PID Bed is failing

  • Hi,
    I can heat the bed of the printer to 120°C in about 5 min but if I try to run PID (M303 H0 S120) I get a fail response from the Duet:

    Auto tune cancelled because target temperature was not reached

    this is my configuration rith now:
    ; Heaters BED
    M307 H0 A77.3 C150.3 D5 S1 B0                       ; H0= Bed A= Gain C= Constant D= Dead Time S= Max PWM
    M305 P0 T100000 B3950 C0 R4700                     ; Set thermistor + ADC parameters for heater 0 (R4700 for duet wifi)
    M143 H0 S140                                        ; Set temperature limit for heater 0 to 140C
    M570 H0 P120 T15				   ; Heater Fault H= heater num. P=seconds before fault T= Permitted excursion from the setpoint

    2.03beta2 (2019-02-16b1)

    any Idea why I cant do PID while I can heat to the target temperature ?

  • Try the new beta 3:

    The heater tuning timeouts have been increased to 30 minutes for bed and chamber heaters (was 20 minutes) and 7 minutes for extruder heaters (was 5 minutes)

  • @martin1454 great! thank you!

  • updated to the last beta3
    now I am getting this result:

    19:28:17Warning: Auto tune of heater 0 failed due to bad curve fit (A=21.6, C=80.4, D=inf)

    19:27:03Auto tune phase 3, peak temperature was 120.1

    19:27:00Auto tune phase 2, heater off

    19:02:12Auto tune phase 1, heater on

    19:02:06M98 P"0:/macros/PID/PID Bed 120"
    Auto tuning heater 0 using target temperature 120.0°C and PWM 1.00 - do not leave printer unattended

    @dc42 what does this mean?

    thank you

  • administrators

    @paboman said in PID Bed is failing:

    Warning: Auto tune of heater 0 failed due to bad curve fit (A=21.6, C=80.4, D=inf)

    That's an odd result, I've never seen that before! The A and D values are clearly wrong, and the C value looks suspicious too. Do you get sensible results if you tune at 100C ?

  • I had to increase the T value a little bit to match the real temperatures to the read ones.
    now it seems to work ok

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