Go Down

Topic: LCD Backlight (Read 522 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.

Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131