Using a Duet 2 board with external stepper drivers



  • Hello,

    I am building a giant 3D-printer (1100x600x500 mm) where I use 24VDC D808 stepper drivers for my motors. I am interested in buying the Duet2 wifi/ethernet but I have some prior questions:

    1. I previously used the Ultratronics pro v1.0 since that one has an option to put in the motors by breakout (without the use of internal stepper drivers) I will only use an internal stepper driver for my extruder, which is a Nema17 motor. For my other motors I want to use breakout pins, in any way not the internal stepper drivers since they are not strong enough. Is it possible to use the pins on the 50-way DCI for connecting my motors without buying the expansion board? I prefer to have everything on one board.
    2. Since I use different motors compared to usual printers, how much work will it be to connect them and make them work?
    3. I will put a 24VDC input on the board which will be needed for the heating bed and the hotend. Will this influence the other ports for anything and if so, what to do about that?
    4. I see that there are two external stepper driver inputs available within the LCD com, how does that work? Just appoint them in the config.g file? And they are called E2 to E8, which sounds like an extruder to me. Is is easy to make these my x-y-z motors, instead of the build-in motor outputs which have the stepper drivers internally? Can I also disable the stepper drivers (I saw something like that on the Duex5) so I can just use the x - y - z inputs on the main board?

    Thanks in advance.

    Kind Regards,

    Peter



  • @peterartechno

    on point 3 , I would say you need a mosfet or use a ac heated bed ?
    Looking at the docs it says 18 amp which is 435 watts max for a 1100 x 600 bed that is a bit low.

    Will this influence the other ports yes the fan will be 24 volt .


  • administrators

    @peterartechno said in Using a Duet 2 board with external stepper drivers:

    Hello,

    I am building a giant 3D-printer (1100x600x500 mm) where I use 24VDC D808 stepper drivers for my motors. I am interested in buying the Duet2 wifi/ethernet but I have some prior questions:

    The Duet 2 can drive carefully chosen Nema 23 motors directly, so you may not need to use external stepper drivers. Duet 3 has even more powerful stepper drivers that can drive some Nema 34 motors directly too. However, if you still want to use external stepper drivers, see https://duet3d.dozuki.com/Wiki/Using_external_stepper_motor_drivers.

    1. I previously used the Ultratronics pro v1.0 since that one has an option to put in the motors by breakout (without the use of internal stepper drivers) I will only use an internal stepper driver for my extruder, which is a Nema17 motor. For my other motors I want to use breakout pins, in any way not the internal stepper drivers since they are not strong enough. Is it possible to use the pins on the 50-way DCI for connecting my motors without buying the expansion board? I prefer to have everything on one board.

    The 5 stepper driver outputs on the 50-pin expansion connector, and the 2 outputs on CONN_LCD all provide 3.3V low-current signals. As most stepper drivers need 5V signals at higher current, some sort of level shifter is usually needed. That's why we make the external stepper driver breakout board.

    1. Since I use different motors compared to usual printers, how much work will it be to connect them and make them work?

    To make them work you will need to set suitable timings for your drivers in the M569 commands in the config.g file on the SD card, but that's about all.

    1. I will put a 24VDC input on the board which will be needed for the heating bed and the hotend. Will this influence the other ports for anything and if so, what to do about that?

    The fan outputs will also be 24V. There are ways of using 12V fans if you need to. [Duet 3 supports both 12V and 24V fans when VIN is 24V.]

    1. I see that there are two external stepper driver inputs available within the LCD com, how does that work? Just appoint them in the config.g file? And they are called E2 to E8, which sounds like an extruder to me. Is is easy to make these my x-y-z motors, instead of the build-in motor outputs which have the stepper drivers internally?

    The names of the outputs are not significant, because you can map any axis or extruder to any stepper motor output, using the M584 command in the config.g file. Internally, the firmware numbers the drivers on the Duet 2 from 0 to 11.

    HTH David


  • administrators

    @peter247 said in Using a Duet 2 board with external stepper drivers:

    @peterartechno

    on point 3 , I would say you need a mosfet or use a ac heated bed ?
    Looking at the docs it says 18 amp which is 435 watts max for a 1100 x 600 bed that is a bit low.

    I agree, you should plan for around 0.4W per sq cm of bed. A bed of that size needs an AC mains voltage bed heater controlled by a zero-crossing SSR.



  • hello,

    Thanks for answering. The MOFSET used for my heating bed will be redirected to another MOFSET with AC 10A on 240V, which is enough power to heat by bed.
    The problem I had with my previous board (Ultratronics) is that my motors and stepper drivers were not activated by this board (signals did not move the motor). I already have big motors, controlled with D808 drivers. I want to use these drivers and have no need for the internal drivers, except for my extruder, which is a regular Nema17.

    I need 12V ports for my fans, but the Duet3 does not support the breakout board for my external stepper drivers so I can't use that one. How to make the fans 12V?

    stepper drivers.jpg motor.jpg

    Does the initial configuration go by sd card or by usb?



  • And @dc42 , there is a +5V input in the DCI, so why is there need for an additional breakbout board? Is that 5V not sufficient?


  • administrators

    @peterartechno said in Using a Duet 2 board with external stepper drivers:

    And @dc42 , there is a +5V input in the DCI, so why is there need for an additional breakbout board? Is that 5V not sufficient?

    The outputs on the expansion header and CONN_LCD only have 3.3v signals levels, so they are not safe to use with a 5V supply.

    The usual way of driving 12V fans from a Duet 2 is to use a step-down converter to generate 12V and feed its output into the centre pin of the V_FAN jumper block.



  • Ah I see I have 24V fans so that will not be a problem. When reading the page of the expansion breakout board, I read that the board will have a voltage of 3.6V. When I follow the instructions, it states that I have to put the STEP+ of my driver in the +5V of my servo connector (one of the two). But if I have more than 2 drivers, how do I set it up within the expansion board?


  • administrators

    You can connect multiple STEP+, DIR+ and ENA+ wires from your driver to the same +5V pin.



  • How does it get the signals then? From all the - pins?


  • administrators

    @peterartechno said in Using a Duet 2 board with external stepper drivers:

    How does it get the signals then? From all the - pins?

    Yes, it's the difference in voltage between the + and - pins at the external driver input that the driver responds to.



  • okay thanks, is there also a limit to how much pins you can connect to the 5V pin? I assume that there is a maximum of amperage that it can hold? I have 3 d808 leadshine stepper drivers.

    Is it also possible to connect the E+, D+ and S+ within the driver and using one cable to get to the 5v?


  • administrators

    Each external driver input pin draws only about 10mA or less, so you can connect as many as necessary to each +5V pin.

    If we ever revise the EBOB design, we'll likely add a +5V pin to each stepper driver output connector to make this type of wiring easier.



  • Thanks for your answer. I found out that my driver also accepts 3.3V (tested with arduino mega). Is it possible to directly connect the 6 pins from the EBOB to the driver? No extra 3.3V pin


  • administrators

    @peterartechno said in Using a Duet 2 board with external stepper drivers:

    Thanks for your answer. I found out that my driver also accepts 3.3V (tested with arduino mega). Is it possible to directly connect the 6 pins from the EBOB to the driver? No extra 3.3V pin

    Yes.


  • administrators

    @peterartechno said in Using a Duet 2 board with external stepper drivers:

    Is it also possible to connect the E+, D+ and S+ within the driver and using one cable to get to the 5v?

    Yes, that too.


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