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new thermistor consider in firmware?

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Hi at all,

i beg you to help me!

i use a arduino mega 2560 and would like to conect a new thermistor to my ultimaker, instead of the one, which is in the printerhead with the nozzle. the wires were no problem, but when i try to connect my pc to the ultimaker with the new thermistor i get a deficiency report.

If i understood some posts correct, i have to change something in the firmware.

Is this correct? And if so, what i have to change?

the new thermistor is this one:





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Don't know where to find a table for that thermistor. Not all 100K thermistors are the same.

According to this:


The beta is 3974. T0=25C, R0=100000 ohms.

Knowing that you can calculate resistance at different temps here:


Then calculate the needed table with this information:


then insert the resulting table into the Marlin firmware in the file thermistor tables.h

Then read instructions on how to build Marlin (the easiest step in tall this but will still take an hour). google "how to build marlin for arduino". Lots of instructions in many places such as here:


and here:


But don't use that version of marlin. Use the ErikZalm version.


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There's already a thermistor table entry for the 'Honeywell 135-104-LAF-J01' which is only off by one letter from the one you're using.... no idea what the difference might be, but maybe they are compatible. To use it, you need to change this line in Marlin's configuration.h file:

#define TEMP_SENSOR_0 -1

to 7 instead of -1.

Since this is a thermistor, not a thermocouple, do you also need to add a pull-up resistor to the motherboard? or is that only for other sensor channels when adding a heated bed? And is the interface board on the printhead no longer needed? I admit I'm almost clueless on the temp sensing hardware, so I'm kinda confused on the specifics...


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Good catch. They use the same tables, so that's great. The only difference is that the LAF is more accurate: 5% instead of the LAG which is 10%. This table probably assumes a 4.7K pullup but it doesn't say.

So now all you have to do is build marlin and change configuration.h to use temp sensor 7 as shown above.


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Hey Guys, I grabbed out that thread cuz I got a question about this topic.

We have a pt100 for the hotend and a pt100 for the heatbed and we wanna connect them directly to that Board V1.5.7.

On our Board there seem to be already those 4.7k Resistors. Are we doing fine connecting those PT100 directly to the "Temp1" and "Temp2" marked connectors just with GND and Siganal?

Do we have to make those changes on

#define TEMP_SENSOR_0 X

#define TEMP_SENSOR_1 X

X: Sensor used here.

Greets and thank you for ya help.

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