Non-electric Television.

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Postby Roland » Fri May 04, 2007 11:03 am

Stephen wrote:Yes, Roland, see my proposal for an optical fibre scanning element at http://www.taswegian.com/NBTV/images/OFSS.pdf . Referring to Figures 1 and 2, you would simply replace the modulated light source 4 (or photoelectric sensor) as shown with the end of the transmission fibre.


Thanks for that - in fact - now I look at it again I wonder if fig 4 might be the best bet. My first batch of fibre optic arrived today and this is the 1mm fibre bundle in a 2mm sheath.

As I suspected its too thick to mount on a Nipkow style disk - but I think it would work quite well in a drum configuration with protruding fibres. Its rigid enough so that centripetal would not be required to make the fibres extend.

I was also thinking of making the drum hub quite large in relation to the length of the fibres to allow plenty of room for the transmission fibre(s).

I think I need to do some drawings to figure at how best to build it. I don't have the facilities or the skill to cope with accurate machining - and I'm not a 'completer/finisher' so I try to avoid projects which require large amounts of work before any results are forthcoming. ;-)

Stephen wrote:I am glad that you are working on this. I wish that I had the time to do so.


Don't worry - I don't have time either ;-) I'm also trying to put the finishing touches to my 8" paper disk monitor as well as completing my 12" club disk version. Tonight rather than do anything useful I spent ages trying to think of an easy design for making the hub of a fibre optic 'drum'! (but it is fun :-))

:-)

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Postby DrZarkov » Fri May 04, 2007 4:30 pm

Yesterday I saw at my local electronics-dealer so called "TOS-link cable" for modern Hifi equipment. This is glas fibre, and it has a kind of connector with a lense. Best of it: It is normed, so we could connect several fully mechanical receivers. I had not enough money with me, so I will buy this weekend one meter of it for testing. I don't think that much light will go through it (or any other glas fibre), maybe a flying spot scanner would be the better option, the advantage is, that it would be easy to mount for many receivers an own cable. Even then I'm afraid the pictore at the monitor will be so dark, you need to watch it in completely darkness, maybe through a hole in a box where you see the picture.
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Postby AncientBrit » Fri May 04, 2007 5:36 pm

I came across a source of cheap fibre optics.

Last December I bought one of those small illuminated table decorations consisting of a 150mm tall plastic Christmas tree with embedded fibres.

At the base are a couple of battery powered bulbs which provide the source for the lighting.

It didn't take much work to "liberate" the fibres when the festive season was over.

Regards,

GL
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Postby DrZarkov » Fri May 04, 2007 6:24 pm

The problem is, that those fibres are very short. Maybe enough for testing, but not for "real" TV.
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Postby DrZarkov » Mon May 07, 2007 4:37 am

Today I've got a Toslink cable, 2.2 metres long. Very astonishing, with normal daylight (it is here cloudy now, and I'm inside), without any lenses there comes light through! These cables would surely be suitable for a non electric NBTV-monitor. A good source for cheap Toslink-cables is www.kabelstudio.de.

Of course you still have no amplifying, so you will need a lense-disc or a mirror-srew (or drum). At www.led-tech.de (a shop in my neighbourhood) they sell small lenses for use with ultra bright LEDs. Maybe they are suitable for a lense-disc.
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Postby Roland » Tue May 08, 2007 6:52 am

DrZarkov wrote:maybe a flying spot scanner would be the better option, the advantage is, that it would be easy to mount for many receivers an own cable. Even then I'm afraid the pictore at the monitor will be so dark, you need to watch it in completely darkness, maybe through a hole in a box where you see the picture.


Yes - I quite agree that a flying spot scanner does seem to have some advantages in this situation. I hadn't considered using this method before you mentioned - but maybe I'll give it a try.

I've been offline over the weekend - but have made a little progress on my fibre optic design. I've bought a large diameter cardboard mailing tube to make the hubs out of. I've also managed to buy some old bearings which I hope to mount the main axel on.

The plan is to have 2 fibre optic units on the same axel - one used for scanning and the other for viewing. Each unit will have 32 fibres - 4 groups of 8 giving an 8 line dsiplay with a high FPS.

