Making a metal detector. The simplest metal detector. Using a high frequency transceiver

Many radio amateurs dream of making a metal detector with their own hands. It can detect metal objects in the ground at different depths. On the Internet, you can find many photo schemes of a metal detector, which are simple in the device. Any novice radio amateur can make them.

Easy assembly

Let's take a simple metal detector circuit as an example. It belongs to the impulse type, but due to the simplicity of its design, it is not able to distinguish between the types of metals. Therefore, it will not be possible to work with such a device in areas where objects made of non-ferrous metal are found.

How to assemble the device

To assemble a diagram of a simple metal detector with your own hands, you will need the following tools and parts:

The presence of the KR1006VI1 microcircuit, and the IRF740 transistor;
The presence of the K157UD2 microcircuit and the VS547 transistor;
Copper conductor 0.5mm (PEV);
NPN transistor;
Body, and various materials for it;
Solder, flux, soldering iron.

Other details are shown in the diagram. In order for the assembled circuit to be securely fixed, a plastic case should be prepared for it.

The bar can be made using a small diameter plastic tube. A metal search coil will be installed at its bottom.

Beginning of work

The circuit of a metal detector device on transistors is a common variant of many models. The assembly begins with the manufacture of the printed circuit board. Further, all radioelements are mounted on it exactly as shown in the diagram.

To make the operation of the device stable, film capacitors are used in the circuit. This will allow you to use it in cold weather without any problems.

Power type for device

The device can operate from a voltage of 9-12 V. Due to its sufficient power, energy is intensively consumed. It is recommended to install up to 3 batteries and connect them in parallel. You can use a small battery that has a charger. Thanks to its capacity, the metal detector will last longer.

Coil mounting

There are different types and schemes for the manufacture of metal detectors, but in the pulse version, inaccuracies are allowed in the installation of the coil. In the manufacture of the mandrel, the winding should be up to 25 turns, and the diameter of the ring is 1900-200mm.

All turns of the coil must be insulated with electrical tape. Reducing the number of turns to 22, and the diameter of the mandrel 270mm will allow detecting objects at a deeper location. The wire cross-section on the coil is 0.5mm.

When the winding is ready, it is fastened to a sturdy case with sufficient rigidity, on which there should be no metal parts. Otherwise, they are able to shield the magnetic field, and the operation of the metal detector will be disrupted. The body can be made of wood or plastic, but so that it can withstand various shocks that can damage the coil.

The leads available on it should be soldered to a conductor of several cores. The best option is a two-wire wire.

The installation of a non-ferrous metal detector circuit is a little more complicated, and high accuracy must be observed in the manufacture of the coil. The number of turns reaches 100pcs, and a vinyl tube is used as a core. A foil is wound on top of the winding, which forms an electrostatic screen.

Setting up the device

If the installation of the circuit is done exactly, then the metal detector will not need additional adjustment. Its sensitivity indicators will be maximum, but fine adjustment is possible through the variable resistance R13. It must be performed until rare clicks begin in the headphones.

If the adjustment fails, then the resistances must be replaced with R12. When the adjustment of the resistor is in the middle, it will be considered normal.

An oscilloscope is suitable for checking the device. It measures the frequency of the transistor T2, and the pulse should last up to 150 ms. The optimum operating frequency is up to 150 Hz.

How to use the device

You should not rush and start working immediately after turning on the metal detector. It should stabilize, so you need to wait up to 20 seconds. After adjusting the resistor appropriately, you can start looking for metal.

Note!

Photo of a metal detector circuit

Note!

Equipment and materials

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

Chip. Both domestic, such as KR1006RVI1, and its analogue of foreign production ( 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 tubing of sufficient length for use as a rod

Material for all body elements - durable plastic

Consumables: any suitable fasteners, electrical tape

Equipment: soldering iron, screwdrivers

This is the minimum set that will be enough to assemble the simplest device. Such a device is perfect for novice treasure hunters.

Assembling the device

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

PCB assembly

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

For a simple metal detector, there are two PCB options:

Microcircuit board NE 555 (or similar domestic

Transistor board.

Even with self-assembly, it is still better to purchase a printed circuit board ready-made. They can be found in any electronics store. The fact is that even if the master decides to assemble the printed circuit board on his own, for its manufacture you will need to buy materials that are hardly possible to make yourself, such as getinax - plates of pressed paper.

Installing electronics on the board

Further, the task of the wizard is to install all electronic elements on the board. The main condition here is to strictly observe 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 homemade metal detector is provided with 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 supply. It can be either a rechargeable battery or several batteries. You can even use unnecessary laptop batteries.

