Mini version of Scophony - its do-able

Forum for discussion of narrow-bandwidth mechanical television

Moderators: Steve Anderson, Dave Moll, Andrew Davie

Mini version of Scophony - its do-able

Postby Gregory » Thu Feb 04, 2016 2:21 am

Of all the mechanical TV systems the one that intrigued me the most was the Scophony TV system. 400 lines and 24 inch screen, not bad for 1938, in fact not bad for now.

I was toying with the idea of making a small system based on the twin mirror drum system used in the Scophony, but limiting the screen size to say 6 x 8 cms with 60 lines. The purpose would not be to copy all the optics Etc of the original but use the main concept of 2 mirror drums to make a compact televisor.

A laser diode pointer could be used as the light source and avoid the lenses, as this would not need focusing if one accept a spot size of around 1mm this would give a 6 x 8 cm display for 60 lines.

First problem would be the high speed line scanner - desperately looking for a polygon mirror to do this, but nothing yet, they use these in laser printers and copiers, but most have the motor embedded on the PCB. The motor could be a hard disk motor, these run up to 15000 RPM and are synchronous, and I have many faulty hard discs.

Any info for any parts going cheap (laser diodes, polygon mirrors Etc) would be most welcome
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Thu Feb 04, 2016 2:12 pm

nbtv wrote:Of all the mechanical TV systems the one that intrigued me the most was the Scophony TV system. 400 lines and 24 inch screen, not bad for 1938, in fact not bad for now.


You picked a hard one but a great project to try .

Heres a link to a chat on the Jeffree cell there 2 pages on Scophony .
viewtopic.php?f=1&t=1366&hilit=polygon+motor

I was toying with the idea of making a small system based on the twin mirror drum system used in the Scophony, but limiting the screen size to say 6 x 8 cms with 60 lines. The purpose would not be to copy all the optics Etc of the original but use the main concept of 2 mirror drums to make a compact televisor.


Well it is possible for sure done a basic nbtv idea see below some time back
viewtopic.php?f=1&t=1557&hilit=octagon

A laser diode pointer could be used as the light source and avoid the lenses, as this would not need focusing if one accept a spot size of around 1mm this would give a 6 x 8 cm display for 60 lines.


MY advice on the laser side is you make it adjustable working with mirrors you don't run it on full power till you know its working and safe to do so ..or you will take an eye out ! :shock:
A laser pointer 1mW 5 mW are to low ....great for a mechanical scope idea but to low for a mechanical television need at least 20 50 mW or more you could start with a laser pointer to workout the scanning at slow speed then replace with a higher laser once you know and need the line mirror to run at the high speed needed does depend on how many mirror faces it has
The laser must be free of electronics that control it or your elecronics will not be able to modulate it .
There is 625 line laser mirror drum television made by a German guy on youtube
https://www.youtube.com/watch?v=FeevMGqWNc8
you might have to use google translate with hes link with this video .Interesting

First problem would be the high speed line scanner - desperately looking for a polygon mirror to do this, but nothing yet, they use these in laser printers and copiers, but most have the motor embedded on the PCB. The motor could be a hard disk motor, these run up to 15000 RPM and are synchronous, and I have many faulty hard discs.


Again the more faces the mirror has less speed your motor has to spin what you want .

On my Scophony link for the jeffree cell page 3 theres information a drawing how to hook up a laser printer mirror motor board ...works most of the time with all the laser printers i have scrapped...read these pages a lot on what you are interested in and problems.

Any info for any parts going cheap (laser diodes, polygon mirrors Etc) would be most welcome
[/quote]

These days they are starting to go cheap on the laser printers as i am now starting to find only 4 sided ones so older the laser printer the better ! colour ones you get 3 polygon mirrors motor boards but they are big a lot of plastic waste to get ride of but great for parts .
In Australia i just find them on the nature strip ...
You could have a go at making one but does not take much to put a glass mirror off and the image will be jumpy you might be a better at construction than me..... a better idea the plastic mirrors that are thin and have a sticky backing and can be cut to size with a stanley knife are your best bet for a home made mirror drum used this idea for the frame mirror on the octagon project .
Vibration is is a big problem for any thing home made using HD or vcr drum for your mirror drum will help ..and you could use a pulley system to get greater speed out of your driving dc motor .
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3951
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Mini version of Scophony - its do-able

