A Guide to Designing an Efficient HMI for Operator Use

Human Machine Interfaces (HMIs) are the link between operators and the complex systems they oversee, translating various mechanical and digital processes into an interactive and often visual format. From displaying real-time performance metrics to enabling direct control of functions, HMIs support simplified decision-making across sectors like manufacturing, utilities, transportation, energy, and more. In this guide, we will look at what it takes to design an HMI system for most operational demands, including which part types are usually implemented in these setups.

Basic Requirements for HMI Functionality

Before selecting specific parts, it is best to plan an HMI layout with consideration given to the following factors:

Environmental Tolerance: Temperature extremes, humidity, dust, and vibration are all common in industrial spaces, and the HMI has to withstand all applicable stressors without degradation.
User Interface Clarity: Information displayed should be easy to read and interpret quickly. Consider screen brightness, layout logic, font size, and color contrast, matching these features to what best fits the HMI screen’s setting, or choose a more analog layout for rugged environments.
Safety and Compliance: An HMI system must adhere to applicable safety and performance standards for its setting, such as those established by IEC, NEMA, or UL. Interfaces should also remain accessible and responsive during emergency situations, allowing operators to take immediate action when necessary.
Data Logging: HMIs that support historical data recording can offer more in-depth diagnostics and performance reviews, which is essential in certain operations.
Modularity: Though it may depend on the goals of the establishment using them, HMI systems should ideally facilitate easy maintenance or future upgrades.

Common Components for HMI Integration

Touchscreens and Display Units

As the primary point of interaction between operators and machinery, display units present critical data and, in many cases, allow for direct control. Non-touchscreen displays are often paired with external controls, while touchscreen models combine input and output in a single interface. Moreover, screen type, size, and resolution can all be tailored to match the complexity and volume of information being communicated.

Popular Subtypes

Resistive Touchscreens: These screens detect pressure applied to two flexible layers that make contact when pressed. Although they have lower clarity and responsiveness compared to other types, their reliability in dusty or moist conditions and compatibility with glove use makes them a frequent choice in industrial settings.
Capacitive Touchscreens: These screens respond to light finger touches and support multi-touch gestures, offering higher sensitivity, clarity, and faster response times than resistive types. However, they require bare skin or compatible styluses, limiting their use in dirtier settings and those requiring gloves or protective gear.

Control Panels and Keypads

In settings where touchscreens are impractical, tactile keypads or membrane switches are durable alternatives. They tend to be used in conjunction with display units to help users easily carry out specific, repetitive operations.

Popular Subtypes

Tactile Keypads: These keypads feature individual mechanical switches beneath each key, providing distinct tactile and audible feedback that helps operators in fast-paced environments confirm inputs without needing to look at the panel.
Membrane Switches: Constructed with multiple flexible layers and pressure-sensitive contacts, membrane switches have a smooth, sealed surface that resists contaminants. Their flat profile allows for easy cleaning and sanitization, serving more sterile environments like food processing lines, medical devices, and cleanrooms.

Enclosures and Mounting Systems

Safeguarding sensitive components like touchscreens, control panels, keypads, and interface modules from environmental hazards or unintended impacts is often a fundamental aspect of designing an HMI system, which enclosures and mounting accessories are made for.

Popular Subtypes

NEMA-Rated Enclosures: These enclosures meet specific protection standards set by the National Electrical Manufacturers Association (NEMA), offering varying levels of resistance to water, dust, oil, and corrosive substances for different components in an HMI layout.
Panel Mounts: Panel mounts allow an HMI screen or keypad to be flush-mounted within a control panel or machine surface, providing a fixed space-saving setup.

Signal Converters and Interface Modules

HMI systems usually need to bridge analog and digital signals or connect with various communication protocols, with signal converters and interface modules filling this role effectively.

Popular Subtypes

Analog-to-Digital Converters (ADC): These modules transform continuous analog inputs, such as voltage signals from sensors, into discrete digital values for precise monitoring and data logging.
Digital I/O Modules: Linking between an HMI and external equipment, these modules manage incoming and outgoing binary signals. Digital input channels receive on/off signals from devices like switches or sensors, while output channels transmit control signals to actuators, alarms, or lights.

Communication Interfaces and Networking Components

To relay data between operators and broader systems like SCADA or MES platforms, communication components must be integrated, such as:

Ethernet Interfaces: These interfaces provide high-speed and stable data transmission, ideal for smart factories and Industry 4.0 environments.
Serial Interfaces (RS-232/RS-485): These interfaces remain widely used in legacy systems or isolated subsystems where simple, point-to-point communication is sufficient.
Wireless Modules: These modules enable remote monitoring and mobile operation.

It is important to note that the communication protocol should always be matched to the control system’s infrastructure to avoid compatibility issues.

Reliably Source HMI Parts from Industrials 360

As we have detailed, designing an efficient and durable HMI requires thoughtful planning of interconnected components. If you are going to source HMI parts that are guaranteed to perform well, Industrials 360 is a go-to solution. Operated by reputable distributor ASAP Semiconductor, this platform presents an extensive catalog of industry-compliant parts from trusted manufacturers.

Whether you are specifically seeking ruggedized displays, interface modules, control panels, or other system parts, Industrials 360 simplifies the sourcing process with easy-to-navigate catalogs and our own search engine. Furthermore, we always strive to offer competitive pricing and fast fulfillment, with experts standing ready to curate fitting procurement options for every customer. We look forward to fulfilling your needs with our unrivaled selection and services, so be sure to get in touch.