Metal detector on one chip k561la7. Repair of electronic equipment - experience, developments, advice

Metal detector on a chip

A similar device has already been described in an article by I. Nechaev under the same name in “Radio”, 1987, N9 1, p. 49. In contrast, the proposed version has only one inductor and a slightly different circuit design, which also makes it possible to do without a variable capacitor.

The diagram of the metal detector is shown in Fig. 1. As in the mentioned design, it has two generators: one is made on elements DD1.1 and DD1.2, and the second is made on elements DD1.3 and DD1.4. The frequency of the first generator (tunable) depends on the capacitance of capacitor C1 and the total resistance of resistors R1, R2. The tuning resistor R1 sets the operating range of the generator, and the variable resistor R2 smoothly changes the frequency of the generator in this range. The frequency of the second generator depends on the capacitance of capacitor C2 and the inductance of the search coil L1.

The signals from both generators are supplied through decoupling capacitors SZ and C4 to a detector made using diodes VD1, VD2 using a voltage doubling circuit. The load of the detector is the BF1 headphones - the difference signal is allocated to them in the form of a low-frequency component, which is then converted by the phones into sound. Capacitor C5 shunts the load at higher frequencies, in other words, it closes the signals of both generators to a common wire.

When the search coil approaches a metal object, the frequency of the second oscillator changes. As a result, the tone of the sound in the headphones changes. Based on this feature, metal objects are detected in the search area, for example, under a sublayer of soil or snow. A metal detector will be of considerable help in determining the location of fittings and hidden wiring during construction work in the house.

In addition to the one indicated in the diagram, the metal detector can use the K176LA7, K176PU1 K176LU2 microcircuits (the last two microcircuits are so-called level converters), K561LA7, K174LA7. K561LN2. Trimmer resistor R1 - SP5-2 variable R2 - SPO-0.5. but other small resistors will also work. Oxide capacitor - K50-12 or other small-sized one with a rated voltage of at least 10 V, other capacitors can be, for example, KM 6

Coil L1 is placed in a ring with a diameter of 200 mm made of aluminum or copper tube with an internal diameter of 8 mm. The ends of the tube should be separated from each other but at some distance so that a short-circuited turn does not result. To wind the coil, use PELSHO wire (in enamel and silk insulation) with a diameter of 0.5 mm, trying to stretch as many turns as possible inside the tube. This operation may seem labor-intensive, so you can use the technique described in the above-mentioned article - first lay pieces of wire inside the tube, and then bend the tube into a ring and connect the pieces in series to obtain a multi-turn coil. The coil terminals are subsequently connected to the printed circuit board, and the tube is connected to the common wire.

Headphones BF1 - TA-4 TON-1 or others, with the highest possible resistance. Power source - battery "Krona" or another, voltage of about 9 V.

Fig.2

Fig.3

Fig.4

Most of the metal detector parts are mounted on a shaped printed circuit board (Fig. 2 and 3) made of single-sided foil fiberglass. The terminals of resistors R1 and R2 are connected to the corresponding circuits of the device either using a wire or printed conductors if the installation is carried out on double-sided foil material. The board is placed inside an L-shape on the ShR connector casing (Figure 4) and attached to one of its halves using a nut screwed from the outside onto the variable resistor R2. To access the screw for adjusting the trimming resistor R, a hole is cut in the casing.

The power source is placed inside a pen-case, which can be either plastic or metal (say, a case for a round flashlight). On top of the handle-case there is a power button SB1 and on the bottom there is a socket X1 for connecting headphones.

The ring with the coil is attached to an adapter made of insulating material, and the adapter is attached to the casing. The result is a compact design that is easy to use.

Setting up a metal detector comes down to selecting the frequency of the first generator. First, the sliders of the trimming and variable resistors are placed in approximately the middle position and the contacts of the SB1 button are temporarily closed. By moving the slider of resistor R1, the lowest tone in the headphones is achieved. If there is no sound, you should select capacitor 2. The work will be easier if you use an oscilloscope. Its input probe is first connected to pin 11 of the microcircuit and the frequency of the first generator is measured, and then the probe touches pin 4 of the chip and the frequency of the second generator is measured. Comparing the measurement results will allow you to quickly determine which capacitor C2 (smaller or larger capacity) needs to be installed in the generator.

