My Pocket Sized NBTV Reciever

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My Pocket Sized NBTV Reciever

Postby jjester6000 » Wed Oct 18, 2017 5:25 am

This is my crude attempt at creating a "portable" mechanical NBTV receiver; I got the Idea while messing around with an 80mm pc case fan, when I had and idea oh how I should complete my quest for a working mechanical television (Yes, this is my first semi-working set). I used an 8cm mini camcorder DVD as my template over a piece of black construction paper, and punched 32 holes with a screw driver. The disk turned out pretty well for me just eyeballing it, but the image it produces is far from perfect. It does not help that the disk is not even very centered. I used a bulb from an old strand of Christmas lights, and made a crude amplifier with some parts I de-soldered from an old AM/FM receiver. With low hopes (after my 12 other attempts at mechanical television) It gave me a distorted image. Since I am not willing to pay for a fan controller, I used a variable resistor to manually control the fans speed. Excited, I jammed the radio into the case of the old AM/FM radio I built the amp from. I am planning on making a proper Nipkow disk by using some plastic from a DVD case, and drilling holes with a proper template. I also want to replace the current amp with a more responsive two transistor amplifier. The last improvement I want to make is adding a speaker that hooks up to the left stereo channel for sound. If there were any actual American NBTV broadcasters, I would implement some sort of short wave receiver into my design to pick up like NBTV.
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Re: My Pocket Sized NBTV Reciever

Postby Robonz » Wed Oct 18, 2017 10:18 pm

That's very interesting, I hope you take photos etc as you go along so we can watch your build. I did some rough calculations using Gary's NipkowDxf program. With an 80mm diameter and 32 lines, your apertures would be around 0.17mm in size. This would give you a screen size of 5.5mm. I am not sure if you could drill holes that small but maybe a needle would work to poke holes. The apertures of the disc needs to be paper thin to avoid parallax if you plan to use a magnifier.

I am not sure of your build skills but a small disc like that could easily go very fast so if you were tricky you could do a 3 turn spiral which would increase the screen size to 16.5mm but then you have to work out how to shutter which spiral is active. The disc speed would be 2250rpm instead of 750rpm.

Cheers
Keith
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Re: My Pocket Sized NBTV Reciever

Postby Klaas Robers » Wed Oct 18, 2017 10:27 pm

Yes, this is generally the way it all starts. And then the result is disappointing. To help you improving:

1. Make a larger disc. The size of the holes in a larger disc is also larger, however still small, smaller than 1 mm. Go for about 30 cm (one foot) diameter.

2. Make a thin metal disc. Small holes in a thin disc are easier made, metal is very dark for light.

3. Use an LED instead of a lamp, an incandescent lamp is far too slow in changing its intensity. LEDs are much faster.

4. Make as much light as you can. I used about 30 ultra bright LEDs together as a light source. The disc takes away almost all the light. You remain 0.1% of what you made.

5. Start with the "One Fieldeffect Transistor" circuit for driving the LED chain. It is simple and does what you want from it.

6. Start with NBTV video signals coming from a CD. They are prooven Ok according to the 32 line standard.

7. Read the website of the NBTVA (http://www.nbtv.org). They have the CDs and also a very usefull booklet called: "NBTV handbook".

Good luck! You will need it.
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Re: My Pocket Sized NBTV Reciever

Postby jjester6000 » Thu Oct 19, 2017 4:53 am

Robonz wrote:That's very interesting, I hope you take photos etc as you go along so we can watch your build. I did some rough calculations using Gary's NipkowDxf program. With an 80mm diameter and 32 lines, your apertures would be around 0.17mm in size. This would give you a screen size of 5.5mm. I am not sure if you could drill holes that small but maybe a needle would work to poke holes. The apertures of the disc needs to be paper thin to avoid parallax if you plan to use a magnifier.

I am not sure of your build skills but a small disc like that could easily go very fast so if you were tricky you could do a 3 turn spiral which would increase the screen size to 16.5mm but then you have to work out how to shutter which spiral is active. The disc speed would be 2250rpm instead of 750rpm.

Cheers
Keith

-I made a better last night disk using a template I made with Gary's, but I could not drill the holes, so I punched them with a 0.20 mm nail and a tack hammer; the lines slightly overlap on each other, but it does not look half bad. Making a three turn spiral is worth a try, but it probably would take a few tries. I may add a proper fan controller in the future, or swap out the whole direct drive system for a belt driven one to keep speed better. I currently am trying trying to put together a better amplifier because this one transistor deal does not seem to cut it.
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Re: My Pocket Sized NBTV Reciever

Postby Robonz » Thu Oct 19, 2017 1:32 pm

I have ordered some very thin black polypropelene today. It could be good for making Nipkow discs. If I can do a 0.17mm hole I can make a disc for you. I will cut a hole and see how small I can go.

Controlling those motors accurately is probably tricky as they are generally brushless dc and have a commutator transistor built inside. A cd brush motor direct drive would probably work well. I think direct drive is good for such a small disc. You may need to add some weight so the flywheel inertia kills off some of the motor cogging.

