Pulse metal detector “Pirate. Simple pulse metal detector “pirate” Schemes of simple metal detectors on ne555 ne

With the onset of spring, more and more often you can see people with metal detectors on the banks of rivers. Most of them are engaged in “gold mining” purely out of curiosity and passion. But a certain percentage actually earn a lot of money from searching for rare things. The secret to the success of such research is not only in experience, information and intuition, but also in the quality of the equipment with which they are equipped. A professional instrument is expensive, and if you have a basic knowledge of radio mechanics, you have probably thought more than once about how to make a metal detector with your own hands. The editors of the site will come to your aid and tell you today how to assemble the device yourself using diagrams.

Read in the article:

Metal detector and its structure

This model costs more than 32,000 rubles, and, of course, non-professionals will not be able to afford such a device. Therefore, we suggest studying the design of a metal detector in order to assemble a variation of such a device yourself. So, the simplest metal detector consists of the following elements.

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 metal detector works like this: the magnetic field lines of the primary field (A) of red color pass through the metal object (B) and create a secondary field (green lines) in it. This secondary field is picked up by the receiver and the detector sends an audible signal to the operator. Based on the principle of operation of emitters, electronic devices of this type can be divided into:

1. Simple, working on the “receive-transmit” principle.
2. Induction.
3. Pulse.
4. Generating.

The cheapest devices belong to the first type.

An induction metal detector has one coil that sends and receives a signal simultaneously. But devices with pulse induction differ in that they generate a transmitter current, which turns on for a while and then turns off abruptly. The coil field generates pulsed eddy currents in the object, which are detected by analyzing the attenuation of the pulse induced in the receiver coil. This cycle repeats continuously, perhaps hundreds of thousands of times per second.

How does a metal detector work depending on its purpose and technical device?

The operating principle of a metal detector varies depending on the type of device. Let's consider the main ones:

• Dynamic type devices. The simplest type of device that continuously scans the field. The main feature of working with such a device is that you must be in motion all the time, otherwise the signal will disappear. Such devices are easy to use, however, they are poorly sensitive.
• Pulse type devices. They have great sensitivity. Often, such a device comes with several additional coils for adjustment to different types of soils and metals. Requires certain skills to set up. Among the devices of this class we can distinguish electronic devices operating at low frequencies - no higher than 3 kHz.

• Electronic devices, on the one hand, do not give a reaction (or give a weak one) to unwanted signals: wet sand, small pieces of metal, shot, for example, and, on the other hand, they provide good sensitivity when searching for hidden water pipes and central heating routes, as well as coins and other metal objects.
• Depth detectors designed to search for objects located at impressive depths. They can detect metal objects at a depth of up to 6 meters, while other models “pierce” only up to 3. For example, the Jeohunter 3D depth detector is capable of searching and detecting voids and metals, while showing objects found in the ground in 3- measured form.

Depth detectors operate on two coils, one is parallel to the ground surface, the other is perpendicular.

• Stationary detectors- these are frames established at particularly important protected sites. They detect any metal objects in people's bags and pockets that pass through the circuit.

Which metal detectors are suitable for making yourself at home?

The simplest devices that you can assemble yourself include devices that operate on the principle of reception and transmission. There are schemes that even a novice radio amateur can do; for this you just need to select a certain set of parts.

There are many video instructions on the Internet with detailed explanations of how to make a simple metal detector with your own hands. Here are the most popular ones:

1. Metal detector "Pirate".
2. Metal detector - butterfly.
3. Emitter without microcircuits (IC).
4. Series of metal detectors "Terminator".

However, despite the fact that some entertainers are trying to offer systems for assembling a metal detector from a phone, such designs will not pass the battle test. It’s easier to buy a children’s metal detector toy, it will be more useful.

And now more about how to make a simple metal detector with your own hands using the example of the “Pirate” design.

Homemade metal detector “Pirate”: diagram and detailed description of the assembly

Homemade products based on the “Pirate” series metal detector are among the most popular among radio amateurs. Thanks to the good performance of the device, it can “detect” an object at a depth of 200 mm (for small items) and 1500 mm (large items).

