Klipper Warning "sense_resistor not specified" for Steppers and Extruder

General Discussion
1

Basic Information:

Printer Model: CoreXY RMS
MCU / Printerboard: MKS PI
Host / SBC: DangerKlipper v0.12
klippy.log

I’d like to know and understand better what the sense_resistor values are or how to find out the correct value. What does it mean and what should I insert?

I have to admit that I try out DangerKlipper since today and I’m not sure if this feature is something coming from that fork.

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First: You may read the documents:

https://www.klipper3d.org/Config_Reference.html#tmc2130

Second: Please attach the klippy.log file to your next post.

3

Thanks, sure klippy.log will follow if required.

I knew already that resistance of the motor sense resistor is default 0.110 ohms.

But is this true? Probably not as the warning suggests. And how to find out or in other words how do you handle this value? I have also a multimeter in case it helps.

I heard this config item is going to become a mandatory field in Klipper soon?

4

This is what you have deleted when you opened this thread:

Fill out above information and in all cases attach your klippy.log file (use zip to compress it, if too big). Pasting your printer.cfg is not needed
Be sure to check our “Knowledge Base” Category first. Most relevant items, e.g. error messages, are covered there

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5

You can look into the data sheet or specs of your used stepper drivers or read it from the actual component.

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  1. This is Danger Klipper, which is a fork that we do not support.
  2. Klipper main line uses 0.11 Ω, if not specified otherwise and will issue no warning, nor is the setting mandatory
  3. You need to consult the manufacturer’s information on the true R-Sense value that your specific driver is using
  4. I have not seen a TMC2209 that had a different value

So please revert to Danger Klipper should you feel the need to discuss this warning.

7

The original Mellow FLY SB2040s did not use 0.11Ω sense resistors on the built in TMC2209 - that, along with the fact that the thermistor pull up resistor on the board wasn’t 4.7k drove me nuts when I first tried to get Klipper working on my Voron 2.4. I can’t remember what the actual value was but it was significantly lower than 0.11Ω and the extruder driver kept tripping out due to high temperature (which should never happen). The schematics are no longer available online and my copy is lost in the bowels of Dropbox.

Along with that, the Duet 3 Mini 5+ has 0.056Ω Sense resistors and they add 0.2Ω for internal resistance for the datasheet specified value of 0.076Ω. (Schematics here: Duet3-Mini5plus/v1.01/Duet3_5+_Ethernet_Schematic_v1.01.pdf at main · Duet3D/Duet3-Mini5plus · GitHub)

In any case, you’re right; the overwhelming majority of boards out there use 0.11Ω but you should always make sure when first using a stepper driver module or a board with built in driver chips. (Just as you should always make sure the pull up resistor on the Thermistor ADC input is 4.7k)

YMMV.

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