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Problems with stepper motors

marco3189

Jun 16, 2013
1
Joined
Jun 16, 2013
Messages
1
Hi

I'm building a goto system for my telescope using an Atmega162 as cpu, two Pololu A4988 stepper drivers and two NEMA-17 motors rated 2,4 V and with 1 ohm resistance per coil.

At the beginning I was able to move them at 300X the sideral rate with acceleration, now I'm able to reach only about 150X the sideral rate. Motors are very instable and if I simply touch with my finger the rotating part it freezes and I need to give it manually a small acceleration. I ear also a strange periodic sound.

At 300X the acceleration doesn't work anymore and if I try to unlock it with my fingers it seems to to a small fraction of rotation and the with strange rumors it blocks again.

Sometimes I forced it to move, maybe I've broken something?

The A4988 has a current regulator that can be tuned with a potentiometer. Before, at 1/4 of turn the A4988 was a little warm and if I increased over the current it was very hot (I've already burned two of them in this way...) , now even at full position the A4988 isn't warm.

For testing the stepper driver I've connected MS1, MS2, MS3 to vcc (16 microstepping), enable to ground and reset to vcc.

Can you help me?

Thank you

Marco
 

wannabegeek

Aug 17, 2011
133
Joined
Aug 17, 2011
Messages
133
I've recently been writing control program for some steppers and found a forum
dedicated to steppers.

http://forums.reprap.org/list.php?160

Sounds like a cool project. The motors I'm programming come with a complete terminal interface, but I've always wanted to try to build my own.

Good luck.
wbg
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
Joined
May 8, 2012
Messages
4,960
Hi Marco and welcome to EP. Schematics are always helpful if not essential. They're easy to post by clicking the paper clip. ;)

Chris
 
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