Metal detector scheme: how to make a simple and effective metal detector with your own hands. Onward, in search of treasure! How to make a powerful metal detector at home with your own hands

THE BEST METAL DETECTOR

Why was the Volksturm named the best metal detector? The main thing is that the scheme is really simple and really working. Of the many metal detector circuits that I personally made, this is where everything is simple, deep-cutting and reliable! Moreover, with its simplicity, the metal detector has a good discrimination scheme - the definition of iron or non-ferrous metal is in the ground. Assembling the metal detector consists in error-free soldering of the board and setting the coils to resonance and to zero at the output of the input stage on the LF353. There is nothing super complicated here, it would be a desire and brains. We look constructive execution of the metal detector and a new improved scheme Volksturm with a description.

Since questions arise during the build to save you time and not force you to flip through hundreds of forum pages, here are the answers to the 10 most popular questions. The article is in the process of being written, so some points will be added later.

1. How does this metal detector work and detect targets?
2. How to check if the metal detector board is working?
3. Which resonance should I choose?
4. What are the best capacitors?
5. How to adjust resonance?
6. How to zero coils?
7. Which coil wire is best?
8. What parts can be replaced and with what?
9. What determines the depth of the search for goals?
10. Power supply for the Volksturm metal detector?

The principle of operation of the Volksturm metal detector

I will try in a nutshell about the principle of operation: transmission, reception and balance of induction. In the search sensor of the metal detector, 2 coils are installed - transmitting and receiving. The presence of metal changes the inductive coupling between them (including the phase), which affects the received signal, which is then processed by the display unit. Between the first and second microcircuits there is a switch controlled by pulses of a phase-shifted generator relative to the transmitting channel (i.e. when the transmitter is working, the receiver is turned off and vice versa, if the receiver is turned on, the transmitter is resting, and the receiver calmly catches the reflected signal in this pause). So, you turned on the metal detector and it beeps. Great, if it beeps, then many nodes are working. Let's figure out why exactly he squeaks. The generator on y6B constantly generates a tone signal. Then it enters the amplifier on two transistors, but the unch will not open (do not miss the tone) until the voltage at the output of u2B (7th pin) allows it to do so. This voltage is set by changing the mode using this same trash resistor. They need to set such a voltage so that the Unch almost opens and misses the signal from the generator. And the input couple of millivolts from the metal detector coil, having passed the amplifying cascades, will exceed this threshold and it will open completely and the speaker will squeak. Now let's trace the passage of the signal, or rather the response signal. On the first stage (1-y1a) there will be a couple of millivolts, up to 50 is possible. On the second stage (7-y1B) this deviation will increase, on the third one (1-y2A) there will already be a couple of volts. But without a response everywhere at the outputs by zeros.

How to check if the metal detector board is working

In general, the amplifier and key (CD 4066) are checked with a finger at the RX input contact at maximum resistance sens and maximum background on the speaker. If there is a change in the background when you press your finger for a second, then the key and the opamp work, then we connect the RX coils with the circuit capacitor in parallel, the capacitor on the TX coil in series, put one coil on top of the other and start reducing to 0 according to the minimum AC reading on the first leg of the amplifier U1A. Next, we take something large and iron and check whether there is a reaction to the metal in the dynamics or not. Let's check the voltage at u2B (7th pin), it should be a trash regulator, change + - a couple of volts. If not, the problem is in this stage of the op-amp. To start checking the board, turn off the coils and turn on the power.

1. There should be a sound when the sens regulator is set to maximum resistance, touch the PX with your finger - if there is a reaction, all the opamps work, if not - check with your finger starting from u2 and change (examine the strapping) of the non-working op-amp.

2. The operation of the generator is checked by the frequency meter program. Solder the plug from the headphones to pin 12 of the CD4013 (561TM2) prudently soldering p23 (so as not to burn the sound card). Use In-lane in the sound card. We look at the generation frequency, its stability is at 8192 Hz. If it is strongly displaced, then it is necessary to solder the capacitor c9, if even after it is not clearly distinguished and / or there are many frequency bursts nearby, we replace the quartz.

