Schemes and printing boards of metal detector. How do it yourself make a metal detector - cost-effective and proven schemes
Many radio amateurs dream of making a metal detector with their own hands. With it, you can detect metal items in the ground at different depths. On the Internet you can find many photos of the metal detector schemes that are simple in the device. Make them can any novice radio amateur.
Simple assembly
For example, take a simple metal detector scheme. It belongs to the impulse type, but due to the simplicity of the design, it is not capable of distinguishing the varieties of metals. Therefore, it will not be possible to work in such a device in the territories where it is found from non-ferrous metal.
How to collect the device
To assemble the scheme of a simple metal detector, the following tools and details will be needed:
- The presence of the KR1006Vi1 chip, and the IRF740 transistor;
- The presence of the K157UD2 chip and transistor SP547;
- Copper conductor 0.5mm (PEV);
- NPN transistor;
- Case, and various materials for it;
- Solder, flux, soldering iron.
Other details are displayed in the diagram. In order for the collected scheme to be securely secured, a plastic case should be prepared for it.
The rod can be done with a plastic tube of a small diameter. In its lower part there will be a coil to search for metal.
Beginning of work
The diagram of the metal detector device on the transistors is a common option of many models. The assembly begins with the manufacture of a printed circuit board. Next, all the radio elements are mounted exactly as shown in the diagram.
To ensure that the device is stable, film capacitors are used in the diagram. This will allow you to use it in cold weather without any problems.
Power Type for Device
The device can work from a voltage of 9-12 V. due to its sufficient power, energy is intensively consumed. It is recommended to install up to 3 batteries, and connect them into a parallel chain. You can use a small battery that has charger. Thanks to its container, the metal detector will work longer.
Installation of coil
There are different types and schemes for the manufacture of metal detectors, but in a pulsed version in the installation of the coil is allowed inaccuracies. When making a mandrel, you should make a winding up to 25 turns, and the diameter of the ring is 1900-200mm.
All coil turns must be insulated with a tape. Reducing the number of turns to 22, and the diameter of the mandrel 270mm will allow detecting objects on a deeper occurrence. The wire section on the coil is used 0.5 mm.
When the winding is ready, it is fixed on a durable case with sufficient rigidity, which should not be metallic parts. Otherwise, they are able to shield the magnetic field, and the work of the metal detector will be broken. The case can be made wooden or plastic, but so that it can withstand various blows that can damage the coil.
The conclusions on it should be soldered to the conductor from several lived. The optimal option is considered a two-housing wire.
Installation of metal detector of non-ferrous metals is a bit more complicated, and in the manufacture of the coil, it is necessary to observe high accuracy. The number of turns reaches 100pcs, and the vinyl tube is used as the core. From above over the winding, a foil is wound, which forms an electrostatic screen.
Setting the device
If the installation of the scheme is performed exactly, the metal detector will not need additional configuration. Its sensitivity indicators will be maximal, but it is possible to finely adjust the variable resistance R13. It must be performed until rare clicks begin in the headphones.
If the setting fails, the resistance must be replaced with R12. When adjusting the resistor will be in the middle, it will be considered the norm.
Oscilloscope is suitable for checking the device. It bothers the frequency of the transistor T2, and the pulse must last up to 150 Moscow time. The optimal frequency of operation is up to 150 Hz.
How to use the device
Do not hurry and start working immediately after turning on the metal detector. It must stabilize, so you need to wait until 20 seconds. After appropriate adjustment of the resistor, you can start looking for a metal.
Note! 
Photo of a metal detector scheme
Note! 
Note! 
The article presents a simple scheme, but a powerful metal detector for 1.5 volts, very simple in repetition. Generators are assembled according to a scheme that has useful propertiesOne of which is the stability of the output voltage (both constant and alternating) when the supply voltage changes. In the vibrational circuit of the search generator on the VT1 transistor enters the L1 coil. It operates at a frequency of about 100 kHz, which is optimal for this type of metal detectors. Its frequency in small limits can be changed by a variable capacitor C2. The second generator (on the VT2 transistor) is exemplary and operates at about 300 kHz.
Generator signals Through resistors R2, R4 are fed to a balanced mixer, where the frequency difference (beats) is selected for the third harmonic of the search generator signal and the first harmonic of the exemplary. This is done to increase sensitivity - when changing the frequency of the search generator at a frequency of 10 hertz, the frequency of the beats varies to 30 hertz, which is more noticeable for rumor.
The signal from the exit of the mixer through the C8 condenser enters the input of the UZB and after the amplification - on the BF1, BF2 headphones. Capacitor C7 suppresses signals with generator frequencies.
When the search generator coil approaches the generation frequency of the generator is changed, so the tone of the signal in the headphones will change. By the nature of the change in tone can be judged by the material from which this subject is made.
Most parts are mounted on a printed circuit board from one-sided foil fiberglass.
