I present to you a very simple scheme metal detector called "Baby FM".
This device has a very important function, it has the selectivity of metals.
The kid FM determines the type of metal, Color or black, which is reported by a characteristic sound.
That is, on black metal, it beeps with one sound, and in color with another.
Here is the circuit itself
The MD contains a minimum of details, because the microcontroller is used in its circuit, it is very easy to assemble, but its detection depth is not very good, from 3 cm to 10-12 cm, which is basically normal for such a simple device. The device has a button for detuning from the ground.
To build, we need:
1) PIC12F675 or 629 (microcontroller)
2) Quartz 20MHz
Capacitors
3) 15pF-2pcs (ceramic)
4) 100nF-1pcs (ceramic)
5) 10uF (electrolyte)
6) 100nF-2pcs (film) and not any other
7) Speaker
8) Button
470 ohm and 10 kΩ resistors
AMS1117- 3.3 volt voltage regulator
The device is very simple and I decided to assemble it without any printed circuit boards. We take a piece of textolite or thick cardboard
We drill holes for parts. As indicated in the diagram
Once again, 100nF capacitors must necessarily be film, as in the photo. With others, it’s not a fact that it will work.
We put all the details as shown in the diagram, solder them together.
This is how the voltage regulator looks and how it should be connected.
Next, you can proceed to the manufacture of a search coil.
For winding the coil, we take any pan or pot, but anything of a suitable diameter. I shook the pan. The wire is preferably 0.3 mm, but I had 0.4 wound it.
That's what it should be
The coil must be stiff and tight. To do this, wrap it with tape, very tightly.
In order for our device to not respond to interference and not give false positives, the coil must be shielded. We take a simple food foil and wrap it with a coil.
The main thing is that the ends of the foil do not close. We wind the wire at one end of the foil and tightly wrap the entire coil again with tape.
We connect the coil, and connect the wire from the foil to the negative on the board.
Now it remains just to flash the microcontroller and that's it, the firmware is below.
For this metal detector you need to connect the headphones from the player, but I only had a small speaker, so that the sound is heard poorly, it will be heard well with the headphones.
You do not need to configure anything, the circuit is simple and basically always works the first time (I always have it the first time)
Whoever doesn’t have a programmer for firmware microcontroller, please contact help with already flashed or in the comments
HERE VIDEO WORKS
FIRMWARE