How to make a metal detector with your own hands: detailed instructions and diagrams. How to make a metal detector with your own hands - cost-effective and proven schemes Homemade metal detectors at home
A metal detector is an electronic device for searching and distinguishing metals, metal objects that can be hidden at different depths under a layer of sand, earth, in the walls of rooms and various structures.
Schematic diagrams of metal detectors made on transistors, microcircuits and microcontrollers are given. A factory-made metal detector is a fairly expensive device, so making a homemade metal detector yourself can save quite a bit of money.
The circuits of modern metal detectors can be built according to different operating principles; we list the most popular of them:
- Beat method (measuring changes in reference frequency);
- Induction balance at low frequencies;
- Induction balance on spaced coils;
- Pulse method.
Many novice radio amateurs and treasure hunters are wondering: how to make a metal detector yourself? It is advisable to start your acquaintance with assembling a simple metal detector circuit; this will allow you to understand the operation of such a device and gain first skills in searching for treasures and products made of multi-colored metals.
Now there is a fairly large selection of multimeters, at very different prices. Now the radio amateur can not be limited to the modest set of functions of the “legendary” M-838. For slightly more expensive, you can purchase a more modern device that is also capable of measuring the frequency of alternating current...
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The metal detector is designed to detect a metal object (well cover, pipe section, hidden wiring). The metal detector consists of a parallel voltage stabilizer (transistors V1 V2) at a high frequency generator (about 100 kHz) on transistor V4, an RF vibration detector (V5) and...
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The metal detector allows you to detect any metal object at a distance of up to 20 cm. The detection range depends only on the area of the metal object. For those for whom this distance is not enough, for example treasure hunters, we can recommend increasing the size of the frame. This should also increase the detection depth. The schematic diagram of the metal detector is shown in the figure. The circuit is assembled using transistors operating in...
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Circuit diagram of a homemade beat metal detector, which is built on five microcircuits. Finds a 0.25mm coin at a depth of 5cm, a pistol at a depth of 10cm, and a metal helmet at 20cm. The schematic diagram of a beat metal detector is shown below. The circuit consists of the following components: a crystal oscillator, a measuring oscillator, a synchronous detector, a Schmidt trigger, an indication device...
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The diagram shown in the figure is a classic metal detector. The operation of the circuit is based on the principle of superheterodyne frequency conversion, which is usually used in a superheterodyne receiver. Schematic diagram of a metal detector with an integrated ULF; it uses two radio frequency generators, the frequencies of which are 5.5 MHz. The first radio frequency generator is assembled on a T1 transistor type BF494, frequency...
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This metal detector, despite the small number of parts and ease of manufacture, is quite sensitive. It can detect large metal objects, such as a heating battery, at a distance of up to 60 cm, while small ones, for example, a coin with a diameter of 25 mm, can be detected at a distance of 15 cm. The operating principle of the device is based on a change in frequency in the measuring generator under the influence of nearby metals and. ..
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A simple compact metal detector is needed to detect various metal objects (for example, pipes, wiring, nails, fittings) in walls under a layer of plaster. This device is completely autonomous, powered by a 9-volt Krona battery, consuming 4-5 mA from it. The metal detector has sufficient sensitivity to detect: pipes at a distance of 10-15 cm; wiring and nails at a distance of 5-10...
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Scheme of a small-sized, highly economical metal detector with good repeatability and high performance characteristics, using widely available and inexpensive parts. An analysis of most common circuits has shown that they are all powered from a source with a voltage of at least 9 V (that is, “Krona”), and this is both expensive and uneconomical. So, assembled on the K561LE5 chip...
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Do-it-yourself metal detector - as the name suggests, such devices are made independently and are designed to search for metal objects and are used for a fairly narrow purpose. However, the methods for their implementation are quite diverse and constitute a whole direction in radio electronics.
Metal detector N. Martynyuk
The metal detector according to N. Martynyuk’s scheme (Fig. 1) is made on the basis of a miniature radio transmitter, the radiation of which is modulated by an audio signal [Рл 8/97-30]. The modulator is a low-frequency generator made according to the well-known symmetrical multivibrator circuit.
The signal from the collector of one of the multivibrator transistors is fed to the base of the high-frequency generator transistor (VT3). The operating frequency of the generator is located in the frequency range of the VHF-FM broadcast range (64... 108 MHz). A piece of television cable in the form of a coil with a diameter of 15...25 cm was used as the inductor of the oscillating circuit.
Rice. 1. Schematic diagram of N. Martynyuk’s metal detector.
