Arduino Televisor by Keith Colson

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Re: Arduino Televisor by Keith Colson

Postby Robonz » Wed Aug 16, 2017 8:58 am

19200/32(lines)/12.5(fps) pixels/line = 48


I thought we would be looking at standard audio sample rate of 44.1 kHz. Is this possible? That would give about 110 or so vertical pixels?
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Re: Arduino Televisor by Keith Colson

Postby Andrew Davie » Wed Aug 16, 2017 10:34 am

Robonz wrote:
19200/32(lines)/12.5(fps) pixels/line = 48


I thought we would be looking at standard audio sample rate of 44.1 kHz. Is this possible? That would give about 110 or so vertical pixels?



My early code was just able to do this, but no - not with the current implementation.
In theory - maybe - just. GitHub will have earlier implementations of my code with the 44.1kHz support, but I abandoned it long ago as impractical with the Arduino.
Early TV was broadcast on low-bandwidth radio and 44.1kHz is much higher resolution than they had - AFAIK. The picture with 19200Hz looks beautiful as shown by my videos, so I truly believe that the resolution isn't an issue and is closer to 'the real thing'. But in the long run, it was an engineering decision/limitation.
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Re: Arduino Televisor by Keith Colson

Postby Robonz » Wed Aug 16, 2017 10:46 am

44.1kHz support, but I abandoned it long ago as impractical with the Arduino.


I am approaching this project to see how good it can be as if the technology was pursued longer. Once I get a complete running unit i will look at the source code and see if I can optimise it so this function is possible. Double the vertical resolution would be really nice.

My motor should arrive in about a week, then I can build the hub. i guess I should start on the chassis now, so i have something to mount all this onto.
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Re: Arduino Televisor by Keith Colson

Postby Robonz » Wed Aug 16, 2017 5:11 pm

A simple question Andrew. What size is your disc e.g diameter of the first aperture and what size is the aperture? I am just trying to gauge if I am in the ballpark.
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Re: Arduino Televisor by Keith Colson

Postby Andrew Davie » Wed Aug 16, 2017 11:14 pm

Robonz wrote:A simple question Andrew. What size is your disc e.g diameter of the first aperture and what size is the aperture? I am just trying to gauge if I am in the ballpark.


Eyeballed with a ruler as best I could. These are the measurements of the disc I use - made by Peter Yanczer. The disc radius is 152.5mm. The outermost scan hole is 7.5mm from the outer edge of the disc. The innermost scan hole is 25mm from the outer edge of the disc. The holes themselves appear to be 0.7mm diameter.

Calculating from that - the width of my (vertical) image is therefore 25-7.5 = 17.5mm + 1/2 hole x2. With 0.7mm holes, we would be looking at 17.5mm from the center of the first hole to the center of the last hole. Thus, 31 x hole distance (+1/2 hole each side on the extreme edge making 32 total). So of those 31, the calculated spacing is 17.5/31 = 0.56mm so I expect I'm getting about 0.14mm overlap. I do have a bit, probably not that much. So my eyeballed 0.7mm is probably a bit high - let's say 0.6mm diameter holes.

With that value, very close to the 0.56 calculated above, so looks good to me.

As to the vertical - outer edge: radius = 152.5-7.5 (outer scanline center) = 145, so circumference at outer scanline = 911mm and /32 to give frame height = 28.47mm.
So my aspect ratio (based on eyeballed measurements) is 28.47:17.5 = 1.62:1 give or take
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I made the hub

Postby Robonz » Sun Aug 27, 2017 6:36 pm

I turned the hub this afternoon on a decent lathe. It is made from 17mm thick acetyl which machined really nice. I hope it doesn't wobble!. It was a fun process. I started by drilling a 5.5mm hole then reamed it out to tight 6mm. I made a mandrel from some 1 inch round aluminium stock. I put a 6mm thread on it so I could tighten the disc on to the mandrel with a nylock nut. I then machined the hub to the following specs.

See attached hub_drawing.pdf

Here is how it all looks. I just need to drill and fit bolts to mate the hub to the disc and fit some set screws to lock the shaft to the motor. The motor should arrive on Monday

Image

And the back

Image

Next the motor mounts and chassis

Cheers
Keith
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Re: Arduino Televisor by Keith Colson

Postby Harry Dalek » Tue Aug 29, 2017 12:15 am

Looks good fingers crossed for wobble free ...its never to bad for a monitor but not good for a camera nipkow .
All i will say is direct drive like this you always get a small amount no matter how good for a monitor again i expect it will work fine ,only way to get true wobble free is to you a vcr head or hard drive something like that and a pulley system ...i did learn the hard way on the nipkow camera and the encoder opto sensor showed me my disk was wobbling .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Arduino Televisor by Keith Colson

Postby Robonz » Wed Aug 30, 2017 9:26 pm

I got a lot of hours in on this today. The motor arrived and it cannot support an axial load without making a grinding noise, bugger! I have redesigned the hub to be supported on its own set of bearings. I spun the hub up on the grindy motor and it wobbles quite a bit even with my special care machining the hub. I hope some shims will sort that out.

