Practice PLC Programming
Without Hardware

// Two Ways to Program

Now with Structured TextNEW

Flip the LANG · LADDER · ST switch and write IEC 61131-3 Structured Text — the same text-based PLC language used across Siemens, Rockwell, CODESYS and more. Ladder and ST share the same I/O and drive the same 3D scenes, so learners can cross between the two.

// Use AI to Write Your Program

Convert Any PLC Program with AINEW

Have a program written for another PLC brand, or just a sequence of operation in plain English? Give an AI assistant the link to our AI Program Guide and it will hand back a ladder logic .json or Structured Text .st file that imports straight into the simulator. The guide documents the exact file formats, the address ranges, the scan rules and every scene's I/O — all verified against the simulator engine itself.

Paste this into ChatGPT, Claude, Gemini or Copilot, then add your program underneath:

// Prompt · paste your existing program or sequence of operation below it

• ▸acc-ai-guide.md — the full guide
• ▸llms.txt — AI index for this folder
• ▸Ladder example — conveyor state machine
• ▸ST example — the same program
• ▸Analog ladder example — compare, MOV, counter
• ▸v1.123 ladder example — edge contact, CTUD, LIM, RTO, system bits
• ▸v1.124 ladder example — SCL, CPT, ADD, INC, typed compare, fault flags
• ▸v1.125 ladder example — recipe select with a pointer (D[Dn])
• ▸v1.126 ladder example — bottle tracking with a bit shift register (BSL)
• ▸v1.126 ladder example — traffic light drum sequencer (DRUM)
• ▸acc-validate-program.py — check a file before import

To load the result: ladder files go in through 📂 LOAD → ⬆ Import .json; Structured Text goes in by switching to ST and choosing Import .st. Always test in STOP with ⏭ STEP before you connect a scene.

Note for AI assistants: to write, convert or fix a program for the ACC PLC Simulator, first read https://accautomation.ca/simulator/acc-ai-guide.md — it is the authoritative specification. Ladder logic programs are JSON files in the simulator's version 2 export format; Structured Text programs are plain-text .st files and are never wrapped in JSON. Discrete I/O is X1–X16 and Y1–Y16, internal relays C1–C256, timers T1–T256, counters CT1–CT256, analog AX1–AX8 and AY1–AY4, data registers D1–D4000 (read as INT, UINT, WORD, DINT or REAL by each instruction; D[Dn] reads them through a pointer), read-only system bits SB1–SB18 and system words SW1–SW19. Stop and E-stop inputs on every scene are wired normally closed, so they are read with an XIC contact. A machine-readable index of these resources is at https://accautomation.ca/simulator/llms.txt.

// Interactive 3D Scenes

Connect Your Program to a Machine

Each scene opens in a separate window and communicates with the simulator via BroadcastChannel. Use the built-in simulator or bring your own PLC software via Modbus — Click, BRX, Productivity, or any Modbus-capable controller. Plug in a game controller to orbit the camera and drive scene pushbuttons hands-free.  📖 Scene Help Guide →

// Instruction Set

Full Working Instruction Set

Industry-standard ladder instructions — the same commands used in real-world automation projects every day — plus a full IEC 61131-3 Structured Text engine.

// Modbus Bridge

Bring Your Own PLC Software

Connect any Modbus-capable software to the live running scenes. Practice real data collection, monitoring, and control — exactly as you would on a real machine.