Metal detectors are used to search for metal in the soil at a certain depth. This device can be assembled independently at home, having at least minimal experience in this matter, or following the clear instructions in the instructions. The main thing is the desire and availability of the necessary tools.

Detailed instructions for the Terminator 3 metal detector with your own hands

This type of design is designed to search for coins. The process of assembling it is completely simple. However, experience in assembling such a tool is still necessary. The Terminator is able to detect an object even if the target of capture is minimal.

To begin, you should prepare the necessary equipment, namely:

• a multimeter that measures speed.
• LC meter
• Oscilloscope.

Next, you need to find a diagram broken down into nodes. Now you can make a printed circuit board into which jumpers, resistors, panels for microcircuits and other parts should be soldered in order. The next step is to clean the board with alcohol.. It is definitely worth checking for defects. You can check whether the board is in working condition as follows:

1. Turn on the power.
2. Turn down the sensitivity control until no sound is heard from the speaker.
3. Touch the sensor connector with your fingers.
4. When turned on, the LED should blink and then go out.

If all actions occurred, then everything was done correctly. Now you can make a coil. It is necessary to prepare a winding enamel wire with a diameter of 0.4 mm, which must be folded in half. A circle is drawn on a sheet of plywood with a diameter of 200 mm and 100 mm. Now you need to drive nails in a circle, the distance between them should be 1 cm.

Next, you can move on to winding the turns. At 200 mm you should make 30 of them, and at 100 - 48. Then the first coil should be soaked in varnish; when it dries, you can wrap it with thread. The thread can be removed, and by soldering the middle, you get a solid winding of 60 turns. Afterwards, the coil must be wrapped quite tightly with electrical tape.. And a 1 cm foil is placed on top, this will be a screen, and more electrical tape is wound on top of it. The ends should come out.

On the second coil it is also necessary to solder the middle. In order to start the generator, you need to connect the first coil to the board. The second coil should be wrapped with a wire of 20 turns, then we connect it to the board. Now you need to connect the oscilloscope minus to minus to the board, and the plus is connected to the coil. Be sure to look at what frequency it will be when you turn it on and remember it or write it down on paper.

Now the coils need to be placed in a special mold so that they can then be filled with resin. Next, the oscilloscope is connected to the board, with the negative pole, the amplitude should reach zero. The coils in the mold are filled with resin to approximately half the depth. When everything is ready, the metal discrimination scale is adjusted.

Parts list for the Terminator 3 metal detector

As parts for the trio metal detector you will need:

If you have these parts, you can assemble the Terminator Pro metal detector yourself.

Circuit diagram of a metal detector with metal discrimination

You can make a metal detector with metal discrimination yourself using the circuit for the Chance pulse device. The process of making a coil is quite simple.

The diagram itself can be found on the Internet. But still, experience in assembling such devices will be useful. Assembling the metal detector should begin with the board.

After the board is manufactured, the microcontroller needs to be flashed. And at the end of the work, we connect the metal detection device to the power supply.

Homemade equipment can be made without complex microcircuits, but using a simple transistor generator. The metal detector will be non-discriminatory. It will detect objects in the ground to a depth of 20 centimeters, and in dry sand - to a depth of 30 centimeters. In this device, the transmitting and receiving coils operate simultaneously.

Terminator 3 metal detector coil

To begin with, you should take winding enamel with a diameter of 0.4 mm. Fold it so that there are two ends and two beginnings. Next, you should wind from two reels at a time.

Now we need to make transmitting and receiving coils; for this, two circles of 200 mm and 100 mm are drawn on a plywood sheet. Nails are driven in along these circles, the distance between them should be 1 cm. 30 turns of enamel wire are wound onto a large mandrel. Then you should apply varnish to the coil and wrap it with thread, then remove it from the winding and solder the middle. This creates one middle wire and two outer wires.

The resulting coil should be wrapped with electrical tape and a piece of foil should be placed on top, and foil again on top. The ends of the windings should go outside.

Now it’s time to move on to the receiving coil. 48 turns are already wound here. To start the generator, you need to connect the transmitting coil to the board. The middle wire is connected to the negative. And the middle terminal of the take-up coil is not used. The transmitting coil requires a compensating coil, on which 20 turns are wound.

We connect the oscilloscope to the board like this: a probe with a minus to the minus of the board, and a plus probe to the coil. Be sure to measure the frequency of the coils and write it down.

After connecting the coils according to the diagram, they must be placed in a special container and filled with resin. The oscilloscope now sets the division time (10 ms and 1 volt per cell). Now you should reduce the amplitude to zero. We wind the turns until the volt value reaches zero. We make a compensating loop at the coil, which will be outside.

The mold should be filled halfway with resin. When everything hardens, you need to connect the oscilloscope and bend the loop inward. Then twist it until the amplitude value becomes minimal. Afterwards, you need to glue the loop, check the balance, and now you can fill the second half of the container with resin. The reel is ready for use.

