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Archive for April, 2009

When Not to Use EtherNet/IP

Thursday, April 23rd, 2009

Had a call from a really nice guy down south today who wants to implement EtherNet/IP. He seems to be really, really competent and sincerely wants to architect the right solution for his application.

 

The only problem is that this application isn’t appropriate for EtherNet/IP. This is a situation where it just doesn’t fit. He and his group are kind of enamored with the technology and the “thrill” of using a name technology.

 

It’s a classic illness that all us engineers are prone to get. We let are enthusiasm for some cool technology get way ahead of the problem we’re trying to solve. I did it with DeviceNet. Long time ago I created this really cool ISA bus coprocessor that was a DeviceNet Master. I got so excited by the technical challenge that I forgot completely about the business issues. The product was a big flop.

 

This guys problem is that he really has an Ethernet Peer-Peer system. He has a number of distributed application components and he wants to add and remove them at will without any reconfiguration.

 

His application reminds me of J1939. That’s a CAN based application layer protocol just like DeviceNet. Only J1939 is all broadcast. Each node publishes its data as needed to the network and who ever needs that data listens for it. There are no masters or slaves. If a node isn’t there the data isn’t published and the listener doesn’t receive it. It’s really simple and straight forward, used in transportation applications. I implemented a system for huge yachts one time. Catepillar engines use it extensively.

 

So this guy wants to do the same thing on Ethernet. One choice is to use CAN and J1939 but the physical distribution of the system prohibits that solution. CAN is good to 1000 feet unless you use extenders.

 

He could use Profinet CBA. But the size and complexity of that mother is just prohibitive. His data is pretty simple. Not sure that CBA makes a lot of sense in his application.

 

Another is proprietary. He could implement a J1939 like proprietary Ethernet application layer but is that the best solution?

 

One of the things he is looking at is Microsoft Robotics Studio. That a system targeted to students that makes it easy to program robots. It supports a bunch of different hardware platforms including PCs which is what our southern friend is using. It has simulation and tools for accessing sensors and actuators. It is designed for distributed systems where the robots can coordinate their actions. Here’s where you can get more information: http://msdn.microsoft.com/en-us/robotics/default.aspx.

 

I’ll have to admit that I didn’t have a good solution for him. Any thoughts from my “legion” of loyal readers? J

What’s In a Name?

Friday, April 17th, 2009

You ever get tired of answering the same question over and over and over? Sometimes it seems that everyone has a question that they ask over and over. When I was growing up my Dad would ask why the more education I got the less intelligent I seemed. My wife would ask when are we going to buy fill-in-the-blank for the house.

 

The question I get from customers over and over again is “What’s A Client and What’s a Server again?” It’s maddening to me but a real need for them. The problem is that the terminology is different than IT terminology. A Client in a manufacturing system is a device that makes connections to a bunch of servers and starts a data exchange. PLCs are the typical Clients. Servers are everything else. All those devices that sit around waiting for a message from a Client asking to connect. Servers have one connection to one client. Clients have lot of connections to lots of servers.

 

While I’m on it can I complain about EtherNet/IP? Who came up with that? Everyone thinks it has something to do with the IP part of TCP/IP. And, of course, it’s hard to spell. I wish I knew how many times I’ve written it without the capital N.

 

Let’s not let ProfiNet off the hook. No, it’s not Profibus on Ethernet. The object model is similar but that’s where the similarity ends. Just Another stupid name that adds to the general confusion in the industry.

 

I can’t pick on the Germans but when they introduced Profinet that had all sorts of sub names for it. It was hilarious. There was Profinet RT, Profinet 2.0, Profinet CBA, Profinet IRT, Isochronous Profinet, Profinet Real Time, Profinet IO and probably a few more that I can’t remember. It took me a few months just to sort out all these names. It turns out that IO, RT, 2.0 are all the same thing. IRT really means isochronous. I’ll explain that sometime in the future.

 

Most industries have their own acronyms. The worst is NASA. I had a friend that did some work there once. [I worked there for 2 days once but after that incident in the I can’t go back]. My buddy told me that they actually give out a dictionary. He would sit in meetings and just keep looking up acronyms. Never really could follow the subject matter of the meetings as it was all one acronym after another.  We have our here for our employees learning industrial networking Industrial Automation Acronyms

 

We could talk about acronyms and stupid names forever but I’ll end this with a few of my favorites:

choke packet
No, it’s not the hold an irate IT Guy put on your Control Engineer last week. It describes a specialized packet that is used for flow control along a network.

color super-twist nematic
Is nematic even a word? If it is a word, what is it, and how does one super twist a nematic anyway? It’s actually something from Sharp Electronics usually referred to in its abbreviated form, CSTN.