You can apply the transistors of the KT312 series, KT315, CT3102 with any letter indexes. Only Germany transistors of the GT309 series, GT313, GT322, GT346 or earlier - P416, P422, P423 with any letter indexes can be used in the balance mixer. In UZMCH, the transistor must be with a large current transmission coefficient, for example, CT3102BM - KT3102EM, CT342BM, CT342BM - from this depends on the volume of the beep. Power switch - any small. Headphones are suitable with resistance from 8 to 32 ohms, they are connected consistently. To connect them on the metal detector case, you can install the socket. The device is powered from an electroplating element or battery size AA or AAA, the maximum current consumed is about 12 mA.
For winding the coil L2, a framework from the circuit of the PC (455 kHz) receiver of foreign production is applied. It consists of ferrite "dumbbells" (on which 66 turns of the wire PEV-2 with a diameter of 0.06 ... 0.1 mm) and the ferric cup covering it, the movement of the coil is adjusted. The frame is enclosed in a metal screen.
The sensitivity of the device to metal objects of different sizes depends on the size of the search coil itself. To search for large-sized items (metal sheet with dimensions of 80x80 cm, the hatch cover of the sewage) is more suitable for a coil with a diameter of about 30 cm. It is achieved with it maximum depth Detection of such objects up to 60 cm.
To search for small items, a coil with a diameter of about 120 mm is better. Such a coil contains 56 turns of the wire of the PAL with a diameter of 0.2 ... 0.5 mm.
The coil of an even greater diameter (for example, 300 mm) is more technologically made from a multi-core shielded "twisted pair" cable, which is used for laying computer local networks. The cable must contain four "pairs", and the coil is four turns of such a cable. First, two outer turns are wound and fasten them in four places insulating tape. Then wound two internal and all are also wrapped with an insulating tape, preferably on a plaid-based basis. The ends of the cable are cut with such a calculation so that there is a "nasty" 5 mm ... 10 mm, and with 15 mm, they remove the outer insulation, and the ends of the wires are cleaned with 5 mm and linger.
All radio components of the device are domestic and have overseas counterparts:
L1 - coil
R1 - 1 com
R2 - 10 com
R3 - 1 com
R4 - 10 com
R5 - 1 com
R6 - 1 com
R7 - 100 com
C1 - 2200.
C2 - 10 ... 240
C3 - 4700.
C4 - 0.047 μF
C5 - 2200.
C6 - 4700.
C7 - 0.047 μF
C8 - 2.2 μF x 16 volts
VT1 - KT315B.
VT2 - KT315B.
VT3 - GT322B
VT4 - GT322B.
Best Metal Detector
Why was Volksturm called the best metal detector? The main thing is the scheme really simple and really working. From a variety of metal detectors schemes that I personally did, it is here that everything is simple, deep and reliably! Moreover, with its simplicity, in the metal detector there is a good discrimination scheme - the definition of iron or non-ferrous metal is in the ground. The assembly of the metal detector consists in an error-free solder of the board and setting the coils into the resonance and at zero at the output of the input stage on the LF353. There is nothing superser, there would be a desire and brains. We look constructive metal detector execution and a new enhanced Volksturm scheme with a description.
Since, in the course of the assembly, questions arise to save your time and not to force the hundreds of pages of the forum, here are answers to the 10 most popular questions. The article in the process of writing, so some items will be supplemented later.
1. Principle of operation and detecting the goals of this metal detector?
2. How to check whether a metal detector work works?
3. What resonance to choose?
4. What condensers are better?
5. How to set up resonance?
6. How to cut coils in zero?
7. What wire for coils is better?
8. What are the details and what can be replaced?
9. What is the depth of the search for goals?
10. Nutrition of the Volksturm Metal Detector?
The principle of operation of the Volksturm Metal Detector
I will try in two words 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 a metal changes the inductive link between them (including phase), which affects the received signal, which is then processed by the indication unit. Between the first and second chip, the switch controlled by the generator shifted by phase relative to the transmitting channel (i.e., when the transmitter works, the receiver is turned off and on the contrary if the receiver is turned on the transmitter rests, and the receiver calmly catches the reflected signal in this pause). So, you turned on the metal detector and it beeps. Excellent, if stamps - it means many nodes work. Let's figure out why it is stamping. The U6B generator constantly generates a tone. Next, it enters the amplifier on two transistors, but the UHH will not open (will not miss the tone) until the voltage at the y2B (7th output) will not allow it. This voltage is set by changing the mode using this very resistor TRACH. They need to set such tension so that the UHR almost opened and missed the signal from the generator. And the input pair of Milvololt from the metal detector coil, passing the amplifying cascades, will exceed this threshold and it will open completely and the speaker will be discovered. Now let's follow the passage of the signal, or rather the response signal. At the first cascade (1-U1A) there will be a pair of Milcivolt, you can up to 50. On the second cascade (7-U1B), this deviation will increase, on the third (1-U2) will already be a couple of volts. But without a response everywhere at the outputs at zeros.
