Is it possible to do the above, or do I need a 5V step-down converter between my 18V 2.2A PSU and the DRV8825’s sleep, reset, m0, m1 and m2 inputs?
VMOT and GND of the DRV8825 will be directly connected to the 18V 2.2A PSU; I am using a single Pololu stepper motor 200 steps/rev. bipolar 3,8V DC 670mA/phase, the same PSU is also powering the Metro Mini and a step-up converter that supplies a 34V 350mA high-power LED. I need a single PSU solution to power everything, but I’d like to use as few parts as possible.
It should be fine to pull those logic pins (nSLEEP, nRESET, M0, M1, and M2) high from that 5V pin on your controller. The current draw of those lines will predominately be from the pull-down resistors on those lines, so it should be very low. If you want to control them on-the-fly, you could also connect them to digital output pins on your controller.
By the way, the DRV8825 can have problems with missed steps when driving motors that have low voltage and current ratings with high VMOT voltages (especially at higher microstep resolutions). It might not be a problem, depending on what you are doing, but if you application requires slow smooth movement, you might consider the A4988 carrier or the DRV8880 carrier; however, please note that these drivers only go down to sixteenth step microstep resolutions.
very helpful answer. I do not want to interactively control these five pins, just pull them high for microstepping to achieve slowest possible smooth motion for a lazy susan/gobo illumination application, for which no jitter-free regular gear motor exists. I need to rotate a 200g “heavy” perforated disk.
That video won me over to microstepping, see from 01:00 mark, and I saw many recommendations for the DRV8825 if one needs to go very slow and smooth. With only 16th I won’t be able to go smooth and slow enough.
So, I calculated with 200 steps/1.8° step angle over 60 seconds @ 6400 steps = a pulse/step every 0,01 (0,009375) seconds = 100Hz = extremely smooth? Eventually, I wanted to get smooth rotation over 1 hour, without gears, so maybe 10 minutes can be done.
Maybe I should also look at a small 400 steps motor? Or maybe your other driver will work with the Pololu motor I bought to go even slower and smoother, while avoiding a large-size stepper motor?
There are a lot of factors that go into how well a stepper motor will work with a stepper motor driver in different conditions, so it is hard to say for sure. However, I suspect for your particular setup, you could get probably smoother motion at slow speeds using the AMIS-30543 carrier like you mentioned. Additionally, lowering your input voltage to something closer to the rated voltage of the motor (but still within the operating voltage range of your driver) could also help.
Thanks, I shall order the AMIS-30543 as an alternative and see how that goes.