Postby Gregory » Fri Feb 05, 2016 12:56 am

Harry,

Thanks for the info and the links - very useful and plenty of food for thought. I have managed to source the polygon mirrors. The ones I found are 12 sided at a very reasonable $5 each, so I ordered four of these, to have spares as well (they are only 7mm thick, so they are only suitable for the line scan). If anybody is interested the link is:

http://opticaldesignsoftware.net/prod034.htm

The frame scan mirrors I think I will have to make, as ideally I would want this 12 sided also but much thicker
Last edited by Gregory on Fri Mar 11, 2016 2:09 am, edited 2 times in total.
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Fri Feb 05, 2016 10:13 am

nbtv wrote:Harry,

Thanks for the info and the links - very useful and plenty of food for thought. I have managed to source the polygon mirrors. The ones I found are 12 sided at a very reasonable $5 each, so I ordered four of these, to have spares as well (they are only 7mm thick, so they are only suitable for the line scan). If anybody is interested the link is:

http://opticaldesignsoftware.net/prod034.htm

The frame scan mirrors I think I will have to make, as ideally I would want this 12 sided also but much thicker


Well on the frame mirror it would rotate very slow once a second at 12 faces which might be a bit harder ,you would have to use a stepper or pulley system or gears to slow down a dc motor ,some steppers can be jerky when rotated very slowly in this case its better fewer faces and the face on the frame mirror is easier i found if a square 4 sided mirror ....works fine i found...you could use 2 flat 12 sided mirrors you can experiment and see .

To get a picture the line speed is critical but not the case on the frame mirror speed that much it will increase and decrease the lines seen ..this is easy to control you would think 2 motor idea would be harder .

The good thing about a 2 mirror disk drum system is it can be a multi system monitor only limited to the speed of your motors.

Your dodecagon mirror if fine for the line speed it will be interesting to find out its limits ,your biggest problem is i see its just a mirror not mounted on a driver
board getting this right is something to think about .

With 12 faces it would do twice the line rate of a polygon which can do 60 line easy on its driver motor board ,i wonder if it could display garys 120 line system ...i would only try it if the mirror was on a correct driver board at those speeds that mirror coming off could do some damage .

Also something i never got around to it might be an idea to defocus the laser for the lower line systems as it looks a bit gappy with the laser lines very thin for 32 lines and such,
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3951
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Mini version of Scophony - its do-able

Postby Gregory » Tue Feb 09, 2016 7:20 am

Well phase 1 of the project has started - polygon mirrors have been ordered and I have now stripped down 3 HDD motors, so now I have to wait for the mirrors to come.

I have checked on the RPM of HDD motors and the standard speeds for HDD appear to be 5000, 7200, 10000, and 15000 RPM, but most, especially the slighter older ones are 7200 RPM

I don't know if the speed is limited by the motor or driver or both but I will be designing a motor driver, so should soon find out.

RPM required with a 12 sided polygon mirror would be

32 lines 12.5 frames/sec = 2000 RPM
60 lines 20 frames/sec = 6000 RPM
120 lines 25 frames/sec = 15000 RPM

Any circuits for a high performance motor driver for HDD motors would be most welcome
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Tue Feb 09, 2016 7:56 pm

nbtv wrote:Well phase 1 of the project has started - polygon mirrors have been ordered and I have now stripped down 3 HDD motors, so now I have to wait for the mirrors to come.

I have checked on the RPM of HDD motors and the standard speeds for HDD appear to be 5000, 7200, 10000, and 15000 RPM, but most, especially the slighter older ones are 7200 RPM

I don't know if the speed is limited by the motor or driver or both but I will be designing a motor driver, so should soon find out.

RPM required with a 12 sided polygon mirror would be

32 lines 12.5 frames/sec = 2000 RPM
60 lines 20 frames/sec = 6000 RPM
120 lines 25 frames/sec = 15000 RPM

Any circuits for a high performance motor driver for HDD motors would be most welcome


I have not had to many go's at using a HDD motor just tried it with a 555 and 4017 count to 3 and reset ..to a driver ic uln2003 that connected to the motor
Sort of worked never got the speeds i wanted ,i was thinking at the time i needed to adjust the pulse width with the frequency increase never got around to it but wanted to use a double ganged variable resistor where i could adjust both at the same time on the 555...lots of ideas on the net how to drive them .

