How to make a metal detector with your own hands: principle of operation, diagrams, step-by-step instructions. A simple do-it-yourself metal detector circuit Make deep metal detectors at home

Finding artifacts underground is a fairly popular activity. For some, this is a profession, others are simply interested in archaeology. There are numerous groups of treasure hunters: both romantics and pragmatic treasure hunters. All these people are united by one passion: searching for metal objects hidden at various depths.

Just because you have an accurate map showing where the treasure is buried, or plans for fighting during the war, this does not guarantee success. You can shovel tons of soil, and the desired item will calmly lie a couple of meters from the active search site.

To search for gold and less valuable metals, you will need a metal detector that you can make yourself.

Important information: The use of such devices is not prohibited by law. However, there are penalties for the consequences of such a search regarding excavations, as well as the recovery of discovered objects.

We won’t go into details; that’s the topic of another article. Simply put: if you find a gold ring on the beach, or a handful of Soviet coins in the forest, there will be no problems associated with the use of electronic search tools.

But for recovered bronze spoons that are 100 years old or older, you can get a real sentence or a large fine.

Nevertheless, devices for searching for metal objects in the depths of the earth are freely sold, and those who want to save money can make a metal detector with their own hands at home.

How the device works

Unlike ground detectors, which work using waves of different frequencies or ultrasound, a metal detector (either factory-made or home-made) works with inductance.

The coil emits an electromagnetic field, which is then analyzed by the receiver. If any object that conducts electric current or has ferromagnetic properties is in the coverage area, the field format is distorted. More precisely, under the influence of the active field of the coil, the object forms its own. This event is recorded by the receiver, and an alert is generated: the instrument needle moves, a tone sounds, and indicator lights light up.

Knowing the operating method, you can calculate the electrical circuit and create a powerful metal detector with your own hands. The complexity of the design depends only on the availability of the element base and your desire. Let's look at several popular options for assembling a homemade metal detector:

The so-called "butterfly"

This nickname was received due to the characteristic shape of the platform on which the inductors are located.

The arrangement of the elements is related to the operating principle. The circuit is made in the form of two generators operating at the same frequency. When identical coils are connected to them, an induction balance is created. As soon as a foreign object with electrical conductivity gets into the electromagnetic field, the balance of the field is destroyed.

Generators are implemented on NE555 chips. The illustration shows a typical diagram of such a device.

The coil for the metal detector (there are two of them, in the diagram: L1 and L2) is made by hand from wire with a cross section of 0.5–0.7 mm². The ideal option is a transformer winding copper core in varnish insulation (removed from any unnecessary transformer). The characteristics do not have to be maintained with pinpoint precision, under one condition: the coils must be identical.

Approximate parameters: diameter 190 mm, each coil has exactly 30 turns. The assembled product must be monolithic. To do this, the turns are grabbed with a mounting thread and filled with transformer varnish. If this is not done, vibration of the turns will throw the circuit off balance.

Electrical diagram

There are two manufacturing options:

• given the small number of elements, you can assemble it on a breadboard by connecting the legs of the parts using conductors;
• For accuracy and reliability, it is better to etch the board according to the proposed drawing.

Any “snot-based” soldering can fail in the field, and you will be offended for wasting your time.

Just like a transistor metal detector, the NE555 device needs fine tuning before use. The diagram shows three variable resistors:

• R1 is designed to adjust the frequency of the generator and achieve that same balance;
• R2 coarsely adjusts sensitivity;
• Using resistor R3, you can set the sensitivity with an accuracy of 1 cm.

Information: This scheme cannot discriminate against metals. The seeker only makes it clear that the object exists. And by the tone of the signal (based on your experience) you can determine the approximate volume and depth of the deposit.

The power supply is quite universal: 9–12 volts. You can select a battery from an uninterruptible power supply, or assemble a power supply from AAA batteries. A good option is 18650 batteries (they are also used for vaping).

