10mA when coil is near to the metal
When the output pin is high the resistor R3 will provide positive voltage to transistor Q1.
Q1 will be turned on and led will glow and buzzer will give the buzz. Resistor r2 is used to
limit the current flow.
Block Diagram of Metal Detector
There are three main parts in the metal detector circuit: the LC Circuit, the Proximity Sensor ,
output LED and the Buzzer. The coil and the capacitor C1, which are connected in parallel, will
form the LC circuit.
Proximity sensor(TDA0161), is triggered by this LC cirucit if any metal is detected.The Proximity
sensor will then turn on the led and produces alarm using buzzer.
LC Circuit: LC circuit has inductor and capacitor connected in parallel.This circuit sarts
resonating when there is same frequency material near to it. The LC circuit charges capacitor
and inductor alternatively.When the capacitor is charged fully ,charge is applied to inductor.
Inductor starts charging and when charge across the capacitor is nil, it draws charge from the
inducutor in reverse polarity. Then inductor charge is reduced and again the process
repeats.Note inductor is a magnetic field storage device and capacitor is electric field storage
device.
Proximity Sensor: The proximity sensor can detect the objects with out any physical
interference. The proximity sensor will work same as infrared sensor, proximity also release a
signal, it will not give output unless and until there is no change in the reflected back signal.
If there is a change in signal it will detect and give the output accordingly. There are different
proximity sensors for example to detect plastic material we can use capacitive type proximity
and for metals we should use inductive type.
Working
The LC Circuit, which consists of L1 (coil) and C1, is the main metal detector part of the circuit.
With the help of this LC Circuit, which is also called as Tank Circuit or Tuned Circuit, the
TDA0161 IC acts as an oscillator and oscillates at a particular frequency.
When the LC circuit detects any resonating frequency from any metal which is near to it,
electric field will be created which will lead to induces current in the coil and changes in the
signal flow through the coil.
Variable resistor is used to change the proximity sensor value equal to the LC circuit, it is
better to check the value when the coil is not near any metal object. When the metal is
detected, the LC circuit will have changed signal.
The changed signal is given to the proximity detector (TDA 0161), which will detect the change
in the signal and react accordingly. The output of the proximity sensor will less than 1mA when
there is no metal detected and it will be around 10mA (usually greater than 8mA) when coil is
near to the metal.
When the output pin is high, the resistor R3 will provide positive voltage to transistor Q1. Q1 will
be turned on and LED will glow (not shown in the circuit) and buzzer will be activated.
Advantages
The Proximity Detector IC TDA0161 based Metal Detector Circuit is a very simple and
easy to construct metal detector that can be used to detect small metals in our homes,
offices and gardens.
There is need for any microcontroller as the Proximity Sensor will be sufficient to
implement the project.
Disadvantages
The main disadvantage of this Metal Detector Circuit is the range of detection. The metal
object has to be at a distance of 10mm for the detector to detect it.
Applications
This simple Metal Detector can be used to identify metals like iron, gold, silver etc.
Since it is a simple project, we can use this in our home to scan for nails, metal scraps
etc. which are not easily spotable by naked eye.
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FILED UNDER: ELECTRONICS, FREE PROJECT CIRCUITS, MINI PROJECTS
Comments
majid says
NOVEMBER 21, 2013 AT 2:56 PM
hi,good time
im from iran
i need many circuits gold scan or metal detector power.
tanks
Reply
ash says
DECEMBER 30, 2013 AT 6:51 PM
informative post thanks
Reply
Raphael says
APRIL 29, 2014 AT 6:25 PM
Thanks for the post.
Reply
Jinu CV says
JULY 25, 2014 AT 4:29 PM
Thank you
Reply
Iokesh says
AUGUST 3, 2014 AT 1:43 PM
good
Reply
Onizuka says
SEPTEMBER 5, 2014 AT 2:18 PM
I am confused at the bobbin inductor part !!
I dunno what it is and why its in pf !!?
Please help !!!
Reply
abhishek says
FEBRUARY 5, 2016 AT 2:28 AM
please send the complete details about the components used in circuit with its design
partif possible please upload a video of circuit working
Reply
Thunga c says
SEPTEMBER 10, 2014 AT 3:28 PM
can u please send a video that how to make this project
Reply
veera says
SEPTEMBER 14, 2014 AT 11:33 AM
Can u send me metal detector circuit componetnts list???
Reply
yaseen says
JANUARY 18, 2016 AT 4:23 AM
nyc, very help full
Reply
Akshatha says
FEBRUARY 4, 2016 AT 12:47 PM
Please post video to do This project And Also List Of Components
Reply
abhishek says
FEBRUARY 5, 2016 AT 2:31 AM
please send complete and exact details about components used in circuit with design
part..and video of circuit working
Reply
saape says
MARCH 10, 2016 AT 12:50 PM
I need information regarding component listso could u pls tell me all the components
used in this ckt
Reply
B.Paulchamy says
JUNE 30, 2016 AT 3:27 AM
Give the metal detector circuit with component list
Reply
Anusha says
JULY 2, 2016 AT 4:41 AM
TDA0161-Proximity sensor
Inductor- 680PF
Transistor- 2N3904
R1,R4,R5-1k;R2-330,R3-120.
RV1-10k
Capacitor-0.047uf-(Quantity-2)
Buzzer
Battery
Led
Reply
Nashiwaya Erasmus says
JULY 13, 2016 AT 6:37 AM
are the two capacitors polarised?
Reply
Jibrin says
JULY 8, 2016 AT 11:48 PM
Plc I need the detailed explanation of the construction of this Metal detector!
Reply
tiriri says
JULY 19, 2016 AT 4:30 AM
please I want a brief notes about the functionality of the project and also how to give a
justification of the project
Reply
Mohammad abrar says
AUGUST 16, 2016 AT 11:04 AM
I Need complete details of metal detector
Reply
Arcel says
AUGUST 28, 2016 AT 4:05 PM
Hi how can i make a off delay timer
Reply
Sahana says
SEPTEMBER 29, 2016 AT 5:33 AM
Please give the component list of metal detector circuit
Reply
monica says
OCTOBER 7, 2016 AT 1:09 PM
what is the value of bobbin inductor with proper unit
Reply
Anusha says
JULY 19, 2017 AT 7:52 AM
It is 680PF
Reply
Kshitij Varshney says
NOVEMBER 1, 2016 AT 4:29 AM
Can we simulate this on Proteus or Multisim?
If yes, then after completing the circuit how am i supposed to show the presence of the
metal ?
Reply
Aderito Magno says
JULY 16, 2017 AT 2:18 AM
Hallo thanks for your project and send me all components the process it final thanks
Reply
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