Test of a simple device

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Test of a simple device

Postby DrZarkov » Wed Feb 21, 2007 8:03 am

Hello, my real name is Volker, I'm new to this forum. I' interested in mechanical TV since I was 12, that was in 1981. I started back in that time making my own very primitive mechanical TV-sets. I never managed back in that time a proper synchronisation and my cameras were very poor. I found nobody else with such a strange hobby, so I concentrated on computers like anybody else and forgot about mechanical TV at the end of the eighties. I found it back some years ago, and now I have time to start experiments again. Internet is such a useful ressource to find information about my unsolved problems, and it is very beautyful to know that I'm not the only one with such a hobby.

So I started again with a simple experiment I fount here: http://www.sptv.demon.co.uk/nbtv/. Well, so simple it is not. I found a small motor even with a gear in an electronic shop, it is of course much too fast, but that problem will be easy to solve. I've tested to connect the LED directly to the output of the soundcard, that does not work. Then I tried the "auxiliary power" circuit like in the description, but 3 Volt seems to be too much for my orange high bright LED, it will not stop to glow. And I learned that one LED is really enough for that small scanning disk I've printed... I've started this evening (yesterday nearly all shops were closed here in Germany, it was carnival), and I know now what I have to improve to make this simple experiment a success... Unfortunally I have to work tomorrow, so no time to continue until tomorrow evening.
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Postby DrZarkov » Thu Feb 22, 2007 8:19 am

Second day: The TV is up, but not yet running. Still trouble with the LED, I have to change the resistor. Even with only 0.5 Volt the light is on, but the output of my laptop is too weak for the LED without extra power...

The scan disk is running, the motor works. I used a variable resistor to correct the speed. Not perfect, but this is only an experiment, before spending "real money"...
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Postby Roland » Thu Feb 22, 2007 11:14 am

Hi,

I'm Roland and I'm brand new to this forum too - though have been reading along avidly these last few days and also have been a member of the NBTVA for a couple of years now.

Anyway I too have been experimenting with very simple Nipkow scanners based on paper disks. My experiments so far can be found at:

http://www.rolandandcaroline.co.uk/html ... al_tv.html

So far I haven't tackled disk synchronisation and am currently working on improving the brightness of the picture. The LEDs I have been using up to now haven't really been bright enough but I plan to rebuild the light panel with much brighter ones. I've also been experimenting tonight with using just a single high brightness LED and a lens to spread the illumination.

I did also purchase some better quality Nipkow disks from the NBTVA clubshop - but haven't yet used them. The monitor base for these is partly built and I hope to restart work on it soon.

Roland.
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Postby DrZarkov » Fri Feb 23, 2007 7:25 am

The LED is now working! I've changed the LED with another one, and I've controlled my transformator: It says 3 Volt, but the output is 3,85 Volt! So I've put a variable resistor in the circuit, and it's working. It could be better, but that will be in the next project with a bigger Nipkow disk.

A much bigger problem is synchronisation. I've tried some testcards I've found in the internet, and it is possible to recognize something wor less than a second. I will try to use a flywheel to make it run better. My second scandisk will be made of aluminium, that's for sure now. Cardboard is o.k. for testing, but that's it. Today I've got the club's newsletter, I think I have to go shopping at the club sales! :wink:
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Postby DrZarkov » Fri Mar 09, 2007 7:44 am

After a short holiday and some days with a flu I continued working on my primitive TV today. It is working, but I'm not happy. It seems to be impossible to hold the picture for more than half a second just with a potentiometer-control and no real synchronisation. The picture has not enough contrast, so all I was able to see is the nbtv-testcard, but in a very poor quality.

Results: It is not worth to start as primitive as the author of that website wrote. I doubt that he really tried it, it will neer work just with the motor of an old battery-fan. (My cheap "Mabuchi" motor which is used in many toys and fans is running even with about 2 Volts at about 1600 RPM, so without a kind of gear it will be impossible. It will not work just to connect an LED directly to the output of a soundcard, it will stay dark, so you need a "resistor amplifier" with auxiliary-power.

So I will not continue on this project, I will now make a "real" NBTV-monitor like in the official handbook. If you want cheap and fast results, you should better buy the kit, but simply a cardboard Nipkow-disc, a toy motor and an LED is not enough.
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Postby Andrew Davie » Fri Mar 09, 2007 10:03 pm

DrZarkov wrote:So I will not continue on this project, I will now make a "real" NBTV-monitor like in the official handbook. If you want cheap and fast results, you should better buy the kit, but simply a cardboard Nipkow-disc, a toy motor and an LED is not enough.


Nonetheless, I consider your experiments and work very interesting, and useful information for those of us who are still learning how it is all done. You are way ahead of me, having achieved a picture -- even for half a second at a time! Many thanks for posting the updates. I look forward to reading your construction diary for your 'real' monitor.

Cheers
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Postby DrZarkov » Sat Mar 10, 2007 5:59 am

Your construction diary is very interesting to me, too. I hope it will help me to avoid some problems, and I think I can learn a lot from your experience.

My first problem: For the club shop I need to pay with a cheque. I didn't know that cheques still exist, here in Germany nobody uses them any more, and I have to ask my bank first if there are any cheques for international payement. Does the club have a normal account at a bank? If yes, I need the so called IBAN and BIC-numbers for european money transfers.
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Postby Roland » Sat Mar 10, 2007 12:31 pm

DrZarkov wrote:Results: It is not worth to start as primitive as the author of that website wrote. I doubt that he really tried it, it will neer work just with the motor of an old battery-fan. (My cheap "Mabuchi" motor which is used in many.


