Even a novice radio amateur can make this design. At the same time, the metal detector has a fairly high sensitivity. Using the proposed device, it is possible to detect a copper coin with a diameter of 20 mm and a thickness of 1.5 mm at a depth of up to 9 cm.

The principle of operation of the metal detector is simple, it is based on comparing two frequencies. One of them is reference (from the reference generator), and the other is changing (from the search generator). Moreover, its deviations depend on the appearance of metal objects in the field of a highly sensitive search coil.

In modern metal detectors, to which the design under consideration can be quite reasonably attributed, the reference oscillator operates at a frequency that differs by an order of magnitude from that which occurs in the field of the search coil.

circuit diagram

The schematic diagram of the metal detector is shown in Figure 1, a. The reference oscillator is implemented on two logic elements ZI-NOT of the DD2 chip. Its frequency is stabilized and is determined by a ZQ1 quartz resonator (1 MHz).

Rice. 1. A simple metal detector on microcircuits: a - a circuit diagram; b - printed circuit board.

The search generator is made on the first two elements of the DD1 chip. The oscillatory circuit here is formed by the search coil L1, capacitors C2 and C3, as well as the varicap VD1. To tune to a frequency of 100 kHz, the potentiometer R2 is used, which sets the required voltage to the varicap VD1.

As buffer signal amplifiers, logic elements DD1.3 and DD2.3 are used, working on a mixer DD1.4. The indicator is a high-resistance telephone capsule BF1, capacitor C10 is used as a shunt for the high-frequency component coming from the mixer.

Details and design

The metal detector is powered by a 9 V direct current source, a Krona battery is used. Capacitors C8 and C9 successfully work as a filter.

The search coil requires special precision and attention in manufacturing. It is desirable to wind the coil on a vinyl tube with an outer diameter of 15 mm and an inner diameter of 10 mm, bent in the shape of a circle with a diameter of 200 mm.

The coil contains 100 turns of GTEV-0.27 wire. When the winding is done, the coil is wrapped with aluminum foil to create an electrostatic shield (reducing the effect of capacitance between the coil and ground).

When winding and wrapping with foil, it is important to prevent electrical contact between the winding wire and the sharp edges of the foil. In particular, “twisting obliquely” will help here.

To protect the aluminum coating itself from mechanical damage, the coil should additionally be wrapped with an insulating bandage tape. The diameter of the coil may be different. But the following rule applies.

The smaller the diameter of the search coil, the higher the sensitivity of the entire device, but the search area for hidden metal objects narrows. With an increase in the diameter of the coil, the effect is reversed.

Working with a metal detector

You need to work with a metal detector as follows. Having placed the search coil in close proximity to the earth's surface, adjust the generator with potentiometer R2, and so that there is no sound in the telephone capsule. bugged.

When the coil moves above the surface of the earth (almost close to the latter), a metal object is found - by the appearance of sound in the telephone capsule.

Device search is just huge popularity. Looking for adults and children, and amateurs and professionals. They are looking for treasures, coins, lost things and buried scrap metal. And the main search tool is metal detector.

There is a great variety of different metal detectors for every “taste and color”. But for many people, buying a ready-made branded metal detector is simply financially expensive. And someone wants to assemble a metal detector with their own hands, and someone even builds their own small business on assembling them.

Homemade metal detectors

In this section of our website about homemade metal detectors, will be collected: best metal detector circuits, their descriptions, programs and other data for manufacturing DIY metal detector. There are no metal detector circuits from the USSR and circuits on two transistors here. Since such metal detectors are only suitable for a visual demonstration of the principles of metal detection, they are not at all suitable for real use.

All metal detectors in this section will be quite technologically advanced. They will have good search characteristics. And a well-assembled home-made metal detector will be a little inferior to factory counterparts. Basically, there are different schemes. pulse metal detectors And metal detector circuits with metal discrimination.

But for the manufacture of these metal detectors, you will need not only desire, but also certain skills and abilities. We tried to break down the schemes of the given metal detectors according to the level of complexity.

In addition to the basic data required to assemble a metal detector, there will also be information on the required minimum level of knowledge and equipment for self-manufacturing of a metal detector.

