Devices capable of detecting metal objects in weakly conducting environments are called metal detectors, or metal detectors. They can be used to search for ferrous and non-ferrous metals. A homemade metal detector for coins is capable of detecting small items at a distance of 10 to 50 cm, and larger metals from 0.5 to 3 m.
The use of metal detectors has been known since ancient times, and a large increase in their production occurred at the end of the 60s. Thanks to progress and a variety of schemes, any novice radio amateur can make a metal detector with his own hands, without resorting to extensive knowledge in electronics. The main advantage of homemade metal detectors is low costs.
Let's assemble a simple metal detector that operates on two frequency generators - a beat metal detector. At the same frequency, the generators are synchronized, but when one of the metal coils enters the field, the frequency in one of the generators changes. As a result, the circuit reproduces the sound of the difference in frequencies of two generators in the dynamics.
To make a homemade metal detector, you need to divide the process into three stages - creating a design, implementing a circuit, and assembling it into a single whole. We will describe an approximate list of tools and materials that may be needed for these purposes. Further on in the article, we will explain in more detail: what a metal detector for gold can be assembled from, and what kind of material is best to use. Let's start by preparing a tool for beginning diggers. To work you will need:
Necessary materials:
Detailed instructions on selecting and searching for parts are described here.
First, you need to decide on the material and fastening of the components of the metal detector and find the necessary components.
As a barbell, you can use a crutch with an armrest, a fishing rod, a pipe made of cross-linked polyethylene or polyvinyl chloride (Fig. 2).
The coils and circuitry will be placed underneath on a stand attached to the rod. So it is important to consider the stiffness of the bar and its material. It is better to give preference to dielectrics, i.e. non-conducting electric current - plastic, wood, etc. It is necessary to make a handle to make it comfortable to hold the metal detector being manufactured. In the case of a crutch, it is not needed, but in another case, you can attach either a bicycle handlebar or another homemade structure.
The stand for the circuit and coils can be made from ordinary plastic. It is easy to trim and weighs little. You will need one bottom sheet, since access to the coils is required to adjust the device. To reduce vibration of the circuit with coils, it is advisable to choose stronger plastic.
After preparing the rod and stand, you need to connect them. You can use fasteners, but do not forget that for the circuit to work properly, you should not bring metal products closer than 30 cm. Therefore, we use good glue, for example, liquid nails. You can use other materials - it all depends on your abilities in plumbing and carpentry.
The wire for the coils must be insulated. Suitable enameled copper wire with a diameter of 0.5 - 0.7 mm grade PEV or PEL. The wire length is about 100 meters. An oil-based varnish is suitable for fixing parts.
The parts can be mounted using a hinged method on PCB or cardboard. For beginning radio amateurs, in specialized stores you can buy processed textolite from the factory or material with holes for parts. You can also make a board yourself from solid unprocessed PCB. To do this, you need to mark the location of the contacts of the radio components on the diagram, then separate the sections of the textolite with a knife and tin the pads and tracks (Fig. 3). We cut off the excess part of the PCB with a plastic saw.
To assemble a working metal detector, radio components can be found at home in old radio equipment, but it is advisable to purchase them in a store. Identical parts must be completely identical and preferably from the same batch. Table 1 provides a list of necessary parts and comments, the implementation of which will lead you to assembling a high-quality metal detector.
After finding all the necessary parts, you can easily assemble the metal detector at home.
Having considered the list of necessary materials and parts, we will answer in detail how to assemble a metal detector from them with your own hands.
To wind the coils, we use any round object with a diameter of 20–25 cm. The number of turns is 30. We bring out one end of the wire and wind it 10 turns, after which, without breaking it, we bring out the second end. We continue winding another 20 turns and bring out the third end. We make the wire leads with a margin of 10 to 20 cm. Remove the resulting winding from the object and wrap it tightly with electrical tape, leaving three wire leads (Fig. 5).
We perform the second coil in a similar way. For the greatest success, we make the coils as identically as possible, with a mirror image.
Let's start assembling the radio components. We arrange the parts on the board and carry out soldering according to the diagram in Figure 4. When using cardboard or material with holes, we connect the parts with insulated wires of any cross-section. When using prepared PCB, we perform soldering to the finished tracks. The circuit can be placed in a wooden or plastic box.
