New NBTV camera project

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Postby Steve Anderson » Fri Jan 04, 2013 1:07 am

aussie_bloke wrote:That project most certainly will be posted in the Off Topic section, I only posted the one picture here just to show what I'm onto next without intention of this project being part of this thread as I know in other threads people go a little off topic then back on topic again.


I'm often to blame for that!

aussie_bloke wrote:Anyhow when I've done a significant amount of work on this project I will start posting the thread in the off topic section along with the data if it's allowed.


It most definitely is!! I did spend quite a bit of time wandering around your site earlier today, you have been busy over the years!! As before, good luck...

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Postby Harry Dalek » Fri Jan 04, 2013 6:21 pm

Good luck on the iconoscope TV camera Troy ,the use of the computer case looks like a great easy case for it .
I suppose due to where the camera lens will be it sort of stuffs a little where the power supply will be if your reusing the computers..relocating it there seems to be heaps of room /
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Postby aussie_bloke » Fri Feb 01, 2013 9:06 pm

G'day all.

Have gotten back onto my NBTV flying spot scanner camera/monitor again after a 2 month hiatus.

I have now drilled the new disc with needle sized holes this time and have mounted it on an ex VCR head drum that rotates freely and mounted the disc and drum on a piece of metal which screws to the wood mount piece that held the original disc on the platform of the unit. I then screwed the image pickup unit (lens, sensor and headamp) to the platform at a suitable height.

Anyways that's my progress so far in refining the camera system. Here below are pics of my progress:
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Postby Panrock » Sat Feb 02, 2013 11:52 pm

Nice work - particularly the condensor unit. :)

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Postby aussie_bloke » Mon Feb 04, 2013 2:57 pm

Thank you Steve :)

Okay I have done some more work on the camera, have been working on a building a rackable lens system to vary the focus for objects at different distances. So I cut some scrap metal railings and placed a rackable base (piece of wood) on the rails and secured it with a couple of metal pieces riveted on the rails. I screwed the railings to the main base with really thick protruding screws to stop the wood sliding out of the railings. Then I cut a piece of chip wood and drilled out a big circle for the lens to fit through and secured it to the base with some brackets and screws. Here below are the pics:
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Postby AncientBrit » Mon Feb 04, 2013 6:57 pm

Hi Troy,

Seeing your work on the disc camera inspired me to revisit my original 1999 design.
Apart from adding gamma correction and improving the black level clipper I decided to add a 'soft' black level clamp at the output of the Head amp prior to system processing.

And that's where I came across a subtle design requirement for camera blanking.

For any clamping or DCR to work there needs to be defined a portion of the video signal at a fixed level, usually true black.
Because of the high gain employed in the Head amp the signal is normally ac coupled.

In a disc camera there is no facility to blank the signal by electronically turning off the tube beam current.
And adding a transmission gate in series with the signal and switching off during blanking still does not resolve the problem because the signal will still ride on average picture level (APL)

The method I employed was to add a cardboard mask dimensioned so that as one hole passes out of the mask another appears.
In my original design I did not provide any "underlap" so the video signal had no porch.
I must admit the design was built quickly and now I'm not sure how I got away with the DCR I originally incorporated.

In my revised design the mask has been made smaller vertically so a porch is introduced on which to clamp.

This of course impacts on the aspect ratio of the displayed picture, but this is also true if you are going to incorporate any form of sync pulse within the blanking area.

Any thoughts on this?

Kind regards,

Graham
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Postby aussie_bloke » Fri Feb 08, 2013 11:22 am

Thanks for your input Graham and good idea too. I didn't know there was even a black level issue with NBTV cameras. Can you possibly post some pics of your schematics and diagrams of your masking as I may incorporate it with my design after I master motor synchronization. I am guessing the mask is positioned horizontally across the bottom of the scanned area am I right?

