CompactLogix 5000 series I/O light flashing

adroit

Member
Join Date
May 2020
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united states
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Hey guys, I'm super new to troubleshooting PLCs and was hoping I could get some guidance

I've got a machine I'm commissioning and it's kind of a stupid situation

I was meant to commission it after it was installed by an installation crew from another state who had to leave the machine partially installed/assembled when the COVID situation sent them packing. I started working on the machine in the 2nd week of May. When I saw the machine after the crew left in march, the machine was energized and the HMI was in its screensaver mode, if I recall correctly.

I wasn't allowed back on site until May because of the end user's COVID restrictions. Because I needed to finish mechanical assembly before trying to run the machine, I didn't even look at anything electronic in the control cabinet. I literally just deenergized the machine, got to work bolting some stuff on, connecting some pre-wired connectors, etc.

After I was done with the installation, I energized the machine and my HMI did not turn on. I find its fuse is blown. I deenergize machine, replace fuse, energize machine, go through equipment vendor reset/rearm procedure, and I have an alarm for one of my VFDs.

Guided by vendor, I find that the ribbon cable for my VFD's communication module had burned out, and also had apparently been routed incorrectly into back cavity of the VFD where it may have gotten hot / been eaten by a cooling fan. The VFD shares the 4a GMA fuse that blew for its 24VDC circuit into the Safe Torque Off Board

They send me a new comm module and ribbon cable, preprogrammed from factory. I replace them, energize machine, reset/rearm -- same alarm

They send me a preprogrammed VFD and comm module as an assembly. I replace VFD, transfer Safe Torque Off board from old unit to new unit, same alarm.

This is when it gets clear this is completely beyond my depth and also the depth of the guy I'm working with at vendor tech support. I don't know what could be relevant information so I'll just share some of my findings and ask what you all think maybe could cause something like this, or what kinds of things I could look at, because I'm completely at a loss and am waiting to hear back from vendor programmer to see if maybe it's a programming issue?

Machine components:
Allen Bradley CompactLogix 5370 1769-L16ER-BB1B (run, ok, and NS solid green, link 1 and link 2 flashing green rapidly, I/O light flashing green slowly)
5 x Allen Bradley 1734 IB8 (network and module status lights are all solid green, input status lights work with corresponding inputs)
3 x Murr remote IO modules (MS and NS solid green, the ethernet port that goes to CompactLogix has solid green and solid orange status lights on it)
Panel View Plus 7 6" HIM (I believe the ethernet port status lights are solid green and solid orange but I didn't make note of that; the IO display on HIM correctly shows IO status from all IO on PLC, expansion modules, and Murr units)
PowerFlex 70 with 20-COMM-ER and Safe Torque Off Board (STS light flashing yellow; Port, Mod, Net A flashing green; LCD display shows "Stopped"; digital inputs into this VFD are correct and I have 24VDC across terminals 6 & 8, and 24VDC across 3 & 4 on safe torque off board--under these conditions pins 1 & 2 read "open" which is correct per AB literature on Safe Torque Off Board; when machine is deenergized pins 1 & 2 read closed, so I know the STO is at least doing *something*; the ENABLE jumper was removed when I installed the Safe Torque Off Board, and obviously I removed the red jumper from pins 1 & 2 of STO connector)

There is an ethernet switch that the Powerflex 70, Panel View Plus 7, and CompactLogix are all connected to. The other ethernet port for ComactLogix goes to the Murr remote IO unit

I am able to connect to the network and see all of these components on the network with Connected Components Workbench, but I can only connect to PowerFlex 70 because I don't have software licenses for getting into the PLC or HIM. I am able to access Murr modules via my web browser. All of these components are on the network with the correct network settings per the tag on the control cabinet door. My powerflex 70 programming is correct per what the equipment vendor gave me (comparison checks out as identical)