Butterfly setting

The principle of operation is described above, so let’s just look at the technology. We set all resistors to the middle position, and ensure that the synchronization of the generators is disrupted. To do this, we fold the coils in a figure eight and move them relative to each other until the squeaking turns into crackling. This is a synchronization failure.

We fix the rings and rotate the resistor R1 until a steady crackling sound appears at even intervals.

By bringing metal objects to the place where the coils overlap (this is the search point), achieve a steady squeak. The sensitivity is adjusted by resistor R2.

All that remains is adjustment with resistor R3, which is used rather to correct the voltage drop in the power source.

Mechanical part

A do-it-yourself metal detector rod is made from a lightweight plastic pipe or wood. The use of aluminum is undesirable as it will interfere with operation. The circuit and controls can be hidden in a sealed housing (for example, a junction box for wiring).

The butterfly finder is ready to go.

Pirate

Another popular pulse model for beginner treasure hunters is the “Pirate” metal detector. It is also easy to make with your own hands, detailed instructions in two versions:

It is advisable to bring the power supply closer to 12 volts, since the quality of operation depends on the voltage. Printed circuit boards have already been tested, both options are shown in the illustration.

The coil (in this case one) is made from the same 0.5 mm transformer wire. The optimal diameter is 20 mm, the number of turns is 25. Since we are making the “Pirate” metal detector with our own hands, the external design fades into the background. Any materials that you were ready to throw away will do.

It is better to make the handle detachable for ease of transportation. We remember that the use of metals is unacceptable.

Sensitivity is adjusted by two variable resistors in real time while searching. No fine tuning of the generator is required.

And if you manage to properly seal the case, you can start searching for “treasures” in the beach surf, and even at the bottom of the reservoir.

It is more difficult to make an underwater metal detector with your own hands, but it will give you an undeniable advantage over your competitors.

Improved performance

You can make a deep metal detector with your own hands from a ready-made “Pirate” without additional costs. There are two ways to do this:

1. Increasing the diameter of the inductor. At the same time, downward permeability increases significantly, but sensitivity to small objects decreases.
2. Reducing the number of coil turns while simultaneously adjusting the circuit. To do this, you will have to sacrifice one coil for experiments. We remove (and cut off) turn after turn until we see that the sensitivity begins to decrease. We remember the number of turns at maximum parameters, and make a new coil for this circuit. Then we change the resistor R7 to a variable one, with similar power parameters. After conducting several experiments with sensitivity, we fix the resistance and change the variable to a constant resistor.

The Pirate metal detector can be assembled using the popular Arduino controller.

It is more convenient to use such a device, but there will still be no metal discrimination.

Having figured out how to make a metal detector with your own hands for amateur tasks, we will briefly examine several serious models.

DIY metal detector Clone PI W

In essence, this is a cheaper version of the professional finder Clone PI-AVR, only instead of an LCD display, a line of LEDs is used. This is not as convenient, but still allows you to control the depth of artifacts.

The best option for the price is the CD4066 chip and ATmega8 microcontroller.

Of course, there is also a printed circuit board layout for this solution, only the control buttons are placed on a separate panel.

Programming ATmega8 is a topic for a separate article; if you have worked with such controllers, no difficulties will arise.

The powerful Clone PI W metal detector, made by yourself, allows you to find metal no more than a meter deep, although without discrimination.

Seeker "Chance"

A similar circuit on the ATmega8 controller is called “Chance”. The principle of operation is similar, only the possibility of screening out (partial discrimination) of ferrous metals has become possible.

A printed circuit board design has also been worked out, which can be successfully replaced with a classic “breadboard” for Arduino

DIY Terminator 3

If you need a homemade metal detector with metal discrimination, pay attention to this model. The scheme is quite complicated, but your efforts pay off with the coins you find, which may turn out to be gold.

The peculiarity of the “Terminator” is the separation of the receiving and transmitting coils. A 200 mm ring is made to emit the signal. 30 turns of wire are laid for it, then it is cut, as a result we get 2 half-coils with a total capacity of 60 turns (see diagram).

