The dream of finding treasure is increasingly being replaced in our time by a more realistic program of searching for precious metals in a natural or artificial environment.
IN modern conditions it is very important to find and extract valuable materials, who turned out to be among the waste, or in another uncontrolled environment.
Equipment is an important component of such search technology.
Search and extraction of gold and valuable metals from waste, garbage, in the natural environment - part of the recycling strategy, technology efficient processing materials used, including .
Searching for them in the ground or in masses of industrial and other waste not only requires the use of equipment, but also stimulates its improvement. Are being created devices of different levels and specializations. There is interest in such equipment among amateurs and enthusiasts of searching for valuable metals.
A metal detector is the most important tool for manually searching for metals in a chaotic natural or artificial environment.
Using such a device, you can search not only for silver, but also for silver and other precious metals.
Device principle any metal detector based on electromagnetic effects.
Here's how it works typical technology metal search:
- Device creates an electromagnetic field.
- Metal an object, secretly located in a foreign environment, affects such a field when falls within its sphere of influence.
- Device detects the impact of an object on the electromagnetic field and signals this.
A large number of metal detector models operate precisely on this principle.
The technical differences of such equipment make it possible to obtain more full information about the fact of detection of a metal object, for example:
- estimate the mass of the find;
- obtain data on the shape, size and configuration of an object;
- specify the location, including depth.
There is a lot of information on the Internet about metal detectors of varying complexity and design. There you can also refresh your memory about the theory of the electromagnetic field, studied at school.
The simplest, primitive metal detectors (usually homemade designs for searching for gold, silver and other metals enthusiasts) collected from ready-made devices and products operating using electromagnetic effects.
Many are familiar with the primitive, but quite workable circuit of a metal detector, in which an electromagnetic field creates a pulse element of a conventional calculator.
Reaction generated field on 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 retain the logical basis of the technology in the form of three components:
- electromagnetic field generator;
- sensor of changes in this field;
- equipment for assessing detected anomalies, signaling this.
Devices of different levels of complexity and functional potential can be divided into groups. Classification based on professionalism and user specializations – one of the generally recognized:
- amateur equipment, assembled by hand and used as a hobby tool or by beginners in metal detecting;
- semi-professional equipment necessary for enthusiastic amateurs and fanatics;
- professional metal detectors for those constantly working in this field;
- special devices for metal detecting experts 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 gardening and country supply stores.
A device for searching and detecting metal is needed not only for recycling, but also for searching for artifacts and treasures. Numerous security systems for everyone well-known frames - one of the technology versions metal search. The settings of these frames are focused on searching for weapons and similar dangerous objects.
Coil
Very important node metal detecting equipment – reel or frame. This is most often a winding of a special configuration, the task of which is to form an electromagnetic field and capture 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 production of reels, frames of the most popular types are sold. The easiest way to make such a purchase is in an online store.
Many lovers make the coil frames yourself. This is done for reasons of cost savings or in the hope of obtaining a better-quality instrument of the author's design.
For this, improvised means are used– plastic products, plywood and even filling the assembly construction foam assembled winding.
The search operator or treasure hunter strives to find the most effective technique working with a metal detector, choosing the desired operating modes of the electronics and the correct techniques for manipulating the coil.
Electronic circuit
The logical element of a metal detector is an electronic circuit. She performs many functions:
- The first task of this component is in creating an electromagnetic signal of the desired format, which is converted into a field using a coil.
- Second task electronic circuit – analysis of field changes captured by the frame, their processing.
- The third task is giving an informing signal to the operator– sound, light, indications of indicators and instruments.
It is best if anyone who wants to assemble an electronic circuit has knowledge of amateur radio or electronic technology. Such a master can not only assemble the required diagram, 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 circuit.
How to make "Pirate" yourself?
One of the most popular models of metal detectors designed for homemade amateur production is the “Pirate”.
This name, containing abbreviated details of its device and the developers' website, wittily reflects the romance of searching for precious metals.
