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Composite to VGA converter Circuit

Discussion in 'Electronic Design' started by [email protected], Dec 4, 2006.

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  1. Guest

    Hey guys, I have pretty basic electronics knowledge, but I'm looking to
    build a circuit that will convert a composite signal to a VGA signal.
    what I want to do is be able to watch TV on a LCD monitor, with out
    buying an expensive converter or expensive monitor with a composite in.
    I was wondering if someone could point me to a schematic for a circuit
    to make this conversion. I've found many circuits that convert VGA to
    composite, but I want to go the other way.

  2. krw

    krw Guest
  3. Guest

    Build??? Forget it, just buy one. And they're not expensive. They're
    like 99$, you can't even buy a good soldering iron for that. And you'll
    need a lot more than basic knowledge to pull this project off anyways.
  4. Good Luck!

    Just find a good school, sign up for whatever courses you need, and
    Go For It!

  5. I've been looking for something similar, with no luck so far. I have a pick
    & place machine which uses a B&W composite monitor (it has a single BNC
    connector) for the vision system. My suspicion is that this is only the "Y"
    portion of the composite. I've been wanting to replace this clunky old
    monitor with a standard flat panel, but most of the cheaper monitors only
    have SVGA.

    I'm not sure if a standard composite to VGA adapter box will work.

    Any thoughts?

  6. linnix

    linnix Guest

    I have an old PC (233 MHz) with the SAA7114 video capture card hooking
    up to a video camera. It capture approx. 3 frames per second and store
    them in a file server. I am using a standard SVGA monitor (flat panel
    can certainly work). I don't see why you can't do the same.
  7. JoeBloe

    JoeBloe Guest

    What he needs is an LCD TV, NOT an LCD PC display.
  8. What probably hasn't been explained to you is the complexity of pulling
    apart the composite signal then reconstructing it in to VGA (which is a
    form of RGB format).

    The most popular way is to digitise the composite video in to a video frame
    buffer... and the reconstruct the VGA (RGB) analogue signal.

    So you are going from analogue (composite) --> digital -->digital
    process-->analogue (VGA).

    This is a very high speed process and surface mount IC's with 100's of pins
    or more.

    Not recommended for Newbies!

    Now that I have steered you away from the design have a look at Averlogic

    Averlogic wont talk to anyone unless the Volume is 10,000 pcs or more.

    Just my 2 cents worth.

  9. Guest

    If you're still interested, read my post "Digital processing of analog
    TV broadcast". I should have a working prototype in about two weeks (I
    better, or I'm in trouble...). The first posts lists all the "blocks"
    you would need to build/buy. You wouldn't necessarily have to do it the
    way I am (digitally). But if you want to, you'll have to do a lot of
    surface mounting (plus make a PCB), or buy a starter board with the
    FPGA already hooked up. Either way would cost considerably more than
    buying something off-the-shelf, unless you have surface mount and PCB
    equipment already.

    Or, you could read some of the posts by other people (in the thread I
    mentioned), who suggest analog chips to get the job done. There might
    be some hope in doing that cheaply, but you'll have to do some design
    work on your own. I don't think many people have published a complete
    "guide" to doing it that way.

    But unless you are interested in this for the challenge, just check
    eBay. I think there are devices under $50 to do this. However, make
    sure they have a good comb filter - 2d/3d adaptive. You will actually
    notice the difference if they simply use a notch filter etc. No TV's
    nowadays do that (that I know), but some converter boxes and cheap PC
    tuner cards still do.

    The BEST solution would just be to buy a better cable tuner box. You'll
    need one anyway, of course. Might as well try to find one with VGA or
    DVI output instead of just composite. I don't have digital cable, but I
    think you can find digital cable boxes like this. Some modern TV's
    actually come with such inputs.

    Good luck
  10. Guest

    Just thought of one more thing. If you can even find a cable tuner box
    with COMPONENT video out (instead of composite), preferably with
    progressive output, then converting to VGA is a *lot* easier. I don't
    really buy the newest-and-best entertainment systems, so I don't know
    if this is common. You'll have to check or search google. If you find
    one of these boxes and are willing to buy it, I'd recommend starting a
    different post called "Composite video to VGA", and you might get more

    (Reason: For component video to VGA, you don't need a comb filter,
    chroma subcarrier lock, or QAM demodulator. You just need to extract
    sync and properly weight R, G, and B. I'd be extremely surprised if
    there weren't single-chip solutions to do that.)

