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>From: "Steve Pattison" <pattist@ozemail.com.au>
>Date: Fri, 10 Mar 2000 16:50:07 +1100
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>Subject: Fwd: Re: Another braille display method
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To: access-l@icomm.ca
From: Martin McCormick martin@dc.cis.okstate.edu
I think the idea of the rotating wheels would work, but the
problem would still be that of cost and mechanical complexity. The
way one presently turns something to the exact position is with a
stepper motor. These things are used in printers, plotters, and CNC
or Computer Numerically Controlled shop machines. They look like a
little electric motor and that is what they are except that they turn
some predictable fraction of their full rotation each time the coils
are excited in a certain sequence. They may divide a rotation in to
200 steps or 50 steps or whatever.
The problem is that they are expensive if one wanted to use
lots of them such as one for each cell. They also draw enough current
that if many of them were run at the same time, they would suck a
battery dry in no time flat or would need a power supply so big that
it could crank the engine of a truck when it wasn't running the
Braille display.
When they aren't actually turning, steppers must be energized
or the shaft will turn freely like a cart wheel. If that was a
Braille wheel, a person's fingers would move it if the power was off
to the stepper. One could have a mechanical break to stop the wheels,
but that's one more electromagnet to draw current and one more
mechanism to maintain.
I want to be clear about one thing. I don't have an agenda
such as a secret plan to sell my version of a Braille display or
printer. I wish I had a plan, secret or otherwise, but I don't right
now.
An affordable Braille display that would revolutionize
computer Braille technology needs to have the following
characteristics or it is doomed to be expensive like all the others.
The individual dots have to make themselves, so to speak.
They should be the result of electrical or possibly fluid or hydraulic
potential that makes dots or bumps everywhere a row and column
intersect and the row and column are energized.
It almost goes without saying that the materials should be
commonly available, cheap, and safe for people to use.
We already have very good electronic Braille displays so the
fun is to come up with a good and cheap electronic Braille display
that gives its operator a proper sensory experience. If you remember
the Blazy speech, Mr. Blazy talked about the need to run one's fingers
over the dots just like what happens when reading Braille embossed on
the page.
The refresh rate of the Braille must be much faster than we
can read so that one doesn't get in to a race with the display.
I thought it was kind of amusing that somebody actually tried
electrical shock stimulation directly to the fingers. Anybody who has
ever worked with electronics has been at least mildly shocked and one
can sure feel the nip of a mild shock, but it is not like touching a
Braille dot and more like getting bitten by a mosquito. I think I'll
pass on reading War and Pease via shock Braille.
The idea of heat is interesting except that human skin doesn't
have anywhere close to enough heat nerve endings to make fine
distinctions like we do with touch. We're kind of stuck with raised
dots or possibly vibrating dots.
Keep the good ideas coming and remember that they have to be
good cheap ideas.
Martin McCormick
Regards Steve,
mailto:pattist@ozemail.com.au
-- This mailing list is sponsored by the National Federation of the Blind, NFB. For more information about the NfB, please call (410) 659-9314, point your internet browser to http://www.nfb.org or Telnet to nfbnet.org.===================END FORWARDED MESSAGE===================
Steve Jacobson E-mail: sojacobson@mmm.com National Federation of the Blind
The Opinions expressed do not necessarily reflect those of the 3M Company
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