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How can I wire a computer monitor to be used as a light table for tracing/drawing.

Discussion in 'LEDs and Optoelectronics' started by electrocutedUnlessHelped, Nov 27, 2013.

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  1. electrocutedUnlessHelped


    Nov 27, 2013
    This is what I have:

    I'm trying to use this battery holder:

    There are two lamps on the top and two lamps on the bottom of the "glass/plastic/whatever", you can see in the photo that the two pink wires are positive going in for each bulb and one white one for the negative(I assume?).

    My question: I apologize if this seems like a simple question to some of you, but I want to be completely sure on how to wire the battery holder into the pink and white wires. Because the battery holder is 12V, can that be split upon two lamps? Or would I need 24V to power two 12V lamps? They ARE 12V lamps, right? Someone told me all LED lamps are 12V. Is it possible to just put the positive battery wire onto BOTH the pink wires?

    In the photo you can also see that I have the inverter (brown chip), is there any way to cut out the green chip and just wire a switch onto that to turn it on instead of requiring the green chip?

    Any information is gladly appreciated!
    Last edited: Nov 28, 2013
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Those white/pink wires got to cold cathode lamps which require several thousand volts to light, and operate at a few hundred volts.

    12V aint going to work.

    Not sure what brown chip or green chip you're talking about (They're generally all black). But my answer would be "No, you probably can't do that".
    Last edited: Nov 30, 2013
  3. Solidus


    Jun 19, 2011
    The inverter is the whole white-ish board assembly. In standard computer monitors, this voltage is stepped up from 12 or 5V to a couple thousand (initialization) and then to several hundred for operation.

    This appears to step the voltage down from 120V to fire the inverter circuit. It would be possible to determine the output end from the input and "jumper it" - that is, provided it steps down to 12V.

    What is the bigger issue here is that

    a) the current for these lamps (not including this display itself) will suck the batteries dry in minutes or so. They require a few mA at several hundred volts, which could be close to an amp or so at 12V.

    b) unless the display is configured as 'normally white' (which it probably isn't), not firing the display with data results in a backlit, but black (not white) image - that is, the pixels in their undriven state are 'off' instead of displaying an inert white. You will have to consult the datasheet to see if this is the case. You can push the image with 'dummy data' but that requires some logic design as well as implementing the display (probably LVDS) protocol.
  4. davenn

    davenn Moderator

    Sep 5, 2009
    The white board is the main SMPS for the monitor, only a small section on the left side is the inverter for the LCD panel fluro's

    Last edited: Dec 3, 2013
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