27 posts in this topic

Im having some trouble with a PLC and looking for a some help. Whats happening is output number 3 is stuck on. I thought maybe it was just the PLC. I pulled the program tried it on a new PLC with no luck. I checked for faults and the handheld shows no major faults. The output that is stuck on is for a door, its telling it that the door is open. Any help would be great.

image1.JPG

image2.JPG

Share this post


Link to post
Share on other sites

Can you post your program?

Share this post


Link to post
Share on other sites

+1 on posting the program. If the output light is on, it's almost always on in the program. Yes, there's a slight chance it's hardware, but if you transferred the program to a second PLC and got the same behavior, you've eliminated that possibility.

Share this post


Link to post
Share on other sites

Also just because output 3 is not in the program does not mean  the program does not have it turned on. If it was on when someone deleted output 3 then it would still be on in the data table. If it is not controlled in the ladder program, check out the data file and see if it had a 1 in the address.

2 people like this

Share this post


Link to post
Share on other sites

Can you force the output to change states? If so, this would seem to eliminate hardware failure.

Share this post


Link to post
Share on other sites

Try a program with 1 rung

 

XIC I:0/0 (a non wired input)  OTE O:0/3

See if that turns it off.

 

Edited by b_carlton

Share this post


Link to post
Share on other sites
On 8/3/2016 at 5:58 AM, TWControls said:

Also just because output 3 is not in the program does not mean  the program does not have it turned on. If it was on when someone deleted output 3 then it would still be on in the data table. If it is not controlled in the ladder program, check out the data file and see if it had a 1 in the address.

I just went through this scenario with a field. Tech. He was freaking out (a little) because 3 analog outputs had large values in them. They were scaled 0-100 but were reading 2xx. I told him to type a 0 in the register and see what happens. Poof... no more big output value :)

1 person likes this

Share this post


Link to post
Share on other sites

That's one reason or would be a very good thing to observe in the data table before"fixing". There is a lot of lessons there on how important data can be that doesn't have instructions writing to it.

1 person likes this

Share this post


Link to post
Share on other sites

I added the file. I'm fairly new at the whole PLC thing. Somehow I got roped into it and have been learning on the fly along with some training from our electrician.

EX66.RSS

Share this post


Link to post
Share on other sites

It is password protected.  Can you remove the password and reupload?

Share this post


Link to post
Share on other sites

Is this program supposed to be blank?

Share this post


Link to post
Share on other sites

No im using the RSL logix lite. I clicked the file to make sure its accessible. I clicked go online and the program came up.

Share this post


Link to post
Share on other sites

Once online.  Save the program and when it ask you if you want to upload the data values click yes.  Then post that file.

Share this post


Link to post
Share on other sites

You need to look at Rung 35.  It has output 3 on.  Do you have a diagram that you can identify the I/O with?

Share this post


Link to post
Share on other sites

Are you talking like a schematic? On the schematic it shows that 3 is suppose to be the door close and 2 is the door open.

Share this post


Link to post
Share on other sites

ALL if the inputs and outputs. Do you know how to add descriptions to your ladder logic? I think what is keeping output 3 on will quickly revel itself once you start documenting your program.

1 person likes this

Share this post


Link to post
Share on other sites

No docs in the program makes it kind of hard to learn programming :) but it's a great way to learn forensic PLC program analysis <-- I made that up. There's no official term that I'm aware of (occasionally there's a modified version of the term that involves expletives and someone's mother or male bovine fecal matter but we won't go there...)

I've attached a blank Micrologix 1000 IO sheet. It's generic but should be a good starting point. The panel builder should have used wire tags. If they didn't they should be drawn and quartered. Do your best to fill in the IO sheet, either from the panel drawings or by tracing wire. Just about everything else can be inferred if you know what the machine does (and sometimes if you don't). 

On the left side of the program software, under data files, you'll see O0 - OUTPUT and I1 - INPUT. Double click either to open it. This is where you can see the status of the IO at a glance. I always start with inputs but it doesn't matter. Down at the bottom there is a box that says Usage. Click that. Every IO point that has an X in it is used in the program in some way. If you right-click the X and select Cross Reference it'll tell you where the IO point lives in the program. Cross reference is your friend. This applies in any data file. Look on the lower right side and you'll see a dropdown selector that is labeled Radix. For digital input / output points you will want to see this as Binary / Subelement. For analog, which you don't have, you'll usually want to see it in Decimal.

On the left side of the program software, up near the top, under Project, you'll see Controller. Expand that and you'll see Controller Properties, Processor Status, IO configuration, Channel Configuration. Double-click Processor Status. Click Usage. There's an X in S:0/1 which is the processor mode status and control bit. If the Radix is Element only change it to Binary / Subelement. You'll see that there is an X in bit 15 and it's labeled First Pass. Right click the X and select Cross Reference. Cross Reference is your friend. You'll see that S:0/1.15 is used in File #2 and File #3. Double Click File #2 and it will take you to where S:0/1.15 is used.

Cross reference is your friend <-- I repeated this because if you don't get anything else out if this you need to understand that cross reference is your friend and so are documented IO points. If they aren't documented then you need to document them. Even if it's not the exact, correct descriptor you need to put something that at least makes sense to you in every used  point. 

My attached form is something that I've evolved to over the years. The panel shop that I use likes it (customer is always right :o) ) or has gotten used to it. You can make it into whatever you want or create your own form.

Last thing, opening and closing windows can get your screens all out of sorts. To put everything back to "stock", click Window, Arrange, Default should be selected, if not then select it, then click OK

2nd Last thing- The point of documenting with an IO sheet is that it's something that you can leave in the panel to quickly let a tech troubleshoot IO problems and it's easier to type the info in Excel and then copy/paste from the Excel worksheet to the Desc: cell in the Data Files rather than vice versa. You can document the PLC only but that doesn't help the electrician unless he has the software. You could document the PLC first and then Export the docs but SLC software breaks the docs up into 5 columns (why???), I think it's 5, it might be 4, and it's a pita to "assemble everything" in Excel. Besides that, in project development the IO sheet comes before the program. At least it does for me.

Micrologix 1000 IO Sheet.xls

Edited by Michael Lloyd

Share this post


Link to post
Share on other sites

TWControls makes a very good point...lack of documentation makes it very difficult to walk through a program.  Document...every...rung.  Those who come along after you will be very glad.

Share this post


Link to post
Share on other sites
Just now, excelparts said:

thanks for all the help and info so far. Im uploading the wiring schematic for the PLC. Would this help me on filling out that IO sheet

It's a good start. See the vertical bar on the middle left that has Com 0 1 2 all the way down to 19? Those are your inputs. The bar on the right side is your outputs

I populated the IO sheet and program with the info for you. I used Tools --> Database--> ASCII Export, change the format to CSV (my preference) to export the database. Before I did that I put an X in the description of all of the IO points. Why? Because X is easy to type and the IO won't export if there's nothing in the description. X is a placeholder. Once the database is exported I copied the cells in the IO sheet into the cells in the exported database. Save the database. Then import the CSV you just saved into your program

Whoever wrote the program should have given you a documented copy of it. Having to do this is a good exercise but it's a needless PITA...

I also included the documented CSV file

Micrologix 1000 IO Sheet.xls

EX6622.CSV

EX6622.RSS

Share this post


Link to post
Share on other sites

Thanks Michael. I looked at our other programs we have and nothing was documented on those either. Any idea what would cause a input to stay on?

Share this post


Link to post
Share on other sites

Ive been playing with this thing. I was able to get output 3 to shut off now output 9 comes on. In the data files it shows a 1 for the input that is stuck on. 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now