Thermistor temperature reading problem.



  • Hello,

    Got a problem with the readings from my extruder head. It's currently fluctuating between 790-900C on the web UI display and but the temperature is slowly climbing. The fluctuations are still over a wide 100C+ range. I'm running out of things to check. I've swapped between both E0 and E1 pins and both have the same problem. Yes changed the configuration when I swapped pins.
    There is 0 power going to the heater. And a manual test shows it's still at ambient temp.

    I've triple checked the Thermistor and it's fine. The ambient temperature is 19C and the resistance is at ~124K. There is very little fluctuation with that measurement. Just your standard changes you'd expect with noise, etc.
    Checked the fuses which were fine. Still, replaced them with new ones. Which are also good.
    Ohm'd the VSSA pin to ground and it's around 1 ohm.

    The Duet3D v2 wifi is being installed into an old cartesian printer oh mine. The thermistor was working fine before I pulled the Arduino/Mega brains.
    Duet version 2.03 firmware but I upgraded to 3.1.1 trying to troubleshoot.
    Under 2.03 firmware I ran M305 commands to try to correct.
    I don't expect M308 commands to be any different.
    That temperature is too high. It can't be corrected.
    And the slowly climbing temp tells me that it's more than just correcting it with thermistor offsets.

    All the steppers and end stops are working so I don't think it's a power source problem.

    Any suggestions?

    Thanks


  • Moderator

    Please post your config.g and also the results of M122 and M98 P"config.g".

    What type of thermistor is it?
    What thermistor values were you using before?



  • The thermistor is some cheap part that came with the machine. Generic settings of 100K worked fine.

    The Heater fault is caused by the high temp sensed.
    Oh leaving the E0 pins in an open state causes the temp to start at approx 40C and slowly climb up. My first guess is a capacitor charging. But without a board schematic.

    ;---------------------------------------------------------------------------------------------------------------------------------
    M98 P"config.g"
    HTTP is enabled on port 80
    FTP is disabled
    TELNET is disabled
    Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 365C

    Error: Heater 1 fault: heater monitor 0 was triggered
    ;---------------------------------------------------------------------------------------------------------------------------------
    M122
    === Diagnostics ===
    RepRapFirmware for Duet 2 WiFi/Ethernet version 3.1.1 running on Duet WiFi 1.02 or later
    Board ID: 08DGM-917DA-G4MS8-6JKD2-3S46Q-TTT3B
    Used output buffers: 3 of 24 (11 max)
    === RTOS ===
    Static ram: 27980
    Dynamic ram: 93740 of which 44 recycled
    Exception stack ram used: 272
    Never used ram: 9036
    Tasks: NETWORK(ready,384) HEAT(blocked,848) MAIN(running,1824) IDLE(ready,80)
    Owned mutexes: WiFi(NETWORK)
    === Platform ===
    Last reset 00:07:28 ago, cause: power up
    Last software reset at 2020-10-20 15:36, reason: User, spinning module GCodes, available RAM 9748 bytes (slot 2)
    Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x0441f000 BFAR 0xe000ed38 SP 0xffffffff Task MAIN
    Error status: 0
    MCU temperature: min 21.8, current 30.8, max 31.2
    Supply voltage: min 23.9, current 24.1, max 24.3, 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: 2020-10-20 20:21:11
    Cache data hit count 774144141
    Slowest loop: 7.20ms; fastest: 0.13ms
    I2C nak errors 0, send timeouts 0, receive timeouts 0, finishTimeouts 0, resets 0
    === Storage ===
    Free file entries: 10
    SD card 0 detected, interface speed: 20.0MBytes/sec
    SD card longest read time 3.6ms, write time 0.0ms, max retries 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 CDDA state: -1
    === AuxDDARing ===
    Scheduled moves: 0, completed moves: 0, StepErrors: 0, LaErrors: 0, Underruns: 0, 0 CDDA state: -1
    === Heat ===
    Bed heaters = 0 -1 -1 -1, chamberHeaters = -1 -1 -1 -1
    === GCodes ===
    Segments left: 0
    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
    USB is idle in state(s) 0
    Aux is idle in state(s) 0
    Trigger is idle in state(s) 0
    Queue is idle in state(s) 0
    Daemon is idle in state(s) 0
    Autopause is idle in state(s) 0
    Code queue is empty.
    === Network ===
    Slowest loop: 15.69ms; fastest: 0.00ms
    Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0) FTP(0) Telnet(0), 0 sessions
    HTTP sessions: 1 of 8

    • WiFi -
      Network state is active
      WiFi module is connected to access point
      Failed messages: pending 0, notready 0, noresp 0
      WiFi firmware version 1.23
      WiFi MAC address 60:01:94:2e:1b:e8
      WiFi Vcc 3.39, reset reason Unknown
      WiFi flash size 4194304, free heap 21480
      WiFi IP address 192.168.0.26
      WiFi signal strength -67dBm, reconnections 0, sleep mode modem
      Socket states: 4 0 0 0 0 0 0 0

    [0_1603250781513_config (2).txt](Uploading 100%)


  • Moderator

    @Dan-DeGagne said in Thermistor temperature reading problem.:

    [0_1603250781513_config (2).txt](Uploading 100%)

    Your config.g failed to upload. Copy and paste would be preferred.



