Equipment designed for potentially explosive environments can place strict requirements on the electrical and thermal energy available within a system.
For an OEM developing intrinsically safe equipment, the LCD should therefore be evaluated as part of the complete electrical design rather than treated as an isolated component.
Display technology, backlighting, power conversion, interface electronics, touchscreens, and supporting circuitry can all influence the electrical characteristics of the finished product.
Focus LCDs supplies and customizes display modules for OEM equipment used in demanding environments. We do not represent our LCD modules themselves as intrinsically safe or independently certified for intrinsic-safety applications. The OEM and its qualified certification or conformity-assessment professionals are responsible for determining whether the complete equipment satisfies the applicable requirements.
This article focuses specifically on LCD engineering considerations for equipment being developed around intrinsic-safety requirements.
Begin With the Display Power Budget
Power consumption is one of the first display-related characteristics an engineering team should evaluate.
The total display subsystem can include more than the LCD panel itself. Backlights, controllers, touch electronics, interface circuitry, power conversion, and other components may all contribute to the electrical energy used by the system.
An OEM should therefore evaluate the complete display assembly rather than looking only at a nominal LCD operating current.
For applications with strict energy limitations, engineers may need to consider whether the required user interface can be achieved with a lower-power display architecture.
A monochrome display, for example, may be appropriate when the application only needs predetermined segments, characters, or relatively simple graphics. A TFT may be appropriate when the product requires a more complex graphical interface, but its complete power requirements should be considered during the system design.
Evaluate the Backlight Separately
The backlight can represent a significant portion of the power used by an LCD assembly.
This makes backlight selection particularly important when the overall system has a limited electrical-energy budget.
Engineers should consider the actual illumination required for the product, including ambient lighting, viewing distance, operating environment, required brightness, and how frequently the backlight needs to operate.
A display does not necessarily need to operate at maximum available brightness at all times.
For some monochrome applications, reflective or transflective configurations may help reduce reliance on the backlight by using ambient light when conditions permit.
Focus LCDs can customize backlight configurations as part of a monochrome display assembly and can also customize backlights surrounding established TFT glass.
Consider Voltage Conversion and Power-Management Circuitry
Display systems sometimes require voltages that differ from the primary system supply.
Depending on the display architecture, supporting electronics may include voltage regulators, boost circuitry, charge pumps, or other power-conversion components.
These circuits should not automatically be described as prohibited in intrinsically safe equipment. However, they can affect stored energy, voltage levels, component selection, and the overall electrical analysis.
An OEM developing equipment around intrinsic-safety requirements should therefore evaluate whether additional voltage-conversion circuitry is necessary and how it affects the complete system.
Where the project requires a custom PCB or PCBA as part of the LCD assembly, Focus LCDs can work with the engineering team on display-related integration requirements.
The final circuit architecture and intrinsic-safety assessment remain the responsibility of the OEM and the appropriate qualified professionals.
Review Stored Energy, Not Just Normal Operating Power
Average operating current is only one consideration.
Electrical components can store energy even when the overall system appears to be relatively low power. Capacitive and inductive elements, power-conversion circuitry, and associated components may therefore need to be considered as part of the intrinsic-safety analysis.
This is one reason a low-voltage display should not automatically be assumed to be suitable for intrinsically safe equipment.
The complete circuit must be evaluated according to the applicable design and certification requirements.
IEC 60079-11 specifically addresses equipment protection by intrinsic safety, while IEC 60079-25 addresses intrinsically safe electrical systems.
Select the Display Interface Early
The interface between the LCD and the customer’s electronics can also affect the system architecture.
Focus LCDs supports display interfaces including SPI, I2C, parallel, RGB, LVDS, MIPI DSI, MCU, and other configurations depending on the display.
Different interfaces can require different controllers, voltage levels, signal counts, supporting components, and PCB architecture.
For equipment with strict electrical requirements, display-interface selection should therefore occur early enough for the supporting electronics to be evaluated as part of the complete design.
Changing the interface late in development can affect the PCB, firmware, power architecture, connector requirements, and qualification work.
Capacitive Touchscreens Require Additional Consideration
The older version of this article stated that capacitive touchscreens should be avoided in intrinsic-safety applications. That is too broad.
A capacitive touchscreen adds electronics to the display subsystem, including a touch controller, FPC or other connections, and associated power requirements.
Those additional components need to be considered in the complete electrical design.
Whether a capacitive touchscreen is appropriate depends on the application, system architecture, and applicable intrinsic-safety requirements.
A resistive touchscreen uses a different architecture, but it should not automatically be considered intrinsically safe either. The complete assembly still requires evaluation.
Focus LCDs can integrate resistive or capacitive touchscreens into display assemblies when appropriate for the application.
