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Pinpointer "Kid FM2V2" with a difference of metals

Pinpointer

Greetings to all metal seekers. In this article I want to share my experience in assembling a wonderful pinpointer Toddler FM2V2, which has high stability and is able to distinguish non-ferrous metal from black. Such a device will become an indispensable tool for lovers of wandering around with a metal detector in search of treasures, as well as good entertainment for your children.
Before proceeding with the assembly of the pinpointer, I want to note that this design is made using a series microcontroller Pic. If you have difficulty programming pic controllers, I advise you to start to master this skill or turn to someone who is already in the subject. In any case, the game is worth the candle, as homemade shows high stability results and will become a real assistant, facilitating the work of the digger. Figure 1 shows the electrical circuit of this miracle device.


Figure 1 - electrical diagram of the pinpointer

In general, the scheme can be divided into several blocks, namely:

  • block voltage Converter, made on a linear stabilizer LM317L. This approach made it possible to increase the stability of the device over a wide range of supply voltage, even when the latter was reduced to 5V.
  • an audible indication unit about the presence of a metal object near the coil, which is made using a amplifying transistor T2 and speaker SP1.
  • light indication unit, as an addition to the sound. The block is made on the LEDs Led1 and Led2. Led1 indicates the presence of non-ferrous metal near the coil, Led2 - black.
  • generator block on transistors T1 and T3. Such a circuit solution provides automatic adjustment of the resonant frequency to the sensor parameters and high thermal stability.
  • Central control unit based on a PIC12F675 or PIC12F629 microcontroller. Firmware for each type of controller goes separately and differs only in that for PIC12F675 a sound indication mode is added when the battery is lower than 5.5V. Otherwise, all functions are identical and you can take the controller, which is easier to get in place.

The following is a list of radio elements used in the circuit.

  • R1, R6, R7, R11 - 10k
  • R2 - 51 ohms
  • R3 - 100 Ohms
  • R4 - 560 Ohm
  • R5, R9, R12 - 1 kOhm
  • R8 - 220 kOhm
  • R10 - 220 Ohm
  • R13 - 3 kOhm
  • D1 - 1N4007
  • LED1 - green (non-ferrous metal)
  • LED2 - red (ferrous metal)
  • C1 - 33 nF (necessarily film)
  • C2 - 1000 uF at 16V
  • C3 - 10 uF at 6.3 V
  • C4, C5 - 15 pF
  • C6 - 100 nF
  • T1, T3 - BC557
  • T2, T4 - BC547
  • VR1 - LM317L
  • SP1 - a booster without an internal generator (suitable from a PC motherboard)
  • Cr1 - 20 MHz thermostable quartz resonator
  • But1 - a clock button without fixing
  • IC1 - PIC12F675 or PIC12F629 (each of these microcontrollers has its own separate firmware.)

Download firmware for PIC12F675: metfm2_675_v2.rar [2.24 Kb] (downloads: 861)

Download firmware for PIC12F629: metfm2_629_v2.rar [2.04 Kb] (downloads: 659)

Since this device was originally conceived as a pinpointer, the following requirements were identified: the compact size of the board and search coil, a monolithic cylindrical body. The water pipe was ideal for the body PVCdiameter 25mm. From this, the requirements for the printed circuit board were determined. Its width should not exceed the inner diameter of the pipe, and the height of the sealed elements should not prevent the board from freely entering the case. Achieve compact sizes SMD Elements. As a result, the etched board looks as follows (photo No. 2).


Photo No. 2 - the appearance of the printed circuit board

The board is designed so that SMD elements are installed on the side of the tracks, and the output elements are on the opposite side. Photo 3 shows a board with sealed SMD elements. They all have size 1206.


Photo No. 3 - pinpointer board with sealed SMD elements

For a microcontroller, it is better to use a socket Dip8, to always be able to extract it and reflash if something goes wrong. I also repeat that the capacitor C1 on the 33 nF it is better to use film, this will provide additional stability of the generator frequency when the ambient temperature changes. There are no special requirements for other elements. Photo 4 shows the view of the board from the side opposite to the tracks.