Parts for assembling a metal detector

The Pirate metal detector is a pulse type device. To make the device you will need to purchase:

1. Materials for making the body, rod (you can use a plastic pipe), holder, and so on.
2. Wires and electrical tape.
3. Headphones (suitable for the player).
4. Transistors – 3 pieces: BC557, IRF740, BC547.
5. Microcircuits: K157UD2 and NE
6. Ceramic capacitor - 1 nF.
7. 2 film capacitors - 100 nF.
8. Electrolytic capacitors: 10 μF (16 V) – 2 pieces, 2200 μF (16 V) – 1 piece, 1 μF (16 V) – 2 pieces, 220 μF (16 V) – 1 piece.
9. Resistors – 7 pieces per 1; 1.6; 47; 62; 100; 120; 470 kOhm and 6 pieces for 10, 100, 150, 220, 470, 390 Ohm, 2 pieces for 2 Ohm.
10. 2 diodes 1N148.

DIY metal detector circuits

The classic circuit of the “Pirate” series metal detector is built using the NE555 microcircuit. 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.

The board can be placed in a simple junction box, which can be purchased at an electrical store. If such a tool is not enough for you, you can try to make a more advanced device; a diagram for making a gold-oriented metal detector will help you.

How to assemble a metal detector without using microcircuits

This device uses Soviet-style transistors KT-361 and KT-315 to generate signals (you can use similar radio components).

How to assemble a metal detector circuit board with your own hands

The pulse generator is assembled on the NE555 chip. By selecting C1 and 2 and R2 and 3, the frequency is adjusted. The pulses obtained as a result of scanning are transmitted to transistor T1, and it transmits the signal to transistor T2. The audio frequency is amplified using the BC547 transistor to the collector, and headphones are connected.

To place radio components, a printed circuit is used, which can be easily made independently. To do this, we use a piece of sheet getinax covered with copper electrical foil. We transfer the connecting parts onto it, mark the fastening points, and drill holes. We cover the tracks with a protective varnish, and after drying, we lower the future board into ferric chloride for etching. This is necessary to remove unprotected areas of copper foil.

How to make a metal detector coil with your own hands

For the base you will need a ring with a diameter of about 200 mm (ordinary wooden hoops can be used as the base), on which 0.5 mm wire is wound. To increase the depth of metal detection, the coil frame should be in the range of 260−270 mm, and the number of turns should be 21−22 vol. If you don't have anything suitable on hand, you can wind a reel on a wooden base.

Copper wire spool on wooden base

Illustration	Description of action
	For winding, prepare a board with guides. The distance between them is equal to the diameter of the base on which you will attach the reel.
	Wind the wire around the perimeter of the fastenings in 20-30 turns. Secure the winding with electrical tape in several places.
	Remove the winding from the base and give it a rounded shape; if necessary, additionally fasten the winding in several more places.
	Connect the circuit to the device and test its operation.

Twisted pair coil in 5 minutes

We will need: 1 twisted pair 5 cat 24 AVG (2.5 mm), knife, soldering iron, solder and multitester.

Illustration	Description of action
	Twist the wire into two skeins. Leave 10 cm on each side.
	Strip the winding and free the wires for connection.
	We connect the wires according to the diagram.
	For better fastening, solder them with a soldering iron.
	Test the coil in the same manner as the copper wire device. The winding terminals must be soldered to a stranded wire with a diameter in the range of 0.5-0.7 mm.

Brief instructions for setting up a DIY metal detector “Pirate”

Once the main elements of the metal detector are ready, we proceed to assembly. We attach all the components to the metal detector rod: the body with the coil, the receiving and transmitting unit and the handle. If you did everything correctly, then additional manipulations with 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.

Is it possible to make an underwater metal detector with your own hands?

The principle of assembling an underwater metal detector is no different from a conventional one, with the only difference being that you will have to work hard to create an impenetrable shell using sealant, as well as to place special light indicators that can report a find from under water. An example of how this will work is in the video:

Do-it-yourself metal detector “Terminator 3”: detailed diagram and video instructions for assembly

The Terminator 3 metal detector has occupied an honorable place among homemade metal detectors for many years. The two-tone device operates on the principle of induction balance.

