OPS: Fire detectors with signal transmission via radio channel.
Wireless solutions in the field of information transmission are rapidly gaining ground. And this is not surprising: on the one hand, the constant growth of copper prices and work related to the installation of cable systems, on the other hand, the development of technologies, the growth of transmission speed and the reduction of the cost of a unit of information transmitted via a radio channel. Wireless solutions have long been used in security systems. And it is not only about the development of technologies, at least in our country. In many ways, the promotion of object radio channel systems is facilitated, oddly enough, by the low level of planning and organization of work. Of course, there are traditional cases of using radio channel detectors — these are primarily cultural sites, religious buildings, i.e. buildings with complex architecture, usually old buildings, where it is often impossible to lay wiring. However, we have a huge amount of real estate being built, when neither at the design stage nor at the construction stage no one even thinks about equipping the facility with a security system. This question arises when the building has already been constructed, the finishing has been done, and the installation of a cable system for the fire alarm system at this stage will cost a lot of money, not to mention the time spent. Of course, this mainly concerns individual construction projects, but there are many cases when this situation arises in more serious projects: a fire alarm is needed, they simply will not allow the facility to be put into operation without it, but there are either no embedded parts for communication lines and alarm loops, or they are already clogged with wiring for electricity, communications, etc.
This is where wireless systems come to the rescue. After all, with the proper skills, you can place detectors, connect and program a fire alarm device in literally a day.
In this article, we will consider wireless solutions for fire alarm systems and focus on radio channel fire detectors. In the simplest case, the system consists of a set of detectors and a control panel (CPC). To solve 95% of problems, only three types of fire detectors by the method of operation are enough: automatic point smoke and heat detectors, as well as a manual one for raising a fire alarm by a person. Moreover, in approximately four out of five cases, smoke fire detectors are used. In general, a radio channel detector consists of three main units: a functional part responsible for determining the fact of fire, a radio channel module that serves to transmit an alarm to the CPC, and a battery power module that ensures autonomous operation of the detector for a long time (at least a year). In most cases, the radio channel module is built directly into the detector, and then this is a complete unified design solution. Sometimes the radio channel module together with the power module is made separately in the form of a radio channel base. Thus, the manufacturer can unify its product line and reduce the overall range of products. In this case, a conventional addressable detector is installed in a specialized mounting base and turns into a radio channel one, which, you must admit, is very convenient.
Currently, there are three officially permitted radio frequency ranges in Russia for the use of radio equipment without special permission: 433/868/2400 MHz. A huge amount of various equipment operates in the 433 range, from car alarms to portable radio stations, the 2400 range is densely occupied by data transmission technologies such as WiFi and Bluetooth. Against this background, the relatively free 868 MHz range (primarily because it became unlicensed not so long ago) seems to me the most suitable for solving the problems of an object radio channel.
A one-way or two-way data transfer protocol can be used to transmit information from the detector to the control panel. One-way data transfer, from the detector to the control panel, significantly simplifies and reduces the cost of the system as a whole, since in this case the detector only needs a radio transmitter, since it does not need to receive data. However, in this case, with a large number of detectors, it is quite difficult to implement anti-collision algorithms that prevent simultaneous data transfer on one frequency by several devices. But for small systems with one or two dozen detectors, such a simple solution is quite suitable and works well. In extreme cases, several transmission subchannels can be used in a number of systems, each of which is allocated its own frequency. When building large systems where hundreds of radio detectors can be installed, a solution based on a two-way radio channel will be more acceptable. With two-way exchange, the system receives functionality of a completely different level: it becomes possible to control actuators via a radio channel. Based on the data on the quality of the radio signal received from the facility devices, the control panel can remotely regulate the power of the facility transmitters, which optimizes energy consumption, significantly simplifies the mechanism for monitoring the performance of detectors, makes it possible to remotely set operating parameters, and much more. But you have to pay for everything, and therefore systems based on a two-way radio channel are still significantly more expensive. In fairness, it should be noted that according to GOST R 53325-2009 on fire automation, systems with a one-way radio channel are actually outlawed, although, in my opinion, this restriction is not technically supported by anything and for a number of categories of facilities, a one-way radio channel, given its greater simplicity and low cost with comparable reliability, is quite justified.
When constructing radio channel systems, three main topologies are used to organize the data transmission scheme: «star», «tree» and «sensor network». When connected in a «star» manner, each detector directly transmits information about its state to the control panel; this communication method is suitable for small objects, when all detectors are within the radio visibility of the control panel. If the scale of the object or a complex interference environment do not allow for direct provision of stable radio communication, a hierarchical structure in the form of a «tree» is used with the use of special devices — radio signal repeaters. The repeater is installed between the detector and the control panel and ensures signal repetition to increase the overall communication range. There may be several repeaters along the path of the radio signal; this characteristic of the system is called the repeater depth. Repeaters can be used with both one- and two-way communication protocols. The most advanced option, however, as well as the most complex, is the «sensor network» type topology (mesh network), where theoretically any device can be both an end point and a repeater. The advantages of this topology are primarily in the survivability of the system itself, since data can be transmitted from each device to each, which makes it possible to build different transmission routes. However, such solutions are more demanding in terms of power supply, since devices must be ready to transmit not only their own information, but also retransmit data from their neighbors. And accordingly, such devices are more expensive than conventional ones, without a built-in retransmission function.
Power supply of devices is a separate big topic in radio channel systems. If the control panel and most repeaters have, as a rule, a stationary power supply, then the detectors must have a battery power supply, sufficient in capacity for long-term (years) operation of the device. Moreover, it is highly desirable that the type of power element used is available for purchase when replacing it, and the cost of the battery does not greatly affect the overall cost of the device and, more importantly, the cost of operating the system. To optimize energy consumption, a number of special circuit and algorithmic solutions are used in detectors. Their essence comes down to the fact that most of the time the detector «sleeps», i.e. is in the micro-energy consumption mode and only occasionally «wakes up» to perform functional work, for example, measure the smoke level and transmit its status to the control panel. For normal operation, a timely notification function about a low battery charge is also necessary, i.e. not half an hour before the device is turned off, but several days or weeks in advance, so that there is time to replace the battery. Some manufacturers even provide two power elements for this: main and backup.
In conclusion, let us consider the most controversial point when assessing radio channel systems — the communication range. Manufacturers of object systems usually announce values of several hundred meters, however, with the proviso that this data is valid for open space. But radio channel fire alarms are not installed in an open field. This is true, but the whole problem is that it is extremely difficult to calculate the passage of a radio signal at an object in advance. There are too many different factors to consider. This includes the material of the walls and ceilings, their thickness, the presence of reinforced barriers, mutual arrangement, which affects the nature of radio signal reflections. Other radio transmitting devices operating in the visibility zone of our radio system can have a significant impact. And what is worst of all, external radio transmitters may not always work, but only at certain intervals, confusing engineers: why does the system work normally during the day, and turn off for half an hour at night. All these factors must be taken into account in detail when designing and installing radio channel systems, because reliability and, most importantly, the stability of data transmission depend on them.
Optical smoke detector JA-80S series OASiS (Jablotron)
This smoke detector reacts to visible smoke or excess temperature (threshold) caused by a fire. If the smoke concentration or temperature exceeds the set value, the detector issues a fire alarm signal to the control panel and simultaneously issues an alarm signal with the built-in siren. The detector performs regular self-testing. The correct operation of the detector can be checked by pressing the test button on the detector cover.
Operating frequency – 868 MHz; Power supply – 1x AA 3.6 V lithium battery; Detection method – optical camera/temperature sensor; Estimated operating time – about 3 years; Communication range – about 300 m (open space); Recommended maximum protected area – 50 cubic meters; Built-in siren power – 80 dB/m; Dimensions – ± 126 mm, height – 65 mm; Complies with EN 54-7, EN 54-5, prEN 54-25, ETSI EN 300220, EN 50130-4 and EN 55022, EN 60950-1.
«Aurora-DR» (IP 21210-3) («Argus-Spectrum»)
Radio channel addressable analog smoke fire detectors (standard and explosion-proof design) operate as part of the wireless addressable analog fire alarm and notification system STRELETS®. Automatic frequency change (10 channels in the 433 and 868 MHz ranges), automatic selection of signal transmission route, two-way protocol.
Powered by a set of batteries: 5 years (main) + 2 months (backup).
The detectors fully comply with Federal Law 123 and GOST R 53325, have a certificate of compliance with SanPiN (does not harm human health, does not interfere with the operation of medical equipment).
They transmit the current (analog) smoke level. They have «distributed intelligence»: analysis of fire signals together with the control panel, as well as the function of automatic dust compensation. Automatic performance monitoring. Patented smoke chamber with 2 dust collectors.
Have a reflector system: protection from background light, built-in protective insect screen, symmetrical smoke chamber. Reed switch: detector testing using a magnet.
Adaptive signal processing: elimination of false alarms.
Addressable radio channel fire detectors: manual IP53510-1 «Ladoga IPR-RK» and smoke IP21210-2 «Ladoga PD-RK» («Rielta»)
The detectors comply with the requirements of GOST R 53325-2009. Two-way radio communication in the 433 MHz frequency range ensures acknowledgement of transmitted notifications. Reliability of information transmission is ensured by automatic transition to a backup frequency in difficult interference conditions and a special exchange protocol «Rielta-Contact-R». The operating time from the main battery is at least 5 years, from the backup battery — at least two months. The communication range in open space is 200 m. The monitoring time and the period of broadcasting are programmed during installation. A computer is not required to install the system. Identification indication. Temperature range -20 °C — +55 °C.
Wireless heat and smoke fire detector ASD-100 (Satel)
The combined fire detector ASD-100 is designed to operate as part of the wireless ABAX fire alarm system and is mounted inside protected premises. It is equipped with smoke and heat detectors that generate an alarm signal when the environmental parameters (smoke and temperature) reach specified threshold values. The detector sends an alarm message via a radio channel to the ABAX system controller, also giving sound and light signals. The ASD-100 sensor is configured remotely using radio communication, and the device is powered by a CR123A lithium battery providing 3 V. The radio communication range provided by the device is up to 150 m in direct visibility, and the reliable design of the detector allows for its scheduled testing no more than 2 times a year.
IQ8Quad Series Addressable Analog Wireless Detectors (Esser by Honeywell)
The wireless fire alarm system is based on the IQ8Wireless technology, which provides wireless connection of IQ8Quad series detectors to a wired system. Special wireless bases are used for their installation, using a radio channel to connect to a transponder or wireless gateway. In this case, all detectors are provided with an individual address and are interpreted by the system as subscribers of a ring loop. The radio communication range in the IQ8Wireless system reaches 300 m in direct visibility, and 4 lithium batteries of 3.6 V with a service life of up to 5 years are used for power supply in wireless bases and radio interfaces. Data exchange in such a fire alarm is carried out at frequencies of 433 MHz (20 channels) and 868 MHz (4 channels), and frequency hopping technology is used to protect against interference and unauthorized influence. The IQ8Quad series detectors used in the Esser radio channel fire system can be smoke, heat, combined, with a gas sensor, as well as with built-in light, sound and speech alarms.