Here the 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" details available to everyone are used, Right assembled circuit fully operational.
Design and operating principle
The design and layout of the “Pirate” metal detector is traditional for equipment of this kind. It is a rod, at the lower end of which there is a coil, and in the upper part – electronic unit with battery.
The location of the electronic unit should leave room for comfortable holding of the rod by hand.
Some craftsmen prefer that sound signal The device was not supplied by a speaker, but by headphones. In this case, the headphone cable departs from the electronic unit.
The technology of operation of the device is pulsed. This allows us 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 technicians. This is why the transistor circuit is used less frequently.
Materials, parts and blanks
In addition to the details and precision indicated on the circuit diagram of the electronic unit, for assembly metal detector for gold and other metals you will need to prepare some materials and blanks:
- a ready-made board for assembling an electronic circuit or foil material for making it yourself;
- power source in the form of any combination of batteries or batteries with a total voltage of 12V;
- enamel wire with a cross section of 0.5 - 0.6 mm for making 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;
- quite durable plastic pipe for the rod;
- coil winding frame;
- consumables - solder, heat-shrinkable casing, electrical tape, screws and fasteners, adhesives and sealants.
It is best to make a printed circuit board for assembling an electronic circuit based on designs presented on the Internet.
Below is one of these samples, suitable for assembling electronics on microcircuits.
The manufacture of the board is carried out by amateurs of homemade electronics, and even then not all of them. Most people who want to create a metal detector themselves prefer to buy such a part.
To assemble the coil you will need a frame or frame, does not contain metal elements. An amateur craftsman can make such a frame from plywood, plastic, or select similar parameters from ready-made plastic products, for example, dishes. The frame can be purchased at finished form or made by yourself
Recommended coil parameters– 25 turns of enamel wire with a diameter of 0.5 mm on a mandrel with a diameter of 190-200 mm. An increase in 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.
The plastic frame for the coil is one of the most common metal detector parts on sale.
The technology for manipulating the coil is such that this very fragile unit can suffer from impacts from uneven ground, stones, and sharp objects. To avoid this the coil on the frame is covered from below with a plastic plate. This plate not only protects the reel, but also ensures that it glides through tall grass. The search becomes more intense.
Assembly procedure and design
To successfully assemble a metal detector It is best to follow this procedure:
- manufacture of printed circuit boards and assembly of electronic circuits;
- choosing a suitable plastic container for it and completing the assembly of the electronic unit;
- coil manufacturing;
- manufacturing a rod of a convenient shape and attaching an electronic unit and coil to it, making connections for an electronic circuit.
Although the order of assembly is not fundamental. For those who manufacture a device for permanent long work in the field of search for non-ferrous metals and subsequent recycling (processing for reuse), important factor is ease of use.
In this case, working out the shape of the rod and the layout of the main elements of the apparatus becomes key factor. Thus, a serious design phase appears in the creation of the device.
It is best to perform this stage of work using life-size modeling. Such modeling can be done using wooden parts suitable form, for example:
- shovel handle;
- plywood pieces of the desired shape;
- scraps from;
- temporary fasteners made from pieces of wire, nails and ropes.
Having made sure that the assembled model of the device will be sufficiently functional and convenient, you can begin the final assembly. Ready-made device, 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 sets details.
Purchasing such a kit allows you to significantly simplify the production 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:
- Manufacturing coils with unusual parameters– in size, from special materials, for example, twisted pair cable.
- Arrangement of additional functional systems, for example, indicating the degree of battery discharge.
- Manufacturing models for underwater work.
- Add-ons electronic circuit, allowing 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, basic advantage self-production of any products, relevant for a metal detector. Here are some others dignity for a homemade device:
- best match to search technology for beginners;
- the possibility of creating the device completely individual form, design and configuration;
- the pleasure of making an effective, efficient device yourself.
Like any amateur-made device, a metal detector not without some drawbacks.
