Mechanical SSTV Steps

Forum for discussion of SSTV topics. Slow Scan television (SSTV) is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or colour.

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Re: Mechanical SSTV Steps

Postby Harry Dalek » Wed Mar 01, 2017 8:58 pm

I will be jumping around here a bit as i find stuff ////Back in August 2011 i had the idea of covering this version off the glow drum with a filter i was also using a DC motor to drive the old polygon motor.
Apart from making the drum look better the filter perhaps a yellow one as for p7 crts i should of tested other colour filters ...it would of been better over the glass monitor screen it also had to be on very tight on the drum or would defocus the laser .
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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: Mechanical SSTV Steps

Postby Harry Dalek » Thu Mar 02, 2017 8:34 pm

March 2013..first images double image running the line drum at half speed double image half the lines half the quality.
By then i was using a stepper motor to direct drive the polygon mirror

youtu.be/MzSn_JCBx4E
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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: Mechanical SSTV Steps

Postby Harry Dalek » Sun Mar 12, 2017 6:43 pm

I got the Monitor out the other day for a look and see if it will still runs ok .today was the first chance i have had to have a look at and study it again , i ended up having to pull it out of the case as i had to remount the glow drum .
Unfortunately the glow drum looks to have a few knocks to it which i didn't notice before but i will use it for now ...
I am changing the power supply finding the little switch mode supply is pushing it driving the 2 stepper motors and electronics runs better testing with a bench supply i have handy .
Running a little ruff but still gos and out does the CRT version in midday room light ,not the best of times to test something phosphorescent.
I have a few ideas on mechanical Slow Scan Television and plan on constructing something like this but smaller //

youtu.be/lk0lnELdzaY
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Re: Mechanical SSTV Steps

Postby Robonz » Tue Nov 14, 2017 5:05 pm

Harry, what kind of laser specs would you recommend for this? 405nm mW??. Is the scan rate able to be sped up using a more powerful laser? Also what software are you using to generate the signal?. I never looked at SSTV but now I saw your glow drum it sparked my interest. i hope I did not ask too many questions.

Cheers
Keitb
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Re: Mechanical SSTV Steps

Postby Harry Dalek » Tue Nov 14, 2017 6:52 pm

Robonz wrote:Harry, what kind of laser specs would you recommend for this? 405nm mW??. Is the scan rate able to be sped up using a more powerful laser? Also what software are you using to generate the signal?. I never looked at SSTV but now I saw your glow drum it sparked my interest. i hope I did not ask too many questions.

Cheers
Keitb


Hi Keith Yep UV laser at around 20mW as i recall i would of got 50mW....just what i could get deal wise at the time its bright enough for the scanning ..
viewtopic.php?f=23&t=1318&start=105
Above before and after i opened it up with the dremel .....plus you need to be able to focus it also you need the raw laser diode not the regulator.... it will filter out the video reason i had to hack it open .
So with that in mind you know what you need what ever you get need to be able to get at the laser diodes pins !
I have half made a tiny version of it with plans on just using dc motors cut out the electronics in the stepper motors ...the frame motor for the little drum is geared for slow speed and have a 4 sided mirror on a flat dvd cd dc motor for the line side of it ...because the line is dc motor controlled it will be very hard to control it will have to be synced .
My plans here are i will use the idea that has worked in the past on using the corners of the mirror with a opto switch for making the mechanical sync this worked very well in past projects with polygon mirrors for the mechanical sync ..planning on the same system as in NBTV motor control but this time using the sstv line sync in the 4046pll or bistable 555 control circuit .
Its very easy to get a picture once your laser modulation works all you have to do line up the lines of your picture i could do this in manual control of the steppers speed ...they still drift but a slight adjustment puts them back on track they are pretty good on staying close to speed.
I made my original monitor drum motor out of junked laser printer stepper motor and the line mirror was glued on a 5inch floppy stepper ......bipolar or unipolar either are ok so there are 2 ways to go motor wise its up to you what you would rather .
The software i used both MMSSTV and chromapix
http://nk7z.net/mmsstv/
http://www.barberdsp.com/index.php/sili ... downloads/
Both have the 8 second SSTV but with the robot vis code the original system didn't have that code ...not much of a problem for this but there are true video files on this section of the forum Steve Anderson has made and there are old video files on you tube .
SSTV is fun made a p7 CRT monitor a while back ...
viewforum.php?f=19
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: Mechanical SSTV Steps

Postby Robonz » Tue Nov 14, 2017 7:57 pm

I was thinking an Arduino glow drum would be fun. It could drive all the stepper motors and take bitmaps from an SD card and put them onto the glow drum.

