Configuring heater faults to kill machine by PS_ON



  • I have PS_ON and external 5V board power to set up and working with a relay that turns off power to the 24VDC PSU. The ATX On/Off control works fine but I also wanted it to cut off machine power in the event of a heater runaway or otherwise exceeding max temp. The wiki pages discussing using PS_ON seem to imply that heater faults can be configured to kill power, but what I've read so far doesn't say how. I've been able to force heater faults but it's not killing my 24VDC power.

    The thermistor and heater setup on H2 is known working.

    These is my limits and fault settings for heater 2:

    M143 H2 S20 A0 C0
    M570 H2 P5 T10

    Right now when I turn on the heater and artificially heat the thermistor beyond the limit temp (20C in the above code example) for 5 seconds, the heater faults out, but it's not killing the system power (motors & heaters). The wiki makes references to PS_ON killing power in the event of a fault but I've not been able to induce this function. What am I missing?


  • administrators

    This feature is implemented in the firmware 1.20 release candidate.



  • RC3 then? I thought I installed RC2 but I’ll go look at the update docs to see what I missed.



  • Maybe you are missing the S parameter in your M570 statement. Did you wait 10 minutes (default S parameter time) after the heater fault for the power to be killed?

    From Version 1.20beta8/New Features:

    • When a heater fault occurs, the print is now paused and all heaters are turned off except bed amnd chamber heaters. After a timeout period (currently fixed at 10 minutes), the print is cancelled, all remaining heaters are turned off, and the firmware attempts to turn the power off as if M81 had been received.

    From Version 1.20beta10/New Features:

    • Heater fault timeout to cancelling print is now configurable (M570 S parameter, in minutes)


  • OK I have now set a shorter timeout (S1). I have RC3 installed now. I'm still not able to get a heater fault to trigger machine shutdown via PS_ON. I've tested that M80 and M81 do function properly, M80 turns on system power, M81 turns off.

    Does the PS_ON trip function only happen after a fault cancels a print? I'm not running a print during my tests in trying to test this feature.

    My adjusted g code relevant to this feature:
    M143 H2 S17 A1 C0
    M570 H2 P5 T10 S1

    I've also tried A0 parameter instead of A1.

    I hold the enclosure thermistor with my fingers to trigger a fault, which is why I'm using such low temp limits. Holding the thermistor quickly turns the heater off and triggers a fault, but holding for two minutes with the above configuration doesn't trip off the machine power.

    Should I be reporting this in the RC2/RC3 thread then?


  • administrators

    Yes the PS_ON only trips if a fault cancels a print.


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