DIY metal detector with metal discrimination, diagram. Metal detector with metal discrimination

In this article we will look at creating a metal detector (metal detector) based on an Arduino board with the ability to discriminate metals. This metal detector will be able to detect small metal objects (for example, coins) at a depth of up to 15 cm, and it will be able to detect large metal objects at a depth of up to 50 cm (and even more). It will also be able to distinguish ferrous metals from nonferrous metals. The metal detector has a fairly simple design and at the same time it provides acceptable sensitivity.

Earlier on our website we reviewed a project for a simple metal detector using Arduino, we recommend reading it to understand the principle of operation of a metal detector.

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:

Simple, working on the “receive-transmit” principle.
Induction.
Pulse.
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.

Parts List

IC1 - K561LE5 (CD4001A);
IC2 - ATTINY2313A;
IC3 - 78L05;
IC4 - 78L05.

R1 – 4.7k;
R2 – 560ohm;
R3 – 1k;
R4 – 1k;
R5 – 470оМ;
R6 – 1k tuning;
R8 – RS09-R-30 10k variable.

C1, C2 – 4700 pF;
C3 – 3300 pF;
C4, C5 – 27 pF;
C6 – 47 uF at 16 V electrolytic;
C8 – 47 uF at 16 V electrolytic;
C7, C9, C10, C13 – 0.1 µF;
C11 – 47 uF at 16 V electrolytic;
C12 – 47 uF at 16 V electrolytic.

oval coil - 24 by 16 centimeters;
number of turns – 50;
wire diameter is 0.3-0.5 millimeters.

twenty-pin socket for microcontroller;
quartz resonator ZQ - 20 MHz;
“RESET” button S1 - any button without fixation;
power switch S2 - MTS-1;
low-impedance headphones, for player;
external headphone jack, soldered to a wire about thirty centimeters long;
Crown battery connector;
battery or crown battery, 9 volts;
cable entry PG7.

The wire connecting the main board and the generator board is two-core, each wire is in the screen, approximately 1 meter long. To install the parts, a one-sided breadboard was used. The housing for the main board is BOX-G01B. Capacitors C1, C2, C3 should be with the lowest possible temperature coefficient (TKE).

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

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.

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 using 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:

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.
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.
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.
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.
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.

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

Types of MI by purpose

DIY surge protector

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

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.
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.
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.

We recommend reading: DIY FM antenna for a music center
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.

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.

Features of deep metal detectors

A deep metal detector is attractive because it can detect objects where other devices are powerless. A good deep metal detector, made by yourself, looks to a depth of 6 meters, and is not hindered by roots, voids or other obstacles. One caveat - with its help you can only detect large objects, and this is understandable, because for the sake of a couple of coins you will not dig a six-meter hole.

And again we return to the same universal model of the “Pirate” detector. It turns out that you can make an in-depth device based on it, and it’s not at all difficult. The modification process is described in this video.

Instrumental search is simply enormously popular. Adults and children, amateurs and professionals are looking for it. They are looking for treasures, coins, lost things and buried scrap metal. The main search tool is a metal detector.

There are a great variety of different metal detectors to suit every taste and color. But for many people, buying a ready-made branded metal detector is simply financially expensive. And some people want to assemble a metal detector with their own hands, and some even build their own small business on their assembly.

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.

Characteristics of metal detectors. How to choose the best?

When choosing the optimal metal detector model, you should take into account a number of criteria and characteristics:

Discrimination. This indicator reflects the ability of the metal detector to distinguish metals from each other. The higher the degree of discrimination of the model, the more accurately it will show the user what metal is in the search area underground or in water: gold, silver, copper or other non-ferrous metals;

Type of coil. Most models use double coils, the so-called Double D, less often mono coils. Preference should be given to models with DD coils. It is worth considering the protection of the coil from moisture, the possibility of changing it and the weight of the coil;

Detection depth. The indicator depends on the detection frequency at which the metal detector operates. 7 kHz – large objects are visible at depth or small ones on the surface. Frequency from 13 kHz is suitable for gold prospecting;

Ground balance. Allows you to make the metal detector more sensitive, eliminate interference and work with soil saturated with minerals;

Number of settings. The best professional metal detector models have many specialized settings. Automatic modes are suitable for novice users;

Weight. Since you can search for artifacts with a metal detector for up to 15 hours (that’s how long batteries and rechargeable batteries last on average), light weight will be an advantageous feature when choosing a model to purchase.

