On-Line, Real-Time, Programming...

Terry Woods

Member
Join Date
Apr 2002
Posts
3,170
Do you use it?

Do you need it?

Do you want it?

No... I'm not just starting another pi$$ing-match. I'm just being curious.
 
1) I use it. (It is often convenient to not have to stop a machine, and it is a time saver.)

2) I don't need it. (I get by fine on PLCs that don't have it, especially if there is a run-time download function available.)

3) I want it. (See 1 above)
 
Do you mean the ability to make changes online without putting the processor in stop mode or affecting the process in any way? If so, then I use it, I need it, and I want it.
 
Yes indeed S7...

I mean ON-LINE, while the process is running, without stopping the processor.

That is, updating, on-line, on-the-fly, while the "stuff" is flying through the process!
 
While I could get by without it, it is just so convenient that it has become a necessity.
Just like PLCs, you can automate your machines without them, but they are just so convenient that they also have become a necessity.
 
I find it extremly handy during debugging something new and I also use it alot to trouble shoot.


When I am trying to find a problem I will build traps so I can se what is going wrong.
 
Doug...

The way I see it... I can update the process, VERY, VERY, CAREFULLY while the process is running!

I find this to be especially important when you have a process that runs 24/7 for long stretches!

Having that ability allows me to fix problems, as they occur, without stopping the process. That assumes, of course, that the problem is not a process-stopper.

I'm not just talking about simply changing timer, or counter, values. I'm talking about changing CODE, on-the-fly!
 
I use it all of the time and would be lost without it. I even use it quite a bit when developing a new project. I have a few SLC's and PLC's laying around that I do testing on. Sometimes when a customer calls and he has this and that problem, I simply load his program in one of my test processors and usually can solve the problem in a short time.
 
Some of mine have the ability...I wish they all did, it’s a pain if not, but I still get by
 
Just out of curiousity- which processors don't allow online edits? I grew up with S5 and S7 which have always supported it, and was suprised to interface with a SLC500 and find that it didn't support it. Are there others?
 
Micro Logix 1000 (AB bricks)

Edit: You have to stop the processor and down load every time...its a pain
 
I work on quite a few machines that don't shut down. While you can get by without it is much more cost efficient not to shut down a huge machine. I also build a lot of one of a kind machines where trouble shooting is easier with online edits. Given that the online editing is so available I wouldn't bya PLC without it unless the customer spec'd it.
 
Definately need it, use it on every job I commission, don't want it as I have it now.

Nothing like being caught out with something you notice in a program that requires tweaking and you have a generator in the middle, or towards the end, of a 24 hour heat run on full load. If you stop the machine you start the heat run again and have to pay for the fuel.

I will not buy a PLC and/or software that does not have the ability to do online changes very easily and quickly. Just absolutely refuse no matter how cheap they are.
 
YES, YES, and YES.

This has got to be one of the most important considerations when purchasing any PLC.

I once did a small project with an AB ML1000. I knew that it didn't support online changes when I bought it but needed something cheap. What a pain in the butt.

However, if one was to carbon copy 1000 projects where the program would never change all of a sudden the cost of the processor out weighs the convenience

I personally prefer the AB model of online changes as opposed to the Siemens style of downloading a block without stopping the process but that's probably just me. I cut my teeth on AB and honestly don't think I will ever like anything else better.

With AB processors (I can't speak for CLX because I haven't used it enough) you can't change hardware configs or resize data tables without stopping the processor. Not being able to change hardware config isn't a big deal because if you need to change the config you are already stopped because you are changing some piece of hardware. Not being able to resize data tables is a pita (some times I just need ONE more floating point register!!)

Anyway I guess it becomes a mute point with CLX because there aren't any data tables??
 
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