A metal detector or metal detector is a device that finds metal-containing objects in a dielectric or low-conductive array. The device helps to detect various metal bodies in the ground, in the array of enclosing structures of buildings and structures, and in the depths of the soil at the bottom of reservoirs. Branded equipment is quite expensive. A do-it-yourself metal detector will cost much less.
A modern electronic device detects the presence of metal objects at a distance. The principle of operation is based on the fact that it picks up its own radio wave reflected from the metal.
When the power is turned on, an electromagnetic field arises in the search device, which is radiated deep into the territory under study. It can be earth, rock, water, wood, or an array of any dielectric. The search coil emits an electromagnetic field.
Eddy currents appear on the upper part of the desired metal. They rush towards, suppressing the electromagnetic field emitted by the metal detector. A sharp drop in the field power of the device fixes its electronic unit. The electronics analyzes the new parameters of the electromagnetic flow and signals the presence of metal.
Gold, silver and copper, unlike iron and nickel, have a higher electrical conductivity. Determining the nature of the metal in the survey area is based on obtaining data on the electrical conductivity of the material.
The difference between simple designs and devices with more sophisticated electronics is that expensive devices determine not only the type of metal, but also the depth of its location, and also have a discrimination option.
Principles of operation of metal detectors
The composition of instrument circuits directly depends on the principle of operation of the metal detector electronics. There are the following types of schemes:
- beating method;
- transmitter-receiver;
- radio frequency;
- pulse-induction;
- resonant-disruptive.
Beat method
This method of action is abbreviated as BFO (beat frequency oscillation). The design of the device is based on an LC generator. Generators of this type have a high frequency stability of the emitted waves.
The LC device receives the actual beat frequency through the search circle coil and compares it with the reference data. The resulting difference is accompanied by a sound signal through the built-in speaker. The frequency used is between 40 and 500 kHz.
BFO devices are characterized by low sensitivity and low level of detuning from wet and mineral soil. The use of this method is most often found in cheap models of domestic production.
transmitter-receiver
The TR/VLF (transmitter-receiver/very low frequency) low-frequency transmitter-receiver has a detection system consisting of 2 coils. They are in the same plane. One of them is in the LC oscillator circuit. When it receives a signal, a low-power signal is reflected at the output of the receiving coil. There is an estimation of the amplitude on the receiving turns and the phase shift between the received and transmitted signal.
VLF-method provides high sensitivity of the device. The metal detector well determines the nature of objects, which occurs due to the evaluation of the characteristics of the phases. The circuitry of the device has a rather complex configuration. Coils must be pre-precisely balanced.
Detuning from the array of the studied medium and discrimination of metal objects is carried out by phase-shifting circuits. The TR/VLF modification analyzes the phase characteristics of electromagnetic fields, which makes it possible to distinguish ferrous metals from their non-ferrous "brothers", to tune out from the earth massif and various extraneous inclusions in its environment.
Metal detectors of this type are characterized by high sensitivity. The resolving quality of the device largely depends on the diameter of the search head. The larger this size, the better the process of detecting metal products in the depth of the array. Based on this principle, the bulk of serial metal detectors are manufactured.
RF
The high-frequency format of the RF device (radio frequency) has 2 coils. They are separated by a certain distance from each other. The emitting coil sends a signal to the outer surface of the target metal. The receiving element captures the reflected signal. The used frequency of radio signals is in the range from 70 to 500 kHz.
A device built according to this principle does not distinguish between the nature of metal bodies, does not “see” small objects. It should be noted that it perfectly recognizes large metal objects at a great distance - in the depths of the array of the studied medium.
Pulse induction
The generator of a pulse-induction device of the PL (pulse induction) format sends a pulsed signal to the oscillatory circuit of the search device. The estimated data is the transition period time - the position of the trailing edge of the voltage pulse. The operating frequency is in the low range - from 50 to 4000 Hz.
resonant disruptive
Disruption of resonance - OR (off resonance) format. The principle of operation of the MI device is based on the method of estimating the magnitude of the signal amplitude in the coil. The circuit is tuned close to resonance with the emitted signal.
The appearance of a metal object in the search zone causes resonance or its complete exclusion. This is marked by an increase or decrease in the amplitude in the oscillatory circuit.
The method is not used in factory-made metal detectors. They are mainly used in the development of home-made amateur radio structures.
What is metal discrimination?