Here are the features of the “Pirate” model that users note:
- energetic charge consumption power batteries;
- no discrimination, that is, precise sensitivity to ferrous, non-ferrous and precious metals;
- limited compared to expensive models sensitivity.
Despite its shortcomings, the Pirate model is very popular. This is explained by simplicity homemade and high performance of an inexpensive device.
Experts involved in the field of recycling believe that the metal detector does not have the ability to discriminate of great importance. All metals found are so valuable that recycling them is always justified. Focusing on finding gold requires not only equipment, but also considerable experience, accompanying knowledge and, of course, Good luck.
Video on the topic
The video presents detailed guide for making and assembling a metal detector “Pirate” with your own hands:
Conclusion
When the metal detector is ready, you can begin work. You need to be aware that not even the 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 seeker has a realistic understanding of search techniques.
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 of the technology in advance with such equipment - this is precisely the basis of its high-quality design.
The success of finding gold increases with experience. Here most important elements such experience:
- the correct choice of metal detector design and its high quality manufacturing with your own hands;
- ability the right choice search sites;
- ability to use the full potential of a metal detector;
- choice the right technology search in different conditions;
- modernization of the metal detector.
Properly assembled and debugged equipment will always help in the search for gold, and this valuable metal will definitely be found.
In contact with
A metal detector is electronic device for searching and distinguishing metals, metal objects that can be hidden at different depths under a layer of sand, earth, in the walls of rooms and various structures.
Schematic diagrams of metal detectors made on transistors, microcircuits and microcontrollers are given. A factory-made metal detector is a fairly expensive device, so self-production a homemade metal detector can save quite a bit of money.
The circuits of modern metal detectors can be built according to different operating principles; we list the most popular of them:
- Beat method (measuring changes in reference frequency);
- Induction balance at low frequencies;
- Induction balance on spaced coils;
- Pulse method.
Many novice radio amateurs and treasure hunters are wondering: how to make a metal detector yourself? It is advisable to start your acquaintance with assembling a simple metal detector circuit; this will allow you to understand the operation of such a device and gain first skills in searching for treasures and products made of multi-colored metals.
Now there is enough big choice multimeters, at very different prices. Now a radio amateur can not be limited to the modest set of functions of the “legendary” M-838. For a little more you can buy more modern device, which is also capable of measuring the frequency of alternating current...
0 329 0
The metal detector is designed to detect a metal object (a well cover, a piece of pipe, hidden wiring). The metal detector consists of a parallel voltage stabilizer (transistors V1 V2) at a high frequency generator (about 100 kHz) on transistor V4, an RF vibration detector (V5) and...
13 5435 6
The metal detector allows you to detect any metal object at a distance of up to 20 cm. The detection range depends only on the area of the metal object. For those for whom this distance is not enough, for example treasure hunters, we can recommend increasing the size of the frame. This should also increase the detection depth. The schematic diagram of the metal detector is shown in the figure. The circuit is assembled using transistors operating in...
9 4988 1
Circuit diagram of a homemade beat metal detector, which is built on five microcircuits. Finds a 0.25mm coin at a depth of 5cm, a pistol at a depth of 10cm, and a metal helmet at 20cm. The schematic diagram of a beat metal detector is shown below. The circuit consists of the following components: a crystal oscillator, a measuring oscillator, a synchronous detector, a Schmidt trigger, an indication device...
11 5122 4
The circuit shown in the figure is a classic metal detector. The operation of the circuit is based on the principle of superheterodyne frequency conversion, which is usually used in a superheterodyne receiver. Schematic diagram of a metal detector with an integrated ULF; it uses two radio frequency generators, the frequencies of which are 5.5 MHz. The first radio frequency generator is assembled on a T1 transistor type BF494, frequency...
