PandaBraille: A Refreshable Electro-Tactile Braille Display with No Moving Parts (VIT University)


Supreeta Ray, Prithvi Monangi, Yamini Dubey, Taranand Mukhopadhyay, Aditya Dubey, Spandana Chervu, Theodore M. Moallem

ABSTRACT

Most of the assistive tools present in the market currently, designed for the people who have blindness  are very costly, not easily repairable and even if available, are not easily accessible by them, the vast majority of which is economically weak. Apart from this, the number of books printed in braille is very limited. In general, new commercially available assistive technologies are far too expensive for them to afford.

Our device uses the novel technology which employs electro-tactile stimulations to create perception of braille characters.  The proposed model is designed to target persons with blindness so that they can learn independently and to give them a new perspective in literacy. The missing sense of sight in them leads them to perceive the world in a different manner. This served as an inspiration to us to use haptics as a tool to help them interact with the environment.

BACKGROUND

Majority of the people who are blind get very few opportunities for proper education and employment, leading to a vicious cycle of constant poverty. With much advancement in science and technology, it is now feasible to bring down the the cost of braille literacy and other assistive tools designed for them so as to reach out the masses.

Our friend Govindaraj, thirty five years of age, is an enthusiastic learner and wants to read novels despite his inability to see. Having blindness by birth and due to his economic constraints, his educational opportunities were limited. This motivated us to design a low cost electronic braille reader, which is flexible and easily accessible.  We aim for it to be utilized as a tool by persons with blindness to educate themselves by reading a wide variety of texts without the economic constraints.

OBJECTIVE

According to a Times of India (TOI) study in 2007, India has the largest population of persons having blindness in the world. In India, out of the two million such children, only three percent receive education. Many tend to fall out of school due to various socio-economic factors. Our aim is to increase literacy among the younger generation as well as the old, so that they can contribute their intelligence to the society and have better chances of employment. This device is also for other people having blindness wanting to read text from e-books and documents present in computers and low-cost smartphones.

DESIGN(Method/Approach)

System Schematic

The current braille reading devices deliver refreshable braille display via combinations of movable pins. The pins are actuated using a complex mechanical technology, which increases the cost, size, and power consumption, while adding a lot of bulk and reducing portability.

Our aim is to create an assistive braille reader, built of inexpensive electronics, which uses a simple circuitry and is based on electrocutaneous (i.e., electro-tactile) mechanism, creating the sensation of braille characters, synchronised with the movement of the hand.

COST AND POWER

The uniqueness of this design is that it eliminates the need for physically moving pins (and designing ways to move them independently), by using electrical stimulation via electrodes to produce a similar perceptual effect and bringing down the cost of the device by fifty times.  The only power requirement is to drive the transformer circuit and the microcontroller, which is as low as nine volts.

CIRCUITRY

The circuit we employ modulates a pulsed input given to the base of a transistor, which drives an audio transformer and generates a voltage amplified version of a spiked waveform.

The waveform thus generated is multiplexed via a complex network of MOSFETs, and fed to a grid of electrodes. The microcontroller can be used to control the shape, frequency and timing of pulses and to activate the corresponding electrodes. Also we exploit the persistence of sensation effect, via which we switch between electrodes with a millisecond delay imperceptible to the skin, thus appearing as simultaneous activation, similar to a braille character.

The device has an integrated optical motion sensor, which gives the feedback of the x-y coordinates, so that the pulsed output can be altered in real-time. This adds flexibility to the user, so that the user can control the speed and position of characters moving across the braille display.

STIMULATIONS

Miniature Stimulators


The quality of the stimulation depends upon the type of electrodes used, the pulsed waveform used for stimulation and the relative placement of the electrodes.
We are using a grid of copper electrodes, with <1 mm tip diameter to produce localised stimulation. Also extensive testing was done  to optimize the intensity of shocks.