  • @Dan-DeGagne said in Thermistor temperature reading problem.:

    Generic settings of 100K worked fine.

    for room temperature yes, because they are all 100k.
    generic settings do not work at temperature of 200C



  • @Phaedrux Gotcha

    ; Configuration file for Duet WiFi (firmware version 3)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool v3.1.4 on Tue Oct 20 2020 15:34:09 GMT-0700 (Pacific Daylight Time)

    ; General preferences
    G90 ; send absolute coordinates...
    M83 ; ...but relative extruder moves
    M550 P"My Printer" ; set printer name

    ; Network
    M552 S1 ; enable network
    M586 P0 S1 ; enable HTTP
    M586 P1 S0 ; disable FTP
    M586 P2 S0 ; disable Telnet

    ; Drives
    M569 P0 S1 ; physical drive 0 goes forwards
    M569 P1 S1 ; physical drive 1 goes forwards
    M569 P2 S1 ; physical drive 2 goes forwards
    M569 P3 S1 ; physical drive 3 goes forwards
    M584 X0 Y1 Z2 E3 ; set drive mapping
    M350 X16 Y16 Z16 E16 I1 ; configure microstepping with interpolation
    M92 X89.27 Y89.27 Z400.00 E420.00 ; set steps per mm
    M566 X900.00 Y900.00 Z12.00 E120.00 ; set maximum instantaneous speed changes (mm/min)
    M203 X12000.00 Y12000.00 Z7200.00 E2400.00 ; set maximum speeds (mm/min)
    M201 X500.00 Y500.00 Z50.00 E250.00 ; set accelerations (mm/s^2)
    M906 X1000 Y1000 Z1000 E1200 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 X210 Y160 Z220 S0 ; set axis maxima

    ; Endstops
    M574 X1 S1 P"xstop" ; configure active-high endstop for low end on X via pin xstop
    M574 Y1 S1 P"ystop" ; configure active-high endstop for low end on Y via pin ystop
    M574 Z1 S1 P"zstop" ; configure active-high endstop for low end on Z via pin zstop

    ; Z-Probe
    M558 P0 H5 F120 T6000 ; disable Z probe but set dive height, probe speed and travel speed
    M557 X15:210 Y15:160 S20 ; define mesh grid

    ; Heaters
    M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin bedtemp
    M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
    M307 H0 B0 S1.00 ; disable bang-bang mode for the bed heater and set PWM limit
    M140 H0 ; map heated bed to heater 0
    M143 H0 S120 ; set temperature limit for heater 0 to 120C
    M308 S1 P"e1temp" Y"thermistor" T100000 B4138 ; configure sensor 1 as thermistor on pin e1temp
    M950 H1 C"e1heat" T1 ; create nozzle heater output on e1heat and map it to sensor 1
    M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit

    ; Fans
    M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency
    M106 P0 S0 H1 T200 ; set fan 0 value. Thermostatic control is turned on
    M950 F1 C"fan1" Q500 ; create fan 1 on pin fan1 and set its frequency
    M106 P1 S0.75 H1 T150 ; set fan 1 value. Thermostatic control is turned on
    M950 F2 C"fan2" Q500 ; create fan 2 on pin fan2 and set its frequency
    M106 P2 S0.75 H1 T150 ; set fan 2 value. Thermostatic control is turned on

    ; Tools
    M563 P0 D0 H1 F0 ; 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

    ; Custom settings are not defined


  • Moderator

    Thanks.

    Is this a newly purchased Duet or an old one previously used?



  • can you swap the bed and hotend thermistors on the board? and see if the reading changes



  • I bought the Duet about 6 months ago. I had tried to install it then but it failed to work so shelved it until now.

    The printer didn't come with a heated bed.
    Yeah, I've tried other thermisters. Just try a couple of new ones I dug up. Same problem.

    But I haven't tested it using the bed temperature pins instead. I'll try that.



  • Its got to be the E0 E1 sensors on the board somewhere. The bed sensor works fine.


  • administrators

    If you are getting readings of ~40C with nothing connected to the E0temp or E1temp pins and the configuration correctly set to use those pins, then it does sound like a hardware fault on the Duet. For example, the corresponding MCU analog inputs might not be soldered, or the thermistor reference resistors may be missing. However, we test all thermistor inputs before the board leaves the factory. Is this a genuine UK-manufactured Duet? Where did you buy it?

    The schematic if you need it is at https://github.com/Duet3D/Duet-2-Hardware/tree/master/Duet2/Duet2v1.04.


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