DIY metal detector detailed. How to make a simple metal detector with your own hands - step-by-step instructions. To assemble a metal detector with your own hands, you will definitely need

There is no need to explain to anyone what a metal detector is. This device is expensive, and some models cost quite a lot.

However, you can make a metal detector with your own hands at home. Moreover, you can not only save thousands of rubles on its purchase, but also enrich yourself by finding a treasure. Let's talk about the device itself and try to figure out what's in it and how.

Step-by-step instructions for assembling a simple metal detector

In this detailed instruction, we will show how you can assemble a simple metal detector with your own hands from available materials. We will need: a regular plastic CD box, a portable AM ​​or AM/FM radio, a calculator, VELCRO type contact tape (Velcro). So let's get started!

Step 1. Disassemble the CD box body. Carefully disassemble the plastic CD case body, removing the insert that holds the disc in place.

STEP 1. Removing the plastic insert from the sidebox

Step 2. Cut 2 strips of Velcro. Measure out the area at the center back of your radio. Then cut 2 pieces of Velcro the same size.

STEP 2.1. Measure approximately in the middle the area on the back of the radio (highlighted in red)
STEP 2.2. Cut out 2 Velcro strips of the appropriate size measured in step 2.1

Step 3. Secure the radio. Use the sticky side to attach one piece of Velcro to the back of the radio and another to one of the inside sides of the CD case. Then attach the radio to the body of the plastic CD case “Velcro to Velcro”.

Step 4. Secure the calculator. Repeat steps 2 and 3 with the calculator, but apply the Velcro to the other side of the CD case. Then secure the calculator to this side of the box using the standard Velcro-to-Velcro method.

Step 5. Setting the radio band. Turn on the radio and make sure it is tuned to the AM band. Now tune it to the AM end of the band, but not to the radio station itself. Turn up the volume. You should only hear static.

Clue:

If there is a radio station that is at the very end of the AM band, then try to get as close to it as possible. In this case, you should only hear interference!

Step 6. Roll up the CD box. Turn on the calculator. Start folding the side of the calculator box toward the radio until you hear a loud beep. This beep tells us that the radio has picked up an electromagnetic wave from the calculator's circuitry.

STEP 6. Fold the sides of the CD box towards each other until a characteristic loud signal is heard

Step 7 Bring the assembled device to a metal object. Open the flaps of the plastic box again until the sound we heard in step 6 is barely audible. Then start moving the box with your radio and calculator close to the metal object and you will hear a loud sound again. This indicates the correct operation of our simplest metal detector.

Instructions for assembling a sensitive metal detector based on a dual-circuit oscillator circuit

Operating principle:

In this project we will build a metal detector based on a double oscillator circuit. One oscillator is fixed and the other varies depending on the proximity of metal objects. The beat frequency between these two oscillator frequencies is in the audio range. When the detector passes over a metal object, you will hear a change in this beat frequency. Different types of metals will cause a positive or negative shift, raising or lowering the audio frequency.

We will need materials and electrical components:

Copper Multilayer PCB Single Sided 114.3mm x 155.6mm	1 PC.
Resistor 0.125 W	1 PC.
Capacitor, 0.1μF	5 pieces.
Capacitor, 0.01μF	5 pieces.
Capacitor, electrolytic 220μF	2 pcs.
PEL type winding wire (26 AWG or 0.4 mm in diameter)	1 unit
Audio jack, 1/8′, mono, panel mount, optional	1 PC.
Headphones, 1/8′ plug, mono or stereo	1 PC.
Battery, 9 V	1 PC.
Connector for binding 9V battery	1 PC.
Potentiometer, 5 kOhm, audio taper, optional	1 PC.
Switch, single pole	1 PC.
Transistor, NPN, 2N3904	6 pcs.
Wire for connecting the sensor (22 AWG or cross-section - 0.3250 mm 2)	1 unit
Wired speaker 4′	1 PC.
Speaker, small 8 ohm	1 PC.
Locknut, brass, 1/2′	1 PC.
Threaded PVC pipe connector (1/2′ hole)	1 PC.
1/4′ wood dowel	1 PC.
3/4′ wooden dowel	1 PC.
1/2′ wooden dowel	1 PC.
Epoxy resin	1 PC.
1/4′ plywood	1 PC.
Wood glue	1 PC.

We will need tools:

So let's get started!

Step 1: Make a PCB. To do this, download the board design. Then print it out and etch it onto the copper board using the toner to board transfer method. With the toner transfer method, you print a mirror image of the board design using a regular laser printer, and then transfer the design onto the copper cladding using an iron. During the etching stage, the toner acts as a mask, preserving the copper traces while like the rest copper dissolves in chemical bath.

Step 2: Fills the board with transistors and electrolytic capacitors . Start by soldering 6 NPN transistors. Pay attention to the orientation of the collector, emitter and base legs of the transistors. The base leg (B) is almost always in the middle. Next we add two 220μF electrolytic capacitors.

Step 2.2. Add 2 electrolytic capacitors

Step 3: Fill the board with polyester capacitors and resistors. Now you need to add 5 polyester capacitors with a capacity of 0.1μF in the places shown below. Next, add 5 capacitors with a capacity of 0.01μF. These capacitors are not polarized and can be soldered onto the board with legs in any direction. Next, add 6 10 kOhm resistors (brown, black, orange, gold).

Step 3.2. Add 5 capacitors with a capacity of 0.01μF
Step 3.3. Add 6 10 kOhm resistors

Step 4: We continue to fill the electrical board with elements. Now you need to add one 2.2 mOhm resistor (red, red, green, gold) and two 39 kOhm resistors (orange, white, orange, gold). And then solder in the last 1 kOhm resistor (brown, black, red, gold). Next, add pairs of wires for power (red/black), audio output (green/green), reference coil (black/black), and detector coil (yellow/yellow).

Step 4.1. Add 3 resistors (one 2 mOhm and two 39 kOhm)
Step 4.2. Add 1 1 kOhm resistor (far right)
Step 4.3. Adding wires

Step 5: We wind the turns onto the reel. The next step is winding turns on 2 coils, which are part of the LC generator circuit. The first is the reference coil. I used 0.4mm diameter wire for this. Cut a piece of dowel (about 13mm in diameter and 50mm in length).

Drill three holes in the dowel to allow the wires to pass through: one lengthwise through the middle of the dowel, and two perpendicularly at each end.

Slowly and carefully wrap as many turns of wire as you can around the dowel in one layer. Leave 3-4mm of bare wood at each end. Resist the temptation to “twist” the wire - this is the most intuitive way to wind, but this is the wrong way. You must rotate the dowel and pull the wire behind you. This way he will wrap the wire around himself.

Pull each end of the wire through the perpendicular holes in the dowel, and then one of them through the longitudinal hole. Secure the wire with tape once you're done. Finally, use sandpaper to remove the coating on the two open ends of the coil.

Step 6: We make a receiving (search) coil. It is necessary to cut the spool holder from 6-7 mm plywood. Using the same 0.4mm diameter wire, wind 10 turns around the slot. My reel has a diameter of 152 mm. Using a 6-7 mm wooden peg, attach the handle to the holder. Do not use a metal bolt (or anything similar) for this - otherwise the metal detector will constantly detect treasure for you. Again, using sandpaper, remove the coating on the ends of the wire.

Step 6.1. Cut out the spool holder
Step 6.2 We wind 10 turns around the groove with a wire 0.4 mm in diameter

Step 7: Setting up the reference coil. Now we need to adjust the frequency of the reference coil in our circuit to 100 kHz. For this I used an oscilloscope. You can also use a multimeter with a frequency meter for these purposes. Start by connecting the coil into the circuit. Next, turn on the power. Connect the probe from an oscilloscope or multimeter to both ends of the coil and measure its frequency. It should be less than 100 kHz. You can, if necessary, shorten the coil - this will reduce its inductance and increase the frequency. Then new and new dimensions. Once I got the frequency under 100kHz, my coil was 31mm long.

Metal detector on a transformer with W-shaped plates

The simplest metal detector circuit. We will need: a transformer with W-shaped plates, a 4.5 V battery, a resistor, a transistor, a capacitor, headphones. Leave only the W-shaped plates in the transformer. Wind 1000 turns of the first winding, and after the first 500 turns, make a tap with PEL-0.1 wire. Wind the second winding 200 turns with PEL-0.2 wire.

Attach the transformer to the end of the rod. Seal it against water. Turn it on and bring it close to the ground. Since the magnetic circuit is not closed, when approaching the metal, the parameters of our circuit will change, and the tone of the signal in the headphones will change.

A simple circuit based on common elements. You need transistors of the K315B or K3102 series, resistors, capacitors, headphones, and a battery. The values ​​are shown in the diagram.

