MD quasar arm electronic switching circuit. Modernization of the circuit. Quasar Arm firmware

TO vazar ARM is a selective metal detector with an LCD screen and the distribution of metals into 16 groups. This is a continuation of the Quasar metal detector project. The new circuit uses a more powerful ARM32 microcontroller and adds additional features.

Technical characteristics of the Quasar ARM metal detector:

· Operating frequency – from 4 to 16 kHz;

· Indication - multi-tone audio and visual LCD screen.

· Power supply – 12 volts.

· The detection depth of a 5 kopeck USSR coin (with a 23 cm DD coil) is 30 cm.

This metal detector has medium difficulty level , for DIY playback! Only people with experience should undertake its production. There are SMD components (which can cause difficulties for a beginner), a programmable microcontroller, and a coil for an IB metal detector, which also causes a lot of trouble if you don’t have the proper experience. But if all these nuances do not bother you, then the device will pleasantly please you. Also, a big bonus when making it is a large number of discussions on the Internet, where a lot of questions have already been discussed!

Improvements in the new Quasar AWS:

· Removed external ADC, which was difficult to purchase.

· Increased sensitivity.

· Frequency range from 4 to 16 kHz.

· Improved sound quality.

· Added three profiles for saving and restoring settings (A, B, C).

· Electronic compensation has been introduced to eliminate coil imbalance.

Scheme of the Quasar ARM metal detector

Download diagram and parts list for the Kvazar ARM metal detector -

Printed circuit board of the Quasar AWP metal detector

Archive with printed circuit board quasar workstation -

Board with screen for Quasar AWP metal detector

For the Quasar AWP metal detector, you can use RC1602A screens with an HD44780 or KS0066 controller.

After making the board for the Quasar AWP metal detector, you need to flash the microcontroller. To program the microcontroller, you can use the st link v2 programmer (it is available in online stores), but for those who have a COM port (a big luxury these days), you can use a simple programmer on your computer according to this diagram (The diagram is taken from here - http://forum.cxem.net/index.php?showtopic=144107&st=20):

Firmware for the Quazar ARM 2.1.2 metal detector (latest at the time of writing) –

Archive with firmware for the Quasar ARM metal detector and a description of their changes -

After flashing the metal detector, it is necessary to carry out test runs and begin manufacturing the search coil.

Operating instructions for the Quasar ARM metal detector -

I found this video description of the manufacturing process of the block and coil of the Kvaraz AVR metal detector:

Part 1, starting with the board

Part 5, let's move on to making a coil for the Quasar metal detector

Part 12, completion and fine-tuning

Conclusion: Quasar ARM is a decent mid-level metal detector. If manufactured correctly, it may well compete with branded analogues. The main purpose of a metal detector is to search for coins. The circuit does not contain expensive and scarce components, but has a number of technological nuances and is demanding on the quality of coil manufacturing. To repeat it, it is recommended to “have” experience in similar products, otherwise the result may disappoint you!

Materials used when writing this article:

· Forum Scheme.net - http://forum.cxem.net/index.php?showtopic=144107&st=0

The FAQ section was created for the convenience of obtaining basic information about metal detectors. Here you can find a description of how to set up, video instructions, diagrams, etc. Answers to frequently asked questions. We recommend that everyone who is interested in this or that device start by studying the information in this section. You can fill out information in this section by contacting the administrator. We welcome the participation of each forum participant. As the section is filled with information, each of us will be able to more fully study the device of interest, its capabilities and characteristics, and receive informational assistance as a foundation for subsequent successful development and maximum effective use.

• Quasar workstation

• Quasar ARM is a selective metal detector with an LCD screen and the distribution of metals into 16 groups. This is a continuation of the Quasar metal detector project. The new circuit uses a more powerful ARM32 microcontroller and adds additional features. This metal detector has an average level of complexity, so you can reproduce it yourself! Only people with experience should undertake its production. There are SMD components (which can cause difficulties for a beginner), a programmable microcontroller, and a coil for an IB metal detector, which also causes a lot of trouble if you don’t have the proper experience. But if all these nuances do not bother you, then the device will pleasantly please you!