3. Checked amplifiers and generator. If everything is in order, but still does not work, change the key (CD 4066).

Which coil resonance to choose

When the coil is connected to series resonance, the current in the coil and the overall consumption of the circuit increase. The target detection distance is increased, but this is only on the table. On real ground, ground will feel stronger the more pump current in the coil. It is better to turn on parallel resonance, and to raise the flair with input stages. And the batteries last a lot longer. Despite the fact that series resonance is used in all branded expensive metal detectors, Sturm needs exactly parallel. In imported, expensive devices, there is a good ground detuning circuitry, therefore, in these devices, serial can be enabled.

What capacitors are better to install in the circuit metal detector

The type of capacitor connected to the coil has nothing to do with it, and if you experimentally changed two and saw that the resonance is better with one of them, then just one of the supposedly 0.1 uF actually has 0.098 uF, and the other 0.11. Here is the difference between them in terms of resonance. I used Soviet K73-17 and green imported pillows.

How to set coil resonance metal detector

The coil, as the best option, is obtained from plaster floats glued with epoxy from the ends to the size you need. Moreover, its central part with a piece of the handle of this very grater, which is processed to one wide ear. On the bar, on the contrary, there is a fork of two fastening lugs. This solution solves the problem of coil deformation when tightening the plastic bolt. The grooves for the windings are made with an ordinary burner, then zeroing and filling. From the cold end of the TX, let's leave 50 cm of wire, which is not initially poured, but twist a small coil out of it (3 cm in diameter) and place it inside the RX, moving and deforming it within small limits, you can achieve an exact zero, but doing this better outdoors, placing the coil near the ground (as in the search) with the GEB turned off, if any, then finally fill with resin. Then the detuning from the ground works more or less tolerably (with the exception of highly mineralized soil). Such a coil turns out to be light, durable, little subject to thermal deformation, and processed and painted is very pretty. And one more observation: if the metal detector is assembled with ground balance (GEB) and with the central position of the resistor slider set to zero with a very small washer, the GEB adjustment range is + - 80-100 mV. If you set zero with a large object, a coin of 10-50 kopecks. the adjustment range increases to +- 500-600 mV. Do not chase the voltage in the process of tuning the resonance - I have about 40V at 12V with a series resonance. In order for discrimination to appear, we turn on the capacitors in the coils in parallel (serial connection is necessary only at the stage of selecting conders for resonance) - there will be a lingering sound on ferrous metals, and a short one on non-ferrous metals.

Or even easier. We connect the coils in turn to the transmitting TX output. We tune one into resonance, and after tuning it, the other. Step by step: Connected, parallel to the coil, poked variable volts with a multimeter at the limit, also soldered a capacitor 0.07-0.08 microfarads in parallel to the coil, we look at the readings. Let's say 4 V - very weak, not in resonance with the frequency. They poked parallel to the first capacitor of the second small capacitance - 0.01 microfarads (0.07 + 0.01 = 0.08). We look - the voltmeter has already shown 7 V. Excellent, let's increase the capacitance, connect it to 0.02 uF - we look at the voltmeter, and there it is 20 V. Great, we go further - we will still add a couple of thousand capacitance peaks. Yeah. Already started to fall, roll back. And so to achieve the maximum readings of the voltmeter on the metal detector coil. Then similarly with the other (receiving) coil. Adjust to maximum and plug back into the receiving jack.

How to zero metal detector coils

To adjust zero, we connect the tester to the first leg of the LF353 and gradually begin to compress and stretch the coil. After filling with epoxy, the zero will definitely run away. Therefore, it is not necessary to fill the entire coil, but leave room for adjustment, and after drying, bring it to zero and fill it completely. Take a piece of twine and tie half of the coil with one turn to the middle (to the central part, the junction of two coils), insert a piece of stick into the loop of twine and then twist it (pull the twine) - the coil will shrink, catching the zero, soak the twine with glue, after almost complete drying again correct the zero by turning the wand a little more and pour the twine completely. Or more simply: The transmitter is fixed in plastic motionlessly, and the receiver is placed on the first one by 1 cm, such as wedding rings. The first output of U1A will be squeaking 8 kHz - you can control it with an AC voltmeter, but it's better just with high-impedance headphones. So, the receiving coil of the metal detector must either be pushed forward or moved from the transmitting coil until the squeak at the output of the op-amp subsides to a minimum (or the voltmeter readings drop to several millivolts). Everything, the coil is brought together, we fix it.

