DIY metal detector - the best ideas. Schemes for making a metal detector with your own hands How to make a metal detector more discriminatory yourself
Greetings to all lovers of metal detecting and metal detecting. Now we will talk about one of the most important concepts in metal search, this concept of discrimination. What is discrimination, why is it needed, how to choose a metal detector based on this concept. So discrimination, if you choose simple explanations, then discrimination is an exception. Excluding unnecessary objects from the search; in this simple sentence lies the secret to understanding this word. If we project on metal detectors and metal detecting, we will still talk in more detail about what discrimination is, how to use this concept. And so, indeed, discrimination serves to ensure that in our search we do not get distracted by unnecessary goals, do not waste time digging them out, do not spoil our nerves, and do not waste our energy. We need to know what lies in the ground, and we need to exclude from the search those objects that we do not need. Well, what the search engine doesn’t need is most likely iron, nails, staples, horseshoes, roofing iron, some other iron products that are very often found in the ground and naturally you absolutely don’t want to be distracted by excavating such items. Manufacturers of different metal detectors use different principles and techniques in the metal detector setup system. I have in my hands the legendary Tesoro Compadre metal detector, this is the simplest metal detector on the market, using an example of which we will introduce you to the discrimination scale adjustment system. , Tesoro Compadre is equipped with only one control, this is a switch combined with a potentiometer. Turning the potentiometer clockwise in the opposite direction quickly and easily adjusts the discrimination level. That is, the linear principle of discrimination and exclusion of objects from the search is implemented here. At the minimum level we are in the all metal mode, that is, in this mode the metal detector gives a sound signal to absolutely all metal objects in the ground, you can detect nails, horseshoes, pieces of roofing, absolutely all the metal that will lie in the ground. But if we turn this potentiometer to the next mark, and here are verbal special marks for the convenience of setting up this metal detector, and by turning the potentiometer to the next mark iro, that is, iron, we will notice when searching that the metal detector has stopped emitting sound signals on iron. That is, we will not hear a response from annoying nails, from the roof, from any other small and medium-sized metal objects. We excluded from the search, discriminated, that’s what discrimination is. By turning the potentiometer even further clockwise to the “foil” foil mark and again checking its search capabilities, we will find that the metal detector has stopped detecting other small objects, but this time made of non-ferrous metals. That is, it will not detect foil, it will not detect small lead shot and other, again, annoying and unnecessary objects. By turning the potentiometer even further, we will exclude even more objects from the search. That is, initially we exclude objects with low conductivity from the search and by turning the potentiometer we gradually move on to metals with higher conductivity and we can also exclude them from the search at will. The fact is that discrimination scales can be divided into many segments, this will mean that the more segments in the discrimination scale a metal detector has, the more precise and more precise you can adjust it. If we are talking about Tesoro Compadre metal detectors, then the discrimination scale of this metal detector has 180 segments, which is a lot. That is, you can configure this metal detector extremely accurately, cutting off unnecessary targets and accepting necessary ones. If we are talking about metal detectors from other manufacturers, about budget metal detectors, then the scale of such metal detectors will not have many segments: 8, 10, 12. That is, you can immediately understand that the greater the number of segments in a given metal detector, the more accurately you can adjust the discrimination scale and the better and more productive it is to use the very concept of discrimination. In digital metal detectors and in several models of Tesoro metal detectors, it is possible to discretely adjust the discrimination scale. That is, you can exclude from the search not only sequentially, but also discretely by isolating a certain sector of finds and excluding it from the search. In conclusion, let us repeat once again what discrimination is. Discrimination is the exclusion of unwanted objects from the search; the metal detector will not emit an audio signal for those objects that are excluded from the search, although they will be in the ground. In this way, you will avoid unnecessary excavations and get maximum pleasure from the search, and naturally you will have time to dig up a much larger number of finds than if your discrimination scale is at a minimum, that is, you will receive signals from all targets. When choosing your metal detector, pay attention to what discrimination system is used in this metal detector, and how many segments in the discrimination scale this metal detector has. Good luck. Let's meet.
Deep-type metal detectors are capable of detecting objects in the ground at a great distance. Modern modifications in stores are quite expensive. However, in this case, you can try to make a metal detector with your own hands. For this purpose, it is first recommended to familiarize yourself with the design of the standard modification.
