OT sockets for Nixies

[Dave McGuire]

On Dec 21, 2007, at 8:58 PM, Tom Peters wrote:
> This is off-topic in terms of the industry involved, but not too  
> far off in the time period this stuff dates from.
>
> I've got some very nice, rather large Burroughs nixies- 7971 types.  
> They're 4.8" high, "British flag" display which looks to be 2.5"  
> high inside the glass. They have 15 segments each-- 14 in the  
> alphanumeric display part of the tube and one sort-of cursor, an  
> underline character with the ends bent downwards.
>
> I hear one can dismember D-shell connectors to get some sockets to  
> solder to a pc board to connect to these. But my problem is driving  
> them.
>
> Anyone know a good way to drive these, four or six of them in an  
> array? I need 170 volts, 21ma all cathodes, between 4.0 and 6.0ma  
> any individual cathode. I was thinking of a pic at  each tube, sort- 
> of a character generator that would take an ascii code and drive  
> the right segments. Some sort of escape code would let you send 16  
> bits to be interpreted literally, i.e. turn on the literal segments  
> corresponding to the bits set, for more fanciful displays.

   B7971 tubes are very nice indeed.  A PIC with lookup tables in  
code memory is a reasonable approach.

   You can gate the 170VDC to the cathodes with MPSA42 transistors  
(NPN, Vceo=300V).  If you'll be multiplexing, you can drive the  
anodes with MPSA92s (PNP, Vceo=300V, effectively the PNP version of  
the MPSA42).  Both are available new in lots on eBay for next to  
nothing.

   I generate the 170VDC for Nixie (and similar) applications from  
12VDC using an MC34063-based step-up switching regulator, the design  
of which is based on a circuit from one of the chip's app notes.  I  
can send you the schematic if that'd be helpful.

           -Dave

-- 
Dave McGuire
Port Charlotte, FL
Farewell Ophelia, 9/22/1991 - 7/25/2007