Solder the coil leads according to the diagram. We solder and bring out two wires with a connector for the battery.
We prepare a stand for the circuit and coils. We select the dimensions taking into account that the distance between the coils must be at least 10 cm, since the circuit and the attached rod must fit between them.
To properly secure the coils, temporarily attach the headphones to the circuit and insert the battery. By slightly moving the coils, we achieve silence in the headphones with single clicks or the highest possible, barely audible sound. We try to bring metal to one of the coils, if we hear significant changes, this indicates the functionality of the metal detector. We fix the coils and the board in this position. If possible, it is better to glue them immediately and then cover them with oil varnish.
For headphones, we make two holes in the rod - bottom and top. Using wire cutters, electrical tape and a soldering iron, we extend the headphone wire to the required length - from the circuit to the human ear area. You need to take growth into account right away. We stretch the wire inside the rod and solder it to the circuit.
We cut off the excess stand and attach the bar to it in a way convenient for you.
The most accurate setting is the absence of clicks in the headphones, and the presence of a barely audible high-frequency squeak.
Adjustment is carried out in three ways:
With good hearing and experience, you can use the manufactured metal detector as a simple metal detector with discrimination, that is, with recognition of types of metal.
If you have figured out how to make the simplest metal detector with your own hands, you can proceed with a small modernization without microcircuits in Figure 9. The list of parts is collected in Table 2.
The new circuit adds an RC circuit consisting of a resistor and a capacitor. It will allow you to achieve increased sensitivity.
Variable resistors have been added to adjust the circuit without touching the coils. This will seal the sensitive unit of the metal detector in a durable box that protects it from shock.
Instead of headphones, you can use a speaker with a capacitor to increase the volume slightly.
In this scheme, the coils are placed one on top of the other, as shown in Figure 10. Before fixing the coils, we adjust them by moving them.
When turned on, we set the variable resistors to the same position and by rotating we achieve precise adjustment. After that, all that remains is to take a metal detector and go in search of nuggets or metals. Tested in practice - if you search on any Russian beach, you can find gold and silver.
A small number of people believe that factory-made devices for detecting metal objects are significantly superior to home-made devices, but this is a mistaken opinion. If you properly make a metal detector with your own hands and configure it, it can surpass branded metal detectors. Which, in turn, will save a considerable amount of money. But in order to build a homemade product, you should know the principle of operation and design.
The device detects metal underground using an electromagnetic field created by a transmitter coil. It begins to interact with the object (almost all metals are conductive), resulting in the formation of an eddy current that vibrates the radio waves of the metal detector coil. Shielding on a computer will pick up interference even from metals that do not conduct electricity, but only if they have electromagnetic properties.
When the equipment begins to pick up interference, it the data is immediately sent to the control unit. This part of the detector produces an audible signal indicating that a find has been found. The sound may be strong or weak. A strong signal indicates that the object is shallow, and a weak signal, on the contrary. There may be a coin at a distance of 50 cm, its signal will be weak. And with the same level of sound alert, large objects in the form of a helmet, weapons, and so on can lie at a depth of 100 cm. This factor must be taken into account.
Some expensive factory models display the received data on a monitor; they are very difficult to build at home. The Pirate detector is the easiest to assemble. Therefore, using his example, you can analyze the process of assembling a homemade device.
If you still can’t make a metal detector at home, then you can go to the store and buy a branded device or order a homemade one from craftsmen who assemble at home. You can find craftsmen through friends or the Internet.
Attention! Beginners who take on assembling a metal detector with their own hands for the first time often get confused by the electronics. As a result, they give up this activity because formulas, diagrams and special terminologies scare them. To build a homemade device, it is enough to understand the essence of the system by plunging into school physics lessons.
One of the most important parts of the device is the board. In the future, all detector components will be attached to it. The most optimal method for creating a board is LUT (laser ironing technology). Manufacturing involves compliance with all stages, the implementation of which must occur in strict order.
A detailed description of assembling a circuit on a homemade metal detector or how to make a board from scratch:
Luding the board tracks is the last step. The entire surface is treated with LTI-120 solution.
