Optical-electronic passive linear. Security volumetric optical-electronic detector - operating principle. Fire optical-electronic detectors

In security systems, a volumetric optical-electronic security detector is an integral element.

It is also used in “smart home” technology, where when warm-blooded objects are detected, the lighting in the room or adjacent area is turned on for a while.

It has become widespread due to its simplicity of design and low cost. The operation of the sensor is based on the sensor's response to infrared radiation.

Since a person is a warm-blooded creature, he reacts to its presence.

Types of detectors

On the market, optical-electronic security detectors are represented by a large number of devices that differ in characteristics and purpose.

According to the method of working with radiation, they are divided into active and passive.

The former themselves emit IR radiation and, based on the received reflected energy, determine the presence or absence of a person in the security zone. The second ones work only for reception.

According to the configuration of the controlled area, they are divided into volumetric, surface and linear. A surface optical-electronic security detector responds to changes in radiation only in one plane.

They are used to control openings, doors, and windows. Linear ones are used when protecting perimeters. A volumetric optical-electronic detector is used when it is necessary to control any sector of space, usually indoors.

Advantages of optical-electronic detectors

The advantages of IR detectors include:

1. accurate determination of the range and angle of the controlled area;
2. ability to work in outdoor conditions;
3. absolute safety for human health.

The disadvantages of IR detectors are:

• false alarms that occur when bright light hits the lens due to warm air currents;
• work in a narrow temperature range.

A conventional sensor that works using the pulse counting method can be fooled when moving slowly.

An optical-electronic detector based on a microprocessor does not have these shortcomings. It is able to compare radiation from a real object with patterns stored in memory, due to this the number of false positives is sharply reduced.

Principle of operation

The main element of an optical-electronic detector is a pyroelectric converter, which converts infrared radiation into electric current.

A faceted Fresnel lens is used to illuminate the pyroelectric detector.

With the help of many small prisms, IR radiation from each sector of the controlled space is supplied to the photoreceiving device.

The signal level at the device output is constantly monitored to ensure that it exceeds a threshold value. When this happens, it means that an object with a temperature above the background has appeared in the security zone.

The sensor issues an alarm signal to the control panel. To reduce the amount of false interference, 2-4 sensors and digital signal processing are used.

Detector design

The detector is a small box with a lens on the front surface. The lens is stamped from plastic in the form of many small lenses.

Each of them has a certain form and orientation in space, depends on whether the sensor is volumetric, surface or linear.

In any case, all lenses direct the collected radiation to the pyroelectric detector. He is on printed circuit board, mounted on the rear wall of the housing.

When the case is opened, a tamper is triggered, which sends a signal to the control panel. To protect the sensor during the “disarmed” mode, an anti-masking circuit is used. She reports the lens being covered with tape or other material.

Lighting control devices have a powerful relay in the housing that is controlled by a sensor. In addition, there is a photocell that allows the light lamps to turn on only in low light conditions.

Features of use

When using IR sensors, it must be taken into account that they should be located in areas where there are no heat fluxes or bright light sources.

Installation of devices must be carried out on hard surfaces, without strong vibration. In permanent structures, the sensor is installed on a wall or ceiling. In rooms made of lungs metal structures they are mounted on load-bearing elements building.

When used as a lighting control device, it is necessary to match the power of the light lamps with the capabilities of the relay or electronic key. The installation point is selected in such a way that there are no obstacles in the control area.

To increase the reliability of intruder detection, it is recommended to use it in conjunction with a microwave sensor. When monitoring window openings, it is necessary to use it together with an acoustic detector.

IR sensors can be used together with video cameras, cameras, light and sound annunciators, turning them on when a warm-blooded object violates the control zone.

TOP 5 models

Pyronix

Pironix company Russian market has been operating for a very long time and has established itself as an excellent manufacturer of inexpensive and reliable IR sensors for security systems.

It provides protection against animals up to 20 kg. It has increased noise immunity from electromagnetic interference, changes in background radiation and convective heat flows.

Tamper-proof protection is provided. Has the ability to work in addressable security systems.

Range 10 m. Captures objects moving at a speed of 0.3-3 m/s. Operates in the range -30+50 ⁰С. Service life 10 years.

Optex

Powered by two alkaline batteries. Radio communication range in open areas is 300 m.

Operating frequency 868.1 MHz. The control sector is 110⁰ with a radius of 12 m.

Designed for indoor use. Additional lenses are provided that provide “corridor”, “curtain” mode and protection from animals.

Video: Surveillance optical-electronic outdoor security detector “Piron-8”

To ensure the protection of a residential building, administrative building or other property, they are used special devices– , security. This article will focus on optical-electronic detectors, their characteristics and varieties.

Smoke detectors

Smoke detectors are the most common sensors fire alarm. They are characterized by rapid susceptibility to combustion products and high speed triggering. Smoke fire safety devices are divided into ionization and optical.

Ionization sensors emit harmless radioactive radiation to analyze sample air masses for the presence of smoke.

Smoke optical-electronic emitters are devices that detect smoke at the initial stage by translucent air in infrared or ultraviolet light.

Design and principle of operation of optical detectors

Optoelectronic sensors are plastic case, where the light emitter, smoke chamber, photodetector and partition are located, which serves to protect the photocell from direct infrared or ultraviolet rays. The device is also protected from external light and dust.

An optical-electronic point fire smoke detector emits radiation in the infrared spectrum into the smoke chamber and registers its reflection with a photodiode. In a “clean” environment, the rays do not reach the photocell, so the light emitter and the receiving unit are at an angle to each other.

But as soon as smoke particles enter the chamber, the density of the medium increases, the infrared radiation is scattered and hits the photodetector. This is how the alarm is turned on - the alarm signal is activated independently or with simultaneous transmission to the monitoring console.

Optical-electronic emitters are not stand-alone devices; they are connected to a cable leading to the control panel. They have low power consumption.

Types and scope

Optical smoke fire detectors are divided into several types:

• point - have a small range of action. Monitor the premises in a specific area where there is a high risk of fire;
• linear – used in large rooms with high ceilings. They are a receiver and an emitter, which are mounted on opposite walls of the room;
• aspiration - they forcibly take air samples for analysis using laser illumination;
• autonomous are the same point devices that operate on their own power source, that is, not connected to the control panel.

Optical-electronic detectors are installed in residential, office premises, in warehouses, in shopping centers, industrial premises and anywhere where there are a lot of electrical appliances and equipment.

It is not recommended to use such devices in dusty, gas-filled and contaminated areas, as such an environment can cause false alarms. Also, smoke detectors are not used in fire and explosion hazardous facilities. In such areas, explosion-proof detectors are used.

Optical fire safety sensor IP 212-45

Below is a description of the main characteristics of optical smoke detectors using the example of IP 212-45 (Marco).

The sensor is used for early detection of fire in a room, accompanied by the release of smoke and combustion products.

Power supply and alarm signal transmission to the control panel is carried out via a two-wire cable. It has several operating modes: duty, “Fire”, “Alarm”.

The device does not respond to open fire, high air temperature and humidity. Operating conditions: humidity 95% at a temperature of +35 degrees; air temperature range from -44 to +55 degrees. Sensitivity 0.05-0.2 dB/m. Response time – 9 seconds.

The device consists of a smoke detector and a socket to which the device is attached. Inside the sensor there is an air sample analysis chamber, as well as an electronic information processing system.

Optical-electronic security detectors

In addition to fire safety sensors, there are also optical-electronic security detectors. They are widely popular and distributed.

Optical-electronic security detectors are devices that provide protection to a closed room or territory by monitoring and detecting unauthorized persons and animals in them. To protect outdoor fenced areas, linear optical-electronic sensors are used.

