Week 15 (02/14/2021)

Figure 1: Tyler Wearing the EEG Helmet

On Tuesday, 02/16/2021, the team completed an amplifier circuit but began experienced a tremendous amount of noise amplification. Despite the amplifier's success, the circuit would occasionally stop collecting data regardless of movement. Dr. Hossein Asghari arrived on Loyola Marymount University's campus on 02/18/2021 to assist on circuit issues. Dr. Asghari noticed that we were using the TEKTRONIX TPP0500B passive probe, and suggested that we use another probe instead. When the probe was switched out with another probe, the noise that was being seen prior reduced tremendously. Following switching the probe, the team had to test each section of the circuit.

First, the output of the electrodes without any parts of the circuit was measured with the oscilloscope. The notch filter was then connected to the output of the electrode to the instrumentation amplifier. The low-pass filter was then connected to the output of the notch filter and the output of each section was measured and observed. During the measurements, the oscilloscope began to malfunction by remaining in an idle state. Upon receiving another oscilloscope, Dr. Asghari, Tyler, and Mark continued to debug the circuit.

EEGLAB was messaged to see if they would be able to assist by pointing out that by looking at the Workspace terminal and clicking on the EEG variable that we would be able to observe the data within the SET file. With the new-found knowledge, and the code that Mark and Dr. Asghari developed and implemented on previously tested EEG datasets, a MATLAB function was created to collect the first channel of the SET file to plot its time domain and frequency domain. Figure 2 illustrates the MATLAB code. Figures 3 and 4 illustrate the output of the MATLAB function output and EEGLAB channel spectra, respectively.

Figure 2: MATLAB Code to Plot Channel 1 Time Domain and Frequency Domain

Figure 3: MATLAB Code Output

Figure 4: EEGLAB Spectra and Maps Output

THIS WEEK

Tyler

• Completed the amplifier circuit for the EEG helmet

• Determined why the EEG circuit was acting abnormally

• Redesigned portions of the EEG circuit following this week's discoveries

Mark

• Determined how to open SET files with the help of the EEGLAB community

• Created a MATLAB function to plot the time domain and frequency domain of one channel out of the 62 channels

• Assisted Tyler on circuit design and debugging
  

NEXT WEEK

Tyler

• Continue to redesign the circuit

Mark

• Assist Tyler on the circuit design

• Perform k-means clustering on EEG data

Memo:

Dr. Hossein Asghari reviewed the EEG circuit and asked Mark and Tyler to test the circuit within the faraday cage to reduce the amount of noise that is being collected by the circuit. Dr. Asghari also reviewed the MATLAB code and reviewed the similarities from the different trials from a single channel of the EEG dataset.