Method #2: Connect the LED backlight via A & K If you would like help, contact our US based technical support people at 48. This is a simple fix and is accomplished by reversing the jumper settings on the PCB (Printed Circuit Board). If you power up your LCD and find the display works, but the backlight is dark, then the LCDs backlight polarity is reversed. I would estimate that 50% of the LCD displays equipped with a LED backlight have pin 15 set to positive and pin 16 set to ground, with the reverse being true for the other 50% of the LCD modules. The interface table below shows pin 15 (Anode) to be positive and pin 16 (Cathode) to be ground. This is to help eliminate any noise in the circuit. Also the supply voltage for the LED is independent of the Logic voltage of the LCD (VLCD). This is the preferred method since all power and signal connections can be made through one header/ IDC cable reducing assembly cost. The most common method to supply power to the LED backlight is through pins 15 and 16 of the header. Method #1: Connect the LED backlight via pins 15 & 16 Other Display technologies such as TFT displays contain a built-in backlight that is on when the display is active and OLED Displays generate their own light and do not require a backlight. The majority of character (alphanumeric), segment (static) and monochrome graphic (dot matrix) LCD displays operate in low lighting conditions and require a LED (Light Emitting Diode) backlight. “ Will your LCD display require a backlight?” This is one of the first questions we ask customers when designing a new LCD Display and for good reason. All three methods will work, but not all are recommended.

This article will be limited to character LCD Displays and the three methods available to connect the LED backlight to a power source. Connect the LED backlight to Character LCD Displays:

Led cathode and anode