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Robonz wrote:That's very interesting, I hope you take photos etc as you go along so we can watch your build. I did some rough calculations using Gary's NipkowDxf program. With an 80mm diameter and 32 lines, your apertures would be around 0.17mm in size. This would give you a screen size of 5.5mm. I am not sure if you could drill holes that small but maybe a needle would work to poke holes. The apertures of the disc needs to be paper thin to avoid parallax if you plan to use a magnifier.
I am not sure of your build skills but a small disc like that could easily go very fast so if you were tricky you could do a 3 turn spiral which would increase the screen size to 16.5mm but then you have to work out how to shutter which spiral is active. The disc speed would be 2250rpm instead of 750rpm.
Cheers
Keith
Robonz wrote:I did some tests today and started a new thread as I plan to use this on my NBTV
viewtopic.php?f=35&t=2480
If you can draw some cad I will cut a disc for you. If you design your disc with 0.2mm apertures and make each aperture a 0.1mm line with no width that will end up as 0.2mm. Make the line length in the orientation of the disc rotation. e.g don't point the line at the center. And rotate the line for each position on the disc. I could easily cut a very accurate 3 spiral too. (so long as the cad is good)
Cheers
Keith
jjester6000 wrote:
Thanks for the offer, (I may take you up on it) I am do know my way around Autodesk Inventor, so I could make you a cad model. The three spiral system seems like the way to go, so maybe it may not need the magnifier after all. My main problem currently is my lack of a fan controller, but I want to keep this as analog as possible. My Idea with this is was something strait forward to build, (Hence the use of an 80 mm case fan) so I don't want to use a fancy controller. I am also thinking of creating a camera in the same way (the sensor could be a calculator solar panel). Sorry I have not uploaded any pictures, but I have just not gotten around to it.
Robonz wrote:The 0.38mm thick black polypropylene arrived this morning. I stuck a really bright focused led behind it, great news, I could not see any light coming through at all. I think this stuff is probably going to be the simplest, cheap and fast way to make a Nipkow disc going forward. I will replace my disc with this when I get the cad done and see how it goes.
If you want a really simple drive I think you could pick up a CD or DVD player assembly and mount your disc on that pretty easily. Being a brush motor you only need to drive it with a single transistor. My modification is to add an electrolytic capacitor across the motor to smooth the brush noise, It works well. You can find the analog motor circuit here http://www.nbtv.wyenet.co.uk/beginners.htm and Yes, I like the analog designs, more authenticity!
For a 3 spiral system we would need a second aperture disc running at 1/3 the main disc speed. Does anyone have drawings for these? I am guessing some spiral slots are needed.
Cheers
Keith
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