SLC to Logix switch

[cmoyer 0]

Greetings all, My employer is currently using SLC and MicroLogix controllers in all of our products. We got in this position by having a 70 year old CTO that was pretty set in his ways about what technology he trusted. Long story short, the CTO is retiring in Dec. and I am wondering about pushing for a switch from SLC and MicroLogix to ControlLogix and CompactLogix. I consider myself to be an advanced user/programmer when it comes to SLC and Micro, but I have little to no experience with control and compact logix. What are the opinions of some of you folks out there regarding the switch from the following points of view? Ease of switch - For someone who is an advanced SLC programmer, how difficult is it to transition from RSLogix 500 to 5000? Cost - what is the price difference we can expect to see between comparable SLC and ControlLogix systems? Technology - What are some of the main advantages of switching from SLC/Micro hardware to Control/CompactLogix hardware? How is the Control/CompactLogix superior to SLC/Micro? I am sure I will come up with some other questions, but I have to go to a staff meeting. Thanks in advance for any replies! cmoyer

[OkiePC 14]

Speed. Memory. Program control. 32 bits. Motion control. The Logix CPUs are much faster than the SLCs. Some of the Micrologix units are pretty quick, but I expect you will see scan times drop to less than 10% of what a SLC can do, and see a reduced need for things like IIM IOM and STI. Any program in a Logix CPU can be set up to run like an STI with a definite period between scans. Tag based memory. You are no longer limited to file types. You can create structures of multiple different file types, and name them how ever you wish. There is typically much more memory in a Logix CPU, but bear in mind that tag names take up extra space for each tag which can eat away at some of that. Still, you will be unlikely to run into memory limitations with most applications. Programs can be scheduled to run independent of one another. You can still use JSR/RET as you normally would, but will also be offered parameter passing to and from routines. You will also find that you can drag and drop programs between projects much easier (if you construct the logic with this in mind and make good use of local (Program Scoped) tags). The Logix line is designed to use 32 bit elements, so you can let go of having to deal with the -32768 to +32767 limit of INTs in the SLC world. This will, for example, make parts counting simpler, double the "width" of your bit sequencer, and give many other advantages. I have not used Logix Motion, but I do vividly remember the pains of dealing with having separate motion control programs and PLC programs that needed to share information. The Controllogix instruction set allows you to do complex motion control with ladder logic in the same controller that runs the rest of the I/O. I personally have only done two Logix projects from scratch, working on a third one. So, I am still green, and still more productive with Logix500. I still prefer many things about Logix5 and 500, but the power of the hardware makes the switch worthwhile when you need more communications, more speed or more memory. I don't like the Logix5000 Find function. I don't like not having full control of the way tags are listed and displayed. I am not real fond of having to download firmware into a brand new CPU. Aside from those minor gripes, I really like the performance, especially the communcations ability and scan speed. I am sure some of the more experienced users can add much more to the conversation. Edited 25 Aug 2010 by OkiePC

[kaiser_will 65]

The best feature of using Logix5000, in my opinion, is User Defined Tags (UDT). Most OEMs, such as yourself, have developed standard UDTs to encompass all of their unique variable/tag names and base logic. My employer, for instance, has a canned UDT with all of their fault bits, status bits and possible input conditions. Copy in the UDT from another program, write basically the same logic for each motion with the same UDT with the source name changed. Blammo...in a few minutes you can crank out a custom program that has all of the HMI and logic features you need. Couple the Logix5000 UDT with a PanelViewPlus and you are in business for smooth integration. If you integrate HMI tags into the base UDT, it is easy to code the PLC and designate all of the HMI functions right out of the gate. Stay away from the PanelViewComponent class, however. Cost is cheaper than a Plus, but you blow the savings on horribly (HORRIBLY) slow web-based development software latency time and the lack of adequate literature.

