Beanie, cameras and charging

The beanie

An ordinary acrylic 2×2 rib-knit beanie with a turned-up cuff goes over the shell. It hides the electronics, keeps the contacts pressed on, and makes the helmet look like a hat. The cuff is a double layer about 6 mm proud of the body, tight enough to hold the hem against the head under the shell's rim. The hem runs at least 4 mm under the rim all round. Behind the ears, where the rim drops for the pod, the hem drops ahead of it so it never runs steeper than 1.6:1. The cuff stands 56 mm from the hem (hem_z in exo/shell_v1.py, exported to the 3D view).

In the 3D view the beanie is simulated as cloth: a knit sheet with stretch, shear and bend constraints, gravity and friction that settles onto the shell, the pod, a low swell over each camera and the head it's on, with its hem held to the hem line. The ribs, the crown's decreases and the folded cuff are built on the settled sheet.

Cameras

Five camera modules sit half-way up the cuff: three across the front (0° and ±72° from straight ahead) and two at ±122° on the slanted parts of the back rim, their long side along the slope. Each is a small board with an image sensor, a lens holder and barrel, a MEMS microphone, a status LED and a 12-way FPC to the hub. It clicks into a cradle on the shell (shell), and the lens comes through the knit in a rubber grommet.

Charging

USB-C, through a moulded eyelet in the back of the cuff, above a small woven label at the hem. The receptacle is on the hub's bottom edge; a tunnel runs straight down from it through the pod wall and opens low on the back of the shell, 11 mm above the hem (shell). The 3D view draws the eyelet half-way up the cuff. The hub holds the contacts' supply off while a cable is plugged in, so it charges only off the head.

Camera board

EXO-450, 16.45 × 18.70 mm: an ESP32-S3-MINI-1 streams each camera's MJPEG and audio over its own Wi-Fi. The hub only powers it, enables it and sends it SYNC and a control UART over the helmet's 12-pin FPC. See camera.