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Z limit switches not doing anything after 1.5.7 PCB upgrade

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I've finally have my ultimaker started after replacing all the electronics (and replacing the 12v fan with a 24v one.)

All my limits are working now, except for the Z limits. Last time I had the machine working, about a year ago, these worked just fine. The limit switches are shorting correctly. Manually shorting the pins does nothing. Shorting the other digital pins to ground doesn't work.

I've upgraded the firmware through Cura, the first run wizard detects all the other limits correctly however it just wont recognise the Z limit no matter what I've tried.

Any ideas?


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X driver

Well, it sounds like you know some electronics. If it were me I would try to figure out this puzzle myself even though it sounds like you could just get UM to send you a new board.

Attached is the relevant part of the schematic (but the 1.5.6 version but should be the same I would think).

I would examine the circled pin and make sure the logic changes when the X moves left versus right on a long move (long move so there is time to measure the voltage without needing a scope).

The pololu like stepper driver uses the same 2 wires to move left versus right and does so by reversing the voltage across the 2 signals that move the stepper. So I don't think it's likely that the pololu could break in this manner. So I think it must be this "dir" signal (direction). It could be another bad arduino or a bent arduino pin (most likely) or a bad solder on either end of that signal. Or a bent pin on the driver. The driver itself could be bad - this seems very unlikely but easy to test by swapping X driver with any other driver.

later edit: just to be clear - this direction signal should be around 5V (logical high) for one direction of moving and 0V (logical low) for the other direction.


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