Photomultiplier Tubes camera build

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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Sun Nov 20, 2016 9:21 am

Klaas Robers wrote:It looks as if your picture is better than your sync pulses.

If you want to try a free running disc, it is better to run the DC-motor on a constant current than on a constant voltage. Due to the fact that the copper wires of the motor run hot, the wire resistance is getting higher and the motor slows down after switching on. If the current is constant (see the attached circuit diagram taken from the latest NBTV-Handbook) the driving torque is kept constant. The disc speed then depends on the air friction of the rotating disc, which is in your case nicely constant in your light tight enclosure. So once the speed is set correctly it will not change any more.


Hi Klass the koala wav was from 2012 the flying spot i forgot i had got it to sync very well towards the end .

I had a look at what i did and it is really the club motor control but with an added ...( LM317 to the motor control )....also to the motor so both ideas in one , and it sure looks good .

I just tried it and it again works ...so this helps a bit more .

So yes Klass the LM317 is added now

Pity about the mechanical distortion of lining up each line i understand it could be a slight wobble to the disk or my encoder is a touch off center so the opto reflector is seeing the spacing a touch off or a bit of both ....something that had me wondering to fix this if the mechanical control is now synced to the crystal clock why not switch the video sync mixer to the 400hz crystal clock ...... the motor control its still motor controlled by both the encoder and crystal circuits and the wanted video might now be undistorted each line lining up ...sounds to good to be true i know i have tried it before and i think there was a framing drift or just touch off begin and end positions like to just have a look at this again .
Attachments
400hzlm317test.wav
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400hz_test.gif
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Last edited by Harry Dalek on Sun Nov 20, 2016 11:03 am, edited 2 times in total.
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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Sun Nov 20, 2016 10:51 am

Well getting better ......today i have given the crystal clock idea a go and it seems to work i am feeding the 4060 crystal 400hz clock to Garys 555 monostable and that to the video sync mixer now that sure fixes the mechanical line problem .

I adjusted the camera for this size you can see the lens via the hole in the cd case the lens is mounted on ...i could not make this out before i can blow up the area with the zoom on the lens to cover all the filming area to move this out of view or most of it ..left it in to show .

So heres the very first tests trying this circuit change .
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crystalkoala.gif
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crystaltoy.gif
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ibcrystalkoalatest.wav
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incrystatoytest.wav
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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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Re: Photomultiplier Tubes camera build

Postby gary » Sun Nov 20, 2016 12:04 pm

Very nice Harry, the slow roll you now get is probably due to the xtal itself - there maybe xtal "experts" who can tell you how to "tweak" that very slight inaccuracy out if you wanted to go to that trouble - hardly worth it though.

Now you can concentrate on the hard stuff, like eliminating noise, depth of field, lighting etc etc etc ;-)

I am prepared to say that you now have a working NBTV camera - congratulations!
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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Sun Nov 20, 2016 5:56 pm

gary wrote:Very nice Harry, the slow roll you now get is probably due to the xtal itself - there maybe xtal "experts" who can tell you how to "tweak" that very slight inaccuracy out if you wanted to go to that trouble - hardly worth it though.

Now you can concentrate on the hard stuff, like eliminating noise, depth of field, lighting etc etc etc ;-)

I am prepared to say that you now have a working NBTV camera - congratulations!


Thanks Gary ! yep i am not that fussy i would start again and fix things i know now would help it now other wise ....i will leave that for the next camera !

Yes not perfect but i am very happy when i can improve it here and there....i still have to see how it gos off battery as well

Theres no framing i suppose from the missing pulse which is on the mechanical side of it i could insert it perhaps .

Crystal has a trimmer have not checked if it has enough range to change any thing .

It has an interesting start up it reminds me of a valve tv warming up as it syncs up then theres a bounce for a time which is the difference i think from the crystal to the encoder syncing the disk ...i took a video i will upload after .

Video below just afternoon indirect room light i like not having to use a lamp lighting !
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crystalharrrysmall.gif
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Re: Photomultiplier Tubes camera build

Postby gary » Sun Nov 20, 2016 6:16 pm

LOL That's great Harry! If I had any of my old cameras working now (instead of packed away in pieces in moving boxes) I would put up a card saying "You're welcome!"
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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Sun Nov 20, 2016 7:55 pm

gary wrote:LOL That's great Harry! If I had any of my old cameras working now (instead of packed away in pieces in moving boxes) I would put up a card saying "You're welcome!"



