Slow Scan Television Experiments

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.

Moderators: Dave Moll, Andrew Davie, Steve Anderson

Re: Slow Scan Television Experiment

Postby Steve Anderson » Sat Nov 08, 2014 8:23 pm

Harry Dalek wrote:....it's a little more sensitive to what supply voltage its using to the end result .

I did mention before the chronic sensitivity of these VCOs to the supply voltage, it simply has to be well regulated, no ifs or buts.
Harry Dalek wrote:...I found the 4046 circuit i need more amplification after the head amp it only changes the VOC bandwidth by about 2khz...

For SSTV use where the frequency span is almost 2:1 you're going to need around half the supply voltage to get that, if using a 12V supply you'll be needing a sync-to-white value of around 4V-6V sitting on a fixed DC value of around the same (4-6V), though it does depend on the R1/C1 values as they're called in the datasheets.

Kinda makes the 5V versions (HC/HCT) look more attractive...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5360
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Slow Scan Television Experiment

Postby Harry Dalek » Sat Nov 08, 2014 9:54 pm

Steve Anderson wrote:I did mention before the chronic sensitivity of these VCOs to the supply voltage, it simply has to be well regulated, no ifs or buts.


Its very much like a 555 timer in that way but i am not complaining just testing i tried it at both 5 and 12 volts it just as expected changed the bandwidth range..i suppose with an lm317 in some ways its an easy fix to adjust the range with out changing part values in the circuit.

For SSTV use where the frequency span is almost 2:1 you're going to need around half the supply voltage to get that, if using a 12V supply you'll be needing a sync-to-white value of around 4V-6V sitting on a fixed DC value of around the same (4-6V), though it does depend on the R1/C1 values as they're called in the datasheets.


The tests i did on the ujt vco it has a very wide frequency range 600 hz to over 10 khz far more than needed ....to me this means in the tests i did with my head amp the slight voltage changes mean a more sensitive VCO ,the 4046 is just the normal sstv bandwidth so needs as you say about 5 volts to get to white.

After todays tests i have been thinking a idea might be instead of working out light or head amp modifications but to increase the frequency top range of the 4046 ,my thinking is as in the ujt vco with its wide range you just adjust the frequency cut off range with the frequency pot the higher the range the oscillator can do the more sensitive to lower voltage changes it is ,so if this makes sense it could make it very sensitive to low light levels if the 4046 range is changed to 10khz as the ujt i should get the same results.

Kinda makes the 5V versions (HC/HCT) look more attractive...




Yes in this way the old 5 volt devices do make more sense but with part value changes the devices we are using at 12 could work at lower voltages to i think :roll:

Steve A.[/quote]
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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby Steve Anderson » Sat Nov 08, 2014 11:03 pm

The 4000 series were the first mass-produced CMOS series that didn't require weird supply voltages like NMOS or PMOS and others that sometimes required negaitve supplies as well (ECL) - horrible. But 4000 soon relised it's shortcomings when interfacing to real logic (even basic 7400 or a slow 1MHz Z80 microprocessor) as being sloth-like, i.e. s.l.o.w...and this varies with supply voltage. It's output drive capability is very limited too.

So along came HC, good for 2-6V, fast, low current consumption which spurred the 78L05 regulators and such (3mA 'do nothing' current). But these have been eclipsed by the likes of the LP2950 series (75uA) and the MCP1702 series (2uA). The 78L05 these days guzzles more current than the real load...if you need battery operation....which is best?

But here, that's probably not our concern. Put simply, the old 4000 series has not much going for it these days, get out of the habit of thinking of 12V, or 9V, unregulated. Regulate, it's so cheap these days.

5V single-supply op-amps are in abundance, admittedly they do have limitations...but watch this space...

The majority of logic families are these days tending towards 3.3V, and 1.8V is closer than the horizon. 5V will be around for some time as evidenced by the 3.3V chips with '5V tolerant inputs'.

