If I need to lower the Rotation speed of a DC motor, but can't change the voltage what is the eaisest way?

Question

I am trying to help my brother with a project for school, he has a disco ball like object hooked up to a DC motor. The motor is spinning it, but it spinning it to fast. It has to be run from a 1.5v D battery, so I can't lower the ammount of voltage at the source. what components could I use to slow the motor down? Also we can't use a different motor.

P.S. I'm good with electronics components so I have no problem using resistors etc...

I did try the potentiometer approach, I don't know what I did, but it started to smoke. I checked it over three times, but kept doing the same thing, if anyone has or knows where I can find a schematic for this approach let me know. This would work great as I'm not sure of the actual speed I need it to move.

Also, would this be changing the current or the voltage?

Answer 1

I do not know much about DC motors, but I do know some about AC motors. In an AC motor if you lower the voltage you will cause iv to run hotter. This is because is not running at its rated speed which causes it to draw more current. More current =More Heat. The remedy for the AC case is a controller that regulates the frequency of the AC current.

Answer 2

You are on the right track with a potentiometer. First, the pot must be capable of handling the amount of current you are passing. Higher wattage pots are usually wire wound and can be quite large when amperage is high. If you wired the pot in parallel with the motor, you are simply using more current and will not slow the motor. Wire the pot in series with the motor to lower the voltage to the motor. Part of the voltage will be dropped across the pot. To select the proper value potentiometer, look at the motor and see if it has an amp or wattage rating on it. Otherwise, you may have to use an amp meter in series with the motor to see how much power (watts) is being used for proper sizing.

Answer 3

Maybe I'm simplifying this but ...
You say you can't change the voltage at the source but since you are considering potentiometers and other voltage regulating devices I'm assuming that you are allowed to change the voltage driving the motor.

If that is the case then why not just use a simple voltage divider w/ a pair of resistors?

http://en.wikipedia.org/wiki/Voltage_divider

Battery connects Vin to ground, DC motor connects Vout to ground.

Answer 4

Build a pulse-width modulation driver for it. All it requires is a 555 IC and a transistor. I'll include a link to a circuit to build it shortly. You can get all the components that you need at Radio Shack.

A PWM will allow you to slow the motor down really slow...more than simply putting a resistor inline to reduce the voltage. Simply dropping the voltage will cause the motor to lose torque, and it won't spin the way you want it to when you put a load on it. a PWM will allow it to spin really slow with load.

Answer 5

Place a diode in series with the battery to drop the voltage to the motor. Use something like a 1N4001. This is rated 1 Amp. It should drop the voltage by about .7 Volts.

Answer 6

Easiest way? Put a piece of cardboard in between one end of the battery and it's contact. Now put a 1.5 volt light bulb with pigtail leads to jump the piece of card board. try a 1 watt bulb first. Your putting the bulb in series with the motor and this should slow it to half the speed.

Answer 7

The pot will control the voltage. Otherwise, try adding load, provided the motor can run continuously under the heavier load, you can slow it down that way effectively.

Answer 8

Use a potentiometer so you can fluctuate the speed

Answer 9

Your potentiometer was too small for the load

Answer 10

Gear reduction