s7-1500 - PLC Programming & Automation

PLC Industry 4.0: OPC UA, MQTT and Real Data Models

September 13, 2026January 21, 2024 by PLC

Timing chart of an MQTT publish trigger: the broker connection drops and returns, a deadband exceeded pulse and a 30 second heartbeat each raise the publish trigger, and a store and forward flush follows the reconnection

What an Industry 4.0 project really changes on the PLC: the OPC UA server, a UDT to JSON data model, MQTT at the edge, retrofits and security.

PLC Scan Time and Cycle Time: Measure It, Then Cut It

September 12, 2026January 19, 2024 by PLC

Timing chart of two 10 ms periodic task cycles showing input image update, program scan, output image update and comms overhead in sequence

Read real scan times with GSV on a ControlLogix and the cycle time view on an S7-1500, then find what is eating them before the watchdog does.

OPC UA PLC Integration: From PLC Tag to SCADA Client

September 12, 2026January 18, 2024 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.

PLC Hardware Components and the Software That Uses Them

September 13, 2026January 6, 1970 by PLC

Timing chart showing a field input rising, the input image bit following at the next input scan, the coil in logic changing during the program scan, and the physical output finally switching after the output scan, about one scan behind the field

What is in a PLC rack and how the software sees it: power supply budget, CPU memory, I/O cards, tasks and routines, and tags against S7 addresses.