# Configuring themristor from old printer **URL:** \ **Category:** General Discussion\ **Created:** [November 24, 2024, 7:50pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236 "2024-11-24T19:50:09Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![pierre286](https://avatars.discourse-cdn.com/v4/letter/p/c6cbf5/32.png) [@pierre286](https://klipper.discourse.group/u/pierre286)\ **Post date:** [November 24, 2024, 7:50pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/1 "2024-11-24T19:50:09Z")
### Basic Information: Printer Model: Dremel 3D20 MCU / Printerboard: Manta-M4P Host / SBC: Pi CM4 klippy.log [klippy(14).log](https://klipper.discourse.group/uploads/short-url/4pxzZTLkbDAxqYigKg9HVRlPYwt.log) (627.7 KB) ### Describe your issue: I’m trying to replace the control board from my old Dremel 3d20 printer. I’m unable to configure the thermistor, it keeps giving me temperatures that are out of range. That is while the heater is at room temperature. I could find no documentation of what kind of thermistor is in the printer. After trying for some time, I’ve decided that I’ll measure its resistance using a multimeter. From my measurements, it seems to be a very unusual type of thermistor: PTC that is around 3 ohms at room temperature (2 ohms at 0C, 2.7 ohms at 20C and 5.3 ohms at 100C). Is there a way to use this thermistor? The attached klipper log has a few trials. Including some junk when I renamed the sensor to check whether klipper is trying to load it or not. But ultimately, when I’m using the actual numbers, it’s saying it’s using “beta” thermistor, without saying why. At this point, I feel like I should probably by another thermistor. Even if I can somehow configure it, I suspect that with such a low resistance, it wouldn’t give me too inaccurate readings anyway. But regardless, I’d like to know if there’s a way to do this. ---
**Author:** ![EddyMI3D](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/eddymi3d/32/1981_2.png) [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)\ **Post date:** [November 24, 2024, 8:32pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/2 "2024-11-24T20:32:59Z")
Hello @pierre286 ! Have you ever tried a simple `Generic 3950` as parameter? ---
**Author:** ![pierre286](https://avatars.discourse-cdn.com/v4/letter/p/c6cbf5/32.png) [@pierre286](https://klipper.discourse.group/u/pierre286)\ **Post date:** [November 24, 2024, 10:05pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/3 "2024-11-24T22:05:46Z")
Hey. Yes, that was the first thing ever I tried. Same result, different numbers. That one is showing only -76C ---
**Author:** ![EddyMI3D](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/eddymi3d/32/1981_2.png) [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)\ **Post date:** [November 25, 2024, 7:30am UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/4 "2024-11-25T07:30:27Z")
Already took in consideration the thermistor might be broken? ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [November 25, 2024, 8:58am UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/5 "2024-11-25T08:58:24Z")
I agree with @EddyMI3D Given your measurements are correct then, at least I do not know any thermistor with these resistance readings. ---
**Author:** ![dockterj](https://avatars.discourse-cdn.com/v4/letter/d/919ad9/32.png) [@dockterj](https://klipper.discourse.group/u/dockterj)\ **Post date:** [November 25, 2024, 12:14pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/6 "2024-11-25T12:14:30Z")
I’m pretty sure it isn’t an NTC thermistor. I think it is a K type thermocouple. There is support in my repo for this but I’m not sure what kind of ADC is on your new board that will support this. There has been some success running klipper on the existing control board. ---
**Author:** ![dockterj](https://avatars.discourse-cdn.com/v4/letter/d/919ad9/32.png) [@dockterj](https://klipper.discourse.group/u/dockterj)\ **Post date:** [November 25, 2024, 2:04pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/7 "2024-11-25T14:04:23Z")
@pierre286 I’m interested in trying to add support for the original printerboard to my repo. Let me know if you want to sell me the original board. thanks! ---
