# BTT Smart filament sensor not working **URL:** \ **Category:** General Discussion\ **Created:** [September 3, 2022, 8:51am UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036 "2022-09-03T08:51:18Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![MaestroLmpio](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/maestrolmpio/32/2240_2.png) [@MaestroLmpio](https://klipper.discourse.group/u/MaestroLmpio)\ **Post date:** [September 3, 2022, 8:51am UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036/1 "2022-09-03T08:51:18Z")
### Basic Information: Printer Model: Ender 5+ MCU / Printerboard: Octopus PRO 429 as CAN Bridge + EBB42 `klippy.log` ### Describe your issue: Hi Guys! Printhead got clogged on almost end of the print, but the printer didn’t get paused. Even when I have Mainsail showing the sensor as “empty”, it did not pause. How can this sensor be debugged? ![2022-09-03 10_32_49-Complete - CE5P_IntegratedLithoLamp_5mm_2pcs_205C __1.6LH__ 120mms__80Fan.gcode](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/f/f2b336a707949b1e15e368bd2e141d70e7345e0e.png) ![IMG_3999](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/3/3119357b4bce89ad447c656cfc70cd485f432521.jpeg) ![IMG_3979](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/3/34dc90b134795e6a3569f3e5ec7e58895545f679.jpeg) [klippyLog.zip](https://klipper.discourse.group/uploads/short-url/gYa3OJEy61oF3mjRUvjbEwdbKzi.zip) (1.3 MB) ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [September 3, 2022, 9:54am UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036/2 "2022-09-03T09:54:54Z")
My experience with this sensor is that it does not work reliably. Stopped using it. You could try to explicitly set a runout\_gcode, e.g. ```auto [filament_motion_sensor motion_sensor] detection_length = 7.0 switch_pin = ^EBBCan:PB3 extruder = extruder pause_on_runout = true runout_gcode: PAUSE ``` Also make sure that the `switch_pin` really does something, e.g. by removing the sensor from the toolhead to be able to simulate a runout. ---
**Author:** ![MaestroLmpio](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/maestrolmpio/32/2240_2.png) [@MaestroLmpio](https://klipper.discourse.group/u/MaestroLmpio)\ **Post date:** [September 3, 2022, 10:51am UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036/3 "2022-09-03T10:51:12Z")
Thanks for the tip to remove the sensor; By disconnecting it I saw there was a crimp failure in the connector at the sensor. It’s working now. ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [January 12, 2025, 8:00am UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036/5 "2025-01-12T08:00:41Z")
> [@chrisk](#): > > the ohly two port options is i2c port or rgb port You need two free pins for this sensor. The I2C pins **could** do this job. On a cursory look, I did not find the schematic for this board, so a definitive answer is difficult. ---
**Author:** ![mykepredko](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/mykepredko/32/2085_2.png) [@mykepredko](https://klipper.discourse.group/u/mykepredko)\ **Post date:** [January 15, 2025, 9:12pm UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036/7 "2025-01-15T21:12:45Z")
First off, in the future, don’t piggyback on a thread that’s over two years old and has marked as “Solved”. In light of this, please start a new “General Discussion” thread and answer the questions that you are given. I’m asking this because to be able to give you an accurate answer, we must know more about your system - saying that you’re using a Hermitcrab Version 2 isn’t enough information. One of the things that I’m confused about is that the Hermitcrab is normally used as a Toolhead controller and I don’t understand why you would connect a filament sensor to the Toolhead controller, which would add mass to the Toolhead when you should be able to connect it to your main controller board where there should be pins available for you to work with. When you’re putting in the General Discussion post, please be as descriptive as possible. ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://klipper.discourse.group/u/chrisk)\ **Post date:** [January 16, 2025, 8:15pm UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036/8 "2025-01-16T20:15:40Z")
sorry for bother, i duplicated the same setup as original poster, was hoping for tip from original poster but i solved it now myself ill delete my posts ---
**Author:** ![EddyMI3D](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/eddymi3d/32/1981_2.png) [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)\ **Post date:** [September 1, 2025, 6:13pm UTC](https://klipper.discourse.group/t/btt-smart-filament-sensor-not-working/4036/9 "2025-09-01T18:13:50Z")
Closed on September 1, 2025, 6:13pm UTC