How to Fake Thermistor Reading to prevent Error message

What is the problem?

I need to get around the built in extruder is too cold fail safe.

What did you already try to solve it?

I tried nothing as i have limited thermistor xp

Have you tried running in safe mode?

No I dont belive i have a safe mode plus irrelavant

Did running in safe mode solve the problem?


Systeminfo Bundle

You can download this in OctoPrint's System Information dialog ... no bundle, no support!)


Additional information about your setup

OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ... as much data as possible

Using my Creality to create a Food Extrusion Machine. I have most of it figured out however i need to fix the problems that come with removing the extrustion head so i just have a cnc that can run gcode without heated surfaces.

The best way would be to build your own firmware and to either disable the cold extrusion protection or to replace the thermistors with dummy thermistors in the config.

The other option would be to measure the resistance of the thermistor at let's say at 20°C and at 40°C, then calculate the approximate value for 200°C and use resistors or a potentiometer with that value instead of the thermistor.

Im ontop of the resistor/pot idea rn. ill post if it works, got the thermistor value chart off the supplier web page so it looks like 4300 ohm resistor will work but we will see.

btw the left hand colum is temp celcius and the next three are min,mean,max kiloohms

Ah good idea to get that chart.
I didn't know those existed.
I would use a potentiometer - it's more flexible :slight_smile:

Oh and another thing. Set the printing temperature to the fake thermistor temperature. Otherwise the thermal runaway protection will probably be triggered.
Within a degree should be fine.

awesome. Ill let you know pot comes tues

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I recently did this for a printer I've been tinkering with to print room temp polymers. I haven't had any issues with having resistors hooked up in place of the thermistor, and since there's no hot end I'm not worried about that side of things. This was on a (formerly known as) Anycubic Kobra Go. It levels the bed, etc. exactly as it should, even cold.

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May I ask which polymers you're printing?

It's going to sound strange, but right now honing in on an organic paste with minimal shrinkage using used coffee grounds as the fill and gum(s) plus cellulose as the binder. I ran across some info that got me started from academic sources, but I'm trying to extend their work. Looking to print seedling pots that last while on the counter but decompose quickly once put in soil and are 100% biodegradable. Kind of a situation of my hobbies colliding with my spouse's.

I have designed the printer with a quick-replaceable "cold-end" so it can be used as a bio-printer too, my daughter is expressing interest in various experiments using hydrogels as both a base and an extruded material.

That sounds very interesting
I would really like to see some of your pots and your modified printer :slight_smile:

It would be great if you find the time to show us your project someday in Showcase

this is cool

I Fixed the issue turns out pot does job perfect. Thanks!


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