Anyways onto another topic, I am pondering what sort of motor to use to drive the disc as now that I'm using a video head drum as a spindle, it is considerably heavier and needs a more powerful DC electric motor. I am thinking of using an ex RC car Kyosho motor (see pic below) however there is no data stamped on it and so apart from it requiring 12V to run I have no idea of the power rating or the current amperage it requires and I was wondering if anyone here knows how many amps this motor uses and a good speed control circuit to build for it?
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Postby gary » Fri Feb 08, 2013 6:24 pm

Troy, just measure the DC resistance across the terminals and use Ohm's law to calculate the current (I = V/R) - this will be close enough for your purposes.

The speed control depends on whether you are going to have a reference signal (i.e. a Xtal locked pulse generator) or not - if you do then the standard club phase locked loop is perfect, otherwise the LM317 based circuit shown here: http://www.nbtv.wyenet.co.uk/cam-mon.htm is often used to good effect. Note the latter is not an exact speed control but suffices in most cases.
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Postby AncientBrit » Fri Feb 08, 2013 6:46 pm

Hi Troy,

The scanning mask is located just in front of the Nipkow disc, after the main primary lens.

The primary lens is really a compound of two convex lenses separated by about 4cm in the cardboard tube to get a managable focal length.

You'll note that I've added an extra piece of masking tape to the bottom of the aperture to give a wider blanking period.

The hum cancellation pickup is not scanned but responds to a filtered average picture content which will include any hum due to 50Hz lighting.
This is then subtracted from the main signal to reduce the effect of hum bars.

I'm revising the circuit so I'll hold fire on publishing until I've refined it.

However you can see the original in the zipped folder 'Disc camera 1999 Vol25_4' which is posted on the previous page.

Cheers,

Graham
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Postby aussie_bloke » Tue Feb 12, 2013 2:12 pm

Troy, just measure the DC resistance across the terminals and use Ohm's law to calculate the current (I = V/R) - this will be close enough for your purposes.


Thanks Gary, have measured the resistance and it's about 4.5 ohms, so 12V divided by 4.5 ohms is about 2.6A, so this motor does run off big current in comparison to other DC motors the same size!


Hi Troy,

The scanning mask is located just in front of the Nipkow disc, after the main primary lens.
The primary lens is really a compound of two convex lenses separated by about 4cm in the cardboard tube to get a managable focal length.

You'll note that I've added an extra piece of masking tape to the bottom of the aperture to give a wider blanking period.

The hum cancellation pickup is not scanned but responds to a filtered average picture content which will include any hum due to 50Hz lighting.
This is then subtracted from the main signal to reduce the effect of hum bars.

I'm revising the circuit so I'll hold fire on publishing until I've refined it.

However you can see the original in the zipped folder 'Disc camera 1999 Vol25_4' which is posted on the previous page.

Cheers,

Graham


Thanks for the tips Gary, I will keep your info in mind should I incorporate a clamping system in mine. Like your pics too of your camera, nice work! :D
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Postby aussie_bloke » Tue Feb 12, 2013 2:37 pm

G'day all.

I have been working away with my NBTV camera once again, been primarily focused on building the enclosure for it to block out as much light as possible. Also I have orded off Ebay for $22 a 200 pack of ultra bright 14000mcd clear LEDs for the monitor section of the NBTV camera so I can get a picture of decent brightness and will do the same for my other NBTV camera projects. I'm still yet to get started on the motor speed/sync circuits as I've mainly been concentrating on the enclosure and LED bank.

Now onto the construction side of things.

Firstly I have half constructed the LED light bank using those ultra bright clear LEDs and compacted 24 of them in a small area of 2x3cm, had to grind the edges to get them to fit. Then I daisy chained the LEDs together as I did with the other LED banks and I get a very nice bright LED light. I am yet to house the LED bank inside a hood with a diffuser but that will come soon.

