SparkFun Forums

[gabriellalevine]

I also am having trouble getting the motor to run as fast as I want . I’m using the sparkfun NEMA17 motors but have tried others too. My motors are rotating about 1-2 rev / sec. I’m using the accelstepper library (see below) code but have also used other code (stepper library).

I’m following the diagram for jumping the microstep pins to ground to set the resolution to FULL STEP (MS1, MS2, and MS3 jumped to Ground) assuming FULL STEP means quickest speed (right?)

However the motors run really slow (like 10 RPM) , but when MS1 is jumped to ground and MS3 and MS2 are floating it seems to run about 1-2 rev/sec but that’s still too slow. I assume I can run these motors much faster and I’m not understanding something about the motor driver.

FYI using arduino w/ library accelstepper : this is what I have in the loop stepper.setMaxSpeed(20000); stepper.setSpeed(20000); stepper.runSpeed();

[jremington]

Can you provide a link to the motor? NEMA 17 is the specification for the mounting plate and has nothing to do with the most important characteristics, which are the rated winding current and the number of steps/revolution.

Stepping motors are not intended to be "fast", rather, they are intended for accurate positioning. The speed with which they can be driven depends on many factors, but the winding current, inductance and motor power supply voltage (the higher the better) are the most important.

[Mee_n_Mac]

It appears that you haven't set an acceleration parameter and I'll guess trying to go to 20,000 RPM all at once is too much. Try setting a lower speed and/or a reasonable acceleration.

Of course this assumes you've got a good supply and set the current limit to some good value.

[gabriellalevine]

Thanks for the responses - I did try with acceleration set to 100 and 1000 and that's the same issue, too slow.
This is the motor I have:
http://www.geckodrive.com/g717-90-4.html, 1.8 degrees per step so 200 steps per rev.
And I'm using a bench power supply providing 35 V and upto 20 Amps, although the motor seems to be drawing less than 0.5 amps.
I understand steppers arent meant to go fast, but I was thinking I could get at least 180 rpm. Am I wrong about this?

[Ross Robotics]

A little off topic, but I like how they list the stepper voltage as 2.4V in the specs.. lol?

[jremington]

The 2.4 V rating is obtained simply by multiplying the winding current rating and winding resistance, and although this number is not particularly useful, it is common for manufacturers to provide it. Motors like this are commonly used with power supplies that provide 10-20 times the voltage rating.

Without extra cooling, the A4988 chip used in the Big Easy Driver can supply only about 1.5 amps/winding before it starts to overheat and shut down, so it is ABSOLUTELY ESSENTIAL that you follow the directions in the BED manual to set the winding current to a reasonable value, like 1.0 amps, for testing purposes. Use full step mode.

It is not useful to monitor the motor power supply current for this purpose, as the motor/driver combination acts like a switching buck regulator. The average winding current will be higher than the power supply current.