Metal detector terminator 3 circuit board. DIY metal detector (circuit, printed circuit board, principle of operation)

A proprietary device known as the Terminator 3 metal detector is used to purposefully search for coins of various denominations. Circuit solutions used in the device provide the limiting sensitivity of inductive sensors, which makes it possible to identify metal objects with a high degree of accuracy.

Device and principle of operation

Metal detectors under this name are assembled according to the classical scheme, in which there are two inductive coils (transmitting and receiving), as well as an additional winding called compensation.

The transmitting coil is connected directly to the oscillator, which generates a pulse signal relative to high frequency... As a result, it begins to emit electromagnetic oscillations (waves), creating an alternating field in the search area. Propagating in the medium under study, this field, in turn, induces voltage oscillations of similar shape in all metal objects.

Note! The field created by the transmitting coil acts on the receiving circuit of the metal detector itself and also induces small amplitude oscillations in it.

In the absence of foreign metal objects, the potentials acting in both coils are balanced by means of an additional compensation winding. When a metallic object appears in the investigated area, the established balance is disturbed. In this case, the sensitive element electronic circuit amplifies the differential signal and directs it to the executive device, which generates notification pulses.

Based on the described principle of operation, the device "MD Terminator 3" includes the following electronic components:

• Generator of a pulse signal that creates a local electromagnetic field;
• "Catcher" or a receiver with the required sensitivity;
• Compensation scheme;
• Differential amplifier with detector;
• Executive device.

The device is designed as a structural module with an external probe-frame, into which the measuring coil itself is built. The main part of the electronic circuit is located in a separate panel containing a power source, as well as elements of indication and sound notification.

The procedure for handling the device can be found in the instructions attached to it.

Technical description

The measurement mode performed by the instrument with the excitation of an alternating electromagnetic field is classified as IB (balance of induction). The metal detector has the following technical indicators:

• Operating frequency - 7-20 kHz (the exact value is set by changing the nominal capacities);
• Ability to select a suitable search mode for metal products ("Discrimination" and "All metals");
• Manual balancing "Ground index".

To the specified operational capabilities, it is necessary to add the availability of autonomous power supply, carried out from a 9 or 12 volt battery.

The depth of detection of coins in the soil (with a working coil with a diameter of 240 mm) is:

• 5-ruble coin (Russia) - 22-24 cm;
• 5 kopecks (from the time of Catherine II) - about 30 cm;
• wartime steel helmet - up to 80 cm.

For a more complete understanding of the principle of detecting coins, it is advisable to familiarize yourself as closely as possible with the VDI scale for this model, which is valid in the "Discrimination" mode and facilitates their identification.

Advantages and disadvantages

The advantages of the product under consideration include the ability to clearly identify objects made of non-ferrous metals (with a probability of 85%). The rest (15%) are cases of detection of iron or heavily rusted objects.

Additional Information. Devices of this class differ significantly from some of their counterparts (Terminator 4, for example), which can only determine the depth of an object.

The list of their advantages can be supplemented by a low indicator of the relative measurement error.

In various situations, such detectors allow detecting objects at depths not exceeding the size of a shovel bayonet, which is not bad at all for this class of devices. For all other indicators, the model under consideration is considered a rather "powerful" device, surpassing the known analogues in its capabilities.

Their disadvantages, in addition to the relative high cost, include low sensitivity to the rusty iron. In some cases, when an erroneous "dirty" signal is issued, indicating something in between ferrous and non-ferrous scrap (or vice versa), a metal covered with a layer of rust is detected. Learning to distinguish a false signal from a useful one is possible only after a long mastery of the techniques of working with this device.

Self-production

Preparation and assembly

In order to make and check a metal detector with your own hands, first of all, you need to assemble its electronic part, and then place individual boards in a suitable case. As an example, consider the device diagram shown below in the text.

Important! For self assembly boards need the ability to professionally handle a soldering iron and master the basic skills of soldering microcircuits.

After purchasing all the electronic elements indicated in the diagram, they are soldered into a printed circuit board, which is located in the case (its general view is given below).