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.

Materials and tools for work

Modern metal detectors differ from their predecessors in their compact dimensions and light weight, which makes them as convenient as possible for long-term work in the field.

The development of microelectronics, which enhances the effect of electrical impulses, helped reduce the mechanical parameters of the device.

Many treasure hunters, who have an understanding of physical science in the scope of the school curriculum, independently assemble metal detectors.

Some parts for assembling the device, as well as ordinary tools from the stock of a skillful owner, can be found in almost every home. To work you will need the following items:

copper wires of different sections;
two current generators, or magnetic coils;
soldering iron with solder and rosin;
screwdrivers;
wire cutters;
pliers;
insulating tape;
a piece of pipe or wooden dowel for the body.

Radio parts for the electronic system of the device can be found in old devices stored in the pantry or purchased on the market.

You need to stock up on a piece of PCB for the board, several 100 kOhm resistors, KT 315 transistors, capacitors C1, 2, 3, 4, stereo headphones and a 4.5 V battery.

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.

Circuit diagram of a metal detector with metal discrimination

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

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

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

However, in order for the equipment to work, a coil is required. It is best if it has low parasitic capacitance. The winding enamel wire is wound onto a reel. And then you can connect it and check the functionality of the metal detector. It is imperative to make a body and a rod for it. And you can start working.

DIY metal detector without microcircuits

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

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:

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.
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:

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

We recommend reading: Zener diode characteristics, marking, principle of operation

Another metal detector coil is made in a similar way.

Start assembling the parts:

Place the elements on the board according to the diagram shown in the picture.
Solder to the tracks on the PCB.
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:

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.
Now fix the coils and the board on the stand with glue. Coat the top of the parts with oil varnish.
Attach your headphones. To do this, make holes in the rod at the top and bottom.
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:

Put on your headphones.
Apply the pieces of aluminum to each coil one at a time.
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.

Terminator 3 metal detector coil

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

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

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

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

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

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

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

Metal detector coil repair

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

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

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

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.

Firmware

zabava1.2.rar — download the program for the microcontroller.

How to write a program to a microcontroller

Schematic diagram of the metal detector Zabava-m1

https://sdelai-sam.su/spravka_K561LE5.html - brief description of the K561LE5 chip. https://sdelai-sam.su/spravka_CD4001A.html - brief description of the CD4001A chip. https://sdelai-sam.su/spravka_78L05. html — brief description of the 78L05 microcircuit. https://sdelai-sam.su/spravka_attiny2313.html — brief description of the ATtiny2313A microcontroller. https://www.sdelai-sam.su/kd521.html — brief description of the KD521 diode. https:/ /sdelai-sam.su/rezistor.html - resistors, marking of resistors, connection of resistors, etc. https://sdelai-sam.su/kondensator.html - capacitors, marking of capacitors, connection of capacitors, etc.

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).

Homemade devices

Purchasing a metal detector with discrimination is quite difficult. These are expensive devices and it will be difficult for a beginner to learn how to use such equipment on their own. Such a device can be made at home. A homemade metal detector will be very different from real pulse devices, but it will help you learn how to use the device in simple search conditions.

Baby FM

This is the simplest metal detector with metal discrimination that you can assemble with your own hands. It is capable of identifying objects made of ferrous and precious metal at depths of up to 12÷15 centimeters. Suitable for searching on beaches. For self-production you will need the following radio components:

Microcontroller PIC12F675.
Quartz resonator rated up to 20 MHz.
Ceramic capacitors: 15 pF - 2 pcs and 100 nF - 1 pc.
Electrolytic capacitor with a nominal value of 100 uF - 1 pc.
Film capacitors with a nominal value of 100 nF - 2 pcs.
Resistors with a resistance of 10 kOhm - 1 pc., with a resistance of 470 Ohm - 1 pc.
Voltage stabilizer type AMS1117 up to 3.3 volts.
Speaker with impedance up to 8 ohms.
Microswitch.