**Author:** ![hcet14](https://avatars.discourse-cdn.com/v4/letter/h/ecd19e/32.png) [@hcet14](https://klipper.discourse.group/u/hcet14)\ **Post date:** [November 25, 2024, 3:49pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/8 "2024-11-25T15:49:23Z")
@pierre286 I think Dremel 3D20 and 3D40 printers are similar. > **[Reviews | Dremel’s 3D20 and 3D40 Idea Builders: 3D Printing for the K-12...](http://www.edtechroundup.org/home/reviews-dremels-3d20-and-3d40-idea-builders-3d-printing-for-the-k-12-classroom)** > > Over the past year I have had the opportunity to review both of Dremel’s 3D printer offerings for K-12 classrooms. I was able to to test out both the 3D20 and 3D40 Idea Builder printers with my... So @STS might provide the solution for your extruder sensor [Printer.cfg for Dremel 3D40](https://klipper.discourse.group/t/printer-cfg-for-dremel-3d40/13372) It looks like the sensor is connected to an ADS1118 [https://www.ti.com/lit/ds/symlink/ads1118.pdf?ts=1732524720011&ref\_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FADS1118%253FkeyMatch%253DADS1118%2526tisearch%253Duniversal\_search%2526usecase%253DGPN-ALT](https://www.ti.com/lit/ds/symlink/ads1118.pdf?ts=1732524720011&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FADS1118%253FkeyMatch%253DADS1118%2526tisearch%253Duniversal_search%2526usecase%253DGPN-ALT) on the original printerboard. It’s probably a K-type thermocouple sensor. You could try to install Klipper on the original printer board. Good luck, hcet14 ---
**Author:** ![dockterj](https://avatars.discourse-cdn.com/v4/letter/d/919ad9/32.png) [@dockterj](https://klipper.discourse.group/u/dockterj)\ **Post date:** [November 25, 2024, 4:00pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/9 "2024-11-25T16:00:47Z")
absolutely correct - and STS’s instructions reference my repo for ADS1118 and k-type thermocouple support in Klipper. The easiest path forward for the OP is to replace the thermocouple with an NTC thermistor. Trying to support a thermocouple on a board with no hardware support for it will be challenging. ---
**Author:** ![hcet14](https://avatars.discourse-cdn.com/v4/letter/h/ecd19e/32.png) [@hcet14](https://klipper.discourse.group/u/hcet14)\ **Post date:** [November 25, 2024, 7:27pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/10 "2024-11-25T19:27:20Z")
Preamble: I don’t know or use any Dremel printer! Assuming 3D20 and 3D40 are using the same hardware > [@dockterj](#): > > STS’s instructions reference my repo for ADS1118 and k-type thermocouple support in Klipper. I read it. Good job! > [@dockterj](#): > > The easiest path forward for the OP is to replace the thermocouple with an NTC thermistor. Perhaps. > [@dockterj](#): > > Trying to support a thermocouple on a board with no hardware support for it will be challenging. I don’t really agree. @STS did a very good job. On the STM32F103RCT6 are a lot of pins available. ![µc](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/4/4c5bd5a4f37c963b23981a01452c652e091c6059.png) @pierre286 could check the available pins to connect a thermistor. Check the datasheet of STM32F103RCT6. But why? Use the instructions from STS and use the original hardware. I guess, pierre286 just wants to run Klipper on his Dremel 3D20? ---
**Author:** ![EddyMI3D](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/eddymi3d/32/1981_2.png) [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)\ **Post date:** [November 25, 2024, 7:42pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/11 "2024-11-25T19:42:03Z")
> [@hcet14](#): > > On the STM32F103RCT6 are a lot of pins available. It’s not a case of enough pins. It’s that thermocouples can produce very small and only slightly voltage differences. Therefore they need an amplifier. ---
**Author:** ![hcet14](https://avatars.discourse-cdn.com/v4/letter/h/ecd19e/32.png) [@hcet14](https://klipper.discourse.group/u/hcet14)\ **Post date:** [November 25, 2024, 7:44pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/12 "2024-11-25T19:44:32Z")
Did you read after “But why?”? ---
