Newsgroups: rec.arts.theatre.stagecraft
Subject: Re: Wanted: Variable Speed Mirror Ball Motor
References: <[email protected]>  <[email protected]>  <[email protected]> 
Tomi Holger Engdahl  writes:
> [email protected] (Cynical Chris) writes:
> > Therefore, wouldn't it be possible to create a variable speed for the
> > motor on a mirror ball?  Or would it be too complicated/expensive for
> > the limited use it would get?
> 
> I have seen two kinds of electrical motors used inside mirror
> ball rotator (or "mirror ball motor" as it is sometimes called).
> 
> The smallest battery powered ones use a small DC motor in them.
> The speed of kind of DC motors can be controlled by varying the
> voltage fed to the motor or using pulse width modulation
> (somewhat like light dimmer). If you happen to have this kind
> of motor you can experiment with it by wiring two wires from
> a laboratory ower supply (voltage range adjustable from 0V to full 
> battery voltage, usually one 1.5V battery in small rotators).
> Using the voltage controller in this laboratory power supply
> you can easily adjust the speed of the motor. That's how this
> can be done easily. (I have tested this). You might be able to make 
> this motor as dimmer speed controllable if you take on non-regulated
> universal wall transformer with 1.5V output and connect that
> to power the motor. This could give a limited dimmer control of
> that motor speed.. (haven't tested this yet).

The later idea also worked well. I took one mirror ball
motor which uses one 1.5V battery to run it and a small
universal transformer which have 1.5V DC output (unregulated).
I connected that small transformer output to the mirror
ball rotator. Then I plugged the transformer to a dimmer
output in parallel with normal lamp acting as a phantom load
(to make the dimmer work well...). When I turned the dimmer
to maximum hat ball rotates somewhat faster than with battery
(the transformer gave around 2V DC out at tis time). When
I used the dimmer to lower the power going to that transformer,
it gave out lower voltage and the motor run somewhat slower.
I got quite nice adjustment range in this way, although the
usable operating range was around ohe third to half of the
light dimmer controlling board slider length.

-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/