[Repairs] XO Backlights
Seth Woodworth
seth at laptop.org
Sat Oct 18 13:52:05 EDT 2008
On Sat, Oct 18, 2008 at 1:29 PM, Ian Daniher <it.daniher at gmail.com> wrote:
> Hello All,
> I'm working on a personal project(aquarium / grow light) involving the LED
> backlights of XOs.
> If any repair center has a few extra from broken screens and don't plan on
> using them, I'd be willing to pay shipping for these parts.
> *If you want to use them in your own project, here's what I've found:*
>
> - Twelve LEDs arranged as follows
>
> LA1... LA4 LB1...LB4 LC1....LC4
>
> - The connector has a single high(14v) line and three grounds. Each
> ground will drive multiple LEDs evenly spaced throughout. This may correlate
> with the above markings, but the LEDs are so bright as to make it difficult
> to tell.
> - Tying together the three grounds successfully allows me to drive all
> LEDs on the bar simultaneously.
> - I can drive the one positive terminal with 12v from a wallwart. I've
> used a computer PSU with great degrees of success.
> - The brightness of the LEDs may be controlled via PWM but is
> definitely controlled by grounding different combinations of the three
> ground terminals.
> - Reversing the voltage on the LED bar will cause between a sixth and a
> third of the LEDs on that bar to fail, indicating that, as expected, while
> all LEDs have very similar, they do not have the same electrical
> characteristics.
>
>
This last bit suggest to me that the LED's are wired in a certain way, not
that they have different properties. I'm confused. Do the lights shut off
on each bar that you have tested? Or just on a specific bar?
--Seth
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