fun with an old LCD panel
Tuesday, October 24 2006
I have an old NP-943 486-based laptop with a greyscale screen. It was my first laptop; I'd exchanged a painting for it back in 1998 when I was planning on using it as a roadtrip computer. (In the end I used a more powerful laptop given to me by a reader and later destroyed by Bathtubgirl in a completely unnecessary fit of rage.) Yesterday I fired up the NP-943 for the first time in years thinking maybe I could figure out a way to make it into a dumb terminal (which would be useful as test equipment with my Arduino projects). While the laptop sounded like it was going through part of the boot process, the screen remained featureless. I tried all the usual tricks but could not get it to come to life. Without a screen it was never going to be a dumb terminal, so I gave up on those plans and decided to experiment with its LCD panel instead. Unlike most LCD panels, this one only had a few wires sending it data. And these were discrete wires too, not printed copper on a transparent ribbon of plastic. Maybe I'd lucked out and this was an internal VGA interface, one I could tap into for my own uses. So I quickly rigged up a VGA test cable to one of my least-necessary PCs so it could generate a low-resolution VGA video signal. By test cable, I mean that one end had was just a bunch of wires with stripped ends to which I could attach other wires with alligator clips. I then tried different connections between these wires and the LCD interface, hoping that a miracle would happen and suddenly there'd be a picture of a BIOS setup screen. But all I got were trippy visual effects, many of which were highly organic in appearance. It wouldn't be diffult to make a sort of flat-panel lava lamp using a panel like this and some circuitry to give it a random series of voltages. With this in mind, I tried feeding an audio signal to some of the LCD panel's pins, but it didn't seem that the audio signal was powerful enough to alter the picture in any observable way.
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