Please Help Using One Shots

[SeanLee]

I think Terry is a A$$ Hole

I am a 2 year graduate as an Industrial Electrician (trouble Shooter)

i am in a Engineering position with no paper that put me here just hard work and a tech school degree



not all electricians are dumb they are just as good as you except with more common sense i think



sorry just had to get that out



i had a problem with a papered engineer here at work and had to fix his dumb *** mistake he created to the process because his calculator told him to make the change

 

[S7Guy]

Don't you KNOW (yet?) that the Output of any rung is looking for a "cause to be ON"?

Well, yes, but in your code the "cause to be on" is always true. It's just code bloat.

Bryan...
Say... has anyone noticed the increase of PLC-Guys from College that are... "trouble oriented" rather than "process oriented"?

Very, very, very, disturbing.

I believe VERY STRONGLY that, that function (trouble oriented) belongs to the on-site Electricians!

Yeah, they (the Electricians) have to be brought up to speed... but... considering what it takes to read a rung... I really have to wonder what the colleges are thinking.

Why does this function belong to electricians? From my experience, some of the best process control guys I've known have had a mechanical engineering background. You are making an assumption that most PLC logic will be in ladder, or that non-electricians are somehow unable to understand ladder logic.

 

[rsdoran]

I think y'all may be reading more into it than what Terry said, he was not knocking electricians, just stated they needed to learn more about the field of automation/plcs; which is true in many cases.

I believe the jab was more pointed to what and how schools are teaching, not so much who it is that is being taught.

The problem is that many electricians, maintenance, etc are trying to come up to speed; therefore the introductory class will lean more to familiarity of instructions and learning to find problems.

Terry, you are stating college but many of the people that come here are not in a University type college, it may say college but it may be more of a vocational/trade school. It may depend but in many cases the curriculum is designed to teach the basics for a service type position instead of design; therefore trouble shooting would be a high priority.

Terry, I am going to attempt to "discuss" Karnaugh maps, which I "think" I do understand BUT your statement about having a history of not understanding YOUR Karnaugh maps is correct. I will explain later.

 

[PeterW]

PeterW said...
"Your 1 and 2 branch contacts cancel each other out, so may as well not be there, a straight connection from power rail to OUT NO will do just the same??"

OMG! PeterW! You are sooo... WRONG!!!

Don't you KNOW (yet?) that the Output of any rung is looking for a "cause to be ON"?

Not sure I understand that statement, all I know if I saw this code in a program:

I would delete the 1 and 2 contacts as they have no use.

the Output of any rung is looking for a "cause to be ON"?

Yes, but there has to be logic there, that code is illogical as it cancels itself out.

I must admit I have never used K Maps, I go further, until stumbling across this site I had never even heard of K Maps!

In college I was taught how to simplify logic problems using boolean maths and to code using flowcharts.

Looking at the code that is derived from the K Map, or even looking at the complications involved in that K Map itself for what is a simple (if not confusing) problem, I'm unsure if I want to ever use K Maps.

What does a K Map look like for a real (complex) problem and how do you derive code form what looks like a sprawling mess.

I can see I'm going to have to look at these things just to satisfy my curiosity now .

 

[rsdoran]

K-Maps are just one step further than a truth table. I am still thinking about some of this but for now I can explain my take on K-Maps.

Terry gets me confused with his K-Maps because I have no idea what he is referencing. Technically a K-Map is simple and can have 3, 4, 5, 6 and possibly up to 8.

This is how a K-Map works.

I just noticed this picture has an error, the second from left BC should show NOT B C.

The picture shows 3 inputs, A, B, & C and now you can determine what the action will be depending on the expression that is developed. A and B and C = y (output). In ladder this is simple:

     A       B      C       y

|---| |-----| |----| |-----( )--|

A and B or C = y

      A      B              y

|----| |----| |---+--------( )--|

|     C           |

|----| |----------+ 

The key to K-maps is developing an expression and the fact that each adjacent position is just a 1 bit move.

Personally I think Terry is great BUT he gets loose from his keepers and gets off into never never land. It is not K-maps that I have a problem but what Terry uses the K-maps for, I do not see that part. Terry has promoted K-maps for years, but he gets to rambling and few can keep up with him, in the past there was an Allen Nelson that could and this thread will provide alot on this subject:
http://www.plctalk.net/qanda/showthread.php?t=1563&highlight=Moore+diagrams

I gave the basics of Karnaugh maps, if you want to learn more check these out:
http://www.patchn.com/Digital/DIGI_8.html

http://www.maxmon.com/kmaps1.htm

I plan to go back and study Terry's earlier post to find the expression(s) he is using, at this point that is the part that confuses me, that and the dynamic aspect.

From the beginning of this thread what was needed was not clear, even though one person stated it was. If it had been clear in the beginning then why so many different pieces of code? My argument is not that the code will not do what you say it will but is the code what was actually needed? I have not seen where that was shown to be fact.

I ain't buying the 5 minute thing either, that shows an ego far worse then those already being shown.

Eventually I will dissect all this and do it myself just to see what I get then I will look at the other final codes. I have other projects to work on so I will not be in a hurry.

 

[Peter Nachtwey]

K
I ain't buying the 5 minute thing either, that shows an ego far worse then those already being shown.

I believe this can be done in much less than 5 minutes once we get a proper description.

