The latest version of OpenEarable is available here.

OpenEarable ExG

Extend the OpenEarable platform with biopotential-sensing capabilities
DESIGN PRINCIPLES
Openness
Extensibility
Easy-to-Use
OpenEarable is licensed under the MIT license!
OpenEarable ExG is a new research project at TECO that aims to extend the OpenEarable platform with biopotential-sensing capabilities. This allows OpenEarable EG to measure electrooculography- (EOG), electromyography- (EMG) and electoencephalography- (EEG) signals, closes the gap of body-phenomena that OpenEarable can sense. OpenEarable ExG's paper received the best paper award at the OpenWearables Workshop at Ubicomp 2024.
DEVELOPED BY
OpenEarable ExG Hardware
OpenEarable ExG Hardware
(A) PCB and components of OpenEarable ExG; (B) 3D-printed in-ear plugs based on Dätwyler Softpulse electrodes in-ear electrodes (C) assembled device with 3D-printed housing and custom in-ear electrodes; (D) user wearing OpenEarable ExG.
OpenEarable ExG Validation Study
OpenEarable ExG Validation Study

(1.A) - (1.F) display brain activity measured via ear EEG for three participants, with eyes open and closed, revealing increased alpha activity when eyes are closed. (2.A) - (2.F) illustrate the rise in signal amplitude measured by ear EMG during jaw muscle clenching for the same participants. (3.A) - (3.E) present smooth pursuit signals measured via ear EOG, showing signal deflection in opposite directions based on the participants' gaze direction.

Sensors

9-axis Inertial Measurement Unit
Bosch BMX160
Inside the main body behind the ear sits a 9-axis inertial measurement unit consisting of an accelerometer, a gyroscope and a magnetometer. Per default, OpenEarable allows streaming IMU data in real-time at up to 50 Hz via BLE.
The most critical component of OpenEarable ExG is the analog digital converter. Analog Devices AD7124-4 has a very high resolution, and a built-in 50 Hz/60 Hz rejection of up to 130 dB. This enables OpenEarable ExG to directly use the sampled data on device, without any latency due to digital filtering, for example for on-device classification of different ExG phenomena
Instrumentation Amplifiers
Cosine COSINA333
To achieve a good common mode rejection (120 dB, VCM < 5V) between the electrodes and even better 50 Hz/60 Hz rejection, two Cosine COSINA333 rail-to-rail instrumentation amplifiers are incorporated in OpenEarable ExG, between Electrode 1 & 2 and the Analog-to-Digital-Converter. The gain of ~50 is set through a 2.2 kOhm resistor
Driven-Right-Leg Active Ground
To increase the 50 Hz/60 Hz rejection even further and provide better signal quality, a Driven-Right-Leg (DRL) circuit is integrated into OpenEarable ExG. This circuit senses the 50 Hz/60 Hz noise at the instrumentation amplifier stage and inverts this signal to feed it back to the body via the GND electrode which is, simplified, comparable to noise cancellation in modern headphones.

Actuators

The actuators in OpenEarable are used to play audio and give visual feedback. In addition, a button allow user input.
RGB LED
OpenEarable has an RGB color LED in the main enclosure behind the ear. The color can be freely configured via BLE.
Button and Switch
The button on OpenEarable can be used to trigger events that are notified via BLE. The switch is used to turn on/off the device.

Citing

OpenEarable ExG has been published as a scientific research paper. If you are using OpenEarable ExG in your work, please cite it as follows.
@inproceedings{lepold2024openearable,
     title={OpenEarable ExG: Open-Source Hardware for Ear-Based Biopotential Sensing Applications},
     author={Lepold, Philipp and R{\"o}ddiger, Tobias and King, Tobias and Kunze, Kai and Maurer, Christoph and Beigl, Michael},
     year = 2024,
     booktitle={Companion of the 2024 on ACM International Joint Conference on Pervasive and Ubiquitous Computing},
     pages={916--920},
}
Karlsruhe Institute of Technology, 2023
Made in Germany
Imprint
tobias.roeddiger (at) kit.edu