Beware of the L33ER

monkeyhead

Member
Join Date
Sep 2004
Location
I'm right here
Posts
656
I replaced a 1769-L35E with a 1769-L33ER. Bad, bad, bad, baaaaaaaaaaad, move!! After many (un-billable) hours trying to recover from that mistake, the 35E is back in place. I thnk we also just did our last job for this customer. o_O

Long story short - The customer noticed overlap faults on the 35E and wanted a fix ASAP. We found the new L33ER was supposed to be a good replacement that offered better performance. So we got one for testing.

Back at the shop everything looked great. The scan times were faster. Wehad the I/O inhibited since it wasn't available at the shop. We stupidly thought the system overhead would be about the same and we knew the scan times on the 35E with all the tasks inhibited.

Since tests all looked good the PM offered the customer a free upgrade to make them happy. We all thought we were doing them right and patted ourselves on the back.

Onsite with the customer watching and the thing just blew up. Overlap faults out the wazoo as soon as we loaded up the new PLC! It took a while, but we finally realized the whole problem was that the compactbus task was using over 40% of the CPU!!!!!!!!!!!!!!!!!!! :eek: It ate up everything we gained on the bench and more.

Rockwell support didn't have answers, but I did find some stuff on their site that show that this new processor just CANNOT handle very much IO.

http://literature.rockwellautomation.com/idc/groups/literature/documents/qr/iasimp-qr007_-en-p.pdf

Page 20 to 22 tell the whole story. I'd recommend avoiding this hunk-of-junk till Rockwell fixes it. Better performance my left foot! It doesn't matter that your program runs faster when the thing uses almost 4 times as much CPU to do the basic job of the PLC and read in the I/O.

Hope this saves someone the headaches I've endured.:confused:
 
Thanks for the info. I have used 3) L33ER units in the past and have very good results. But I dont have any high speed inputs or fast RPI's in my systems. Mostly just Digital I/O and some Analog. All my RPI's are 20ms+ so I guess I am not taxing the processor very much.

What service was your L33 in? I assume that you have some very fast RPI's.
 
this might NOT have anything to do with your problem ... if fact, it probably doesn't ...

but ...

just for kicks, take a look at this post ...

http://forums.mrplc.com/index.php?showtopic=26162&p=125399

preview: it involves the I/O scan cycle on various COMPACT-logix systems - and how the I/O transfers can be affected by the task PRIORITY settings ...

tip: listen to the first WAV file included and see if you think that this MIGHT have some bearing on your situation ...
 
What story is this document telling? You're using a 5370 L3 processor, so for 5 digital and 3 analog modules a 1ms RPI (which is insanely fast) will utilize 41% or the processor as opposed to a 59% for the 1769-L35E. That seems better, not worse. I don't think this is saying that 5 digital and 3 analog are the absolute max but is just using those as an example setup. Could the problem be too many I/O modules in general (and thus the problem with the original processor)? Could your RPI be set way too fast? According to this document, 5ms is plenty fast for an RPI. If you're using 40% of the processor maybe its set faster than that? Could you slow it down further?
 
Last edited:
I replaced a 1769-L35E with a 1769-L33ER. Bad, bad, bad, baaaaaaaaaaad, move!! After many (un-billable) hours trying to recover from that mistake, the 35E is back in place. I thnk we also just did our last job for this customer. o_O

Long story short - The customer noticed overlap faults on the 35E and wanted a fix ASAP. We found the new L33ER was supposed to be a good replacement that offered better performance. So we got one for testing.

Just make sure that if you decide to set the firmware of this to v20.13 (to work with RSL5k 20.03) that you get a good copy of the firmware...'cause you need to re-burn the firmware every time you want to download the whole program to the PLC. Yeah, crazy.
 
According to the specs, you are outside the recommended RPI with 8 modules.

