An open-hardware robot head with human-scale eyes: a camera that looks out through a real pupil, eyelids that blink and follow gaze, a glowing iris, and brows. Iris is built at 1.25 x human scale around nine Feetech bus servos and four custom boards.
Status: not yet built. This repository holds the complete mechanical design (parametric CadQuery source, STEP and STL for every printed part), the motion and board-fit checks, and the system documentation. The four boards are released in their own repositories (below) and fit the mechanism in CAD. No head has been printed, assembled or powered, and the firmware is not written.
This is the hub repository for the Iris project. Part of HeyPCB's open robot boards.
Most robot eyes are either screens or a single pan-tilt camera. Iris tries to move like a human eye:
- Real optics. The right eye carries an OV2640 camera whose lens sits 2 mm behind a Dia 5.6 mm pupil, under a clear cornea. At 1.25 x scale that pupil reads as a normal 4.3 mm human pupil.
- Human gaze geometry. One cradle tilts both eyes together (as human eyes do), and each eye pans on its own, so Iris can converge on a near face. Pan is as fast as a human saccade (a 20 deg move in about 49 ms against 65 ms, est.); tilt, which moves the whole cradle, runs about 30 % slower (est.).
- Eyelids that are lids. Each eye has an upper and a lower lid, nested spherical visors that turn about the eye's horizontal axis. Their margins meet at the corners like a real fissure, they follow gaze, blink in under 100 ms and cannot touch each other or the cornea.
- A living iris. Twelve RGB LEDs on a ring board inside each eye light a translucent iris from behind.
- Senses. A forehead strip with a time-of-flight sensor (vergence distance), ambient light, two microphones 108 mm apart (sound direction) and a touch pad.
- One cable to run it. USB-C PD at 9 V (a 27 W charger or a PD power bank), with a second USB-C port for data.
- Parametric CadQuery source for every printed part (P1-P17), generated STEP and watertight STL
(
cad/,cad/out/parts/). - 9 x Feetech SCS0009 on one 1 Mbps half-duplex bus with position feedback: pan x2, tilt, four lids, two brows.
- Inside-out pan forks and exact 1:1 parallelogram linkages: every joint angle equals its servo angle.
- Motion check over 80 540 pose evaluations: no collisions, at least 0.5 mm between moving parts and 0.3 mm between static ones (verification).
- Board fit with the four released boards (KiCad STEP): every mounting hole on its boss axis (0.00-0.01 mm), no interference over the full motion range, cable routes kept free.
- Headless renders and a gaze-and-blink animation, regenerated from the source.
flowchart LR
PWR["USB-C PD 9 V"] --> B2
DATA["USB-C data"] --> B2
B2["B2 Brainstem\npower, servo bus, amp"] -->|"H1 / H2"| B1["B1 Cortex\nESP32-S3 (on the tilt cradle)"]
B1 -->|BROW| B4["B4 Brow\nToF, light, 2 mics, touch"]
B1 -->|"RING_R / RING_L"| B3["B3 Iris ring x2\n12 RGB LEDs per eye"]
CAM["OV2640 (right eye)"] -->|"24P FPC"| B1
B2 -->|"6 V bus"| S["9 x SCS0009\npan x2, tilt, lids x4, brows x2"]
B2 --> SPK["speaker"]
Details, power tree, the binding interconnect contracts and the as-built connector positions: docs/system.md.
