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Thermistor Stops Reading at 185c

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    Thermistor Stops Reading at 185c

    Well I finally got my new control board, hot end, and aluminum heated print bed. (Haven't been on here in a while because it's taken me all damn year to get all the parts.)
    Got it all together, and most of it works, but I'm still having trouble with ABS printing.
    Before I calibrate the steppers, I need to make sure the thing will even extrude plastic, and it's not.
    My thermistor is accurate up until about 185c, but then it stops reading.
    The hot end will go up to 250c no problem (using a candy thermometer to calibrate) but the on-board thermistor only reads up to 185.
    I've done PID calibration, which helped it get to 185 faster and more smoothly, but it still only reads until that point.
    I've ordered a different thermistor already just in case I can't solve this in software, but then I'll just be waiting even longer to start printing again.
    I hope somebody can tell me that I'm just stupid and I'm not seeing the obvious solution here.

    #2
    What is the spec of the thermistor? 10k @25 or 100k @25 degrees?

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      #3
      It's listed as an NTC 100k. The M105 readings are inconsistent for some reason, despite the temp being accurate until 185c.
      I'm on a Mega 2560, RAMPS 1.4
      Additionally if you have any advice on the X axis not working at all, and the Y homing moving the z motor, but direction controls not doing anything on either X or Y, that's my newest issue.
      The Z axis works just fine, and independently the motors all work fine.

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        #4
        I've just gone through the setup of my printer which uses a Ramps board, have you checked your configuration.h file, I found that if the end stops are configured wrong then the axis wouldn't move because it thought the end stop was triggered, the end stop may need to be inverted?

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          #5
          Best I've gotten is the Z stop works perfectly, the Y home function still moves the Z motor, but stops when I press the Y stop, and the X does nothing.
          EDIT: Well I figured out my stepper problem. The kit I bought has 2 dead stepper drivers, yay.
          SO I have to buy some new ones for that now.
          Still have thermal problem though, so any help would still be appreciated.
          Last edited by Inventor; 08-28-2017, 07:01 PM.

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            #6
            Good news you sorted the steppers, the thermistor .... is it inserted into the heater block correctly? slave in another thermistor? take it out and heat it with a soldering iron?
            Just some thoughts

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              #7
              Figured out the thermistor. Turns out the resistance table for the closest match was for a heated bed, and the readings only went up to 180. So I had to do some maths and some testing and I got it up so it reads accurately up to 245.
              It's a little rough, but it works.
              This victory would be more satisfying if I didn't have 2 dead stepper controllers and have to wait for new ones, but at least now I know how to do this if I have to later.
              Attached Files

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                #8
                Good you fixed the issue and learned some things alot the way

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                  #9
                  Yes indeed. Hopefully the thermistor I have coming in the mail won't need this, but if it does, at least now I know how to.
                  If not for my two dead stepper controllers I'd be printing some upgrades for my printer right now.
                  Oh well, c'est la vie...

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