My Stoopid Stuff
  • Home
  • Projects
  • Blog
  • Lec'tronics
  • Links
  • CNC
  • Quick Recipes
  • 3D Printer Tips

Testing a Thermistor Input on an Ender3 and CR10S Pro

7/31/2020

0 Comments

 
INFORMATIONAL ONLY - if you try this, it is at your own risk.

I do not recommend doing this, I only did this myself out of curiosity and to help a user on Thingiverse.com who had tested or swapped all the usual suspects but found his thermistor was never reading above 150C - which caused a thermal runaway situation which the firmware could not detect (very dangerous).  It's a really odd problem since the person had checked the resistance through the entire wiring on the thermistor down to the ribbon connector on the board side and it all checked out.  He was pretty much out of options and was about to plop down 80 bucks or so on a replacement board which may have been inevitable anyway.  I don't know what the result of his efforts was, but hope he got it sorted out.  In any case, I was trying to think of another way to test the input on the board itself, and thought of replacing the 100K Ohm thermistor with a 100K Ohm potentiometer, which after doing some searching is not a novel idea.  This would rule out any issue with the thermistor and I'd be able to control the voltage that the thermistor input detected directly using the potentiometer (for testing only).  I'm no expert on this stuff, but from my understanding, the ramps based boards out there just use a simple voltage divider, with a 4.7KOhm resistor on the upstream leg and the thermistor on the downstream leg going to an ADC input to the board.  I've used this setup in a couple of projects to control ADC inputs with a potientiometer or resistors, and don't know of another way to do it really.

The test setup worked, but in practice it did not work well since I used a "linear taper" potentiometer, where the thermistor is not linear in it's rate of change to temp.  In other words it was sketchy when I adjusted the potentiometer above about 160C as the displayed temp.  I think an "audio taper" potentiometer would have been better for this.  Because my printers use a 100K NTC thermistor I tested with a 100K Ohm potentiometer.

Below are some pics of the setup I used for this test.  The first set is from the Ender3 and the 2nd is from the CR10S Pro.  On the Ender3 I just unplugged the original thermistor and swapped in the 100K Ohm potentiometer in it's place using some dupont jumpers.  I first set the potentiometer to around what my thermistor read at room temp (which was around 90Kohms) so when it was connected it would not trigger any thermal protection on the printer when I first tried it.


The CR10S Pro was trickier since the thermistor connects to a breakout board, and the dupont connectors did not fit (too large).  Here I took a fan connector I had and just shoved the wires into the mini breadboard I was using the the potentiometer.  It worked but was a bit clumsy, since I also jammed a couple jumpers in the breadboard to help hold the wires from the connector.  As with the Ender3, I preset the potentiometer to around 90K Ohms before setting it up.  On the CR10S Pro I noticed what is probably a software difference because adjustment of the potentiometer could cause the display to show -10C if I went to quickly which was easy since after 160C or so it was just a hairs breath of change needed to move the temps greatly (since it is a nonlinear scale and I used a linear pot).  Still I was able to get it to read 185C and as high as 300C even as touchy as the adjustment was.  When I put it back together I screwed up through and installed the thermistor in the connector which is one back from where it should have gone.  Once I fixed that though it worked as before.
This really proves nothing but I thought it was an interesting thing and may help me with testing thermistor inputs should the need arise.
0 Comments



Leave a Reply.

    Picture

    Stoopid Me

    Welcome to my Stoopid corner of teh Internet.  It's mostly gonna be 3D printing stuff, but I also post some recipes, projects, and the occasional rant here as well.  More Stoopid stuff is updated regularly.

    I recently joined the Amazon Associate program, so some of the links on this site are Amazon affiliate links. This means that, at zero cost to you, I will earn an affiliate commission if you click through the link and finalize a purchase.  This will help to support this site, and pay for more Stoopid Stuff.

    Archives

    March 2023
    February 2023
    January 2023
    November 2022
    October 2022
    September 2022
    August 2022
    July 2022
    April 2022
    February 2022
    January 2022
    December 2021
    November 2021
    October 2021
    September 2021
    August 2021
    July 2021
    June 2021
    May 2021
    April 2021
    March 2021
    February 2021
    January 2021
    December 2020
    November 2020
    October 2020
    September 2020
    August 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    November 2017
    September 2017
    August 2017
    June 2017
    December 2016
    October 2016
    September 2016
    July 2016
    March 2016
    February 2016
    September 2015
    August 2015
    June 2015
    May 2015
    April 2015
    March 2015
    February 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    July 2014
    June 2014
    May 2014
    April 2014
    March 2014
    February 2014
    November 2013
    August 2013
    July 2013
    June 2013
    May 2013
    April 2013
    March 2013
    January 2013
    December 2012
    November 2012
    October 2012
    September 2012
    August 2012

    Categories

    All

    RSS Feed

      Contact Form (Name is optional)

    Submit
Powered by Create your own unique website with customizable templates.