If interference or malfunctions occur in the operation of the device due to the mutual influence of the generators, it is recommended to solder a capacitor with a capacity of 0.01...0.1 μF between pins 7 and 14 of the microcircuit.

The method of working with the device is the same as with I. Nechaev’s metal detector.

V. YAVORSKY Kyiv

The same circuit, but with a different printed circuit board and design, is described in the article A simple metal detector based on the K176LE5 chip books by Adamenko M.V. "Metal detectors" M.2006 (Download book).

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 translate 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:

If you have lost a ring, a key, a screwdriver... and you know the approximate location of the loss, then do not despair! You can assemble a metal detector with your own hands or ask a radio amateur you know to assemble simple DIY metal detector. Below is a diagram of an easy-to-make and time-tested metal detector, which (with certain skills) can be made in one day. The simplicity of the described metal detector is that it is assembled on just one very common chip K561LA7 (CD4011BE). Setup is also simple and does not require expensive measuring instruments. To configure the generators, an oscilloscope or frequency meter is sufficient. If everything is done without errors and from serviceable elements, then these devices will not be needed.

Sensitivity of this metal detector:

metal jar lid “sees” up to 20 cm, cell phone up to 15 cm, Krona battery up to 10 cm, 5 ruble coin up to 8 cm.

At this distance the tone of the oscillator in the headphones barely changes; at a closer distance the tone increases. The larger the metal area, the greater the detection distance. Distinguishes between diamagnetic materials and ferromagnetic materials.

For making a metal detector we will need:

1. Chip K561LA7 (or K561LE5, analogue of CD4011);
2. Transistor - low-power low-frequency, for example - KT315, KT312, KT3102, analogues: BC546, BC945, 2SC639, 2SC1815, etc.);
3. Diode - any low-power one, for example - kd522B, kd105, kd106, analogues: in4148, in4001, etc.;
4. Variable resistor - 3 pcs (1 kOhm, 5 kOhm, 20 kOhm with a switch or a separate switch);
5. Fixed resistor - 5 pcs (22 Ohm, 4.7 kOhm, 1.0 kOhm, 10 kOhm, 470 kOhm);
6. Ceramic, or even better, mica capacitors - 5 pcs: 1000 pF -3 pcs, 22 nF -2 pcs, 300 pf);
7. Electrolytic capacitor (100.0 uF x 16V) - 1 piece;
8. Wire PEL, PEV, PETV, etc., with a diameter of 0.4-0.7 mm;
9. Low impedance headphones (from the player);
10. Battery 9V.

Metal detector circuit

Appearance of the metal detector board

In the case of an old pocket radio (you can use the case from a soap dish, a shoe-cleaning sponge, or in the housing from the electrical junction box.

Attention! To eliminate interference and the influence of human hands when touching the regulators, the housings of variable resistors must be connected to the minus of the board.

If the metal detector circuit is properly soldered, the elements are in good working order and have the correct values, and the search coil is properly made, the device operates without problems. If, when you turn on the headphones for the first time, you do not hear a squeak or change in frequency when adjusting the “FREQUENCY” control, then you need to select a resistor (10 kOhm) , standing in series with the regulatorand/or a capacitor in this generator (300 pF). Thus, we make the frequencies of the reference and search generators the same.

When the generator is excited, whistling, hissing, and distortion appear, solder a 1000 pF capacitor (1H0 aka 102) to the pin. 6 chips per case.

Using an oscilloscope or frequency meter, look at the signal frequencies at pins 5 and 6 of the K561LA7. Achieve their equality using the above-described adjustment method. The operating frequency of the generators itself can vary from 80 to 200 kHz.

A protective diode (any low-power one) is needed to prevent damage to the microcircuit when the battery is turned on by mistake (which often happens:).

Making a metal detector coil

The coils are wound on a mandrel with a diameter of 15-25 cm (for example, a bucket or on a shuttle made of thick wire or plywood - the smaller the diameter, the less sensitivity, but the greater the selectivity of small metals). Choose for what purpose you need it.

