Metal detector from remote control

Anyone can assemble a very simple metal detector with their own hands without understanding electronics at all. With it you can search for metal objects both in the ground and in the wall. The design consists of only three items, which almost everyone probably has lying around in a drawer without use.

Will need

• Unnecessary remote control for any device.
  
• AM/FM radio.
  
• Wire for making coils with a diameter of 0.4-0.2 mm.

Making a metal detector from a remote control and a radio receiver

The first step is to make a coil. Here you need to understand that all sizes and numbers of turns are selected exclusively experimentally, and the example below is not ideal.
Take a 0.35 mm wire and wind a coil with a diameter of 10 cm. The number of turns is 50. To prevent it from unwinding, secure it with electrical tape or nylon ties.

Let's sort out the bullets. We clean the enameled leads and solder them parallel to the infrared LED.


Next, we assemble the remote control. Be sure to put good batteries in it. Turn on the radio and set it to the “AM” range (medium waves).

Press any button on the remote control.

We place the receiver near the remote control, and the coil a little further away.

Repeated sounds should be heard in the receiver, which should disappear when the button is released. By rotating the receiver's tuning wheel, we achieve minimal audibility of these vibrations.
We bring a metal object to the coil at some distance. The sound should be amplified.

That's all. The sensitivity, when adjusted correctly, is quite acceptable: it is enough to detect steel dowels or reinforcement in the wall.
This metal detector operates on the principle of parasitic harmonics. As soon as the metal is brought close to the coil, its inductance changes, and therefore the frequency of the signal and all harmonics. What the radio receiver actually picks up.
To increase sensitivity, you need to experiment with the coil by changing its size and number of turns. And with a radio receiver, changing bands and making precise searches by adjusting.

Watch the video

See the video for an example of work: