The perimeter refers to the length of the boundaries of a closed figure or, in relation to security systems, the territory and border of the protected object. If we compare electronic security systems installed indoors and outdoor systems, perimeter security alarms are considered more complex and expensive. The sensors of such alarms are located outdoors, so they are exposed to temperature changes and various precipitation. In addition, the following negative factors affect the operation of perimeter security sensors:
- Fog and other weather phenomena;
- Wild or domestic animals;
- Birds;
- Tree branches and other vegetation.
Due to fairly frequent false alarms, many security companies avoid connecting territory or perimeter security alarms to their centralized surveillance consoles. At the same time, such an alarm system is the first line of security for a facility and performs a vital function in ensuring security.
Content:
What is a perimeter security alarm?
Perimeter alarm is a combination of various types of sensors, connecting lines and information processing units. The perimeter can consist of long sections, so instead of conventional sensors used indoors, special systems are used on the perimeter. In addition to reliable protection from climatic conditions, such devices must block areas 40-100 meters or more in length. The following types of sensors are used to operate perimeter alarms:
- Infrared optical systems;
- Cable vibration sensors;
- Radio wave systems;
- Microwave devices.
Optical sensors
consist of two compact blocks, one of which is a transmitter and the other a receiver of infrared radiation. The transmitter contains an infrared laser, the beam of which hits the photodiode of the receiver. When the beam crosses, the sensor is triggered and an alarm signal is generated.
The distance between blocks can reach up to 80-100 meters. They are usually mounted on brackets above the fence and protect against climbing attempts. Using such sensors, you can block approaches to a building or structure. In this case, the system turns on only at night. The infrared beam is completely invisible, but the transmitter and receiver are almost impossible to hide.
Vibration sensors are used only on lightweight fences made of metal mesh, barbed wire or corrugated sheet. This security system consists of a special cable that is attached to the fence using zip ties. Typically, two lines are mounted on the mesh fence, which are connected to the controller.
In the event of an attempt to enter the territory of the facility or destruction of the fence, the cable, at the slightest deformation, creates electrical charges on the sensor conductors, which are supplied to the controller and activate the device to issue an alarm signal. The sensitivity of the vibration system can be easily changed to block false alarms.
Radio wave systems They are two pieces of cable laid in parallel. An electromagnetic field is created between two spaced apart conductors. Any foreign object will cause field distortion, which is detected by the signal processing unit. Radio wave alarms can be installed on any fences made of non-magnetic material - brick, wood and concrete slabs.
With the help of this type of alarm, you can protect the territory without any obstruction at all. To do this, it is enough to lay parallel lines shallow underground. If an intruder crosses this area, it will trigger burglar alarm. One linear sensor provides protection for a fence section up to 120 meters long.
Microwave Perimeter Security Systems consist of a receiver and a transmitter. Being spaced at a distance of up to 60 meters, they create a volumetric zone between themselves. As soon as the intruder tries to cross the blocked area, an alarm is generated. The sensors are installed at a distance of 1.5 meters from the ground and 40-50 cm from the plane of the fence.
Advantages and disadvantages
The perimeter security system has its advantages and disadvantages. First of all, such an alarm system is capable of alerting security and sounding an alarm long before an intruder enters the premises. Sensors will detect violations of the perimeter at distant approaches and allow security to take appropriate measures.
A video surveillance system is often integrated into a perimeter alarm system, which makes the security system extremely effective. A perimeter security alarm system can be organized with duplication of important sections of the perimeter various types sensors The main disadvantages of such alarms are the following:
- Difficulty in installation and configuration;
- High cost of work;
- Low noise immunity;
- High percentage of false positives.
Installing such an alarm requires certain preparatory work, often associated with cutting down trees and bushes. When choosing types of security sensors, you should pay attention to power lines, pipelines and industrial sources of electromagnetic radiation. It is quite difficult to adjust the sensitivity of perimeter security alarm devices, especially where there is a high probability of animals appearing.
Current models
The most common perimeter alarm systems are
The market for systems to protect objects from break-ins and unforeseen incidents is saturated with sensors that help establish comprehensive control over housing. However, not every device is capable of providing reliable security, and connecting low-quality, cheap equipment leads to unexpected problems. As an alternative to motion sensors, a simple and fail-safe laser alarm is used, which is triggered when an object enters the beam spectrum.
What is the operating principle of a laser beam alarm?
Alarms with a laser beam are usually purchased in ready set, but if desired, you can make them yourself without spending a lot of effort and money. The entire operating principle of a laser alarm is associated with a special infrared beam, which is directed at a certain angle to the opposite wall of the room where the photocell is mounted.
