Character LCDs: An Engineer’s Choice for New Designs
WHAT IS A CHARACTER LCD?
Character displays are low-power and an excellent choice for portable, battery powered products such as medical, industrial and data Loggers. These displays are popular because they are inexpensive, are easily programmed, have a wide range of sizes available and have short lead-times, They will also continue to be in production for many years.
Character displays do just what their name suggests. They display characters such as letters, numbers and punctuation marks. Custom programming can create charts and graphics.
Below is a breakdown of display options available for any character LCDs.
8×1 Character LCD with LED Backlight
Mounting holes are the copper plated holes on the edge of the PCB where screws are inserted to attach the LCD to the customer’s mother board.
Mounting holes on each corner of a character LCD with copper plating
Character displays are classified by the number of characters they can display.
A 20×2 means there are 2 rows of 20 characters. Other popular sizes include: 8×1,16×1,16×2, 20×4 and 40×4.
The overall size of the LCD glass is what determines the piece price. The larger the glass size, the more expensive your display will be.
20×4 character LCD with blue LED backlight.
There are three types of fluids available for a monochrome character LCD.
TN (Twisted Nematic)
TN is the cheapest and has low contrast, but it performs better in colder temperatures than STN and FSTN. A great option when pennies count.
STN (Super Twisted Nematic)
STN provides a wider viewing angle than TN for about a 5% increase in price. Most character displays are STN.
FSTN (Film Super Twisted Nematic)
FSTN provides the widest viewing angle and sharpest contrast. This fluid is the best choice for medical, aviation and automotive products.
BACKLIGHT: LED BACKLIGHT
LEDs ( Light Emitting Diodes) are an older technology, but recent improvements have greatly improved its brightness. LEDs are now the industry standard, replacing older EL and CCFL backlights.
LEDs are DC (Direct Current) and can be driven directly off batteries. DC doesn’t generate any noise or electrical interference associated with AC (Alternating Current).
They are available in a wide selection of colors including: Red, Blue, White, Green, Yellow/Green, RGB (Red, Green, Blue) and many others. There is no price or lead time difference between colors.
Transmissive polarizers are used when the display will only be read with a backlight on. This type of polarizer is great for products that will be used indoors only or in low light only conditions.
Transflective polarizers are excellent for direct sunlight and allow a backlight to be used for nighttime operation.
Reflective polarizers are the best for direct sunlight, but they will block the illumination of your backlight.
STN Character LCD with transflective polarizer and LED backlight for daytime and nighttime operation
TEMPERATURE RANGE: -30C TO +80C
Adding a heater or heat film allows a character display to operate in colder environments. Focus Displays can add any additional hardware necessary to keep your display operating as the temperature drops below -30C.
All character displays contain a built in Controller/Driver (C/D) for quick/fast programing. Many have the option to choose between 4-bit or 8-bit MPU interfaces,
The C/D contains a built-in character table that eliminates the need to address and refresh each dot. Instead, the customer’s processor transmits a hex number to the C/D to display the desired character.
Controller Drivers on a Custom Character LCD
6:00 or bottom view is the most common viewing angle for character displays. If you’re not sure which one to choose, opt for bottom view.
Other options include 12:00 (top view), and 3:00 and 9:00 (rare)
DOT CONFIGURATION: 5X8
Each character has five (5) dots in the X direction and eight (8) dots in the Y direction. It is possible to order a display with additional dots, such as 10×12, to create larger characters. The larger characters improve readability at a distance.