To assemble a metal detector with your own hands, you will definitely need:

This list will provide the necessary tools, materials and equipment for self-assembly of all metal detectors without exception. For many circuits, you will also need various additional equipment and materials, here are just the basic ones for all circuits.

1. Soldering iron, solder, tin and other soldering accessories.
2. Screwdrivers, pliers, wire cutters and other tools.
3. Materials and skills for the manufacture of printed circuit boards.
4. Minimum experience and knowledge in electronics and electrical engineering as well.
5. As well as straight arms - they will be very useful when assembling a metal detector with your own hands.

Here you can find schemes for self-assembly of the following models of metal detectors:

	Principle of operation	IB
	Metal Discrimination	There is
	Maximum search depth
		There is
	Operating frequency	4 - 17 kHz
	Difficulty level	Average

	Principle of operation	IB
	Metal Discrimination	There is
	Maximum search depth	1-1.5 meters (Depends on coil size)
	Programmable microcontrollers	There is
	Operating frequency	4 - 16 kHz
	Difficulty level	Average

	Principle of operation	IB
	Metal Discrimination	There is
	Maximum search depth	1 - 2 meters (Depends on the size of the coil)
	Programmable microcontrollers	There is
	Operating frequency	4.5 - 19.5 kHz
	Difficulty level	High

The dream of finding a treasure is increasingly being replaced in our time by a more realistic program for searching for precious metals in a natural or artificial environment.

In modern conditions it is very important to find and extract valuable materials, turned out to be among the waste, or in another uncontrolled environment.

Hardware is an important component of such a search technology.

The search and extraction of gold and valuable metals from waste, garbage, in a natural setting is part of the recycling strategy, the technology for the efficient processing of used materials, including.

Searching for them in the ground or in a mass of industrial and other wastes not only requires the use of equipment, but also stimulates its improvement. Are being created devices of different levels and specializations. There is an interest in such equipment among amateurs and enthusiasts in the search for valuable metals.

A metal detector is the most important tool for manually searching for metals in a chaotic natural or artificial environment.

With the help of such a device, you can search not only, but also, silver, and other precious metals.

Device principle any metal detector based on electromagnetic effects.

Here is how a typical metal detecting technology works:

1. device creates an electromagnetic field.
2. Metal an object, secretly located in a foreign environment, affects such a field when falls within his sphere of influence..
3. device captures the effect of the object on the electromagnetic field and signals it.

Most metal detector models work on this principle.

Technical differences of such equipment allow obtaining more complete information about the fact of detection of a metal object, for example:

• estimate the mass of the find;
• get data about the shape, size and configuration of the object;
• specify the location, including depth.

There is a lot of information on the Web about metal detectors of varying complexity and design. There you can brush up on the electromagnetic field theory, studied at school.

The simplest, primitive metal detectors (usually these are self-made designs for searching for gold, silver and other metals by amateur enthusiasts) assembled from finished devices and products working with the use of electromagnetic effects.

Many are familiar with the primitive, but quite workable metal detector circuit, in which the electromagnetic field creates a pulsed element of a conventional calculator.

reaction created field on the detected metal objects picks up the simplest household radio. The signal about such a find is audible, quite distinct and understandable.

More complex amateur and professional metal detecting devices preserve the logical basis of technology in the form of three components:

• electromagnetic field generator;
• a sensor for changes in this field;
• equipment for evaluating detected anomalies, signaling this.

Devices of different levels of complexity and functional potential can be conditionally divided into groups. Classification based on professionalism and specialization of users - one of the generally recognized:

• amateur equipment assembled by oneself and used as a hobby tool or by beginners in the search for metals;
• semi-professional equipment necessary for enthusiastic amateurs and fanatics;
• professional metal detectors for permanent workers in this field;
• special devices for metal searchers in difficult conditions - at depth, under water, with the release of precious metals.

The distribution of search equipment is such that many devices of this type can be purchased at garden and country equipment stores.

An apparatus for searching and detecting metal is needed not only in the recycling business, in the search for artifacts and treasures. Numerous security systems, all well-known frames - one of the versions of the technology metal search. The settings of these frames are focused on the search for weapons and similar dangerous items.

