Temperautre Defective at -50.88oC

edited November 2014 in Extruder & Bed
Hi All

I have a slight issue with trying to sense temperature and was wondering if anyone can please help.

I have a J Head with temp sensor in, this is an epocs sensor.

Resistance reading: around 100k
V reading out the T pins: around 4.5 to 5

When i heat up the temp sensor it changes the resistance also the voltage from the pins. That should mean that everything is working well, however on my software i am getting a reading of -50.88 degrees C

Please may someone help me fix this issue.

I have an Arduino mega with Ramps 1.4 using repetier firmware and host

Kind Regards


  • Make sure you have selected the right sensor type. If it doe snot change with heating extruder, the sensor pin in firmware does not match the pins where you connected.
  • hmm, I have tried a few different sensor types. What pin on the arduino does repetier look at for T0 please? I will try plugging it directly into there as a test.
  • T0 would be TEMP_0_PIN = analog pin 13. Be aware that T0 has an 4,7K resistor between 0v and 5v in addition to your thermistor.
  • OK well i have tried all of the above, and all i get is the minimum temp i set the thermoster to have, I have tried doing a generic table, working out my beta and testing, still not working. my thermistor definitely works. Is there something stupid that I am doing?

    I have tried using analogue 3 off to the side of the board too which also does not work.

    I must be doing something really wrong nobody else seems to get this same problem.

    It would be brilliant if someone could take a look at my code and check to see what I am doing wrong.


    Any help would be much appreciated. This the last hurdle to getting my printer extruding as everything else works.

  • Oh, I dont get -50.88 now  I usually get whatever the thermisters lowest value is on the settup. i.e. -20. This can also be held at 0.0 depending on which thermister i select. but none of them not even my custom tables actually give me a value that changes.
  • You can send 

    M105 X0

    tehn you see also the raw values. I guess they are 0 or 4095 every time meaning no sensor is attached to the pin you said it should read. The pin is defined by


    or whatever you selected there. Be aware to use an analog pin number, not a digital one.
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