Those who are interested in the structure and principle of operation of metal detectors often come across the expression "metal discrimination" in search of the necessary information. The metal detector discrimination function determines the direction of the search for a particular group of metal objects. Installing a metal detector to detect non-ferrous metals allows you to ignore iron-containing inclusions in the soil mass.
Units equipped with a display can show a discrimination scale from "0" to "99". The more the indicator of the device tends to 0, the lower the electrical conductivity of the found metal object.
In some models, the discrimination ruler is graduated for such types of metals as iron, nickel, zinc, aluminum, gold, copper and silver. The device can make a correction for the inclusion of a ligature in the main composition of the material. The type and amount of ligature in the metal changes its electrical conductivity.
Metals are practically non-existent in their pure form, so there are options in complex high-level devices to "ignore" metals such as iron, nickel and aluminum. The metal detector will respond to the detection of gold, silver and copper.
Selective discrimination of metals allows you to reduce the time spent on detecting unnecessary objects and not wasting energy on digging unnecessary holes.
Assemble a PIRATE metal detector with your own hands
Members of military historical societies, local historians and treasure hunters are often preoccupied with finding cheap models of metal detectors.
The desire to assemble a metal detector with your own hands is primarily caused by an economic factor. The finished product of the factory performance is quite expensive. There are models costing up to several tens of thousands of rubles. The mass media publishes a lot of "recipes" for the manufacture of home-made devices.
To detect metal-containing objects in the ground, you can make a metal detector with a Pirate scheme.
Pirate- an impulsive metal detector with a simple electronic circuit. The name has nothing to do with sea robbers. The Latin abbreviation consists of two abbreviations: PI (impulse principle) and RAT (name of the author's site).
MI PIRATE assembly instructions
To make a homemade metal detector, you need to prepare several items in advance - this is a search circle with a coil, an electronic control unit and a holding rod.
search circle
It can be cut from construction plywood, plastic or other dielectric material. The circle is a rim ø 180 - 210 mm with a winding wire wrapped around it (24 - 25 turns) ø 0.5 mm. To increase the detection distance, the search circuit is made ø 260 - 270 mm and wrapped with the same conductor in the amount of 21-22 turns.
Rod holder
Any dielectric length gauge is used as this part. It can be a wooden holder for gardening tools, mops or a polymer tube. A search circle is attached to the lower end of the rod. At the top, the housing of the electronic control unit is often attached. The length of the rod is determined by the owner of the equipment himself - according to his height.
Control block
For the body of the electronic unit, various box-shaped plastic products are used. The main thing is that the case should be free, but at the same time, the circuit of the device and batteries could fit compactly. The filling of electronics is assembled on the basis of transistors and microcircuits.
Varieties of PIRATE metal detector microcircuits
Of all the known circuits of home-made metal detectors, designs assembled on the following elements are known:
Ne 555
The main control component of the circuit is the Ne 555 microcircuit. As an analogue, a domestically produced microcircuit KR1006VI1 can be used. 
PCB variant on Ne 555 On transistors
PCB variant of a metal detector on transistors Tl 0722 and Ne 555
The electronic unit of the Pirate metal detector is assembled on two microcircuits. This greatly simplifies the circuitry of the device.
K561la7
The basis of the MI circuit is the K561la7 microcircuit. The microprocessor consists of 4 sectors. The first two emit a background of a certain frequency, the 3rd element detects the reflected signal from the desired metal object, and the 4th sector compares the level of the output and receiving frequencies.
Different values of these parameters cause a signal to be sent through the amplifier to the speaker of the device.
The electronic unit is powered by a krone battery. Its capacity is enough to use the device for a long time.
Completing elements for assembling the electronic circuit of the Pirate metal detector on K561la7
- Capacitors are often used used, but it is necessary to check their capacity. Ceramic elements work well. For the manufacture of the scheme, the details will be required:
100 uF - 1 pc.;
1000 pF - 3 pcs.;
22 pF - 2 pcs.;
300 pF - 1 pc. - Used fixed resistors are also used by extracting them from old circuits. They retain their quality characteristics for many years.
22 Ohm - 1 pc.;
1 kOhm - 1 pc.;
4.7 kOhm - 1 pc.;
10 kOM - 1 pc.;
470 kOhm - 1 pc. - Variable resistors are best bought at an electrical supermarket or on the radio market:
1.5 kOhm - 1 pc., 20 kOhm - 1 pc. - The K561la7 chip is enclosed in a protective DIP case. The legs are numbered from the notch on the microcircuit case, starting counterclockwise.
