1st Time PLC - Need Help

Hoegenauer · Apr 10, 2003

Would someone be willing to help me get started.. I have a GE Fanuc Micro PLC that I need to program for the following sequence.

PB Start Button - drives a cylinder to end - activates end switch - drives home - activates home switch - drives another cylinder to end - activates end switch - returns this cylinder home - end sequence.

I was not sure how to build the sequntial logic since the two cyliders will be both at home three different times in the sequence - therefor, I cannot rely on just the switch conditions. I am sure that this is such a simple application, but I just dont see the solution..

Thanks.

Trey Hoegenauer

Steve Etter · Apr 10, 2003

I suspect that all you are missing is the recongition that you are not tied down to only using your real-world devices when it comes to writing a program. What I mean is that you can (and almost always MUST) create internal flags to help you with your logic:

PB Start Button
Set Flag 1: 1st Move Started
drives a cylinder to end - activates end switch - drives home - activates home switch
Reset Flag 1 and
Set Flag 2: 1st Move Complete
Since Flag 2 is set
drives another cylinder to end - activates end switch - returns this cylinder home
Reset Flag 2
end sequence.

The key here is that you know you don't want your second motion to occur until the first one is done. So be it. Create a flag that marks the conditon is done so you need to differentiate which is which.

Is that any help?
Steve

paradym · Apr 10, 2003

Sorry about having to using a G.E. PLC... just kidding

Not sure about G.E.'s nomenclature, substitute the correct terms as necessary

Xxx = Inputs
Cxx = Internal relays
Yxx = Outputs

Code:

+   Start PB                           +
+     X0                   C0          +
+----]  [----------------( SET )------ + Cycle Start
+                                      +
+                         CYL 1 RET    + 
+     C0                    Y0         +
+----]  [-----------------( OUT )------+ Cylinder 1 retract soleniod
+                                      +
+                                      +
+  Cyl 1 end SW                        +
+     X1                     C0        +	
+----]  [------------------( RST )-----+ Cylinder 1 at end limit
+                    |                 +
+                    |       C1        + 
+	            +----( SET )------+ Cylinder 1 
+                                      + extend to home limit 
+                                      +
+                                      +
+     C1                     Y1        +
+----]  [------------------( OUT )-----+ Cylinder 1 extend soleniod
+                                      +
+                                      +
+ Cyl 1 home SW                        +
+    X2                       C1       +
+----]  [-------------------( RST )----+ Cylinder 1 at home limit
+                     |                +
+                     |       C2       +
+                     +-----( SET )----+
+                                      +
+                                      +
+                           CYL 2 RET  + 
+    C2                        Y2      +
+---]  [--------------------( OUT )----+ Cylinder 2 retract to limit
+                                      +
+                                      +
+  Cyl 2 end sw                        +
+     X3                        C2     +	
+----]  [---------------------( RST )--+ Cylinder 2 at end limit 
+                      |               +
+                      |        C3     +
+                      +-----( SET )---+ 
+                                      + 
+                                      +
+    C3                        Y3      +
+---]   [--------------------( OUT )---+ Cylinder 2 extend to home 
+                                      + limit
+                                      +
+  Cyl 2 home SW                       +	
+      X4                    C3        +
+-----]  [-----------------( RST )-----+ Cylinder 2 at home limit 
                                         and Sequence end

Hope my expanding on Steve's post helps, a only one of a 101 ways to do this control.

Don't forget, There are no stops in this or safety's in this example

1st Time PLC - Need Help

Hoegenauer

Member

Steve Etter

Lifetime Supporting Member + Moderator

paradym

Member

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