Pololu A4983 Stepper Driver

Good day,

I need some help with my Pololu A4983 Stepper Driver that i bought the other day,
https://www.pololu.com/catalog/product/1182

I hooked everything up as in the picture in the link above, and nothign worked. i used 5v as my motor power as to not blow anything as my electronic experiences have lead me many times :cry: .

I now see that the motor voltage range stated is [8v - 35v] can the voltage not be less that this?

As the stepper i wish to use says 4v and 1.3A but if i then put 8v through there it is going to use allot of current and probably blow the chip?

What am i to do?

Hello.

The listed operating voltage range is the actual range of the device, so you should not expect it to work outside of that range. However, it is fine to use this driver with a stepper motor rated for a lower voltage. Please see the first FAQ for more information:

pololu.com/catalog/product/1182/faqs

- Ben

Yes, ok i know the voltage can be higher than the motor says,

But when i put 12v into that (4v 1.3A) motor its going to draw allot of amps? is it not?

Ok, so i see that they say i must use the build in current limiters.

Do these work 100% ( i really don’t want to cook my chip).
And how do i go about setting it to the right amount? i see its just a variable resister that you turn?

I am not sure what you mean by “work 100%”. We test each board before it ships, so you definitely should have received a fully functional board. There are many ways to damage them through misuse, however. I suggest you read the product page carefully before you make any connections, and double-check everything before you apply power (although it sounds like you have already connected 5V power to this driver, which could have broken it if you had your connections wrong).

Given how nervous you seem to be and your claim that you have fried many electronics components in the past, you should pay special attention to the warnings on the product page. If you want, you can post a picture of your setup for me to look at before you actually apply power. Whenever you physically change your connections, make sure power is disconnected, and be careful not to short anything. If you aren’t very good at soldering, I recommend you look online for a good soldering tutorial so you can be sure to have good, clean connections.

The procedure for setting the current limit is described in detail on the product page. If you have any questions about the described procedure, please ask.

- Ben

ok i know i sounded abit noobish,

But i am just being over cautious as i have blown things in the past, but simply from just over power them. i So i have learnt from my mistakes.

That is why i am asking on the forum before doing, cause i have learnt.

K so i will have a look into the current limiter.

What i meant by does it work 100% is that.

Is it no better to just supply the motor with the correct voltage rather than a higher voltage and then limit it?
And will the chip not get warmer with it having to do current limiting?

And another question. Is it possible to damage the chip (if wired correctly?) Cause it has current protection and temperature protection. So with these in place it shouldn’t be possible to overheat the chip correct? How do i know if the limit or temperature protection has kicked in? will it just shut down?

Thanks

Performance will be better if you use a higher voltage and set an appropriate current limit. Also, it is not an option to use 4 V (your stepper motor’s rated voltage) with this driver. The current is limited in a way that does not waste significant power.

The overtemperature and overcurrent protections should generally prevent the driver from being damaged when pushed beyond its intended limits, but it is never a good idea to rely upon such protections as there’s always a chance the damage could be done before they even kick in. For example, if you are not adding a heat sink, you should set the current limit to something under an amp per coil. If the driver overheats, the outputs turn off until it cools off.

- Ben

Thanks for your reply, It was very helpful.

Pk that is what i wanted to know. I was planning on keeping it under 1A. And i would rather not test the protection mechanisms. but its good to know they are there in case…

On the heat sink note…
How would one even attach a heat sink to such a small chip?
Would mounting a small powerful fan over the chip help much? ie. 1.5A ? Or would a full on heat sink and a fan be needed?

On the site it says u need a heat sink, but it doesn’t elaborate on it.

Adding onto my questions,

Q1:
You said,

now where do i find the ideal balance ?

Cause surely the higher voltage i go the more it is going be PWMed so it will have a smaller duty cycle (i think)
I don’t know, but i am assuming there is a formula some where that will provide me with the optimal voltage to power my steppers?

Q2:
With the micro stepping. Smaller is more accurate as it turns less. But does the power / torque lessen as well with the micro stepping? if i want maximum strength (im not concerned about speed at this stage) do i want to use full step?

Thanks

Ideal in what sense, and why do you think that a smaller duty cycle is worse? In general, higher voltage allows for higher step rates and slightly more torque. If the voltage is too high, though, the driver might not be able to achieve very low current limits, which could in turn make the smaller microstepping resolutions function poorly. Another issue with higher voltages is that they raise the risk of damaging LC voltage spikes on application of power (see the warnings on the product page for more information).

You should use whatever voltage, within reason, is convenient for your application (e.g. 12 V is fairly common). If you find you need more speed or torque, then you can look into raising it.

The short answer is that microstepping should not have a significant impact on torque. The long answer is that things can get complicated with steppers, and you might see a difference of a few percent. I did a little searching around and found this post that talks a bit about those complexities:

cnczone.com/forums/stepper_m … post127081

- Ben

Thank you very much for your input!!

You answered all my questions :smiley:

Will putting a cap on vmot and ground help with the voltage spikes you where talking about?

Yes, assuming it is the right kind (e.g. at least 47 uF electrolytic).

- Ben