Detecting loss of connection through RSLinx

[welby]

I am fairly new to Linx/OPC/and PLC's in general, but I've done ok up to this point.

I am writing an application that communicats to the plc using opc via the rslinx sdk. I am looking for the best way to monitor the state of the plc connection. I bascially need a toolbar in my app that will turn red whenever the plc/app communications is lost.

In the past, we have used a heartbeat timer to periodically listen for data from the plc, and confirm the connection with that method. Is this the only way, or is there a better way?

Thanks for the help.

Welby

 

[averytc]

I like to watch the scan toggle and set an alarm if I lose it, but that's similar to a hartbeat timer.

Charlie

 

[bernie_carlton]

Don't the OPC engine have a failure state indication?

 

[surferb]

Your heartbeat isn't a bad idea. Simple. Effective.

They might have status tags - that's up to the OPC server. I've used their troubleshooting tools within RSLinx, but I don't know if they have status tags automatically set up - I've never noticed them while browsing the PLC address structure in an OPC client.

You can also tie it to the OPC "quality code". 192 is "good data", go figure...

Don't the OPC engine have a failure state indication?

 

[Ken Roach]

RSLinx Classic has some Pre-Defined Objects that provide information on the Server itself and its connection to the controller.

In RSLinx online help, search for the keyword "predefined objects" to see all the objects.

@IsPresent is a pre-defined object corresponds with a "Red X" in an RSWho browse. It used to be that this had to be a PLC-5 controller type but I've used it successfully with an ordinary Logix connection too.


The general syntax in an OPC link is:

=RSLINX|PLCTalk!'@IsPresent'

 

[surferb]

Good to know - Thanks, Ken. Is there an online reference (from the help) that you could link in?

RSLinx Classic has some Pre-Defined Objects that provide information on the Server itself and its connection to the controller.

In RSLinx online help, search for the keyword "predefined objects" to see all the objects.

@IsPresent is a pre-defined object corresponds with a "Red X" in an RSWho browse. It used to be that this had to be a PLC-5 controller type but I've used it successfully with an ordinary Logix connection too.


The general syntax in an OPC link is:

=RSLINX|PLCTalk!'@IsPresent'

 

[welby]

Thanks for the replies, they all gave me somthing to think about.

The way I ended up going was watching the PLC clock for the seconds. If I do not receive a datachange every second, then I know I lost connection.