4 Sep
2008
4 Sep
'08
10:49 a.m.
Roy wrote:
On Wednesday 03 September 2008 23:21, bfranchuk at
jetnet.ab.ca wrote:
> William Blair wrote:
> > Right now, my goal is to build just an astable multivibrator clocking a
> > 4-bit counter. To show the alternating state of the multivibrator, I'll
> > light the tube from below through the hole in the center of the socket
> > with a two-color LED and the states of the counter tubes will be
> > indicated by lighting them from below with a red or blue LED. I've got
> > the special effects visualized, but that's the really easy part.
>
> Would not a green & red Ne-2 would fit the mood better.
> If you have the HV why not go nixe tube?
Given 4-bit binary, how many more tubes do you think
it'd take to do the
1-of-10 decoding?
No more tubes, if you're clever enough! Look at the HP AC-4 schematics and
manuals; they are very very clever, and I believe that this decoding-with-neon-
logic scheme predates HP. Many other 4-tube decimal counter modules from
other companies (I have a buttload of Berkeley Nucleonics ones) use the
same principle with very slight variations.
Using green and red NE-2's is probably out; they have different threshold voltages,
although with some good characterization you could probably do it.
Not only do I have 40-year-old modules that do this stuff, I've also built it with
6SN7's and modeled it with SPICE. For lowish speed counters (<100kHz) the
tolerances
do not have to be tight.
Requisite AC-4 references:
http://www.hparchive.com/Manuals/HP-AC-4A-4B-Manual.pdf
http://www.prc68.com/I/HPac4a.shtml
Patents named in AC-4 documents, find them at http://www.google.com/patents/
2,404,047 (1946)
2,410,156 (1946)
2,521,788 (1950) I believe this is the first place where I see the neon decoding scheme
2,538,122 (1951)
2,762,915 (1956)
Tim.