Rotating magnet filament monitor - frame errors?



  • Hi there,

    I just got my rotating magnet filament monitor delivered. Installation and configuration was a no-brainer (except for the pin assignment on the sensor PCB, which I could not find anywhere - so I just made a 1:1 connection between the two molex KK connectors).

    config.h contains

    M591 D0 P3 C3 S0 R70:130 L24.8 E3.0
    

    as per documentation.

    So I fired up a test print - the infamous xyz calibration cube, at 0.3mm layers.

    First 33 layers went fine - then a DWC popup appeared.
    "Extruder 0 reports sensor not working"

    M122 says

    [...]
    Extruder 0: pos 274.22, ok, measured sens 33.79mm/rev min 22% max 136% over 54.6mm, errs: frame 49 parity 0 ovrun 0 pol 0 ovdue 0
    

    M591 D0 says

    Duet3D rotating magnet filament monitor v2 on input 3, disabled, sensitivity 24.80mm/rev, allow 70% to 130%, check every 3.0mm, current pos 107.2, measured sensitivity 35.64mm/rev, min -1% max 146% over 142.9mm
    

    So I suspect there is something wrong.

    • "errs: frame 49" is indicative of frame errors (?)
    • "min -1%" seems way off

    What to check? What to do?

    On a side note, I was able to resume the print to finish without further problems though.

    Thanks,
    Andreas



  • Update: I got a shielded cable installed.

    M122 now reports only 4 from errors, but nonetheless the job stalls mid-print with "Extruder 0 reports sensor not working".

    Also, M591 D0 reports

    Duet3D rotating magnet filament monitor v2 on input 3, disabled, sensitivity 24.80mm/rev, allow 70% to 130%, check every 3.0mm, current pos 0.0, measured sensitivity 31.29mm/rev, min -2% max 129% over 1204.2mm
    

    Hmm, "min -2%" - not really better ...

    Any thoughts, @dc42 @T3P3Tony ?


  • administrators

    @themelle

    It is either an issue with the PCB, the wiring noise or possibly an issue with magnet registration.
    how long is the cable between the monitor and the Duet?



  • @t3p3tony

    The cable is about 50cm long and shielded. It contains four wires, and I used all of them by using a single wire for both GND and +3.3V, and combined two wires for SIGNAL. Could this have any negative influence leading to signal noise?


  • administrators

    Which version Duet is it? The older ones have more filtering on the regular endstop inputs, which might be contributing to the framing errors. If so then you can connect the filament monitor to one of the endstop inputs on CONN_LCD instead.

    When you get the "sensor not working" report, is there a regular pattern of red flashes from the LED on the filament monitor?



  • @dc42 Thanks for joining in 🙂

    The printer is driven by a Duet Wifi 1.04 running RRF 2.04RC1.

    When the "sensor not working" popup appears, the sensor does flash green all the time at around 1Hz. No red flashes as far a I can tell you.


  • administrators

    Confirm that you are running firmware 2.03 or 2.04RC1 ?



  • This post is deleted!


  • @dc42
    Sure, can confirm firmly 😉

    M122
    === Diagnostics ===
    RepRapFirmware for Duet 2 WiFi/Ethernet version 2.04RC1 running on Duet WiFi 1.02 or later
    [...]
    


  • As I need to get this issue sorted out in time I changed the sensor cable routing to be as far away from stepper wires as possible.

    The test print stopped once with the infamous "sensor not working" message, but went otherwise fine.

    Mid-print pause

    M122
    Extruder 0: pos 0.00, ok, measured sens 25.32mm/rev min 13% max 111% over 6476.1mm, errs: frame 10 parity 0 ovrun 0 pol 2 ovdue 0
    
    M591 D0
    Duet3D rotating magnet filament monitor v2 on input 3, disabled, sensitivity 24.80mm/rev, allow 70% to 130%, check every 3.0mm, current pos 0.0, measured sensitivity 25.32mm/rev, min 13% max 111% over 6476.1mm
    

    After the print

    M122
    Extruder 0: pos 211.29, ok, measured sens 25.34mm/rev min 93% max 105% over 175.3mm, errs: frame 11 parity 0 ovrun 0 pol 2 ovdue 0
    
    M591 D0
    Duet3D rotating magnet filament monitor v2 on input 3, disabled, sensitivity 24.80mm/rev, allow 70% to 130%, check every 3.0mm, current pos 211.3, measured sensitivity 25.34mm/rev, min 93% max 105% over 175.3mm
    

    Measured sensitivity seems pretty consistent throughout both runs runs, and the second run even seems to have produced what I would call "real" min/max extrusion percentages.

    But the framing errors did not go away, and "pol" errors (What are those?) did show up.
    So I assume it is basically not an issue with cross talk between sensor and stepper cables.

    @dc42 @T3P3Tony
    How can we further progress on this topic?

    Thanks in advance!


  • administrators

    When it reports "sensor not working", what pattern of flashes do you see on the sensor LED?



  • @dc42 The LED flashes green at around 1Hz.



  • @dc42 Any clues yet? Anything that I can try, measure, test?


  • administrators

    Green flashes at 1Hz are normal when there is no filament motion AFAIR.

    In case it's a wiring issue, can you see the red endstop LED on the Duet flashing in time with the green LED on the filament monitor?



  • @dc42 Thanks for your input.
    I'll try to verify this, probably on friday. Will come back to you with results 😉



  • @dc42 Got around to give it another try. When the sensor flashes, the end stop LED does not light up at all.



  • @dc42 Did another test - strange thing is the LED now flashes red at around 1Hz when the "sensor not working" popup appears.
    Also, the popup appeared tithes time for the first time immediately after starting the print from DWC, but way before any moves of the print head or extruder, as heating up had barely begun.


  • administrators

    @themelle, if the sensor LED flashes only red then it is reporting an error condition back to the Duet.

    If it gives several red flashes, pauses, then repeats, it is flashing an error code (count the number of flashes). When it does this, the Duet will record framing errors.



  • This post is deleted!


  • @dc42, I know, there are some error codes listed over there (https://duet3d.dozuki.com/Wiki/Duet3dFilamentMonitor_RotatingMagnetVersion).
    But the red flashing is not paused in between - it is flashing at around 1Hz continuously ...


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