Terminator 3 is a metal detector for finding coins, working on the principle of induction balance (IB). The Terminator 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, the great advantage of the Terminator is the ability to recognize metal at the limit of sensitivity (even with minimal target capture, it detects it quite accurately).
Technical characteristics of the Terminator-3 metal detector:
How it works - 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 of Catherine - up to 30 cm.
Helmet - 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.
Power metal detector - 9 - 12 volts.
The picture below shows the division 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 a high level of difficulty for self-production . Therefore, it will be extremely difficult for a beginner to do this. Collect this scheme we recommend to people who have sufficient experience in electronics and metal detector manufacturing! But if you feel the strength in yourself, then the manufacturing process of the 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: Multimeter with capacitance measurement, Oscilloscope andlc meter. But this equipment can be replaced by computer emulators, circuits and programs for which are freely available on the Internet.
Scheme of the metal detector Terminator-3
For the convenience of manufacturing and setting up a metal detector, you will also need terminator-3 diagram broken down into nodes:
Multiple versions PCB layout for metal detector Terminator 3 can be downloaded in this archive -
Parts list for the manufacture of the Terminator-3 metal detector in *.doc format (For the board with SMD resistors) —
We make a metal detector Terminator-3 with our own hands
We make printed circuit boards. Then we solder the jumpers into the board, then the smd resistors, then the panels for the microcircuits and then the rest of the details.
Capacitors in the board must be metal-film with high thermal stability. It is also recommended using a tester to select parts that are as identical as possible in terms of parameters on two parallel amplification stages and the values \u200b\u200bof capacitors C1 and C2 (So that everything is as identical as possible), this will greatly facilitate your setup. Also tuning resistor It's better to use a multi-turn.
After soldering the metal detector, the board must be washed with alcohol, dried and visually checked for defects and stickiness. Then, without a coil, you can already check the performance of your board. We turn on the power of the metal detector, unscrew the sensitivity control until a constant sound appears in the speaker, and touch the sensor connector with your fingers, the sound should be interrupted for a second. When turned on, the LED should flash and turn off. If 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
Production of coil ring 200mm for metal detector Terminator-3
For its manufacture, we need a winding enamel wire 0.4 mm in diameter. We fold it in half in advance (So that we have 2 ends and 2 beginnings), or we wind it in parallel from 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, in increments of 1 cm, we drive in cloves around the entire circumference (preferably in cambric, so as not to damage the wire insulation when winding).
We wind 30 turns on a mandrel of 200 mm, folded in two with a wire. Then we impregnate the coil with varnish, and after drying, wrap it with a thread. Then we remove it from the mandrel and solder the middle, getting a whole winding of 60 turns. We got 2 extreme and one middle branch.
Then we tightly wrap the coil with electrical tape, wind aluminum foil for the screen over the electrical tape, with a gap of 1 cm, and again wind the electrical tape over the foil to protect the foil. We first bring the ends of the windings out.
Then we wind the receiving coil on a 100mm mandrel - 48 turns, also with a double wire. And then he gets drunk. The middle output of the transmitting coil is connected to the minus on the board to start the generator, and the middle output 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 in a common screen.
Now we connect the TX (transmitting coil) to the board, connect the middle output and the screen of the coil to the minus of the board, We connect the oscilloscope, the negative probe to the minus of the board, and the positive probe to one of the ends of our coil. When adjusting the coil, there should be no metal objects around it !!! And so we connect everything and look at the oscilloscope, what frequency is obtained. Then we write down the value and put the coil aside.
We do the same with the RX receiving coil, measure its frequency, ideally it should be lower than the TX frequency by 100 Hz. 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 terminal of RX is isolated, and proceed to the mixing of the coil. We connect the coils according to the diagram below.
