westinghouse PLC 1100

[jameel]

Hello every body
we have a Westinghouse PLC 1100 , for one of our mixer machines,this PLC is old and has alot of problems,so i am changing it with HITACHI PLC.
So converted most of the ladder diagram of Westinghouse to HITACHI , but some commands of the Westinghouse in the ladder diagram i do not know what it means.
like HR0014 and above that i see BS0004 and BC0004
So any body can tell me what is this HR0014 , is it internal relay or what.I hope i can get some detailed answer.
Thank you very much
Jameel Massry

 

[Johnny T]

I believe that a HR is a Holding Register. I've never used a Westinghouse before but I found this thread that refers to it..


http://www.plctalk.net/qanda/showthread.php?t=27463&referrerid=3796

Sorry I can't be more help..

Cheers

JT ;-)

 

[OZEE]

One discussion I always have when starting to replace an old, obsolete PLC is whether we really want to just convert the old program or if we want to start over.

If you "just convert" the program, you not only convert any old, existing problems into the new program, but you also introduce a whole new set of conversion errors. A couple of years ago, I was involved in a PLC conversion that was actually a 4th generation conversion -- and every prior conversion had its own set of new problems -- that were never resolved, only worked around. This makes for a very, very hard program to manage and troubleshoot. I'm currently looking at a program that's been converted at least once before that is a horrible mess -- I'm going to recommend that we just start over...

The main hazard of starting over is the same as any startup. Some things will work, some won't. But as you'll soon learn if you haven't already -- there are many things that won't convert directly from an old program to a new one. Even within the same brand. PLC technology has evolved and we can do things much better now. Some old PLCs didn't have built in timers. Some didn't have one-shots.

Plus starting over will give you the excuse to really fix those old programming issues that were never quite right and to add functionality that you really need now that your process has also evolved.

 

[Johnny T]

I'm with OZEE on this one. A lot of the time it takes the same amount of time to convert software and then debug it as it does to just write the software from scratch.

There are things to take into consideration however.. in order to write the software from scratch you need to be familiar with the functionality of the machine. If you aren't then conversion is sometimes better.

I would say that the main plus in writing the software from scratch is the fact that you end up knowing the software intimately. You can take advantage of the new technology (as mentioned in OZEE's post) so that you can use Timers and One shots instead of maybe relying on counting scans for timers etc etc.

You can fully comment the software and also write it in such a way as to make it easier to maintain in the future.

 

[kevin combes]

As already stated HR = Holding register, basically a 16 bit location for storing data. The BS is bit set and BC is bit clear, in ab speak that is otl and otu, or latch and unlatch. The number after the BS is the bit number within a Holding register to set or clear.

In your example it looks like bit four is set/cleared in holding register 14.

if you want any more help just keep posting and i will reply.



regards
kevin