Anyway, I'm getting off-topic again...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 5360
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Re: Slow Scan Television Experiment

Postby Harry Dalek » Sun Nov 09, 2014 10:56 am

Steve Anderson wrote:The 4000 series were the first mass-produced CMOS series that didn't require weird supply voltages like NMOS or PMOS and others that sometimes required negaitve supplies as well (ECL) - horrible. But 4000 soon relised it's shortcomings when interfacing to real logic (even basic 7400 or a slow 1MHz Z80 microprocessor) as being sloth-like, i.e. s.l.o.w...and this varies with supply voltage. It's output drive capability is very limited too.

So along came HC, good for 2-6V, fast, low current consumption which spurred the 78L05 regulators and such (3mA 'do nothing' current). But these have been eclipsed by the likes of the LP2950 series (75uA) and the MCP1702 series (2uA). The 78L05 these days guzzles more current than the real load...if you need battery operation....which is best?

But here, that's probably not our concern. Put simply, the old 4000 series has not much going for it these days, get out of the habit of thinking of 12V, or 9V, unregulated. Regulate, it's so cheap these days.

5V single-supply op-amps are in abundance, admittedly they do have limitations...but watch this space...

The majority of logic families are these days tending towards 3.3V, and 1.8V is closer than the horizon. 5V will be around for some time as evidenced by the 3.3V chips with '5V tolerant inputs'.



Anyway, I'm getting off-topic again...

Steve A.



I do just use regulated power supplies for the projects ,of late i just use a power supply i made its dual regulated 12 and 5 volts there are times where something works best at a specific voltage i then tend to use the Lm317 .
I am glad the new Ic's still can do up to 5 volts i think forgetting what you have would kill a ic or 2 other wise .

No worries i did learn here i do have many old circuit boards scrapped from 70s gear so i may come across those old IC's

BTW going off here as well any one that needs to get an old ic out of a double side soldered PCB heating it off the board i am sure many have found a very hit or miss thing ,and you would be lucky to get out with out braking the ic's leads i found a fool proof way but you need a dremel , the cutting tools like a mini angle grinder.
You have to cut the ic out of the circuit board and leave a little of the board around the ic so you have a little rectangle of board with the ic on it close as you can do ....then you turn it over to the board side cut it right down between the ic leads and the side of the ic same other side ..then whats left is a just a very thin board just with the leads soldered either side ....i then cut the board between each lead whats left is just a tiny square soldered to each lead then its very easy to desolder ......with the bits left you can get ics out with out damage ,its amazing how fast you can do this once you get the knack of it ,its a little bit of work but you get some thing for nothing which other wise would be a waste of time trying .

Back to the project

I am going to try adjusting a 4046 VCO today and see if i can duplicate or better the UJT VCO .
Last edited by Harry Dalek on Sun Nov 09, 2014 4:20 pm, edited 3 times in total.
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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby Harry Dalek » Sun Nov 09, 2014 11:52 am

Just found i have a few IC's from dual soldered board i have cut out and stages between cutting out desoldering...... so a picture is easier to understand i suppose.
Attachments
IMG_9124.JPG
IMG_9124.JPG (487.67 KiB) Viewed 20563 times
IMG_9120-crop.JPG
IMG_9120-crop.JPG (24.58 KiB) Viewed 20563 times
IMG_9121-crop.JPG
IMG_9121-crop.JPG (50.68 KiB) Viewed 20563 times
IMG_9122-crop.JPG
IMG_9122-crop.JPG (60.63 KiB) Viewed 20563 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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby gary » Sun Nov 09, 2014 1:38 pm

Scroungineering is good for the technical soul... (and wallet)
gary
 

Re: Slow Scan Television Experiment

Postby Harry Dalek » Sun Nov 09, 2014 4:13 pm

gary wrote:Scroungineering is good for the technical soul... (and wallet)


OH yes Gary for sure it helps !
The bane of an electronic recycler is the double sided PCB its hard enough to get 2 lead components off the board with out damaging them but for a long time i found ics impossible i would always made a mess of it trying to reuse ,i tried desoldering and heat guns small butane torch and such but the cutting them out is the best way i have found for those and its very quick as i said once you do a few and know what to do .