I think viewing will have to be in the dark and the scanning unit will have to be encased in its own box - complete with the object/picture that you are trying to view. The box could then either be very brightly lit or alternatively have many fibre optic ends mounted in it for a flying spot style scanner.

For lighting I am going to use high powered LEDs which is certainly a bit of a cheat. I'm also going to drive the axel by electric if I can find a suitable sized motor. Curiously enough the main reason for keeping the RPS fairly low (and hence the need to scan more than one frame per revolution) was that I didn't think I would be able to find proper bearings quickly/cheaply so I was concerned about friction. Also at the same car boot sale I picked up the bearings - I also found an old bicycle dynamo - so maybe I will drive this as a motor and achieve 750RPS after all (or maybe I'll just rig it up to my spare club disk ;-) )

Light transmission still seems to be the biggest problem and I've got a fair bit more building to do before I see just how much of a problem it really is.

:-)

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Postby Stephen » Tue May 08, 2007 7:21 am

Roland wrote:The plan is to have 2 fibre optic units on the same axel - one used for scanning and the other for viewing. Each unit will have 32 fibres - 4 groups of 8 giving an 8 line dsiplay with a high FPS.
I think that the fibre optic scanning elements should work fine. You just need to make sure that the ends of the fibres in the "optical commutator" are close enough so that as the fibre end for one line passes out of range of the end of the transmission fibre that the succeeding end starts to enter it. Otherwise the top and bottom of the reproduced image shall vignette.
Roland wrote:For lighting I am going to use high powered LEDs which is certainly a bit of a cheat. I'm also going to drive the axel by electric if I can find a suitable sized motor.
That makes sense. You can substitute limelights for lighting and oil-fired drive engines later if the system looks workable.
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Postby DrZarkov » Tue May 08, 2007 5:01 pm

For the optical commutator you could possibly use very small lenses like they are sold for ultra bright LEDs separately. The light-source of such a LED is about the same size like the glas fibre, the result behind the lense is similar to a normal LED.

Talking about cheating: I would make a normal club standard 32 line monitor, you could use the signal from a club disc transfered through a single LED connected to the speaker output from the CD-player transported by the glas fibre cable to test the monitor.

BTW: Last week I was thinking too how to make a non electric TV with Nipkow-discs. Without seeing you pdf I came out to a very similar solution. It seems to me the easiest way to get results. But currently I'm busy to make my "normal" NBTV monitor, so I wait for your results first, that will help me to avoid mistakes :D
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Postby Roland » Wed May 09, 2007 11:05 am

Well the .5mm fibre optic turned up today. This is bare solid fibre which is much more flexible than the previous stuff. I think its suitable to use on a Nipkow disk - although it will add to the air resistance.

Another project for me to try when I have more time ;-)

:-)

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Postby Roland » Wed May 09, 2007 11:24 am

DrZarkov wrote:Of course you still have no amplifying, so you will need a lense-disc or a mirror-srew (or drum). At www.led-tech.de (a shop in my neighbourhood) they sell small lenses for use with ultra bright LEDs. Maybe they are suitable for a lense-disc.


Thanks for this suggestion - these lenses do look useful and I haven't seen anything like them in the UK. As you mention they could also be used for the optical commutator in the drum arrangment I'm planning on.

I did a few quick calculations and as I intend to use 1mm fibre - the 8 line display will only be 8mm (at most) in width. Therefore the optical commutator only has to cover an 8mm width also although it also needs to cover the 11.25 degree angle over which each fibre travels when it is active in the display.

As well as lenses - I have a few ideas around mirrors which I hope also to try out.

I could of course make each line up out of more than one fibre but I think that 32 fibres is plently to deal with inside the hub anyway.

The other thing I hadn't counted on was the aspect ratio of the picture. I expected the fibres to be pretty short - and I wasn't wrong! The picture is likely to be very tall compared to its width. ;-)

:-)

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Postby DrZarkov » Wed May 09, 2007 4:26 pm

The picture is likely to be very tall compared to its width


Just make the disc smaller!
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Synchronisation problem solved!

