1 Topic by agentsmith

  • agentsmith
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  • Registered: 2013-06-14
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Topic: Pololu DRV8825 drivers

Hi guys,
I see some of you are replacing stock stepper motor drivers with DRV8825 that allows 1/32 microstepping.
As I'm interested in erasing moirè effect I see on straight walls, I'd like to replace the extruder driver.

Is it possible to replace just this driver or shall I replace all of them?
Does it make sense to buy a complete set of drivers or one spare is enough?
If I understood correctly to enable 1/32 microstepping is a matter of shorting the right pins like the datasheet says, or do you need to alter anything in the firmware too?


Thanks !

Nick

2 Reply by 2n2r5

  • 2n2r5
  • 2n2r5
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Re: Pololu DRV8825 drivers

You can replace just the extruder if you want. This will definitely clean up those straight walls. That is what I use.

I have a complete set but that is because I am a bit over zealous when it comes to upgrades. 

You shouldn't need to change your jumper configuration on the board. 1/32 uses the same configuration as 1/16 of the a4498. You will need to change your steps/mm in the firmware. It should be double what you have now.

As always, check for more information on the forums.
http://www.soliforum.com/post/18295/#p18295

Good luck. I really like this mod.

SD3 w/ mods:
Glass bed with QU-BD heat pad upgrade, threadless ballscrew w/ 8mm smooth rod, spectra line belt replacement, lawsy MK5 extruder, Lawsy replacement carriage, E3D hotend, Ramps 1.4 w/ reprap discount controller, DRV8825 drivers, 12v 30A PS, Acrylic case, Overkill Y-idlers, Filament alarm, Extruder fan + more.

2n2r5's Website

3 Reply by spapadim

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Re: Pololu DRV8825 drivers

Have one on order, quick question: what's Vref set to? Same current limit (which would be .192V * 2.5/2, if not mistaken) or higher? TIA

4 Reply by ronsii

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Re: Pololu DRV8825 drivers

Here is Adrian's post about the vref settings ---> http://www.soliforum.com/topic/2817/ste … ref-chart/

5 Reply by spapadim

  • spapadim
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Re: Pololu DRV8825 drivers

ronsii wrote:

Here is Adrian's post about the vref settings ---> http://www.soliforum.com/topic/2817/ste … ref-chart/

Thanks.. So same limit. Weird, though, Pololu says limit = Vref*2 forDRV8825 and Vref*2.5 for A4988, so it seems to me multiplier should be 1.25, not 2 as table suggests (based on R2/3 values). Anyway, I'll give it a go..

6 Reply by spapadim

  • spapadim
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Re: Pololu DRV8825 drivers

FWIW, I replaced the extruder driver (only) with a DRV8825. Seems to work fine with 0.24V for limit.  Did several prints (but only one with long straight walls so far), helps significantly with moire.

No moire, so the 1/18in wobble is noticeable again (which had almost disappeared after a simple anti-backlash, or so I thought), esp in .2mm prints.  Perhaps it's time to stop postponing Z-axis hacks... smile