Learn PLC programming with interactive lessons PLCPractice is free and ad-free. Learn controls concepts, write Ladder Logic and Structured Text, and test your work in browser-based simulators embedded in lessons.
PLC Basics — What PLCs and industrial PCs are, how I/O addresses and tags reach the program, and the IEC 61131-3 programming languages.Ladder Foundations — Binary signals, truth tables, and the core logic gates (AND, OR, NOT) that underpin all ladder logic.Boolean to Ladder — Translating real-world control requirements into Boolean expressions and then into ladder rungs.Scan and Memory — How a PLC scan reads inputs, runs the program, and writes outputs: execution order, scan time, and what the controller remembers.Core Patterns — Seal-in circuits, start/stop logic, interlocks, permissives, and alarm latches — the building blocks of real programs.Data & Math — Comparison and math instructions for thresholds, totals, resets, and numeric decision-making in ladder logic.Timing & Events — Timers (TON, TOF, retentive on-delay), counters (CTU, CTD), one-shots, and edge detection for event-driven logic.Sequences — Step-by-step machine sequences: step numbers or one bit per step, transitions, timeouts, fault steps, and reset to idle.The World and How It Connects to a PLC — The field devices a PLC reads and drives, normally open and normally closed wiring, and how sinking and sourcing circuits are wired.Analog & Process Control — Continuous signals, engineering units, scaling, alarms, HMI setpoints, and feedback control in Ladder and Structured Text.Debugging — Reading rungs systematically, common mistakes, truth-table debugging, and scan-cycle debugging techniques.PID Control — Understand feedback, tune a process, handle operating changes, and diagnose poor responses with embedded experiments and a final commissioning review.Structured Text: Foundations — Variables and data types, combined logic, IF decisions, and state across scans, written as Structured Text and checked over scans.Structured Text: Practical Control — Edges, counters, timers, state, and sequences written as Structured Text, with checks that judge behavior over scans.Structured Text: Working with Collections — Arrays, FOR loops, and WHILE and REPEAT loops in Structured Text, with checks on ordinary and boundary data.Structured Text: Debugging and Reuse — Debug with live values and test cases, write your own functions and function blocks, build a small machine controller from a specification, and read and translate existing programs.Start with the beginner guide or open the Ladder Logic simulator , Structured Text studio , or PID practice simulator .