A device that allows you to search for metal objects located in a neutral environment, for example, soil, due to their conductivity is called a metal detector (metal detector). This device allows you to find metal objects in various environments, including in the human body.
Largely due to the development of microelectronics, metal detectors, which are produced by many enterprises around the world, have high reliability and small overall and weight characteristics.
Not so long ago, such devices could most often be seen with sappers, but now they are used by rescuers, treasure hunters, public utilities workers when searching for pipes, cables, etc. Moreover, many "treasure hunters" use metal detectors that they assemble with their own hands .
Metal detectors on the market operate on different principles. Many believe that they use the principle of pulsed echo or radar. Their difference from locators lies in the fact that the transmitted and received signals operate constantly and simultaneously, in addition, they operate at the same frequencies.
Devices operating on the principle of "reception-transmission" register the signal reflected (re-radiated) from a metal object. This signal appears due to the impact on a metal object of an alternating magnetic field, which is 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:
At the same time, metal detectors of this class have certain disadvantages:
In other words, devices of this type must be configured by hand before operation.
Other devices are sometimes referred to as a beat detector. This name comes from the distant past, more precisely from the time when superheterodyne receivers were widely used. Beating is a phenomenon that becomes noticeable when two signals with close frequencies and equal amplitudes are summed. The beating consists in pulsing the amplitude of the summed signal.
The pulse frequency of the signal 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, the so-called difference frequency is isolated.
Such a scheme was used for a long time, but today, it is not used. They were replaced by synchronous detectors, but the term remained in use.
The beat metal detector works using the following principle - it registers the frequency difference from two generator coils. One frequency is stable, the second contains an inductor.
The device is set up by hand so that the generated frequencies match or at least are close. As soon as metal enters the coverage area, the set parameters change and the frequency changes. The frequency difference can be recorded in many ways, ranging from headphones to digital methods.
Devices of this class are characterized by a simple sensor design, low sensitivity to the mineral composition of the soil.
But besides this, during their operation it is necessary to take into account the fact that they have high energy consumption.
The structure of the metal detector includes the following components:
All devices included in the metal detector are waterproof.
This is the relative simplicity of the design and allows you to make metal detectors with your own hands.
The market offers a wide range of metal detectors 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.
The second parameter is the frequency of operation. The thing is that low frequencies allow the metal detector to see to a fairly large depth, but they are not able to see small details. High frequencies allow you to notice small objects, but do not allow viewing the ground to a great depth.
The simplest (budget) models operate at one frequency, models that are classified as average price levels use 2 or more frequencies in operation. There are models that use 28 frequencies when searching.
Modern metal detectors are equipped with such a function as metal discrimination. It allows you to distinguish the type of material located at depth. At the same time, when ferrous metal is detected, one sound will sound in the searcher's headphones, and another when non-ferrous metal is detected.
Such devices are referred to 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 able to detect 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.
There are many models of devices on the market for searching for metal in the ground, walls, etc. Despite its external complexity, making a metal detector with your own hands is not so 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:
The metal detector circuit is not complicated, and you can find it either in the vastness of the global network, 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. A simple metal detector can be assembled with your own hands using a soldering iron or another available method. The main thing at the same time, 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, a wire with a cross-sectional diameter of 0.3 mm is used, of course, this will depend on the selected circuit. By the way, the wound coil must be protected from the effects of extraneous radiation. To do this, it is screened with your own hands using ordinary food foil.
To flash the controller, special programs are used, which can also be found on the Internet.
If a novice "treasure hunter" has no desire to get involved with microcircuits, there are schemes 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 with your own hands. But before you start making it, you need to understand how a typical circuit works.
The scheme of a deep metal detector is not the simplest and there are several options for its execution. Before assembling it, it is necessary to prepare the following set of parts and elements:
Nominal parameters, quantity depend on the selected circuit diagram of the device. To assemble the above elements, you will need a soldering iron, a set of tools (screwdriver, pliers, wire cutters, etc.), material for making the board.
The process of assembling a deep metal detector is approximately as follows. First, a control unit is assembled, the basis of which is a printed circuit board. It is made from textolite. Then the assembly scheme is transferred directly to the surface of the finished board. After the drawing has been transferred, the board must be etched. To do this, use a solution that includes hydrogen peroxide, salt, electrolyte.
