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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Postby Harry Dalek » Sun Jun 26, 2011 8:25 pm

gary wrote:Sorry Harry, I must have missed something, what's that slow flashing light over the entire scene?, otherwise it's starting to show some promise.


Hi Gary

Oh thats my camera when it does video recording a red light flashes .

Yes i like this idea, laser and new scanning idea seems good. :)

Oh there are dark spots on drum this drums been knocked around a bit over the last few months..have to repaint it .

I have some Orange glow powder on the way from ebay with a green laser this stuff glows red ....only works with red and orange glow powder...just to play with ...and see but this project i am happy now with the blue laser and this type of glow paint ...still have to make another or repaint this one ...see how i go with modulation tests.
Last edited by Harry Dalek on Sun Jun 26, 2011 8:39 pm, edited 1 time in total.
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Postby gary » Sun Jun 26, 2011 8:39 pm

harry dalek wrote:Oh thats my camera when it does video recording a red light flashes .


What a pain! I'd like to see a video without that flashing - can it be turned off or masked in some way? also it would be interesting to see it in dimmed conditions so it has more contrast.

Cheers.
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Postby Harry Dalek » Sun Jun 26, 2011 9:00 pm

gary wrote:
harry dalek wrote:Oh thats my camera when it does video recording a red light flashes .


What a pain! I'd like to see a video without that flashing - can it be turned off or masked in some way? also it would be interesting to see it in dimmed conditions so it has more contrast.

Cheers.


Hi Gary

I will see if i can mask it off i am not sure if its there for auto focus or just to show its recording video ....i have other cameras but this one is good for low light with out it going grainy .

i took those this afternoon have not done night tests yet but should be good if thats showing the lines in room light .

i am also only using part of the laser light to part of the edge of the polygon mirror...still looks ok

I think on the contrast i am not sure if i could get black, the other drum i did the first was painted over black paper but with the paint colour and depending as you might be thinking looks better in the dark perhaps shades might look better ...i can see the differance between the start of line and end which is good theres a fade ..

i think a lot of people think glow paint lasts for hours which it does but on the the charging levels i want it will write over any faded image but the image would more than likly stay there just getting dimmer at night levels ...in the day it fades quick in seconds again all depending on how much you charge the glow paint .
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Postby Harry Dalek » Mon Jun 27, 2011 12:27 am

gary wrote:
harry dalek wrote:

What a pain! I'd like to see a video without that flashing - can it be turned off or masked in some way? also it would be interesting to see it in dimmed conditions so it has more contrast.

Cheers.


Hi Gary i did the night test, it was harder for me had a bit of tin foil over the record light thing.

So not many hands left to fiddle with it looked at the video and i didn't do to bad with the focus ...you can see the lines a fair way along the drum..

i think when i start the scan up you see the distance it lasts is good looks better to the eye cameras never as good .

After i finished i did some on off laser tests if i could make out the gaps between lines and that works i couldn't film that this time as i always tell my kids i am not an octopus.

i will see what i can come up with next time i do a test .
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Picture 083_xvid.avi
THE NIGHT TEST
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Postby Harry Dalek » Mon Jun 27, 2011 4:58 pm

I have been looking into other glow in the dark powders paint ...

I have found that the White powder glows black if hit by uv light this would give the correct shades of gray something to look into ...

My orange powder came today and did some tests it was not what i was expecting its still a uv light glow in the dark powder but glows yellow oh well might go back on my word later and do a drum with the stuff ...

Theres a lot of different types really has me interested ever since Steve came up with the idea to do a mechanical sstv and got me going on another project i would love to see it used in nbtv as well ...i am sure if you charge what ever you use with the right amount of uv light it should work .

http://www.glowpaint.com.au/UV-Blacklight-Powder
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Postby Klaas Robers » Tue Jun 28, 2011 8:17 pm

Harry, if you look through a sheet of yellow plastic, or use a Yellow Filter as was used in the time of black and white photography, you will suppress the visibility of the blue light of the laser and see only the green fluorescence of the painted tin. I also used that in 1973 in front of the screen of my 7BP7 SSTV monitor tube.

