How to make a simple metal detector with your own hands - step-by-step instructions. Homemade metal detectors: simple and more complex - for gold, ferrous metal, for construction Schemes of super metal detectors all metals reviews
Even the most serious and respectable citizens feel a slight excitement when they hear the word “treasure”. We literally walk through treasures, of which there are immeasurably many in our land.
But how can you look under the soil layer to know exactly where to dig?
Professional treasure hunters use expensive equipment, the purchase of which can pay for itself after one successful find. Archaeologists, builders, geologists, members of exploration societies use equipment provided by the organization in which they work.
But what about novice treasure hunters on a budget? You can make a metal detector at home with your own hands.
To understand the subject, consider the design and operating principle of the device
Popular metal detectors operate using the properties of electromagnetic induction. Main components:
- transmitter – generator of electromagnetic oscillations
- transmitting coil, receiving coil (in some models the coils are combined for compactness)
- electromagnetic wave receiver
- decoder that separates the useful signal from the general background
- signaling device (indicator).
The generator, using a transmitting coil, creates an electromagnetic field (EMF) around it with specified characteristics. The receiver scans the environment and compares field performance with reference values. If there are no changes, nothing happens in the circuit.
- When any conductor (any metal) enters the field of action, the basic EMF induces Foucault currents in it. These eddy currents create the object's own electromagnetic field. The receiver detects the distortion of the basic EMF and gives a signal to the indicator (audio or visual alert).
- If the object being examined is not metallic, but has ferromagnetic properties, it will shield the underlying EMF, also causing distortion.
Important! There is a misconception that the soil in which searches are carried out should not be electrically conductive.
This is wrong. The main thing is that the electromagnetic or ferromagnetic properties of the environment and the search objects are different from each other.
That is, against the background of certain characteristics of the EMF generated by the search environment, the field of individual objects will stand out.
Types of metal detectors
Understanding the features of different circuits will help not only to choose a ready-made detector. If you decide to build a metal detector for coins with your own hands, you do not need to install a detector for water pipes or fittings in concrete.
You should initially know what the device is for, since universal metal detectors are expensive, both when purchased and when assembled yourself. In addition, a narrow-profile device is more compact and lightweight.
Main settings
- Search depth. Determines the penetrating power for standard primers: below this band the coil will not respond to artifacts.
- Coverage area: the wider it is, the less time it will take to “comb through”. True, selectivity and sensitivity are reduced.
- Selectivity: selecting the required object from a variety of objects. For example, when searching for gold jewelry on the beach, your device will not respond to steel hairpins or coins.
- Sensitivity: the higher it is, the more likely it is to find small objects. True, the coil reacts to various debris, such as nails or hairpins.
- Noise immunity. The detector sensor is affected by many extraneous factors: thunderstorms, power lines, mobile phones, etc. It is necessary to filter them out.
- Autonomy: this means both energy consumption and battery charge reserve.
- Discrimination is the ability to distinguish artifacts by type. Let's look at this parameter in more detail.
Indication of device readings is carried out using an LCD indicator (VDI scale, Amplitude scale (size, location of the object), battery voltage indication (battery charge level)) and sound signals of different tones. The heart of the metal detector is the already familiar Atmega8-16PI microcontroller in conjunction with an external ADC. The use of an external ADC is due to the expansion of the set of functions of the device - the introduction of such a set of functions without an external ADC is physically impossible due to the small internal resource of the microcontroller.
I will give some characteristics of the device. Sensitivity for 5kop USSR coin up to 25cm. Selection by metals under ideal conditions: the “blacker” the metal, the lower its conductivity, and the closer to the left edge of the VDI scale the readings will be; the more “colored” the metal is, the greater its conductivity; accordingly, the readings on the scale will be closer to the right edge (the readings on the scale depend on the choice of device firmware and may change). Discrimination function: turning on one of the four masks one by one, you can tell the device not to react to “ferrous” metals to the desired extent (up to complete elimination of the influence of ferrous metal). Barrier function: at 16 levels it helps to detach from the influence of “earth” and other external factors.
