Let’s consider a PLC program for drilling on a drilling machine.
I/O assignments
Input Stop button X000 Operation start button X001 Fall start button X002 (Consider this to be an auto-return type pushbutton.) Fall end limit switch X003 Rise end limit switch X004 output Drill rise output Y000 Drill fall output Y001 Drill rotation output Y003
Explanation of operation
- When operation start button X001 is pressed, drill rotation output Y003 operates and the drill starts to rotate.
- When stop button X000 is pressed, drill rotation output Y003 becomes nonoperational, and drill operation stops.
- If fall start button X002 is pressed during drill rotation, drill fall output Y001 operates, and the drill starts to fall. When the drill finally reaches the position of the fall end limit switch, fall end limit switch X003 turns ON, and the drill fall operation stops.
- Three seconds after the drill fall operation stops, drill rise output Y000 operates, and the drill rises.
- The drill rise operation ends when rise end limit switch X004 turns ON after drill rise operation has begun.
Ladder Diagram
Operation
(1)When input X001 is turned ON, output Y003 operates. When input X000 turns ON, output Y003 becomes nonoperational.
(2)If input X002 is turned ON while output Y003 is operating, output Y001 operates. When input X003 is turned ON, output Y001 becomes nonoperational.
(3)If input X003 is held in an ON state, timer T0 starts to count. After three seconds, the T0 contact turns ON.
(4)When timer T0 turns ON, output Y000 operates. When input X004 turns ON, output Y000 becomes nonoperational.
You can practice this plc program at a free simulator link in the below
Basics of Ladder Logic – PLC simulator tutorial