Hello Doramason.
For your test with the nema14 4V 0.8A 5ohm, the minimum current with the drv8825 is: 1.44V/5ohm= 0.288A.
You have tested with:
- In 1/16, the second microstep is 10%, so 0.8Ax0.1=0.08A or 0.08<0.288 it's not good.
- In 1/8, the second microstep is 20%, so 0.8Ax0.2=0.16A or 0.16<0.288 it's not good.
- In 1/4, the second microstep is 38%, so 0.8x0.38=0.304A or 0.304>0.288 it' good.
Your test confirm what i saw in the datasheet.
For 9V power supply:
- The minimum voltage with drv8825: 9V*0.12=1.08V
- The minimum current with your motor (nema 14 4V 0.8A 5ohm): 1.08/5=0.216A
So for :
- In 1/32, the second microstep is 5%, so 0.8x0.05=0.04A or 0.04<0.216 it's not good.
- In 1/16, the second microstep is 10%, so 0.8Ax0.1=0.08A or 0.08<0.216 it's not good.
- In 1/8, the second microstep is 20%, so 0.8Ax0.2=0.16A or 0.16<0.216 it's not good.
- In 1/4, the second microstep is 38%, so 0.8x0.38=0.304A or 0.304>0.216 it's good.
So no change with 9V power supply.
For the potentiometer it' nothing just be careful when you set the vref...
For the hot nema17, set the vref to something smaller until the motor temperature is good.