Setting the current limit on the A4988 Driver

Support Motor controllers/drivers and motors
1

Hi there

I just bought this Stepper Motor https://www.pololu.com/product/1477 . Each phase draws 1 A at 8.6 volts. I will be using the motor in Bipolar mode to microstep with the black addition of the A4988 driver. The driver has the 50Mohm sense resistors

I would like to limit the current by calculating the reference voltage that corresponds to your desired current limit and then adjust the current limit potentiometer until you measure that voltage on the VREF pin.

In this case should I set the VREF to 500mV?

Many thanks
Fiona

2

Hello Fiona,

I am sorry you are having problems setting your current limit. 500mV would not be correct for setting the current limit to 1A per phase using the formula provided in the “Current limiting” section of the A4988 black edition product page:

VREF = 8 ⋅ 1 ⋅0.050 = 400mV

Can you try setting your VREF voltage to 400mV and see how that works for you?

-Derrill

3

Hi Derrill

Thanks , I will be testing this in the next few days and get back to you then. We will try setting it to 400mV and see how that works

Your help is most appreciated
Fiona