Postby Stephen » Fri May 18, 2007 1:17 am

Well let us say that Roland proves the viability of non-electric television that I proposed. We all start building our Stirling engine-powered non-electric television systems. How do we synchronise the displays with the cameras? All that we have between them is an optical fibre or rod, and possibly a speaking tube for audio.

Hmm, a speaking tube...what if a Stirling engine drives a pump of the hydraulic or pneumatic type. The camera and display motors of identical displacement of the hydraulic or pneumatic type connect to the pump in series. Since they are powered by the same volume of fluid, they must rotate at the same angular velocity and they therefore are locked to each other.

The only extra item needed for complete synchronisation is a framing control. This could be a knob to manually rotate the display motor housing about its shaft axis.

Now for a complete full-colour non-electric television system we have an optical fibre or rod, a speaking tube and a synchronisation line of the hydraulic or pneumatic type. Well, for a hydraulic system there would have to be a return line too, so perhaps pneumatic is better.
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Re: Synchronisation problem solved!

Postby Roland » Fri May 18, 2007 10:48 am

Stephen wrote:Well let us say that Roland proves the viability of non-electric television that I proposed.


Well I am still working on it - but progress is slow.

I've decided I will stick to the club standard of 32 holes after all.

The optical commutator will be mounted at one end of the drum and consist of the 32 fibre ends in a circle around the shaft. The transmission fibre will be as mounted as close to this circle as possible - but obviously won't rotate with the shaft so that each of the drum fibes will in turn pass the transmission fibre as the drum rotates.

By substituting a LED for the transmission fibre I will be able to test the drum without having to build the camera at the same time just by using a standard club signal.

As mentioned before I've obtained some bearings and some tubing for the hubs. I've used CoralDaw to make a drilling template for the hub and I'm just debating what the hole spacing should be. Currently I've set it at 1mm but as the fibre is only 1mm in diameter also - this may leave black lines. On the other hand a 32x48mm picture (before maginifcation) is quite appealing :-)

A colleague has kindly found some other sized cardboard tube for experimentation and also a length of M12 threaded rod for the shaft. This morning I managed to buy some M12 nuts too.

The main area I've not tackled is the motor. Of course I plan to use a Stirling hot air engine in the long run but for the moment I need a small electric motor - a bit bigger than the usual NBTVA cassete motor sort.

I have some spare plastic drive belt material so I may 'borrow' the motor from my (very old and worn) lathe and belt that up to this new shaft. Alternatively if it would stop raining here I will get back to my usual hobby of visiting car boot sales where old motors are not too hard to come by.

Anyway - thought I should give a progress report. I think I'm better at talking about this than actually doing - but hopefully I'll get down to building it soon! ;-)

:-)

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Re: Synchronisation problem solved!

Postby Stephen » Fri May 18, 2007 12:33 pm

Roland wrote:Anyway - thought I should give a progress report. I think I'm better at talking about this than actually doing - but hopefully I'll get down to building it soon! ;-)
Thanks for the Report, Roland. I think that you shall find the optical fibre drum the finest sort of optical scanning display that you can make. It shall have absolutely no distortion and remarkable efficiency. It is probably the best choice for both electric and non-electric television. I think that your optical fibre drum project in itself is just as exciting as the non-electric television experiment.

I was just thinking that with a common Stirling engine driven pneumatic pump that drives the pneumatic motors for the camera and display scanning elements there is no need for a constant frame rate. Since the motors run in series, they could vary over a considerable range as long as they are fast enough to eliminate flicker. You could adjust the Stirling engine to make the pneumatic pump deliver enough air so that the system runs at a minimum of 50 fps, but if it drifts up to 75-100 fps, all the better. "Problems" that electric television encounters like full colour, synchronisation and flicker disappear with pneumatically synchronised colour non-electric television. Pneumatically synchronised television has a nice ring to it!
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Postby Klaas Robers » Sat May 19, 2007 6:47 am

Why do you want to use Stirling Engines? Isn't it much easier to use a steam engine? You will have much less problems in getting enough torque using a steam engine than with a Stirling Engine..... I know Stirling Engines, I have two of them. They are difficult to start up, while a steam engine just runs.
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