After the circuit is assembled, you can proceed to a visual check of the quality of the PCB soldering. But first, it is thoroughly wiped with a clean flannel soaked in solvent, which allows you to clean the connecting paths and contacts from the remaining traces of flux.

Customization

After assembling and connecting individual units, they proceed to setting up each of the device modules, which will require the following measuring equipment:

• Single-channel oscilloscope of any type;
• Modern multimeter with full set functions;
• Universal generator or "LC meter";
• Electronic frequency meter.

When setting up the assembled device using an oscilloscope, the presence of a radiating signal and the absence of voltage at the input of the amplifier in rest mode are checked.

The required frequency of the emitted signal is set according to the frequency meter by changing the capacitance of the output oscillatory circuit. Using the same oscilloscope, the presence of a useful signal at the input of the amplifier and the output of the detector in the measurement mode is checked.

Functional check

The test begins with the fact that the control knob for the sensitivity of the device is twisted to the maximum so that a stable sound signal is heard in the speaker.

After that, touch the frame with the inductive sensor with your hand and watch the sound change. If at the same time it is immediately interrupted, this means that everything has been done correctly, and the circuit is working properly. V otherwise you should check the entire circuit stage by stage, using the same oscilloscope.

Note! The control LED should blink and immediately go out after being connected to the power circuit. When the voltage is removed, it lights up and then gradually fades out.

In conclusion, we note that the final adjustment of the device is carried out at the place of its use (taking into account the soil in the zone possible search). For complete confidence in the performance of the device, it is recommended to test it on various samples of metal parts.

Video

Hello to all comrades, today we will try to figure out what kind of metal detector is this - the Terminator? Have you heard about such a device? In particular one of popular models- the third. I have a friend whom we met on the Internet thanks to our hobby, has "Terma" and this is what he told me about this device.

Photos on the internet are full, all different modifications:

The usual "three":

Terminator M model:

Well, and another photo of two homemade products at once:

First and foremost, this is a homemade metal detector, which means that ordinary people make it, or rather those who are good at circuits and electronics. If you don’t “fumble” about it, then you will not be able to do it yourself.

They do it according to schemes that are a dime a dozen on the Internet. The most important thing is that there are a lot of nuances here and each "developer" makes the device for himself - he changes, improves, adapts something. Here is the general scheme - it is guaranteed that you can collect this MD yourself:

And this is how the board looks like, where everything is already soldered:

“Terma” has several varieties - here you can talk about the “Trio” model, it has been improved, some gadgets have been added to make the search more convenient and comfortable. There is already 2-tone identification in "Trio" and in comparison with older models it is more convenient for them to search.

The Terminator-4 model is already considered outdated, but those who started with it speak warmly about this model and continue to use it. It was “invented” already in 2007, while the “troika” is already 2009.

Three and four - devices are one-tone most often (however, now they have already begun to collect two-tone models), but the "Trio" is already a two-tone one. So if you decide to buy a thermal, then it's better to take a two-tone model. Still, when there is no display that helps in detecting, and you have to navigate only by sound, then the more tones, the better. And here one-tone homemade products, of course, lose out to factory devices, which have several tones by default.

There are also PRO models and a recent novelty - 2012. We will not talk about them here yet, because at the price they are already comparable to devices of a professional level.

Which is better, the Terminator or Garrett ace 250?

As you can see, this is an MD practically from one price category, the third "term" on thematic forums can be bought for 4-5 thousand rubles. Whereas 250 ICQ costs 2 times the minimum.

However, at such a low price in terms of depth, Thermik makes an asya, he sees color targets deeper. Of course, if everything is correctly configured and the operator fumbles.

On the other hand, ICQ's convenience and information content is an order of magnitude higher, and if you complete newbie in a cop, then I would advise you to take a factory device better. And ICQ is still time-tested - decent machine entry level.

Does this MD have a pinpointer?

An urgent question, because now they have perked up to put DD coils on them and without a pin you have to dig huge holes and even the search technology, when you spend on a target crosswise, does not help. The answer is that there is no pinpointer, and therefore we recommend buying an inexpensive manual pin from this list.

How well does he see small targets?

The design of this MD is such that he sees the "small things" just fine and easily makes all the entry-level devices - floats and ICQs. Again, remember that it will be difficult to master this device from the very beginning.

