Optical filament runout sensor:

Marlin setting:

define FILAMENT_RUNOUT_SENSOR

if ENABLED(FILAMENT_RUNOUT_SENSOR)

define NUM_RUNOUT_SENSORS 1 // Number of sensors, up to one per extruder. Define a FIL_RUNOUT#_PIN for each.

define FIL_RUNOUT_INVERTING true //false // Set to true to invert the logic of the sensor.

//#define FIL_RUNOUT_PULLUP // Use internal pullup for filament runout pins.
//#define FIL_RUNOUT_PULLDOWN // Use internal pulldown for filament runout pins.

Necessary parts:

4x15 mm soft spring
Optical end stop: https://www.aliexpress.com/item/32972342907.html?spm=a2g0o.productlist.0.0.70dc15eebTHpAe&algo_pvid=f68dd1be-7d39-49bb-9e41-7288e3432f8c&algo_expid=f68dd1be-7d39-49bb-9e41-7288e3432f8c-0&btsid=0be3743b15880101146465242e17cd&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

Delta

No

No

0.2mm

30%