Duet 3 Heated Bed Faulting



  • I'm also having an issue with a fault on my heated bed.

    It's giving me the message that the temp didn't rise as quickly as expected.

    I don't think it's picking up the thermistor correctly, usually it idles around 25C, and now it's about 30C

    I'm using the equivalent settings as I was using previously on my Duet 2 Ethernet and 2.04

    Here's my previous heater section,

    M307 H0 B0 S1.00                            ; Disable bang-bang mode for the bed heater and set PWM limit
    M305 P0 T100000 B3590 R4700                 ; Set thermistor + ADC parameters for heater 0
    M143 H0 S130                                ; Set temperature limit for heater 0 to 130C
    M301 H1 S0.70                               ; Set heater 1 PWM limit to 70%
    M305 P1 T100000 B4388 C7.060000e-8 R4700    ; Set thermistor + ADC parameters for heater 1
    M143 H1 S290                                ; Set temperature limit for heater 1 to 290C
    

    And here's my current heater section,

    M308 S0 P"temp0" Y"thermistor" T100000 B3590          ; configure sensor 0 as thermistor on pin temp0
    M950 H0 C"out0" T0                                    ; create bed heater output on out0 and map it to sensor 0
    M143 H0 S130                                          ; set temperature limit for heater 0 to 130C
    M307 H0 B0 S1.00                                      ; disable bang-bang mode for the bed heater and set PWM limit
    M140 H0                                               ; map heated bed to heater 0
    M308 S1 P"temp1" Y"thermistor" T100000 B4388 C7.06e-8 ; configure sensor 1 as thermistor on pin temp1
    M950 H1 C"out1" T1                                    ; create nozzle heater output on out1 and map it to sensor 1
    M143 H1 S290                                          ; set temperature limit for heater 1 to 290C
    M307 H1 B0 S0.70  
    


  • @blt3dp said in Duet 3 SBC software/firmware upgrades:

    M305 P0 T100000 B3590 R4700
    M308 S0 P"temp0" Y"thermistor" T100000 B3590

    The missing R value in the new definition is the likely cause of the idle discrepancy. It MIGHT also explain the fault.



  • @Danal

    I do think it has something to do with, unfortunately if I throw R4700 in my m308 command the temp goes to 9.8C



  • Duet 3 AFAIK use a 2200 ohm sense resistor so change the R from 4700 to 2200 and you should be back on track.



  • Adding R2200 to my M208 command has taken care of the temperature reading, it’s on line with what I used to see.

    But, it still faults. I don’t think it’s a wiring issue. I can connect my heated bed directly to mains wiring (it’s 120VAC @ 4A) and DWC shows the temperature rising at a normal rate.

    I’ve bench tested the SSR just in case and it’s working fine.

    It really does look like the Duet’s not controlling it like it used to in 2.04



  • Perhaps take a look at M570, and adjust the timing of a fault.


  • administrators

    @blt3dp, the M307 H0 command you posted suggests that you haven't run heater tuning on the bed heater.

    To get default bed heater parameters, make sure that the M141 H0 command to declare the bed heater comes before the M307 H0 command. Otherwise, when the firmware sees the M307 command with no A C or D parameter, it will assume default parameters for an extruder heater.



  • @dc42 Correct, I haven’t run tuning in the bed heater. I knew it was a thing for hotends but I’ve never done it for the bed on any of my machines. I guess cause all my past machines have set the bed to bang-bang. Didn’t seem necessary to tune the PID parameters if I wasn’t using that mode. Which brings the question:

    Using a SSR to switch a mains powered bed, PID or Bang-Bang?

    I also tried the M141 H0 and it didn’t seem to change anything, I’ll PID tune.

    Edit: Sure M141 is right? Guide wiki says that’s for setting chamber temp.

    Edit again: guessing you meant the M140, prob a typo? I’ll try that before the M307



  • M140 H0 before the M307 didn’t appear to change anything.


  • Moderator

    @blt3dp said in Duet 3 Heated Bed Faulting:

    Using a SSR to switch a mains powered bed, PID or Bang-Bang?

    PID is almost always going to be the way to go.



  • I’ll try a PID tune.



  • PID tuning did fix it, I'm still receiving a notification stating the heater is over powered and would reach 260C if left on at full power. Everything related to my bed can handle well in excess of 140C so I have a thermal fuse in place that will trip at 130C and kill it. How might I adjust or supress the heater overpowered message?



  • @blt3dp said in Duet 3 Heated Bed Faulting:

    How might I adjust or supress the heater overpowered message?

    you can not. that is just a warning.



  • @Veti said in Duet 3 Heated Bed Faulting:

    you can not. that is just a warning.

    I thought that might be the case, no worries.


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