What is this metal detector for - by coins or by war?

Here the answer suggests itself - most often this model is discussed on the forums dedicated to the cop in the war (in particular, Reibert), which means that they use it for this purpose. They dig casings, helmets, rifle bolts and other interesting things for war seekers. However, antiquity diggers using this device put it higher than ICQ 250 and 34 Minelaba graters, first of all, in terms of detection depth.

With which MD is the Terminator most often compared?

Most often they compare with devices of the same level - in particular, with MD "Cardinal Profi" from the office "Shturmlab". However, as diggers note, the Thermic is more balanced, with fewer glitches (Cardinal often starts by waving the reel on dewy grass). Well, I also note that the food is enough longer.

In general, after communicating with my comrade, I got the impression that the device is actually very worthy, well, it's not for nothing that it has so many fans and esteem. Plus, they are actively improving it, adding all the new chips.

And now I have already seen quite sophisticated metal detectors with a convenient panel and a nice design on sale. And according to their characteristics, they declare that they compete with the Minelab medium and top-end detectors - 705 grater and Exp. So this MD is worth paying attention to. Well, if you are friends with a soldering iron and fumble in all sorts of circuits and transistors - then maybe you should try to assemble it yourself? Fortunately, the internet is full of schemes, and there are many thematic forums.

And finally, the video of the cop with "Term-4" - the quality is so-so, but what finds and most importantly - a new, lyrical song about diggers. I advise you to look even purely because of her. Well, it is clearly seen that with this MD it is quite possible to dig old coins.

It seems that there are simply no other signals, some are coin ones) And there are no false ones either, which indicates good sedimentation from the soil and general setting device.

And here is the test video about the "Trio" model - here it is already more fun and clearer:

Here are some characteristics of the Terminator 3 metal detector: detection depth - 5 rubles Russia - 22-24cm; Catherine's penny - 27-30cm; helmet - about 80cm. The detection depth is given for medium-mineralized soil (chernozem) with a sensor with a diameter of 240 mm along the wire. I want to say a little about discrimination: if in other devices of this class there is a certain discrimination threshold when detecting a target (i.e., the device sees an object at the depth of maximum detection, but cannot recognize the type of metal from which the object is made), then in Terminator this drawback practically absent - the device recognizes most objects at the maximum detection depth.

I'll make a reservation right away - the assembly and adjustment of this IB device will be almost impossible for users who are just starting their journey in mastering radio electronics, and experienced electronics engineers can make mistakes. What, scared? But not everything is so sad - you just need to properly prepare and not rush. And the forum will help you with this. Firstly, for the assembly and adjustment of the device, we need devices such as a multimeter, an oscilloscope, an LC meter (to select elements according to identical characteristics for both metal detector channels), we may also need a generator and a frequency meter. Of course, such a set of devices costs a lot of money, and not every DIYer can afford to purchase it, but you can try to create a virtual measuring complex based on personal computer... Fortunately, there is a bunch of useful programs for these purposes.

The software can be downloaded as on our old website elwo.ru. Finally, one important note for beginners - if you are not confident in your abilities, it is better to build a simpler IB Volksturm metal detector for a start (master the basics, the principle by which the IB device as a whole is based will become clear). Below is the basic diagram of the Terminator 3 metal detector.

Terminator3 is a single-tone metal detector based on the IB principle. Simple as three kopecks and reliable as a bulldozer. This is a clean coin with a simple modification that allows you to search for gold on the beach while ignoring most of the colored debris. Although the T3 is a coin, it can also be used to search through the war and to collect scrap metal. But for this, it is necessary to enter the "all metals" mode into the circuit (which is provided for in the circuit and on the board), initially the circuit was without this mode.

The circuit is made with a non-standard use of logic as an op-amp. The downside is that the CU of the mikruh themselves is unknown (therefore, for averaging the parameters of the mikruh, the cascades are paralleled), well, the noise level is higher. It is possible to apply the corresponding logic in this scheme, but it is not necessary, since the scatter of parameters will be even greater. The only thing is that it is possible to replace the sound generator with a domestic microcircuit without prejudice. I would also like to add that in terms of depth and accuracy of target identification (color / non-color), the Terminator3 metal detector performs on a par with branded brands in the middle price category, and a cut above inexpensive branded MDs. This is not only my personal observation, but the general opinion is quite a large number the people who used it. It goes without saying that so it was - you need to collect and configure it as expected, and not as necessary.