Before you begin the repair, you should prepare the following tools:

• Stationery knife;
• Incandescent lamp;
• A container for glue, preferably flat;
• Special or epoxy resin;
• Medium and fine sandpaper;
• Small spatula.

First of all, you need to dry the coil using an incandescent lamp. And use a utility knife to widen the cracks on it. Squeeze the glue onto a flat surface and mix with a spatula. Apply this substance to the coil. In places of cracks, you can apply more resin. Now you should wait until it all hardens thoroughly. And then sand it, using first medium and then fine sandpaper. This procedure will help smooth out all the unevenness. In this fairly simple way, you can revive the oldest coil from a metal detecting device.

Printed circuit board for the Terminator 3 device

A printed circuit board for this type of equipment can be made and configured independently. The board diagram for Terminator 3 is available on the Internet. Once it is found, you can begin manufacturing the printed circuit board. After that, jumpers, SMD resistors and panels for microcircuits are soldered into it. The capacitors on the board must have high thermal stability.

DIY metal detector sensor

Before starting work, it is necessary to prepare a device that will accurately measure capacitance and inductance. Now you should take the housing for the reel and make PCB inserts into the ears. Pieces of fabric are used for compaction. The upper surface of the ears should be sanded. The fabric must be impregnated with epoxy resin. When everything is dry, you should sand everything and insert a sealed lead-in, thus making grounding. Next you need to apply a special Dragon varnish.

Now windings are made, which are tied with threads. All windings are placed in a coil and capacitors are glued. Everything can be connected and configured. A housing is required for pouring. Mandatory: there should be no metal nearby. After pouring, the epoxy should be sanded and dried thoroughly. The sensor is suitable for the Terminator 3 and Terminator 4 metal detectors, which are the most popular models of devices.

Metal detector Terminator 3: reviews

Many people consider this model of device popular. The positive qualities include:

• Finding objects made of non-ferrous metal.
• No false positives.

And the following are identified as negative features:

• Rusty iron is detected rather poorly.
• You may lose some of your finds.

The search depth of the device is higher than that of other similar models. Basically this is 30 centimeters using the example of a coin.

Metal detector Sokha 3: diagram and description

The metal detector has an operating frequency of 5 to 17 kHz. Its power supply is 12 Volts. Its ground balance is manual.

The circuit of this device is not entirely simple, since it contains two microcontrollers. The diagram can be found on the Internet. The device itself has good characteristics. However, due to the lack of detailed assembly information, difficulties may arise in the manufacture of the device.

Metal detector circuit

Today I would like to present to your attention a diagram of a metal detector, and everything related to it, what you see in the photograph. After all, it is sometimes so difficult to find the answer to a question in a search engine - Diagram of a good metal detector

In other words, the metal detector has a name Tesoro Eldorado

The metal detector can operate in both the search mode for all metals and background discrimination.

Technical characteristics of the metal detector.

Operating principle: induction balanced
-Operating frequency, kHz 8-10kHz
-Dynamic operating mode
-Precise detection mode (Pin-Point) is available in static mode
-Power supply, V 12
-There is a sensitivity level regulator
-There is a threshold tone control
-Ground adjustment is available (manual)

Detection depth in the air with a DD-250mm sensor In the ground, the device sees targets almost the same as in the air.
-coins 25mm - about 30cm
-gold ring - 25cm
-helmet 100-120cm
-maximum depth 150cm
-Consumption current:
-No sound approximately 30 mA

And the most important and intriguing thing is the diagram of the device itself

The picture is easily enlarged when you click on it

To assemble the metal detector you need the following parts:

So that you don’t have to spend a long time setting up the device, do the assembly and soldering carefully; the board should not contain any clamps.

For tinning boards, it is best to use rosin in alcohol; after tinning the tracks, do not forget to wipe the tracks with alcohol

Parts side board

We begin assembly soldering jumpers, then resistors, further sockets for microcircuits And all the rest. One more small recommendation, now regarding the manufacture of the device board. It is very desirable to have a tester that can measure the capacitance of capacitors. The fact is that the device These are two identical amplification channels, therefore the amplification through them should be as identical as possible, and for this it is advisable to select those parts that are repeated on each amplification stage so that they have the most identical parameters as measured by the tester (that is, what are the readings in a particular stage on one channel - the same readings on the same stage and in another channel)

Making a coil for a metal detector

Today I would like to talk about the manufacture of a sensor in a finished housing, so the photo is more than words.
We take the housing, attach the sealed wire in the right place and install the cable, ring the cable and mark the ends.
Next we wind the coils. The DD sensor is manufactured according to the same principle as for all balancers, so I will focus only on the required parameters.
TX – transmitting coil 100 turns 0.27 RX – receiving coil 106 turns 0.27 enameled winding wire.

