Writing a program for lab.

I just started learning Plc so bare with me. The program I have to write uses two inputs, an increase and decrease, to go into and up/down counter through a timed based contact on .01 sec. The accumulated value in the counter should be placed in the output of the analog channel. Verify that the output changes with the accumulated value in the counter. Make sure that the accumulated value in the counter is never less than zero or greater than 32,767. The info I have is in the pix I uploaded. Teacher isn't much help.

You should start by reading the lab and completing the step-by-step that has been given to you.

Members here will not do your homework for you, but they will answer specific questions you have. The problem is you have not really asked any questions, you have just informed us that you have an assignment.

Here's a hint. If you program an XIC instruction addressed to a timer's .DN bit ahead of the TMR instruction, you have created a self-resetting timer. Because of the way you programmed it, that timer's .DN bit is a one-shot pulse.

I never asked anyone to do my homework sparky. My teacher is a first year teacher with no degree in teaching, just field experience. We Never opened the class book which was a waste. We just get lab packets without going through any examples or nothing. Basically here's the lab do it. I'm assuming I have to use the greater then less then instructions with my program. I've never used them before I'm not sure what address to put on them. And no we never went over greater then less then instructions. Also for scp if I use a xic what do I put for the address there's no dn bit. I can only work on this 1 once a week in class. It would help if I had a simulator at home

I have often wondered why students in PLC classes feel like the teacher has to explain in detail every instruction to them before they can attempt to use them. Would it not be beneficial to learn how to use the help file?

After talking to some of the people in our facility, I think i have figured out part of the issue. They have told me on a regular basis that "I can't use that instruction because the teacher hasn't gone over it." To me, this methodology inhibits people from self learning. To me, it promotes the behavior of "I haven't ever seen that before, therefore i don't know how it works and I cannot fix it."

I believe PLC classes should focus more on explaining how a scan works, difference between data types, IO types, form, structure, how to use the software and help files, and programming best practices. Why do you need to waste someones time explaining how ADD, SUB, GRT, and other basic instructions work? I think this time would be better spent explaining how to map out a process and develop some sort of flow chart or sequence of how a lab is supposed to work BEFORE you begin programming and let the student figure out what instruction to use to make a bit come on with the pressure is GREATER THAN a setpoint.

Maybe I just don't understand because I've never had the luxury of taking vocational PLC classes? Maybe the local classes are just that bad? Has this been others experience as well?

Carfreak2017 said:

I never asked anyone to do my homework sparky. My teacher is a first year teacher with no degree in teaching, just field experience. We Never opened the class book which was a waste. We just get lab packets without going through any examples or nothing. Basically here's the lab do it. I'm assuming I have to use the greater then less then instructions with my program. I've never used them before I'm not sure what address to put on them. And no we never went over greater then less then instructions. Also for scp if I use a xic what do I put for the address there's no dn bit. I can only work on this 1 once a week in class. It would help if I had a simulator at home

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Normally, I don't even respond to these types of posts but this one one hit a nerve. I apologize to the rest of the forum members.

Most of this post by Carfreak2017 reeks of a bad attitude. Many of us on the forum are self taught and some haven't gotten a degree. Even so, we are glad to help but you need to know that we are free volunteers. You need to not get offended with what others reply, just be thankful for all the good info and shrug off any info that you can't use.
TheLearningPit.com has some very good info, There are many great posts by Ron Beaufort here on the forum and on YouTube as well. Also, just remember that PLC programming is a lifetime job and will be an ongoing learning experience.

Carfreak2017 said:

Teacher isn't much help.

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????

We got off on the wrong foot. I'm sorry I came across as arrogant, I was just short on time and trying to explain that we didn't really have enough info to "help you" with your problem because you didn't ask a question.

One lesson you will learn in the field, is that you will often be given a set of instructions and may not realize what is going on or why. That is your job to learn utilizing all resources available. When you are the tech called to a problem machine, you must find the info you need, though it is too bad he didn't give you a basic rundown of how to use the software. The reason controls guys get and retain higher paid jobs is because we posses an ability to solve complex problems, but none of us learned how to do it over night. We used manuals, books, our intuition, experiences of others, and any other resource available to us to figure something out.

In this case, drag an instruction on to the rung and press "F1" and it will bring up help for the instruction. Then google the instruction and find some relevant info if you are still confused.

