How to code a sequence as done in Yokogawa Sequence table in ABB 800xA?
I need to replicate/code a sequence as done in a Yokogawa sequence chart.
The basic conditions to be met are listed below:
1) The sequence conditions (in the table), each and every condition needs to be checked every one second.
2) The condition that decided the execution of each step is specified as "Output Only When Conditions Change State". ie. if on first scan condition is detected as true it executes the action, however on the second scan if condition remains true the action is not executed. The action is executed again only when the condition toggles On/Off again.
It is more or less like a cause and effect table except with restrictions on the execution requirement.
How can I implement the same in ABB 800xA?
Please refer to the attached image.
Couldnt find any attachment to your question.. Can you re attach?
Probably if I understood you correctly, you can start with copying the variables to dummy variables ( say, Var_Old ) in the same step where you are writing the logic to check the variables.
Then add a parallel brach with following conditions
1) transition block with a condition that it should be executed only if "Var_Old is not equal to Var". This should have actual logic.
2) transition block with a condition that it should be executed only if "Var_Old is equal to Var". This should be loop back to starting step.