DRV8825 Drive Current

I want to use the DRV8825 Stepper Motor Driver with a Raspberry PI. My problem is stepper motor phase coil resistance is only 2.5 ohms, and the VMOT is at 24VDC. According to ohm’s law, the current will be 9.6 Amps !!! Should Ibe worried about this high current?. The motor"s spec sheet states the max coil is 1.5A. Am I missing something here?.


Our stepper motor drivers, including the DRV8825 use active current limiting which prevents the stepper motor from drawing too much current. Your stepper motor should have a rated current specification which will tell you what to set the driver’s current limit to, and you can find instructions for how to set the current limit on the driver’s product page under the “Current limiting” header. Keep in mind, if you set the current limit higher than what the driver can continuously handle, then it is likely that at some point the driver’s over-temperature thermal shutdown will trigger causing the stepper motor to become deenergized.

By the way, applications that require precise timing, like generating step signals for stepper motor drivers, can be tricky with a Raspberry Pi. You might consider using one of our Tic Stepper Motor Controllers since they support a variety of control interfaces that I expect to be easier to implement with a Raspberry Pi, like USB, TTL serial, and I2C. In fact, we have a Linux version of our Tic control center software for Raspberry Pi, and the Tic user’s guide includes a few Python examples.

- Patrick

OK, thanks for the great info.

Here is a link to the stepper motor spec sheet (model FY42EM150A )::::

If I understand you correctly the max amp (1.5A) is what I need to be worried about. Am I correct?

Yes, you are correct. Since your motor’s rated current is 1.5 A, and since the DRV8825 can continuously handle that much current, I would suggest setting the driver’s current limit to 1.5 A.

- Patrick

OK, thanks for your great help and support. ( ͡° ͜ʖ ͡°)

I plan to set Vref to 0.650V to ensure I don’t overheat the DRV8825 (with a heat sink on the chip).

One more question if I may. Where can I find the PCB footprint of the break-out board?

You can find a dxf drill guide and a dimension diagram that show the board dimensions and the locations of all the board’s holes on the product page under the “Resources” tab.

- Patrick

Thank you for the link.

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