[paulengr 44]

I'll add a couple more things that haven't been mentioned. First, AOI's. Basically, you can write your own instructions. And you can optionally protect everything inside the instruction if necessary. This allows you to create say a "pump starter" instruction and have just one routine to handle all your pumps. With some clever programming, this feature alone can not only save time but the library that you can build up fairly quickly can make programming much more "template" based. Second, there are MAJOR differences in how IO is handled. First off, like the PLC-5, the reason SCP is missing is because you don't need it. The standard way of doing things in Logix 5000 is that all the scaling is done in the IO itself. The PLC tag contains "GPM", not some arbitrary 15 bit number that has to be manually scaled to the correct value. In addition analog cards also offer automatic settings for alarms. Diagnostic IO is available that can be fuse protected with electronic fuses (basically you can't short out a card), and it has diagnostics so that it automatically detects shorts, open circuits, or backwards wiring on 24 VDC systems. IO is true "RUIP" (removal and insertion under power) and autoconfigures itself. In addition you can even add/remove IO (depending on the IO network) online while everything is running. Recently they also added "AOP's" which is a way that third party vendors can create IO "face plates" that the IO system automatically handles so that everything (drives, IO, AMCI resolvers and encoders, etc., etc.) are directly programmable from within the programming environment instead of relying on cryptic MSG or BTR commands. For instance with Powerflex series drives, you just add the AOP, tell Logix 5000 where the drive is at, and it automatically comes up with all the configuration information and pre-built interface code. Third, there are a host of little features that make life nice. For instance, there are alarm calls built into the PLC. If you pony up for RS-View, it interfaces to this alarm system. The alarms are buffered at the PLC level, so it is impossible for a "missed alarm" to ever occur. Very nice if you are trying to catch one of those "transient" type conditions. RS-View SE especially is very overpriced and the alarm system is a memory pig, but if you really need it, it's there. Fourth, there are dozens of new instructions inside a new language that you can get called function block programming. For instance the PIDE that is in there is much better than the standard PID instruction, although again the learning curve is even steeper.

[TConnolly 13]

I am a big fan of the ControlLogix/CompactLogix platforms, but often when I'm faced with these kinds of questions I ask myself, "If I were writing the check, if it were my own company and my own money, what would I do?" While the SLC is getting a little long in the tooth, the Micrologix family is new and still expanding. In fact there are rumors of yet another new powerful addition to the ML line soon to be out. The ML1400 is already a respectable system that can take the place of most SLCs. For many applications the ML remains a viable choice and will continue for a long time. The ML line is the most economical of the the AB PLCs. As for cost, it depends a little on system configuration but as a general rule of thumb a Compactlogix is cheaper than a SLC 500, but a Micrologix is cheaper than both. A ControlLogix is quite a bit more expensive and if all you are doing is replacing SLCs (as opposed to adding a new feature rich system) then it is probably overkill. Using a Compactlogix in place of SLCs in the future is probably a good move, but whether its a good move with the Micrologix is another question that bears some analysis. You may want to analyze if some of the new Micrologix processors can be used in place of the SLCs. Be careful in making a technology change for technology's sake. If you are making products for other users and the Micrologix is dong the job then making the switch might actually harm the bottom line - either you are going to have to increase the price of your product or you are going to have to raise the price of your product.

[cmoyer 0]

OK! Thanks for the replies, it was exactly the sort if info I was looking for. After considering the replies here, I am going to push for control/compact to replace SLC, but I don't think it makes sense to replace the Micros we are using at this time. Every Micro we have used is either a 1100 or 1400, which are the latest in the line and we have been happy with them. Most of the tasks that the PLCs perform in our systems are HVAC/Balance of Plant related, so there isn't a lot of processor power required. The only reason that we have to go SLC sometimes is simply I/O scale. However, we are panning on upgrading our manufacturing pant next year to increase production. The goal is to get 3X what we are seeing now, so there will be tons of new equipment, controls, etc... We are currently using SLCs in the plant and I really think the switch to ControlLogix makes sense there. Once again, thanks for the helpful replies! cmoyer