So, basically, my powerflex 70 is receiving the digital inputs it needs to run, but it won't run. the I/O light on PLC is flashing like it isn't seeing something on the network, but I'm seeing everything on the network, and clearly the HIM is communicating with the PLC and expansion/remote IO modules because their statuses are correctly reflected on the HIM IO display

I verified all of the components for inputs into PLC are working properly in reality, and that the PLCs are getting correct inputs based on observable reality (laser sees reflector, limit switch is/isn't hitting a striker, prox is/isn't seeing its target, contact relay is/isn't energized, etc.) and also whether that component is normally open or normally closed

When I force my PowerFlex 70 to run by pressing the red button and then the green button, it rapidly switches back and forth between "Fwd" and "Rev" and "chatters" the motor it controls

I found this in the installation instructions for my Powerflex 70:
KYJ6rti.png


I'm thinking that maybe the programmer messed up in his programming and the Powerflex 70 is getting conflicting logical results (fwd and rev) at the same time, but I'm not seeing "DigIn CflctB" on my LCD display. I'm just getting the yellow flashing STS light. Drive status 2 (parameter 210) is xx00000000000001, for what that's worth

Some of the PLC inputs for the machine itself have confusing names, and are logically "inverted" or whatever--there are 2 inputs for "Process up" and "Process down" that are for normally closed limit switches (currently it is in the "down" position in reality, and I/Os reflect that) and there are two inputs for "Dispenser up" and "dispenser down" that are normally open proxes, but on the HIM these are also called "Process up" and "Process down"

Am I way off base thinking this could have been some human error where programmer named different PLC inputs the same thing and got them mixed up when he was creating the programming, creating logical contradictions that are forcing this Powerflex 70 not to run unless I manually force it to?

Or is there something really stupid I'm overlooking here?

It's just completely beyond my depth and I've spent a week on the phone with the equipment vendor tech support and feel like I've gotten nowhere on this

I only have Connected Components Workbench and RSlinx Classic Lite (or whatever the free version is called) and to be honest I had never downloaded or used either until encountering this issue on this job. As far as I know, I have no way to connect to the PLC or HIM without paying for the software licenses, and my employer doesn't seem to keen on doing that (I don't blame them--I don't know how to use the software anyway!)

Thanks in advance for any guidance you can give me

Even if you just point me in the direction of where I can look to learn more about this stuff, it would be greatly appreciated
 
A few initial thoughts: if ethernet connected, it would be very common to not use any hardwired IO at all. Your statement of 24v between terminals 6 & 8 makes me wonder if you are using wired I/O. If you are, there would likely be a jumper between terminals 7 & 8 to connect voltage reference for inputs to 24V common. The +24 voltage source for the inputs would come from terminal 9. If terminal 1 (digital in 1) is set to the default setting of STOP, you would need that input on to run. Check what the inputs are programmed to be.

It sounds like PLC code is controling the drive when you try to manually run it. You might be able to disconnect ethernet from the drive to manually test run. Of course make sure that wouldn’t break anything or anyone.

Here’s a few links to literature you might already have and something I created with disclaimer of no guarantees but it might help provide some insight.

http://www.plctalk.net/qanda/showthread.php?p=814907#post814907

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/20a-um001_-en-p.pdf

https://literature.rockwellautomation.com/idc/groups/literature/documents/in/20a-in009_-en-p.pdf

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/20comm-um015_-en-p.pdf
 
Welcome to the PLCTalk forum community !

For a first post, that's a fantastic amount of detail and candor. Thanks !

Your system sounds like it was designed with the minimum amount of controller capacity. The 1769-L16ER supports 6 local expansion modules, and you have 5. It supports 4 network "nodes" in the I/O tree, and you are using all four.

I've been in similar situations early in my career, told to go commission a PLC controlled system without the software tools. That is, frankly, an unreasonable expectation for an employer. It's one thing to empty the goal, another to ask the goalie to drop his stick too.