When I'm doing an electrician's work I'm often not given details on how it works, just what I need to build. These wires go here.

Does your instruction sheet give you the parameters to put into the instructions? It looks like it contains addresses for the SCP instruction.

The SCP instruction "scales" values. Think y=mx + b. It uses your x input, which can be an HMI input, an analog input or any number of other inputs and scales them to the values to give a y output and then copies that over to an analog output. In this case the output value is copied over to N7:0 which is an integer file. RSLogix breaks different data types into files. B3 is the default binary file type, and there are several others. The output will then be stored in N7:0 and can be referenced elsewhere in the program.

Keep a note pad with you while you work through the labs. Write down your questions and then take them to your instructor when complete if necessary or post here and others will be happy to help you. Once you have a complete and working lab, it would be much easier for your instructor to explain it to you.

Hope this helps.

Helliana said:

..

Maybe I just don't understand because I've never had the luxury of taking vocational PLC classes? Maybe the local classes are just that bad? Has this been others experience as well?

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Well, one time I was at a job site and the local tech can barely assist me, during break this same tech tells me he teaches PLC at the local CC.

So...

I have taken PC programming class at local CC and had amazing teacher too as well.

If your teacher sucks, might as well go through every youtube videos you can find instead of wasting time in class.

Helliana I've never heard of the help file till you mentioned it. Let me ask you something helliana, you may or may not be able to solve this what is 2x-y-2z=-3? To someone that has never taken algebra before they wouldn't know where to start. How can you self learn if you don't know where to start and have never seen any examples. I thought the purpose of a teacher was to teach.

Jrwb4gbm it seems like your the one that felt offended, you seem a little sensitive. You even said this one hit a nerve. Not once have I been out of line so not sure why you think I have a bad attitude or why you thought I got offended when I have simply just stated facts.

Sparkie thanks for the feedback!

Close to half the class has dropped due to the lack of teaching, I however must push on or I can't take my next class.
Thanks everyone that helped. This was my first time using a forum so excuse my lack of knowledge for asking the right questions.

Hi there carfreak.

I had the fortunate opportunity to attend RSlogix class for beginners and intermediate. followed up by a four day on FTV.

In the two years since then I have forgotten almost all of it. It was unfortunate but I never had the chance to use it. Customers wanted the cheaper units.

2 months ago Customer wanted a beast of a machine built, and insisted on CompactLogix.

I felt like a kid riding a bike for the first time. I was gonna fall off any minute, and completely intimidated by any RSLogix.

60 days ago, I cracked open Logic Designer for the first time, wrote 600 lines of ladder, on 9 different subroutines. I was in this forum every day, asking some of the most horrendously stupid questions. Some of the time, no one answered. I now know why. A little more digging thru all the online PDF's for logix and there it was, the answer to my stupid question. 2 hours ago, we put power to her, and except for some stack light issues, it was a flawless start up. It would have never happened without the generosity of the members of this forum.

RSLogix isn't easy...........................ya gotta earn it.

There is a person on this forum, I don't want to tell you his handel cause i can't remember it completely and I'll butcher it if i try. At the bottom of all his posts is a link titled "How to ask a question" I suggest you read it. I need to go back and re read it. I was where you are 60 day ago........................

Just remember one thing........................a support staffer from another platform told me this a couple four years ago. "If ya turn it on.........ya gotta remember to turn it off.

And one other thing.......you have stumbled into one of the best support forums on this side of the net. This place has a bazzillion pages of old post. Found alot of answers there.

So stick around...........see what goes on............read a couple dozen posts.........read "how to ask a question".......pretty soon you'll start to think like a programmer. And don't forget to show some respect...............these are very smart people, they do this for free.

good luck

P.s Don't ever argue with a moderator.

Here you go John courtesy of fellow member rdrast

http://www.catb.org/~esr/faqs/smart-questions.html#intro

Carfreak2017 said:

I just started learning Plc so bare with me. The program I have to write uses two inputs, an increase and decrease, to go into and up/down counter through a timed based contact on .01 sec. The accumulated value in the counter should be placed in the output of the analog channel. Verify that the output changes with the accumulated value in the counter. Make sure that the accumulated value in the counter is never less than zero or greater than 32,767. The info I have is in the pix I uploaded. Teacher isn't much help.

Click to expand...

Let's try another aproach....

