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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Radio game Find the mine. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur The sapper profession is one of the most honorable and responsible in the army. During the Great Patriotic War, our brave sappers saved the lives of thousands of Soviet soldiers and civilians by unraveling and disarming the most ingenious mine traps of the enemy. Millions of unexploded mines and shells remained on the fields of heroic battles. The camouflaged ammunition depots abandoned by the retreating enemy were fraught with mortal danger. Then volunteers came to the aid of military sappers - osoaviakhimovtsy. The Soviet government in February 1944 gave Osoaviakhim a difficult, responsible and honorable task. The Defense Society was entrusted with the work of complete demining and collection of ammunition in all areas liberated from the Nazi invaders. Huge arable areas, meadows and forests had to be explored and cleared of mines. Osoaviakhim was entrusted with the most difficult task of clearing the coastal areas of the Black and Azov Seas, the Krasnodar Territory, the Rostov Region, the Crimea, the Ukrainian SSR and the Byelorussian SSR. Society activists took part in the demining of public and residential buildings, power plants, factory buildings, roads and bridges. To imagine the scale of the work done by the Osoaviakhimists, it is enough to say that in 1944-1946 alone, the teams of the Society neutralized and destroyed 76 million anti-tank and anti-personnel mines, artillery shells and air bombs. In the Smolensk region alone, so many mines and air bombs were discovered and destroyed that it would take 3000 railway cars to transport them. 1000 shells were found in the basement of the Kyiv State University. The Nazis wanted to destroy this historical monument and the most important cultural center of Ukraine. A team of miners from Osoaviakhim eliminated this dangerous hearth. There are thousands of such examples. Even in our time, old, but still fraught with formidable power, unexploded mines and shells are occasionally found. Only an excellent knowledge of military equipment and the ability to apply it in a variety of conditions helps sappers to successfully fulfill their complex duties. Maybe one of you guys will also be a miner, but for now ... for now, we offer you the game "Find the" mine "". Everything in this game is real, except mines. Rather, there are "mines", only they do not explode.
For the game you need mine detectors and "mines". You must make mine detectors yourself, and a massive (2-3 kg) piece of ferromagnetic metal - cast iron or steel - can serve as a "mine" when searching on the ground. You can use a heating battery section, an old iron, a piece of a water pipe, a grate, etc. Indoors, a thin plate of ferromagnetic metal (a piece of roofing iron, tin from cans, etc.) can serve as a "mine". In both cases, it is only necessary that the metal be ferromagnetic, that is, that it be attracted by an ordinary permanent magnet. As you can see, the "mine" is quite simple. Making a mine detector is somewhat more difficult. Here you need knowledge of the basics of radio engineering and the ability to assemble simple electronic devices. SIMPLE MINO DETECTOR For the manufacture of such a mine detector (see appearance), a body and a core made of transformer steel with windings from a conventional electric bell are required. The simplest mine detector is a low (sound) frequency generator with inductive feedback, assembled on a single transistor.
Schematic diagram of the mine detector generator is shown in fig. 1. As can be seen from the diagram, for the manufacture of a mine detector, in addition to a bell transformer, a capacitor C1 is required, the capacitance of which is selected when setting up the device, one transistor of the MP40 type, a power source - four D-0,06 batteries or a KBS-type battery and headphones (headphones). The generator is so simple that when using serviceable parts and connecting them according to the circuit diagram, it starts working without additional configuration and adjustment. The pitch of the sound of the generator is changed by selecting the capacitance of the capacitor C1. Structurally, the mine detector generator is assembled in the housing from the bell. The bell transformer should be disassembled and the yoke removed (the jumper that closes the W-shaped core). This is necessary so that the generator, having an open W-shaped core of the transformer, is sensitive to the approach of foreign ferromagnetic objects. If such a core is brought closer to an object made of ferromagnetic material (Fig. 2), then the inductance of the transformer windings changes, and, consequently, the oscillation frequency of the generator. The action of the simplest mine detector is based on this property.
Its sensitivity is low, that is, it detects ferromagnetic objects in the immediate vicinity of the open part of the core. This property of the mine detector allows it to be used when playing indoors because its operation is not affected by reinforced concrete floor reinforcement, large nails and other ferromagnetic objects that are usually found indoors. The bell housing with the generator assembled inside it is fixed on a wooden handle 80-100 cm long as shown on the drawing. If you do not have a bell that can be converted into a simple mine detector, a core from a small transformer is suitable for this purpose. It is very convenient to use the output transformer from the mains tube radio. The transformer should be carefully disassembled, remove all rectangular plates, leaving only the W-shaped ones. The secondary winding, made with a thick wire and containing 80-120 (sometimes more) turns, is used as a feedback winding (winding II in Fig. 1). A winding with a large number of turns and made with a thinner wire in the mine detector will be winding I. The case for such a mine detector can be a can of candy, a case from an MKU-48 type relay, and any other ready-made case suitable for the size. COMPLEX MINO DETECTOR For the game "Find a mine" in an open area, a more sensitive mine detector is needed, capable of detecting a "mine" buried in the ground to a depth of 10-15 cm, hidden under rubble or brick. Such a mine detector is arranged somewhat differently. Its appearance is shown on the drawing, and the block diagram is in Fig. 3.