  11. lemonjuice

    lemonjuice Guest

    The fastest way
    This one is LCD suitable

    Otherwise if you like building things.
    I have a circuit somewhere which we used that converts NTCS to VGA.
    If you don't want to buy anything all ready then I'll send it to you
    at your gmail address.
    The circuit we used decombines the horizontal and vertical sync
    signals and doubles the horizontal scan rate to the standard 31.47KHz
    or something like that, VGA standard by a reading process of a PLL
    at twice the write frequency of the A/D converter into a buffer
    memory. We used 3 6 bit converters for the RGB digital output and
    another 3 for the digital to analog conversion at the monitor input
    end but later discovered that 8 bit ones worked much better.
    Care has to be ensured in keeping noise between the modules down.
    The more space you can get between them the better they work.

    BTW 17" LCD monitors that work as TV's in my area cost only 50 bucks
    more then the 17" LCD monitors. Is it worth all the hassle building
    this stuff?
    And they cost only a bit more then 100 bucks the converter modules
    given above.

    The modules I gave above are not proffesional level equipment because
    the prices will be well above those levels but a lot depends on
    whether your eyesight can tell the difference!
    IMO your image still looks better on your TV or get the LCD/TV

  12. lemonjuice

    lemonjuice Guest

    Lucky you that you got sun there.
    Assuming you don't mean butt but buy. A scart signal usually has
    combined Horizontal and Vertical scan signal. You need to seperate
    those for monitors.
    Maybe you like this one

  13. It comes and goes, now comes, I am up the roof fixing it.
    Last week wind force 8, now they predict it again.... weather radar
    show showers generating upwind.....
    But 10 degrees C in December, I love it (could be -10 for that matter,
    for the US guys: 0 C means freezing).
    Yea sure, I type this between other things, never look at the screen....

    The VGA monitors will not work on SCART anyways, because the H freq range
    does not allow down to 15625 Hz.

    I like it, it is what the OP wants to make, but he wants it as exercise in FPGA.
    Sure cannot beat that price.
  14. JoeBloe

    JoeBloe Guest

    I noticed it doesn't mention what the output res is. Also, it just
    says "high resolution output picture".

    So it would be 640 by 480 or a 720 by something array size.

    Hopefully the latter.
  15. Guest

  16. Impressive.

    I was arguing against PAL in FPGA elsewhere in the discussion with the OP.
    (against doing PAL / NTSC demod digital), and I just found a warning in a
    German TV station (Vox) news bulletin that states:
    'Test HDTV receivers before you buy these on a normal PAL transmission,
    as those are still the majority you will view, and many of these new
    receivers show horrible PAL pictures'.
    It did not say if it was due to rescaling errrors from PAL to 1920x1080,
    or decoding errors, but clearly even these high end manufacturers
    either had no full size clue, or did cut corners.
    That probably can be traced down to chipsets used......
    But now they can say: 'See how bad analog PAL was compared with HDTV?'
    Chances are that if they ever looked at analog PAL in the studio they would
    think it was HDTV :)

    Video is all f*cked up, nobody has a clue, like audio, speakers with 1000W on
    a 12V 2A AC (or DC if you must) adapter, mp3 audio, soundblasters EMU10k1.....
    And 400 000 gates FPGA PAL decoders while you can do it _better_ with 5
    People are afraid of tuned circuits and inductors and trimpots.
    But OK mpeg2 rules..... makes little differerence, never did..... looks
    bad but they tell me it is better, so and I payed for it so it must be.

    It is a bit like buying a Volkswagen, and then reading all the Volkswagen
    adds that show you how great Volkswagen is, to stabilize your self respect
    so you convince yourself you made the right choice.
    Even every time the Mercedes overtakes you .
  17. jasen

    jasen Guest

    ISTM if you have a monochrome input you only need a sync detector

    something might be salvagable from an old TV....
  18. No, the VGA monitor will not work with TV line frequences (15625 Hz),
    check you moniotor specs.

  19. That might be a bit of an overkill. Think about how a color TV set
    works. The demodulated signal is essentially in composite format. The
    set's internal circuitry has to separate the individual color signals
    and extract sync signals from that.

    There are probably some one chip (plus a few discretes) solution for
    that suitable for sub $100 analog color TV sets.

    All this assumes the use of a multisync VGA monitor so as not to have to
    fiddle with scan frequency shifting.
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