VGA connector to Composite video!

[xheavenlyx]

Well, this must be there somewhere, but cannot find the exact thing I am looking for So I am presenting this wierd thought provoking idea...

You know you PC has a VGA(Video Graphics Array) connector output to your LCD screen (the 15pin) and many of salvaged LCd's use the composite video input.

So i was thinking if its possible to make a rough converter for this. Well to take care of the resolution we can set it explicitly on the PC side. I am asking about this so that I can connect a small LCD I have (emerson dual lcd crappy dvd player) to my laptop screen output which is a VGA out.

I have seena few converters but well, since we are already crazy, then its better to make one.

Any ideas?


Here are ome refferences:
http://en.wikipedia.org/wiki/VGA
http://www.mp3car.com/vbulletin/showthread.php?t=51041 (mp3car.com amazing forums!!)


Products:
http://www.grandtec.com/ultimateEZ.htm
http://www.ramelectronics.net/html/PC-TV_GWB-4000.html (Wireles!!!!!)

[atari2600a]

They operate at different frequencies. Composite is ~15KHz, & VGA is ~35KHz. Plus, VGA consists of sync, R, G , & B. Composite consists of Chrominance(sp?) & Luminance signals. It will be hard building a converter yourself (if you're up to the challenge)...

[gannon]

Fairly easy to get RGB out at 15Khz if you force it using a program like Power Strip, but I don't think you can just combine the RGB signals and sync to get composite, you need to put it through an IC.

Considering the price of the components and the fact that most are SMT only, it'd be easier/cheaper to get a card with tv out or buy a cheaper converter box.

[tom61]

I've only seen a DIY converter to PAL or black and white video:
http://www.epanorama.net/links/videocircuits.html#pc2tv

However, if you're really a hardcore programmer, the shear and utter bandwidth availible each RGB pin is more than enough to do composite video on its own. Think about it, your card has to vary the signal quite fast (vertical 60Hz times horizontal 31kHz refresh rate for basic 640x480, and the refresh rates go up dramitcally from there) and at two to the eigth power variable output. Since you can get basic composite out of a fast PIC, a video card should be able to drive a full-color display.

[timmeh87]

with some cards you might be able to force NTSC resolutions with powerstrip directly.

my matrox millenium G400 supports composite striaght out of the vga port.

[xheavenlyx]

lol, I guess Ill stick to the converter, thanks a lot though!

Basically, having an LCD lying arround is fruitful, but not enough if it cant accept VGA inp.

I can use it as a second screen at home though:) connect it to my PC Video card's composite outp or use it as a portable game console monitor. But for a portable car PC I guess its better to buy a normal VGA TFT, i guess (or use the converter)

[adric22]

Actually, YES you CAN output NTSC from a VGA port. I was amazed myself..

Check out the bottom of this page:

http://galaxy22.dyndns.org/shuttlecraft ... index.html

The way the PS-One screen is running in DOS is by using a TSR program which you run that will reconfigure your VGA card to output an NTSC framerate and sync. The catch? The catch is it will still be RGB when it comes out. If you want to run it into a composite device, you have two choices. One is to take one of the colors (probably green) and make that the luminance signal. Or, you can take all 3 and combine them together to make a luminance signal. So the thing is, you are only going to get grayscale... but you can literally run a TV from any VGA port with just a cable and a couple of resistors. As long as you don't mind it being in black and white. Besides doing this on my PS-One LCD, I also did this on a regular color television set (with the black and white method) and it was surprisingly readable.

Another catch.. If you are using a laptop computer, you will likely need to set your LCD/CRT mode to external output only. Otherwise, if your internal LCD is still active, it will screw up the sync rates.

Also.. so far this method only works in DOS and in Linux / Xwindows. The Windows drivers always set the sync back to normal. However, some video cards have a windows control panel (Like powerstrip) which would allow you to set it back to 15 khz.

[gannon]

But as I've mentioned, another problem occurs while trying to convert the rgb+sync to composite.

[xheavenlyx]

Well, here is a site I came accross from mp3car.com . May be helpful.

http://mpro.no-ip.com/lcd2.htm

Here the VGA 12 pin connector can be connected directly connected to the inputs of the LCD but NOT the composite video input of the LCD.

So for this we have to open up the screen

As some have pointed above, the method is directly to the power strip!

[gannon]

Yep, RGB is fairly easy with either powerstrip, special drivers, or linux. Although to get true C-Sync you need circuitry, just combining H & V-sync normally works fine.