The 555 timer is configured in astable mode to generate a continuous oscillating signal. This signal is fed to the search coil.
Resistors (R1, R2, R3):
R1 and R2 form a voltage divider to set the threshold voltage for the LM358 comparator. R3 is connected to the discharge pin (pin 7) of the 555 timer.
Capacitors (C1, C2):
C1 and C2 are timing capacitors for the 555 timer. They determine the frequency of the oscillating signal.
Inductor (Search Coil):
The search coil is connected to the output of the 555 timer and generates a magnetic field. When a metal object comes near the coil, it induces a change in the magnetic field.
Operational Amplifier (LM358):
The LM358 is configured as a comparator. It compares the voltage from the search coil with the threshold voltage set by the voltage divider.
Potentiometer (Variable Resistor):
The potentiometer adjusts the sensitivity of the metal detector by changing the threshold voltage.
Diodes (D1, D2):
D1 protects the 555 timer from reverse voltage. D2 prevents the discharge pin from pulling down the voltage on the threshold pin.
LED:
The LED lights up when a metal object is detected.
Buzzer:
The buzzer produces an audible signal when a metal object is detected
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