Microstepping and Current setting Guide

Hi everyone!

Im new to all this, and decided to build a simple XY table before moving on the Repraps. Ive got everything build up with the appropriate electronics, my only question is about the electronics.

Im using the A4982 Stepsticks and Stepper motors rated 12v and 0.33 Amps. Currently the stepsticks are in full step mode and i want to set them to 8th step, can i just set the MS1, MS2 pins on the stepsticks to the appropriate step settings or do i need to also set the current potentiometer according to the new step setting? im confused, as i dont want to burn anything out!

Cheers!

The current control setting is generally independent of the microstep setting so you shouldn't have to re-adjust your pots if you've already set them for full-step mode. It's always a good idea, though to feel your motors when first working with a new setup - they'll get pretty warm to the touch, but they shouldn't be too hot for you to be able to keep your finger on it. The A4982 has over-current and over-temperature protection, so it should shut itself off before burning (or blowing) up.

Edited 1 time(s). Last edit at 10/31/2013 11:02PM by LoboCNC.

Thats clears a alot of things up but im still confused on how i should set the right current for my motors?

My motors are rated 12v 0.33 amps, currently they are getting pretty warm.

I measured the current in oil coil, in full step mode and it came exactly at 0.33amps, does that mean the current is set correctly?

There are instructions on the Pololu A4988 page for setting the current limit on that board. If, as they claim, the A4982 Stepstick board is compatible those instruction may also apply to it. BUT --- I DON'T KNOW. Do it at your own risk, or ask the Stepstick people.

...R

Edited 1 time(s). Last edit at 11/02/2013 12:17PM by Robin2.

current will be regulated by the a4988 chip, however because the motor is rated at 12v, this is the current you would use at 12v. it is likely that these motors will not work very fast at 12v, but i would like to be proven wrong.

when motor begins to move its resistance increases, and voltage is increased to compensate and increase current again. since voltage can only increase to 12v, your speed will likely be 1/3 to 1/4 that of other motors.

jamesdanielv Wrote:
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> the current you would use at 12v.

Just to clarify - this is the current limit at all voltages.

However if you are driving the motor with a 12v supply you would expect only to see 0.33A even if the current limit on the driver board is set for a higher figure. You will need to check the setting of the driver board using the proper method. As explained on the Pololu website measuring the current in the coils with an ammeter is not practical.

I agree with James that a higher voltage may be needed to get maximum speed. The A4988 can accept 35 volts input.

...R