20x4 Character LCD with LED Backlight (Parallel Interface), White on Blue
This 20-character, 4-line parallel liquid crystal display provides a large viewing area. It features white text on a blue background with an LED backlight and uses the common HD44780 interface, so sample interface code is widely available for a variety of microcontrollers. This display is electrically compatible with the LCD that is included as part of some of our Orangutan X2 robot controller packages, although the physical interface is different.
You can find sample HD44780 LCD interface code written for a variety of AVR microcontrollers as part of the Pololu AVR library.
|1||Vss||ground (0 V)|
|2||Vdd||5 V logic supply voltage|
|4||RS||H/L register select signal|
|5||R/W||H/L read/write signal|
|6||E||H/L enable signal|
|7-14||DB0 – DB7||H/L data bus for 4- or 8-bit mode|
|15||A (LED+)||backlight anode|
|16||K (LED-)||backlight cathode|
Using Contrast and the Backlight
As shown in the diagram above, a potentiometer whose output is connected to Vo will allow you to set the contrast for optimal viewing of your display.
This LCD has an LED backlight. The voltage drop across the LEDs is typically about 3.2 V and the recommended current through the LEDs is 72 mA. This LCD includes a 25.5 Ω resistance (two 51 Ω resistors in parallel) in series with the backlight, so an external current-limiting resistor is not required for backlight supply voltages up to 5 V. For higher voltages, you should add a current-limiting resistor RLIMIT as shown above where:
RLIMIT = (VBACKLIGHT – 3.2V) / 0.072A – 25.5Ω
Any voltage above the diode-drop voltage will work (as long as you choose the appropriate value for your external current-limiting resistor for voltages over 5 V). You can also use a PWM-controlled MOSFET to achieve variable dimming of the backlight if so desired.
Note: No cables or connectors are included with this product, but a straight or right angle male header can be purchased separately to be soldered into the through-holes. We also have 1×16-pin female headers and crimp connector housings to mate with the male headers. This LCD is intended for use with 5V systems.
|Size:||98 x 60 x 14 mm|
|Viewing area:||76 x 26 mm|
|Dot size:||0.55 x 0.55 mm|
|Character size:||2.95 x 4.75 mm|
|Minimum logic voltage:||4.8 V1|
|Maximum logic voltage:||5.2 V1|
|Typical LED backlight voltage drop:||3.2 V2|
|Typical LED backlight current:||72 mA|
|Supply current:||1.2 mA|
- HD44780 interface datasheet (330k pdf)
- This document details the HD44780 parallel interface that is an industry standard for dot-matrix LCDs.
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