The receiving coil is located inside, 48 turns with a diameter of 100 mm.

The adjustment is made using an oscilloscope; after achieving optimal amplitude results, the windings are fixed in the housing by pouring epoxy resin.

Then an experimental hands-on adjustment of the discrimination switch is performed. For this, real objects made of various metals are used, and their type is marked on the mode switch (after verification).

Radio amateurs are working on an improved version of Terminator 4, but there is no practical copy yet.

Simple metal detectors from ready-made electrical appliances

Bottom line

Regardless of the complexity of the design, making a homemade metal detector will require a lot of time and effort from you. Therefore, out of curiosity, such devices are not made. But for professional use, this is an excellent alternative to factory copies.

Video on the topic

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

Characteristics:
- 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. I’ll 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 for yourself.

We wind the coil on anything of a 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 in the opposite direction; 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, so that you can select a live microcircuit and not have to worry about desoldering and soldering.

Purchased chips

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.

Metal detectors or metal detectors are a diverse family of measuring instruments, the operation of which is based on differences in the electromagnetic radiation of objects.

Using a metal detector

Professional highly sensitive metal detectors are used in the daily work of various inspection points; they are used to conduct search and investigative activities of police and rescue services.

A huge army of amateur treasure hunters around the world practice long and leisurely hikes with metal detectors. Sometimes such entertainment brings income and even fame.

Nowadays, an industry of detector (recognition) devices has already been established for all occasions, differing not only in operating principles, but also in a wide range of prices and technical characteristics.

Simple magnetic detectors

The operating principle of the simplest metal detector is based on electromagnetic induction - the device contains an electromagnetic coil, which, due to oscillations and distortions of its field, detects nearby electrically conductive and ferrous-magnetic materials, creating an audio or visual signal.

The first experience of assembling a metal detector at home can be the beginning of a serious hobby: new design solutions and even inventions in this field of applied radio electronics are not excluded even at the amateur level.

The diagram shows the structure of a simple low-frequency magnetic detector.

Hundreds of different designs are used in the production of metal detectors. In order to implement one of them yourself, you will need to make a printed circuit board with your own hands, purchase the necessary coils, transistors, resistors, capacitors, etc., and assemble the device.

Metal detector made from improvised means

Another option is to assemble a metal detector from available materials; it is more suitable for humanists and novice technicians with a passion for finding treasures and lost artifacts.

During operation of such a homemade device, electromagnetic waves emitted by the calculator are caught on the AM band of the receiver.

An indicator of the location of an object in this device is the rotation of the electromagnetic field during re-emission, which changes the parameters of the sound signal. A photo of such a do-it-yourself metal detector can be found on the Internet and at the end of our material.

To use such a prefabricated version, you do not need a detailed diagram or assembly instructions, but compliance with certain requirements for the two main components of a homemade detector, namely a properly working calculator and a radio receiver.

Both devices must be from the cheapest category, the receiver must have an AM band and a magnetic antenna, and the calculator must emit pulsed radio interference during operation.

To work on the model, you will also need a suitable sized plastic box with an opening lid, like a book, which will become the body of the finder.

An old CD box is ideal for these purposes. To attach the parts you will need double-sided tape.

Metal detector assembly

• Securing the instruments inside the case: a strip of tape is attached to the back of the instruments, then the calculator is placed at the base of the box, the receiver is on the inside of the lid.
• Setting up the receiver: you need to turn on the receiver at maximum volume and select the upper position of the AM range, free from radio broadcasts and interference.
• Adjusting the calculator: when the calculator is turned on, the receiver should respond with a sharp noise, hum or wheezing; if this does not happen, you need to adjust the range.
• Fixing the position: we begin to smoothly close the box until the sound disappears or becomes more uniform and fix the box doors in this position, using a cube of foam plastic, rubber bands, etc.
• The metal detector is ready. If there is a product with electromagnetic radiation nearby, the receiver will sound an alarm.

