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Why Graphic LCDs Fit Your New Design

Why Graphic LCDs Fit Your New Design

Aug 21st 2020

Somewhere along Interstate 40 — west of Gallup, but not quite to Holbrook— it appeared. A steaming cup of coffee.

Not sure if it was regular or decaf? Cream or sugar? Artificial sweetener?

It didn’t matter. It just looked good. A little note below, in perfect 14-point Arial or Times New Roman, suggested I take a coffee break. Who am I to argue with good advice?

A minute later, it vanished and was replaced with my current speed, tire pressure and fuel range. No, it isn’t magic, it’s a graphic LCD.

Why are graphic LCDs so popular for new product designs?

Graphic displays are just what their name suggest. They display letters, numbers, punctuation marks, icons etc. One second you notice you’re five miles over the speed limit, a few seconds later you have a check engine notification.

Other advantages include displaying:

  • Any size letter or number
  • Any written language
  • Images or icons
  • Blinking or fading in and out
  • Positive/negative mode.
    • Positive mode is dark pixels on a light-colored background
    • Negative mode is lighter colored pixels on a darker background

Graphic displays consist of dots spaced across the glass. Each dot can be individually addressed (turned on or off) to create whatever image the programmer needs.

For example, a 128x64 graphic display, means there are 128 dots along the horizonal (X axis) and 64 dots along the vertical (Y axis).

Monochrome vs Color Graphic Displays

Monochrome Graphic Displays:

Monochrome means one color background and a different color pixel. Common configurations include black pixels on a white or grey background, blueish pixels on a yellow background, and white pixels on a dark blue background.

Most monochrome displays are positive mode. This means the display is readable without the backlight, but it does need to be on to read it at night.

Positive mode excels at daytime readability in direct sunlight (sunlight readable). They draw less power (around 1mA without backlight) than negative mode and offer a sharp contrast.

Note: A backlight will increase the display’s thickness by 3mm to 5mm. Backlights can draw from 15ma up to 90ma.

Monochrome is popular in industrial, construction, transportation, and other outdoor/harsh environment industries. Many of these industries prefer a multi-color display because some monochrome display technologies can provide a sharper contrast than a color module.

They are easier to program since you don’t have to choose each pixel’s color. Touch panels (TPs) are optional, but most TPs on monochrome displays are resistive.

Some customers request an RGB backlight. This allows the entire display to glow in a variety of colors.

Set the background color to green when the machine is operating normally, yellow if something needs attention and to a red background to indicate a critical condition.

 Color Graphic Displays:

TFT (Thin Film Transistor) and OLED ( Organic Light Emitting Diode) displays are the two most common types of multi-colored graphic displays.

Depending on the chosen interface, they can produce between 64,000 (64K) to 64,000,000 (64M) unique colors by using a combination of Red, Green and Blue (RGB).

Many contain a faster interface (LVDS, RGB and HDMI) to display videos.

Touch panels are available on most TFTS and OLEDs. Resistive touch panels (RTP) is the most common for outdoor applications and capacitive touch panels (CTP) for multi-touch applications.

Color displays can suffer readability in direct sunlight. Two solutions are:

  1. Increase the backlight's brightness to outshine the sun.
  2. Increasing the brightness of a TFT up to or greater than 700 Nits helps with readability. The increased brightness draws more power but can be dimmed for nighttime operation.

    Note: One nit is equivalent to one candela per square meter. It is common to see both nits and cd/m 2 used as the measure for the brightness of a display device.

  3. Transflective Polarizer

A polarizer is a semi-reflective material on glass. It reflects some of the ambient light and allows some to pass.

A majority of TFTs are transmissive. That means the backlight must be on to be readable. If the backlight is not bright enough in sunlight, then the display will appear washed out and difficult to read.

Transflective polarizers allow more sunlight to be reflected. The more ambient sunlight reflected, the higher the contrast.

A backlight can be used for night-time operation.