My disco ball spins too fast

mrflippy

We bought a cheap mini disco ball (like $5 at Walgreens or something) a few months back. It works alright, except it spins way to fast, so it doesn't do the disco effect. If I spin it slower manually, it does the effect just fine, so I figure if I can find a way to slow it down, it'll be good. My initial idea was to open it up and throw some extra resistors in there, but after reading up on things on the internet, extra resistance may not actually slow down electric motors like that.

I'm hoping someone here has an idea for how to do this. I assume the best options are either to mess with the electronics, or to somehow modify the gear(?) system it has. I don't really know much about electric stuff unfortunately. It runs on 3 AA batteries in the base, has 3 colored LEDs on the top of the base.

I'm not really out much money if there's no good way to do this, but I thought it would be neat to get it working.

A few pictures:

Figgy

I'm thinking anything you do to modify this thing is going to eventually just burn out the motor. I guess you could try to create a new gear that's smaller than the one on the bottom of the second pic, which would make the main shaft spin slower (I think). You'd need to find new elastic that fit the new gear setup, though.

Witchdr

Mechanically if you can find bigger gears (in this case it's belt driven and i don't know what the proper name for the part is) it can slow down the ball, but you are working with limited space you might not be able to get it slow enough and keep it in the case.


It's been a while since i've taken circuits, but you won't be able to change the voltage to the motor with just resistors, you'll just change the current. It looks battery operated, so you can try to use a lower voltage batter (you'll just have to adjust it so the leads can properly contact a smaller batter.)

edit:
Note: For the following, while I did get an A in my circuits class :P It has been about 5 years since i took it and i could be wrong about the following:

Reading your post a little more closely i noticed it is batter opperated (3 AA), are the batteries in series or parallel? I believe you can slow the motor down by lowering the voltage applied to it. If your batteries are in series then the voltage is added (i think all rounded batteries are 1.5 volts so in series you'd have 4.5 volts to the motor) in parallel the batteries share one voltage (so you'd have 1.5 volts total). So you can fiddle around with this to change the voltage to your motor.

Aioua

You can make a dummy battery in like 2 seconds with a piece of dowel and a wire.

Witchdr

Aioua wrote:

You can make a dummy battery in like 2 seconds with a piece of dowel and a wire.

yeah i forgot about that, you're just trying to close the circuit if you remove a battery.

tech_hunter

Lowering the voltage is a good suggestion but wont that affect the LED's?

Demerdar

I would try lowering the voltage and if there is an LED issue than you might be SOL.

Draygo

lowering the voltage shouldnt affect the leds.

Lepton

Witchdr wrote:

edit:
Note: For the following, while I did get an A in my circuits class :P It has been about 5 years since i took it and i could be wrong about the following:

Reading your post a little more closely i noticed it is batter opperated (3 AA), are the batteries in series or parallel? I believe you can slow the motor down by lowering the voltage applied to it. If your batteries are in series then the voltage is added (i think all rounded batteries are 1.5 volts so in series you'd have 4.5 volts to the motor) in parallel the batteries share one voltage (so you'd have 1.5 volts total). So you can fiddle around with this to change the voltage to your motor.

The batteries will be in series. You don't want to wire batteries in parallel because it doesn't increase the voltage and if the voltage of the batteries varies by a small amount, you could end up damaging them. So you could rig it to run on fewer batteries.

Similarly, you could also add resistors to the circuit. That should slow down the motor, which should depend on how much current is flowing through it.

illig

replace the on/off switch with a potentiometer? i did that a lot in my old PC case modding days to be able to control the case fan RPM

Donovan Puppyfucker

Install a small pot inline with the positive wire to the motor.

Pel

You need to reduce the gearing, as another poster said. Find bigger pulleys for the big ones or smaller pulleys for the small ones. Or else you could possibly jury- rig it by adding a looser belt to one of them so the power is not transmitted as effectively, or by adding a resistive load to part of the transmission system (a brake). A small tab of metal or plastic, for example, that you could glue to the bottom of the case that would rub against one of the pulleys and slow it down. Little motors like that don't have a ton of power so it wouldn't take much. Another idea might be to add some extra weight to the ball itself. All of these solutions will negatively impact your battery life, of course, but would probably be workable for someone without much mechanical experience. Ultimately reducing the gearing is your most efficient bet, but also the most difficult.

Lankysean

Can you crack the globe in half? Maybe you could throw some extra weight in there to slow it down without messing with the LEDs.