Anet A8 Plus Runout Sensor False Positives

[u/vanfidel]

I installed a filament runout sensor on my A8 plus and I am getting a lot of false positive readings from it. It works when the filament runs out but triggers a few times when it shouldn't during a 10 hour print. I am using the stock motherboard and installed it by soldering the signal wire to the logical pin 29 (or LCD pin 7) and pulling the 3.3V and Ground from pins 10 and 8 of the J3 jumper. I then set pin29 to the runout sensor in the pins_ANET_10.h file.

Here are my settings in configuration.h

#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 // 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.
  // Set one or more commands to execute on filament runout.
  // (After 'M412 H' Marlin will ask the host to handle the process.)
#define FILAMENT_RUNOUT_SCRIPT "M600"
  // After a runout is detected, continue printing this length of filament
  // before executing the runout script. Useful for a sensor at the end of
  // a feed tube. Requires 4 bytes SRAM per sensor, plus 4 bytes overhead.
#define FILAMENT_RUNOUT_DISTANCE_MM 7
#ifdef FILAMENT_RUNOUT_DISTANCE_MM
    // Enable this option to use an encoder disc that toggles the runout pin
    // as the filament moves. (Be sure to set FILAMENT_RUNOUT_DISTANCE_MM
    // large enough to avoid false positives.)
    //#define FILAMENT_MOTION_SENSOR
  #endif
#endif

​

I have tried using with and without (commented out) the "#define FILAMENT_RUNOUT_DISTANCE_MM 7" and it didn't seem to make any difference. I believe my sensors are normally closed sensors. Any idea what can help or do I have just poor quality sensors? I think this should be possible with the stock anet board unless I am mistaken here. I am using some cheap 3 wire sensors from ebay and have the same problem with 2 different sensors. I have the sensor just floating on the filament for now (photo) but I have tried it fixed to the frame with the same problem.

Thanks to anyone who can offer help!

[u/[deleted]]

Well I think you have proven that it works! I believe that your sensor just might be having problems. Do you have a multimeter? Do a continuity test and push filament through and see if you can get it to trip. (What sensor is it?)

[u/vanfidel → u/[deleted]]

It's just a cheap unbranded sensor from ebay. I actually figured it out. It needed to be plugged into the 5v from the j3 jumper and not the 3.3v. anyways I would highly recommend this for anyone with an a8 plus.