How to Make a Metal Detector?
This application is a simple metal detector application. It has been made and tested using the BC547 transistor and a small number of electronic elements.
This circuit basically works according to the working principles of the FM transmitter circuit. The resistor and capacitor connected to the base circuit of the transistor create a voltage fluctuation. This ripple changes the frequency of the LC circuit in the collector line of the transistor. The circuit is a voltage-controlled oscillator circuit.
The capacitor after the LC circuit and the 10K resistor separate and filter the sound frequency that the ear can hear. And as a result, this filtered signal is transmitted to the buzzer.
The coil wire used in the circuit is taken from an old transformer. It is an insulated copper wire with a thickness of 0.5 mm and a length of 1.5 meters.
We made 8 turns of winding with the help of a 6 cm diameter glass. That is, the diameter of the coil is 6 cm. We measured this coil with an inductance meter and found the Henri value of 6.3 micro. Together with the 1nF capacitor, it forms the LC circuit and the center frequency is calculated as 2 MHz. Thanks to the oscillation occurring on the base side of the BC547 transistor, shifts occur at this 2 MHz frequency. We transferred these frequency shifts to the audio output with the RC filter.
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