Re: [CAD_CAM_EDM_DRO] Re: .9 deg/step motor

jeffdavis516 wrote:

> --- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> > jeffdavis516 wrote:
> >
> > > Does anyone know why a Vextra 8 wire .9 deg per step stepper motor
> > > would not work correctly with a bipolar driver? I have tried this
> > > motor with Dan Mauch's 2 Amp driver and it only goes back and
> forth
> > > when I jog the axis. I know that the driver works because I
> tried a
> > > normal 1.8 deg per step motor and that stepper works fine.
> >
> > Are you absolutely sure that you have to coils wired correctly? if
> you
> > have them wired up to the wrong phases, it will not move properly.
> > You might start with just half of the coils, and see which ones make
> > it work right. If you have it wired either in series or parallel
> with
> > just one of the windings backwards, it nullifies the flux for that
> > winding, and the motor will behave just as you describe.
> >
> > Jon
>
> Hi Jon,
>
> Sorry it took me so long to get back with you. I was able to get the
> motor to run correctly if as you say I only use two of the four
> phases. If I use phase A and B or C and D but I can't seem to make
> the motor work when I try to combine all four phases. I have tried
> series and parallel using Mariss wiring diagram PDF file to no
> avail. I will keep looking, maybe I did something wrong. Servos are
> so much easier. :)

Well, there is really very little advantage in using the extra coil in parallel,
and using it in series is even worse. So, if it works OK with just one
coil, you should get 90+% of the motor's performance. By splitting the
current in two parallel coils, you can run the motor just a little cooler,
but the performance change would be so small it would be hard to
measure. You could add one coil at a time, and flip the polarity until
it works properly. If you add one coil, and the motor will not work with
it in either polarity, then that coil you just added should be paralleled
with the OTHER coil (in otherwords, if you have A and B connected,
and you add what you think is A' in parallel with A, and it doesn't work
in either polarity, then the new coil is really a B' coil, not A', and should
be paralleled with B.) I don't think you can go wrong doing it that way,
one at a time. But, the performance gain would be pretty small.

Jon