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Who made a metal detector from available elements. Powerful DIY metal detector Pirat

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

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

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

There are four types of metal detectors:

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

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

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

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

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

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

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

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

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

Making a high frequency metal detector

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

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

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

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

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

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

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

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

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

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

Assembling a pulse detector

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

· 9 volt battery;

· Amplification transistor 250+;

· A small 8 ohm speaker will do.

Assembling the search coil

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

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

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

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

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

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

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

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

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

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

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

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

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

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


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

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

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

Materials you will need for work:

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

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

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

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


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


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

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

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

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

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

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

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

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

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

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

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

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

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

Even the most serious and respectable citizens feel a slight excitement when they hear the word “treasure”. We literally walk through treasures, of which there are immeasurably many in our land.

But how can you look under the soil layer to know exactly where to dig?

Professional treasure hunters use expensive equipment, the purchase of which can pay for itself after one successful find. Archaeologists, builders, geologists, members of exploration societies use equipment provided by the organization in which they work.

But what about novice treasure hunters on a budget? You can make a metal detector at home with your own hands.

To understand the subject, consider the design and operating principle of the device

Popular metal detectors operate using the properties of electromagnetic induction. Main components:

  • transmitter – generator of electromagnetic oscillations
  • transmitting coil, receiving coil (in some models the coils are combined for compactness)
  • electromagnetic wave receiver
  • decoder that separates the useful signal from the general background
  • signaling device (indicator).


The generator, using a transmitting coil, creates an electromagnetic field (EMF) around it with specified characteristics. The receiver scans the environment and compares field performance with reference values. If there are no changes, nothing happens in the circuit.

  • When any conductor (any metal) enters the field of action, the basic EMF induces Foucault currents in it. These eddy currents create the object's own electromagnetic field. The receiver detects the distortion of the basic EMF and gives a signal to the indicator (audio or visual alert).
  • If the object being examined is not metallic, but has ferromagnetic properties, it will shield the underlying EMF, also causing distortion.

Important! There is a misconception that the soil in which searches are carried out should not be electrically conductive.

This is wrong. The main thing is that the electromagnetic or ferromagnetic properties of the environment and the search objects are different from each other.

That is, against the background of certain characteristics of the EMF generated by the search environment, the field of individual objects will stand out.

Types of metal detectors

Understanding the features of different circuits will help not only to choose a ready-made detector. If you decide to build a metal detector for coins with your own hands, you do not need to install a detector for water pipes or fittings in concrete.

You should initially know what the device is for, since universal metal detectors are expensive, both when purchased and when assembled yourself. In addition, a narrow-profile device is more compact and lightweight.

Main settings

  1. Search depth. Determines the penetrating power for standard primers: below this band the coil will not respond to artifacts.
  2. Coverage area: the wider it is, the less time it will take to “comb through”. True, selectivity and sensitivity are reduced.
  3. Selectivity: selecting the required object from a variety of objects. For example, when searching for gold jewelry on the beach, your device will not respond to steel hairpins or coins.
  4. Sensitivity: the higher it is, the more likely it is to find small objects. True, the coil reacts to various debris, such as nails or hairpins.
  5. Noise immunity. The detector sensor is affected by many extraneous factors: thunderstorms, power lines, mobile phones, etc. It is necessary to filter them out.
  6. Autonomy: this means both energy consumption and battery charge reserve.
  7. Discrimination is the ability to distinguish artifacts by type. Let's look at this parameter in more detail.

If you have lost a ring, a key, a screwdriver... and you know the approximate location of the loss, then do not despair! You can assemble a metal detector with your own hands or ask a radio amateur you know to assemble simple DIY metal detector. Below is a diagram of an easy-to-make and time-tested metal detector, which (with certain skills) can be made in one day. The simplicity of the described metal detector is that it is assembled on just one very common chip K561LA7 (CD4011BE). Setup is also simple and does not require expensive measuring instruments. To configure the generators, an oscilloscope or frequency meter is sufficient. If everything is done without errors and from serviceable elements, then these devices will not be needed.

