Flying spot scanner mark 2 the Resurrection

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Postby gary » Fri Aug 23, 2013 1:20 pm

Harry Dalek wrote:
Klaas Robers wrote:For my disc monitor I used a DC motor from a video disc player. Nice and strong. It has a magnetic speed pick up, with a small magnetic ring having 18 pulses per revolution. So I had to invent something difficult to match the 18 pulses per frame with the 32 (31) from the CD signal. It took me more than one year to come to a reliable and still simple enough system.


Yes i to used one ,that one on the drum monitor but never used the Ac pulse i have another in my shed i might scrap to use in the future and i have 2 other small ones that do the same thing ...pulses per turn i need to test if i ever use them .
Did you make use of the large neon laser ?

It is easiest to start with two identical sync systems, e.g. 32 per revolution with or without one missing. Then the 'only" thing you have to do is see that the pulses come in at the same rate and at the same moments.


Thats true thats easiest even for me to work out!
I am going to take Garys advice and buy the laser printer for the next encoder (my wife had trouble with the new printer last night ended up she hadn't had the usb plugged in but gave me an excuse to mention the laser printer idea which she liked :wink: ) cheaper than buying the ink cartridges for this HP/


But in your case Harry it's not so difficult. Klaas had to work out a way of getting it to work with different pulses per frame as it had to work with an NBTVA format signal. With your camera you are generating the pulse train with some kind of oscillator so you can make it anything you want, so you can just match what's coming out of the motor pulse generator.

For instance, if you had what Klaas had, 18 pulses per revolution your oscillator would be set at 18 x 12.5 = 225 Hz - when the speed controller locks the 2 signals the disk will be rotating at 12.5 frames a second or 750 rpm.

I am not saying you should do that by the way, only that you CAN.

It might be a fun experiment someday.

BTW, before you buy a laser printer see if you can get a test print out to take home first - that way you can make doubly sure it is IR absorbing.
Perfecting an NBTV system is like trying to slam a revolving door...
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Postby Harry Dalek » Sat Aug 24, 2013 3:57 pm

But in your case Harry it's not so difficult. Klaas had to work out a way of getting it to work with different pulses per frame as it had to work with an NBTVA format signal. With your camera you are generating the pulse train with some kind of oscillator so you can make it anything you want, so you can just match what's coming out of the motor pulse generator.


Tell you what would be useful a variable pc display theres a lot of set standards but nothing really to fine tune stuff thats a bit off frequency between standards not nbtv Standard or your own new idea .

I will take that good advice on board .

Back to NBTV Standard my big problem at the moment is correct speed control the motor was changed but i forgot i have extra mass on the disk with the 32 LEDS this might be causing a swing in the frequency reason its not working the same as before .

For instance, if you had what Klaas had, 18 pulses per revolution your oscillator would be set at 18 x 12.5 = 225 Hz - when the speed controller locks the 2 signals the disk will be rotating at 12.5 frames a second or 750 rpm.


Thanks for that i am dreadful working maths out that will come in useful when i get around to playing with those different motors.

I am not saying you should do that by the way, only that you CAN.


Well that helps me knowing how to use them so thanks Gary .

It might be a fun experiment someday.


Yes for sure i will use them .

BTW, before you buy a laser printer see if you can get a test print out to take home first - that way you can make doubly sure it is IR absorbing.


I don't want to go further till i have a good encoder ,i think i can look into this for next week .
What brand is yours BTW that would be a good one for a news letter topic on what works what doesn't .
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 gary » Sat Aug 24, 2013 4:54 pm

Tell you what would be useful a variable pc display theres a lot of set standards but nothing really to fine tune stuff thats a bit off frequency between standards not nbtv Standard or your own new idea .


That would be NBTVAnalyser.


What brand is yours BTW that would be a good one for a news letter topic on what works what doesn't .


I have a Konica-Minolta and a Brother HL-2140 - the Konica-Minolta's toner is running out and it is too expensive to replace it - it's still ok for draft copies though.

I use the Brother for things like encoders and other things that need full quality - works well for $50 - when the toner runs out I'll scrap it and buy another - not worth buying toner or cartridges these days becuase of their lousy pricing schemes.

All laser printers should work as the toner is generally standard (AFAIAA) but better safe than sorry.
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Postby Klaas Robers » Fri Aug 30, 2013 12:26 am

I am sure that the Baird system couldn't work. Yes there is a peak at 375 Hz (he had 30 lines), but even if there is a black bar at the beginning of every line, then the PHASE of the 375 Hz is defined by the brightness distribution on the neighbouring lines as well. The TDK Nipkow monitor used a sharp selective 375 Hz LC-circuit to extract the 375 Hz, but that will never work, as then PHASE is strongly influenced by the video content.

It was even that Baird used a tilting mechanism in his flying spot scanner, by changing the vertical position of a window in the outgoing flying light spot. I think he didn't realise that all Nipkow disc receivers should follow this tilting actions in the studio, by slowing down and speeding up their disc. This is a not working system.

It is the late PA0KT who did Nipkow-TV broadcasts on 80 meters in the years 1937 - 1939, that is after the BBC stopped the Baird broadcasts, who used a blacker than black sync pulse and also published a working sync separator annex DC restorer. There was no frame sync. This young man Freek Kerkfof (PA0KT) did really understand how it should work.
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