Next project, larger 32 line NBTV 40cm Nipkow disc televisor

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Next project, larger 32 line NBTV 40cm Nipkow disc televisor

Postby aussie_bloke » Fri May 04, 2012 11:39 pm

G'day all.

I am already now gotten started on my next mechanical televisor project which is of course a larger version of my very first televisor, about twice the size! I am going to make a 40cm (16 inch) 32 line NBTV standard Nipkow disc televisor. Looking for what I could find available to make the disc, I found a sheet of plywood that is roughly 4mm thick which I am going to try to make a Nipkow disc out. However two problem factors come to mind, first one is it weighs probably something over 500g so I need a bigger badder motor, second it being plywood when cutting It may possibly split and peel. But will give it a shot anyhow, so far I have drawn the disc on the wood and have marked the holes. I used my brother's big 16" drum cymbal to draw the circle as I didn't have a big bad protractor and to mark the holes I printed the NBTV 32 line Nipkow disc template at 40cm to 4 pieces of paper and sticky taped them to the wood as precisely as possible and punched the holes with a tool that looks like a screwdriver but has a nail like pointy end (what is it called???) pressing through the white holes on the template into the wood. Anyhow will do the cutting, drilling and sanding tomorrow and see how it turns out. In the meantime here's some pics I've taken showing the process I just described in marking the disc.
Attachments
040520126961.jpg
NBTV 32 line template printed to 4 pieces of paper and stuck to plywood
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Closeup of the template showing a coupe of the holes punched
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040520126964.jpg
Sheet of plywood which I'll be cutting and drilling into a 40cm Nipkow disc
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040520126966.jpg
Closeup of the plywood showing the punch marked holes
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Re: Next project, larger 32 line NBTV 40cm Nipkow disc telev

Postby gary » Sat May 05, 2012 10:05 am

G'day

aussie_bloke wrote:G'day all.

I found a sheet of plywood that is roughly 4mm thick which I am going to try to make a Nipkow disc out.



One problem you will find with that is that the disk is too thick and may cause some of the apertures to be obscured when viewed at a comfortable distance (given the size of the image). At best it will cause the viewing angle to be limited to "straight on". Think of it this way, instead of the light having to come through a pin hole it now has to come down a long tunnel so a lot of the light hits the wall instead of your eye.

One way around this that people have tried is to countersink the holes from the back - this is difficult, but not impossible, to do accurately.

Another way is to make the holes much larger and cover with thin cardboard or aluminium foil, etc. and make the smaller aperture in that.

Yet another way is to reduce the size of the plywood disk to just less than the innermost aperture and use it as a backing for a thin cardboard disk of the full size. The sheets of black artists cardboard available from most news agents does a good job.

Yet another way, and one that I personally use almost exclusively now, is to make the holes larger to seat optical quality acrylic balls like these:
http://www.smallparts.com.au/store/part ... ls/wide/1/

These are expensive to buy in Oz (quick), but can be ordered from the US (slower) at a fraction of the price.

The major advantage of the latter method is that you need only one bright LED as the light source.

An example of one of mine is shown here:
http://www.taswegian.com/NBTV/forum/dow ... hp?id=2756

and a poor example of it's performance here:
http://www.taswegian.com/NBTV/forum/dow ... hp?id=2755

aussie_bloke wrote:...it weighs probably something over 500g so I need a bigger badder motor,


You can cut large holes, or spokes in the disk to reduce weight. If you do it is probably a good idea to then cover the holes/spokes with paper/foil/plastic to reduce wind turbulence - although being nicely stiff and strong that may not be necessary.

aussie_bloke wrote:...a tool that looks like a screwdriver but has a nail like pointy end (what is it called???)


An awl?

aussie_bloke wrote:drilling


Note that even for a 16" disk the apertures should be around .03" (1/32") (.762 mm).

Good luck!
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Postby Metallica Man X » Sat May 05, 2012 4:43 pm

haha, you're using the same disk picture I used for my televisor XD But hey, who not? It works!

I'm looking forward to see how well your super disk works out :)
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Postby aussie_bloke » Sat May 05, 2012 11:11 pm

Thank you Gary for the tips, I will implement them the best way I see fit. I have drilled the holes with a 2mm drill bit, so I guess that might be a bit big then so will opt to drill the holes bigger and stick on something thin with smaller aperture punched into it, will first test as it is and see how the pictures come up. Ahh yes "awl" that's what those tools are called, yep that's what I used.

Anyways I have now cut and sanded the disc and drilled the holes. As expected the plywood did split and chip away a bit but fortunately not to the point of abandoning the plywood disc idea. Here below are some photos of my process of cutting and sanding the disc, as seen I made did with what I had available as I didn't have all the necessary tools that someone with a well setup woodwork shop would have.

