1747-L40C communications

usstrap · Mar 11, 2013

Have an old 1747-L40C running process machinery. Over the years, outputs fail, etc and got to the point that I had to replace. Bought a used unit from Ebay but it will not communicate. I have the old laptop with serial port, got the PIC and know it works. Have old copy of the APS software and know it works. This replacement PLC unit shows power but CPU FAULT light is blinking. I cannot get computer to recognize this PLC so can go no further. Can anyone get me on a correct path?

dmargineau · Mar 11, 2013

The flashing FAULT LED denotes a Major CPU fault, however, this should not restrict the communications capabilities of a functional processor.
Refer to Page 8-6 of http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1747-um009_-en-p.pdf
for probable causes and mitigation solutions.
In order to connect to the CPU and "solve" the FAULT condition, you will need a Serial (RS232) Port PC running RSLogix 500 + RSLinx Lite (or the APC software) and either a 1747-PIC, 1747-KE or a 1747-KF3 adapter in order to connect to the CPU.
Refer to Appendix A of the above posted link in order to setup the CPU comminications.
You might have another shot if you could secure a 1747-DTAM-E hand held programmer; clearing S:1/3, S:5 and S:8 memory addresses might return the CPU to a functional state.

usstrap · Mar 11, 2013

I appreciate you responding. I have computer with RXLogix 500 but only USB ports and serial adapter cable. I have the 1747-PIC but trying the 'who active' will not connect.
With my old PC with APS software and the PIC, I had no problem with the identical PLC, it just doesn't recognize that there is anything connected.

bernie_carlton · Mar 11, 2013

PIC won't work with a USB - RS232 adapter.

Ken Roach · Mar 11, 2013

Let's take a step back: You say you have an old computer, with a serial port and APS software, and a 1747-PIC that is known to work.

But that computer won't browse the "new" 1747-L40C on DH-485.

If this were my system, I would keep trying with that old computer. As Bernie mentioned, you can't use RS-232 converters of any sort with the 1747-PIC. The 1747-UIC is the standard way to connect to DH485 from a modern computer.

If the confirmation the old computer being "known to work" is not very recent, do it again by finding another SLC-5/0x controller to connect with.

The two configuration variations I would try are attempting to use DH485 at 9600 baud, and try node numbers 0, 1, and 2 for the RSLinx driver.

usstrap · Mar 12, 2013

I hooked up to the PLC I'm trying to replace and my stuff will connect straight up. I'm asking the Ebay seller if he can exchange this machine with another. Many thanks to you folks for trying to help.

alan_505 · Mar 12, 2013

The last 1747-L40 that i worked on we replaced it with a ML1200, the only problem was that the inputs and outputs were on the opposite side for each type of processor.
Surely a new ML1100 would be cheaper that an old 1747-L40.

usstrap · Mar 13, 2013

You are probably correct but this machine is on a budget and I have to scrape. I have an old 7 slot rack here with I/O cards that will fit this application if processor can be modified in the program. I:O/18 would have to become I:3/2 I think. Can this be done with RSLogix? Old processor 1747-L40C. This one = 1747-L542B. Ladder stuff should function fine.

OkiePC · Mar 13, 2013

usstrap said:
You are probably correct but this machine is on a budget and I have to scrape. I have an old 7 slot rack here with I/O cards that will fit this application if processor can be modified in the program. I:O/18 would have to become I:3/2 I think. Can this be done with RSLogix? Old processor 1747-L40C. This one = 1747-L542B. Ladder stuff should function fine.

Yes, you can change the processor type and then move the I/O.

See here for some tips on that last part:
http://www.plctalk.net/qanda/showthread.php?t=4673

usstrap · Mar 14, 2013

I changed the processor and I/O config no problem. The database shows all I/O at both addresses but the ladder display still shows the old base unit addresses and errors re the unconfigured I/O. How do I put this right? I really appreciate your help.

OkiePC · Mar 14, 2013

Can you post the original file (zip it first) and explain which slots or points move and to where?

usstrap · Mar 14, 2013

Uh, I'm brand new to this and I wouldn't know how to do this. email me at [email protected] and I'll send directly. Thanks again.

dmargineau · Mar 14, 2013

Zip the RSLogix 500 .RSS file.
In the bottom of the PLC.net window choose "Go Advanced"; you will be given the option to Attach Files; choose it, point the utility to the recently zipped file ( Browse) and then "Upload" it; "Submit" your Reply.

Mickey · Mar 14, 2013

usstrap said:
I changed the processor and I/O config no problem. The database shows all I/O at both addresses but the ladder display still shows the old base unit addresses and errors re the unconfigured I/O. How do I put this right? I really appreciate your help.

Brute force. Click on search then use the replace option.
See picture.

I would list all the old addresses and then put next to them the new addresses
and get to it.

usstrap · Mar 14, 2013

Ok this should be it. I moved the I/O by search/replace; there weren't that many. My next brick wall will be finding the card for this rack that can talk to a OIT that is connected. I really appreciate you guys giving your time.

1747-L40C communications

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