I made a very interesting discovery last night when I was about to whip that LCD panel out the window for not working after all the effort I put into the project…

You probably already know where the panel came from, so I won’t repeat that.

The 50,000-foot view of the project is that I want to take an analog VGA signal coming out of a plain ol’ VGA card, and pass it into an old TFT LCD panel via its digital interface (6-bit RGB interface for a total of 512 colours). To simplify the project, I only want to use one bit per colour (8 colours total) so I’m not messing around with so much componentry.

The first challenge was getting power to the LCD’s backlight. As we may already know, there’s a CCFL (cold-cathode fluorescent lamp?) backlight on pretty much every TFT LCD out there — it provides the “backbone” of the bright light that emits from your LCD. Powering one of these things is a challenge as it requires about 400V (at about 2mA), with a kickoff voltage of about 1500V. I managed to find an inverter from my local electronics store that could supply a 900V kickoff with a 400V output, and after finding just the right wall-wart to power it, that did the trick.

After seeing a constant backlight, I worked long and hard getting the panel interface “buzzed-out” (using the continuity function of a multimeter to find out which pins correspond to which loose wires). After that, I attached all the loose cables to my breadboard containing a simple amplifier/inverter circuit and hoped for something on the screen. Nothing.

In the middle of all this, I grabbed a used oscilloscope on eBay (fantastic deal) and tested my circuit out the wazoo. Needless to say, the scope said it was all working perfectly. Whatever

I was convinced that everything was shot to hell (burnt panel, or destroyed circuitry somewhere), when I decided to just check the breadboard connections versus the pins on the interface connector on the panel. Sure enough, something wasn’t right.

I actually managed to label all the loose wires BACKWARDS! That’s right, pin 1 was labeled 15, 2 labeled 14, and so on. At least pin 8 was okay. ;)

Anyway. It now seems to work, as you can see in the picture. I rule.