Steppers: chopping drivers and current limiting?

Hi all, I'm hoping someone here with experience with stepper motors and 'chopping' drivers can help me.

Basically, I had to change my design for a project that was using 6v servos and 12v DC gear motors to a bunch of 6v steppers. Since I already had a voltage regulator circuit built for 12v-6v, it was not that big of a deal. However, now I need 4 outputs @ around 800mA each, and my poor LM317 can only do 1.5A. Not to mention, it's already getting darned hot with only one motor attached.

I'm using (four of) the 'easydriver' stepper controllers, which claim to be chopping drivers using the allegro A3967 ( http://www.allegromicro.com/en/Products/Part_Numbers/3967/ ) driver chips.

As I understand it, such a chopping driver constantly measures the voltage (and in fact, tries to drive it higher than might normally be allowed) feedback (?) from the motor and reduces the voltage when it gets too much feedback. (Ok, so that might not be the most accurate way to state that.)

With this in mind, would it be safe to get rid of the 12v-6v regulator all together and run straight 12v to the easydriver, or would I risk ruining my steppers?

Thanks,
!c

Others will most likely be able to talk more knowledgably about this than I can but as I recall you can put quite a bit of voltage though a stepper (much more than it is rated for) if you are using a chopper drive. It is important not to excede the rated amperage. A few years ago I built a CNC machine based on the Picstep driver (http://www.fromorbit.com/projects/picstep/) using these steppers(http://web3.automationdirect.com/adc/Shopping/Catalog/Motion_Control/Stepper_Systems/Motors_-z-_Cables/STP-MTR-23079)

I limited the current but was able to easily put 24 volts thru them with no real issues. They don't really even get warm.

I would be more concerned whather the easy driver can take 12V.

If you are interested there are a bunch of driver designs at http://pminmo.com/ and a lot of relavent info at http://www.cnczone.com

I hope this helps a little,
John

Ok, then I should be good. The easydriver can handle up to 30V, and it lets me adjust the amperage, wherein the top-end is actually right around the current limit of the steppers.

This would be a great boon, as the LM317 generates so much heat, that I was concerned about packaging. Definitely wanted to avoid any fans in the equation.

!c

I'm not much of a electronics guru but does the controller limit the current? I think this is important since if the stepper draws too much current it will burn up the controller (I found this out the hard way)

John

Update: it works perfectly using 12V instead of 6V. In fact, it works even better as there's no "whine" when the motor is braking, with 6V input, it would whine terribly, even when adjusted to the lowest possible current load that allowed the motor to move.

John, yes, it limits current. You can see from this page: Easy Driver stepper motor driver it has a 'current limit pot' that you adjust to allow current flow from 150mA to 750mA.

!c