A branded device, known as the Terminator 3 metal detector, is used to purposefully search for coins of various denominations. The circuit solutions used in the device provide the ultimate sensitivity of inductive sensors, which makes it possible to identify metal objects with a high degree of accuracy.
Metal detectors under this name are assembled according to classical pattern, 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 self-oscillator, which generates a pulse signal of a relatively high frequency. As a result, it begins to radiate electromagnetic oscillations (waves), creating an alternating field in the search area. Propagating in the medium under study, this field, in turn, induces voltage fluctuations similar in shape in all metal objects.
Note! The field created by the transmitting coil affects 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 metal object appears in the area under study, the established balance is disturbed. In this case, the sensing element electronic circuit amplifies the difference signal and sends it to the actuator that generates alert pulses.
Based on the described principle of operation, the device "MD terminator 3" includes the following electronic components:
The device is designed as a constructive module with a remote probe-frame, into which the measuring coil itself is built. The main part of the electronic circuit is located in a separate console containing a power source, as well as indication and sound alert elements.
Refer to the instruction manual that comes with the device for instructions on how to use the device.
The mode of measurements carried out by the device with the excitation of an alternating electromagnetic field is classified as IB (balance of inductions). The metal detector has the following technical indicators:
To these operational capabilities should be added the presence autonomous power supply from a 9 or 12 volt battery.
The depth of detection of coins in the ground (with a working coil with a diameter of 240 mm) is:
For a more complete understanding of the principle of detecting coins, it is desirable to familiarize yourself with the VDI scale for this model in as much detail as possible, which is valid in the "Discrimination" mode and facilitates their identification.
The advantages of the product under consideration include the possibility of a clear identification of objects made of non-ferrous metals (with a probability of 85%). The rest (15%) are cases of finding iron or heavily rusted objects.
Additional Information. Devices of this class differ significantly from some of their counterparts (Terminator 4, for example), capable of determining only the depth of an object.
The list of their advantages can be supplemented by a low relative measurement error.
In various situations, such detectors make it possible to detect objects at depths not exceeding the size of a spade bayonet, which is not bad at all for this class of devices. For all other indicators, the model under consideration is considered to be a fairly “powerful” device, surpassing the well-known analogues in its capabilities.
Their disadvantages, in addition to the relative high cost, include low sensitivity to rust-affected iron. In some cases, when issuing an erroneous "dirty" signal, indicating something in between black and non-ferrous scrap (or vice versa), metal covered with a layer of rust is detected. It is possible to learn to distinguish a false signal from a useful one only after a long mastery of the methods of working with this device.
In order to make and test 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 below.
Important! Self-assembly of boards requires the ability to professionally handle a soldering iron and master the basic skills of soldering microcircuits.
All radio-electronic elements indicated in the diagram, after their acquisition, are sealed into a printed circuit board, which is placed 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 soldering of the printed circuit board. But first, it is carefully wiped with a clean flannel soaked in solvent, which allows you to clean the connecting tracks and contacts from the remaining traces of flux.
After assembling and connecting individual nodes, they proceed to configure each of the device modules, which will require the following measuring equipment:
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 is checked in the measurement mode.
The test begins with the fact that the sensitivity control knob of the device is unscrewed to the maximum so that a steady sound signal is heard in the speaker.
After that, you should touch the frame with the inductive sensor with your hand and follow the change in sound. If at the same time it is immediately interrupted, this means that everything is done correctly, and the circuit is working. Otherwise, you should check the entire circuit cascade by cascade using the same oscilloscope.
Note! The control LED after applying to the power circuit should blink and immediately go out. When the voltage is removed, it lights up, and then gradually fades.
In conclusion, we note that the final adjustment of the device is carried out at the place of its application (taking into account the soil in the area of possible search). For complete confidence in the performance of the device, it is recommended to test it on various samples of metal parts.
For many years, the Terminator metal detector has taken pride of place in the ranks of homemade metal detectors. Over the years, many improvements have been made, resulting in various modifications of this instrument. Consider the two-tone metal detector Terminator 3 (Fig. 1), which operates on the principle of induction balance. In fact, this is an advanced Terminator 4 metal detector. Its main features are: low power consumption, metal discrimination, non-ferrous metal mode, gold only mode and very good performance search depth, in comparison with semi-professional branded metal detectors. With a relatively small investment of money and time, anyone can assemble the Terminator 3 metal detector with their own hands, if they strictly follow the detailed instructions in this article.