How to check whether the board is working
In general, the amplifier and key (CD 4066) is checked with a finger at the RX input contact with the maximum Sens resistance and the maximum background on the dynamics. If the change in the background is when pressing a finger for a second, the key and the operating rooms work, then connect the RX coils with the circuit condenser in parallel, the condenser on the TX coil sequentially, we give one coil to another and begin to reduce in 0 by the minimum AC indication on the first leg of the amplifier U1A. Next, we take something big and iron and check there is a reaction to metal in the dynamics or not. We will check the voltage on the U2B (7th output) it should be a trash regulator, change + volt. If not, the problem is in this Cascade of OU. To start checking the board, turn off the coil and turn on the power.
1. Must go sound when the sensor regulator is positioned on the maximum resistance, totto the finger on the Px - if there is a reaction, all the operatingors work, if not, we check the finger starting with U2 and change (survey the strapping) of non-working OU.
2. The generator operation is verified by the frequency meter program. Plug from headphones soldered to 12 withdrawal CD4013 (561TM2) prudently dropping P23 (so that the sound card does not burn). In the sound card to use in-lane. We look at the generation frequency, its stability is 8192 Hz. If it is strongly shifted, then the C9 capacitor should be harvested, if after it is not clearly highlighted and / or a lot of frequency bursts nearby - replace quartz.
3. Checked amplifiers and generator. If everything is fine, but still does not work - change the key (CD 4066).
What resonance to choose
When connecting the coil into a serial resonance, the current in the coil and the overall consumption of the circuit increases. Increases the distance detection distance, but it is only on the table. On the real soil, the earth will feel the stronger than the larger the pumping current in the coil. It is better to turn on parallel resonance, and raise the input cascades. Yes, and the batteries are enough much longer. Despite the fact that consistent resonance is used in all branded expensive metal plates, in the storm you need it precisely parallel. In imported, expensive devices, good configuration schematics from the ground, therefore, in these devices can be allowed to be allowed.
What condensers are better to install in the scheme metal detector
The type of capacitor connected to the coil is not when, and if it was experimentally changed two and saw that with one of them the resonance is better, then it is simply one of the supposedly 0.1 μF really has 0.098 Igf, and the other 0.11. So the difference between them in resonance is obtained. I used Soviet K73-17 and green imported pillows.
How to set up resonance coils metal detector
Coil like the most the best wayIt turns out of plastering grads glued with epoxy resin 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, the fork of two bunches of fastening. This solution allows you to solve the problem of deformation of the coil, when tightening a plastic bolt. The windings for the windings make the usual delicate, then setting the zero and fill. From the cold end TX, we will leave 50 cm. Wires, which originally not to fill, and press the small coil from it (with a diameter of 3 cm) and place it inside the RX, moving and deforming it in small limits, you can achieve an accurate zero, but to do it It is better on the street by placing the coil at the Earth (as when searching) with the geb disconnected if it is, then finally pour the resin. Then the detuning from the Earth, it works more, less tolerable (the exception is strongly mineralized soil). Such a coil is obtained easy, durable, little prone to thermodood, and treated and painted very pretty. And one more observation: if the metal detector is assembled with downtown (GEB) and under the central location of the resistor's engine to set zero a very small washer, the geba adjustment range is 80-100 mV. If you set the zero large subject of a coin 10-50 kopeck. The adjustment range increases to + - 500-600 mV. For voltage in the process of adjusting the resonance, do not chase - I have about 40V with a 12V power with a consistent resonance. To discriminate, condensers in the coils turn on in parallel (the sequential inclusion is only needed at the selection stage for resonance) - on ferrous metals there will be a long sound, color - short.
Or even easier. We connect the coils in turn to the transmitting TX output. We configure one in the resonance, and configuring it - another. Step by step: they connected, parallel the coil was twisted by a multimeter at the limit variables, the condenser 0.07-0.08 ICF soldered the coil parallel to the coil, see the testimony. Suppose 4 V is very weak, not in resonance with a frequency. Pressed parallel to the first condenser of the second small capacity - 0.01 μF (0.07 + 0.01 \u003d 0.08). We look - already showed a voltmeter 7 V. Excellent, we will increase the container, connect to 0.02 μF - we look at the voltmeter, and there are 20 V. Great, we are going on - another dock is a couple of thousand peaks of tanks. Yeah. Already the beginning fall, roll up back. And so to achieve maximum voltmeter readings on a metal detector coil. Then, similarly on the other (reception) coil. Configure maximum and connect back to the receiving socket.
