Motorised Filter Wheel Conversion for Manual 2" Wheels – Wheelly (INDI / Ekos)

What it is

Wheelly motorises a manual filter wheel without modifying it: the printed parts clamp around the wheel body and can come off again. A NEMA 14 stepper turns the filter disc through a spring-loaded friction clutch with a co-printed TPU tyre; an AS5600 magnetic encoder on the wheel axis reads where the disc actually is; a Seeed XIAO ESP32-S3 runs it and talks to Ekos/KStars through a native INDI driver.

Will it fit my wheel?

Designed and tested on a manual 5-position wheel for 2" filters with a 158 mm × 23 mm body (StarDikor). Other wheels: the CAD is parametric (CadQuery) and comes with a parameter editor — body diameter, height, disc radius and a few more describe your wheel; see chapter 1 of the assembly guide. The number of slots is a firmware setting (up to 12), not a CAD change. If your wheel is not 158 mm, regenerate the parts before printing: the STLs here fit the reference wheel only.

Features

• Closed loop on the measured angle, with configurable tolerances: a move that ends out of tolerance raises an alert in Ekos instead of silently imaging through the wrong filter.

• Calibration, tolerances and motor settings from the Ekos panel.

• Native INDI driver, shipped with INDI Library since v2.2.5: install INDI and pick Wheelly in Ekos, nothing to build.

• Printed in ASA; TPU for the clutch tyre and the gaskets.

Printing

• Material: ASA for the parts that stay on the telescope (PETG is fine for a test fit; tolerances were measured on ASA). TPU 87A for tyre and gaskets (the one tested; up to 95A is calculated, not tried).

• Multi-material: the clutch hub and its tyre are co-printed (ASA + TPU). The gaskets can be co-printed with the collar or printed separately.

• Single-material printer (not tested yet): print the tyre alone in TPU, flat. Print the hub collar-down and add a pause at the first layer of the last Ø46 shoulder (12.5 mm above the bed; check in the slicer preview that it is the layer where the shoulder appears). At the pause, push the tyre down over the core, teeth into the dovetail slots, flush with the top; the print then closes the shoulder over it. The tyre and the core are drawn with no clearance, so it is a tight push fit.

• 0.4 mm nozzle, 0.20 mm layers, 5 perimeters, 4 solid top and bottom layers, 60 % infill.

• Supports: breakaway, only under the box collar and around the clutch hub; no soluble supports.

• Do NOT enable the slicer's hole compensation: holes are already compensated in the model (0.2 mm, measured on ASA).

• Orientation: the STLs are already on their bed face; the reasons are in chapter 0 of the guide. Multi-material: load the files of one coprint group together and accept "multi-part object", then assign ASA and TPU.

• Total: about 167 g ASA and 2.5 g TPU with supports (slicer estimate, settings above), 14 parts.

Hardware you need (full list with quantities in the guide, chapter 0)

• NEMA 14 stepper 14HS10-0404S, TMC2208 driver, Seeed XIAO ESP32-S3, AS5600 module with a Ø8×1 diametrically magnetised magnet

• 2× F695ZZ flanged bearings, one compression spring (0.9 wire, Ø6.7, 13.5 mm)

• Heat-set inserts: 9× M3 Ø5.0×3.0, 1× M4 Ø6.3×8.1, 3× M2.5, 2× M2; M2–M4 screws

• Perfboard 70×30 with JST XH sockets, a few passives, GX12 2-pin connector, 12 V supply

Assembly, firmware and driver

Step-by-step assembly guide, rendered from the CAD model, in English and Italian (14 chapters, from heat-set inserts to first checks): https://teoteo.github.io/Wheelly/
Firmware, INDI driver, parametric CAD and wiring: https://github.com/teoteo/Wheelly

How it was made

The parts are designed as parametric CadQuery code, written with the help of an AI assistant; the design decisions, the measurements and the test prints are the author's.

Licence

Printed files here: CC BY. The whole project: CERN-OHL-P-2.0 hardware, MIT firmware, LGPL-2.1+ driver, CC-BY-4.0 docs — commercial use allowed. The Wheelly name and logo are not under an open licence; what you may do with them is in TRADEMARK.md in the repository.

Changelog

• v0.1.1 – first release.

Questions and measurements of other wheels are welcome in the comments. If you build one, a Make with your wheel model in the description helps others know it fits theirs.

The project is free and stays free; if you want to support it: https://github.com/sponsors/teoteo