A4988 Stepper Motor Driver with low volt stepper

Hello all.

I’ve bought Stepper Motor: Bipolar, 200 Steps/Rev, 28×45mm, 4.5V, 0.67 A/Phase
pololu.com/catalog/product/1206

and A4988 Stepper Motor Driver Carrier
pololu.com/catalog/product/1182
and it is rated at minimum 8 Volt
now I’m applying for driver 7.5V and my stepper heated as iron.
but if decrease to <= 5V - it don’t even spinning .
and at 6V engine whistles - issue a very similar sound even when it is not spinning, and this whistle stopped at 7.5V … but stepper very hot.

should I had to take another driver ? for example low voltage:
pololu.com/catalog/product/2134

Hi.

It is generally bad practice to supply electronics with voltages outside the range they are rated for, so you shouldn’t supply the A4988 driver with less than the 8V minimum it requires. For stepper motors, the important rating not to exceed is their current rating. This means you can use the current limiting feature of the A4988 and still drive your motor at a voltage above its rated voltage. For more information about this, please read the FAQ on the subject on this page.

Regarding using the low-voltage driver, if you would like to use a lower voltage with your motor, then you could use the DRV8834, but if you can power the A4988 above 8V, then you shouldn’t need it.

- Zeeshan

Hello.
Thank you for answer !

I’ve read about current limiting but I don’t understand how to use it ?
Should I just rotate this resistor and check when my stepper motor will not overheat ?
Also I don’t understand your mention about driver - [quote]but if you can power the A4988 above 8V, then you shouldn’t need it.[/quote] - so if I can supply voltage above than 8V from my power supply, then I don’t need low-volt driver ?

[quote=“d00m”]I’ve read about current limiting but I don’t understand how to use it ?
Should I just rotate this resistor and check when my stepper motor will not overheat ?[/quote]

You should really use a more rigorous method to set the current limit. You can follow the instructions on the A4988 product page under the section Current Limiting. If there are specific things you don’t understand, let me know and I will try to clarify.

Yes, that is correct.

- Zeeshan

Thank you for you help but…

Unfortunately I don’t understant how to use this method for current limiting…
Do I need rotate this potentiometer or not ?

my stepper - Stepper Motor: Bipolar, 200 Steps/Rev, 28×45mm, 4.5V, 0.67 A/Phase
but I need minimum 8V for driver…
so I’ve connected to my power supply which can supply 3/4.5/5/6/7.5/8/9/12 V and 2.25A - so it is maximum current
I’ve choosed 7.5V

should I change power supply or it is possible setup current via driver ?

[quote=“d00m”]Unfortunately I don’t understant how to use this method for current limiting…
Do I need rotate this potentiometer or not ?[/quote]

Yes, you will need to rotate the potentiometer, which will change the VREF voltage. You should monitor that voltage and make sure it corresponds to the appropriate current limit for your stepper motor.

[quote=“d00m”]my stepper - Stepper Motor: Bipolar, 200 Steps/Rev, 28×45mm, 4.5V, 0.67 A/Phase
but I need minimum 8V for driver…
so I’ve connected to my power supply which can supply 3/4.5/5/6/7.5/8/9/12 V and 2.25A - so it is maximum current
I’ve choosed 7.5V

should I change power supply or it is possible setup current via driver ?[/quote]

7.5V is not an appropriate voltage for something that has an 8V minimum. Using a part like this outside of its operating voltage range is a good way to damage it. I suggest you supply the driver with 12V.

- Zeeshan

Then I need use voltmeter and monitor voltage on 17 pin ?
but what voltage I need to see ? Is it depends on voltage from power supply ?

I’ve tried supply 8V but my stepper gets much hotter so I decrease to 7.5 V
And why you suggest supply 12V ? I don’t understand how 12V will be better than 7.5V or 8V…

and thank you once more for you help and explanations… seems things gets better )

ok
I’ve tried to do something.
As described at pololu.com/catalog/product/1182 under “Current limiting” reference voltage should be measured on the “ref” pin and then current limit could be calculated by this formula:
Current Limit = VREF × 2.5

So if my motor is “3.8V, 0.67 A/Phase” then I need set reference voltage to
0.67 == vref*2.5
=>
vref == 0.67 / 2.5 == 0.268

Is it right ?
I connected my voltmeter to pin 17 and GND and began to turn the potentiometer until I saw ~0.25-0.27 on volmeter (it was about 0.87 if I remember correctly).
But, in spite of this, stepper still get hotter.
So I suppose that I did something wrong…

[quote=“d00m”]I’ve tried supply 8V but my stepper gets much hotter so I decrease to 7.5 V
And why you suggest supply 12V ? I don’t understand how 12V will be better than 7.5V or 8V…[/quote]

12V is better than 7.5V or 8V because it is within the operating range of the part (and, generally speaking, higher supply voltage allows for better stepper motor performance). The heat in the stepper motor is from the current, which is independent of the supply voltage if the current limit is being set correctly.

[quote=“d00m”]ok
I’ve tried to do something.
As described at pololu.com/catalog/product/1182 under “Current limiting” reference voltage should be measured on the “ref” pin and then current limit could be calculated by this formula:
Current Limit = VREF × 2.5

So if my motor is “3.8V, 0.67 A/Phase” then I need set reference voltage to
0.67 == vref*2.5
=>
vref == 0.67 / 2.5 == 0.268

Is it right ?
I connected my voltmeter to pin 17 and GND and began to turn the potentiometer until I saw ~0.25-0.27 on volmeter (it was about 0.87 if I remember correctly).
But, in spite of this, stepper still get hotter.
So I suppose that I did something wrong…[/quote]

That looks right to me. Please keep in mind that warmth is not necessarily an indication of a problem.

- Zeeshan

Then.

According see how they solved this problem.
I can use my stepper motor (1.7A, 2.55V) with the A4988?
Only I have to adjust the potentiometer to the voltage calculated?
So; Imax = Vref * 2.5; then Vref = Imax/2.5; then Vref = 1.7 / 2.5 = 0.68v?
Whether applied in VMOT voltage? can be 8v or 12v?

The measurement I have to do between the top of the variable resistor and GND? like in the picture?

From already thank you very much.

regards

Juan Matias

Hello, Juan.

You should be able to use your stepper motor with the A4988 and the calculation in your post is correct, but since that driver can only handle 1A per phase you would have to set your current limit to about 1A (VREF = 0.4V). However, doing that would limit the torque that your stepper motor could produce. From your picture it looks like you might be using additional cooling, so you might be able to get more current out of the driver, but the exact amount is something you would have to determine. The A4988 operates between 8 - 35V, so using either 8V or 12V for VMOT should work. Measuring VREF like you did in the picture is fine.

By the way, our DRV8825 carrier can handle 1.5A per phase and in many cases can be used as a drop-in replacement for the A4988, so you might consider using that instead.

- Amanda

Thank you very much, Amanda. :smiley: :smiley: :smiley:

In future projects I will have in mind the DRV8825 .

Saludos!!

Juan