Recently I saw a documentary about the history of the television. And to my surprise they showed that there existed a mechanical television before the well known CRT televisions.
Those mechanical televisions or televisors were pretty smart and simple.
A CRT is simply an electron beam that scans a surface covered with a luminescent phosphor line by line. And the intensity of the beam is then directly proportional with the whiteness of that particular spot on the screen.
A televisor works in a very similar way. But instead of an electron beam, holes are used. Holes in a spirally pattern on a disk scan a small area as the disk rotates. After that particular area an electrical lamp varies its intensity. Bright means a bright spot wherever a hole is located.
There are some videos on youtube from people who have built other televisors. With more lines and far better image quality than this one. (but they aren't made out of cardboard)
This instructable documents the build of such a very small 24 line televisor completely from scrap cardboard, scavenged electronic parts a laptop and an arduino.
The image quality is very, very low but it is built out of cardboard and it has only 24 lines.
But it was a fun build.
If you want a good display, there are much better alternatives, (pretty much everything is a better alternative).
A lot of things that I did here were a first for me so I had to improvise and will have missed out on probably much more efficient solutions. So, expect some very naive approaches.
But the final result kind of works and can display something in a recognisable way. (But that's about it)
I have updated some things and mentioned what could be done better.
This is the general structure of the instructable:
Step 2-8: Building the cardboard hardware of the televisor.
Step 9: Building a led lamp.
Step 10: Making a speedometer to register the rotating speed of the disc.
Step 11: Writing a program to convert normal photo's/images to a sound file. (to modulate the lamp)
Step 12: The electronics.
Step 13: Arduino to control the speed of the disc.
Step 14: Results
Have a good read. And thank you to the people in the comments who gave a lot of good advice.
The Device itself is made out of white, pressed cardboard.
Most of it is of 0.8 - 1 mm thick. This cardboard is easy to cut and quite strong.
The disc is also made out of cardboard but a thicker and stiffer piece. ~1.6 mm thick.
However I think it would be best if something else is used such as wood or plastic. Because this cardboard likes to flex and bend and as you will see the disc must enter in a narrow split and this bending can cause friction.
Three simple circuits are made. Two require a MOSFET to switch the larger currents.
A single rail op amp is used to amplify the audio signal.
More on the electronics in step 12.
LEDs are used as the light source of the televisor.
An arduino is used to control the motor speed.
To convert images to audio and play them to drive the LEDs.