A single transistor works well for my motor control but I have a PI controller running on an Arduino to make it super easy.
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Re: My Pocket Sized NBTV Reciever

Postby Robonz » Thu Oct 19, 2017 2:36 pm

I did some tests today and started a new thread as I plan to use this on my NBTV
viewtopic.php?f=35&t=2480

If you can draw some cad I will cut a disc for you. If you design your disc with 0.2mm apertures and make each aperture a 0.1mm line with no width that will end up as 0.2mm. Make the line length in the orientation of the disc rotation. e.g don't point the line at the center. And rotate the line for each position on the disc. I could easily cut a very accurate 3 spiral too. (so long as the cad is good)

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Re: My Pocket Sized NBTV Reciever

Postby jjester6000 » Fri Oct 20, 2017 7:23 am

Robonz wrote:I did some tests today and started a new thread as I plan to use this on my NBTV
viewtopic.php?f=35&t=2480

If you can draw some cad I will cut a disc for you. If you design your disc with 0.2mm apertures and make each aperture a 0.1mm line with no width that will end up as 0.2mm. Make the line length in the orientation of the disc rotation. e.g don't point the line at the center. And rotate the line for each position on the disc. I could easily cut a very accurate 3 spiral too. (so long as the cad is good)

Cheers
Keith


Thanks for the offer, (I may take you up on it) I am do know my way around Autodesk Inventor, so I could make you a cad model. The three spiral system seems like the way to go, so maybe it may not need the magnifier after all. My main problem currently is my lack of a fan controller, but I want to keep this as analog as possible. My Idea with this is was something strait forward to build, (Hence the use of an 80 mm case fan) so I don't want to use a fancy controller. I am also thinking of creating a camera in the same way (the sensor could be a calculator solar panel). Sorry I have not uploaded any pictures, but I have just not gotten around to it.
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Re: My Pocket Sized NBTV Reciever

Postby Harry Dalek » Fri Oct 20, 2017 7:22 pm

jjester6000 wrote:
Thanks for the offer, (I may take you up on it) I am do know my way around Autodesk Inventor, so I could make you a cad model. The three spiral system seems like the way to go, so maybe it may not need the magnifier after all. My main problem currently is my lack of a fan controller, but I want to keep this as analog as possible. My Idea with this is was something strait forward to build, (Hence the use of an 80 mm case fan) so I don't want to use a fancy controller. I am also thinking of creating a camera in the same way (the sensor could be a calculator solar panel). Sorry I have not uploaded any pictures, but I have just not gotten around to it.


The problem with a fan motor for a camera idea is there would be to much wobble even using a cd dvd motor as i have done this even gives wobble. you will not see it but its there alright ...fine i suppose if you are just doing a direct link to a mechanical monitor or your monitor is on the same disk .
If you want to make the video signal it will play havoc with the mechanical sync ...
A camera is much harder than a monitor they are more fussy , you would be better off using a small hard drive or vcr head as the mount they will not wobble .
With all these things the Quality you get depends on the original idea and the time you put into the construction .
To make a camera or monitor you need motor control even if just an old LM317 and change the voltage to it ,i would test your fan motor with that and see how well it can be controlled .
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Re: My Pocket Sized NBTV Reciever

Postby Robonz » Fri Oct 20, 2017 7:26 pm

The 0.38mm thick black polypropylene arrived this morning. I stuck a really bright focused led behind it, great news, I could not see any light coming through at all. I think this stuff is probably going to be the simplest, cheap and fast way to make a Nipkow disc going forward. I will replace my disc with this when I get the cad done and see how it goes.

If you want a really simple drive I think you could pick up a CD or DVD player assembly and mount your disc on that pretty easily. Being a brush motor you only need to drive it with a single transistor. My modification is to add an electrolytic capacitor across the motor to smooth the brush noise, It works well. You can find the analog motor circuit here http://www.nbtv.wyenet.co.uk/beginners.htm and Yes, I like the analog designs, more authenticity!

For a 3 spiral system we would need a second aperture disc running at 1/3 the main disc speed. Does anyone have drawings for these? I am guessing some spiral slots are needed.

Cheers
Keith
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Re: My Pocket Sized NBTV Reciever

Postby jjester6000 » Mon Oct 23, 2017 3:21 am

20171015_185240.jpg
Robonz wrote:The 0.38mm thick black polypropylene arrived this morning. I stuck a really bright focused led behind it, great news, I could not see any light coming through at all. I think this stuff is probably going to be the simplest, cheap and fast way to make a Nipkow disc going forward. I will replace my disc with this when I get the cad done and see how it goes.

If you want a really simple drive I think you could pick up a CD or DVD player assembly and mount your disc on that pretty easily. Being a brush motor you only need to drive it with a single transistor. My modification is to add an electrolytic capacitor across the motor to smooth the brush noise, It works well. You can find the analog motor circuit here http://www.nbtv.wyenet.co.uk/beginners.htm and Yes, I like the analog designs, more authenticity!

For a 3 spiral system we would need a second aperture disc running at 1/3 the main disc speed. Does anyone have drawings for these? I am guessing some spiral slots are needed.

Cheers
Keith


Tha}t using a CD drive motor is a pretty good idea; the only reason i've been using the fan was because it was easy to attach the disk to and keep stable, my main problem was before was gatting the disk to spin at a constant speed. This is because I tried to completely design every aspect myself, (Including a hand drawn 14 line Nipkow Disk) but I realised that an 80mm fan was the best way to go (^I was also experimenting with building my own CRT display and Vidicon tube at the time). One of your disks would be better than mi@8:ne, so I will draw up a cad file as soon as I have time (since I have been out of town for the past few days).
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Re: My Pocket Sized NBTV Reciever

Postby Viewmaster » Tue Oct 24, 2017 10:29 pm

If you really wish to struggle making a small NBTV, try making the World's smallest one ........
.........With scanning holes pricked with a needle and are .004" diameter (4 thou ) !!

http://www.retinascope.co.uk/nipkow.html
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