Another interesting thread. Have a look at the thread running
http://www.plctalk.net/qanda/showthread.php?t=20085I have not made very complimentary comments about BACnet. What I have written is only the half of it and I have been a good boy and not mentioned names. If I ever see BACnet again I will scream - until someone can prove to me that it has graduated to a mature technology. LON - forget it.
Analog points jumper selectable from 0-5v,0-10v,0-20ma,4-20ma
Been around in a lot of PLCs for years and with some brands you can set an input card for all of these and -10 +10v. Not to mention mean reads built in (buffer for average of say 16 reads), scaling, paek hold, input disconnection function (4-20ma, -10 +10v and 1-5v etc etc).
Programs copied from one panel to another with drag/drop
Not always drag and drop but easy anyway.
The entire network can be backed up with a click of button (or reloaded)
Yes.
The processors card have upgradable RAM
Not as available. Most now have flash cards that can be used for a lot of things.
No limits on SCADA tags (we use Citect here)
My preference also. They have a hiuge installation at Olympic Dam in Ozz that has been claimed as the largest SCADA system in the world. My understanding is that there are over 1 million tags and a lot of PLCs out there. Apparently, the scan time on the SCADA is about 2 seconds - pretty awesome.
Peer comms, directly program points on other panels with prioritys
Yes - I do that to nine PLCs via modem on line in a live power station from my home office.
Ask your average PLC control guy to write a simple PID loop and tune it and they shudder, not because they don’t understand as much as the software is cumbersome and confusing. I know..I know .. AB self tuning loops…how long did that take.
Been around for quite a while now. Omron had it a while ago.
A programmer was asked to do a dew point calculation on a SLC and the end result was the expensive purchase of a separate device.
SLC is a bit old. The newer Omron PLCsa have 64 bit maths including floating point. Should not be too difficult for someone that is in to that level of maths. I am not.
Seriously it was a *****..and a micro second matered..I can honestly say a DDC controller could not have done it..
They are too slow for that.
That has been available in some PLCs for many years now.
I have just read about ControlFlash for ControlLogix....
You have been able to flash upgrade many PLCs for some years now. Most do not allow the operation on the network but at the actual processor. Do not forget that DDC does not normally control machinery that could kill someone. Better, in my view, to make you go to the machine and do the flash upgrade to make sure you do not kill someone.
Thats the problem with 30-40 year olds, they think they know everything.
Younger ones just out of uni are far worse believe me. Know everything - all most of them ever know is how to do calculations - absolutely no pratical experience at all. Should be locked up in a cage because they do not want to listen and take advice - then wonder why the thing does not work and all us old blokes say "I told you so". Have done that many times. By the way, they all run rings around me with maths and theory.
CLX output cards can only be owned by one processor. Input cards can have multiple owners.
It has been possible to do something similar for many years with some brands on networked PLCs by mapping the input to the network - that way any PLC on the network can use the input. Not difficult - I do it over a network all the time. By the way, I am not talking about send and receive commands but mapped I/O - map bit 3200.01 in one PLC and read it as exactly the same bit number automatically in every PLC in the network. Most useful.
