According to the communication engineering principle of the access control system, there are several transmission lines in the access control system:
power cable
Most of the power supply of the access control system comes from the UPS of the equipment room, so as to avoid the malfunction of opening the door during sudden power failure. The power cord is usually in a 220V AC transfer mode to reduce the voltage drop on the power line. Beside the controller, equipped with a regulated power supply, the AC 220V power supply is converted into a DC 12V power supply, which is supplied to the controller and the electric lock respectively. Most of the electric locks used in the access control system belong to the 12V DC power supply mode. At the moment when the electric lock is broken, due to the action of the electric lock middle line package (electromagnet coil), a strong current is generated on the power line, which easily causes power supply fluctuation, and this power fluctuation is extremely stable for the controller. Unfavorable, so in the access control system with high reliability requirements, the controller and the electric lock respectively use different power modules, that is, when 220V AC power is supplied to the controller, after the two 12V DC power modules are respectively rectified/regulated, Supply the electric lock and controller separately. The selection of various power cords is basically based on an electrician's manual, using a standard power cord.
Controller signal line
There are three sets of signal lines in the controller, which are respectively connected to the card reader, the lock status sensor in the electric lock and the exit button. These three signal lines can be replaced by twisted pairs in the integrated wiring. In order to avoid electromagnetic interference in the space, the signal line of the card reader should be shielded, and the other two lines can be shielded or unshielded.
Remote network signal line
There is a signal line from the controller to the management computer. Its transmission protocol is mostly RS485. When it is close, it may be RS232 (to reduce one RS232/RS485 converter). When the transmission rate is fast, It uses TCP/IP protocol and uses Ethernet transmission. Twisted pair cables can be used for all three protocols, but shielded wires are basically required in the product manual of the access controller when transmitting RS485 or RS232. In order to avoid electromagnetic interference, this signal line should be shielded twisted pair. When the controller needs to use the output hard contact to directly control the hard disk video recorder (synchronous recording when the card is opened), the control cable (2-core) should be shielded to avoid the small amplitude of the input signal of the hard disk video recorder. False triggering due to electromagnetic interference. However, if the power supply of the illuminator is directly transmitted by a hard contact, the power cord should be used. According to the above analysis, when transmitting power (power supply for electric locks, controllers, and lamps), the power cord should be used. The cross-sectional area can be calculated based on the voltage drop and heat generated by the current, or it can be obtained from the electrician's manual. When transmitting sensor signals and control signals, shielded or unshielded wires should be selected according to the card reader and controller installation manual. With the increasing number of gates controlled by the access control system, the requirements for system network transmission speed and wiring safety are getting higher and higher, and the construction of the access control system is also required to simultaneously carry out the construction of the integrated wiring system. The use of network twisted pair as the transmission line of the access control system has become the main choice for the cable of the access control system. According to the analysis of various access control cables, the network twisted pair can be used for the signal lines and control lines between the card reader, the controller, and the management computer.
In the case of simultaneous access control systems and integrated wiring, network twisted pairs with distances shorter than 20 meters often do not meet the utilization value in integrated wiring engineering and become engineering waste lines. However, for these short-rejected wires, for distributed controllers, the exit button signal line, the card reader signal line, and the lock status signal line are often used as wiring. For the remote network signal line using TCP/IP protocol, it is necessary to use twisted pair transmission, which can completely realize signal remote transmission using the standard star structure of the integrated wiring system. The RS485 line and the RS232 line can also use the network twisted pair. According to the installation principle of the access controller, these devices should be shielded twisted pair to avoid malfunction caused by electromagnetic interference.
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