It should be noted that even with the simplicity of the circuit, in the end the device turns out to be quite powerful and consumes a significant amount of energy. When searching for a long time, you should take care of the availability of spare batteries, and it is best to use rechargeable batteries, which will avoid the trouble of discharging the batteries at the most inopportune moment.

Assembling the coil

Since the assembled device is a pulsed one, 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 provide additional protection against moisture ingress.

To make the coil more sensitive, the frame diameter can be increased to 250 mm, while at the same time the number of cable turns can be reduced to 21-22. After winding and insulating the coil, it must be installed on a rigid base. It is imperative that it is made of non-metallic material. High-impact plastic can be used. Such a coil will become more sensitive to non-ferrous metals, and with a few additional modifications, it will theoretically be able to generate signals from precious metals that do not lie too deep in the soil.

Enclosing the coil in a sturdy housing is very important, as 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. Thus, the coil is reliably protected from shocks.

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

Setting up the device

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

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

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

Working with a metal detector

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

Make a metal detector at home

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

The metal detector works according to the following principle:

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

According to the principle of operation, 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 just those in which two coils are combined into one common one.

· Pulse. They work on the basis of an impulse emanating from the transmitter. After a pulse is released, it is immediately disabled and enabled when a new pulse is needed.

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

· Dynamic... A device that is simple in design and operation, continuously scanning the area of action of the created field. The key principle of working with such a metal detector is the need to be constantly on the move, otherwise the signal will disappear. The disadvantage of such seekers is a rather low level of sensitivity.

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

· Electronic... These detectors are good for finding large metal objects with 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 from unnecessary objects, such as metal debris.

· Deep the detector is designed to search for objects located at a considerable depth underground. Such devices are capable of picking up a signal even at a depth of 6 meters, while the rest most often work at a depth of no more than 3. Such a device works on the basis of two coils, like others. But here their position relative to the earth's surface is changed. One of them is parallel to the ground, the second is perpendicular.

· Another option that interests search engines to a lesser extent 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 of calculating the presence of any metal items in the bags and the internal people that pass through the set frame.

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

How to make a metal detector with your own hands

It is best to consider the manufacture of a metal detector from domestic parts for beginners on the basis of the Pirate model. This option has long been included in the top of homemade metal detectors. It is widely demanded among lovers of self-assembly, and in its finished form is a device with good indicators of depth and search accuracy. It allows you to detect objects at a depth of 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 on this diagram, the comparison will be in favor of the "Pirate". In addition, the circuit of this metal detector is even easier to assemble, it consists of fewer parts and assemblies.

One of the possible disadvantages of this model is the lack of a discrimination function. A simple circuit of a metal detector simply cannot provide the ability to connect a discriminator. But with experience, seekers learn to independently determine which metal is giving out a signal from a field fluctuation.

Metal detector device "Pirate"

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

· Long plastic tube for the bar. All other equipment will be attached to it. Well in this case, PVC water pipes are suitable.

· Material for the housing of the control unit. Any durable plastic container of suitable size can be used.

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

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

· Copper cable per coil

Insulating tape

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

· Two microcircuits: K157UD2 and NE 555

· Capacitors. Better to use ceramic and film.

· Electrolyte capacitors, 5 in total.

· Resistors of different resistance levels

"Pirate" - a metal detector on two microcircuits. This is where the chip is used NE 555 or its domestic counterpart.

The device starts with a comparator. One of its outputs is connected to a generator (creating an electromagnetic field), the other to the receiving coil, and the third to a 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 the corresponding sound alarm.

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

If the standard device is not enough, then there is an option to make a more perfect model for gold. The power of the device assembled according to the usual scheme is not enough to react to gold and objects from it, so it is easy to find an improved scheme on the network.

Can I use radio parts?

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

Collect the Pirate Finder PCB?

A printed circuit board for such a device can be made independently, but this cannot be done from scrap materials. For manufacturing, you will need a sheet of special material - getinax. It is a pressed board made of thick paper impregnated with epoxy resin. Additionally, it must be covered with special copper foil, which is used in electrical engineering.

On such a board, you need to transfer all the connecting elements, mark the places for fasteners and carefully drill holes in them. All tracks must be covered with a special protective varnish, and as soon as it dries, the board must be dipped into a chlorine solution. This gives additional protection to areas where the protective layer of copper foil is at its thinnest.

