Thermistors and tuning the PID
Posted: Mon May 14, 2012 1:44 am
Spent the day trying to debug my Marlin settings. Here is the first strange thing I discovered:
21 to 200°C in about 37 sec.
Not bad, but what is this ripple on the top?
Here are some close-ups of the graphs:
After looking into thermistortables.h in Marlin's source files I discovered that the table for setting 6 - EPCOS 100k, which I was using, has errors in it. I spent quite some time learning about thermistor internals and ended up verifying and using setting 1 - 100k thermistor
While going through the source I disabled the timeout check in line 230 in temperature.cpp which was giving me PID Autotune failed! timeout errors and could not complete the PID auto-tuning process.
This is the result:
Looks good!
21 to 200°C in about 37 sec.
Not bad, but what is this ripple on the top?
Here are some close-ups of the graphs:
After looking into thermistortables.h in Marlin's source files I discovered that the table for setting 6 - EPCOS 100k, which I was using, has errors in it. I spent quite some time learning about thermistor internals and ended up verifying and using setting 1 - 100k thermistor
While going through the source I disabled the timeout check in line 230 in temperature.cpp which was giving me PID Autotune failed! timeout errors and could not complete the PID auto-tuning process.
This is the result:
Looks good!