DIY pinpointer: diagram, description. Homemade pinpointer
They differ quite a lot. It should also be taken into account that devices of this type has its own sensitivity. The main element of a pinpointer can be safely called a coil. It is most often installed in an orthogonal type. However, in this situation, much depends on the accuracy class of the device. In order to assemble a simple pinpointer with your own hands, you need to familiarize yourself with the known configurations.
Two-wire capacitor model
To make this type of pinpointer with your own hands, you must first prepare a housing for the device. To do this, many experts recommend using an ordinary flashlight. The main problem at this stage is finding good modulator. As a rule, a nonlinear analogue is selected for a two-wire capacitor. The coil itself must be located in the front of the device. Batteries should be installed behind the modulator. You can also remove them from a flashlight. The minimum battery capacity must be 200 mAh. This is enough for 25 minutes of continuous operation.
Using Three-Wire Capacitors
Making a pinpointer with three-wire capacitors with your own hands is quite difficult. The modulator in this case is only suitable for the linear type. Nowadays it is not easy to find it in radio electronics stores. It should also be taken into account that the coil must be installed under the amplifier. Some additionally equip devices with zener diodes. They are ideal for increasing the sensitivity of the model. In this situation, batteries can be used as standard from a flashlight.
Interrupt Model
To assemble this type of pinpointer with your own hands, you must first take the body of the flashlight. The modulator must maintain a minimum threshold frequency of 200 Hz. All this will allow the sensitivity of the device to be maintained at a high level. As a tester this device used quite often. To activate the interrupt mode, a regulator must be installed in the design.
Most often it is used of the push-button type. In this case, it is necessary to pay attention to the features of the body that belonged to the flashlight. It is better to choose a simple coil for this purpose. However, it must withstand the maximum input voltage at 15 V. All this will improve the accuracy of the readings.
Modification "Baby-FM2"
Assembling the Malysh-FM2 pinpointer with your own hands is quite simple. This device differs in that its sensitivity is low. However, the cost of the model is extremely low, and for home use This device fits perfectly. The modulator in this case is used of a nonlinear type. It is mounted directly next to the regulator.
Most often on the market you can find rotary analogues. The inductor can withstand a maximum input threshold voltage of 10 V. It should also be noted that of this device high current conductivity. This was achieved by installing a zener diode. Next, to assemble the Malysh-FM pinpointer with your own hands, you need to solder the capacitors. Only after this are the contacts connected to the zener diode. At the end of the work, all that remains is to secure it rechargeable batteries in the case.
Pinpointer with low sensitivity transistors
You can make a low-sensitivity pinpointer with your own hands using transistors thanks to a device such as a beeper. It is installed in the housing immediately behind the modulator. The amplifier for this device is suitable only for the pulse type. In this case, you can select different capacitors for the device. However, they must withstand a minimum input threshold voltage of 5 V.
It should also be noted that zener diodes are installed in devices quite often. Their maximum frequency is welcome at 200 Hz. It is important to consider that the accuracy of the readings depends on the transmission width of a given element most often does not exceed 3 microns. Batteries for the model are selected with a capacity of no more than 600 mAh. This is enough for the device to work continuously for 30 minutes.
High sensitivity model
How to make a high sensitivity pinpointer with your own hands? To understand this issue, you should understand that the coil you will need for assembly is quite powerful. It must withstand a minimum threshold voltage of 20 V. It should also be noted that modulators in this case are suitable only for the linear type. The accuracy of the readings also depends on the type of condensate.
In this situation, many experts advise using open-type models. On average, the capacitance parameter of these elements fluctuates around 5 pF. However, in this situation, much depends on the capacitor manufacturer. If we talk about a zener diode, then it is used with increased resistance. This is necessary to increase the sensitivity of the device. Batteries for this model should be selected with a capacity of at least 900 mAh.
Modification Minimax-PP
To assemble a Minimax-PP pinpointer with your own hands, you need to select a beeper of the PP20 series. It should also be noted that vibration mechanisms are installed in devices of this type. In this case, a wide variety of indicators are used. If we talk about the coil, then in this case it is used of the orthogonal type. This component must withstand a threshold input voltage of at least 15 V. In this case, the resistance in the circuit should not exceed 4 Ohms.
