Quick correction to my last post. The formula should have been:

Imotor = (d*Vb-Vemf)/(d^2*Rw+Rm)
Ibatt=d*Imotor

where Imotor is motor winding current, Vb is battery (or supply) open
circuit voltage, Rw is the resistance of the battery (or supply) and all
the wiring connecting it to the circuit. Rm is the resistance of the motor
plus switching element plus any wire between them.

Vemf is the motor back EMF. This is what I left out.

Sean

At 07:11 AM 6/14/2003 -0400, you wrote:
> > >     Well, it all depends one what you want to do. You could
> > simply drive the
> > > motor with a 50% duty cycle waveform and probably get an average pretty
> > > close to 1.5V. The one great thing about motors is that they have a very
> > > high inductance, which means they filter incoming pulsed waveforms quite
> > > well. The frequency of operation isn't too critical, I'd say
> > anywhere from
> > > 400Hz to maybe 2000Hz would PROBABLY be OK.
> >
> > Ok, I'll have to experiment with different frequencies and duties.  An
> > excuse for another project - I keep thinking that a PWM generator would
> > be useful.  :-)
> >
> > > Going lower might result in some vibration, going higher will get into
> > > efficiency issues.
> >
> > What are the efficiency issues?
>
>

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