The security and prevention project is a system that aims to maintain social and public safety, and comprehensively uses security technology and other science and technology to establish functions (or combinations thereof) such as intrusion prevention, theft prevention, robbery prevention, explosion prevention, and explosion-proof security inspection. The project implemented. The security protection project involves many disciplines such as electronics, machinery, materials, computers, and network information. The technology is relatively advanced and the composition is relatively complicated. The scale and function of each project are not the same. Therefore, some problems appear after the completion of the security project is inevitable. .
The causes of various problems are various and involve many factors, such as system design, equipment selection, on-site environment, construction quality, personnel quality, and material quality. During the entire implementation process of the project, we should proactively think of ways to plan solutions, system design, equipment selection, installation and debugging, and take precautions to prevent and avoid various problems. This is a daunting and complicated task. The participants need to have a relatively solid professional theoretical knowledge and rich practical experience. However, no matter how hard we try to think of and accomplish, the problem has always been with us, and we cannot avoid it. This article does not discuss how to prevent or avoid the occurrence of problems. It simply summarizes and enumerates some common problems that are easy to occur after the completion of the safety precautions project, and the frequency of occurrence is relatively high. At the same time, the possible solutions are described and are for reference only.
I. Classification of Security and Prevention Engineering Subsystems
The safety precautions project can be divided into several subsystems according to its functions, generally including: intrusion alarm system; video surveillance system; entrance and exit control system; electronic inspection system; parking management system; building intercom system; explosion-proof safety inspection system; emergency broadcast system Wait. There are many “versions†of this sort according to function in the industry. According to the detailed level of classification, the principle of classification, etc., there are many kinds of classification results, but the frequency of use in security prevention projects is high, indispensable and cannot be replaced. There are several kinds of application subsystems. Because these subsystems are used frequently and widely used, problems often arise in these systems. Some of these problems are common problems that arise in various systems, such as power supply failures, line transmission failures, and on-site interference. Some of them are system-specific issues such as image quality problems in video surveillance systems, false alarms in intrusion alarm systems, and so on. Problems that occur at the same time or in conjunction with each other, such as the linkage of video surveillance systems and intrusion alarm systems. In order to facilitate analysis and discussion, this article will categorize various common problems according to subsystems.
Second, common problems and solutions (A) video surveillance system
Video surveillance system generally consists of three parts: front-end equipment, transmission lines, control and display equipment. The front-end equipment mainly includes cameras, heads, and decoders to obtain information on monitoring targets; the transmission lines transmit the information obtained by the front-end equipments to the control center through video lines and communication lines, and supply power to the front-end equipments through the power cords; The display device mainly includes a matrix control host, a video recorder, a monitor, an image splitter, a power supply, a console, a TV wall, a control cabinet, etc. to complete the processing, switching, segmentation, and control of the transmitted information. In the video surveillance system, the failure of the equipment itself is generally relatively rare, even if it appears, it is relatively easy to solve, and most problems often appear in the construction, installation process of the transmission line laying, connection, control equipment connection. The following briefly describes some common faults in the video surveillance system.
1. No image display, no video signal failure phenomenon Description: The line is normally connected, after power on, the central control room display terminal no image display, hard disk recorder "no video signal", matrix, graphics dividers and other "Nosignal" prompt exists.
Analysis of the reasons: This phenomenon can generally be concluded that the front-end video signal is not normally transmitted back to the control device. The camera may not be normally powered and there is no work. The power line is disconnected, the camera is not powered on, the video line is disconnected, and the BNC head is not soldered securely.
Solution: First check whether the camera is powered on, whether it is working properly; if the camera is not powered, check the power supply, transformer, power cable, etc.; if the camera is powered on, you can use the exclusion method to connect the camera directly to the display terminal to observe, if not yet displayed, Then determine the camera failure, if there is an image display, you can determine the video transmission line is faulty, check the video cable and BNC connector, confirm the replacement of the cable or re-welding the BNC connector.
2. No image display, there is a video signal failure phenomenon Description: After the normal connection of the line, after power on, the central control room display no image display on the terminal, black screen, hard disk recorder "no video signal", matrix, graphic dividers and other "Nosignal" prompt does not exist.
Analysis of reasons: This phenomenon is similar to the first phenomenon described above but with essential differences. In general, transmission line failures can be ruled out, and no indications such as “no signal†or “Nosignal†appear. It is proved that the front-end video signal has been sent back to the control device. It may be that there is no illumination at the scene; the camera lens aperture is closed; the camera angle is not adjusted well; the monitor brightness is not adjusted properly; the camera power supply power is not enough.
Solution: First confirm that the scene lighting conditions are good, the camera surveillance area is the visible area, the display brightness parameters are set properly, then adjust the camera lens aperture, if there is still no image display, you can replace the camera test with the exclusion method, if the fault persists, then replace the power test .
3. The image quality is not good, there is interference This problem is a kind of fault phenomenon with high frequency of occurrence. It has various manifestations and complex reasons. It is a fault phenomenon that is not very good to deal with. It needs concrete analysis of specific problems, and it is targeted. solve. The following classifications are based on different failure phenomena.
A. Symptom Description: A black bar or white bar appears on the picture screen, and it slowly scrolls up or down.
Analysis of the cause: This phenomenon is generally caused by power interference or ground loop.
Solution: On the control panel, connect only the camera output signal with no problem to the nearest power source. If the above-mentioned interference phenomenon does not appear on the monitor, it means that the control panel has no problem; the next step is to use a portable monitor. Proximity to the video output of the front-end camera, and check each camera one by one; if so, proceed with processing; if not, the interference is caused by ground loops and other causes.
B. Symptom Description: There is a grainy disturbance on the image screen. When it is light, it will not overwhelm the normal image. In severe cases, the image cannot be viewed (or even destroy the synchronization).
