One day I had a chance to start assembling a Quasar. I’ll skip assembling the block, because... There’s nothing complicated there, I’ll stick with the reel. According to the Author's recommendations, a DD sensor was used with the following parameters: outer diameter 230 mm, in the transmitting coil TX - 40-45 turns of 0.5 mm wire, RX - 200 turns of 0.2 mm wire. The TX circuit is connected according to a circuit with series resonance, the approximate capacitance is 0.3 uF. It was tuned to a frequency of 8.5 kHz, but in general the device can operate at a frequency of 4.5 - 9 kHz. The RX circuit is connected according to a parallel resonance circuit, and is tuned to a frequency 1.5 - 2 kHz below the TX resonant frequency.

Subtleties:

We wind the second coil in the opposite direction relative to the first (the current of the DD coil should flow in one direction), since we wind the coil on the same template, the second coil will turn out to be inverted and the current will flow in the opposite direction.

To obtain a minimum voltage in the future (after filling with epoxy, the coil will be slightly unbalanced), when winding the last turns of the transmitter coil, wind them with a margin so that you get a loop at the bottom of the “tuning turns” coils, and do not fill them. Now that everything is filled with resin, move this loop in different directions until you achieve the minimum voltage on the receiver coil, then you can finish pouring.

The coils were wound on mandrels and soaked in “88” glue. Coil stiffness
after drying, it is such that they can be bent to obtain the desired configuration.

The terminal of the receiving circuit that is closest to Cx (i.e., the internal terminal) should sit on ground. This nuance affects the quality of the balance.

If the detuning of the ground and ferrite is in the minus, re-solder the ends in places in the PX and everything will go to +.

When adjusting from the ground, the value should not be more than +80, roughly speaking it should be from 0 to +35, the adjustment from the ground affects the sensitivity. The less interference, the weaker the intuition.

If with foil, then shield only the RX (lower receiving) coil. TX - may not be shielded. If you shield both, then only through the insulation between them. If you cover
graphite, then completely without any gaps.

The sealed lead-in must be located in the TX field, the coil leads must not pass through Cx (the center is the intersection of the coils)

The auto balance button must be pressed with the sensor raised, and then lowered and raised.

For 5 kopecks of the USSR in black soil with a 25cm DD coil there should be a sensitivity of at least 25cm with clear discrimination. VDI can jump at 30cm, about 1-2 sectors with a figure of 3 segments (but there should be no gaps between segments, such gaps will exist if the target is made of black metal) and there should be a high sound signal on both sides of the swing, so you need to choose what to trust more: VDI or audio signal. In Quasar everything depends on the coil parameters...

DIY metal detector Quasar ARM

Metal detector Quasar AVR is selective equipment with the ability to recognize metals. Signal processing is direct. In the unit, the VDI scale consists of 16 columns and it is possible to remove any of the metals from the search. The Quasar Avr has a multi-tone sound indicator. The latest modifications of the equipment have an operating frequency of up to 17 kHz. This indicator depends on the search coil.

You can make a Quasar Avr metal detector with your own hands - the level of complexity of the circuit is average. The Quasar coil and programmable microcontroller create certain problems for radio amateurs. This type of metal detector can be manufactured by people who have experience in developing similar devices. It will be difficult for beginners to make the board and coils on their own.

The metal detector is equipped with a display, thanks to which you can quickly recognize metal.

Quasar has buttons that allow you to control the device:

1. “Up / Barrier + / Autotune”;
2.Enter / OK / Ground balance" ;
3.“Right (+) / PinPointer”;
4.“Left (-) / Backlight”;
5."Menu/Esc";
6."Down/Barrier-/Autotune".

Creation of the Quasar AVR coil

The DD type coil must have a diameter of 230 millimeters. The number of turns of the external winding should consist of 40-45 turns, the diameter of the wire should be 0.5 millimeters. The internal winding should consist of 200 turns of wire with a diagonal of 0.2 millimeters.
The external winding should be connected to a metal detector with series resonance, the condensate capacitance should be 0.3 mF. Connecting the internal winding to a device with parallel resonance.
It’s not difficult to create a Quasar Avr metal detector with your own hands if you stick to the basic diagram.

