Homemade metal detectors, or how to make a metal detector with your own hands

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.

Metal detector and its structure

Professional metal detector Garrett AT Pro for searching military trophies and coins

This model costs more than 32,000 rubles, and, of course, non-professionals will not be able to afford such a device. Therefore, we suggest studying the design of a metal detector in order to assemble a variation of such a device yourself. So, the simplest metal detector consists of the following elements.

Design elements of a standard metal detector

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 principle of operation of the metal detector

The metal detector works like this: the magnetic field lines of the primary field (A) of red color pass through the metal object (B) and create a secondary field (green lines) in it. This secondary field is picked up by the receiver and the detector sends an audible signal to the operator. Based on the principle of operation of emitters, electronic devices of this type can be divided into:

1. Simple, working on the “receive-transmit” principle.
2. Induction.
3. Pulse.
4. Generating.

The cheapest devices belong to the first type.

The simplest metal detector will make you lose a couple of extra pounds. You'll be walking and digging a lot

An induction metal detector has one coil that sends and receives a signal simultaneously. But devices with pulse induction differ in that they generate a transmitter current, which turns on for a while and then turns off abruptly. The coil field generates pulsed eddy currents in the object, which are detected by analyzing the attenuation of the pulse induced in the receiver coil. This cycle repeats continuously, perhaps hundreds of thousands of times per second.

Design and principle of operation of the device

Metal detectors on the market operate on different principles. Many believe that they use the principle of pulse echo or radar. Their difference from locators lies in the fact that the transmitted and received signals act constantly and simultaneously; in addition, they operate at the same frequencies.

The principle of operation of the metal detector

Devices operating on the “receive-transmit” principle record the signal reflected (re-emitted) from a metal object. This signal appears due to the exposure of a metal object to an alternating magnetic field generated by the metal detector coils. That is, the design of devices of this type provides for the presence of two coils, the first is transmitting, the second is receiving.

Metal detector circuit

Devices of this class have the following advantages:

• simplicity of design;
• Great potential for detecting metallic materials.

At the same time, metal detectors of this class have certain disadvantages:

• metal detectors can be sensitive to the composition of the soil in which they search for metal objects.
• technological difficulties in the production of the product.

Other devices are sometimes called beat metal detectors. This name comes from the distant past, more precisely from the times when superheterodyne receivers were widely used. Beating is a phenomenon that becomes noticeable when two signals with similar frequencies and equal amplitudes are summed. The beat consists of pulsating the amplitude of the summed signal.

The signal pulsation frequency is equal to the difference in the frequencies of the summed signals. By passing such a signal through a rectifier, it is also called a detector, and the so-called difference frequency is isolated.

This scheme has been used for a long time, but nowadays it is not used. They were replaced by synchronous detectors, but the term remained in use.

A beat metal detector works using the following principle - it registers the difference in frequencies from two generator coils. One frequency is stable, the second contains an inductor.

The device is configured with your own hands so that the generated frequencies match or at least are close. As soon as metal enters the action zone, the set parameters change and the frequency changes. The frequency difference can be recorded in a variety of ways, from headphones to digital methods.

Devices of this class are characterized by a simple sensor design and low sensitivity to the mineral composition of the soil.

Typical design

The metal detector includes the following components:

1. The coil is a box-type structure that houses the signal receiver and transmitter. Most often, the coil has an elliptical shape and polymers are used for its manufacture. A wire is connected to it connecting it to the control unit. This wire transmits the signal from the receiver to the control unit. The transmitter generates a signal when metal is detected, which is transmitted to the receiver. The coil is installed on the lower rod.
2. The metal part on which the reel is fixed and its angle of inclination is adjusted is called the lower rod. Thanks to this solution, a more thorough examination of the surface occurs. There are models in which the lower part can adjust the height of the metal detector and provides a telescopic connection to the rod, which is called the middle one.
3. The middle rod is the unit located between the lower and upper rods. Devices are attached to it that allow you to adjust the size of the device. On the market you can find models that consist of two rods.
4. The top rod usually has a curved appearance. It resembles the letter S. This shape is considered optimal for attaching it to the hand. An armrest, a control unit and a handle are installed on it. The armrest and handle are made of polymer materials.
5. The metal detector control unit is necessary to process the data received from the coil. After the signal is converted, it is sent to headphones or other display devices. In addition, the control unit is designed to regulate the operating mode of the device. The wire from the coil is connected using a quick release device.

Metal detector design

All devices included in the metal detector are waterproof.

The principle of operation of the metal detector

A metal detector (hereinafter referred to as MI), also called a metal detector, is an electronic device that generates a directed electromagnetic field (primary signal) and detects its changes when the field comes into contact with metal objects. During the propagation of electromagnetic waves in an inhomogeneous physical environment, they interact with metals, creating eddy currents on their surfaces that generate their own electromagnetic fields. The MI receiving equipment records these fields (secondary signal) and informs the searcher about the detected find by audio or visual means.

How does a metal detector work depending on its purpose and technical device?

The operating principle of a metal detector varies depending on the type of device. Let's consider the main ones:

• Dynamic type devices. The simplest type of device that continuously scans the field. The main feature of working with such a device is that you must be in motion all the time, otherwise the signal will disappear. Such devices are easy to use, however, they are poorly sensitive.
• Pulse type devices. They have great sensitivity. Often, such a device comes with several additional coils for adjustment to different types of soils and metals. Requires certain skills to set up. Among the devices of this class we can distinguish electronic devices operating at low frequencies - no higher than 3 kHz.

Sometimes treasure hunters get lucky and find very interesting things.

• Electronic devices, on the one hand, do not respond (or give a weak response) to unwanted signals: wet sand, small pieces of metal, shot, for example, and, on the other hand, they provide good sensitivity when searching for hidden water pipes and central heating routes, and also coins and other metal objects.
• Depth detectors are designed to search for objects located at impressive depths. They can detect metal objects at a depth of up to 6 meters, while other models “pierce” only up to 3. For example, the Jeohunter 3D depth detector is capable of searching and detecting voids and metals, while showing objects found in the ground in 3- measured form.

The Jeohunter 3D depth detector monitor shows what is under your feet in real time.
Depth detectors operate on two coils, one is parallel to the ground surface, the other is perpendicular.

• Stationary detectors are frames installed at particularly important protected sites. They detect any metal objects in people's bags and pockets that pass through the circuit.

Metal detector in the subway. You have probably passed through such a detector more than once, having previously emptied all the pockets

What is metal discrimination?

Those who are interested in the structure and operating principle of metal detectors often come across the expression “discrimination of metals” when searching for the necessary information. The metal detector's discrimination function determines the direction of the search for a particular group of metal objects. Installing a metal detector to detect non-ferrous metals allows you to ignore iron-containing inclusions in the soil mass.

Units equipped with a display can display a discrimination scale from “0” to “99”. The more the device indicator tends to 0, the lower the electrical conductivity of the found metal object.

In some models, the discrimination line is graduated for types of metals such as iron, nickel, zinc, aluminum, gold, copper and silver. The device can make corrections for the inclusion of ligature in the main composition of the material. The type and amount of alloy in the metal changes its electrical conductivity.

Metals are practically never found in their pure form, so in complex high-level devices there are options that allow you to “ignore” metals such as iron, nickel and aluminum. The metal detector will respond to the detection of gold, silver and copper.

Selective discrimination of metals allows you to reduce the time spent on detecting unnecessary objects and not waste energy on digging unnecessary holes.

Types of MI by purpose

DIY surge protector

In accordance with their intended purpose, MI is divided into the following types:

1. Soil models designed for underground surveys in the upper layers of soil. Devices in this category are the most common among metal detectors and treasure hunters who can assemble a metal detector with their own hands at home. The simplest homemade product has low accuracy and does not always distinguish between different types of metals. Professional instruments can detect small grains of gold, ignoring other metals.
2. Depth models designed to detect targets at a depth of up to 6 meters. However, they can only “see” large objects with an area of ​​over 400 square meters. see. Deep devices are in demand by engineering services as route finders, by geologists as specialized georadars for searching for native gold, etc.
3. Underwater metal detecting devices operating underwater. They are subject to increased requirements for the tightness of the search system. The operating conditions of underwater MI in sea and fresh water differ significantly. Underwater detectors use only sound indication.

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Please note! Underwater MI can be used on the surface in the mode of a conventional ground metal detector. Searchers only need to adjust the length of the rod and the position of the stop to make it more convenient to use the device.

