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Simple and reliable metal detector with your own hands
A simple economical metal detector with your hands on one chip

If you have lost the ring, the key, the wrapper... and you know the approximate place of loss, don't despair! You can assemble a metal detector with your own hands or ask a fellow radio amateur to assemble a simple metal detector with his own hands. Below is a diagram of a simple-to-manufacture and years-tested metal detector, which (with certain skills) can be done in one day. The simplicity of the metal detector described is that it is assembled on just one very common Chip K561LA7 (CD4011BE). The setup is also simple and does not require expensive measuring devices. An oscillograph or frequency meter is enough to set up generators. If everything is done without errors and from the correct elements, then these devices will not be needed.

Sensitivity of this metal detector:



metal lid from the can "sees" up to 20 cm, cell phone up to 15 cm, battery "crown" up to 10 cm, 5 rubles coin up to 8 cm .

At this distance, the tone of the generator in the headphones barely changes, at closer distance the tone increases. The larger the metal area, the greater the detection distance. Distinguishes diamagnetics and ferromagnetics.

To make a metal detector, we will need:



Microchip K561LA7 (or K561LE5, analogue CD4011);
Transistor - low-frequency low-frequency, for example - CT315, CT312, CT3102, analogues: VS546, Sun945, 2SC639, 2SC1815, etc.);
Diode - any low-power, for example - k522B, kd105, k106, analogues: in4148, in4001, etc.;
Variable resistor - 3 pieces (1 kom, 5 kOm, 20 kom with switch or switch separately);
Permanent resistor - 5 pieces (22 Om, 4.7 kOm, 1.0 kOm, 10 kOm, 470 kOm);
Ceramic, and even better mica capacitors - 5 pc: 1000 pf -3pc, 22n -2pc, 300pf);
Electrolytic capacitor (100.0 mcff x 16B) - 1pc;
A PEL wire or PEV with a diameter of 0.6-0.8 mm;
Low-key headphones (from the player);
Battery 9B.
Metal detector scheme

The appearance of the metal detector board



In the case of the old pocket receiver (you can use the body from the soap dish, from under the sponge to clean the shoes or in the case from the electric connector box.

Attention! To eliminate interference and influence of human hands when touching regulators - the case of variable resistors must be connected with the minus boards.

With the right soldering metal detector scheme, the health and correct value of the elements, the correctly made search coil device works without problems. If the first turn on the headphones do not hear the squeak and changes in frequency when adjusting the regulator "PRATE" - then you need to pick up a resistor (10 kOm). standing sequentially with the regulator and/or capacitor in this generator (300 pf). In this way, we make the same frequencies of sample and search generators.

When the generator is excited, the whistling, hissing, distortions solder the capacitor 1000 pf (1H0 same 102) from the out. 6 chips per case.
How to make a simple metal detector with your own hands; step-by-step instruction
An oscillograph or frequency-to-be see the frequency of signals on outputs 5 and 6 K561LA7. To achieve their equality by the above method of customization. The working frequency of generators can range from 80 to 200 kHz.

A protective diode (any low-power) is needed to prevent damage to the chip when the battery is turned on incorrectly (which is often the :).

Making a metal detector coil



The coils are reeled on a 15-25 cm diameter (e.g. a bucket or a large wire or plywood shuttle - the smaller the diameter, the less sensitivity, but the greater the selectivity of small metals). Choose for what purpose you need it.

The wire is used in the lacquer insulation of PEL, PEV, with a diameter - 0.5 - 0.7 mm (well suited from old colored TVs with a loop demagnetizing kinescope or deflective system) and contains about 100 turns (you can wind 80 to 120 turns). On top of the wire wrap tightly with tape.

Then the coil on top of the tape wrap a strip of foil, leaving 2-3 cm unwrapped area. Foil can be taken from some types of cables or in extreme cases - cut into strips of 2 cm wide foil from chocolate 🙂

Next on top of the foil wrap not insulated wire (better puddle). The beginning of the wire will remain on the coil, and the end of the solder on the body, ie minus the power of the board.

We're still tightly wrapped in duct tape.

The resulting finished coil is fixed to the dielectric (for example, non-foiled textolite or hetinax). Then it is attached to the hold.

We combine the coil with the scheme with a double screened wire (screen on the body). The wire can be taken from old cords to rewrite from tape recorder to tape recorder or cord to connect the TV with DVD, etc.

The correct work of the metal detector: when the regulator is turned on the "frequency" in the headphones, we set a low-frequency drone, when approaching the metal the frequency changes.

The second option is that the buzz in the ears "does not stand," set zero beatings, i.e. combine the two frequencies. In the headphones then there will be silence, but as soon as the coil is brought to the metal - the frequency of the search generator changes and the headphones appear squeaking. The closer to the metal, the higher the frequency in the headphones. But sensitivity in this way is not great. The device will react only when generators are built strongly, for example, when the lid is brought to the lid from the jar.