LED BACKLIGHT

Features

• LED backlit modules are 2-5mm thicker than an EL or non-backlit module.
• Longer life ( more than 100,000 hours ) than EL lamps at the sacrifice of power and module size.
• Operation is possible by the same +5 V supply as used for the modules. (Standard color yellow-green)
• The LED backlight illumination is available in yellow-green, green, white, red, and amber.
• The brightness of the backlight can simply be adjusted by a resistor or a potentiometer
• In most cases, 1 lamp failing does not make the backlight unusable.

Using Methods of BKL

There are 5 methods of using LED in character type:

• This is the most common type to light the LED by external of 4.2V to Jp2 between pin 1 and pin 4.
• Lighting the LED through a limiting current resistance which we already included in our LCM by external voltage of 5V to Jp2 between pin 1 and pin 4.
• Providing 4.2V by pin 15 and pin 16 of the interface to light LED.
• Providing 5V by pin 15 and pin 16 of the interface to light the LED through a limiting current resistance which we already included in our LCM.
• We can light the LED only by inner voltage through a limiting resistance without any external power supply.

Resistors for LED Backlight

Limit resistors must be used for array backlit modules. Refer to the specific module specification for recommended and/or maximum backlight ratings. LEDs are arranged in serial pairs and operated in parallel . The lamp will require 4.2VDC. Brightness can be set or controlled by selecting the proper limit resistor. Select a resistor that will drop the remaining voltage at the desired current. For example, if 200mA produces the desired brightness and the supply voltage is +5VDC, the limit resistor will drop 0.8VDC (5.0 - 4.2). Therefore, E/I = R = 0.8/0.2 - 4ohms.

Variable brightness can be controlled with a digital potentiometer or pulse-width modulated circuit.