Schemes of homemade high sensitivity metal detectors. Do-it-yourself small-sized sensitive metal detector (quartz metal detector). To assemble a metal detector with your own hands, you will definitely need
Device search is just huge popularity. Looking for adults and children, and amateurs and professionals. They are looking for treasures, coins, lost things and buried scrap metal. And the main search tool is metal detector.
There is a great variety of different metal detectors for every “taste and color”. But for many people, buying a ready-made branded metal detector is simply financially expensive. And someone wants to assemble a metal detector with their own hands, and someone even builds their own small business on assembling them.
Homemade metal detectors
In this section of our site about homemade metal detectors, 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 and circuits on two transistors here. Since such metal detectors are only suitable for a visual demonstration of the principles of metal detection, they 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 home-made metal detector will be a little inferior to factory counterparts. Basically, there are different schemes. pulse metal detectors And metal detector circuits with metal discrimination.
But for the manufacture of these metal detectors, you will need not only desire, but also certain skills and abilities. We tried to break down the schemes of the given metal detectors according to the level of complexity.
In addition to the basic data required for assembling a metal detector, there will also be information on the required minimum level of knowledge and equipment for self-manufacturing of a metal detector.
To assemble a metal detector with your own hands, you will definitely need:
This list will provide the necessary tools, materials and equipment for self-assembly of all metal detectors without exception. For many circuits, you will also need various additional equipment and materials, here are just the basic ones for all circuits.
- Soldering iron, solder, tin and other soldering accessories.
- Screwdrivers, pliers, wire cutters and other tools.
- Materials and skills for the manufacture of printed circuit boards.
- Minimum experience and knowledge in electronics and electrical engineering as well.
- As well as straight arms - they will be very useful when assembling a metal detector with your own hands.
Here you can find schemes for self-assembly of the following models of metal detectors:
 |
Principle of operation | IB |
| Metal Discrimination | eat | |
| Maximum search depth | ||
| eat | ||
| Operating frequency | 4 - 17 kHz | |
| Level of difficulty | Middle | |
 |
Principle of operation | IB |
| Metal Discrimination | eat | |
| Maximum search depth | 1-1.5 meters (Depends on coil size) | |
| Programmable microcontrollers | eat | |
| Operating frequency | 4 - 16 kHz | |
| Level of difficulty | Middle | |
 |
Principle of operation | IB |
| Metal Discrimination | eat | |
| Maximum search depth | 1 - 2 meters (Depends on the size of the coil) | |
| Programmable microcontrollers | eat | |
| Operating frequency | 4.5 - 19.5 kHz | |
| Level of difficulty | Tall | |
In recent years, many respected European publishing houses have paid considerable attention to various technical devices used in search operations. Every year, new books with descriptions of various devices arrive on the shelves of bookstores. It should be recognized that, in general, these devices are difficult to assemble and adjust and can hardly be recommended for repetition by novice radio amateurs.
Nevertheless, in one of the books published as part of the "Elektronicke hledace" series by the popular European publishing house "BEN", the author relatively recently, not without surprise, discovered a metal detector circuit that seemed very familiar. The main element with which the presence of metal objects is analyzed in this device is quartz. At the same time, the results of the analysis are evaluated both visually and aurally.
circuit diagram
The design offered to the attention of readers is one of the variants of metal detectors of the FM (Frequency Meter) type, that is, it is a device based on the principle of analyzing the frequency deviation of the reference oscillator under the influence of metal objects that have fallen into the area of the search coil.
Upon careful study of the circuit diagram, you can see that this device is an improved version of the metal detector discussed in the previous section. One of the main distinguishing features of this design is still the analyzer, made on the Q1 quartz element. In addition, in an improved version of the metal detector, in addition to the pointer instrument, an acoustic signaling circuit is used as an indicator.
Since in the proposed circuit (Fig. 2.16) the numbering of elements has been changed, a new element base is used, and an additional cascade has been added, the author considered it necessary to consider its features in more detail.
As in the previous design, the circuitry of this metal detector is based on a measuring generator, a buffer stage, an RF oscillation detector, an analyzer and an indicator device.
