Multiplexing Nixies

[Tom Peters]

At 10:26 PM 3/6/2007 -0500, you wrote:
> > My great treasure is a box of Burroughs 7971 nixies.  [...]
>
> > They have 15 segments each making designing for them a challenge.
>
>15?  I'd naïvely expect to see eight segments radiating from the
>centre, to the corners and the centres of the edges, and eight more
>segments around the edge, for a total of 16.  Are two of them joined or
>something?

Nope. 15 segments addressable. Segments 1, 2, 3, 4, 5, and six form the 
outside box, from top going clockwise. Two for each side, one across the 
bottom (4) and top. Then the verticals (split) and horizontals. Then a 
diagonal in each quadrant. Then the "cursor," a sort of flattened caret 
under all the other segments. Picture an inverted V, but with a flat 
instead of a point, an as wide as the other segments.

They have another tube, the 5971, that has no caret and no split center 
vertical, thus 13 segments. But the 8971 and 7971 have 15.

> > What I want it a device I can build with a PIC or two that will
> > display the time and maybe the temp, plus a scrolling alpha numeric
> > message uploaded to it via a USB port.
>
>Since you'll have to have a host on the other end of the USB line,
>maybe just upload a stream of 16-bit values (well, 15-bit values, but
>padding them to 16 bits each is probably easist) and let the host deal
>with character generation?
>
> > I see USB port boards for PIC use all over the place, but I'm fairly
> > daunted by the prospect of designing a circuit flexible enough to
> > drive 6x15 segment nixies.  Maybe a character generator in addition
> > to the main PIC??
>
>Why bother?  Why not just generate 15-bit values for display, rather
>than generating 7-bit values that mean something to a human looking at
>an ASCII table and then contriving external hardware to convert them to
>the 15-bit values the hardware actually needs?
>
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