E3d Revo Thermistor Incorrect Suddenly

bhanan

Hello,
I have a Mini 5+ installed on a Prusa mk2s with a bondtech i3 extruder and an e3d Revo hotend. It was functioning fine until I left it off for a couple weeks. When I turned it back on my hotend thermistor is reading ~90c consistently, even though the bed thermistor is reading room temp, around 20c. I haven't changed anything in the config files, and according to everything my config file is correct? Here is the gcode that I believe corresponds to that thermistor.

; Hotend heater
M308 S1 P"temp0" Y"thermistor" B4725 C7.060000e-8 ; configure sensor 1 as thermistor on pin temp0

I have tried a new revo heater cartridge/thermistor and it behaves the same. What am I missing?

droftarts

@bhanan try adding T100000 to the M308 line, eg:

M308 S1 P"temp0" Y"thermistor" T100000 B4725 C7.060000e-8 ; configure sensor 1 as thermistor on pin temp0

Ian

bhanan

@droftarts I tried this with no luck, it still shows incorrectly. Also, just to add to this, when I attempt to heat it up it obviously does not heat up enough to melt the filament, but the curve is smooth and it hold temperature without any of the drops and spikes that I usually see with a failing thermistor.

dc42

@bhanan do you have a free thermistor input on the Duet? If so then try making the thermistor connection to that one and adjusting the M308 command in config.g accordingly.

bhanan

@dc42 I believe I do. I will try that and get back to you, thank you!

bhanan

@dc42 I do not have a spare but I used the bed heater input as a test and it reads correctly on that input, including reading temp increases from holding it in my hand. When I unplug it from the bed input and plug it into the hotend thermistor input it immediately jumps to the abnormally high temp. Here is the code I see in my config.

; ##### Heaters
; Bed Heater
M308 S0 P"temp1" Y"thermistor" B4725 C7.060000e-8 ; configure sensor 0 as thermistor on pin temp1
M950 H0 C"out0" Q25 T0 ; create bed heater output on out0 and map it to sensor 0, PWM frequency: 25Hz
M307 H0 R0.262 C338.0 D10.52 S1.00 V11.8 B0 ; Bed tuning values, enable PID
M140 H0 ; Bed uses Heater 0
M143 H0 S120 ; Set temperature limit for heater 0 to 120C Bed
; Hotend heater
M308 S1 P"temp0" Y"thermistor" B4725 C7.060000e-8 ; configure sensor 1 as thermistor on pin temp0
M950 H1 C"out1" T1 ; create nozzle heater output on out1 and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit
M143 H1 S295 ; set temperature limit for heater 1 to 295C
M302 S170 R170

Phaedrux

When and where did you purchase the mini5?

Did you change your configuration when you swapped it to the bed temp input?

bhanan

@Phaedrux I did not change any config when I swapped inputs. I purchased it from Filastruder in August 2023,