We lay the coils in a pre-prepared form for pouring epoxy. We take an oscilloscope, a negative probe to the minus of the board, positive to the C5 output, set the division time to 10 ms on the oscilloscope and division to 1 volt per cell. We look at our picture on the 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 solder it again. And we observe a decrease in amplitude. We do this procedure until the amplitude becomes zero. Then decrease the volts/div and keep winding 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 winding which it will begin to grow again. This position is our intermediate balance. Now we fix the coil, make a loop of 10-15 cm from the CX output, and bring it outside of our fill, this will be our compensating loop, which will help us bring the coil to the bottom.
We spill the sensor with epoxy resin but only half the depth of the mold. Then, after solidification, we take an oscilloscope, we bend our loop into the inside of the form and begin to twist and turn it, trying to find the minimum amplitude value. After such a position is found, we fix the loop with glue, re-check the balance, and fill our form to the end.
After you have made the coil, you need to adjust the Terminator 3 metal discrimination scale
The correct setting should look like the table below
This is how the finished homemade coil for the Terminator-3 metal detector looks like
You can also make a DD coil for terminator 3. Detailed description production of DD coils for metal detector TERMINATOR 3 —
Conclusion:Terminator 3, although quite complicated to manufacture and set up, will require some effort from you. 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 medium-sized metal detectors. price category, and in addition to 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, Elektrodych from the md4u.ru forum
When writing this material, data from sites were used:
- radioskot.ru
- cxem.net
- md4u.ru
For those who do not want to spend money on a branded device, I suggest assembling a terminator 3 metal detector.
The search performance of this device can compete on par with purchased brands costing under $200. Circuit solutions of the Terminator are practically the same as in branded devices of the TESORO line, but easier to set up and manufacture.
The device showed itself from the best side, discrimination on high level, low current consumption of the device, low cost and availability of parts, as well as the ability to work on heavy soils. The device board has been tested and works with a bang.
Specifications:
The principle of operation is inductively balanced
Operating frequency, kHz 7-14kHz
Operating mode dynamic
Food, V 9-12
There is a sensitivity level control
Threshold control
Ground balance is manual.
Air detection depth with DD-250mm sensor
Coins 25mm - about 30-35cm
Gold ring - 30cm
Helmet 100-120cm
Maximum depth 150cm
Consumption current:
Silent approximately 35 mA
Metal detector scheme:
Board in .lay format:
We transfer the tracks to the textolite with the help of LUT (Laser Ironing Technology).
We poison the board, for example, in ferric chloride.
We ludim tracks and drill holes for the details.
We start the assembly by soldering 16 jumpers, then carefully solder smd resistors, then sockets for microcircuits and everything else.
It is better to take a variable resistor threshold regulator multi-turn (more comfortable setting), but you can get by with the usual one, in this case you need to turn it more carefully.
The board is ready to be inserted into the case. The MC10 chip and its harness can be omitted, this is a low battery indicator.
A small recommendation regarding the manufacture of the device board. It is desirable to have a tester that can measure the capacitance of capacitors. The device has two identical amplification channels, therefore, the amplification through them should be as identical as possible, for this it is desirable to select those details that are repeated in each amplification stage so that they have the most identical parameters measured by the tester (that is, what readings in specific cascade on one channel - the same readings on the same cascade and in another channel), and it is also desirable to select loop capacitors C1 and C2 with the same readings on the tester, this will greatly facilitate your device setup.
Coil making
The DD sensor is made according to the same principle as for all balancers.
TX is the transmitting coil and RX is the receiving coil. Number of turns - 30 turns with wire folded in half wire diameter: 0.4 enameled winding. Both the transmitting and receiving coils are wound with a double wire (that is, there should be 4 ends of the wire), we determine the arms of the windings with the tester and connect the beginning of one arm to the end of the other, we get the average output of the coil. The middle output of TX is connected to the minus of the board (without this, the generator will not start), the middle output of RX is needed only for frequency tuning, after tuning for frequency (resonance) it is isolated and the receiving coil turns into a normal one (without output).