To repeat Chance, first of all, you need to visit the author’s page fandy.vov.ru, where circuits, firmware, configuration bits for flashing the microcontroller, a description of the operation of the buttons and other useful information are located. The main, rare and most expensive parts of the device are the ADC chip and LCD indicator. An analogue of the ADC chip (MCP3201) is the ADS7816 chip, for which the author wrote corrected firmware (0.8.4). The next important part of the metal detector is the LCD indicator. With all the variety and current abundance of such components, the most suitable, in my opinion, are reliable and fairly cheap indicators from Winstar, which are superior in price/quality ratio to indicators from the domestic manufacturer MELT. When purchasing an indicator, you should select it based on the following instructions: character-synthesizing indicator, 2 lines of 16 characters each, Cyrillic support (the ability to use the indicator in any other development), the presence of a built-in HD44780 controller. You can view and download datasheets and pinouts on the Winstar website. The archive also contains a list of parts.
The OP37 operational amplifier can be replaced with a cheaper and more common analog NE5534P. The ICL7660S DC/DC converter can, although not advisably, be replaced with a similar one without the letter S (with the letter S at 12 volts, without it at 10 volts, it will work, but with an overload). The microcontroller is our old friend Atmega8-16PI (Atmega8-16PU, Atmega8A-PU). The controller is programmed using a simple programmer, which was used when programming the microcontroller for the Clone device. Here are the device parameters and a step-by-step description of the programming process for this controller. The most important thing here is not to forget about the configuration bits! Archive for microcontroller.
The planar coil of the metal detector is made on a dielectric frame 4 mm thick and wound with wire with a diameter of 0.65 - 0.8 mm. The coil template is shown in the figure below. The device rod is manufactured using the technology described in the article. You can assemble a metal detector on the author’s printed circuit board or use a much easier to replicate (for beginners) board from DesAlex - see the drawing on the forum. I myself remade 5 of these coils - I changed the number of turns, the thickness of the frame from 2 to 6 mm. The best result was obtained on a 4mm frame, the number of turns is the same as the author’s, the inductance is 389uH. Experiments with home-winding/rewinding did not affect the final result (noted by many who repeated this device), that is, a spread of +-10% does not affect anything. Although each result will be different from the other (diameter of the wire, quality of the wire, presence of impurities, quality of winding, waterproofing of the coil (varnish, epoxy, paint)), the quality and length of the supply cable - everything affects the quality factor of the search element.
A correctly assembled device does not require adjustment and is fully operational! In conclusion, I would like to thank the author of the metal detector (AndyF) for the excellent pulse metal detector with discrimination, as well as DesAlex for the reliable printed circuit board, without which the device would not have received such widespread popularity among radio amateurs and outdoor enthusiasts, which is the search for historical relics! Material provided by Elektrodych .
Discuss the article METAL DETECTOR CHANCE
A metal detector is used to search for objects with certain electromagnetic characteristics, namely metals. In professional activities, 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 sell 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 detailed instructions on the Internet. 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 gold prospecting and construction work differ in design and technical characteristics. 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. They have 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. The detection depth is less than a meter in dry soils, which is 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 home-made 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 in various 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
This device contains 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 the quality of 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 are obtained. 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 coils catch various types of pickups well, 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.
Computer disks, plates and saucers can serve as its mandrel, and you can calculate the winding yourself. It is impossible to wind a volumetric version without calculations using computer programs.
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.
Instrumental search is simply enormously popular. Adults and children, amateurs and professionals are looking for it. They are looking for treasures, coins, lost things and buried scrap metal. And the main search tool is metal detector.
There are a great variety of different metal detectors to suit every taste and color. But for many people, buying a ready-made branded metal detector is simply financially expensive. And some people want to assemble a metal detector with their own hands, and some even build their own small business on their assembly.
Homemade metal detectors
In this section of our website about homemade metal detectors, I 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 or circuits with two transistors here. Since such metal detectors are only suitable for visually demonstrating the principles of metal detection, but 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 homemade metal detector is not much inferior to its factory-made counterparts. Basically, there are various schemes presented here pulse metal detectors And metal detector circuits with metal discrimination.
But to make these metal detectors, you will need not only desire, but also certain skills and abilities. We tried to break down the diagrams of the given metal detectors by level of complexity.
In addition to the basic data required to assemble a metal detector, there will also be information about the required minimum level of knowledge and equipment for making a metal detector yourself.
To assemble a metal detector with your own hands, you will definitely need:
This list will contain the necessary tools, materials and equipment for self-assembly of all metal detectors without exception. For many schemes you will also need various additional equipment and materials, here are just the basics for all schemes.
- Soldering iron, solder, tin and other soldering supplies.
- Screwdrivers, pliers, wire cutters and other tools.
- Materials and skills for making a printed circuit board.
- Minimum experience and knowledge in electronics and electrical engineering as well.