Now I see that the drum rotates very slowly, so you can see the picture building up while it scrolls up slowly. This has an extra advantage. If you write e.g. about 3 frames around the rotating drum, the previous picture is faded out much deeper than it was on the screen of the 7BP7 CRT, as in principle you have 3 screens that are used one after the other, in stead of just one.
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Postby Harry Dalek » Tue Jun 28, 2011 10:26 pm

Klaas Robers wrote:Harry, if you look through a sheet of yellow plastic, or use a Yellow Filter as was used in the time of black and white photography, you will suppress the visibility of the blue light of the laser and see only the green fluorescence of the painted tin. I also used that in 1973 in front of the screen of my 7BP7 SSTV monitor tube.

Now I see that the drum rotates very slowly, so you can see the picture building up while it scrolls up slowly. This has an extra advantage. If you write e.g. about 3 frames around the rotating drum, the previous picture is faded out much deeper than it was on the screen of the 7BP7 CRT, as in principle you have 3 screens that are used one after the other, in stead of just one.


Hi Klaas

Thanks for posting I had no idea about the yellow filter thing mmmm interesting ,i will try and track something down i have filters of just about all colours and between i used years ago in colour photo developing ...now what have i done with them when i need them !!!

But i will try it out Klaas.

Yes a trip to my junk box to find something that i could test my stepper motor circuit on led to this idea ....i know what you are thinking on having say more scans on the drum so its all in view is something that popped into my head as well when i got it going but i didn't think of say 3 extra new scans ,i would be getting ahead of my self but sounds good thing to try if i can get there ; ).

One thing that i was thinking if i can get this thing going is it might be able to do P16 or and perhaps P32 line but might be pushing my luck with those ideas.

As you know i will have it on its side so the scan will look like a sort of curved crt but i don't think it will look to bad seeing the lines painted on half a tin is pretty viewable and yes again i agree to try and scan part of the drum ...i have not played to much around with speeds yet i am remaking a stepper motor controller just for this and thinking about the
best way to control that polygon mirror ...thinking of using my sstv circuit lm565 PLL horizontal sync feeding to a 555 timer monostable pwm circuit for this ...
Last edited by Harry Dalek on Fri Jul 01, 2011 9:36 pm, edited 1 time in total.
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Postby Harry Dalek » Fri Jul 01, 2011 8:11 pm

Hi

Today i finished the drums own stepper motor drive circuit its a cross between these two circuits.

I have made it up to the 4 led indicators for the steps...then i have used the L293 dual motor drive ic instead of using the transistors...only difference is all the +voltages are 5 volts which my stepper motor seems to work off .

Speed control is more than i need for the slow drum .

i am up to controlling the speed of the polygon motor i have a few ideas how to sync them but see what works might not work first go ...

So doing its circuit on another board..... should really breadboard them.

BTW my 7474 is out of the tetex 2000 tetex transmitter printer i scrapped
a few weeks back .

:roll:
Attachments
Picture 085.jpg
My stepper motor drive
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Stepper-Motor-Controller2-15apr2010.jpg
Stepper-Motor-Controller2-15apr2010.jpg (122.97 KiB) Viewed 11777 times
L293D_bipolar_stepper.png
L293D_bipolar_stepper.png (5.85 KiB) Viewed 11777 times
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Postby Harry Dalek » Sat Jul 02, 2011 6:12 pm

I sort of jumped ahead today as i wanted to case the project.

I had an old empty case i got some time back at a reuse shop ,i had to cut a hole for the screen and neaten that up ,put some glass in for viewing keeping the drum dust free and safe .

I also made it large enough to see the workings ...sort of looks like an old p7 monitor of the time..which i like .

