Slice Engineering High Temperature Thermistor issue  

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justin.g11
(@justin-g11)
New Member

Hi all. Just upgraded my MK2.5s with the bondtech multi-geared extruder and the Mosquito hotend (with the high temperature thermistor and 50W heater cartridge). Have successfully built everything, calibration is perfect, upgraded the firmware to the relevant bondtech/mosquito/ht v3.8.1 from Bondtech's website. Nozzle temperature is reading 60C at ambient room temperature. I've tried a PID calibration - no effect. Thermistor resistance is about 500K ohms at room temp which is about right for that thermistor according to the Slice Engineering RT table. My only thought is that the firmware is using the wrong temperature table, but I don't know how to check. Any thoughts?

 

Posted : 18/04/2020 8:26 pm
charles.h13
(@charles-h13)
Famed Member

Did you adjust the temperature table for the thermistor?  

Posted : 18/04/2020 10:53 pm
Karl Herbert
(@karl-herbert)
Famed Member
Posted by: @justin-g11

Hi all. Just upgraded my MK2.5s with the bondtech multi-geared extruder and the Mosquito hotend (with the high temperature thermistor and 50W heater cartridge). Have successfully built everything, calibration is perfect, upgraded the firmware to the relevant bondtech/mosquito/ht v3.8.1 from Bondtech's website. Nozzle temperature is reading 60C at ambient room temperature. I've tried a PID calibration - no effect. Thermistor resistance is about 500K ohms at room temp which is about right for that thermistor according to the Slice Engineering RT table. My only thought is that the firmware is using the wrong temperature table, but I don't know how to check. Any thoughts?

 

Depending on the thermistor used, you have to use the correct table in thermistortables.h. You may have to create a new table. The entry (tablenumber) is to be changed in Configuration_prusa.h (#define TEMP_SENSOR_0).

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 19/04/2020 12:43 am
justin.g11
(@justin-g11)
New Member

@karl-herbert

Having dug through the code, I can see from the variants\1_75mm_MK25S_Bondtech-RAMBo13a-SliceE_HT-Mosquito.h file:

#if defined(E3D_PT100_EXTRUDER_WITH_AMP)
#define TEMP_SENSOR_0 247
#elif defined(E3D_PT100_EXTRUDER_NO_AMP)
#define TEMP_SENSOR_0 148
#else
#define TEMP_SENSOR_0 800
#endif

and have confirmed that it is using TEMP_SENSOR_0 = 800 (based on checking the default PID settings defined in the firmware using M503).

And the thermistortable.h file contains:

#if (THERMISTORHEATER_0 == 800) || (THERMISTORHEATER_1 == 800) || (THERMISTORHEATER_2 == 800) || (THERMISTORBED == 800)
const short temptable_800[][2] PROGMEM = {
// R25 =500 KOhm, beta25 = 3800 K, 4.7 kOhm pull-up, Slice engineering 450c
{22*OVERSAMPLENR,500},
{23*OVERSAMPLENR,490},
{25*OVERSAMPLENR,480}, ....

I don't understand what the x-axis values are (the y-axis is clearly temperature) and how these correspond to the resistance values on the RT chart. However, I guess that these values are incorrect? I'm going to reinstall the old E3d thermistor and see how the temperature reads.

 

Cheers

Justin

Posted : 19/04/2020 12:12 pm
justin.g11
(@justin-g11)
New Member

I'm not the only person with this issue. Seems to be a problem with the BondTech firmware:

 

https://github.com/BondtechAB/Bondtech_Prusa_i3/issues/12

Posted : 19/04/2020 12:53 pm
Karl Herbert
(@karl-herbert)
Famed Member

@justin-g11

include this in thermistortables.h and change to nr. 248 in Configuration_prusa.h:

