Engineering notes
The PLC-Ladder blog
Ladder and function block diagrams, structured text, simulation, and the maths that bites when control logic meets a real machine. Written by the people building the compiler.
One Rung or Five? How to Count Networks in Ladder Logic
A network is one output, not one condition. The reset-latch example shows why the same behaviour can be one rung or two, and how timers and math count.
Testing PLC Logic Like a Protection Engineer: CSV Injection Files
Protection engineers inject a table of quantities and check what trips. The same method for PLC logic: CSV scenarios, checked at the outputs, not internals.
What Is a Function Block Diagram (FBD)? Ladder's Sibling, Explained
The IEC 61131-3 function block diagram explained: blocks, pins and wires flowing left to right, how it relates to ladder logic, and where each view wins.