Coil

Very important node metal search equipment - coil or frame. This is most often a winding of a special configuration, the task of which is to form an electromagnetic field and catch its reaction to the detection of a metal body foreign to the search environment.

In most designs the coil is placed on a long rod– a handle to move it near the search area.

For amateur manufacturing of coils, frames of the most popular types are sold. The easiest way to make such a purchase is in an online store.

Many lovers make coil frames yourself. This is done for reasons of cost savings or in the hope of obtaining a higher quality instrument of the author's design.

For this, improvised means are used.- plastic products, plywood and even filling the assembled winding with mounting construction foam.

The search operator or treasure hunter seeks to find the most effective technique for working with a metal detector, choosing the right electronics operating modes and the correct methods of manipulating the coil.

Electronic circuit

The logical element of the metal detector is an electronic circuit. She performs many functions:

1. The first task of this component is in creating an electromagnetic signal of the desired format, which is converted into a field by means of a coil.
2. The second task of the electronic circuit is analysis of field changes caught by the frame, their processing.
3. The third task is giving an informing signal to the operator- sound, light, readings of indicators and instruments.

It is best if a person who wants to assemble an electronic circuit independently has knowledge of amateur radio or electronic technology. Such a master can not only assemble the desired circuit, but also change and improve the design.

Many electronic devices are quite simple, even a beginner can assemble them. The resulting device will be operational without configuration if the assembler exactly followed the recommendations of the developer of such a scheme.

How to make "Pirate" yourself?

One of the most popular models of metal detectors designed for DIY amateur production is the Pirate.

Abbreviated for his device and developer's website, this name wittily captures the romance of finding precious metals.

Here main advantages of this model:

• simplicity of device and assembly;
• low cost of parts and materials;
• sufficient operating parameters;
• recognized convenience for beginners.

The electronic circuit of this model does not require programming. In "Pirate" parts available to everyone are used, correctly assembled circuit is fully functional.

Design and principle of operation

The design scheme and layout of the "Pirate" metal detector is traditional for equipment of this kind. It is a rod, at the lower end of which is installed coil, and at the top - electronic unit with battery.

The location of the electronic unit should leave room for convenient holding of the rod by hand.

Some masters prefer that the sound signal of the device is given not by a speaker, but by headphones. In this case, the headphone cable leaves the electronic unit.

The technology of the device is pulsed. This makes it possible to provide very good sensitivity indicators for this class of equipment. Below is a diagram of an electronic unit on microcircuits.

A similar circuit can be assembled using transistors instead of microcircuits. This version may require additional settings available only to experienced radio masters. That is why the transistor circuit is used less frequently.

Materials, parts and blanks

In addition to the details and precisely indicated on the circuit diagram of the electronic unit, for assembly metal detector for gold and other metals you need to prepare some materials and blanks:

• a ready-made board for assembling an electronic circuit or foil material for its self-production;
• power source in the form of any combination of accumulators or batteries with a total voltage of 12V;
• enamel wire with a cross section of 0.5 - 0.6 mm for the manufacture of a coil;
• stranded copper wire for connections with a cross section of at least 0.75 sq. mm;
• housing for the electronic unit - a plastic container of a suitable size;
• Sufficiently strong plastic pipe for the rod;
• frame for winding the coil;
• consumables - solder, heat-shrinkable cambric, electrical tape, screws and self-tapping screws, adhesives and sealants.

A printed circuit board for assembling an electronic circuit is best done according to the model of developments presented on the Internet.

Below is one of these samples suitable for the assembly of electronics on microcircuits.

Fans of home-made electronics are engaged in the manufacture of the board, and even then not all. Most people who want to create a metal detector on their own prefer to buy such a part.

For coil assembly frame or frame required containing no metallic elements. An amateur craftsman can make such a frame from plywood, plastic, or pick up a similar one in terms of parameters from finished plastic products, for example, dishes. The frame can be purchased ready-made or made independently.

Recommended coil parameters- 25 turns of enamel wire with a diameter of 0.5 mm along a mandrel with a diameter of 190-200 mm. Increasing the diameter by 30% will lead to an increase in the sensitivity of the device, provided that the number of turns is reduced to 20-21.