How to reduce metal dealer coils in zero
To adjust zero, we connect the tester to the first leg LF353 and we begin to compress, stretch the coil. After the epoxy bay - Nolik will definitely run away. Therefore, it is necessary to pour not the whole coil, but leave space for adjustment, and after drying, bring to zero and pour finally. Take a piece of twine and half the coil to tie in one turn to the middle (to the central part, the place of connecting two coils) insert a piece of a piece of sticks after which it is twisted (pulling the twine) - the coil will shrink, catching the spike sponge to be impregnated with glue, after almost complete drying Again, to adjust the nolik by turning the wand more slightly and pour the twine finally. Or easier: the transmitted is fixed in plastic stationary, and the reception is superimposed on the first 1 cm, such as wedding rings. At the first pin, U1a will be a peak of 8 kHz - can be controlled by a voltmeter of alternating current, but better just high-level headphones. So the receiving coil of the metal detection must be shifted, then shifted with transmitting until the output of the OU does not appeal to a minimum (or the testimony of the voltmeter will not fall to several milcialt). Everything, the coil is reduced, fix.
Which wire for search coils is better
Wire for winding coils does not matter. From 0.3 to 0.8 there will be any, it will still have to pick up the capacitance to adjust the contours to the resonance and the frequency of 8.192 kHz. Of course, a thinner wire is quite suitable, just what it is thicker, the kindness and, as a result of a little - better. But if you wind 1 mm - it will be quite hard to carry. On a sheet of paper, we draw a rectangle 15 to 23 cm. From the left upper and lower angle, we deposit 2.5 cm, and connect their line. We also do the same with the right top and bottom corners, but we post 3 cm. In the middle of the bottom we put the point and on the point left and right at a distance of 1 cm. We take Phaneur, we put this sketch and drive the carnations to all points specified. We take the wire of the PEV 0.3 and wind 80 turns of the wire. But honestly, no difference how many turns. All the same, the frequency of 8 kHz will be exhibited in a condenser resonance. How many wounds - so much wound. I wind 80 turns and a condenser 0.1 of the ICF, if you wog up 50 - the container, respectively, somewhere 0.13 μF will have to have. Next, without removing from the template, wind the coil is thick thread - such as wiring harnesses. After covering the coil with varnish. When dried, remove the coil from the template. Then there is a winding of the coil with insulation - FUM tape or tape. Next is the winding of the foil coil of the coil, you can take a ribbon from electrolytic capacitors. TX The coil can not be shielded. Do not forget to leave the gap in the screen 10 mm, in the middle of the coil. The foil winding is on the tinned wire. This wire, along with the initial contact of the coil, we will have a mass. And finally winding the coil with a tape. The inductance of coils is about 3.5 mg. Capacity is about 0.1μF. As for the fill of the coil epoxy, I did not stick it at all. Just tightly climbed the tape. And nothing, two seasons went away with this metal detector without setting. Pay attention to the moisture insulation of the circuit and search coils, because you will have to mock the grass. Everything should be hermetically - otherwise the moisture will fall and the setting will float. Worsen sensitivity.
What details and what can be replaced
Transistors:
BC546 - 3pcs or kt315.
BC556 - 1pc or kt361
Operations:
LF353 - 1pcs or change to a more common TL072.
LM358N - 2pcs
Digital microcircuits:
CD4011 - 1pc
CD4066 - 1pc
CD4013 - 1pc
Resistors permanent, 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 \u200b\u200b- 1pc
Resistors variables:
100K - 1pc
330K - 1pc
Capacitors are notolar:
1NF - 1pc
22nf - 3pcs (22000pf \u003d 22nf \u003d 0.02222222222
220NF - 1pc
1MKF - 2pcs
47NF - 1pc
10nf - 1pc
Electrolytic condensers:
220MKF on 16V - 2pcs
The dynamic miniature.
Quartz resonator on 32768 Hz.
Two supermarket LEDs of different color.
If you can not get imported chips, here are the domestic analogues: CD 4066 - K561T3, CD4013 - 561TM2, CD4011 - 561L7, LM358N - kr1040ud1. The LF353 chip is there is no direct analogue, but boldly put LM358N or better TL072, TL062. It is not necessary to put the operational amplifier precisely - LF353, I simply raised the reinforcement on the U1A replacing the resistor in the negative feedback circuit of 390 kΩ per 1 mΩ - sensitivity increased significantly by percentage of 50, though after this replacement gave zero, I had to glue the coil in a certain place Scotch tape slice of aluminum plate. Soviet three kopecks feels over the air at a distance of 25 centimeters and this is 6 volts when nutrition, the current consumed without indication is 10 mA. And do not forget about the panels - convenience and simplicity settings will increase significantly. CT814 transistors, KT815 - to the transmitting part of the metal detector, CT315 in UH. Transistors - 816 and 817 It is desirable to choose with the same gain coefficient. Replace on any appropriate structure and power. In the metal detector generator, a special hour quartz is installed at a frequency of 32768 Hz. This standard is absolutely for all quartz resonators, which are in any electronic and electromechanical clock. Including wrist and cheap Chinese wall / desktops. Archives with a printed circuit board for the option and for (option with manual detuning from the Earth).
What depends the depth of the search for goals
The greater the diameter of the metal dealer coil, the more deeply. In general, the depth of detection of the target with this 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 the detection of the object and even sometimes loss of small goals. For objects with a coin, this effect is observed with an increase in the coil size over 40 cm. Total: a large search coil, has a greater depth of detection and greater capture, but less accurately detects the target than the small one. The big coil is ideal for finding deep and large goals, such as treasures and large objects.
