> I want to occasionally control a ~1.5V DC motor from a PIC circuit
> running from 3V.  The speed isn't critical.  Power consumption, both
> while the motor is running and when not, is important (it's battery
> powered, and this will be where the bulk of the energy goes), and space
> could be important later.  It's a one-off hobby project, so I'm not
> worried about saving every last penny in components.
>
> It seems like overkill including a full SMPS.  Would it work to feed a
> pulsed 3V to the motor through a transistor at a suitable (possibly
> empirically determined) duty?  I'm a bit worried about (a) ruining the
> motor, and (b) wasting lots of current in the protection diode during
> the off periods.

        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. Going lower might result in some
vibration, going higher will get into efficiency issues. If audible noise is
a concern of yours you may have to add more filtering elements, a cap will
likely be enough, something more elaborate may be required in some
situations though. How "beefy" a motor are we talking about? TTYL

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