28 Feb
2003
28 Feb
'03
1:35 a.m.
On Fri, 28 Feb 2003, William Donzelli wrote:
I've looked recently inside an Anita MK IV calculator and a doubt that you
would want to use that many tubes with heaters in that small a case...
The thyratons it uses are cold cathode and quite small. It also uses 1
Decatron tube...
Peter Wallace
I'm
fascinated by the idea of making counters, logic gates, and
memory elements using neon lamps, but repeated google searches reveal very,
very little hard information (other than there were such circuits).
I seem to remember seeing some stuff about this in old trade magazines,
like Proceedings of the IRE or Electronics. Check a good library (maybe
on from a tech school).
Also, I've read a few pages on early
calculators (such as the Anita) using
something similar to neon lamps for logic gates and ring counters, though
the pictures lead me to believe they are actually 4-lead gas triodes or
thyratrons of some kind. Do you know what these beaties actually were?
I don't know, but frankly, I don't see why you would want to use gas
triodes over regular triodes for low power logic. If anything, the long
term instability of the gas tubes might be a problem (note that neon
bulbs degrade quite obviously, but submini triodes last forever). Finally, I've repeatedly run across mention
that neon device switching is
slow, but how slow are they?
It depends on the tube. Some of the industrial gas tubes are indeed slow,
but they have no need to go fast, controlling motors and relays and things.
Some ring counters (Dekatrons) can go reasonably fast - 100 KHz is
reasonable. Of course, most reasonable people would call 100 KHz slow.
William Donzelli
aw288(a)osfn.org