Detailed description metal detector settings Terminator 3. Firstly, you need to look at the diagram where the nodes are indicated, here we will be guided by the nodes, in the future it will be useful for setting. So an auto-generator - generates current fluctuations when you connect a transmitting coil (hereinafter TX) to it. These vibrations come out of the MC1 microcircuit in the form of a meander (like rectangular patterns on ancient Greek temples and amphoras). Now the receiving coil (hereinafter RX), it also has a current induced by TX (which creates a field) and for this current (field) it must be balanced with TX (that is, subtract the RX field from the TX field), and for this we need a compensation coil (hereinafter CX). In the DD sensor CX is virtual, in the “RING” sensor it is real in the form of a coil. Here we connect it so that the current in it runs in the opposite direction to the RX board) and by gradually unwinding the turns from it, we balance TX and RX in current (this is called reduction to zero, the balance is simply put).

We control the balancing using an oscilloscope, achieving the minimum amplitude in all positions of the v / division knob in turn. When the point is reached when the amplitude starts to rise again, the tuning loop comes into play (it is done from one of the ends of the CX). But before that we must tune TX and RX in frequency, while RX is done 100Hz lower than TX (this will be the starting point when further adjusting the "window" of the metal scale) The coils are connected one by one to the generator of the device and the oscilloscope and are tuned to the desired frequency.

The CX does not need to be tuned in frequency. We get that when a metal object is under the sensor, the balance is disturbed (in one direction or another, depending on the metal), and the current starts to run in RX, which goes from it to preamplifier there it is amplified and fed to the sync detector (see diagram), and the sync detector (SD) detects the phases of the incoming signal and outputs all this to the amplification channels, in the channels this matter is amplified and goes to the MC8 composer, the task of the comportor is to compare the signal levels in the channels and if they are match then the comparator gives permission to trigger the sound generator. In general, all balancers work this way with minor differences, the differences relate mainly to the methods of balancing from the ground. In Terminator, phase detuning (notch, in other words).

Checking the metal detector board after soldering: Turn on the power on a freshly made and thoroughly washed from the flux board, do not connect the sensor, unscrew the feeling handle until a constant beep of the speaker appears, touch the sensor connector with your finger - the sound should be interrupted for a second. If so, then everything is in order and the board is soldered correctly and without jambs. When the power is turned on, the diode should blink and go out, when the power is turned off, the diode lights up and slowly goes out. Looking ahead: The battery discharge indication looks like this: the device starts emitting frequent signals with the same time interval, the diode is constantly on, the sensitivity drops sharply. Files different versions printed circuit boards you are in the archive.

Frequency tuning. All settings are made with the cable with which the device will continue to work. You cannot change its length after adjustment. If you have experience in making sensors for a balancer, then it will be easier for you. Next, read the winding technology for the Terminator 3 metal detector. Video on setting up the device and latest versions boards and firmwares, see the forum. Authors of the project: a2111105, Yatogan, Radiogubitel, Electrodych.

Discuss the article METAL DETECTOR TERMINATOR

Terminator 3 is an Induction Balance (IB) coin detector... The Terminators scheme was developed based on the Tesoro metal detectors. But it has a number of differences, both in the operation of the metal detector itself, and the process of its manufacture and adjustment is simplified. Also, a great advantage of the Terminator is the ability to recognize metal at the limit of sensitivity (even with minimal target acquisition, it detects it quite accurately).

Technical characteristics of the Terminator-3 metal detector:

Working Principle - IB (Balance Induction)

Depth of detection of objects in the ground with a coil of 240 mm:

5 rubles Russia - 22-24 cm.

5 kopecks Ekaterina - up to 30 cm.

Hard hat - up to 80 cm.

Operating frequency - 7-20 kHz (Depends on the coil and capacitors C1 and C2).

Search modes - "Discrimination" and "All metals" are switched.