Any object falling within a given spectrum creates refraction that can send a signal to a special detector. After reporting a violation, the built-in speaker will notify residents or security of the intrusion.
The laser detector kit includes the following construction materials:
- Relay;
- The simplest microcircuit from a flashlight;
- Photocell;
- Power unit;
- Resistor;
- Detector;
- Generator.
Due to the fact that the laser light flux does not scatter and is constantly directed in one direction, using a reflector system you can create a varied pattern that cannot be avoided. Small pieces of mirrors located at a certain angle at different ends of the room are used as reflectors.
The process of assembling laser elements and parts
The assembly principle consists of sequential soldering of individual alarm elements to the board. First of all, you need to decide on the place where the laser alarm and photocell will be installed. Most often, such mechanisms are mounted in the lower part of the room at a level of 30 cm from the floor, which allows you to hide the device from prying eyes.
The video shows an experiment with laser signaling:
The installed laser on one side of the wall is connected to a relay and power supply, and in the opposite place, at a distance of no more than 10 m, a photocell is attached with the expectation that the beam will fall vertically onto the lens. When an object enters the spectrum of the beam, the photocell begins to heat up, the relay transmits a signal to the resistor, and the latter to the detector.
The siren acts as a repeller, emitting a signal with a power of up to 100 dB, which can be heard at a distance of about 100 m.
A conventional lithium battery should be used as a power supply, since it will consume a minimum amount of energy and is practically necessary to issue an alarm signal.
Modern radio amateurs propose to integrate a communication module for the functionality of the system, which will make it possible to send an SMS or voice message to a specific number, which will not only scare away the robber, but also try to detain him.
Modern security systems are developing at a rapid pace due to the increase in the overall crime situation in the world. Passive means - private or personal security - are no longer relevant, and in order to protect yourself, your property and business, modern protection systems against intruders are widely used, and they are constantly being improved. And the comprehensive integration of various systems allows you to more effectively solve the security issue without overpaying extra money.
This type of signaling uses radio signal transmission similar to the same standard used in mobile communications. The kit includes a base or control unit connected to any cellular operator and wireless sensors. The SIM card installed in the unit will receive an alarm call.
For greater reliability, some manufacturers provide the use two and three SIM cards– in case the main one is out of the access zone. Wireless sensors are connected to the station, allowing for complete control over the room. The system is controlled using SMS or key fob buttons. If there is a connected video camera, a photo is sent to email when the alarm is triggered.
The big advantage of these devices is no wires and no need to install them.
These alarms are used to protect a dacha, house, apartment, garage, warehouse, office - any real estate.
Important! Before choosing a GSM alarm manufacturer, you need to decide at what temperature it will have to be operated and whether it can operate in a mode that does not depend on an uninterrupted power supply.
Perimeter security systems
Such systems make it possible to identify and prevent intruders from entering a fenced area in advance. The principle of their operation is based on the recognition of vibration or changes in the electric field.
Set protective device includes:
- various types of sensors;
- sensor cable;
- warning subsystem;
- object motion analyzer;
- computer with special software.
Perimeter devices can be combined with access control and video surveillance systems. In case of using stationary systems barriers are required to secure sensors and cables.
The most popular perimeter defense lines are:
- vibration;
- capacitive;
- radio wave;
- radio beam.
Important requirements for the installed system:
- coverage of the territory line and the absence of dead zones;
- protection of the device from climatic conditions;
- absence of railway tracks and trees near the protected area;
- possibility of grounding.
To protect against false alarms, a meteorological module is used, which allows taking into account the impact of atmospheric phenomena on the equipment.
Read more about perimeter alarm systems.
Autonomous security systems
This is a compact system that has the function of notifying the owner of illegal entry into the territory. They are suitable for small and poorly protected facilities, as well as for facilities that do not have a communication line. easy to use, inexpensive, have no monthly fee as a working condition and do not require operator participation to control the system.
An attacker will not be able to disable the autonomous alarm system on his own, since it is not connected to the household power supply. The device is powered using batteries of various types.
The sensors that are used when operating an autonomous security system are:
- acoustic;
- infrared;
- vibration;
- reed switches (responsive to changes in the magnetic field).
Principle of operation autonomous system security: when installed around the perimeter of a protected object, if a moving object is detected, the sensors transmit information to the central controller, which emits a sound signal.
Alarm data is divided into two types:
- centralized – transmit information from sensors to a central security point;
- autonomous – make decisions about notification independently, without interacting with controllers.
The disadvantages of these systems include: vulnerability to electronic signals in a metropolitan area and interference caused by reinforced concrete structures.