The receiver for tuning is connected instead of the transmitter and is tuned 100Hz-150Hz below the transmitter. Balancing is carried out by shifting the coils (as on wedding rings) relative to each other. The balance should be within 20-30mV, but not higher than 100mV. Coils after winding are tightly wrapped with threads, impregnated with varnish. After drying, tightly wrap with electrical tape around the entire circumference. It is shielded from above with foil, between the end and the beginning of the foil there must be a gap of 1 cm uncovered by it, in order to avoid a short-circuited turn. Each of the coils is tuned in frequency separately, there should not be any metal objects nearby.
I didn't bother too much with the case :))
On the signet, instead of C1.1 and C1.2 (TX contour conduits), only one conder (C1) is placed, the frequency at which the entire device will operate will depend on its capacity, so it is not necessary to be tied to the exact value of the capacitor that is indicated on scheme. For example, we put C1 on TX with a capacity of 100nf, and I put C2 on RX with 100nf + 3.3nf, and at the same time I get an operating frequency of the device of 10.5KHz. You can set other ratings (that is, increase or decrease the frequency of the device, within reasonable limits, of course). The device can operate from 7KHz to 20KHz. The lower the frequency - the deeper it will take the target, but at the same time there will be worse discrimination on some targets, and vice versa, the higher the frequency, the less depth, but better discrimination to some targets (such as gold for example).
Correct assembly of the board, start by checking the correct power supply to all nodes. Take the circuit and the tester, turn on the power on the board, and referring to the circuit, go through the tester at all points of the nodes where power should be supplied. Where there should be 4 volts, then there should be 4 volts (well, plus / minus a few millivolts), and so on for all points. The second point: - The same applies to checking the assembly, unscrew the feeling knob to the maximum and turn on the power to the board - the speaker should make a continuous sound, when the feeling knob is turned down, the sound should disappear. If so, then the board is collected correctly.
Then we set all the knobs to zero (that is: the B \ G knob - the ferrite is not cut out, and the discrim knob - not a single color is cut out, the switch is in the "color only" mode), set C5 to start with 4n7, ran the ferrite over the coil ( if there was a double beep, then everything is fine, if a single beep, then the ends were transferred to the TX in places), connected the oscil probe to the C5 output and move the coils to achieve a minimum amplitude.
So the device works, on which TX or RX coil to solder additional capacitors when setting up the reaction to metals. If the ferrite is visible on the entire R8 range, then on RX, if the ferrite is not visible on the entire R8 range, then on TX. Chocolate foil is on one end of the scale, copper is on the other end. This is where you get your bearings.
Here, for reference, the entire VDI scale, with the discrim knob at a minimum, the device should see all non-ferrous metals, when winding the discrim, all metals should be cut in order to copper, copper should not be cut, if the device works like this, then it is configured correctly.
3. Search sensor "ring" for a metal detector. Take a piece of plywood or a piece of chipboard, draw with a compass a circle of the diameter you need for the 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 a diameter for the TX (let's say 200mm) and drive in the lining 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 30 turns with this wire (and you will get 60 turns as if you were winding with a single wire). They wound it, got two beginnings and two ends on the coil (and inside it turns out two arms of the winding), impregnate the coil with varnish without removing the mandrel and let it dry (the selected varnish should not corrode the enamel of the wire), then tightly tie it with threads around the entire circumference (you can with 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: there must be exactly the same resistance between the middle conclusion and each of the extreme ones, if so, then connected correctly. Then you wrap the coil tightly with electrical tape, wind the foil screen on top (the screen should not have a short-circuited turn), that is, leave either a gap between its beginning and end of about a centimeter and a half, or overlap through the tape. From above, you also wrap the screen with electrical tape in order to avoid damage to it, having previously, of course, soldered the wire to the screen. RX do exactly the same, only the diameter is half as much and the number of turns is 48 with double wire.
