How to make a metal detector with your own hands - cost-effective and proven schemes. Do-it-yourself high-sensitivity metal detector Scheme of a metal detector with three transistors and quartz

Even the most serious and respectable citizens, at the word "treasure" experience a slight excitement. We literally walk through treasures, of which there are immeasurably many in our land.

But how do you look under the soil layer to know exactly where to dig?

Professional treasure hunters use expensive equipment, the purchase of which can pay off after one successful find. Archaeologists, builders, geologists, members of search societies - use the equipment provided by the organization in which they work.

But what about novice treasure hunters on a limited budget? You can make a metal detector at home with your own hands.

To understand the subject, consider the design and principle of operation of the device

Popular metal detectors work using the properties of electromagnetic induction. Main components:

• transmitter - generator of electromagnetic oscillations
• transmitting coil, receiving coil (in some models, the coils are combined for compactness)
• electromagnetic wave receiver
• decoder that separates the useful signal from the general background
• signaling device (indicator).

The generator, with the help of a transmitting coil, creates an electromagnetic field (EMF) around it with specified characteristics. The receiver scans the environment and compares the field performance with the reference. If there are no changes, nothing happens in the scheme.

• When a conductor (any metal) enters the zone of action of the field, the base EMF induces Foucault currents in it. These eddy currents create their own electromagnetic field of the object. The receiver determines the distortion of the base EMF and gives a signal to the indicator (sound or visual notification).
• If the object under test is not metallic, but has ferromagnetic properties, it shields the underlying EMF, also causing distortion.

Important! There is an erroneous opinion that the soil in which searches are made should not be electrically conductive.

This is wrong. The main thing is that the electromagnetic or ferromagnetic properties of the medium and search objects should be different from each other.

That is, against the background of certain characteristics of the EMF formed by the search environment, the field of individual objects will stand out.

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 VT1 transistor and a buffer stage - an emitter follower assembled on a VT2 transistor, separated by a ZQ1 quartz resonator from an indicator device - a detector on a VD2 diode with a DC amplifier on a VT3 transistor. 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 getipak 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 Tina D9 detector diode with any letter index. The quartz frequency can be in the frequency range from 90 kHz to 1.1 MHz. Cable - type RK-50.

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 website 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 to assemble 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.

1. Soldering iron, solder, tin and other soldering accessories.
2. Screwdrivers, pliers, wire cutters and other tools.
3. Materials and skills for the manufacture of printed circuit boards.
4. Minimum experience and knowledge in electronics and electrical engineering as well.
5. 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	There is
	Maximum search depth
		There is
	Operating frequency	4 - 17 kHz
	Difficulty level	Average

	Principle of operation	IB
	Metal Discrimination	There is
	Maximum search depth	1-1.5 meters (Depends on coil size)
	Programmable microcontrollers	There is
	Operating frequency	4 - 16 kHz
	Difficulty level	Average

	Principle of operation	IB
	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

Deep type metal detectors are able to detect objects in the ground at a great distance. Modern modifications in stores are quite expensive. However, in this case, you can try to make a metal detector with your own hands. For this purpose, it is first of all recommended to familiarize yourself with the design of the standard modification.

Modification scheme

When assembling a metal detector with your own hands (the diagram is shown below), you need to remember that the main elements of the device are a damper on a microcontroller, a capacitor and a handle with a holder. The control unit in the devices consists of a set of resistors. Some modifications are made on drive modulators that operate at a frequency of 35 Hz. Directly racks are made with narrow and wide plate-shaped plates.

Assembly instructions for a simple model

Assembling a metal detector with your own hands is quite simple. First of all, it is recommended to prepare a tube and attach a handle to it. Installation requires high conductivity resistors. The operating frequency of the device depends on many factors. If we consider modifications on diode capacitors, then they have high sensitivity.

The operating frequency of such metal detectors is about 30 Hz. The maximum detection distance of an object is 25 mm. Modifications are capable of working on lithium-type batteries. Microcontrollers for assembly will be required with a polar filter. Many models fold on open type sensors. It is also worth noting that experts do not recommend using high sensitivity filters. They greatly reduce the accuracy of detecting metal objects.

Model series "Pirate"

You can make a Pirate metal detector with your own hands only on the basis of a wired controller. However, first of all, a microprocessor is prepared for assembly. To connect it, you will need Many experts recommend the use of grid capacitors with a capacitance of 5 pF. Their conductivity should be maintained at a level of 45 microns. After you can start soldering the control unit. The stand must be strong and support the weight of the plate. Plates larger than 5.5 cm in diameter are not recommended for 4V models. System indicators are optional. After fixing the block, it remains only to install the batteries.

Using reflex transistors

Making a do-it-yourself metal detector with reflex transistors is quite simple. First of all, experts recommend installing a microcontroller. Capacitors in this case are suitable for a three-channel type, and their conductivity should not exceed 55 microns. At a voltage of 5 V, they have a resistance of approximately 35 ohms. Resistors in modifications are used mainly of the contact type. They have a negative polarity and cope well with electromagnetic vibrations. It is also worth noting that during assembly it is allowed to use the maximum plate width for such a modification is 5.5 cm.

Model with convection transistors: expert reviews

You can assemble a metal detector with your own hands only on the basis of a collector controller. In this case, capacitors are used at 30 microns. If you believe the reviews of experts, then it is better not to use powerful resistors. In this case, the maximum capacitance of the elements should be 40 pF. After installing the controller, it is worth taking up the control unit.