Modification scheme
When assembling a metal detector with your own hands (the diagram is shown below), you need to remember that the main elements of the device are a damper on a microcontroller, a capacitor and a handle with a holder. The control unit in the devices consists of a set of resistors. Some modifications are made on drive modulators that operate at a frequency of 35 Hz. The racks themselves are made with narrow and wide plate-shaped plates.
Assembly instructions for a simple model
Assembling a metal detector with your own hands is quite simple. First of all, it is recommended to prepare a tube and attach a handle to it. High conductivity resistors will be required for installation. The operating frequency of the device depends on many factors. If we consider modifications based on diode capacitors, then they have high sensitivity.
The operating frequency of such metal detectors is about 30 Hz. Their maximum object detection distance is 25 mm. Modifications can operate on lithium batteries. Microcontrollers for assembly will need a polar filter. Many models fold on open-type sensors. It is also worth noting that experts do not recommend using high sensitivity filters. They greatly reduce the accuracy of detecting metal objects.
Model series "Pirate"
You can make a “Pirate” metal detector with your own hands only using a wired controller. However, first of all, a microprocessor is prepared for assembly. To connect it you will need Many experts recommend using grid capacitors with a capacity of 5 pF. Their conductivity should be maintained at 45 microns. Afterwards you can start soldering the control unit. The stand must be strong and support the weight of the plate. For 4 V models, it is not recommended to use plates with a diameter larger than 5.5 cm. System indicators do not need to be installed. After securing the unit, all that remains is to install the batteries.
Using reflex transistors
Making a metal detector with reflex transistors with your own hands is quite simple. First of all, experts recommend installing a microcontroller. In this case, capacitors are suitable of a three-channel type, and their conductivity should not exceed 55 microns. At 5 V they have a resistance of approximately 35 ohms. Resistors in modifications are mainly used of the contact type. They have negative polarity and cope well with electromagnetic vibrations. It is also worth noting that during assembly it is allowed to use the maximum width of the plate for such a modification is 5.5 cm.
Model with convection transistors: expert reviews
You can assemble a metal detector with your own hands only on the basis of a collector controller. In this case, capacitors are used at 30 microns. If you believe the reviews of experts, then it is better not to use powerful resistors. In this case, the maximum capacitance of the elements should be 40 pF. After installing the controller, it is worth working on the control unit.
These metal detectors receive good reviews for their reliable protection against wave interference. For this purpose, two diode-type filters are used. Modifications with display systems are very rare among homemade modifications. It is also worth noting that power supplies must operate at low voltage. This way the battery will last for a long time.
Using Chromatic Resistors
With your own hands? The model with chromatic resistors is quite simple to assemble, but it should be taken into account that capacitors for modifications can only be used on fuses. Experts also point out the incompatibility of resistors with pass filters. Before starting assembly, it is important to immediately prepare a tube for the model, which will be the handle. Then the block is installed. It is more advisable to select modifications at 4 microns, which operate at a frequency of 50 Hz. They have a low dispersion coefficient and high measurement accuracy. It is also worth noting that searchers of this class will be able to successfully work in conditions of high humidity.
Model with a pulse zener diode: assembly, reviews
Devices with pulsed zener diodes are distinguished by their high conductivity. If you believe the reviews of experts, then homemade modifications can work with objects of different sizes. If we talk about the parameters, their detection accuracy is approximately 89%. You should start assembling the device with a stand blank. Then the handle for the model is mounted.
The next step is to install the control unit. Then a controller is mounted, which runs on lithium batteries. After installing the unit, you can start soldering the capacitors. Their negative resistance should not exceed 45 ohms. Expert reviews indicate that modifications of this type can be made without filters. However, it is worth considering that the model will have serious problems with wave interference. In this case, the capacitor will suffer. As a result, the battery of models of this type quickly discharges.
Application of low frequency transceiver
Low-frequency transceivers in models significantly reduce the accuracy of the devices. However, it is worth noting that modifications of this type can successfully work with small objects. At the same time, they have a low self-discharge parameter. In order to assemble the modification yourself, it is recommended to use a wired controller. The transmitter is most often used with diodes. Thus, conductivity is ensured at around 45 microns with a sensitivity of 3 mV.
