NBTV Camera Question

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Postby gary » Mon May 14, 2012 9:52 am

harry dalek wrote: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 .


Sorry Harry, what do you mean "with no light levels"? Are you saying you are getting high output from the sensors even in dark conditions? That would probably mean you are picking up RF (e.g. motor noise) or the circuit is going into oscillation.

I am confused here because didn't you show us the circuit working with your hand waving in front of it?

Are you still using the mic input or have you moved to the line input?

What levels do you measure when you display it on your CRO?

Have you tried reducing the gain on the record channel using the PCs mixer?

Motor noise is a problem at the best of times - and one reason I decouple all of the sensitive circuitry by running from batteries to begin with - that doesn't help the rf (that's why you enclosed it in a metal box) but prevents the noise being coupled into you circuit via the power rails. - even so - the motor noise won't prevent you getting a picture - it'll just show up as spots in you picture - you can see them in them in my example that you posted a link to at the beginning of this thread.
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Postby Harry Dalek » Mon May 14, 2012 4:50 pm

Klaas Robers wrote: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.


Hi Klaas i suppose if it gets to that it wouldn't be to hard to make a box and just have the lens poking out of lens sized hole .

On the sensor side of things i told gary about this a while back but i would be interested what you think and others think about my past system try.

When i first tried a camera monitor i knew that the light sensor had to modulated the light of the monitor i had made ,i tried amplifying it but don't think i could do this right at the time(things never change ) !,it was a photo transistor and i came up with the idea of instead amplifying it let the transistors light range just vary and an oscillator ...at the time i didn't know the band width needed and it did modulate the neon light at the time
but band width wise who knows.
What i am interested in is i still think this is a cleaner way of doing it ...my camera sensor was behind the nipkow ...so different to this .
Also what is more sensitive to low light my past experiments i was thinking a photo transistor then ldr then the solar cell.
Using the circuits it to me always seems to be the change in resistance that is used including the solar cell ?
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Postby Harry Dalek » Mon May 14, 2012 5:53 pm

Hi gary

No but when i hook it up to the mic input of the laptop tried it on 2 programs both off scale theres a little bit of noise on the scope line...have to look if theres a way of dropping the mic jacks level i see there a line in level control in xp volume control..haven't tried that .



The motor noise you can see soon as it starts very big spikes on the scope
i am pretty sure its because i have the power to every thing going into that one 8 wire cable ..perhaps i need to have the sensor power removed from this



It worked ok before my rewiring to the case ...i also noticed which isn't hard with seeing whats on the scope when it happens when my light torch switches to flash i can now see the same sort of effect its power is via the cable now to this was not a problem before this rewiring as well..at least on normal light mode theres no problem ...but i can see this is the problem for the motor ...



Gary my lap top does not have a line input just mic... : (



Have you tried reducing the gain on the record channel using the PCs mixer?

Yes didn't help its either 0 or full no between ....did drop dropping the voltage to the circuit but that drops its sensitivity...perhaps just a variable resistor will do the trick.

Yes gary that rf from the motor was over running every thing i think because it and the sensor power supply wires are together in that cable and shielded cable at that not far for the rf to travel to suppose made a transformer in a way :roll:

I will work onit more tonight....well just put the pot in that worked one down ......now i can record to the mic input ,now lets see if i can fix the motor problem.
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Postby gary » Tue May 15, 2012 10:17 am

Do you have snubbing caps across the motor's terminals?
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Postby Harry Dalek » Tue May 15, 2012 6:18 pm

gary wrote:Do you have snubbing caps across the motor's terminals?


No Gary will try ! ...

thanks i wanted to know what audio recoding program you were using i will check them out .

I downloaded 3 32 line nbtv live soundard programs to see if i can see something in time ,does your software do it ? i am always just using vlc player to play wave files back for the monitors never really tried or had much use for a live soundcard program till now.



i didn't get much out of the sensor at the low light levels last night i did have it reduced in voltage and the new pot due to that motor noise ,I can see from playing around with it its a bit of a balancing act between how much light you have and how sensitive the sensor circuit is .

I have to try repeat what i was getting the other night out of the sensor with every thing running .
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Postby gary » Tue May 15, 2012 6:38 pm

Yes TBP does it, that was specifically what it was designed for.

Since you don't have sync yes you can use TBP in syncless mode.

I have a lot of NBTV analysis software I developed for this purpose too, so I suggest you send a copy of something to me as soon as practical - I should be then able to tell you how it's looking.

BTW you usually only get sporadic spikes out of the motor so it should prevent you getting a picture, snubbing caps should help too.

