Pololu 20x4 Character LCD with LED Backlight (Parallel Interface)

Overview

This 20-character, 4-line parallel liquid crystal display achieves a large viewing area in a compact package. It features a yellow-green LED backlight and uses the common HD44780 interface, so sample interface code is widely available for a variety of microcontrollers. This is the same LCD that is included as part of some of ourOrangutan X2robot controller packages.

You can find sample HD44780 LCD interface code written for a variety of AVR microcontrollers as part of thePololu AVR library.

Pinout

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.

The backlight in this LCD is composed of LEDs in series. The total voltage drop across these LEDs is typically 4.2V and the recommended current through the LEDs is 180mA. You should use a current limiting resistor R_LIMITas shown above where:

R_LIMIT= (V_BACKLIGHT– 4.2V) / 0.18A

In the diagram above, V_BACKLIGHTis shown as 5V, but you are not restricted to 5V; any voltage above the diode-drop voltage will work as long as you choose the appropriate value for your current-limiting resistor. 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 a2×8 shrouded box headerand 20",16-conductor ribbon cablecan be purchased separately. The box header can be soldered into the through-holes on the left or right side of the LCD PCB and the cable is designed to plug into the header.

16-conductor ribbon cable with 20×4 character LCD and 16-pin shrouded box header.