What is the best wire for search coils

The wire for winding the coils does not matter. Anyone will go from 0.3 to 0.8, you still have to select a little capacity to tune the circuits to resonance and to a frequency of 8.192 kHz. Of course, a thinner wire is quite suitable, just the thicker it is, the better the quality factor and, as a result, the flair is better. But if you wind 1 mm, it will be quite heavy to carry. On a sheet of paper, draw a rectangle 15 by 23 cm. Set aside 2.5 cm from the upper left and lower corners, and connect them with a line. We do the same with the upper and lower right corners, but set aside 3 cm each. In the middle of the lower part, put a dot and a dot on the left and right at a distance of 1 cm. We take plywood, apply this sketch and drive carnations into all points indicated. We take the wire PEV 0.3 and wind 80 turns of wire. But to be honest, it doesn't matter how many turns. Anyway, the frequency of 8 kHz will be set to resonance with a capacitor. How much they wound - so much they wound. I wound 80 turns and a capacitor of 0.1 microfarads, if you wind, let's say 50, you will have to put the capacitance, respectively, somewhere around 0.13 microfarads. Further, without removing from the template, we wrap the coil with a thick thread - like how wire harnesses are wrapped. After we cover the coil with varnish. When dry, remove the coil from the template. Then comes the winding of the coil with insulation - fum tape or electrical tape. Next - winding the receiving coil with foil, you can take a tape of electrolytic capacitors. The TX coil can be left unshielded. Don't forget to leave a 10mm BREAK in the screen, in the middle of the coil. Next comes the winding of the foil with tinned wire. This wire, together with the initial contact of the coil, will be our mass. And finally winding the coil with electrical tape. The inductance of the coils is about 3.5mH. The capacitance is about 0.1 microfarads. As for filling the coil with epoxy, I did not fill it at all. I just wrapped it tightly with duct tape. And nothing, I spent two seasons with this metal detector without changing the settings. Pay attention to the moisture insulation of the circuit and search coils, because you have to mow on wet grass. Everything must be sealed - otherwise moisture will get in and the setting will float. Sensitivity will deteriorate.

What parts and what can be replaced

transistors:
BC546 - 3pcs or KT315.
BC556 - 1pc or KT361
Operatives:

LF353 - 1pc or change to the more common TL072.
LM358N - 2pcs
Digital ICs:
CD4011 - 1pc
CD4066 - 1pc
CD4013 - 1pc
Resistors, power 0.125-0.25 W:
5.6K - 1pc
430K - 1pc
22K - 3pcs
10K - 1pc
390K - 1pc
1K - 2pcs
1.5K - 1pc
100K - 8pcs
220K - 1pc
130K - 2pcs
56K - 1pc
8.2K - 1pc
Resistors variable:
100K - 1pc
330K - 1pc
Capacitors non-polar:
1nF - 1pc
22nF - 3pcs (22000pF = 22nF = 0.022uF)
220nF - 1pc
1uF - 2pcs
47nF - 1pc
10nF - 1pc
Electrolytic Capacitors:
220uF at 16V - 2pcs

The speaker is tiny.
Quartz resonator at 32768 Hz.
Two super-bright LEDs of different colors.

If you cannot get imported microcircuits, here are domestic analogues: CD 4066 - K561KT3, CD4013 - 561TM2, CD4011 - 561LA7, LM358N - KR1040UD1. The LF353 chip has no direct analogue, but feel free to put LM358N or better TL072, TL062. It is not at all necessary to install an operational amplifier - LF353, I just raised the gain by U1A by replacing the resistor in the negative feedback circuit 390 kOhm with 1 mOhm - the sensitivity increased significantly by 50 percent, although after this replacement it went zero, I had to glue it to the coil in a certain place tape a piece of aluminum plate. The Soviet three kopecks feels through the air at a distance of 25 centimeters, and this is when powered by 6 volts, the current consumed without indication is 10 mA. And do not forget about the panels - the convenience and ease of setup will increase significantly. Transistors KT814, Kt815 - in the transmitting part of the metal detector, KT315 in the ULF. Transistors - 816 and 817, it is desirable to choose with the same gain. Replaceable with any appropriate structure and capacity. A special watch quartz is installed in the metal detector generator at a frequency of 32768 Hz. This is the standard for absolutely all quartz resonators that are in any electronic and electromechanical watches. Including wrist and cheap Chinese wall / desktop. PCB archives for the variant and for (manual ground balance variant).

