wire up standard steppers as regular motors ?

On Apr 2, 5:02 pm, "pogo"

You can wire them up as steppers with drivers, and have 2 inputs:
1-direction  (0=fd, 1=bk)
2-on/off

Not with DC. You can use a step clock source (like a 555) feeding a
driver of some sort and wind up with something that does not require a
processor to run, but the driver board is not optional with DC on a step
motor.

You might and that is a definite maybe, get a step motor to run on AC
with a transformer and a capacitor or two, but it would be fixed speed
(slow), very quirky and probably take a good bit of fooling with.

With a DC motor, a processor, driver and a shaft position encoder, you
can make them behave a little like a step motor, in that you can direct
them to a specific position. Generally they are better than steppers for
motion control.

Good Luck,
Bob

Yeah sounds like more trouble than its worth -- which is what I suspected. But
still interesting to think about ...

Actually, during the sporge attack, I posted to Gordon's blog site about
wanting to drive a hard drive BLDC spindle motor, a similar problem to
what you propose if I'm not mistaken, and was actively encouraged to drop
the idea, as being not worth the effort.

Still, I'd love to obtain a small and simple circuit which could spin
those babies under s/w control 8-).

Cheers,
Rob.
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writes:


asking the question:

In a word, no.  They require the coils to be energized in sequence.
I don't really know, though, whether a brushless DC motor controller
chip could be used to control a stepper...

On Apr 2, 5:02 pm, "pogo"

Ok here's an idea...  rotary switch attached to the output shaft
of the motor...  time the switch to turn on the correct coil depending
on shaft rotation...

all the stepper motor is :  stationary magnet(s) on rotor,
electromagnets
around stator..  wires come out of case for each coil, no timing done
in
case (need external driver circuit)

a standard DC motor is the same deal, except with stationary
electromagnets
and rotating permanent magnets..... it als has a switch inside it to
time the ON/OFF sequence of the coils...  on one side of the switch
is
the brushes, the other contact is the commutator on the rotor.


so put a rotary switch on it... I dunno if you'll be able to run at
anything
besides a constant speed...  and it might be hard to find a (number of
stepper
coils) contact rotary switch...  IE a 4 position rotary switch for 4
coil stepper

Rich

asking the question:

can be driven forward/backward like a "normal" DC

     Now that's using the wrong tool for the job.  That might
have been worth trying in, say, 1965.  But now, there are these
things called ICs...

     There are little kits that have a stepper motor driver IC
like a UCN5804, a timer to drive it, and a speed control knob.

                    John Nagle

Can you provide a link to one of those little kits????????

Cheers,
Rob.
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I was replying to this question:


so, it might be "wrong tool for the job" but it is a reply to someone
who asked "how to do the job without the right tool"....


Rich

On Apr 2, 8:02 pm, "pogo"

asking the question:

can be driven forward/backward like a "normal" DC

to minimize the number of gizmos in my junk box for

by upgrading the electronics to drive them later.

short answer: yes it can be done.  no you don't want to.

rambling answer:

fundamentally stepper motors are the same as brushless dc motors: they
both consist of a permag rotor in a rotating field generated by a
multiphase stator coil.  beyond that theoretical design, however,
there are still a lot of design tradeoffs.  steppers are designed for
small step sizes, relatively low speed use, and high holding torque at
low speeds.  brushless dc motors are designed for high efficiency,
minimal cogging, and high speeds.

so basically, you can use a stepper as a brushless dc motor without
much trouble because in theoretical terms they're the same thing, but
you'd be an idiot to try it, because absolutely every design parameter
of the stepper has been optimized for the opposite application as what
you're trying to do.  it's like asking "why bother having both a barge
and a sailboat when you can just attach a sail to the barge?"

-chris.