Updates to my mechanical set

Forum for discussion of narrow-bandwidth mechanical television

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Re: Updates to my mechanical set

Postby Harry Dalek » Fri Jul 20, 2018 8:08 pm

smeezekitty wrote:Thank you. I was mulling over 3d printing a mirror drum system. But I don't know if my 3d printer is precise enough.
Also, I find scophony systems are very interesting. But probably quite hard to build. Especially without using a laser.


A 2 what ever system drum disk mirror idea gives you more flexibility ...as in a standard mirror drum will give you the screen size but you are again stuck as a Nipkow disk at that line rate ......where as change the speed of a 2 what ever system makes it multi system same as a electronic tv but limited to how fast you can drive it so made for your very multi system software .
I have made this and that with the old polygon mirror motor scrapped from laser printers .....lasers and mirrors are a problem but safe if you follow some safe procedures you can use a led if you want to view off the mirrors but i find that not to pleasant as a viewing screen .
viewtopic.php?f=1&t=1557&hilit=octagon
Since you have a 3d printer much easier to make some thing nice such as Gregory and he's device.
viewtopic.php?f=1&t=2090&hilit=octagon
Think this below would more be your thing
You might be more interested in Holtzman's monitor ,i have made 2 first version working below manual syncing touch off here .
Picture 178.avi
(18.11 MiB) Downloaded 251 times

The mistake i made on my second was the main drum plastic was to flexible a wobble at 60 line speed caused line wobble at 32 not to bad but got worse at increased line speed
viewtopic.php?f=1&t=1486&hilit=2+drum+monitor&start=90
..Maksim Holtzman is a much better constructor than me and he's monitor gave beautiful pictures as you see in the you tube videos went to 2 colour as well ...gives you an idea of screen size and why i like these over a Nipkow .
viewtopic.php?f=1&t=1269&hilit=holtzman
viewtopic.php?f=1&t=1388&hilit=holtzman&start=45

youtu.be/EXpA9HNiyHg

youtu.be/ToJuNt7eM6c

youtu.be/4PbA5Vc0jwQ
Last edited by Harry Dalek on Sat Jul 21, 2018 10:02 am, edited 2 times in total.
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Re: Updates to my mechanical set

Postby FlyMario » Fri Jul 20, 2018 11:05 pm

Quite fascinating work! I do have a couple of questions if you guys don't mind indulging me.

As your video looked very much in sync (perfect IMHO), I wonder if you are allowing the machine to automatically sync with the first frame or are you using some controls (perhaps fingers) to move the vertical lines in their proper place. As in line 1 being in line 1's lane. I had been looking at the specs a lot of the signals and there seems to be no vertical sync on frame 32. I keep thinking this is a great way to have a frame sync. Though I don't know if that is really practical. Is this a common practice? Has there been much luck with it? Most mechanical TV's I see have the lines out of order. Not yours though, as far as I can tell.

Is your mechanical TV running 2 colors or 3? It looks great but I wondered.

Are you able to use one audio track to get a color image or is there some other process involved?

Thanks!
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Re: Updates to my mechanical set

Postby Harry Dalek » Sat Jul 21, 2018 9:54 am

FlyMario wrote:
Is your mechanical TV running 2 colors or 3? It looks great but I wondered.

Are you able to use one audio track to get a color image or is there some other process involved?

Thanks!

The youtube ones are Maksim's monitor he used mechanical switching for the framing drums stepper motor the small one ..... he has 4 ldr sensors and leds and a disk between with also 4 holes which turns with the line drum .......the ldr's and leds which are wired into a what is really a mechanical H bridge circuit ! ....
That disk with the 4 holes as it rotates switches the stepper motor for framing and so to be locked to the line drum ..i think the 4 hole disk can be adjusted to select the framing position ...i just went with a 555 timer stepper circuit to control speed manually as i wanted multi system on the line drum and adjust the line and frame drum separately for experiments in line and frame speed....but he's is a very elegant solution.
2 colour system use's left and right channels...to get sound you need a sound card with more than 2 channels stereo standard...as smeezekitty has done.
The builds are in the links posted .apart from colour which i don't think was mentioned.
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Re: Updates to my mechanical set

Postby smeezekitty » Sat Jul 21, 2018 11:18 am

FlyMario wrote:As your video looked very much in sync (perfect IMHO), I wonder if you are allowing the machine to automatically sync with the first frame or are you using some controls (perhaps fingers) to move the vertical lines in their proper place. As in line 1 being in line 1's lane. I had been looking at the specs a lot of the signals and there seems to be no vertical sync on frame 32. I keep thinking this is a great way to have a frame sync. Though I don't know if that is really practical. Is this a common practice? Has there been much luck with it? Most mechanical TV's I see have the lines out of order. Not yours though, as far as I can tell.

That is exactly the reason for the missing sync pulse on the 32nd line (not frame). It allows a sync system to achieve frame sync. Many people around here have some sort of frame sync system.
It is true that some mechanical TVs are only manually synced (mine was when I first built it). But that gets exhausting really fast.
Is your mechanical TV running 2 colors or 3? It looks great but I wondered.