**Author:** ![EddyMI3D](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/eddymi3d/32/1981_2.png) [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)\ **Post date:** [November 25, 2024, 7:48pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/13 "2024-11-25T19:48:43Z")
As long the ADS1118 is on the board… ---
**Author:** ![hcet14](https://avatars.discourse-cdn.com/v4/letter/h/ecd19e/32.png) [@hcet14](https://klipper.discourse.group/u/hcet14)\ **Post date:** [November 25, 2024, 7:50pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/14 "2024-11-25T19:50:39Z")
You may ask @STS or @pierre286. > [@hcet14](#): > > Preamble: I don’t know or use any Dremel printer! Assuming 3D20 and 3D40 are using the same hardware ---
**Author:** ![STS](https://avatars.discourse-cdn.com/v4/letter/s/958977/32.png) [@STS](https://klipper.discourse.group/u/STS)\ **Post date:** [November 25, 2024, 8:02pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/15 "2024-11-25T20:02:29Z")
Hi guys, I have never seen a 3D20 motherboard. On the 3D40 motherboard the ADS1118 is present. My instructions have pictures of the 3D40 motherboard. Does the one on the 3D20 look very similar or different. Here a picture on the 3D40. It is U302 placed above the ribbon cable to the print head. ![ADS1118_placement](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/5/58d3dff737f9129f7ac3c6a251a465f3c6364048.jpeg) ---
**Author:** ![STS](https://avatars.discourse-cdn.com/v4/letter/s/958977/32.png) [@STS](https://klipper.discourse.group/u/STS)\ **Post date:** [November 25, 2024, 8:06pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/16 "2024-11-25T20:06:19Z")
actually just searched through my computer and found some data that I had collected at that time. Someone had done a Marlin configuration file for the 3D20 and it lists the ADS1118. It also lists all the pins, so you have a way simpler job than I had 😉 [all needed info.txt](https://klipper.discourse.group/uploads/short-url/aeEJFtvoDzk2OGk5oUAKf9x9e9L.txt) (18.2 KB) ---
**Author:** ![hcet14](https://avatars.discourse-cdn.com/v4/letter/h/ecd19e/32.png) [@hcet14](https://klipper.discourse.group/u/hcet14)\ **Post date:** [November 25, 2024, 8:36pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/17 "2024-11-25T20:36:40Z")
Thanks STS. ---
**Author:** ![dockterj](https://avatars.discourse-cdn.com/v4/letter/d/919ad9/32.png) [@dockterj](https://klipper.discourse.group/u/dockterj)\ **Post date:** [November 25, 2024, 9:43pm UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/18 "2024-11-25T21:43:53Z")
It’s more than that too - you also need a cold juntion temperature reading. Much simpler to change to a thermistor for a board that doesn’t support thermocouples. ---
**Author:** ![hcet14](https://avatars.discourse-cdn.com/v4/letter/h/ecd19e/32.png) [@hcet14](https://klipper.discourse.group/u/hcet14)\ **Post date:** [November 26, 2024, 9:15am UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/19 "2024-11-26T09:15:58Z")
> [@EddyMI3D](#): > > It’s not a case of enough pins. It’s that thermocouples can produce very small and only slightly voltage differences. Therefore they need an amplifier. Either I wasn’t clear enough or you got me wrong. I was referring to a thermistor! It’s just possible to connect the thermistor to the original printer board, if there is an ADC pin available. That’s why I proposed > [@hcet14](#): > > @pierre286 could check the available pins to connect a thermistor. Check the datasheet of STM32F103RCT6. ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [November 26, 2024, 11:46am UTC](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236/20 "2024-11-26T11:46:07Z")
> [@hcet14](#): > > I was referring to a thermistor! It’s just possible to connect the thermistor to the original printer board, if there is an ADC pin available. That’s why I proposed This may seem a bit blunt advice, as you cannot just connect a thermistor to a free MCU pin without the hardware to support it, e.g. the necessary voltage divider etc. [Next page](https://klipper.discourse.group/t/configuring-themristor-from-old-printer/20236.md?page=2)