Consistent hotend temperature offset
Hey folks!
Some rubber ducking, some troubleshooting here...
On my VCore 3.1 that I recently put back together, I have an issue with my hotend thermistor readings.
I'm using the latest RatOS build (2.x), Octopus board, EBB42. I started using the Rapido hotend with their stock thermistor, and had a reading of about 6 degrees instead of the room's 21. I changed the hotend for a mosquito, with another type of thermistor, and had the exact same reading.
I had to change the Octopus board, so I'm left with a potential faulty EBB42 (pullup resistor?).
I was unable to fix it in the software (the new config is more plug'n'play, but less easy to tweak) so I ended up modifying the filament needed temp in the slicer.
I'd appreciate some of your thoughts on this, I'm waiting for a new EBB42.
Thanks a lot!
29 Replies
Hello
so you mind to share your config files?
and RatOS 2.X is not the latest image.
2.1 Rc2 (updatable to Rc3) is.
Hey! Thanks for jumping in 😄 I should have been more precise, you are right!
I'm on the 2.1 RC3, all is up to date.
I don't know if that helps, but I didn't see this issue when I was with RatOS 1. But I also rebuilt the printhead, so I might have damaged the EBB.
The thermistor is an NTC 100K
IIRC there isn't a pullup resistor for the thermistors as they are a variable resistor and a pullup would throw them off
I see in the RatOS.cfg this line:
sensor_type: NTC 100K MGB18-104F39050L32
Is there a different NTC100K selectable in the configurator to try?That's all there is. I ran with the ATC before, when I had the rapido, but had the same discrepancies on the readings.
This is why I think the problem is either the EBB42 or software.
But since there is not a pullup resistor, and since the problem appeared with RatOS 2, it might be a conf issue, yes.
For the record, I already re-installed the whole OS, without any improvement.
Does the thermistor show a different reading if you het it up, like with a heat gun or lighter?
The usual causes of thermistor issues is a short or an open. For it to read something in the middle but inaccurate is unusual
It shows a proper reading, just with an offset. I can print well if I lower the filament temperature by 15deg or so.
If I heat the thermistor, I have a different reading, yes.
Basically, my sensor is on the B option:
Some rapidos came with a faulty thermiator that read wrong just like yours. You can compensate by setting your temp lower like you found, or replace it
I changed my rapido to a mosquito, exact same readings 🙈.
okay, THAT is weird. Was there any connectors or wiring in common?
The EBB42 is! I changed the USB cable as well (seems to easily break). Could it be a software issue, though? I could re-install V1 to try...
I can re-crimp all cable for extra-measure, but from XP, bad crimping leads to the target C, not the target B :/
It does not make any sense. Brand new EBB42, I recrimped all wires...
I'm still 20deg out
Can you remove the hotend from the rest of the assembly and see if you get the same reading? I'm wondering if ther eis some electrical interference or something touching where it shouldn't or....
Did it
klipper is in panic because of the sensor "readings".
I did a PID tuning, and it worked fine.
Tomorrow I'll flash the whole OS, and re-install things again.
If that does not work, I'll push the RatOS v1
that reported temp is saying something is shorted
its way too little resistance
Even less than it was saying before
can it be the USB cable? because the EBB board is new, and the wires are new too
I was also thinking that some common ground was not working, maybe between the octopus and RPI
What would you suggest me trying?
Can't be the USB, as that is all digital communication. This is between the sensor and the EBB
Hm. If something wasn't grounded right, or some leakage current somewhere... yeah maybe?
Grab a multimeter, stick one on a good ground like the power supply ground and start poking around, see if you can find a ground that isn't at zero?
Thanks for the tip, I'll add this to the list of things to try. Since I'm not comfortable at all with electronics, I might do it last...
I'll try it tomorrow. Thanks for your help, I'm happy not to be alone on this mess hahaha.
its a long shot, i dunno whats goin on
but that you get the same with a differnet EBB and changed hotends/thermistor..
Can I have your honest opinion? Am I fixating about the potential soft issue? Or RPI?
Or is it possible?
also, verify it once it is up to temperature, some of the termistors are error prone at room temp but are fine when getting to the hotend temp for printing
dunno what you mean by "soft issue", and unless the thermistor is connected to the rpi it isn't that either
sorry, I meant software, like a conf or something related to code
Have you selected the correct thermistor?
I tried with 2 different ones, the one from rapido, and the one for mosquito. Each time reading the package and double checking on the configurator.
The story is, I had a running printer with RatOS 1, but the part cooling fan was not properly recognized. Since it went super well on the VC4.0 I bought, I figured that I could update the printer. I wired things exactly the same, and installed RatOS 2.
I'm not saying it must be that, but I'd like to know if it could.
I'm going to test everything we've talked about tomorrow anyway. It's just to get a grasp on the machine.
Might be worth trying to select other thermistors in the configurator and see if any give the right number back :/