Industrial Engineer · phase 3 of 16
Rung
Horizontal network of conditions and instructions in ladder logic.
The Explain card
- Plain English
- A rung is one horizontal line of ladder logic between the two power rails. Conditions on the left decide whether power reaches the instructions on the right.
- Example
- Rung 14 has a limit switch contact and a timer done bit in series, feeding an output coil. If both are true, the coil is on for that scan.
- Why it matters
- Rungs are solved top to bottom, left to right, so where a rung sits changes when its result is available. A coil written on two different rungs takes the value of the last one, and that is one of the oldest bugs in the trade.
- Hook
- One line, one decision, evaluated every scan.
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.