It consists of two generators and one mixer-amplifier. The first generator, the frequency of which is constant and equal to approximately 465 kHz, is assembled on the transistor T1 (see Fig. 4) according to the capacitive three-point circuit. The second generator is assembled on a transistor T3 according to the same scheme, but with the difference that its inductor L2 is made in the form of a ring placed outside, and the generator frequency, which is also 465 kHz, can be changed within small limits using a variable capacitor C11.
The low-frequency mixer-amplifier is assembled on a transistor T2. The mine detector operates as follows. When the power is turned on (see circuit diagram), both generators start to work, creating high-frequency oscillations. The high-frequency voltage from the generator, assembled on the transistor T1, is fed through the capacitor C6 to the base of the mixer (transistor T2). The base of the same transistor, through the capacitor C10, receives high-frequency oscillations from the transistor T3. In the load of the mixer-amplifier, the sum, difference and other combination frequencies are formed as a result of the conversion of two high-frequency oscillations. We are only interested in the frequency difference of the generators. The fact is that we cannot hear either the sum of high-frequency oscillations or other combination frequencies. If the oscillation frequencies of the generators are equal, in phones that are included in the collector circuit of the mixer-amplifier transistor, we will not listen to low-frequency signals. As soon as the frequency of one generator changes, we will immediately hear a low-frequency signal, the frequency of which is equal to the difference in the frequencies of the generators. Let, for example, the frequency of the first generator is 465 kHz. Using capacitor C11, we can set the frequency of the second generator to 464 kHz. Then in phones we will hear a signal with a frequency equal to 466 kHz - 464 kHz = 1 kHz. If a massive metal object is brought closer to the inductor L2, then the inductance of the coil will change, which means that the oscillation frequency of the second generator will also change, and we will fix a sharp change in the tone of the sound. The operation of the mine detector is based on this phenomenon. Structurally, this mine detector is made in a case from a pocket receiver. The device is mounted on a getinax board 60x60 mm in size. The location of parts on the circuit board is shown on the drawing. The installation of the mine detector is carried out in the usual way. You can even make a printed circuit board. The inductor L1 contains 200 turns wound without a frame. The inner diameter of the coil is 11 mm, the wire is PELSHO 0,1, the winding is of the "universal" type. This design uses one section from the intermediate frequency circuit of the Record receiver, from which 60 turns are unwound. The inductor L2 contains 14 turns of PEL 0,25 wire, wound in the form of a ring with a diameter of 350 mm. For strength and protection against mechanical damage, the coil must either be wrapped with several layers of insulating tape, or placed in a protective sheath made from the outer insulation of the coaxial cable. This mine detector is also mounted on a wooden handle 80-100 cm long (on the drawing). Rules of the game. "Find the" mine "" collective game. It can be carried out both indoors and outdoors. The game is played by two teams. In addition, an unlimited number of spectators-fans can watch the game. The number of participants in each team should be no more than 3-5 people. Depending on the presence of mine detectors, the search for "mines" is carried out either simultaneously by all members of the team, or by one person from each team. In the first case, each participant finds an unlimited number of "mines", in the second, the total number of "mines" must be equal to the number of team members, and each participant in the game finds only one "mine". The team that quickly clears the allotted area on the ground or indoors wins. Before the start of the game, secretly from the participants, the members of the jury set and mask "mines". Indoors, it is allowed to "mine" not only floors, but also walls, furniture and other items. It is only necessary to take into account that it is impossible to put "mines" on central heating radiators, iron sheets, door hinges, handles and other metal objects. As already mentioned, as "mines" installed indoors, lids from cans, pieces of roofing iron and other metal plates can be used, which are very convenient to mask with a thin carpet, sheet of paper, wallpaper, or linoleum. The thoroughness of the disguise depends entirely on the ingenuity of the jury members. The game "Find a mine" in an open area will be more interesting and visual. A plot of land measuring 20x20 meters; marked with pegs with a whip - this is a "mine" field on which the corresponding number of "mines" is masked. The entire area is divided in half, determining the search location for each team Burying "mines" deeper than 10 cm is not recommended, as this will greatly complicate the search. Teams go to the start from any shelter where the participants of the game were when the "mines" were installed and camouflaged. If each participant has an individual mine detector, both teams start the search in full force. The one who finds the "mine" goes to the start of the game, and the judges record the time spent searching for each participant. The team with the least total search time wins. If there are only two mine detectors, the search is carried out by one participant from each team at a time. The one who found the "mine", as in the previous case, returns to the start, and the jury records the search time spent by each participant. With a large number of people who want to take part in this game, you can recruit 8-4 teams that will search simultaneously in several “mined” areas of the same size. Author: E. Bornovolokov
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