  Technical characteristics of the Quasar ARM metal detector:

  • Operating frequency – from 4 to 16 kHz;
   
  • Indication - multi-tone audio and visual LCD screen.
   
  • Power supply – 12 volts.
   
  • The detection depth of a 5 kopeck USSR coin (with a 23 cm DD coil) is 30 cm.
   
   

  Improvements in the new Quasar AWS:

   
  • Removed external ADC, which was difficult to obtain.
   
  • Frequency range from 4 to 16 kHz.
   
  • Improved sound quality.
   
  • Three profiles have been added to save and restore settings (A, B, C).
   
  • Electronic compensation has appeared to eliminate coil imbalance.
   
     

A metal detector is a means of finding car keys lost in the garden or sewer hatches under the leaves during autumn :)

This metal detector is called Quasar (Quasar), it was developed by Andrei Fedorov, but not without the help of members of the md4u.ru forum, who gave advice and reported errors during testing of new versions of the software.

Quasar is a metal detector with direct processing, working on the principle of induction balance. The main advantages of such metal detectors are the ability to detune from the ground, as well as the difference between metals in their resistance and ferromagnetic properties.

This metal detector can determine what metal lies underground, although not with 100% probability, but it can easily determine non-ferrous metals from ferrous ones, and in most cases which non-ferrous metal is located under its coil.

It can notify the owner about metal underground using sounds of different tonality (frequency), and display information on a sixteen-character two-row display in the form of a histogram. It has a bunch of settings, but first things first.
Be careful, there are a bit more pictures below.

In the current implementation we have:

• Automatic ground tuning
• Automatic resonance tuning and manual mode
• Volume adjustment
• Adjusting display brightness
• Pinpointer mode
• Setting the low supply voltage limit for auto shutdown
• Ferrite calibration with the possibility of adjustment
• Ability to select voiced targets (mask)
• Several sound schemes for voice acting
  • Scheme 1: Frequency varies smoothly depending on the VDI target throughout the entire range
  • Scheme 2: Frequency varies smoothly depending on VDI from 0 (90) to 41 (131) degrees. Targets below 0 are sounded in a low tone, above 41 - in a high tone
  • Scheme 3: Targets below 0 (90) are sounded in a low tone, above 0 (90) - in a high tone
• Three coarse gain levels
• 30 smooth gain levels
• Soil filter
• View coil balance in real time

The circuit is not complicated, there are no particularly scarce parts. You can download it

Let's start with the barbell. It remains with a simpler implementation of the "Volksturm sm+geb" metal detector. It was made from PVC pipes with adapters at 45 degrees. Before gluing, this design looked something like this:

After gluing we have a working stick:

The reel seat was made using plastic bolted connections, used in the same plumbing fixtures, which is then attached to the reel using epoxy glue and can be detached from the rod:

We made the armrest from the photodrum of a large A3 format copier :) That is, we attach a little grinder, a drill, to a rod and it turns out that the whole structure held up pretty well.

We wrap the handle with something soft, then close it with a large-diameter heat-shrink tube, warm it up, and you get a comfortable, ergonomic handle :)

We're almost done with the mechanics, we'll paint it later. We will not talk in detail about how the board was made; we will only dwell on the essential points. The Cradex Z5 case with dimensions 103*90*40 fits perfectly under the printed circuit board developed by one of the forum participants for microcircuits in DIP packages. Link to the board at the end of the article.

We buy parts, measure how suitable the board design is, and take electric capacitors from the low-ESR series.

Textolite was etched in ammonium persulfate. Poison quickly and beautifully. Just fill it with warm water, about 80 degrees.

Afterwards the display is soldered and turned on for the first time - testing.

If one line of dark rectangles is visible on the screen after power is applied, the screen is working and this is its self-test mode - when power is applied, but control commands have not yet been received (there has been no initialization).

