Plc 5 Vs Control Logix

I NEED AS MUCH INFO ON THIS SUBJECT AS POSSIBLE SUCH AS GOOD POINTS AND BAD WE ARE THINKING OF CHANGING FROM PLC-5 TO CONTROL LOGIX AND I NEED TO KNOW IF IT WILL BENIFIT US OR NOT ANY HELP WOULD BE GREAT THANKS

Depends a lot on you & your company!

Jason, if you are familiar with the PLC-5 family and have a history with it and the 1771 I/O system, then changing to Control Logix is going to be a fairly big step. The two are only the same in the respect that they are both made by AB and both are PLCs. That is where the real similarity ends. The Control Logix equipment is the next generation of PLCs from AB and the PLC-5 along with the SLC500 are old by comparison and due for extinction in the near future. So, to change or not to change? I would change for the future of your company if you are going to be around a fairly long time but only on new installations or on new systems that you produce. Leave the existing PLC-5s in place until they **** out. Control Logix opens up new vistas and opportunities in PLC programming that the PLC-5 did not offer. At your age and others in your company, I would say that if it makes monetary sense, then go for it. Plan on a lengthy learning curve to get to the level of competency you have with the PLC-5 though.

I generally agree with randylud but I'm not quite as polarized.
The first thing you will notice about CLX is the data adressing. Files are gone. Addresses are tag-based. This is the single biggest thing to get around. In addition to that you have aliasing, user defined data types (structures), and arrays. After that, if you aren't doing anything real complex, I think it programs much like an SLC5. The base Logix5000 package does not support SFCs, although I think that is available as an option.
The next thing you would notice about CLX versus PLC5 is that the CLX family is much faster. Scan times that would be in the 20 msec class in a PLC5 will probably be in the 1-2 msec area with CLX.

Originally posted by randylud
Leave the existing PLC-5s in place until they **** out.

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You need to look at this two ways. I suspect you will still be able to get a brand new PLC5 for the next ten years. You can still get a new PLC2, I think, and that hasn't been an active product for 10 years. However, you still want some control over your destiny. Some day you WON'T be able to get a PLC5. You need to be changed over by then. Finding out you can't get a PLC5 is not the time to decide you need to change.

Originally posted by randylud
Control Logix opens up new vistas and opportunities in PLC programming that the PLC-5 did not offer.

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This has been my experience when switching to CLX. It can do everything the old stuff can do and more. Like I said above, the SFC thing may cause you a problem with the base Logix5000 package. But outside of that, you can probably look as CLX as SLC5 on steroids. The more straightforward your process the more similar they appear. As your process gets more complicated the differences tend to be more pronounced. Motion is a good example. It is handled quite differently in CLX than in PLC5. So if you have some motion axes you will have some learning to do.

I guess my bottom line on this is for new stuff go with CLX. You will get a performance boost for a lower cost. But unless you have the time and want the experience I wouldn't jump into changing out a PLC5 with a CLX, especially if your reason is parts obsolecense. It's just not an issue.

Keith

5 vrs Logix

I agree with the above posts about upgrading. I have a 5/30 program that I am converting. One customer wants CompaqLogix while the other insists on SLC505. They are both paying for the programming so no big deal. There is no easy way to convert the programs from PLC5 to Logix especially if you don't use tags. It is very time consuming and I think easier to reprogram instead of trying to convert it. The logix does have some nice features though.

Converting the PLC5 to the SLC505 was no big deal. That Octal addresing (0-15 vrs 0-7 and 10-17) can be a headache though and any address above 255.

If your company is willing to let you go though the learning curve, go for it, it will be great expierence down the road.

The learning curve is worth the effort

You'll be able to buy a PLC5 in 10 years' time, but don't expect the price to be at all comparable to today's. Even today, the price of PLC5 vs CLX is unfavourable - it will only get worse.

Definitely switch to CLX for new work. To get your feet wet, look at replacing a small, older system (5/15 or 5/25 if you have them). You can re-use the I/O. All you would need is a processor and DH/RIO card in a 4-slot chassis. Replace the PLC5 with an ASB and you're away. If commissioning goes badly, put the PLC5 back, go away and think about it, and try again later.

If you're using SFC's, there's some additional learning to do. Since the CLX doesn't have program files like the PLC5, actions and transitions have to be entered as structured text (an action can call a ladder routine). Also the SFC editor is less rigid (I'm still undecided on which I prefer).

As Keith hinted, the base programming package only includes ladder. I recommend getting the full package, as the function blocks and SFC's are the best and most powerful parts.

Speaking of Structured Text...

Has Rockwell fixed the very long scan times associated with Structured Text in CLX yet? I heard about this quite a while ago and haven't checked back into it.

