filament runout sensor for Prusa mk2s printer

This is a very simple filament runout sensor to be added to your Prusa mk2s.

I have choosen, for reliability reasons to use an endstop switch instead of an optical sensor.
They are very cheap, easy to find on aliexpress
https://s.click.aliexpress.com/e/\_9AZ9pU

I use the Normally Open switch so that the contact is closed when the filament is inserted.

Prusa firmware is easily modified to activate the filament runOut option.
It does trigger the G600 Gcode command as soon as the filament is cut. It is the regular command to change filament.

The sensor snaps on the extruder without any screw. Even the lid is inserted and fixed using a filament "rivet" (see picture).

The sensor is designed to fit this exact type of switch...

The two wires of the switch go to the Y_Max connector on the mini Rambo board. They are connected to the S and - pins of the connector. There is no polarity you can swap the two pins !

Optionnaly you can add to the calibration menu section "Show End Stops" the display of the filament status. (0 = filament inserted)

Print Settings

Printer Brand:

Prusa

Printer: 

i3 MK2S

Rafts:

No

Supports: 

No

Resolution:

.2

Infill: 

40

Filament:

none PLA 
 

Notes: 

you can add a little "spring" to the sensor by bending the bottom part into hot water.
While doing ths the sensor will stay in place even if no filament is inserted

compilation

download latest fimware source

Latest firmware is 3.2.3 while writing this note !
It can be found here : https://github.com/prusa3d/Prusa-Firmware/releases/tag/v3.2.3

mod the firmware to activate the filament runout

follow these 3 (or 4) steps : (see pictures)

• in file configuration-prusa.h uncomment this line 
• in file pins.h change the FR__SENS pin to 24 (which is the Y_MAX pin)
• in file Marlin_main.cpp add these lines to enable input "pullup" on pin FR_SENS
• optionnaly, activate display of the filament runout switch in the calibration menu 

Category: 3D Printer Parts