Photo No. 4 - board on the side of mounting the output elements

So, we figured out the board, but this is not enough. There are several more steps ahead before getting the finished pinpointer. One of these steps is the manufacture of a sensor (coil). This is a rather painstaking task, which requires some preparation and preliminary calculations.
To begin with, let's determine the diameter of the wire that is available and the diameter of the coil itself. In my case, there was an enameled copper wire with a diameter 0.4mm. As for the diameter of the coil, the following rules must be taken into account: the larger the diameter, the more sensitive the device, i.e. he is able to detect a metal object at a farther distance, and vice versa, with a decrease in diameter, the sensitivity decreases. Since my plans were to use the housing 25mm, it was decided to wind the coil on the rim, diameter 20mmto be able to hide it inside the case. Water pipe was ideal for the mandrel 20mm and a pair of lids from eggplant with water, the distance between which is about 10mm. (photo No. 5).


Photo No. 5 - Mandrel for winding a coil (d = 20mm)

When the technical part is ready, the question arises, how many turns to wind? The program will help to answer this question. Coil32. Download the program on, run and perform a series of actions below.
First, unpack the archive with the program and run the file Coli32.exe. After that, the main window appears, shown in screenshot No. 6


Screenshot 6 - Coil32 program after launch

In the initial state, the program does not have plugins for the calculations we need. Therefore, they need to be downloaded. The program itself allows you to do this. To do this, go to the menu "Plugins"and select"Check for Updates", as shown in the screenshot above. After that, the corresponding window shown in screenshot No. 7 will open.


Screenshot 7 - Plugin Manager

Install all the plugins offered by the program using the buttons "Download"and close the manager. The program will ask you to restart, we agree and after restarting again go to the menu"Plugins". Now there is a whole list of additional calculators from which we need only one with the name."Multi loop"(screenshot number 8)


Screenshot No. 8 - selection of the necessary plug-in for calculating the pinpointer coil

In the window that appears, fill in the cells with the necessary parameters, namely:

  • Inductance - 1500 μH (L1 coil in the diagram)
  • The inner diameter D is 20mm (as discussed above, I make a small coil)
  • Wire diameter d - 0.4mm (I only had one in stock)


After that, we click the calculate button and we get the result shown in screenshot No. 9:


Screenshot 9 - result of calculation of coil parameters for pinpointer

As can be seen from the screenshot, you need to wind 249 turns of wire 0.4mm on the 20 millimeter rim to get the treasured 1500mcHthat the scheme requires from us. We will not argue - we will wind ...
To somehow facilitate the winding process, I have assembled a masterpiece of engineering from a children's table, a small vice, and other improvised trash. The result is shown in photo No. 10.


Photo No. 10 - preparation for coil winding

Immediately I notice that the coil is wound in bulk. It makes no sense to try to lay turns, but still it is better to distribute the wire evenly over the entire winding area. For the convenience of counting the turns, it is better to put a mark on the restrictive end - it is easier to track each revolution passed. During winding, it is better to turn off the mobile phone and close in a separate room so that no one can get off the account. After the work is done, it is necessary to carefully remove the coil from the frame and pull it with threads around the entire perimeter, as shown in photo No. 11.


Photo No. 11 - Freshly baked pinpoint reel

To add strength to the coil and prepare it for shielding, we wrap it with ordinary stationery tape, as shown in photo No. 12


Photo No. 12 - preparation for shielding

Since the pinpointer works on the principle of measuring the frequency of the oscillatory circuit, this implies high requirements for frequency stability and protection from interference. If the frequency of the generator provides us with stability, then shielding the coil will provide protection from interference.
For shielding, you can use ordinary food foil, which almost everyone has in the kitchen or something like that. Foil the coil, leaving a small empty sector in the area of ​​its findings. This is required in order not to get a short-circuited loop through which the signal will not pass at all. A stripped copper wire is additionally wound on top of the foil, which will subsequently be soldered to the general minus on the board. Below is a photo No. 13, which clearly shows the screening process.


Photo 13 - shielded coil

To keep this whole thing and not fall apart, you need to strengthen the coil with another layer of adhesive tape or electrical tape. And only after that you can relax and consider the coil completely ready. The result of my efforts is shown in photo No. 14.


