Rockwell Flex I/O issue

Hi All, time for me to ask a question,...

I have a PLC5/80 with an existing Flex I/O rack 13 on RIO (1794-ASB), with 5 digital cards already installed and working.
I need to add an analog input card 1794-IE8, but due to the panel layout I am using an extender cable (1794-CE1).
When the card is installed this way (slot 5) there is no response using BTW/BTR, but if I relocate it to slot 0, then it works fine.
I am now trying this on the bench, as I cannot shuffle the I/O in the panel.

Question is - is there an issue using Flex I/O analog cards and extender cables, as that is what my initial studies suggest?

I am away to play about with the position of the cable/slots/cards to try further diagnostics to solve the issue, and I have raised a service ticket with Rockwell (they have only given me a standard response - check knowledgebase - which I have).

Thanks in advance for any help/input/suggestions.

If it's undamaged and installed properly (and the contacts and terminal blocks it's connected to are likewise undamaged), a 1794-CE1 cable works exactly like the sliding contacts on the FLEXBus rail connection itself.

FLEX I/O has no slot position or distance from adapter dependencies for any type of module. Analog modules can be in Slot 0, or Slot 7, or anywhere in between.

If the FLEX Adapter is configured for Standard addressing, then as you noted the 1794-IE8 added after five discrete modules would be addressed as Rack 13, Group 05, Slot 0.

Are you using something other than Standard addressing mode ?

Hi Ken, thanks

yes, racking my brains here, just nobody here to bounce my thoughts with....see holidays!

Aye, tis all standard setup.

I did however find that my test rig 1794-ASB had bent pins, (probably due to my over-zealous ham-fisted apprentice - not taught by me!) so that will be getting ditched...that has been replaced with a working version, and IE8 in slot 0 works with the cable, so I will go and extend it out til slot 5.

Just been back at the real rack and I notice that the 24V is a tad low at 19.5V...wonder if that is an issue for powering up analog cards? The spec does say it will work down to 19.2V...

Bent pins will definitely cause the problems you're describing. The FLEXBus is essentially eight two-wire serial connections in parallel, so bending the bottom pins of the bus connector can affect just the rightmost slots.

19.5 volts is a little low, but the range is conservative. It ought to work, but check it again once it actually starts driving loads.

Ken,

Just thought I would come back to you on this one, although I have not resolved it fully.

Checked all the pins/configuration on the plant - all OK.

Simulated the entire rack in my test facility, then got another RIO Adapter, this time a 1794-ASB Series E, and tested it with the same settings as we have on the live system.

Did an auto-configure and it gave me rack 13 AND 14.

Did a bit of digging, and lo and behold they have changed the dip-switch configuration, SW2 3&4 now have either 32 channel cards OR 230.4 kBaud communication, depending on switch position....Duh! So it seemed to be trying to use 32 channel cards, hence it gave me 2 racks for the price of 1..

The live plant had an adapter 1794-ASB series C....so now swapped that out for the new one and it works...so now need to check out the old one on my test facility.

hopefully we always get there in the end.......

Thanks for the update !

The 1794-ASB has had a very long life... I remember when they were introduced in 1994.

When they got the high-density options in Series E, it really drew a line between the earlier Series and the Series E because of the DIP switch changes. I kept both of the user manuals in the same binder with the Series E circled and highlighted to remind myself which one I was grabbing.