The manufactured board must be inspected. You need to make sure that all the track lines are clearly visible and the holes are in their places. After that, all the necessary elements are soldered onto the made metal detector board:
The most difficult thing is to find the K157UD2 amplifier. Because it hasn't been produced for a long time. Therefore, it is preferable to look for modern analogues that match the characteristics of the Soviet version.
To make a coil, you need a frame with a cross-section of 20 cm. An average of 25 turns are wound on it, but the total number can be changed up or down. Craftsmen advise adjusting the amount of wire winding by testing the device on a coin. It may turn out to be either 23 or 26 wikis. This is the only way to determine the farthest detection distance of a small object. It is advisable to use PEV wire half a centimeter thick.
After the master has decided on the amount of wire, it should be wound tightly around the frame. Insulated tape is applied to all homemade coils. There is no need to make a thick protective coating; one layer is enough so that the turns are not visible. The work with the homemade coil can be considered complete.
In addition to the board and coil, you will have to supplement the metal detector with other necessary accessories that will significantly improve its performance. Experienced experts recommend equipping the device with the following devices:
Important! The entire skeleton and other parts of the metal detector should not be metal. Their presence can distort the electromagnetic field. It is better to give preference to plastic.
First of all, on the detector with potentiometers sensitivity is adjusted. You need to achieve uniform crackling. It is advisable to set it up on a small object. A DIY metal detector made at home should detect it at a distance of 30 cm. It will show a Soviet ruble at a depth of 45 cm. Larger objects are detected from a distance of 100 cm.
At very great depths, the device will not be able to find coins and similar small pieces of iron. Experienced treasure hunters are, of course, capable by sound, approximately understand the parameters of the detected object, but it is impossible to distinguish the type. In this case, a beginner will very often stumble upon nails and other unnecessary pieces of iron.
Making a metal detector with your own hands is not too difficult. Homemade models are great for training for novice treasure hunters. You can get a lot of experience and even an important find from them. In addition, you do not have to spend money on purchasing the device. And after honing your skills, you can buy a professional detector with a monitor that will even look for coins at great depths.
A metal detector is used to search for small metal objects in the soil. But a store-bought product of this kind is quite expensive. To assemble it yourself, it is enough to know the principle of its operation and have a little understanding of electrical engineering.
At the same time, the simplest scheme does not allow determining the type of metal; the discrimination function, in other words, determining the type of find, somewhat complicates the design of the metal detector, but at the same time significantly expands the owner’s capabilities when searching.
To assemble a metal detector with metal discrimination with your own hands, you need to have basic knowledge and be able to work with a soldering iron. The cost of a self-assembled device will be lower than that of a factory-made analogue.
Metal detectors generally operate on the principle of electromagnetic induction. The transmitting coil generates electromagnetic radiation that penetrates the ground. Reception - receives signals from metal objects located in the ground. Often the functions of both coils are combined into one - a transceiver search coil. The control circuit generates an audible signal indicating that a metal object has entered the search zone; in addition, a visual indicator in the form of a lamp or LCD panel can be used.
Metal detectors are usually assembled according to a classical design and consist of the following main parts:
All elements of the search structure are placed on a bar; the length of the bar is selected based on the anatomical characteristics of the owner.
A discriminator, in other words, a determinant, based on the properties of the object’s material, is usually built into the control circuit; its task is to more accurately determine the characteristics of the find based on disturbances in the electromagnetic field.
The generator creates an electromagnetic field with predetermined characteristics around the search coil. The shape of the field and its depth depend both on the characteristics of the generator and on the shape of the coil itself.
When searching, if there are no disturbances in the electromagnetic field, nothing happens. But when a conductive object enters the electromagnetic field zone, it creates Foucault currents. When a disturbance hits the receiver, it must determine the approximate type of object and transmit information about it to the alarm device. The same story happens when an object with ferromagnetic properties appears in the search field. The characteristics of the soil affect the search field, but at the same time, with the correct settings of the characteristics of the metal detector, more precisely the radiation parameters, this interference can be minimized.