The operation of such devices is based on the optical principle of operation, that is, using infrared rays and reflective lenses.

Optical-electronic security detectors are divided into: active and passive.

Passive sensors

Passive devices burglar alarm They record the movement of an unwanted object in a controlled area with a certain mass and speed different from a given value.

They are used to identify persons who have entered the premises through doors, windows, and hatches. Such devices do not react to stationary objects, even at high temperatures.

Passive detectors include a receiver, lenses, and an electronic signal analysis unit. The sensors detect infrared radiation from a warm object, which falls on the Fresnel lens and is converted by a pyroelectric receiver into a special electrical signal.

The signal then goes to an amplifier and an electronic information processing system. When the device sets infrared radiation values ​​higher than the specified value, an alarm signal is activated and transmitted to the control panel.

Passive security devices have a low detection range of 10-20 meters. The range of detectable speeds starts at 0.3 m/sec.

To eliminate false alarms from various radiation sources, filtration structures (“white” filter, “black” mirror) are located inside the device, blocking the penetration of other optical radiation onto the pyroelectric element of the sensor.

According to the type of detection area, passive sensors are divided into: volumetric optical-electronic, surface and linear.

Advantages passive sensors are the fixation of foreign objects even of small size (small animals); aesthetic appearance; ease of installation and configuration; high sensitivity and speed of intruder detection.

The disadvantages of passive detectors are the fact that an intruder is detected after he has entered the building; sensitivity to warm air currents from a draft or heater.

Active sensors

Active optical-electronic detectors provide a linear protection zone. The design of the device consists of two blocks: an emitter and a photodetector, between which an optical protection area is formed.

The infrared light sensor sends signals to the receiver with specified parameters.

If an obstacle appears in the working area of ​​the device, the IR rays are interrupted and do not reach the photodetector.

Analyzing the duration of beam interruption, the detector generates an alarm signal. There are single-block devices, where the light emitter and photodetector are enclosed in one housing.

The devices do not react to thermal radiation, therefore they are used in open air areas. Operating features of active security sensors are.

Optical-electronic detectors.

Optical-electronic There are two types of detectors various types: passive and active. In this lecture we will consider only detectors used for security alarm purposes. The fire component will be discussed in a lecture dedicated to fire detectors. Let me remind you that passive detectors do not emit anything into the environment, but only analyze incoming information. Active for the purpose of intrusion detection, they emit something into the environment and, based on the response received, draw appropriate conclusions. Active detectors can be either monoblock (emitter and receiver in one housing), or two or more block, when the emitter and receiver are separated.

Let's consider first

Passive optoelectronic detectors

Currently passive optical-electronic infrared ( IR) detectors occupy a leading position when choosing to protect premises from unauthorized intrusion at security facilities. Aesthetic appearance, ease of installation, configuration and maintenance give them priority over other detection means.

The operating principle of passive optical-electronic IR detectors is based on the perception of changes in the level of infrared radiation of the temperature background, the sources of which are the human body or small animals, as well as all kinds of objects in their field of vision.

Infrared radiation is heat that is emitted by all heated bodies. In passive optical-electronic IR detectors, infrared radiation hits a Fresnel lens, after which it is focused on a sensitive pyroelectric element located on the optical axis of the lens

Passive IR detectors receive streams of infrared energy from objects and are converted by a pyro receiver into an electrical signal, which is supplied through an amplifier and a signal processing circuit to the input of the alarm notification generator.

Passive infrared detectors are designed to detect a person within the detection zone. The main task of the detector is to detect infrared radiation from the human body. As can be seen from Figure 1, the thermal radiation of the human body is within the spectral range of electromagnetic radiation with wavelengths of 8-12 microns. This is the so-called equilibrium glow of the human body, the maximum radiation length of which is completely determined by temperature and for 37°C corresponds to approximately 10 microns. There are a number of physical principles and corresponding devices that are used to detect radiation in the specified spectral range. For passive infrared detectors, a sensing element with an optimal sensitivity/cost ratio should be used. Such a sensitive element is a pyroelectric photocell.

Rice. 1. Spectral dependence of the glow intensity: the sun, a fluorescent lamp, an incandescent lamp, the human body and the transmission spectrum of a number of filters blocking visible light: a silicon filter, a clear silicon filter, a filter with a cut-off wavelength of 5 μm, and a filter with a cut-off wavelength of 7 μm.

The phenomenon of pyroelectricity consists in the appearance of an induced potential difference on opposite sides of a pyroelectric crystal during non-equilibrium short-term heating. Over time, electrical charges from external electrical circuits and the redistribution of charges within the crystal lead to relaxation of the induced potential. From the above it follows:

interruption frequency (Hz).

Rice. 2. Dependence of the magnitude of the pyroelement response signal on the interruption frequency of the recorded thermal IR signal.

1. For effective pyroelectric registration of thermal radiation, it is necessary to use a chopper with an optimal radiation interruption frequency of about 0.1 Hz (Fig. 2). On the other hand, this means that if a lensless design of a pyroelectric element is used, it will be able to register a person only when he enters the radiation pattern (Fig. 3, 4) and when leaving it at a speed of 1 - 10 centimeters per second.

Rice. 3, 4. Coupled radiation pattern shape packaged pyroelectric element in the horizontal (Fig. 3.) and vertical (Fig. 4.) planes.

2. To increase the sensitivity of the pyroelectric element to the magnitude of the temperature difference (the difference between the background temperature and the temperature of the human body), it is necessary to design it to maintain the minimum possible dimensions in order to reduce the amount of heat required for a given increase in the temperature of the sensitive element. The size of the sensing element should not be excessively reduced, as this will lead to an acceleration of the relaxation characteristics, which is equivalent to a decrease in sensitivity. There is an optimal size. The minimum sensitivity is usually 0.1°C for a 1 x 2 mm pyroelectric element with a thickness of several microns.

Rice. 5. Appearance of the sensitive element of a pyroelectric passive IR detector.

You can clearly formulate the conditions for detecting a person using an infrared detector. The infrared detector is designed to detect moving objects with a temperature different from the background value. Range of recorded movement speeds: 0.1 - 1.5 m/sec. Thus, the infrared detector does not register stationary objects, even if their temperature exceeds the background level (a stationary person) or if an object with a temperature different from the background moves in such a way that it does not cross the sensitive zones of the detector (for example, moves along the sensitive zone). Of course, strictly speaking, the sensitive element does not register movement at all; it registers the temperature measurement in a separate part of space, which is a consequence of human movement. You must always remember that the sensitive element detects movement not “towards the detector”, but across it. Getting rid of this disadvantage occurs due to the design of the lenses.

Naturally, the high sensitivity of the infrared detector is achieved by using a lens system for concentrating incoming radiation (Fig. 6). In an infrared detector, the lens system performs two functions.

Rice. 6. Options for forming the radiation pattern of IR detectors depending on the type of lens system.

Firstly, the lens system serves to focus the radiation on the pyroelectric element.

Secondly, it is designed to spatially structure the sensitivity of the detector. In this case, spatial zones of sensitivity are formed, which ,e As a rule, they have the shape of “petals”, and their number reaches several dozen. An object is detected whenever it enters or exits sensitive areas.

Typically, the following types of sensitivity diagram are distinguished, which is also called the radiation diagram.

1). Standard - fan-shaped in azimuth and multi-tiered in elevation (Fig. 6a).

2). Narrow-beam - single- or double-beam, long-range in azimuth and multi-tiered in elevation (Fig. 6b).

3). Curtain-like - narrowly focused in azimuth and fan-shaped in elevation (Fig. 6c).

There is also a circular radiation pattern (in particular, for detectors installed on the ceiling of a room), as well as a number of others.

