controllogix relay output won't energize

CABLETRAY

Member
Join Date
May 2010
Location
Ontario
Posts
4
Hey guys,

I have a 1756 OW16I series A card. I am trying to energize bit 15 to pull in a coil on a motor contactor. Our panel is configured in such a way that the output side of the card is fused and the L1-0 to L1-15 side is jumpered at 115v AC.

In this particular case, i chose Output 15. I jumpered 115v to L1-15 and programmed Output 15 to come on when the start button was pressed. It did not work. I tried forcing on the output 15 and it works. I tried bypassing the button, and it did not work. I see the rung is true, but the output does not come on. The only way i am able to make it energize is by forcing it on. What am i missing here.

This type of relay output card has worked for me in the past. I will try another bit, or card, but if anyone has a suggestion i would appreciate your thoughts...

Thanks
 
welcome to the forum ...

are you sure that your ladder is being "scanned" by the processor? ...

suggestion: Cut-and-Paste the rung to an "old" part of your program and see if it works there ... or ... right-click the "output" (the OTE instruction) and see if you can "Toggle" it on and off ... (this is NOT the same thing as a Force) ... if you can Toggle the bit on and off that's another indication that your rung is NOT being scanned/executed by the processor ...

if that's your problem, then you might need to read up on the JSR instruction ... or post your ACD project file and we'll take a look at it for you ...
 
Last edited:
when I worked at a tech school (another lifetime ago) my very first "teaching project" was to set up a brand new PLC training program for the apprentices from the local paper mill ... Mr. Holcombe was the engineer who told me EXACTLY which skills he wanted me to cover ā€“ and EXACTLY which topics he wanted me to leave out ... there were two skills at the top of the list as "absolutely MUST be mastered" ...
(1) the first was how to download a program from a floppy disk into a replacement PLC-5 processor ... (he was tired of being dragged out of bed in the wee hours of the morning to do a ten-minute job) ...

(2) the second skill was how to recognize an UN-SCANNED subroutine ...

when his technicians ran into precisely the problem that we're discussing in this thread, they would think:

"Well, the XIC is turning green on the screen ā€“ so the INPUT is OK. And since we can force the device in the field on and off, then the OUTPUT must be OK. That only leaves the processor ā€“ so let's swap it out with a spare." ...

according to Mr. Holcombe, that common mistake was costing the mill at LEAST $4,000.00 a pop - even though there was NOTHING wrong with the processor ... the old processor had to be sent off to be officially tested and "re-commissioned" before it could be reinstalled again ā€“ and the official testing wasn't cheap ...

so here I am about 20 years later - and NONE of Mr. Holcombe's basic lessons have changed ...
 
I don't know if this is something that can be 'taught' per se. The only way to really learn it is to experience it, losing time and/or money as a consequence. Mom says "Don't touch the stove, it's hot". That doesn't really sink in until the day you accidentally touch it and get burned... "Okay, NOW I understand what Mom was talking about!"... ;)

šŸ»

-Eric

P.S. I learned about hot stoves and unscanned subroutines by the burning method. I don't plan on getting burned ever again!... :ROFLMAO:
 
I don't know if this is something that can be 'taught' per se.

oh, yes indeed, Eric, it CAN be taught ... here's a quick (somewhat condensed) run-down on how this particular lesson goes in the Boot Camp classes ...

by Tuesday afternoon all of the students have already wired up two or three inputs and two or three outputs to their PLC workstations ... I make everyone put a SYMBOL (nickname) of "GREEN_BUTTON" on one of those inputs ā€“ and the symbol of "COIL" on the contactor coil that they've wired up ...

the next exercise is to add a new ladder file (#4) to their programs ... they're told to put one rung into that new ladder file ā€“ so that the GREEN_BUTTON controls the COIL ... dirt simple ...

the problem is that on each student workstation, none of the new rungs work ... so now we go around the room ā€“ station by station - and talk through a troubleshooting exercise ...

we all bear witness as Student Sam presses his GREEN_BUTTON ... the XIC on his screen highlights in green ... he releases the GREEN_BUTTON ... the XIC loses its "green on the screen" indication ...