A wire is used in varnish insulation PEL, PEV, PETV..., with a diameter of 0.4 - 0.7 mm (well suited for old color TVs with a kinescope demagnetization loop or deflection system) and contains about 100 turns (you can wind from 80 to 120 turns ). Wrap the wire tightly with electrical tape.

Then we wrap the coil over the electrical tape with a strip of foil, leaving 2-3 cm of the unwrapped area. You can take foil from some types of cables or, as a last resort, cut foil from a chocolate bar into strips 2 cm wide :)

We wrap everything tightly with electrical tape again.

Photo of the finished coil. All that remains is to wrap the top with electrical tape.

We attach the resulting finished coil to a dielectric (for example, non-foil PCB or getinax). Next we attach it to the holder.

We connect the coil with the circuit with a double shielded wire (screen to body). The wire can be taken from old cords for dubbing from tape recorder to tape recorder or a low-frequency (audio-video) cord for connecting a TV to a DVD, etc.

Correct operation of the metal detector: When you turn on the “frequency” control in the headphones, we set a low-frequency hum; when approaching metal, the frequency changes.

The second option is to stop the buzzing in your ears by setting the beats to zero, i.e. combine two frequencies. Then there will be silence in the headphones, but as soon as we bring the coil to the metal, the frequency of the search generator changes and a squeak appears in the headphones. The closer to the metal, the higher the frequency in the headphones. But the sensitivity with this method is not great. The device will react only when the generators are strongly detuned, for example, when brought close to a jar lid.

Location of parts on the board for a chip in a DIP package

Location of parts on the board for a chip in an SMD package

Zotov A., Sergey V., Volgograd region.

This metal detector circuit can be discussed on our

Do you want to make this metal detector?

But you don’t have the parts and board?

Several metal detector options from the set

You can order them

Kit for making a metal detector

After reading a little on amateur radio forums production of metal detectors, found that most people collecting metal detectors, in my opinion, are unfairly written off beat metal detectors- so called BFO metal detectors. Allegedly, this is the technology of the last century and “children’s toys.” — Yes, this is a simple and unprofessional device that requires certain skills and experience in handling. It does not have a clear metal selectivity and requires adjustment during operation. However, it is also possible to perform a successful search under certain circumstances. As an option - beach search- perfect option for a metal detector on beats.

Place to search with a metal detector.

You need to go with a metal detector where people lose something. I'm lucky to have a place like this. Not far from my house there is an abandoned river sand quarry, where people constantly relax in the summer, drinking and swimming in the river. It’s clear that they are constantly losing something. In my opinion, the best place for searching with a metal detectorBFO I can't think of it. Lost items are instantly buried at a shallow depth in dry sand and it is almost impossible to find them manually. Some kind of mysticism. I remember when I was a child I dropped my apartment keys in the sand there. Here I am standing, the keys fell here, but no matter how much I dug up that area, it was all to no avail. They literally fell through the ground. Just an enchanted place. At the same time, on this “golden” beach, I constantly found other people’s keys, lighters, coins, jewelry and phones in the sand. And on my last trip with a metal detector, I found a woman’s thin gold ring. It was almost at the surface, slightly sprinkled with sand. Perhaps it was just luck. Actually, it was for this beach that I made my metal detector.

Advantages of a beat metal detector.

Why exactly BFO? - First of all, this is the most simple metal detector option. Secondly, it has at least some signal dynamics depending on the properties of the object. Not really pulse metal detector- “beeping” for everything the same. I in no way want to belittle advantages of a pulse metal detector. This is also a wonderful device, but it is not suitable for a beach littered with corks and foil. Many will say that a beating metal detector does not distinguish the properties of an object, howls and buzzes at everything the same. However, it is not. After practicing on the beach for a couple of days, I became quite good at identifying foil as a sharp and profound change in frequency. Beer bottle caps cause a strictly defined frequency change that needs to be remembered. But the coins emit a weak, “point” signal - a subtle change in frequency. All this comes with experience, patience and good hearing. Beat metal detector- it’s still "auditory" metal detector. The analyzer and signal processor here is a person. For this reason, you must search on headphones, and not on the speaker. Moreover, the best option is large headphones, not earplugs.

Metal detector design.

