NBTV Camera Question

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Postby gary » Sat May 12, 2012 5:31 pm

harry dalek wrote:Not sure if i can record a syncless video i suppose baird did it ?as i can just plug that in to the pc when ever now.


Damn right you can, however, if your disk is not running at a constant speed it makes it difficult, although not impossible, to get a steady picture.

Please note that all of Chris Longs recordings from the early days (some of which are posted on this forum) are without sync.

If you do that, you may not see much, but if you send it to me I may be able to timebase correct it for you (depending on how bad it is).

harry dalek wrote:As you see i have relocated the light sensor box and have added a lens which is a giant version of the one used on the sensor which i hope does the same thing but amplified ,its at a distance where the sensor fills all the lens area ,i also have a bit more the azimuth and elevation control of it if need be .So i hope it sees more area than the tiny sensor does .


That may work, on the other hand it may reduce your depth of field and angle unnecessarily. Try it, it it doesn't work you can always take it out - I found the dome cell by itself is good enough.

harry dalek wrote:I suppose also an easier way would be just to use a larger solar cell panel
I think the dome sensor is just a more efficient solar cell for its size ...


You could also use several cells in series.


BTW what is that lens at the back of the laser pen used for?
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Postby Harry Dalek » Sat May 12, 2012 6:14 pm

Hi Gary
I do have a plan on a syncless idea at times i can get the thing the nipkow pretty much steady ...i have the idea of first displaying a nbtv test card what ever on my little monitor when i get that to the right speed and try to get it steady speed then use the camera nipkow light to scan something and record the sensor signal ,,,i should be close or spot on then using another video as a speed indicator.Reason for this i have not tested the camera to monitor so cheating here in a way till i get that going .

I have another idea i am pretty sure has been done i have read about some where in the news letters as another little way to test the sensor .
Or a not so good sensor is to just project a tiny transparent drawing slide idea instead of reflecting off something that way you could project right to it ....last resort not my want but i suppose a stepping stone that should really be tried first really before dropping light level for lower light level pick up .


I will see if i can track down chris posts on hes camera sounds interesting !

Yes the large dome lens is an idea for no other reason i was thinking my pick was just seeing some lines not all of them i may very well be wrong but no great loss to see either way .

I didn't have a laser pen gary i will look at my photos again the light is a luxeon pen not a laser well not yet any way :wink:
You mean my lens to amplify the Monitors nipkow size ...with my eyes believe me i need that !

OH yes when or if i manage to scan something and post it it would be interesting if you can sync it ..i am still a while away on this part .but sync less i could try now .
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Postby gary » Sat May 12, 2012 8:30 pm

harry dalek wrote:Hi Gary
I do have a plan on a syncless idea at times i can get the thing the nipkow pretty much steady ...i have the idea of first displaying a nbtv test card what ever on my little monitor when i get that to the right speed and try to get it steady speed then use the camera nipkow light to scan something and record the sensor signal ,,,i should be close or spot on then using another video as a speed indicator.Reason for this i have not tested the camera to monitor so cheating here in a way till i get that going .


Well the real problem is in the variation of speed because without sync it's non-trivial to keep in track - the actual speed is not that important, it's more how constant it is.

harry dalek wrote:
I have another idea i am pretty sure has been done i have read about some where in the news letters as another little way to test the sensor .
Or a not so good sensor is to just project a tiny transparent drawing slide idea instead of reflecting off something that way you could project right to it ....last resort not my want but i suppose a stepping stone that should really be tried first really before dropping light level for lower light level pick up .


I think your first test should just be some letters (e.g. NBTV) on a white card - if it can't pick that up then anything else is sure not going to work.

harry dalek wrote:I didn't have a laser pen gary i will look at my photos again the light is a luxeon pen not a laser well not yet any way :wink:

I thought I recalled that you were going to use a laser with the collimating lens off, anyway it looks like a laser pen and I was just using it as a marker, I have never heard of a luxeon pen - perhaps you mean a luxeon torch?

harry dalek wrote:You mean my lens to amplify the Monitors nipkow size ...with my eyes believe me i need that !


Ok, now I am confused... shouldn't that be on the other side of the disk from the FSS? or are you using that 2 extra holes trick?

harry dalek wrote:OH yes when or if i manage to scan something and post it it would be interesting if you can sync it ..i am still a while away on this part .but sync less i could try now .


Without sync it is more difficult, but not impossible, I timebase corrected several of Chris Long's nbtv video and they don't have sync. I just can't promise I can do it, it will depend on the video.

I suggest you DO record some video without sync as a first iteration. At the very least it will give you an idea how well your sensor system is working.
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Postby Harry Dalek » Sat May 12, 2012 9:20 pm

Hi gary

I thought I recalled that you were going to use a laser with the collimating lens off, anyway it looks like a laser pen and I was just using it as a marker, I have never heard of a luxeon pen - perhaps you mean a luxeon torch?

