Learn Structured Text, Ladder Logic, and TwinCAT from real industry experience. The lessons cover the skills you use on the job, with only the theory you need.
1Write real IEC 61131-3 code: IF/THEN, FOR loops and function blocks, as used on modern PLCs.
Learn relay contacts, coils, timers and counters, the basics every PLC programmer needs.
Debug faults, trace signals and fix machines, step by step, the way field techs work every day.
Short, focused lessons from a real maintenance technician.
Write code in our browser-based ST simulator without any hardware.
Download projects for TwinCAT, Siemens, or Omron PLCs.
CodeSchool ST is a free, browser-based platform for learning Structured Text (ST), the high-level text language of the IEC 61131-3 standard for Programmable Logic Controllers (PLCs). Whether you work with Siemens S7, Allen-Bradley / Rockwell RSLogix, CODESYS, TIA Portal, Beckhoff TwinCAT, or Schneider Electric platforms, the ST syntax you learn here carries over to each of them.
Our interactive PLC simulator lets you write, compile, and run Structured Text programs directly in your browser, with nothing to download and no license to buy. Practice with TON timers, CTU/CTD counters, function blocks, arrays, FOR/WHILE loops, CASE statements, and IF/THEN/ELSE logic. The built-in PLC code editor has syntax highlighting, real-time error checking, and variable monitoring, much like professional IDEs such as CODESYS and TIA Portal.
Beyond Structured Text, CodeSchool ST includes a ladder logic to structured text converter, an industrial HMI dashboard simulator, and tutorials that run from PLC programming for beginners to advanced topics. Learn motor control, conveyor systems, tank level monitoring, PID control, and industrial automation concepts that automation engineers use every day.
> Hi, I'm Ali Harrirou — the engineer behind tryplc.com.
I built this platform to make industrial automation, PLC programming, and robotics accessible to engineers, students, and technicians worldwide.
If you face any issues, find a bug, or have a feature request — please don't hesitate to reach out. I personally read and respond to every message.