Video: How to properly make a metal detector with your own hands

The first transistor contains a master oscillator with a frequency of 100 Hz, and the second transistor contains a search oscillator with the same frequency. As a search coil, I took an old plastic bucket with a diameter of 250 mm, cut it off and wound a copper wire with a cross-section of 0.4 mm2 in the amount of 50 turns. I placed the assembled circuit in a small box, sealed it and secured everything to the rod with tape.

Circuit with two generators of the same frequency. There is no signal in standby mode. If a metal object appears in the field of the coil, the frequency of one of the generators changes and sound appears in the headphones. The device is quite versatile and has good sensitivity.

A simple circuit based on simple elements. You need a microcircuit, capacitors, resistors, headphones, and a power source. It is advisable to first assemble coil L2, as shown in the photo:

A master oscillator with coil L1 is assembled on one element of the microcircuit, and coil L2 is used in the search generator circuit. When metal objects enter the sensitivity zone, the frequency of the search circuit changes and the sound in the headphones changes. Using the handle of capacitor C6 you can tune out excess noise. A 9V battery is used as a battery.

In conclusion, I can say that anyone who is familiar with the basics of electrical engineering and has enough patience to complete the job can assemble the device.

Principle of operation

So, a metal detector is an electronic device that has a primary sensor and a secondary device. The role of the primary sensor is usually performed by a coil with a wound wire. The operation of the metal detector is based on the principle of changing the electromagnetic field of the sensor by any metal object.

The electromagnetic field created by the metal detector sensor causes eddy currents in such objects. These currents cause their own electromagnetic field, which changes the field created by our device. The secondary device of the metal detector registers these signals and notifies us that a metal object has been found.

The simplest metal detectors change the sound of the alarm when the desired object is detected. More modern and expensive samples are equipped with a microprocessor and a liquid crystal display. The most advanced companies equip their models with two sensors, which allows them to search more efficiently.

Metal detectors can be divided into several categories:

• public devices;
• mid-range devices;
• devices for professionals.

The first category includes the cheapest models with a minimal set of functions, but their price is very attractive. The most popular brands in Russia: IMPERIAL - 500A, FISHER 1212-X, CLASSIC I SL. Devices in this segment use a “receiver-transmitter” circuit operating at ultra-low frequencies and require constant movement of the search sensor.

The second category, these are more expensive units, have several replaceable sensors and several control knobs. They can work in different modes. The most common models: FISHER 1225-X, FISHER 1235-X, GOLDEN SABER II, CLASSIC III SL.

Photo: general view of a typical metal detector

All other devices should be classified as professional. They are equipped with a microprocessor and can operate in dynamic and static modes. Allows you to determine the composition of the metal (object) and the depth of its occurrence. The settings can be automatic, or you can adjust them manually.

To assemble a homemade metal detector, you need to prepare several items in advance: a sensor (a coil with a wound wire), a holder rod, an electronic control unit. The sensitivity of our device depends on its quality and size. The holder bar is selected according to the person’s height so that it is convenient to work. All structural elements are fixed to it.

This is what keeps a person from purchasing metal detectors, which cost a lot of money, but do not guarantee that anything will be found or not.

On the other hand, if you got such a device practically for nothing, then you wouldn’t have to walk through the forests in search of mythical treasures. Even on a personal plot, it is possible to dig up several meters of pipe or abandoned cable, which, when delivered to a collection point, can bring money. But, as you know, they are never superfluous.

In this case, you need to figure out whether it is possible to make a metal detector from a radio or disks with your own hands without the use of microcircuits, how complicated this process is and whether it requires any specific knowledge, whether the circuits of simple metal detectors are complex, what is required for this, and what is the algorithm for such work.

What is a metal detector

Such a device, homemade or made in a factory, is designed to search for any metal under a layer of soil, regardless of whether it is pieces of iron, copper or something even more valuable. Such devices are used not only by gold miners, but also by various archaeological groups, patriotic communities (in search of remains and objects left in the ground after the Second World War) and even sappers when demining territories.

The shapes, as well as the circuits of metal detectors, are different. This could be a disk mounted on a handle, or it could be some kind of microphone. The essence of this device does not change from this - when any metal object is detected at a shallow depth, it emits a certain sound using a buzzer built into it, signaling the discovery.