The sensitivity of this device largely depends on the capacitors. There are two of them in the standard scheme. One of them must be installed near the coil. In this case, the second one is attached to the output of the modulator. The main problem of these devices can be considered the low bandwidth at the level of 2 microns. Due to this, amplifiers are used quite rarely in devices of this type.
Device with integrated controller
Assembling this type of pinpointer with your own hands (the diagram is shown below) is quite simple. First of all, you need to choose a good case for the device. At the same time, the integral type controller does not take up much space. If desired, it can be purchased at any store with radio equipment, and it costs extremely little. A distinctive feature of this element can be safely called good conductivity. The capacitors in this case are installed of a two-electrode type. Their resistance value on average fluctuates around 2 ohms.
It should also be noted that the coil must be installed first. To do this you will have to use a blowtorch. Next, the modulator is attached directly. In this case, there should be batteries in the back. It is not advisable to use an amplifier in this case. This is due to the fact that the sensitivity of the device decreases significantly due to an increase in the limiting frequency of the device.
Using Multilayer Capacitors
A do-it-yourself pinpointer with multilayer capacitors is assembled (the diagram is shown below) only if there are orthogonal coils. Modulators in this case are suitable for linear and nonlinear types. It should also be taken into account that vibration mechanisms are often installed in devices of this type. However, beepers can be found quite often.
Zener diodes are often used to increase the sensitivity of the device. At the same time, cardiode analogues are especially popular these days. To install them you will have to use In general, it should be noted that models with multilayer capacitors are universal and are ideal for home use. With their help, a person can quickly find out the exact location of the wiring in the wall.
Model on a monolithic board
Assembling this type of pinpointer with your own hands is quite simple. These devices are distinguished not only by increased accuracy of readings, but also by good sensitivity. This model is suitable for professionals. The device must be assembled by fixing the modulator. In this case, many experts recommend using linear analogues.
However, nonlinear modifications are also common. Beepers in this case are installed behind the coil. The input threshold voltage of the device should not exceed 20 V. For this purpose, zener diodes must be installed. In this case, the regulators are soldered as desired. At the end of the work, all that remains is to secure the batteries.
Pinpointer with resonant regulator
To assemble a device with a resonant regulator, you must prepare a blowtorch in advance. First of all, a high-quality modulator is selected for the device. In this situation, many experts still recommend using linear analogues. It is quite difficult to find them in the store, but they should cost little. On average, their conductivity parameter is 3 microns. Due to this, the input threshold voltage can be expected to be at a level of 15 V. A wide variety of zener diodes are suitable for the device. They must keep the maximum resistance at 5 ohms. It should also be noted that the device with regulators does not need beepers.
In this case, it is advisable to install the coil last. In this case, special attention must be paid to the insulation of the wiring. It should also be remembered that the device case must be completely sealed. For this purpose, as an option, you can use a rubber seal. The regulator must be directly soldered to the modulator. Capacitors in this situation are used mainly of the field type. The minimum battery capacity must be 800 mAh.
We present to you one of our new developments - a sensitive pinpointer. This device is designed to search for small metal objects. Used in conjunction with a metal detector during excavations - it is convenient to check the excavated ground for the presence of small coins, as well as to search for metal fittings in the walls. Among the advantages, I note the simplicity and repeatability of the circuit, dynamic mode combined with static mode, auto-tuning, high sensitivity, the presence of a VCO - (VCO).Schematic diagram of a homemade pinpointer:
The circuit was tested with a ferite rod with a diameter of 8 mm, length 50 mm, 320 turns of 0.3 wire. Ring with a diameter of 40 mm wire 0.14 - 150 turns. The test on the ground was carried out with a ring coil. With sudden movements or rotation of the coil around its axis, it reacts to the magnetic field of the earth, but this is not particularly annoying since the search is carried out with smooth movements and without rotational movements.
A flat coil can be made from a fiberglass plate cleared of copper.
The 78L05 integrated stabilizer can be replaced with a similar one with an output voltage of 5 volts. If a VCO (voltage controlled generator) is not needed, then resistor R16 needs to be reconnected to pin 12 of U1B - shown with a dashed line.
