DRV 8825 Potentiometer not changing voltage

Other Hardware Motors, Mechanics, Power and CNC
1

I'm trying to wire a Nema 17 stepper motor to a DRV-8825 driver by following this tutorial. I got to the part at around 7:15 where he adjusts the current with the potentiometer on the driver. This isn't working for me. No matter what I do, my meter reads ~10.8 VDC when I first measure, and over the course of around 15 seconds, it steadily drops to ~9.87 VDC.

Here is a picture what I've done.

Here is a link to the powe supply I'm using. 12V/2A.

I've confirmed that there is 12V acorss the VMot and Gnd pins, so it seems like the power supply is working right. I can't figure out why changing the potentiometer doesn't adjust the voltage.

Thanks.

2

Do you have the motor connected? Look through this page, down near the bottom.

3

No, I thought I wasn't supposed to connect the motor until I get the current limit set, so that I don't fry the motor.

4

No current can flow if there's no path for it... Also the chip is totally reliant on the inductance
of the motor windings to function at all.

The idea is the module is set to minimum setting at the start of the procedure.

Overloading the motor for a few seconds will only mean it heats up at a faster rate - only if you leave
it for minutes will it start to cook.

5

I've connected the motor to the driver and gotten the potentiometer to adjust the voltage to ~0.7V. It is a 2A motor so I this should be okay I think. There is no load on the motor right now, I'm just trying to get it to turn for now, but it doesn't.

I know this is an Arduino forum and I'm trying to control it through a Raspberry Pi, but I figured there's probably some overlap in knowledge, at least at this very basic end of the spectrum. Let me know if that's not appropriate.

I've confirmed that the two pins I'm using for the STEP and DIR pins on the driver are active and have 3.3V. Past that I'm not sure where to troubleshoot. I tried turning an LED on and off to make sure I could at least do that, and it works, so I assume I have something wired incorrectly. I don't think I've fried the motor because I've been checking it and never got really hot. It doesn't get hot at all, in fact, it stays cold like it's not getting any power.

I've rewired a couple things since the first post, so here's some updated pictures if it helps.

[Album] imgur.com
6

Alive.

7

Does the enable pin need to be tied LOW?

8

DRV8825 has internal pull-downs on all the logic pins. You need to pull #RESET and #SLEEP high for it to
operate.

I'd check all these logic pins are getting their voltages correctly. If so the motor should lock in position
as the current comes on.

Note with many modules you have to measure the voltage from the potentimeter itself to ground as
the large via that's supposed to be used for this in Pololu boards is copied wrongly in the clones!