Do-it-yourself deep metal detector: diagram, instructions and reviews. Simple and reliable do-it-yourself metal detector Simple and powerful do-it-yourself metal detector

You can buy for about 100-300 dollars. The price of metal detectors is strongly related to their detection depth, not every metal detector can "see" coins at a depth of 15 cm. .

This article will consider an example of assembling a powerful metal detector called Pirat with your own hands. The device is able to catch coins underground at a depth of 20 cm. As for large objects, it is quite possible to work at a depth of 150 cm.

Video of working with a metal detector:

This metal detector received such a name due to the fact that it is a pulse, this is the designation of its first two letters (PI-impulse). Well, RA-T is consonant with the word radioskot - this is the name of the developers' site, where the homemade product was posted. According to the author, the Pirate is going to be very simple and fast, even basic skills in working with electronics are enough for this.

The disadvantage of such a device is that it does not have a discriminator, that is, it cannot recognize non-ferrous metals. So working with him on areas contaminated with various kinds of metals will not work.

Assembly materials and tools:
- microcircuit KR1006VI1 (or its foreign analogue NE555) - a transmitting node is built on it;
- transistor IRF740;
- K157UD2 microcircuit and VS547 transistor (the receiving unit is assembled on them);
- wire PEV 0.5 (for winding the coil);
- NPN type transistors;
- materials for creating the body and so on;
- electrical tape;
- soldering iron, wires, other tools.

The remaining radio components can be seen in the diagram.

You also need to find a suitable plastic box for mounting the electronic circuit. You will also need a plastic pipe to create a rod on which the coil is attached.

Metal detector assembly process:

Step one. We create a printed circuit board
The most difficult part of the device is, of course, the electronics, so it is advisable to start with it. First of all, you need to make a printed circuit board. In total there are several options for boards, depending on the radio elements used. There is a board for NE555, and there is a transistor board. All the necessary files for creating the board are in the article. You can also find other board options on the Internet.

Step two. We install electronic elements on the board
Now the board needs to be soldered, all electronic elements are installed exactly as in the diagram. In the picture on the left you can see the capacitors. These capacitors are film type and have high thermal stability. Thanks to this, the metal detector will work more stably. This is especially true if you use a metal detector in the fall, when it is already quite cold outside.

Step three. Power supply for metal detector
To power the device, you need a source from 9 to 12 V. It is important to note that the device is rather voracious in terms of energy consumption, and this is logical, because it is powerful. One krone battery is not enough for a long time, it is recommended to use 2-3 batteries at once, which are connected in parallel. You can also use one powerful battery (best rechargeable).

Step four. Assembling a coil for a metal detector
Due to the fact that this is a pulse metal detector, the accuracy of the coil assembly is not so important here. The optimal diameter is a mandrel of 1900-200 mm, in total you need to wind 25 turns. After the coil is wound, it must be carefully wrapped on top with electrical tape for insulation. To increase the detection depth of the coil, you need to wind it on a mandrel with a diameter of about 260-270 mm, and reduce the number of turns to 21-22. The wire is used with a diameter of 0.5 mm.

After the coil is wound, it must be installed on a rigid body, there should be no metal on it. Here you need to think a little and look for any case that is suitable in size. It is needed in order to protect the coil from shock while working with the device.

The leads from the coil are soldered to a stranded wire with a diameter of about 0.5-0.75 mm. It is best if these are two wires twisted together.

Step five. Setting up a metal detector
When assembling exactly according to the scheme, it is not necessary to adjust the metal detector, it already has maximum sensitivity. For more fine tuning metal detector, you need to turn the variable resistor R13, you need to achieve rare clicks in the speaker. If this is achieved only in the extreme positions of the resistor, then it is necessary to change the value of the resistor R12. The variable resistor should adjust the device for normal operation in the middle positions.

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A very interesting device is this Krot-M and its continuation M2 / M3. It is quite easy to make it with your own hands. In this article you can find all the information you need to build it.

Let's start with the characteristics and description.