Some experts recommend installing mesh filters, which increase the security of models. To increase conductivity, only transition type modules are used. The main disadvantage of such devices is considered to be controller burnout. If such a breakdown occurs, it is problematic to repair the metal detector yourself.
Using a High Frequency Transceiver
On high-frequency transceivers, you can assemble a simple metal detector with your own hands only on the basis of an adapter controller. Before installation, a stand for the plate is prepared as standard. The average conductivity of the controller is 40 microns. Many specialists do not use contact filters during assembly. They have high thermal losses and are capable of operating at 50 Hz. It is also worth noting that lithium batteries are used to assemble the metal detector, which recharge the control unit. The sensor itself in modifications is installed through a capacitor, the capacitance of which should not exceed 4 pF.
Model with longitudinal resonator
Devices with longitudinal resonators are often found on the market. They stand out among their competitors with their high accuracy of identifying objects, and at the same time they can work in high humidity. In order to assemble the model yourself, a stand is prepared, and a plate should be used with a diameter of at least 300 mm.
It is also worth noting that to assemble the device you will need a contact controller and one expander. Filters are used only on mesh lining. Many experts recommend installing diode capacitors that operate at a voltage of 14 V. First of all, they discharge little of the battery. It is also worth noting that they have good conductivity compared to field analogues.
Using selective filters
Making such a deep metal detector with your own hands is not easy. The main problem is that a regular capacitor cannot be installed in the device. It is also worth noting that the plate for modification is selected from 25 cm in size. In some cases, the racks are installed with an expander. Many experts advise starting assembly by installing the control unit. It must operate at a frequency of no more than 50 Hz. In this case, the conductivity depends on the controller used in the equipment.
Quite often it is selected with a lining to increase the security of the modification. However, such models often overheat and are not able to work with high accuracy. To solve this problem, it is recommended to use conventional adapters that are installed under the capacitor units. A do-it-yourself metal detector coil is made from a transceiver block.
Application of contactors
Contactors are installed in devices together with control units. Stands for modifications are used of short length, and plates are selected at 20 and 30 cm. Some experts say that devices should be assembled on impulse adapters. In this case, capacitors can be used with low capacitance.
It is also worth noting that after installing the control unit, it is worth soldering a filter that can operate at a voltage of 15 V. In this case, the model will maintain a conductivity of 13 microns. Transceivers are most often used on adapters. Before turning on the metal detector, the level of negative resistance is checked on the contactor. The specified parameter is on average 45 Ohms.
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Even the most serious and respectable citizens feel a slight excitement when they hear the word “treasure”. We literally walk through treasures, of which there are immeasurably many in our land.
But how can you look under the soil layer to know exactly where to dig?
Professional treasure hunters use expensive equipment, the purchase of which can pay for itself after one successful find. Archaeologists, builders, geologists, members of exploration societies use equipment provided by the organization in which they work.
But what about novice treasure hunters on a budget? You can make a metal detector at home with your own hands.
To understand the subject, consider the design and operating principle of the device
Popular metal detectors operate using the properties of electromagnetic induction. Main components:
- transmitter – generator of electromagnetic oscillations
- transmitting coil, receiving coil (in some models the coils are combined for compactness)
- electromagnetic wave receiver
- decoder that separates the useful signal from the general background
- signaling device (indicator).
The generator, using a transmitting coil, creates an electromagnetic field (EMF) around it with specified characteristics. The receiver scans the environment and compares field performance with reference values. If there are no changes, nothing happens in the circuit.
- When any conductor (any metal) enters the field of action, the basic EMF induces Foucault currents in it. These eddy currents create the object's own electromagnetic field. The receiver detects the distortion of the basic EMF and gives a signal to the indicator (audio or visual alert).
- If the object being examined is not metallic, but has ferromagnetic properties, it will shield the underlying EMF, also causing distortion.
Important! There is a misconception that the soil in which searches are carried out should not be electrically conductive.
This is wrong. The main thing is that the electromagnetic or ferromagnetic properties of the environment and the search objects are different from each other.
That is, against the background of certain characteristics of the EMF generated by the search environment, the field of individual objects will stand out.
