Mechanical Television: Incredibly simple, yet entirely bonkers



in my last video we explored how analog television works you can check out the whole video either through this card or through the link in the description but here's a brief overview at its core analog television is just an amplitude modulated radio transmission where the strength of a signal dictates brightness of a light source with the strong signal producing a bright light and a weak signal producing little to no light the television set uses an electromagnet to deflect the source of light an electron beam in a pattern called a raster which is really just a ton of horizontal line this has the effect of producing a glowing series of lines on the face of a picture tube the electronics of the TV set line up the incoming signal with the movement of the beam to create an image with each part of the image being drawn brightly or darkly along with the signals instantaneous strength with everything in alignment you get an image by far the most complicated part of making an image appear on the screen is making that raster pattern the electronic components and other crucial parts such as the picture tube and deflection yoke are primitive by today's standards but still pretty complicated we really just need a way to make a repeating pattern of lines from a light source there's got to be a simpler way to do it enter mechanical television the earliest televisions actually got some of their inspiration from fax machines really and relying on a couple of important developments so first it was about the fax machine facsimile transmission actually predates the telephone what with images such as signatures being commercially reproduced over telegraph wires as far back as 1865 and the earliest fast flight device being invented by Scottish inventor Alexander Bain in 1846 now I'm simplifying a great deal here but the theory was that if you could synchronize the movement of a scanning device with a drawing device you could replicate an image if you scanned a piece of paper line by line and sent a signal over a wire to match the darkness of the ink you could reproduce the image by syncing up a drawing mechanism with the scanning one these early fax machines worked but they were very slow nevertheless they showed us that you could via election mechanical means reproduce an image fast forward to 1884 and 23 year-old Paul Julius Gottlieb nipped cow the nitkowski this is the core of most mechanical vision systems this cow realized that a spinning disk could methodically scan an image line by line simply by placing evenly spaced holes in a spiral pattern this is a homemade nipkow disk I took a really awful vinyl record that I'd be happy to destroy and marked 32 divisions around the circumference like 32 very skinny pie slices then I methodically drilled a hole along these lines with each hole being drilled 1/32 of an inch roughly point 8 millimeters closer to the center than the left the result is a spiral pattern of holes this might not seem like much but it's actually extremely clever if you put a square fish shaped mask in front of the holes its height being slightly less than the distance between the holes you've made a device which mechanically creates a raster scan using these physical holes John Logie Baird realized that with this nip Cal disc you could in theory focus an image with a lens onto the disk and you could use a light sensor to give an instantaneous reading of how bright each part of the image was with the holes in the nib calvinist certainly has a way to divide the image the transmittable pieces back in 1873 Willoughby Smith discovered the photo conductivity of selenium and with this knowledge Baird used some selenium to create the light sensor for his televisor I've mounted this NIT Cal disc to an AC motor which will spin it at 1800 rpm giving a complete revolution of 30 times per second before I turn it on look through the mask I've put an extremely bright LED behind the disc so you can see the holes as I slowly turn the disc you'll see that only one hole is visible at a time and each hole gets closer to the left than the next one when I switch the motor on the holes blend into the moving line and as it gets faster the line seems to widen into a square this square is very uneven because my homemade nib cal disc was made hastily and with poor precision but here's the key only one of the holes is actually visible through the mask at any given moment it's just moving too fast to see Baird used the selenium light sensor to create a signal from an image being scanned by the disc and on the receiving end another identical disc would spin at precisely the same speed and a light source such as a neon lamp with various brightness along with the signal strength presented by the light sensor and thus you'd get an image I shall now attempt to show you how this works now before you get too excited I will admit that my mechanical television doesn't work as well as I had hoped and that's all on my insistence and using crap a headline around rather than going through the process to make a proper led driver however I hope you'll get an understanding of what's going on this 10 watt LED chip is what we'll use is a light source it's really bright and importantly it can react very quickly to changes in the voltage it receives first I'll simply power the LED continuously as the disc spins up the lines start to blend into each other and eventually the whole screen is illuminated now I'm going to switch the LED on and off at a higher and higher frequency first five Hertz the screen appears to just be flashing nothing too extraordinary but you might be able to see some odd stuff happening as the light switches States now I'll switch it on and off at 60 Hertz something odd starts to be visible here see if the disc makes a complete revolution 30 times per second and with the light flashing at twice that frequency only some of the holes are lit up as the disc passes over the LED now let's move to 1800 Hertz frequencies that are a multiple of 30 will appear stable as an even number of pulses fit within each revolution if you mess with that though things