Introduction
With the evolving technology around the globe, security systems have continued to experience rapid improvements. This has been facilitated by increased sophistication of hardware and software products. Industries have benefited greatly from these improvements especially in terms of security. One of the major innovations that have arisen from these sophistications has been the integration of radar systems in security systems. The RADEC-M automatic door sensors have proved to be a success in this field. This paper provides an analysis of the RADEC-M sensors with focus on their functionalities and how they have revolutionized the security systems. These sensors are used in automatic doors. Their main capability lies in their unique identification of people and vehicles while providing the direction and speed detection specifications of each.
System Specification
The RADEC system has three main types of sensors that work in unison to achieve three objectives. These include the motion sensor whose sole purpose is to monitor movement into and out of the door, the velocity or speed sensor that determine the speed of objects or persons gaining entry or exit through the door and the directional sensors that monitor the direction of the person or object in relation to the position of the sensor (Rapid, 2013, RapidOnline).
RADEC-M systems rely heavily on the 24GHz technology that has been integrated with microprocessors controls. It provides detection capabilities and relays the collected data to the computer system that converts the received signals to reliable data that can uniquely identify the object approaching the route. The 24GHz technology is a portion of the electromagnetic spectrum that operates within the microwave range of frequencies (Rapid, 2013, RapidOnline). It therefore offers a swift and accurate detection of objects through a single motion of the object. The flexibility offered by the detector that use this technology means they can be mounted on any location ranging from walls and ceilings and still provides a wide survey of the location.
The sensors continuously generate microwave that cover the designated route while relaying the information to the connected computer system. The transmitters generate the microwaves which are then reflected on the ground and other regions that it has been set to cover. When there is no motion in the area under cover, the frequencies of both the transmitter and detector remain identical. The presence of motion within the area of survey alters the frequency of the ray that is reflected back to the detector so that the two waves now differ. This difference in motion is relayed to the computer system as presence of an object along the route (Honey, G. 2007).
Earlier sensors utilized the ultrasound detection methods detectors were fitted to monitor sound disturbances by moving objects. The detectors would then relay the information to the computer system and these disturbance would be recorded as an intrusion and hence the presence of an object. The ultrasound detectors had several weaknesses as compared to the RADEC-M sensors. Firstly, these detectors could did not have the ability to distinguish vehicle motion from human beings. This is one of the unique features of the RADEC-M sensors. Vehicle movement is generated as a constant and compact reflected frequency while the arm and leg movement is generated as a constantly reflected and altered signal. The door can be set to open automatically for vehicles and people. If it is a common door for both, the system can be configured to completely open the door for vehicles and partly for humans (Rapid, 2013, RapidOnline). This is because the signals are distinct and the interpretation at the computer level offers this distinction that will subsequently vary how the door opens. Similarly, for accurate functioning, there was need to install several sensors on an area that a single RADEC-M sensor would cover. This was purposely as a result of the limitations offered by the speed of sound especially along surfaces.
The ultrasound detectors therefore required a lot of technical integration to ensure that all sound detectors are able to work in unison and relay approximately similar data to the detectors and subsequently to the computer system. This meant that such systems hardware and software components required complex logical designing which would prove costly especially during maintenance. The innovation of RADEC-M sensors solved most of these limitations that were a characteristic of the ultrasound systems.
The RADEC-M sensors have a detection speed of 0.1m/s which makes them suitable for detecting moving objects even to a speed of 60km/hr. The RADEC-M sensors works on the Doppler principle whereby it is capable of determining the velocity of a fast approaching object (Rapid, 2013, RapidOnline). This Doppler technology also has an ability to show whether the object is moving away from the door or approaching the door. The detectors pick reduced frequencies as the object moves away from the door while for an approaching object, the frequency increases. The radar compares the received signals with those of the transmitter and the difference is analyzed by the high tech computer systems and integrated software to show the distance of the object in relation to the door. To allow this, the sensor is programmed with direction monitoring which allows it to detect only movements away or towards the door. This is known as stereo direction monitoring. It also prevents the system from keeping the doors open due to undesired signals.
The block diagram showing the basic signal processing
They also possess a vertical detection filed angle of 00 to 450 with increments of 50. On the horizontal detection field the range is 150 to the left and right. The positioning of the detector does not limit the detection angle ranges making the apparatus effective for a wide range of environments. The temperature values have little or negligible effect on the quality of detection but can offer optimum detection rates within the range of -200to +600. The RADEC-M sensors supply voltage varies between a DC voltages of between 12V to 30V. The equipment has an ability to cover a detection area with dimensions of 2.5m by 3.5m at an installation height of 2.2mm at angle 300 (Rapid, 2013, RapidOnline).