I saw your laser driver schematic. I am not sure it is right, It looks like the laser is being driven in constant voltage mode. While you can get away with it on some lasers, I thought it should have been a constant current mode to compensate for temperature change. Maybe I am missing something

[url]lasercc.png[/url]
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Re: Mechanical SSTV Steps

Postby Harry Dalek » Tue Nov 14, 2017 8:51 pm

Robonz wrote:I was thinking an Arduino glow drum would be fun. It could drive all the stepper motors and take bitmaps from an SD card and put them onto the glow drum.

I saw your laser driver schematic. I am not sure it is right, It looks like the laser is being driven in constant voltage mode. While you can get away with it on some lasers, I thought it should have been a constant current mode to compensate for temperature change. Maybe I am missing something

[url]lasercc.png[/url]


Yes i would like to see a Arduino version of this idea .
BTW the paint should be fine i started of with grainy paint and tried powder results will also be grainy so a fine paint is better.
Yes i have forgotten to put in a current limiting resistor in that schematic no one till now has ever asked me ! i will get the box its in down in a day or 2 and tell you the value i used .
Its Pulse width modulated very safe i would never Am modulate a laser it just takes a spike in a nano second to kill it ....
So you know your stuff you picked the mistake i always going to update the circuit arr no ones ever going to ask me :lol:
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Re: Mechanical SSTV Steps

Postby Andrew Davie » Tue Nov 14, 2017 9:58 pm

Harry Dalek wrote:So you know your stuff you picked the mistake i always going to update the circuit arr no ones ever going to ask me :lol:


I'm going to use that excuse from now on! ;)
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Re: Mechanical SSTV Steps

Postby Harry Dalek » Wed Nov 15, 2017 2:24 pm

Andrew Davie wrote:
Harry Dalek wrote:So you know your stuff you picked the mistake i always going to update the circuit arr no ones ever going to ask me :lol:


I'm going to use that excuse from now on! ;)


Pretty much Andrew guna do it but never got around to it ,then it was if some one asks i'll tell them 8)
Well todays the day ....
Keith output of the LM317 i have a 2 switches they go to that output then to 2 current limiting resistors ones a 37 ohm others 30 ohm 17 ohm when both on ...then one or both are connected then to the laser diode ...result is either a duller or brighter laser....The levels for the laser are controlled by the trimmers before the mosfet gate .
I will draw it up again and post it later with this posting
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Re: Mechanical SSTV Steps

Postby Robonz » Wed Nov 15, 2017 9:41 pm

Interesting Harry, you really have a mix of constant current, constant voltage and linear modulation going on there. Theoretically there should only be constant current and digital control of the mosfet, but if that is working for you then that's great. Even with my poor understanding of the circuit you probably want to add a small capacitor to the laser diode + and the negative as the LM317 will not likely match the transient response you are asking from it.

I have never built a laser modulator before so its something I am keen to have a play with. When my lasers arrive I will have a crack at it and see if I can blow up some lasers haha.

For paint on the drum I have some "aqua glow powder" from Ebay. I was thinking I could mix that with some clear acrylic paint and air brush it on. Do you thing that would work?

Cheers
Keith
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Re: Mechanical SSTV Steps

Postby Harry Dalek » Thu Nov 16, 2017 2:38 pm

Robonz wrote:Interesting Harry, you really have a mix of constant current, constant voltage and linear modulation going on there. Theoretically there should only be constant current and digital control of the mosfet, but if that is working for you then that's great. Even with my poor understanding of the circuit you probably want to add a small capacitor to the laser diode + and the negative as the LM317 will not likely match the transient response you are asking from it.

I have never built a laser modulator before so its something I am keen to have a play with. When my lasers arrive I will have a crack at it and see if I can blow up some lasers haha.

For paint on the drum I have some "aqua glow powder" from Ebay. I was thinking I could mix that with some clear acrylic paint and air brush it on. Do you thing that would work?