Its main features are: low power consumption, metal discrimination, non-ferrous metals mode, gold only mode and very good search depth characteristics, compared to semi-professional branded metal detectors. We offer you the most detailed description of the assembly of such a device from folk craftsman Viktor Goncharov.

How to make a metal detector with your own hands with metal discrimination

Metal discrimination is the ability of the device to distinguish between the detected material and classify it. Discrimination is based on different electrical conductivities of metals. 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.

Learn how to make a homemade professional metal detector using improvised materials in this video:

Features of deep metal detectors

Metal detectors of this type can detect objects at great depths. A good metal detector, made by yourself, looks to a depth of 6 meters. However, in this case the size of the find must be substantial. These detectors work best for detecting old shells or large enough debris.

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, however, in this case, the efficiency and focus of the search is reduced. The second version of the detector is a point detector; it works directed inward over a small diameter. You need to work with it slowly and carefully. If your goal is to build such a metal detector, the following video can tell you how to do it.

If you have experience in assembling such a device and using it, tell others about it!

The other day, while surfing the Internet, I came across an interesting and very simple circuit for a metal detector, built on the basis of a 555 timer, a coil and several additional components. The thought immediately arose: does this really work? I started looking for evidence and quickly found this. video. Naturally, the next thought was to make a metal detector with your own hands.

The instructions I presented show how to assemble a metal detector literally from available materials.

You will need:

• Timer chip 555 (SE555/NE555);
• Resistor 47 KOhm;
• Two 2.2 uF capacitors;
• Battery 9V;
• Buzzer;
• Copper wire 0.2 mm in diameter;
• Wires;
• Adhesive tape/adhesive tape;
• Cardboard;
• Glue.

Metal detector circuit

The diagram was not developed by me, I borrowed it. I just added a switch and used a buzzer instead of a 10uF capacitor and an 8Ω speaker (impedance).

Coil

For me this was the most difficult stage. A calculator for calculating coils was very helpful in this matter. I calculated that a 90mm diameter coil would need about 250 turns, and a 70mm diameter coil would need about 290 turns, resulting in 10mH.

I made the reel frame out of cardboard. I wound 260 turns of copper wire 0.2 mm in diameter.

Metal detector circuit test

I assembled the entire circuit on a breadboard to check its functionality. The test can be watched on video.

The test was successful, and I made a printed circuit board on which I assembled all the components.

How to make a metal detector handle

Since I am making a simple metal detector with my own hands, I will continue to use simple and affordable materials. It was decided to make the handle also from cardboard. Three identical parts were prepared, in which holes were made for the battery. Then these parts were glued together. When the glue had dried, I made a hole for the switch. I attached the circuit, connected the battery, switch and glued the coil.

Final test

A simple metal detector circuit, unfortunately, will not allow for serious work. But there’s nothing wrong with that, because it’s an excellent educational practice for beginners. Personally, I found it interesting to assemble this device.

I wish you success in the assembly and positive emotions in the tests.

Based on materials from the site: instructables.com

The “Pirate” metal detector circuit is very popular and understandable even to a novice radio amateur. The Pirate metal detector has quite good characteristics, despite the simplicity of the circuit and the availability of parts. It can be assembled easily, in an evening, requires virtually no settings or firmware, and starts working immediately after assembly! Below I will present detailed instructions for assembling the Pirate metal detector!

Technical characteristics of 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:

To operate the Pirate metal detector, a voltage of 9-14 volts is required. You can use regular batteries or AA batteries or two batteries connected in parallel, but I would advise spending a little money and buying a battery for an uninterruptible power supply; it can easily be mounted on the 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, that’s what I used!

Coil:

The search coil for the Pirate metal detector is also easy to make. Wound on a 190 mm frame. and contains 25 turns of 0.5 mm PEV wire. The spool can be wound on an embroidery hoop; by the way, this method is quite common. Personally, I take an ordinary saucepan, wind a coil on it and tie it all together with electrical tape, then I make a frame out of thin plywood and secure it to it. Here, as they say, to each his own, as it suits.

