How To Correctly Set The Motor Current Limit On An A4988 Stepper Motor Driver

In this Tutorial video, I'm going to be showing you how to correctly set the motor current limit on an A4988 stepper motor driver. These drivers have become popular for CNC, 3D printing, robotics and Arduino projects because they're relatively cheap and really easy to use, they only require two pins to provide full control of a stepper motor.

There are two methods to do this, the one is to use a multimeter to physically measure the current flowing through one of the coils and the second method, which is the one we’re going to look at, is to calculate adjust the reference voltage on the driver, which doesn’t require the motor to be hooked up or powered.

Components Required

If you've got any Tutorial requests or suggestions, let me know in the comments section below. I'm always looking for suggestions.

[FamilyHomeTheater]

Liked simply because you took the time to get good sharp up-close video!

[davidgiardini]

Thank you, you save me a lot of time. I did it on my 3d printer directly.

[MatthewUpp]

The sense resistors on the driver board in the video are 0.100Ω
(R100). Should that not be used instead of 0.068Ω ?
I understand that the sense resistor values used vary depending on the manufacturer but I want to make sure I am not missing something.

[Antbond]

Awesome tutorial! Strangely enough, my potentiometer on my A4988 board doesnt go above 0.78 when I need it to go to a value of 1.2.

[TomTRobot]

It would have been nice to include a confirmation using the voltmeter and a stepper coil. It seems that one advantage of the approach measuring the current through a stepper coil and measuring current through the multimeter would be that you may not need to do any calculations since you'd be able to read the current directly. However, you would need to be careful to start with the pot at minimum current and then increase from that point. Another advantage is that you;d have no doubt that your setting was correct.

[harshithramsundararaman]

I have a question. I am using 24 volts to power the Nema 17 bipolar motor. Is the process for setting the Vref the same? All I have to connect si the logic pwoer supply and then connect reset and sleep and then adjust the potentiometer to adjust the vref?

[ColdWarVet]

You should place the GND right at the chip not on the arduino, you want to measure what the chip sees as pwr and gnd. Granted there may not be enough current to produce a voltage drop but its always BEST practice to GND at the device you are measuring same goes with power. You probably want to ensure STEP is pulled low.

[kiranshashiny]

The Vref is set to 0.48v, but one out of 6 or 7 times the motor spins in opposite direction !
I have my DIR set to to clockwise, and it works fine, until suddenly the motor DIR spins **anticlockwise** !, and them goes back to it's programmed DIR ( i.e clockwise )

I have a Nema 17 and have used the formula as per data sheet and your video.

[kiranshashiny]

The NEMA motor is spinning good, until I touch the POT of the A4988 with a small screw driver and then suddenly the motor starts to shiver, and tries to jump/ rattle !
The Vref is set to 0.48v, Current sensing Resistance is 0.068, Imot = 0.9 and DIR is set to clockwise and it's running fine until I touch the A4988/Pot with a small screw driver ( Like I 'm shorting some internal circuitry)

[BasWasAlBezet]

When you say "the maximum motor current", does that mean per phase or for both phases combined? The datasheet for my stepper just says "1A max per phase" and it has two phases, so does that mean the maximum motor current is 2A or should I stick to 1A?

[blackbox]

Sir, Great video. Learned a lot. I have purchased a stepper motor from the local market. It has following details:
TYPE 17PM-K310-33VS
NO. T4524-01
MINEBEA-MATSUSHITA MOTOR CORPORATION.

There are no other details. I cannot find a datasheet. I am using CNC shield 3 & A4988 driver. What voltage should I set?
Thanks

[CineMuck]

Hi! Thanks for the video!
I'm driving my stepper driver from a Piu Pico that has a 3, 3V output.
Does that have any effect on the Voltage I need to set?

[sajadmohammadi]

Thanks for tutorial. I did exactly what you explained, but there is strange noise from stepper motor after every single motion. Imax is 1A, Rs equals to 0.2, therefore Vref is 1.6 minus 10% for safety. I would appreciate your help.

[cotomaznaczyc]

No matter what I do, the voltage on the motor driver never changes when I rotate the screw. Two A4988s and one tc2209 and it's the same behavior with all of them. Any idea what I could be doing wrong?

[heitorgoku]

What kind of screwdriver do you need for that potentiometer? None of the ones I have can turn the danm thing.

[dzarren]

Where does the 8 come from in the reference voltage formula? Thanks!

[leahcornelius]

a note for anyone watching, the heatsink must be placed on the UNDERSIDE of the PCB. The datasheet shows there are 4 thermal vias (small holes in the pcb) leadigng to the bottom of the board where the headsink can be attached. The chips's top is very thermally-insulating and so a heatsink on top will do practically nothing. Annoyingly the pins on the breakouts are not long enough after attaching the headsink to the ender side for breadboards or female connectors. Youll have to solder it to a stripboard instead (or replace the pins/flip round etc). Airflow is a bigger factor for cooling these chips, make sure to use a radial fan over an axial fan and the airflow should be perpendicular to the board &/or headsink.

[dtted]

my resistance on the board is 0.2 Ohms, is that a problem? That seems a lot compared to yours

[SakibAhmed-hrbd]

some people use a different formula
current limit = Vref * 2.5
what is the difference?

[BroMalte]

Hello Michael, thank you for the video, i think it made me understand the idea correctly.
I've found my sense resistors (Rs) values, to be 0, 1, my max amps to be 0, 6A, and calculated the Vref to be 0, 48V.
My datasheet however seems to think i need to reverse calculate it because the math is:
ItripMAX = Vref/(8*Rs), indicating that my Vref has to be around ~0.75Volts, however when installed like this my Motor tends to just vibrate instead of actually starting to turn as needed every other/third time i activate the stepper.
Do you have any idea what could be wrong?
Cheers from Denmark