Ground balance - manual.

Metal detector power supply - 9 - 12 volts.

The picture below shows the separation of the VDI scale for the Terminator-3 metal detector.

Thanks to this, the Terminator is able to effectively distinguish gold items from other metals.

Making a metal detector "Terminator 3" with your own hands

Terminator 3 has high level difficulties for self-made ... Therefore, it will be extremely difficult for a beginner to do this. Gather this scheme we recommend to people with sufficient experience in electronics and metal detector manufacturing! But if you feel the strength in yourself, then the process of making "Terminator-3" will be described further and all the information necessary for this will be collected.

For the manufacture and adjustment of the Terminator-3 metal detector, in addition to the standard set of equipment, you will need: A multimeter with capacitance measurement, an oscilloscope andLC meter... But this equipment can be replaced with computer emulators, schemes and programs for which are freely available on the Internet.

Metal detector circuit Terminator-3

For the convenience of manufacturing and setting up a metal detector, you will also find it useful Terminator-3 diagram with a breakdown into nodes:

Multiple versions PCB layout for metal detector Terminator 3 can be downloaded in this archive -

Parts List for manufacturing metal detector Terminator-3 in * .doc format (For a board with SMD resistors) -

We make a metal detector Terminator-3 with our own hands

We make a printed circuit board. Then we solder the jumpers into the board, then the resistors, then the panels for the microcircuits and then the rest of the parts.

Capacitors in the board must be metal-film with high thermal stability. It is also recommended, using a tester, to select the most identical parts in terms of parameters on two parallel amplification stages and the ratings of capacitors C1 and C2 (so that everything is as identical as possible), this will greatly facilitate your setup. It is also better to use a multiturn trimmer resistor.

After soldering the metal detector, the board must be washed with alcohol, dried and visually checked for defects and stickiness. Then, without the coil, you can already check the functionality of your board.... We turn on the power supply of the metal detector, unscrew the sensitivity control until a constant sound appears in the speaker, and touch the sensor connector with our fingers, the sound should be interrupted for a second. When turned on, the LED should blink and go out. If everything is so, then the board is soldered correctly. And you can start making the coil.

Making a coil for a Terminator-3 metal detector with your own hands

Making a coil ring 200mm for the Terminator-3 metal detector

To make it, we need a 0.4 mm diameter winding enamel wire. We fold it in half in advance (so that we have 2 ends and 2 beginnings), or we wind it in parallel with 2 coils. Next, on a sheet of plywood, draw a circle with a diameter of 200 mm for the TX coil - the transmitting coil, and 100 mm for the RX coil - the receiving coil.

Then, with a step of 1 cm, we drive in the carnations around the entire circumference (preferably in cambric, so as not to damage the wire insulation during winding).

On a 200 mm mandrel we wind 30 turns, folded in two wires. Then we saturate the coil with varnish, and after drying we wind it with a thread. Then we remove it from the mandrel and solder the middle, having received a one-piece winding of 60 turns. We got 2 extreme and one middle bend.

Then we wind the coil tightly with electrical tape, over the electrical tape we wind the aluminum foil for the screen, with a gap of 1 cm, and over the foil we again wind the electrical tape to protect the foil. We first bring the ends of the windings out.

Then we wind the take-up coil on a 100mm mandrel - 48 turns, also with a double wire. And then he gets drunk. The middle terminal of the transmitting coil is connected to the minus on the board to start the generator, and the middle terminal of the receiving coil is needed only for tuning, then it is isolated and not used. The compensating coil is wound with a single wire - 20 turns. Its diameter is selected so that it fits snugly inside behind the shielded transmitting coil.

We take the cable for the coil 4-core common screen.

Now we connect the TX (transmitting coil) to the board, the middle terminal and the screen of the coil are connected to the minus of the board, We connect the oscilloscope, the negative probe to the minus of the board, and the positive one to one of the ends of our coil. When tuning the coil, there should be no metal objects around it !!! And so we connect everything and look at the oscilloscope what frequency it turned out. Then write down the value and put the coil aside.

