PCB Schematic Draft

Corrections from my microscope inventory sheet: (1) U1 is a 6-pin small IC (marking "T18 AU8 2DZ"), not 10-lead — please make the U1 placeholder 6 pins. (2) R6's marking is ambiguous between 103 (10k) and 105 (1M) — keep it annotated as "verify by measurement". (3) There may be an R5 on the silkscreen — add a note, not a part. (4) D1-D3 might be LEDs rather than rectifier diodes — annotate as "confirm diode vs LED". (5) C1-C3 values are unmeasured — annotate. Keep all these as visible open questions on the schematic notes rather than guessing values.

Thought for 10 sec

flux

I’ll apply those corrections: swap U1 to a 6-pin placeholder, adjust the uncertain annotations, and update the schematic notes/open questions without adding R5 as a component.

Worked for 1 min 45 sec

flux

U1 is now a 6-pin placeholder with no assumed pinout. I’m updating the part notes so the uncertainties stay visible instead of encoded as guessed values.

Worked for 4 mins 50 sec

flux

Applied the microscope-inventory corrections: U1 is now a 6-pin placeholder, R6/C1-C3/D1-D3 are annotated as uncertain, and possible R5 is documented as a note only.

Open items:

U1 pins are intentionally floating until trace mapping confirms pinout.
R6, R7, C1-C3, D1-D3 type/polarity, and possible R5 still need measurement/confirmation.
ERC still reports expected unresolved placeholder pins and missing MPNs for generic draft parts.

Updated files: Schematic Capture Notes and Project Specification.

Suggested next steps:

Measure R6/R7 and C1-C3.
Confirm D1-D3 with diode/LED test mode.
Provide U1/U2 continuity maps so I can wire the placeholders correctly.

Clean notes and review

Arrange schematic groups

Create measurement checklist

Add photo map plan

Check BOM placeholders

Files

Schematic

Layout

Preview

Design History File — NSS-Bridge-3

Status

Draft / reverse-engineering stage.

Device Classification

This project concerns an auricular peripheral nerve-field stimulator / TENS-class wearable PCB. Final regulatory classification is not determined and depends on intended claims, jurisdiction, output limits, labeling, and clinical use.

Intended Use

Current project use is reverse-engineering analysis only. The reconstructed schematic is not validated for human, animal, therapeutic, diagnostic, or clinical use.

Applicable Standards to Investigate

ISO 14971 — medical device risk management.
IEC 60601-1 — medical electrical equipment safety.
IEC 60601-1-2 — EMC.
IEC 60601-2-10 — nerve and muscle stimulator requirements.
IEC 62304 — medical device software lifecycle, if firmware exists.
IEC 62366-1 — usability engineering.
ISO 10993 — skin-contacting material biocompatibility.
FDA / EU MDR / UKCA / Health Canada requirements depending on jurisdiction and claims.

Design Inputs

Table

Input	Status
Coin-cell powered wearable board	Captured
Approx. 35 mm x 15 mm two-layer, 1.0 mm PCB	Captured for layout stage
Three electrode pads E1-E3	Captured
Return ring contact RING	Captured as net/contact placeholder
U1 marking T18 AU8	Identity/pinout unknown
U2 marking LBVC B041	Identity/pinout unknown
Output voltage/current/waveform limits	Unknown
Human-use safety requirements	Not validated

Design Outputs Created

Initial schematic component set with supplied designators.
Named netlist for VBAT, GND, VSTIM, STIM_OUT1, STIM_OUT2, STIM_OUT3, and RING.
Preliminary safety risk documentation.

Verification and Validation Needs

Identify U1 and U2 or fully map their pins by continuity and measurement.
Confirm all passive values by measurement or high-resolution photos.
Confirm diode polarity and electrode routing.
Measure output waveform on dummy loads before any body contact.
Characterize maximum output voltage/current, pulse width, frequency, duty cycle, charge per pulse, DC offset, and single-fault behavior.
Verify safe behavior during power-up, power-down, brownout, open electrode, intermittent contact, and shorted electrode conditions.

Traceability Matrix

Table

Requirement / Concern	Current design output	Verification status
Coin-cell power input	B1 to `VBAT`/`GND`	Needs physical confirmation
Boost stimulation rail	U2/L1/C3/R6/R7 to `VSTIM`/`FB_DIV`	Placeholder only
Electrode outputs	R3/R4/D1-D3/E1-E3	Needs polarity/routing confirmation
Return electrode	`RING` net/testpoint placeholder	Needs layout geometry
Human safety	Safety/FMEA docs started	Not validated

Open Items

Exact U1 identity and pinout.
Exact U2 identity and pinout.
Exact R7 value.
Exact C1-C3 values.
Exact diode MPNs and orientation.
Whether J1 VBUS/data pins connect to anything.
Stimulation limits and waveform.
Mechanical ring geometry and via stitching pattern.

Status
Device Classification
Intended Use
Applicable Standards to Investigate
Design Inputs
Design Outputs Created
Verification and Validation Needs
Traceability Matrix
Open Items