Photomultiplier Tubes camera build

[Harry Dalek]

Testing today heres one of the kids toys at a bit of distance from the camera sorry about the reflection....and my son Charlie helping me as i don't have a Stooky bill handy
Quality on the short clip for upload is better and not the same as these gifs best to put on repeat ...VLC player is good for this .
Still a problem at some distance with levels ...i did find there was light leaking in from my curry can which the PMT was in the effect was a static ...i will have to seal around the sides on the testing .
I ended up changing the sync pulse width looks to me like i should of also reduced the hight also more /

[Harry Dalek]

I so far have not be able to get the camera to work above negative 630 volts a touch below yes ..i have hooked up a 1 meg pot up just works using that on the high setting what ever it reduces the voltage to need to look into that ....and again only on the 630 voltage setting every thing else is either to high or to low ...sort of lucky i had a few voltages to choose from on my bench top power supply to start off with ./

I tried a few setting changes on the preamp and the pot into the video sync mixer they both gave a level change one in gain other in brightness looking at other NBTV wav videos on Garys scope as i mentioned in the last post i am next looking into the sync level ,it looks to me on black level mine is still way to large which i think the effect on the camera is a limit on the gray scale ...more than likely only getting half /

I also had a disaster with the PMT coming loose from the Nipkow housing ...on 630 volts ...it still seems to work ok lucky i was not on full voltage!

Also noticed the effect of bar lines if you use a fluro as lighting works still apart from that not that you would want it !

Lucky i went with the bench power supply first up , i can see trying it on battery inverter i will have to deduce the voltage some what way to high for this at the moment .

Day 3 so far so good

[Panrock]

Congratulations on what you are achieving Harry! Kids' toys make a great subject for NBTV televising. I shall try to attach an .avi of my own PMT camera televising "Micky", as viewed on a mechanical monitor. I seem to remember my camera had a rather narrow dynamic range, and to get reasonable results the lighting had to be just right.

I also attach a photo of the camera as it appears now, gently decaying and falling apart in the workshop, unused and unloved for several years. I could send it to Australia for Christmas, but would it work upside down?

Steve O

[Harry Dalek]

Hi Steve thanks for the reply there yes getting there i can see it is very fussy on the correct light levels voltages and such ...i am lucky i didn't stick with a higher voltage on my PMT or i would of got nothing but a white screen .
Your PMT camera is much harder than mine 3 tubes and in colour ..its what i saw that made me want to try to make one..it is sad after a project is over they end up in a corner in the shed in my case ...but for now i still want to improve it best i can a touch more so i will try again in the coming days .
Any case i am very happy to get my first direct light camera going had a go at 2 others over the years ..
Now i know what to expect i will make a other in the future a touch better ...this one still needs to be run off battery power then i will be happy .

[gary]

I tried a few setting changes on the preamp and the pot into the video sync mixer they both gave a level change one in gain other in brightness looking at other NBTV wav videos on Garys scope as i mentioned in the last post i am next looking into the sync level ,it looks to me on black level mine is still way to large which i think the effect on the camera is a limit on the gray scale ...more than likely only getting half /

Harry you should be able to adjust the levels of the signal within TBP to get the grey level you want.

If you record and post some of the signal I can check it and make suggestions on how to adjust TBP for best performance.

Cheers.

[Harry Dalek]

Hi Gary
Thanks for that i will do //if you are on line i have just made some videos will upload just checking them my self !

[Harry Dalek]

I did some videos for Gary to check came out very clear live but i did a dreadful job of recording them !
Rushed job rushed looking results//
I also recorded whats coming out of the lm311 encoder circuit and the 555 mono for pulse width ....sync to video sync mixer

BTW Steve i forgot i would love to see your camera going again please do post any thing here i have only really seen mickey mouse shot ...whats its limits in distance ? mine i can see picture fades away with distance more than likely due to lack of light only really tried a room work so far .

Edit ok i have worked out the videos have been recorded inverted inverting then back they play fine ...

[Harry Dalek]

Here's My other son William helping my out with the camera today apart from inverting the video thats all i have done with this one he's very close to the camera as i was filming some toys bit earlier and focus was this distance.Now i just need correct lighting !
And putting it together !

[Harry Dalek]

Just a look at the PMT i gave it a bit of clean and cleaned out the Nipkow holes as i noticed some were clogged up a bit this pig toy gif was done before the clean

[gary]

Looking good Harry, I have looked at one of the 2 signals you sent me and I can see that if you could get your disk speed more consistent you should be getting some darn good pictures. The speed doesn't have to be exact but it should be as consistent as possible over at least a frame period - at the moment it fluctuates considerably over just a line period which distorts the line length considerably. I think that even if you increased the mass of the disk with a circular weight of some kind to get more of a flywheel effect I would expect a big improvement. On the other hand improving your speed control mechanism would be even better.

