» Electronics » Metal detectors "The simplest metal detector on the chip K176LA7

The simplest metal detector on a chip K176LA7

The simplest metal detector on a chip K176LA7

This article will show you how to make it very simple. metal detector from almost improvised materials. Despite its simplicity, the metal detector works, it can find a coin at a depth of 10 cm, a pan at a depth of 30 cm, and the device sees a sewer hatch at a depth of 60 cm. This is certainly not much, but for such a simple device it’s pretty good. However, if you work with him on the beach or just build for informational purposes, then you will not lose time in vain.

Materials and tools for homemade:
- A complete list of the details of the board can be seen in the diagram, it includes the K176LA7 chip;
- wire for the coil (PEV-2 0.08 ... 0.09 mm);
- armored magnetic circuit;
- epoxy;
- headphones;
- soldering iron with solder;
- materials for creating a rod, body, and so on.

The process of manufacturing a metal detector:

Step one. A few words about the scheme
L1 must be wound on a frame with three sections with a trimming core and placed in an armored magnetic circuit with a diameter of 8.8 mm made of 600NN ferrite. In total, the coil has 200 turns of PEV-2 wire 0.08 ... 0.09 mm.

The L2 coil is made from a piece of aluminum tube with a diameter of 6-9 mm and a length of 950 mm. Through it you need to thread 18 pieces of wire with good insulation. Next, the tube must be bent using a mandrel, in diameter it should be about 15 cm. The wire segments are connected in series. The inductance of this kind of coil should be in the range of 350 μH.

The ends of the tube do not need to be closed, but one of them must be connected by a common wire.

For the scheme described above, the author used a rubber hose with a metal base inside, as well as a solid wire, varnished. In order not to damage the insulation, tweezers with rubber tubes at the ends were used. The winding must be fixed as carefully as possible, otherwise the device will give false positives.

Well, then the board is placed in a metal, but not magnetic case.

It is important to note the fact that the cable going from the board to the coil must be shielded.

Step Two Further assembly and configuration
To adjust the capacitor knob, you need to turn it to the middle position, and then by rotating the tuning core L1, you need to ensure that there are no beats in the headphones. The setting will be correct if a buzz is heard in the headphones when you turn the variable capacitor knob a small angle.

The adjustment is carried out at a distance of at least one meter from massive metal objects.

The author was able to increase the sensitivity of the device if the core of the tuning coil was screwed to the stop, and by adjusting the settings using an alternating capacitor to achieve almost complete absence of sound in the headphones. At the same time, if you turn on the headphones at full power, the sound will be quiet.

If it is so that the sound in the headphones is not heard at all, it is necessary to check the presence of a U-shaped signal at pins 4 DD1 and DD2, for such purposes an oscilloscope will be needed. At pin 11 and 8, DD3 should be a mixture of signals.

It should also be noted that the original circuit indicates a resistance of R3 300 kOhm, but the headphones will not work with such resistance. It needs to be replaced with 3 kOhm. Instead of 5600 pF capacitors, the author also used at 4700 pF, since the first could not be found.

The disadvantages of the circuit include the fact that the chamber is sensitive to ambient temperature, in this regard, the device must be constantly tuned with a variable capacitor, achieving zero beats.

Step three. The final stage of assembly
The author recommends filling the coil with epoxy, this will allow you to securely fix the wires. Otherwise, there will inevitably be false positives, since in the search process you have to touch stones, sticks and other obstacles, moreover, the coil can be easily damaged. Instead of epoxy, wax or plasticine is suitable, which must be melted and filled. Paraffin should not be used, since it becomes brittle after solidification and does not have elasticity. If the choice fell on plasticine, then you need to make sure that it does not leak out, warming up in the sun.

Among other things, in the circuit, gently replace the resistor R3, its rating should be 300 kOhm. You also need to adjust the frequency of the model generator so that confident and clear clicks are heard in the headphones. The sensitivity of the device is determined by the frequency of clicks, the lower it is, the better. With these settings, the author finds a penny coin of the USSR at a depth of 10 cm, which lies horizontally.