Assembling the coil

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

It is convenient to rewind on a pre-prepared board or any flat surface. The distance between the turns must be kept approximately at a level 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, you can attach it to the detector and test its functionality.

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 a little solder.

The procedure in this case is as follows:

· To begin with, the wire must be rolled up in a pigtail into two skeins, leaving about 10 cm on both sides.

· Then - strip the winding, freeing the cable cores for connection.

· Connect the cores according to the scheme, 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 with a soldering iron to the stranded cable.

Assembling the Pirate metal detector from finished parts

Once all the structural elements are ready, the complete assembly can begin. All parts are attached to a sufficiently long rod. A convenient rubber handle is attached on top, a control unit enclosed in a plastic case is just below, and a coil at the very bottom. If everything is done correctly, no mistakes were made during the assembly of the elements - the device is ready for operation, no additional manipulations will have to be made.

Instrumental search is extremely popular. Looking for adults and children, and amateurs and professionals. They are looking for treasures, coins, lost things and buried scrap metal. And the main tool for searching is metal detector.

There is a great variety of different metal detectors, for every "taste and color". But for many people, buying a ready-made branded metal detector is simply financially costly. And someone wants to assemble a metal detector with their own hands, and someone even builds their own small business on assembling them.

Homemade metal detectors

In this section of our site about homemade metal detectors, will be collected: best metal detector circuits, their descriptions, programs and other data for manufacturing metal detector with your own hands... It does not wake up metal detector circuits from the USSR and circuits on two transistors. Since such metal detectors are only suitable for a visual demonstration of the principles of metal detection, they are not at all suitable for real use.

All metal detectors in this section will be quite technologically advanced. They will have good search performance. And a competently assembled homemade metal detector wakes up a little to yield to factory counterparts. Basically, various schemes are presented here. impulse metal detectors and metal detector circuits with metal discrimination.

But for the manufacture of these metal detectors, you need not only desire, but also certain skills and abilities. We tried to break down the schemes of the given metal detectors according to the level of complexity.

In addition to the basic data required for assembling a metal detector, there will also be information about the required minimum level of knowledge and equipment for making a metal detector on your own.

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 only the basic for all schemes.

Soldering iron, solder, tin and other soldering accessories.
Screwdrivers, pliers, wire cutters and other tools.
Materials and skills for manufacturing a printed circuit board.
Minimal experience and knowledge in electronics and electrical engineering as well.
And also straight arms - they will be very useful when assembling a metal detector with your own hands.

Here you can find diagrams for self-assembly of the following metal detector models:


	Principle of operation	IB
	Discrimination against metals	there is
	Maximum search depth
		there is
	Working frequency	4 - 17 kHz
	Difficulty level	Average


	Principle of operation	IB
	Discrimination against metals	there is
	Maximum search depth	1-1.5 meters (Depends on coil size)
	Programmable microcontrollers	there is
	Working frequency	4 - 16 kHz
	Difficulty level	Average


	Principle of operation	IB
	Discrimination against metals	there is
	Maximum search depth	1 - 2 meters (Depends on coil size)
	Programmable microcontrollers	there is
	Working frequency	4.5 - 19.5 kHz
	Difficulty level	High

This article will focus on one of the simple metal detectors, the assembly of which can be carried out with available Soviet radio parts. These include transistors labeled KT and MP, as well as resistors and capacitors from popular radio equipment. Most of the necessary parts can be found without problems in old radio devices.

The diagram consists of five nodes, the structure of which can be viewed in Figure 1:

Master frequency generator used to create a reference frequency.
Search frequency generator. Its frequency will change when metal is found.
Low frequency amplifier for increasing the signal difference between the generators.
Node that reproduces sound.
Power supply.

This device resembles a two-transistor metal detector, but it adds a sound amplifier, and, despite its simplicity, it has good metal detection rates. It is perfect for bulk search and collection of ferrous metal. If you find radio parts and a little time, then you can easily assemble a metal detector using this informative article as an example.

Assembling schematic elements

The assembly of the circuit can be carried out on a one-sided foil-coated PCB. Guided by Figure 2, which shows a diagram of a metal detector on transistors, we count the number of connections and create an appropriate number of contact pads with a sharp object. After tinning, the board is ready for assembly of parts (Fig. 3). For a better build, you can think of and draw a homemade PCB.

