Mechanical SSTV Steps

Forum for discussion of SSTV topics. Slow Scan television (SSTV) is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or colour.

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Postby Harry Dalek » Tue Apr 26, 2011 1:09 am

Hi still working over time on project heres some photos of tonights experiments ..not having the led a mm or so from the glow paint sure makes the light levels drop i can only vew in the dark or partly darkened room.

I have been looking into if any mechanical sstvs have ever been made i think from what i have found all use paper in a fax type idea either normal paper or electrostatic ..

Theres a nice bit on a fax sstv using electrostatic paper in 73 magazine from 1973 i have, when i have time i will grap and post it . gos into how to make it fax or sstv .

I am not really interested in the later sstv converters to fast scan and colour ...sort of lost its diy slowly over the years from the later 70s .

I agree with steve that sstv was at its best at 8sec B/w these days you may as well just use the internet for photos if you go down the road which way of sending photos is better ...for me classic 8 sec was the original and the best and you can still make it ...

My project ...to fix light levels i need to either increase that or reduce the screen size ...smaller rotating mirrors ...

I will any case get back to the sstv modulating the led now and see what happens .
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Postby Harry Dalek » Tue Apr 26, 2011 4:12 pm

Ok here is the only other mechanical sstv idea i have come across so far in project form .

hope you find it of interest as i did .
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Postby Harry Dalek » Fri May 13, 2011 2:49 pm

Hi all

Have not been on for a while as i have been ironing out some problems with the design....

I was going to swap as you saw and go with the flat screen idea but i don't have enough light doing it this way ..i don't have a blue laser yet so i am stuck with using the uv led and using this idea it would be to dim once i start modulating the led.

So thinking about the problems i have on what i want it to do ...

I have gone back to the rotating drum with the uv led close up with a dvd lens this gives me a raster much better than in my past videos as i was using a high brightness white led which must have a wide freq range in light up to the uv.

I have worked out using a stroboscope using a luxeon led i can stop the drum rotating and view any thing on the drum, read or what ever rather nice effect ...took me a while to work out its not just the freq of the strobe but the pulse width ,that range controls the focus .

The luxeon is a white one but must be more in the yellow as it does not effect the glow paint even if you try and burn a dot onit by putting it up to it for a while .

So just what i wanted ,the strobe effect but not effecting the drum .

My next experiment is to see if the strobe still works with the raster light on the glow drum ,this i am not sure about but i am going with it as a mechanical one would work and does for nbtv ...if it doesn't i expect a drum effect that its stationary and the image is blured as its still rotating .

I know its much easier to to with a non moving screen and i could still just stop the drum after a scan but i want to try.

And yep paper monitor again would be easier and work on a rotating drum but thats been done perhaps not with a strobe but been done.

When i get motivated again i will stick up some more video photos .
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Postby Harry Dalek » Wed May 18, 2011 12:02 am

Just updating working out the a correct viewing on the msstv scan system i have to hook up the uv led to a timer fast enough to give me dots or dashes to test the strobe on the drum as the drum rotates at speed ...i can see i works on the drum and make it stationary but haven't got to testing that part yet ...if it does i can move on if not ..on to another redesign ! i don't think i want to stop the drum after every scan to see a fading image and to sync it would be hell as well, need to see it line for line scanning down.

Which i have been thinking about i would have a half a can of some size a view screen cut out of it i would then bolt a a plastic transparent screen paint that with the glow paint inside side of the can ..then have this can via a arm bolted to the 8 sec up down dvd arm i am now using for the uv led .

This is my vertical movement .

The Horizontal i would like a rotating led but don't know how to do this via wiring , thinking of a uv led on a vibrating Hd voice coil arm via a rod movement to match the plastic glow paint screen size .

This would swing the uv led close behind the glow paint screen and give me the same focused raster dot as using the other system idea .

reason i would use a curved screen instead of flat thus a half can will do !

I was also thinking of a rotating can with 2 holes either side and a led array held in the can ...so i am not giving up easy
...still have to do the above test if i see what i want to i will post ,sorry i takes me a while to do this stuff !
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Postby Harry Dalek » Thu May 19, 2011 12:50 am

Hi i did my experiment on the tin with light pulses written on the drum and got it up to speed the stroboscope idea does not work on the light there were well written gaps in the lines written on the drum from a timer so i know if this does not work its only going to work if you write it to the drum and stop it to view .It could be because the glow paint reflects the light from the strobe in the gaps to close the the amount of light the glow paint is giving off at the same time ...perhaps again it would be better if the glow paint was dark .

In any case not really what i want so i will move on to the next plan i want to view it live not stop it like a fax drum ...i am going to start and build the extra bits needed tomorrow ..i will start with the slow moving viewing screen then work on the Horizontal side ...

i will post pictures as i construct.
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Postby M3DVQ » Thu May 19, 2011 1:00 am

how about a larger drum with a slot rotating in the opposite direction so that it sweeps across the glowing drum to freeze the image. Sort of like a zoetrope
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Postby Harry Dalek » Thu May 19, 2011 4:47 pm

M3DVQ wrote:how about a larger drum with a slot rotating in the opposite direction so that it sweeps across the glowing drum to freeze the image. Sort of like a zoetrope


Hi

I tried a disc but was not getting results i expected then i swapped to the stroboscope luxeon light i went electronic....worked great for the drum but trying to stop the light between timer gaps i wrote on the drum with the uv light did not seem to work ...