Now I will have to work out what motor will be good for the task, I have a 3 speed AC electric fan motor I ripped out of one of my old broken fans, will test it and see if it will perform up to the task of driving the disc. Also bought a bunch of yellow LEDs to make the light bank, wanted to use white LEDs but they were expensive so I thought yellow will be the next best thing and it's different to the usual orange, anyone here used yellow LEDs in their televisors???

Anyhow here are the pics:
Attachments
050520126969.jpg
My makeshift workbench to saw the disc, stool and G-clamp
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Done the roughcuts, next follows the finer cuts and sanding
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A reasonably accurate cut disc after a lot of filing and sanding after the rough cuts with hacksaw
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A bit of chip-away of the outter layer of plywood from the filing
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050520126973.jpg
Disc completely cut, filed, sanded and holes drilled
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050520126974.jpg
Holes in disc drilled with 2mm drill bit, some burring evident but it will be removed before put disc is put to use
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Postby gary » Sat May 05, 2012 11:52 pm

Yeah at 2mm that would mean you would be getting more than 50% overlap of the scan lines - you'd get a picture but it would be very blurry I would think.

I should have mentioned, if you didn't already realise it, that you can prevent a lot of chip-out by having a backer board against the plywood whenever you drill or cut.

Not sure how you will control the speed of the fan motor - but a mechanical braking system may be the go.

Good luck.
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Postby aussie_bloke » Sun May 06, 2012 12:00 am

gary wrote:Yeah at 2mm that would mean you would be getting more than 50% overlap of the scan lines - you'd get a picture but it would be very blurry I would think.

I should have mentioned, if you didn't already realise it, that you can prevent a lot of chip-out by having a backer board against the plywood whenever you drill or cut.

Not sure how you will control the speed of the fan motor - but a mechanical braking system may be the go.

Good luck.


I actually did place a piece of wood underneath to drill the holes, but when deburring with a drill bit there was a bit of chip-out.

I will see how the disc will run as is with the 2mm holes and see how blurry the image turns out, if it looks bad I will enlarge the holes and stick the smaller holed pieces of material over them to get the better image.

Yeah the mechanical braking has indeed came to my mind with speed control, I have been testing that with my little televisor by braking the cardboard disc with my finger and it worked more efficiently than continuously adjusting the DC motor speed.

Anyhow will work on it and see how this set will progress and will keep you's updated.
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Postby Viewmaster » Sun May 06, 2012 12:16 am

Nice to see someone else making their own Disk. If the plywood doesn't make out you might consider MDF, if you can get it in your area.
MDF will not split and is very machinable.
Re Gary's mention of the tunnel effect, you might carefully countersink the holes on one side to reduce the tunnel length.....there is always light at the end of the tunnel (!)

If you finish up with plywoood, don't forget to have a fire extinguisher nearby just in case it catches fire. :wink:
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Postby gary » Sun May 06, 2012 10:18 am

aussie_bloke wrote:I have been testing that with my little televisor by braking the cardboard disc with my finger and it worked more efficiently than continuously adjusting the DC motor speed.


Yes a trick used to good effect by many over the years ;-)
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Postby aussie_bloke » Mon May 07, 2012 1:06 am

Viewmaster wrote:Nice to see someone else making their own Disk. If the plywood doesn't make out you might consider MDF, if you can get it in your area.
MDF will not split and is very machinable.
Re Gary's mention of the tunnel effect, you might carefully countersink the holes on one side to reduce the tunnel length.....there is always light at the end of the tunnel (!)

If you finish up with plywoood, don't forget to have a fire extinguisher nearby just in case it catches fire. :wink:


Thanks for the suggestion. I am not so sure about countersinking the plywood due to it's chipping away and also I've already drilled them too big being 2mm in diameter so will be opting for covering the holes with cardboard with a small hole in it.

Anyhow more updates on my progress with this larger televisor. I have loosely mounted the plywood Nipkow disc onto my AC multi-tapped electric motor being held only by blu-tack and I powered the motor up and it seems to be spinning at a decent speed. I'll have to actually mount the disc on the rear end so I get the anti-clockwise motion. So that being done and good, I have then worked on building my LED bank light box putting 20 yellow leds together in a 5:4 ratio and at a size close enough to cover the area of the spiralled holes in the disc.