The I/O light on the CPU flashing green, and the Net A light on the PowerFlex comms board flashing green are consistent with the controller not successfully creating an I/O connection to the drive over Ethernet. That's also consistent with the normal setting of an A-B drive network interface, to Stop the drive when the network connection is lost.

That might even explain the "chatter" when you try to run the drive manually, as the broken I/O connection interrupts and stops the drive. I haven't ever tried that with a PowerFlex as I usually use either discrete-only or network-only control.

One tool we *can* use is the built-in webpage for the CompactLogix; just point an ordinary web browser at its IP address and navigate to the section that shows the I/O Connections.

Post, if you can, a screenshot of the RSLinx Classic browse that shows the IP addresses of the devices on the network.

If you have access to the *.ACD file for the CompactLogix, Forum members might be able to have a look at it via outside-the-forum connections, or you could ZIP and attach it to a post if that's allowed by your employer.
 
A few initial thoughts: if ethernet connected, it would be very common to not use any hardwired IO at all. Your statement of 24v between terminals 6 & 8 makes me wonder if you are using wired I/O. If you are, there would likely be a jumper between terminals 7 & 8 to connect voltage reference for inputs to 24V common. The +24 voltage source for the inputs would come from terminal 9. If terminal 1 (digital in 1) is set to the default setting of STOP, you would need that input on to run. Check what the inputs are programmed to be.

It sounds like PLC code is controling the drive when you try to manually run it. You might be able to disconnect ethernet from the drive to manually test run. Of course make sure that wouldn’t break anything or anyone.

Here’s a few links to literature you might already have and something I created with disclaimer of no guarantees but it might help provide some insight.

http://www.plctalk.net/qanda/showthread.php?p=814907#post814907

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/20a-um001_-en-p.pdf

https://literature.rockwellautomation.com/idc/groups/literature/documents/in/20a-in009_-en-p.pdf

https://literature.rockwellautomation.com/idc/groups/literature/documents/um/20comm-um015_-en-p.pdf

Thank you. At a glance, the bit in your "thing you created" about changing the 20-COMM-ER parameters seems like it could yield useful diagnostic information, and is something I can do with my limited software capabilities. As far as "not killing anyone" goes, I can disconnect T1, T2, T3 from my drive very easily to guarantee that. I'll run it by my equipment vendor tech support on Tuesday to see what they think (this is a brand new machine that has never been commissioned so I am very much in "I will change things that you tell me to change" mode with this process)

As far as programming goes, I believe this is a snapshot of what you are getting at as far as the "digital in" parameters:

TdWQVlr.png


As you can see, Digital In 1-5 are set to 0 and 6 is set to 1.

Here is a chicken-scratch diagram of wiring to my Powerflex 70:

Ox8zBgu.png


Red ink are the pin testing measurements I was describing in my earlier post

Please let me know if you have trouble reading or interpreting that terrible diagram haha. To be clear, there's a jumper wire between terminals 4 and 8

Welcome to the PLCTalk forum community !

For a first post, that's a fantastic amount of detail and candor. Thanks !

Your system sounds like it was designed with the minimum amount of controller capacity. The 1769-L16ER supports 6 local expansion modules, and you have 5. It supports 4 network "nodes" in the I/O tree, and you are using all four.

I've been in similar situations early in my career, told to go commission a PLC controlled system without the software tools. That is, frankly, an unreasonable expectation for an employer. It's one thing to empty the goal, another to ask the goalie to drop his stick too.

Tell be about it! Sometimes I feel like they hired me to be a cook to work in a cafeteria, then when I said "hey, there's no kitchen!" they looked at me like I was supposed to build it

As far as the level of detail/candor goes, this is completely outside my wheelhouse, so I don't even know what information is pertinent haha. I hope I didn't dump too much useless info on you

The I/O light on the CPU flashing green, and the Net A light on the PowerFlex comms board flashing green are consistent with the controller not successfully creating an I/O connection to the drive over Ethernet. That's also consistent with the normal setting of an A-B drive network interface, to Stop the drive when the network connection is lost.

