adccommunitymod (AutomationDirect) asked a question.
DL05 Heartbeat
Created Date: May 30,2007
Created By: Chris_H
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I have limited experience in PLC's. I need to create a "heartbeat " value in DL05 holding register 1 that changes every 100 seconds in order that a PC that communicates with the PLC can monitor that the PLC is running and generate an error message if the heartbeat stops changing. Can anyone give me an example of how to do this ?? regards Chris_H
Created Date: May 30,2007
Created by: Tech Guy
You could just monitor the SP5 contact or use it to trigger a counter. It is a 100ms on, 100ms off pulse generated by the PLC CPU.
Created Date: May 30,2007
Created by: chris.zeman
The easiest solution (I can think of) would be this:
1. Read the heartbeat bit from the PLC.
2. If the bit is high, reset it.
3. Set up your ladder logic to set the bit every time it is reset.
If you ever read the bit's state as being low, you know there's a problem.
Created Date: May 30,2007
Created by: chris.zeman
Hey! That works too! http://forum1.automationdirect.com/board/smile.gif
I was typing my message, walked away, and finished when I returned. hehehehe
Created Date: May 30,2007
Created by: franji1
Don't forget you'll probably want to handle a comm error as a "dead " 05. However, you must also consider the fact that the 05 may be fine, but just the comm link failed (e.g. someone pulled the cable).
TRULY Dead 05 (e.g. power down) results in a communication/timeout error to the PC.
However, a comm/timeout error from the polling machine does NOT NECESSARILY imply a TRULY dead 05, just (minimally) a dead comm link, and (probably) a truly dead 05, but not necessarily.
If this is a mission critical application, you must consider this possibility as part of the designed response of your PC behavior.
http://forum1.automationdirect.com/board/eek.gif
Created Date: May 31,2007
Created by: AZRoger
Does the DL05 have the Watch Dog Timer, SP51? If so, you could just monitor that. Is there something special about "holding register 1 "?
Created Date: June 01,2007
Created by: Chris_H
Thanks All,
I'll have a play around and try these suggestions.
Chris H
Created Date: May 30,2007
Created by: Chris_H
I have limited experience in PLC's.
I need to create a "heartbeat " value in DL05 holding register 1 that changes every 100 seconds in order that a PC that communicates with the PLC can monitor that the PLC is running and generate an error message if the heartbeat stops changing.
Can anyone give me an example of how to do this ??
regards
Chris_H