Structurally I decided to make a metal detector foldable and compact. So that it fits into a regular bag, so as not to attract the attention of “normal” people. Otherwise, when you get to the search site, you look like an “alien” or a scrap metal collector. For this purpose, I bought the smallest (two-meter five-legged) telescopic rod in the store. Left three knees. The result was a fairly compact folding base, on which I assembled my metal detector.

The entire electronic unit was assembled in the 60x40 plastic wiring box I already loved. The end cap, the power compartment partition and the power compartment cover were also made from its plastic. The parts were glued together with superglue and mounted on M3 bolts. Fastening metal detector electronic unit to the rod is made in the form of a metal bracket, which is inserted into place of the fishing reel with fishing line and secured with the standard nut of the rod. The result is an excellent lightweight and durable design. On the outside of the unit there is a power button, a coil connection socket (a five-pin socket from a “grandfather’s” tape recorder), a frequency regulator and a headphone jack.

Metal detector circuit board was made on site by laying out the paths with a waterproof marker. For this reason, unfortunately, I cannot provide a seal. Surface mounting - no holes - "lazy" - my favorite. It is also important, after assembling the board, to cover it with any varnish to protect it from moisture and debris. In field conditions this is very important. For example, I lost one day because some debris got inside under the microcircuit. The metal detector just stopped working. And I had to return home, disassemble it, blow it out and open the board with varnish.

Diagram of a beat metal detector.

The circuit itself (see below) was redesigned and optimized by me from two metal detector circuits. This is "" - Radio magazine, 1987, No. 01, pp. 4, 49 and " High sensitivity metal detector" - Radio magazine, 1994, No. 10, page 26.

The result is a simple and functional circuit that provides stable low-frequency resulting beats - what is needed to determine by ear the slightest changes in frequency.

The stability and sensitivity of the metal detector are ensured by the following circuit solutions:

The reference and measuring generators are separated- made in separate microcircuit packages - DD1 and DD2. At first glance, this is wasteful - only one logical element of the microcircuit package is used out of four. That is, yes, the reference generator is assembled on only one logical element of the microcircuit. The remaining three logical elements of the microcircuit are not used at all. The measuring generator is built in exactly the same way. It would seem that it makes no sense not to use the free logical elements of the microcircuit package. However, this is precisely what makes a lot of sense. And it consists in the fact that if, for example, you assemble two generators in one microcircuit package, they will synchronize each other at close frequencies. It will not be possible to obtain the slightest changes in the resulting frequency. In practice, this will look like a sharp change in frequency only when a massive metal object is close to the measuring coil. In other words, sensitivity sharply decreases. Metal detector does not react to small objects. The resulting frequency seems to “stick” to zero—up to a certain point, there are no beats at all. They also say - “ dumb metal detector", "dull sensitivity". By the way " Metal detector on a chip" - Radio magazine, 1987, No. 01, pp. 4, 49 is built on just one microcircuit at all. This effect of frequency synchronization is very noticeable there. It is completely impossible for him to search for coins and small objects.

Also, both generators must be shielded with separate small screens made of tin. This increases by an order of magnitude stability and sensitivity of the metal detector as a whole. It is enough to simply solder small partitions made of tin at minus between the generator chips to ensure that the parameters of the metal detector are improved. The better the screen, the better the sensitivity (the influence of the generators on each other is weakened and plus protection from external influences on the frequency).

Electronic tuning.

Comparator on DD3.2 – DD3.4.

This circuit element converts the sinusoidal signal from the output of the DD3.1 mixer into rectangular pulses of double frequency.

Firstly, rectangular pulses are clearly audible at hertz frequencies as clear clicks. While a sinusoidal signal of hertz frequencies is already difficult to distinguish by ear.

Secondly, doubling the frequency allows the adjustment to come closer to zero beats. As a result, by adjusting you can achieve a “clicking” sound in the headphones, the change in frequency of which can already be detected when you bring a small coin to the coil at a distance of 30 cm.

Generator power stabilizer.

