Don't want to burn up my motor

Support Motor controllers/drivers and motors
1

I have a NEMA 17 stepper with a Current/Phase of .35A.

C140-A+datasheet.jpg2480×3201 436 KB

I understand I need to “current limit” your A4988 with the tiny potentiometer. I have 2 separate power sources: a Raspberry Pi plugged into the VDD and GND pins to power the board itself and a 12V 2A motor supply plugged into VMOT and GND, with a diode, of course.
When I follow the video instructions and test the poten. itself (as REF), I ONLY get the voltage from the Pi (3.3V or 5)…I’m confused about the math. I would think the poten. would tune down the incoming 12V from my ps, not the incoming voltage from the Pi. Did I connect something wrong, or, is the poten. indeed supposed to be tuning down the board power (and then based on that, some magical things accordingly tune down the per phase amperage? I’m really excited to get my motor spinnin’; please help!

P.S. I also have the RESET and SLEEP connected together; I think I see that this…“enables the board”

2

The current limit adjustment potentiometer on the A4988 is powered by VDD. You can see how it is connected to the supply and driver in our schematic for the board. There is a little more information about how the VREF pin (which the wiper of the potentiometer is connected to) is used to set the current limit on the driver in the A4988 datasheet.

If your VREF voltage is not changing when you turn the potentiometer, can you post pictures here that show how you have the board connected including any soldered connections you made? Also, what two points are you measuring the VREF voltage at with your multimeter?

-Nathan