Custom segment LCDs allow engineers to design the display around the product rather than designing the product around an available standard display.
This guide focuses on static and multiplexed segment LCDs that do not contain an integrated controller/driver interface. These displays are commonly used when an application needs defined numbers, symbols, icons, annunciators, or other predetermined information rather than a fully graphic user interface.
Because monochrome LCDs can be customized at the glass level, engineers have considerable control over the dimensions, shape, segment layout, viewing characteristics, backlight, connector configuration, and other elements of the display assembly.
This article covers the primary considerations when beginning a custom segment LCD design.
What Is a Custom Segment LCD?
A segment LCD uses individually defined areas of liquid crystal to display predetermined information.
Unlike a graphic LCD, where individual pixels can be controlled to create changing images, a segment display is designed around specific characters, numbers, symbols, or icons that the product needs to present.
Examples can include:
- Numerical values
- Units of measurement
- Battery indicators
- Status icons
- Warning symbols
- Bar graphs
- Custom annunciators
- Product-specific symbols
This can make segment LCD technology a practical option when the information displayed by the product is known in advance.
Static vs. Multiplexed Segment LCDs
One of the early design decisions is whether the LCD will use static or multiplexed drive.
A static, or direct-drive, segment LCD drives individual segments directly.
A multiplexed segment LCD allows multiple segments to share common drive connections, which can reduce the number of connections required as the number of segments increases.
The appropriate approach depends on the number of segments, electrical architecture, available connections, controller or driver being used, and other application requirements.
Additional background is available in our guide to static and multiplexed segment LCDs.
Start With the Information the LCD Must Display
The segment layout is one of the most important parts of the design.
Before developing the LCD glass, the engineering team should determine exactly what information the display needs to communicate.
That may include:
- Number of digits
- Character locations
- Decimal points
- Symbols
- Units
- Status indicators
- Warning icons
- Bar graphs
- Customer-specific graphics
It is useful to consider not only what the product needs today but also what may be required throughout the planned life of the design.
Adding a necessary annunciator during the initial design process is generally easier than discovering later that the user interface requires information the glass was never designed to display.
Define the Mechanical Requirements Early
Because custom monochrome LCD glass can be designed around the application, engineers should define the available mechanical envelope as early as possible.
Important information can include:
- Overall display dimensions
- Viewing area
- Available enclosure space
- Connector location
- PCB location
- Mounting requirements
- Orientation
- Other mechanical constraints
Custom segment LCDs can be developed in rectangular, square, or non-standard shapes when required by the application.
Mechanical requirements should be coordinated with the rest of the product design so the LCD, enclosure, PCB, connector, and user interface work together.
Choose the Appropriate Viewing Configuration
The appearance of a segment LCD depends on several design choices.
These can include:
- LCD mode
- Polarizer configuration
- Viewing direction
- Background appearance
- Segment appearance
- Backlighting
Technologies such as TN, STN, and FSTN provide different viewing characteristics and visual appearances.
The right configuration depends on factors such as the product environment, desired contrast, viewing angle, lighting conditions, and user-interface requirements.
Engineers can learn more about these options in our TN, STN, and FSTN LCD guide.
Consider the Backlight Requirements
A backlight may be necessary when the display must remain readable in low-light or dark environments.
The appropriate backlight depends on the application.
Important considerations can include:
- Required brightness
- Backlight color
- Power consumption
- Available space
- Viewing conditions
- Product operating environment
Power consumption can be particularly important in battery-powered or portable equipment.
Rather than selecting the brightest available backlight automatically, the engineering team should determine the amount of illumination actually required for the product and operating environment.
Focus LCDs can customize backlight configuration as part of a monochrome LCD assembly.
Transmissive, Transflective, and Reflective Operation
Polarizer selection also affects how the display performs under different lighting conditions.
A display may be designed for reflective, transmissive, or transflective operation depending on the application.
A transmissive display relies primarily on illumination from behind the LCD.
A reflective display is intended to use ambient light.
A transflective configuration combines characteristics of both approaches and may be useful when the display needs to operate across varying lighting conditions.
The appropriate choice depends on how and where the finished product will be used.
The existing backlight photographs in this article can remain useful if they accurately demonstrate the visual differences between configurations.