A plastic frame for a coil is one of the most common metal detector parts on sale.

The coil manipulation technology is such that this very fragile assembly can suffer from impacts on uneven ground, stones, and sharp objects. To avoid this the coil on the frame is covered from below with a plastic plate. Such a dish not only protects the coil, but also provides a sliding mode on tall grass. The search becomes more intense.

Assembly order and design

For a successful metal detector assembly it is best to follow this procedure:

• PCB manufacturing and electronic circuit assembly;
• selection of a suitable plastic container for it and completion of the assembly of the electronic unit;
• coil manufacturing;
• manufacturing a conveniently shaped rod and attaching an electronic unit and coil to it, making connections to the electronic circuit.

Although the order of assembly is not fundamental. For those who manufacture an apparatus for continuous long-term work in the field of non-ferrous metal search and subsequent recycling (recycling for reuse), ease of use is an important factor.

In this case, the study of the shape of the rod and the layout of the main elements of the apparatus becomes a key factor. Thus, a serious design phase appears in the creation of the device.

The best way to do this step is to use life size simulation. Such modeling can be done using wooden parts of a suitable shape, for example:

• shank for a shovel;
• plywood pieces of the desired shape;
• scraps from;
• temporary fasteners from pieces of wire, nails and ropes.

After making sure that the assembled model of the device will be functional and convenient enough, you can proceed to the final assembly. Finished apparatus, usually, does not require configuration, it is completely ready to work. You can start searching for metal by choosing the desired level of sensitivity and the correct tactics for manipulating the coil.

Assemblers who need to assemble their apparatus as quickly as possible, can use ready-made kits.

The purchase of such a kit allows you to greatly simplify the manufacture of "Pirate". There is one of the proposals.

Users of the Pirate metal detector, who have skills in amateur radio, modify the design of this device. That's just several directions such improvements:

1. Manufacturing coils with unusual parameters- by size, from special materials, for example - twisted-pair cable.
2. The device of additional functional systems, for example - indication of the degree of discharge of the battery.
3. Manufacturing underwater models.
4. Add-ons electronic circuit, to distinguish between metals(creating a discrimination function).

A simple, inexpensive and reliable metal detector "Pirate" works properly in a variety of conditions.

Homemade metal detector - pros and cons

Cheapness, base advantage self-manufacturing of any products is relevant for a metal detector. Here are some more dignity on a homemade device:

• the most relevant search technology for beginners;
• the possibility of creating a device of a completely individual shape, design and configuration;
• the pleasure of making an efficient, workable device on your own.

Like any device made by an amateur, a metal detector not without some shortcomings.

Here are the features of the Pirate model that users note:

• vigorous charge consumption batteries;
• no discrimination, that is, accurate sensitivity to ferrous, non-ferrous and precious metals;
• limited compared to expensive models sensitivity.

Despite the shortcomings, the Pirate model is very popular. This is due to the simplicity of home-made manufacturing and the high performance of an inexpensive device.

Recycling professionals believe that the discrimination capabilities of a metal detector are not of great importance. All found metals are so valuable that their processing is always justified. Orientation to the search for gold requires not only equipment, but also considerable experience, accompanying knowledge and of course Good luck.

Related videos

The video provides a detailed guide to the manufacture and assembly of the Pirate metal detector with your own hands:

Conclusion

When the metal detector is ready, you can start working. You need to be aware that not a single most advanced apparatus will allow you to find only golden hidden objects.

A metal detector will help you find valuable metal, and it is very likely that it will be gold. It is best if the future metal and gold prospector has a real understanding of the search technique.

Many features of the operation of finished equipment are very important for those who develop and assemble their own models. You need to have an idea about the technology of work in advance with such equipment - this is the basis of its high-quality design.

The effectiveness of the search for gold increases with experience. Here the most important elements such experience:

• the right choice of metal detector design and its high-quality do-it-yourself manufacturing;
• the ability to correctly select the search site;
• the ability to use the full potential of the metal detector;
• choosing the right search technology in different conditions;
• metal detector upgrade.

Properly assembled and debugged equipment will always help in the search for gold, and this valuable metal will definitely be found.