Required parts:

Pirate metal detector diagram:

The pirate metal detector consists of transmitting and receiving units. The transmitting unit consists of a pulse generator which is assembled on the NE555 microcircuit and a powerful switch on the IRF740 transistor. The receiving unit consists of a K157UD2 microcircuit 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 install any bipolar NPN structure with N ke not lower than 200 volts, you can even unsolder it from an energy-saving lamp or phone charger; 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 diagram and board are in the general archive. By the way, the pulse generator can also be assembled using transistors:

A little about the details:

Assembling the Pirate metal detector:

First, of course, you need to prepare the board. To do this, open the Sprint-Layout program and print a blank of our future board, then transfer the drawing in any convenient way onto 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 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 transfer it using a carbon copy.

Be sure to clean the board with fine sandpaper and degrease it with acetone before applying the design, so the image will transfer well and the etching process will be faster and more reliable. After the board is etched, you need to wipe off 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 parts onto the board. To do this, we also open the signet in the Sprint-Layout program and look at where the parts are located. I strongly advise you to install sockets for microcircuits, just in case. First of all, solder the jumpers, there are 2 of them in the circuit, and one is located under the NE555 chip, so if you forget about it, it will be difficult to find the fault, since I’m sure you won’t remember these jumpers! Legs from resistors can be used as a jumper.

When all the parts are in place, all that remains is to solder the taps to the variable resistors, coil, speaker and power.

The coil, as I said above, is wound on a 19-22 cm frame and contains 25 turns. To search for smaller objects, you can wind a coil less than 15 cm - 17 turns or 10 cm - 13 turns. To search for ferrous metal, it is of course better to use a coil with a diameter of 19 cm.

I want to say a few words about the tonality of the sound. He seemed too rude to me. You can change the tonality by selecting capacitor C1, I replaced it with 47nf and the sound became higher.

It is better to take a speaker like 3GDSH TRYD 4070-02 8 Ohm so the sound will be much more powerful, I replaced the old speaker in my metal detector with this one. The speakers from the headphones also perform very well.

A link to the printed 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 Pirate metal detector in action:

Powered metal detector pirat, from 12 volts, you can use regular batteries, but it is better, of course, 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 190 mm frame. and contains 25 virks, PEV wires 0.5 mm.

• Current consumption 30-40 mA

Pirat metal detector diagram:

Chip NE555:

Transistor IRF740:

Variable resistors:

This is how it should work:

For K157UD2 it is better to install an adapter socket, and for NE555 You can also install it, it won’t hurt!))

The lady conducted tests on a medium reel with a diameter of 15 cm. So the gold ring caught in the air at 18 cm, scissors 30 cm. table lamp 50cm. which isn't bad enoughThe circuit of the “Pirate” metal detector is very simple and understandable even for novice radio amateurs. It consists of two microcircuits 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 custom MD “Pirate”, write to kavinskiy on Skype or write comments! Thank you!

The pirat metal detector is powered by 12 volts, you can use regular batteries, but it is better, of course, to take a good battery, for example from a screwdriver. Personally, I use it, or rather the batteries that are in it.

The search coil of the Pirat metal detector is wound on a 190 mm frame. and contains 25 virks, 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 easily available.

Required parts for assembly:

pirate_details

Pirat metal detector diagram:

ON UD2 (1)

The circuit uses 2 microcircuits (NE555 and K157UD2). They are quite common. K157UD2 - you can pick it out of old equipment, which I did with success.

pirate_microshema1

Chip NE555:

NE555N

Transistor IRF740:

pirate_transistor_1

Variable resistors:

pirate_rezistor_1

Be sure to take 100nF film capacitors, like these, take the voltage as low as possible:

pirate_condensatori

Print out the board sketch on plain paper:

pirate_pechatka_1

We cut a piece of textolite to its size:

pirate_pechatka_2

We apply it tightly and press it with a sharp object in the places of future holes:

pirate_pechatka_2

This is how it should work:

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 look exactly the same as on the paper template. And we poison the board.

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_wire

I wound the coil on a simple pan, 190 mm in diameter. After which, I wrapped everything with duct tape:

pirate_katuschka

According to the diagram, the coil has a diameter of 19 cm and contains 25 turns. I’ll immediately note that the coil needs to 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 three coils of 23cm (25 turns), 15cm (17 turns) and 10cm (13-15 turns). If you need to dig up scrap metal, then use a large one; if you are looking for small things on the beach, then use a smaller reel, but you’ll figure it out for yourself.

pirate_katuschka_3

pirate_katuschka_2

The coil should be as level as possible. The speaker took the first one he came across.

