100 ohm resistor

This topic contains 5 replies, has 3 voices, and was last updated by Profile photo of cave cave 8 months ago.

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  • #17114
    Profile photo of Oscar
    Oscar
    Participant

    Hey guys im building a mpcnc right now and im wondering, why do i need the 100ohm resistor and/or would it work with a 220 ohm one?
    I’ve heard that you don’t need it if you are only planning to use it as a cnc router (which i am), and that you can just change something in the marlin firmware.

    #17115
    Profile photo of Ryan
    Ryan
    Keymaster

    220 won’t work, pretty sure unless you change the thermistor value in the firmware. I think it would read too high of a temp.

    The firmware change is easy, under thermister we have number 11, you just change it to a zero I believe and reflash it. There are actually notes in the firmware file. You might also need to disable temp checking in repetier if you do this.

    #17117
    Profile photo of Oscar
    Oscar
    Participant

    Thanks for the fast reply, i will test the firmware change. Better than buying a set of resistors.

    #17119
    Profile photo of Ryan
    Ryan
    Keymaster

    Sorry for being lazy and not looking at the firmware, I was having my first cup of coffee.
    You can change this line
    #define TEMP_SENSOR_0 11

    To either 0 (not used) or the new firmware has a 998 (always show 25C) 998 would be best!

    #17121
    Profile photo of Oscar
    Oscar
    Participant

    It’s ok I completely understood your first reply.

    #21363
    Profile photo of cave
    cave
    Participant

    Not 100 ohm.
    100,000 ohm (100K).

    I used a plug from one of the stepper driver cables and soldered the resistor to the shortened wires, a bit fiddly but better than soldering directly to the header pins on the board.

    But the firmware isn’t that scary to adjust, if you prefer.

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