Funny enough i made a zoetrope for my daughter last weekend and i tested one of the image animation strips on the drum with the stroboscope and that works great you can speed up reverse slow down stop the animation ...

The system i used could be used but you have to stop the drum after the scan theres enough glow to see what ever is written for some time ...if i fail on the new idea i think i am stuck with that ..

The best way would be to use a blue laser on the flat screen idea with the rotating mirror ...to do it as i tried with the uv led is very hard to focus the light and theres a lot of light loss ,but with a blue laser this is the way to do it ...need to get one of those buggers one day .

The new idea i started on today is a bit of a reverse of the drum idea to at least slow down the screen so i can see whats written onit in real time .

The screen moves but slowly at the 8sec rate ...
And the led does the horizontal movement on a HD voice coil arm ...this worked for a laser at 12hz for nbtv so 15 or 16 hz isn't to much different ..
This is the first idea i will try i am interested to see how a drum would work with a raster hole and a line of leds held on the inside of the drum as it rotates draws a line..have to be close to the screen but could not be any worse than a mm or so it has to be anyway a lens and one uv led does ...only thing here is light loss worse mmm ? i still think the screen would again have to have a bit of a curve to it .

For testing i will see how well a small flat screen works the screen should have a curve to it to match the arm swing to keep the uv led and lens dot in focus ..thats why i was thinking of a plastic thickness of say plastic fizzy drink bottle .

I have painted a small screen today for testing and mounted the voice coil.

I could go for that drum with the hole idea when i make one if the focus and light levels are ok ...would give a larger raster ...i will muck around with it and let you know .
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Postby Harry Dalek » Fri May 20, 2011 12:22 am

More sstv monitors for those interested...Keep the original alive i say ! computer modes are ok but i have noticed no one bothers with the best.
Don't need a pc for this one.
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Postby Harry Dalek » Sat May 21, 2011 9:06 pm

Hi

Putting some ideas to the test today i started to try the vibrating
horizontal idea but i had these ideas so could not help my self and did some tests .

first photo is what i had planed but it was too tight a fit and the drum wobble put that idea to an end for now unless i find something with a better fit .

So in the other photos i have a cut away screen ,i can at least with this sort of adjust it in and out and does not effect the drum.

The idea is the screen moves up at the 8sec rate there is a raster hole in the drum the uv leds would be in a line in the drum in line with the hole ...
as it draws one raster line screen moves up waiting for the next turn of the drum for the next hole in the drum ...number of holes to screen size and smaller slower drum spin ..any case have not got to this part yet and just have that size screen as it was best curve fit and the vertical movement is about that height anyway .

Doing a uv led test the led could be half way in the tin it does not effect the light to the screen that much doing it that way.

What i would love to do is have the dvd lens embedded in the drum and rotate the led to give least amount of light loss .

I did make one mistake i should i painted the inside of the screen seems to work better if the light hits is directly ..mine hits it through the plastic from behind .

anyway thats what i am up to at the moment like always thing could change with the next idea .
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i really wanted it to look and work like this but the fit it too close and theres a bit of a wobble to the drum and it slows the drum..it just needs to be a mm bigger .Oh well...plan two.
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Postby Harry Dalek » Tue May 24, 2011 8:42 pm

Hi just looking at some forums as i was interested in if glow paint of different types glow to different light frequencies ..

And i did learn something from this post...zinc red glow in the dark powder looks like something else i could try with my green laser .

Oh on the project have been working last few days i plan to do the led for the drum thursday did a 2 led test tonight seems to give enough light just with the drum hole i might do another drum with a lens on instead of just a hole and see the difference .


http://laserpointerforums.com/f66/revie ... 37953.html



First Rule: the light's wavelength has to be shorter than a threshold to do any charging (shorter wavelengths have more energy per photon). If it's too long a wavelength, then it will not do any charging regardless of how bright it is. Also, shorter wavelengths than necessary (excess energy per photon) have no additional charging effect. One photon of the threshold energy or greater, one atom gets bumped into an excited state and higher photon energy doesn't get to do it twice or anything.

UV is wavelengths SHORTER than the visible spectrum, infrareds are LONGER wavelengths than the visible spectrum. IR is totally wrong, the opposite of what we need.

Zinc red is the ONLY type which can be charged with a green laser. And, BTW, the effect kicks ass. You can even mix in a little red with other colors and it doesn't show up strong and fades quickly under normal circumstances but hit it with a green laser and you get an awesome blazing track of red that fades quickly.