get weird bubbling the frequency of just attack makes the pattern move in relation to the disk the holes in the disk are directly responsible for creating the patterns you see without the disk the led appears to just be continuously illuminated but it's not it's flashing really quickly the disk allows for that flashing to be visible because it physically obscures different parts of the light source over time this is just like the electron being in the CRT television except instead of electromagnets moving a beam across the surface of a picture tube the light source is physically moved to be the location of these holes it's a pretty crafty way of producing a raster scan and it actually works this is the best imagery I could get my televisor to produce this pattern was generated through manipulating audio samples in audacity to give you an idea of how poorly this mechanical PD works well the image I intended to make was not a map of the world as this vaguely suggests but that of a circle here's a look at true video what you're seeing here is a very low contrast a very low resolution image of Seth Meyers I mean obviously how could you not recognize him yeah okay it's garbage but you can see here that there's certainly something there and it's moving slightly like a talk show host Ted Mike when said talk show host is talking on his show to make this image I simply place my phone behind the televisor with the screen brightness all the way up and I place the solar panel with an audio cord patched into it into one of my trusty tascam dr-05 audio recorders which I use all the time in fact there's one in my pocket right now and yes that's directly from a solar garden light the solar panel would produce a high current whenever it saw bright light and it would produce low current with left like the as the disc spun it would only allow the tiniest bit of damage through to the solar panel at any given time this would produce a quickly varying signal with amplitude corresponding to image brightness the tascam would just encode these relative brightnesses as sound samples at a sample rate of 48 kilohertz and then because I'm really lazy I just hooked my LED into an audio amplifier and played that sound back the LED would become brighter with a stronger signal from the amplifier though as it's a diode it would filter out any AC components of the signal quite honestly I'm amazed it produces anything at all I opened the file in audacity just to see what it looked like and it's pretty intriguing here's what it sounds like for those interested now in case it's not obvious let's go over the reasons mechanical television didn't catch on first up until now I have not let you hear what this sounds like here's what a 12-inch vinyl disc sounds like at 1800 rpm I'm sure that would never diddle but aside from that there are just so many practical concerns with mechanical TV first of all the image is tiny and it's a horribly low resolution only 32 lines that's the only reason a signal can be recorded as an audio file not a lot of bandwidth is needed because the disc obscures almost all of the light source hardly any light gets through this LED is freakin bright it's painful to look at directly and yet through the NIT powders nearly all the light is blocked and it produces a dull image when these devices were first in development the light source would often be a neon lamp like the orange light in a power strip switch imagine cause dark damage would be with only that for a light source one of the biggest troubles with mechanical television is image synchronization because we're using a big spinning thing to divide the light of the chunk the disc has to be in precisely the right place if you want the image to land where it should if we take the mask away you can see that the image just repeats itself over and over but each of jacent image is actually shifted one line up or down the most critical part of synchronization was ensuring the disk is spinning at the exact same speed as a scanning disk of a camera but it would also be necessary to slow down or speed up the disk in flight increments to get the image aligned with the viewing left and with the top and bottom in the right place but the most damning problem is that of geometry imagine we wanted to make a display with the resolution and size of this small CRT television well the face of the tube is about 15 centimetres wide with 480 lines of resolution there would need to be 480 holes in the NIT count disk remember only one hole can be seen for the mask at once for this to work so the holes would have to be at a minimum 15 centimeters apart so that if circumference would have to be 72 liters with the diameter of roughly 23 metres or 75 feet I live in a building that stick stories tall a mechanical television to rival this TV would be taller than my building and it would have to spin at 1,800 rpm just like this one to make 30 frames per second possible this thing scares me spending that fast I'm pretty sure it's 75 foot disk will just explode in fact let's do the math a 72 metres circumference means that the edge of the disk would travel 2.16 km/s or well above Mach 6 yeah if the disc we're rolling it would make it from New York to Los Angeles in about 35 minutes not in a straight line mind you but by traveling along actual roads so the bear television system didn't get too far it was certainly genius and is an important part of the history of television when it was far too limited clunky and to be honest had crappy image quality I've added some links in the description to videos of mechanical televisions that actually work and I think you'll agree that they're pretty cool but it's a damn good thing they didn't become mainstream as always thank you so much for watching if you like this video a thumbs up would be most appreciated I am absolutely thrilled but this channel has over 21,000 subscribers now I never thought that would be possible if you're not one of the people in that number and you like this video I humbly ask that you become one of them by pressing that subscribe button I'm doing my best to keep videos like this heading your way and I'll see you next time

