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Made by Ashvin Verma, Siddharth Mishra, and
Inspiration: We were looking for something cool to do and learn about and found the concept of Brain-Computer Interfaces and measuring brain activity really fascinating.
Goal: Measure signals from electrodes attached to the scalp, process it to reduce noise (especially 60 Hz) and amplify it to maximize fidelity. TLDR: to make a low-cost and standalone compact hobbyist EEG.
Description: The board is powered via USB which provides a 5V supply; we use an LDO to step it down to 3.3V for our ESP32. We use an op-amp (AD620) to take a difference of the voltage signal measured at the two points of our electrode, with a neutral electrode attached to earlobes as a reference. This signal is then amplified using an InAmp (CA3130) and an RC low-pass band filter is used to attenuate higher frequency components as brain-waves are usually in the domain of 1-30 Hz. We then feed this signal into the ESP32's analog input. We plan to display frequency (FFT) and PSD waterfall (STFT) brainwave representations.
Schematic and BOM
Schematic and BOM
We had a slight messup where we confused a couple of inputs on an op-amp and changed around the value of resistances to give the baseline voltage we needed for our signal; the schematics given are corrected.
the squiggles are sort of mesmerizing
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