Free technical library
Fire and security alarm systems (OPS). Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Security devices and object signaling
Comments on the article
For a clearer understanding of the principles of operation OPS below are the elementary schemes of the security and fire alarm system, giving a sound or light signal in case of fire or unauthorized entry to the object.
In burglar alarms, as a rule, make or break electrical contacts are used. The type of sensors where the electrical circuit closes or opens mechanically includes wire loops, magnetic switches, mechanical switches, etc. A number of such circuits are associated with a control device (Fig. 110).
Rice. 110. Alarm device with contact sensors of various types.
Very often, a light sensor is used in the security system, the principle of operation of which is based on the use of a photocell (Fig. 111).
Rice. 111. Placement of the components of the photosensor.
A light source is installed at one end of the protected area, which illuminates a photocell located at the opposite end of the area. The sensor works in standby mode until the light flow that hits the photocell is stopped: for example, the intruder blocks it with his body. In this case, an alarm will sound.
On fig. 112 shows a multi-sensor system that allows you to control a large area, divided into separate sectors according to the number of photocells. In this case, the only source of light is located in the center of the protected area. To protect a small object (for example, a safe or other metal objects), a proximity detector can be used - a device that reacts to the approach of someone. Rice. 113 shows the use of this means to guard the safe.
Rice. 112. Alarm system with several photocells and a common light source.
Rice. 113. Connecting a proximity detector to a floor safe.
On fig. 114 shows a block diagram of such a detector.
Rice. 114. Structural diagram of the proximity detector.
Two variable capacitors connected in series are connected to the generator output having a low frequency (LFO) (10-100 kHz).
The protected object is connected to the connection point of two capacitors through which the control circuit is connected to the generator output. It is necessary to adjust the capacitors in such a way that the energy from the LFO is supplied to the circuit in sufficient quantity, and the contacts that turn on the siren are not closed. When a potential intruder approaches an object or sensor at a certain distance, part of the electromagnetic energy begins to flow to it, thereby reducing the signal level at the input of the control circuit and causing the alarm to go off.
To protect the premises inside the facility, an ultrasonic device is used that responds to any movement. The action of this sensor is based on the Doppler effect. The principle of operation of ultrasonic alarm is shown in fig. 115.
Rice. 115. Structural diagram of ultrasonic signaling.
The receiver receives part of the reflected signal, then it is amplified to a certain level, which makes the operation of the mixer possible. Then, for comparison, the signal comes from the emitter unit to another input of the mixer. If it encounters a moving object on its way, then the signal entering the circuit changes its frequency by the amount determined by the speed of the object. If the ultrasound coming from the transmitter is not reflected from moving objects, then both inputs of the mixer receive signals of the same frequency. In burglar alarms, a changeover contact is used as a sensor. Single-channel control devices are triggered by closing the sensor contacts (HP sensor) (Fig. 116).
All sensors are connected to each other in parallel, the alarm is triggered when one or more contacts are closed.
There are security devices that also work with normally closed (NC) sensor contacts. In this case, they are connected in series with each other. When one of the sensors opens, an alarm is triggered (Fig. 117).
Rice. 117. Burglar alarm with normally closed sensors.
Multi-channel burglar alarms operate with both HP and NC sensors. The siren turns on if one of them changes its normal position (Fig. 118).
Rice. 118. Multi-channel burglar alarm.
Author: Korshevr N.G.
See other articles Section Security devices and object signaling.
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 transparent human cells
28.08.2020
Octopuses, squids and other sea creatures can become invisible by using special tissues in their bodies to control the reflection of light. Researchers at the University of California have created human cells that have similar transparent abilities.
The project belongs to the field of science, aimed at the development and construction of cellular systems and tissues with controlled properties for the transmission, reflection and absorption of light.
The team's research was inspired by how Doryteuthis opalescens squids can avoid predators by dynamically switching color from near transparent to opaque white. The researchers then borrowed some of the intercellular protein particles involved in this biological cloaking technique and found a way to inject them into human cells to test whether the light-scattering abilities could be passed on to other animals.
This species of squid has all the reflective specialized cells called leucophores that can change the way light is scattered. Within these cells are leukosomes, membrane-bound particles that are made up of proteins known as reflectins that can produce iridescent camouflage.
The researchers had to genetically modify human embryonic kidney cells to express reflexin. And it worked: the proteins assembled into particles inside the cells, changing the scattering of light.
|
Other interesting news:
▪ Intel Alder Lake vPro Processors
▪ Nokia camcorder for capturing panoramic video
▪ Fast biofuel from algae
▪ Greenhouse vodka
▪ Rapid Cold Brew Coffee Maker for cold drinks
News feed of science and technology, new electronics
Interesting materials of the Free Technical Library:
▪ section of the site Alternative energy sources. Article selection
▪ article social science. Crib
▪ How did the US develop in the late 1950s and 1960s? Detailed answer
▪ article Machinist of dust pumps. Standard instruction on labor protection
▪ article About connecting apartment calls. Encyclopedia of radio electronics and electrical engineering
▪ article Who touched the mirror? Focus secret. 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