After winding, the coils are tightly wrapped with thread and impregnated with varnish.

After drying, wrap tightly with electrical tape around the entire circumference. The top is shielded with foil; between the end and the beginning of the foil there should be a gap of 1 cm not covered by it, in order to avoid a short-circuited turn.

It is possible to shield the coil with graphite; to do this, mix graphite with nitro varnish 1:1 and cover the top with a uniform layer of tinned copper 0.4 wire wound on the coil (without gaps), connect the wire to the cable shield.

We put it into the case, connect it and roughly bring the coils into balance, there should be a double beep for the ferrite, a single beep for the coin, if it’s the other way around, then we swap the terminals of the receiving winding. Each of the coils is adjusted in frequency separately; there should be no metal objects nearby!!! The coils are tuned with an attachment for measuring resonance. We connect the attachment to the Eldorado board in parallel with the transmitting coil and measure the frequency, then with the RX coil and a selected capacitor we achieve a frequency 600 Hz higher than that obtained in TX.

After selecting the resonance, we assemble the coil together and check whether the device sees the entire VDI scale from aluminum foil to copper; if the device does not see the entire scale, then we select the capacitance of the resonant capacitor in the RX circuit in steps of 0.5-1 nf in one direction or another, and in addition the moment when the device will see foil and copper at a minimum of discrimination, and when the discrimination is turned up, the entire scale will be cut out in turn.

We finally reduce the coils to zero, fixing everything with hot glue. Next, to lighten the coil, we glue the voids with pieces of polystyrene foam, the foam sits on the hot glue, otherwise it will float up after filling the coil.

Pour the first layer of epoxy, without adding to the top 2-3mm

Fill in the second layer of resin with color. An aniline dye is a good choice for dyeing fabric; the powder comes in different colors and costs a penny. The dye must first be mixed with the hardener, then the hardener must be added to the resin; the dye will not dissolve in the resin immediately.

To assemble the board correctly, start by checking the correct power supply to all components.

Take the circuit and the tester, turn on the power on the board, and, checking the circuit, go through the tester at all points on the nodes where power should be supplied.
When the discrimination knob is set to minimum, the device should see all non-ferrous metals

, when screwing the discrim, they should be cut out

all metals in order up to copper should not be cut out if the deviceit works this way, which means it is configured correctly. The discrimination scale needs to be selected so that it fits completely into a full turn of the discrimination knob, this is done by selecting c10. When the capacity decreases, the scale stretches and vice versa.

I present to you the diagram and design a simple metal detector to make with your own hands

Fig.1. Schematic diagram of a metal detector

The circuit is based on two NE555 chips. There are transmitting (Tx) and receiving (Rx) coils, so the circuit can be divided into two parts. The left side is a square pulse generator. The timing components R1, R2, C1 are selected so that the output frequency is about 700 Hz. This is the frequency of the audible range. The pulses are transmitted through current-limiting resistor R3.

Both coils are located in space in such a way that they together form a certain overlap zone and the system is in induction balance. In this case, there is zero voltage in the receiving coil and the right side of the circuit does not react in any way. If a metal object appears nearby, an imbalance occurs and an audible signal appears.
The signal from the receiving coil is amplified by transistor VT1 and fed to the input of the second microcircuit. A KT3102EM is used as a bipolar transistor VT1; it can be replaced with any similar one with a high gain. A voltage divider is formed using four resistors R5 - R8. Variable resistors are used to configure the metal detector. R6 is a trimmer and is adjusted after the mutual placement of the coils. And R7 and R8 are used for coarse and fine adjustments; they should be installed on the device body (provide easy access to them).
The sound signal is created thanks to the piezo emitter BA1, which can be taken from an unnecessary multimeter. But when testing the circuit, I liked the sound of the piezo emitter with a built-in oscillator. Despite the fact that a pulse signal is generated at the output of DD2, it will not only signal well, but will also allow you to detect the slightest changes in sound when a metal object is detected.

Creating Reels

To wind the metal detector coils, you will need an enameled winding wire with a diameter of 0.3 mm. In my case, the maximum permissible diameter of 0.7 mm was used.
The optimal diameter for winding a coil is approximately 15-16 cm. You should select some round object (for example a bucket) to wind the coil around. But you can use the device. To do this, hammer nails into a clean wooden surface in a pre-drawn circle.

The inner diameter in my case is 15.5 cm. I wound 25 full turns. The number of turns can and even should be made more than mine, for example about 50 turns. The winding wire itself can be taken from unnecessary electric motors or power transformers.
When the coil is wound, carefully remove it from the device and wrap it with paper tape. As a result, you need to make two absolutely identical coils. Next, use a knife to scrape off the varnish and after cleaning, these ends need to be tinned.

Windings tend to bend and lose their correct geometry, so the coils need to be completely wrapped, for example, with paper tape. After this, they need to be flattened a little where they overlap each other. They are often made to look like the letter "D" as shown in the picture below.

It is convenient to use a sandwich panel as a base for search coils, which is used for slopes of plastic windows.

The board will be located at some distance from the search coils and it is not recommended to use ordinary wires. To connect the coils to the board, I used a shielded wire, if I'm not mistaken from the microphone.

Shielded wire for connecting the coils to the board.

The central wire must be soldered to the beginning of the coil, and the other to the minus of the power supply as shown above.
Naturally, the wires for both coils will be separate so that there is no interference.

Coil location and settings

Setting up the system begins before gluing the coils to the base.

We set the trimming resistor R6 to approximately 90 kOhm, and set the adjusting resistors R7 and R8 to the middle position. Now you need to move the coils. The device will produce sound in two positions. With wide and narrow overlap. I recommend fixing the coils at their narrow overlap as shown in the figure below (position 2). According to my observations, in position 2 the sensitivity is better and more accurate positioning occurs.

After this you need to glue it well to the base. I did this using hot glue. But if you wish, you can make recesses in the base for the coils and fill them with epoxy.

After the glue has hardened, you need to adjust the settings again. We do not touch R7 and R8 for now, they are set in the middle position and resistor R6 needs to achieve a position in which the sound emitter crackles a little and, so to speak, is in a borderline position between silence and squeaking (on the verge of breakdown). In the future, when using the metal detector, you will only need to adjust the position of R7 and R8. This is due to the fact that the device is not ideal, the coils are not shielded, and the settings will deteriorate if the battery voltage is lost.

Revision option

If desired, you can make additional modifications to the coils - shielding from external electromagnetic fields ("Faraday shield"). This is done after the initial covering of the windings, which was described earlier (with paper tape or electrical tape). Then you need to take long strips of aluminum foil and wrap the coils. This is not done completely, but leaves a gap of about 1-2 cm at the point where the wires exit. The foil is connected to the end coil and connects to the power supply minus. After this, the coil is covered with electrical tape.

I didn't do this because I was afraid of losing sensitivity.

Metal detector design

After soldering the components, it is advisable to remove the remaining flux and rosin from the surface of the board, because they can adversely affect the operation of the circuit.
I decided to place the board in a metal box, and to avoid short circuits with solder joints, the bottom of the case was covered with electrical tape. Later I will most likely choose a plastic case.

Always pay attention to the rigidity of the cables, because... It would be a shame if something comes off during use.
The circuit will be powered by a crown battery. The circuit has low power consumption, but it is still better to install an alkaline battery, it will ensure the device operates for several “cops”.

The handle was made of a metal-plastic water pipe, and closer to the base it was continued with plastic tubes so that the coils did not react to the metal-plastic handle itself. The design turned out to be quite light. The shielded wires were laid with electrical tape. I installed the box with the metal detector board higher so that the adjusting resistor was at hand.

Advice

Every time before using a metal detector, you should use a variable resistor to make the emitter quickly crackle. The faster the crack, the greater the sensitivity.

First find

Experiment: I buried a coin with a diameter of 2.5 cm in the ground at a depth of 25 cm. When scanning, the coils were at a distance of 5 cm from the ground. At the same time, the metal detector emitted a distinct signal. I assume that large metal objects will “ring” deeper.

In any case, it takes me some time to get used to the metal detector and, after some searching, to draw the final results of its capabilities.

This article has a video that shows the process of creating a metal detector and its testing.

List of radioelements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
DD1, DD2	Programmable timer and oscillator	NE555	2			To notepad
VT1	Bipolar transistor	KT3102EM	1			To notepad
R1	Resistor	1 kOhm	1			To notepad
R2	Resistor	100 kOhm	1			To notepad
R3	Resistor	470 - 680 Ohm	1			To notepad
R4	Resistor	2 - 2.2 MOhm	1			To notepad
R5	Resistor	10 kOhm	1			To notepad
R6	Trimmer resistor	100 kOhm	1			To notepad
R7	Variable resistor	100 - 500 kOhm	1	Rough tuning

This is almost akin to searching for treasures. Some are stopped by the fact that they live far from mountains or rivers in order to look for nuggets by washing sand. Others do not understand radio components to know how to extract gold from them. Still others prefer to look for precious metal using a metal detector, but do not have the funds to buy it. Fortunately, the device is quite simple, and even without being a radio amateur, you can make it yourself.

Operating principle

What is a metal detector? This is a device that, using certain radiation, finds metal located underground, without direct contact with it. The response data that comes back helps to identify the find and informs about it using an audio or visual signal.

The principle of operation of the metal detector

The electromagnetic field that the device emits comes into contact with metals, in this case gold, which provokes the appearance of eddy currents on their surface. By measuring electrical conductivity, metals are identified and data about this is transmitted by a signal.

