[personal] Shaft encoder in HP2631B printer

[Rod Smallwood]

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