SOLVED Thermistors in Duet 2 FW 3.x



  • Hi,

    I have recently made the switch to the FW3 on my Duet v2 ....

    And now I'm configuring it, today it's Thermistor ... and it's a question about the thermistor on the bed, the DWC reads a strange temperature, 273.1 Cº .... and of course, when the ambient temperature is 32 ºC, it seems strange to me ...

    I attach the thermistor configuration in "config.g", by default in the web configurator ...

    ; Heaters
    M308 S0 P "bedtemp" Y "thermistor" T100000 B4138 R4700 ; M305 P0 T100000 B4350 R4700 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 B1 S1.00 ; enable bang-bang mode for the bed heater and set PWM limit
    M140 H0 ; map heated bed to heater 0
    M143 H0 S100 ; set temperature limit for heater 0 to 100C
    M308 S1 P "e0temp" Y "thermistor" T100000 B4138; configure sensor 1 as thermistor on pin e0temp
    M950 H1 C "e0heat" T1; create nozzle heater output on e0heat and map it to sensor 1
    M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit

    Here I put the configuration that I had with the FW 2.x, with which it was working ...

    ; Heaters
    M307 H0 B0 S1.00 ;Disable bang-bang mode for the bed heater and set PWM limit
    M305 P0 T100000 B4350 R4700 ; M305 P0 T100000 B3950 R4700 Set thermistor + ADC parameters for heater 0 M305 P0 T100000 B4138 R4700
    M143 H0 S90 ; Set temperature limit for heater 0 to 90C
    M305 P1 T100000 B4350 R4700 ; Set thermistor + ADC parameters for heater M305 P1 T82202 B4371 R4700
    M307 H1 A312.4 C95.9 D12.8 S1.00 V23.9 B0
    M143 H1 S245 ; Set temperature limit for heater 1 to 245C

    What can be?


  • administrators

    @peirof said in Thermistors in Duet 2 FW 3.x:

    M308 S0 P "bedtemp" Y "thermistor" T100000 B4138 R4700 ; M305 P0 T100000 B4350 R4700 configure sensor 0 as thermistor on pin bedtemp

    I think the M308 command has failed because there is a space between Y and "thermistor". Try removing it.



  • Not....

    in the config.g file there was NO such space ...

    Can I add something else .... I have tried to disconnect the thermistor from the bed ... and DWC, with the bed thermistor disconnected, continues to show the same value -273.1.

    It shows the same, if the thermistor is connected than disconnected ...



  • Let's draw a stupid veil on the matter .....

    Well .... it turns out that the connector to the duet board had come loose .... once reconnected .... it seems to work ....



  • one ask...

    in FW v2, when there is some problem with thermistor, DWC show 2000 C.....

    Now? -273? or other


  • administrators

    I'm glad you found the problem. A disconnected thermistor has always shown -273C in RRF. Other temperature sensor faults give a reading of 2000C.



  • @dc42 how I can know the kind of temperature sensor? Think its termopar... Different configuration?


  • administrators

    @peirof said in Thermistors in Duet 2 FW 3.x:

    @dc42 how I can know the kind of temperature sensor? Think its termopar... Different configuration?

    Measure the resistance of the sensor at room temperature. If it's a sort used in 3D printing:

    <10 ohms: thermocouple
    100-120 ohms: PT100
    1000-1200 ohms: PT1000
    Around 10K: 10K thermistor
    Around 100K: 100K thermistor
    Around 500K: 500K thermistor


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