Metal detectors can have different wave parameters, return signal processing techniques, additional functions and much more. Therefore, before you start making a device, you need to decide what exactly you want to get as a result.

The standard frequency for metal detectors is 6–20 kHz, but for gold it should be slightly higher, 14–20 kHz or more. This is because gold often occurs in tiny nuggets, so higher sensitivity is needed. If there is such a possibility, then it is good to have a device with a multi-frequency customizable search, then it will be possible to increase the number of objects that it recognizes.

Among all the metal detector circuits on the Internet, experts advise choosing devices with balanced induction, which have two coils in the head and a powerful electronic circuit. Also of great interest are circuits that have a receiver-transmitter operating principle, operating at high frequencies, about 20 kHz, which makes it possible to distinguish non-ferrous metals from ferrous ones.

Common parameters

Various technical methods can be used to design a metal detector. Much depends on the conditions in which it will be used. Therefore, the idea of ​​what requirements the device must meet must be defined as clearly as possible. The following device parameters are distinguished:

• sensitivity - a characteristic that determines how small objects the detector can detect;
• selectivity - the ability to identify metals and react to specific ones;
• resistance to interference - the ability not to respond to extraneous radio signals from radio stations, cars, lightning strikes and others;
• energy consumption - how much the device consumes and how long the built-in battery or batteries last;
• penetrating power - the depth at which the device can recognize metals;
• dimensions of the device;
• search area size - the area covered by the device without changing its location.

Resolution is the main parameter, in turn, it is also a composite one. There are one or two signals at the output of the device, and there are more properties that determine the object and its location. For example, if you lower the frequency of the generator, you can achieve an increase in the search and penetration area, but lose in sensitivity, as well as mobility due to the increase in the size of the coil.

Diagram of a simple metal detector

The peculiarity of the design of the metal detector is that all of the above parameters, in combination or individually, depend specifically on the frequency of the coil. Thus, this characteristic is decisive when designing the device. By frequency, metal detectors are divided into the following:

• ultra-low frequency: frequency up to several hundred hertz, low mobility, high power consumption, complex in design and signal processing;
• low-frequency: hundreds, thousands of Hz, low sensitivity, high noise immunity, simple design, permeability depends on power - from 1 to 4 m, mobile;
• high frequency: tens of kHz, simple design, permeability up to 1.5 m, poor noise immunity, so-so discrimination, good sensitivity;
• high-frequency: radio frequencies, typical “gold”, excellent discrimination, small permeability, up to 80 cm, low consumption, other parameters are poor.

Device design

The device, which does not require absolutely any knowledge in radio engineering, can be assembled with your own hands, having: a calculator, a radio receiver, a box with a hinged lid made of plastic or cardboard, and double-sided tape. The calculator must be as cheap as possible to serve as a basis for radio interference, and the receiver must not be immune to interference.

DIY metal detector, instructions:

• We unfold the box, forming it into a book.
• We fix the calculator and receiver in the box, the latter in the lid.
• Turn on the receiver and look for a free area at the top of the AM band.
• Turn on the calculator: the receiver should make a sound, set it to maximum volume.
• If there is no tone, we adjust until it appears.
• Fold the lid so that the tone disappears. In this position, the magnetic vector of the primary pulses will be perpendicular to the axis of the magnetic antenna rod.
• We fix the cover.

Thus, it is quite simple to assemble a primitive device, but in order to obtain more data, you already need to have some knowledge and skills in radio electronics. On the Internet you can find a suitable one from many schemes.

Today we will talk about how to make a highly sensitive metal detector with your own hands at home from scrap materials. We will also consider assembly methods, visual photos, circuit boards, diagrams and drawings of homemade metal detectors and metal detectors with different operating principles

The operation of a metal detector is based on the principle of magnetic attraction. Thanks to this, a magnetic field is created by the device through the search coil, and then the magnetic field is directed into the ground. The second coil of the metal detector receives return signals and reports the find using a tone signaling device. The moment the coil is passed over the ground and a metal object is detected near the magnetic field, the tone will change in pitch. This change in the field means that you are near the search object.

It is necessary to take into account the fact that the larger the coil, the more sensitive the metal detector becomes, although in modern devices it is often necessary to install small search heads, but equipped with powerful circuits. But how can you make it yourself and for free?

There are four types of metal detectors:

1. Ultra Low Frequency (ELF) finder: The simplest of the home remedies, it is not difficult to make. Has the ability to track various metals (with special settings). The most widely used type.

2. Pulse metal detector (ID): a deep device, capable of detecting objects located very deep. Popular among professional gold hunters because it is primarily tuned to non-ferrous metals.

3. Beat detector: can detect any metal or mineral in the range of its pulse (to a depth of up to 1 meter), if you make it yourself, you can distinguish only metals of a certain group. This is the cheapest and simplest type of device.

