1 Topic by aeschneider.tech

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Topic: Broken Thermister

So in taking apart the hot end to clean it, the wire and casing on the thermister broke. Solicare doesn't replace things that happen due to "user negligence", and are asking $20 bucks for it. I'm not that familiar with thermisters - does anyone know where I can buy this guy without paying $20 bucks?

Also, apparently this Solicare thing is a big ol' joke.

2 Reply by akhs001

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Re: Broken Thermister

I broke mine yesterday.monday i buy a new thermistor from grobotronics.its cheap,only 1,5 euro

3 Reply by trayracing

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Re: Broken Thermister

How do you know it's the right one?

4 Reply by carl_m1968

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Re: Broken Thermister

trayracing wrote:

How do you know it's the right one?


Don't they just use the standard 100k thermistor?

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5 Reply by grob

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Re: Broken Thermister

carl_m1968 wrote:
trayracing wrote:

How do you know it's the right one?


Don't they just use the standard 100k thermistor?

There are a few different common types of the 100k glass-bead thermistor, and their temperature/resistance curves vary a bit - especially at the higher temperatures where we use them. It's worth knowing which kind you're getting (the grobotronics website is a bit vague on the matter...), but the penalty for getting it wrong is only in the order of 10C or so, so don't panic. Most fit best to the type 1 curve in marlin, which is probably what's already in your firmware.

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6 Reply by trayracing

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Re: Broken Thermister

carl_m1968 wrote:

Don't they just use the standard 100k thermistor?

]

Not sure what you mean by "standard". A lot of places make 100k thermistors, which usually means they have 100k ohm resistance at 25C. However, we don't print at 25C, and thermistor temperature response can vary lot. This is why Marlin has a choice of tables to compile in. For example, the 100K thermistor E3D uses needs a different table than the compiled into the stock Press firmware.

To further complicate things, thermistors are often characterized by their cold temperature and "beta", which attempts to express the response curve. However, beta ends up being an approximation for a stated range of temperatures, and usually these are much lower than printing temps. (like 0/100, or 25/85 C).
Vendors usually have a data table available too which covers the full range.

For example, the oft quoted Epcos B57540G0104F000, is 100k with a beta 0/100 is 4036. The Semitec 104GT-2 on the other hand, is also 100k but has a beta 25/85 of 4267. (BTW, Mouser neglected to mention the temperature pair in their data sheet so I went to the manufacturers web site.)  In any case, the tables for these two parts are different enough at printing temperatures to warrant different tables.

Anyhow, I dunno what your thermistor is, or whether table 1 in the press firmware is close enough. Might be. Aim low on temps to start with, and increase slowly. You will probably find some reported temp range that works OK for you, which may or may not match what other people work at. If you don't mind your own personal temprature scale, then you're mostly good. Beware that the firmware has both a minimum extrusion temp, and a maximum allowed temp to safeguard your printer and your life, and these may not work correctly if you're miscalibrated r use an underrated part.