Below is a list of the necessary parts and instructions for some of them:

14 resistors with a power of 0.125 W. Denominations:
1. R1, R5 - 100 kOhm;
2. R2, R6, R11 - 10 kΩ;
3. R3, R7 - 1 kΩ;
4. R4, R8 - 5.1 kΩ;
5. R9 - 6.2 kΩ;
6. R10, R13 - 220 kOhm;
7. R12 - 3.9 kOhm;
8. R14 - 3 kOhm.
14 capacitors, preferably heat-resistant:
1. Electrolytic 6 V: C10, C14 - 47 μF; C12, C13 - 22 μF;
2. Variable capacitors C7 - up to 10 pF / from 150 pF;
3. Trimmer capacitor C8 - 6/25 pF;
4. C1, C11 - 47 nF;
5. C2, C6 4.7 nF;
6. C3 - 100 pF;
7. C4 - 47 pF;
8. C5, C9 - 2.2 nF.
Five transistors:
1. 3.1 VT1, VT2 - KT315. As analogs, you can use KT3102, KT312 or KT316;
2. 3.2 VT3, VT4, VT5 - MP35. You can replace it with MP from 36 to 38;
3. 3.3 VT6 - MP39. MPs from 40 to 42 are also suitable;
2 diodes D9Zh, or others - D18, D2, GD 507.
A 4.5 V battery in the form of three AA batteries. You can use a 9 V krone battery, but in this case it is necessary to change the electrolytic capacitors to a voltage higher than 9 V.
Speaker with impedance from 5 to 100 Ohm. Speakers made from children's toys, intercoms, radios, or a headphone will do.
Battery connector (fig. 4).
Micro switch or toggle switch for shutdown.

Metal detectors cannot work without coils, which play the main role in the device. In the next paragraph of the article, we will describe in detail their role in the work and the manufacturing process.

Generator Coil Creation

The primary coil L1 is exemplary and, together with the capacitor C3, serves to create the master frequency of the generator. Secondary coil L2 works in the same way, but it is done without a core. This allows metal objects to act on it and change the frequency of the generator, which leads to a frequency difference for the signal.

The following describes how to make homemade reels without much difficulty.

The L1 coil frame requires a metal rod with a diameter of 8 mm and a length of 3 cm. You can use an antenna with a radio. It is necessary to wind whatman paper on the rod. We do this in order to be able to adjust the frequency by moving the rod relative to the coil, therefore it is important that the Whatman paper fits very tightly to prevent spontaneous movement. After the final setting of the metal detector in the last step, you can fix the rod with glue. A sample coil is shown in Figure 5.

We wind the coil L1 with a PEV wire with a diameter of 0.2 - 0.3 mm. We wind 110 turns on whatman paper strictly in one row, trying not to allow gaps or gaps between the turns. At the 16th turn, we make a tap without breaking the wires. After winding, the wire can be varnished, but it is necessary to observe the availability of movement of the metal rod inside. We connect the wire according to the diagram.

The second coil L2 is made in the form of a rectangular frame measuring 12 x 22 cm. The frame can be made of plastic, plexiglass, plywood and other non-conductive material. We make a tray or assemble only a supporting rectangle in which it will be possible to lay the winding in bulk. The finished samples can be seen in Figure 6.

The wire, as in the first case, we choose the PEV brand, but with a diameter of 0.4 - 0.6 mm. We wind 45 turns, drawing a conclusion on the 10th turn. After complete manufacture and adjustment of the metal detector, it will be possible to fix and insulate the winding with varnish. The connection to the circuit is carried out with a shielded cable with at least two cores. These cables are used in high-quality audio equipment and in trunk communication lines, they can also be purchased at an electronics store.

Manufacturing of a metal detector structure

First of all, you need to decide what material to make the barbell from. It is better to give preference to a dielectric material in order to eliminate problems in the operation of the metal detector. There are many options: PVC pipe, telescopic fishing rod, wooden pole. When choosing, it is worth considering indicators such as weight, flexibility, disassembly ability, convenience.

If you plan to spend a lot of time searching for metal, the light weight and comfortable armrest with a handle will save you a lot of energy. But do not forget that lightweight material can bend. In the case of a PVC pipe, this can be compensated for by filling it in with sand or additional supporting structures. With a collapsible bar, there will be no transportation problems. To implement this idea, you can visit a plumbing store and assemble an excellent metal detector with your own hands on various adapters (Fig. 7).

After you have decided on the choice of the rod, you need to fix the coil on it. Everything is simple - no metal. Use plastic fasteners, pre-fixed ears on the coil frame, adapters, or just reliable glue.

We place the circuit in a plastic box. Small holes can be made for the speaker for good audibility. The board, speaker, primary coil and battery box can be secured with adhesive. We place the box a meter from the search coil and fasten it in a convenient way - using plastic fasteners or glue.

