Re: Help!! Your opinion on the direction of Industrial technology devices?

HoPpeR© trading at 1492¥ wrote:

With floating contacts and kilovolt isolation? Famous last words: I
don't see semiconductors replacing circuit breakers in general use.

Jerry
--
Engineering is the art of making what you want from things you can get.
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Yeah, and it's hard to find those force-guided triacs and transistors
for my safety systems.

proclaimed to the world:


And I agree that there is a place for contacts. I would not think of
eliminating a circuit breaker or contactor as a safety device in a
circuit, but......think of all the applications where the triac has
replace the poor overworked contactor or even made possible high speed
switching. Don't read more into what I said than I did. Triac and
transistors are the solid state equilivelent of the E-M switch. Both
have their pluses and minuses. There are applications where I would
much rather have ten relays in my design if it would eliminate the
need for a PLC and I have done this. At the same time there are
application where I would be hard pressed to do what was needed
without a PLC. I've seen logic written that takes 20 pages that I
rewrote in two lines because the guy writing it appeared to have very
little imagination and I have seen code that blew me away. The key to
good engineering is to use all that is available, not just what is new
and sexy.

Be well,

HoP

The preceding message represents personal opinions
and/or advice that may prove incorrect or harmful. But then maybe not.
Feel free to disregard.

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HoPpeR© trading at 1492¥ wrote:

Your initial remark implied that you would. When statements like that
are allowed to pass unchallenged, onlookers may be deceived. I'm
probably overly sensitive about that.


I can only guess what that sentence means. When a sentence is
unambiguous, I assume it's either a joke or you mean what you write.


Tell me about it! (See my sig.)


--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

proclaimed to the world:


I find it is very difficult not to be ambiguous without putting in
more effort that I am willing for each sentence. I try but never reach
that goal. I apologize.

I am also new here and am used to being on a support group where
people are talking about things that are indeed muddy. Mental health
is not cut and dried. Again I will try to make the transition as
smooth as possible.

Be well,

HoP

The preceding message represents personal opinions
and/or advice that may prove incorrect or harmful. But then maybe not.
Feel free to disregard.

 ------- Words have no Warranty ------
 ------- No View without Merit  ------

On Sat, 09 Jul 2005 17:15:35 -0400, HoPpeR© trading at 1492¥

 There are applications where I would

Me too. Except you can now buy a plc for about what 10 relays and
sockets cost and it has the relays (or triacs/xistors) in them
already.


 I've seen logic written that takes 20 pages that I

Naw, he was programming using TIP. (To Impress Peons). I'm with you, I
see it every day.

On the other hand, I once got called into an engineer's office for
using "un-needed complex programming" on a project. I had used a shift

Steve Cothran wrote:

The day I learned to program with ladder diagrams, I had gotten called
in by the mechanical group (I was part of an instrumentation and
circuit-design shop that acted as consultants) to design a hardware
shift register that could be set, advanced, and read by a TI PLC
controlling a turntable bearing parts. It was only a package of
flip-flops and another of gates, and I had it running in under an hour.
When I brought it over, I asked why it wasn't programmed in the PLC.
They told me that, according to the TI field engineer and confirmed by
his boss, a shift register couldn't be built in ladder logic. The mantra
was "You can do everything, and only those things, that you can do with
relays."* I borrowed a small PLC with manual that people used for
getting familiar, and learned how it worked. The rungs of the ladder
were evaluated sequentially, so proper organization can make a race
impossible. I programmed the shift register by the time the mech boys
got back from lunch and gave it to them. The next month, the circuit was
in TI's application magazine without attribution or thanks.