Krot-M is a rather serious device, it is selective, based on a microcontroller.

Relatively inexpensive and easy to assemble. As for reliability, some people claim that it can falsely work, or react to swings. In most cases, all this is the result of incorrect setup and assembly, the use of bad or incorrect parts. Of the pluses, I would like to note: an easy setup menu, good detection depth, relative cheapness.

Characteristics:

• Coin d = 25 mm - up to 30 cm.
• A medium-sized metal object (helmet) - up to 1 meter.
• The maximum sensitivity is up to 1.5 meters.
• The principle of operation is inductive balance (IB).
• The sensor diameter is from 10 to 30 cm.
• Sound indication - multi-tone, from 2 to 14 tones.
• Visual indication (VDI) - present.
• Operating frequencies (depending on the firmware) - from 6 to 12 kHz.
• Search mode - selective mode.
• Consumption current - up to 90 mA.
• Operating voltage - from 4.8 to 9 V.

Scheme MD Krot-m

Below we provide a diagram and a printed circuit board Krot-M

All this can be downloaded in one archive, a board in .lay format

Here is the wiring diagram for the coil.

Scheme MD Krot-2M

And now hold the Krot-2m circuit and its printed circuit board. There will be 2 types of printed circuit boards in the archive, for the Z78 case and the Z80 case. Also inside there will be recommendations for assembly and installation in the case, a list of parts and additional diagrams.

That's basically all about this metal detector. Here are some more firmware and some recommendations:

Only the latest firmware is provided, if you need an earlier one, then go to the author's website and download it for yourself. Change in this firmware.

In the manufacture of the metal detector, a beat circuit was chosen (Fig. 1). It contains two high-frequency LC oscillators on transistors VT1, VT2, a balanced mixer on transistors VT3, VT4 and an ultrasonic frequency converter on transistor VT5.
Generators are assembled according to a scheme that has a number of useful properties, one of which is the stability of the output voltage (both DC and AC) when the supply voltage changes. The coil L1 is included in the oscillatory circuit of the search generator on the transistor VT1. It operates at a frequency of about 100 kHz, which is optimal for this type of metal detector. Its frequency can be changed within small limits by a variable capacitor C2. The second generator (on transistor VT2) is exemplary and operates at a frequency of about 300 kHz.
The generator signals through resistors R2, R4 are fed to a balanced mixer, where the frequency difference (beats) of the third harmonic of the search generator signal and the first harmonic of the exemplary one is separated. This was done to increase sensitivity - when the frequency of the search generator is changed by 10 Hz, the beat frequency changes by 30 Hz, which is more noticeable by ear. In addition, the effect of mutual "pulling" of the oscillator frequencies is noticeably reduced, which manifests itself as the impossibility of setting the beat frequency close to zero.
The signal from the output of the mixer through the capacitor C8 is fed to the input of the ultrasonic frequency converter and, after amplification, to the head phones BF1, BF2. Capacitor C7 suppresses signals with oscillator frequencies.
When the search generator coil approaches a metal object, the generation frequency changes, so the signal tone in the headphones will also change. By the nature of the change in tone, one can judge the material from which this object is made.
Most of the parts are mounted on a printed circuit board made of one-sided foil-coated fiberglass, the drawing of which is shown in fig. 2. MLT, C2-23 resistors are used, oxide and variable capacitors are imported, the rest are K10-17, and it is desirable to use capacitors C1, C3, C5, C6 with a minimum TKE - this will increase the thermal stability of the metal detector.