HI Gary i know to get to this point on cameras i have to thank you lots of good advice over the years and days still.
I bet on your cameras they would be interesting to see .it would be great if you got the chance to show the cameras on the forum one day and document them ,but i know what its like with moving and boxes i still have stuff from 2001 move down here packed away .
From the sounds of it you have made a fair few over the years !
BTW my sons got a kick out of seeing them selfs on TBP via the camera ...i turned the screen so they could view them selfs
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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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Re: Photomultiplier Tubes camera build

Postby gary » Sun Nov 20, 2016 8:05 pm

They are great - very clear!

I think I have built 6 cameras over the years only 2 remain and they are in pieces.

I do intend to get back into it as soon as I have finished building my garden shed and a few other landscaping and yard things - I wish I had your skills in the garden! ;-)
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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Sun Nov 20, 2016 8:20 pm

gary wrote:They are great - very clear!

I think I have built 6 cameras over the years only 2 remain and they are in pieces.

I do intend to get back into it as soon as I have finished building my garden shed and a few other landscaping and yard things - I wish I had your skills in the garden! ;-)


Yes have to see some one make one who knows what they are doing ! please do a build one day again:wink: i just never have any plans just an idea and depends if i have enough skills failing and success evening out a bit now....the direct light camera was something i wanted to make 3rd time lucky it seems .

Oh the Gardening visa versa on ya !
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Re: Photomultiplier Tubes camera build

Postby Klaas Robers » Mon Nov 21, 2016 6:36 am

Harry, you show always (wildly) moving subjects. In this way it is impossible to see for us how well your Nipkow disc is synchronized to the 400 Hz of the crystal clock. Make a card with a black horizontal line and place that stable in front of the camera. Then we can see two things:

1 in how far the disc itself is hunting or stable rotating. You can also see huw fast the disc stabilises after switching on.

2 in how far the apertures in your disc are correctly punched / drilled, because deviations will show a crooked line in steds of a straight line.

A camera is not always meant for moving scenes.......

The use of the crystal stable 400Hz pulse is obvious, however your sync pulses coming from the disc show the jitter in the encoder disc.
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Re: Photomultiplier Tubes camera build

Postby gary » Mon Nov 21, 2016 10:04 am

Klaas Robers wrote:Harry, you show always (wildly) moving subjects. In this way it is impossible to see for us how well your Nipkow disc is synchronized to the 400 Hz of the crystal clock. Make a card with a black horizontal line and place that stable in front of the camera. Then we can see two things:

1 in how far the disc itself is hunting or stable rotating. You can also see huw fast the disc stabilises after switching on.

2 in how far the apertures in your disc are correctly punched / drilled, because deviations will show a crooked line in steds of a straight line.

A camera is not always meant for moving scenes.......

The use of the crystal stable 400Hz pulse is obvious, however your sync pulses coming from the disc show the jitter in the encoder disc.


Yes Klaas it would be good to see a test card held steady which is what I asked for a few posts back but then I realised he has a somewhat limited viewing area - sort of like "tunnel vision" at the moment (surely something related to his optics and how they are arranged and should be easy to fix) - he waves it around to get the whole card in view - and thus I didn't press him on it.

Harry hasn't shown any pictures of the signal in "free run" but he has shared some of the wav files which can be used to observe much of what you refer to. The sync jigger is now more-or-less solved as this gif shows - it also shows the slow roll I refer to - this is almost identical to the slow roll Vic and Peter have experienced with their crystal generated signals used for test VSB - thus my assumption, and I would be surprised if I am wrong, that the slow roll is due to the frequency being a little off in the xtal (which could possible be "tweaked". Klaas, you would have a better idea of that than I would, I would suggest.

If Harry does an experiment where he starts recording and then switches the camera on we would also get to see how fast it stabilises.

The other things like the accuracy of the disk, noise (which he definitely need some help with) etc is something he should now be able to do since he has a fairly stable picture, viz.:

(Note: this is the original signal played back in "free run" - i.e. no sync processing or timebase correction.)

output.gif
output.gif (1.54 MiB) Viewed 4170 times


Please note that these gifs go through a fair amount of processing and aren't totally representative of the real signal, however they give a good idea of it, obviously going to the original wave signal is preferable.
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Re: Photomultiplier Tubes camera build

Postby Steve Anderson » Mon Nov 21, 2016 6:37 pm

What's needed Harry is the camera being 'locked off' to a stable non-moving test image. i.e. the camera doesn't move nor the subject and of a reasonable duration. Boring maybe, but it's the only way to analyse what's happening within the camera.