What determines the depth of the search for goals

The larger the diameter of the metal detector coil, the deeper the flair. In general, the depth of target detection with a given coil depends primarily on the size of the target itself. But with an increase in the diameter of the coil, there is a decrease in the accuracy of object detection and even sometimes the loss of small targets. For objects the size of a coin, this effect is observed when the coil size is increased above 40 cm. In summary: a large search coil has a greater detection depth and greater capture, but detects the target less accurately than a small one. The large coil is ideal for finding deep and large targets such as treasures and large objects.

According to the shape of the coil are divided into round and elliptical (rectangular). An elliptical metal detector coil has better selectivity than a round one, because it has a smaller magnetic field and fewer foreign objects fall into its field of action. But the round one has a greater detection depth and better sensitivity to the target. Especially on weakly mineralized soils. The round coil is most commonly used when searching with a metal detector.

Coils with a diameter of less than 15 cm are called small, coils with a diameter of 15-30 cm are called medium and coils over 30 cm are called large. A large coil generates a larger electromagnetic field, so it has a greater detection depth than a small one. Large coils generate a large electromagnetic field and, accordingly, have a large detection depth and search coverage. Such coils are used to view large areas, but when using them, a problem may arise on heavily littered areas because several targets can fall into the field of action of large coils at once and the metal detector will react to a larger target.

The electromagnetic field of a small search coil is also small, so with such a coil it is best to search in areas heavily littered with all sorts of small metal objects. The small coil is ideal for detecting small objects, but has a small coverage area and relatively shallow detection depth.

Medium coils work well for general purpose searches. This size of the searchcoil combines sufficient search depth and sensitivity to targets with different sizes. I made each coil with a diameter of about 16 cm and put both of these coils in a round stand from under an old 15" monitor. In this version, the search depth of this metal detector will be as follows: an aluminum plate 50x70 mm - 60 cm, a M5-5 cm nut, a coin - 30 cm, bucket - about a meter These values are obtained in the air, in the ground it will be 30% less.

Power supply of the metal detector

Separately, the metal detector circuit draws 15-20 mA, with the coil connected + 30-40 mA, totaling up to 60 mA. Of course, depending on the type of speaker and LEDs used, this value may vary. The simplest case - power was taken by 3 (or even two) series-connected lithium-ion batteries from mobile phones at 3.7V and when charging discharged batteries, when we connect any power supply to 12-13V, the charge current starts from 0.8A and drops to 50mA in an hour, and then you don’t need to add anything at all, although a limiting resistor certainly doesn’t hurt. As in general, the simplest option is a 9V crown. But keep in mind that a metal detector will eat it in 2 hours. But for customization, this power option is the most it. Krona under any circumstances will not give out a large current that can burn something in the board.

