Heater Fault reative to Power Fluxuation?



  • 0_1552443550792_b36e4a69-2cf9-4917-8ed7-d95818779843-image.png
    Referencing post: https://forum.duet3d.com/topic/4417/heater-pid-tuning/4

    I believe this event is caused by a fluctuation in power provided by the local substation. The printer was in standby with a temp of 210C for PETG.

    Perhaps a transformer switch over or to many air conditioners switched up just then... Regardless a small brown out. Not enough to fully reset the hardware but enough to cause some faults, it seems. Input voltage should be 24V normal, and 5V constant is received over USB. My more robust systems were not effected, maybe a larger capacitive buffer?? I do not have any UPS in service. I would say that voltage dropping to anything less than 2V under expected should be reason for a fault, just not thermal. -Maybe some one more familiar with the Firmware code can explain what is happening during a brown out?

    I noted on comment 4, that M570 can be used to create an offset value to help with false positive error detection in the heater Thermal Runaway circuit. So if I understand it correctly, I input a time value to IGNORE a difference so that the temp can catch up?

    This particular event I have no means of simulating to see if it has been resolved. Perhaps this is not something that can be resolved if the source is infect a Brown Out caused by a local Transformer? Perhaps the result will always be a thermal fault, if the heater is active when the brown out happens?

    This fault never happens when I am working with the machine or on the computer watching, always when I have stepped away. Since this fault is not happening while a print is in progress or during warm up, I do not suspect a power supply issue at this time.


  • administrators

    If you ran heater tuning using a recent firmware version, and you copied all the discovered M307 parameters including the V parameter across to config.g (or used M500 and config-override.g), then heater power is already compensated for changes in the VIN voltage. However, heater power goes as the square of the voltage; so if you have only 9.3V available to power a 24V heater, then the maximum power output that the firmware can command is only 15% of the rated power of the heater.

    The other issue you face is that the stepper drivers shut down below about 9.5V.



  • All makes sense and is expected.
    So I should expect a UPS would cure this, but what do you think? Can a code be used to tell the firmware to ignore the glitch? Maybe this is something that can be added as an auto recovery function using a statement that says if the power drops and the temp drops, glitch happens only one time in X amount of time ignore and restore the temp. But if it happens several times, engage Thermal Protection?

    I guess it is fruitless to speculate a fix when I am not even quite sure what the cause is?

    Yes. Fully Tuned. M303 stored using M501. No issues there. Temp seem stable and extruding more or less as expected with no reason suspect any issues withe tuning or hardware.

    If you tune heater tuning using a recent firmware version, and you copied all the discovered M307 parameters including the V parameter across to config.g (or used M500 and config-override.g), then heater power is already compensated for changes in the VIN voltage. However, heater power goes as the square of the voltage; so if you have only 9.3V available to power a 24V heater, then the maximum power output that the firmware can command is only 15% of the rated power of the heater.

    During the event, the stepper motors are disabled. I never leave them enabled.
    Only the heater is on, to alleviate warm up time and possible clogs.

    The other issue you face is that the stepper drivers shut down below about 9.5V.


  • administrators

    @rflulling said in Heater Fault reative to Power Fluxuation?:

    During the event, the stepper motors are disabled. I never leave them enabled.

    if stepper motors are disabled and then re-enabled, they are quite likely to jump to a new position 4 full steps from the original one.



  • I see. This is not an issue I have experienced. Addressing this reply from the standpoint of normal operation and standby to operational, I recognized from day one that as soon as the motors were disabled, End Stops were lost, this complicated setup very much. But once the config was stable, loss of end stop was no longer an issue, as G28 XYZ is built into my startup script.

    @dc42 said in Heater Fault relative to Power Fluctuation?:

    @rflulling said in Heater Fault relative to Power Fluctuation?:

    During the event, the stepper motors are disabled. I never leave them enabled.

    if stepper motors are disabled and then re-enabled, they are quite likely to jump to a new position 4 full steps from the original one.


 

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