Quasar AVR diagram

All components are freely available and their prices are low. The operating characteristics of the device are quite good and it will compete with branded entry-level metal detectors.

List of parts for Quasar workstation

Setting up Quasar AVR

Metal detector Quasar AVR has the following characteristics:

The volume level can be adjusted within 0-7 units. For this purpose, you must use the buttons from the Left (decrease) and Right (increase) menus;
The response threshold value is 1-30. Adjustment is made using the Up (increase) and Down (decrease) buttons located on the screen;
There is a ground balance. To enable this mode, press the OK button in the main menu of the screen. For the readings to be correct, it is necessary to turn on the mode when the sensor is raised above the ground. Raising and lowering it will allow you to achieve the smallest response deviation from the ground. To save the results, you must click OK. If you exit the menu using the Esc key, the changes will not be saved;
·mask – with its help you can close sectors that do not arouse interest;
The screen is backlit. It is always on the menu. The Left and Right keys in the main menu allow you to turn the backlight on/off;
·you can adjust the backlight level. The Left and Right buttons increase or decrease its brightness;
·change volume in the range 1-32. In order to increase or decrease the sound, you must use the Left and Right keys;
sound delay – when metal is detected, the signal disappears for several seconds;
· ferrite calibration. The Up or Down buttons allow you to switch the ferrite calibration to automatic mode. A small piece of ferrite must be passed over the coil several times, but not close to the sensor. The obtained deviation results can be saved by clicking on the OK button;
·sensor balance – allows you to control the level of imbalance during operation;
·You can adjust the transmission frequency. This function allows you to set the frequency of the external coil and tune its circuit to resonance.
Configuring the Quasar AVR metal detector is carried out as follows:
1.It is necessary to supply power without connecting sensors. Initially, the operation of the controller is checked. If the LED constantly blinks, this indicates that the Quasar AVR metal detector circuit is connected incorrectly. If the display is working properly, an error message will appear on it. If the controller is output correctly, the LED blinks 1-2 times and loading continues;
2.Using a trim resistor, you need to set the best image quality;
3. The frequency of the external coil is manually adjusted to the resonant frequency of the sensor;
4. record deviations during ferrite calibration.

For better performance, you need to perform the following manipulations:

• R29 - select the resistor resistance so that the voltage value on the indicator is equal to the voltage on the battery;

• R9 - select a value so that the current consumption of the output stage of the device is equal to the true value. We measure the voltage drop across this resistance, then measure the current readings in the Quasar menu, and calculate the resistance of this resistor using Ohm’s law.

• R3 - by adjusting this resistance one of the important settings is made - the quality factor of the TX circuit. The recommended value is 5...6. Using a donkey, we measure the peak-to-peak voltage swing (Vpp) of capacitor C6 (I strongly recommend installing a jumper on the board, and the capacitor itself in the sensor). Next, you need to divide the resulting value by 5 (the swing voltage). By selecting a resistor we make the result 5...6. If the quality factor is underestimated, we will not be able to achieve maximum sensitivity. If the quality factor is too high, the sensitivity will be too high and, as a consequence, problems with discrimination and false positives

• R7 - by selecting this resistor, the gain of the input stage of the metal detector is adjusted. For inexperienced radio amateurs I recommend achieving 50, and for professional ones - 100 higher.

All the information necessary to make a QUASAR metal detector with your own hands

Quasar is a selective IB metal detector with metal recognition and direct signal processing. The VDI scale in Quasar is divided into 16 columns, with the ability to remove any of the columns from the search (Closing them with a mask) as well as audio multi-tone indication. In the latest firmware versions, the Quasar's operating frequency can be up to 17 kHz and depends on the search coil.

