Re: need components for stepper drivers

At 00:00 30/09/2002 +0000, you wrote:

>At 6:26 PM +0100 09-29-02, Tony Jeffree wrote:
> >The Allegro 3977 does up to 8 microsteps & up to 2.5A at 35V. There's a
> >3-axis board available from http://www.xylotex.com/
> >
> >What is the application you have in mind?
>
>Thanks Tony. The 3977 looks good. Jeff Demand said they were a little
>fussy about supply voltage, and that unplugging a powered motor was
>most likely to be fatal (to the controller). Have you had any such
>trouble? Also, I'm a little concerned about limited availability
>(Newark only).

I haven't used the 3977 yet - I have some samples, but have not had the
time to play with them. I have ordered a Xylotex board to replace the
unipolar driver on my Taig mill, so that will give me a chance to see how
they perform. So far, I have used the L297/L298 combination - not
microstepping, but they work pretty well. With those, I have on occasions
plugged/unplugged motors while powered up & have yet to fry a 298, although
this is generally not to be recommended.

>I'm the fellow who designed the Sherline CNC controller
> (see http://www.bmumford.com/cncindex.html)

Nice work. I have also designed a stand-alone indexer
(www.divisionmaster.com) - that uses the 297/298 combination.

>I'm thinking about a more versatile CNC package for sale to Sherline
>customers. So I need something fairly robust that can be reproduced
>with readily available parts. I used the unipolar Allegro 7044 in the
>existing controllers, but am considering a bipolar driver this time.
>The Xylotex product isn't too expensive, and I'm not opposed to
>buying a solution instead of reinventing the wheel.

I'll let you know how I get on with the Xylotex board. With the 20 TPI
screws on the Taig I don't expect to see much advantage to using
microstepping as, with 1/2 stepping, you are already at .000125" per
half-step. I guess you would get a smoother travel, but there's less of an
incentive to use microstepping compared with larger machines with much
coarser pitch screws.


Regards,
Tony