[lsfoils]

Here is a very good read for anyone thinking about micro stepping.

http://lists.newsforindustry.com/cgi...Kr0CKf0BEHx0Af

Chart at the bottom of the page says a lot...

[bb99]

Thanks for the link! That article is talking purely about micro stepping. But what if you combined micro stepping with a chopper controller? I guess the first question is; can a chopper controller do micro stepping? If so, how would the numbers in the chart change (if at all)?

--bb99

[pminmo]

choppers vs microstepping. The Allegro 3977 does both. Just thinking off the top of my head, I'm not sure you could do microstepping without chopping.

[kfong]

Definitely go the microstepper route, lower motor resonance and smoother performance.

Try this, 3amps and up to 55volts. The nice thing is it is a microstepping chopper driver board. Software is online and the design works great. Very smooth at 8 microsteps.

http://www.embeddedtronics.com/microstep.html

Kin Fong
http://www.embeddedtronics.com

[ballendo]

Microstepping requires that the current level in the stepper coils be controllable.

Chopping is the most common way these days to control current in a stepper motor coil.

There are other ways to control the current in a stepper coil.

Therefore the answer is that you CAN do microstepping without chopping. The linistepper is an example of one approach.

But choppers are more common and more efficient...

Hope this helps,

Ballendo

Originally posted by pminmo
choppers vs microstepping. The Allegro 3977 does both. Just thinking off the top of my head, I'm not sure you could do microstepping without chopping.

[Mariss Freimanis]

"Chopping" is a particularly noxious way simple switching drives use to regulate motor currents. They are characterized by hissing, squealing and grunting sounds from the motor that result from two free-running oscillators that interact by alternatingly phase-locking and breaking phase lock (it's what makes all the unpleasant noise).

This is the method used by all the common L297/298 and Allegro circuits floating around the web.

Generally, don't trust circuits developed by integrated circuit manufactures. This is anti-intuitive I realize. You would think an IC manufacturer would have the best application notes and a circuit to match. Fact is, they are IC circuit mfgs, not motor drive design engineers. If you have any doubts, why does their stuff hiss and squeal?

The reason is most motor drive ICs are considered a backwater by IC mfgs and they assign the greenest engineeers to those products. They mean well but their designs are naive.

That is the reason I eschew the ready-made solutions and I "roll my own". A proper motor drive should be synchronous, i.e. a clocked PWM (pulse width modulated) design. It should be silent while stopped or turning at low or moderate speeds, it should not squealing like stuck pig.

The other drawbacks of packaged IC designs are too numerous to deliniate: no 2nd order damping, no reversion to full-step reference at higher speeds, etc, etc.

Mariss

[woodcam]

Sounds very interesting, are you using a PIC to navigate the idiosincrocies "eschewed"?????

[Mariss Freimanis]

Nope. 4000 Series CMOS.

Mariss