On Monday 01 May 2006 10:14 pm, rtstofer wrote:
The other day I mentioned my owl with the head moved by a servo.
Well, it works pretty well but it is not as mechanically smooth as I
would like.
So, I have fitted a 42mm stepper motor rated 3.15V @ 1A (per energized
winding I suppose). I intend to move the motor 30 steps either side
of 'center' and take about 3 seconds to do it. A total of 120 steps
or about 40 steps per second. I don't know if I will bother with
velocity ramping.
Hmm. I hadn't really thought that most of those smaller steppers I have on
hand here would be of all that much use, but... :-)
Wandering the Internet I notice two distinct ways of energizing the
windings for full steps: energize only one winding at a time or
energize two adjacent windings at a time and keep the rotor locked
between windings.
For my purposes, with a low inertia load, wouldn't just a single
energized winding work well? I'm only thinking of full steps (because
I don't have enough PWM pins) and I don't need much torque.
Yes, I would tend to think so. I've been reading all sorts of stuff on
steppers (and then falling into the whole CNC thing too :-) for a while now,
perhaps as long as a couple of years or so, after realizing how big and
heavy that box of steppers I had was turning out to be.
Since I don't need detent torque either, is there any reason to not shut off
all of the windings when the system is idle?
Seems to me that the most you gain from doubling up on the energized windings
like that is more torque (and of course some finer positioning too, but...).
I forget if it was Ian Harries' pages or maybe that was in Jones on Steppers,
both of which I'd highly recommend if you haven't read 'em yet.
I know I could use one of the stepper drivers we bought earlier but I don't
think this application is worth the effort. Four MOSFETs ought to do it.
Yes. I was actually originally planning to use salvaged bipolars here but
since I recently acquired a number of MOSFETs too, I may just have a go at
making an H-bridge or 3 out of them.
Since the model operates on 9V, I will use a couple of 6 ohm 10 watt forcing
resistors (I think; I may just drop the voltage somehow).
Volts will get you speed, and amps will get you torque... :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