47 thoughts on “Mechanical Television: Incredibly simple, yet entirely bonkers

  1. Didn't analog TV (except for France who always has to do things the other way around compared to the rest of the world) use negative modulation and as such the image would become darker as stronger the amplitude is?

  2. This may be the best explanation of how a television works out of the dozens of times I've heard one, but I still find a huge portion of these types of things to be magic.

  3. Great that you tried to build one! Here's an idea: Similar to incremental sensors (mouse wheels in mechanical mice), where, instead of using holes, high precision sensors use reflection of a light beam and etch tiny equidistant strips on a glass disk, it might be possible to use the same trick here; and, what would happen if you shrink the mechanics down into the microscale, using MEMS tech.

  4. Last I knew, there was a demonstration system (using about a 2 inch or smaller screen) using this technology in the Melbourne Science Museum in Australia. You push a button to start the discs spinning and make the low-resolution image appear.
    For some reason, the light used is red and all you can see while the discs are stopped is a single red dot.

  5. Philo Farnsworth tried to help Baird, but Baird stubbornly stuck to his mechanical system. Later, when Farnsworth was fighting with RCA to keep them from stealing his invention, there was to be a demonstration of Farnsworth's all electric television in the Crystal Palace, which burned almost completely after a fire started in the women's cloakroom. Baird's TV stuff was also in there and mostly destroyed. Back then RCA never licensed a patent. If they didn't invent a thing but wanted it, they'd try to buy exclusive rights for a one time payment. If the patent holder refused, RCA would just steal the idea and start making it, using their huge amounts of money to out spend legal challenges from patent holders.

    Farnsworth was the first inventor who would not be bought nor bullied by RCA. Their last effort to "prove" their guy, Vladimir K. Zworykin, had "invented" electronic television (coincidentally shortly after Farnsworth had given him a tour of his laboratory) was to put together a team who had never worked on television and told them to make Zworykin patent work. What they came back with was essentially identical to Farnsworth's version because it was the only way they could make it work.

    RCA, for the first time ever, licensed a patent. But they'd dragged things out so long they didn't have to pay Farnsworth for very many years before his patent expired. For a long time after, RCA would promote the idea that they had invented television, while Farnsworth's own TV equipment manufacturing company foundered. RCA did develop the color TV standard that was compatible with then current monocrhome receivers, after CBS' incompatible color system was rejected by the NTSC.

  6. Philo Farnsworth tried to help Baird, but Baird stubbornly stuck to his mechanical system. Later, when Farnsworth was fighting with RCA to keep them from stealing his invention, there was to be a demonstration of Farnsworth's all electric television in the Crystal Palace, which burned almost completely after a fire started in the women's cloakroom. Baird's TV stuff was also in there and mostly destroyed. Back then RCA never licensed a patent. If they didn't invent a thing but wanted it, they'd try to buy exclusive rights for a one time payment. If the patent holder refused, RCA would just steal the idea and start making it, using their huge amounts of money to out spend legal challenges from patent holders.

    Farnsworth was the first inventor who would not be bought nor bullied by RCA. Their last effort to "prove" their guy, Vladimir K. Zworykin, had "invented" electronic television (coincidentally shortly after Farnsworth had given him a tour of his laboratory) was to put together a team who had never worked on television and told them to make Zworykin patent work. What they came back with was essentially identical to Farnsworth's version because it was the only way they could make it work.

    RCA, for the first time ever, licensed a patent. But they'd dragged things out so long they didn't have to pay Farnsworth for very many years before his patent expired. For a long time after, RCA would promote the idea that they had invented television, while Farnsworth's own TV equipment manufacturing company foundered. RCA did develop the color TV standard that was compatible with then current monocrhome receivers, after CBS' incompatible color system was rejected by the NTSC.

  7. I tried this as well and found that recording from a phone screen or computer screen in my case doesn't work
    But I aimed some studio lights on me and filmed myself and got way better results
    The sync was off but I could clearly make out my outline
    Plus I was using an 8 hole disc for testing so I would think you'd get better results on a 30 hole disc

  8. Thank you so much for making this video. The mechanical TV technology itself was obviously hopeless, but it did manage to finally answer for me how old TVs full of diodes, ICs, and resistors still qualified as "Analog"

  9. Mechanical tv.. did take off, for projectors.
    It was superseded by spinning mirrors, later vibrating mirrors.
    The decedents to mechanical tv is the mem mirror projector.

  10. To synchronize the disks they developed a system of electrically driven tuning forks for timing, until the development of quartz crystals this was the best system for clock accuracy.
    The first electronic wrist watches in the 1960s used tiny tuning forks.

  11. In the 70's they built infrared scanners based on mech. tv. A scanning disk paired with an infrared sensor, these were a fraction of the cost and size of other infrared cameras available at the time.

  12. 21k in Aug 2017, currently 297k in Mar 2019 – congrats – methinks traditional television is in its death-throes. Maybe they should wheel Baird's contraption out again, to try and stem the rate they're losing viewers. Last one out, turn off the TV.

  13. I guess that you realize that when CBS created color television, a rotating color disc was used with a conventional CRT. Problem was, the cabinet in which the CRT and spinning color wheel was enclosed would have to be a minimum of 4 times that of a regular TV cabinet. Being that this would have been impractical for home use, the CBS system was relegated to industrial usage. Meanwhile, Philips invented a CRT which had 3 color guns inside it which alternated projecting upon the screen which had a mask of rows of the color dots. RCA supported this system and color TV in the home was realized. Fast forward several decades or so, color CRTs were growing in sized, not only in surface area, but also in depth. Bigger was better, correct? Well, bigger screen required a larger cabinet. Rear projection had been around for awhile, but not in the home. Enter the giant screen TV's in a large cabinet. Oh, and guess what was inside these giant, rear projection TV's, besides and electron gun and mirrors? Right! It was the return of the infamous spinning mechanical color wheel. Because of magnifying mirrors and lenses, the color wheel size could be reduced to a fraction of the size of the cabinet and screen.

  14. Its funny because I have a complete working understanding of modern televisions, digital is so simple, yet old analogue televisions seem way more technical and, really pushing what was available at the time.

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