#if (THERMISTORHEATER_0 == 248) || (THERMISTORHEATER_1 == 248) || (THERMISTORHEATER_2 == 248) || (THERMISTORBED == 248) // Mosquito 500k high temp thermistor - not tested, no guarantee
const short temptable_248[][2] PROGMEM = {
{ 22*OVERSAMPLENR , 500 },
{ 23*OVERSAMPLENR , 490 },
{ 25*OVERSAMPLENR , 480 },
{ 27*OVERSAMPLENR , 470 },
{ 29*OVERSAMPLENR , 460 },
{ 32*OVERSAMPLENR , 450 },
{ 35*OVERSAMPLENR , 440 },
{ 38*OVERSAMPLENR , 430 },
{ 41*OVERSAMPLENR , 420 },
{ 45*OVERSAMPLENR , 410 },
{ 50*OVERSAMPLENR , 400 },
{ 55*OVERSAMPLENR , 390 },
{ 60*OVERSAMPLENR , 380 },
{ 67*OVERSAMPLENR , 370 },
{ 74*OVERSAMPLENR , 360 },
{ 82*OVERSAMPLENR , 350 },
{ 91*OVERSAMPLENR , 340 },
{ 102*OVERSAMPLENR , 330 },
{ 114*OVERSAMPLENR , 320 },
{ 127*OVERSAMPLENR , 310 },
{ 143*OVERSAMPLENR , 300 },
{ 161*OVERSAMPLENR , 290 },
{ 181*OVERSAMPLENR , 280 },
{ 204*OVERSAMPLENR , 270 },
{ 229*OVERSAMPLENR , 260 },
{ 259*OVERSAMPLENR , 250 },
{ 290*OVERSAMPLENR , 240 },
{ 325*OVERSAMPLENR , 230 },
{ 364*OVERSAMPLENR , 220 },
{ 407*OVERSAMPLENR , 210 },
{ 453*OVERSAMPLENR , 200 },
{ 501*OVERSAMPLENR , 190 },
{ 551*OVERSAMPLENR , 180 },
{ 603*OVERSAMPLENR , 170 },
{ 655*OVERSAMPLENR , 160 },
{ 706*OVERSAMPLENR , 150 },
{ 755*OVERSAMPLENR , 140 },
{ 801*OVERSAMPLENR , 130 },
{ 842*OVERSAMPLENR , 120 },
{ 879*OVERSAMPLENR , 110 },
{ 910*OVERSAMPLENR , 100 },
{ 936*OVERSAMPLENR , 90 },
{ 948*OVERSAMPLENR , 85 },
{ 958*OVERSAMPLENR , 80 },
{ 975*OVERSAMPLENR , 70 },
{ 988*OVERSAMPLENR , 60 },
{ 998*OVERSAMPLENR , 50 },
{ 1006*OVERSAMPLENR , 40 },
{ 1011*OVERSAMPLENR , 30 },
{ 1013*OVERSAMPLENR , 25 },
{ 1015*OVERSAMPLENR , 20 },
{ 1018*OVERSAMPLENR , 10 },
{ 1020*OVERSAMPLENR , 0 }
};
#endif

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 19/04/2020 3:31 pm
justin.g11
(@justin-g11)
New Member

Urgh. Reminds me again why I hate C. The chart you posted is the same as the one in the BondTech github, but for ID 800. I have a feeling the actual values are incorrect.

I've swapped the HT thermistor out for the old E3D one and flashed the relevant software. I'll wait for BondTech to fix their firmware.

 

Cheers for your help.

Posted : 19/04/2020 4:00 pm
zoltan
(@zoltan)
Member Moderator

In reality you do not need such a long thermistor table, when you are not using temperatures higher than 300°C. You can skip lines between 310 °C and 490°C. Line with temp 500 you can keep when Marlin is checking for security reason your thermistor is not shortcut. 

even an old man can learn new things 🙂
Standard I3 mk3s, FW 3.9.0, no closed box, sketchup , fusion 360, PrusaSlicer, Windows 10
PRUSA MINI FW 4.1.0, technical background...
Posted : 19/04/2020 4:19 pm
Karl Herbert
(@karl-herbert)
Famed Member

@justin-g11

Alternatively, you could use a pt100. There are temperature tables for this and they also fit. I have installed a pt100 upgrade, but i need this high temperatures only for printing PEEK.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 19/04/2020 5:01 pm
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