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Prusa MK2 X-axis motor backfeed question  

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andrey.r
(@andrey-r)
Active Member
Prusa MK2 X-axis motor backfeed question

Hey guys,

I just found out that my mk2 lights up the display if I move the extruder along the axis without it even being powered on...

It looks that the motor's backfeeding generates enough current to momentarily power on the system... so, is there a possibility that it might damage the rambo board or is there any safety built-in? I looked the manual thoroughly but couldn't find anything that says to move the extruder/heatbed slowly to prevent the backfeed. I didn't have a clue that backfeed might happen so to speak. If there is no safety built-in someone might unknowingly damage the board.

Check the video

Postato : 30/03/2017 4:20 am
Knickohr
(@knickohr)
Utenti Moderator
Re: Prusa MK2 X-axis motor backfeed question

Looking at the schematic, you will find stepper motor driver.

OK; it's the Rambo, not the Mini-Rambo, but anyway, they are identical at this point.

So it's save, dont worry about, these ICs has protection ciruits implemented. It's only cosmetical.

Thomas

Postato : 30/03/2017 9:16 am
andrey.r
(@andrey-r)
Active Member
Topic starter answered:
Re: Prusa MK2 X-axis motor backfeed question

Thank you Thomas! 💡

Postato : 30/03/2017 4:47 pm
JeffJordan
(@jeffjordan)
Utenti Moderator
Re: Prusa MK2 X-axis motor backfeed question

...these ICs has protection ciruits implemented...
in fact this "protection circuit" (diode against Vcc) is directing the generated current into the power trunk (instead of destroying the stepper driver) which let's the whole printer electronics flash alive when you use the stepper motors as generators.
:mrgreen:

but nothing to worry about...

dem inscheniör is' nix zu schwör...

Postato : 31/03/2017 1:55 pm
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