I got most of the cad done today. It is still missing the lens holder, light source mount and fork sensor mount. Its not looking bad though. Here is the cad as it looks.

Front
Image

Top
Image

Mounts for motor and bearings
Image

Reviewing this I have not left room for the light source. Derp. Also the platform looks a little low now too. hrrmm

Cheers
Keith
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Re: Arduino Televisor by Keith Colson

Postby Harry Dalek » Wed Aug 30, 2017 10:24 pm

That's the way it go's Keith plan 1 to plan 2 even when the motor can handle the disk with plan 1 idea its some times the hub and other times the disk is warped by a tiny amount .
I Like your plan 2 nice fix :wink:
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Draft Assembly

Postby Robonz » Thu Aug 31, 2017 11:47 am

.
Thanks Harry, your kind comments are motivating! Cheers

I cut all the bits up and assembled them, everything fit perfectly which is unusual, but I will take it. I am disappointed with the motor. It is quite noisy. I will need to keep my eye out for a quality one. I wonder if I have one in my box of motors. The disc has about 3mm of warp in it. I may try annealing it in the oven when the wife is out haha.

Image

The coupling is some silicone vacuum hose
Image

The picture looks like it is quite precise and it is very bright.
Image

The pixel overlap look as good as I could have hoped for I guess
You can even see the rectangular apertures are looking pretty decent.
Image

Next: mount the light source and speed sensor

Cheers
Keith
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Re: Arduino Televisor by Keith Colson

Postby Andrew Davie » Thu Aug 31, 2017 12:23 pm

I'm in total awe of your manufacturing skills! Awesome.
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Arduino Televisor by Keith Colson

Postby acl » Thu Aug 31, 2017 5:14 pm

Hi All,

I think Doug Pitt from his humble beginnings of the club would be really proud of what is being achieved using the latest CAD and microcontroller technology.

Regards Chris Lewis
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Sensor and Light mounted

Postby Robonz » Fri Sep 01, 2017 8:18 pm

Hey, thanks for all the positive comments Andrew and Chris. All I can say is the best tool I ever purchased was a laser cutter.

More progress: I got the light source and the sensor fork mounted up today. I made a lot of little mistakes as it is getting to the end of the week and I guess I am a bit tired, but I got there.

Here is a picture of the 30 watt light source mounted up. I laser cut some 4.5mm opal diffuser and it just fits with not many threads left on the holder. I guess I could engrave a mounting ring to make it sit deeper.

Image

Here is the sensor fork, it looks a bit like a penguin for some reason, haha
Image

And here it is all completed
Image

I will call this mechanically complete except for the lens mount.

NEXT: The Electronics! ,I think I will start a new thread for this

Cheers
Keith
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It's Alive

Postby Robonz » Sat Sep 09, 2017 9:21 pm

After completing the electronics bar the audio speaker, I turned it on and it worked, I was expecting to have to mess with something but no, it just worked. The PID overshoots really bad but that is going to the fun bit to fix. The camera ran out of battery so I only have poor images to look at

100_8016.JPG


The image looks fairly sharp

100_8009.JPG


Attached is a video. Its noisy due to the crappy gearbox on that RS motor. I can work on that.



The forum is crawling tonight, I can barely upload and I have a 100meg connection
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Re: Arduino Televisor by Keith Colson

Postby Andrew Davie » Sat Sep 09, 2017 11:06 pm

Well, how about that! Congratulations!

That brought a big smile to my face. I think you have a fantastic scanning disk there, and it's great to see such a sharp image first-up. What I also notice is the beautiful steady frame - although the PID may need to be adjusted on the initial synch, it appears to be doing an awesome job when locked. I see it has "frame locked" to the correct scanline, too - that is something I'm quite proud of and when you see how simple it is in the code... kind of cool.

As to the PID overshooting, it's actually just a single value to change in the source code. The spin-up has a couple of stages, and it's the switch-over that is custom-set for each particular televisor. That switch-over takes account of the inertia and friction of the disk and clearly (expectedly) our disks are different. But, fingers crossed, easy peasy fix :)

I also note with interest the modifications you have made to the power 12V and 7V feeds, and the infra-red connections.

If you're like me you've probably already spent quite some time just watching the thing, mesmerised. :) One thing that's not immediately obvious with the LCD UI - the track position shown on the bar on the bottom is actually interactive - it's a "seek" bar as well, so you can slide back and forth to get to different parts of the video. Of course when that happens, the disk will need to re-synch and that may be a pain until you/we get that PID changeover correct. I'm really stoked, though, that the frame is extremely stable in the video you posted.

As to that, I did some small edits on your post to fix up the embedded image links. I also converted the video from MOV to MP4 (with "web optimised") which allows it to be embedded in the post inside "video" tags for auto-play. I checked the web host support site - they do not list any issues with speed, so I don't know what's going on there.

Anyway, well done. Let me know when you get sick of your one and only NBTV8 video and want some more stuff to watch :)
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