AB 1746-NI8 Analog Card

While this is fresh on my mind, let me pose a question which has me stumped. I have a SCL 5/03 16kM OS 302 Series C FRN 3-8 i.e. (1747-L532E). In slot 3 there is an 8 ch analog input card, 1746-NI8 Input Class 1 (or 3).

If i ask the PLC to read its own IO, it is class 3 and it doesn't work - no input is read. If i tell it in the
"IO configuration" that the card is Class 1, it works - sort of - for a few hours or some of the IO on the card works and other doesn't. If i use a program that downloads the IO configuration, then it works just fine.

WHY? Should i buy a new IO card? Is this abnormal behavior?

narlin

It may be a configuration problem. Can you post your program?


edit: You may want to look at this threads.
http://www.plctalk.net/qanda/showthread.php?t=64976

And this thread, which is actually about a Micrologix but SLC500 NI8 analog card configuration is talked about in it and if you'll follow the graphic you should still be able to figure out the NI8 module configuration. http://www.plctalk.net/qanda/showthread.php?t=66559

Narlin:

Post your PLC Program (Zip it first, Forum Rule)

Stu....

I will read the posted links first and then after looking at the various CDA's i will post the program. I don't think there is anything confidential, but the program is large - 39 subroutines and some of them pretty long.

i will get back to this tomorrow. The behavior hasn't changed for a couple of years - it'll still be here.

OK. I could use your help. I have attached (i hope -1st time) the zipped RSS file. The correct manual for the 1746 NI8 analog card can be found here or google. From reading the manual it is obvious that one is supposed to transfer the channel configuration word to the card with an instruction such as COPY FILE. Where source is #N10:0 and dest is #O:3.0 Length 1 "or words to that effect".

Problem is that in searching the code with the cross reference and even searching by printing out a searchable pdf print, i don't find anywhere that the channel configuration has ever been told to the processor. Yet it knows! This thing has been mostly working (including today) since 2006. How it does that?

I need nourishment. I'll check back.

narlin

the following bits have been turned on in EACH of SEVEN words of your module's OUTPUT table ...

bit 0 = 1
bit 2 = 1
bit 9 = 1
bit 11 = 1

this pattern sets up the module for 4 to 20 mA input signal;
50 Hz filter;
and enables the channel ...

it looks like someone just typed the bit patterns mentioned above into the following words:

O:3.0
O:3.1
O:3.2
O:3.3
O:3.4
O:3.5
O:3.6 ...

(apparently the last channel is not being used by your system - so O:3.7 has been left with all bits as ZEROs) ...

as long as these values stay "as set" then the module will just accept the configuration and go to work ... the idea of COPYING the data into the output words at startup is usually done – but as long as the proper bit patterns end up in the output words, the magic will happen ...

obvious that one is supposed to transfer the channel configuration word to the card with an instruction such as COPY FILE. Where source is #N10:0 and dest is #O:3.0 Length 1 "or words to that effect".

Click to expand...

Normally that's the way it is done. But you can simply set the bits manually in the configuration word(s) and if nothing else is writing to those words it will work.

See picture

Ron types faster then I do.

Cool! I see it in the output data file. My explanation for the off again on again behavior is that when i save files, the prgm often asked if i want to save the data files as well. Since, when i code i always set the init data in code, it is common to tell the RS500 prgm NO. I am not interested in saving the data files.

Wrong! This is one case where the data files really are needed.

Thank you.

Ron, nice to hear from you. Keep up the fast typing.

narlin

I would highly recommend moving the Data with the First Scan Bit. That way if the Memory is ever cleared, the Processor is replaced etc, the proper Data will be moved to the NI8.

The NI8 is a configurable Card. If you Upload the current PLC Program File, and then Configure the NI8 Card in the I/O Configuration, it should create a Copy (COP) Rung to configure the NI8. You may need to modify the Configuration, then change it back to get it to generate the Rung. Then you can either use that, or modify it to an existing Data Table. If you can't do a Download, you can insert the Rung and Data Table Values Online.

To see how this works, create your own empty PLC Project with the same PLC, and insert an NI8 in the I/O Configuration.

You might want to rethink the Saving Data Tables option.

Stu....

Stuart? I fully intend to add code that will initialize the analog card. Understanding how it works is invaluable.

narlin

This thing has been mostly working (including today) since 2006.

Click to expand...

It is amazing how many ways some programmers come up with to "protect" their jobs. Somehow, it never seems to work, and the guy who set those Slot 3 bits is probably long gone and forgotten. It seems if they spent more time writing good user-friendly programs with full documentation, they wouldn't have to worry so much about getting canned...

Narlin,

RSLoigx500 will generate the code and create the data tables for your. See the links I posted above and follow the prompts. Even though the graphic was for a micrologix if you click the advanced button then it will take you through setup for your NI8 module and it will insert a rung to do the COP the configuration file for your.

So. I looked carefully at Alaric's comments and let RSLogix 500 generate a line of code for me. Couldn't be much easier than that.