Sign in to follow this  
Followers 0
Bering C Sparky

Micrologix with Opto 22 SNAP I/O

9 posts in this topic

Has anyone ever used Opto 22 with micrologix or might have some knowlage on the subject? I have to wait until Monday to call the company to get info from them so thought I would throw this out on the forum and see if i can get some info. I am looking to add some remote I/O into 5 seperate machines. (See previous post "220vac INPUT MODULES for more details) I am seeing on opto 22 site they are saying their SNAP I/O will work with micrologix controlers as remote I/O using EtherNet/IP. They state that when it is used with Control Logix or Compact Logix then the Opto 22 remote I/O units process most of the information locally and then just pass off needed information back to the Rockwell Device. I have not been able to find very much specific information regarding how it will function with the Micrologix from there sight but here is a quote from there webpage: "SNAP I/O™ from Opto 22 can augment an A-B ControlLogix or CompactLogix system—or another PLC system that uses EtherNet/IP (such as MicroLogix 1100/1400 or SLC 5/05)—by doing exactly that: providing intelligent remote I/O that offloads many I/O functions, especially those involving the heavy analog signal processing required by most process control applications." A few questions I have are: 1) Can you realy do this with micrologix and can you give example of how it would set up and communicate? 2) If this will work what are the limits as to how may different remote I/O racks can be used? 3) EtherNet/IP and ethernet same thing? (I have read they are not and that when they are put together on the same network they dont get along well. Is this true) 4) If EtherNet/IP is different that the ethernet network my plc's are connected to now how to set up so micrologix can communicate with Opto 22 and still be able to pass information onto my existing network to HMI's and Scada that already exist. 5) If this will all work do I simply see the remote I/O in my RSLogix data table and use it just as if it were actually connected to the Micrologix or will the remote I/O have to be programed with Opto 22 compatable software, and if that is the case will I be able to use this information for existing HMI and Scada? Thanks in advance for any input. BCS

Share this post


Link to post
Share on other sites
1 - Yes, this will probably work, but as I said in your other thread, you'll have to use explicit messaging (MSG instruction) to send and receive data. It will not be particularly fast, and you'll have to be careful how you program it so that you don't get into weird states if the comms drops out. For example, make sure that the Opto stuff turns off outputs on comms loss. 2 - This has to do with how fast you push the communications. You'll set up at least one send and one receive MSG instruction for each station. There are a limited number of connections you can make at a time, so you'll have to write some code so that the MSG instructions are called in sequence with a short delay between calls so that things don't get bogged down. With this method, the number of stations is essentially limitless, but the more you add, the longer it will take between polling a single station, which means the I/O updates are slooow. 3 - In the most basic terms, Ethernet is the hardware and top-level communications protocol (how packets are sent and when). Ethernet/IP is the fieldbus or machine level protocol (what the packets contain). There are other Ethernet-based fieldbuses (Modbus/TCP, Profinet, etc.), but they all use the same basic Ethernet structure. You can mix networks containing multiple fieldbuses, but it's usually better to separate them. This has more to do with network loading than any "fighting" between the fieldbuses. 4 - As long as you don't have a huge number of devices, you should be fine. Most likely anything that is talking to the Micrologix over Ethernet will be using the Ethernet/IP protocol anyway. 5 - Most likely the Opto will just need an IP address and information about the I/O connected to the head device. You will be using explicit messaging commands on the Micrologix to connect to the Opto rack and push or pull data between the Opto and a data blocks (usually integers) on the Micrologix. You'd then use those data block as your inputs and outputs. I'd create dedicated blocks for the inputs and outputs. The HMI and SCADA should probably just look at the data blocks on the Micrologix rather than poll the Opto device directly. Simpler that way. If you were doing this with a CompactLogix, you'd be able to set up implicit messaging, which means adding the Opto devices to the I/O configuration. All the messaging would then be done automatically, with much better speed and reliability, and the I/O would show up similar to 1769 I/O cards in the tag list.

Share this post


Link to post
Share on other sites
Jeremy's comments are excellent, and I agree that this is do-able but I'm not nearly as enthusiastic about it as Opto-22 is. When you read their white papers and technical documents, they do claim that MicroLogix 1100 and 1400 and SLC-5/05 and even Micro 850 can work with Opto-22 SNAP over EtherNet/IP. They do a very good job of explaining the difference between explicit and implicit messaging in the "Using Intelligent SNAP I/O with Allen-Bradley Logix Systems" document. But in the very next breath... they move on to illustrating I/O connections with CompactLogix and ControlLogix. Even the only explicit messaging example I found showed a configuration message in ControlLogix, not "continuous data exchange" messaging with MicroLogix. This topic is frustrating to me because the vendors and salesmen get to make the sale and then I'm stuck explaining the downside and the difficulty. And when I complain to the salesmen, they say "but you made it work, right ?", and when I answer in the affirmative, they say "so it works ! I was right !".