By combining elements of other radio devices in a simple detector, you can observe the operating principle of metal detectors in action and enjoy your first search expedition.

Note!

Such a detector, assembled at home, can be tested to search for coins or metal construction debris lying in the surface layer of the earth in almost any area, on any open ground.

Photos of do-it-yourself metal detectors

Note!

Note!

Now, perhaps, there is no person who does not know what a metal detector or metal detector is. But let us remind you once again that this is a device that allows you to determine the hidden location of metals. The metal detector is very popular among amateur archaeologists and treasure hunters. The device is quite expensive, and some models are even sky-high, which is why most radio amateurs prefer to assemble it themselves. In today's article we will look at how to make a metal detector with your own hands, the operating principle of the device, popular circuits, as well as assembly and configuration features.

Read in the article

How does a metal detector work?

A metal detector, or metal detector, is an electronic device consisting of a primary sensor (coil with winding) and a secondary unit. Metal detection devices are divided into several types:

1. "reception and transmission";
2. induction;
3. pulse;
4. generator

Devices in the mid-price category are mainly of the “receive-transmit” type. The operating principle of such metal detectors is based on the transmission and reception of electromagnetic waves. The main elements of a device of this type are two coils: one is transmitting, and the second is receiving. The first coil transmits electromagnetic waves that freely pass through a neutral medium and which, when colliding with metal objects, are reflected and transmitted to the receiving device. After the reflected signal hits the second coil, the operator is informed by a buzzer that the target has been found.

An induction-type metal detector operates on the same principle as transmit-receive devices. The main difference between them is the number of coils with winding. An induction metal detector has one coil that sends and receives a signal simultaneously. Pulse devices are insensitive to the concentration of salts in the soil and include in their design a coil, the electromagnetic field of which creates eddy currents on the metal surface that are captured by the detector. This principle of operation reduces the possibility of discrimination, which can complicate the search.

Generator-type metal detectors come in different types, but they are all built on the basis of an LC generator. They have a low level of sensitivity and are generally designed to find only one type of metal. Metal detectors can also be divided into three categories:

1. common use;
2. middle class;
3. professional equipment.

Functional and technical parameters of metal detectors

Before choosing and buying a good metal detector, you should clearly decide in what environment the search work will be carried out. It is also necessary to take into account the expected size of the objects being sought and the depth of their location. Let's look at the main characteristics that you need to pay special attention to when purchasing a detector:

• operating principle;
• operating frequency of the device;
• sensitivity;
• ground balancing;
• target designation;
• discriminator;
• additional functions.

The operating principle and operating frequency of the detector are the main characteristics that determine the capabilities of the device and show which category it can be classified into (simple ground, middle class or professional). Sensitivity determines the depth of objects with which the device can operate. As a rule, this figure ranges from 100−150 mm to 600−1500 mm. However, there are depth models designed to search for objects at a depth of 5 meters. The discriminator makes it possible to configure the device to search for a specific type of metal. This allows the operator not to be distracted by metallized debris.

What types of metal detectors can you make yourself?

You can purchase a detector at a specialized store or make a metal detector with your own hands at home. There are schemes that even a novice radio amateur can do. Devices that you can assemble yourself include:

• "butterfly";
• device without microcircuits (IC);
• model "Pirate";
• "Terminator 3" etc.

There is information on the Internet that you can supposedly assemble a metal detector from your phone with your own hands. Remember two words - this is fiction. There are some applications that allow you to include a tablet or smartphone in the detector circuit, but it is impossible to make a full-fledged device for searching for metals and recognizing them.

How to assemble a “Pirate” metal detector with your own hands: detailed instructions

Models of the “Pirate” series cost about $100–300. This cost is due to the device’s ability to detect objects at a depth of 200 mm (for small items) and 1500 mm (large items). Let's look at the features of assembling and setting up a device for detecting metals, as well as its components.

