“Last winter 2, having read interesting articles about pinpointers and having studied the circuits available on the Internet, I decided not to repeat these circuits, but to try to develop my own. I immediately looked towards a small but “smart” microcontroller . The attempt was successful. I spent the whole season with it (of course, the target is found by the "Mole-M" MD, but the "Gnome-M" pinpointer helps to localize it) and I can no longer imagine how you can do without it... After all, I really want to quickly see what was “ringing” in the ground there .)"
Pin assistant on cop number one!
I present:Pinpointer "GNOM-M" (2010)
Scheme
.
Co. It is better to install film capacitors C2 and C3. To improve thermal stabilityTherefore, it is recommended to install a PTC thermistor with R2.
Scheme from TSV with keys
This is what the outside of the case might look like A
.
.
Principle of operation The pinpointer is based on measuring the quality factor of an oscillating LC circuit. The approach of metal objects to the circuit leads to energy loss (reduction of quality factor) and, as a result, a decrease in the signal amplitude on the LC circuit. Measurement, processing, all combing and signal generation to the emitter are carried out by a program programmed into the microcontroller.Manufacturing: Manufacturing boards (when printing, check the “mirror” box)
It is not complicated and requires only the skill of installing SMD components, although it is also possible to manufacture it on DIP-pin components. About the parts used. The sensor of the device is a ferrite rod (the kind used in transistor receivers) 5-10 cm long and 8-10 mm in diameter. The coils are wound one on top of the other and contain 200 turns of insulated copper wires 0.2-0.3 mm . It is necessary to observe the polarity of the connection, therefore, if there is no generation (frequency 15-20 kHz), it is necessary to change the ends of any of the windings. Changes to the coil parameters are allowed - wire, length and diameter of the rod.
Tincture comes down to selecting a voltage of 1.0 V on the 2nd pin of the microcontroller using trimming resistor R2, in the absence of metal objects nearby.
Design The pinpointer can be anything - a sensor board and AA batteries or a lithium battery allows you to fit, for example, the device into housing Z-23, orplastic water pipe with an outer diameter of 20mm.
ATtiny13-T - changing the tone period ( 03.09.2016)
More
A pinpointer is a device that is part of the family of metal detectors. Used to search for metal objects in a variety of conditions, including underwater. The name of the device comes from English pin pointer, which translates as "dot pointer". The simplest pinpointer is small in size, similar to a flashlight. It may be quite useful for finding hidden electrical wiring in the wall.
A pinpointer is a metal detection detector. It determines the exact location of the metal at a fairly shallow depth, approximately about 5 cm. People who search for coins or other valuables made of metal, including archaeological ones, are called treasure hunters. They operate pinpointers in a variety of locations, from official excavations to waste dumps. Factory models of metal detectors are not always convenient for such purposes, and besides, they cost a lot of money. Therefore, it makes sense to assemble your own pinpointer according to the diagram. The device is most effective for use in a newly formed hole or dump soil. The soil may be scattered over a dense volume of grass or a large amount of foliage, which obviously makes routine searching difficult for treasure hunters. Knowledgeable and experienced people say that in this situation, a pinpointer is the best choice.
To assemble a pinpointer with your own hands, you will need certain tools. The main elements will be:
It is worth noting that for different models, the list of necessary materials and tools may change during the assembly process. Basic skills in the manufacture of such boards will also be useful; knowledge in the field of electrical engineering and experience in it are welcome.
The fundamental provisions of the device model are the following parameters:
When assembling a pinpointer with your own hands, you must take into account the basic principle of its operation - the level of quality of measuring the oscillatory circuit. When a metal object approaches it, a loss of energy power occurs. As a result of this process, the amplitude of the signal on the circuit decreases.
To increase the sensitivity of the device in the assembly, it is better to use film capacitors C2 and C3. The radiating element ZP-1 must be piezoceramic.
The process of making a pinpointer with your own hands is not difficult, but it still requires certain skills in working with SMD components. Another option would be a DIP output element. A ferrite rod, which can be removed from an unnecessary transistor receiver, will become a sensor. The rod should be about 110 cm in length and 10 mm in diameter. Winding in coils occurs on the principle of superimposing one on top of the other. The material for it should be a wire in an insulating winding. The wire must be copper with a diameter of 0.3 mm. The required number of turns should be 200 pieces.
