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Character LCDs Explained Part 1

Character LCDs Explained Part 1

Aug 27th 2018


Besides the fact that Engineers and Designers are expected to develop new products in less time, they also carry the added burden of sourcing the best components for their new design. One of the most critical and expensive components is the LCD.

No one wants a display module that goes End-Of-Life (EOL) just months after their product receives UL or CSA approval. Nor do they want to select a model that is single sourced, expensive, or suffers from a long lead-time that holds up production schedules and kills profits.

And most of all, they want a display that makes their product look good – really good.

Although there is no perfect LCD technology, Character LCDs come close to satisfying key points on new product designs. Below are available options when selecting a character LCD Display.

Character configurations and sizes:

Start with the size of the display and the number of characters displayed.

Standard configurations include 8x1,8x2,16x1,16x2,16x4, 20x2, 20x4 and 40x4. The first number represents the number of characters in each row; the second number represents the number of rows.

Avoid odd-ball arrangements such as 12x1 and 12x2 to keep from being single sourced.

The number of characters does not affect cost, but the size of the overall LCD does. Each configuration comes in a variety of sizes. In other words, there are four different sizes of a 16x2 alone.

LED Backlight:

For nighttime readability, backlights are available as standard features on all character LCDs. The backlight will add between 50 cents to one dollar per LCD depending on the overall size of the glass.

There is no tooling (NRE) cost to add a backlight unless you are ordering a custom character LCD.

LED (Light Emitting Diode) have replaced older EL (Electroluminescence) displays.

Backlight power is independent of the LCD power, so it can be turned off and on to extend battery life.

LED half-life:

LEDs have a half-life of 50K to 70K hours if not overdriven, far exceeding the 4K half-life of EL technology.

Increasing the LEDs current will increase the brightness of the backlight, but also reduce the LED’s half-life. There are other ways to make the backlight brighter without overdriving it.

What is LED Half-life?

LEDs slowly dim over time. Half-life is the time, in hours, of how long the backlight can operate before its brightness is at 50% of what it originally was when first turned on.

So, if the half-life is rated at 50K hours, then the brightness of your backlight will be half as bright at 50K hours. If the backlight is on for an additional 50k hours, it will be half as bright as it was at 50K hours, or in other words, the LED will only be 25% as bright as when it was first turned on.

LED voltage options:

LED backlights are available in 3.3V (great for battery powered products) and 5V.

The five-volt option works better for colder temperatures.

LED backlight colors:

There are several popular LED colors, including: Yellow/Green, Blue, Pure-Green, White, Red and RGB (Red/Green/Blue).

There is not different in cost or lead-time for any color.

Next article:

  • Making the backlight brighter
  • Adding a heater for cold weather operation
  • Choosing an interface