In contact with

The principle of operation of the devices described below is based on a comparison of the oscillation frequencies of two generators: an exemplary one and a tunable one, which changes the frequency under the influence of the desired metal object on its oscillatory circuit. Compared with other known methods - bridge (the imbalance of the measuring bridge is recorded, one of the arms of which is connected to the search coil), phase shift (the phase shift of the oscillations of the exemplary and tunable generators is measured), transmitter-receiver (the RF energy re-radiated by the object is recorded) - comparison method frequency values ​​(in other words, the beat method) is less efficient, but easier to implement. The metal detectors built using it are compact, do not require careful tuning and measures for hard frequency stabilization, are unpretentious in operation, which is why they are widely used.

The devices offered to the attention of readers are made on an accessible element base and can be successfully used in construction, utilities to search for manholes and covers of wells, drain grates, etc. hidden under a layer of earth, debris or snow.

Figure 1. Schematic diagram of a metal detector on a K176LP2 chip

The metal detector, the schematic diagram of which is shown in fig. 1, assembled on just one K176LP2 chip. One of its elements (DDI.1) is used in the exemplary generator, the other (DDI.2) - in the tunable one. The oscillatory circuit of the exemplary "generator consists of a coil L1 and capacitors C1, C2, tunable - from the search coil L2 and capacitor C4; the first is rebuilt with a variable capacitor O, the second - with a selection of capacitor C4.

On element DD1.3, an oscillation mixer with exemplary and variable frequencies is made. From the load of this node - the variable resistor R5 - the difference frequency signal is fed to the input of the DDI.4 element, and the AF voltage amplified by it is sent to the head phones BF1.

The device can detect a five-kopeck coin not up to a depth of 60 mm, and the lid of a sewer well - at a depth of up to 0.6 m.

A metal detector assembled according to the scheme shown in fig. 2. Here, the K118UN1D (DA1) microcircuit is used as a mixer and amplifier of the difference frequency oscillations. The exemplary and tunable generators of this device are also identical in circuit, each of them is made on two inverters (DDI.1, DDI.2 and DD2.1, DD2.2, respectively), the elements DD1.3 and DD2.3 are buffer (weaken the influence mixer for generators). The exemplary generator is tuned to a given frequency by a variable capacitor C1, a tunable one - by selecting a capacitor C2

Figure 2. Schematic diagram of a metal detector

You can increase the sensitivity of a metal detector that uses the beat method by tuning the exemplary generator to a frequency 5 ... 10 times higher than the frequency of the tunable one. In this case, beats occur between the oscillations of the exemplary oscillator and the nearest in frequency (5 ... 10th) harmonic of the tunable generator, and the detuning of the latter, say, by only 10 Hz leads to an increase in the frequency of the difference oscillations by 50 ... 100 Hz.

It is in this way that the increased sensitivity of the device is achieved, the scheme of which is shown in Fig. 3. It can be used to detect a five-kopeck coin at a depth of up to 100 mm, and a well cover at a depth of up to 0.65 m.

Figure 3. Scheme of a metal detector with a quartz resonator

The exemplary generator of the metal detector is made on two elements of the DD2 chip and is tuned to a frequency of 1 MHz. The required frequency stability is provided by the ZQ1 quartz resonator.

The tunable generator uses two elements of the DD1 chip. Its oscillatory circuit L1 C2 C3 VD1 is tuned to a frequency several times lower than the exemplary generator. To adjust the circuit, a VD1 varicap is used, the voltage on which is regulated by a variable resistor R2.

The mixer is made on the DDI.4 element, the elements DD1.3 and DD2.3 are used as buffer elements.

As in both previous designs, BF1 headphones serve as the search indicator.

Each of the metal detectors is mounted on a printed circuit board made of foil fiberglass with a thickness of 1.5 mm. The drawing of the board and the location of the details of the first of them (according to the diagram in Fig. 1) are shown in fig. 4, the second (Fig. 2) - in fig. 5, the third (Fig. 3) - in fig. 6. The boards are designed for the installation of fixed resistors MLT-0.125 (MLT-025, VS-0.125), capacitors KT-1 (C2-C7 - in the first, C2, C5-C8 - in the second, C2, C3, C5-C7 - in the third), KM-4 or K10-7V (respectively C8-SYU; NW, C4, C9-C12, C15, C16; C2, NW, C5-C7) and K50-6 (the rest).

