We will be using an MQTT broker in Node-RED to communicate to the productivity PLC clients. 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, perfect 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 and programming the AEDES MQTT Broker in Node-RED. A productivity P2000, P1000, and Node-RED will be the clients communicating to the broker. The PLC simulator inputs on each controller will control the outputs on the other controller. This will demonstrate the communication capability for publishing and subscribing to this IoT platform. Let’s get started.
A human-machine interface (HMI) is present in some form for every PLC. The HMI connects a user to a machine system to exchange information or control data. This interaction with the system can be through hardware or software.
HMIs offer different people information and control in many ways for the automated system. Operators, supervisors, mechanics, electricians, engineers, and programmers all have different needs. The machine HMI(s) must provide or make the information easy for all the people who use the system.
We will now look at some of the ways that human-machine interfaces (HMI) are used in automated systems today. Let’s get started.
Accelerate Learning …
In this Covid-19 world, we are continuing to adapt. Social distancing, mask-wearing, hygiene, etc are the way we currently live. Video conferencing with Zoom, Teams, and Google Meet are the norm in business today. Information is knowledge, and everyone more than ever wants to be able to see, control and summarize production data on a regular basis. Open intuitive technologies are available to communicate like never before. Industrial plant data is rapidly changing. Factory 4.0 benefits are being seen and everyone wants to take advantage. We are looking forward to the New Year and new possibilities for implementing your control solution.
Each year we like to take a few minutes and reflect on the past, current, and future of ACC Automation. You have helped us to build the site that you see today through questions, comments, and suggestions. Thank you.
Invented in 1968 by Dick Morley, the programmable logic controller (PLC) is a simple rugged industrial computer. This free plc training series is designed for everyone to learn about these controllers. PLCs are constantly evolving and continue to be the best option for a variety of industrial automation applications.
Even though the PLC is changing, core items remain the same. We will be discussing this in more depth for each of the components mentioned in the picture above. Let’s get started learning about PLCs.
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.
Node-RED Modbus TCP can recover from communication errors automatically. Options are available to you the programmer to continue the Node-RED flow upon detection of these errors.
Broken Ethernet cable, Modbus Server power, and Node-RED Client offline are just a few of the errors that can occur on the industrial plant floor. Our Node-RED program must account for and be tested for each of these conditions.
We will be communicating Modbus TCP (Ethernet) to our Click Plus PLC. Using the catch node we will detect and display errors that may occur. Let’s get started.