Such devices operate on the basis of the physical law according to which electromagnetic induction operates. Its components are a transmitter, which, upon receiving a signal, sends it to a warning device (audio or visual), the signal receiver itself and a buzzer or screen. Electromagnetic waves are sent to the surface and reflected. If the transmitted signal returns unchanged, nothing happens in the circuit, but provided that any metal enters the signal transmission area, the returned wave turns out to be distorted and this is recorded by the transmitter, which gives an audio or visual alert.

Operating frequencies

A metal detector combines complex parameters that are sometimes mutually exclusive. For example, if you lower the frequency generated by the generator, you can achieve a greater search depth, but this will increase energy consumption, and also reduce sensitivity, as well as mobility due to the increase in the coil. But basically all the parameters, one way or another, are tied to the frequency of the generator, and therefore such devices are classified precisely according to the parameter of operating frequency ranges.

VLF

The circuit of a simple metal detector that operates in the range from approximately 100 to 500-600 Hertz is called ultra-low frequency. Such devices are amateur, with a power of no more than a hundred watts. Such devices are weak and it is almost impossible to recognize the signal without the use of computer processing.

LF

The next class of metal detectors is low-frequency. A little more powerful than the previous ones, the circuit is simple, they are resistant to interference, but the sensitivity is still quite low. With an energy consumption of more than 10 Watts, the possible search depth will be about 5 meters. Their inconvenience is also that, in addition to metal, they also react to large fragments of stone or concrete. The best signal is detected on ferrous metals, and therefore such a metal detector is also called a magnetic detector. They have low sensitivity to soil properties.

IF

Another classification is metal detectors of higher frequencies - several tens of kilohertz. They have less good noise immunity compared to LF. Convenient when performed using the pulse mode, which will be discussed a little later. The disadvantage of such devices is that with increased mineralization or in swampy areas, they completely stop receiving the changed signal, as a result of which they do not “see” metals.

HF

The most powerful metal detector, suitable for searching for precious metals, but at shallow depths. Not bad for finding gold items lost by vacationers in the sand on the beaches. The depth of penetration of the signal into the ground is no more than 80–90 cm. The results of the work depend on the power of the transmitter coil; they work with the result only on dry non-magnetic soil, which includes sand.

Pulsers

Such metal detectors are the best equipment in the line. They stand separately from other similar devices. The fact is that current flows to the coil in a pulsed mode. It is possible to set the pulse frequency in low ranges, and the duration, which determines the area of ​​the spectral composition, in high or high frequencies. Thus, you get a metal detector that combines the best qualities of all categories of detectors, or a device that can be reconfigured, depending on the required parameters.

How to make a metal detector with your own hands?

Based on the fact that the cost of such detectors is very high, it makes sense to look into the possibility of making a simple metal detector with your own hands at home. Homemade products require practically no costs, except, of course, a small amount of time.

Since the design of the metal detector is quite simple, to operate it you will need two disks (CD and DVD), headphones, a regular calculator, a 9-volt battery (“crown”), electrical tape and glue, and you assemble it practically on your knees.

So, detailed instructions for assembling a metal detector with your own hands.

To assemble a metal detector from disks, you need to adhere to the following algorithm of actions:

• The headphone plug is not required, so it is cut off and the wires are stripped to a length of about 1 cm.
• Each stripped wire is divided into two equal parts, one of which will go to the mirror part of the disk, and the second to the power element.
• Provided that the mirror surface of the disks is on both sides, one of the parts of the wire is attached to it separately using glue. If the discs are single-sided, then everything is simpler. The contact side is the writing side.
• The wires on the CDs and DVDs themselves are secured with electrical tape.
• When the calculator is turned on, it is secured with the same electrical tape between the disks, and the battery is secured to the surface of the DVD.

At this point the work is completed and the metal detector using improvised means is ready. As you can see, the process is completely uncomplicated and inexpensive, both financially and in time.

Of course, if you make a metal detector whose circuits are so simple, then its characteristics will not be comparable to professional devices, but you can find elementary structures in the ground with its help.

If you need a more powerful device than a simple metal detector, it can be made from an old radio.

Metal detector from radio

Using this method, you can make a detector that will be more powerful than a simple metal detector. To do this, you will need an empty CD case, a calculator, an AM radio, double-sided tape and electrical tape.

On the inside of the disc box, a radio is glued to double-sided tape, and on the other side - a calculator in the turned on state. The receiver sets the highest frequency in the AM range, or the one closest to it, at which there are no extraneous sounds other than noise.