Analysis of reasons: This phenomenon has more complicated reasons. It may be that the quality of the video transmission line is not good, especially the shielding performance is poor (the shielding network is not a good quality copper network, or the shielding network is too thin to be shielded); The line resistance of the video line is too large, resulting in a large attenuation of the signal is also aggravating the cause of the fault; the characteristic impedance of the video line is not 75 ohms, and the parameter exceeding the specification is one of the causes of the failure; the power supply system is not "clean" The power supply referred to here is not "clean" and refers to the superimposition of interference signals on the normal power supply. The interference signals on this power supply mostly come from equipment that uses thyristors in the power grid, especially large currents. High-voltage thyristor equipment, the pollution of the power grid is very serious, such as the power grid in the power SCR FM speed control device, SCR rectifier, SCR AC and DC conversion devices, etc.; or system There are strong sources of interference nearby.
Solution: If the cable quality problems, of course, the best way is to replace all the cables, replace the cable to meet the requirements; if the power supply system is not "clean" caused, as long as the entire system uses clean power or online UPS power supply Basically, it can be solved; if there is a strong interference source near the system, the solution is to strengthen the shielding of the camera, as well as the grounding of the pipeline of the video cable.
C. Description of fault phenomena: Deep and chaotic large-area moiré interference occurs on the image screen, so that the image is completely destroyed and the image and synchronization signals cannot be formed.
Analysis of the reasons: This phenomenon is generally caused by the short circuit and open circuit of the core wire of the video cable and the shielded network. This type of fault often occurs on BNC connectors or other types of video connectors.
Solution: Check carefully and process all BNC connectors that are connected to the camera with the interference.
D. Symptom Description: Several vertical bars with equal spacing are generated on the image screen.
Analysis of reason: This phenomenon is generally caused by the mismatch of the characteristic impedance of the transmission line, which is caused by the impedance mismatch caused by the characteristic impedance of the video transmission line is not 75 ohms. This interference phenomenon is caused by the characteristic impedance and distribution of the video cable. The parameters did not meet the requirements caused by the synthesis.
Solution: Generally, it can be solved by the method of “connecting resistors at the beginning†or “terminating resistors at the terminalsâ€.
E. Symptom Description: There are several fine fringes on the image screen.
CAUSE ANALYSIS: This phenomenon is generally due to a strong, high-frequency spatial radiation source near the transmission system, system front-end or central control room.
Solution: The solution to this situation is to strengthen the front-end and center equipment shielding, the use of steel pipe transmission lines and pipelines and a good grounding.
　　 4. The interference of the elevator camera image The interference problem of the elevator camera is a fault phenomenon often encountered in the project. This problem involves the cooperation with special special equipment (elevators), poor cable layout environment (elevator hoistway), and the construction site has Certain dangers and other reasons are often not easy to solve. The following analysis and explanation of this issue are separately given.
Symptom Description: The common phenomenon is that the image is displayed normally when the elevator is at a standstill. When the elevator is running, the image quality is obviously reduced, and the image is obviously disturbed. Even the image disappears. This phenomenon is particularly serious at the moment of starting and stopping the elevator; when other elevators are running, other The image quality of the elevator has been significantly reduced, interfered with, and even the image has disappeared. This is particularly serious at the moments when the elevator starts and stops. The image quality of the elevator camera is not good and various interference phenomena occur.
Analysis of Causes: The causes of various types of interference related to elevators are relatively complex. When dealing with problems, we must carefully analyze the reasons and apply the right medicine to the problem so that we can solve problems quickly and accurately. Power cables, lighting, fans, control, communications, and other cables are usually placed in elevator shafts, and various cables generate electromagnetic radiation. Similar to the principle of antenna reception, the coaxial cable will also “receive†these interferences, ie, it will interfere with the electromagnetic field and generate interference currents on the cable. This interference induced current will also cause interference induced voltage on the longitudinal resistance of the cable outer conductor (woven mesh). (Electromotive force), this interference induced voltage just in series in the video signal transmission circuit "long ground" in the formation of interference; elevators are now basically the use of AC variable frequency speed control technology, and the frequency conversion governor itself is also very strong The high-frequency spurious interference, this interference signal can enter the video surveillance system through the power line and space radiation, interfere with the video image; from the elevator car to take power directly, the elevator lighting lamp usually uses electronic ballasts, When electronic ballasts work, they also produce strong AC parasitic interference output, affecting video image quality.
Solution methods and matters needing attention: The installation of a video anti-jamming device is a convenient and quick method; selecting a video cable with a small attenuation coefficient, good shielding performance, and high tensile strength can improve its anti-jamming capability and reduce video attenuation. Consider carefully the problem of transmission attenuation. When selecting the cable, the thick cable is better than the thin cable. The SYWV physical foam cable is better than the solid SYV cable. The high-knit cable is better than the low-knit cable, and the copper core cable is better than the copper-clad steel cable. Copper braided wire is superior to aluminum-magnesium alloy braided wire; reasonable wiring can effectively avoid the interference signal being “coupled†through the cable, minimize the parallel bundle distance from other cables, and keep the video cable away from interference; the video cable exits the elevator shaft Should be in the middle of the well, because at this time the length of the video cable accompanying the well is only about half the depth of the well, and the shortest is the natural introduction of the least interference; in the elevator shaft, the video line is close to the vertical line of the well, and this part The cable runs through the metal pipe or metal slot to shield the influence of interference on this part of the cable; the power supply of the camera should be preferably centralized DC power supply, as far as possible Avoid taking power from the elevator car; video cable from the elevator shaft exit to the control center should take the metal pipe or take the metal slot to shield the impact of environmental interference on this part of the cable, and pay attention to this part of the shielding and shielding in the elevator shaft , should make electrical connection; video camera metal casing, NC head housing, coaxial cable outer conductor and other video signal "ground", and the elevator car, rails, etc. to be insulated; in special circumstances can use the signal line single end Grounding ground input method.
　 5. PTZ, high-speed ball can not control, control failure This problem is also a high frequency of failure phenomena, there are also a variety of forms of expression, the reason is also complex and diverse, and processing requires more practical experience and strong The theoretical knowledge, and careful analysis of the causes of failure, to determine a reasonable and targeted solution. The following classifications are based on different failure phenomena.
A. Symptoms Description: The pan/tilt does not work or does not rotate at all after use, but it can operate normally during installation and commissioning.
