The video shows the stepper motor in action, and how the gears move from Braille rod to rod (removed to show the gears underneath).

One thing you might notice right away – the speed. Working with Acrylic, while visually pretty, is not good for fast movement as it flexes too much. Also, since this is the prototype, I’m going slow-but-working versus fast-but-jamming (the driver chips really heat up when the motors stall).

In any case, I’ve gotten pretty well all I can from the Acrylic model prototype, and now it’s time for prototype 2. So here’s the (possibly only) video of the Acrylic model in action – enjoy!

For example, why this particular gear design – and why so big?

The design of the display is an inverted rack and pinion gearing, with the racks moving over the gear, positioning the Braille half-characters under a detecting window. Since there are eight possible half character patterns (three dots either on or off, meaning two to the third power), we need to move as many as eight positions to go from one character to another. While that’s the maximum, fortunately, the average is four (and by positioning the primary characters near the center of the rod, we can improve further on that).

So since moving is important, I decided to use one gear tooth per character position, or eight teeth to move the entire rod. I could have used fractions of that (for example, two gears per character), but there were problems:

• When more than one gear is used per tooth, positioning becomes an issue – is the ‘top’ position we detect for the correct position, or is it one off? When using a single tooth per character position, when that tooth is at top (12 o’clock or 0 degrees) then we have a character displayed – simple.
• More teeth means smaller gears, which streamlines the device – however, it means more travel to reach each position. This actually slows down the device, rather than speeds it up.

This latter point is important; although this device was never meant to compete with piezoelectric devices with near-instant updates, it still needs respectable update times. And so what would they be?

The estimates I am working off of (provide by a local Blind techhead) are that most blind people read Braille anywhere from 30 to 120 words per minute, and at an upper limit, a few can read 150 words per minute. Despite Grade 2 Braille not being a straight character for character translation of text, I’m guesstimating that 150 words per minute translates into 750 characters per minute (assuming 6 chars/word on average, including spaces), or about 15 characters a second. For the Audrey display, with its half characters, that means a top speed to aim for is 30 rods updated a second!

So, one way to get these times is by using a big gear, with fewer teeth, and less turning needed to move the racks. I’m currently using a 20 tooth gear not just for speed, but also to match my stepper motors. Using 1.8 degree steppers, which have 200 positions/steps per revolution, I need to evenly divide the teeth into this number, or I risk being out of alignment, since a tooth always must end up at the topmost/0 degree position so that a character is lined up properly (try the problem with a 48 position stepper of 7.5 degree steps, and you’ll see the problem, and the need for a different tooth count like 16). And books I’ve read recommend at least 15 teeth per gear for performance – ergo, the 20 tooth gear was born.

Now, with the 20 tooth gear, on average, a rack/rod/pin change is 4 movements of each tooth – which is 4/20=1/5 of a revolution, or 72 degrees, or 40 steps. So to get that 30 updates a second, I’d need to move 30 times that, or six complete revolutions on average. Six per second ends up being 360rpm, pretty perky for a stepper motor! And that doesn’t include movement from side to side as it shifts to the next rack.

There are solutions to this problem:

• Use larger gears. While my 20 tooth gear is a compromise, you can use more. Imagine a 200 tooth gear: now each step moves a character position, and you are moving 10 times faster in updates. However, a 200 tooth gear would be about 10 times larger, so now you’d be looking at a floor model device!
• You could replace the solid gear with a flexible belt. But remember that the speed of updates is how fast the MOTOR turns. So the belt would only update as fast as the wheel driving it can turn. One advantage however is you can now place the wheel on its side with some careful twisting of the belt, allowing you to have a shorter display device, and larger (=faster) gear wheel.
• Use multiple motors. One goal in my design is to make it possible to use multiple motors and gears in the display. Since parallel gears can update simultaneously this way, I effectively divide the work evenly between motors. In effect, four motors turns a 40 character display into a 10 character one, in terms of speed of updates.
• Settle for slower. 150 words per minute is the upper limit, but don’t forget, the 30 words per minute lower limit is 20% of the maximum speed, equivalent to about 60rpm, or one revolution a second, and much more manageable. So while speed ‘readers’ will chomp at the bit at that speed, it will be fast enough to use.

