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 » Thu Jul 14, 2011 1:42 am

gary wrote:Another tack on the concept...

http://www.youtube.com/watch?v=9X_q6Db53jQ


Hi Gary

Interesting yes hes got that mm at least distance between the uv led and the glow paper ..again a lot of computer power and electronics .

I am on a bit of a brake as i broke my laser :cry: i hooked it up to my power supply instead of the pwm circuit by mistake and it was ....!

i have a 3 week wait till the next laser comes from china ...i have infact got 3 coming .....just in case its the kiss of death in my hands !

Before it went to the great blue laser god in the sky i tested the new orange glow powder tin it needs a little more light than the paint but it lasts much longer and there a nice contrast between the yellow light and the dark orange .....only thing it looks like a rusty tin so not as pretty.

On the backing colour the glow paint should be painted on i found this web site and its interesting as it has been tested .

http://www.waynesthisandthat.com/glow.htm

It doesn't work as well but if you charge the paint with uv light say with just a few uv leds and use a red laser you could do it in reverse and have a red laser doing the work ,i only have 1mw so it doesn't dechange the uv at high speeds due to that ...but its another way of doing it .

So have a bit of a wait till i can test it again. in the mean time i will work on sync side of it ,when i did strobe test to see the line gaps the lines were a bit wobbly .
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Postby Harry Dalek » Thu Jul 21, 2011 11:22 am

Hi i am back :wink:

New blue laser turned up from china 2 days ago and i have been experimenting again.

Testing both glow tins today and worked out how to adjust the lasers dot at last ...i worked it out with a uv led but it was to long to fit in my case with out hitting the circuit boards works a lot smaller with a laser .

I have another idea with that glow powder mixing it with paint but not sure how well it will work ...works good just not a pretty tin ! more a prettying idea than any thing .

My new laser works off 1.5 volts so i am using Steves laser PWM circuit as i can keep this laser safe...If steve you see this i am wondering would a zener diode be a good idea across the laser ?

Will see if i can get that laser modulating soon i need put an amp between the sstv circuit and steves pwm circuit ...well i think ! have not hooked them up together yet...

Just worked out how to pretty the glow powder tin ,i have used a Blue plastic folder used for paper documents i cut it out and taped it around the tin ,i had a few colours and blue works best more than likly due to the uv light is blue and can pass through the stuff...i have it 2 lays thick ...

i will try it on the drum motor once i have time ...bit more electronics to night to match up the sstv board to the laser pwm board .

On the orange drum it has a chrome paint backing then the glow powder then the plastic cover...has a good point of protecting the ruff tin from loss of powder due to handling .
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Lens glued to laser drops lasers dot by some amount
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Test can not see it in photo but dot is very small drops the lasers dot from 2 or 3mm to below 1 or below depending on focus distance
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glow pant tin and orange glow powder tin
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the orange tin work great but its ugly !
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Arrrr one day soon !
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back on the project
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New idea to pretty my glow powder tin
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Postby Harry Dalek » Sun Jul 24, 2011 6:04 pm

Been working on the electronics more of late as i said in my last post ...i have now connected the sstv board that deals with the video to Steve's Laser PWM circuit ...i put a bit of amplification between the two via a scrapped ic i had handy the Lm 386 a nice little ic that does the job rather well...Seems to work on my testing red laser...

To connect it to the blue i have to adjust steves circuits lm317 regulator down to 1.5v .

I sort of have every thing to do it now :shock:

I think from the last test i did before i got this laser there was a bit of drift in speed to the polygon mirror so not sure how well this part of it will work ..

Just a matter of hooking it up to my monitor and see what happens

:roll:

I will show results might be a few days as i am back to work tomorrow might not have time tonight.
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Postby Harry Dalek » Sun Aug 07, 2011 8:59 am

Letting you know how its going both my PWM circuits do not work with any of my violet 404nm lasers ...the second laser i have tried is too dim when connected to it runs at the same voltage as my red laser which modulates fine connected to it ...same story on the other PWM circuit .