All described parts must be assembled on a printed circuit board. It can be made by etching or as follows:

Cut a piece of plexiglass or textolite 35 mm wide and 80 mm long.
Translate the schematic diagram of the device onto a piece.
Drill holes for radio components.
Solder all elements using copper jumpers.

Due to the fact that there are very few elements in the circuit, this installation method can be considered the simplest and fastest.

During assembly, the order in which the voltage stabilizer is connected must be strictly observed. The diagram is shown below.

Coil

To make a transmitter coil you will need copper wire with a cross section of 0.3–0.4 mm. It is necessary to prepare the frame for winding in advance. Its diameter should not exceed 180 mm. Exactly 55 turns need to be wound onto the frame. Such a coil will allow the transmission of frequency pulses at 17–19 kHz.

After winding, you need to remove the wound wire from the frame and reinforce it with insulating tape in several places. Afterwards, you need to wrap the entire coil with tape as tightly as possible. It is very important that all turns are in close contact with each other.

After insulation, 1 layer of foil is applied to the coil. The foil is also secured at the ends with insulating tape.

Important! At the point where the ends of the coil wire exit, it is necessary to leave at least 5 centimeters of surface free from foil.

At the final stage, the coil is wrapped with a pre-tinned piece of wire. The winding is carried out in increments of 1 centimeter. After the first tests, the sensitivity of the coils can be increased. To do this, you will have to unwind several turns of the wire, measuring the total resistance. The best and most stable operation can be achieved with a resistance of no more than 2 ohms.

Connection

After the coil has been wound and insulated, the ends of all wires need to be connected. This is done as follows:

One end is connected to the controller via pin “5”, in parallel with capacitor C7.
The second end is through resistor R2, in parallel with capacitor C6, to pin “6” of the controller.
Both ends of the shielding wire are connected to the minus terminal of the circuit diagram.

You can further upgrade the device if you gradually reduce the capacity of the listed capacitors. The frequency response will increase, and the current consumption will increase significantly.

After connecting, you need to flash the controller firmware. The file can be found on the Internet.

The Malysh FM metal detector does not require configuration. It is necessary to assemble the printed circuit board into a convenient sealed box and select a convenient holder to secure all the parts. It is very important to use an additional frame made of plastic or plywood for the reel. After assembly, you can turn on the device and test its abilities on metal objects. The device is powered by a 9–12 volt battery or rechargeable battery.

Volksturm

The circuit of a metal detector with discrimination of metals of this type is also simple. The main feature of this device is the presence of two coils at once. This ensures a high penetration depth into soils of varying textures. The ability to discriminate between metals based on electrical conductivity is also increased. Bringing the coils closer together helped achieve this result. They touch each other, which reduces the speed of signal transmission from the coil to the controller. For assembly you will need the following parts:

3 transistors BC546 or their domestic analogue KT 315.
1 transistor BC556. Can be replaced with KT 361.
Operational signal amplifier LF353 or TL072 - 1 pc.
Amplifier LM358N.
One chip each CD 4011, 4013, 4066.
Fixed resistors 5.6K, 430K, 10K, 390K, 1.5K, 220K, 56K, 8.2K - 1 piece; 22K - 3 pcs; 1K - 2 pcs; 100K - 8 pcs; 130K - 2 pcs.
Variable resistors 100 and 330K - 1 pc.
Non-polar capacitors with a nominal value of 1nF, 220nF, 47nF, 10nF - 1 piece; 22nF - 3 pcs; 1 mkF - 2 pcs.
Electrolytic capacitors with a voltage of 16 volts and a nominal value of 220 mkF - 2 pcs.
Quartz resonator - 32768 Hz.
Speaker.
LEDs - 2 pcs.

All parts are assembled on a circuit board with strict adherence to the schematic diagram. At the testing stage, many capacitors will have to be selected additionally. Resistors are also selected. It depends on the voltage and resistance of the coils. If the resistance is high, the TL072 operational amplifier may fail due to overheating.

