Prototype 10

Bill of materials: bom_p10.ods
Components:
Date: 2023-05-31

An EMG neural interface with the following features:

Modular:
- A power module with Arduino microcontroller, battery, and power converter
- 1-8 (typically 2) electrode modules with up to 4 electrode pairs each
- Connected via standard 2.54mm (0.1 inch) dupont connectors
Sampling rate of up to 500Hz, 8-bit resolution, max 8 signals
Supports up to 17 electrodes total: 8 signal electrode pairs + 1 ground electrode
Battery-powered (1x AAA battery, 1.2V, ~6h of usage)
Wireless, using Bluetooth Low Energy (BLE)
AI-based gesture prediction and keyboard emulation (see Python Library + GUI)
GNURadio integration for plotting the raw signals + FFT

Changelog

Changes compared to :

Fixed aggressive filtering of signals by changing passive highpass filter capacitors C1-C8 from 100pF to 100nF. (This was covered in a blog post)
Changed the gain for all amplifiers to 251x. (Some amplifiers had a gain of 501x due to a sensitivity bug, this is not necessary anymore.)
Replaced the Arduino Nano 33 BLE Sense with a Arduino Nano 33 BLE, since it has all required features at ~66% of the cost
Replaced uncomfortable spacer screw electrodes with rounded dome nuts

Changes compared to Prototype 9.1:

Added PsyLink logo to PCBs
Added "OFF" and "ON" labels to power switch
Simplified power LED circuit
Moved the external power pins (J7) away from the center of the battery, so the pin headers are not physically in the way when removing the battery.
Better labels on electrode module
Moved EX1 pin closer to EX5 and EX4 pin closer to EX8, so one can use a 2-pin pin header instead of 2 separate 1-pin pin headers, for faster assembly
Jumpers to activate built-in electrodes are now closed by default for faster assembly. To disable them, please cut the jumpers carefully with a short knife. To reactivate them, solder them together.
Larger solder pads on instrumentation amplifier footprint for faster assembly