Equipment and materials

To assemble a homemade metal detector with your own hands, you will need the following components and tools:

• Chip. Both domestic, type KR1006RVI1, and its foreign analogue are suitable ( NE 555)

• Copper wire for coil winding

• Transistors of various formats ( BC 547, IRF 740, NPN, etc.)

• Finished printed circuit board or material for its manufacture

• Plastic or metal tube long enough to be used as a barbell

• The material for all body elements is durable plastic

• Consumables: any suitable fasteners, electrical tape

• Equipment: soldering iron, screwdrivers

This is the minimum set, which will be enough to assemble a simple device. This device is perfect for beginner treasure hunters.

Assembling the device

To assemble the simplest metal detector, you need to go through several steps.

PCB assembly

Electronics are traditionally the most complex part of any device. In this case, it is impossible to do without microcircuits, so it would be logical to start the assembly with a printed circuit board.

For a simple metal detector there are two PCB options:

• Chip board NE 555 (or similar domestic

• Transistor board.

Even with self-assembly, printed circuit board It’s still better to buy it ready-made. They can be found in any radio electronics store. The fact is that even if the master decides to assemble a printed circuit board himself, to make it he will need to buy materials that are hardly possible to make himself, such as getinaks - pressed paper boards.

Installing electronics on the board

Next, the master’s task is to install all the electronic elements on the board. The main condition here is to strictly follow the electrical circuit diagram of the metal detector. The further operation of the entire device depends on the accuracy of soldering.

To increase the stability of the metal detector, it is recommended to additionally install film capacitors on the board. They have increased thermal stability. This is especially true for use in cold weather, for example, with frequent searches in the fall.

Power supply

Powerful circuit a homemade metal detector is provided by any power source with a total voltage of 9 to 12V. But it is believed that the sensitivity of the device is better when using a 12V power source. This can be either a battery or several batteries. You can even use unnecessary ones batteries from laptops.

It is worth noting that even with the simplicity of the circuit, the device ends up being quite powerful and consumes a significant amount of energy. During long-term searches, you should take care of the availability of spare batteries, and it is best to use rechargeable batteries, which will avoid troubles with the batteries draining at the most inopportune moment.

Coil assembly

Since the assembled device is a pulse device, the accuracy of the coil assembly is less important here. The best option is to use a frame with a diameter of about 200 mm. You need to wind 25 turns of copper cable. After winding is completed, the coil must be additionally wrapped with any electrical tape. This will ensure additional protection from moisture.

To make the coil more sensitive, you can increase the frame diameter to 250 mm, while simultaneously reducing the number of cable turns to 21-22. After winding and insulating the coil, it must be installed on a rigid base. It is extremely important that it is made of non-metallic material. Impact-resistant plastic can be used. Such a coil will become more sensitive to non-ferrous metal, and with minor additional modifications it will theoretically be able to produce signals from precious metals, not lying too deep in the soil.

Encapsulating the coil in a durable housing is very important because it is located at the very bottom of the boom and often comes into contact with the ground, low-growing plants, grass, rocks and debris. This way the coil is reliably protected from impacts.

The leads from the coil must be soldered to a wire, or better yet, to a twisted pair.

Device setup

If the assembly was carried out according to detailed instructions, then the metal detector does not need additional settings, since by default it will have the highest possible sensitivity. But if more is needed fine tuning, you can twist the resistor R 13, achieving rare single clicks in the device’s dynamics.

But if this effect can be achieved only in the extreme position, then it is better to change the resistor to R 12. Clicks in the dynamics during normal operation should occur in the middle positions. If you have an oscilloscope, this device can easily measure the frequency and speed up the setup process.

The frequency for normal operation should be approximately 130-150 Hz.

Working with a metal detector

Immediately after turning on, you need to wait a little (about 15 seconds) for the device to stabilize its operation. By adjusting the resistor R 13 until the desired state, you can proceed directly to search operations.

Make a metal detector at home

Not everyone knows how to make a metal detector with their own hands at home.The basis of the operation of any metal detectors is the transmission and response reception of electromagnetic waves. The key elements of this type of device are: two coils (sometimes combined into one). The first coil is transmitting, the second is responsible for receiving the response signal emanating from detected objects.

