[Repairs] XO Backlights

[Ian Daniher]

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.

Best,
-- 
Ian Daniher
--
OLPC Support Volunteer
OLPCinci Repair Center Coordinator
--
it.daniher at gmail.com
Skype : it.daniher
irc.freenode.net: Ian_Daniher
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