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Calculate max RPM for stepper motor
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Calculate max RPM for stepper motor

by gaudrylab on Wed Jul 18, 2018 5:59 pm

Hello everyone,

I am running this stepper motor from Adafruit

https://www.adafruit.com/product/324

and I am curious what the maximum RPM is that I can expect from it when driving it with the recommended 12V. I am currently using this driver

https://www.amazon.com/gp/product/B0721 ... UTF8&psc=1

on a Raspberry Pi 3 and it is very slow. Perhaps only a couple of RPMs. I am curious what the limitations of the motor are before troubleshooting the code and driver.

Thank you,

gaudrylab
 
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Joined: Wed Jul 18, 2018 5:41 pm

Re: Calculate max RPM for stepper motor

by adafruit_support_bill on Wed Jul 18, 2018 7:52 pm

There are a number of factors that determine the maximum RPM:

That board uses a PCA9685 PWM chip to control a pair of TB6612 motor driver chips.
The PCA9685 has an i2c interface, so one limit will be the speed of the i2c bus.

Another limit will be the software library you are using. The combination of the i2c bus speed and the library overhead will govern the maximum step rate that can be generated by your program.

The TB6612 drivers are simple constant voltage drivers, so another limit will be the inductance of the motor windings. That will limit the torque that can be generated for each step.

And then there is the load. Since stepper motor torque decreases with step rate, the higher the load, the lower the maximum step rate.

adafruit_support_bill
 
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