The coil shape is divided into round and elliptic (rectangular). The elliptical coil of the metal detector has the best selectivity compared to the round, because it is less than the width of the magnetic field and there are less extraneous objects in its field. But the round has a greater depth of detection and better sensitivity to the goal. Especially on weakly mineralized soils. The round coil is most often used when searching with a metal detector.
The coils with a diameter of less than 15 cm are called small, the coil with a diameter of 15-30 cm is called medium and coils over 30 cm - large. The big coil generates a greater electromagnetic field, so it has a large detection depth than small. Big coils generate a large electromagnetic field and, accordingly, have a greater depth of detection and coating when searching. Such coils are used to view large areas, but when using them, there may be a problem on highly messenger sites because in the field of the action of large coils can be caught several goals and the metal detector will react to a larger goal.
The electromagnetic field of a small search coil is also small, so with such a coil is best to search in the territories highly lit for all sorts of small metal objects. The small coil is ideal for detecting small objects, but has a small area of \u200b\u200bcoating and a relatively small detection depth.
For universal search, medium coils will fit well. This search coil size combines a sufficient depth of search and sensitivity to goals with different sizes. I made every coil with a diameter of about 16 cm and both of these coils laid in a round stand from under the old monitor 15. "In this embodiment, the depth of this metal detector will be the following: aluminum plate 50x70 mm - 60 cm, nut M5-5 cm, coin - 30 cm, bucket - near the meter. These values \u200b\u200bare obtained in air, in the ground will be 30% less.
Metal detector power
Separately, the metal detector scheme pulls 15-20 mA, with a connected coil + 30-40 mA, and there is up to 60 mA. Of course, depending on the type of dynamics used and LEDs, this value may vary. The simplest case - the power took 3 (or even two) consistently connected lithium ion batteries from Mobile by 3.7V and during charge of discharged batteries, when you connect any power supply to 12-13V, the charge current starts from 0.8A and drops to 50m An hour and then do not need to add something at all, although the restrictive resistor of course does not prevent. As general, the most simplest option - Krona on 9V. But note that the metal detector will eat it in 2 hours. But to configure this power option. Crown under any circumstances will not give 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 have only a multimeter from the devices, I downloaded the virtual laboratory of records OL. Assemmed the adapter, a simple generator and drove into a single oscilloscope. It seems like some picture. Next, I started searching for radio components. Since the sizes are mostly laid out in the "Lay" format, Sprint-layout50 downloaded. I found out that such a laser and ironing technology of manufacturing printed circuit boards and how to train them. Put the board. By this time, all microcircuits were found. What I did not find in my shed, I had to buy. I began to solder jumpers, resistors, microcircuit sockets, and quartz from the Chinese alarm clock on the fee. Periodically checking the resistance on the power tires so that no snotes were. I decided to start collecting the digital part of the device as the easiest. That is a generator, divider and switch. Collected. Put the generator chip (K561L7) and the divider (K561TM2). B / ear microcircuits, out of some boards discovered in the shed. Submitted power 12V controlling current consumption by amermeter, 561TM2 became warm. Replaced 561TM2, filed food - zero emotions. We measure the voltage on the legs of the generator - on 1 and 2 legs of 12V. I change 561l7. I turn on - at the exit of the divider, there are generation on 13 legs (I observe on a virtual oscilloscope)! The truth is not so good, but for the absence of a normal oscilloscope - will go. But on 1, 2 and 12 legs there is nothing. So the generator works, you need to change TM2. Installed the third chip of the divider - beauty at all outputs is generation! For myself, I concluded that the chips need to be filled as careful! This is the first step of the building made.
Now configure the metal detector's fee. The "SENS" regulator did not work - sensitivity, I had to throw out the C3 capacitor after that the sensitivity adjustment earned as it should. I didn't like the sound that occurs in the extreme left position of the "Thresh" regulator - threshold, got rid of this replacing the resistor R9 with a chain of a successively connected resistor by 5.6 kΩ + condenser by 47.0 μF (negative condenser withdrawal from the transistor). While there is no LF353 chip instead of her LM358, the Soviet three kopecks feels with it at a distance of 15 centimeters.
I turned on the search coil on the transmission as a sequential oscillating circuit, and on the reception as a parallel oscillating circuit. Called the first transmitting coil, connected the collected design of the sensor to the metal detector, the oscilloscope parallel to the coil and at the maximum amplitude, the capacitors picked up. After that, the oscilloscope connected to the receiving coil to the receiving coil and at the maximum amplitude, the condensers were picked up on RX. The adjustment of the contours in the resonance takes, in the presence of an oscilloscope, a few minutes. TX and RX windings in me contain 100 turns of the wire with a diameter of 0.4. We start mixing on the table, without a case. Just so that there were two wrap with wires. And to make sure that work and the possibility of information is generally - the collapse of the coil from the DRA half the meter. Then zero will be accurate. Then impoverish the coil of the flask about 1cm (as wedding rings) shift - to move away. The zero point can be quite accurate and catch it immediately difficult. But it is.
