When I needed a megaphone, I became acquainted with the prices of Chinese industrial products: as it turned out, they cost from 1500 to 8000 rubles., and found that such a device can collect a couple of hours with her hands. A megaphone (or loud speaker), an electrical circuit which recommend and bring forth, be useful for sports, in advertising, in conditions of constant excessive noise, playing games with the child and even in the minibus for broadcasting information to passengers in the rear seats.
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This miniature power pack sits in the battery compartment handheld radios, calculators and other miniature electronic equipment where they need to be connected to AC power. After capacitor C1, Zener diode V1 and V2 (see diagram) we obtain the rectified current voltage of 15 V. It is used to supply voltage to the transistor V4. During the negative half-wave current of the diode V3 returns to the power supply portion stored in the power transformer.
Many people keep different Pets, communication with which brings a lot of pleasant moments for both children and adults. However, there are those animals, which are also constantly live with the man and often visited his home (for example, mice, rats). But they are uninvited guests and even harmful, as they are considered (and probably not without reason), carriers of different pathogens of dangerous infections.
When performing electrical work have to drill a very large number of holes in the walls and partitions. In a brick or prefabricated houses not to dispense with carbide drills. However, such a tool is not enough for a long time: the working edges of the drill bits become dull and crumble and need to be sharpened. This is typically done using special “green” wheels, but they are expensive and wear out quickly. Faced with this problem, I started looking for alternative technology and stopped at electroerosion grinding devices.
On the instructions of the enterprises of Dzerzhinsk-khimpromenergo in the design office of the school # 2 of Dzerzhinsk, Gorky region, the guys have designed and built a device for measuring the pressure of neutral media in the pipes — an electronic pressure gauge. One of its founders, a student of the tenth class Sergey Whalin, said that the installation or repair of compressors necessary to carry out Express-analysis of the condition of the equipment. Devices, testifying to the extent necessary for a specific production, yet.
The quality of cement is usually determined by destruction of the samples. Moreover, this process lasts from seven to twenty-eight days. To speed it up decided young technicians of the radio circle of the pioneer city of Iskitim of the Novosibirsk region. “The task we were given in Vries cement plant — said the group members Zaitsev. — Together with the guys we have designed and built an instrument (Fig. 1), which brand of cement you can determine almost instantly”.
In recent years in our country and abroad is rapidly developing a new kind of consumer electronics device for home games. The name given to a special prefix to the TV, allowing you to create on the screen the imitation of various sports, military, and other games. These devices are built on the basis of the so-called telegraphic circuits or large integrated circuits.
For portable electronic equipment need a small volume and weight of the power supply. To solve this problem relatively simply by replacing passive LC and active RC filters.
Smoothly change the brightness of room lighting or hall comfortable with the thyristor voltage regulator (see Fig.). The scheme allows you to adjust the load voltage ranging from 220 V to 0, 25 W to 1 kW. But if the thyristors to supply the radiators, then it will increase to 1.5 kW. The main elements of the regulator, the thyristors V1, V2, included a counter each other and parallel to the load. They alternately pass current in one or in the other direction.
In many cities on the lively streets and highways have electronic thermometers. Some of them, with light of a mercury column, like an ordinary thermometer, the other made in the form of a digital display. To make such devices themselves is not available to everyone. But the simplified design of the indicator can be manufactured by the forces of the circle of automation students.