I decided to assemble a metal detector called Butterfly, which is so popular among novice radio amateurs.This is a metal detector on beats and is nicknamed a butterfly because of the presence of two coils that look like a butterfly.In this article I will tell you how to build, configure and test it.
The metal detector is made on two generators on two transistors, the frequencies of which should almost coincide.This is almost the difference in frequencies that we should hear in the dynamics.If the frequency of one generator is 300 kHz and the other is 305 kHz, then we will hear a difference of 5 kHz in the dynamics.I wound the coils on a frame with a diameter of 9 cm with a wire of 0.14 mm and contain turns of 30 + 10.Transistors can be used such as BC548, etc.
Check first the operation of one generator and then the other.If there is no frequency meter, take the frequency of the generator to the radio receiver on long waves.I got the frequency of one generator somewhere 276 kHz and the other 277 kHz, the difference is 1 kHz, so I will hear it in the speaker.If the frequency of one generator is more or less by tens of kHz from another generator, then wind-wind the coils at the coil, which contains 30 turns, otherwise you will not hear anything.
But here’s the bad luck.If you assemble a metal detector according to the scheme from the Internet and set it up correctly, you will hear a barely audible sound in the speaker, the sound will be heard well in the headphones, but not in the speaker.At least it didn’t work out for me, I changed different speakers with different resistances.
In order for the metal detector to work loudly, it is necessary to assemble a simple low-frequency amplifier on a chip, I chose the LM386.I didn’t connect the input anywhere, I soldered a 3 cm long wire to this output.
Now the work is fully checked.Position the coils approximately as shown in the photo.You can leave the sound mode and adjust it so that there will be maximum sensitivity to metal.But you can adjust it without sound, while the sensitivity will be lower.For ten rubles, the chuyka is about 7-8 cm, I did not adjust it further.
This metal detector can be classified as experimental.The main disadvantage is the departure of the frequency and therefore it will sometimes have to be adjusted, this is if in the maximum sensitivity mode.
