How it works

The head: a cap over the knob you already use

The tilt control of an inter-pane blind is a small fluted knob on a thin flexible shaft. BlindBot's head is a printed cup whose internal splines drop into those flutes. You push it up over the knob from below; a slim tail behind it docks into the existing hook cleat so the reaction torque — and the weight — is carried by the frame, not by the fragile shaft and its clip joint.

Cutaway render of the head: cup, O-ring clutch, geared stepper — Cutaway: knob cup with splines / TPU liner, O-ring clutch, 28BYJ-48 geared stepper (mounting ears snipped), cable groove in the tail.

Torque safety, in layers

Mechanical clutch: an O-ring slips just above the blind's running torque.
Current limits: the driver firmware runs at low current; homing uses even less.
Soft end stops: motion is clamped just inside the calibrated hard stops.
Push-fit release: pull the head off by hand at any time — that is the manual override.

Never force the sealed mechanism. The blinds live between two panes of glass; if something jams, the unit cannot be opened for repair. Design so it slips, never so it pushes harder.

One controller, two heads

A pocket-size box (Seeed XIAO ESP32C6 + two quiet TMC2209 stepper drivers) hides low behind a curtain. Thin white 4-core flat cable runs up the frame edge to each head. The firmware serializes moves so both blinds never run at once.

Electronics schematic: XIAO ESP32C6, two TMC2209 drivers, button and LED — Controller electronics: USB-C 5 V input, polyfuse, XIAO ESP32C6, TMC2209 ×2 (addressed by strap), light-pipe LED, calibration button.

Position without sensors

A geared stepper driven slowly under light load does not lose steps. A guided calibration records the two hard stops and the horizontal position. After anyone turns the knob by hand (the clutch slips), one button press re-homes gently into the closed-up stop.

Matter tilt mapping

The controller exposes itself as a Window Covering device with tilt and position-aware tilt — no lift. 0 % = slats horizontal (open); 100 % = closed in your preferred direction. Each sash is its own tile. Control is local to your home network after the first commissioning.