| Board | Repository | Where | What |
|---|---|---|---|
| B1 Cortex | HeyPCB/iris-cortex | rear plate of the tilt cradle | ESP32-S3-WROOM-1-N16R8, camera FPC, LED-ring drivers, sensor and harness hub; 80 x 40 mm, 4 layers |
| B2 Brainstem | HeyPCB/iris-brainstem | base plate | USB-C PD (CH224K, 9 V), 6 V / 5 A servo buck, 5 V logic buck, INA226, servo bus and 10 ports, MAX98357A; 64 x 80 mm, 4 layers |
| B3 Iris ring x2 | HeyPCB/iris-ring | inside each eyeball | 12 x WS2812C-2020 behind the iris; Dia 18 / 7.6 mm annulus, 0.8 mm, 2 layers |
| B4 Brow | HeyPCB/iris-brow | behind the forehead | VL53L1X, APDS-9306, 2 x ICS-43434, touch pad; 116 x 12 mm, 2 layers |
| Scale | 1.25 x adult human |
| Eyeballs | Dia 30.0 mm, 78 mm apart (centre to centre) |
| Camera | OV2640, 68.7 deg FOV, in the right eye; the left eye carries a matching dummy |
| Pan, each eye | +-35 deg, independent (version and vergence; 14.6 deg per eye converges on a face at 150 mm) |
| Tilt, both eyes | +25 deg up / -30 deg down |
| Upper lids | -40 ... +55 deg margin (rest +19), follow tilt 1:1 |
| Lower lids | -50 ... -6 deg margin (rest -20), follow tilt at half gain |
| Brows | +-20 deg roll each |
| Actuators | 9 x Feetech SCS0009 (0.10 s/60 deg at 6 V, 2.3 kg.cm, 0.293 deg feedback) |
| Speed (est.) | 20 deg saccade in about 49 ms (human 65 ms); blink closing about 78 ms (human 92 ms) |
| Sensors | ToF 4 m, ambient light, stereo I2S microphones, capacitive touch, servo position / load / temperature |
| Power | USB-C PD 9 V; about 6 W typical; >= 27 W charger or PD power bank |
| Size | 176 W x 148 H x 143 D mm (152 mm with the nose) |
| Printed parts | 36 parts from 27 files, 505 cm3 solid volume (636 g if printed solid) |
 |
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| Mechanism: tilt cradle, inside-out forks, nested lids, pushrods | Exploded view |
Gaze poses (directions from the robot's point of view) and a blink
All images are rendered headlessly from the CAD by python -m cad.render.
| Path | Contents |
|---|---|
cad/ |
parametric CadQuery source (how to run) |
cad/out/parts/ |
STEP + STL of every printed part, in assembly position |
cad/out/iris_assembly.step |
rest-pose assembly with purchased-part and board envelopes |
cad/out/envelopes/ |
SCS0009 and OV2640 envelopes (from datasheet dimensions, not vendor CAD) |
cad/out/parts.json, check.json, fit.json |
parts list, motion check, board fit |
docs/system.md |
architecture, power tree, interconnect contracts |
docs/mechanism.md |
kinematics, ranges, linkage geometry, servo IDs, changes from the spec |
docs/assembly.md |
print settings, bill of materials, step-by-step build |
docs/firmware.md |
behaviour notes for the firmware (not written yet) |
docs/verification.md |
what was checked in CAD and what must be bench-tested |
media/ |
renders and the animation |
"Spec N" in these files names a section of the Iris system specification v0.1, the design-input
document the boards and this CAD were drawn from. The spec itself is not published: its binding
tables (interconnect contracts, board mounting) are copied in docs/system.md,
and docs/mechanism.md lists every place the build departs from it.
To regenerate everything:
pip install -r requirements.txt
python -m cad.build && python -m cad.check && python -m cad.fit && python -m cad.renderHardware, including the CadQuery source, the generated CAD files and the documentation: CERN-OHL-S-2.0 (CERN Open Hardware Licence Version 2, Strongly Reciprocal).
The Iris mechanism was drawn from scratch for this project. It takes only general ideas from earlier open animatronic eyes, servo-driven lids hinged on the eye's horizontal axis and a camera inside the eyeball, and none of their geometry:
- Will Cogley's eye mechanisms: Snap-Fit Eye Mechanism (CC BY-NC-SA 4.0), Animatronic Eye Mechanism e3.2 (MakerWorld Standard Digital File License), and the Instructables Simplified 3D Printed Animatronic Dual Eye Mechanism and Animatronic Eye Mechanism.
- The InMoov eye mechanism (Thingiverse 86387, CC BY-NC).
Iris differs where it matters: independent pan per eye (for vergence) instead of a coupled single pan, inside-out forks instead of external yokes, a shared Helmholtz tilt cradle, and nested spherical lids. Those designs are non-commercial; nothing from them is in this repository.
Human-eye reference values (sizes, ranges, saccade and blink timing) come from the published sources cited in the Iris system specification v0.1.