[Harry Dalek]

Looking good Harry, I have looked at one of the 2 signals you sent me and I can see that if you could get your disk speed more consistent you should be getting some darn good pictures. The speed doesn't have to be exact but it should be as consistent as possible over at least a frame period - at the moment it fluctuates considerably over just a line period which distorts the line length considerably. I think that even if you increased the mass of the disk with a circular weight of some kind to get more of a flywheel effect I would expect a big improvement. On the other hand improving your speed control mechanism would be even better.

Hi Gary
I'm Still using one of the original nipkow's i was testing on the first flying spot camera so it has the cut out encoder stuck on the disk ...as i recall no matter how good i am at cutting it would never be as good as a direct encoder print out ..now the pulse widths must be a touch out each line ....Remember all the problems i had with the reflective opto switch ...i now can use a print out i have not bothered up to now as i was not sure the thing would work so just used what i already had .

This might help as well so will look into that .

Will have a think about what i can use as a fly wheel a am sure i have something in my shed .

I am using the 4046 pll over the 555 bistabe i just have both wired up ,one works depending on if i have plugged its ic in and pulled the other out ,i did a lot of just in case with this see what was better .

Well i will work on your advice...here's a short test i tried of me if i kept in the focus area might of been better

[gary]

Hi Gary
I'm Still using one of the original nipkow's i was testing on the first flying spot camera so it has the cut out encoder stuck on the disk ...as i recall no matter how good i am at cutting it would never be as good as a direct encoder print out ..now the pulse widths must be a touch out each line ....Remember all the problems i had with the reflective opto switch ...i now can use a print out i have not bothered up to now as i was not sure the thing would work so just used what i already had .

This might help as well so will look into that .

Will have a think about what i can use as a fly wheel a am sure i have something in my shed .

I am using the 4046 pll over the 555 bistabe i just have both wired up ,one works depending on if i have plugged its ic in and pulled the other out ,i did a lot of just in case with this see what was better .

Well i will work on your advice...here's a short test i tried of me if i kept in the focus area might of been better

Oh Harry, my apologies, yes I see by closer inspection that the line variation is constant across frames so yes it is your encoder at fault not the speed of the disk (although that is varying somewhat too but nowhere near as badly as I thought).

Well that's different - when you put a new encoder on that problem should be solved - I can't wait to see it, it should make a BIG difference.

[Harry Dalek]

Oh Harry, my apologies, yes I see by closer inspection that the line variation is constant across frames so yes it is your encoder at fault not the speed of the disk (although that is varying somewhat too but nowhere near as badly as I thought).

Well that's different - when you put a new encoder on that problem should be solved - I can't wait to see it, it should make a BIG difference.

Hi Gary

I will look into printing an encoder out ,i should have time to mount and test tomorrow ...

Yes it could could well be that we will find out for sure tomorrow plus if there is still a problem .

Ii i need more mass on the disk i was thinking of using large steel washer i would think a fly wheel effect would work better on the edge of a disk than closer to the center but might be enough for that little cd motor any case i will see how the encoder improves it .

I have up loaded another me try today with the cleaner Nipkow holes apart from one trouble maker may be i have one over lapping ...any way what i did was waving my glasses about like a fool ( have to be careful not to brake them or my NBTV days are over till i get a replacement !) and again i see the focus was much closer to the lens than i was expecting BTW you may notice i have my gardening hat on .....Increasing the light levels just into the room with the blinds up you get the effect of that wavy black bar above my head when you decrease the light levels that tends to go flat ...you also get the bright white spots from any thing reflecting back to the lens that is to white ...so its either a better picture with lower light levels that look washed out or like this with more light ...
Not sure this is an encoder problem...see what happens tomorrow.

[gary]

Oh Harry, my apologies, yes I see by closer inspection that the line variation is constant across frames so yes it is your encoder at fault not the speed of the disk (although that is varying somewhat too but nowhere near as badly as I thought).

Well that's different - when you put a new encoder on that problem should be solved - I can't wait to see it, it should make a BIG difference.

Hi Gary

I will look into printing an encoder out ,i should have time to mount and test tomorrow ...

Yes it could could well be that we will find out for sure tomorrow,if there is still a problem .

Ii i need more mass on the disk i was thinking of using large steel washer i would think a fly wheel effect would work better on the edge of a disk than closer to the center but might be enough for that little cd motor any case i will see how the encoder improves it .