You can attach any mop stick to the resulting structure. After this, all that remains is to configure the detector. To do this, you need to move the doors of the box apart or move until a sharp sound appears. After moving the doors apart, the same, barely noticeable sound is heard and the box is fixed in this position. After the work has been done, when approaching the metal, the same sound will be heard, but in a sharper sound range.

Of course, you cannot assemble a good metal detector with your own hands, but an acceptable one is quite possible.

Needed or not

Of course, if a person is not engaged in professional excavations, there is no point in purchasing such a device - it is simply throwing away a considerable amount of money. But for home use, you can assemble a simple metal detector. Of course, it won’t help you find treasures buried in the bowels of the earth, but a simple metal detector with your own hands or from a radio is quite capable of determining the location of a metal frame behind a gypsum board wall or the location of hidden wiring in the concrete floors of houses, which is already important. Well, making a metal detector at home without the use of microcircuits using a phone (the description of the work is identical to assembling a metal detector with your own hands from disks or a radio, but a phone is used instead of a calculator) is not difficult.

Not so often, but losses still happen in our lives. For example, we went into the forest to pick mushrooms and berries and dropped the keys. It will not be so easy to find them in the grass under the leaves. Don’t despair: a homemade metal detector, which we will make with our own hands, will help us. So I decided to collect my first metal detector. Nowadays, few people decide to make a metal detector. Homemade devices were popular twenty to twenty-five years ago, when there was simply nowhere to buy them.
Modern metal detectors from manufacturers such as Garrett, Fisher and many others have high sensitivity, metal discrimination, and some even have a hodograph. They are able to adjust the ground balance and tune out electrical interference. Thanks to this, the detection depth of a modern coin metal detector reaches 40 cm.

I chose a scheme that was not very complicated, so that it could be repeated at home. The principle of operation is based on the difference in the beat of two frequencies that we will pick up by ear. The device is assembled on two microcircuits, contains a minimum of parts, and at the same time has quartz frequency stabilization, thanks to which the device operates stably.

Metal detector circuit on microcircuits

The scheme is very simple. It can easily be repeated at home. It is built on two 176 series microcircuits. The reference oscillator is made on La9 and stabilized by quartz at 1 MHz. Unfortunately, I didn’t have this, I had to set it to 1.6 MHz.

The tunable generator is assembled on the K176la7 microcircuit. To achieve zero beats, varicap D1 will help, the capacity of which varies depending on the position of the variable resistor R2 slider. The basis of the oscillatory circuit is the search coil L1, when it approaches a metal object, the inductance changes, as a result of which the frequency of the tunable generator changes, which is what we hear in headphones.

I use regular headphones from a player, the emitters of which are connected in series in order to put less load on the output stage of the microcircuit:

If the volume turns out to be too much, you can introduce a volume regulator into the circuit:

Details of a homemade metal detector:

• Microcircuits; K176LA7, K176LA9
• Quartz resonator; 1 MHz
• Varicap; D901E
• Resistors; 150k-3pcs., 30k-1pc.
• Variable resistance resistor; 10k-1pcs.
• Electrolytic capacitor; 50 microfarads/15 volts
• Capacitors; 0.047-2pcs., 100-4pcs., 0.022, 4700, 390

Most of the parts are located on the printed circuit board:

I placed the entire device in an ordinary soap dish, shielding it from interference with aluminum foil, which I connected to a common wire:

Since there is no place on the printed circuit board for quartz, it is located separately. For convenience, I removed the headphone jack and frequency control from the end of the soap dish:

The entire metal detector unit was placed on a piece of ski pole using two clamps:

The most important part remains: making the search coil.

Metal detector coil

The sensitivity of the device and resistance to false alarms, the so-called fontons, will depend on the quality of the coil’s manufacturing. I would like to immediately note that the depth of detection of an object directly depends on the size of the coil. So, the larger the diameter, the deeper the device will be able to detect the target, but the size of this target should also be larger, for example, a sewer manhole (the metal detector simply will not see a small object with a large coil). Conversely, a small-diameter coil can detect a small object, but not very deep (for example, a small coin or ring).

