Novice Help/Novice Tips

Hi, first time poster just wondering if anyone has any tips for a novice of the PLC world, I've worked with them a fair bit within schooling and at work, but would love to become more advance. So any suggestions, books, exercises, practice problems to try and figure out or even just things you wish you new starting out, if you could please post them here, i'd greatly appreciate it.

Thanks in advance.

Here are my rules when hiring a programmer:

#1. When it come to ladder logic KISS!
#2 If you are programming anything that someone else will have to trouble-shoot use only ladder logic and refer to #1.
#3 HMI's should always have a logical layout and a consistent menu bar.
#4 Just because you found a fancy instruction that will reduce a hundred or even a thousand rungs doesn't make it worth using. PLC's are fast and can scan thousands of rungs in micro-seconds. Again see #1.

#5 Document document document document.
#6 If the customer will pay for it, always include an Operators and Technicians manual with plenty of screen shots.
#7 In-house test test test. Then have someone you work with test it, especially a non-programmer. You will be amazed at what they find before you go start it up.
#8 Google is you best friend for finding just about anything you may be having trouble with. I see it on this site all the time, someone posts how do I do X, and a quick Google search find it right away.
#9 This goes for any problem. Explain it to a co-worker or friend. I am amazed over the years how doing this helps me come up with an idea that solves the problem.
#10 Most importantly never take work home with you, life is to short.




And now since your from Canada I'll tell you my only Canadian joke. How did the come up with the name Canada? They put all the letters in a bag and started pulling them out and said "C a, N a, Da" Sorry it's an oldie, but then so am I. Good luck.

Thank you loads of great tips here, and nice joke !

Watch all eleven of these videos: Ron Beaufort PLC Boot Camp Preview

try this...


http://engineeronadisk.com/V2/book_PLC/engineeronadisk.html

JaxGTO said:

#1. When it come to ladder logic KISS!
#2 If you are programming anything that someone else will have to trouble-shoot use only ladder logic and refer to #1.
#4 Just because you found a fancy instruction that will reduce a hundred or even a thousand rungs doesn't make it worth using. PLC's are fast and can scan thousands of rungs in micro-seconds. Again see #1.

Click to expand...

I have to disagree... Ladder logic is great for Boolean logic, but when you start calculating it becomes unwieldy really fast.

Instead it is best to know what are Ladder Logic, FBD and ST's strengths and use them accordingly.
This isn't easy obviously, but documenting the functions (or sub routines if you're in that kind of thing) saying what it does, what each signal does and what goes where saves time for whoever has to understand the code.

A good example of this is a Valve or Motor block. Everyone will have a pretty good idea of what that will do, leaving them to look at the logic around the motor block and not needing to look inside. This is achievable by being consistent and documenting things appropriately.

Here is a great website for getting started. They have a very good simulator for Logix 500. I don't recall the exact price but it's not very much. Great way to learn a lot of ways to program.
http://thelearningpit.com/

cardosocea said:

I have to disagree... Ladder logic is great for Boolean logic, but when you start calculating it becomes unwieldy really fast.

Instead it is best to know what are Ladder Logic, FBD and ST's strengths and use them accordingly.
This isn't easy obviously, but documenting the functions (or sub routines if you're in that kind of thing) saying what it does, what each signal does and what goes where saves time for whoever has to understand the code.
.

Click to expand...

For beginner, I would say stick to Ladder, ESPECIALLY if the beginner comes from a PC Software world. Because... you have to break them out the PC programming habit first Once ladder is mastered then learn how to incorporate other programming language into it.

harryting said:

For beginner, I would say stick to Ladder, ESPECIALLY if the beginner comes from a PC Software world. Because... you have to break them out the PC programming habit first Once ladder is mastered then learn how to incorporate other programming language into it.

Click to expand...

I don't think we disagree... Give ladder to any programmer to understand Boolean conditions and that will always be preferred as it's the most straightforward way possible to understand what's wrong.

What I disagree is the way to achieve this by forcing Ladder instead of making the person see the strengths of each language. However, truth be told, that will usually land with the customer.

Document, Document, Document, Document

Annotating your code is one of the most important HABITS that you need to develop.

When describing your bits, USE VERBS.

Don't just call label it

    Flow Switch

    FS-100

------| |------

Instead, be more descriptive of the process:

     Product

  Is Detected

    FS-100

------| |------

In this way, you know that -| |- means Product IS Detected and -|/|- means Product IS NOT Detected.

When describing your rungs, describe what you INTEND to happen, not what the rung is doing.

So often, I read descriptions that read something like: "When FS-100 is made, one-shot move a 0 into Total." That's not particularly helpful, because I can see the same thing in the code.

But if it said something like: "When Product is showing up at the flow switch, this is the starting point by which we'll measure how much product we're sending. Clear the Total at the start of the process."

Now you understand WHY the components are there. You might even realize that, if the flow gets interrupted for some reason, the ONS will drop out, and fire again when restarting, giving you a low total. So you might want to come up with a better way of detecting "Start of the process". The comment may remain unchanged, but the code will change.