Let's consider the options design beamforming systems (Fig. 7). This optical system can be either a lens or a mirror. Manufacturing a conventional lens system to meet the requirement of forming a spatially structured radiation pattern is an expensive task, so conventional lenses are not used in passive infrared sensors. So-called Fresnel lenses are used. A conventional lens uses a special spherical surface shape to deflect light directionally (focusing), and the lens material has an optical refractive index that is different from the refractive index of the surrounding medium. The Fresnel lens uses the phenomenon of diffraction, which manifests itself in particular in the deflection of a light beam when passing through a narrow slit. The Fresnel lens is made by stamping and is therefore inexpensive. The disadvantage of using a Fresnel lens is the inevitable loss of half the radiation energy as a result of its diffraction deflection by the lens in a direction other than the direction toward the pyroelectric element.

Rice. 7. Design options for security passive infrared detectors: with a Fresnel lens and with a mirror focusing system.

A mirror lens is more efficient than a Fresnel lens. It is made from plastic by stamping, followed by coating the structured surface with a reflective coating that does not change its properties over time (up to 10 years). The best coverage is gold. Hence the higher, approximately twice the cost of passive infrared detectors with a mirror system compared to a lens system. In addition, detectors with a mirror system are larger in size compared to detectors equipped with Fresnel lenses.

Why are more expensive detectors with a mirror system for concentrating incoming radiation used? The most important characteristic of a detector is its sensitivity. The sensitivity is almost the same per unit area of ​​the detector entrance window. This, in particular, means that if a passive infrared detector with increased sensitivity is designed, they are forced to increase the size of the radiation concentration zone - the area of ​​the entrance window, and, therefore, the detector itself (the maximum sensitivity of modern passive infrared detectors allows detection of a person at a distance up to 100 meters). If we assume the presence of losses of the useful signal due to the imperfection of the lens, then it is necessary to increase the gain of the electronic circuit for processing the electrical signal generated by the sensitive element. Assuming the same sensitivity, the gain electrical diagram in a mirror detector is two times less than in a detector with a Fresnel lens. This means that detectors with a Fresnel lens have a higher probability of false alarms caused by interference in electronic circuit. Quite often both technologies are used together, as in the Astra-5sp detector. And the main zone is formed by zones made of Fresnel lenses, the anti-sabotage zone is directly under the detector - a small mirror made in a rather artisanal way. In general, the market for security detectors is filled with fairly cheap products, the price of which ranges from 300-900 rubles per piece, with a significant bias towards the lowest price. Naturally, in such conditions it is not possible to talk about any gilded mirrors.

Once again let's return to the optical design of the detector. In addition to the lens system and the optical “cutting” filter installed directly in the housing of the sensitive element, to reduce false alarms caused by various radiation sources, various optical filter elements are used (“white” filter, “black” mirror, etc.), task which minimize the entry of extraneous optical radiation onto the surface of the pyroelectric element.

The entrance window of most IR detectors is made in the form of a “white” filter. This filter is made of a material that scatters visible light, but at the same time does not affect the propagation of infrared radiation. Due to its low cost, cheap detectors use polyethylene similar in its properties to that used for food bags, while more expensive ones use polyethylene. milky, which transmits IR rays well, but has a poorly visible spectrum, which is what we need.

Fresnel lenses are constantly being improved. Primarily by giving the lens a spherical shape, which minimizes aberrations compared to the standard cylindrical shape. In addition, additional structuring of the radiation pattern in the vertical plane is used due to the multifocal geometry of the lens: in the vertical direction, the lens is divided into three sectors, each of which independently collects radiation onto the same sensitive element.

I will dwell in more detail on the structure of that part of the detector, which most electricians call the lens. This is a piece of polyethylene on which rectangles of various sizes are extruded, inside of which some concentric circles, or parts thereof, are visible. In most cases, in the upper part we see about 12-15 vertically elongated rectangles, in the middle part there are 5-6 more square-like rectangles, and in the lower part there are usually 3 almost square rectangles. It is necessary to correctly understand that every of these rectangles is a Fresnel lens, so we have a certain matrix of lenses. In order to distinguish an intruder at the edge of the detection zone, which is usually 10-12 meters, it must be divided into the number of elementary zones we need, which is what the upper set of rectangles does. The number of elementary zones will correspond to the number of rectangles. Naturally, in the middle part of the detector detection zone, it is no longer necessary to divide it into such a number of elementary zones, and their number is already reduced to 5-6, and in the near zone - to 3. When considering the matrix of lenses, pay attention to important feature– the vertical sides of rectangles in different tiers are always shifted relative to each other. This was done specifically to be able to detect an intruder in the worst movement for the detector “toward the detector”. Even if the intruder accidentally got exactly into the middle of the elementary sensitive zone and moves straight towards the detector, then in another tier he will not be able to get into the middle of the elementary zone and will be detected by it. When placing the detector, it is necessary to take into account that its maximum revealing abilities precisely when the intruder moves across sensitive areas.

The problem of counteracting physical shielding of a detector, which boils down to installing a screen in front of it that blocks its “field of view” (so-called “masking”), is very relevant. Technical means of counteracting camouflage constitute a system anti-masking detector Some detectors are equipped with built-in IR LEDs. If an obstacle appears in the detection zone of the detector, and therefore in the range of the LEDs, then the reflection of the LED radiation from the obstacle is perceived by the detector as an alarm signal. Moreover, periodically (in existing models - once every 5 hours) the detector self-tests for the presence of reflected radiation from IR LEDs. If during self-testing the required signal does not appear at the output of the electrical circuit, an alarm signal generation circuit is triggered. Detectors with functions anti-masking and self-testing are installed at the most critical facilities, in particular where it is possible to counteract the operation of the security system.

Another way to increase the noise immunity of a detector is to use a quadratic sensitive pyroelectric element together with the use of microprocessor signal processing. Different companies solve the problem of creating a quadratic element in various ways. For example, the OPTEX company uses two conventional double pyroelements located side by side. The main task of the system is to identify and “weed out” events caused by simultaneous illumination of both pyroelements (for example, headlights) or electrical interference.

Quite a lot of companies use a special design of a quadruple pyroelectric receiver, where four sensitive elements are located in one housing.In this case, pyroelements located both in the horizontal and vertical planes are included in opposite directions. Such a detector will not respond to small animals (mice, rats), which are often found in warehouses and are one of the reasons for false alarms (Fig. 8). The use of multi-polar connections of sensitive elements in such a detector makes “noise” false alarms impossible.

The ADEMCO company is so confident in the perfection of the quadratic detector it has developed that it has announced a bonus payment if the owner of the detector records a false alarm.

Another precaution is the use of conductive film coatings applied to inner surface entrance window to counteract radio frequency interference.

An effective method of increasing the noise immunity of detectors is the use of the so-called “dual technology”, which consists in using a combined detector that implements passive infrared and active radio wave (sometimes ultrasonic) principles of operation. Such detectors will be discussed in subsequent lectures.

Rice. 8. Operation of a multi-channel noise pulse selection system using the example of the operation of a quadratic security passive IR detector.

Due to the detection principle, it is very difficult for such detectors to detect an intruder if ambient temperature approaches the temperature of the human body. In such cases, the detector simply goes blind, and for our southern region, temperatures of 35-40 degrees in summer are not at all uncommon, especially in closed, unconditioned rooms with insufficiently insulated roofs and walls. Invented to combat this problem temperature compensation. The essence of its work is that when the temperature in the room approaches critical (37 degrees Celsius), the detector abruptly increases sensitivity (usually by an order of magnitude). Of course, this reduces its noise immunity, but it allows you to detect the intruder in these extreme conditions. When the temperature drops, the detector returns sensitivity to normal.

