Micrologix 1200

[mattman463]

Have a bad output on a Micrologix 1200. Moved wire over to an available output, changed program to associate with new output. downloaded program change to processor. once back in run mode, new output does not work. light never comes on for output and no power ever comes out of it, even though all conditions are met for it to turn on....changed to another available output and same result. any ideas?

 

[glenncovington]

Check the output terminal block. Outputs numbers are in groups and have a supply power connection. Be sure there is a supply for the new output number.

 

[mattman463]

It is wired up correctly. If I force the output on, I get a light and power, but in run mode I don't get it

 

[parky]

Also, do a cross refference of the program to check it's not being written to, although it's not originally wired, it could be that the program is a generic program but some functions are not enabled, had this once, we had a bad output, there appeared to be a couple of spares, however, turned out these were programmed in the PLC with a false contact in the logic to disable them, so I was turning on the output but later on in the program it was turning it off again, as the input/output update is done usually beginning or end of scan it never drove the output.

 

[mattman463]

That was a thought of mine too, but I don't see anywhere that it is being disabled and or turned off...

 

[parky]

Well, there is a possibility that there may be a mask but unlikely, i.e. load a word with a bit pattern then AND it if that is possible in MLX. Another could be indirect address but again unlikely i.e. it is being pointed to indirectly again if that is possible in MLX, otherwise like has been posted, is there power on the common terminal for that output, although many PLC's do not use the power to the output to drive the LED as it may be in the circuitry before the opto isolator or relay output.

 

[Mickey]

Did the "Bad output ever work"

Have you looked at the logic online to see if the output is on?

Is the logic for this output in a subroutine? (If so, is subroutine being called?)

Can you post the program, it's .rss file (zip it first ) ?

 

[drbitboy]

Have a bad output on a Micrologix 1200. Moved wire over to an available output, changed program to associate with new output. downloaded program change to processor. once back in run mode, new output does not work. light never comes on for output and no power ever comes out of it, even though all conditions are met for it to turn on....changed to another available output and same result. any ideas?

I am not quite clear about something: without an active force, are you using the online mode and seeing the output memory bit in the PLC program, e.g. O:0.0/0, with a value of 1, and simultaneously you are not seeing any voltage at the physical output itself?

The point I am making is that the during the program scan, the program may write a value to a bit in PLC-internal memory, and that bit is a proxy for, but it is not, the physical output itself.

So is the question being asked "Why is the value 1, which I see in the PLC-internal memory at address O:0.0/0 using RSLogix 500 in online mode, not being transferred to a physical electrical voltage or current signal on the terminals?"

Or is the question "Why is the value 0, which I see in the PLC-internal memory at address O:0.0/0 using RSLogix 500 in online mode, when I believe all the conditions in the ladder program should cause the logic to assign that value to 1?.

 

[I_Automation]

Is your output control in Ladder 2, or 3 to 16? Or up to 99?


If a subroutine is not being called the IO will show their state when monitoring online, but not be scanning that rung. I have also come across subroutines that are called, but before a certain rung there was a conditional RET that ended that subroutine.


Also look at data file 0 for the outputs and click usage, see if along with the X's for used binary addresses there is a W for O:0 word.



When I first read your headline my first thought was of a ML that I ended up replacing for a customer. O:0/5 output died, then a week later 0/4, followed by 0/3 at which point there were no spare outputs to move to. That one was the Common trace on the circuit board going to that bank of 6 outputs failing.