How to make a metal detector that distinguishes gold

From here is the beginning of any metal detector device. If you have mastered this device, know that you, God willing, are on the right path in learning for better devices.

It consists of the transmitter, which in turn consists of two transistors for transmission, where the first transistor with the first file sends an electromagnetic signal with the same value as the signal that the second transistor sends with the second file, and here we control the signal through a variable capacitor or two variable capacitors on the first file or on both the first and second files, This method consists of a transistor number (2), a capacitor 104 number (8), a capacitor of 220 microns, and a resistance of 10 kOhm number (4). Here, two coils are connected on the two transistors in the transmitter circuit, and they are united by the third transistor, which is called the synthesizer, to send the unified signal to the amplification Here, we control the signal by means of a variable capacitor or two variable capacitors on the first coil or on both the first and second coils.

The receiver: The receiver here consists of three consecutive transistors with several resistors and capacitors. It is a simple way to amplify the signal with three transistors. We should not forget here to mention that this simple device is a metal detector of the type bfo.

Device details:

This device consists of transistor number (2) for transmission, where transistor number (1) with file number (1) sends an electromagnetic signal with the same value as the signal sent by transistor number (2) with file number (2), and here we control the signal through a variable capacitor Or two variable capacitors on the first coil or on both coils No. (1) and No. (2), and this method consists of a transistor number (2), a capacitor 104 number (8), a capacitor of 220 microns, and a resistance of 10 kilo ohms number (4), and here the radio is connected to one end The two files to obtain the total frequency and the other two ends of the other file are connected to a variable capacitor to tune the signal.

It is a device consisting of a simple transmitter of 2 npn transistors, two capacitors for each transistor, each of 100 nanometers, with four resistors of 10 kOhm.

Each transistor oscillates when the circuit is connected to electrical power, and when there is a file on each transistor, it produces two similar frequencies and the same value, provided that two coils of equal diameter and number of turns are placed, and when the metal approaches any file, the frequency changes.

When the frequency of one of the files changes, there becomes a difference between the two frequencies with a certain value that does not exceed 7 kilohertz in most cases, which is an audio value or a frequency within the audible audio frequency, but it cannot be heard before going through the stages of amplifying this audio frequency.

It goes through the first stage of amplification, which is the stage of mixing the two frequencies together and showing the difference with the amplification. This is done by means of a third transistor, and this stage ends.

The reception stage: It consists of 3 npn transistors, through which the resulting audio frequency is amplified to the stage of reaching the

speakers, where the sound appears very clearly.