Metal detector circuit
Today I would like to present to your attention a diagram of a metal detector, and everything related to it, what you see in the photograph. After all, it is sometimes so difficult to find the answer to a question in a search engine - Diagram of a good metal detector
In other words, the metal detector has a name Tesoro Eldorado
The metal detector can operate in both the search mode for all metals and background discrimination.
Technical characteristics of the metal detector.
Operating principle: induction balanced
-Operating frequency, kHz 8-10kHz
-Dynamic operating mode
-Precise detection mode (Pin-Point) is available in static mode
-Power supply, V 12
-There is a sensitivity level regulator
-There is a threshold tone control
-Ground adjustment is available (manual)
Detection depth in the air with a DD-250mm sensor In the ground, the device sees targets almost the same as in the air.
-coins 25mm - about 30cm
-gold ring - 25cm
-helmet 100-120cm
-maximum depth 150cm
-Consumption current:
-No sound approximately 30 mA
And the most important and intriguing thing is the diagram of the device itself
The picture is easily enlarged when you click on it
To assemble the metal detector you need the following parts:
So that you don’t have to spend a long time setting up the device, do the assembly and soldering carefully; the board should not contain any clamps.
For tinning boards, it is best to use rosin in alcohol; after tinning the tracks, do not forget to wipe the tracks with alcohol
Parts side board
We begin assembly soldering jumpers, then resistors, further sockets for microcircuits And all the rest. One more small recommendation, now regarding the manufacture of the device board. It is very desirable to have a tester that can measure the capacitance of capacitors. The fact is that the device These are two identical amplification channels, therefore the amplification through them should be as identical as possible, and for this it is advisable to select those parts that are repeated on each amplification stage so that they have the most identical parameters as measured by the tester (that is, what are the readings in a particular stage on one channel - the same readings on the same stage and in another channel)
Making a coil for a metal detector
Today I would like to talk about the manufacture of a sensor in a finished housing, so the photo is more than words.
We take the housing, attach the sealed wire in the right place and install the cable, ring the cable and mark the ends.
Next we wind the coils. The DD sensor is manufactured according to the same principle as for all balancers, so I will focus only on the required parameters.
TX – transmitting coil 100 turns 0.27 RX – receiving coil 106 turns 0.27 enameled winding wire.
After winding, the coils are tightly wrapped with thread and impregnated with varnish.
After drying, wrap tightly with electrical tape around the entire circumference. The top is shielded with foil; between the end and the beginning of the foil there should be a gap of 1 cm not covered by it, in order to avoid a short-circuited turn.
It is possible to shield the coil with graphite; to do this, mix graphite with nitro varnish 1:1 and cover the top with a uniform layer of tinned copper 0.4 wire wound on the coil (without gaps), connect the wire to the cable shield.
We put it into the case, connect it and roughly bring the coils into balance, there should be a double beep for the ferrite, a single beep for the coin, if it’s the other way around, then we swap the terminals of the receiving winding. Each of the coils is adjusted in frequency separately; there should be no metal objects nearby!!! The coils are tuned with an attachment for measuring resonance. We connect the attachment to the Eldorado board in parallel with the transmitting coil and measure the frequency, then with the RX coil and a selected capacitor we achieve a frequency 600 Hz higher than that obtained in TX.
After selecting the resonance, we assemble the coil together and check whether the device sees the entire VDI scale from aluminum foil to copper; if the device does not see the entire scale, then we select the capacitance of the resonant capacitor in the RX circuit in steps of 0.5-1 nf in one direction or another, and in addition the moment when the device will see foil and copper at a minimum of discrimination, and when the discrimination is turned up, the entire scale will be cut out in turn.
We finally reduce the coils to zero, fixing everything with hot glue. Next, to lighten the coil, we glue the voids with pieces of polystyrene foam, the foam sits on the hot glue, otherwise it will float up after filling the coil.
Pour the first layer of epoxy, without adding to the top 2-3mm
Fill in the second layer of resin with color. An aniline dye is a good choice for dyeing fabric; the powder comes in different colors and costs a penny. The dye must first be mixed with the hardener, then the hardener must be added to the resin; the dye will not dissolve in the resin immediately.
To assemble the board correctly, start by checking the correct power supply to all components.
Take the circuit and the tester, turn on the power on the board, and, checking the circuit, go through the tester at all points on the nodes where power should be supplied.
