HMI Design Best Practices: How to Build Operator Interfaces That Actually Work

HMI DESIGN REQUIREMENTS

HMI DESIGN connects operators to PLC-based control systems, conveyor systems, machine controls, and material-handling equipment.

Required functions:

Display equipment status.
Display operating mode.
Display active faults.
Display alarm history.
Provide authorized commands.
Display interlock conditions.
Display production data.
Support troubleshooting.
Separate operator functions from maintenance functions.
Maintain consistent screen structure.

Applicable environments:

Manufacturing plants.
Warehouses.
Distribution centers.
Conveyor systems.
Sorter systems.
Accumulation conveyors.
Pallet conveyor applications.
Packaging equipment.
Machine control panels.
Material-handling systems.

An effective HMI provides the information required for a decision and the controls required for an authorized action.

1. DEFINE OPERATOR TASKS

Start with documented tasks.

Required task categories:

Normal operation.
System startup.
System shutdown.
Product changeover.
Manual operation.
Jam recovery.
Alarm response.
Equipment inspection.
Maintenance access.
Emergency stop reset.
Production review.

Document each task using a screen outline or storyboard.

Record:

Required data.
Required command.
Required permission level.
Required alarm message.
Required feedback.
Required interlock information.
Required recovery action.

Organize screens around operator tasks. Do not organize screens around PLC racks, I/O addresses, or software routines.

AutomationDirect identifies storyboards as a starting point for documenting screen content, navigation, status indicators, manual functions, setpoints, and fault displays.

2. BUILD A SCREEN HIERARCHY

Use a defined hierarchy for every industrial automation project.

LEVEL 1: SYSTEM OVERVIEW

Display:

Entire conveyor line.
Major zones.
Sorter locations.
Merges.
Transfers.
Palletizer infeed.
Inbound and outbound areas.
Current system state.
Active alarms.
Throughput.
Backlog.
Equipment availability.

Use Level 1 for system awareness.

LEVEL 2: AREA OVERVIEW

Assign one screen to each major operating area.

Examples:

INBOUND CONVEYOR.
SORTER FEED.
ACCUMULATION ZONE.
PACKING LINE.
SHIPPING CONVEYOR.
PALLET TRANSFER.
DIVERT AREA.

Display:

Area operating state.
Zone states.
Start and stop commands.
Auto or manual mode.
Main setpoints.
Local interlocks.
Active area alarms.
Upstream and downstream conditions.

LEVEL 3: EQUIPMENT DETAIL

Provide detailed screens for specific equipment.

Examples:

Variable frequency drives.
Photoeyes.
Diverters.
Lifts.
Motors.
Safety devices.
Accumulation zones.
Sorter sections.
Pneumatic components.

Display:

Device state.
Device permissive.
Device fault.
Feedback signal.
Command signal.
Fault code.
Manual jog function.
Maintenance information.
Related alarm history.

LEVEL 4: DIAGNOSTICS

Restrict advanced functions by role.

Include:

I/O status.
PLC communication status.
Drive diagnostics.
Sensor diagnostics.
Timer values.
Counter values.
Calibration functions.
Historical trends.
Configuration values.

Provide navigation between levels in one or two selections.

3. STANDARDIZE THE LAYOUT

Use a fixed layout across screens.

STATUS BAR

Keep the status bar visible.

Display:

SYSTEM STATE: RUNNING, STOPPED, FAULTED.
OPERATING MODE: AUTO, MANUAL, MAINTENANCE.
ACTIVE RECIPE OR ORDER.
ACTIVE ALARM COUNT.
COMMUNICATION STATUS.
CURRENT DATE AND TIME.
USER LEVEL.

PROCESS AREA

Use the center area for the operating process.

Display:

Conveyor flow.
Equipment state.
Product movement.
Zone availability.
Jam location.
Interlock status.
Major process values.

Use left-to-right graphics when material flow follows that direction. Use consistent symbols for motors, photoeyes, drives, diverters, and safety devices.

NAVIGATION AREA

Place navigation in a consistent location.

Include:

HOME.
OVERVIEW.
AREA SELECT.
ALARMS.
TRENDS.
MAINTENANCE.
USER LOGIN.
HELP.

Separate navigation buttons from process commands. Do not place screen-selection buttons beside high-consequence commands without visual separation.

4. CONTROL COLOR AND GRAPHICS

Use color as an information code.

Recommended assignments:

GRAY: Inactive, unavailable, or static.
WHITE: Active or normal operating state.
GREEN: Running or permitted.
AMBER: Warning, inhibited, or attention required.
RED: Fault, alarm, or emergency condition.
BLUE: Measured value, selection, or user-entered data.

Document the color standard in the HMI design specification.

Requirements:

Use low-saturation backgrounds.
Use high contrast for text.
Use 2D symbols.
Use consistent line weights.
Use consistent equipment symbols.
Use consistent alarm colors.
Use color-blind-accessible status indicators.
Use text and icons with color.
Reserve bright colors for abnormal conditions.

Avoid:

Decorative animation.
3D equipment drawings.
Excessive gradients.
Flashing normal-state objects.
Multiple meanings for one color.
Bright backgrounds.
Unnecessary movement.

Animate only when movement communicates a required operating condition, such as product position on a conveyor or a changing process state.

5. DISPLAY DECISION-READY INFORMATION

Present values with context.

Required data format:

Value.
Unit of measure.
Normal range.
Alarm limit.
Setpoint.
Timestamp where applicable.

Examples:

CONVEYOR SPEED: 150 FPM.
MOTOR LOAD: 62%.
AIR PRESSURE: 80 PSI.
CARTONS PER HOUR: 1,240.
ZONE OCCUPANCY: 75%.
DRIVE TEMPERATURE: 48°C.
JAM TIMER: 12 SECONDS.