You wind the compensation coil (CX) with a single wire, turns 20. The mandrel for the compensation coil must be selected so that after winding it is tightly inserted inside the TX, taking into account the fact that your TX is already shielded. The cable for the sensor is four-wire in a common shield. And so your coils are ready, and the board is soldered and checked for jambs when soldering. Take the TX and connect it to the board generator (according to the diagram), the middle output of the coil is connected to the minus of the board (otherwise the generator will not start), the coil screen must also be connected to the minus of the board (that is, to the cable screen) and turn on the power. Turn on the oscilloscope, connect the negative probe of the oscilloscope, respectively, to the minus of the board, and connect the positive probe to one of the extreme terminals of the coil, and see what frequency you get on the TX. At all settings, there should be no metal objects near the coil. And so they measured the TX, you got the frequency, for example, 10KHz, wrote down the result on a piece of paper and you can disconnect the coil and put it aside. You do the same with RX, that is, connect it instead of TX to the generator of the device and measure it with an oscilloscope in the same way. Let's say the frequency you got at TX is 10KHz, 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 hertz). To do this, you need to change the capacitance of the loop conduit (either C1 to TX or C2 to RX). In the case under consideration, it is better to do this on the TX loop capacitor, it is necessary to add one capacitor with a capacity of 500pf in parallel to it, thereby lowering the frequency and control this matter on the oscilloscope (do not turn off RX), (MORE CAPACITY OF THE LOOP CAPACITOR - LESS FREQUENCY , AND VICE VERSA). After adjusting the frequency to the one you need, add up the capacitance of the entire garland of soldered conduits and instead of this garland put one of the same capacity and leave it at TX. And that's what you got, 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 setting them to zero (that is, to balance the current). After tuning in frequency, the middle output of RX is no longer needed, it is simply isolated and that's it, only two ends remain on RX.
Setting to zero - balancing: We connect the coils according to the laid out connection diagram and bring them to zero (balance) as follows: Take a pre-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 connection diagram, connect the negative probe of the oscilloscope to the minus of the board, and the positive probe to the C5 output, 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 takes, it will accordingly occupy a lot of cells, since at this stage you do not have any balance and your task is to achieve the minimum number of cells in all volts / divisions of the oscilloscope. To do this, solder one of the ends of the CX which is connected directly to the RX, wind one turn from the CX, cut it off, re-solder the end of the CX to the RX and observe a decrease in the cells occupied by the amplitude on the oscilloscope. You do this procedure (that is, unwinding the turns from CX) until the given volt / division of the oscilloscope becomes just a straight line, then switch the volt / division knob on it to the next position in the direction of decrease, and repeat the procedure. And so on until at the smallest volt / division you have the minimum number of cells involved in the amplitude - this is the balance of the entire sensor (or reduction to zero). By zero is meant such a position of the amplitude - when it is minimal, it is worth throwing away one more turn and the amplitude will start growing again (this is called overcompensation). After zeroing, the sensor can be filled with epoxy. It is poured in several stages, 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 at the root, but leave the end of it longer (15 centimeters) and solder this long end to the RX, this will be your tuning loop, it will come in handy when you half-solder the sensor with epoxy, with with this loop, you will finally bring the balance to zero by laying and moving it back and forth, so it should remain uncast with epoxy. So, you left this loop, poured the sensor with epoxy (a little), the loop remained free, after the epoxy dried, 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 for everyone to bend, and at the same time look at the oscilloscope in which position of the loop there 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 they checked that everything is in order and your balance has not gone away, after that you can continue to add epoxy along with this loop. If you cut off the excess, then solder this cut off coil back, insulate the soldering point, then everything is as written.
DD sensor for Terminator metal detector. 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 the wire folded in half is 30 turns. So: - We make a mandrel for DD - that is, draw a circle on plywood (the diameter can be arbitrary from 150mm to 350mm), we cut it in two (we get a half D of the correct shape) and we drive in wagon studs around the perimeter of this half, do not forget about the cambric. We wind two halves of D on this mandrel (naturally in turn). We connect the ends of the windings in each half in the same way as they did in the "RING" sensor, that is, we also get three outputs on each of the halves. We also tune in frequency as we did it with the coils of the "RING" sensor. Now attention: - IT IS IMPOSSIBLE IN NO EVENT TO DEFORM THE HALVES, BECAUSE WHEN THE SHALF OF THE HALVES IS BREAKED, THEIR FREQUENCY CHANGES. So, we tuned both halves to the desired frequency (RX at 100 Hz lower than TX), marked the RX half so as not to confuse the halves, put it in the form prepared for pouring, connected both halves to the board (each in its place, do not forget that only two extreme outputs are connected in the RX half, and the middle output is isolated and it doesn’t connect to anything and didn’t forget to shield them by itself), we connected an oscilloscope and set it to zero.