Particular attention should be paid to the polarity of the connection in a homemade pinpointer. If there is no generation at a frequency of 15 kHz, you need to change the extreme points of any winding. The characteristics of the coil (such as length, wire, rod diameter) can be changed. But it is worth remembering what will directly affect the sensitivity of the device.
The pinpointer is configured by selecting the voltage in the area of the second pin of the microcontroller itself. This must be done using trimming resistor R2. At the time of adjustment, there should be no metal objects around the device. This will allow you to achieve the most effective sensitivity. A voltmeter will help in the measurement. To do this, you will need a device with a high resistance level, such as an oscilloscope.
How to make a pinpointer in this version will tell you how the frequency meter works. The assembly diagram will not cause any particular difficulties. The operation is based on the operation of an electronic FM frequency meter. There is discrimination against ferrous metals, the search depth for objects is limited to 60 cm, the operating frequency is at 19 kHz.
All required parts are simple and accessible. A little attention should be paid to capacitors, which must have thermally stable characteristics. These could be the K71 models from the old Soviet multimeter. It is not recommended to use ceramic ones, they will not work.
Important! The stability of the device directly depends on the quality of the capacitor!
The power source for the pinpointer can be batteries or other rechargeable elements with a voltage of 9-12 V. The printed circuit board itself will only need 10 mA, the rest will be “pulled” by the speaker, an alternative to which can be headphones.
Do-it-yourself analog pinpointer is quite easy to assemble. Its effectiveness lies in finding small objects, such as coins.
Capacitors for this type of metal detector for the generator are selected as film type. The voltage must be 100 V or higher. The contour coil can be mounted on a ferrite rod, the diameter of which should be 10 mm. You can also use the rod from the magnetic antenna built into old radios. The nominal length of the rod should be 10 cm. For winding in a coil, an enameled wire is taken and wound in 4 layers. After completing this process, it is necessary to treat the coil with a special varnish in a homemade pinpointer. Finally, the coil will need to be crimped with heat shrink tubing.
The circuit of a fairly simple analog pinpointer is for people who search for coins, but cannot afford to buy a professional pinpointer. I collected this sample personally and confirm its full functionality. I designed a printed circuit board specifically for it, which can be found at the end of the article. In terms of characteristics, the pinpointer is quite good, perfect for target designation of a find....
MINIMAX-PP-2 pinpointer circuit
And finally, a few photos of the assembled board.
Greetings to all lovers of metal detecting. In this article I want to share my experience of assembling a wonderful pinpointer Baby FM2V2, which has high operational stability and is able to distinguish non-ferrous metal from ferrous metal. Such a device will become an indispensable assistant for those who like to wander around with a metal detector in search of treasures, as well as good entertainment for your children.
Before we begin assembling the pinpointer, I would like to note that this design is made using a series microcontroller PIC. If you are having difficulty programming pic controllers, I advise you to first master this skill or contact someone who is already in the subject. In any case, the game is worth the candle, since the homemade product shows high stability results and will become a real assistant, making the digger’s work easier. Figure No. 1 shows the electrical diagram of this wonderful device.
Figure No. 1 - electrical circuit of the pinpointer
In general, the scheme can be divided into several blocks, namely:
Below is a list of radioelements used in the circuit.
Since this device was originally conceived as a pinpointer, the following requirements were determined: compact size of the board and search coil, monolithic cylindrical body. The water pipe was ideal for the housing PVC, diameter 25mm. From here the requirements for the printed circuit board were determined. Its width should not exceed the internal diameter of the pipe, and the height of the sealed elements should not prevent the board from freely moving inside the case. Compact dimensions were achieved through partial use SMD elements. As a result, the etched board looks like this (photo No. 2).
Photo No. 2 - appearance of the printed circuit board
The board is designed in such a way that SMD elements are installed on the side of the tracks, and the output elements are installed on the opposite side. Photo No. 3 shows a board with sealed SMD elements. They all have a size 1206 .
