thermocouple FAULT LED

  • Hey everyone!

    I have a problem. Before I connected my heat bed, all thermocouples ( seven in total on four daughterboards) worked well. After I connected the heated bed, all fault LEDs of the thermocouples started to shine.

    I removed all the thermocouples and connected them one by one and checked each one to see if it worked. The first and second one worked most of the time. I did many variation in the connection sequence, but anytime the fault LEDs started to shine.

    I hope you can understand my problem. It is difficult to describe.

    Thank you.

  • administrators

    The FAULT LED illuminated means that the chip on the daughter board was unable to read the thermocouple.

    What type of thermocouple are you using?

    Thermocouples must be insulated from any metal parts whose temperatures they are measuring. The thermocouple cartridges that E3D sells have insulation between the thermocouple junction and the outer casing, so they should work OK. Many other types of thermocouple don't have any insulation, just a bare junction.

    Another possible source of problems is the wring. Thermocouples are normally supplied with twisted pair wires, and these must be used right up to the daughter board. Using twisted pair wire minimises interference pickup by induction.

    The FAULT LED will also light up if the thermocouple is disconnected or broken.

    HTH David

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