We looked at the basic operation and design of passive infrared security detectors. In general, all constructive tricks used by certain companies have one goal - to reduce the likelihood false alarm detector, since a false alarm leads to unjustified costs of responding to an alarm, and also entails moral damage for the owner of the protected property.

Detectorsare constantly being improved. At the present stage, the main directions for improving detectors are increasing their sensitivity, reducing the number of false alarms, and differentiating moving objects based on their authorized or unauthorized presence in the detection zone.

As a source of electrical signal, each sensitive pyroelectric element is also a source of random noise signals. Therefore, the task of minimizing fluctuation interference, which can be solved by circuit technology, is relevant. Various methods of dealing with noise are used.

Firstly, electronic discriminators of the input signal at the upper and lower levels are installed in the detector, which minimizes the frequency of interference (Fig. 9).

Rice. 9. Threshold system for two-way limitation of the noise signal level of a security passive infrared detector.

Secondly, a mode of synchronous accounting of pulses arriving through both optical channels is used. Moreover, the circuit is designed in such a way that a useful optical signal at the input leads to the appearance of a positive electrical pulse in one channel and a negative one in the other. The output uses a subtraction circuit. If the source of the signal is a noise electrical signal, it will be identical for the two channels and the resulting signal at the output will be missing. If the signal source is an optical signal, the output signal will be summed.

Third, the pulse counting method is used. The essence of this method is that a single object registration signal does not lead to the formation of an alarm signal, but sets the detector into the so-called “pre-alarm state”. If within a certain time (in practice it is 20 seconds) the object registration signal is not received again, the pre-alarm state of the detector is reset (Fig. 10). This method must be used carefully and only used when justified. It must be remembered that the detector may not have a chance to detect the second impulse, and it will rest peacefully covered with a cardboard box.

Rice. 10. Operation of the pulse counter system.

The remarkable property of forming a detection zone with a matrix of Fresnel lenses allowed manufacturers to create a unified design of the detector and change its properties by replacing the matrix. Thus, one and the same detector can be made three-dimensional, you can create a “long beam” zone - it sees far but narrowly, you can create a “curtain” detector, with the help of which you can cut off the parts of the object we need using a detection zone similar to a curtain.

As a rule, all detectors require a 12 V DC electrical supply. The current consumption of a typical detector is in the range of 15 - 40 mA. An alarm signal is generated and transmitted to the security control panel via an output relay with normally closed contacts.

The use of solid-state relays instead of conventional ones also made it possible to reduce energy consumption. Let me remind you that these detectors are passive, which also allows for minimal current consumption. Like most security detectors, passive infrared detectors are repairable, i.e. when an intruder is detected, it will go into the “alarm” state; if there is no further movement registration, it will be restored to the “normal” state. Typically, for ease of maintenance, the detector has a built-in red LED, which signals the “alarm” state, but can also transmit other additional messages.

For normal placement of the detection zone in space, it is necessary to take into account the manufacturer’s recommended installation height for the detector, which is usually 2.2-2.5 meters for a wall-mounted version. Let me also remind you that reorienting the detector (sideways, upside down) is not allowed.

When choosing a detector, you must remember that they have different temperature ranges, and if you install a detector that operates down to 0 degrees in an unheated room, you can expect problems with operation in winter when there is frost.

The industry produces detectors for installation indoors, as well as in open areas; the latter have the appropriate climatic design.The typical service life of passive infrared detectors is 5 - 6 years.

Examples of detectors

With a detection zone of the “long beam” type: Astra-5 isp. B, Foton-10A, Photon-15A, Photon-16.

With a curtain-type detection zone: Astra-5 version. B, Astra-531 isp. IK, Ikar-Sh, Ikar-5B, Foton-10B, Foton-10BM, Foton-15B, Photon-16B, Photon-20B, Photon-22B, Foton-Sh, Foton-Sh-1, Foton-Sh2.

With volumetric detection zone: Astra-5 isp. A, Astra-5 Spanish. AM, Astra-511, Astra-512, Astra-7 isp. A, Astra-7 Spanish. B, Photon-9, Photon-9M, Photon-10, Photon-10M, Photon-10M-01, Photon-12, Photon-12-1, Photon-15, Photon-16, Photon-17, Photon-19, Photon-20, Photon-21, Photon-22, Icarus-1A, Icarus-2/1, Icarus-5A, Icarus-7/1.

Active optical-electronic detectors.

Linearoptical-electronic detectors (active IR detectors), as a rule, have a two-block design and consist of an emitter unit (EB) and a photoreceiver unit (PD), forming an optical system. The emitter generates a stream of infrared radiation (infrared beam) with specified characteristics, which reaches the receiver. The appearance of an optically opaque object in the detection zone of the detector causes an interruption of the IR beam (or a decrease in its power) entering the receiver, which analyzes the magnitude and duration of this interruption and, in accordance with a given algorithm, generates an alarm notification by changing the resistance of the contacts connected to the AL. There are also detectors that have a single-block design, the optical system of which consists of an emitter and a photodetector, combined in one housing, as well as a reflector (reflector). The entrance windows BI and BF are usually closed with special filters (sometimes these filters are made integral with the detector housing cover). The diagram of an active IR detector is shown in Figure 11.

The advantage of active IR detectors is that they detective the ability does not depend on the characteristics of the thermal radiation of a person (the intruder). They are also insensitive to changes in the characteristics of thermal radiation from surrounding objects (background) and emerging thermal interference, which is very important when operating in open areas.

Figure 11 - Scheme of an active IR detector

The disadvantages of active IR detectors include their ability to form only a linear detection zone, which leads to a narrow scope of application. This problem can be partly solved by organizing a surface detection zone through the use of detectors that generate several IR beams, or by constructing an IR barrier from several detectors. But at the same time, the size of the detection zone for the first option will be small, and the second option will require increased financial costs. Disadvantages include sensitivity to optical flare.

Recently, some manufacturers have made attempts to create an active security detector using an IR laser. Thus, the Japanese company Optex recently began producing a detector that uses the principle of scanning the surrounding space with a laser beam.

Main functional characteristics of active IR detectors and their impact on application and security tactics

Active IR detectors form a linear detection zone. They can be used to organize the first line of security of objects (blocking long engineering fences, windows or doors outside the building, gates, ventilation shafts and ducts, etc.). Because active infrared detectors form a linear detection zone; their use will be influenced by the shape of the protected object, depending on the characteristics of the landscape and the object itself. Protected objects must be straight, otherwise the object is divided into several straight sections, to block which a separate detector is used (see Figures 12, 13).

Figure 12 - Incorrect use of an active IR detector

Figure 12 shows misuse active IR detector. In zones A and B, it is possible for an intruder to penetrate through a guarded fence. At the same time, in zone B, the detector detection zone is located outside the protected object, where there is a high probability of its accidental overlap (swaying tree branches, actions of random passers-by, etc.), which will lead to the formation of a false alarm notification.

Figure 13 - Scheme of security of an object of complex shape

Figure 13 shows approximate diagram protection of an object of complex shape using several detectors. The division of the object into sections must be done in such a way that an intruder cannot penetrate the object without blocking the IR beam, i.e. the maximum distance between the fence sheet and the IR beam (an imaginary line between the BI and the BF) should be less than the size of a person (approximately 300 - 350 mm).

The main functional characteristics of an active IR detector are the maximum operating range, safety factor, sensitivity and noise immunity.

The maximum operating range is the maximum possible distance over which the emitter and receiver of the detector can be separated, provided that it complies with the requirements of the national standard.

The safety factor is the maximum value of reducing the flow of infrared energy that does not lead to the formation of an alarm notification. This coefficient characterizes the detector’s resistance to meteorological factors (rain, snowfall, fog). The minimum permissible values ​​of the safety factor depend on the operating range and are given in the national standard. Because There is no precipitation in the premises; the requirements for the safety factor of detectors intended for indoor use are significantly lower than similar requirements for detectors intended for outdoor use.