Coil

This model has 2 coils: transmitting and receiving. The parts differ in their shape from the usual ones. They are square in shape with rounded corners. For production you need:

On a standard sheet of paper, draw a rectangle with sides 14.5 and 23 cm.
On the left side of the rectangle, step back 2.5 cm from each corner.
On the right side 3 cm.
Cut the corners according to the diagram.
Attach the sheet to the plywood.
Insulate 8 nails with insulation tape.
Drive nails into the corners of the template. Afterwards it is very important to bite off the nail heads. This will protect the varnish insulation of the winding when removed from the frame.
Wind 80 turns of copper wire with a cross section of 0.3–0.4 mm onto the workpiece. It is very important to wrap only on insulated nails.

After winding is completed, the coil is fastened in several places with nylon thread. Next, you need to carefully remove the coil from the frame and wrap it tightly with insulating tape. Wind one layer of capacitor foil over the tape. Wind a copper wire pre-tinned with tin on top of the foil in increments of 1 cm. Connect the end of this wire to the beginning of the coil.

The second coil is assembled using the same principle, except that there is no need to wrap it with foil and an additional screen.

Both coils must be fixed with one edge overlapping each other. The contact of the edges should not be along the entire length, but only in two places. Both coils and their locations will require precise mounting. They should not sag or bend due to vibration. Any deformation will affect sensitivity and overall performance.

After assembly, you need to connect both coils to the previously assembled board. To do this, you need to connect the beginning of the shielded transmitting coil and the end of the receiving coil. This contact is extended with a stranded wire and connected to the “TX” contact on the board. Both remaining ends are connected to minus. When you turn on the device, there will be about 4 volts of voltage at the coil outputs. It will have to be strengthened by selecting capacitors. You will need to unsolder the contacts again and solder capacitors with a nominal value of 0.02 μF into the gap. Thus, after applying voltage, a voltage of up to 20 volts will appear at the outputs of the coils. This will increase the penetrating power of the metal detector, while still having the power to work with coils of this size. Such a high voltage will require the user to equip the device with a powerful 12-volt battery. A regular “Krona” may only be enough for 1.5 hours of searching.

After connecting the power, you will need to configure the coils for reception and transmission. To do this, you need to place a metal object under them and adjust the position by sound. This is done as follows:

The long sides of the shielded coil must be compressed by 0.5 cm. As the tone and volume increase, the edges are fixed. You can use a wooden spacer.
Then the second coil is adjusted in the same way. You need to achieve an increase in volume and tone by squeezing the long edges.
At the final stage, the general position relative to each other is adjusted. It is necessary to bring both elements closer and further apart until the highest pitch is fixed. Additionally, you can control the resistance of parts when approaching. The smallest setting will be the best.

Once the highest tone is found, both elements are tightly fixed to the frame. Next, you need to assemble the board in a sealed box, connect variable resistors to it and secure the LEDs. It is very important to reliably insulate both windings. Even slight humidity will lead to complete failure or settings failure.

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:

Selecting a circuit for working in river and sea water.
Manufacturing of printed circuit board.
Connecting the power supply.
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.
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.

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

We recommend reading: Pinout of different types of USB connectors: pinout of micro and mini usb, pinout features

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.

Best Inexpensive Budget Metal Detectors for Beginners

Garrett Pro Pointer AT

The smallest and brightest metal detector

detection method – pinpointer;
detection frequency – 11.5 kHz;
purpose – underwater, ground;
sensitivity setting – yes;
ground balancing – yes;
batteries, quantity – crown, 1.

Pros: the highest quality inexpensive pinpointer, which is sold in online stores at a price below 7,000 rubles. The device can be considered as a stand-alone device for beginning diggers, or as an addition to the main metal detector for advanced users and professionals. It does an excellent job of localizing a target during excavations with millimeter precision: in a dump of soil or in the walls of a pit.

Garrett Pro Pointer AT is the most popular pinpointer among users, with maximum ratings after use and the “Buyer’s Choice” status. Waterproof up to 3 meters, can be used underwater. Active detection area 360 degrees.

Control 3 sensitivity and detection depth modes with just one button. The bright, signature orange “carrot” color will ensure you don’t lose your Garrett Pro Pointer during excavations. Implemented light, sound and vibration notification of the target. Backlight function in case of loss.