You can replace the transistors of the KT3102 pinpointer with any low-power silicon ones, you can use another sound emitter with a voice coil resistance of at least 100 Ohms, but it’s better to use a piezo one - it will be economical and loud enough. LED - any super-bright one.
This pinpointer is powered by a 9-volt KRONA battery. On printed circuit board The pinpointer leaves space for soldering current collector springs for connection to the battery. There is also space left on the board for a flat coil. The coils in this case can be of any design.
Capacitors C2 and C3 must be film or others but with zero TKE, the remaining capacitors can be of any type.
The “threshold” regulator does not have to be installed, but with its help you can increase the sensitivity and also reduce it when necessary. So I recommend not removing it. The sensitivity of the pinpointer is very high, the small gold ring begins to feel with manual adjustment from 7 cm.
Here is an archive in LAY format; when you hover the cursor over an element, the position of the element is displayed. Material sent by Slavake.
Discuss the article PINPOINTER
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.
Purpose of the device
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 spread over a dense volume of grass or a large number of foliage, which obviously complicates the usual search for treasure hunters. Knowledgeable and experienced people say that in this situation, a pinpointer is the best choice.
Parts for assembly
To assemble a pinpointer with your own hands, you will need certain tools. The main elements will be:
- Soldering kit: a certain amount of tin, solder and the soldering iron itself.
- A diverse set of screwdrivers or a set of attachments for a screwdriver base handle.
- Clamping tools: pliers, pliers. Cutting: wire cutters or similar object.
- To assemble a printed circuit board, you need to stock up on profile material.
It is worth noting that for different models During the assembly process, the list of necessary materials and tools may also change. 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.
Schematic diagram of a pinpointer
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.
Assembly technology
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 high level resistance, such as an oscilloscope.
Electronic frequency pinpointer
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.
Analog pinpointer
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
According to the diagram, I think there will be no questions, all the elements are labeled on the printed circuit board, please note that some details on the board do not match the diagram, since I wired it to match what was in the local radio store!!!
All capacitors used in the generator must be film capacitors with an operating voltage of at least 100 volts.
Regarding the L1 contour coil, I wound it on a piece of ferrite rod with a diameter of 10 mm. from the magnetic antenna of an old radio. The length of the rod is 10 cm. I wound the coil in 4 layers with enameled wire with a diameter of 0.35 mm. the number of turns is 450. After winding, I impregnated the coil with tsapon varnish and crimped it on top with a heat-shrink tube.
According to the printed circuit board, it is one-sided with the use of both deep and SMD components, the buzzer is not just a speaker, but a speaker with a generator!
And finally, a few photos of the assembled board.
Soon I will post a short video of this pinpointer in action.
Download schematic and PCB file
(developer Petrucho – md4u forum)
Pinpointer is a special type of metal detector, which has a unique compactness and is designed to clarify the location of metal targets when searching. Such a detector does not have great sensitivity, it simply does not need it, but it very accurately “shows” the location of metal objects.
Thanks to this, it is used to accurately identify a find during a search, inspecting the walls of buildings to find fittings, metal supporting structures, hidden wiring, hiding places, etc.
Pinpointer Minimax PP-2 is a simple, reliable and small-sized metal detector, developed by one of the forum participants on md4u under the nickname Petrucho. It has been tested on land and in water, and works great in the salty waters of the Black Sea.
First, let's get acquainted with technical characteristics device (TTX):
Supply voltage…………………….. 3-5 Volts;
Current consumption………………………….. 18 mA;
Indication………………………………….. sound (fixed tone);
Coin detection range…………. 5 cm (5 kopecks USSR).
See a short introductory video about the operation and performance characteristics of the pinpointer below.
So, let's take a look at the device diagram (picture below).
I provide a description of the operation of the Minimax PP-2 pinpointer from the author (part of the text used was taken from the author’s website, the md4 forum and personal correspondence with the author). So:
...It is based on the principle of measuring quality factor. The circuit is quite simple - only 1 microcircuit and 4 transistors. The circuit can be powered within 3-5.5 Volts (5.5 Volts is the maximum possible power supply for the MCP602 chip).