If a metal object is brought closer to the inductor of the oscillating circuit, the generation frequency will noticeably change. The closer the object is brought to the coil, the greater the frequency shift will be. To record frequency changes, a conventional FM radio receiver is used, tuned to the frequency of the HF generator.
The receiver's automatic frequency control system should be disabled. If there is no metal object present, a loud beep is heard from the receiver's speaker.
If you bring a piece of metal to the inductor, the generation frequency will change and the volume of the signal will decrease. The disadvantage of the device is its reaction not only to metal, but also to any other conductive objects.
Metal detector based on a low-frequency LC generator
In Fig. 2 - 4 shows a circuit of a metal detector with a different operating principle, based on the use of a low-frequency LC oscillator and a bridge frequency change indicator. The search coil of the metal detector is made in accordance with Fig. 2, 3 (with correction of the number of turns).
Rice. 2. Metal detector search coil.
Rice. 3. Metal detector search coil.
The output signal from the generator is fed to a bridge measuring circuit. A high-resistance telephone capsule TON-1 or TON-2 is used as a bridge null indicator, which can be replaced with a pointer or other external alternating current measuring device. The generator operates at frequency f1, for example, 800 Hz.
Before starting work, the bridge is balanced to zero by adjusting the capacitor C* of the oscillating circuit of the search coil. The frequency f2=f1 at which the bridge will be balanced can be determined from the expression:
Initially, there is no sound in the telephone capsule. When a metal object is introduced into the field of the search coil L1, the generation frequency f1 will change, the bridge will become unbalanced, and a sound signal will be heard in the telephone capsule.
Rice. 4. Diagram of a metal detector with an operating principle based on the use of a low-frequency LC generator.
Metal detector bridge circuit
The bridge circuit of a metal detector using a search coil that changes its inductance when metal objects approach is shown in Fig. 5. An audio frequency signal from a low-frequency generator is supplied to the bridge. Using potentiometer R1, the bridge is balanced for the absence of an audio signal in the telephone capsule.
Rice. 5. Bridge circuit of a metal detector.
To increase the sensitivity of the circuit and increase the amplitude of the bridge unbalance signal, a low-frequency amplifier can be connected to its diagonal. The inductance of the L2 coil should be comparable to the inductance of the L1 search coil.
Metal detector based on a receiver with the CB range
A metal detector operating in conjunction with a mid-wave superheterodyne radio broadcast receiver can be assembled according to the circuit shown in Fig. 6 [R 10/69-48]. The design shown in Fig. 1 can be used as a search coil. 2.
Rice. 6. A metal detector operating in conjunction with a superheterodyne radio receiver in the CB range.
The device is a conventional high-frequency generator operating at 465 kHz (the intermediate frequency of any AM broadcast receiver). The circuits presented in Chapter 12 can be used as a generator.
In the initial state, the frequency of the HF generator, mixing in a nearby radio receiver with the intermediate frequency of the signal received by the receiver, leads to the formation of a difference frequency signal in the audio range. When the generation frequency changes (if there is metal in the field of action of the search coil), the tone of the sound signal changes in proportion to the amount (volume) of the metal object, its distance, and the nature of the metal (some metals increase the generation frequency, others, on the contrary, lower it).
A simple metal detector with two transistors
Rice. 7. Scheme of a simple metal detector using silicon and field-effect transistors.
The diagram of a simple metal detector is shown in Fig. 7. The device uses a low-frequency LC generator, the frequency of which depends on the inductance of the search coil L1. In the presence of a metal object, the generation frequency changes, which can be heard using the BF1 telephone capsule. The sensitivity of such a scheme is low, because It is quite difficult to detect small changes in frequency by ear.
Metal detector for small quantities of magnetic material
A metal detector for small quantities of magnetic material can be made according to the diagram in Fig. 8. A universal head from a tape recorder is used as a sensor for such a device. To amplify weak signals taken from the sensor, it is necessary to use a highly sensitive low-frequency amplifier, the output signal of which is fed to the telephone capsule.
Rice. 8. Diagram of a metal detector for small quantities of magnetic material.
Metal indicator circuit
A different method of indicating the presence of metal is used in the device according to the diagram in Fig. 9. The device contains a high-frequency generator with a search coil and operates at frequency f1. To indicate the signal magnitude, a simple high-frequency millivoltmeter is used.
Rice. 9. Schematic diagram of a metal indicator.