One of the halves (let's say TX) laid in the form must be fixed, for which we glue it with some kind of quick-drying glue to the bottom of the form in about 5-6 places around the perimeter, and move the other half (in this case RX) relative to the first and observe a decrease on the oscilloscope amplitude (it is necessary to achieve a minimum amplitude per volt / division of 0.02V). You need to move the half very carefully, literally half a millimeter, because the amplitude grows 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 specified volt / division, and fix the second half in this position (in in our case RX). After that, you can fill with epoxy in the same way as the "RING" in several stages, after each stage of pouring (when the epoxy has already dried up) it is necessary to check whether the balance has left. Lastly, the straight part of the half that was moved is poured (in our case, RX) , since in the event of a loss of balance, we can restore it with the help of a small (literally micron) bending or bending this straight part of the half. Again, I repeat: bending is allowed literally a millimeter (to avoid frequency drift), although even in this case, most likely the frequency will have to be corrected If the balance has gone too far, then you will have to correct it by putting pieces of various metals into the sensor (which is not desirable).The body for the DD sensor, or the method of pouring the DD sensor, must be rigid and not subject to deformation during the same reasons as described above.
Setting the scale of metals. First, after balancing, we check the correctness of the connection. It is done like this: The metal discrimination knob is at zero, the ground balance knob is in the middle position, the feeling knob is adjusted, the mode switch is in the “color only” position, take a piece of ferrite 1cm x 1cm and some kind of 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. If on the contrary, then we change the ends to TX in places. It is best to take several targets from different non-ferrous metals (because the device can not always give a reaction to copper - it after all, it has not been configured yet) in short, the general meaning of checking the correct connection is that a single signal should sound on a non-ferrous target, and a double signal on a piece of ferrite. If so, then the coils are turned on correctly. discrim to 0Kom and adjust the scale of non-ferrous metals.This is done by adding or reducing the capacitance of the loop capacitors.Depending on where we will be d add or reduce capacitance (on TX or on RX) phase "window" in 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 (toward the foil), if on RX, the “window” moves towards high-conductivity metals, such as copper. In general, we look at the table and, based on what your device “sees” after balancing, we figure out where we should add contour conduits (on TX or on RX). We ensure that all non-ferrous metals listed in the table are visible, and a piece of ferrite is cut out at the same time in the position of the BG knob about 40 K. Capacitors C5 and C12 also move this "window" a little, but we correct it more subtly with them. Personally, I set C5 to 10nf and don’t touch it anymore, C12 is pre-set according to the maximum amplitude on leg 12 of the preamplifier (MC2), and then by position C12 after the main setting I achieve more accurate and final setting metal scales. That's basically the whole setup. In fact, the device is configured much faster than I wrote all this. Its target detection range and the correctness of discrimination will depend on the quality of the tuning work you have done, so approach this matter responsibly. Good luck with your metal detector. Authors: a2111105 and Elektrodych.
Discuss the article SEARCH COILS FOR METAL DETECTOR TERMINATOR
A metal detector is a very specific and unusual tool that not every person may need. Despite its uniqueness, a metal detector is the dream of many people. Most people try to purchase such equipment, but you can do it yourself. Detailed instructions for the "Terminator 3" metal detector and a diagram are offered by many specialized forums. Look for this information in this article.
Metal detector "Terminator 3"
This metal detector model is considered by many to be one of the most popular. The developers of the device are users of one of the forums on the Internet.