Sorry did mean luxeon torch not pen, pretty strong for small one .



Ok, now I am confused... shouldn't that be on the other side of the disk from the FSS? or are you using that 2 extra holes trick?

I wanted to do that but theres hardware in the way so i have sacrificed a few lines 3 or 4 at the start between it and the torch line start to keep it easy since i had to keep it on this side i suppose once i see it i could do an extra few holes and a mask no big problem with these disks since i have so many .


Without sync it is more difficult, but not impossible, I timebase corrected several of Chris Long's nbtv video and they don't have sync. I just can't promise I can do it, it will depend on the video.

I couldn't find them on the forum but saw hes on you tube think one was a nipkow and others a monitor used to do the scanning ...No thats okay no problem Gary yes i expect BAD ! perhaps very BAD ! but i hope its better nothing hearing chris talk and explain the hes cameras working sort of gives me hope and seeing yours as its one of those things you have to see to believe the things work like that .

I suggest you DO record some video without sync as a first iteration. At the very least it will give you an idea how well your sensor system is working.[/quote]

Yes i think this is the next step and i understand it needs to be easy thing a letter letters or shape worry about gray scale things later but a recognizable thing would be good ...i forgot to i need to make a little mask for that light i will do that and record.
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Postby gary » Sat May 12, 2012 10:02 pm

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Postby Harry Dalek » Sat May 12, 2012 11:57 pm

gary wrote:http://www.taswegian.com/NBTV/forum/viewtopic.php?p=3939#3939


Thanks for that gary you have a good memory where stuff is !
Thats a big wow very interesting i really liked the toby mug rotating have to pinch that rotating idea for the future i like it .

Chris and he's friends there really show off how well it can be done ,you syncing the video is very well done !

I was meaning to ask since you said once you have made a fair few camera ideas over the years ...how did the first one go since i am almost in the same boat but did try 30 years ago so sort sort of second go here .
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Postby gary » Sun May 13, 2012 12:30 am

harry dalek wrote: i really liked the toby mug rotating have to pinch that rotating idea for the future i like it .


Here's my own Toby just for laughs...

harry dalek wrote:Chris and he's friends there really show off how well it can be done.

I was meaning to ask since you said once you have made a fair few camera ideas over the years ...how did the first one go since i am almost in the same boat but did try 30 years ago so sort sort of second go here .


Yes, my own early efforts (circa 1968) were of the most rudimentary kind (mosttly shadows and silhouettes) and were definitely not up to Chris's standards (also of the same period).

But I was working alone and in complete and utter ignorance that there was anyone else in the world silly enough to have an interest in this hobby.

Chris had the advantage of being very interested in amateur radio and so had access to information and equipment I could only dream of which, no doubt, helped him, but on top of that he had, and still has, a great knack of seeking out sources of information.

Of course, in 1968, there were no sources of NBTV video so my first project had to be a camera/monitor not dissimilar to that which you are now working on. The main difference being that I used 2 disks mounted on a common shaft - I used a phonograph motor to turn the disks and recorded the output on tape - alas only one tape now survives and I have been, so far, unable to decode the video - I think it may have been very early light tests and so no actual picture is present. I used to have a picture of the first unit but alas it has disappeared in the mists of time.

I regret that I have very little in the way of records of my systems over the years, mainly because, not having any kids, I have never been able to justify having a decent camera/corder - that remains the same to this day - all the shots I have posted to this forum have been made with a borrowed camera/corder or a webcam.

But Harry, do not despair, as you can see my recent results have been made with a complete and utter bodge of very simple components, so I am sure you will see your own smiling face very soon ;-)

BTW, although seeing a picture on your first monitor is exhilarating, NOTHING compares to seeing the pictures taken by your own camera.
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Postby Harry Dalek » Sun May 13, 2012 3:02 am

Gary i'm up a bit late tonight so off to bed soon but well done ,the video of your mug sort of has a 3D look about it..i sort of like the way these cameras images look...

1968 yes would not have been much info apart from the odd bit in electronics Australia mag you have been in the hobby a long time !

I was just finishing off some soldering with room light plugged my sensor into the computer its level is to high it seems tried to drop it back via the program but still to high...might have to wack a pot in to adjust it before the pc...so i will see if its not needed once its in the dark just working with the nipkow light.

I am busy tomorrow mothers day during the day so hope to work more onit tomorrow night i want to do a test record as soon as i can .
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Postby gary » Sun May 13, 2012 10:19 am

harry dalek wrote:I was just finishing off some soldering with room light plugged my sensor into the computer its level is to high it seems tried to drop it back via the program but still to high...might have to wack a pot in to adjust it before the pc...so i will see if its not needed once its in the dark just working with the nipkow light.


