backlight of 2x16 lcd

FYP Starter Pack, ICs, Voltage Regulator, Resistor, Capacitor......

backlight of 2x16 lcd

Postby kwlew » Tue Mar 15, 2011 9:00 pm

Can i just directly connect the LED+ to 5V and LED- to ground, or need to connect the LED+ to the microcontroller pin?
kwlew
Newbie
 
Posts: 13
Joined: Thu Feb 24, 2011 11:40 am

Re: backlight of 2x16 lcd

Postby FloatingMachine » Wed Mar 16, 2011 11:13 am

You can connect the LED+ directly to 5V if you do not need to control the back light.

Otherwise, you can use a transistor to turn on/off the back light with your MCU.
FloatingMachine
Newbie
 
Posts: 10
Joined: Wed Mar 16, 2011 10:10 am

Re: backlight of 2x16 lcd

Postby Brian Griffin » Wed Mar 16, 2011 11:28 am

kwlew WROTE:Can i just directly connect the LED+ to 5V and LED- to ground, or need to connect the LED+ to the microcontroller pin?


You can do both, but for the microcontroller, connect it to a transistor first.

Btw, put a current limiting resistor inside with the LED too.
PIC - UIC00B from Cytron (replacement for my broken PICKit 2), Pickit 3, MikroC for PIC
dsPIC - MikroC for dsPIC, mikromedia board (dsPIC33)
AVR - AVR Dragon
Parallax - Prop tool
User avatar
Brian Griffin
Enthusiast
 
Posts: 403
Joined: Mon Jan 17, 2011 9:36 am

Re: backlight of 2x16 lcd

Postby kwlew » Wed Mar 16, 2011 3:03 pm

if i just directly connect the LED+ to 5V, then do i need put any resistor between it? if so, what value will suitable?
Thanks.
kwlew
Newbie
 
Posts: 13
Joined: Thu Feb 24, 2011 11:40 am

Re: backlight of 2x16 lcd

Postby ABSF » Thu Mar 17, 2011 2:15 pm

My GLCD backlight is using 4x SMD 100 ohms resistors in parallel making it 25 ohms. You may try resistors between 25 to 100 ohms. Just see which one is best for your eyes.

Allen
The next war will determine NOT who is right BUT what is left.
User avatar
ABSF
Professional
 
Posts: 810
Joined: Wed Nov 10, 2010 9:32 am
Location: E Malaysia

Re: backlight of 2x16 lcd

Postby FloatingMachine » Fri Mar 18, 2011 11:08 am

I always connect the LED+ to 5V directly without any problem. There are already a current limiting resistor on the LCD. Just that the 7805 might can a bit hot.
FloatingMachine
Newbie
 
Posts: 10
Joined: Wed Mar 16, 2011 10:10 am

Re: backlight of 2x16 lcd

Postby robosang » Sun Mar 20, 2011 11:31 am

I think Cytron did share about this in one of their article, the robot magazine, but cannot remember which version.

According to the author, the backlight can be directly connected with 5V, but the current consumption is quite high and will further increase the load of the 5V regulator, end up? Your 7805 is hot :D . The author share the method of controlling the backlight using PWM via a NPN transistor. With this configuration, you can control the brightness from the microcontroller and further control the current consumption.

And normally you don need such high density light to look at the character on LCD. You can try the value on SK40C's schematic, I just apply what is being use by Cytron and it work fine for me, if I am not mistaken is around 50 Ohm.
robosang
Expert
 
Posts: 1239
Joined: Wed Jun 10, 2009 5:37 pm


Return to Electronic Component

Who is online

Users browsing this forum: No registered users and 9 guests

cron