Therefore, I first wound a medium-sized reel, so to speak, a universal one. Looking ahead, I want to say that the metal detector was designed for all occasions, that is, the coils should be of different diameters and they can be changed. To quickly change the coil, I installed a connector on the rod that I pulled out of an old tube TV:

I attached the mating part of the connector to the coil:

As a frame for the future reel, I used a plastic bucket that I bought at a hardware store. The diameter of the bucket should be approximately 200 mm. Part of the handle and bottom should be cut off from the bucket so that a plastic rim remains, onto which 50 turns of PELSHO wire with a diameter of 0.27 millimeters should be wound. The connector should be attached to the part of the remaining handle. We insulate the resulting coil using electrical tape in one layer. Then we need to shield this coil from interference. To do this, we need aluminum foil in the form of a strip, which we will wrap on top so that the ends of the resulting screen do not close and the distance between them is approximately 20 millimeters. The resulting screen should be connected to a common wire. I also wrapped it with electrical tape on top. Of course, you can soak it all with epoxy glue, but I left it that way.

After testing a large coil, I realized that I needed to make a small one, the so-called sniper, to make it easier to detect small objects.

The finished coils look like this:

Setting up a finished metal detector

Before you start setting up your metal detector, you need to make sure that there are no metal objects near the search coil. The setup consists of selecting the capacitance of capacitor C2 in order to obtain the maximum level of beats that we hear in headphones, since there are many harmonics in the signal (we need to highlight the strongest one). In this case, the slider of the variable resistor R2 should be as close to the middle as possible:

I made the rod from two parts, the tubes were selected in such a way that they fit into each other very tightly, so I didn’t have to come up with a special fastening for these tubes. An armrest and handle were also made to make it easier to wire above the ground. As practice has shown, this is very convenient: the hand does not get tired at all. When disassembled, the metal detector turned out to be very compact and literally fits into a bag:

The appearance of the finished device looks like this:

In conclusion, I would like to say that this metal detector is not suitable for people who are going to work in the old-fashioned way. Since it doesn't discriminate against metals, you'll have to dig for everything. You will most likely be very disappointed. But for those who like to collect scrap metal, this device will be of help. And just as entertainment for children.

A device that allows you to search for metal objects located in a neutral environment, such as soil, due to their conductivity is called a metal detector (metal detector). This device allows you to find metal objects in various environments, including in the human body.

Largely thanks to the development of microelectronics, metal detectors, which are produced by many enterprises around the world, are highly reliable and have small overall and weight characteristics.

Not so long ago, such devices could most often be seen among sappers, but now they are used by rescuers, treasure hunters, and utility workers when searching for pipes, cables, etc. Moreover, many “treasure hunters” use metal detectors, which they assemble with their own hands .

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.

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.

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.

In other words, devices of this type must be configured with your own hands before work.

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.

But besides this, when operating them, it is necessary to take into account the fact that they have high energy consumption.

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.

All devices included in the metal detector are waterproof.

It is this relative simplicity of design that allows you to make metal detectors with your own hands.

Types of metal detectors

There is a wide range of metal detectors on the market, used in many areas. Below is a list that shows some of the varieties of these devices:

1. Ground. These devices are designed for searching with your own hands for scrap metal, jewelry, coins, etc.
2. Deep. These devices are used to search for the above-mentioned metal products at great depths.
3. Underwater. Devices of this type are designed to operate underwater. They can work at different depths.
4. Metal detectors for searching for gold. These devices allow you to find gold and gold jewelry in any environment.
5. Security devices. These devices are used to detect metal products on the human body and in luggage. Such devices are made in the form of arches and are installed at the entrance to places with large crowds of people, for example, at train stations, shopping centers, etc.
6. Industrial. This equipment is part of conveyor lines. Their main task is to detect metal in other substances. For example, in a mined sand-soil mixture.
7. Army. The military uses such devices to detect mines, unexploded shells, bombs, etc. with their own hands. The military calls such devices mine detectors.
8. Do-it-yourself devices are most often assembled by novice “treasure hunters”.

The use of modern materials allows us to design and manufacture devices with high accuracy in detecting metals in different environments. The use of microelectronics has made it possible to minimize their overall weight parameters. In addition, the simplicity of the electrical circuit allows you to make a metal detector with your own hands at minimal cost.

Main settings

Like any technical device, a metal detector has certain parameters that characterize its functional properties.

Detection depth

In the first place is the depth of metal detection. By the way, many companies producing such devices do not indicate the maximum depth at which their products can detect metal products. And if such a figure is indicated, then most likely this is data obtained during laboratory tests. That is, real field conditions differ significantly from laboratory (test) conditions.

