Davinci Pro 1.0 Bed Thermister

dpmanter

Hello looking for help with the bed thermistor of the Davinci Pro and Duet3d WiFi. The temp is reading 2000 C. I have traced all the wires and tested VSSA fuse.

VSSA to Ground = < 5 Ohm
Resistance of thermistor = 430 kOhm at 20 C

Here is my config.g
; Heaters
M305 P0 T100000 B3950 C0 R4700 ; Set thermistor + ADC parameters for heater 0
M143 H0 S120 ; Set temperature limit for heater 0 to 120C
M305 P1 T100000 B4388 C0 R4700 ; Set thermistor + ADC parameters for heater 1
M143 H1 S280 ; Set temperature limit for heater 1 to 280C

What am I missing?

Thanks.

T3P3Tony

@dpmanter 430k is high for a 100k thermistor. Is that right, you are using a 500k thermistor? If it's correct then you need to adjusts the T parameter to match, and 500k is very high so it might read open circuit at lower temperatures

Do you have the datasheet of the thermistor?

dpmanter

Thanks @T3P3Tony

I set the thermistor to M305 P0 T400000 B3950 C0 R4700
and now it reads 21.5 C. Measure the bed with Infrared Thermometer and that reads 21.8 C. All is right with the world.

I wish XYZPrinting listed more info about the components in their printers.

uli

For your information:
In monitor mode of the da Vinci 1.0 Pro I got:
330k-->29°C
99.8k-->62°C
46.9k-->96°C
With these data the RRF configuration tool calculated:
R25: 388403 Ω
β: 3670 K

Best regards

Uli