- The KT-315 transistor can be replaced with KT3102, BC546, or similar low-frequency similar elements. Looking at the front of the transistor, the conclusions are distinguished, from right to left - the emitter, collector and base.
- The diode can be selected from such radio components as: kd522B, kd105, kd106. Before soldering, the diode must be ringed in order to accurately distinguish the anode from the cathode.
- As a signaling device, you can use the headphones of an mp 3 player or something similar.
- Power supply - battery type krone 9 v. and contact group.
DIY underwater metal detector
A model of this type in the factory version costs a lot of money. Making it yourself is a tempting prospect. With its help, on the seabed among boulders and pebbles, it is quite possible to find dropped valuable items - rings, chains of gold and silver, and so on. With the help of such devices, many artifacts of considerable value were found.
The schemes of the structure of electronic blocks are used the same as for land-based counterparts, but with some features. This requires ensuring the complete tightness of the device. The coil is covered with sealed insulating materials, up to the use of epoxy resin.
Small-diameter PVC pipes are used as the casing. Pipes perform two functions at the same time - the housing of the electronic unit and the holding rod.
An electronic circuit with connectors for connecting power and the batteries themselves are placed in the pipe. A variable resistor is fixed on the head of the connectors - to change the sensitivity
It is very important to make a hermetic blockage of the end hole of the pipe in such a way that the screw of the plug enters the connection with the head of the variable resistor.
Light-emitting diodes (LEDs) are used as signaling devices for detecting metals. They have to be powered from the built-in speaker inside the case. When the desired metal enters the field of the coil, the light indicators react with their glow.
Some craftsmen make models with external control of the device using a magnet. By passing a magnet along the body of the metal detector, the operating mode of the device is changed.
Conclusion
Owning a homemade metal detector causes a craving to explore the world around you. If the study of certain places in nature does not lead the owner of the device to enrichment, then it will certainly bring great benefits for healing the body through long walks in the fresh air.
Powered by pirat metal detector, from 12 volts, you can use ordinary batteries, but of course it’s better to take a good battery, for example, from a screwdriver. Personally, I use it, or rather the batteries that are in it.
search coil metal detector pirate, wound on a frame 190 mm. and contains 25 wires, PEV wires 0.5 mm.
- Current consumption 30-40 mA
Diagram of the Pirat metal detector:
Chip NE555:
Transistor IRF740:
Variable resistors:
Here's how it should turn out:
For K157UD2 it is better to put an adapter socket, and for NE555 you can put it too, it won't hurt!))
The lady conducted the tests on an average coil with a diameter of 15 cm. So the golden ring caught 18 cm through the air, scissors 30 cm. table lamp 50cm. which is not bad enoughThe scheme of the Pirate metal detector is very simple and understandable even for novice radio amateurs. It consists of two chips that do not need to be flashed or programmed. It is very easy to assemble, you just need to solder all the parts in the right places!))
Attention! I make to order MD "Pirate", write to Skype kavinskiy or write comments! Thank you!
The pirat metal detector is powered by 12 volts, you can use ordinary batteries, but it’s better to take a good battery, for example, from a screwdriver. Personally, I use it, or rather the batteries that are in it.
Pirat metal detector search coil wound on a 190 mm frame. and contains 25 wires, PEV wires 0.5 mm.
Metal detector characteristics:
Current consumption 30-40 mA
Reacts to all metals, no discrimination
Sensitivity 25 mm coin - 20 cm
Large metal objects - 150 cm
All parts are inexpensive and readily available.
Required parts for assembly:
pirate_detali
Diagram of the Pirat metal detector:
ON LE2 (1)
The circuit uses 2 microcircuits (NE555 and K157UD2). They are quite common. K157UD2 - you can pick it out of the old equipment, which I did with success.
pirate_microshema1
Chip NE555:
NE555N
Transistor IRF740:
pirate_transistor_1
Variable resistors:
pirate_resistor_1
Capacitors 100nF must be taken film, like this, we take the voltage as little as possible:
pirate_condensatori
We print a sketch of the board on plain paper:
pirate_pechatka_1
We cut out a piece of textolite to fit its size:
pirate_pechatka_2
We apply it tightly and with a sharp object we push through the places of future holes:
pirate_pechatka_2
Here's how it should turn out:
pirate_pechatka_3
pirate_pechatka_4
pirate_pechatka_5
After drilling, you need to draw tracks. You can do this through photoresist, LUT, or simply paint them with Nitro varnish with a simple brush. The tracks should turn out exactly the same as on the paper template. And we charge a fee.
