Power-on delay and loudspeaker protection device. Scheme, description

Free technical library

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

Power-on delay and loudspeaker protection device. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Speakers

Comments on the article

An analysis of the functionality of both simple [1] and more complex [2, 3] turn-on delay and loudspeaker protection devices shows that when implementing them, there is no need to create two protection channels, since the emergency state of one of the channels should exclude the possibility of operating the amplifier at all. There is also no need for protection operation indicators, since their functions can be performed by the loudspeakers themselves. In view of these circumstances, the author managed to significantly simplify the loudspeaker protection device.

The schematic diagram of this device is shown in the figure. It consists of an input low-pass filter R1R2C1, a time relay on a transistor VT1 and elements R1-R4, C1 and a key on a transistor VT2. At the moment the power is turned on, the capacitor C1 starts charging through the resistors R1, R2. During the time of its charging, the transistor VT1 will be open, VT2 will be closed and the current will not flow through the relay winding. Resistor R3 eliminates the influence of the base current of the transistor VT1 on the charging of the capacitor and increases the positive threshold of the protection device. When the capacitor is charged, the voltage at the base of transistor VT1 will drop and it will close, and the key transistor VT2 associated with it will open and current will flow through the relay winding K1. The relay will work, and its closed contacts K1.1 and K1.2 will connect the speakers to the amplifier. The turn-on delay is approximately 4 s.

Power-on delay and loudspeaker protection device

If a constant voltage of positive polarity appears at any of the outputs of the amplifier, this will lead to a partial discharge of the capacitor C1, opening the transistor VT1 and closing the transistor VT2. As a result, the current through the relay winding will stop and its contacts will disconnect the loudspeakers from the amplifiers. If a constant voltage of negative polarity appears at the outputs of the latter, then it will go directly through the diode VD1 to the base of the transistor VT2, close it and thus de-energize the relay K1, the contacts K1.1, K1.2 of which will open and turn off the speakers from the amplifier again. Diodes VD1, VD2 limit the maximum negative voltage based on the input transistor VT1 at 1,3 V.

Although both in the loudspeaker protection mode and in the turn-on delay mode, the capacitor C1 is charged through the same circuits, the protection response time is an order of magnitude shorter, since for this the capacitor needs to change its potential by only a few volts. Protection operation thresholds are no more than ±4 V.

A properly manufactured device starts working immediately and does not require configuration. Diodes can be used any silicon. The remaining elements are desirable to apply those indicated in the diagram. Relay K1 - RES-9. passport RS4.524.200 with a winding resistance of approximately 400 ohms. Any other relay that operates at the selected supply voltage is also suitable, but in this case, you need to select the resistor R4, on which the negative threshold of the protection operation depends. The device is operational when the supply voltage changes in the range of 20 ... 30 V. With a different supply voltage, it will be necessary to change the resistance of the resistor R4.

The disadvantage of this device is the need to power it from a source with ripples of not more than 1 V, otherwise false positives are possible.

Literature

Voishvillo A. About ways to turn on the load of LF amplifiers. - Radio, 1979, No. 11, p. 36, 37.
Baraboshkin D. Power amplifier protection unit. - Radio, 1983, No. 8, p. 62, 63.
Loudspeaker protection devices. - Radio, 1986, No. 10, p. 56 - 58.

Author: Yu.Zalisky, Lviv, Ukraine

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

The chances of meeting aliens are almost zero 28.03.2018

A team of scientists led by physicist Claudio Grimaldi refined the so-called Drake equation by calculating the area of the galaxy that could be filled with signals from aliens. Calculations have shown that even if signals from distant worlds reach us, then by that time the civilization that sent them will almost certainly cease to exist.

Frank Drake himself, for whom the equation is named, is also a professor emeritus at the SETI Institute in Mountain View, California, and the University of California, Santa Cruz. In 1961, he suggested that technological civilizations are dying at a constant rate; and when a civilization dies and stops broadcasting signals, they diverge like concentric circles on water. As a result, part of the Milky Way should be filled with these phantom signals.

However, if a civilization has existed for less than 100 years - the time it takes for light to cross the galaxy - then the coefficients of signals reaching Earth while the civilization is still in existence are vanishingly small. So, for example, humanity has been sending such signals for about 000 years, but the area of the Milky Way occupied by them is only 80%. Thus, if signals sent by a distant civilization reach us, then by that moment it will already cease to exist, and we will not be able to meet.

Other interesting news:

▪ Service for shared rides on self-driving vehicles

▪ AOC technology will reduce the harm of monitors to vision

▪ Yeast fungi will be sent into outer space

▪ Yogurts are good for heart and vascular health

▪ The inscription on the diamond

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Audio Art. Article selection

▪ article HIV infection (AIDS). Basics of safe life

▪ article How did you find the locator in bats? Detailed answer

▪ article Static charge on a moving object. Children's Science Lab

▪ article Platinization of metals. Simple recipes and tips

▪ article Unusual photography. Chemical experience

Leave your comment on this article:

All languages of this page

Home page | Library | Articles | Website map | Site Reviews