1. Special metal detectors:

• security devices for detecting metal products in luggage, clothing or on a person’s body during inspection;
• industrial metal detectors as part of conveyor lines, signaling the presence of metals in products;
• military devices, collectively called mine detectors;
• detectors tuned exclusively to gold objects.

Characteristics of depth detectors

Such metal detectors are capable of detecting objects at great depths. A high-quality device, which is made by hand, is capable of looking to a depth of 6 m. But in such a situation, the dimensions of the object must be large. Such metal detectors function better than others for identifying old shells or large fragments.

There are two types of depth detectors: frame and transceiver on a rod. The frame one covers large areas for scanning, but in such a situation it is difficult to determine the exact location of the desired object. The second option is a point device that works purposefully in depth at small diameters. Work with him is carried out slowly and carefully.

A metal detector is designed to identify objects that differ in electrical or magnetic parameters from the environment in which they are located. Today, many people prefer to make such devices themselves. To have an idea of ​​how to create this device yourself, you need to have certain skills.

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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.

Classification by frequency

In addition, metal detectors are classified by operating frequency. Exist:

Metal detectors operating at ultra-low frequencies. Such devices are used only by professionals. They have good technical parameters, but their operation requires tens of watts of energy. Usually installed on special vehicles with high-capacity batteries and equipment that allows you to determine the size, shape and structure of detected objects.

Metal detectors with a higher operating frequency range. (up to several tens of KHz). They are more difficult to assemble than low-frequency ones. Their penetrating ability is up to one and a half meters. Detects small objects well. They are rarely used due to their low technical characteristics.

The simplest homemade metal detector

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 about how a man who had assembled a metal detector and was looking for scrap metal with it found a box of ammunition 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 you won’t be able to search for coins with it, since it reacts mainly to large metal objects.

Browse products for inventors. Link to the store.

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

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

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

The assembly diagram is simple!

DIY electronics in a Chinese store.

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

Cardboard metal detector board

Its downside

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

Metal detector coils

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

Thus, you can make 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 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.

How to make a simple metal detector for searching on the beach

In this article I will tell you how to build a simple metal detector for searching for coins and jewelry on the beach. It consists of one chip - the NE555N timer, a coil and several other radio components.

To assemble the metal detector you will need:

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

Instead of an electromechanical sound emitter, you can use a 10 µF capacitor and any speaker with an 8 Ohm impedance, connected in series.

The idea for the metal detector was taken from the book “499 NE555 Timer Circuits.” I just added a switch between the battery and the chip, and I also use an electromechanical sound emitter from an old electronic alarm clock instead of a speaker.

Components for assembling the electronic circuit of the Pirate metal detector on K561la7

1. Used capacitors are often used, but their capacity must be checked. Ceramic elements work well. To make the circuit you will need the following parts: 100 uF – 1 pc.; 1000 pF – 3 pcs.; 22 pF – 2 pcs.; 300 pF – 1 pc.
2. Used fixed resistors are also used by removing them from old circuits. They retain their quality characteristics for many years. 22 Ohm – 1 pc.; 1 kOhm – 1 pc.; 4.7 kOhm – 1 pc.; 10 kOhm – 1 pc.; 470 kOhm – 1 pc.
3. It is better to buy variable resistors in an electrical supermarket or at a radio market: 1.5 kOhm - 1 pc., 20 kOhm - 1 pc.
4. The K561la7 chip is housed in a protective DIP format housing. The legs are numbered from the notch on the chip body, starting counterclockwise.
5. The KT-315 transistor can be replaced with KT3102, BC546, or similar low-frequency elements with similar characteristics. Looking at the front part of the transistor, the terminals are distinguished, from right to left - emitter, collector and base.
6. The diode can be selected from such radio components as: kd522B, kd105, kd106. Before soldering, the diode must be ringed in order to accurately distinguish the anode from the cathode.
7. You can use headphones from an mp3 player or something similar as a signaling device.
8. Power supply: 9 V Krona battery. and contact group.

DIY metal detector: step-by-step instructions

The preparatory part is over. Now proceed to the main part. To make a metal detector, first take care of the rod:

1. Cut a piece of durable plastic. The base should accommodate the circuit and coils. Please note that the distance between the coils should be at least 10 cm.
2. Glue (use liquid nails) the stand to the rod.

