Connecting External Stepper Drivers
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I have not tried a DRV8825 however standard stepstick work out the box. I connected to E2 on the expansion port, step,dir and enable, pins 5,6,7 as shown on this diagram:
https://duet3d.com/wiki/Duet_WiFi_wiring_diagramsAlso supply 3.3V and ground from the expansion header and VIN and ground from the power supply. I used a spare RAMPS 1.3pcb I had laying around and just populated 1 stepper driver and power in components however you could use strip board equally easily.
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Tony, you should supply 3.3V to the stepstick not 5V, because you are using 3.3V drive signals.
iDevelo, you must also connect a 100uF capacitor across the 12V/24V supply close to the 12V and ground stepstick pins, to absorb the motor back emf during deceleration. You could solder it to the top of the stepstick.
For DRV8825 you will need to increase the step pulse width in the M569 command for that driver. AFAIR, 2us is enough. Also bear in mind that DRV8825s can be problematic with low inductance motors, especially with 24V power. See http://cabristor.blogspot.co.uk/2015/02/drv8825-missing-steps.html. You may be better off using an A4988 stepstick. If you use it for one of the extruders, it shouldn't be too noisy.
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Ok I'll use 4988's
I still need the capacitor right?
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I meant 3.3V - edited the post
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Ok I'll use 4988's
I still need the capacitor right?
Yes, the capacitor is essential with any plug-in driver.
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What drive number is E2, E3 etc..?
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The expansion header has E2 to E5 as shown in the wiring diagram:
https://duet3d.com/wiki/Duet_WiFi_wiring_diagramsWhen setting up axis etc these are Drive number 5- 9
So as David shows in the IDEX documentation E2 is drive 5
https://duet3d.com/wiki/Configuring_multiple_independent_X-carriages_on_a_Cartesian_printerE.g.
M584 X0 Y1 Z2 U3 E4:5
Where the second extruder is assigned to drive 5, ie E2 on expansion header
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The E2 pins on the expansion connector will be driver number 5, E3 will be 6, and so on.
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Thanks i should have guessed.
My last issue is no matter what i connect to the 4988 it ignores everything. Steps/mm etc..
I added U to it and X moves normally but U moves really rapid.
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Well barring an issue with the A4988 itself have you checked that your enable line is low? Also if it is enabled then the motor should be powered and thus held.
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Well barring an issue with the A4988 itself have you checked that your enable line is low? Also if it is enabled then the motor should be powered and thus held.
Not sure what you mean.
Also i should jumper RESET and SLEEP right?
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Have you configured the microstepping control inputs to the driver? To get x16 microstepping you need to connect the MS1, MS2 and MS3 inputs to +3.3V.
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Have you configured the microstepping control inputs to the driver? To get x16 microstepping you need to connect the MS1, MS2 and MS3 inputs to +3.3V.
Nope! I was thinking this is simple! So I just connect those pins to the 3.3v pin?
This is so not my strong point!
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Sorry, This diagram is helpfull:
https://www.pololu.com/product/1182Checkout the minimum wiring diagram but add that you need to connect MS1-3 to 3.3V as David has already said.
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Yeah i got everything correct apart from supplying 3.3v to the MS* pins.
All working thanks!
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Great!
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Glad it's working. With 1.15e and 1.16 series firmware, you no longer need to tie the Enable line to ground, you can connect it to the correct Enable line on the expansion connector instead.
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Awesome. I'll run up a page on the wiki when I get chance. If your wiring up a stepper from scratch on a PCB then it not so easy if it's a first time job!
