Compact vs. Control Logix

phebejtsov · Nov 13, 2007

I was wondering if you can help me with a PLC selection or steer me in the right direction.

I have a quote for an Allen Bradley Compact Logix (1769-L35E Controller & 1769 compact I/O). The PLC will be communication via modbus to/from Bently & DCS. It will also be hardwired to/from Monitoring System, DCS, SIS & CCC.

There are 38 AI's, 1 AO, 17 DI's & 20 DO's (76 total i/o giving me 15% spares). These i/o's are PID loops, pressure, flow & temperature transmitters. I'm sure there will be more i/o's.

Currently the compact logix can support 3 banks with 30 i/o per bank. The compact logix holds 1.5 mb of RAM and 64 MB of nonvolatile memory on a compact flash. And I've looked at the selection guide on the AB website.
How comparable is the compact logix vs. control logix? Price, future expansion, speed? Any advice will help. Thanks!

SNK · Nov 13, 2007

If given the choice, always go for the CONTROLOGIX. Bigger, better, is the std for Rockwell.
Compactlogix is just that, a more compact, inexpensive way of acheiving the same thing....some limitations of software, (Same version Logix5000)

TConnolly · Nov 13, 2007

With that much analog IO, go for the Control Logix with an L61 processor. The 1756 analog IO modules are smart modules and will do most of the scaling and alarming for you in the modlule.

The CompactLogix was brough out to mainly target SLC500 sized systems as an economical replacement for the SLC while extending the c-logix instruction and programming down to the smaller systems.

JesperMP · Nov 13, 2007

I think that posssibly the smallest CompactLogix 1769-L31 can do the job.

The PLC will be communication via modbus to/from Bently & DCS. It will also be hardwired to/from Monitoring System, DCS, SIS & CCC.

I suggest that you describe the communication needs as precisely as possible. Which protocols, how many connections, what does "SIS", "CCC" and "Bently" stand for ? What do you mean by "hardwired" ? I think that this is where you risk going in the wrong direction.
For a CompactLogix or ControlLogix, the natural choice for a connection to the supervisory control is Ethernet, not Modbus.

careed_25 · Nov 13, 2007

I work with both product in a coal mining environment. From my experience I would go with the Control logix scenario. One main reason I perfer this setup is that the modules are hot-swapable meaning that the different i/o cards can be pulled out and replaced with the program running. Of course you will get i/o errors but where I find this useful is when an Ethernet module goes bad all we have to do is pull that one out and replace with a new one without shutting down the belt which keeps production rolling.

Gerry M · Nov 13, 2007

You have alot of analog I/O and control loops. Look at the analog spec.'s and you will find the average Compact logix AI is about 0.3% acuracy and the Controllogix is 0.1% or better.

Other than that the Controllogix seems to be developed more for higher end app.'s as has been previously stated. As far as money goes, if you can afford the DCS, then you can afford the Controllogix.

phebejtsov · Nov 13, 2007

Example of Hookups

I really appreciate all the responses, attached is the basic hookup of system. The reason I've asked about the comparision (control vs compact logix) is that we sold the compact logix to the customer and i wanted to give a good arugment to use the control logix.

JesperMP · Nov 14, 2007

Halfway there.

So what serial protocol is there between "PLC" and "Monitor system (vib & temp)" ? I guess that the "Monitor system (vib & temp)" is the "bently" you mentioned before - Bently Nevada maybe ?

And what ethernet protocol is there between "PLC" and "DCS" ?
What system is the DCS ?
Does it support AB protocols natively ?
Does it support OPC ?

I am betting the machine is a compressor or turbine, and all the various i/o shall do is to monitor alarms. A compactlogix will be more than enough. The fancy stuff happens in the "CCC antisurge".

For arguments for ControlLogix against CompactLogix, hmmm... maybe RIUP is important for the customer ? Do the customer already have ControlLogix in some other proces or machine ?
Depending on the communication needs, a ControlLogix may be a better choise.

curlyandshemp · Nov 14, 2007

phebejtsov said:
I was wondering if you can help me with a PLC selection or steer me in the right direction.

I have a quote for an Allen Bradley Compact Logix (1769-L35E Controller & 1769 compact I/O). The PLC will be communication via modbus to/from Bently & DCS. It will also be hardwired to/from Monitoring System, DCS, SIS & CCC.

