Hotend thermistor issue

General Discussion
1

Basic Information:

Printer Model: Voron 2.4
MCU / Printerboard: Manta M8Pv2
Host / SBC: CB2
klippy.log

Hi everyone
I’ve just build a Voron 2.4 and now i am on the configuration.
But i have a problem with the temperature of the hotend.
I use the Phateus Rapido V2 HF hotend, the thermistor is a PT1000. But the displayed temperatur is (when its off) always around 30deg. The roomtemp is something around 20deg.
My config:

[extruder]
.....

sensor_type: PT1000
sensor_pin: EBBCan:gpio27
....

The sesonr is connectet to the SB2209(RP2040)

Any ideas?
Thank you!

2

Please attach the klippy.log (as it was requested) to your next post. Maybe there is something to find in other parts.

3

Thanks for your reply.
Sorry for that. I will upload it when i’m at home.

1 Like
4

klippy.log (71.3 KB)
Well, here’s my klippy-log.
Thank you!

5

As far as I can see you connected your PT1000 like a normal NTC thermistor.
That means its resolution is limited, by ADC resolution and a reference resistor (4.7k).

This is not my calculation, but I hope they will give some idea of available resolution:

image
image1059×767 122 KB

So, around 30 degree it will have resistance ~1100ohm.
So, according to calculations will give you signal around 0.0013 V/C.
With 12bit adc those should give you a precision around 0.0008 / 0.0013 = 0.615C degree per bit.

There are RP2040 errata: RP2040-E11
Because of it the real usable resolution can be as low as 8.7 bits.
With approximation 0.615 * 8 (3bits) = 4.9C error.

So, probably you just hit one of those points, where resolution is biased, or you need to try to measure everything (and reference resistor with pretty high precision) and then you can get slightly better output.

Or you can just use it at expected working range and measure how it is behave at printing temperature, as said above on average there will be a resolution less then 1 degree.

Hope it helps.

6

Thank you very much!!

A few minutes ago, i’ve found the solution on the “official” voron-forum.
Link: https://forum.vorondesign.com/threads/bbt-sb2209-pt1000-problem.1184/

This config work for me (but i will confirm the temps anyway) :

# Sensor Hotend
sensor_type: MAX31865
sensor_pin: EBBCan:gpio9
spi_software_sclk_pin: EBBCan:gpio10
spi_software_mosi_pin: EBBCan:gpio8
spi_software_miso_pin: EBBCan:gpio11
rtd_nominal_r: 1000
rtd_reference_r: 4300
rtd_num_of_wires: 2
rtd_use_50Hz_filter: True

But thank you anyway for your research!

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7

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