New Pololu DRV8825 " truly an A4988 "drop in" replacement?

[Alex]

Anyone try the new DRV8825?

http://www.pololu.com/catalog/product/2133

It says "Drop In" replacement.  From the last discussion on the previous generation, it turned out that one was not drop in and problems with the stepping?

I wasn't smart enough to follow the rest of the conversation, but will this one be a true drop in?  Or will there still be stepping issues?

If it does just drop in, then I set it for 1/16 microstepping and everything else should be good? no configuration.h changes, RAMPS jumper settings.. etc

Thanks in advance.

[Jim Morris]

I use them, they are "almost" a drop in replacement with some caveats.

1. The micro stepping jumpers need to be changed as the default 1/16 all in for a4988 is 1/32 on the drv8825.
2. They only work when the 12v is on, and the vRef can only be set with 12v on (unlike a4988)
3. the vref needs to be set differently Current Limit = VREF × 2 as opposed to 2.5 on a4988.

They loose their micro stepping place when the 12v goes off unlike a4988 which keeps it as long as 5v is on.

Other than that they work pretty well.

[Larry Knopp]

Jim,

Any noticeable, obvious benefit or advantage over the a4988?

--
You received this message because you are subscribed to the Google Groups "MendelMax Support" group.
To unsubscribe from this group and stop receiving emails from it, send an email to mendelmax+...@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.
 
 

[Alex]

Thanks Jim.

For point 2, if I run 24V on my RAMPS does that mean I will not be able to use these?  Mega is powered by USB, I could do 12V to it through barrel jack if that will address this.

[Jim Morris]

yea they work fine at 24v. Just make sure your 100uF caps on the ramps are 30v or better.

[Jim Morris]

The main benefit for me is the 1/32 microsteps, much quieter, but you need more than an AVR to run fast at that stepper frequency, I use Smoothie for that on an arm.

Also (less important to  me) is they support higher current steppers if you got them.

I also like the ones Panacutt sells... http://www.panucatt.com/product_p/sd8825.htm

But if you are running at 1/16 and under 1.5 amps I don't think there is any advantage over regular pololu a4988

[Larry Knopp]

Thanks Jim!

As always, really appreciate the real-world experience and analysis.

[JohnD]

FWIW, I'm using Roy's (Panacutt ), and they work fine as pololu replacements.  Some people claim that the 8825's produce a high pitched noise when the steppers a locked, but if they do, I can't hear it.

Same as Jim's experience, 1/32 is pointless unless you are running faster than an AVR.