Define the Electrical Interface
A custom segment LCD must also work with the customer’s electronics.
The engineering team should identify the intended driver architecture and electrical requirements early in the project.
Relevant information can include:
- Static or multiplexed operation
- Segment and common requirements
- Connector configuration
- Pinout
- FPC requirements
- PCB integration
- Available controller or driver circuitry
These requirements should be coordinated with the approved display drawing and the customer’s electronics before production.
Do Custom Segment LCDs Have Minimum Order Quantities?
Custom segment LCD projects generally have production requirements because the display is manufactured specifically for an individual design.
However, there is no single minimum order quantity that applies to every custom segment LCD.
Production requirements can depend on factors such as:
- Glass dimensions
- Display construction
- Backlight
- Connector or FPC requirements
- Assembly configuration
- Expected production demand
Focus LCDs confirms project-specific production requirements during the quotation process.
If the final production quantity is not yet known, an estimated annual usage can help begin the discussion and can be refined as the product moves closer to production.
Does a Custom Segment LCD Require Tooling?
Custom segment LCD development generally requires tooling and engineering work because the glass and assembly are being developed for a specific application.
The exact scope depends on the display design.
The development process may include:
- Requirements review
- Engineering design
- Custom glass development
- Drawings and specifications
- Backlight development when applicable
- Connector or FPC requirements
- Prototype or sample evaluation
- Production documentation
Tooling requirements, prototype requirements, costs, and other commercial terms are established for the individual project during the quotation process.
How Are Prototype Displays Handled?
Prototype or sample requirements are determined according to the needs of the project.
When prototypes are appropriate, they allow the engineering team to evaluate the custom segment LCD before ongoing production.
Evaluation may include:
- Mechanical fit
- Segment layout
- Electrical operation
- Viewing performance
- Contrast
- Backlight operation
- Connector or FPC fit
- Integration with the PCB and enclosure
If changes are required, the design should be reviewed and the applicable drawings or specifications updated before production approval.
Replacing a Discontinued Segment LCD
Custom segment LCD development can also be useful when an existing display becomes obsolete or is no longer available.
In these situations, the objective may be to develop a replacement that works within the requirements of an existing product.
The engineering team may need to evaluate characteristics such as:
- Glass dimensions
- Viewing area
- Segment layout
- Pinout
- Electrical characteristics
- Connector arrangement
- Backlight
- Viewing mode
- Mechanical fit
A replacement project should be evaluated carefully because the original display may have characteristics that are not immediately obvious from its external dimensions.
When documentation for the original LCD is available, it can provide a useful starting point for engineering review.
Plan for the Product Lifecycle
For OEM equipment, the display may remain part of the product for many years.
Changing a display later can affect:
- Mechanical design
- PCB layout
- Firmware
- User interface
- Optical performance
- Qualification
- Documentation
- Manufacturing procedures
For that reason, custom segment LCD design should consider not only the prototype but also the expected production life of the equipment.
Expected annual usage, qualification requirements, product lifecycle, and supply continuity should be discussed early in the program.
Additional information is available in our LCD lifecycle risk management for OEM programs.
What Information Should You Provide for a Custom Segment LCD?
A project can usually begin more efficiently when the engineering team provides as much information as is currently available.
Useful information can include:
- Overall glass dimensions
- Viewing area
- Segment layout or concept
- Required numbers, symbols, and icons
- Static or multiplexed drive requirements
- Viewing mode
- Backlight requirements
- Connector or FPC requirements
- Operating environment
- Expected annual usage
- Target production schedule
- Existing drawings or specifications, if replacing another display
Not every requirement needs to be finalized before the first discussion. Focus LCDs can work with the engineering team to identify which items still need to be defined.
Start a Custom Segment LCD Design
Custom segment LCDs provide significant flexibility when a standard display cannot meet the requirements of the product.
Focus LCDs can customize monochrome displays at the glass level, including size, shape, resolution, segment layout, backlight, connector configuration, viewing mode, and other elements of the display assembly.
Our engineering team supports OEM customers from initial display development and prototyping through production.
Contact Focus LCDs to discuss a custom segment LCD project, or contact our engineering support team if you need help defining the display requirements.
