The access control system is a subsystem of the access management system. Usually, it adopts technologies such as credit card, password or human biometric identification. Under the control of the management software, it manages the entrance and exit of personnel or vehicles, so that the people who have obtained the approved entry and exit are free to pass. For those who should not go in and out, it is forbidden. Therefore, in many places where the identity of people and vehicles needs to be checked, the access control system has become an indispensable configuration item. In this issue, we will discuss the technology of access control network communication applications.
Engineering principle and transmission line
Engineering principle
The engineering principle of the access control system is basically similar to that of other automatic control systems or intelligent building systems. Its operation can be divided into three parts: sensing, management and execution, but it is relatively compact and relatively simple.
Sensing: Card readers, PIN pads, various biometric readers, exit buttons, and lock status sensors are all sensor components. Their task is to accept commands, upload signals or post-check (biometric).
Management: The controller and management software bear the management function of the access control system. After receiving the information sent by the sensor, they judge whether to open the door according to the time, card number and other information. If the door is opened, the door opening command is issued to the electric lock. When the lock status information is received, the timing starts and the timeout alarms.
Execution: When the electric lock receives a command to open or close the door (power or power off), its "execute" command adjusts the working state to match the command. The lock status sensor in the electric lock plays a role of feedback and supervision.
Some controllers can use relays to output control signals to control linked cameras and lights.
Transmission line
According to the working principle, 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 in the equipment room to avoid malfunction during power failure. The power cord is usually in a 220V AC transfer mode to reduce the voltage drop across the power supply. 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 in the power line, which is liable to cause power fluctuation, and this power fluctuation is extremely disadvantageous for the stable operation of the controller. Therefore, in an access control system with high reliability requirements, the controller and the electric lock respectively use different power supply modules, that is, 220V AC power supply to the controller, and the two 12V DC power supply modules are respectively rectified/regulated and respectively supplied. Electric lock and controller. The selection of various power cords is basically based on an electrician's manual, using a standard power cord.
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