5 5118 2
This metal detector, despite the small number of parts and ease of manufacture, is quite sensitive. It can detect large metal objects, such as a heating battery, at a distance of up to 60 cm, while small ones, for example, a coin with a diameter of 25 mm, can be detected at a distance of 15 cm. The operating principle of the device is based on a change in frequency in the measuring generator under the influence of nearby metals and. ..
19 5048 0
A simple compact metal detector is needed to detect various types of metal in walls under a layer of plaster. metal objects(e.g. pipes, wiring, nails, fittings). This device is completely autonomous, powered by a 9-volt Krona battery, consuming 4-5 mA from it. The metal detector has sufficient sensitivity to detect: pipes at a distance of 10-15 cm; wiring and nails at a distance of 5-10...
8 4915 0
Scheme of a small-sized, highly economical metal detector with good repeatability and high performance characteristics, using widely available and inexpensive parts. An analysis of most common circuits has shown that they are all powered from a source with a voltage of at least 9 V (that is, “Krona”), and this is both expensive and uneconomical. So, assembled on the K561LE5 chip...
18 5688 1
Continuous operation at maximum depth settings can help retrieve deep targets. Otherwise, it is not practical to adjust the depth. It is best to test the increase in detection depth in a specially prepared place in the field or on your own plot of land.
Here 9 tips on how to achieve maximum depth performance of a metal detector coil.
1. Sensitivity
Adjusting sensitivity is the most popular way to increase depth. Typically, as sensitivity increases, depth also increases. But keep in mind that there is also by-effect, since too high sensitivity can reduce the likelihood of identifying the target, as well as drive you crazy with constant, chaotic sounds.
2. Ground balance
Every modern metal detector usually has a ground balance function. Correctly identifying and installing it is a direct path to increasing depth. After all, a lot depends on the mineralization of the soil, including the depth at which you will detect targets.
3. Move the coil as close to the ground as possible
A simple calculation: if you can bring the coil closer to the ground by 1.5 cm, then the detection depth will increase by the same 1.5 cm. Sometimes this is enough to catch a weak signal from a coin. Sometimes grass makes it difficult to move the reel closer to the ground. In this case, take a larger and heavier reel; it will be easier for it to crush vegetation. However, take care of its additional protection.
4. Reduce discrimination
Very deep targets are often detected incorrectly by a metal detector. But you will never detect these many false positives if the level of discrimination is too high, for example, as with the Coins programs. Reducing discrimination to a minimum can lead to success. Maybe you'll unearth an ancient artifact rather than just another nail.
5. Elimination of interference
There is a lot of interference in civilized places, as well as near power lines and buried cables. Operating electrical appliances also emit quite a lot of noise. Usually in such cases the sensitivity is reduced, and this reduces the depth. Therefore, it is better to try to work away from interference. Also turn off your cell phone and remove all metal objects from your pockets. Don't wear shoes with metal elements. Do not fold the cables from the reel onto the reel itself.
6. Special settings and devices
Read the instructions for your metal detector inside and out. Your device may have some unique parameters that can help you better hear and see deep targets. Some detectors are specially designed to amplify deep but weak signals, for example, recently there has been some excitement among domestic search engines regarding the deep firmware of the AKA Signum MFT metal detector. Or also good result allows the use of deep nozzles. XP released one recently for Deus.
7. Large coil
Search coils large sizes provide greater detection depth and clearer target readings. Carefully! A large reel can be heavy. Therefore, it would be good to purchase a special unloader for the metal detector, which makes it easier to carry the device. Let us remember that a large coil cannot be effective in areas heavily littered with iron and on highly mineralized soils.
8. Experiment with wiring speed
For example, moving fast with the Fisher F75 gives you a better chance of finding deep targets than moving slowly. Again, refer to the user manual and tirelessly test to see what travel speed for your metal detector gives a deeper penetrating signal.
9. Wear headphones
If you use a regular metal detector speaker, then quite naturally you may simply not distinguish signals from deep targets. With headphones, you are distracted from external noise and pick up fast, weak signals. If you don’t want to use headphones for some reason, then try a series air tests and remember sounds for the most distant purposes. Sometimes tiny, unnoticeable changes in audio tone do not show up on the detector's display.