Analysis of reasons: Only the pan/tilt head mounted on the camera is allowed to use the hoisting method. In this case, the hoisting method leads to an increase in the operating load of the pan/tilt. Therefore, the transmission mechanism of the pan/tilt will be damaged soon after use. Even if the total weight of the camera and its protective cover exceeds the load-bearing weight of the PTZ, especially the PTZ used outdoors, the weight of the protective cover is often too large, and often the PTZ will not turn (especially the vertical direction can't move) ) Problem; Outdoor PTZ due to high ambient temperature, too low, waterproof, antifreeze measures and failure and even damage.
Solution: Use the device strictly according to the technical parameters and environment requirements of the PTZ and the camera. After eliminating the other reasons to confirm the PTZ and other device problems, consider repairing or replacing the device.
B. Symptom Description: When the distance is too far, the keyboard cannot be controlled by the decoder on the camera (including the lens) and the head.
Analysis of reason: This is mainly because the control signal is too attenuated when the distance is too far, and the control signal received by the decoder is too weak.
Solution: At this time, a relay box should be installed at a certain distance to amplify the shaping control signal.
6. DVR-related faults DVR equipment involves the computer-related knowledge and applications, the use of the process will often appear "inexplicable" failure, and often are not well resolved, no way to start. The following classifications are based on different failure phenomena.
A. Symptom Description: Digital video recorder can not start.
Analysis of the reasons: the host power switch failure; host power supply damage; the host motherboard or CPU card is bad; the main system hard disk boot area is damaged, or the hard disk itself fails; the operating system is destroyed.
Solution: The above reasons should be carefully analyzed and eliminated one by one.
B. Symptoms Description: Digital hard disk video recorder crashes (images that are monitored on the spot or the time information superimposed on the image does not go away).
Analysis of reasons: software problems, including failure of the operating system or monitoring software in the PC-based hard disk host base, monitoring software problems for the embedded hard disk video recording host, a file in the system software being destroyed, and the disk in the host computer having a disk Bad roads; host power supply is not enough; host too many hard drives, too much heat; the host video card heat is too large and so will cause a crash.
Solution: Reinstall the system or monitoring software for the PC hard disk host; the embedded host needs to upgrade the software; repair or replace the hard disk; replace the high-power power supply; replace the video card or replace the host.
C. Symptom Description: Automatic shutdown.
Analysis of reasons: Today's mainstream motherboards have a temperature monitoring function on the CPU. Once the CPU temperature is too high and exceeds the temperature set in the motherboard BIOS, the motherboard will automatically cut off power to protect the relevant hardware. On the other hand, power management and virus software in the system can also cause automatic shutdown.
Solution: If the above abrupt shutdown phenomenon occurs frequently, first confirm whether the CPU heat dissipation is normal. Open the chassis and visually check whether the fan blades are working properly. Then enter the BIOS options to see the fan speed and CPU operating temperature. If the fan is a problem, perform related dust removal maintenance on the fan or replace the fan with better quality. If the power supply is aged or damaged, it can be confirmed by replacing the power supply. If the power supply is broken, replace it with a new one to prevent burning the hardware. Of course, it may also be poisoning, enter the system, cover the installation of power management from the installation CD, and then thoroughly kill the virus. At the same time, it is necessary to constantly update the antivirus software virus database and use less pirated disks. Do not download unsolicited mail attachments.
D. Symptoms Description: Hard disk video recorders often crash after the hardware upgrade, restart, such as adding hard drives, increase burner, replace high-performance graphics cards.
Analysis of the reasons: When upgrading a DVR, for example, installing a high-speed optical drive, the speed is high and the power consumption is also large, which increases the load of the power supply and causes a crash or restart. The original power supply did not take into consideration current power consumption of hard disks, video cards, and high-speed optical drives, so the output power of the power supply was not too high. Plus, some no-name power supplies themselves “shrink†and could not provide enough power when the system The increase in the number of equipment, power consumption becomes larger, the output voltage of poor quality power supply will be sharply reduced, eventually leading to system instability, automatic restart phenomenon.
Solution: Replace a high-quality, high-quality power supply.
(II) Intrusion alarm system
Intrusion alarm system is also called anti-theft alarm system. It is generally composed of four parts: the front-end detection element, transmission line, alarm host and computer host. The front-end detection elements mainly include door magnetic switches, glass break detectors, emergency alarm buttons, and infrared intrusion detectors. These devices form a three-dimensional, all-directional distribution control network, collect field conditions and transmit various types of signals. Return to the host. The transmission line transmits the information obtained by the front-end detection element to the alarm host through the communication line, and powers the front-end detection element through the power line. The alarm host makes an alarm when there is alarm information input, just like the human brain, and it is the processing part of the entire system. The computer host is equipped with a system supporting alarm management software. The alarm management software is a management software directly connected to the alarm host. The alarm host can be managed. The alarm data and alarm mode of the alarm host are expressed in the form of tables and maps. The failure of the alarm system is mostly caused by false alarms, and many fault phenomena are related to the brand and model of the alarm system. In other words, the alarm systems of different brands and models will have unique technologies of their own systems. Characteristics, including the phenomenon of failure, so the fault phenomenon of the alarm system should be a specific analysis of specific issues to find targeted solutions. The following is a brief analysis of the failures of false alarms.
Symptom Description: It is generally believed that there is no dangerous situation. The alarm signal sent by the anti-theft alarm system is false alarm. The definitions of false alarms in some western countries refer to alarm signals that are not required for actual situations, and do not include those caused by adverse natural climates and other special environments that cannot be manipulated by alarm companies and users.
Analysis of reasons: There are various causes for false alarms in the alarm system. Some of them are the quality problems of the equipment itself, some are operational problems of the operators, and some are the influence of the natural environment. To sum up, there are the following: a. Equipment caused by equipment quality problems Failures are usually caused by damage to components or poor production processes (such as soldering, etc.), or they may be caused by changes in factors such as ambient temperature, component manufacturing processes, equipment manufacturing processes, usage time, storage time, and power supply load. Faults caused by changes in component parameters; b. false alarms caused by improper equipment selection during system design. For example, the use of shock detectors near sources (airfields, railroads) can easily cause false alarms in the system, and they often appear in bats. The use of ultrasonic probes in the place will also make the system falsely alarm. This is because the bat emits ultrasonic waves, and high-frequency sounds such as electric bells and metal impact sounds can cause false alarms of glass break detectors; c. Installation location of detection equipment, Improper alarm due to improper installation angle, eg passive infrared Intrusion detectors can cause false alarms when installed against air conditioners and ventilation fans. d. Inadequate alarms due to environmental noises. For example, hot air flow can cause false alarms from passive infrared intrusion detectors, and high-frequency noise can cause glass break detectors. Incorrect alarms, intrusion alarms caused by intrusion of small animals, etc.
