Solutions for a Local HMI System

Publish Date: Feb 02, 2017 | 0 Ratings | 0.00 out of 5 | Print


Often you need to attach a local human machine interface (HMI) directly to the controller to ensure operator or technician access. Usually in the same enclosure as the controller, these local HMIs are single units cabled or attached directly to the controller.

Switch and LED C Series Module

Figure 1. The NI 9344 works well as a local HMI interface for technicians.


The NI 9344 is a user-programmable switch and LED C Series module that inserts directly into the CompactRIO or CompactDAQ chassis and gives technicians a method to quickly interact with a deployed system. Each switch acts as a digital input channel for debugging code, starting and stopping processes, or clearing errors. Each LED is powered by a digital output channel and can be programmed to provide both status and diagnostic updates to the end user.


An effective addition to a system, the switch and LED module can be used with another HMI method to provide both a public, user-facing interface method as well as a private, technician-accessible debugging method.


Learn more about the NI 9344 user-programmable switch and LED C Series module.


Component Displays

An inexpensive local UI option for interacting with your controller is a component display. Depending on your needs, these displays range in cost from the low $10s to $100s, but they provide basic functionality such as soft buttons or simple text displays with 16 x 2 characters. This unpackaged component is wired directly to the target device via USB, serial, or digital lines, and shows information to an operator who is near the device.


Figure 2. Component displays offer an inexpensive option to display simple information on a local HMI attached to a controller.


Many of these types of HMIs are board-level products or components to a larger system that you can directly integrate into your final mechanical design. Because component displays are not enclosed products, you can typically find a lower cost HMI option. These types of displays are designed to provide more basic functionality such as soft front panel buttons or basic system data. Typically, component displays cannot offer graphics capabilities like the streaming video or 1 kHz refresh rates found in OSs like Windows or Linux.


You can use an Amulet touchscreen display module from NI and the Amulet LabVIEW API on the LabVIEW Tools Network to communicate over an RS232 serial interface to your controller. The display provides a graphical interface with touch feedback to the controller application, making it a rich technician HMI, or a modest operator interface.



Learn more about Amulet touchscreen component displays.


Embedded UI and Monitors

An Embedded UI displayed on a monitor attached to your controller provides the richest HMI when compared to any other local HMI option. NI touch screen monitors make ideal HMIs for CompactRIO, CompactDAQ, and PXI controllers, and are fully supported in Windows and NI Linux Real-Time with an embedded UI. In this approach, the controller’s resources are used to both run your control and monitoring application and drive the graphics of the UI.


When compared to the more traditional HMI approach of attaching a panel PC or touch panel computer to your controller, the embedded UI solution reduces the system hardware cost, system maintenance, and software development complexity, but it does consume more controller resources than component displays, the switch and LED C Series module, or other remote HMI options.


The CompactRIO platform supports Embedded UIs through the built-in DisplayPort, and provides the software flexibility you need to efficiently consolidate the HMI and control tasks in the same application. To enable this consolidation, the LabVIEW development environment and the NI Linux Real-Time OS expose task prioritization to you so you can assign a higher priority to the control tasks over the HMI tasks running in the same application. You can further isolate tasks with processor core assignment of task execution in LabVIEW. Additionally, you can move some of the control tasks to the onboard FPGA if you need more isolation and hardware reliability.


Figure 3. The Embedded UI capabilities of the CompactRIO platform eliminate the need for a stand-alone HMI by incorporating it directly into your controller.



Learn More About the CompactRIO Platform

Explore LabVIEW Software Architecture Best Practices for Embedded UIs

Solutions for Remote HMI

A local HMI is often a requirement, but a remote HMI, which doesn’t need to be co-located with the controller and can include multiple HMI terminals for a single controller, can also be a powerful addition to an embedded control and monitoring solution. It can even replace a local HMI entirely.


Learn more about Remote HMI solutions.


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