There are 38 AI's, 1 AO, 17 DI's & 20 DO's (76 total i/o giving me 15% spares). These i/o's are PID loops, pressure, flow & temperature transmitters. I'm sure there will be more i/o's.

Currently the compact logix can support 3 banks with 30 i/o per bank. The compact logix holds 1.5 mb of RAM and 64 MB of nonvolatile memory on a compact flash. And I've looked at the selection guide on the AB website.
How comparable is the compact logix vs. control logix? Price, future expansion, speed? Any advice will help. Thanks!

I'm assuming your are you a card such as this for the Modbus interface?

SLC_Integrator · Nov 14, 2007

JesperMP said:
I think that posssibly the smallest CompactLogix 1769-L31 can do the job.

I suggest that you describe the communication needs as precisely as possible. Which protocols, how many connections, what does "SIS", "CCC" and "Bently" stand for ? What do you mean by "hardwired" ? I think that this is where you risk going in the wrong direction.
For a CompactLogix or ControlLogix, the natural choice for a connection to the supervisory control is Ethernet, not Modbus.

Bently Nevada Machine Monitoring equipment (3500 perhaps?) & CCC AntiSurge/Performance Controllers (Probably Series 4) both talk Modbus RTU from all the ones I have interfaced to a DCS.

I'll need a little more detail on which particular DCS before I can comment on its Modbus capabilities though, some legacy DCs systems havnt yet embraced ethernet, unfortunately.
SIS is the Safety Instrumented System, could be anything from a Triconex to a ProSafe to an S7400-FH, again we need a little more detail here.

As already mentioned, on the PLC side, if your wanting a Logix platform to talk Modbus you may as well plan on getting a ProSoft card.

phebejtsov · Nov 16, 2007

The DCS system is a Delta V 600m away from the PLC. I've been reading the compact logix selection guide and it seems that the DH-485 protocal will be on the RS-232 phsyical layer. Since RS-232 communication distance is 50' max, Ethernet/IP seems to be the choice.

Is it possibe to use a modbus/profibus bridge to cover that distance?

SLC_Integrator · Nov 16, 2007

phebejtsov said:
The DCS system is a Delta V 600m away from the PLC. I've been reading the compact logix selection guide and it seems that the DH-485 protocal will be on the RS-232 phsyical layer. Since RS-232 communication distance is 50' max, Ethernet/IP seems to be the choice.

Is it possibe to use a modbus/profibus bridge to cover that distance?

You seem to be getting a little confused on your protocols.

Delta V supports Modbus RS232/485 and Profibus DP.
It does not support EthernetIP.
These are you communications choices. The RS485 PLC-to-DCS link can go up to 3000feet or so, more if you use fiber links (which I reccommend).
If you get a Prosoft card for the Compactlogix you can use Port 1 to poll all the other Modbus-capable equipment (Bently Nevada, CCC, SIS etc) and Port 2 can be the Modbus RS485 slave for the DCS to talk to.
Then all you need to do is make sure the PLC arranges the data internally how you need it and in the correct format for the DCS to read it.

pablo2000 · Nov 19, 2007

DeltaV can communicate on Ethernet/IP using a DeltaV Virtual I/O Module (VIM) interface card from Mynah technologies. The VIM emulates four serial I/O cards, acquiring the last 8-wide carrier of a DeltaV system. Mynah provide a Modbus and Ethernet/IP driver for the card.
Check out the website:

http://www.mynah.com/vim_network_gateway.asp

Pmendez2083 · Nov 19, 2007

I would go with a Control logix it has more power and they are hot swappable. this is good in the feild and they can borrow down the network with RSlinks and look at your DH45 or controlnet,devicenet,ext. this is chassic base its build alot better then the compact.

SLC_Integrator · Nov 19, 2007

Pmendez2083 said:
I would go with a Control logix it has more power and they are hot swappable. this is good in the feild and they can borrow down the network with RSlinks and look at your DH45 or controlnet,devicenet,ext. this is chassic base its build alot better then the compact.

Its also twice the cost:
Cheapest CompactLogix CPU ~$1500
Cheapest ControlLogix CPU~ $3100

Seen as its most likely going to be a Prosoft/Modbus application with no devicenet/controlnet etc then drilling down with Linx offers no gains.
If budget is a concern and uptime is not critical I would say go with the CompactLogix.

Compact vs. Control Logix

phebejtsov

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SNK

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TConnolly

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phebejtsov

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curlyandshemp

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SLC_Integrator

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