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    First time autotuning… Questions

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    • vbtalentundefined
      vbtalent
      last edited by

      Martin,

      Who’s support Should I be contacting?

      Is this a lulzobt issue or a duet related issue?

      VB,

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      • vbtalentundefined
        vbtalent
        last edited by

        Thinking about to how to isolate this problem and I’m assigning that I could use my E3D hotend and connect it to the BED connectors to see if its a BED problem or a Duet problem, would that make sense or would you advise against that idea?

        VB,

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        • deckingmanundefined
          deckingman
          last edited by

          As I understand it, when you try and tune the bed heater, or when you simply try and heat the bed, the power supply voltage drops. Is that correct? If so, it would indicate that either there is a problem with the power supply not being up to the job, or there is a possible short on the bed heater. Using Ohms law, you ought be able to calculate what the resistance of the bed heater should be . If you know the wattage and voltage then you can calculate the current. Wattage is Voltage x Current so to keep the maths simple, if the bed is 240Watt and the voltage is 24v then the current is 240/24 = 10 Amps. Ohms Law is V=IR so R is V/I = 24/10 = 2.4 Ohms. Do the maths for your bed heater then measure the resistance across the heater terminals and see if it's correct. Also check that there isn't continuity between V+ and ground as that would indicate a short. If the heater checks out OK, then the problem is with the power supply (or wiring).

          You could try connecting the hot end to the bed terminals but typically a hot end will only have 30 or 40 Watt heater but the bed will be much more so it might not help much.

          BTW Heater 0 is the bed and heater 1 is the hot end but it looks like you've already realised that.

          Ian
          https://somei3deas.wordpress.com/
          https://www.youtube.com/@deckingman

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          • vbtalentundefined
            vbtalent
            last edited by

            @deckingman:

            As I understand it, when you try and tune the bed heater, or when you simply try and heat the bed, the power supply voltage drops. Is that correct? …

            Correct, simply turning on the bed heater with it wired up causes the power supply to somewhat shut down, not sure how to describe it?

            You could try connecting the hot end to the bed terminals but typically a hot end will only have 30 or 40 Watt heater but the bed will be much more so it might not help much.

            Will this cause any damage to either the hot end or bed to simply wire it up and turn the heater on its lowest setting to test if its a load issue?

            I unwired the heater from the board and simply turned the heater on via the interface. It looks like the voltage output was appx. 24volts on the Duet and the red light came on, so I'm leaning towards the duet being in a good state but without a load on it is that a reasonable assumption?

            As for the heater, its a 340 watt 24v heater which I think would calculate into 1.42 ohms based on your example and it actually measures in at 1.2 from the earlier picture I posted.

            3 questions come to mind, does it matter the positive and negative terminals of the bed heater since it is essentially a big resister or is there more to it than that, could they be reversed? Also, does the thermistor only play the role of temperature sensor in the puzzle? and does the config.g file have any impact on the type of issue I'm experiencing with the setting I posted earlier?

            Thanks.

            VB,

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            • dc42undefined
              dc42 administrators
              last edited by

              The only part of the bed heater that might be sensitive to polarity is the indicator LED, if it has one; and many bed heaters have two antiparallel LEDs to make them work on either polarity.

              What is the specification of the power supply?

              Check that the screws on the Duet VIN terminal block are tight..

              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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              • vbtalentundefined
                vbtalent
                last edited by

                Finally figured it out with all your help and as usual it was user error.. I failed to check that the power supply was set for 110v it was set for 220v, ugh!!

                So I was able to successfully run an autotune on the bed but there are some things I don't understand on the results that were generated.. https://drive.google.com/open?id=1C3dOzSSwoPW5EW1-TuV4BozbI-GM_eyY

                Why couldn't I run an autotune with S120 as the heater is rated for 120C?

                https://www.lulzbot.com/store/parts/24v-silicone-heater

                Why the warning message, is that generic in nature or something to be concerned with?

                VB,

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                • dc42undefined
                  dc42 administrators
                  last edited by

                  The default bed temperature limit is 110C. You can increase it using the M143 command.

                  The warning message is telling you that if there was a fault and the heater got left on at full power, it would get very hot. You might want to consider adding a thermal cutout, and/or turn the power supply voltage down a little (and then return retune both heaters).

                  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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                  • vbtalentundefined
                    vbtalent
                    last edited by

                    @dc42:

                    …You might want to consider adding a thermal cutout, and/or turn the power supply voltage down a little (and then return both heaters).

                    Thanks Dave, are you saying that you think the bed heater is defective?

                    Could you elaborate a little more…

                    VB,

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                    • dc42undefined
                      dc42 administrators
                      last edited by

                      Sorry, I made a typo and it got auto corrected to 'return' instead of 'retune'.

                      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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                      • vbtalentundefined
                        vbtalent
                        last edited by

                        No worries… thanks for clarifying.

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