The circuit is assembled on a circuit board. Finding a board for sale for a specific scheme is problematic, so let's create it on our own. Below is the exact plan of action for successful circuit board creation:
The size of the circuit itself should be 104 × 66 mm, so when printing, we reduce the image to the desired size. You can also download the circuit board and the program for processing and printing it from the link.
We cut off the excess edges, leaving 10 mm in reserve on each side. We buy a foil textolite corresponding to the size of the scheme with a margin of 10 mm on all sides. We clean the textolite with sandpaper to a shine, while trying not to completely erase the copper layer;
The manufacturing process can be viewed in the video below.
The scheme of the metal detector is shown in Figure 3. Based on it and the drawing of the circuit board, we assemble the board.
Parts marked with an asterisk in the diagram can be selected empirically to improve the performance of the device. But for starters, it is recommended to assemble everything strictly according to the scheme, and experiment when you get to the device settings.
The list of parts and comments on them are indicated in the table in Figure 4, and Figure 5 shows the pinout of microcircuits and transistors.
We start soldering by connecting the jumpers on the side of the radio components. To do this, we use a varnished or insulated wire of the smallest cross section. Jumpers are marked on the wiring diagram with simple thin lines.
From the side of the tracks, we solder smd parts - radio elements of miniature size and increased thermal stability. They are highlighted yellow. Then solder the connectors for the microcircuits and the remaining parts. For adjustment elements, turning on and off, changing the mode, batteries, sound and light indication - we output wires to fix these parts on the case. For adjusting resistors we find suitable caps. We also remove the connector for the sensor wire. A sample of the assembled board with a connector, regulators and switches is shown in Figure 6.
Capacitor C2.3 and switch SA3 are assembled by surface mounting.
To check the operability of the assembled circuit, we connect a 9 V battery. When the device is turned on, the LED should light up and go out, as well as when it is turned off. When you touch the sensor connector, the sound of the metal detector should stop for a short period of time. At the maximum position of the sensitivity control, there should be a tonal sound, and at the minimum, there should be no sound. Do not forget to check all the control voltages on the circuit. To do this, we turn on the tester's constant voltage mode within 20 V. We apply the negative probe to the minus of the board, and measure the voltage at the points according to the scheme with the positive one.
The case is made from any plastic box of the required size and is fixed on the metal detector rod. You can use the case from other metal detectors, such as terminator m or terminator trio. We sign buttons and controls in accordance with the functions performed.
With the successful creation of such a circuit, you will gain valuable experience that will be needed to assemble the most complex metal detector with your own hands.
An important part of any metal detector is the sensor. It consists of coils in the housing, which are searched by transmitting and receiving a signal.
To assemble the metal detector sensor, you will need the following set of components:
First of all, you need a housing for the sensor coils. For a high-quality metal detector, it is recommended to buy a ready-made ring-type case. You can also make it yourself, but this will require a lot of time and a high degree of skill and ingenuity. In the purchased case, there will already be recesses for coils of the required diameter, an output for the wire and attachments for the rod. The sensor rod can be made from any durable stick, PVC pipe and other dielectric material.
We wind the outer winding, hereinafter referred to as TX. We select the diameter according to the body, about 20 cm. We wind the winding clockwise on a round object of the same diameter, for example, on cut foam. The winding is made by two folded wires in the amount of 30 turns. You should get 4 outputs, of which we connect 2 outputs of different wires from different sides. Tightly fasten the winding sections with threads and varnish. After drying, we isolate the winding with electrical tape and wrap it with foil on top. At the end of the winding, we do not connect the foil, we leave a gap of 1-2 cm. We solder and lead out the wire to the foil, and again wrap the TX coil with electrical tape.
The inner winding, called RX, is made in the same way, but with a diameter 2 times smaller. The number of turns is 48. Just like in the TX coil, we connect two wires together.
The middle winding is called compensation or CX. We wind counterclockwise 20 turns with a single wire, taking into account that it must fit in the groove with TX. We do not isolate or varnish this winding.
You should get three coils corresponding to Figure 8. The coils will be fixed after adjusting the sensor.
The following is detailed instructions for assembly and final adjustment of coils. For this we need an oscilloscope. You can use a computer as an oscilloscope. There should be no metal objects near the metal detector. To set up, follow 2 steps.
