Low Cost Electroencephalogram (EEG)

=Problem Definition= In order to better educate high school students about brain function, we are developing an educational, low cost EEG that can be made in classrooms by students. During this year, we are going to determine the least expensive and most easily reproducible way to create and EEG for under $100. =Background= The biggest barrier to introducing high school students to basic neuroscience is the staggering cost of an EEG and the corresponding software. Instead of spending $800 on an EEG device like Emotive, and hundreds of dollars per month on the related software, this new EEG design will deliver open source software and instructions for an easily reproducible hardware design to open neuroscience and basic engineering to all high school students.

=Specifications=

=Design Considerations= =Project Learning=

Electrode Research
We have tested several different types of electrodes to use for the EEG. We bought a sample pack of medical grade gold cup electrodes in order to get a base line signal to compare our electrodes to. The main candidates that we have tested are silver cup electrodes, 3D printed electrodes, and DIY electrodes using metal plates. The table below shows the finding of our testing. From this testing we decided to use silver cup electrodes because they are less expensive than gold cup electrodes but measure the same quality of signal.

Signal Research
The EEG signals are voltage fluctuations resulting from the currents produced by neurons in the brain. These EEG signals have very small magnitudes, typically around 50&mu;V. The frequencies of the EEG signals that we are measuring range from 1Hz-50Hz. The following table describes the ranges of frequencies of EEG signals.



Instrumentation Amplifiers
The instrumentation amplifier is a differential amplifier that amplifies the difference between a channel input and the reference signal. It also reduces common mode noise from the signals. There will be 1 instrumentation amplifier per channel.



Filters
The signals from the electrodes are very noisy. The biggest source of noise that we have found is 60Hz electrical hum from the power system. This frequency is very close to the frequencies that we are attempting to measure which makes it difficult to remove. This noise reduces measurement accuracy therefore, it needs to be removed. We are removing the noise by using a low pass filter with a cutoff frequency of 55Hz. In order to have a steeper roll-off, we are using a Chebyshev filter.



=Hardware Design=



The channel input signal used for the LTspice simulation is a 100µV, 50Hz sine wive added to a 10mV, 10kHz sine wave to represent the EEG signal and the common mode noise.

The resulting output signal is a 50Hz signal with an amplitude of ~60mV. This is what we would expect from a 100µV, 50Hz input signal.

=Team Members=

=Additional Documentation=

Project Schedule

Schedule

Meeting Minutes

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Design Review

Client Interview

Client Interview