PID Autotuning with Heatbed On

When autotuning is started with M303 command, firmware disables all others extruders and heatbed.
That way autotune tunes up with only one resistance heater (witch makes only small deviation of voltage ~ 11.8V).
In real print, when I use two extruders and heatbed, voltage drops as low as ~10V. Autotuned PID parameters do not allow heater to get close to desired temperature.
If I move temp limit to higher value, PID allows heater to heat more then in last step (but less then set limit).

This means that Auto PID tuning can not find correct values in case of higher resistance.
If you can allow at firmware side for heatbed and other exturders not to be disabled on autotuning, maybe I could get correct PID values.


  • The autotune bypasses the heater control loop and some more as it needs to do it's own thing. That is the reason why it disables all heaters. They would otherwise keep running full power. 

    I've put it in my todo to see if that can be combined. But can not say when it will appear.
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