Metal Detector

This is my metal detector, detect metal using Mosfet and opamps and pair of coil.

component

1) IRLZ44N

2)Opamp LM324

3)Resistor 10k, 1k , 6.2k

4) Bc557 pnp transistor

5)Bc546 npn transistor

6)100mh inductor

7)171uF capacitor

8)22pf capacitor

9)buzzer

10) copper coil of 38 turns.

11)50k pot

ZVS circuit .Basically it generates sine wave one the both side of the coil. When the metal comes around the coil the frequency of zvs gets effected . Here you can see three sine waves generated by the Zvs oscillator. We will take the right sided sine wave and will multiply with a Schmitt trigger square wave

Schmitt trigger made by op amp is creating square wave . At the place of 50k resistor we will use a 50k potentiometer to adjust the tuning . We will multiply the square wave with the sine wave of the zvs

After multiplying the waves we will cut the useless frequencies by the low pass filter . In that case we will cut down high

frequency which is 1/2 Sine (2 PI t(50.5Khz)) and then we can hear audible sound .

after filtering you can see the resulting signal is just few HZ .

with the help of the schmitt comperator the signal gets inverted and cleaned up.

With the High Pass RC filter the inverted signal gets chopped of .So we can hard a sudden click . because one sudden click has multiple harmonics .

for a sudden click we will use a comparator . the pulse width will remain same regarding the change of the input frequencies.

Fed the signal in to the buzzer and enjoy your circuit

https://youtube.com/shorts/SnaiSga-t00?si=SqZ5jsqi09lrI0ma