Cuckoo Egg
I have no musical talent or appreciation. It’s just not in me so I actually didn’t know about this. If you download copy protected songs you might find a Cuckoo Egg. If you hear something other than the song; like a cuckoo clock sound effects you’ve found a Cuckoo Egg.  Cuckoo on you for not spending 99 cents and buying the CD in the first place!

GoogleWhack
This term actually has a couple of different meanings. In marketing circles it means a penalty that google imposes on your web site by ranking it really low. In search queries, a Googlewhack is a search quiery that produces just one result.

Send me your favorite acronyms – I’ll start a collection and post them. Later…

IT’S A CRAZY WORLD OUT THERE…

Thursday, April 9th, 2009


I don’t think that I’m crazy. Well, I usually don’t think it anyway but is the world getting crazier and crazier?

Hearing from lots of customers and they are telling me stories that make my hair curl. At least they would make my hair curl if I had hair. Maybe makeing my skin crawl is a better analogy.

    Craziness #1. Customer number one has a messaging device. By messaging devices I mean those kinds of devices that send message packets as opposed to I/O. This particular customer has little presence in any networked-based automation application as they don’t have any networking capability. Sounded fine. That’s my best customer. RTA helps customers get networked-enabled. I gave him a very cost effective way to get EtherNet/IP and Modbus TCP enabled.

    Here’s the craziness. Their management has decreed that they can’t spend any money. No investment at all. Nothing. Even if it expands the number of customers that might want their product. Just nuts to not expand your market when sales are down.

    Craziness #2. This customer is a large manufacturing concern in Michigan. They’ve been around a long time and use VME extensively. Unfortunately, VME isn’t very popular any more. There are no spare parts and it is only a matter of time until this house of cards falls apart. But guess what? Management says we aren’t spending any money. That will last until the production line goes down. Then it will be a fire drill and I’ll get a bunch of extra money from them. OK with me.

    Craziness #3. Another guy is telling me that he is going to use free EtherNet/IP, free Modbus TCP and as soon as he can find it, free Profinet IO. In the end it will cost him more than if he had bought everything from me. But no one will really know. His costs will be in travel, additional engineering labor, customer dissatisfaction and lost opportunities to do other projects. His accountants and management won’t be able to measure that cost. But he is getting that software for free…

Maybe it’s time for me to go a little crazy. I think I’ll run for Congress. Normal rules don’t apply and craziness is expected.

Please send your John Rinaldi for Congress donations to my office. Cash only. Unmarked bills.

History: Know it or You’re Doomed to Repeat it

Friday, April 3rd, 2009

I love history, especially American History. My favorite is the revolutionary era. I just finished the two volume John Adams book. It was really fascinating. Everything about his life was so different from ours. Travel was excruciatingly slow. It took him weeks to get from Boston to Washington. Letters, slow to write, slow to send and receive, were the only form of communication. Medical care was almost non-existent. When sick, you went to bed and either you got better or you died. Very little help except for some herbal recipes.

 

History seems to be a favorite topic in Industrial Automation today. I am hearing a lot from customers who want to collect history data. They need to analyze trends, quality data, machine performance and more.

 

There are lots of problems to solve in this area.

 

First there are the PLC issues. PLCs especially the ones with the meatball on the front are notorious for closed architectures. Even if you know how to access their data table you still have access problems. Can you get the data reliably and deterministically? If you are going to save the data to a database you will want both a timestamp and the knowledge that the data is synchronized the way you want and delivered on time every time.

 

The database side is another issue for PLC History. There are more databases than hairs on my head… Oops – bad example. There are more databases out there then old girlfriends that want to cut off parts of my anatomy.

 

Everybody has a favorite database. Getting the history data into your favorite database can be a challenge. The large ones from the really well known companies provide all sorts of mechanisms to capture data. Smaller ones from lesser known companies can give you more challenges than you want.

 

I’ve been thinking a lot about history now days. Not just American either – cool ways of moving process data into these databases. Stay tuned, I’ll have more to say about it in the next few months.

RTA, Inc. - The Industrial Networking Home for DeviceNet, EtherNet/IP, Ethernet Drive,
Modbus TCP, Modbus RTU, PROFINET CBA, PROFINET IO, BACnet, IEC 61131-3,
IEEE 1588, AS-Interface, PROFIBUS, EtherCAT and other networks.
© 2009 Real Time Automation, Inc.
www.rtaautomation.com


 
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