> Borrow or buy a 'fan speed control' commonly used for ceiling fans to see

> > if the
> > motor slows down smoothly. A fan dimmer is just like a like light dimme=
r,
> > except that the pot starts out at max voltage instead of minimum,
> > and often has a trimpot adjustment to set the minimum speed to
> > something other than zero output.
>
> Unfortunately this motor runs on roughly 18VAC, which makes it a bit
> harder to find a fan control for. Good thought though!
>

What do you have for AC supply now?
If you have a center tapped transformer, and only want two speeds,
use a relay to switch between using the full output, and half of it.

Phase control is phase control A fan dimmer will work at 18VAC.
You just won't get the full range of control. You won't get to 100% output
because the R/C for the diac is too long at low supply voltage.
If that is a problem (80% max) you can fix that by reducing
the value of the C disharging into the diac to fire the triac (since you'd
have a harder
time replacing the pot with 1/5 the value).

The alternative is to put the fan dimmer on the input to the transformer
that is
currently supplying the motor, but most dimmers can't handle the inductance
of an unloaded transformer very well. The usual issue is lack of holding
current
at low values of output, which you can 'fake out' by using a 3W christmas
light bulb or equivalent. This also gives you a motor power level
indication.

R
--=20
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