I talked to Stan today about what steps to do to implement the new stepper driver:
Our steppers are Nema 17, (17hs15-0404s). They are spec’ed for 12V, 0.4A.
- Set the current limit on the DRV8825 to the maximum stepper current. (0.4A) (Important! Read more about setup here)
- Power the drivers with 24v. This will charge the inductors faster, and then the current limiting will kick in, keeping the steppers from burning out.
- Set microstepping with jumpers on the m0,m1,m2 pins. Higher micorstepping does higher fidelity in exchange for lower torque and speed. Our physical gearing is already fine, so we will start with full steps and go lower if needed.
Note: The coil pairs are Red-Black, Green-Blue. (One datasheet we looked at was incorrect)
Stan’s library looks fully featured for what we need, and the initial software implementation appears to be straightforward. In the future, I want to have more intelligent decisions on velocity by looking ahead one or more points, and not needing to stop after each line.
We are also making the wiring:
Enable: D8 needs to be set to LOW to enable the DRV8825s. Set D8 to high to disable the DRV8825s.
Stepper shield pins:
Driving Servo: On the CNC shield, Pin D9 is passed through to END STOPS X±, and D10 is connected to END STOPS Y±. You can connect the servo to either of these pins.