rad0 wrote:
>
> > I assume that your stepper is rated for this current?
> it's rated for 2.0 amps, but I needed to limt it to 1.25 for the
> 5804 controller

Why use the UCN5804? Why not sequence direct
from a PIC and use 4 transistors if you only
need crude half stepping?

> This motor is for a sherline mill, a cnc setup, so performance is an issue?

Yes, the sherlines have a lot of static friction
and at 20 turns/inch you will also need decent
motor speeds, probably about 5 revs/second. A
microstepping driver will be a lot better.


> I don't really understand what voltage is OK or what voltage should be used
> for this motor.  On the list of specs, it says 3.2V.  What is this? a
> minimum?
>
> I guess 2.0 amps is all you need to worry about.  Then the power generated,
> or heat to be dissapated away somehow?  is this true?

Both true, the label rating is usually the
"half copper" rating, ie 2 of the 4 coils
activated, each at 3.2v 2A. That gives your
max heat value, 3.2 x 2 (x2 coils) = 12.8W

If you decide to drive the motor bipolar (in
full copper) mode you need to derate that to
0.707 x amps = 1.4A per coil and about 4.5v
per coil.

You sound to be having difficulties with this
and the UCN5804 are not a cheap chip. Also
like all small stepper chips they are trash
(my view) and only good for disposable printers
for the consumer market.

If you have a nice Sherline metalworking mill
+ motors, worth probably $1000 why not spend $75
more and get 3 Linistepper boards from:
http://www.piclist.com/techref/io/stepper/linistep/index.htm

James Newton is offering these stepper kits at
a fraction more than the parts cost and half of
the (small) profit goes to support the piclist. The
design is my own and is RUGGED and will last the
distance, with heavy duty 5 amp transistors doing
the hard work instead of a flimsy DIP chip.

Possibly the best benefit is that it does
microstepping in 1200 and 3600 step modes, MUCH
better smoothness and precision than what you will
get from your 5804 chip. This makes a difference
with resonance and when cutting curves.
-Roman

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