Jerry
_______________________________________________
* I can build a shift register with relays, but only by cheating; slower
relays here, faster ones there; otherwise, race. A parlor trick not
suited for production.
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

proclaimed to the world:


Jerry, the first true PLC I worked with was an Atcom. I don't think
they make PLC now at all, but the idea of programming in ladder logic
was not really though of then. Ladder logic programming came about
because the things didn't sell because nobody knew how to program
using their assembler which was very similar to basic except it
overcame the problems of real time execution. I had been playing with
basic programming for years on first the Apple II and then the first
PCs. You could do just about anything. Ladder logic was something
pretty strange to me. At that time I had not designed anything in
ladder logic, but used others drawings to troubleshoot existing
pre-PLC machines. I ate up the Atcom unit. I could do anything with
it. No one else could though and in a year or two the Atcom 64 was
history and Ladder Logic was selling like the next great thing. It
wasn't great. It was an assembly program that forced the constraints
of the old world of putting relays together to for basic logic
functions and it came about because there was an established world of
engineers that understood how to write this stuff. I was a
salesman/tech rep then and I could sell the idea of using PLCs to the
engineers with ladder logic. The guys that taught in school could
understand ladder logic and the transition for them to teach PLC
programming became a reasonable task.

The last I worked with AB, they had started the Advanced Programming
Software which was in essence going back to what Atcom had to start
out with. The differences is that AB is in essence now trying to use
the free form basic programming style to write logic, then convert it
back into the highly structured ladder logic of old. It does not work
well. Square pegs, round holes.

Now my version of things is about five years dated. I hope things have
changed for the better, but from what I can tell so far it has not.
What I saw from the times that I was asked to teach courses back then,
it was very rare for any student to be able to make the leap beyond
the strictures of ladder logic programming but then the generation of
guys that had experience in computer programming had not gotten into
the schools. I was either considered a wizards wizard or a kook by
most controls teachers. There just were not very many people around
that knew both computers and controls. Now I feel like a fossil. I
have to commend you for making the leap beyond the false strictures of
RLL.

 What Tim does with embedded controls is a step beyond this and works
the basic area that I feel everyone should be at, but this will never
be because things get designed and built so that the most people can
use them. That means building on top of what was and that is never the
most compact and efficient way to do things.

I'm not for sure why I wrote all this. It is good to have someone to
tell this to that understands for one. It has always been an irritant
to me that things are not perfect. I am an idealist and that is my
downfall most of the time. I insist on trying to make the world do
things the way I see as the right way and it never does.

Be well,

HoP

The preceding message represents personal opinions
and/or advice that may prove incorrect or harmful. But then maybe not.
Feel free to disregard.

 ------- Words have no Warranty ------
 ------- No View without Merit  ------

Your version of things is more like 25 years dated! I went through the same
thing you did in about 1978!!

You are correct, ladder logic was designed so that PLCs could be used and
understood by people who don't have formal training in programming, and that
is exactly why PLCs are successful today. Now, people with formal
programming experience look askance at ladder logic, and tell me how much
easier everything is in C++, until I ask them to make edits in a running
processor, or change data values change as the machine runs, etc.etc.

You are also correct that ladder logic has its limitations, and that is why
all except lowest end PLCs now offer multiple programming languages. AB
currently offers ladder, sequential function chart, function block and
structured text (a kissing cousin of PASCAL.) If ladder logic doesn't work
for you, there are other choices. In the specific case of the AB product,
these are true languages, they are not pretty faces put in front of ladder
logic.

And really, what is so terrible about ladder? All it is is Visual Boolean!
For fiddling with individual bits, why not?

However, and this is probably your real point, and awful lot of people learn
a little bit of ladder and never go any further. It is true that you can do
almost anything in ladder, but unless you are willing to learn past the
point of timers and counters it is usually the most difficult possible way.
Yes, you can do a shift register with coils and contacts, but why not LEARN
the shift instructions!

What is happening in the PLC industry today is interesting. Basically, the
worlds of the PC, the PLC and the DCS are coming together, and the new
products combine important features of each. Communications and networking
is now the BASIS of PLC architecture, rather than an afterthought.
User-defined data structures and techniques have replaced the old data table
designs. Use of OPC data servers has made PLCs interoperable with PCs.

Point is, if you want to do anything important with PLCs today, ladder logic
is just a tiny part of the picture, rather than the WHOLE picture as it was
25-30 years ago. If you understand modern PC programming and architecture
the new PLCs will be very easy for you. If you understand nothing past coils
and contacts you will NEVER get anywhere with the new generation of PLCs.

