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Communication open and after some time "Error cannot communicate with the PLC with the specified unit ID""


vince1004

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Hi everyone,

I am using SD card explorer in order to retrieve some files from the device Advantage Pro EL Lyophilizer from SP Scientific, to do so I am connecting to the device via LAN.

TCP settings, PLC name, port number are all correct and I am able to check the connection.

I use Unit ID 0 (direct)

But after a certain time the "listing of files" stop and the following error message « Cannot communicate with the specified UnitID  » is displaying. After this happen, it is impossible to communicate anymore with the device I have to unplug the ethernet cable and plug it again to be able to communicate with it.

The same with Remote access, I can communicate with it for sometime, but after about 1-2 minutes of using it the same error message is displaying.

Do you have any idea how to solve this problem?

Thank you

 

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  • 2 years later...

Hi,

I am having the same problem. 
I connect to the PLC and start downloading data, but within 5-10 minutes I receive the error message:

 « Cannot communicate with the specified UnitID  »

Using a V350-J-TA24 PLC and a VPN connection from UniCloud.

To reconnect I have to disconnect the VPN from UniCloud and connect again.  And then the port will change from 20256 to 20257 - or the other way around.
The file I need to get will take around 30 minutes to download this way, but it is impossible, when I get disconnected every 10th minute.

Is it possible to increase download speeds?
Is is possible to keep a stable connection?  

Any help would be much appreciated.


Jacob Bauer

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  • MVP 2021

This might need creator input as it involves UniCloud, but as well as stuff already mentioned here....

1).  Do you have SB168 set on during powerup on the plc?

2).  In Remote access do you have the Configuration/Communication-Auto-Reconnect ticked?

3).  Have you tried longer timeouts?

4).  During the disconnect do you see anything being "explained" in the lower left window area, that might help pin the cause?  This might be best found by setting up a screen capture video, rather than twiddling your thumbs waiting...waiting..waiting.

cheers, Aus

 

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  • 2 weeks later...

Thanks for answering so fast Ausman, sorry that my reply has been delayed till now.
All in all my experience with SD-cards haven't been to good. I just don't find it stable/reliable. I have a setup with an internet connected router, a plc and a lot of data being stored from sensors. Is it possible to send the data directly to a server instead? The UniCloud solutions becomes a bit expensive, if you have many or frequent data points. 

1) Not sure.

2) I do not see the Auto-recconnect tick, that you are talking about.

3) These are the connection settings - how long timeouts would you recommed?

image.png.da3e0dda573893b7f885d1e449088158.png

Timeout was set to one second in the communication with the router - increased it to 3 - seems to be a bit more stable. 

image.png.ec88eb5847ab10b4e5909b1d2ef3c4d7.png

4) Sadly I didn't see anything in the screen-recording - except the  « Cannot communicate with the specified UnitID  » .


Cheers, Jacob Bauer

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  • MVP 2021
17 minutes ago, Jacob Bauer said:

Is it possible to send the data directly to a server instead?

Of course - that's what a SCADA does. I have several customers that use SCADA to collect data from PLCs that I have programmed. It works very reliably.

Be sure you have reasonable values set as Power-Ups for SI 101 - 106, as applicable.

On 8/24/2020 at 3:45 AM, vince1004 said:

But after a certain time the "listing of files" stop and the following error message « Cannot communicate with the specified UnitID  » is displaying. After this happen, it is impossible to communicate anymore with the device I have to unplug the ethernet cable and plug it again to be able to communicate with it.

SI 103-106 should help with this. This allows the connection to drop after the specified time period (note the the time units are 100ms). I usually put in 10 or 20 for this.

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  • MVP 2021

Hi Jacob,

1).  Crucial that this is ON.  This can be checked quite easily remotely using Remote Access, and once connected using Info mode to navigate to SB168.  Once into the System Bits area, only use up/down arrows and Esc during navigation to avoid upsetting something else.

2).  I gave you an incorrect reference, sorry.  I forgot you were using SD explorer, this tick is in Remote Access.  However, I think you should do a test run using Remote Access, with the tick done and settings with say a 5 second timeout and 3 retries.  In Remote Access under Tools you can access your data tables that are in the PLC memory.  It would be interesting to see how quickly they get read from the plc.  Once Data Tables window opens, it will show all the Data Tables in the PLC, and Connection/Read Structure and Values from PLC will start the read process.  The length of time to do this, and stability of the process, might give some clue to issues.  This procedure can also let you directly play with timeouts and retry settings, reducing them to quickest that are stable.  These should then be achievable elsewhere.

Flex's suggestions re Scada triggered a little bell in my head.  Hook into the PLC using SD card explorer and ensure that all of the folders where you have your data tables being stored DO NOT have any files listed that aren't the 8.3 naming format.  In deleting files using Card Explorer, sometimes things go astray and the plc will foul things up, and leave a file name that doesn't match the 8.3 it needs, and this consequently creates issues if you're doing things sequentially.  The only way to cure this issue is for the card to be removed and the file(s) manipulated externally.  I've attached a little screenshot of what I have on one remote card at present that I haven't yet cured with a site visit, which does a daily log.  The 27_1 is the sort of thing I'm talking about.  If somehow this gets included in your transfer things will likely stop at that point.

DeleteError.jpg.6b11acbee4ecebe020eb2929fa51eeed.jpg

cheers, Aus

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On 12/5/2022 at 11:12 AM, Jacob Bauer said:


All in all my experience with SD-cards haven't been to good. I just don't find it stable/reliable. I have a setup with an internet connected router, a plc and a lot of data being stored from sensors. Is it possible to send the data directly to a server instead? The UniCloud solutions becomes a bit expensive, if you have many or frequent data points. 
 

I can give you the solution that you are looking for. I Inherited a project with a bunch of PLCs, the SD card storage solution + trends recording of the PLCs was not good enough, and the process to collect all that data and dump it in the same place was slow and painful... plus time-to-time I got corrupted SD cards.

You can do it even better without OPC server and please avoid using spread sheets to store your data.

 

Take note, this will save you a lot of Money and it's even more powerful than UniCloud, and relatively easy to implement and it is scalable.... and the best of all no licenses needed:

1. Enable a field Bus to collect the data: MODBUS TCP/IP is the best way.

2. Get a Server and Connect your PLCs to  the same network. 

3. Use InfluxDB OSS  as database: InfluxDB Times Series Data Platform | InfluxData | InfluxData, You will need to configure Telegraf (InfluxDB data collector agent) to use MODBUS TCP/IP.

4. Use Grafana Grafana OSS | Metrics, logs, traces, and more to create dashboards and trends, to analyze and visualize your data.

This Stack IS way more powerful than any SCADA software for monitoring the data.

 

 

 

 

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