Thermistors readings changed

General Discussion
1

Basic Information:

Printer Model: Artillery sidewinder x2
MCU / Printerboard: SKR PICO
Host / SBC Notebook with raspberry os
klippy.log
klippy.log (3.9 MB)

Describe your issue:

Hi everyone!

One is never learning…
I had been running skr mini e3 v3 before and during a nozzle changed happened to possibly short my thermistor. The room temperature readings gone up over 200c even when the thermistor was not plugged in. (No response for heating or anything) Contacted BTT and they sent me a replacement board. But I never figured out what happened with the board.

Now I’m running the machine with an SKR Pico and a very similiar issue happened, except the teamperature reading gone down by about - 80c and I can still print with accordingly adjusted temp settings.

So basically I just want to understand how the thermistors work and see if my issue is fixable without changing the board again.

Thanks

…

2

You essentially have 3 possibilities:

  1. Defect in the wiring → Check / replace
  2. Defect thermistor (not uncommon) → Replace
  3. Killed board

This board has only two thermistor ports, but by swapping the thermistors between hotend and bed to the respectively other port, you can verify the above points (provided that the other port is still delivering good readings).

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  1. The most common thermistor used in 3D printers is of the NTC type. These ‘approach’ short circuit at high temperature, and ‘approach’ open circuit at low temperature. It can be good to know when troubleshooting.
  2. There are many different NTC thermistors for 3D printers. Your printer.cfg must have the correct settings for the temperature to be displayed correctly.
  3. If your motherboard has 1 defective input, you may be able to use another. I use Z-endstop on my motherboard (BTT E3 RRF). Then you also have to take into account that that input has a 10 kohm resistor to 3.3 volts. Usually it is 4.7kohm.
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4

This z-endstop solution sounds good. As you mentiond the difference in resistors.
What should be the difference in config? May I see that part of your config?

Cheers

5

The important thing is MAY. I have not checked your motherboard.

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I know don’t worry. Just never heard it can work with endstop ports.

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If this is the correct form:

Then you only have 4 ADC inputs (BTT E3 RRF has 12). These 4 are:
GPIO26_ADC0 THB
GPIO27_ADC1 TH0
GPIO28_ADC2 ZDIR
GPIO29_ADC3 SERVO ADC3
GPIO26 and GPIO27 are your thermistors now. GPIO28 is used for Z direction. Then there will only be GPIO29 left. What is already there must then be moved to another input. I don’t know if this is possible. And that GPIO29 has no resistance to 5V (this was 3.3V on my BTT E3 RRF), so this has to be made.
I don’t know what is possible or what you are comfortable doing with such changes.

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Thanks!
It’s really something to start with.

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If this is the correct schematic for the SKR MINI E3:

Here there are 6 inputs that have ADC. 2 is used for temperature measurements. Unfortunately, the other 4 are used for controlling stepper motors.

And finally, you must change printer.cfg corresponding to the changes you have made with the hardware. Now it is no longer standard.

Edit:
I didn’t get the link right.
I would also like to add:

“#pullup_resistor: 4700”
You can change this if you have something else.

1 Like
10

I do have the Pico and the mini too. Will see if I can salvege any of these. I have an octopus as well (without steppers at the moment) So in the worst case I will use a multi mcu config. The info you wrote is very usefull! Thanks again!

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