When the discrimination knob is set to minimum, the device should see all non-ferrous metals
, when screwing the discrim, they should be cut out
all metals in order up to copper should not be cut out if the deviceit works this way, which means it is configured correctly. The discrimination scale needs to be selected so that it fits completely into a full turn of the discrimination knob, this is done by selecting c10. When the capacity decreases, the scale stretches and vice versa.
I offer for repetition a simple metal detector that I personally assembled recently and successfully operated. This metal detector operates on the transmit-receive principle. A multivibrator is used as a transmitter, and an audio amplifier is used as a receiver. The schematic diagram was published in Radio magazine.
MD receiver circuit - second option
Metal detector parameters
Operating frequency - about 2 kHz;
- detection depth of a coin with a diameter of 25 mm - 9 cm;
- iron sealing lid from a jar - 25 cm;
- aluminum sheet measuring 200x300 mm - 45 cm;
- sewer hatch - 60 cm.
The search coils connected to it must be exactly the same in size and winding data. They must be positioned so that in the absence of foreign metal objects there is practically no connection between them; examples of coils are shown in the figure.
If the transmitter and receiver coils are positioned this way, the transmitter signal will not be heard in the receiver. When a metal object appears in the vicinity of this balanced system, under the influence of the alternating magnetic field of the transmitting coil, so-called eddy currents arise in it and, as a result, its own magnetic field, which induces an alternating EMF in the receiving coil.
The signal received by the receiver is converted by phones into sound. The metal detector circuit is really very simple, but despite this, it works quite well, and the sensitivity is not bad. The multivibrator of the transmitting unit can be assembled using other transistors of a similar structure.
The metal detector coils have a size of 200x100 mm and contain about 80 turns of 0.6-0.8 mm wire. To check the operation of the transmitter, connect headphones instead of the L1 coil and make sure that sound is heard in them when the power is turned on. Then, by connecting the coil in place, they control the current consumed by the transmitter - 5...8 mA.
The receiver is configured with the input closed. By selecting resistor R1 in the first stage and R3 in the second, a voltage equal to approximately half the supply voltage is set on the collectors of the transistors, respectively. Then, by selecting resistor R5, they ensure that the collector current of transistor VT3 becomes equal to 5...8 mA. After this, opening the input, connect the receiver coil L1 to it and, receiving the transmitter signal at a distance of about 1 m, make sure that the device is working.
Nowadays, many people try not to buy metal detectors, but to assemble them with their own hands. As a rule, it is believed that something made by hand is much worse than branded items. Practice has shown that a high-quality product can compete with metal detectors made in production.
It goes without saying that such a device may look a little worse in terms of aesthetics, but in terms of technical data, it will be competitive.
General information on metal detectors
Before you start build your own metal detector, you need to find out the principles of its operation and what types such equipment can be divided into.
Design
Metal detectors are mainly divided into five types. They differ in search depth and type of metal. They have a variety of functions that simplify the work, but still, even with such differences, some similar features can be identified.
Principle of operation
The structure of a metal detector system may seem complicated only at first glance. In fact, the whole process is simply the attraction of metal products using a magnetized coil. While the coil begins to attract metal parts, magnetic waves pass through it, and after that a signal is heard.
It is worth noting that the coils operate at low or high frequencies. If the equipment operates at low frequencies, then metal products will mainly be found only at a depth of four meters. In addition, a metal detector that operates at low frequencies can only detect large samples, while small metal parts on the surface will go undetected. A metal detector that reacts at high frequencies, on the contrary, finds only small details on the surface, but cannot work at a depth of more than two meters and search for large objects.
Type varieties
Metal detectors can be divided into 5 types, taking into account the device that is responsible for transmitting and receiving the signal.
How to make a metal detector with your own hands?
Making your own homemade metal detector is not too difficult, even if you do not have certain skills in electrical engineering and the system itself. Today there are quite a large number of metal detectors that can be assembled at home. They differ in the circuits that have to be used to create the control unit, materials and complexity of assembly.
As a rule, the most complex metal detector is assembled according to a scheme where it is necessary to install two generators into the system structure at once. This is quite difficult for a beginner. There is also a simpler type of metal detector that can be easily made at home, using only available materials.
Frame
The assembly of a homemade metal detector must begin with the development of the housing. It should be a simple barbell that can be welded or connected with fasteners. In fact, there are no defined frames for the case. Here, each person can make a barbell for themselves, but it is important to remember some factors.