To be fair I think the best part of that particular website is the Nipkow disk. There is a high resolution one which can be easily scaled and adjusted to you needs. I print it out on thin card and then stiffen it with an old CD-ROM.

I didn't attempt to use the soundcard based electronics (I built my own 3 transistor amp for use with a CD player) and I now use a 555 based PWM circuit to control the speed. Initially I just used a reostat style control.

My paper disk monitor is now pretty much finished - but the picture quality could be better. These last 2 nights I've been working on my next monitor using a 12" plastic disk from the NBTVA clubshop and this should be better.

However I'm not done with paper disks yet. My current paper disk monitor is of an odd design (looks not unlike a record player) and whilst its been fun - I can see how to build a better one. Not least I'll try making some new paper Nipkow disks as with practice and experimentation they steadily improve.

One last point I'll make is that for me there is more to this hobby than final picture quality. Hand punched disks and crude electronics are very much in the spirit of how things were done back in the 1920s/30s.

:-)

Roland.

http://www.rolandandcaroline.co.uk/
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Postby DrZarkov » Sat Mar 10, 2007 5:05 pm

Of course a perfect picture quality is not the intention, any second-hand TV from ebay would do it better. It is the fun of doing it it yourself. But it should really work. Indeed, the Nipkow disk is working fine. In the dark ages before Internet I made them myself, a few good ones and a lot of bad ones. (All of them of cardboard.) This is now much easier, even buying is now an option, thanks to the club.
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Postby gary » Sat Mar 10, 2007 5:53 pm

I tried this method quite a while ago with reasonable success. Like you I couldn't get the leds to light when directly driven by the soundcard but found it quite reasonable when using a biasing resistor and battery. I didn't use a rheostat, just the finger on the disk and could manage stability for a few seconds with practice. It certainly proved the concept and shows how easily it can be done, which for me is part of the attraction of NBTV.

Has anyone tried his new(ish) method of synchronising the motor with pulses from the right channel?
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Postby DrZarkov » Thu Apr 19, 2007 6:26 am

I gave not up my simple device, because it is ideal for testing things. Here an old photo, still with the first cardboard-disc (which had too big holes...) and with the 1-transistor video driver:
Image

But today I've improved it a lot: I've got two very cheap mini-nf-amplifier kits (1 Watt), from LC-Electronics, type L 130 for 5,65 EUR. The kits are made around an IC LM 386. I thought they are o.k. for audio, but then I thought why not try them as video-drivers?

I was surprised by the excellent results! The picture is bright (the device has now 2 LEDs, but I will increase that number up to 6, if possible), the contrast is good. After improving the disc and if I manage to hold the picture long enough (it yet has no synch), I'll try to make some photos of the picture.

Image
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Postby Roland » Fri Apr 20, 2007 10:39 am

DrZarkov wrote:I gave not up my simple device, because it is ideal for testing things. Here an old photo, still with the first cardboard-disc (which had too big holes...) and with the 1-transistor video driver:


Thanks for posting the pictures - its interesting to see how you have contructed your device.

Just for comparison please find below a recent picture of my own simple device. Whats not visable in the picture is the wired remote control for the motor speed. I've since improved the amp (interesting to hear about your LM386 experiments - I'm still on the lookout for alternative simple display drivers) but otherwise its pretty much as it is now.

:-)

Roland.
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Postby DrZarkov » Fri Apr 20, 2007 4:22 pm

We use the same Nipkow-disc, which is "suboptimal", but surprisingly good working. My monitor will get a remote controll, too, that's where you inspired me. ;-)

Yesterday I changed the two LEDs with an array of 6 LEDs. This afternoon I will start to drill holes in the aluminium disc I've got from a friend. From another friend I will get tomorrow an old video-recorder for my other project, the "luxury" NBTV monitor.

Roland, I see that you now have the disc horizontal mounted. I thought about building in my simple device into a suitcase from an old grammophone (with everything missing inside, of course, I will not slaughter a grammohone). I thought about using a shaving-mirror instead of the magnifying glas. How about your experiencies with a horizontal spinning disc?
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Postby Roland » Sat Apr 21, 2007 11:26 am

DrZarkov wrote:Roland, I see that you now have the disc horizontal mounted. I thought about building in my simple device into a suitcase from an old grammophone (with everything missing inside, of course, I will not slaughter a grammohone). I thought about using a shaving-mirror instead of the magnifying glas. How about your experiencies with a horizontal spinning disc?


The horizontal spinning has been just fine - at least with the paper disk. The disk is backed with an old CD / CD-ROM to stiffen it which certainly helps. The main thing to ensure is that you leave enough gap under the disk for the light source. I didn't and I've had to mount the light source parallel to the disk and use a small 45deg mirror.

I have built a more conventional monitor with a plastic club disk and I don't think this type of disk would work horizontally as it flexes too much. Maybe I could stiffen it though.

The old grammaphone suitcase is a good idea. I have a nice box from one of the tape recorders I broke up for parts. I was hoping to make a portable monitor where lifting the lid exposed the disk and moved the viewing mirror/lens into position. The only problem is the box is a little small and I think I'd need to use a 6" disk. I'll probably give it a go though.

I've attached a photo of my club disk (12") monitor. This is just a mock up at this stage - but since taking the photo I've actually had it working in this form.

:-)

Roland.

PS glad you liked the remote control! ;-)
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