I repeat what i said earlier too, you really want as much gain as possible, sure you are amplifying the noise by doing so, but you really should be working to eliminate the noise because when you reduce the gain you reduce the video signal too and it is normally very low, besides the signal to noise ratio will be the same unless it is introduced by the sound card.

I am still concerned about you using the mic input of a laptop - they are notoriously noisy. An old P4 salvaged from your dump shop would do a better job.

Edit: I hate to nag but believe me, I have been through all of these "gotchas" many times. ;-)
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Postby Harry Dalek » Tue May 15, 2012 8:49 pm

Hi gary

I have your software some where on here thats very good i didn't know it could do that as well ! i am impressed ...

I have a lot of NBTV analysis software I developed for this purpose too, so I suggest you send a copy of something to me as soon as practical - I should be then able to tell you how it's looking.

Thanks Gary I want to do that just need to get it to work like the other night then at least i can tell its the nipkow light and not noise.
I played around last night recording but i think it was just random noise, on one of the programs i was using i could see the speed change in the nipkow but this could just of been motor noise to ..i will believe it when i see some sort sync line thats its working ..

BTW you usually only get sporadic spikes out of the motor so it should prevent you getting a picture, snubbing caps should help too.

Ok i does worry me but i have not tried your idea it was reduced by passing the cable ..i can always as you did go to batteries .

I repeat what i said earlier too, you really want as much gain as possible, sure you are amplifying the noise by doing so, but you really should be working to eliminate the noise because when you reduce the gain you reduce the video signal too and it is normally very low, besides the signal to noise ratio will be the same unless it is introduced by the sound card.

The circuit i am using best results i have got so far are running it off 12volts gain gos up with voltage ,i was thinking of pushing the voltage up a bit more but i don't want to brake it i think the Bc549s can be run up to 30 volts so it tempting to go a bit more .

I am still concerned about you using the mic input of a laptop - they are notoriously noisy. An old P4 salvaged from your dump shop would do a better job.

I am sort of stuck with this for the testing ,i could use my wifes desk top when i know its working .

Edit: I hate to nag but believe me, I have been through all of these "gotchas" many times. ;-)[/quote]

Don't worry Gary i would never complain about that ...when i know your happy with the progress so am i ,i know i am getting it right then ! :)
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Postby gary » Tue May 15, 2012 8:58 pm

Just one thing Harry, the voltage rail is really only an issue if the gain of your circuit is causing clipping - it shouldn't be with the recommended supply rail.

Just another - having worked on this kind of thing for years and years I am very adept at determining what is noise and what isn't - also I am pretty experienced at getting a signal out of the noise - so if you think you should be getting something give it to me and I'll soon let you know if there is something useful there - often it is a good clue as to what might be wrong.
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Postby Harry Dalek » Wed May 16, 2012 1:11 am

gary wrote:Just one thing Harry, the voltage rail is really only an issue if the gain of your circuit is causing clipping - it shouldn't be with the recommended supply rail.

Just another - having worked on this kind of thing for years and years I am very adept at determining what is noise and what isn't - also I am pretty experienced at getting a signal out of the noise - so if you think you should be getting something give it to me and I'll soon let you know if there is something useful there often it is a good clue as to what might be wrong.


Gary it seems okay now i just played around with it tonight .
Did a recording is a bit half hearted go as i didn't check the speed i was more interested if i could see the sensor pick up a little test card ...i am pretty sure its way off but you may be able to tell me if some thing is happening there or not.
I am trying to post it but the net is pretty slow today i will try again tomorrow...bit of a pain when its like this .
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Postby Harry Dalek » Sat May 19, 2012 10:19 am

Been working on the project and getting a lot of help and advice from Gary so this has gotten me to another stage .

I can now hear and record the raw video without sync i think the video is still poor but its above or equal to the noise level at least ...

I have found distance and size of the projected raster is very important for the light sensor to receive it .

it very similar to receiving a DX radio signal and seeing a tv image that weak in the snow....

I have swapped the luxeon torch with a 100mw green laser i had handy with a different lens that lets me defocus the laser beam to a round circle size depending on the distance to the projected object ...in my case just small or large enough for the nipkow scan ....

Did this to see if i could get more light and still stay small i am not sure if the torch was still good enough as i didn't test the torch the same way as this laser for the raster size and scan distance for signal strength ,so be it this is where i am at and what i was up to since the last post .

Heres wav sound of the best recording i have made not viewable no sync and speed may be off but you can hear the nbtv and the snow to give you an idea perhaps gary can decode it fingers crossed ...the noise where it varies is my fingers crossing the test card ..remember its not a viewable file at the moment just sound so you will not see much.
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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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Postby Harry Dalek » Wed May 23, 2012 5:16 pm

Sorry for the long delay again for those interested in this project ,i will update more often now .