Various experiments were done with the width, duty cycle and frequency of pulses to determine the haptic spatial and temporal resolutions, which were then found to be roughly 5 mm and 50 millisecs respectively. This finding was then used in the aforementioned multiplexing circuit. The pulses used are monophasic which are fed into the the transformer through a bipolar junction transistor. The other data pins of the controller work as control pins for the gating of MOSFETs associated with active electrodes. The output across one of the transformer terminal is connected to the drain of all MOSFETs in parallel, and the source is connected to the corresponding active electrodes, thus working as a switch. The other terminal of the transformer is connected to the common reference electrode. The stimulating pulse appears across only those electrodes that are gated by the microcontroller, forming a short circuit path completing the circuit for electrical stimulation.

PORTABILITY

It fits in your pocket !

The device is divided into three layers, the lowest layer consisting of the motion sensor and the corresponding circuit, the next layer has a microcontroller and the topmost layer is  the multiplexing circuit. The end product can  be plugged into any  computer or smartphone and can be slided on any available surface thus making the entire device extremely compact, compatible, lightweight, user friendly and safe.

In the manufacturing phase, the optical sensor circuitry, the microcontroller, the stimulation and multiplexing units will be printed on a single printed circuit board,thus further reducing the space and bulkiness of the device.

RESULTS and CONCLUSION

The perception of sequence was felt through the electrodes. This gave the sense of directionality in spatial and temporal domain, hence enabling the person to perceive data.

The design of the prototype is such that it is not only portable but also easy to use. Also,  from the commercial point of view, the design is feasible as it uses inexpensive and easily available components that makes the device low cost, hence giving it an edge over the other similar products in the market. The present prototype can further be moulded to suit user’s requirements. For example, a memory chip can be included in it to store any text file or any other data that the user wants to retrieve.

FUTURE WORK

The scope of this project is very large and can be integrated into a variety of applications. Java software can be developed to read each character in the given text one by one and send it serially to the microcontroller which will be programmed to actuate the respective electrodes which form a sensible braille character.

The device can be integrated with a small camera underneath to capture text from any book, newspaper, article or any surface, and then do image processing and present it on the electrotactile display screen.  Apart from that, the prototype can be used to know about various surface textures.

One of our long-term goals is also to have real-time power generation in the device by integrating small wheels beneath the device, which rotate inbuilt motors when the device is in motion,generating enough power to run the circuit hence making it independent of the battery source.

ACKNOWLEDGEMENTS

THE TEAM : ( L to R ) Supreeta Ray, Prithvi Monangi, Yamini Dubey, Taranand Mukhopadhyay, Aditya Dubey, Spandana Chervu, Theodore M. Moallem


We would like to thank Govindraj and everyone who has helped us to reach at this stage and are still in  collaboration with us. We would also like to thank Sabriye Tenberken who offered us her feedback during the testing of our circuit.

REFERENCES

1.http://timesofindia.indiatimes.com/india/India-has-largest-blind-population/articleshow/2447603.cms?intenttarget=no.

2. “Electrotactile and Vibrotactile Displays for Sensory Substitution Systems”, Kurt A. Kaczmarek, Student Member, IEEE, John G. Webster, Fellow, IEEE, Paul Bach-y-Rita, and Willis J. Tompkins, Senior Member, IEEE , IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 38, NO. 1, JANUARY 1991

3. “Electrical stimulation of mechanoreceptors ”, AM Echenique, JP Graffigna , Gabinete de Tecnología Médica, Universidad Nacional de San Juan Av. Libertador 1109 (oeste), San Juan, Argentina

4. “Electrocutaneous Stimulation for Sensory Communication in Rehabilitation Engineering”, ANDREW Y. J. SZETO, member, IEEE, and FRANK A. SAUNDERS

5. “Practical aspects of Audiology TACTILE AIDS for the hearing impaired”, Edited by IAN R. SUMMERS, 617.8, Whurr Publishers, London, ISBN 1-870332-17-2

avatar

,