Rostock MAX Thermistor calibration

[BlindDevil]

I'm working through a few issues but first things first.
With no thermistors connected, temperatures on extruder reads 244.58 degrees C and Bed reads 89.88 degress C.
Plugged thermistors back in and no change in temperature readout.
Started PID calibration with M303 S200 and it fails with temperature too high.
Started calibration again M303 S250 and the line wiggles but no change.
Room temperature is in the high 70s.
Checked continuity to both thermistors and resistance is around 85kohms.
Checked voltage on extruder power and it's same as 12V supply.
Extruder does start to warm on the M303 test.
Checked voltage on bed power and it is 0V no changes.
Same results on Repetier-Host Mac 0.56 and Repetier-Host Windows 0.90C
Same results with Repetier-Firmware 0.71 an 0.83
LCD display lit but just blinks on then off on uploads.

[Jimustanguitar]

If the display doesn't show a difference between the thermistor being plugged in and not being plugged in at all, it sounds like you have a wiring problem.

Are you getting that 85k Ohm reading at the far end of the wires where they're connected to the Rambo?

[johnoly99]

Blind

It sounds like you either have shorted out the thermistor inputs on the RAMBo via the hotend wiring, or you have the wrong board type or thermistor config in the firmware. That's the only two ways that can happen?

[BlindDevil]

Are you getting that 85k Ohm reading at the far end of the wires where they're connected to the Rambo?

I took the resistance measurement both at the thermistor ends and at the end of the lines.

[BlindDevil]

Blind

It sounds like you either have shorted out the thermistor inputs on the RAMBo via the hotend wiring, or you have the wrong board type or thermistor config in the firmware. That's the only two ways that can happen?

if it were a short in the wiring, shouldn't there be a change in the chart values plugging it in and out?

I'll look at the firmware for the thermistor definition.

[BlindDevil]

Update: 100K Thermistor is correctly selected in Repetier firmware. Still not calibrating or reading correct temperature.

[BlindDevil]

Update:
Was able to turn on bed and run M303 calibration targeting 95 degrees but temperatures are still out of range.

Reran extruder calibration and rechecked wiring; values still flat, so i think the circuitry on the board is bad or not configured correctly.

what voltage should i expect on the outputs applied to the thermistor?

[lordbinky]

You may want to try remounting the thermistors to with super-extra-uber care for good clean contact with the hotend and bed. Really, be careful because those thermistor leads are waiting and hoping for an excuse to break.

edit: If you do go that route, you might want to try and see if you can get a proper response /see a change between body temp, room temp, and an ice cube while you have the thermistors free.

[Jimustanguitar]

If you remove the thermistor to re-mount it, screw its leads directly into the Rambo to see what that does.

[BlindDevil]

UPDATE:
checked over the extruder wiring and confirmed a resistance measurement at the connector into the board.
board shows a voltage of 200mV on the connector.

put some OUT_P_I inside the raw and converted temperature routines to monitor the ports.
confirmed extruder does warm up but no temperature reading/change.

Configuration.h defines:

Code: Select all

#define EXT0_TEMPSENSOR_PIN TEMP_0_PIN

pins.h defines:

Code: Select all

#define TEMP_0_PIN     0

is this correct?

i was wondering how i could get the extruder to use the same temperature table as the heated bed since that one is closer but I don't quite know how that is configured.