pirate_pechatka_6
pirate_pechatka_7
pirate_pechatka_8
For K157UD2 it is better to install an adapter socket, and for NE555 you can also install it, it won't hurt!))
pirate_montag_1
pirate_montag_2
pirate_montag_3
To wind the search coil, you need a copper wire with a diameter of 0.5-0.7 mm
pirate_provod
I wound the coil on a simple pan, 190 mm in diameter. after which, wrapped everything with tape:
pirate_katuschka
According to the scheme, the coil is 19 cm in diameter and contains 25 turns. I note right away that the coil must be made of such a diameter based on what you will be looking for. The larger the coil, the deeper the search, but a large coil does not see small details well. The small coil sees small details well, but the depth is not great.
I immediately wound myself three coils 23cm (25 turns), 15cm (17 turns) and 10cm (13-15 turns). If you need to dig up scrap metal, then we put a large one, if you look for small things on the beach, then the coil is smaller, well, you'll figure it out yourself.
pirate_katuschka_3
pirate_katuschka_2
The coil should be as flat as possible. The speaker took the first one that came across.
Now we connect everything and try the circuit for performance.
After applying power, you need to wait 15-20 seconds until the circuit warms up. We put the coil away from any metal, it is best to hang it in the air. After we start twisting the 100K variable resistor until clicks appear. As soon as the clicks appear, twist in the opposite direction, as soon as the clicks disappear, that's enough. After that, we also adjust the 10K resistor.
At the expense of the K157UD2 chip. In addition to the one I dug out, I asked a neighbor for 1 more and bought two at the radio market. I inserted the purchased microcircuits, turned on the device, but it refused to work. I racked my brains for a long time, until I just put another microcircuit (the one that I soldered). And everything immediately worked. So that's what a transitional socket is for, in order to pick up a live microcircuit and do not suffer with soldering and soldering.
Everything is ready, it remains only to make a bar and place the board in the case and in search of treasures)
pirate_ready
And finally, I throw a video of the work of the pirate!
The lady conducted the tests on an average coil with a diameter of 15 cm. So the golden ring caught 18 cm through the air, scissors 30 cm. table lamp 50cm. which is not bad enough for such a metal detector.
You can download the printed circuit board in Sprint-Layout format here!for such a metal detector.
Metal detector circuit board
You can download the printed circuit board in Sprint-Layout format!
The metal detector market is represented by a large number of models from different companies. The cost of individual copies can be several times higher than the price of basic versions. The deeper the device searches, the more expensive it is. Not every metal detector, for example, is able to find a small coin lying at a depth of only 5 cm. The presence of a metal recognizer and a display for adjusting the operation of the metal detector also increase the price of devices.
The simplest model of a metal detector - a pirate - can be assembled by hand. The circuit is so simple that even a novice radio amateur can handle it. The name of the device comes from the abbreviation of the English word for impulse (PI) and the site on which the circuit was first posted for free access (RAT - radioskot.ru). A pirate is able to find coins at a depth of up to 20 cm. For larger objects, an indicator of 180 cm is also possible. The only problem is that this model cannot be used in soil contaminated with heterogeneous metal: there is no pirate metal detector circuit with metal discrimination.
Assembly materials and tools
Stock up on the following a set of radio components and materials:
- chip KR1006VI1 or imported NE 555 - the basis of the future assembly;
- transistor IRF 740;
- chip K157UD2, transistor VS547 - the basis for the receiving node;
- wire PEV 0.5 - for the manufacture of the coil;
- NPN transistors;
- materials for the manufacture of the case.
Tools required for mounting a metal detector:
- soldering iron;
- insulating tape;
- drill 1 mm.
A diagram with a set of other parts can be downloaded below.
For the electronic circuit, you will also need a plastic box. For the manufacture of the rod to which the coil will be attached, it is necessary to purchase a piece of plastic pipe.
