The term amplifier is very ambiguous. It can be a hydraulic booster, well-known to motorists, a magnetic amplifier that was once used in automation systems. Electromechanical and relay amplifiers are also known.

The principle of operation of all amplifiers is the same: under the influence of a weak control signal, a powerful output signal appears at the output of the amplifier. Naturally, to obtain an output signal of high power requires an external energy source.

For example, controlling a relay coil requires a fraction of a watt of power, while contacts can switch a load of several kilowatts. As they say, there is a gain in power. But in this article only electronic amplifiers will be briefly reviewed. They are the most common node of various devices and devices ...

One of the most common malfunctions of modern DVD players is poor reading of data from the disc or even a complete lack of reading. There are about a dozen reasons for this problem. One of the first on the list is the loss of emission of a laser diode, both a CD and a DVD diode. More often than the last.

Hence the selective reading, that is, the device does not read DVD discs, but perfectly “catches” and plays CDs. Or exactly the opposite. As repair practice shows, on average, the head of a DVD player lasts from 3 to 5 years. And every year this figure decreases, as well as the cost of heads.

What to do if your player does not read DVD discs, treacherously signaling “NO DISK” for all your attempts to watch your favorite movie after a hard day? Well, as I said, there can be about a dozen reasons ...

In many descriptions, the comparator is compared with conventional lever scales, as in a bazaar: a standard is placed on one bowl - weights, and the seller begins to put goods, such as potatoes, on the other. As soon as the weight of the product becomes equal to the weight of the weights, more precisely a little more, the cup with weights rushes up. Weighing is over.

The same thing happens with the comparator, only in this case the role of weights is played by the reference voltage, and the input signal is used as a potato. As soon as a logical unit appears at the output of the comparator, it is considered that the voltage comparison has occurred. This is the very “a bit more”, which in the directories is called the “threshold sensitivity of the comparator”. Novice hams - electronics engineers often ask how to check a particular part. To check the comparator, you don’t need to collect any complex circuit ...

The name comparators comes from the Latin compare - compare. Devices in which measurement is carried out by comparing with a standard work on this principle. For example, equal-arm scales or electric potentiometers.

The principle of action distinguishes between electrical, pneumatic, optical and even mechanical comparators. The latter are used for checking end length measures. The first comparator was used in Paris by Lenoir in 1792.

In this article we will not consider in detail mechanical and other comparators, since our task is voltage comparators. At present, comparators are mainly used in integrated design. Few people would think of assembling a comparator from discrete transistors. Moreover, comparators are used as part of some chips ...

Integral timer 555 found another application in three-phase inverters, or as they are often called frequency-controlled drives.The main purpose of "chastotnikov" is the regulation of the rotational speed of three-phase asynchronous motors. In the literature and on the Internet you can find many schemes of home-made frequency drives, interest in which has not disappeared to date.

The whole idea is this. The rectified mains voltage with the help of the controller is converted to three-phase, as in an industrial network. But the frequency of this voltage can change under the influence of the controller. The methods of change are different, from simple manual control to regulation by an automation system.

The block diagram of a three-phase inverter is shown in the figure. Points A, B, C show the three phases to which the induction motor is connected. These phases are obtained by switching transistor switches ...

The 555 timer is widely used in control devices, for example, in PWM - speed controllers of DC motors.

Everyone who has ever used a cordless screwdriver must have heard a squeak coming from inside. This is whistled by the motor windings under the influence of the pulse voltage generated by the PWM system. Another way to regulate the speed of the engine connected to the battery is simply indecent, although it is possible.

For example, simply connect a powerful rheostat in series with the engine, or use an adjustable linear voltage regulator with a large radiator. The circuit is quite simple and everything is based on a multivibrator, although converted into a pulse generator with an adjustable duty cycle, which depends on the ratio of the charge speed and the discharge of the capacitor ...

Quite often, in various schemes, voltage converters are required. The most typical example is powering a device from a car battery. Typically, such voltage converters are push-pull based on various specialized microcircuits. But, if the power of the converter is small, it is quite possible to create one on the basis of the 555 timer (KR1006VI1). A diagram of one of the possible options is shown in the figure.

The circuit contains a self-oscillating multivibrator already familiar from previous articles about the 555 timer, the output of which is connected to a gate of a powerful field-effect transistor. The stabilization device is a threshold device, almost a comparator, with a threshold threshold set by the zener diode. The stabilization device works as follows ...

With the modern development of electronics in China, it seems that you can buy anything you want: from home theaters and computers to simple products such as electrical outlets and plugs.

Somewhere between them are all kinds of timers, flashing Christmas lights, clocks with thermometers, power controllers, temperature controllers, photorelay and much more. As the great satirist Arkady Raikin said in a monologue about the deficit: “Let everything be, but let something be missing!” In general, just what is included in the “repertoire” of simple amateur radio designs is lacking. Despite such competition from the Chinese industry, the interest of amateur designers in these simple designs has not been lost so far. They continue to be developed and in some cases find worthy application in small home automation devices ...