September-14th-2020, 05:16 AM
Hi there,
first of all a word to the NL 50-MPI. This device works nearly with a zero delay. So once a command is coming via Ethernet port it is instantly sent out on MPI side. But there are differences in the performances of the S7 PLCs on MPI. Some S7 PLCs of older types are responding on a request in 25msec ... newer ones in 1-2msec. If you have luck you have a new PLC and you are getting good response times.
To use Node-RED with NL 50-MPI you need MPI nodes. There are two offerings:
a. https://flows.nodered.org/node/node-red-contrib-s7comm
b. https://flows.nodered.org/node/node-red-contrib-s7
I don't know the advantages of each to them. So you have to give it a try yourself which one is better.
You say that you have to read 100 variables ... I can recommend to you if it is possible to read adjacent variables that are lying next to each other in one command. So not 20 times DBB 0, 1, ... 19 and so on but DB 100 of a length of 20 bytes in one shot instead. Then you can divide them in Node-RED faster than 20 separate reads would cost you time.
I know Node-RED includes also a mysql node. I have never use it. You have to read the documentation about how it works.
What I did not understand is the fact what you want to do with all the data after it was written to the mysql database. I have read "saving money" on licenses for an OPC server ... I think you mean OPC UA server not OPC server, right? So I know there are also OPC UA server nodes available in Node-RED. Overall I think nobody can give you a guarantee about the performance. I personally see no problem in using 5 NL 50-MPI devices with Node-RED to read data in 1-2 minutes from 5 PLCs. I hope the S7 Node-RED nodes support multiple IP addresses for multiple NL 50-MPI cause I don't know.
Good luck with your project.
first of all a word to the NL 50-MPI. This device works nearly with a zero delay. So once a command is coming via Ethernet port it is instantly sent out on MPI side. But there are differences in the performances of the S7 PLCs on MPI. Some S7 PLCs of older types are responding on a request in 25msec ... newer ones in 1-2msec. If you have luck you have a new PLC and you are getting good response times.
To use Node-RED with NL 50-MPI you need MPI nodes. There are two offerings:
a. https://flows.nodered.org/node/node-red-contrib-s7comm
b. https://flows.nodered.org/node/node-red-contrib-s7
I don't know the advantages of each to them. So you have to give it a try yourself which one is better.
You say that you have to read 100 variables ... I can recommend to you if it is possible to read adjacent variables that are lying next to each other in one command. So not 20 times DBB 0, 1, ... 19 and so on but DB 100 of a length of 20 bytes in one shot instead. Then you can divide them in Node-RED faster than 20 separate reads would cost you time.
I know Node-RED includes also a mysql node. I have never use it. You have to read the documentation about how it works.
What I did not understand is the fact what you want to do with all the data after it was written to the mysql database. I have read "saving money" on licenses for an OPC server ... I think you mean OPC UA server not OPC server, right? So I know there are also OPC UA server nodes available in Node-RED. Overall I think nobody can give you a guarantee about the performance. I personally see no problem in using 5 NL 50-MPI devices with Node-RED to read data in 1-2 minutes from 5 PLCs. I hope the S7 Node-RED nodes support multiple IP addresses for multiple NL 50-MPI cause I don't know.
Good luck with your project.
„You never fail until you stop trying.“, Albert Einstein (1879 - 1955)