Solution: In view of the above causes of false alarms, it is generally considered to eliminate the faults from the following points: a. Use the replacement method to eliminate the fault of the device itself. If it is a device fault, repair or replace the device and solve the problem. If the fault of the device is eliminated, then Continue to find the reasons; b. due to improper device selection caused by the wrong alarm, after confirming the reasons can consider using other detectors instead of existing detectors; c. detector installation location and angle caused by false alarms according to the site conditions to adjust The position and angle of the detector are not affected by the best; d. The false alarm caused by environmental harassment is generally considered replacing the Shuangjian or Sanjian detectors (detectors of several different principles detect the “target†at the same time, and the alarm will only be issued Alarm detectors are used to eliminate false alarms, such as microwave-passive infrared detectors, voice-vibrating glass breaker detectors, and ultrasonic-passive infrared detectors.
(III) Access Control System
The entrance and exit control system is extended from the traditional sense of the access control system. It is generally considered that the entrance and exit control system is the access control system in the project, mainly considering the wide application of the access control system and the importance of the access control system in terms of function. The following mainly focuses on the access control system for analysis and discussion. The access control system consists of a reading section, a transmission section, a management/control section and an execution section, and corresponding system software, and generally includes a card reader, a controller, an electromagnetic lock, an exit button, a card, and a computer. The failure of the access control system is related to system software and controllers.
1. In an independent access control system, it is often impossible to open the door, that is, after the card is swiped or the password is entered, the lock cannot be opened.
Cause analysis and solution: First determine the validity of the card or password. Under normal circumstances, the card or password will not be lost. If the lock is not unlocked and the situation is urgent, the power supply of the access control will be directly cut off, the lock will be opened, and the general access lock will be powered off; the second is that some poor quality electric plug locks will work for a long time and will be caused by external reasons. If the mechanical locks up, if the lock can't be unlocked, it can be directly powered off. Then, if the lock is not working, shake or toggle until the lock is unlocked.
2. In an independent access control system, the card or password can open the door, and the internal exit switch cannot open the door.
Analysis of the reasons and solutions: Open the door switch to see if the inside of the wiring is normal, such as broken or disconnected wires, connected to eliminate faults; if the system is used for access control power supply, but also check the access control power is good or bad; There may also be problems with access control machines, which can be solved one by one.
Concluding Remarks The security protection project involves many disciplines such as electronics, machinery, materials, computers, and network information. The technology is relatively advanced and the composition is relatively complex. The causes of various problems are various and involve many factors. After the completion of the project, we should analyze the specific issues in detail and carefully look for the cause of the problem. The general principle is to simplify the problem from the simple to the most complex. After the determination, a reasonable and operational rectification plan should be studied and formulated according to the cause of the problem. It should be as fast, accurate, and economical as possible. The problem should be solved with the least time, labor, and economic costs. Of course, the best solution is to prevent problems from occurring. This requires us to actively consider ways to plan solutions, system design, equipment selection, installation and commissioning during the entire implementation of the project. Eliminate and avoid the emergence of various problems
PTZ failure may have the following aspects
1. Unable to control PTZ 2. Unable to control the decoder 3. Some functions cannot be achieved 4. The signal indicator of the code converter does not work
1. The code turn light does not flash software settings (lights do not flash, mainly the code converter does not work, first set up from the software to solve this problem)
1. Decoder settings in the software (decoder protocol, COM port, baud rate, parity, data bits, stop bits)
2. Replace a COM port (check if the COM port is damaged)
3. Hardware, such as the above settings, still can not be used normally, open the 9-pin to 25-pin converter interface. Check whether the wiring is 2-2, 3-3, 5-7. If it is correct, check if the power of the code converter is normal (available with a multimeter for voltage and current testing (9V, 500MA)). No problem can be determined by the code converter. Damaged 2. There is no control over the relay sound in the decoder decoder.
1. Check if the decoder is powered.
2. Check the code converter to pull out the output 485 signal.
3. Check if the decoder protocol is set correctly. Check whether the baud rate setting is consistent with the decoder (check the address code setting is consistent with the selected camera (detailed address code dialing table, see the decoder manual)
5. Check the decoder and the code converter wiring is wrong (1-485A, 2-B; some decoder is 1-485B, 2-A)
6. Check whether the decoder works normally (when the old decoder powers off after a minute, if there is a self-test sound; when the software controls the PTZ, there will be voltage changes between the UP, DOWN, AUTO ports of the decoder and the PTCOM port. According to the decoder, the condition may be 24VOR220V, some of the decoders will have a switch signal change on these ports), if any, the decoder works normally, otherwise it is a decoder failure. Check whether the fuse of the decoder has been burned out.
3. Unable to control PTZ 1. Check if the sixth item above is normal. Decoder 24V or 220V power supply port output is normal 3. Directly power the UP, DOWN, and PTCOM lines of the PTZ to check if the PTZ can work normally.
