s7-1500 - PLC Programming & Automation

Redundant PLC Systems: ControlLogix Pairs and S7-1500R/H

Timing chart of a redundancy switchover: chassis A stops being primary, chassis B takes over, the remote I/O connections drop for a few RPIs and come back, and the pair stays unsynchronised until the repaired chassis requalifies

What a 1756-RM2 pair buys you, the design restrictions nobody mentions until commissioning, real switchover times, and when redundancy is the wrong answer.

OPC UA PLC Integration: From PLC Tag to SCADA Client

by PLC

Timing chart of an OPC UA subscription showing 250 ms sampling pulses, a PLC tag value change, and notifications leaving at the 1 second publishing interval

Connect a PLC to SCADA with OPC UA: KEPServerEX channels, the S7-1500 built-in server, certificate trust, subscription rates and why OPC DA kept breaking.