I have up loaded another me try today with the cleaner Nipkow holes apart from one trouble maker may be i have one over lapping ...any way what i did was waving my glasses about like a fool ( have to be careful not to brake them or my NBTV days are over till i get a replacement !) and again i see the focus was much closer to the lens than i was expecting BTW you may notice i have my gardening hat on .....Increasing the light levels just into the room with the blinds up you get the effect of that wavy black bar above my head when you decrease the light levels that tends to go flat ...you also get the bright white spots from any thing reflecting back to the lens that is to white ...so its either a better picture with lower light levels that look washed out or like this with more light ...
Not sure this is an encoder problem...see what happens tomorrow.

Hi Harry, on further reflection I think I have to go back to my initial analysis - your disk "appears" to be hunting. Have a look at the following snapshot:

speed problem.jpg (8.97 KiB) Viewed 12184 times

Looking at the sync bar (which is quite narrow BTW), the bar is wavy and quite jagged - I think the waviness is due to your disk "hunting" - that is speeding up and then slowing down, and the jaggedness of the line is due to minor variations in the encoder.

When I step through the wave file the sync bar waves up and down sinusoidally - a tell tale sign that your disk speed is hunting around the required speed for some reason.

So maybe a flywheel would help - personally I think you would be better off with one of the voltage regulator type speed controls as the speed will still vary but much more slowly - that is common type of speed control for cameras so it can't be too bad. Just a thought though.

I actually have some software that can use the sync zero crossing position to correct that waviness - if I can find it I will see how well it works on your signal.

PS: A flywheel must be well balanced, adding a washer to the outside of the disk will ensure chaos - unless you add other washers to balance it up - a real pain in the proverbial to do.

Old cassette, tape, and VCR players are full of flywheels - I bet you have hundreds of them.

I think I saw a tacho encoder on the inside of your sync encoder - have you tried using that to check your disk speed (using a 50hz light source)?

[Harry Dalek]

Hi Harry, on further reflection I think I have to go back to my initial analysis - your disk "appears" to be hunting. Have a look at the following snapshot:

When i view on my sound card scope 1.46 on the frequency screen it shows me it sticks to the around the wanted 400hz but yes theres a slight wobble hunting as you say ..no perfect for sure ....see gif below

Looking at the sync bar (which is quite narrow BTW), the bar is wavy and quite jagged - I think the waviness is due to your disk "hunting" - that is speeding up and then slowing down, and the jaggedness of the line is due to minor variations in the encoder.

I can adjust the sync bar i have it to narrow setting by the sounds of it i will adjust that back to a touch wider ...
I have got off my bottom and printed out a new encoder and fixed it to the disk so far no missing pulse added ....i will see in the morning if the hunting slight swing is any better ..it must be a mechanical problem or something to do with the feed back as i am using a crystal clock with the 4046.

When I step through the wave file the sync bar waves up and down sinusoidally - a tell tale sign that your disk speed is hunting around the required speed for some reason.

OK i can see this is not good enough and look into it .

So maybe a flywheel would help - personally I think you would be better off with one of the voltage regulator type speed controls as the speed will still vary but much more slowly - that is common type of speed control for cameras so it can't be too bad. Just a thought though.

Garry i do have control of the feed back to the motor as a panel control ,but never thought of true manual control ...it works very well with a stepper motor on SSTV still drifting but slow very slow i did try a dc motor to see but it was much faster and very hard to control over the stepper idea .
I haven't tried this but it come to mind as i recall reading posts reversing the inputs for the clock and encoder circuits to the PLL some times makes a difference .
I will observe how this gos and try some thing else one at a time if there is still hunting .

actually have some software that can use the sync zero crossing position to correct that waviness - if I can find it I will see how well it works on your signal.

OH that would be interesting to see it fixed up if you can find it .

PS: A flywheel must be well balanced, adding a washer to the outside of the disk will ensure chaos - unless you add other washers to balance it up - a real pain in the proverbial to do.

mmmm yes can cause more of a problem i was thinking of 2 inch,,,,ish steel washer just glued over the disk hole position think any thing to large i might not even get the disk to move on start up ..

Old cassette, tape, and VCR players are full of flywheels - I bet you have hundreds of them.

OH yes didn't think of that, again depends on if my little motor with motor control can start up ...it might as a could still kick start it with the feed back panel control come to think of it

I think I saw a tacho encoder on the inside of your sync encoder - have you tried using that to check your disk speed (using a 50hz light source)?

OH that is a left over from the flyspot days its now under the new encoder printout