It is made on diode VD1, transistor VT1, capacitor C1 and milliammeter (microammeter) PA1. A quartz resonator is connected between the output of the generator and the input of the high-frequency millivoltmeter. If the generation frequency f1 and the frequency of the quartz resonator f2 coincide, the needle of the device will be at zero. As soon as the generation frequency changes as a result of introducing a metal object into the field of the search coil, the needle of the device will deviate.
The operating frequencies of such metal detectors are usually in the range of 0.1...2 MHz. To initially set the generation frequency of this and other devices of similar purpose, a variable capacitor or a tuning capacitor connected in parallel with the search coil is used.
Typical metal detector with two generators
In Fig. Figure 10 shows a typical diagram of the most common metal detector. Its operating principle is based on the frequency beats of the reference and search oscillators.
Rice. 10. Diagram of a metal detector with two generators.
Rice. 11. Schematic diagram of the generator block for a metal detector.
A similar node, common to both generators, is shown in Fig. 11. The generator is made according to the well-known “three-point capacitive” scheme. In Fig. Figure 10 shows a complete diagram of the device. The design shown in Fig. 1 is used as search coil L1. 2 and 3.
The initial frequencies of the generators must be the same. The output signals from the generators through capacitors C2, SZ (Fig. 10) are fed to a mixer that selects the difference frequency. The selected audio signal is fed through the amplifier stage on transistor VT1 to the telephone capsule BF1.
Metal detector based on the principle of frequency interruption
The metal detector can also operate on the principle of disrupting the generation frequency. The diagram of such a device is shown in Fig. 12. If certain conditions are met (the frequency of the quartz resonator is equal to the resonant frequency of the oscillatory LC circuit with the search coil), the current in the emitter circuit of transistor VT1 is minimal.
If the resonant frequency of the LC circuit changes noticeably, the generation will fail, and the readings of the device will increase significantly. It is recommended to connect a capacitor with a capacity of 1 ... 100 nF in parallel to the measuring device.
Rice. 12. Circuit of a metal detector that works on the principle of disrupting the generation frequency.
Metal detectors for searching for small objects
Metal detectors, designed to search for small metal objects in everyday life, can be assembled according to those shown in Fig. 13 - 15 schemes.
Such metal detectors also operate on the principle of generation failure: the generator, which includes a search coil, operates in a “critical” mode.
The operating mode of the generator is set by adjusted elements (potentiometers) so that the slightest change in its operating conditions, for example, a change in the inductance of the search coil, will lead to disruption of the oscillations. To indicate the presence/absence of generation, LED indicators of the level (presence) of alternating voltage are used.
Inductors L1 and L2 in the circuit in Fig. 13 contain, respectively, 50 and 80 turns of wire with a diameter of 0.7...0.75 mm. The coils are wound on a 600NN ferrite core with a diameter of 10 mm and a length of 100... 140 mm. The operating frequency of the generator is about 150 kHz.
Rice. 13. Circuit of a simple metal detector with three transistors.
Rice. 14. Scheme of a simple metal detector using four transistors with light indication.
Inductors L1 and L2 of another circuit (Fig. 14), made in accordance with the German patent (No. 2027408, 1974), have 120 and 45 turns, respectively, with a wire diameter of 0.3 mm [P 7/80-61 ]. A 400NN or 600NN ferrite core with a diameter of 8 mm and a length of 120 mm was used.
Household metal detector
A household metal detector (HIM) (Fig. 15), previously produced by the Radiopribor plant (Moscow), allows you to detect small metal objects at a distance of up to 45 mm. The winding data of its inductors are unknown, however, when repeating the circuit, you can rely on the data given for devices of similar purposes (Fig. 13 and 14).
Rice. 15. Scheme of a household metal detector.
Literature: Shustov M.A. Practical circuit design (Book 1), 2003
Now, perhaps, there is no person who does not know what a metal detector or metal detector is. But let us remind you once again that this is a device that allows you to determine the hidden location of metals. The metal detector is very popular among amateur archaeologists and treasure hunters. The device is quite expensive, and some models are even sky-high, which is why most radio amateurs prefer to assemble it themselves. In today's article we will look at how to make a metal detector with your own hands, the operating principle of the device, popular circuits, as well as assembly and configuration features.
Read in the article
How does a metal detector work?
A metal detector, or metal detector, is an electronic device consisting of a primary sensor (coil with winding) and a secondary unit. Metal detection devices are divided into several types:
- "reception and transmission";
- induction;
- pulse;
- generator
Devices in the mid-price category are mainly of the “receive-transmit” type. The operating principle of such metal detectors is based on the transmission and reception of electromagnetic waves. The main elements of a device of this type are two coils: one is transmitting, and the second is receiving. The first coil transmits electromagnetic waves that freely pass through a neutral medium and which, when colliding with metal objects, are reflected and transmitted to the receiving device. After the reflected signal hits the second coil, the operator is informed by a buzzer that the target has been found.