Terry's Karnaugh maps confuse me too. He is not using them in the proper way. I know what he is trying to do and he is right about it being about history. I would call it state. K-maps do not have tranisition lines but then you have seen that now.

 

[Terry Woods]

I have, since my last post, discovered that I have accidentally omitted more arrows than I thought. I'll post the complete map tomorrow.

Then, I'll take you through the how and why of the map, and how I use the map AND THE "RULES" to develop the subsequent code.

The "RULES" are the ultimate EVERYTHING! And those "Rules" should be a direct reflection of the stated expectations!

I'll also include the case where the Reverse-Switch is turned ON... as yet, I haven't given any thought to the case where the Reverse-Switch is turned OFF. I'm sure that will have problems of it's own.

 

[monkeyhead]

I learned K-maps in school as part of my digital electronics course. When I was doing them often for my classes, they were soooooooooo much easier than boolean simplification.

Define input and output states... plug into map... circle the groups... derive formula... translate to digital circuit (or in this case, ladder)

I admittedly don't use them often and at this point would have to pull out my notes and example problems to remember all the specific steps.

I do remember that the example problem that helped me the most was using a K-map to design a 4-bit gray-code to binary converter (or vice versa):
1. The input and output states are all concretely defined
2. There's a bazillion and one examples of these circuits to compare your end result to
3. The output is easy to test, so you are freed up to concentrate on deriving the formulat from the map and translating it to logic devices.

 

[Terry Woods]

In response to Post-151 onward...

Seanlee...
What exactly is your bitc#... complaint?
As far as Electricians... Ron handled that well.
As far as two-year-degree guys getting degrees in trouble-shooting... THEY HAVEN'T GOT A CLUE! Ohhh... they can do graphics! Yeah, right... that'll help!

S7 and PeterW...
You just don't get it, do ya? Hmmm... Imagine that...

Ron...
Please clarify the "5 minute thing" for me. Wha-zat?

That aside... Never-Never-Land is where it happens!

As in... WISHING MAKES IT SO!

Ron... your description, much like Peter's mind-set, is a STATIC K-MAP.

There really is, believe it or not, such a thing as a DYNAMIC K-MAP!

Peter said...
"Terry's Karnaugh maps confuse me too. He is not using them in the proper way. I know what he is trying to do and he is right about it being about history. I would call it state. K-maps do not have tranisition lines but then you have seen that now."

Proper way? Who hasn't used a Crescent-Wrench as a hammer?

Yes... HISTORY is EVERYTHING.

A Rose by any other name is a Rose!

As far as K-Maps NOT having transition lines... that is totally bogus!

As I said... I will follow up and explain this stuff... but not tonight!

 

[geniusintraining]

I dont get it...sorry

Terry,

All due respect…I don’t get it, I understand K-map’s and I like what you have done, I read everyone and understand or try to understand the logic…

But why? Do you use these? Or is this what you would like for us (newbees) to do to learn the logic? And understand the way the plc looks at the logic?

To me its much easier to write the logic in STL then convert that to ladder, I’m sure that K-maps have there place but I don’t see where, it seems that you could write the code in half the time you could write the K-map

 

[rsdoran]

Terry, for the 5 minute thing look at post 134.

I am following Terry, albeit very slowly. I was slow, very slow, with creating code when I came to this site but have learned so much from so many but Terry's insistence on K-maps made me look into it more and it is helping me, I just get lost on some of Terry's posts at times.

This is my take on the subject, have you ever seen people that could just glance at something and then spit out programming like it was nothing? I am fairly certain Terry, Lancie, Steve, and many others are in that category.

Each person is different in how they think but Terry is promoting the K-maps to help people learn a way to think that may allow them to be faster and possibly more efficient. In other words once you learn the details on what K-maps can do, you may be able to use them in your head and not on paper.

History is the key word here, our lives and how we think are based on our history i.e. how you think and who you are is based on actions or inactions of your past.

Terry is promoting that same concept with plcs, each action or inaction, is based on history and a K-map can offer that history or future. I guess you could say it is just a method to enhance your conceptual thinking, something I have problems with.

All I ask Terry is please take a valium or whatever is needed and do not go rambling when you explain it.

 

[monkeyhead]

GIT - Boolean simplification and K-Maps are ways to design the most efficient logic circuits that you can. They work increadibly well when you are trying to use the least amount of devices, and have well defined input and output states.

They are also good when you know your input and output states and want to quickly develop the logic that will give you those states without having to think through the entire solution. This is when they are a real time saver.

I find with most of the PLC stuff I do, that it is more event driven than state driven and I'm not as keen as how to define my input and output states, so I don't tend to use them unless I have very specific states I'm trying to acheive.

 

[S7Guy]

In response to Post-151 onward...
S7 and PeterW...
You just don't get it, do ya? Hmmm... Imagine that...

Sure I get it. You have posted a code snippet that contains redundant code. What I would really like to see is a K-Map example with some practical results.

 

[Staines]

GIT - Boolean simplification and K-Maps are ways to design the most efficient logic circuits that you can. They work increadibly well when you are trying to use the least amount of devices, and have well defined input and output states.

Yeh, they are good when yer starting out. But after a while (maybe years) you will find the K-map in your head. When you start to standardize your PLC structure, you tend not to use them anymore.

 

[geniusintraining]

Thanks monkeyhead, I guess I just have not had the need and/or the use for one (yet)

But I still don’t see that they would speed things up?, it seems that it would make more work