Paulo Balbino
Member
Hello,
I am trying to detect when the PLC changes from STOP to START mode. This can be considered an edge case scenario, but I would to analyze all potential problems on this approach.
Hardware: PLC Schneider Electric M221CE24R
Programming software: Ecostruxure Machine Expert Basic
Current scenario:
Assuming I have configured the "Fallback Behavior" to "Fallback values"
When the mode from PLC is changed to STOP mode (by manually switching the mode button of the PLC to STOP), all the (Q) outputs are disabled
Then when changed back to RUN it will set everything back to the previous state.
Assuming I have configured the "Fallback Behavior" to "Maintain values"
When the mode switch from PLC is changed to STOP mode, the (Q) outputs stays the same
Then when changed back to RUN it will continue processing the ladder normally
What problem I am trying to solve:
On this project, activation of outputs/relays are related to turning on high power systems. So there must be a delay between enabling each of the outputs (which is implemented on the ladder).
If the PLC during operation is switched to STOP mode, if configured to "Fallback values" when put to RUN again it will simply enable all the outputs (which will enable all the high power systems at the same time)
In case of "Maintain values" it will keep the values during STOP which is ok for some of these outputs (related to high power system activation) but for other parts of the operation for example a motor which is operating since the ladder is not executing no sensor (collision sensor/switches) input will prevent/stop the motor.
If I can have a way to detect this scenario (STOP to RUN mode) on ladder I can handle this case.
Another question: Should I care about this case? This case will only be a concern when someone physically opens the control panel and set the PLC to STOP mode. My main concern is safety.
Thanks a lot
Paulo
I am trying to detect when the PLC changes from STOP to START mode. This can be considered an edge case scenario, but I would to analyze all potential problems on this approach.
Hardware: PLC Schneider Electric M221CE24R
Programming software: Ecostruxure Machine Expert Basic
Current scenario:
Assuming I have configured the "Fallback Behavior" to "Fallback values"
When the mode from PLC is changed to STOP mode (by manually switching the mode button of the PLC to STOP), all the (Q) outputs are disabled
Then when changed back to RUN it will set everything back to the previous state.
Assuming I have configured the "Fallback Behavior" to "Maintain values"
When the mode switch from PLC is changed to STOP mode, the (Q) outputs stays the same
Then when changed back to RUN it will continue processing the ladder normally
What problem I am trying to solve:
On this project, activation of outputs/relays are related to turning on high power systems. So there must be a delay between enabling each of the outputs (which is implemented on the ladder).
If the PLC during operation is switched to STOP mode, if configured to "Fallback values" when put to RUN again it will simply enable all the outputs (which will enable all the high power systems at the same time)
In case of "Maintain values" it will keep the values during STOP which is ok for some of these outputs (related to high power system activation) but for other parts of the operation for example a motor which is operating since the ladder is not executing no sensor (collision sensor/switches) input will prevent/stop the motor.
If I can have a way to detect this scenario (STOP to RUN mode) on ladder I can handle this case.
Another question: Should I care about this case? This case will only be a concern when someone physically opens the control panel and set the PLC to STOP mode. My main concern is safety.
Thanks a lot
Paulo