4. Check whether the power supply interface is connected wrongly. Check whether the circuit is connected to the wrong (the old decoder is UP, DOWN, etc. and PTCOM directly to the cloud platform power supply, each line directly connected to the camera and PTZ each line can be; some decoders for the independent power supply interface 4. PTZ Some functions of the control cannot be used 1. The interface cannot be operated (can't click or click without any response)
1. Follow the above steps to check the code turn 2. Install the corresponding PTZ control patch 3. Notify the supplier 2. Click on the time code to turn on the light or there is a relay inside the decoder, but some functions cannot be controlled. Check whether the wiring of the function part that can not be controlled by the inspection is correct, whether the PTZ, lens and other equipment are in good condition, whether the voltage of the decoder function port is on, and whether the output of the switch is normal. If the pan/tilt operation is abnormal during the control, if the rotation cannot be stopped, first test the port separately (power it directly to the port for control). If it is normal, check if the corresponding port of the decoder works properly. When you open the software, the video will generate a mosaic
The causes of various problems are various and involve many factors, such as system design, equipment selection, on-site environment, construction quality, personnel quality, and material quality. During the entire implementation process of the project, we should proactively think of ways to plan solutions, system design, equipment selection, installation and debugging, and take precautions to prevent and avoid various problems. This is a daunting and complicated task. The participants need to have a relatively solid professional theoretical knowledge and rich practical experience. However, no matter how hard we try to think of and accomplish, the problem has always been with us, and we cannot avoid it. This article does not discuss how to prevent or avoid the occurrence of problems. It simply summarizes and enumerates some common problems that are easy to occur after the completion of the safety precautions project, and the frequency of occurrence is relatively high. At the same time, the possible solutions are described and are for reference only.
I. Classification of Security and Prevention Engineering Subsystems
The safety precautions project can be divided into several subsystems according to its functions, generally including: intrusion alarm system; video surveillance system; entrance and exit control system; electronic inspection system; parking management system; building intercom system; explosion-proof safety inspection system; emergency broadcast system Wait. There are many “versions†of this sort according to function in the industry. According to the detailed level of classification, the principle of classification, etc., there are many kinds of classification results, but the frequency of use in security prevention projects is high, indispensable and cannot be replaced. There are several kinds of application subsystems. Because these subsystems are used frequently and widely used, problems often arise in these systems. Some of these problems are common problems that arise in various systems, such as power supply failures, line transmission failures, and on-site interference. Some of them are system-specific issues such as image quality problems in video surveillance systems, false alarms in intrusion alarm systems, and so on. Problems that occur at the same time or in conjunction with each other, such as the linkage of video surveillance systems and intrusion alarm systems. In order to facilitate analysis and discussion, this article will categorize various common problems according to subsystems.
Second, common problems and solutions (A) video surveillance system
Video surveillance system generally consists of three parts: front-end equipment, transmission lines, control and display equipment. The front-end equipment mainly includes cameras, heads, and decoders to obtain information on monitoring targets; the transmission lines transmit the information obtained by the front-end equipments to the control center through video lines and communication lines, and supply power to the front-end equipments through the power cords; The display device mainly includes a matrix control host, a video recorder, a monitor, an image splitter, a power supply, a console, a TV wall, a control cabinet, etc. to complete the processing, switching, segmentation, and control of the transmitted information. In the video surveillance system, the failure of the equipment itself is generally relatively rare, even if it appears, it is relatively easy to solve, and most problems often appear in the construction, installation process of the transmission line laying, connection, control equipment connection. The following briefly describes some common faults in the video surveillance system.
1. No image display, no video signal failure phenomenon Description: The line is normally connected, after power on, the central control room display terminal no image display, hard disk recorder "no video signal", matrix, graphics dividers and other "Nosignal" prompt exists.
Analysis of the reasons: This phenomenon can generally be concluded that the front-end video signal is not normally transmitted back to the control device. The camera may not be normally powered and there is no work. The power line is disconnected, the camera is not powered on, the video line is disconnected, and the BNC head is not soldered securely.
Solution: First check whether the camera is powered on, whether it is working properly; if the camera is not powered, check the power supply, transformer, power cable, etc.; if the camera is powered on, you can use the exclusion method to connect the camera directly to the display terminal to observe, if not yet displayed, Then determine the camera failure, if there is an image display, you can determine the video transmission line is faulty, check the video cable and BNC connector, confirm the replacement of the cable or re-welding the BNC connector.
2. No image display, there is a video signal failure phenomenon Description: After the normal connection of the line, after power on, the central control room display no image display on the terminal, black screen, hard disk recorder "no video signal", matrix, graphic dividers and other "Nosignal" prompt does not exist.
Analysis of reasons: This phenomenon is similar to the first phenomenon described above but with essential differences. In general, transmission line failures can be ruled out, and no indications such as “no signal†or “Nosignal†appear. It is proved that the front-end video signal has been sent back to the control device. It may be that there is no illumination at the scene; the camera lens aperture is closed; the camera angle is not adjusted well; the monitor brightness is not adjusted properly; the camera power supply power is not enough.
Solution: First confirm that the scene lighting conditions are good, the camera surveillance area is the visible area, the display brightness parameters are set properly, then adjust the camera lens aperture, if there is still no image display, you can replace the camera test with the exclusion method, if the fault persists, then replace the power test .
3. The image quality is not good, there is interference This problem is a kind of fault phenomenon with high frequency of occurrence. It has various manifestations and complex reasons. It is a fault phenomenon that is not very good to deal with. It needs concrete analysis of specific problems, and it is targeted. solve. The following classifications are based on different failure phenomena.
A. Symptom Description: A black bar or white bar appears on the picture screen, and it slowly scrolls up or down.
Analysis of the cause: This phenomenon is generally caused by power interference or ground loop.
Solution: On the control panel, connect only the camera output signal with no problem to the nearest power source. If the above-mentioned interference phenomenon does not appear on the monitor, it means that the control panel has no problem; the next step is to use a portable monitor. Proximity to the video output of the front-end camera, and check each camera one by one; if so, proceed with processing; if not, the interference is caused by ground loops and other causes.
B. Symptom Description: There is a grainy disturbance on the image screen. When it is light, it will not overwhelm the normal image. In severe cases, the image cannot be viewed (or even destroy the synchronization).
Analysis of reasons: This phenomenon has more complicated reasons. It may be that the quality of the video transmission line is not good, especially the shielding performance is poor (the shielding network is not a good quality copper network, or the shielding network is too thin to be shielded); The line resistance of the video line is too large, resulting in a large attenuation of the signal is also aggravating the cause of the fault; the characteristic impedance of the video line is not 75 ohms, and the parameter exceeding the specification is one of the causes of the failure; the power supply system is not "clean" The power supply referred to here is not "clean" and refers to the superimposition of interference signals on the normal power supply. The interference signals on this power supply mostly come from equipment that uses thyristors in the power grid, especially large currents. High-voltage thyristor equipment, the pollution of the power grid is very serious, such as the power grid in the power SCR FM speed control device, SCR rectifier, SCR AC and DC conversion devices, etc.; or system There are strong sources of interference nearby.
