monkeyhead
Member
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.
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!!!!!!!!!!!!!!!!!!! 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.
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!!!!!!!!!!!!!!!!!!! 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.