We do the same with the RX coil, measure its frequency, ideally it should be the lower TX frequency at 100Hz. If this is not the case, then it is necessary to adjust the frequency by selecting a loop capacitor. As a result, you should get, for example, 9.1 kHz TX and 9.0 kHz RX.

Now the middle RX pin is isolated and we can begin mixing the coil. We connect the coils according to the diagram below.

We put the coils in a pre-prepared mold for pouring with epoxy resin. We take an oscilloscope, a minus probe to the minus of the board, plus to the C5 output, set the division time on the oscilloscope to 10 ms and divide 1 volt per cell. We look at our picture on an oscilloscope, there is no balance yet, so the vertical amplitude will be large. Then we wind one turn from the CX (compensation coil) from the soldering side to the RX, bite off this turn and re-solder it. And we observe a decrease in amplitude. We carry out this procedure until the amplitude becomes zero. Then we decrease the volt / division and continue to wind the turns until we get to 0 at the lowest resolution of your oscilloscope. It is clear that it will not be ideal, but you need to find the number of turns, after which it will start to grow again. This position is our intermediate balance. Now we fix the coil, from the CX terminal we make a loop of 10-15 cm, and bring it out of our fill, this will be our compensating loop, which will help us to reduce the coil.

Spill the sensor with epoxy, but only half the depth of the mold. Then, after freezing, we connect the oscilloscope, bend our loop into the inside of the shape and begin to twist and groove it, trying to find the minimum value of the amplitude. After this position is found, we fix the loop with glue, check the balance again, and fill in our shape to the end.

After you have made the coil, you need to adjust the metal discrimination scale of Terminator 3

The correct setting should look like the table below

This is what a finished home-made coil for a Terminator-3 metal detector looks like

You can also make a DD coil for terminator 3. Detailed description of manufacturing DD coil for metal detector TERMINATOR 3 -

Conclusion:Terminator 3, although quite difficult to manufacture and configure, will require some effort on your part. But a neatly and correctly assembled metal detector will delight you with the quality of its work and pleasant finds, Terminator Three will work on an equal footing with branded metal detectors of the middle price category, and besides your labor, it will require low material costs.

The following people should be thanked for the development of the Terminator-3 metal detector: a2111105, Yatogan, Radiogubitel, Electrodych from the md4u.ru forum

When writing this material, we used data from the sites:

• radioskot.ru
• cxem.net
• md4u.ru

3. Search sensor "ring" for a metal detector. Take a piece of plywood or a piece of chipboard, draw with a compass the circle of the required diameter for TX (the diameter can be arbitrary, the main condition is that the diameter of the RX is half the diameter of the TX) and so, draw the diameter for TX (let's say 200mm) and drive lining along this circle carnations a centimeter apart. Then you take a pre-prepared wire folded in two (that is, it has two ends and two beginnings) and wind this wire 30 turns (and then you get 60 turns as if you were winding with a single wire). We wound it, got two beginnings and two ends on the coil (and inside it turns out two winding arms), soak the coil with varnish without removing it from the mandrel and let it dry (the selected varnish should not corrode the enamel of the wire), then tie it tightly with threads along the entire circumference (you can distance of 5 cm from each other) and remove from the mandrel, then take the tester and by measuring the resistance in the shoulders determine which ends you need to connect. Connect these ends and you get three leads on the coil (two extreme and one middle), the correctness of the connection of the ends is checked simply: between the middle lead and each of the extreme there should be exactly the same resistance, if so, it means they connected correctly. Then you wind the coil tightly with electrical tape, wind the foil screen on top (the screen should not have a short-circuited loop), that is, leave either a gap between its beginning and the end of about a centimeter and a half, or make an overlap through the electrical tape. From above, you also wrap the screen with electrical tape in order to avoid damaging it, having previously, of course, soldered a wire to the screen. Do RX in the same way, only the diameter is half and the number of turns is 48 with a double wire.

