Strange short-to-ground, only at random



  • I searched everywhere but couldn't find anything like my problem. I have this short-to-ground on driver 3 (extruder) that happens at random times, maybe it is after 10 minutes of starting printing without problems (extruding and all), maybe it happens after 3 hours of straight printing without problem.
    When motor is not connected it won't give any error. When moving using the Duet Web Control won't give any error. I even tried extruding (without filament inserted) 10000mm at 5000 feedrate, both directions and it went fine. I tried swapping the extruder to driver 4 and it printed 10h straight and didn't give any problem in two weeks of testing. Driver itself looks fine, no hole. What the hell could it be?

    Diagnostic at idle with driver 3 connected
    M122
    === Diagnostics ===
    RepRapFirmware for Duet 2 WiFi/Ethernet version 3.0 running on Duet WiFi 1.02 or later
    Board ID: 08DDM-9FAM2-LW4T8-6J9D0-3SN6L-92XHY
    Used output buffers: 3 of 24 (21 max)
    === RTOS ===
    Static ram: 30516
    Dynamic ram: 91880 of which 0 recycled
    Exception stack ram used: 256
    Never used ram: 8420
    Tasks: NETWORK(ready,688) HEAT(blocked,1240) MAIN(running,3676) IDLE(ready,156)
    Owned mutexes:
    === Platform ===
    Last reset 00:00:13 ago, cause: power up
    Last software reset at 2020-03-18 17:48, reason: User, spinning module GCodes, available RAM 8276 bytes (slot 3)
    Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0041f000 BFAR 0xe000ed38 SP 0xffffffff Task 0x4e49414d
    Error status: 0
    Free file entries: 10
    SD card 0 detected, interface speed: 20.0MBytes/sec
    SD card longest block write time: 0.0ms, max retries 0
    MCU temperature: min 33.6, current 36.3, max 36.8
    Supply voltage: min 12.1, current 12.1, max 12.3, under voltage events: 0, over voltage events: 0, power good: yes
    Driver 0: standstill, SG min/max not available
    Driver 1: standstill, SG min/max not available
    Driver 2: standstill, SG min/max not available
    Driver 3: standstill, SG min/max not available
    Driver 4: standstill, SG min/max not available
    Date/time: 2020-03-18 18:07:07
    Cache data hit count 24063528
    Slowest loop: 2.12ms; fastest: 0.09ms
    I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
    === Move ===
    Hiccups: 0(0), FreeDm: 169, MinFreeDm: 169, MaxWait: 0ms
    Bed compensation in use: none, comp offset 0.000
    === MainDDARing ===
    Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0
    === AuxDDARing ===
    Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0
    === Heat ===
    Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
    Heater 1 is on, I-accum = 0.0
    === GCodes ===
    Segments left: 0
    Stack records: 2 allocated, 0 in use
    Movement lock held by null
    http is idle in state(s) 0
    telnet is idle in state(s) 0
    file is idle in state(s) 0
    serial is idle in state(s) 0
    aux is idle in state(s) 0
    daemon is idle in state(s) 0
    queue is idle in state(s) 0
    autopause is idle in state(s) 0
    Code queue is empty.
    === Network ===
    Slowest loop: 21.96ms; fastest: 0.00ms
    Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0)
    HTTP sessions: 1 of 8

    • WiFi -
      Network state is running
      WiFi module is connected to access point
      Failed messages: pending 0, notready 0, noresp 0
      WiFi firmware version 1.23
      WiFi MAC address 5c:cf:7f:41:30:a5
      WiFi Vcc 3.44, reset reason Turned on by main processor
      WiFi flash size 4194304, free heap 23208
      WiFi IP address 192.168.109.121
      WiFi signal strength -76dBm, reconnections 0, sleep mode modem
      Socket states: 0 0 0 0 0 0 0 0

