6: Ladder Logic

Contributed by Tony R. Kuphaldt
Instructor (Instrumentation and Control Technology) at Bellingham Technical College
Sourced from All About Circuits

6.1: “Ladder” Diagrams
Ladder diagrams are specialized schematics commonly used to document industrial control logic systems. They are called “ladder” diagrams because they resemble a ladder, with two vertical rails (supply power) and as many “rungs” (horizontal lines) as there are control circuits to represent.
6.2: Digital Logic Functions
6.3: Permissive and Interlock Circuits
6.4: Motor Control Circuits
6.5: Fail-safe Design
6.6: Programmable Logic Controllers (PLC)