Materials needed to assemble a powerful metal detector with your own hands

To make a metal detector you will need the following materials and components:

• IC KR 1006VI1 or NE 555 (foreign equivalent) to create a transmitting unit;
• transistor IRF 740;
• IC K 157UD2 and transistor BC 547 for assembling the receiving unit;
• NPN type transistors;
• PEV 0.5 wire to create a coil;
• materials for the manufacture of the body, rod, etc.;
• a plate covered with copper sheet for making a printed circuit board;
• wires;
• insulating tape;
• side cutters;
• soldering iron;
• scalpel;
• Screwdriver Set;
• pliers;
• various types of fasteners.

Assembling a metal detector with your own hands: diagrams

Currently, there are many circuits for the “Pirate” metal detector, since some radio amateurs have begun to modernize them to suit their needs. All options will not be considered, only the most proven and most popular.

NE555 detector circuit

The classic circuit of a metal detector of the “Pirate” series, built on the NE555 IC timer. The operation of the device depends on a comparator, one output of which is connected to the IC pulse generator, the second to the coil, and the output to the speaker. If metal objects are detected, the signal from the coil is sent to the comparator, and then to the speaker, which notifies the operator of the presence of the desired objects.

DIY metal detector assembly without microcircuits

Unlike the previous circuit, this device uses Soviet-style transistors KT-361 and KT-315 to generate signals (you can use similar radio components).

DIY printed circuit board

The parts have been purchased, the diagram is available, and now you need to assemble it all. To place radio components, a printed circuit is used, which can be easily made independently. To do this, you will need a piece of sheet getinax covered with copper electrical foil. Transfer the selected diagram to the workpiece, mark the tracks connecting the parts, and drill holes in the places where they are attached and soldered. Cover the tracks with protective varnish, and after drying, lower the future board into ferric chloride for etching (removing unprotected areas of copper foil).

After the board is ready, you can install and solder the radio components. The next step is to check the circuit using measuring instruments.

Metal detector coil - how to make it yourself

Due to the fact that the Pirate metal detector is a pulse-type device, accuracy when assembling the coil is not important. For the base you will need a ring with a diameter of about 200 mm, onto which you need to wind 25 turns of 0.5 mm PEV wire. To increase the depth of metal detection, the coil frame should be in the range of 260−270 mm, and the number of turns should be 21−22 vol. Next, the mandrel with the wire must be well wrapped with insulating tape.

Place the finished coil in a housing made of dielectric material. To do this, you can use suitable-sized cases from faulty “throw away” household appliances. By the way, this will protect the coil from mechanical damage while working with the detector. The winding terminals must be soldered to a stranded wire with a diameter in the range of 0.5-0.7 mm. It is best to use twisted pair cable.

Checking and setting up the metal detector

We attach all the components of the device to the metal detector rod: the body with the coil, the receiving and transmitting unit and the handle. If the control circuit is assembled correctly, then adjustment of the device will not be required, since it initially has maximum sensitivity. Fine tuning is performed using variable resistor R13. Normal operation of the detector should be ensured with the regulator in the middle position. If you have an oscilloscope, then use it to measure the frequency at the gate of transistor T2, which should be 120−150 Hz, and the pulse duration should be 130−150 μs.

The video shows how to set up a metal detector.

How to make an underwater metal detector with your own hands

Sometimes search work has to be moved from land to water. What to do in this case, because the electronics will fail? There are, of course, special devices for working underwater, but you can make a deep metal detector with your own hands. To do this, you can take the most ordinary homemade detector and place all the components in hermetically sealed housings. In addition, it is worth slightly modifying the device and installing light indicators instead of an audible alarm.

How to make a Terminator 3 metal detector with your own hands: detailed instructions

The Terminator 3 model has long been popular among radio amateurs, and over the many years of its existence the device has received many improvements. We offer step-by-step instructions on how to make a metal detector yourself at home. The device has low power consumption, can be configured to search for certain types of metal, and has good depth characteristics.

Tools

Before making a homemade metal detector, you need to prepare the following tools:

• soldering iron or soldering station;
• solder, tin, rosin;
• pliers, round nose pliers, side cutters;
• Screwdriver Set;
• hacksaw for metal;
• oscillography and other instrumentation.