Back again to the SSTV side of things

I did a little rebuild of the 4046 VCO just to test it with different caps and resistances it really only came down to dropping the resistance a bit and with the head amp its very sensitive to light now ,i hope this is enough now for reflection changes it seems more than enough in room light .
Once again i will have to put it the test .
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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby M3DVQ » Mon Nov 10, 2014 3:16 am

Be careful cutting old PCBs up and wear a good dust mask. There were some rather nasty chemicals in the resins used in some older boards, not to mention the the fibres themselves in fibreglass boards. :!:

Not trying to be a H&S killjoy or tell anyone how to suck eggs, but just a warning to anyone who hadn't considered it. :wink:

I have a friend who favours the heat gun approach but I just ended up burning the boards when I tried that (and that really makes a toxic mess!). After that I tried sawing them up with the death wheel in the rotary tool but couldn't get the hang of that either. I was trying to get sockets off old motherboards but they're multilayer of course and I found I was really struggling to get through the power and groundplanes.
M3DVQ
Just nod and pretend you understand me
 
Posts: 338
Joined: Sat Feb 10, 2007 10:52 am
Location: Lincolnshire

Re: Slow Scan Television Experiment

Postby Harry Dalek » Mon Nov 10, 2014 6:52 pm

M3DVQ wrote:Be careful cutting old PCBs up and wear a good dust mask. There were some rather nasty chemicals in the resins used in some older boards, not to mention the the fibres themselves in fibreglass boards. :!:

Not trying to be a H&S killjoy or tell anyone how to suck eggs, but just a warning to anyone who hadn't considered it. :wink:

I have a friend who favours the heat gun approach but I just ended up burning the boards when I tried that (and that really makes a toxic mess!). After that I tried sawing them up with the death wheel in the rotary tool but couldn't get the hang of that either. I was trying to get sockets off old motherboards but they're multilayer of course and I found I was really struggling to get through the power and groundplanes.


Yes its either dust or fumes ,having tried both the cutting is much easier but yes a dust mask and willing to get dusty is the price you pay !

But i have to say again once you know the procedure you can get to the last stage in that last photo i posted of the ic with all pins free ready to desolder in a few minutes ,you can go like a production line once you get going.

The torch approach is not good if it doesn't kill you in fumes or set the board alight the heat would not be very good for the component ,i just gave up on the heating it out to hit or miss.

You need to work on the part its self not the whole board you need to see what you are doing , so cut the part out as in the photo hold it flat on a table cut between the ic and socket turn around do the other side then you are left with thin strips only on either side of the ic or sockets pins then again cut between each pin ,the last part just makes desoldering easy pessy ,its like knife in butter ....OH and if you are like me and in any case where glasses! and or safety glasses..
Attachments
adremeltool.jpg
adremeltool.jpg (47.53 KiB) Viewed 20543 times
download.jpg
download.jpg (3 KiB) Viewed 20543 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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby Harry Dalek » Thu Nov 13, 2014 1:18 pm

Back on track here on the SSTV experiments .

I rebuilt the head amp to a different design and tried it with the 4046 vco with a reflecting test ,my goal was to try and get room light control out of the circuits from reflecting natural room light.

I Used this Photo of old Groucho Marx and used the black coat part and gray back ground part of the photo just moving the sensor between the two ,i am getting the results i wanted .

Only thing with the new head amp is i must i have the polarity wrong way on the head amps op amp as i am getting a reverse results of light detecton levels than i was getting before in the old head amp design.

I am next going to print out a a gray scale test patterns and move the sensor between the shades of gray ,looks good just playing around with it.

If it works with the line mirror only i should be able to make a mechanical scanned test card as i was doing with the star case generator .

i ended up reusing the ca3140e so far it seemed to out do some other opamps i tried .

The light sensor is a 3DU5C no other reason but i have a few to test .
Attachments
Screen 00014.jpg
swinging he head amps light sensor between the dark and lighter areas of this photo
Screen 00014.jpg (33.19 KiB) Viewed 20516 times
IMG_9125.JPG
its detecting the light changes between coat and background gray
IMG_9125.JPG (299.46 KiB) Viewed 20516 times
Screen 00015.jpg
Screen 00015.jpg (23.99 KiB) Viewed 20516 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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby Harry Dalek » Fri Nov 14, 2014 1:05 pm

I printed out a gray scale test card and sweeping the head amp by hand as steady as i could i can see the bar shades are detected speed and distance from the printed out sheet will cause variations in shades a bit but its picking it up alright in natural room light.

