At home, we often have to work with electric tools and devices (electric drills, rotary hammers, circular saws, electric planers, etc.) at a considerable distance from the outlet. And if the extension cord is long (more than 25 m), it becomes difficult to unwind, wind and store it. Therefore, we decided to make a portable extension cord (see. Fig.).

The extension cord consists of a base, a pillar, and a wire-mounted reel. A plug connector is connected to one end thereof, and a plug to the other. The bobbin is mounted on the axis with the help of curly washers and is locked with the wing nut.

The stand consists of a pipe curved in the form of a bracket 1 / 2–3 / 4" and two corners welded to it. In turn, the axis on which the bobbin with the wire is mounted is welded to the top ...

The name of Oleg Vladimirovich Losev today is known only to a narrow circle of specialists. What a pity: his contribution to science, to the development of radio engineering is such that it entitles this ascetic scientist to the grateful memory of his descendants.

Pupil of the fifth grade of the real school of the pre-revolutionary Tver Oleg Losev quietly rummaged that evening in his half-secret home radio laboratory, which he equipped with money saved from school breakfasts and made another electric squeaker. And no one could have thought that in a modest polite boy who stood out among classmates with a deep understanding of physics, a love of experimentation, the personality of a purposeful researcher is formed.

It all began with a public lecture on wireless telegraphy, as they called radio at that time, which was delivered by the head of the Tver radio receiving station B. M. Leshchinsky. At fourteen, Oleg Losev makes the final choice: his calling is radio engineering ...

Typically, electric motors are divided into three groups: large, medium and low power. For low power engines (we will call them micromotors), the upper limit of the power is not set, usually a few hundred watts. Micromotors are widely used in household appliances and devices (now every family has several micromotors - in refrigerators, vacuum cleaners, tape recorders, players, etc.), measuring equipment, automatic control systems, aviation and space technology, and other areas of human activity.

Single-phase asynchronous micromotors are the most common type, they satisfy the requirements of most electric drives of devices and apparatuses, differing in low cost and noise level, high reliability, do not require maintenance and do not contain moving contacts ...

They say that you won’t save much on matches, and yet ... A simple and practical electronic match, the description of which I propose, will save you from the need to constantly monitor so that the matchboxes do not remain empty.

The “match” acts as follows. Electricity accumulated by the capacitor from the 220 V network is converted into a spark, from which gas ignites in the burner of the stove. The charge time to the amplitude value of the mains voltage is 2 - 3 s, and for its discharge, only 0.1 s is sufficient.

Structurally, the “match” is made in the form of a cylinder consisting of two halves. Radioelements are located inside one, the other protects the ends of the arrester from accidental short circuit, otherwise the “match” included in the network immediately disables the diode ...

Surprisingly, a fact.Yesterday, a good friend of mine, a homemade friend of mine, called me to see why the circular did not start. He says that before she worked perfectly, then a neighbor took her for a while, and now the circular does not start. The peculiarity of the machine was that it installed a two-kilowatt three-phase electric motor, included in a single-phase network according to the "triangle" scheme, with two blocks of capacitors - working and starting.

To determine the malfunction, we first measure the resistance of the motor windings. The resistance of the windings is usually tens of ohms. In this case, the resistance very quickly changes from zero to the maximum value. This is affected by the effect of capacitors. While they are charging, the resistance drops to zero. As the capacitors charge, the resistance increases, and when the capacitors are fully charged, their resistance equals infinity, so the ohmmeter shows the resistance of the motor windings ...

In 1963, a large family of Trinistors appeared another "relative" - triac. How does he differ from his "brothers" - trinistors (thyristors)? Remember the properties of these devices. Their work is often compared with the action of an ordinary door: the device is locked - there is no current in the circuit (the door is closed - there is no passage), the device is open - an electric current appears in the circuit (the door opened - enter). But they have a common flaw. Thyristors pass current only in the forward direction - this way an ordinary door easily opens "from itself", but no matter how much you pull it towards you - in the opposite direction, all efforts will be useless.

By increasing the number of semiconductor layers of the thyristor from four to five and equipping it with a control electrode, scientists found that a device with such a structure (later called a triac) is capable of passing electric current in both forward and reverse directions ...

Everyone knows that working with a low-voltage electric soldering iron is safe and convenient. In production and in educational laboratories, low-voltage small-sized soldering irons have long been universally used, but in everyday life we ​​most often have to be content with dangerous and bulky tools that operate on 220 V mains. make low voltage soldering iron power supply it’s not difficult for yourself.

The power supply is the simplest capacitive AC load limiter.

In the first, desktop version, the device is made in a light metal case, has two switches and one control indicator of the mains voltage, signaling about three switching modes.

