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darelleman

Ultimaker Original HB Thermistor Firmware

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Hi all,

I've been trying to fit my Ultimaker Original with a DIY heated bed that I am making. I am currently stuck trying to get the 100k thermistor I bought to work correctly. I bought a pack of 100k NTC 3950 thermistors specifically labeled for 3D printers. On the listing for these thermistors it states "use TEMP_SENSOR 11 in Marlin firmware " but I am using the bUltimaker firmware builder which has preset options for thermistors. I have tried both options that mentioned 3950 but to no avail. The thermistor clearly works, yet reads 23 degrees Celsius while my standard reads 32 degrees Celsius. So I can tell that the curve is off, I just can't figure out why that would be so and how I can fix this. Do any of the options in the firmware builder align to Temp_Sensor 11? If not what can I do other than compile Marlin myself? I greatly appreciate any help, as I am currently very stuck.

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Well here is the line of code they are talking about when they say to use #11:

 

https://github.com/Ultimaker/Marlin/blob/Marlin_v1/Marlin/thermistortables.h#L567

 

As you can see it's the 3950 thermistor.  It doesn't say what pullup resistor to use.  Did the place that sold these to you tell you what pullup resistor to use?  Usually it's 4.7K but some of these have other pullups.  If you look at the builder "none" is #0 and if you count down 11 from there it's that one.  That's #11.

 

Are you sure your bed isn't 23C?  32C seems awfully hot.  23C sound like typical room temperature.  You could heat the bed to 60C and put some PLA on there under a small towel for a few minutes and after things settle bend the pla and it should stay bent at 60C and not at 45C (it gets soft, similar to clay around 52C).

 

Ask the manufacturer of the thermistor what pullup you should use for "marlin sensor 11".  Most use 4.7K but some use 1K pullups.  Did you install a 4.7K pullup?

 

 

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