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Development of a Refreshable Braille Display

Design and development of a micro motor driven braille display and keyboard.

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Visually impaired people require Assistive Technologies in order to use computers and smartphones for gathering information. Speech synthesizers can be impractical in lots of situations and therefore digital braille displays can be used to extend or even replace the audio feedback. As braille readers are either pricey or have a lack of functionality, the efforts to rework technologies of those devices is increasing. Available concepts for braille cells are analysed and requirements of an affordable alternative functional principle for the design is developed. The evaluation reveals a motor driven braille cell mechanism is most cost efficient. Furthermore, the interoperability with computer and smartphone interfaces is of high importance to achieve a great usability. From these deducted requirements a prototype concept is developed and implemented in form of 3D printed braille actuator cells, a microprocessor controlled main unit and a custom printed circuit board for less than 110

Total Costs of Braille Display Prototype : 


The total material costs of all required components for the braille display are listed below

3D Printed Components7.81 €
Electronic Components68.94 €
Screws and Brass Inserts4.91 €
Motor Based Cell Version 2 (8 Cells)22.48 €
Total Costs104.14 €

Details at https://github.com/ChrisUlbi/BrailleDisplay

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  • 4 × Braille Modules Braille modules holding two braille displays
  • 1 × Keyboard Input
  • 1 × Case 3D printed case
  • 1 × Microcontroller
  • 1 × Real Time Clock

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  • Introduction

    chrisulbinger09/03/2017 at 16:38 0 comments

    Acknowledgements

    I would like to show my gratitude to Vijay Raghav Varada for the development and documentation of their prototype covering important components required

    Introduction

    Mechanical refreshable braille cells are based on different technologies in devices on the market. These have to be analysed and evaluated in order to find the appropriate one to implement. Since the most data about braille displays and readers on the market are not available as open source and their costs can exceed several thousand Euros, the aim of this thesis is to design and develop a concept and prototype of a universal and highly interoperable refreshable braille reader at low costs. Therefore it is required to analyse the usage behaviour of braille display users and evaluate the methods and technologies in order to find solutions if the manufacturing costs can be reduced significantly while keeping state of the art standards or optimizing them. Evaluations of manufacturing refreshable braille displays in terms of rapid prototyping technologies are to be conducted.

    Thereby this thesis deals with the development of a design and if these can be transformed to a prototype while ensuring to meet the predetermined requirements. Therefore the research for requirements is based on:
    • Evaluation of braille cell technologies
    • Design and development of 3D printable components
    • Implementation of open source available resources for the software application
    • Design and implementation of required electronics
    • Analyse, maintain and improve the state of the art standards

  • Basic Requirements

    chrisulbinger09/03/2017 at 16:29 0 comments

    The basic requirements are deducted from braille market research as well as state of the art devices:

    • Refreshable display of minimum eight cells each holding six-dots
    • Reading the content of files on an SD card for stand-alone operation
    • Computers and portable devices can be connected via USB and Bluetooth
    • Eight braille input keys and space bar
    • Four-way arrow and selection control keys
    • Two panning control bars
    • Date, time and calculator function
    • Rechargeable battery with additional wireless charging
    • Audio and haptic feedback

  • Firmware Structure

    chrisulbinger09/03/2017 at 16:28 0 comments

    Firmware Structure

    First, the braille display will initiate all required hardware components during start up. This includes the serial communication through a USB as well as a wireless Bluetooth connection. Furthermore, the keyboard and braille cells are prepared for use. This is followed by the initialisation process of the menu tree, the SD card and real time clock. After the initialisation is successfully done, the main body of the firmware is started.
    In this loop the commands received either by the user through keyboard inputs or by commands via serial interface are processed. Depending on the currently activated intended use of the braille device, the text which should be displayed is gathered. These characters are prepared in a reader friendly way through pre-processing. The battery status is checked continuously in order to give a feedback to the user. All occurring events and errors are logged and sent to connected devices such as smartphones or computers for analysis.


