Metal detector circuit using arduino is an electronics device which is used to detect metallic abject like metal coins, iron ore, aluminum or silver and gold etc. This device can be used in a place where metal detection is mandatory like hospital, airport etc. because it can be harmful.
We had already posted a simple metal detector circuit using transistors and RC components. The working principal is same excepting processing circuit. The metal detector circuit posted here uses arduino uno board or equivalent. This project can be used to detect buried cable or any metallic object. This device starts to beep whenever it detects any metallic object.
Practical inductors (coils) uses at RF frequencies and above have an inductance rating in henrys and a maximum current rating. Inductor store energy in the surrounding magnetic field and loss (dissipate) energy in their winding resistance.
Circuit Description of metal detector using arduino:
This metal detector circuit is shown in figure 1. This metal detector circuit is designed using a arduino uno board or equivalent, search coil, buzzer, 1N4148 diode and few other electronic components like resistor capacitor etc.
Construction of search coil: A search coil comparison of 26 turns of wire, centre-tapped. 24 SWG to 36 SWG gauge of wire can be used. Here we had constructed search coil by winding the wire over 10 cm diameter watch box as shown in figure 2.
Instead of ferrite core coil we had use air core coil because when search coil detects any metal, that metal piece act as core of search coil. Thus, the overall inductor increases. Inductance of inductor is depending upon inner core of coil.
Formula for calculating inductance of inductor is:
Where, = absolute permeability and its value is for free space or air.
N = Number of turns
A = Inner core are in m2
l = length of wire in meter
Here we had used parallel LC circuit. The parallel LC circuit is sometimes called tank circuit. Energy is stored in each reactive element (L and C), first in one and then released to the other. The transfer of energy between the two elements will occur at a natural rate equal to the resonant frequency and is sinusoidal in form. The diode D1 is basically used as resistor because it reduces the voltage. Resistor R1 is used as current limiting resistor and thus limit the current to arduino pin.
For audio visual effect we had used a buzzer and a LED. When metal is detected, both buzzer and LED is activated.
LR tank circuit is connected to analog pin A4 and A5 which supply pulse and thus emf is generate. This generated emf is stored in capacitor. The voltage across the capacitor is available at arduino analog pin. Arduino read this voltage by using ADC, process it and produce output.
Software: The software code of Metal detector circuit using arduino is written in arduino programming language and compiled using arduino IDE. You can directly download the software code and use it into your metal detector project.
Components used in Metal Detector using Arduino
R1 = 330 Ω, resistor
R2 = 1 KΩ, resistor
C1 = 10nF, ceramic capacitor
D1 = 1N4148, diode
BUZ1 = Buzzer
LED1 = 5mm any color LED
Arduino UNO Board or equivalent