Using Steves for this project

I have not done it yet but i thinking since i have tried lasers on a 555 timer again not a blue one but connecting it as a monostable and using the output of steve pwm circuits Lm311 to control this timer this should get it working ....i am a bit iffy about using a transistor after the lm311 as in a type of luxeon driver idea in case the laser dies again .

I would still be using a lm317 to power it just the 555 timer would be doing the high speed switching ....

So this has been giving me a bit of grief ...blue lasers current rating lasers threshold must be higher than a red lasers.
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Postby Harry Dalek » Sun Aug 07, 2011 12:16 pm

Happy to report experimenting with the 555 timer and violet laser diode seems to work ...i had a circuit made up but does infact have a transistor driving the laser i tested it on my red laser just incase before hand .

Sweeping the pulsed laser across the glow tin i can see the mark and gaps fine and laser is now at a good strength . i will now add the monostable 555 to steves PWM circuit and see how that gos ....

Theres a you tube video of as guy who made a 555 timer laser transmitter its just a 46khz astable with what looks like a audio feed to pin 5 i think this is still pwm sort of fm seems to get very clear audio with this simple circuit .

http://www.youtube.com/watch?v=FWSh3x3IdCE
This link to a LED version shows about how the laser one i think works..
http://www.industrial-electronics.com/laser_13.html

reason i am saying this is the bandwidth is fine for nbtv too ..thats my next try if steves circuit fails to pwm my monostable ..i think it will work but as its doing it fine other wise just a bit of information.
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Postby Harry Dalek » Sun Aug 07, 2011 6:07 pm

Hi all i finished the circuit and slight changes to steve's like the transistor and voltage control of the lm317....its a quick draw so i hope i have not made any mistakes !
But testing it with the violet laser it modulates it fine by the looks of it ,i tested out side the project so could just see it flashing away on the sstv signal .
I did notice its inverted its brighter on black and less on white so i will have to put a video inverter in there some where .

So a little step ahead again i was thinking i was closer last time but getting there . :wink:
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Postby Steve Anderson » Sun Aug 07, 2011 9:28 pm

harry dalek wrote:I did notice its inverted its brighter on black and less on white so i will have to put a video inverter in there some where .:


Harry, if you're getting 'wrong polarity' light when modulated, just reverse the inputs to the LM311, feedback isn't used so it's of no consequence to the '311 which way around the inputs are.

In fact thinking a little further on this, you don't need the second 555...even so there should be a resistor between pin 3 of the second 555 and the base of the BC107...I guess that's a simple drawing error...also you may be seeing effects that the trigger input to a 555 must rise before its output, what happens if it doesn't I'm not sure.

Added later...in fact adding the second 555 will totally undo the modulation!..or should, the frequency from the first 555 is constant, the second 555 will trigger as a result of the frequency not the modulation...what 'flickering' you're seeing may be a result of the paragraph above.

Below is my suggestion, this should be good for up to a 300mA laser, the BC107 200mA. The 2N2222 will drop one ot two hundred mV, so allow for that. I've drawn a red laser...but I'm sure you know what I mean...R110 would of course be a low-value preset in practice...make sure it doesn't go open-circuit (the usual failure mode of presets) otherwise say goodbye to the laser...eventually fit a couple of fixed resistors in its place to give the correct voltage out of the LM317...

The diode and 47 Ohm resistor is drawn wrong...sorry to point that out...

Steve A.
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Last edited by Steve Anderson on Sun Aug 07, 2011 10:24 pm, edited 1 time in total.
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Postby Harry Dalek » Sun Aug 07, 2011 10:14 pm

Steve Anderson wrote:
harry dalek wrote:I did notice its inverted its brighter on black and less on white so i will have to put a video inverter in there some where .:


Harry, if you're getting 'wrong polarity' light when modulated, just reverse the inputs to the LM311, feedback isn't used so it's of no consequence to the '311 which way around the inputs are.