Since my last post my laser has come and gone :cry: Once wiring it in for good i killed it for good miss wiring some caps over the dual power supply.

It worked fine for the project and was used in testing...i did like the light its diffused better than a torch luxeon and you can direct it better to a smaller area such as th nipkow holes .

Gary has helped me process this unsynced video to get something out of the snow i will up load after i post ths you should be able you see my eye of the world drawing at the end ..if you keep an eye out at the moving about at the bottom of the test card ....i used that card in the above and used this laser for this video.
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With the laser this is not a laser focus this is a laser defocused and via the nipkow hole.
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This is the laser without the nipkow
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only few lines shown of a close lens setting scan test
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aaa.avi
You may just see the eye of the world drawing at the end
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Last edited by Harry Dalek on Thu May 24, 2012 1:19 am, edited 2 times in total.
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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Postby Harry Dalek » Wed May 23, 2012 6:12 pm

I am a long ways from finishing and very happy with my poor results i am pleased easy !

I can see it is something even i in time can get working and i find the camera thing very new and interesting .

Again i have to point out with a lot of help and advice from gary its making it go easier ...it is harder than i was expecting at the start but well worth the time :wink:

I have made a new light detector made useing 2 little solar panels and the same circuit with one change adjustable feed back to the first transistor .

Will post a circuit in time .

The reason for upgrading or trying was the surface area the sensor sees i wanted a larger detecting area to do away with a lens .

I am going to see if i change the dome sensor circuit i can get it to the higher amplification of this new one.

Results so far its strong enough but i have to find out where its picking up a 50hz hum and i am thinking its my multi strobing torch it flashes with a different fash rate with each turn off and on and i think the last which looks on always to me may be at 50 hz ...if not i will walk arounf the room again with my cystral eye phone and this solar cell light sensor and try and find it ....could be picking up the mains its pretty sensitive ,i may have to go all battery .
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Last edited by Harry Dalek on Wed May 23, 2012 6:47 pm, edited 1 time in total.
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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Postby Harry Dalek » Thu May 24, 2012 4:09 pm

Today i have placed 2 encoder printouts on 2 of my nipkows and i will be doing the electronics for it tonight .

I tracked down the 50hz hum on my video and it was coming from the lap top power supply cable ....if any one else out there makes a head amp it or a spare with a crystal ear phone has come in very handy working with the light sensor where the various noise problem levels are coming from ...Tvs lighting and in my case the lap top screen and as i said the ac power supply ,earlier one it was my motor for the nipkow as well till i put a cap across it even the last the light torch its self the torch was giving off pulses .


:roll:
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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Postby Harry Dalek » Sun May 27, 2012 5:41 pm

Last few days been having a lot of trouble with the encoder disk and reflective light sensor ...Again with advice from Gary we tracked it down to being the encoder disk and or the light sensitive photo trany there was enough reflection off the black part of the encoder disk to stop it working stop the light chopping in other words .
There are 2 ways to fix this first and i went this way use the black of the cd which was darker than the print out and enough for it to work so i cut out the black print out parts and used the cd for that part ...this worked i get a nice on off signal now each slot .
The other way i didn't try being lazy was solder in a pot to the emitter of the photo trany to make it less sensitive to the light being relected back from the print out black slot ...may have worked but thats for another time .

As you see in the photos thats the way i made it and you can see the camera has picked up the IR light from the IR LED while working ...getting a nice correct speed pulses now via this .

The camera is getting closer to being what it is being built to be ...Its really a dual project with all the help from gary i don't think i would of got this far .
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My reflective sensor circuit
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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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Postby Harry Dalek » Tue May 29, 2012 10:02 pm

Yesterday i filmed a few videos with my Now i can say it NBTV 32 line CD disk camera as its pretty viewable now .

The images are still not wonderful but i know i can improve on it ..you can now clearly see the iron cross and the ABC letters .

Its an angled scan i keep forgetting this to line it up to the scan lines .

Once again with help from Gary processing the raw video on one channel and sync pulses on the other of this wav recording ,,,,it seems to work .

I still have to make a video sync mixer my self but for me this is a high light of the build ... so it can be done with a 195 lumens torch and cd !

Oh and a very close up view of me bit to much zoom this time sorry!!!!
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heres the test card used
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my first vis]deo sync test2[1].wav-out-sans audio.avi
My Iron cross ABC video.....
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my first test me[1].wav-out.avi
close up of me .... very close can only view this small see my eye : )
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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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