Slice engineering/Mosquito hotend thermistor settings

hypnolobster

It's mentioned all over that the thermistor that Slice Engineering sells for the Mosquito has specific firmware requirements, and that it's an option in the reprap configurator. Am I missing something or is it not? There are a ton of options, but I can't find any information on which it would be as it's definitely not in there by name.

Weirdly, I also currently get -274c temp/fault. I'm hoping that's due to a setting rather than an issue with the thermistor.

; Heaters
M308 S0 P"temp1" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin temp1
M950 H0 C"out1" T0                           ; create bed heater output on out1 and map it to sensor 0
M143 H0 S120                                 ; set temperature limit for heater 0 to 120C
M307 H0 B0 S1.00                             ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0                                      ; map heated bed to heater 0
M307 H0 A115.0 C276.6 D1.5 V23.8 B0			 ; autotune result feb 28, 2020
M308 S1 P"temp2" Y"thermistor" T100000 B4138 ; configure sensor 1 as thermistor on pin temp2
M950 H1 C"out2" T1                           ; create nozzle heater output on out2 and map it to sensor 1
M143 H1 S320                                 ; set temperature limit for heater 1 to 320C
M307 H1 B0 S1.00                             ; disable bang-bang mode for heater  and set PWM limit

Currently wired as hotend on out2, thermistor on temp2. The bed and it's thermistor are functioning on out1, temp1

hypnolobster

update, I found this
https://forum.duet3d.com/topic/9755/heater-fault-slice-engineering-mosquito-magnum/7

and added various versions to my M308 line, and while it sort of works, it's a full 10c off. Currently using :

M308 S1 P"temp2" Y"thermistor" T500000 B4723 C1.196220e-7

and it's sitting around 10c vs my bed which seems accurate around 20.8c.

I'm also confused about M308 vs M305, because I'm not having success using M305 and removing the thermistor settings from M308.

matt3o

I have a slice thermistor too and my educated guess is that it's not reliable at (very) low temps. It makes sense being a thermistor for high temps. I added H6 option to add 6 degrees in the low end, but it's purely cosmetic.

I checked with a thermal camera and I'd say as soon as you reach 100C the reading is accurate.

dc42

@matt3o said in Slice engineering/Mosquito hotend thermistor settings:

I have a slice thermistor too and my educated guess is that it's not reliable at (very) low temps.

That's correct, high temperature thermistors have such a high resistance (typically 500Kohms at 25C) that with the usual thermistor reading circuits, the accuracy and resolution at low temperatures are very poor. You may even get "thermistor disconnected" errors when you start the printer on a cold day. The accuracy gets better at higher temperatures.

Some builds of RepRapFirmware support the H parameter for M305 or M308 commands. This can be used to adjust the reading at low temperatures.