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Auto-magic sync for Nipkow displays

From: "Robert Parratt (FoodHawk)" <>
Date: Sun, 5 Sep 1999 21:25:54 +0100

I've been thinking about Nipkow displays and have come to the following
conclusions: (Please note my remembrance of the electronics module of
physics is a bit shaky)

A discreet motor controller should be used.
This needs to be connected to two circuits. One kicks in when the computer
starts a vertical blank and spins the tape/disc at top speed until the
vertical sync hole is detected. It then stops.
If the computer is not in vertical blanking then the second circuit is used.
If frequency to voltage converters are connected to horizontal sync hole
detector and the computers horizontal sync then an op-amp (can't remember
configuration name) can be used to ensure the tape/disc runs at exactly the
right speed. The only problem I can see is ensuring the physical and logical
horizontal syncs are synched. I think the vertical sync mechanism may sort
this out. The frequency to voltage converters may have to be custom designed
so as to perceive the vertical blank as not existing.

As long as the display has as many lines as the data being fed this idea
should ensure perfect width and a steady (non-rolling) picture.
The only problem I can see is the tape stretching due to the changes in
speed (does this happen, or is it only changes in direction). How can this
be circumvented.

I was thinking of using a very low end PIC to make a projection clock based
on this technology, perhaps using parts from a 3.5 inch disk drive and disk
using well placed holes.  How well does the technology lend itself to
projection at low resses, and is a disk opaque enough?

On an aside I saw these cool fake flame things at
E(uropean)C(omputer)T(rade)S(how) (very unimpressed - DreamCast was okay,
new GeFORCE 256 cards quite fast, g-string (only) clad women with complete
body makeup nice ;) Anyway, they were a fan, a bit of fabric and some
coloured lights. Looked very realistic, so I've decided to make one. Anyone
else tried these?

--
Atoms has finally been released!
www.doldev.freeserve.co.uk


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