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.
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.
From your picture, it does not look like you have one of our DRV8825 driver carriers (our DRV8825 boards are purple). Some knock-off versions of the DRV8825 carriers have known issues with the VREF via, as discussed in this RepRap blog post. If you got those DRV8825 boards somewhere else, I suggest contacting the manufacturer to see what they recommend.
It was a gift, but I sent the person who bought it for me this link, and the bag it came in says Pololu. The board looks purple to me, although a very dark purple. The bag says X0018YED15, if that means anything. I thought it was a part or model number, but a Google search doesn’t return anything. Perhaps a serial number.
Can you post some better pictures of both sides of the DRV8825 board that clearly show the components and solder joints? Also, can you post a short video of how you are trying to measure VREF while setting it?
I took it all apart so I could rewire it a little more clearly for the video and pictures, and it seems to be working now. The potentiometer is very sensitive, and seems to go between ~0.5 V and ~1.7 very quickly, but 0.5 V is fine for what I’m doing, so I’m just going to leave it there and test the motor. Thanks for the help, I’ll check back if I have more problems.
Since the last post, I think I’ve gotten the potentiometer part working, where I can set the current limit, but after that I can’t get the motor to actually turn. I’m trying to control it through a Raspberry Pi, and I know that’s not exactly what this forum is for, but I thought someone here might know a little more than me about it.
I’ve confirmed that I have 3.3V from the two output pins that are connected to the DIR and STEP pins on the driver, but from here I’m not sure how to troubleshoot the problem.
Your connections seem fine, but the way your header pins are installed looks like it could be a problem. Can you post close-up pictures of both sides of your DRV8825 carrier so we can see the soldering and pin length?
Also note, the DRV8825 will only step the motor when you transition the step pin’s signal from logical low to high, so you will need to provide a toggling signal like that to test the driver (simply tying it high will not cause the motor to step).
I will take the pictures when I get home tonight, but nothing is soldered right now, it’s all just connected through the breadboard.
I didn’t realize that it would only step when the step pin signal is changed, so that may be a problem. I think the tutorial video code was doing that, but when I was trying to do it on my own afterward, I just had the step and dir pins at a constant logical high, assuming that would just make it spin.