Specific values ​​of the maximum operating range and safety factor for each detector model are established by the manufacturer.

To ensure the possibility of application at various objects, most modern active IR detectors have the ability to adjust the range. As a rule, the adjustment is discrete, each value corresponds to a certain range of range. It is not allowed to operate the detector if the actual range does not correspond to the range established during adjustment. If the actual range exceeds the established one, the safety factor may be insufficient, which in the presence of precipitation (heavy snow, rain, dense fog) can lead to malfunction of the detector (manifested in the form of a false alarm notification and the impossibility of arming). If the actual range is lower than the established one, the power of IR radiation hitting the receiver will be excessive, which in some cases may lead to the intruder being missed. Excessive signal power also determines the presence of active IR detectors with a minimum operating range. The distance between the BI and the BF should not be less than value specified in the operational documentation attached to the detector.

The sensitivity of an active IR detector is the duration of interruption of the infrared beam, when exceeded, the detector must generate an alarm notification. The minimum permissible sensitivity value for detectors operated in open areas is regulated by the national standard and is 50 ms.

This value is determined taking into account the anthropometric characteristics of a person and corresponds to the intruder crossing the detector detection zone while running at maximum speed. Modern detectors provide discrete sensitivity adjustment up to a value of 400 - 500 ms.

It is recommended to set the sensitivity value taking into account the most likely time the intruder will remain in the detection zone, which depends on its size and speed of movement. For example, if the detector is installed in an open space where an intruder will be able to run and cross the area at high speed, the sensitivity should be set to high (50 ms). If the intruder does not have the opportunity to take off and move at high speed (for example, when blocking a narrow space between two fences), the sensitivity value can be set in the range of 100 – 200 ms. If the intruder is forced to remain in the security zone for a sufficiently long time, for example, when overcoming a blocked area by crawling or climbing over a fence (fence), the sensitivity value can be set in the range of 400 - 500 ms. The correctness of the choice of sensitivity value must be checked after installing and configuring the detector at the site by performing test crossings of the zone in the most probable ways and with the highest possible speed. After each crossing of the detection zone, the detector must generate an alarm notification. Except in justified cases, it is not recommended to set the maximum sensitivity (50 ms), because this reduces the noise immunity of the detector.

Noise immunity is the duration of interruption of the infrared beam, if not exceeded, the detector does not generate an alarm notification. The minimum permissible noise immunity value for detectors operated in open areas is regulated by the national standard and is 35 ms. This value is determined taking into account the size and speed of movement of the most likely obstacles, such as falling leaves, flying birds, etc.

In modern domestic detectors, a change in noise immunity occurs automatically simultaneously with a change in sensitivity during the process of its adjustment. The use of a dual (synchronized) IR beam contributes to increasing the noise immunity of the detector. The relationship between sensitivity and noise immunity for modern domestic active IR detectors is given in Table 1.

Table 1

The influence of external factors on the operation of active IR detectors and recommendations for reducing it

1) Temperature factor. Ambient temperature has an effect Negative influence on the operability of the detector, if its value exceeds the permissible operating temperature values ​​​​set for this detector. To reduce the likelihood of the detector overheating, you should, if possible, avoid installing it in places where it will be exposed to prolonged exposure to direct sunlight, and also use protective hoods. For use in areas where winter time Very low temperatures are often observed (minus 40 °C and below), it is necessary to choose detectors that have built-in automatic heating of the board and optics. The lower value of the operating temperature range for modern domestic detectors is minus 40 °C; with built-in heating, it drops to minus 55 °C. If the air temperature has dropped below the permissible values ​​of the detector, it is necessary to take into account that it may not detect the intruder; it is advisable to organize security of the object by patrolling.

2) Optical flares. The cause of high illumination can be both the sun and sources artificial lighting. The presence of an illumination detector on the entrance window of the BF, the actual value of which exceeds the norms established in the national standard (more than 20,000 lux from natural lighting and light sources powered by direct current sources, and 1000 lux from light sources (including fluorescent lamps), powered by AC mains), may cause false alarms or miss the intruder. To eliminate the influence of this factor on the operation of the detector, it must be installed in such a way that direct sunlight does not fall on the input window of the BF (this is especially true during sunset or sunrise, when various protective visors are ineffective) and radiation from powerful lighting devices (spotlights, powerful fluorescent lamps, etc.). Most active IR detectors included today in the “List...” are resistant to natural light up to 30,000 lux.

3) Precipitation. Atmospheric precipitation has a negative impact on the safety factor of the detector due to the attenuation of radiation due to its scattering by water drops or snowflakes. They can also cause the appearance of moisture in the housings of the detector units, which can cause loss of its performance. In winter, icing of the entrance windows of the detector units is also possible. The safety factor of modern detectors, as a rule, allows them to function properly in the presence of precipitation, but if it is particularly intense, a malfunction of the detector may occur (manifested in the form of constant generation of an alarm notification and the impossibility of arming). In this case, it is necessary to organize security of the object by patrolling. To reduce the harmful effects of precipitation, you can use protective visors, and you should carry out maintenance (cleaning the entrance windows of ice and snow) of the detector more often. It is necessary to use detectors with a higher degree of shell protection (not lower than IP54 according to GOST 14254), and carefully seal the inlet process holes in the housings of the units during installation. If the detector is installed at a small height from the ground or other surface (for example, directly above the fence), a gradually increasing layer of snow (drift) can block the detection zone of the detector, which will cause the constant generation of a false alarm notification. The detector detection zone can also be blocked by the resulting icicles if it is located under any protruding structures and their elements. To prevent disruption of the normal operation of the detector, it is necessary to clear the snow accumulating in the detection zone and promptly remove the resulting icicles. If the detector is installed along the top edge of the fence, it is recommended to shift it from the axis of the fence into the object.

4) Electromagnetic interference(EMF). The source of EMFs that can affect the operation of the detector can be either operating high-power electrical equipment or atmospheric electrical discharges (thunderstorm). For outdoor use, detectors should be used that have resistance to EMF in accordance with GOST R 50009 (electrostatic discharge, electromagnetic field, electrical pulses in the power supply circuit) of at least degree 3. When installing detectors outdoors, it is necessary to lay long connecting lines that are exposed to EMF. To reduce the influence of EMF on the operation of the detector, it is necessary to lay all connecting lines in metal hoses (steel pipes) and use grounding.

5) Changing the position in space of structures on which detector blocks are attached. These changes can be either natural or man-made. They may be caused, for example, by vibration due to the operation of any mechanisms or the movement of heavy vehicles, seasonal ground movements, repair and other work carried out in the immediate vicinity of the detector installation site. Their consequences may be false alarms and a decrease in the safety factor. To prevent the influence of this factor on the operation of the detector, it is necessary, if possible, to install it on foundations that are not subject to vibration, deformation, and have a stable foundation (load-bearing walls of permanent buildings, etc.).

6) Presence of fine fine particles in the air. These particles can be of both natural (dust, pollen) and man-made (dust, soot, etc.) origin. Their settling on the detector input window leads to a decrease in the safety factor. To combat this phenomenon, in facilities with a high content of dust or soot in the air, the detector should be serviced more often. Operational Features active IR detectors.

Power supply for active detectors, as a rule, can be carried out from a direct current source with a rated voltage of 12 or 24 V. For power supply of detectors operated in open areas (especially with long power lines), it is recommended to use sources with a rated voltage of 24 V. Power supply for built-in heating (if available), as a rule, is carried out from a separate source connected to terminals specially designed for this purpose.The output power of the sources must match the load.