That might even explain the "chatter" when you try to run the drive manually, as the broken I/O connection interrupts and stops the drive. I haven't ever tried that with a PowerFlex as I usually use either discrete-only or network-only control.

Just my luck that this thing has some goofy control programming!

One tool we *can* use is the built-in webpage for the CompactLogix; just point an ordinary web browser at its IP address and navigate to the section that shows the I/O Connections.

Am I understanding correctly that when I am connected to the ethernet switch with my laptop, I can look at my CompactLogix I/O connections by typing its IP address into my web browser? This is the same thing I did to look at my Murr remote I/O modules, but I did not know I could do this with the CompactLogix

Post, if you can, a screenshot of the RSLinx Classic browse that shows the IP addresses of the devices on the network.

I hope this is what you are after (it is from Connected Components Workbench):

OtCtG4T.jpg


Sadly I do not have a screenshot with the CompactLogix "tree" expanded. The IPs match the info on the tag on control cabinet door, for what that's worth

If you have access to the *.ACD file for the CompactLogix, Forum members might be able to have a look at it via outside-the-forum connections, or you could ZIP and attach it to a post if that's allowed by your employer.

I do have the .ACD file, as well as a photo of the IO status from the HIM while the issue is happening, if that is something that someone can "plug in" to the code to see what it produces. (I have basically no idea how this stuff works and am learning as I go)

I'm hesitant to post it on the forums but if someone wants to volunteer to take a look at it I will gladly PM or email it to them if they think I've got enough information for them to help narrow my focus

Thank you for taking the time to read my posts! As much of a nightmare as this project has been, I feel like I'm finally starting to have some idea about what I can look into to sharpen my skills and grow in this field, which feels good. I came into this from automotive repair a year ago, and my employer lacks resources and support necessary to do the basics of the job (commissioning, repairs, maintenance) efficiently, let alone this technical stuff. I haven't even known what to ask them for to help me fill in those gaps, or who even to ask, or how to look into it myself, etc.

It feels good to see a glimmer of light at the end of the tunnel in terms of a path forward with this career, and just the information I've been exposed to (blindly) troubleshooting this issue with vendor tech support has given me insights and clarity I was sorely lacking before
 
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A Rockwell studio 5000 service edition is about $750 dollars. With what you’ve uncovered in a short amount of time I’d say you’d be able to figure it out if you had access to it. Thank you for the detail you provided.

On the other hand this is your vendors problem. I’d never leave a customer on a wild goose chase for something like this. Whoever wrote the program, if competent should be able to diagnose an issue like this in a few minutes if they can see it live.

Until you can get the controller happy with the IO connections you are just chasing your tail. Unless it is something as simple as an IP address being wrong, I think you’re going to bang your head in the wall until they get you some good help on the phone.

If you do obtain access to the code please post it because that is really the only thing I see that we will be able to find any errors.

I don’t know what this machine does but 750 dollars is chump change to be able to quickly fix an issue these days. If you do obtain the software I’d be happy to guide you along over the phone or teamviewer.
 
Thanks for the additional detail !

The Murr subsystem must consist of one Ethernet-connected base block (the CUBE20 DI8) with more than one expansion modules connected to it, rather than multiple Ethernet nodes.

While you've said that the IP addresses on a label in the cabinet match the IP addresses you see in a network browse (that's the RSLinx browse), that doesn't mean for sure that the I/O "tree" in the CompactLogix is configured as the documentation says.

The fact that the modules are on a Class A IP network (10.x.y.z) is also a bit of an eyebrow-raiser; I try very hard not to use enterprise network addresses for my automation devices, and the use of such network addresses makes my Spidey-senses tingle that somebody was setting up a machine inside their shop network without thinking about how it would be installed onsite.

It would be useful to see what the PowerFlex HIM module displays when you physically remove the conductor on Digital Input 6 (Enable), or when you hit the e-stop and trip that Safe Torque Off feature.