Again a big problem is centering the mirror and keeping it there might be able to do it as i used to with the screw plate that holds the platters on if the mirror hole fits .

See how you go with the motor are you planning manual or automatic speed control ? i used a opto switch on one a while back worked very well rest of the project didn't but i had speed control :roll:

uploaded a polygon list here are a few different types your 12 sided one pretty good for NBTV nice and cheap to using those first 2 shapes would be a problem ! :D
Attachments
termin3.png
termin3.png (10.58 KiB) Viewed 7615 times
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3951
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Mini version of Scophony - its do-able

Postby Gregory » Thu Feb 11, 2016 9:55 pm

I have been looking further on the web into HDD motor drivers and from info available it seems to get these motors running to a high speed most use a PWM driver which monitors the back EMF to know exactly where the rotor position is.

Don't now if this is necessary but I have ordered and added to the shopping list a couple of cheap ready made drivers with PWM control to see if this can spin the motor to at least 6000 RPM.

Initially the line scan motor will be with manual speed control but at some stage it will probably be necessary to make the motor driver, as it will have to synchronise the motor to the line sync, and with ready made drivers, this may be difficult.

Also I have ordered a cheap stepper motor driver {$5} for the frame line motor. This should be ideal for driving the motor as with 3 amp rating and micro-stepping, it should provide smooth rotation, even at low revs, as this would give (200 x 16) 3200 virtual steps per revolution
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Fri Feb 12, 2016 8:28 am

Gregory wrote:I have been looking further on the web into HDD motor drivers and from info available it seems to get these motors running to a high speed most use a PWM driver which monitors the back EMF to know exactly where the rotor position is.

Don't now if this is necessary but I have ordered and added to the shopping list a couple of cheap ready made drivers with PWM control to see if this can spin the motor to at least 6000 RPM.

Initially the line scan motor will be with manual speed control but at some stage it will probably be necessary to make the motor driver, as it will have to synchronise the motor to the line sync, and with ready made drivers, this may be difficult.

Also I have ordered a cheap stepper motor driver {$5} for the frame line motor. This should be ideal for driving the motor as with 3 amp rating and micro-stepping, it should provide smooth rotation, even at low revs, as this would give (200 x 16) 3200 virtual steps per revolution


HI Gregory

Yes for sure give it ago i will go back to HDD at some stage i have a draw full of old scrapped HDDs so i will be interested in your experiments !

This is how i controlled my polygon motor board worked very well ,control was spot on keeping it at 400 hz no drift ...

viewtopic.php?f=1&t=1795&hilit=mirror+camera
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3951
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Mini version of Scophony - its do-able

Postby Gregory » Fri Feb 12, 2016 9:14 pm

Hi Harry,

Thanks for the link and a very interesting project on the camera and must have been a lot of hard work. Did you find the oscillating mirror for the frame worked well, and produced a sawtooth type movement.

Back to the line scan driver - also found that a TDA5140A Ic can be used to drive an HDD motor with very few external components.


tda514a.jpg
tda514a.jpg (22.39 KiB) Viewed 7515 times


TDA5140A.pdf
(174.37 KiB) Downloaded 299 times


At the moment i'm over in the UK for 14 days but hopefully when back should have all the parts come through and get going with the line scan mirror and driver. Hoping to get the mirror spinning as stable as possible so the sync signal required to lock will be minimal.
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Sat Feb 13, 2016 4:02 pm

Gregory wrote:Hi Harry,

Thanks for the link and a very interesting project on the camera and must have been a lot of hard work. Did you find the oscillating mirror for the frame worked well, and produced a sawtooth type movement.

Back to the line scan driver - also found that a TDA5140A Ic can be used to drive an HDD motor with very few external components.


tda514a.jpg


TDA5140A.pdf


At the moment i'm over in the UK for 14 days but hopefully when back should have all the parts come through and get going with the line scan mirror and driver. Hoping to get the mirror spinning as stable as possible so the sync signal required to lock will be minimal.


