28 Jan
2010
28 Jan
'10
6:43 a.m.
Use a light beam, an analog optical gate and a photocell
Regards
Rod Smallwood
-----Original Message-----
From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org]
On Behalf Of Tony Duell
Sent: 27 January 2010 20:09
To: cctalk at classiccmp.org
Subject: Re: [personal] Shaft encoder in HP2631B printer
I wonder if one of those Nernst glowers emits many
electrons. I've had
this pipe dream lately to build a triode to operate in open air, and
I've been pondering what to use for a filament/cathode. Googling so far
has not revealed anyone else this crazy. ;)
You are going to have problems. The mean free path of an electron in air
at atmospheric pressure is pretty short (I forget how short, but it can
be looked up). You need to have the overal distance between the
electrodes to be less than that.
There was a proposable to make field emitting triodes (rather than
thermionic ones) using eteched silicon structures. Those would work
without a vacuum due to their small size. The reuslt would be
radiation-hard chips.
-tony