Hello everyone.In this article I will tell you how to make a simple metal detector on a chip and a radio receiver, how it works and setup.
The metal detector consists of two parts:CD40106 chips and a radio receiver for long or medium waves.The chip consists of six Schmitt triggers, on one of which, these are pins 2 and 1, a sine generator with a frequency of several hundred kilohertz is assembled.The generator coil emits a signal, let’s say at a frequency of 300 kHz.We install a radio receiver tuned to a frequency of 301 kHz next to the coil.We will hear the difference between the two frequencies of 1 kHz in the receiver.But if you bring the metal to the coil, the sound will be distorted due to a change in frequency.This distortion of the sound we will hear in the receiver and this is called beating.But the receiver should be with single-band modulation, only then there will be a whistle sound and other sounds, but you can also use a regular receiver, then we will hear changes in the carrier sound, while the sensitivity of the metal detector will be slightly less.
The coil is wound on a frame with a diameter of 9 cm with a wire of 0.14 mm and contains 40 turns.The coils must be well bonded, otherwise the frequency of the generator will move away from any change in the arrangement of the coils.
The signal on the coil can be checked with an oscilloscope.We see a slightly distorted sinusoid with a frequency of 323 kHz with a good scope, this is when powered by 3.7 Volts.
We have a radio receiver nearby and turn on the generator.We select a single-band reception on the receiver and bring the metal to the coil and hear the sound change.You can set up the receiver so that a squeak will be heard and it will change from metal.You can adjust it so that the drum roll will be heard and change from the metal next to the coil.
