Reduce backlight of custom lcd controller manually

Hello World,

I am not sure where to put this question, but here i think are a lot of smart people with a lot of knowledge and understanding of hardware and software.

I am building my own custom ardunio laptop. I am using a LCD controller kit that i have hooked up to a display.

Everything is working, but the battery for the screen is using to much energy. Also the brightness of the screen is too much. Using hardware and software switching makes the screen appear less bright but this is not really effecting the back-light. It just makes it look like so.

Using my brain i figured out what cables are used for only the back-light of the LCD. Which raised extreme interest in lowering the brightness somehow.

I want to put an resistor in between the cables in a way that the brightness will be lowered.

However i have no clue what cables, and what the cables mean. And i hope someone here can tell me this, or redirect me to some other forum where i can be helped.

The link to the LCD controller manual : http://m5.img.dxcdn.com/CDDriver/CD/sku.275804.pdf

I took a photo of the cables that are used for the back-light, could not upload it here so :

http://oi67.tinypic.com/2r4os9j.jpg

Thanks for help !

bump

idmaster: bump

All right, all right, that is generally considered bad manners here, but I didn't see the original so ...

idmaster: I am not sure where to put this question, but here I think are a lot of smart people with a lot of knowledge and understanding of hardware and software.

Well, I doubt we would dispute that. :roll_eyes:

Yes, "Displays" sounds as good a spot as any.

idmaster: Using hardware and software switching makes the screen appear less bright but this is not really effecting the back-light. It just makes it look like so.

Now what do you mean by that?

Do you mean "PWM"? "Pulse Width Modulation" is switching the light (that is, the backlight) on for only a proportion of the time, so on average, its brightness is reduced. That is exactly what you want to do. If however you mean altering the LCD drive to darken the screen, then clearly that is not going to work so well.

So are you controlling (switching) the backlight or not so far?

idmaster: I want to put a resistor in between the cables in a way that the brightness will be lowered.

No you do not. That means most or all of the power is wasted in the resistor - you reduce overall power consumption, but not by as much as you reduce the light output.

What you want to do is to use PWM, though if it is a scanned (continually refreshed) display you will have a problem as there will be an interaction between the backlight switching on and off and the part of the screen which is scanned at that moment. In that case, you need a switchmode constant-current converter which efficiently feeds a reduced current to the backlight (all this, presuming the backlight is in fact LEDs) using PWM but smoothing the current with an inductor.