Figure 4. Drawing of the printed circuit board of the metal detector Fig. 1

Figure 5. Drawing of the printed circuit board of the metal detector Fig. 2

Figure 6. Drawing of the printed circuit board of the metal detector Fig. 3

To tune the generators in frequency, variable capacitors with a solid dielectric were used from small-sized transistor receivers "Mir" (in the first device) and "Planet" (in the second). Of course, it is possible to use any other capacitors that are suitable in terms of dimensions and values ​​of the minimum and maximum capacitances, including trimmers PDA-3 with a capacity of 25 ... 150 pF.

Variable resistors R5 (Fig. 1) and R2 (Fig. 3) are small-sized of any type.

In order to reduce the size of the mounted boards in height, the oxide capacitors C11 of the first metal detector and C9 of the third are installed parallel to the boards (their terminals are bent at an angle of 90°). The quartz resonator is mounted on a separate board made of fiberglass, fixed parallel to the main one from the side of the parts.

Coils L1 of metal detectors assembled according to the diagrams in fig. 1 and 2, wound on ferrite (600NN) ring magnetic cores of size K8X6X2. In the first, the coil contains 180 turns of PELSHO 0.14 wire, in the second - 50 turns of PELSHO 0.2. Winding in both cases is uniform around the entire perimeter of the magnetic circuit. In the first device, the coil is glued with BF-2 glue directly to the printed circuit board, in the second (due to lack of space) - to a small corner bent from sheet polystyrene, 1.5 mm thick and glued to the board with the same glue.

The search coil of each of the three metal detectors is wound in a ring bent from a vinyl plastic tube with an outer diameter of 15 and an inner diameter of 10 mm. The outer diameter of the ring of the first device is 250, the second and third are 200 mm, the number of turns is 100 and 50, respectively, the wire is PELSHO 0.27. After winding, the ring is wrapped with aluminum foil tape for electrostatic shielding (required to eliminate the effect of capacitance between the coil and ground). When winding the tape, it should be remembered that electrical contact between its ends is unacceptable (otherwise a closed loop is formed).

To protect against damage, the foil is wrapped with one or two layers of PVC insulating tape. A view of the finished coil, made by the described method, is shown in Fig. 7.

Figure 7. Metal detector coil

It should be noted that the diameter of the search coil can be either smaller or larger than the specified values. With its decrease, the "capture zone" narrows, but the device becomes more sensitive to small objects, while increasing it, on the contrary, the "capture zone" expands, and the sensitivity to small objects decreases.

To indicate the search in all devices, head phones TON-2 are used.

You can power the metal detectors from the Krona or 7D-0.115 battery, and if the dimensions do not bother you, then from two 3336 batteries or six 316, 332 cells connected in series.

Together with the power source, the mounted board and controls are placed in a small flat metal box (brass, tinned sheet 0.4 ... 0.6 mm thick) and the latter is fixed on a rod (see photo in the intro to the article) made of duralumin pipes with an outer diameter of 16 ... 20 mm (you can use an old ski pole). A search coil is attached to its opposite end. The angle between the plane of its turns and the axis of the rod is 55...800. For convenience of storage and transportation of the metal detector, it is advisable to make the search coil removable, providing for this purpose a suitable coaxial connector. It is desirable to connect the coil with the device board with a coaxial cable (its capacitance per unit length is smaller and more stable than that of a shielded wire).

Setting up a metal detector according to the scheme in fig. 1 is reduced to tuning its oscillators to a frequency of approximately 100 kHz. The tunable generator is tuned to this frequency by selecting capacitor C4, the exemplary one - by capacitor C2, having previously set the rotor of capacitor C1 to the middle position. The exemplary frequency is selected so that the frequency of the sound signal in the telephones is within 500 ... 1000 Hz.

Similarly, but at a frequency of about 300 kHz, the generators of the second device are tuned (tunable - by selecting capacitor C2, exemplary - by the variables C1 themselves).