In addition to those indicated in the diagram, transistors of the KT312, KT315, KT3102 series with any letter indices can be used in generators. In a balanced mixer, only germanium transistors of the GT309, GT313, GT322, GT346 series or earlier - P416, P422, P423 with any letter indices can be used. In UZCH, the transistor must be with the highest possible current transfer coefficient, for example, KT3102BM-KT3102EM, KT342BM, KT342VM - the volume of the sound signal depends on this. Power switch - any small-sized. Headphones - with a resistance of 8 to 32 ohms, they are connected in series. To connect them, you can install a socket on the body of the metal detector. The device is powered by a galvanic cell or an AA or AAA battery, the current consumption is about 12 mA.
For the manufacture of the L2 coil, a unified frame was used from the IF circuit (455 kHz) of a foreign-made receiver (Fig. 3). It consists of a ferrite "dumbbell" (on which 65 turns of PEV-2 wire with a diameter of 0.06 ... 0.1 mm are wound) and a ferrite cup covering it, by moving which the coil inductance is regulated. The frame is enclosed in metal screen.
The sensitivity of the device to metal objects of different sizes depends on the size of the search coil. To search for large objects (a sheet of metal measuring 80x80 cm, a sewer manhole cover), a coil with a diameter of about 30 cm is more suitable. With it, the maximum detection depth of such objects is up to 70 cm, and at the same time small objects (coins, metal bottle caps ) are not found.
To search for small objects, a coil with a diameter of about 12 cm is better suited. Such a coil contains 56 turns of PEL wire with a diameter of 0.2 ... 0.5 mm. The wire is wound on a mandrel, then wrapped with insulating tape and shielded with foil. The screen must not form a short-circuited loop! Another layer of electrical tape is wound over the screen. The coil is connected to the board with a shielded wire, preferably a thin coaxial cable. The shield must be connected to one of the terminals of the L1 coil and the outer sheath of the coaxial cable.
A coil of a larger diameter (30 cm) is more technologically produced from a multicore shielded twisted pair cable, which is used for laying computer local networks. The cable must contain four such "pairs", and the coil - four turns of such a cable. First, two outer turns are wound and fastened in four places with insulating tape. Then two inner ones are wound and everything is also wrapped with insulating tape, preferably on a cloth basis. The ends of the cable are cut in such a way that there is an "overlap" of 0.5 ... 1 cm, and the outer insulation is removed from them by 1.5 cm, and the ends of the wires are stripped by 0.5 cm and tinned (Fig. 4). The shielding braid of the multi-core cable is cut off on one side and connected to one of the conductors on the other - this will be the output of the coil connected to the common wire (positive output of the power source), and the screen of the coaxial cable is also soldered here.
All wires are connected in series with each other - the end of the first is connected to the beginning of the second, etc. If they have a different color, this will facilitate the work. For example, a wire in blue insulation is connected to a shielding braid, its end is connected to the beginning of a wire in blue-white insulation, the end of which is connected to a wire in green insulation. The joints are isolated (Fig. 5). The color of the wires is chosen arbitrarily, based on the convenience of their connection. The result is a coil containing 32 turns. It has good rigidity and moisture resistance. In the absence of a stranded cable, the coil can be wound with the same wire as the previous one.
printed circuit board, a variable capacitor, a switch and a battery are installed in a case of a suitable size. After checking the performance and adjusting the board with the elements, it is poured with paraffin - this will protect against moisture and give additional rigidity to the structure.
Adjustment is carried out in the following sequence. The rotor of the capacitor C2 is set to the middle position. By adjusting the L2 coil, they listen to the beat signal and achieve the loudest sound. Its frequency is set as low as possible, the sensitivity of the metal detector will be maximum. During operation, the frequency is adjusted by capacitor C2. By the nature of the change in the frequency of the sound signal, it is possible to distinguish between non-ferrous and ferrous metals. The nature of its change depends on whether the frequency of the exemplary generator of the frequency of the third harmonic of the search generator is higher or lower. Therefore, by first bringing the metal detector coil to an object made of a known metal (for example, to a car body), you can find out.

Deep type metal detectors are able to detect objects in the ground at a great distance. Modern modifications in stores are quite expensive. However, in this case, you can try to make a metal detector with your own hands. For this purpose, it is first of all recommended to familiarize yourself with the design of the standard modification.