An induction-type metal detector operates on the same principle as transmit-receive devices. The main difference between them is the number of coils with winding. An induction metal detector has one coil that sends and receives a signal simultaneously. Pulse devices are insensitive to the concentration of salts in the soil and include in their design a coil, the electromagnetic field of which creates eddy currents on the metal surface that are captured by the detector. This principle of operation reduces the possibility of discrimination, which can complicate the search.
Generator-type metal detectors come in different types, but they are all built on the basis of an LC generator. They have a low level of sensitivity and are generally designed to find only one type of metal. Metal detectors can also be divided into three categories:
- common use;
- middle class;
- professional equipment.
Functional and technical parameters of metal detectors
Before choosing and buying a good metal detector, you should clearly decide in what environment the search work will be carried out. It is also necessary to take into account the expected size of the objects being sought and the depth of their location. Let's look at the main characteristics that you need to pay special attention to when purchasing a detector:
- operating principle;
- operating frequency of the device;
- sensitivity;
- ground balancing;
- target designation;
- discriminator;
- additional functions.
The operating principle and operating frequency of the detector are the main characteristics that determine the capabilities of the device and show which category it can be classified into (simple ground, middle class or professional). Sensitivity determines the depth of objects with which the device can operate. As a rule, this figure ranges from 100−150 mm to 600−1500 mm. However, there are depth models designed to search for objects at a depth of 5 meters. The discriminator makes it possible to configure the device to search for a specific type of metal. This prevents the operator from being distracted by metallized debris.
What types of metal detectors can you make yourself?
You can purchase a detector at a specialized store or make a metal detector with your own hands at home. There are schemes that even a novice radio amateur can do. Devices that you can assemble yourself include:
- "butterfly";
- device without microcircuits (IC);
- model "Pirate";
- "Terminator 3" etc.
There is information on the Internet that you can supposedly assemble a metal detector from your phone with your own hands. Remember two words - this is fiction. There are some applications that allow you to include a tablet or smartphone in the detector circuit, but it is impossible to make a full-fledged device for searching for metals and recognizing them.
How to assemble a “Pirate” metal detector with your own hands: detailed instructions
Models of the “Pirate” series cost about $100–300. This cost is due to the device’s ability to detect objects at a depth of 200 mm (for small items) and 1500 mm (large items). Let's look at the features of assembling and setting up a device for detecting metals, as well as its components.
Materials needed to assemble a powerful metal detector with your own hands
To make a metal detector you will need the following materials and components:
- IC KR 1006VI1 or NE 555 (foreign equivalent) to create a transmitting unit;
- transistor IRF 740;
- IC K 157UD2 and transistor BC 547 for assembling the receiving unit;
- NPN type transistors;
- PEV 0.5 wire to create a coil;
- materials for the manufacture of the body, rod, etc.;
- a plate covered with copper sheet for making a printed circuit board;
- wires;
- insulating tape;
- side cutters;
- soldering iron;
- scalpel;
- Screwdriver Set;
- pliers;
- various types of fasteners.
Assembling a metal detector with your own hands: diagrams
Currently, there are many circuits for the “Pirate” metal detector, since some radio amateurs have begun to modernize them to suit their needs. All options will not be considered, only the most proven and most popular.
NE555 detector circuit
The classic circuit of a metal detector of the “Pirate” series, built on the NE555 IC timer. The operation of the device depends on a comparator, one output of which is connected to the IC pulse generator, the second to the coil, and the output to the speaker. If metal objects are detected, the signal from the coil is sent to the comparator, and then to the speaker, which notifies the operator of the presence of the desired objects.
DIY metal detector assembly without microcircuits
Unlike the previous circuit, this device uses Soviet-style transistors KT-361 and KT-315 to generate signals (you can use similar radio components).
DIY printed circuit board
The parts have been purchased, the diagram is available, and now you need to assemble it all. To place radio components, a printed circuit is used, which can be easily made independently. To do this, you will need a piece of sheet getinax covered with copper electrical foil. Transfer the selected diagram to the workpiece, mark the tracks connecting the parts, and drill holes in the places where they are attached and soldered. Cover the tracks with protective varnish, and after drying, lower the future board into ferric chloride for etching (removing unprotected areas of copper foil).