Consider Whether the Application Needs a TFT
Display selection should begin with the information the user actually needs to see.
If the product only requires numerical values, status indicators, fixed symbols, or relatively simple graphics, a monochrome display may provide a less complex architecture than a full-color TFT.
Monochrome displays can also be customized at the glass level.
Focus LCDs can customize dimensions, shape, resolution, segment layout, character or graphic configuration, viewing mode, backlight, connector or FPC configuration, and other components within a monochrome display assembly.
For equipment where power and circuit complexity are important constraints, this flexibility can be useful.
That does not mean monochrome technology is inherently intrinsically safe. It means the engineering team may have additional options for creating the required interface while controlling the complexity of the display subsystem.
TFT LCD Design Requires a Different Approach
TFT displays can also be used in equipment designed for demanding environments, but TFT customization differs from monochrome customization.
Focus LCDs does not modify the TFT glass itself.
Instead, customization can be applied to the components surrounding the TFT panel, such as custom FPC cables, backlights, resistive or capacitive touchscreens, cover glass, optical bonding, adhesives, and custom PCB or PCBA assemblies when incorporated into the LCD assembly.
The engineer should evaluate the complete TFT subsystem, including the controller, interface, backlight, touch electronics, and required power architecture.
More information about the distinction between monochrome and TFT customization is available on our custom display solutions page.
Operating Temperature Still Matters
Intrinsic safety and operating temperature are separate engineering considerations, but temperature can still affect the system design.
The selected LCD should have a documented operating-temperature range appropriate for the intended environment.
The engineering team should also consider heat generated by the backlight, controllers, power circuitry, and other components in the final enclosure.
If additional thermal-management components such as heaters are being considered, their electrical and thermal effects must also be included in the system-level design.
Where possible, selecting a display whose documented operating range already supports the expected environment can reduce additional system complexity.
For more information, see LCDs with special temperature ranges.
Environmental Protection Is a Separate Requirement
Equipment intended for hazardous environments may also need protection against moisture, dust, chemicals, impact, or other environmental conditions.
Those requirements should not be confused with intrinsic safety.
Cover glass, optical bonding, adhesives, sealing, and mechanical design can improve the suitability of a display assembly for a demanding environment, but those characteristics do not by themselves make the equipment intrinsically safe.
Focus LCDs can provide value-added integration including custom cover glass, touchscreens, optical bonding, adhesives, and other display-assembly components.
The OEM should evaluate those environmental requirements alongside, but separately from, the electrical protection strategy.
Consider Qualification and Lifecycle Before Selecting the LCD
Equipment requiring extensive qualification or certification can be particularly expensive to redesign after production begins.
A display change may affect mechanical dimensions, PCB layout, firmware, backlighting, electrical characteristics, optical performance, touch integration, documentation, and other areas of the product.
That makes lifecycle planning an important part of display selection.
An OEM should consider expected production life, anticipated quantities, critical display characteristics, potential component changes, and the engineering cost of qualifying a replacement later.
For additional information, see our LCD lifecycle risk management for OEM programs.
LCD Design Checklist for Intrinsically Safe Equipment
Before selecting or customizing the display, the engineering team should consider:
- What information must the user interface display?
- Is a monochrome LCD sufficient, or is a TFT required?
- What is the available power budget for the complete display subsystem?
- Is a backlight required continuously, intermittently, or not at all?
- What brightness is required in the actual operating environment?
- What interface and controller architecture will be used?
- Are voltage-conversion circuits required?
- What supporting electronics are part of the display assembly?
- Is a touchscreen required, and what electronics does it add?
- What operating-temperature range is necessary?
- Are heaters or other thermal-management components being considered?
- What environmental protection is required?
- Which display characteristics would be difficult to change after qualification?
- What production lifecycle is expected for the equipment?
These questions give the OEM and display supplier a clearer starting point for evaluating the display portion of the overall system.
Work With Focus LCDs on the Display Requirements
Focus LCDs’ role in an intrinsic-safety project is to support the display portion of the design.
We can work with OEM engineering teams on display technology, backlights, interfaces, FPCs, touchscreens, cover glass, optical bonding, adhesives, PCB integration, and other display-related requirements.
We do not certify the finished equipment or represent the LCD module itself as intrinsically safe.
The applicable protection strategy, circuit analysis, certification, and final system compliance should be established by the OEM and qualified professionals responsible for the complete product.
For a broader explanation of intrinsic safety at the equipment level, see Intrinsically Safe Designs: What OEM Engineers Should Know.
Contact our engineering support team to discuss the display requirements for equipment being developed for a hazardous environment.
Reference
IEC, IEC 60079-11:2023 – Equipment protection by intrinsic safety “i”. The current IEC listing also reflects corrections and interpretation sheets incorporated through 2026.
