Driving a Generic Scrolling Text Display

corkers

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Join Date
Jan 2004
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Melbourne
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Happy Easter all.

Relates to AB PLC5/80E

I am having a mental black with the following request... I have been asked to set up a generic scrolling text display to display a series of faults eg "C518 EStop Fault", "C518 Mech OL Fault" so on and so forth.

The display is a dumb ascii device which requires a string of text to be sent to it via the PLC5s serial port (AWT command).

I have got the logic to display the fault developed (a series of ACN and AWTs).

My problem is that I have a mental black on how to display multiple faults in a sequence. My code has each individual bit trigger a MOV that move the fault text to ST99:0 which is the source for the AWT command. I am thinking that I can use a TON which is activated by the DN bit of the AWT command but I just can't get my head around the logic.

Any help would be appreciated. I know the method i am employing is not the most elegant however I need to set this up so maintenance can go in and make simple changes. Once the core faults are setup I will be msg fault data from about 20 PLC to this PLC to display additional faults.

Andrew
 
I'm not clear on what you're looking for but, then again maybe this'll break the logjam -

Since messages are coming from other PLC's, could you assign each message a place in a string file? That is, message #1 (from wherever) goes in ST100:0 and so on. Now set up some logic to sequentially check the lengths on each element in ST100. If the length is zero no message is required. If the length is greater than zero a fault message needs to be displayed so the corresponding string element will be copied to ST99:0 for transmission to the display and a timer started. When the timer is done the length scanning logic resumes looking for the next nonzero string length. When the fault is cleared you will have to reset the string length for the related message number so the length scanner will skip over it.
 
similar application

I found out that string files in a plc start consuming memory very quickly. Also, the plc has trouble with some character strings needed by the sign for formatting.

This is why I store my messages in a print only object in the PanelView. I use the least significant bit setting to print the most significant alarm. Once that alarm is cleared, the next alarm is displayed, and so on, effectively stepping the operator through each step in the alarm clearing/troubleshooting process.

All is needed in the plc is to put your alarms in order from most significant to least significant (1 to n).

You can also then use a message display object on one of your panel view screens to mimick the signs. Can be great for troubleshooting when your signs aren't working. Or just convenient for the operator standing at the panelview to see.

Example of alarm order:

1. Cable Safety Tripped Conveyor 201[instructs operator to reset cable safety].
2. Motor Starter Fault Conveyor 201
3. Press Reset Button Conveyor 201

4. Cable Safety Tripped Conveyor 202.
.
..
...
etc.

Then for the last alarm I use a solid underscore to let you know that the sign is working yet no alarms

[conveyor 201 is upstream of this conveyor and has to start before this conveyor. That is why 201 has a higher priority]

Oh, and you connect the sign cable to the panelview printer port.

Hope this helps
 
I agree this is a clumsy way of achieving what is required the persons in charge of the $$$$, are to tight to cough up for a HMI or even an inview solution. If nothing else it makes me think...

Just to clarify I have no problems displaying the messages although the processor memory util is creeping up alarmingly quickly (I know its preferable to not let it get past 75-85%). There is some existing logic that uses a FBC and outputs to a 4 digit BCD display. The existing solution piggybacks this and works quite well. However it is differcult to add new faults especially those from other processors on DH+.

I was thinking of using a sequenced output command but it seems a little complex if i have to check the length for each new message.

To simplify my problem disregard the display and think of it as purely a series of bits that relate to an individual fault and when the bit goes high copy a word to a buffer that is scrolled through periodically. ie

Most simply
If B3:0/1 PLCBATLOW goes high then copy/mov ST100:0 to ST99:0

More complex
If B3:0/1 PLCBATLOW goes high then copy/mov ST100:0 to ST99:0
display for 2 sec
And If B3:0/2 PLCNOTRUN goes high then copy/mov ST100:1 to ST99:0
display for 2 sec
If B3:0/1 PLCBATLOW still high then copy/mov ST100:0 to ST99:0
display for 2 sec
And If B3:0/2 PLCNOTRUN still high then copy/mov ST100:1 to ST99:0
and so on and so forth

hope this makes it clearer?!?!?!

Andrew
 
I battled with something similar a while back. Have a look at THIS thread where a few different ideas were discussed.

The indirect addressing scheme worked like a charm in my application!... (y)

beerchug

-Eric
 

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