Step by step assembly of a metal detector
PCB manufacturing
We start with the most difficult - electronics. According to the instructions, we will make a printed circuit board. There are several options for this part, depending on the radio elements involved. This is a board for the NE 555 chip, and a variant for transistors. We find a sketch on the network and print it on a sheet of paper. According to these dimensions, we cut out a piece of textolite. We impose a sketch on the workpiece and outline the locations of future holes. We drill the workpiece with a drill or drilling machine. Then we draw tracks using photoresist or LUT (laser-ironing technology).
Another option is to paint them with a brush using nitrolac. Tracks must exactly repeat the scheme. At the last stage, we poison the board with hydrogen peroxide.
Mounting radio elements on the board
Soldering the elements to the board, strictly adhering to the chosen scheme. Do not forget about the need for capacitors, which ensure the stable operation of the device, which is especially important in the spring and autumn seasons, when a sharp temperature drop is possible.
In this assembly, film capacitors.
The metal detector needs a 9 - 12 volt power source. Note that the device is energy-consuming due to considerable power. Therefore, it is necessary to use 2 - 3 batteries in parallel or, much more preferably, a rechargeable battery.
Coil
Since the metal detector is pulsed, the accuracy when assembling the coil is not very important. The diameter of the frame is on average 190 - 200 mm. The number of turns of the coil is 25. The turns must be well insulated, so we wrap the part tightly with electrical tape. To increase the detection depth, it is necessary to increase the diameter of the frame (260 - 270 mm), and limit the number of coils (up to 22). The cross section of the used wire is 0.5 mm.
The next step is to mount the coil on a rigid base (it should not be made of metal). Look for a suitable rounded case that will protect this part of the metal detector during search work.
The conclusions from the coil must be soldered to a stranded wire (0.5 - 0.75 mm). It would be preferable to use two separate wires twisted together.
Machine setup
If the metal detector is built exactly according to the scheme, it will not require additional adjustment: it is at maximum sensitivity. For fine adjustment, it is necessary to twist the resistor R 13 so that distinct, infrequent clicks are heard. If such a result is possible only with extreme unscrewing of the resistor, then there is a need to change the value of the resistor R 12. The device is tuned with the middle position of the resistor.
If you have an oscilloscope, you need to measure the frequency at the gate of transistor T2. The pulse duration should be 130 - 150 µs, and the operating frequency - 120 - 150 Hz.
The turned on device must stabilize, for this it needs up to about 20 seconds. Then we carry out tuning with the help of a resistor and proceed to search work.
The Pirate metal detector circuit is very popular and understandable even to a beginner radio amateur. The Pirate metal detector has quite good characteristics, despite the simplicity of the circuit and the availability of parts. It is easy to assemble, in an evening, it does not require any settings or firmware, it starts working immediately after assembly! Below I will present detailed instructions for assembling the Pirate metal detector!
Specifications MD Pirate:
Current consumption 30-40 mA
Supply voltage 9-14 volts
No discrimination, reacts to all metals
Sensitivity coin 25 millimeters - 20 cm
Large metal objects - 150 cm
Nutrition:
The Pirat metal detector requires a voltage of 9-14 volts. You can use ordinary batteries or AA batteries or two crowns connected in parallel, but I would advise you to spend some money and buy a battery for an uninterruptible power supply, it can be easily mounted on a metal detector rod and the charge will last for a long time. You can also use a battery from a screwdriver, by the way, at first, I used it!
Coil:
The search coil for the Pirate metal detector is also easy to make. Wound on a frame 190 mm. and contains 25 turns of PEV wire 0.5 mm. The coil can be wound on an embroidery hoop, by the way, this method is quite common. Personally, I take an ordinary pan, wind a coil on it and tighten it all with electrical tape, then I make a frame out of thin plywood and fix it on it. Here, as they say, to each his own, to whom it is convenient.
Required details:
Pirate metal detector scheme:
The pirate metal detector consists of a transmitting and receiving nodes. The transmitting node consists of a pulse generator, which is assembled on an NE555 chip and a powerful key, on an IRF740 transistor. The receiving node consists of a K157UD2 chip and a BC547 transistor.
