Skip to content

hardware.md

Latest commit

 

History

History
161 lines (118 loc) · 7.59 KB

hardware.md

File metadata and controls

161 lines (118 loc) · 7.59 KB
Raw

Ezra — Hardware Specification

Version: 0.3
Stage: Pre-prototype (Investor Demo Build)

Component Selection Table

Compute

Component Part Manufacturer Notes
System on Chip CM4 (4GB RAM / 32GB eMMC) Raspberry Pi Foundation Prototype only; production target: custom ARM SoC
Security Element SLB 9670 TPM 2.0 Infineon PPG template and FIDO2 key storage
I/O Expander MCP23017 Microchip GPIO expansion for button inputs and LED control

Cellular & Wireless

Component Part Manufacturer Notes
LTE Modem EC25-A Mini PCIe Quectel Cat 4 LTE, North America bands
Antenna FXP73 flex LTE Taoglas Embedded in chassis perimeter
WiFi / Bluetooth Integrated RPi Foundation CM4 onboard 802.11ac + BT 5.0
SIM Slot Nano SIM + eSIM — Dual SIM support

Audio

Component Part Manufacturer Interface Notes
Speaker GF0401 (2W, 4Ω, 40mm) Dayton Audio Analog Tuned for 200Hz–8kHz voice
Amplifier MAX98357A Maxim I2S 3.2W Class D, filterless
MEMS Mic (×4) SPH0645LM4H Knowles I2S Golden-rectangle perimeter array, phi-derived spacing
DSP / Wake Word TrulyHandsfree SDK Sensory SPI Wake word "Ezra," always-on < 10mW

Biometric / Identity

Component Part Manufacturer Interface Notes
PPG Sensor MAX30102 Maxim/Analog Devices I2C Red 660nm + IR 880nm
Optical Window Sapphire disc, 12mm × 1.5mm Industrial optics supplier — < 2% loss at sensor wavelengths
Optical Adhesive NOA61 UV adhesive Norland — Window to sensor bonding

Passive Regulation Signals

The PPG subsystem is a continuous relationship sensor, not just an unlock mechanism. It should sample opportunistically on pickup and during natural palm contact, then feed local trend models for heart rate, HRV, recovery state, stress-load trend, sympathetic arousal, cold-hand/circulation state, respiratory rhythm trend, and baseline drift. This is product guidance data, not diagnostic data.

Regulatory constraint: do not claim medical diagnosis, disease detection, treatment, or clinical accuracy unless Ezra enters a formal regulated medical pathway. Default positioning is pattern intelligence and personal regulation.

Haptic

Component Part Manufacturer Interface Notes
Actuator L5 LRA Lofelt — ±3g peak force, 50–300Hz
Driver DRV2605L Texas Instruments I2C Arbitrary waveform RAM
Isolation Sorbothane 40 duro Sorbothane — Actuator mount isolation

Thermal (Warmth)

Component Part Manufacturer Notes
Thermoelectric element Thin thermal module / resistive warming plate TBD Production target for 21mm crowned body with 8mm edge thickness
Demo Peltier Element TEC1-12706 Generic 40×40mm, 6A max, 51W; benchtop/investor demo only
MOSFET Driver IRL3803 Vishay PWM control via CM4 GPIO
Heat Spreader 1mm copper sheet, 50×40mm McMaster-Carr Hot side to chassis mass
Thermal Interface Fujipoly XR-m (3 W/mK) Fujipoly Element to spreader

Illumination

Component Part Manufacturer Notes
COB LED Array BXRE-27G1000-C-73 (1,200 lm) Bridgelux Main flood/beam element
TIR Optic TIR-T-H-10 (10° beam) LEDiL 60m beam throw
LED Driver AL8861 Diodes Inc. Constant current, PWM dimming
Ambient Ring SK6812 RGBW, 5mm, ×8 Worldsemi Notification color language

Power

Component Part Manufacturer Notes
Battery Custom Li-ion pouch, target 5,500–6,500mAh equivalent geometry TBD Largest central internal component; conformal or stacked pouch layout under crowned shell
Charging IC BQ25895 Texas Instruments USB-C PD, 18W input
Wireless charging receiver Qi2/MagSafe-compatible receiver module TBD Hidden centered rear coil; validate certification path with WPC
Magnetic alignment ring N52 magnet ring array TBD Hidden under rear shell, sized for common phone magnetic charger puck alignment
USB-C Connector HRO TYPE-C-31-M-17 HRO IP54 rated
Fuel Gauge MAX17048 Maxim 1% accuracy SoC estimation
DC-DC (5V rail) TPS62133 Texas Instruments CM4 power supply
DC-DC (3.3V rail) AP2112K-3.3 Diodes Inc. Sensor power rail

Power Budget (Estimated)

Subsystem Active (mA @ 3.7V) Standby (mA)
CM4 (idle) 400 80
CM4 (voice processing) 900 —
LTE Modem (connected) 350 15
Audio (playback) 180 2
PPG sensor (active) 5 0.7
LRA (active) 200 0
Peltier (active, 50% PWM) 3,000 0
COB LED (max) 1,000 0
Misc (MCUs, sensors) 30 8

Typical use (voice + calls, no warmth/LED): ~1,800mA average → 6,000mAh / 1,800mA ≈ ~3.3 hours of active-heavy use
Standby (LTE connected, PPG monitoring): ~110mA → 6,000mAh / 110mA ≈ ~54 hours

Thermal Constraints

The benchtop TEC1-12706 draws up to 22W (6A × 3.7V) at full duty cycle and is too bulky for the phone-scale enclosure. Production hardware needs a thin thermal module or resistive warming plate sized for burst warmth notifications (3–10 seconds), coupled to the palm-side shell through a graphite spreader. The chassis and mineral shell act as thermal reservoirs.

Design constraint: Limit Peltier duty cycle to 30-second maximum per activation. Software-enforced cooldown of 60 seconds between activations to prevent thermal accumulation.

PCB Architecture

The device uses three PCBs:

  1. Main board: CM4 carrier, LTE modem, power management, USB-C, battery connectors
  2. Sensor board: MAX30102, DRV2605L, MCP23017, MAX17048, ambient LED ring
  3. Audio board: MEMS mic array, MAX98357A, speaker connector

Boards connect via FFC (flat flexible cable) with ZIF connectors. This allows sensor and audio boards to be positioned independently of the main board geometry.

Mechanical Interface Points

Feature Location Tolerance
Speaker aperture Upper face center ±0.3mm
Sensor window Lower face center ±0.1mm (optical alignment critical)
Qi receiver coil Rear center, hidden behind shell ±0.5mm
Magnetic alignment ring Rear center around coil, hidden behind shell ±0.5mm
USB-C port Lower edge ±0.2mm
Internal glow / ambient light pipe Perimeter groove or thinned mineral window ±0.5mm
Peltier contact zone Lower rear face ±1mm
Battery access (service) None (sealed) —

Mechanical Envelope

Parameter Target
Length 108mm
Tail width 66mm
Head width 63mm
Center thickness 21mm
Edge thickness 8mm
Top shell wall 3.2mm
Bottom shell wall 2.8mm
Mass target 210g

The exterior must carry subtle tactile asymmetry: narrower head for flashlight/directional speaker/mic orientation, fuller tail for battery and biometric mass, a shallower thumb-side sweep, rounder finger-side squeeze contour, rearward crown offset of roughly 5mm, and a biased underside contact patch. The asymmetry should be felt more than seen.

Hardware spec current as of April 2026. Prototype build may substitute components based on availability.