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.
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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...