It should be noted right away that assembling a metal detector with your own hands according to detailed instructions will be very difficult for those who have never been interested in this before and have not used such equipment. It will be really difficult to perform such work, but you should not be afraid of this: it is enough to carefully prepare for the process and collect all the necessary details and elements.
Depth of detection
The metal detector can search for coins and other objects at different depths:
- Five rubles - 22-24 cm.
- Catherine's penny - 27-30 cm.
- Helmet - about 80 cm.
- Beer can - a meter or more.
All given parameters are calculated for sensors with 240 mm wire and chernozem soil. Separately, it is worth mentioning the discrimination of the Terminator 3 metal detector by many users, which is completely unfair: unlike its counterparts, which can only determine the depth of an object, this model determines the metal from which the object is made.
Assembling the metal detector
To assemble and configure the metal detector, you will need the following equipment:
- Oscilloscope.
- Multimeter.
- Generator.
- LC meter.
- Frequency meter.
When buying the entire listed set for a metal detector, you will have to pay a tidy sum. In order to save money, many users prefer to limit themselves to a virtual measuring complex based on personal computer. Find the right one software, designed for such purposes, can be found on the Internet.
Metal detector scheme
By its design, the "Terminator 3" metal detector is a standard coin that has undergone some changes that allowed it to detect gold and ignore other non-ferrous metals. When using a scheme with a special "all metals" mode, the device can search for any scrap metal. The standard scheme allows you to search for coins with a metal detector, nothing more.
The non-standard application of logic as an op amp is the basis of a metal detector circuit. The disadvantage of this is the extra noise and unknown KU of all microcircuits. Of course, it is possible to use domestic logic to create a device, but this threatens with too large a spread of parameters. You can reduce damage and avoid additional problems by replacing the sound chip with a domestic analogue.
Cost of a metal detector
The price of the metal detector "Terminator" is in the middle range. When compared with similar devices of the same category, the "Terminator 3" bypasses them in terms of such parameters as the accuracy of object identification and search depth. Cheaper counterparts are significantly inferior to "Terminator 3" in all respects.
Setting up the metal detector
On the metal detector diagram, certain nodes are marked, which are taken into account, since during further assembly you will have to focus on them. This may also be needed during the setup process of the metal detector.
The emission of current oscillations by the generator is carried out after connecting the transmitting coil to it. Similar fluctuations come out of the MC1 microcircuit in the form of a meander.
The current induced by the TX and creating the field is transmitted through the receiving coil. According to the generated field, the search coil is balanced with the TX: in other words, the RX field is subtracted from the TX field. For this purpose, a compensation coil CX is used. Depending on the sensors, its representation changes: in the case of the DD CX sensor, the coil is virtual, in the “RING” CX sensor it is real. It is connected in such a way that the direction of current flow in it is opposite to the receiving coil. Balancing RX and TX is achieved by unwinding from the compensation coil.
The oscilloscope controls the balance reduction, due to which the minimum amplitude is set in all positions of the knob. One end of the compensation coil is used to make a tuning loop, which is activated after the amplitude reaches a certain point, at which it begins to increase again. TX and RX must be pre-tuned in frequency, while TX must be 100 Hz higher than RX. You can tune all the coils to the desired frequency by connecting them to the generator of the Terminator 3 metal detector and the oscilloscope.
It is not necessary to tune the CX by frequency. When a metal object appears under the sensor, the balance is disturbed, which provokes the flow of current into the RX, which is then fed into the preamplifier and the sync detector, which captures the phases of the incoming signal and outputs them to the amplifying channels. In the latter, all the received parameters are amplified and fed to the MS8 comparator, which compares the received signal levels and activates the sound generator.
The principle of operation of almost all metal detectors is similar to each other, with the exception of some nuances. In most cases, they affect the detuning of the device from the ground. In the case of the "Terminator M" metal detector, the detuning is phase.
Checking the instrument board
After soldering all the details of the circuit, the printed circuit boards of the metal detector are checked. This is done in order to check the quality of the soldering of the circuit and its performance.
The check is performed as follows:
- The printed circuit board of the metal detector is thoroughly washed from traces of flux left after soldering. It is advisable to remove all residues, since in the future they can cause breakdowns and malfunctions.