The Quasar metal detector circuit has an average level of complexity (The only component in short supply is the MCP3201, so there is already a metal detector circuitand Quasar AVR where, thanks to replacing the microcontroller, this problem was also eliminated). But the presence of a programmable microcontroller and coil for Quasar, as for any other selective metal detectors, creates some difficulties for radio amateurs. The manufacture of Quasar is carried out by people with experience in the manufacture of metal detectors. In general, the Quasar metal detector has medium difficulty level for making it yourself.

Download the Quasar metal detector diagram in pdf format —

The presence of an accessible screen makes the Quasar a very convenient and easily repeatable metal detector with metal recognition.

Working screen of the metal detectorQUASAR as follows:

Metal detector discrimination scaleQUASAR divided as follows:

The KVASAR metal detector is controlled by 6 buttons:

• SW1"Up / Barrier+ / Autotune"
• SW2"Enter / OK / Ground balance"
• SW3"Right (+) / PinPointer"
• SW4"Left (-) / Backlight"
• SW5"Menu/Esc"
• SW6"Down/Barrier-/Autotune"

Firmware for the Quasar metal detector Version 1.4.5 (the latest firmware version for today) –

For flashing the microcontroller of the Quasar metal detector, programming fuses must be arranged as follows:

Making a coil for the KVASAR metal detector

The developer of the Quasar metal detector gives a brief description of the search coil he made. Coil type DD with outer diameter 230 mm. TX – 40-45 turns with 0.5 mm wire and RX – 200 turns with 0.2 mm wire. The TX winding is connected to a metal detector with serial resonance, the capacitance of the capacitor is 0.3 mF, the resonant frequency is 8.192 kHz, the RX winding is connected to a metal detector with parallel resonance, and is adjusted to a frequency 1.5 - 2 kHz below the TX resonant frequency.

Below is diagram for connecting such a coil to the Quasar metal detector

Description of launching and setting up the KVASAR metal detector with oscillograms -

Description of the menu and settings in the Quasar metal detector -

Conclusion: The QUASAR metal detector has a simple circuit and inexpensive components (microcontroller, screen, etc.), which makes it very attractive for self-production. In operation, Quasar shows quite pleasant characteristics and good results, and can easily compete with entry-level branded metal detectors.

The metal detector project received its continuation in versions and QUASARAVR, Therefore, it’s worth starting to manufacture these particular versions of the metal detector, since the author has stopped releasing firmware updates for QUASAR!

When writing, materials from the author’s website were used - http://fandy.ucoz.org/

All questions about the Quasar metal detector can be asked in the comments to this article. And also write your review, wishes and suggestions for adding to this material.

QUASAR ARM (Quasar ARM) is a metal detector with direct processing, developed on a modern basis using an ARM processor.

Main characteristics of the device:

• DD sensor 30x32 cm 6-11 kHz.
• Multi-level display backlight is adjustable.
• Multi-tone dubbing with the ability to select dubbing options in relation to search conditions.
• Target designation function (pinpointer).
• Metal discrimination - is grouped into 16 sectors, three sectors go to ferrous metal, the rest to non-ferrous metal.
• Possibility of masking each of 16 sectors, Masking of unnecessary metals.
• Ground balance setting is automatic, with manual adjustment if necessary.
• Device microprocessor, based on STM32 (fast signal processing).
• Device weight: 1.3 kg fully assembled.
• Numerical VDI display on display.
• Information is displayed on a liquid crystal display and contains readings - supply voltage, battery charge, VDI scale (upper), “slider scale” distance to target, mask (type of metal).
• Adjustable rod.
• Possibility of installing/changing software; in-circuit programming of the device is provided (this item must be performed by a specially trained person who has the necessary equipment and skills). To date, they have been released with firmware 2.1.8 and 2.1.9, but in practice we have seen that 2.1.4 is currently the best of the existing ones.

Main characteristics of this assembly:

• Samsung 2600 lithium-ion battery(actual capacity) mAh 3.7 V;
• DC-DC power converter-stabilizer 3.7-6.3 V;
• collapsible, adjustable rod, lower part - impact-resistant plastic, upper part - high-strength aluminum;
• high quality board, factory-made, double-sided with a protective mask and metallized holes.