Naturally, in this circuit, the supply voltage noticeably affects the frequency of generators DD1.1 and DD2.1 metal detector. Moreover, each of the generators is affected differently. As a result, with the battery draining a little The beat frequency of the metal detector also “floats”. To prevent this, a five-volt stabilizer DA1 was introduced into the circuit to power generators DD1.1 and DD2.1. As a result, the frequency stopped “floating”. However, it should be said that on the other hand, due to the five-volt power supply of the generators, several The sensitivity of the metal detector has decreased generally. Therefore, this option should be considered optional and, if desired, generators DD1.1 and DD2.1 can be powered from the crown without a DA1 stabilizer. You just have to adjust the frequency manually more often using a regulator.

Metal detector coil design.

(See diagram below).

Since this not a pulse metal detector, butBFO, then the search coil (L2) is not afraid of metal objects in its design. We don't need a plastic bolt. That is, we can safely use a metal (but only open!) frame and a regular metal bolt for the hinge to make it. Subsequently, when setting up the circuit, all the influences of the metal in the structure will be brought to zero by the tuning core of the L1 coil. The L2 coil itself contains 32 turns of PEV or PEL wire with a diameter of 0.2 - 0.3 mm. The diameter of the coil should be about 200 mm. It is convenient to wind on a small plastic conical bucket. The resulting turns are completely wrapped with electrical tape and tied with thread. Next, this entire structure is wrapped in foil (cooking foil for baking). Tinned wire is wound on top of the foil in several turns around the entire perimeter of the coil. This wire will be the output of the foil screen of the coil. Once again everything is wrapped together with electrical tape. The coil itself is ready.

The frame on which the reel will be located and with which it will be attached to the fishing rod is made of springy steel (not soft) wire 3-4 mm. It actually consists of three parts (see figure) - two twisted wire loops of the hinge, which will be connected by a bolt to each other and a wire ring threaded into the tube from the dropper (the ring should not be a closed turn).

This entire structure, together with the finished wire spool, is also tied together with threads and electrical tape.

The joint itself with the reel is attached to the rod by tying it with nylon threads and gluing it with epoxy resin.

It is advisable not to wet the coil during the search process, and especially not to use it for underwater searching. It is not airtight. Moisture that gets inside can destroy it over time.

Coil L1 (see diagram) is wound on a frame from a small-sized radio receiver with a metal screen and a tuning core. The coil contains 65 turns of PEV wire with a diameter of 0.06mm

Me and Diode. © site.

In this detailed article we will talk about how to make a pirate metal detector yourself and with your own hands, we will break everything down, all aspects of its assembly. Starting from the principle of operation to the list of popular faults.

First, a little history, where this device came from, what are the reviews from diggers, and let’s look at its characteristics.

Pirat is not a conqueror of the sea at all, but an abbreviation. PI means that this metal detector is pulsed, and rat is the website of the author of this MD, radioscot. As for the reviews, the pirate has gained fame as a simple and inexpensive device; usually novice detector creators start with it. Reliability depends on the author and the quality of his build. After assembly, it is immediately ready for use and does not require any configuration.

Characteristics of the pirate metal detector:

Here, a lot also depends on the creator of this device, the parts used and the diameter of the coil. Let us give, as an example, the value declared by the author:

• Supply voltage 9 – 12 volts.
• Current consumption 30-40 mA.
• Coin detection depth (25mm) – 20 cm.
• The detection depth of large metals is 150 cm.

Parts List:

The list of necessary parts for the pirate metal detector is attached as an image below. All these radio components are not difficult to get, with the exception of the comparator microcircuit, it is relatively rare, but you can find it in stores; there are enough of them in old Soviet technology. Now the question of what parts are needed has disappeared, let's move on.

Pirate metal detector circuit

The classic pirate circuit diagram is based on the ne555 chip, here is its drawing.

Pirate metal detector circuit for NE555

This electrical circuit consists of two blocks - a pulse generator and a comparator. Briefly, the operating principle is as follows: a pulse generator sends its pulses to one input of the comparator, and a pulse from the coil is supplied to the second input of the comparator. If there are signals at the two inputs of the comparator, then there is one at its output too, the signal from the output goes to the speaker, and it notifies us - there is metal here. In addition, there are diagrams on the Internet, MD pirate using tl072 and k561la7 microcircuits. No specific information was found on k561la7, so if you have anything to say about this, we are waiting for you in the comments and will definitely add it to the article.