    Diagnostic after 10 minutes of printing fine and then short-to-ground error
    M122
    Error: short-to-ground reported by driver(s) 3
    === Diagnostics ===
    RepRapFirmware for Duet 2 WiFi/Ethernet version 3.0 running on Duet WiFi 1.02 or later
    Board ID: 08DDM-9FAM2-LW4T8-6J9D0-3SN6L-92XHY
    Used output buffers: 3 of 24 (20 max)
    === RTOS ===
    Static ram: 30516
    Dynamic ram: 92004 of which 0 recycled
    Exception stack ram used: 512
    Never used ram: 8040
    Tasks: NETWORK(ready,592) HEAT(blocked,1240) MAIN(running,3668) IDLE(ready,156)
    Owned mutexes:
    === Platform ===
    Last reset 00:14:45 ago, cause: power up
    Last software reset at 2020-03-18 17:48, reason: User, spinning module GCodes, available RAM 8276 bytes (slot 3)
    Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0041f000 BFAR 0xe000ed38 SP 0xffffffff Task 0x4e49414d
    Error status: 10
    Free file entries: 10
    SD card 0 detected, interface speed: 20.0MBytes/sec
    SD card longest block write time: 227.8ms, max retries 0
    MCU temperature: min 34.8, current 36.9, max 37.2
    Supply voltage: min 11.1, current 11.3, max 12.4, under voltage events: 0, over voltage events: 0, power good: yes
    Driver 0: standstill, SG min/max 0/336
    Driver 1: standstill, SG min/max 0/492
    Driver 2: standstill, SG min/max not available
    Driver 3: short-to-ground standstill, SG min/max 0/497
    Driver 4: standstill, SG min/max not available
    Date/time: 2020-03-18 18:06:11
    Cache data hit count 2294753149
    Slowest loop: 492.27ms; fastest: 0.09ms
    I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
    === Move ===
    Hiccups: 0(0), FreeDm: 169, MinFreeDm: 125, MaxWait: 172019ms
    Bed compensation in use: mesh, comp offset 0.000
    === MainDDARing ===
    Scheduled moves: 17, completed moves: 17, StepErrors: 0, LaErrors: 0, Underruns: 0, 0
    === AuxDDARing ===
    Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0
    === Heat ===
    Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
    Heater 0 is on, I-accum = 0.3
    Heater 1 is on, I-accum = 0.4
    === GCodes ===
    Segments left: 0
    Stack records: 3 allocated, 0 in use
    Movement lock held by null
    http is idle in state(s) 0
    telnet is idle in state(s) 0
    file is idle in state(s) 0
    serial is idle in state(s) 0
    aux is idle in state(s) 0
    daemon is idle in state(s) 0
    queue is idle in state(s) 0
    autopause is idle in state(s) 0
    Code queue is empty.
    === Network ===
    Slowest loop: 160.22ms; fastest: 0.00ms
    Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0)
    HTTP sessions: 1 of 8

    • WiFi -
      Network state is running
      WiFi module is connected to access point
      Failed messages: pending 0, notready 0, noresp 0
      WiFi firmware version 1.23
      WiFi MAC address 5c:cf:7f:41:30:a5
      WiFi Vcc 3.44, reset reason Turned on by main processor
      WiFi flash size 4194304, free heap 24280
      WiFi IP address 192.168.109.121
      WiFi signal strength -73dBm, reconnections 0, sleep mode modem
      Socket states: 0 0 0 0 0 0 0 0

    config
    config.g



  • I'm sure it's unrelated but you need to look into a better power supply. Looking at your log from when the printer was running your voltage is dropping all the way down to 11.1 so I can see that causing issues.

    I would lower your extruder acceleration quite a bit...10000 is rather high, especially for a non-geared extruder which I'm assuming you have due to the low steps/mm on the extruder. I would also raise the instantaneous speed change on the extruder to something between 800-1500.

    I just wondering if that real high acceleration on the extruder is causing the issue.



  • @JamesM said in Strange short-to-ground, only at random:

    Looking at your log from when the printer was running your voltage is dropping all the way down to 11.1 so I can see that causing issues.

    it can indeed be a relation between voltage drop and the short-to-ground error, but still odd the board doesn't report any under voltage events.

    the heaters are likely the big current draws, but you could try reducing the motor currents and see if it helps, and of course a though examination of the wiring and crimps. (power off before disconnecting anything)



  • I was just going to replace power supply before this whole virus lockdown. I'll look into it as soon as possibile.

    Accelerations and instantaneous speed change were settings that I got from the Anet A8 defaults with reprapconfgurator.

    I'll try adjusting values you both said and report back, but I somewhat feel this isn't it because when I plugged same motor same config to driver 4 (changing only the mapping), i worked flawlessly for days. I'll report as soon as I have another short-to-ground or success



  • Ok so I lowered motor current to 0.7A, lowered acceleration to 5000 and increased instantaneous speed change to 1000. Then printed at 20°C lower both hotend and hotbed, to drain less current at print time. A 5 hours print went through without any issue.
    I don't know what parameter did the magic but maybe it was reducing the overall drawed current. Maybe driver 4 draws less current so even with same config it went just borderline.
    Thanks both for your tips!



  • All of the suggestions were aimed at reducing the peak current which dropped the voltage when they converged on the same time.

    Anyways, hopefully it'll leave you with a working machine till the world gets back on track and you can replace the supply.



  • @Velixa Of those I would think lowering the acceleration. I personally would lower it a bit more down to 1500-2000 range.

    Hopefully that took care of it, but still do something about your power supply. Another thing to check is the VIN connections on the duet. I've seen many people hooking the power, bed and hotend heaters up without the ferrules and they can loosen up over time and cause issues.


  • administrators

    I can think of two possible causes:

    1. Duet is mounted above a conductive surface, and the underside of the motor connector sometimes touches that surface.

    2. A temperature-dependent fault on the Duet, most likely in the driver.


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