First of all, the material that is selected for the manufacture of the case must be strong enough to withstand the weight of an adult for a long time. In addition, we must not forget about the size of such a bar, because if you choose the wrong length for your height, each time you search for metal objects you will have to stand in a bent state for several minutes.
Many people simplify the task of creating a body by using a simple crutch, which also has an armrest. A crutch can be easily selected to suit your height, and it is not too expensive.
Search coil
Making a homemade search coil is quite difficult, but it is possible. The first step is to start creating a device for winding the coil. First you need to take a simple board measuring 18 by 18, nails and cambric.
After this, you need to draw an even circle on the board and drive at least 16 nails along its diameter, so that they protrude slightly by about 2 cm. After this, cambrics are installed on the nails, which are tightly wrapped with copper wire. At the end of the work, the entire copper circle is firmly secured with threads, which need to be wound around the entire diameter and treated with epoxy resin.
You need to leave a 4 cm long lead, tighten the coil with electrical tape and shield it with foil. The copper wire needs to be tinned to a length of 1.25 cm and then re-wind it onto the reel. Then the action is repeated, or, more precisely, the coil is wrapped with electrical tape. You will also need to solder a contact pad to the coil terminal.
Control block
To create a control unit you will need:
All the necessary parts can be found in an old transistor type receiver. To assemble the control unit, you will need to find a suitable housing and install all the parts.
The circuit and coil are connected together using shielded wire. The cable screen is soldered to the coil terminal, insulation is installed, and the cable is fixed to the housing using electrical tape.
Conclusion
Making an entry-level metal detector is quite simple at home using available tools. All you need to do is follow the instructions and diagrams for assembling the equipment. The result is a model that can be used to search for small metal objects at a depth of up to 1 m.
There is probably no need to tell you what this electronic device is intended for. Everything is clear to everyone. These devices are used by sappers, at airports, in intelligence agencies, and in various institutions related to security in one way or another. But that is not all.
Metal detector in the 90s
These devices in the 90s of the twentieth century helped people not to die of hunger. During those difficult times, you could often see young people and others walking the streets with metal detectors. The device was used to search for metals and alloys. In particular, in cities near which large industries were located, it was possible to dig up real wealth with its help.
Basically, these guys made metal detectors with their own hands and looked for waste from metallurgical plants or native metals that remained in the bowels of the earth. The latter were used in the construction of routes. After all, many asphalt and dirt roads were covered with slag, and often in its composition one could find metal and an alloy of iron and manganese - ferromanganese. At the end of the 90s, it had already become quite expensive. In one day of such work on city and country roads one could earn as much as a factory worker earned in a week. Since many people were unemployed, this activity became especially popular. After all, this alloy is one of the components for creating steel of various grades at the same metallurgical plants.
Metal detectors today
Today, the topic of searching with the help of electronic devices is not so widely developed. However, these devices are still popular among certain groups of people. They wander through the places of former glory of valiant Soviet soldiers, trying to dig up something valuable from historical objects. For example, you can find coins from the time of the Patriotic War, German ones of course. And some people manage to dig up really valuable things. You just need to know where to look.
What can you really find?
Unless you pick up the device yourself and walk along the city roads or through memorable and historical places, you will hardly believe how many interesting objects the earth stores. And for this you should build a metal detector with your own hands.
Coins
Often you can dig them up. During the times of Ancient Rus', coins of the Arab East were used for trade. Then they used coins of Byzantine and Tatar production. Silver bullion is now found in the form of money.
Today in Crimea (and this is where well-preserved objects can be found) you can see people with these devices.
Crosses, icons, coils
Every self-respecting Christian wore a cross in Ancient Rus'. All crosses were different from each other, depending on the type and its purpose. You can often find so-called vests.
Buckles, buttons, various household items
This group of items is very numerous. Most of them have been used since the Bronze Age and are still used today. Often the objects were made of bronze, copper or iron.
Echoes of War
This is the most popular group of items that are searched for purposefully. They are especially popular among collectors. Enthusiasts are searching, getting them, and restoring them. Some end up in museums, some end up in your hands.