Harry that is normal. What kind of light bulbs do you have? What you are seeing is probably a high AC mains component (100 hz) which can be filtered out or you can switch to CFL.

Don't reduce the level, you will need every bit you can get I assure you.

Edit: Oops, and I should have said, yeah the best thing to do is switch it off - not to save the planet (because it won't) but to venerate the name of The Man Who Saw the Future ;-)
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Postby Harry Dalek » Sun May 13, 2012 6:57 pm

Yes Gary i did one last adjust of the voltage going into the sensor ,i had a 317 adjusting it inside the sensor box but i think i need this adjustable from my case more than likely as you say might have to push it to get every bit out of the sensor .

The recording program i have handy on this laptop is power sound editor and wavepad which i haven't tried the first seems to me like the sensors output is to much for that mic input ...if theres one you find good let me know .

The lights are cfl's direct it direction of the room lighting i can see the sine waveform of the mains AC on my scope.

Yes i will be doing all first tests in the dark i can see all things like the tv room lighting such effect it to much noise ..it was good and clean when i tested it with no lighting apart from the nipkow scan lighting in the room the other night.

It now depends if i can get it to record at a good level on the laptop.
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Postby Klaas Robers » Sun May 13, 2012 7:07 pm

Harry, be aware that when you run a camera-monitor, that the slightest amount of light leak from your light box to the sensor of the camera will set the system into oscillation. The sensor is very sensitive, which is also needed, and the lightbox gives very much light, which is also very much needed, that it is difficult to prevent light leakage. Especially in the open setup that I see in your photos this is almost impossible.

So don't be surprised if
- the camera works,
- the monitor works,
- but both connected gives you an uncontrollable oscillator.
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Postby gary » Sun May 13, 2012 7:08 pm

Using the mic input is not a great idea (too noisy) - better to use the line input - that'll reduce your level :-). Any sound recorder will work. I use Cool Edit. Audacity is good also.

The frequency of CFLs is RF so you shouldn't be getting AC mains hum from them.
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Postby gary » Sun May 13, 2012 7:25 pm

Klaas Robers wrote:Harry, be aware that when you run a camera-monitor, that the slightest amount of light leak from your light box to the sensor of the camera will set the system into oscillation. The sensor is very sensitive, which is also needed, and the lightbox gives very much light, which is also very much needed, that it is difficult to prevent light leakage. Especially in the open setup that I see in your photos this is almost impossible.

So don't be surprised if
- the camera works,
- the monitor works,
- but both connected gives you an uncontrollable oscillator.


Klaas I was going to mention this myself, but keep in mind this is an FSS camera so the sensor is in front of the unit and pointed at the scene. When I was testing my FSS I was able to have the image displayed on a computer screen without any trouble - having said that, the delay through the soundcard and software may have prevented oscillation I suppose.

It will be interesting to see if the small amount of light (in comparison with the flying spot) projected on the scene from the monitor would trigger oscillation - if so maybe the monitor could be turned away from the scene via a 45 degree mirror - the subject won't be able to see it but the camera man can ;-)

I haven't taken into consideration that there may be light *directly* from the light box - I am assuming that will be enclosed enough that very little light would be picked up by the sensor.

In addition I think that the sensor box can be disconnected from the camera itself and moved to an optimal position (it should be - position of the sensor is critical to a good picture).
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Postby Harry Dalek » Mon May 14, 2012 1:23 am

Hi thanks for the comments and help there Gary Klaas i have run out of time today but i have found a big problem i didn't have last time i tried and thats motor noise ,i have hooked up a few other things so it could be from that wiring .

The signal level from the sensors still to high to record off scale on the pc sound card recording program ...even with no light levels tried to drop the voltage to the sensor that drops the sound level also drops its the sensors level so i think i need to just put a pot in and see .

I was hoping to record some thing today but looks like i have more head scratching !

I don't really have a light noise problem from stray light from it more light noise if i leave things on ...in the room,i can see that on the scope.

The lens didn't seem to improve the levels on the scope but i might have it wrong way around ...oh well try again tomorrow.
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Postby Klaas Robers » Mon May 14, 2012 7:36 am

Gary, you know that the light from the lightbox is 1000 x as bright as the light that comes through the Nipkow disc. It is the direct light that changes its brightness steered by the photo detector(s). If you displayed your camera picture on a computer display then the directy correlation in the fluctuations of the light is gone and the danger is gone as well.

In a well screened closed system it is possible to light-screen the light box output from the photo cell. Barriers painted matt black may help. But I see the very open set up of Harries and just wanted to warn him so he will know where the unexpected results might come from.
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