[dubious]

Hi folks

Im new to driving steppers and Im looking for a little advice. Ill start out with what I have

a pair of japan servo (nema 17 size?) bipolar steppers that I would like to drive, they are rated at 12 volts and I measure 37.5 ohms across the coils (I know I won't have much torque, but it should be enough, for now)

a handful of laptop power supplies rated at 16v and 4.5amps

I was suprised that I could drive these steppers straight off of an atmel ATtiny12 with some authority at slow speeds for a while, but then it stopped working.... Then I went looking for small stepper drivers without too many external components and I found the allegro A3966 http://www.allegromicro.com/datafile/3966.pdf it is rated for 30v and 650 ma

Now for the questions, has anbody used an A3966, any comments or suggestions for other driver parts.

What should limit the current to for this stepper, do I just use V=IR and come up with 427ma or is it more complicated than that?

thanks for any help
Marc

[kreutz]

Hi folks

Im new to driving steppers and Im looking for a little advice. Ill start out with what I have

a pair of japan servo (nema 17 size?) bipolar steppers that I would like to drive, they are rated at 12 volts and I measure 37.5 ohms across the coils (I know I won't have much torque, but it should be enough, for now)

a handful of laptop power supplies rated at 16v and 4.5amps

I was suprised that I could drive these steppers straight off of an atmel ATtiny12 with some authority at slow speeds for a while, but then it stopped working.... Then I went looking for small stepper drivers without too many external components and I found the allegro A3966 http://www.allegromicro.com/datafile/3966.pdf it is rated for 30v and 650 ma

Now for the questions, has anbody used an A3966, any comments or suggestions for other driver parts.

What should limit the current to for this stepper, do I just use V=IR and come up with 427ma or is it more complicated than that?

thanks for any help
Marc

I haven't used the A3966, the limitation I see on that chip is the use of only one reference voltage, common for both channels. It limits the use of the chip to full and half step applications. If you plan to use only full or half step you can also use L297 (chopper and translator), and L293 (1 amp) or L298 (2 amps), and save the Atmel chip.

[dubious]

In this particular case the AVR will be the end of the line for computing, and half stepping should be good enough, Im still wondering if I should target for 427ma or something higher?

[kreutz]

In this particular case the AVR will be the end of the line for computing, and half stepping should be good enough, Im still wondering if I should target for 427ma or something higher?

It all really depends on your motors and mechanical system requirements (maximum speed, acceleration, and load).