Author schemes deliberately did not provide for the design of the block of devices for solder and flux, since these sets usually take up relatively much space. Therefore, the unit has only a curly stand for a soldering iron, which, when carried, can be removed inside and does not protrude beyond the dimensions of the unit ...

An important design feature of any welding machine is the ability to adjust the operating current. In industrial apparatuses, different methods of adjusting the current are used: shunting with various types of chokes, changing the magnetic flux due to the mobility of the windings or magnetic shunting, using active ballast resistances and rheostats. The disadvantages of this adjustment include the complexity of the design, the bulkiness of the resistances, their strong heating during operation, inconvenience when switching.

The most optimal option is to make it with taps while winding the secondary winding and, changing the number of turns, change the current.However, this method can be used to adjust the current, but not to adjust it over a wide range. In addition, the regulation of the current in the secondary circuit of the welding transformer is associated with certain problems.

So, significant currents pass through the control device, which leads to its cumbersomeness, and for the secondary circuit it is almost impossible to choose such powerful standard switches so that they can withstand currents up to 200 A. Another thing is the primary winding circuit ...

A nozzle made with your hands will protect the small child from electric shock.

It is known that children like to touch sockets with their fingers, insert cloves and scissors there. They probably subconsciously try to imitate their parents in this way. In this case, the child’s hands may be exposed to electric current. And needles, small pins, paper clips, screws, screws and nails can remain inside the electrical outlet and cause a short circuit in it. At the same time, a short circuit can be a source of fire in your apartment. To prevent this, of course, you can install a factory outlet with a fuse, or you can make such protection yourself.

To do this, it is necessary to prepare a protective disk made of thin plastic with a thickness of 2-3 mm, dimensions along the inner diameter of the socket for the plug in the socket. Drill two holes for the plug in our disk - false panel ...

The article was written specifically for the 250th anniversary of the DISCOVERY of freezing mercury.

St. Petersburg Academy of Sciences, opened in 1725. just had to become at the same time a leader in the study of cold physics. “The nature of our locality is surprisingly favorable for conducting experiments with the cold,” wrote G.V. Kraft, one of the first Petersburg professors. However, he immediately warned that in the nature of the cold there is a lot of unknown. “Until now, the aforementioned qualities are shrouded in such darkness that it took them several years to illuminate, and perhaps a whole life century was needed, and not only one, but many insightful gifts.” He was right.

The academies of England, Italy, France, Germany, Holland and even Sweden lay in a strip of mild climate. Technologically, it is easier to obtain high temperatures for experimental needs than cold. Even in antiquity, man could receive high temperatures sufficient for smelting iron ores. But before he learned to liquefy gases, getting low was very problematic. Only in 1665 physicist Boyle was able to reduce the temperature of the aqueous solution by only a few degrees. He achieved this by dissolving ammonia in water.

And why then did people need low temperatures? First of all, for scientists to calibrate thermometers used for meteorological measurements, where there are temperatures hitherto unknown to old-timers. It was the manufacturers of thermometers that began to select such substances and solvents that would lower the temperature of the solutions as much as possible. Such a composition was invented by the Dutch master of scientific instruments D. Fahrenheit. He recommended the use of crushed ice for this purpose, in which concentrated nitric acid would be added. In Russia, such a composition began to be called curious matter ...

Electricity consumption varies with the time of day. In the morning and evening, consumption increases significantly due to the lighting network and household load, during the day - due to industrial consumers. The lowest consumption occurs at night.

Uneven energy consumption leads to an unstable load of power plants, which adversely affects the operation of their equipment.For a uniform load, generators of neighboring power plants are included in parallel operation.

High-voltage power lines included in a single system form a closed ring, which provides two-way power to consumers. When the load increases, additional generators are turned on, and when the load decreases, standby generators are turned off.

All these technical measures are designed to ensure uniform loading of the power system throughout the day. However, in addition to technical measures, there are economic measures. These include a multi-tariff electricity metering system ...

Many people know that modern LEDs are more effective than incandescent lamps, and some models can argue with fluorescent lamps. But rarely does anyone think about what changes these technologies promise us.

Almost two trillion dollars - so many new LEDs will save earthlings in the next 10 years, provided they are widely implemented. In energy units, the savings will be expressed in 18.3 terawatt hours. Reducing CO2 emissions over this “LED” decade will be 11 gigatons, and oil consumption will drop by almost a billion barrels. And 280 average power plants can be closed.

Yes, professors Jung Kyu Kim and Fred Schubert from Rensselaer Polytechnic Institute approached the forecast of the future of solid-state lighting systems. They tried to go beyond the scope of saving electricity "for one house" and imagine what our world will be like, in which LEDs will become much more widespread ...