- The board power is turned on without sensor activation.
- The sensitivity knob is unscrewed until a steady sound signal appears from the speaker.
- To interrupt the speaker signal, just touch the sensor connector with your finger. The interruption of the emitted sound signal when touched indicates that the metal detector board was soldered correctly.
- After the power is turned on, the LED blinks and goes out. When the power is turned off, the diode lights up and gradually fades.
Low battery indication
When discharging battery the metal detector beeps at regular intervals. This is accompanied by a continuous burning of the LED and a sharp decrease in the sensitivity of the sensors.
The frequency settings of the metal detector are carried out using the cable with which the device will be operated in the future. The cable length remains unchanged after making all the necessary frequency settings.
Metal detector "Terminator Trio"
"Terminator Trio" is a two-tone metal detector equipped with a 250 x 300 mm DD coil. Equipped with four setting modes - "Sensitivity", "Volume", "Discrimination" and "Ground Balance" - and a switch between ordinary and non-ferrous metals.
Advantages
The advantage of the "Terminator Trio" metal detector is the confident detection of non-ferrous metal objects. The device finds non-ferrous metal in 85% of all operations, the remaining 15% are iron and rusty items.
Another plus is the absence of false positives. Many analogues react to the edges of dug pits, grass stalks or small wires, which the Terminator Trio does not sin with.
disadvantages
The only drawback of the metal detector is the poor detection of rusty iron. In almost all situations, when the device gives a dirty signal, that is, a mixture of black with an admixture of color or, conversely, a color with an admixture of black, there is a rusty metal object.
Of course, this shortcoming can be simply ignored, however, there is a possibility of losing some of the finds due to an incorrect signal. It is possible to distinguish between a pure color signal and a dirty signal only when gaining experience with a metal detector.
Search Depth
The reviews left by users on the "Terminator" indicate that the maximum search depth of the metal detector is superior to that of another model - "Asi 250" with a standard coil. Despite such assurances, in practice it turns out that according to this criterion, "Terminator" is equal to "Ace". When searching in the air for 50 Ukrainian kopecks, the detection depth is 32 centimeters, while searching on the ground for the same coin is limited to 26-28 centimeters with reduced sensitivity. Basically, a metal detector allows you to detect objects at a depth of no more than a bayonet of a shovel, which, however, can be a very good indicator for such a device.
The metal detector "Terminator Trio" cannot be attributed to devices that can start searching immediately after being turned on. The cost of the device is several times less than the cost of the new ACE 250 model, but at the same time, the "Terminator" is more suitable for those seekers who want to try their hand at instrumental search.
Results
It's not that hard to assemble. This will require certain financial and time costs, but at the same time, a user who has assembled a metal detector on his own receives certain advantages as a bonus.
"Terminator 3" is a rather powerful device in comparison with similar branded metal detector models. Given the fact that you can assemble it yourself with the possibility of saving money, it is more affordable, profitable and attractive to users.
Correctly assembling and setting up a metal detector in the absence of the necessary experience is quite difficult. Novice radio amateurs at specialized forums are provided detailed instructions and manuals that will allow you to carry out all the work correctly and without errors, which is very important when working with electronics.
The advantage of the "Terminator 3" metal detector and subsequent models is the possibility of self-assembly of the device and an affordable price. You can find the necessary schemes on the Internet at specialized forums of specialists professionally engaged in the search for metal objects. The creators of the device are always ready to give advice to those who plan to assemble a metal detector on their own.
In this article, I would like to lay out the circuit of a metal detector called Terminator-3. He justified himself both by frequent assembly by radio amateurs, and by good search characteristics, which is discussed further in the sequel. The design of this metal detector, developed by Yatogan (Yatogan, MD4U forum) and Radio Gubitel (Radiogubitel, MD4U forum), has a circuitry similar to the devices of the famous Tesoro company, but is much easier to set up. The impetus for the spread of this development was the printed circuit boards (with modifications and improvements) of another do-it-yourselfer - A2111105 (MD4U forum, Soldering iron forum).