4. Radio Detector: Can detect metals hidden up to 1 meter in the ground. It is made very quickly, within a few minutes, this is the best option for demonstrating the principle of operation of the device or for presenting it at children's art fairs. He's not that popular.

Regardless of the type of metal detector you plan to make yourself, most detectors have a similar design assembly. What and how can you make the most primitive metal detector?

1. Control box: consists of a board, microspeaker, battery pack and microprocessor.

2. Holder: connects the command block and the coil. Often reaches the size of a human being.

3. Magnetization coil: this is the part that senses the metal, as well as the source of the MF. Also known as a "search head", "loop" or "antenna", consists of disks.

4. Stabilizer (optional): needed to control the position of the detector.

Making a high frequency metal detector

A high-frequency metal detector differs from other models in that it uses two coils at once:

· transfer coil: the outer circuit of the coil that contains the wires. Electricity is transmitted through these cables, which creates a magnetic field.

· receiving reel: a reel with a coil of wire. This part receives, processes and amplifies the frequencies coming from the metal in the ground, and, therefore, signals the discovery of treasure.

Step-by-step instructions, photos and diagrams for beginners on how to make a high-frequency metal detector:

1. You need to assemble a command block. It can be made from a computer, laptop or radio.

2. Find the highest AM frequency on the radio. Check that the receiver is not tuned to a radio station.

3. Now we assemble the search head. To do this, cut out two circles from an ordinary thin plywood sheet. One is about 15 centimeters in diameter, the other is slightly smaller – 10-13. This is necessary so that one ring can fit into another. Now you need to cut out small wooden sticks to position the rings parallel to each other. .

4. From these plates we take 10-15 turns of enameled copper wire with a cross-section of 0.25 mm from the outer circle. Now you need to attach the structure to the block.

5. Pole connection. Mount the head on the bottom end, radio detector on the top.

6. Now you need to turn on the radio frequency, you should hear a faint tonal sound. You may need to do a little work with the radio settings. If necessary, you can attach headphones to the kit for better audibility.

Assembling a pulse detector

You need to assemble the control unit. Hack a regular transistor type radio to find usable parts. We will need:

· 9 volt battery;

· Amplification transistor 250+;

· A small 8 ohm speaker will do.

Assembling the search coil

You need to cut 3 rings from 3mm plywood, the diameter of one is 15 cm and the diameter of two is 16 cm. Use wood glue to make a sandwich, with a 15cm circle in the center.

Along the edge, equip the plywood with 10 turns of wire, as in the method above.

Setting up a radio station. Make sure the tone is sounding and the radio is out of range.

Turn on the block. You may need to tilt it. Also, before making a metal detector with your own hands, you need to check the board settings; perhaps it will not search for metals due to the board settings.

Attach the search head to the shaft. Test your metal detector on a plug or other metal parts. Important: before you make a powerful metal detector with your own hands, you need to select a higher-frequency receiver, in which case we advise you to buy a special unit for the detector in a radio store or take the Terminator metal detector as a starting point.

In principle, everything is quite simple, you just need to find everything you need and make a metal detector at home yourself. Here's another way:

1. To make a metal detector at home, you will first need to find an empty box from a regular CD.

2. Now you need to find the radio and glue its back wall to the first flap of the disc box. For this purpose, you can use double-sided tape or special adhesive tape.

4. Now that such a device is almost ready, it’s time to start setting it up. Turn on the radio and make sure that the device is working, and that it is operating on the AM band. At the same time, it is also necessary to ensure that no other radio stations operate on this frequency. Now you should make the sound bigger and make sure that you don’t hear anything else except noise from the receiver.

5. Now we check the functionality of the created metal detector. We begin to close the box. At a certain moment you will hear a strong sound. This means that the radio was able to pick up the electromagnetic waves that were emitted by the calculator.

6. When you open the box slightly, this noise will disappear. Now it is enough to open the box slightly so that the noise is not strong, but audible. In this position, present the box to any metal object. After this, you can hear this loud noise again. A loud sound indicates that the metal detector model is working. In this case, you can use it to look not only for metal things lost in the house, but also to go to the forest or to another place in order to find something interesting, and maybe even precious. But it’s still better to use such a device at home.

Even the simplest DIY metal detector needs an inductive coil. It is a ring with a diameter from 6-8 cm to 14-16 cm, depending on the size of the metal objects to be looked for. To make a homemade coil, take a blank of a suitable diameter, onto which an enameled copper wire with a cross-section of 0.4-0.5 mm is wound. The number of turns can be calculated using a well-known formula that takes into account the diameter of the coil. After winding, the coil is carefully removed from the workpiece and secured with insulating tape. It will protect it from mechanical damage and atmospheric moisture. After this, a foil screen is wound over the coil with a gap of approximately 10-15 mm in length.

