Neon bulb logic elements link?

[Allison]

>
>Subject: Re: Neon bulb logic elements link?
>   From: "Eric Smith" <eric at brouhaha.com>
>   Date: Wed, 25 May 2005 14:18:31 -0700 (PDT)
>     To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>Tom Jennings wrote:
>> For neon, from flawed memory, strike-over is around 100V, and
>> sustain around 80V.  [...]   You could probably make a coincident-voltage
>> memory from them... but they'd be slow I think, but pretty.
>
>Sounds like a fun project!
>
>Lessee...  If the numbers are 80V and 100V...
>
>You have an X-Y matrix.  Steady state, you apply +7.5V to each X line,
>and +97.5V to each Y line, so each tube has 90V across it.
>
>You turn on a particular tube by dropping the X line to 0V and raising
>the Y line to +105V.  The selected tube sees 105V, while the other tubes
>in the same row and column see 97.5V.
>
>I'm guessing that if you measure the current in those lines, you can
>tell when it strikes, or maybe you just wait long enough before dropping
>the lines back to the steady state.
>
>To turn off a particular tube, you raise the X line to 15V and drop
>the Y line to 90V.  Now there's only 75V across the selected tube,
>while other tubes in the same row and column will still have 75V.
>Again, there should be a current drop when the selected tube turns
>off.
>
>And you read a tube either by trying to turn it on, or trying to turn
>it off.  If the current doesn't change enough, it hasn't flipped.
>
>The voltages will need to be controlled fairly well, since the
>margins are narrow.
>
>Will neon bulbs have reduced lifetime if you run them on DC?
>
>Eric

The numbers for the common NE2 were more like 65 and 90V and
are also sensitive to light!  Neons for logic were burned in
for consistant threshold and extinguish voltages.

Oh, and they are relatively slow.

Other uses for Neons is they behave above the stike voltage
like a zener diode so it's not uncommon to tsee them used
as a 90V offset or reference.

Allison