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Regulatory and Safety Notes — Wearable EEG BCI Acquisition Board

Status

Draft design-stage notes for a non-medical human-connected EEG/BCI prototype.

Intended Use

Non-medical research/prototype use only.
Not intended for diagnosis, treatment, patient monitoring, or life-sustaining operation.
Human-subject testing requires institutional review, informed consent, and an independent safety review.

Wireless / EMC Notes

U3 ESP32-WROOM-32E provides Wi-Fi/Bluetooth radio functionality.
Preserve module integration requirements: antenna edge placement, no copper under antenna keepout, no shielding/enclosure metal over antenna, and follow Espressif certification conditions.
Likely documentation needed for a productized device: FCC Part 15/CE RED technical file, BOM, schematic, PCB layout, module datasheet/certification, user manual, and lab test reports.

Battery and Charging Safety

U4 MCP73831 charges a single-cell LiPo from VBUS.
J5 LiPo polarity must be mechanically/keying verified.
If the chosen LiPo cell lacks protection, add protected-cell requirement or include protection/fuel-gauge circuitry in the design.
Verify charger thermal performance and charge current before enclosing the wearable.

Human-Connected Electrode Safety

Table

Hazard	Source	Current Mitigation	Open Action
Excess electrode current	Power fault or BIAS drive fault	4.7k series resistors per channel, ESD clamps to AGND, 1k BIAS series resistor	Independent leakage/current-limit analysis required
ESD into AFE	Electrode handling	ESD601 clamps to AGND on CH1–CH8	Confirm clamp capacitance/leakage is acceptable for EEG bandwidth
Ground/USB coupling to user	USB-connected PC while electrodes attached	None beyond circuit-level grounding	Consider battery-only operation during human recording or medically isolated USB
RF/switching noise in EEG band	ESP32 and switchers near AFE	Layout zoning planned	Validate with noise measurements and shielding strategy
Incorrect electrode pinout	J3 cable mismatch	J3 pinout documented	Confirm mating cable before use

Preliminary FMEA

Table

Subsystem	Failure Mode	Effect	Severity	Mitigation
LiPo/charger	Overcharge/thermal fault	Battery damage, heat	8	Use protected cells, verify MCP73831 thermal design
Power tree	+5V0A over/undervoltage	ADS1299 malfunction	6	Bring-up rail checks, LDO validation
Electrode input	ESD surge	AFE damage, false readings	6	Series resistors and ESD clamps
Bias drive	Incorrect BIASREF/BIASINV/BIASIN topology	Bad common-mode control or unsafe electrode drive	8	Finalize ADS1299 bias circuit before human testing
USB connection	Non-isolated PC ground coupling	User leakage/ground loop risk	9	Prefer battery-only acquisition or isolated USB for human tests
ESP32 RF	Antenna keepout violation	Poor radio/EMC failures	5	Edge placement and no-copper keepout

Productization Open Items

Decide whether this remains a lab prototype or becomes a regulated product.
If productized, prepare full FCC/CE documentation and safety risk file.
For any medical claims or clinical use, create a formal design history file and follow applicable medical-device standards; current design is not sufficient for that use.