Duel Z motors.



  • Back on this after being on the road for over a week and hoping to get my board and parts in this week. Just found the frame we will be using will have two Z motors. Could someone please advice how to control the second Z motor so that both would move exactly the same?
    Thanks



  • Forget to add from the reading on this site it appears that i would set that up in the
    M584 in the C code. How would you wire up the second home switch. Have reviewed it and not exactly sure. Will reread again.



  • The Duet has 2 Z motor connectors (ZA and ZB) which are wired in series and by default they can be used to control a pair of motors as one. So all you have to do is connect both motors.



  • thanks. i will be using regular microswitches for the home switch. looking at documentation it says to wire the switches from left to right signal, +3.3v, Gnd. if using a two wire then connect the wires to GND and Signal. I assume the circuit board will see the home switch as true when the GND is connected to the Signal pin and the +3.3v signal is used to power up some type of 3 wire sensor. Would this be correct. Only purchased one board to test and hate to do something stupid which is why i am asking a lot of questions.
    Thanks


  • administrators

    @irondesk40 said in Duel Z motors.:

    I assume the circuit board will see the home switch as true when the GND is connected to the Signal pin and the +3.3v signal is used to power up some type of 3 wire sensor.

    You can set up the firmware to treat the switch as triggered when the contacts are closed as you suggest (which would be a normally-open switch), or when they are open (normally-closed switch). It's more usual to use a normally-closed switch. With most microswitches, that means using the two outer terminals. And yes, the +3.3V pin is for optical, Hall and similar endstops that need power.



  • Just as an addendum to what @dc42 was saying:

    The reason that most switches are configured normally closed is for safety. A normally closed (The signal pin sees ground all the time except when triggered) switch has to be present and connected to allow movement. If something goes wrong, and the switch is disconnected, a wire gets pulled from a connector, or cut by the printer's motion, the printer will see this as the endstop being triggered, which will result in an error condition, and it will stop, instead of grinding away trying to move past its limits.

    A normally open switch configuration is the same untriggered as it is disconnected, in a home motion, for example, the printer motors can attempt to move the printer much further than it is physically capable of moving. This can put a lot of strain on belts, motors, mechanical mountings and bearings.

    For the physical connection, the board has an internal resistor that will allow current to flow to the signal pin, so that it sees "high" voltage whenever the switch itself is open (not connecting), but when the switch closes between ground and signal, the voltage at the signal pin will be "low". So you are actually looking for high (~3.3V) at the signal pin to show that the endstop has been triggered. The firmware can be reversed so that it reads the other way around instead, but this is the better method.


 

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