100k NTC 3950 thermistor as option

Comments

• Repetier

  February 2016

  I have added it as type 14.
• madias

  March 2016

  Thank you very much!
• QJNeo

  September 2017

  The table won't work for me, that's a 40C different for 260C
  
  Here's my experiment from the same thermostat, which I bought from Aliexpress, stated as 100k NTC 3950 too.
  The temperature is +/- 5C from true value(in my case) above 180C.
  I highly suggest using a thermocouple on multimeter to calibrate your thermostat.
  Here's my reference:
  http://reprap.org/wiki/RDB_calibrations
  
  The purchase link is at the bottom.
  
  Temperature (C), Ohm
  
  
  https://www.aliexpress.com/item/FreeShipping-Long-distance-3D-Printer-J-head-Hotend-for-1-75mm-3-0mm-E3D-Bowden-Extruder/2041826923.html?spm=a2g0s.9042311.0.0.ZDC8F3
  
• Repetier

  September 2017

  NTC 3950 is just a generic curve according to a certain formula. They are normed at 25°C having 100K resistance. The further you come away from this position, the bigger the errors may come. Even for quality thermistors where they give you the formula parameters their datasheet shows a deviation.
  
  So yes, NTC 3950 thermistors are just a cheap solution to spare a correct datasheet for all temperatures and depending on the source they may also vary in how they react at these temperatures. In addition there are also tolerances and 5% tolerance means at 300°C an error of up to +/-15°C would be possible.
• Marcus

  December 2017

  i have the same thermistor and repetier shows me 162 degrees at my extruder with no heating 
  i cant find any mistake 
• Repetier

  December 2017

  Is it connected to a thermistor input or wrongly on a thermocouple input?
  
  What resistance does it have at room temperature. Should be around 100K (for 25°C).
• Cheddy

  February 2018

  I also have a generic NTC 3950 thermistor that is reading 200C, but thermocouple measurement inside the heater block shows only 168C. I will try it with the table values suggested by QJNero above.
  
• Marco67

  October 2018 edited October 2018

  There's a simple solution for this, implemented in MarlinKimbra firmware, i hope soon a similar solution in Repetier:
  
  

  M305 - Set thermistor and ADC parameters: H[heaters] H = 0-3 Hotend, H = -1 BED, H = -2 CHAMBER, H = -3 COOLER,
   *          A[float] Thermistor resistance at 25°C, B[float] BetaK, C[float] Steinhart-Hart C coefficien, R[float] Pullup resistor value,
              L[int] ADC low offset correction, O[int] ADC high offset correction, P[int] Sensor Pin

  With "M305 B4250" now i've not over 2° of error from 190 to 250°.
  With Repetier firmware i read "210°" in the display but the nozzle is at 187!!!!!
  
• david_h

  August 2020

  Repetier said:

  I have added it as type 14.

  Hi, Is it possible to get the data file for this thermistor please?
  
  
  
• Repetier

  August 2020

  From Extruder.cpp
  
  

  #define NUMTEMPS_14 46

  const short temptable_14[NUMTEMPS_14][2] PROGMEM = {

  { 1 * 4, 8 * 938 }, { 31 * 4, 8 * 314 }, { 41 * 4, 8 * 290 }, { 51 * 4, 8 * 272 }, { 61 * 4, 8 * 258 }, { 71 * 4, 8 * 247 }, { 81 * 4, 8 * 237 }, { 91 * 4, 8 * 229 }, { 101 * 4, 8 * 221 }, { 111 * 4, 8 * 215 }, { 121 * 4, 8 * 209 }, { 131 * 4, 8 * 204 }, { 141 * 4, 8 * 199 }, { 151 * 4, 8 * 195 }, { 161 * 4, 8 * 190 }, { 171 * 4, 8 * 187 }, { 181 * 4, 8 * 183 }, { 191 * 4, 8 * 179 }, { 201 * 4, 8 * 176 }, { 221 * 4, 8 * 170 }, { 241 * 4, 8 * 165 }, { 261 * 4, 8 * 160 }, { 281 * 4, 8 * 155 }, { 301 * 4, 8 * 150 }, { 331 * 4, 8 * 144 }, { 361 * 4, 8 * 139 }, { 391 * 4, 8 * 133 }, { 421 * 4, 8 * 128 }, { 451 * 4, 8 * 123 }, { 491 * 4, 8 * 117 }, { 531 * 4, 8 * 111 }, { 571 * 4, 8 * 105 }, { 611 * 4, 8 * 100 }, { 681 * 4, 8 * 90 }, { 711 * 4, 8 * 85 }, { 811 * 4, 8 * 69 }, { 831 * 4, 8 * 65 }, { 881 * 4, 8 * 55 }, { 901 * 4, 8 * 51 }, { 941 * 4, 8 * 39 }, { 971 * 4, 8 * 28 }, { 981 * 4, 8 * 23 }, { 991 * 4, 8 * 17 }, { 1001 * 4, 8 * 9 }, { 1021 * 4, 8 * -27 }, { 1023 * 4, 8 * -200 }

  };
  
  that is what gets used for it.
• david_h

  August 2020

  thanks