Metal Detectors Working, Types & Applications
Metal Detector
Nowadays, the metal detector is used to identify metallic devices such as bombs, guns for security purpose. To avoid any illegal or unauthorized entry of metallic objects, bombs, knives, guns within the luggage bags of the person carrying them in public places like theatres, shopping malls, parks, airports, hotels, railway stations. A security system is developed by using proximity sensor which is named as a metal detector. So, a metal detector is used in many robotic or electronics projects to detect any present metals which are nearby or the existence of hidden items within objects. This article gives an overview of metal detector working principle and applications.
What is Metal Detector?
In the year 1960, the first metal detector was established and was used in industrial applications and mineral prospecting. A metal detector is an electronic device that comprises of an oscillator which generates an AC current that passes via a coil generating an alternating magnetic field. When a part of the metal is nearby to the coil, eddy current will be induced in the metal object & this generates a magnetic field of its own. If an extra coil is used to measure the magnetic field, the magnetic field can be changed and sensed due to the metal object. The metal detectors are used to sense the weapons and also used in the construction industry to identify the steel reinforcing bars in pipes, concrete, wires, pipes buried in walls & floors.
Metal detector types are classified into three types such as BFO (Beat Frequency Oscillation), TR( Transmitter or Receiver) and VLF(Very Low frequency)
How Does a Metal Detector Work?
The metal detector working is, when the electromagnetic field is transmitted from the search coil into the earth. Metals in the electromagnetic field will become strengthened & resend an electromagnetic of their own. The metal detector comprises of a search coil which receives the retransmitted field & alarms the user by generating a response of the metal. Minelab metal detectors are accomplished by discriminating between dissimilar types of targets and can be fixed to ignore unwanted metal objects.
Working of a Metal Detector
Battery
The main purpose of the battery is to provide the power to the detector.
Control Box
The control box comprises of the electronics of the detector. When the transmit signal is generated, the receive signal is processed and transformed into a target response.
Search Coil
The electromagnetic field can be transferred by the search coil of the detector into the ground & receives the electromagnetic field return from a metal object.
Electromagnetic Field Transmission
The transmitted electromagnetic field energizes metal objects to allow them to be sensed.
Target
Here, a target is a metal object that can be sensed by a metal detector. In this, the target is treasure which is sensed and that is a good target.
Undesirable Target
These metal objects are generally attracted to a magnet like nails and also non-ferrous like bottle tops. If the metal detector is fixed to discard unwanted targets, then the response of the target will not be generated for those targets.
Receive Electromagnetic Field
The receive electromagnetic field is produced from energized targets & it is received by the search coil
Response of the Target
When the metal detector detects the metal object, then it generates an audible sound like a beep. Various Minelab detectors also generate a visual display of target information.
Metal Detector Circuit Diagram
The metal detector circuit built with an LC circuit, buzzer and simple proximity sensor. In LC circuit, capacitor and inductor are connected in parallel. When the circuit detects any metal near to it, then the circuit activates the proximity sensor and its glow the LED and makes a buzzer.
Metal Detector Circuit
When this circuit has any resonating frequency from any target which is near to it, then the electric field will be created, which will lead to induce current in the coil and change the S/L in the flow of the S/L through the coil.
The value of the sensor can be changed by using a variable resistor, that is equal to the LC circuit. When the metal is detected, the circuit will have new signal and respond accordingly.When the metal object is sensed by the coil, the sensor’s o/p will be of 1mA. When the coil is close to the target, then the o/p of the sensor will be around 10mA.
When the output pin is high, the resistor R3 will offer a positive voltage to the Q1 transistor to turn ON the LED, which will glow and generate a buzzer sound. Here, resistor R2 is mainly used to restrict the current flow.
A Metal Detector Circuit using IC 555
This circuit uses an IC 555, which is used to detect the magnets and metals. When the magnet is near to the 10mH choke, then the output frequency varies. This circuit can be powered from a power supply, which can give an o/p DC voltage between 6-12 volts. When a metal object is near to the L1 coil, then it generates a change of output oscillation frequency and buzzer sound.
Metal Detector Circuit using 555 IC
Android Application based Metal Detector Robotic Vehicle
The main goal of this project is to design a robotic vehicle which can sense metals near to it on its track, and this robot is controlled by an android application
This project comprises of a metal detector circuit which is interfaced to the control unit, that produces a buzzer sound to the user when a metal object is close to it. A microcontroller is used for the desire operation.
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At the transmitter side, an Android OS based application is used to send instructions to the receiver. The robot vehicle moves right, left, forward and backward. At the end of the receiver, two motors are interfaced to the microcontroller for the vehicle’s movement.
The android phone performs as a remote whereas Bluetooth device at the receiver end is fed to the 8051 microcontroller to drive DC motors through motor driver IC for particular operation. This circuit is placed in the robotic vehicle and the operation of the robot is carried out mechanically if it notices any metal object below, then the robot vehicle senses a metal, it generates a buzzer sound. In the future, this project can be enhanced by fitting a wireless camera to the robot vehicle, so that the robotic vehicle movement can be controlled remotely by the operator by watching it on a screen.
RF Technology based Metal Detector Robotic Vehicle
The main intention of this project is to design a robotic vehicle that can detect metal objects near to its track and this robot vehicle can be controlled by an RF technology using the remote.
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A metal detector circuit is located on the robot’s vehicle. The operation of the robot vehicle is carried out if it detects any metal objects below, then the robotic vehicle detects the metal and generates a buzzer sound to give an alert to the operator of a possible metal object near to its path.
Furthermore, this project can be enhanced by placing a wireless camera on the robot vehicle so that the operator can control the movement of the robot remotely by watching it on a screen.
This is all about metal detector circuit, metal detector working and application of metal detector. Hope this article gives brief information regarding metal detector and its working principles. Furthermore, any queries please share your technical knowledge by commenting in the comment section below.
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