The Do-More Designer Programming Software (2.9) or higher includes a Modbus I/O Scanner with some profiles for Modbus Server (Slave) devices. This will greatly reduce the time it takes to implement and troubleshoot communications in your projects. Modbus communications are done independent of the PLC scan time and will have little or no ladder logic for the program.
Last time we communicated to a Solo process temperature controller via Modbus RTU RS485. (twisted pair) We manually set the Modbus IO scanner, reading the present value (PV) and set value (SV) of the Solo. The writing of the set value (SV) located within the BRX Do-More controller was also done. This was all be done without using any ladder logic code. We will now use the Modbus profile in the Modbus IO Scanner to connect a Click Plus PLC to our RS485 network. Using the Modbus scanner to write and read instructions we will also show how to use the ladder logic code with our scanner. Let’s get started.
The newest version of the Do-More Designer Programming Software (2.9) includes a Modbus I/O Scanner. This Modbus scanner will simplify Modbus RTU serial communications to any device. Communications are done independent of the PLC scan time and will have little or no ladder logic for the program.
We will be communicating to a Solo process temperature controller via Modbus RTU RS485. (twisted pair) Setting up the Modbus IO scanner and reading the present value (PV) and set value (SV) of the Solo. We will also write the set value (SV) located within the BRX Do-More controller. Communications will happen without using any ladder logic code. Let’s get started.
All Solo Standard Process Temperature Controllers that support RS-485 serial communications can use the SL-SOFT configuration and monitoring software. This free package will communicate to monitor multiple SOLO controllers using Modbus RTU or Modbus ASCII protocols.
We will be installing the SL-SOFT configuration and monitoring software package on our Windows 10 PC. Communicating through our Waveshare USB to RS485 adapter, Modbus RTU will be used as the protocol to establish communication. Let’s get started.
Many questions come from serial communications using the Click PLC. Most of these questions deal with communication timing when using multiple send and receive instructions. We will show you how to deal with serial communication timing in the Click PLC.
Receive and Send instructions will allow you to send and receive serial data to an external device. The communication method that you set up can be ASCII or Modbus. ASCII (American Standard Communication for Information Interchange) can be used to send to devices such as a printer. Receiving ASCII can be used for connecting barcode scanners to the PLC. The barcode will be read as an ASCII string in the PLC. Modbus serial communication (Modbus RTU) is a standard protocol used in many automation devices.
We will demonstrate the Send and Receive instruction by communicating Modbus RTU to a Solo Temperature Controller. Parameters from the Solo process temperature controller will be read using multiple receive instructions. The send instruction will be used multiple times as well to set the Set Value (SV) and Limits of the SV value entered in the temperature controller. The set values will only be changed when required. Let’s get started.
Node-RED will be used on the Raspberry Pi 4 to communicate serial Modbus RTU to a Solo process temperature controller and Click PLC using twisted pair RS485. This will be done on the same serial network so the devices will be daisy-chained together on the two wires.
We will be reading the PV (present value) and SV (set value) of the Solo temperature controller and then writing these values into the Click PLC. An SV value will then be read from the Click PLC and if it has changed, the value will be written to the SV of the Solo controller. Let’s get started.
We will be installing an industrial USB to RS485 converter on our computer. The Waveshare USB to serial port is a 2-wire USB to RS-485 serial communication adapter for RS485 use. It does not require an external power supply or complicated configuration.
It has a Type A (plug) USB connector for the computer side and screw terminals for the RS485 connections. This is an industrial USB to RS485 converter that has an FT232RL chip inside. It features embedded protection circuits such as lightning-proof, resettable fuse, ESD (Electrostatic Discharge) protection, and TVS (Transient Voltage Suppression) diode, etc. All of these features are packed within a small form size.
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We will be installing the driver for this USB to serial converter and connecting it to our computer. Node-RED will be used to communicate Modbus RS485 protocol to a Solo process temperature controller. Let’s get started.