Metal detector characteristics:
detection depth - 5 rubles Russia - 22-24cm;
Catherine's penny - 27-30cm;
helmet - about 80 cm;
beer can under - 1 meter.
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 threshold of discrimination when detecting a target (i.e., the device sees an object at the depth of detection limit, but cannot recognize the type of metal from which the object is made), then in the 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 even 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, to assemble and set up the device, we need such devices as a multimeter, an oscilloscope, an LC meter (for selecting elements according to identical characteristics for both channels of the metal detector), you may also need a generator and a frequency meter. Of course, such a set of devices costs a lot of money, and not every do-it-yourselfer can afford to purchase it, but you can try to create a virtual measuring complex based on a personal computer. Fortunately, there are a lot of useful programs for these purposes.
Device diagram: in the "document" at the bottom of the material
Terminator3 is a single-tone metal detector based on the IB principle. Simple as three pennies and reliable as a bulldozer. This is a pure coin box with a little tweak to allow you to search for gold on the beach while ignoring most of the colored junk. Although the T3 is a coin box, it can also be used to search for war and collect scrap metal. But for this it is necessary to enter the “all metals” mode into the circuit (which is provided for on the circuit and on the board), initially the circuit was without this mode.
The circuit is made with non-standard use of logic as an op-amp. The downside is that the KU of the mikruhs themselves is unknown (therefore, to average the parameters of the mikruhs, the cascades are paralleled), and the noise level is higher. It is possible to use domestic logic in this scheme, but it is not necessary, since the spread of parameters will be even greater. The only thing is that it can be replaced without damage with a domestic chip sound generator. I would also like to add that in terms of depth and accuracy of target identification (color / non-color), the Terminator 3 metal detector is on a par with branded brands of the middle price category, and a cut above inexpensive branded MDs. This is not only my personal observation, but the general opinion of a fairly large number of people who used it. Of course, for it to be so - you need to assemble and configure it as expected, and not as you have to.
Detailed description of the Terminator3 metal detector setup. Firstly, you need to look at the diagram where the nodes are indicated, that's actually the nodes and we will navigate, in the future it will come in handy for configuration. So the oscillator - generates current fluctuations when you connect a transmitting coil to it (hereinafter referred to as TX). These vibrations come out of the MC1 microcircuit in the form of a meander (like rectangular patterns on ancient Greek temples and amphorae). Now the receiving coil (hereinafter RX), it also has an induced current TX (which creates a field) and it must be balanced with this current (field) 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 with respect to RX (I will explain how to determine this later, when at least one is soldered by someone board) and by gradually unwinding the turns from it, we balance the TX and RX in current (this is called zeroing, the balance in other words).
Balance control is controlled by 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 growing again, the tuning loop comes into play (it is made from one of the ends of the CX). But before that, we must adjust the TX and RX in frequency, while doing the RX 100 Hz lower than the TX (this will be the starting point when further adjusting the "window" of the metal scale) Coils one by one are connected to the generator of the device and the oscilloscope and tuned to the desired frequency.
CX does not need to be tuned in frequency. We get that when a metal object appears under the sensor, the balance is disturbed (in one direction or another, depending on the metal), and a current starts to run in RX, which enters the preamplifier from it, where it is amplified and fed into 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 gets to the comporator MC8, the task of the comporator is to compare the signal levels in the channels and if they match, then the comparator gives permission to work the sound generator. In general, all balancers work this way with slight differences, the differences relate mainly to the methods of ground balance. In the Terminator, the detuning is phase (cutting, in other words).
Checking the metal detector board after soldering: Turn on the power on the board freshly made and thoroughly washed from the flux, do not connect the sensor, unscrew the sense knob until a constant beep sounds from the speaker, 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.
Frequency setting. All settings are made with the cable with which the device will continue to work. You cannot change its length after customization. If you have experience in manufacturing sensors for a balancer, then it will be easier for you.