Sensitivity:

• 2 kopecks 1817 = 30 cm (in the ground);
• 1 ruble 1817 = 45 cm (in the ground);
• average detection range by air = 30-55 cm for coins;
• large metal objects up to 150 cm;
• maximum depth (machine) - 2 meters;
• cuts off nails and other debris

Equipment:

• Coil 6-11 kHz, DD 30x32 cm.
• Control block.
• Collapsible rod.
• Lithium-ion battery.
• Charger.
• User manual.

It should be especially emphasized that the quality of the Quasar ARM metal detector (I prefer the Latin spelling Quasar ARM) fundamentally depends on the quality of manufacturing and layout of the printed circuit board (there are more than ten options sold, and not all are good), the quality of components and installation, and especially - on the quality of the sensor. Therefore, it is funny to read negative reviews about the device as a whole, based on the experience of assembling clumsy parts from parts found in the trash. Moreover, judging by information from various specialized forums, such ugly crafts make up the bulk of the instruments and sensors offered for purchase. Faster, cheaper, and that will do - apparently, this is the main goal of most sellers (I by no means speak for everyone). Of course, this approach entails a lot of negative reviews about the device, although it would be wise to write a review about the manufacturer. To set up a Quasar workstation well and make a decent sensor, you need not only knowledge and experience, but also normal measuring equipment, not to mention the ability to use it. Craftsmen often make do with a Chinese tester from a flea market... this is also possible, but is it worth expecting a good result? Another point, many “Kulibins”, without even having basic knowledge in the field of electronics, try in every possible way to “modify” and “improve” the author’s circuit (I often cite it as an example of high-quality development), created by a professional. Based on these, so to speak, improvements, printed circuit boards are then hastily laid out and immediately put on sale. What can I say... only that such crafts have nothing to do with the real Quasar ARM and any reviews about such “Quasars” are nothing more than a painting of one’s own incompetence. Here and further we will talk exclusively about devices assembled with direct hands according to the author’s scheme.

Review of the Kvazar ARM metal detector

Quasar AWP, assembled by me on the author's board revision 1.4, the firmware current at the time of writing this review is version 2.2.10. A family of homemade sensors from a sniper rifle to a “steering wheel” for medium frequencies of 7..9 kHz. The scheme is the author's, no changes.

I can immediately responsibly declare that a Quasar AWP correctly assembled from high-quality components, equipped with a well-made sensor, has search characteristics that are often superior to the top devices of leading manufacturers in their segment (single-frequency ground-based IB devices). This does not negate the mandatory understanding of the principles of operation and the ability to configure the Quasar workstation for specific conditions, as, indeed, any branded metal detector.

In addition to Quasar ARM, I collected and tested analog devices such as Tesoro Vaquero and Lobo, Whites Classic in different variations, some ancient Fisher... they were all single-tone, I personally didn’t like it. The plans are to build something like Golden Mask 4, two-tone analog... but these are plans. From digital cameras I collected Quasar AVR, pulse variants of Clone (author Andy_F), Fortuna-M. Among the branded ones were “Koshchei-25K”, Terka-705, I tried new digital Whites, now I use Deus (studied and touched up and down). This is all to say that I have something to compare with. It may seem to some that I am “singing praises” to the device... this is not so. He, like everything in the world, has shortcomings, I will definitely write about them. Therefore, without false modesty, I can say that my review of Quasar AWP will be objective and honest.

So, from the very beginning.

Schematic diagram. As an electronics engineer by training and hobby, I rate the circuit 4.9 points out of 5.0. Here it is appropriate to quote a teacher-professor: “Only the Lord God knows the strength of materials perfectly, I know a B, and all of you (students) know a C at best!” No matter how much I looked at the diagram, I couldn’t improve anything (I’m not a guru, of course, but I have experience in development and implementation in production). Do it differently - yes, but improve it - no.