After the board is ready, you can install and solder the radio components. The next step is to check the circuit using measuring instruments.
Metal detector coil - how to make it yourself
Due to the fact that the Pirate metal detector is a pulse-type device, accuracy when assembling the coil is not important. For the base you will need a ring with a diameter of about 200 mm, onto which you need to wind 25 turns of 0.5 mm PEV wire. To increase the detection depth of metals, the coil frame should be in the range of 260−270 mm, and the number of turns should be 21−22 vol. Next, the mandrel with the wire must be well wrapped with insulating tape.
Place the finished coil in a housing made of dielectric material. To do this, you can use suitable-sized cases from faulty “throw away” household appliances. By the way, this will protect the coil from mechanical damage while working with the detector. The winding terminals must be soldered to a stranded wire with a diameter in the range of 0.5-0.7 mm. It is best to use twisted pair cable.
Checking and setting up the metal detector
We attach all the components of the device to the metal detector rod: the body with the coil, the receiving and transmitting unit and the handle. If the control circuit is assembled correctly, then adjustment of the device will not be required, since it initially has maximum sensitivity. Fine tuning is performed using variable resistor R13. Normal operation of the detector should be ensured with the regulator in the middle position. If you have an oscilloscope, then use it to measure the frequency at the gate of transistor T2, which should be 120−150 Hz, and the pulse duration should be 130−150 μs.
The video shows how to set up a metal detector.
How to make an underwater metal detector with your own hands
Sometimes search work has to be moved from land to water. What to do in this case, because the electronics will fail? There are, of course, special devices for working underwater, but you can make a deep metal detector with your own hands. To do this, you can take the most ordinary homemade detector and place all the components in hermetically sealed housings. In addition, it is worth slightly modifying the device and installing light indicators instead of an audible alarm.
How to make a Terminator 3 metal detector with your own hands: detailed instructions
The Terminator 3 model has long been popular among radio amateurs, and over the many years of its existence the device has received many improvements. We offer step-by-step instructions on how to make a metal detector yourself at home. The device has low power consumption, can be configured to search for certain types of metal, and has good depth characteristics.
Tools
Before making a homemade metal detector, you need to prepare the following tools:
- soldering iron or soldering station;
- solder, tin, rosin;
- pliers, round nose pliers, side cutters;
- Screwdriver Set;
- hacksaw for metal;
- oscillography and other instrumentation.
Diagram, selection of parts and circuit board
To manufacture the control unit, it is necessary to make a circuit board on which all the necessary radio components will be placed. The circuit presented below must be transferred to a getinax plate coated with copper foil and a circuit board must be made in the same way as described above in the article for the Pirate metal detector. The size of the circuit should be within 104x66 mm, and the board blank should be 10 mm larger on each side.
We will describe in detail how to prepare a printed circuit board for a metal detector in step-by-step instructions:
Illustration | Process description |
We take a textolite plate coated with copper foil. Degrease chemically or mechanically (sand). | |
We apply the diagram to the plate, cover the tracks with a protective varnish and subject the workpiece to etching (described above, as for the “Pirate” metal detector). Using a thin drill, drill holes for radio components and fastenings to the body. | |
We place the radio components in accordance with the diagram and carry out the wiring. | |
This is what the finished Terminator 3 metal detector board will look like. |
Metal detector coil
This is, in fact, the most sensitive part of the device. She is responsible for scanning the space underground. Let's look at the steps to create a simple coil for a metal detector:
Illustration | Process description |
On a piece of plywood we draw two circles corresponding to the diameters of the coils - internal and external. We drive nails around the perimeter of the circle. The diameter of the outer winding TX should be within 200mm. The coil is made from two folded wires. We wind 30 turns on the nails. |
|
We tie the winding around the circumference with threads. We take out the nails, cover the resulting coil with varnish, and after it dries, wrap it with electrical tape and foil. In exactly the same way, we make the internal winding RX, which is half the size of TX and contains 48 turns of wire. |
|
We place the coils in the housing and wire the wires that will be connected to the control unit. | |
This is what the finished metal detector frame will look like. |
Homemade metal detector: detailed description of assembly diagram and setup
We discussed in detail the stages of assembling the board and the main elements of the metal detector earlier, now we are faced with the very last and most important steps: assembling the case and setting up the device.
Illustration | Process description |
We take a suitable box or make the case ourselves. We drill holes for trimming resistors and a connector. We mount the finished board and regulators in the case. | |
We close the case, connect the metal detector frame and attach everything to a plastic pipe with a handle. The metal detector is assembled and ready for use. |
This video will help you set up your metal detector.