In fact thinking a little further on this, you don't need the second 555...even so there should be a resistor between pin 3 of the second 555 and the base of the BC107...I guess that's a simple drawing error...



Steve A.


Hi steve ...i had not thought of reversing the lm311 inputs but thats a big help ...i had not tried the resistor as it sort of worked it was in the pwm motor control circuit this is from to its transistor but naughty me didn't put it in also because i had a pot in the test circuit between the 555 output and the transistors base ,didn't seem to effect it i suppose apart from higher or lower signal level ...but even so i am a hobbist and not trained and i will wack it in i do listen ! : ) .

I did try the transistor without the 555 but it didn't light up the laser i was using the 1.5v one didn't seem to work ..i had not tried this 100mv 4 volt laser with just the transistor but.

I was also wondering what effect the 555 timer monostable adjustable would have by varying pulse width of those pulses...would it be like a contrast control ? mmm i am thinking that but not sure .

I am off to queensland for a week in 2 days so don't have much more time to play with it till i am back .
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Postby Steve Anderson » Sun Aug 07, 2011 10:32 pm

harry dalek wrote:I was also wondering what effect the 555 timer monostable adjustable would have by varying pulse width of those pulses...would it be like a contrast control?


For contrast control simply vary the signal level into the input of this modulator...the level out of the PC sound-card or whatever you're using, no need to add complexity.

There's no reason I can see why my suggestion above shouldn't work...others? It may be these lasers you're using are quite fussy on applied voltage, not having used them I don't know but a few hundred mV could make all the difference...especially if it's a few hundred mV too many!

Steve A.

Harry, re-read my posting above, I have edited it, it's possibly diffferent now to when you first saw it...
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Postby Harry Dalek » Sun Aug 07, 2011 10:38 pm

Steve Anderson wrote:
harry dalek wrote:I did notice its inverted

In fact thinking a little further on this, you don't need the second 555...even so there should be a resistor between pin 3 of the second 555 and the base of the BC107...I guess that's a simple drawing error...also you may be seeing effects that the trigger input to a 555 must rise before its output, what happens if it doesn't I'm not sure.

Added later...in fact adding the second 555 will totally undo the modulation!..or should, the frequency from the first 555 is constant, the second 555 will trigger as a result of the frequency not the modulation...what 'flickering' you're seeing may be a result of the paragraph above.

Below is my suggestion, this should be good for up to a 300mA laser, the BC107 200mA. The 2N2222 will drop one ot two hundred mV, so allow for that. I've drawn a red laser...but I'm sure you know what I mean...R110 would of course be a low-value preset in practice...make sure it doesn't go open-circuit (the usual failure mode of presets) otherwise say goodbye to the laser...eventually fit a couple of fixed resistors in its place to give the correct voltage out of the LM317...

Steve A.


HI steve must of been typing as i was ...OK the 555 is a no goer you think ...
i was thinking it was ok as i did a half black and half white test card to see if the lasers brightness would change between the 2 it was less on the white and picked up on the black ...was changing on tv test pattern cards i was trying but who knows i was dimming the laser right down to see the it , full brightness and focus you can not tell by eye .

I will try your transistor circuit ...! as i said i had tried something like it but not with the current laser i will let you know how it gos ..thanks steve !
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Postby Harry Dalek » Sun Aug 28, 2011 12:13 am

Steve Anderson wrote:[
Harry, if you're getting 'wrong polarity' light when modulated, just reverse the inputs to the LM311, feedback isn't used so it's of no consequence to the '311 which way around the inputs are.



Below is my suggestion, this should be good for up to a 300mA laser, the BC107 200mA. The 2N2222 will drop one ot two hundred mV, so allow for that. I've drawn a red laser...but I'm sure you know what I mean...R110 would of course be a low-value preset in practice...make sure it doesn't go open-circuit (the usual failure mode of presets) otherwise say goodbye to the laser...eventually fit a couple of fixed resistors in its place to give the correct voltage out of the LM317...

