Metal Detectors are used in various places to detect metals that are dangerous, such as airports, shopping malls, cinemas, etc. We have previously made a very simple Metal detector without a microcontroller; now we incorporate an Arduino to make the Metal Detector. The coil and capacitor that will be used in this project will be responsible for detecting metals. We have built this metal detector project using an Arduino Nano. All electronics lovers should find this project very interesting. A very loud buzzer will start beeping the moment the metal detector detects it.

Arduino (any) Coil 10nF capacitor Buzzer The 1k resistor 330-ohm resistor LED 1N4148 diode Breadboard or PCB Connecting jumper wire

9v Battery

Any time there is current passing through the coil, a magnetic field is generated around it. Magnetic fields generate electric fields when they are changed. The Faraday Law states that due to the Electric field, a voltage is generated across the coil that opposes the change in magnetic field. The result is an increase in current, causing the voltage to oppose the change in magnetic field. The Inductance value is measured in Henrys using the following formula L = (μο * N2 * A) / l Were, L- Inductance in Henries μο- Permeability, its 4π*10-7 for Air N- Number of turns A- Inner Core Area (πr2) in m2 l- Length of the Coil in meters Any metal that comes into contact with the coil causes the coil to change its inductance. The type of metal determines the change in inductance. Non- magnetic metals have a smaller magnetic moment, while iron has a greater magnetic moment.

Inductance value changes drastically depending on the core of the coil. As you can see in the figure below, the inductors have an air-cored core, so there is no solid core in these inductors. This is basically just a lot of coils lying around. No matter what the inductor generates, its magnetic field flows in nothing or air. Inductors with low inductances are used in these applications. When the values of a few microHenry are required, these inductors are used. If your value is greater than a few milliHenry, then this is not the right choice. An inductor with ferrite core can be seen in the following image. Despite the large inductance values of these Ferrite Core inductors. In this case, the coil wound within the inductor is air cored, so when a metal object is brought to the coil it serves as a core.

Inductance of the coil changes or increases greatly when this metal acts as a core. By adding a metal piece to the LC circuit, a significant amount of inductance is introduced, altering the overall impedance or reactants of the circuit. In this Arduino Metal Detector Project, we need to figure out how to detect metals by measuring the inductance of the coil. Thus, we did this by using the LR circuits (Resistor-Inductor Circuits) that we described previously. A coil with about 20 turns has been used here with a winding of around 10 cm in diameter. A tape roll has been used to wind up wire on, and the wire has been wound around it. Metal Detectors are used to detect land mines, detect weapons such as knives and guns at airport security checkpoints, conduct geophysical prospecting, archaeology and treasure hunting. The whole Metal Detector Project has been controlled by an Arduino Nano. Indicators such as LEDs and buzzers are used for metal detection. For the detection of metals, coils and capacitors are used. Reduced voltage is also achieved by using a signal

diode. Additionally, a resistor is used to limit the current flowing through the Arduino pin.

The metal detector on this Arduino is a little challenging to use. The high pass filter of the LR is fed the block wave or pulse generated by the Arduino. Therefore, each transition will be marked by short spikes caused by the coil. Having a coil with a high inductance result in pulses with a shorter pulse length. We can measure the inductance of a coil with the help of these shock pulses. Due to the very short duration of the spikes (approx. 0.5 microseconds), it is very difficult to successfully measure inductance with that. The capacitor we used instead of this, is charged by rising impulses or spikes. The capacitor was charged with a few pulses so that A5 on the Arduino can read its voltage. This capacitor's voltage is read using ADC by Arduino. Cap Pin was made the output pin as soon as the voltage was read and set to low, quickly discharging the capacitor. About 200 microseconds are required to complete this process. The measurement was repeated and the resulting average was taken to produce the best results. Using that method, we can calculate Coil's approximate inductance. Using the result, we transfer the data to LED and buzzers to see whether metal is present. The complete code that follows this article will help you understand how the program works. At the end of this article, you will find the full Arduino code. We will use two Arduino pins in this project, one to generate block waves that will be fed into the coil, and the second to read voltage from the capacitor. We have also connected LEDs and buzzers to two other Arduino pins besides these two.