The Chance pulse metal detector proposed for repetition was developed by the famous designer Andrei Fedorov and has received recognition from radio amateurs both in our country and abroad. This metal detector is a kind of continuation of the Clone series of devices and embodies the most advanced developments in the field of building these metal detectors. In addition to metal selection, the device has a discrimination function: by turning on software-built masks, you can achieve a detuning from ferrous metals when searching.Indication of device readings is carried out using an LCD indicator (VDI scale, Amplitude scale (size, location of the object), battery voltage indication (battery charge level)) and sound signals of different tones. The heart of the metal detector is the already familiar Atmega8-16PI microcontroller in conjunction with an external ADC. The use of an external ADC is due to the expansion of the set of functions of the device - the introduction of such a set of functions without an external ADC is physically impossible due to the small internal resource of the microcontroller.
I will give some characteristics of the device. Sensitivity for 5kop USSR coin up to 25cm. Selection by metals under ideal conditions: the “blacker” the metal, the lower its conductivity, and the closer to the left edge of the VDI scale the readings will be; the more “colored” the metal is, the greater its conductivity; accordingly, the readings on the scale will be closer to the right edge (the readings on the scale depend on the choice of device firmware and may change). Discrimination function: turning on one of the four masks one by one, you can tell the device not to react to “ferrous” metals to the desired extent (up to complete elimination of the influence of ferrous metal). Barrier function: at 16 levels it helps to detach from the influence of “earth” and other external factors.
To repeat Chance, first of all, you need to visit the author’s page fandy.vov.ru, where circuits, firmware, configuration bits for flashing the microcontroller, a description of the operation of the buttons and other useful information are located. The main, rare and most expensive parts of the device are the ADC chip and LCD indicator. An analogue of the ADC chip (MCP3201) is the ADS7816 chip, for which the author wrote corrected firmware (0.8.4). The next important part of the metal detector is the LCD indicator. With all the variety and current abundance of such components, the most suitable, in my opinion, are reliable and fairly cheap indicators from Winstar, which are superior in price/quality ratio to indicators from the domestic manufacturer MELT. When purchasing an indicator, you should select it based on the following instructions: character-synthesizing indicator, 2 lines of 16 characters each, Cyrillic support (the ability to use the indicator in any other development), the presence of a built-in HD44780 controller. You can view and download datasheets and pinouts on the Winstar website. The archive also contains a list of parts.
The OP37 operational amplifier can be replaced with a cheaper and more common analog NE5534P. The ICL7660S DC/DC converter can, although not advisably, be replaced with a similar one without the letter S (with the letter S at 12 volts, without it at 10 volts, it will work, but with an overload). The microcontroller is our old friend Atmega8-16PI (Atmega8-16PU, Atmega8A-PU). The controller is programmed using a simple programmer, which was used when programming the microcontroller for the Clone device. Here are the device parameters and a step-by-step description of the programming process for this controller. The most important thing here is not to forget about the configuration bits! Archive for microcontroller.
The planar coil of the metal detector is made on a dielectric frame 4 mm thick and wound with wire with a diameter of 0.65 - 0.8 mm. The coil template is shown in the figure below. The device rod is manufactured using the technology described in the article. You can assemble a metal detector on the author’s printed circuit board or use a much easier to replicate (for beginners) board from DesAlex - see the drawing on the forum. I myself remade 5 of these coils - I changed the number of turns, the thickness of the frame from 2 to 6 mm. The best result was obtained on a 4mm frame, the number of turns is the same as the author’s, the inductance is 389uH. Experiments with home-winding/rewinding did not affect the final result (noted by many who repeated this device), that is, a spread of +-10% does not affect anything. Although each result will be different from the other (diameter of the wire, quality of the wire, presence of impurities, quality of winding, waterproofing of the coil (varnish, epoxy, paint)), the quality and length of the supply cable - everything affects the quality factor of the search element.
A correctly assembled device does not require adjustment and is fully operational! In conclusion, I would like to thank the author of the metal detector (AndyF) for the excellent pulse metal detector with discrimination, as well as DesAlex for the reliable printed circuit board, without which the device would not have received such widespread popularity among radio amateurs and outdoor enthusiasts, which is the search for historical relics! Material provided by Elektrodych .
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