At this point, you have assembled a simple transistor metal detector that needs fine tuning and testing.

Setting up the device

Tuning a metal detector is to create the same frequency in both generators. When this result is achieved, the lowest, barely audible tone will be emitted from the speaker.

First, remove all metal objects from the range of the metal detector. We take into account concrete walls and floors, as they may contain metal reinforcement. We expose all variable capacitors to the middle position. By changing the position of the rod in the L1 coil, we achieve the desired tone or its absence. With the further operation of the device, we use the capacitor C7 to adjust it. After tuning, we bring a metal object at various distances from the search coil and make sure that the metal detector is working.

If the metal detector does not work, we check the blocks and circuit details. We start the check with transistors, and then we check the diodes. To check the sound amplifier, it is enough to remove the resistor R9 from the generators and connect it to the audio output of any device that reproduces sound (Fig. 8).

If the parts and the amplifier are in working order, then we set up the transistor generators. To do this, we try to change the values of the capacitor C4 and the resistor R2 for the master oscillator, and the resistor R6 for the search oscillator. You can try to start the second generator with a trimmer capacitor C8.

Not everyone can afford to buy a metal detector. And to search for iron, it is not at all necessary to purchase an expensive device. It is enough to assemble it yourself. And he will find it too.

By the way, I will say that I saw a report on TV, how a man who assembled a metal detector and was looking for scrap metal with its help found a box with cartridges from the civil war in the forest.

I myself have been trying to assemble such a device for a long time and it even worked! But it will not work to search for coins with its help, since it reacts mainly to large metal objects.

And so, to assemble a simple metal detector, we need:

~ two transistors KT315 or similar;
~ two 1000 pF capacitors;
~ two capacitors 10000 pF;
~ two resistors 100 kOhm.

In addition, the following are useful: a 3.7-5 volt battery, headphones, an enamel-insulated wire with a diameter of 0.5-0.7 mm.

The assembly diagram is the simplest!

The spools can be wound on a regular saucepan. After ten turns, a loop is made and the winding of the remaining twenty turns continues.

The body is made of any material, preferably airtight. The bar can be piled from pipes. The coils are placed on the same plane at a distance of 10 cm.

If, when you turn on the device, a squeak appears in the headphones, then you need to adjust the device - change the distance between the coils. Or customize with ferrite.

Thus, you can earn money by searching for scrap metal for a good branded device. And a good deed will be done - the earth will be cleansed. Well, the metal will be reused.

The photos in the article are mine, taken back in 2014. And the first picture with the diagram is taken from open sources.

How to make an uncomplicated beach metal detector

In this article, I will show you how to put together a simple metal detector for finding coins and jewelry on the beach. It consists of one microcircuit - the NE555N timer, a coil and several other radio components.

Expect to spend up to 300 rubles on the construction of this metal detector!

Required materials

To assemble a metal detector you will need:

timer IC NE555N, in DIP package;
resistor 47 kOhm;
two capacitors 2.2 μF, 16 V;
a piece of a contact breadboard;
9 volt battery, switch, battery block;
electromechanical sound emitter;
100 meters of copper wire with a diameter of 0.2 mm;
some thick cardboard and glue.

Instead of an electromechanical sounder, you can use a 10uF capacitor and any 8 ohm speaker connected in series.

Metal detector circuit

The idea of a metal detector is taken from the book “ 499 circuits on timer NE555". I just added a switch between the battery and the IC, and I also use an electromechanical sounder from an old electronic alarm clock instead of a speaker.

Search coil

The hardest part of a metal detector is its coil. I calculated that a 90mm coil should have approximately 260 turns of 0.2mm diameter lacquered copper wire. Moreover, its inductance will just be about 10 millihenry.

I wound the coil neatly, loop to loop. To prevent the wires from unraveling, I wrapped the winding on top with white electrical tape.

If you want to make a coil with a larger diameter in order to increase the target detection range, then there are several online calculators on the network with which you can calculate it.

Circuit board

I have placed all the electronic components on a piece of breadboard. The connections were made with the most common wire that was at hand. Soldering the board itself took no more than 15 minutes.

The size of the board is approximately equal to the size of a matchbox.

Frame

For simplicity, I decided to make the handle of the metal detector out of cardboard. The handle is fitted with a circuit board, a switch and a battery.

All this was cut out of thick cardboard and glued with PVA glue. After the glue was dry, I made holes in the cardboard for the board and wires.