The resulting screen should not be a short-circuited loop. A tinned copper wire must be wound over the screen in 1 cm increments, which is connected to the braid of the coaxial cable leading to the electronic unit. The coil is connected to the circuit with a two-wire coaxial cable.

It is recommended to make several coils with different internal diameters, which will allow them to be connected for each specific case. In conclusion, all that remains is to design the metal detector structurally: place the electronic unit in a sealed case, protected from moisture and dust, and install the inductive coil on the end of a non-metallic pole of the required length. A small speaker or headphones can be used as a source of sound signal generated by an electronic circuit if the device is to be used in noisy places. The device is powered from an autonomous current source - a battery or accumulator.

A deep homemade metal detector differs from a surface one in its higher sensitivity, which allows you to find metal objects at depths of up to several meters. In addition, such devices provide selectivity, allowing small objects to be ignored. In technological terms, such a device is no different from the one described above. As a rule, the inductive coil for a deep metal detector is made of a larger diameter (up to 300 mm) and has better protection from external interference. Setting up such a device may require the use of electronic measuring equipment. This will allow you to achieve the required level of sensitivity of the device.

Any metal detectors operate based on the principles of “Foucault currents” known from the school curriculum. We will not go into details of the experiments. When the search coil and a metal object come closer, a change in frequency occurs in the generator, which the device reports with an audio signal. If you hear a squeaking sound in your headphones, it means there is something metal lying underground. Modern inventors are working on two tasks: increasing search depth; improvement of identification parameters of devices; reduction of energy costs; convenient operating characteristics.

How to make a metal detector at home? It’s worth getting a little acquainted with electronics and reading physics for the 7th grade of high school. Experience with some tools and available materials will be useful. It is necessary to study and test a number of electrical circuits in order to choose the one that will really work

Materials you will need for work:

small generator (from an old tape recorder); quartz resonator; film capacitors and resistors; vinyl or wooden ring for the search coil; plastic, bamboo or wooden cane holder; aluminium foil; wires for coil winding; piezoelectric emitter; metal box – screen; headphones for receiving sound signals from the device; two identical transformer coils; 2 Krona batteries; perseverance and patience.

Sequence of assembling a search metal detector A search coil is made from a plywood circle with a diameter of 15 cm: the wire is wound in turns (15-20) onto a template. The stripped ends are soldered to the connecting cable. A layer of thread is wound around the perimeter of the coil over the wire for fastening. All parts of the circuit are soldered on a PCB board in the following order: capacitors, resistor system, quartz filter, signal amplifier, transistor, diodes, search generator. A soldered board is inserted into the prepared case, connected to the search coil and mounted on a holder stick. The signal from the search coil reflected by a metal object increases the frequency of the generator. Amplified by a quartz filter, it is converted by an amplitude detector into a constant pulse that produces sound.

The principle of operation of a metal detector comes down to the fact that when a metal object approaches the inductor coil of the generator - the main unit of the device - the frequency of the generator changes. The closer the object and the larger it is, the stronger its influence on the frequency of the generator.

Now let’s look at the design of a simple metal detector assembled using two transistors. Metal detector circuit The generator is made on transistor VT1 according to the three-point capacitor circuit. Generation is formed due to positive feedback between the emitter and base circuits of the transistor. The frequency of the generator depends on the capacitance of capacitors C1-C3 and the inductance of coil L1. As the coil approaches a metal object, its inductance changes - it increases if the metal is ferromagnetic, for example iron, and decreases if the metal is non-ferrous - copper, brass.

But how can you monitor the change in frequency? For this purpose, a receiver assembled on a second transistor is used. This is also a generator, assembled, like the first one, according to a three-point capacitive circuit. Its frequency depends on the capacitance of capacitors C4-C6 and the inductance of coil L2 and is not much different from the frequency of the first generator. The required frequency difference is selected using a coil trimmer. In addition, the cascade on transistor VT2 also combines the function of a detector that identifies low-frequency oscillations of high-frequency oscillations arriving at the base of the transistor. The detector load is BF1 headphones; capacitor C1 bypasses the load for high frequency oscillations.

The oscillatory circuit of the receiver is inductively coupled to the generator circuit, therefore, currents flow at the frequency of both generators, as well as a current of the difference frequency, in other words, the beat frequency, in the collector circuit of transistor VT2. If, for example, the frequency of the main generator is 460 kHz, and the frequency of the receiver generator is 459 kHz, then the difference will be 1 kHz, i.e. 1000 Hz. This signal is heard in phones. But as soon as you bring the L1 search coil closer to the metal, the sound frequency in the phones will change; depending on the type of metal, it will either decrease or become higher.

Instead of those indicated in the diagram, P401, P402 and other high-frequency transistors are suitable. Headphones are high-impedance TON-1 or TON-2, but their capsules must be connected in parallel so that the total resistance is 800...1200 Ohms. The sound volume in this case will be slightly higher. Resistors - MLT-0.25, capacitors - KLS-1 or BM-2.
Coil L1 is a rectangular frame with dimensions of 175x230 mm, consisting of 32 turns of PEV-2 0.35 wire (PELSHO 0.37 wire is suitable).

