Intent
Not a real lawnmower — no blade, no cutting deck. This is the navigation/electronics platform: prove out a real zero-turn-mower-style drivetrain, dual-mode control, edge sensing, and a simple coverage map, deliberately de-risked before ever considering whether a cutting mechanism belongs on top of it.
How it works
- 2 fixed drive wheels (differential/skid-steer — the exact mechanism real zero-turn mowers use, scrub and all) plus 2 passive casters for support. This replaced an earlier 4-actuator "swerve drive" design that was mechanically ambitious well past what the prototype needed.
- Two modes: a live WiFi "RC" mode (the ESP32 hosts a small web page a phone connects to and drives directly), and an autonomous mode that biases its random-bounce turns toward less-visited ground using a simple in-RAM visit-frequency grid — a technique called IRandomWalk. Not full SLAM: no lidar, no camera.
- IR-reflectance sensors, not a camera, handle edge/obstacle detection — enough for this job without dragging in image processing the ESP32 can't handle.
- An independent design review flagged the original single-channel encoder plan as a real, compounding risk alongside the drivetrain's inherent wheel scrub — upgraded to true two-channel quadrature encoders to fix the direction-sensing gap.
Hardware
| Part | Role |
|---|---|
| ESP32 Feather | Brain — needs WiFi and far more GPIO/RAM than this repo's other ATtiny85 projects |
| 4-channel motor FeatherWing | Drives the 2 fixed drive wheels; 2 of 4 channels used, 2 spare for later |
| N20 gear motors + true quadrature encoders | Drivetrain — upgraded from a single-channel encoder plan after design review |
| 2× IR reflectance sensors | Front-left and front-right — deliberately two, not one, so the rover knows which way to turn away from an edge |
| Custom 3D-printed chassis + motor mounts | Sized to the N20 motors' actual shaft, not started yet |
| 2 separate batteries | Single-cell LiPo for ESP32 logic; a 4×AA pack for motor power — kept electrically separate per the FeatherWing's own spec |
Most of the BOM is real, DigiKey-verified stock (checked 2026-08-31). Still open: the logic LiPo (routed to Adafruit directly to avoid a marketplace polarity risk) and the caster wheels (not a DigiKey category). The chassis and motor mounts are 3D-printed, not purchased.
Status & next steps
- Drive motors/encoders picked — revised to true quadrature
- IR sensor count and placement decided
- Most real parts sourced and DigiKey-verified
- RC web-page control scheme designed
- Design the 3D-printed chassis and motor mounts — real CAD work, not started
- Update firmware for true quadrature encoding (2 pins per encoder)
- Write the differential-drive odometry + coverage-grid firmware
- Bench bring-up, then chassis assembly — nothing physically built or flashed yet