The first step in tuning is to equalize the frequency of the coils:
We connect the TX winding according to the scheme. The wire with shielded foil is connected to the common shielded contact of the connecting wire, and then to the minus of the board. We turn on the device. We attach the negative probe of the oscilloscope to the minus of the board, and the positive probe to one of the coil terminals. We measure and record the frequency.
In the same way, we connect the RX coil instead of TX and measure the frequency.
The RX winding frequency must be 100 Hz less than the TX frequency. The adjustment is carried out by parallel connection of 500 pF capacitors to capacitor C1. For example, the frequency of the TX and RX coils is 16500 and 15900 Hz, respectively. Therefore, we need to lower the oscillator frequency for the TX coil by 500 Hz. To do this, without disconnecting the RX coil, we connect additional capacitors until we reach the RX frequency of 15400 Hz. For convenience, in the circuit we adjust all the capacitances of the capacitors and replace them with a capacitor with a capacitance of this sum.
The second step is balancing the coils:
We settle all the windings in the case and make the connection according to Figure 8. We make the connection of CX and RX with a margin, for future adjustment. We connect the minus of the oscilloscope to the minus of the board, and the plus to the output of the capacitor C5 and the RX coil. We set the time/div to 10 ms on the oscilloscope, and the volt/div to 1 V.
The setting is to achieve the minimum amplitude. You will have to constantly solder and solder the output of the CX coil in order to reduce the number of turns. As soon as we have reached the minimum amplitude, we switch the volt / division regulator to the next lower value.
So we repeat until we reach the smallest amplitude value at the smallest volt / division.
After that, you can fill half of the circuit with epoxy, leaving the adjustment loop CX and RX free. After drying, we again check the amplitude with an oscilloscope and adjust it by moving the loop. Having chosen the optimal position of the loop, we try, without moving it, to fix it with super glue. And after one more check, we completely fill the coil with epoxy glue (Fig. 9).
The assembled sensor can also be used on terminator pro, terminator trio and terminator m metal detectors, with the correct and high-quality circuit settings.
To configure, turn on the SA2 switch in the non-ferrous metal only mode. The cutoff point of the ferrite should be in the region of 40 - 50 kOhm, so we set the ground balance regulator R8 to this range. If the cutoff point is in the range of 0 - 40 kOhm - add a capacitance to C2 in parallel, and if 50 - 100 kOhm - add a capacitance to C1. The discrimination regulator R7 should be equal to zero, so we unscrew it to its extreme position clockwise. We bring non-ferrous metal and ferrite to the metal detector. If two signals sound on the ferrite, and one on the non-ferrous metal, the windings are connected correctly, if vice versa, we swap the conclusions of the TX coil.
With a decrease in capacitance C1, a shift towards the foil occurs, and with a decrease in capacitance C2, towards aluminum. We achieve the visibility of all metals from the table, the visibility of copper and the cutoff of ferrite with a ground balance of 40 - 50 kOhm. Capacitor C12 make an additional adjustment.
After setting up the metal detector terminator 3, we enter the search area and turn on the metal detector with the SA1 switch. We approach and move away the sensor from the ground. When giving signals, gradually unscrew the R8 soil regulator counterclockwise, achieving the absence of signals to the ground, and make sure that copper is visible. It is desirable to mark the successful position of the regulator. By turning the discrimination control R7 counterclockwise, we cut out the metals we do not need. The cutting takes place alternately from the foil and further, according to the table in Figure 10. With the R29 sensitivity knob, you can increase the visibility range of metals and adjust false alarms. The SA2 switch is recommended to be set to the all-metal mode, as it slightly increases the detection range. Switch SA3 can turn on the mode - only gold, which works when the mode is turned on - all metals.
Since the price of non-ferrous metals and old coins can be very high, when searching in the right area, you can quickly pay for a home-made metal detector.
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 at a high level, low current consumption of the device, cheapness 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 the smd resistors, then the 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 a 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 short-circuited coil. 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 on 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 you unscrew the feeling knob 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 is a double beep, then everything is fine, if it is single, then the ends are switched to the TX in some places), connect the oscillator 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.
Easy to assemble and set up, along with an enviable sensitivity. The device showed itself from the best side, discrimination at a high level - linearly removes the entire VDI scale, low current consumption of the device, cheapness and availability of parts, as well as the ability to work on heavy soils (very easy to build up from the ground), all this made (t3) excellent a device for middle-level search engines. Make yourself such a device and you will see for yourself. The device board has been tested and works with a bang.
