Choosing an Allen Bradley PLC to learn on

Join Date
Apr 2012
Location
New Jersey
Posts
1
I currently work at an industrial parts supplier and I have found some of the automated aspects of our business fascinating (particularly the conveyor system). In a couple of years, I could see myself working on control systems in manufacturing, building automation, or autonomous vehicles.

To get some basic facility with PLCs, I have done a range of projects using a hobby-grade PLC, the Arduino (http://www.arduino.cc/). These include making things including a thermostat for a computer, a light controller for a room, and a GPS-guided autonomous RC car.

Through apprenticing with some of the maintenance folks at my facility, going to trade shows, and looking around online, it seems that Allen Bradley is the industry standard for automation systems in manufacturing and conveying in the US. To get some experience with their line of PLCs, I am planning to buy a short stretch of conveyor, photo eyes, drives, etc. to tinker around with in my garage.

One puzzle I'm trying to figure out is which Allen Bradley PLC system to include in my test conveyor system. More specifically, I'm trying to decide between the Micrologix line with RSLogix 500 or the CompactLogix line with RSLogix 5000. I chose these as options because they seemed to be relatively inexpensive while still getting good exposure to Allen Bradley's PLC technology. A CompactLogix system would be substantially more expensive than a Micrologix system. Is it worth the cost for my purposes? What would be some of the main features that I would forgo learning about if I were to go with a Micrologix-based system as against a CompactLogix-based one?

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www.jeffsinventions.com
 
Last edited:
Hi Jeff,

If you can afford it, go for the Compactlogix. Every major company that can afford to is phasing out the old SLC/micrologix and PLC-5 family of AB processors and moving to the Control/Compactlogix family. Sure, you will still run into the old systems for years to come, but employers want to see CLX experience more than anything.
If you choose to go with Micrologix, you will not get to work with a tag-based addressing system like CLX offers. The disadvantage here is that almost all HMI's work on tag-based systems, so a tag-based PLC, versus a numeric "data-table" addressing scheme, is easier to develop HMI applications for.
One big con of using CLX instead of micro for home use is that you can get a version of Micrologix programming software as a free online download from Rockwell, but RSLogix 5000 software will set you back big $, even for entry level software.

Hope this helps,

Cheers,
Dustin
 
Micrologix (The RSLogix 500) doesn't use tag based addressing, instead using a file, word, bit addressing. It also doesn't support the same communications options (or at least support them at the same level) that the CompactLogix and ControlLogix platforms do. Ethernet/IP, Devicenet, Controlnet, etc.

An RSLogix 5000 system will give you access to Add-on Instructions, which are a handy thing I hear (Never used them myself).

Personally I use Micrologix/SLC and RSLogix 500 more often. Mainly because I have hundreds of very small machines that we chose the Micrologix for. It all depends on what you plan on using. If I had more large systems with Control or CompactLogix, I'd be more willing to buy compactlogix for some of our smaller systems, since it'd be a more standard system throughout my shop.
 
For learning purposes, I'd say there'd be nothing wrong with getting yourself a little micrologix 1100. You can then use the freely available RSlogix 500 trial version downloadable from the A-B website. the micrologix 1100 is not a bad little machine for what it is (and costs). You can do online edits (always handy) and it has a built in ethernet port so you could program as well as tinker around with an HMI at the same (some free / trial options out there too). I think it's beneficial for any PLC programmer to understand bit / byte and file addressing before moving onto a tag based PLC. It's not that difficult a transition anyway.
 
If it is just a small application, the ML1100 using the free download software is good to reduce costs. Also, I have used this combination on a large number of small machines.
Once familiar with this, and you need more IO, I would usually go up to the ML1400 and use the RSLogix 500 Compact, only about $200 and can program the entire ML range.
The Compact Logix and the associated programming software starts to get a bit pricy, so I would only go for this if you plan on making a career of it or if the ML range just won't do the job.
 

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