I have to adjust my light sensor holder and try this experiment again with the mirrors that works then i will get the motors going .
Attachments
Screen 00016.jpg
test 1
Screen 00016.jpg (33.98 KiB) Viewed 20506 times
Screen 00017.jpg
test 2
Screen 00017.jpg (56.46 KiB) Viewed 20506 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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby Harry Dalek » Sat Nov 15, 2014 7:59 pm

I tried the NE5534N low noise op amp and found it made the head amp more sensitive than it with the CA3041 ,its a pretty cloudy day today and room light is low still controlled the VCO on reflection light off my test card .
The good thing it inverted the light signal back to 2400hz for white light and 1500 for black that was handy .
Heres the circuit has 2 controls gain and voltage control to adjust with different op amps, also tried TLO71 with it but again so far the 5534 wins .

Found some information on the 3DU5C light sensor peak Wavelength 880 nm so a bit to say the least in the IR range a good reason natural light from a window into the room worked and not so good in artificial light my case compact fluro room lighting which looking at some charts doesn't give off IR ,the light sensor is less sensitive from green light to IR but seems still useful ,i will more than likely test some others i have now knowing this.
Attachments
Screen 00018.jpg
NE5534 test
Screen 00018.jpg (34.41 KiB) Viewed 20493 times
IMG_9128-crop.JPG
IMG_9128-crop.JPG (149.2 KiB) Viewed 20493 times
Screen 00021.jpg
Screen 00021.jpg (201.43 KiB) Viewed 20493 times
FT Wavelength.png
FT Wavelength.png (17.08 KiB) Viewed 20493 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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby Harry Dalek » Sun Nov 16, 2014 7:47 pm

I got off track today on the light tests as the wiring and boards starting to get messy needed to put it on some thing.

But any way i have got back to thinking about the line motor control which i never really finished ,i have to do it via a stepper motor syncing the line motor to the electronic clock going to pinch the NBTV version and try and get it to work at the slower sstv 15hz speed which might or might not work ,i suppose it really needs to work or each line will drift /
The Mirrors are on a pulley system again and that can cause problems as well as in noise transmitted to the opto switch as in vibrations from the light chopper.

BTW the drawing was done a bit quick i forgot a resistor on pin 2 of the 555 bistable and its a 10k pot on the lm311 Comparator.
Attachments
IMG_9130-crop.JPG
IMG_9130-crop.JPG (220.16 KiB) Viewed 20481 times
IMG_9133.JPG
IMG_9133.JPG (373.16 KiB) Viewed 20481 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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

Re: Slow Scan Television Experiment

Postby gary » Sun Nov 16, 2014 7:59 pm

Won't you experience "cogging" with that circuit Harry?
gary
 

Re: Slow Scan Television Experiment

Postby Harry Dalek » Sun Nov 16, 2014 11:24 pm

gary wrote:Won't you experience "cogging" with that circuit Harry?


I haven't tried it yet gary clogging i hope not ! i have run the stepper to get 15 hz out of my 4 mirrors but some thing that comes to mind i forgot about the electronic clock frequency has to be much higher than 15 hz to run the stepper circuit ,what that is i can find out by testing at the opto switch when i get that 15hz there by adjusting the main clock, then i can do the same taking the frequency of that clock and know what the higher frequency needed is.
I am not sure if it is possible to sync two different frequencies but perhaps if i can divide that then back down to 15 hz just for the bistable to sync the two for motor control ..I sort of wonder to that 15 hz would be hard for a DC motor the normal way for motor control.

I could try a crystal clock and forget about syncing after i find out what frequency i need for the stepper...or i suppose i could just try and see either way and find out/

problems problems :roll:
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: 5364
Joined: Fri Sep 26, 2008 4:58 pm
Location: Australia

PreviousNext

Return to SSTV

Who is online

Users browsing this forum: No registered users and 6 guests

cron