VGA to composite wiring

RabbitwabbitRabbitwabbit
edited July 2009 in Hardware
Hi, from a 15 pin VGA socket, does anyone know which pins you would use to connect into the video component plug (the yellow plug). I know what the pin out diagram looks like, but I'm struggling to know which pins to use to carry the signal.

Comments

  • lordbeanlordbean Ontario, Canada
    edited July 2009
    I've never heard of a VGA to composite adapter... any video card that's been TV-compatible has always come with a round plug of some sort that either directly or through a manufacturer-specific adapter plugs into composite...

    That, and the adapter for DVI to HDMI, but that doesn't help in this case.

    This may not mean that it's impossible to do, but I'm inclined to think the VGA signal just isn't compatible with standard composite.
  • RabbitwabbitRabbitwabbit
    edited July 2009
    Lordbean, Many Thanks for your response - and this may very well be why I'm struggling. I have seen a number of aftermarket converters such as this http://cgi.ebay.co.uk/VGA-TO-RCA-S-VIDEO-COMPOSITE-Converter-CABLE-ADAPTER_W0QQitemZ400058745734QQcmdZViewItemQQptZLH_DefaultDomain_3?hash=item5d255c0386&_trksid=p3286.c0.m14&_trkparms=65:12|66:2|39:1|72:1690|293:1|294:50
  • lordbeanlordbean Ontario, Canada
    edited July 2009
    Well, if the adapters exist (which apparently they do), it obviously isn't impossible... I wouldn't even know where to start in terms of the pinouts though.
  • RabbitwabbitRabbitwabbit
    edited July 2009
    Many thanks anyway. If I find it I'll post the answer.
  • RichDRichD Essex, UK
    edited July 2009
    What you ar e describing is not component. Component has three separate plugs for video one for red, one for green and one for blue signal. You then have a separate cable for audio. What you are describing is a standard AV phono where all three colours are sent down the same core.

    What are you trying to do? As we may be able to help with an alternative solution.
  • ardichokeardichoke Icrontian
    edited July 2009
    Rich, he didn't say component, he said composite, which is correct. Composite uses one barrel plug for video and two for stereo audio.
  • RichDRichD Essex, UK
    edited July 2009
    ardichoke wrote:
    Rich, he didn't say component, he said composite, which is correct. Composite uses one barrel plug for video and two for stereo audio.

    Composite in the heading component in the text.

    If it is composite then I dont know if it is possibel as I suspect that VGA uses a component output which means you will need something to combine the signal.
  • lordbeanlordbean Ontario, Canada
    edited July 2009
    He described composite, and the adapter on ebay he linked is composite, so that's what I assumed it was. This is why I said I've never seen an adapter before... I suspect the signals are quite different.
  • RabbitwabbitRabbitwabbit
    edited July 2009
    Guys - Thanks for your comments - and I can confirm I am referring to composite. I was hoping to butcher a VGA plug and output to a yellow composite plug as the input device I want to go into only has composite input.
  • ardichokeardichoke Icrontian
    edited July 2009
    It may be possible but from what I've read it will require some circuitry. I can't seem to find any schematics premade so you would probably have to find the VGA specification and the composite video specifications then develop a circuit that will convert them. If you're not that skilled in electronics you'd need to find someone who is (my roommate from college could probably do this... if he weren't lazy). I'd say the the opportunity cost here is higher than the cost of just buying that cable from ebay.
  • ThraxThrax 🐌 Austin, TX Icrontian
    edited July 2009
    Circuitry is required for this kind of conversion.
  • RabbitwabbitRabbitwabbit
    edited July 2009
    Ardichoke, I'm tempted to agree with you, but the picture on Ebay just seems to be the vga plug straight to composite (unless there's some wizardry built into the vga plug itself). I'll have to buy one, use it, then pull it apart just to satisfy my tiny mind.
  • RabbitwabbitRabbitwabbit
    edited July 2009
    Thrax, Thanks - I'll bow to your superior knowledge.
  • ardichokeardichoke Icrontian
    edited July 2009
    The circuitry is probably minor enough that they can do it in-line and hide it in the wires insulation. My EE roommate in college did this with an S-Video to composite converter that he designed and made. Unfortunately he used a soldering gun that was too powerful and damaged a capacitor causing the picture to be black and white instead of color.
  • lordbeanlordbean Ontario, Canada
    edited July 2009
    Who wouldn't want to watch the matrix in black and white?

    But seriously, I find that interesting. I didn't know it was possible to implement an inline circuit like that.
  • drasnordrasnor Starship Operator Hawthorne, CA Icrontian
    edited July 2009
    Composite simply combines the separate luma and chroma signals present in S-Video so that circuit is fairly trivial to implement inline. On the other hand, the conversion from VGA to composite is not trivial. Not only are the electrical signals completely different in structure but the content of the signals are also completely different.

    On the plus side, there are some ASICs that make the conversion magically happen. You can find them in cheap Chinese electronics like the one your eBay link points to.

    -drasnor :fold:
  • RabbitwabbitRabbitwabbit
    edited July 2009
    Thanks everyone - I'll go and buy one as it appears to be much more complicated than I first thought.
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