Can anyone inform me of why one should (or not) choose Rockwell's Logix architecture over its competitors? What is Logix good at/what does it leave to be desired? What are the alternatives?

Thanks!

 

1) Integrated motion commands in Ladder Logic diagram.

All speed and position data is stored in the ControlLogix processor. Positions, speeds, torque, and faults are accessable in the ladder logic.

2) Tag name database.

Rather than using B, N, I, and O registers (or the equivalent, e.g. M, Q, & I in Siemens), ControlLogix uses a tagname database. These tagnames are stored in the processor, which makes reading the code easier when the original program is not available. It also avoids the difficulties of searching through register files looking for associated data. e.g. N7:13 vs. CycleCount. More importantly, there is no chance of accidentally over-writing things. In Siemens or Modicon if you declare a double at byte offset 10 and then an integer at byte offset 12 you will get BAD results.

3) User-defined data types and indexable arrays.

User define data types and indexable arrays make the program easier to write, debug, and maintain. Combining groups of data, for example product SKU number and dimensions, into a single tag makes finding data in the tag database much easier.

4) Task scheduling.

ControlLogix allows a system to be broken down into tasks with different scan rates. Critical tasks can be given a high priority and scan rate, while non-time critical tasks are given lower scan rates. This typically allows a processor to have large programs while maintaining desired performance.

5) Price/Performance.

ControLogix is considerably less expensive than equivalent PLC-5 parts, roughly equivalent to SLC-500 pricing. It is as fast as a PLC-5, but has additional capabilities. The ControlLogix's smaller size also reduces costs associated with cabinet space. Relative to other manufacturers it is competitive. But a Siemens PLC has 32K of memory, vs. 750KB in a ControlLogix.

6) Expandability.

ControlLogix can add just about anything you want, including dual processors in one chasis, redundant processors in seperate chasis, almost every industrial network imaginable, etc.

7) Simplicity.

Everything is done in one application, RSLogix 5000. Compare this to Siemens Step 7; there is a project manager, a code editor, a symbol editor, a cross-reference program, and a PID parameter assignment application. An RSLogix program is one .ACD file; a Step 7 program is upwards of 250 files in 40 nested folders. In Modicon's Concept structures are hand-coded in a text document and then imported.

That's my $0.02

-James Ingraham
Sage Automation, Inc.

 

First, I assume that you mean the ControlLogix PLCs (as opposed to SLC and PLC architecture).

It depends on what competitor you are comparing it to and what your application is. However, in general:

Pros
- Excellent integration with servo motors. The commands to the servo motors are placed directly in the ladder logic. Really neat!
- Powerful networking and I/O control
- Scalable from small to large (CompactLogix to ControlLogix)
- Many data types possible in the data table (32 bit integers, floating point, arrays, types, etc.)
- Easily integratable with other Rockwell products (RSView, RSLinx, etc.)

Cons
- Expensive hardware and networks (such as Devicenet)
- Software is expensive and, in my humble opinion, not very good (actually, its awful)
- Difficult (but not impossible) to integrate with other third party hardware and software

 

The control logix processors, especially the latest versions, are the best you can buy. Also very expensive, but the fastest and with fantastic programming tools.

But like anything you have to consider the context. For example, if you wish to control some drives sitting on a Profibus then you will probably need to employ the SST profibus card using control logix, and I have never used this card without difficulty.

If you need to interface with something like InTouch, then you need to carefully consider and structure your data communications (extra carefully if you need to exchange 10's of thousands of tags) whereas a Siemens processor and HMI or PCS7 provides an integrated solution - this means once you figure out how to do what you have to do it's easier to do.

Localizing the PLC programming experience, however, using the ControlLogix line is like driving a Ferrari (never driven a Ferrari but I heard it's something else). You can perform mathematical operations (easily) on mixed data types. I/O modules are hot-swappable without any configuration changes (out of the box). Logix5000 (the programming tool) is flat-out fun to use. User defined datatypes and integrated motion control instructions introduce lots of programming power. Also, and most importantly for you based on the nature of your question, this line is easy to learn how to use. All reasons why it is expensive.

 

A totally integrated motion/logic architecture is by far the smartest way to handle machinery control. If for no other reason than the fact that all programming is done from one program. This eliminates the need to communicate between different systems, and in some cases between different manufacturers.

If you would like to explore a second source for a totally integrated motion/logic, try www.glcontrols.com. G&L offers all of the features of the Rockwell architecture, however since G&L has had this platform for the last 14 years, it is a much more mature system.

Joe Rizzolo

 

Not that I especially disagree with your assessment, but is there anything you feel is better? I've tried Step 7, Modsoft, Concept, Proworx, Think & Do, Labview, RSLogix 5, 500, and 5000, DirectSoft, and many others. RSL5K is no worse than any of the ones I've tried. I'd love to know if there's something that stands above the crowd.

-James Ingraham
Sage Automation, Inc.

 

The software package offered by G&L Motion Control called PiCPro is an integrated programming package that is easy to understand and use, but provides more power than any of the packages listed. In addition it also allows for the creation of User Defined Function Blocks, has built-in drive tuning software, and a functional oscilloscope. All within the same package. It meets IEC 1131 and allows for ladder, function block and statement list programming. If you use it once, you will never try anything else.
Their MMC version lists for $295.

Use this link to go to a powerpoint presentation.

http://www.glcontrols.com/ie/technicalinformation/presentations.asp#Promotional

 

Thanks! i want informaion about contactors and what is aprencibal to use it.

 

No. A CLX 5550 (the origina CLX processor has a scan rate of .5ms/K ladder memory. The fastest PLC-5 are 2ms/K. WHen you move up to the 5555 and especially the 60 series (5561, 5562, and 5563), the speed differences are major.