The metal detector works on the following principle:

Power magnetic rays emanating from the device pass through metal objects, which creates an additional (secondary) magnetic field. The receiving coil detects the appearance of such a field and sends information about it to the control unit, which activates the warning system.

Based on their operating principle, such devices can be divided into:

· Simple. The cheapest devices that work according to the banal but effective principle of “transmission-reception”.

· Induction. These are exactly the kind in which two coils are combined into one common one.

· Pulse. They work based on a pulse emanating from a transmitter. After releasing a pulse, it immediately turns off and turns on when it is necessary to generate a new pulse.

There is another classification of devices based on their technical features:

· Dynamic. A device that is simple in design and operation, continuously scanning the coverage area of ​​the created field. The key principle of working with such a metal detector is the need to constantly be in motion, otherwise the signal disappears. The disadvantage of such seekers is quite low level sensitivity.

· Pulse devices. Have increased sensitivity, however, they require experience and additional configuration skills. Sometimes such a device is equipped with several coils at once, each of which is applied to various types metals and soil in the area where work is carried out. Among metal detectors of this type, the most popular are electronic devices that operate at a low frequency level - around 3 kHz.

· Electronic. Such detectors are good for searching for large metal objects, having a good level of sensitivity. However, on the other hand, they can miss small artifacts, since they are often configured to ignore small signals, most often emanating from unnecessary objects, such as metal debris.

· Deep The detector is designed to search for objects located at significant depths underground. Such devices are capable of detecting a signal even at a depth of 6 meters, while others most often operate at a depth of no more than 3. This device operates on the basis of two coils, like others. But here their position relative to the earth's surface has been changed. One of them is located parallel to the ground, the second is perpendicular.

· Another option that is of less interest to search engines is stationary metal detectors. These are nothing more than frames that can often be seen at especially important objects: stadiums, metro stations. They are ways to calculate the presence of any metal products in bags and internal people, which pass through the installed frame.

The simplest of metal detectors, which base their work on the “transmission-reception” principle, also have a simple design and assembly principle, so these devices are best suited for manufacturing with my own hands. What is important here is only the competent selection of parts in accordance with the instructions, and the presence of minimal experience in working with radio electronics.

How to make a metal detector with your own hands

Making a metal detector from domestic parts for beginners is best considered on the basis of the “Pirate” model. This option has been in the top for a long time homemade metal detectors. It is widely in demand among amateurs self-assembly, and in its finished form it is a device with good indicators of search depth and accuracy. It allows you to detect objects at a depth of up to 1.5 meters, which can be called a good indicator for devices with such a simple design.

Among devices of this level there is another scheme based on frequency beats. But if you compare the characteristics of the “Pirate” with the devices in this diagram, the comparison will be in favor of the “Pirate”. In addition, the design of this metal detector is also easier to assemble and consists of fewer parts and components.

One of the possible disadvantages of this model is the lack of a discrimination function. Simple scheme a metal detector simply cannot provide the ability to connect a discriminator. But with experience, seekers learn to independently determine which metal produces a signal from field vibrations.

Metal detector device "Pirate"

This detector is a pulse type device. To understand how to assemble such a device yourself, you need to know how a metal detector works, and then you will need to purchase:

· Long plastic tube for a barbell. All other equipment will be attached to it. Well suited in this case water pipes from PVC.

· Material for the control unit housing. You can use any suitable size container made of durable plastic.

· Speaker. Anything, for example, a small Chinese portable radio, will do. The main condition is a resistance level from 8 to 50 Ohms.

· Headphones with jack mini-jack (3.5 mm ). Any headphones from your phone will do, mp 3-player or any similar device

· Copper cable on reel

· Electrical tape

· Transistors of various types: BC 547, IRF 740 and BC 557

· Two microcircuits: K157UD2 and NE 555

· Capacitors. It is better to use ceramic and film.

· Electrolytic capacitors, 5 pieces in total.

· Resistors of various resistance levels

“Pirate” is a metal detector based on two microcircuits. This is where the chip is used NE 555 or its domestic equivalent.

The operation of the device begins with a comparator. One of its outputs is connected to the generator (creating the electromagnetic field), the other to the receiving coil, and the third to the speaker for sound signaling.