How i think it will work is in a p7 crt the scan is top to bottom ..to do this with the drum system i made it will rotate up from the bottom of the drum to the top that way the picture should scan up showing the top line first so on till i get to the bottom of the scan line ..sort works like a crt in reverse so am not sure yet but i think the polygon or video its self might have to be reversed...my brain hurts thinking about it... i will worry about it when i get up to that ..

let you know how it go's hope you find it of interest.
Attachments
Picture 092.jpg
i cut out the viewing hole for the project and put some glass in to keep it neat
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Picture 098.jpg
painted the inside black
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Picture 100.jpg
i wanted to mount the drum horizontal so in this case means i had to cut a unwanted gear and some steel away
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Picture 103.jpg
Want it to look like this
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Picture 106.jpg
Picture 106.jpg (371.74 KiB) Viewed 11760 times
Picture 114.jpg
Picture 114.jpg (341.67 KiB) Viewed 11760 times
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Postby Harry Dalek » Sun Jul 03, 2011 4:06 pm

Yesterday i worked out how to mount the drum ,today its bolted in along with
power supply and slots for holding the circuit boards .

First is done the stepper motor one,so i am just going to start and wire it in and power it up to the drum .

i also have gone back to the original drum i painted on black paper as you may have noticed when the laser lights up the glow paint the tin label is visible not good for what i want it to do so a blank background is best not sure if it effects it better or not if you use a black or white back to the paint perhaps ...i did notice glow paint on a HD platter with an uv led test it was brighter ...perhaps more experiments will see if a mirrored background is better.

I am using a computer psp its a long type and fits nice just behind the drum ,due to space it just seemed easier to go with it ..i need a dual supply for the 741's in the sstv circuit board and the drums stepper motor board runs off a single 5volt supply .

Getting there nice knowing where i will fit every thing now and the drum is safe from my boys ! .





:shock:
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Picture 117.jpg
Picture 117.jpg (262.51 KiB) Viewed 11743 times
Picture 119.jpg
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Postby gary » Sun Jul 03, 2011 5:50 pm

Well, it certainly looks the part - good job Harry!
Perfecting an NBTV system is like trying to slam a revolving door...
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Postby Harry Dalek » Mon Jul 04, 2011 6:53 pm

gary wrote:Well, it certainly looks the part - good job Harry!


Thanks gary getting there ! i was going to try and make a case for it but i am not that great a wood worker ! i know what needs to be done but i don't have the tools to do to great a job ,so the old steel case came in handy.

I am going to work some more on it tonight .

i will post as i get stuff going...
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Postby Harry Dalek » Fri Jul 08, 2011 3:47 pm

Just an update where i am at ...

I am just about finished with the polygon motor circuit ...

The sync part of it is still up in the air till i test it ...what i am hoping is the the 565 pll which does lock on to the sstv horz sync can be used for at least motor speed ....this pll is connected to a 555 timer monostable which then feeds a L293 h bridge dual ic only using half on this ...So its sort of a phase loop lock PWM motor control ..as well being able to reverse the polygon motor if need be ...i have sort of made it so its still usable in parts if it doesn't work for the lock idea ..

Also been thinking of a light S resistor or transistor in the monostable part of the circuit which will change resistance to the polygon movement thus pulse width and so motor speed of the polygon as it rotates ...not sure yet if i will just use the lasers light flashing past the edge of the polygon or tack a wheel on the motor that drive the polygon and brake up the light via that way ...

I will just see what happens with the circuit and work from there ..once i have it connected i can do the laser tests ...i have a laser Pwm board in a case ready to go...

Pictures show first the polygon circuit board i was talking about others ,back of the case with power supply and stepper motor control board front case i was testing speed control...
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Picture 1.jpg
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Picture 2.jpg
Picture 2.jpg (219.83 KiB) Viewed 11708 times
Picture 3.jpg
Picture 3.jpg (266.54 KiB) Viewed 11708 times
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Postby gary » Thu Jul 14, 2011 12:49 am

Another tack on the concept...

http://www.youtube.com/watch?v=9X_q6Db53jQ
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Postby Klaas Robers » Thu Jul 14, 2011 1:31 am

This reminds me of Hell Schreiber, but that was completely mechanical, also the line scan.
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