Important! Metal discrimination is one of the functions of a metal detector, which allows you to determine which category a find belongs to. It works by separating the material of an object according to the conductivity of electromagnetic waves. This will eliminate various debris and ferrous metals from the search area.
There are several working circuits of a metal detector intended for self-assembly: from the simplest “Pirate” type to the more complex “Chance” type, with metal discrimination. The latter is worth talking about in more detail.
The main thing in any metal detector is the coil. You can use either a factory-made coil from a store or make it yourself. To work, you will need copper winding wire 0.67-0.82.
You can make a simple coil of 90 turns of winding wire for a 100-1200 mm mandrel, but with such a coil design, discrimination will not work correctly. Therefore, it is proposed to assemble a search coil from two windings: an external one with a diameter of 210 mm from 18 turns and an internal one with a diameter of 160 from 24 turns. For ease of manufacture, marking and winding of contours should be done on a plate made of non-magnetic material, for example, plexiglass or thick cardboard.
In addition, it is worth sealing the winding; for this you can use any non-magnetic materials, this will increase the resistance of the metal of the product to moisture.
We'll take the metal detector control unit from Andrey Fedorov. This scheme has already proven itself on the positive side and has been tested many times.
The printed circuit board can also be made independently: from textolite, with a foil pattern applied using the materials provided below. Usually, skills in working with printed circuit boards are sufficient for this. Drawing conductive paths according to a pre-made sketch is a fairly simple process. An iron or a hair dryer is sufficient for this purpose.
Its base is a microprocessor of the ATmega8 type, with a converter of the MCP3201 type. A microcontroller of this type is quite scarce, but despite this, it is sold in a number of online stores. Finding it and purchasing other components will not cause any special problems. Soldering of the control panel is carried out according to the diagram below.
When soldering, you need to carefully monitor the placement of parts and elements on the board. The circuit is quite complex, and the failure of one or two elements will throw all the work down the drain. Don't forget about safety precautions when soldering.
Important! It is worth clarifying that the circuit uses an ICL7660S voltage converter; the letter S indicates that this converter operates with voltages up to 12V. This is what you need to use; when using the ICL7660, the converter may fail due to overheating.
You can download a drawing of the printed circuit board and a full description of the assembly from this link www.miriskateley.com/.
To make a coil, a winding wire with a diameter of 0.6-0.8 mm is used; when winding, you need to carefully monitor its condition to prevent damage to the enamel coating. The base is a circle made of non-magnetic, electrically permeable material with a diameter of at least 250 mm.
A complete list of materials used and the possibilities of replacing them with analogues
| Detail | Analogue | Quantity |
|---|---|---|
| NE5534 | 1 | |
| Converter MCP3201 | 1 | |
| ICL7660s converter | 1 | |
| ATMega8 controller | 1 | |
| Zener diode TL431 | 1 | |
| Voltage stabilizer 78l05 | 1 | |
| Quartz at 11.0592 MHz | 1 | |
| Diodes 1N4148 | KD522 | 10 |
| Diode 1N5819 | KD510 | 1 |
| Diodes HER208 | HER207 | 2 |
| Transistors 2SC945 | 5 | |
| Transistors IRF9640 | 2 | |
| Transistors A733 | 2SA733 | 2 |
| Capacitors, ceramics | 13 | |
| Electrolytic capacitors of different ratings | 8 | |
| Resistors | 27 | |
| Buttons art. SWT5 | 6 | |
| LCD QC1602A | 1 |
The firmware is installed via a connection to the USB port of a personal computer. Programming is carried out using the “Gromov programmer”; for firmware you need to find on the Internet the free UniProf program from Mikhail Nikolaev.
The latest version of firmware can be downloaded here radiolis.pp.ua.
Any current source with a voltage from 9 to 12 V is used to power the circuit.
The metal detector is assembled on a rod; the control unit is conveniently placed in a housing made of high-strength plastic, on its upper part. The coil is fixed at the bottom of the device. To fix it on the rod, it will be enough to fix the coil wires on a non-magnetic base.
It should be noted that high-quality insulation of the wires and the entire control unit from moisture is necessary. The main use of this device is in the field, which is why this issue is so important.