Solution: If the cable quality problems, of course, the best way is to replace all the cables, replace the cable to meet the requirements; if the power supply system is not "clean" caused, as long as the entire system uses clean power or online UPS power supply Basically, it can be solved; if there is a strong interference source near the system, the solution is to strengthen the shielding of the camera, as well as the grounding of the pipeline of the video cable.
C. Description of fault phenomena: Deep and chaotic large-area moiré interference occurs on the image screen, so that the image is completely destroyed and the image and synchronization signals cannot be formed.
Analysis of the reasons: This phenomenon is generally caused by the short circuit and open circuit of the core wire of the video cable and the shielded network. This type of fault often occurs on BNC connectors or other types of video connectors.
Solution: Check carefully and process all BNC connectors that are connected to the camera with the interference.
D. Symptom Description: Several vertical bars with equal spacing are generated on the image screen.
Analysis of reason: This phenomenon is generally caused by the mismatch of the characteristic impedance of the transmission line, which is caused by the impedance mismatch caused by the characteristic impedance of the video transmission line is not 75 ohms. This interference phenomenon is caused by the characteristic impedance and distribution of the video cable. The parameters did not meet the requirements caused by the synthesis.
Solution: Generally, it can be solved by the method of “connecting resistors at the beginning†or “terminating resistors at the terminalsâ€.
E. Symptom Description: There are several fine fringes on the image screen.
CAUSE ANALYSIS: This phenomenon is generally due to a strong, high-frequency spatial radiation source near the transmission system, system front-end or central control room.
Solution: The solution to this situation is to strengthen the front-end and center equipment shielding, the use of steel pipe transmission lines and pipelines and a good grounding.
　　 4. The interference of the elevator camera image The interference problem of the elevator camera is a fault phenomenon often encountered in the project. This problem involves the cooperation with special special equipment (elevators), poor cable layout environment (elevator hoistway), and the construction site has Certain dangers and other reasons are often not easy to solve. The following analysis and explanation of this issue are separately given.
Symptom Description: The common phenomenon is that the image is displayed normally when the elevator is at a standstill. When the elevator is running, the image quality is obviously reduced, and the image is obviously disturbed. Even the image disappears. This phenomenon is particularly serious at the moment of starting and stopping the elevator; when other elevators are running, other The image quality of the elevator has been significantly reduced, interfered with, and even the image has disappeared. This is particularly serious at the moments when the elevator starts and stops. The image quality of the elevator camera is not good and various interference phenomena occur.
Analysis of Causes: The causes of various types of interference related to elevators are relatively complex. When dealing with problems, we must carefully analyze the reasons and apply the right medicine to the problem so that we can solve problems quickly and accurately. Power cables, lighting, fans, control, communications, and other cables are usually placed in elevator shafts, and various cables generate electromagnetic radiation. Similar to the principle of antenna reception, the coaxial cable will also “receive†these interferences, ie, it will interfere with the electromagnetic field and generate interference currents on the cable. This interference induced current will also cause interference induced voltage on the longitudinal resistance of the cable outer conductor (woven mesh). (Electromotive force), this interference induced voltage just in series in the video signal transmission circuit "long ground" in the formation of interference; elevators are now basically the use of AC variable frequency speed control technology, and the frequency conversion governor itself is also very strong The high-frequency spurious interference, this interference signal can enter the video surveillance system through the power line and space radiation, interfere with the video image; from the elevator car to take power directly, the elevator lighting lamp usually uses electronic ballasts, When electronic ballasts work, they also produce strong AC parasitic interference output, affecting video image quality.
Solution methods and matters needing attention: The installation of a video anti-jamming device is a convenient and quick method; selecting a video cable with a small attenuation coefficient, good shielding performance, and high tensile strength can improve its anti-jamming capability and reduce video attenuation. Consider carefully the problem of transmission attenuation. When selecting the cable, the thick cable is better than the thin cable. The SYWV physical foam cable is better than the solid SYV cable. The high-knit cable is better than the low-knit cable, and the copper core cable is better than the copper-clad steel cable. Copper braided wire is superior to aluminum-magnesium alloy braided wire; reasonable wiring can effectively avoid the interference signal being “coupled†through the cable, minimize the parallel bundle distance from other cables, and keep the video cable away from interference; the video cable exits the elevator shaft Should be in the middle of the well, because at this time the length of the video cable accompanying the well is only about half the depth of the well, and the shortest is the natural introduction of the least interference; in the elevator shaft, the video line is close to the vertical line of the well, and this part The cable runs through the metal pipe or metal slot to shield the influence of interference on this part of the cable; the power supply of the camera should be preferably centralized DC power supply, as far as possible Avoid taking power from the elevator car; video cable from the elevator shaft exit to the control center should take the metal pipe or take the metal slot to shield the impact of environmental interference on this part of the cable, and pay attention to this part of the shielding and shielding in the elevator shaft , should make electrical connection; video camera metal casing, NC head housing, coaxial cable outer conductor and other video signal "ground", and the elevator car, rails, etc. to be insulated; in special circumstances can use the signal line single end Grounding ground input method.
　 5. PTZ, high-speed ball can not control, control failure This problem is also a high frequency of failure phenomena, there are also a variety of forms of expression, the reason is also complex and diverse, and processing requires more practical experience and strong The theoretical knowledge, and careful analysis of the causes of failure, to determine a reasonable and targeted solution. The following classifications are based on different failure phenomena.
A. Symptoms Description: The pan/tilt does not work or does not rotate at all after use, but it can operate normally during installation and commissioning.
Analysis of reasons: Only the pan/tilt head mounted on the camera is allowed to use the hoisting method. In this case, the hoisting method leads to an increase in the operating load of the pan/tilt. Therefore, the transmission mechanism of the pan/tilt will be damaged soon after use. Even if the total weight of the camera and its protective cover exceeds the load-bearing weight of the PTZ, especially the PTZ used outdoors, the weight of the protective cover is often too large, and often the PTZ will not turn (especially the vertical direction can't move) ) Problem; Outdoor PTZ due to high ambient temperature, too low, waterproof, antifreeze measures and failure and even damage.
