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4.7K Thermistor instead of 10K Thermistor

Posted by jsluke

jsluke

4.7K Thermistor instead of 10K Thermistor
November 22, 2013 10:40AM

Registered: 11 years ago
Posts: 44

My local store only had a 4.7K Thermistor and I was hoping to press ahead with the Heatbed installation on a Prusam Mendel i2.

The spec says use a 10K Thermistor. Can I get away with a 4.7K Thermistor? Should I put a 4.7K Resistor in series?

Thanks.

James.

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Azrael_UK

Re: 4.7K Thermistor instead of 10K Thermistor
November 22, 2013 11:49AM

Registered: 11 years ago
Posts: 30

This will depend on your firmware, I don't think there's intrinsic any problem with using a 4K7 thermistor for the bed, but you will have to either choose a firmware that has support for that value, or be willing to write your own thermistor table for it.

Edited 1 time(s). Last edit at 11/22/2013 11:49AM by Azrael_UK.

Prussa i2 Comissioned 4-Nov-2013
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uncle_bob

Re: 4.7K Thermistor instead of 10K Thermistor
November 22, 2013 12:15PM

Registered: 11 years ago
Posts: 1,433

Most of the contorl boards / firmware are set up for a 100K thermistor and either a 1K or 4.7K pull up resistor. With a normal 4.7K pull up, a 4.7K thermistor will give you almost no data at all running at higher temperatures. It would be ideal for measuring room temperature.

If you are shopping for resistors, be sure to get the 1% variety. They directly impact the accuracy of your temperature measurement.

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jsluke

Re: 4.7K Thermistor instead of 10K Thermistor
November 25, 2013 09:34AM

Registered: 11 years ago
Posts: 44

Many thanks - have ordered a 100K Thermistor.

Thanks.

James.

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uncle_bob

Re: 4.7K Thermistor instead of 10K Thermistor
November 25, 2013 12:39PM

Registered: 11 years ago
Posts: 1,433

While you are waiting for the thermistor, make sure you know which standard curve in the firmware matches the thermistor. If that's not clear from the data you now have. Email the guy and see what he says.