DH+ Problem

Have a niggling problem on DH+ network.

The network has 25 nodes connected
(6 PV500s,1 PV1400, a 3rd party SCADA system, the rest SLC504s)
Everything had been working smoothly, now when operators press a button on the PV1400 it takes anything up to 3 mins for that command to occur(button indicates action has occur).
No program changes have occured to either device for at least 6-8 months.
The PV1400 communicates with only 1 504 and the SCADA node.
We believe that it may be the DM areas of 504 concerned and the
PV1400.I don't believe that BTR and/or BTW are being used.
(Checking that tonight and will reprogram if necessary)

Have checked the obvious like moving button to another area of screen.
All other nodes seem content and are functioning correctly
At the moment, I would prefer not to segregate/disconnect network as there are 2 unmanned boilers on network and disruption to steam will occur.(Will do if all else fails)

RSLinx shows no discrepencies or faults

Have gone to AB Knowledgebase and am going to test using CRO.
Am I missing the obvious, is there any other "simple" tests that could be recommended?

Thanks in advance

Craig

Craig S said:

I don't believe that BTR and/or BTW are being used.
(Checking that tonight and will reprogram if necessary)

Click to expand...

Being DH+ you won't find any BTR/BTW's, at least not related to anything on the DH+ network.

We believe that it may be the DM areas of 504 concerned

Click to expand...

What do you mean by DM areas?



The rudimentary first thing I would do is check all terminations, looking for loose or corroded wiring, and also verify that the terminating resistors are in place and functioning.


Are you sure that the communication round trip is what is taking so long? Maybe there is logic in the PLC that is delaying your indication that the action took place...

Thanks for the reply,

DM = Data Memory

Have checked all connections, tested Ok.

The PV button is "Momentary" and colour of button changes when internal bit is on. So PLC code is Ok

Used RSLinx "Driver Diagnostics" and found that 4 PVs had a great number of "Total Bad Packets Recieved" ranging from 120-700.
While PV1400 is minimal 1-2 at most.

Until fault is found I believe that network has a definite problem and is being "seen" or "more noticable" at this PV than others.

Have taken onboard your suggestions

Thanks again

Craig S

Supply a little more details.

Is the one button the only problem?
How is the button addressed?
What response is taking 2-3 min, is it a PLC, real world,output or a panel view color change?
Is the panelview only using DH+ communications?
Is the button in question DH+ or RI/O?(I don't understand the BTR/BTW statement)

Roger

A few more questions; at the risk of repeating rogerhollingsworth

Craig S said:

DM = Data Memory

Click to expand...

What made you think it's memory (of the SLC) related?

The PV button is "Momentary" and colour of button changes when internal bit is on. So PLC code is Ok

Click to expand...

By this, do you mean that the "write tag" is addressing the same bit as the "indicator tag"?

And, is this where the delay occurs?

93lt1 and rogerhollingsworth
Thanks for the reply.

Apologies for not responding sooner, saw machine run first hand tonight since problem,ended up looking through mountains of code and found problem was in fact SCADA system.

Have rectifed fault.

Craig