In fact, the details are quite common, but if you still couldn’t find them, try using analogues. The NE555 timer can be replaced with a domestic analog KR1006VI1. Instead of the IRF740 transistor, you can put any bipolar NPN structure with N ke not lower than 200 volts, you can even drop it from an energy-saving lamp or charging from a phone, in extreme cases, even KT817 will do. Transistors BC557 and BC547, for domestic KT3107 and KT3102. The K157UD2 operational amplifier has a complete analogue of the KR1434UD1V, it can also be replaced with an imported TL072, but in this case, you will need to redo the board pinout, since it has 8 legs. I also have a Pirate metal detector on TL072, the circuit and the board are in the general archive. By the way, the pulse generator can also be assembled on transistors:
A little about the details:
Chip K157UD2 and K157UD3
Chip NE555 
Transistor IRF740 
Film capacitors
Correct connection of resistors.
Pirate metal detector assembly:
To get started, of course, you need to prepare a fee. To do this, open the Sprint-Layout program and print the blank of our future board, then transfer the drawing in any convenient way to the prepared board, etch it and drill holes for the parts. I use LUT technology, although I don’t have a laser printer, I do it at work.
But when it is not possible to print on a laser printer, you can make a drawing on an inkjet printer, then cut off the fiberglass of the desired shape, attach the drawing to the board and mark the holes with a sharp object, then drill and draw the tracks manually with a permanent marker. Well, or through a carbon copy to translate.
Be sure to clean the board with fine sandpaper and degrease with acetone before applying the pattern, so the image will translate well and the etching process will be faster and more reliable. After the board is etched, it is necessary to erase the toner or marker again with acetone and rub it a little with sandpaper.
Then we take a soldering iron and tin the tracks with tin. After tinning, be sure to wipe off excess rosin with acetone in order to avoid problems in the future. If desired, you can ring the tracks.
Now you need to solder all the details on the board. To do this, we also open the signet in the Sprint-Layout program and see where which parts are located. I strongly advise you to put IC sockets, just in case. First of all, solder the jumpers, there are 2 of them in the circuit, and one is under the NE555 chip, so if you forget about it, it will be difficult to find a malfunction, because I'm sure you won't remember these jumpers! As a jumper, legs from resistors are suitable.
When all the details are in place, it remains only to solder the taps to the variable resistors, coil, speaker and power.
A correctly assembled circuit starts working immediately, without any settings.
The coil, as I said above, is wound on a rim 19-22 cm and contains 25 turns. To search for smaller objects, you can wind a coil of less than 15 cm - 17 turns or 10 cm - 13 turns. To search for ferrous metal, of course, it is better to use a coil with a diameter of 19 cm.
I want to say a few words about the tone of the sound. He seemed too rude to me. You can change the tone by selecting capacitor C1, I replaced it with 47nf and the sound became higher.
It is better to take a speaker of the type 3GDSH TRYD 4070-02 8Ohm so the sound will be much more powerful, I replaced the old speaker in my metal detector with it. Also, the speakers from the headphones do a very good job.
A link to the circuit board, as well as a list of parts needed to assemble the Pirate, which can be bought very cheaply on AliExpress with free shipping, are at the end of the video article!
And finally, a video of the work of the Pirate metal detector:
Do-it-yourself Pirate metal detector assembly description, 3 types of suitable boards, answers to popular questions about proper soldering. 3 nuances about soldering boards + TEST for somo verification.
TEST:
small test- What circuits are most suitable for use on a metal detector?
a) Transistor or NE555.
b) KR 1006 VI1, NE555 or Am2504.
- What is the preferred scheme to install on a Pirate and why?
a) Transistor - it will increase the range of the device.
b) NE555 as it will provide better stability in operation.
- What power source is connected to the board for the operation of the metal detector?
a) One Krona battery.
b) Four Kron batteries connected in parallel.
c) One battery.
- When assembling an apparatus on a transistor, what does the resistor R1 mean?
a) Generation frequency.
b) Pulse duration.
Answers:
- a) To assemble a metal detector with your own hands, it is advisable to use a transistor board or NE555.
- b) It is preferable to use the NE555 board for installation on the detector. Thus, the operation of the equipment is significantly stabilized.
- b), c) For the normal functioning of the metal detector, a power source is used in the form of four Kron batteries connected to each other or one battery. Both sources are suitable, but for simplicity they put a battery and do not waste time connecting the batteries.
- a) R1 on the transistor means the generation frequency. The pulse length is denoted as R2.
Definition: The Pirate (MP) metal detector is a pulse-type device with a scheme that is understandable for self-assembly. The metal detector consists of a small number of elements and a coil.