The good news is that, with one or more of these options, I believe the Audrey Device can meet its goal. While it won’t have the speed of a $7,000 device, it won’t have the price tag either. Plus, being Open Source, others can take the device and improve it (including speeding it up). And I am confident that once the device gets “out there”, people WILL speed it up, proving the benefit of the Open Source model yet again.

• N.Krishnaswamy of Vidya Vrikshah. produces a Braille kit for Blind children to learn. He also is the designer of a wheeled Braille display, called the Natesan. The Natesan in turn has spawned a prototype, possibly out this year, called the ‘The Quixote’, by Bristol Braille Technology.
• Bristol Braille Technology is the manufacturer of The Quixote, which will be offered Open Source as well, once ready.
• The Multi-Line Braille Display by Paul D’Souza goes one better than the Audrey display (or 25 better!) with multiple lines, giving a whole page of text displayed at a time.

If you’re interested in the forefront of Braille display , I recommend you visit these links – looking them over, I find myself quite positive that 2012 WILL be a significant year for the Blind!

I had an interesting email recently, and in answering it I thought the responses would benefit other visitors – so here it is a mini FAQ of the project so far:

• How will this display be marketed?
  Currently, it’s design only, not marketing. Once I have a design I like, I plan to manufacture it if I can raise the funds. However, since I will be publishing all details online, and will be available (time permitting) to answer questions, I believe anyone could start manufacturing them, even if I am unable to.
• Who will write a screenreader so it can be used with a computer?
  The design uses a serial (USB) port running at 9600 baud, which is a common communication protocol. I have talked to the folks involved with brltty, a Braille text driver suitable for Linux system; I believe it can be adapted readily to their protocol, which is a very common one in the Linux world (it comes installed I believe on all Linux distributions by default). As well, the source code to the device will be published, meaning that even if a particular protocol or device or software program is not supported, a programmer should be able to adapt it.
• What is your time table for developing the product?
  As for the timeline, I am currently working on improving the first prototype, and hope to have a second prototype by early February. This next one will be a full 40 characters (instead of the initial five) and will be close to the final product – barring unforeseen occurrences.
• There have been other attempts to develop a cheap Braille display but they didn’t amount to anything, so what’s the likelihood that you would develop a marketable product?
  I agree that there have been many failed Braille devices – in my initial research, I saw that and realized much of it was because of closed source designs. So I decided to make all research Open, so that anyone could make it. I hope by February to have enough source code and designs online that anyone could build it, company or individual, and get reasonable performance (note: because of the design, it likely will never compete with a $7000 device on speed, however, I’m hoping that is the only lack). As for the likelihood, I don’t see any technical challenges in the current design, only time and resources. I’m committed to getting this out and – God willing – I will.

I hope this answers some questions out there!

One aspect of the Braille Display Project has always been funding. Currently, I pay for all parts and supplies pretty much by myself (at least until the win at ASC V). That’s expected; money is in short supply these days, and I knew I’d be going it alone when I started.

But you know how it is: you either spend money or time, one way or another. So to cut down on time, I decided to open an offer to generate support. The offer, at IndieGoGo, is for contributions to help pay for more and better supplies and tools, speed up the project, and most importantly, raise awareness!

What’s IndieGoGo? For those familiar with KickStarter, you already know (IndieGoGo is easier for Canadians to set up on than KickStarter). For others, these sites are incubators of a sort: they handle the donations and rewards payouts (called ‘Perks’), and provide a convenient place to manage all aspects of the project. In my case, I set a deadline (late January), a level amount ($1,500), and what my perks would be for contributors. The best one is the $50 level, which provides a link on this site – you can see the thank you list at the top of the sidebar on the right – which is ideal for search engine notice and possibly sending traffic to your site!

Please consider a contribution – and please tell others of this project campaign. As always, the more people thinking about a Braille Display Project, the more likely the Blind will have a powerful new low-cost tool in the new year!