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Home/Guides/Pi PLC programming/Ladder logic on a Pi
GUIDE5 min readUpdated Jun 2026

Ladder logic on a Raspberry Pi

Your controls team's relay diagrams, running on a Pi — no Python required.

SHORT ANSWER

Ladder logic — the relay-diagram language most plant electricians already read — runs on a Pi through IEC 61131-3 soft-PLC runtimes like OpenPLC and CODESYS. That means an existing controls engineer can program a Pi with familiar rungs and contacts instead of learning a scripting language, lowering the barrier to a Pi-based control project.

Ladder (LD)
one of five IEC 61131-3 languages
IEC
OpenPLC/CODESYS
both run ladder on a Pi
this guide
Familiar
no Python for the controls team
—

01Same language, new hardware

Ladder diagrams map contacts and coils to inputs and outputs exactly as on a PLC. On a Pi, the soft-PLC runtime scans the rungs and drives industrial I/O — so the mental model your team already has transfers directly.

02When to mix in code

Keep deterministic interlocks in ladder for readability and auditability, and drop into structured text or Python only where ladder gets awkward — like vision or ML, which run beside the ladder logic on the same Pi.

Common questions

The ones we're asked on every first call.

No. With OpenPLC or CODESYS you write ladder logic just like on a PLC. The Python/AI layer is optional and only comes in for capabilities a PLC couldn't do anyway.

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