"S7 in" node failed to read data from S7-1200 PLC

Hello,

I have a difficult point with "S7 IN" node.

Normally I can read data from PLC by using "S7 IN" node, but sometime the "S7 IN" node can post a error message "Failure (Bad values)", it seems like IOT lost connection with PLCs within several seconds.  If at that time the IOT is reading data from PLC, the data will be lost.

The IOT is connecting with 10 PLCs.

Attachment is the error message picture.

Anyone knows the reason? Share with me pls!

Thanks in advance!

 Hi bergmanu,

 I attached the node-red flow.

 There is none a special tag/DB, you can see in my flow, every time accessing variables are   getting  the same DB address.

 best regard!

bergmanu

Hi, 

can you please share your node-red flow? Maybe there is a configuration error.

Is this appearing when accessing a special tag / DB in the PLC? 

Best regards!

 Hi,

 My IOT2040 is communicating with 13 PLCs(ST10\ST20\------\ST150\ST160), and the error can   come from every PLC, so every PLC can lost data.

 I attached another picture, which shows several PLCs post error message at the same time.

 Best regard!

bergmanu

Hi, 

thanks! 

Is this behavior only occuring for the PLC ST10 or also for other PLCs? 

In your screenshot it can be seen that the error is coming from node ST10. 

Which PLCs are you using? 

Best regards!

 Hi bergmanu,

 I have a new try, I copy the flow from IOT2040 to my PC and deploy on PC, then I monitor them at   the same time, the error only occurs in IOT.

 I attached a video which shows the error moment, in the video left half part is about IOT, the right   is flow deployed on my PC. You can see when the error occurs in IOT, at the same time PC flow is   normally.

 Could you give me additional suggestion?

 Thanks in advance!

AutoGen_4158900

 Hi,

 My IOT2040 is communicating with 13 PLCs(ST10\ST20\------\ST150\ST160), and the error can   come from every PLC, so every PLC can lost data.

 I attached another picture, which shows several PLCs post error message at the same time.

 Best regard!

bergmanu

Hi, 

thanks! 

Is this behavior only occuring for the PLC ST10 or also for other PLCs? 

In your screenshot it can be seen that the error is coming from node ST10. 

Which PLCs are you using? 

Best regards!

 

 Hi bergmanu,

 The frequency of errors is not fixed, it is maybe from 10 minutes to 20 minutes.

 There is none such a 'syslog' file, and I find a 'node-red.log', so I take a picture when the error   occurs. I add a attachment.

  I also think it maybe a "performance" issue, so I deploy another IOT2040 on other production   line,  this time I just connect one PLC. The error also can occur, but the frequency is long, maybe   2  hours.

Best regards!

bergmanu

Hi, 

thanks for the test with a PC. 

Maybe this is a "performance" issue with the IOT2050. Too much connections/data. 

How long does it take until the error appears? Is there any entry in /var/log/syslog just before the errors appear? 
You can check that with

cat /var/log/syslog | grep node

 Best regards!

 Hi bergmanu,

Sorry for update the answer late!

Recently I have tried different ideas, and I got some conclusions.

If I just reduce the count of connecting PLC, do not reduce the count of variable, the errors occurred frequency as before. There are about 30 variables will be read from one PLC.

If I just reduce the count of variable, do not reduce the count of connecting PLC, the errors occurred frequency go down obviously. There are 12 PLCs connecting with one IOT.

If I reduce the count of PLC and variable at the same time(variables reduce to about 10, PLCs reduce to 2), the error may disappeared. I test one day, there is no error.

So I think the count of variable may affected the performance of IOT more.

I don't know how about IOT2050, I'm buying two IOT2050, but the delivery time maybe a bit long .

Best regard!

bergmanu

Hi, 

ah right, syslog is only in IOT2050. For IOT2040 the node-red.log exists. 

The errors before and after seem to be errors from a database access, don't think this has anything to do with the s7 errors. 

Okay, this would have been my next idea, to check how it behaves with less PLCs. But that it appears with only PLC is strange. Haven't heard of any problems with using a single PLC. 

How many tags are you reading with this single PLC? 

Best regards!