Motion sensors for alarm: types and models, principle of operation, installation
Complex alarm systems in modern versions rarely do without the use of sensor elements. Depending on the type of detectors, they can detect third parties in the protected area, monitor gas and water leaks, record the facts of opening doors and breaking windows. The most popular motion sensors for alarm, which may be several on the object. They allow to detect the presence of intruders in the covered area, so they are also called presence detectors. In this case, the performance of such sensors may be different - they differ in performance and principle of operation.
Presence sensor in the alarm system
The sensing element of sensors of this type performs one task - it captures any movements that are performed in its zone of action.By the way, similar models of detectors are used in lighting systems. For example, when a user enters a room, the sensor sends a signal to the controlling controller, from which the response command is then sent to the luminaire to turn on.
In signaling, the response algorithm of the system as a whole is slightly different. The sensor also records the movement of the object, after which the received signal is sent to the control panel. After processing, the system then sends the appropriate signals to the owner of the house or the security service. In such an infrastructure, there is a motion sensor for GSM signaling, the controller of which can send commands via the cellular communication channel to the SIM cards. This is the most popular way of communication for such systems. An important feature of sensors designed specifically for protection is increased fixation accuracy and sensitivity. These parameters are important because of the extreme undesirability of registering false signals, which are a weak point of presence detectors.
Motion sensors differ in construction design, data transmission method and principle of operation.As for the design, they can be modular and monoblock. The devices of the first type are a case base in which individual sensitive elements can be integrated. This is convenient from the point of view of installation: once having installed a body block at a working point, in the future, you can not think about changing the directionality of the sensors. It is enough to replace the sensitive segment - and the system will be completely reoriented.
Monoblock devices are small and are mounted once without the possibility of replacing the sensitive filling. By the method of data transmission, you can select a wireless motion sensor for signaling and traditional models that are connected via cable. Wireless detectors are more popular because they require minimal effort in installation and are organically introduced into almost all modern security systems.
Wired models have an advantage in the form of power supply reliability and communication stability - they cannot be disabled by third-party radio jammers, for example.But at the same time, cabling not only requires extensive installation work, but even if there is no proper masking, it can find itself in front of an intruder. According to the principle of operation, ultrasonic, infrared and electromagnetic sensors can be distinguished. They should be considered separately.
Ultrasonic Motion Sensors for Alarm
Until recently, ultrasonic models were considered the standard. They operate on the principle of reflection of sound waves, in a constant mode, generating acoustic fields at frequencies of 20-60 kHz. The advantages of such devices include price availability, versatility in terms of the characteristics of the object of detection, tolerance for temperature fluctuations. But there are also disadvantages with which the ultrasonic principle of the motion sensor works, this is a weak sensitivity and discomfort for animals, which, unlike humans, can pick up the frequencies of a constantly working field.
How do electromagnetic sensors work?
In general, the principle of operation is the same; only the sensor generates not an ultrasonic, but an electromagnetic field, and by registering reflection signals it detects the presence of a third-party object. As a rule, the frequency is at the level of 5.8 GHz.Among the advantages that microwave motion sensors have for signaling, independence from temperature and humidity in the security zone, the compact size of the sensing element and the ability to fix conductive objects even behind thin walls and partitions are noted. However, the same advantages in the form of an extended field of action eventually turn into a disadvantage, which will be expressed by the highest rate of false positives among all types of presence detectors. In addition, the very emission of electromagnetic waves is unsafe for humans.
How does the infrared motion sensor work?
This is the most modern principle of operation of sensors for alarm. It is based on thermal radiation and fixation of the already optical reflection from the target object. Therefore, we can talk about the combined filling of sensors. This principle of operation of the motion sensor will be clearer if you first turn to traditional infrared radiators. They, unlike other heaters, do not heat the air, but the objects in the room. In turn, the detectors of this type also emit warm waves, but as a return signal, the built-in lenses capture the infrared light.
What is the benefit of using such sensors? Unlike previous wave diffusers, they are completely harmless to people and animals, provide high accuracy of detection and allow you to perform wide sensitivity settings. At the same time, an infrared motion sensor may become unstable in rooms with other sources of warm radiation, which limits its scope.
How are the presence sensors installed?
Usually installation work is done with the help of complete fittings. Manufacturers complement sets of fasteners, hardware and holders. For installation, it is enough to make several holes in the fixing place and fix it with screws or self-tapping screws. In rare cases, motion sensors for signaling are attached with adhesive solution or, even more rarely, with self-adhesive tapes. This mainly applies to light electromagnetic devices and only in cases of temporary use of the sensor.
The best sensor models
In the budget segment of the entry-level models may be interested in proposals from the company "Siberian Arsenal".In particular, the Rapid model with a range of 18 m is capable of detecting objects moving at a speed of 0.3–3 m / s. The cost of this solution is only 400 rubles.
For a more demanding consumer, we can recommend the option from the middle class - Foton-16. This infrared detector cost 800 rubles. with a small field of coverage of 12 m, but with a special antimasking channel, a spherical lens for high-precision signal processing and increased resistance to damage.
If you plan a multifunctional alarm system for a home with a premium class motion sensor, then you can pay attention to the Paradox HD77 device. This proposal is estimated at 17-18 thousand rubles, but this amount is justified by the fact that, in addition to the main function, the sensor also takes pictures from an integrated HD camera, the “picture” of which can also be configured to fix unwanted presence.
In choosing the right sensor, it is important to take into account external factors and operating conditions of the security system. For example, an alarm for a dacha with a motion sensor is more likely to be guided by a wide field of coverage, physical reliability of components, and power supply autonomy.Therefore, it will be necessary to choose from wire-type detectors that will have a high class of security - at least IP54. For a city apartment you can safely buy a compact wireless model of the infrared sensor. But in this case it is important to calculate in advance the risks of false positives by adjusting the sensitivity level of the sensor accordingly.