The oscillatory circuit of the high-frequency generator, made on the transistor T1, consists of a coil L1 and capacitors C3-C6. The operating frequency of the RF generator depends on the deviation of the inductance of the search coil L1, as well as on the change in the capacitances of the tuning capacitor C4 and the adjusting capacitor C3. In the absence of metal objects near the coil L1, the frequency of oscillations excited in the RF generator must be equal to the frequency of the quartz element Q1, that is, in this case, 1 MHz.
Rice. 2.16.
Schematic diagram of an advanced quartz metal detector
After a metal object is in the coverage area of the search coil L1, its inductance will change. This will change the oscillation frequency of the RF generator. Next, the RF signal is fed to the buffer stage, which ensures the matching of the generator with subsequent circuits. An emitter follower made on a transistor T2 is used as a buffer stage.
From the output of the emitter follower, the RF signal through the adjusting resistor R7 and quartz Q1 goes to the detector, made on the diode D2. Due to the high quality factor of quartz, the slightest changes in the frequency of the measuring oscillator will lead to a decrease in the impedance of the quartz element. As a result, a low-frequency signal is supplied to the input of the DC amplifier (the base of transistor T3), the change in the amplitude of which provides a corresponding deviation of the arrow of the indicator device.
The load of the UPT, made on the transistor T3, is a pointer device with a total deflection current of 1 mA. When the switch S2 is closed, the audio signal generator, made on the transistor T4, is turned on in the load circuit. The metal detector is powered from a source B1 with a voltage of 9 V.
Details and design
As in some designs discussed earlier, any breadboard can be used to make a metal detector with a quartz element. Therefore, the used parts are not subject to any restrictions related to overall dimensions. Installation can be both hinged and printed.
The search coil L1 (fig. 2.17) is similar to the coil used in the metal detector, which was discussed in the previous section.
Instead of transistors of the BC108 type indicated in the diagram, almost any domestic low-power silicon transistors, for example, of the KT315B type, can be used in this design. Instead of a 1N4001 (D2) type diode, it is recommended to use any germanium diode of the D2 or D9 series with any letter index.
Rice. 2.17.
Coil construction L1
As an element Q1, you can use any quartz element with a frequency from 900 kHz to 1.1 MHz. The power source for V1 can be a Krona battery or two 3336L batteries connected in series. The board with the elements located on it and the power supply are placed in any suitable plastic or wooden case. A variable resistor R7, switches S1 and S2, connectors X1 and X2, as well as an indicator PA1 are installed on the housing cover.
The search coil L1 should be installed at the end of a suitable handle 100-120 cm long. The coil is connected to the device board with a multicore shielded cable.
Establishment
The main condition for high-quality tuning of this device is the absence of large-sized metal objects at a distance of at least 1.5 m from the search coil L1.
The direct adjustment of the metal detector should begin with setting the desired frequency of oscillations generated by the RF generator. The RF oscillation frequency must be equal to the frequency of the Q1 quartz element. It is recommended to use a digital frequency meter to make this adjustment. In this case, the frequency value is first roughly set by changing the capacitance of the capacitor C4, and then precisely by adjusting the capacitor C3.
In the absence of a frequency meter, the setting of the RF generator can be carried out according to the readings of the PA1 indicator. Quartz Q1 is an element of communication between the measuring and indicating parts of the device, so its resistance at the time of resonance is high. Thus, the minimum reading of the pointer instrument PA1 will indicate the fine tuning of the oscillations of the RF generator to the frequency of the quartz.
The sensitivity level of this device is regulated by resistor R7.
Operating procedure
In the practical use of this metal detector, the variable resistor R7 should set the arrow of the indicator PA1 to zero on the scale. In this case, to a certain extent, changes in operating modes due to battery discharge, changes in ambient temperature, or deviations in the magnetic properties of the soil are compensated.
If, during operation, any metal object appears in the area of \u200b\u200bthe search coil L1, the arrow of the indicator PA1 will deviate. In this case, when the contacts of switch S2 are closed, an audible signal will appear in the headphones.
A metal detector circuit similar in principle of operation from chapter 2.7 of the book by Adamenko M.V. "Metal Detectors" on the page Quartz metal detector
The entire collection of Adamenko M.V. "Metal detectors" M.2006 can be downloaded from the page Download free books and articles about metal detectors.