You won't see some components on the board from the parts side, because... I couldn't find them in the DIP form factor. This is an adjustable zener diode TL431, a pair of filter capacitors and not beautiful wires in the area of ​​the operational amplifier, because We couldn’t find the original one, we took a similar one, but it had a slightly different pinout - we had to be tricky :)

Let's start working with the body. You need to make several holes in it - for the screen, control buttons, coil connector and power connector. The case must also be insulated from moisture - otherwise the device may begin to malfunction or fail. For the convenience of cutting a hole for the screen, we took a screen with the same functionality, only with a blue filter, since our green one was already soldered to the board with a permanent connection.

It stood up perfectly, but :) When we tried to try it on for our screen, disappointment knew no bounds :) They turned out to have different sizes. I had to finish it.

In the end, everything worked out. Tried it on, connected it, it works :)

The upper front panel was recessed flush with the plastic so that it did not protrude, because then it was planned to cover it all with film and a sticker. The screen itself was secured with a large amount of hot-melt adhesive. This type of connection has two advantages: water will not get inside and there are no bolted connections, which would then still have to be sealed.

They poured it with a regular heat gun, and where it didn’t warm up well, they helped with a hairdryer from a soldering station. At this moment, the screen itself may change color to bluish or some other color due to heating; the main thing here is not to overdo it. After cooling, the color returns to normal and everything works normally.

We made the board for the buttons ourselves, because... there was no suitable ready-made one for this building. There will be a file at the end of the article. The diodes in it are smd.

And so, all the holes are made, the button board, speaker, power connectors and coil connections are also sealed with hot-melt adhesive.

Regarding the design, we thought for a long time about what color to choose. We chose the black option.

The technology is simple. We print the picture and cut out a hole for the screen. They cut with a scalpel. Next, glue the film under the screen of the design, then take a transparent, matte, self-adhesive film and glue the resulting pie onto the plastic, cut out the excess film and you’re done!

The block was attached to the rod using a piece of thick plexiglass, cut into strips and bent under the influence of local heating, screwed with one side to the box, the other to the “pipe holders” or whatever this crap is called...

By the way, later the two outer fastenings were removed, that is, the whole thing held up perfectly even on two fastenings.
So, after carrying out all these operations, we painted the bar and this is what came out:

Separately, it remains to talk about the coil. We can say that this is the most sensitive element and it must be assembled so that when searching for and touching all kinds of grass and other objects, it does not “microphone” and reacts only to the phase change caused by the metal under the sensor. We immediately wanted to make the coil as it should be, we wound the coils... By the way, all the wires were taken from an old CRT monitor. Its demagnetization loop fit perfectly under the transmitting TX coil, a thinner wire was found in another coil, the wire to the metal detector unit was taken from its non-detachable VGA cable, in general there were enough wires from there :)

After two coils have been wound, one of them (receiving, RX) must be wound into a screen made of foil or graphite. If it is foil, then it is necessary to make sure that there is no short-circuited turn from this screen; if it is graphite, then it is necessary that the resistance from the center to the edges of the coil is approximately 1 kOhm.

After selecting a resonant capacitor (the device, of course, adjusts itself, but we selected the frequency closer to 9 kHz), it was time to fill these coils in a mold with epoxy resin. And then a dispute broke out with the box and the Internet. The box says to dilute in a ratio of 1:5. One in five, damn it! Considering that we already had some experience working with epoxy, where the ratio of 10-12:100 was mentioned everywhere, some misunderstanding arose. But they decided to do as written, the manufacturer won’t write garbage on the box :) And they didn’t even decide to test it with a small volume of this resin. I want to go to the cops as soon as possible! In short, they started pouring it, then they changed their minds, because the proportions of resin and hardener were just right for 10-12:100, and then they forgot how much of what they had already poured... In general, they ruined the solution, but they tried to fill it in :)

And it didn’t even think about freezing. What to do? We pulled the coils out of the mold, cleaned them of all the resin, and another idea came to mind. After all, our CRT monitor is a kind of cornucopia for building a metal detector :) The stand from it was also useful. We take it, remove everything unnecessary, attach the coils, fill in epoxy in normal proportions, drill holes - ready!