So here's the latest pics:
Attachments
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Disc mounted on AC motor
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Disc mounted on AC motor
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Disc mounted on AC motor, seen is blu-tack holding the disc to motor to test it
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Multi-tapped fan AC motor
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20x LED bank display
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20x LED bank display
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060520126981.jpg
20x LED bank display
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Postby Harry Dalek » Tue May 08, 2012 4:26 pm

Good luck troy with this one ,never tried a wooden disk ,i tend to use records when i need some thing round.
Also never tried an AC motor to drive the disk so yours is a bit different in that way to me .
How are you going to control the AC motor ? i have a circuit and parts can be got from jaycar if you need it ,think you could pulse width control this with the circuit just need a 555 timer clock at worst a little amp ...i can see that the PLL could be hooked up to this as well.
You may just want to use a light dimmer and try that ?
i don't like the idea of manual braking a AC motor with brushes brush less ones might be safer but think both have a bit of a kick to them if you tried to slow them down by force ,recall in one of my book posts they use to do this with a paddle with rubber i suppose like a big bike brake / i wonder how many motors went up in smoke trying this back then.
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Postby aussie_bloke » Wed May 09, 2012 12:55 am

harry dalek wrote:Good luck troy with this one ,never tried a wooden disk ,i tend to use records when i need some thing round.
Also never tried an AC motor to drive the disk so yours is a bit different in that way to me .
How are you going to control the AC motor ? i have a circuit and parts can be got from jaycar if you need it ,think you could pulse width control this with the circuit just need a 555 timer clock at worst a little amp ...i can see that the PLL could be hooked up to this as well.
You may just want to use a light dimmer and try that ?
i don't like the idea of manual braking a AC motor with brushes brush less ones might be safer but think both have a bit of a kick to them if you tried to slow them down by force ,recall in one of my book posts they use to do this with a paddle with rubber i suppose like a big bike brake / i wonder how many motors went up in smoke trying this back then.


Thanks for the suggestions, will keep them all in mind, just for testers when I first get this set assembled I will manually brake it just to see if it's making good pictures while in sync and will take it from there to incorporate AC motor speed and sync control.

Anyways been further working on construction of my larger televisor, today I have been customising the fan motor to be used for my televisor and started construction on the base. For the motor I cut off the long shaft end at the front as I am using the rear side for anti-clockwise rotation and have cut the stork at the bottom of the motor and I added makeshift mounts to the bottom of the motor using small door hinges sawn off each other and am going to mount the motor on a block of wood nailed to the base. I've screwed a self tapping wooden nut to the end of the threading of the motor shaft (couldn't find a nut to fit so had to opt for that) for the Nipkow disc to lean against, gonna use another self tapped wood nut to hold the disc firm between them and reinforce with superglue. For the base I used an old wooden box I use to use as a light bulb videotape baking oven (it failed miserably). Anyhow disaster struck with the motor, when I opened it up and was tinkering with it a bit it fell to the concrete and one of the windings broke causing the motor not to function, so after a bit of swearing and whinging like a depressed emo I pulled the two broken wires out a bit, put a layer of tape over the area of the coil and then soldered a wire link to the two tiny coil wires and sat it over the tape and it fixed the problem so back in business. And of course had some annoying problems with nailing the wood mount pieces as the wood split so next round I decided to drill holes a size smaller than the nail where I am going to hammer the nails and that solved that issue. Then next issue encountered was screwing the motor to the wood as the self tapping screws screwed in and stripped the self tap thread when trying to tighten them, so will use screw and nut instead when I get back to it tomorrow. Anyhow that's the progress made for now, I am pretty much utilizing resources I have already available at home as I can't budget nor could be bothered going out to different stores for resources unless I really have to. Here below are the pics of what I've done today:
Attachments
080520126988.jpg
Fan motor modified with front shaft end and bottom stalk cut off and door hing mounts added to bottom and wood nut on shaft to support disc
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080520126990.jpg
Wood box (ex videotape baking box) I'm using as a base to mount the motor assembly and light box on and of course the electronics
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080520126994.jpg
Motor and mount on top of base
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Motor sitting on top of its mount
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Nipkow disc added to the motor assembly sitting on mount on base
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080520126997.jpg
Top view of motor with disc on base, as seen the disc is not aligned but that's because disc is loosely sitting on motor shaft
080520126997.jpg (474.26 KiB) Viewed 6800 times
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Postby Metallica Man X » Thu May 10, 2012 6:32 pm

Man, that thing's gonna be a real monster! 8)
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Postby aussie_bloke » Fri May 11, 2012 9:44 am

Success, just got the televisor up and ready enough for testing and she works ooh yeah!!! :D

Talking about the progress leading up to the testing stage since last update, I have done the following:

I have made the box for the 20 LED bank out of a few layers of cardboard paper, lined the inside walls with silver chrome cellophane to hopefully intensify the lighting and stretched a piece of plastic bag over the front end to diffuse the LED bank, the light box measures 5cm in length, 3cm in width and 3.8cm in height.

