Slowing down a 12 volt motor

[shee290]

Hello, just wondering how I can slow down a 12 volt motor. Example a light you would see on a mail truck or plow truck that spins.

Can I simply put in a rheostat or potentiometer in line between the power supply and motor, or is there some more things I need to do.

I am building a light house( small one) and want to slow the rotation of the light down.

Any info or help would be greatly appreciated.

[gonzo0815]

Re: Slowing down a 12 volt motor

I would lock around for a PWM regulator. You can build it by your oqn, or buy it as a DIY kit. But i have no clue, how far you can slow it down. For real slow rotation, consider an steping motor.

[dood]

Re: Slowing down a 12 volt motor

Chances are, for the slow spin speed you're looking for, you're going to have to go with a stepper. A standard electric motor will get stuck. They all have different stalling speeds, though.

[PeteS in CA]

Re: Slowing down a 12 volt motor

Depending on how much current is needed, you may be able to use an LM317 adjustable O/P voltage linear regulator with a potentiometer in the voltage adjustment network.

[Galvanized]

Re: Slowing down a 12 volt motor

I've changed out a number of those emergency light over the years and they were all two wire. That means the light and motor are on the same circuit. So the motor wiring will need to be seperated or the light will dim.
You will need to know motor wattage, my guess would be 24 watts max. Why not keep it real simple, just use a wire wound ballast resistor and a DPDT switch. I would think running the motor at 7 volts or more would be OK.
If you're in The States, check BGMicro.com for $0.49 ballast resistors. Just use OHM's Law to figure voltage drop and the number of ballasts needed.