Unstable Hotend Temperature with Canbus

General Discussion
1

Setup:
Voron 2.4 350mm
Octopus 1.1, Utoc, Sht36v2 without the max chip, Rapido 1 UHF with Pt1000,
Jumper on for 1100 (as instructed for PT1000 in mellow docs), cpap cooling fan

klippy.zip (2.7 MB)

Hello everyone,

I’m facing a bit of a puzzling issue and could use some assistance. Despite scouring the internet and consulting with people, I’ve hit a roadblock with my current situation. Your input would be greatly appreciated.

This isn’t my first time working with a CAN bus setup, but it is my first time using a PT1000 on a CAN bus board. The problem I’m encountering is that the temperature readings are consistently unstable, fluctuating by a few degrees Celsius.

The instability in temperature readings during the initial warm-up phase is causing problems as it doesn’t stabilize enough to trigger the next step in the prcess.

Here are the steps I’ve taken to address the issue so far:

-I’ve tuned the pid values multiple times, both with and without a fan.
-I’ve tested both configurations of the pull-up resistor, using values of 1100 and 4700, as well as testing without the jumper (4700).
-I’ve verified the CAN connection by running the command: “ip -details -statistics link show can0” and there don’t appear to be any dropped packages or errors.
-I’ve measured the resistances of the PT1000 using a multimeter and compared them to the values specified in the PT1000 table, and they match.
-I’ve also tried using the thermistor from my Dragon HF with the SHT36V2, and while it’s not as unstable as the PT1000, it’s still exhibiting some fluctuation.

I’m incredibly thankful for any help or insights you can provide. Your assistance means a lot to me! :blush:

1 Like
2

I’d say this is a hardware issue with your CAN board. I run the sht36-v2 too and see no such issues with a PT1000 or Semitec thermistor, with nothing special configured.

3

Ok thanks. Anyway I can verify that the can bus board is the problem?

4

I have tested my old sb2040 with the pt1000 and had no problems. So I guess it is a broken sht36v2 out of factory … disappointing.

5

I’m not sure it could be a hardware issue unless there is a soldering problem or poor quality resistor/cap in the circuit. The input 3.3V line could have an issue? The circuit is dead simple. I reckon it has to be a firmware problem with the sampling speed, resolution or noise of the PT1000 sensor on the micropin.

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I have the same hardware as you and noticed my rapido2 with pt1000 had a similar behavior where it wasn’t stable and varied +/-2 or 3 degrees. However, i had my configured for 4700ohm w/o the jumper.

I found a similar post in the duet forum: PID Tuning RTD PT1000 from the 1LC | Duet3D Forum

6

I have had the same issue on 5 or 6 SHT36v2 boards in a row. Not one has worked correctly for me. I have reached out to Mellow as well to see if they have any input.

7

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