Now we connect everything and test the circuit to see if it works.

After applying power, you need to wait 15-20 seconds until the circuit warms up. We place the coil away from any metal, it is best to hang it in the air. Then we begin to twist the 100K variable resistor until clicks appear. As soon as the clicks appear, turn it in the opposite direction; as soon as the clicks disappear, that’s enough. After this, we also adjust the 10K resistor.

Regarding the K157UD2 microcircuit. In addition to the one I picked out, I asked one more from a neighbor 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 simply installed another microcircuit (the one I removed). And everything started working right away. So this is why you need an adapter socket, so that you can select a live microcircuit and not have to worry about desoldering and soldering.

Everything is ready, all that remains is to make a rod and place the board in the case and look for treasures)

pirate_gotoviy

And lastly, I’m throwing in a video of a pirate at work!

The lady conducted tests on a medium reel with a diameter of 15 cm. So the gold ring caught in the air at 18 cm, 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 capable of finding a small coin lying at a depth of only 5 cm. The presence of a metal recognizer and a display for setting up the operation of the metal detector also increases the price of the devices.

The simplest model of a metal detector - a pirate - you can assemble it yourself. 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 made publicly available (RAT - radioskot.ru). The pirate is able to find coins at a depth of up to 20 cm. For larger objects, an indicator of 180 cm is possible. The only problem is that it will not be possible to use this model in soil contaminated with dissimilar metals: there is no pirate metal detector circuit with metal discrimination.

Materials and tools for assembly

You need to stock up on the following a set of radio components and materials:

• microcircuit KR1006VI1 or imported NE 555 - the basis of the future assembly;
• transistor IRF 740;
• microcircuit K157UD2, transistor VS547 - the basis for the receiving unit;
• wire PEV 0.5 - for making a coil;
• NPN transistors;
• materials for making the case.

Tools required for installing a metal detector:

• soldering iron;
• insulating tape;
• drill 1 mm.

The diagram with a set of other parts can be downloaded below.

For the electronic circuit you will also need a plastic box. To make a rod to which the reel will be attached, you need to purchase a piece of plastic pipe.

Step-by-step assembly of a metal detector

PCB manufacturing

Let's start with the most difficult one - 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 both a board for the NE 555 chip and an option for transistors. We find a sketch online and print it on a piece of paper. We cut out a piece of PCB according to these dimensions. We put the sketch on the workpiece and mark the locations of future holes. We drill the workpiece using a drill or drilling machine. Then we draw the tracks using photoresist or LUT (laser ironing technology).

Another option is to paint them with a brush using nitro varnish. The tracks must exactly follow the pattern. At the last stage, we etch the board with hydrogen peroxide.

Installation of radio elements on the board

Solder the elements to the board, strictly adhering to the chosen scheme. Do not forget about the need for capacitors that ensure stable operation of the device, which is especially important in the spring and autumn seasons, when sudden temperature changes are possible.

The capacitors in this assembly are film capacitors.

The metal detector requires a power source of 9 - 12 volts. Note that the device is energy-consuming due to its considerable power. Therefore, it is necessary to use 2 - 3 batteries with a parallel connection or, which is much preferable, a charging battery.

Coil

Since the metal detector is pulsed, accuracy when assembling the coil is not too 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 skeins (to 22). The cross-section of the wire used 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 housing that will protect this part of the metal detector during search work.

The leads 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.

Setting up the device

If the metal detector is built exactly according to the diagram, it will not require additional adjustment: it is set to maximum sensitivity. For precise adjustment, you need to twist the resistor R 13 so that distinct, infrequent clicks are heard. If such a result is possible only when the resistor is twisted to the extreme, then there is a need to change the value of the resistor R 12. The device is configured with the resistor in the middle position.

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 should be 120 - 150 Hz.

The turned on device should stabilize, for this it needs about 20 seconds. Then we make the adjustment using a resistor and begin the search work.