Printed circuit board. From the point of view of signal wiring, the author’s one is good, but it’s a little difficult to make on your own due to the large number of vias, and it was also originally designed for a non-standard and scarce type of display. You can install a regular one on it, with a couple of “extra” wires, this is not critical. Otherwise, it’s one of the best, if not the best. There will be a separate review about all other boards.

Components used. Widespread, not scarce and not expensive. The total cost does not exceed $40 if you buy everything new. It is better to use an OLED display, but it is somewhat more expensive than a regular LCD.

Repeatability. High... no, highest. Everything works without any adjustments to the hardware, the main thing is to assemble it correctly from serviceable components and properly rinse the board from flux. The operation is practically independent of the variation in the parameters of the parts - a sign of a high-quality circuit design.

Flexibility of settings. Everything you need for an effective search. It is especially worth noting the perfectly working sensor imbalance compensator (allows you to work normally even with a “floating” sensor, or with an “almost suitable” factory one), switchable automatic ground balance with adjustable reaction time, a set of ground filters (speeds) for all occasions, 8 memorized profiles , arbitrary mask for voice acting. Vector cutting of soil, allowing you to very accurately “cut” it without loss of range (well, almost without loss). There is a static pin mode with discrimination and VDI display. The set of settings corresponds to a professional level, so it is advisable to understand the issue a little and not use it at random. However, by default everything is fine.

Voice acting, display. Three voice-over schemes, including polyphony (scheme 1), which I consider the most informative. The sound is soft and pleasant. Adjusting the volume of weak signals, several additional ones. options, including thrashhold. 16-sector signograph, display of VDI number, signal strength, battery charge level, current ground angle, transmitter current. Signograph display delay adjustment. Again we see a set for a professional. Very informative and convenient. The latest versions of the circuit and board have a built-in FM transmitter for using wireless headphones. It works great, all adjustments are in the menu. Do you know many devices with wireless “ears” by default and with transmitter adjustments?

Depth. Depends on the settings, mainly on the filter. The threshold also affects. The slower, the deeper. On the slowest filter with threshold 3, with a DD25cm sensor, you can “feel” a patch of tips at 35..38cm. This is in light soil, for example, Deus with a 28cm sensor catches only barely better, “at the end”, at similar “depth” settings.

Identification and division of goals. In fact, everything here depends more on the sensor and settings. But if we compare with identical sensors, then at maximum speed the Quasar ARM approximately corresponds in speed to the Deus in “second gear”, that is, Reactivity = 2 (out of 5). Very good, with a small sensor on the garbage it is very comfortable. The separation with the appropriate filter settings is excellent, the separation of color against the background of black signals is also at the Deus level, no subjective differences were found. If they see, then both devices, if they don’t see, then both.

Stability, overall comfort. On high. If the same Deus with “quiet” settings turns into a pumpkin, then the Quasar ARM almost does not lose in depth. That is, with a normal Quasar, it is more comfortable to search for an automated workplace than with a Deus, this is in clean places. In the trash, Deus has no equal, but if there are not many signals, you can walk with Quasar in almost silence, and Deus will be a little babbling - but he is also somewhat deeper. Quasar ARM is one of the most comfortable in search of all the devices that I have had.

Flaws. What would it be like without them... true, they are all subjective, but still. To begin with, I don’t like the small number of voice-over schemes and the inability to customize the frequencies and volumes of the sectors to suit you. In the same Koshchei-25K, Fortuna-M it was and it’s convenient. I really hope that the author will eventually listen to this opinion, it is not only mine. Then the speed, it (after Deus) seems a little insufficient for strong trash cans. In pin mode, sometimes (rarely) it “starts up”, it is cured by resetting it with the “left” button (this binds to the current response level). I’m attracted to the ears: for an effective search it requires some knowledge in this area, an understanding of the physics of processes. However, like any other professional device.

Conclusion: Quasar ARM is, in my opinion, the best of the home-made devices in terms of the totality of characteristics. No more, no less.