When, I raised the reinforcement in the RX path of MD, he began to work unstable on the maximum sensitivity, this was manifested that after passing over the goal and its detection was given a signal, but it continued and after the goals before the search coil did not have any manifested in the form of intermittent and oscillating sound signals. With the help of an oscilloscope, the reason for this was found: during the operation of the dynamics and a minor feeding drawdown of the supply voltage, "zero" and the MD scheme goes into an auto-oscillating mode, to exit from which you can only download the triggering threshold. It did not suit me therefore I put it on the food of KR142EN5A + over the bright white LED to raise the voltage at the output of the integral stabilizer, the stabilizer to a higher voltage was not in me. Such an LED can be used even to illuminate the search coil. The speaker connected to the stabilizer, MD after that it became immediately very obedient all began to work as it should. I think the Volksturm is really the best homemade metal detector!
Recently, this scheme has been proposed, which will allow us to turn Volksturm S in Volksturm SS + GEB. Now the device will have a good discriminator as well as the selectivity of metals and tuning from the soil, the device rolls on a separate board and is connected instead of C5 and C4 capacitors. The scheme of refinement and in the archive. Separate thanks for information on the assembly and configuration of the metal detector to everyone who participated in the discussion and modernization of the scheme, especially helped in the preparation of the material of the electrocity, festka, XXX, SLAVAKE, EW2BW, REDKII and other radio amateurs colleagues.
What is the metal detector to explain to anyone. The device is dear, and some models are quite decent.
However, you can make the metal detector with your own hands at home. Moreover, you can not only save thousands of rubles on its acquisition, but also to get rich, finding a treasure. Let's talk about the appliance itself and try to figure out what in it and how.
Step-by-step instruction for assembling a simple metal detector
In this detailed instructions We will show how you can collect with your own hands the simplest metal detector from the remedies. We will need: a plain plastic box from a CD disc, portable AM \u200b\u200bor AM / FM radio, calculator, VelCro contact tape (velcro). So, proceed!
Step 1. Disassemble CD CD Box CD. Carefully disassemble the compact disc plastic box, remove the insert that holds the disk on the spot.
Step 1. Removal of plastic insert from SidiboxStep 2. Cut 2 velcro strips. Squeeze the area in the center of the rear of your radio. Then cut 2 pieces of velcro of the same size.
Step 2.1. Memore approximately in the middle area on the back of the radio (highlighted in red) 
Step 2.2. Cut 2 velcro of the corresponding size measured in step 2.1 Step 3. Secure the radio. Attach one velcro on the back of the radio and second to one of the inner sides of the CD box. Then attach the radio on the body of the plastic box of the CD "Velcro to Velcro".
Step 4. Secure the calculator. Repeat steps 2 and 3 with a calculator, but apply the velcro on the other side of the CD box. Then secure the calculator on this side of the box with the standard Velcro method.
Step 5. Setting Radio Range. Turn on the radio and make sure it is configured to AM Range. Now adjust it to the end of the AM range, but not to the radio station itself. Increase the volume. You must only hear some interference.
Prompt:
If there is a radio station, which is at the very end of the AM range, then try to get to it as close as possible. At the same time, you should hear only some interference!
Step 6. Roll the CD box. Turn on the calculator. Start turning the side of the box with the calculator towards the radio until you hear a loud beep. This beep signals us that the radio caught the electromagnetic wave from electrical circuit Calculator.
Step 6. We are folding the parties CD boxing to each other until the characteristic loud signal is heard. Step 7. Apply the collected device to a metal object. Open the flaps of the plastic box again, so that the sound we heard in step 6 is barely heard. Then start moving the box with your radio and the calculator close to the metal object and you again hear a loud sound. This indicates the correct work of our simplest metal detector.
Instructions for assembling a sensitive metal detector based on a two-circuit oscillator scheme
Operating principle:
In this project, we will build a metal detector based on the dual circuit of the oscillator. One oscillator is fixed, and the other varies depending on the proximity of metal objects. The frequency of the beats between these two frequencies of oscillators is in the sound range. At the time of the detector over the metal object, you will hear a change in this frequency of the beats. Different types of metals will cause a positive or negative shift, lifting or lowering the sound frequency.
