PLC circuits
Start-Stop from Three Places with a PLC
What is start-stop from three places with a PLC?
It is a circuit in which a motor is started and stopped from three locations using a PLC. The six buttons and the overload contact go to separate PLC inputs; the series and parallel button connections of the classic circuit move into the program.
Where is it used?
It is used on long belt lines, machines with several operator stations and large plants. With a PLC, adding a new control point takes only one input and one line in the program.
PLC wiring and ladder program
The power circuit is a direct-on-line starter. Because each button has its own input, the PLC also knows which button was pressed; this can be passed to an operator panel or a fault log. How the classic circuit's series connection is written in the program is instructive for understanding ladder logic.
The benefit
Wiring gets simpler, troubleshooting gets easier and the system can grow. With the same logic, systems controlled from dozens of points can be built.
Parts used
- Motor 3~
- M1
- PLC
- PLC1
- Start button (NO)
- S4, S5, S6
- Stop button (NC)
- S1, S2, S3
Run it in the simulator.
This circuit is ready in the CoilPath library. Open it, press the buttons and follow the current. It also comes with a wiring view and a panel layout.