How to make a metal detector with your own hands
In the era of the popularity of ferromanganese and high prices for it, grimy young people did not shy away from digging in the ground to earn a little money. More often they purchased devices to search for their prey in numerous markets or from various specialists who, by chance, were fired from radio factories or TV repair shops. One way or another, these professionals assembled the metal detector with their own hands from radio components left in stores using various schemes and technologies. The guys often argued about who had the better and more technologically advanced device. After all, back then it was actually a working tool, and not a hobby device, as it is nowadays.
Those who had at least a little knowledge of electronics also made their own metal detectors. But these guys weren't interested in digging a metallurgical ingredient out of the ground. But it seems we have deviated from the topic.
Principle of operation
Before moving on to assembling various circuits, you need to look at the operating principle of these devices.
The operation of a metal detector is based on the principles of magnetic attraction. The device creates a magnetic field through one coil. The second receives return signals. Then, if found, it sends a return signal through an audible alarm. You can even make a special metal detector for non-ferrous metals with your own hands.
The larger the coil, the more sensitive the device will be. Although in modern devices, and especially in industrial models, the coil is small. But there are amplifiers on microcircuits.
Types
An ultra-low frequency finder is the simplest device. Every schoolchild knows how to make a metal detector with his own hands using an ultra-low frequency circuit. But this does not mean that such a seeker is ineffective. Just the opposite. With proper setup, you can achieve good results.
The pulse finder is a deeper device. With its help you can easily find jewelry, coins and other small items at great depths. Such schemes are popular among professional treasure hunters.
A device that operates on beats allows you to detect absolutely any metal object or mineral in the bowels of the earth at a depth of up to a meter. It is designed for certain types of alloys. This is a cheap device to assemble.
The radio detector is capable of detecting metals at a depth of up to a meter. It's easy to do. This is a suitable device for beginners, but is not popular among diggers.
A primitive metal detector using one transistor
If you still have a long-wave radio receiver in working condition at home, then even if you have little knowledge of electronics, you can assemble a metal detector attachment for this receiver.
To make a metal detector with your own hands, the diagram is drawn without much difficulty. The circuit diagram represents the most common LC generator, designed for frequencies in the region of 140 KHz. The coil for the device, which is used as an oscillating circuit, should contain 16 turns of the simplest insulated wire up to 0.5 mm in diameter. The coils must be laid on plywood of suitable sizes. Fix the resulting contour to the base using glue. This is how you usually make a coil for a metal detector with your own hands.
Required Parts
You can use absolutely any resistors and capacitors for this device. As a transistor, a low-power high-frequency one with reverse conductivity will suffice. This could be the popular and easily available KT315. Or KT3102 with any letter index.
To assemble this simple metal detector with your own hands, the circuit is assembled either by surface mounting or on a pre-prepared board made of getinax or textolite.
Setting up a simple metal detector
After the part is ready, we need to place it next to our coil. The device should have a comfortable handle. The radio receiver must be mounted on the finder handle, and then tuned to a frequency around 140 kHz. You will hear a squeak or squeak. If you bring the coil closer to a metal object, the sound in the headphones will change its tone.
Despite the fact that these are the simplest metal detectors in design and layout, making them with your own hands is elementary; the sensitivity of such devices makes it possible to work at depths of up to 200 mm.
High frequency finder
This assembly scheme is a little more complicated than the previous one. But also much more effective. Its difference is that there are two coils.
The first is the outer contour. A magnetic field is created directly in this coil. The second is the receiving circuit. This part is designed to receive, process, and amplify signals that come from the earth.
Making a deep metal detector with your own hands
First you need to assemble the so-called command block. To create it, an old computer, an equally old laptop or a radio will do. Then you need to find the highest frequency in the AM band. You need to make sure that there is no radio station on the frequency.
Search head
To assemble the search head, you need to cut two circles from thin plywood. One of them should have a diameter of about 15 cm, the second should be made a little smaller. This is done so that the rings can be inserted into each other. Then we need to cut out small pieces of wood so that our head rings are parallel.
After this, 10-15 turns of enameled wire with a cross-section of 0.25 mm from the outer circle should be removed from the plates. You also need to secure the resulting structure. For everything to work, you need to connect the head from the bottom and the detector from the top.
It's time to turn on our frequency. A faint tonal sound will be heard. It's better to use headphones.
Metal detector "Pirate"
Assembling the device is not difficult at all. The device circuit does not contain programmable microcircuits; it is easy to make and configure this metal detector with your own hands. Detailed instructions will help with this. Also, this scheme does not contain expensive or scarce parts. "Pirate" in its parameters can surpass foreign, quite expensive industrial analogues.