Photo No. 14 - a completely ready coil

Most of the work is done. We solder everything into a single whole and check the operation of the pinpoint on the table. The best battery for powerKRONA"with a special holder for it. My pinpointer worked the first time and I didn’t find any difficulties. Even with a coil flattened under the future case, it works stably (photo No. 15)


Photo No. 15 - pinpointer is ready for placement in the housing

Since the pinpointer is supposed to be used in harsh field conditions, it needs a strong and airtight housing. In my opinion, the most optimal and affordable option is to use tap water PVC pipe diameter 25mm and about 25cm. It lies perfectly in the hand and easily accommodates all the elements of the device. Also, one of the ends of the pipe is cut off at an angle of about 60 degrees. This will allow you to place the coil at an angle convenient for searching and will make it possible to split earth lumps with a pointed end. Photo No. 16 shows the appearance of my case.


Photo No. 16 - casing from a water pipe

I decided to take the power switch and reset button out and attach it at the base of the pipe. Also, do not forget about the LEDs - holes should be made for them in a place convenient for perception - I have them located approximately in the center. I didn’t make a hole for the speaker, it is already perfectly audible. Below, in photo No. 17, a method of attaching a switch and a reset button is shown.


Photo No. 17 - mounting location of the switch and reset button

A coil is mounted on the opposite side. To fix it inside the pipe, I used hot glue. And in order to close it from mechanical damage - I cut out a plug from the PCB in the form of a slice. The result is shown in photo No. 18.


Photo No. 18 - mounting of the coil and plug made of textolite

After the hot melt has cooled, you can glue the plug. This is best done with super-glue, sprinkling loose-fitting places with ordinary baking soda. When super-glue and baking soda interact, a solid substance is formed that resembles glass. In this way, you can eliminate all the cracks in the pinpoint housing. The sizing result is shown in photo No. 19.


Photo No. 19 - fastening the plug with super-glue and soda

The back side of the device is covered with foam rubber cut along the diameter of the pipe. You can of course buy a stub, but everything is fine with me already. In general, the device turned out to be ergonomic, fits well in the hand and does not take up much space. A general view of the finished pinpointer is shown in photo No. 20.


Photo No. 20 - appearance of the finished pinpointer

Well, in the end I want to give two video tests, without which the article would not be complete. I advise everyone to have such an assistant with them.


Testing for metal differences:

[media = https: //www.youtube.com/watch? v = k2A3dyajoE4]
Range Testing:

[media = https: //www.youtube.com/watch? v = lLJv1Y4CW5U]
9.5
9.5
9.2

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62 commentary
Guest Ilnar
Roman, hello, could you update the link to the sketch for the aquacontroller on Arduino?)
Saber
thanks for your kindness
Author
Saber
Good afternoon. An interesting device. I want to repeat this. Can I request a PCB file
Guest Dmitry
Good afternoon. An interesting device. I want to repeat it. Can I ask for a PCB file at demon@7fm.by
Author
LEDs are soldered by wires. It seemed to me that it was more convenient.
Guest Alexander
Why are there LEDs across the signet, and in the finished product along the case? Something does not fit here ...
nor how can I get it to work already 3 boards made etched differently, at different peaks, different coils. 0 reactions. on one board, both lights are on and that's it. maybe I do not sew peaks correctly? programmer k150
vladimir gaidov
good afternoon, do not throw off the link to the printed circuit board?
Guest Alexander
Pinpointer "Kid FM2" with a difference of metals.
Guest Alex
[quote = Guest Alexey] Is there a fee in lei?
Sori saw late. We will try. ATP in advance.
Guest Alex
And there is no fee in lei?
Author
I didn’t think that there would be so many who want to repeat the pinpointer on my board. Yes, the old link is really unavailable, so I post the working link for download circuit board.
Reverse polarity protection - yes.With successive switching on, the economy decreases and the minimum operating voltage increases, therefore, with this switching on, you need to use a Schottky diode or germanium.
Mike
Can you assign the assignment of diode D1 to the parallel battery? Reverse polarity protection? Then is it more logical to turn it on sequentially?
Guest Sergey
Author
I cited above link to the board
I found and eliminated the short, the power on the m to go on the 1st leg 3.5v and on the 2nd 2.1v, and also no signs of life.
Is Crohn warming? Great current. Somewhere shorted power. Call the capacitors, carefully see if the copper is etched between the tracks on the board.
When applying power, no reaction, only the crown is heated.
Good day. Tell a beginner what I did wrong?

