Issue with Z axis driver (Error: short-to-ground on drivers 2)



  • I have been battling an issue with my duet3d wifi board for the past couple months. At first I assumed it was user error on my end, but at this point I am leaning more towards an issue on the board itself. Whether it's me or the board I'd love to get some assistance and see what might be causing this issue.

    As the title of the post states my issue is on driver 2, Z axis movement with a short-to-ground Error. I am using a dual Z set up with the following stepper motors:

    Iverntech NEMA 17 Stepper Motor Amazon link


    Iverntech NEMA 17 Stepper Motor with Integrated 310mm T8 Lead Screw

    Specifications:

    • Led screw diameter: 8mm

    • Lead screw length: 310mm (±1mm)

    • Step angle : 1.8 degree

    • Nut material: Brass

    • Holding Torque: 400mN*m

    • Thrust(full step): 12.5kg

    • Rated Current/Phase: 1.5A

    • Rate Voltage: 3.3v

    • Rated Resistance/Phase: 2.2ohms ± 10%

    • T8 refers to an acme-thread, 4-lead rod, much better suited for this application. The correct pulses per mm for this rod, assuming a 1.8 degree step motor, and 1/16 step setting on the driver, is 400. This rod moves the nut 8 mm per revolution.


    0_1535413811453_2018-08-25_2226.png

    When both of these motors are plugged into Drive 2 (ZA & ZB) and I attempt to home Z with a simple limit switch either one motor will fail to rotate or both will grind in an effort to home the axis. This will result in a homing failed and will always throw a "short-to-ground driver 2" error.

    When one stepper is in ZA and the other in E1 the bed will move as desired and home without issue, but I still get the "short-to-ground driver 2" error.

    0_1535413786283_2018-08-27_1727.png

    In my efforts to troubleshoot this issue I have done the following:

    • I've placed the board on a hard wood frame with no metalic debre on top or below to eliminate any sort of short possibility.

    • I have replaced the wiring 3+ times and have tested with a multimeter for shorts in the wiring from the stepper motors to the board itself.

    • I have run M906 which shows currents are at 85% of rated:

       Motor current (mA) - X:1445, Y:1445, Z:1275, E:0:0:0:0:0:0:0:0:0, idle factor 30%
      
    • I have also run M122:

       M122
       === Diagnostics ===
       Used output buffers: 3 of 32 (13 max)
       === Platform ===
       RepRapFirmware for Duet 2 WiFi/Ethernet version 1.21 running on Duet WiFi 1.02 or later
       Board ID: 08DDM-9FAM2-LW4S4-6J1DG-3S86M-1MSZX
       Static ram used: 16152
       Dynamic ram used: 100448
       Recycled dynamic ram: 2184
       Stack ram used: 1224 current, 4448 maximum
       Never used ram: 7840
       Last reset 00:01:26 ago, cause: software
       Last software reset at 2018-08-27 17:25, reason: User, spinning module GCodes, available RAM 7760 bytes (slot 2)
       Software reset code 0x0003 HFSR 0x00000000, CFSR 0x00000000, ICSR 0x0441f000, BFAR 0xe000ed38, SP 0xffffffff
       Error status: 0
       Free file entries: 10
       SD card 0 detected, interface speed: 20.0MBytes/sec
       SD card longest block write time: 0.0ms
       MCU temperature: min 32.7, current 33.7, max 33.8
       Supply voltage: min 24.3, current 24.4, max 24.6, under voltage events: 0, over voltage events: 0
       Driver 0: standstill, SG min/max 0/73
       Driver 1: standstill, SG min/max 0/80
       Driver 2: short-to-ground standstill, SG min/max 0/379
       Driver 3: standstill, SG min/max not available
       Driver 4: standstill, SG min/max 31/217
       Date/time: 2018-08-27 17:26:52
       Slowest main loop (seconds): 0.014308; fastest: 0.000046
       === Move ===
       MaxReps: 2, StepErrors: 0, LaErrors: 0, FreeDm: 240, MinFreeDm 236, MaxWait: 604525135ms, Underruns: 0, 0
       Scheduled moves: 7, completed moves: 7
       Bed compensation in use: none
       Bed probe heights: 0.000 0.000 0.000 0.000 0.000
       === Heat ===
       Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1
       === GCodes ===
       Segments left: 0
       Stack records: 1 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.
      

