At 12:49 AM 4/9/2013, Alistair Bell wrote:
>oh here is a nice compact (ha!) model
>
>http://www.criticalvelocity.com/item.php?itemid=spdc03
>
>mind you, it could be hidden somewhere remote, and the 0-5 VDC
>signal used to control (ie small potentiometer behind stock switch)

Bound to be room under the dash somewhere.

>here is a smaller one
>
>http://www.bakatronics.com/shop/item.aspx?itemid=880
>
>but only 8 - 12 V

8-30 volts, it says.  And it's not really that much smaller, just
different shape.  The circuit board is almost four inches long.

>David, know off hand what the voltage ends up being after going
>through the low speed resistor?

That would depend on how fast the motor is turning.  Ok, that was a
uSoft answer (correct but useless) sorry.  It doesn't matter because
the PWM will supply full voltage all the time, and control the power
available to the motor by changing the duty cycle of the pulse train.

A possible issue with these things would be noise injection into the
audio gear, dunno if it would be a problem in practice.

Yrs,
d