Re: [ATM] help required - or?

["Bob May" <rmay@nethere.com>]

Most stepper motor drivers are switching devices as the stepper
motor easily responds to them by moving to the appropiate
position.  By driving all of the windings of a 3 or more phase
stepper motor, you can position it to any point by varying the
power to each of the windings.  This, of course, requires an
analog power control as you may be putting like 35% of the power
to one phase and other amounts to other phases of the motor and
thus getting a particular angle on the motor shaft.  This also
ends up making the motor vibrate less as there is no sudden jump
in power as you move the phases input to the motor.  For small
steppers, there are power amplifier chips that will do the job
very nicely.  Two for each winding in a push-pull arrangement
like driving a speaker that sits between them (electronically!)
will do nicely.  The power cap. of these chips is such that they
will work really good.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net

----- Original Message -----
From: Mark Cowan <toolontop@yahoo.com>
To: <atm@atmlist.net>
Sent: Wednesday, May 21, 2008 2:05 PM
Subject: Re: [ATM] help required - or?


> Oh, there's also a commercially available stepper driver
intended for hi-speed
> CNC rigs that goes well beyond microstepping by providing full
phase control,
> it uses what amounts to an audio amp design and might suit.
Sorry I can't find
> any links to that, though you can probably search it out.
>
> Best,
> Mark
>
> --- Vladimir Galogaza <vladimir.galogaza1@zg.t-com.hr> wrote:
>
> > To speed up interferogram collection in Phase Shift
Interferometry
> > Bath interferometer, (PSI Bath), I am using a motor to rotate
a final
> > polarizer. Goal is to rotate a polarizer at 5 rpm.
> > Therefore motors I used have some gear boxes to reduce the
speed
> > of the output shaft.
> > But motors rotate at high speed and any imbalance in rotor
caused vibration
> > is sensed by interferometer. Motors that have inherently low
speed are not
> > available
> > (to me at least). Stepper motors will do in principle but
stepping jerks are
> > terrible. I have mounted motors to dumping cushions but
interferometer is
> > very sensitive and isolation was always insufficient.
> > Does anybody has idea how to solve this problem? I count on
ATM ingenuity.
> > ( and traditional sense for low $$$ solutions).
> >
> > Regards
> > Vladimir.
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
>
>
>
>
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
>

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