A homemade metal detector of this type is a rather complex device, but at the same time, its assembled cost is somewhat cheaper than its industrially produced counterparts. This product is highly efficient, quite economical in energy consumption, but at the same time has all the necessary functions for finding treasures or metal objects. The discriminator is sufficient to determine metal-non-metal characteristics and identify non-ferrous metals. According to reviews, when using this type of metal detector, a small coin can be found at a depth of up to 20 cm, a steel helmet of the SSh-40 type can be found at a depth of up to half a meter.
A metal detector is an 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 making a homemade metal detector yourself 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:
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.
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If you are faced with the urgent question of how to make a metal detector with your own hands at home, now we will find the answer. Let's look at the step-by-step creation of three types of metal detectors with diagrams, videos and step-by-step photos.
Malysh FM is one of the simplest metal detectors available today. The circuit is perfect for creating a pinpointer.
Malysh FM works on the principle of a frequency meter (previously it was used in the Koschei FM MI). The circuit of the metal detector is simple; the search coil is also easy to make with your own hands at home. It is for this reason that Malysh FM has found popularity among radio amateurs, despite minor shortcomings, which we will discuss below.
The new idea that arose among the creators of Koshchei FM also had its pitfalls. The operation of the metal detector was unstable due to constant drift, and the search depth was relatively small. However, in Malysh FM they tried to eliminate these problems programmatically and something came of it.
Diagram of the Malysh FM metal detector
Note! The better the quality of the capacitors, the more stable the metal detector will work!
The board and firmware for the Malysh FM metal detector can be downloaded below.
Files for download:
The coil for the Malysh FM metal detector is as important as high-quality capacitors. Together with capacitors, it forms an oscillatory circuit with a frequency of 19 kHz.
The Malysh FM metal detector circuit can be used as a pinpointer or a beach metal detector.
Data for winding the coil: a wire with a cross section of 0.1–0.18 mm (95 turns) is used on a rim with a diameter of 70 mm.
The photo below is an example of commercially produced Malysh FM pinpointers:
Next, the turns are removed from the rim and tightly wound together with thread, then aluminum foil is wound onto the coil to shield the coil, and a screen break is made at the point where the ends of the coil come out (Gap without foil). Then tinned copper wire is wound into a spiral onto the foil, and we connect it with a cable to the minus on the metal detector board. To connect the coil to the metal detector board, a microphone wire (2 wires in a common screen) is well suited; we solder the wires to the ends of the coil, and “screen to screen”.
A self-assembled CHANCE metal detector with a coil with a diameter of 25 can find a wedding ring at a distance of 18 cm, and a helmet at a distance of 40–45 cm. The maximum search depth is 1 meter.
Metal detector circuit CHANCE
Diagram of control buttons for the CHANCE metal detector
The MI CHANCE circuit contains a microcontroller, so to successfully assemble it you will need an in-circuit programmer. The circuit also contains a number of rather expensive components: a screen, a processor and an ADC.
In terms of assembly itself, the device is no more complicated than Tracker PI-2 and Clone PI-W, and in terms of setup it is even simpler, since it does not even have a traditional trimmer for balancing the op-amp.
Particular attention should be paid to the MCP3201 ADC; only after purchasing it can you proceed to further assembly of the device, since it is very difficult to find.
According to the scheme - MCP3201, but there are also analogues - ADS7816, ADS7817, ADS7822, LTC1285, LTC1286, SP8528 (they may differ in some ways).
After this, the next important item is the LCD indicator, as the most expensive part, its price is about 10 dollars. Any indicators on the built-in HD44780 controller are suitable (almost all of them are exactly like this); they are produced by many companies, so it is very difficult to give specific markings. It is best to simply choose an LCD indicator with a built-in controller for two lines of 16 characters. Whether it supports the Cyrillic alphabet or not is not important. Whether it has a backlight or not is also not important if it is not planned to be used in the dark or in basements/catacombs. But in any marking of the required indicator there will be “1602” - indicating that this is a sign-synthesizing indicator with two lines of 16 characters each.
If you are holding such an indicator in your hands for the first time, it is better to “get to know it better” right away. It’s good if you find a datasheet for it, but you can do without it if you carefully examine it. We connect +5 V from an external source to pin 2 of the indicator, and the ground to pins 1 and 5. Usually, the holes and the screen of the indicator itself sit on ground, and the printed power conductors are wider than the signal ones - this will also help to understand it better and more correctly.
