We will now be looking at simple data logging using a Click PLC with an Ethernet port. Node-RED will be used to communicate to the controller via Modbus TCP protocol. Information collected will be then stored in an SQLite SQL database. A Raspberry Pi 4 single-board computer will be used for the Node-RED collecting and storing. The update time will be two times a second (500 mSec). This method is ideal for quickly determining how things are operating.
Analysis or display of the information will be done with a spreadsheet. The spreadsheet will be run on a windows computer. Let’s get started.
We will now look at the connection to our SQL database using a spreadsheet application. Previously we used Node-RED to communicate Modbus TCP and RTU to our Click PLC and Solo Temperature Controller. The information collected from the controllers was then put into an SQLite SQL database.
Spreadsheets like Excel are great for analysis of the data. We will be connecting to our SQLite SQL database with WPS spreadsheets. This will be accomplished by using an ODBC driver as the translator between the database and spreadsheet. Let’s get started.
Node-RED can easily log data to a database. SQL (Structured Query Language) can be used to communicate to a SQL database. Databases separate analysis from the data unlike spreadsheets like Excel. The database is designed to hold more information than spreadsheets and allow multiple users to access the information.
We will be creating an SQLite SQL database. SQLite Studio will be used to design the structure of the database. (Tables) Installing the node-red-sqlite-node palette will allow us to log the information from our Solo process temperature controller, Click PLC, and dashboard variables. Let’s get started.
Node-RED can easily connect to industrial controls using Modbus communication. Modbus is a master-slave type of communication. Masters will always send the commands to read or write to the slaves on the network. The slaves will respond if the communication is directed at them.
We will be installing the node-red-contrib-modbus palette. This will allow us to communicate Modbus serial (RS485) RTU to a Solo process temperature controller. We will then use Modbus Ethernet TCP to communicate to a Click PLC.
Note: When using Modbus TCP (Ethernet) the master is referred to as the Client and the slave is a Server.
Node-RED will be used to create a single Modbus flow. We will communicate to our Solo process temperature controller using Modbus RTU on a serial RS485 network. The present and set values of the controller will be read. These values will then be written to our Click PLC using an Ethernet Modbus TCP network. A set value from an analog input on the Click will be used to then write to the Solo. This will happen every 200 milliseconds or 5 times per second.
Let’s get started using Node-RED for Modbus communication.