Logging Alarms in RSLogix5000

Hi All,

I'm trying to create a log of alarm instances over a period of time so I can see which alarms trigger the most.

I have an array critical_alarms[20] of type DINT. Say alarm critical_alarms[5].28 triggers I want to add a 1 to its tally. I want to store this tally in another array.

Does anyone know the best way to implement this or maybe another way to go about it?

I'm currently using the FBC instruction but not sure if this is the best way to go. Has anyone out there implement an alarm log before?

You could use ladder. Anytime your alarm comes in use a ons (oneshot) and execute an add instruction of 1 to another DINT that stores the tally.

I'm confused by your example.
Why are you addressing critical_alarms[5].28 at the bit level? Are you saying every bit of every array element can be a digital alarm? Are you trying to keep track of 20 alarms, or 20*32bits = 640 alarms?

elmatador said:

You could use ladder. Anytime your alarm comes in use a ons (oneshot) and execute an add instruction of 1 to another DINT that stores the tally.

Click to expand...

I've thought of this but it would mean 640 rungs as there are 640 alarms.

DamianInRochester said:

I'm confused by your example.
Why are you addressing critical_alarms[5].28 at the bit level? Are you saying every bit of every array element can be a digital alarm? Are you trying to keep track of 20 alarms, or 20*32bits = 640 alarms?

Click to expand...

Yes, 640 different alarms.

chrisk_81 said:

I've thought of this but it would mean 640 rungs as there are 640 alarms.

Click to expand...

WOW! Yea thats gonna be pain. Why don't you write it out in structured text. You can easily write it in excel or notepad. It will be easy to copy paste.

elmatador said:

WOW! Yea thats gonna be pain. Why don't you write it out in structured text. You can easily write it in excel or notepad. It will be easy to copy paste.

Click to expand...

Does rslogix 5000 allow structured text?

RSLogix5000 supports Structured Text, Sequential Function Chart, and Function Block Diagram on the professional versions of the software.

Are you using Control Logix or Compact Logix?

There is no reason you can't set up another array of 640 elements (ie DINTs) and then just reference the elements indirectly.

I don't think you will want to check all 640 of your triggers every scan. Maybe you will, I don't know.

I would make another array of 640 dints to serve as the trigger count
I would make another array of 20 dints to serve as a trigger buffer.
I would create another subroutine to check for alarm trigger changes.

To start out with, you would copy the whole alarm trigger array into the buffer array.

After that, you can do a loop to check for a change in value.
If you detect a change in value (ie buffered value does not equal current value) do a bit compare to see if a new alarm bit is high. Whichever bit is high, increment the associated register in your 640 element array by one. Write the bit compare such that it is utlizing indirect addressing.

Now just cycle through until you have accounted for all 20 dints.

This does sound like a good use for a structured text approach, but a ladder implemenation would not be that bad. The amount of code will be minimal as long as you use a looping structure and indirect/indexed addressing.

I'm using control logix I'll have to check if I'm using the professional version.

I do know some structured text but how would you suggest I code the bit comparison?

you can use ladder

use a for loop. reference your array with an index for example array[x].y

you will need to do nested loops, one for the dint, and one for the bit level.