Thermocouple issue with Duet3 6HC-3HC



  • I try to connect thermocouples type K on a Duet3 6HC, value read is always 2000°C.
    I have one Thermocouple daughter board (V1.1) on the Duet3 6HC
    The config.g is like that :
    M308 S1 P"spi.cs0" Y"thermocouple-max31856" K"K"

    Note : same problem with the 3HC
    M308 S1 P"1.spi.cs0" Y"thermocouple-max31856" K"K"
    read 2000°C too.

    I tried 2 different Thermocouple daughter board and 3 thermocouples.

    Any idea ?

    PS : RRF3 3.0 rc1 on both 6HC and 3HC


  • administrators

    Try sending those M308 lines from the console, to see if any errors are reported.

    You can also send M308 S1 with no other parameters, and that should tell you the last error for that sensor.



  • 18/12/2019 à 21:40:15 M308 S1 P"0.spi.cs0" Y" thermocouple-max31856" K"k"
    No error reported

    18/12/2019 à 21:41:01 M308 S1
    Sensor 1 type Thermocouple (MAX31856) using pin (spi.cs0,serial3.rx), reading 37.5, last error: success, thermocouple type K, reject 50Hz


  • administrators

    @steevebecker said in Thermocouple issue with Duet3 6HC-3HC:

    18/12/2019 à 21:40:15 M308 S1 P"0.spi.cs0" Y" thermocouple-max31856" K"k"
    No error reported

    18/12/2019 à 21:41:01 M308 S1
    Sensor 1 type Thermocouple (MAX31856) using pin (spi.cs0,serial3.rx), reading 37.5, last error: success, thermocouple type K, reject 50Hz

    Looks like it's working then. Where are you seeing the 2000C readings? If you add a sensor name to the M308 command (A parameter) then you will be able to see the sensor temperature in the Extras tab of DWC, without having to assign a heater to use it.



  • Yes, I read 2000°C in DWC:

    c548d0f7-d6a8-4fe1-878b-99dd538b2b8e-image.png
    Tried that :
    M308 S1 P"spi.cs0" A"TC0" Y"thermocouple-max31856" K"k"
    It works!
    0fef8027-9bc9-4422-85be-c1b8ffb74464-image.png

    I installed the thermocouple card on the EXP3HC (with the thermocouples wired) and ran a :
    M308 S1 P"1.spi.cs0" A"TC0" Y"thermocouple-max31856" K"k"

    I get that :
    e44f6c61-4b97-482c-a3cf-3ed72bd64c2f-image.png

    M308 S1 :
    Sensor 1 type Thermocouple (MAX31856) using pin 1.spi.cs0, last error: sensor short to other wiring, thermocouple type K, reject 50Hz

    Strange, it is the same TC board and same wiring...



  • How... Sorry...
    I thought that the limitation of the thermocouple that must be on the same card as the heater was fixed in version 3.0RC1

    It seems not.
    It works with Thermistor but not with TC.

    If I setup the TC on 6HC and the heater on 6HC too, it works, DWC show the temperature.



  • Do you have any idea when this is going to be implemented?
    (just to know if I'll have to change the TCs by Thermistors to do my tests at the beginning of the year)


  • administrators

    @steevebecker said in Thermocouple issue with Duet3 6HC-3HC:

    How... Sorry...
    I thought that the limitation of the thermocouple that must be on the same card as the heater was fixed in version 3.0RC1

    It seems not.
    It works with Thermistor but not with TC.

    If I setup the TC on 6HC and the heater on 6HC too, it works, DWC show the temperature.

    For safety reasons, I recommend that temperature sensors are connected to the same board as the heater. Currently, I believe a heater on the main board using a sensor on an expansion board works, but not the other way round.



  • I'm sorry, I misspoke. Actually, I want to use 2 heaters and 2 thermocouples with the EXP3HC card.
    Do you think it should work?


  • administrators

    @steevebecker yes, if you have a prototype 3HC though most of them did not have the modification to make to temperature daughter boards work.



  • M308 S1 A"TC0" P"1.spi.cs0" Y"thermocouple-max31856" K"k"
    Give no error but read 2000°C.
    100b89fb-c0c5-4d8a-b991-9e61ed360dab-image.png

    M308 S1
    Sensor 1 type Thermocouple (MAX31856) using pin 1.spi.cs0, last error: sensor short to other wiring, thermocouple type K, reject 50Hz

    Yes, it is a prototype... bought in October.
    Can I made the modification myself ?


  • administrators

    @steevebecker said in Thermocouple issue with Duet3 6HC-3HC:

    Yes, it is a prototype... bought in October.
    Can I made the modification myself ?

    Yes, here are the details.

    Duet3Expansion1-v09-SPI-mod.odt .



  • It works fine, thank you...

    The last thing is the Z Probe connected to the expansion board.
    Do you have an idea when it will be supported ?


  • administrators

    @steevebecker said in Thermocouple issue with Duet3 6HC-3HC:

    It works fine, thank you...

    The last thing is the Z Probe connected to the expansion board.
    Do you have an idea when it will be supported ?

    What type of Z probe is it?



  • It is a ZProbe we made ourself.
    An electromagnet takes out a rod, on this rod is fixed a blade which hides or not a standard optical endstop.
    b8211d45-db7b-42ee-8fd3-88c0541a454a-image.png


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