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.
Suppanel is an Android app that is used to create a human machine interface (HMI). This HMI panel can be created on your computer, tablet or phone using the appropriate operating system or software. You can use this software to create panels that you can control or modify values in your automated system. These panels can be shared with other Suppanel users.
We will be creating a Suppanel Panel to monitor and control a Solo Process Temperature Controller via the Click programmable logic controller (PLC). The Click will be communicating to the Solo with serial RS485 using Modbus RTU protocol. The Suppanel HMI will be communicating to the Click PLC using Ethernet Modbus TCP protocol.
Programmable Logic Controller (PLC) programming is often thought as something everyone can do easily. We often design the system, install the hardware and then start to think about the PLC program and programmers. This approach can be improved. The landscape of PLC programming is changing and we must also change.
Computer Programming / PLC Programming
I believe that with all of the new functions of the PLC processor, you would be better served by someone that can do additional computer programming. Ladder logic has been taught in our schools for about 20 years or more. The basic bit programming in the ladder is easily understood. Connecting to the manufacturers dedicated software shows the power flow from left to right and shows the logic solved from top to bottom.
Some applications are fine if you are just replacing a few relays, however, today’s manufacturing floor must be integrated. The existing hardware in the plant must also be connected to the PLC system. This will allow connection of data logging, email, vision system, motion control, HMI, computer servers, etc.
Ladder logic and the standardization of PLC’s on the plant floor has long been a topic for discussion and debate. The benefits were that anyone can look and understand the PLC logic to troubleshoot the system. Today the PLC can do a lot more. Visually it can indicate /display its own troubleshooting and diagnostics to the engineer, electrician and/or operator in a variety of ways. You no longer need the skills on the plant floor all of the time. Using HMI (Human Machine Interface), computer screens, indication lights, and email, just to name a few, information can be passed for troubleshooting and diagnostics. The investment in the program and integration of the system in your plant will pay for itself time and time again.
I believe that PLC programmers need more than just this programming language. They must have the network and high-level language skills to be capable of integrating the entire plant floor.
Let me know what you think? Are we teaching the new generation the right way?
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