PLC glossary
Rising edge
The moment a signal changes from FALSE to TRUE. A signal held TRUE is not another rising edge.
- Also called
- positive edge, FALSE-to-TRUE
- On site
- A bottle arriving beneath the sensor creates one rising edge.
- Siemens
- R_TRIG in SCL; P contact or P_TRIG in LAD.
- Rockwell
- ONS/OSR in Ladder; OSRI or explicit previous-input logic in ST.
Taught in: Count events, not scans
Practise it on a 3D rig
- Count the arrivalsCount each bottle once. Stop at three.
- Count with a one-shotOne bottle covers the sensor for many scans. Count it once.
- Count bottles as they leaveCount each bottle as it clears the sensor, not as it arrives.
- It never reaches threeSomething keeps clearing the count. Find it.
- Review the AI: One bottle, one countCheck a bottle that stays under the sensor.