These metal detectors receive good reviews for reliable protection against wave interference. For this purpose, two diode-type filters are used. Modifications with display systems are very rare among homemade modifications. It is also worth noting that power supplies must operate at low voltage. Thus, the battery will last a long time.

Using Chromatic Resistors

With your own hands? A model with chromatic resistors is quite easy to assemble, but it should be borne in mind that capacitors for modifications are only allowed to be used on fuses. Experts also point out the incompatibility of resistors with feed-through filters. Before starting the assembly, it is important to immediately prepare a tube for the model, which will be a handle. Then the block is installed. It is more expedient to select modifications for 4 microns, which operate at a frequency of 50 Hz. They have a small scattering coefficient and high measurement accuracy. It is also worth noting that seekers of this class will be able to successfully work in conditions of high humidity.

Model with a pulsed zener diode: assembly, reviews

Devices with pulsed zener diodes are distinguished by high conductivity. If you believe the reviews of experts, then home-made modifications are able to work with objects of different sizes. If we talk about the parameters, then their detection accuracy is approximately 89%. It is worth starting the assembly of the device with a rack blank. Then the handle for the model is mounted.

The next step is to install the control unit. Then the controller is mounted, which is powered by lithium batteries. After installing the unit, you can start soldering the capacitors. Their negative resistance should not exceed 45 ohms. Expert reviews indicate that modifications of this type can be made without filters. However, it should be borne in mind that the model will have serious problems with wave interference. This will damage the capacitor. As a result, the battery in models of this type is quickly discharged.

Application of the low frequency transceiver

Low-frequency transceivers in models significantly reduce the accuracy of the devices. However, it is worth noting that modifications of this type are able to successfully work with small objects. At the same time, they have a small self-discharge parameter. In order to assemble the modification with your own hands, it is recommended to use a wired controller. The transmitter is most often used on diodes. Thus, conductivity is provided at around 45 microns with a sensitivity of 3 mV.

Some experts recommend installing mesh filters, which increase the security of models. To raise the conductivity, only transitional type modules are used. The main disadvantage of such devices is the burnout of the controller. With such a breakdown, it is problematic to repair the metal detector with your own hands.

Using a high frequency transceiver

On high-frequency transceivers, you can assemble a simple metal detector with your own hands only on the basis of a transitional controller. Before starting the installation, a rack for the plate is prepared as a standard. The conductivity of the controller is on average 40 microns. Many specialists do not use contact filters when assembling. They have high heat losses and are capable of operating at 50 Hz. It is also worth noting that lithium batteries are used to assemble the metal detector, which recharge the control unit. The sensor itself for modifications is installed through a capacitor, in which the capacitance should not exceed 4 pF.

Longitudinal resonator model

There are often devices with longitudinal resonators on the market. They stand out from their competitors with high accuracy in determining objects, and at the same time they can work in high humidity. In order to independently assemble the model, a stand is prepared, and a plate should be used with a diameter of at least 300 mm.

It is also worth noting that to assemble the device, you will need a contact controller and one expander. Filters are used only on a mesh lining. Many experts recommend installing diode capacitors that operate at a voltage of 14 V. First of all, they discharge the battery a little. It is also worth noting that they have good conductivity compared to field counterparts.

Using Selective Filters

Making such a deep metal detector with your own hands is not easy. The main problem is that a conventional capacitor cannot be installed in the device. It is also worth noting that the modification plate is selected from 25 cm in size. In some cases, the racks are installed with an expander. Many experts advise starting the assembly with the installation of the control unit. It must operate at a frequency of no more than 50 Hz. In this case, the conductivity depends on the controller that is used in the equipment.

Quite often, it is selected with a lining to increase the security of the modification. However, such models often overheat, and are not able to work with high accuracy. To solve this problem, it is recommended to use conventional adapters that are installed under the capacitor units. A do-it-yourself coil for a metal detector is made from a transceiver unit.

Application of contactors

Contactors are installed in the devices together with control units. Racks for modifications are used in short lengths, and plates are selected at 20 and 30 cm. Some experts say that devices should be assembled on impulse adapters. In this case, capacitors can be used with low capacitance.

It is also worth noting that after installing the control unit, it is worth soldering a filter that can operate at a voltage of 15 V. In this case, the model will maintain a conductivity of 13 microns. Transceivers are most often used on adapters. Before turning on the metal detector, the level of negative resistance is checked on the contactor. The specified parameter averages 45 ohms.

If you have a long-wave transistor receiver in good condition, you can easily assemble a simple attachment to it - a metal detector. The metal detector circuit is a conventional LC oscillator, at a frequency of about 140 kHz. The coil of the oscillating circuit L1 is 12 cm in diameter, contains 16 turns of wire (any insulated mounting or varnished winding will do, with a diameter of 0.25 - 0.5 mm). The turns are laid on a platform of plywood of a suitable size and fixed, for example, with glue - "cold welding" or "liquid nails".

Resistors and capacitor - any type, low-power high-frequency transistor, reverse conduction.
Suitable - KT315, KT3102 with any letter. The circuit is assembled on a board made of getinax or textolite, printed wiring is not necessary, the parts can be connected with any insulated mounting wire.

After assembly, the circuit, together with the power source, is located next to the coil on a plywood platform, with a wooden handle of a convenient length. The receiver is attached to the handle and tuned to a reception frequency close to 140 kHz, until a sound resembling a squeak appears. When the coil approaches a metal object, its tone will change.

Despite the simplicity of the scheme, in terms of its sensitivity, such a metal detector is practically not inferior to industrial designs.
With it, metal objects such as a gold ring or a coin can be detected at a depth of up to 20 cm.