    Lastly a copy of my current config.g , As a note: my z-probe is not currently set up, i'm waiting on a diode for "NPN output normally-open inductive or capacitive sensor" from the Duet3d.dozuki wiki

    ; Configuration file for Duet WiFi (firmware version 1.21)
    ; executed by the firmware on start-up
    ; generated by RepRapFirmware Configuration Tool on Sat Aug 25 2018 16:35:03 GMT-0600 (Mountain Daylight Time)
    
    	; General preferences
    	G90                                 ; Send absolute coordinates...
    	M83                                 ; ...but relative extruder moves
    	M555 P1                             ; Set firmware compatibility to look like RepRapFirmare
    	M667 S1                             ; Select CoreXY mode
    
    	; Drives
    	M569 P0 S1                          ; Drive 0 goes forwards
    	M569 P1 S1                          ; Drive 1 goes forwards
    	M569 P2 S1                          ; Drive 2 goes forwards
    	M569 P4 S1			    ; Drive 4 goes forwards  (Z2 in the E1)
    
    	;Dual Z
    	M584 X0 Y1 Z2:4			    ; Two Z motors connected to driver outputs 2 and 4 
    
    	M350 X16 Y16 Z16:16 I1                   ; Configure microstepping with interpolation
    	M92 X80 Y80 Z1600                        ; Set steps per mm
    	M566 X500 Y500 Z10                       ; Set maximum instantaneous speed changes (mm/min)
    	M203 X6000 Y6000 Z240                    ; Set maximum speeds (mm/min)
    	M201 X500 Y500 Z5                        ; Set accelerations (mm/s^2)
    	M906 X1445 Y1445 Z1275 I30               ; Set motor currents (mA) and motor idle factor in per cent
    	M84 S30                                  ; Set idle timeout
    
    	; Axis Limits
    	M208 X0 Y0 Z0 S1                         ; Set axis minima
    	M208 X290 Y290 Z310 S0                   ; Set axis maxima
    
    	; Endstops
    	M574 X1 Y1 Z1 S0                         ; Set active low endstops
    
    	; Z-Probe
    	M558 P0 H0 F120 T6000                    ; Disable Z probe but set dive height, probe speed and travel speed
    	M557 X50:300 Y50:300 S20                 ; Define mesh grid
    
    	; Heaters
    	M307 H0 B0 S1.00                         ; Disable bang-bang mode for the bed heater and set PWM limit
    	M305 P0 T100000 B4725 C0 R4700           ; Set thermistor + ADC parameters for heater 0
    	M143 H0 S120                             ; Set temperature limit for heater 0 to 120C
    	M305 P1 T100000 B4725 C7.060000e-8 R4700 ; Set thermistor + ADC parameters for heater 1
    	M143 H1 S280                             ; Set temperature limit for heater 1 to 280C
    
    	; Fans
    	M106 P0 S0.75 I0 F500 H0 T45             ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned on
    	M106 P1 S0.75 I0 F500 H0 T45             ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
    	M106 P2 S1 I0 F500 H0 T45                ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on
    
    	; Tools
    	M563 P0 D H                              ; Define tool 0
    	G10 P0 X0 Y0 Z0                          ; Set tool 0 axis offsets
    	G10 P0 R0 S0                             ; Set initial tool 0 active and standby temperatures to 0C
    
    	; Automatic saving after power loss is not enabled
    
    	; Custom settings are not configured
    

    This printer has not been fully set up because I have been stuck on getting the z-axis to more properly. Any help would be greatly appriciated.



  • Hi,

    Do you have any other stepper motors you could connect in lieu of the Z axis motors that are NOT part of the printer?

    If not could you remove the existing Z axis stepper motors so they are completely isolated from ground?

    The goal being to be certain they are or are not the related to the problem causing the short report.

    Frederick



  • Frederick,

    Thank you for the input. I have one extra stepper, so here is what I did to follow your suggestion:

    1. I disconnected the 2 steppers set to Driver 2 and switched my config.g to the single stepper(ZA position, jumpers on ZB)

    2. Connected the external stepper and connected the board back to main power supply.

    3. Booted up the duet3d, homed X and Y just to make sure everything was still good. Then homed Z. Imediatly received the "Error: short-to-ground on drivers 2" fault but the stepper still rotated.

    4. Lastly, I swapped out a different set of wire just to double check and received the same "short-to-ground" fault.

    Regards,
    Ryan



  • Hi,

    How is your Duet mounted?

    Any chance there is a wire or something touching the underside and creating the short?

    I have four sets of Duet WiFi/Duex5 combos in my printers and have never seen that error so I really haven't a clue where the short could be occurring on the board.

    Frederick



  • The duet is currently on a rather nice cut of hickory, free from excess wire. There is also nothing resting on the duet and the wires are connected with the connectors that came with the board. There is a small gap for free air to pass under the board, so it doesn't over heat.