Keith

good question

Ive been meaning to ask this same question.
Where I work everything is plc5 and slc. I dont think the company has any plans to change this, but, I always think I should think ahead. What exactly do you mean by files are gone? As in program file 2, program file 3 etc.? And as far as tag-based Ive been working with RSVIEW for about a month now, which uses a tag database, is that the same concept you are referring to? I know all this may seem obvious to some of you but not for me. Gracious.

K,
I haven't used CLX SFC's or ST in anger yet, so am unaware of any scan time issues. What was the rumour?

BB,
Right. No program file 2, 3, etc. and no MCP's and no data table.
In place of program files, you have tasks, programs, and routines. There can be 31 tasks, one of which may be continuous, the rest periodic (vaguely similar to an STI file). Each task can contain a number of programs (vaguely similar to MCP's). Each program can contain a number of routines which you program in ladder, function block, SFC, or ST.
In place of data table, you have tags which can be bits, bytes, words, reals, timers, counters, user-defined structures, plus a lot more, or arrays of all the above. You give each tag an arbitrary name (up to 40 characters). Where it all ends up in processor memory is irrelevant.

In place of program files, you have tasks, programs, and routines. There can be 31 tasks, one of which may be continuous, the rest periodic (vaguely similar to an STI file). Each task can contain a number of programs (vaguely similar to MCP's). Each program can contain a number of routines which you program in ladder, function block, SFC, or ST.

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IEC Gerry.

CLX is definitelly interesting platform but I will not repeat
what you have read already. Let me mention few things that
were left out so far...

We all love more speed, more memory, more everything...
But RSLogix5000 is not quite mature (in my opinion, not
even by long shot) and that's despite many improvements
over years.
Note: We are talking about version 12 and version 13 is
about to be released any day now ("silver bullet").
Yes it can work and it does get job done but even copy
and paste still doesn't work 100% and all the time.
If you have to support many customers, be prepared to install
couple of different versions because not everyone has time
and money to keep upgrading each CPU every 6-12 months.

CPUs come with only 200 byte of firmware, the other 20Mb
you have to load yourself. That's fine if you have other
rack at hand with loaded CPU and fast connection such as
Ethernet. It's only too bad if you have to do it on
customers site, on week end when this the first CPU they
got - because you are about to spend few hour(s) on
downloading via lousy 19.2kbps.

Higher speed is possible of course - with additional cards
and usually only after you had to spend the time to download
the firmware to the CPU. The mentioned communication card
costs extra so don't write off the SLC505 just yet.

CLX as hardware platform suffers from thermal problems.
In one machine with a rack populated with CPU and 4x M02E
cards we had to exchange all of them over past 4 years - despite
plenty of room, decent cooling and no other active components
in the cabinet - except the 24V power supply (100W).

The problem was finally resolved with array of small fans
sitting on top of the rack - strapped with cable ties to
the rack perforations.

The picture I painted is slightly on the dark side but I guess
it's better if you find out sooner...

Regarding the memory sizes of the ControlLogix versus SLC5/0x.
Is there any rule of thumb for estimating the memory size required compared to the SLC5/0x processors.

Example: If i have a 16K SLC and a customer wants to use a CLX with the same machine operations as the SLC,
would I have to use 16K x 4 = 64K or is there some other magic multiplier.

The sizes of memory available are huge compared to SLC5/0x.
Any one with experience in this?
The same memory problem must apply to PLC5 if converting processors.

It depends a lot(!) on programming style and how good you use memory.
In other words you will have to make your own fomula.
Some things cost more than the others but until you find something better try this:

CLX_MEM = X*SLC_MEM + 150

If you know how to ese every bit, you can use 10 as X value.
If you want more relaxed rule of thumb, try 20-30.

panic,
what is Rockwells response to the thermal problems that you have experienced ?

And what is the "150" in your formula ? Words, KWords, or..

They have sent their people couple times to investigate
but there was no conclusion or the didn't share it with us.
As far as I know the CPU and first two M02Es were replaced free
of charge, the later ones maybe not don't know for sure).

I got the formula from one salesman and everything was suposed
to be in k. Note that SLC memory is expressed in kwords so you
have to double the number before using it in formula.

It's supposed to be just the rule of thumb and certain
structures can waste huge amounts of memory like arrays
of bool (each bool is taking 32-bit - in other words it
uses only about 3% of occupied memory).

Gerry, thanx for the excellent explaination. Is the rack adressing still the same as rslogix, such as if I write a ladder would I make O:010/09 the output or would it just become a tag as in south pump on. This sounds kinda nice but I work with alot of old reliance DCS stuff which was limited to 11 characters and I always find myself looking at outputs like SPPPL_ONTD, which OBVIOUSLY means SOUTH PIT PUMP PILOT LIGHT ON TIME DELAY but its not always so obvious. Sorry, I had to rant for a second there... anyway just wondering about the rack adressing. I will search the A.B. site and try to get a better grasp. Thanx again.