You wind the compensating coil (CX) with a single wire, 20 turns. The mandrel for the compensating must be chosen so that after winding it is tightly inserted inside the TX, taking into account that the TX is already shielded. The cable for the sensor is four-core in the common screen. And so the coils are ready for you, and the board is soldered and checked for jambs when soldering. Take TX and connect it to the board generator (according to the diagram), the middle terminal of the coil is connected to the negative of the board (otherwise the generator will not start), the coil shield must also be connected to the negative of the board (that is, to the cable shield) and turn on the power. Turn on the oscilloscope, connect the negative probe of the oscilloscope to the minus of the board, respectively, and connect the positive probe to one of the extreme terminals of the coil, and see what frequency you got on the TX. With all settings, there should be no metal objects near the coil. And so we measured TX, the frequency turned out for you, for example, 10KHz, wrote down the result on a piece of paper and you can disconnect the coil and put it aside. Do the same with RX, that is, connect it instead of TX to the generator of the device and measure it in the same way using the oscilloscope. Let's say the frequency you got at TX is 10 kHz, and at RX it is 9.5 kHz, that is, you need to adjust the frequency on RX so that it is 100 hertz lower than the TX frequency (in other words, drive out the difference of 400 Hz). To do this, you need to change the capacity of the loop conductor (either C1 to TX, or C2 to RX). In the case under consideration, it is better to do this on a contour condenser TX, it is necessary to add in parallel to it one condenser with a capacity of 500pf, thereby lowering the frequency and control this matter on the oscilloscope (do not turn off RX at the same time), (MORE CAPACITY OF THE LOOP CONDENSER - LESS FREQUENCY , AND VICE VERSA). After adjusting the frequency to the one you need, add up the capacity of the entire garland of soldered conduits and instead of this garland put one of the same capacity and leave it on the TX. And then you got it, for example: TX = 9.6KHz, and RX = 9.5KHz, then turn off RX. That's it, the coils are tuned in frequency and now you can start tuning them to zero (that is, balancing the current). After tuning in frequency, the middle RX pin is no longer needed, it is simply isolated and that's it, there are only two ends on the RX.

Setting to zero - balancing: We connect the coils according to the laid out wiring diagram and bring them to zero (balance) as follows: Take a prepared form for filling the future sensor with epoxy, put all three coils (TX, CX and RX) there, connect them to the board according to wiring diagram, connect the negative probe of the oscilloscope to the minus of the board, and the positive probe to the output C5, set the time / division on the oscilloscope to 10ms, and the volt-division to 1 volt per cell, turn on the device and the oscilloscope and see how many cells the vertical amplitude occupies, it will accordingly occupy many cells, since at this stage you have no balance and your task is to achieve the minimum number of cells on all volt / divisions of the oscilloscope. To do this, unsolder one of the ends of CX, which is connected directly to RX, wind one turn from CX, cut it off, re-solder the end of CX to RX and observe a decrease in the cells occupied by the amplitude on the oscilloscope. Perform this procedure (that is, unwinding the turns from the CX) until there is just a straight line on the given volt / division of the oscilloscope, then switch the volt / division knob on it to the next downward position, and repeat the procedure. And so on until at the smallest volt / division you have the minimum number of cells engaged in the amplitude - this is the balance of the entire sensor (or reduction to zero). Zero means such a position of the amplitude - when it is minimal, it is worth throwing off one more turn and the amplitude will start to grow again (this is called overcompensation). After zeroing, the sensor can be filled with epoxy. It is poured in several steps, so that when the epoxy dries, it does not disturb the tuned balance. When unwinding the last turn, it is necessary not to completely cut off this turn to the root, but leave a longer end from it (15 centimeters) and solder this long end to the RX, this will have a tuning loop, it will come in handy when you half-fill the sensor with epoxy, with using this loop, you will finally bring the balance to zero by laying and moving it back and forth, so it should remain unapplied with epoxy. So, you left this loop, poured the sensor with epoxy (a little), the loop remained free, after the epoxy dried, you connected the oscilloscope, turned on the device, folded this dangling end in the form of a loop, as in the figure, put it inside the coil and start moving it there- here, and bend in every way, and at the same time look at the oscilloscope in which position of the loop will be the smallest amplitude. When you have found the desired position of the loop, fix it in this position (you can use a few drops of glue in different places) then check that everything is in order and the balance has not gone away, after that you can continue to pour in epoxy with this loop. If you cut off the excess, then solder back this cut off turn, insulate the soldering point, then everything is as written.