A device that allows you to search for metal objects located in a neutral environment, such as soil, due to their conductivity is called a metal detector (metal detector). This device allows you to find metal objects in different environments, including in the human body.
Largely thanks to the development of microelectronics, metal detectors, which are produced by many enterprises around the world, are highly reliable and have small overall and weight characteristics.
Not so long ago, such devices could most often be seen among sappers, but now they are used by rescuers, treasure hunters, and utility workers when searching for pipes, cables, etc. Moreover, many “treasure hunters” use metal detectors, which they assemble with their own hands .
Design and principle of operation of the device
Metal detectors on the market operate on different principles. Many believe that they use the principle of pulse echo or radar. Their difference from locators lies in the fact that the transmitted and received signals act constantly and simultaneously; in addition, they operate at the same frequencies.
Devices operating on the “receive-transmit” principle record the signal reflected (re-emitted) from a metal object. This signal appears due to the exposure of a metal object to an alternating magnetic field generated by the metal detector coils. That is, the design of devices of this type provides for the presence of two coils, the first is transmitting, the second is receiving.
Devices of this class have the following advantages:
- simplicity of design;
- Great potential for detecting metallic materials.
At the same time, metal detectors of this class have certain disadvantages:
- metal detectors can be sensitive to the composition of the soil in which they search for metal objects.
- technological difficulties in the production of the product.
In other words, devices of this type must be configured with your own hands before work.
Other devices are sometimes called beat metal detectors. This name comes from the distant past, more precisely from the times when superheterodyne receivers were widely used. Beating is a phenomenon that becomes noticeable when two signals with similar frequencies and equal amplitudes are summed. The beat consists of pulsating the amplitude of the summed signal.
The signal pulsation frequency is equal to the difference in the frequencies of the summed signals. By passing such a signal through a rectifier, it is also called a detector, and the so-called difference frequency is isolated.
This scheme has been used for a long time, but nowadays it is not used. They were replaced by synchronous detectors, but the term remained in use.
A beat metal detector works using next principle– it registers the frequency difference from two generator coils. One frequency is stable, the second contains an inductor.
The device is configured with your own hands so that the generated frequencies match or at least are close. As soon as metal enters the action zone, the set parameters change and the frequency changes. Frequency difference can be recorded different ways, ranging from headphones to digital methods.
Devices of this class are characterized by a simple sensor design and low sensitivity to the mineral composition of the soil.
But besides this, when operating them, it is necessary to take into account the fact that they have high energy consumption.
Typical design
The metal detector includes the following components:
- The coil is a box-type structure that houses the signal receiver and transmitter. Most often, the coil has an elliptical shape and polymers are used for its manufacture. A wire is connected to it connecting it to the control unit. This wire transmits the signal from the receiver to the control unit. The transmitter generates a signal when metal is detected, which is transmitted to the receiver. The coil is installed on the lower rod.
- The metal part on which the reel is fixed and its angle of inclination is adjusted is called the lower rod. Thanks to this solution, a more thorough examination of the surface occurs. There are models in which the lower part can adjust the height of the metal detector and provides a telescopic connection to the rod, which is called the middle one.
- The middle rod is the unit located between the lower and upper rods. Devices are attached to it that allow you to adjust the size of the device. On the market you can find models that consist of two rods.
- The top rod usually has a curved appearance. It resembles the letter S. This shape is considered optimal for attaching it to the hand. An armrest, a control unit and a handle are installed on it. The armrest and handle are made of polymer materials.
- The metal detector control unit is necessary to process the data received from the coil. After the signal is converted, it is sent to headphones or other display devices. In addition, the control unit is designed to regulate the operating mode of the device. The wire from the coil is connected using a quick release device.
All devices included in the metal detector are waterproof.
