Allen Bradley PLC Selection

Hi,

I need help to select a Allen Bradley PLC other than Control Logix and Compact Logix.

In the project we have around 190 Analog Input (to PLC) and around 8 Analog output (from PLC), i.e around 200 Analog I/Os.

I am interested in the reason for not using one of the current platforms from A-B for a current project. Analog data handling is one of the things that the ControlLogix family does much better than the preceding families of controllers.

You could do this with an SLC-5/0x controller and a rackful of 1746-NI16I or -NI16V modules, plus an extension rack with a 1746-NO8I or -NO8V module.

You could also use FLEX or CompactBlock I/O, with DeviceNet or RIO scanners.

To get the best results from this Forum, post supporting information about your application.

Control Logix and Compact Logix are not used because of cost issues.

Regarding SLC500, its heard that Rockwell is not promoting that now.

Is it possible to do with a MicroLogix PLC (or two MicroLogix PLCs)?

randheerp said:

Control Logix and Compact Logix are not used because of cost issues.

Regarding SLC500, its heard that Rockwell is not promoting that now.

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The 500 is being phased out, as the Compact Logix platform is it's successor. I don't know about your other requirements, since it seems you only care about cost, but for that number of analogs, I would definitely go with a full ControlLogix rack.

randheerp said:

Is it possible to do with a MicroLogix PLC (or two MicroLogix PLCs)?

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Absolutely not.

Just stating large numbers of analog I/O points doesn't tell me anything about your application, so I really can't say whether a MicroLogix is appropriate for it or not.

In general, I would not use a MicroLogix controller for a high-analog-I/O-count system.

The largest CPU in the MicroLogix family is the MicroLogix 1500 model 1764-LRP, which can run 16 expansion modules, and the highest density Analog Input modules for the 1769 platform are 8-channel modules. That gives you 128 analog inputs, well short of your goal.

Selecting a controller or I/O system requires more thought than the number of I/O channels. You need to consider isolation, and accuracy, and speed, and communications.

The Rockwell Automation "Integrated Architecture Builder" software can help you compare various controller and I/O platforms quickly.

Of course, IAB is aimed at ControlLogix and CompactLogix because those are the modern controller platforms. But it also provides estimators for distributed I/O platforms and for SLC and MicroLogix controllers.

That might be a good tool for you to run on your own, in conjunction with well-considered, thoughtful questions here on the PLCTalk.net Forum.

I fully respect your valuable suggestions. We have givne the proposal to the customer with Control Logix and Compact Logix but he says that cost is too much.

Customer got some advice that it can be done through a Multiplexer which will be connected to ML PLCs. So I thought of discussing it in this Forum...

Allen Bradley and low cost don't go together.

If it is possible to break up your application into several semi independent functional units, you may then be able to have several ML PLCs, communicating with each other serially or by Ethernet. In theory at least.
In practice, a compactlogix is good value when you need a lot of analog IO. If this is too much, then maybe they should go with another brand of PLC. Automation direct has a high spec PAC with a nice low price. Haven't tried it though, so don't know how good it is.

Ok. Thanks Mr.Doug_Adam...

Analog Multiplexers? Really?

Thats taking a step back into the 80's and just make a troubleshooting headache for yourself and the end customer.

Someone made the statement AB and cheap don't go together and that is true. If cost is that much of a issue looking at a system from a lower priced brand but don't use multiplexers.

Im in searching this 08 channel analog output card 1746-NO8I but not available in pakistan any alternate? (all 08 channel in use)

Could you not consider compactlogix with point I/O very flexible and probably the most cost effective AB route.

Steve

Use controllogix processor and flex i/o modules.

I hope he decided after 5 years.

Multiplexers? Tell your customer he is an absolute idiot! Have been pulling those bloody things out forever! They fail invariably.

jkerekes said:

I hope he decided after 5 years.

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Right!?! That's quite a zombie thread.