If you make the click frequency high, then the presence of metal under the search coil can be determined by the change in sound.

The author also collected another such device and he found a problem - the lack of sound in the headphones. The solution was to remove the capacitor C7 from the circuit. The author also removed the volume control, as the sound itself became quieter. With such refinement, the device did not lose sensitivity.

A case for a device made of plastic can be bought at a radio store; it cost the author 31 rubles. To shield the scheme from cardboard, you need to cut the “shirt” and wrap it with foil. The edges of the foil are attached to the cardboard with tape, then with the help of a stapler a wire is attached and connected to the minus.

Also, an electrolytic capacitor of 47-100 microfarads must be installed in the circuit after turning on the power with a voltage of at least 10V.

To create L2, the author used the wire that he found, it has a diameter of 0.5 mm. A wire of 0.3-0.7 mm is suitable for such purposes. You can conduct experiments with core materials, they can be brass or ferrite.
8.3
6.3
7.7

Add a comment

    • smilesmilesxaxaokdontknowyahoonea
      bossscratchfoolyesyes-yesaggressivesecret
      sorrydancedance2dance3pardonhelpdrinks
      stopfriendsgoodgoodgoodwhistleswoontongue
      smokeclappingcraydeclarederisivedon-t_mentiondownload
      heatirefullaugh1mdameetingmoskingnegative
      not_ipopcornpunishreadscarescaressearch
      tauntthank_youthisto_clueumnikacuteagree
      badbeeeblack_eyeblum3blushboastboredom
      censoredpleasantrysecret2threatenvictoryyusun_bespectacled
      shokrespektlolprevedwelcomekrutoyya_za
      ya_dobryihelperne_huliganne_othodifludbanclose
8 comments
There is a sense in the diode filter: the ability to capture a very close frequency of the second generator by one generator decreases, that is, in fact, the resolution increases. Correctly write that to power the generators you need to add an electrolyte, preferably after each of the decoupling diodes. Another important role is played by the wiring of the common wire of the generators.
In gives, ah! DO NOT replace the resistor R3! At first I thought it was my typo xaxa
A Ivan_Pokhmelev correctly noticed that the power filter is fake. I now looked again, indeed, the power pins of the DD1 and DD2 microcircuits are connected after the filter.
Throw out R5, R6, C9. Put 1 diode to protect against power overload and after it an electrolyte at 470 uF and everything will work. I wrote earlier that there will be no tie between the generators, not that sensitivity, there is no gain there. Beats simply arise from the difference in the frequencies of the generators.
No offense, but after reading ....., I was bald xaxa
The filter in the diagram is not drawn correctly: for some reason, the power supply D1 and D2 is combined after the resistors. It is better to use diodes than resistors for isolation.
What I want to say. I have been collecting this circuit for a very long time. Declared here, the characteristics of the detection range correspond to real ones. But in sunny weather it was almost impossible to work. Frequency constantly floated away from heating, it was necessary to adjust. The purpose of the inverters DD3.1 and DD3.2 is not clear. You can’t connect the inputs of unused elements to a common wire or to power? Why invert the signal 2 times. The value of R4 is too high, there will be no smooth volume control. Either reduce or take high-impedance headphones. Reduce the power filter resistors, but it is better to throw out and supply 470-1000 μF x 16 V. Will not pull. Not that sensitivity.
Author
I did not understand it myself, so the brain automatically ignored the cheto ... Sorry)

PMR - Transnistrian Moldavian Republic
A PMR is that, I'm sorry.
P.S. From the phone It's hard to write and search ....
What is the meaning of an absurd nutrition filter? Actually, DD1 and DD2 need separate chains to reduce mutual influence.
he cost the author 31 rubles.
In fact, not 31 rubles, but 31 rubles PMR. Do not mislead people!
Turning on a sound emitter with a resistance of 65 Ohms through a 10 kOhm alternator is a rather strange solution.
Fastening the coil to the rod with a metal bracket is no less strange solution.

We advise you to read:

Hand it for the smartphone ...