The kit includes a mounting ring, a case for carrying the metal detector, and a set of batteries. In the rating of metal detectors, this is the lightest and cheapest device.

Cons: the kit comes with a weak battery, it is better to immediately replace it with a more powerful one.

Bounty Hunter Junior

The best gift for a child

detection method – VLF;
maximum detection depth – 0.5 m;
coil design – mono;
detection frequency – 6.5 kHz;
sensitivity setting – no;
tonal identification – yes;
ground balancing – no;
discriminator – yes;
batteries, quantity – crown, 2.

Pros: a popular inexpensive model of a metal detector from the American company Bounty Hunter with a good search depth is perfect for children from 5 to 16 years old or novice treasure hunters. The coil of this budget metal detector is located in one block. It operates with a detection frequency of 6.5 kHz, which allows the metal detector to be used for searching at a depth of up to 0.5 m.

The distinctive characteristics of the device include the ease of setting up the metal detector and controlling it. The built-in discriminator will help distinguish metals in the soil and highlight non-ferrous metals. Sound comes from the built-in speaker.

Users note the low weight of the metal detector design – 500 grams. Considering the full range of advantages of the device and its low price in online stores, the new Bounty Hunter Junior can be considered as an excellent gift for a child for the summer.

Cons: no armrest, your arm may get tired. Afraid of water.

Minelab Go-Find 44

The best metal detector for beginners

detection method – VFLEX;
maximum detection depth – 0.8 m;
detection frequency – 7.8 kHz;
sensitivity setting – yes;
tonal identification – yes;
ground balancing – automatic;
discriminator – yes;
batteries, quantity – AA, 4.

Pros: in first place in the ranking of the best inexpensive metal detectors is a model from Minelab, a famous company among treasure hunters. The Go-Find 44 detects metals and objects using the VFLEX method, which is the company’s own development and is considered an improved version of VLF. Thanks to discrete signal processing, the number of errors is minimized.

A ground metal detector for searching for coins will be an excellent option for beginners. A durable, molded construction made of high-quality plastic will ensure long-term operation of the Go-Find 44. The device weighs just over 1 kg.

The detection frequency of 7.8 kHz allows you to find coins, lost jewelry and metal products at a depth of up to 80 cm. The information is displayed on the screen. There are 5 search modes available, headphone connection. The size of the metal detector changes and adapts to the user, from 55 to 130 cm.

Go-Find 44 runs on 4 AA batteries. Easily replaced with rechargeable batteries. One charge lasts for 40 hours. A special characteristic of the metal detector is the presence of Bluetooth; the device can be connected to a smartphone and change its settings and configurations.

Cons: not found

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.

Main settings

To determine the appropriate criteria for a homemade design, it is necessary to study the basic technical parameters.

Detection depth

The principle of operation of the metal detector

This data is not always provided in the accompanying documentation. Even when the depth is indicated in the technical data sheet, this value should not be understood as a certain value. The fact is that for control measurements they use a uniform soil composition and maintain stable temperature and humidity. In a real situation, natural and other external factors will significantly worsen the results obtained under ideal conditions.

For your information. High-quality factory metal detectors are capable of detecting a product made of conductive material at a depth of 1.5-3 m. “Deep” modifications operate up to a maximum of 5-6.5 meters.

Operating frequency

You can increase the search depth by using a reduced frequency. In this case, the selectivity of the work process is significantly deteriorated. However, long waves bend around small objects, which is accompanied by a deterioration in sensitivity.

For your information. In professional metal detectors, the user can choose from more than two dozen different frequencies. With such equipment, the choice of the optimal research mode under certain conditions is simplified.

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:

Empty CD box.
A radio receiver capable of operating in the AM range.
Calculator.
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 Clone PI at home - diagram and detailed instructions

Clone PI is a non-metal detection pulse metal detector that can handle a variety of coil sizes. When using a ring with a diameter of 20 cm, MI Clone can find a coin at a depth of up to 25 cm, and large metal - up to 1 meter.

The Clone is based on the circuit of the Tracker PI-2 metal detector with some changes made to it.

