Seems Like Simple Troubleshooting - I/O Issue

[iadapt]

Hey, I have a micrologix 1000 with RSLogix 500 Pro software. in a small program I have 3 inputs and I watch them change on the data table but the output will not energize. I can force it on but it will not change state using the inputs. I readdressed and changed output pins even but I get the same thing. Any ideas?
Its got to be something easy right?

 

[Ron Beaufort]

quick guess ...

do you have the rungs in a NEW ladder file (other than #2) - and if so, did you put a JSR into #2 to "jump" to the new subroutine file ??? ...

if this is your problem, then the NEW ladder file isn't being executed/scanned by the processor ...

if this isn't it, consider posting your RSS file ...

 

[bernie_carlton]

Please post the program

 

[Lare]

plc is of course at run not at stop state?

p.s this is too simple

 

[Ken Roach]

The MicroLogix 1000 only supports one ladder logic program file; good old default Program File 2. So it's definitely being executed.

Be absolutely certain the MicroLogix 1000 is in RUN mode. The MicroLogix 1000 models don't have a physical Run/Prog mode switch, so only a power cycle or a command from RSLogix 500 will put it into RUN mode.

It also can fake you out with the Forces status flag; forces show as "always enabled" in the Status area of RSLogix 500. Forcing is supported by the MicroLogix 1000 (somehow I had it in my head it wasn't) and the controller even has a FORCE indicator on the front, but it doesn't have the "forces installed by not enabled" feature of the traditional SLC/MicroLogix operating system.

 

[iadapt]

The update guys is that I had to have my tech un-wire the PLC entirely and I then tested the I/O and the output indicator light came on and the output relay closed. Therefore my guess is that there is a wiring issue. I am going to find out today when I supervise the rewiring of the panel. Thoughts?

 

[gbeaker]

If you can force it on, it is not a wiring issue.

 

[Ken Roach]

Ron was kind enough to remind me that the MicroLogix 1000 has pre-defined ladder files that cannot be changed, rather than having a single ladder file (like the PLC-2). I blame a lack of sleep and caffeine.

Only Ladder 2 is executed automatically, so the previous advice of "make sure you have the correct JSR instructions" is good advice.

It looks like this is a wiring issue anyhow, so good luck on it !

 

[Ron Beaufort]

maybe we're not all talking about the same thing ...

let's spend a few seconds and define what "on" really means here ...

(1) having the OTE instruction turn green on the screen means "on" ...

well, that's not always correct ...

(2) having a status of ONE in the output's bit/box on the data table means "on" ...

that's not always correct either ...

(3) giving an "on" signal to the output module's switching device (relay/transistor/etc.) means "on" ...

that's another definition that's not always correct ...

(4) having the field device (valve, pump, etc.) energized/running/etc. means "on" ...

BINGO! ... now THAT one is the only definition that tends to impress the bo$$ ... so – in my personal opinion – that's the only definition that really does mean "on" ...

now then – which definition are we looking at here? ... once we're sure about THAT – then we're getting closer to isolating the piece of the puzzle that's giving us the problem ...

 

[Geospark]

maybe we're not all talking about the same thing ...

Most definitely not Ron!

...and as for the "puzzle", well that began at Post #1...

Hey, I have a micrologix 1000 with RSLogix 500 Pro software. in a small program I have 3 inputs and I watch them change on the data table but the output will not energize. I can force it on but it will not change state using the inputs. I readdressed and changed output pins even but I get the same thing. Any ideas?
Its got to be something easy right?...

...The update guys is that I had to have my tech un-wire the PLC entirely and I then tested the I/O and the output indicator light came on and the output relay closed. Therefore my guess is that there is a wiring issue. I am going to find out today when I supervise the rewiring of the panel. Thoughts?

I have a couple of thoughts...

Because your original information is so vague, it makes it very difficult for us to decipher what your logic is doing, or is supposed to do?

While trying to figure out what you have in terms of ladder logic, the terms "input" and "output", to me, and I'm sure others here, only represent the physical I/O. What instructions you are using with the I/O addresses, and the order in which they are programmed, is what we really need to know in order to decide, if we can, whether the program is at fault here, or something else. Unless you yourself fully understand the logic and how it is actually executing, then for me, the logic cannot be ruled out just yet.

For instance, we do not know if the output address is assigned to an OTE, OTL, OTU instruction? We "might" be assuming it's an OTE instruction, but that would just be an assumption.

Likewise, we do not know if the input addresses are assigned to an XIC or an XIO instruction? We "might" be assuming they are using an XIC instruction, but that would just be an assumption.

Also, the order of, and type of, input instructions placed on a rung, or rungs, before attempting to manipulate the output instruction(s), is very important. Could one rung be setting an output instruction true, while the next is setting the same addressed output instruction false?

How many times are the input addresses used?

Are they XIC or XIO?

How many times is the output address used?

Is the output address assigned more than once to an output instruction?

We could be assuming all manner of logical permutations here, even for what "sounds" like a simple piece of ladder logic.

Removing the wiring "may" just be removing the logical order in which the input instructions manipulate the output instruction(s), giving the sense that the wiring is at fault. When, perhaps, it still "may" be the logic that is at fault here?

Normally...

You seek help...

We request specific feedback or provide suggestions or answers...

If feedback, we analyse it and then make suggestions or provide answers...

Three main requests were made...

Is the Subroutine running (JSR)?

Is the controller in RUN mode?

Can you provide a copy of your logic?

To which you answered none...

Your update only adds to the confusion...

You now think it must be the wiring (maybe it is?)...

The point I'm making is you are seeking advice, receiving advice, but also ignoring that advice.

At this stage, we are simply spectators to your on going saga, wondering what will happen next? A real whodunnit?

Regards,
Grumpy George