Sensitive compact metal detector using a quartz resonator
Metal detectors based on beat registration turn out to be insensitive when searching for metals with weak ferromagnetic properties, such as, for example, copper, tin, silver. It is impossible to increase the sensitivity of metal detectors of this type, since the difference in beat frequencies is hardly noticeable with conventional indication methods. A significant effect is the use of quartz metal detectors. The metal detector, the schematic diagram of which is shown in fig. 1, a, consists of a measuring oscillator, assembled on a transistor VT1, and a buffer stage - an emitter follower, assembled on a transistor VT2, separated by a quartz resonator ZQ1 from an indicator device - a detector on a diode VD2 with a DC amplifier on a transistor VT3. The load of the amplifier is a pointer device with a total deflection current of 1 mA.
Fig.1. (Small size sensitive metal detector)
Due to the high quality factor of the quartz resonator, the slightest changes in the frequency of the measuring oscillator will lead to a decrease in the impedance of the latter, as can be seen from the characteristic shown in Fig. 1b, and this will eventually increase the sensitivity of the device and the accuracy of measurements.
Preparation for the search consists in tuning the oscillator to the parallel resonance frequency of quartz equal to 1 MHz. This setting is made by capacitors of variable capacitance C2 (roughly) and trimmer capacitor C1 (finely) in the absence of metal objects near the frame. Since quartz is an element of communication between the measuring and indicating parts of the device, its resistance at the moment of resonance is large and the minimum reading of the pointer device indicates the fine tuning of the device. The sensitivity level is regulated by a variable resistor R8.
A feature of the device is the ring frame L1, made from a piece of cable. The central core of the cable is removed and six turns of PEL-type wire 0.1-0.2 mm 115 mm long are pulled instead. The design of the frame is shown in fig. 1, a. This frame has a good electrostatic screen.
The rigidity of the frame structure is ensured by placing it between two discs made of plexiglass or getinaks with a diameter of 400 mm and a thickness of 5-7 mm.
The device uses KT315B transistors, a reference diode - a zener diode 2S156A, a detector diode of the D9 type with any letter index. The quartz frequency can be in the frequency range from 90 kHz to 1.1 MHz. Cable - type RK-50.
List of radio elements
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| VT1-VT3 | bipolar transistor | KT315B | 3 | To notepad | ||
| VD1 | zener diode | KS156A | 1 | 2S156A | To notepad | |
| VD2 | Diode | D9 | 1 | With any letter index | To notepad | |
| C1 | Trimmer Capacitor | 2-15 pF | 1 | To notepad | ||
| C2 | variable capacitor | 140-680pF | 1 | To notepad | ||
| C3 | Capacitor | 5100 pF | 1 | To notepad | ||
| C4 | Capacitor | 820 pF | 1 | To notepad | ||
| C5 | Capacitor | 15 pF | 1 | To notepad | ||
| C6, C9 | Capacitor | 0.1uF | 2 | To notepad | ||
| C7, C8 | electrolytic capacitor | 100uF 12V | 2 | To notepad | ||
| R1 | Resistor | 1 kOhm | 1 | To notepad | ||
| R2, R7 | Resistor | 3.9 kOhm | 2 | To notepad | ||
| R3 | Resistor | 15 kOhm | 1 | To notepad | ||
| R4 | Resistor | 12 kOhm | 1 | To notepad | ||
| R5 | Resistor | 330 kOhm | 1 | To notepad | ||
| R6 | Resistor | 560 ohm | 1 | To notepad | ||
| R8 | Variable resistor | 25 kOhm | 1 |
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 on your own can save a lot of money.
Schemes of modern metal detectors can be built according to different principles of operation, we list the most popular of them:
- Beat method (measuring the change in the reference frequency);
- Induction balance at low frequencies;
- Induction balance on spaced coils;
- impulse 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, get the first skills in finding treasures and products made of multi-colored metals.
The metal detector is designed to detect a metal object (well cover, pipe section, hidden wiring). The metal detector consists of a parallel voltage regulator (transistors V1 V2) at a high (about 100 kHz) frequency generator on a transistor V4, an RF oscillation detector (V5) and...
13 5088 6
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 depth of detection. The schematic diagram of the metal detector is shown in the figure. The circuit is assembled on transistors operating in the mode ...
