Introduction
Welcome to the Rungs.dev Documentation! This guide is your comprehensive resource for learning how to build PLC programs in Rungs.dev using both Ladder Logic (LD) and Structured Text (ST).
What is Rungs.dev?
Rungs.dev is a web-based PLC simulator for learning, building, and testing PLC programs in Ladder Logic and Structured Text. Directly from your browser, you can:
- Design ladder diagrams
- Write Structured Text code
- Simulate program execution in real time
- Write unit tests and validate program behavior
- Plot live values over time with trend charts
- Get help from the built-in AI assistant
- Share projects with others—all without installing any software
Modeled on Studio 5000 Logix Designer
Rungs Studio is modeled on Allen-Bradley / Rockwell Studio 5000 Logix Designer®. Tag types, instruction names, expression evaluation, and program structure mirror Logix Designer conventions, so the concepts you learn here map to familiar Logix 5000 patterns. Rungs is a learning tool, not a substitute for Logix Designer — edge cases and platform-specific behavior may differ.
Who is this documentation for?
Whether you're a student, instructor, hobbyist, or professional in industrial automation, this documentation covers both ladder logic fundamentals—rungs, power flow, bit instructions, timers, counters, compare, and math—and Structured Text programming, along with tag management, testing, and trend analysis workflows.
Thank you for choosing Rungs.dev — let’s get started.
Rockwell Automation, Allen-Bradley, Logix 5000, and Studio 5000 are trademarks or registered trademarks of Rockwell Automation, Inc. rungs.dev is not affiliated with, authorized, or endorsed by Rockwell Automation.