The diode and 47 Ohm resistor is drawn wrong...sorry to point that out...

Steve A.



Hi Steve

Just to let you and all know how its going ...I finished the modulation circuit but as i said been fault finding ..first up i stuffed up on your PWM 555 timer diode after the timers out put it was mis shaping the ramp which ended up being i used a tiny zener diode by mistake ...so fixed that .
For the transistor circuit after the LM311 I didn't have a 2n2222 and used a BC107 ..guess what again a no goer !No mistakes this time just didn't work these Violet uv Lasers are fussy ...I went looking in my junk box of transistors and tested about 100 to see which bugger would switch the laser on in a transistor switch circuit ...so i have ended up using an old 2sb400 transistor radio metal can type must be from the 60's or 70's..but works the other i could of used but theres no data i could find onit Fmps2369 one other so warn could not read the type but its another old am radio can type trany.

Modulating these buggers is harder than i was expecting live and learn !

I first up tested the laser to see it if was working modulating with a pc signal generator first low frequency pulses to see it flashing by eye up to 10hz...next up to higher frequencies and manually sweeping the laser across a spare glow tin and i can see the gaps in the pulses so that lasers switching ok via Steves circuit and the other circuits .
Did it again with a SSTV signal i can see the gaps or differences in major light level changes on my glow tin .

Now Steve i inverted the inputs to the LM311 but


:oops:

Because i used a 555 timer last time that inverted the video signal ...now not using that and doing the above i inverted it again !!!!!!! Yakes tell you what since i will be trying photos i will invert them and that should fix it without more soldering ...

I can see thinking things will get easier when i do the scanning is not going to happen so expect horizontal trouble shooting next .
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Postby Harry Dalek » Thu Sep 01, 2011 12:47 am

Some experiments today ..

Not really happy with the glow powder tin its showing up a lot of faults on the tin where theres more or less powder but it does hold the lines longer .

Did a test with the signal generator adjusting the polygon to the square wave gaps in the raster line at different frequencies ,this seems to work fine .

Whats no so good is once i start the drum up i don't get line stripes as i was hoping so far more than likely due to the drum not in sync with the test signal.

Its still all free running on manual speed control need see if i can sync the pll to the slow scan horizontal.

I still have a bit of work to do modulation seems very tight not to much volume and visa versa get it right and if flashes away nicely .

Oh well do a bit more thinking

:roll:
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glow powder tin bit scratchy looking on a full scan
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Postby gary » Sat Sep 10, 2011 11:23 am

Harry, here is another variation on the theme in case you missed it:

http://www.youtube.com/watch?v=vpwfHulW ... r_embedded
Perfecting an NBTV system is like trying to slam a revolving door...
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Postby Harry Dalek » Sat Sep 10, 2011 5:49 pm

gary wrote:Harry, here is another variation on the theme in case you missed it:

http://www.youtube.com/watch?v=vpwfHulW ... r_embedded

Hi Gary
My internet speed has dropped back to ancient times so i will look at the you tube link when i get my speed back ...I have seen a fair few people doing glow paint images but they all seem to be using computer controled servos even the laser modulator is as well.
Thanks for the link i will check it out love seeing other peoples gadgets.
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Postby gary » Sat Sep 10, 2011 7:54 pm

harry dalek wrote:Hi Gary
My internet speed has dropped back to ancient times so i will look at the you tube link when i get my speed back ...I have seen a fair few people doing glow paint images but they all seem to be using computer controled servos even the laser modulator is as well.
Thanks for the link i will check it out love seeing other peoples gadgets.


Harry, you are either downloading too many movies or you need a new ISP/plan - where are you? Back O'Bourke? ;-)

(for comparison purposes I am on 500G download - I never get close...)
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