Siemens 505 Redundance

  • Thread starter Jairo Javier Rodriguez
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Jairo Javier Rodriguez

I have a pseudo redundant system with PLC´s SIEMENS 545 using two Peer Links modules, the secondary PLC´s in when the primary is cut off but the primary plc data is not copy in the secondary PLC. The redundance in the 505 is made in the PLC program. Any body know this redundant routine or have any paper or information of redundant programming routine for PLC 505 series. I know that can use redundant modules but can not change the original hardware configuration in the system. Thanks in Advance, Eng. Jairo Rodríguez

Gilles Allard

I do not fully understand your post and without looking at the 545 program, I do not guarantee that my answer is correct. The PeerLink modules will exchange data between 545 (16 words per PeerLink module per scan) So, the Peerlink may be used to update the backup controller with important state data. PeerLink may also be used in a bidirectional data exchange. This ensures that the two PLC are somewhat data-synchronized but redundancy requires more that that. Where are located your I/Os? In the PLC chassis or in a remote base? If they are in the PLC chassis, you have to duplicate the I/O modules and install a switch (multipole relay) to select if the outputs are coming from one chassis or the other. If the I/Os are in a remote base, the solution may be to use a 2541 module from CTI. Look at: This module will be installed in the remote base and will supervise 2 PLCs. The I/O base will failover to the backup PLC in case of master PLC malfunction. I hope this help. Gilles