If you have a ready-made base, attach a stand to it on which the metal detector chip will be placed.

To create coils, do this:

1. Take a round base (can be made from a board) with a diameter of 20–25 cm.
2. Make 30 turns of insulated wire. When winding the first and last turns, leave two leads 4 cm long.
3. Remove the spool from the base.
4. Wrap it with electrical tape without touching the terminals.

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Another metal detector coil is made in a similar way.

Start assembling the parts:

1. Place the elements on the board according to the diagram shown in the picture.
2. Solder to the tracks on the PCB.
3. For protection, close the circuit in a plastic box.

The main components of the device are ready. Now all that remains is to assemble a simple metal detector. Do it like this:

1. Solder the leads from the coils, as well as two wires from the batteries or accumulator, to the homemade board. An example of the circuit is shown in the photo above.
2. Now fix the coils and the board on the stand with glue. Coat the top of the parts with oil varnish.
3. Attach your headphones. To do this, make holes in the rod at the top and bottom.
4. Pass the cord through the hole and solder its end to the board. Increase the length of the wire using a soldering iron and electrical tape.

All that remains is to adjust and check the metal detector:

1. Put on your headphones.
2. Apply the pieces of aluminum to each coil one at a time.
3. Wait for maximum silence and secure the aluminum with glue.

The metal detector is ready for treasure hunting. To make it, the following components were needed: a rod, a stand for a microcircuit, coils, headphones, a battery, and a metal detector circuit. If you have good hearing, you can discern deviations in the sound waves that indicate the type of metal.

Preparing parts

At the first stage, your task is to decide on the materials on which the working parts of the metal detector will be attached, namely the speaker, coil, generators and microcircuits. You can use anything here. It could be an old fishing rod or a crutch.

The circuit and coils should be at the bottom, and should be attached to the main body. It is best to use dielectric materials, and the best option is wood and plastic.

It is recommended to make a handle at the base for convenient use.

It is worth considering that it is better to avoid using metals in the design, but if this is not possible in your conditions, place metal parts no closer than 30 cm from the coils

Remember to use insulated wires. The length needed is about 100 m of wire with a diameter of about 0.7 mm.

Schemes of homemade MI

Factory-made metal detecting equipment is presented on the market with quite expensive professional-level electronic systems, so enthusiasts constantly exchange information on how to make a homemade metal detector at home with minimal financial costs. Step-by-step instructions for assembling and debugging the device allow you to create a fully functional metal detector from available radio components. Metal detectors, including a do-it-yourself mine detector, the circuit of which is identical to those developed for standard MIs, are made using transistors and microcircuits. The kit for DIY circuits also includes:

• capacitors of various types: ceramic, film, electrolytic;
• resistors;
• resonators;
• controllers.

Additional Information. Quite often, circuits of amateur metal detecting equipment use the NE 555 microcircuit, which is a universal timer that generates single and repeating pulses with stable timing characteristics.

A worthy competitor to a metal detector on microcircuits is a metal detector on transistors, in which signals are generated using transistors KT-361 and KT-315 or similar radio components produced since Soviet times.

Simple metal detectors from ready-made electrical appliances

• A metal detector can be made from a radio receiver by adding a simple HF transmitter to it:

  
  The search coil is wound from 0.5 mm² wire: 16 turns 12 cm. When a metal object enters the range of action, a receiver tuned to the MW/LW range will change the tone of the sound.

• A homemade metal detector made from a cell phone is nothing more than a myth. Upgrading its electrical circuit at home is not feasible, and it is technically impossible to make a standard mobile phone work as a metal detector.
• In fact, there is no need to make a metal detector out of a magnet. You simply bring a powerful neodymium magnet to the place where there is a metal object and physically feel the force of attraction. Of course, this only works with metals that have ferromagnetic properties (iron, steel).

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:

Homemade underwater metal detector

The process of manufacturing, assembling and setting up a metal detector designed for underwater metal detection is identical to the work on creating a conventional MI. However, it is necessary to point out two significant differences that accompany the manufacture of underwater MI:

• all equipment must be placed in a sealed housing that does not allow parts to come into contact with moisture;
• To report a discovery from under the water, it is advisable to use special light indicators.