- And also straight hands will be very useful when assembling a metal detector with your own hands.
Here you can find diagrams for self-assembly of the following models of metal detectors:
 |
Principle of operation | I.B. |
| Metal discrimination | There is | |
| Maximum search depth | ||
| There is | ||
| Operating frequency | 4 - 17 kHz | |
| Difficulty level | Average | |
 |
Principle of operation | I.B. |
| Metal discrimination | There is | |
| Maximum search depth | 1-1.5 meters (Depends on the size of the coil) | |
| Programmable microcontrollers | There is | |
| Operating frequency | 4 - 16 kHz | |
| Difficulty level | Average | |
 |
Principle of operation | I.B. |
| 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 | |
It was developed on the basis of the already known device "Terminator Pro". Its main advantage is high-quality discrimination, as well as low current consumption. Also, assembling the device will not be expensive, and it can work on any type of soil.
Here are brief characteristics of the device
According to the principle of operation, the metal detector is also pulse-balanced.
The operating frequency is 8-15 kHz.
As for the discrimination mode, it uses two-tone voice acting. When iron is detected, the device emits a low tone, and if non-ferrous metal is detected, the tone will be high.
The device is powered from a 9-12V source.
There is also the ability to adjust sensitivity and there is manual ground adjustment.
Well, now about the main thing, about the detection depth of the metal detector. The device is capable of detecting coins with a diameter of 25 mm at a distance of 35 cm in the air. A golden ring can be caught at a distance of 30 cm. The device detects a helmet at a distance of about 1 meter. The maximum detection depth is 150 cm. As for consumption, without sound it is about 35 mA.
Materials and tools for assembly:
- mini drill (the author has a homemade one from a motor);
- wire for winding the coil;
- four-core shielded cable;
- soldering iron with solder;
- materials for the manufacture of the case;
- printed circuit board;
- all the necessary radio components and their ratings can be seen in the photo of the diagram.
Metal detector manufacturing process:
Step one. Board manufacturing
The board is made by etching. Next, you can drill holes, their diameter is 0.8 mm. For these purposes, the author uses a small motor with a drill installed.
Step two. Board assembly
Assembly must begin by soldering the jumpers. After this, you can install panels under the microcircuits and solder other elements. For quality assembly, it is very important to have a tester that can measure the capacitance of capacitors. Since the device uses two identical amplification channels, the gain along them should be as close as possible to the same value, that is, be the same. Both channels of the same cascade must have the same readings when measured by the tester.
You can see what the already assembled circuit looks like in the photo. The author did not install a unit that determines the degree of battery discharge.
After assembly, the board must be checked with a tester. You need to connect power to it and check all strategically important inputs and outputs. Everywhere the power supply must be exactly the same as in the diagram.
Step three. Assembling the coil
The DD sensor is assembled according to the same principle as for all similar balancers. The transmitting coil is designated by the letters TX, and the receiving coil by RX. In total, you need to make 30 turns of wire folded in half. The wire used is enameled, with a diameter of 0.4 mm. Both the receiving and transmitting coils are formed by double wires, resulting in four wires at the output. Next, the tester needs to determine the arms of the windings and connect the beginning of one arm to the end of the other, as a result, the middle terminal of the coil is formed.
To fix the coil after winding, you need to wrap it well with thread and then soak it with varnish. After the varnish has dried, the coils are wrapped with electrical tape.
Subsequently, a screen of foil is made on top; between the beginning and the end you need to make a gap of about 1 mm to avoid a short-circuited turn.
The middle TX pin must be connected to the board ground, otherwise the generator will not start. As for the average RX output, it is needed for frequency adjustment. After adjusting the resonance, it needs to be insulated and the receiving coil turns into a regular one, that is, without a lead. As for the receiving coil, it is connected instead of the transmitting coil and set to 100-150 Hz lower than the transmitting coil. Each coil must be configured separately; when tuning, there should be no metal objects near the coil.
To balance, the coils are shifted, as can be seen in the photo. The balance should be within 20-30 mV, but not more than 100 mV.
The operating frequencies of the device range from 7 kHz to 20 kHz. The lower the frequency, the deeper the device will go, but at low frequencies the discrimination becomes worse. Conversely, the higher the frequency, the better the discrimination, but the smaller the detection depth. The golden mean can be considered a frequency of 10-14 kHz.
To connect the coil, a four-core shielded wire is used. the screen is connected to the body, two wires go to the transmitting coil and two to the receiving coil.