Reply To: Current limit Stepper drivers drv8825

New Home Forum Mostly Printed CNC – MPCNC Troubleshooting – MPCNC Current limit Stepper drivers drv8825 Reply To: Current limit Stepper drivers drv8825



Haha, sorry. Maybe I shouldn’t have jumped onto this thread to ask. You’re also at the bottom of a tunnel of thoughts that has built up since right about when the website went down. And then there’s the additional pain of you having to deal with that yesterday, sorry.

I’ve never used steppers or drivers at all, except the ones in my wanhao i3, which required zero knowledge from me. So I’m also trying to understand it myself. I’m a software engineer, but I also have a degree in electrical, so I’m trying to get my head around it (you’re not responsible for my education though, so if I’m bothering you, I won’t be offended if you tell me).

When I did my testing, with no microstepping (trying to just follow that video you linked to), I did try to move the potentiometer to 1.065V (which is 1.5Vx0.71 for single step) and I measured the Vref, and it was about 1V-1.1V (I didn’t write it down, sorry). That seems to correlate with your rule of thumb. It also had a very slight hum to it right when I got to 1V. The only thing is that I was only running one motor, and I think you should be able to double that to hit the theoretical max, since X, and Y have two motors.

I’m fine with leaving them where they were shipped. At least until I start making a mess of chips.

Can you answer these two specific questions though?

1) Is the drv8825 the same as the pololu one? Does it have the same Rsense as those chips? I’m either not understanding something, or this has a different Rsense.
2) When you were talking about your 0.7V and 1.1V above, you were talking about driving two of your stock motors, or just one?