Cheers
Keith


Hi Keith ...with the lasers best to run it a touch below its operating voltage so yep constant operating voltage and never use a trimmer on the regulator no capacitors i was worried as that is what stops it working with you use the lasers regulator board ...As i recall i was going to use Steve Andersons laser transmitter but it was designed for a red laser it would not light up a UV laser they must use more current i ended using this idea below in part .
Best to power the laser up from low and work your way up till you can just see it and then see if you can modulated it then increase to just under the lasers operating voltage and yep i always have a current limiting resistor to the laser diode ..trying to run it full ball from the start does not take much to kill them all i will say .
I have used glow powder mixed with paint sort of works the problem is it will be grainy you will be disappointed when viewing images like trying to print an image on sand paper pretty much for a test drum and you might knock it around a bit its ok and for test images .....the spray can stuff is what you want the clear type is fine ,the yellow matt type finish is grainy thats one first i tried and got images on ....do you have Bunnings in New Zealand keith ? they sell the brand i used ...its also very hard to get an even finish when using powder you get areas with more and others lacking ..
BTW i like the idea of another being made ...it'll the only one in New Zealand ! :wink:
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Re: Mechanical SSTV Steps

Postby Robonz » Thu Nov 16, 2017 2:57 pm

Hi Harry

...with the lasers best to run it a touch below its operating voltage

My point is lasers do not have an operating voltage. They only have an operating current to my knowledge. The voltage can vary during operation etc. I have some 317's coming tomorrow so will have a fiddle and see what I can come up with. I have an idea I can digital modulate the adjust pin which should make it switch more sharply. I will scope my ideas and get back to you.

I saw Bunnings had the glow paint. I am sure it is not as nice as the "aqua" powder I have, so I want to try and see if I can spread the powder evenly. I guess you need to spray paint it under a black light to see what you are doing!

Another "arr no ones ever going to ask me" on your circuit is "triangle wave" I believe it is a sawtooth when using the diode on the 555 like that.

Yes, I love the glow drum design and you are the only person I have seen to build one, very inspiring Harry!

Cheers
Keith
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Re: Mechanical SSTV Steps

Postby Harry Dalek » Thu Nov 16, 2017 4:52 pm

Robonz wrote:Hi Harry

...with the lasers best to run it a touch below its operating voltage

My point is lasers do not have an operating voltage. They only have an operating current to my knowledge. The voltage can vary during operation etc. I have some 317's coming tomorrow so will have a fiddle and see what I can come up with. I have an idea I can digital modulate the adjust pin which should make it switch more sharply. I will scope my ideas and get back to you.


The current has to be constant but they all have different operating voltages make sure you know what you lasers limit is as they can be any thing from 3 to 6 volts the ones i was playing with .
Yes the voltage can be varied but only up to its operating maximum voltage ...do a few lasers in and you tend to be careful with these little beasts .

I saw Bunnings had the glow paint. I am sure it is not as nice as the "aqua" powder I have, so I want to try and see if I can spread the powder evenly. I guess you need to spray paint it under a black light to see what you are doing!


Some thing i forgot to mention when charged and glowing what ever is under the paint will become transparent ,i was experimenting with first giving the can a coat of Black paint then the glow paint .
If you have a look a few posts pages back i was experimenting with orange glow powder .

Another "arr no ones ever going to ask me" on your circuit is "triangle wave" I believe it is a sawtooth when using the diode on the 555 like that.


Its a triangle wave pretty much as i recall looking on the scope any case a sawtooth will also do its mentioned in the schematic its a triangle waveform .

Yes, I love the glow drum design and you are the only person I have seen to build one, very inspiring Harry!

Cheers
Keith


I had the idea of a mechanical p7 screen for SSTV,,,,, the rotating drum after many try's seemed the best idea as you see in my posts i ran into many dead ends.
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: Mechanical SSTV Steps

Postby Harry Dalek » Thu Nov 16, 2017 10:53 pm

Another reason Keith to run the laser from low light levels for the start for testing is getting your scan line correct and not over shooting ..as you can understand lasers and rotating mirrors can be dangerous more so UV as our eyes can't see its correct brightness ,same laser power at another wavelength say green would be blinding both would do the same to your eyes just Uv you would not know as much .

Also i forgot been a few years but this was an adjustment to the 4th 741 ic the one before the LM311 Help from from Steve Anderson that can be used i used it ...it was to do away with the 2 trimmers after the LM311 and better grey scale but i found they were still of use so left them in ...
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Re: Mechanical SSTV Steps

Postby Robonz » Thu Nov 16, 2017 11:19 pm

Hi Harry, that's good advice

I made 2 watt laser scanning module which is mounted in my lounge to make a blue sky effect, also a half watt red heavily defocused on to a mirror ball. It uses the same laser polygon mirror. It looks great when I run my smoke machine. It's so powerful it will burn the wall if I let it stop. I programmed the laser to turn off if the mirror drops below a certain speed for safety. I have built quite a few laser projects in the past. I need to get a better picture for you, but you get the idea.

[url]laser_sky.jpg[/url]

And here is one of my robots with a custom camera/laser range finder. I blew a few lasers making that one. It can measure distance in stereo 400 times a second
https://www.youtube.com/watch?v=5SS7I66ut9w
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