Features of the organization of the IR barrier

The interval between detectors should be chosen in such a way that an intruder would not be able to get between the IR beams without blocking them. For outdoor applications, a spacing of approximately 350 mm can be recommended. To organize an IR barrier, you can use detectors that have several operating frequencies. This is necessary to eliminate the influence of radiation from one detector on the operation of the neighboring one. If it is necessary to use more detectors in the barrier than the number of operating frequencies, they must be installed in such a way that the IR rays of detectors operating at the same frequency are directed towards each other (Figure 14). In the same way, you can organize a two-beam barrier from detectors that have the same operating frequency.

Figure 14 - Example of a barrier for IR detectors operating at the same frequency

If it is necessary to create an IR barrier in the horizontal plane, the detectors must be installed in such a way that the emissions of the same operating frequency of closely located BIs are multidirectional and cannot simultaneously fall on the input window of one BU (Figure 15).

Figure 15 – Example of an IR barrier in the horizontal plane

Configuring the detector parameters necessary for operation at each specific object is done either using switches or programming. The parameter programming process is outlined in operational documentation supplied with the detector. After installing the detector on site and connecting the power supply, you need to configure mutual arrangement emitter and receiver of the detector. Rough adjustment is carried out visually by approximate alignment of their optical axes or according to the readings of the IR radiation indicator (if this indicator is available). Some detector models (for example, IO209-32 "SPEC-1115") have a special optical sight for this purpose. After completing the rough adjustment, it is necessary to adjust (fine tune) the blocks. It is carried out by smoothly rotating the block in different directions at a small angle in the horizontal and vertical planes using the adjustment devices provided by the detector design (screws or flywheels). The adjustment process is controlled depending on the specific model of the detector, either by the readings of a voltmeter connected to a special connector, or by changing the built-in light indication. The adjustment is considered complete when the voltmeter shows maximum readings or when there is a light indication, the type of which is indicated in the operational documentation. ATTENTION. Adjustment of the detector blocks ensures the presence of a BF on the input window required power IR radiation, as well as achieving the maximum safety factor, is a necessary and mandatory procedure, even if after rough adjustment the detector goes into standby mode and is able to generate an alarm notification when crossing the detection zone.

Remote control of operation is designed to check the functionality of the detector from a central monitoring console. It is carried out by short-term switching of an output specially designed for this purpose and a positive power supply output. As a result, a short-term interruption of the BI radiation occurs, after which the detector must issue an alarm notification. This function requires additional wiring, but may be useful when protection of perimeters long distance or difficult access to the detector (for example, in winter). If the detector is installed in such a way that its detection zone is directed along an extended surface (fencing, wall, etc.) .P), the re-reflection effect may appear, which consists in the fact that in addition to direct IR radiation, the re-reflected radiation will also fall on the input window of the BF (Figure 16). As a result, with sufficient power re-reflected radiation, the detector will not generate alarm notifications when the main one is blocked. This effect can also manifest itself during precipitation of low intensity, when IR radiation is reflected from snowflakes and water drops.

Figure 16 – Reflection effect

To eliminate the negative influence of the reflection effect, modern domestic detectors provide the possibility of turning on the so-called. “intelligent signal processing mode”, the essence of which is that the detector generates an alarm notification when the IR radiation power at the input window of the BF decreases by approximately 70%.

On domestic market active IR detectors are currently represented mainly by products of the Russian company SPEC JSC (St. Petersburg), Japanese companies Optex and Aleph, German Bosch and some others.

Today, only detectors produced by SPEC JSC fully comply with the requirements of domestic national standards and ETT. Below are recommendations for their selection for the protection of various objects, taking into account the main features and characteristics. It should be noted that the design features of active IR detectors, especially those intended for use in open areas, determine their high cost. Therefore, the use of most of them will be most appropriate at fairly important facilities.

The choice of single-beam detectors (or with dual synchronized IR beams) is usually made taking into account the maximum operating range. It is not advisable to use a detector with maximum working range actions that significantly exceed the actual size of the protected object. For operation in areas where very low temperatures are often observed in winter (minus 40 °C and below), it is necessary to choose detectors that have built-in automatic heating of the board and optics. Installation, connection, configuration and operation of detectors must be carried out in strict accordance with the attached operational documentation. Some detectors can also be used indoors. In this case, their maximum operating range is increased due to lower safety factor requirements, which must be reflected in the operational documentation. Each active IR detector included in the list is assigned symbol type “IO209-ХХ/У”, where “I” means the type of product (detector), “O” – scope of application (security), “2” – characteristics of the detection zone (linear), “09” – principle of operation (optical electronic), “XX” is the serial number of the development, registered in the prescribed manner, separated by an oblique fraction “U” – the serial number of the design modification (if there are several modifications).

Figure 17 - IO209-16 “SPEC-7”

IO209-16 "SPEC-7".The multi-beam detector is available in two versions (modifications): IO209-16/1 “SPEC-7-2” (forms 2 beams with an interval of 350 mm) and IO209-16/2 “SPEC-7-6” (forms 6 beams with an interval of 70 mm). The emitters and photodetectors are mounted in single housings (the so-called CI and CF columns). The detector is recommended to be used to protect gate openings, gates, and block access to windows and doors of a building from the outside. At the same time, IO209-16/2 “SPEC-7-6” is capable of detecting a hand extended through the detection zone. Both versions of the detector have a working range from 0.4 to 15 m (in the open air), 4 sensitivity values. It is possible to use up to 5 detectors in the IR barrier. In this case, the CIs are combined by a synchronization line. CFs can either be synchronized or each work with its own settings. Maximum length synchronization lines between neighboring CIs or CFs - no more than 10 m. Synchronization allows you to save money by laying a smaller number of loops. It is possible to configure the number of IR rays, the simultaneous intersection of which is necessary to generate an alarm notification, which increases the detector’s resistance to the intersection of the detection zone by small animals, birds, etc. The detector can also be used indoors.

IO209-17 “SPEC-8” The detector has a dual IR beam in the horizontal plane, 4 operating frequencies, 4 sensitivity values, built-in heating. The detector range is from 35 to 300 m. The detector is recommended to be used for blocking straight sections of long perimeters, incl. in areas with cold climates.

Figure 18 - IO209-17 “SPEC-8”

Figure 19 - IO209-22 “SPEC-11”

IO209-22 “SPEC-11”The maximum operating range is 150 m (outdoors). The detector has 1 IR beam, 2 operating frequencies, 2 sensitivity values. This detector is intended for use in explosive zones of class 1 and 2 of premises and outdoor installations in accordance with GOST R 52350.14 (classes B-Ia, B-Ib, B-Ig according to PUE) and other regulatory documents governing the use of electrical equipment in explosive areas. Explosion-proof design of the “explosion-proof shell” type. Explosion protection marking 1 Ex d IIB T5 X. The detector can also be used indoors. Application at other sites is impractical due to high cost.

IO209-29 “SPEC-1112” Detector with two horizontally located unsynchronized IR rays. Thanks to the presence of two output relays, the detector allows you to determine the direction in which the intruder is crossing the protection zone (when the beams intersect in one direction, one relay opens, when they cross in the other direction, the second one opens). The operating range is from 10 to 150 m. The detector has built-in heating, 4 operating frequencies, 2 sensitivity values. Recommended for the protection of various objects, incl. in areas with cold climates.

Figure 20 - IO209-29 “SPEC-1113”

IO209-29 “SPEC-1113” The detector has a single-block design with a reflector, 5 operating frequencies, 4 sensitivity values. Working range - from 5 to 10 m (outdoors). There is no built-in heating. It is recommended to use it for blocking gate openings, wickets, air duct outlets, ventilation shafts and other small objects. Due to its relatively low cost, it would be advisable to use the detector, incl. for the protection of ordinary objects, individual housing construction objects, etc. The detector can be used indoors.

