You have really opened up a can of worms here, Stan.
We use Integrator 30s at our plant. They cause a lot of pain in both set up
and operator usage. The work is done in the PLC 5s and the I/A is used for
operator interface. The Basic Processing Cycle of the AB Gateways is 2
seconds. Our CP30s and CP40s have a BPC of 0.5 seconds.
Configuration involves setting up a lot of redundant (in the I/A) blocks to
get information in and out of the PLC. Take a GDEV block for instance.
There must be a CIN (or part of a MCIN) block to bring in the MA status.
Another is needed for the device state (ON/OFF). Another pair of
connections is necessary to send the desired states back out. That is four
blocks so far. If the mismatch state detection is not monitored by the PLC,
then another I/A block is required. If it is done by the PLC, then you can
have two more blocks to detect mismatch conditions (1 for open mismatch and
1 for close mismatch). Five (or 6) blocks (or block connections) are needed
to do what one GDEV can do in an I/A system. You can reduce the total
number of blocks by using MCINs and MCOUTs. (Remember that MCINs have 32
connections and MCOUTs only have 16.)
If this situation ever needs troubleshooting, it quickly becomes a
nightmare. DO NOT lose your cross-reference sheets from the start up. Your
inputs are here, your outputs are there, your mismatch sensing is somewhere
else. There is nowhere to link your displays for control details, because
there are 4 (or 5 or 6) I/A blocks (or block connects) per PLC device.
As far as operator usage, think how long it takes to change a valve to
manual and open it. The operator sets the valve to manual. It can take up
to 2 seconds before the PLC gets the information. It can take up to another
2 seconds before the confirmation comes back that it is in manual. It can
take 2 more seconds to send out the desired change of state and another 2
seconds before the operator has confirmation that the valve actually opened
and the process does not have to be repeated. Eight seconds! The operators
believe that the I/A is causing the problem!
Analog controls have similar issues, except for mismatch configuration.
But, you may run into problems with ranges of the I/O. We pass information
in and out of the PLC via integer tables that typically have a range of
0-4095. In some places the range is 0-32766. Our scale tanks have a weight
range of 0-220,000 lbs., so we compromise them by measuring in units of 10
lbs.
There is more, but I think you are getting my general impression of an I/A
to AB cluster. I should stop while I can still use language fit for the
dinner table. I firmly believe that this should be addressed in the future
by Foxboro and/or Allen Bradley. I am okay with pushing online upgrades
this year, but next year...!
-----Original Message-----
From: Stan Brown [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, May 03, 2000 6:42 AM
To: [EMAIL PROTECTED]
Subject: Integrator 30's vs. AB Stations
I would like to hear other users options on the ppros & cons of
these 2
different ways of conecting an Allen Bradley PLC (or PLC's) and a
Foxboro IA system.
Yhe PLC's would be PLC5's, and the IA would be serries 50 stations.
--
Stan Brown [EMAIL PROTECTED]
843-745-3154
Charleston SC.
-----------------------------------------------------------------------
This list is neither sponsored nor endorsed by the Foxboro Company. All
postings from this list are the work of list subscribers and no warranty
is made or implied as to the accuracy of any information disseminated
through this medium. By subscribing to this list you agree to hold the
list sponsor(s) blameless for any and all mishaps which might occur due to
your application of information received from this mailing list.
To be removed from this list, send mail to
[EMAIL PROTECTED]
with "unsubscribe foxboro" in the Subject. Or, send any mail to
[EMAIL PROTECTED]
