Octal Optics...
A suggestion, if I may?...
It may not matter, especially if you are just making a general enquiry, but mentioning the actual module's catalog number might help better jog some people's memories, which may then help them provide you with more specific experiences. But I'm sure general recollections will suffice?
Aabeck said:
I just had a weird one last night and was wondering if anyone else has ever seen this.
A SLC5/05, 7 slot rack. One thermocouple input, One 18 TRIAC output, all the rest are 24VDC IO.
The TRIAC only has 2 used outputs and they both died last night. I reprogrammed to other outputs, and still nothing. I tried the other bank using the other 120 input & nothing. Thre was 120 going into the card. The unused outputs, even the "bad" ones, showed leakage voltage when not wired.
I shut the PLC off, reseated the card, and when powered up the CPU faulted. Online it showed the IO count for the card in slot 3 was wrong and would not reset. IO config showed a 16 TRIAC card.
I went offline and did a IO Read and it read slot 3 as "Module 4" not any known type of IO card.
I had to get another TRIAC card and replace it and it works fine now.
Has anyone seen a TRIAC, or other digital output card, ever shut down completely like this? First one since I started on PLC 2's.
I've definitely had a couple of AC solid state triac output modules fail in the past, and not just SLC 1746, also 1769 and 1771, but not 1756, that I can remember? But I've seen various modules fail in general and would not single out AC triac modules for any particular reason. Generally they are pretty robust. Overtemperature probably being their "Kryptonite"?
Out of interest, what type of load is wired to the 2 used triac outputs?
I would also agree that degraded or badly plugged chassis slot connectors can play a roll in premature module failure and also I've had to replace a chassis or two for slot failures after having first swapped out the suspected modules to no avail. We always carry a couple of different sized spare SLC chassis, just in case.
I've just a question or two on what you've mentioned (in
Bold above) on the apparent number of output points you were/are seeing for this module. How did you come to realize that the original, and possibly replacement module, had/has "18" output points?
You also mentioned that the IO Configuration was incorrectly reading this "18" point module as a "16 TRIAC card". Can I ask if, under the IO Configuration, you have an "18 TRIAC card" available for selection in the list of modules, or what is the IO Configuration reading the replacement module as being now?
Again, the catalog number for the module would have helped verify my thinking here, but off the top of my head I do not believe there exists a 1746 18 point AC output module, unless there's some third-party module I'm not aware of?
If you don't correct my recollection here, then what I'm suspect is that you may have been viewing the module's labelling where either or both the filter and door have octal labels fitted?
The reason I'm thinking this is because octal labelling for a 16 point module will display the highest point as "17" octal and not "15" decimal, as perhaps we might expect. This "17", if viewed quickly while also seeing "0" for the first point, might suggest to us that there are "0 - 17" module points (decimal), which of course would appear to be a module density of "18" points.
Without getting into the reasons for using octal labelling too much, the SLC modules are shipped with decimal labels as standard. If the SLC I/O is being installed in an older PLC system (PLC-5, etc.), which uses octal numbering, then we can order an Octal Label Kit to convert the module numbering. I've also seen second-hand or remanufactured modules purchased with octal labelling fitted and then used in a decimal SLC system without having removed the octal labelling. It can be misleading, when unwittingly encountered.
Example 16 point module Decimal/Octal numbering...
DEC 00 = OCT 00 DEC 08 = OCT 10
DEC 01 = OCT 01 DEC 09 = OCT 11
DEC 02 = OCT 02 DEC 10 = OCT 12
DEC 03 = OCT 03 DEC 11 = OCT 13
DEC 04 = OCT 04 DEC 12 = OCT 14
DEC 05 = OCT 05 DEC 13 = OCT 15
DEC 06 = OCT 06 DEC 14 = OCT 16
DEC 07 = OCT 07 DEC 15 = OCT 17
Anyway, knowing the catalog number for the module would set us straight here on the actual density, and you could set us straight on the labelling, if it is a factor here?
Regards,
George
