LOGIX 5000 multiple output question

Hello,

I'm trying to implement parts of a program sent to me from tech support, they are currently out on calls toady and was wondering if in the logic attached as a picture, what happens.

Basically does the timer time out then execute the "FLL' command or do they both happen at the same time as long as rung is true?

Thanks

The file command is active as long as the rung is true. People get a little confused when they see serial rungs like that one. The timer is activated first and then the file command, but they are both controlled by the preceeding logic.
I personally don't like to see logic like that in my programs, and I don't write code like that. It shows signs of being lazy. Unless a branch start command puts you over the available program memory.

wnkook

In ControlLogix programs can be written vertically as well as horizontally. Quite often this makes it more readable or efficient but the same rules apply. If all of the conditions leading up to an output are true then the output is on, this is true regardless if the condition is an input contact or an output coil.

The others have answered your question but I wanted to add a point.

For the rung to operate as you asked in your original question (timer times out and then executes the FLL) their would need to be an XIC instruction using the timer done bit in between the TON and the FLL.

This method of programming I personally do not regard as lazy as it is more efficient with memory, scans faster, and in most cases is easier to read. I think it is all what you are used to though.

Good Luck!

OG

Operaghost, and Sekeeley,

The reason use old-timers do not like to see two outputs in series is that PLC Ladder Logic was originally (and still is to some extent) based on Relay Ladder Logic. And in relay logic, two relay coils in series is a definite wiring error. Each coil receives only 1/2 half the voltage needed to energize it. Does that make logical sense? If it confuses the mind, then why do it? With the latest breed of PLC's, I haven't seen many programs that have a problem with running out of memory or having a too-long scan time.

There oughtta be a few rules a fellow can depend on!

This old-timer got into the habit over 20 years ago on the PLC3. You may not need to worry about memory so much any more, but it's a lot easier to view one line of series outputs than scrolling up & down through multiple parallel branches.

That's probably the best selling point Gerry. It really cuts down on searching and cross referencing since it's all right there on one rung. You are right about memory and scan time not (usually) being a big issue. I think that whatever is easiest to read and what the people troubleshooting it are used to is always the best solution.

But then again, remember when we thought "Gee, why would anyone ever need 640K of RAM or a 10MB Hard drive?" I could use older examples but that's a whole different thread now isn't it!

One thing I actually liked about these older limitations was it made you be more efficient with your program. I came across a ControlLogix program at a customer several months ago that was just bleeding memory. It was horribly inefficient and the programmer basically said "Ah, we got 8MB, we'll never use it all". I wanna talk with him again in a year or so and see how it looks then.

Ok, off-topic I'm sorry.

OG