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bed pid tune strange

boelleboelle
in Questions & Answers
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)

Comments

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

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