Re: Voltage to steppers

Hi,
First, doubling your voltage will significantly increase the
performance of your motors. I would definitely recommend going to
24V if your Allegro parts can handle that. It is most often
recommended to run a stepper above it's rated 'running' voltage (not
to be confused with it's MAXIMUM voltage), but you should not run a
motor over it's rated current.
Now, assume that you've gone to 24V and you still can't get the
performance you would like. Then I would suggest new steppers.
There are some on eBay that I have tried out. The title reads:
3 NEMA 23 Stepper Motors CNC 4 Sherline Taig
so if you search for some of those words, you will comes up with 3
steppers for $25.00 (their MAXimum voltage is 65V, not to be confused
with their running voltage). I have used them with my Allegro
drivers chips (A3977SED) with good results. You don't state which
chips you have. These motors require 1.75A/phase in series mode.
The Allegro A3977SED (bipolar drivers) can handle that, but some
other Allegro chips can't. The A3977SEDs can handle a MAXIMUM of 35V
(typical running Max voltage of 30V) and 24V is a good, safe, and
common supply. Of course you may have unipolar drives. These motors
are 8 wire and can be configured for that too.

Well, I hope that helps some.

Jeff
http://www.xylotex.com



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "pwrcntrl <info@c...>"
<info@c...> wrote:

> I have a home-grown machine that uses small 55mm 12V steppers. I

have

> driven them with an embedded controler & Allegro driver chips,

which

> make it fairly straightforward. The setup uses round ground

thompson

> shafting and linear bearings and moves quite freely, however, the
> little motors only have enough torque to drive consistently in

either

> 1/2 or wave drive. I would more importantly like to see some more
> speed. during free moves...it doesn't need torque beyond what is
> required to move itself around.
>
> From what I have been reading here while lurking (from people like
> Dave M, of the Basic Stamp list - Hi Dave!) it seems that it is
> common practice to drive steppers above their rated voltage, is

that

> correct?
>
> If so, what will driving my 12V motors at say 24V do? It seems you
> guys were talking about 10X rated V, so I'm wondering what 2X will
> do....
>
> Perhaps I should just change motors. Of course they will have to be
> inexpensive say $20- and with 1/4 inch shaft. If I need to go over
> the V rating of the driver chips, I may have to re-think

everything...