Industrial Engineer · phase 3 of 16
Sequence / State Machine
Logic that advances equipment through defined operating states based on commands, conditions, and transitions.
The Explain card
- Plain English
- A state machine holds the machine in one named state at a time and moves to the next only when a defined condition is met. Each state decides which outputs are on.
- Example
- Idle waits for start, Filling runs the pump until the level is reached, Mixing runs the agitator for two minutes, and Draining opens the valve until empty before returning to Idle.
- Why it matters
- A machine with a single state variable can always answer the question of where it is and why it stopped. Logic without one tends to have three phases fighting over the same valve and a technician guessing which won.
- Hook
- One number that says exactly what the machine is doing.
Where it sits in the deck
Phase 3: PLC Program Organization and Execution
How the logic is arranged and how the scan actually runs it, which is the difference between code that works and code that works every time.