We connect pin 3 of the indicator to ground through a 22 kOhm trimmer resistor (as in the device diagram). Turn on and rotate this adjuster to achieve a beautiful display of the entire top line of the indicator. It is advisable to also understand the backlight - it is displayed on the opposite side of the indicator by two separate pins, and can be duplicated on pins 15 and 16 (usually). We find where the “plus” is, where the “minus” is, and try to power it from +5 V, preferably through a 200 Ohm resistor (as in the diagram). Now you are well acquainted with the indicator, you have adjusted the contrast and you can be sure that you will no longer have problems because of it.
Now, as for the rest of the configuration, from the op amp (according to the scheme it is OP37) so far only NE5534P has turned out to be working, which is much cheaper than the specified OP37 and more common. A positive voltage converter from +12 V to negative -12 V can be used without the letter S in the name. Instead of the field grass KP505 there is KP501A.
The process of assembling the CHANCE metal detector must begin with the manufacture of a printed circuit board. You can download a drawing of the printed circuit board and other materials for assembling the CHANCE metal detector with your own hands from below.
Files for download:
The assembled board of the CHANCE metal detector looks like this:
CHANCE 2D metal detector board
CHANCE 3D metal detector board
All firmware versions for download:
To flash the microcontroller firmware, set the configuration bits as in the figure below:
And this is what the assembled block looks like:
After connecting the coil, you can already fully test the metal detector. But to fully work with the metal detector, you should put it in the case and make a rod for it.
In operation, CHANCE showed itself to be a simple and reliable metal detector, but with discrimination, everything is not very rosy. In reality, the device only filters out small iron debris and small nails, but beer caps are already causing difficulties. Also, the device, like other pulse metal detectors, does not see gold chains well.
Video with the launch of MI CHANCE on the table:
Clone PI is a non-metal detection pulse metal detector that can handle a variety of coil sizes. When using a ring with a diameter of 20 cm, MI Clone can find a coin at a depth of up to 25 cm, and large metal - up to 1 meter.
The Clone is based on the circuit of the Tracker PI-2 metal detector with some changes made to it.
The Clone PI metal detector has the following differences from the original (Tracker PI-2 Metal Detector):
Clone PI metal detector circuit diagram
Attention: the latest firmware versions for the metal detector were released for the PIC18F252 microcontroller!
The Clone metal detector circuit contains several expensive elements: an LCD screen, an MCP3201 ADC and a microcontroller. Before you start making a metal detector, be sure to purchase an ADC, as purchasing one may be difficult!
Also, the metal detector circuit contains a programmable microcontroller, so to make it you will need a programmer with support for programming microcontrollers - PIC18F252 and the ability to use it.
On the screen, the Clone Pi metal detector displays the following information:
The assembly of the Clone PI metal detector, as mentioned above, should begin with the search and purchase of parts for the manufacture of a printed circuit board. After this, you can proceed to the direct process of manufacturing and assembly.
First of all, you need to etch the printed circuit board:
Clone PI metal detector circuit board
Then we carefully inspect the board to identify unsoldered areas and “sticks”. If everything is good, you can start programming the microcontroller.
Firmware, printed circuit board drawings and other materials that you may need when creating a Clone Pi metal detector with your own hands at home can be downloaded below.
Files for download:
After programming, we install the microcontroller on the board, and you can already see the first fruits of your labor.
It is better to supply power to the metal detector through a fuse (2–5 A). In case of short circuit or soldering error, it can save your board!
A simple search coil for the Clone PI metal detector can be made with your own hands from winding enamel wire with a diameter of 0.6–0.8 mm, winding 25 turns on a mandrel with a diameter of 25–27 cm. You can use a saucepan or other suitable round object as a mandrel.
Then we wrap the coil turns tightly with electrical tape or tape. To the ends of the coil we solder a twisted stranded wire with a cross-section of 0.75 mm and a length of 1–1.3 meters. For ease of use, protecting the coil from shock and giving it an aesthetic appearance, you can put it in the following housing:
