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Temp sensor fault when extruder motor engaged

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  • undefined
    darkstarone
    last edited by darkstarone 8 Jul 2019, 05:48 2 Aug 2019, 01:52

    Hello,

    I've been troubleshooting an issue in which the second extruder temp sensor on my machine reads completely fine, except when the opposite extruder motor engages (printing or just extruding filament). I have replaced all the wiring from the daughter-board to the thermistor, and even replaced the thermistor to ensure it's not shorting on the block or something like that. All insulation and wiring is clean and new.

    When the extruder engages, the temp instantly reads 2000C and the duet complains about short to other wiring after the sensor read fault.

    Any ideas what could be causing that?

    undefined 1 Reply Last reply 2 Aug 2019, 22:09 Reply Quote 0
    • undefined
      dc42 administrators @darkstarone
      last edited by 2 Aug 2019, 22:09

      @darkstarone said in Temp sensor fault when extruder motor engaged:

      I have replaced all the wiring from the daughter-board to the thermistor

      Which daughter board is that?

      Duet WiFi hardware designer and firmware engineer
      Please do not ask me for Duet support via PM or email, use the forum
      http://www.escher3d.com, https://miscsolutions.wordpress.com

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      • undefined
        darkstarone
        last edited by darkstarone 8 Apr 2019, 05:29 4 Aug 2019, 05:17

        I'm using a thermocouple board purchased from Filastruder:

        https://www.filastruder.com/products/temperature-sensor-boards-for-duet?variant=31621167044

        The thermocouple wiring for the first hotend runs down the same bundle and path as the secondary, and works 100% rock solid with no fluctuations. It is completely unaffected by movement of the primary or secondary extruder motor.

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        • undefined
          darkstarone
          last edited by 4 Aug 2019, 07:44

          I did another test in which I swapped the problematic thermocouple to the other input on the daughterboard, and it does the same thing. I did the same test on the other known good cable (both inputs tested) and it seems to work fine. This must be some sort of short as indicated by the error message but I cannot locate it anywhere visible or with a multimeter. The wiring has solid continuity when tested with a multimeter. The cabling is a continuous flex Igus with 24 wires in it, twisted pair all the way down to DIN mounted breakout terminal. I tried replacing the cable to the problematic thermistor on the other side of the breakout terminal with new wiring, and moved completely away from the extruder wiring. Unless there's a break/cut internally in the flex cable somewhere that's making contact, I'm having trouble locating the cause.

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          • undefined
            thomas_rudloff
            last edited by 4 Aug 2019, 08:01

            Cross talk? One cable is running closer to the stepper cable? Switching of the stepper might cause large transients. I assume the filtering capacitors on the thermocouple board are way to small. I do not know how to put a shield on the thermocouple cable since it has two different wires and the end at thermocouple board makes the cold junction opposed to the hot junction at the heating block.

            I just viewed the picture of the product. They omitted the capacitors at all. Works fine on production test, but not in real world.

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            • undefined
              dc42 administrators
              last edited by dc42 8 Apr 2019, 20:25 4 Aug 2019, 20:25

              Which version of the thermocouple daughter board do you have? The older one with MAX31855 chips didn't have the extra capacitors, but the wiki page about connecting thermocouples tells you how to add them. The newer one with MAX31856 chips has the capacitors.

              Duet WiFi hardware designer and firmware engineer
              Please do not ask me for Duet support via PM or email, use the forum
              http://www.escher3d.com, https://miscsolutions.wordpress.com

              undefined 2 Replies Last reply 5 Aug 2019, 00:19 Reply Quote 0
              • undefined
                darkstarone @dc42
                last edited by 5 Aug 2019, 00:19

                @dc42 I'd have to double check, but they were purchased within probably the last 6-9 months from Filastruder so I'd hope they were the newer ones. I believe my config is setup for the newer ones, but not seeing any capacitors on it. I'll upload a picture of what I've got a bit later today.

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                • undefined
                  darkstarone
                  last edited by 5 Aug 2019, 04:36

                  @dc42 Here is what I have

                  alt text
                  alt text

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                  • undefined
                    darkstarone @dc42
                    last edited by 7 Aug 2019, 03:41

                    This post is deleted!
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                    • undefined
                      darkstarone
                      last edited by 7 Aug 2019, 05:37

                      Tried moving the wire to a spare set in the bundle and still experiencing the same issue. If the 2nd thermistor is disconnected, there is no short triggered.

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