Over the past few months I have been brainstorming with the NK Group, which has brought together
volunteer scientists and engineers in England, the USA and India. The goal is to design and fabricate
a very low cost refreshable braille display.
Such a device is used
by blind persons to read any form of text document. An array of "dots" defines a braille character, most often referred to as a braille cell, that
is equivalent to an alphabetic character A-Z. By lightly scanning a finger over the dots a braille reader
can develop the skills to become a proficient book reader.
However, it can take blind children a long time to learn the "braille alphabet" and sheets of braille
text are both bulky and expensive to print (emboss) and distribute to schools.
Thus there is a need for a so-called refreshable braille display. This device replaces multiple sheets of embossed braille with a line of braille cells. Each cell has six(6) plastic dots that can be changed, between an 'up' and 'down' position, to continuously present braille text to a reader.
These displays may be a very simple
manual device, as shown being used here:
Photo: Worth Trust, Katpadi, India (2007)
or, perhaps, a micro-processor controlled electro-mechanical device.
Relatively sophisticated electro-mechanical displays are available in the USA, but they are expensive - $1,800 - 6,000.
There is no way a child in a third world country will get to use one of these displays.
So the NK Group has been experimenting with a manual learning device, which is being produced
in India for less than U$10. It's based upon a series of plastic, rotating, octagonal disks and is called
the Natesan block:
The 6-dot braille cells can display the English alphabet (A-Z), numbers (0-9) and punctuation signs. For example,
the braille cells at the left of the above block, on the most visible face, are displaying 's' and '='.
Now the goal of the NK Group is to use the Natesan block as the basis for a low-cost,
microprocessor controlled braille display. To that end we have been studying basic mechanisms that may be applied to reliably move, and then hold, selected disks in the proper positions for a short line of braille cells.
A previous post ['Engineering Design' July 26,2009] showed a
preliminary 3D model for a stepper motor driving a typical octagonal disk.
In an email to the group yesterday, I wrote: "With my coffee this morning I tried to sketch out
the torsion spring setup for disk rotational position retention:"
NK then commented: "The torsion spring idea indeed is neat and simple. I really envy the facility
with which you churn out 2D or 3D graphic representations of ideas so easily and rapidly."
It's actually only in the past few years that I have gotten around to exploiting the "drawing
tools" now
so readily available on our personal, and laptop, computers. I never really developed any one of the variety of artistic
skills exhibited by my grandparents, but I guess I did get along ok with my simple hand-drawn engineering "sketches" for a long time!
As a digression from group activities I brought up an on-going interest in a branch of
mathematics known as topology. Here is a tile
version of the "impossible triangle" originally described by Sir Roger Penrose, FRS (1931- ),
a theoretical physicist at Oxford University:
Maybe I'll follow-up with a post showing how M.C. Escher used this mapping of 3D-to-2D
information to produce some stunning illusionary drawings.