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Teacup problem: Temperature scaled incorrectly?

Posted by aeram00 
Teacup problem: Temperature scaled incorrectly?
June 19, 2012 12:21PM
Hi everyone,

I've been trying to debug a problem in my Teacup firmware and it's driving me nuts. Everything works fine except that the temperature is reading around 4.75 C when I send an M105 through Arduino's serial monitor at room temperature; when I heat it up enough to melt plastic it'll read around 58-60 C, which is way too low. I think the temperature table is correct because when I use the exact same table with a simple Arduino script I found on the RepRap wiki I get a more reasonable value of around 20 C.

I'm using a Generation 2 electronics set (with a Duemilanove and Atmega 328) I used to control a Sherline mill (with spindle removed and extruder attached) and I'm trying to get it working with a Prusa I just built. I've always had this temperature scaling problem, but I used to work around it by telling Skeinforge to extrude at 60 C. But now with my new Prusa I would really like to exercise better temperature control and so I want to get this issue resolved.

So far Teacup's been great in every regard except for this little annoying glitch. What setting in Teacup could be scaling my temperature improperly?

Any and all help is appreciated!

--Aaron
Re: Teacup problem: Temperature scaled incorrectly?
June 20, 2012 07:06AM
Teacup uses thermistor tables with higher accuracy than the usual firmwares. To convert a table from elsewhere to Teacup, you have to multiply all the right values of the value pairs in the table by four. To see the difference, you can compare a Sprinter thermistor table [github.com] (the first one) with one from Teacup [github.com] (almost the same thermistor).

ThermistorTable.double.h also has a long comment inside, explaining how to make your custom table, adding even more accuracy.


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