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Build the Eyeboard Open Source Eye-Tracking Project

Build the Eyeboard Open Source Eye-Tracking Project

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When 18-year-old Honduran makerLuis Cruzmet a quadriplegic high school classmate andlearned about the challenges he and other folks with disabilities face in the light of expensiveassistive communication technologies, he was inspired to devise a solution. What Luis came upwith is the Eyeboard: an inexpensive yet reliable human-computer interface that detects eyemovements using electrooculography (EOG), a biomedical technique based on picking upsignals from electrodes placed around the eyes, which in this case enables users who cantmanipulate a mouse or trackpad to move a cursor on a screen. Luis wrote about his project in aneye tracking feature on the pages ofMAKE Volume 29, alongside Zach Liebermans EyeWriterproject. Here is Luis article on the Eyeboard design and development:

The eyeball generates a voltage of 0.4mV1.0mV (millivolts) between its cornea in front andretina in back. If you attach electrodes on opposite sides of the eye, theyll pick up some of thisvoltage, depending on where the eyeball is pointing. Looking straight ahead, with the cornea andretina equidistant between the electrodes, there will be no voltage. But with the eyeball angled toone side, you can measure a microvolt-level signal between theelectrodes nearer the cornea and the one opposite. EOG can track both horizontal and verticalmovements, but horizontal is easier and more useful. My system, like many others, only tracks

http://intelsath.com/http://intelsath.com/http://intelsath.com/http://makeprojects.com/Project/Eyeboard-Electrooculography-EOG-System/1686/1http://www.makezine.com/29http://www.makezine.com/29http://www.instructables.com/id/The-EyeWriter-20/http://www.instructables.com/id/The-EyeWriter-20/http://www.instructables.com/id/The-EyeWriter-20/http://blog.makezine.com/2012/02/23/build-the-eyeboard-open-source-eye-tracking-project/eyeboard_make-volume-29/http://intelsath.com/http://makeprojects.com/Project/Eyeboard-Electrooculography-EOG-System/1686/1http://www.makezine.com/29http://www.instructables.com/id/The-EyeWriter-20/http://www.instructables.com/id/The-EyeWriter-20/

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horizontal using 3 electrodes: one right next to each eye,and the ground electrode centered on thebridge of the nose or forehead.

A processor chip or even an oscilloscope cannot detect such small voltages, so the EOG systemmust amplify them, while also filtering out any noise from nearby electrical devices and wiring.You can see the circuit I built to accomplish this, along with step-by-step instructions for

building my EOG system and programming its microcontroller chip, at makeprojects.com.To amplify the signal initially, I use an INA118 instrumentation amplifier chip configured with a100 resistor between pins 1 and 8, which gives it a gain of 501. The INA118 chips highCMRR (common-mode rejection ratio) of 110dB eliminates common signals that go into bothinputs, which removes some noise at the start of the signal path.

Noise from electrode circuits tends to come at high frequencies, so mine uses 2 passive low-passfilters in sequence, to reduce this noise above their cutoff frequency of around 16Hz. With thecircuit I used, the formula for the cutoff is 1 /2RC, where R is resistance and C is capacitance,so with a 100k resistor and a 0.1F cap, this comes out to 15.9Hz, which is fine; eyemovements arent so fast that filtering cuts out anything important.

Finally, a capacitor zeroes the signal by removing the DC offset added by the resting potentialbetween the eyes, and a voltage follower circuit lets you connect a higher source impedancedevice than the EOG outputs impedance, which is useful to connect an oscilloscope ormultimeter for troubleshooting. To power the system, I use two 7805 voltage regulators wired ina trick way to supply the circuit with +5V, 5V, and ground (0V), eliminating the need for a dualpower supply.

To process the amplified signal when the eyes move horizontally, I feed it into the analog-digitalconverter pin of an AT-mega328P microcontroller thats programmed to send the data to acomputer via serial port. A Python script on the computer then sends the data to a C++ applet Iwrote, which lets the user spell out messages. Looking to the left scrolls down through letters,and looking to the right selects them. To make wearing the electrodes more comfortable, Imounted them to some glasses modded with a headband and super glue. Ive built severalprototypes of these EOG glasses with good results.

Im still improving this EOG system, including looking for ways to make it more comfortable towear. Im pleased to have developed a system for less than $200 that enables disabled people,like my classmate, to communicate, when commercial versions of the same cost a minimum of$10,000. Id also like to create inexpensive EOG-interface systems for other applications, such ascontrolling a wheelchair or a television. I just graduated from high school, and what I need mostof all in order to pursue these ideas is a scholarship, sponsor, or other funding source so that Ican study electrical engineering in the United States.

Heres the Reuters coverage of Luis project from December 2011:

Build your own Eyeboard by following the instructions Luis shared on Make: Projects.

From the pages of MAKE Volume 29:

http://makeprojects.com/Project/Eyeboard-Electrooculography-EOG-System/1686/1http://makeprojects.com/Project/Eyeboard-Electrooculography-EOG-System/1686/1http://makeprojects.com/Project/Eyeboard-Electrooculography-EOG-System/1686/1http://makeprojects.com/Project/Eyeboard-Electrooculography-EOG-System/1686/1

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We have the technology (to quote The Six Million Dollar Man), but commercial tools forexploring, assisting, and augmenting our bodies really can approach a price tag of $6 million.

Medical and assistive tech manufacturers must pay not just for R&D, but for expensive clinicaltrials, regulatory compliance, and liability and doesnt help with low pricing that thesedevices are typically paid for through insurance, rather than purchased directly. But manygadgets that restore peoples abilities or enable new superpowers are surprisingly easy tomake, and for tiny fractions of the costs of off-the-shelf equivalents. MAKE Volume 29, theDIY Superhuman issue, explains how.

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Posted by Goli Mohammadi | Thursday February 23rd, 2012 6:19 PMCategories: Biology,Computers, MAKE Magazine,Make: Projects |No Comments

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