BioAmp EXG Pill

Professional-grade analog front-end amplification for ECG, EMG, EOG, and EEG biosensing on one tiny board

Sep 28, 2021

Electroencephalography (EEG) Walkthrough

by Deepak Khatri

Electroencephalography (EEG) is an electrophysiological monitoring method to record the brain’s electrical activity on the scalp. During the procedure, electrodes consisting of small metal discs with thin wires are pasted onto the scalp. The electrodes detect tiny electrical charges that result from brain-cell activity. Those charges are then amplified to appear on a computer screen. It is typically non-invasive, with the electrodes placed along the scalp. The resulting signal is called an electroencephalogram, an example of which is shown below:

How to Create an Electroencephalograph With BioAmp EXG Pill

An EEG is performed using an instrument called an electroencephalograph to produce a record called an electroencephalogram. Electrodes are commonly placed on the forehead, as shown in the diagram below, when recording frontal-cortex EEG signals.

To record nice clean EEG signals with BioAmp EXG Pill, all you need is the Analog Serial Out sample Arduino sketch. If you want some more control we also have a Fixed Sampling example sketch for recording EEG and other biopotential signals at a specific sampling rate. You can also use the EEG Filter example sketch for recording EEG at a sampling rate of 256.0 Hz and a frequency of 0.5 - 29.5 Hz. The image below shows the fourth-order Butterworth IIR digital bandpass filter used in the EEG Filter example sketch.

Frontal EEG Recording

The video below shows a frontal electroencephalography (EEG) recording for both open- and closed-eye positions. The transition between the signals is also very clearly visible. To get an even better EEG signal, it’s recommended to use a dedicated ADC like the Texas Instruments ADS115 (16-bit) or ADS131M08 (24-bit). On the new BioAmp EXG Pill v1.0, we recommend creating a solder bridge on the back side of the PCB to set the narrow bandpass option.

Note: BioAmp EXG Pill is not a certified medical device and should not be treated like one.

What People Have Made With BioAmp EXG Pill

Padmalaya Rawal of PR Robotics created a drowsiness-detection machine. He is basically detecting blinks using the BioAmp EXG Pill and if their is no blink in a set amount of time, the Buzzer + LED will get triggered to indicate drowsiness. To create this you just have to flash the Drowsiness Detection Arduino Sketch onto your Arduino-compatible board and do the electrode placement for EOG vertical eye movement recording. To learn more, see the YouTube video below:

References

  1. https://en.wikipedia.org/wiki/Electroencephalography
  2. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/electroencephalogram-eeg
  3. https://github.com/upsidedownlabs/BioAmp-EXG-Pill

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