이름 : Warren
이메일 : warrenmccormick@yahoo.co.in
연락처 :
예식일 : Kids, Work and Rs485 Cable
문의내용:

The normal way to implement this is with a two wire system with differential signal levels. The RJ11 socket in the Unitronics PLCs provides six signal pins. Especially when the transmission is carried over a long wire outdoor, the wires is potential to carry the dangerous signal like lightning or other high voltage induction. This provides high noise immunity and allows distances up to 4,000 ft (1200 meters). The RS485 interface allows the creation of multi-point networks. A symmetrical pin-layout allows two DTEs, data terminal equipment, to be connected directly without use of a modem or other DCE, data communication equipment. By using two jacks, up to 31 L485 boards can be connected in parallel for daisy chaining using readily available CBL03 data cables with no need for a hub. If we want to connect a PC with an Unitronics PLC, for example for programming or debugging reasons, we need a connection cable which is on one side fitted with a female DB9 connector, and on the other side with an RJ11 jack. Below you will see a cabling example for one master and two slaves in a full-duplex and a half-duplex situation.

With RS485 it is possible to set-up a multi-point application with one master and several slaves. The RS485 system used for Modbus communication provides a main cable (Bus or backbone), to which all the devices have to be connected with branches (also known as stubs) that are as short as possible. On some PLC models it is possible to mix RS232 and RS485 communications. This module is powered by the RS232 port from the connecting computer. The only way to add RS232 capabilities to the Jazz PLCs is by using the MJ20-PRG programming port add-on module. This MJ20-PRG module clicks in the PLC and provides one RJ11 socket for serial communications with a PC. Therefore the pin assignment is a little bit different from the default pin assignment on the RJ11 socket. The existence of an RS485 port on the socket makes it even a little bit more difficult. The diagram below shows a basic RS485 cable for use with the RJ11 socket on Unitronics PLCs. It shouldn’t however be a surprise that the pin assignment on the RJ11 socket on Unitronics PLCs is different from the two systems mentioned above. When the DSR and DTR signals are not used, the two pins can be used for simultaneous RS485 communication.

Pin 1 and 6 however are reassigned to the A and B lines when the port is used in RS485 mode. When in RS485 mode, only in 1 and 6 are reassigned. In order to avoid errors when many devices are connected, cables of the same colour should be used for all the connections to the terminals A and cables of the same colour should be used for all the connections to the terminals B of the various devices (e.g. white for A and blue for B). Can I mix Laureate LT transmitters and meters on the same RS485 line? Not more than one breakout board is required per RS485 line. If the PC is connected to the multiple Laureate instruments on an RS485 bus via an Ethernet-to-RS-485 gateway board or a USB-to-RS485 gateway board, use Laurel’s free XLOG2 datalogging software. Use Laurel’s 6-wire data cables CBL03-1 (1 ft) and CBL03-7 (7 ft) to interconnect meters if these lengths fit your application.

Laureate meter and LT series transmitters support the Modbus RTU protocol and Laurel’s simpler ASCII character based Custom ASCII protocol. If multiple analog input meters or transmitters are digitally addressed in command mode on an RS485 line using the Modbus RTU protocol or the Custom ASCII protocol, the rate becomes about 2 readings per second. Setup is the same when multiple meters are interconnected via cables CBL03, except that all meters now need to be set to a different digital address via their front panel. These cables allow the dual RJ11 jacks of the RS485 option board of Laureate meters (digital interface ordering option 2) to be daisy chained and to be addressed digitally with no need for a hub. Almost all devices include these, certainly the USR box, and you shouldn’t need to worry about these unless something really weird goes on. The A signals of all devices should be connected with each other and the same goes for the B signals. Grown up RS485 devices (the expensive industrial stuff) has isolated interfaces, but the kind of cheap stuff we use at home does not. On the Raspberry Pi, we also installed a 1-Wire Pi Plus board, and this is used with a temperature sensor fitted in the shed to monitor the air temperature, which is also posted to the MQTT server and Home Assistant.