Sorting Data Arrays in CLX

[ElectronGuru 82]

I have a customer who wants to put counters on 35 alarms, and make the 5 top-most occurring alarms available for display on an HMI. I've put a branch rung under each alarm condition with a counter and move instruction. The MOV moves the accumulators' values to designated, corresponding spots in a newly created array of 35 DINTS. The problem is in sorting the data from lowest highest. I believe the SRT instruction sorts data within the array, but not the array tags themselves. This would lead to the wrong data being placed on each alarm accumulator tag in the array. Writing compare instructions or expressions that analyze 35 pieces of data against each other, either in FactoryTalk or ControlLogix, seems impractical, if not impossible. 

We're using 1769-L30ER controllers and PanelView 6 & 7 HMIs.

Any ideas? Please tell me there's a simple instruction or two I don't know about that will accomplish this.

Edited 14 Apr 2020 by ElectronGuru

[pcmccartney1 141]

Wow! The SRT is pretty much useless.

Wondering if the way to attack it is outside the PLC.  Say using an excel spreadsheet that does the sorting to another array tag that is read back into the PLC and therefore the HMI?

[BobLfoot 302]

I'm basing my thoughts on you having an array of 35 DINTS {ALARM_COUNT[36]} and an array of 35 Alarm  Message Strings {ALARM_MESSAGE[36]}.

You'd need 5 passes through the DINT Array looking for the Maximum Value.  

The loop or subroutine acts like this.

Place the Value 0 into Pointer_to_Alarm DINT and Value of 0 into Maximum_Value DINT.

Loop through ALARM_COUNT[1] to ALARM_COUNT[35] .

If the ALARM_COUNT[#] value is bigger than Maximum_Value update Maximum_Value and Location into Pointer_to_Alarm.

At end of loop - Zero Out the value in ALARM_COUNT[Pointer_to_Alarm] and move Pointer_to_Alarm to Top_Alarm_1.

Repeat the loop and load Top_Alarm_2

Once you've loaded Top_Alarm_3, 4 & 5 you can use those pointers to load the messages that the PV will display.

Quite doable, but you'll learn pointers and in directs tom make it work.

 

[ElectronGuru 82]

Pcmaccartney1, I had thought about this. I have exported tag sets and they slide easily into most spreadsheet programs. We'd need another, external processor (like a cheap laptop) on each machine for the sole purpose of handing the conversions, OR have to write the data arrays (probably via MSG instructions) to a server for multiple machines. In the first scenario it's just not practical or financial feasible. In the second, we'd likely eat up too much band width on the network to make it worth the while. 

BobLfoot, I appreciate you taking the time to lay that out. I'll start working on banging out some code.

Thanks, guys!

[destination unknown 3]

Another option is to have an array of UDT with two elements:

AlarmCount & AlarmID

Then do a bubble sort on the AlarmCount (and move AlarmID at the same time when sorting)

[ElectronGuru 82]

destination unknown, I'm not sure how I'd code a bubble sort in ladder logic. 

[destination unknown 3]

In Ladder you could use "For" like this:

Main -> For i -> For J -> Sort Logic 

 

Main

i_Routine

 

J_Routine

 

Edited 15 Apr 2020 by destination unknown

[destination unknown 3]

Or in ST

[BobLfoot 302]

Destination Unknown - 30+ years and I never gave coding a bubble sort in ladder much thought, but you've nailed it beautifully.

[ElectronGuru 82]

destination unknown, I hate to ask but could you please post your tags and UDTs? The code itself makes sense to me but I'm fighting with the array subscripts, and think maybe I'm missing something simple but critical in the one of my temp arrays or UDTs.

[ElectronGuru 82]

destination unknown, never mind, I got it! This is crazy brilliant and I appreciate the help. It would never have occurred to me to try to bubble up data in ladder. Truly appreciate the insight.