On Sun, 10 Jul 2005 11:10:18 -0400, "BFoelsch"


I mean that the end of the story dates back five years because I have
not worked in that long because of sickness. The tale does start 25
years ago indeed.


Changing during a run is a big plus.


Well I think you have not caught the reason why I am here, taking the
time to share and learn. I have been out of the field for five years
mostly and want to learn where the industry has moved too. I would
have to check but I think that the version of APS I have from AB is
the original. You are answering questions I have about where they have
good without me having to buy a new version and finding out, only to
be disappointed.


Nothing, but it has it's limits and when that was all there was and
this did not have to be true, that was terrible. For some basic stuff
it is great. I once needed to do something quick and cheap for a pump
station. The designers had forgotten to include any pump logic like
alternations and turning the damn things on and off according to
pressure. They supplied the sensors, but nothing else. I had been
hired to commission the station and it was way back in the sticks. I
happened to have a relay block with an embedded controller that I was
able to program on site that day that did everything I needed. It only
had four outputs and two inputs, but that is all I needed. For this
ladder works just fine.


Yes it is, and when I got sick it was just starting. In the past I
have spent a lot of time being frustrated at waiting for the industry
to adopt what I thought should have been obvious. The large majority
of my business has been taking care of something someone else
designed. My business is in a rural area too. I don't choose which PLC
I work on. I got really tired of seeing all my profit go towards
buying the programmers and software necessary to work on all the
different manufactures versions of the same thing. I was really
frustrated trying to integrated two different systems. Or five. I was
frustrated having to be the one to here the end users complain about
these same things. I was bitching about the stupid idea of putting all
the controls into one box at a wastewater plant and watching that box
fry in the middle of the night as the entire plant goes down and goes
into flood mode. DCS you say? I was screaming about this at the
seminars back before the term was coined.


And I do understand the whole picture. My point is that it should have
started out that way. It was obvious to me then. It was obvious to me
back when each programmer was writing his own bubble sort sub that it
should be done right with the minimal amount of code and then set as
the standard. It was obvious that the OS on PCs need not take 552 megs
of memory. It was also obvious that Microsoft was making it's
customers pay for sloppy programming.

But then I am, as I said, an idealist at heart and have to work hard
to be pragmatic in a less than ideal world. It is rare that I get to
say the things I am saying now to someone that understands the first
bit. I'm not knocking individuals but I do have a problem with some of
the industries short sightedness. I can't change what has happened. I
can talk about it and maybe things will change some in the future.
It's said that history repeats itself. I've seen this many times.
Coming up the way I have in the industry I get to see what a lot of
controls designers do not. I see the problems maintaining the systems
after the plant is built and commissioned. I'm the guy that is hired
to straighten out the mess that is left after a lot of engineering
firms are fired from the job. I'm also the guy that get's screwed out
of being paid because the customer then wants that engineering firm to
pay for me fixing there shortsightedness. It's seldom that this
happens. I get stuck in the middle.

I also am tired of seeing a lot work on my part go for nothing because
I had to go back and learn something like ladder logic versions of
programming PLCs that I thought was backward thinking to start out
with, then only to see that abandoned for the "new" way which is
actually a poorer version of what I was advocating in the first place.
[insert big sigh here]

Intellectually I understand these things and know that to do well I
have to work with the way things are and find a way to make that work
in my favor. This is why I am excited about finding sci.engr.control.
I see this place as a way for me to better understand what is
happening and take control of that knowledge. I really do not know
enough of the history of this place. That will come. I can see that
there are people here that know more about certain areas of the
industry than I do. Hooray! I am opinionated but that opinion changes
and I'm hoping that you will be a part of changing it. I also hope
that I will add something to the knowledge and opinion of everyone
here. If that happens then we all gain.

I'll be doing my part of learning about what is new and improved in
the controls industry since I dropped out. Your reply has helped me
towards that goal and I thank you. I really do not disagree with
anything you said other than perhaps you are reading more into what I
said that was there.


Be well,

HoP

The preceding message represents personal opinions
and/or advice that may prove incorrect or harmful. But then maybe not.
Feel free to disregard.

 ------- Words have no Warranty ------
 ------- No View without Merit  ------