On Wed, 3 Feb 2010 10:35:40 -0000, Vass wrote:


"Chris J Dixon" wrote in message
...
Vass wrote:

I've got a kids kit of a walking giraffe than I have salvaged the motor
and
gearbox from.
It runs on a single AAA battery.
but even with the gearbox, the end spindle is turning way too fast for the
job I have for the unit.
Is there a resistor or some other thingymebob that I can put in line from
the battery to the motor
that will half (approx) its speed?

To a first approximation, DC motor speed varies with voltage, so
if you connect a series resistor of roughly the same resistance
as the motor itself, this may do what you want. A down side is
that the torque will also reduce, and you may not have enough
power for your needs.


hmm torque is an issue, its going to swing a 4 foot length of thin timber
(balanced with axis in the centre obviously)

If it was me, I'd try it with the length of timber in place. You never
know, the air resistance might do the slowing down for you. If not, try
putting a small diode (about 10p, from Maplins) in series with the battery.
This will drop 0.6 or 0.7 Volts, irrespective of load, so will roughly
halve the voltage to the motor. They do need to be the right way round,
or no current will flow. However, with such a small battery voltage there
may be some difficulties in getting the motor to start spinning, esp. with
that load attached.