What is RS485? > 자유게시판

Although the potential difference between the data-pair conductors determines the signal without officially involving ground, the bus needs a ground wire to provide a return path for induced common-mode noise and currents, such as the receivers' input current. If you do this, the system may radiate high levels of EMI, because the common-mode return current finds its way back to the source, regardless of where the loop takes it. The entire daisy chain network is ultimately connected to a PLC (Programmable Logic Controller), facilitating data exchange between multiple devices and the central control system. Within such a system, RS-485 serves a pivotal role as a bridge, establishing communication of flow information between the central control system and each valve box. This robustness is the main reason why RS-485 is well suited for long-distance networking in noisy environment. It is designed to handle long-distance communication and is known for its robustness and noise immunity.

RS-485 cables typically have two twisted pairs of wires for differential signaling, allowing for greater immunity to electromagnetic interference. The cables also have a balanced line configuration, which helps to further enhance noise rejection and signal integrity. In practice, Cat 5 cables have been used successfully in many installations, but there are some concerns. Overall, RS485 cables are known for their robustness, reliability, and versatility, making them a popular choice for industrial automation, building control systems, and other applications requiring stable and secure communication over extended distances. If you are planning to replace the cable between two existing RS485 nodes, you need a way to talk to the nodes on either side, and that would still be RS485. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. ● Use scientific and reserved solutions for 485 bus projects with long lines and heavy loads. Differential mode interference is transmitted between two signal lines and belongs to symmetrical interference. This utilization of a differential signal transmission mode effectively mitigates interference and enhances overall communication reliability.

• USB bulk transfer mode. • Entire USB to RS485 translation protocol handled by the electronics in the cable. 2. Ordinary twisted pair shielded cable STP-120Ω (for RS485 & CAN) one pair 18 AWG, the cable outer diameter is about 8.2mm. Suitable for indoor, pipeline and general industrial environment. The cable is shielded to further protect against interference and noise. Termination resistors also reduce electrical noise sensitivity due to the lower impedance. Among various topological structures, the Daisy Chain topology is considered the optimal choice for RS-485 due to its minimal impact on signal integrity. The characteristic feature of the Daisy Chain topology is the sequential connection of each device along a single line, what is rs485 cable not forming a loop structure. Network topology refers to the arrangement of various nodes (such as computers, servers, switches) in a computer network. End of line termination resistor (120 ohm 1/4 watt) to be installed at both ends of network. When in use, it is recommended that both ends of the armor layer be grounded and the innermost shielding end is grounded. In a computer system, SCSI-2 and SCSI-3 may use this specification to implement the physical layer for data transmission between a controller and a disk drive.

B- lines, with high and low voltages representing binary 1 and 0 (on and off), ensuring reliable data communication. Grounds between buildings may vary by a small voltage, but with very low impedance and hence the possibility of catastrophic currents - enough to melt signal cables, PCB traces, and transceiver devices. 5) together, preferably through shield, so there is no difference between grounds that could arise through using local grounds over the 1 km distance. Then the same difference is preserved between the two signals. Use a wire or shielded wire to connect the GND ground of all 485 devices, so as to avoid the potential difference between all devices that affects communication. Your 485 to 232 converter should have some information in the manual to tell you what cabling is needed to connect it, but since you are asking, it obviously doesn't say, or isn't clear. ● If the communication distance is too long, such as over 500 meters, it is recommended to use a repeater or 485 HUB to solve it. The recommended arrangement of the wires is as a connected series of point-to-point (multidropped) nodes, i.e. a line or bus, not a star, ring, or multiply connected network.