After the board is etched, holes must be made in it to install the circuit components. After the board has been tinned. The most important step is coming. Do-it-yourself installation and soldering of parts on a prepared board.
To wind the coil with your own hands, use a wire of the PEV brand with a diameter of 0.5 mm. The number of turns and the diameter of the coil depend on the chosen scheme of the deep metal detector.
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 the Android OS.
But in fact, after installing such an application, he will really be able to find metal objects, but only pre-magnetized ones. He will not be able to search and, moreover, discriminate against metals.
Under the name "Kid FM".
This device has a very important function, it has a selectivity of metals.
Kid FM determines the type of metal, Colored or black, which is indicated by a characteristic sound.
That is, on black metal it squeaks with one sound, and on non-ferrous metal with another.
Here is the schematic
The MD contains a minimum of details, because a microcontroller is used in its circuit, it is very easy to assemble, but its detection depth is not very good, from 3 cm to 10-12 cm, which is basically normal for such a simple device. The instrument has a ground balance button.
For assembly we need:
1) PIC12F675 or 629 (microcontroller)
2) Quartz 20MHz
Capacitors
3) 15pF-2pcs(ceramic)
4) 100nF-1pc (ceramic)
5) 10uF (electrolytic)
6) 100nF-2pcs (film) and no others
7) Speaker
8) Button
Resistors 470 Ohm and 10 KOhm
AMS1117 - 3.3 volt voltage regulator
The device is very simple and I decided to assemble it without any printed circuit boards. We take a piece of textolite or thick cardboard
To wind the coil, we take any pan or pot, and anything of a suitable diameter. I shook on the pan. The wire is preferably 0.3 mm, but I had 0.4 wound it.
Here's what should happen
For this metal detector, you need to connect headphones from the player, but I only had a small speaker, so the sound is not audible, it will be well heard with headphones.
You don’t need to configure anything, the circuit is simple and basically always works the first time (I always do it the first time)
Who does not have a programmer for flashing the microcontroller, please contact me to help with the already flashed ( [email protected]) or in a comment
HERE IS THE VIDEO OF WORK
Today, a very promising direction in search instrumentation is the development and production of pulsed metal detectors. Unlike conventional microwave metal detectors, pulsed metal detectors have a much greater search depth and work perfectly on soils with high mineralization, especially on sea beaches.
In addition to the fact that the pulse metal detector has the best search depth, it also has the highest sensitivity among all metal detectors. Thanks to these characteristics, the search for gold and historical artifacts becomes much more efficient. Significantly increase the chances of finding some valuable item of small size, lying at a certain depth.
Another indisputable advantage of the Minelab SDC2300 impulse metal detector is its versatility in working with any soil. Sometimes the increased mineralization of the soil creates certain difficulties for searching for any objects using a conventional metal detector. The impulse metal detector does not have such difficulties - it works perfectly both on any type of soil, or in the coastal zone, and in sea water.
I would also like to say that a pulsed metal detector is much more efficient than other types of metal detectors in the vicinity of antennas, power lines and other structures that create electromagnetic interference. The well-designed design of this instrument minimizes the effects of such interference.
When connecting deep coils, the impulse metal detector easily turns into a deep metal detector, which allows you to search for large metal objects at a sufficiently large depth. However, the search for small artifacts in this case becomes impossible.
Until recently, pulsed metal detectors had one significant drawback - they did not have a metal discrimination function. When searching for artifacts, it was difficult or almost impossible to determine what type of metal was in the ground without first digging it out.
However, technologies are developing more and more intensively every day, and now pulsed metal detectors have also received the metal discrimination function in their arsenal. This circumstance makes the impulse metal detector more preferable for searching for gold, compared to other metal detectors.
Thanks to the discrimination function, the Minelab SDC2300 pulse metal detector can now be configured to search for artifacts made from non-ferrous metals. This significantly expands the capabilities of the device and allows it to be used when searching for objects made of non-ferrous metals both in the forest, in the field, in mountainous areas, and in the coastal strip or in flooded areas.
If you have an interest in a pulse metal detector, you can buy it at the Treasure Detector store. Buying a pulse metal detector requires a careful study of all its technical characteristics.
There are several options for Minelab GPZ7000 Minelab SDC2300 devices. After reviewing all the characteristics you are interested in, you can ask clarifying questions to an online consultant right on the store page.