Solution: Use the device strictly according to the technical parameters and environment requirements of the PTZ and the camera. After eliminating the other reasons to confirm the PTZ and other device problems, consider repairing or replacing the device.
B. Symptom Description: When the distance is too far, the keyboard cannot be controlled by the decoder on the camera (including the lens) and the head.
Analysis of reason: This is mainly because the control signal is too attenuated when the distance is too far, and the control signal received by the decoder is too weak.
Solution: At this time, a relay box should be installed at a certain distance to amplify the shaping control signal.
6. DVR-related faults DVR equipment involves the computer-related knowledge and applications, the use of the process will often appear "inexplicable" failure, and often are not well resolved, no way to start. The following classifications are based on different failure phenomena.
A. Symptom Description: Digital video recorder can not start.
Analysis of the reasons: the host power switch failure; host power supply damage; the host motherboard or CPU card is bad; the main system hard disk boot area is damaged, or the hard disk itself fails; the operating system is destroyed.
Solution: The above reasons should be carefully analyzed and eliminated one by one.
B. Symptoms Description: Digital hard disk video recorder crashes (images that are monitored on the spot or the time information superimposed on the image does not go away).
Analysis of reasons: software problems, including failure of the operating system or monitoring software in the PC-based hard disk host base, monitoring software problems for the embedded hard disk video recording host, a file in the system software being destroyed, and the disk in the host computer having a disk Bad roads; host power supply is not enough; host too many hard drives, too much heat; the host video card heat is too large and so will cause a crash.
Solution: Reinstall the system or monitoring software for the PC hard disk host; the embedded host needs to upgrade the software; repair or replace the hard disk; replace the high-power power supply; replace the video card or replace the host.
C. Symptom Description: Automatic shutdown.
Analysis of reasons: Today's mainstream motherboards have a temperature monitoring function on the CPU. Once the CPU temperature is too high and exceeds the temperature set in the motherboard BIOS, the motherboard will automatically cut off power to protect the relevant hardware. On the other hand, power management and virus software in the system can also cause automatic shutdown.
Solution: If the above abrupt shutdown phenomenon occurs frequently, first confirm whether the CPU heat dissipation is normal. Open the chassis and visually check whether the fan blades are working properly. Then enter the BIOS options to see the fan speed and CPU operating temperature. If the fan is a problem, perform related dust removal maintenance on the fan or replace the fan with better quality. If the power supply is aged or damaged, it can be confirmed by replacing the power supply. If the power supply is broken, replace it with a new one to prevent burning the hardware. Of course, it may also be poisoning, enter the system, cover the installation of power management from the installation CD, and then thoroughly kill the virus. At the same time, it is necessary to constantly update the antivirus software virus database and use less pirated disks. Do not download unsolicited mail attachments.
D. Symptoms Description: Hard disk video recorders often crash after the hardware upgrade, restart, such as adding hard drives, increase burner, replace high-performance graphics cards.
Analysis of the reasons: When upgrading a DVR, for example, installing a high-speed optical drive, the speed is high and the power consumption is also large, which increases the load of the power supply and causes a crash or restart. The original power supply did not take into consideration current power consumption of hard disks, video cards, and high-speed optical drives, so the output power of the power supply was not too high. Plus, some no-name power supplies themselves “shrink†and could not provide enough power when the system The increase in the number of equipment, power consumption becomes larger, the output voltage of poor quality power supply will be sharply reduced, eventually leading to system instability, automatic restart phenomenon.
Solution: Replace a high-quality, high-quality power supply.
(II) Intrusion alarm system
Intrusion alarm system is also called anti-theft alarm system. It is generally composed of four parts: the front-end detection element, transmission line, alarm host and computer host. The front-end detection elements mainly include door magnetic switches, glass break detectors, emergency alarm buttons, and infrared intrusion detectors. These devices form a three-dimensional, all-directional distribution control network, collect field conditions and transmit various types of signals. Return to the host. The transmission line transmits the information obtained by the front-end detection element to the alarm host through the communication line, and powers the front-end detection element through the power line. The alarm host makes an alarm when there is alarm information input, just like the human brain, and it is the processing part of the entire system. The computer host is equipped with a system supporting alarm management software. The alarm management software is a management software directly connected to the alarm host. The alarm host can be managed. The alarm data and alarm mode of the alarm host are expressed in the form of tables and maps. The failure of the alarm system is mostly caused by false alarms, and many fault phenomena are related to the brand and model of the alarm system. In other words, the alarm systems of different brands and models will have unique technologies of their own systems. Characteristics, including the phenomenon of failure, so the fault phenomenon of the alarm system should be a specific analysis of specific issues to find targeted solutions. The following is a brief analysis of the failures of false alarms.
Symptom Description: It is generally believed that there is no dangerous situation. The alarm signal sent by the anti-theft alarm system is false alarm. The definitions of false alarms in some western countries refer to alarm signals that are not required for actual situations, and do not include those caused by adverse natural climates and other special environments that cannot be manipulated by alarm companies and users.
Analysis of reasons: There are various causes for false alarms in the alarm system. Some of them are the quality problems of the equipment itself, some are operational problems of the operators, and some are the influence of the natural environment. To sum up, there are the following: a. Equipment caused by equipment quality problems Failures are usually caused by damage to components or poor production processes (such as soldering, etc.), or they may be caused by changes in factors such as ambient temperature, component manufacturing processes, equipment manufacturing processes, usage time, storage time, and power supply load. Faults caused by changes in component parameters; b. false alarms caused by improper equipment selection during system design. For example, the use of shock detectors near sources (airfields, railroads) can easily cause false alarms in the system, and they often appear in bats. The use of ultrasonic probes in the place will also make the system falsely alarm. This is because the bat emits ultrasonic waves, and high-frequency sounds such as electric bells and metal impact sounds can cause false alarms of glass break detectors; c. Installation location of detection equipment, Improper alarm due to improper installation angle, eg passive infrared Intrusion detectors can cause false alarms when installed against air conditioners and ventilation fans. d. Inadequate alarms due to environmental noises. For example, hot air flow can cause false alarms from passive infrared intrusion detectors, and high-frequency noise can cause glass break detectors. Incorrect alarms, intrusion alarms caused by intrusion of small animals, etc.