Photo No. 3 - pinpointer board with soldered SMD elements
For a microcontroller it is better to use a socket DIP8, so that you can always remove it and reflash it if something goes wrong. I also repeat that the capacitor C1 on 33 nF It is better to use a film one, this will ensure additional stability of the generator frequency when the ambient temperature changes. There are no special requirements for the remaining elements. Photo No. 4 shows a view of the board from the side opposite to the tracks.
Photo No. 4 - board from the mounting side of the output elements
So, we've sorted out the board, but that's not enough. There are still several stages ahead before receiving a finished pinpointer. One of these stages is the manufacture of the sensor (coil). This is a rather painstaking task that requires some preparation and preliminary calculations.
To begin with, let's decide on the diameter of the wire that is available and the diameter of the coil itself. In my case, I found an enameled copper wire with a diameter 0.4mm. Regarding the diameter of the coil, the following rules must be taken into account: the larger the diameter, the more sensitive the device, i.e. it is capable of detecting a metal object at a longer distance and, conversely, as the diameter decreases, the sensitivity decreases. Since my plans were to use the case 25mm, it was decided to wind the reel on a frame with a diameter 20mm to be able to hide it inside the case. A water pipe was ideal for the mandrel 20mm and a pair of lids from eggplants 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 answer this question Coil32. Download the program using, launch and perform a series of actions given below.
First, unpack the archive with the program and run the file Coli32.exe. After this, the main window appears, shown in screenshot No. 6
Screenshot No. 6 - Coil32 program after launch
In its 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 you need to go to the menu " Plugins" and select " from the drop-down list " Check for updates", as shown in the screenshot above. After which the corresponding window will open, shown in screenshot No. 7.
Screenshot #7 - Plugin Manager
We 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 we go back to the menu " Plugins". Now here is a whole list of additional calculators from which we only need one with the name " Multi loop" (screenshot No. 8)
Screenshot No. 8 - selecting the necessary plugin for calculating the pinpointer coil
In the window that appears, fill the cells with the necessary parameters, namely:
After that, press the calculate button and get the result shown in screenshot No. 9:
Screenshot No. 9 - the result of calculating the coil parameters for a pinpointer
As you can see from the screenshot, you need to wind 249
turns of wire 0.4mm on 20 millimeter frame to get the coveted 1500μH, which the scheme requires of us. We won't argue, we'll just talk...
In order to somehow facilitate the winding process, I assembled a masterpiece of engineering from a children's table, small vices, and other improvised rubbish. The result is shown in photo No. 10.
Photo No. 10 - preparation for winding the coil
I will immediately notice that the reel is winding in a heap. There is no point in trying to lay the turns, but it is still better to distribute the wire evenly over the entire winding area. To make it easier to count turns, it is better to put some kind of mark on the limiting end - this makes it easier to track each revolution completed. While winding, it is better to turn off your mobile phone and lock yourself in a separate room so that no one can lose count. After the work is done, you need to carefully remove the spool from the frame and tighten it with threads around the entire perimeter, as shown in photo No. 11.
Photo No. 11 - Freshly baked pinpointer coil
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 operates on the principle of measuring the frequency of an oscillating circuit, this entails high requirements for frequency stability and protection from interference. If frequency stability is ensured by the generator circuit, then protection from interference will be provided by shielding the coil.
For shielding, you can use ordinary food foil, which almost everyone has in their kitchen, or something similar. We wrap the coil with foil, leaving a small empty sector in the area of its terminals. This is required in order not to get a short-circuited turn through which the signal will not pass at all. A stripped copper wire is additionally wound on top of the foil, which will later be soldered to the common negative on the board. Below is photo No. 13, where you can clearly see the shielding process.
Photo No. 13 - shielded coil
In order for this whole thing to hold together 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 - completely finished coil
Most of the work is done. We solder everything into a single whole and check the operation of the pinpointer on the table. Battery is best for power supply" KRONA"with a special holder for it. My pinpointer worked the first time and I didn’t find any difficulties. Even with the coil flattened under the future housing it works stably (photo No. 15)
Photo No. 15 - the pinpointer is ready to be placed in the case
