Newsletter Issue # 7

Real Time Automation's - Best Darn Newsletter 

IN THIS ISSUE
How Real Time Automation Came to Be
Profibus Overview
Fun Facts and Trivia



STEAL OF THE MONTH...
Free RTA whoopie cushion this month only!

Email your name and address to: jladd@rta- automation.com by August 10th to claim your steal of the month.


SIDE BLOGS
7/5/12
Profinet IO on Windows and Linux
6/25/12
Implementation Guide to OPC UA
6/1/12
Las Vegas USB Interfaces
5/18/12
OPC Day Europe 2012
4/10/12
EtherNet/IP EDS Update

3/291/12
Two Fathers with Recap



YOUNG GUN AUTOMATION INSERT - Practical tips and information for young engineers.
 
 


 

The RTA Creation Story

A Column of personal opinion by John Rinaldi, Founder and Owner of Real Time Automation.

I’ve never told the story of RTA’s creation in these pages. But with so many new customers every month it’s probably time to retell it. Some of it is kind of hilarious. Some of it kind of sad. Some makes me cringe with embarrassment.

Back in the 1980s I was at Kimberly-Clark Corporate R&D in the Controls Group. In those days we designed controls for their Tissue and Feminine Products conveyor lines. As is typical of many young men of that age, I was very headstrong.

I shot my mouth off quite a bit in those days. After all I had 2 years of experience and knew exactly how that corporation should be run. Well, I shot my mouth off once too much. Criticized my boss, very publicly in front of a room full of people including his boss. Soon after, I found myself with a new job, new wife and enough severance to spend a month hanging out in Europe.

I landed in a new department at a place called Allen-Bradley. I was in the Sensor Engineering department. We did Robotics, Vision, Barcode and a thing called the 2760-RB communications module. Very cool stuff in those days. Very cool place to be. Or so I thought.

I loved the people there. Made some good friends - we had quite a cast of characters. Will, just imported from GE, was our leader. Will’s door was “always open”. Just don’t walk through it as I learned on one occasion. Not as receptive as he claimed to be.

We didn’t make much money in that department. In fact, we were losing $1,000,000 per month. I was told not to worry about it – we’re a billion dollar corporation. So, at review time I reminded them that “Hey, remember how a million bucks a month isn’t a big deal. I’ll take a $5,000 a month raise.” All of a sudden, it IS a big deal. I didn’t get the raise.

In those days we used something called Lotus; a predecessor to Excel. Every month Will showed us his spreadsheet, and my gosh, there’s a sales spike just around the corner! And every month the spike moved out a month. We had bets going on how many months he could keep a straight face showing us that spreadsheet with the traveling spike. I lost $25 on the bet.

Some of the other characters included Leisure Suit Larry who never, and I mean never, washed his hair. Leisure suits had been out of style, for maybe 15 years, but Larry still wore that same blue leisure suit every day. (Confession – at one time in my life I had an ORANGE leisure suit that I thought looked good on me.)

Then there was Resume Rob. Rob came in from (say this very slowly, in a hushed, reverent tone) “I B M”. He had degrees. Lots of them. He had experience. Lots of it. He had personality, a can do attitude, a real leader we were told. Hired to show us how to build embedded products. The savior arrives tomorrow! An Engineers Engineer, they said. I B M after all! 

INCOMPETENT. Completely inept. Gone in 90 days. I don’t know this as a fact but I think they dropped him out of the clock tower one night.

Then there was my Group Manager; we'll call him Tim. Tim actually started RTA in a weird way. Tim was another one of the GE refugees. Seems like GE unloaded a whole boatload of “special” managers on Allen-Bradley in the mid 80s. They really were ”special”.

I worked on RF Tags in those days. My job was the software in the tag. When the tag hit the RF field, it powered up and my software sent the data out, bit by bit, byte by byte. Software. I didn’t know a thing about RF and still don’t.

Tim shows up at my office one day to ask what it might take to make this system work in Japan. “Nothing”, I reply. It powers up, I send out 8 bits, no matter what country we’re in.

So, he goes up to my whiteboard and gives me a tutorial on the Kanji character set. I sit and listen passively trying to figure out where this is going. Finally, after 20 minutes, he sits down and asks me again. “What is it going to take to get this system to work in Japan?”

“NOTHING” I almost shout. “As far as I know, they use 8 bits to a byte in Japan too”. To which he proceeds to tell me that it won’t work in Japan because our system is something something mhz and that frequency is not approved in Japan.  Then he leaves.

Guy came to my office. Asked me a question he knew the answer to. Wasted 20 minutes of my time on a useless tutorial on the Kanji character set. And, we’re losing a million dollars a month.

Decided right then and there that I wasn’t corporate material. RTA was born a month later…

THANKS TIM
Trivia Challenge

· Conscription is another name for what?

· An upside down flag is a symbol of what?

· What US dollar bill was discontinued in 1966, and reinstated in 1976?

·  On August 18, 1920 who got the right to vote in the US?

· True or False - It is agaisnt the law to fly any flag higher than the US flag at any time, anywhere in the US.

 

Answers located on bottom of page.


