Re: [CAD_CAM_EDM_DRO] Re: determining stepper motor current

Alan,
I'm not familiar enough with typical 17 motors, but .8A x 1.2 ohm
gives about 1 volt and that's barely .75 watt.
My guess is .8 amp would be fine or push up to 1 amp watching any
bad heating. The only problem would be saturating the iron at some
point. If they do what you want there, stick with it.
RichD

alanhunt2001 wrote:

>
> Hi Rich,
> I'm using a bench power supply at the moment set to 30v - it can
> deliver upto 3A but is only giving about 150ma at the moment per
> motor. How can I determine the current rating of the motor as the
> only info given is the resistence - 1.2ohm?
>
> thanks
>
> alan
>
> --- In CAD_CAM_EM_DRO@yahoogroups.com, RichD <cmsteam@s...> wrote:
> > alan,
> > The ref volts is the chopper cutoff current setting reference.
> > VRef divided by sense res ohms = current setting.
> > or
> > Max current times sense res = VRef
> >
> > The motor rating is the max setting for VRef calc.
> > Set it to the max allowed for the motor.
> > OTOH, what voltage is your power supply? The L298 allows ~30 max.
> > This is where the Omph! comes from.
> > RichD
> >
> > alanhunt2001 wrote:
> > >
> > > I have a Step 4 cnc machine for which I've built a new controller
> > > based on L297/298 combo (as the original went up in smoke) I'm
> > > having trouble determining the vref setting. The motors are
> marked
> > > nanotek - munich 1.8deg/step 1.2ohm. '17' size and I think they
> were
> > > originally set up for a max current of 0.8A. I am trying them at
> the
> > > moment with vref=0.4v and with sense resistors of 0.5ohm , but
> the
> > > motors do not have any of their original torque.
> > >
> > > As I understand, I am effectivly setting the current as the peak
> > > current which will be much less then the average current. I am
> wary
> > > of increasing the current without any more data on the motors.
> > >
> > > any suggestions will be appreciated.
> > >
> > > alan