Figure 21 - IO209-32 “SPEC-1115”

IO209-32 “SPEC-1115”Available in four versions, characterized by maximum operating range and the presence of built-in heating:

a) IO209-32/1 “SPEC-1115” has a range from 1 to 75 m;

b) IO209-32/2 “SPEC-1115M” has a range from 1 to 75 m and built-in heating;

c) IO209-32/3 “SPEC-1115-100” has a range from 1 to 100 m;

d) IO209-32/4 “SPEC-1115M-100” has a range from 1 to 100 m and built-in heating.

Detectorhas a dual IR beam in the vertical plane, 4 operating frequencies, 4 sensitivity values. Recommended for the protection of various objects, incl. in areas with cold climates (for versions with the letter “M”).

IO209-29 “SPEC-1117”This detector is a simplified modification of the SPEC-1115 detector and has a lower cost, making it advisable to use it, incl. and for the protection of ordinary objects, individual housing construction objects, etc. The detector has a dual IR beam in the vertical plane, 1 operating frequency, 2 sensitivity values.

Imported detectors present on the domestic TSO market often do not correspond to the current national standard and ECT in terms of resistance to low ambient temperatures and switching parameters of output relays. Also, foreign manufacturers do not provide the value of the safety factor in the technical characteristics of their detectors.

A list of regulatory and technical documentation, the requirements of which must be taken into account when studying this topic.

1. R78.36.026-2012 Recommendations. Usage technical means detection based on various physical principles for the protection of fenced areas and open areas.

2. R78.36.028-2012 Recommendations. Technical means for detecting intrusion and threats of various types. Features of selection, operation and application depending on the degree of importance and danger of objects.

3. R78.36.013-2002 – “Recommendations. False alarms of technical security means and methods of combating them.”

4. R78.36.036-2013 " Toolkit on the selection and use of passive optical-electronic infrared detectors."

5. R78.36.031-2013 “Inspection of objects, apartments and MHIG accepted for the centerlized security."

6. R78.36.022-2012 “Methodological manual on the use of radio wave and combined detectors to increase detection ability and noise immunity.”

7. GOST R 50658-94 Alarm systems. Part 2. Requirements for security alarm systems. Section 4. Ultrasonic Doppler detectors for enclosed spaces.

8. GOST R 50659-2012 Radio wave Doppler detectors for indoor and outdoor areas. General technical requirements and test methods.

9. GOST R 54455-2011 (IEC 62599-1:2010) Security alarm system. Test methods for resistance to external influences, modified in relation to the international standard IEC 62599-1:2010 Alarm systems. Part 1: Environmental Test Methods.

10. GOST R 50777-95 Alarm systems. Part 2. Requirements for security alarm systems. Section 6. Passive optical-electronic infrared detectors for enclosed spaces.

11. GOST R 51186-98 Passive security sound detectors for blocking glazed structures in enclosed spaces. General technical requirements.

12. GOST R 54832-2011 Point security detectors magnetic contact. General technical requirements.

13. GOST R 52434-2005 Optical-electronic active security detectors. General technical requirements.

14. GOST 31817.1.1-2012 Alarm systems. Part 1. General requirements. Section 1. General provisions.

15. GOST 52435-2005 Technical means of security alarm. Classification. General technical requirements and test methods.

16. GOST R 52551-2006 Security and safety systems. Terms and Definitions.

17. GOST R 52650-2006 Security detectors combined radio wave with passive infrared for enclosed spaces. General technical requirements and test methods.

18. GOST R 52651-2006 Linear radio wave security detectors for perimeters. General technical requirements and test methods.

19. GOST R 52933-2008 Surface capacitive security detectors for premises. General technical requirements.

20. GOST R 53702-2009 Surface vibration detectors for blocking building structures of enclosed spaces and safes.

21. GOST 32321-2013 Surface shock-contact security detectors for blocking glazed structures in enclosed spaces.General technical requirements.

22. List of technical safety equipment that satisfies the “Unified technical requirements to centralized surveillance systems intended for use in private security units" and "Unified technical requirements for object security subsystems intended for use in private security units."

23. www.ktso.ru

24. www.guarda.ru

Self-test questions.

1. What is the sensitive element in PIR detectors?

2. Why is the detection zone of the PIR detector divided into tiers?

3. What are the main types of detection zones for PIR detectors?

4. What type of detection zone does the active infrared detectors we reviewed have?

5. Give an example of an active infrared detector.

To control the volume of premises, infrared detectors are most often used. These are some of the most common types of technical security devices that have proven themselves to be reliable devices with at an affordable price. A passive infrared detector is designed to detect the movement of an intruder in a controlled area. They are called passive because they react to changes in environmental parameters. The principle of their operation is based on measuring the flow of thermal radiation, i.e., using a pyroelectric element, the device registers changes in infrared radiation, converts it into an electrical signal and analyzes the measured data using a digital processor. As a result of calculations, the processor makes a decision about the presence or absence of motion in the detection zone. For this purpose, the board has a relay with normally closed or normally open contacts.

The detection zone formed by the Fresnel lens is the most important criterion when choosing detectors to solve various types of problems depending on the configuration of the protected premises - length, width, ceiling height, presence of interference, etc. In most cases, the optimal solution is a sensor with a three-dimensional detection zone; such products are equipped with a standard lens that provides a maximum detection range of about 12-15 meters and a detection area angle in the horizontal plane of 90° (for example, or ). For monitoring large rooms ideal option There will be ceiling volumetric sensors that will protect the volume of premises 360° around its own axis. When installed at a height of 5 meters, the diameter of the detection zone can reach 15 meters (). In rooms where the installation of IR detectors with a volumetric zone may lead to incorrect operation with the generation of frequent erroneous alarms, it is advisable to use products with a reduced detection zone of the “curtain” type, having an angle in the horizontal plane of 7°-10°. Thus, these products generate a detection plane that “covers” the protected window or door opening. Individual devices, for example, can adjust the angle within 2°-16°. In private houses and apartments where pets are constantly present, it is especially advisable to use similar sensors of the “curtain” or “beam” type, the lenses of which cut off part of the detection beams, thus allowing you to ignore the movement of pets weighing up to 25 kg and measuring about 30x100 cm To ensure the required detection zone, it is necessary to strictly adhere to the installation rules in compliance with the required height.

Operating conditions also affect the correct operation of passive optical-electronic detectors. Manufacturers do not recommend installing infrared sensors in close proximity to the openings of ventilation ducts, windows and doors, where convection can be created. air currents, and also next to heating devices. Despite the resistance to light illumination up to 6500 lux, direct exposure to radiation from sources of natural and artificial lighting is extremely undesirable. To reduce the influence of high ambient temperatures on stable operation, thermal compensation circuits are used in infrared detectors. It is possible to use several passive infrared detectors in one room without the risk of false alarms. Many models support discrete sensitivity adjustment.

All products presented in this section have an external light indication of the activity and power status of the sensor, which can be disabled using a jumper. A microswitch installed on the board protects against unauthorized opening of the case. The line includes devices designed to operate outdoors and in hazardous areas with the appropriate degree of protection.

Lecture 6

Active optical-electronic detectors

Active optical-electronic detectors are used to protect internal and external perimeters, windows, shop windows, and individual objects. They generate an alarm when the reflected flow (single-position detectors) changes or the received flow (two-position detectors) of optical radiation energy stops (changes) caused by the movement of the intruder in the detection zone. The operating principle of the detectors is based on the directional propagation, reception and analysis of received infrared radiation.

The detection zone of the detector has the form of an invisible beam barrier between the emitter and the receiver, formed by one or more parallel narrowly directed beams located in the vertical plane; it differs from detector to detector, usually in range and number of beams.

