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Accurate Table for 3950 Thermistor replacing Robo Thermistor

Discussion in 'Mods and Upgrades' started by Lance Weston, Oct 6, 2019.

  1. Lance Weston

    Lance Weston Active Member

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    I am using 3950 thermistors for my hotend and found tables from RepRap. I have included the tables for the original Robo thermostat and the RepRap 3950. I checked my hotend with a Fluke 189 and a type K thermocouple. Worst case error from 170C to 240C was 1.4C. This is better than the manufacturing tolerances and I was pleasantly surprised.

    If you are not comfortable inserting a table into the Marlin code then just remove an existing table an put this one in it's place. At the top of the table I have given the number 14. Change that to the table number you are replacing and rename to the replaced table name.
     

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    #1 Lance Weston, Oct 6, 2019
    Last edited: Oct 7, 2019
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  2. EmbraceNext

    EmbraceNext New Member

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    How do you go about doing this in marlin for a robo r2? I have done some firmware editing on an ender3 but never a robo r2. But absolutely would like to learn.
     
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Well, the Robo (all of them) use Marlin (R2/C2 -> 1.1 and R1 -> 1.0)

    The R2/C2 complicate this just slightly by having the controller connected to a Raspberry Pi (inside, under the deck). You can SSH to the Raspberry Pi, make sure VNC is running and then connect via VNC to the Pi operating system.

    Then install the Arduinio IDE on it and connect to the controller and load whatever changes you want.

    It is a little more complex simply because the Pi is there, but it is not hard.
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I actually have all of my FDM printers fronted with with a Raspberry Pi running OctoPi -- it is just the best way to use them.

    (one of the DLP printers uses a Raspberry Pi on the front-end as well and the other DLP printer uses some custom firmware they did for it that accomplishes the same thing)
     
  5. Lance Weston

    Lance Weston Active Member

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    Hi Mark,
    I have wanted to make changes to the R2 as well. Could we just use a long USB cable to a computer and run Marlin directly to the R2 mainboard?
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yes, if you unplug the pi and then plug in the USB cable from your PC and select ARDUINO MEGA 2560 as the board type it will work as well. However then you have to disconnect the computer and reconnect the Pi once you are done.

    It is easier (for me at least) to simply VNC to the Pi (a type of remote desktop) and then use the Arduino compiler on the Pi which is already connected to the controller. VNC software is available for the Pi and the PC or a Mac. Easy to install on the Pi as well since it is already bundled onto the OS -- you just activate it so that it runs on boot.
     
  7. Lance Weston

    Lance Weston Active Member

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    I have been loathe to install the latest/last Jason code because I did not know how to return if it had a problem. Do you know of anyone that has done it? Do you know how to save the existing code if we need to go back?
     
  8. Lance Weston

    Lance Weston Active Member

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    I have been loathe to install the latest/last Jason code because I did not know how to return if it had a problem. Do you know of anyone that has done it? Do you know how to save the existing code if we need to go back?
     
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    All you can do is download previous versions from Robo () and then reload them.
    The binary/compiled data loaded over is not easily accessible.
    Robo would sometimes host HEX files... like here:

    https://help.robo3d.com/hc/en-us/articles/115000722572-How-to-update-R2-firmware

    which could then be loaded from the LCD front-end.
    If you want to customize it you could do it that way and compile/save HEX file on a PC/Mac and then load that over via the LCD.
     
  10. Lance Weston

    Lance Weston Active Member

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    I had no idea that I could do that. I have compiled a hex code of R2 with the 3950 thermister on the hotend using the last code Jason sent me:
    https://drive.google.com/open?id=1L-QN3e3FZD8jxy02a0ITAxBg5rGRlb5s

    If I am correct I could just put that hex file on the jump drive and update. I also downloaded the Robo R2 file from Robo. If I am correct I could use that to restore if there is a problem.

    Am I correct?
     
  11. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    You are correct sir :)
     
  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    For what it is worth that will not (as far as I know) reset the flash EPROM contents so parameters you have stored there (Z offset is a famous one, there are others) will NOT get reset when you reload the firmware. Normally this is a good thing, just as long as you are expecting it :)
     
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  13. Lance Weston

    Lance Weston Active Member

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    when current print is finished I will install update and report back.
     
  14. Lance Weston

    Lance Weston Active Member

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    The good news is that the files I posted are the latest ones that Robo released and they downloaded and worked from the LCD. To my surprise there was very little difference between the two curves as measured. The 3950 curve consistently had the hotend 2% higher than the display. The Robo epcos curve ran 3% higher than the display in a small range 2% higher in the rest. 2% and 3% are well within the tolerances of the parts. I see no reason to implement the 3950 curve for 1% more accuracy in a tiny range.

    The results do not reflect expected results so I reloaded and measured twice as a sanity check.
     
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