ClassicLadder is a free, open-source Ladder Logic software program primarily used to implement Programmable Logic Controller (PLC) logic within LinuxCNC for automation and CNC machine customization. A step-by-step tutorial designed for beginners introduces the core fundamentals of graphical PLC programming without requiring expensive, industrial hardware. Key Concepts Taught in the Tutorial
The guide teaches beginners how to map hardware signals into soft-logic instructions. It focuses heavily on the basic visual components of a ladder program, which mimics traditional electrical schematic diagrams.
Rungs: Horizontal lines read from left to right and top to bottom that dictate the execution flow.
Power Rails: The two vertical boundaries representing virtual power flowing from the positive left rail to the neutral right rail.
Inputs (I): Virtual or physical hardware triggers mapped into the software interface.
Outputs (Q): Coils positioned on the far right of a rung that activate specific functions or hardware relays when energized.
Internal Bits (B): Software-based internal memory relays used to store temporary logic states. Step-by-Step Programming Sequence
A beginner tutorial breaks down the setup and programming workflow into four sequential phases. 1. Software Integration and Initialization
To begin, users must load the ClassicLadder real-time module. This is achieved either directly through a Hardware Abstraction Layer (HAL) configuration command or using the LinuxCNC Setup Wizard. Once loaded, the module adds a refresh command directly into the machine’s real-time processing thread to continuously evaluate the program. 2. Mastering the Basic Instructions
Beginners learn the four fundamental logic elements to populate their first rung:
Normally Open Contact (XIC): Passes power only when the associated input variable is active or True.
Normally Closed Contact (XIO): Passes power continuously until the associated variable becomes active, breaking the circuit.
Standard Output Coil (OTE): Turns on a bit or peripheral device when a continuous path of power reaches it.
Negated Output Coil: Operates inversely by turning off when power reaches it. 3. Building Basic Logic Rules PLC Basics: Ladder Logic
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