Now I had to make changes with the mounting of the Nipkow disc onto the motor shaft due to major troubles with the wooden self-tapping nuts, boy there was so much frustration trying to find a suitable way to mount the disc as I experienced failure after failure. Firstly the wood nut split when I tried screwing the disc to it, so I changed it for a more stronger wood nut I made, no splitting happened but the disc was not well aligned at all and was very wonky and spun like crap. So I went to the hardware store to look for nuts that fit the fan shaft, whilst M8 nuts were close fit, the threading was not M8 standard. I tried screwing the nut on hoping it would screw on even if it damaged the thread but it only went on a bit before the vice grips started slipping at the other end of the shaft and I literally had them clamped on He-Man tight!!! lol So I then tried whatever else came to mind, so I put a few layers of heat shrink up the shaft toward the motor, drilled one of the M8 nuts and slipped it down to the heat shrink, then placed some washers on, then disc, then washer, then another M8 nut which screwed on enough to tightly secure the disc. The disc was still wonky on a tilt so I tilted the disc till it was reasonably straightened. Firing up the motor the disc is still a bit wonky but tolerable, it did made the base it was mounted on move around the floor haha so I stuck a couple of heavy objects on top to keep the base sturdyl

Now I finally had the motor and disc secured and ready, it was time for testing. I mounted the light box on a few pieces of wood in position and blu-tacked it to the base (will nail it in later) and I then borrowed the LED light control circuit from my small televisor and soldered it to the 20 LED bank. I then connected my MP3 player to the light circuit and fired it all up and as the motor picked up speed I started seeing pictures forming which was fantastic!:D The AC motor was spinning a bit fast so since I had the AC motor connected to my variac I lowered the voltage from 240V mains standard to about 200V and that slowed the motor down a bit. To slow the motor further and keep the picture synchronised I used a piece of wood with a piece of cut towel on it and that worked very well because not only could I easily slow the motor speed to sync, it was quite easy to keep the motor speed constant and a nicely synchronised and so the picture on the screen is nice and mostly stable! So my large mechanical televisor is now working woohoo!!!:D

There is a problem however, the pictures are dim but I guess it might be due to the disc being a bit thick, but nevertheless I'm getting pictures!!!:D So I got my MP3 player with NBTV stuff I put on there and connected it to the light control circuit and played them and they came up very dim but overall very good and quite recognizable despite the aperture holes being 2mm in diameter but of course a bit blurry as Gary mentioned. And also the pictures look even more straighter than on my smaller televisor too! I will work out a plan to improve the apertures for max brightness and viewing angle but for now it’s satisfactory. There is another strange issue I'm having with the pictures, they seem to be back to front which is noticeable when viewing letters and numbers, I wonder what might be causing that to occur???

Anyhow here below are pictures of my progress with my televisor leading up to testing stage, unfortunately due to dimness of the picture I was unable to photograph it on my phone camera but will soon find ways and means of doing so, just need a low light sensitive camera. Anyways here’s the pics:
Attachments
100520127004.jpg
Light box rear side
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100520127005.jpg
Light box front side
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100520127006.jpg
Nipkow disc in motion
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Nipkow disc in motion top view
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100520127008.jpg
Televisor roughly assembled for testing
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100520127010.jpg
Wood with towel cloth used for manual braking of the disc
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100520127011.jpg
Heavy objects placed on top of televisor base to hold it still and sturdy while disc is in motion
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Postby gary » Fri May 11, 2012 9:59 am

aussie_bloke wrote:There is another strange issue I'm having with the pictures, they seem to be back to front which is noticeable when viewing letters and numbers, I wonder what might be causing that to occur???


Your disk is on backwards - as the apertures are moving upwards across the gate the outermost aperture should be first, in your case it will be the innermost.

I look forward to seeing some video of the pictures. Well done.
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Postby aussie_bloke » Fri May 11, 2012 12:07 pm

gary wrote:
aussie_bloke wrote:There is another strange issue I'm having with the pictures, they seem to be back to front which is noticeable when viewing letters and numbers, I wonder what might be causing that to occur???


Your disk is on backwards - as the apertures are moving upwards across the gate the outermost aperture should be first, in your case it will be the innermost.

I look forward to seeing some video of the pictures. Well done.


Thanks for letting me know but that is really bad news for me as I had so much of a hard time trying to get the disc remotely aligned on the motor shaft with limited resources I had plus the nut is threaded on there. I have just put the disc in the right way and had a really bad time trying to get it aligned again and now the nut is literally stuck on there that when I try to turn it either way, the vice grips clamping the other end of the shaft is slipping. Anyhow the disc is aligned as best I could get it and have just superglued it once again and I hope it will work still, will find out later today.
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