The 10 Biggest Rs485 Cable Mistakes You Can Easily Avoid > 자유게시판

In fact, there is no such thing as an RS485 cable since RS485 is a protocol for serial communication (like between inverter and Zero export device) and Ethernet is a protocol for carrying internet data (between router and inverter) whereas CAT6 is a cable standard. A CAT6 cable can theoretically carry data for 100m but after 80m, there would be signal attenuation and it would be impractical. Without termination resistors, signal reflections off the unterminated end of the cable can cause data corruption. We trickle charge a battery pack at the end of our RS485 run so that peak loads are not a problem and the 25mA we put through the cable is sufficient on average to power our load. 4. Having a large enough battery bank is critical. 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. Although many applications use RS-485 signal levels, the speed, format, and protocol of the data transmission are not specified by RS-485. RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems.

Multiple receivers may be connected to such a network in a linear, multidrop bus. RS-485 standard conformant drivers provide a differential output of a minimum 1.5 V across a 54-Ω load, whereas standard conformant receivers detect a differential input down to 200 mV. RS-422 and RS-485 Standards Overview and System Configurations, Application Report (pdf). If a star configuration is unavoidable, special RS-485 repeaters are available which bidirectionally listen for data on each span and then retransmit the data onto all other spans. Be sure to use a wire pair such as the blue and blue/white pair for the data lines and a third wire or pair twisted together for the common connection. 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. The diagram below shows potentials of the A (blue) and B (red) pins of an RS-485 line during transmission of one byte (0xD3, least significant bit first) of data using an asynchronous start-stop method.

Under some conditions it can be used up to data transmission speeds of 64 Mbit/s. 1. I can use any brand LFP 48v battery including DIY batteries. You have used battery to each load so need not to transmit power via cable right? Or you have transmitted power via cable and also kept provision for battery? Ideally, the two ends of the cable will have a termination resistor connected across the two wires. This allows RS-485 to implement linear bus topologies using only two wires. RS-485 does not define a communication protocol; merely an electrical interface. All communication cabling to be installed in a daisy chain configuration, no T’s are permitted. Star and ring topologies are not recommended because of signal reflections or excessively low or high termination impedance. This connection may be used to limit the common-mode signal that can be impressed on the receiver inputs. Care must be taken that an SC connection, especially over long cable runs, does not result in an attempt to connect disparate grounds together - it is wise to add some current limiting to the SC connection. Splicing of communications cable is not permitted.

If you need more information on the cable & protocol, refer to the article below. DH 485 is a proprietary communications protocol used by Allen-Bradley in their line of industrial control units. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement industrial control systems, including the most common versions of Modbus and Profibus. SC, G or reference, the common signal reference ground used by the receiver to measure the A and B voltages. 5 should work in your situation because of the voltage you will be running (5-10V) and your signal is not high frequency (above 500Mhz) in the first place. And the results before was a degraded signal that the devices near the end would interpret the signal incorrectly. It should be connected to earth ground at one end only and not connected to any other ground points along the way. However this contradicts the facts that an idle mark state is a logical one and the termination polarization puts B at a higher voltage in Profibus guidelines. With Modbus, BACnet and Profibus, A/B labeling refers A as the negative green wire and B as the positive red wire, in the definition of the D-sub connector and M12 circular connector, as can be seen in Profibus guides.