All this showed its efficiency already in the first mine on the Sozh River:

As for the power supply of the metal detector - at the moment it comes from a regular 12 V lead battery, which you carry with you in your briefcase, but there is little buzz from this method. There are immediate plans to build a power supply on one 18650 element (about 2Ah at 3.7 V), make an indication of the charge level, charge from USB and a 3.7-7 converter, because It is from this voltage that the metal detector is powered. It would be possible to go up to 5 Volts, bypassing the stabilizer for the controller and ADC, but it is better to swing the coil at a higher voltage, then the sensitivity will be higher, but more on that in another article. It consumes about 100 mA at 7 V, so from one 18650 battery you can count on approximately 10 hours of operation. And the main thing is that this thing will be much lighter than a lead battery, which will allow it to be mounted together with the block on a rod.

The promised boards in lay format for the Quasar metal detector, as in this article.

All the best!

DIY metal detector Quasar ARM

Metal detector Quasar ARM is a balanced selective metal detector with metal discrimination and an LCD screen. Quasar AWP is a continuation of the project of a metal detector based on the AT Mega32 microprocessor “Quasar AVR”. The updated device circuit uses a more powerful ARM32 microcontroller and implements additional features, which will be described below.

Technical characteristics of the Quasar ARM metal detector:

• Power supply 6-9 V

• The operating principle is single frequency, IB.

• Operating frequency – from 4 to 20 kHz;

• Indication - audio multi-tone, and visual LCD screen

• Coin detection depth 5 kopecks. USSR (with 23 cm DD coil) – 30 cm.

• Electronic compensation to eliminate coil imbalance.

• FM modulator for wireless headphones

• Coil current control unit

• Self-diagnosis of the device when turned on

Scheme of the Quasar ARM metal detector

Printed circuit board Quasar ARM

This board is made for surface mount elements (SMD), which significantly saves time and money for the manufacture of the Quasar ARM metal detector. The board has cutouts for installing coil and power connectors. The dimensions of the board are designed to fit the very common Gainta 1910 case

List of parts for Quasar workstation

Instructions for assembling the Quasar AWP board from the author of the board

Metal detector board Quasar ARM rev.05a designed for self-assembly of the Quasar ARM selective metal detector. The scheme differs from the author's in some modifications:

• Protection against polarity reversal of the power connection has been improved taking into account the minimum voltage drop in this node.

• There is an electronic power switch off the device from the front panel with a button. When turned off, the metal detector does not consume current, thereby eliminating consumption when the device is turned off.

• The display is powered by a separate voltage stabilizer; the display supply voltage level of 3.3 V or 5 Volts is selected by the type of voltage stabilizer installed.

• The board has the ability to assemble a current control unit in the search sensor

• The board has the ability to assemble an FM transmitter unit for connecting wireless headphones

• The board is designed for installation in a factory serial Gainta G1910 case

Do-it-yourself quasar workstation board assembly

The payment is collected in several stages:

1) Assemble a protection circuit against polarity reversal of the battery, a power supply circuit, and solder the power stabilizers. Check the functionality of the assembled components. Power management: briefly press the power button - the power turns on. Press and hold the button - the board's power is turned off.

2) Assemble the rest of the device, wash the board using special means or an ultrasonic bath.
3) Flash the STM32 processor via USART or SWD interface.
4) Connect the display, turn on the device, adjust the screen contrast
5) When installing an FM transmitter, the sound automatically switches to it; you must turn off the FM transmitter in the settings menu to output sound to the speaker.
6) Connect the device to the search sensor, configure it, check operation.

Some nuances when assembling the board:

Jumper JC2 shorts when

• You do not install an FM transmitter on the board or the selected firmware version is lower than 2.2.2, in this case, if you do not install jumper JC2, no sound will be output to the speaker

Jumper JC1 is shorted when:

• You are not assembling the current control unit in the search sensor (circled with a yellow marker), and you need to install a stabilizer (green marker) LM1117-5.0 and a 10 Ohm resistor R10, in the case when the unit is assembled you need to install LM1117-ADJ and R10 5, 1 Ohm

Display Power Stabilizer:

• For a regular LCD display, it is recommended to install a stabilizer LM1117-5.0, for an OLED - LM1117-3.3

Mounting the display on the metal detector board

Elements of an FM transmitter V are highlighted with a yellow marker, elements indicated by a green arrow must be sealed in any case.