Homemade metal detector

And now a description of the metal detector assembly process from one of the visitors. Since I only have a multimeter from the devices, I downloaded the virtual laboratory Zapisnykh O.L. from the Internet. I assembled an adapter, a simple generator and drove an oscilloscope to idle. It looks like it's showing a picture. Then I started looking for radio components. Since prints are mostly laid out in the “lay” format, I downloaded “Sprint-Layout50”. I found out what laser-ironing technology for manufacturing printed circuit boards is and how to etch them. Removed the fee. By this time, all microcircuits were found. What I did not find in my shed, I had to buy. I started soldering jumpers, resistors, microcircuit sockets, and quartz from a Chinese alarm clock to the board. Periodically checking the resistance on the power rails so that there is no snot. I decided to start by assembling the digital part of the device, as the easiest. That is, a generator, a divider and a switch. Collected. I installed a generator chip (K561LA7) and a divider (K561TM2). Used microcircuits, torn out from some boards found in a shed. I applied 12V power while controlling the current consumption by an ammeter, 561TM2 became warm. Replaced 561TM2, powered up - zero emotions. I measure the voltage on the legs of the generator - on legs 1 and 2 12V. I change 561LA7. I turn it on - at the output of the divider, there is generation on the 13th leg (I watch it on a virtual oscilloscope)! The picture is really not so hot, but in the absence of a normal oscilloscope, it will do. But there is nothing on 1, 2 and 12 legs. So the generator is working, you need to change TM2. I installed the third divider chip - there is beauty at all outputs! For myself, I concluded that you need to solder the microcircuits as carefully as possible! This is the first step in the construction.

Now we are setting up the metal detector board. The "SENS" regulator did not work - the sensitivity, I had to throw out the capacitor C3 after that the sensitivity adjustment worked as it should. I did not like the sound that occurs in the extreme left position of the "THRESH" regulator - the threshold, got rid of this by replacing the resistor R9 with a chain of series-connected 5.6 kΩ resistor + 47.0 uF capacitor (negative terminal of the capacitor on the transistor side). While there is no LF353 chip, instead of it, I put LM358, with it the Soviet three kopecks feel in the air at a distance of 15 centimeters.

I included the search coil for transmission as a series oscillatory circuit, and for reception as a parallel oscillatory circuit. I set up the transmitting coil first, connected the assembled sensor structure to the metal detector, the oscilloscope parallel to the coil and selected the capacitors according to the maximum amplitude. After that, I connected the oscilloscope to the receiving coil and picked up the capacitors on the RX according to the maximum amplitude. Setting the circuits to resonance takes, with an oscilloscope, several minutes. The TX and RX windings each contain 100 turns of wire with a diameter of 0.4. We start mixing on the table, without the case. Just to have two hoops with wires. And in order to make sure that it works and that it is possible to mix in general, we will separate the coils from each other by half a meter. Then zero will be exactly. Then, having overlapped the coils by about 1 cm (like wedding rings), move - move apart. The zero point can be quite precise and not easy to catch right away. But she is.

When I raised the gain in the RX path of the MD, it began to work unstably at maximum sensitivity, this manifested itself in the fact that after passing over the target and detecting it, a signal was issued, but it continued even after there was no longer any target in front of the search coil, this manifested itself in the form of intermittent and oscillating sound signals. With the help of an oscilloscope, the reason for this was also discovered: when the speaker is operating and there is a slight drop in the supply voltage, "zero" goes away and the MD circuit goes into a self-oscillating mode, which can only be exited by coarsening the sound signal threshold. This didn’t suit me, so I put a KR142EN5A + extra bright white LED on the power supply to raise the voltage at the output of the integral stabilizer, I didn’t have a stabilizer for a higher voltage. Such an LED can even be used to illuminate the search coil. The speaker connected to the stabilizer, after that the MD immediately became very obedient, everything started to work as it should. I think Volksturm is really the best homemade metal detector!

Recently, this refinement scheme has been proposed, which will turn the Volksturm S into the Volksturm SS + GEB. Now the device will have a good discriminator, as well as metal selectivity and ground detuning, the device is soldered on a separate board and connected instead of capacitors c5 and c4. Scheme of completion and in the archive. Special thanks for the information on assembling and setting up the metal detector to everyone who took part in the discussion and modernization of the circuit, especially Elektrodych, fez, xxx, slavake, ew2bw, redkii and other radio amateur colleagues helped in the preparation of the material.

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

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

Scheme of a metal detector on microcircuits

The circuit is very simple. It can be easily repeated at home. It is built on two microcircuits of the 176 series. The reference oscillator is made on la9 and stabilized by quartz at 1 MHz. Unfortunately, I didn’t have this, I had to set it to 1.6 MHz.

The tunable generator is assembled on a k176la7 chip. Varicap D1 will help to achieve zero beats, the capacitance of which varies depending on the position of the variable resistor R2 engine. The basis of the oscillatory circuit is the search coil L1, when it approaches a metal object, the inductance changes, as a result of which the frequency of the tunable generator changes, which we hear in the headphones.