Share this post


Link to post
Share on other sites
I finally found an example of an EEM instruction in the SLC-5/05 and an MSG instruction in the MicroLogix 1100/1400 in the Document 1909 user's guide. http://documents.opto22.com/1909_IO4AB_Users_Guide.pdf But guess what ? There are no examples of how to successfully interlock or sequence the message instructions. You're going to need more than one, right ? That's because it's a little complicated. And because you have to trade off between how much bandwidth you want for monitoring or HMI use and how much you want to dedicate to this sort-of-remote-IO connection. So now I'll stop fear-mongering and let's talk about some of the nuts and bolts. You need at least one MSG instruction to read "Input" data and at least one to write "Output" data. I think each one is considered a separate CIP connection. The MicroLogix 1400 Series B supports 32 CIP connections, but can only originate 16 of them. So it looks to me like there's a hard limit of 8 SNAP brains you'd be able to connect to a single MicroLogix 1400 controller. The SNAP configurator is... it's not terrible. But it's another software configuration package and another backup that you need to have available if you are going to use these devices. And if you have a successor trying to troubleshoot your MicroLogix and he finds MSG instructions where he expects to find ordinary I/O modules, then you're going to feel your ears burning. Those old threads you read probably included some fairly pointed language from me. And yet I am considering installing a Micro 830 as a remote I/O unit over Modbus, because I'm trying to save on I/O wiring labor for a remote pushbutton console. I'm such a hypocrite.

Share this post


Link to post
Share on other sites
Hello Jeremy & Ken, Thank you both for sharing your wealth of knowlage on the subject. I am able to absorb most of what you are saying but must admit that at my level of experience some of this still flys over my head just out of reach. I have seen the MSG that you speak of before in a real application. We have an old Plc5 system onboard that has some remote I/O and an HMI using RIO and I belive that this is similar to what you are describing here. I have see this in the program but have never personaly had to do anything with it. I make changes and add things to the Plc5 all the time but I am doing it on the PLC5 processor side not through the MSG instructions. As far as the EtherNet/IP, Modbuss/TCP, Profinet, well lets just say I still have some homework to do on the subject. (maybe another post at another time) Thus far all the stuff I have built from the ground up has been with Micrologix and Factory talk or Panelbuilder, so just program and plug it into the network and it works. I have worked in ContrlolLogix, SLC, and PLC5 also but only to add things or make changes to existing programs, never built these from the ground up. I have never tried to get differerent formats/platforms to play nice together. The systems we have onboard like this were already in place when I got here. Guess this is my next hurtle to overcome. I have conceded to the fact that ControlLogix is the way to go for this project and will begin looking into the different systems and pricing. As far as "Pointed Language" from you Ken in the old post, from what I seen you were acutally the voice of reason, but TW was getting on him pretty good. I seen on that Post that you are located in our home port. Are you anywhere near Pier 90 (around the Magnolia Bridge area?) If so would you be interested in doing any one on one instruction. I would be more than happy to compensate you for your time. Thanks again to you both for taking the time to help me out and trying to explain things in terms and on a level I can comprehend. BCS Edited by Bering C Sparky

Share this post


Link to post
Share on other sites
BCS, if you end up buying Opto-22 I/O for this project then I'd be happy to spend some time characterizing it and measuring the performance with you. Heck, even if not I'll buy you a pitcher at the Highliner. I'm currently far out of my homeport. It's a little sobering working on parts for the 787 in a building that was flattened by LeMay's Superfortresses in the spring of '45.
1 person likes this

Share this post


Link to post
Share on other sites
Kon'nichiwa I assume by your last post you are in the land of the rising sun! And I thought my job was cool. Sounds like a plan Ken, would be great to meet you. Obviously you are a busy man but If you get a moment while brousing the forum, take a look at my other thread "220vac input" and look at my last post. If you dont mind, let me know what you would do for this application. I would welcome the input from someone with experince, before I go and order big $$$ worth of stuff. Kansha, BCS

Share this post


Link to post
Share on other sites
Ken, I sympathize with your pain getting things to work! I don't usually have the luxury of picking the equipment, I usually get dumped into a project and asked to make things work with what is there. I've used Modbus/TCP based remote I/O with a CompactLogix and a Red Lion HMI acting as the gateway, and it wasn't pretty. Fortunately it wasn't a particularly high-speed application.

Share this post


Link to post
Share on other sites
830 as remote I/O?????? Ken Roach what? ????? The only reason I don't report your account as hacked is because it is Modbus. I might have to ask Chris to monitor your account for more crazy post. I am having my local AB rep sample shop a 2080 Dnet card just to play with. I don't plan on using this as a control source just a play with and understand dnet a little better.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0