Date   : Wed, 25 May 2005 14:05:18 +0100
From   : ben@...
Subject: Re: Penman Plotters

julesrichardsonuk@... wrote:
> Do these things take various widths of paper?

Mine used to work on A4 and A3 paper quite happily. I guess there must
be a limit, but you wouldn't dream of using a toy like the Penman on anything
larger anyway.

> Give it a good clean too; make sure there isn't dust / dirt clogging up
> the IR detectors...

Yeah, done that! The slotted discs and detectors seem to be fine, as it 
moves forward and back nicely at startup, but it just isn't seeing the
edge of the paper as it should. I have tried on all sorts of backgrounds
too, though the "proper" background is of course matt black.

I once met the bloke who invented them; he told me that the very first 
model didn't even have wheels, as they aren't strictly necessary for the
geometry to work. It just ran on the naked motor spindles! The only problem
with that, was that the paper got cut to shreds.

He also gave me a bit of a tutorial on BAMs (Binary Angular Measures, or
something). Very cute. If you work in BAMs, you can change an angle by
90 or 180 degrees (or whatever it was, I forget!) merely by shifting a
register.