Hi, Carfreak2017,

Welcome to the Forum

We would be happy to assist you in solving this problem and to help you along the way as you learn to program and enter the wonderful world of Automation.

As a rule, forum members will coach, give you hints and nudge you in the right direction toward solving any class work items.
We will also give you an answer to any direct, "specific" questions you.

We do like to see you give it a shot first on your own, that way we have some reference as to what your thought pattern is toward the problem at hand.
This will show us where you need to correct or alter how you look at ladder logic.

Lets get you started one step at a time and we can go from there.

Please try to place just the part below into your ladder logic and lets have a look at how you think it should to be done.
(Screen shot it or take a photo with your camera and post it. I will not be able to open your .rss file as I only have the free AB software)

uses two inputs, an increase and decrease, to go into and up/down counter through a timed based contact on .01 sec.

Click to expand...

I will check back in a while to see if you have returned and posted this.
If so we can work on this together or I am sure another forum member will step in to assist you without hesitation.
We will check the work you post to see if you are hitting the mark or not and help guide you through it, an onto the next step.

BCS

Just to answer something that was brought up in an earlier post also.

RSLogix does have a help menu, it is a great resource for getting information about your individual instructions.

At the top of RSLogix you will see "Help" on the tool bar.
Press this and select instruction help.
A box with all the instructions to choose from will be on this screen.
Start simple by pressing on XIO and XIC.
Read about them and also click on the related topic list at the bottom of each of these instruction pages.

Next you know you will need an up and down counter.
I don't see one that will go up and down in the free software, so if you don't see one in you instruction set tab (timers/counters) then read up on individual counters both up (CTU) and down (CTD)

Your assignment also looks to call for a timer since it mentions a .01 time based contact.

Read up on the TIME ON DELAY (TON) instruction.

This could also be referring to using a system based tag that transitions every .01 seconds.
I was going to look that up since I don't remember if RSLogix 500 supports that or not and if they do I don't remember the system tag address.
But my VM just crashed, so I can't look it up at the moment.

I see no one asked what level you have even gotten to yet in your class.
Have they gone over any basic instructions with you yet?
Do you understand what XIC and XIO and OTE are?

Not judging or anything, just need to know where to start with getting you onto the right path.
Don't want to start at "D" if so far you have have only learned "A" & "B" so far.

Hang in there, once you pick up just a few basics.....this stuff gets real fun.

It is like playing golf, when you first start you know you have to hit the ball in the hole.....but its not as easy as it looks.
Then you play a bit and you can start to enjoy the game.
Both require you to work at them and you can get better each time you play.

BCS

I'm 82% sure I know what school you are going to just based on description of your "teacher". If I'm right, I feel sorry for you because you spent good money on a useless class, and it can be very frustrating.

Just to clear things up, you are indeed coming off as whining and complaining. However, I know full well that reading 2D text causes a lot meaning and expression to be lost when communicating with humans, so I'm going to give you the benefit of the doubt and assume that you are just frustrated and not actually trying to pi$$ people off.

Here is a link to one of best friends you can have when first starting out.

http://literature.rockwellautomation.com/idc/groups/literature/documents/rm/1747-rm001_-en-p.pdf

The help file in 500 is nice, but with this you don't have to have the software in front of you.
If you intend to ever go into a PLC related field you will need to know all the instructions in chapters 1-4 before you will be able to do much of anything. The nice thing is that you are given examples of how to use each instruction, so that will guide you along in how to address each parameter. And almost all of the instructions will carry over to Logix 5000 as well, so that will give you a jump on the next class. If a specific instruction trips you up, and you just can't sort out what it does, or how it does it, please pop in and ask. When you do ask a question please try to be as specific as you can, and if possible include a copy of the program you are working on. *zip it first, Forum rules*.

I'm just going to toss my opinion in here of some of the previous replies just to help keep the fire burning

If you choose to go down the "self taught" road, you really don't get to complain about how bad your teacher is. However, when you pay for a class you have a reasonable expectation that you will be taught something, and not left to fend for yourself. I'm relatively certain that if Ron B. simply sat his students in front of a trainer and told them to "figure it out", few people here would have ever heard of him. I'm not trying to say that ever tiny bit of information should be spoon fed, but the fact that Carfreak didn't know there even was a help file, shows that his instructor is failing to provide the bare minimum value that should be expected from a paid class.


Good luck, and holler if you need a hand.
Bubba.