Sensitivity of this metal detector:

metal jar lid “sees” up to 20 cm, cell phone up to 15 cm, Krona battery up to 10 cm, 5 ruble coin up to 8 cm.

At this distance the tone of the oscillator in the headphones barely changes; at a closer distance the tone increases. The larger the metal area, the greater the detection distance. Distinguishes between diamagnetic materials and ferromagnetic materials.

For making a metal detector we will need:

  1. Chip K561LA7 (or K561LE5, analogue of CD4011);
  2. Transistor - low-power low-frequency, for example - KT315, KT312, KT3102, analogues: BC546, BC945, 2SC639, 2SC1815, etc.);
  3. Diode - any low-power one, for example - kd522B, kd105, kd106, analogues: in4148, in4001, etc.;
  4. Variable resistor - 3 pcs (1 kOhm, 5 kOhm, 20 kOhm with a switch or a separate switch);
  5. Fixed resistor - 5 pcs (22 Ohm, 4.7 kOhm, 1.0 kOhm, 10 kOhm, 470 kOhm);
  6. Ceramic, or even better, mica capacitors - 5 pcs: 1000 pF -3 pcs, 22 nF -2 pcs, 300 pf);
  7. Electrolytic capacitor (100.0 uF x 16V) - 1 piece;
  8. Wire PEL, PEV, PETV, etc., with a diameter of 0.4-0.7 mm;
  9. Low impedance headphones (from the player);
  10. Battery 9V.

Metal detector circuit

Appearance of the metal detector board

In the case of an old pocket radio (you can use the case from a soap dish, a shoe-cleaning sponge, or in the housing from the electrical junction box.

Attention! To eliminate interference and the influence of human hands when touching the regulators, the housings of variable resistors must be connected to the minus of the board.

If the metal detector circuit is properly soldered, the elements are in good working order and have the correct values, and the search coil is properly made, the device operates without problems. If, when you turn on the headphones for the first time, you do not hear a squeak or change in frequency when adjusting the “FREQUENCY” control, then you need to select a resistor (10 kOhm) , standing in series with the regulatorand/or a capacitor in this generator (300 pf). Thus, we make the frequencies of the reference and search generators the same.

When the generator is excited, whistling, hissing, and distortion appear, solder a 1000 pF capacitor (1H0 aka 102) to the pin. 6 chips per case.

Using an oscilloscope or frequency meter, look at the signal frequencies at pins 5 and 6 of the K561LA7. Achieve their equality using the above-described adjustment method. The operating frequency of the generators itself can range from 80 to 200 kHz.

A protective diode (any low-power one) is needed to prevent damage to the microcircuit when the battery is turned on by mistake (which often happens:).

Making a metal detector coil

The coils are wound on a mandrel with a diameter of 15-25 cm (for example, a bucket or on a shuttle made of thick wire or plywood - the smaller the diameter, the less sensitivity, but the greater the selectivity of small metals). Choose for what purpose you need it.

A wire is used in varnish insulation PEL, PEV, PETV..., with a diameter of 0.4 - 0.7 mm (well suited for old color TVs with a kinescope demagnetization loop or deflection system) and contains about 100 turns (you can wind from 80 to 120 turns ). Wrap the wire tightly with electrical tape.

Then we wrap the coil over the electrical tape with a strip of foil, leaving 2-3 cm of the unwrapped area. You can take foil from some types of cables or, as a last resort, cut foil from a chocolate bar into strips 2 cm wide :)

We wrap everything tightly with electrical tape again.

Photo of the finished coil. All that remains is to wrap the top with electrical tape.

We attach the resulting finished coil to a dielectric (for example, non-foil PCB or getinax). Next we attach it to the holder.

We connect the coil with the circuit with a double shielded wire (screen to body). The wire can be taken from old cords for dubbing from tape recorder to tape recorder or a low-frequency (audio-video) cord for connecting a TV to a DVD, etc.

Correct operation of the metal detector: When you turn on the “frequency” control in the headphones, we set a low-frequency hum; when approaching metal, the frequency changes.