CompactLogix Performance and Capacity

*Digital and Analog (any mix): 1-4 modules can be scanned in 1.0ms
5-16 modules can be scanned in 1.5ms
17-30 modules can be scanned in 2.0ms
1769-HSC (High Speed Counter): Add 0.5ms for each used
1769-SDN (DeviceNet Scanner): Add 1.5ms per module

"Guideline: Set the RPI for CompactLocal Bus modules to 5ms or higher (5ms is
default in v16 or higher), unless faster RPIs are required for your application. See
information below for impacts of faster RPIs"

On my lab processor (L35E) if I set the RPI to 1.0ms with 6 modules, I do see a sizeable CPU usage (40%) for the virtual backplane. If I set the RPI to 20.0ms for all modules the virtual backplane CPU usage drops down to 2.5%.

Another Note, on an L35E processor with Version 19.11 firmware (probably others too) you can set the RPI individually for each module on the LocalBus, this has proven beneficial to me, I can use a real fast RPI when it's necessary, otherwise; why waste the CPU cycles just to scan I/O real fast that doesn't benefit from it?
 
Jeff,

I know you've been burned by the 20.00 -> 20.03 divide and have posted some information on it. Would you mind posting some of the sources and context for that comment about burning the firmware every time you do a download ?

Is that specific to a CompactLogix, or is it a general principle in v23 ? Are there Knowledgebase articles or release notes describing it ?

I have a system running v16 on 1756-L61 controllers and I'm considering a Windows 7 upgrade for everything, so I figure go to v23 so I have the very latest firmware that the 1756-L61 will run.

But if it means altering how downloads work, I'm not sure I want to do it.
 
Ron - Awesome post in that link! Thanks for info.

Regarding FW/SW rev - tried the latest and greatest 20 and 21 FW. With the latest Logix/Studio5k available. negligable gains on V21/Studio

Regarding I/O - 10 discrete modules with mixed RPI's between 5 and 20 ms including one pro-soft for data comms with a DB server. Performance was still pretty dismal with them all set at 20 ms, and the mechanical process was way less stable with all the additional variation. The reason we didn't go L4 was in hopes of eventuall getting rid of the pro-soft card since the L33ER can supposedly do TCP messaging (finally...)

Blame us all you want. We own not starting out on a higher ed processor like ControlLogix (or most non-Rockwell PLC/PAC's out there). This L33ER IO performance isn't well documented in any catalog, selection guides, or normal specification documentation. I had to go out of my way to find it. Kept getting documents about the L33ER being 2-3X the performance though... o_O

Anyway you spin it, the new product is WORSE at handling I/O than any of it's predecessors in the CompactLogix family. Look at all the charts in that section sense of just how much worse. It's uggggggly.
 
I hate to be a "me too", but that was really an informative (and another thing to worry about ) post ... thank you Ron. ...that was something... I liked the audible output idea... I hope to remember that. I think that might also prove useful for other situations... lotta times I put a counter somewhere to see if something happens ... maybe a chirper would be a nice option. Certainly was the ticket in your demonstration

I just ordered, received, and am in the process of programming 3 L16ER CompactLogix controllers.

I am hoping that my application will not be affected by the problem you mention, but it does have time sensitive aspects. I am one of those who assumed that the ControlLogix and CompactLogix were essentially the same thing.

Does the chirper I/O problem apply to the embedded I/O as well, or just the modules?
 
Last edited:

Similar Topics

Most people are aware by now, but for those contemplating ordering AB equipment on eBay because it has a great price, I want you to look closely...
Replies
10
Views
1,270
Sorry, have to vent here. I've used a number of Digi products over the years with success. We recently installed a number of the Digi ONE IAP...
Replies
27
Views
7,932
Hey guys, On my system, i got prop valve controling cylinder on the left and right to adjust the center of a lumber before it get in a woodmill...
Replies
8
Views
820
Hi Friends, I have an upcoming project were I need 20 pcs of ModBus TCP Clients / AOI. to control 10 devices I use 20 transactions to control 10...
Replies
4
Views
695
We have a machine that has a 1769-L33ER and we were wanting to connect it to our plant network. Currently has a local network for drives and HMI...
Replies
1
Views
815
Back
Top Bottom