It is this relative simplicity of design that allows you to make metal detectors with your own hands.
Types of metal detectors
There is a wide range of metal detectors on the market, used in many areas. Below is a list that shows some of the varieties of these devices:
Most modern metal detectors can find metal objects at a depth of up to 2.5 m; special deep products can detect a product at a depth of up to 6 meters.
Operating frequency
The second parameter is the operating frequency. The thing is that low frequencies allow the metal detector to see to a fairly great depth, but small parts they are unable to see. High frequencies allow you to notice small objects, but do not allow you to view the ground to great depths.
The simplest (budget) models operate at one frequency; models that fall into the middle price range use 2 or more frequencies. There are models that use 28 frequencies when searching.
Modern metal detectors are equipped with a function such as metal discrimination. It allows you to distinguish the type of material located at depth. In this case, when ferrous metal is detected, one sound will sound in the search engine’s headphones, and when non-ferrous metal is detected, another sound will sound.
Such devices are classified as pulse-balanced. They use frequencies from 8 to 15 kHz in their work. Batteries of 9 - 12 V are used as a source.
Devices of this class are capable of detecting a gold object at a depth of several tens of centimeters, and ferrous metal products at a depth of about 1 meter or more.
But, of course, these parameters depend on the device model.
How to assemble a homemade metal detector with your own hands
There are many models of devices on the market for detecting metal in the ground, walls, etc. Despite its external complexity, making a metal detector with your own hands is not that difficult and almost anyone can do it. As noted above, any metal detector consists of the following key components - a coil, a decoder and a power supply signaling device.
To assemble such a metal detector with your own hands, you need the following set of elements:
- controller;
- resonator;
- capacitors of various types, including film ones;
- resistors;
- sound emitter;
- Voltage regulator.
Do-it-yourself simple metal detector
The metal detector circuit is not complicated, and you can find it either on the vast world wide web or in specialized literature. Above is a list of radio elements that are useful for assembling a metal detector with your own hands at home. You can assemble a simple metal detector with your own hands using a soldering iron or other accessible way. The main thing is that the parts should not touch the body of the device. To ensure the operation of the assembled metal detector, power supplies of 9 - 12 volts are used.
To wind the coil, use a wire with a cross-sectional diameter within 0.3 mm; of course, this will depend on the chosen circuit. By the way, the wound coil must be protected from exposure to extraneous radiation. To do this, shield it with your own hands using ordinary food foil.
To flash the controller firmware, special programs are used, which can also be found on the Internet.
Metal detector without chips
If a novice “treasure hunter” has no desire to get involved with microcircuits, there are circuits without them.
There are simpler circuits based on the use of traditional transistors. Such a device can find metal at a depth of several tens of centimeters.
Deep metal detectors are used to search for metals at great depths. But it is worth noting that they are not cheap and therefore it is quite possible to assemble it yourself. But before you start making it, you need to understand how a typical circuit works.
Scheme deep metal detector not the simplest and there are several options for its implementation. Before assembling it, you need to prepare the following set of parts and elements:
- capacitors different types– film, ceramic, etc.;
- resistors of different values;
- semiconductors - transistors and diodes.
Nominal parameters, quantity depend on the selected schematic diagram device. To assemble the above elements, you will need a soldering iron, a set of tools (screwdriver, pliers, wire cutters, etc.), and material for making the board.
The process of assembling a deep metal detector looks something like this. First, a control unit is assembled, the basis of which is printed circuit board. It is made from textolite. Then the assembly diagram is transferred directly to the surface of the finished board. After the drawing is transferred, the board must be etched. To do this, use a solution that includes hydrogen peroxide, salt, and electrolyte.
After the board is etched, it is necessary to make holes in it to install the circuit components. After tinning the board. The most important stage is coming. Do-it-yourself installation and soldering of parts onto a prepared board.
To wind the coil with your own hands, use PEV brand wire with a diameter of 0.5 mm. The number of turns and the diameter of the coil depend on the selected circuit of the deep metal detector.
