Setup problems

[wally3D]

Hello,

I'm having a strange behavior with a new Duet WIFI setup. I've begun wiring the board for testing purposes. I have the thermocouple board installed, and the latest firmware. With the extruder motor connected to hotend with known working thermocouple and heater(24v), I observe normal behavior when heating up the extruder to operating temp. It reaches the set point fine and stays stable. When I use the web control panel to extrude some filament, it works as it should, but instantly the temp graph hits 2000 degrees and eventually the tool is flagged as failed. Jogging any XYZ motor does cause this fault. The actual error on the console is:
Error: Temperature reading fault on heater 1: I/O error .
Occasionally it will put out this instead:
Error: Temperature reading fault on heater 1: short to Vcc

The displayed temp will continue flip between 2000 and the actual temp from this point on as it cools down.

I do not have any other hotends with thermistors to test to see if the thermocouple board is at fault. When switching thermocouple channels, I get the same behaviors. I have swapped out the motors. Reinstalling the firmware (1.15e) did not change this either. I've swapped heaters and motor cables as well. My config.g is barebones, as I have not moved on to setting up the rest of the hardware.

Any ideas on how to resolve this?

Thanks, -kurt

; Configuration file for Duet WiFi
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool on Sun Oct 30 2016 03:31:15 GMT-0500 (Central Daylight Time)
 
; General preferences
M111 S0 ; Debugging off
G21 ; Work in millimetres
G90 ; Send absolute coordinates...
M83 ; ...but relative extruder moves
M555 P2 ; Set firmware compatibility to look like Marlin
 
M667 S1 ; Select CoreXY mode
M208 X0 Y0 Z0 S1 ; Set axis minima
M208 X300 Y210 Z400 S0 ; Set axis maxima
 
; Endstops
M574 X1 Y2 Z1 S0 ; Define active high microswitches
;M558 P0 X0 Y0 Z0 H5 F120 T6000 ; Set Z probe type to modulated, the axes for which it is used and the probe + travel speeds
;G31 P600 X0 Y0 Z2.5 ; Set Z probe trigger value, offset and trigger height
 
; Drives
M569 P0 S1 ; Drive 0 goes backwards
M569 P1 S1 ; Drive 1 goes forwards
M569 P2 S1 ; Drive 2 goes forwards
M569 P3 S0 ; Drive 3 goes forwards
M350 X16 Y16 Z16 E16 I1 ; Configure microstepping with interpolation
M92 X87.489 Y87.489 Z800 E420 ; Set steps per mm
M566 X900 Y900 Z12 E120 ; Set maximum instantaneous speed changes (mm/min)
M203 X6000 Y6000 Z180 E1200 ; Set maximum speeds (mm/min)
M201 X500 Y20 Z250 E250 ; Set accelerations (mm/s^2)
M906 X800 Y800 Z800 E800 I30 ; Set motor currents (mA) and motor idle factor in per cent
M84 S30 ; Set idle timeout
 
; Heaters
 
M305 P0 R4700 H0 L0			; Put your own H and/or L values here to set the bed thermistor ADC correction
M305 P1 X100
M106 P1 T45 H1
M307 H1 A344.9 C124.9 D25.0 B0
M570 H1 P8 T15				; Increase to allow extra heating time if needed
 
;M143 S260 ; Set maximum heater temperature to 260C
;M305 P0 T10000 B3988 C0 R4700 L0 H0 ; Set thermistor + ADC parameters for heater 0
;M305 P1 T100000 B4138 C0 R4700 L0 H0 X100 ; Set thermistor + ADC parameters for heater 1 and remap it to channel 100
 
; Tools
M563 P0 D0 H1 ; Define tool 0
G10 P0 X0 Y0 ; Set tool 0 axis offsets
G10 P0 R0 S0 ; Set initial tool 0 active and standby temperatures to 0C
 
; Network
M550 PKurtBot				; Machine name (can be anything you like)
M551 Preprap                        ; Machine password (used for FTP connections)
M540 P0xBE:0xEF:0xDE:0xAD:0xFE:0xED ; MAC Address
M552 S1
;*** Adjust the IP address and gateway in the following 2 lines to suit your network
M552 P0.0.0.0				; IP address (0 = use DHCP)
M554 P192.168.1.1                   ; Gateway
M553 P255.255.255.0                 ; Netmask
M555 P2                             ; Set output to look like Marlin
;M575 P1 B57600 S1			; Comms parameters for PanelDue
 
; Fans
M106 P0 S0.3 I0 F500 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
M106 P1 S1 I0 F500 H1 T45 ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned on
M106 P2 S1 I0 F500 H1 T45 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on
 
; Custom settings are not configured
 
 

[dc42]

Does the problem start as soon as you energise the extruder motor, and do you get correct readings if you then turn the motors off by sending M84? If so then the thermocouple wires are picking up interference from the extruder motor wires. The thermocouple wiring must be twisted pair all the way from the thermocouple back to the interface board, and you may need to separate it from the extruder motor cable, or use two twisted pairs for the extruder motor wires too - one for each phase.

[wally3D]

Thanks for responding.

The spiking occurs when initiating an extrude from the machine control panel. The heater faults almost immediately, so I can't get the M84 command in quickly enough. The motor wires are twisted pairs.

The thermocouple I am using has a braided metal sleeve around the wires the entire cable length and a metal capsule at the end, so I am not sure how I could isolate it further. I did isolate its cable from the bundle and it did improve things. Now I am able to extrude without it shutting down immediately due to a fault, as well as issue the M84 command. The heater will eventually fault as I send more extrude commands, however. The temp graph shows fewer 2000 degree spikes, and now I can see small spikes in the negative direction, about 10-15 degrees. This suggests to me that there is now less interference. Still a long way to go though.

I have ordered a capsule thermocouple that has a fiber braided casing, perhaps that will improve things further.

[dc42]

Someone else reported something similar in another thread, with a similar-sounding thermistor. AFAIR it turned out that there was a short circuit between the braid and one of the thermocouple wires.