Generic 3950 Thermistor not working when attached to toolboard

General Discussion
1

Basic Information:

Printer Model: CUSTOM
MCU / Printerboard: LY-DP5
Host / SBC: Rpi2b
klippy.log
klippy (5).log (2.8 MB)

Working config/thermistor changed to incorporate new toolboard leads to no thermistor reading

My thermistor was working fine plugged into the mcu DP5 directly. Ive plugged it into a newly installed SHT36-V3 toolboard, and changed the sensor pin in my printer.cfg and regardless of whether the thermistor is plugged into the new board or not, the temperature reads -30c ish in mainsail. I’m operating the fans from the SHT36-V3 suggesting the new board is communicating correctly with the mcu.

I’ve put the schematic for the temp sensor side-by-side below from the two boards, in the hope that someone a bit more knowledgeable can spot the difference and if/how my config needs to change further.

I note that the capacitors are different sizes and that, ADC_POWER is not defined, so could be different to the 3.3v on the DP5 mcu board? It is a 12v system currently. I don’t have the j7 jumper installed, so the in-series pull-up resistance is 4.7k ohm in both cases. The gpio27 pin address is correct according to the boards drawings and example config.

[extruder]
#sensor_pin: HEAT0_TEMP
sensor_pin:SHT36:gpio27
sensor_type: Generic 3950

image
image501×316 11.7 KB

2

Ah - i just plugged it back into the DP5 mcu to check the thermistor was still working. it did not. Does this mean i need a new thermistor, is there a way to test it? Any idea what went wrong?

3

It is not uncommon for thermistors to fail. It could also be the cable, especially at or in the connector.

4

Thanks i checked the one on the bed by measuring the resistance across it and saw a reasonable reading. I did the same on the extruder one, and got no reading. So i think its pretty conclusive that i must’ve broken the cable internally somehow when fitting it. Fat fingers. Replacements arrive tomorrow.