    Regards,
    Ryan



  • @grahamcracker said in Issue with Z axis driver (Error: short-to-ground on drivers 2):

    The duet is currently on a rather nice cut of hickory, free from excess wire. There is also nothing resting on the duet and the wires are connected with the connectors that came with the board. There is a small gap for free air to pass under the board, so it doesn't over heat.

    Regards,
    Ryan

    Hmm...

    Perhaps dc42 will jump in here with some info about possible causes of that message.

    Did you try it with nothing connected to the Z-axes connectors?

    Frederick


  • administrators

    Please check the underside of your Duet to make sure that there are no solder bridges between adjacent pins of either of the Z motor connectors. We had an instance of this recently, which our testing didn't pick up because we test the Duets with 2 jumpers fitted in the Zb position.

    Also try this: power down, disconnect both Z motors from the Duet, and power up again. Then try to home or otherwise move Z. Do you get the same message?



  • After checking the underside of the board there was no solder between any of the adjacent pins. The error message does not show up after disconnecting the motors.

    So far the message shows when any motor of mine is in the following configurations: Za & Zb, Za and E1, and just Za.

    Regards,
    Ryan



  • @grahamcracker said in Issue with Z axis driver (Error: short-to-ground on drivers 2):

    After checking the underside of the board there was no solder between any of the adjacent pins. The error message does not show up after disconnecting the motors.

    So far the message shows when any motor of mine is in the following configurations: Za & Zb, Za and E1, and just Za.

    Regards,
    Ryan

    I assume you put the Duet connectors on the motor wires yourself?

    Did you check the wiring to be sure you had the correct configuration?

    Frederick


  • administrators

    @grahamcracker said in Issue with Z axis driver (Error: short-to-ground on drivers 2):

    After checking the underside of the board there was no solder between any of the adjacent pins. The error message does not show up after disconnecting the motors.

    So far the message shows when any motor of mine is in the following configurations: Za & Zb, Za and E1, and just Za.

    If the problem does not show up when the motors are disconnected but you try moving them as if they were, then it does suggest a problem in your wiring. Please use a multimeter to check the resistances as follows:

    • Between pins 1 & 2 of the 4-pin connector: 2.2 ohms
    • Between pins 2 & 3 3 and 4 of the 4-pin connector: 2.2 ohms
    • Between all other pairs of pins on the 4-pin connector: infinite
    • Between every pin on the 4-pin connector and the body of the motor: infinite

    EDIT: to be clear, by "4-pin connector" I mean the connector on the end of the motor cable that connects to the Duet, after unplugging it from the Duet; not the connector on the Duet itself.

    Do your X and Y motors work correctly? If so, do they work when you plug them into Za or E1?



  • @dc42 said in Issue with Z axis driver (Error: short-to-ground on drivers 2):

    Between pins 1 & 2 of the 4-pin connector: 2.2 ohms
    Between pins 2 & 3 of the 4-pin connector: 2.2 ohms

    Hi,

    That doesn't seem right to me.

    Frederick



  • @dc42

    Did you by chance mean:

    Between pins 1 & 2 of the 4-pin connector: 2.2 ohms
    Between pins 2 & 3 3 & 4 of the 4-pin connector: 2.2 ohms?

    Like this:
    0_1535482656666_2018-08-28_1249.png

    If so, this is how the motor's wiring has been configured and checked with a multimeter. When I get home from work I will confirm once more and rewire a new cable just to be certain.

    Lastly, the x and y motors do work splendidly, I will test with Za and E1.

    @fcwilt
    I did put the connectors on myself. I purchased a crimp tool from amazon for the job:
    IWISS Crimping tool, Amazon link

    And for the wiring I used the duet3d wiring guide for the board and components.

    Regards,
    Ryan



  • Hello
    I got similar problem with x axis, moreover my driver got fried. The problem was in motor wiring. One of the wires was crimped to much and got broken under insulation. The first thought was the motor problem because during X homing motor was shaking (short moves forward and backward) and "Error: short to ground driver 0" after second attempt to homing driver got fried. I checked wires and one of them was cut under insulation. Made new wire and remaped X motor to driver 5 and it runs with no problems. If one of the motor wires was cut why there was "Short to ground error"??? I am willing to replace fried TMC driver.

    @dc42 can You provide me some advice in replacing fried driver.

    As advice for anyone making own wires. Do not crimp terminal around insulation too strongly. The terminal blades may damage wire and always check wires with multi-meter. RUSH is Your greatest enemy.


  • administrators

    @grahamcracker said in Issue with Z axis driver (Error: short-to-ground on drivers 2):

    Did you by chance mean:
    Between pins 1 & 2 of the 4-pin connector: 2.2 ohms
    Between pins 2 & 3 3 & 4 of the 4-pin connector: 2.2 ohms?

    Yes, I did - sorry for the mistake.


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