Monday, February 8, 2010

MAX6675 Thermocouple Digital Interface



Here's my MAX6675 hooked up and talking to my arduino via SPI. It reports the temperature of the thermocouple every 1/4th of a second with a precision of 0.25 degrees and an accuracy of about 2 degrees. This particular thermocouple may prove a bit awkward for my extruder, but I haven't yet found any bead-ended ones that could handle more than 250 celsius locally.

Code is in my github repository, and there are also some notes on the wiki about how to adapt this to a reprap extruder controller board.

In other news, my FiveD on Arduino project is coming along nicely. It's at the stage where I need to complete my mechanical construction and start testing with an actual machine. Feel free to help me on that score ;)


  1. 2°C accuracy should work but it is definately not good enough for a good extruder.
    I don´t suppose they make ones with 1 °C or 0.5°C accuracy?

  2. Marcus, I think it's pretty good considering the thermocouple puts out just 41uV per degree, and that all the more accurate methods I have available don't work above about 150 celsius.. will have to see if it's accurate enough, and what forms the innacuracy takes

  3. I think that slight variations in placement of the thermocouple will have a bigger impact on the accuracy... 2'C seems to be enough. I have different extruders that need a different temperature setting to get the same results, ideally they would be the same, but you can manage since you already have to adjust the temperature experimentally.

  4. Magnificent soldering skills with your prototyping method.. I'm playing with thermocouples right now I have the original RepRap thermocouple board thou.

    Playing with PID control of bed and extruder temperatures. Great work..