Solution: In view of the above causes of false alarms, it is generally considered to eliminate the faults from the following points: a. Use the replacement method to eliminate the fault of the device itself. If it is a device fault, repair or replace the device and solve the problem. If the fault of the device is eliminated, then Continue to find the reasons; b. due to improper device selection caused by the wrong alarm, after confirming the reasons can consider using other detectors instead of existing detectors; c. detector installation location and angle caused by false alarms according to the site conditions to adjust The position and angle of the detector are not affected by the best; d. The false alarm caused by environmental harassment is generally considered replacing the Shuangjian or Sanjian detectors (detectors of several different principles detect the “target†at the same time, and the alarm will only be issued Alarm detectors are used to eliminate false alarms, such as microwave-passive infrared detectors, voice-vibrating glass breaker detectors, and ultrasonic-passive infrared detectors.
(III) Access Control System
The entrance and exit control system is extended from the traditional sense of the access control system. It is generally considered that the entrance and exit control system is the access control system in the project, mainly considering the wide application of the access control system and the importance of the access control system in terms of function. The following mainly focuses on the access control system for analysis and discussion. The access control system consists of a reading section, a transmission section, a management/control section and an execution section, and corresponding system software, and generally includes a card reader, a controller, an electromagnetic lock, an exit button, a card, and a computer. The failure of the access control system is related to system software and controllers.
1. In an independent access control system, it is often impossible to open the door, that is, after the card is swiped or the password is entered, the lock cannot be opened.
Cause analysis and solution: First determine the validity of the card or password. Under normal circumstances, the card or password will not be lost. If the lock is not unlocked and the situation is urgent, the power supply of the access control will be directly cut off, the lock will be opened, and the general access lock will be powered off; the second is that some poor quality electric plug locks will work for a long time and will be caused by external reasons. If the mechanical locks up, if the lock can't be unlocked, it can be directly powered off. Then, if the lock is not working, shake or toggle until the lock is unlocked.
2. In an independent access control system, the card or password can open the door, and the internal exit switch cannot open the door.
Analysis of the reasons and solutions: Open the door switch to see if the inside of the wiring is normal, such as broken or disconnected wires, connected to eliminate faults; if the system is used for access control power supply, but also check the access control power is good or bad; There may also be problems with access control machines, which can be solved one by one.
Concluding Remarks The security protection project involves many disciplines such as electronics, machinery, materials, computers, and network information. The technology is relatively advanced and the composition is relatively complex. The causes of various problems are various and involve many factors. After the completion of the project, we should analyze the specific issues in detail and carefully look for the cause of the problem. The general principle is to simplify the problem from the simple to the most complex. After the determination, a reasonable and operational rectification plan should be studied and formulated according to the cause of the problem. It should be as fast, accurate, and economical as possible. The problem should be solved with the least time, labor, and economic costs. Of course, the best solution is to prevent problems from occurring. This requires us to actively consider ways to plan solutions, system design, equipment selection, installation and commissioning during the entire implementation of the project. Eliminate and avoid the emergence of various problems
PTZ failure may have the following aspects
1. Unable to control PTZ 2. Unable to control the decoder 3. Some functions cannot be achieved 4. The signal indicator of the code converter does not work
1. The code turn light does not flash software settings (lights do not flash, mainly the code converter does not work, first set up from the software to solve this problem)
1. Decoder settings in the software (decoder protocol, COM port, baud rate, parity, data bits, stop bits)
2. Replace a COM port (check if the COM port is damaged)
3. Hardware, such as the above settings, still can not be used normally, open the 9-pin to 25-pin converter interface. Check whether the wiring is 2-2, 3-3, 5-7. If it is correct, check if the power of the code converter is normal (available with a multimeter for voltage and current testing (9V, 500MA)). No problem can be determined by the code converter. Damaged 2. There is no control over the relay sound in the decoder decoder.
1. Check if the decoder is powered.
2. Check the code converter to pull out the output 485 signal.
3. Check if the decoder protocol is set correctly. Check whether the baud rate setting is consistent with the decoder (check the address code setting is consistent with the selected camera (detailed address code dialing table, see the decoder manual)
5. Check the decoder and the code converter wiring is wrong (1-485A, 2-B; some decoder is 1-485B, 2-A)
6. Check whether the decoder works normally (when the old decoder powers off after a minute, if there is a self-test sound; when the software controls the PTZ, there will be voltage changes between the UP, DOWN, AUTO ports of the decoder and the PTCOM port. According to the decoder, the condition may be 24VOR220V, some of the decoders will have a switch signal change on these ports), if any, the decoder works normally, otherwise it is a decoder failure. Check whether the fuse of the decoder has been burned out.
3. Unable to control PTZ 1. Check if the sixth item above is normal. Decoder 24V or 220V power supply port output is normal 3. Directly power the UP, DOWN, and PTCOM lines of the PTZ to check if the PTZ can work normally.
4. Check whether the power supply interface is connected wrongly. Check whether the circuit is connected to the wrong (the old decoder is UP, DOWN, etc. and PTCOM directly to the cloud platform power supply, each line directly connected to the camera and PTZ each line can be; some decoders for the independent power supply interface 4. PTZ Some functions of the control cannot be used 1. The interface cannot be operated (can't click or click without any response)
1. Follow the above steps to check the code turn 2. Install the corresponding PTZ control patch 3. Notify the supplier 2. Click on the time code to turn on the light or there is a relay inside the decoder, but some functions cannot be controlled. Check whether the wiring of the function part that can not be controlled by the inspection is correct, whether the PTZ, lens and other equipment are in good condition, whether the voltage of the decoder function port is on, and whether the output of the switch is normal. If the pan/tilt operation is abnormal during the control, if the rotation cannot be stopped, first test the port separately (power it directly to the port for control). If it is normal, check if the corresponding port of the decoder works properly. When you open the software, the video will generate a mosaic
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