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temperaturecontrol-thermistor-choice [2017/01/25 15:45] arthur |
temperaturecontrol-thermistor-choice [2021/01/08 15:57] (current) |
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| There are different models of thermistors. Each hotend or heated bed has one, and it's a specific given type. Different thermistor models translate a given temperature into different resistances. This means you must tell Smoothie which exact thermistor model you have, to be sure Smoothie can read it correctly. | There are different models of thermistors. Each hotend or heated bed has one, and it's a specific given type. Different thermistor models translate a given temperature into different resistances. This means you must tell Smoothie which exact thermistor model you have, to be sure Smoothie can read it correctly. | ||
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| + | This is done using the **thermistor** option in the configuration file. You pass it the name of your thermistor, and it will configure the math correctly accordingly. | ||
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| + | < | ||
| + | temperature_control.hotend.thermistor | ||
| + | </ | ||
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| + | Smoothie does not know the name of all the thermistors in existence. At the moment these are the ones it knows about: | ||
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| + | ^ Name ^ Beta for 0-80°C ^ Beta for 185-230°C ^ I for Steinhart Hart ^ J for Steinhart Hart ^ K for Steinhart Hart ^ Part number ^ | ||
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| + | **In case you have a thermistor that is not known to Smoothie** you can simply define the parameters in config. There are two methods, using the beta value ( good but not perfect ), and using the Steinhart Hart algorythm ( perfect ). | ||
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| + | **Using beta values :** | ||
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| + | Set the beta value in the configuration file : | ||
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| + | < | ||
| + | temperature_control.hotend.beta | ||
| + | </ | ||
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| + | <callout type=" | ||
| + | The betas published by most manufacturers, | ||
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| + | For the 185-230°C this results in readings being about 7-10°C too high. | ||
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| + | This means beta values are usually good for a heated bed, but not for a hotend. | ||
| + | </ | ||
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| + | If the thermistor is 100K ohms at 25°C then this is usually enough. | ||
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| + | You can also set r0,t0,r1,r2 but this is not usually needed as the defaults are sufficient. | ||
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| + | If you do not know what thermistor model you have, contact the designer or seller of your 3D printer, | ||
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| + | **Using the Steinhart Hart algorythm :** | ||
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| + | This is the recommended method. Set the parameters in the configuration file : | ||
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| + | < | ||
| + | temperature_control.hotend.coefficients 0.000722376862540841, | ||
| + | </ | ||
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| + | To find what the Steinhart Hart coefficients for a given thermistor are, please read the [[SteinhartHart]] page. | ||
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| + | If you have the temperature curve for your thermistor, you can also define three points on that curve, and let Smoothie calculate everything : | ||
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| + | < | ||
| + | temperature_control.hotend.rt_curve | ||
| + | </ | ||
