How to implement NTSC video output to an oscilloscope ?

Discussion in 'The Projects Forum' started by Externet, May 30, 2016.

  1. Externet

    Thread Starter AAC Fanatic!

    Nov 29, 2005
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    Hi.
    For a plain old analog oscilloscope, would it be too complex ? How is it done ? There is NTSC generator IC's, to produce composite video; but how to manipulate the non-raster oscilloscope signals ?
     
  2. joeyd999

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    Jun 6, 2011
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    It be much easier, and cheaper, to buy an old black-and-white TV on eBay and call it an oscilloscope.
     
  3. Externet

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    ¿? Question was not about easy or difficult, nor price, nor color or not, nor where to buy, nor pretending what it is or it is not.
     
  4. bertus

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  5. Externet

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    Thanks. o_O Sorry, cannot understand. Implementing a composite video output connector to an oscilloscope in order to display the signal in an external "TV" like display.

    That chip seems to be the reverse. :(
     
  6. bertus

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    Hello,

    For showing a picture on the scope, you would need sawtooth signals that are in sync with the incoming signal on the X and Y channel.
    The Z (intensity) channel would have the video signal as input.

    Bertus
     
  7. joeyd999

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    Yes. And a black-and-white TV does *exactly* this. That was the point of my post above.
     
  8. BR-549

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    Sep 22, 2013
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    An NTSC signal needs to sync with a raster to display the video.
    A scope is a vector (non-raster) driven device.
    An old analog tv receiver will give you that raster, that the NTSC signal needs.
    Like joey and others have said.
    You will need a NTSC source also. There are converters that receive digital signals from the antenna and give a NTSC output.
    For your old analog set.
    One can look at an NTSC signal on a scope, and see the video signal between syncs, but it doesn't look like a picture. It's just one line of a picture.
     
  9. Externet

    Thread Starter AAC Fanatic!

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    It is not about showing any picture on the scope. It is about showing the waveform on an external composite video display. "Implementing a NTSC video output to an oscilloscope" Perhaps re-wording different... Adding a composite video output connector to your oscilloscope rear panel.

    And you still have it wrong !
    How will you transfer the waveform shown on an oscilloscope to your easy cheap ebay b&w whatever tv screen ?
     
  10. GopherT

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    Nov 23, 2012
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    Why do you want to do that?
     
    joeyd999 likes this.
  11. bighand

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    Apr 2, 2009
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    The problem with this is that the horizontal sweep time of the built-in display varies according to the timebase you're using, while an external display is built for a specific type of video signal only and is expecting a fixed line frequency of about 15kHz. You can't just feed the signal into the external display because the display won't be able to lock onto the signal.
     
    Last edited: Jun 1, 2016
  12. Externet

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    Nov 29, 2005
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    Yes. Agree. Fully. That is one of the hurdles.
    Now, what circuitry would have to be implemented to 'mount' the oscilloscope displayed waveform onto a composite sweep ?

    The dumbest way would be aiming a little cctv camera to the oscilloscope screen. There you go. Composite output, instantly.
    Now; how to do it electronically tapping the oscilloscope circuitry ?
     
  13. kubeek

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    Sep 20, 2005
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    Digitize the trace, convert to raster and output as ntsc? Unles you want to hack the TV into an independent x and y, aka oscilloscope, then I don´t see a lot of different options.
    This might be possible in analog, but i guess the need to store the trace and process it will still be there.
     
  14. RichardO

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    May 4, 2013
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    What you need is one of these? :D Some versions allowed the stored image to be scanned off the CRT for printing. :)
    https://en.wikipedia.org/wiki/Tektronix_4010

    Or... maybe a scan converter instead of a o'scope. ;) A scan converter uses (used) a tube that was sort of like a CRT of an X-Y scope with a TV camera looking at the screen. :)

    I believe that the ones I worked with had magnetic deflection for both writing and reading the stored image. Maybe you can find one surplus. They were made decades ago by Hughes Aircraft and a company I can't remember the name of right now.
    http://www.google.com/patents/US4212072
     
  15. RichardO

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    I got distracted with scan converter history and forgot to mention that searches for "scan converter" and "scan converter vga to composite" turns up some modern digital ones that can convert from computer screen format (such as VGA) to NTSC.

    I assume that you want "real time" video so using a DSO that outputs a computer file of screen shot is a nonstarter...

    Note that a USB scope can do same. But when used with a scan converter you can get real time TV video.

    p.s. The other company that produced tube-based scan converters was Princeton Electronic Products.
     
  16. AnalogKid

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    Aug 1, 2013
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    It's still not clear to me what you want to do:

    1. Display a stable composit video signal on a scope screen - the video signal voltage with horizontal and vertical sync pulses, not the viewable image.
    2. Take a composit video signal and display the video image on a scope screen.
    3. Convert some arbitrary signal displayed on a scope screen into an NTSC video signal that can be recorded and /or displayed on a TV monitor with a composit video input.
    4. Something else.

    1 is the easiest, and needs sync separator circuits. 2 is creating most of the guts of a TV, without the high power magnetic deflection amplifiers. 3 is the hardest, and is basically a scan converter as mentioned above. It may not be as sexy as an all-electronic circuit solution, but nothing will give you faster, guaranteed results than a camera (of whatever output format you want) pointed at the scope screen. This is how the first scan converters in the 60's worked for things like the Gemini and Apollo missions video, satellite video from Europe, etc.

    Massive amount of video systems information:
    http://www.epanorama.net/links/videosignal.html

    ak
     
    Last edited: Jun 6, 2016
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