Laser devices
The principle of its operation is extremely simple and is based on a photo relay: when an attacker crosses a laser beam aimed at a special photocell, refraction is created, as a result of which the relay is turned off and the sensor is activated, then a signal is sent to a special detector. The system can be additionally equipped with a siren, but more often when triggered, an alert signal is sent directly to the police station on duty, inaudible to the intruder. This allows you to gain time and catch the criminal red-handed.
Such alarms are used to protect premises and garden areas.
Advantages of a laser security system:
- mobility;
- possibility of camouflage.
Among the disadvantages we can name high cost of the device and a high percentage of false positives(birds, animals). If desired, such a system is easy to assemble.
GPS alarm
This type of security system is based on the principles of operation of global positioning systems, or satellites. The accuracy of determining the location of an object ranges from 3 to 20 meters.
The device itself is quite compact; it is often used to monitor living objects: children, elderly relatives, pets. You can also use it to protect against theft of valuables - a painting, furniture, a book.
It has become widespread in the development of security systems to protect cars from opening and theft.
To protect the premises, the kit includes a video camera and a video transmission channel to a mobile phone, there is also the possibility of voice communication and the presence of infrared illumination for shooting in the dark.
This type of security alarm does not require cable laying, and is also ahead of other systems in terms of speed of notification to the owner, which makes her very attractive. The disadvantages include dependence on uninterrupted cellular communication and high cost.
Infrared alarm
The operation of this system is based on the use of infrared sensors. When an intruder crosses the infrared beam, the sequence of pulses supplied to the receiver is disrupted, the circuit is closed, and an alarm signal is sent to the duty station.
The device consists of:
- infrared transmitters and receivers;
- power supply;
- indication and signaling units.
IR detectors are divided according to their operating principle into:
- active;
- passive,
by type of detection zone - on:
- volumetric;
- superficial;
- linear.
The infrared protection system, depending on the model, is equipped with a temperature sensor, built-in microphone, remote or built-in camera, loudspeaker, shock, movement, and door opening sensors.
Infrared alarms are most often used in the Smart Home system.
The correct choice of security alarm system is dictated by both objective conditions and technical characteristics premises or space in need of protection, as well as cost and many other factors. Consultation with a specialist will help you decide on the choice of device and will guarantee peace of mind for the owner.
In this article we will tell you how to make a laser alarm. The idea is to make such an alarm as shown in movies about superheroes.
This laser alarm simulates a stretch when a thin wire is stretched 20 centimeters above the ground (floor). When an intruder enters the protected area and pulls a tripwire, an alarm is activated. What if you do a laser alarm and a tripwire at once? That's right, this will turn out to be quite interesting.
The alarm system discussed in the article is primarily intended for use in airsoft, but it can also be used to protect residential premises, garages, etc.
The principle of operation of a laser pointer alarm is quite simple.
The PIC16F688 microcontroller controls the laser module that sends the beam, which must be returned through the mirror. The reflected beam is received by a photoresistor. The PIC16F688 microcontroller checks the state of the photoresistor and if the laser beam is blocked, it activates a sound signal.
The laser signaling circuit is quite simple and is shown in the following figure:
To change operating modes, use switch S3 - select the operating mode: laser and / or stretching:
- Laser + stretching.
- Stretching.
The photoresistor must be placed inside the tube to prevent it from being exposed to sunlight or other light sources. To eliminate the possibility of accidental activation of the laser alarm.
And the laser pointer needs to be modified by soldering the wires to the place where the batteries are installed.
The following figure shows the laser module and photoresistor tube.
To combine both elements, they must be aligned and glued together, for example, by cold welding or plastic. Thus, they are assembled parallel to each other.
For the stretch version, a microswitch is used, located in the upper part of the laser alarm housing. The mikrik lever protrudes above the body, through the window, so that fishing line, thread or thin wire can be hooked onto it.
Now you can finally finish the case by making holes for the LEDs, power button, mode switches and siren.
When installing the emitter with the receiver, please note that it must be possible to adjust this part of the laser alarm.
The alarm uses a modified portable PC beeper because it is quite small and very loud. But him electronic circuit must be modified so that it can be connected to the PIC16F688 microcontroller.
Upon completion of assembly, it is necessary to check the functionality of the alarm from laser pointer.
The scheme works as follows. When the power is turned on, the device enters setup mode, checks the laser and lets us know if the reflected beam has returned correctly to the receiver. At this point you need to adjust the mirrors. If the reflected beam is adjusted correctly, the red LED lights up.
After adjusting the beam, you need to press the button 1 time to exit the setup mode and enter the operating state.
If the laser beam is blocked, the PIC16F688 microcontroller will turn off the laser and activate the siren.
The siren will work until you press the button. Voices)