405nm will charge ANY glow power color effectively, it is visible as a purple color but does not appear very bright to the human eye which loses sensitivity in this area. 375 nm is mostly invisible to the human eye so you'd see a burst of the glow powder's color and little or no purple, however, it's potentially more dangerous to deal with an invisible, higher energy 375nm laser, and it may be harder to get a shorter wavelength laser with the same charging power as a 405nm (fewer photons).

What's the maximum wavelength? Well, blue LEDS are usually centered around 470nm but their actual emissions are a bell curve of wavelengths, around +/-40 nm but the actual amount of light is much lower once you get even +/- 20nm from the center. I can say that the blue LED has SOME ability to charge glow powders but it's not very strong because apparently only the minority of its light at the upper end is a sufficiently short wavelength to have an effect. But I can say 405nm is completely effective for sure!

Sorry but the reality is you need a blue laser but they're currently expensive. Most of those out there have been removed from a Playstation 3! Given time, they'll become more available and much cheaper. No one can say when. You can get them on eBay. But note that many "blue" lasers are indeed blue- ~470nm- and probably won't charge glow powder. You need 405nm.

You can use a <405nm LED to trace a line or dots on the surface, but it MUST be in contact with the surface or you'll get a wide, fainter area. An LED can be focused into a "sort of" narrow beam with the right optics but it'd be pretty extreme optics (large, and carefully chosen).

All this is a limitation of the physics and we can't change physics, you'll get the same answer anywhere.
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Postby Andrew Davie » Thu May 26, 2011 11:48 pm

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Postby Harry Dalek » Fri May 27, 2011 1:28 am

Andrew Davie wrote:http://www.rotorbrain.com/blog/2009/05/ghostmatrix.html

Perhaps of interest?
Cheers
A


Hi Andrew

Thanks for the post

Boy thats a lot of electronics to do low definition writing yakes.

Gary showed a guy doing pictures photos using a blue laser but that was computer controlled ..

Both show the Glow paint or a type they were using can be used for a fax sstv idea but its being programed to do it .

I am more interested in doing it simple as ,once you start using computers and processing power of many ic's it sort of to me like trying to make a radio for 100 dollars that works less an one you can buy.

mine might end up being crappy but there will be no computer control its forbidden !

I used to watch this show
http://www.youtube.com/watch?v=vkVVSiUfEag

Secret life of machines heres part one on Fax

look for the others 2 and 3 the are about to

Also look at the vcr one and television episodes they are of interest to us as well Love that show !

The demonstration on a string fax just to show how it works is interesting
as could have the phosphorescent on the string running passed a uv led
as its modulating and rewinds back on the other drum to draw the picture .

I have also worked out another way to do it using one of the drums i used in my cat food tv posts the Helix drum but i will finish this idea first.
It would with a mask allow a flat scan of the uv light across a flat surface.
So no curves and keep things in focus little optics needed.

I have another post for a sstv mechanical system i have found coming soon just have to post when i have time .





Harry
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Postby Harry Dalek » Fri May 27, 2011 2:00 pm

Hi today i was doing a quick test of the uv led array.. it will be mounted via a arm in line with the drum raster hole.

It doesn't seem to matter to much rotating past each led theres enough light spread between till the next led ..so i will try this see how it gos..

So try and get out in the shed when i can get a few minutes of work in and get back to where i was up to with the last idea...nothing exciting yet but getting there.

Heres also some interesting bits out of 73 mag on Slow scan television circuits and a sstv using a fax drum.
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Its not to bad for day time
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Postby Harry Dalek » Sat May 28, 2011 9:58 pm

Hi after my youngest son knocked my project on the floor of the garage it put it back together this afternoon to test it ..did something to the reset reed switches but apart from that its back .

I mounted the uv leds on a arm with a twist adjustment so i could line it up with the scan edge either side of the glow paint screen.

The light levels are a bit low still once the drums up to speed but only have one raster hole at the moment i will just try a lens with another drum as i know with the first idea it writes well even in day light with only one led.it was hard to take night photos its about the same as the rotating mirror idea but better focus at the moment ,getting there .

The moving screen works well so i should see patterns if i hook it up to a timer now in real time.
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Postby Harry Dalek » Mon May 30, 2011 11:54 pm

Today i tried an Embedded dvd laser lens on the drum ,that seems to work much better than just a hole .

The focus was great i am wondering it i should increase the uv array now mmm

The photos don't show it as its pretty bright but the line is very thin and the light is at a point ...

Need to do a motor test again now .

you might think the glow paint glows anyway when hit by light but it really only stays bright depending on how much light intensity is directed to it more it stays bright longer less quicker it fades ...get the right amount as i did on my first gos with the rotating glow long enough for a 8 secs glow .

The first gos it would work in day light and at night was spot on ..i am just trying to get back to the light levels really needed for the project so a lot of thinking and trying out different ideas ...

I do have now a blue laser of the right frequency for this glow paint coming its the same type as my green laser with adjustable lens ...should have it a 2 weeks if it takes the same time as the green one.

Doing this project with a laser would be easy i'd be hooking up my slow scan tv circuits up by now but till then i really want to see if i can get the light levels with the leds its looking good again .
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This is the light levels via the dvd lens at night
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The fade is very good at night
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