OK ... discussion time: WHAT do we know about the system at this point? ... "It ain't working," is the usual reply ...

WHAT "ain't working" boys and girls?" ... let's break the system down into components ... at this point we KNOW that the GREEN_BUTTON is wired correctly ... we KNOW that the GREEN_BUTTON's contacts are good ... we KNOW that the PLC's input circuit is good ... we KNOW that the address that Student Sam has used for the GREEN_BUTTON is the correct address ... so, in other words, we KNOW that at least the left end of the rung IS indeed "working" ...

now for the right end of the rung ...

the OTE for the COIL does NOT turn green on the screen to match the indication from the GREEN_BUTTON ... try to "toggle the bit" and see what happens ... clunk! ... the contactor energizes ... now "toggle the bit" again ... un-clunk! ... the contactor de-energizes ... so ā€“ what does THAT tell us? ...

at this point we KNOW that the COIL is wired correctly ... we know that the COIL is good ... we KNOW that the PLC's output circuit is good ... we KNOW that the address that Student Sam has used for the COIL is the correct address ... so, in other words, we KNOW that the right end of the rung IS indeed "working" ...

so ... the LEFT end of the rung is OK ... and the RIGHT end of the rung is OK ... and there's NOTHING ELSE on the rung ... so why isn't the whole thing "working"? ...

back to the idea that the "thingies" that we've programmed on the rung are called "instructions" ā€“ and they're called "instructions" for a good reason ... they are intended to "instruct" the PLC processor WHAT TO DO as he executes the rung ...

the point is that the PLC is neither "reading" ā€“ nor "obeying" these particular instructions ...

now I go to the whiteboard and sketch ladder file #2 ā€“ which IS being scanned by default ... and we KNOW that to be a fact because each student has been programming example rungs into ladder file #2 since bright and early Monday morning ... and THOSE rungs have all been working as expected ...

then I sketch the new ladder file #4 that we've just created ā€“ and I show the XIC for the GREEN_BUTTON ā€“ and the OTE for the contactor COIL ...

then (using the red marker for emphasis) I go to the bottom of ladder file #2 and sketch in a new rung with a JSR instruction to call ladder file #4 ... "everybody go put this new rung into your program" ...

within 60 seconds or so the lab is merrily clunk ā€“ clunk ā€“ clunking away ... well, all except for Little Johnnie's station ... he's the student who put his JSR right at the end of ladder file #4 ...

so now let's all go help Johnnie figure out why his station still won't work ... more fun and games ...

this teaching approach WORKS (with a full 100% money-back guarantee) ... the key to its success is that the instructor isn't just "talking to" the students ā€“ or showing them PowerPoints ā€“ or overhead transparencies ... instead the students are presented with a VALID ā€“ REAL-WORLD problem ā€“ and they're forced to ANALYZE the problem step-by-step ... then once they've recognized the elements of the problem (and NOT UNTIL then) are they finally coached through finding the solution to the problem ...

from Eric Nelson:

The only way to really learn it is to experience it,

BINGO! ... that's precisely my point ... they've just experienced it ... we've just made FULL-BODY CONTACT with the course material ...

and then the "REAL FUN" starts ... this is where the "Evil Instructor" enters the picture and now tries to confuse the students by spouting off nonsense such as:

(1) but yes, the rung WAS being executed ā€“ because the "power-rails" were green ...

(2) but yes, the rung WAS being executed ā€“ because why else would the XIC turn green when we pressed the button? ...