As for a 'reasonable duration' over to Gary and Klaas..

What Gary also wants is a recording of the 'wind up' to normal speed from rest with the same non-moving subject and camera. The 'wind-down' may be useful too.

If the file ends up too big for the forum we'll work something out. If possible record it as a mono wave file at (say) 24kHz sample rate direct out of the camera...Gary/Klaas over to you there.

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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Mon Nov 21, 2016 7:00 pm

OK fellas i will post up a test card and start up card .

I know the answer will be thats its no perfect but it is for me i am happy :wink: i can stick something in front of it and know what it is ....a slight wobble to the disk drift so on i am sure could be improved ..if the wills still there for me my goal is a portable battery nbtv camera here that i can take it on a tripod stick it in the yard and film record the signal to my samsung phone .
Of all the problems i didn't think i would have and that is to much light so that might be a down fall unless i pick the right time end of day .
Still have not tested the battery supply yet the inverter voltage needs dropping this RCA PMT is way more sensitive than i was thinking at the start
I will show what i can to day as loosing day light ....
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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Mon Nov 21, 2016 8:12 pm

Steve Anderson wrote:What's needed Harry is the camera being 'locked off' to a stable non-moving test image. i.e. the camera doesn't move nor the subject and of a reasonable duration. Boring maybe, but it's the only way to analyse what's happening within the camera.

As for a 'reasonable duration' over to Gary and Klaas..

What Gary also wants is a recording of the 'wind up' to normal speed from rest with the same non-moving subject and camera. The 'wind-down' may be useful too.

If the file ends up too big for the forum we'll work something out. If possible record it as a mono wave file at (say) 24kHz sample rate direct out of the camera...Gary/Klaas over to you there.

Steve A.


Darn i just missed your post Steve on the 24 bit i did 16
i will put these up and perhaps try again just wrong time of the day to do this stuff ...
I didn't think a test card test as Gary Klaas asked for so sorry about that guys you got to be blunt with me :roll: ..i was thinking more artistic in the demonstrations i can see i must be more scientific !
Ok what i have here is ......because i can switch between the encoder sync and the crystal...via ...a...Switch :D it was easy to do a encoder sync start up and a crystal and normal play between the two so hope it is helpful ...the encoder starts up quicker and the crystal has a bounce for 2min 30 sec before you can't notice it with the eye ...Still rather the crystal ///
I can see any movement of the camera will cause a problem here so tripod work only i should think .
Now the test card is a few nbt...and a bit of v letters of my hand drawn test card from 2012 its the letters in that picture notice i had to angle it reason i had not tried this much .Had to use a torch touch off the image to not wash it out .
OH what i did forget to do was check the frequency of 400hz on the encoder i have an fine tuning adjustment on the back of the panel some time i knock it and it can go off ..i put that there in case i need to adjust it every thing will be inside the can when circuit board and pmt are mounted ....so just in case its off and your wondering ..
Yes gary the tunnel effect is the distance my pmt is from the lens i just guessed it i was thinking the size of the raster would be meaningless to the PMT / Picking it up the raster it would be displayed like on you software right size i hoped ...but looks like it should of been mounted a touch closer to the lens ..but thats ok i know now thats some thing for next time .
Last wav is under the picture
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nbtvcrystal.wav
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nbtvencoderl.wav
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nbtvencoderlstartup.wav
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IMG_0597.JPG
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mononbtvcrystalstartup.wav
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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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Re: Photomultiplier Tubes camera build

Postby gary » Mon Nov 21, 2016 8:53 pm

Sorry Harry I don't understand the difference between

nbtvcrystal.wav which is good
and nbtvencoderl.wav which is bad

Can you point out the different circuitry - I was under the understanding that whatever speed control you were using you were using the encoder. If you are not using it with the crystal circuitry what is controlling the speed of the motor?

You now have me absolutely and totally confused.
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Re: Photomultiplier Tubes camera build

Postby Harry Dalek » Mon Nov 21, 2016 8:57 pm

Hang on sec gary i will check !
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