Mechanical scanning television

This project explores the early days of television. Above you see a view from the back side of a mechanically scanning television. The black disk spins and the holes, aligned in a spiral pattern, create vertical scan lines for projected light to shine through. In this case, [Eckhard Etzold] is using red, green, and blue LEDs to create a color picture. As you can seen in the video after the break it does a pretty good job. The main problem being that the scanning disc on a mechanical TV has to be much larger than the actual image. How big would the disk need to be and how fast would it spin to produce a forty inch image? We still think this is a better method than transmitting video data in parallel.

Disc spin-up

Color video demo

[Thanks LeJupp]

34 thoughts on “Mechanical scanning television

  1. If they were concerned about how big the spinning disk would get, I wonder why they didn’t replace it with wide strip of something with holes in it. Like a long loop of leather that can be folded on rollers into a more compact box. That would also get rid of that distortion in the image.

  2. The embedded video doesn’t show this off very well, but gives you a good idea of whats going on.
    This video shows it up to speed and in full colour, even if I don’t support the choice of video:

    I think it’s a great project and yes, why don’t these TVs use the side of a drum instead of the flat of a disk. This would simplify alignment at the cost of having a non-flatscreen display I guess.

  3. Most awesome mechanical TV’s use a mirror screw, which is an awesome sight even all by itself. But unlike the Nipkow disc, the screw is notoriously hard to manufacture. I’d like to see some drum-TV’s too, though.

  4. They have been around for longer than a regular TV.

    As 23-year-old German university student, Paul Nipkow proposed and patented the first electromechanical television system in 1884.[1] Although he never built a working model of the system, variations of Nipkow’s spinning-disk “image rasterizer” for television became exceedingly common, and remained in use until 1939.

    This design predates Regular tube TV’s by a VERY long time.

  5. Perhaps svofski can make one of these out of another old hard drive? :-) I think if spun at 7200rpm and the platter is divided up into 8 segments, it is possible to get 30fps at 32 lines, or 15fps interlaced with 64 lines (and really tiny holes)?

  6. This gets all kinds of awesome coolness points, but it’s a lot easier to build one when you can use a computer to supply the data. Try it when the only signal source is ANOTHER spinning wheel and you have to match both its speed and phase exactly… and then deal with variable radio reception conditions. Despite all that there was quite a lot of hobby level work on TV before the CRT was harnessed to do away with the mechanical scanner.

    The reason they didn’t use a cylinder or bandsaw blade is that that disk is rotating really, really, really fast. You can see how long it takes to spin up in the first vid. And you have to get an even and rapidly variable light source as large as the image on the other side of the scanning pinholes.

  7. The vertical black bars are an artifact of the video, like recording an old CRT monitor with a camcorder.

    32 line mechanical TV runs at something like 12.5 FPS, the camera records 30. They don’t divide evenly, hence the scanlines.

    This is really impressive stuff, considering the video fits in a single mono audio channel and can be produced completely by analog means (if you were determined to do so).

  8. @localroger: both transmitting and receiving discs were driven by synchronous AC motors, there was no other sync, but AC was good enough. Phase could drift away though, and there were even wired remote controls that would let you adjust the phase without standing up.

    Re: HDD reuse, heh. I thought of that. But you need a large disc for sufficiently large display. Like in this project in the article: it’s a necessity. HDD platter would give image like 10mm across and the holes would have to be very precise and small. Maybe a vinyl LP disc spun at 7200rpm? I don’t know, sounds totally safe :D

  9. @LeJupp: I can’t find it now, but I remember reading a story about an (I think Australian) inventor who built a giant Nipkow disc TV set and got killed when the disk broke or fell lose.

    But I can’t find any reference material now so I could just had had a bad dream :)

    1. Mechanical television you have many ways of making a camera and televisor google NBTV forum and you will see the many ways to do this as a hobby .
      Believe me every way under sun has been thought of The nipkow disk is the easiest way .I enjoy the harder ways my self .

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