If you use a coil of 280 mm, then the coins are at a distance of up to 20 cm, and large metal - up to 1.5 meters.
The metal detector got its name from the manufacturers of the circuit - PI, which means impulse action. RAT stands for Radio Cattle, the manufacturer's website.
Many searchers are interested in how to set up a Pirate Metal Detector for coins. A self-assembled apparatus does not distinguish between metals and coins at a distance, but with the help of it they learn to look for metal parts. For beginners, this is a good experience. Also a big advantage of the Pirate model is the ease of assembly and the fact that all components are easy to find. In addition, parts are inexpensive and are sold at any radio store.
Also, it is not necessary to install various programmable elements on the Pirate, and this will greatly simplify the life of radio amateurs. Even if a person is extremely superficially familiar with the process of assembling electrical equipment, it will not be difficult for him to assemble a metal detector with his own hands.
How to make a Pirate Metal Detector with your own hands? We pass the test and follow the instructions.
Pirat Metal Detector Parts List for NE555 Circuit
This Pirate Metal Detector radio kit is suitable for NE555 circuit.
Radio components are very easy to find in old electronics. And if not enough - there are many specialized stores.
Also for assembly you need to find additional parts and tools:
- The wire that will be wound on the coil. Suitable PEV 0.5.
- Chip NE555. It will install a node for transmission.
- Plastic material for making the case.
- Tape or duct tape.
- Small soldering iron.
Having found everything you need, just assemble the Pirate Metal Detector with your own hands at home.
2 detailed schemes for assembling the MP with your own hands
To assemble the Pirate metal detector, 2 schemes are used. For the first option, you need to find the NE555 chip - it was used in Soviet times and it was an analogue of the KR 1006 VI1.
NE555But if it is not possible to find NE, then a transistor circuit is used. It is advisable to still try to get NE555, since the stability of the vehicle will increase significantly.
If there is a desire to assemble an apparatus on a transistor, then you will also have to choose the duration and frequency. Such transistors have a variety of parameters. You need to use an oscilloscope. Resistor R1 - generation frequency. R2 is the pulse range.
2 printed circuit boards of the Pirate metal detector: sorting it out on the shelves
After soldering the board, you need to connect the power.
If you wish, you can use Crowns connected to each other. 4 pieces are enough for normal operation. But it is easier to connect one battery (9V).
In the case of using a battery, it must be borne in mind that one will not be enough, since the voltage will often drop, and this will cause a tuning failure.
If you examine the soldered finished board, then you need to look at the capacitors located on the left side. They are film-like, having great thermal stability. If you install them, it will positively affect the stability of the device.
More board options:
- PCB for MP on tl072.
- PCB on MP sprint layout.
- MP and microchip with gong.
- K157ud2. Sometimes people are interested in how to replace k157ud2 in MP. The KR1434UD1A board will do.
Board example
3 nuances of making a basket coil for MP with your own hands
It is not difficult to make a coil for MP with your own hands. The high accuracy of the coil assembly does not play a big role if it is used on impulse equipment. Not everyone knows how to wind a coil on an MP - it is simply wound on a two-hundred-millimeter mandrel or a little less. It is necessary to use 25 turns of enamel wire with a diameter of 0.5 mm.
- The coils will need to be processed with electrical tape.
- To increase the depth of the search for metals, a coil of 270 mm is wound - 22 turns with the same wiring.
- To calculate the coil, it is advisable to study the parameter table for different sizes. It is better to use a wire having a diameter of 0.5-0.6 mm. But if they could not be found, then 0.4 mm will do. The table shows the sensor diameters, number of turns, section diameter/wiring, inductance and resistance.
In order for the Pirate Metal Detector to work without interruption, we fix the coil in a housing that does not contain any metal. In the image, the author of the work used a polypropylene cabin. This is a very good option without the use of metal inside. In this matter, the masters are given complete freedom of creativity - the main thing is that there is no metal.
Any body made of plastic material is used. Also, some people, to save time, wrap the product with electrical tape or tape. But this option does not look too aesthetically pleasing, and therefore it is still preferable to take a plastic tube as a basis - the choice is very wide and it will not be difficult to find the right one in the nearest plumbing store.
When making a plastic frame, we completely exclude impacts on the ground and grass at the site of the search for metal parts. The housing for the MP coil can be found on the net. Many aesthetes order products used on factory units and put them on their homemade products - thus achieving the aesthetic beauty of the product.