Author
By popular demand, I post a link to the PCB file: (link)
Please drop the link to the board. Thanks in advance.
Author
Thank you, I tried to describe in as much detail as possible. PCB file sent. Good luck in the assembly.
Hello!
Author
Hello, I sent the file.
Good day!
Author
pogranec,
I confirm. In the manufacture of a 15cm sensor, it is necessary to wind 61 turns of wire 0.4. It is necessary to shield completely, but to provide a gap so that there is no closed loop. For those who want to see more diameter and depth, this device is not suitable, here you need to look towards pulsed MD, etc. The principles of frequency measurement do not allow to further increase the detection depth without loss of stability.
Ie if you wrap a thin wire and leave a circle, then the sensitivity will be better?

Yes. And for this method you need a larger number of turns (for feeling). The limit is imposed by the meter on the PIC675 (in frequency) and the capacitive effect of the coil.
A large frame (on this principle)> 1m will not give anything (in the sense of increasing depth). Tk here we need a specifically concentrated inductance. Design constraints.
There are large frames, but they are based on other principles ....
pogranec
The diameter of the coil is 150 m for 1 turn, yes, large, it is no longer convenient to wear. I saw how in the desert they were looking for meteorites, so there was a frame somewhere about 3 m in diameter. And with a diameter of 150 m, perhaps put on some barge to search for something at the bottom of a river or sea, in theory, the detection range of the metal should be up to 200 m from the center of the coil. Probably the sensitivity increases with a decrease in the number of turns and a decrease in the diameter of the wire, since the magnetic permeability improves, and it is even better to use not one wire but several (braid). Or another variant of the square section of the wire (bus), and not a round coil, but a square, or hexagonal
Ie if you wrap a thin wire and leave a circle, then the sensitivity will be better?
What's the point?
Inductance: 1500 µH
Inner Diameter D: 150,000 mm
Wire diameter d: 0.4 mm
=> Number of coil turns: N = 1.1
=> Loop thickness T = 0.42 mm
The sensitivity shown by the top starter in Vidio is low (for a pinpoint). The wire can be used thinner ~ 0.27mm. A strongly flattened coil has less sense. The author of the circuit and the program (Eddy71) max squeezed the sensitivity out of the circuit and PIC675.
pogranec
Yes, I thought more. It turns out that the larger the diameter of the coil, the fewer turns, hmm, which means that there is such a diameter of the coil, where there is only 1 turn, it probably deeply detects, is not it?
You want to make a bigger reel. And I thought less. Then everything is right
Inductance: 1500 µH
Inner Diameter D: 150 mm
Wire diameter d: 0.4 mm
=> Number of coil turns: N = 61.2
=> Loop thickness T = 3.13 mm
Maybe I'll look again now
pogranec
I think you took 15 mm (1.5 cm), instead of 15 cm (150 mm) or a typo? but 15 mm is also useful, thanks
308 turns program says
1-----------------------------------------------------------------------
plugin: Multi-Turn Round Loop v11.2.7.66

Inductance: 1500 µH
Inner Diameter D: 15 mm
Wire diameter d: 0.4 mm
=> Number of coil turns: N = 308
=> Hinge thickness T = 7.02 mm
Inoy
61 turns for the diameter of the coil - 15 cm, but thanks, how UTB you so quickly defended)). And at the expense of screening the coil only from above, its detection range will increase, and how else can you increase the detection depth?
Quote: Inoy
Quote: New Standard
Roman1984
I want to do 15 cm, but for a 15 cm diameter coil, the number of turns seems to be different, should it beat 249? But what if the coil is shielded only from above and below is not, will sensitivity improve?


The number of turns depends on the diameter of the wire.

If you have a wire of 0.4 as the author, then only 61 turns are needed
Inoy
Well, yes, I mean, with the same wire diameter as in the author on a small coil
Quote: New Standard
Roman1984
I want to do 15 cm, but for a 15 cm diameter coil, the number of turns seems to be different, should it beat 249? But what if the coil is shielded only from above and below is not, will sensitivity improve?


The number of turns depends on the diameter of the wire.
Roman1984
I want to do 15 cm, but for a 15 cm diameter coil, the number of turns seems to be different, should it beat 249? But what if the coil is shielded only from above and below is not, will sensitivity improve?
Roman1984,
Thanks. I will throw mail in PM.
Author
Yes, of course, I didn’t insert the print in the article, but I can drop the file into the mail if there is a need.

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