Passive loudspeaker protection system. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Speakers
Comments on the article
Under such a heading in "Radio" No. 7 for 1997, M. Korzinin described a device for protecting the AU from dangerous overvoltages. It requires up to two dozen (or more) high-frequency rectifier diodes to protect one loudspeaker head. Meanwhile, by replacing circuits of a large number of diodes with a diode bridge and including a powerful composite transistor in its diagonal, a more economical protection device can be obtained (see figure).
This device, like the one made on diodes, works effectively only with tube or transistor amplifiers without a common voltage feedback, i.e., having an output impedance comparable to the load.
Transistor VT1 together with zener diodes VD5, VD6 and LED overload indicator HL1 form the equivalent of a powerful voltage limiter. The threshold for its operation depends on the parameters and the number of low-power zener diodes in the base circuit of a powerful transistor. As the latter, any device of the KT827 or KT825 series is suitable (with a corresponding change in the polarity of switching on the bridge diodes and the zener diode circuit). Due to the high current transfer coefficient of the base of the transistor, the current through the elements in the base circuit will not exceed 10 ... 20 mA.
The calculation of the limiter is reduced to determining the voltage on the zener diodes, which should be less than the limiting voltage by the sum of the voltage drops on the bridge diodes, the HL1 LED and the base-emitter junctions of the transistor (in total - about 6 ... 6,5 V).
To protect powerful low-frequency or wide-range heads, a more powerful limiter is also required. In this case, it is recommended to use two transistors connected in parallel, the emitter circuits of which include low-resistance resistors (with a resistance of 0,2 ... 0,3 Ohm). If the current transfer coefficient of the base of the transistors is more than 2000, then a separate threshold circuit with zener diodes is not required for each of them.
The power dissipated by the transistor will be significantly reduced if a lamp from a car headlight is included in its collector circuit. In a cold state, the resistance of its thread is small, and as the lamp warms up, it increases several times. As a result, the power dissipated in the transistor is reduced.
Author: A.Sokolov, Moscow
See other articles Section Speakers.
Read and write useful comments on this article.
<< Back
Latest news of science and technology, new electronics:
Artificial leather for touch emulation
15.04.2024
In a modern technology world where distance is becoming increasingly commonplace, maintaining connection and a sense of closeness is important. Recent developments in artificial skin by German scientists from Saarland University represent a new era in virtual interactions. German researchers from Saarland University have developed ultra-thin films that can transmit the sensation of touch over a distance. This cutting-edge technology provides new opportunities for virtual communication, especially for those who find themselves far from their loved ones. The ultra-thin films developed by the researchers, just 50 micrometers thick, can be integrated into textiles and worn like a second skin. These films act as sensors that recognize tactile signals from mom or dad, and as actuators that transmit these movements to the baby. Parents' touch to the fabric activates sensors that react to pressure and deform the ultra-thin film. This ... >>
Petgugu Global cat litter
15.04.2024
Taking care of pets can often be a challenge, especially when it comes to keeping your home clean. A new interesting solution from the Petgugu Global startup has been presented, which will make life easier for cat owners and help them keep their home perfectly clean and tidy. Startup Petgugu Global has unveiled a unique cat toilet that can automatically flush feces, keeping your home clean and fresh. This innovative device is equipped with various smart sensors that monitor your pet's toilet activity and activate to automatically clean after use. The device connects to the sewer system and ensures efficient waste removal without the need for intervention from the owner. Additionally, the toilet has a large flushable storage capacity, making it ideal for multi-cat households. The Petgugu cat litter bowl is designed for use with water-soluble litters and offers a range of additional ... >>
The attractiveness of caring men
14.04.2024
The stereotype that women prefer "bad boys" has long been widespread. However, recent research conducted by British scientists from Monash University offers a new perspective on this issue. They looked at how women responded to men's emotional responsibility and willingness to help others. The study's findings could change our understanding of what makes men attractive to women. A study conducted by scientists from Monash University leads to new findings about men's attractiveness to women. In the experiment, women were shown photographs of men with brief stories about their behavior in various situations, including their reaction to an encounter with a homeless person. Some of the men ignored the homeless man, while others helped him, such as buying him food. A study found that men who showed empathy and kindness were more attractive to women compared to men who showed empathy and kindness. ... >>
| Random news from the Archive Unraveled the reason for the fresh smell of the forest after the rain
25.01.2015
We begin to smell when molecules of a smelling substance reach the receptors in our nose. If the substance itself is liquid or solid, then the fastest way to smell is to spray tiny drops of liquid containing the desired substance into the air. Air fresheners work according to this principle - gas from a canister under pressure sprays an aerosol into the air, and the room is instantly filled with the desired aroma. However, in the forest, no one runs around with a can of air freshener. It turns out that there is some other, natural method for obtaining an aerosol.
If the source of the forest smell is on the ground, and the only thing that distinguishes a wet forest from a dry one is falling drops of water, then the key to the puzzle is most likely in them. Armed with high-speed video cameras, a team of MIT researchers set out to see what happens when a raindrop hits a porous surface. It turned out that at the moment of impact, microscopic air bubbles form at the boundary between the fallen drop and the surface. These bubbles, like in a glass of champagne, begin to rise up and, having come to the surface, throw microdrops of water into the air. An aerosol cloud forms over a fallen raindrop, containing substances that the water carried away from the soil surface. And a light breeze will already spread the smell of geosmin throughout the forest.
Naturally, the researchers did not limit themselves to discovering the very fact of aerosol formation by falling drops, but carried out a detailed study of this mechanism. After conducting about 600 experiments in various conditions, they found that the most aerosol is formed with moderate rainfall and average soil moisture. During a heavy downpour, the bubbles inside the droplets simply do not have time to form, and sandy and clay soils contribute to the best aerosol formation.
In addition to forest odors from the ground, aerosols can lift bacteria or spores into the air, which can spread over long distances. And if in the forest the probability of inhaling something very dangerous and poisonous is very small, then in large cities a walk after a little summer rain may not be as useful as it seems.
|
Other interesting news:
▪ Skin graft without scars and scars
▪ Kateeva YIELDjet Explore Pro Inkjet System
▪ Electron studies nanostructure
▪ Finding toxins with mussels
▪ The meaning of life helps to sleep peacefully
News feed of science and technology, new electronics
Interesting materials of the Free Technical Library:
▪ site section Electric meters. Article selection
▪ article Fire table. Tips for the home master
▪ article In which country is the practice of sleeping while working in a sitting position common? Detailed answer
▪ Anu's article. Legends, cultivation, methods of application
▪ article Generator on a photoresistor. Encyclopedia of radio electronics and electrical engineering
▪ article The Incredible Knot. Focus Secret
Leave your comment on this article:
All languages of this page
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua
2000-2024
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese