Optoelectronic detectors are devices in which optical devices and sensors of various designs are used to detect an alarm event. Further processing of the received signal is carried out by an electronic circuit. Such devices are widely used in both security and fire alarm systems.
The main reasons for their popularity are:
- high efficiency;
- the possibility of forming detection zones of various configurations;
- relatively low price.
The optical part of these detectors operates in the infrared (IR) range of radiation. There are various versions of infrared sensors that differ in the principle of operation, purpose and application features.
Passive.
Used in security alarm systems. Their main advantages are economic availability and a wide range of applications. The principle of operation is based on the analysis of the difference in IR radiation between the sectors formed by special lenses (Fresnel).
The receiver of the infrared stream is a pyroelectric module that generates electrical impulses processed by electronics.
Modern detectors quite often use microprocessor signal processing, which increases their reliability, efficiency and resistance to interference.
Active.
They evaluate changes in the intensity of the IR beam generated by their transmitter. Structurally, the receiving and transmitting parts can be placed in separate blocks installed opposite each other. In this case, the part of the space between them is controlled.
With a monoblock design, a special reflector is used to return the beam to the device. Such detectors are used in security and fire systems.
The operation of such devices is considered in sufficient detail in the article about linear sensors used in fire alarms.
In addition to the "classic" wired devices that use relays to transmit information about their state, there are addressable optoelectronic detectors. By transmitting a signal to the receiving and control device, they add their own code, unique for each product, to the information.
Due to this, it becomes possible to localize an alarm event with an accuracy up to the location of the sensor installation. Their cost, of course, is higher, but in some cases it is worth it.
Another technology is addressable analog. It implies the transmission of digitized data of the scanned parameter, on the basis of which the decision to generate an alarm is made by the control panel. Such detectors are mainly used in fire protection systems.
The last thing worth noting is the signal transmission methods. There are actually two of them:
- wired;
- radio channel.
SECURITY OPTO-ELECTRONIC DETECTORS
The principle of operation of security optoelectronic devices is described at the beginning of this article. As for detection zones, passive infrared detectors allow you to use all possible options:
- bulk;
- surface (curtain);
- linear (beam).
Active ones work according to the last (ray) principle.
All of them are inherently motion sensors, that is, they detect the movement of an object in a protected area. For surface and linear, it would be more correct to say - the intersection of the detection zone. You can see more about how it works.
FIRE OPTO-ELECTRONIC DETECTORS
Optoelectronic devices used in fire alarm systems and automatic fire extinguishing installations belong to smoke detectors. According to the type of detection zone, they are divided into:
- point;
- linear.
Point ones incorporate a smoke chamber. It is a kind of labyrinth at the beginning and end of which an emitter and a photodetector are installed. When smoke gets inside, IR radiation is scattered, which is recorded by the electronic circuit of the device.
The scope of such detectors is very wide, they are installed in offices, shops, hotels and other similar facilities. According to the type of information signal formation, they are divided into:
- threshold;
- targeted;
- addressable analog.
According to the method of communication with fire alarm devices, these detectors are wired and wireless (radio channel).
In general, these are quite versatile sensors that allow solving various issues of providing fire safety. It is somewhat inconvenient, and sometimes economically impractical, to use them for installation in rooms of a large area and (or) a large distance from the ceiling.
In this case, linear optoelectronic detectors are used in fire alarm systems. They do not have a gas chamber and control the optical density of the medium by analyzing the parameters of the infrared beam. For these purposes, a receiver and a transmitter are required, that is, such devices are active.
A general limitation on the use of optoelectronic fire detectors is rooms with a high dust content. In addition, such devices may be affected by electromagnetic interference. But this largely depends on the model of the sensor.
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Lecture 6
Active optical-electronic detectors
Active optical-electronic detectors are used to protect internal and external perimeters, windows, shop windows, individual items. They generate an alarm notification when the reflected flow changes (single-position detectors) or the received flow (two-position detectors) stops (changes) of optical radiation energy caused by the movement of the intruder in the detection zone. The principle of operation of the detectors is based on the directed distribution, reception and analysis of the 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 narrow beams located in a vertical plane; it differs from detector to detector, as a rule, by the range and the number of beams.
Install the emitter and receiver on strong, non-deformable structures;
Do not expose the receiver to sunlight and car headlights, as well as direct sunlight on the lenses, as this can lead to overheating and premature failure of photodiodes and LEDs.
The influence of these factors can be eliminated by using opaque screens; prevent foreign objects from being closer than 0.5 m from the space through which the beam passes.
Typical representatives of this class of products are the detectors of domestic production "Vector" and "SPEK".
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, it is possible to obtain detection zones 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 principle of operation of the detectors is based on registering the difference between the intensity of infrared radiation coming 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 man various sections whose bodies have a temperature of 25 ... 36 ° C. Obviously, the intensity of IR radiation from a person will depend on many factors, such as his clothes. Nevertheless, if a person appears on an object that does not have sources of IR radiation with a changing temperature, the total IR radiation flux from the controlled area also changes. These changes are recorded by a passive optical-electronic infrared detector.
The sensitive element of the detector is a pyroelectric transducer, 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 transducer (pyroelectric element). Two pyroelements are connected in anti-parallel and connected to a source follower mounted in the same housing. Thus, this is not just a pyroelement, but a pyro receiver that converts the input signal - thermal IR radiation into an electrical signal and pre-processes it. The counter-parallel 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 input of the amplifier will be zero. With asymmetric illumination of the pyroelements, their signals will differ and a current will appear at the input of the amplifier. The signals from the pyro receiver are processed by a logic block that controls the output element of the detector circuit, which issues an alarm notification to the alarm loop of the control panel.
The use of a pyro receiver with two sensitive areas can significantly reduce the likelihood of false alarms under the influence of external factors, such as convective air currents, light interference, etc.
The detection zone of the detector is a spatial discrete system, consisting of elementary sensitive zones in the form of rays arranged in one or more 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 also consists of two beams. A typical volumetric detector detection zone is shown in fig. 7.1.
The detection zone of the detector is formed using a special optical system. The most widely used optical systems with a Fresnel lens. This is a structure made of a special material (polyethylene) that has the required optical properties. The lens consists of separate segments, each of which forms a corresponding beam of the detector's detection zone. Standard detection zones
can be corrected by gluing individual segments of the Fresnel lens. In this case, individual beams are excluded from the detection zone.
Conventionally, detector detection zones can be divided into three main types:
Surface type "fan", "curtain", "curtain" or "beam barrier";
Linear type"corridor";
Volumetric, including the “cone” type for ceiling detectors.
Typical detection zones of passive optical-electronic infrared detectors are shown in fig. 7.2.
To ensure stable operation of the detector, it is recommended to adhere to the following rules:
Do not install the detector above heating appliances;
Do not point the detector at air conditioners, radiators, fans warm air, 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 burglar alarms. 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 performance characteristics in their classes.
Typical representatives of this class of products are domestically produced detectors of the "Photon", "Icarus", "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 ultrahigh frequency (SHF) 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, while in two-position detectors they are structurally made in the form of two separate blocks.
The detection zone of the detector (as with ultrasonic detectors) has the shape of an ellipsoid of rotation or a teardrop shape 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 principle of operation of single-position radio wave detectors, as well as for 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 principle of operation of two-position detectors is based on the creation in the space between the transmitter and receiver electromagnetic field, which forms the detection zone in the form of an elongated ellipsoid of rotation and registers changes in this field when the intruder crosses the detection zone. They are used to protect the perimeter.
In radio wave detectors, as already noted, are used electromagnetic waves ultra high frequency. Length
wave is usually about 3 cm (10.5 ... 10.7 GHz). The main advantage of centimeter waves, in comparison with light and acoustic waves, is their almost complete insensitivity to changes and inhomogeneity of the air environment.
Microwave radio waves propagate in a straight line. Objects whose permittivity differs from air are an obstacle for centimeter waves, but most often they are translucent. Items that have solid metal surfaces, are opaque reflective obstacles.
To ensure the stable operation of radio wave detectors, it is recommended to adhere to the following rules:
Do not install detectors on conductive structures (metal beams, wet brickwork etc.), since a double ground loop appears between the detector and the power source, which can cause a false alarm of the detector;
Move out of the detection zone oscillating or moving objects with a significant reflective surface, as well as large-sized objects that can create "dead" zones, or form the detection zone in such a way that these objects do not fall into it.
In the presence of "dead" zones, it is necessary to ensure that they do not form a continuous path to material values for the intruder; for the period of protection, lock doors, windows, vents, transoms, hatches, and also turn off ventilation and power switching installations; prevent plastic pipes and window panes from entering the detection zone, through which water can move.
Effective methods to reduce the influence of these factors are as follows:
Fixing objects that can move;
Selection of the appropriate direction of radiation of the detector, as well as the use of radio-tight screens, for example, in the form of metal meshes in front of objects whose vibrations or movement cannot be eliminated;
Elimination of the possibility of triggering the detector when small animals and insects appear in the detection zone by choosing the height of the detector suspension and orienting its radiation direction parallel to the floor;
Selection of an appropriate delay of the detector response time and treatment of the detector installation site with special chemicals;
Disabling fluorescent lighting sources for the period of protection.
If this is not possible, care must be taken to ensure that there are no vibrations of the fittings of the luminaires, flashing or other transient processes in the lamps themselves, which usually occur before the failure of the lamp; do not orient the detector to window openings, thin walls and partitions, behind which movement of large-sized objects is possible during the protection period; do not use detectors at objects near which powerful radio transmitting means are located.
Typical representatives of this class of products are domestically produced detectors of the Argus, Volna, Fon, Radiy, Linar series.
Optoelectronic detectors.
Optoelectronic There are two fundamentally different types of detectors: passive and active. In this lecture, we will consider only detectors used for burglar alarm purposes. The fire component will be discussed in a lecture on fire detectors. Let me remind you that passive detectors do not emit anything into the environment, but only analyze the incoming information. Active for the purpose of detecting penetrations, they radiate something into the environment and, based on the response, draw the appropriate conclusions. Active detectors can be either monoblock (emitter and receiver in one housing), or two or more block ones, when the emitter and receiver are separated.
Consider first
Passive optoelectronic detectors
Currently passive optoelectronic infrared ( IR) detectors occupy a leading position in the choice of protection of premises from unauthorized intrusion at the objects of protection. Aesthetic appearance, ease of installation, configuration and maintenance make them a priority compared to other detection tools.
The principle of operation 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 body of a person 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 enters the Fresnel lens, after which it is focused on a sensitive pyroelectric element located on the optical axis of the lens
Passive IR detectors they receive infrared energy flows from objects and are converted by the pyro receiver into an electrical signal that enters through the amplifier and the signal processing circuit to the input of the alarm generator.
Passive infrared detectors are designed to detect a person who is within the sensitivity zone. The main task of the detector is to detect the infrared radiation of the human body. As can be seen from Figure 1, the thermal radiation of the human body is within the spectral range 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 related devices that are used to detect radiation in the indicated spectral range. For PIR detectors, a sensitive element with an optimal sensitivity/cost ratio should be used. Such a sensitive element is a pyroelectric photocell.
Rice. Fig. 1. Spectral dependence of the luminescence 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 coated silicon filter, a filter with a cutoff wavelength of 5 μm and a filter with a cutoff wavelength of 7 μm.
The phenomenon of pyroelectricity consists in the occurrence of an induced potential difference on opposite sides of a pyroelectric crystal during its nonequilibrium short-term heating. With time electric charges from external electrical circuits and redistribution of charges inside the crystal lead to relaxation of the induced potential. From the above it follows:
interruption frequency (Hz).
Rice. Fig. 2. Dependence of the value 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 the pyroelectric element is used, it will be able to register a person only when he enters the radiation pattern (Fig. 3, 4) and exits it at a speed of 1 - 10 centimeters per second.
Rice. 3, 4. Paired pattern shape corpsed pyroelectric element in 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, maintaining 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 dimensions of the sensitive element must 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 around 0.1°C for a 1 x 2 mm pyro element, a few microns thick.
Rice. Fig. 5. Appearance of the sensitive element of the 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 (still person) or if an object with a temperature different from the background moves in such a way that it does not cross the detector's sensitive zones (for example, it 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 single part of space, which is a consequence of a person's movement. It must always be remembered that the sensitive element detects movement not “on the detector”, but across. 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 the concentration of incoming radiation (Fig. 6). In an infrared detector, the lens system performs two functions.
Rice. 6. Options for forming the directional diagram of IR detectors depending on the type of lens system.
First, the lens system serves to focus the radiation on the pyroelectric element.
Secondly, it is intended for spatial structuring of the detector sensitivity. In this case, spatial zones of sensitivity are formed, which ,e as a rule, they have the form of "petals", and their number reaches several tens. The object is detected every time it enters and exits sensitive areas.
Usually, the following types of sensitivity diagram are distinguished, which is also called a radiation pattern.
one). The standard one is fan-shaped in azimuth and multi-tiered in elevation (Fig. 6a).
2). Narrowly directed - 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 pattern (in particular, for detectors installed on the ceiling of the room), as well as a number of others.
Consider options design beamforming systems (Fig. 7). This optical system can be either lens or mirror. The manufacture of a conventional lens system, taking into account the requirement for the formation of a spatially structured radiation pattern, is an expensive task, so conventional lenses are not used in passive infrared sensors. The so-called Fresnel lenses are used. In a conventional lens, for directional light deflection (focusing), a special spherical surface shape is used, the lens material has an optical refractive index that is different from the refractive index environment. 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 cheap. The disadvantage of using a Fresnel lens is the inevitable loss of half of the radiation energy as a result of its diffraction deflection by the lens in a direction other than the direction to the pyroelectric element.
Rice. 7. Design options for security passive IR detectors: with a Fresnel lens and with a mirror focusing system.
The mirror lens is more efficient than the Fresnel lens. It is made of plastic mass 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 one. In addition, detectors with a mirror system are larger than detectors equipped with Fresnel lenses.
Why use more expensive detectors with a mirror system for concentrating incoming radiation? The most important characteristic the detector is its sensitivity. Sensitivity is practically the same in terms of unit area of the detector's input window. This, in particular, means that if a passive infrared detector is designed with increased sensitivity, then they are forced to increase the size of the radiation concentration zone - the area of \u200b\u200bthe entrance window, and, therefore, the detector itself (the maximum sensitivity of modern passive infrared detectors allows detecting 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. Under the condition of the same sensitivity, the gain of the electrical circuit in a mirror detector is two times less than in a detector with a Fresnel lens. This means that in detectors with a Fresnel lens, there is a higher probability of false alarms caused by interference in the electronic circuit. Quite often, both technologies are used together, so in the Astra-5sp detector. And the main zone is formed by zones of Fresnel lenses, the anti-sabotage zone directly under the detector is a small mirror made in a rather handicraft way. In general, the market for security detectors is filled with fairly cheap products, the price of which ranges from 300-900 rubles apiece with a significant advantage towards the lowest price. Naturally, in such conditions, it is not possible to talk about some kind of gilded mirrors.
Once again, let's return to the optical scheme of the detector. In addition to the lens system and the optical “cut-off” filter installed directly in the sensor housing, various optical filter elements (“white” filter, “black” mirror, etc.) are used to reduce false positives caused by various radiation sources. which minimize the incidence of extraneous optical radiation on 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 their cheapness, cheap detectors use polyethylene similar in properties to those used for food bags, while more expensive ones use milky color, which transmits IR rays well, but a poorly visible spectrum, which is what we need.
Fresnel lenses are constantly being improved. First of all, by giving the lens a spherical shape that 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 on 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 squeezed out, inside of which certain concentric circles, or parts of them, are visible. In most cases, we see about 12-15 vertically elongated rectangles in the upper part, 5-6 more square-like rectangles in the middle part, and usually 3 almost square rectangles in the lower part. It is necessary to correctly understand that everyone of these rectangles is a Fresnel lens, so we have a matrix of lenses. In order to distinguish an intruder at the edge of the detection zone, and this 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 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 a matrix of lenses, pay attention to important feature– the vertical sides of the rectangles in different tiers are always shifted relative to each other. This was done specifically to be able to detect the intruder in the worst movement for the detector "to the detector". Even if the intruder accidentally hit exactly in the middle of the elementary sensitive zone and moves directly to the detector, then in another tier he will not be able to get into the middle of the elementary zone in the same way and will be detected by it. When placing the detector, it must be taken into account that its maximum detective abilities precisely when the intruder moves across sensitive zones.
Very relevant is the problem of counteracting the physical shielding of the detector, which comes down to installing a screen in front of it that overlaps its “field of view” (the so-called “masking”). Technical means of counteracting masking constitute a system antimasking 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 area of the LEDs, 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. In the event that the necessary signal does not appear at the output of the electrical circuit during the self-test, the alarm generation circuit is triggered. Detectors with functions antimasking 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 the detector is the use of a quadratic sensitive pyroelement in conjunction with the use of microprocessor signal processing. Different firms solve the problem of creating a quadratic element in different ways. For example, the OPTEX company uses two conventional dual pyroelements located side by side. The main task of the system is to isolate and “screen out” events caused by the simultaneous illumination of both pyroelements (for example, headlights) or electrical interference.
Quite a lot of companies use a special design of a quad pyro receiver, where four sensitive elements are located in one housing.At the same time, pyroelements are turned on in the opposite direction, located both in horizontal plane, as well as vertically. Such a detector will not respond to small animals (mice, rats), which are often found in warehouses and are one of the causes of false alarms (Fig. 8). The use of a bipolar connection of sensitive elements in such a detector makes it impossible for "noise" false alarms.
ADEMCO is so confident in the perfection of the quadratic detector developed by it that it announced the payment of a bonus if the owner of the detector fixes its false operation.
Another precaution is the use of conductive film coatings applied to the inside surface of the entrance window to counteract RF interference.
An effective method of increasing the noise immunity of detectors is the use of the so-called "double 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 the following lectures.
Rice. 8. The operation of a multi-channel system for selecting noise pulses on the example of the operation of a quadratic security passive IR detector.
Due to the principle of detection, it is very difficult for such detectors to detect an intruder if the ambient temperature approaches the temperature of the human body. In such cases, the detector simply goes blind, and for our southern region, a temperature of 35-40 degrees in summer is not at all uncommon, especially in closed, unconditioned rooms with insufficiently insulated roofs and walls. To combat this problem, a thermal compensation. The essence of its work lies in the fact that when the temperature in the room approaches the critical one (37 degrees Celsius), the detector increases sensitivity stepwise (usually by an order of magnitude). Of course, this reduces its noise immunity, but it allows you to detect an intruder in these extreme conditions. When the temperature drops, the detector returns sensitivity to normal.
We examined the basics of operation and design of passive infrared security detectors. In general, all constructive tricks used by certain companies have one goal - to reduce the likelihood of a false alarm of the detector, since a false alarm leads to unjustified costs for responding to an alarm, and also causes moral damage to 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 on the basis of 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 problem of minimizing fluctuation interference, which can be solved by circuitry, is topical. Are used different methods noise control.
Firstly, electronic discriminators of the input signal are installed in the detector for the upper and lower levels, 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 IR detector.
Secondly, the mode of synchronous counting of pulses coming from both optical channels is applied. 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 another. The subtraction scheme is applied at the output. If the source of the signal is a noise electrical signal, it will be identical for two channels and at the output the resulting signal will be missing. If the signal source is an optical signal, then the output signal will be summed.
Thirdly, the pulse counting method is applied. The essence of this method is that a single object registration signal does not lead to the formation of an alarm, but sets the detector to 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 with caution and only when warranted. It must be remembered that the detector may not have a chance to fix 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 detector design and change its properties by replacing the matrix. Thus, the same detector can be made voluminous, it is possible to create a “long beam” zone - it sees far, but narrowly, it is possible to create a detector - a “curtain”, with which we can cut off the necessary parts of the object using a detection zone similar to a curtain.
As a rule, all detectors require a 12 V DC power supply. The current consumption of a typical detector is in the range of 15 - 40 mA. The alarm signal is generated and transmitted to the security control panel by means of an output relay with normally closed contacts.
The use of solid-state relays instead of conventional relays also made it possible to reduce energy consumption. Let me remind you that these detectors are passive, which also allows you to have a minimum current consumption. Like most security detectors, PIR detectors are recoverable, i.e. when an intruder is detected, it will go into the "alarm" state, in the absence of further movement registration, it will be restored to the "normal" state. Usually, for ease of maintenance, the detector has a built-in red LED that signals the "alarm" state, but can also transmit other additional messages.
For the normal placement of the detection zone in space, it is necessary to take into account the detector installation height recommended by the manufacturer, which is usually 2.2-2.5 meters for a wall-mounted version. Let me also remind you that reorientation of the detector (sideways, upside down) is not allowed.
When choosing a detector, it must be remembered that they have different temperature ranges, and if you install a detector that operates up to 0 degrees in an unheated room, then you can expect problems in operation in winter with frost.
The industry produces detectors for installation indoors, as well as outdoors; the latter have the appropriate climatic design.Typical service life of passive infrared detectors is 5 - 6 years.
Detector examples
With a detection zone of the "long beam" type: Astra-5 isp. V, Photon-10A, Photon-15A, Photon-16.
With a detection zone of the "curtain" type: Astra-5 isp. B, Astra-531 isp. IR, Ikar-Sh, Ikar-5B, Photon-10B, Photon-10BM, Photon-15B, Photon-16B, Photon-20B, Photon-22B, Photon-Sh, Photon-Sh-1, Photon-Sh2.
With volumetric detection zone: Astra-5 isp. A, Astra-5 isp. AM, Astra-511, Astra-512, Astra-7 isp. A, Astra-7 isp. 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, Ikar-1A, Ikar-2/1, Ikar-5A, Ikar-7/1.
Active optical-electronic detectors.
Linearoptoelectronic detectors (active IR detectors), as a rule, have a two-block design and consist of an emitter unit (BI) and a photodetector unit (BF), forming an optical system. The emitter generates a stream of infrared radiation (infrared beam) with specified characteristics, which falls on 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) that enters the receiver, which analyzes the magnitude and duration of this interruption and, in accordance with the specified algorithm, generates an alarm notification by changing the resistance of the contacts connected to the alarm loop. 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 input windows of the BI and BF are usually closed with special filters (sometimes these filters are made as one piece with the cover of the detector housing). The scheme of the 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 (intruder). They are also insensitive to changes in the characteristics of the thermal radiation of surrounding objects (background) and the resulting thermal interference, which is very important when operating in open areas.
Figure 11 - Diagram 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. In part, this problem can be solved by organizing a surface detection zone through the use of detectors that form several IR beams, or by building 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 an increase in financial costs. The disadvantages include sensitivity to optical illumination.
Recently, some manufacturers have attempted to create an active security detector using an IR laser. So, the Japanese company Optex has recently launched a detector that uses the principle of scanning the surrounding space with a laser beam.
The main functional characteristics of active IR detectors and their impact on the use and tactics of protection
Active IR detectors form a linear detection zone. They can be used to organize the first line of protection of objects (blocking of extended engineering fences (fences), windows or doors outside the building, gates, ventilation shafts and channels, 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 the incorrect use of an active IR detector. In zones A and B, an intruder can enter through a guarded fence. At the same time, in zone B, the detection zone of the detector 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 protection of the object complex shape
Figure 13 shows exemplary scheme protection of an object of complex shape with the help of several detectors. The breakdown of the object into sections should be done in such a way that the intruder could not 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 BP) should be less than the dimensions 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 at 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 the reduction in the flow of infrared energy, which does not lead to the formation of an alarm notification. This coefficient characterizes the resistance of the detector to meteorological factors (rain, snowfall, fog). The minimum allowable safety factors 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 operation are significantly lower than those for detectors intended for outdoor operation.
Specific values of the maximum operating range and safety factor for each detector model are set by the manufacturer.
To ensure the possibility of use on various objects, most modern active IR detectors have the ability to adjust the range. As a rule, the adjustment is discrete, each of its values corresponds to a certain range of range. It is not allowed to operate the detector if the actual range does not match the range set during the adjustment. If the actual range exceeds the set one, the safety factor may turn out to be insufficient, which, in the presence of precipitation (intense snow, rain, dense fog), may lead to a malfunction of the detector (manifested in the form of a false alarm notification and the impossibility of arming). If the actual range is below the set power of the IR radiation falling on the receiver, it will be excessive, which in some cases may lead to the intruder being missed. Excessive signal power is also due to the fact that active IR detectors have a minimum range. The distance between the BI and the BF must not be less than the value specified in the operational documentation attached to the detector.
The sensitivity of an active IR detector is the duration of the interruption of the infrared beam, above which the detector should generate an alarm notification. Minimum permissible value sensitivity 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 by running at maximum speed. Modern detectors provide discrete sensitivity adjustment up to 400 - 500 ms.
It is recommended to set the sensitivity value taking into account the most probable time the intruder stays in the detection zone, which depends on its size and movement speed. For example, if the detector is set to open space, where the intruder will be able to run up and cross the zone at high speed, you should set high sensitivity (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 stay in the zone for a sufficiently long time, for example, when crawling over a blocked area or climbing a fence (fence), the sensitivity value can be set in the range of 400 - 500 ms. The correctness of the sensitivity value selection must be checked after installing and configuring the detector at the facility by making test crossings of the zone with the most likely ways and at 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.
Interference immunity is the duration of the interruption of the infrared beam, in the absence of which the detector does not generate an alarm notification. The minimum permissible value of noise immunity 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, the change in noise immunity occurs automatically simultaneously with the change in sensitivity in the process of its adjustment. An increase in the noise immunity of the detector is facilitated by the use of a dual (synchronized) IR beam in it. The relationship between sensitivity and noise immunity for modern domestic active IR detectors is shown in Table 1.
Table 1
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Parameter |
Meaning |
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Sensitivity, ms |
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Noise immunity, ms |
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Influence of external factors on the operation of active IR detectors and recommendations for its reduction
1) temperature factor. The ambient temperature has a negative impact on the performance of the detector, if its value exceeds the allowable values of the operating temperature set for this detector. To reduce the possibility of overheating of the detector, if possible, avoid installing it in places where it will be exposed to direct sunlight for a long time, and also use protective visors. 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. The lower value of the operating temperature range for modern domestic detectors is minus 40 °С, in the presence of built-in heating it drops to minus 55 °С. If the air temperature has dropped below the admissible values of the detector, it must be taken into account that it may not detect the intruder, it is advisable to organize the protection of the object by patrolling.
2) Optical flare. The reason for high illumination can be both the sun and sources artificial lighting. The presence of a light detector at the input window of the BF, the actual value of which exceeds the norms established in the national standard (more than 20,000 lux from natural light and light sources powered by DC sources, and 1000 lux from light sources (including fluorescent lamps) powered by AC mains) can cause false alarms or skip the intruder. To exclude 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 BF entrance window (this is especially important during sunset or sunrise, when various protective visors are ineffective) and radiation from powerful lighting devices (spotlights, powerful fluorescent lamps, etc.). Most of the active IR detectors included in the "List of ..." today are resistant to natural light up to 30,000 lux.
3) Precipitation . Atmospheric precipitation has a negative effect on the safety factor of the detector due to the attenuation of radiation due to scattering by water drops or snowflakes. They can also cause moisture to appear in the housings of the detector blocks, which can cause the loss of its performance. In winter, the input windows of the detector units may also become iced. The safety factor of modern detectors, as a rule, allows them to function properly in the presence of precipitation, but in the case of their special intensity, a malfunction of the detector may occur (manifested in the form of a constant generation of an alarm notification and the impossibility of arming). In this case, you should organize the protection of the object by patrolling. For decreasing harmful effects atmospheric precipitation, you can use protective visors, you should carry out more often Maintenance(cleaning the entrance windows from ice and snow) of the detector. It is necessary to use detectors with more a high degree protection of the shell (not lower than IP54 in accordance with GOST 14254), carefully seal the inlet technological openings in the housings of the blocks during installation. If the detector is installed at a low height from the ground or other surface (for example, directly above the fence), a gradually increasing layer of snow (snowdrift) can block the detector's detection zone, which will cause a constant generation of a false alarm. The detection zone of the detector can also be blocked by the formed icicles if it is located under any protruding structures and their elements. To prevent a malfunction of the detector, it is necessary to clear the snow accumulating in the detection zone, remove the formed icicles in a timely manner. If the detector is installed along the upper edge of the fence, it is recommended to move it from the axis of the fence into the object.
4) Electromagnetic interference(EMP). The source of EMF that can affect the operation of the detector can be as a working electrical equipment high power, and atmospheric electrical discharges (thunderstorm). For outdoor use, detectors should be used that have resistance to EMF according to GOST R 50009 (electrostatic discharge, electromagnetic field, electrical impulses in the power supply circuit) of at least 3 degrees. When installing detectors outdoors, it is necessary to lay long connecting lines exposed to EMF. To reduce the effect 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 the detector blocks are fixed. These changes can be both natural and man-made. They can 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 positives 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 bases that are not subject to vibration, deformation, and have a stable foundation ( bearing walls capital buildings, etc.).
6) The presence of solid fine particles in the air. These particles can be of both natural (dust, plant pollen) and technogenic (dust, soot, etc.) origin. Their settling on the input window of the detector leads to a decrease in the safety factor. To combat this phenomenon, in areas with a high content of dust or soot in the air, more frequent maintenance of the detector should be carried out. Operational features of active IR detectors.
Power supply of active detectors, as a rule, is allowed to 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 a large length of power loops), it is recommended to use sources with a rated voltage of 24 V. Power supply of built-in heating (if any), 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 the detectors should be chosen in such a way that the intruder does not have the opportunity to crawl between the IR beams without blocking them. For outdoor applications, a spacing of about 350 mm can be recommended. To organize an infrared barrier, detectors with several operating frequencies can be used. This is necessary to exclude the influence of the radiation of one detector on the operation of the neighboring one. If it is necessary to use detectors in the barrier in excess of the number of operating frequencies, they must be installed in such a way that the IR beams of the detectors operating at the same frequency are directed towards each other (Figure 14). In the same way, it is possible to organize a two-beam barrier of detectors having one operating frequency.
Figure 14 - Example of barrier 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 radiation of the same operating frequency of closely located PIs is multidirectional and cannot simultaneously fall on the input window of one BP (Figure 15).
Figure 15 - An example of an IR barrier in the horizontal plane
Setting the parameters of the detector, necessary for operation at each specific object, is carried out either using switches or by programming. The process of programming parameters is described in the operational documentation attached to the detector. After installing the detector on the object and connecting the power supply, it is necessary to adjust the relative position of the emitter and detector receiver. Coarse adjustment is carried out visually by approximate alignment of their optical axes or according to the indications of the IR radiation indicator (if this indicator is available). In some models of detectors (for example, IO209-32 "SPEK-1115"), a special optical sight is provided for this purpose. After completion of coarse adjustment, it is necessary to perform adjustment (fine adjustment) of the blocks. It is carried out by smoothly turning the block in different directions at a small angle in the horizontal and vertical planes using the adjustment devices (screws or flywheels) provided for by the design of the detector. The adjustment process is controlled, depending on the specific detector model, either by the readings of a voltmeter connected to a special connector, or by a change in the built-in light indication. Adjustment is considered completed at the maximum readings of the voltmeter or in the presence of light indication, the type of which is indicated in the operational documentation. ATTENTION. Alignment of the detector blocks ensures the presence of the necessary IR radiation power at the BF input window, as well as the achievement of the maximum safety factor and is a necessary and mandatory procedure, even if, after a rough adjustment, the detector goes into standby mode and is able to generate an alarm notification when crossing the zone detection.
Remote operation control is designed to check the detector's performance from the central monitoring console. It is carried out by short-term switching of the output specially designed for this purpose and the positive output of the power supply. As a result, a short-term interruption of the BI radiation occurs, after which the detector must issue an alarm notification. This feature requires padding additional wire, but may be useful when perimeter security long 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 (fences, walls, etc.) .P), the effect of re-reflection may appear, which consists in the fact that, in addition to direct IR radiation, 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 low-intensity precipitation, when IR radiation is reflected from snowflakes and water drops.
Figure 16 - Reflection effect
To eliminate the negative impact of the reflection effect in modern domestic detectors, it is possible to turn 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 BF input window decreases by about 70%.
On the domestic market active IR detectors are currently represented mainly by the products of the Russian company SPEC CJSC (St. Petersburg), Japanese firms Optex and Aleph, German Bosch and some others.
To date, only detectors manufactured by CJSC "SPEK" 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 operation in open areas, determine their high cost. Therefore, the use of most of them will be most appropriate at fairly important facilities.
The selection of single beam detectors (or dual synchronized IR beam) is generally based on the maximum operating range. It is not advisable to use a detector with a maximum operating range that significantly exceeds 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 the 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 the lower requirements for the safety factor, which should be reflected in the operational documentation. Each active IR detector included in the list is assigned a symbol of the type "IO209-XX / U", where "I" means the type of product (detector), "O" - scope (security), "2" - characteristic of the detection zone ( linear), "09" - the principle of operation (optical-electronic), "XX" - serial number development, registered in in due course, through the oblique fraction "Y" - the serial number of the design modification (if there are several modifications).
Figure 17 - IO209-16 "SPEK-7"
IO209-16 "SPEK-7".The multibeam detector is produced in two versions (modifications) IO209-16/1 "SPEK-7-2" (forms 2 beams with an interval of 350 mm) and IO209-16/2 "SPEK-7-6" (forms 6 beams with an interval of 70 mm). The emitters and photodetectors are mounted in single housings (the so-called KI and KF columns). The detector is recommended to be used to protect gate openings, gates, blocking access to windows and doors of the building from the outside. At the same time, IO209-16/2 "SPEK-7-6" is able to detect a hand extended through the detection zone. Both versions of the detector have an operating range of 0.4 to 15 m (outdoors), 4 sensitivity settings. 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 be both synchronized and each work with its own settings. The maximum length of the synchronization line between adjacent CIs or CFs is no more than 10 m. Synchronization allows you to save money by laying a smaller number of loops. It is possible to set the number of IR beams, the simultaneous intersection of which is necessary to generate an alarm notification, which increases the detector's resistance to crossing the detection zone by small animals, birds, etc. The detector can also be used indoors.
IO209-17 "SPEK-8" The detector has a double infrared beam in the horizontal plane, 4 operating frequencies, 4 sensitivity values, built-in heating. The range of the detector is from 35 to 300 m. The detector is recommended for blocking straight sections of long perimeters, incl. in areas with cold climates.
Figure 18 - IO209-17 "SPEK-8"
Figure 19 - IO209-22 "SPEK-11"
IO209-22 "SPEK-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 regulating the use of electrical equipment in explosive zones. Explosion-proof design of the "flame-proof shell" type. Explosion protection marking 1 Ex d IIB T5 X. The detector can also be used indoors. Application on other objects is impractical due to the high cost.
IO209-29 "SPEK-1112" Detector with two horizontal out of sync IR rays. Due to the presence of two output relays, the detector allows you to determine the direction of the EA crossing by the intruder (when the beams cross in one direction, one relay opens, and when the beams cross in the other direction, the second one). Operating range - 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 "SPEK-1113"
IO209-29 "SPEK-1113" The detector has a single block design with a reflector, 5 operating frequencies, 4 sensitivity values. Operating range - from 5 to 10 m (outdoors). There is no built-in heating. It is recommended to use for blocking gate openings, gates, air duct outlets, ventilation shafts and other small objects. Due to the 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 "SPEK-1115"
IO209-32 "SPEK-1115"It is produced in four versions, differing in the maximum working range and the presence of built-in heating:
a) IO209-32/1 "SPEK-1115" has a range of 1 to 75 m;
b) IO209-32/2 "SPEK-1115M" has a range of 1 to 75 m and built-in heating;
c) IO209-32/3 "SPEK-1115-100" has a range of 1 to 100 m;
d) IO209-32/4 "SPEK-1115M-100" has a range of 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 a cold climate (for versions with the letter "M").
IO209-29 "SPEK-1117"This detector is a simplified modification of the "SPEK-1115" detector and has a lower cost, due to which it will be advisable to use it, incl. and for the protection of ordinary objects, individual housing construction objects, etc. The detector has a double infrared beam in the vertical plane, 1 operating frequency, 2 sensitivity values.
Imported detectors present on the domestic TCO market often do not comply with the current national standard and ETT in terms of resistance to impact low temperatures environment and switching parameters of output relays. Also, foreign manufacturers in the technical characteristics of their detectors do not give the value of the safety factor.
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. The use of technical detection tools based on various physical principles for the protection of fenced areas and open areas.
2. R78.36.028-2012 Recommendations. Technical means of detecting intrusions and threats various kinds. 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 means of protection and methods of dealing with them.
4. R78.36.036-2013 "Methodological guide for the selection and use of passive optical-electronic infrared detectors".
5. R78.36.031-2013 "Survey of objects, apartments and MHIG accepted as a centerlysed security."
6. R78.36.022-2012 "Methodological guide for the use of radio wave and combined detectors in order to increase the detecting ability and noise immunity."
7. GOST R 50658-94 Alarm systems. Part 2. Requirements for burglar alarm systems. Section 4. Ultrasonic Doppler detectors for enclosed spaces.
8. GOST R 50659-2012 Doppler radio wave detectors for indoor and outdoor areas. General technical requirements and test methods.
9. GOST R 54455-2011 (IEC 62599-1:2010) Intrusion alarm system. Test methods for resistance to external influencing factors, 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 burglar alarm systems. Section 6. Passive optical-electronic infrared detectors for enclosed spaces.
11. GOST R 51186-98 Passive burglar alarms for blocking glazed structures in enclosed spaces. General technical requirements.
12. GOST R 54832-2011 Security point detectors magnetic contact. General technical requirements.
13. GOST R 52434-2005 Optoelectronic 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 alarms. Classification. General technical requirements and test methods.
16. GOST R 52551-2006 Security and safety systems. Terms and Definitions.
17. GOST R 52650-2006 Combined radio wave and passive infrared security detectors 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 rooms. General technical requirements.
20. GOST R 53702-2009 Vibrating surface security detectors for blocking building structures of enclosed spaces and safes.
21. GOST 32321-2013 Shock-contact surface security detectors for blocking glazed structures in enclosed spaces.General technical requirements.
22. A list of technical security equipment that satisfies the "Unified technical requirements for 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
Questions for self-examination.
1. What is a 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 PIK detectors?
4. What type of detection zone does the active infrared detectors we have reviewed have?
5. Give an example of an active infrared detector.
These instruments are devices that use optical instruments and sensors to detect an unauthorized event. The final analysis of the signal takes place in the electronic circuit. Optoelectronic detectors are often used in security and fire alarm systems.
The main reasons why they are so popular are:
- high efficiency;
- different areas of location;
- small cost.
The optical part of these devices operates in the infrared region of radiation. There are many ways to install infrared devices.
Passive
Applied in security systems. The main advantages are low price and a wide range of applications. Passive devices analyze changes in IR radiation.
Active
The principle of operation consists of estimating the difference in the intensity of the IR beam, which is produced by the emitter. The emitter and receiver can be in different blocks and in one. In the first case, only that part of the territory that is between them is protected.
If both devices are in the same module, then a special reflector is used.
There are also addressable optoelectronic devices that transmit the control panel signal and indicate a unique code for any device. Thanks to this, you can accurately find out the place where the sensor worked. However, the price of such devices is higher, but if you want reliable system, then this is the best option.
There is another type of detectors - addressable analog. This option transmits the digitized information to the control panel, where it is decided whether to apply the alarm signal.
There are several options for transferring data: wired and radio channel.
Security detectors
The location zones of these devices can be volumetric, surface, and linear. Any of these types is a motion sensor, it turns out that it detects movement in a protected area.
The use of surface devices is constrained by the blocking of structures indoors. Linear are usually used for outdoor areas.
Optoelectronic devices are negative to the presence of air currents and to extraneous light sources.
Active linear devices are smaller than others, dependent on the influence of external factors. But they are difficult to set up, especially when using devices with a large radius of action.
Fire detectors
This type of device is divided into turned and linear detectors. In the first case, the device has a smoke block and is a labyrinth with a transmitter and receiver at the ends. If smoke penetrates inside, then the IR radiation is scattered and this is noted by the receiver.
Such devices are used in many facilities, mainly service, that is, offices, shops, and so on. According to the type of data signal sending, optoelectronic detectors are divided into threshold, and addressable analog. How to connect with devices fire system divided into wired and radio channel.
Such devices are quite versatile and help in ensuring fire safety. But for large spaces this species detectors should not be used.
In such cases, linear optoelectronic devices are better suited. They control the air density by processing the IR parameters. Line detectors include a transmitter and a receiver and are active devices.
Popular Models
Arton-IPD 3.1M
Optical spot fire smoke detector SPD-3.1 (IPD-3.1M). The device is designed to detect fires in enclosed spaces of buildings and structures, accompanied by the appearance of smoke. When triggered, it transmits a signal to the control panel.
Designed for continuous round-the-clock operation on a direct current or alternating two-wire fire alarm loop. The rated supply voltage of the loop is 12 or 24 V. To operate the detectors with the control panel according to the four-wire scheme for connecting the detectors, the MUSH-2 loop matching module is used.
Astra-7B (IO409-15B)
The announcer is security volumetric optical-electronic. Designed to detect penetration into the protected area and generate an alarm notification by opening the output contacts of the alarm relay.
Mounted on the ceiling, the detection zone is circular, maximum height installations up to 5 meters. Microprocessor-based signal analysis, temperature compensation, resistance to external illumination, case opening control, optoelectronic relay. It can work at temperatures from -30 to +50 C and humidity up to 95%.
AMBER
Designed to detect intrusion into the protected area of a closed room. Generates an alarm by opening the relay contacts. Widely used in security alarm systems.
It detects movement in a zone with a range of 12m and a width of 20m, a viewing angle of 90 degrees. The recommended installation height is 2.4m. Supply voltage 12V, operates at temperatures from -30 to +55C. Detects movement at speeds of 0.3..3 m/s.
Useful video
The video explains in detail the device and the principle of operation of devices using the example of a smoke autonomous detector DIP-34AVT from the company.
Conclusion
Optoelectronic emitters are a common and effective component for fire and security alarm systems. Their main advantages include relatively low price, versatility, and reliability.
The main limitation on the use of such devices is problems when working in an environment with a high content of dust, that is, in industrial premises. Optoelectronic detectors are also subject to electromagnetic interference.
Infrared detectors are most often used to control the volume of premises. These are one of the most common types of technical security devices that have proven to be reliable devices with affordable price. The passive infrared detector is designed to detect the movement of an intruder in a controlled volume. 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 device, the device registers a change 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 issues a decision on the presence or absence of motion detection in the area. To do this, 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 for solving various kinds of tasks, depending on the configuration of the protected room - length, width, ceiling height, presence of interference, etc. In most cases, the optimal solution is a sensor with a volumetric 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 ). To control large rooms ideal option there will be ceiling-mounted volumetric sensors that will protect the volume of the 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 volume zone can 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, which has an angle in the horizontal plane of 7°-10°. Thus, these products generate a detecting plane that "overlaps" 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 such sensors of the “curtain” or “beam” type, the lenses of which cut off part of the detecting beams, thus making it possible 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 mounting infrared sensors in the immediate vicinity of ventilation duct openings, windows and doors, which can create convection air currents, as well as next to heating appliances. Despite the resistance to glare with illumination up to 6500 lux, direct exposure to radiation from natural and artificial lighting sources is highly undesirable. To reduce the impact high values ambient temperature for stable operation in infrared detectors, thermal compensation circuits are used. It is possible to use several PIR 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 sensor activity and power status, 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 for outdoor use and in hazardous areas with an appropriate degree of protection.