An industrial park smart parking lot fiber optic modem application case
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A parking lot is a public place for parking vehicles, and its main purpose is to store vehicles and collect parking fees. Since the parking lot has the functions of storage and charging, it is particularly important for vehicle access control (to prevent the loss of vehicles and prevent people from evading tolls). The parking lot was first managed manually (that is, the security registered at the entrance and exit of the vehicle is used to monitor the entry and exit of the vehicle), but the purely manual operation is prone to errors and possible corruption. With the continuous development of computer technology and electronic technology, people have produced intelligent parking lot systems to implement digital management of parking lots.
The intelligent parking lot system is a collection of computer technology, video surveillance technology, data communication technology andsmart cardA system composed of various technologies such as technology, and its main equipment includes various smart devices such as entrance and exit barriers, entrance and exit card readers, card issuers, and vehicle detection coils. Generally speaking, smaller parking lots generally have only one entrance and exit, that is, cars enter and exit together, and vehicles enter and leave through the same entrance, so that the data of vehicle entry and exit only needs to be stored on the computer in the entrance and exit booth. Management work can be completed, but if there are multiple entrances and exits in a relatively large parking lot, the entry and exit of vehicles may not be carried out at the same entrance and exit. If the data of each entrance and exit cannot be connected to the Internet, it will appear when the car leaves At that time, the computer cannot recognize the smart card and understand the entry and exit of the vehicle, so that it cannot effectively implement management. Large parking lots need to connect all entrances and exits through a certain communication line to achieve unified management.
The current intelligent parking lot system equipment basically has RS-485 communication interface. The communication distance of RS-485 bus can reach 1,200 meters, and it can reach 6 kilometers with the addition of 485 repeaters. It is used in parking lots. The system is generally sufficient, but the RS-485 bus wiring specifications require hand-in-hand wiring, and need to use shielded twisted pairs for separate wiring. Relatively speaking, the wiring cost is relatively high. In many cases, the parking lot system will use a variety of communication methods to achieve the purpose of networking based on on-site conditions. Here we introduce a case of using optical fiber and RS-485 bus combined communication.
Due to the large number of factories in an industrial park, the number of vehicles entering and leaving the park is also large. Due to the large area of the park, the park provides multiple entrances and exits for vehicles to enter and exit, making the management of the entire park very cumbersome. Vehicle management in the industrial park was initially implemented by means of security guards. Vehicles are required to enter and exit at designated entrances and exits, that is, they must leave at the entrance and exit to ensure that the security can effectively control the vehicles. Later, many vehicles needed to leave from another entrance and exit due to various reasons, which caused many disputes. From the perspective of the convenience of the factories in the park, the management office of the park decided that vehicles can leave at any entrance and exit, but when leaving, the security needs to use walkie-talkies and The guard box that enters will be released after communication. However, this caused great delays to the passage of vehicles, which resulted in a certain number of complaints.
After many discussions, the Industrial Park Management Office decided to build an intelligent parking system to implement unified management of vehicles in the park. Due to the presence of multiple vehicle entrances and exits in the park, it is necessary to build an entrance/exit barrier, entrance/exit card reader and card issuer at each entrance and exit. The implementation of unified management means that all data of each entrance and exit needs to be networked to the monitoring center for unified management. Since the parking lot system equipment has RS-485 bus interface, the construction party decided to use RS-485 bus to connect all the equipment. However, during the project construction evaluation, it was found that the entrances and exits are located in different directions in the park. If the bus topology connects all the devices, it needs to be wired around the entire park, which requires a large amount of construction and high construction costs.
The construction party discovered that there was a peripheral video surveillance project in the early stage of the park. Since the project was laying an optical cable around the park wall, the remaining optical fiber lines were still available for use due to redundancy considerations. The construction party decided to use fiber optic lines to transmit the relevant data of the parking lot system. It uses the N-271SM optical fiber modem of Shenzhen Guoke Weiye Communication Technology Co., Ltd. to complete this work. N-271 provides the function of serial port to optical fiber, which can convert RS-485 data signal into optical signal. After transmission through optical fiber, It is restored to RS-485 data signal and provided to the computer. It supports point-to-multipoint ring network operation mode, and its specific wiring conditions are as follows:
There are five entrances and exits in the park, and all data needs to be collected to the monitoring center. Six N-271 fiber optic modems are used here, of which a Master N-271 is placed in the monitoring center, and a Slave N-271 is placed at each of the five entrances and exits. 271 (respectively called ABCDE). Each N-271 has two optical fiber interfaces, which are connected and connected respectively. The specific wiring topology is: the connection outlet of the Master 271 in the monitoring center is connected to the inlet of A, and the outlet of A is connected to the outlet of B. The access ports are connected and connected in turn to connect the BCDE. Finally, the E port is connected to the Master 271 access port of the monitoring center, thus forming a topological structure of an optical fiber ring network. All N-271s communicate via optical fiber connections. All 485 devices in the parking lot system are connected to the N-271’s RS-485 interface, so that the data of the system can be exchanged through optical fiber.
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