Use trends for conditions that change over time.

Recommended trends:

Motor load.
Conveyor speed.
Drive temperature.
Jam frequency.
Throughput.
Accumulation time.
Product count.
Sensor failure frequency.

Use analog indicators when range and direction matter. Use numeric displays when exact values matter.

Do not display every available PLC tag. Display the information required for operation, troubleshooting, and maintenance.

6. DESIGN ACTIONABLE ALARMS

An alarm must identify a condition and support a response.

Each alarm record should include:

Alarm name.
Equipment location.
Alarm priority.
Active or cleared status.
Acknowledged or unacknowledged status.
Date and time.
Cause.
Operator action.
Reset requirement.

Examples:

ZONE 04 PHOTOEYE BLOCKED
- Location: Accumulation Conveyor 04.
- Check: Product position.
- Check: Photoeye lens.
- Check: Wiring.
- Reset: Clear obstruction and acknowledge.
SORTER NOT READY
- Location: Sorter Feed.
- Check: Downstream permissive.
- Check: Safety circuit.
- Check: Drive fault.
- Reset: Restore permissive and reset fault.
DOWNSTREAM FULL
- Location: Shipping Conveyor.
- Check: Downstream accumulation.
- Check: Transfer device.
- Action: Stop upstream release.

Use alarm priorities based on required action. Suppress duplicate and non-actionable messages. Maintain an alarm history for recurring faults.

Alarm design should support the site’s documented alarm philosophy and applicable high-performance HMI practices. Emerson provides reference material on high-performance HMI design and abnormal-condition management.

7. PREVENT OPERATOR ERRORS

Use interface controls that match operating permissions.

Required controls:

Disable unavailable commands.
Display the reason for a disabled command.
Require confirmation for full-line stops.
Require authorization for configuration changes.
Separate AUTO, MANUAL, and MAINTENANCE modes.
Display the current mode on every relevant screen.
Provide feedback after every command.
Block incompatible commands.
Protect setpoints by user level.
Record user actions where required.

Touchscreen requirements:

Provide large touch targets.
Space adjacent buttons.
Separate START and STOP controls.
Avoid critical buttons near screen edges.
Support gloved operation where applicable.
Maintain readable text at the installed viewing distance.
Provide clear feedback after touch input.

Do not use a confirmation dialog for every routine operation. Use confirmation for actions with line-wide, safety-related, or production-impacting consequences.

8. CONNECT HMI DESIGN TO THE PLC AND CONTROL PANEL

HMI performance depends on the complete control system.

Coordinate:

PLC tag structure.
HMI tag naming.
Alarm definitions.
Equipment states.
Interlock logic.
Drive status.
Safety status.
Network architecture.
Panel layout.
Electrical schematics.
FLA calculations.
Commissioning documentation.

A screen cannot compensate for undefined PLC states or incomplete control logic. Define the relationship between PLC logic, HMI objects, alarms, and field devices before development.

Conveying Controls L.L.C. provides full system concept and design, PLC and HMI-based platforms, procurement and specification services, machine control wiring, conveyor control wiring, panel control wiring, and comprehensive schematic drawings.

Review the AUTOCAD WORK service for schematic drawing support. Review ELECTRICAL ASSEMBLY for control panel assembly services.

9. TEST THE INTERFACE BEFORE DEPLOYMENT

Complete testing in defined stages.

FUNCTIONAL TEST

Verify:

Navigation.
Commands.
Setpoints.
User permissions.
Alarm activation.
Alarm acknowledgment.
Alarm clearing.
Interlock messages.
Mode changes.
Communication loss response.

SIMULATION TEST

Test conditions without production equipment where possible.

Include:

Motor faults.
Sensor failures.
Downstream blockages.
Drive communication loss.
Safety circuit interruption.
Product accumulation.
Power recovery.
PLC restart.
HMI restart.

OPERATOR REVIEW

Review storyboards and live screens with:

Plant managers.
Facility engineers.
Operators.
Maintenance personnel.
System integrators.
Operations managers.

Record corrections. Update screen standards. Re-test affected functions.

10. DOCUMENT AND MAINTAIN THE STANDARD

Create an HMI design standard for repeatable deployment.

Document:

Screen hierarchy.
Color assignments.
Symbol library.
Font sizes.
Button styles.
Alarm priorities.
Naming conventions.
User roles.
Navigation rules.
Equipment templates.
Trend requirements.
Diagnostic requirements.
Revision control.

Apply the standard to new control panels, conveyor upgrades, machine modifications, and replacement HMIs.

Conveying Controls L.L.C. has more than 35 years of experience supporting electrical control systems for conveyor and material-handling applications. Services include concept development, design, component procurement, schematic documentation, panel assembly, FLA calculations, PLC and HMI implementation, and end-to-end customer support.

Review TECHNICAL SUPPORT for support capabilities and supported automation equipment.

HMI DESIGN CHECKLIST

Define operator tasks.
Create screen storyboards.
Build a four-level hierarchy.
Standardize layouts.
Use low-saturation backgrounds.
Limit color.
Label units of measure.
Display interlocks.
Provide actionable alarms.
Separate operating modes.
Protect maintenance functions.
Test abnormal conditions.
Review screens with operators.
Document the standard.
Connect HMI requirements to PLC logic and control panel documentation.

IMPLEMENT

For HMI design, conveyor control wiring, machine control wiring, panel control wiring, schematic drawings, FLA calculations, and PLC/HMI-based industrial automation systems, CONTACT CONVEYING CONTROLS L.L.C..

CONVEYING CONTROLS L.L.C.
630-389-8209
info@conveyingcontrols.com