When metal objects are detected within the created field, a signal about this from the receiving coil is sent to the comparator, and then to the speaker, which emits a corresponding sound alarm.

The finished assembled board, with the elements placed on it, is placed in a regular junction box. You can make it yourself from durable plastic, or you can buy it at any radio equipment store.

If a standard device is not enough, then there is an option to make a more advanced model for gold. The power of a device assembled according to a conventional circuit is not enough to react to gold and objects made from it, so it is easy to find an improved circuit on the Internet.

Can parts from a radio be used?

To create a signal in this model, transistors of the KT-361 and KT-215 samples are perfect. These are USSR-style parts and can be found in any old radio, or in any radio equipment from those times.

Build the Pirate finder circuit board?

You can make a printed circuit board for such a device yourself, but you won’t be able to do it from scrap materials. For production you will need a sheet special material– getinaxa. It consists of pressed slabs of thick paper impregnated with epoxy resin. Additionally, it must be covered with a special copper foil, which is used in electrical engineering.

You need to transfer all the connecting elements to such a board, mark the places for fastenings and carefully drill holes in them. All tracks must be coated with a special protective varnish, and as soon as it dries, the board must be immersed in a chlorine solution. This gives additional protection to areas where the protective layer of copper foil is thinnest.

Coil assembly

As a base, you need a ring made of any non-metallic material with a diameter of about 200 mm. Even a wooden hoop may work. Copper wire is wound onto the selected base, approximately 30 turns. To increase sensitivity, it is necessary to increase the ring diameter to 250-260 mm, and reduce the number of turns to 20-22.

It is convenient to wind on a pre-prepared board or any flat surface. The distance between the turns must be maintained approximately equal to the diameter of the base. In several places, for reliability, it is necessary to additionally strengthen the coil winding with electrical tape.

The coil is ready, it can be connected to the detector and tested for performance.

Also, the coil can be assembled from a minimal set of available tools in just a few minutes. To do this, in addition to a twisted pair of 2.5 mm cable, you will need a minimum set of tools: a soldering iron, a multitester, a sharp knife and some solder.

The procedure in this case is as follows:

· First, you need to twist the wire into two skeins, leaving about 10 cm on both sides.

· Then, clean the winding, freeing the cable cores for connection.

· Connect the wires according to the diagram, for reliability, solder them with a soldering iron and apply solder.

· Test the presence of a signal using a multitester; attach the ends of the winding to a multi-core cable with a soldering iron.

Assembling the “Pirate” metal detector from ready-made parts

Once all structural elements are ready, full assembly can begin. All parts are attached to a fairly long rod. A comfortable rubber handle is attached to the top, a control unit enclosed in a plastic case is located just below, and a coil is located at the very bottom. If everything is done correctly, no mistakes were made when assembling the elements - the device is ready for use, no additional manipulations will be necessary.

Anyone can assemble such a device, even those who are completely far from electronics, you just need to solder all the parts as in the diagram. The metal detector consists of two microcircuits. They do not require any firmware or programming.

Power supply is 12 volts, you can use AA batteries, but it’s better to use a 12V battery (small)

The coil is wound on a 190mm mandrel and contains 25 turns of PEV 0.5 wire

Specifications:
- Current consumption 30-40 mA
- Reacts to all metals, no discrimination
- Sensitivity 25 mm coin - 20 cm
- Large metal objects - 150 cm
- All parts are inexpensive and easily accessible.

List of required parts:
1) Soldering iron
2) Textolite
3) Wires
4) Drill 1mm

Here is a list of required parts

Diagram of the metal detector itself

The circuit uses 2 microcircuits (NE555 and K157UD2). They are quite common. K157UD2 - can be picked out from old equipment, which I did with success

Be sure to take 100nF film capacitors, like these, take the voltage as low as possible

Print out the board sketch on plain paper

We cut a piece of textolite to its size.

We apply it tightly and press it with a sharp object in the places of future holes.

This is how it should turn out.

Next, take any drill or drilling machine and drill holes

After drilling, you need to draw tracks. You can do this through, or simply paint them with Nitro varnish with a simple brush. The tracks should look exactly the same as on the paper template. And we poison the board.

In the places marked in red, place jumpers:

Next, we simply solder all the components into place.