Stages of making an underwater MI with your own hands:

1. Selecting a circuit for working in river and sea water.
2. Manufacturing of printed circuit board.
3. Connecting the power supply.
4. Placing the finished board with a power supply in a sealed container. Craftsmen recommend using a sealant tube as a housing. LED indicator lights are displayed on the outer surface of the tube. Each joint is additionally sealed with silicone sealant.
5. Making a rod from a thin-walled stainless pipe or an ordinary plastic water pipe. The body of a fishing rod is used quite often.

Important! The bar should not be too light so as not to float, but also very heavy so as not to sink to the bottom.

1. Fastening the assembled block with the printed circuit board to the rod.
2. Winding the search coil. The reel body is a standard polypropylene pipe. The wound wire is filled with sealant.
3. Soldering the coil leads to a stranded wire.
4. Visual assessment of product tightness. Any cracks and joints that “do not inspire confidence” in terms of tightness are filled/covered with sealant.
5. Checking for leaks in water.

Features of deep MI

Deep MI uses RF technology, which is effective in the high-frequency range. The transmitting and receiving coils are mutually perpendicular and can operate at several frequencies simultaneously. Deep devices are insensitive to small targets; their objects are large objects located in areas with differences in ground levels.

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If you turn to the numerous forums of metal detecting enthusiasts that fill the Internet, you will notice the high level of manufacturing and adjustment of home-made structures that are described there. Self-made metal detectors are not inferior to factory-made search equipment, although they are many times cheaper. In Fig. Below is a homemade “deep sink”, the frame of which is made of durable polymer tubes.

Coil installation

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

When the winding is ready, it is attached to a durable housing 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 impacts that can damage the coil.

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

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

Checking and setting up the metal detector

After all the components of the metal detector are connected, you can begin checking and setting it up. The sensitivity of the device is adjusted by rotating the potentiometer knobs. You need to ensure that a slight crackling sound is heard in the speakers. This is absolutely normal, since it is almost impossible to eliminate all electromagnetic interference.

Then they begin testing on real metal objects. A well-tuned metal detector should detect a metal plate with a diameter of 25 mm (which corresponds to a 5 ruble coin) from a distance of about 30 cm.

After testing the device on coins, you can test the distance from which the detector operates on larger or smaller pieces of metal. This will allow you to prepare for work in real “field” conditions.

Metal detector made from a radio and calculator

As promised at the beginning of the article, we will tell you how to make a metal detector using a radio and a calculator. Let us immediately note that such a device is definitely not suitable for searching for metals even under a thin layer of earth. But you can try to use it as a detector of hidden wiring in walls. For such a device you will need:

1. Empty CD box.
2. A radio receiver capable of operating in the AM range.
3. Calculator.
4. Double-sided tape.

To make a metal detector, you need to do the following operations:

• stick double-sided tape on the inside of the CD box flaps;
• attach a radio receiver to one leaf;
• A calculator is attached to the second flap.

That's it, the metal detector is ready. All that remains is to configure it. To do this, both devices need to be turned on and the radio set to operate at the maximum frequency. Then, by changing the mutual inclination of the calculator and the receiver, it is necessary to ensure that only a slight noise background from the electromagnetic waves emitted by the calculator is heard from the radio speaker. This position needs to be fixed, and you can begin testing the device by bringing it to metal objects and recording the change in sound.

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.

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.

Homemade metal detector - pros and cons

Cheapness, the basic advantage of making any products yourself, is relevant for a metal detector. Here are some other advantages of a homemade device:

• best match to search technology for beginners;
• the ability to create a device with a completely individual shape, design and configuration;
• the pleasure of making an effective, efficient device yourself.

Like any device made by an amateur, a metal detector is not without some drawbacks.

Here are the features of the “Pirate” model that users note:

• high battery consumption;
• lack of discrimination, that is, precise sensitivity to ferrous, non-ferrous and precious metals;
• limited sensitivity compared to expensive models.

Despite its shortcomings, the Pirate model is very popular. This is explained by the simplicity of homemade production and the high performance of an inexpensive device.

Recycling experts believe that the discrimination capabilities of a metal detector are not of great importance. All metals found are so valuable that recycling them is always justified. Focusing on finding gold requires not only equipment, but also considerable experience, related knowledge and, of course, luck.