Pirate metal detector circuit using transistors

This is the second version of the scheme from the developer. What is used here as a generator is not a microcircuit, but transistors, in the original version the Soviet KT-361 and KT-361. But no one prohibits experiments; other transistors with similar parameters will work well.

Circuits for microcontroller versions: Pirate 2, Pirate 3, Pirate 4 will not be included. As for the scheme for gold, there is no need for any separate manipulations. It is enough to assemble an ordinary pirate and test it; it should react to any metals. Some people need to download patterns for printing, you can click on the image and save it to your computer. If you redesigned the circuit yourself, we will be happy to add your version to the article.

So we talked in detail about the pirate metal detector circuit.

Pirate metal detector board

Transistor board

Here, by the way, is the board for tl072, if anyone is interested. On SMD parts.

Board sizes:

• On transistors - 30x76.
• On NE555 - 30x80.
• SMD on TL072 - 26×35.

Pirate metal detector coil

Now let's talk about how to make a coil for a pirate metal detector with your own hands.

There are many variations of coil winding. The classic option is to take a 0.5 PEV wire and wind 25 turns on some frame with a radius of 19-20 cm. It is recommended to solder directly, and once the whole circuit is working, start experimenting with various plugs and adapters. If you like twists, there shouldn’t be any; sensitivity greatly depends on this.

Some people make a coil for a pirate metal detector from twisted pair. This is a very good reel option. To make it, we need approximately 2.5 - 2.7 twisted pair wires. We find the middle and make a mark, then we make a ring and also mark it as in the figure below. We fix this whole thing and begin to bend the ends of the ring on both sides. This must be done tightly, without gaps. There should be about 3 turns.

Wire pinout for twisted pair coil

Depth coil for pirate metal detector.

To increase the depth and sensitivity of a pirate metal detector, you need to properly make a coil. The technique is as follows:

1. We wind 25 turns.
2. We test by unwinding one turn at a time and cutting them off, the sensitivity will increase.
3. We find the moment when sensitivity begins not to increase, but to decrease.
4. We calculate the number of turns and wind a new coil with this number of turns + 1 or 2 turns.
5. Maximum sensitivity has been reached.

This increases the pirate's sensitivity. A lot also depends on the quality of the tracks. You can also play around with resistor R7.

Parameters at which the maximum depth was achieved:

• Number of turns - 10.
• Coil resistance is 2 Ohms.
• Wire thickness – 0.45.
• Diameter – 20 cm.
• Resistor R7 – 75 Ohm.

Setting up a pirate metal detector

Does not require special setup. All you have to do is assemble the board and turn it on. After 5-10 seconds it starts making sounds. Using variable resistors, we adjust this sound until it clicks - ready, this is maximum sensitivity, shovel in hand and go.

Metal detector pirate does not work

Let's look at the list of malfunctions, their causes and ways to eliminate them.

Malfunction: After assembly there are no signs of life.

Remedy: If you soldered with solder pastes or any acids, it is highly recommended to wipe the board with alcohol and dry it. If this does not help, then you need to check every part for serviceability, these are the main reasons.

Malfunction: NE555 or another part is heating up.

Remedy: check the tracks for short circuits, check the ratings and serviceability of all parts. Look at the tips from the first malfunction and go through them.

Metal detector pirate with metal discrimination

Metal detector pirate underwater

Usually a collected pirate is ready for underwater hunting. The main thing is to well insulate the housing and coil - the entire electronic part. Well, we need to come up with something with an indication. If, of course, you don’t dive with it, then you can leave everything as it is, but under water, you won’t hear any sound. Usually, for such purposes, a light indication is made.

Modernization of the pirate metal detector

Because the pirate is very simple, it is very easy to layer various gadgets and improvements on it. We will now look at some of them.

Tone sound.

It is very easy to attach a tone to the pirate, you will see the circuit and PCB below.

Battery discharge monitoring circuit

Here are a few improvements, use them for your health.

Conclusion: here we have figured out how to make a pirate metal detector yourself. The article is quite complete, but, like everything, it is imperfect. If you have any additions to it, we are waiting for you in the comments below.

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