Duet Wifi 2 third party pt100 board



  • Is it possible to use a third party daughter pt100 breakout board with the Duet Wifi 2?
    Thanks in advance


  • administrators

    Yes, if it uses the MAX31865 chip. See the wiki.



  • @crazyjane, to the best of my knowledge, one important point to bear in mind in this context is that the 3rd party board needs to have a 400R reference resistor for the board to work properly (i.e. give correct readings) when hooked up to the Duet.

    Based on the schematics, 400R is the value of the reference resistor on the Duet's daughter board (although in some cases it's noted as 430R - don't ask me why), and, again as far as I know, that's the value used by the Duet's firmware (unless there's a way of tweaking this value in the settings - I haven't looked into that).

    For my machine, I've actually made my own custom little daughter board for the PT-100 based on the MAX31865 & a 400R reference resistor (I didn't want to use the Duet's as I didn't want the daughter board to sit on top of the controller), and it works great 🙂

    Hope it helps.
    SnowCrash

    edit: for anyone reading this, as @dc42 helpfully noted below, the reference resistor's value can indeed be set in config.g, so please disregard my comment above about needing to use a 400R reference resistor. Instead, just remember to tweak that value in the settings.



  • Thank you both for your replies, much appreciated!
    I had read the Wiki but obviously missed the information, I'll check again. I'm also intrigued by the idea of building my own board, so I might give that a try, as I'm retired now I have time on my hands and need to keep busy'


  • administrators

    @crazyjane

    See:
    https://duet3d.dozuki.com/Wiki/PT100_temperature_sensor_daughter_board

    and

    https://duet3d.dozuki.com/Wiki/Connecting_PT100_temperature_sensors

    The type linked for older Duets is a compatible board. Saying that I do not want to dissuade you from rolling your own board! The KiCAD sources for our daughterboard are here:

    https://github.com/T3P3/TempDaughterboards/tree/master/MAXTempRTD


  • administrators

    @snowcrash said in Duet Wifi 2 third party pt100 board:

    @crazyjane, to the best of my knowledge, one important point to bear in mind in this context is that the 3rd party board needs to have a 400R reference resistor for the board to work properly (i.e. give correct readings) when hooked up to the Duet.

    Based on the schematics, 400R is the value of the reference resistor on the Duet's daughter board (although in some cases it's noted as 430R - don't ask me why), and, again as far as I know, that's the value used by the Duet's firmware (unless there's a way of tweaking this value in the settings - I haven't looked into that).

    For my machine, I've actually made my own custom little daughter board for the PT-100 based on the MAX31865 & a 400R reference resistor (I didn't want to use the Duet's as I didn't want the daughter board to sit on top of the controller), and it works great 🙂

    Hope it helps.
    SnowCrash

    It's possible to use 430R or another value for the reference resistor instead of 400R, if you specify the value of that resistor in the R parameter of the M305 command.


 

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