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

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

Details of a homemade metal detector:

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

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

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

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

With the help of two clamps, I placed the entire metal detector unit on a segment of a ski pole:

The most important part remains: to make a search coil.

Coil for metal detector

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

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

I fixed the mating part of the connector on the coil:

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

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

The finished coils look like this:

Setting up the finished metal detector

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

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

The appearance of the finished device looks like this:

In conclusion, I would like to say that this metal detector is not suitable for people who are going to work in the old way. Since it does not discriminate by metal, you will have to dig everything in sight. You will most likely be very disappointed. But for those who like to collect scrap metal, this device will help. Yes, and just as entertainment for children.

Of course, I'm not a fan of this business with metal detectors (especially if it's deep, it takes a long time to dig to the first tin :)), I decided to assemble this one, because I like such electronic devices, there is a choice through the menu, several levels of discrim, and a cut-off barrier , which can be successfully used for preliminary determination of the type of metal.

In general, the device was a success, the main thing is reliable discrimination by metals, many thanks to the author, it is quite suitable for the role of the people.

Now about how I assembled it, and what materials I used.

For your review, I provide materials for a single assembly of the device, and since the circuit does not need to be adjusted after assembly, therefore it is desirable do not deviate from the author's recommendations in the scheme.

So we decided on the components, everything is in stock

you can start assembling.

I used the printed circuit board here from the principle of block construction, the main reason for this is to make a compact circuit on the existing parts,

and also in my case, the receiving and transmitting parts of the circuit turned out, on different boards, although this does not matter much, since the receiving and transmitting parts of the circuit do not work at the same time, but still .........

printed circuit board in Sptint Layout attached

Appearance

It turned out like this "sandwich"

Sensor manufacturing: there are no special requirements for the sensor: follow the author's recommendations on the resistance value and inductance value (author's coil L = 400 uH, R = 1.7 Ohm, copper wire 0.63-0.75, frame thickness 5 mm). And do not use electrically conductive parts to mount the coil (all parts and PVC glue).

You start winding such a coil (from above, then into the slot and from below, then again into the slot and from above, etc., in general, it’s clear what’s what ...
The main number of slots should be the same as in the photo.

When the assembled circuit worked

You can proceed to the complete assembly of the device.

First, we give the sensor an "aerodynamic" shape, and then - a thin fabric, fiberglass impregnated with epoxy.

Rod (lower part): I used an epoxy rod (Sovdepov production), it is also ideal to use a link from a telescopic rod. Many people will use a PVC pipe from a plastic water supply system, a large selection of fittings allows you to make designs of any shape, the material is correct, but it is too flexible in terms of rigidity, it bends, this is a disadvantage, this problem can be slightly smoothed out by inserting a wooden insert into the pipe, also coated with epoxy.

This is how the assembled metal detector looks like

In working order

In transport condition

I Russified the firmware a little, I like that this small menu of the device is in Russian, I know that many people prefer direct text without allegory, and I am one of those.

Sensitivity to 5kop. (Russia) 23cm, VDI starts showing at 15cm

Cut-off barrier.

There is a division: silver-copper-aluminum, bronze-brass-lead, nickel-stainless steel-silver, but not everything is perfect here, of course. For example, iron may appear in the brass-aluminum region, and tin cans may appear in the nickel-stainless steel-silver region.

Also, one metal can manifest itself in three sectors at once quite clearly.

Discrimination.

1) practically does not differ from the "no discrimination" mode

2) nickel, stainless steel are confidently determined, but the pieces of iron can also climb well.

3) iron is well cut off, there are separate squeaks with weak responses, nickel is cut a little, stainless steel and canning sheet will crawl through.

4) the mode is cut all but 15-16 sectors

Supply voltage; any movement starts already from 7 volts.

The consumed current, at a voltage of 12V, is in the region of 85-110mA.

The article was written to give hope to those who also begin to engage in amateur radio and follow, summarized and summarized to help people from wasting time and money, when repeating, contact the sourcehttp://fandy.vov.ru author Andy_F.