In both Maksim's video and my own, it is a 2 color system. I believe he used a red/cyan system where I have a red/green system (just because of what LEDs I had).
I mix it so that the red is mapped to the red LEDs and green and blue is mapped to the green LEDs with blue having a lower gain than green. I also mess with the brightness and gamma settings to get the best color reproduction possible given the limitations of a 2 color system.
Are you able to use one audio track to get a color image or is there some other process involved?

As Harry mentioned, I have 4 channel audio. Many (desktop) sound chips provide 4 channel or 5.1 channel outputs. It can be tricky to find software that works with it though.
1 = red
2 = green
3 = left audio
4 = right audio

You could also dedicate three channels to R,G,B color and the fourth for mono audio. But I don't have the parts necessary to do a 3 channel color system.

I attached a .wav file which is the first minute of the scooby doo NBTV video + audio in case you want to see how it is laid out. It is 16 FPS instead of the usual 12.5 FPS so it won't play back on normal viewer software.
Attachments
scooby_st_color.zip
(7.26 MiB) Downloaded 208 times
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Re: Updates to my mechanical set

Postby smeezekitty » Mon Jul 30, 2018 6:40 pm

Inspired by Robonz
record_000006.avi
(2.74 MiB) Downloaded 239 times

https://streamable.com/dbyzb

What do you guys use for diffusion material? I am using a layer of masking tape. It does an OK job defusing the light but you can see the pattern in the tape in bright parts of the picture so that isn't ideal.
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Re: Updates to my mechanical set

Postby gary » Mon Jul 30, 2018 7:54 pm

smeezekitty wrote:Inspired by Robonz
record_000006.avi

https://streamable.com/dbyzb

What do you guys use for diffusion material? I am using a layer of masking tape. It does an OK job defusing the light but you can see the pattern in the tape in bright parts of the picture so that isn't ideal.


I must have tried every diffusing material known to man over the years, I even ground a sheet of glass using a grinding compound. One day I read that Scotch tape (the semi transparent kind) worked well and I think it is as good as anything I have tried, BUT the trick is you place a piece of it over EVERY aperture.

I don't need to bother with diffusing anymore because I have switched over entirely to bead disks (even for cameras), you don't need to diffuse one LED light source so no light loss and it is as bright as. Easy peasy.
Perfecting an NBTV system is like trying to slam a revolving door...
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Re: Updates to my mechanical set

Postby FlyMario » Mon Jul 30, 2018 11:31 pm

You put a piece of masking tape over each hole? Wow! Seems that would still pass brightness variances. What if we bounced the light off the inside of the box? I scratched the hell out of some plexiglass and was proud until I turned on the LEDs.

Has anyone tried something I have below before? I am sure you have. Have it all white so that you don't have a reflector creating any definitions. The LED's I plan on is an array of 4x4 or 6x6 normal 20ma LEDs.
Attachments
LightBoxReflect.jpg
FlyMario
 

Re: Updates to my mechanical set

Postby smeezekitty » Tue Jul 31, 2018 4:30 am

gary wrote:I must have tried every diffusing material known to man over the years, I even ground a sheet of glass using a grinding compound. One day I read that Scotch tape (the semi transparent kind) worked well and I think it is as good as anything I have tried, BUT the trick is you place a piece of it over EVERY aperture.

I don't need to bother with diffusing anymore because I have switched over entirely to bead disks (even for cameras), you don't need to diffuse one LED light source so no light loss and it is as bright as. Easy peasy.

Huh. Diffusing every aperture is something I didn't think of.

Has anyone tried something I have below before? I am sure you have. Have it all white so that you don't have a reflector creating any definitions. The LED's I plan on is an array of 4x4 or 6x6 normal 20ma LEDs.

The issue I see is that "white" parts of the image appear transparent through the disk. That means you'll see the inside of the lightbox through the picture. You want the diffusing material as close to the disk as possible to avoid depth effects.
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Re: Updates to my mechanical set

Postby Andrew Davie » Tue Jul 31, 2018 6:31 pm

I was most successful (with diffusion) using several layers of greaseproof paper and one layer of the plastic lids used for dogfood cans.
Whatever it takes, I guess!
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Re: Updates to my mechanical set

Postby Klaas Robers » Wed Aug 01, 2018 8:59 pm

The best way for diffusing is an internally white light box, where the direct light (not "reflected" of the LEDs is not visible in the output window. The diffuse white walls scatter the light in all directions, and it can " escape" only through the window. The walls should be as close as possible 100% reflecting the light, white is much better than a mirror.

How do you make almost 100% reflecting white walls? Use the so called magnesia that athletes use to make their hand dry and not slippery. This is Magnesiun Oxide and is a fine powder. Paint the inside of your box and before the paint is dry, spread the powder over the sticky paint. Let it dry and remove the loose powder. This gives a 98% reflective matt surface. I still do not know how to make such a box, but with 3D-printing this should be easily possible.

Next it is wise to paint the back side of the Nipkow disc also white. Then most of the light is kept inside the light box, as the disc itself is also a wall of the box. Then the escape window is only the aperture of the disc.
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Re: Updates to my mechanical set

Postby smeezekitty » Mon Jul 15, 2019 7:49 am

For some reason, the FET on one of the color channels died (the LEDs were on regardless of the contrast control). I replaced it and it's back in business.
Since it is *well* below the rating of the BUZ11, my only guess is ESD damage.
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