(3) but yes, the rung WAS being executed ā€“ because otherwise the OTE would not have been able to turn the COIL in the field off and on when we manually toggled the bit ...

and so on and so on ... specifically, the instructor is now (in a convincing tone of voice) presenting exactly the same mistakes and misconceptions that have been passed around the job site for years ... and now (on Tuesday afternoon of a five-day class) even students with less than two days of PLC experience are quite capable of shooting down each one of those misconceived ideas and erroneous "rules of thumb" ā€“ and showing the instructor what's wrong with each one of his seemingly plausible ā€“ but nonetheless incorrect - statements ...

so a word of advice to anyone trying to "teach" this type of stuff to your co-workers, etc. ... quit trying to TELL them how things are "supposed to work" ā€“ and instead, introduce them to what causes things NOT to work ... you'll be amazed at how fast people will be able to learn ā€“ and how much they'll enjoy doing it ...
 
Last edited:
Same Problem, no results yet

Hello, I was reading through this post and I see that I have just about the same problem. I've tried everything that was suggested by everyone which was pretty good advice but I think I might have a little bit of a different problem. When I try to energize my coil it will not show that it's latched or energized and the logic.. the channel status indicator blinks intermittently but will not energize. Any and all advice will be greatly appreciated. Thanks folks. Okay we'll try that how do I send it
 
Hello, I was reading through this post and I see that I have just about the same problem. I've tried everything that was suggested by everyone which was pretty good advice but I think I might have a little bit of a different problem. When I try to energize my coil it will not show that it's latched or energized and the logic.. the channel status indicator blinks intermittently but will not energize. Any and all advice will be greatly appreciated. Thanks folks. Okay we'll try that how do I send it

Everything you have said suggests that you have your output coil addressed more than once in your application.

If that is the case, the rung that is turning your output "on", is being defeated by another rung that turns your output "off" again.

The cross-reference tool is a great way to find where the output is being written to more than once in your application.

If your application is Logix5000 (ControlLogix, CompactLogix, FlexLogix, DriveLogix, GuardLogix, etc.), then use the "Destructive" column of the cross-reference window to show you where the output is being written to. Driving a physical output more than once is generally considered to be "bad practice".
 
Last edited:
Problem Solved!

Controllogix using RSLogix 5000. First of all I had to post to say thanks for the for the much appreciated help(Thanks daba!)
The first thing I did when I got to work this morning was to open up my application and look for the destructive bits. As it turns out the tech who worked on the application before me used FBD to program with which was why I completely missed the programmed output. Although I'm not too familiar with programming using FBD I managed to program what I needed and everything seems to be working fine. It's good to know that when someone reaches their programming knowledge limit, you have a website like this that you can turn to for help. So hats off to everyone on this website who contributes. But this time I have to direct my props to 'daba'. Thanks for the super advice mate! Cheers!
 
Controllogix using RSLogix 5000. First of all I had to post to say thanks for the for the much appreciated help(Thanks daba!)

No problem....

You might also like to know that you can "double-click" the column headers in the Cross-Reference display to Sort by that column. If you do this on the "Destructive" column, (you may need to do it twice), you can bring all the "Y"s to the top of the list. It's a great time-saver if there's a lot of cross-references for a tag.

"Destructive" just means that the instruction can write to, and therefore possibly change the value of, that particular tag.

Most-times (of course there are exceptions), a BOOL tag will only have one "Y", and it'll be right there, top of the list.
 
Thanks daba, I'll soak the extra tips in to memory. I was just about at my wits end, so believe me when I say how much I appreciate your knowledge and your time! Thanks for making my day! Cheers!
 

Similar Topics

Hi everyone i have a customer, who wants to show an alarm on the machine, if the I/O forces are enabled and set, on at ControlLogix L81E with...
Replies
3
Views
138
Does anyone know of a way to detect if someone is online with the controller in ControlLogix (from logic) I'm thinking that maybe there is a CIP...
Replies
7
Views
292
I've never paid attention to this, is this normal?
Replies
13
Views
418
Hi. I need suggestions. I want accumulate operating hours from a simple XIC condition, so I'm thinking a RTO with a 60000 or 3 600 000 preset, 1...
Replies
7
Views
225
Hello, So i managed to read the string coming from control logix and put a string display in PanelView 800. Now I am struggling to do the other...
Replies
1
Views
115
Back
Top Bottom