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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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31st Dec 2006, 11:18 pm | #1 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Help with homebrew televisor needed
Hi,
With all the recent talk about 32 line mechanical televisions I've decided to try and make one I've found a Peter Smith based circuit on this site http://bs.cyty.com/menschen/e-etzold...anningdisc.htm which seem easy enough (even for me) to follow. I'll probably have more questions as the build gets going, but just for now can I have some thoughts about making the Nipkow disc? I've found information about how to draw it, but I'm having trouble finding out about diameter, weight and suitable materials I also found in an old 1928 article that suggests the holes should be square, is it worth going to all that trouble? Another question is about the brightness of the LED's. I've found some orange ones with a brightness of 4000mcd. Would the suggested number of six be bright enough? Many Thanks David |
22nd Jan 2007, 1:42 pm | #2 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Help with homebrew televisor needed
Things are going remarkable well, apart from the Nipkow disc. Several attempts to make one has failed miserably so I have decided to do the sensible thing and buy one from the NBTVA.
I'm a bit confused as to why their disc has a 1.5 turn spiral. I thought there was only supposed to be one hole in the frame at any one time. Wouldn't a 1.5 turn spiral show two in a frame? Thanks David |
22nd Jan 2007, 5:32 pm | #3 |
Retired Dormant Member
Join Date: Mar 2005
Location: Braunschweig, Germany
Posts: 208
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Re: Help with homebrew televisor needed
Hi David,
the cited web page belongs to me. The making of a Nipkow disk is very difficult. I have bought the Nipkow disk from Peter Yanczer. His Nipkow disks are laser cut and operate very well. For more information see http://www.televisionexperimenters.com/stuff.html As an alternative you can order the disk from the NBTV web site. But before ordering a disk, please check the thread https://www.vintage-radio.net/forum/...ad.php?t=13264 Kind regards Eckhard |
22nd Jan 2007, 7:19 pm | #4 | |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Help with homebrew televisor needed
Hi Eckhard,
Sorry, I didn't know it was your website...but at least I can now thank you now! Quote:
I've noticed the Peter Yanczer disc before, but it seems a bit expensive, certainly alot more expensive than the NBTV version. ... I still don't get why the NBTVA's version has a 1.5 turn spiral, I wonder if it's to do with aspect ratio . Thanks David |
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22nd Jan 2007, 9:26 pm | #5 | ||
Retired Dormant Member
Join Date: Mar 2005
Location: Braunschweig, Germany
Posts: 208
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Re: Help with homebrew televisor needed
Hi David,
Quote:
Quote:
Source: http://www.nbtv.wyenet.co.uk/cam-mon.htm Kind regards Eckhard |
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2nd Feb 2007, 10:03 am | #6 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Help with homebrew televisor needed
I've just got one more part of the televisor to make, the LED array, but I've got confused .
Please look half way down this page at the 'The LED light source' section http://www.nbtv.wyenet.co.uk/beginners.htm I don't understand the choice of resistors in either of their examples. I'm using the first design but if the supply voltage is 12V and each of the LED's are 2V 20mA then I would expect the resistors to be 330R not 22R? However, this is such a common and popular design, I've got a feeling that I've missed something Thanks David |
2nd Feb 2007, 12:55 pm | #7 |
Retired Dormant Member
Join Date: Apr 2006
Location: Shrewsbury, Shropshire, UK.
Posts: 67
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Re: Help with homebrew televisor needed
In the text it says the LEDs are 50mA rated, and that additional voltage is dropped across a driver transistor.
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4th Feb 2007, 6:56 pm | #8 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Help with homebrew televisor needed
It's now finished and should work but all I can get is a negative image .
What on earth have I done wrong? Thanks David |
4th Feb 2007, 11:10 pm | #9 |
Retired Dormant Member
Join Date: Dec 2003
Location: North London, UK.
Posts: 6,168
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Re: Help with homebrew televisor needed
Sounds like the audio is inverted somewhere. Won't make any difference to sound reproduction unless you are one of those golden eared folks who claim to be able to detect absolute polarity but will certainly make video negative.
Either use a different CD player or an inverting amplifier stage between it and the televiser. |
5th Feb 2007, 1:35 pm | #10 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,130
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Re: Help with homebrew televisor needed
Apologies if I'm missing something here, but could it be as simple as the leads being the wrong way round?
__________________
Mending is better than Ending (cf Brave New World by Aldous Huxley) |
5th Feb 2007, 4:18 pm | #11 | ||
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Help with homebrew televisor needed
Quote:
Quote:
I'm, actually, staring in amazement at a test card 'F' . It's got a bit of a wobble and a, sort of, spirally line passing through it but it's not bad! If I can get it better I'll post a picture Thanks David |
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10th Feb 2007, 11:18 pm | #12 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Help with homebrew televisor needed
Oh well, It's now working really well. I wanted to post a picture of the test card image but I've found it impossible to take a, decent, photo so I've posted a couple of pictures of the contraption instead.
Ok, it's not rocket science and it's not pretty, but it certainly challenged me and I like it . Now... what about a colour version! David |
11th Feb 2007, 2:54 pm | #13 |
Nonode
Join Date: Feb 2005
Location: Worcestershire, UK.
Posts: 2,534
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Re: Help with homebrew televisor needed
Very nice! Well done
Steve
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https://www.radiocraft.co.uk |
11th Feb 2007, 5:26 pm | #14 |
Retired Dormant Member
Join Date: Dec 2003
Location: Solingen, Germany
Posts: 727
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Re: Help with homebrew televisor needed
Hi, I like it! Did you use a vinyl record as a Nipkow disc?
Kind regards, Darius |
11th Feb 2007, 6:26 pm | #15 |
Nonode
Join Date: Jun 2004
Location: Norwich, Norfolk, UK.
Posts: 2,543
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Re: Help with homebrew televisor needed
No, I tried to make it from a 12" record, but I found it too difficult to drill the holes accurately
The Nipkow disc you see was purchased for only £9 from the NBTVA Regards David |
12th Jun 2007, 9:45 am | #16 |
Retired Dormant Member
Join Date: Jun 2007
Location: Herongen, Germany
Posts: 65
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Re: Help with homebrew televisor needed
If you still want to make your own Nipkow-disc, I have several discs in a PDF-format on my website. Just download them and print them out. Not as perfect as the laser cut discs from the club or from Peter Yantczer, but they are working well (and don't cost anything;-).
http://www.retrocom.de/zarkov1.html |