PLC Viewer

PLCViewer is a Windows desktop app for monitoring industrial PLCs live over Ethernet. It supports the Keyence KV-X310 over MC protocol, through a client I wrote from scratch, and the Delta DVP-12SE over Modbus TCP. Engineers can find a PLC on the local network, watch I/O as live status lamps, browse and search data registers, and export values to CSV.

Because it connects to machines that may be running in production, safety drove the design. The app only reads by default. Writing a register needs a hashed password, an on-screen confirmation showing the old and new value, and a read-back to verify the change. Writing locks again automatically after 10 minutes.

For the Delta PLC, I built a Program tab: an editor, error checker and simulator for ladder-logic instruction lists. It runs the program on the PC, scan by scan, against the PLC's real inputs. Engineers can test logic on a bench before downloading it to the machine, and errors are flagged by line as they type. The interpreter supports contacts, branches, timers, counters and arithmetic, and is covered by 79 automated tests.