Modification scheme

When assembling a metal detector with your own hands (the diagram is shown below), you need to remember that the main elements of the device are a damper on a microcontroller, a capacitor and a handle with a holder. The control unit in the devices consists of a set of resistors. Some modifications are made on drive modulators that operate at a frequency of 35 Hz. Directly racks are made with narrow and wide plate-shaped plates.

Assembly instructions for a simple model

Assembling a metal detector with your own hands is quite simple. First of all, it is recommended to prepare a tube and attach a handle to it. Installation requires high conductivity resistors. The operating frequency of the device depends on many factors. If we consider modifications on diode capacitors, then they have high sensitivity.

The operating frequency of such metal detectors is about 30 Hz. The maximum detection distance of an object is 25 mm. Modifications are capable of working on lithium-type batteries. Microcontrollers for assembly will be required with a polar filter. Many models fold on open type sensors. It is also worth noting that experts do not recommend using high sensitivity filters. They greatly reduce the accuracy of detecting metal objects.

Model series "Pirate"

You can make a Pirate metal detector with your own hands only on the basis of a wired controller. However, first of all, a microprocessor is prepared for assembly. To connect it, you will need Many experts recommend the use of grid capacitors with a capacitance of 5 pF. Their conductivity should be maintained at a level of 45 microns. After you can start soldering the control unit. The stand must be strong and support the weight of the plate. Plates larger than 5.5 cm in diameter are not recommended for 4V models. System indicators are optional. After fixing the block, it remains only to install the batteries.

Using reflex transistors

Making a do-it-yourself metal detector with reflex transistors is quite simple. First of all, experts recommend installing a microcontroller. Capacitors in this case are suitable for a three-channel type, and their conductivity should not exceed 55 microns. At a voltage of 5 V, they have a resistance of approximately 35 ohms. Resistors in modifications are used mainly of the contact type. They have a negative polarity and cope well with electromagnetic vibrations. It is also worth noting that during assembly it is allowed to use the maximum plate width for such a modification is 5.5 cm.

Model with convection transistors: expert reviews

You can assemble a metal detector with your own hands only on the basis of a collector controller. In this case, capacitors are used at 30 microns. If you believe the reviews of experts, then it is better not to use powerful resistors. In this case, the maximum capacitance of the elements should be 40 pF. After installing the controller, it is worth taking up the control unit.

These metal detectors receive good feedback for reliable protection against wave interference. For this purpose, two diode-type filters are used. Modifications with display systems are very rare among homemade modifications. It is also worth noting that power supplies must operate at low voltage. Thus, the battery will last a long time.

Using Chromatic Resistors

With your own hands? A model with chromatic resistors is quite easy to assemble, but it should be borne in mind that capacitors for modifications are only allowed to be used on fuses. Experts also point out the incompatibility of resistors with feed-through filters. Before starting the assembly, it is important to immediately prepare a tube for the model, which will be a handle. Then the block is installed. It is more expedient to select modifications for 4 microns, which operate at a frequency of 50 Hz. They have a small scattering coefficient and high measurement accuracy. It is also worth noting that seekers of this class will be able to successfully work in conditions of high humidity.

Model with a pulsed zener diode: assembly, reviews

Devices with pulsed zener diodes are distinguished by high conductivity. If you believe the reviews of experts, then home-made modifications are able to work with objects of different sizes. If we talk about the parameters, then their detection accuracy is approximately 89%. It is worth starting the assembly of the device with a rack blank. Then the handle for the model is mounted.

The next step is to install the control unit. Then the controller is mounted, which is powered by lithium batteries. After installing the unit, you can start soldering the capacitors. Their negative resistance should not exceed 45 ohms. Expert reviews indicate that modifications of this type can be made without filters. However, it should be borne in mind that the model will have serious problems with wave interference. This will damage the capacitor. As a result, the battery in models of this type is quickly discharged.

Application of the low frequency transceiver

Low-frequency transceivers in models significantly reduce the accuracy of the devices. However, it is worth noting that modifications of this type are able to successfully work with objects small size. At the same time, they have a small self-discharge parameter. In order to assemble the modification with your own hands, it is recommended to use a wired controller. The transmitter is most often used on diodes. Thus, conductivity is provided at around 45 microns with a sensitivity of 3 mV.