    Bluetooth Mode
    By selecting this mode, the device will transfer all data in a formatted way to the desired device via Bluetooth. The connection is established by selecting the braille display in the Bluetooth settings of the smartphone, tablet or computer.
    USB Mode
    The braille device is able to connect to other devices via USB through a serial interface as well as a Human Interface Device (HID). This allows the braille reader to send characters and keyboard inputs directly to the desired device. Additionally all occurred events and pressed keys are transferred through a serial interface to the device in a formatted protocol.
    Book Reader
    The book reading application of the braille reader is capable of opening every document containing ASCII formatted characters. Books and other documents in an electronic format can be translated to the required standard through RoboBraille and other converting tools. Scrolling through the document is automatically achieved through pressing the panning bars.
    Date and Time
    The braille display houses a real time clock with an additional battery. Therefore the user can gather information about the current time, date and weekday by selecting the desired information in the menu.
    Radio
    A digital radio receiver allows visually impaired people to hear music and gather information on the news. The user can therefore plug in commonly used headphones and adapt the volume. The frequency of the radio can be changed and adapted by pressing the panning bars and is displayed in braille. Additionally eight radio stations are preconfigured and can be directly accessed by pressing the button on the corresponding keyboard.
    Calculator
    An additional application allows the user to calculate simple mathematical tasks. The calculator includes the four basic operators and displays the input as well as the result in a formatted way.

  • Discussion

    chrisulbinger09/03/2017 at 16:25 0 comments

    Discussion

    Comparing the variety of concepts for braille cells, the aspects of this master thesis have to be considered. The focus lies on prototyping and manufacturing in a cheap and easily reproducible manner. The widely spread technology covering the piezoelectric effect has the advantage of easy access and high precision. However the dots require high voltage to be embossed. This high energy needed, leads to additional effort in designing the power supply. Furthermore the costs for the cells, even in higher amounts, is a significant disadvantage for this technology. The promising concept using electromagnetic mechanism shows a possibility to be manufactured as a prototype using available materials. The construction is relatively small in size and easy to replace due to the modular design. The costs compared to the piezoelectric mechanism is reduced, which makes this technology attractive. Additionally the number of dots can be adapted as required without significant additional effort. The number of individual parts as well as the balancing of the electromagnetic effects are less promising than the technology using micro motors. This version has the best cost efficiency among the covered technologies for braille cells. All required components can be either 3D printed or ordered. Therefore this braille cell technology fits best for the prototyping and research application.
    The first version of the braille cell based on micro vibration motors has less production costs compared to the second version. However, all motors have to be soldered individually by hand, which increases the time and effort to manufacture significantly. Therefore the second version simplifies it by using a printed circuit board which has the contact pads already printed on. This can be screwed to the braille module and decreases the manufacturing time. Additionally the number of individually required components per module is minimized.
    The dot size dimensions within a cell is designed according to the recommended standard referred as Marburg Medium. Due to the size of the motors, the spacing between the cells had to be increased.

    As the wireless charging solution compared to a cable based one is limited in current, the charging time is increased. Nevertheless the effort for blind people to recharge the handheld device is decreased significantly, as it just has to be placed on top of it without any further actions.
    As one of the purposes of this device is the handheld usage, high battery lifetime is a high priority. The low energy consumption of the components leads to a lifetime of up to 24 hours of continuous usage. The rechargeable battery is standardized in size and can be replaced easily as required. During the development phase, batteries with higher capacity were unavailable for delivery. However, for a similar price there are rechargeable batteries on the market with a capacity of 3450mAh, which increases the continuous reading capability to nearly 32 hours.
    The case is designed for four braille modules, which result in a maximum of 8 characters. As the modules are easily replaceable and extendable, the braille display can be designed and manufactured in any size. For prototyping and testing reasons the number of characters is limited to eight. A major advantage of the designed case and construction is that all parts can be 3D printed as required. This includes the buttons and switches, which have printed braille labels implemented. Therefore the user can recognize the designated use of the individual buttons by tactile reading.
    Braille varies significantly in different languages. This is not only limited to abbreviations but also concerning special characters and punctuations. At the current state of the development of the braille display, there is a hardcoded braille chart implemented. This chart consists out of braille in grade 1 in an adapted form of the published table from EBU. For further usage and development, the chart has to be expanded for most...

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  • Conclusion

    chrisulbinger09/03/2017 at 16:24 0 comments

    Conclusion

    As the focus lies on the possibility to manufacture braille cells according to CAD drawings via rapid prototyping technologies, the micro motor based version shows great promises. Further improvements on the design have to be made in order to minimize the distance between the braille cells to comply completely with the recommended Marburg Medium dot dimensions. Software applications are implemented using either open source resources or free available products. This results in an easy extension related to additional application to be supported by the device. The communication between the braille display with computer and smartphones is achieved through a developed protocol. In order to be supported by commonly used software application on those devices, either a protocol of available products on the market has to be adapted or the developed protocol has to be implemented in the software plug-ins of smartphones and computers.

    All in all the concept and implementation proves that a braille display can be manufactured and developed through prototyping techniques as well as open source software applications in order to decrease the costs significantly while keeping state of the art technologies. The predetermined requirements can be met while being additionally extendable.

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