If your proteus does not correctly display Cyrillic characters on the LCD (this only applies to the Chance ru.nex file),

for the correct display of the Cyrillic alphabet, unpack this library into a folder models proteus,

and then proteus will correctly display Cyrillic.

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

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

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

The 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 pulsed echo or radar. Their difference from locators lies in the fact that the transmitted and received signals operate constantly and simultaneously, in addition, they operate at the same frequencies.

Devices operating on the principle of "reception-transmission" register the signal reflected (re-radiated) from a metal object. This signal appears due to the impact on a metal object of an alternating magnetic field, which is generated by the metal detector coils. That is, the design of devices of this type provides for the presence of two coils, the first is transmitting, the second is receiving.

Devices of this class have the following advantages:

simplicity of design;
great ability to detect 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 by hand before operation.

Other devices are sometimes referred to as a beat detector. This name comes from the distant past, more precisely from the time when superheterodyne receivers were widely used. Beating is a phenomenon that becomes noticeable when two signals with close frequencies and equal amplitudes are summed. The beating consists in pulsing the amplitude of the summed signal.

The pulse frequency of the signal 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, the so-called difference frequency is isolated.

Such a scheme was used for a long time, but today, it is not used. They were replaced by synchronous detectors, but the term remained in use.

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

The device is set up by hand so that the generated frequencies match or at least are close. As soon as metal enters the coverage area, the set parameters change and the frequency changes. The frequency difference can be recorded in many ways, ranging from headphones to digital methods.

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

But besides this, during their operation it is necessary to take into account the fact that they have high energy consumption.

Typical design

The structure of the metal detector includes the following components:

The coil is a box-type design, it houses the receiver and transmitter of the signal. 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 coil 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 with the rod, which is called the middle one.
The middle shaft is the node located between the lower and upper shafts. Fixing devices are fixed on it, allowing you to adjust the size of the device. on the market you can find models that consist of two rods.
The top bar is usually curved. It resembles the letter S. This form is considered optimal for fixing it on the hand. An armrest, a control unit and a handle are installed on it. The armrest and handle are made of polymeric materials.
The metal detector control unit is required to process the data received from the coil. After the signal is converted, it is sent to headphones or other means of indication. In addition, the control unit is designed to adjust the operating mode of the device. The wire from the coil is connected using a quick-release device.

All devices included in the metal detector are waterproof.

This is the relative simplicity of the design and allows you to make metal detectors with your own hands.

Varieties of metal detectors

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

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

Operating frequency

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

The simplest (budget) models operate at one frequency, models that are classified as average price levels use 2 or more frequencies in operation. There are models that use 28 frequencies when searching.

Modern metal detectors are equipped with such a function as metal discrimination. It allows you to distinguish the type of material located at depth. At the same time, when ferrous metal is detected, one sound will sound in the searcher's headphones, and another when non-ferrous metal is detected.

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

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

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

How to assemble a homemade metal detector with your own hands

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

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

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

The simplest do-it-yourself metal detector

The metal detector circuit is not complicated, and you can find it either in the vastness of the global network, or in specialized literature. Above is a list of radio elements that are useful for assembling a metal detector with your own hands at home. A simple metal detector can be assembled with your own hands using a soldering iron or another available method. The main thing at the same time, the parts should not touch the body of the device. To ensure the operation of the assembled metal detector, power supplies of 9-12 volts are used.

To wind the coil, a wire with a cross-sectional diameter of 0.3 mm is used, of course, this will depend on the selected circuit. By the way, the wound coil must be protected from the effects of extraneous radiation. To do this, it is screened with your own hands using ordinary food foil.

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

Metal detector without chips

If a novice "treasure hunter" has no desire to get involved with microcircuits, there are schemes without them.

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

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

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

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

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

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

After the board is etched, holes must be made in it to install the circuit components. After the board has been tinned. The most important step is coming. Do-it-yourself installation and soldering of parts on a prepared board.

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

A little about smartphones

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

But in fact, after installing such an application, he will really be able to find metal objects, but only pre-magnetized ones. He will not be able to search and, moreover, discriminate against metals.