We will need materials and electrical components:
| Copper multi-layer printed circuit board, one-sided 114.3 mm x 155.6 mm | 1 PC. |
| Resistor 0.125 W. | 1 PC. |
| Condenser, 0.1μF. | 5 pieces. |
| Condenser, 0.01μF. | 5 pieces. |
| Condenser, electrolytic 220μF | 2 pcs. |
| Winding PAL type wire (26 AWG or 0.4 mm in diameter) | 1 unit. |
| Audio connector, 1/8 ', mono, mounting on the panel, optional | 1 PC. |
| Headphones, 1/8 'plug, mono or stereo | 1 PC. |
| Battery, 9 in | 1 PC. |
| Binding connector 9 in battery | 1 PC. |
| Potentiometer, 5 com, audio taper, optional | 1 PC. |
| Switch, single-pole switch | 1 PC. |
| Transistor, NPN, 2N3904 | 6 pcs. |
| Wire for connecting the sensor (22 AWG or cross section - 0.3250 mm 2) | 1 unit. |
| Speaker wired 4 ' | 1 PC. |
| Speaker, small 8 ohm | 1 PC. |
| Locking, brass, 1/2 ' | 1 PC. |
| Threaded PVC Trumpet Connector (1/2 'Hole) | 1 PC. |
| 1/4 'Wooden Dowel | 1 PC. |
| 3/4 'Wooden Dowel | 1 PC. |
| 1/2 'wooden dowel | 1 PC. |
| Epoxy resin. | 1 PC. |
| 1/4 'plywood | 1 PC. |
| Carbon black | 1 PC. |
We will need tools:
So, proceed!
Step 1: Make a printed board. To do this, download the design of the board. Then print it and protect it on the copper board using the toner translation method on the fee. Using the toner transmission method, you print the mirror image of the board design using a conventional laser printer, and then transfer the pattern on the copper lining with the iron. At the etching stage, toner acts as a mask, keeping the copper tracks, at that time as the rest copper dissolves B. chemical bath.
Step 2: Fill the fee with transistors and electrolytic capacitors . Start with soldering 6 NPN transistors. Pay attention to the orientation of the legs of the collector, the emitter and the transistor base. Basic leg (B) is almost always in the middle. Next, add two 220μF electrolytic capacitor.
Step 2.2. Add 2 electrolytic capacitor Step 3: Fill the board with polyester capacitors and resistors. Now you need to add 5 polyester capacitors with a capacity of 0.1μF in places shown below. Next, add 5 capacitors with a capacity of 0.01μF. These capacitors are not polarized and they can be soldered in feet feet in any direction. Next, add 6 resistors for 10 kΩ (brown, black, orange, golden).
Step 3.2. Add 5 capacitors with a capacity of 0.01μF 
Step 3.3. Add 6 resistors 10 com Step 4: We continue to fill the electrical fee elements. Now you need to add one resistor 2.2 MΩ (red, red, green, golden) and two 39 com (orange, white, orange, golden). And then hit the last resistor of 1 com (brown, black, red, gold). Next, add wiring pairs to power (red / black), output audio (green / green), reference coil (black / black) and detector-coil (yellow / yellow).
Step 4.1. Add 3 resistors (one on 2 mΩ and two to 39 com) 
Step 4.2. Add 1 resistor for 1 com (extreme right) 
Step 4.3. Add wires Step 5: Wash the coil to the coil. The next step is the winding of turns on 2 coils, which are part of the LC generator lc. The first is a reference coil. I used a 0.4 mm wire in diameter for this. Cut a piece of dowel (about 13 mm in diameter and 50 mm in length).
Drill three holes in a dowel to pass through them with wiring: one longitudinally through the middle of the dubel, and two perpendicular at each end.
Slowly and carefully wore so many turns of the wire as you can around a dowel in one layer. Leave 3-4 mm naked wood every end. Hold down from the temptation to "twist" the wire is the most intuitive way of winding, but this is the wrong way. You must rotate the dowel and pull the wire. So he wrapped the wire.
Through each end of the wire through perpendicular holes in the dowel, and then one of them through the longitudinal hole. Secure the wire ribbon as soon as you finish. At the end, use sandpaper to remove the coating on two open coil ends.
Step 6: We make a reception (search) coil. It is necessary to cut the coil holder with 6-7 mm plywood. Using the same wire of 0.4 mm in diameter, wind 10 turns around the groove. My coil has a diameter of 152 mm. Using a wooden peg of 6-7 mm attach the handle to the holder. Do not use a metal bolt for this (or something similar) - otherwise the metal detector will constantly detect you a treasure. Again, using the sandpaper, remove the coating at the ends of the wire.
Step 6.1. Cut the coil holder 
Step 6.2 Wash 10 turns around the groove with a wire of 0.4 mm in diameter 
Step 7: Setting the reference coil. Now we need to adjust the frequency of the support coil in our chain up to 100 kHz. For this I used the oscilloscope. You can also use a multimeter with a frequency meter for these purposes. Start with connecting the coil into the chain. Next, turn on the power. Connect the shut from the oscilloscope or the multimeter to both ends of the coil and measure its frequency. It should be less than 100 kHz. You can, if necessary, shorten the coil - this will reduce its inductance and increase the frequency. Then new and new dimensions. As soon as I achieved a frequency of less than 100 kHz, my coil was 31 mm in length.
