bed pid tune strange

boelle

so i wanted to do a pid tune of the bed just to be sure

M303 P1 S100

it goes to 100 with no issue, i get

13:12:55.466 : Info:PID Autotune start

13:15:28.608 : bias: 170 d: 84 min: 99.01 max: 100.89

13:16:11.591 : bias: 235 d: 19 min: 99.01 max: 100.78

but the temp climbs to 108 and in the end i get a timeout

what could be the reason for this? the firmware can see that the temp is above 100 but yet it keeps heating (led flash very fast)

Repetier

The autotune uses a mathematical algorithm to test swinging behaviour. It sets pwm to bias +/- d. After your last test this means it wants cooling with 235-19 = 216 pwm setting which seems enough to heat further. So the algorithm was diverging too much for your wanted target temperature.

You could test with 90°C and see if it does converge in that case. Guess the algorithm has some limitations on what it can work with.

boelle

oki... wil try and figure what the highest temp it can do

are there any "hidden" parameters i can change to go higher?

boelle

hmm... i think my thermistor is bad again

replaced it 2 months ago

i tried 90 and temp was hovering at arround 65

60 still works