This means that when doing real work with your own hands, the detection depth will be slightly less than indicated in the passport. Why is this happening? The fact is that the composition of the soil has a significant impact on the capabilities of the metal detector. In fact, it is one thing to search in river sand, and another in soil with a high iron content. Metal products, especially those that remain at depth for a long time, oxidize and change their properties, and this affects the ability to detect an object.

Most modern metal detectors can find metal objects at a depth of up to 2.5 m; special deep products can detect a product at a depth of up to 6 meters.

Operating frequency

The second parameter is the operating frequency. The thing is that low frequencies allow the metal detector to see to a fairly large depth, but they are not able to see small details. High frequencies allow you to notice small objects, but do not allow you to view the ground to great depths.

The simplest (budget) models operate at one frequency; models that fall into the middle price range use 2 or more frequencies. There are models that use 28 frequencies when searching.

Modern metal detectors are equipped with a function such as metal discrimination. It allows you to distinguish the type of material located at depth. In this case, when ferrous metal is detected, one sound will sound in the search engine’s headphones, and when non-ferrous metal is detected, another sound will sound.

Such devices are classified as pulse-balanced. They use frequencies from 8 to 15 kHz in their work. Batteries of 9 - 12 V are used as a source.

Devices of this class are capable of detecting a gold object at a depth of several tens of centimeters, and ferrous metal products at a depth of about 1 meter or more.

But, of course, these parameters depend on the device model.

How to assemble a homemade metal detector with your own hands

There are many models of devices on the market for detecting metal in the ground, walls, etc. Despite its external complexity, making a metal detector with your own hands is not that difficult and almost anyone can do it. As noted above, any metal detector consists of the following key components - a coil, a decoder and a power supply signaling device.

To assemble such a metal detector with your own hands, you need the following set of elements:

• controller;
• resonator;
• capacitors of various types, including film ones;
• resistors;
• sound emitter;
• Voltage regulator.

Do-it-yourself simple metal detector

The metal detector circuit is not complicated, and you can find it either on the vast world wide web or in specialized literature. Above is a list of radio elements that are useful for assembling a metal detector with your own hands at home. You can assemble a simple metal detector with your own hands using a soldering iron or other available method. The main thing is that the parts should not touch the body of the device. To ensure the operation of the assembled metal detector, power supplies of 9 - 12 volts are used.

To wind the coil, use a wire with a cross-sectional diameter within 0.3 mm; of course, this will depend on the chosen circuit. By the way, the wound coil must be protected from exposure to extraneous radiation. To do this, shield it with your own hands using ordinary food foil.

To flash the controller firmware, special programs are used, which can also be found on the Internet.

Metal detector without chips

If a novice “treasure hunter” has no desire to get involved with microcircuits, there are circuits without them.

There are simpler circuits based on the use of traditional transistors. Such a device can find metal at a depth of several tens of centimeters.

Deep metal detectors are used to search for metals at great depths. But it is worth noting that they are not cheap and therefore it is quite possible to assemble it yourself. But before you start making it, you need to understand how a typical circuit works.

The circuit of a deep metal detector is not the simplest and there are several options for its implementation. Before assembling it, you need to prepare the following set of parts and elements:

• capacitors of various types - film, ceramic, etc.;
• resistors of different values;
• semiconductors - transistors and diodes.

Nominal parameters and quantity depend on the selected circuit diagram of the device. To assemble the above elements, you will need a soldering iron, a set of tools (screwdriver, pliers, wire cutters, etc.), and material for making the board.

The process of assembling a deep metal detector looks something like this. First, a control unit is assembled, the basis of which is a printed circuit board. It is made from textolite. Then the assembly diagram is transferred directly to the surface of the finished board. After the drawing is transferred, the board must be etched. To do this, use a solution that includes hydrogen peroxide, salt, and electrolyte.

After the board is etched, it is necessary to make holes in it to install the circuit components. After tinning the board. The most important stage is coming. Do-it-yourself installation and soldering of parts onto a prepared board.

To wind the coil with your own hands, use PEV brand wire with a diameter of 0.5 mm. The number of turns and the diameter of the coil depend on the selected circuit of the deep metal detector.

A little about smartphones

There is an opinion that it is quite possible to make a metal detector from a smartphone. This is wrong! Yes, there are applications that install under Android OS.

But in fact, after installing such an application, he will actually be able to find metal objects, but only pre-magnetized ones. It will not be able to search for, much less discriminate against, metals.