A little about smartphones
There is an opinion that it is quite possible to make a metal detector from a smartphone. This is wrong! Yes, there are applications that install under Android OS.
But in fact, after installing such an application, he will actually be able to find metal objects, but only pre-magnetized ones. It will not be able to search for, much less discriminate against, metals.
A metal detector is used when searching for objects with certain electromagnetic characteristics, namely metals. IN professional activity This device is used by inspection services, archaeologists, geologists and professional treasure hunters. In addition, a metal detector is often used in construction, for example, to detect reinforcement, wiring and profiles in walls.
Professional equipment has a very significant drawback - very high cost, which varies depending on the detection depth, interface type and metal recognition function.
The need for a metal detector also arises among ordinary people. Often these are those who decided to try themselves as a treasure hunter. Unlike professionals, who are provided with equipment or provided by an organization, novice amateurs do not always want to purchase an expensive device. This is due to the fact that such a purchase will not be used for professional use and is unlikely to realize itself.
For an amateur who is just starting to work with these devices, a self-assembled metal detector may be suitable. Homemade devices are relatively easy to make; there are many on the Internet detailed instructions. Anyone can assemble a metal detector with their own hands if they have the desire and the required components for assembly; and their assembly can be done even by those who have little knowledge of radio installation. Homemade devices can have both relatively weak characteristics and not be inferior to expensive branded products. Before assembling the device, you need to know its structure and types.
In order to understand what kind of metal detector you need to assemble, you need to decide on the list of work to be carried out, as well as which metals will be the target of the search. Externally similar devices for searching for gold and construction work differ in design and technical specifications. The following general search device parameters exist:
Search discrimination can occur in three ways:
- Spatial, which indicates the location of the found object in the electromagnetic field zone, as well as its depth.
- Geometric, showing the size and shape of the found object.
- Qualitative, determining what properties the found material has.
Operating frequency range
Metal detectors operate in a certain frequency range:
- Ultra-low frequency, up to several hundred Hz. Powerful metal detectors that require high voltage, impressive dimensions, and computer signal decoding make these devices unsuitable for amateur use.
- Low frequency, up to several kHz. Quite simple circuits and design, good noise immunity and insensitive to the ground. They have penetration, depending on the supplied voltage, up to 5 meters. They react most acutely to ferrous metals and reinforced concrete structures.
- High frequency, up to tens of kHz. Possess more complex circuits, but are less demanding on coils. Relative noise immunity and detection depth of up to one and a half meters. They work very poorly in wet and mineral soils.
- Radio frequency, used to search for non-ferrous metals, such as gold. Detection depth less than a meter in dry soils, are very critical to the design and quality of the coils used.
Classification by search type
There are many search methods, but many of them are applicable only in professional activities, and are not feasible in homemade devices. More applicable at home include:
- Without receiver (parametric).
- On the beats.
- Accumulation phase.
- Transceiver.
Parametric metal detector
These devices do not have a receiving coil or receiver, and detection of an object occurs due to its influence on the generator coil; changes in its parameters, such as the frequency and amplitude of the generated oscillations, are recorded by different possible ways. They are quite easy to assemble and have relatively high noise immunity. They are often used as magnetic detectors due to their low sensitivity.
Transceiver device
The device consists of transmitting and receiving coils, an EM vibration transmitter, and can also be equipped with a discriminator that will detect only certain metals.
The coil creates an electromagnetic field; If there are materials in its zone that have an excellent electromagnetic field, the receiver picks them up and gives an audible signal about detection. If an object is detected that does not have electrically conductive properties, but has ferromagnetic characteristics, then it will distort the electromagnetic field due to shielding.
These devices achieve the best performance in their operating frequency range, but their independent production requires a high-quality system of coils, which must be ideally positioned relative to each other.
