DC power for stir plate question

I finished my stir plate build a couple hours ago and I'm having problems getting the bar to spin continuously...I think the DC charger is giving it too much power because even when turned on to the lowest speed, the bar will spin okay for just a couple seconds as the fan is speeding up...then once it hits peak speed, the bar gets thrown.

I'm currently using a 12V / 1000mA charger. So I found a couple other options laying around the house...which do you think would work best:

12V / 200mA...or a 5V / 2.5A (2500mA)?

Try different sized stir bars. It could be that or the distance between your magnets... If that doesn't work, you may also want to adjust the height between magnets & stir bar by raising or lowering the plate above it somehow...

I encountered similar issues. My solution was to modulate the power to the transformer/charger using an ordinary rotary style light dimmer. The wall wart is a 12v DC 500 ma version. Any of your chargers should work as well so long as they are DC. Here's a video of my DIY stirplate. The video is supposed to demonstrate the improved speed control and silent operation:

smaller stir bar actually did the trick.

Thanks guys...

Cool!