Hi Gregory
Problem with the oscillating mirror is there is a time delay from one swing to the other with a polygon mirror it is like and electronic line scan ,scan ends and instantaneous start for the next line and all in the right direction line after line .
With a rocking mirror you get more of a sine wave effect scanning so it has the effect of one line is scanned forward and as the mirror rocks back it scans backwards to the start position it is not instantaneous like a sawtooth ...
Gary was saying at the time since i was using this for the frame mirror it should of been running at half the frame rate ...might of been the reason i was getting double images of the led .
I should really try a monitor one day using resonance to find out for sure ,best using mirrors with very little mass and does have the benefit of one mirror for line and one for the frame scanning ..my experiments on this can be found here which might be of interest
viewtopic.php?f=1&t=1768&hilit=resonance

The HDD motor driver ic looks interesting needs feed back control or can use it ,it might just work like the polygon laser printer motor board just need voltage and clock pulse for manual control to start off with ,you will get it spinning with that .
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3951
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Mini version of Scophony - its do-able

Postby Gregory » Sun Feb 14, 2016 5:18 am

Looking for a polygon mirror for the frame scan similar to the photo below - if anyone can help or has one to sell please contact me.

scanning mirror.jpg
scanning mirror.jpg (4.45 KiB) Viewed 7479 times


Alternatively if anyone has any experience making one with accuracy - any info would be of great help, Thanks
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Sun Feb 14, 2016 9:34 am

Gregory wrote:Looking for a polygon mirror for the frame scan similar to the photo below - if anyone can help or has one to sell please contact me.

scanning mirror.jpg


Alternatively if anyone has any experience making one with accuracy - any info would be of great help, Thanks


The Frame mirror is the easier one as it runs slow ,that is one you can make more easy than a line mirror.

i went the easy way and just went for some thing with 4 sides a large Lego like block would do and slick on plastic mirrors ...if you use glue it tends to throw off the direction of the mirror even a little amount !

You need something with accurate flat sides for the mirror may be you can find some thing with more than 4 sides but that is all that's needed really and i stuck mine on a stepper motor can control that frame speed better .

See what you can find !
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3951
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Mini version of Scophony - its do-able

Postby Gregory » Thu Mar 03, 2016 7:35 am

Quick update, now the 12 sided polygon mirrors have arrived, looks excellent quality, but a little heavier than expected.

Also the stepper motor driver for the frame scan arrived, so as soon as the PWM driver for the HDD line scan motor gets here, should be ready to start to test the HDD motor to see if I can get it to spin and hopefully reach 6000 RPM needed for 60 lines
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Gregory » Sun Mar 06, 2016 6:45 am

The PWM driver for the HDD motor finally arrived. Unfortunately I have to make a special flange for the polygon mirror to fix onto the HDD motor, so for the moment the first test is with the motor unloaded using a 12v Dc supply for the PWM driver.

photo 1.jpg
photo 1.jpg (68.52 KiB) Viewed 7289 times


For the HDD motor which is basically a 3 phase motor and 12 poles 12 Hz from the PWM driver will give 60 RPM. The HDD motor spun smoothly over nearly the entire range settings of the potentiometer on the PWM driver with virtually no noise. When set on maximum the frequency measured with the scope was 3960 Hz which results in a maximum speed of 19800 Hz. Unfortunately this is without the mirror so the speed will probably be a lot lower with the mirror.

photo2.jpg
photo2.jpg (149.27 KiB) Viewed 7289 times


Although the mirror is heavier and thicker than needed, I suppose the upside maybe the flywheel effect will give a more stable spin speed.

photo3.jpg
photo3.jpg (41.08 KiB) Viewed 7289 times


Next test will be with the mirror on, as soon as I can get the flange made.
Last edited by Gregory on Mon May 09, 2016 5:12 am, edited 1 time in total.
Gregory
Laboratory Assistant
 
Posts: 37
Joined: Wed Feb 10, 2016 5:06 pm
Location: Nicosia, CYPRUS

Re: Mini version of Scophony - its do-able

Postby Harry Dalek » Sun Mar 06, 2016 9:38 pm

Hi Gregory

Good looking mirror will do the job for sure .

Just have to get the balance correct on the motor which it needs to be or your raster will sway every 12 lines .

The frame mirror is much easier you can make that yourself even just to see it work till something better comes along .

The mirror looks like it has angled mirror on the top as well ? this is good for the frame mirror if you did get another.

You will have it all going in no time,got the motor going easypeasy 8)
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.
User avatar
Harry Dalek
"Fester! Don't do that to 'Thing'"
 
Posts: 3951
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Next

Return to Mechanical NBTV

Who is online

Users browsing this forum: No registered users and 4 guests