advice on purchasing plc

I am installing new vacuum pumps in a chemical processing area. I want to use a PLC to run the pumps (they will have starters, solenoid valves, temperature, pressure and level switches on the ancillary equipment). I would like a panelview in my production area (Class I Div 2) and want to know if the cheaper Micrologix will work. I can find a lot of them second-hand along with AB Panelviews. We currently have PLC5 and SLC500's on site but they're all full and I think way too expensive for new hardware for them. I would like to stay with AB because we already own the software.

Any suggestions?

Micrologix work fine. Probably AB's biggest selling product.

In a nutshell, what are the limitations of micrologix??? Can thay control VSD's? Is there a limit to the amount of IO that can be connected to them? I assume if if I need more IO, I can just ethernet between PLC's and all can communicate. At the end of the day (probably over the next 2 years) I want to pull out all of my start/stop buttons, Newport indicators and Fuji controllers and plop them in to PLC's so my plant operators can sit in a control room instead of having to be on the floor looking at these big panels. There's probalby going to be a couple hundred I/O sometime. I'm hoping Micrologix 1500's will work. Please advise.

Have you spent anytime studying the sales info for the various MicroLogix products? As you navigate down through those links on that page, you'll see the capabilities of the different models.

Can thay control VSD's?

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How do you plan to control the VSDs? "Traditional" I/O or one of the communication protocols? What do you plan to do with the VSDs -- just turn them on/off or a large scale, tightly integrated, PID-based processing system?

Is there a limit to the amount of IO that can be connected to them?

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Yes - depends on model selected.

I assume if if I need more IO, I can just ethernet between PLC's and all can communicate.

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Not necessarily a good assumption...

I want to pull out all of my start/stop buttons, Newport indicators and Fuji controllers and plop them in to PLC's...

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How much analog will there be? What kind of analog?

... so my plant operators can sit in a control room instead of having to be on the floor looking at these big panels

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There are contributions that operators make out on the floor other than looking at panels. You don't necessarily want them off the floor - because then you lose their personal contact with production. In every plant I've ever been in, there are other non-PLC things that operators need to know. They're using their other physical senses to make various evaluations -- they listen for strange noises, look for leaks or broken components, smell for smoke or chemical releases, etc... You lose this when you just plop 'em in a control room with a couple of computer monitors...




Before you just start throwing PLCs into your system, you need to define what your system needs to be at the end of your automation project. Always define first. You don't want to just start throwing PLCs in with the ASSumption (not knowing for sure...) that they will be able to do what you need, then discovering at the end, when you're trying to tie all the pieces together, that your ASSumption was wrong...

FIRST define your system -- What I/O do you need? How many? External comm's? How will the operator interface with the system? Are there other subsystems or other PLCs that will need communication from this system? etc. etc. etc. Make these definitions independent of your PLC hardware -- e.g., 200 24vdc inputs, 250 24vdc outputs, 12 4-20ma analog inputs, 48 VFDs by ControlNet, etc.

THEN select your hardware to fit your needs.

THEN finish defining HOW your system will work. Flow charts. How do things start and stop? What causes a fault or alarm? How will the alarm be indicated, silenced, acknowledged, cleared, reset? etc.

THEN start writing code.

From your response, there's obviously a bit more for me to think about.
I would like to upgrade my plant from a vintage 1980's facility to something a bit more current. Panelview's out on the floor instead of Newport indicators and Fuji controllers for temperature loops (PID opening and closing steam or cooling valves).

I suppose, as you've stated, listing the I/O and type of I/O is the first step, then defining , what I ultimately want at the end of the day is the way to get the project started.

Thanks for your time and advice. I'll follow up in a few days when I get these lists together and see what options are out there for me.

Again, thanks for the advice.

newtoplcs said:

In a nutshell, what are the limitations of micrologix???

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You are asking about a very wide gamut product.
They range from very simple to pretty sophisticated.

Stay away from the ML1000.

Be aware that the ML1500 does not support online programming, but the ML1100 and ML1400 do support online programming. The 1100 and 1400 also have built in ethernet.

With the exception of the IO limitation the Micrologix 1100 and Micrologix 1400 are equal to or superior to the SLC500 is most ways. There are some specialty areas where the ML is not the better choice, but it sounds like for your application the ML1400 would be just fine.

If you are really looking to upgrade then consider stepping up to the CompactLogix or ControlLogix. The Compact Logix is price competitive with the SLC500 platform and the ControlLogix is less than a PLC5.

newtoplcs said:

Panelview's out on the floor instead of Newport indicators and Fuji controllers for temperature loops (PID opening and closing steam or cooling valves).

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I am all for upgrading... but if they are working and working good then just upgrade the new incoming equipment.

If you do upgrade and you have a budget then you should also look at other PLC manufactures, from your comment I think the budget is part of your decision. If not then I agree with Alaric the CompactLogix is a great line... I do think you need to go with a modular design, not fix... I have a feeling you will be changing a few things along the way and this makes it easier.

You should make a list of everything you are going to control and every input you need (also what type, analog, digital) then we could help you better

One more thing...

What kind of communiactions do you need? Ethernet? local network? or none

Here's a good link to that may help you also...

http://raise.rockwellautomation.com/catalog/_0_16.asp?onKil=http://www.ab.com/raise

Do yourself a favour. Place a phone call to your local Allen Bradley distributor and get him to make a site visit. Show him what you have, explain where you want to be in ?? years time and tell him what your budget constraints are.
This will not cost you a cent and may even get you a free lunch.
If you start to do an upgrade and you head down the wrong track then the results will not be want you want or the cost to change track halfway through will be exorbitant.
Regards Alan Case

be careful, when you select your i/o network & upper level network, (i.e, SCADA or MES).

from my experience: Profibus DP is much better than Device Net or Control Net, Ethernet TCP /IP is more flexible when its a matter of information sharing.

Bhaskar