Some experts recommend installing mesh filters, which increase the security of models. To raise the conductivity, only transitional type modules are used. The main disadvantage of such devices is the burnout of the controller. With such a breakdown, it is problematic to repair the metal detector with your own hands.

Using a high frequency transceiver

On high-frequency transceivers, you can assemble a simple metal detector with your own hands only on the basis of a transitional controller. Before starting the installation, a rack for the plate is prepared as a standard. The conductivity of the controller is on average 40 microns. Many specialists do not use contact filters when assembling. They have high heat loss, and they are ways to operate at a frequency of 50 Hz. It is also worth noting that lithium batteries are used to assemble the metal detector, which recharge the control unit. The sensor itself for modifications is installed through a capacitor, in which the capacitance should not exceed 4 pF.

Longitudinal resonator model

There are often devices with longitudinal resonators on the market. They stand out from their competitors with high accuracy in determining objects, and at the same time they can work in high humidity. In order to independently assemble the model, a stand is prepared, and a plate should be used with a diameter of at least 300 mm.

It is also worth noting that a contact controller and one expander are required to assemble the device. Filters are used only on a mesh lining. Many experts recommend installing diode capacitors that operate at a voltage of 14 V. First of all, they discharge the battery a little. It is also worth noting that they have good conductivity compared to field counterparts.

Using Selective Filters

Making such a deep metal detector with your own hands is not easy. The main problem is that a conventional capacitor cannot be installed in the device. It is also worth noting that the modification plate is selected from 25 cm in size. In some cases, the racks are installed with an expander. Many experts advise starting the assembly with the installation of the control unit. It must operate at a frequency of no more than 50 Hz. In this case, the conductivity depends on the controller that is used in the equipment.

Quite often, it is selected with a lining to increase the security of the modification. However, such models often overheat, and are not able to work with high accuracy. To solve this problem, it is recommended to use conventional adapters that are installed under the capacitor units. A do-it-yourself coil for a metal detector is made from a transceiver unit.

Application of contactors

Contactors are installed in the devices together with control units. Racks for modifications are used in short lengths, and plates are selected at 20 and 30 cm. Some experts say that devices should be assembled on impulse adapters. In this case, capacitors can be used with low capacitance.

It is also worth noting that after installing the control unit, it is worth soldering a filter that can operate at a voltage of 15 V. In this case, the model will maintain a conductivity of 13 microns. Transceivers are most often used on adapters. Before turning on the metal detector, the level of negative resistance is checked on the contactor. The specified parameter averages 45 ohms.

If you have lost a ring, a key, a screwdriver... and you know the approximate place of loss, then do not despair! You can assemble a metal detector with your own hands or ask a friend of a radio amateur to assemble simple do-it-yourself metal detector. Below is a diagram of a metal detector that is easy to manufacture and proven over the years, which (with certain skills) can be made in one day. The simplicity of the described metal detector is that it is assembled on just one very common microcircuit K561LA7 (CD4011BE). The setup is also simple and does not require expensive measuring instruments. An oscilloscope or frequency meter is enough to tune the generators. If everything is done without errors and from serviceable elements, then these devices will not be needed.

The sensitivity of this metal detector:

jar metal lid “sees” up to 20 cm, cell phone up to 15 cm, “krone” battery up to 10 cm, 5 ruble coin up to 8 cm.

At this distance, the tone of the generator in the headphones barely changes; at a closer distance, the tone increases. The larger the metal area, the greater the detection distance. Distinguish between diamagnets and ferromagnets.

