# Stepper motor speed - Driver or motor limitation?

Hi,
I’m using a A4988 driver and the motor start to stop when I try step values of 500 steps per second. Is this a motor or driver limitation?

I tried with diferents motors and the result is ± the same, some motors start to flip at 350 steps per second and another goes to 550/600.

The motors I tried are:
pololu.com/catalog/product/1204
PF35T-48L4
vexta px245-03aa-c6 - 2-pahse 12v 0.4A

The power source is a 9v 2A. I measured the current consumption with a multimeter and it never go higher than 1A with A4988 the current limiting in the max.

How can I estimate the max motor speed?

Thanks

Hello.

Could you clarify what you meant by the “motors start to flip”?

In general, the step rate is limited by the stepper motor. Based on the datasheet you gave for the PF35T, 500 steps per second seems like a reasonable maximum speed. However, I expect you to get more than 500 steps per second from the nema 8 hybrid bipolar stepper motor (#1204). Do you have a load on your stepper motor? This graph, for the nema 8 hybrid bipolar stepper motor, should give you an idea what pulse rates you can expect form it at certain loads. Most stepper motor datasheets have similar pull out torque curves that can give a good approximation of the maximum speed of a stepper motor at certain loads

It sounds like you might have not set the current limit appropriately. Please refer to the “Current limiting” section under the “Description” tab on A4988 driver product page for instructions on how to set the current limit using Vref. You might also consider using a power supply with a higher voltage. By using a higher voltage along with active current limiting, the current is able to ramp up faster, which lets you achieve higher step rates than you could using the rated voltage. In addition, since the vexta stepper motor you mentioned has a rated voltage of 12V, you will only be able to get the maximum amount of torque and speed from that motor when using a supply voltage of at least 12V.

- Jeremy