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. Keep on Reading!
The real-time clock on the Click Plus can now be more accurate. A network time service (NTP or SNTP) has been added to the Click Plus controller. This will allow the time to be synchronized with an internet time server or local network. Daylight savings time is quickly implemented with just a memory retentive bit that we can turn on and off based on the time change in the area.
We will be setting up the network time service on our Click Plus. The real-time clock (RTC) will be updated via the internet time service. Daylight savings time and the RTC will also be programmed. This will be based on our previous Click Real-Time Clock post. Let’s get started. Keep on Reading!
We will now look at the MQTT communication capability using our Click plus PLC.
MQTT stands for Message Queuing Telemetry Transport. This simple ‘publish and subscribe’ communication protocol, does not take too many resources.
Constrained devices with low bandwidth are ideal for MQTT. This protocol provides machine-to-machine (M2M) connectivity which is ideal for the Internet of Things. (IoT) This protocol is not for remote IO or real-time (deterministic) applications. MQTT is a good solution for applications that move data from hundreds or thousands of machines (sensors) to clients in many networks.
We will be installing a windows based broker called Mosquitto. The Click Plus PLC will be one of the clients publishing and subscribing to the MQTT broker. Node-RED will be the other client publishing and subscribing to the MQTT broker. Each client will share information. Let’s get started. Keep on Reading!
The Click Plus PLC has now been released. This can only be programmed with version 3.00 or higher of the Click Programming Software. Version 3.00 will program all of the Click PLC CPU units and add additional features to the Click Ethernet CPU units.
Features of the new Click PLUS PLC (C2-0xCPU) includes the following:
• Micro USB
• DHCP support
• DNS support
• Wi-Fi (programming and Modbus TCP)
• Bluetooth (Wi-Fi) provisioning
• SD Card (Data Logging)
• Data Logger
• Network Time Service
• MQTT (Publish/Subscribe)
• Required PLC Password
• Disable Ports
• Strong Password Support
• Disable Ping Response
• Encrypted Password Transfer
We will be installing version 3.00 of the Click programming software on our windows 10 computer. After starting the software we will review some of the new features. Let’s get started. Keep on Reading!
The click plc has a real-time clock that will allow us to control outputs based on a date or time of day. This real-time clock (RTC) can be set from the click programming software or through the program of the controller. Our programs in the click can use the following calendar and clock values:
SD19 – RTC Year – 4 digits (2021)
SD20 – RTC Year – 2 digits (21)
SD21 – RTC Month – (00 to 12)
SD22 – RTC Day – (00 to 31)
SD23 – RTC Day of the Week – 1 Sunday to 7 Saturday
SD24 – RTC Hour – (00 to 23)
SD25 – RTC Minute – (00 to 59)
SD26 – RTC Second – (00 to 59)
We will be using the RTC – Real Time Clock in a sample program. This program will turn on an output Monday to Friday from noon until 1 pm. It will also adjust for daylight savings time. Let’s get started. Keep on Reading!