Assembly into the case and mounting the board:

• Install the board on the back of the case and mark the holes, drill holes for I eat power supply and coil connections

• Paste additional stands according to the selected height 3 or 2 mm

• Install connectors and speaker

• Install and secure the metal detector board

• Cut holes for the display and buttons according to the drill in the top cover. The hole for the headphone jack is marked according to the fact

(scheme upgrade)

Metal detectorQuasar-ARM, one of the most popular digital devices today.

This one is very good, and you can verify this by typing the corresponding name in an Internet search or on YouTube...

And yet, of course, the device has weak points, which we will modernize.

Let's start with the device diagram.

Let's start with upgrading the device generator, or rather the Tx drive circuit.

The signal from the microcontroller through resistance R17 1 kOhm is sent to a level matching circuit made on BC846 transistors, then the signal goes to a circuit similar to the Mosfett “driver” (controlling the opening and closing of field-effect transistors in the IRF7105 assembly)…

Everything seems to be fine, everything works, we see satisfied users. But the problem is that the parts market does not always offer us good and cheap elements. Often this is unreliable China, and most importantly, if you buy a cheap device (cheaper than competitors), then this means cheap components.

So, this unit has already failed 3 times in my experience. It was necessary to change the BC846 transistor, and it also came to replacing the IRF7105 itself.

More than a dozen elements work in this unit, which means that the possibility of failure of at least one of the 10 elements is fraught with failure of the entire device.

What to do?

There are several options. One of them is to pass the signal from R17 through the 74NS14 microcircuit element. This is how cascades of devices such as Groza or Anker and others work. They have been working for many years and no complaints.

But how justified is this? What if this is not quite the right step?!

Well... after looking through the information on the Internet, I, with the help of my good friends, found a specialized microcircuit - TC4420 (possibly similar to it).

This microchip in the SOIC-8 package already contains both a driver and a field assembly for a load of up to 1.5 Amps!

The result is 1 micro-piece instead of 10 parts. Everything ingenious is simple!

Scheme of the modified cascade.

You can, of course, not stop there and painlessly throw away C4, VD2, VD3, and also replace resistor R2 (10 Ohms) with an acceptable current in the Tx coil (up to 1-2 Ohms). Then the current in the coil will increase...

However, experiments with R2 have shown that the sensitivity of the device when the Tx coil current changes from 50 mA to 80 mA increases by only 3-5 cm, per 5 kopeck USSR coin. But the gluttony of the device is increasing, which means the batteries will discharge faster...

There's a lot to think about here. To begin with, the sensitive part of the receiving amplifier U1A is sensitive to everything on both inputs (legs 2 and 3). So the quality of the signal (reference voltage) must be perfect.

But as always, not everything is as perfect as we would like. Often now on the market of radio elements the MCP6022 microcircuit is made in China and is of dubious quality. It exhibits the following “symptoms” - noise at the U1B output, up to saturation (+3.3 Volts). Moreover, the device works perfectly if it works for no more than 30 minutes to 1.5 hours. And damage occurs during long-term operation.

Everything falls into place if you warm up the microcircuit (for example, with a soldering iron 8 leg MCP6022 (+3.3 Volts). But this is only a temporary salvation, because

The solution to the problem is to replace the Chinese MCP6022 microcircuit with an AD8606 (American company Analog Devices), or a real MCP6022 from Microchip.

The second problem with this unit is the 10 µF SMD capacitors. Which are often so bad that they cannot even hold that voltage (1.65 Volts) and over time or immediately fly out, simply turning into a resistor.

The solution is to replace it with SMD tantalum polar capacitors in the required size.

Changes to the “correct” sensor of the device are still only in process... The rest has already been tested and works.

And finally... minor changes in the circuit that can be ignored.

You can remove unnecessary nodes for programming from the boards, leaving only one (I use SWD), as well as a circuit for adjusting the contrast on the LCD screen - if you use OLED screens.

Photos - before and after the changes.

Good luck to everyone in instrument making and searching. Let your Quaza-ARM will bring you cool finds and mood!

Alexander Serbin (Kharkov)