9 4577 1
The scheme of a homemade metal detector on beats, which is built on five microcircuits. Finds a coin 0.25mm at a depth of 5cm, a pistol at a depth of 10cm, a metal helmet at 20cm. A schematic diagram of a beat detector is shown below. The circuit consists of the following units: a crystal oscillator, a measuring oscillator, a synchronous detector, a Schmidt trigger, an indication device...
11 4724 4
The circuit 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. A 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 BF494 type T1 transistor, frequency ...
5 4744 2
This metal detector, despite the small number of parts and ease of manufacture, has a fairly high sensitivity. 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, at a distance of 15 cm. The principle of operation of the device is based on a change in the frequency in the measuring generator under the influence of nearby metals and. ..
18 4600 0
A simple compact metal detector is needed to detect various metal objects in the walls under a layer of plaster (for example, pipes, wires, nails, fittings). This device is completely autonomous, powered by a 9 volt battery type "Krona", 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...
8 4502 0
The scheme of a small-sized, highly economical metal detector with good repeatability and high performance, using widely available and inexpensive parts. An analysis of most common circuits showed that they are all powered by a source with a voltage of at least 9 V (that is, "Krona"), and this is both expensive and uneconomical. So, assembled on a K561LE5 chip ...
18 5140 1
The metal detector circuit does not have any features, it is simple and accessible for repetition even by beginner radio amateurs. As is often written in books and magazines, with proper installation and serviceable parts, it starts working right away. The printed circuit board of the device is shown in the figure, it is made for SMD components, all parts are installed from the foil side, and no drilling is required. Search coil manufacturing requires high...
The scheme of a homemade metal detector on beats, which is built on five microcircuits. Finds a coin 0.25mm at a depth of 5cm, a pistol at a depth of 10cm, a metal helmet at 20cm.
circuit diagram
A schematic diagram of a beat detector is shown below. The scheme consists of the following nodes:
- crystal oscillator,
- measuring generator,
- synchronous detector,
- Schmidt Trigger,
- display device.
The crystal oscillator is implemented on inverters D1.1 - D1.3. The oscillator frequency is stabilized by a quartz or piezoceramic resonator with a resonant frequency of 32768 Hz (clock quartz).
Rice. 1. Schematic diagram of a quartz metal detector on beats.
The R1C2 chain prevents the excitation of the generator at higher harmonics. Through the resistor R2, the OOS circuit is closed, through the resonator Q1, the POS circuit is closed.
The generator is characterized by simplicity, low current consumption from the power source, reliable operation at a supply voltage of 3-15 V, does not contain trimmers and overly high-resistance resistors.
An additional counting trigger D2.1 is needed to generate a signal with a duty cycle exactly equal to 2, which is required for the subsequent synchronous detector circuit.
The measuring generator is implemented on a differential stage on transistors VT1, VT2. The POS circuit is implemented galvanically, which simplifies the circuit. The load of the differential stage is the oscillatory circuit L1C1.
The generation frequency depends on the resonant frequency of the oscillatory circuit and, to some extent, on the mode current of the differential stage. This current is set by resistor R3.
To convert the low-voltage output signal of the differential stage to the standard logic levels of digital CMOS microcircuits, a cascade circuit with a common emitter on a VTZ transistor is used.
The shaper with a Schmidt trigger on the D3.1 element provides steep pulse edges for the normal operation of the subsequent counting trigger.
An additional counting trigger D2.2 is needed to generate a signal with a duty cycle exactly equal to 2, which is required for the subsequent synchronous detector circuit.
The synchronous detector consists of a multiplier implemented on the D4.1 "XOR" element and an integrating chain R6C4. Its output signal is close in shape to a sawtooth, and the frequency of this signal is equal to the difference between the frequencies of the quartz oscillator and the search oscillator.
The Schmidt trigger is implemented on the D3.2 element and generates rectangular pulses from the sawtooth voltage of the synchronous detector.
The display device is simply a powerful buffer inverter, implemented on the three remaining inverters D1.4-D1.6, connected in parallel to increase the load capacity. The load of the display device is the LED and the piezo emitter.
Details
Coil L1 is wound on a mandrel with a diameter of 160 mm, and has 100 turns of PEV wire - 0.2 mm.