A transmit-receive metal detector with one coil is called inductive. Its creation is simpler due to the fact that there is no need to select coils, but it is necessary to separate the secondary weak signal relative to the emitted primary one.
Phase sensitive device
These metal detectors are presented as pulse detectors with one coil or devices with two coils, each of which is influenced by a separate generator.
In the case of a pulsed phase-sensitive metal detector, the emitted pulses upon collision with the desired metal are delayed, and during an increasing phase shift, the discriminator is triggered and sends a signal. The closer the device is to the object, the more frequent the signals become. The popular homemade metal detector “Pirate” with metal discrimination works on this principle.
The principle of operation of a device with two coils is based on the fact that the electromagnetic fields of the two coils are synchronized and work in time; and when the field is distorted, desynchronization occurs and the discriminator begins to emit signals. This type of device is easier to manufacture than a single coil device, but the depth of possible detection is reduced.
Based on the harmonic principle
IN this device Structurally there are two coils: working and supporting. The reference oscillating coil is small, protected from extraneous interference, or stabilized by a resonator. The frequency of the working search coil depends on the presence of the desired objects in the radiation zone.
Before starting the search, they are tuned to match the frequencies and, as a result, a single-tone sound. A change in tone means that metal objects enter the zone of the electromagnetic field, and the size and depth of the object are determined from the level of change.
Metal detector coils
The main requirement for quality homemade devices is competent manufacturing of the coil and its reliable shielding.
When creating a device, the device circuit is adjusted to the coil until optimal values. If the metal detector works with an incorrectly selected coil, it will have very poor performance. In this regard, when choosing an option for manufacturing, you need to carefully look at the description of the coil. If it is not complete enough, it is better to make another device.
The size of the coil is also important. Wide ones penetrate the ground deeper, but if large objects are detected, their signal will block potentially necessary small objects. Also, to increase detection depth, you need to have a wider coil.
It is common to use coils with a diameter of up to 90 mm when searching for profiles and fittings, up to 150 mm for small items, and diameters up to 600 mm for searching large-sized iron.
It would be ideal if the metal detector is designed to work with coils of different sizes.
Noise immunity
The reels catch well various types tips, and There are 2 common ways to increase noise immunity:
Baskets
These coils are available in flat and volumetric versions; they are stable, less sensitive to interference, and have high discrimination. For a beginner, it is easier to wind a flat reel.
Its mandrel can be computer disks, plates and saucers, and you can calculate the winding yourself. The volumetric option is to be wound without calculation using computer programs impossible.
Simple DIY metal detector
This version of a homemade metal detector consists of a signal decoder, a signaling device and a coil. To assemble it you will need:
- PIC12F675 chip or its analogs and programmer for firmware.
- Resonator at 20 MHz.
- Voltage stabilizer AMS1117.
- 15 pF and 100 nF ceramic capacitors, 10 µF electrolytic and 100 nF film capacitors.
- Resistors 470 Ohm, 10 kOhm.
- Sound emitter.
Soldering is carried out using a hinged or mounting method; a voltage of 9-12 V is required to power the circuit. The stabilizer controls the output 3.3 V.
The coil is wound on a 10 cm mandrel with a wire with a cross section of 0.3 mm. It is required to tightly wind 90 turns, and wrap the resulting structure tightly with tape and place it in a Faraday shield.
The result is a fairly powerful metal detector for deep searching, which can be set to discriminate: when detecting ferrous and non-ferrous metals, a sound of different frequencies will be emitted.
Professional metal detectors are often quite expensive and beyond the reach of amateurs. There are diagrams of metal detectors on the Internet; some of them can be assembled with your own hands, without any special radio installation skills or professional equipment. If desired, you can even assemble an underwater metal detector that will work equally both on land and in water.
In order for a self-assembled device to ideally meet all possible requirements, it is necessary to understand the design of the metal detector and decide on the type of search work that will be carried out with the device after its assembly. This will help you choose exactly the version of the metal detector that a novice treasure hunter needs.