L2 coil design. Two cylindrical paper frames 6 contain pieces of a rod with a diameter of 7 mm made of 400NN or 600NN ferrite: one (1) 20...22mm long, permanently fixed, the other (2) 35...40mm (movable - for adjusting the coil). The frames are wrapped with paper tape 3, on top of which a coil L2 (5) - 55 turns of PELSHO wire (possibly PEV-1 or PEV-2) with a diameter of 0.2 mm is wound. The coil terminals are secured with rubber rings 4.
Power sources - battery 3336, switch SA1 - toggle switch, connector X1 - two-socket block.

Transistors, capacitors and resistors are mounted on a board made of insulating material. The board is connected to coils, a battery, a switch and connector, and an insulated stranded wire. The board and other parts are placed in a glued plywood case with dimensions of 40x200x350 mm. Coil L1 is attached to the bottom of the case, and coil L2 is placed inside the coil at a distance of 5...7 mm from its turns. A board is attached next to this coil. The connector and switch are attached from the outside to the side wall of the case. A wooden handle about a meter long is attached to the top of the case (preferably with glue).

Setting up a metal detector begins with measuring the operating modes of the transistors. Having turned on the power, measure the voltage at the emitter of the first transistor (relative to the common wire - the power plus) - it should be 2.1V. More precisely, this voltage can be selected using resistor R2. Then measure the voltage at the emitter of the second transistor - it should be 1 V (set more precisely by selecting resistor R4). After this, by slowly moving the tuning core of the L2 coil, a loud, clear, low-frequency sound appears in the headphones.

By bringing a tin can closer to the search coil, the beginning of a change in the sound tone is recorded. As a rule, this occurs at a distance of 30...40 cm. By more accurately adjusting the frequency of the second generator, the highest sensitivity of the device is achieved.

Frequency generators of 160 kHz and 161 kHz, respectively, are assembled on elements IC1.1 and IC1.2. Where C1, L1 is the oscillatory circuit of the first generator, C4, L2 is the oscillatory circuit of the second generator. The inductance of the second generator L2 is a search coil. A mixer is assembled on element IC1.3, at the output of which we obtain a frequency difference between the generators equal to 1000 Hz. When a metal object appears near the search coil, its inductance changes and changes the frequency of the generator, which in turn changes the frequency at the mixer output. Variable resistor R5 is a volume control. Element IC1.4 is used as a buffer amplifier stage, cutting off unnecessary frequencies and amplifying the signal. A push-pull amplifier is assembled using elements VT1, VT2, VT3, designed to work with headphones with a resistance of 32-200 Ohms.

The IC1 chip is of the CD4030 type. It can be replaced with any other chip OR CMOS technology. VT1, VT3-BC547, VT2-BC557. All electrolytic capacitors are rated at 16V. Resistors with a power of 0.125W. Supply voltage - 6V.
Coil L1 - inductance 100 mH.
Search coil L2 - 140 turns of wire with a diameter of 0.8 mm, coil diameter - 150 mm.

Tuning comes down to tuning the generators to frequencies of about 160 kHz with a difference of 1 kHz.

When a metal object enters the working area of ​​the coil, the inductive coupling between the coils changes. In this case, a signal appears at the terminals of coil L2, limited in amplitude (if the object is large) by diodes VD1 and VD2, which is subsequently amplified by the action of the operational amplifier DA1.1.

At the output of the filter, which is built on this operational amplifier, a constant voltage appears, increasing as the coils approach the metal target. Next, the voltage goes to the inverting input in the comparator DA2.1. It compares this voltage with the reference voltage supplied to its second input.

When the comparator is triggered, its output voltage decreases, this leads to the closure of transistor VT3, and the sound generator made on the basis of the DA2.2 microcircuit is activated. From the sound generator the signal goes to the amplifier, and from there to the main telephone from the hearing aid. You can adjust the volume using variable resistor R38.
To wind the coil, a circle with a diameter of 14 cm is used. For each coil, 200 turns of copper wire with insulation are supposed to be made. The wire should have a diameter of 0.27 mm and should be removed from the middle of the coil. Before removing the finished spool from the frame, you need to bandage it, and after removing it, wind the thread around it so that the turns fit more tightly to each other. The removed coil is configured as in Figure 2 and secured with threads to a plastic plate. There should be a transmitting coil at the bottom, and a receiving coil at the top.

The take-up coil must have an aluminum screen with a hole designed to prevent short-circuited turns. It is necessary to connect the coil leads to the device using a shielded cable. The vertical turns of the coils should be separated by distances of 25 mm. The last step is to secure the coils with glue or sealant.