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Heat bed problem possibly solved??? Maybe... Partly

Discussion in 'Troubleshooting' started by wthierry, Jul 28, 2017.

  1. wthierry

    wthierry Active Member

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    Sorry to start another Heat bed thread, But I was able to somewhat solve it without changing out my board, or re wiring it. I took the tips from Jeffrey:
    Also Note that Robo engineer Allen McAfee also made this change in their code on github 3 days ago.

    https://github.com/Robo3D/Marlin/commit/997bf4b6a1caa53c91e153e622cc780992f9e59do

    I have tested this 2 times, one with only the change to 255, that let me get to 90 degrees before disconnecting. I then also increased the timeout, and am currently past 91 degrees and trying to get to 100.

    Allen made the change to 255 on git hub, but didn't make the timeout change. I can upload the hex file if anyone wants to try it.
     
    #1 wthierry, Jul 28, 2017
    Last edited: Jul 28, 2017
    mark tomlinson likes this.
  2. wthierry

    wthierry Active Member

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    Well I managed to get to above 92 then it happened again. So progress, but not yet perfect....
     
  3. wthierry

    wthierry Active Member

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    Im pretty sure its the timeout combined with not enough power getting to the heated bed. I can get above 90 now, but it starts struggling to get past 92 or 93 for an obscene amount of time.
     
  4. wthierry

    wthierry Active Member

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    hmm, ok, I can heat the bed up now, but now the zaxis wont raise :( So going back to the old version....
     
  5. Kilrah

    Kilrah Well-Known Member

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    Link is broken, correct one is https://github.com/Robo3D/Marlin/commit/997bf4b6a1caa53c91e153e622cc780992f9e59d

    For some reason he also committed a swap between Z and E1 pins. IMO he's got a damaged mainboard, swapped that for his own use and forgot to leave it out from the commit... I commented on github. You should revert that and rebuild (or move the Z motor plug to E1 connector...)

    I would actually try 254 instead of 255 to still keep PWM, but not sure of the difference.
     
  6. wthierry

    wthierry Active Member

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    Sorry to be clueless, but what is PWM and why should I keep it enabled?

    thanks
    wes
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    PWM is how the boards drive the steppers (edit: and the heaters). (Pulse Width Modulation) an A/C signal (square wave) for the DC motors. :) ... the varying pulsewidth (duty cycle) determines motor drive signal
    Not confusing at all
     
    #7 mark tomlinson, Jul 29, 2017
    Last edited: Jul 29, 2017
  8. Kilrah

    Kilrah Well-Known Member

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    PWM is doing on/off at a pretty high frequency, and varying how much of the time the "thing" is ON.
    I just tried both 254 and 255 with no difference, so 255 is fine. I thought <255 would enable a higher PWM freq than Marlin's usual ~5Hz temp polling through an actual hardware PWM output, but it isn't the case. Problably wouldn't have been of much use anyway due to the massive thermal inertia of a bed.

    The original 200 was however a bit stupid since that meant only at most 200/255 = 78% of actual available heating power was used.
     
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  9. wthierry

    wthierry Active Member

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    Damn, Im a software engineer, and didnt notice he changed the pins. I was all obsessed about the PWM setting and the timeout.... reversed this change. will try a print at 85 or 90 now.
     
  10. wthierry

    wthierry Active Member

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    Good news, I heated it up to 90 like a champ, and its plugging away now on a print! Thanks guys for your help. Hope some of the others with heat problems see this thread. There is still an issue, cannot seem to get to 100, but 90+ seems to work great with ABS.
     
  11. wthierry

    wthierry Active Member

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    Has anyone else tried this except me? I am happy with the result.
     

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