The internal wiring system of RADEC-M sensor (Rapid, 2013, RapidOnline)
The cable path is the hollow part where the cable running from the Control Panel enters the sensor. This cable houses the wires that are responsible for transmitting the microwave from the detector to the control panel and from the control panel to the transmitter.
The 12-24V DC/AC power converter distributes the received power to the internal components of the sensor. It is crucial in converting the AC to DC or DC to AC when there is unexpected power surges so as to ensure the continuous operation of the sensors.
The indicator light is the lenses that focus the microwaves generated by the transmitter to the area of focus.
The antenna provides a signal boost. It boosts the signals received from the control panel before sending them to the transmitter and the detected signals before they are sent to the control panel by the detector. The purpose is to ensure high quality signal to and from the control panel for higher chances of accuracy.
Input/ COM ports are the internal ports of communication. The received signal from the control panel is channeled into the sensor system through one of the ports that is designated for input while the signals from the detector are passed through the output port to the respective wire that transmits the signal to the control panel (Sullivan, R. J., 2000).
The screw holes are purposely designed to offer tight fit for the tightening screws.
Once the signal is relayed to the control panel, the control panel has mechanisms that convert the analog signals from the detector and transmitter to digital signals. These digital signals are relayed to the computer system without altering their meaning. The control panel must therefore possess high synchronization mechanisms so that the value of the signal is not altered during conversions as this would lead to incorrect response of the automatic door. The computer system has software whose input is the signals from the detectors. This signal input is then taken through the logical analysis by the software. Depending on the results produced by the logical analysis, the software activates a special integrated hardware that controls the opening and closing of the automatic door. While the software provides the logical analysis of the signal, the hardware pert of the computer system provides the physical analysis but under the control of the software (PEPPERL+FUCHS, 2012, RADAR SENSORS FROM PEPPERL+FUCHS).
When there are objects in motion around the area under survey of RADEC-M sensor, the value of the transmitter and detector are similar. The software reads this similarity as logical “0” which implies a lack of input. In this state, the whole system is reset to default. A difference in value is fed to the software as a logical “1” and depending on the magnitude and direction of the value the software sets the values to alter the hardware as expected (Honey, G. 2007).
Advantages
- The RADEC-M sensors are effective for a wide range of conditions. Weather conditions such as light and temperature have negligible effect on the accuracy of the results it conveys.
- The RADEC-M sensors have a high degree of accuracy. The ability to distinguish between vehicles and humans explains the levels of accuracy and preciseness that they could offer.
- These sensors do not offer limitations as to where they can be fitted as microwaves can travel in any direction from the source. Whether placed on walls or on the ceiling, the sensors will offer the same quality of signals (Sullivan, R. J., 2000).
- The RADEC-M sensor that does not need any peripherals therefore proving easy to handle, install and maintain. The complexity of ultrasound systems especially on the hardware side means that the maintenance costs sometimes could exceed the installation and purchase.
Disadvantages
- The RADEC-M sensors are very expensive to purchase since they are latest technology in security systems for monitoring movements in industries and buildings where high security levels are required. Their prices are proportional to their accuracy levels.
Components
The Control Panel
This is the interface between the sensor wiring and the computer cabling. It also serves as the power connection point for the whole system. The analog signals relayed by the detectors are converted to digital signals once they enter the control panel. It provides the compromise between the analog part of the system and the computer software and applications that are used to analyze the relayed signals. It also harbors the backup battery for the system (PEPPERL+FUCHS, 2012, RADAR SENSORS FROM PEPPERL+FUCHS).
The Detectors
These are located in the RADEC-M equipment. They receive the waves reflected by the object in motion and transmit them to the control panel. The value they submit to the Control panel is compared with that of the transmitter to determine intrusion or movement (Sullivan, R. J., 2000).
The Transmitters
They produce the 24GHz microwave that is reflected towards the area under cover. Their focus on an object is the key to accuracy of the signals relayed.
The power supply
It powers the whole system from the RADEC-M to the control panel and the computer systems.
The Keypad
This component controls the opening and closing of the doors depending on the signal sent by the computer system.
The Alarm control Unit
This unit interprets the signal received from the computer to notify the necessary parties of some movement at the door.
Radio Receivers
They receive all signals from the installed sensors, synchronize them and relay them to the computer system in an orderly manner. They are located within the control panel.
Bibliography
Honey, G. 2007, Intruder alarms, Oxford, Newnes.
PEPPERL+FUCHS, 2012, RADAR SENSORS FROM PEPPERL+FUCHS, Retrieved from http://files.pepperl-fuchs.com/selector_files/navi/productInfo/doct/tdoct1903a_eng.pdf
Rapid, 2013, RapidOnline, Retrieved from http://www.rapidonline.com/electronic-components/radar-motion-detector-radec-m-519651/#techSpecs
Sullivan, R. J., 2000, Microwave radar: Imaging and advanced concepts, Boston, Artech House.