Diagram, selection of parts and circuit board

To manufacture the control unit, it is necessary to make a circuit board on which all the necessary radio components will be placed. The circuit presented below must be transferred to a getinax plate coated with copper foil and a circuit board must be made in the same way as described above in the article for the Pirate metal detector. The size of the circuit should be within 104x66 mm, and the board blank should be 10 mm larger on each side.

We will describe in detail how to prepare a printed circuit board for a metal detector in step-by-step instructions:

Illustration	Process description
	We take a textolite plate coated with copper foil. Degrease chemically or mechanically (sand).
	We apply the diagram to the plate, cover the tracks with a protective varnish and subject the workpiece to etching (described above, as for the “Pirate” metal detector). Using a thin drill, drill holes for radio components and fastenings to the body.
	We place the radio components in accordance with the diagram and carry out the wiring.
	This is what the finished Terminator 3 metal detector board will look like.

Metal detector coil

This is, in fact, the most sensitive part of the device. She is responsible for scanning the space underground. Let's look at the steps to create a simple coil for a metal detector:

Illustration	Process description
	On a piece of plywood we draw two circles corresponding to the diameters of the coils - internal and external. We drive nails around the perimeter of the circle. The diameter of the outer winding TX should be within 200mm. The coil is made from two folded wires. We wind 30 turns on the nails.
	We tie the winding around the circumference with threads. We take out the nails, cover the resulting coil with varnish, and after it dries, wrap it with electrical tape and foil. In exactly the same way we make the internal winding RX, which is half the size of TX and contains 48 turns of wire.
	We place the coils in the housing and wire the wires that will be connected to the control unit.
	This is what the finished metal detector frame will look like.

Homemade metal detector: detailed description of assembly diagram and setup

We discussed in detail the stages of assembling the board and the main elements of the metal detector earlier, now we are faced with the very last and most important steps: assembling the case and setting up the device.

Illustration	Process description
	We take a suitable box or make the case ourselves. We drill holes for trimming resistors and a connector. We mount the finished board and regulators in the case.
	We close the case, connect the metal detector frame and attach everything to a plastic pipe with a handle. The metal detector is assembled and ready for use.

This video will help you set up your metal detector.

Features of a DIY metal detector with a metal discrimination circuit

Metal detectors with a simple circuit allow you to detect hidden objects, but in order to find out which ones you will have to work with a shovel. Instead of a gold coin or a military helmet, you can find just a piece of pipe and spend a lot of time on it. To make the task easier for search engines, detectors began to be equipped with discriminators that make it possible to distinguish the type of metal and allow various types of debris to pass through. The simplest methods for determining the types of metals were implemented in old instruments and entry-level devices and had two modes - “all metals” and “non-ferrous”. The discrimination function allows the operator to respond to a phase shift of a certain magnitude, compared to a configured (reference) level. In this case, the device cannot distinguish between non-ferrous metals.

Professional metal detectors use discriminators with range selection. The microprocessor systems used in such devices make it possible to program the device to respond only to certain groups of metals. Discrimination is useful in littered areas, but reduces detection depth by 10−20%.

Assembly features of a deep metal detector

A deep-type metal detector is a special device capable of detecting objects hidden at a great distance from the surface of the earth. It is at considerable depth that the most interesting and valuable objects can be found. Some models can detect metals at a distance of 4 to 6 m underground.

There are two types of deep metal detectors: frame and transceiver on a rod. The first type of device is capable of covering a large area of ​​land for scanning. Thus, the search speeds up, but has a negative impact on performance. The second version of the detector works in a small area, but better determines the center of the target. With such a device it is good to search in grass, forest or reeds. Therefore, when choosing the type of metal detector, you need to determine under what conditions the scanning will be carried out.

If you have experience assembling a metal detector yourself, tell others about it! If you have questions for the author of the article, ask him in the comments.