For K157UD2 it is better to install an adapter socket.

To wind the search coil you need a copper wire with a diameter of 0.5-0.7 mm

If there is none, you can use another one. I didn’t have enough varnished copper wire. I took an old network cable.

He took off the shell. There were enough wires there. Two cores were enough for me, and they were used to wind the coil.

According to the diagram, the coil has a diameter of 19 cm and contains 25 turns. Let me immediately note that the coil needs to be made of such a diameter based on what you will be looking for. The larger the coil, the deeper the search, but a large coil does not see small details well. The small coil sees small details well, but the depth is not great. I immediately wound three coils of 23cm (25 turns), 15cm (17 turns) and 10cm (13-15 turns). If you need to dig up scrap metal, then use a large one; if you are looking for small things on the beach, then use a smaller reel, but you’ll figure it out yourself.

We wind the coil on anything of suitable diameter and wrap it tightly with electrical tape so that the turns are tightly next to each other.

The coil should be as level as possible. The speaker took the first one available.

Now we connect everything and test the circuit to see if it works.

After applying power, you need to wait 15-20 seconds until the circuit warms up. We place the coil away from any metal, it is best to hang it in the air. Then we begin to twist the 100K variable resistor until clicks appear. As soon as the clicks appear, turn it reverse side, as soon as the clicks disappear, that’s enough. After this, we also adjust the 10K resistor.

Regarding the K157UD2 microcircuit. In addition to the one I picked out, I asked one more from a neighbor and bought two at the radio market. I inserted the purchased microcircuits, turned on the device, but it refused to work. I racked my brains for a long time until I simply installed another microcircuit (the one I removed). And everything started working right away. So this is why you need an adapter socket, in order to select a live microcircuit and not have to worry about desoldering and soldering.

Purchased chips

Today there are a large number of ways to make a metal detector at home completely independently, without the help of specialists. Some of them require certain knowledge of physics, as well as skills in working with electrical and radio devices. Others do not require any special skills, and any beginner can assemble a metal detector at home with their own hands.

How to make your own metal detector from disks

It’s quite easy to make a metal detector at home with your own hands. using two discs - CD and DVD. This method is very simple and does not require any complex components. All you need for this is:

• CD and DVD disc. It is advisable to take double-sided ones, then the sensitivity of the metal detector will be much higher.
• Any calculator you have at hand, you can take the simplest and cheapest one
• headphones
• crown size battery
• glue and tape

Sequence of actions

The metal detector is ready you can start testing it. For ease of use, you can attach a comfortable handle to the metal detector. To search for coins and metal in the ground, the power of such a device will not be enough, but in the house it can always be useful. For example, to search for hidden wiring, a walled-up wall, or to find a metal profile under a sheet of drywall.

Metal detector made from a radio and calculator

In order to make such a metal detector, the following things are needed:

1. Empty CD box
2. The simplest and cheapest calculator
3. Radio receiver operating on AM frequency
4. Double-sided tape or tape
5. Nails
6. Wooden mop stick

Assembly order

Device assembly sequence next.

Thus, you can assemble a metal detector at home with your own hands, even without special knowledge and skills. But it should be borne in mind that such metal detectors not suitable for serious searches metal objects underground, because their range of action is small. For complex tasks you should try to assemble a “butterfly” or “terminator” type device. On the one hand, if everything works out, you can save a good amount of money, but on the other hand, according to experts, such homemade metal detectors don't always work as intended.

Many people unreasonably believe that homemade metal detectors are inferior in many respects to branded samples produced at the factory.

But in fact, structures that are correctly assembled with your own hands sometimes turn out to be not only better, but also cheaper than “factory” competitors.

Worth knowing: most treasure hunters and local historians to save money cash, try to choose the cheapest options. As a result, they either assemble metal detectors themselves or purchase homemade custom devices.

Beginners, as well as people who do not understand electronics, are at first intimidated by the abundance of not only special terminology, but also various formulas and circuits. However, if you delve a little deeper, everything immediately becomes clear, even with the knowledge gained in school physics lessons.

Therefore, it is worth, first of all, to understand the principle of operation of a metal detector, what it is and how you can assemble it yourself at home.

