PLC and HMI Questions and Answers

In this article, we share the basics questions and answers on PLC and HMI for industrial automation professionals.

PLC and HMI Questions and Answers

Do HMIs have printing capabilities?

It varies depending on the manufacturer. Some HMIs will come with specific printers that are compatible, while others will not have printing capabilities

Some HMIs have the capability to install the user’s own drivers for the printer of choice.

How does one program an HMI?

There are a few third party programs that can be used to create an HMI graphical user interface, such as CodeSys.

Some HMIs come standard with their own proprietary software, which provides the functions specific to that HMI.

Lastly, some HMI’s come with SDK packages so the user can program the HMI in his/her native language.

What does an HMI do?

With an HMI the user will have a centralized unit of control, which allows for decisions based on real time events in a visual manner. That HMI must be in constant communication with a controller so the HMI can receive real time data from controller.

The HMI accesses specific registers on the controller and makes decisions based on the state of those registers. Most controllers deal with heavy wiring, and without a user interface they require manual input (wiring) to toggle certain registers.

This is accomplished through software and makes the application simple and easy to perform.

How does the HMI communicate with other devices?

The HMI must be connected to a device, whether it is through Ethernet (RJ45), serial communication (RS232, USB or RS422), or wireless.

The two devices baud rates must be in sync, so that no miscommunication occurs.

What if my Controller is not supported by this HMI?

If the software that came with the HMI does not have a universal controller option, then third-party software may be used.

Most software has a generic universal controller, in case the controller being used is not considered compatible with the HMI.

What are the benefits of an HMI over a desktop?

An added benefit of an HMI is that it is application-specific. In other words, a panel will not allow for internet browsing, solitaire game play, or update reminders unless it pertains to the task at hand.

HMIs provide absolute control; meaning that you may give the user limited access to specific features, or full access depending on how the interfaces are created.

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