Features of a DIY metal detector with a metal discrimination circuit
Metal detectors with a simple circuit allow you to detect hidden objects, but in order to find out which ones you will have to work with a shovel. Instead of a gold coin or a military helmet, you can find just a piece of pipe and spend a lot of time on it. To make the task easier for search engines, detectors began to be equipped with discriminators that make it possible to distinguish the type of metal and allow various types of debris to pass through. The simplest methods for determining the types of metals were implemented in old instruments and entry-level devices and had two modes - “all metals” and “non-ferrous”. The discrimination function allows the operator to respond to a phase shift of a certain magnitude, compared to a configured (reference) level. In this case, the device cannot distinguish between non-ferrous metals.
Professional metal detectors use discriminators with range selection. The microprocessor systems used in such devices make it possible to program the device to respond only to certain groups of metals. Discrimination is useful in littered areas, but reduces detection depth by 10−20%.
Assembly features of a deep metal detector
A deep-type metal detector is a special device capable of detecting objects hidden at a great distance from the surface of the earth. It is at considerable depth that the most interesting and valuable objects can be found. Some models can detect metals at a distance of 4 to 6 m underground.
There are two types of deep metal detectors: frame and transceiver on a rod. The first type of device is capable of covering a large area of land for scanning. Thus, the search speeds up, but has a negative impact on performance. The second version of the detector works in a small area, but better determines the center of the target. With such a device it is good to search in grass, forest or reeds. Therefore, when choosing the type of metal detector, you need to determine under what conditions the scanning will be carried out.
If you have experience assembling a metal detector yourself, tell others about it! If you have questions for the author of the article, ask him in the comments.
This is what keeps a person from purchasing metal detectors, which cost a lot of money, but do not guarantee that anything will be found or not.
On the other hand, if you got such a device practically for nothing, then you wouldn’t have to walk through the forests in search of mythical treasures. Even on a personal plot, it is possible to dig up several meters of pipe or abandoned cable, which, when delivered to a collection point, can bring money. But, as you know, they are never superfluous.
In this case, you need to figure out whether it is possible to make a metal detector from a radio or disks with your own hands without the use of microcircuits, how complicated this process is and whether it requires any specific knowledge, whether the circuits of simple metal detectors are complex, what is required for this, and what is the algorithm for such work.
What is a metal detector
Such a device, homemade or made in a factory, is designed to search for any metal under a layer of soil, regardless of whether it is pieces of iron, copper or something even more valuable. Such devices are used not only by gold miners, but also by various archaeological groups, patriotic communities (in search of remains and objects left in the ground after the Second World War) and even sappers when demining territories.
The shapes, as well as the circuits of metal detectors, are different. This could be a disk mounted on a handle, or it could be some kind of microphone. The essence of this device does not change from this - when any metal object is detected at a shallow depth, it emits a certain sound using a buzzer built into it, signaling the discovery.
Such devices operate on the basis of the physical law according to which electromagnetic induction operates. Its components are a transmitter, which, upon receiving a signal, sends it to a warning device (sound or visual), the signal receiver itself and a buzzer or screen. Electromagnetic waves are sent to the surface and reflected. If the transmitted signal returns unchanged, nothing happens in the circuit, but provided that any metal enters the signal transmission area, the returned wave turns out to be distorted and this is recorded by the transmitter, which gives an audio or visual alert.
Operating frequencies
A metal detector combines complex parameters that are sometimes mutually exclusive. For example, if you lower the frequency generated by the generator, you can achieve a greater search depth, but this will increase energy consumption, and also reduce sensitivity, as well as mobility due to the increase in the coil. But basically all the parameters, one way or another, are tied to the frequency of the generator, and therefore such devices are classified precisely according to the parameter of operating frequency ranges.
VLF
The circuit of a simple metal detector that operates in the range from approximately 100 to 500-600 Hertz is called ultra-low frequency. Such devices are amateur, with a power of no more than a hundred watts. Such devices are weak and it is almost impossible to recognize the signal without the use of computer processing.
LF
The next class of metal detectors is low-frequency. A little more powerful than the previous ones, the circuit is simple, they are resistant to interference, but the sensitivity is still quite low. With an energy consumption of more than 10 Watts, the possible search depth will be about 5 meters. Their inconvenience is also that, in addition to metal, they also react to large fragments of stone or concrete. The best signal is detected on ferrous metals, and therefore such a metal detector is also called a magnetic detector. They have low sensitivity to soil properties.
