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DC Neg. voltage generator

T

Tlafeir

Gawd
Joined
Sep 9, 2000
Messages
652
Hello,

From the labs of Tracy the great comes another frankeninvention...

A while ago, I came across a 6" sharp TFT LCD, that accepts only RGB+Composite sync inputs... After discovering how rather difficult and annoying the task is, I decide it wasn't wort the effort to configure it to my original needs (VGA monitor).

Today, after rummaging thru my closet, I come across my old 2.3" radioshack 'optimus' LCD tv... Its the old kind, tiny screen, CCFL backlight, battery hog. On a whim, I took it apart.. After checking out the circuit board I find 4 solder pads - R G B and CSync.. (Damn, I love old electronics, not all integrated.. ) Instantly, an idea forms (thing 1000w halogen) Yup, the guts of this TV are just begging to be mated with this LCD.......

Soooooo, the fun begins.. I have all the pinouts of the LCD, and I have the controller board of the system the LCD was ripped out of (inverter, etc). My biggest challenge at this moment (other than finding my solder) is to generate -8 vdc .. Any suggestions?
 
I know this is off the thread, in that it doesn't address your last question, but if you still wanted to use the 6" as a monitor the RGB + compostie sync. is quite readily available on your computer's HD15 VGA output. Pin 1, 2, & 3 are RGB respectivley and pin 13 & 14 are horizontal and vertical sync. To combine the sync. signals into one "composite sync." pulse simply use two 100ohm resistors... one end of each resistor attahced to pin 13 and pin 14 and the other end of the resistors combined to the sync in put of the LCD.


13 -/\/\/\/\-----|---------Composite sync. Input
14 -/\/\/\/\-----|

I have done this many times for this very purpose.


OT:
An adjustable negative voiltage regulator of the LM79xx family should work.
 
how much current do you need the -8 voltage to sink?

if it's less than 5A you can use an LM1084-adj, and adjust it to -8V...

if you're need more than 5A it may be better to go to a switching regulator...

THe datasheet for teh LM1084 tells you exactly how to generate a negative voltage
 
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