The second option is to stop the buzzing in your ears by setting the beats to zero, i.e. combine two frequencies. Then there will be silence in the headphones, but as soon as we bring the coil to the metal, the frequency of the search generator changes and a squeak appears in the headphones. The closer to the metal, the higher the frequency in the headphones. But the sensitivity with this method is not great. The device will react only when the generators are strongly detuned, for example, when brought close to a jar lid.

Location of parts on the board for a chip in a DIP package

Location of parts on the board for a chip in an SMD package

Zotov A., Sergey V., Volgograd region.

This metal detector circuit can be discussed on our

Do you want to make this metal detector?

But you don’t have the parts and board?

Several metal detector options from the set


You can order them

Kit for making a metal detector

(in the set all necessary parts and circuit board)

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 you 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 housing, 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 using 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′ wooden dowel 1 PC.
3/4′ wood 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 their 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: The next step is to wind 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. 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.

Today, there are many different ideas on the Internet that allow you to make a metal detector with your own hands at home. Some of them require certain skills in working with electrical appliances, soldering and understanding of simple electrical circuits, while some do not require any knowledge in these areas to create. However, there are many non-working, fake methods floating around the Internet, captivating with their simplicity and accessibility. It is very easy for an inexperienced person to fall for the bait of deceivers - to spend time and effort on making a device that is obviously not working and lose all interest in it. But don’t be discouraged, then readers of “” will be provided with an interesting and really working scheme for creating a homemade metal detector!

Idea No. 1 – Discs in action!

Surely you have already seen or heard that you can make the simplest metal detector yourself using a CD and DVD disc, as shown in the photo. The scheme is quite simple and does not require any professional tools or skills.

This instruction is the most popular due to the availability of the necessary components and the ease of assembly; you just need to connect a couple of wires and the crown together and the device is ready. At the same time, the characteristics of this device are attributed to be quite good - it finds a coin at a distance of 25-30 cm, which is quite enough for searching for coins and treasures. However, unfortunately, this instruction is fake.

The fact is that the metal detector itself is a rather complex device; its operation is based on several physical phenomena at once. Therefore, a calculator and a pair of disks cannot even remotely replicate its operating principle, no matter what the creators of such instructions claim, who sometimes write that they even find treasures with the help of such homemade products.

It is very easy to understand that you are being deceived even without knowledge of the laws of physics. The wires from the headphones that need to be attached to the disk do not actually contact it in any way, since the copper is under a layer of varnish insulation, which must be removed by firing and labor-intensive cleaning of carbon deposits; of course, none of the authors of the instructions does this in their devices . Consequently, the headphones are simply not connected to any circuit, and there can be no talk of any work, much less metal detecting.

A real metal detector operates on the basis of an induction balance; its design must have at least one coil of copper wire. When a metal object enters the field of the coil, its characteristics or the received signal, depending on the design, change. These changes are recorded and amplified by the circuit, and also displayed in a form understandable to humans, usually by means of sound signals.

Video instructions for assembling a metal detector from disks

Idea No. 2 – Metal detector according to the “Pirate” scheme

This is a scheme that has been tested by many DIYers and allows you to achieve good results. It contains two microcircuits, so you will have to make a small printed circuit board or assemble the device on a breadboard. But don’t be alarmed, anyone can make this option if they put in the necessary effort. Below is an electronic circuit diagram of the device and a printed circuit board for it.

The coil is made of enameled copper wire with a diameter of 0.5 mm. Winding should be done on a frame with a diameter of 200-260 mm, the number of turns from 21 to 25. For reliability, it is better to install the coil in a protective plastic casing, which can then be attached to a handle made of PVC pipes.

After assembling the metal detector, it must be checked. The procedure for use is as follows: turn on the device away from metal objects for about 30 seconds so that its operation is more stable, then rotate the variable resistor knob for coarse and fine adjustment, you need to achieve rare clicks. When metal enters the action area, you will hear a characteristic sound.

Below is a detailed video assembly instruction, which clearly shows all the stages of creating a homemade metal detector.