For impulse metal detectors, as well as for other types of metal detectors, we give a guarantee. All search equipment, including impulse metal detectors, has certificates of conformity and is delivered anywhere in Russia. All metal detectors in our store are from original manufacturers. We wish you happy shopping and successful searches.
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.
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.
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.
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.
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.
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 reviews 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.
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.
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.
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 small objects. 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.
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 losses and are capable of operating at 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.
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.
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.
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.
Coming to the moment of choosing a metal detector, you need to clearly understand what exactly you want to get as a result of your searches. This time will be spent for the pleasure of being in nature and the possible discovery of any finds, or you want to purposefully look for certain artifacts that relate to military topics or the search for coins, jewelry and other items reflecting the stages of historical development other than militaristic.
The amount of future investment in the purchased metal detector depends on the choice made at this stage.
Eight-segment metal discrimination scale on the Bounty Hunter Platinum display
So, if you want to find objects made of iron or alloys containing a significant part of it, then it makes sense to choose a metal detector based on the detection depth, because. the inclusion of the discrimination function directly affects this indicator, and not for the better.
If the purpose of the search is non-ferrous metals (copper, bronze, silver, gold) or products made from them, then the discrimination mode is your good helper, since it will allow you to configure the device to exclude iron-containing objects from the detection area. And this, in turn, will allow you not to dig dozens of extra holes, which will save your strength, nerves and time at the next exit.
Exclusion from the search for targets that are undesirable for detection based on their electrical conductivity.
Depending on the level of professionalism of the metal detector, the options for setting the discrimination of metals change. The closer the device is to the initial level, the more simplified this process and, quite logically, the setting itself is less accurate.
If the metal detector is equipped with a display, then it must have a visual image of the discrimination scale, which usually displays an indication of the object from 0 to 99. What does this mean? The closer the indicator is to zero, the lower the electrical conductivity of the detected object.
If we consider the electrical conductivity of pure metals, then the discrimination scale of the metal detector should look like this:
iron/nickel/zinc/aluminum/gold/copper/silver
This gradation is observed almost everywhere, but with a caveat - as a rule, not only the names of metals, but also products made from them are indicated on the scale. Such an approach is absolutely fair considering that in most cases for the manufacture of a particular item, whether it be jewelry, coins or beer caps, not refined metal is used, but its alloy. And, depending on which metal was used as a ligature (additive), the electrical conductivity of the product itself also changes.
For example, zinc, nickel, platinum, and copper are added to gold jewelry, depending on the production technology. The first three metals have electrical conductivity closer to iron, i.e. even less than that of aluminum, therefore, when gold jewelry is detected, a value between aluminum and iron will be displayed on the discrimination scale, respectively, the sound signal of the metal detector will be low.
If more copper was used in the manufacturing process than other ligatures, then the signal will be higher (subject to polyphony) and the indicator will show the presence of metal in the segment from aluminum to copper.
As a rule, budget metal detectors are able to separate metals only into non-ferrous and ferrous ( variable discrimination), as well as provide the user with the ability to search for all metals (all metal mode).
Higher-level devices have the ability to customize the metal detector to exclude from the search a group of metals with a certain conductivity ( selective discrimination). For example, a detector can exclude signals from iron, nickel and aluminum, but respond to targets from silver and copper.
For the convenience of users, manufacturers include pre-set discrimination modes in the metal detector settings, for example, "coins", "coins and jewelry", "relics", "all metals", which makes it easier for a novice treasure hunter to work with the device. After all, you can use such a metal detector on the principle of "turned on and went", initially without delving into the subtleties of the settings. And having studied its work in practice, already consciously, based on the goals of the search, create your own discrimination masks (unless, of course, such an opportunity is built into the purchased metal detector).
Conclusion
Summing up the conversation about metal discrimination, make a conclusion for yourself which finds will be the target of your search and decide whether it is worth overpaying for this feature or not. If it is still difficult to make a final decision, do not forget that the metal detector can always be switched to the "all metals" mode by turning off the discrimination function.
Good luck in your search!
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Rash 22.11.2018
Great explanation, thank you very much!
Eee 03.10.2018
Thank you. Och is intelligible.
Guest 02.12.2017
Really good article. And I didn’t think about additives (ligatures) in jewelry at all ... it seems that the metal detector needs to be reconfigured ....