IF
Another classification is metal detectors of higher frequencies - several tens of kilohertz. They have less good noise immunity compared to LF. Convenient when performed using the pulse mode, which will be discussed a little later. The disadvantage of such devices is that with increased mineralization or in swampy areas, they completely stop receiving the changed signal, as a result of which they do not “see” metals.
HF
The most powerful metal detector, suitable for searching for precious metals, but at shallow depths. Not bad for finding gold items lost by vacationers in the sand on the beaches. The depth of penetration of the signal into the ground is no more than 80–90 cm. The results of the work depend on the power of the transmitter coil; they work with the result only on dry non-magnetic soil, which includes sand.
Pulsers
Such metal detectors are the best equipment in the line. They stand separately from other similar devices. The fact is that current flows to the coil in a pulsed mode. It is possible to set the pulse frequency in low ranges, and the duration, which determines the area of the spectral composition, in high or high frequencies. Thus, you get a metal detector that combines the best qualities of all categories of detectors, or a device that can be reconfigured, depending on the required parameters.
How to make a metal detector with your own hands?
Based on the fact that the cost of such detectors is very high, it makes sense to look into the possibility of making a simple metal detector with your own hands at home. Homemade products require practically no costs, except, of course, a small amount of time.
Since the design of the metal detector is quite simple, to operate it you will need two disks (CD and DVD), headphones, a regular calculator, a 9-volt battery (“crown”), electrical tape and glue, and you assemble it practically on your knees.
So, detailed instructions for assembling a metal detector with your own hands.
To assemble a metal detector from disks, you need to adhere to the following algorithm of actions:
- The headphone plug is not required, so it is cut off and the wires are stripped to a length of about 1 cm.
- Each stripped wire is divided into two equal parts, one of which will go to the mirror part of the disk, and the second to the power element.
- Provided that the mirror surface of the disks is on both sides, one of the parts of the wire is attached to it separately using glue. If the discs are single-sided, then everything is simpler. The contact side is the writing side.
- The wires on the CDs and DVDs themselves are secured with electrical tape.
- When the calculator is turned on, it is secured with the same electrical tape between the disks, and the battery is secured to the surface of the DVD.
At this point the work is completed and the metal detector using improvised means is ready. As you can see, the process is completely uncomplicated and inexpensive, both financially and in time.
Of course, if you make a metal detector whose circuits are so simple, then its characteristics will not compare with professional devices, but you can find elementary structures in the ground with its help.
If you need a more powerful device than a simple metal detector, it can be made from an old radio.
Metal detector from radio
Using this method, you can make a detector that will be more powerful than a simple metal detector. To do this, you will need an empty CD case, a calculator, an AM radio, double-sided tape and electrical tape.
On the inside of the disc box, a radio is glued to double-sided tape, and on the other side - a calculator in the turned on state. The receiver sets the highest frequency in the AM range, or the one closest to it, at which there are no extraneous sounds other than noise.
You can attach any mop stick to the resulting structure. After this, all that remains is to configure the detector. To do this, you need to move the doors of the box apart or move until a sharp sound appears. After moving the doors apart, the same, barely noticeable sound is heard and the box is fixed in this position. After the work has been done, when approaching the metal, the same sound will be heard, but in a sharper sound range.
Of course, you cannot assemble a good metal detector with your own hands, but an acceptable one is quite possible.
Needed or not
Of course, if a person is not engaged in professional excavations, there is no point in purchasing such a device - it is simply throwing away a considerable amount of money. But for home use, you can assemble a simple metal detector. Of course, it won’t help you find treasures buried in the bowels of the earth, but a simple metal detector with your own hands or from a radio is quite capable of determining the location of a metal frame behind a gypsum board wall or the location of hidden wiring in the concrete floors of houses, which is already important. Well, making a metal detector at home without the use of microcircuits using a phone (the description of the work is identical to assembling a metal detector with your own hands from disks or a radio, but a phone is used instead of a calculator) is not difficult.
The smell of travel, the aroma of adventure, or the prosaic ridding of your summer cottage from various metal debris may suggest the idea of purchasing a special device. Professional metal detectors, reviews of which are known to everyone, are quite expensive. But they meet all the requirements of real professional diggers. You need to choose. Reviews will help you understand this difficult matter. Or you can make this device yourself.
Where are metal detectors used?
In addition to searching for real treasures and surveying private land plots for soil purification, metal detectors are used in various areas:
- to locate cables and pipelines;
- to assist in archaeological excavations;
- in civil engineering and forensics;
- in the sapper troops.