Operating modes:
- dynamic search for all metals
- discrimination without threshold background
Specifications:
- The principle of operation is inductively balanced
-Working frequency, kHz 8-10kHz
-Dynamic operation mode
- Precise Detection Mode (Pin-Point) No
-Meals, At 9-12
- There is a sensitivity level control
- There is a threshold tone control - There is a ground detuning (manual)
Air detection depth with DD-250mm sensor
- coins 25mm
- about 35cm
-gold ring
- 30cm
- helmet 100-120cm
-max depth 150cm
- Current consumption: - Silent approximately 35mA
Metal detector scheme
The circuit requires almost no adjustment, but it is "almost" true if you assembled the board without using flux, but only rosin in alcohol. Also, soldering should be neat - there should be no clamps and sticky, after assembly, be sure to rinse the board with alcohol.
Parts side fee
We start the assembly by soldering 16 jumpers, then carefully solder the SMD resistors, then the sockets for the microcircuits and everything else. not stable, did not turn it up and the feel dropped a lot, in other matters you get used to it and the setting becomes not difficult at all.
Below is a photo of the board with resistors and the pinout of the components.
The board is ready to be inserted into the case. The MC10 chip and its harness can not be installed, this is a low battery indicator, it is expensive.
Coil making
The DD sensor is made according to the same principle as for all balancers, so I will focus only on the required parameters.
TX is the transmitting coil and RX is the receiving coil. number of turns: 30 turns with a wire folded in half wire diameter: 0.4 enameled winding Both the transmitting and receiving coils are wound with a double wire (that is, 4 ends of the wire should be obtained), we determine the winding arms with a tester and connect the beginning of one arm to the end of the other, it turns out middle 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 wound 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 !!! Coils can be shielded with graphite, for this we mix graphite with nitro varnish 1: 1 and cover it with an even layer on top of 0.4 tinned copper wire wound on a coil (without gaps), we connect the wire to the case.
Another small recommendation, now regarding the manufacture of the device board. It is highly desirable to have a tester that can measure the capacitance of capacitors. The fact is that the device has two identical amplification channels, so the amplification through them should be as identical as possible, and for this it is desirable to select those details that are repeated on each amplification stage so that they have the most identical parameters measured by the tester (that is, which readings in a specific cascade on one channel - the same readings on the same cascade and in another channel), and it is also desirable to select the C1 and C2 contour conduits with the same readings on the tester, this will greatly facilitate your device setup.
On my 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 exactly to the conder rating that is indicated on scheme. For example, I 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. But you can set other values (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 the discrimination to some targets (such as gold for example). Therefore, I think that it is better to choose, as they say, the "golden mean" - this is approximately 10KHz - 14KHz.
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 you unscrew the feeling knob 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 a double beep sounds, then everything is fine, if it is single, then the ends are switched to TX in places), connect the oscilloscope 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! edge of the scale, copper on the other edge. This is where you get your bearings.
Here, for reference, the entire VDI scale, with the discrim knob position at a minimum, the device should see all non-ferrous metals, when the discrim is wound, all metals should be cut in order to copper, it should not be cut less, if the device works like this, then it is configured correctly
Here are some characteristics of the "Terminator 3" metal detector: detection depth - 5 rubles Russia - 22-24cm; Catherine's penny - 27-30cm; helmet - about 80 cm. 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 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 it, but you can try to create a virtual measuring complex based on personal computer. Fortunately, there are a lot of useful programs for these purposes.
The software can be downloaded as on our old site elwo.ru. Finally, one important note for beginners - if you are not confident in your abilities, it is better to assemble a simpler Volksturm IB metal detector first (master the basics, the principle by which the IB device as a whole is built will become clear). Next, I give the basic scheme of the Terminator 3 metal detector.
Terminator3 is a single-tone metal detector according to the IB principle. Simple as three pennies and reliable as a bulldozer. This is a clean coin box with a little tweak that allows you to search for gold on the beach while ignoring most of the colored debris. 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 par with medium-sized branded brands. price category, and head and shoulders above inexpensive branded MD. This is not only my personal observation, but the general opinion is quite a large number the 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 TX current (which creates a field) and it must be balanced with TX by this current (field) (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 begins to grow 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 stop 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 various versions printed circuit boards you are in the archive.
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. Further, read the winding technology for the Terminator3 metal detector. Video on setting up the device and latest versions boards and firmware look at the forum. Project authors: a2111105, Yatogan, Radiogubitel, Elektrodych.
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