The Clone PI metal detector has the following differences from the original (Tracker PI-2 Metal Detector):

Using an AVR microcontroller instead of a PIC controller.
Using an LCD screen without LEDs for indication.
Availability of fast and slow auto-tuning.
All controls of the metal detector are push-button (without variable resistors).

Clone PI metal detector circuit diagram

Clone PI is a pulse metal detector of average complexity; for a beginner it will be difficult to manufacture. However, a person with some experience in assembling metal detectors or other electronics will be able to handle it.

The Clone metal detector circuit contains several expensive elements: an LCD screen, an MCP3201 ADC and a microcontroller. Before you start making a metal detector, be sure to purchase an ADC, as purchasing one may be difficult!

Also, the metal detector circuit contains a programmable microcontroller, so to make it you will need a programmer with support for programming microcontrollers - PIC18F252 and the ability to use it.

On the screen, the Clone Pi metal detector displays the following information:

Response level (“fast” and “slow” sliders).
Supply voltage.
Threshold (the inverse value of sensitivity).
Volume.
A sign that auto-tuning is active (the response exceeds the threshold in any direction).
A sign of slow auto-adjustment (response deviation in the positive direction) coincides with the sound alarm.
Indicator that the display backlight is on.

The Klon metal detector performed quite well in operation. With high-quality assembly, the Clone practically does not differ in search characteristics from Tracker PI and other pulse metal detectors.

DIY metal detector assembly Clone PI

The assembly of the Clone PI metal detector, as mentioned above, should begin with the search and purchase of parts for the manufacture of a printed circuit board. After this, you can proceed to the direct process of manufacturing and assembly.

First of all, you need to etch the printed circuit board:

After manufacturing the printed circuit board, it is necessary to solder all the radio components into it. It is better to install microcircuits on sockets. We also connect control buttons, a screen, a speaker and connectors for the coil and power supply of the metal detector to the board. After soldering is completed, the board must be washed with alcohol and dried thoroughly.

Then we carefully inspect the board to identify unsoldered areas and “sticks”. If everything is good, you can start programming the microcontroller.

Firmware, printed circuit board drawings and other materials that you may need when creating a Clone Pi metal detector with your own hands at home can be downloaded below.

Files for download: klon-pi.rar

After programming, we install the microcontroller on the board, and you can already see the first fruits of your labor.

If the metal detector turns on, shows everything on the screen, makes sound and responds to control buttons, then you can proceed to making a search coil. If something doesn’t work, then we return to the stage of visual inspection, checking the board according to the diagram and identifying assembly defects!

Manufacturing a search coil for the Clone PI metal detector

A simple search coil for the Clone PI metal detector can be made with your own hands from winding enamel wire with a diameter of 0.6–0.8 mm, winding 25 turns on a mandrel with a diameter of 25–27 cm. You can use a saucepan or other suitable round object as a mandrel.

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.

Functional and technical parameters of metal detectors

Before purchasing a high-quality metal detector, you need to decide on the search environment. It is necessary to take into account the potential dimensions of the desired objects and the depth of their occurrence. Key indicators that are emphasized when purchasing a device:

principle of influence;
frequency;
susceptibility;
weight;
soil balancing;
target designation;
discriminator;
auxiliary functionality.

The operating principle and operating frequency are the main indicators that determine the capabilities of the device and show which class it can be classified into.

Operating principle

The generator creates an electromagnetic field with predetermined characteristics around the search coil. The shape of the field and its depth depend both on the characteristics of the generator and on the shape of the coil itself.

Metal detector Terminator 3

When searching, if there are no disturbances in the electromagnetic field, nothing happens. But when a conductive object enters the electromagnetic field zone, it creates Foucault currents. When a disturbance hits the receiver, it must determine the approximate type of object and transmit information about it to the alarm device. The same story happens when an object with ferromagnetic properties appears in the search field. The characteristics of the soil affect the search field, but at the same time, with the correct settings of the characteristics of the metal detector, more precisely the radiation parameters, this interference can be minimized.

Important! Metal discrimination is one of the functions of a metal detector, which allows you to determine which category a find belongs to. It works by separating the material of an object according to the conductivity of electromagnetic waves. This will eliminate various debris and ferrous metals from the search area.