On Mon, 22 Jun 1998, de.vlieger wrote:

> ...
> However, does anyone have a PIC solution to the feedback control
> problem: i.e. a regulated constant speed by measuring the actual motor
> speed and comparing it to the desired speed.
>
> An additional limitation is that the hardware should be very small (SMD
> components) in order to fit in models.
>
> ...
> Another solution may be to count the number of rotations within a
> certain time, e.g. with a hall sensor or a tacho. IMHO this seems not
> the most appropriate way because of the available space in the model
> (but suggestions are welcome).

I haven't got any part numbers handy, but hall sensors can be made very
small (I've once used one made by Siemens that was so tiny that I lost it
by dropping it onto the carpet; it was never seen again...). Using another
resistor you could feed a variable voltage to a PIC A/D converter. By
attaching tha sensor to an appropriate point at the motor housing, rpm
measurement is possible.

Just my 2c.

Georg.