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Topic: LCD Backlight (Read 591 times) previous topic - next topic


I have got an 16X2 LCD HD44780 form Spark Fun working that shows a temperature reading.  I am using the LCD 4 bit library and it works fine.  My question is , how do I turn on backlighting?  I believe this is available on pins 15 & 16 from the LCD.



Look at the data sheet but normally you just apply power to the pins.


Just don't forget to check the documentation for the display to see if a current limiting resistor is needed.

I almost fried a display by not putting a currentlimiting resistor in line with the power to the backlight.


If it's an LED backlight, it almost certainly needs an external current limiting resistor.  There's a chance it has one built in, but I wouldn't risk burning out the backlight by just applying power without confirming it.

LCD's also use EL-backlights, which are more difficult to power (they need high voltage, high frequency AC at very tiny current), but I doubt a nice modern purchase from Sparkfun would use that.


Hi - Thanks for the advice.  Here are some of the specs from the datasheet.
Can I just connect a resistor and an on off type button between pin 15 and pin 1?

1. 5X8 dots with cursor
2. Built-in controller (KS0066U or Equivalent)
3. +5V power supply(Also available for +3.0V)
4. 1/16 duty
5. BKL to be driven by pin1,pin2,or pin15,pin16,or A,K
6. N.V.optional

Pin #  Symbol    Function
1.        VSS       GND
2.        VDD       +5V
15.        A        +4.2V for LED
16.        K        Power supply for BKL(0V)


Can I just connect a resistor and an on off type button between pin 15 and pin 1?

It is pin 15 to Pin 2 through a resistor.
You will also need to connect pin 16 to pin 1



15.        A        +4.2V for LED
16.        K        Power supply for BKL(0V)

Just to clarify, A stands for Anode which you connect to positive, K stands for Cathode (yeah, it's confusing), which you connect to ground.

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