The basic communication mechanism of S485 and RS232 is the same. His advantage is that it makes up for the shortcoming of RS232 communication distance and can not carry out network management of multiple devices at the same time. The computer connects multiple 485 devices (access controllers) in turn through the RS232 RS485 converter, and polls the devices on the bus in turn. The wiring label is 485+ 485-, corresponding to 485+ 485- of the link device (controller). Communication distance: The distance between the farthest device (controller) and the computer is theoretically 1200 meters. It is recommended that the customer control within 800 meters and the best control within 300 meters. If the distance is too long, you can purchase 485 repeater (extension) (please buy it from a professional converter manufacturer, where the repeater is placed in the middle of the bus or at the beginning, please refer to the manufacturer's manual.) The repeater can theoretically be extended to 3000 meters. The number of loads: how many devices (controllers) a 485 bus can carry. This depends on the selection of the communication chip of the controller and the communication chip of the 485 converter. Generally, there are 32, 64, 128, and 256 This kind of choice, this is the theoretical number. In actual application, according to the scene environment, communication distance and other factors, the number of loads does not reach the number of indicators. The micro-farming company controller and converter are designed in 256 units, and it is actually recommended that the customer control each bus within 80 units. If there are hundreds of thousands of controllers, please use multi-port serial card or 485HUB to solve. For details, please refer to "If the number of system controllers is more than one hundred, how to network?" Resolutely prohibit the use of passive 485 converters. Please refer to "Why is the use of passive 485 converters prohibited?" 485 communication bus (must twisted pair, or one of the network cables), if you use ordinary wires (no twist), the interference will be very large, communication is not smooth, and even communication is not possible. Each controller device must be hand-in-hand, and there must be no star connection or fork. If there is a star connection or a fork, the interference will be very large, the communication will be poor, and even the communication will not be possible. Correct schematic diagram of RS485 wiring SHENZHEN CHONDEKUAI TECHNOLOGY CO.LTD , https://www.szfourinone.com
