Thenar – portable and affordable Braille display for visually impaired people

A quick survey showed that the Braille display is an electromechanical device that can fully replace traditional paper Braille and provides the access to any electronic text. Although there are a great number of speech synthesizers and myriad audiobooks, according to researches the literacy of a person can be developed only by reading. The cool fact is that when a visually impaired person reads Braille, he/she activates the same parts of the brain as a sighted person does.

The heart of the Braille display is a row of several so-called Braille cells, that form a text line. Each Braille cell is a 2×4 matrix of tiny pins moving in and out of the surface forming a Braille character.

 The pins are moved by piezoelectric actuators. Displays have from 10 to 80 cells, and the more cells the better. Hence the frequency of pressing the button decreases making it easier for a reader. 40-cell displays are the most popular. Hence Braille displays have become the only interface for reading nowadays. However, the cost of even 14-cell displays starts from 1000 dollars. In this matter, displays are unaffordable devices for buying for most people.

Another fact is due to the high prices of Braille displays and the lack of updated paper-Braille books the average literacy rate among visually impaired people is lower than 5% even in developed countries. This shocking statistic looks like it describes the Middle ages time.

I love reading. But frankly saying I’m not ready to pay for a Kindle-like device eight or even one thousand dollars. By the way, sliding a reading finger over an 80-character Braille line doesn’t cover an average-length sentence, you will have to press the button to refresh the line and then continue reading.

I decided to work on this issue to make such devices more affordable for visually impaired people and improve their quality of life.

The idea and the first prototype

The first idea in a way to decrease a display price was to define the minimum number of cell in it, and at the same time, this number should be sufficient for comfortable reading (without the constant need to refresh the text line). So I thought it following way:

  1. The boundary values of cell quantity are zero to infinity.
  2. If we have zero cells, a display becomes a text-synthesizer, which is not our goal. That’s why the number of cells should be at list one.
  3. In the case of one cell we get minimal price and minimal comfortability in sliding reading-finger over the Braille-line; in the case of an infinite number of cells, we get maximum comfortability as well as a price.
  4. So the obvious solution is to connect the ends of that long text line to form a circle and let a reader slide his finger around the outer surface of the ring.
  5. This solution has two problems: sliding a finger around a ring is not comfortable, and it still needs to be refreshed by pressing a button.
  6. We have one more initial condition: reading-finger can read (feel/recognize) only on character at the time.
  7. I decided to combine and rearrange these processes, and then divided them between two hands.
  8. Finally, we get the following: reading-finger lay on a sole Braille-cell, sliding around a ring was replaced by rotating a jog dial with the finger of another hand. Refreshment of the Braille character happens with each step revolution of the jog dial.
  9. This approach provides full control of the text stream (forward and backward), and the most important – gives the feeling of reading the endless text-line. To be honest, the last statement I perceived long after.
  10. In addition, the new device needs the following minimal features:
  • Braille trainer;
  • Saving and reading books from SD-card;
  • Voice and Vibro menu;
  • Rechargeable battery;

Having this idea I started making a prototype. The next problem I faced was to find the Braille-cell module. Unfortunately, my search for that modules was unsuccessful. So as a temporary solution, I decided to make my own Braille-cell from electromagnetic relays. The cell looked really ugly but it worked more or less. It was enough for that moment to check and confirm the viability of that idea.

First of all, I dissembled a standard cheap 5v relay to check out its inner dimensions. There was enough room for drilling a hole in a base and put the pin through it. I made pins from the nylon fly line and glued them to the relay armature. Later it appeared it had been a bad idea. Pins went through the plastic tubes to avoid their bending because nylon is a flexible material.

After that, I designed a case for 6 relays. They were set in 4 rows in order to minimize the distance between pins. It should decrease the friction between pin and tube and fit the standard dimensions of Braille cell in the other end. Several turns on and offs of the relay revealed that nylon pins were not a good idea – it broke.

Then I decided to use another material – the copper core of a power lead. It was easy to form the shape and solder one end to the relay armature. It was much better than nylon.

Having done with the Braille cell module, I sketched the case of the device and get its dimensions. There was enough space for electronics and a battery. I didn’t know how to design a PCB, so soldered electronic components to each other with point-to-point wiring. There were not much wiring and modules inside, so it worked more or less well. As for the jog dial, I chose an encoder with a printed ribbed cylinder knob on it. I tried to make the diameter as much as possible, and it was almost as the depth of the device. As a microcontroller, I have chosen the Arduino platform. Its computation capacity is more than enough to process the encoder signal, read text files from an SD card, control the relays, and playback mp3 audio files for menu navigation. 

Making Thenar more stable and easy to assemble

In 2019 I was teaching the course of 3d-modeling and printing in local MakerSpace. So I decided to test my idea that anyone can assemble Thanar, on those of my students who were interested in this project. As a result, I expand my course to a prototyping course, where students would learn prototyping on the example of the production of my device. At the end of the course, we planned to gift electronic Braille books to participants of the local blind people society. More about you can find here.

In general, the concept was viable, however, it was too difficult to assemble and solder the heart of the device – Braille Cell. 

Then I found a manufacturer of piezoelectric Braille cells Metec-AG from Germany (Metec-AG B11 Cell), and their cells are way reliable and cost not too much (about $30).

So I continued working on the device. The first prototype showed that the cylinder knob had a very small contact surface with a finger. In order to extend the contact surface, the knob had to be replaced with some kind of caterpillar. I designed an updated and more reliable and handy jog dial. It works really well and gives the feedback clicking, which helps in navigating in a text. In order to minimize the cost of the final product, I tried to avoid specific components and utilize only common electronic components and modules. The caterpillar was made of a standardized rubber GT2 tooth belt for 3d printer.

The enclosure of the device had been improved along with inner parts. The jog dial moved lower to the natural position of the thumb.

From an Ugly Duckling Into the Thenar

With help of a professional designer, I ended up following the shape of the project. This shape does not only look fancy and futuristic but also very handy and fits almost all sizes of palms. Moreover, the designer suggested the naming – Thenar.

In addition, there are other improvements.

I do not like buttons and holes on the enclosure, so tried to avoid them. For this reason, a designed the jog dial with hidden buttons under the ribbed belt. So the control and switch buttons are hidden and do not need a specific place on the enclosure.

I added a dock station, which has wireless charging and magnets in it in order to correctly position Thenar in it.

While working on the enclosure, I printed details divided into patches. This approach lets not reprint big parts several times while choosing sizes of fitment holes.

Hours of sanding, priming, and painting give the final form of the project.

Now I’m preparing to launch the campaign on the Kickstarter to make Thanar even more affordable for people who need Braille readers in daily life.

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