[BetterSense]

I'm looking at driving 2-phase, 1.8 degree/step stepper using microstepping/sine-wave drive. I don't need to increase position resolution, but I need to minimize vibration to a bare minimum for an optical application. I have never had a fancy microstepping driver so I was wondering--do the 1/8th and 1/16th-stepping microstep drivers really result in a significantly smoother-running motor compared to full or half-stepping with an H-bridge?

I will probably implement my own microstepping in software. Does anyone know the PWM frequency used by microstepping drivers? I looked at the datasheet for this one

Pololu - A4988 Stepper Motor Driver Carrier

But it never says what the actual PWM frequency is. I'm guessing like 5kHz but it would be nice to know so that I can copy it.

[packrat]

Maybe this site can help. They have the code in a link near the bottom of the page.
AVR-Based Stepper Motor Driver (STMD)

Hope it helps, cary

[BetterSense]

They did post source code, but it's in assembly language and I can't read that well enough to figure out the PWM frequency they are using.

[neilw20]

Worth a look 2.5A 45v MOSFET 32 step micro-stepping, by TI. Not too expensive.
DRV8825PWP
http://www.ti.com/sitesearch/docs/un...v8825&linkId=1
External current sense resistor.
Looks like nice to run on 24 or 36v at first glance.
Leave a bit of margin on the absolute max ratings. Say 2A and 36v.

If you don't need a lot of speed you can run at a lower supply voltage, or only run at the higher voltage while doing a rapid move.

Leave the micro-stepping to the chip. You won't do it better in software (IMHO)

This might work well, as the control available is more flexible than many other chips. Big end of town like TI do this sort of thing well.

Just build it from the app notes. All the design is done for you.

[James Newton]

If you need smooth stepping, as long as you can use unipolar motors and don't need more than about 100 watts of drive power (which sounds quite reasonable for your project) then /nothing/ beats a Linistepper for smooth movement. It doesn't only use PWM, but because it is a linear driver, it can use RC smoothing of the steps. And you can tune that by increasing the size of the caps so that you get almost a true sinewave at the motor. Check out the pictures of the waveforms on the home page:
linistepper.com

And we have a page specifically on smooth motion:
techref.massmind.org/techref/io/stepper/linistep/smoother.htm

And yes, I'm biased, as I sell the kits, but ask around... we have a good reputation.

[H500]

I use 20khz PWM on my designs. And yes, 1/8 stepping is MUCH smoother than full or half stepping at low speeds.