Filament detector

The filament detector module allows you to add automated hardware to your machine to check that the filament is advancing correctly.

This is done by adding an encoder, that rotates as the filament advances, and sends pulses to the Smoothieboard.

The Smoothieboard then compares those pulses against the current theoretical position of the extruder.

If a difference is detected, the filament is not advancing correctly, which means that there is a problem with the pushing of the filament.

Configuration options

Option Example value Explanation
filament_detector.enable true This module is activated only if this is set to true
filament_detector.encoder_pin 1.30 This is the pin the encoder is connected to. Must be an interrupt pin
filament_detector.bulge_pin 1.31 OPTIONAL This is the pin the bulge switch is connected to. If this switch is triggered ( by a bulge in the filament ) and the filament is moving, this will trigger an alarm
filament_detector.seconds_per_check 2 How many seconds between filament position checks, must be long enough for several pulses to be detected, but not too long
filament_detector.pulses_per_mm 204 The number of pulses the encoder produces for every millimeter of filament movement


The H/W for this is usually made of an R/C car wheel encoder like this A 3mm bolt goes through it and the filament runs over the shaft and turns the encoder wheel. The module counts the encoder pulses and compares it to how far the filament has moved, if there are no pulses then it triggers the suspend.
This is better than a simple switch as it only triggers if the filament was actually extruded, and only triggers if no pulses were detected.
It will not trigger if there was no extrusion.

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