When assembling the coils, the use of metal should be avoided - it will interfere with the work on the search and it will not work to achieve its goal. This will have an extremely negative effect on the equipment. The conclusions from the coil must be soldered to a wire with several cores. It should have a cross-sectional diameter of 0.5 mm or a little more. Ideally, these should be several wires twisted together.
Homemade coil for MP is ready. Assembling a Pirate Metal Detector with your own hands is not as difficult as it might seem. And do not forget that, first of all, a metal detector is made for a specific purpose - metal search. And therefore, choosing a certain special design of the coil is superfluous. Only aesthetes and perfectionists should think about this. A coil wrapped with tape will give the same result as a part in a factory case.
Do-it-yourself metal detector "Pirate"
2 nuances about setting up and working with equipment
If the metal detector is assembled without errors, then there is practically no need to adjust it. Many are wondering how to increase the sensitivity of the Pirate Metal Detector. This can be achieved when small clicks begin to sound in the column. When it happens at the extreme points of the resistor, then the value of R12 is changed to the middle position. This is the only way to increase the sensitivity of the MP.
The oscilloscope controls: the frequency of the generator, the duration of the pulse. The pulse is 130-150 µs, and the ideal frequency is 120-150 Hz.
Working with a metal detector
Turn on. It will take half a minute to stabilize, after which the resistor R13 must be adjusted. After all the manipulations, we begin the search for metal.
How to avoid 4 mistakes
The Pirate metal detector is a simple device, and therefore it cannot have many malfunctions and they are quickly eliminated.
- When overheating or incorrect operation of the device occurs, you must immediately make sure that the ratings of all parts and assembly are correct.
- There are situations when the sound comes from the device, but it does not react to metals. The reason is T1, or diode D1. To fix the problem, the parts will have to be replaced with serviceable ones.
- The IRF740 is heating up. It is necessary to inspect the resistor R6. If it has the correct value, then lower it. For example, when it was 150th, then we set it to 100th. To better solve the problem, we use a variable resistor with a value of 200 ohms. Next, you should choose such a resistance so that the IRF740 stops heating up. After the necessary selection of resistance, we make sealing.
- T3 heats up, or burned out. Such a nuisance happens due to the fact that the master chose the wrong speaker. The resistance of a good speaker should be 8 ohms, the power should be 0.5 w.
The use of such tips in most cases helps to cope with all problems.
It is also important to know 3 nuances about soldering boards
To solder wires and boards, you need to know about several important nuances of work:
- Before starting the operation, it is imperative to choose a suitable soldering iron. The range of equipment for soldering boards is 15-30 watts. Above can not be used, otherwise the board will burn. An acoustic unit is ideal for work because of its small size and low degree of heating.
- To properly solder the board, it must be very well cleaned. This is how a strong connection is achieved. A soapy solution is prepared for processing, and then the entire surface is wiped with a napkin. The metal after processing is qualitatively wiped from soap. Sometimes dense deposits are noticeable on the boards - they are removed with a special compound sold in an electrician's store. The area must be very well cleaned until a shine appears.
- Contacts on the board must be correctly positioned. First, small resistors are connected, and then we move on to large parts.
TOP 3 soldering irons for circuit boards
For high-quality processing of the board, you should use a soldering machine. The best manufacturers:
- Ersa is a German company. Fingers are expensive and need to be purchased for professional use.
- Chinese devices Quick are not inferior in quality, but the prices are much lower.
- Budget option Luckey. Ideal for beginners.
Answers to 5 frequently asked questions about board soldering
- How long do you need to keep the soldering iron for a secure fit?- 3-4 seconds is enough.
- Do you need to add a lot of solder?- The main thing is to completely cover the contact with them. If a drop does this, then this amount is enough.
- What color should the solder be - shiny or matte?- Closer to the first option.
- Need to use protective equipment?- Be sure to wear goggles so that the hot part does not get into the eye.
- What temperature can the chip withstand?- No more than 230 degrees.
It is easy to assemble all the parts for the Pirate Metal Detector with your own hands if you follow the instructions. Reviews and characteristics on the MP are mostly positive.
If there are still ambiguities on the manufacture of the Pirate Metal Detector with your own hands, then a detailed video instruction on the Internet will answer the remaining questions.
Homemade MP, made by hand, is perfect for a beginner.