Then, I glued the searchcoil to the handle with hot melt glue. In the last step, I also glued the board and the battery inside the handle using hot glue.

Conclusion

The metal detector works as follows: as long as there are no metal objects near the coil, the sound emitter beeps at the same frequency; when a metal object is brought up, the tone of the sound changes towards a higher one.

According to my measurements, the detection range of a large coin through the air was 5 - 7 centimeters!

Simple metal detector kid FM-2 improved

I present to your attention a diagram of a more improved metal detector Kid FM-2. The baby fm2 metal detector is not so difficult to assemble with your own hands, despite its significant changes. This is perhaps the simplest selective metal detector that even a novice radio amateur can assemble.

You have probably heard, and perhaps collected, such metal detectors as "Baby" and "Baby FM-2". But progress does not stand still, and therefore we have a diagram of a more improved Kid FM-2 metal detector. The new version adds LED indication of metals, added a power-on alert function, enhanced alert sound, the device became much more stable in operation.

Scheme of the improved metal detector Kid FM-2

Specifications and Features:

Supply voltage - 9 Volts
The detection depth of metals is about 15 cm.
Selection of metals - black, non-ferrous
Metal LED indication - black, non-ferrous
Power on indicator

So, this printed circuit board of the Kid FM-2 metal detector is designed to use DIP components, which would be convenient for everyone, since many novice radio amateurs have not yet encountered SMD components.

Capacitors C5-22nF and C1-100nF must be foil

Voltage stabilizer AMS1117 -3.3v

This is how the finished board of the "Kid FM-2" metal detector looks like

View from the side of the tracks

After assembling the board, we start making the coil.

The standard coil contains 150 turns, wire diameter 0.3, and is wound on a rim of 150 mm. But I decided to slightly reduce the diameter to 10-11 cm in order for the metal detector to see small objects better, the detection depth decreases, but the sensitivity increases. I didn't have a 0.3 wire, and so I wound 0.4 on a 10 cm rim, 130 turns.

So, after the coil is wound, it is necessary to tighten it very tightly with tape.

Now it is imperative to shield the coil so that the metal detector does not react to interference and there are no false alarms. We take food foil and wrap the coil tightly. Please note that the ends of the foil must not touch each other!

Then we take the wire, strip the end and tie the coil to one edge of the screen, then pull it together and wrap it tightly with tape again.

We connect the coil to the board. The wire from the screen must be soldered to the minus of the board.

Now it remains to flash the microcontroller and that's it, you can use it)

If you do everything correctly, then the device should work without problems when you turn it on for the first time. Carefully check the ratings of the parts and do not forget that the capacitors C2-22nF and C6-100nF must be foil, NOT ceramic!

When turned on, the device should emit a characteristic sound similar to "peak-foote", which means that the device has turned on and is working correctly.

IMPORTANT! "According to the scheme there are 8 resistors, and in photo 9" - the 9th resistor (100 Ohm), I myself put it additionally on the second LED, although it is possible not to put it! The 1N4007 diode can also be omitted, as I did!

The printed circuit board, firmware, as well as a list of parts that can be bought very cheaply on AliExpress with free shipping is below the video!

Video of the metal detector baby FM-2 v2

Good DIY metal detector

It was already a few years ago. I wanted to do something to keep my hands busy, and to while away the evenings, bringing the treasure hunting season closer. It was decided to assemble a metal detector. For the assembly I chose the Pirate metal detector scheme. Since it is not complicated, the device itself is quite interesting. The assembly began with a search for parts. I even had to go to the workshop for some resistors. When everything was found, it was necessary to prepare a printed circuit board, namely to etch it using the LUT method. Then the matter was small: to solder all the details. Well, check the finished board. The first time it did not turn on. The K157UD2 microcircuit turned out to be faulty. By changing it, the scheme worked!
Now you can do the corpus. In its capacity, the body was taken from Koschey 5I, a new front panel was made. It's up to the coil. For the coil, a frame was cut out with a jigsaw and a groove was carved along the side face, where the coil winding was wound, a cable with a connector was soldered. The bar was made of plastic pipes and fittings. The armrest is cut from a sewer pipe. It turned out all the same culturally enough. The device turned out to be light, but not rigid enough.
The result is a working high-quality device. Its only drawback is the lack of discrimination against metals. Therefore, it can be said that it is not suitable for searching for coins. After all, both nails and coins ring the same.
But with its help, you can successfully dig for scrap metal and hand it over to collection points, thereby making money! There is a video with a test of this unit. It was filmed by me in the spring of 2015.