PLC-LadderEngineering 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.
Free Online PLC Simulator: Test Ladder Logic Without Hardware
Test ladder logic in your browser before hardware: how the scan cycle works, what to simulate (seal-ins, timers, interlocks) and a worked conveyor example.
PLC Code Generators: What AI Can Draft — and What Must Be Verified
The trust problem with generated control logic, why a PLC code generator should produce drafts rather than artifacts, how a compile-and-repair loop works, a worked example of an ambiguous request and the assumptions it surfaces, and what gets refused.
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 Definition and Basics
What a function block diagram (FBD) is in IEC 61131-3: blocks, pins and wires, how FBD relates to ladder logic, and where each view wins.