For the minimum size of the pinpointer, it is recommended to use either 2 AA or AAA elements, or one 3-volt lithium battery (or lithium battery 3.7 Volts). For example, LIR123 (photo below).
A self-oscillating LC generator with voltage resonance (series resonance) is assembled on elements Q1,Q2, D1,D2, R1,R2, C1,C2,C3 and L1. Oscillatory circuit formed by the total capacitance of capacitors C1, C2, C3 and inductance L1.
Recharging of C1, C3 occurs relative to the power buses through the base-emitter junctions of the transistors and also through the protective diodes D1, D2. Due to this, transistors Q1, Q2 operate in switching mode (the bases of transistors Q1, Q2 “dangle” relative to the power buses within +- 0.7 Volts).
Of course, the generator has a rather long linear mode when switching from one state to another. The switching time is approximately 1/10 of the period. This is due to the fact that the switching of transistors occurs when the growth rate of the sine function is small.
Is this good or bad? It’s good in the sense that fewer harmonics are driven into the circuit - as a result, a fairly clean sine wave. Not good from a consumption point of view. If it were possible to eliminate the linear section, then the current consumption would decrease by 2..3 mA.
Yellow - voltage at the collectors of the generator transistors.
Blue - voltage on the coil.
A power filter is implemented on C4 and L2 to eliminate false interference through the positive power bus.
The negative half-wave of the alternating voltage removed from the inductor is rectified by a half-wave rectifier at D3, R3, C5.
Additional signal filtering for low-frequency interference, for more stable operation - R4, C6.
Capacity C7 sets the “target tracking” speed of the dynamic mode. If the stability of the threshold is unsatisfactory (the device “poorly holds” the adjusted threshold), the capacitance C7 should be increased.
Also, for good and stable operation of the Minimax PP-2 pinpointer, film or polystyrene capacitors should be used in the circuit.
In the diagram these are the following parts: C1, C2, C3, C5, C6, C7. The remaining capacitors, resistors and other parts of the circuit can be used in SMD design.
The pinpointer search sensor can be made to operate at different frequencies. Coil L1 is wound with varnish insulated wire with a diameter of 0.25-0.3 mm and consists of 700-500 turns, respectively. Coil L1 is wound on ferrite with a diameter of 10 mm and a length of 5-7 cm. For maximum sensitivity, you can wind the coil closer to the edge of the rod.
If 1-1.5 cm of sensitivity is not critical, but you still want to make the dimensions (diameter) of the pinpointer smaller, then winding is done to the width of the entire ferrite rod.
Also, after manufacturing the search element and checking the functionality of the circuit, it is necessary to impregnate (fill) the turns of the L1 coil with epoxy resin or varnish. This will give the search element rigidity and stability in operation.
Pinpointer signals that a metal target has been found sound signal. This sound is produced by a buzzer (piezoelectric element with a built-in audio frequency generator) with an operating voltage of 5-6 Volts.
Now the nuances.
At the output of the diode assembly D3, there may be a signal of decent amplitude.
Therefore D3 must have reverse voltage more than 100 Volts and at the same time it must be high-frequency.
Possible replacements for the DMN2075U field effect transistor
In SOT-23 package:
IRLML2502 NTR4501N Si2302ADS BSS138
In TO-92 housing:
BS108 BSN254 BSN304 ZVNL110 ZVNL120 ZVNL535 ZVN4424
Well, there are many more options...
Replacing transistors Q1 and Q2
MMBT4403 on KT361, KT3107, BC327, BC328...
MMBT4401 on KT315, KT3102, VS337, VS338…
The pinpointer's power supply is not stabilized, so it is recommended not to be greedy and use good alkaline batteries. They have very little internal resistance right up to the discharge!
Possible modernization of the pinpointer.
Instead of a buzzer, the device can use an LED or a vibration motor at the user’s request.
If you use the device according to the principle of plug and play all day, the batteries will not fail quickly, but they will not last long.
Well, if you work in the “press-check-release” power button mode, then alkaline batteries will last for a season or more!!!
…
And finally, a pinpointer board developed by one of the MD4U forum members.
Good luck to everyone in making it - it's awesome!
Alexander Serbin (Kharkov)
