Author Topic: A4988 stepper driver  (Read 487 times)

arrius1226

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A4988 stepper driver
« on: April 29, 2017, 08:02:46 PM »
https://www.amazon.com/gp/aw/d/B00LOF1CA2/ref=sxts1?ie=UTF8&qid=1493520679&sr=1&pi=AC_SX236_SY340_QL65

So I bought a Chinese knock off on eBay a 80cm x 100cm with a 5w laser. Got it all together with some struggles. I had a heck of a time getting a program to work right with good firmware (I used benbox I used every resource I could) eventually I bought t2laser ( I will solely be using it, well done zak  and thanks for tech support). So after some testing I swapped the motor drivers on the board after have some serious issue with the x axis. I swapped y and x around and suddenly found my x axis working and my y not ( they worked prior to the swap). Was a easy troubleshoot. Right out of the box I have to replace a drivers .. may be my fault for not tuning ahead of time.  But I am really new to this but I learned something new I'd figure I'd share as well. What better way to join a community then to try to help others. So far all the resources here have helped me greatly. I ordered the one above.. has heat sink built in and will report my findings Monday when the part comes in.



Ps: my power is currently out so this was typed by phone lol I'm not too graceful with a touch screen keyboard so forgive me for typos or grammar. Thank you all
« Last Edit: April 29, 2017, 08:04:51 PM by arrius1226 »
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Stonemull

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Re: A4988 stepper driver
« Reply #1 on: April 29, 2017, 09:25:15 PM »
These drivers are most commonly called Pololu

You can get them a lot cheaper than that especially if you buy a few at a time, bought these last time I think.
https://www.aliexpress.com/item/5pcs-lot-Reprap-Pololu-A4988-Stepper-Motor-Driver-Module-with-Aluminum-HeatSink-Adhseive-for-Ramps-1/32615281292.html

Have you read up on how to set the current correctly ? For these lasers pretty much turn up the pot if not enough torque and turn it down if motor or driver gets hot.
At the speeds we move at you generally will not need a heatsink, mine works fine at feed 3500 and does not even get warm,

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mrehmus

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Re: A4988 stepper driver
« Reply #2 on: April 29, 2017, 10:35:27 PM »
There appears to be a replacement board for the Pololu that will handle larger currents and voltage. I bought one of these packages:
https://www.banggood.com/CNC-Shield-4-X-DRV8825-Driver-Kit-For-Arduino-3D-Printer-p-1134939.html
Have not tried them yet.
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Stonemull

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Re: A4988 stepper driver
« Reply #3 on: April 30, 2017, 03:40:31 AM »
Looks like you can drop them straight in after all, https://www.pololu.com/product/2133
The fault output had me worried.
So you will need to set the software to 160 steps/mm instead of 80 since 1/32 steps but should be ok after that.


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Zax

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Re: A4988 stepper driver
« Reply #4 on: April 30, 2017, 04:36:47 AM »
Edit: It looks like they are pin compatible so you should get the same 1/16th microstepping if using an Eleks board.

You will lose top speed though as Grbl is limited on the step pulse frequency. 1/16th already has plenty of resolution and as you increase the microsteps you lose torque (not that the lasers need much).
« Last Edit: April 30, 2017, 04:39:22 AM by Zax »

Stonemull

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Re: A4988 stepper driver
« Reply #5 on: April 30, 2017, 06:22:45 AM »
Nah mate, Eleks board pulls mode 0,1 and 2 high, that is 16 microsteps on a A4988 and 32 microsteps on these guys.
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Zax

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Re: A4988 stepper driver
« Reply #6 on: April 30, 2017, 07:58:42 AM »
I must have missed that, it looked like the same pinout. Why the heck would they change it, so they're not drop in compatible. I wish they would have dip switches on the driver instead of relying on the board, which as we know doesn't always have a way to change it. You could still override with the board if you set the dip switches off (no microstepping), seems that would be the best of both worlds.

arrius1226

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Re: A4988 stepper driver
« Reply #7 on: April 30, 2017, 05:27:18 PM »
Sadly I have a Eleks copy. I have considered later buying a mana 2 axis board and just keep parts back as needed. I have as i said the Ebay buy because of the size i wanted.

I have studied the method of checking voltage. Any difference at all in DRV8825 vs A4988 ? only thing i saw was increase max voltage and a build in voltage reg.

Part comes in tomorrow so fingers crossed i have found the solution. I am eager to start engraving. Also got my first project set aside with even larger ones in the pipeline.
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ggallant571

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Re: A4988 stepper driver
« Reply #8 on: April 30, 2017, 05:44:55 PM »
www.pololu.com has a nice article on adjusting the current limiters.
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