How it works

The operating principle of this device is to use electromagnetic field. It is created by the transmitter coil and after a collision with an object that conducts current (and this is most metals), eddy currents are created that introduce distortion into the EPM of the coil.

In cases where the object is not electrically conductive, but has its own magnetic field, the interference it creates will also be caught due to shielding.

After this, changes in the electromagnetic field are sent directly to the control unit, which emits a special sound signal to notify that a person has been found, and in more expensive models displays data on the display.

It is worth examining how such devices are created following the example of a “Pirate” type metal detector.

Metal detector "Pirate"

Making a printed circuit board with your own hands

First you need to create a printed circuit board, where all the nodes of the metal detector will be located in the future. The best method is laser-iron technology or simply LUT.

To do this, it will be necessary to perform the manufacturing steps in the following sequence:

1. First, it is necessary, using exclusively a laser printer, to print the corresponding diagram created through the Sprint-Layout program. It is best to use light weight photo paper for this.
2. We prepare the PCB workpiece, first sand it, and then clean it with a solution. It should have dimensions 84x31.
3. Now on top of the blank we place photo paper with the diagram on the front side on which it was printed. Cover with an A4 sheet and begin ironing with a hot iron in order to transfer the marking scheme to the textolite.
4. After fixing the circuit from the toner, we place it all in water, where we carefully remove the paper with our fingers.
5. Next, if there are smeared areas, we correct them using a regular needle.
6. Now the board needs to be placed in the solution for several hours copper sulfate(ferric chloride can also be used).
7. The toner can be removed without any problems with any solvent, such as acetone.
8. We drill holes for later placement of structural elements (the drill must be very thin).
9. The last stage is to lay out the board tracks. To do this, a special solution “LTI-120” is smeared on the surface, which needs to be spread over the solder of the soldering iron.

Installing elements on the board

This stage of creating a metal detector consists of installing all the elements on the created board:

1. The main microcircuit is the domestic KR1006VI1 or its foreign analogue NE555. Please note that before installation, a jumper must be soldered under it.
2. Next, a two-channel amplifier K157UD2 is installed. You can buy it or take it from Soviet tape recorders.
3. After this, 2 SMD capacitors are mounted, as well as one resistor type MLT C2-23.
4. Now you need to solder two transistors. One must be NPN structure, and the other PNP. It is advisable to use BC557 and BC547. However, analogues will also work. As field effect transistor It is recommended to take IRF-740 or other options with similar characteristics.
5. The capacitors are installed last. They should be taken with a minimum TKE indicator, which will increase the thermal stability of the entire structure.

Please note: The hardest thing will be to get the K157UD2 amplifier out of this circuit. The reason is that it is already an old chip. That is why you can try to find similar modern options with similar parameters.

The creation of a homemade coil is made on a frame with a diameter of 20 cm. The total number of turns should be approximately 25 pieces. This indicator is based on the fact that PEV wire is used, which has a diameter of 0.5 mm.

However, there is a certain peculiarity. The total number of turns can be changed up or down. To find the most optimal option, you need to take a coin and check in which case there will be the longest distance to “catch” it.

Other elements

A signal speaker can be used taken from a portable radio. It is important that it has a resistance of 8 ohms (Chinese options can be used).

To carry out the adjustment, you will need two potentiometer models of different power: the first is 10 kOhm, and the second is 100 kOhm. To minimize the influence of interference (it will be difficult to eliminate it completely), it is recommended to use a shielded wire that will connect the circuit and the coil. The metal detector's power source must be at least 12 V.

When the entire structure has been tested for functionality, it is necessary to make a frame for the future metal detector. However, here we can only give some recommendations, because everyone will create it from the items at hand:

• to make the bar more convenient, it is worth purchasing 5 meters of ordinary PVC pipe (which are used in plumbing), as well as several jumpers. It is worth installing a special palm rest at its upper end to make it more comfortable to hold. For the board, you can find any box of the appropriate size that needs to be mounted on the rod;
• To power the system, you can use a battery from a regular screwdriver. Its advantages are low weight and high capacity;
• When creating the body and structure, keep in mind that there should not be any unnecessary metal elements in them. The reason is that they significantly distort the resulting electromagnetic field of the future device.

