On Sat, Jan 07, 2006 at 06:23:28PM -0500, David VanHorn wrote:
> > How would I maintain the current control then? I do need to be able to
> > drive the motors at high speed as well as low speed, so a constant
> > current driver is a must.
> 
> 
> The difference between an op-amp configured to provide a voltage, and one
> configured to provide a current, is one resistor.
> Two LM-12 chips or similar would give you a butt-kickin analog drive with
> about +/- 35V compliance.
> Connect one side of the windings to ground, and drive the other side with a
> voltage to current converter made with the LM-12.
> 
> Now you have no chopping products to worry about or get rid of, and you can
> microstep at whatever level you like without worrying about interactions
> with the chopping frequency and the stepping.

Thanks for the suggestion, I looked into it a bit more, and if seems
like a very effective "delux" method. The time to develop it still
concerns me, so I'll probably propose to the lab that I first get a
cheap(er) off the shelf stepper driver kit based on the LMD18245 chip
that I already have used and know works fairly well and then upgrade
that to the op-amp design if they still have problems.

-- 
pete@petertodd.ca http://www.petertodd.ca
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