Install the emitter and receiver on durable, non-deformable structures;

Avoid exposing the receiver to sunlight and car headlights, as well as direct sunlight, as this can lead to overheating and premature failure of photodiodes and LEDs.

The influence of these factors can be eliminated by using lightproof screens; do not allow foreign objects to be located closer than 0.5 m from the space through which the beam passes.

Typical representatives This class of products are detectors domestic production"Vector" and "SPEC".

Passive optical-electronic detectors

Passive optical-electronic infrared detectors are the most widely used. This is due to the fact that with the help of optical systems specially designed for them, detection zones can be obtained quite simply and quickly various shapes and sizes and use them to protect objects of almost any configuration: residential, industrial, commercial and administrative premises; building structures: shop windows, windows, doors, walls, ceilings; open areas, internal and external perimeters; individual items: museum exhibits, computers, office equipment, etc.

The operating principle of the detectors is based on recording the difference between the intensity of infrared radiation emanating from an intruder penetrating into the controlled area and the background temperature at the protected object. All bodies with a temperature above absolute zero are sources of infrared radiation. This also applies to the person various areas whose bodies have a temperature of 25...36°C. Obviously, the intensity of IR radiation from a person will depend on many factors, for example, his clothing. However, if a person appears at an object that does not have sources of IR radiation with varying temperatures, the overall flow of IR radiation from the controlled area also changes. These changes are recorded by a passive electro-optical infrared detector.

The sensitive element of the detector is a pyroelectric converter, on which infrared rays are focused using a mirror or lens optical system (the latter are currently the most widely used). Modern detectors use a double pyroelectric converter (pyroelement). Two pyroelements are connected back-to-back and connected to a source follower mounted in the same housing. Thus, this is no longer just a pyroelectric element, but a pyroelectric receiver that converts the input signal - thermal IR radiation into an electrical signal and pre-processes it. The back-to-back connection of pyroelements makes it possible to implement the following algorithm for their operation. If the IR radiation incident on both pyroelements is the same, then the current generated by them is equal in magnitude and opposite in direction. Therefore, the input signal at the amplifier input will be zero. If the pyroelements are illuminated asymmetrically, their signals will differ and a current will appear at the amplifier input. Signals from the pyro receiver are processed by a logical block, which controls the output element of the detector circuit, which issues an alarm message to the alarm loop of the control panel.

The use of a pyroelectric detector with two sensitive areas can significantly reduce the likelihood of false alarms under the influence of external factors, such as convective air flows, light interference, etc.

The detection zone of the detector is a spatial discrete system consisting of elementary sensitive zones in the form of rays located in one or several tiers or in the form of thin wide plates located in a vertical plane. Since the detector's pyro-receiver has two sensitive areas, each elementary sensitive zone of the detector consists of two beams. A typical volumetric detection zone of a detector is shown in Fig. 7.1.

The detector detection zone is formed using a special optical system. The most widely used optical systems are those with a Fresnel lens. This is made from special material(polyethylene) structure having the required optical properties. The lens consists of separate segments, each of which forms a corresponding beam of the detector detection zone. Standard detection zones

can be corrected by gluing individual segments of the Fresnel lens. In this case, individual rays are excluded from the detection zone.

Conventionally, detector detection zones can be divided into three main types:

Surface type “fan”, “curtain”, “blind” or “radial barrier”;

Linear type"corridor";

Volumetric, including “cone” type and ceiling detectors.

Typical detection zones of passive electro-optical infrared detectors are shown in Fig. 7.2.

To provide stable operation it is recommended to adhere to the detector following rules:

Do not install the detector above heating appliances;

Do not point the detector at air conditioners, radiators, warm air fans, spotlights, incandescent lamps and other sources that cause rapid temperature changes;

Do not expose the detector to direct sunlight;

Do not allow animals and objects (curtains, partitions, cabinets, etc.) that can create “dead” zones to be in the detection zone.

Modern passive optical-electronic infrared detectors use digital signal processing, carry out constant self-monitoring, have increased resistance to various destabilizing factors and an optimal price-quality ratio. All this makes them the most common class of security alarm detectors. The variety of their types, produced by the world's leading companies engaged in the production of security equipment, creates constant competition in the consumer market. Basically, detectors from different companies have approximately the same tactical and technical characteristics in their classes.

Typical representatives of this class of products are domestically produced detectors of the “Photon”, “Ikar”, “Astra” series.

Radio wave detectors

Radio wave detectors can be used to protect the volumes of enclosed spaces, internal and external perimeters, individual items and building structures, open areas. They generate an intrusion notification when the field of electromagnetic waves of ultra-high frequency (microwave) is disturbed, caused by the movement of the intruder in the detection zone. Radio wave detectors are single-position and two-position. In single-position detectors, the receiver and transmitter are combined in one housing, and in two-position detectors they are structurally designed as two separate blocks.

The detection zone of the detector (as with ultrasonic detectors) has the shape of an ellipsoid of rotation or drop-shaped and differs from detector to detector, as a rule, only in size. A typical detection zone of a single-position detector is shown in Fig. 7.3.

The operating principle of single-position radio wave detectors, like ultrasonic ones, is based on the Doppler effect, which consists in changing the frequency of the signal reflected from a moving object. Single-position radio wave detectors are used to protect the volume of premises, open areas, and individual objects. The operating principle of two-position detectors is based on the creation of an electromagnetic field in the space between the transmitter and the receiver, forming a detection zone in the form of an elongated ellipsoid of rotation and recording changes in this field when an intruder crosses the detection zone. They are used for perimeter protection.

In radio wave detectors, as already noted, electromagnetic waves of ultra-high frequency are used. Length

waves are usually about 3 cm (10.5... 10.7 GHz). The main advantage of centimeter waves, compared to light and acoustic waves, is their almost complete insensitivity to changes and heterogeneity of the air environment.

Microwave radio waves travel in a straight line. Items, the dielectric constant which differs from air, are an obstacle for centimeter waves, but most often a translucent obstacle. Objects with solid metal surfaces are opaque reflective obstacles.

To ensure stable operation of radio wave detectors, it is recommended to adhere to the following rules:

Do not install detectors on conductive structures ( metal beams, damp brickwork, etc.), since a double ground loop occurs between the detector and the power source, which can cause false alarms of the detector;

Move oscillating or moving objects that have a significant reflective surface, as well as large objects that can create “dead” zones, outside the detection zone, or form the detection zone in such a way that these objects do not fall into it.

If there are “dead” zones, it is necessary to ensure that they do not create a continuous path for the violator to material values; during the security period, lock doors, windows, vents, transoms, hatches, and also turn off ventilation and power switching installations; Do not allow plastic pipes and window glass through which water may move into the detection zone.

Effective methods reducing the influence of these factors are the following:

Securing objects that can move;

Selection of the appropriate direction of radiation of the detector, as well as the use of radio-proof screens, for example in the form metal mesh in front of objects whose vibration or movement cannot be eliminated;

Eliminating the possibility of the detector triggering when small animals and insects appear in the detection zone by selecting the height of the detector suspension and orienting the direction of its radiation parallel to the floor;

Selecting the appropriate delay for the detector response time and treating the detector installation site with special chemicals;

Disabling sources fluorescent lighting for the period of protection.

If this is not possible, it is necessary to ensure that there are no vibrations in the fixtures, blinking or other transient processes in the lamps themselves, which usually occur before the lamp fails; do not point the detector at window openings, thin walls and partitions behind which movement of large items is possible during the security period; Do not use detectors on objects near which powerful radio transmitting equipment is located.

Typical representatives of this class of products are domestically produced detectors of the Argus, Volna, Fon, Radium, and Linar series.