Checking the metal detector

First of all, you need to adjust the sensitivity using potentiometers. The threshold will be a uniform, but not very frequent, crackling.

So, he will have to “find” a five-ruble coin from a distance of approximately 30 cm, but if the coin is the size of a Soviet ruble, then from about 40 cm. He will “see” large and voluminous metal from a distance of more than a meter.

Such a device will not be able to search for small objects at significant depths. In addition, he will not be able to distinguish between the size and type of metal found. That is why, while searching for coins, you may come across ordinary nails.

This model of a homemade metal detector is suitable for people who are just starting to master the basics of treasure hunting or do not have the necessary funds to purchase an expensive device.

Their this video You will learn how to make a homemade metal detector:

Hello readers! Today I want to talk about how to assemble a metal detector with your own hands. When you really want to buy something, but there is no money for it, you have to postpone the purchase until later or take out a loan. Credit is expensive. And the thought arises in my head: “If only I could find a treasure.” Which one? That's right, a metal detector. This article will tell you how this device works and what parts are needed to assemble it.

The design of metal detectors consists of the following main elements:

1. The coil receives and transmits an electromagnetic signal, scanning the surface with the desired metal.
2. The control unit processes the signal received from the coil, notifies the user with a graphic or sound signal, and also allows you to manually configure the operating modes of the detector.
3. The lower rod fixes the reel and adjusts its angle.
4. The middle rod is an intermediate link between the lower and upper rods and allows you to adjust the height of the metal detector.
5. Upper rod. The control unit is located here, as well as a comfortable handle with an armrest so that the user’s hands do not get tired from holding the metal detector for a long time.

The metal detector emits an electromagnetic field through a coil. When metal or any other conductive material is in this field, the field is distorted and weakened. The control unit detects this and sends a signal.

More electrically conductive non-ferrous metals distort the field emitted by the detector more than ferrous metals.

Therefore, sensitive electronic circuits allow you to create devices with metal discrimination that can distinguish non-ferrous metal from ferrous metal.

Types of metal detectors

Metal detectors are divided into:

• induction;
• pulse;
• phase sensitive;
• parametric.

What types can you make at home with your own hands?

Parametric and phase-sensitive detectors are well suited for homemade products. They are easy to make, and the parts for them cost mere pennies. To assemble it yourself, it is enough to have basic knowledge of radio engineering.

Metal detectors with phase accumulation are much more sensitive than parametric ones. They have good discrimination and can find even small jewelry, making them a favorite tool for beach gold diggers. On dry sand it is possible to find earrings and rings at a depth of up to 38 cm.

Basic parameters

Search method

Induction metal detectors (MD) consist of a transceiver inductor coil.

When the emitted signal hits a metal object, it is reflected back and recorded by the receiver. These devices are quite simple to make with your own hands, but their sensitivity greatly depends on the type of soil and the quality of the coil.

Pulsed MDs excite eddy currents in the search zone and measure the secondary damped electromagnetic field. The sensitivity of these devices is higher and does not depend on the type of soil. However, they consume a lot of electricity, which does not allow them to work in autonomous mode for a long time.

Phase-sensitive MDs can be:

1. Impulse. The receiver and transmitter here are one and the same element. It records the phase shift of the signal reflected from the metal. The increase in phase shift causes clicks in the headphones: the closer the MD is to the metal, the more frequent they become, eventually merging into a single sound. The work of the popular metal detector “Pirate” is based on this method.
2. Double-circuit. Consist of 2 symmetrical generators and 2 detectors. A metal object disrupts the synchronization of the generators, and the same clicks occur, merging into a continuous tone.
   

   Double-circuit ones are easier to make with your own hands than pulse ones.

3. Parametric MDs have neither a receive nor a transmit coil, making them simple, cheap, and popular for DIY assembly. An LC generator creates an electromagnetic field at audio frequency. Any metal near the metal detector changes the parameters of the coil detector, which affects the frequency and amplitude of the generated signals. The diagram of such devices is easy to find. However, their sensitivity is low and does not allow complex searches. Parametric MDs are divided into:
4. Frequency MD. They emit multi-frequency signals. When approaching metals, the device detects a change in frequency.
5. Metal detectors that record changes in the quality factor of the circuit. When the distance between the device and the metal decreases, the device records this.

Detection depth

The detection depth depends on the diameter of the coil, electronic circuit and operating frequency. The larger the diameter of the wire coil, the more powerful the emitted electromagnetic field and the lower its frequency, the deeper the detection zone of a DIY metal detector.

However, as the search depth increases, the metal detector’s sensitivity to small objects deteriorates, and its selective capabilities also decrease. The energy consumption and weight of the device increases, which makes it difficult to hold the metal detector in your hands for a long time.

Operating frequency

Based on the frequency of operation, MDs are divided into:

1. High frequency. They operate at frequencies of several hundred kHz. They are used in devices designed to search for gold, as they have excellent discrimination. But they sharply lose sensitivity on wet and magnetic soils, as well as at depths greater than 40 cm.
2. Mid-frequency. Operating frequency up to several tens of kHz. The requirements for the quality of the coil are lower, good sensitivity. Detection depth is up to 1.5 meters, provided that the soil is dry and low-mineralized.
3. Low frequency. They operate at frequencies from hundreds of Hz to several kHz. These are deep metal detectors that detect objects up to 5 meters underground. They are easy to make with your own hands. Disadvantages: low sensitivity and high power consumption. Suitable as magnetic detectors, as well as for searching for large objects made of ferrous metal (fittings, wiring).
4. Ultra-low frequency. They are not suitable for amateur searches, as they have high power consumption and large dimensions, and special programs are required for signal processing. Operating frequency up to several hundred Hz. These metal detectors cannot be held by hand, so they are mounted on a car.

Step-by-step instructions for assembling a simple homemade metal detector with your own hands

Required tools and materials

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

1. Tools: wire cutters, knife, small saw, screwdriver, soldering iron.
2. Materials: wire, solder, flux, glue, electrical tape, radio components, wooden or plastic stick.

Dielectrics (polymers, wood, glue) must be used as a rod, as well as elements for its fastening, so that they do not interfere with the operation of the metal detector.

Preparing parts

You need to prepare the board on which it will be mounted electrical diagram. Even cardboard can be used as a board. The location of future parts is marked on it by hand and holes are made.

Radio components are bought in a store or soldered from old equipment. However, you need to make sure that the details are the same. This will make it easier to coordinate the operation of the two detectors.

Metal detector circuits for manufacturing

Sensitive metal detector based on a dual-circuit oscillator circuit

Manufacturing stages:

1. Transistors, resistors and capacitors are placed on the board and soldered according to the diagram below.
2. Solder two wires from the battery compartment, as well as two piezoelectric speakers.
3. Wind the wire onto a round frame with a diameter of about 22 cm. After 10 turns, make a wire tap 20 cm long. The wire at the tap site is not torn, but folded in half by hand. Make another 20 turns. The result should be three leads 20 cm long: the beginning of the wire, the end and the outlet after the 10th turn.
4. Remove the coil from the frame, holding the coils with your hands, and secure tightly with electrical tape.
5. Wind a second coil, which should mirror the first. Remove it from the frame and secure it with electrical tape.
6. Solder the leads of the coil detectors according to the diagram.
7. Assembling the stand. The coils are placed at a distance of approximately 15 cm from each other, and a board is attached between them.
8. The detectors are adjusted before mounting. Turn on the metal detector and, moving the coils with your hands, achieve maximum silence. They bring metal to one of them. If the sound changes noticeably, it means the metal detector is working.
9. The elements are fixed with glue and covered with oil varnish.
10. Attach the handle to the stand.

On a transformer with W-shaped plates

This is a simple parametric metal detector with inductive feedback. Allows detection hidden wiring, reinforcement in walls and ceilings, as well as large metals in the soil. A low-power transformer is used from any radio receiver. To turn a transformer into a detector with your own hands, you need to open its magnetic circuit: remove the frame, straight jumpers and windings.

There are two schemes for converting a transformer. The first one uses old windings, the second one rewinds them.

In the first case, the W-shaped plates need to be folded together and windings put on them. Winding in diagram II is network, winding I is step-down by 12 V. Capacitor C1 adjusts the tone of the sound. Instead of the MP40 transistor, you can use KT361.