Now onto the enclosure. I bought a couple of chipboards from Bunnings Warehouse for $5.75 each and have cut them to the desired sizes to fit around the camera. In the front panel I cut/filed a hole just big enough for the lens to peep through and on the back I cut a rectangular hole to see the monitor, I will be mounting a magnifying glass inside a yoghurt container and stick it over the hole to magnify the picture. I also cut 4 pieces of timber into rods so I can nail each panel to them to make the enclosure. During construction I made silly mistakes with the dimensions of the panels, I made the height too small so I had to cut some smaller pieces of chipboard to make up the height, plus made the back panel too small in width so had to add an extra piece to make up the width and cut another piece to nail to both pieces of panel to connect them. Anyhow despite the booboos it's coming along nicely. I now only have to put the top lid on and connect the magnifying glass inside yoghurt container to the rear panel and it's done.

Here below are the pics of the construction to date:
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Postby gary » Tue Feb 12, 2013 3:00 pm

Nice progress Troy.

Looks a good buy on the LEDs - that lot should do you for a few projects!

One tip though: When you make a boo boo - don't tell anyone - make it into a "feature". For instance if you have to add another panel, put a hinge on it and call it an "access panel". Alternatively put a bit of moulding across the join and say "I'm looking for that antique look". You'll learn. After all, if it's good enough technique for our top pollies - it's good enough for us! ;-)

Keep up the good work!
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Postby gary » Tue Feb 12, 2013 3:09 pm

PS: I like the way you wired up the LEDs - very neat!
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Postby aussie_bloke » Sat Feb 16, 2013 4:06 pm

Thanks Gary :)

Okay more construction updates.

The enclosure is now finished and sits nicely over the camera plus I have also added to the enclosure the magnifying glass housed inside a yoghurt container to the viewing area to magnify the picture.

Next I have finished constructing the LED light box with the ultra bright clear LEDs and have mounted it on a block of wood and secured it to the front left side of the disc where the monitor is suppose to be.

I then decided to test the camera out so I quickly rigged up the old DC motor and speed control circuit and LED driver circuit and so it's in a makeshift complete state for testing.

Testing it out, the white LEDs are obviously a MASSIVE improvement over the much dimmer yellow LEDs so I can see a nice clear picture and can even photograph it with my camera. I first noticed I had the dome sensor wired the wrong way so I got an inverted picture, so had to fix that up to had to open the can and switch the wires around. After getting that right, I had to adjust the signal level low enough to get decent greyscales as I was getting silhouette B&W so did that and whilst there appears to be noise, the pictures look very good. Anyhow I placed some items in front of the lens and the pictures look so much more detailed with the holes in the record being needle sized instead of 1mm which is great! :D

Now that the camera is pretty well working good I am finally ready to get started on the motor sync and speed control circuitry so will have to now get crackin on that!

Anyways here's pics of my latest construction updates and some monitor shots:
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Postby aussie_bloke » Wed Feb 20, 2013 9:14 pm

Okay I have now finally gotten into the sync/speed circuitry side of things :D. Harry has kindly been helping me with valuable info in constructing a sync circuit involving an encoder disc and an opto-fork circuit type arrangement involving an IR LED and phototransistor.

I've constructed his circuit and have tested it out with the encoder disc and it works like a charm as I get pulses on the oscilloscope when passing it over the opto fork, the white strips on the disc will reflect IR light and the black strips will absorb the IR light, hence pulse on, pulse off! :) I then stuck the encoder disc to the Nipkow record disc and rigged up the sync circuit to test it out while the Nipkow disc is spinning and it works very nicely and I'm getting a nice consistent set of pulses which can be seen in one of the pictures below :).

Now that I've perfected the sync circuit I have been pondering on a suitable speed control circuit for my 2Kyosho RC car motor that needs 2.67A to drive it and it didn't take me long to find a feasible circuit to try which is the motor speed control portion of this circuit http://www.nbtv.wyenet.co.uk/speedctrlckt.gif . So I made only the motor portion of the circuit on my breadboard for testing and voila it works great!!! :D So I now have a suitable speed control circuit for my high powered RC car motor.

Just got message from Harry that there is another stage to the sync circuitry I need to still construct which is the monostable with filter, so will be working on that next.

Anyways here's my latest construction pictures:
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