Sports treasure hunting
One type of active hobby - sports treasure hunting - is becoming increasingly popular among enterprising and enthusiastic people. What's interesting about this case?
- The element of the unknown is always exciting. How to make a metal detector at home? What lies beneath the surface of the earth? Until you get it and try it, you won’t know.
- Whose device will “look” deeper under the ground? Who can better determine the quality of a metal trinket that has lain in obscurity for many years?
- And if this piece of hardware also has value, that’s the extent of the joy of the inventor, who independently figured out how to make a metal detector at home from improvised materials.
- At rallies and competitions, of course, coins are buried specifically to determine the capabilities of homemade and factory detectors.
What is the operating principle of metal detectors based on?
Any metal detectors operate based on the principles of “Foucault currents” known from the school curriculum. We will not go into details of the experiments. When the search coil and a metal object come closer, a change in frequency occurs in the generator, which the device reports. If a squeak is heard in the headphones, it means that there is something metal lying underground.
Modern inventors work on two problems:
- increasing search depth;
- improvement of identification parameters of devices;
- reduction of energy costs;
- convenient operating characteristics.
What do you need to stock up on to make a detector?
How to make a metal detector at home? It’s worth getting a little acquainted with electronics and reading physics for the 7th grade of high school. Experience with some tools and available materials will be useful. It is necessary to study and test a number of electrical circuits in order to choose the one that will really work. Materials you will need for work:
- small generator (from an old tape recorder);
- film capacitors and resistors;
- vinyl or wooden ring for the search coil;
- plastic, bamboo or wooden cane holder;
- aluminium foil;
- wires for coil winding;
- piezoelectric emitter;
- metal box - screen;
- headphones for receiving sound signals from the device;
- two identical transformer coils;
- 2 Krona batteries;
- perseverance and patience.
Search metal detector assembly sequence
A search coil is made from a plywood circle with a diameter of 15 cm: the wire is wound in turns (15-20) onto a template. The stripped ends are soldered to the connecting cable. A layer of thread is wound around the perimeter of the coil over the wire for fastening.
All parts of the circuit are soldered onto PCB in the following order: capacitors, resistor system, quartz filter, signal amplifier, transistor, diodes, search generator. A soldered board is inserted into the prepared case, connected to the search coil and mounted on a holder stick.
The signal from the search coil reflected by a metal object increases the frequency of the generator. When amplified, it is converted by an amplitude detector into a constant pulse, which produces sound.
How to dig up asphalt and go off the beaten path?
Not all those who are wondering how to make a metal detector at home think about the fact that the earth is an electrical conductor. However, this very fact can greatly influence search performance. "AKA" metal detectors, in which the creators have mathematically calculated and minimized the influence of the Earth's electromagnetic field, process the entire wave flow. In addition, the signal reflected from the object is sent to the device’s monitor. The device shows a certain image by which you can determine what kind of piece of iron lies under the soil layer:
- or is it a pile of coins;
- maybe it's an ancient nail;
- mine or fragment;
- helmet or ;
- single metal object.
A smart detector reports the depth of an object. Patented technology for averaged visualization of search objects allows you to decide whether to dig in a given location. The device has a convenient design and is easy to prepare for use.
The most enthusiastic inventors love to do everything themselves. Some even complicate the process for themselves and figure out how to make a simple metal detector at home. And it doesn’t matter that he can only find an old button at a depth of 5-6 cm from the surface. But how much pride the creator gets from the process itself!
Have all the treasures been dug up yet?
And maps with legendary treasures captivate not only treasure-hungry seekers. Historians, researchers and archaeologists have been searching for years for what Napoleon took from Moscow. And what about the wealth looted by Stenka Razin? Where are they lying, who are they waiting for? Have pirate treasures already been found on the Caribbean islands?
From some sources it is known that the ataman’s prey is quietly waiting for the lucky ones on one of the islands of the Caspian Sea. And the gold taken out by Napoleon, it turns out, was recaptured and hidden by the Cossacks. And they drove the French to Paris. But only one returned, and even then he could not recognize the area. While he was waiting for winter, he fell ill and died. Since those times, a sheet of paper with a plan has remained in one of the archives, on which the designations of all the chests and ten barrels of gold are marked.
Russia is not Europe, and there were no banks in the old days. Where they could, they hid wealth there from spiteful critics and robbers. So, even if the find is not such a big one, but a smaller one, it’s still nice. How to make a metal detector at home? If you really want it, you just need to try.
As a favorite character said in one famous film, we will search!