Options
For power supply you will need from 9 to 12 V. The current consumed by the device is up to 40 mA. Sensitivity will be up to 150 cm subject to large metal objects.
How is the element base for a metal detector made?
The “Pirate” type circuit consists of two nodes. This is a transmitting circuit, which consists of a pulse generator based on KR1006VI1 and a switch made from an IRF740 transistor. The receiver is made on the basis of the K157UD2 microcircuit and the VS547 transistor.
The coil should have 190 mm in diameter. The number of turns on the PEV wire is 0.5 - 25. The transistor in the circuit can be pulled out of an ordinary energy-saving light bulb or any charger for mobile phones. A properly assembled “Pirate” metal detector with your own hands practically does not need to be configured.
"Terminator"
The device has good capabilities. For example, the device will detect a coin with a denomination of 5 Russian rubles from 25 cm. The finder will recognize a German military helmet from 80 cm. These values are given on the condition of a coil with a diameter of 240 mm. "Terminator" can recognize metals even at the maximum working depth.
It is worth saying that beginners are unlikely to be able to assemble a “Terminator” metal detector with their own hands. The device requires careful setup. Even experienced craftsmen sometimes make mistakes when assembling this circuit. The main thing here is not to rush.
In order to assemble the Terminator, you will need a multimeter, as well as an oscilloscope and an LC meter. They are not available to every person. However, you can try to create a special software and hardware complex based on a regular home personal computer.
Description
The terminator is a single-tone device that operates from pulsed beats. The finder is great for finding coins. Also, if you make a little modification, you can look for gold on the beaches, while completely ignoring any other metals. "Terminator" is also suitable for searching for any other objects from any alloys.
In conclusion
So, we found out how to make a “Pirate” metal detector with our own hands, and also looked at “Terminator”. As you can see, by devoting a minimal amount of free time and effort to the assembly, you can get a rather interesting, and most importantly, workable tool with which you can find ancient objects, and possibly expensive coins.
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. And the main search tool is 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.
Homemade metal detectors
In this section of our website about homemade metal detectors, I will be collected: best metal detector circuits, their descriptions, programs and other data for manufacturing DIY metal detector. There are no metal detector circuits from the USSR or circuits with two transistors here. Since such metal detectors are only suitable for visually demonstrating the principles of metal detection, but are not at all suitable for real use.
All metal detectors in this section will be quite technologically advanced. They will have good search characteristics. And a well-assembled homemade metal detector is not much inferior to its factory-made counterparts. Basically, there are various schemes presented here pulse metal detectors And metal detector circuits with metal discrimination.
But to make these metal detectors, you will need not only desire, but also certain skills and abilities. We tried to break down the diagrams of the given metal detectors by level of complexity.
In addition to the basic data required to assemble a metal detector, there will also be information about the required minimum level of knowledge and equipment for making a metal detector yourself.
To assemble a metal detector with your own hands, you will definitely need:
This list will contain the necessary tools, materials and equipment for self-assembly of all metal detectors without exception. For many schemes you will also need various additional equipment and materials, here are just the basics for all schemes.
- Soldering iron, solder, tin and other soldering supplies.
- Screwdrivers, pliers, wire cutters and other tools.
- Materials and skills for making a printed circuit board.
- Minimum experience and knowledge in electronics and electrical engineering as well.
- And also straight hands will be very useful when assembling a metal detector with your own hands.
Here you can find diagrams for self-assembly of the following models of metal detectors:
 |
Principle of operation | I.B. |
| Metal discrimination | There is | |
| Maximum search depth | ||
| There is | ||
| Operating frequency | 4 - 17 kHz | |
| Difficulty level | Average | |
 |
Principle of operation | I.B. |
| Metal discrimination | There is | |
| Maximum search depth | 1-1.5 meters (Depends on the size of the coil) | |
| Programmable microcontrollers | There is | |
| Operating frequency | 4 - 16 kHz | |
| Difficulty level | Average | |
 |
Principle of operation | I.B. |
| Metal discrimination | There is | |
| Maximum search depth | 1 - 2 meters (Depends on the size of the coil) | |
| Programmable microcontrollers | There is | |
| Operating frequency | 4.5 - 19.5 kHz | |
| Difficulty level | High | |