For metal detector manufacturing we will need:

1. Chip K561LA7 (or K561LE5, analogue of CD4011);
2. Transistor - low-power low-frequency, for example - KT315, KT312, KT3102, analogues: BC546, BC945, 2SC639, 2SC1815, etc.);
3. Diode - any low-power, for example - kd522B, kd105, kd106, analogues: in4148, in4001, etc .;
4. Variable resistor - 3 pcs (1 kOhm, 5 kOhm, 20 kOhm with a switch or a switch separately);
5. Fixed resistor - 5 pcs (22 Ohm, 4.7 kOhm, 1.0 kOhm, 10 kOhm, 470 kOhm);
6. Ceramic, and even better mica capacitors - 5 pcs: 1000 pF -3 pcs, 22 nF -2 pcs, 300 pF);
7. Electrolytic capacitor (100.0 microfarad x 16V) - 1 pc;
8. Wire PEL, PEV, PETV, etc., with a diameter of 0.4-0.7 mm;
9. Low-impedance headphones (from the player);
10. Battery 9V.

Metal detector scheme

The appearance of the metal detector board

In a case from an old pocket radio (you can use a case from a soap dish, from a sponge for cleaning shoes or in the housing from the electrical junction box.

Attention! To eliminate interference and the influence of human hands when touching the regulators, the cases of variable resistors must be connected to the minus of the board.

With a properly soldered metal detector circuit, serviceability and the correct value of the elements, a correctly made search coil, the device works without problems. If, when you turn on the headphones for the first time, you don’t hear a squeak and a change in frequency when adjusting the “FREQUENCY” knob, then you need to choose a resistor (10 kOhm) , in series with the regulatorand / or a capacitor in this generator (300 pF). Thus, we make the frequencies of the exemplary and search generators the same.

When the generator is excited, the appearance of whistling, hissing, distortion, solder a 1000 pF capacitor (1H0 aka 102) with a pin. 6 chips per case.

Using an oscilloscope or frequency meter, look at the signal frequencies at pins 5 and 6 of the K561LA7. Achieve their equality by the above described setup method. The very operating frequency of the generators can range from 80 to 200 kHz.

A protective diode (any low-power one) is needed to prevent damage to the microcircuit when the battery is turned on by mistake (which often happens :).

Making a metal detector coil

Coils are wound on a mandrel with a diameter of 15-25 cm (for example, a bucket or on a shuttle made of thick wire or plywood - the smaller the diameter, the lower the sensitivity, but the greater the selectivity of small metals). Choose for what purpose you need it.

A wire is used in lacquer insulation PEL, PEV, PETV ..., with a diameter of 0.4 - 0.7 mm (well suited for old color TVs with a kinescope degaussing loop or a deflecting system) and contains about 100 turns (you can wind from 80 to 120 turns ). We wrap tightly with electrical tape over the wire.

Then we wrap the coil over the electrical tape with a strip of foil, leaving a 2-3 cm area not wrapped. Foil can be taken from some types of cables or on extreme case- cut the foil from the chocolate into strips 2 cm wide 🙂

Once again tightly wrap with electrical tape.

Photo of the finished coil. It remains to wrap the top with electrical tape.

We fix the resulting finished coil on a dielectric (for example, non-foil textolite or getinaks). Next, we attach it to the holder.

We connect the coil with the circuit with a double shielded wire (screen on the case). The wire can be taken from old cords for dubbing from a tape recorder to a tape recorder or a low-frequency (audio-video) cord for connecting a TV to a DVD, etc.

Proper operation of the metal detector: when turned on with the “frequency” regulator in the headphones, we set a low-frequency rumble, when approaching the metal, the frequency changes.

It is possible the second option, so that the hum in the ears “does not stand”, set zero beats, i.e. combine two frequencies. Then there will be silence in the headphones, but as soon as we bring the coil to the metal, the frequency of the search generator changes and a squeak appears in the headphones. The closer to the metal, the higher the frequency in the headphones. But the sensitivity of this method is not great. The device will react only when the generators are strongly detuned, for example, when brought to the lid of a can.

Location of parts on the board for a microcircuit in a DIP package

The location of parts on the board for the microcircuit in the SMD package

Zotov A., Sergey V., Volgograd region

This metal detector scheme can be discussed at our

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Multiple metal detector options from the set

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Metal detector kit

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