Profibus Overview

Profibus is a hot topic around our offices right now. Our whiz kids on the other side of the wall from me are releasing Profibus to ASCII, Modbus RTU, Modbus TCP, EtherNet/IP and a whole bunch of other gateways.

Profibus is an interesting technology for a lot of reasons. It is still the dominant protocol of Europe. Profinet has made a start there but it will be years and years before the number of Profinet nodes is anywhere close to Profibus.

Every August I go to the Profinet International (PI) conference in Phoenix. (Why in August? It’s cheap. Who wants to be in Phoenix in August?) Carl Henning, the Assistant Sheriff of Profinet International, always shows a chart with phenomenal numbers for Profibus. Something like 11, 12 or 13 million nodes. Not sure where they are now but it’s huge.

By the way, you’ll know Carl if you see him. Since I designated him the Assistant Sheriff of PI, he’s been wearing a 10 gallon hat and a badge. I guess he kind of likes the title and the outfit. All city boys want to be cowboys.

Like everything else German, Profibus has a couple of variations. There’s Profibus FMS (Fieldbus Message Specification), Profibus PA (Process Automation) and Profibus DP (Decentralized Periphery). DP is all I am going to talk about here. Honestly, I know almost nothing about the others beyond how to spell them. DP is the one with the majority of the nodes anyway.

So, why is Profibus so dominant? One factor is that it is the preferred way to connect to a Siemens PLC. Rockwell has a lot of traction in the US but Siemens is worldwide and growing strong in the US.

I was shocked a few years ago when US Navy ships started using Siemens PLCs. Thought for sure that Rockwell could have leaned on a few senators to make sure that our ships would have American made programmable controllers but that didn’t happen. Siemens is a very tough competitor for Rockwell.

Probably the biggest factor in its success is its speed. Profibus DP operates at a startling 12 Meg. That’s 24 times DeviceNet’s max speed. It’s not Ethernet but it’s plenty fast for most everything except some Motion Control Applications.

They get this amazing speed by using a souped up RS485. Special connectors and components are necessary to achieve that kind of performance.

Profibus is a Master – Slave kind of network. Masters, also called Controllers are usually Siemens S7 PLCs. Masters send outputs to Slave devices. Slave devices send Inputs back to the Masters. You can have up to 127 Slave devices and like DeviceNet, there is only one Master per network.

It doesn’t move a lot of data. The IO transfer size is adequate at 244 bytes, but for the kinds of devices used in Discrete Automation, 244 bytes is just fine.

Just like many of the other protocols, there is a buffer in the PLC (Profibus Master) that gets moved to the device (Profibus Slave) and a buffer in the device that gets moved to the Master. These buffers are moved cyclically. Lots and lots of my customers tend to think that just because there is data moving in two directions that it must be request – response. It’s not.

The data representation causes some heartache for a device vendor. There is some confusing terminology. It’s vastly different than Modbus RTU, Modbus TCP, EtherNet/IP or DeviceNet data representations.

Profibus devices look like an I/O rack to the controller. An I/O rack has some number of slots. Each slot can have a module in it. Just like in a physical world, a Profibus device with a virtual I/O rack could have a 16-bit Input module in Slot 1 and a 4 channel Analog output device in Slot 2. Even if the device is a weigh scale, it has to somehow adapt its data to this I/O rack data representation. It takes a bit for a device designer to wrap their head around that.

The GSD file is how that data representation is communicated to the Controller. The GSD is the Profibus equivalent of the DeviceNet EDS file only it’s more functional. The GSD tells the controller not only about the I/O rack configuration but is the link to integrating that configuration with the data table of the controller. And, of course, everything better match or nothing works right.

There are a few things I don’t like about Profibus. For one, it’s expensive. You really can’t implement it in software – there are performance and system issues that make it extremely difficult.

There are two ways to get into the Profibus DP world. One, you buy the ASIC from Siemens or one of a few other vendors. The ASICs aren’t cheap. Especially in low quantities. Or you could buy something like NetX from Hilscher. That works fine but you are going to pay even more for all the additional functionality that you get in a NetX product. (NetX, by the way, is another one of those amazing German automation products.)

You need special connectors on your product for Profibus, special cables, and a way to configure your device. Configuration is usually done with three switches to set the Profibus address (1-127). I’ll admit that’s a plus, generally you just set the address and you’re done.

I also don’t particularly care for the data representation. It’s kind of an anachronism in 2012. We’re tied to a structure developed 50 years ago and can’t get away from it. Don’t see a way out of it though.

The real upside for the user community is that there are a lot of Profibus devices around. They’re fast, reliable and highly functional. You do get value for your money in the Profibus world.

As I said earlier, don’t expect Profibus to go away. It’s too functional and too good at moving data in and out of a controller to be displaced by Ethernet.

 

Fun Facts
 


· US presidents John Adams, Thomas Jefferson, and James Monroe all died on the Forth of July.

· Over 150 million hot dogs are consumed on the Forth of July.

· Though the British were once our adversary, today trades between the US and the United Kingdom are valued over 90 billion dollars, making them our sixth leading trade partner.

· The temperature required for the proper reaction of elements to create blue fireworks is very tough to acheive. This makes blue the hardest color firework to create.

 
  Trivia Answers:The Draft; Distress or Danger; The $2.00; Women; True
   
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