4 réponses
Here is a simple method for Grafcet / Ladder translation
Xn=step number
tn=transition
/=negation
Xn=[Xn-1 & Tn + Xn] & (/Xn+1)
Be careful with "or" and "and" transitions
there can be several steps or transitions in "or" or "and"
example= with 3 steps
Step1=[step 3 and the one or more transitions before step 1 + step 1] and not step 2.
and so on.
The init step should never be the first one written in the ladder
use an internal bit written as follows
init or /init activates the init bit. Use this bit for all the initial steps of your grafcet
It only activates once during the first scan
We always write the grafcet first and then the outputs are written at the end
As in telemechanics
Preliminary (Input processing, module initialization, etc.)
Chart (Grafcet)
Post (outputs)
I name my internal bits that I use for each step like this step1= X1, step2=X2
When I search for a step in my program, I only type example X1
For Allen Bradley PLCs
I create 3 base files there can be several grafcet files but I always keep one that is posterior
One preliminary file
one Chart (Grafcet) file
one Posterior file
There must be only one place where an output is activated
If an output is activated in several places, it complicates the diagnosis
Good luck
Xn=step number
tn=transition
/=negation
Xn=[Xn-1 & Tn + Xn] & (/Xn+1)
Be careful with "or" and "and" transitions
there can be several steps or transitions in "or" or "and"
example= with 3 steps
Step1=[step 3 and the one or more transitions before step 1 + step 1] and not step 2.
and so on.
The init step should never be the first one written in the ladder
use an internal bit written as follows
init or /init activates the init bit. Use this bit for all the initial steps of your grafcet
It only activates once during the first scan
We always write the grafcet first and then the outputs are written at the end
As in telemechanics
Preliminary (Input processing, module initialization, etc.)
Chart (Grafcet)
Post (outputs)
I name my internal bits that I use for each step like this step1= X1, step2=X2
When I search for a step in my program, I only type example X1
For Allen Bradley PLCs
I create 3 base files there can be several grafcet files but I always keep one that is posterior
One preliminary file
one Chart (Grafcet) file
one Posterior file
There must be only one place where an output is activated
If an output is activated in several places, it complicates the diagnosis
Good luck
I recommend the approach by "lanfeust54" which eliminates the risk of having 2 active steps at the same time.