Moving steppers by hand & 12V in series for 24V

  • When I move my carriage around by hand and the Duet is unplugged I see some led light up and fans turning. Is the back feeding current into the board harmful? Should we avoid moving the carriage by hand?

    2nd question. Can two 12V fans be wired in series on a 24V Duet? I know its not optimal but could this lead to any damage?

    Thank You

  • administrators

    1. Avoid moving the motors by hand as far as possible, but if you must then move them slowly.

    2. There is no guarantee that the fans will share the voltage evenly, so I advise against connecting fans in series.

  • Thank you.

    One more question about the connections to the X-carriage. I read in an older post you said you can combine the common positive to reduce the wire count to the carriage.

    You can use a common positive (V_FAN) wire for both fans.

    If I have two extruders, two thermistors, x endstop, Z-probe, one heatsink fan, and one part fan, Can I combine any other common conductors? can the endstop and Z-probe share anything?

  • administrators

    If the fans are the same voltage as the extruder heaters, you can use a common positive wire for both extruder heaters and both fans, but make sure it can carry the combined current - in particular the full current draw of both heaters.

    If you have an endstop switch on the X carriage, and it's a simple 2-wire microswitch or it is using 3.3V power (not 5V or greater) then the Z probe and the endstop switch can share the ground wire, and the +3.3V wire if the endstop switch needs it.

    The two thermistors can share the VSSA wire.

    For the next generation Duet, we may make a hot end board that would need just a 2-pin power connector and an RJ11 connection.

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