Matching Stepper Motors, Drivers, and CNC shield

Other Hardware Motors, Mechanics, Power and CNC
1

Hi all,

I'm a beginner doing my first CNC project, so forgive the basic level of my question.

I've bought the motors below and an Arduino Uno, and I've just ordered a CNC Shield V3 to power them. The page for the CNC shield says I also need to get "Pololu A4988 compatible stepper drivers".

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However, on a previous post about these motors I was advised that "the cheap A4988 drivers won't handle your motor." and directed towards this MP6500 driver. So I have two questions:

  1. will the MP6500 driver work with the CNC shield?
  2. Why won't the A4988 driver work with my motor? It seems like the rated voltage and current (2.4V/1.5A) isn't too high.

Thanks in advance for any advice.

2

A4988 is what RAMPS 1.4 suggests and since your motor looks similar, I'd go with what your shield documentation recommends. I suspect that the advice you were given is because the driver can't supply the maximum rated current for your motor. I'm not convinced that matters here.

3

Thanks for the reply. So, does that mean that my motors might be a bit weaker than they could be, but they won't fry the chips or anything? If that's the case I'll take your advice. I'm only building a pen plotter so they don't have to be super strong, I just don't want to damage any of the hardware I just spent my money on.

4

There are pots on the Pololu drivers that let you dial the current down (don't touch them when they are powered up) and that's recommended for the Prusa Reprap I assembled using A4988 boards, so if it works for a 3D printer, I think your plotter should be fine.

5

For a 1.5A steppers DRV8825 modules might be a better choice, less likely to shutdown through overheating. Thus if you are stuck with A4988's a slightly lower current setting might be needed for reliable operation, perhaps 1.3A.

6

With heat sinks and forced air cooling 1.5A should be no problem with good quality DRV8825 drivers (Pololu brand, for instance).

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7

Sorry again for my rookie questions, but is the DRV8825 interchangeable with the A4988 in the CNC shield, just able to deliver more current?

EDIT: Googled it a bit and the answer appears to be yes. Thanks for the advice everyone!

8

Yes, the DRV8825 is a direct replacement for the A4988, just able to handle more current and the DRV8825 will allow X32 microstepping where the A4988 is max X16.

Make sure to set the coil current limit on the DRV8825 module before using the motors. The Pololu DRV8825 page has instructions (and a video) on how to set the coil current limit.

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9

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