PID Bed is failing

paboman

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 ?
thx

Martin1454

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)

https://forum.duet3d.com/topic/9781/duet-firmware-2-03beta3-available

paboman

@martin1454 great! thank you!

paboman

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

dc42

@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 ?

paboman

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