Metal detector on a transformer with W-shaped plates
SAMI simple scheme Metal detector. We will need: a transformer with W-shaped plates, a 4.5 V battery, a resistor, a transistor, a condenser, headphones. In the transformer, leave only W-shaped plates. Mix 1000 turns of the first winding, and after the first 500 turns, make a removal of PAL-0.1 wire. Wash the second winding 200 turns with a wire PEL-0.2.
Secure the transformer at the end of the bar. Seat it from water from entering water. Turn on and close to the ground. Since the magnetic circuit is not closed, then the parameters of our scheme will change when approaching the metal, and the signals are changed in the headphones.
Easy diagram on common elements. You need to transistors of the K315B or K3102 series, resistors, capacitors, headphones, power item. Ratings are shown in the diagram.
Video: how to make a metal detector (metal detector) with your own hands
The first transistor is assembled by a setting generator with a frequency of 100 Hz, and a search generator with the same frequency is assembled. As a search coil, an old plastic bucket took a diameter of 250 mm, cut it and wrapped the copper wire with a cross section of 0.4 mm2 with a number of 50 turns. The assembled scheme was placed in a small box, sleevered and everything secured on the rod with a tape.
Scheme with two generators of the same frequency. There is no signal in standby mode. If a metal object appears in the coil field, the frequency of one of the generators changes and the sound appears in the headphones. The device is quite universal and has good sensitivity.
Easy scheme on simple elements. Chip, condensers, resistors, headphones, power supply. It is advisable to first collect the L2 coil, as shown in the photo:
On one element of the chip, the default generator with the coil L1 is collected, and the L2 coil is used in the search generator circuit. If the sensitivity zone of metallic items changes the frequency of the search circuit and the sound in headphones changes. The C6 capacitor handle can rebuild extra noises. The battery is used as a battery with voltage 9V.
In conclusion, I can say that every person familiar with the basics of electrical engineering can collect the device and possessing enough patience to bring the work started to the end.
Principle of operation
So, the metal detector is an electronic device where there is a primary sensor and a secondary device. The role of the primary sensor performs, as a rule, a coil with a wound wire. The work of the metal detector is based on the principle of changing the electromagnetic field of the sensor by any metal object.
The electromagnetic field created by the metal detector sensor causes vortex currents in such subjects. These currents cause their electromagnetic field that changes the field created by our instrument. The secondary device of the metal detector registers these signals and signals us about the finding of a metal object.
The simplest metal detectors change the sound of the alarm when the desired item is detected. More modern and expensive samples are equipped with a microprocessor and a liquid crystal display. The most advanced firms equip their models with two sensors, which allows you to search more efficiently.
Metal detectors can be consecrated to several categories:
- general use devices;
- middle class devices;
- devices for professionals.
The first category includes the cheapest models with a minimum set of functions, but they have the price very attractive. The most popular brands in Russia: Imperial - 500A, Fisher 1212-X, Classic I SL. The instruments of this segment use the "receiver - transmitter" scheme operating on the ultra-low frequency and require constant movement of the search sensor.
The second category is more expensive aggregates, have several replaceable sensors and several handles of controls. Can work in different modes. The most common models are: Fisher 1225-X, Fisher 1235-X, Golden Saber II, Classic III SL.
Photo: general form Typical metal detector All other devices should be attributed to professional. They are equipped with a microprocessor, can work in dynamic and static modes. It is possible to determine the composition of the metal (subject) and the depth of its location. Settings can be automatic, and you can adjust them manually.
To build a self-made metal detector, you need to prepare a few items in advance: the sensor (coil with wrapped wire), a rod holder, the electronic unit Control. The sensitivity of our device depends on its quality and sizes. The rod holder is selected by the growth of man so that it is convenient to work. All structural elements are fixed on it.
If you have a long-wave transistor receiver in a good condition, you can easily assemble a simple console to it - a metal detector. The metal detector circuit is an ordinary LC generator, at a frequency of about 140 kHz. The coil of the oscillatory circuit L1 12 cm in diameter, contains 16 turns of the wire (any insulated mounting or lacquered winding, with a diameter of 0.25 - 0.5 mm). The coils are stacked on a pad from plywood suitable size and fixed, for example, with the help of glue - "cold welding" or "liquid nails".
Resistors and capacitor - any type, transistor low-power high-frequency, reverse conductivity.
Suitable - CT315, CT3102 with any letter. The scheme is collected on a hatinax or textolite board, the printed installation is not required, the details connections can be made by any, isolated mounting wire.
After assembly, the scheme, together with the power source, is located next to the coil on the site of plywood, with a wooden handle of a convenient length. The receiver is attached to the handle and adjusts to the frequency of reception close to 140 kHz, until the sound occurs like a creak. When the coil approaches the coil to any metal object, its tonality will change.
Despite the simplicity of the scheme, in its sensitivity, such a metal detector is practically not inferior to industrial samples.
With it, such metal objects such as a gold ring or coin can be detected at a depth of 20 cm.
