Orbiter Smart Filament Sensor (OSS) Complete Kit for Orbiter Extruder by LDO Motors

LDO Smart Filament Sensor for Orbiter V2.0 and V2.5 — Runout, Auto-Load and Tangle Detection for Klipper

The LDO Smart Filament Sensor (OSS) is a purpose-built add-on for the Orbiter V2.0 and V2.5 extruder that goes far beyond basic runout detection. Designed by Dr. Lorincz Robert (Orbiter Projects) and manufactured by LDO Motors, this updated version adds filament tangle detection and an onboard ATtiny412 microcontroller for hardware-level signal filtering — eliminating the false positives that plague software-only sensor implementations in Klipper.

This kit comes mostly pre-assembled. Compatible with the Smart O2 Orbitool Toolhead PCB for a clean, direct plug-in connection.

⚠️ Not recommended for use with MMU or multi-material systems. The tangle detection mechanism is not compatible with multi-spool setups.
⚠️ Klipper minimum extrusion temperature must be configured. Set min_extrude_temp to at least 180 °C in your extruder config — cold extrusion enabled (set to 0) will break the auto-load macro.

Filament Tangle Detection — Stops the Print Before the Failure Happens

Tangled filament is one of the most common causes of print failures — and one of the hardest to diagnose after the fact. By the time you notice the problem, hours of print time are already wasted. The Smart Sensor solves this proactively. A spring-loaded tangle ring monitors the tension in your PTFE tube at the filament entry point. When the pulling force on the filament exceeds approximately 2 kg for more than one second — the threshold that indicates a genuine tangle — the sensor signals Klipper to pause the print immediately and alert you before any under-extrusion or layer failure occurs.

⚠️ False tangle triggers can occur with long PTFE runs, oversized or hard-turning spools, or high-acceleration moves with an improperly secured PTFE tube. Secure your PTFE tube at the filament entry side for reliable tangle detection.

ATtiny412 Onboard Microcontroller — Hardware Signal Filtering

Klipper's native filament sensor handling relies on software debouncing, which leaves it vulnerable to false runout events caused by fast accelerations, vibration, or noisy signal lines. The Smart Sensor eliminates this with a dedicated 8-bit ATtiny412 microcontroller on the PCB whose sole job is signal conditioning, debouncing, and plausibility checking before any signal reaches Klipper. The result is a sensor that won't pause your print from a false trigger — only from a real event. The micro also controls the RGB LED ring directly, providing cleaner state indication than is achievable through Klipper macros alone.

RGB Status Ring — Instant Visual Feedback at the Toolhead

A push-fit collet clip surrounds the filament entry with an RGB illuminated ring that gives you real-time status at a glance — no need to check your screen or console:

Filament Auto-Load and One-Button Unload

Insert filament and the sensor detects its presence immediately — triggering your configured Klipper auto-load macro automatically. No manual commands, no console interaction. When you need to swap filament, press the dedicated unload button on the sensor body to trigger the retract sequence. Both actions happen at the toolhead, where you're actually working, not at a screen across the room.

6mm Steel Ball Mechanism — Friction-Free Filament Detection

Instead of making filament contact directly with a plastic switch lever — which would wear down quickly under continuous extrusion — the sensor uses a 6mm steel ball as the intermediary. The filament presses the ball, the ball presses the switch. This removes all friction wear from the detection mechanism and dramatically extends the sensor's service life, especially important in high-cycle print farms or long continuous print sessions.

MJF Printed Housing — Precision Fit for Orbiter V2

The sensor housing is produced in MJF (Multi Jet Fusion) nylon — not FDM printed. MJF yields tighter dimensional tolerances than desktop FDM printing, which matters here: the PCB position relative to the filament path has been calibrated to within 0.3 mm to prevent false runout detections caused by housing print tolerances. This is the same housing LDO provides with their official kits — not a printable substitute.

Specifications

What's in the Box

What's NOT Included

Who Is This For?

If you're running an Orbiter V2.0 or V2.5 on a Voron, a CoreXY, or any Klipper-based printer and you still don't have a filament sensor — or you're running the older basic runout sensor and tired of false positives — this is the direct upgrade. The tangle detection alone makes it worth it for anyone printing long overnight jobs or running a multi-printer setup where you can't babysit each machine. The hardware signal filtering eliminates the flakiness that makes most Klipper filament sensor implementations unreliable in practice.

Resources

• Orbiter Projects — Smart Sensor official documentation and notes
• Orbiter Sensor GitHub — config files, schematics, KiCad files, 3D design files

Browse our full electronics and control board selection at 3D Printer Electronics, or explore all toolhead and extruder upgrades at 3D Printer Upgrades.