DD sensor for metal detector Terminator. The wire winding technology is the same as for the "RING" sensor, that is, with a wire folded in half. The number of turns on each half of a wire folded in half is 30 turns. So: - We make a mandrel for DD - that is, we draw a circle on plywood (the diameter can be arbitrary from 150mm to 350mm), cut it in two (half D of the correct shape is obtained) and drive in clapboard nails along the perimeter of this half, do not forget about the cambric. as they did in the "RING" sensor, that is, we also get three outputs on each of the halves. We also adjust the frequency as we did it with the coils of the "RING" sensor. Now attention: - DO NOT DEFORM THE HALVES IN ANY CASE, BECAUSE IF THE SHAPE OF THE HALVES IS DIFFERENT, THEIR FREQUENCY CHANGES. So, we tuned both halves to the desired frequency (RX lower than TX), marked the RX half so as not to confuse the halves, put it in the mold prepared for pouring, connected both halves to the board (each in its place, do not forget that only two extreme terminals are connected in the RX half, and the middle terminal is isolated and does not connect to anything, and they themselves did not forget to shield them), connected the oscilloscope and set to zero.

One of the halves (say TX) laid in the mold must be fixed, for which we glue it with some kind of quick-drying glue to the bottom of the mold at about 5 and 6 places around the perimeter, and move the other half (in this case RX) relative to the first and observe the decrease on the oscilloscope amplitude (it is necessary to achieve the minimum amplitude per volt / division 0.02V). You need to move the half very carefully, literally half a millimeter, because the amplitude rises and falls very sharply and you need to catch the position of the halves relative to each other, at which there will be a minimum amplitude at the indicated volt / division, and in this position fix the second half (in in our case RX). After that, you can pour epoxy in the same way as the "RING" in several stages, after each stage of pouring (when the epoxy has already dried) it is necessary to check whether the balance is gone. , since in the case of a loss of balance, we can restore it with the help of a small (literally micron) bending or bending of this straight part of the half. Again I repeat: bending is allowed literally a millimeter (in order to avoid frequency drift), although even in this case, the frequency will most likely have to be corrected . If the balance is gone too much, then you will have to correct it by placing pieces of various metals in the sensor (which is not desirable). The housing for the DD sensor, or the method of filling the DD sensor, must be rigid and not subject to deformation during the operation of the sensor, all according to the same reasons as described above.

Setting the scale of metals. First, after balancing, we check the correctness of the connection. This is done as follows: The metal discrimination knob is at zero, the ground balance knob is in the middle position, the sense knob is adjusted, the mode switch is in the “color only” position, we take a piece of ferrite 1cm x 1cm and some copper, turn on the device and wave the ferrite first above the sensor, then copper, there should be a double beep on the ferrite, and a single beep on the copper. after all, not yet configured), in short, the general meaning of checking the correctness of the connection is that a single signal should sound on a colored target, and a double signal on a piece of ferrite. If so, then the coils are turned on correctly. discrimination to 0K and adjust the scale of non-ferrous metals. This is done by adding or decreasing the capacity of loop capacitors. Depending on where we are going to add or decrease the capacity (on TX or RX) the phase "window" into which our scale should fall and will shift in one direction or another. If we reduce the capacitance on TX - the "window" moves towards low-conductive metals (towards the foil), if on RX - the "window" moves towards highly conductive metals such as copper. In general, we look at the table and based on what your device "sees" after balancing, we figure out where to add contour conduits (on TX or RX). in the position of the BG knob about 40K. Capacitors C5 and C12 also move this "window" a little, but we adjust them more subtly. Personally, I set C5 - 10nf and don't touch it anymore, C12 is preliminarily set to the maximum amplitude on the preamplifier leg 12 (MC2), and then with the C12 position after the main setting, I achieve a more accurate and final setting of the metal scale. In general, that's the whole setting. In fact, the device is set up much faster than I wrote all this. The quality of the tuning work performed by you will determine its target detection range and the correctness of the discrimination, therefore, approach this matter responsibly. Good luck with making your metal detector. Authors: a2111105 and Electrodych.

Discuss the article SEARCHING COILS FOR METAL DETECTOR TERMINATOR