The tunable generator of the third metal detector is tuned (selecting capacitor C2 with the middle position of the resistor R2 slider) to a frequency of 100 ... 200 kHz. The task is reduced to ensuring that, with the greatest possible frequency ratio of the exemplary and tunable oscillators, a loud difference frequency signal is obtained in telephones. The frequency of the tunable generator is controlled by a frequency meter at the output of the DD1.3 element or a wave meter brought to the search coil L1.

The frequency of the ZQ1 quartz resonator can be any within 0 5 .1.8 MHz, however, if it is more than 1 MHz, it is advisable to turn on the frequency divider on the K176 or K561 series chip between the exemplary oscillator (or rather, the output of the DD2.3 buffer element) and the mixer, reducing the reference frequency to 0.5...1 MHz.

R. SKETERIS. Panevezys, Lithuanian SSR

Many radio amateurs dream of making a metal detector with their own hands. With it, you can detect metal objects in the ground at different depths. On the Internet, you can find many photo metal detector circuits that are easy to use. Any novice radio amateur can make them.

Easy Assembly

For example, let's take a simple metal detector circuit. It belongs to the impulse type, but due to the simplicity of the design, it is not able to distinguish between types of metals. Therefore, it will not be possible to work with such a device in areas where non-ferrous metal objects are found.

How to assemble the device

To assemble a simple metal detector circuit with your own hands, you will need the following tools and parts:

• The presence of the KR1006VI1 chip, and the IRF740 transistor;
• The presence of a K157UD2 chip and a VS547 transistor;
• Copper conductor 0.5mm (PEV);
• NPN transistor;
• Case, and various materials for it;
• Solder, flux, soldering iron.

Other details are shown in the diagram. In order for the assembled circuit to be securely fixed, a plastic case should be prepared for it.

The bar can be made using a plastic tube of small diameter. A metal search coil will be installed in its lower part.

Beginning of work

The device circuit of a metal detector on transistors is a common option for many models. The assembly begins with the manufacture of the printed circuit board. Further, all radio elements are mounted on it exactly as shown in the diagram.

To ensure stable operation of the device, film capacitors are used in the circuit. This will allow you to use it without problems in cold weather.

Power type for the device

The device can operate from a voltage of 9-12 V. Due to its sufficient power, energy is intensively consumed. It is recommended to install up to 3 batteries and connect them in parallel circuit. You can use a small battery that has a charger. Due to its capacity, the metal detector will work longer.

Coil mounting

There are different types and schemes for the manufacture of metal detectors, but in the pulse version, inaccuracies are allowed in the installation of the coil. In the manufacture of the mandrel, winding up to 25 turns should be made, and the diameter of the ring is 1900-200mm.

All turns of the coil must be insulated with electrical tape. Reducing the number of turns to 22, and a mandrel diameter of 270mm will allow you to detect objects at a deeper location. The cross section of the wire on the coil is 0.5 mm.

When the winding is ready, it is attached to a strong case with sufficient rigidity, on which there should be no metal parts. Otherwise, they are able to shield the magnetic field, and the operation of the metal detector will be disrupted. The body can be made of wood or plastic, but so that it can withstand various impacts that can damage the coil.

The findings on it should be soldered to a conductor of several cores. The best option is a two-wire wire.

Mounting the circuit of a non-ferrous metal detector is a little more complicated, and high accuracy must be observed in the manufacture of the coil. The number of turns reaches 100 pieces, and a vinyl tube is used as a core. A foil is wound on top of the winding, which forms an electrostatic screen.

Instrument setup

If the installation of the circuit is done exactly, then the metal detector will not need additional tuning. Its sensitivity indicators will be maximum, but fine adjustment is possible through the variable resistance R13. It must be performed until rare clicks begin in the headphones.

If the setting fails, then the resistance must be replaced with R12. When the resistor adjustment is in the middle, this will be considered normal.

An oscilloscope is suitable for checking the device. It measures the frequency of the transistor T2, and the pulse should last up to 150 msec. The optimum operating frequency is up to 150 Hz.

How to use the device

Do not rush and start working immediately after turning on the metal detector. It should stabilize, so you need to wait up to 20 seconds. After adjusting the resistor accordingly, you can start looking for metal.

Note!

Photo of the metal detector circuit

Note!

Note!