In the second case, windings of 1000 turns (in Scheme I) and 200 turns (in Scheme II) are wound on W-shaped plates. For winding I, PEL-0.1 wire is used. After 500 turns, a tap is made. Winding II is wound with PEL-0.2 wire.

The transformer is sealed and placed on the bottom rod of the metal detector. When approaching metal, the tone of the signal in the headphones will change.

On transistors

Also simple scheme, consisting of transistors K315B or K3102, capacitors, resistors, headphones and batteries.

The first transistor creates a master oscillator, the second - a search oscillator. If you bring metal close to the coil, sound appears in the headphones. Detailed diagram is given below.

On the K561LE5 chip

The circuit consists of a microcircuit, headphones, resistors and capacitors. Coil L1 is connected to the master oscillator, and L2 is connected to the search oscillator of the microcircuit. A metal object affects the frequency of the search generator, changing the sound in the headphones. It is adjusted by MD capacitor C6. It eliminates unnecessary noise. The device supply voltage is 9 V.

How to assemble with your own hands without using microcircuits

This is the easiest option to assemble. So to speak, for dummies. You don't even need to solder anything. The metal detector is built from a calculator, a radio and a cardboard or CD box. The receiver and calculator should be taken as simple as possible, without protection from electromagnetic interference.

The principle of operation is based on the fact that the calculator creates radio interference in the AM range, and the receiver picks it up. Making a metal detector with your own hands consists of the following stages:

1. Set the radio to the highest AM range, but at the same time free from stations. Only interference should be heard.
2. Glue the receiver with double-sided tape on the back side to one flap of the CD box. Glue the calculator to the other sash.
3. Turn on the calculator. When the shutter is fully open, the receiver should enhance its sound.
4. Fold the box smoothly. When the angle between the receiver and the calculator is approximately 90°, the radio will go silent.
5. Fix the box in this position.

When metal enters the MD's coverage area, the field vector will rotate and the receiver will again intensify its sound. Depending on the design of the receiver, it may turn out that at an angle of 90°, the sound, on the contrary, is enhanced. In this case, the angle between the doors of the box is gradually increased, achieving a weakening of the tone.

PCB assembly

There are several options for wiring boards yourself. The figures below show circuit diagrams for wiring boards for metal detectors on a double-circuit oscillator, on a transformer, transistors and on a K561LE5 microcircuit.

Do-it-yourself electronics must be placed in a plastic case to avoid interference.

How to make a reel

An enameled copper wire with a diameter of 0.4–0.6 mm and a frame of the required size are used. The diameter of the frame depends on the purpose of using the metal detector:

• up to 9 cm – suitable for searching for reinforcement and profiles;
• 14-18 cm – for searching for small jewelry;
• 22-50 cm – for searching for large and deep-lying objects.

Also, for proper operation of the metal detector, you need to monitor the inductance of the coil. Inductance can be measured with a special device or calculated on the Internet using a calculator.

You can buy a frame for the reel in a store or make it yourself. Plywood or durable plastic are suitable for this. It is best to use plastic (polycarbonate, computer disk, bucket), as it has the least effect on the electromagnetic field and does not absorb moisture.

Location of parts on the board for a chip in a DIP package

If a chip in a DIP package is used, then the parts are placed as in the figure below.

Location of parts on the board for a chip in an SM package

Below is a diagram of the arrangement of parts when using a microcircuit in an SM package.

Brief instructions for setting up the device

The general rule when adjusting a metal detector with your own hands is to achieve the lowest sound in the “idle” mode, so that squeaks or clicks appear only when a metal object is detected. This can be achieved by changing the inductance of the coils, the capacitance of the capacitor or the resistance of the resistor.

Modernization

To make the metal detector better at finding small jewelry, you need to increase its operating frequency.

The sensitivity of the device also increases when an additional RC circuit is added to the circuit.

Installing variable resistors allows you to configure the device yourself without touching the coils.

The use of speakers with capacitors makes the sound produced louder. It is also useful to create a secure mounting for the coils and control unit. Protection from shocks and shocks will reduce interference, and settings will be less likely to be lost.

Conclusion

Now you know how to make a metal detector with your own hands. I will be glad if this article helps you find the treasure. Subscribe to new articles and share useful information on social networks.