Because most of your digital inputs are disabled, the drive isn't looking for a discrete Start or Stop, and you're not getting a "Stop Asserted" because of a missing input on DI 1, which with the default "Stop-CF" setting has to be held +24V high to give the drive a "not STOP".

If you experiment again with trying to start the drive from the buttons on the HIM module, do it with the Ethernet cable disconnected.
 
Now there are some troubleshooting steps I'm capable of taking. I like it, thank you!

5618 was nice enough to pour over some of the code for me and he sent me this screenshot of the ladder logic of the alarm that won't clear:

sF6KYQZ.jpg


We were wondering if that bit might not go off if the PLC lost comms to the drive while it was faulted?

I'm speculating something along the lines of PLC won't enable the drive because it's faulted -> drive won't communicate over network because the PLC isn't enabling it kind of situation, but I really don't know enough about this stuff to speculate lol

I really appreciate all of your help
 
Is the fault indication on the drive? Your first statement is correct. If the drive faults with an active connection the fault bit will turn on. If connection is lost the fault bit will still be on. If the drive is faulted the and won’t clear then the fault condition is not remedied or there is no connection.

Ask whoever looked at the file for you to post the network settings tab for the powerflex 70. We can compare those to what is actually in the drive. Since it was preprogrammed for you and the parameters did not come from the plc there is a possibility of error there.
 
When you say the network settings tab, is that something in the PLC programming or the VFD itself?

Here are the non-default 20-COMM-ER parameters from my Powerflex 70 programming in Connected Components Workbench:

xMjo7pu.png

o4VuXfS.png


As far as faults go, here is what was stored in drive when I was connected to it live with CCW:

vn606LQ.png

ERsUOpe.png

4JuKE45.png


I clicked "clear trip" shortly after that screenshot was taken, which did not change the issue

The LCD HIM on Powerflex 70 just shows "Stopped" or "Not enabled" (I can't remember when it shows which--I know one is when e-stop is in and the other is when it's reset/rearmed). The alarm bell on HIM isn't displayed. It is just "F->, Stopped/Not Enabled, blank (no alarm bell), Auto, some sort of icon that looks like an eye with eye lashes" at the top of the LCD HIM on the Powerflex 70

Let me know if this isn't the info you were after, and if you wanted something from the PLC programming

I can reach out to 5618 or I can probably grab it for you -- he sent me an xps file that is a report of all the PLC programming, so I think whatever you're after is in there, I would just need to know how to find it
 
This matches the IO tree, at least of the saved file. I won’t be drilling down to drive parameters today. I don’t have a profile installed for 5.001 of this drive. I already had 4.12 profiles. I just added 5.06. The notes for that indicate its for V31+ and it didn’t help with this. That’s a battle for another day.

There’s GSV code for connection status. Unfortunately there’s no HMI indication of that. Adroit, you might be able to get a trial license from your distributor. If you had a V30 installer, it would run for a grace period to get you online to see what’s happening. It’s probably worthwhile getting a license for at least a service edition but maybe standard edition so you could edit if desired.

Without getting online, your best indication of connection seems to be the LEDs. I don’t know the details of that well enough to comment without devices at home to test.

Print to XPS is the only non-paper option I have on my development system. I used Sumatra PDF reader (free open source) on another system to print to PDF but that was over 2gb so I just sent the XPS. Windows 10 apparently had an XPS viewer that was dropped from recent versions but can be added.
 
I also had a quick look at the *.ACD file.

The IP addresses in the I/O tree for the Murr block and the PowerFlex 70 match the ones that are verified via web browser and RSLinx, so it's probably not something simple like a mismatched IP address.

The I/O connection status LED on a CompactLogix will flash green when one or more of the cyclic I/O connections has not been established, or has broken.

That could be one of the local expansion I/O connections, or the networked ones. Because the five local POINT modules have solid green status LEDs and the status of points on them and the MURR networked modules appear to be properly updated in the status displays on the PanelView, then those connections are likely running correctly.

So we're back to the PowerFlex.

Electronic Keying is disabled, so that's not the problem. It could be a DataLinks issue, so I'm going to look into that next.

PF70_Connection.PNG
 
On the note of software licenses, I actually have some questions about selecting software that would be right for what I'm doing, and how to go about it

First, I work with a number of different equipment vendors who I imagine use a range of software to program their machines. Do you think a good way of determining appropriate software coverage might be to reach out to my vendors and ask them "hey, which software versions do you think I should have in order to work on your machines?"

I'd make a list of each vendor and their recommendations, with any notes about years of production corresponding to each version or whatever, get a quote from my AB distro, then follow back up with the vendors to see what they think about different options given to me by the distro, then present to my bosses

Something else I am wondering, is would having access to any of these software licenses be of use to me with more "normal" issues with commissioned equipment? If it could help speed up my troubleshooting by quickly narrowing my focus, I could see that as a way to "sell" it to my bosses

For example, let's say I have (a machine) not doing (a thing) despite seemingly being told to do that thing. Obviously I would do the simple troubleshooting first, like checking that the corresponding PLC input is lighting up when I manipulate the controls, seeing if the fuse for the circuit is intact, status lights and displays on VFDs and other components, etc. But if everything looks intact and it was a machine that was running before (something happened), would I be able to, say, plug into the PLC and go to the section of the code for (doing a thing) and see what is missing in my live data in the ladder logic? Then that could narrow my focus with which component/circuit to look at in the machine when I compare the component name in programming to the electrical schematic for the machine?

I work on such a wide variety of equipment, it can be tedious and time consuming to wrap my mind around a) what a machine is meant to do and b) how it is meant to achieve that result before I can narrow my focus on troubleshooting the machine. I think some sort of ability to have an efficient and generic troubleshooting process for machines with AB PLCs (pretty much everything I work on has an AB PLC or a printed circuit board as its CPU)

Any insight about how I might go about determining appropriate software licenses and "selling" this tool to my bosses would be much appreciated
 
I think the connection between the PowerFlex 70 and the CompactLogix has the wrong size settings. I'm going to chase this down while posting updates.

"DataLinks" are a way of adding specific drive parameters to the cyclic I/O connection so that they are updated every few milliseconds, rather than being accessed through messaging instructions. The nomenclature and numbering can be a little confusing because the feature has evolved (from 16 bit to 32 bit) yet retained backward compatibility (from DPI to SCANPort).

The evidence is here in the Drive Peripheral Interface (DPI) Master-Slave Connection parameters for the 20-COMM-ER itself. The drive is "configured" to run DataLinks A and B as well as the ordinary Command/Status + Reference/Feedback connection, but it's actually only running the Command/Status + Reference/Feedback.

We should be able to resolve this with CCW, since that gives you access to all the drive and 20-COMM-ER parameters.

DataLink_Actual.PNG
 
Interesting!

Pardon my ignorance if I am again completely off base, but I wonder if this is something that would make sense if this machine had run before with PowerFlex 70 installed and programmed as configured?

I can imagine the PLC might do different things if it had lost connection with a faulted drive vs establishing connection for the first time with that drive, but I just don't know enough to say for sure

I guess my question is, is it conceivable the "wrong size settings" issue wouldn't have presented itself in the factory but would present itself under these conditions when replacing the drive in the field?
 
The DataLinks are selected as part of the Device Definition -> Connection Format in Studio 5000. Attached is a screenshot of how these DataLinks are set up to add the Fault Code and the Output Current to the data that's transmitted by the drive to become PLC Input tags, and the Positive Torque Limit to be send from the PLC's Output tags to the drive.

It's often overlooked that the DataLink "pointer" parameters are the first step of getting DataLinks working. ENABLING those as part of the Master-Slave Connection is the next step.

DataLink_Definitions.png
 

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